ES267073A1 - Production of regenerated cellulose materials - Google Patents

Abstract

Regenerated cellulose filaments are made by spinning viscose of viscosity at least 150 poises at 15 DEG C. of Y-value at least 40 and containing cellulose of degree of polymerization at least 400, in an aqueous acid bath containing 60-120 g./l. sulphuric acid, 100-250 g./l. of anhydrous sodium sulphate, 10-150 g./l. of anhydrous zinc sulphate and 1-40 g./l. of formaldehyde, stretching the spun filaments in the bath, stretching them further in a second dilute aqueous acid bath at high temperature, and then completing the regeneration of the cellulose without allowing the filaments to relax, either by winding them and subjecting the wound filaments to treatment in aqueous acid while in wound condition, or by treating them in a third acid bath and thereafter cutting them to staple fibre. Preferably the degree of polymerization of the cellulose is between 500 and 800, the Y-value of the viscose is between 50 and 80 and its viscosity at 15 DEG C. between 200 and 400 poises. The viscosity of the viscose and the degree of polymerization of the cellulose contained therein are determined on the viscose at the time of spinning. The viscose may also contain 1-40 g./kg. of formaldehyde and a modifier which is an amine, polyamine, a polyoxyalkylene compound or a condensation product of an amine and a dithiocarbamate in a proportion of 0,3-10% by weight relative to the alpha cellulose content of the viscose. The coagulating bath may also contain a modifier which is an amine, a polyamine, a polyoxyalkylene compound or a dithio-carbamate, in a proportion of 0,1 to 10 g./l. Specified coagulating bath temperatures range from 45 DEG -55 DEG C. The filaments may be stretched 30-50% in the coagulating bath, and further stretched by 60-120% in the second bath. In spinning continuous filaments, the spun filaments may be wound on bobbins and allowed to remain thereon in contact with acid until the Y-value is sufficiently reduced. In making staple fibres, the bundle of filaments emerging from the second bath may be freed of carbon disulphide and fixed under tension in a hot acid bath and cut to staple fibre. Filaments so made have an elongation less than 10% both in the dry state and in the wet state, and a very high modulus (3,25% elongation in the wet state under a tension of 0,5 g./denier). They have at least 80% skin and show secondary swelling between 50% and 80%.