Process for producing ultrahigh viscosity polycaprolactam

Claim 1

A PROCESS FOR INCREASING THE VISCOSITY OF EPSILONCAPROLACTAM POLYMERS TO PRODUCE POLYMERS HAVING RELATIVE FORMIC ACID VISCOSITY OF AT LEAST ABOUT 200, MEASURED IN AQUEOUS 90% FORMIC ACID TO AT 10% CONCENTRATION AND 25*C. AS SPECIFIED IN ASTM TEST NO. D-789-53T, SAID VISCOSITY REMAINING STABLE WITHIN 50 UNITS DURING AT LEAST 10 MINUTES WORKING IN A MELT EXTRUDER, WHICH PROCESS CONSISTS ESSENTIALLY OF PASSING AN ATMOSPHERE OF DRY INERT GAS AT A RATE OF AT LEAST 2 VOLUMES OF GAS MEASURED AT STANDARD TEMPERATURE AND PRESSURE CONDITIONS PER VOLUME OF REACTION MIXTURE PER HOUR AND AT RATE IN THE RANGE BETWEEN ABOUT 20 AND ABOUT 50 CUBIC FEET OF GAS (STP) PER HOUR PER SQUARE FOOT OF EXPOSED SURFACE OF THE BELOW DEFINED REACTION MIXTURE, OVER THE EXPOSED SURFACE OF A REACTION MIXTURE OF EPSILON-CAPROLACTAM POLYMER WHICH POLYMER HAS RELATIVE FORMIC ACID VISCOSITY OF AT LEAST ABOUT 50 AND HAS END GROUPS AVAILABLE FOR FURTHUR POLYMERIZATION TO RELATIVE FORMIC ACID VISCOSITY OF AT LEAST 200; ANY NON-POLYMERIZABLE MATERIAL DISSOLVED IN SAID REACTION MIXTURE BEING NON-ACIDIC; THE WHOLE BODY OF SAID REACTION MIXTURE INCLUDING ALL SURFACES BEING MAINTAINED AT TEMPERATURES IN THE RANGE BETWEEN ABOUT 240*C. AND 275*C. AND BEING SUBJECTED TO SMOOTH, THOROUGH STIRRING UNTIL THE RELATIVE FORMIC ACID VISCOSITY THEREOF HAS RISEN TO AT LEAST ABOUT 200.