Abstract: The present invention is directed to an improved internal mold release system for the production of low density molded foam parts. The process comprises reacting a reaction mixture of an isocyanate and at least one organic compound containing isocyanate-reactive hydrogens in the presence of a blowing agent, a catalyst, a surfactant, an IMR, and, optionally, a reinforcing agent, in a closed mold. The IMR comprises:a) mixed esters comprising the reaction product of i) aliphatic dicarboxylic acids, ii) aliphatic polyols, and iii) monocarboxylic acids with 12 to 30 carbon atoms in the molecule. The IMR may additionally comprise b) and/or c) wherein:b) represents a compound comprising the reaction product of i) N,N-dimethylpropylene diamine with ii) a compound selected from the group consisting of tall oil, C.sub.8-20 monofunctional carboxylic acids, and mixtures of C.sub.