Internal mold release agent for use in reaction injection molding

A process for the production of optionally cellular, polyurethane elastomer moldings by reacting a reaction mixture comprising

• (I) a polyisocyanate which is liquid at room temperature,
• (II) a polyether polyol having a molecular weight of about 3000 to 7000,
• (III) about 5 to 50% by weight, based on the weight of component (II) of a chain extender comprising a member selected from the group consisting of 1-methyl-3,5-diethyl-2,4-diamino benzene, 1-methyl-3,5-diethyl-2,6-diamino benzene and 1,3,5-triethyl-2,4-diamino benzene and
• (IV) an internal mold release agent mixture comprising
• (a) about 0.5 to 10% by weight, based on the weight of components (II) and (III) of zinc stearate and
• (b) a compatibilizer comprising a nitrogen-containing, isocyanate-reactive polyether in an amount sufficient to solubilize the zinc stearate so that when the internal mold release agent mixture is in admixture with components (II) and (III), the zinc stearate possesses improved resistance to precipitation, said reaction mixture being processed as a one-shot system by the RIM process at an isocyanate index of about 70 to 130.

An isocyanate-reactive composition for use in a RIM process which comprises

• (II) an isocyanate-reactive polymer having a molecular weight of about 1800 to 12,000,
• (III) about 5 to 50% by weight, based on the weight of component (I) of a chain extender comprising a sterically hindered aromatic diamine and
• (IV) an internal mold release agent mixture comprising
• (a) about 0.5 to 10% by weight, based on the weight of components (II) and (III) of a zinc carboxylate containing 8 to 24 carbon atoms per carboxylate group and
• (b) a compatibilizer comprising a member selected from the group consisting of nitrogen-containing, isocyanate-reactive, acyclic compounds and nitrogen-containing, isocyanate-reactive polymers in an amount sufficient to solubilize the zinc carboxylate so that when the internal mold release agent mixture is in admixture with components (II) and (III), the zinc carboxylate possesses improved resistance to precipitation.