Polyurethane casting process

Claim 1

A PROCESS FOR THE PREPARATION OF A POLYURETHANE CASTING WHICH COMPRISES REACTING AN HYDROXYL POLYESTER OBTAINED FROM A DICARBOXCYLIC ACID HAVING AT LEAST FIVE CARBON ATOMS AND A DIHYDRIC ALCOHOL HAVING AT LEAST FIVE CARBON ATOMS AS ESSENTIALLY THE SOLE COMPONENTS OF SAID HYDROXYL POLYESTER, SAID HYDROXYL POLYESTER HAVING A MOLECULAR WEIGHT OF FROM ABOUT 900 TO ABOUT 1200, WITH FROM ABOUT 0.4 TO ABOUT 0.7 MOL OF AN ORGANIC DIISOCYNATE PER MOL OF SAID HYDROXYL POLYESTER AT A TEMPERATURE OF FROM ABOUT 80*C. TO ABOUT 150*C. UNTIL THERE ARE NO LONGER FREE -NCO GROUPS PRESENT IN THE REACTION MIXTUR AND AN HYDROXYL TERMINATED POLYESTER URETHANE IS OBTAINED WHICH HAS AMOLECULAR WEIGHT OF FROM 2000 TO ABOUT 3000 AND THEN REACTING THE RESULTING HYDROXYL TERMINATED POLYESTER URETHANE IN A SECOND STEP WITH AN EXCESS OF FROM ABOUT 20 TO ABOUT 300 MOL PERCENT AN ORGANIC DIISOCYNATE BASED ON THE FREE HYDROXYL GROUPS OF SAID HYDROXYL TERMINATED POLYESTER URETHANE TO OBTAIN AN -NCO TERMINATED INTERPOLYMER, MIXING SAID -NCO TERMINATED INTERPOLYMER WITH AN ORGANIC CROSS-LINKING AGENT SELECTED FROM THE GROUP CONSISTING OF A POLYHYDRIC ALCOHOL AND A POLYAMINE REQUIRED TO REACT WITH ALL OF THE -NCO GROUP OF SAID -NCO TERMINATED INTERPOLYER, CASTING THE RESULTING MIXTURE IN A MOLD AND ALLOWING IT TO CURE AT A TEMPERATURE OF AT LEAST ABOUT 50*C. UNTIL A SOLID SUBSTANTIALLY NONPOROUS POLYURETHANE PLASTIC IS OBTAINED.