GB391158A - Improvements in the manufacture and treatment of artificial materials - Google Patents

Abstract

Artificial filaments, threads, ribbons, &c. containing organic derivatives of cellulose, in particular cellulose acetate, are stretched after having been subjected to a softening or swelling treatment with solution of solvents or swelling agents in a medium which is a non-solvent for the cellulose derivative, which medium also contains a substance such as a salt, sugar, &c. having the property of reducing the solubility of the solvent &c. in the non-solvent medium in order to augment its softening effect on the material to be treated. The salts preferred are normal salts that are insoluble in the solvent or swelling agent and are substantially non-hydrolysed by the non-solvent; in particular, they are sodium acetate, sodium or ammonium chloride, ammonium nitrate or sulphate and potassium acetate, and in fact any salt which has the effect of preventing the delustring action of hot or boiling aqueous liquors, or which is capable of restoring the lustre of delustred materials, see Specifications 246,879 and 259,266, [both in Class 2 (ii), Cellulose &c.]. The concentration of the salt, sugar, &c. determines to some extent the lustre of the products, the lustre increasing with the concentration, so that products of high, medium or low lustre or of matt appearance may be obtained. The material may be treated in the form of hanks, or while travelling from bobbin to bobbin or from a spinning machine to a winding apparatus, or as a warp; and the stretching may be effected by positively-driven rollers or by means of liquid or gaseous currents, for example, the assisting agents may be caused to flow and thus apply tension to the materials; and the stretching may be effected in a number of stages, preferably with a rest period between the stages as referred to in Specification 370,430, or as a very gradual operation. The stretching may be uniform, or local strained effects may be produced as by the local application of the p assisting agent. After or towards the end of the stretching operation, the solvent or swelling agent may be removed as by washing, preferably, in order to conserve the lustre of the materials, with a salt solution or with a solution of the solvent in lower concentration, see Specification 328,911, [Class 2 (ii), Cellulose &c.]. The treated materials may be subjected to other treatments, for example with solvents or swelling agents to modify their lustre, or with alkali solutions to produce a partial or complete saponification of the materials, which saponification may be assisted by solvents or swelling agents present either in the saponifying baths or carried over in the materials from the stretching operation. Specifications 277,089, 323,790, [both in Class 2 (ii), Cellulose &c.], and 343,062 also are referred to.