Draft Document. Description of the Printing Processes Technical Annex1

Transcription

1 Draft Document Description of the Printing Processes Technical Annex1

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3 1 1 Overview 3 2 Offset (lithography) Printing materials and products Process description Chemicals Waste Environmental burden Potential for improvements Expectations for the future 30 3 Flexography Printing materials and products Process description Chemicals Waste Environmental burden Potential for improvements Expectations for the future 44 4 Gravure Printing materials and products Process description Chemicals Waste Environmental burden Potential for improvements Expectations for the future 55 5 Screen Printing materials and products Process description Chemicals Waste Environmental burden Potential for improvements Expectations for the future 65 6 Letterpress Printing materials and products Process description Chemicals Environmental burden Potential for improvements Expectations for the future 74 7 Digital printing Printing materials and products Process description Chemicals Waste Environmental burden Potential for improvements Expectations for the future 79

4 2 8 Post-press or finishing Finishing products Process description Chemicals Waste Environmental burden Potential for improvements Expectations for the future 87 9 Bibliography 88

5 3 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 Letterpress was the earliest form of printing but has been superseded by offset.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,

6 4 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.

7 5 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 Heatset weboffset printing Coldset weboffset printing cleaning cleaning 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

8 6 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 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 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.,

9 7 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

10 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

11 9 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 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 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.

12 10 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.

13 11 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 copies up to copies, which means more cleaning than in web offset presses. Larger-size sheet-fed presses print up to 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 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

14 12 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 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:

15 13 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 % 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 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

16 14 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.

17 15 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 Pre-press, image preparation Chemical/ Process Examples of chemicals used Chemical compound Photographic film and paper Emulsion of silver halide and gelatine Developer Developing of film and paper Hydroquinone, phenidone, metol, potassium or sodium sulphite, potassium carbonate, potassium or sodium hydroxide, potassium bromide, sodium silicate Fixer Fixing of film or paper Ammonium thiosulphate, sodium acetate, sodium sulphite, glacial acetic acid Cleaning solutions Cleaning the rollers in the developing machine Sulpamic acid, thiocarbamide,, sodiumhydrogen sulphate, chromium salts, surfactants Correcting fluid Correcting exposed film Potassium ferricyanide, potassium permanganate Proof print developer Developing of proof print in the wet process Sodium carbonate, sodium hydroxide, surfactants Colour foils Proof print process Platemaking Chemical/ Process Examples of chemicals used Chemical compound Offset printing plates Both negative or positive plates can be used. Aluminium, paper or plastics, diazopolymers, photopolymers, binders, dyestuff. Silicones (waterless plates). Plate developer positive Developing of positive offset Alkaline solution as sodiumphospat, sodium

18 16 Plate developer negative plate. Developing of negative offset plate. 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. 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 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 Mineral oil based 50% Vegetable oil based 40% Comments Process Examples of chemicals used UV-curable 10% Printing 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

19 17 Varnish Mineral oil based 40% Vegetable oil based 40% Cleaning solvents Fountain solution UV-curable 20% Aliphatic products 25% Alicyclic products 10% Aromatic products 20% Vegetable oil esters products 10% Hybride products 30% Other solvent products 5% Cleaning the blankets, ink rollers, ink ducts, impression cylinder etc. Wet the surface of the printing plate. inks). UV-inks: pigment, prepolymers, monomers + oligomers (acrylates), photoinitiator and additives. Bindings: Mixture of oils, resins, alkyds. Solvents: Mineral oils distillate with different boiling range. Vegetable oils. Isopropyl alcohol Additive to fountain solution. isopropyl alcohol. Anti-set-off powder (sheetfed offset) Plate cleaner/image preserver Different process chemicals as ink preserver, tack reducer, dryers 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. Additives such as catalytic driers, antioxidants, waxes, plasticizers and fungicides (vegetable inks). UV-varnish: Prepolymers, monomers + oligomers (acrylates), photoinitiator and additives. Aliphatic, alicyclic and aromatic hydrocarbons, vegetable oil esters, fatty acids, glycol ethers Glycol ethers, 2-butoxy ethanol, phosphoric acid, citric acid,, wetting agents, surfactants, corrosion inhibitors, gum arabic, biocide as isothiazoline. Starch, chalk. 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.

