Aqueous polymer dispersion for use in water based glossy lacquers

A process for the preparation of an aqueous polymer dispersion obtained by the emulsion polymerization of α,β-ethylenically unsaturated monomers comprising a monomer composition A and a monomer composition B wherein the Tg of monomer composition A after emulsion polymerization and the Tg of monomer composition B after emulsion polymerization differ from each other such that one of the said Tg is at least 60° C. higher than the other of the said Tg, said higher Tg being at least 40° C., and wherein each of monomer composition A and monomer composition B comprise at least one of:

• 1) one or more compounds selected from the group consisting of alkenyl aromatic monomer, acrylonitrile, an alkyl, (hetero)cycloalkyl or aralkyl ester of acrylic acid and methacrylic acid having 4-22 C-atoms, acrylamide and methacrylamide, acrylamide and methacrylamide N-substituted with an alkyl, cycloalkyl or aralkyl group having 1 to 18 carbon atoms, vinyl acetate, and vinyl versatate, with up to 25 wt. % of the selected compounds optionally having a second functional group capable of reacting with a curing agent;
• and
• 2) an ethylenically unsaturated carboxylic acid,
• such that a combination of monomer composition A and monomer composition B comprises at least 80 wt. % of the selected compounds of (1), about 0.1 to about 5 wt. % of the carboxylic acid of (2), and about 0.1 to about 5 wt. % of a nitrogenous adhesion promoting copolymerizable monomer, wherein at least 60 wt. % of the carboxylic acid of (2) is comprised in the one of either monomer composition A or monomer composition B that contains less than 40 wt. % of said adhesion promoting copolymerizable monomer;
• said process comprising feeding a reactor with monomer composition A from a holding means containing monomer composition A while simultaneously feeding monomer composition B to the holding means containing monomer composition A, wherein the mass flow of monomer composition A to the reactor is 1.1 to 11 times higher then the mass flow of monomer composition B to the holding means containing monomer composition A.