Patent ID: 8097658

Claim:
A process for the production of fire-resistant, molded, medium density polyurethane foam comprising: a) introducing into a mold a composition comprising: (1) 50 to 90 parts by weight of a polyurethane foam forming reactive mixture, (2) 10 to 50 parts by weight of solid flame retardant comprising (i) a melamine coated ammonium polyphosphate, (ii) zinc borate, and, optionally, (iii) one or more metal oxides or hydrates thereof, in amounts such that (A) the weight ratio of ammonium polyphosphate to zinc borate ranges from 3:1 to 1:3; and (B) the polyurethane foam produced comprises at least 5% by weight, based on 100% by weight of the foam, of zinc borate; b) allowing the composition introduced into the mold to cure to form the medium density polyurethane foam; and c) removing the medium density polyurethane foam from the mold in which less time elapses between steps b) and c) than when a solid flame retardant composition comprising ammonium polyphosphate which has not been coated with melamine and zinc borate is included the polyurethane foam forming reactive mixture ( 1 ).