Aqueous polymer dispersions and their use as binder for coating undercoats

Aqueous dispersions obtainable by first producing polymerized "in situ" which contienemonomeros hydrophilic and hydrophobic, in which in an aqueous polymerization medium seed is first placed only 0.1 to 10% by weight of the total amount of by at least one monomer a and / or B and 0.1 to 10% by weight of a hydrophilic monomer having the general formula in which the variables have the following meanings: n> = 0 to 2 R1, R2, R3> = independently of one another hydrogen or a methyl group X> = oxygen or the imino group (NH) and Y> = hydrogen, alkali metal or ammonium (monomer mixture I) and the polymerization is conducted in the presence of at least one emulsifying and porradicales initiator (polymerization stage 1), in which the polymerization of a copolymer with a monomer mixture II (polymerization stage 2) quecontiene 40 is - 60% by weight of monomer a whose homopolymers have a temperature of transicio n to vidrioinferior at 20 ° C 15 to 30% by weight of monomer B whose homopolymers have a transition temperature of glass porencima 50 ° C from 0.1 to 5% by weight carboxylic acids, sulfonic, phosphonic and / or fatty amides & alpha;, s- unsaturated [monomer C] which can form copolymers with monomers B 0-5% monomer weight ethylenically unsaturated containing keto groups and / or adhesivosdiferentes monomers C ethylenically unsaturated nitrogen containing [monomer D] 0-5 % by weight other monomers E ethylenically unsaturated and a third step of polymerizing a copolymer polymerized with a monomer mixture III, which contiene0 - 5% by weight of monomer a whose homopolymers have a transition temperature lower glass at 20 ° C 10 to 30% by weight of monomer B whose homopolymers have a transition temperature of glass porencima 50 ° C from 0.1 to 5% by weight carboxylic acids, sulfonic, phospho nicos and / or fatty amides & alpha;, s- unsaturated [monomer C] which can form copolymers with monomers B] 0-5% monomer weight ethylenically unsaturated containing keto groups and / or adhesivosdiferentes monomers C ethylenically unsaturated nitrogen containing [monomer D] 0 to 5% by weight other ethylenically unsaturated monomers E.