Method of high speed yarn texturing

Claim 1

In a process of texturing multifilament polyethylene terephthalate partially oriented apparel yarn, by crimping operations comprising carrying drawn yarn by a stream of hot steam through an energy tube at high linear velocity to strike first, at an oblique angle, an unyielding barrier within a covered chamber which includes a perforate moving confining surface; allowing the compressible fluid to escape through the perforations in the moving surface; conveying the yarn toward the outlet from the chamber on said surface, traveling at lower linear velocity than that of the incoming yarn, whereby the yarn collects in a plug downstream from the point of impingement of the yarn with the barrier; and removing the yarn from the chamber when the plug reaches the outlet from the chamber: the improvement which comprises, in combination, drawing said yarn in steam, heated to temperature in the range from 235° C. to 300° C., at draw ratio in the range from 1.65 to 2.0; heat-setting the yarn in drawn state, by contact between the yarn and such heated steam using at least sufficient total heat and residence time to bring the density of the resulting heat-set yarn to at least 1.378 g./ml., followed by heating the yarn at constant length -- in advance of subjecting it to the above recited crimping operations -- by passing the yarn around a heated roll at contact time of about 0.1 second, said roll being heated to temperature of about 145° to 165° C.; and supplying the resulting hot, dimensionally stabilized yarn directly, without winding up, at linear velocity of at least 2500 meters per minute, into the energy tube for the above crimping operations.