Patent ID: 6194537
Filing Date: 2001-02-27
Classification: C08G,C08J,D01F

Abstract:
Nylon 6 chip having a relative viscosity (measured at 25.degree. C. on a solution of 1 g of nylon 6 in 100 ml of 96% strength sulfuric acid) of 2.2 to 4.8, formed from hydrolytic polymerization of caprolactam in the presence of dicarboxylic acids as chain regulators, subsequent processing of the polymer melt into chip, extraction of the low molecular weight fractions from the chip with water and subsequent drying of the chip, which comprises, the temperature at which the extract water is evaporated does not exceed 120.degree. C. the extract water from the extraction of the chip, comprising a mixture of caprolactam and its oligomers, being admixed with fresh lactam and then concentrated through evaporation of the water content and the concentrate being recycled into the polymerization and the concentration of the cyclic dimer being less than 1% by weight after the polymerization has ended, wherein the continuous polymerization is carried out without application of pressure in a closed system.