DEVELOPMENT OF SURFACE-TREATED MAGNESIUM HYDROXIDE-COMPRISING MATERIAL

Abstract

The present invention refers to a process for the preparation of a surface-treated magnesium hydroxide-comprising material, a surface-treated magnesium hydroxide-comprising material as well as the use of the surface-treated magnesium hydroxide-comprising material in polymer composition, in paper making, paper coatings, agricultural applications, paints, adhesives, sealants, composite materials, wood composite materials, construction applications, pharma applications and/or cosmetic applications as well as surrounding materials, wherein the surface treatment agent of the surface-treated magnesium hydroxide-comprising material is undergoing a reaction with the surrounding material.

Claims

1. A process for the preparation of a surface-treated magnesium hydroxide-comprising material, the process comprising the steps of: a) providing at least one magnesium carbonate-comprising material, b) calcining the at least one magnesium carbonate-comprising material of step a) at a temperature in the range between 450 to 750° C. to obtain a magnesium oxide-comprising material, c) slaking the magnesium oxide-comprising material of step b) to obtain a magnesium hydroxide-comprising material, d) adding at least one surface-treatment agent to the aqueous suspension obtained in step c) in an amount ranging from 0.05 to 10 mg surface treatment agent per m.sup.2 of the specific surface area of the at least one magnesium oxide-comprising material as obtained in step b), wherein the specific surface area (BET) is measured using nitrogen and the BET method according to ISO 9277:2010 and wherein the at least one surface treatment agent is a compound according to Formula (I), ##STR00007## wherein R.sup.1 is a hydrolysable alkoxy group, and R.sup.2, R.sup.3 and R.sup.4 are independently from each other selected from the group consisting of hydrogen, a hydroxyl group, an alkyl group, a vinyl group, an alkoxy group, an acyloxy group, an acryloxy group, a methacryloxy group, an ethacryloxy group, a carboxyl group, an epoxy group, an anhydride group, an ester group, an aldehyde group, an amino group, an ureido group, an azide group, a halogen group, a phosphonate group, a phosphine group, a sulphonate group, a sulphide group or disulphide group, an isocyanate group or masked isocyanate group, a thiol group, a phenyl group, a benzyl group, a styryl group, a benzoyl group and a fully or partially halogenated alkyl group having from 1 to 20 carbon atoms, and u, v and w are independently from each other an integer from 0 to 24, e) drying the aqueous suspension during or after step d) at ambient or reduced pressure until the moisture content of the obtained surface-treated magnesium hydroxide-comprising material is in the range from 0.001 to 20 wt.-%, based on the total weight of the surface-treated magnesium hydroxide-comprising material.

2. The process according to claim 1, wherein the amount of magnesium carbonate in the magnesium carbonate-comprising material of step a) is from 80.0 to 99.9 wt.-%, based on the dry weight of the magnesium carbonate-comprising material, preferably from 90.0 to 99.5 wt.-%, more preferably from 95.0 to 99.3 wt.-% and most preferably from 98.0 to 99.0 wt.-%, based on the dry weight of the magnesium carbonate-comprising material.

3. The process according to claim 1, wherein the magnesium carbonate-comprising material has i) a weight median particle size d.sub.50 value in the range from 0.1 μm to 20 μm, preferably in the range from 0.25 μm to 15 μm, more preferably in the range from 0.5 μm to 10 μm and most preferably in the range from 1 μm to 6 μm and/or ii) a top cut (d.sub.98) of ≤50 μm, preferably of ≤30 μm, more preferably of ≤20 μm and most preferably of ≤15 μm and/or iii) a specific surface area (BET) of from 0.5 to 150 m.sup.2/g as measured using nitrogen and the BET method according to ISO 9277:2010, preferably from 1 to 80 m.sup.2/g, and more preferably from 40 to 70 m.sup.2/g and/or iv) a moisture pick-up susceptibility of from 35 to 80 mg/g, preferably from 40 to 70 mg/g, and more preferably from 50 to 60 mg/g.

4. The process according to claim 1, wherein the calcination step b) is carried out at a temperature in the range between 500 to 700° C., and preferably at a temperature in the range between 550 to 650° C.

