GB372835A - Improvements in the manufacture of artificial filaments, threads and the like - Google Patents

Abstract

Hollow artificial silk &c. of more or less low lustre is made by the dry spinning method by applying a precipitant to the filaments at an early stage of their drying, and subsequently producing a rapid evaporation of the solvent. The precipitant which is preferably applied to the filaments immediately on extrusion, may be employed in the form of vapour, but is preferably employed as a liquid; and it may be applied as a spray either to the filaments or to the spinning nozzle, or carried by the additional evaporative medium injected into the region of the spinning nozzles according to the methods of Specifications 325,233, [Class 2 (ii), Cellulose &c.], and 341,075, or the liquid precipitant may be applied as a film to the spinning nozzle according to the method of Specification 371,360, the spinning being carried out either downwardly or upwardly. The necessary rapid evaporation of the solvent may be produced by means of heating devices grouped below the point of application of the precipitant, or by increasing the rate of flow of the evaporative medium at this point as by the use of the collector devices of Specifications 300,998, 304,674, and 326,232, [all in Class 2 (ii), Cellulose &c.]. The method is particularly applicable for the production of filaments &c. from solutions of cellulose acetate and other organic esters of cellulose, and of cellulose ethers. Precipitants that may be used with acetone-soluble cellulose acetate are alcohols such as ethyl and amyl alcohols, esters such as butyl acetate and propionate, and ethers such as dipropyl ether, but it is preferred to employ liquids of very high precipitating power such as benzene, toluene, xylene and other cyclic hydrocarbons, and aliphatic hydrocarbons, for example, petroleum fractions boiling between 60 and 120 DEG C.; the action of the precipitant is improved in some cases by the addition of water thereto or to the spinning solution, or the precipitant may be added to the spinning solution. It is preferred to employ a precipitant which is less volatile than the solvent of the spinning solution, and in producing the rapid evaporation of the solvent to employ temperatures above its boiling-point but below the boiling-point of the precipitant. The filaments may be improved in strength or their lustre may be modified by treatment either continuously with their manufacture or otherwise, according, for example, to the processes of Specifications 277,089, 323,790 and 336,217, [all in Class 2 (ii), Cellulose &c.], the filaments being stretched with or without the application of solvents or swelling agents which may be derived from the spinning solution or may be incorporated in the precipitant liquid. The spinning solutions may contain substances that modify the lustre of the filaments, for example, the substances specified in Specifications 338,490, [Class 2 (ii), Cellulose &c.], 341,897, 343,949, 346,678 and 346,793. Specifications 314,404, 327,740, [both in Class 2 (ii), Cellulose &c.], 355,652, and 355,720 also are referred to.