United States Environmental Protection Agency Risk Reduction Engineering Laboratory Cincinnati, OH ,45268 Research and Development EPA/600/SR-93/086 July 1993 ? EPA Project Summary Ink and Cleaner Waste Reduction Evaluation for Flexographic Printers Gary D. Miller, William J. Tancig, Michael J. Plewa, and Paul M. Randall The report summarized here de- scribes the technical and economic ef- fects that occurred when a flexographic label print shop changed the type of ink and cleaning agent used in the shop. The changes were undertaken as the best way to eliminate all hazardous materials. The company's management mandated the switch out of concern for its employees and with the inten- tion of limiting possible future waste liability. Hence, the traditional alcohol- based inks and alcohol solvent clean- ing agents gave way to water-based inks and an aqueous cleaner. From a technical point of view, there is general agreement in this shop that the water-based inks yield better qual- ity labels. Labor is reduced largely be- cause the water-based inks are more easily removed from the pans, rollers, and plates. Ink splashes and spills are also quickly removed by sponging ei- ther with water or with the aqueous cleaner. As a result of these process modifi- cations, solvent emissions to the plant air have been reduced about 80%. The toxicity of the gaseous and liquid wastes has also been reduced approxi- mately 90%. Hazardous liquid wastes have been eliminated while wastewater sent to the sanitary sewer has in- creased. Solid wastes have remained relatively unchanged. The water-based inks brought about major savings because most of the liq- uid wastes do not now require disposal as hazardous wastes. The ink wastes are presently acceptable at the local public waste treatment plant The clean- ing towels and wipers are now either rinsed within the plant or sent to a commercial laundry; formerly, they had to be labeled as hazardous and segre- gated for special disposal. Though un- treated ink washes are acceptable to the waste treatment plant, the company has chosen to filter theirs through a special absorbent to remove all color. The used absorbent is acceptable in the local landfill. For this company, these changes in- volved no capital expenditures other than the absorbent unit. With the levels of various alcohols evaporated during printing now greatly reduced, the em- ployees enjoy a cleaner and healthier plant environment. This summary was developed by EPA's Risk Reduction Engineering Laboratory, Cincinnati, OH, to announce key findings of the WRITE program demonstration that is fully documented in a separate report (see ordering in- formation at back). Introduction A Waste Reduction Innovative Technol- ogy Evaluation (WRITE) (with the Illinois Department of Energy and Natural Re- sources [ENR] and the U.S. Environmen- tal Protection Agency [EPA]) was designed to (1) quantitatively compare the volume and toxicity of any waste generated dur- ing printing and released as gaseous, liq- uid or solid waste before and after switch- ing to water-based inks and a detergent cleaner and (2) determine the economic Printed on Recycled Paper ------- effect of modifying a traditional printing technology. This project evaluated flexographic print- ing of labels in commercial quantities. The participating firm was a narrow-web flexographic printer, MPI Label Systems, Inc., of University Park, IL MPI Label Sys- tems' plant is in a modern, one-story, clear span building. Its printing capabilities are based on several narrow-web flexographic presses each capable of printing one to six colored inks. Several years ago, management di- rected the company's eight plants to elimi- nate the use of all hazardous and toxic materials. The incentives included a de- sire to eliminate employee exposure to any liquid or gaseous hazards resulting from handling these materials and an equal desire to minimize the possibility of future litigation resulting from use of such sub- stances. The decision forced each plant to sub- stitute water-based inks for alcohol-based inks, and at the same time, change from alcohol solvent cleaning agents to aque- ous type cleaning agents. Water-based inks were substituted for those formulated with alcohols since the water-based inks were already available on the commercial market. Implementing this change, however, required extensive cooperation between the ink manufacturer and the printing plant because of different printing conditions, changing customer re- quirements, and the paper stock require- ments associated with the water-based Inks. Because water-based inks are easier to remove or clean with