Process for the preparation of functionalised polymer particles

A process for the preparation of monodisperse amine-functionalised vinyl polymer particles wherein said polymer particles have a mode particle size of greater than 100 μm, which process comprises

• (a) obtaining a first particulate polymer seed material having a mode particle diameter of at least 70 μm;
• (b) using said first seed material, performing a first suspension polymerization to yield a second particulate polymer seed material having a mode particle diameter greater than that of said first seed material and, using said second seed material, performing at least one further suspension polymerization to yield a particulate polymer seed material, whereby the increase in mode particle volume in step (b) is at least ×2;
• wherein at least one of the suspension polymerizations effected in step (b) involves
• (i) forming an aqueous dispersion comprising a polymer seed material, an organic compound which is a non-initiator or a first polymerization initiator having a molecular weight of less than 5000 daltons and a water solubility of less than 10−2 g/L at 25° C., a hydroxyalkylmethylcellulose stabilizer and a first monomer;
• (ii) allowing said organic compound and said first monomer to diffuse into the seed material to produce an activated seed material;
• and
• (iii) contacting said activated seed material with a second monomer and with a second polymerization initiator whilst effecting suspension polymerization thereof, and that in at least the final suspension polymerization of step (b) the second monomer comprises amino styrene and at least one further vinylic monomer, and said second polymerisation initiator is an azo initiator.