Intumescent flexible polyurethane foam

Claim 1

In a process for the manufacture of a flexible, resilient, flame retardant and intumescent polyurethane foam from a reaction mixture comprising at least one polyester polyol, said polyester polyol being the reaction product of at least one polyhydric alcohol with at least one polycarboxylic acid or anhydride or with a lactone and having a hydroxyl functionality of greater than 2 and a molecular weight of from about 400 to about 5000; at least one organic polyisocyanate; at least one blowing agent; at least one surfactant; at least one catalyst; at least one melamine derivative of the formula ##STR2## wherein A, B, D, E, F, and G are selected from the group consisting of hydrogen, methylol, and ROCH 2 -- in which R is an alkyl radical having from 1 to 4 carbon atoms, with the proviso that in said formula at least one of A, B, D, E, F, and G is methylol or ROCH 2 --; and at least one flame retardant selected from the group consisting of triesters of phosphoric acid, halogenated triesters of phosphoric acid, and halogenated hydrocarbons: the improvement wherein the amount of said melamine derivative is from about 10 to about 30 parts by weight per 100 parts by weight of said polyester polyol; the amount of said flame retardant is from about 20 to about 60 parts by weight per 100 parts by weight of said polyester polyol; and wherein said reaction mixture also comprises from about 50 to about 200 parts by weight per 100 parts by weight of said polyester polyol of hydrated alumina; whereby the flame retardancy and intumescent properties of said polyurethane foam are increased.