Waterborne polyurethane coating compositions

1. An aqueous polyurethane coating composition comprising:

(a) a water-dilutable hydroxy-functional polyacrylic resin comprising a reaction product of:

(A1) an olefinically unsaturated hydroxy-functional monomer;

(A2) an olefinically unsaturated monomer that comprises an ionic group or a potentially ionic group; and

(A3) an olefinically unsaturated monomer that does not comprise an ionic group, a potentially ionic group, or a hydroxyl group;

(b) a water-dilutable aminoplast resin; and

(c) a water-dilutable polycarbonate-polyurethane resin,

wherein the polycarbonate-polyurethane resin is non-functional.

2. The aqueous polyurethane coating composition of claim 1 , wherein the hydroxy-functional polyacrylic resin component (a) has a weight average molecular weight of 500-100000, a hydroxyl number of 16.5 to 264 mg KOH/g and an acid number of 5 to 125 mg KOH/g.

3. The aqueous polyurethane coating composition of claim 1 , wherein the aminoplast resin component (b) comprises a melamine-formaldehyde condensation product.

4. The aqueous polyurethane coating composition of claim 1 , wherein the polycarbonate-polyurethane resin component (c) is characterized by a glass transition temperature of between −60° C. and 0° C.

5. The aqueous polyurethane coating composition of claim 1 , wherein the polycarbonate-polyurethane resin component (c) is characterized by a viscosity at 25° C. of less than 500 mPa·s in an 38% to 42% solids aqueous dispersion.

6. The aqueous polyurethane coating composition of claim 1 , further comprising an additional polyol resin selected from the group consisting of water-dispersible hydroxy-functional polyester resins and water-dispersible hydroxy-functional polyether-polyurethane resins.

7. A glass substrate at least partially coated with the coating composition of claim 1 .

8. A glass container at least partially coated with the coating composition of claim 1 .

9. The aqueous polyurethane coating composition of claim 1 , wherein the aminoplast resin component (b) comprises an oligomeric methylated melamine-formaldehyde condensation product comprising imino groups, methoxymethyl groups, and methylol groups.

10. The aqueous polyurethane coating composition of claim 9 , wherein an equivalent ratio of methylol groups and alkoxylmethyl groups of component (b) to hydroxyl groups of component (a) is at least 0.05:1.

11. The aqueous polyurethane coating composition of claim 1 , wherein the polycarbonate-polyurethane resin component (c) comprises a reaction product of a polycarbonate polyol and a polyisocyanate selected from the group consisting of 4,4′-diisocyanatodicyclohexylmethane, isophorone diisocyanate, 1,6-hexamethylene diisocyanate, and 1-methyl-2,4(2,6)-diisocyanatocyclohexane.

12. The aqueous polyurethane coating composition of claim 11 , wherein the polycarbonate polyol has a number average molecular weight range 500 to 6000.

13. The aqueous polyurethane coating composition of claim 1 , comprising:

99% to 1% by weight on a solids basis of the water-dilatable hydroxy-functional polyacrylic resin and a water-dilutable aminoplast resin; and

1% to 99% by weight on a solids basis of the water-dilutable polycarbonate-polyurethane resin

wherein the weight percents total 100% by weight.

14. The aqueous polyurethane coating composition of claim 13 , comprising:

40% to 90% by weight on a solids basis of the water-dilutable hydroxy-functional polyacrylic resin; a water-dilutable aminoplast resin; and

60% to 10% by weight on a solids basis of the water-dilutable polycarbonate-polyurethane resin

wherein the weight percents total 100% by weight.

15. The aqueous polyurethane coating composition of claim 1 , wherein the weight ratio on a solids basis of the hydroxy-functional polyacrylic resin to the aminoplast resin is from 55:45 to 85:15.

16. The aqueous polyurethane coating composition of claim 15 , wherein the weight ratio on a solids basis of the hydroxy-functional polyacrylic resin to the aminoplast resin is from 60:40 to 70:30.

17. The aqueous polyurethane coating composition of claim 1 , further comprising a silane-functional adhesion promoter.

18. The aqueous polyurethane coating composition of claim 17 , wherein the adhesion promoter is selected from the group consisting of γ-mercaptopropyl-trimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylsilane hydrolysate, 3-glycidyloxypropyltriethoxysilane, and combinations of any thereof.

19. A substrate at least partially coated with the coating composition of claim 1 .

20. The substrate of claim 19 , wherein the coating exhibits microhardness of no greater than 90 N/mm 2 , direct impact strength of at least 60 in-lbs, and reverse impact strength of at least 20 in-lbs.