PROCESS TO PREPARE SURFACE-MODIFIED MINERAL MATERIAL, RESULTING PRODUCTS AND USES THEREOF

Abstract

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.

Claims

1. A product obtained by 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.sup.2 of the total surface of the mineral material.

2. The product of claim 1, wherein the suspension of step (a) has a pH of 7 to 10.

3. The product according to claim 1, wherein the suspension of step (a) has a pH of 8 to 9.

4. The product according to claim 1, wherein the mineral material is talc.

5. The product according to claim 1, wherein the mineral material is calcium carbonate.

6. The product according to claim 1, wherein the mineral material is surface-reacted calcium carbonate.

7. The product 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 product 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.

9. The product according to claim 1, wherein the mineral material provided in step (a) has a BET specific surface area of 5 to 150 m.sup.2/g.

10. The product according to claim 1, wherein the mineral material provided in step (a) has a BET specific surface area of 5 to 60 m.sup.2/g.

11. The product according to claim 1, wherein the mineral material provided in step (a) has a weight median diameter (d.sub.50) of 0.2 to 5 m.

12. The product according to claim 1, wherein the mineral material provided in step (a) has a weight median diameter (d.sub.50) of 0.5 to 2 m.

13. The product 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.

14. The product 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.sup.2 of the total surface of the mineral material.

15. The product 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.

16. The product 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.

17. The product 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.

18. The product according to claim 1, wherein the agent is provided in the form of an aqueous solution having a pH of 0 to 5.

19. The product 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.

20. The product according to claim 1, wherein the phosphonic acid-comprising compound is an alkyl diphosphonic acid.

21. The product according to claim 1, wherein the phosphonic acid-comprising compound is 1-hydroxyethane 1,1-diphosphonic acid (HEDP).

22. The product 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).

23. The product according to claim 1, wherein the metal of the metal cation or metal-comprising cationic compound is aluminium or zirconium.

24. The product according to claim 1, wherein a base is added before and/or after the agent.

25. The product according to claim 24, 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.

26. The product according to claim 24, wherein the base is a basic polyphosphate or a basic phosphonate.

27. The product according to claim 24, 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.

28. The product according to claim 24, 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.

29. The product according to claim 24, 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.

30. The product according to claim 1, wherein the mineral matter is precipitated calcium carbonate or ground calcium carbonate.

31. The product according to claim 1, wherein in step (d), step (i) is preformed and the product is a filter cake of surface-modified mineral material.

32. The product according to claim 1, wherein in step (d), step (ii) is preformed and the product is a centrifuge cake of surface-modified mineral material.

33. The product according to claim 1, wherein in step (d), step (iii) is preformed and the product is a concentrated surface-modified mineral material.

34. The product according to claim 1, wherein in step (d), step (iv) is preformed and the product is a dried surface-modified mineral material.

35. Paper, plastics, sealants, paints, concretes or cosmetics comprising the product according to claim 1.

36. The product according to claim 1, which is an aqueous suspension of mineral material having a pH between 5 and 10, comprising at least one additive: (a) in the form of an aqueous solution or a stable aqueous colloid having a pH of less than 6; (b) 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, where said metal is selected from the group consisting of: aluminium, zirconium, zinc, cobalt, chrome, iron, copper, tin, titanium and mixtures thereof, and where said phosphonic acid-comprising compound and said 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 (c) in an amount corresponding to from 0.04 to 1 mg by dry weight of agent per m.sup.2 of the total surface of the mineral material, wherein the additive facilitates dewatering of the suspension.

Description

EXAMPLES

Measurement Methods

Solids Content of a Suspension or Dispersion (% by Weight)

[0110] Solids contents were determined using a Mettler LP16 PM100 mass balance equipped with an LP16 IR dryer.

pH of a Suspension or Dispersion

[0111] Suspension or dispersion pH values were measured using Seven Multi instrumentation from Toledo at 25 C.

Specific Surface Area (SSA) of a Particulate Material (m.sup.2/g)

[0112] The specific surface area was measured using Gemini V instrumentation from Micrometrics, via the BET method according to ISO 9277 using nitrogen, following conditioning of the sample by heating at 250 C. for a period of 30 minutes.

