Development of polyvinyl acetate emulsion with reactive PVA as protective colloid and investigate its reactivity

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Recently, acetoacetylated PVA (AAPVA) that replaced the reactive acetoacetyl group with part of the PVA side-chain was introduced, and waterproof type polyvinyl acetate emulsion (EPVAc) that uses it as the protective colloid of the emulsion adhesive was synthesized due to investigate the characteristic of this EPVAc. Its physical property and wood bonding performance was investigated.1)It was proven that dissolution and hygroscopicity of EPVAc films with AAPVA as the protective colloid were improved. And, it was proven that the degree of the plasticization of films by the moisture absorption was low and that it holds the lowering of the storage modulus by the heating treatment for EPVAc films with AAPVA as the protective colloid.3)The waterproof performance of EPVAc using AA PVA was higher than EPVAc using normal PVA, and the wood bonding performance was rapidly improved, especially in the case of the heating treatment at 120℃.And using acetoacetylated (AA) PVA with various degrees of acetoacetylation and ordinary partially saponified PVA, the following facts were obtained as the result of examining the reactivity with an added isocyanate compound (pMDI) in AA PVA aqueous solution and the formation of crosslinking by heat treatment as compared with ordinary PVA.1)The rate of consuming NCO groups in the PVA aqueous solution was higher with AA PVA than with ordinary PVA. The reactivity of the AA group in AA PVA for the NCO group in pMDI was higher than that of the OH group.2)The crosslinking density of PVA, which was calculated from the E' value of the rubber flat region of the cured film, increased with the degree of acetoacetylation.The ability of the PVA aqueous solution to bond wood improved by the addition of pMDI. Curing at 120℃ resulted in superior waterproof adhesion for AA PVA.