Improvements in or relating to the manufacture of polyamide filaments

摘要

In the manufacture of polyamide filaments by melting polycaprolactam chips at 250 DEG -295 DEG C. under an inert gas at a pressure of 0,5-5 atmospheres and melt spinning the polyamide, the chips have been washed with water but not dried or only incompletely dried and contain over 1/4 % by weight of water and the polyamide is maintained in a molten condition for a period not exceeding in minutes the expression:- in which e=the base of the natural logarithms, T=temperature in DEG C., P=pressure in atmospheres of inert gas, E=sum of the free amine and carboxyl end groups in the polymer expressed in gram equivalents per million grams. The determination may be carried out on a sample of the polymer taken from the melt pool or on a sample of the extruded filaments. The earlier stages of the washing of the chips may be carried out with aqueous solutions, e.g. of caprolactam, pure water being subsequently used. The time during which the polyamide is maintained in a molten condition is preferably not more than 80% of the specified maximum permissible period. The inert gas may be nitrogen, steam, helium or hydrogen, preferably steam at within 3% of the prevailing atmospheric pressure. It is preferable to use polyamide chips containing over 3 1/2 % of water, e.g. up to 7% or over provided their water content is not so high as to cause caking or paste formation. Specifications 461,237, 653,757, 676,585, 747,913, 813,527, French Specification 882,461 and U.S.A. Specification 2,241,321 are referred to.