aqueous agents when wet, a terpene-type (d-limonene) cleaner was initially tried. Later, a dilute aqueous solution of detergent proved to be even easier to handle, odor free, and less expensive. As cleaning agents are Introduced to the commercial market, MPI Label Systems routinely tests them to de- termine if they can improve their process and be even safer for the environment. , Printing Background Most printing operations function in a similar manner. Ink of the desired color and viscosity is supplied to the printing press where a rotating roller continually removes a thin layer of ink from the reser- voir. This thickness is carefully and pre- cisely controlled. Ink is then applied to the printing plate, followed by transfer to the printing stock. In the case of flexography, the plate is flexible and is wrapped around a separate roller. Customarily, when print- ing labels, a continuous sheet of paper receives an ink imprint of the image on the plate. When more than one color is involved, a separate plate is used for each color; each plate must be in registration for all the colors to be properly placed and rendered. Paper stock for most labels is a two-ply material. The top ply, on which the labels are printed, normally has its bottom sur- face coated with an adhesive that ad- heres to the silicone-treated top surface of the bottom ply. Immediately after the plate applies ink to the label stock paper, the web moves through a heated drying area (70°C for this plant's press). Each dry label is then pressured by a steel cutting die that physically severs the top ply of label stock but does not remove the label from the surrounding blank stock. Moments after a label is severed from the surrounding stock by the die cutter, the print-free waste paper stock is peeled away from the bottom ply and collected on a separate roll destined for incineration or a landfill. The labels, still adhering to the bottom ply, go to another roll and are processed for shipment to customers. Waste Reduction Wastes are generated at most stages of the printing process. Ink wastes result when the reservoir, the various rollers, and the printing plate are cleaned at the end of a run. Excess ink in the reservoir can be collected for reuse, but the other ink quantities removed during cleaning generally remain as waste. MPI Label Sys- tems keeps a 50-gal barrel of water adja- cent to each press. During cleanup when water-based inks are used, soiled parts and cleaning towels are rinsed in this wa- ter to remove ink residues. At the end of the week, barrels of rinse water are trans- ferred to an ink splitting device that ab- sorbs the various ink pigments on a cellu- lose-based porous material; the nearly clear filtrate passes through for disposal in the sanitary sewer, with permission from the local water treatment plant. The pig- ment-colored cellulose is accepted at the local landfill along with paper wastes from the print line. Some paper wastes accu- mulated during setup operations are un- avoidable, although an experienced printer is usually able to minimize them. Excep- tional amounts of waste labels are, how- ever, occasionally generated during the production of multicolor labels because of color registration difficulties. The adhesive- based, print-free stock surrounding each label is collected on a separate waste roll. Most printing processes begin with a photographic negative. Developing the negative generates a number of chemical wastes that usually require special treat- ment for either recycling or disposal. The photographic chemicals used in produc- ing the master negative account for small amounts of waste, though the silver is usually recovered. At least for flexography, the plate is developed after exposure to a bright light and by washing away the un- exposed areas with a solution. In nearly every step of the printing pro- cess, some volatile chemicals are released into the air. In some cases, this occurs as a result of process design; in other in- stances, it occurs simply because of the volatile nature of the materials. These volatiles can range from water to various alcohols, plastic ; thickeners, homogeniz- ers, and chemical diluents. Each ink loses volatile material as a result of storage in the open.ink reservoir; during rotation on the various rollers that determine the film thickness to be applied to the plate; as lost material on the plate; and during the heated drying phase. The ink ultimately reaches a rub-off-free state after the ma- terial on which it is printed passes through the heated drying zone. In addition to vola- tile losses associated with the inks, adhe- sive and solvent molecules