Tin-containing polyurethane resin

1. A tin-containing polyurethane resin having a melting temperature of 40 to 180° C., measured by DSC at a heating rate of 10 K/min and prepared by carrying out a condensation reaction between a diorganotin compound and carboxyl groups of a carboxyl-functional polyurethane resin, wherein the molar ratio between the tin and the carboxyl groups is 1:2-20, wherein the diorganotin compound is selected from the group consisting of diorganotin oxides and diorganotin dialkanoates, and wherein the carboxyl-functional polyurethane resin is selected from the group consisting of polyurethane dicarboxylic acids and polyurethane monocarboxylic acids.

2. The tin-containing polyurethane resin of claim 1 , wherein the melting temperature is from 40 to 150° C.

3. The tin-containing polyurethane resin of claim 1 having a solubility of less than 10 g per liter of butyl acetate or water at 20° C.

4. The tin-containing polyurethane resin of claim 1 having a tin content of 0.5 to 8 wt.-%, calculated as elemental tin metal.

5. A liquid coating composition which contains a binder A and, as an optional component, a crosslinker B for the binder A, and solid particles of the tin-containing polyurethane resin of claim 1 .

6. The coating composition of claim 5 containing water and/or organic solvent(s) and having a solids content of 35 to 75 wt.-%, wherein the solids content consists of the resin solids content, the solid particles of the tin-containing polyurethane resin and the optional components chosen from the following: pigments, fillers and non-volatile additives.

7. The coating composition of claim 5 or 6 , wherein the average particle size of the solid particles of the tin-containing polyurethane resin is 1 to 100 μm.

8. The coating composition claim 5 , wherein the solid particles of the tin-containing polyurethane resin are contained in a proportion of 0.5 to 10 wt.-%, relative to the resin solids of the coating composition.

9. The coating composition of claim 5 , wherein the binder A is a hydroxyl-functional binder and wherein the crosslinker B is a free or blocked polyisocyanate crosslinker.

10. The coating composition of claim 5 , wherein the solid particles of the tin-containing polyurethane resin are present as a catalyst, and wherein a catalyst component in the coating composition consists of the solid particles of the tin-containing polyurethane resin.

11. The tin-containing polyurethane resin of claim 1 , wherein the diorganotin compound is a diorganotin oxide.