GB768480A - Process for the production of articles from viscose solutions - Google Patents

Abstract

Fibres, filaments, bristles, strips, foils and like products are made by extruding a solution of viscose which has a degree of xanthation (molecular ratio of -CSS- units to glucose units) of 0.25-0.45, and in which the cellulose has a degree of polymerization greater than 400, into an aqueous coagulating bath containing 50-75 per cent of caustic soda at 50-100 DEG C. The xanthated product is then decomposed rapidly by the action of heat, preferably by steam at 100-180 DEG C., washed free from caustic alkali, stretched and dried. Desirably, the viscose solution contains a high concentration of caustic soda, preferably 8.5-13 per cent, and has an a -cellulose concentration of 6-11 per cent. To prevent undesirable swelling effects, which are pronounced at low alkali concentrations, the concentrated caustic alkali adhering to the product is preferably removed by washing at 70-100 DEG C. with 3-5 per cent caustic soda solution, which may also contain sodium sulphate or sulphide, to reduce swelling, the remaining caustic alkali being then removed by treatment with hot water. These washes may be carried out in counter-current. Preferably, the products are stretched before maximum swelling occurs, that is, between extrusion and heat treatment, and subsequent stretches are also applied. After washing, but before drying, the articles may be cleaned, softened or otherwise treated in known manner. Specification 323,747, [Class 2 (ii)], is referred to.