A method for the filtration of viscous - spinning dopes

摘要

Liquid, e.g. synthetic film-spinning material, is introduced at 2 in the figure (not shown), to a vessel where it is mixed with granules of polyvinyl chloride introduced from a dosing device 3. The mixture is pumped (4) to a filter 1 furnished with horizontal filter elements each provided at the top only with metal fabric and covered already with a mixture of P.V.C. granules and viscose. When the pressure difference is excessive, filtration is interrupted and the contents of the filter passed back to the container for the liquid (not shown). The filter cake on the elements is freed from viscose by compressed air introduced at 5 and is then washed with water from pipe 6. Next, the elements are rotated by motor 7 to throw off the cake and suspend it in a little water, the resulting suspension being fed to an agitator 8 where soda lye is introduced from a container 9 and heating is effected by introducing steam. The suspension is agitated and pumped (10) to the inside of a screen 12 rotating partly submerged in water in a conical vessel 11. Here, impurities float off into a funnel 14, while the P.V.C. granules sink through the screen, and are dehydrated in a suction strainer or centrifuge 13 for return to the dosing device 3. Instead of P.V.C. there may be used polyethylene, polypropylene, polyacrylonitrile, metal powder or metal chips.