Alkoxysilane treatment of a calcium carbonate-comprising material

Abstract

Some embodiments of the invention include a process for the surface-treatment of a calcium carbonate-comprising material, a surface-treated calcium carbonate-comprising material obtained by such a process and the use of such a surface-treated calcium carbonate-comprising material.

Claims

1. A process for surface-treatment of a calcium carbonate-comprising material, the process comprising the steps of: a) providing an aqueous suspension of at least one calcium carbonate-comprising material having a solids content in the range from 5 to 90 wt.-%, based on the total weight of the aqueous suspension, b) adjusting the pH-value of the aqueous suspension of step a) to a range from 7.5 to 12, c) adding at least one surface-treatment agent to the aqueous suspension obtained in step b) in an amount ranging from 0.05 to 10 mg surface treatment agent per m.sup.2 of the surface area of the at least one calcium carbonate-comprising material as provided in step a), wherein the at least one surface treatment agent is a compound according to Formula (I), ##STR00006## 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 and a benzoyl group, and u, v and w are independently from each other an integer from 0 to 24, d) mixing the aqueous suspension obtained in step c) for a period of time ranging from 1 second to 60 minutes at a temperature in the range from 30 to 120° C., and e) drying the aqueous suspension during or after step d) at a temperature in the range from 40 to 160° C. at ambient or reduced pressure until the moisture content of a surface-treated calcium carbonate-comprising material is in the range from 0.001 to 20 wt.-%, based on the total weight of the surface-treated calcium carbonate-comprising material, wherein (i) the surface-treated calcium carbonate-comprising material has a hydrophobicity of below 1.7:1 volumetric ratio of water:ethanol measured at 23° C. (±2° C.) with a sedimentation method and (ii) at least 68 wt % of the surface treatment agent added in step c) is bound to the calcium carbonate comprising material.

2. The process according to claim 1, wherein the pH-value in step b) is adjusted to the range from 7.5 to 12 by adding at least one base.

3. The process according to claim 2, wherein the at least one base of step b) is selected from the group consisting of calcium hydroxide, magnesium hydroxide, calcium hydrogen carbonate, sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonium hydroxide, primary amines, secondary amines and tertiary amines and mixtures thereof.

4. The process according to claim 1, wherein the at least one calcium carbonate-comprising material is selected from the group consisting of ground calcium carbonate, preferably marble, limestone, dolomite, chalk, precipitated calcium carbonate, vaterite, calcite, aragonite, surface-reacted calcium carbonate, wherein the surface-reacted calcium carbonate is a reaction product of natural ground or precipitated calcium carbonate with carbon dioxide and one or more H.sub.3O.sup.+ ion donors in an aqueous medium, wherein the carbon dioxide is formed in situ by a H.sub.3O.sup.+ ion donor treatment and/or is supplied from an external source and mixtures thereof.

5. The process according to claim 1, wherein mechanical dewatering, centrifugation or filtration, is carried out during step d), and/or the surface-treated calcium carbonate-comprising material is washed with water during and/or after step d).

6. The process according to claim 1, wherein the process comprises a further step f) of adding at least one base to the aqueous suspension during or after step c) to readjust the pH-value to the range from 7.5 to 12.

7. The process according to claim 6, wherein the at least one base added in step f) is selected from the group consisting of lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide and mixtures thereof.

8. The process according to claim 1, wherein (a) 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 (b) the at least one surface-treatment agent is selected from triethoxysilane, trimethoxysilane, triethoxyvinylsilane, trimethoxyvinylsilane, 3-(2,3-epoxypropoxy)propyl-trimethoxysilane, triethoxysilylpropyltetrasulphide, 3-mercaptopropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-aminopropyltriethoxysilane, methyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, dodecyltriethoxysilane, n-octadecyltriethoxysilane, phenyltriethoxysilane, 3-butenyltriethoxysilane and combinations thereof.

9. The process according to claim 1, wherein the solids content of the aqueous suspension of step a) is in the range from 10 to 70 wt.-%, based on the total weight of the aqueous suspension; and/or the calcium carbonate-comprising material is a surface-reacted calcium carbonate and the specific surface area of the surface-reacted calcium carbonate as measured by the BET nitrogen method according to ISO 9277:2010 is in the range from 1 to 250 m.sup.2/g or the calcium carbonate-comprising material is a ground calcium carbonate or a precipitated calcium carbonate and the specific surface area of the ground calcium carbonate or the precipitated calcium carbonate as measured by the BET nitrogen method according to ISO 9277:2010 is in the range from 1 to 100 m.sup.2/g.

10. The process according to claim 1, wherein the pH-value is adjusted in process step b) to the range from 7.8 to 11.5.

11. The process according to claim 1, wherein the amount of the at least one surface-treatment agent added in step c) is in the range from 0.07 to 9 mg surface-treatment agent per m.sup.2 of the surface area of the calcium carbonate-comprising material.

