Patent GB-1472931-A (GB)
Title: Yarn production method
IPC: D02G3/22
Filed: 1974-04-26
Abstract: 1472931 Simultaneously drawing and false twisting multifilament yarn to produce yarn having fibrils UNITIKA Ltd 26 April 1974 [28 April 1973 30 Aug 1973] 18509/74 Headings D1F and D1W A method of producing a yarn resembling a spun yarn comprising simultaneously falsetwisting and drawing a "feed yarn" at an elevated temperature and at a draw ratio which is less than the "ultimate draw ratio" of the feed yarn wherein, during false-twisting the feed yarn is twisted so as to have (a) not more than 31000/#D' turns per metre and (b) individual filaments flattened along at least part of the length thereof, whereby at least some of the flattened parts of the filaments are broken during the detwisting step of the false twisting. The factor D' is the number obtained by dividing the total denier of the feed yarn by the draw ratio used, the "feed yarn" is defined as a multifilamentary synthetic thermoplastic yarn each of whose filaments has an elongation at break of at least 80%, and the "ultimate draw ratio" is defined as the draw ratio at breaking. The feed yarn filaments may comprise: a polyester having an intrinsic viscosity of from 0.4 to 1.3 and a birefringance of from 5 x 10<SP>-3</SP> to 40 x 10<SP>-3</SP>; a polyether ester having an intrinsic viscosity of from 0.5 to 0.7 and a birefringance of from 2 x 10<SP>-3</SP> to 35 x 10<SP>-3</SP>; a polyamide, e.g. nylon 6, having an intrinsic viscosity of from 0.9 to 2.1 and a birefringance of from 20 x 10<SP>-3</SP> to 40 x 10<SP>-3</SP>; or a polyacrylonitrile. The intrinsic viscosity of the polyester and polyether ester is as measured in a 1:1 by weight mixed solvent of phenol and tetrachloroethane at 20‹C, and the intrinsic viscosity of the polyamide is as measured in 96% by weight sulphuric acid at 30‹C. The feed yarn may have a circular or hollow cross-section, and may be a ply yarn or a twisted yarn. The feed yarn filaments may have different physical properties, e.g. may have different colour, and may each have a denier of from 1 to 6. There may be 24 filaments in the feed yarn. The feed yarn is drawn between rolls 2, 6, Fig. 3 while being heated at 3 and false twisted at 5, e.g. by a pin twister or by a friction twister. The filaments flattened by drawing are said to be broken in the detwisting zone, and the distance between false twister 5 and rolls 6 may be variable, or a holding point provided, to control breakage. The flattened parts may have cross-sections whose ratio of short to long dimesion is from 1:2 to 1:7. The temperature of heater 3 may lie between the softening point of the filaments and a temperature of two thirds the softening point in degrees belsius. The draw ratio may be 0.80 to 0.90 the ultimate ratio. The coherency or heat stability of the yarn may be improved by false twisting, and heating, by true twisting, or by the application of a fluid vortex flow or a bonding agent. The yarn produced has fibrils within the yarn of irregular length, some of which extend from the yarn. The individual filaments may be crimped and intertwined, and occasionally S and Z twists may exit alternately along the yarn.