Method for producing emulsion polymers

A process for preparing emulsion polymer particles by preparing an aqueous emulsion comprising a multistage emulsion polymer comprising:

• i) a seed;
• ii) a swell seed comprising 0 to 100% by weight of at least one nonionically ethylenically unsaturated monomer and 0 to 40% by weight of at least one monoethylenically unsaturated hydrophilic monomer, based in each case on the total weight of a core stage polymer comprising the seed (i) and the swell seed (ii);
• iii) a first shell comprising 85% to 99.9% by weight of at least one nonionically ethylenically unsaturated monomer and 0.1% to 15% by weight of at least one hydrophilic monoethylenically unsaturated monomer;
• iv) a second shell comprising 85% to 99.9% by weight of at least one nonionically ethylenically unsaturated monomer and 0.1% to 15% by weight of at least one hydrophilic monoethylenically unsaturated monomer;
• v) at least one plasticizer monomer having a ceiling temperature of less than 181° C.;
• vi) neutralizing to a pH of at least 7.5 or more, the resultant emulsion polymer particles with a base;
• vii) a third shell comprising 90% to 99.9% by weight of at least one nonionically ethylenically unsaturated monomer and 0.1% to 10% by weight of at least one hydrophilic monoethylenically unsaturated monomer;
• and
• viii) optional further shells comprising at least one nonionically ethylenically unsaturated monomer and at least one hydrophilic monoethylenically unsaturated monomer.