GB324061A - Improvements in or relating to the manufacture of artificial filaments and the like - Google Patents

Abstract

324,061. Dreyfus. H. July 9, 1928. Drawings to Specification. Apparatus for making filaments. - When spinning artificial silk &c. especially cellulose acetate silk &c. bv the dry spinning method in which the threads are withdrawn from the spinning cells or chambers and are wound up outside as is described for example in Specifications 165,519 and 198,023, there is maintained within the spinning cells or chambers a vacuum or a pressure below atmospheric whereby filament-formation may be carried out at appreciablv lower temperatures and in the case of low boiling point solvents even at ordinary temperatures, or alternatively, spinning solutions containing solvents of higher boiling point than those ordinarily employed may be used, in particular solutions as obtained directly in the acetylation process. The present method is of especial advantage in the production of cellulose or voluminous filaments, the bubbles or cellular spaces being obtained by the generation of gases or vapours in the extruded filaments, preferably by the methods of Specifications 317,097 and 317,098. The process although particularly applicable to the production of artificial silk, may also be applied to the manufacture of artificial straw or ribbon either by the use of appropriately-shaped spinning nozzles or by causing a number of filaments to unite to. form a flat tape ; or a number of filaments may be caused to unite along their whole length to give a single filament of high denier. Bv the use of reduced pressure in the cells the lustre of the products is naturally controlled according to the degree of vacuum and the proportion of moisture in the atmosphere. The apparatus used may be that described in Specifications 165,519 and 198,023, suitable provision being made in order to secure uniform conditions in the cells of a spinning installation as bv adopting the arrangement described in Specification 203,092, the individual cells being, for example, connected to the exhaust system by means of constricted passages each provided with a manometer, the constriction and manometer together acting as a flow meter, and being also provided with a separate connection to an exhaust system to be used at starting, the connection to the normal exhaust system having previously been adjusted with the aid of the flow meter before the cells have been exhausted. The cells may be cylindrical and provided with heating jackets or with batteries of heating pipes which may pass from a header at one end of the cells and then return through the cells to a. second header at the same end as the first header; and the heating devices may be subdivided so as to permit the supply of heat at different levels in the cells to be brought under control. To minimize leakage into the cells at the outlet aperture for the thread, this may be of a size just sufficient to take the cutter, or the thread may pass out through the nip of a pair of rollers, fitting closely the casing of the cell; or, alternatively, a jet of the air discharged by the air pump &c., may be directed at the outlet in such a manner as to oppose the entry of air into the cell. In many cases it is advantageous to employ in conjunction with a reduced pressure in the cell, a circulation of the air or gas therein as by the employment of a circulating-device, a solvent-recovery plant being included in the circuit. For producing the vacuum in the cells there may be used an air pump, jet pump, ejector or other vacuumproducing device; and the solvent may be recovered from the exhausted atmosphere by passage through absorbers supplied with an appropriate absorbent liquid, for example, water if acetone is the solvent used, or an hydrocarbon oil in other cases, or, alternatively, a coudensing- plant of the jet or surface type, supplied if necessary with cooled liquid, may he added.