12. The process according to claim 1, wherein step d) is carried out at a temperature in the range from 45 to 115° C.

13. The process according to claim 1, wherein step e) is carried out until the moisture content of the surface-treated calcium carbonate-comprising material is in the range from 0.005 to 15 wt.-%, based on the total weight of the surface-treated calcium carbonate-comprising material.

14. The process according to claim 1, wherein step e) is carried out at a temperature in the range from 50 to 155° C.

15. The process according to claim 1, wherein the process comprises a further step after or during step e) of deagglomerating the surface-treated calcium carbonate-comprising material of step d) or e).

16. The process according to claim 1, wherein all process steps are fully or partially batch or continuous processes.

Description

EXAMPLES

1 Measurement Methods

(1) In the following the measurement methods implemented in the examples are described.

(2) Moisture Pick Up Susceptibility

(3) The moisture pick up susceptibility of a material as referred to herein is determined in mg moisture/g after exposure to an atmosphere of 10 and 85% relative humidity, respectively, for 2.5 hours at a temperature of +23° C. (±2° C.). For this purpose, the sample is first kept at an atmosphere of 10% relative humidity for 2.5 hours, then the atmosphere is changed to 85% relative humidity at which the sample is kept for another 2.5 hours. The weight increase between 10 and 85% relative humidity is then used to calculate the moisture pick-up in mg moisture/g of sample.

(4) The moisture pick up susceptibility in mg/g divided by the specific surface area in m.sup.2/g (calculated based on the specific surface area BET) corresponds to the “normalized moisture pick up susceptibility” expressed in mg/m.sup.2 of sample.

(5) Volatile Onset Temperature

(6) The “volatile onset temperature” has been determined by analysis of the thermogravimetric analysis (TGA) curve. TGA analysis described hereafter—begin to evolve, as observed on a TGA curve, plotting the mass of remaining sample (y-axis) as a function of temperature (x-axis), the preparation and interpretation of such a curve being defined hereafter. TGA analytical methods provide information regarding losses of mass and volatile onset temperatures with great accuracy, and is common knowledge; it is, for example, described in “Principles of Instrumental analysis”, fifth edition, Skoog, Holler, Nieman, 1998 (first edition 1992) in Chapter 31 pages 798 to 800, and in many other commonly known reference works. TGA is performed using a Mettler Toledo TGA 851 based on a sample of 500±50 mg and scanning temperatures from 25 to 550° C. at a rate of 20° C./min under an air flow of 70 ml/min.

(7) The skilled man will be able to determine the “volatile onset temperature” by analysis of the TGA curve as follows: the first derivative of the TGA curve is obtained and the inflection points thereon between 150 and 350° C. are identified. Of the inflection points having a tangential slope value of greater than 45° relative to a horizontal line, the one having the lowest associated temperature above 150° C. is identified. The temperature value associated with this lowest temperature inflection point of the first derivative curve is the “volatile onset temperature”.

(8) Humidity of Calcium Carbonate

(9) A 10 g powder sample has been heated in an oven at 150° C. until the mass is constant for 20 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.

(10) Hydrophobicity

(11) Various mixtures of different water and ethanol have been prepared. The reported data are based on volume/volume ratios (volume water/volume ethanol). The different steps are listed hereafter: a) A 100 ml glass beaker has been filled with 50 ml of a water/ethanol mixture. b) Through a sieve (mesh size: approximately 1 mm) 0.5 g of the coated mineral material has been added on the top of the liquid surface. c) After 30 s the amount of material which sank to the bottom of the beaker was identified (visual estimation).

(12) The procedure has been repeated with different water/ethanol blends until the composition has been identified where approximately 50 wt.-% of the material sinks to the bottom of the beaker.

(13) pH

(14) The pH of a suspension is measured at 25° C. using a Mettler Toledo Seven Easy pH meter and a Mettler Toledo InLab® 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° C. (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).

(15) Solids Content

(16) The solids content (also known as “dry weight”) was determined using a Moisture Analyser HR73 from the company Mettler-Toledo, Switzerland, with the following settings: temperature of 120° C., automatic switch off 3, standard drying, 5 to 20 g of product.

(17) Specific Surface Area BET

(18) 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 250° C. for a period of 30 min. Prior to such measurements, the sample is filtered within a Buchner funnel, rinsed with deionised water and dried overnight at 90 to 100° C. in an oven. Subsequently the dry cake is ground thoroughly in a mortar and the resulting powder placed in a moisture balance at 130° C. until a constant weight is reached. The specific surface area is measured before any surface treatment. We assume that the surface treatment does not alter the BET surface area.

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

(20) Weight median grain diameter and grain diameter mass distribution of a particulate material were determined via the sedimentation process, i.e. an analysis of sedimentation behaviour in a gravitational field. The measurement was made with a Sedigraph™ 5100.

