| 摘要 |
Alkali cellulose is xanthated in a stationary vessel provided with a stirrer mechanism by evacuating the vessel, introducing nitrogen and/or carbon disulphide until the pressure inside the vessel is restored to atmospheric, spraying carbon disulphide into the vessel and simultaneously introducing alkali cellulose crumbs continuously, the delivery of carbon disulphide and of alkali cellulose to the vessel being carried out in such a way that the introduction of the two reactants is completed at the same time and all particles of the alkali cellulose come into contact with the carbon disulphide as soon as possible after entering the vessel. In the example a vertical cylindrical vessel is evacuated through a vacuum pipe, a sliding-plate valve between the vessel and a gravity feed hopper being closed. The pressure inside the vessel is then restored to atmospheric by introducing nitrogen and a small amount of carbon disulphide. The sliding-plate valve is then opened and alkali cellulose crumbs are introduced via the gravity feed hopper, between which and the plate valve is a rotary segmental hopper (segmentally compartmented feed drum), in constant flow into the vessel. At the same time the amount of carbon disulphide necessary for xanthation is introduced through ring sprayers, the introduction of both reactants being completed in 14 minutes, after which the plate valve is closed. The mixture is slowly stirred by means of a vertical-shaft mechanical stirrer and xanthation is completed in 40 minutes at 32-33 DEG C. Dilute aqueous caustic soda solution for dissolving the xanthate is finally introduced through another ring sprayer coaxial with the stirrer shaft.
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