Water-based barrier coatings

1. A method for barrier coating a subject, comprising:

providing a water-based barrier coating composition containing:

(A): (i) 40 to 95% by weight of a total weight of (A), an aqueous polymer composition obtainable by free radical (co)polymerizing an ethylenically unsaturated monomer blend containing:

(a) 0 to 70% by weight of at least one optionally substituted styrene,

(b) up to 100% by weight of at least one C1-C4-alkyl (meth)acrylate,

(c) 0 to 10% by weight of other ethylenically unsaturated copolymerizable monomers, in a presence of,

(d) 0 to 40% % by weight of degraded starch having a molecular weight M n of 500 to 10,000, wherein a sum (a)+(b)+(c)+(d) is 100%;

(ii) 2 to 55% by weight of the total weight of (A) of polyvinyl alcohol (PVA), optionally polymerized together with components of (i);

(iii) 2 to 30% by weight of the total weight of (A) of a plasticizer;

(iv) 5 to 30% by weight of the total weight of (A) a composition containing C16-C18 alkenyl ketene dimer, optionally as a mixture with rosin, whereby a ratio of the C16-C18 alkenyl ketene dimer:rosin is from 100:0 to 25:75;

(v) 5 to 20% by weight of the total weight of (A) of a gelling agent; and

(B): a filler, wherein a ratio of (A):(B) is from 2:5 to 1:1; and

applying the water-based barrier coating composition to at least part of a surface of a subject by

applying the water-based barrier coating composition as a first water-based coating composition, wherein said first water-based coating composition contains (A) and (B), to at least part of a surface of a subject to obtain a precoated subject; and

then applying the second water-based barrier coating composition as a second water-based composition, wherein said second water-based coating composition comprises (A) but does not contain (B), to at least a precoated surface of the subject to obtain a top coated subject.

2. A method as claimed in claim 1 , wherein the first water-based coating composition comprises:

0% by weight of (iv), and the second water-based coating composition comprises:

more than 0% by weight of (iv).

3. A method as claimed in claim 1 , wherein said subject is paper or paperboard.

4. A method as claimed in claim 1 , wherein said subject is a food packaging.

5. Method for barrier coating a subject with a water-based barrier coating composition, as claimed in claim 1 for forming a grease barrier on paper or paperboard.

6. A method as claimed in claim 1 , wherein a sum (i)+(ii)+(iii)+(iv)+(v) is 100%.

7. A method as claimed in claim 1 , wherein the PVA (ii) is selected from a group consisting of fully or partially hydrolyzed grades having molecular weight equal to or less than 50000.

8. A method as claimed in claim 1 , wherein the plasticizer (iii) is selected from a group consisting of glycerol, polyethylene glycol (PEG), sorbitol, and mixtures thereof.

9. A method as claimed in claim 1 , wherein the gelling agent (v) is a protein or an alginate.

10. A method as claimed in claim 9 , wherein the gelling agent (v) is selected from a group consisting of corn, zein, whey, casein, soy protein, carboxy methyl cellulose and gluten.

11. A method as claimed in claim 10 , wherein the gelling agent (v) is gluten.

12. A method as claimed in claim 1 , wherein the filler (B) is talc or kaolin.

13. A method as claimed in claim 1 , wherein the aqueous polymer composition (i) is obtained by free radical (co)polymerization of ethylenically unsaturated monomer blend comprising:

(a) 0 to 70% by weight of at least one optionally substituted styrene,

(b) up to 100% by weight of at least one C1-C4-alkyl (meth)acrylate, and

(c) 0 to 10% by weight of other ethylenically unsaturated copolymerizable monomers, in a presence of,

(d) 0 to 40% by weight of degraded starch having a molecular weight Mn of 500 to 10,000, and

(e) a graft-linking, water-soluble redox system as free radical initiator for the free radical emulsion copolymerization,

wherein a sum (a)+(b)+(c)+(d) is 100%.

14. A method as claimed in claim 1 , wherein components of (i) and (ii) are polymerized together.

15. A method as claimed in claim 14 , wherein a mixture of (i) and (ii) is a free radical emulsion copolymerization of ethylenically unsaturated monomers comprising:

(a) 0 to 60% by weight of at least one optionally substituted styrene,

(b) up to 100% by weight of at least one C1-C4-alkyl (meth)acrylate, and

(c) 0 to 10% by weight of other ethylenically unsaturated copolymerizable monomers, and (ii), in the presence of:

(d) 0 to 40% by weight of degraded starch having a molecular weight Mn of 500 to 10,000, and

(e) a graft-linking, water-soluble redox system as free radical initiator for the free radical emulsion copolymerization.

16. A method as claimed in claim 15 , wherein the amount of starch (d) is 0% by weight.

17. A method as claimed in claim 15 , wherein a ratio of (i):(ii) is from 45:55 to 60:40.

18. A method as claimed in claim 14 , wherein an amount of (i) is 45 to 60% by weight of the total weight of (A) and the amount of (ii) is 40 to 55% by weight of the total weight of (A).

19. A method as claimed in claim 1 , wherein the mixture of (i) and (ii) is a blended mixture.

20. A method as claimed in claim 1 , wherein an amount of (i) is 50 to 95% by weight of the total weight of (A), and an amount of (ii) is 2 to 20% by weight of the total weight of (A).

21. A method as claimed in claim 19 , wherein an amount of starch (d) is 20 to 40% by weight.

22. A method as claimed in claim 21 , wherein an amount of component (iv) is from 2 to 15% by weight of the total weight of (A).

23. A method as claimed in claim 1 , wherein a ratio of alkenyl ketene dimer:rosin (iv) is from 8:2 to 2:8.

24. A method as claimed in claim 1 , wherein a glass transition temperature (Tg) of the (co)polymer is from −40° C. to 50° C.

25. A method as claimed in claim 1 , wherein an amount of (a) is 20 to 60%, by weight.

26. A method as claimed in claim 1 , wherein the monomer component (b) is n-butyl acrylate.