5. The process according to claim 1, wherein R.sup.1, R.sup.2, R.sup.3 and/or R.sup.4 are independently from each other a methoxy or an ethoxy group, and/or the at least one surface-treatment agent is selected from triethoxysilane and/or trimethoxysilane and preferably is selected from the group consisting of triethoxyvinylsilane, trimethoxyvinylsilane, 3-(2,3-epoxypropoxy)propyl-trimethoxysilane, triethoxysilylpropyltetrasulphide, 3-mercaptopropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-aminopropyltriethoxysilane, methyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, dodecyltriethoxysilane, n-octadecyltriethoxysilane, phenyltriethoxysilane, 3-butenyltriethoxysilane, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, 1H,1H,2H,2H-perfluorooctyltriethoxysilane and combinations thereof and most preferably is triethoxyvinylsilane, trimethoxyvinylsilane, n-octadecyltriethoxysilane,1H,1H,2H,2H-perfluorodecyltriethoxysilane, 1H,1H,2H,2H-perfluorooctyltriethoxysilane and combinations thereof.

6. The process according to claim 1, wherein the amount of the at least one surface-treatment agent added in step d) is in the range from 0.01 to 9 mg surface-treatment agent per m.sup.2 of the surface area of the at least one magnesium oxide-comprising material as obtained in step b), preferably in the range from 0.1 to 8 mg surface-treatment agent per m.sup.2 of the surface area of the at least one magnesium oxide-comprising material as obtained in step b) and most preferably in the range from 0.11 to 6 mg surface-treatment agent per m.sup.2 of the surface area of the at least one magnesium oxide-comprising material as obtained in step b).

7. The process according to claim 1, wherein step e) is carried out at a temperature in the range from 20 to 200° C., preferably from 40 to 160° C., more preferably in the range from 50 to 155° C., even more preferably from 70 to 150° C. and most preferably from 80 to 110° C.

8. The process according to claim 1, wherein step e) is carried out until the moisture content of the obtained surface-treated magnesium hydroxide-comprising material is in the range from 0.005 to 15 wt.-%, preferably in the range from 0.01 to 10 wt.-% more preferably from 0.05 to 5 wt.-%, and most preferably from 0.06 to 1 wt.-%, based on the total weight of the surface-treated magnesium hydroxide-comprising material.

9. The process according to claim 1, wherein mechanical dewatering, preferably by centrifugation or filtration, is carried out before and/or during step e), and/or the surface-treated magnesium hydroxide-comprising material is washed with water during and/or after step d).

10. The process according to claim 1, wherein the process comprises a further step g) after or during step e) of deagglomerating the surface-treated magnesium hydroxide-comprising material of step d) or e), and preferably step g) is carried out after step e).

11. The process according to claim 1, wherein the surface-treated magnesium hydroxide-comprising material obtained in step e) has i) a weight median particle size d.sub.50 value in the range from 0.1 μm to 20 μm, preferably in the range from 0.25 μm to 15 μm, more preferably in the range from 0.5 μm to 10 μm and most preferably in the range from 1 μm to 6 μm and/or ii) a top cut (d.sub.98) of ≤50 μm, preferably of ≤30 μm, more preferably of ≤20 μm and most preferably of ≤15 μm and/or iii) a specific surface area (BET) of from 15 to 150 m.sup.2/g as measured using nitrogen and the BET method according to ISO 9277:2010, preferably from 20 to 80 m.sup.2/g, and more preferably from 30 to 70 m.sup.2/g and/or iv) a moisture pick-up susceptibility of from 0.1 to 10 mg/g, preferably from 0.5 to 7 mg/g, and more preferably from 1 to 5 mg/g.

12. The process according to claim 1, wherein the magnesium carbonate-comprising material of step a) is selected from the group consisting of magnesium carbonate hydrate (MgCO.sub.3*xH.sub.2O), non-hydrated magnesium carbonate (MgCO.sub.3), magnesium carbonate hydroxide hydrate ((MgCO.sub.3).sub.z*Mg(OH).sub.2*xH.sub.2O), and non-hydrated magnesium carbonate hydroxide ((MgCO.sub.3).sub.z*Mg(OH).sub.2), preferably is selected from the group consisting of magnesite, barringtonite, nesquehonite, hydromagnesite and mixtures thereof and most preferably the magnesium carbonate-comprising material is hydromagnesite.

