GB362785A - Manufacture of artificial threads, bands, films and the like - Google Patents

Abstract

Artificial threads, bands, films, &c., of cellulose or cellulose derivatives are prepared from solutions prepared from a cellulose pulp made from the wood of deciduous trees, e.g. beech or aspen, by the sulphite process, such pulp being subjected to refining by means of alkali. Such pulp forms a substitute for cotton, yielding clear solutions and white products. In the manufacture of viscose only about one-fourth of the usual quantity of fresh alkali lye is necessary for mercerization. In examples, (1) viscose is prepared unripened alkali cellulose obtained by mercerizing refined beech wood pulp with 18 per cent caustic soda for 3 hours at 16 DEG C., the solution being spun after a single filtration into a sodium bisulphate bath: (2) beech-wood pulp, refined by a known alkaline refining process, is treated with freshly precipitated basic copper sulphate and then with ammonia to obtain a 10-20 per cent solution: (3) refined beech-wood pulp is sprinkled in a closed vessel with glacial acetic acid and allowed to remain for some hours and is then gradually introduced into an esterifying mixture of glacial acetic acid, acetic anhydride and sulphuric acid monohydrate, the temperature being kept down by cooling so that in 3-4 hours it rises from 10 to 20-30 DEG C.; a clear solution results, which is hydrolysed to give acetone solubility, and precipitated and, if necessary, lightly bleached and dried; a 20 per cent acetone or acetone-alcohol solution may be worked up on a casting-machine to produce films.