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Draft Document Description of the Printing Processes Technical Annex1

10 November 2003

Technical Annex 1, Printing processes 10 November 2003

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DRAFT 1 2 Overview Offset (lithography) 2.1Printing materials and products 2.2Process description 2.3Chemicals 2.4Waste 2.5Environmental burden 2.6Potential for improvements 2.7Expectations for the future Flexography 3.1Printing materials and products 3.2Process description 3.3Chemicals 3.4Waste 3.5Environmental burden 3.6Potential for improvements 3.7Expectations for the future Gravure 4.1Printing materials and products 4.2Process description 4.3Chemicals 4.4Waste 4.5Environmental burden 4.6Potential for improvements 4.7Expectations for the future Screen 5.1Printing materials and products 5.2Process description 5.3Chemicals 5.4Waste 5.5Environmental burden 5.6Potential for improvements 5.7Expectations for the future Letterpress 6.1Printing materials and products 6.2Process description 6.3Chemicals 6.4Environmental burden 6.5Potential for improvements 6.6Expectations for the future Digital printing 7.1Printing materials and products 7.2Process description 7.3Chemicals 7.4Waste 7.5Environmental burden 7.6Potential for improvements 7.7Expectations for the future 3 4 6 6 15 19 22 26 30 33 34 34 37 39 40 42 44 45 46 46 48 51 52 54 55 56 57 57 59 61 63 64 65 66 66 66 68 71 73 74 75 75 75 77 78 78 79 79

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DRAFT 8 Post-press or finishing 8.1Finishing products 8.2Process description 8.3Chemicals 8.4Waste 8.5Environmental burden 8.6Potential for improvements 8.7Expectations for the future Bibliography 80 80 80 83 84 85 86 87 88

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Description of printing processes

1 Overview

The printing industry is a very diversified industry, owing to the multiplicity of printing processes utilized, the size of the plants, and the products it produces. Lithography (offset), flexography, gravure, and screen are the major conventional machine printing processes. Letterpress was the earliest form of printing but has been superseded by offset. Today letterpress finds only limited applications in simple text, such as business cards. Electronic/digital printing processes have developed during the last fifteen years. Electronic/digital printing include xerography and laser printing; ink jet printing; magnetography; thermal printing; ion deposition printing; and direct charge deposition printing. Lithography, gravure, and flexography are the dominant processes; lithography is the most widely used printing process today. The various electronic/digital printing processes are gradually becoming a major force in the industry and have to a great extent created new market opportunities and niches rather than being a replacement for conventional printing processes. Conventional printing processes can be divided into three major steps: prepress, press, and postpress, figure 1. All prepress operations follow the same initial stages of converting the original matter, which can be of either conventional or digital origin, into an image carrier such as a plate, cylinder or stencil. The image carrier are used in the printing processes to transfer the printing ink onto the substrate (paper, board, plastic, etc.). Press refers to actual printing operations. Postpress primarily involves the assembly of printing materials, and consists of binding and finishing operations.

Computer "digital files"

Prepress Photography

Image carrier preparation

Printing

Finishing Finished product

Figure 1

Individual graphic companies may incorporate a whole series of processes, from original pattern to finished product, but many specialise in, for example, printing, reproduction, or bookbinding. A single printing plant can also utilise several different printing processes, such as offset and screen, or different types of offset, such as sheet-fed offset and heat-set web offset. Many printing plants have now also complemented their equipment with different kinds of digital presses. The choice of printing process is usually based upon technical and commercial considerations, such as length of run, required print quality, choice of substrate, speed of printing and drying, and the end use of the product. A wide variety of products are produced and printed on many different types of materials. Examples of products that can be produced are newspapers, magazines, books, greeting cards, calendars, brochures,

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leaflets, stamps, labels, business forms, passports, cheques, tickets, envelopes, paper or plastic bags, food packaging, gift-wrap paper, cans, decals, T-shirts, and wall coverings. Depending on the printing process, the substrates for printing can be different types of papers, coated and uncoated boards, corrugated boards, plastics, metal, ceramic, glass, cork, wood, and fabrics. A printed matter is made up of differently-sized dots (screened), which are created with a special camera or with the help of a computer (scanner). Colour pictures are separated and a picture is made for each colour: yellow, blue, red, and black. These colours are always used when printing a colour picture, and are printed separately on top of each other. The four primary colours are often called process colours, and a colour scale called the European Scale is principally used. To create spot colours, e.g., a special colour for a logotype, a different colour scale, named PMS (Pantone Matching System), is used. The PMS-scale consists of thirteen primary colours, but by mixing these before printing, a large number of colours can be created. In the following description of the different printing processes, only the most typical inks are mentioned. For every printing process there are many varieties of printing inks. There are many factors that affect the ink formulation, such as the type of printing press, printing speed, type of substrate, or the intended use of the printed product (food wrappers, wallpaper, etc.).

2 Offset (lithography)

Lithography, a planographic process, is today usually referred to as "offset." Offset printing dominates the printing industry both in Europe and the U.S., accounting for as much as 50 percent of all conventionally printed materials. However, the market for offset printing is decreasing. Offset printing is suited for printing both text and illustrations in short to medium length runs of up to 1 million impressions. Offset is a planographic printing method, meaning that the printing and the nonprinting areas are on the same plane, and the substrate is pressed into contact with the whole surface. Offset works on the principle that ink and water do not mix. Images on the plates are first dampened with water and then with ink. The ink adheres to the image area, the water to the non-image area. Then the image is transferred to a rubber blanket and from the rubber blanket to paper. That's why the process is called "offset" ­ the image does not go directly to the paper from the plates, figure 2.

Figure 2

There are three basic offset press designs: unit-design, common impression cylinder design, and blanket to blanket design.

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The unit-design press consists of a plate cylinder, a rubber blanket cylinder, and an impression cylinder together with the inking and damping rollers. The simplest offset press consists of only one unit, a singlecolour unit press. A common impression cylinder press or satellite machine consists of two ore more sets of plate and rubber blanket cylinders sharing a common impression cylinder. Two or more colours can be printed at a single station. Most sheet-fed presses are built on the blanket-to-impression principle, and web-fed machines most often are built on the blanket-to-blanket principle. Sheet-fed printing presses are available from single-colour to multicolour configurations, and web-fed presses are usually available as four-colours or more. Most of the presses consist of four printing units, one printing unit for each primary colour for printing colour pictures. In a multicolour sheet-fed press the sheet travels on transfer cylinders or chain grippers between the units. Depending on the type of substrate or the products printed there are three types of offset printing sub processes: sheet-fed, heat-set web, and cold-set web offset, figure 3.

Computer "digital files"

Film processing

Proofing

Digital proofing

Film assembly

Platemaking

Sheetfed offset printing cleaning

Heatset weboffset printing cleaning

Coldset weboffset printing cleaning

Drying

Figure 3

Finishing

On sheet-fed presses the substrate is fed into the press one sheet at a time while web presses feed paper continuously from a large roll, which is later cut to size.

Finished product

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Most sheet-fed presses can print only one side of the sheet at a time but there are presses that can print on both sides simultaneously. Web-offset presses print on both sides of the paper at the same time. Web-fed presses are faster than sheet-fed presses and are better suited for long-run works. A variation of the offset process is waterless offset printing, where printing is done without water. The plate for waterless offset has an ink repellent silicone rubber layer on top of a ink receptive photopolymer coating surface. Printing presses for waterless offset normally must be equipped with cooling systems. Waterless offset today appears mostly in the sheet-fed offset process. The digital presses which do not have variable printing are based on waterless offset technology, figure 4.

Figure 4

2.1 Printing materials and products

The most common products are newspapers, magazines, brochures, books, catalogues, posters, leaflets, cartons, envelopes, and forms. Printing is done primarily on paper, but can also be done on various types of cardboard, metal foil, metal, and plastic.

2.2 Process description

2.2.1 Pre-press, image preparation

The first step in the printing process, imaging, produces an image of the material (text, diagrams, and pictures) to be printed, figure 5. This process is fairly similar for all printing except for digital printing, where this step does not exist. The pre-press stages of image preparation have changed from a lot of manual steps where text and pictures were handled separately to where it is done electronically. Electronic imaging processing systems can produce text and pictures and then arrange them in the correct position on the page. The imaging process begins with composition and typesetting. Composition involves the arrangement of text, pictures, and diagrams into the desired format. Earlier, this used to be performed manually and included a lot of different steps, but today high-performing computers and graphic-oriented programs are used. If pictures are to be printed in several colours, these must be separated into four colours and exposed on film, but today this can be stored in the computers. The pictures are also often screened, i.e.,

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the pictures consist of a large number of very small dots instead of a whole field. Once the desired format and images are assembled, the data are exposed onto photographic material in an image-setter. The photographic emulsion on the film or paper is composed of silver halide and gelatine. Developing and fixing of the photographic film or paper is often done by machine, with subsequent rinsing stages and then drying. The film and paper are accompanied by a certain amount of liquid when they are transferred to the next bath. Depending on the fixing bath's silver concentration, the design of the equipment, and the flow of rinsing water, the quantity of photographic chemicals and silver vary in the rinsing water. The rollers in the developing machine need regular cleaning because of silver deposits. Cleaning of the rollers can be done with a brush and a household detergent. Earlier it was common to use cleaning agents containing chromium, and this may still be used in a few places. A proof print is often made for checking the reproduction process, or for submitting to the customer for checking and approval, or used internally by the printer as a working guide. Many different methods exist; wet proofing is the traditional method of producing colour proofs. Today, proofs can be made directly from the data in the computer, being shown on the screen or printed out with an inkjet or laser printer. It is the same technology as printers/presses that are used for digital printing. Small quantities of toners or inkjet ink are used for proof printing.

Scan original Record original

Computer "digital files"

Filmexposure

Developing

Fixing

Rinsing

Drying

Correcting

Rinsing

Figure 5

Recopying Film exposure

Finished film

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2.2.2 Platemaking

The printing form in offset today consists principally of an aluminium plate, which is covered with a thin light-sensitive coating, 1-3 µm thick, figure 6. In small-format offset, paper and plastic can be used, as the demands on the strength of the plate are not that great. Earlier, multi-metal plates were used and they could either be presentized or had to be in-plant coated. There are two types of plates, negative and positive working plates, and they differ in the chemistries of their light-sensitive coatings. The positive working plates can, after developing, be cured in a specially constructed oven, which increases the plate life up to three times.

Plate making, polymer plates

Computer "digital files"

Finished film

Plate exposure

Developing

Rinsing

Gumming

Baking

Finished printing plate

Figure 6

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The montage foil is copied to an offset plate. The montage can be either in the form of a film or a digital file. The film is placed over the offset plate. Then a framed glass sheet is placed over the film and a vacuum is applied to pull them tightly together. The plate is exposed to ultraviolet light which hardens the coating on the plate to make it insoluble in water or other solvents. The next step in the platemaking process is developing, which is made in automatic plate developing machines. Developing might also be made manually. Most developing machines are constructed with three separate sections: developing, rinsing, and gumming. Gumming of the plate is done to protect it from oxidation. Cleaning of plate developing machines can in most cases be done with detergent and a sponge or brush. The plate for waterless printing is exposed in UV. The light-sensitive layer is coated with a non-printing layer consisting of rubber silicone. Ink is accepted in the image areas where the silicone has been removed. The offset plate can be exposed with a digitally driven laser in an image- or platesetter instead of exposing through a film. The technique is referred to as computer-to-plate, CTP. It is still an expensive technique but will become increasingly common. 2.2.3 Printing

The completed plate is stretched around the plate cylinder in the printing press. The plate is continually moistened with water, named damping solution or fountain, via damping rollers from the damping unit. There are different types of moistening systems, e.g., brush feeding units, film damping units/alcohol damping units, or mist damping units. The print-accepting parts of the plate repels the water. In waterless offset printing there is no damping solution. In waterless offset printing the plate has an ink repellent silicone rubber layer and a ink receptive photopolymer coating surface instead. Otherwise the technology is the same as for wet offset. From the ink fountain the ink passes a number of ink rollers before reaching the plate cylinder with the plate. The ink sticks to the ink-accepting parts and the plate is pressed against a rubber-clad blanket cylinder, on which the printing picture deposits its ink. The blanket cylinder is, in turn, pressed against the printing substrate and there deposits the printing ink. The press is then fine-tuned to ensure that registration and ink-water balance is accurate and identical on all copies coming off the press (make-ready). All copies generated in make-ready are waste paper.

2.2.3.1 Sheet-fed offset printing

The majority of smaller offset printing plants are sheet-fed offset plants. A few heat-set web offset printing plants also have a number of sheet-fed offset presses. In most sheet-fed offset presses, printing is first done on one side of the sheet, and when the run is finished, the stacker is turned over and the other side of the sheet is printed. See figure 7 for the principle. Products printed in the sheet-fed offset process are, for example, posters, business cards, pamphlets, brochures, magazines, books, annual reports, lottery tickets, maps, and packaging of carton board or tin plate.

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Figure 7

Ink Oxidisation drying inks are normally used in sheet-fed offset printing. The ink dries through oxidation, but the drying can be expedited with the help of an IR-dryer, especially when printing on uncoated paper. The IR-dryer is most often installed after all the inks have been printed on the substrate. Ultraviolet drying inks exist, but these require special UV-dryers to harden the ink, and drying is done after printing each colour. Anti-set-off powder is sprayed on the sheets to prevent the ink from smearing and sticking onto the back of the sheet as the printed material is stacked. In most cases, the ink is added manually to the ink fountain, but it is becoming more common that the ink is pumped through pipes from 200-liter drums to the respective ink fountain. In the cases when the ink is added manually, the inks are delivered in smaller packages, from 1 kg up to 20 kg. It also happens that the ink is packaged in a pressure-controlled ink tube, from where the ink is fed into the ink fountain. In multicolour presses, standard inks are usually used for the four primary colours, and additional printing units can be used for special colours or for lacquering of the printed material. When standard inks are used the ink is not changed, and ink rollers and ink train do not need to be cleaned between different printing jobs. Damping solution The type of damping unit used for sheet-fed offset presses is to a large part film damping units. In older printing presses, the system consists of two fabric covered plate rollers and a distributing roller. The fabric covered plate rollers need to be cleaned from ink from time to time. This cleaning usually occurs in special machines, either with solvents and warm water, or with the help of high-pressure units and water. In modern sheet-fed presses the fabric-covered plate rollers have been excluded. Damping solution is most often delivered in concentrated form and is diluted to a 2-4 % solution before being used in the printing press, either manually or in an automatic mixing system. Isopropyl alcohol, IPA, is the most common additive used in damping solutions. It is added to the damping solution at a rate of 2 to 15 percent. The IPA-concentrate in the damping solution can either be added automatically when the concentration goes down, or the IPA addition is set at a certain preset amount. The latter alternative means that the IPA concentration in the damping solution can vary strongly.

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In older sheet-fed presses the damping solution normally recirculates separately for each printing unit. The damping solution is pumped to the press and the surplus flows back to the damping solution tank. In some systems the damping solution is filtered to get rid of ink residue and paper dust. In modern plants with alcohol damping units, cooling is done with a common damping solution tank for all the printing units, in order to reduce the vaporisation of IPA. The majority of IPA used, about 90%, evaporates into the air during the printing process, and is released into the surrounding air as fugitive emissions through the ventilation system. The other 10% accompanies the product or goes to sewage or as waste. Cleaning In sheet-fed offset presses smaller runs are usually printed, from 1.000 copies up to 10.000 copies, which means more cleaning than in web offset presses. Larger-size sheet-fed presses print up to 50.000 copies or even more. Modern sheet-fed offset presses are increasingly equipped with various automatic cleaning systems. Cleaning of the press occurs most often between press runs, during the press run, and during the makeready as adjustments are made to the press and plates, as well as at the and of the day. The frequency of press washes depends on many factors, including paper dust and dried ink accumulation, the quality of the paper, and the habits of the particular press operator. Blankets are cleaned after the press run or after a colour change. With larger runs the rubber blanket and offset plate must be cleaned after a while of printing in order to remove paper dust. Many sheet-fed offset presses, in particular larger or modern sheet-fed presses, are now equipped with automatic rubber blanket washers. During a press run the rubber blankets can be cleaned while the press is still printing, but at slower speed. There are different types of rubber blanket washers, such as:

· ·

washblanket system brushblanket system.

In manual cleaning, solvent-soaked rags and, in many cases also water, is usually used. Water must be used to get rid of paper dust on the rubber blanket. Cleaning of fountain pans and emptying of the damping system is done at varying intervals at the printing plants. Some printing plants clean the system every week, while other do it only once or twice a year. When changing inks or at the end of a shift, the bulk of the ink is scraped off the rollers and ink fountain to be used at a later time. Normally solvent is sprayed on the ink rollers and the ink thins. The resulting solvent/ink waste is scraped from the inkrollers with a blade and collected in a tray.

2.2.3.2 Heat-set web offset printing

Products printed in the heat-set web offset process include magazines, other periodicals, catalogues and direct mail products. Printing in heat-set is usually done on coated, glossy papers. For the principle, see figure 8. When printing with heat-set web offset the same type of plate is used as with sheet-fed offset, but as printing is done on a web from a roll to the folded product the same type of ink cannot be used because

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of the risk of smudging. Printing is done on both sides simultaneously, and after all the colours have been printed, the web passes a gas-fired oven with hot-air outlets. Immediately after leaving the oven, the paper is run through a series of metal rollers that have refrigerated water flowing through them. These chill rollers cool the paper and set the ink into the paper. The web also passes through an unit to replace moisture to the paper. In many cases there is also the possibility of coating the web with a silicone solution.

Figure 8

The inks used in heat-set web offset dry primarily through evaporation of high-boiling solvent components. This occurs when the web passes a drying tunnel with a temperature of 180-220°C. The solvents that evaporate in the dryer are burnt in an afterburner. During incineration, the organic materials in the polluted air stream are oxidised, primarily into carbon dioxide and water. There exist dryers which have thermal incineration integrated with the dryer. The dryers with integrated incineration are programmed so that printing cannot occur unless the dryer and the incinerator are operational. In heat set web press, the ink is usually pumped in pipes from 200-liter drums or larger containers to the respective ink units. Standard inks can be delivered in re-usable containers and the amount of ink residue left in the containers can be reused by the ink manufacturer. Special inks are most often delivered in smaller packages, and are normally added manually to the ink fountain. When changing inks or at the end of a shift, the majority of the ink is scraped off from the ink fountain and disposed as waste or reused. Cleaning of the ink rollers is done either by spraying them with solvent, thus thinning the ink, which can then be removed using the web or by hand, using rags and solvent. Modern heat-set web offset presses, but also a number of older presses, are equipped with a variety of automatic cleaning systems. Cleaning of the press occurs most often between press runs, during the press run and during the makeready as adjustments are made to the press and plates, as well as at the and of the day. Many heat-set web offset printing plants operate day and night throughout the week, which means that no comprehensive cleaning of the press takes place until the end of the week. The frequency of press washes depends on many factors, including paper dust and dried ink accumulation, the quality of the paper, and the habits of the particular press operator. Blankets are cleaned after the press run or after a colour change. With larger runs the rubber blanket and offset plate must be cleaned after a while of printing in order to remove paper dust. During a press run the rubber blankets can be cleaned while the press is still printing, but at slower speed. Modern heat-set web offset presses, but also older presses, are now equipped with automatic rubber blanket washers. There are different types of rubber blanket washers, such as:

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· · ·

washblanket system, where a textile web which is pre-soaked with a solvent is used. Usually, this is a solvent with a low steam pressure (<0,01 kPa). brushblanket system, where a rotating brush roller, with the help of solvent and maybe water, removes ink and paper dust. The used cleaning liquid is guided to a container. spraying nozzles and a moving web.

The type of damping units used in heat-set web offset presses are mostly film damping units but brush feeding units or mist damping units might also occur. In older printing presses, the system consists of two fabric covered plate rollers and a distributing roller. The fabric covered plate rollers need to be cleaned from ink from time to time. This cleaning usually occurs in special plants, either with solvents and warm water, or with the help of high-pressure units and water. In modern heat-set web offset presses there are no fabric-covered plate rollers. Damping solution is most often delivered in concentrated form and is diluted to a 2-4 % solution before being used in the printing press, either manually or in an automatic mixing system. Principally, there is a recirculation of the damping solution, which is at the same time cleansed of ink residue and paper dust through filtration. The damping solution is continually pumped to the press and the surplus then flows back to the damping solution tank. Isopropyl alcohol, IPA, is the most common additive used in damping solutions. It is added to the damping solution at a rate of 2 to 15 percent. The IPA-concentrate in the damping solution can either be added automatically when the concentration goes down, or the IPA addition is set at a certain preset amount. The latter alternative means that the IPA concentration in the damping solution can vary strongly. Most heat-set web offset presses add IPA to the damping solution, which helps cool the ink, which in turn is required in faster printing presses. In modern plants with alcohol printing units cooling is done with a common damping solution tank for all printing units, in order to reduce the vaporisation of IPA. Cleaning of the damping pans and emptying of the damping solution system is done at varying intervals at the printing plants. Some printing plants clean the system every week, while other do it only once or twice a year. The dryer extracts air from the press room containing IPA and solvents. It is estimated that about 10-20 % of the used IPA and solvents are burned in the dryer. The remaining 80-90% of the used IPA evaporates during the printing process and is released into the surrounding air as fugitive emissions through the ventilation system.

