GB927586A - Process for making composite polyester yarns - Google Patents

Abstract

Yarn which yields soft, uniformly bulky, knitted or woven fabrics (see Group IX) combines at least one group of continuous filaments of a polyester, e.g. polyethylene terephthalate or naphthalate, having a zero load residual shrinkage of 0-20% and a residual shrinkage at 0,05 grams per denier load of at least 1,2% less than the zero load residual shrinkage, with a second group of continuous polyester filaments having a zero load residual shrinkage at least 20% higher than the zero load residual shrinkage of the first group. Residual shrinkage is defined as the capability remaining or existing in the filament or yarn for linear contraction under the specified tension in water at 100 DEG C. for an exposure time of five minutes, and methods of its determination are described. The groups of filaments may be extruded from the same spinneret or several and/or separate spinnerets, and attenuated to the same final length and to produce similar properties of tenacity and, in consequence, of dyeability, but under different conditions, e.g. of "superstretching", i.e. drawing without orientation, heating, stretching and/or relaxing, to produce the different shrinkage properties. As shown in Fig. 1, bundles 1,11, of melt-spun filaments 2, 21, pass around forwarding rolls 4, 41, which tension the filaments and determine the spinning speed. Bundle 1 is forwarded to roll 5 which is heated to a temperature of 130 DEG -180 DEG C., roll 6 which is heated to a temperature up to 120 DEG C., a drawing or snubbing pin 9, and roll 7. Bundle 11 is <PICT:0927586/IV(a)/1> <PICT:0927586/IV(a)/2> forwarded to roll 51, optionally around snubbing pins 11, roll 71, and may then relax as it is heated by a hot plate (not shown). Rolls 5, 51, rotate at the same peripheral speed as rolls 4, 41, and the speeds of rollers 6 and 7 or 71 are progressively higher. The filaments may also be heated by plates 10, 101, or roll 7. Each roll co-operates with a canted separator roll 8. In the process represented in Fig. 2, a group of filaments passes from roll 5 and separator 8, under a drawing pin 17 in a liquid bath 16, through guides 19, around draw rolls 18 which may be heated, and combines with another group of filaments emerging from draw rolls 181. In other embodiments, Figs. 3 and 4 (not shown) all the filaments are drawn, and may be heated by rolls, curved plates and/or liquid baths, but one group only is subsequently relaxed or the two groups are relaxed to different extents. Specifications 695,567 and 868,496 are referred to.