(21) The volume-based median particle diameter of the surface-reacted calcium carbonate was determined by using a Malvern Mastersizer 2000.

(22) The processes and instruments are known to the skilled person and are commonly used to determine grain size of fillers and pigments. The measurements were 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 ultrasound.

(23) Intra-Particle Intruded Specific Pore Volume

(24) The intra-particle intruded specific pore volume has been calculated from a mercury intrusion porosimetry measurement using a Micromeritics Autopore IV 9500 mercury porosimeter having a maximum applied pressure of mercury 414 MPa (60 000 psi), equivalent to a Laplace throat diameter of 0.004 μm (˜nm). The equilibration time used at each pressure step is 20 s. The sample material is sealed in a 5 cm.sup.3 chamber powder penetrometer for analysis. The data are corrected for mercury compression, penetrometer expansion and sample material compression using the software Pore-Comp (Gane, P. A. C., Kettle, J. P., Matthews, G. P. and Ridgway, C. J., “Void Space Structure of Compressible Polymer Spheres and Consolidated Calcium Carbonate Paper-Coating Formulations”, Industrial and Engineering Chemistry Research, 35(5), 1996, p 1753-1764).

(25) The total pore volume seen in the cumulative intrusion data can be separated into two regions with the intrusion data from 214 μm down to about 1-4 μm showing the coarse packing of the sample between any agglomerate structures contributing strongly. Below these diameters lies the fine interparticle packing of the particles themselves. If they also have intraparticle pores, then this region appears bi modal. The sum of these three regions gives the total overall pore volume of the powder, but depends strongly on the original sample compaction/settling of the powder at the coarse pore end of the distribution. The sum of these three regions gives the total overall pore volume of the powder, but depends strongly on the original sample compaction/settling of the powder at the coarse pore end of the distribution.

(26) By taking the first derivative of the cumulative intrusion curve the pore size distributions based on equivalent Laplace diameter, inevitably including pore-shielding, are revealed. The differential curves clearly show the coarse agglomerate pore structure region, the interparticle pore region and the intraparticle pore region, if present. Knowing the intraparticle pore diameter range it is possible to subtract the remainder interparticle and interagglomerate pore volume from the total pore volume to deliver the desired pore volume of the internal pores alone in terms of the pore volume per unit mass (specific pore volume). The same principle of subtraction, of course, applies for isolating any of the other pore size regions of interest.

(27) XRF Method

(28) Tablets were produced by fusing the surface-treated calcium carbonate-comprising mineral and lithium tetraborate (Li.sub.2B.sub.4O.sub.7).

(29) The elemental composition of the sample tablets was measured by sequential, wavelength dispersive X-ray fluorescence.

2 Starting Materials

(30) 2.1 Surface Treatment Agents

(31) TABLE-US-00001 TABLE 1 Surface treatment agents. Surface treatment agent number Name Supplier Properties (1) Triethoxyvinylsilane Aldrich Purity 97% (CAS: 78-08-0) order Refractive number Index: 1.3960 175560 Flash Point: 44° C. (2) n-Octadecyltriethoxysilane Gelest Purity >95% (CAS: 7399-00-0) order Refractive number Index: 1.4386 SIO6642.0 Melting Point: 10-12° C. Flash Point: <150° C. (3) (3-Aminopropyl)triethoxy- Aldrich Purity >98% silane order Refractive (CAS: 919-30-2) number Index: 1.4225 A3648 Flash Point: 104° C. (4) Phenyltriethoxysilane Gelest order Purity >95% (CAS: 780-69-8) number Refractive SIP6821.0 Index: 1.4718 Flash Point: 96° C. (5) 5,6-Epoxyhexyltriethoxysilane Gelest order Purity >97% (CAS: 86138-01-4) number Refractive SIE4675.0 Index: 1.4254 Flash Point: 99° C. (6) Hydroxymethyltriethoxysilane Gelest order Purity >50% (CAS: 162781-70-6) number Boiling Point: SIH6175.0 76° C. - initial (ethanol) Flash Point: 15° C. (7) [Hydroxy(polyethyleneoxy)propyl]triethoxysilane Gelest order Purity >50% (8-12 EO) (CAS: not number Refractive found) SIH6188.0 Index: 1.401 Boiling Point: 76° C. - initial (ethanol) Flash Point: 12° C. (8) (Heptadecafluoro-1,1,2,2,- Gelest order Purity >95% tetrahydrodecyl)triethoxysilane number Refractive (CAS: 101947-16-4) SIH5841.2 Index: 1.3419 Flash Point: >85° C.
Hydrolysis of the Treatment Agent:

(32) The surface treatment agent was diluted with an ethanol/water (1/1, wt.-%/wt.-%) blend to a concentration of 5 wt.-% and heated under stirring to 70-80° C. Under continuous stirring the heated emulsion was treated with 5 wt.-% solid sodium hydroxide (quantity dry sodium hydroxide based on the quantity of surface treatment agent) and stirred for approximately 5 min. The hot emulsion was then used directly for the surface treatment trial.

