WHITE UV-ABSORBING SURFACE-REACTED CALCIUM CARBONATE DOPED WITH A TITANIUM SPECIES

Abstract

The present invention refers to a white UV-absorbing surface-reacted calcium carbonate doped with a titanium species, comprising calcite and hydroxyapatite in a weight ratio of from 99:1 to 1:99 based on the dry weight of the calcite and the dry weight of the hydroxyapatite and having a specific surface area of from 15 m.sup.2/g to 200 m/.sup.2g, wherein the titanium species is present in an amount from 0.01 to 20 wt.-% of titanium element, based on the total dry weight of the surface-reacted calcium carbonate. Furthermore, the present invention refers to a process for producing the white UV-absorbing surface-reacted calcium carbonate doped with a titanium species, the use of said white UV-absorbing surface-reacted calcium carbonate doped with a titanium species as well as an article comprising said white UV-absorbing surface-reacted calcium carbonate doped with a titanium species.

Claims

1. A process for producing a white UV-absorbing surface-reacted calcium carbonate doped with a titanium species comprising the steps of: a) providing a calcium carbonate-comprising material, b) providing at least one H.sub.3O.sup.+ ion donor, c) providing at least one titanium comprising substance, and d) treating the calcium carbonate-comprising material of step a) with the at least one H.sub.3O ion donor of step b) in an aqueous medium to form an aqueous suspension of surface-reacted calcium carbonate, and wherein the at least one titanium comprising substance of step c) is added before and/or during and/or after step d).

2. The process of claim 1, wherein the calcium carbonate-comprising material is a natural ground calcium carbonate and/or a precipitated calcium carbonate.

3. The process of claim 1, wherein the calcium carbonate-comprising material is in form of particles having a weight median particle size d.sub.50(wt) from 0.05 to 10 m, and/or a weight top cut particle size d.sub.98(wt) from 0.15 to 55 m.

4. The process of claim 1, wherein the at least one H.sub.3O.sup.+ ion donor is selected from the group consisting of phosphoric acid, citric acid, an acidic salt, tartaric acid and mixtures thereof.

5. The process of any one of claim 1, wherein the molar ratio of the at least one H.sub.3O.sup.+ ion donor to the calcium carbonate-comprising material is from 0.01 to 4.

6. The process of claim 1, wherein the at least one titanium comprising substance is selected from the group consisting of a titanium salt, a titanium hydroxide, a titanium dioxide, and mixtures thereof.

7. The process of claim 1, wherein the at least one titanium comprising substance is provided in an amount from 0.1 to 20 wt.-% of titanium element, based on the total dry weight of the calcium carbonate-comprising material.

8. The process of claim 1, wherein in step d) the calcium carbonate-comprising material is treated with a solution comprising the at least one H.sub.3O: ion donor of step b) and the at least one titanium comprising substance of step c).

9. The process of claim 1, wherein in step d) the pH value of the obtained aqueous suspension of surface-reacted calcium carbonate is from 4.5 to 11.

10. The process of claim 1, wherein step d) is carried out at a temperature from 20 to 95 C.

11. The process of claim 1, wherein the process further comprises a step e) of separating the white UV-white absorbing surface-reacted calcium carbonate doped with a titanium species from the aqueous suspension obtained in step d) and/or wherein the process further comprises a step f) of drying the surface-reacted calcium carbonate doped with a titanium species after step d) or after step e), if present, at a temperature in the range from 60 to 600 C.

12. A white UV-absorbing surface-reacted calcium carbonate doped with a titanium species, comprising calcite and hydroxyapatite and having a specific surface area of from 15 m.sup.2/g to 200 m.sup.2/g, measured using nitrogen and the BET method according to ISO 9277:2010, wherein the weight ratio of calcite to hydroxyapatite is from 99:1 to 1:99 based on the dry weight of the calcite and the dry weight of the hydroxyapatite, and wherein the titanium species is present in an amount from 0.01 to 20 wt.-% of titanium element, based on the total dry weight of the surface-reacted calcium carbonate.