2.2.3.3 Cold-set web offset printing

Products printed in the cold-set web offset process include newspapers, journals, directories, business forms, and books with nothing but text or only a few illustrations. Printing in cold-set web offset is done mainly on uncoated wood-containing paper or recycled waste paper, which are fairly absorbent. The ink used for cold-set dries through oxidation or adsorption by the paper, but the drying can be expedited with the help of an IR-dryer, especially when printing on coated paper. The IR-dryer is most often installed after all the inks have been printed on the substrate. When printing forms, which happens in narrow web presses, even UV-drying inks can be used. These inks require special UV-dryers to harden the ink, and drying is done after printing each colour. In presses for printing forms, the ink is usually added manually, but it also happens that it is pumped to the printing

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units. The inks are normally delivered in smaller packages (<20 kg), but can also be delivered in 200-liter drums. Printing of newspapers is done exclusively in large four-colour presses which print on both sides simultaneously. For newspaper presses the ink is pumped through pipes from 200-liter drums or larger containers to the respective ink units. Standard inks can be delivered in reusable containers and the colour residue left in the container can be reused by the ink manufacturer. Larger newspaper printers often have stationary ink tanks, and the ink is delivered in tanker trucks and is pumped from the tanker truck into the stationary ink tanks. Special inks are most often delivered in smaller packages and are usually added manually to ink fountain. When changing inks or at the end of a shift, the bulk of the ink is scraped off the ink fountain and disposed as wasted or reused. Cleaning of the ink rollers is done either by spraying them with solvent, thus thinning the ink, which can then be removed using the web or by hand using rags and solvent. The ink used for newspaper printing has lower viscosity than other offset inks, which means that so-called ink mist occurs. To prevent the ink mist from spreading in the press and the room, there are covers by the printing cylinder. These covers are in many cases removed and cleaned outside the press, in special cleaning machines. Modern cold-set web offset presses, but also a number of older presses, are equipped with a variety of automatic cleaning systems. Cleaning of the press occurs most often between press runs, during the press run and during the makeready as adjustments are made to the press and plates, as well as at the and of the day. Many newspaper printing plants operate day and night, which means that comprehensive cleaning of the press takes place, for example, once a week. The frequency of press washes depends on many factors, including paper dust and dried ink accumulation, the quality of the paper, and the habits of the particular press operator. Blankets are cleaned after the press run. With larger runs the rubber blanket and offset plate must be cleaned after a while of printing in order to remove paper dust. During a press run the blankets can be cleaned while the press is still printing but at slower speed. Modern newspaper presses, but also older presses, are now equipped with automatic rubber blanket washers. There are different types of rubber blanket washers, such as:

· · ·

washblanket system, where a textile web which is pre-soaked with a solvent is used. Usually, this is a solvent with a low steam pressure (<0,01 kPa). brushblanket system, where a rotating brush roller, with the help of solvent and maybe water, removes ink and paper dust. The used cleaning liquid is guided to a container. spraying nozzles and a moving textile web system are often built in together with mist damping units.

The type of damping unit which is used for newspaper presses is mostly film damping units but brush feeding units or mist damping units might also occur. Mist damping units are increasingly common in newspaper presses. In this system, lower concentrations of the damping solution are needed. In printing presses for printing forms, film damping units are mainly used. In older printing presses the system consists of two fabric covered plate rollers and a distributing roller. The fabric covered plate rollers need to be cleaned from ink from time to time. This cleaning usually occurs in special machines, either with solvents and warm water, or with the help of high-pressure units and water. In modern cold-set web offset presses there are no fabric-covered plate rollers. Damping solution is most often delivered in concentrated form and is diluted to a 2-4 % solution before being used in the printing press, either manually or in an automatic mixing system.

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Isopropyl alcohol, IPA, is the most common additive used in fountain solutions for the presses for formprinting. It is added to the fountain solution at a rate of 2 to 15 percent. The IPA-concentrate in the damping solution can either be measured continually and added automatically when the concentration goes down, or the IPA addition is set at a certain preset amount. The latter alternative means that the IPA concentration in the damping solution can vary strongly. IPA is usually not used in newspaper presses. Mainly, there is a recirculation of the damping solution by pumping it continually from the damping solution tank to the press and the surplus flows back to the damping solution tank through an overflow pipe. At the same time, it is cleaned from ink residue and paper dust through filtration. In mist damping units there is a certain surplus of damping solution which is not recirculated but that is usually released as sewage. In modern presses for printing forms, which use alcohol damping units, cooling is done with a common damping solution tank for all the printing units, in order to reduce the vaporisation of IPA. Part of the IPA in the damping solution, less than 10%, accompanies the paper/product, while the remaining 90% of the used IPA evaporates into the air during the printing process, and is released into the surrounding air as fugitive emissions through the ventilation system. Cleaning of damping pans and emptying of the damping solution system is done at varying intervals at the printing plants. Some printing plants clean the system every week, while other do it only once or twice a year.

2.3 Chemicals

2.3.1 Pre-press, image preparation

Process

Chemical/ Chemical compound

Examples of chemicals used

Photographic film and paper Developer Developing of film and paper

Fixer Cleaning solutions

Correcting fluid Proof print developer Colour foils

Emulsion of silver halide and gelatine Hydroquinone, phenidone, metol, potassium or sodium sulphite, potassium carbonate, potassium or sodium hydroxide, potassium bromide, sodium silicate Fixing of film or paper Ammonium thiosulphate, sodium acetate, sodium sulphite, glacial acetic acid Sulpamic acid, thiocarbamide, , Cleaning the rollers in the sodiumhydrogen sulphate, chromium salts, developing machine surfactants Correcting exposed film Potassium ferricyanide, potassium permanganate Developing of proof print in the Sodium carbonate, sodium hydroxide, wet process surfactants Proof print process

2.3.2

Platemaking

Process

Both negative or positive plates can be used. Developing of positive offset

Chemical/ Chemical compound

Offset printing plates

Examples of chemicals used

Aluminium, paper or plastics, diazopolymers, photopolymers, binders, dyestuff. Silicones (waterless plates). Alkaline solution as sodiumphospat, sodium

Plate developer positive

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Plate developer negative plate. Developing of negative offset plate. metasilicate, alkalihydroxide. Surfactants. Alkalis. Solvents such as benzyl alcohol, diethanolamine, poly vinyl alcohol, ethylene glycol, fenoxiethanol or propanol. Surfactants. Gum arabic, dextrines, carboxymethylcellulose. Biocides as formaldehyde, kathon or bronophol. Fluorides, acids, dimetyl-formamid, cyclohexanon or tetrahydrofuran. Propylene glycol, diethylene glycol, diethylene glycolamine. Diethylene glycolether, alcohols, ethyl butyric acid, dyestuff Isoparaffins. Biocides such as kathones.

Gumming

Gumming of the offset plate to protect and preserve the plate Correcting fluid Manually remove dirt particles etc. from the plate. Pre-treatment solution Binding between silicone and (waterless plate) light-sensitive layer. After-treatment solution Inking ensures differentiation (waterless plate) between image and non-image areas. Plate cleaner (waterless plate) Take away residues of silicones. Plate system cleaner Cleaning the plate developing machines.

2.3.3

Printing

Sheet-fed offset

Inks: Inks generally consist of two main components, pigment and vehicle. Pigments can be grouped into three categories: carbon blacks, inorganic pigments, and organic pigments. The vehicle is a liquid in which the pigment is dispersed. The vehicle can be a solvent into which a suitable binder is dissolved. The binder is a resin and is the non-volatile part of the vehicle that solidifies and holds the pigment particles in a dried film. An ink can also contain other ingredients, depending upon the drying mechanism of the vehicle: driers to catalyse the oxidation drying of vegetable oils, photoinitaiator (UV-drying) monomers, polymers, and oligmers. Other possible components are: oil modified alkyd resins to form flexible films with high gloss, plasticizers and other additives as waxes to improve rub resistance or rub reducers to reduce the tack.

Sheet-fed offset

Chemical/ Chemical compound

Ink

Comments

Mineral oil based 50% Vegetable oil based 40% UV-curable 10%

Process

Printing

Examples of chemicals used

Pigment such as calcium carbonate, carbon black, aluminium hydroxide, phtalocyanine, rhodamin etc. Bindings: Mixture of oils, resins, alkyds. Solvents: Mineral oils distillate with different boiling range. Vegetable oils. Additives such as catalytic driers, antioxidants, waxes, plasticizers and fungicides (vegetable

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inks). UV-inks: pigment, prepolymers, monomers + oligomers (acrylates), photoinitiator and additives. Varnish

Mineral oil based 40% Vegetable oil based 40% UV-curable 20%

Bindings: Mixture of oils, resins, alkyds. Solvents: Mineral oils distillate with different boiling range. Vegetable oils. Additives such as catalytic driers, antioxidants, waxes, plasticizers and fungicides (vegetable inks). UV-varnish: Prepolymers, monomers + oligomers (acrylates), photoinitiator and additives.

Cleaning solvents

Aliphatic products 25% Alicyclic products 10% Aromatic products 20% Vegetable oil esters products 10% Hybride products 30% Other solvent products 5%

Aliphatic, alicyclic and aromatic hydrocarbons, Cleaning the blankets, ink rollers, ink ducts, impression vegetable oil esters, fatty acids, glycol ethers cylinder etc.

Fountain solution

Wet the surface of the printing plate.

Glycol ethers, 2-butoxy ethanol, phosphoric acid, citric acid, , wetting agents, surfactants, corrosion inhibitors, gum arabic, biocide as isothiazoline. isopropyl alcohol. Starch, chalk.

Isopropyl alcohol Anti-set-off powder (sheetfed offset) Plate cleaner/Image preserver Different process chemicals as ink preserver, tack reducer, dryers

Additive to fountain solution. Prevent the sheets from smearing and sticking to other sheets. Cleaning the plate from dried ink, dirt etc. To prevent the ink from drying, change the viscosity of the ink, to make the ink dry faster etc.

Petroleum distillates, phosphoric acid, acetic acid, propylenglycol ethers, surfactants

Heat-set web offset

Inks: Inks generally consist of two main components, pigment and vehicle. Pigments can be grouped into three categories: carbon blacks, inorganic pigments, and organic pigments. The vehicle is a liquid in which the pigment is dispersed. The vehicle can be a solvent into which a suitable binder is dissolved. The binder is a resin and is the non-volatile part of the vehicle that solidifies and holds the pigment particles in a dried film. An ink can also contain other ingredients, depending upon the drying mechanism of the vehicle: driers to catalyse the oxidation drying of vegetable oils, photoinitaiator (UV-drying) monomers, polymers, and oligmers. Other possible components are: oil modified alkyd resins to form flexible films with high gloss, plasticizers and other additives as waxes to improve rub resistance or rub reducers to reduce the tack.

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Heat-set web offset

Chemical/ Chemical compound

Ink

Comments

Mineral oil based 95% Vegetable oil based 5%

Process

Printing

Examples of chemicals used

Pigment such as calcium carbonate, carbon black, aluminium hydroxide, phtalocyanine, rhodamin etc. Bindings: Binding components: Resins, alkyds. Solvent components: Mineral oils distillate with different boiling range often between 240°C to 300°C. Additives such as catalytic driers, antioxidants (butylhydroxytoluen or hydroquinon), waxes, plasticizers complexbinders.

Cleaning solvents

Aliphatic products 25% Alicyclic products 15% Aromatic products 5% Vegetable oil esters products 10% Hybride products 40% Other solvent products 5%

Aliphatic, alicyclic and aromatic hydrocarbons, Cleaning the blankets, ink rollers, ink ducts, impression vegetable oil esters, fatty acids, glycol ethers cylinder etc.

Fountain solution

Wet the surface of the printing plate.

Glycol ethers, 2-butoxy ethanol, phosphoric acid, citric acid, , wetting agents, surfactants, corrosion inhibitors, gum arabic, biocide as isothiazoline. Isopropyl alcohol. Petroleum distillates, phosphoric acid, acetic acid, propylenglycol ethers, surfactants

Isopropyl alcohol Plate cleaner/Image preserver Different process chemicals as ink preserver, tack reducer, dryers

Additive to fountain solution. Cleaning the plate from dried ink, dirt etc. To prevent the ink from drying, change the viscosity of the ink, to make the ink dry faster etc.

Cold-set web offset

Inks: Inks generally consist of two main components, pigment and vehicle. Pigments can be grouped into three categories: carbon blacks, inorganic pigments, and organic pigments. The vehicle is a liquid in which the pigment is dispersed. The vehicle can be a solvent into which a suitable binder is dissolved. The binder is a resin and is the non-volatile part of the vehicle that solidifies and holds the pigment particles in a dried film. An ink can also contain other ingredients, depending upon the drying mechanism of the vehicle: driers to catalyse the oxidation drying of vegetable oils, photoinitaiator (UV-drying) monomers, polymers, and oligmers. Other possible components are: oil modified alkyd resins to form flexible films with high gloss, plasticizers and other additives as waxes to improve rub resistance or rub reducers to reduce the tack.

Cold-set web offset

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Chemical/ Chemical compound

Ink

Comments

Mineral oil based 40% Vegetable oil based 50% UV-curable 10%

Process

Printing

Examples of chemicals used

Pigment such as calcium carbonate, carbon black, aluminium hydroxide, phtalocyanine, rhodamin etc. Bindings: Mixture of oils, resins, alkyds. Solvents: Mineral oils distillate with different boiling range. Vegetable oils, such as drying oils, semidrying oils and drying oils. Additives such as catalytic driers, antioxidants, waxes, plasticizers and fungicides (vegetable inks). UV-inks (formprinting): pigment, prepolymers, monomers + oligomers (acrylates), photoinitiator and additives.

Cleaning solvents

Aliphatic products 30% Alicyclic products 15% Aromatic products 10% Vegetable oil esters products 10% Hybride products 30% Other solvent products 5%

Aliphatic, alicyclic and aromatic hydrocarbons, Cleaning the blankets, ink rollers, ink ducts, impression vegetable oil esters, fatty acids, glycol ethers cylinder etc.

Fountain solution

Wet the surface of the printing plate. Additive to fountain solution. Cleaning the plate from dried ink, dirt etc. To prevent the ink from drying, change the viscosity of the ink, to make the ink dry faster etc.

Phosphate salts, silicates, wetting agents, dextrin, surfactants, corrosion inhibitors, gum arabic, biocide as isothiazoline. Isopropyl alcohol. Petroleum distillates, phosphoric acid, acetic acid, propylenglycol ethers, surfactants

Isopropyl alcohol (formprinting) Plate cleaner/Image preserver Different process chemicals as ink preserver, tack reducer, dryers

2.4 Waste

2.4.1 Pre-press, image preparation

Film or paper containing silver EWC-code 09 01 07: normal waste Film developer: hazardous waste EWC-code 09 01 01 Fixer: hazardous waste EWC-code 09 01 04 Rinsing water from film development, depending on the silver concentration: hazardous waste EWCcode 09 01 06 Proof print developer: hazardous waste EWC-code 09 01 01 Colour foils can be sent for incineration Cleaning agents for the film developing machines containing chromium salts: hazardous waste

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Correcting fluids, depending on contain of chemicals: hazardous waste Ion exchange resin, in the case the rinsing water from film developing is treated in an ion exchanger, containing silver: hazardous waste Filter from film developing machine, containing residue of film developer. Rags or wipes containing cleaning agents with chromium salts: hazardous waste. UV lamps: hazardous waste EWC-code 20 01 21. Computers and other electronic equipment. Can be hazardous waste EWC-code 16 02 13. The management of hazardous waste is subject to strict regulatory requirements in EC legislation. Packages such as boxes, cans, plastic film, metal or plastic bands. Sorted and recycled or incinerated, depending on the legislation of the country. 2.4.2 Platemaking

What is mentioned as waste are examples of kinds of waste that can be produced, but there is variation between different printing plants and different countries. Some of the waste that is mentioned in this section does not appear as waste in many places, as it is discharged as sewage instead. What is mentioned as waste in this section can also appear in the section environmental burden, discharges to water. All waste must be taken care of according to EC laws or individual country laws and rules. Aluminium plates should be sent to recycling. Plates for waterless offset should be sent to recycling. Other plates, paper, or plastic can be sent to incineration. Plate developer, positive or negative: hazardous waste EWC-code 09 01 01 and 09 01 02. Plate developer, solvent-based: hazardous waste EWC-code 09 01 03. Plate developer containing silver: hazardous waste EWC-code 09 01 02. Cleaning agents for the plate developing machines containing chromium salts: hazardous waste. Rags or wipes containing cleaning agents with chromium salts: hazardous waste. UV lamps: hazardous waste EWC-code 20 01 21. Computers and other electronic equipment. Can be hazardous waste EWC-code 16 02 13. The management of hazardous waste is subject to strict regulatory requirements in EC legislation. Packages such as boxes, cans, plastic film, metal or plastic bands. Sorted and recycled or incinerated, depending on the legislation of the country. Protective foil from offset plate. Can be sent to incineration. Filter from plate developing machine, which contains residue of plate developer. Plate coating, residue of plate coating can occur at the bottom of the plate developing machine. Ion exchanger resin, in the case the rinsing water from CTP plates with silver, is treated in an ion exchanger. 2.4.3 Printing

Sheet-fed offset

What is mentioned as waste are examples of kinds of waste that can be produced, but there is variation between different printing plants and different countries. Some of the waste that is mentioned in this section does not appear as waste in many places, as it is discharged as sewage instead. What is mentioned as waste in this section can also appear in the section environmental burden, discharges to water. All waste must be taken care of according to EC laws or individual country laws and rules. Paper waste should be sent to recycling. Sheet-fed offset ink, depending on the contain, can be hazardous waste or normal waste.

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Sheet-fed offset ink, UV-ink, not cured: hazardous waste EWC-code 08 03 12. Offset varnishes, depending on the contain, can be hazardous waste or normal waste. Offset varnishes, UV-curing, not cured: hazardous waste EWC-code 08 03 12. Cleaning agents containing solvents: hazardous waste. Shop towels/cleaning rags, containing organic solvents, ink, or varnish: hazardous waste EWC-code 15 02 02. Paper rolls from automatic washing, containing organic solvents, ink, or varnish: hazardous waste EWC-code 15 02 02. Spray cans, not empty: hazardous waste. UV-lamps from curing UV-inks and varnishes: hazardous waste EWC-code 20 01 21. Computers and other electronic equipment. Can be hazardous waste EWC-code 16 02 13. The management of hazardous waste is subject to strict regulatory requirements in EC legislation. Fountain solution when cleaning the system. Filters from filtration of the fountain solution. Water for removal of paper dust or to prewet the plate before restarting. The water is held in a bucket and contains residues of ink, plate cleaner, and solvents. Blankets. Packages such as boxes, corrugated cardboard, cans, drums, plastic film, metal or plastic bands. Sorted and recycled or incinerated, depending on the legislation of the country.

Heat-set web offset

What is mentioned as waste are examples of kinds of waste that can be produced, but there is variation between different printing plants and different countries. Some of the waste that is mentioned in this section does not appear as waste in many places, as it is discharged as sewage instead. What is mentioned as waste in this section can also appear in the section environmental burden, discharges to water. All waste must be taken care of according to EC laws or individual country laws and rules. Paper waste should be sent to recycling. Heat-set offset ink, depending on the contain, can be hazardous waste or normal waste. Cleaning agents containing solvents: hazardous waste. Shop towels/cleaning rags, containing organic solvents, ink, or varnish: hazardous waste EWC-code 15 02 02. Paper rolls from automatic washing, containing organic solvents, ink, or varnish: hazardous waste EWC-code 15 02 02. Spray cans, not empty: hazardous waste. Computers and other electronic equipment. Can be hazardous waste EWC-code 16 02 13. The management of hazardous waste is subject to strict regulatory requirements in EC legislation. Fountain solution when cleaning the system. Filters from filtration of the fountain solution. Water for removal of paper dust or to prewet the plate before restarting. The water is held in a bucket and contains residues of ink, plate cleaner, and solvents. Silicone when cleaning the system. Catalyst. Blankets. Packages such as boxes, corrugated cardboard, cans, drums, plastic film, metal or plastic bands. Sorted and recycled or incinerated, depending on the legislation of the country.

Cold-set web offset

What is mentioned as waste are examples of kinds of waste that can be produced, but there is variation between different printing plants and different countries. Some of the waste that is mentioned in this

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section does not appear as waste in many places, as it is discharged as sewage instead. What is mentioned as waste in this section can also appear in the section environmental burden, discharges to water. All waste must be taken care of according to EC laws or individual country laws and rules. Paper waste should be sent for recycling. Cold-set offset ink, depending on the contain, can be hazardous waste or normal waste. Offset ink formprinting, UV-ink, not cured: hazardous waste EWC-code 08 03 12. Cleaning agents containing solvents: hazardous waste. Shop towels/cleaning rags, containing organic solvents, ink or varnish: hazardous waste EWC-code 15 02 02. Paper rolls from automatic washing, containing organic solvents, ink or varnish: hazardous waste EWC-code 15 02 02. Spray cans, not empty: hazardous waste. UV-lamps from curing UV-inks: hazardous waste EWC-code 20 01 21. Computers and other electronic equipment. Can be hazardous waste EWC-code 16 02 13. The management of hazardous waste is subject to strict regulatory requirements in EC legislation. Fountain solution when cleaning the system. Filters from filtration of the fountain solution. Water for removal of paper dust or to prewet the plate before restarting. The water is held in a bucket and contains residues of ink, plate cleaner, and solvents. Blankets. Packages such as boxes, corrugated cardboard, cans, drums, plastic film, metal or plastic bands. Sorted and recycled or incinerated, depending on the legislation of the country.

2.5 Environmental burden

2.5.1 Pre-press, image preparation

Emissions to air There are normally no emissions from film developing, but small amounts of emissions can occur from developers and fixers such as sulphur compounds and acetic acid. Discharges to water A certain amount of fix accompanies the film or paper when it is transferred to the rinsing bath. Depending on the design of the equipment and the flow of the rinsing water, variation occurs in the quantity of silver and chemicals in the rinsing water. Emissions to water from the pre-press process can be silver compounds in the rinsing water and chemical compounds from proof print developing.

When cleaning film developing machines, a cleaning agent containing chromium might be used. During rinsing, small amount of the cleaning agent containing chromium might be discharged as sewage. Film developing machines can in most cases be cleaned with detergent and a sponge or brush, and the rinsing water discharged as sewage.

Example of chemical/chemical products and raw materials

Emissions to air:

Ammonia Sulphur componds Acetic acid

Photographic paper, film Volatile compounds Foils (masking-, blanking-, colour-) Film developer Fixer solution Correcting fluids Proofs developer

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Figure 9

2.5.2 Platemaking

Emissions to air There are normally no emissions from platemaking. Some small amounts of VOC emissions, such as alcohols from developers, and ozone from exposing, can occur. Discharges to water Part of the photosensitive coating is dissolved in the developer during the developing process. A certain amount of developer accompanies the plate when it is transferred to the rinsing bath. Depending on the design of the equipment and the flow of the rinsing water, variation occurs in the quantity of chemicals in the rinsing water. The rinsing water is causing a COD load of approximately 0.3 g O2/l. In many developing machines for CTP plates there is the option of recirculating the water for a certain amount of time. As a result, the rinsing water becomes more contaminated. Samples of the rinsing water taken from different plate types show in most cases that the water can be discharged as sewage. In some cases slightly higher levels of, e.g., copper occur, or the rinsing water can be nitrification inhibiting. The nitrification inhibiting causes problems for water treatment plants that have this type of cleaning step for reducing the nitrification.

For offset plates containing silver, the rinsing water, if it exists, should be treated in the same way as rinsing water for film developing. When cleaning the plate developing machines, a cleaning agent containing chromium might be used when plates containing silver have been developed. When these plates are rinsed, small amounts of cleaning agent containing chromium might be discharged as sewage.

