Finely divided, cationic or amphoteric, aqueous polymer dispersions, process for their preparation, their use, cationic or amphoteric protective colloids and their preparation

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 DEG 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 on