GB991771A - Methods and apparatus for processing thermoplastic yarns - Google Patents

Abstract

991,771. Finishing yarns. DEERING MILLIKEN RESEARCH CORPORATION. Feb. 27, 1962 [Feb. 27, 1961], No. 7613/62. Heading D1F. [Also in Division B5] A method of processing a running length of thermoplastic yarn which is in such a state that on heating it will increase in bulk and shrink in length, comprising positively overfeeding the yarn through a narrow elongated tube which is heated so that each part of the yarn becomes heated to processing temperatures of 100‹C. to 225‹C. for at least 1/ 2 second, the temperature not exceeding the sticking temperature of the yarn, the overfeed being between 1% and 25% and less than the maximum amount of shrinkage possible at the processing temperatures, and the tube being associated with means for positively passing gas through the tube with the yarn so that the total rate of flow through the tube is substantially greater, e.g. by 10-50% than the rate which would be induced by windage. Preferably the yarn has had latent stress induced in it by edge crimping. The yarn may be a multifilament of denier e.g. 300-15, 000, and may be formed from e.g. nylon, polyester, cellulose triacetate, polypropylene or polyvinyl alcohol. The yarn may be fed at 20 yards per minute, or more, into a tube 1 to 20 feet long and of inside diameter less than <SP>1</SP>/ 2 inch. The tube may be straight, bent, or coiled. The gas may be directed into the tube as a jet from a capillary, which may itself be heated, inserted into the entrance of the tube. Preferably, the linear velocity of the gas, e.g. compressed air, nitrogen or superheated steam, is greater than the linear velocity of the yarn in the tube. In one embodiment, (Fig. 1) thermoplastic yarn 2 from package 1 passes over tension regulator 5 and is fed by yarn advancing rolls 11, 12 to one end 31 of tube 30, which is heated by EMF source 36. Gas from supply 41 is injected into tube 30 from small heated tube 40. The gas emitted from open end 43 of tube 40 (Fig. 3) causes the overfed yarn 2 to billow into a loose structure 2a. As the yarn becomes heated, the overfed length is taken up as the yarn shrinks and becomes bulked 2b. The bulked yarn is taken up by second advancing rolls 21, 22, and is guided by means 50 to take up package 51. Tube 30 may be of stainless steel if electrically heated, or of glass, ceramic or chromeplated copper or brass if heated by the hot air from tube 40. In a further embodiment (not shown) the apparatus of Fig. 1 is incorporated in a unitary drawing, crimping and heat-processing apparatus. The yarn is first drawn e.g. 2: 1 to 10: 1 between a first yarn advancing means and second heated yarn advancing means e.g. a heated roll, and then edge-crimped by passage over a blade adjacent the heated roll before entering the heated tube 30.