KR20080102198A - Titanium dioxide pigment coated with hollow bodies, and production method - Google Patents

Abstract

The invention relates to a coated titanium dioxide pigment that has good opacity and good retention and is used in decorative paper. Also disclosed is a method for producing said pigment. The inventive pigment is characterized by a surface coating containing aluminum oxide phosphate and attached hollow bodies. The inventive production method is characterized in that an aluminum component and a phosphorus component are first introduced into a TiO2 suspension while the pH value does not drop below 10. Then the hollow bodies are added, whereupon at least one acidic component is added such that the pH value of the suspension is lowered to a value ranging between 4 and 9. In an alternative embodiment of said method, the suspension has a pH value of less than 4 when the aluminum component and the phosphorus component are added.

Description

Titanium dioxide pigment coated with hollow bodies, and production method

The present invention relates to high opacity titanium dioxide pigments, methods for their preparation and their use in decorative laminating paper or decorative foils.

Decorative laminates and decorative foils are part of the decorative thermoset coatings which are preferably used for furniture surface finishing, laminated flooring and interior finishing. Laminate is, for example, a term used to refer to a material in which various impregnated layers of paper or paper and cardboard or fibreboard are pressed together. The use of special synthetic resins achieves exceptionally high resistance of the laminate to defects, impacts, chemicals and heat.

Decorative laminates (hereinafter also intended to mean decorative foils) can be used to make decorative surfaces, where, for example, decorative laminates are used as facing paper to hide unsightly wood surfaces. Not only does it function, but also functions as a carrier for synthetic resins.

Requirements placed on decorative laminated paper include, in particular, opacity (hiding force), light fastness (dye resistance), color fastness, wet strength, suitability for impregnation and printability.

The economic efficiency of the process for producing decorative laminated paper is determined, among other things, by the opacity of the pigment in the paper. In principle, titanium dioxide based pigments are very suitable for achieving the required opacity of decorative laminated paper. During the papermaking process, the titanium dioxide pigment or titanium dioxide pigment suspension is usually mixed with the pulp suspension. In addition to pigments and pulp as feedstock, auxiliaries such as wet strength enhancers and further additives, if necessary, are also used. The interaction between the individual components (pulp, pigment, auxiliaries and additives, water) forms paper and determines the retention of the pigment. Retention capacity is the capacity to retain all inorganic materials on paper during manufacture.

It is known that the improvement of opacity can be achieved by special treatment of the surface with titanium dioxide pigment.

US 5,942,281 A and US 5,665,466 A apply a first layer of aluminum oxide phosphate at an acidic value of pH 4 to 6 and a second layer of aluminum oxide at pH 3 to 10, preferably approximately pH 7. Surface treatment methods for precipitation are described. Retention retention is achieved with a third layer of magnesium oxide, as a result of which the pigment produced is characterized by a continuous layer of aluminum oxide phosphate, aluminum oxide and magnesium oxide.

US Pat. No. 6,962,622 B2 describes a titanium dioxide pigment blend consisting of a pigment having a high anticorrosive (pigment type A) and a pigment having a coating settling in fluff form and having an increased content of SiO ₂ and Al ₂ O ₃ (pigment type B). have.

US 6,143,064 A describes coatings of pigment particles with precipitated sodium carbonate, wherein the sodium carbonate particles have a size of 30 to 100 nm. Titanium dioxide coated with sodium carbonate achieves higher opacity in paper. In this document, calcium particles are assumed to function as spacers, since pigment particles are better distributed in paper. The minimum distance between the pigment particles is said to correspond approximately to the size of the pigment particles.

US Pat. No. 5,886,069 A and US Pat. No. 5,650,002 A describe TiO ₂ pigment particles exhibiting both a continuous inorganic coating and a discrete inorganic particle coating having a diameter of 5 to 100 nm. The surface coating order can be chosen at random because it can be in the form of discrete particles. A colloidal suspension of discrete particles can be prepared by mixing with a TiO ₂ slurry.

US 2003 0024437 A1 describes pigment blends in which surface spherical particles, such as sodium carbonate, silicon oxide, aluminum oxide, zirconium oxide or titanium dioxide, have precipitated pigment particles in situ.

