GB342779A - Improvements in the production of viscose for the manufacture of artificial silk - Google Patents

Abstract

Viscose for the manufacture of artificial silk and films is made by using as the initial material the product obtained by treating cellulose such as wood pulp or linters according to the process of Specification 268,505, [Class 2 (ii), Cellulose &c.], that is, by treatment with alkali and carbon disulphide under conditions such that a water-insoluble product results, and subsequently treating such product with a mild oxidizing agent. The oxidized product so obtained, either in the form of sheets or in loose fibrous condition, is then subjected to the action of caustic alkali and carbon disulphide; thus, the material is soaked in or treated with caustic alkali solution of more than 15 per cent strength, is then pressed and treated with carbon disulphide in amount which is the less the greater the degree of conversion effected in the first stage of the process, and the viscose is finally obtained by solution of the product in water or caustic alkali solution. The solution may be employed directly, or it may be treated according to the process of Specification 264,261, [Class 2 (ii), Cellulose &c.]. To the caustic alkali solution used in the second stage of the process there may be added a reducing agent such as sodium sulphide or sulphite, glucose, etc.; or the reducing agent may be added at a later stage, for example, during the treatment with carbon disulphide, or subsequently as during the mixing, and in fact the separate addition of a reducing agent may be omitted since alkali sulphides formed during the treatment with carbon disulphide may serve for this purpose; alternatively, the reduction may be effected by hydrogen &c. preferably in the presence of a hydrogenating catalyst. Oxidizing agents suitable for use in the first stage of the process are nitrous acid, bichromates, peroxides, ferricyanides, &c. in the presence of weak acids, sulphurous acid in the presence of sodium acetate, bisulphites in the presence of weak acids, ferric or cupric salts, and air or oxygen with or without the aid of oxidizing catalysts; in an example, nitrous acid is used, the product having first been neutralized or rendered faintly acid with acetic or sulphurous acid. Specifications 126,174, 240,717, 286,331, 286,332, 309,053 and 318,088, [all in Class 2 (ii), Cellulose &c.], also are referred to.