Aqueous polyurethane dispersion comprising a terephthalic acid polyester

1. An aqueous polyurethane dispersion obtained by the reaction of at least:

(A) 30 to 60% per weight of one polyisocyanate with two or more isocyanate groups,

(B) 15 to 50% per weight of one polyester component comprising

(B1) a polyesterpolyol with a weight average molecular weight of 300 to 900 g/Mol, comprises structural units derived from derived from 3-methyl-1,5 pentandiol,

(C) 1.5 to 8% per weight of one ionic group introducing compound with at least one sulphonate and/or carboxylate group and at least one isocyanate reactive group,

(D) 1 to 8% per weight of one diol with a weight average molecular weight of 62 to 400 g/Mol,

(E) 0.1 to 4% per weight of one polyol with a weight average molecular weight of 62 to 400 g/Mol, having three or more hydroxyl groups,

(F) 0.5 to 12% per weight of one amino functional and/or aminohydroxyl functional compound, wherein the sum of all percentages adds up to 100.

2. The dispersion according to claim 1 , wherein the weight average molecular weight of the polyesterpolyol (B1) is 400 to 800.

3. The dispersion according to claim 1 , wherein the polyol component (B) additionally comprises a polyesterpolyol (B2) with a weight average molecular weight of 1000 to 4000 g/Mol, having structural units derived from terephthalic acid.

4. The dispersion according to claim 3 , wherein the weight average molecular weight of the polyesterpolyol (B2) is 1500 to 3500.

5. The dispersion according to claim 3 , wherein the polyesterpolyol (B2) comprises structural units derived from 3-methyl-1,5 pentandiol.

6. The dispersion according to claim 3 , wherein the ratio between the polyesterpolyol (B1) and the polyesterpolyol (B2) is between 100:0 to 40:60.

7. The dispersion according to claim 1 , wherein the polyisocyanate (A) has two isocyanate groups.

8. The dispersion according to claim 1 , wherein the ionic group introducing compound (C) comprises N-(2-aminoethyl)-2-aminoethane sulphonate and/or dimethylol propionic acid.

9. The dispersion according to claim 1 , wherein the diol (D) comprises one or more compounds selected from the group consisting of ethanediol, di-ethyleneglycol, tri- ethyleneglycol, tetraethyleneglycol, 1,2-propanediol, di-propyleneglycol, tri-propyleneglycol, tetrapropyleneglycol, 1,3-propanediol, butanediol-1,4, butanedio-1,3, butanediol-2,3, pentanedio-1,5, hexanedio-1,6, 2,2-dimethyl-1,3-propanediol, 1,4-dihydroxycyclohexane, 1,4-dimethylolcyclohexane, octanedio-1,8, decanediol-1,10, dodecanediol-1,12, neopentylglycol, 1,4-cyclohexanediol, 1,4-cyclohexane-dimethanol, 1,4-, 1,3-, 1,2-dihydroxybenzene, 2,2-bis-(4-hydroxyphenyl)-propane (bisphenol (A)), and 3-Methyl-1,5-pentandiol.

10. The dispersion according to claim 1 , wherein the polyol (E) comprises one or more compounds selected from the group consisting of trimethylolpropane, glycerine, pentaerythrite, and dipenthaerytrite.

11. The dispersion according to claim 1 , wherein the amino functional and/or aminohydroxyl functional compound (F) comprises one or more compounds selected from the group consisting of 1,2-ethanediamine, 1-amino-3,3,5-trimethyl-5-aminomethyl-cyclohexane, diethylenetriamine, diethanolamine, ethanolamine, N-(2-hydroxyethyl)-ethylenediamine and N,N-bis(2-hydroxyethyl)-ethylenediamine.

12. A method comprising coating a substrate with the dispersion according to claim 1 .

13. A coating obtained by applying the dispersion according to claim 1 .

14. The dispersion according to claim 1 , wherein the polyisocyanate (A) comprises one or more compounds selected from the group consisting of hexamethylene diisocyanate, 1,4-diisocyanatocyclohexane, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane, 4,4′-diisocyanato-dicyclohexyl-methane, and 4,4′-diisocyanato-dicyclohexylpropane-(2,2).