| 摘要 |
1,250,819. Polyvinyl alcohol compositions. NIPPON GOHSEI KAGAKU KOGYO K.K. 24 March, 1969 [25 March, 1968; 10 Feb., 1969], No. 15346/69. Heading C3P. A polyvinyl alcohol composition consists essentially of polyvinyl alcohol and 0.1 to 5% by weight, based on the weight of the polyvinyl alcohol, of an additive which is the product obtained by partially hydrolysing polyvinyl acetate in the presence of an acidic catalyst in an alcoholic solution until 20% to 70% by mole of acetate groups of the polyvinyl acetate are hydrolysed. The polyvinyl alcohol is the watersoluble resin obtained by partially or completely hydrolysing a homopolymer or copolymer of a vinyl ester in the presence of an alkaline catalyst according to a conventional method or such a polymer modified by acetalysation or urethanation to the extent that water-solubility is retained. In the examples, the additive is prepared by hydrolysing polyvinyl acetate in methanolic solution in the presence of monomethyl sulphate, dimethyl sulphate, sulphuric acid, hydrochloric acid and phosphoric acid as catalysts. A conventional polyvinyl alcohol is prepared using sodium hydroxide. The composition is prepared by dissolving the polyvinyl alcohol and additive in methanol and evaporating. The composition may be used as a protective colloid in the emulsion polymerization of vinyl acetate in the presence of water, sodium phosphate, and potassium persulphate. |