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Other plate developing machines can in most cases be cleaned with detergent and a sponge or brush, and the rinsing water can then be discharged as sewage. 2.5.3 Printing

Sheet-fed offset

Emissions to air VOC: IPA or ethanol has been the most common additive used in fountain solutions and one of the main contributors to VOC emissions from sheet-fed offset printing. Between 90 and 100% of used IPA is emitted to the air as fugitive emissions.

VOC is also emitted from solvents used when cleaning different parts of the offset press. By using solvents with lower vapour pressure, such as vegetable based cleaning agents or high boiling aliphatic solvents, emissions can be reduced. Ozone: Emission of ozone is produced by the UV-lamps for UV-inks. The emitted amount is low compared to other sources. The environmental impact is negligible when the ozone is exhausted to the atmosphere as it quickly degrades into oxygen.

Discharges to water Used fountain solution and waste water are often discharged to the sewage system when cleaning the dampening system. The waste water from cleaning can contain alkali, fungicides, and solvents.

Samples taken on a number of different damping solutions show that they are nitrification inhibiting. The nitrification inhibiting causes problems for water treatment plants that have this type of cleaning step for reducing the nitrification. Some of the tensides in the fountain solution that substitutes IPA have a low biodegrability. These types of tensides should not be discharged to sewage systems. Damping systems with covered plate rollers can be washed with high pressure. Sometimes solvents will be used. The water contains amounts of ink, fountain solution, and maybe solvents. The quantity depends on how dirty the rollers are. When cleaning the press, in particular the blanket, water is used for removal of paper dust or to prewet the plate before restarting. The water is held in a bucket and contains residues of ink, plate cleaner, and solvents.

Heat-set web offset

VOC:

Emissions to air

In heat-set offset printing the main environmental problem is the emission of combustion gases from the drying of the ink in a hot air heated dryer. About 85 % of the mineral oil in the ink (containing 30-35% mineral oil) is evaporated in the dryer. In a heat-set afterburner, the VOC's mainly oxidise to CO2 and H2O. In the EC VOC-directive (1999/13/EC) the emission limits for treated gases are 20 mg C/Nm3 for

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a solvent consumption of >25 tons/year or 100 mg C/Nm3 for a solvent consumption of 15-25 tons/year. The main types of afterburners in heat-set are the catalytic, recuperative, or regenerative thermal oxidation. In a catalytic afterburner cleaning occurs between approximately 200°C and 350°C depending on the type of catalyst used. A heat exchanger is used between ingoing and outgoing air. Catalytic oxidisers are sensitive to overheating as well as contamination by, for example, silicone. The incineration temperature for thermal oxidation lies in the interval 750 ­ 1000°C. Conventional thermal incineration is done with an open flame, recuperative oxidation, and fuel in the form of gas must be added to maintain the temperature. A heat exchanger is used between ingoing and outgoing air. In a regenerative system two beds with heat-retaining materials are normally used. A heater is placed between the two beds. The air first passes one bed, where it is heated; it then enters the burn chamber, which is usually gas heated, and then passes the other bed, where heat is discharged. The direction of the flow is shifted after a time, and the functions of the respective beds are changed from air heating to air cooling, and vice versa. Cleaning with thermal oxidation has, as a rule, slightly higher cleaning efficiency than catalytic oxidation, but consumes more energy. IPA or ethanol has been the most common additive used in fountain solutions and one of the main contributors to VOC emissions from printing. About 90 % of used IPA is emitted to the air as fugitive emissions. VOC is also emitted from solvents used when cleaning different parts of the offset press. By using solvents with lower vapour pressure such as vegetable based cleaning agents or high boiling aliphatic solvents emissions can be reduced. The dryer extracts air from the press room containing IPA and solvents. It is estimated that about 10 % of the used IPA and solvents are burned in the dryer. In the EC VOC-directive (1999/13/EC) the emission limit for fugitive emissions is 30% of solvent input for a solvent consumption of >15 tons/year.

NOx: Emission of NOx is produced when gases are burned at high temperatures, >700°C, as thermal or regenerative systems. The NOx emissions from thermal or regenerative are <100 mg/Nm3. Higher temperature means higher emission of NOx but lower emission of VOC. Discharges to water: Used fountain solution and waste water are often discharged to the sewage system when cleaning the dampening system. The waste water from cleaning can contain alkali, fungicides and solvents. Samples taken on a number of different damping solutions show that they are nitrification inhibiting. The nitrification inhibiting causes problems for water treatment plants that have this type of cleaning step for reducing the nitrification. Some of the tensides in the fountain solution that substitutes IPA have a low biodegrability. These types of tensides should not be discharged to sewage systems. Damping systems with covered plate rollers can be washed with high pressure. Sometimes solvents will be used. The water contains amounts of ink, fountain solution, and maybe solvents. The quantity depends on how dirty the rollers are.

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When cleaning the press, in particular the blanket, water is used for removal of paper dust or to prewet the plate before restarting. The water is held in a bucket and contains residues of ink, plate cleaner, and solvents.

Cold-set web offset

Emissions to air: VOC: IPA or ethanol has been the most common additive used in fountain solutions and one of the main contributors to VOC emissions from form offset printing. Between 90 and 100% of used IPA is emitted to the air as fugitive emission.

VOC is emitted from solvents used when cleaning different parts of the offset press. By using solvents with lower vapour pressure such as vegetable based cleaning agents or high boiling aliphatic solvents emissions can be reduced. Ozone: Emission of ozone is produced by the UV-lamps for UV-inks in formprinting. The emitted amount is low compared to other sources. The environmental impact is negligible when the ozone is exhausted to the atmosphere as it quickly degrades into oxygen.

Discharges to water: Used fountain solution and waste water are often discharged to the sewage system when cleaning the dampening system. The waste water from cleaning can contain alkali, fungicides, and solvents.

Samples taken on a number of different damping solutions show that they are nitrification inhibiting. The nitrification inhibiting causes problems for water treatment plants that have this type of cleaning step for reducing the nitrification. Some of the tensides in the fountain solution that substitutes IPA have a low biodegrability. These types of tensides should not be discharged to sewage systems. Damping systems with covered plate rollers can be washed with high pressure. Sometimes solvents will be used. The water contains amounts of ink, fountain solution, and maybe solvents. The quantity depends on how dirty the rollers are. When cleaning the press, in particular the blanket, water is used for removal of paper dust or to prewet the plate before restarting. The water is held in a bucket and contains residues of ink, plate cleaner, and solvents.

2.6 Potential for improvements

2.6.1 Pre-press, image preparation

2.6.1.1 Re-using of developer

A regenerating system, including filtration and addition of worn-down components in the developer, can be connected to the developing machine to extend the life-time of the developer. This can reduce the amount of developer used by about 40%.

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2.6.1.2 Re-using of fixer

A recirculating electrolytic recovery system removes silver from the fixer solution and the fixer solution can then be reused in the process. By reusing the desilvered fix, less fresh fixer solution is needed to replenish the bath. Less silver is carried over to the rinsing water, as the solver concentration in the fix bath is lower with an electrolytic system. This can reduce the amount of fixer used by about 70%.

2.6.1.3 Recirculating of the rinsing water

There are different types of systems of recycling the rinsing water in the developing machine, but the principle is the same. The rinsing water passes through a filter and recirculates between the rinsing tank in the developing machine and a tank connected to the machine. To prevent growth of micro-organisms, the system can use UV-radiation, or biocides can be added. In some systems, the water is used for mixing new fixing solution from powders or concentrates. In these systems the water consumption is reduced and no silver will end up in the sewage system.

2.6.1.4 Treatment of the rinsing water

To reduce the silver content in the rinsing water, an ion exchanger can be used. This method can be used when a recirculating system is not an alternative. Many developing machines can be connected to a single ion exchanger. 2.6.2 Platemaking

Not using silver halide CTP plates. If silver halide CTP plates are used, the rinsing water should be treated in a similar manner as rinsing water from film processing. Reuse the rinsing water in the plate developing machine if it is possible. 2.6.3 Printing

Sheet-fed offset

Substitute high vapour pressure organic solvents/cleaning solvents. By using cleaning agents with low vapour pressure, such as vegetable oils esterfied with alcohol, one decreases the VOC emission. Cleaning agents with a vapour pressure below 0,01 kPa are defined as not being volatile organic solvents (VOC). These cleaning agents have a flash between 100-150°C. Using these types of cleaning agents will also lead to improvements in health and fire safety. As the vegetable cleaning agents are made from a renewable source, they will not increase the emission of greenhouse gases. High boiling solvents have the same advantages in emission, health, and fire safety as the vegetable ones but the are not renewable and more toxic. The European SUBSPRINT project (Substitution of Organic Solvents in the Printing Industry) has ranked the products on the market in the following order:

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1. 2. 3. 4. 5. 6. 7. Vegetable based cleaning agents Mixture of vegetable based cleaning agents and high boiling solvents. High boiling solvents with a flash point about 100°C Medium boiling solvents with a flash point between 55 and 100°C. Aromatic-free solvents Terpene-based solvents Traditional products based on petrochemical volatile mixtures, like white spirit.

It has been estimated that offset printing companies in the European Union (EU) use about 100 million litres of organic solvents per year.

Automatic cleaning Using automatic washing systems for blankets and the impression cylinder limits the amount of cleaning solvent needed and often even reduces the total amount. In modern systems vegetable based cleaning agents and high boiling solvents can be used without harm to the press. Cleaning dampening rollers Automatic high-pressure cleaners using water should be used for cleaning the dampening rollers from inks, rather than cleaning solvents. Distillation of solvents and reusing of cleaning agents Some cleaning solvents can be reused after distillation. This process will not reduce emissions but results in a reduction in the amount of solvents used. The amount of waste decreases and raw materials are saved. IPA reduction It is possible to reduce the percentage of IPA to 5% or even lower. This can be done if the water quality is good. A deionisation system for source water/raw water can be used to get a better quality of the water. Alternatives to IPA Alcohol substitutes, such as glycol ethers, can be used in some damping systems. These substitutes have a higher boiling point than the alcohol dampeners. Whether a substitute is applicable is a question of interactions between the ink, press type, paper, type of dampening system, and printing constraints. Some of the tensides in the fountain solution that substitutes IPA have a low biodegrability. Waterless offset Printing plants that use IPA as an additive to the fountain solution can reduce the VOC emissions by changing to waterless printing as no fountain solution is used.

Heat-set web offset

Substitute high vapour pressure organic solvents/cleaning solvents By using cleaning agents with low vapour pressure, such as vegetable oils esterfied with alcohol, one decreases the VOC emission. Cleaning agents with a vapour pressure below 0,01 kPa are defined as not being volatile organic solvents (VOC). These cleaning agents have a flash between 100-150°C. Using these types of cleaning agents will also lead to improvements in health and fire safety. As the vegetable cleaning agents are made from a renewable source, they will not increase the emission of greenhouse gases. High boiling solvents have the same advantages in emission, health, and fire safety as the vegetable ones but the are not renewable and more toxic. The European SUBSPRINT project (Substitution of Organic Solvents in the Printing Industry) has ranked the products on the market in the following order:

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1. Vegetable based cleaning agents 2. Mixture of vegetable based cleaning agents and high boiling solvents. 3. High boiling solvents with a flash point about 100°C 4. Medium boiling solvents with a flash point between 55 and 100°C. 5. Aromatic-free solvents 6. Terpene-based solvents 7. Traditional products based on petrochemical volatile mixtures, like white spirit. 8. It has been estimated that offset printing companies in the European Union (EU) use about 100 million litres of organic solvents per year.

Automatic cleaning Using automatic washing systems for blankets and the impression cylinder limits the amount of cleaning solvent needed and often even reduces the total amount. In modern systems vegetable based cleaning agents and high boiling solvents can be used without harm to the press. Cleaning dampening rollers Automatic high-pressure cleaners using water should be used for cleaning the dampening rollers from inks, rather than cleaning solvents. Distillation of solvents and reusing of cleaning agents Some cleaning solvents can be reused after distillation. This process will not reduce emissions but results in a reduction in the amount of solvents used. The amount of waste decreases and raw materials are saved. IPA reduction It is possible to reduce the percentage of IPA to 5% or even lower. This can be done if the water quality is good. A deionisation system for source water/raw water can be used to get a better quality of the water. Alternatives to IPA Alcohol substitutes, such as glycol ethers, can be used in some damping systems. These substitutes have a higher boiling point than the alcohol dampeners. Whether a substitute is applicable is a question of interactions between the ink, press type, paper, type of dampening system, and printing constraints. Some of the tensides in the fountain solution that substitutes IPA have a low biodegrability. Mist damping units Mist damping units are still not common in heat-set presses but are becoming increasingly so. When using mist damping units IPA does not need to be added. Heat-set afterburner Exhaust gases from heat-set presses contain volatile organic compounds from inks, IPA, and cleaning agents. The exhausted gases also smell badly. The concentrations of the emissions depends, for example, on the amount of ink on the printing product and if the waste gases are recirculated. The VOC concentration in the waste gases can vary from 1 up to 6 g/Nm3. The efficiency of afterburner systems is 95-99%.

Cold-set web offset

Substitute high vapour pressure organic solvents/cleaning solvents By using cleaning agents with low vapour pressure, such as vegetable oils esterfied with alcohol, one decreases the VOC emission. Cleaning agents with a vapour pressure below 0,01 kPa are defined as not

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being volatile organic solvents (VOC). These cleaning agents have a flash between 100-150°C. Using these types of cleaning agents will also lead to improvements in health and fire safety. As the vegetable cleaning agents are made from a renewable source, they will not increase the emission of greenhouse gases. High boiling solvents have the same advantages in emission, health, and fire safety as the vegetable ones but the are not renewable and more toxic. The European SUBSPRINT project (Substitution of Organic Solvents in the Printing Industry) has ranked the products on the market in the following order: 1. 2. 3. 4. 5. 6. 7. Vegetable based cleaning agents Mixture of vegetable based cleaning agents and high boiling solvents. High boiling solvents with a flash point about 100°C Medium boiling solvents with a flash point between 55 and 100°C. Aromatic-free solvents Terpene-based solvents Traditional products based on petrochemical volatile mixtures, like white spirit.

It has been estimated that offset printing companies in the European Union (EU) use about 100 million litres of organic solvents per year.

Automatic cleaning Using automatic washing systems for blankets and the impression cylinder limits the amount of cleaning solvent needed and often even reduces the total amount. In modern systems vegetable based cleaning agents and high boiling solvents can be used without harm to the press. Cleaning dampening rollers Automatic high-pressure cleaners using water should be used for cleaning the dampening rollers from inks, rather than cleaning solvents. Distillation of solvents and reusing of cleaning agents Some cleaning solvents can be reused after distillation. This process will not reduce emissions but results in a reduction in the amount of solvents used. The amount of waste decreases and raw materials are saved. IPA reduction(formprinting) It is possible to reduce the percentage of IPA to 5% or even lower. This can be done if the water quality is good. A deionisation system for source water/raw water can be used to get a better quality of the water. Alternatives to IPA (formprinting) Alcohol substitutes, such as glycol ethers, can be used in some damping systems. These substitutes have a higher boiling point than the alcohol dampeners. Whether a substitute is applicable is a question of interactions between the ink, press type, paper, type of dampening system, and printing constraints. Some of the tensides in the fountain solution that substitutes IPA have a low biodegrability.

2.7 Expectations for the future

2.7.1 Pre-press, image preparation

The photographic process is becoming less common and will almost disappear as the process will be digitalized and the image will be transferred to the printing plate or directly to the printing press.

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2.7.2 Platemaking

The process is more digitalized. Today the CTP-process is installed in more and more plants. In the CTPprocess the digital image is transferred from the computer directly to the printing plate. The exposing can be done by an IR or visible laser or by UV-light. The exposed plate has to be developed by chemicals but thermo printing plates are coming which do not use chemicals. The thermo plates today is exposed by laser and have to be developed. For the new thermo plates, the laser burns and transforms the exposed area of the coating to dust particles and mist. Chemicals for the film-process, such as film, developer, and fixer, disappear when the CTP technique is used. Some of the CTP plates contain a coating of silver halide. The silver halide plates have to be developed by traditional photographic chemicals. 2.7.3 Printing

Sheet-fed offset

Development of direct-to press systems. In these systems, computer controlled equipment allows the application of the image directly to the printing cylinder while the cylinder is mounted on the press. Increasing automation of press operations, such as inking control, temperature control of inks, and press cleaning.

Heat-set web offset

Development of direct-to press systems even if it will take longer time than for sheet-fed offset. In these systems, computer controlled equipment allows the application of the image directly to the printing cylinder while the cylinder is mounted on the press. Increasing automation of press operations, such as inking control, press cleaning, temperature control of inks, water, and chill rollers. Waterless plates will be more common in heat-set printing.

Cold-set web offset

Development of direct-to press systems specially for form printing presses. In these systems, computer controlled equipment allows the application of the image directly to the printing cylinder while the cylinder is mounted on the press. Increasing automation of press operations, such as inking control, temperature control of inks, and press cleaning. In newspaper printing presses a new technology to reduce the use of solvents for cleaning blankets is now tested in Sweden. By not using the inefficient and time consuming washing method, the newspaper printing company plans to save 400 machine hours and 1300 man hours per year. The technology is simple, releasing paper fibres in two steps and thereafter removing them with the vacuum cleaner. The paper web is vacuum cleaned from loose paper fibres and the blankets do not have to be

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cleaned every day, week, or even month. The basic theory behind the technology is that the build-up on blankets consists of paper fibres and ink, and that there will be no build-up without paper fibres.

Figure 10

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3 Flexography

Flexography is a method of direct rotary printing that uses resilient relief image plates of rubber or photopolymer material. The print image consists of a raised surface, known as relief printing, that can be inked and pressed onto the substrate. Non-image areas are below the printing surface and are not reproduced. The resilient rubber or photopolymer image carriers are suited for printing millions of impressions. Ink is applied to the raised image on the plate, which transfers the image to the printing substrate. Fastdrying inks, either solvent, water-based or UV-curable, are used. As the inks dry very quickly, the printed matter can, directly after leaving the press, be cut, folded, stacked etc. It can print on a wide variety of absorbent and non-absorbent substrates. This makes flexography the predominant method used for printing flexible bags, wrappers, and other packaging. There have been a series of technical advances in flexography starting in the late 1980s, resulting in quality improvements and machine printing speeds. The market for flexography has been increasing with an annual growth rate of about 6% during the 1990s. Flexographic printing accounts for 15-20 percent of all conventionally printed materials. Within the packaging industry, flexographic print represents more than 50% in North America and 35% in Europe. For the principle see the figure 10.

Figure 10

Both sheet-fed presses and web presses are used in flexographic printing. Sheet-fed printing presses are used for printing corrugated board. Web presses are used for other packaging materials and for newspaper printing.

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DRAFT 3.1 Printing materials and products

Flexography is mainly used for packaging printing and the substrate can be different types of flexible plastic films, laminates, metal foils, corrugated board, almost all sorts of papers, such as tissue paper, packaging paper, newsprint paper, wallpaper etc. The most common products are plastic carrier bags, paper bags, paper sacks, beverage cartons, gift-wrap paper, envelopes, labels, forms, wallpapers, newspapers, sanitary products, napkins, corrugated containers, and folding cartons.

3.2 Process description

3.2.1 Pre-press, image preparation

The first step in the printing process, imaging, produces an image of the material (text, diagrams, and pictures) to be printed. This process is fairly similar for all printing except for digital printing, where this step does not exist. The pre-press stages of image preparation have changed from a lot of manual steps where text and pictures were handled separately to where it is done electronically. Electronic imaging processing systems can produce text and pictures and then arrange them in the correct position on the page. The imaging process begins with composition and typesetting. Composition involves the arrangement of text, pictures, and diagrams into the desired format. Earlier, this used to be performed manually and included a lot of different steps, but today high-performing computers and graphic-oriented programs are used. If pictures are to be printed in several colours, these must be separated into four colours and exposed on film, but today this can be stored in the computers. The pictures are also often screened, i.e., the pictures consist of a large number of very small dots instead of a whole field. Once the desired format and images are assembled, the data are exposed onto photographic material in an image-setter. The photographic emulsion on the film or paper is composed of silver halide and gelatine. Developing and fixing of the photographic film or paper is often done by machine, with subsequent rinsing stages and then drying. The film and paper are accompanied by a certain amount of liquid when they are transferred to the next bath. Depending on the fixing bath's silver concentration, the design of the equipment, and the flow of rinsing water, the quantity of photographic chemicals and silver vary in the rinsing water. The rollers in the developing machine need regular cleaning because of silver deposits. Cleaning of the rollers can be done with a brush and a household detergent. Earlier it was common to use cleaning agents containing chromium, and this may still be used in a few places. A proof print is often made for checking the reproduction process, or for submitting to the customer for checking and approval, or used internally by the printer as a working guide. Many different methods exist; wet proofing is the traditional method of producing colour proofs. Today, proofs can be made directly from the data in the computer, being shown on the screen or printed out with an inkjet or laser printer. It is the same technology as printers/presses that are used for digital printing. Small quantities of toners or inkjet ink are used for proof printing. 3.2.2 Platemaking

Flexographic plates are relief plates made of either rubber or UV light sensitive photopolymers attached to a steel cylinder, a metal plate, or a polyester ribbon, depending on printing method. Formerly, rubber plates were used as printing forms but today the photopolymer plates are the most common, as they offer superior quality and performance at a lower cost.

