Patent GB-286619-A (GB)
Title: Process for the treatment of sheets of cellulose pulp for use particularly in the manufacture of viscose and apparatus for carrying out such treatment
IPC: C08B1/12
Filed: 1928-03-05
Abstract: 286,619. Jardin, L. C. P. March 4, 1927, [Convention date]. Alkali cellulose. - Sheets of wood pulp which are required to take up a determined quantity of caustic alkali lye, are treated in such a manner that at the end of the operation the desired amount of lye remains in the sheets without the necessity of subjecting them to the usual pressing. Thus, the sheets 1, Fig. 1, of wood pulp are suspended by cords 4 from separating plates 2<a> which are themselves freely suspended on a frame 2. The frame is suspended by means of a hook 8, at the end of cable 9 connected to a winch 11, a counterbalance weight 12 and a weighing-device 13 being interposed in the length of the cable. The frame is suspended above a vat 3 provided with a circulating pump 7 leading to spray pipes 5 and with upper and lower liquidlevel indicators 14, 15. The vat is filled with the mercerizing-lye, and into this the frame 2 charged with wood pulp sheets, is lowered. After a period of time, insufficient for complete absorption to take place, the frame is lifted, and the amount of liquid absorbed determined by noting the weight of the liquid shown by the upper level indicator 14; and if necessary the sheets are again immersed by lowering the frame, which is again lifted. By means of the pump 7, liquid is transferred to a recuperating tank, until the amount of liquid remaining in the vat 3 is just sufficient to finish the soaking of the sheets; and this liquid is now by means of the valves 16, 17, sprayed over the sheets as they hang, raised above the vat, until the latter is empty, a final check being given by the reading of the weighing-device 13. The frame with its sheets is now moved away horizontally and carried to a point above the hopper of the disintegrator, when the sheets are released as by withdrawing the cords 4. In another arrangement shown in Figs. 3, 4 and 6, the sheets 1 of wood pulp are supported vertically in a vat 3, again separated into sections by separators 2a resting on its rim. A known amount of mercerizing lye is contained in a tank 35, which by a suitable arrangement of connecting pipes and cocks can be put into communication with vats 38, 39, a pump 37, and the treatment vat 3; by means of the pump 37, the liquid is withdrawn from the tank 35, and is circulated through the materials in the vat 3 in such a manner as to leave the tanks 38, 39 completely filled with liquid. To enable the liquid to circulate in the vat 3, the sheets of wood pulp are provided with central openings, as are also the separators 2a but the openings in these are somewhat smaller, and the liquid is supplied to one end of the vat through a central pipe 21, a second connection 24 at the upper part of the vat serving for the return of the liquid. After the preliminary soaking above referred to, the tank 38 is cut out and its contents passed to the recuperation apparatus; the liquid in the tank 39 and that in the vat 3 is circulated bv means of the pump, the valves being so controlled that the liquid is withdrawn through a connection 28 at the bottom of the vat and in such a manner that the tank 39 always remains full; this is continued until there is no surplus liquid in the treatment vat, the requisite quantity being now entirely absorbed by the sheets of pulp. During the process of absorption, swelling of the sheets occurs; to maintain the pile in an open condition, the end plate 31 is mounted on a screw press 33, 34, and from time to time this is actuated to release the pressure. The impregnation being completed, the vat 3 is moved to a point above the hopper 50 of the disintegrator; the hinged bottom 53 of the vat is then permitted to fall down, and the screw press actuated to release the sheets which fall directly into the hopper.