| abstract |
Disclosed are voided latex particles, useful as opacifying agents for coating compositions containing organic solvents. The particles have a hollow interior, which substantially maintains its integrity after the particles are placed in contact with an organic solvent at 25°C for 30 days. The particles also have a hydrophilic polymeric interior shell surrounding the hollow interior that is swellable with an aqueous swelling solution. The particles have first and second polymeric intermediate shells, surrounding the interior shell, formed from polymers that are different from each other and different from the interior shell polymer. Finally, the particles have an outer polymeric shell, surrounding the interior shells, which is formed from up to 100% by weight, as polymerized units, of methyl methacrylate. The interior shells and the outer shell each have a Tg greater than 60°C. Also disclosed is a multi-stage emulsion process for making the particles. |