Verfahren zur Herstellung von teilweise acyliertem Polyvinylalkohol

摘要

In a process for the manufacture of partially acylated polyvinyl alcohol by the hydrolysis of carboxylic acid esters of polyvinyl alcohol at a raised temperature in the presence of water and an acid catalyst, the ester is hydrolysed to a desired content of aryl groups, the hydrolysis catalyst is eliminated, the resulting mixture is subjected to vibration while the carboxylic acid formed is removed by extraction, and the carboxylic acid and extraction agent are recovered from the extract by fractional distillation. The catalyst can be eliminated mechanically or by neutralization e.g. to a pH of 2,0 to 2,5. The carboxylic acid can be extracted with ethyl acetate, ketones or ethers, either alone or in admixture with a sparingly water-soluble liquid such as benzene, cyclohexane or trichlorethane. Vibration can be produced by a solid oscillating in the liquid, by an oscillating diaphragm or by a pump. In examples, the process is applied to polyvinyl acetate hydrolysed to 25 and 15 mols per cent, respectively, of acetyl groups with mixed sulphuric and naphthalene sulphonic acids and with perchloric acid. Extraction is effected with a mixture of ethyl acetate and benzene.