Process for preparing aqueous dispersions

Core-shell particles obtained by a process comprising:

• (1) preparing an aqueous polymer dispersion, and
• (2) separating core-shell particles therefrom,
• wherein (1) comprises:
• a) preparing an initial charge of an aqueous emulsion of a long chain alkyl alcohol or a seed latex by polymerization of an alkyl (meth)acrylate in an aqueous medium comprising an emulsifier to a seed particle radius ranging from 3.0 to 20.0 nm
• b) adding from 25.0 to 45.0 parts by weight of a first composition
• comprising:
• A) from 50.0 to 99.9 parts by weight of an alkyl (meth)acrylate having from 1 to 20 carbon atoms in the alkyl radical,
• B) from 0.0 to 40.0 parts by weight of an alkyl acrylate having from 1 to 20 carbon atoms in the alkyl radical,
• C) from 0.1 to 10.0 parts by weight of a crosslinking monomer, and
• D) from 0.0 to 8.0 parts by weight of a styrenic monomer of the formula (I)
• where each of the radicals R1 to R5, independently of the others, is hydrogen, a halogen, a C1-6-alkyl group or a C2-6-alkenyl group, and the radical R6 is hydrogen or an alkyl group having from 1 to 6 carbon atoms, emulsified in water with an emulsifier, to said aqueous emulsion or seed latex, and
• polymerizing the added monomers to a conversion of at least 85.0% by weight, based on the total weight of components A), B), C) and D),
• c) adding from 35.0 to 55.0 parts by weight of a second composition
• comprising
• E) from 80.0 to 100.0 parts by weight of a (meth)acrylate,
• F) from 0.05 to 10.0 parts by weight of a crosslinking monomer, and
• G) from 0.0 to 20.0 parts by weight of a styrenic monomer of the formula (I), emulsified in water with an emulsifier, to the aqueous polymer emulsion of step (b), and
• polymerizing the added monomers to a conversion of at least 85.0% by weight, based on the total weight of components E), F) and G),
• d) adding from 10.0 to 30.0 parts by weight of a third composition comprising:
• H) from 50.0 to 100.0 parts by weight of an alkyl (meth)acrylate having from 1 to 20 carbon atoms in the alkyl radical,
• I) from 0.0 to 40.0 parts by weight of an alkyl acrylate having from 1 to 20 carbon atoms in the alkyl radical, and
• J) from 0.0 to 10.0 parts by weight of a styrenic monomer of the formula (I), emulsified in water with an emulsifier, to the aqueous polymer emulsion of step (c),
• and polymerizing to a conversion of at least 85.0% by weight, based on the total weight of components H), I) and J),
• where the parts by weight given for the compositions b), c) and d) give a total of 100.0 parts by weight,
• wherein
• e) each polymerization is carried out at a temperature in the range from above 60 to below 90° C. and
• f) the relative proportions of all of the substances are selected in such a way that the total weight of components A) to J), based on the total weight of the aqueous dispersion, is greater than 50.0% by weight, the product particles have a particle size ranging from 150 to less than 250 nm, and the amount of coagulate in the dispersion is 0.1% or less by wt, based on the total weight of the dispersion.