Research & Development Center, Dai Nippon Printing Co., Ltd.; 250-1 Wakashiba, Kashiwa-shi 277-0871 Japan
There have been many studies on the fabrication of microcapsules by the use of various techniques. Among these techniques, liquid phase separation method is most promising for microencapsulation of trimellitic anhydride (TMA) since it provides TMA microcapsules without using an aqueous solution. TMA, used as foaming control agent in the field of printing, was microencapsulated by liquid phase separation (called solvent displacement method) in organic solvents. The solubility parameters were used in order to determine the raw materials of TMA microcapsules. Considering the solubility parameters of polymer, copoly (ethylene/methacrylic acid) was used as the capsule wall material. In our experiments, two kinds of solvents, toluene (solvent (a)) and Isopar-L (solvent (b)), were used. The following conditions were adopted: (1) The wall material was completely dissolved in solvent (a); (2) TMA powder was well dispersed in solvent (a) but was not dissolved in solvent (a); and (3) the wall material and TMA powder were not dissolved in solvent (b). By using the mixtures of lecithin and basic barium petronate (BBP) or basic calcium petronate (BCP) as charge control agents, TMA microcapsules were charged both positively and negatively. The liquid toner prepared in this study was applicable to a commercial printing machine. Furthermore, the foaming control effects satisfied the requirements for products in the printing industry.