| 摘要 |
Polyvinyl alcohol is produced in a solid filterable form by subjecting a polyvinyl ester or a copolymer of a vinyl ester to alcoholysis with a saturated aliphatic alcohol containing 3-6 carbon atoms in the presence of 12-100% of water and 1-10% of an acid, the percentages being calculated on the weight of the polymer or copolymer, at a temperature of 60 DEG -95 DEG C. The polymeric ester may be a polymer of vinyl acetate, vinyl propionate, vinyl stearate or vinyl benzoate, or a copolymer of these monomers with themselves or with vinyl chloride, crotonic acid, acrylic acid or methacrylic acid or esters of these acids with saturated alcohols containing 1-4 carbon atoms. The acids may be hydrochloric acid, sulphuric acid, benzene sulphonic acid, toluene sulphonic acid, naphthalene sulphonic acid, kogosin sulphonic acid, and phenyl-kogosin sulphonic acid. Solvents which are not alcohols, such as gasoline having a boiling range of 50 DEG -160 DEG C., benzene, toluene or xylene, acetone, methyl ethyl ketone, methyl acetate, isopropyl acetate, butyl acetate or ethyl butyrate, may also be added. The polyvinyl alcohols produced are obtained in a granular form and are nearly colourless. Alcoholysis is preferably effected at 65 DEG -85 DEG C. The treatment of ethylene/vinyl acetate/fumaric ester interpolymers is excluded. |