13. The surface-reacted calcium carbonate doped with a titanium species of claim 12, wherein the surface-reacted calcium carbonate doped with a titanium species has (i) a specific surface area of from 25 m.sup.2/g to 180 m.sup.2/g, measured using nitrogen and the BET method according to ISO 9277:2010 and/or (ii) a volume determined median particle size d.sub.50(vol) from 1 to 100 m, and/or (iii) a volume determined top cut particle size d)s(vol) from 2 to 150 m, (iv) an intra-particle intruded specific pore volume in the range from 0.1 to 2.3 cm.sup.3/g, calculated from mercury porosimetry measurement.

14. The surface-reacted calcium carbonate doped with a titanium species of claim 12, wherein the weight ratio of calcite to hydroxyapatite is from 80:20 to 20:80 based on the dry weight of the calcite and the dry weight of the hydroxyapatite, and/or wherein the titanium species is present in an amount from 0.05 to 15 wt.-% of titanium element, based on the total dry weight of the surface-reacted calcium carbonate.

15. (canceled)

16. (canceled)

17. An article comprising a white UV-absorbing surface-reacted calcium carbonate doped with a titanium species according to claim 12, wherein the article is selected from paper products, engineered wood products, plasterboard products, polymer products, hygiene products, medical products, healthcare products, filter products, woven materials, nonwoven materials, geotextile products, agriculture products, horticulture products, clothing, footwear products, baggage products, household products, industrial products, packaging products, building products, construction products, paints, coatings, sealants, adhesives, feed, cosmetics, water treatment products, catalysis products, gas treatment products, sun protection products for plants and parts thereof, or cosmetic formulations providing chemical or physical sun protection.

18. The process of claim 1, wherein the at least one H.sub.3O.sup.+ ion donor is phosphoric acid.

19. The process of claim 1, wherein the at least one titanium comprising substance is selected from the group consisting of titanium bromide, titanium fluoride, titanium iodide, titanium chloride, titanyl sulfate, and mixtures thereof.

20. The process of claim 1, wherein step d) is done by solvent evaporation and/or pressure filtration.

21. The surface-reacted calcium carbonate doped with a titanium species of claim 12, wherein the weight ratio of Calcite to hydroxyapatite is from 60:40 to 40:60 based on the dry weight of the calcite and the dry weight of the hydroxyapatite, and/or wherein the titanium species is present in an amount from 0.5 to 5 wt.-% of titanium element, based on the total dry weight of the surface-reacted calcium carbonate.

Description

FIGURES

[0267] FIG. 1: UV-Vis spectroscopy of GCC and samples 1 to 8 measured at 340 nm at room temperature

[0268] FIG. 2 shows a SEM image of sample 4

[0269] The scope and interest of the invention will be better understood based on the following examples which are intended to illustrate certain embodiments of the present invention and are non-limitative.

Examples Section

1. Measurement Methods

[0270] The following measurement methods were used to evaluate the parameters given in the examples and claims.

BET Specific Surface Area (SSA) of a Material

[0271] The BET specific surface area was measured via the BET process according to ISO 9277:2010 using nitrogen and a ASAP 2460 instrument (Micromeritics GmbH, Germany), following conditioning of the sample by heating at 100 C. for a period of 30 minutes. Prior to such measurements, the sample was filtered, rinsed and dried at 110 C. in an oven for at least 12 hours.

Particle Size Distribution (Volume % Particles with a Diameter <X), d.sub.50 Value (Volume Median Grain Diameter) and Des Value of a Particulate Material:

[0272] Volume median grain diameter d.sub.50 was evaluated using a Malvern Mastersizer 3000 Laser Diffraction System. The d.sub.50 or d.sub.98 value, measured using a Malvern Mastersizer 3000 Laser Diffraction System, indicates a diameter value such that 50% or 98% by volume, respectively, of the particles have a diameter of less than this value The raw data obtained by the measurement are analysed using the Mie theory, with a particle refractive index of 1.57 and an absorption index of 0.005.

[0273] The weight median grain diameter is determined by the sedimentation method, which is an analysis of sedimentation behaviour in a gravimetric field. The measurement is made with a Sedigraph, 5120, Micromeritics Instrument Corporation. 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 is 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 super sonicated.

[0274] The processes and instruments are known to the skilled person and are commonly used to determine grain size of fillers and pigments.

