Alcohol-free lithographic printing

Alcohol-free lithographic printing

J. Cleaner Prod. Vol. 5, No. 3, pp. 203-205, 1997 0 1997 Elsevier Science Ltd PII: SO959-6526(97)00021-8 ELSEVIER Alcohol-free lithographic All r...

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J. Cleaner Prod. Vol. 5, No. 3, pp. 203-205, 1997 0 1997 Elsevier Science Ltd

PII: SO959-6526(97)00021-8

ELSEVIER

Alcohol-free

lithographic

All rights reserved. Printed in Great Britain 09594526/97 $17.00 + 0.00

printing

Peter Bitto and Darrell Reeve DSC Chemport (Australia) Victoria 3061, Australia

Pty Ltd, P.O. Box 29, 41 Jesica Rd, Campbellfield,

Isopropyl alcohol has been in common use in lithographic fountain solutions for many years. It is flammable, volatile, toxic and expensive, and much of it is lost during production. This paper presents a new process that eliminates the alcohol by replacing it with a powerful magnetic field that has been proven effective in several commercial operations. 0 1997 Elsevier Science Ltd. All rights reserved Keywords: lithographic;

printing; fountain

solution;

Introduction Alcohol has been used as a fountain solution additive for at least 50 years, and its flammability, volatility and toxicity have been of considerable concern. In the process of printing, all the alcohol that is included in the fountain solution at the start is lost through evaporation into the atmosphere. Even with these disadvantages and the high cost of the alcohol, it is still used because of its benefits to the lithographic printing process, including increased printing speed, quality of print and reduction in waste paper. This paper discusses a revolutionary, non-chemical alternative to the use of alcohol.

How alcohol works Alcohol, in most cases isopropyl alcohol, provides four main advantages: 1. It reduces the surface tension of the fountain solution, providing more efficient and faster wetting of the printing plate. 2. It increases the degree of hydrogen bonding of the water molecules, resulting in increased viscosity of the water which is transferred better through the roller train of the dampening system and delivers more fountain solution to the printing plate. 3. The combined effects of delivering more water to the printing plate and of the water spreading on the surface of the plate faster give a much more effective and efficient dampening. The speed, quality and efficiency of the printing process are more than doubled with the maximum press speed of a sheetfed press rising from 7000-8000 to 13 000-18 000 impressions per hour. 4. Alcohol evaporates in the process of dampening

magnetic

(13-15% alcohol in the fountain solution tray to only l-2% in the solution on the printing plate): by the time this mixture and the ink are transferred to the printing blanket, most of the alcohol has evaporated. This evaporation removes alcohol from the system so that it cannot interfere with the rheology of the ink. Also, the evaporation removes the excess heat generated by friction during the printing process and therefore cools the system. The ink-water balance is wider, the viscosity of the ink is more constant (printing a sharper dot) and the plate cleaning process is much faster. If the alcohol is removed, the water setting on the press must be increased (sometimes giving catch-up or tinting problems), the ink-water balance will be more difficult to maintain (can cause an increase in piling and emulsification) and the fountain solution viscosity will be reduced (less efficient plate wetting).

The environmental

challenge

A fountain solution that substitutes for alcohol but which behaves in a similar way would be very desirable. Most substitutes have been successful in matching only one feature of the alcohol (for example, reduction of surface tension with other solvents, surfactants and blends). No substitutes have been found that will increase the hydrogen bonding of water to the same degree as alcohol (e.g. glycol ethers, glycols, polyglycols and surfactants). Other problems include nonevaporation, absorption by the printing inks, aggressive attack on the image area of the plate, blanket or rollers, sensitivity to ink and paper changes, and toxicity. The search for chemical substitutes has become very frustrating, and some radical thinking led to the search for a physical method to achieve the desired results. It has been known for many years that the use of

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Alcohol-free

lithographic

printing:

P. Bitto and D. Reeve

magnetic or electric fields can have dramatic effects on the physical behaviour of conductive solutions.

Lithographic alcohol eliminator

Shieldi

The unit is a very simple magnetic device which contains several pairs of very powerful new-generation, patented, neodynium magnets placed along a tube through which the fountain solution is circulated to the press. It is a non-chemical and environmentally friendly alternative to alcohol. The unit is like an electric generator, consisting of a magnetic housing which contains a rotor (Figure 1). The rotor consists of a coil of copper wire which rotates between the magnets, cutting through the magnetic field and generating electricity. The stronger the magnets, the faster the rotation and the more copper in the coil, the more electricity is generated. The fountain solutions are aqueous bases of various gums, organics and salts such as phosphates, nitrates, citrates, carbonates, sulphates, etc. which render them electroconductive. If the copper coil is replaced by the flow of the fountain solution, it will also generate an electric charge (Figure 2). The strength of the charge will depend on the strength of the magnetic field, the speed of the fountain solution and its composition. A better result can be obtained by selecting more suitable salts, capable of stronger ionization. The unit has been successfully tested with most commercial fountain solutions. Practical tests on numerous press installations demonstrate that, in every case, irrespective of the fountain solution, the alcohol level on the press can be reduced by at least go%, without any adverse effects on press performance or print quality (Figure 3). The inventor of the system has, naturally, formulated fountain solutions that optimize the performance of the units and give the best results in combination with each other. Each magnet in the system is permanent and gives in excess of 2500 gauss of magnetic force. No more

