Aqueous polyurethane dispersions

An aqueous dispersion containing a polyurethane and from 5 to 60% by weight, based on the polyurethane, of an adhesion-improving polymer, wherein the polyurethane consists essentially of

• (a) organic diisocyanates,
• (b) dihydroxy compounds which have a molecular weight of from more than 500 to 5,000 and contain no ionic groups or groups convertible into ionic groups,
• (c) compounds having one or two functional groups reactive toward isocyanate and at least one ionic group or group convertible into an ionic group and
• (d) compounds having at least 3 isocyanate groups or at least 3 functional groups reactive toward isocyanate,
• (e) with or without compounds which differ from (c) and have two functional groups reactive toward isocyanate and a molecular weight of from 60 to 500, and compounds (d) are used in amounts such that the functionality F of all components, which is defined by the quotient ##EQU3## is from 2.01 to 2.5, and the polyurethane or a prepolymer thereof is prepared in a water-miscible solvent boiling below 100.degree. C. and, after addition of the adhesion-improving polymer, is dispersed in water and, in the case of the prepolymer, the further reaction to give the polyurethane is then carried out.