Process for preparing self-binding pigment particles

1. A process for preparing self-binding pigment particles comprising the following steps:

a) providing a suspension comprising at least one calcium carbonate containing material,

b) providing an anionic polymeric binder that comprises at least one modified polysaccharide,

c) providing at least one cationic polymer selected from the group consisting of one or more polyamines, polyethyleneimines, polyacrylamides, cationic epichlorohydrin resins, polydiallyldimethylammonium chlorides, cationic starches, cationic guars, and any mixture thereof,

d) mixing the suspension of step a) and the binder of step b), and

e) grinding the mixed suspension of step d) so that the particle size of the calcium carbonate material is reduced and self-binding pigment particles are obtained, wherein the at least one cationic polymer of step c):

i) is mixed in step d) with the suspension of step a) and the binder of step b), and/or

ii) is mixed with the suspension obtained after grinding step e), and the obtained mixture is deagglomerated,

wherein the binder of step b) is added in an amount from 0.001 to 20 wt.-% based on the total weight of the dry calcium carbonate containing material, and

wherein the at least one cationic polymer of step c) is added in an amount from 0.001 to 20 wt.-% based on the total weight of the dry calcium carbonate containing material, and

wherein the grinding step e) is carried out until the fraction of self-binding pigment particles having a particle size of less than 2 μm is greater than 20 wt.-% based on the total weight of the pigment particles, as measured with a Mastersizer 2000.

2. The process of claim 1 , wherein in step d) the suspension of step a) is, in a first step, mixed with the binder of step b), and then, in a second step, is mixed with the at least one cationic polymer of step c).

3. The process of claim 2 , wherein in the first step the suspension of step a) is mixed with a first part the binder of step b), the obtained mixture is ground and then mixed with the remaining part of the binder of step b).

4. The process of claim 1 , wherein in step d) the binder of step b) is, in a first step, mixed with the cationic polymer of step c), and then, in a second step, is mixed with the suspension of step a).

5. The process of claim 1 , wherein in step d) the suspension of step a) is mixed with the binder of step b) and the cationic polymer of step c) in one step.

6. The process of claim 1 , wherein the cationic polymer is added in an amount such that the charge density of the obtained self-binding pigment particles is lower compared to self-binding pigment particles not containing the cationic polymer.

7. The process of claim 1 , wherein the cationic polymer is added in an amount such that the charge density of the obtained self-binding pigment particle is between −100 and −5 μEq/g.

8. The process of claim 1 , wherein the cationic polymer is added in an amount such that the charge density of the obtained self-binding pigment particle is between −80 and −10 μEq/g.

9. The process of claim 1 , wherein the cationic polymer is added in an amount such that the charge density of the obtained self-binding pigment particle is between −70 and −15 μEq/g.

10. The process of claim 1 , wherein the at least one calcium carbonate containing material is selected from the group consisting of calcium carbonate, calcium carbonate containing minerals, mixed calcium carbonate based fillers, and any mixture thereof.

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

12. The process of claim 1 , wherein the at least one calcium carbonate containing material of step a) is provided in form of particles having a weight median particle diameter d 50 value from 0.1 to 100 μm.

13. The process of claim 1 , wherein the at least one calcium carbonate containing material of step a) is provided in form of particles having a weight median particle diameter d 50 value from 0.5 to 50 μm.

14. The process of claim 1 , wherein the at least one calcium carbonate containing material of step a) is provided in form of particles having a weight median particle diameter d 50 value from 5.0 to 25 μm.

15. The process of claim 1 , wherein the at least one calcium carbonate containing material is provided in form of particles have a specific surface area of from 0.1 to 200 m 2 /g.

16. The process of claim 1 , wherein the at least one calcium carbonate containing material is provided in form of particles have a specific surface area of from 1 to 25 m 2 /g.

17. The process of claim 1 , wherein the at least one calcium carbonate containing material is provided in form of particles have a specific surface area of from 2 to 15 m 2 /g.

18. The process of claim 1 , wherein the suspension of step a) has a solid content of at least 1 wt.-% based on the total weight of the suspension.

19. The process of claim 1 , wherein the suspension of step a) has a solid content of from 1 to 90 wt.-% based on the total weight of the suspension.

20. The process of claim 1 , wherein the suspension of step a) has a solid content of from 20 to 75 wt.-% based on the total weight of the suspension.

21. The process of claim 1 , wherein the suspension of step a) has a solid content of from 45 to 65 wt.-% based on the total weight of the suspension.

22. The process of claim 1 , wherein the at least one modified polysaccharide is a carboxymethyl derivate, a carboxymethyl hydroxypropyl derivate, and/or a carboxymethyl hydroxyethyl derivate of a polysaccharide.

23. The process of claim 1 , wherein the at least one modified polysaccharide is selected from the group consisting of one or more carboxymethylcelluloses, anionic starches, anionic guars, and any mixture thereof.

24. The process of claim 1 , wherein the at least one modified polysaccharide has a degree of substitution of hydroxyl groups from 0.4 to 2.0.