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Depending on the field of application and presses, the flexographic plates are made of different materials which differ in thickness, hardness, light-sensitivity, elasticity, structure, and resistance against chemicals. Rubber plates are produced in three basic steps. The first step is the production of a master pattern plate (metal or hard photopolymer material) using a photomechanical process, in which the non-illuminated surfaces are washed away with an acid solution. Once finished, the master pattern plate is placed in a mould press to produce a matrix mould by pressing the mould material, often plastic, against the master pattern plate under controlled temperature and pressure. In the last step the matrix mould is then used to make a rubber flexographic plate, where a rubber sheet is pressed into the mould under pressure and elevated temperature. The production of photopolymer flexographic plates is a direct-to-plate process that does not need an original plate or mould. There are two types of process, depending on whether solid sheets of photopolymer or liquid photopolymer are used. The two processes are similar in general outline and in both processes, exposing the plates with UV-light, including both the backside and the front of the plate. First, the backside of the plate is exposed to determine the relief depth. The photographic negative is then placed between the photopolymer and the UV light source, hardening the image area. Lastly, the unexposed polymers are washed out in a solution of a mixture of hydrocarbons, and the plates are then dried with IR- and hot air blowers. Lately, water-washable systems are becoming more and more common. Post-exposure ensures complete polymerisation of the printing plate. Finally residual tackiness is removed with oxidising chemicals or UV-light. Today there are digital flexographic plates, where the printing image is exposed directly onto the plate without using film. The plate consists of a carrier, photopolymer, and a thin upper layer of a black plastic material. A highly effective laser burns away the non-printing areas in the black layer. Then as the plates are dried, washed out, and postexposed, the printing areas are completely cross-linked and hardened. Laser gravure of flexographic plates or rollers can be done either in a system which reads from film and from there transfers data and engraves the rollers and sleeves, but the engraving can also be done directly from the computer. Often rubber is used for laser engraving but even plastic materials can be used. After engraving no further processing is needed. 3.2.3 Printing

There are three main types of printing presses used for flexographic printing: stackpress or multi-cylinder press, central impression cylinder press (CIC), and in-line press. Only one side of the substrate can be printed at a time. All types of presses employ a plate cylinder, a metering cylinder known as the anilox roll, an impression cylinder, and an ink tray. Some presses use a third roller as a fountain roller. The printing plates are mounted onto the printing cylinder with a double-sided adhesive. There are two traditional types of ink feed systems, the two-roll system and the enclosed doctor blade (chambered doctor blade system) system that improves the ink distribution and the print quality. The multi-cylinder press is characterized by one or more printing units arranged vertically on either side of the press frame. Each unit has its own plate cylinder which prints one colour of a multicolour impression. The in-line press is similar to the multi-cylinder press except the printing units are arranged one behind the other in a horizontal line. The most modern and common press is the central impression cylinder press (CIC). The printing units are arranged around a single impression cylinder. The press consists of two to eight colour printing units. Each station consists of an ink tray, fountain roller, anilox roller, doctor blade, and a plate cylinder.

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The two-roll flexographic printing system consists of a smooth rubber fountain roll rotating in an open ink tray. The fountain roll is partially submerged in the ink tray. Ink is transferred from the fountain roll to an engraved, chrome-plated anilox roll. The anilox roll transfers the ink to the plate cylinder which then deposits the ink onto the substrate. The anilox roll is covered with cells and how much ink is transferred to the printing plate depends on the depth and structure of the cells. The amount of ink that is printed on the substrate is dependent on the anilox cell volume. It is possible to add a reverse-angle doctor blade to shear the ink from the surface of the anilox roll. The purpose of the blade is to increase the removal of surface ink and a more controlled inking of the plates. In an enclosed doctor blade system two doctor blades are used. The reverse angle blade acts as the true doctor blade and wipes excess ink from the anilox roller and the other blade is used for sealing the contained inking unit or chamber. The ink is delivered from the ink pump to the inking unit and then back to the pump ­ a closed loop. The inks used for flexography are liquid and contain solvent or water. There are also UV-curable inks. Solvent-based and water-based inks are dried using evaporation, whereas UV-cured inks are cured by chemical reactions. To adjust the viscosity of the ink during the printing, the ink is diluted with solvents or water depending on the type of ink. Solvent-based inks are widely used in flexographic printing processes, and the solvents are primarily volatile organic compounds. Water-based inks can be used when printing on paper or corrugated cartons. The primary solvent in water-based inks is water, but they can also contain varying percentages of organic solvents. Water-based inks are less flammable than solvent-based inks and are easier to store and use. UV-cured inks are a comparatively new ink technology in flexographic printing industry, and are used when printing labels and small carton boxes on special machinery. After each printing unit, the substrate is fed into a overhead dryer and heated air is blown over the substrate so the ink is dry before it goes to the next printing unit. After the substrate has been printed with all colours, it can be fed through an additional overhead tunnel to remove most of the residual solvents or water. The finished product is then rewound in a roll or is fed through a cutter. The methods of drying are heated air, IR, or micro-wave. The entire ink tray must be cleaned by hand wiping with solvent/water when two-roll or single doctor blade systems are used. Only the chamber has to be cleaned manually when enclosed doctor blades chambers are used. The chamber system can be cleaned in a wash tub. There are some automated washup systems where the doctor blades can be cleaned in the printing position. In most systems, the first stage is a recirculation mode where used dirty water/solvent is used for the initial cleaning. The dirty water/solvent is returned to a common tank after each wash and can be reused many times. Ink left over after the first stage is removed using partially dirty water/solvent. Clean water/solvent is used for a final rinse only. When the water/solvent in stage 1 becomes too dirty to be effective, it is processed or disposed as hazardous waste. Stage 2 becomes stage 1, and so on. Alternative methods for cleaning the anilox rolls to reduce or eliminate the need for solvents are becoming more and more common today. These alternatives are ultra-sonic cleaning, dry ice, lasers, polyethylene beads, and sodium bicarbonate. The solvents used are similar to the solvents in the solvent-based ink or water for water-based ink. When using water-based inks it is important that the cleaning is done when the ink is not yet dry. Dried waterbased ink does not dissolve again in water and has to be resolved in aggressive organic solvents. Dried solvent-based ink can be resolved in a solvent, depending on type of solvent used in the ink.

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DRAFT 3.3 Chemicals

3.3.1 Pre-press, image preparation

Process

Chemical/ Chemical compound

Examples of chemicals used

Photographic film and paper Developer Developing of film and paper

Fixer Cleaning solutions

Correcting fluid Proof print developer Colour foils

Emulsion of silver halide and gelatine Hydroquinone, phenidone, metol, potassium or sodium sulphite, potassium carbonate, potassium or sodium hydroxide, potassium bromide, sodium silicate Fixing of film or paper Ammonium thiosulphate, sodium acetate, sodium sulphite, glacial acetic acid Sulpamic acid, thiocarbamide, , Cleaning the rollers in the sodiumhydrogen sulphate, chromium salts, developing machine surfactants Correcting exposed film Potassium ferricyanide, potassiumpermanganate Developing of proof print in the Sodium carbonate, sodium hydroxide, wet process surfactants Proof print process

3.3.2

Platemaking

Process

Plates of rubber or photopolymer can be used. Washing out unexposed, nonpolymerised, areas of the plates.

Chemical/ Chemical compound

Flexographic printing plates

Examples of chemicals used

Base of steel, aluminium or polyester. Rubber Photopolymer coating containing acrylates. Perchloro ethylene (not common today) Aliphatic hydrocarbons Cycloaliphatic hydrocarbons Alcohols Sulphuric acid Silicones Magnesium plate Nitric acid

Plate washing

After treatment agents Defoamer Plate etching compound

Reduce surface stickiness Eliminate foaming during the etching process. Etching the metal plate in the process of a rubber plate.

3.3.3

Printing

Inks: Inks generally consist of two main component, pigment and vehicle. Pigment can be grouped into three categories: carbon blacks, inorganic pigments, and organic pigments. The vehicle is a liquid in which the pigment is dispersed. The vehicle can be a solvent into which a suitable binder is dissolved. The binder is a resin and it is the non-volatile part of the vehicle that solidifies and holds the pigment particles in a dried film. A water-based ink must contain at least 85% water in its volatile components in order to qualify as a non solvent-based ink. An ink can contain of other ingredients as well, depending upon the drying mechanism of the vehicle: driers, photoinitaiator (UV-drying) monomers, polymers, and oligmers. Other possible components are: oil modified alkyd resins to form flexible films with high gloss, plasticizers, and other additives as waxes to improve rub resistance or slip and water repellence. Flexoprinting Chemical/ Chemical compound

Comments

Process

Examples of chemicals used

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Solvent-based ink 50% Printing on paper or plastic Pigment inorganic (white pigments) organic (most common). Bindings: cellulose nitrate, polyamide resin, maleinresin. Solvents: Alcohols such as ethanol, propanol, isopropanol or isobutanol. Alkyl acetates such as ethyl acetate, propyl acetate or butylacetate. Glycolethers. Additives such as polyethylene waxes, chelates, or plasticizers. Water-based inks 35% Printing on paper or plastic Pigment inorganic (white pigments) organic (most common). Bindings: copolymers of 2-3 acrylates. Solvents: Alcohols such as ethanol, propanol, isopropanol or isobutanol. Glycol ethers. Water. Defoaming agents: silicone Additives such as fungicides, surfactants, plasticisers and waxes. Amides or nitrogenous compounds: monoethyl amine, amides tallow hydrogenated, ammonium hydroxide or ammonia. UV-inks 15% Printing on paper or plastic Pigment: inorganic (white pigments) organic (most common). Bindings: polyester or polyurethane acrylate prepolymer. Monomers such as dipropylene glycol diacrylate, 1,6 Hexanediol diacrylate or hydroxypropylacrylate. Photoinitiators as aromatic ketones. Additives as plasticisers and waxes. Solvents

Alcohols 35% Alkyl acetates 15% Glycolethers 15% Aromatic hydrocarbons 15% Aliphatic carbons 15 % Others 5%

Cleaning, adjusting the viscosity of the ink.

Alcohols as ethanol, propanol, isopropanol or isobutanol. Alkyl acetates such as ethyl acetate, propyl acetate or butylacetate. Glycolethers Aromatic hydrocarbons Aliphatic hydrocarbons.

Cleaning solutions

Cleaning equipment uses waterbased ink

Alkalis, detergents, solvents, or sodium bicarbonate.

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DRAFT 3.4 Waste

3.4.1 Pre-press, image preparation

Film or paper containing silver EWC-code 09 01 07: normal waste Film developer: hazardous waste EWC-code 09 01 01 Fixer: hazardous waste EWC-code 09 01 04 Rinsing water from film development, depending on the silver concentration: hazardous waste EWCcode 09 01 06 Proof print developer: hazardous waste EWC-code 09 01 01 Colour foils can be sent for incineration Cleaning agents for the film developing machines containing chromium salts: hazardous waste Correcting fluids, depending on contain of chemicals: hazardous waste Ion exchange resin, in the case the rinsing water from film developing is treated in an ion exchanger, containing silver: hazardous waste Filter from film developing machine, containing residue of film developer. Rags or wipes containing cleaning agents with chromium salts: hazardous waste. UV lamps: hazardous waste EWC-code 20 01 21. Computers and other electronic equipment. Can be hazardous waste EWC-code 16 02 13. The management of hazardous waste is subject to strict regulatory requirements in EC legislation. Packages such as boxes, cans, plastic film, metal or plastic bands. Sorted and recycled or incinerated, depending on the legislation of the country. 3.4.2 Platemaking

What is mentioned as waste are examples of kinds of waste that can be produced, but there is variation between different printing plants and different countries. Some of the waste that is mentioned in this section does not appear as waste in many places, as it is discharged as sewage instead. What is mentioned as waste in this section can also appear in the section environmental burden, discharges to water. Photopolymer plates aluminium base should be sent for recycling of the metal. Photopolymer, hardened. Photopolymer, not hardened: hazardous waste. Rubber plates. Wash-out solution, organic solvents: hazardous waste. Wash-out solution, perchloroethylene: hazardous waste. Acids such as etching solutions, after treatment agents: hazardous waste. Metal hydroxide sludge: hazardous waste. Distillation sludge: hazardous waste. Rags or wipes containing solvents: hazardous waste. UV-lamps from curing UV-inks: hazardous waste EWC-code 20 01 21. Computers and other electronic equipment. Can be hazardous waste EWC-code 16 02 13. Protective foil from flexographic plates. Can be sent for incineration. Filter from plate developing machines, which contains residues of photopolymers. The management of hazardous waste is subject to strict regulatory requirements in EC legislation. Packages such as boxes, drums, plastic film, metal or plastic bands. Sorted and recycled or incinerated, depending on the legislation of the country.

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3.4.3

Printing

What is mentioned as waste are examples of kinds of waste that can be produced, but there is variation between different printing plants and different countries. Some of the waste that is mentioned in this section does not appear as waste in many places, as it is discharged as sewage instead. What is mentioned as waste in this section can also appear in the section environmental burden, discharges to water. All waste must be taken care of according to EC laws or individual country laws and rules. Paper waste should be sent for recycling. Plastic waste should be sent for recycling or for incineration. Water-based ink: hazardous waste EWC-code 08 03 12 . Solvent-based ink: hazardous waste EWC-code EWC-code 08 03 12. UV-ink, not cured: hazardous waste EWC-code 08 03 12. UV ink, completely cured. Distillation sludge: hazardous waste. Solvents: hazardous waste. Cleaning agents containing alkalis. Water from cleaning the press and equipment used water-based ink. Shop towels/cleaning rags, containing organic solvents or inks: hazardous waste EWC-code 15 02 02. UV-lamps from curing UV-inks: hazardous waste. Computers and other electronic equipment. Can be hazardous waste EWC-code 16 02 13. The management of hazardous waste is subject to strict regulatory requirements in EC legislation. Packages such as boxes, corrugated cardboard, cans, drums, plastic film, metal or plastic bands. Sorted and recycled or incinerated, depending on the legislation of the country.

3.5 Environmental burden

3.5.1 Pre-press, image preparation

Emissions to air There are normally no emissions from film developing, but small amounts of emissions can occur from developers and fixers such as sulphur compounds and acetic acid. Discharges to water A certain amount of fix accompanies the film or paper when it is transferred to the rinsing bath. Depending on the design of the equipment and the flow of the rinsing water, variation occurs in the quantity of silver and chemicals in the rinsing water. Emissions to water from the pre-press process can be silver compounds in the rinsing water and chemical compounds from proof print developing.

When cleaning film developing machines, a cleaning agent containing chromium might be used. During rinsing, small amount of the cleaning agent containing chromium might be discharged as sewage. Film developing machines can in most cases be cleaned with detergent and a sponge or brush, and the rinsing water discharged as sewage. 3.5.2 Platemaking

Emissions to air

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VOC: VOC is emitted when wash-out solution containing organic solvent is used. The process is often carried out in sealed equipment but there will still be emissions of VOC to the air. Solvent can be recycled by using vacuum distillation. Ozone: Emission of ozone is produced by the UV-lamps. The emitted amount is low compared to other sources. The environmental impact is negligible when the ozone is exhausted to the atmosphere as it quickly degrades into oxygen.

Discharges to water Wastewater from etching the metal plates contains high concentrations of heavy metals and is low in pH. The metals in the wastewater can be reduced via sedimentation.

Water to wash-out the water-washable printing plates can be contaminated by reactive photo polymers and cleaning agents. This water can have an inhibiting effect on the nitrification process, which can be a problem for water treatment plants that have this type of cleaning step for reducing the nitrification. The wash-out water can undergo pre-treatment, such as different types of filtration, floccation, sedimentation, or biologically-absorptive treatment using active carbon. 3.5.3 Printing

Emissions to air VOC: During printing and cleaning, especially from printing with solvent-based ink, there are significant VOC emissions. The vapours are normally not recovered because of the variety of solvents. The exhaust gases can be treated in an afterburner where the VOC's mainly oxidise to CO2 and H2O. The main types of afterburners in flexographic printing are the catalytic, recuperative, or regenerative thermal oxidation.

In a catalytic afterburner cleaning occurs between approximately 200°C and 350°C depending on the type of catalyst used. A heat exchanger is used between ingoing and outgoing air. Catalytic oxidisers are sensitive to overheating as well as contamination. The incineration temperature for thermal oxidation lies in the interval 750 ­ 1000°C. Conventional thermal incineration is done with an open flame, recuperative oxidation, and fuel in the form of gas must be added to maintain the temperature. A heat exchanger is used between ingoing and outgoing air. In a regenerative system two beds with heat-retaining materials are normally used. A heater is placed between the two beds. The air first passes one bed, where it is heated; it then enters the burn chamber, which is usually gas heated, and then passes the other bed, where heat is discharged. The direction of the flow is shifted after a time, and the functions of the respective beds are changed from air heating to air cooling, and vice versa. Cleaning with thermal oxidation has, as a rule, slightly higher cleaning efficiency than catalytic oxidation, but consumes more energy. In the EC VOC-directive (1999/13/EC) the emission limit for waste gases is 100 mg C/Nm3 for a solvent consumption of >15 tons/year. In the EC VOC-directive (1999/13/EC) the emission limit for fugitive emissions is 25% of solvent input for a solvent consumption of 15 - 25 tons/year and 20% of solvent input for a solvent consumption of >25 tons/year.

Ozone:

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Emission of ozone is produced by the UV-lamps for UV-inks. The emitted amount is low compared to other sources. The environmental impact is negligible when the ozone is exhausted to the atmosphere as it quickly degrades into oxygen. Treating

Discharges to water When printing with water-based inks the press is cleaned with water which is sometimes added with alkalis, detergents, or solvents. The waste water can have an inhibiting effect on the nitrification process, which can be a problem for water treatment plants that have this type of cleaning step for reducing the nitrification. The waste water can undergo pre-treatment, such as different types of filtration, floccation, sedimentation, or biologically-absorptive treatments using active carbon.

Waste water can also occur but in small quantities from the cleaning process when solvent inks have been used.

3.6 Potential for improvements

3.6.1 Pre-press, image preparation

3.6.1.1 Re-using of developer

A regenerating system, including filtration and addition of worn-down components in the developer, can be connected to the developing machine to extend the life-time of the developer. This can reduce the amount of developer used by about 40%.

3.6.1.2 Re-using of fixer

A recirculating electrolytic recovery system removes silver from the fixer solution and the fixer solution can then be reused in the process. By reusing the desilvered fix, less fresh fixer solution is needed to replenish the bath. Less silver is carried over to the rinsing water, as the solver concentration in the fix bath is lower with an electrolytic system. This can reduce the amount of fixer used by about 70%.

3.6.1.3 Recirculating of the rinsing water

There are different types of systems of recycling the rinsing water in the developing machine, but the principle is the same. The rinsing water passes through a filter and recirculates between the rinsing tank in the developing machine and a tank connected to the machine. To prevent growth of micro-organisms, the system can use UV-radiation, or biocides can be added. In some systems, the water is used for mixing new fixing solution from powders or concentrates. In these systems the water consumption is reduced and no silver will end up in the sewage system.

3.6.1.4 Treatment of the rinsing water

To reduce the silver content in the rinsing water, an ion exchanger can be used. This method can be used when a recirculating system is not an alternative. Many developing machines can be connected to a single ion exchanger.

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3.6.2

Platemaking

Using water washable plates or laser engraving plates instead of solvent washable plates. Reusing and filtering the water used for developing of water-washable plates if it is possible. 3.6.3 Printing

Enclosed doctor blade Enclosed doctor blade chambers reduce the ink evaporation and reduce the amount of solvents added for adjustment of the ink. Printing with four-colour process The limited number of inks in four-colour printing process printing can minimize the amount of mixed colour inks used, and eliminate residues of unusual colour at the end of each job. Water-based inks or UV-inks Using water-based inks, if it is possible, reduces the emissions of VOC even if they contain a low concentration of solvents. UV-inks do not emit VOC. At present UV-inks are used when printing labels and small carton boxes on narrow presses. Distillation of solvents and waste ink Solvents and waste inks can be reused for equipment cleaning after distillation. This process will not reduce emissions but results in a reduction in the amount of solvents used. The amount of waste decreases and raw materials are saved. Using computerized ink blending Software and specialized equipment is a help when blending ink, and reduces surplus ink and reuses press return ink. Installing automatic on-press cleaning When paired with solvent recovery, on-press cleaning systems use much less cleaning solution than hand cleaning.

Cleaning in different steps The first stage is a recirculation mode where used dirty water/solvent is used for the initial cleaning. The dirty water/solvent is returned to a common tank after each wash and can be reused many times. Ink, left after the first stage, is removed using partially dirty water/solvent. Clean water/solvent is used for a final rinse only. When the water/solvent in stage 1 becomes too dirty to be effective, it is processed or disposed as hazardous waste. Stage 2 becomes stage 1, and so on.

Alternative methods to clean anilox rolls Instead of cleaning with solvents alternative methods, such as ultra-sonic cleaning, dry ice, lasers, polyethylene beads, or sodium bicarbonate can be used. Recirculate warm press air Warm air from dryers for both solvent-based and water-based inks can be recirculating, which reduces the energy requirements.

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Reuse of ink waste Some ink manufacturers offer the service of taking back ink waste for use in the production of new black ink.

3.7 Expectations for the future

3.7.1 Pre-press, image preparation

The photographic process is becoming less common and will almost disappear as the process will be digitalized and the image will be transferred to the printing plate or directly to the printing press. 3.7.2 Platemaking

The process is more digitalized. Laser-engraved rubber plates will be more common. Reusing and recycling the photopolymer plates, trim scrap, and polyester cover sheets can be future improvements. 3.7.3 Printing

Increasing automation of press operations like inking control and press cleaning. Development of the UV-curing inks so they can be more widely used.

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4 Gravure

Different production methods are applied in gravure printing, depending on the products: publication gravure and packaging gravure printing. Large gravure presses are the largest available of any of the printing processes, with a web width of over 3,5 metres and up to 16 printing units. Gravure printing is particularly used for long print runs and very high quality. Rotogravure presses run at very high speed: 15 metres per second and more. A modern gravure press can print about seven million four-colour pages per hour. Gravure printing uses a depressed or sunken surface for the image. In gravure the image carrier is a cylinder. The cylinder is made of copper plated onto steel and covered with a thin layer of chromium to extend the life of the cylinder. The image areas consist of honeycomb-shaped cells or wells all of the same size but of varying depth that are etched or engraved into the copper layer of the cylinder. The unetched areas of the cylinder represent the non-image or un-printed areas. The gravure cylinder rotates with its lower part dipping in the ink. For the principle see the figure 11.

Figure 11

The ink used for gravure printing is very fluid, with a very low viscosity that allows the ink to be drawn into the engraved cells in the cylinder. The excess ink is scraped off the cylinder with a doctor blade and collected in a small trough and recirculated back to the main ink storage. The ink remaining in the recessed cells forms the image by direct transfer to the substrate as it passes between the plate cylinder. Web-fed gravure presses account for almost all publication, packaging, and product gravure printing. Product gravure printing is used in the textile industry but also used to print wallpaper, wallboard, and floor coverings. Web-fed gravure presses for flexible packaging and foil laminating are narrow- or medium-width presses. The large-width web presses are mainly for printing magazines and catalogues. Sheet-fed gravure presses are used for printing very high quality impressions for art books and posters and short runs of high quality packaging material. Sheet-fed gravure presses are also used to produce proof copies prior to large rotogravure runs.

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DRAFT 4.1 Printing materials and products

Gravure printing is most common for long-run magazines, mail-order catalogues, newspaper weekend colour supplements, advertising inserts, stamps, currency, bank notes, security documents, greeting cards, and gift wrapping paper. Also, gravure printing is used for a variety of packaging products, such as cigarette cartons, cosmetic cartons, and food packaging. Even furniture laminates, panelling, wallpaper, wallboard, imitation tiles for floors and walls, and textiles are printed in gravure presses. The substrate can be coated and uncoated papers, packaging paper, cartons, different types of flexible plastic films, metallised papers and vinyls, laminates, and textiles.

