finely divided polymer dispersions containing starch, processes for their preparation and use as tail in paper production

A polymer dispersion finely divided containing starch, which is obtainable by emulsion polymerization free radical ethylenically unsaturated monomers in the presence of at least one redox initiator and starch, which are used (a) 15 to 35% in weight of at least one optionally substituted styrene, (b) 65 to 80% by weight of at least one alkyl acrylate of C1-C12 and / or methacrylate C1-C12, (c) 0 to 10% by weight of at least another copolymerizable ethylenically unsaturated monomer as the ethylenically unsaturated monomers, and the sum of (a) + (b) + (c) equals 100% based on the content of active monomer and used (d) 15 to 40% by weight of at least one starch gradient having a Mw molecular weight from 1000 to 65 000 g / mol, based on the total weight of the solids content of components (a) + (b) + ( c) + (d), such as starch, and the polymerization is carried out in the presence of at least 0.01% by weight, co n based on the monomers used, of at least one chain transfer agent containing terpene and wherein the polymer dispersion optionally comprising an aluminum compound.