GB683646A - Improvements in and relating to the production of viscose rayon threads and the like - Google Patents

Abstract

A continuous process for the production and treatment of artificial thread comprises the steps of extruding viscose into an aqueous coagulating bath to form a thread, treating the thread with an aqueous solution of dilute sulphuric acid at a temperature not less than 40 DEG C. and at the same time with an aqueous solution of an oxidizing agent, and then washing and drying. The sulphuric acid solution preferably contains at least 0.5 per cent of sulphuric acid and it may contain up to 4 per cent. The solution may also contain sodium sulphate or other salt. The oxidizing agent may be sodium hypochlorite or sodium chlorite. The treatment may be carried out while the thread is passing in helical turns along a thread-advancing reel or a pair of thread-advancing rollers. The freshly spun thread may be stretched between the coagulating bath and the liquid treatment device. The treated is completely regenerated and is substantially free from coloured impurities, sulphur compounds and elementary sulphur. In an example, viscose containing 8 per cent of cellulose and 7 per cent of caustic soda and having an ammonium chloride number of 10 is extruded into a coagulating bath containing 10 per cent sulphuric acid, 22 per cent sodium sulphate and 1 per cent zinc sulphate. The thread obtained is passed in helical turns round a thread-advancing reel which stretches it. It is treated on the reel with a solution of dilute sulphuric acid containing sodium sulphate at 60 DEG C. and also with a solution of sodium hypochlorite. Uniform and simultaneous treatment is achieved by placing the jet of hypochlorite solution in the stream of dilute acid solution. The thread is passed to a second reel upon which it is washed and then to another reel upon which it is dried. Specifications 413,413, 413,414, [both in Group IX], 474,973, 475,023, 652,594 and 661,940 are referred to.