Aqueous polymer dispersion and process of making the same

An aqueous dispersion comprising a multistage polymer, wherein the multistage polymer comprises at least a first polymer and a second polymer,

• wherein the second polymer comprises structural units of an ethylenically unsaturated siloxane monomer of formula (I), (II), or (III),
• wherein, in formula (I), R is an ethylenically unsaturated group, and j and k are each independently in the range of from 0 to 100, and j+k=5 to 100;
• wherein, in formula (II), R is an ethylenically unsaturated group, R1 is a hydroxyl, alkyl, aryl, alkoxyl, aryloxy, alkyl ether, or aryl ether group, and m is from 1 to 100;
• wherein, in formula (III), R is an ethylenically unsaturated group, R1 and R2 are each independently a hydroxyl, alkyl, aryl, alkoxyl, aryloxy, alkyl ether, or aryl ether group, n is from 1 to 5, and p is from 1 to 100;
• wherein the multistage polymer comprises, by weight based on the weight of the multistage polymer, 4.5% or more of structural units of the ethylenically unsaturated siloxane monomer;
• and
• wherein the coagulum content of the aqueous dispersion is less than 2,000 ppm after filtration through a 44 micron sieve.