Preparation of an aqueous dispersion of acrylate-siloxane copolymer particles

A method of preparing an aqueous dispersion of acrylate-siloxane copolymer particles comprising the steps of:

• 1) adding a first portion of an aqueous monomer emulsion into a stirred vessel containing water and a surfactant and heating the contents of the vessel to a temperature in the range of from 80° C. to 95° C.;
• then
• 2) adding a first portion of an initiator to the vessel to form, over time, an aqueous dispersion of seed polymer particles;
• then
• 2) gradually adding a second portion of the aqueous monomer emulsion and a second portion of the initiator to the vessel;
• 4) maintaining the temperature in the range of from 80° C. to 95° C. for a sufficient time to achieve substantially complete conversion of the monomers to polymer particles comprising structural units of the monomers;
• then
• 5) adding a redox initiator package to the vessel;
• wherein the monomer emulsion comprises, based on the weight of monomers, a) from 40 to 98.8 weight percent of an acrylate monomer;
• b) from 0.1 to 5 weight percent of an acid monomer;
• and c) from 1 to 59.8 weight percent of a siloxane acrylate monomer of formula I:
• where R is H or CH3;
• R1 is H or CH3;
• and
• each R2 is independently CH3 or O—Si(CH3)3;
• Y is —CH2— or —CH2CH2—;
• and
• x is 0 or 1;
• with the proviso that when x is 1, R1 is H;
• when Y is —CH2—, R1 is H;
• and when Y is —CH2CH2—, R1 is CH3 and x is 0.