Solvent borne polyurethane composition

1. A solvent borne polyurethane composition comprising:

I) 10 to 90 wt % of at least a non-film-forming polyurethane A with a weight average molecular weight (Mw) in the range of from 5,000 to 23,000 g/mol;

II) 90 to 10 wt % of at least a film-forming polyurethane B with a weight average molecular weight (Mw) in the range of from 25,000 to 100,000 g/mol; where i)+ii) add up to 100%; and

III) a liquid medium, wherein

the polyurethanes selected from the group consisting of polyurethane A, polyurethane B and both polyurethanes A and B, in the composition have a polymodal molecular weight distribution.

2. A solvent borne polyurethane composition according to claim 1 having a viscosity of less than or equal to 10,000 mPa-s at any solids content in the range of from 20 to 75 wt % in a solvent comprising greater than or equal to 70 wt % of at least one solvent having an evaporation rate (ER) greater than or equal to 1 times the ER of butyl acetate defined as 1.00 in dimensionless units, ER being measured according to ASTM D3539.

3. A solvent borne polyurethane composition according to claim 1 , wherein 15 to 85 wt % of each of the polyurethanes A and B in the composition have a Mw at least 10,000 g/mol greater than the Mw of a remaining 85 to 15 wt % of each of the respective polyurethanes A and B in the composition.

4. A solvent borne polyurethane composition according to claim 1 with the proviso that 35 to 70 wt % of each of the polyurethanes A and B in the composition have a Mw of at least 5,000 g/mol greater than a remaining Mw of 20 to 50 wt % of each of the respective polyurethanes A and B in the composition.

5. A solvent borne polyurethane composition according to claim 1 , wherein the Mp of each of the polyurethanes A and B in the composition is in the range of from 6,000 to 60,000 g/mol.

6. A solvent borne polyurethane composition according to claim 1 , wherein the PDi of each of the polyurethanes A and B in the composition is in the range of from 1.3 to 10.

7. A solvent borne polyurethane composition according to claim 1 , where for each of the polyurethanes A and B in the composition the Mp is in the range of from 6,000 to 60,000 g/mol and the PDi is in the range of from 2.8 to 6.

8. A solvent borne polyurethane composition according to claim 1 , where polyurethane A is obtained by reacting components comprising:

(i) 8 to 45 wt % of at least one polyisocyanate;

(ii) 0 to 5 wt % of at least one isocyanate-reactive polyol with a weight-average molecular weight in the range of from 50 to 200 g/mol;

(iii) 40 to 92 wt % of at least one isocyanate-reactive polyol with a weight-average molecular weight in the range of from 201 to 20,000 g/mol;

(iv) 0 to 9 wt % of a chain-extending and/or chain-terminating component not comprised by (i), (ii), or (iii); and

(v) 0 to 3 wt % of an isocyanate-reactive polyol not comprising (ii), (iii) or (iv);

where (i), (ii), (iii), (iv) and (v) add up to 100%; and

optionally in the presence of a liquid medium.

9. A solvent borne polyurethane composition according to claim 1 , where polyurethane B is obtained by reacting components comprising:

(i) 10 to 20 wt % of at least one polyisocyanate;

(ii) 0 to 3 wt % of at least one isocyanate-reactive polyol with a weight-average molecular weight in the range of from 84 to 200 g/mol;

(iii) 70 to 89 wt % of at least one isocyanate-reactive polyol with a weight-average molecular weight in the range of from 350 to 5,000 g/mol;

(iv) 3 to 8 wt % of a chain-extending and/or chain-terminating component not comprised by (i), (ii), or (iii);

(v) 0 to 3 wt % of an isocyanate-reactive polyol not comprised by (ii), (iii) or (iv);

where (i), (ii), (iii), (iv) and (v) add up to 100%; and

optionally in the presence of a liquid medium.

10. A process for obtaining a solvent borne polyurethane composition according to claim 1 , comprising the step of blending polyurethane A and polyurethane B.

11. A process for obtaining a solvent borne polyurethane composition according to claim 9 , comprising the following steps:

1) preparing an isocyanate-terminated prepolymer;

2a) reacting the isocyanate groups of isocyanate-terminated prepolymer with 0.1 to 0.6 stoichiometric equivalents of at least one active-hydrogen containing chain-terminating compound;

2b) reacting the isocyanate groups of the isocyanate-terminated prepolymer obtained in step 2a) with 0.1 to 1.2 stoichiometric equivalents of at least one active-hydrogen containing chain-extending compound;

2c) optionally reacting the isocyanate groups obtained from step 2b) with 0 to 1.0 stoichiometric equivalents of at least one active-hydrogen chain-terminating compound.

12. A process for obtaining a solvent borne polyurethane composition according to claim 9 , comprising the following steps:

1) preparing an isocyanate-terminated prepolymer A;

2a) reacting the isocyanate groups of isocyanate-terminated prepolymer A with 0 to 0.95 stoichiometric equivalents of at least one active-hydrogen containing chain-terminating compound;

2b) reacting the isocyanate groups of isocyanate-terminated prepolymer A with 0 to 0.95 stoichiometric equivalents of at least one active-hydrogen containing chain-extending compound; where steps 2a) and 2b) together are in the range of from 0.1 to 1.8 stoichiometric equivalents;

3) optionally introducing an isocyanate-terminated compound B;

4a) reacting the isocyanate groups of the isocyanate-terminated prepolymer obtained in steps 2a) and 2b) and isocyanate groups of the isocyanate-terminated compound B introduced in step 3) with 0 to 1.0 stoichiometric equivalents of at least one active-hydrogen containing chain-terminating compound;

4b) reacting the isocyanate groups of the isocyanate-terminated prepolymer obtained in steps 2a) and 2b) and the isocyanate groups of the isocyanate-terminated compound B introduced in step 3) with 0 to 1.2 stoichiometric equivalents of at least one active-hydrogen containing chain-extending compound;

where steps 4a) and 4b) together are in the range of from 0 to 1.2 stoichiometric equivalents;

where the process comprises at least one step with an active-hydrogen containing chain-extending compound and at least one step with an active-hydrogen containing chain-terminating compound;

where if 0 wt % of the isocyanate-terminated compound B is introduced then step 2a) comprises 0.1 to 0.95 stoichiometric equivalents of at least one active-hydrogen containing chain-terminating compound and at least a step 2a) is performed before a step 2b).

13. An ink comprising a solvent borne polyurethane composition according to claim 1 , a colorant, and optionally an additional organic solvent.

14. An ink according to claim 13 having a viscosity in the range of from 10 to 100 seconds when measured using a Ford Cup 4 at 20° C.

15. A process for printing an image on a substrate comprising applying an ink according to claim 13 .

16. A process according to claim 15 , wherein the image is printed on the substrate by a flexographic printing process.

17. A process according to claim 15 , wherein the image is printed on the substrate by a gravure printing processes.

18. A laminate comprising a substrate printed with a solvent borne polyurethane composition according to claim 1 .