Clean Technology in Screen Printing: The role of the auxiliaries
Aditya Chandavarkar, Silversheen
Date of Issue: June 2009; Ver.: 1.0
Copyright © 2009 SilversheenTM . All rights reserved.
Clean Technology has been growing over the last decade with a dramatic increase recently. Clean Technology is a way of thinking, rather than a set of 'hard technologies'
: it concentrates not on a product but on the human benefit which it delivers and on avoiding environmental damage at source. It is also important to change the mindset from just selling products to providing services. It uses fewer resources and lays emphasis on pollution prevention & waste minimization therefore it causes less environmental damage than alternative means. This in turn makes it economically competitive in the long run. (Clift, 1999; Clift, 2004). Clean technology has been defined by the United Nations Environment Programme (UNEP) as (Starket & Welford, 1905):
“A conceptual and procedural approach to production that demands that all phases of the life-cycle of a product or of a process should be addressed with the objective of prevention or minimization of short- and long-term risks to human health and to the environment”.
Need for Clean Technology in Screen Printing
Along with traditional criteria like performance, quality and cost, it is equally important to take the environment into account in the design and redesign of products and processes. This focus on the environment helps create cleaner products and technologies that minimize environmental impacts throughout their life cycles while fulfilling their function effectively, efficiently, and economically. Given the large size of the printing industry, it is not surprising that it also generates a significant amount of pollution & it is all the more important to adopt cleaner technology. The major advantages of cleaner technology in screen printing are:
· Eliminating toxic chemicals from all products used for screen printing.
· Reducing impact of the chemicals during their entire life cycle.
· Reduction of waste at source.
· Prevents pollution, improves quality and reduces cost.
· Improved health & safety conditions for employees
In this article we will be laying emphasis on the auxiliaries. Auxiliaries in this case are the reducers, retarders, cleaning aids & other products used in the printing industry other than printing ink. Reports mentioning use of printing inks based on cleaner technologies have been around for quite some time now. However these allied products are also vital when making the switch to cleaner technology and it is about time to start discussing about them.
Performance Factors - Volume utilized to achieve efficient results govern the performance of the auxiliaries. Optimum formulation is also vital as auxiliaries formulated should have improved properties in such a way that comparatively less volume is required to reach the effectiveness of the products with conventional components. For example in the case of cleaning aids, screen cleaning time also plays a role in dictating the performance.
Chemical Composition & Toxicity - The components used in the auxiliaries should be easily biologically degradable, for reasons of fire hazard, chemicals with a flash point >55oC should be used & components must exhibit low odour. The toxicity of components used in these products should play an important role during selection. The major factors affecting the toxicity are vapour pressure, saturation conc, evaporation rate, VOC content & high work place exposures should be taken into consideration when formulating the product.
Cost Effectiveness is an important parameter when it comes to the printing business. However when switching to cleaner technology there is a tradeoff between the cost of the product as compared to the reduced environmental impact which is achieved by using such products which is advantageous in the long run.
Thus it is important to keep the performance, chemical composition, environmental impact & cost effectiveness in mind while formulating the product to achieve the ideal clean technology product for efficient & safe screen printing.
Conventional Solvents & their disadvantages
Some of the solvents used in the industry include Nitrobenzene, ODCB Ortho Dichlorobenzene, DMF Dimethylformamide, Toluene, Xylene, Methylene Chloride, Trichloroethylene. The toxicity & their potential hazard properties of the same are given in Table 1.
| Components | CAS No. | Flash Point | Vapour Pressure @ 25oC (mm Hg) | HAP | Carcinogen |
| Nitrobenzene | 88oC | 0.245 | Yes | Inadequate Data | |
| Ortho Dichlorobenzene | 95-50-1 | 66oC | 1.56 | Yes | Inadequate data |
| Dimethylformamide | 58oC | 3.7 | Yes | Yes | |
| Toluene | 4oC | 28.4 | Yes | Inadequate data | |
| Xylenes | 1330-20-7 | 25oC | 6.72 mm Hg @t 21°C | Yes | Inadequate date |
| Methylene Chloride | 75-09-2 | N/A | 349 mm Hg @ 20°C | Yesa | Yes |
| Trichloroethylene. | 79-01-6 | N/A | 74 | Yesa | Yes |
Table 1: Basic toxicity and potential hazard properties of conventional solvents
Note
a - Identified as one of 33 HAPs that present the greatest threat to public health in urban areas
HAP: HAP List is a list of hazardous air pollutants maintained by the US EPA. This list contains those pollutants that cause or may cause cancer or other serious health effects, such as reproductive effects or birth defects, or adverse environmental and ecological effects.
Flash point is the lowest temperature at which a liquid can form an ignitable mixture in air near the surface of the liquid. The lower the flash point, more the fire hazard.
Vapour Pressure: The vapour pressure of a liquid is the pressure exerted by its vapour when the liquid and vapour are in dynamic equilibrium.
Carcinogen: Carcinogens are agents that can cause cancer. In industry, there are many potential exposures to carcinogens. Generally, workplace exposures are considered to be at higher levels than for public exposures. Material safety data sheets (MSDSs) should always contain an indication of carcinogenic potential. Data has been sourced from OSHA (U.S Government agency) http://www.osha.gov/SLTC/carcinogens/
These solvents pose a risk to humans and the environment due to combination of reasons such as high VOC content, lower flash points (<>oC), high vapor pressures, high saturation concentrations, high toxicity, increased risk of health & safety hazard for employees and being hazardous air pollutants. Conventional solvents used in the Indian market also pose long term negative effects ranging from lung irritation to damaging the central nervous system.
TecleanzTM EnvirOprint – Silversheen’s contribution to clean technology in screen printing
At Silversheen we are working on TecleanzTM EnvirOprint series which has been specially designed keeping the clean technology principles in mind. It provides you with complete safe solutions to assist you in the printing protocol. The key features of the EnvirOprint series include improved biodegradability compared to conventional components, low odour, low VOC content, flash point >60oC, low Toxicity leading to increased handling safety, compatibility with all ink systems & improved performance compared to conventional solvents
Aditya Chandavarkar is Manager - Marketing & Product Development for Silversheen
Further Information:
Silversheen,
Unit No. 3. Sheetal Industrial Estate No. 6,
Navghar, Vasai (East), Thane 401210, India
tel: +91 0250 2390647
e-mail: agchandavarkar@silversheen.com
web: www.silversheen.com
References
R. Starket, R. Welford, (1996), A Reader: Business and the Environment. Publisher: Taylor & Francis
Crift R., (2004), Review of Clean Technlogy – an introduction. Journal of Chemical Technology & Biotechnology 62(4): 321 – 326
Schollig M., (2008), Optimised Screen Cleaning. Specialist Printing Issue 2: 14
Office of Environmental Health Hazard Assessment (OEHHA). (2000), Chronic Toxicity Summary - N,N-Dimethylformamide, Determination of Noncancer Chronic Reference Exposure Levels Batch 2A. Available online at http://www.oehha.org/air/chronic_rels/pdf/68122.pdf
Report on Carcinogens, Eleventh Edition; U.S. Department of Health and Human Services, Public Health Service, National Toxicology Program. Available online at http://ntp.niehs.nih.gov/ntp/roc/toc11.html
The Clean Air Act Amendments of 1990 List of Hazardous Air Pollutants. Available online at
http://www.epa.gov/ttn/atw/orig189.html
http://toxnet.nlm.nih.gov
http://www.osha.gov/SLTC/methylenechloride/
