Sodium silicate extended polyurethane foam

Abstract

Polyurethane foam products having relatively noncombustible properties, low flame spread ratings and low smoke generating tendencies when exposed to fire can be produced by combining aqueous sodium silicate into the foam forming composition which also includes a viscous, hydroxyl-terminated polyester and a polyisocyanate prepolymer or quasi-prepolymer along with a suitable catalyst, surfactant and halogenated alkane blowing agent. The aqueous sodium silicate ingredient constitutes from about 30 to 60 percent by weight. The aqueous sodium silicate has a weight ratio of SiO.sub.2 /Na.sub.2 O of 2.4 to 3.0 and contains 25 to 75 percent by weight water. The resulting foam, with a density of 1.5 to 4.5 pounds per cubic foot, has a K-factor less than 0.26 and is useful as a thermal insulating substance, especially in building panels.

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