GB557004A - Improvements in or relating to the production of artificial yarns and similar articles - Google Patents

Abstract

557,004. Artificial yarns &c. ; cellulose derivatives. DREYFUS, H. March 20, 1941, Nos. 3813, 7868, 13197, and 14506. [Class 2 (ii)] Artificial yarns and the like made of an acetone-soluble cellulose acetate of a viscosity of at least 40 (measured by comparing the rate of flow of a 6 per cent. solution of the acetate in acetone with that of glycerine, which is taken as 100) are subjected to a stretching operation so as to obtain products of high dry and wet tenacity. The stretched materials may be subjected to saponification, which may be carried to completion. The cellulose acetate may be obtained by treating cellulose with acetic anhydride, acetic acid, and sulphuric acid in fairly high proportion, e.g., 10-15 per cent. of the weight of the cellulose, and maintaining a low temperature not exceeding about 30‹ C. Alternatively, a mild acetylation using a low proportion of sulphuric acid, or ferric, stannic, or zinc chloride, preferably with hydrochloric acid, may be effected at a temperature up to about 50‹ C. The acetylating medium may contain water-immiscible solvents such as methylene or ethylene dichloride, ethylidene chloride, or chloroform. The subsequent ripening is preferably carried out with fairly high proportions of added water, e.g. 40-50 per cent. of the cellulose when 10-15 per cent. of sulphuric acid has been used as catalyst, or up to 100 per cent. when 1 or 2 per cent. of sulphuric acid has been used. The acetyl content of the ripened cellulose acetate may be 50-53 per cent. calculated as acetic acid. The artificial yarns may be obtained by spinning a solution of the acetate in acetone, dioxane, methylene ethylene ether, or acetone and water or alcohol. High viscosity spinning solutions may be used. Hot solutions may be spun into a cool atmosphere. Stretching of the yarns may be effected with the aid of acetone, dioxane, wet steam, or hot water. Saponification may be effected by means of ethylene diamine, aniline, or caustic soda. Regenerated cellulose yarns of dry tenacity of 8-9 grams per denier and of wet tenacity 75-90 per cent. of the dry tenacity may be obtained. The yarns may be formed into cords or knitted, woven, or other fabrics, e.g. cords or fabrics for parachutes, sails and tents. Specifications 207,562, [Class 2 (ii)], and 443,707, are referred to. The Provisional Specifications describe also the stretching of filaments, yarns, films and foils of cellulose organic derivatives, including cellulose propionate, butyrate, and acetostearate. Specifications 438,584, 438,585, 438,586, 438,587, 438,655, 438,656, and 443,773 are referred to .