Single-component polyurethane system comprising aqueous or water-soluble polyurethanes

1. A polyurethane system comprising

A) an aqueous solution of a water-soluble, hydroxy-functional polyurethane containing urea groups and having a hydroxyl group content in the range of from 2% to 10% by weight and a level of urea groups, calculated as —NH—CO—NH—, derived from amino alcohols having a primary or secondary amino group and at least one hydroxyl group in the range of from 3% to 20% by weight, based in each case on the weight of said hydroxy-functional polyurethane containing urea groups, wherein the aqueous solution has a solids content of from 65 to 75%;

B) a crosslinker which contains no free isocyanate groups and is optionally hydrophilicized; and

C) optionally, further aqueous dissolved and/or dispersed and/or organically dissolved, optionally hydroxy-functional oligomers and/or polymers.

2. The polyurethane system of claim 1 , wherein said polyurethane system comprises

A) from 30% to 98% by weight of said aqueous solution of a water soluble, hydroxy-functional polyurethane containing urea groups;

B) from 2% to 70% by weight of an optionally hydrophilicized polyisocyanate crosslinker having blocked isocyanate groups and/or amino resin crosslinkers and/or urea resin crosslinkers; and

C) from 0% to 65% by weight of other aqueous or organically dissolved and/or dispersed, optionally hydroxyl-functional oligomers and/or polymers;

wherein the sum of the percentages of A), B), and C) equal 100% by weight and is based on the solids content of said polyurethane system.

3. The polyurethane system of claim 1 , wherein said water-soluble, hydroxy-functional polyurethane containing urea groups is obtained by preparing a NCO-functional prepolymer by single-stage or multi-stage reaction of

a) at least one hydroxy- and/or amino-functional hydrophilicizing agent having at least one acid group and/or the salt of an acid group, or having at least one tertiary amino group and/or the salt of a tertiary amino group;

b) at least one polyol;

c) at least one polyisocyanate; and

d) optionally, other hydroxy- and/or amino-functional compounds, different from a), b), and e);

and reacting said NCO-functional prepolymer with

e) an amino alcohol component comprising an amino alcohol having a primary or secondary amino group and at least one hydroxyl group, wherein the fraction of amino alcohols having a secondary amino group, based on the total amount of e), is at least 60% by weight;

wherein the tertiary amino groups or acid groups in the resulting water soluble, hydroxy-functional polyurethane containing urea groups which originate from a) are optionally present in their salt form as a result of whole or partial neutralization.

4. The polyurethane system of claim 1 , wherein said aqeuous solution of a water-soluble, hydroxy-functional polyurethane containing urea groups is obtained by preparing a NCO-functional prepolymer by single-stage or multi-stage reaction of

a) at least one hydroxy- and/or amino-functional hydrophilicizing agent having at least one acid group and/or the salt of an acid group, or having at least one tertiary amino group and/or the salt of a tertiary amino group;

b) at least one polyol;

c) at least one polyisocyanate; and

d) optionally, other hydroxy- and/or amino-functional compounds, different from a), b), and e);

reacting said NCO-functional prepolymer with

e) an amino alcohol component, comprising an amino alcohol having a primary or secondary amino group and at least one hydroxyl group, wherein the fraction of amino alcohols having a secondary amino group, based on the total amount of e), is at least 60% by weight;

and dissolving the resulting water soluble, hydroxy-functional polyurethane containing urea groups in water, wherein said dissolution is preceded or accompanied by the reaction of the acid groups or tertiary amino groups of a) with a neutralizing agent.

5. The polyurethane system of claim 3 , wherein component e) is an amino alcohol having exclusively one secondary amino group and one or two hydroxyl groups.

6. The polyurethane system of claim 1 , wherein B) is an amino crosslinker resin and/or a urea crosslinker resin or a crosslinker resin containing blocked NCO groups.

7. A polyurethane obtained from the polyurethane system of claim 1 .

8. The polyurethane of claim 7 , wherein said polyurethane is a paint, coating material, sealant, liquid ink, printing ink, size, adhesion promoter, or reactive diluent applied in one or more layers.

9. A substrate coated with the polyurethane of claim 7 .

10. The polyurethane system according to claim 1 , wherein the aqueous solution has a solids content of 67 to 75%.

11. The polyurethane system according to claim 3 , wherein:

a) is selected from the group consisting of 2-(2-aminoethylamino)ethanesulfonic acid, the adduct of IPDA and acrylic acid, dimethylolpropionic acid and hydroxypivalic acid;

b) is a hydroxy-functional compound selected from the group consisting of:

b1) polyesters,

b2) low molecular weight compounds with molecular weights of 62 to 500 g/mol,

b3) polycarbonates,

b4) C2 polyethers, C3 polyethers, and

b5) C4 polyethers;

and wherein the aqueous solution has a solids content of 67 to 75%.