Patent GB-343062-A (GB)
Title: Improvements in the production of artificial filaments, films and like materials
IPC: D01D5/06
Filed: 1929-08-06
Abstract: When manufacturing filaments, threads, ribbons, films, &c. from cellulose acetate or other organic esters of cellulose or from cellulose ethers by wet spinning processes, there is employed a coagulation bath containing a relatively high concentration of a solvent for the cellulose derivative as in the processes of Specifications 340,324 and 340,326, together with a salt, sugar or other polyhydric alcohol, or other substance adapted to reduce the solubility of the solvent in the non-solvent coagulating medium.  The high concentration of the solvent necessarily present during the formation of the filaments &c. need not only be derived from the coagulation bath; thus, a solvent of higher boiling point than the coagulation medium may be added, as described in Specification 340,436, to the spinning solution; or the solvent may be wholly contained in the spinning solution in which case proportions of 100 per cent or more with respect to the cellulose derivative are necessary.  As a further modification the filaments immediately after coagulation may be carried directly into a bath containing a high concentration of solvent as in the process of Specification 340,437, together with the salt, sugar or other added substance.  In all cases it is preferred to employ solvents which are of higher boiling point than the non-solvent medium of the coagulation or after-treatment bath.  The method is particularly applicable to aqueous coagulation &c. baths, the added substances being such as are capable of exerting an osmotic pressure.  Salts that are particularly suitable for use in the process are those that are non-hydrolyzable and are insoluble in the solvent employed in the spinning solution or coagulation or after-treatment bath, for example, those that are employed to prevent the delustring action of hot aqueous media or which are capable of restoring lustre, see Specifications 246,879 and 259,266, [both in Class 2 (ii), Cellulose &c.], the best results being obtained with sodium acetate or chloride, ammonium sulphate, chloride or nitrate, and potassium acetate.  Sugars &c. that are suitable are, for example, glucose, sucrose, xylose, mannitol, cellulobiose, and y-cellulose or other degradation or depolymerization products of cellulose.  The salts and sugars &c. are used in concentrations below those at which separation of the solvent occurs, in general in concentrations not greater than 15-20 per cent and 30 per cent respectively, preferably in concentrations of 1-10 per cent and 5-20 per cent.  The lustre of the product is determined to some extent by the concentrations of the solvent and of the salt, sugar, &c., being greater as the concentrations are higher.  During coagulation or after-treatment, the materials may be stretched so as to produce fine denier products.  The solvent carried by the treated threads &c. may be removed by washing or other suitable manner; for example, the products may be washed with water or other non-solvent medium, salt solutions or solutions of solvents of lower concentration; and the threads may be wound up on bobbins or collected in centrifuges, or twisted and wound on cap-spinning devices as described in Specification 340,326.  The products of high lustre are delustrable by hot or boiling aqueous media or by moist steam; thus, products exhibiting a pearly lustre and soft to handle are obtained by treatment with boiling aqueous liquors, the materials not being subjected to tension during such treatment. The products of low lustre obtained according to the present process are not affected by the usual delustring agencies.  The lustre of the delustred products may be restored by treatment with salt solutions or solvents as described in Specifications 259,265 and 259,266, [both in Class 2 (ii), Cellulose &c.].  Products exhibiting differential effects are obtained by combining the yarns of low lustre with yarns of high lustre as obtained in the present process or by the ordinary dry spinning method; and such mixed products may be subjected to delustring agencies for the purpose of modifying the lustre of the highly lustrous portion. Specifications 177,868 and 179,234, [both in Class 2 (ii), Cellulose &c.], and, in the second Provisional Specification, 336,217, [Class 2 (ii), Cellulose &c.], 340,325 and 343,062, also are referred to.