Patent GB-1190078-A (GB)
Title: Novel Silk-like Polyester Yarns and process for producing them
IPC: D02G3/00
Filed: 1967-07-13
Abstract: 1,190,078. Producing silk-like polyester yarns. E. I. DU PONT DE NEMOURS & CO. 13 July, 1967 [13 July, 1966], No. 32386/67. Heading B5B. [Also in Divisions C3 and D1] A silk-like multifilament yarn consists of non-round synthetic linear condensation polyester filaments of at least two types having " shrinkabilities " differing by at least 1À7%, having average " shape factors " greater than 13, being free from voids and free from delustrants or containing, as the sole delustrant, not more than 0À1% by weight of titanium dioxide, containing a surface-roughening agent of such a nature and in such proportion that the surface roughness of the filaments is such that the coefficient of hydrodynamic friction between the filaments and a polished chromium surface is less than 0À70 in the " flooded test " or less than 0À45 in the " film test " and having an average denier per filament of from 0À75 to 1À5. The yarn may be produced by melt-spinning the polyester into which the surface-roughening agent has been incorporated through non- round spinneret orifices and drawing the resulting filaments to produce filaments having average shape factors greater than 13 and averaging 0À75 to 1À50 denier per filament, some of the filaments of the polyester being subjected to a heat treatment at a temperature differing from that at which some of the other filaments of the polyester are subjected, so as to produce two groups of filaments having shrinkabilities differing by at least 1À7% and combining the two groups of filaments into a yarn, the heat-treatment taking place before, during, or after drawing and combining the groups of filaments. The difference between the shrinkabilities of the two types of filaments is defined as the difference between the " boiloff" shrinkage of the higher shrinkage component measured under a restraining tension of 0À02 gram per denier and expressed as a percentage of the original sample length, and the dry heat shrinkage of the lower shrinkage component, measured at 160‹ C. with no restraining tension, similarly expressed as per cent of the original sample length. Shape factor is defined by the expression P<SP>2</SP>/A where P is the perimeter of the cross-section, of the filament and A is the area of its cross-section. The surface-roughening agent may be a finely divided inert material having a refractive index within about 0À15 of the refractive index of the polymer. A preferred material for use in polyethylene terephthalate is purified Kaolinite having a particle size in the 0À5-5 micron range. Other agents which may be used include finely divided calcium terephthalate, potassium acetate, aluminium silicate, potassium terephthalate and potassium 3,5-di-(carbomethoxy) benzene sulphonate. The coefficient of hydrodynamic friction (f k ) of the filaments is determined by hanging a test filament over a ¢-inch diameter polished chrome-plated mandrel attaching a 0À3 gram weight to one end of the filament and a strain gauge to the other end, rotating the mandrel at 1800 r.p.m. and flooding the area of contact of the filament and the mandrel with a drop of a mineral lubricating oil having a viscosity of 50 Saybolt-Seconds at 100‹ F. Strain gauge readings are then immediately taken for the " flooded " test. For the film test the oil is wiped from the mandrel leaving only a thin film of oil on the mandrel and further strain gauge readings are taken. The coefficient y friction is calculated according to the equation: where l n  is the natural logarithm, T 2  is the strain gauge reading and a is the angle of wrap in radians. The polyester used in the examples is a copolyester of polyethylene terephthalate containing 2 mol. per cent 5-sodium sulphoisophthalate radicals. The proportions of roughening agents used in the example range from 0À8 to 2À9%.