Continued from Part 1

By Ronald Golden, courtesy of Radtech

Pressure-Sensitive Adhesive Case Study
The most complete published quantitative analysis comparing ultraviolet and waterborne technologies was a 1997 study of the conversion to UV curing from thermal curing of waterborne inks and coatings for exterior aluminum can decoration and coating at Coors Brewing Company. A previous RadTech Report explained how the conversion resulted in a reduction of up to 80 percent in total energy usage in BTU, including electrical power and natural gas. Greenhouse gas emissions showed a corresponding reduction of up to 67 percent. Moreover, these benefits were achieved at a lower net cost for the finished product.
      The RadTech Sustainability Task Force was seeking a more recent study to develop a similar comparison using current energy and emissions factors. BASF Corporation generously provided RadTech with the raw data from their eco-efficiency evaluation of waterborne, solvent and UV web-applied pressure sensitive adhesives4 as the basis for the following quantitative analysis.
      The higher solids of the UV coating also means reduced energy required to transport the coating from the formulator to the application site. Table 4 shows the transportation energy required to deliver enough of each type of coating to cover 76,800,000 square meters at an applied coat weight of 20 g/m2.
Table 5 shows a comparison of the total energy requirements of each of the three technologies, normalized to Btu/square meter of coated surface. Conversion of electrical energy MWh to Btu is based on an average heat rate of 9.713 million Btu/MWh; conversion of natural gas usage to Btu is based on 1,031 BTU per cubic foot.
      On a normalized basis (BTU per square meter of coated substrate) the UV-cured resin requires up to 89 percent less energy, compared to solvent and waterborne systems.

Greenhouse Gas Emissions
Both generation of electrical energy and combustion of natural gas generate corresponding greenhouse gas emissions.
Factors for conversion of electrical MWh and combustion of various fuels to greenhouse gas emissions are based on data published by the U.S. Energy Information Administration and the U.S. Environmental Protection Agency (EPA).9 On a normalized basis (MT CO2 per million square meters of coated substrate), the UV-cured resin generates up to 87 percent less carbon dioxide, compared to thermal curing solvent and waterborne systems.

UV-Cured Products Are Recyclable
Trials at Beloit Corporation confirmed that UV/EB inks and coatings repulp easily.10 Mill scale trials show that UV/EB-coated waste can be incorporated into standard furnish with no detrimental effects on product quality. The study concluded that UV- and EB-printed and coated paper can be recycled into tissue and/ or fine paper grades using commercially available equipment.
      Moreover, the high gloss and abrasion resistance of UV- and EBcured coatings in some cases, can enable replacement of laminated structures with printed inks and coatings. Laminated paper and plastics are difficult to recycle due to problems with separating two incompatible types of materials. UV/EB printed inks and coatings break down under recycling process conditions, permitting effective recycling of both paper and plastic structures that formerly were intractable in laminated form.

Summary
In summary, UV and EB curing have numerous "sustainability" characteristics:

• Substantial reductions in energy demand.


• Substantial reductions in fossil fuel usage.


• Substantial reductions in greenhouse gas emissions.


• Reduced transportation costs and emissions.


• Safer workplace.


• Recyclable inks, coatings and product wastes.


• Positive performance advantages and economic returns.

Where Do We Go From Here?
The RadTech Sustainability Task Force has already developed "cradleto- grave-to-cradle" life cycle analyses for the various coating and printing technologies, including energy usage, carbon footprint, transportation, emissions controls, waste, recyclability and more at each stage of production of raw materials and finished products, as well as the end use of the products and their disposal and recycling. Current plans include working with industry, academic and government partners on demonstration projects to develop additional data and practical insights. The resulting data will be used to develop additional quantitative analyses, as well as a working model for technology comparison, including economic factors.

Ronald Golden, Ph.D., offers consulting services through FocalPoint Consulting, Marietta, GA.

Mon Nov 03 13:09:00 CST 2008