4.2 Process description

4.2.1 Pre-press, image preparation

The first step in the printing process, imaging, produces an image of the material (text, diagrams, and pictures) to be printed. This process is fairly similar for all printing except for digital printing, where this step does not exist. The pre-press stages of image preparation have changed from a lot of manual steps where text and pictures were handled separately to where it is done electronically. Electronic imaging processing systems can produce text and pictures and then arrange them in the correct position on the page. The imaging process begins with composition and typesetting. Composition involves the arrangement of text, pictures, and diagrams into the desired format. Earlier, this used to be performed manually and included a lot of different steps, but today high-performing computers and graphic-oriented programs are used. If pictures are to be printed in several colours, these must be separated into four colours and exposed on film, but today this can be stored in the computers. The pictures are also often screened, i.e., the pictures consist of a large number of very small dots instead of a whole field. Once the desired format and images are assembled, the data are exposed onto photographic material in an image-setter. The photographic emulsion on the film or paper is composed of silver halide and gelatine. Developing and fixing of the photographic film or paper is often done by machine, with subsequent rinsing stages and then drying. The film and paper are accompanied by a certain amount of liquid when they are transferred to the next bath. Depending on the fixing bath's silver concentration, the design of the equipment, and the flow of rinsing water, the quantity of photographic chemicals and silver vary in the rinsing water. The rollers in the developing machine need regular cleaning because of silver deposits. Cleaning of the rollers can be done with a brush and a household detergent. Earlier it was common to use cleaning agents containing chromium, and this may still be used in a few places. A proof print is often made for checking the reproduction process, or for submitting to the customer for checking and approval, or used internally by the printer as a working guide. Many different methods exist; wet proofing is the traditional method of producing colour proofs. Today, proofs can be made directly from the data in the computer, being shown on the screen or printed out with an inkjet or laser printer. It is the same technology as printers/presses that are used for digital printing. Small quantities of toners or inkjet ink are used for proof printing.

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4.2.2 Cylinder preparation

The gravure image carrier consists of a steel cylinder covered with a base layer of copper. On top of the base layer of copper another copper layer (Ballard shell) is deposited by electrolysis. The engraving is done on the Ballard shell. To obtain a hard surface layer, the cylinders are chromed after the engraving. When the print run is completed, the Ballard shell is pulled off. This is possible because the cylinder has been treated with a separating solution between the base copper and the Ballard shell. Both the copper and the chromium layers are applied using electrolysis processes. The top layer of copper is deposited by electrolysis in an electrolyte of copper sulphate, sulphuric acid, deionised water, and a small amount of a hardener containing tiocarbamide. Chrome plating is applied in a very thin layer not to change the shape of the cells engraved in the copper. The electrolyte used in chrome plating consist of chromic acid, sulphuric acid, deionised water, and small amount of organic additives. The cylinder is polished both after the copper plating and the chrome plating to get rid of irregularities. The steps in preparation of a cylinder can be as follows: Degreasing: can be done electrolytically in an alkali solution or manually. Treatment with a separating solution. Copperisation and washing. Polishing. Engraving or chemical etching. Degreasing. Chroming and washing. Polishing. Electromechanical engraving has almost entirely replaced chemical etching in the preparation of gravure cylinders. Chemical etching is mostly used in packaging gravure for special applications. In chemical etching a pigment paper/-film is used that has been sensitised to light by submerging it in a bath of bichromate and water. The film/paper has been coated with a smooth gelatine resist. After exposing the pigment paper/-film is adhered to the cylinder and rinsed with water. To develop the relief of gelatine the cylinder is developed in alcohol. Finally, the image is then etched into the cylinder with ferric chloride in a strong hydrochloric acid solution which creates the printing cells on the cylinder. Electro-mechanical engraving is performed using a computer-controlled lathe-type cutting machine. The lathe uses a diamond tool to engrave patterns. The image to be engraved is wrapped around the drum of the scanner and a scanning head moves across the scanning drum as the drum spins and sends impulses to the computer-controlled cutting machine. Today digital engraving is becoming widespread. The image is created using a image handling computer. The steps of creating, copying, and rescanning film can be avoided. 4.2.3 Printing

There are several types of web presses in gravure printing, including publication presses, packaging presses, label presses, and folding carton presses. A typical web gravure press is highly automated and consists of multiple printing units, and a publication press usually has eight to ten printing units (one per colour and one for monochrome text and illustration for each paper side). The printed product will either be stitched and finished in a single operation or done as a bindery product including steps as binding, trimming, and addressing. Packages are usually printed on only one side, so the number of printing units in a packaging press is usually fewer than in a publication press. Packaging presses are often equipped with stations to laminate, fold, cut, and crease paper boxes in a continuous process.

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The cylinder is rotated in a fountain of fluid ink and the cells fill up. The surplus ink is scraped from the cylinder surface by using a doctor blade. The ink is only left in the engraved image area. During printing the paper passes between a rubber-covered impression roller and the gravure cylinder. The impression roller applies pressure to the paper and the ink in the cells on the cylinder is transferred to the paper. Gravure uses ink, which has a very low viscosity state from the use of solvents, in order to fill the tiny cells in the cylinder. The ink must dry quickly, particularly on high speed web presses, so the ink has to dry before the paper reaches the next printing unit on the press. The ink is dried by high volume air dryers between each individual printing unit because wet inks cannot not be overprinted without smearing and smudging. In publication printing, the solvents used in the ink are often toluene and xylene, while packaging inks use a variety of volatile organics compounds like alcohols. Water-based inks can be used for lower quality of packaging products. It is used very sporadically. The toluene solvent-laden air from the dryers is passed through a solvent recovery system or solvent vapour incinerator. Today many presses are encapsulated and all the air in the encapsulation is removed by ventilation to the recovery system. A recovery system often uses beds of activated carbon to absorb the solvent. Saturated beds are regenerated by steam. The heated solvent-laden steam is led through a cooler and the water and toluene separate by gravity. Most of the solvent in the ink is recovered and reused in the process. If incineration is used the solvent is destroyed. After printing has been completed, the printing cylinders are removed from the printing press. The cylinders are often washed in a closed washing unit. In the washing unit, other press equipment can also be washed. Washing is usually done with toluene, whose deposit can be connected to the recovery system. In many cases a distillation unit is connected to the washing unit, and contaminated toluene is recycled there. The printing cylinders can also be washed in a closed high pressure system with an alkali solution. Manual washing of the press is done with toluene-soaked rags.

4.3 Chemicals

4.3.1 Pre-press, image preparation

Process

Chemical/ Chemical compound

Examples of chemicals used

Photographic film and paper Developer Developing of film and paper

Fixer Cleaning solutions

Correcting fluid Proof print developer Colour foils

Emulsion of silver halide and gelatine Hydroquinone, phenidone, metol, potassium or sodium sulphite, potassium carbonate, potassium or sodium hydroxide, potassium bromide, sodium silicate Fixing of film or paper Ammonium thiosulphate, sodium acetate, sodium sulphite, glacial acetic acid Sulpamic acid, thiocarbamide, , Cleaning the rollers in the sodiumhydrogen sulphate, chromium salts, developing machine surfactants Correcting exposed film Potassium ferricyanide, potassium permanganate Developing of proof print in the Sodium carbonate, sodium hydroxide, wet process surfactants Proof print process

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4.3.2 Cylinder preparation

Process

Cylinders for printing. Coppering of cylinder Chroming of cylinder

Chemical/ Chemical compound

Gravure cylinders Copper anodes Platinised titanium and lead anodes Copper sulphate Sulphuric acid

Examples of chemicals used

Base of steel plated with copper. Copper Platinum Titanium Lead Copper sulphate Sulphuric acid

Chromium trioxide Hardener Separating solution

Ingredient in the copper bath for electrolysis Ingredient in both the copper bath and chromium bath for electrolysis Ingredient in the chromium bath for electrolysis. Hardening of the copper A separating layer between the base copper and the top copper. Polishing the copper and chromium layer after plating. Polishing the copper and chromium layer after plating. Dechroming process Dechroming process Correcting process Ingredient in etching bath Preparation of the steel cylinder before base coppering. Cleaning, deoxidising and degreasing of the cylinder before coppering and chroming. Correcting mistakes on the cylinder Ingredient in the etching process Sensitising solution for pigment paper/film Etching process Developing and drying of the cylinder in etching process Manual degreasing Wastewater treatment process Electrolytic degreasing, pH adjusting and neutralising the effluent from the wastewater treatment process Wastewater treatment process Wastewater treatment process

Chromium trioxide Thiocarbamide Silver nitrate Egg albumin Sodium sulphate Bentonite Pumice Citric acid Polishing stone, abrasive paper Alkali metal salts Hydrochloric acid

Polishing products

Polishing stone, abrasive paper Dechroming products Hydrochloric acid

Nickel products Degreasing and cleaning products

Nickel salts Caustic soda Inorganic salts Surface active additives Phosphoric acid Zinc chloride Earth metal salt Ferric chloride Alkali dichromate Gelatine Ethanol Toluene, ethanol Sodium sulphite Sodium hydroxide

Correction solutions Ferric chloride Alkali dichromate Pigment paper/film Alcohol Toluene, ethanol Sodium sulphite Sodium hydroxide

Floccating agents Percipitant

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4.3.3 Printing

Inks: Inks generally consist of two main components, pigment and vehicle. Pigment can be grouped into three categories: carbon blacks, inorganic pigments, and organic pigments. The vehicle is a liquid in which the pigment is dispersed. The vehicle can be a solvent into which a suitable binder is dissolved. The binder is a resin and it is the non-volatile part of the vehicle that solidifies and holds the pigment particles in a dried film. A water-based ink must contain at least 85% water in its volatile components in order to qualify as a non solvent-based ink. An ink can contain of other ingredients as well, depending upon the drying mechanism of the vehicle: driers, modified alkyd resins to form flexible films with high gloss, plasticizers, and other additives, such as waxes to improve rub resistance or slip and water repellence.

Gravure printing

Chemical/ Chemical compound

Publication ink

Comments

50%

Process

Printing on paper

Examples of chemicals used

Pigment: inorganic and organic (most common). Bindings: ethylhydroxyethylcellulose, phenolresin, hydrocarbon resin Solvents: Toluene Xylene. Additives such as polyethylene waxes, chelates, or plasticizers.

Solvent-based packaging inks

30%

Printing on paper or plastic

Pigment inorganic (white pigments) organic (most common). Bindings: cellulose nitrate, polyamide resin, acrylates, hydrocarbon resin, maleinresin. Solvents: Ethanol, propanol, isopropanol, ethyl acetate, isopropyl acetate, ethoxy propanol. Additives such as polyethylene waxes, chelates, or plasticizers.

Water-based packaging inks

20%

Printing on paper or plastic

Pigment inorganic (white pigments) organic (most common). Bindings: polyvinyacetate, polyester-, maleinand acrylateresin, ammonia, amines. Solvents: ethanol, isopropanol water. Defoaming agents: silicone Additives such as fungicides, surfactants, plasticisers and waxes.

Solvents

Cleaning, adjusting the viscosity of the ink.

Toluene Ethanol, isopropanol, ethylacetate, aliphatic hydrocarbons.

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4.4.1 Pre-press, image preparation

Film or paper containing silver EWC-code 09 01 07: normal waste Film developer: hazardous waste EWC-code 09 01 01 Fixer: hazardous waste EWC-code 09 01 04 Rinsing water from film development, depending on the silver concentration: hazardous waste EWCcode 09 01 06 Proof print developer: hazardous waste EWC-code 09 01 01 Colour foils can be sent for incineration Cleaning agents for the film developing machines containing chromium salts: hazardous waste Correcting fluids, depending on contain of chemicals: hazardous waste Ion exchange resin, in the case the rinsing water from film developing is treated in an ion exchanger, containing silver: hazardous waste Filter from film developing machine, containing residue of film developer. Rags or wipes containing cleaning agents with chromium salts: hazardous waste. UV lamps: hazardous waste EWC-code 20 01 21. Computers and other electronic equipment. Can be hazardous waste EWC-code 16 02 13. The management of hazardous waste is subject to strict regulatory requirements in EC legislation. Packages such as boxes, cans, plastic film, metal or plastic bands. Sorted and recycled or incinerated, depending on the legislation of the country. 4.4.2 Cylinder preparation

What is mentioned as waste are examples of kinds of waste that can be produced, but there is variation between different printing plants and different countries. Some of the waste that is mentioned in this section does not appear as waste in many places, as it is discharged as sewage instead. What is mentioned as waste in this section can also appear in the section environmental burden, discharges to water. Copper (Ballard shell) with chromium should be sent for recycling of the metal. Copper dust should be sent for recycling of the metal. Etching solutions: hazardous waste. Copper bath: hazardous waste. Chromium bath: hazardous waste. Alkaline degreasing agent: hazardous waste. Solvents: hazardous waste. Filter from the copper bath: hazardous waste. Metal hydroxide sludge: hazardous waste. Rags or wipes containing solvents: hazardous waste. Computers and other electronic equipment. Can be hazardous waste EWC-code 16 02 13. The management of hazardous waste is subject to strict regulatory requirements in EC legislation. Packages such as boxes, corrugated cardboard, cans, drums, plastic film, metal or plastic bands. Sorted and recycled or incinerated, depending on the legislation of the country.

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4.4.3 Printing

What is mentioned as waste are examples of kinds of waste that can be produced, but there is variation between different printing plants and different countries. Some of the waste that is mentioned in this section does not appear as waste in many places, as it is discharged as sewage instead. What is mentioned as waste in this section can also appear in the section environmental burden, discharges to water. All waste must be taken care of according to EC laws or individual country laws and rules. Paper waste should be sent for recycling. Plastic waste should be sent for recycling or for incineration. Water-based ink: hazardous waste EWC-code 08 03 12. Solvent-based ink: hazardous waste EWC-code EWC-code 08 03 12. Solvents: hazardous waste. Distillation sludge: hazardous waste. Water from cleaning the press and equipment used water-based ink. Shop towels/cleaning rags, containing organic solvents or inks: hazardous waste EWC-code 15 02 02. Computers and other electronic equipment. Can be hazardous waste EWC-code 16 02 13. The management of hazardous waste is subject to strict regulatory requirements in EC legislation. Packages such as boxes, corrugated cardboard, cans, drums, plastic film, metal or plastic bands. Sorted and recycled or incinerated, depending on the legislation of the country.

4.5 Environmental burden

4.5.1 Pre-press, image preparation

Emissions to air There are normally no emissions from film developing, but small amounts of emissions can occur from developers and fixers such as sulphur compounds and acetic acid. Discharges to water A certain amount of fix accompanies the film or paper when it is transferred to the rinsing bath. Depending on the design of the equipment and the flow of the rinsing water, variation occurs in the quantity of silver and chemicals in the rinsing water. Emissions to water from the pre-press process can be silver compounds in the rinsing water and chemical compounds from proof print developing.

When cleaning film developing machines, a cleaning agent containing chromium might be used. During rinsing, small amount of the cleaning agent containing chromium might be discharged as sewage. Film developing machines can in most cases be cleaned with detergent and a sponge or brush, and the rinsing water discharged as sewage. 4.5.2 Cylinder preparation

Emissions to air Galvanic baths are usually fitted for air extraction. The following emissions can occur from the different electrolytic and etching processes:

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drochloric acid from dechroming or etching baths Cr6 from chroming bath, but a baffle separator with aerosol screen reduces the emissions. VOC from the alcohol, when developing and drying the cylinder in the etching process.

Discharges to water Rinsing water is used after degreasing, deoxidation, and during the polishing process. The waste water contains copper, chromium (both Cr3 and Cr6) and sometimes nickel, and is low in pH. The metals in the wastewater can be reduced via sedimentation.

4.5.3

VOC:

Printing

Emissions to air

During printing and cleaning, especially when printing with solvent-based ink, there are significant VOCemissions. The vapours from the packaging printing are normally not recovered because of the variety of solvents, but publication printing plants normally have recovery systems with activated carbon to absorb the solvent. A very large percentage of the toluene is recovered, but there are still some losses of toluene compared to the solvent input. Fugitive emissions and the printed product still contain some toluene. The exhaust gases from the packaging printing plants can be treated in an afterburner where the VOC's mainly oxidise to CO2 and H2O. The main types of afterburners in packaging printing are the catalytic, recuperative, or regenerative thermal oxidation. In a catalytic afterburner cleaning occurs between approximately 200°C and 350°C depending on the type of catalyst used. A heat exchanger is used between ingoing and outgoing air. Catalytic oxidisers are sensitive to overheating as well as contamination. The incineration temperature for thermal oxidation lies in the interval 750 ­ 1000°C. Conventional thermal incineration is done with an open flame, recuperative oxidation, and fuel in the form of gas must be added to maintain the temperature. A heat exchanger is used between ingoing and outgoing air. In a regenerative system two beds with heat-retaining materials are normally used. A heater is placed between the two beds. The air first passes one bed, where it is heated; it then enters the burn chamber, which is usually gas heated, and then passes the other bed, where heat is discharged. The direction of the flow is shifted after a time, and the functions of the respective beds are changed from air heating to air cooling, and vice versa. Cleaning with thermal oxidation has, as a rule, slightly higher cleaning efficiency than catalytic oxidation, but consumes more energy. In the EC VOC-directive (1999/13/EC) the emission limit for waste gases is 100 mg C/Nm3 for a solvent consumption of >15 tons/year for packaging printing and 75 mg C/Nm3 for a solvent consumption of >25 tons/year for publication printing. In the EC VOC-directive (1999/13/EC) the emission limit for fugitive emissions is 25% of solvent input for a solvent consumption of 15 - 25 tons/year and 20% of solvent input for a solvent consumption of >25 tons/year for packaging printing. For publication printing the emission limit for fugitive emissions is 15% of solvent input for existing plants and 10% for new plants for a solvent consumption of > 25 tons/year.

Discharges to water

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The condensed steam from the solvent recovery contains about 0,38 to 0,54 g of toluene per litre. The condensed steam can be used for cooling purposes in a cooling tower or led through a stream of bubbles but some plants lead it back to the steamer. The treated water contains about 1 to 10 mg of toluene per litre and can be discharged to sewage. When printing with water-based inks the press is cleaned with water which is sometimes added with alkalis, detergents, or solvents. The waste water can have an inhibiting effect on the nitrification process, which can be a problem for water treatment plants that have this type of cleaning step for reducing the nitrification. Waste water can also occur but in small quantities from the cleaning process when solvent packaging inks have been used.

4.6 Potential for improvements

4.6.1 Pre-press, image preparation

4.6.1.1 Re-using of developer

A regenerating system, including filtration and addition of worn-down components in the developer, can be connected to the developing machine to extend the life-time of the developer. This can reduce the amount of developer used by about 40%.

Re-using of fixer A recirculating electrolytic recovery system removes silver from the fixer solution and the fixer solution can then be reused in the process. By reusing the desilvered fix, less fresh fixer solution is needed to replenish the bath. Less silver is carried over to the rinsing water, as the solver concentration in the fix bath is lower with an electrolytic system. This can reduce the amount of fixer used by about 70%.

4.6.1.2 Recirculating of the rinsing water

There are different types of systems of recycling the rinsing water in the developing machine, but the principle is the same. The rinsing water passes through a filter and recirculates between the rinsing tank in the developing machine and a tank connected to the machine. To prevent growth of micro-organisms, the system can use UV-radiation, or biocides can be added. In some systems, the water is used for mixing new fixing solution from powders or concentrates. In these systems the water consumption is reduced and no silver will end up in the sewage system.

4.6.1.3 Treatment of the rinsing water

To reduce the silver content in the rinsing water, an ion exchanger can be used. This method can be used when a recirculating system is not an alternative. Many developing machines can be connected to a single ion exchanger.

4.6.1.4 Cylinder preparation

Filmless engraving will increase. Substitution of separating solutions containing silver. Treatment of the waste water containing copper, chromium or nickel by percipitation, flocculation, and sedimentation before discharging.

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Reducing the emissions of chromium (Cr6) from the chromium bath by installing a baffle separator and leading the collected fluid back to the bath. 4.6.2 Printing

Water treatment The waste water from cleaning the packaging press printing with water-based inks can undergo pretreatment, such as different types of filtration, floccation, sedimentation, or biologically-absorptive treatments using active carbon to reduce the nitrification effect. If it is possible, the treated water can be reused for cleaning. Distillation of solvents and waste ink Solvents and waste inks can be reused for equipment cleaning after distillation. This process will not reduce emissions, but results in a reduction in the amount of solvents used. The amount of waste decreases and raw materials are saved. Continuous measurement and control of recycling plant Concentration- or time control of the recycling plant is common, but can be made more effective by instead being volume-controlled. The regeneration of the carbon bed can be controlled so that it starts before the break-through of the carbon bed. This requires the installation of flow measurement and an integration unit, which controls when recycling starts. General ventilation for toluene recycling To reduce fugitive emissions from the ventilation system, the exit air can be led to a recycling plant.

4.7 Expectations for the future

4.7.1 Pre-press, image preparation

The photographic process is becoming less common and will almost disappear as the process will be digitalized and the image will be transferred to the printing plate or directly to the printing press. 4.7.2 Cylinder preparation

Today cylinders can already be engraved with laser techniques, but new laser technology will be developed. Development of cheaper alternatives to the copper-plated cylinder, such as photopolymer plastic cylinders. 4.7.3 Printing

Better management and control of the recycling plant. Development of the water-based inks for packaging and maybe even for publication printing so that they can be more widely used. Even UV-curing inks for packaging printing will probable appear in the future.

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5 Screen

The screen process was originally known as silk screen because the first material used as mesh carrier was silk. Screen printing has been particularly suitable for short-run works due to its low set-up costs. Screen printing plants are mostly small and medium sized businesses. Often the plants have only 1 to 5 employees. Almost any surface or substrate of any size, shape, or thickness including awkward, uneven, or moulded surfaces can be printed using the screen process. The printing inks are specially formatted to match the type of substrate used. The ability to print variable thickness of ink and with special inks means that products withstanding harsh outdoor weather conditions or laundering usually are screen printed. Screen is referred to as a stencil process and the image carrier is called a screen. The ink is squeezed through small holes in the screen and thereby transferred to the substrate, figure 12. Some screen printing presses are still manually operated but most commercial and industrial screen printing today is done with automated presses.

Figure 12

Three main types of screen presses are used for screen printing: flatbed (the most widely used), cylinder and, rotary. Flat-bed and cylinder presses use a flat screen and a three step reprocating process to perform the printing operation. Rotary screen presses are design for continuous , high speed web printing. In narrow-width rotary screen presses labels, scratch cards, and packaging products are printed while wallpaper, vinyls, floor coverings, and textiles are printed in larger and wider rotary screen presses.

