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United States Environmental Protection Agency

Air and Radiation

EPA 600-SR-93-149

REPLACEMENT OF HAZARDOUS MATERIAL IN WIDE WEB FLEXOGRAPHIC PRINTING PROCESS

The Lustreprint Company hosted the test and operated the equipment. Test design and management was by Erie County Environmental Compliance Services, (ECECS), Buffalo, New York. The test personnel were supplied by Recra Environmental, Incorporated on contract to ECECS.

Technology/Testing

A wide web flexographic printing firm substituted water-based inks for solvent-based inks when manufacturing flexible packaging, using plastic sheet substrates (e.g., plastic bags for bread). The project objectives were to evaluate the technical feasibility (particularly as related to process implementation and performance), the economic effect, and the resulting change in VOC emissions achieved by the substitution. The technical evaluation was to quantify the reduction in both volatile and liquid-phase solid hazardous wastes.

This is a study of the effectiveness and applicability of ink substitutions to reduce waste in a wide web (greater than 16 in. wide) flexographic printing process. The Lustreprint Company prints flexible packaging whose products are used in the food and snack industry and in medical, industrial and consumer applications. Printing is completed on a number of different web materials, (commonly polypropylene (acrylic coated, Saran coated, and uncoated corona pretreated), cellophane (Saran coated), polyester (both metallized and unmetallized), polyethylene. and nylon (both Saran coated and uncoated)). At the time of this study, Lustreprint used one Hudson/Sharp 48 in., central impression six-color flexo press and one Heinrich (W&H) five-color flexo stack press.

New York's regulations require that a facility reduce overall plant emissions to within the compliance level of 100 tons/yr. As an option, Lustreprint chose to reduce the use of solvent-based inks and adhesives. The first step eliminated solvent-based adhesive used in laminating. This was followed by a phase-in of water-based inks in the printing operation. The company goals are to reduce all volatile organic air emissions to an extent that would eliminate the need for costly air abatement and permitting and to eliminate all liquid-phase solid waste, at the facility.

To achieve these goals, ink use was monitored over four, one week long, study periods: 3 weeks when both water-based and solvent-based inks were used and 1 week when only solvent-based inks were used. Historical data for emissions and waste generation were extrapolated for comparison with the weekly experimental data. From the 4-week ink use and waste analysis data, the VOCs, released as emissions from the printing process, could be calculated. A material accounting approach was used for three calculations. All liquid wastes generated during the test periods were segregated and analyzed for percent volatile constituents. Substituting water-based inks required press modifications.

The most significant retrofit was installation of an Enercon corona discharge treater.

Modifications to the Hudson/Sharp 48 inch, central impression, six-color, flexographic printing press included upgrading drying capacities and using enlarged exhaust and supply fans.

Because of prohibitive costs, the Heinrich (W&H) press was not modified or retrofitted and was not used in the water-based ink tests. Future plans would include replacing this press with one that could accommodate the ancillary equipment required for water-based ink use.

Ink metering rolls were replaced to facilitate drying. Pumps were also replaced to accommodate the new printing inks. Additional ductwork and noise abatement equipment were needed.

Table 1 shows the VOC emissions as a function of ink use, based on historical data.

TABLE 1 VOC EMISSIONS BASED ON INK USE 1990

Month

Ink used

(lb/wk)

VOCs calculated

(lb/wk)

April

3,038

2,111

May

1,681

1,700*

June

2,686

2,289

July

2,109

1,731

August

2,945

2,345

*This value is derived from the historical operational data and attributed to high makeup solvent use during the event.

Table 2 provides information on the total pounds and percent of ink used, calculated VOC emissions, and VOC emissions as a percentage of ink used for each of the four 1-week-long evaluation periods.

A review of the quality assurance sheets indicates that the use of water-based inks typically did not change product quality although some problems arose after customer use, depending upon the ultimate use of the packaging, what the package contained, and the means by which the packages were sealed. Heat and stress of the printed package material caused by the package folding and sealing process at times resulted in a loss of ink adhesion.

Some combinations of water ink and solvent ink were incompatible. Water inks did not provide a consistent opaque white for lamination to cover metallized films and resulted in "blocking" (or transfer of print) when printing on Saran-coated materials, especially cellophane. In most cases, however, depending on the surface printed, no difference was noted with the use of water-based inks.

Normal propyl alcohol added in small amounts (less than 1%) to prevent water ink foaming at the ink pan and to assist in ink wetting was beneficial. Variations of the pressure sensitive "stickyback" material used to attach the printing plates to the plate cylinder (solid versus cushioned stickyback) also enhanced printed solid plate backgrounds without pin-holding. The plate material may also have an effect. Photo polymer plates work well with water but are more expensive than rubber. Nylon plates are a possible compromise with a longer life than rubber plates.

Table 2. Ink and VOC Emission Data for 4-Week Study Period

Measured Parameter

Week 1

Week 2

Week 3

Week 4

No. of inks

23

32

33

22

Solvent ink (lb)

1,112

1,746

2252

549

Water ink (lb)

1,251

508

0

688

Total ink (lb)

2,363

2,254

2,252

1237

Solvent ink (%)

47.1

77.5

100

44.4

Water ink (%)

52.9

22.5

0

55.6

VOC emissions (lb)

(calculated)

827.5

1,251.7

1,571.5

509.0

VOC emissions (%)

(% of ink total)

35.0

55.5

69.8

41.1

Waste (lb)

55.6

20.0

0

0

Waste VOC content

lb

54.3

4.7

0

0

 

VOC Reduction

Substituting with water-based ink reduced the emissions generated from the printing p each percent increase in water-based ink use, the calculated reduction in VOC emissions was (Table 3).