evaporate from the adhesive-coated label surfaces as a result of simple exposure to the air. As with many chemicals, only a few mol- ecules per cubic meter can, in some cases, create breathing .distress for hypersensi- tive individuals, and the sensitive individu- als must leave the contaminated area. Cleaning agents used on the press will also evaporate into the air. These clean- ing solvents can range in type from water with small concentrations of detergents to various organic chemicals. Procedure The project compared the volume and toxicity of any gaseous and liquid wastes produced by the printing process before and after switching to water-based inks and an aqueous cleaner and then deter- mined the economics of such process changes. Laboratory measurements estimated the solvent loss from the inks by measuring the portion of the inks that evaporate and the materials used in the plant and by basing the calculations on the composi- tion of the inks. Laboratory measurement of solvent loss by evaporation for each ink was used to estimate the percent volatiles. The amount of ink on waste labels Was estimated by subtracting the total number of labels printed from the number of labels acceptable as product. These results were compared with the weight of volatiles in each ink as reported on i:he material safety data sheets. The alcohol-based ink con- tains six volatile components; four of them ------- are alcohols, and ethyl alcohol and iso- propyl alcohol are present in the largest amounts. By comparison, the water-based ink contains four volatile components, with most of the volatiles being water (65%) and isopropyl alcohol (5%). Some of the water, about 24%, is bound to the resins and does not evaporate on drying. Both the solvent cleaner previously used and the new detergent cleaner contain over 97% volatiles; again the detergent cleaner is mostly water. The amount of ink and other materials disposed of as liquid waste was determined gravimetrically, using a special rotating apparatus that exposed a continual and new thin film of ink to a constant, low-pressure air jet while the entire apparatus was kept at 70°C, for two printing runs. This approach minimized burning, charring, or spattering of ink as its viscosity continued to increase during solvent evaporation. This particular test was run in triplicate; samples achieved constant weights, ± 5 mg. Results Emissions from Inks and Cleaners Because MPI Label Systems no longer uses alcohol-based inks nor permits them in the plant, the actual emissions of these inks during in-plant runs was not mea- sured. The percent solids in each ink (and indirectly, thereby, the amount evaporated) was determined gravimetrically in the labo- ratory. These measurements (Table 1) in- dicate the proportion of the alcohol-based ink that evaporated was 48% compared with 56% to 62% for the water-based inks. To .estimate emissions that would have resulted from using solvent-based inks, it was assumed that the same amount of solids (or ink retained on the labels after drying) would have been used for printing the labels with alcohol-based inks as was used in printing with water-based inks. Then the total amount of ink that would have been used and the weight evapo- rated were calculated by using the per- cent loss factor determined in the labora- tory. Since a smaller percentage of alco- hol-based ink was lost to evaporation, more solids per gram of ink would be applied to the labels than with the water- based ink. Thus, less total alcohol-based ink was assumed to be used and less total weight of components would be lost via evaporation. The in-plant measurement results are shown in Table 2. The water- based inks-use data were obtained during two evaluated runs: One run was approxi- mately 55,000 labels; the other about 250,000. In each case, the total weight of ink materials added and the weight of materials remaining at the end of the run were measured. The difference was the weight of material that was assumed to be either evaporated to the shop air, dried on the labels, or wasted. The portions evaporated and retained as solids were calculated with the use of the laboratory data presented in Table 1. The press operators at MPI Label Sys- tems estimated that about the same total amount of either ink is required for a job. Thus, this emission analysis is conserva- tive for the alcohol-based ink. For com- parison, the volume of alcohols evapo- rated during a printing run was calculated from the known formulations based on the total amount of ink used during each print- ing run. The laboratory evaporation loss results also agree quite well with the total volatile component