Improvements in and relating to apparatus for use in the production of viscose

Apparatus for ageing alkali cellulose preparatory to conversion into viscose comprises a silo merceriser having a stationary ageing compartment through which the alkali cellulose passes vertically downwards, mechanical pickers to remove crumbs continuously or intermittently from the bottom of the compartment, and means for cooling the alkali cellulose during or after or both during and after its removal by the pickers. The apparatus enables the subsequent xanthation to be effected at a lower temperature than the ageing of the alkali cellulose. The mechanical pickers may have cooling surfaces with which the alkali cellulose will come in contact during its removal. They may consist of a number of rotatable shafts or rollers each provided with picker fingers or cutting blades and the shafts or rollers may be hollow to permit passage of cooling liquid. The alkali cellulose may be discharged from the bottom of the ageing compartment into an inclined rotatable cylindrical drum provided with a jacket which may be supplied with a cooling medium. Alternatively, the space beneath the pickers may be enclosed to form a discharge hopper and the air temperature and humidity may be controlled to cool and alkali cellulose falling through it. The temperature in the ageing compartment may be maintained at 40-45 DEG C. and the alkali cellulose may be cooled by the pickers or by the cooling drum to 20-30 DEG C. The crumbs may be subjected to a light opening treatment before passing to the xanthation stage. The apparatus may be used in the production of viscose by a continuous process. As shown in Fig. 1, the silo merceriser 5 has an ageing compartment 6 provided with a supply hopper 9, cone distributer 10, and a jacket 12 through which heating or cooling fluid may be passed. At the bottom of the compartment 6 are the mechanical pickers, each picker comprising a roller 15 which is hollow and which has cutting blades 16. The rollers are geared together and operated from a single drive, adjacent rollers rotating in opposite directions. A small clearance is provided between adjacent rollers and the cutting blades do not intermesh. Cooling liquid is passed through the interior of the hollow rollers. The cooled alkali cellulose crumbs pass from the pickers to the discharge hopper 17 and through outlet 18 to a xanthating churn. As shown in Fig. 4, the alkali cellulose crumbs are discharged into a cooling drum 30 which is rotated by mea