Random copolymerized polyamide resin and process for preparing the same

摘要

A random copolymerized polyamide resin is prepared by reacting a lactam of the formula (I): <IMAGE> (I) wherein R1 is a C2-11 alkylene group optionally substituted with a substituent having 1 to 6 carbon atoms, with a hexamethylenediamine-adipic acid salt while concentrating the aqueous solution of the salt to a concentration of at least 70% by weight and while maintaining a uniform reaction phase at all times by controlling the pressure over and the temperature of the reaction medium such that the hexamethylenediamine-adipic acid salt does not precipitate, said pressure being up to not greater than 2 kg/cm2xG and said temperature being up to not greater than 150 DEG C., and then mixing in the solution of the lactam of formula (I) thereby effecting copolymerization and forming a polyamide resin having a relative viscosity measured by the sulfuric acid solution method (1% at 25 DEG C.) of 1.5 to 8.0.