(33) 2.2 Mineral Pigments

(34) TABLE-US-00002 TABLE 2 Mineral pigments. Intra-particle intruded specific pore BET Chemical volume surface d.sub.50 Humidity Sample nature (cm.sup.3/g).sup.a [mg/m.sup.2] [μm] [wt.-%] A Surface-reacted 0.864 139 4.53 6.77 calcium carbonate B Ground calcium — 3.3 1.7 0.03 carbonate (marble) .sup.afor the pore diameter range of 0.004 to 0.23 μm.

3 Experiments

Example 1 (Comparative)

(35) 400 g of surface-reacted calcium carbonate A was mixed for 10 min at 1 000 rpm and 120° C. in the Somakon mixer (Somakon Verfahrenstechnik UG; Germany). 2 wt.-% of surface treatment agent 1 was added and the blend was mixed for further 10 min at 120° C. and 1 000 rpm. After cooling down to room temperature the sample was removed from the mixer and stored in a sealed container.

(36) As measured by XRF 93 wt.-% of surface treatment agent 1 was immobilised on the surface.

(37) The treated sample was further washed by diluting with a mixture of ethanol/water (1/1, wt.-%/wt.-%) to a solids content of 20 wt.-% and heating it up to 80° C. The hot suspension was filtered and rinsed once with 100 ml of the fresh ethanol/water mixture. The washed sample was dried at 120° C. for 7 hours.

(38) Subsequent XRF analysis revealed that only 33 wt.-% of the treatment agent was remaining on the sample surface. This means, the surface treatment agent is only insufficiently attached to the carbonate surface.

Example 2 (Inventive)

(39) 8.0 g of surface treatment agent number 3 is diluted with an ethanol/water (1/1, wt.-%/wt.-%) blend to a concentration of 5 wt.-% and heated under stirring to 70-80° C. Under continuous stirring the heated emulsion is treated with 5 wt.-% solid sodium hydroxide (quantity dry sodium hydroxide based on the quantity of surface treatment agent) and stirred for approximately 5 min.

(40) 400 g of surface-reacted calcium carbonate A was mixed with 1 600 g deionized water in order to obtain a suspension of approximately 20 wt.-%. The suspension was stirred with a VISCO JET CRACK of 12 cm diameter (300 to 500 rpm; VISCO JET Rührsysteme GmbH, Germany) at room temperature. The pH was adjusted with calcium hydroxide (solid powder) to a value of 10.5. The pH adjustment was stopped when the pH was stable within ±0.2 units for 5 min, the reported pH values are the end values.

(41) The suspension was heated to 90° C. (±5° C.) under constant stirring. The hot emulsion of the treatment additive was added over a period of approximately 1 min. The blend was further stirred for 30 min at 90° C. The suspension was dried in an oven for 10 hours at 120° C. to a moisture content of below 1 wt.-%. The resulting dry crumbles were de-agglomerated in an IKA A 11 basic analytical mill for 1 min and stored afterwards in a sealed container.

(42) As measured by XRF 80 wt.-% of surface treatment agent 3 was immobilised on the mineral surface.

(43) The treated sample was further washed by diluting with a mixture of ethanol/water (1/1, wt.-%/wt.-%) to a solids content of 20 wt.-% and heated to 80° C. The hot suspension was filtered and rinsed once with 100 ml of the fresh ethanol/water mixture. The washed sample was dried at 120° C. for 7 hours.

(44) Subsequent XRF analysis revealed that 85 wt.-% of the treatment agent was remaining on the sample surface. The treatment agent is well attached to the carbonate surface.

Example 3 (Comparative)

(45) 400 g of surface-reacted calcium carbonate A was mixed with 1 600 g deionized water in order to obtain a suspension of approximately 20 wt.-%. The suspension was stirred with a VISCO JET CRACK steered of 12 cm diameter (300 to 500 rpm; VISCO JET Rührsysteme GmbH, Germany) at room temperature. The pH was adjusted with calcium hydroxide (solid powder) to a value of 10.5. The pH adjustment was stopped when the pH was stable within ±0.2 units for 5 min, the reported pH values are the end values.

(46) The suspension was heated to 90° C. (±5° C.) under constant stirring. 4 wt.-% of surface treatment agent 2 was added over a period of approximately 1 min. The blend was further stirred for 30 min at 90° C. The suspension was dried in an oven for 10 h at 120° C. to a moisture content of below 1 wt.-%. The resulting dry crumbles were deagglomerated in an IKA A 11 basic analytical mill for 1 min and stored afterwards in a sealed container.

