Graft copolymers and compositions thereof

A method for improving the dirt pick-up resistance of a paint or coating comprising the step of adding a graft copolymer comprising:

• a) a macromonomer, wherein the macromonomer comprises in polymerized form a first monoethylenically unsaturated monomer selected from a group consisting of esters of methacrylic acid and acrylic acid with straight or branched alcohols having 1 to 3 carbon atoms and no more than 5 mole percent of an addition fragmentation chain transfer agent;
• and
• b) at least one side chain on the macromonomer, wherein the at least one side chain comprises at least 95 wt.-% of acrylic acid in polymerized form, to the paint or coating.

A method of making a graft copolymer comprising:

• a) polymerizing a first monoethylenically unsaturated monomer selected from the group consisting of esters of methacrylic acid and acrylic acid with straight or branched alcohols having 1 to 3 carbon atoms, in presence of an addition fragmentation chain transfer agent in an amount so that the so formed polymer does not contain more than 5mole percent of the addition fragmentation chain transfer agent, in an aqueous mixture at a temperature in a range of 50° C. to 100° C. to form a macromonomer in a first aqueous emulsion;
• and
• b) polymerizing the macromonomer in the first aqueous emulsion with an amount of acrylic acid to form a graft copolymer having at least one side chain comprising at least 95 wt.-% acrylic acid on the macromonomer in a second aqueous emulsion.