13. A surface-treated magnesium hydroxide-comprising material, having a specific surface area (BET) of from 15 to 150 m.sup.2/g as measured using nitrogen and the BET method according to ISO 9277:2010 and a moisture pick-up susceptibility of from 0.1 to 10 mg/g, wherein the magnesium hydroxide-comprising material has been treated with at least one surface treatment agent that is a compound according to Formula (I), ##STR00008## wherein R.sup.1 is a hydrolysable alkoxy group, and R.sup.2, R.sup.3 and R.sup.4 are independently from each other selected from the group consisting of hydrogen, a hydroxyl group, an alkyl group, a vinyl group, an alkoxy group, an acyloxy group, an acryloxy group, a methacryloxy group, an ethacryloxy group, a carboxyl group, an epoxy group, an anhydride group, an ester group, an aldehyde group, an amino group, an ureido group, an azide group, a halogen group, a phosphonate group, a phosphine group, a sulphonate group, a sulphide group or disulphide group, an isocyanate group or masked isocyanate group, a thiol group, a phenyl group, a benzyl group, a styryl group, a benzoyl group and a fully or partially halogenated alkyl group having from 1 to 20 carbon atoms, and u, v and w are independently from each other an integer from 0 to 24.

14. A surface-treated magnesium hydroxide-comprising material according to claim 13, having a moisture pick-up susceptibility to specific surface area (BET) ratio of 0.001 to 0.5 mg/m.sup.2, preferably from 0.005 to 0.4 mg/m.sup.2 even more preferably from 0.01 to 0.15 mg/m.sup.2 and most preferably from 0.06 to 0.09 mg/m.sup.2.

15. Use of a surface-treated magnesium hydroxide-comprising material according to claim 14 in a polymer composition, in paper making, paper coatings, agricultural applications, paints, adhesives, sealants, composite materials, wood composite materials, construction applications, pharma applications and/or cosmetic applications.

16. Use of a surface-treated magnesium hydroxide-comprising material according to claim 14 in a surrounding material, wherein the surface treatment agent of the surface-treated magnesium hydroxide-comprising material is undergoing a reaction with the surrounding material upon addition of the surface-treated magnesium hydroxide-comprising material into the surrounding material, wherein the surrounding material is preferably a polymer formulation and most preferably a polyolefin formulation, a polyvinylchloride formulation or a polyester formulation and/or the reaction is preferably a crosslinking reaction.

Description

DESCRIPTION OF THE FIGURES

[0280] FIG. 1 shows the evaluation of the: Normalized moisture pickup susceptibility ̆ in function of the thermally treated and hydrophobized hydromagnesite, using surface treatment agents No. 1, No. 2 or No. 3

[0281] FIG. 2 shows the S E M pictures of 1) Fresh hydromagnesite without surface treatment agent

[0282] FIG. 3 shows the SE M pictures of 2) surface-treated magnesium hydroxide comprising material treated with surface treatment agent No. 1

[0283] FIG. 4 shows the SE M pictures of 3) surface-treated magnesium hydroxide comprising material treated with surface treatment agent No. 2

[0284] FIG. 5 shows the SE M pictures of 4) surface-treated magnesium hydroxide comprising material treated with surface treatment agent No. 3

[0285] FIG. 6 shows the BET values (mg) of the magnesium carbonate-comprising material before and after calcining at different thermal treatment temperatures (éC) between 100 éC and 900 éC. Thevalue at ‘0_ mean that this sample is a freshly prepared sample at room temperature.

[0286] FIG. 7 shows the correlation of the employed amount of surface treatment agent vs. the normalized water pickup in examples 8 to 13

EXAMPLES

1. Measurement Methods

[0287] In the following, the measurement methods implemented in the examples are described.

Humidity of Fresh Hydromagnesite

[0288] A 10 g powder sample was heated in an oven at 150 éC until the mass is constant for 15 min. The mass loss has been determined gravimetrically and is expressed as wt. % loss based on the initial sample mass. This mass loss has been attributed to the sample humidity.

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

[0289] Weight median grain diameter and grain diameter mass distribution of a particulate material were determined using Malvern Mastersizer 3000. T his device determines the size of powders and slurries within the range of 0.1 to 900 ≈m by means of laser diffraction. The analysed materials were measured in solid phase, by Aero S. For that purpose, a ca. 2 poly-spoons of dry sample is introduced into the Aero S through the corresponding sieve. The processes and instruments are known to the skilled person and are commonly used to determine grain size of fillers and pigments.

