| 摘要 |
Rigid foams having improved insulation properties are made by reacting a polyisocyanate with an isocyanate-reactive material in the presence of a blowing agent mixture composed of from about 1 to about 30% by weight of at least one C2-C5 polyfluoroalkane and from about 70 to about 99% by weight of an HCFC, preferably an HCFC selected from chlorodifluoromethane, 1,1-dichloro-1-fluoroethane, 1-chloro-1,1-difluoroethane and mixtures thereof.
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