Water-dilutable polyurethane dispersions
Water-dilutable polyurethane dispersions comprising structural units derived from polyisocyanates A, polyols B having a number-average molar mass M n of at least 400 g/mol, compounds D that contain at least two groups reactive towards isocyanate groups and at least one group capable of anion formation, low molar mass polyols E that do not carry any further groups reactive towards isocyanate groups, compounds G that are monofunctional towards isocyanates or contain active hydrogen of different reactivity and that are different from the compounds E, characterised in that the polyols B contain a mass fraction of polycarbonate polyols B 1 of at least 85%, and the use thereof in coating compositions
1. Water-dilutable polyurethane dispersions comprising structural units derived from polyisocyanates A, polyols B having a number-average molar mass M n of at least 400 g/mol, compounds D that contain at least two groups reactive towards isocyanate groups and at least one group capable of anion formation, low molar mass polyols E that do not carry any further groups reactive towards isocyanate groups, compounds G that are monofunctional towards isocyanates or contain active hydrogen of different reactivity and that are different from the compounds E, characterised in that the polyols B contain a mass fraction of polycarbonate polyols B 1 of at least 85%, wherein the polycarbonate polvols B 1 are derived from mixtures of alkylene ether alcohols having from 2 to 4 carbon atoms in the alkylene group, and from 4 to 20 carbon atoms in total, and alpha,omega-dihydroxvalkanes.
2. The water-dilutable polyurethane dispersions according to claim 1 , characterised in that they additionally comprise structural units derived from low molar mass polyols C with M n of less than 400 g/mol.
3. The water-dilutable polyurethane dispersions according to claim 1 , characterised in that they additionally comprise structural units derived from compounds H that are different from B, C, D, E and G and contain at least two groups reactive towards NCO groups.
4. The water-dilutable polyurethane dispersions according to claim 1 , characterised in that the polycarbonate polyols B 1 have a number-average molar mass M n of from 400 g/mol to 5000 g/mol and a hydroxyl number of from 30 mg/g to 280 mg/g.
5. The water-dilutable polyurethane dispersions according to claim 1 , characterised in that there are used as component B 1 only difunctional polycarbonate polyols B 1 .
6. The water-dilutable polyurethane dispersions according to claim 1 , characterised in that up to 5% of the mass of the polycarbonate polyols B 1 are trivalent or higher-valent polycarbonate polyols.
7. The water-dilutable polyurethane dispersions according to claim 1 , characterised in that the polycarbonate polyols B 1 contain only terminal OH groups.
8. The water-dilutable polyurethane dispersions according to claim 1 , characterised in that component B comprises further poiyois selected from the group consisting of polyether polyols, acrylate polyols and polyolefin polyols.
9. Coating compositions comprising water-dilutable polyurethane dispersions according to claim 1 .