Surface-reacted precipitated calcium carbonate, process to make same, and uses thereof

Patent metadata

Field	Value
Publication number	US-10280309-B2
Application number	US-73499208-A
Country	US
Kind code	B2
Filing date	Dec 2, 2008
Priority date	Dec 12, 2007
Publication date	May 7, 2019
Grant date	May 7, 2019

Abstract

The present invention relates to a process for the preparation of a surface-reacted precipitated calcium carbonate (PCC) pigment having an insoluble, at least partially crystalline calcium salt on its surface. In the process of the present invention, a PCC containing pigment is contacted with H 3 O + ions and a solubilized anion in an aqueous medium in the presence of excess solubilized calcium ions to form the surface-reacted PCC having an insoluble, at least partially crystalline calcium salt of the anion formed on its surface.

First claim

The invention claimed is:

1. A process for the preparation of a pigment comprising a surface-reacted precipitated calcium carbonate (PCC), the process comprising the following steps:
a) providing at least one precipitated calcium carbonate (PCC)-comprising pigment; and
b) contacting the PCC-comprising pigment in an aqueous medium with at least one anion that is solubilized in an aqueous medium and forms water-insoluble calcium salts in the presence of excess solubilized calcium ions that are present in the aqueous medium, wherein the anion is in the form of a soluble neutral or acid salt, or is in the form of an acid, wherein the anion is a phosphate-comprising anion, PO 4 3− , HPO 4 2− , an oxalate anion (C 2 O 4 2− ), a carbonate-comprising anion in the form of CO 3 2− , a phosphonate anion, a succinate anion or a fluoride anion, wherein the anion is added in a quantity corresponding to between 5 and 50% by weight, based on the weight of said PCC provided in step a), and wherein the PCC-comprising pigment in the aqueous medium, the at least one anion, and excess solubilized calcium ions are mixed so as to develop a laminar flow;
to form a slurry of surface-reacted PCC comprising an insoluble, at least partially crystalline calcium salt of said anion formed on the surface of at least part of the PCC provided in step a), wherein the excess solubilized calcium ions are provided by the addition to the aqueous medium of:
(i) H 3 O + ions by addition of an acid or an acid salt that provides all or part of excess solubilized calcium ions in the aqueous medium, wherein the acid or acid salt is a sulphur-comprising acid, sulphuric acid, hydrochloric acid, perchloric acid, formic acid, lactic acid, acetic acid, or nitric acid, or an acid salt thereof, or a soluble calcium acid salt thereof, and/or
(ii) a soluble neutral calcium salt that provides all or part of excess solubilized calcium ions in the aqueous medium.

2. The process according to claim 1 , wherein the PCC-comprising pigment of step a) is hydrophilic.

3. The process according to claim 1 , wherein the PCC-comprising pigment of step a) is obtained from a process involving at least one step of comminution.

4. The process according to claim 3 , wherein the step of comminution is a wet grinding step.

5. The process according to claim 4 , wherein upon wet grinding the PCC-comprising pigment of step a), the pH of the wet grinding slurry is observed to rise by more than 2.

6. The process according to claim 1 , wherein the PCC-comprising pigment of step a) has a weight median diameter of 0.01 to 10 μm.

7. The process according to claim 1 , wherein the PCC-comprising pigment of step a) has a weight median diameter of 0.5 to 2 μm.

8. The process according to claim 1 , wherein the PCC-comprising pigment of step a) further comprises one or more of talc, clay, plastic hollow-sphere pigments or titanium dioxide.

9. The process according to claim 1 , wherein the PCC-comprising pigment of step a) consists of PCC.

10. The process according to claim 1 , wherein the PCC-comprising pigment of step a) is provided in the form of an aqueous slurry.

11. The process according to claim 10 , wherein the slurry has a pH of less than 11 prior to step b).

12. The process according to claim 10 , wherein the slurry has a pH of less than 10.5 prior to step b).

13. The process according to claim 10 , wherein PCC-comprising pigment is dispersed.

14. The process according to claim 1 , wherein the H 3 O + ions provide all or part of said excess solubilized calcium ions by dissolution of the PCC to liberate calcium ions.

