Flexible polyurethane foams and process for producing same

A method for producing a low density, flexible polyurethane foam by the reaction of an active-hydrogen-containing component with an organic polyisocyanate compound, wherein the active-hydrogen-containing component comprises an active hydrogen compound, an additive, and a blowing agent, the only blowing agent being carbon dioxide which is generated by the reaction of water with free isocyanate groups, and wherein the organic polyisocyanate compound is a mixture of diphenylmethane diisocyanate and polyphenylmethane polyisocyanate in a ratio of not more than about 1.0 mole of diphenylmethane diisocyanate per mole of polyphenylmethane polyisocyanate, wherein the diphenylmethane diisocyanate comprises

• (a) from about 20% by weight to about 50% by weight of a mixture of 2,2'- and 2,4'-isomers, and
• (b) from about 80% by weight to about 50% by weight of 4,4'-isomer,
• the isocyanate mixture containing not more than about 60% by weight of the 4,4'-isomer of diphenylmethane diisocyanate, and the polyphenylmethane polyisocyanate having an average functionality of not less than about 2.9 and containing less than about 35% by weight of diphenylmethane diisocyanate.