As can be seen from Table 3, for Weeks 1 and 2, the VOC generation decreased in proportion to the percentage of water-based ink used. A 52.9% water-based ink use resulted in a 53.3% reduction in VOC emissions. Similarly, in Week 2, a water-ink use rate of 22.556 resulted in a VOC emission reduction of 23.4%.

For Week 4, the corresponding reduction in VOC emissions was less significant: a 55.6% water ink use rate reduced VOC emissions only 43.3% Total ink use for Week 4 was 1,237 lb of combined water ink and solvent ink. This amount is approximately half of the amount used during the other 3 weeks of the study. The number of different inks used in Week 4 is, however, comparable with that used Week 1. With the same number of ink changes at the printing stations and with each change requiring a cleaning before adding new ink, the amount of cleaning make-up solvent relative to total ink use is expected to increase. The contribution of VOC emissions from clean-up solvents reduced the effectiveness of VOC reduction by water inks.

TABLE 3, VOC REDUCTION

Week

Total ink

(lb)

Factored*

VOC (lb)

Water ink

(%)

Reduced

VOC (lb)

Reduction

(%)

1

2,363

1,772

52.9

827.5

53.3

2

2,254

1,634

22.5

1,252.7

23.4

3

2,252

1,633

0.0

1,571.5

0.0

4

1,237

897

55.6

509.09

43.3

*Calculated by taking 72.5X of the total ink quantity.

Waste Reduction

Historically, 315 gal of solid waste was generated each month. This translates to approximately one-and-one-half, 55 gal drum or 424 lb/wk. The printing operations during Week 1 were an 87% decrease from normal in solid waste generation (from 424 lb to 55.5 lbs); and 100% elimination of solid waste generation in Weeks 3 and 4.

Note that much of this waste decrease can be attributed to factors other than the type of ink used. The WRITE Program evaluation and the use of the waste generation from increased awareness of press operators and deterred waste generation. This induced press operators to reuse solvent for additional cleaning or reuse in the solvent inks.

Economic Analysis

An economic analysis of the changeover from solvent to water-based ink is included as part of this project.

Fixed, variable, and overhead costs are affected by this substitution and are considered. Fixed costs include the purchase and installation of new equipment (primarily the Enercon corona discharge treater) and costs for replacing equipment ancillary to the central impression cylinder press, such as pumps, dryer upgrade, ink pans, etc.

Variable cost adjustments include the premium paid, or reduced cost, for water-based inks. Disposal costs were calculated by using the amount of waste solvent ink generated in gals and the most recent disposal cost figures provided by Lustreprint. Other variable costs included variations in labor hours and utilities.

Overhead costs also play a role in determining the cost savings. Items such as the time previously expended for regulatory compliance, insurance costs, employee equipment and safety training, and OSHA compliance were expected to be reduced as a result of removing hazardous waste from the shop floor. These potential cost savings were estimated from existing figures where available.

Based on these costs, payback period was calculated (Table 4).

The payback period could be further reduced by eliminating the solid waste disposal. With the complete changeover to water inks and the planned purchase of an ink splitter, at approximately $8,000, an additional savings for solid waste disposal would be possible. The payback period would then be reduced by 0.53 year.

TABLE 4. PAYBACK PERIOD

Variable

Initial Investment

Projected Savings

Payback Period, year

Current process revisions

$62,901

$24,587

2.56

Adding an $8000 ink splitter

$70,901

$34,887

2.03

Full water-based ink conversion

$62,901

$117,078

0.54

Conclusions

By installing an in-line corona treater, higher surface tension water-based inks could be used. This, in turn, reduced VOC emissions approximately 72,5%, when compared with those for solvent-based inks. The water-based ink formulas contain about 20% solvent. For a process using a quantity of approximately 2250 lb of solvent-based ink (weekly), VOC emission levels were about 1570 lb. For every 1% increase in water-based ink use, VOC emissions were reduced 14 lb.

The substitution of water based inks did not adversely affect product quality or nonhazardous scrap waste generation. Some changes in operating procedures were, however, necessary because of the nature of water-based inks. The average reduction of 95% of liquid F003 waste from waste ink and cleaning solvents recorded during the study period resulted from operational practice changes.

The payback period for the corona treater and equipment modifications is 2.56 years. Additionally, through segregation of wastes once full implementation of water-based inks is achieved, the payback period could be reduced to 0.54 years.

This successful implementation of water-based inks in flexographic wide web printing should be considered as a VOC source reduction method for similar printing operations.

Report

The full report, entitled "Replacement of Hazardous Material in Wide Web Flexographic Printing Process" by P.B. Kranz, et al., is available as EPA/600/SR-93/149.

For more detailed information about pollution prevention opportunities in the printing industry visit the PNEAC web site at www.pneac.org , call the PNEAC toll free number at 1-888-USPNEAC, or contact :

  • Graphic Arts Technical Foundation - Gary Jones or Rick Hartwig (412/741-6860)
  • Printing Industries of America - Ben Cooper (703/519-8115)
  • Illinois Hazardous Waste Research & Information Center - Gary Miller (217/333-8940) or Debra Jacobson (630/472-5019)
  • University of Wisconsin - Wayne Pferdehirt (608/265-2361), Keith West (920/465-2940) or Bob Gifford (608/262-1083)

 


Reasonable effort has been made to review and verify information in this document. Neither PNEAC and its partners, nor the technical reviewers and their agencies, assume responsibility for completeness and accuracy of the information, or its interpretation. The reader is responsible for making the appropriate decisions with respect to their operation, specific materials employed, work practices, equipment and regulatory obligations.  It is imperative to verify current applicable regulatory requirements with state and/or local regulatory agencies.

 

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