data shown on the material safety data sheets. Concentrations of each volatilized com- ponent in the plant air were calculated Table 1. Weight Loss Data from Laboratory Evaporation at 7CPC Material Initial wt., gm Water-based 12.17 black ink Water-based 12.05 green ink Water-based 12.22 purple ink Alcohol-based 15.38 black ink Detergent cleaner 12.56 Average of triplicate runs Dry wt., Wt. loss, gm gm 5.30 6.87 5.04 7.01 4.66 7.57 7.99 7.38 0.28 2.22 Std. dev., gm 0.42 0.21 0.20 0.60 0.03 %Loss 56.5 58.2 61.9 48.0 97.8 based on the volume of air in the shop area and the air exchange rate (Table 3)^ These concentrations are the levels ex- pected during continual operation of the press assuming all six print stations are being used to apply ink. Ammonia and dimethanolamine levels were highest for the water-based inks. For the alcohol- based inks, isopropyl alcohol, methyl al- cohol, n-propyl alcohol, ethyl alcohol, ethyl acetate, and Varnish Makers and Painters (VM&P) naphtha levels were higher. : Liquid Wastes The amount of liquid wastes generated from printing with the water-based inks was measured during the two printing runs. These wastes (consisting of ink left in the reservoir, and on rollers, gaskets, and plates) were produced during cleanup at the end of each run. For the green labels, 24.6 g of ink and 44.3 g of cleaner were used. A more experienced operator only produced 56.4 g of liquid waste from prirtt- ing the purple labels. The concentration of ink and cleaner components estimated to be present in the wastewater from the facility (before treatment) is shown in Table 4. These concentrations were estimated assuming that each day the ink pans were all in Use and cleaned out into a 50-gal tank, every week the tank was discharged, and most of the waste resulted from use of the cleaners. From the water-based inks, over 85% of the liquid waste was water. Other constituents of concern were acrylic resin, azo pigments, and isopropyl alcohol. Con- centrations of constituents from the alco- hol-based inks, if they had been disposed of in the same manner, were estimated to be much higher. Toluene, isopropyl alco- hol, acetone, resins, pigments, and ethyl alcohol were the major constituents of con- cern. Before implementing the use of water- based ink and detergent cleaner, the sol- vent-based waste ink was disposed of as a hazardous waste and was thus mani- fested. No liquid ink wastes were sent to the sanitary sewer before the use of wa- ter-based inks. Although the total amount of liquid solvent-based waste manifested in a year was on company records, this information was considered proprietary and was not made available for the purposes of this project. It was not possible to di- rectly measure the amount of alcohol- based ink and cleaner wastes that would have been generated from printing runs similar to those evaluated with the water- based inks. Company officials reported that in their experience, the amount of solid and liquid wastes generated are es- ------- Table 2. In-Plant Ink Use and Estimated Emissions Green Labels Parole Labels Measured Water-based ink Alcohol-based ink Water-based Alcohol-based ink ink Total Ink used, Ink solids on labels, Weight evaporated, g 1459 609.8 849.1 1175 609.8 565.2 399.2 152.1 247.1 293.1 152.1 141.0 Table 3. Estimated Concentration of Air Emissions, \ig/L Components Water-based ink Purple Labels Green Labels Alcohol-based Ink Water-based ink Alcohol-based ink Isopropyl alcohol Ammonia 5.3 1.1 7.3 6.0 1.2 9.2 Dimethyl 1.1 ethanolamlne Water 58 Methyl alcohol n-propyl alcohol Ethyl alcohol Ethyl acetate VM&P naphtha ~ - 3.3 4.5 15 2.9 4.6 1.2 62 4.1 5.6 18 3.6 5.7 * Not applicable. sentially the same for both ink types. The main difference, however, is that liquid wastes from the water-based inks did not have to be disposed of as hazardous wastes for this project. Evaluation of Changes in Toxicity Toxicity reduction evaluations for the Ink and cleaner wastes were accomplished with the Degree-of-Hazard scheme devel- oped and used by the Illinois Hazardous Waste Research and Information Center. The equivalent toxic concentration was calculated for four printing scenarios: (1) green alcohol-based ink with solvent-based cleaner; (2) purple alcohol-based ink with solvent-based cleaner; (3) green water- based ink with detergent cleaner; and (4) purple water-based ink with detergent cleaner. For estimated emissions to the air, the alcohol-based inks and cleaners had relative toxicities about 10 times higher than those for the water-based emissions. The same reduction was found in the liq- uid waste comparison. In actuality, no liq- uid wastes were