| 摘要 |
Esters of a polyvinyl alcohol with aceto-acetic acid are prepared by reacting a polyvinyl alcohol with diketene, the reaction being preferably effective under substantially anhydrous conditions at a temperature of 60-175 DEG C., preferably 100-150 DEG C., in the presence of an inert solvent, preferably a liquid amide of a monocarboxylic acid in which the carboxylic acid residue contains from 1 to 6 carbon atoms, such as dimethyl formamide. The polyvinyl alcohol employed may be a partially or completely hydrolyzed polyvinyl carboxylate such as polyvinyl acetate, propionate, laurate, stearate and benzoate, or a partially or completely hydrolyzed vinyl carboxylate interpolymer such as vinyl chloride-vinyl acetate interpolymer, vinyl acetate-vinyl butyrate interpolymer and ethylene-vinyl acetate interpolymer, a preferred polyvinyl alcohol being water-soluble and having a viscosity in 4 per cent water solution ranging from 5 to 70, preferably 20 to 50 centipoises at 20 DEG C. Generally, amounts of diketene are employed so that from 5 to 100 per cent of the available hydroxyl groups in the polyvinyl alcohol are acylated; the reaction product may be obtained from solution in the inert solvent by precipitation by pouring into methanol or benzene. Specification 654,856 is referred to. The Specification as open to inspection under Sect. 91 refers also to reacting a polyvinyl alcohol with 1-butene-1,3-diones of the general formula <FORM:0654855/IV (a)/1> wherein R and R1 are hydrogen or hydrocarbon radicals which may be aliphatic or aromatic. This subject-matter does not appear in the Specification as accepted. |
