GB358512A - Improved process for the production of fine threads from cellulose compounds - Google Patents

Abstract

Artificial threads composed of cellulose derivatives, particularly cellulose acetate silk, are fixed by stretching in the presence of a swelling medium or a mixture of swelling media which have only a slight dissolving capacity for the cellulose derivative, and also of an organic substance which is capable of precipitating the cellulose derivative from its solution in organic solvents and is adapted to repress the slight solvent power of the swelling medium. Suitable swelling agents are methylene chloride, chloroform, tetrachlorethane, and mixtures thereof; and the following may be used as precipitants,-carbon tetrachloride, trichlorethylene, perchlorethylene, benzene and its homologues, benzine and other hydrocarbons. The composition of the bath and its temperature depend on the conditions of treatment. The process may follow on directly from the production of the threads either by dry or wet spinning processes, or it may be applied to the finished products; and stretching may take place either in the treatment bath, or after the threads have left the bath and while still saturated with liquid. Stretching which may be performed in one or a series of stages, may be effected by drawing the threads over guides arranged in zig-zag formation or by the aid of other mechanical arrangements offering frictional resistance to the passage of the threads, or by passing the threads over a series of rollers &c. rotating at increasing peripheral speeds, or by giving the threads an extended air run, or by drawing the threads through the bath at relatively high speeds. The stretching may be from 300-800 per cent or more, normally producing threads with filaments of 2, 1, 0,5 deniers or even finer filaments; and there may be used as starting material threads having filaments of unusually high litre of 10, 20 deniers or even higher. The residue of the treating bath are usually removed by evaporation; and the drying is carried out under conditions such that shrinkage of the threads is prevented. The stretched threads have an increased dry and wet strength, a reduced elongation, and a lustre approaching that of natural silk; and the cross section of the filaments is rounded and more uniform. For examples, baths consisting of mixtures of methylene chloride and carbon tetrachloride or benzene are used in the fixing of cellulose acetate silk. Specification 336,217, [Class 2 (ii), Cellulose &c.], and 352,445 are referred to. Reference has been directed by the Comptroller to Specification 323,790, [Class 2 (ii), Cellulose &c.].