GB255527A - Improved manufacture of artificial silk - Google Patents

Abstract

255,527. Lanfry, M. P., and Brandenberger, J. E. April 22, 1925. Cellulose xanthates, processes for making filaments from.-For the manufacture of hollow glossy fibres of artificial silk from viscose to which alkali carbonate has been added, the proportion of caustic alkali to cellulose in the viscose is less than 1 : 1.2, and the proportion of sulphuric acid and sodium sulphate in the coagulating bath is as given by the diagram; it is convenient to use a viscose containing 7.3 per cent of cellulose, the practical working limits as regards the proportion of caustic alkali being 4-6 per cent. The curves shown on the diagram serve to correlate the ripeness of the viscose, the proportion of caustic soda in the viscose, the density of the coagulating bath, and the proportions of sulphuric acid and sodium sulphate in the bath. Thus, in the case of a viscose containing 4 per cent of caustic soda and 7.3 per cent of cellulose, while using a coagulating bath containing 145 gr. of sulphuric acid per litre. filaments showing the best gloss are obtained if the proportion of sodium sulphate in the bath lies between the limits indicated by the curves A-A; similarly, if the bath contains 125 gr. of sulphuric acid per litre, then the proportion of sodium sulphate is given by the curves B-B; the curves A<1>-A<1> and B<1>-B<1> apply when a viscose containing 6 per cent of caustic soda is employed; for other conditions, the necessary data are obtained by interpolation. The carbonate necessary for the production of hollow fibres may be introduced as such into the viscose solution; alternatively, it may be formed therein by the addition of carbonic acid or bicarbonate, in which case the quantity added must be sufficient to react with at least 0.5 per cent of the caustic soda; in an example, the carbonate is used in the proportion of 3 per cent with respect to the viscose solution. Specifications 143,253, 189,639, 189,973, and 214,197 are referred to.