GB359976A - Improvements in the production of cellulose derivative products - Google Patents

Abstract

Artificial filaments, yarns, threads, ribbons, bristles, films, &c., of fine denier and high strength are provided by spinning solutions of cellulose esters or ethers into a medium and removing the same from said medium while the filaments &c. are liquid or substantially liquid, i.e. the substance is still capable of flowing easily, and thereafter setting the products. Cellulose esters include cellulose acetate, formate, propionate, butyrate and other carboxylic acid esters, and cellulose nitrate; viscose is excluded, but is included in Specification 359,975. Cellulose ethers include methyl, ethyl and benzyl cellulose. The liquid employed is preferably a non-solvent bath for the cellulose derivative and for the solvent of the spinning solution. Water or aqueous solutions are suitable for solutions in solvents such as tetrachlorethane, chloroform, ethylene chloride, ethylene bromide, methylene chloride and dichlorethylene. Where these solvents are employed with solvents miscible with water, e.g. alcohols, the solubility or miscibility may be decreased by dissolving in the aqueous bath calcium chloride, sodium acetate, &c. Paraffin oil and like liquids may be employed with water-miscible solvents. Baths may be used which dissolve out some of the spinning solution solvent provided the products are still liquid or substantially liquids, e.g. alcohols, acetic or like acids may be added to baths and for water-miscible solvents. The specific gravity of the bath may be such that the products rise or fall therethrough, or spinning may be started up by a coagulating bath or by dry methods and the liquid bath then introduced. The length of the liquid bath depends upon the amount of "draw-down"; generally, a length up to a few inches suffices. Solidification of the products may be effected by wet or dry methods. Suitable wet coagulating baths are those described in Specifications 177,868, 179,234, [both in Class 2 (ii), Cellulose &c.], 340,234, [Group III], 340,235, [Group XXXVIII], and 343,062; or coagulating baths containing mineral acids, mineral acid esters, or organo-mineral acids may be employed, e.g. as described in Specifications 334,838 and 334,853, [Class 2 (ii), Cellulose &c.]. Dry spinning conditions may be adjusted to produce any desired type of product, e.g. products of rounded cross section and of dull or high lustre. The products may be drawn out to very fine deniers. In examples: (1) a solution of high acetyl content cellulose acetate, produced as in Specification 309,201, [Class 2 (ii), Cellulose &c.], is dissolved in tetrachlorethane with, if necessary, a small amount of alcohol, and is spun downwardly into a vessel having a partition extending to within about 3 inches of the bottom and filled with tricresyl phosphate, the filaments being carried around a guide below the partition; after spinning has been started, water is carefully run into the nozzle compartment until it extends 1-2 inches below the nozzle; (2) a 20-25 per cent solution of acetone-soluble cellulose acetate dissolved in ethylene dichloride containing a small amount of alcohol is spun upwardly through a bath comprising 50 per cent of petroleum spirit, b.p. 60-120 DEG C. and 50 per cent ethylene dichloride; after spinning has commenced a saturated aqueous solution of common salt is slowly and carefully run into the bottom of the bath until the nozzle is immersed 1-2 inches; (3) a spinning solution as in (2) is spun upwardly through a cup such as described in Specification 351,718, having an overflow 1-2 inches above the nozzle; initially the cup is filled with benzene or petroleum ether and the filaments are set by a dry-spinning process; after starting, water is run into the cup until the benzene or petroleum has been entirely displaced and spinning is continued by the dry-spinning process. The filaments &c. may be further treated, e.g. by stretching in the finished condition; or by the process of Specification 359,971, with or without stretching. Suitable solvents or softening agents for the latter treatment include aqueous solutions of thiocyanates; zinc chloride; acetic, formic and lactic acids; diacetone alcohol; methyl or ethyl lactate; acetone; mono- and di-ethers or esters or ether-esters of olefine glycols and polyolefine glycols such as the mono- and di-methyl and ethyl ethers of ethylene glycol, glycol mono acetate, methyl glycol acetate, dioxane, mono methyl and ethyl ethers or propylene glycol, and the mono ethyl ether of diethylene glycol; phenols; formaldehyde, acetaldehyde; mono-, di- and tri-acetins; dichlorethylene; mineral acids, sulphonic acids and other organo mineral acids or acid esters of mineral acids, &c.