The study of esterifying reaction between epoxy resins and carboxyl acrylic polymers in the presence of tertiary amine

In this article, the fixed gel/nongel point and critical gel point experiments are designed for formulating the regulation of esterification reaction between epoxy resin and carboxyl acrylic polymer in the presence of tertiary amine in organic solvent. Ternary diagrams are employed to illustrate experimental results. It is disclosed that some factors, such as mole ratio of the ternary reactants, molecular weight of epoxy resin, even the hydrophilic solvent content of system, play important roles in the gelling effect of esterification reaction. In order to explain these experimental results, a suggested reaction process is put forward and, subsequently, a critical gel equation is derived from Carothers gelation theory. The equation provides an explicit connection between the critical gel composition and the relevant parameters of the reaction system such as average carboxyl functionality of acrylic resin, average molecular weight of epoxy resin, the base intensity of tertiary amine, and the solid content of system. The regressive critical gel curve based on the equation is well consistent with the experiment data. It expresses that the suggested reaction process is reasonable. Finally, based on the critical gel equation, the important factors that influence the esterification result are discussed qualitatively. All the achievements are beneficial to understanding the reaction process and avoiding useless gelation in preparing the water-reducible compositions.