| 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 percent by weight of at least one C2-C5 polyfluoroalkane and from about 70 to about 99 percent by weight ofan HCFC, preferably an HCFC selected from chlorodifluoromethane, 1,1-dichloro-1-fluroethane, 1-chloro-1,1- difluoroethane and mixtures thereof.
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