[0275] Porosity Measurements

[0276] Portions of the white UV-absorbing surface-reacted calcium carbonate doped with a titanium species or of the titanium dioxide were characterized by mercury porosimetry for porosity, intruded total specific void volume, and pore size distribution using a Micromeritics Autopore V 9620 mercury porosimeter. The maximum. applied pressure of mercury was 414 MPa, equivalent to a Laplace throat diameter of 0.004 m. The equilibration time used at each pressure step is 20 s and the sample material is seal in a 3 cm.sup.3 chamber powder penetrometer. The data were corrected using Pore-Comp (P. A. C. Gane et al. Void Space Structure of Compressible Polymer Spheres and Consolidated Calcium Carbonate Paper-Coating Formulations (Industrial and Engineering Chemistry Research 1996, 35 (5), 1753.sup.1764) for mercury compression and penetrometer effects, and also for elastic sample compression. By taking the first derivative of the cumulative intrusion curves the pore size distributions based on equivalent Laplace diameter, inevitably including pore-shielding, was revealed. Volume defined median pore diameter was calculated from the mercury intrusion curve, and volume defined pore size polydispersity as full width at half maximum (FWHM) is calculated from the pore size distribution curve.

X-Ray Diffraction (XRD)

[0277] XRD experiments are performed on the samples using rotatable PMMA holder rings. Samples are analyzed with a Bruker D8 Advance powder diffractometer obeying Bragg's law. This diffractometer comprises a 2.2 kW X-ray tube, a sample holder, a --goniometer, and a VANTEC-1 detector. Nickel-filtered Cu-K radiation is employed in all experiments. The profiles are chart recorded automatically using a scan speed of 0.7 per min in 2 (XRD GV_7600). The resulting powder diffraction patterns are classified by mineral content using the DIFFRACsuite software packages EVA and SEARCH, based on reference patterns of the ICDD PDF-2 database (XRD L.TM_7603).

[0278] 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. 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 using the Rietveld approach such that the calculated pattern(s) duplicates the experimental one.

Reflectance Measurements

[0279] Reflectance analysis was carried out with a double beam PerkinElmer Lambda 950 IJV/Vis/NIR spectrophotometer equipped with a 150 mm integrating sphere with PMT and InGaAs detectors,

[0280] The prepared dry compositions were measured by reflectance spectroscopy. The analysis was performed with the dry composition loaded into a sealed aluminum cup for powder samples, which was placed flush with the reflectance port of the integrating sphere. The spectrophotometer was scanned in the range 280 nm-800 nm in steps of 2 nm. A Spectralon white standard was used as 100% baseline. To get a proxy for the absorption spectrum of the dry composition, the measured reflectance spectrum was converted using the Kubelka-Munk equation K-M=K/S=(1-R).sup.2/2R, where R is the reflectance and K and S are the absorption and scattering coefficient, respectively.

(XRF) Measurements

[0281] 11.5 g dry sample was pressed to a tablet, using a press at 400 kN. The elemental composition of the sample was measured by sequential, wavelength dispersive X-ray fluorescence (using an ARL PERFORMX X-ray fluorescence spectrometer, Thermo Fisher Scientific, Inc., USA). The quantification was made by means of an external calibration which was especially prepared for calcium carbonate.

Brightness R and Paper Opacity

[0282] Brightness R and dcor paper opacity were measured on the obtained dcor papers as prepared below over a white and black underlay. The dcor papers were stored for 24 h at 231 C. and 502% relative humidity and afterwards measured at the same temperature and humidity. The measuring was performed with a Elrepho-Spectrophotometer 3300 ERIC (Lorentzen & Wettre) according to ISO 2471:2008.sup.12. A measuring orifice XLAV (diameter 34 mm), a D65/10 light source and a R457 filter has been used.

[0283] The opacity is calculated from the quotient of the mean of the reflection R of the black background and the mean value of the reflection factor R of the white background and is expressed in %.

CIELAB Coordinates

[0284] The color values (CIELAB L*, a*, b* coordinates) were measured on the obtained dcor papers as prepared below over a white and black underlay. The dcor papers were stored for 24 h at 231 C. and 502% relative humidity and afterwards measured at the same temperature and humidity. The measuring was performed with a Elrepho-Spectrophotometer 3300 ERIC (Lorentzen & Wettre) according to iSO 5631.sup.2:2015.sup.11 (light D65). A measuring orifice XLAV (diameter 34 mm) has been used.

