Hindered amines to slow down reactivity in producing rim elastomers

Abstract

A process for preparing a polyurea reaction injection molded (RIM) elastomer is described. A hindered polyetherpolyamine is first obtained by reacting a polyol having two or more hydroxyl groups with an effective amount of long chain alkyl epoxide to give an at least partially hindered intermediate having hydroxyl terminations; and then aminating at least one of the hydroxyl terminations on the intermediate to primary amine groups to give an at least partially hindered polyetherpolyamine. The hindered polyetherpolyamine is then reacted with a polyisocyanate in the optional presence of a catalyst to give a polyurea RIM elastomer. The long chain alkyl group provides steric hindrance to the primary aliphatic amine group, which slows down the reactivity of the amine. The slower reactivity of the amine group is useful in RIM and RRIM compositions since it allows for longer shot or flow times, which in turn permit larger parts to be made from existing equipment.