Preparation of polyurethane elastomers

Claim 1

THE PROCESS FOR THE PREPARATION OF A STABILIZED BRANCHED CHAIN POLYURETHANE ELASTOMER WHICH COMPRISES THE STEPS OF (1) HEATING AT A TEMPERATURE OF ABOUT 90*C. FOR ABOUT 60 MINUTES M MOLES OF (A) A POLYMERIC DIHYDROXY COMPOUND HAVING A MOLECULAR WEIGHT BETWEEN 750 AND 5000 SELECTED FROM THE CLASS CONSISTING OF POLYESTERS, POLYETHERS AND POLYESTER AMIDES WITH M + 1 MOLES OF (B) AND ORGANIC DISSOCYANATE, M BEING BETWEEN 1 AND 10, TO FORM (C) A LINEAR POLYURETHANE HAVING TERMINAL ISOCYANATO GROUPS, (2) HEATING AT A TEMPERATURE OF ABOUT 120*C. FOR ABOUT 3 TO ABOUT 5 HOURS N + 1 MOLES OF SAID (C) LINEAR POLYURETHANE HAVING TERMINAL ISOCYANATO GROUPS WITH N MOLES OF (D) A BIFUNCTIONAL COMPOUND REACTIVE WITH SAID ISOCYANATO GROUPS SELECTED FROM THE CLASS CONSISTING OF LOW MOLECULAR WEIGHTS DIOLS, DIAMINES AND DICARBOXYLIC ACIDS, N BEING BETWEEN 1 AND 10, TO FORM SEQUENTIALLY (E) AN UNSTABLE LINEAR POLYURETHANE HAVING TERMINAL ISOCYANATO GROUPS AND CONTAINING SAID BIFUNCTIONAL COMPOUND AND THEN (F) AN UNSTABLE BRANCHED CHAIN POLYURETHANE ELASTOMER HAVING AT SUBSTANTIALLY ALL TERMINAL PORTIONS THEREOF FREE ISOCYANATO GROUPS, THE RATIO BY WEIGHT OF FREE ISOCYANATO GROUPS TO THE UNSTABLE BRANCHED CHAIN POLYURETHANE ELASTOMER BEING IN THE RANGE OF FROM 0.3% TO 2%, AND (3) MIXING AT A TEMPERATURE FROM ABOUT 40*C. TO ABOUT 70*C. SAID (F) UNSABLE BRANCHED CHAIN POLYURETHANE ELASTOMER HAVING AT SUBSTANTIALLY ALL TERMINAL PORTIONS THEREOF FREE ISOCYANATO GROUPS WITH (G) AN AMINOALCOHOL, THE PROPORTION OF SAID AMINOALCOHOL USED CORRESPONDING TO THE QUANTITY OF THE AMINO GROUPS THEREIN EQUIVALENT TO THE NUMBER OF FREE ISOCYANATO GROUPS IN THE UNSTABLE BRANCHED CHAIN POLYURETHANE ELASTOMER, TO FORM (H) A STABILIZED BRANCHED CHAIN POLYURETHANE ELASTOMER HAVING THE BRANCHES TERMINATED BY HYDROXYL GROUPS.