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“Cleaner Blowing Agents” are required to have Zero-Ozone
Depletion Potential in Rigid Polyurethanes. The most commonly used
Hydrocarbon blowing agent HCFC 141b is being phased out in USA.
Newer regulatory norms are expected to be introduced and HCFC 141b
will be completely eliminated by January 1, 2005 in the USA.
The phase-out date for production of HCFC-22 and HCFC-142b,
which have lower ozone-depletion potential, is Jan 1, 2007. The
latter two have had limited use in rigid PUR foam, mostly as blends
with HCFC-141b.
A newer agent, HFC 245fa, is relatively superior as cost-effective
formulation for building and construction, appliances and automotive
integral-skin foams. North American appliance makers and laminators
have been faster in adopting alternative blowing agents.The main
contenders for refrigeration foams are HFC-245fa and HFC-134a, the
later in use in Europe along with USA. A majority of appliance makers
favor the non-flammable HFC-245fa, as it has been shown to yield
the lowest cabinet energy consumption. HFC 245fa is very expensive
but very effective in producing rigid foam for refrigerator with
good insulation characteristics. However, the advantages of superior
physical properties as well as cost of HCFC-141b cannot be matched
by any of the alternatives. As compared to HCFC-141b, the HFCs cost
approximately 1.5 to 4 times more. Several new developments have
been aimed to optimize the level of expensive HFC 245fa to prevent
significant cost increase of the formulation. Apparently higher
water level along with HFC245fa help in reducing the level. A newly
developed blowing agent enhancer also helps in lowering levels of
HFC245fa by at least 10-20% level. This new additive reduces the
viscosity and thus helps to reduce the level of HFC245fa. Great
Lakes is introducing novel flame retardants which can work more
effectively with hydrocarbon blowing agents to meet the flammability
requirements of the flexible foam products.
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