The invention describes a process for the preparation of a particulate polymer, said process comprising: i) forming an aqueous dispersion comprising a particulate polymer seed material and a first organic compound; ii) allowing said first organic compound to diffuse into said seed material to produce a pre-swollen seed material; iii) contacting said pre-swollen seed material in aqueous dispersion with said first organic compound and a second organic compound, preferably one which is soluble in said first organic compound; iv) allowing or causing said first and second organic compounds to pass into said pre-swollen seed material to produce an activated seed material; v) contacting said activated seed material with a monomer and effecting suspension polymerization thereof.

The invention provides a process for the preparation of polymer particles having a mode particle size of at least 50 .mu.m which process comprises (a) obtaining a first particulate polymer seed material having a mode particle diameter of no more than 50 .mu.m; (b) using said first seed material, performing a suspension polymerization involving the steps: (i) forming an aqueous dispersion comprising a polymer seed material, an organic compound (e.g. a polymerization initiator) which has a molecular weight of less than 5000 Daltons and a water solubility of less than 10.sup.-2 g/L at 25.degree. C., a stabilizer and optionally an organic solvent (e.g. acetone or a portion of the monomer mentioned below); (ii) allowing said organic compound to diffuse into the seed material to produce an activated seed material; and (iii) contacting said activated seed material with a monomer (e.g. styrene) and with a polymerization initiator and effecting suspension polymerization thereof and (c) optionally impregnating and/or heat treating and/or surface modifying the particulate product of step (b).

The invention provides a process for the preparation of a particulate polymer having a mode particle size of at least 200 .mu.m, the improvement comprising the use of substantially monodisperse polymeric particles as polymerization seeds in a suspension polymerization preparation of said particulate polymer.