| 摘要 |
PROBLEM TO BE SOLVED: To provide an industrially advantageous method for producing polyvinyl acetal capable of efficiently removing unreacted aldehyde from a reaction mixture obtained by the acetalization reaction of a polyvinyl alcohol resin.SOLUTION: The method for producing polyvinyl acetal comprises: a step for obtaining a reaction mixture liquid containing polyvinyl acetal by reacting a polyvinyl alcohol resin with aldehyde in the presence of an acid catalyst in an aromatic hydrocarbon solvent; a step for converting residual aldehyde to an aqueous salt of an alkali metal sulfate by mixing the reaction mixture liquid with not less than 0.5 weight times water containing an alkali metal bisulfite by not less than 1 mole equivalent to the aldehyde remained in the liquid; and a step for recovering an aromatic hydrocarbon solvent layer containing the polyvinyl acetal by separating the mixture liquid mixed with the water containing the alkali metal bisulfite into the aromatic hydrocarbon solvent layer containing polyvinyl acetal and an aqueous layer containing the aqueous salt. |