[OBJECTIVE AND SUMMARY OF THE INVENTION]

It is an object of the present invention to provide another titanium dioxide pigment for use in decorative laminates with good opacity and good retention. It is a further object of the present invention to provide a process for the production of titanium dioxide pigments of this kind.

The object is achieved by a titanium dioxide pigment containing titanium dioxide particles and the coating containing aluminum phosphate, aluminum oxide and a hollow body.

The above object is further,

(a) providing an aqueous suspension of uncoated titanium dioxide particles,

(b) adding an aluminum component and a phosphorus component,

(c) adding a hollow body,

(d) setting the pH value of the suspension in the range of 4-9, by a process for the production of coated titanium dioxide pigments.

Further advantageous forms of the invention are described in the dependent claims.

Hereinafter, "oxide" also means the corresponding hydrous oxide or hydrate. All data described below in relation to pH values, temperatures, weight percent or volume percent, etc., should be interpreted to include all values within the respective measurement accuracy ranges known to those skilled in the art. When "equivalent weight" or "equivalent content" is used in connection with the present application, it indicates the minimum amount of ingredients, and when the amount is added, the properties of the mixture are affected in the system of measurement accuracy.

The titanium dioxide pigment according to the invention is characterized by the use of a hollow body. The hollow body may comprise a hollow spherical contour or spheres comprising hollow microspheres or hollow microspheres. The present invention includes the use of a hollow body during work up. The hollow body adheres to the particle surface and acts as a spacer between each pigment particle. The hollow body can be of inorganic and organic nature. The hollow body preferably has an average diameter of 5 to 1,000 nm. The hollow body is characterized by the inclusion of air, which may not be present until after the pigment has dried.

Organic hollow bodies are used, for example, as thickeners. The hollow body acts as a spacer between the pigment particles, thereby increasing the hiding power by exploiting the beneficial difference in refractive index between the pigment and the air, due to its trapped air. "[" Quality Improvement-Ropaque ™ Opaque Polymer for Improving the Quality of Paints and Coatings ", Phanomen Farbe 2/98, 1/99]. See also "Hollow latex particles: synthesis and applications" (McDonald et al., Advances in Colloid and Interface Science 99 (2002) 181-213) for the preparation of organic hollow spheres. Exemplary matters are described in "Nanoengineering of Inorganic and Hybrid Hollow Spheres by Colloidal Templating" (Caruso et al., Science 1998, Vol. 282, p. 1111). 02/074431 A1 describes a process for the production of inorganic hollow bodies and their use in catalysts and photonics.

In the process according to the invention, the layer of aluminum-phosphorus compound in the hollow body and, if applicable, in the blend with aluminum oxide, is settled on the TiO ₂ particle surface. The composition depends on the amount of aluminum and phosphorus components used. For simplicity, this layer is referred to below as the aluminum oxide phosphate / hollow sphere layer.

The workup process on which the invention is based starts with an aqueous, preferably wet milled TiO ₂ suspension (step (a)). If appropriate, wet milling is carried out in the presence of a dispersant. TiO ₂ comprises uncoated TiO ₂ particles, ie TiO ₂ base material particles produced by the sulfate process (SP) or chloride process (CP). Typically, the base material is added to aluminum at a ratio of 0.3 to 3% by weight, calculated as Al ₂ O ₃ , while oxidizing titanium tetrachloride to titanium dioxide in the CP process, and the oxygen surplus of the gas phase is 2 to 15. Add%; For example, it is stabilized by doping with Al, Sb, Nb or Zn in the SP process.

TiO ₂ particles produced by the chloride process are preferably used. The process is carried out at a temperature of 80 ° C. or lower, preferably 55 to 65 ° C.

The suspension in step (a) may preferably be set to alkaline or acidic with a pH value greater than 9 or less than 4.

In step (b) aluminum and phosphorus components are added. Suitable aluminum components for the surface treatment according to the invention include alkaline or acid reactive water soluble salts such as sodium aluminate, aluminum sulfate, aluminum nitrate, aluminum chloride, aluminum acetate and the like. This choice should not be construed as limiting. The aluminum component should be calculated as Al ₂ O ₃ and added in an amount of 1.0 to 5.0% by weight, preferably 1.5 to 4.5% by weight, in particular 2.0% by weight, based on TiO ₂ particles.