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DRAFT 5.1 Printing materials and products

Almost any material can be screen printed, including paper, cardboard, wood, metal, textiles, plastics, cork, leather, fur, ceramics, electronic circuit boards, and glass. Screen printed products include billboards, posters, greeting cards, decals, banners, wallpaper, T-shirts, hats, ceramic tiles, CD-discs, and bottles.

5.2 Process description

5.2.1 Pre-press, image preparation

The first step in the printing process, imaging, produces an image of the material (text, diagrams, and pictures) to be printed. This process is fairly similar for all printing except for digital printing, where this step does not exist. The pre-press stages of image preparation have changed from a lot of manual steps where text and pictures were handled separately to where it is done electronically. Electronic imaging processing systems can produce text and pictures and then arrange them in the correct position on the page. The imaging process begins with composition and typesetting. Composition involves the arrangement of text, pictures, and diagrams into the desired format. Earlier, this used to be performed manually and included a lot of different steps, but today high-performing computers and graphic-oriented programs are used. If pictures are to be printed in several colours, these must be separated into four colours and exposed on film, but today this can be stored in the computers. The pictures are also often screened, i.e., the pictures consist of a large number of very small dots instead of a whole field. Once the desired format and images are assembled, the data are exposed onto photographic material in an image-setter. The photographic emulsion on the film or paper is composed of silver halide and gelatine. Developing and fixing of the photographic film or paper is often done by machine, with subsequent rinsing stages and then drying. The film and paper are accompanied by a certain amount of liquid when they are transferred to the next bath. Depending on the fixing bath's silver concentration, the design of the equipment, and the flow of rinsing water, the quantity of photographic chemicals and silver vary in the rinsing water. The rollers in the developing machine need regular cleaning because of silver deposits. Cleaning of the rollers can be done with a brush and a household detergent. Earlier it was common to use cleaning agents containing chromium, and this may still be used in a few places. A proof print is often made for checking the reproduction process, or for submitting to the customer for checking and approval, or used internally by the printer as a working guide. Many different methods exist; wet proofing is the traditional method of producing colour proofs. Today, proofs can be made directly from the data in the computer, being shown on the screen or printed out with an inkjet or laser printer. It is the same technology as printers/presses that are used for digital printing. Small quantities of toners or inkjet ink are used for proof printing. 5.2.2 Stencil preparation

The screen image carrier consists of a screen mesh made of nylon, polyester, or fine mesh stainless steel. Printing screens are fabric mesh screens stretched and affixed tightly onto a aluminium, wood, or steel frame. The thread count and diameter of the screen determine the ink deposited onto the substrate. A finer mesh will deposit a thinner ink deposit. The image is defined by a stencil or mask which is adhered to the screen, blocking portions of the screen while leaving other portions unblocked. The function of the stencil is to cover the non-printing area of the screen. There are various methods of applying a stencil

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onto the screen, such as hand-cut film, indirect photostencil, direct coating, direct/indirect photostencil, wet-direct photostencil, and digital or laser imaging techniques. A hand-cut film stencil is stuck to the screen mesh, using an adhesive, masking tape or heat. In the direct coating process, a light-sensitive emulsion is applied on the whole screen and is allowed to dry. The screen is then exposed to UV radiation through a film positive. The unexposed image areas are removed with sprays of water. In the indirect photostencil process, a sensitive stencil film is fixed to the screen mesh. After a positive film is placed onto the stencil film, it is placed in a vacuum frame and exposed with UV light. It is then developed in hydrogen peroxide and the unexposed areas are removed with water. In the direct/indirect stencil process, an unsensitised photographic film is laminated to the screen and then sensitised by application of a photosensitive emulsion. It is then processed in a similar way as the direct and indirect processes. In the wet-direct photostencil process, a positive film is held in direct contact with a wet photopolymer emulsion and then exposed to UV light. The unexposed areas of the emulsions are then removed. In the digital imaging technique, a computer is interfaced with a special inkjet printer which prints a special UV-ink onto the screen. The stencil is exposed with UV-light and then the unexposed ink is washed away. In the laser imaging technique, digital information from a computer is used and a laser hardens the nonimage areas of the emulsion coated on the screen. On the edge of the frame there are open fabrics that are filled with a filler. Fillers can even be used for retouching of mistakes that occurred during exposing. Then the frame is ready for printing. The screen must first be thoroughly cleaned and degreased before coating. The degreasing is necessary, otherwise the film stencil will not properly adhere to the screen. The screen is cleaned with a degreaser, pumice-based abrasive, and warm water. These steps remove grease from the surface and roughens it so the film stencil adheres well to the screen. After printing, the frames must be cleaned carefully before being used again. The ink has to be removed before the emulsion is removed. Ink and the emulsion can be removed by high pressure screen washers or automatic screen washers. A "ghost image" is a shadow of the original image that remains on the screen and has to be removed before the screen can be used again in the process. 5.2.3 Printing

The printing process may range from manual to fully automatic presses. The flatbed presses are the most common and are primarily used for printing on flat substrates. The press consists of a bed or vacuum table holding the substrate in position during printing, a carriage that holds the screen, and a squeeze. Cylinder presses are used to print on regular or irregular-shaped substrates. A cylinder press consists of a carriage, a squeeze, and an impression cylinder that carries the substrate. Both flatbed presses and cylinder presses use the same three step printing process. Ink is poured on the screen in the first step and the screen is then moved into position over the substrate. After that the squeeze is

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pressed against the mesh and drawn over the image to squeeze the ink through the small holes in the mesh onto the substrate. Finally, the screen is lifted away from the substrate. Rotary presses are often used in textile and wallpaper printing. The cylinders are nickel-plated screens that are porous in the image areas and solid in the non-image areas. The squeeze is fixed inside the rotating screen cylinder. The squeeze remains stationary, forcing the ink through the rotating cylinder printing screen as the substrate passes beneath. Ink is constantly pumped into one end of the cylinder during printing. The inks used for screen printing include traditional solvent-based inks, UV-curable inks, water-based inks, plastisols or water-based inks for textile printing. The chemical composition of the ink used varies depending on the substrate printed and the end product produced. The solvent-based inks used frequently for printing on paper and board (paper inks) and plastics (plastic inks) dry primarily through evaporation. In manual presses, the printed material is withdrawn from the press and racked in separate sheets for natural drying. Drying of the solvent-based and water-based inks is usually done in the press by infrared technique or a variety of air-dryers. The UV-curable inks will dry by exposing them to UV-radiation. Before printing, the inks are often diluted 10-30% and other substances are added as retarders (in order to avoid ink drying in the fabric during the printing). During printing, the mesh can be sprayed with mesh opener (solvent or water, depending on the ink) to prevent the ink from drying in the fabric during stops. After printing, the screen has to be cleaned. Excess ink in the screen can be scraped off for reuse on another job. The screen is often cleaned in the place where the stencil is prepared.

5.3 Chemicals

5.3.1 Pre-press, image preparation

Process

Chemical/ Chemical compound

Examples of chemicals used

Photographic film and paper Developer Developing of film and paper

Fixer Cleaning solutions

Correcting fluid Proof print developer Colour foils

Emulsion of silver halide and gelatine Hydroquinone, phenidone, metol, potassium or sodium sulphite, potassium carbonate, potassium or sodium hydroxide, potassium bromide, sodium silicate Fixing of film or paper Ammonium thiosulphate, sodium acetate, sodium sulphite, glacial acetic acid Sulpamic acid, thiocarbamide, , Cleaning the rollers in the sodiumhydrogen sulphate, chromium salts, developing machine surfactants Correcting exposed film Potassium ferricyanide, potassium permanganate Developing of proof print in the Sodium carbonate, sodium hydroxide, wet process surfactants Proof print process

5.3.2

Stencil preparation

Process

Stencil preparation and printing

Chemical/ Chemical compound

Screenframe to which a mesh is tightly stretched and secured.

Examples of chemicals used

Frame of wood, aluminium, or steel. of nylon, polyester, or stainless steel. Mesh

Light-sensitive emulsion and Exposing of the stencil

Tripropylenglycol diacrylate, polyester acrylate,

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film diazonium salts, p-toluensulfonic acid, polyvinyl alcohol, phthalocyanine pigments, plasticisers, fungicides. Polyvinyl alcohol, water, volatile solvents Sodium hydroxide, acetic acid, calcium carbonate, silicates, surfactants Sodium hydroxide, sodium hypochlorite N-methyl pyrrolidone, glycol ethers, sodium metaperiodate, periodic acid.

Filler, retouch lacquer Decreasing agents Ghost image remover Decoating products

Edge-machine and retouching after exposure Degreasing the stencil before coating. Remove ghost image from the screen. Cleaning of the stencil after printing

5.3.3

Printing

Inks: Inks generally consist of two main components, pigment and vehicle. Pigment can be grouped into three categories: carbon blacks, inorganic pigments, and organic pigments. The vehicle is a liquid in which the pigment is dispersed. The vehicle can be a solvent into which a suitable binder is dissolved. The binder is a resin and it is the non-volatile part of the vehicle that solidifies and holds the pigment particles in a dried film. A water-based ink must contain at least 85% water in its volatile components in order to qualify as a non solvent-based ink. An ink can contain of other ingredients as well, depending upon the drying mechanism of the vehicle: driers, photoinitaiator (UV-drying) monomers, polymers, and oligmers. Other possible components are: oil modified alkyd resins to form flexible films with high gloss, plasticizers, and other additives, such as waxes to improve rub resistance or slip and water repellence.

Screen printing

Chemical/ Chemical compound

Solvent-based ink

Comments

35%

Process

Printing on paper or plastic and other substrates

Examples of chemicals used

Pigment inorganic and organic (most common). Bindings: alkyd-, acrylics-, phenol resin, cellulose derivates. Solvents: aliphatic and aromatic hydrocarbons, cyclohexanone, alcohols, glycol ethers, isoforone, glycols, glycol esters. Additives such as polyethylene waxes, defoaming agents, drying agents or plasticizers.

Water-based inks

30%

Printing on paper or plastic

Pigment inorganic and organic (most common). Bindings: poly acrylates, poly urethane, synthetic resins. Solvents: glycol ethers, aliphatic hydrocarbons water. Additives such as fungicides, surfactants, plasticisers, defoaming agents and waxes. Amides or nitrogenous compounds: monoethyl amine, ammonia.

UV-inks

30%

Printing on different substrate

Pigment: inorganic and organic (most common). Bindings: prepolymer of urethane, epoxy and esther.

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Monomers such as 1,6 Hexanediol diacrylate or N-vinyl-2-pyrrolidone. Photoinitiators such as acetophenone, hydroquinone, benzildimethylketal. Additives such as methoxyphenol, plasticisers and waxes. Textile inks 5% Printing on textile Pigment: Bindings:. Monomers such as: . Photoinitiators such as. Additives such as . Solvents

Alcohols 15% Glycolethers 10% Aliphatic hydrocarbons 15% Aromatic hydrocarbons 25% Esters 10% Ketones 5% Acrylates 15% Others 5%

Thinners for the ink.

Water-based: water, alcohols, glycol ethers. Solvent-based: Aliphatic and aromatic hydrocarbons, esters, ketones, glycol ethers, alcohols. UV-inks: Di and triacrylates.

Mesh opener

Prevent inks from drying in the fabrics

N-methylpyrrolidone, diacetone alcohol, dimethyl monobuthylether, tannine acid.

5.4 Waste

5.4.1 Pre-press, image preparation

Film or paper containing silver EWC-code 09 01 07: normal waste Film developer: hazardous waste EWC-code 09 01 01 Fixer: hazardous waste EWC-code 09 01 04 Rinsing water from film development, depending on the silver concentration: hazardous waste EWCcode 09 01 06 Proof print developer: hazardous waste EWC-code 09 01 01 Colour foils can be sent for incineration Cleaning agents for the film developing machines containing chromium salts: hazardous waste Correcting fluids, depending on contain of chemicals: hazardous waste Ion exchange resin, in the case the rinsing water from film developing is treated in an ion exchanger, containing silver: hazardous waste Filter from film developing machine, containing residue of film developer. Rags or wipes containing cleaning agents with chromium salts: hazardous waste. UV lamps: hazardous waste EWC-code 20 01 21. Computers and other electronic equipment. Can be hazardous waste EWC-code 16 02 13. The management of hazardous waste is subject to strict regulatory requirements in EC legislation. Packages such as boxes, cans, plastic film, metal or plastic bands. Sorted and recycled or incinerated, depending on the legislation of the country.

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5.4.2 Stencil preparation

What is mentioned as waste are examples of kinds of waste that can be produced, but there is variation between different printing plants and different countries. Some of the waste that is mentioned in this section does not appear as waste in many places, as it is discharged as sewage instead. What is mentioned as waste in this section can also appear in the section environmental burden, discharges to water. Stencil residues. Plastic sludge. Cleaning agents containing alkalis. Emulsion, non-cured residues: hazardous waste. Solvents from cleaning, organic solvents: hazardous waste. Rags or wipes containing solvents: hazardous waste EWC-code 15 02 02. UV-lamps from curing UV-inks: hazardous waste EWC-code 20 01 21. Filters from automatic screen washers. Computers and other electronic equipment. Can be hazardous waste EWC-code 16 02 13. The management of hazardous waste is subject to strict regulatory requirements in EC legislation. Packages such as boxes, cans, plastic film, metal or plastic bands. Sorted and recycled or incinerated, depending on the legislation of the country. 5.4.3 Printing

What is mentioned as waste are examples of kinds of waste that can be produced, but there is variation between different printing plants and different countries. Some of the waste that is mentioned in this section does not appear as waste in many places, as it is discharged as sewage instead. What is mentioned as waste in this section can also appear in the section environmental burden, discharges to water. All waste must be taken care of according to EC laws or individual country laws and rules. Paper waste should be sent for recycling. Plastic waste should be sent for recycling or for incineration. Water-based ink: hazardous waste EWC-code 08 03 12 . Solvent-based ink: hazardous waste EWC-code EWC-code 08 03 12. UV-ink, not cured: hazardous waste EWC-code 08 03 12. UV ink, completely cured. Distillation sludge: hazardous waste. Solvents: hazardous waste. Shop towels/cleaning rags, containing organic solvents or inks: hazardous waste EWC-code 15 02 02. UV-lamps from curing UV-inks: hazardous waste. The management of hazardous waste is subject to strict regulatory requirements in EC legislation. Packages such as boxes, corrugated cardboard, cans, drums, plastic film, metal or plastic bands. Sorted and recycled or incinerated, depending on the legislation of the country.

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5.5.1 Pre-press, image preparation

Emissions to air There are normally no emissions from film developing, but small amounts of emissions can occur from developers and fixers such as sulphur compounds and acetic acid. Discharges to water A certain amount of fix accompanies the film or paper when it is transferred to the rinsing bath. Depending on the design of the equipment and the flow of the rinsing water, variation occurs in the quantity of silver and chemicals in the rinsing water. Emissions to water from the pre-press process can be silver compounds in the rinsing water and chemical compounds from proof print developing. When cleaning film developing machines, a cleaning agent containing chromium might be used. During rinsing, small amount of the cleaning agent containing chromium might be discharged as sewage.

Film developing machines can in most cases be cleaned with detergent and a sponge or brush, and the rinsing water discharged as sewage. 5.5.2

VOC:

Stencil preparations

Emissions to air

Screen cleaning is the dominating source of emissions to air. Traditionally, a lot of volatile organic solvents have been used to clean the screens, but non-volatile solvents are more common today. Emissions from the stencil making are negligible.

Ozone:

Emission of ozone is produced by the UV-lamps. The emitted amount is low compared to other sources. The environmental impact is negligible when the ozone is exhausted to the atmosphere, as it quickly degrades into oxygen.

Discharges to water

Waste water accumulates from the decoating, degreasing, and developing of the stencil processes. Rinsing water from developing stencils contains reactive acrylates and is toxic to water-living organisms. It has an inhibiting effect on the nitrification process, which can be a problem for water treatment plants that have this type of cleaning step for reducing the nitrification. From screen cleaning, the rinsing water can contain solvents, ink residues, periodate, and alkalis. 5.5.3

VOC:

Printing

Emissions to air

During printing and drying with printing with solvent-based ink, there are significant VOC-emissions. The vapours are normally not recovered or treated with an afterburner because of the variety of solvents and because the concentration in the exhausted air is usually not that high. In the EC VOC-directive (1999/13/EC) the emission limit for waste gases is 100 mg C/Nm3 for a solvent consumption of >30 tons/year.

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In the EC VOC-directive (1999/13/EC) the emission limit for fugitive emissions is 20% of solvent input for a solvent consumption of >30 tons/year for rotary screen printing on textile and paper.

Ozone:

Emission of ozone is produced by the UV-lamps for UV-inks. The emitted amount is low compared to other sources. The environmental impact is negligible when the ozone is exhausted to the atmosphere, as it quickly degrades into oxygen.

Discharges to water There is no discharge to water from the printing process.

5.6 Potential for improvements

5.6.1 Pre-press, image preparation

5.6.1.1 Re-using of developer

A regenerating system, including filtration and addition of worn-down components in the developer, can be connected to the developing machine to extend the life-time of the developer. This can reduce the amount of developer used by about 40%.

Re-using of fixer A recirculating electrolytic recovery system removes silver from the fixer solution and the fixer solution can then be reused in the process. By reusing the desilvered fix, less fresh fixer solution is needed to replenish the bath. Less silver is carried over to the rinsing water, as the solver concentration in the fix bath is lower with an electrolytic system. This can reduce the amount of fixer used by about 70%.

5.6.1.2 Recirculating of the rinsing water

There are different types of systems of recycling the rinsing water in the developing machine, but the principle is the same. The rinsing water passes through a filter and recirculates between the rinsing tank in the developing machine and a tank connected to the machine. To prevent growth of micro-organisms, the system can use UV-radiation, or biocides can be added. In some systems, the water is used for mixing new fixing solution from powders or concentrates. In these systems the water consumption is reduced and no silver will end up in the sewage system.

5.6.1.3 Treatment of the rinsing water

To reduce the silver content in the rinsing water, an ion exchanger can be used. This method can be used when a recirculating system is not an alternative. Many developing machines can be connected to a single ion exchanger. 5.6.2 Stencil preparations

Using non-volatile ink removers. Using water-based fillers. Wastewater undergoes pre-treatment as different types of filtration, floccation, or sedimentation.

Distillation and reuse of solvents

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Solvents can be reused for screen cleaning after distillation. This process will not reduce emissions but results in a reduction in the amount of solvents used. The amount of waste decreases and raw materials are saved.

5.6.2.1 Cleaning in two steps

In the first cleaning step, very small quantities of water are used to take away most of the contaminants. This water can be in-plant treated or sent off as waste. In the next step, much more water is used, and as it is not that polluted, the cleaning water can be discharged to water. 5.6.3 Printing

Water-based inks or UV-inks Using UV-inks or water-based inks, if it is possible, to reduce the emissions of VOC. Water-based inks contain a low concentration of solvents. UV-inks do not emit VOC. Distillation of solvents and waste ink Solvents and waste inks can be reused for equipment and screen cleaning after distillation. This process will not reduce emissions, but results in a reduction in the amount of solvents used. The amount of waste decreases and raw materials are saved. Using computerized ink blending Software and specialized equipment is a help when blending ink, and reduces surplus ink and reuses press return ink.

5.7 Expectations for the future

5.7.1 Pre-press, image preparation

The photographic process is becoming less common and will almost disappear as the process will be digitalized and the image will be transferred to the printing form or directly to the printing press. 5.7.2 Stencil preparations

The process it will be more digitalized. The digital and laser techniques utilize less chemicals and produce less waste. Laser-engraved rubber plates will be more common. 5.7.3 Printing

Development of water-based inks so that they can be more widely used.

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6 Letterpress

Letterpress, a relief process, is the oldest method of all the printing processes and used to be the major printing process, but has since the early 1970s been replaced by the offset and flexographic printing processes. The market for letterpress printing will continue to decrease. Letterpress is a relief printing method, meaning that the printing areas are raised above the non-printing areas. Ink is applied to the raised areas on the plate and transfer the printed image onto the substrate. The printing plates were traditionally made of a metal alloy consisting of a mixture of lead, tin, and antimony. Today the majority of the letterpress printing plates are polymer plates, but magnesium printing plates are still in use in a few places. The plate process is similar to the one used in the flexography process. Most printed matter in letterpress is in black only or black and a spot colour. An ink fountain roller places the ink on the inking plate. There are both sheet-fed flatbed presses and rotary presses. Sheet-fed flatbed presses are classified into two groups - platens and cylinders. Flatbed cylinder presses are slow, not more than 5 000 impressions per hour, and jobs formerly done on this type of press are today done in rotary letterpress or offset press. Most of the cylinder presses are today not used for printing, but for embossing, scoring, cutting, and creasing after the inking rollers have been removed. Even platen presses are used for the non-printing processes, such as embossing, cutting, and creasing, but also for hot-foil blocking on special presses. There are two types of rotary presses, sheet-fed and web-fed. Rotary web-fed presses are the most common type of letterpress printing today, and is used for newspaper printing and for printing labels.

6.1 Printing materials and products

The most common products are labels, newspapers, roll tickets, vouchers, pads, business cards, forms, letterheads, and overprinting on envelopes. Printing is principally done on paper, but can also be done on various types of cardboard, metal foil, metal, and plastic.

6.2 Process description

6.2.1 Pre-press, image preparation

The first step in the printing process, imaging, produces an image of the material (text, diagrams, and pictures) to be printed. This process is fairly similar for all printing except for digital printing, where this step does not exist. The pre-press stages of image preparation have changed from a lot of manual steps where text and pictures were handled separately to where it is done electronically. Electronic imaging processing systems can produce text and pictures and then arrange them in the correct position on the page. The imaging process begins with composition and typesetting. Composition involves the arrangement of text, pictures, and diagrams into the desired format. Earlier, this used to be performed manually and included a lot of different steps, but today high-performing computers and graphic-oriented programs are used. If pictures are to be printed in several colours, these must be separated into four colours and exposed on film, but today this can be stored in the computers. The pictures are also often screened, i.e., the pictures consist of a large number of very small dots instead of a whole field. Once the desired format and images are assembled, the data are exposed onto photographic material in an image-setter.

