Improvement for the preparation of polyamides

Claim 1

IN A PROCESS FOR PREPARING POLYAMIDE FROM PREPOLYMER OF POLYAMIDE-FORMING LACTAMS AND W-AMINOCARBOXYLIC ACIDS TO FORM A SOLID POLYMER HAVING INCREASED RELATIVE VISCOSITY, THE IMPROVEMENT COMPRISING SUBJECTING SAID PREPOLYMER IN FINELY DIVIDED FORM TO SOLID PHASE POLYMERIZATION AT TEMPERATURES BELOW THE MELTING POINT OF SAID POLYAMIDE IN AN INERT CYCLIC HYDROCARBON HAVING A BOILING TEMPERATURE BETWEEN 180* AND 210*C. AND AT THE BOILING TEMPERATURE OF SAID INERT CYCLIC HYDROCARBON WHILE CONTINUOUSLY REMOVING WATER FORMED UNTIL WATER IS NO LONGER SEPARATED AND THE POLYMERIZATION IS SUBSTANTIALLY COMPLETED, SAID INERT CYCLIC HYDROCARBON BEING A NONSOLVENT FOR SAID POLYAMIDE AND SAID PREPOLYMER HAVING A PARTICLE SIZE OF NOT MORE THAN 5 MM., SEPARATING THE INERT CYCLIC HYDROCARBON FROM THE RESULTING PRODUCT, REMOVING INERT CYCLIC HYDROCARBON STILL ADHERING TO SAID RESULTING PRODUCT AND RECOVERING A UNIFORM POLYAMIDE HAVING INCREASED RELATIVE VISCOSITY.