| abstract |
A finely divided, cationic or amphoteric, aqueous polymer dispersion which is obtainable by emulsion polymerisation of ethylenically unsaturated monomers in the presence of a cationic or amphoteric protective colloid, wherein first the cationic or amphoteric protective colloid is prepared by polymerising a monomer blend in the presence of at least one first polymerisation initiator in an organic solvent, and is carried out in a pressurised reactor at a pressure of at least 1720 kPa and at a temperature of at least 150° C., which monomer blend comprises at least one ethylenically unsaturated monomer carrying an amine group, to provide a resin, then combining the resin, with an acid and water, to form the cationic or amphoteric protective colloid, thereafter carrying out an emulsion polymerisation by introducing a monomer mixture into an aqueous medium containing said cationic or amphoteric protective colloid and at least one second polymerisation initiator, wherein said monomer mixture comprises at least one ethylenically unsaturated water insoluble monomer. The composition is useful as a sizing agent for paper. |