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The photographic emulsion on the film or paper is composed of silver halide and gelatine. Developing and fixing of the photographic film or paper is often done by machine, with subsequent rinsing stages and then drying. The film and paper are accompanied by a certain amount of liquid when they are transferred to the next bath. Depending on the fixing bath's silver concentration, the design of the equipment, and the flow of rinsing water, the quantity of photographic chemicals and silver vary in the rinsing water. The rollers in the developing machine need regular cleaning because of silver deposits. Cleaning of the rollers can be done with a brush and a household detergent. Earlier it was common to use cleaning agents containing chromium, and this may still be used in a few places. A proof print is often made for checking the reproduction process, or for submitting to the customer for checking and approval, or used internally by the printer as a working guide. Many different methods exist; wet proofing is the traditional method of producing colour proofs. Today, proofs can be made directly from the data in the computer, being shown on the screen or printed out with an inkjet or laser printer. It is the same technology as printers/presses that are used for digital printing. Small quantities of toners or inkjet ink are used for proof printing. 6.2.2 Platemaking

Letterpress plates are relief plates made of UV light sensitive photopolymer but magnesium plates are also used. There are two types of process, depending on whether solid sheets of photopolymer or liquid photopolymer are used. The two processes are similar in general outline and in both processes exposing of the plates by UV-light include both the backside and the front of the plate. First the backside of the plate is exposed to determine the relief depth. The photographic negative is placed between the photopolymer and the UV light source, hardening the image area. Lastly, the unexposed polymers are washed out in a solution of a mixture of hydrocarbons, and the plates are then dried with IR- and hot air blowers. Lately, water-washable systems have become more and more common. Post exposure ensures complete polymerisation of the printing plate. Finally, residual tackiness is removed with oxidising chemicals or UV-light. 6.2.3 Printing

The printing plate is mounted in the press and the raised areas of the plate are inked with an inking roller that transfers ink from an inking plate to the image carrier. A platen press consist of two flat surfaces called the bed and the platen. The printing form containing the image is placed on a flat surface. The printing form (plate) is inked with an inking roller. The substrate is placed on another flat surface (the bed) and pressed against the inked plate producing the impression. On platen presses, the relief printing form can be in a vertical or horizontal position but the most common is the vertical position. These presses are used for printing letterheads, business cards, and envelope overprinting. Most cylinder machines are today used for embossing, scoring, cutting, and creasing after the inking rollers have been removed. As these presses very seldom are used for printing, no descriptions of the presses are included here. Newspapers can be printed on rotary letterpresses, but these presses have been superseded by offset printing presses. Rotary letterpress is also used for printing books, packaging, and business forms. Narrow-width reel-fed rotary presses are used for printing self-adhesive labels.

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The inks used for letterpress printing are very similar to the offset inks. Originally, the inks for letterpress printing were oil-based and dried by absorption of the ink to the surface of the substrate. Today, other types of inks are also used, including oxidation drying inks, heat-set inks, UV-inks, and cold-set inks. UVinks is often used at label printing. Cleaning of the press occurs most often between press runs, during the press run, and during the makeready as adjustments are made to the press and plates, as well as at the and of the day. The frequency of press washes depends on many factors, including paper dust and dried ink accumulation, the quality of the paper, and the habits of the particular press operator. When cleaning the press manually, solvent-soaked rags are usually used.

6.3 Chemicals

6.3.1 Pre-press, image preparation

Process

Chemical/ Chemical compound

Examples of chemicals used

Photographic film and paper Developer Developing of film and paper

Fixer Cleaning solutions

Correcting fluid Proof print developer Colour foils

Emulsion of silver halide and gelatine Hydroquinone, phenidone, metol, potassium or sodium sulphite, potassium carbonate, potassium or sodium hydroxide, potassium bromide, sodium silicate Fixing of film or paper Ammonium thiosulphate, sodium acetate, sodium sulphite, glacial acetic acid Sulpamic acid, thiocarbamide, , Cleaning the rollers in the sodiumhydrogen sulphate, chromium salts, developing machine surfactants Correcting exposed film Potassium ferricyanide, potassium permanganate Developing of proof print in the Sodium carbonate, sodium hydroxide, wet process surfactants Proof print process

6.3.2

Platemaking

Process

Plates of photopolymer or rubber can be used. Washing out unexposed, nonpolymerised, areas of the plates.

Chemical/ Chemical compound

Letterpress printing plates

Examples of chemicals used

Base of steel or aluminium. Photopolymer coating containing acrylates. Rubber. Perchloro ethylene (not common today) Aliphatic hydrocarbons Cycloaliphatic hydrocarbons Alcohols Sulphuric acid Silicones Magnesium plate. Nitric acid

Plate washing

After treatment agents Defoamer Plate etching compound

Reduce surface stickiness Eliminate foaming during the etching process. Etching the magnesium plate when this plate is used.

6.3.3 Inks:

Printing

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Inks generally consist of two main components, pigment and vehicle. Pigment can be grouped into three categories: carbon blacks, inorganic pigments, and organic pigments. The vehicle is a liquid in which the pigment is dispersed. The vehicle can be a solvent into which a suitable binder is dissolved. The binder is a resin and it is the non-volatile part of the vehicle that solidifies and holds the pigment particles in a dried film. An ink can contain of other ingredients as well, depending upon the drying mechanism of the vehicle: driers to catalyse the oxidation drying of vegetable oils, photoinitaiator (UV-drying) monomers, polymers, and oligmers. Other possible components are: oil modified alkyd resins to form flexible films with high gloss, plasticizers, and other additives, such as waxes to improve rub resistance or rub reducers to reduce the tack.

6.3.3.1 Letterpress printing

Chemical/ Chemical compound

Ink

Comments

Mineral oil based 75% Vegetable oil based 20% UV-curable 5%

Process

Printing

Examples of chemicals used

Pigment such as calcium carbonate, carbon black, aluminium hydroxide, phtalocyanine, rhodamin etc. Bindings: Mixture of oils, resins, alkyds. Solvents: Mineral oils distillate with different boiling range. Vegetable oils. Additives such as catalytic driers, antioxidants, waxes, plasticizers and fungicides ( vegetable inks). UV-inks: pigment, prepolymers, monomers + oligomers (acrylates), photoinitiator and additives.

Varnish

Mineral oil based 50% Vegetable oil based 40% UV-curable 10%

Bindings: Mixture of oils, resins, alkyds. Solvents: Mineral oils distillate with different boiling range. Vegetable oils. Additives such as catalytic driers, antioxidants, waxes, plasticizers and fungicides ( vegetable inks). UV-varnish: Prepolymers, monomers + oligomers (acrylates), photoinitiator and additives.

Cleaning solvents

Aliphatic products 25% Alicyclic products 10% Aromatic products 30% Vegetable oil esters products 10% Hybride products 20% Other solvent products 5%

Cleaning the ink rollers, cylinders, ink ducts etc.

Aliphatic, alicyclic and aromatic hydrocarbons, vegetable oil esters, fatty acids, glycol ethers

Anti-set-off powder (sheet-

Prevent the sheets from

Starch, chalk.

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fed printing) Different process chemicals as ink preserver, tack reducer, dryers smearing and sticking to other sheets. To prevent the ink from drying, change the viscosity of the ink, to make the ink dry faster etc.

6.3.4

Waste

6.3.4.1 Pre-press, image preparation

Film or paper containing silver EWC-code 09 01 07: normal waste Film developer: hazardous waste EWC-code 09 01 01 Fixer: hazardous waste EWC-code 09 01 04 Rinsing water from film development, depending on the silver concentration: hazardous waste EWCcode 09 01 06 Proof print developer: hazardous waste EWC-code 09 01 01 Colour foils can be sent for incineration Cleaning agents for the film developing machines containing chromium salts: hazardous waste Correcting fluids, depending on contain of chemicals: hazardous waste Ion exchange resin, in the case the rinsing water from film developing is treated in an ion exchanger, containing silver: hazardous waste Filter from film developing machine, containing residue of film developer. Rags or wipes containing cleaning agents with chromium salts: hazardous waste. UV lamps: hazardous waste EWC-code 20 01 21. The management of hazardous waste is subject to strict regulatory requirements in EC legislation. Packages such as boxes, cans, plastic film, metal or plastic bands. Sorted and recycled or incinerated, depending on the legislation of the country. 6.3.5 Platemaking

What is mentioned as waste are examples of kinds of waste that can be produced, but there is variation between different printing plants and different countries. Some of the waste that is mentioned in this section does not appear as waste in many places, as it is discharged as sewage instead. What is mentioned as waste in this section can also appear in the section environmental burden, discharges to water. All waste must be taken care of according to EC laws or individual country laws and rules. Photopolymer plates, aluminium based, should be sent for recycling of the metal. Photopolymer, hardened. Photopolymer, not hardened: hazardous waste. Rubber plates. Wash-out solution, organic solvents: hazardous waste. Wash-out solution, perchloroethylene: hazardous waste. Acids such as etching solutions, after treatment agents: hazardous waste. Metal hydroxide sludge: hazardous waste. Distillation sludge: hazardous waste. Rags or wipes containing solvents: hazardous waste.

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UV-lamps from curing UV-inks: hazardous waste EWC-code 20 01 21. Computers and other electronic equipment. Can be hazardous waste EWC-code 16 02 13. Protective foil from letterpress plates. Can be sent for incineration. Filters from the plate exposing machine, which contains residues of photopolymers. The management of hazardous waste is subject to strict regulatory requirements in EC legislation. Packages such as boxes, cans, plastic film, metal or plastic bands. Sorted and recycled or incinerated, depending on the legislation of the country.

6.3.6

Printing

What is mentioned as waste are examples of kinds of waste that can be produced, but there is variation between different printing plants and different countries. Some of the waste that is mentioned in this section does not appear as waste in many places, as it is discharged as sewage instead. What is mentioned as waste in this section can also appear in the section environmental burden, discharges to water. All waste must be taken care of according to EC laws or individual country laws and rules. Paper waste should be sent for recycling. Letterpress ink, depending on the contain, can be hazardous waste or normal waste. Cold-set letterpress ink, depending on the contain, can be hazardous waste or normal waste. Letterpress ink, UV-ink, not cured: hazardous waste EWC-code 08 03 12. Letterpress varnishes, depending on the contain, can be hazardous waste or normal waste. Letterpress varnishes, UV-curing, not cured: hazardous waste EWC-code 08 03 12. Cleaning agents containing solvents: hazardous waste. Shop towels/cleaning rags, containing organic solvents, ink, or varnish: hazardous waste EWC-code 15 02 02. Spray cans, not empty: hazardous waste. UV-lamps from curing UV-inks and varnishes: hazardous waste EWC-code 20 01 21. Computers and other electronic equipment. Can be hazardous waste EWC-code 16 02 13. The management of hazardous waste is subject to strict regulatory requirements in EC legislation. Packages such as boxes, corrugated cardboard, cans, drums, plastic film, metal or plastic bands. Sorted and recycled or incinerated, depending on the legislation of the country.

6.4 Environmental burden

6.4.1 Pre-press, image preparation

Emissions to air There are normally no emissions from film developing, but small amounts of emissions can occur from developers and fixers such as sulphur compounds and acetic acid.

Discharges to water

A certain amount of fix accompanies the film or paper when it is transferred to the rinsing bath. Depending on the design of the equipment and the flow of the rinsing water, variation occurs in the

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quantity of silver and chemicals in the rinsing water. Emissions to water from the pre-press process can be silver compounds in the rinsing water and chemical compounds from proof print developing. When cleaning film developing machines, a cleaning agent containing chromium might be used. During rinsing, small amount of the cleaning agent containing chromium might be discharged as sewage. Film developing machines can in most cases be cleaned with detergent and a sponge or brush, and the rinsing water discharged as sewage. 6.4.2

VOC:

Platemaking

Emissions to air

VOC is emitted when wash-out solution containing organic solvent is used. The process is often carried out in sealed equipment but will still emit VOC to the air. Solvent can be recycled by using vacuum distillation.

Ozone: Emission of ozone is produced by the UV-lamps. The emitted amount is low compared to other sources. The environmental impact is negligible when the ozone is exhausted to the atmosphere, as it quickly degrades into oxygen. Discharges to water

Wastewater from etching the magnesium plates contains high concentrations of heavy metals and is low in pH. The metals in the wastewater can be reduced via sedimentation. Water to wash-out the water-washable printing plates can be contaminated by reactive photo polymers and cleaning agents. This water can have an inhibiting effect on the nitrification process, which can be a problem for water treatment plants that have this type of cleaning step for reducing the nitrification. The wash-out water can undergo pre-treatment, such as different types of filtration, floccation, sedimentation, or biologically-absorptive treatments using active carbon. 6.4.3

VOC:

Printing

Emissions to air

VOC is also emitted from solvents used when cleaning different parts of the letterpress. By using solvents with lower vapour pressure, such as vegetable based cleaning agents or high boiling aliphatic solvents, emissions can be reduced.

Ozone:

Emission of ozone is produced by the UV-lamps for UV-inks. The emitted amount is low compared to other sources. The environmental impact is negligible when the ozone is exhausted to the atmosphere, as it quickly degrades into oxygen.

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6.5.1 Pre-press, image preparation

6.5.1.1 Re-using of developer

A regenerating system, including filtration and addition of worn-down components in the developer, can be connected to the developing machine to extend the life-time of the developer. This can reduce the amount of developer used by about 40%.

6.5.1.2 Re-using of fixer

A recirculating electrolytic recovery system removes silver from the fixer solution and the fixer solution can then be reused in the process. By reusing the desilvered fix, less fresh fixer solution is needed to replenish the bath. Less silver is carried over to the rinsing water, as the solver concentration in the fix bath is lower with an electrolytic system. This can reduce the amount of fixer used by about 70%.

6.5.1.3 Recirculating of the rinsing water

There are different types of systems of recycling the rinsing water in the developing machine, but the principle is the same. The rinsing water passes through a filter and recirculates between the rinsing tank in the developing machine and a tank connected to the machine. To prevent growth of micro-organisms, the system can use UV-radiation, or biocides can be added. In some systems, the water is used for mixing new fixing solution from powders or concentrates. In these systems the water consumption is reduced and no silver will end up in the sewage system.

6.5.1.4 Treatment of the rinsing water

To reduce the silver content in the rinsing water, an ion exchanger can be used. This method can be used when a recirculating system is not an alternative. Many developing machines can be connected to a single ion exchanger. 6.5.2 Platemaking

Using water-washable plates or laser engraving plates instead of solvent-washable plates. Reusing and filtering the water used for developing water-washable plates, if possible. 6.5.3 Printing

Substitute high vapour pressure organic solvents/cleaning solvents By using cleaning agents with low vapour pressure, such as vegetable oils esterfied with alcohol, one decreases the VOC emission. Cleaning agents with a vapour pressure below 0,01 kPa are defined as not being volatile organic solvents (VOC). These cleaning agents have a flash between 100-150°C. Using these types of cleaning agents will also lead to improvements in health and fire safety.

As the vegetable cleaning agents are made from a renewable source, they will not increase the emission of greenhouse gases. High boiling solvents have the same advantages in emission, health, and fire safety as the vegetable ones but the are not renewable and more toxic. The European SUBSPRINT project (Substitution of Organic Solvents in the Printing Industry) has ranked the products on the market in the following order:

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1. 2. 3. 4. 5. 6. 7. Vegetable based cleaning agents Mixture of vegetable based cleaning agents and high boiling solvents. High boiling solvents with a flash point about 100°C Medium boiling solvents with a flash point between 55 and 100°C. Aromatic-free solvents Terpene-based solvents Traditional products based on petrochemical volatile mixtures, like white spirit.

Distillation of solvents and reusing of cleaning agents Some cleaning solvents can be reused after distillation. This process will not reduce emissions, but results in a reduction in the amount of solvents used. The amount of waste decreases and raw materials are saved.

6.6 Expectations for the future

As the use of this printing process decreases from year to year, there are no really developments in this process.

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7 Digital printing

In digital printing, digital files go directly from the creator to the press, computer-to-print. Digital printing can be two types of processes: fixed image data and variable image data printing. Digital printing with fixed image data uses printing plates, while no plates or any other type of physical image carrier is used with variable image data printing. In digital printing with fixed image data, computer-to-press system, the printing process is similar to that of offset printing. The image is created by laser ablation of a silicone plate of aluminium or polyester. The presses use waterless offset litho technology for printing. In this description of digital printing, only the process with variable image data printing is described. In digital printing, a new image can be printed each time a new page or file is downloaded digitally. It means that the image area can be new for every new copy. Digital printing is used for printing from one copy up to thousands of copies. Digital printing machines are also used for the production of colour proofs of printed materials, which will be printing using one of the traditional printing technologies. There is no distinct border between digital printing and digital colour proofing. As digital printing systems are constantly developing, there will be a lot of changes during the next 10 to 15 years in digital printing. Some of the more advanced machines can produce prints that can compete with the more traditional printing processes. An increasing amount of jobs are taken away from the traditional printing processes, especially sheet-fed offset printing and screen printing. There are a wide range of digital printing technologies, such as electrostatic, electrophotography, magnetographic, ink jet, ion deposition, thermal transfer, and dye sublimation. The electrophotography system and ink jet printing are the most widely used systems and the principles for these systems will be described under the printing process.

7.1 Printing materials and products

The most common products are technical manuals, spare parts catalogues, books, posters, banners, Tshirts, forms, labels, and direct mail. Which substrate can be used depends on the printing system. Only paper can be used in some systems, but in ink jet printing a wide variety of substrates, such as plastics, sandpaper, textiles, metal, glass, pills, and even fruit can be printed.

7.2 Process description

7.2.1 Platemaking

There is no platemaking in digital printing. 7.2.2 Printing systems

Electrophotography

The electrophotographic process, also called xerography, is used in copy machines, laser printers, and digital presses. An electrostatic charge is applied to a photoconducting layer on a rotating drum. Near the drum is a corona ­ a wire within a metal housing and attached to a high-voltage power supply. When the power is on, the surface of the drum is charging.

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The photoconducting layer is exposed with light from a laser or LED unit. The areas on the charged drum that have been exposed with light lose their charges. Controlled levels of light from the laser or LED unit define the image. More light exposure to the drum means more toners will be applied to the area. Charged toner is then applied to the drum, adhering only to the image areas ­ developing a latent electrostatic image on the drum. The toner is transferred off the charged drum onto the final substrate. The toner is heat-fused onto the substrate to give the visible image. There are systems that use either solid toners or liquid toners. In the liquid toner system, the image is transferred from the drum to a heated blanket and then to the substrate, not directly to the substrate as in the solid toner system. Toners consist mostly of pigment, soot in the black toner or colorant, dispersed in thermoplastic resins. Toner resins often soften and will be flowish around 65-67°C. Liquid toners consist of pigmented toner and carrier, which normally consists of high-boiling aliphatic hydrocarbons. Toners for use with high speed laser printers and copiers are usually a two-component system which consists of toner particles plus a charge control agent and 90% polymer binder, dry lubricants, and cleaning additives such as zinc stearate and silicone oil. Systems that use toners do not have to clean the machines with solvents. Cleaning is done by vacuum cleaning or by dry rags.

Inkjet

From digitally supplied information it is possible to produce one-off colour prints of varying sizes, but this can also be used to print on any shape or texture of substrate. It competes with screen printing in many types of printed products. Inkjet printers operate by directing small droplets of ink from a nozzle onto the printing substrate. There are different technologies applied to ink jet printers, such as continuous ink jet and drop-on-demand, in which there are different ways of producing the droplets, such as piezoelectric, thermal jet or bubble jet, and by hot melt. In a drop-on-demand system, drops of ink are produced only when they are needed to form part of the image. A continuous jet printer operates by pumping ink through a narrow nozzle towards the substrate to be printed. After the ink has split into droplets, the droplets are given an electric charge. The droplets are then passing between two charged deflector plates. The charged ink droplets can be directed onto the substrate and the drops of ink which have no charge are deflected away into a recycling reservoir. There is one nozzle for each colour.

A piezoelectric jet printer has a pumping membrane near the nozzle opening; this pumping membrane is

made to move with the help of a piezo crystal. Droplets are generated intermittently according to the electronic signals received and forced onto the substrate.

A bubble jet printer uses a small heating element to create pressure droplets within the reservoir. The ink boils creating a bubble which forces an ink droplet through the nozzle and onto the substrate. A hot melt jet printer is an extension of the bubble jet principle. In a hot melt printer, the ink is supplied as solid sticks of coloured wax. The wax is melted into a reservoir where it is kept fluid by a heating

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element. The liquid hot ink is then directed onto the substrate, and when reaching the substrate, the liquid ink returns to its original solid state. Ink formulations for inkjet inks must be designed to match the type of print head being used. They often consist of a blend of different solvents that hold the colorant, binder, and additives in solution. Dyes are usually used but pigments are sometimes used; however, these must not exceed 3 µm in particle size. Today, there are both alcohol-, oil-, and water-based inks, but ultraviolet-curable inks have also been developed. The main drying mechanism for inkjet printing inks is evaporation drying, except for UV-inks. Cleaning of the print head and other parts of the machines is usually done with a solvent similar to the one in the ink. Very small amounts of solvents are used.

7.3 Chemicals

7.3.1 Digital printing

Inks: Inks generally consist of two main components, pigment and vehicle. Pigment can be grouped into three categories: carbon blacks, inorganic pigments, and organic pigments. The vehicle is a liquid in which the pigment is dispersed. The vehicle can be a solvent into which a suitable binder is dissolved. The binder is a resin and it is the non-volatile part of the vehicle that solidifies and holds the pigment particles in a dried film. An ink can contain of other ingredients as well, depending upon the drying mechanism of the vehicle: driers to catalyse the oxidation drying of vegetable oils, photoinitaiator (UV-drying) monomers, polymers, and oligmers. Other possible components are: oil modified alkyd resins to form flexible films with high gloss, plasticizers, and other additives, such as waxes to improve rub resistance or rub reducers to reduce the tack. Digital printing Chemical/ Chemical compound

Toner

Comments

Process

Printing, electrophotographic process

Examples of chemicals used

Pigment such as carbon black, azo compounds, quinacridane, xanthrene, and phthalocyanines compounds. Bindings: thermoplastic resins as styrene-acrylate copolymers, and polyesters. Solvents: aliphatic hydrocarbon, light mineral oil. Additives: charge control agents such as sulfonic acids, carboxylic acids and their salts, complexed azo dyes, and highly acrylated phenazines, Cleaning additives such as aluminium or zinc stearate, and silicone oil. Polyester resins Copper-, zinc- and ferricoxide Colour dyes such as azo yellow, azo magenta, and phthalocyanine or pigment. Bindings: resins such as styrene-acrylate copolymers, and polyesters. Solvents: aliphatic hydrocarbon, iso- paraffines, alcohols, glycol ethers, and ketones. Additives: charge control agents such as sulfonic acids, carboxylic acids, and their salts UV-inks: pigment, prepolymers, monomers +

Developer Ink

Solvent based 50% Water based 30% Oil based 30% UV-curable 5%

Magnetic transferring of toner from printform to the substrate Printing, inkjet

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oligomers (acrylates), photoinitiator, and additives. Aliphatic hydrocarbons, iso- paraffines, alcohols, glycol ethers, and ketones.

