(169f) Preparation of Emulsion-Suspension Composite Polymer Particle Via Seed-Coagulation Process

Emulsion-suspension polymerization is a method for recovering the emulsion polymer as an emulsion-suspension composite polymer particle. The basic principle of this method is that the emulsion system is converted to the suspension system by adding the ethylene-type monomer and the coagulant to the emulsion polymer. The composite particle obtained by this technique is spherical in shape and has reduced water contents, like the suspension polymerized particle, compared with the coagulated particle of the emulsion polymer, and thus this method is considered more advantageous than conventional emulsion polymerization processes. However, this method has not evolved as a widely used industrial manufacturing method because many issues remained to be solved which is caused by the difficulties of operation at the emulsion-suspension converting stage. Based on these backgrounds, we have attempted to develop a new method obtaining the emulsion-suspension composite particles by elucidating the mechanism of the composite particle formation process at the emulsion-suspension converting stage. According to the results of the mechanism study, it is obvious that the composite particle is formed through the seed-coagulation process whereby the emulsion polymer is deposited on the surface of the monomer droplet. This result indicates that the seed-coagulation of the emulsion polymer would also occur in the case of using a suspension polymer particle instead of the monomer droplet as a seed material. We also discovered that the emulsion-suspension composite particle, the suspension polymer particle coated with emulsion polymers, is formed by adding the coagulating agent to the mixture of the water dispersion of emulsion and suspension polymer mixture under the stirred condition, and from an industrial perspective, this simple procedure has many excellent features.