Heinz Ziemann

1,1,1,4,4,4-Hexafluorbutane (R 356), a potential CFC substitute

Abstract As part of the world-wide efforts to limit the antropogenic depletion of the stratospheric ozone layer, there is an intensive search for substitutes for all chlorine-containing compounds used in refrigeration. Beside the H-CFCs with reduced ozone depletion potential (ODP), to date only perfluoroalkanes with a high greenhouse potential have been put forward as blowing agents in PUR rigid foams. We consider 1,1,1,4,4,4-hexafluorbutane (R 356) to be the better alternative than the above-mentioned substitutes. In spite of the C4-carbon framework, the physical properties of hexafluorbutane are very similiar to those of R 11. R 356 is not combustible, nor is a gas-air-mixture explosive. Hexafluorbutane also seems to be well-suited from the ecological point of view: by definition, its ozone depletion potential is zero. Due to the partial hydrocarbon character, R 356 is rapidly decomposed in the atmosphere, and thus contributes only minimally to the greenhouse effect. A synthetic route is presented, and an overview given of properties of the technical application of R 356 in PUR rigid foam.