(47) Hydrophobicity measurements of the dried powder showed that in a water/ethanol blend of 90/10 volume %/volume % 50 wt.-% of the material sank down to the bottom.

Example 4 (Inventive)

(48) 16.0 g of the surface treatment agent number 2 was diluted with an ethanol/water (1/1, wt.-%/wt.-%) blend to a concentration of 5 wt.-% and heated under stirring to 70-80° C. Under continuous stirring the heated emulsion is treated with 5 wt.-% solid sodium hydroxide (quantity dry sodium hydroxide based on the quantity of surface treatment agent) and stirred for approximately 5 min.

(49) 400 g of surface-reacted calcium carbonate A was mixed with 1 600 g deionized water in order to obtain a suspension of approximately 20 wt.-%. The suspension was stirred with a VISCO JET CRACK steered of 12 cm diameter (300 to 500 rpm; VISCO JET Rührsysteme GmbH, Germany) at room temperature. The pH was adjusted with calcium hydroxide (solid powder) to a value of 10.5. The pH adjustment was stopped when the pH was stable within ±0.2 units for 5 min, the reported pH values are the end values.

(50) The suspension was heated to 90° C. (±5° C.) under constant stirring. The hydrolysed surface treatment agent 2 was added over a period of approximately 1 min. The blend was further stirred for 30 min at 90° C. The suspension was dried in an oven for 10 hours at 120° C. to a moisture content of below 1 wt.-%. The resulting dry crumbles were de-agglomerated in an IKA A 11 basic analytical mill for 1 min and stored afterwards in a sealed container.

(51) Hydrophobicity measurements of the dried powder showed that in a water ethanol blend of 55/45 volume %/volume % 50 wt.-% of the material sank down to the bottom.

Example 5 (Inventive)

(52) 2.0 g of surface treatment agent number 2 is diluted with an ethanol/water (1/1, wt.-%/wt.-%) blend to a concentration of 5 wt.-% and heated under stirring to 70-80° C. Under continuous stirring the heated emulsion is treated with 5 wt.-% solid sodium hydroxide (quantity dry sodium hydroxide based on the quantity of surface treatment agent) and stirred for approximately 5 min.

(53) 400 g of ground calcium carbonate B was mixed with 1 600 g deionized water in order to obtain a suspension of approximately 20 wt.-%. The suspension was stirred with a VISCO JET CRACK steered of 12 cm diameter (300 to 500 rpm; VISCO JET Rührsysteme GmbH, Germany) at room temperature. The pH was adjusted with calcium hydroxide (solid powder) to a value of 10.5. The pH adjustment was stopped when the pH was stable within ±0.2 units for 5 min, the reported pH values are the end values.

(54) The suspension was heated to 90° C. (±5° C.) under constant stirring. Hydrolysed surface treatment agent 2 was added over a period of approximately 1 min. The blend was further stirred for 30 min at 90° C. The suspension was dried in an oven for 10 hours at 120° C. to a moisture content of below 1 wt.-%. The resulting dry crumbles were de-agglomerated in an IKA A 11 basic analytical mill for 1 min and stored afterwards in a sealed container.

(55) Hydrophobicity measurements of the dried powder showed that in a water ethanol blend of 55/45 volume %/volume % 50 wt.-% of the material sank down to the bottom. The water pick-up was 3.8 mg/g.

(56) The treated sample was further washed mixed with an ethanol/water (1/1, wt. %/wt.-%) to a solids content of 20 wt.-% and heating it up to 80° C. The hot suspension was filtered and rinsed once with fresh ethanol/water. The washed sample was dried at 120° C. for 7 hours.

(57) After the washing step, the water pick-up was 0.8 mg/g. In a 65/35 water/ethanol blend (volume %/volume %) 50 wt.-% of the material sank down.

Example 6 (Inventive)

(58) 4.0 g of the surface treatment agent number 2 is diluted with an ethanol/water (1/1, wt.-/wt.-%) blend to a concentration of 5 wt.-% and heated under stirring to 70-80° C. Under continuous stirring the heated emulsion is treated with 5 wt.-% solid sodium hydroxide (quantity dry sodium hydroxide based on the quantity of surface treatment agent) and stirred for approximately 5 min.

(59) 400 g of ground calcium carbonate B was mixed with 1 600 g deionized water in order to obtain a suspension of approximately 20 wt.-%. The suspension was stirred with a VISCO JET CRACK steered of 12 cm diameter (300 to 500 rpm; VISCO JET Rührsysteme GmbH, Germany) at room temperature. The pH was adjusted with calcium hydroxide (solid powder) to a value of 10.5. The pH adjustment was stopped when the pH was stable within ±0.2 units for 5 min, the reported pH values are the end values.