2. Material and Equipment

[0285] calcium carbonate-comprising material: [0286] GCCI: Ground marble calcium carbonate from Carrera, Italy. The ground calcium carbonate had a medium weight based particle size distribution d.sub.50 of 7.9 m, as determined by sedimentation. [0287] GCCII: Ground marble calcium carbonate obtained from Hustadmarmor, Norway The ground calcium carbonate had a medium weight based particle size distribution d.sub.50 1.7 m, as determined by sedimentation.

[0288] H.sub.3O.sup.+ ion donor: [0289] Phosphoric acid (H.sub.3PO.sub.4) available from VWR Chemicals (ortho phosphoric acid 85%)

[0290] Titanium comprising substance: [0291] Titanium oxysulfate I TiOSO42O available from Sigma-Aldrich under the number 14023-1

[0292] Titanium dioxide [0293] a non-porous titanium dioxide with a specific surface area (SSA) of 6.8 m.sup.2/g and a medium weight based particle size distribution d.sub.50 1.7 m, as determined by sedimentation

[0294] Wet Strength Agent: [0295] solution of an adipinic acid diethylene triamin epichlorhydrin copolymer (Giluton XP 14, BK Giulini GmbH)

3. Sample Preparation

White UV-Absorbing Surface-Reacted Calcium Carbonate Doped with a Titanium Species I

[0296] 165 g of GCCI is added into 940 mL of water. The slurry is mixed at 75 C., for 15 minutes. The resulting mixture is called GCCI slurry.

[0297] A H.sub.3PO.sub.4 solution is prepared by using 58 g of phosphoric acid in 107 mL. of distilled water (Solution A). Solution A is added to the GCCI slurry with a flowrate of 15 g/min, with a full addition time of ca. 10 minutes.

[0298] For a 2.5 wt % of titanium, 13.6 g of the titanium comprising substance is added to 1.1 L of water. The salt addition is to be performed in portions and under stirring.

[0299] Afterwards, the solvent is eliminated by solvent evaporation (in an oven at 100 C. over night) or pressure filtration (vacuum filtrationwater pump vacuum at room temperature).

[0300] Different inventive and comparative experiments are performed as listed below. Each sample was dried at 125 C. and 300 C.

TABLE-US-00001 Addition of H.sub.3O.sup.+ ion donor and Sample name Titanium comprising substance Solvent elimination Sample 1 Ti salt in the H.sub.3PO.sub.4 solution Solvent evaporation Sample 2 Ti salt before the H.sub.3PO.sub.4 solution Sample 3 Ti salt after the H.sub.3PO.sub.4 solution Sample 4 Ti salt in the H.sub.3PO.sub.4 solution Pressure filtration Sample 5 No H.sub.3PO.sub.4, only Ti salt Solvent evaporation Sample 6 Only H.sub.3PO.sub.4 Pressure filtration Sample 7 Sample 6 + Ti salt Pressure filtration

[0301] The obtained samples have been analyzed using UV-Vis spectroscopy. The total reflectance of the samples at 340 nm was measured at room temperature as shown in FIG. 1.

White UV-Absorbing Surface-Reacted Calcium Carbonate Doped with a Titanium Species II GCCII Slurry Preparation

[0302] 7 liters of an aqueous suspension of ground calcium carbonate is prepared in a mixing vessel by adjusting the solids content of GCCII such that a solids content of 14 wt.-%, based on the total weight of the aqueous suspension, is obtained. The slurry is mixed at 70 C., for 15 minutes.

Sample 8

[0303] Whilst mixing the GCCII slurry, 1391 g of phosphoric acid at 23 wt. % is added over 60 minutes. Throughout the whole addition the temperature of the suspension is maintained at 70 C. 1.sup.1 C. After the addition of the phosphoric acid, the suspension is stirred for additional 5 minutes before removing it from the vessel and allowing it to cool.

