Patent ID: 8242229

Claim:
A polyurethane elastomer comprising the reaction product of: (a) an NCO-terminated prepolymer prepared by reacting: (1) diphenylmethane diisocyanate having a 2,4′-MDI isomer content of greater than 80% by weight, with (2) a high molecular weight polyol selected from the group consisting of polyalkyleneether polyols having a number average molecular weight of 250 to 10,000, polyester polyols having a number average molecular weight of 250 to 10,000 and mixtures thereof, at a temperature of between 30° C. and 150° C. for a time sufficient to form the NCO-terminated prepolymer, with the OH groups of said polyol being reacted with the NCO groups of said diphenylmethane diisocyanate in an stoichiometric ratio of NCO groups to OH groups in the range of 1.5:1 to 20:1; (b) an aliphatic diisocyanate selected from the group consisting of the isomers of 1,1′-methylene-bis-(4-isocyanatocyclohexane), 1,4-cyclohexane diisocyanate, isophorone diisocyanate 1,3-xylylene diisocyanate, hexamethylene diisocyanate, the isomers of m-tetramethylxylylene diisocyanate (TMXDI), mixtures thereof and prepolymers thereof; and (c) an aliphatic and/or aromatic di- or polyamine; wherein the reactants - are present in amounts such that the equivalent ratio of NCO groups to the sum of NCO-reactive groups of the resultant elastomer is in the range of from 0.8:1 to 1.2:1.