Process for molding polyurethane foams

In a process for producing a foam plastic which readily separates from the mold in which it has been foamed wherein a foamable reaction mixture containing an organic polyisocyanate, an organic compound having a molecular weight of about 62 to about 10,000 which contains reactive hydrogen atoms, a catalyst for the acceleration of the isocyanate/reaction hydrogen reaction, and a blowing agent is charged to the mold and reacted, the improvement which comprises adding to said active hydrogen containing component or to the foamable reaction mixture as a third stream an esterification reaction product of about 0.8 mol to about 4 mols of ricinoleic acid and 1 mol of a long chain fatty acid containing more than 8 carbon atoms which is substantially free of alcoholic hydroxyl groups, in an amount sufficient to improve the mold release properties of the resulting molded product.