which mandates that a company generating hazardous waste is forever respon-

Transcription

1 Ink a vs. Plastisol Water-based Qlozces Opinion by Allen Sales When comparing water-based and plascradle-to-grave waste-management legislation which mandates that a company generating hazardous waste is forever respon- Allen Sales is president of TAL-INK (Marietta, tisol textile inks, it is first important to sible for that waste, regardless of its means Ga.). He s been know that from a chemical standpoint the of disposal. Thus, a waste generator must associated with raw material (the monomer) used in each know the disposition of its hazardous the garmentwaste (typically accomplished through product is similar. screen-printing Plastisol is made form a hydrocarbon obtaining and keeping on file - even industry for over resin known as polyvinyl chloride (PVC), after the generating business closes or is 25 years, and with w% e water-based inks are made from a sold - disposal documentation from a the development modified-hydrocarbon resin known as certified removal company, hired specifiof water-based acrylic. As a function of processing, the cally for the purpose). So the main environmental drawback in the use of plastisol textile inks for 15. levels of volatile organic compounds (VOCs) in both systems are reduced to a point that, in fact, they re both considered low-voc products. The VOCs in waterbased systems are further reduced by the introduction of water which constitutes approximately 50 percent of the base resin used in such products. Beyond chemistry, the real difference is in the manner in which both inks are inks, even though their VOCs are rendered inert during processing, is that they still represent a potential hazard to the environment. This is because they re removed from screens with solvents which themselves are typically 100 percent VOCs. On-site reclamation of spent solvents is not (to my knowledge) available at this time, so all solvents, including solventremoved from screens and equipment - bearing rags, must be removed from your itself only significant if you understand that any waste that s not disposed of judiciously becomes a potential environmental hazard. facility by the certified handler. On the other hand, the main environmental drawback in the use of water-based inks is the disposal of liquid effluent resulting from the cleaning (typically accomplished with water) of screens and equipment. Although spent solvents will Conservation and Recovery A continued on page 30 IIINF 1902 PWINTWFAR MACATlNF 17

2 NOTE TO READERS: The following feature is an Opinion/ ditorial presentation and does not necessarily reflect the views of Printwear Magazine. Qur intention is to offer an uncensored, dialogue on a topic of continuing industry dispute - water-based verfus plastisol ink systems - via essays from supporters of each system followed by rebuttals to one another s positions. Please bear in mind that the authors of these essays are manufacturers of their respective inks, and were permitted to present their own positions in the best possible light. They were also allowed to be as outspoken as they wished about their competitors products - in other words, no holds barred. Accordingly, we urge that before relying on any of the assertions presented below, readers seek authentication from other sources such as local authorities, product manufacturers and literature, the SPA1 and Printwear s in-depth coverage of the subject, last month.

3 Dry/cure scenario: Though many point to curing as a water- based drawback, the author claims that, given the right clrcumstances, it needn t be a problem. not be approved for this type of disposal, it is likely that your local water district will approve drain disposal of water-based effluent; this permission is obtained by sending them copies of your MSDSs. There are a variety of reclamation systems currently available, designed for treating water-based effluent on site, which remove the solid particles from the water, leaving clean water that can be reused or drained. The solid remains of these systems can be reclaimed for recycling. Fire hazard One of the most dramatic differences in the waste products from the two systems is flammability. Solvents of any type, whether fresh or spent, are flammable and must be properly stored; you may need special cabinets and permits for storage. Ventilation is also a solvent concern. Do you recirculate air in your facility sufficiently to remove accumulated solvent fumes? You ll need floor-level fans and vents too, since solvent fumes (heavier than the ambient atmosphere) cling to the floor rather than traveling up to where most venting is located - just like solvents, these fumes are ignitable when found in concentration. The fire department will also want to inspect your MSDSs to determine the best way to handle a fire in your shop if one occurs. If solvents are present, they may elect to only control, rather than extinguish, a fire, due to toxic fumes and solvents low flash points(70- ZOOOF). Since water-based effluent is not flammable, it does not present the same problems in use or when stored for disposal or reclamation. The water-based inks themselves have no flash points because they re made without solvents. In the removal process, these inks are further diluted with water, further reducing the fire hazard. In practice ; We all know that plastisol inks may be left in the screens on press for long periods of time. This is not the case with waterbased inks, which must be removed from the press immediately to prevent drying-in and loss of screens. However, this need not be a problem in a shop properly prepared to use water-based inks. Housekeeping is also an issue. In the plastisol shop, we typically see open buckets of ink as well as ink-laden squeegees, screens and so on. With waterbased inks, care must be taken to replace ink-container lids and to clear screens, squeegees and spatulas. Water-based inks, when spilled, will dry and can be easily removed; cleaning up a plastisol spill is quite a different situation. Thus you will notice that in a water-based shop there are little or no solvent odors. The physical act of applying the two

