High modulus, high impact polyurethane/polyurea RIM

A process for the production of a molded polyurethane/urea elastomer from a reaction mixture by a reaction injection molding process, wherein said reaction mixture comprises:

• A) a methylenebis(cyclohexyl isocyanate) prepolymer having an isocyanate group content of from 12 to 27% by weight, an average isocyanate functionality of less than 2.3, having a monomer content of greater than about 25%, and containing urethane or urea groups, said prepolymer being prepared by reacting
• A1) methylenebis(cyclohexyl isocyanate) with
• A2) at least one compound selected from the group consisting of:
• a) at least 6.5% by weight of one or more compounds containing at least two hydroxyl groups or at least two amine groups and having a molecular weight of less than 500, and
• b) at least 10% by weight of a compound having a molecular weight of at least about 600, and containing polytetramethyleneoxy groups, polyethyleneoxy groups, or polyester groups;
• and
• B) an isocyanate-reactive blend comprising:
• B1) from 35 to 55% by weight of one or more polyether polyols having a number average molecular-weights of at least about 2000 to about 10,000, and containing from 1.5 to 4 hydroxyl groups,
• B2) from 45 to 65% by weight of one or more organic chain extenders having molecular weights of from about 60 to about 500, and being selected from the group consisting of diols, triois, primary amines, secondary amines, amino alcohols, and mixtures thereof,
• wherein said isocyanate-reactive blend has an OH:NH equivalent ratio of from 1:1 to 15:1 and wherein the %'s by weight of components B1) and B2) totalling 100%,
• and
• C) from 0.1 to 10% by weight, based upon 100% by weight of component B), of one or more catalyst for catalyzing the reaction between the isocyanate groups and the isocyanate-reactive groups,
• wherein the reaction mixture is processed via a one-shot process at an isocyanate index of from 80 to 130.