Preparation of a Cross-linkable Emulsion and its Effectiveness as the Binder Resin of Water-based Printing inks Curable at Ambient Temperature

Abstract

The proposed resin system mainly comprises two components: a nano-sized emulsion and a crosslinking agent, adipic dihydrazide. The nano-emulsion was prepared through soapless emulsion polymerization of acrylic monomers in the presence of a reactive amphiphillic block copolymer, which was synthesized through living polymerization of diacetone acrylamide and acrylic acid. The nano-emulsion was narrowly distributed in size and the average diameter is around 50 nm. The nano-emulsion was very stable even at 45 wt.%. DSC analysis showed that the polymer of the emulsion had a low glass transition temperature (Tg) (about 15 °C), but the emulsion still remained stable at a wide temperature range (4-50 °C) despite the addition of the cross-linker. Emulsion films were coated with the mixture of the nano-emulsion, the cross-linker and a small amount of leveling agent by spin-coating method, and this was followed by drying at ambient temperature. SEM analysis indicated that the border of particles had disappeared and a uniform film was obtained. Investigation on dissolution behaviors of the emulsion films showed that cross-linking reaction occurred with the evaporation of water. With the drying of the film at ambient temperature, a tough and transparent cross-linked film was prepared, which had good water/solvent resistance. This self-crosslinking resin system might be used as the binder resin for water-based printing inks which can be effectively cured at ambient temperature.