Abstract: A method for producing a flexible polyurethane foam by the reaction of an active-hydrogen-containing component composed of an active hydrogen compound, a blowing agent, and an additive with an organic polyisocyanate compound: said blowing agent being carbon dioxide which is generated by the reaction of water with free isocyanate groups, said organic polyisocyanate compound being a mixture of diphenylmethane diisocyanates and polyphenylmethane polyisocyanate, which the mixture contains said diphenylmethane diisocyanate and said polyphenylmethane polyisocyanate in a mixing ratio of not more than 1.0 and 4,4'-MDI in a ratio of not more than 60% by weight based on the whole isocyanate mixture, and said polyphenylmethane polyisocyanate having an average functionality (hereinafter referred to as "f") of not less than 2.9 and containing diphenylmethane diisocyanate in an amount of less than 35% by weight.

Abstract: A method for producing a flexible polyurethane foam by the reaction of a mixture of an active hydrogen compound, a blowing agent, and an additive with an organic polyisocyanate, where water is used for generating carbon dioxide as the blowing agent; and the organic polyisocyanate is a mixture of(a) an isocyanate-terminated prepolymer prepared by reacting, with diphenylmethane diisocyanate, one or more of alkylene-polyols constituted of ethylene oxide units and an alkylene oxide units of three or more carbon atoms in an addition-polymerization molar-ratio of from 40/60 to 0/100, having an average functionality of three or more, and having an average molecular weight of from 9000 to 30000, and(b) a polyphenylmethane-polyisocyanate, in a mixing ratio of (a) to (b) in the range of from 20/80 to 80/20 by weight.