GB403106A - Improvements in or relating to the production and treatment of artificial filaments,threads, ribbons and the like - Google Patents

Abstract

When stretching artificial filaments, threads, yarns, foils, &c. of cellulose acetate and other ester or ether of cellulose, the extensibility and tensile strength are improved by subjecting the materials while travelling to a shrinking treatment prior to the stretching operation. Shrinking is effected by treatment with shrinking agents while the materials are subjected to at most a moderate tension, or alternatively the tension is subsequently released. Shrinking and stretching may take place continuously with the production of the threads &c., or as a separate operation. The shrinking agents are generally liquids having a swelling solvent or latent solvent action upon the cellulose ester &c., strong swelling agents, such as methylene or ethylene chloride, ethyl lactate, chloroform, dichlorethylene and tetrachlorethane being preferred; and the shrinking agent may be used in aqueous solution or in admixture with organic diluents. The shrinking agent is preferably applied by passing the materials through a bath containing the agent, but it may also be applied by means of rollers, wicks &c., or as a spray or in the form of vapour, for example, when treating threads continuously with their production by dry spinning, the vapour of the shrinking agent may be introduced into the cell at a point remote from the spinning jets. To assist shrinking or to permit this to take place, the materials are passed round rollers or between nip rollers moving with decreasing peripheral speeds, and the shrinking agent whether liquid or vapour may be caused to move in a direction counter to that of the threads &c. in the manner of Specifications 375,424 and 375,425. The shrinking agent may be removed before the stretching operation, or the same agent may be used to effect the necessary softening required in both operations, in fact a single bath may be used, the shrinking and stretching stages being determined by rollers placed at appropriate points and moving at appropriate speeds. Shrinking and stretching may be applied to the materials in warp formation as in Specification 371,461, and the stretching may be carried out as in Specification 323,790, [Class 2 (ii), Cellulose &c.], or in stages with or without a rest period as in Specification 370,430. The shrinking and stretching agents may be removed by evaporation or by washing, for example, with solutions of the softening agent of decreasing concentration as for example by the method of Specification 401,679. In examples, methylene chloride-benzene and aqueous dioxane are used both in shrinking and stretching. Specifications 277,089, 336,217, [both in Class 2 (ii), Cellulose &c.], 389,823 and 392,185 also are referred to. The Provisional Specification includes the treatment of hanks and other packages, and it refers to the use as the shrinking agent of the coagulation bath in a wet spinning process, and mentions that suitable baths are those of Specifications 177,868, 179,234, [both in Class 2 (ii), Cellulose &c.], 340,324, and 340,326.