Waterborne crosslinkable dispersions

1. A waterborne dispersion comprising

(A) polymer P;

(B) amphiphilic block copolymer obtained with a controlled radical polymerization process and comprising at least blocks [A] and [B], whereby

block [A] comprises ethylenically unsaturated monomer(s) bearing water-soluble and/or water-dispersible functional groups (monomer(s) (i)), and

block [B] comprises ethylenically unsaturated monomer(s) different from monomer(s) (i) (monomer(s) (ii)); and

(C) crosslinker,

wherein the polymer P is crosslinkable and comprises ethylenically unsaturated monomer(s) bearing crosslinkable functional groups different from monomer(s) (i) and monomer(s) (ii) (monomer(s) (iii)) in an amount of from 2 to 7.5 wt. %, based on the total weight of monomers used to prepare the polymer P,

the amount of block copolymer is from 3 to 15 wt. %, based on the total weight of monomers used to prepare the block copolymer and polymer P and the weight average molecular weight of the block copolymer is in the range of from 7,000 to 50,000 g/mol;

and wherein

the calculated glass transition temperature of the block copolymer is from 50 to 150° C., the acid value of a composition consisting of block copolymer and polymer P is from 3 to 16 mg KOH per g of the composition consisting of block copolymer and polymer P,

and wherein

an equivalent molar ratio of crosslinkable functional groups present in the crosslinker to crosslinkable functional groups present in the block copolymer and polymer P is from 0.5 to 1.0, wherein the equivalent molar ratio is calculated by dividing the molar amount of crosslinkable functional groups present in the crosslinker by the molar amount of crosslinkable functional groups present in the block copolymer and polymer P, which molar amounts are calculated from the amount of crosslinkable functional monomers (iii) which are used for preparing the block copolymer and polymer P and from the amount of crosslinker which is added to the coating composition.

2. The waterborne dispersion according to claim 1 , wherein the ethylenically unsaturated monomer(s) (iii) bearing crosslinkable functional groups are ketone functional ethylenically unsaturated monomer(s).

3. The waterborne dispersion according to claim 2 , wherein the ketone functional ethylenically unsaturated monomers are selected from the group consisting of (meth)acrolein, diacetone acrylamide, vinyl methyl ketone, and any mixture thereof.

4. The waterborne dispersion according to claim 2 , wherein the ketone functional ethylenically unsaturated monomers is diacetone acrylamide.

5. The waterborne dispersion according to claim 1 , wherein the crosslinker is a dihydrazide functional compound (containing two hydrazide groups (O═C—NHNH 2 )) with a molar mass below 1000 g/mole.

6. The waterborne dispersion according to claim 1 , wherein block [A] has a Hansch parameter of less than 1.5 and block [B] has a Hansch parameter of at least 1.5.

7. The waterborne dispersion according to claim 1 , wherein the amount of ethylenically unsaturated monomer(s) (ii) in block [B] is at least 75 wt. % relative to the total weight amount of monomers used to prepare block [B].

8. The waterborne dispersion according to claim 1 , wherein at least 90 wt. % preferably of the total amount of monomers (i) present in the block copolymer-polymer composition is present in block [A].

9. The waterborne dispersion according to claim 1 , wherein the water-soluble and/or water-dispersible functional groups are carboxylate groups.

10. The waterborne dispersion according to claim 1 , wherein the block copolymer is a diblock copolymer [A] x [B] y ,

wherein block [A] has an average degree of polymerization x where x is an integer from 3 to 200, and

wherein block [B] has an average degree of polymerization y where y is an integer >10 and wherein y>x.

11. The waterborne dispersion according to claim 10 , wherein x is an integer from 3 to lower than 50.

12. The waterborne dispersion according to claim 10 , wherein y is an integer >150.

13. The waterborne dispersion according to claim 1 , wherein the polymer P is obtained by an emulsion polymerization effected in the presence of the block copolymer.

14. The waterborne dispersion according to claim 1 , wherein the polymer P further contains ethylenically unsaturated monomer(s) (ii) different from (i) and (iii).

15. The waterborne dispersion according to claim 1 , wherein the ethylenically unsaturated monomer(s) (ii) are selected from the group consisting of C 1-12 alkyl(meth)acrylate monomers and any mixtures thereof.

16. The waterborne dispersion according to claim 1 , wherein the polymer P is present in a polymer composition and at least 20 wt. % of the polymer composition has a polymer fraction with a calculated glass transition temperature >5° C., and <90° C.

17. The waterborne dispersion according to claim 1 , wherein the weight average molecular weight of the block copolymer-polymer composition is in the range of from 100,000 to 500,000 g/mol.

18. The waterborne dispersion according to claim 1 , wherein the block copolymer is obtained via reversible addition-fragmentation chain transfer (RAFT) polymerization in the presence of a control agent and a source of free radicals, and the RAFT polymerization is effected in solution.

19. The waterborne dispersion according to claim 1 , wherein the waterborne dispersion is a one-pack system.

20. A coating composition comprising the waterborne dispersion of claim 1 .

21. A coating composition according to claim 20 , wherein the coating composition further comprises titanium dioxide in an amount of 15 to 40 volume-% relative to the volume of non-volatile material in the coating composition.

22. A coating composition according to claim 20 , wherein the coating composition is a one-pack system.

23. A method of coating a substrate comprising the steps of (1) applying the coating composition from claim 20 to a substrate and (2) drying the coating composition.

24. The method according to claim 23 , wherein the substrate is aluminum or pre-treated aluminum.

25. The method according to claim 23 , wherein the substrate is a profile for an architectural article.

26. An article having a coating deposited thereon, wherein the coating is obtained by depositing a coating composition according to claim 20 to a substrate and drying the coating composition.

27. An article according to claim 26 , wherein the article is a profile for an architectural article.

28. The article according to claim 26 , wherein the substrate comprises aluminium.

29. The article according to claim 26 , wherein the coating passes the detergent resistance test in AAMA 2604-17, section 8.7.4 and the detergent resistance test described in AAMA 2605-17, section 8.7.4.

30. The waterborne dispersion according to claim 1 , wherein the polymer P comprises ethylenically unsaturated monomer(s) (iii) bearing crosslinkable functional groups in an amount of from 2 to 5 wt. %, based on the total weight of monomers used to prepare the polymer P.

31. The waterborne dispersion according to claim 1 , wherein the amount of the block copolymer is from 4 to 12 wt. %, based on the total weight of monomers used to prepare the block copolymer and polymer P.

32. The waterborne dispersion according to claim 5 , wherein the dihydrazide functional compound is adipic dihydrazide.