Foam formulation with Transcend as an alternative to HCFC-22
As a replacement for HCFC-22 for pour-in-place blowing agent formulations for PU rigid foams French Arkema Group, Paris, offers its range of Transcend PU blends.
The company points out that it has done tests which have shown that a combination of Transcend additive and HFC-134a can produce foams having at least the equivalent and, in some cases, better overall performance compared to HCFC-22 and HFC-134a in generic pour-in-place rigid PU foam formulations. In addition to easier handling, as demonstrated by the lower vapour pressures and faster blowing agent addition time to the polyol pre-blend, formulations containing 10-20 weight percent Transcend additive (weight percent of the total blowing agent) have improved flow, gives adequate dimensional stability, and very good adhesion. Thermal conductivities with Transcend PU blends are also fullyacceptable.
The product is a liquid at room temperature (boiling point 48°C), does not deplete the ozone layer, and has a low global warming potential (GWP) because of its very short atmospheric lifetime. In 2005, Transcend additive was approved as a replacement for CFCs and HCFCs in rigid PU foams under the US EPA’s Significant New Alternatives Policy (SNAP). A formal listing in the Federal Register occurred in March2006. Particularly noteworthy are the improved time for adding the blowing agent to the polyol blend and the improvement in adhesion of the Transcend PU blends versus both HFC-22 and HFC-134a. Transcend additive is based on trans-1, 2-dichloroethylene (TDCE), and can be added to hydrocarbon (HC) and HFC foamformulations.
Arkema offers an interactive calculator, available via its website, to show formulators the monetary savings they may realise by using Transcend additive in their foam formulations. Producers can enter raw material costs for all their formulation components and determine the economic advantage that they may realise by using the Arkema productadditive.
The use of HCFC-22 will be phased out across North America in “pour foam applications” on 1March2008 (this regulation does not include marine foamapplications).