Process for the control of pitch

1. A process for the control of pitch associated with pulp in an aqueous medium comprising pitch, the process comprising (a) contacting the aqueous medium with (i) surface-reacted natural calcium carbonate or (ii) an aqueous suspension comprising surface-reacted natural calcium carbonate having a pH of greater than 6.0 measured at 20° C., to obtain a composite comprising calcium carbonate and pitch, wherein the surface-reacted natural calcium carbonate is a reaction product of natural calcium carbonate with carbon dioxide and one or more acids; and (b) separating the composite from the aqueous medium.

2. The process according to claim 1 , wherein the surface-reacted natural calcium carbonate is prepared as an aqueous suspension having a pH of greater than 6.5, measured at 20° C.

3. The process according to claim 1 , wherein the surface-reacted natural calcium carbonate is prepared as an aqueous suspension having a pH of greater than 7.0, measured at 20° C.

4. The process according to claim 1 , wherein the surface-reacted natural calcium carbonate is prepared as an aqueous suspension having a pH of greater than 7.5, measured at 20° C.

5. The process according to claim 1 , wherein the national calcium carbonate is marble, calcite, chalk and dolomite, limestone or mixtures thereof

6. The process according to claim 1 , wherein the acid has a pK a at 25° C. of 2.5 or less.

7. The process according to claim 6 , wherein the acid is hydrochloric acid, sulphuric acid, sulphurous acid, hydrosulphate, phosphoric acid, oxalic acid or mixtures thereof.

8. The process according to claim 7 , wherein the acid is phosphoric acid.

9. The process according to claim 1 , wherein the natural calcium carbonate is reacted with the acid and/or the carbon dioxide in the presence of at least one silicate and/or silica, aluminium hydroxide, earth alkali metal aluminate, magnesium oxide, or mixtures thereof.

10. The process according to claim 9 , wherein the at least one silicate is aluminium silicate, calcium silicate or alkali metal silicate.

11. The process according to claim 1 , wherein the surface-reacted natural calcium carbonate has a specific surface area of from 5 m 2 /g to 200 m 2 /g, measured using nitrogen and the BET method according to ISO 9277.

12. The process according to claim 1 , wherein the surface-reacted natural calcium carbonate has a specific surface area of from 20 m 2 /g to 80 m 2 /g, measured using nitrogen and the BET method according to ISO 9277.

13. The process according to claim 1 , wherein the surface-reacted natural calcium carbonate has a specific surface area of from 30 m 2 /g to 60 m 2 /g, measured using nitrogen and the BET method according to ISO 9277.

14. The process according to claim 1 , wherein the surface-reacted natural calcium carbonate has a specific surface area of 43 m 2 /g, measured using nitrogen and the BET method according to ISO 9277.

15. The process according to claim 1 , wherein the surface-reacted natural calcium carbonate has a mean grain diameter d 50 of from 0.1 to 50 μm, measured according to the sedimentation method.

16. The process according to claim 1 , wherein the surface-reacted natural calcium carbonate has a mean grain diameter d 50 of from 0.5 to 25 μm, measured according to the sedimentation method.

17. The process according to claim 1 , wherein the surface-reacted natural calcium carbonate has a mean grain diameter d 50 of from 0.8 to 20 μm, measured according to the sedimentation method.

18. The process according to claim 1 , wherein the surface-reacted natural calcium carbonate has a mean grain diameter d 50 of from 1 to 10 μm, measured according to the sedimentation method.

19. The process according to claim 1 , wherein the surface-reacted natural calcium carbonate has a mean grain diameter d 50 of from 4 to 7 μm, measured according to the sedimentation method.

20. The process according to claim 1 , wherein the aqueous suspension of surface-reacted natural calcium carbonate is stabilized with one or more dispersants.

21. The process according to claim 1 , wherein the surface-reacted natural calcium carbonate is used in powder form and/or in the form of granules.

22. The process according to claim 1 , wherein the surface-reacted natural calcium carbonate is added in an amount of 0.05- 25wt.-%, based on the weight on oven (100° C.) dry fibers added.

