HMLS-fibers made of polyester and a spin-stretch process for its production

摘要

HMLS filaments consisting of a polyester, from 0.1 to 2.5% by weight of an incompatible, thermoplastic, amorphous, polymeric additive having a glass transition temperature of from 90 to 170 C. and a ratio of its melt viscosity to that of the polyester component of from 1:1 to 7:1, and from 0 to 5.0% by weight of conventional additives, where the polymeric additive is present in the filaments in the form of fibrils having a mean diameter of 80 nm.;Process for the production of these HMLS filaments by static mixing with shearing of the polyester and of the polymeric additive and, optionally, of the additives, spinning of the mixture at a spinning take-off speed of from 2500 to 4000 m/min to give spun filaments which are stretched, heat-set and wound up, where the concentration of the polymeric additive is determined as a function of the pre-specified spinning take-off speed and the desired birefringence of the spun filaments.