Particle Size Distribution (Mass % Particles with a Diameter <X) and Weight Median Grain Diameter (d.sub.50) of a Particulate Material

[0113] Weight median grain diameter and grain diameter mass distribution of a particulate material were determined via the sedimentation method, i.e. an analysis of sedimentation behaviour in a gravimetric field. The measurement is made with a Sedigraph 5120.

[0114] The method and the instrument are known to the skilled person and are commonly used to determine grain size of fillers and pigments. The measurement was carried out in an aqueous solution of 0.1 wt % Na.sub.4P.sub.2O.sub.7. The samples were dispersed using a high speed stirrer and ultrasonic.

Isoelectric Point of a Mineral Material

[0115] The isoelectric point of a mineral material is evaluated in deionised water at 25 C. using Malvern Zetasizer Nano ZS instrumentation.

Water Pick-Up of a Particulate Material

[0116] The water pick-up of a particulate material is determined by first drying the material in an oven at 110 C. to constant weight, and thereafter exposing the dried material to an atmosphere of 80% relative humidity for 60 hours at a temperature of 20 C. The water pick-up corresponds to the % increase in weight of the material following exposure to the humid environment, relative to the dried material weight.

Materials

[0117] Precipitated calcium carbonate (PCC) was obtained by bubbling CO.sub.2 gas through a 13 to 15 C. suspension of lime having a solids content of about 15% by dry weight and containing between 0.05 and 1% of a slaking additive. The obtained PCC suspension had a solids content of about 17% by dry weight and the PCC material had a specific surface area of between 10 and 12 m.sup.2/g.

[0118] The surface-reacted calcium carbonate (SRGCC) was prepared in a 10 m.sup.3 reactor. Dry natural calcium carbonate having a d.sub.50 of 1 m was filled into this vessel along with water to form a suspension having a solids content of 10% by dry weight. 25% phosphoric acid (calculated dry/dry, said phosphoric acid being provided in the form of a 30% solution) was then added to the vessel over a time period of 60 minutes under stirring. Thereafter, 20 kg of a lime suspension (200 L of a 10% suspension) was introduced into the vessel.

[0119] Potassium hydroxide (KOH), in the form of granules, was obtained from Fluka.

[0120] Potassium pyrophosphate (K.sub.4P.sub.2O.sub.7), in the form of a 60% by dry weight aqueous solution, was obtained from Chemische Fabrik Budenheim.

[0121] 1-Hydroxyethane-1,1-diphosphonic acid (HEDP), in the form of a 60% by dry weight aqueous solution, was obtained from Chemische Fabrik Budenheim.

[0122] Sodium pyrophosphate (Na.sub.4HEDP), in the form of a 25% by dry weight aqueous solution, was obtained from Chemische Fabrik Budenheim.

[0123] Aluminium hydroxide (Al(OH).sub.3), sold under the commercial name Martinal OL-107 in the form of a powder, was obtained from Martinswerk.

[0124] Potassium HEDP (K.sub.4HEDP) was synthesized by adding 90 g of KOH to an aqueous solution of HEDP previously formed by adding 200 g of water to 108 g of the 60 weight % aqueous solution of HEDP under stirring. The obtained clear solution had a pH of 12.0 and a concentration of K.sub.4HEDP of 33.5 g/100 g of water.

[0125] Lithium HEDP (Li.sub.4HEDP) was synthesized by adding 113 g of LiOH to 2 200 g of a 7% aqueous solution of HEDP under stirring. The obtained suspension had a pH of 11.6.

[0126] Al-HEDP chelate complexes, in the form of an aqueous colloidal solution in which the weight ratio of Al(OH).sub.3:HEDP was 1:5, 1:8 and 1:10, were prepared as follows: aluminium hydroxide powder was added to the 60% HEDP solution in the necessary amount with respect to the desired weight ratio under stirring until a homogeneous white suspension was obtained. This suspension was then heated under continued stirring (at approximately 500 rpm) until a colloidal suspension developed. The solution temperature was then allowed to settle to approximately 23 C. The final dry weight of each of the colloidal suspension was 62 to 65% and the final pH 1.8.

