|Chemical alternatives for Screen Reclamation||United States||-||Full scale|
PUBLISHING, PRINTING AND REPRODUCTION OF RECORDED MEDIA # 9
The Design for the Environment (DfE) Screen Printing Project is a cooperative effort between the screen printing industry and the U.S. Environmental Protection Agency (EPA) to help screen printers improve their performance to protect the environment. Aim of the project is to provide printers information about chemical risk and pollution prevention along with performance and cost information, so that they can incorporate environmental concerns into day-to-day functioning.
Printers, EPA, product manufacturers and the screen printing trade association are all concerned with minimizing the environmental and health hazards of screen reclamation chemicals currently used in printing shops. Through DfE, these groups worked together to evaluate alternative screen reclamation products. A total of eleven alternative chemical "systems" were evaluated. Most "systems" included an ink remover, an emulsion remover, and a haze remover.
Cleaner Production Principle
Material substitution; Process/ product modification
Cleaner Production Application
This project was entirely voluntary and involved almost all sectors of the screen printing industry:
|Manufacturers donated their products for evaluation,|
|staff from Screenprinting and Graphic Imaging Association International (SGIA) coordinated the field demonstrations,|
|the Screen Printing Technical Foundation (SPTF) performed initial product testing,|
|printers nationwide evaluated the products in their facilities, and|
|EPA staff conducted the risk assessment of the products.|
One advantage of this coordinated effort is the consistency of the evaluations. Results can be compared to determine which of the alternatives may be a viable substitute for the current reclamation products.
This case study highlights one alternative system, referred to as "Chi". This system, is a real, commercially available screen reclamation system; however, "Chi" is a masked name. The actual trade name for this alternative system (or for any of the alternative systems demonstrated) is not used in this case study. Trade names were masked for several reasons:
|One of the goals of the DfE project is to illustrate the process of searching for and evaluating cleaner alternatives. DfE encourages to incorporate environmental concerns in facility's decision-making processes and into discussions with suppliers. By masking trade names, DfE encourages to discuss the characteristics of the products used, or are considering using, with the suppliers. This case study and the DfE project will help to know what characteristics to look for in the screen reclamation products while purchasing.|
|Since every screen printing shop is different, manufacturers recognize that their product's performance may vary greatly depending on both the operating conditions and the varying opinions of the different printers using the products. In order to get their full cooperation before the results were available, some manufacturers asked that the product names be masked.|
To compare the cost and risk of Alternative System Chi to a known system, a baseline was established using a traditional solvent-based screen reclamation system. The traditional system used in the comparison consists of lacquer thinner as the ink remover, a sodium periodate solution as the emulsion remover, and a xylene/ acetone/ mineral spirits/ cyclohexanone blend as the haze remover. These chemicals were selected because screen printers indicated they were commonly used in screen reclamation. In both the cost and risk comparisons, it was assumed that these chemicals were applied manually to 6 screens per day, each 2,127 in2 (approximately 15 ft2) in size.
Performance was evaluated in two phases:
Since conditions vary from printer to printer, it was realised that it would be useful to evaluate performance based on the experiences and opinions of the experts and the people who used the alternative products in their facilities during the month-long demonstrations. Each product system was demonstrated in two or three facilities to get a more complete evaluation of performance under a variety of operating conditions.
During laboratory testing three imaged screens were reclaimed using Alternative system Chi. One had been inked with a solvent-based ink, the second with an ultraviolet-curable (UV) ink, and the third with a water-based ink. In the lab, two applications of the Chi ink remover were required to remove the solvent-based ink. The ink dissolved more easily on the other two screens (with UV-curable ink and water-based ink), however, an ink residue or haze remained on all of the screens after applying the ink remover. On two of the screens, the stencil started to deteriorate during the ink removal process, indicating that this product may not be applicable for in-process ink removal. The emulsion remover easily dissolved the stencil with only light scrubbing, leaving no emulsion residue behind. When additional ink remover was applied (used as a haze remover in this product system), it removed the ink residue and lightened the stain on all three screens.
|System Chi/ Ink Remover||Diethylene glycol series ethers; Propylene glycol series ethers; N-methyl pyrolidone; Ethoxylated nonylphenol|
|Traditional System/Ink Remover||100% Lacquer thinner, consisting of : 30% Methyl ethyl ketone; 20%
Naphtha light aliphatic; 20% Toluene;
15% n-butyl acetate; 10% Isobutyl isobutyrate; 5% Methanol.
|Alternative System Chi/ Emulsion Remover||Sodium periodate; Water|
|Traditional System/ Emulsion Remover||1% Sodium periodate; 99% Water|
|Alternative System Chi/ Haze Remover||Diethylene glycol series ethers; Propylene glycol series ethers; N-methyl pyrrolidone; Ethoxylated nonophenol|
|Traditional system/ Haze Remover||10% Xylene; 30% Acetone; 30% Mineral spirits; 30% Cyclohexanone|
Performance of various alternatives
At Facility C, the alternative ink remover worked well, although some of the workers who used it thought that it acted more slowly than their standard product (a solvent blend). Facility D found the alternative ink remover worked well, especially on metallic inks.