Suitable phosphorus components are inorganic compounds such as alkali phosphates, ammonium phosphates, polyphosphates, phosphoric acid and the like. This choice should not be construed as limiting. Disodium hydrogen phosphate or phosphoric acid is particularly suitable. The phosphorus component is calculated as P ₂ O ₅ and added at a concentration of 1.0 to 5.0% by weight, preferably 1.5 to 4.0% by weight, in particular 2.0 to 3.0% by weight, based on TiO ₂ particles.

The Al and P components can be added to the suspension individually or simultaneously in any order.

Subsequent step (c) involves adding an organic or inorganic hollow body having an average diameter of 5 to 1,000 nm, preferably 400 to 600 nm.

For example, it is conceivable to use Ropaque ™ manufactured by Rohm & Haas as organic hollow spheres. Ropaque ™ consists of styrene / acrylic copolymer beads. Other latex or polymeric hollow spheres may also be suitable. However, this should not be construed as limiting the invention. Rather, all organic hollow spheres that exhibit the required particle diameter in the range of 5 to 1,000 nm and are stable at the resulting pH value are considered in principle.

Inorganic hollow spheres discussed in the art generally include both glass hollow ceramics and ceramic hollow spheres, and mainly comprise TiO ₂ hollow spheres. Again, this represents the required intermediate particle diameter of 5 to 1,000 nm, and all kinds of inorganic hollow bodies which are stable at the pH value generated can in principle be used in the inventive arrangements. One skilled in the art will select an appropriate hollow body based on construction conditions such as workability, cost and the like.

The hollow body is added in an amount of 1 to 15% by weight, based on the uncoated TiO ₂ particles.

In a further subsequent step (d), the pH value of the suspension is set in the range of 4-9 by adding a pH adjusting component. The pH adjusting component used may be an acid or a lye. Examples of acids that can be used are sulfuric acid, hydrochloric acid, phosphoric acid or another suitable acid. Moreover, corresponding acid reactive salts such as aluminum sulfate may be used in place of the acid. It is also possible, for example, to use an acidic metal salt solution of cerium, titanium or zirconium to cause sedimentation to occur with the aluminum oxide phosphate / hollow sphere layer. Preferably sodium hydroxide solution is used as lye. Alkali reactive salts are also suitable. One skilled in the art is familiar with suitable pH adjusting compounds. Therefore, this selection should not be construed as limiting the invention.

In a subsequent step (e), the alkaline and acidic aluminum components (e.g. sodium aluminate / aluminum sulfate) are added simultaneously, an alkaline aluminum component such as sodium aluminate and an acid such as sulfuric acid or hydrochloric acid, or It has proved advantageous to apply a layer of aluminum oxide to the aluminum oxide phosphate / hollow sphere layer in a way to maintain the pH value in the range of 4-9 by adding an acidic aluminum component with lye, for example NaOH. In this regard, one of these components may be added in a manner such that the pH value remains constant in the range of 4 to 9, or the component may be added in a variable combination within the range of 4 to 9 during the addition. Can be added. Those skilled in the art are familiar with this process. For example, lye or acid (eg NaOH / H ₂ SO ₄ ) or alkaline or acidic reactive salt solution (eg sodium aluminate / aluminum sulfate) is suitable for setting the pH value. It has proved particularly advantageous to carry out the treatment at a preset pH value in step (d).

If necessary, the pH value can be adjusted in step (f), for example by using lye / acid (e.g. NaOH / H ₂ SO ₄ or HCl) or by using an alkaline / acid salt solution such as sodium aluminate / aluminum sulfate. Subsequently set to 5-8.

