Semicontinuous microemulsion copolymerization of vinyl acetate and butyl acrylate: high solid content and effect of monomer addition rate

Abstract

Vinyl acetate and butyl acrylate were copoly- merized in microemulsion under monomer-starved condi- tions by a semicontinuous process using different monomer addition rates (Ra). A mixture of sodium dodecyl sulfate and polyethylene glycol dodecyl ether (Brij®35) were used as surfactants. Potassium persulfate was the initiator. High copolymer content latexes (around 40 wt.%), average particle diameters (Dp)<50 nm and polymer-to-surfactant ratios (12 to 14, weight/weight) were obtained with weight average molar masses (Mw) between 180,000 and 760,000. Dp and Mw of the copolymers decrease as Ra is decreased. As Ra increases, a shoulder in the molar mass distribution was observed at high values of Mw, which was ascribed to chain transfer to polymer. Homogeneous copolymer com- positions were observed throughout the reaction, which cannot be obtained by the usual batch process.