Miniemulsion polymerization process using polymeric co-surfactant

Abstract

An essentially stable monomer miniemulsion characterized by small monomer droplet size is prepared and is then polymerized to a polymer latex under free radical polymerization conditions. The monomer miniemulsions herein include, in addition to water, a surfactant, and a monomer or mixture thereof, one or more polymers which function as a polymeric co-surfactant. The monomer miniemulsions are characterized by average monomer droplet size of 10 to 500 nanometers, preferably 80 to 150 nanometers. The amount of polymer added as a co-surfactant is about 0.5 to about 5 percent by weight based on monomer weight. The monomer emulsion may contain either a single monomer or a monomer mixture. The monomer emulsion is polymerized under conventional emulsion polymerization conditions yielding a polymer latex having an average polymer particle size of 10 to 500 nanometers, preferably 80 to 150 nanometers, and a narrow particle size distribution, i.e., a polydispersity index of about 1.05 to about 1.40. A representative monomer is methyl methacrylate and a representative polymer as co-surfactant is polymethyl methacrylate.

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