Kontinuierliches Verfahren zur Herstellung von Polyvinylacetat zum Herstellen von Polyvinylalkohol

摘要

An improved process for the continuous production of poly(vinyl alcohol) which involves purifying poly(vinyl acetate) paste exiting from a polymerization reactor and dissolving the substantially pure poly(vinyl acetate) in a hydrolytic alcohol-containing solvent for subsequent saponification to produce poly(vinyl alcohol). Poly(vinyl acetate) paste, containing poly(vinyl acetate), vinyl acetate, and solvent, is heated to a temperature above the glass transition temperature but below a temperature which will degrade the poly(vinyl acetate) and is fed into a flashing area of an extruding devolatilization device. Vinyl acetate and solvent are flashed through vent ports in the flashing area of the devolatilization device and can then be recycled to a polymerization reactor, if desired. A substantially pure poly(vinyl acetate) melt, exiting the flashing area, is conveyed to a mixing area of the devolatilization device where it is mixed with a hydrolytic alcohol-containing solvent to form a solution for subsequent processing in a saponification unit.