A PROCESS FOR PREPARING SOLID ELASTOMERIC POLYURETHANES HAVING REDUCED SURFACE SKINNING

摘要

This invention relates to solid elastomeric polyurethanes preparedby reacting, in an open mold at an isocyanate index of 80 to 120,(a) an isocyanate prepolymer having an isocyanate content of 3 to15% by weight and a number average molecular weight of 550 to20,000 prepared by the reaction of(1) organic polyisocyanates having 2 to 3 NCO groups, and(2) isocyanate-reactive polyester polyols having two to threeisocyanate-reactive hydroxyl groups and a number averagemolecular weight of 400 to 10,000 and prepared in thepresence of an esterification catalyst, and optionallycontaining other isocyanate-reactive compounds,wherein the equivalent ratio of isocyanate groups to isocyanate-reactive groups is 1.2:1 to 34:1;(b) a diol chain extender, optionally in admixture with a crosslinkerand/or an amino-containing chain extender and/or crosslinker;(c) 0.001 to 10% by weight, based on the weight of the isocyanateprepolymer, of a catalyst; and(d) 0.01 to 5% by weight, based on the isocyanate prepolymer, ofsurface skinning retardants consisting of (1) certain carboxylicacids and derivatives thereof, (2) 1,2-diketones, 1,3-diketones, andaromatic hydroxyketones; (3) mono- and dihydric phenols, (4) N-substituted ureas and thioureas, and/or (5) certain phosphoruscompounds.