Polymer particles with an average primary particle diameter of from 50 nm to 10 μm, comprising, based on their total weight: A) from 10 to 100% by weight of a polymer phase A, obtainable by free-radical copolymerization of an oil-in-water miniemulsion with a monomer mixture as the oil phase, comprising i) 30 to 99.9% by weight of one or more mono-ethylenically unsaturated monomers I with at least one C 12 -C 48 n-alkyl side chain; ii) 0 to 60% by weight of one or more mono-ethylenically unsaturated monomers II with at least one C 1 -C 11 n-alkyl and/or one C 3 -C 48 i-alkyl side chain; iii) 0.1 to 20% by weight of one or more monomers III with at least two non-conjugated ethylenic double bonds; iv) 0 to 69.9% by weight of one or more (hetero)aromatic, mono-ethylenically unsaturated monomers IV; v) 0 to 40% by weight of one or more other mono-ethylenically unsaturated monomers V; and B) from 0 to 90% by weight of a polymer phase B, obtainable by the subsequent free-radical graft copolymerization, in the presence of the polymer phase A obtained after step A), of a monomer mixture comprising i) 0 to 100% by weight of one or more monomers VI from the group of C 1 -C 10 alkyl (meth)acrylates; ii) 0 to 100% by weight of one or more (hetero)aromatic mono-ethylenically unsaturated monomers VII; iii) 0 to 50% by weight of one or more other mono-ethylenically unsaturated monomers VIII; wherein the weight percentages of the monomer mixtures employed in the respective steps add up to 100% by weight, wherein, if a polymer phase B is present, then polymer phase A forms an inner core and polymer phase B forms an outer shell. A) from 10 to 100% by weight of a polymer phase A, obtainable by free-radical copolymerization of an oil-in-water miniemulsion with a monomer mixture as the oil phase, comprising i) 30 to 99.9% by weight of one or more mono-ethylenically unsaturated monomers I with at least one C 12 -C 48 n-alkyl side chain; ii) 0 to 60% by weight of one or more mono-ethylenically unsaturated monomers II with at least one C 1 -C 11 n-alkyl and/or one C 3 -C 48 i-alkyl side chain; iii) 0.1 to 20% by weight of one or more monomers III with at least two non-conjugated ethylenic double bonds; iv) 0 to 69.9% by weight of one or more (hetero)aromatic, mono-ethylenically unsaturated monomers IV; v) 0 to 40% by weight of one or more other mono-ethylenically unsaturated monomers V; and i) 30 to 99.9% by weight of one or more mono-ethylenically unsaturated monomers I with at least one C 12 -C 48 n-alkyl side chain; ii) 0 to 60% by weight of one or more mono-ethylenically unsaturated monomers II with at least one C 1 -C 11 n-alkyl and/or one C 3 -C 48 i-alkyl side chain; iii) 0.1 to 20% by weight of one or more monomers III with at least two non-conjugated ethylenic double bonds; iv) 0 to 69.9% by weight of one or more (hetero)aromatic, mono-ethylenically unsaturated monomers IV; v) 0 to 40% by weight of one or more other mono-ethylenically unsaturated monomers V; and B) from 0 to 90% by weight of a polymer phase B, obtainable by the subsequent free-radical graft copolymerization, in the presence of the polymer phase A obtained after step A), of a monomer mixture comprising i) 0 to 100% by weight of one or more monomers VI from the group of C 1 -C 10 alkyl (meth)acrylates; ii) 0 to 100% by weight of one or more (hetero)aromatic mono-ethylenically unsaturated monomers VII; iii) 0 to 50% by weight of one or more other mono-ethylenically unsaturated monomers VIII; i) 0 to 100% by weight of one or more monomers VI from the group of C 1 -C 10 alkyl (meth)acrylates; ii) 0 to 100% by weight of one or more (hetero)aromatic mono-ethylenically unsaturated monomers VII; iii) 0 to 50% by weight of one or more other mono-ethylenically unsaturated monomers VIII;