GB211446A - Improved manufacture of cellulose films, threads, tubes or the like - Google Patents

Abstract

In the manufacture of films, threads, tubes, &c. from viscose, the solution issuing in the desired shape from a hopper or draw-plate, passes into a suitable coagulating-bath, and after withdrawal therefrom immediately and directly passes into a conversion bath in which the film &c. is converted into cellulose, the resulting film being finally washed and then treated with glycerine in order to preserve its flexibility. A suitable coagulating-bath consists of a solution of ammonium sulphate either alone or together with an acid or a base, or sodium sulphate and acid; for the conversion, a dilute solution of sulphuric acid is suitable. After conversion, the film is washed with hot or cold water, and then desulphurized by treatment with a hot solution of sodium sulphide or caustic soda; the film is now washed with hot water, followed if desired by cold-water washing, and bleached as a next step. For the bleaching there may be used a solution of sodium hypochlorite or chloride of lime containing a low concentration of active chlorine, the film being subsequently treated with acid; or the film may be first treated with a solution of sodium or potassium hypochlorite, then washed, and finally treated with acid; or it may be treated with an aqueous solution of chlorine. After bleaching, the film is washed with a stream of hot or cold water, and after passage through squeezing rollers is treated with the glycerine bath; the film is finally squeezed and passed to the drying-apparatus. When a coloured film is to be made, the bleaching baths are replaced by dye baths. Dyeing and desulphurizing may be carried out simultaneously by the addition of sulphur dyes to the desulphurizing bath; alternatively, sulphur or direct dyes may be added to the original viscose solution. The viscose solution employed may be loaded with sulphate of baryta, kaolin, &c.ALSO:Films, threads, tubes, &c. consisting of cellulose regenerated from viscose are coloured by passing the film &c. through dye baths, and dyeing and desulphurizing may be carried out simultaneously by adding sulphur dyes to the desulphurizing bath, consisting of a solution of sodium sulphide or caustic dye. Alternatively, sulphur or direct dyes may be added to the original viscose solution.