[0127] Sn-HEDP chelate complexes, in the form of an aqueous colloidal solution in which the weight ratio of Sn(OH).sub.2:HEDP was 1:4, were prepared as follows: Sn(OH).sub.2 was freshly synthesized by adding 75 mL of ammonia to an aqueous solution of 20 g of SnSO.sub.4 in 100 g of water. The obtained suspension was filtered on a Buchner funnel filter to obtain a filter cake. This filter cake was then added to 100 g of an aqueous 60% HEDP solution under stirring until a homogeneous suspension was obtained. The suspension was subsequently heated to a temperature of between 90 and 95 C. under stirring at 500 rpm until a milky colloidal suspension developed. The suspension temperature was then allowed to cool to about 23 C. The final colloidal suspension had a solids content of 67% by dry weight and the final pH was 0.9.

[0128] Co-HEDP chelate complexes, in the form of an aqueous solution in which the weight ratio of Co(OH).sub.2:HEDP was 1:10, were prepared as follows: 9.3 g of Co(OH).sub.2 was added to 155 g of an aqueous 60% HEDP solution under stirring until a homogeneous suspension was obtained. The suspension was then heated to a temperature of between 90 and 95 C. under stirring at 500 rpm until a milky paste developed. The paste was then diluted with water to 27% by dry weight; the obtained solution had a violet colour and was allowed to cool to 23 C. The solution pH was of 0.85.

[0129] Ti-HEDP chelate complexes, in the form of an aqueous colloidal solution in which the weight ratio of Ti(SO.sub.4).sub.2:HEDP was 1:5, were prepared as follows: 15 g of a 60% titanyl sulphate solution was added to 150 g of a 60% HEDP solution under stirring and heating to 95 to 98 C. until a clear colloidal suspension developed. The suspension was then allowed to cool to approximately 23 C. The final solids content of the suspension was 60% by dry weight and the final pH<1.

Example 1

Lab-Scale Examples

[0130] In this example, the process of the present invention is compared to prior art processes.

[0131] The additive system listed in the Table below is added under stirring using an IKA RW 20 stirrer at 500 rpm, to an aqueous suspension of 150 g of undispersed ground natural calcium carbonate suspension having an isoelectric point of about 9 and a specific surface area of approximately 11 m.sup.2/g, and wherein 75% by dry weight of the particles have a diameter of less than 1 m; the initial solids content of this suspension is 20% by dry weight.

[0132] Thereafter, each of the suspensions of Table 1 were filtered over a time period of 30 minutes using a 3 m pore size Rotilabo round filter located in a Buchner funnel filter (70 mm in diameter; 30 mm in height) equipped with a 1 L vacuum flask connected via an M7 2C diaphragm vacuum pump from Vacuubrand GmbH (suction capacity: 2.4 m.sup.3/h).

[0133] The solids contents of the resulting filter cakes are given in Table 1. The collected material in the filter cakes was then dried and the water-pick value determined.

TABLE-US-00001 TABLE 1 Test 1 2 3 4 Invention (IN)/ PA PA IN IN Prior Art (PA) Type of Additive none HEDP K.sub.4HEDP K.sub.4P.sub.2O.sub.7 System followed by followed by followed by Na.sub.4HEDP Al(OH).sub.3:HEDP 1:8 Al(OH).sub.3:HEDP 1:8 Amount of none 0.25 HEDP +0.20 0.20 K.sub.4HEDP + 0.20 0.20 K.sub.4P.sub.2O.sub.7 + 0.20 Additive System (% by dry weight Na.sub.4HEDP Al(OH).sub.3:HEDP Al(OH).sub.3:HEDP on dry weight of for a total of 0.45 for a total of 0.40 for a total of 0.40 mineral material) Amount of Agent 0.18 mg 0.18 mg (g dry agent/m.sup.2 Al(OH).sub.3:HEDP/m.sup.2 Al(OH).sub.3:HEDP/m.sup.2 mineral material) CaCO.sub.3 CaCO.sub.3 pH of mineral 8.4 8.5 8.3 material suspension following additive system addition Final filter cake 42.3 43.5 46.1 49.0 solids content (% by weight) Water pick up (% 0.24 0.28 0.36 weight increase)

[0134] The above table shows that relative to the untreated calcium carbonate, not only does the resulting filter cake present a significantly higher solids content, but further the obtained calcium carbonate material treated by the process of the invention (test 4) has a 50% greater degree of water pick-up, attesting to a greater natural hydration layer. Comparing tests 2 and 3 furthermore shows that only the process of the invention, implementing a chelate complex instead of a chelant alone, leads to the desired results.

