Process to prepare surface-modified mineral material, resulting products and uses thereof
The present invention refers to a process to modify at least part of the surface of at least one mineral material, and to the use, as an additive in an aqueous suspension of mineral materials having a pH between 5 and 10, of at least one agent, wherein the additive allows for the formation of a low volume, high solids content filter or centrifuge cake on dewatering the suspension.
1. A process for manufacturing a surface-modified mineral material in which at least part of the surface of a mineral material is modified, the process comprising the following steps:
(a) preparing an aqueous suspension of mineral material having a solids content of from 10 to 80% by weight, based on the weight of the suspension, and at a pH of 5 to 10, wherein the mineral matter comprises calcium carbonate or talc;
(b) contacting the aqueous suspension of mineral matter of step (a) with at least one agent so that at least part of the surface of the mineral matter is modified;
(c) obtaining a suspension of the surface-modified mineral material from step (b) having a pH which is less than 10 and which is greater than 7 if the isoelectric point of the mineral material provided in step (a) is greater than 7, or a pH that is greater than the isoelectric point of the mineral material provided in step (a) if the isoelectric point is 7 or lower; and
(d) subjecting the suspension of the surface-modified mineral material from step (c) to one or more of: (i) filtration on a filtration medium to form a filter cake of surface-modified mineral material, (ii) centrifugation to form a centrifuge cake of surface-modified mineral material, (iii) concentration by thermal or mechanical methods to form a concentrated surface-modified mineral material, and (iv) drying to form a dried surface-modified mineral material;
wherein the agent is:
(i) in the form of an aqueous solution or a stable aqueous colloid having a pH of less than 6;
(ii) formed by mixing, in an aqueous environment, at least one phosphonic acid-comprising compound with one or more metal cations or metal-comprising cationic compounds, wherein the metal is selected from the group consisting of aluminium, zirconium, zinc, cobalt, chrome, iron, copper, tin, titanium and mixtures thereof, and wherein the phosphonic acid-comprising compound and the metal cations or metal-comprising cationic compounds are dosed such that the molar ratio of phosphonate hydroxyl groups: metal cation or metal comprising cationic compound is from 10:1 to 2:1; and
(iii) added in step (b) in an amount corresponding to from 0.04 to 1 mg by dry weight of agent per m 2 of the total surface of the mineral material.
2. The process according to claim 1 , wherein the suspension of step (a) has a pH of 7 to 10.
3. The process according to claim 1 , wherein the suspension of step (a) has a pH of 8 to 9.
4. The process according to claim 1 , wherein the mineral material is talc.
5. The process according to claim 1 , wherein the mineral material comprises calcium carbonate and dolomite.
6. The process according to claim 1 , wherein the mineral material comprises surface-reacted calcium carbonate.
7. The process according to claim 1 , wherein the mineral material comprises calcium carbonate and one or more of dolomite, a Group IIA and/or IIIA element-comprising phyllosilicate, montmorillonite, talc, magnesite, magnesium-comprising chlorite, and kaolin clay.
8. The process according to claim 1 , wherein the mineral material is a calcium carbonate.
9. The process according to claim 1 , wherein the aqueous suspension of step (a) comprises less than 0.1% by weight, based on the weight of dry mineral material, of a polyacrylate-based dispersant.
10. The process according to claim 1 , wherein the mineral material provided in step (a) has a BET specific surface area of 5 to 150 m 2 /g.
11. The process according to claim 1 , wherein the mineral material provided in step (a) has a BET specific surface area of 5 to 60 m 2 /g.
12. The process according to claim 1 , wherein the mineral material provided in step (a) has a BET specific surface area of 10 to 50 m 2 /g.
13. The process according to claim 1 , wherein the mineral material provided in step (a) has a weight median diameter (d 50 ) of 0.2 to 5 μm.
14. The process according to claim 1 , wherein the mineral material provided in step (a) has a weight median diameter (d 50 ) of 0.5 to 2 μm.
15. The process according to claim 1 , wherein the suspension in step (a) has a solids content of 20 to 80% by weight, based on the weight of the suspension.
16. The process according to claim 1 , wherein the suspension in step (a) has a solids content of 40 to 75% by weight, based on the weight of the suspension.
17. The process according to claim 1 , wherein the suspension in step (a) has a solids content of 50 to 70% by weight, based on the weight of the suspension.
18. The process according to claim 1 , wherein the agent is dosed in step (b) in an amount corresponding to from 0.1 to 0.75 mg by dry weight of agent per m 2 of the total surface of the mineral material.
19. The process according to claim 1 , wherein the agent is dosed in step (b) in an amount corresponding to from 0.1 to 5%, by dry weight relative to the dry weight of mineral material.
20. The process according to claim 1 , wherein the agent is dosed in step (b) in an amount corresponding to from 0.15 to 0.75%, by dry weight relative to the dry weight of mineral material.
21. The process according to claim 1 , wherein the agent is dosed in step (b) in an amount corresponding to from 0.15 to 0.5%, by dry weight relative to the dry weight of mineral material.
22. The process according to claim 1 , wherein the agent is provided in the form of an aqueous solution having a pH of 0 to 5.
23. The process according to claim 1 , wherein the agent is provided in the form of an aqueous solution having a pH of between 0.5 to 4.5.
24. The process according to claim 1 , wherein the phosphonic acid-comprising compound is an alkyl diphosphonic acid.
25. The process according to claim 1 , wherein the phosphonic acid-comprising compound is 1-hydroxyethane 1,1-diphosphonic acid (HEDP).
26. The process according to claim 1 , wherein the phosphonic acid-comprising compound is a selected from the group consisting of methylene diphosphonic acid (MDP), hydroxymethylene diphosphonic acid (HMDP), hydroxycyclomethylene diphosphonic acid (HCMDP), 1-hydroxy-3-aminopropane-1,1-diphosphonic acid (APD), aminotri (methylenephosphonic acid) (ATMP), diethylenetriaminepenta(methylenephosphonic acid) (DTPMP) and phosphonosuccinic acid (PSA).
27. The process according to claim 1 , wherein the metal of the metal cation or metal-comprising cationic compound is aluminium or zirconium.
28. The process according to claim 1 , wherein a base is added before and/or after the agent.
29. The process according to claim 28 , wherein the base is selected from the group consisting of sodium silicate, sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium aluminate, a basic polyphosphate, a basic phosphonate, and any mixture thereof.
30. The process according to claim 28 , wherein the base is a basic polyphosphate or a basic phosphonate.
31. The process according to claim 28 , wherein the base is a potassium salt of pyrophosphate, an alkali compound of HEDP, or a sodium and/or potassium and/or lithium compound of HEDP.
32. The process according to claim 28 , wherein the base is added in an amount of greater than or equal to 0.1% by dry weight, relative to the dry weight of mineral material.
33. The process according to claim 28 , wherein the base is added in an amount of from 0.2 to 0.5% by dry weight, relative to the dry weight of mineral material.
34. The process according to claim 1 , wherein in step (d) the suspension of step (c) is concentrated by thermal or mechanical methods, or dried.
35. The process according to claim 1 , wherein the mineral matter is precipitated calcium carbonate.
36. The process according to claim 1 , wherein the mineral matter is ground calcium carbonate.