Latent cross-linking aqueous dispersions containing polyurethane

A latent-crosslinking aqueous polyurethane dispersion comprising:

• I) a disperse phase (P.I) comprising
• Ia) a polyurethane (Ia) which has hydrophilic groups which make it dispersible in water and also has carbodiimide groups but essentially no carboxyl groups;
• or
• Ib) a physical mixture of
• Ibi) a polyurethane (Ibi) which has hydrophilic groups which make it dispersible in water but has essentially no carbodiimide or carboxyl groups, and
• Ibii) a carbodiimide (Ibii) which has essentially no hydrophilic groups which make it dispersible in water;
• and
• II) a coherent aqueous phase (P.II) comprising a dissolved form of a polycarboxylic acid II which has no carbodiimide groups but has a solubility of at least 1 g/l at 25° C. in said coherent aqueous phase P.II,
• wherein said polyurethane (Ia) and said polyurethane (Ibi) comprise diisocyanates and diols,
• wherein said diols contain no sulfonate groups and
• i) from 10 to 100 mol % of said diols, based on the overall amount of diols, have a molecular weight from 500 to 5000 g/mol, and
• ii) from 0 to 90 mol % of said diols, based on the overall amount of diols, have a molecular weight from 60 to 500 g/mol.