Step (d), the amount of the aluminum compound used in step (e) and step (f), when calculated as Al ₂ O _3, to be added to the amount of the already-Al ₂ O ₃ used in step (b). The total amount of aluminum compound used in steps (b) to (f) is ideally from 1.0 to 9.0% by weight, preferably from 3.5 to%, based on the uncovered TiO ₂ particles calculated as Al ₂ O ₃ 7.5% by weight, in particular 5.5% by weight. Similarly, the amount of the component that is used to enable in step (d) and step (e), calculated as P ₂ O _5, to be added to the amount of P ₂ O ₅ used in step (b). The total amount of phosphorus compounds used in step (b) internally step (e) is ideally from 1.0 to 5.0% by weight, preferably from 1.5 to 5.0, based on uncovered TiO ₂ particles, calculated as P ₂ O ₅ 3.5% by weight, in particular 2.0 to 3.0% by weight.

Along with the Al and P components, for example, other metal salt solutions of Ce, Ti, Si, Zr or Zn can be added to the suspension in step (b) and subsequently in the aluminum oxide phosphate / hollow sphere layer. It is precipitated together on the particle surface in step (d) as phosphate or oxide.

Prior to step (e) or after step (e), additional inorganic layers (eg, Zn, Ti, Si containing compounds) as known in the art may be applied.

In a preferred embodiment of the process according to the invention, the starting point is an alkaline TiO ₂ suspension. Subsequently, step (a) preferentially comprises setting the pH value of the suspension to at least 10 using a suitable alkaline compound, for example NaOH. If wet milling is performed, this should ideally be done before the milling operation.

In step (b), the aluminum and phosphorus components are each added to the suspension in the form of an aqueous solution. During the addition of these components, the pH of the suspension is maintained at a value of at least 10, preferably at least 10.5, particularly preferably at least 11.

Sodium aluminate is particularly suitable as the alkaline aluminum component. When acid reactive compounds such as aluminum sulphate are used, the pH value drops below 10 by their addition, and this effect has been proven to be advantageously offset by the addition of a suitable alkaline compound such as NaOH. Those skilled in the art are familiar with suitable alkaline compounds and with the amounts required to maintain the pH at a value of 10 or greater.

For phosphorus components where the pH value drops below 10 by addition, likewise, this effect has been proven to be advantageously offset by the addition of a suitable alkaline compound such as NaOH. Those skilled in the art are familiar with suitable alkaline compounds and with the amounts required to maintain the pH at a value of 10 or greater.

The Al and P components can be added to the suspension in any order, individually or simultaneously with each other.

In a subsequent step (c), an organic or inorganic hollow body with an average diameter of 5 to 1,000 nm, preferably 400 to 600 nm is added, wherein the pH value of the suspension falls below 10, preferably below 10.5, in particular below 11 Do not. In a subsequent step (d), the pH adjusting component is added to obtain a pH value of 4-9.

In another embodiment of the process according to the invention, the surface treatment according to the invention is initiated in an acidic pH range.

In this case, step (b) involves the addition of aluminum and phosphorus components such that the pH value of the suspension is subsequently less than 4. One skilled in the art can freely reduce the pH value in step (a) with a suitable acid, or freely reduce the pH value in step (b) to less than 4 by using a suitable combination of ingredients and adding acid if necessary. For example, a phosphoric acid / sodium aluminate or disodium hydrogen phosphate / aluminum sulfate combination is suitable. These components may be added to the suspension in any order, individually or simultaneously with each other.

In step (c) only hollow bodies suitable at acidic pH values are used.

In step (d), the pH adjusting component is added again to obtain a pH value in the range of 4-9.

The surface treated TiO ₂ pigment is separated from the suspension by filtration methods known to those skilled in the art, and the filter cake obtained is washed to remove soluble salts. In order to improve the light fastness of the pigments of the laminate, nitrate containing compounds (e.g., KNO ₃ , NaNO ₃ , Al (NO ₃ ) ₃ ) are calculated as NO ₃ before or during the subsequent drying, 0.05 To the washed filter paste in an amount of from 0.5% by weight. For example, during subsequent milling in a steam mill, organic compounds, such as polyalcohol (trimethylolpropane), selected from the ranges commonly used in the production of TiO ₂ pigments and familiar to those skilled in the art can be added to the pigments. . As an alternative to adding nitrate containing compounds before or during drying, these materials may be added during milling.

Compared with reference pigments, the pigments prepared according to the invention exhibit improved opacity and are optimally suitable for use in decorative laminates or decorative veneers.

