抄録
Ethylene-vinyl acetate copolymer (EVAc) with 63.09% vinyl acetate content, was saponified heterogeneously in a methanol and water mixture using an alkali catalysis. A sharp boundary between reacted (EVA) and unreacted (EVAc) layer was observed by microscopy in the cross section of membrane, which taken out in the course of saponification and dyed with Rodamine 6G. The thickness of reacted layer changed in the same manner as the degree of reaction with the reaction time. After the extraction of the unreacted layer with solvent, vinyl acetate group was hardly observed in reacted layer by infrared analysis. The rate of advance of the boundary front was identical with that of transport of alkali ion into the polymer, however, the diffusibility of alkali ion into the saponified layer was extremely greater than the rate of advance of boundary front. From above results, it was found that the alkaline saponification of EVAc in heterogeneous system was controlled by the mechanism of boundary reaction which was similar to the Case II type diffusion.