Sample 9

[0304] Separately, a titanium comprising substance solution is prepared in phosphoric acid via the slow addition of the titanium comprising substance dissolved in deionized water such that the final concentration is 40.5 wt % H.sub.3PO.sub.4 and 6.9 wt. % TiOSO.sub.4H.sub.2O. This solution is subsequently diluted with more distilled water such that H.sub.3PO.sub.4 has a concentration of 23 wt. %.

[0305] Whilst mixing the GCCII slurry, 1075 g of the titanium comprising substance solution is added over 60 minutes. Throughout the whole addition, the temperature of the resulting mixture is maintained at 70 C. +/1 C. Then, the resulting mixture is stirred for additional 5 minutes before removing it from the vessel and allowing it to cool.

Sample 10

[0306] Separately, a titanium comprising substance solution is prepared in phosphoric acid via the slow addition of the titanium comprising substance dissolved in deionized water such that the final concentrations is 40.5 wt. % H.sub.3PO.sub.4 and 6.9 wt,% TiOS.sub.4H.sub.2O. This solution is subsequently diluted with more distilled water such that H.sub.3PO.sub.4 has a concentration of 23 wt. %.

[0307] Whilst mixing the GCCII slurry, 2093 g of the titanium comprising substance solution is added over 60 minutes. Throughout the whole addition, the temperature of the resulting mixture is maintained at 70 C. + 1 C. Then, the resulting mixture is stirred for additional 5 minutes before removing it from the vessel and allowing it to cool.

[0308] Afterwards, the solvent in the resulting mixture is eliminated by pressure filtration in a water pump vacuum over a Buchner funnel. Each sample was dried at 125 C. The obtained samples have been analyzed using UV-Vis spectroscopy. The total reflectance of the samples at 340 nm was measured at room temperature

[0309] From FIG. 1 it can be seen that comparative sample 6 has a total reflectance similar to the total reflectance of the raw GCCI. When comparing sample 6 with samples 1 to 4, it can be seen that these samples have much lower total reflectance values between 62 and 77%. Therefore, it has been shown that the addition of the at least one titanium comprising substance is possible before and/or during and/or after step d) (samples 1 to 3). Furthermore, the solvent elimination has no influence on the obtained white UV-absorbing surface-reacted calcium carbonate doped with a titanium species as can be seen from samples 1 and 3.

[0310] It can be seen that comparative sample 8 has a total reflectance of 93.79%. When comparing sample 8 with samples 9 and 10, it can be seen that these samples have much lower total reflectance values between 86 and 90%. Therefore, by the inventive process a white UV-absorbing surfacereacted calcium carbonate doped with a titanium species can be prepared.

TABLE-US-00002 Sample 8 Sample 9 Sample 10 Reflectance at 340 nm in % 93.79 89.39 86.53

[0311] The samples 1 to 10 were analyzed by XRD and XRF and additionally, the surface area was evaluated using BET technique.

TABLE-US-00003 Sample XRD (%) XRF (%) SSA name calcite hydroxyapatite S Ti (m.sup.2/g) Invention Sample 1 42 55 3.4 2.5 72 Yes Sample 2 42 54 3.3 2.6 76 Yes Sample 3 47 48 3.6 2.5 58 Yes Sample 4 45 54 1.7 2.6 70 Yes Sample 5 94 0 2.8 2.6 9 No Sample 6 47 52 0.04 0.01 60 No Sample 7 45 54 0.72 2.8 12 No Sample 8 49 41 0.02 <0.01 41.3 No Sample 9 62 38 0.43 0.65 36.3 Yes Sample 10 37 63 0.87 1.03 56.8 Yes

[0312] From samples 1 to 4 and 9 and 10 it can be seen that by the inventive process of the present invention it is possible to prepare white UV-absorbing surface-reacted calcium carbonate doped with a titanium species.

[0313] From sample 5 it can be seen that without the addition of a H.sub.3O.sup.+ ion donor no hydroxyapatite is formed. Furthermore, the BET value is below 15 m.sup.2/g.

[0314] From samples 6 and 8 it can be seen that without the addition of a titanium, comprising substance no titanium is present.

