METHOD OF POLYVINYL ALCOHOL SYNTHESIS Russian patent published in 1994 - IPC

FIELD: chemical technology. SUBSTANCE: polyvinyl alcohol is synthesized by saponification of polyvinyl acetate. Dispersion of polyvinyl acetate is mixed initially with aqueous alkali solution at 0-20 C. Prepared reaction mixture is kept for 1.0-1.5 h at temperature 25 C, not above, and saponification is carried out at 70-80 C. After saponification the concentration of electrolyte in reaction medium must be 2.5 g-equiv./l, not less. After saponification the isolation of polyvinyl alcohol in the form of powder-like form is carried out. To improve the granules isolation the suspension precipitate of polyvinyl alcohol is heated up to 90-140 C. It is possible to add 1.2-2.5 wt. - % polyvinyl alcohol in the form of aqueous solution to the suspension precipitate. Also, to improve the isolation of polyvinyl alcohol precipitate can be heated, and polyvinyl alcohol aqueous solution can be added. Method can be used for plastics making. EFFECT: improved method of polyvinyl alcohol synthesis. 2 cl, 1 tbl