Patent ID: 8901239
Filing Date: 2014-12-02
Classification: C08F,G03G

Abstract:
1. A process for preparing a particulate solid comprising the steps i) to iv): i) providing a dispersion of polymer particles in a liquid medium, said polymer being obtained or obtainable by the copolymerisation of at least the monomers in components a) to d): a) 45 to 90 parts of one of more hydrocarbyl (meth) acrylates each having a homopolymer Tg of from 90 to 130° C. and having no hydrophilic groups; b) 10 to 55 parts of one or more ethylenically unsaturated monomers each having homopolymer Tg of below 90° C. and having no hydrophilic groups; c) 0 to 40 parts of one or more styrenic monomers having a homopolymer Tg of at least 90° C. and having no hydrophilic groups; d) 0 to 10 parts of one or more ethylenically unsaturated monomers each having at least one hydrophilic group; wherein all the parts are by weight; and the polymer particles are stabilised by a surfactant which at least partially adsorbs onto the surface of the polymer particles and the surfactant has one or more carboxylic acid groups; ii) associating the particles to form clusters of particles by adjusting the pH of the liquid medium by the addition of an acid; iii) optionally stabilising the clusters, against further association, broadening of particle size distribution or growth in particle size by addition of further surfactant, and/or by a change in pH to convert reversibly ionisable groups to ionic form; iv) heating the clusters above the glass transition temperature of the polymer in the polymer particles in step i).