Process for the control of pitch
The present invention relates to a process for the control of pitch in an aqueous medium by adding surface-reacted natural calcium carbonate or an aqueous suspension comprising surface-reacted calcium carbonate and having a pH greater than 6.0 measured at 20° C., to the medium, wherein the surface-reacted calcium carbonate is a reaction product of natural calcium carbonate with carbon dioxide and one or more acids, the use of the surface-reacted natural calcium carbonate for pitch control, as well as to a combination of a surface-reacted natural calcium carbonate and talc for pitch control, and the resulting composites.
1. A composition comprising surface-reacted natural calcium carbonate and pitch adsorbed thereon from an aqueous medium, wherein the composition is obtained by (a) contacting an aqueous medium containing pitch 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., wherein the surface-reacted natural calcium carbonate is a reaction product of natural calcium carbonate with carbon dioxide and one or more acids, and wherein the carbon dioxide is formed in situ by the acid treatment and/or is supplied from an external source; and (b) separating the composition from the aqueous medium.
2. The composition according to claim 1 , wherein the surface-reacted natural calcium carbonate in (ii) is an aqueous suspension having a pH of greater than 6.5, measured at 20° C.
3. The composition according to claim 1 , wherein the surface-reacted natural calcium carbonate in (ii) is an aqueous suspension having a pH of greater than 7.0, measured at 20° C.
4. The composition according to claim 1 , wherein the surface-reacted natural calcium carbonate in (ii) is an aqueous suspension having a pH of greater than 7.5, measured at 20° C.
5. The composition according to claim 1 , wherein the national calcium carbonate is marble, calcite, chalk and dolomite, limestone or mixtures thereof.
6. The composition according to claim 1 , wherein the acid has a pK a at 25° C. of 2.5 or less.
7. The composition according to claim 6 , wherein the acid is hydrochloric acid, sulphuric acid, sulphurous acid, hydrosulphate, phosphoric acid, oxalic acid or mixtures thereof.
8. The composition according to claim 6 , wherein the acid is phosphoric acid.
9. The composition 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 composition according to claim 9 , wherein the at least one silicate is aluminium silicate, calcium silicate or alkali metal silicate.
11. The composition 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 composition 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 composition 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 composition 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.
15. The composition 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.
16. The composition 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.
17. The composition 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.
18. The composition 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.
19. The composition 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.
20. The composition according to claim 1 , further comprising talc.
21. The composition according to claim 20 , wherein the talc has a purity of >90 weight-%.
22. The composition according to claim 20 , wherein the talc has a purity of >95 weight-%.
23. The composition according to claim 20 , wherein the talc has a purity of >97 weight-%.
24. The composition according to claim 20 , wherein the talc particles have a d 50 value of 0.1 to 50 μm, measured according to the sedimentation method.
25. The composition according to claim 20 , wherein the talc particles have a d 50 value of 0.2 to 40 μm, measured according to the sedimentation method.
26. The composition according to claim 20 , wherein the talc particles have a d 50 value of 0.3 to 30 μm, measured according to the sedimentation method.
27. The composition according to claim 20 , wherein the talc particles have a d 50 value of 0.4 to 20 μm, measured according to the sedimentation method.
28. The composition according to claim 20 , wherein the talc particles have a d 50 value of 0.5 to 10 μm, measured according to the sedimentation method.
29. The composition according to claim 20 , wherein the talc particles have a d 50 value of 1, 7 or 7 μm, measured according to the sedimentation method.
30. The composition according to claim 20 , wherein the talc has a specific surface area of between 3 and 100 g/m 2 .
31. The composition according to claim 20 , wherein the talc has a specific surface area of between 7 and 80 g/m 2 .
32. The composition according to claim 20 , wherein the talc has a specific surface area of between 9 and 60 g/m 2 .
33. The composition according to claim 20 , wherein the talc has a specific surface area of between 10 and 50 g/m 2 .
34. The composition according to claim 20 , wherein the talc has a specific surface area of 30 or 51 g/m 2 .
35. The composition 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.
36. The composition according to claim 1 , wherein the composition is separated from the aqueous medium by sedimentation or filtration.
37. The composition according to claim 1 , wherein the composition is separated from the aqueous medium by surface filtration, depth filtration and/or alluvium filtration.
38. The composition according to claim 1 , wherein the aqueous medium is brought into contact with the surface-reacted natural calcium carbonate and the composition is separated from the aqueous medium by surface filtration, depth filtration and/or alluvium filtration.