ES362928A1 - Production of yarns - Google Patents

Abstract

Thermoplastic elastomeric yarns in which the yarn material contains at least 85% by weight of segmented polyurethane ("Spandex" yarns) are treated by simultaneously stretching the bare yarn to an extent of less than 200% of its length prior to stretching and subjecting it to a temperature at or above its sticking temperature in the range 215-300 C. over a period of time not exceeding 30 seconds. The process may be carried out on a covering machine as part of a covering operation on the bare Spandex yarn or as part of a winding operation, e.g. when winding bare Spandex yarn from one package to another. The yarn may be treated under such conditions of stretching and temperature as to result in increased elongation at break. Advantageously, the bare yarn may be stretched whilst it is being caused to run over and preferably in contact with an electrically heated plate. In the covering machine shown in the diagrammatic drawing, a bare Spandex yarn Y is drawn from a supply package 1 and finally wound up on to a take-up package 2. The covering machine comprises two covering spindles 3 and 4 which support bobbins 5 and 6 of covering threads. The Spandex yarn Y runs freely right through the spindles 3 and 4, and the latter are spaced apart axially in, and arranged to rotate about, a straight upward portion of the path of travel of the yarn. The yarn Y passes from the supply package 1 over the first and second feed wheels 8 and 9, the wheel 9 being driven at a higher peripheral speed than wheel 8 to stretch the yarn and the yarn being at the same time heated by being guided through a heater 7 incorporating an electrically heated plate 71 over and in contact with which the yarn travels. The covered stretched yarn after its passage through the covering spindle 4 passes round a take-up roller 10 and is laid evenly upon the package 2 by the traversing guide 11. The temperature of the plate 71 may be measured by means of a Thermophil temperature probe. The sticking temperature of the bare Spandex yarn is defined as the temperature at which the yarn will just stick to a heated brass block when held against the surface of the block for 5 seconds with a 200 gram weight. The temperature of the block is measured by means of a Thermophil temperature probe.