(60) The suspension was heated to 90° C. (±5° C.) under constant stirring. Hydrolysed surface treatment agent 2 was added over a period of approximately 1 min. The blend was further stirred for 30 min at 90° C. The suspension was dried in an oven for 10 hours at 120° C. to a moisture content of below 1 wt.-%. The resulting dry crumbles were de-agglomerated in an IKA A 11 basic analytical mill for 1 min and stored afterwards in a sealed container.

(61) Hydrophobicity measurements of the dried powder showed that in a water ethanol blend of 50/50 volume %/volume % 50 wt.-% of the material sank down to the bottom. The water pick-up was 2.8 mg/g.

(62) The treated sample was further washed mixed with an ethanol/water (1/1, wt.-%/wt.-%) blend to a solids content of 20 wt.-% and heating it up to 80° C. The hot suspension was filtered and rinsed once with fresh ethanol/water. The washed sample was dried at 120° C. for 7 hours.

(63) After the washing step, the water pick-up was 0.5 mg/g. In a 50/50 water/ethanol blend (volume-%/volume-%) 50 wt.-% of the material sank down.

Example 7 (Comparative)

(64) 400 g of ground calcium carbonate B was mixed for 10 min at 1 000 rpm and 120° C. in the Somakon mixer (Somakon Verfahrenstechnik UG; Germany). 2 wt.-% of the surface treatment agent 2 was added and the blend was mixed for further 10 min at 120° C. and 1 000 rpm. After cooling down to room temperature the sample was removed from the mixer and stored in a sealed container.

(65) Hydrophobicity measurements of the dried powder showed that 50 wt.-% of the material sank down to the bottom in a water ethanol blend of 65/35 volume %/volume %.

Example 8 (Inventive)

(66) 16.0 g of the surface treatment agent number 4 was diluted with an ethanol/water (1/1, wt.-%/wt.-%) blend to a concentration of 5 wt.-% and heated under stirring to 70-80° C. Under continuous stirring the heated emulsion is treated with 2.5 wt.-% solid potassium hydroxide (quantity dry potassium hydroxide based on the quantity of surface 4 treatment agent) and stirred for approximately 5 min.

(67) 400 g of dry ground calcium carbonate B was mixed with 1 600 g deionized water in order to obtain a suspension of approximately 20 wt.-%. The suspension was stirred with a VISCO JET CRACK steered of 12 cm diameter (300 to 500 rpm; VISCO JET Rührsysteme GmbH, Germany) at room temperature.

(68) The suspension was heated to 90° C. (±5° C.) under constant stirring. 2 wt.-% of hydrolized surface treatment agent 4 was added over a period of approximately 1 min. The blend was further stirred for 30 min at 90° C. The suspension was dried in an oven for 10 h at 120° C. to a moisture content of below 1 wt.-%. The resulting dry crumbles were deagglomerated in an IKA A 11 basic analytical mill for 1 min and stored afterwards in a sealed container.

(69) The treated sample was further washed mixed with an ethanol/water (1/1, wt.-%/wt.-%) blend to a solids content of 20 wt.-% and heating it up to 80° C. The hot suspension was filtered and rinsed once with fresh ethanol/water. The washed sample was dried at 120° C. for 7 hours.

(70) Subsequent XRF analysis revealed that 74 wt.-% of the treatment agent was remaining on the sample surface. The treatment agent is well attached to the carbonate surface.

Example 9 (Inventive)

(71) 16.0 g of the surface treatment agent number 5 was diluted with an ethanol/water (1/1, wt.-%/wt.-%) blend to a concentration of 5 wt.-% and heated under stirring to 70-80° C. Under continuous stirring the heated emulsion is treated with 2.14 wt.-% solid potassium hydroxide (quantity dry potassium hydroxide based on the quantity of surface 5 treatment agent) and stirred for approximately 5 min.

(72) 400 g of dry ground calcium carbonate B was mixed with 1 600 g deionized water in order to obtain a suspension of approximately 20 wt.-%. The suspension was stirred with a VISCO JET CRACK steered of 12 cm diameter (300 to 500 rpm; VISCO JET Rührsysteme GmbH, Germany) at room temperature. The pH was adjusted with calcium hydroxide (aqueous solution) to a value of 9.0. The pH adjustment was stopped when the pH was stable within ±0.2 units for 5 min, the reported pH values are the end values.

(73) The suspension was heated to 90° C. (±5° C.) under constant stirring. 2 wt.-% of hydrolysed surface treatment agent 5 was added over a period of approximately 1 min. The blend was further stirred for 30 min at 90° C. The suspension was dried in an oven for 10 h at 120° C. to a moisture content of below 1 wt.-%. The resulting dry crumbles were deagglomerated in an IKA A 11 basic analytical mill for 1 min and stored afterwards in a sealed container.

(74) The treated sample was further washed mixed with an ethanol/water (1/1, wt.-%/wt.-%) blend to a solids content of 20 wt.-% and heating it up to 80° C. The hot suspension was filtered and rinsed once with fresh ethanol/water. The washed sample was dried at 120° C. for 7 hours.

