Process for the preparation of optionally cellular polyurethane polyurea molded parts with improved demolding characteristics

Claim 1

In a process for the one-shot preparation of a cellular, microcellular, or non-cellular polyurethane polyurea polymer by reaction injection molding wherein said polymer is formed through the reaction of an isocyanate, a polyol and a chain extender, in the presence of suitable catalysts and optionally, blowing agents, additives, and auxiliaries, the improvement comprising selecting a chain extender containing in excess of 70 percent by weight relative to the total chain extender weight, of an aromatic diamine component comprising (a) from 80 to 50 percent by weight of at least one sterically hindered primary aromatic diamine whose amino groups are sterically hindered with respect to reaction with polyisocyanates by the presence of at least one alkyl substituent in the ortho position of each amino group, and (b) from 20 to 50 percent by weight of a reactive aromatic diamine selected from the group consisting of unsubstituted, primary aromatic diamines, substituted primary aromatic diamines, and mixtures thereof, wherein the amino groups of said diamines do not exhibit any reduced reactivity with respect to polyisocyanates as a result of electrophilic substituents and/or steric hindrance, wherein the foregoing percents by weight are based on the total weight of mixture of (a) and (b).