23. The process according to claim 1 , wherein the surface-reacted natural calcium carbonate is added in an amount of 0.25- 10 wt.-%, based on the weight on oven (100° C.) dry fibers added.

24. The process according to claim 1 , wherein the surface-reacted natural calcium carbonate is added in an amount of 0.5- 2 wt.-%, based on the weight on oven (100° C.) dry fibers added.

25. The process according to claim 1 , wherein the pH of the aqueous medium comprising pitch is adjusted to a value of >6 prior to the addition of the surface-reacted natural calcium carbonate.

26. The process according to claim 1 , wherein the pH of the aqueous medium comprising pitch is adjusted to a value of >6.5 prior to the addition of the surface-reacted natural calcium carbonate.

27. The process according to claim 1 , wherein the pH of the aqueous medium comprising pitch is adjusted to a value of >7 prior to the addition of the surface-reacted natural calcium carbonate.

28. The process according to claim 1 , wherein the aqueous medium comprises mechanical pulp, ground wood, TMP (thermo mechanical pulp), chemithermo-mechanical pulp (CTMP), chemical pulp, kraft pulp, sulphate pulp, or recycled pulp used in the paper making process.

29. The process according to claim 1 , wherein talc is added to aqueous medium comprising pitch.

30. The process according to claim 29 , wherein the talc has a purity of >90 weight-%.

31. The process according to claim 29 , wherein the talc has a purity of >95 weight-%.

32. The process according to claim 29 , wherein the talc has a purity of >97 weight-%.

33. The process according to claim 29 , wherein the talc has a purity of >100 weight-%.

34. The process according to claim 29 , wherein the talc particles have a d 50 value of 0.1 to 50 μm, measured according to the sedimentation method.

35. The process according to claim 29 , wherein the talc particles have a d 50 value of 0.2 to 40 μm, measured according to the sedimentation method.

36. The process according to claim 29 , wherein the talc particles have a d so value of 0.3 to 30 μm, measured according to the sedimentation method.

37. The process according to claim 29 , wherein the talc particles have a d so value of 0.4 to 20 μm, measured according to the sedimentation method.

38. The process according to claim 29 , wherein the talc particles have a d so value of 0.5 to 10 μm, measured according to the sedimentation method.

39. The process according to claim 29 , wherein the talc particles have a d so value of 1, 7 or 7 μm, measured according to the sedimentation method.

40. The process according to claim 29 , wherein the talc has a specific surface area of between 3 and 100 g/m 2 .

41. The process according to claim 29 , wherein the talc has a specific surface area of between 7 and 80 g/m 2 .

42. The process according to claim 29 , wherein the talc has a specific surface area of between 9 and 60 g/m 2 .

43. The process according to claim 29 , wherein the talc has a specific surface area of between 10 and 50 g/m 2 .

44. The process according to claim 29 , wherein the talc has a specific surface area of 30 or 51 g/m 2 .

45. The process according to claim 29 , wherein the talc is added in an amount of 0.05- 25 wt.-%, based on the weight on oven (100° C.) dry fibers.

46. The process according to claim 29 , wherein the talc is added in an amount of 0.25- 10 wt.-%, based on the weight on oven (100° C.) dry fibers.

47. The process according to claim 29 , wherein the talc is added in an amount of 0.5- 2 wt.-%, based on the weight on oven (100° C.) dry fibers.

48. The process according to claim 1 , wherein the aqueous medium is brought into contact with the surface-reacted natural calcium carbonate by surface filtration, depth filtration and/or alluvium filtration.

49. The process according to claim 1 , wherein the composite is separated from the aqueous medium by sedimentation or filtration.

50. The process according to claim 1 , wherein the composite is separated from the aqueous medium by surface filtration, depth filtration and/or alluvium filtration.

51. The process according to claim 1 , wherein the aqueous medium is brought into contact with the surface-reacted natural calcium carbonate and the composite is separated from the aqueous medium by surface filtration, depth filtration and/or alluvium filtration.