Mineral oil barrier

1. A liquid coating composition comprising

at least one terephthalate ionomer comprising anionic substituents selected from sulfonate, carboxylate and/or phosphate groups, wherein the at least one terephthalate ionomer has an acid value of at least 1 mg KOH/g ionomer,

at least one calcium carbonate containing filler, and a buffer,

wherein the pH of the liquid coating composition is in the range from 6.5 to 11.

2. The composition of claim 1 , wherein the at least one terephthalate ionomer comprises the anionic substituents in an amount from 0.1 to 20 mol-%, based on the total amount of the at least one ionomer.

3. The composition of claim 1 , wherein the at least one terephthalate ionomer comprises the anionic substituents in an amount from 0.5 to 10 mol-%, based on the total amount of the at least one ionomer.

4. The composition of claim 1 , wherein the at least one terephthalate ionomer comprises the anionic substituents in an amount from 1 to 5 mol-%, based on the total amount of the at least one ionomer.

5. The composition of claim 1 , wherein the at least one terephthalate ionomer is a sulfonated terephthalate ionomer.

6. The composition of claim 1 , wherein the at least one terephthalate ionomer is a sulfonated terephthalate ionomer comprising sulfonate groups in an amount from 0.1 to 6 wt.-%, based on the total weight of the at least one ionomer.

7. The composition of claim 1 , wherein the at least one terephthalate ionomer is a sulfonated terephthalate ionomer comprising sulfonate groups in an amount from 1 to 5 wt.-%, based on the total weight of the at least one ionomer.

8. The composition of claim 1 , wherein the at least one terephthalate ionomer is a sulfonated terephthalate ionomer comprising sulfonate groups in an amount from 2 to 4 wt.-%, based on the total weight of the at least one ionomer.

9. The composition of claim 1 , wherein the at least one calcium carbonate containing filler is selected from the group consisting of calcium carbonate, calcium carbonate containing minerals, and mixtures thereof.

10. The composition of claim 1 , wherein the at least one calcium carbonate containing filler is calcium carbonate.

11. The composition of claim 1 , wherein the at least one calcium carbonate containing filler is ground calcium carbonate.

12. The composition of claim 1 , wherein the at least one calcium carbonate containing filler is in a form of particles having a weight median particle size d50 from 0.05 to 7 μm.

13. The composition of claim 1 , wherein the at least one calcium carbonate containing filler is in a form of particles having a weight median particle size d50 from 0.1 to 5 μm.

14. The composition of claim 1 , wherein the at least one calcium carbonate containing filler is in a form of particles having a weight median particle size d50 from 0.2 to 3 μm.

15. The composition of claim 1 , wherein the at least one calcium carbonate containing filler is in a form of particles having a weight median particle size d50 from 0.3 to 2 μm.

16. The composition of claim 1 , wherein the composition has a solids content is in the range from 25 wt.-% to 75 wt.-%, based on the total weight of the composition.

17. The composition of claim 1 , wherein the composition has a solids content is in the range from 30 wt.-% to 67 wt.-%, based on the total weight of the composition.

18. The composition of claim 1 , wherein the composition has a solids content is in the range from 45 wt.-% to 65 wt.-%, based on the total weight of the composition.

19. The composition of claim 1 , wherein the composition has a solids content is in the range from 50 wt.-% to 62 wt.-%, based on the total weight of the composition.

20. The composition of claim 1 , wherein the wt.-% ratio of the at least one terephthalate ionomer to the at least one calcium carbonate containing filler is in the range from 95:5 to 20:80.

21. The composition of claim 1 , wherein the wt.-% ratio of the at least one terephthalate ionomer to the at least one calcium carbonate containing filler is in the range from 60:40 to 20:80.

22. The composition of claim 1 , wherein the wt.-% ratio of the at least one terephthalate ionomer to the at least one calcium carbonate containing filler is in the range from 55:45 to 30:70.

23. The composition of claim 1 , wherein the wt.-% ratio of the at least one terephthalate ionomer to the at least one calcium carbonate containing filler is in the range from 50:50 to 45:65.

24. The composition of claim 1 , wherein the composition further comprises a complexing agent.

25. The composition of claim 24 , wherein the complexing agent is ammonium zirconium carbonate.

26. The composition of claim 1 , wherein the at least one terephthalate ionomer is a polyalkylene terephthalate ionomer.

27. The composition of claim 1 , wherein the at least one terephthalate ionomer is a polyethylene terephthalate ionomer.

28. The composition of claim 1 , wherein the at least one terephthalate ionomer is co-polymerized with a hydrophobic compound.

29. The composition of claim 1 , wherein the at least one terephthalate ionomer is co-polymerized with a hydrophobic compound comprising a C6 to C24 straight chain fatty acid, a C6 to C24 branched fatty acid, a triglyceride thereof, or any mixture thereof.

30. A process for producing the liquid coating composition of claim 1 comprising the steps of:

a) providing an aqueous solution and/or dispersion of at least one terephthalate ionomer comprising anionic substituents selected from sulfonate, carboxylate and/or phosphate groups, wherein the at least one terephthalate ionomer has an acid value of at least 1 mg KOH/g ionomer,

b) providing at least one calcium carbonate containing filler,

c) mixing the aqueous solution and/or dispersion of the at least one terephthalate ionomer of step a) and the at least one calcium carbonate containing filler of step b),

wherein a buffer is added

(i) during step a), or

(ii) during steps a) and b), or

(iii) during steps a) and c), or

(iv) during steps a), b) and c)

to provide in the obtained liquid coating composition a pH in the range from 6.5 to 11.

31. The process of claim 30 , further comprises the step of adding a complexing agent before, during and/or after step c).

32. A packaging material comprising

a cellulose-based substrate having a first and a reverse side, and

at least one barrier layer being in contact with the first side or the reverse side of the substrate,

wherein the at least one barrier layer comprises at least one terephthalate ionomer and at least one calcium carbonate containing filler, and a buffer,

wherein the at least one terephthalate ionomer comprises anionic substituents selected from sulfonate, carboxylate and/or phosphate groups and has an acid value of at least 1 mg KOH/g ionomer.

33. A process for producing the packaging material of claim 32 comprising of the following steps:

A) providing a cellulose-based substrate having a first and a reverse side,

B) applying a liquid coating composition according to claim 1 on the first side of the substrate to form a barrier layer, and

C) drying the barrier layer.

34. The process of claim 33 , which further comprises carrying out steps B) and C) on the reverse side of the substrate to manufacture a packaging material being coated on the first and the reverse side.

35. A barrier layer for packaging materials comprising the liquid coating composition of claim 1 comprising at least one terephthalate ionomer and at least one calcium carbonate containing filler as a barrier layer, wherein the at least one terephthalate ionomer comprises anionic substituents selected from sulfonate, carboxylate and/or phosphate groups and has an acid value of at least 1 mg KOH/g ionomer.

36. A packaging material for food packing applications and/or food displays comprising the barrier layer according to claim 35 .