(75) Subsequent XRF analysis revealed that 79 wt.-% of the treatment agent was remaining on the sample surface. The treatment agent is well attached to the carbonate surface.

Example 10 (Inventive)

(76) 16.0 g of the surface treatment agent number 6 was diluted with an ethanol/water (1/1, wt.-%/wt.-%) blend to a concentration of 5 wt.-% and heated under stirring to 70-80° C. Under continuous stirring the heated emulsion is treated with 2.9 wt.-% solid potassium hydroxide (quantity dry potassium hydroxide based on the quantity of surface 6 treatment agent) and stirred for approximately 5 min.

(77) 400 g of dry ground calcium carbonate B was mixed with 1 600 g deionized water in order to obtain a suspension of approximately 20 wt.-%. The suspension was stirred with a VISCO JET CRACK steered of 12 cm diameter (300 to 500 rpm; VISCO JET Rührsysteme GmbH, Germany) at room temperature. The pH was adjusted with calcium hydroxide (aqueous solution) to a value of 9.5. The pH adjustment was stopped when the pH was stable within ±0.2 units for 5 min, the reported pH values are the end values.

(78) The suspension was heated to 90° C. (±5° C.) under constant stirring. 2 wt.-% of hydrolysed surface treatment agent 6 was added over a period of approximately 1 min. The blend was further stirred for 30 min at 90° C. The suspension was dried in an oven for 10 h at 120° C. to a moisture content of below 1 wt.-%. The resulting dry crumbles were deagglomerated in an IKA A 11 basic analytical mill for 1 min and stored afterwards in a sealed container.

(79) The treated sample was further washed mixed with an ethanol/water (1/1, wt.-%/wt.-%) blend to a solids content of 20 wt.-% and heating it up to 80° C. The hot suspension was filtered and rinsed once with fresh ethanol/water. The washed sample was dried at 120° C. for 7 hours.

(80) Subsequent XRF analysis revealed that 78 wt.-% of the treatment agent was remaining on the sample surface. The treatment agent is well attached to the carbonate surface.

Example 11 (Inventive)

(81) 25.0 g of the surface treatment agent number 7 was diluted with an ethanol/water (1/1, wt.-%/wt.-%) blend to a concentration of 5 wt.-% and heated under stirring to 70-80° C. Under continuous stirring the heated emulsion is treated with 4.9 wt.-% solid potassium hydroxide (quantity dry potassium hydroxide based on the quantity of surface 7 treatment agent) and stirred for approximately 5 min.

(82) 400 g of surface reacted calcium carbonate A was mixed with 1 600 g deionized water in order to obtain a suspension of approximately 20 wt.-%. The suspension was stirred with a VISCO JET CRACK steered of 12 cm diameter (300 to 500 rpm; VISCO JET Rührsysteme GmbH, Germany) at room temperature. The pH was adjusted with calcium hydroxide (aqueous solution) to a value of 9.5. The pH adjustment was stopped when the pH was stable within ±0.2 units for 5 min, the reported pH values are the end values.

(83) The suspension was heated to 90° C. (±5° C.) under constant stirring. 5 wt.-% of hydrolysed surface treatment agent 7 was added over a period of approximately 1 min. The blend was further stirred for 30 min at 90° C. The suspension was dried in an oven for 10 h at 120° C. to a moisture content of below 1 wt.-%. The resulting dry crumbles were deagglomerated in an IKA A 11 basic analytical mill for 1 min and stored afterwards in a sealed container.

(84) The treated sample was further washed mixed with an ethanol/water (1/1, wt.-%/wt.-%) blend to a solids content of 20 wt.-% and heating it up to 80° C. The hot suspension was filtered and rinsed once with fresh ethanol/water. The washed sample was dried at 120° C. for 7 hours.

(85) Subsequent XRF analysis revealed that 84 wt.-% of the treatment agent was remaining on the sample surface. The treatment agent is well attached to the carbonate surface.

Example 12 (Inventive)

(86) 16.0 g of the surface treatment agent number 8 was diluted with an ethanol/water (1/1, wt.-%/wt.-%) blend to a concentration of 5 wt.-% and heated under stirring to 70-80° C. Under continuous stirring the heated emulsion is treated with 4.6 wt.-% solid potassium hydroxide (quantity dry potassium hydroxide based on the quantity of surface 8 treatment agent) and stirred for approximately 5 min.

(87) 400 g of surface reacted calcium carbonate A was mixed with 1 600 g deionized water in order to obtain a suspension of approximately 20 wt.-%. The suspension was stirred with a VISCO JET CRACK steered of 12 cm diameter (300 to 500 rpm; VISCO JET Rührsysteme GmbH, Germany) at room temperature. The pH was adjusted with calcium hydroxide (aqueous solution) to a value of 9.5. The pH adjustment was stopped when the pH was stable within ±0.2 units for 5 min, the reported pH values are the end values.