Cleaning solvents

Cleaning of the print head or other parts of the press

7.4 Waste

7.4.1 Digital printing

What is mentioned as waste are examples of kinds of waste that can be produced, but there is variation between different printing plants and different countries. Some of the waste that is mentioned in this section does not appear as waste in many places, as it is discharged as sewage instead. What is mentioned as waste in this section can also appear in the section environmental burden, discharges to water. All waste must be taken care of according to EC laws or individual country laws and rules.

Photoconducting layer. Paper waste should be sent for recycling. Toners, depending on the contain, can be hazardous waste or normal waste. Inkjet ink, depending on the contain, can be hazardous waste or normal waste. Inkjet ink, UV-ink, not cured: hazardous waste EWC-code 08 03 12. Cleaning agents containing solvents: hazardous waste. Shop towels/cleaning rags, containing organic solvents or inks: hazardous waste EWC-code 15 02 02. UV-lamps from curing UV-inks and varnishes: hazardous waste EWC-code 20 01 21. Computers and other electronic equipment. Can be hazardous waste EWC-code 16 02 13. The management of hazardous waste is subject to strict regulatory requirements in EC legislation. Packages such as boxes, corrugated cardboard, cans, drums, plastic film, metal or plastic bands. Sorted and recycled or incinerated, depending on the legislation of the country.

7.5 Environmental burden

7.5.1 Digital printing

Emissions to water There are no emissions to water.

VOC:

Emissions to air

VOC is emitted from inkjet ink using solvents and when cleaning different parts of the machines. The emitted amount is low compared to other sources.

Ozone:

Emission of ozone is produced by the UV-lamps for UV-inks or from coronas in copy machines. The emitted amount is low compared to other sources. The environmental impact is negligible when the ozone is exhausted to the atmosphere, as it quickly degrades into oxygen.

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7.6.1 Digital printing

To save energy, the equipment should have a stand-by function when not in use. Used cartridges for powders and toners should be reused if possible. Today digital printing is said to be the cleanest technology solution of all the printing processes.

7.7 Expectations for the future

The process is increasing in importance and the systems will be faster and be able to compete with other printing processes.

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8 Post-press or finishing

Post-press or finishing operations include mechanical operations like cutting, folding, gathering, and stitching but also binding, varnishing, and laminating. Most printed products need some finishing operation. The most frequent part of the finishing operations is cutting or trimming. Notices, showcards, brochure-, magazine-, and catalogue covers, book and disc jackets, are often varnished or laminated to give a more glossy appearance or to improve the durability of the product. The finishing process can be done in-line or on-line with the printing press or at separate places. In some printing plants, the finishing operations are performed as a department of the plant. Many plants are specialised in finishing. In the packaging printing, such as flexography and gravure printing, finishing operations such as joining different layers of paper, plastic, and metal foils are common. Most offset and gravure web presses have integrated cutters and folders, as well as equipment for slicing and perforating. Each finishing operation is described separately under process descriptions.

8.1 Finishing products

Almost all printed products need some finishing operations, such as cutting and folding. For printed products such as books and catalogues, finishing operations can include folding, gathering or insetting, binding, and trimming; the cover can be varnished or laminated. Newspapers can be folded, gathered, stitched or glued, and trimmed. Packaging products are often laminated or varnished.

8.2 Process description

8.2.1 Cutting and trimming

Cutting and trimming operations are carried out on a guillotine. The machines are built in many sizes, capacities, and configurations. They often consist of a flat bed that holds the stack of paper to be cut. A back guide at the back of the guillotine holds the stack of paper in place. To hold the paper stack in place while it is cut, a clamp is lowered into contact with the top of the paper stack. Cutting a printing product to its finished size is called trimming. Most offset and gravure web presses have integrated cutters, as well as equipment for slicing and perforating. 8.2.2 Folding

Folding is mostly done on buckle or knife folder machines, but also by hand. Knife folders use a knife to force the paper between two contra-rotating rollers. Buckle folders use a buckle plate and three contrarotating rollers. There are machines that use a combination of knife and buckle folders. Folding operations include converting sheets into simple folded products, such as pamphlets or folded sheets, known as signatures, and multiple signatures are then assembled and bound into books and magazines. A sheet of paper has to be folded so that pages appear in correct sequence.

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Most offset and gravure web presses are equipped with folders. 8.2.3 Gathering and insetting

Separately folded sections of a job must be collected together to complete sets for binding. Gathering is the process of placing folded sheets next to one another while insetting is the process of placing one folded sheet inside another. An insert is not the same as an inset. An insert is a loose piece of paper or folded sheet which is inserted between the leaves of a book, pamphlet, or newspaper, and is not secured to the product. 8.2.4 Stitching

Stitching is a way of binding folded sheets together. In thread-stitching, the folded sheets are bound together with a thread by sewing machines. This can also be done by hand, but it is not very common today. Thread-stitching is mainly used for better quality bookbinding products. Wire stitching is the fastest and cheapest method of binding folded sheets together. Wire stitching is used for newspapers, magazines, booklets, and leaflets. The wire, fed from a reel, is cut and driven by a stitching head in the machine through the fold of the signatures in the back. 8.2.5 Spiral wire binding and plastic comb binding

Books, calendars, and pads can be bound with a spiral wire or plastic combs. After trimming, a series of holes are punched or drilled through the pages and cover and then a metal wire or plastic comb is run through the holes. 8.2.6 Adhesive binding

Adhesive binding can be done in the printing plant or at special binding plants. Adhesive binding is used for books, paperbacks, magazines, catalogues, packaging, and newspapers. In the adhesive binding process, a pile of paper is clamped together in a press and the binding edge is milled or roughened. An adhesive is then applied before a suitable lining or cover is attached to the back. Hot-melt and water-based dispersion adhesives are the main types of adhesives used for binding, but polyurethane hotmelt adhesives, adhesives with solvents, or animal hot adhesives can also be used. The water-based dispersion or cold PVA adhesive is dried as the backs of the books pass over a heating system. This is necessary if the binding block is going to be cut directly after binding. A dispersion adhesive consists mainly of copolymers of polyvinyl acetate, but also contains biocides and plasticizers. Hot-melt adhesives are solid and are warmed up to 150-190°C to be fluid in a hot glue tank, and can then be applied to binding blocks. A hot-melt adhesive has a very short "open time" before it is cooled down and forms a solid bond. A hot-melt adhesive consists of a vinylacetate/polyethene polymer, stabilizer, resins, and fillers. Changing of adhesives in a machine is not done very often. It is not necessary to clean the machine after finishing a job, as long as the machine does not remain out of use for a long time. Cleaning of machines is mostly done in connection with a changing of adhesives. Water can be used when cleaning machines and tools from water-based dispersion adhesives. Smaller amount of waste water can be produced from the cleaning process and is discharged to the sewage system.

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8.2.7 Varnishing and lacquering

A printing product can, by application of a varnish or a lacquer on the printed surface, get protection or a special brightness. The varnish/lacquer can be applied overall or just on spots of the surface. When the entire printed surface is to be lacquered, no separate printing form is needed when lacquering in special lacquering machines. Varnishing or lacquering can be done in-line the printing process or by plants that have specialised in lacquerings; the lacquering is then done on special lacquering machines. Water-based dispersions and UV-curing lacquerings are the main types of lacquerings, but solvent-based lacquers can also be used. After lacquering, the printing product passes through a dryer. Varnish is a colourless ink, and is applied like an ink through the ink unit in the printing press. When changing from ink to lacquer in the printing press, a careful cleaning must be done. Blankets are cleaned after the press run, and for larger runs, the rubber blankets and offset plates must be cleaned after a period of printing in order to remove paper dust. Many sheet-fed offset presses, especially larger or modern sheet-fed presses, are today equipped with automatic rubber blanket washers. During a press run the blankets can be cleaned while the press is still printing, but at a slower speed. When cleaning manually, solvent-drenched rags and, in many cases also water, is usually used. Water must be used to get rid of paper dust on the rubber blanket. Water-based lacquer can be applied through an in-line coating system fitted to the printing press or through the dampening unit or ink unit in an offset press, but also through separate off-line units. Lacquer that has not dried is cleaned off with water. Dried lacquer has to be cleaned regularly with solvents such as acetone, alcohol, or etylacetate. UV-curing lacquer can be applied through a in-line coating system fitted to the printing press or through separate off-line units in special lacquer machines or in screen presses. Cleaning is usually done only during longer breaks in the laquering, and is then done with alcohols. 8.2.8 Laminating

Lamination is the process where a plastic film is applied to the printed surface by wet or dry adhesives on one side of the sheet. The film covers the entire surface and cannot be applied on selected areas as in lacquering. Most laminating is done by special plants. In printing packaging plants, laminating usually is done in-house but in a special printing press. Laminating can be done with solvent-based systems, urethane systems, water-based systems or with a thermal foil. In the solvent-based system, an adhesive-coated film passes through an oven at a temperature of 60-80°C to get rid of the solvent before the film is pressed on to the printed surface. The solvent-based system is becoming less common, and is being replaced with the waterbased system or the two-component urethane system. In the urethane system, two components are mixed and react together to form a film. In the water-based system, an adhesive consisting of an emulsion of copolymers is applied to the film and then dried in an IR-dryer at a temperature from 70°C up to 100°C. Thermal lamination, where the adhesive is already applied to the film and then applied to the printed surface at a temperature about 100-120°C, is becoming more common, and many of the special plants and printers are using this system.

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8.3.1 Adhesive bindings

Process

Binding

Chemical/ Chemical compound

Water-based dispersion adhesive

Examples of chemicals used

Copolymers of polyvinylacetate, polyethene, polyacrylate, or polyvinylalcohol Biocides such as benzisothiazolines Plasticizers such as phthalates, glycerol. Polyethene/vinylacetate Wax, stabilizer, resins, fillers Aliphatic, alicyclic and aromatic hydrocarbons, acetone, alcohols

Hot-melt adhesive Cleaning solvents Cleaning of the machines and tools

8.3.2

Varnishing and lacquering

Comments

Mineral oil based 40% Vegetable oil based 40% UV-curable 20%

Chemical/ Chemical compound

Varnish

Process

Varnishing a printed surface

Examples of chemicals used

Bindings: Mixture of oils, resins, alkyds. Solvents: Mineral oils distillate with different boiling range. Additives such as catalytic driers, antioxidants, waxes, plasticizers.

Water-based lacquer

25%

Lacquering a printed surface

Bindings: polyacrylate, copolymers of polyacrylate Solvents: glycols, glycol ethers Additives such as catalytic driers, antioxidants, waxes, plasticizers and fungicides

UV-curing lacquer Solvent-based lacquer

65% 10%

Lacquering a printed surface Prepolymers, monomers + oligomers (acrylates), photoinitiator, and additives. Lacquering a printed surface Solvents: ethanol, butanol, propanol and ethylacetate. Wax, resin, plasticizer, and additives

Cleaning solvents

Cleaning the machines and tools

Aliphatic, alicyclic and aromatic hydrocarbons, alcohols, acetone, glycol ethers

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8.3.3

Laminating

Comments

40% 10%

Chemical/ Chemical compound

Laminating foils Solvent-based adhesive

Process

Laminating a printed surface Laminating a printed surface

Examples of chemicals used

Plastic film of polyethene, polypropene, polyacetate Resins, plasticizer, wax, additives Solvents: ethyl, isopropyl and n-propyl alcohols and their acetates, methoxy and ethoxypropanols, aliphatic hydrocarbon

Water-based adhesives

40%

Laminating a printed surface

Copolymers of polyvinylacetate, polyethene, polyacrylate or polyvinylalcohol Biocides such as benzisothiazolines Plasticizers such as phthalates, glycerol.

2-component adhesives Cleaning solvents

10%

Laminating a printed surface Polyurethane prepolymer, polyether/ester Cleaning the machines and tools Aliphatic, alicyclic and aromatic hydrocarbons, alcohols, acetone

8.4 Waste

8.4.1 Adhesive bindings

What is mentioned as waste are examples of kinds of waste that can be produced, but there is variation between different printing plants and different countries. Some of the waste that is mentioned in this section does not appear as waste in many places, as it is discharged as sewage instead. What is mentioned as waste in this section can also appear in the section environmental burden, discharges to water. All waste must be taken care of according to EC laws or individual country laws and rules. Paper waste should be sent for recycling. Adhesive residue, depending on the contain, can be hazardous waste or normal waste. Shop towels/cleaning rags, containing organic solvents and adhesives: hazardous waste EWC-code 15 02 02. Computers and other electronic equipment. Can be hazardous waste EWC-code 16 02 13. The management of hazardous waste is subject to strict regulatory requirements in EC legislation. Packages such as boxes, corrugated cardboard, cans, drums, plastic film, metal or plastic bands. Sorted and recycled or incinerated, depending on the legislation of the country. 8.4.2 Varnishing and lacquering

What is mentioned as waste are examples of kinds of waste that can be produced, but there is variation between different printing plants and different countries. Some of the waste that is mentioned in this section does not appear as waste in many places, as it is discharged as sewage instead. What is mentioned as waste in this section can also appear in the section environmental burden, discharges to water.

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All waste must be taken care of according to EC laws or individual country laws and rules. Paper waste should be sent for recycling. Varnish, depending on the contain, can be hazardous waste or normal waste. UV-curing lacquer, not cured: hazardous waste EWC-code 08 03 12. Water-based lacquer: normal waste. Cleaning agents containing solvents: hazardous waste. Shop towels/cleaning rags, containing organic solvents, varnish or lacquer: hazardous waste EWCcode 15 02 02. Paper rolls from automatic washing, containing organic solvents and varnish: hazardous waste EWCcode 15 02 02. UV-lamps from curing UV-lacquer: hazardous waste EWC-code 20 01 21. Computers and other electronic equipment. Can be hazardous waste EWC-code 16 02 13. The management of hazardous waste is subject to strict regulatory requirements in EC legislation. Packages such as boxes, corrugated cardboard, cans, drums, plastic film, metal or plastic bands. Sorted and recycled or incinerated, depending on the legislation of the country. 8.4.3 Laminating

What is mentioned as waste are examples of kinds of waste that can be produced, but there is variation between different printing plants and different countries. Some of the waste that is mentioned in this section does not appear as waste in many places, as it is discharged as sewage instead. What is mentioned as waste in this section can also appear in the section environmental burden, discharges to water. All waste must be taken care of according to EC laws or individual country laws and rules. Paper waste should be sent for recycling. Laminating foils, plastic foils, can be sent for incineration. Adhesives residues, depending on the contain, can be hazardous waste or normal waste. Cleaning agents containing solvents: hazardous waste. Shop towels/cleaning rags, containing organic solvents and adhesives: hazardous waste EWC-code 15 02 02. Computers and other electronic equipment. Can be hazardous waste EWC-code 16 02 13. The management of hazardous waste is subject to strict regulatory requirements in EC legislation. Packages such as boxes, corrugated cardboard, cans, drums, plastic film, metal or plastic bands. Sorted and recycled or incinerated, depending on the legislation of the country.

8.5 Environmental burden

8.5.1

VOC:

Adhesive bindings

Emissions to air

VOC is emitted from solvent-based adhesives. By using solvent-free adhesives, solvent emissions can be reduced.

Discharges to water

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Small quantities of wastewater can be produced from the cleaning process when water-based dispersion adhesives have been used. The waste-water can have high nitrification effects and be toxic to water-living organisms, depending on the contain of the adhesive. 8.5.2

VOC:

Varnishing and lacquering

Emissions to air

VOC is emitted from lacquering with solvent-based lacquers. The vapours are not recovered, as the lacquers contain a variety of solvents. Lacquering with UV-drying lacquers or water-based lacquers is an alternative, as is some type of treatment of the exhausted gases to reduce the VOC emissions.

Discharges to water Small quantities of wastewater can be produced from the cleaning process when water-based lacquers have been used. The waste-water can have high nitrification effects and be toxic to water-living organisms, depending on the contain of the lacquer.

8.5.3

VOC:

Laminating

Emissions to air

There are significant VOC-emissions, especially from laminating with solvent-based adhesives. The vapours are not recovered as the adhesives contain a variety of solvents. Laminating with water-based adhesives or using a urethane system or thermofoiling can be an alternative, as is incineration of the exhausted gases to reduce the VOC emissions.

Discharges to water Small quantities of wastewater can be produced from the cleaning process when water-based dispersion adhesives have been used. The waste-water can have high nitrification effects and be toxic to water-living organisms, depending on the contain of the adhesive.

8.6 Potential for improvements

8.6.1 Adhesive bindings

Not using solvent-based adhesives or using treatment equipment as catalytic incinerators for the exhausted gases containing solvents. 8.6.2 Varnishing and lacquering

Not using solvent-based lacquers or using treatment equipment as catalytic incinerators for the exhausted gases containing solvents. 8.6.3 Laminating

Not using solvent-based adhesives or using treatment equipment as catalytic incinerators for the exhausted gases containing solvents.

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DRAFT 8.7 Expectations for the future

8.7.1 Adhesive bindings

Developments of adhesives that will not create problems in the de-inking process. 8.7.2 Varnishing and lacquering

No new technology is known. 8.7.3 Laminating

Development of the two-component urethane system, as well as of UV-curing adhesives.

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DRAFT

9 Bibliography

Books, reports etc. Andersson, U., Flexografi, Framtidens tryckmetod för dagstidningar. Examensarbete vid KTH. 1989. Antonsson, A., et al. Lackering i grafisk industri, teknik, ekonomi,miljö. Arbetarskyddsnämnden. 1996. Brodin, L., J. Korostenski. Bästa tillgängliga teknik i grafiska branschen (BAT). Vägledning och tillämpning. Intergraf, Grafiska Miljörådet, et al. 1999 Brodin, L., J. Korostenski. Miljöbelastningar från grafisk industri i Sverige. Grafiska Miljögruppen. 1995. Brodin, L., J. Korostenski. Miljöbelastningar från grafisk industri i Sverige Screen-, Flexo-, Digitaltryck och efterbehandling. Grafiska Miljögruppen. 1997. CEPI, Annual Statistics 2000 Dalhielm, R., et al. Miljöprofilering ­ livscykelanalyser av grafiska produkter. IMT Teknikrapport nr 4/95. 1995. Davis, S. Is Blanket Washing taking you to the Cleaners? SBEAP Facts. December 2001. DeJidas, L. Alcohol-Free Printing, SecondSight Number 74 GATF World. 1999. Drivsholm, T., et al. Miljoeffekter og ressourceforbrug for 3 grafiske produkter i et livscykelperspektiv. Miljoprojekt nr. 341. Miljo och Energiministeriet Miljostyrelsen. 1997. Fleck, W., et al. Printing and the Environment. Guidance on Best Avaible Techniques (BAT) in Printing Industries. Integraf/EGF. 1999. Grafiska Miljörådet, et al., Kemikalier i grafiska och tidningsbranschen. 2002. Grafiska Yrkesnämnden, Flexografi.1991. Grafiska Yrkesnämnden, Offsettryckning. 1991. Grafiska Yrkesnämnden, Rullrotationstryckning. 1994. Grafiska Yrkesnämnden, Screenteknik. 1987. Grafiska Yrkesnämnden, Tryckfärg. 1992. Hallberg, Å. Grafisk ordbok för medianvändare. Natur och kultur. 2001. Hallberg, Å. Klart för tryck. Spektra. 1985. Impel Network, Printers, Good practice fact sheet. Swedish Environmental Protection Agency. 2000. Johansson, K ., et al. Grafisk kokbok. Guiden till grafisk produktion. Kapero grafisk utveckling. 1998. Johansson, M. Livscykelanalys av arkoffsettryckning. framkom verksamhetsutveckling AB, Rapport 2002:09. Dec. 2002. Lauritsen, K., et al. Renere teknologi i den grafiske branche. Miljoprojekt nr. 169. Miljo och Energiministeriet Miljostyrelsen. 1991. Seedorff, L., et al. Oplosningsmiddelfattige serigrafifarver. Miljoprojekt nr. 176. Miljo och Energiministeriet Miljostyrelsen. 1991. Silfverberg, E ., et al. Best available techniques (BAT) for the printing industry. Nordic council of ministers. Tema Nord 1998:593. 1998. Silfverstolpe, M., et al. Recycling of printed products. The environmental council of the Swedish Printing Industry, et al. 2000. Speirs, H. Introduction to printing and finishing. Pira BPIF Publishing. 1998. Stiftelsen TEM vid Lunds universitet, Vattenburen tryckning inom flexo. Nordisk Industrifond. 1994. Swedish Environmental Protection Agency, The Graphic Industry, industry fact sheet. 1990. Thompson, B., Printing Materials: Science and Technology. 1998. Todd, R., Printing inks, formulation principles, manufacture and quality control testing products. PIRA International. 2000. Törnklev, L. Grafisk tryckteknik, metoder, material, mätteknik. Spektra. 1987. Umweltbundesamt, Berlin, Integrierter Umweltschutz bei bestimmten industriellen Tätigkeiten. Teilband ll ,,Bedrucken", AFC Consult, BiPTO beratungsgesellschaft, Okopol Institu für Ökologie und Politik GmbH.

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Wallström, E, et al. Miljoparametre ved flexografisk trykning. Del 1. Miljoprojekt nr. 481. Del 2. Miljoprojekt nr. 482. Miljo och Energiministeriet Miljostyrelsen. 1999. Widing, A., et al. Handbok för miljöanpassad produktutveckling (MPU) av trycksaker. Framkom. 2000. Widing, A., et al. Miljönyckeltal för den grafiska mediebranschen. IMT Teknikrapport nr 6/99. 1999. Widing, A., et al Miljönyckeltal för tidningsföretag. Handbok för beräkning och användning. Framkom. 2002. Widing, A., et al Miljönyckeltal för grafisk industri. Handbok för beräkning och användning. Framkom. 2002. Wihlenborg, A. Tryckfärg, Sammansättning, förekomst och utveckling. Kemikalieinspektionen 2/92. 1992. Viilo, T. Livscykelanalys för vissa pappersprodukter. Jämförelse Italien ­ Finland. Tekniska Utvecklingsenheten, Helsingfors. Voss, P. Water-based Adhesives. Solventless lamination reduces flexible packaging VOCS. Flexo Magazine. February 2002. Web sites(http://) www.cepe.org www.edstroem.com www.emcentre.com www.epa.gov www.era.eu.org www.gpmu.org.uk www.howstuffworks.com www.ippaper.com www.mediaresourcepartners.com www.miljonet.org www.msu.edu www.oxydry.com www.plastisol_ink.printersbest.com www.pneac.org www.rrz.uni-hamburg.de www.screenprintingusainc.com www.techsolve.org www.ttab.se www.wmrc.uiuc.edu

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