| 摘要 |
Polyisocyanurate foams are prepared by reacting together an organic polyisocyanate, a polyol, a trimerization catalyst, and a blowing agent which comprises a mixture of (a) methylene chloride and (b) a fluorocarbon blowing agent selected from the group consisting of halogen-substituted hydrocarbons containing at least one fluorine atom and mixtures of said halogen-substituted hydrocarbons containing at least one fluorine atom, said methylene chloride comprising up to about 40 weight percent of said blowing agent mixture, the remainder of said mixture comprising said fluorocarbon blowing agent. Laminates of such foams exhibit a high degree of fire resistance, low smoke evolution on combustion, low foam friability, good compressive strength and dimensional stability, and high insulation properties. |
