The present invention relates to the use of aqueous polymer dispersions of a polymer P obtainable by emulsion polymerization of ethylenically unsaturated monomers M in the presence of at least one anionic emulsifier as binders in a waterborne coating formulation having a pH of at least pH 9.5. The polymer dispersion is an aqueous polymer dispersion of a polymer P obtainable by emulsion polymerization of ethylenically unsaturated monomers M in the presence of at least one anionic emulsifier, where the monomers M comprise or consist of the following monomers M1, M2 and optionally M3 and/or M4 a) 90 to 99.9% by weight, based on the total weight of monomers M, of monomers M1 selected from the group consisting of C1-C20 alkylesters of acrylic acid, C1-C20 alkylesters of methacrylic acid, C5-C20 cycloalkylesters of acrylic acid, C5-C20 cycloalkylesters of methacrylic acid, and monovinylaromatic monomers, where the relative amount of monovinylaromatic monomers does not exceed 15% by weight, based on the total weight of monomers M; b) 0.1 to 5% by weight, based on the total weight of monomers M, of monomers M2 selected from monoethylenically unsaturated monomers bearing at least one carboxyl group; c) 0 to 2% by weight, based on the total weight of monomers M, of one or more monoethylenically unsaturated monomers M3 bearing at least one sulfate or sulfate group; and d) 0 to 5% by weight or less than 0.5% by weight, based on the total weight of monomers M, of one or more ethylenically unsaturated non-ionic monomers M4 different from the monomers M1, M2 and M3; 25 whereby the emulsion polymerization is carried out in the presence of a base in such an amount sufficient to neutralize more than 20 mol-%, in particular at least or more than 25 mol-% and especially at least 30 mol-% of the carboxyl groups of all monomers M2.