GB243350A - Improvements in or relating to the production of artificial silk, filaments, threads, bands, ribbons and the like - Google Patents

Abstract

Artificial silk, horsehair bands, ribbons &c. are prepared from solutions of acetone-soluble cellulose acetates which have been prepared in the cold by means of a solvent mixture of methylene chloride and an alcohol or other addition. The alcohol &c. must be used in such limited amount as not to impart inflammable properties to the solution; the limit in the case of alcohol is a proportion corresponding to 30 per cent of the solution, and in the case of acetone, 20 per cent. By the use of methylene chloride very highly concentrated solutions can be obtained, such solutions permitting a very high speed of spinning and a very short spinning distance; and the spinning can be carried out either by the evaporative method or by a wet process using a bath of high boiling point solvent from which the methylene chloride can be recovered by distillation. The spinning conditions can be varied within wide limits by the addition of larger or smaller quantities of solvents such as dichlorethylene; and the speed of evaporation of methylene chloride is such that there may be spun either fine silk-like filaments or thick filaments resembling horsehair, or even thin tubes &c. To the spinning-solutions there may be added softening-agents, colouring matters, and filling-materials especially bronze powder or dyes insoluble in water. Methylene chloride by itself has no solvent action in the cold for either class of cellulose acetate; but by the addition of a small quantity of alcohol or its homologues, perfect solution is obtained without the application of heat; even an addition of 10 per cent of alcohol will enable this effect to be obtained, although it is preferred to employ about 25 per cent of alcohol. Alcohol or its homologues may be replaced by other solvents or by mixtures of solvents and non-solvents or by mixtures of non-solvents. In examples, acetone-soluble cellulose acetate is dissolved in the cold in a mixture of methylene chloride and alcohol, and in a mixture of methylene chloride, benzene and alcohol. The Specification as open to inspection under Sect. 91 (3) (a) refers to the use of methyl alcohol, ethyl formate, and a mixture of ethyl acetate and alcohol, as additions to the methylene chloride; to the preparation of solutions of mixtures of acetone-soluble and chloroform-soluble cellulose acetates; to the use of methylene chloride as a diluent for solutions of cellulose acetate for the purpose of homogenizing the solutions and for decreasing their inflammability; and it includes examples of the preparation of solutions with the aid of mixtures of triacetin, methylene, acetone and methyl alcohol, and also a modified process in which the cellulose acetate solutions are applied as a coating to nitrocellulose silk, threads, ribbons, &c. for the purpose of rendering these articles non-inflammable. This subject-matter does not appear in the Specification as accepted.