Specific Surface Area BET

[0290] The specific surface area is measured via the BET method according to ISO 9277:2010 using nitrogen, following conditioning of the sample by heating at 100 éC for a period of 60 min After performing the thermal treatment of the non-upgraded pigment, the sample was directly stored in a bottom-flask containing an inert atmosphere (N.sub.2) to prevent contact with air.

pH Measurements

[0291] The pH of a suspension is measured at 25 éC using a Mettler Toledo Seven Easy pH meter and a Mettler Toledo I nLab.sup.+ Expert Pro pH electrode. A three point calibration (according to the segment method) of the instrument is first made using commercially available buffer solutions having pH values of 4, 7 and 10 at 20 éC (from Aldrich). The reported pH values are the endpoint values detected by the instrument (the endpoint is when the measured signal differs by less than 0.1 mV from the average over the last 6 s).

XRD Method

[0292] Samples were analysed with a Bruker D8 Advance powder diffractometer obeying Bragg ̆s law. This diffractometer consists of a 2.2 kW X-ray tube, a sample holder, a J-J goniometer, and a V.sub.i NTEC-1 detector. Nickel-filtered Cu Ka radiation was employed in all experiments. The profiles were chart recorded automatically using a scan speed of 0.125 é per second in 2J (XRD GV_7600). The resulting powder diffraction pattern can easily be classified by mineral content using the DIFFRAC.sup.suite software packages EVA and SEARCH, based on reference patterns of the ICDD PDF 2 database (XRD LTM_7603). Quantitative analysis of diffraction data refers to the determination of amounts of different phases in a multi-phase sample and has been performed using the DIFFRACsuite software package TOPAS (XRD LTM_7604). In detail, quantitative analysis allows to determine structural characteristics and phase proportions with quantifiable numerical precision from the experimental data itself. This involves modelling the full diffraction pattern (Rietveld approach) such that the calculated pattern(s) duplicates the experimental one. The Rietveld method requires knowledge of the approximate crystal structure of all phases of interest in the pattern. However, the use of the whole pattern rather than a few select lines produces accuracy and precision much better than any single-peak-intensity based method.

Moisture Pick Up Susceptibility

[0293] The moisture pickup susceptibility of a material as referred to herein, is determined in mg moisture/g of solid, after exposure to an atmosphere of 10 and 85% relative humidity, respectively, for 2 hours at a temperature of +23 éC (ĕ 2 éC). For this purpose, the sample is first kept at an atmosphere of 10% relative humidity for 2 hours, then the atmosphere is changed to 85% relative humidity at which the sample is kept for another 2 hours, finally the atmosphere is changed to 10% of humidity for 30 minutes.

[0294] The weight increase is then used to calculate the moisture pick-up in mg moisture/g of sample.

[0295] The moisture pick up susceptibility in mg/g divided by the specific surface area in mg (calculated based on the specific surface area BET) corresponds to the ‘normalized moisture pick up susceptibility_ expressed in mg/m of sample.

Scanning Electron Microscope (SEM)

[0296] The prepared samples were examined by a Sigma VP field emission scanning electron microscope (Carl Zeiss AG, Germany) and a variable pressure secondary electron detector (VPSE) and/or secondary electron detector (SE) with a chamber pressure of about 50 Pa.

2. Starting Materials

2.1. Surface Treatment Agents

[0297]

TABLE-US-00001 TABLE 1 Surface treatment agents Surface treatment agent number Name Supplier Properties (1) n-Octadecyltriethoxysilane Gelest Purity >95%; (CAS: 7399-00-0) order number Refractive Index: SI06642.0 1.4386; Melting Point: 10-12éC; Flash Point: <150éC (2) 1H,1H,2H,2H- Sigma-Aldrich Purity: 97%; Perfluorodecyltriethoxysilane order number Refractive Index: 97% (CAS: 101947-16-4) CDS010752- 1.342; 250 mg Boiling Point: 209-230éC; Flash Point: >110éC (3) 1H,1H,2H,2H- Aldrich Purity: 98%; Perfluorooctyltriethoxysilane order number Refractive Index: (CAS: 51851-37-7) MK BX 9419V 1.344; Flash Point: 97éC

2.2. Mineral Pigments

[0298]

