GB546657A - Process for the improvement of viscose textile materials by esterification - Google Patents

Abstract

546,657. Esterifying cellulosic textile materials; dyeing processes. COTOPA, Ltd., and TRENCH, J. KNIGHTS-. Feb. 4, 1941, No. 1462. [Classes 2 (ii) and 15 (ii)] Fibres, or fabrics of regenerated cellulose from viscose are treated with an aqueous alkali solution, then with an aqueous lower aliphatic acid, i.e. an acid up to and including butyric acid, of not less than 90 per cent strength, and then with an esterifying medium containing the lower aliphatic acid, its anhydride, and a heavy metal halide as catalyst. The treatment increases the weight of the materials, renders fabrics resistant to shrinking and creasing, improves the wet tensile strength, and imparts a linen-like finish. Esterification may result in the production of cellulose acetates of 20-62.5 per cent combined acetic acid. The materials may be dyed before or after the esterification. Specified dyes which are suitable for dyeing before the esterification are substantive dyes such as Chloramine Fast Orange W.S., Solar Yellow 2R, and Primuline after-treated with hypochlorite; developed colours such as Diazo Fast Scarlet BL# #- naphthol, Diazol Black SD# m-toluylene diamine ; vat dyes such as Sandothrene Yellow NGC, Durindone Pink FFS, Caledon Dark Blue 2RDS, and Indanthrene Brown BR; sulphur dyes such as Thional Black T. Mixed yarns or fabrics containing viscose and cotton fibres may be treated, and since cotton is more resistant to esterification, the viscose fibres may be made resistant to direct cotton dyes while the cotton still retains affinity for such dyes. Differential dyeing effects may thus be obtained. In an example, viscose yarn, fabric, or sliver, is treated with hot dilute caustic soda, washed, dried, treated with warm concentrated acetic acid, and centrifuged. The material is then treated with a solution containing acetic anhydride, acetic acid, and zinc chloride, ferric chloride, or other metal halide catalyst, for several hours until the material contains up to about 45 per cent. combined acetic acid. To obtain further esterification, the partially acetylated material may be treated in a fresh bath containing zinc chloride, benzol, acetic acid, and acetic anhydride. Toluene or xylene may be used instead of benzol. The Provisional Specification describes also the use of perchloric acid as catalyst for the esterification.