20 18 Heat-set web offset Chemical/ Chemical compound Ink Mineral oil based 95% Vegetable oil based 5% Cleaning solvents Fountain solution Comments Process Examples of chemicals used Aliphatic products 25% Alicyclic products 15% Aromatic products 5% Vegetable oil esters products 10% Hybride products 40% Other solvent products 5% Printing Cleaning the blankets, ink rollers, ink ducts, impression cylinder etc. Wet the surface of the printing plate. Pigment such as calcium carbonate, carbon black, aluminium hydroxide, phtalocyanine, rhodamin etc. Bindings: Isopropyl alcohol Additive to fountain solution. Isopropyl alcohol. Plate cleaner/image preserver Different process chemicals as ink preserver, tack reducer, dryers 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. 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. Aliphatic, alicyclic and aromatic hydrocarbons, vegetable oil esters, fatty acids, glycol ethers Glycol ethers, 2-butoxy ethanol, phosphoric acid, citric acid,, wetting agents, surfactants, corrosion inhibitors, gum arabic, biocide as isothiazoline. Petroleum distillates, phosphoric acid, acetic acid, propylenglycol ethers, surfactants 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

21 19 Chemical/ Chemical compound Comments Process Examples of chemicals used Ink Mineral oil based 40% Vegetable oil based 50% Cleaning solvents Fountain solution Isopropyl alcohol (formprinting) Plate cleaner/image preserver Different process chemicals as ink preserver, tack reducer, dryers UV-curable 10% Aliphatic products 30% Alicyclic products 15% Aromatic products 10% Vegetable oil esters products 10% Hybride products 30% Other solvent products 5% Printing Cleaning the blankets, ink rollers, ink ducts, impression cylinder etc. 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. 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. Aliphatic, alicyclic and aromatic hydrocarbons, vegetable oil esters, fatty acids, glycol ethers 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 2.4 Waste Pre-press, image preparation Film or paper containing silver EWC-code : normal waste Film developer: hazardous waste EWC-code Fixer: hazardous waste EWC-code Rinsing water from film development, depending on the silver concentration: hazardous waste EWCcode Proof print developer: hazardous waste EWC-code Colour foils can be sent for incineration Cleaning agents for the film developing machines containing chromium salts: hazardous waste

22 20 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 Computers and other electronic equipment. Can be hazardous waste EWC-code 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 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 and Plate developer, solvent-based: hazardous waste EWC-code Plate developer containing silver: hazardous waste EWC-code 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 Computers and other electronic equipment. Can be hazardous waste EWC-code 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 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.

23 21 Sheet-fed offset ink, UV-ink, not cured: hazardous waste EWC-code Offset varnishes, depending on the contain, can be hazardous waste or normal waste. Offset varnishes, UV-curing, not cured: hazardous waste EWC-code Cleaning agents containing solvents: hazardous waste. Shop towels/cleaning rags, containing organic solvents, ink, or varnish: hazardous waste EWC-code Paper rolls from automatic washing, containing organic solvents, ink, or varnish: hazardous waste EWC-code Spray cans, not empty: hazardous waste. UV-lamps from curing UV-inks and varnishes: hazardous waste EWC-code Computers and other electronic equipment. Can be hazardous waste EWC-code 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 Paper rolls from automatic washing, containing organic solvents, ink, or varnish: hazardous waste EWC-code Spray cans, not empty: hazardous waste. Computers and other electronic equipment. Can be hazardous waste EWC-code 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

24 22 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 Cleaning agents containing solvents: hazardous waste. Shop towels/cleaning rags, containing organic solvents, ink or varnish: hazardous waste EWC-code Paper rolls from automatic washing, containing organic solvents, ink or varnish: hazardous waste EWC-code Spray cans, not empty: hazardous waste. UV-lamps from curing UV-inks: hazardous waste EWC-code Computers and other electronic equipment. Can be hazardous waste EWC-code 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 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 Photographic paper, film Foils (masking-, blanking-, colour-) Film developer Fixer solution Correcting fluids Proofs developer Emissions to air: Ammonia Sulphur componds Acetic acid Volatile compounds

25 23 Figure 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 O 2 /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.

26 24 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 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 Emissions to air VOC: 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 CO 2 and H 2 O. In the EC VOC-directive (1999/13/EC) the emission limits for treated gases are 20 mg C/Nm 3 for

27 25 a solvent consumption of >25 tons/year or 100 mg C/Nm 3 for a solvent consumption of 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 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/nm 3. 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.

28 26 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 Pre-press, image preparation 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%.

29 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% 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 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 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 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 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:

30 28 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. 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 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:

31 29 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/nm 3. 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

32 30 being volatile organic solvents (VOC). These cleaning agents have a flash between 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. 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. 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 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.

33 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 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

34 32 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