GB464116A - Improvements in the manufacture of viscose rayon - Google Patents

Abstract

Sulphur is removed from viscose rayon by adding to the spinning bath or to a treating bath, at any convenient stage of the manufacture, a quaternary phosphonium or ternary sulphonium salt, at least one radical of which consists of a long or branched carbon chain containing not less than eight carbon atoms. The process may be carried out under neutral, acid, or mild alkaline conditions, or it may be used in conjunction with the usual sodium sulphide or other desulphurizing bath. In this latter case it enables a lower concentration of the sulphide than usual to be used and it may be carried out at a lower temperature. The phosphonium or sulphonium salt may be added to an acid coagulating bath or to a subsequent washing bath, or to a bath in which the dried or undried crude undesulphurized filaments or fabrics are treated. In view of their fatty nature, the sulphonium or phosphonium salts lubricate the filaments and facilitate winding. Dimethyl hexadecyl sulphonium methyl sulphate, benzyl ethyl dodecyl sulphonium chloride, and stearamido benzyl dimethyl sulphonium chloride are suitable sulphonium salts. Cetyl triethyl phosphonium bromide, and dodecyl triethyl phosphonium bromide are suitable phosphonium salts. In an example, viscose solution is spun into a coagulating bath containing dilute sulphuric acid, sodium sulphate, and 1,5 per cent of dimethyl hexadecyl sulphonium methyl sulphate.