15. The process according to claim 1 , wherein the acid or acid salt that provides all or part of the excess solubilized calcium ions is sulphuric acid, hydrochloric acid, acetic acid, or nitric acid, or an acid salt thereof, or a soluble calcium acid salt thereof.

16. The process according to claim 1 , wherein following the addition of said H 3 O + ions, the pH of the aqueous medium temporarily drops to a value below 6.0.

17. The process according to claim 1 , wherein the anion of step b) is a phosphate-comprising anion, PO 4 3− , or HPO 4 2− .

18. The process according to claim 1 , wherein the anion of step b) is a carbonate-comprising anion that is generated in situ via the introduction of gaseous CO 2 to the slurry.

19. The process according to claim 1 , wherein the anion in step b) is added in a quantity corresponding to between 15 and 30% by weight, based on the weight of said PCC provided in step a).

20. The process according to claim 1 , wherein the anion in step b) is contacted with the PCC after contacting the PCC with the acid or acid salt, or the soluble neutral calcium salt.

21. The process according to claim 1 , wherein the excess solubilized calcium ions are provided by addition of sulphuric acid, hydrochloric acid or acetic acid.

22. The process according to claim 1 , wherein the excess solubilized calcium ions are provided by addition of a soluble neutral calcium salt selected from the group consisting of CaCl 2 and Ca(NO 3 ) 2 .

23. The process according to claim 1 , wherein the solubilized calcium ions are provided in a quantity corresponding to greater than or equal to 3% by weight, based on the weight of said PCC provided in step a).

24. The process according to claim 1 , wherein the solubilized calcium ions are provided in a quantity corresponding to greater than or equal to 5% by weight, based on the weight of said PCC provided in step a).

25. The process according to claim 1 , wherein step b) is carried out at a temperature of above 50° C.

26. The process according to claim 1 , wherein step b) is carried out at a temperature of above 60° C.

27. The process according to claim 1 , wherein step b) takes place in the presence of at least one compound selected from the group consisting of silicate, silica, earth alkali metal aluminate, or mixtures thereof.

28. The process according to claim 27 , wherein the silicate is an aluminium silicate or an earth alkali metal silicate.

29. The process according to claim 10 , wherein step b) takes place in the presence of an inert gas, which is bubbled through the slurry.

30. The process according to claim 10 , wherein step b) takes place in the presence of an additive which increases the ionic strength of the slurry.

31. The process according to claim 30 , wherein the additive which increases the ionic strength of the slurry is an inert, non-calcium salt.

32. The process according to claim 31 , wherein the inert, non-calcium salt is NaCl or KNO 3 , or mixtures thereof.

33. The process according to claim 1 , wherein the aqueous phase of the surface-reacted PCC slurry formed in step b) is replaced with deionised water.

34. The process according to claims 33 , wherein the removed aqueous phase is re-introduced as a source of calcium ions.

35. The process according to claim 1 , wherein the process is a continuous process.

36. The process according to claim 1 , wherein the slurry of surface-reacted PCC formed in step b) is concentrated.

37. The process according to claim 1 , wherein a dispersant is added to the slurry of surface-reacted PCC formed in step b).

Assignees

• Gerard Daniel E
• Gane Patrick A C
• Schoelkopf Joachim
• Weitzel Hans Joachim
• Omya Int Ag

Inventors

• Gerard Daniel E
• Gane Patrick A C
• Schölkopf Joachim
• Weitzel Hans-Joachim

Classifications

• C09C1/022 Primary

  Treatment with inorganic compounds · CPC title

• C01P2004/61

  Micrometer sized, i.e. from 1-100 micrometer · CPC title

• C01P2004/62

  Submicrometer sized, i.e. from 0.1-1 micrometer · CPC title

• D21H17/69

  modified, e.g. by association with other compositions prior to incorporation in the pulp or paper · CPC title

• C01P2006/12

  Surface area · CPC title