TABLE-US-00002 TABLE 2 Mineral pigment Normalized Moisture moisture pick up pick up BET surface susceptibility susceptibility d.sub.50 Humidity Chemical nature [m.sup.2/g] (mg/g) (mg/m.sup.2) [lm] [wt.-%] Hydromagnesite 62.07 57.46 0.92 5.26 3.51 (Used abbreviation in the text: HMG)

3. Experiments

Example 1 (Comparative)

[0299] 8 g of fresh HMG (dried at 100 éC overnight) was putted in a 250 mL beaker, then 54 g of distilled water was added. The slurry was heated up-to 90 éC, the system was kept under reflux to prevent the evaporation of the used solvent. In parallel, 0.34 g of the surface treatment agent No. 1, corresponding to a 0.0056 g/m.sup.2, was added in a 50 mL container to 3.20 g of Ethanol/H.sub.2O mixture of 1-to-1 ratio. The latter solution was heated up to 70 éC, then 530 .Math.L of a 10 wt.-% solution of KOH was added, the mixture was kept for 6 minutes. Finally, the solution containing the surface treatment agent No. 1 was added to the slurry and left under mixing for 30 minutes. The upgraded slurry was next filtrated under vacuum using cellulose based filters of (Whatman Rundfilter Art. Nr. 9060202, 90 mm, 589/2 No. 1 & 2). The filter cake was dried overnight at 110 éC, then deagglomerated manually using a mortar and a pestle.

Example 2 (Comparative)

[0300] 8 g of fresh HMG (dried at 100 éC overnight) was thermally treated at 300 éC for 2 hours, then putted in a 250 mL beaker with 54 g of distilled water. The slurry was heated up-to 90 éC, the system was kept under reflux to prevent the evaporation of the used solvent. In parallel, 0.40 g of the surface treatment agent No. 1, corresponding to a 0.0056 g/m.sup.2, was added in a 50 mL container to 3.70 g of Ethanol/H.sub.2O mixture of 1-to-1 ratio. The latter solution was heated up to 70 éC, then 615 .Math.L of a 10 wt.-% solution of KOH was added, the mixture was kept for 6 minutes. Finally, the solution containing the surface treatment agent No. 1 was added to the slurry and left under mixing for 30 min. The upgraded slurry was next filtrated under vacuum using cellulose based filters of (Whatman Rundfilter Art. Nr. 9060202, 90 mm, 589/2 No. 1 & 2). The filter cake was dried overnight at 110 éC, then deagglomerated manually using a mortar and a pestle.

Example 3 (Comparative)

[0301] 8 g of fresh HMG (dried at 100 éC overnight) was thermally treated at 4006 for 2 hours, then putted in a 250 mL beaker with 54 g of distilled water. The slurry was heated up-to 90 éC, the system was kept under reflux to prevent the evaporation of the used solvent. In parallel, 1.62 g of the surface treatment agent No. 1, corresponding to a 0.0056 g/m.sup.2, was added in a 50 mL container to 14.70 g of Ethanol/H.sub.2O mixture of 1-to-1 ratio. The latter solution was heated up to 70 éC, then 2.47 mL of a 10 wt.-% solution of KOH was added, the mixture was kept for 6 minutes. Finally, the solution containing the surface treatment agent No. 1 was added to the slurry and left under mixing for 30 min. The upgraded slurry was next filtrated under vacuum using cellulose based filters of (Whatman Rundfilter Art. Nr. 9060202, 90 mm, 589/2 No. 1 & 2). The filter cake was dried overnight at 110 éC, then deagglomerated manually using a mortar and a pestle.

Example 4 (Inventive)

[0302] 8 g of fresh HMG (dried at 100 é overnight) was thermally treated at 600 éC for 2 hours, then putted in a 250 mL beaker with 54 g of distilled water. The slurry was heated up-to 90 éC, the system was kept under reflux to prevent the evaporation of the used solvent. In parallel, 0.68 g of the surface treatment agent No. 1, corresponding to a 0.0056 g/m.sup.2, was added in a 50 mL container to 6.30 g of Ethanol/H.sub.2O mixture of 1-to-1 ratio. The latter solution was heated up to 70 éC, then 1.05 mL of a 10 wt.-% solution of KOH was added, the mixture was kept for 6 minutes. Finally, the solution containing the surface treatment agent No. 1 was added to the slurry and left under mixing for 30 min. The upgraded slurry was next filtrated under vacuum using cellulose based filters of (Whatman Rundfilter Art. Nr. 9060202, 90 mm, 589/2 No. 1 & 2). The filter cake was dried overnight at 110 éC, then deagglomerated manually using a mortar and a pestle.

