Abstract
The alcoholysis of polyvinyl acetate in ethyl alcohol solution catalyzed by sulfuric acid is accompanied by a side reaction leading to formation of a certain amount of polyvinyl sulfate. Aqueous solutions of the polyvinyl monosulfates possess a comparatively high emulsifying capacity, which increases with increase in the bound sulfur content, comprising 0.06β0.08% for 1β5% sulfuric acid in the reaction medium. Attempts to incorporate the sulfate group to a great degree with the objective of obtaining sulfated polymers of specific properties (efficient emulsifiers, stabilizers, ion exchangers etc.) did not yield satisfactory results when methods described in the literature were employed. Direct sulfation of polyvinyl acetate with subsequent conversion to polyvinyl alcohol or the sulfation of polyvinyl alcohol, to obtain a derivative with a large ester content, is impossible, owing to stereochemical hindrance. Because of this we investigated the possibility of sulfating the polymer during the process of alcoholysis of polyvinyl acetate in ethyl alcohol. It was found that under the reaction conditions for various amounts of acetate residual groups polyvinyl alcohol may be obtained with a varying content of acid or neutral esters. Under the chosen conditions a hitherto undescribed acid sulfuric acid ester of polyvinyl alcohol with 10β15% bound sulfur content was obtained. In contrast to the original polyvinyl alcohol soluble in water this sulfurβcontaining product dissolved in ethyl alcohol, water or aqueous alcohol. Neutral sulfates of polyvinyl alcohol are soluble only in ethanol but not in water. The acid sulfates possess high emulsifying and stabilizing properties. If the reaction is carried out in methanol, esterification of the acid sulfuric acid ester of polyvinyl alcohol takes place as a side reaction. The resultant products are devoid of emulsifying properties.