Patent GB-325233-A (GB)
Title: Improvements in processes and apparatus for the dry-spinning of solutions of cellulose derivatives
IPC: D01D5/04
Filed: 1928-08-13
Abstract: 325,233. British Celanese, Ltd., Briggs, J. F., and Roberts, R. P. Aug. 13, 1928. Apparatus for making filaments.-The uniformity and character of filaments prepared by extruding a solution of a cellulose derivative into a cell through which flows an evaporative medium in counter-current to the direction of passage of the filaments are controlled by introducing additional evaporative medium into the said current in the region of the jet. Cellulose derivatives, which may be spun in this manner, comprise, for example., cellulose acetate, formate, propionate or butyrate, or methyl, ethyl, or benzyl celluloses, or the condensation products of cellulose and glycols or other polyhydric alcohols. Any suitable device mav be employed for introducing the additional evaporative medium. Thus, for example, a perforated or slotted tubular ring, a straight or curved perforated or slotted pipe or a jet or jets may be arranged at the desired level in the cell. The additional medium may be introduced in the plane of the jet face or on either side thereof and its direction may be the same as or opposed to the passage of the filaments or may be normally or otherwise arranged with respect thereto. The admission of the additional medium is preferably controlled by fitting the feed pipe with a constriction and a valve and flow meter as described in Specification 203,092 and the drawoff from the cells may be controlled in a similar manner. The additional medium may be introduced under pressure, but the suction of the draw-off devices may be used to aspirate the desired amount of medium, which may be cold or heated to any desired degree and may contain a proportion of solvent or other vapours. The whole or substantially the whole of the current evaporative medium flowing through the cell may be constrained to pass through the immediate vicinity of the filaments, for example by means of collector devices as described in Specification 300,998, and the cells may be of the type wherein the end remote from the jet is open to the atmosphere of the spinning room or wherein a relatively large number of jets are arranged in each cell as described in Specification 304,674. The spinning solution may, for example, be spun downwardly into an upwardly moving current of evaporative medium or upwardly into a downwardly moving current. In the apparatus shown in Fig. 1, the jets 6 arranged for downward spinning are supported by the filter chambers 7, each of which is surrounded by a tubular ring 8. These rings can be connected singly or in pairs by a tube 9, which communicates through the feed pipe 10 to a suitable source of supply of evaporative medium. Each ring 8 may be at the level of or above or below the jet 6. The rings o may be fitted on the under side with perforations or slots 11, Fig. 2 (a), when the ring is above the jet 6, or with perforations 12, 13 or slots 12<a>, 13<a>, Fig. 2 (b) and (c), from which evaporative medium is directed radially inwardly or inwardly and downwardly, when the ring is at or below the level of the jet 6. Alternatively a continuous slot may be formed round the rings. In the apparatus shown in Figs. 3 and 4, a perforated tube 15 of U.form is connected by a pipe 16 to a supply of evaporative medium and is so arranged with respect to a line jet 17 that slots or perforations' 18 in the two limbs of the tube direct the medium into the vicinity of the filaments 19 issuing from the jet 17. The tube 15 may be arranged at the level of the jet or above or below the jet. In the apparatus shown in Fig. 5, a perforated or slotted ring or tube 20 is conected by a pipe 21 to a supply header 22, which serves to deliver evaporative medium to any desired number of devices 20. In order to control the amount, of medium introduced into the cell 23 through the ring, a valve 24 is inserted in the pipe 21 and is operated in accordance with a flow meter 25 connected to the pipe 21. The draw-off of solvent-laden evaporative medium from each cell is controlled as described in Specification 203,092 by suction through a pipe 26 under control of a valve 27 into a header 28, a flow meter 29 enabling the flow to be observed. Heating of the additional evaporative medium may be effected, if desired, by means of heating devices arranged inside or outside the cell. Thus. the pipe connecting the ring to the source of evaporative medium may pass through the whole or part of the length of the cell before reaching the ring. The heating of the counter-current of evaporative medium passing through the cell may be effected outside the cell or inside by jackets surrounding the whole or a part of the length of the cell, by a coil or coils inside the cell or by banks or other arrangements of pipes extending through several cells, control means being preferably provided whereby uniform or regulated variations of temperature mav be effected along the height of the cell. The filaments or threads may be wound or twisted and wound continuously with their production, for instance by submitting them to a cup-spinning operation as described in Specification 198,023, preferably outside the cell. They may be subjected to any desired operations such as moistening, lubricating, stretching or sizing at any suitable point in their travel to the winding or twisting and winding devices. The Provisional Specification refers also to spinning solutions of thiocarbamic or alkoxyalkaryl esters of cellulose.