Example 5 (Comparative)

[0303] 8 g of fresh HMG (dried at 100K overnight) was thermally treated at 900 éC for 2 hours, then putted in a 250 mL beaker with 54 g of distilled water. The slurry was heated up-to 90 éC, the system was kept under reflux to prevent the evaporation of the used solvent. In parallel, 0.23 g of the surface treatment agent No. 1, corresponding to a 0.0056 g/m.sup.2, was added in a 50 mL container to 2.10 g of Ethanol/H.sub.2O mixture of 1-to-1 ratio. The latter solution was heated up to 70 éC, then 350 .Math.L of a 10 wt.-% solution of KOH was added, the mixture was kept for 6 min. Finally, the solution containing the surface treatment agent No. 1 was added to the slurry and left under mixing for 30 min. The upgraded slurry was next filtrated under vacuum using cellulose based filters of (Whatman Rundfilter Art. Nr. 9060202, 90 mm, 589/2 No. 1 & 2). The filter cake was dried overnight at 110 éC, then deagglomerated manually using a mortar and a pestle.

Example 6 (Inventive)

[0304] 8 g of fresh HMG (dried at 100K overnight) was thermally treated at 600 é for 2 hours, then putted in a 250 mL beaker with 54 g of distilled water. The slurry was heated up-to 90 éC, the system was kept under reflux to prevent the evaporation of the used solvent. In parallel, 1.02 g of the surface treatment agent No. 2, corresponding to an iso-molar value of the surface treatment agent No. 1 in the Example 4, was added in a 50 mL container to 9.33 g of Ethanol/H.sub.2O mixture of 1-to-1 ratio. The latter solution was heated up to 70 éC, then 480 .Math.L of a 10 wt.-% solution of KOH was added, the mixture was kept for 6 min. Finally, the solution containing the surface treatment agent No. 2 was added to the slurry and left under mixing for 30 min. The upgraded slurry was next filtrated under vacuum using cellulose based filters of (Whatman Rundfilter Art. Nr. 9060202, 90 mm, 589/2 No. 1 & 2). The filter cake was dried overnight at 110 éC, then deagglomerated manually using a mortar and a pestle.

Example 7 (Inventive)

[0305] 8 g of fresh HMG (dried at 100K overnight) was thermally treated at 600 é for 2 hours, then putted in a 250 mL beaker with 54 g of distilled water. The slurry was heated up-to 90 éC, the system was kept under reflux to prevent the evaporation of the used solvent. In parallel, 0.87 g of the surface treatment agent No. 3, corresponding to an iso-molar value of the surface treatment agent No. 1 in the Example 4, was added in a 50 mL container to 7.96 g of Ethanol/H.sub.2O mixture of 1-to-1 ratio. The latter solution was heated up to 70 éC, then 480 .Math.L of a 10 wt.-% solution of KOH was added, the mixture was kept for 6 min. Finally, the solution containing the surface treatment agent No. 2 was added to the slurry and left under mixing for 30 min. The upgraded slurry was next filtrated under vacuum using cellulose based filters of (Whatman Rundfilter Art. Nr. 9060202, 90 mm, 589/2 No. 1 & 2). The filter cake was dried overnight at 110 éC, then deagglomerated manually using a mortar and a pestle.

Example 8 (Comparative)

[0306] 8 g of fresh HMG (dried at 100K overnight) was thermally treated at 600 é for 2 hours, then putted in a 250 mL beaker with 54 g of distilled water. The slurry was heated up-to 90 éC, the system was kept under reflux to prevent the evaporation of the used solvent. Finally, the slurry was filtrated under vacuum using cellulose based filters of (Whatman Rundfilter Art. Nr. 9060202, 90 mm, 589/2 No. 1 & 2). The filter cake was dried overnight at 110 éC, then deagglomerated manually using a mortar and a pestle.