[0315] From sample 7 it can be seen that by merely mixing of the surface-reacted calcium carbonate and the titanium comprising substance the BET is 12 m.sup.2/g and, therefore, below the claimed value of the white UV-absorbing surface-reacted calcium carbonate doped with a titanium species Without being bound to any theory, the inventors believe that by merely mixing the surface-reacted calcium carbonate and the titanium comprising substance, the pores on the surface are clogged.

[0316] Furthermore, from sample 4 a SEM picture has been made. It can be seen that due to the treatment of the calcium carbonate-comprising material with the at least one H.sub.3O.sup.+ ion donor, and at least one titanium comprising substance a white UV-absorbing surface-reacted calcium carbonate doped with a titanium species is obtained, that has a unique structure with a high surface area wherein the pores of the obtained product are not clogged.

[0317] Therefore, it has been shown by the examples that by the inventive process of the preset invention it is possible to prepare a white UV-absorbing surface-reacted calcium carbonate doped with a titanium species, comprising calcite and hydroxyapatite and having a specific surface area of from m/g to 200 m.sup.2Ig, measured using nitrogen and the BET method according to ISO 9277.sup.2010, wherein the weight ratio of calcite to hydroxyapatite is from 99:1 to 1:99 based on the dry weight of the calcite and the dry weight of the hydroxyapatite, and wherein the titanium species is present in an amount from 0.01 to 20 wt.-% of titanium element, based on the total dry weight of the surface-reacted calcium, carbonate.

[0318] Additionally, the d.sub.50 and the intra-particle intruded specific pore volume of the samples were analyzed

TABLE-US-00004 Intra-particle intruded specific pore volume (for the range 0.004-d* m) Sample name d.sub.50 (m) (cm.sup.3/g) d* (m) Sample 1 8 Sample 2 8 Sample 3 12 Sample 4 12 Sample 5 2 Sample 6 11 Sample 7 12 Sample 8 3.04 0.403 0.18 Sample 9 1.88 0.147 0.13 Sample 10 3.14 0.318 0.18 TiO.sub.2 0.4 0

Preparation and testing of dcor paper

Different Dcor Papers have been Prepared as Follows:

[0319] 80 g of an oven dry (German term otro or Ofen trocken) eucalyptus standard pulp with a Schopper Riegler degree of 30 SR and 4.5 g of wet strength agent are diluted in 10 dm.sup.3 tap water. Afterwards the respective filler is added in the amount shown in the table below. The obtained suspension is stirred for 10 minutes with a paddle mixer. 15 sheets of 80 g/m.sup.2 are formed using a Rapid-Kothen hand sheet former available from LGS Senkel, Mhlheim a.d. Ruhr, are formed from each sample.

[0320] Each sheet is wet pressed and dried using the Rapid-Kothen drier at 115 C. The composition of the dcor paper is given in the table below.

TABLE-US-00005 Pulp * TiO.sub.2 * Sample 9 Sample 10 Sample 8 Wet strength agent Sample Invention [wt.-%] [wt.-%] [wt.-%] [wt.-%] [wt.-%] [wt.-%] 11 No 70 30 4 12 Yes 70 24 6 4 13 Yes 70 24 6 4 14 No 70 24 6 4 * The sum of the fiber/pulp and the filler always amounts 100 parts by weight. The wet strength agent is added in addition to the 100 parts by weight.

TABLE-US-00006 Ry D65 Opacity L a b Sample Invention D65/10 in % in % (white) (white) (white) 11 No 79.1 79.5 91.3 1.52 4.85 12 Yes 79.8 80.9 91.6 1.53 4.77 13 Yes 80.2 82.4 91.8 1.52 4.75

[0321] From the above measurements it can be seen that the inventive white UV-absorbing surface-reacted calcium carbonate doped with a titanium. species can be used in paper applications, especially in paper making, for example in dcor paper making. Samples 12 and 13 show an improved opacity, improved brightness R and an improved whiteness L* in comparison to sample 11, even if less TiO.sub.2 is present in these dcor papers.

[0322] Therefore, a part of the titanium dioxide in dcor paper, which is a high-priced product can be replaced by the inventive white UV-absorbing surface-reacted calcium carbonate doped with a titanium species and still the dcor paper has improved properties like improved opacity, improved brightness R and an improved whiteness L*.