Vulcanization process for preparation of polyurethane tires

Claim 1

A process for the manufacture of a vulcanized elastomer which comprises (1) forming a mix comprising (a) at least one functional liquid diene prepolymer having reactive mobile hydrogen functions and a degree of functionality of between 1.8 and 2.0; (b) a reinforcing filler; and (c) a vulcanizing system comprising sulfur, zinc oxide, and an accelerator having no mobile hydrogen; and adding to the mix (d) a hydrocarbon chain lengthening bifunctional compound having reactive isocyanate groups and in such amount that the ratio of the number of reactive isocyanate groups of the hydrocarbon chain lengthening bifunctional compound to the number of reactive mobile hydrogen functions of the functional liquid diene prepolymer in the resultant mix is equal to one; (2) in a first stage, heating the resultant mix to a temperature of from 20° C. to about 140° C. to obtain exclusively a chain lengthening reaction between the functional liquid diene prepolymer and the hydrocarbon chain lengthening bifunctional compound; and (3) in a second stage, further heating the resultant mix to a higher temperature of from about 145° C. to about 200° C. to effectuate the vulcanization of the chain lengthened reaction product formed at the end of the first stage.