GB340324A - Improvements in the production of artificial materials by wet spinning processes from solutions of organic derivatives of cellulose - Google Patents

Abstract

For the wet-coagulation process for the manufacture of artificial filaments, threads, films &c. by the extrusion of solutions of cellulose acetate or other organic ester of cellulose or of cellulose ethers, there is employed a coagulation bath containing a relatively high proportion of solvent for the cellulose derivative. The filaments &c. on emergence from the bath may be in so plastic a state that if brought together they will coalesce. The following may be employed as non-solvents in the coagulation baths,-water; methyl and ethyl alcohol and their homologues; hydrocarbons such as benzene, toluene, gasoline and kerosene. Organic solvents less volatile than the non-solvent media are preferably employed; for example, with water or alcohol as the non-solvent there may be used diacetone-alcohol, diethyl tartrate, mono- or di-acetin, and ethyl lactate; and mixtures of solvents of low volatility may be employed, or a solvent of high volatility such as acetone may be used in conjunction with a solvent of low volatility such as diacetone-alcohol. The concentration of the solvent depends on the spinning conditions and the type of product desired, in the case of artificial filaments the concentration is higher according as the denier number of the filaments is lower; generally however concentrations of 25-65 per cent are suitable. Before collecting the products, excess of solvent should be washed out or otherwise removed to prevent coalescence of the filaments, for example, by washing with water, salt solutions, or solutions of solvents of concentrations lower than that of the liquids adhering to the filaments, conveniently by washing with solutions of decreasing concentrations, for example, as by the process of Specification 328,911, [Class 2 (ii), Cellulose &c.]. The washing may be effected by spraying or in a centrifugal spinning box. The solvents employed are preferably such that by reason of their innocuous properties a residue of the solvent may be permitted to remain in the washed products. During coagulation a stretch may be applied so as to produce filaments of one denier or less even with the use of relatively large spinning orifices. By adjusting the proportion of the solvent in the coagulation bath, products of various degrees of lustre may be obtained, generally the lustre being higher as the proportion of solvent is greater. The products obtained are distinctive in that although wet-spun their lustre is reduced by moist steam and hot or boiling aqueous media, and in that ironing or treatment with solvents does not increase the lustre of the non-lustrous products. The finished products may be subjected, while under tension or not, to treatment with solvents still further to improve their qualities. Specifications 177,868, 179,234, 309,201, 311,790, 312,095, and 312,096, [all in Class 2 (ii), Cellulose &c.], are referred to.