| 摘要 |
Rigid foams having good 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 70% by weight of a low boiling hydrogen containing chlorofluorocarbon, such as chlorodifluoromethane (HCFC-22) and from 30 to 99% by weight of a C2-C5 polyfluoroalkane, such as 1,1,1,3,3-pentafluoropropane (HFC-245fa).
|
