Polyurethane foams

A flexible flame-retardant polyurethane foam prepared by the process which comprises reacting a tolylene diisocyanate with a polyalkylene ether polyol having from 20 to 70% primary hydroxyl groups in a foam forming reaction mixture having an isocyanate index of less than 150 and containing (a) a compound which promotes trimerization of tolylene diisocyanate, (b) an amount of a compound containing labile halogen which inhibits heat aging of the foam caused by said trimerization promotor, and (c) a blowing agent, said polyalkylene ether polyol having a reactivity such that said reaction mixture, in the absence of special measures to the contrary, produces a closed cell foam;

• and said reaction mixture contains an additional polyol which is different in its constitution from said polyalkylene ether polyol and which is a polyethylene ether glycol or a poly(oxyethylene) poly(oxypropylene glycol) wherein the poly(oxypropylene) content has a molecular weight of 500 to 2000 and wherein from 20 to 80% of its weight is oxyethylene groups at least some of which are in non-terminal positions, and said additional polyol is from 2 to 40% by weight of the total polyol.