Example 2

Lab-Scale Examples

[0135] This example illustrates various embodiments of the invention.

[0136] The additive systems listed in Tables 2 and 3 below are added, under stirring using a Dispermat dissolver at 1 500 rpm, to an aqueous suspension of 500 g of undispersed ground natural calcium carbonate having an isoelectric point of about 9 and a specific surface area of approximately 11 m.sup.2/g, and wherein 75% by weight of the particles have a diameter of less than 1 m; the initial solids content of this suspension is 70 to 75% by dry weight.

[0137] Thereafter, each of the suspensions of Tables 2 and 3 were filtered over a time period of 30 minutes using a 3 m pore size Rotilabo round filter located in a Buchner funnel filter (70 mm in diameter; 30 mm in height) equipped with a 1 L vacuum flask connected via an M7 2C diaphragm vacuum pump from Vacuubrand GmbH (suction capacity: 2.4 m.sup.3/h). In all cases, a compact high solids content filter cake was obtained in which the mineral maintained a hydration layer.

TABLE-US-00002 TABLE 2 Test 5 6 7 8 Invention (IN)/ IN IN IN IN Prior Art (PA) Type of K.sub.4P.sub.2O.sub.7 K.sub.4HEDP Li.sub.4HEDP Al(OH).sub.3:HEDP Additive followed by followed by followed by 1:5 System Al(OH).sub.3:HEDP Al(OH).sub.3:HEDP Al(OH).sub.3:HEDP followed by 1:5 1:5 1:5 K.sub.4P.sub.2O.sub.7 Amount of 0.25 K.sub.4P.sub.2O.sub.7 + 0.20 0.25 K.sub.4HEDP + 0.20 0.25 Li.sub.4HEDP + 0.20 0.20 K.sub.4P.sub.2O.sub.7 + 0.25 Additive System (% by Al(OH).sub.3:HEDP Al(OH).sub.3:HEDP Al(OH).sub.3:HEDP Al(OH).sub.3:HEDP dry weight on for a total of 0.45 for a total of 0.45 for a total of 0.45 for a total of 0.45 dry weight of CaCO.sub.3) Amount of 0.18 mg 0.18 mg 0.18 mg 0.23 mg Agent (g dry Al(OH).sub.3:HEDP/m.sup.2 Al(OH).sub.3:HEDP/m.sup.2 Al(OH).sub.3:HEDP/m.sup.2 Al(OH).sub.3:HEDP/m.sup.2 agent/m.sup.2 CaCO.sub.3 CaCO.sub.3 CaCO.sub.3 CaCO.sub.3 mineral material) pH of mineral 8.3 8.5 8.6 8.9 material suspension following additive system addition

TABLE-US-00003 TABLE 3 Test 9 10 11 12 Invention (IN)/ IN IN IN IN Prior Art (PA) Type of Additive Na.sub.4HEDP Ti(SO.sub.4).sub.2:HEDP 1:5 K.sub.4P.sub.2O.sub.7 K.sub.4P.sub.2O.sub.7 System followed by followed by followed by followed by Al(OH).sub.3:HEDP 1:5 Na.sub.4HEDP Sn(OH).sub.2:HEDP 1:7 Co(OH).sub.2:HEDP 1:10 Amount of 0.10 Na.sub.4HEDP + 0.18 0.75 0.50 K.sub.4P.sub.2O.sub.7 + 0.50 0.20 K.sub.4P.sub.2O.sub.7 + 0.20 Additive System Ti(SO.sub.4).sub.2:HEDP + 0.25 (% by dry Al(OH).sub.3:HEDP Sn(OH).sub.2:HEDP Co(OH).sub.2:HEDP weight on dry for a total of 0.28 Na.sub.4HEDP for a total of 1.00 for a total of 0.40 weight of for a total of 1.00 CaCO.sub.3) Amount of 0.16 mg 0.69 mg 0.45 mg 0.18 mg Agent (g dry Al(OH).sub.3:HEDP/m.sup.2 Ti(SO.sub.4).sub.2:HEDP/m.sup.2 Sn(OH).sub.2:HEDP/m.sup.2 Co(OH).sub.2:HEDP/m.sup.2 agent/m.sup.2 CaCO.sub.3 CaCO.sub.3 CaCO.sub.3 CaCO.sub.3 mineral material) pH of mineral 8.6 7.6 7.4 9.0 material suspension following additive system addition

