Abstract A process for the manufacture of a polyurethane foam which comprises forming a reaction mixture containing an organic polyisocyanate, an organic polyol and an inert blowing agent having a boiling point not exceeding 50*C. at atmospheric pressure under such a pressure that the blowing agent is substantially in condensed form and releasing the pressure on said reaction mixture whereby it expands to form a froth which subsequently cures to form a foam, the reaction mixture having been brought to such a temperature, either before or during the release of pressure, that the rate of generation of reaction heat in said froth during the curing period is substantially equal to the rate at which heat is dissipated from the froth to its surroundings.
A process as claimed in claim 1 wherein the polyisocyanate is tolylene diisocyanate or crude diphenylmethane diisocyanate.
Claim 2
Dependent Claim
19 words
A process as claimed in claim 1 wherein the blowing agent is dichlorodifluoromethane or trichlorofluoromethane or a mixture thereof.
Claim 3
Dependent Claim
33 words
A process as claimed in claim 1 wherein the polyisocyanate and polyol are allowed to react together to some extent to form a quasi-prepolymer before the pressure on the reaction mixture is released.
Claim 4
Dependent Claim
48 words
A process as claimed in claim 1 wherein the froth is formed in a mould so as to fill the said mould after which the mould outlet is closed and a further quantity of froth is introduced so as to produce a foam having a dense integral skin.