25. The process of claim 1 , wherein the at least one modified polysaccharide has a degree of substitution of hydroxyl groups from 0.5 to 1.8.

26. The process of claim 1 , wherein the at least one modified polysaccharide has a degree of substitution of hydroxyl groups from 0.6 to 1.6.

27. The process of claim 1 , wherein the at least one modified polysaccharide has a degree of substitution of hydroxyl groups from 0.7 to 1.5.

28. The process of claim 1 , wherein the binder of step b) is a carboxymethylcellulose having an intrinsic viscosity from 5 to 500 ml/g.

29. The process of claim 1 , wherein the binder of step b) is a carboxymethylcellulose having an intrinsic viscosity from 10 to 400 ml/g.

30. The process of claim 1 , wherein the binder of step b) is a carboxymethylcellulose having an intrinsic viscosity from 20 to 350 ml/g.

31. The process of claim 1 , wherein the binder of step b) is in form of a solution or dry material.

32. The process of claim 1 , wherein the binder of step b) is in form of a solution having a binder concentration from 1 to 70 wt.-% based on the total weight of the solution.

33. The process of claim 1 , wherein the binder of step b) is in form of a solution having a binder concentration from 2 to 30 wt.-% based on the total weight of the solution.

34. The process of claim 1 , wherein the binder of step b) is in form of a solution having a binder concentration from 3 to 15 wt.-% based on the total weight of the solution.

35. The process of claim 1 , wherein the binder of step b) is in form of a solution having a binder concentration from 4 to 10 wt.-% based on the total weight of the solution.

36. The process of claim 1 , wherein the binder of step b) is added in an amount from 0.005 to 15 wt.-% based on the total weight of the dry calcium carbonate containing material.

37. The process of claim 1 , wherein the binder of step b) is added in an amount from 0.01 to 10 wt.-% based on the total weight of the dry calcium carbonate containing material.

38. The process of claim 1 , wherein the binder of step b) is added in an amount from 0.05 to 5 wt.-% based on the total weight of the dry calcium carbonate containing material.

39. The process of claim 1 , wherein the at least one cationic polymer of step c) is in form of a solution or dry material.

40. The process of claim 1 , wherein the at least one cationic polymer of step c) is in form of an aqueous solution having a concentration from 1 to 70 wt.-% based on the total weight of the solution.

41. The process of claim 1 , wherein the at least one cationic polymer of step c) is in form of an aqueous solution having a concentration from 2 to 55 wt.-% based on the total weight of the solution.

42. The process of claim 1 , wherein the at least one cationic polymer of step c) is in form of an aqueous solution having a concentration from 5 to 50 wt.-% based on the total weight of the solution.

43. The process of claim 1 , wherein the at least one cationic polymer of step c) is in form of an aqueous solution having a concentration from 30 to 50 wt.-% based on the total weight of the solution.

44. The process of claim 1 , wherein the at least one cationic polymer of step c) is added in an amount from 0.005 to 15 wt.-% based on the total weight of the dry calcium carbonate containing material.

45. The process of claim 1 , wherein the at least one cationic polymer of step c) is added in an amount from 0.01 to 10 wt.-% based on the total weight of the dry calcium carbonate containing material.

46. The process of claim 1 , wherein the at least one cationic polymer of step c) is added in an amount from 0.05 to 5 wt.-% based on the total weight of the dry calcium carbonate containing material.

47. The process of claim 1 , wherein the at least one cationic polymer of step c) is added in an amount from 0.5 to 2.5 wt.-% based on the total weight of the dry calcium carbonate containing material.

48. The process of claim 1 , wherein the grinding step e) is carried out at a temperature from 5 to 110° C.

49. The process of claim 1 , wherein the grinding step e) is carried out at a temperature from 10 to 100° C.

50. The process of claim 1 , wherein the grinding step e) is carried out at a temperature from 15 to 80° C.

51. The process of claim 1 , wherein the grinding step e) is carried out at a temperature from 20 to 25° C.

52. The process of claim 1 , wherein the grinding step e) is carried out in batch or continuously.

53. The process of claim 1 , wherein the process further comprises a step of concentrating the obtained suspension of self-binding pigment particles.

54. A self-binding pigment particle suspension obtained by the process of claim 1 .

55. A paper, plastic, paint, coating, concrete or agriculture product comprising the self-binding pigment particle suspension of claim 54 .

56. The paper, plastic, paint, coating, concrete or agriculture product of claim 55 , wherein the self-binding pigment particle suspension is used in wet end processes of a paper machine, in a cigarette paper, board and/or coating application, or as a support for rotogravure and/or offset and/or ink jet printing and/or continuous ink jet printing and/or flexography and/or electrography and/or decoration surfaces, or the self-binding pigment particle suspension is used to reduce sun light and UV exposure of plant leaves.

57. The process of claim 1 , wherein the grinding step e) is carried out until the fraction of self-binding pigment particles having a particle size of less than 2 μm is greater than 40 wt.-% based on the total weight of the pigment particles, as measured with a Mastersizer 2000.