discharged to the sewer when the company was using alcohol- based inks and cleaners. Therefore, the relative toxicity of these wastes increased from zero. Offsetting this is the fact that the undiluted alcohol-based wastes were previously sent to a landfill in the waste- containing drums. Economic Analysis The approximate annual savings at MPI Label Systems resulting from the ink and cleaner change is estimated by the plant manager to total at least $16,500 (Table 5). There is essentially no difference in raw material costs'for the inks and clean- ers. The overall productivity of the plant has increased, but the economic value pf this increase could not be determined. Annual waste disposal and handling ac- count for at least a savings of $15,000. The facility saves about $500 each year because of a lowered insurance premium based on improved working conditions. Savings because of new wiping materials (nondisposable) equals about $1,000 an- nually. ' Conclusions ; The results from the change to water- based ink and cleaner at MPI Label Sys- tems are both definite and significant: Solvent emissions to the plant air have been reduced by at least 80%. Toxicity of these emissions has gone from potentially hazardous to humans to essentially harmless. Solid waste generated and destined for local landfills has been noticeably reduced in volume and is no longer classified as hazardous. This waste is mostly bu|k paper for which a recycling system is being sought. Additionally, these changes neither in- curred capital costs nor increased opera- tional expenses. Rather, the plant annu- ally enjoys a significant saving associated with reduced waste disposal, insurance, and cleaning material costs. The shop manager at MPI Label Systems contends that associated benefits include 1. Water-based jnks are easier to clean from pans, plates, and rollers when wet. 2. Water-based ink waste is more easily disposed. 3. Water-based ink spills are easier to clean up when wet. 4. Waste going to a landfill is no longer classified as hazardous, reducing MPI Label Systems' long-term liability. 5. Expensive solvents are not required for cleaning. 6. Employees are enjoying a cleaner, safer work environment. 7. Customers are receiving a better product. 8. Corporate concerns regarding hazardous materials are minimized. The full report Was submitted in fulfill- ment of CR-815829 by Illinois Hazardous Waste Research and Information Center under the sponsorship of the U.S. Envi- ronmental Protection Agency. ------- Table 4. Estimated Concentrations of Components in Wastewater, Purple Labels i Components Isopropyl alcohol Ammonia i Dimethyl ethaholamine Water Resins : Pigment Methy alcohol n-propyl alcohol Ethyl alcohol Ethyl acetate VM&P naphtha Toluene* Acetone* Isopropyl alcohol* Diacetone alcohol* ' Water* Water-based ink 159 26.6 26.6 2090, 2.4 1.0 - - - - - - - - - 44.3 Alcohol-based ink 344 * - - 713 713 159 211 690 132 211 6370 2350 2350 634 - Water-based ink 317 52.8 52.8 4230 1290 528 - _ - - - - - - - 11700 it c-g^c/a Alcohol-based ink 687 - - _ 1510 1510 291 423 1400 264 423 6370 2350 2350 634 - * Not applicable. * Constituents of cleaners , Table 5. Economic Summary of Savings Using Water-Based Inks and Cleaners Parameter Savings Water-based inks ; Printing speed ' Raw Materials . Waste disposal and handling Aqueous cleaners Disposal Raw materials Overall Savings . Insurance liability ; Inventory Wiping materials Annual total Approximately 10% faster None Minimum annual savings = $10,000 Minimum annual savings = $5,000 None Approximately $500/yr None Annually at least $1,000 At least $16,500 ArU.S. GOVERNMENT PRINTING OFFICE: 1993 - 750-071/80016 ------- ------- ------- Gary D. Miller and William J. Tancig are with Hazardous Waste Research and Information Center, Champaign, IL 61820. MichaelJ. Plewa is with University of Illinois at Urbana-Champaign Institute for Environmental Studies, Champaign, IL 61820. Paul M. Randall is the EPA Project Officer (see below). The complete report, entitled "Ink and Cleaner Waste Reduction Evaluation for Flexographic Printers," (Order No. PB93-191286; Cost: $17.50, subject to change) will be available only from: National Technical Information Service 5285 Port Royal Road Springfield, VA 22161 Telephone: 703-487-4650 The EPA Project Officer can be contacted at: Risk Reduction Engineering Laboratory U.S. Environmental Protection Agency Cincinnati, OH 45268 United States Environmental Protection Agency Center for Environmental Research Information Cincinnati, OH 45268 Official Business Penalty for Private Use $300 BULK RATE POSTAGE & FEES PAID i EPA PERMIT No. G-35 EPA/600/SR-93/086 ------- |