Vacuum-thermal treatment of polymerized caprolactam to reduce the content of low molecular weight constituents therein

Claim 1

A PROCESS FOR THE TREATMENT, PRIOR TO SPINNING, OF HIGH MOLECULAR WEIGHT POLYMERIZED CAPROLACTAM TO REDUCE THE CONTENT OF LOW MOLECULAR WEIGHT MONOMERIC AND OLIGOMERIC CAPROLACTAM CONSTITUENTS THEREIN TO AT MOST ABOUT 2.5% THEREOF, WHICH COMPRISES SUBJECTING RESINOUS POLYMERIZED CAPROLACTAM, CONTAINING THEREIN MORE THAN 2.5% BY WEIGHT OF LOW MOLECULAR WEIGHT MONOMERIC AND POLYMERIC CAPROLACTAM CONSTITUENTS, AT A TEMPERATURE ABOVE THE MELTING POINT THEREOF TO VACUUM TREATMENT AT A PRESSURE OF UP TO ABOUT 0.6 TORR FOR A PERIOD BETWEEN ABOUT 15-100 MINUTES TO REMOVE THE VOLATILE CONSTITUENTS PRESENT, FOLLOWED BY THERMAL TREATMENT AT A TEMPERATURE ABOVE THE MELTING POINT OF THE CAPROLACTAM POLYMER AND AT A PRESSURE ABOVE ABOUT 0.6 TORR FOR A PERIOD OF BETWEEN ABOUT 1-4 HOURS, TO ATTAIN AN EQUILIBRIUM RATIO OF MONOMERIC CAPROLACTAM TO OLIGOMERIC OLIGOMERIC CAPROLACTAM IN THE RATIO RANGE OF SUBSTANTIALLY ABOUT 60:40 TO 70:30, THE REPEATING THE VACUUM TREATMENT FOLLOWED BY THERMAL TREATMENT AT LEAST ONE MORE TIME, WHEREBY TO OBTAIN A TOTAL CONTENT OF MONOMERIC AND OLIGOMERIC CAPROLACTAM CONSTITUENTS OF AT MOST ABOUT 2.5% BY WEIGHT OF THE RESINOUS POLYMERIZED CAPROLACTAM WITH THE EQUILIBRAUM RATIO OF MONOMERIC CAPROLACTAM TO OLIGOMERIC CAPROLACTAM AFTER THE LAST THERMAL TREATMENT BEING WITHIN THE RATIO RANGE OF SUBSTANTIALLY ABOUT 60:40 TO 70:30.