RIM elastomers based on prepolymers of cycloaliphatic diisocyanates

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

• A) an 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% by weight, and containing urethane or urea groups, said prepolymer being prepared by reacting
• A1) a cycloaliphatic diisocyanate
• with
• A2) at least one compound selected from the group consisting of:
• a) at least 6.5% by weight, based on the combined weight of A1) and A2)a), of one or more compounds containing at least two hydroxyl or amine groups and having a molecular weight of less than 500,
• and
• b) at least 10% by weight, based on the combined weight of A1) and A2)b), 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 55 to 90% by weight of one or more polyether polyols having number average molecular weights of from about 1000 to about 8000 and containing from 1.5 to 4 hydroxyl groups,
• B2) from 10 to 45% by weight of a mixture of organic chain extenders having molecular weights of from about 60 to about 500, and being selected from the group consisting of diols, triols, primary amines, secondary amines, amino alcohols, and mixtures thereof, wherein said mixture of chain extenders has an OH:NH equivalent ratio of from 1:2 to 20:1,
• with the %'s by weight of components B1) and B2) totalling 100%, and
• C) from 0.1 to 10% by weight, based upon the 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 133.