Described are aqueous polymer dispersions for composite film lamination, comprising a dispersed polymer and a dissolved polymer, and also a multistage process for preparing them from ethylenically unsaturated, radically polymerizable monomers. In a first stage, a first polymer is prepared by radical emulsion polymerization. In a second stage, an aqueous polymer dispersion is prepared in the presence of the first polymer. The monomers of the first stage comprise monomers with acid groups. The dissolved polymer comprises monomers having oxazoline groups, and also water-soluble monomers. The aqueous polymer dispersions can be used as adhesive for producing composite films.