GB787557A - Improvements in the production of artificial filamentary materials - Google Patents

Abstract

<PICT:0787557/IV (a)/1> In wet-spinning wherein the filaments are drawn through a tube through which coagulating liquid flows, the speed of the coagulating liquid in the tube over all except the final inch is arranged to lie between the extrusion speed and the draw-off speed of the filaments and to be higher at the output end than at the input end; and to be independent of the friction between the filaments and the liquid. The rate of flow of the coagulating liquid is controlled by adjusting the rate of supply to the tube, and the increase in speed as it passes through the tube is achieved by reducing the diameter of the tube, in one or more stages, and the transition from a wider to a narrower section may be gradual. The speed of the coagulating liquid should not exceed the speed of the filaments, except during the final inch or less, where a restricted outlet causes a local rise in speed of the liquid. The method is stated to reduce the proportion of filament breakages when a high rate of draw-off is used. As shown, filaments are spun from the jet 3 into a cylindrical vessel 1 containing coagulating liquid which is fed in at 5 and passes up the setting tube 2. The vessel 1 may have a conical upper portion or may be wholly conical. The setting tube 2 has a flared lower end which is positioned 1/4 to 4 ins. from the jet face. The tube has a diameter of 0.25-0.8 in. at its lower end, 0.1-0.45 in. at its upper end and a restricted orifice 11. The filaments are drawn-off and stretched by the godet 16, entrained liquid being removed by pigtail guide 15 and led into the collecting head 12 by inverted funnel 14. The filaments pass over skew rollers 18 partly immersed in a washing bath and thence over a second godet 20 to a collecting device or to further treatment means. The invention is of particular value in the manufacture of cellulose acetate by extruding an acetone solution of cellulose acetate into an aqueous solution of diethylene glycol diacetate or of acetone, but it may be used in other wet-spinning processes, e.g. in the spinning of acetic acid solutions of cellulose acetate into aqueous acetic acid containing a high concentration of a salt such as an alkali metal acetate. Specifications 695,559, 697,967, 787,556, 787,558, 787,559 and 787,561 also are referred to.