Zero ODP HFC Blowing Agents for Appliance Foam

Although HCFC-141b has been selected as the best replacement for the blowing agent CFC-11 used in refrigerator or freezer foams in North America, it is only an interim solution in the ongoing efforts to replace CFCs. Under investigation are hydrofluorocarbons (HFCs) which have zero ozone depletion potential (ODP). Papers have been presented at SPI conferences in 1991 and 1993 on one of these compounds, 1,1,1,4,4,4-hexafluorobutane or HFC-356mffm [1,2]. HFC-356mffm, like HCFC-141b, is a liquid with a low boiling point that offers low thermal conductivity in rigid polyurethane foams. It can be processed in existing processing equipment. It is nonflammable and does not form explosive mixtures with air. In addition, it offers good compatibility with appliance plastic food liners. Other potential zero ODP candidates are the isomers of HFC-245. The most promising of these is HFC-245fa. HFC-245fa is a liquid which boils at 150°C (59°F). It is highly miscible with many different polyols. It is reported to be nonflammable and produces foams with low thermal conductivity. Preliminary reports indicate it has shown good compatibility with plastic refrigerator liners, promising toxicity evaluation results, and feasibility of manufacture. The purpose of this paper is to present new information on foam formulations made with HFC-356mffm and one of the isomers of HFC-245. Our studies have shown that HFC-356mffm and HFC-245fa produce low thermal conductivity foams from masterbatches that do not separate upon aging. Information as to the processing of these systems in machinery will be presented. Results of these studies will be compared to a commercial HCFC-141b appliance foam system.