Powerful Neodynium Magnets

T Fountain Solution flow in Figure 2

Alcohol

Rotor (coil of copper wire)

than 0.1% of the magnetic strength is lost over 100 years. It has been shown that aqueous solutions, when subjected to powerful magnetic fields, will have an increased level of hydrogen bonding. This will, in turn, proportionally increase the viscosity of the water or fountain solution to the printing plate. The ionization of the electrolytes can be illustrated by looking at a molecule of trisodium phosphate. In the first stage, the molecule will develop a single negative charge. In the second stage it will develop a double negative charge. In the final stage it will develop a triple negative charge which is extremely powerful:

Figure 1

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The printing plates are made of anodized aluminium (positive charge) and will strongly attract the negatively charged fountain solution. This results in rapid wetting

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Reduction

Figure 3

Na,P04+Na2P0,

Magnetic Field

4

3

Alcohol-free

of the plate, effectively mimicking the surface tension reduction achieved by alcohol. The mechanism of wetting is different but the end-result is the same. The effect, similar to including isopropanol in the fountain solution, is achieved by the process in a nonchemical way. Laboratory tests and plant trials in the printing industry indicate other benefits: ?? Reduction

of calcium deposits on the rollers and the printing plate. The range of salts (calcium, magnesium, sodium, hydrogen, carbonate, chloride) present in tap water can lead to a range of printing problems. The calcium can react with the fatty acids in the printing ink, forming calcium soaps which deposit onto the surface of the rubber rollers, causing glazing, stripping and roller hardening. They can also deposit onto the non-image area of the printing plate, sensitizing it and resulting in dot gain and background tinting problems. Subjecting hard water to a powerful magnetic field will alter the crystalline structure of the salts dissolved in the water (nucleation) and prevent deposition. This fact is commonly used in the treatment of boiler feed water to prevent scale build-up. The system prevents salt deposition onto the inking and dampening rollers and into the grain of the non-image area of the printing plate. The life of the rollers is extended, waste is reduced and quality of print is increased. ?? Reduced ink emulsijication. Printing inks are formulated to take up 4060% water during interaction with the fountain solution on the press. If the takeup is high, emulsification occurs and the ink has greater affinity for wet surfaces, causing plate tinting, ink feedback into the dampening system, blanket piling and strong ink contamination of the fountain solution. The ink/water emulsion is charged, consisting of the negatively charged oil-based printing ink, surrounded by the positively charged outer layer of surfactants and water. When this is subjected to a strong magnetic field, the charges are disrupted and the system falls apart or becomes de-emulsified. Thus, the process will break down the emulsion, providing a cleaner fountain solution with less contamination and with the added advantages of cleaner running, fewer wash-ups, less waste and higher quality print.

lithographic

printing:

P. Bitto and D. Reeve

?? Reduced

blanket piling. This is achieved by the effect of the magnetic field on hard water. The process will reduce the deposition of calcium carbonate fillers present in the paper onto the surface of the blanket which, with poor-quality stock, is one of the major causes of blanket piling. ?? Retardation of bacterial growth in the fountain solution. The positive and negative, small, discrete electrical charges present on the bodies of bacteria can be disrupted by magnetic fields, resulting in retardation of their ability to reproduce. The mechanism is not fully understood but the end-result is cleaner, less-contaminated dampening systems and reduced levels of chemical biocides. a Real benefits to non-alcohol dampening systems such us brush and turbo dampening. Commercial tests have shown increased efficiency of the dampening systems and substantially reduced water settings on the presses. There has been a more even distribution of the fountain solution on the plate as well as increased print quality and reduced waste.

Economic benefits The typical unit costs about US$800 and the average pay-back achieved commercially has been less than 6 months, depending on the usage rate of isopropanol for the press.

Conclusions The process is a non-chemical, environmentally friendly system which offers a low-cost alternative to isopropanol with the added benefits of cleaner running, better print quality and reduced waste. The units are very simple to install and do not require electrical connections. They are totally maintenance-free and will perform during the entire life of the press. The process is not a cure for all problems. It will not compensate for incorrectly set presses, faulty rollers, poor water quality or insufficient press maintenance. The basic principles and requirements of lithographic printing still apply. However, this Australian invention provides an alternative to costly and polluting alcohol evaporation. More detailed information can be obtained from the authors.

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