(88) The suspension was heated to 90° C. (±5° C.) under constant stirring. 3 wt.-% of hydrolysed surface treatment agent 8 was added over a period of approximately 1 min. The blend was further stirred for 30 min at 90° C. The suspension was dried in an oven for 10 h at 120° C. to a moisture content of below 1 wt.-%. The resulting dry crumbles were deagglomerated in an IKA A 11 basic analytical mill for 1 min and stored afterwards in a sealed container.

(89) The treated sample was further washed mixed with an ethanol/water (1/1, wt.-%/wt.-%) blend to a solids content of 20 wt.-% and heating it up to 80° C. The hot suspension was filtered and rinsed once with fresh ethanol/water. The washed sample was dried at 120° C. for 7 hours.

(90) Hydrophobicity measurements of the dried powder showed that in a water/ethanol blend of 35/65 volume %/volume % 50 wt.-% of the material sank down to the bottom.

(91) TABLE-US-00003 TABLE 3 Summary and results. Surface Surface Surface treatment Base for treatment treatment Surface agent hydrolysing Base for agent before agent after Mineral treatment dosage.sup.a) surface Suspension the pH washing [wt.- washing.sup.b) Trial pigment agent [wt.-%] treatment agent pH adjustment %] [wt.-%] Hydrophobicity 1 A 1 2 — n.d. — 93 33 n.d. (comparative) 2 (inventive) A 3 2 NaOH 10.5 Ca(OH).sub.2 80 85 n.d. 3 A 2 4 — 10.5 Ca(OH).sub.2 n.d. n.d. 90/10 (comparative) 4 (inventive) A 2 4 NaOH 10.5 Ca(OH).sub.2 n.d. n.d. 55/45 5 (inventive) B 2 0.5 NaOH 10.5 Ca(OH).sub.2 n.d. n.d. 55/45 (65/35).sup.c 6 (inventive) B 2 1 NaOH 10.5 Ca(OH).sub.2 n.d. n.d. 50/50 (50/50).sup.c 7 B 2 2 — n.d. — n.d. n.d. 65/35 (comparative) 8 (inventive) B 4 2 2.5% KOH — — — 74 9 (inventive) B 5 2 2.14% KOH 9 Ca(OH).sub.2 — 79 10 (inventive) B 6 2 2.9% KOH 9 Ca(OH).sub.2 — 78 11 (inventive) A 7 5 4.9% KOH 9-10 Ca(OH).sub.2 — 83 12 (inventive) A 8 3 4.6% KOH 9-10 Ca(OH).sub.2 — — 35/65 .sup.a)wt.-% referring to the mass of mineral pigment; .sup.b)referring to the amount before the washing step; .sup.cafter the washing step; n.d. = not determined.

(92) The data of examples 1 and 2 (Table 3) show that the surface treatment agent can be attached stronger to the surface of the calcium carbonate-comprising material when the process according to the present invention is used. As can be seen in Table 3 93 wt.-% of a surface-treatment agent can be located on the surface of a calcium carbonate-comprising material by a process known to the skilled person. However, after a washing step only 33 wt.-% of this surface-treatment agent are located on the surface which refers to a total amount of 31 wt.-%. Contrary to that 80 wt.-% of a surface-treatment agent can be located on the surface of a calcium carbonate-comprising material by the inventive process. After a washing step still 85 wt.-% of this surface-treatment agent are located on the surface which refers to a total amount of 68 wt.-%. Therefore, it has been shown that it is possible to attach a surface-treatment agent stronger to the surface of a calcium carbonate-comprising material by the inventive process. Due to this stronger attachment one is possible to produce a surface-treated calcium carbonate comprising material with a relative high amount of surface-treatment agent after the washing step on the surface of the calcium carbonate-comprising material.

(93) The hydrophobicity as given in Table 3 is expressed as the water/ethanol ratio at which 50 wt.-% of the surface-treated calcium carbonate-comprising material sinks. In case that a high water content in the water/ethanol blend is needed to let 50 wt.-% of the surface-treated calcium carbonate-comprising material sink, the hydrophobicity of this material is low, whereas a lower amount of water in the water/ethanol blend for letting 50 wt.-% of the surface-treated calcium carbonate-comprising material sink means that this material has a high hydrophobicity. The hydrophobicity of the surface-treated calcium carbonate-comprising material correlates directly with the quality of the surface treatment of the calcium carbonate-comprising material. The comparison of the inventive trials 4 to 6 with comparative examples 3 and 7 shows that the process according to the present invention allows to manufacture surface-treated calcium carbonate-comprising material with improved hydrophobicity. Therefore, the data show that, by applying the inventive process surface-treated calcium carbonate-comprising materials with an improved quality of surface-treatment can be obtained.