| 摘要 |
PROBLEM TO BE SOLVED: To obtain a water-sol. film for packaging an acidic substance which film has water solubility not decreasing with the lapse of time and is excellent in dissolution rate in water, toughness, and mechanical strengths by forming a sulfonated polyvinyl alcohol resin into a film. SOLUTION: A vinyl ester and a sulfonated monomer are copolymerized in bulk or in soln. using an alcohol, etc., as the solvent in the presence of a free radical polymn. initiator, and the resultant copolymer is saponified partly or to a high degree by the action of an alkali or acid catalyst, thus giving a sulfonated polyvinyl alcohol resin having a sulfo group content of 0.1-20mol%, a viscosity average degree of polymn. of 300-10,000, and a degree of saponification of 40-100mol%. 100 pts.wt. thus obtd. resin is compounded with 0-50 pts.wt. plasticizer, dissolved or dispersed in water, and formed into a 10-100μm-thick film, thus giving a water-sol. film which is used for packaging an acidic substance and of which an aq. soln. or dispersion with a concn. of 1wt.% has a pH of 5 or lower. |
