Method and composition for closed cell foam formation

A process for producing rigid foam from the reaction of a polyol and an organic polyisocyanate including the step of incorporating into at least one of said polyol and said polyisocyanate an effective amount of an ethoxylated (propoxylated propylene glycol) to sufficiently emulsify the reactants during mixing to produce small, uniform cell sizes in said rigid foam produced thereby, said ethoxylated (propoxylated propylene glycol) having an HLB value of less than about 4 and incapable of producing, on standing, a visible reaction product such as a skin or other indications of solids formation, gas evolution or an increase in the viscosity of said isocyanate when mixed with said polyisocyanate independently of said polyol.