GB1452355A - Crimping process - Google Patents

Abstract

1452355 1452355 Crimping filaments E I DU PONT DE NEMOURS & CO 23 May 1974 23155/74 Headings D1F and D1W Latent crimp due to asymmetric shrinkage is introduced into filaments spun from a single thermoplastic polymer, e.g. a polymer or polyester or polyamide, by drawing the filaments to provide substantially break elongation and boilshrinkage desired and then passing them over a durable, wear-resistant curved surface 17 havinig a radius of curvature of 0.5 to 7.5 mm, at a speed of at least 900 yards per minute, ie.. 1370 om. per sec, under tension so as to generate by friction all of the heat required to provide the asymmetric shrinkage characteristics substantially without heating the wear-resistant surface. other than by contact with the filaments. The filaments are drawn to provide a break elongation of 15-40%, preferably 25-35% and a boiloff shrinkage of 5-25%, preferably 8-16%. Boiloff shrinkage is measured by comparing filament length before and after 30 minutes exposure in boiling water. The filaments pass over the texturing surface at a speed within the range 1000-4500 yards per minute, i.e. 1525-6860 cm per sec, and the temperature of the filaments fed to the surface is within the range 25-110‹C. During frictional contact with the surface the tension on the filaments filaments undergoes a change of 0.7-7 grams per filament with 1-2 grams per filament for polyesters and 4-5 grams per filament for polyamides. The surface is contacted by the filaments for a distance of 0.5- 15 mm., preferably 1-10 mm. and is provided by a ceramic, glass or stainless steel pin preferably having a diameter of 3-10 mm. The arc of contact of the filaments with the pin is 30-180‹, preferably 45-90‹. The friction coefficient of the pin surface is 0.2-1.2, preferably 0.4-0.8. The filaments being fed to and removed from the surface are stretched by not more than 10%, preferably by 2-5%. After drawing, the filaments have a denier of 1.5-10, preferably 2-5, per filament. The filaments may be treated as pant of a multifilament yarn of 10-200, preferably 17-50, filaments, and the yarns have counts of from 70/34 to 190/34. In one embodiment, Fig. 8, filaments 10 are melt-spun from a spinneret 11 and converge as they contact a first finish-applying roll (not shown). They proceed around feed rolls 12, through a steam draw jet 13, over a second finishing applying roll 14 and around draw rolls 15 onto which they are guided by a traversing mechanism 16. The filaments pass around an unheated texturing pin 17 with a change of direction #, are tensioned by pulling rolls 18 and pass over a postdraw finish roll 19 to a wind-up 20. Crimp is developed by a sulbsequent heat relaxation treatment. Alternatively, the wind-up 20 may be omitted and the filaments passed through heating means on a conveyor in relaxed condition and then cooled prior to being wound. In another modification a yarn is melt-spun and drawn and later pintextured in a separate operation. In Fig. 9, drawn yarn passes from a package 21 through a tension gate 22, over a roller 23, around feed rolls 24 and stretch rolls 25, over a texturing pin 26 with a change of direction # and over a roller 27 to a wind-up 28. The yarn makes several wraps around the rolls 24, 25. In the Examples, polyethylene terephthalate are first pin textured and then bulked by being passed into a jetted stream of heated compressible fluid which impinges the filaments against a screen surface on a rotating drum. Various polyesters and polyamides are specified. A single linear, polyester textile filament produced as described above has asymmetric shrinkage properties and a treated side, a minor portion of the cross-section extending along the treated side being distinguishable from the remainder of the dross-section by a difference in refractive index, in which the minor portion has a continuity along the filament such that less than 5 per cent of the filament length is occupied by discontinuities longer than 2 millimetres, the number of such discontinuities is less than 30 percent of the total number of all discontinuities, and the average length of all discontinuities is less than 2 millimetres; and the filament is capable of crimping when given a heat-relaxing treatment for 5 minutes in air at 180‹C such that, when viewed under high magnification, the treated surface is marked by closely spaced, parallel ripples which extend transverse to the filament length along the outer radius of the crimp bends.