The emulsion remover worked well at both print shops, dissolving the stencil quickly and easily.
Alternative system Chi did not include a haze remover; instead the manufacturer recommended applying the ink remover again to remove any remaining haze. Facility D found their screens were clean after the emulsion remover and a haze remover was not needed. At Facility C, the haze remover lightened the haze, however, a ghost image remained on the screen that continued to build up over time. For light haze, the haze remover was acceptable, but in most cases, this facility needed to dehaze the screen again with another product.
At both facilities, the performance of alternative system Chi was comparable to the performance of the facilities' standard screen reclamation products. The consistent performance of the product at SPTF and in the two print shops demonstrates that System Chi can work under a variety of operating conditions. When compared to the traditional system described in this case study, a switch to alternative system Chi significantly reduced risks and costs while maintaining the expected screen reclamation performance. Although the alternative system described in this case study may prove to be a viable alternative in many printing shops, it may not be the solution for all types of screen printing operations.
For information on the other alternative product systems, and alternative technologies refer to the project's full technical report, called the Cleaner Technologies Substitutes Assessment (CTSA).
Environmental and Economic Benefits
The performance of the demonstration project showed that both of the participating print shops could reduce their costs for screen reclamation by switching from the traditional system to alternative system Chi. As with the risk comparisons, costs of alternative system Chi were compared to the costs of using the traditional system. Again, it was assumed 6 screens were reclaimed daily and that all screens were 2,127 in2 (approximately 15 ft2) in size for both the traditional and the alternative systems. The cost estimate for each reclamation system included labor time spend to reclaim the screen, the cost of an average quantity of reclamation products, and the cost of hazardous waste disposal for RCRA-listed waste or RCRA characteristic waste (ignitable, based on flash-point reported on the product's MSDS); the RCRA-listng applies to the traditional system ink remover only.
For Facility C, their reclamation cost per screen would drop form $6.27/screen to $3.89/screen. This would lead to annual savings of $3,560. At Facility D, the reclamation cost of $6.27/screen using the traditional system would decrease to $3.25/screen for the alternative system. Over a year, the savings would amount to $4,520. The difference in costs between the facilities is due to differences in the quantity of product used and the labor time required per screen as recorded by the employees.
Whether using traditional screen reclamation chemicals or an alternative system, chemicals can get into body either through skin when one contact the product or through the lungs when one breathe in the chemical vapors. Some chemicals have a lower tendency to evaporate or to enter the body through the skin, and different chemicals have different effects; some more harmful than others. The risks associated with inhalation of the chemicals in alternative system Chi were found to be negligible, while there is a clear concern for chemical inhalation risk with the traditional system. With the traditional system, daily inhalation of toluene and methyl ethyl ketone in the ink remover, and acetone in the haze remover could lead to eye, nose, and throat irritation, headaches, or fatigue.
Applying either the alternative system Chi or the traditional system products regularly without wearing gloves can be harmful to health. These armful effects through skin contact are attributed to diethylene glycol series ethers in the alternative ink and haze removers, and sodium periodate in the emulsion remover. In the traditional system, these effects are from the toluene, methyl ethyl ketone, acetone, and sodium periodate. If the workers wear gloves regularly, the risks from either system are negligible.
Based on the EPA assessment, none of the chemicals in either the traditional system or alternative system Chi were found to be hazardous to the general population in the quantities used for screen reclamation. Although the general population impacts were low, a reduction in the use of the traditional chemicals could reduce a facility's releases of hazardous materials. Traditional screen cleaning solvents often have a high VOC content, contain hazardous air pollutants regulated under the Clean Air Act, or contain a RCRA listed or characteristic waste. Substituting an alternative product for these screen reclamation chemicals could reduce the regulatory burden.
This case study was submitted by the US EPA's Design for the Environment Program to UNEP IE. It was edited for the ICPIC diskette in June 1997.
Subsequently the case study has undergone a technical review by Dr Prasad Modak at Environmental Management Centre, Mumbai, India, in September 1998.