Amine functional anionic polymer dispersion and coating compositions thereof

A process for the preparation of an aqueous anionically stabilized polymer dispersion comprising the steps

• a. a first emulsion polymerization of a first monomer mixture comprising acid functional monomers M1 comprising acid groups and less than 2 wt % (relative to the total weight of the first monomer mixture) amine functional monomers M2 comprising amine groups to form a first phase polymer dispersion of an acid functional oligomer P1 having a number average molecular weight MnP1 between 500 and 50,000 g/mole (as determined by GPC using THF in combination with acetic acid) and a Fox glass transition temperature TgP1 of at least 0° C.,
• b. adding a base to increase the pH in a range between 6 and 11,
• c. a second emulsion polymerisation in the presence of the first phase polymer dispersion P1 of a second monomer mixture comprising amine functional monomers M2* having sterically hindered secondary amine or tertiary amine groups and less than 2 wt % (relative to the total weight of the second monomer mixture) acid functional monomers M1 to form a second phase of an amine functional polymer P2 having a Fox glass transition temperature TgP2 of at least 0° C.,
• d. wherein TgP2 is lower than TgP1 by at least 5° C. and
• e. wherein the resulting anionically stabilized polymer dispersion comprises dispersed particles having within the particles separate unmixed first and second phases, wherein the Fox Tg is calculated based on constituting monomers in the monomer mixtures not including chain transfer agents or reactive surfactants.