Caprolactam polymerization

Claim 1

PROCESS FOR POLYMERIZING EPSILON-CAPROLACTAM TO A POLYMER OF RELATIVE VISCOSITY IN FORMIC ACID OF AT LEAST ABOUT 25, MEASURED UPON WASHED, DRIED POLYMER IN AQUEOUS 90% FORMIC ACID AT 25*C. AND CONCENTRATION OF 11 GRAMS PER 100 CC. OF SOLVENT, IN WHICH PROCESS WATER IS THE SOLE REACTIVE ADDITIVE AND WHICH PROCESS FURTHER COMPRISES BRINGING THE CAPROLACTAM STARTING MATERIAL AT PH 5.7 AS MEASURED IN WATER SOLUTION OF 20% LACTAM CONCENTRATION, WITHIN A RANGE OF DEVIATION NOT MORE THAN 2.0 MILLIEQUIVALENTS OF NEUTRALIZING AGENT PER KILOGRAM OF LACTAM; HEATING A SOLUTION OF SAID LACTAM AND WATER WITH AGITATION UNDER AN ATMOSPHERE OF INERT GAS AT ABOUT ATMOSPHERIC PRESSURE TO TEMPERATURE IN THE RANGE BETWEEN ABOUT 180*C. AND ABOUT 230*C., AND SIMULTANEOUSLY ESTABLISHING A CONCENTRATION OF WATER IN THE RANGE BETWEEN ABOUT 0.1% AND ABOUT 2.0% OF WATER BY WEIGHT OF THE REACTION MIXTURE; THEN HEATING THE RESULTING REACTION MIXTURE WITH AGITATION TO POLYMERIZING TEMPERATURES IN THE RANGE OF ABOUT 240*C. TO ABOUT 290*C. UNDER AN ATMOSPHERE OF INERT GAS AT ABOUT ATMOSPHERIC PRESSURE; THEN CONTINUING THE HEATING IN THE RANGE 240*C-290*C. WITH AGITATION TO A WASHED, DRIED POLYMER RELATIVE VISCOSITY IN 90% FORMIC ACID OF AT LEAST 25; AT LATEST JUST BEFORE THE EXTRUSION PHASE OF THE PERIOD OF HEATING AT 240*-290*C., PROVIDING A GAS ATMOSPHERE HAVING HIGHER WATER VAPOR PRESSURES THAN SAID FIRST MENTIONED ATMOSPHERE, SAID WATER VAPOR PRESSURES ULTIMATELY REACHING A LEVEL VALUE WHICH IS MAINTAINED FOR AT LEAST 2 HOURS, IN THE RANGE BETWEEN ABOUT 1 AND ABOUT 50 POUNDS PER SQUARE INCH ABSOLUTE WITH TEMPERATURE LIKEWISE MAINTAINED CONSTANT WITHIN ABOUT $2*C. DURING AT LEAST THESE LAST 2 HOURS BEFORE EXTRUSION; AND EXTRUDING UNDER GAS PRESSURE OVER A TIME PERIOD OF AT LEAST ABOUT 3 HOURS POLYMER AT THE DESIRED FINAL VISCOSITY FROM THE RESULTING POLYMER MELT, SAID POLYMER MELT BEING EQUILIBRATED WITH MOIST INERT GAS WITH DEWPOINT, AT EXTRUSION PRESSURE, OF ABOUT 90*C. TO ABOUT 95*C. AND SAID MELT BEING MAINTAINED AT TEMPERATURE CONSTANT WITHIN ABOUT $2*C. THROUGHOUT THE MELT AND AT THE WALLS OF THE REACTION VESSEL.