4 Our btggest fans: Ventilation, claims the author, must also circulate at ground level in a plastisol shop, because solvent fumes are heavier than ambient air.. systems will vary with each individual s prefer. Some equipment manufacturers do not believe water-based inks are suitable for manual printing. I don t adhere to this theory, though, simply because the equipment itself cannot differentiate between plastisol and water-based ink in the screen. I believe instead that if the printer is adept at running water-based production... it will work. There are, though, some things you just cannot do with water-based inks. No, you can t leave them in screens overnight. With a flood coat, though, we ve left them idle in our screens for over an hour with no ill effects. For the automatic printer, some equipment adjustment will be necessary (such as lowering squeegee pressures). Another change all printers will have to make is to water-resistant emulsions, available from most emulsion manufacturers. When making screens for water-based inks, you must make sure the emulsion is totally dry. These emulsions are made with polyvinyl alcohol (PVA), a chemical that, unless bone dry, will absorb water out of the ink and cause premature screen breakdown. Though this is often blamed on the inks, it s usually a function of improper screen making. The cure Despite many printers applying the terms curing and drying synonymously, they re not the same. Since both plastisol and water-based inks are based on hydrocarbon resins, they both need to be cured; water-based, though, must first be dried. Although water-based inks will air dry, their washfastness will suffer; thus, a proper dry/cure scenario - achieved at times and temperatures that vary from 360 F for 45 seconds in electric dryers to 350 F for two minutes with gas - is strongly advised. The most important thing overall is driving that water out quickly. This requires maintaining an ink temperature of 212 F (to boil the water off) and is most easily achieved by heating the ink rapidly at the front end. Good air flow is then required to remove water vapor from the chamber (the shorter the chamber, the more need for high air flow), while the remaining length of the heat chamber actually cures the ink. Fnr Insert Circle Reader Service No. 206 JUNE 1993 PRINTWEAR MAGAZINE 33

5 Dryinglcuring is a very important aspect and must be done correctly. So remember that what is a proper cure for the guy across the street may not be proper for you. You must experiment with your equipment, your ink and your overall pro- CedUre. The bottom line A question every screen printer considering a change should be asking is: How much is this going to cost me? If it doesn t benefit your company financially, a change or even a partial change may be unwise. However, such change may come upon you not by choice but by necessity. There are advantages to water-based inks to which both consumers and legislators are sensitive. For consumers, these include soft hand (especially after washing) and breathabilty. Water-based prints can be lighter and brighter. Many water-based inks will take on the appearance of dyes that actually do have a more appealing look and feel. As for legislators, they care little for aesthetics. To them, the important water-based differences concem the hazard and environmental considerations described above. Basic materials cost, though, is still a factor. Water-based inks are not usually priced higher than plastisol (if they are, you may well be paying too much for water!). Some manufacturers use higher quality raw materials than others - obviously, the better the quality, the higher the price. As a printer and a consumer, you will have to test several products to determine the one most suitable for you. The most important things to consider are these: washfastness, color brilliance and printability. Remember, if you can t run it, don t buy it. Some facts * Both the toxicity levels and the fire hazard of spent solvents are significantly higher than those of effluent generated by water-based inks. * Solvents are 100 percent VOC and cleaning units in most areas must be closed when not in use; some areas of the couniq quire a permit for their operation. * When using solvents, you may need to improve your ventilation system to insure the safety of your employees. * Permits may be obtainable from your local water district that allow you to flush designated amounts of water-based effluent; or, it can be treated on site with currently available reclamation systems. * You should qualify for lower insurance rates if solvents are removed from your shop. Ea I Fire safety: Given the customary presence of solvents in a plastisol shop, says the author, flash points, vapors, dirty rags and other fire hazards are a concern. I Rebut t a I by Stuart ]ones There is no question that the presence and use of solvents can raise concerns for any print shop. However, many plastisol users are currently flushing their approved effluent down the drain - legally - in conjunction with the many water-soluble cleaning agents now available. Also, the reclamation systems which remove solids from the effluent can be used with plastisols which have been cleaned up with one of the aforementioned cleaning agents. With the use of solvents greatly reduced or eliminated, your choice has just become simpler yet. For shops that cannot eliminate the use of solvents (those, for example, using ink systems for other than textile printing), there are solvent-recovery and -distillation systems available which allow the reclamation of used solvents; some large plastisol users have already converted to this method of disposal. For most operations, the improved process efficiencies attributed to the use of plastisols will more than pay the cost of converting to one of these systems.