Aqueous latexes formed from polymer/CO2 suspensions.: 2.: Hydrophilic surfactants in water

Stable aqueous latexes were made by transporting viscous liquid poly(2 ethylhexl acrylate) suspensions in carbon dioxide into water containing hydrophilic surfactants. The surfactants were composed of poly(ethylene oxide) hydrophilic blocks and either poly(propylene oxide) or poly(butylene oxide) anchor blocks. The polymer suspensions were synthesized in supercritical CO(2) utilizing poly(dimethylsiloxane) g pyrrolidonecarboxylic acid as a stabilizer. Rapid expansion of these suspensions through a nozzle into the aqueous solution produces stable latexes. Alternatively, CO(2) may be vented from the polymer suspensions, and the resulting viscous polymer may be redispersed in an aqueous surfactant solution with mild stirring. Polymer concentrations up to 40 g in 100 g of water were stabilized with low concentrations of hydrophilic surfactant. The latexes may be utilized as environmentally benign coatings and adhesives without the need for organic solvents.