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Study on ketalization reaction of polyvinylalcohol by ketones. III. Reaction between polyvinylalcohol and methyl ethyl ketone and behavior of polyvinylketal in water
Author(s) -
Nakamura Naofumi,
Aoshima Sadahito,
Higashimura Toshinobu
Publication year - 1988
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1988.070360813
Subject(s) - chemistry , acetone , ketone , solvent , hydrolysis , solubility , dissolution , polymer chemistry , thermal decomposition , organic chemistry , nuclear chemistry
Ketalization reaction of polyvinylalcohol (PVA) by methyl ethyl ketone (MEK), dimethyl‐sulfoxide (DMSO) as solvent, under the presence of acidic catalyst, in homogeneous system was carried out, and the synthesis of polyvinylketal with any ketalization degree was successfully performed. The reaction mechanism of PVA with MEK is identical with that with acetone: for both cases, the equilibrium constant is ca. 0.07 at 40°C and the heat of reaction is 7.5 kcal/mol. Films prepared from the polyvinylketal were soaked in water and degree of swell, solubility, and hydrolysis of films were measured. The reaction of film with water, in acidic side, easily proceeds, and at first the film swells; then, as deketalization reaction proceeds, the film dissolves in water. With polyvinylketal of the ketalization degree of above 15 mol %, dissolution time is controlled by both ketalization degree and pH of water, which reveals that deketalization reaction proceed proportionally to proton concentration at 37°C. On the other hand, in the neutral condition where hydrolysis does not proceed at all, polyvinylketal of ketalization degree of 10–40 mol % dissolves in water at 0°C. The polyvinylketal obtained by MEK is more stable in water than that from acetone since MEK has hydrophobicity.