TABLE-US-00004 TABLE 4 Test 13 14 15 Invention (IN)/ IN IN IN Prior Art (PA) Type of Additive Premixture in a 1:1: Premixture in a 1:1: Premixture of System weight ratio of weight ratio of KOH and [Al(OH).sub.3:HEDP K.sub.4P.sub.2O.sub.7 and K.sub.4P.sub.2O.sub.7 and 1:5], pH 3.7 [Al(OH).sub.3:HEDP [Al(OH).sub.3:HEDP 1:5], pH 4 1:5], pH 4 Amount of 0.4 of the premixture 0.3 of the premixture 0.4 of the premixture Additive System (% by dry weight on dry weight of CaCO.sub.3) Amount of Agent 0.18 mg 0.14 mg (g dry agent/m.sup.2 Al(OH).sub.3:HEDP/m.sup.2 Al(OH).sub.3:HEDP/m.sup.2 mineral material) CaCO.sub.3 CaCO.sub.3 pH of mineral 8.5 8.7 8.1 material suspension following additive system addition

Example 3

Lab-Scale Examples

[0138] This example illustrates various embodiments of the invention.

[0139] The additive systems listed in Table 5 below are added, under stirring using a Dispermat dissolver at 1 500 to 5 000 rpm, to an aqueous suspension of 500 g of the indicated mineral material; the initial solids content of this suspension is 40 to 42% by dry weight.

[0140] Thereafter, each of the suspensions of Table 6 were filtered over a time period of 30 minutes using a 3 m pore size Rotilabo round filter located in a Buchner funnel filter (70 mm in diameter; 30 mm in height) equipped with a 1 L vacuum flask connected via an M7 2C diaphragm vacuum pump from Vacuubrand GmbH (suction capacity: 2.4 m.sup.3/h). In all cases, a compact high solids content filter cake was obtained in which the mineral maintained a hydration layer.

TABLE-US-00005 TABLE 5 Test 16 17 18 19 Invention IN IN IN IN (IN)/ Prior Art (PA) Type of PCC SRGCC Talc Talc mineral material Mineral 18 30 45 45 material specific surface area (m.sup.2/g) Type of K.sub.4HEDP K.sub.4HEDP K.sub.4P.sub.2O.sub.7 K.sub.4P.sub.2O.sub.7 Additive followed by followed by followed by followed by System Al(OH).sub.3:HEDP 1:5 Al(OH).sub.3:HEDP 1:5 Al(OH).sub.3:HEDP 1:10 Al(OH).sub.3:HEDP 1:10 Amount of 0.5 K.sub.4HEDP + 0.17 0.2 K.sub.4HEDP + 0.17 0.2 K.sub.4P.sub.2O.sub.7 + 0.2 0.2 K.sub.4P.sub.2O.sub.7 + 0.4 Additive Al(OH).sub.3:HEDP Al(OH).sub.3:HEDP Al(OH).sub.3:HEDP Al(OH).sub.3:HEDP System (% for a total of 0.67 for a total of 0.37 for a total of 0.4 for a total of 0.6 by dry weight on dry weight of CaCO.sub.3) Amount of 0.09 mg 0.06 mg 0.04 mg 0.08 mg Agent (g dry Al(OH).sub.3:HEDP/m.sup.2 Al(OH).sub.3:HEDP/m.sup.2 Al(OH).sub.3:HEDP/m.sup.2 Al(OH).sub.3:HEDP/m.sup.2 agent/m.sup.2 PCC SRGCC Talc Talc mineral material) pH of 9.3 8.5 8.1 8 mineral material suspension following additive system addition