Example 9 (Comparative)

[0307] 8 g of fresh HMG (dried at 100K overnight) was thermally treated at 600 é for 2 hours, then putted in a 250 mL beaker with 54 g of distilled water. The slurry was heated up-to 90 éC, the system was kept under reflux to prevent the evaporation of the used solvent. In parallel, 0.11 g of the surface treatment agent No. 1, corresponding to a 0.09 mg/m.sup.2, was added in a 50 mL container to 1.1 g of Ethanol/H.sub.2O mixture of 1-to-1 ratio. The latter solution was heated up to 70 éC, then 17.6 .Math.L of a 10 wt.-% solution of KOH was added, the mixture was kept for 6 minutes. Finally, the solution containing the surface treatment agent No. 1 was added to the slurry and left under mixing for 30 min. The upgraded slurry was next filtrated under vacuum using cellulose based filters of (Whatman Rundfilter Art. Nr. 9060202, 90 mm, 589/2 No. 1 & 2). The filter cake was dried overnight at 110 éC, then deagglomerated manually using a mortar and a pestle.

Example 10 (Comparative)

[0308] 8 g of fresh HMG (dried at 100K overnight) was thermally treated at 600 é for 2 hours, then putted in a 250 mL beaker with 54 g of distilled water. The slurry was heated up-to 90 éC, the system was kept under reflux to prevent the evaporation of the used solvent. In parallel, 0.13 g of the surface treatment agent No. 1, corresponding to a 0.11 mg/m.sup.2, was added in a 50 mL container to 1.1 g of Ethanol/H.sub.2O mixture of 1-to-1 ratio. The latter solution was heated up to 70 éC, then 17.6 .Math.L of a 10 wt.-% solution of KOH was added, the mixture was kept for 6 minutes. Finally, the solution containing the surface treatment agent No. 1 was added to the slurry and left under mixing for 30 min. The upgraded slurry was next filtrated under vacuum using cellulose based filters of (Whatman Rundfilter Art. Nr. 9060202, 90 mm, 589/2 No. 1 & 2). The filter cake was dried overnight at 110 éC, then deagglomerated manually using a mortar and a pestle.

Example 11 (Comparative)

[0309] 8 g of fresh HMG (dried at 100K overnight) was thermally treated at 600 é for 2 hours, then putted in a 250 mL beaker with 54 g of distilled water. The slurry was heated up-to 90 éC, the system was kept under reflux to prevent the evaporation of the used solvent. In parallel, 0.23 g of the surface treatment agent No. 1, corresponding to a 1.99 mg/m.sup.2, was added in a 50 mL container to 2.1 g of Ethanol/H.sub.2O mixture of 1-to-1 ratio. The latter solution was heated up to 70 éC, then 350 .Math.L of a 10 wt.-% solution of KOH was added, the mixture was kept for 6 minutes. Finally, the solution containing the surface treatment agent No. 1 was added to the slurry and left under mixing for 30 min. The upgraded slurry was next filtrated under vacuum using cellulose based filters of (Whatman Rundfilter Art. Nr. 9060202, 90 mm, 589/2 No. 1 & 2). The filter cake was dried overnight at 110 éC, then deagglomerated manually using a mortar and a pestle.

Example 12 (Comparative)

[0310] 8 g of fresh HMG (dried at 100 éC overnight) was thermally treated at 600 é for 2 hours, then putted in a 250 mL beaker with 54 g of distilled water. The slurry was heated up-to 90 éC, the system was kept under reflux to prevent the evaporation of the used solvent. In parallel, 0.92 g of the surface treatment agent No. 1, corresponding to a 7.99 mg/m.sup.2, was added in a 50 mL container to 8.4 g of Ethanol/H.sub.2O mixture of 1-to-1 ratio. The latter solution was heated up to 70 éC, then 1410 .Math.L of a 10 wt.-% solution of KOH was added, the mixture was kept for 6 minutes. Finally, the solution containing the surface treatment agent No. 1 was added to the slurry and left under mixing for 30 min. The upgraded slurry was next filtrated under vacuum using cellulose based filters of (Whatman Rundfilter Art. Nr. 9060202, 90 mm, 589/2 No. 1 & 2). The filter cake was dried overnight at 110 éC, then deagglomerated manually using a mortar and a pestle.

