Verfahren zur Herstellung von gekraeuseltem und kraeuselbarem Garn

In a combined process of drawing and crimping undrawn or incompletely drawn, low or zero twist yarn composed wholly or mostly of continuous filaments of a synthetic linear polymer, e.g. a polyamide, polyester, polypropylene, polyurea or polyurethane, the yarn, as it approaches a draw roll, is caused to engage frictionally a flange on the roll which thereby rapidly rotates the yarn about its axis and so imparts false-twist thereto. The twist is set by passage of the yarn around a heated snubbing pin or over a hot plate or by hot nitrogen, steam, infra-red radiation, molten metal, or a high frequency electrical field, with which the action of a swelling agent may be combined. The draw roll, and/or the yarn in the vicinity of the surface thereof, may be cooled, as by an air jet or circulation of a fluid in the roll. The feed roll (or the snubbing pin) may be offset in relation to the draw roll so that the yarn approaches the latter at an acute angle to the axis thereof. The flange may be integral with or detachable from the draw roll and of material which withstands abrasion and grips the yarn, e.g. glass, ceramics, polyamide, polyurethane, alumina, carborundum, stainless steel, or elastomer such as rubber or synthetic rubber; the contour constitutes a surface of rotation generated and defined by a curved "geodesic" line connecting the points at which the yarn makes and breaks contact therewith, and may be convex, conical or concave. The potential crimp induced by the falsetwisting and setting operations is developed, prior or subsequent to twisting the yarn and/or converting it into fabric, by relaxation, the effect of which may be assisted by (gradually applied) heat, e.g. by hot air and steam. The relaxation may occur within controlled limits, e.g. the yarn may be overfed as it proceeds from draw roll to forwarding nip rolls via a hot zone: if the nip rolls are heated this zone is unnecessary. Additional heat-setting, optionally with swelling agents, e.g. water or steam, may be effected after relaxing the yarn.