GB849417A - Improvements relating to the manufacture of viscose - Google Patents

Abstract

<PICT:0849417/IV(a)/1> <PICT:0849417/IV(a)/2> <PICT:0849417/IV(a)/3> In a process for the production of viscose spinning solutions in a continuous working operation, alkali cellulose is continuously prepared by passing cellulose webs through a hot caustic soda solution, and measured quantities of the alkali cellulose in small loose crumbly and initially ripened condition are rapidly mixed together with the necessary measured quantity of carbon bisulphide and xanthated while mixing, the still loose and crumbly cellulose xanthate being supplied in small measured quantities to an associated quantity of caustic soda solution, the suspension containing the xanthate being homogenised and the viscose solution being advanced to a final ripening stage. Apparatus suitable for carrying out the above process comprises a dipping trough containing the hot caustic soda solution, means for advancing cellulose webs through the trough thereby to produce alkali cellulose, means for shredding the alkali cellulose, a xanthation device in which measured quantities of the shredded and initially ripened alkali cellulose are rapidly mixed with a measured quantity of carbon bisulphide and xanthated to produce cellulose xanthate, means for suspending measured quantities of the cellulose xanthate in caustic soda solution, means for homogenising the suspension to produce a viscose solution and means for advancing the viscose to a final ripening stage. As shown, cellulose webs 3 may be advanced by rollers 4 into the upper part 5 of a caustic soda dipping trough. Lightly touching rollers 9 may compress webs 3 as they pass from upper to lower parts 5, 6 of the dipping trough. The webs 3 may be subjected to strong pressure by rollers 11 before passing to mixing and crushing worm 15, which shreds webs 3. Thence the shredded alkali cellulose is advanced via an initial ripening device (not shown) to a xanthation device, e.g. shown in Fig. 2. The initially ripened shreds of alkali cellulose may be weighed out by the measuring balance, fall through a shaft 16 into a compartment of a bucket-wheel 17, which is rotated in housing 18. The compartment containing a known quantity of alkali cellulose may be subsequently evacuated via pipe 19, the latter also being used to admit a measured quantity of carbon disulphide to the compartment. On reaching position IV, the sulphidised shreds may drop through a gas tight shaft 20 into mixer 21, and thence are discharged to a controlled feed weighing device (not shown) before passing to the homogenising means. The latter may comprise the apparatus shown in Fig. 3, i.e. vessel 24, having a cover 25, p filling sheet 26, spray pipe 27, stirrer 28 and ring valve 29. Examples are given.