AQUEOUS DISPERSION OF POLYURETHANE AND CONDENSATION RESIN

Aqueous dispersions comprising a polyurethane and from 5 to 60% by weight, based on the polyurethane, of a polymer which improves the adhesion, the polyurethane being composed essentially of (a) organic polyisocyanates (b) dihydroxy compounds having a molecular weight of more than 500 to 5000 g/mol, which contain no ionic groups or groups which can be converted into ionic groups (c) compounds having at least one functional group which is reactive towards isocyanate, and at least one group which is ionic or can be converted into an ionic group (d) if desired, compounds which are different from (c), contain at least two functional groups which are reactive towards isocyanate, and have a molecular weight of from 60 to 500 g/mol and the polyurethane or its prepolymer is prepared in a water-miscible solvent and, after addition of the polymer which improves the adhesion, is dispersed in water and, in the case of the prepolymer, is then reacted further to form the polyurethane, characterised in that the polymer which improves the adhesion is a condensation product of a compound (I) selected from aromatic compounds having one aromatic ring, two condensed aromatic rings or two aromatic rings which are linked by a C1-C8-alkylene group, which on at least one ring are substituted by at least one hydroxyl group and, on the aromatic rings, if desired, by from 1 to 3 C1-C12-alkyl or C1-C12-alkoxy groups, or mixtures of these compounds, with a compound (II) selected from compounds having 2 to 20 carbon atoms and at least one keto or aldehyde group, a C4 to C16-diolefin, compounds having from 2 to 10 carbon atoms and at least one triple bond, mixtures thereof or mixtures thereof with formaldehyde, not more than 70 mol % of the compound (II) comprising formaldehyde.