Example 13 (Comparative)

[0311] 8 g of fresh HMG (dried at 100K overnight) was thermally treated at 600 é for 2 hours, then putted in a 250 mL beaker with 54 g of distilled water. The slurry was heated up-to 90 éC, the system was kept under reflux to prevent the evaporation of the used solvent. In parallel, 2.07 g of the surface treatment agent No. 1, corresponding to a 17.99 mg/m.sup.2, was added in a 50 mL container to 18.9 g of Ethanol/H.sub.2O mixture of 1-to-1 ratio. The latter solution was heated up to 70 éC, then 3170 .Math.L of a 10 wt.-% solution of KOH was added, the mixture was kept for 6 minutes. Finally, the solution containing the surface treatment agent No. 1 was added to the slurry and left under mixing for 30 min. The upgraded slurry was next filtrated under vacuum using cellulose based filters of (Whatman Rundfilter Art. Nr. 9060202, 90 mm, 589/2 No. 1 & 2). The filter cake was dried overnight at 110 éC, then deagglomerated manually using a mortar and a pestle.

TABLE-US-00003 TABLE 3 Summary and results. Thermal Base for BET of the Normalized treatment Surface hydrolysing surface Moisture Moisture temperature Surface treatment surface treated pick up pick up Mineral (TéC) for 2 treatment agent treatment HMG susceptibility susceptibility d.sub.50 Example pigment hours agent No. dosage .sup.a) agent (m.sup.2/g) (mg/g) (mg/m.sup.2) (.Math. m)  1 (comparative) HMG — 1 5.6 KOH 52.39 45.13 0.86 5.26  2 (comparative) HMG 300 1 5.6 KOH 63.96 57.32 0.89 —  3 (comparative) HMG 400 1 5.6 KOH 57.08 66.08 1.15 —  4 (inventive) HMG 600 1 5.6 KOH 36.90 3.60 0.09 3.75  5 (comparative) HMG 900 1 5.6 KOH 19.15 4.98 0.25 —  6 (inventive) HMG 600 2 — .sup.b) KOH 41.53 3.01 0.072 4.59  7 (inventive) HMG 600 3 — .sup.b) KOH 52.49 3.22 0.061 1.98  8 (Comparative) HMG 600 — —  — 60.50 32.19 0.53 —  9 (Comparative) HMG 600 1 0.09 KOH 68.43 30.71 0.448 10 (Comparative) HMG 600 1 0.11 KOH 41.62 18.36 0.441 11 (Comparative) HMG 600 1 1.99 KOH 56.11 18.03 0.32 12 (Comparative) HMG 600 1 7.99 KOH 52.46 8.84 0.17 13 (Comparative) HMG 600 1 17.99 KOH 26.11 13.75 0.52 .sup.a) Ratio: Surface treatment agent (mg)/BET of the thermally treated but non-upgraded HMG (m.sup.2/g)  ; .sup.b) The amount of surface treatment agent No. 2 and No. 3 was calculated based on an iso-molar value calculated from the Example 4. indicates data missing or illegible when filed

TABLE-US-00004 TABLE 4 Concentration of the surface treatment agent in ethanol/water mixture in the examples. Surface treatment Example agent [g] Ethanol/Water [g] concentration 1 0.34 3.2 0.11 2 0.4 3.7 0.11 3 1.62 14.7 0.11 4 0.68 6.3 0.11 5 0.23 2.1 0.11 6 1.02 9.33 0.11 7 0.87 7.96 0.11 9 0.11 1.1 0.10 10 0.13 1.1 0.12 11 0.23 2.1 0.11 12 0.92 8.4 0.11 13 2.07 18.9 0.11

[0312] As can be seen from table 4 in all the examples nearly the same concentration of surface treatment agent in ethanol/water mixture has been used.

[0313] The data of examples 4, 6 and 7 (Table 3) show that the surface-treated magnesium hydroxide comprising material has a large surface area in combination with a low moisture pick up susceptibility when the process according to the present invention is used.

[0314] As can be seen in Table 3 as well as from FIG. 1 the surface-treated magnesium hydroxide-comprising materials that have been prepared by the inventive process have a normalized moisture pick up susceptibility of between 0.061 to 0.09 m Contrary to that, surface-treated magnesium hydroxide-comprising materials that have been prepared with the same surface treatment agent than used in example 4 but have been calcined at temperatures below 450 éC or above 750 éC have much higher normalized moisture pickup susceptibilities of between 0.25 to 1.15 m

[0315] Therefore, it has been shown that it is possible to prepare a surface-treated magnesium hydroxide-comprising material by the inventive process that has a large surface area in combination with a low moisture pick up susceptibility.