Self-activated polymer particles with a narrow size distribution and procedure for production thereof

Abstract

A procedure for preparing compact and spherical self-activated polymer particles of vinyl monomers having a narrow or monodisperse size distribution in accordance with a special precipitation polymerization process in a polar organic medium, possibly in an organic polar medium mixed with water. The medium is a good solvent for the monomer and a poor solvent for the polymer. All ingredients are initially dissolved in the medium and when polymerization has been initiated, formed polymer precipitates from solution and by the aid of the dispersion stabiliser the polymer particles are kept apart as free spherical beads. The polymerization takes place with a temperature profile which produces a scattered chain length distribution, increases the conversion speed and reduces the particle size distribution. The method for producing the particles also achieves an increased degree of freedom for the production of particles with a certain particle size in a given conversion time. The particles, which may be cross-linked, can also be made functional either by an active group through copolymerization or by grafting reactions at a late stage of polymerization or in a subsequent treatment stage.