POLY(VINYL ACETATE) AND POLY(VINYL ACETATE-CO-ETHYLENE) LATEXES VIA DISPERSION POLYMERIZATIONS IN CARBON-DIOXIDE

The preparation of stable dispersions of poly(vinyl acetate) or ethyle ne/vinyl acetate copolymers via dispersion polymerizations in a carbon dioxide continuous phase has been investigated. The effectiveness of stabilizers of various chemical compositions and architectures was com pared. Both fluorinated and siloxane-based stabilizers including homop olymers, block copolymers, and reactive macromonomers were employed. E ffects of variations in the reaction temperature, pressure, stabilizer composition, stabilizer concentration, and use of cosolvents on the r esulting product were investigated. A turbidimetry technique was used successfully to monitor dispersed-phase volume fractions, particle siz es, and number densities during the polymerizations and to give the fi nal particle sizes at the end of the polymerizations. The fluorinated stabilizers gave rise to smaller particles and more stable latexes whe n compared to the siloxane-based stabilizers.