Abstract: This invention relates to polymer particles that are acid-free in the swellable polymer core and to hollow polymer particles derived therefrom, and to a process for the production of these particles. The acid-free core advantageously decreases the polymer particle's affinity to water. Applicants have discovered that non-carboxylated latexes having a variety of Tg's will swell at temperatures higher than the Tg of the polymer. These latex particles are useful as opacifying plastic pigments for various coatings and particularly as gloss-enhancing plastic pigments for paper and paperboard coatings. Preparation of the hollow polymer particle comprises the use of (meth)acrylate ester monomers, vinyl esters of carboxylic acids or a mixture thereof which are hydrolyzable and swellable at higher temperatures in alkaline environments. The particles may be encapsulated with a hard shell.

Abstract: This invention relates to a process of making hollow polymer latex particles without the use of acid in the swellable polymer core; the latexes are useful as opacifying plastic pigments for various coatings and particularly as gloss-enhancing plastic pigments for paper and paperboard coatings. Known methods for preparing hollow latexes require cores containing acid or acidic monomers to enable swelling to core at room temperature. The existence of acid in the polymer disadvantageously increases the polymer's affinity to water. Applicants have discovered that non-carboxylated latexes having a variety of T.sub.g 's will also swell at higher temperatures. The mechanism entails the use of acrylate and methacrylate ester monomers which are hydrolyzable and swellable at higher temperatures in alkaline environments. Such mechanisms for making swollen latexes provide for a wide variety of potential end-uses as well as a wide variety of potential latexes.