Melt polymerization of ε-caprolactam

Claim 1

A process for the preparation of linear polyamide from ε-caprolactam, the steps of the method comprising heating an initially present polymerizable polyamide forming ε-caprolactam composition to a temperature from about 180° to 300° C. in the presence of about 0.5 to 10 mole of water per mole of initially present composition, to convert at least a major portion of the composition to polymer while under superatmospheric pressure, removing water from a polymer at a pressure not greater than about atmospheric pressure, maintaining the polymer under an inert atmosphere and subsequently cooling the polymer to provide solidified polymer having polymerized therein ε-caprolactam, the improvement which comprises providing in the polymerizing composition before a majority of the polymerization has occurred from about 0.01 to less than about 0.6 mole percent based on the initially present composition of primary and secondary amines or mixtures thereof which boil under atmospheric pressure at temperatures not less than about 245° C. of the Formula (I): ##STR2## where R 1 and R 2 are individually selected from the group consisting of hydrogen, alkyl radicals, cycloalkyl radicals, cyclooxyamidoalkyl radicals, amidoalkyl radicals, aromatic radicals, aralkyl radicals, alkyl sulfonate radicals, alkyl sulfide, alkaryl radicals, such radicals containing up to 18 carbon atoms, where R 1 and R 2 together are collectively considered, R 1 and R 2 together represent a divalent alkylene radical and after removing water, maintaining the polymer at a temperature of from 240° to 280° Centigrade for a period of from about 6 to 12 hours while contacting the polymer with an inert gas at a rate of from about 5 to 300 cubic centimeters per minute of a gas at standard temperature and pressure per 300 grams of polymer to thereby obtain a polyamide containing less than about 3 weight percent methanol extractable.