Aqueous PU dispersions with improved adhesion

1. A process for preparing polyester-polyurethane dispersions comprising:

A) reacting

i) one or more polyol components having a number average molecular weight of at least 300 daltons, at least 60% by weight of component i) being a polyester polyol with the fraction of aromatic carboxylic acid groups relative to all of the carboxylic acid groups used to prepare said polyester polyol being at least 60 mol %,

ii) optionally one or more polyol components having a number average molecular weight of 62 to 299 daltons, and

iii) optionally a compound which is monofunctional for the purposes of the isocyanate polyaddition reaction and has an ethylene oxide content of at least 50% by weight and a number average molecular weight of at least 400 daltons, with

iv) a polyisocyanate to form a prepolymer,

B) dissolving the prepolymer in an organic solvent,

C) reacting the prepolymer with v) one or more aliphatic and/or alicyclic primary and/or secondary polyamines having a number average molecular weight of 60 to 300 daltons, said polyamine optionally being in combination with hydrazine or hydrazine hydrate, and vi) a hydrophilicized aliphatic diamine,

D) precipitating the product from C) by adding water to form a dispersion, and

E) removing the organic solvent.

2. The process according to claim 1 , wherein the fraction of aromatic carboxylic acid groups, relative to all of the carboxylic acid groups used to prepare the polyester component, in the polyol component i) is at least 70 mol %.

3. The process according to claim 1 , wherein the fraction of aromatic carboxylic acid groups, relative to all of the carboxylic acid groups used to prepare the polyester component, in the polyol component i) is at least 80 mol %.

4. A polyester-polyurethane resin dispersion dispersions obtained according to the process of claim 1 .

5. A coating system comprising a substrate and one or more coating films, wherein at least one of the coating films comprises the polyester-polyurethane resin dispersion according to claim 4 .

6. A coating composition comprising

a) 15 to 45 parts by weight of the aqueous polyester-polyurethane resin dispersion of claims 4 ,

b) 15 to 45 parts by weight of a hydroxy-functional, aqueous or water-dilutable binder,

c) 0 to 60 parts by weight of inorganic fillers and/or matting agents,

d) 1 to 60 parts by weight of a polyisocyanate,

e) 0.1 to 30 parts by weight preferably parts of pigments and

f) 1 to 15 parts by weight of customary coatings auxiliaries,

with the sum of the components totaling 100.

7. The coating composition according to claim 6 , wherein

a) the aqueous polyester-polyurethane resin dispersion is present in an amount of 25 to 37.5 parts by weight,

b) the hydroxy-functional, aqueous or water-dilutable binder is present in an amount of 25 to 37.5 parts by weight,

c) the inorganic fillers and/or matting agents are present in an amount of 4 to 45 parts by weight,

d) the polyisocyanate is present in an amount of 2.5 to 30 parts by weight,

e) the pigment(s) is present in an amount of 5 to 25 parts by weight and

f) the customary coatings auxiliaries are present in an amount of 1.5 to 10 parts by weight,

with the sum of the components totaling 100.

8. The coating composition according to claim 6 , wherein

a) the aqueous polyester-polyurethane resin dispersion is present in an amount of 30 to 35 parts by weight,

b) the hydroxy-functional, aqueous or water-dilatable binder is present in an amount of 30 to 35 parts by weight,

c) the inorganic fillers and/or matting agents are present in an amount of 7.5 to 30 parts by weight,

d) the polyisocyanate is present in an amount of 4 to 20 parts by weight,

e) the pigment(s) is present in an amount of 10 to 20 parts by weight and

f) the customary coatings auxiliaries are present in an amount of 2 to 6 parts by weight,

with the sum of the components totaling 100.