Development of room-temperature curing aqueous emulsion-type acrylic adhesive II: effect of monomer composition on the final adhesive strength

In a series of studies, development of a new aqueous emulsion-type adhesive for use with wood or paper, which does not release formaldehyde or volatile organic solvents, was attempted. For the purpose of increasing both initial and final adhesive strengths, we selected a system consisting of acrylic monomers copolymerized with functional monomers such as diacetone acrylamide and some cross-linking agents such as dihydrazide or polymeric methylene diphenyl diisocyanate (pMDI). It was found that dihydrazide cross-linker was effective for both the initial and final adhesive strengths, suggesting contribution of hydrazone bonds to the bonding strengths. Cross-linking with pMDI might be slow and was not important in the initial bonding. However, its cross-linking effect might develop gradually, because the adhesive showed good final strengths using pMDI as a cross-linker.