GB474401A - Improvements in or relating to cellulose derivative filaments, yarns, fibres and thelike - Google Patents

Abstract

A process for the production of improved crimped yarns comprises subjecting yarns with a basis of organic derivatives of cellulose to the operations of twisting, setting the twist, untwisting and thereafter the yarns or the filaments or fibres composing them to treatment with a bath of hot aqueous liquor. Preferably, the yarns contain a high proportion, e.g. more than 50 per cent of filaments or fibres of flat cross-section. The yarn may be of continuous filaments or staple fibres, or may be converted from one to the other before or after the hot aqueous treatment which may be applied to staple fibres. When the material is at some stage converted to staple fibres, they may be mixed with other fibres. A suitable method of preparing filaments with flat cross-section for use according to the invention is to spin a solution containing cellulose derivative in a lower concentration than that necessary to produce bulbous filaments, e.g. 20--24 per cent. The operations of twisting, setting the twist and untwisting may be effected according to Specifications 424,880, 442,073, and 464,981, [all in Group IX]. The aqueous liquor is preferably boiling or almost boiling, and may contain a small proportion, e.g. 1 gram/litre of a wetting agent. The treatment may be for \ba1/2\be--1\ba1/2\be hours at the boil, and may be followed by washing in warm or hot water. The process may be combined with a delustring treatment, e.g. by incorporating a white pigment either in the spinning solution or as an aftertreatment in the materials. Salts, e.g. sodium chloride or sulphate, or sugars in concentration of 10--20 per cent may be added to the aqueous treatment bath to diminish its delustring effect. The hot aqueous treatment may be effected under pressure at a temperature above 100 DEG C. Advantageously, the hot aqueous treatment may be applied to a doubled yarn having a light doubling twist in reverse direction to any twist in the constituent yarns, e.g. obtained from 2 or 3 yarns, having either no twist or light twist, i.e. not more than 5 turns/inch in the same direction, twisted together with a relatively high degree of twist, the twist set, e.g. by steam, and then untwisted to leave a light residual doubling twist in the reverse direction to that in the constituent yarns. The production of such a doubled yarn may precede or follow a separate twisting, setting and untwisting process, in which the twist may be false. For products of high denier, two doubling operations may be employed. A doubling operation may be combined with a direct conversion process from a continuous filament to a staple fibre yarn. Specifications 246,879, 260,312, [both in Class 15 (ii)], 424,683, 424,752, 424,830, 424,879, [all in Group IX], and 459,781 also are referred to.