The surface treatment method according to the invention is usually carried out in a batch manner. However, it is also possible to process continuously, in which case a suitable mixing device, for example a device familiar to those skilled in the art, should ensure sufficient mixing.

Examples of the present invention are described below, but the examples are not intended to limit the scope of the present invention.

Example

The pH value of the sand milled TiO ₂ suspension from the chloride process with a TiO ₂ concentration of 350 g / l was set to 10 with NaOH at 60 ° C. While stirring, 2.0% by weight of Al ₂ O ₃ was added to the suspension in the form of a sodium aluminate solution. After stirring for 15 minutes, 2.4% by weight of P ₂ O ₅ was added in the form of disodium hydrogen phosphate solution. Then, it was stirred for an additional 15 minutes. Subsequently, a 30% Ropaque Ultra Emulsion (polymer hollow beads made by Rohm and Haas), in which the styrene / acrylic copolymer active component content corresponds to 2% by weight based on TiO ₂ , is further added. Stir for 15 minutes. In the next step, the pH value was set to 5 by adding an aluminum sulfate solution corresponding to 2.6% by weight of Al ₂ O _{3 to the} suspension. Subsequently, 0.7% by weight of Al ₂ O ₃ was added in the form of adding sodium aluminate and aluminum sulfate solution together so that the pH value was maintained at 5.

After stirring for 30 minutes, the pH value of the suspension was set to about 5.8 using alkaline sodium aluminate solution, filtered and washed to remove the water soluble salts. And drying the washed filter paste in a spray dryer, NO ₃ was added to 0.25% by weight in the form of NaNO _3, which was steam milling subsequently.

Transmission electron microscopy of the pigments of this example shows hollow spheres attached to the pigment surface (see FIGS. 1A and 1B).

Reference Example :

The pH value of the sand milled TiO ₂ suspension from the chloride process with a TiO ₂ concentration of 350 g / l was set to 10 with NaOH at 60 ° C. While stirring, 2.0% by weight of Al ₂ O ₃ was added to the suspension in the form of a sodium aluminate solution. After stirring for 15 minutes, 2.4% by weight of P ₂ O ₅ was added in the form of disodium hydrogen phosphate solution. Then, it was stirred for an additional 15 minutes. In the next step, the pH value was set to 5 by adding an aluminum sulfate solution corresponding to 2.6% by weight of Al ₂ O _{3 to the} suspension. Subsequently, 0.8% by weight of Al ₂ O ₃ was added in the form of adding sodium aluminate and aluminum sulfate solution together to keep the pH value at 5.

After stirring for 30 minutes, the pH value of the suspension was set to about 5.8 using alkaline sodium aluminate solution, filtered and washed to remove the water soluble salts. And drying the washed filter paste in a spray dryer, NO ₃ was added to 0.25% by weight in the form of NaNO _3, which was steam milling subsequently.

Test method and test result

Test Methods

It is important to compare decorative laminated papers with the same ash content in order to test the optical properties of the decorative laminated paper and thus the quality of the titanium dioxide pigment. A decorative laminated sheet was prepared having a sheet weight of approximately 80 g / m 2 and ash content of approximately 30 g / m 2. Those skilled in the art are familiar with the procedure and the auxiliaries used.

The titanium dioxide content (ash) and pigment retention of the sheet were then measured.

a) ash content

The amount of paper produced was incinerated in a rapid incinerator at 900 ° C. to determine the titanium dioxide content. The weight of the residue was measured to obtain TiO ₂ content (% by weight) based on mass (ash). The following formula was used as the basis for calculating the ash content.

Ash content [g / m 2] = (ash [wt%] x grammage [g / m 2]) / 100 [%]

b) holding power

Retention force is defined as the ability to retain all the inorganic material in the paper sheet on the wire of the paper machine. “One-pass retention” as determined herein refers to the percent retention in a single pass through a paper machine. The ash content (%) related to the mass content of the pigment used relative to the total solids in the suspension yields the following retention.

Holding capacity [%] = {ash [%] × (pig weight [g] + pulp weight [g])} / pig weight [g]

c) optical properties

The optical properties of the pigment in the laminate were measured.

To this end, the decorative laminate was impregnated with a modified melamine impregnated resin and pressed to form a laminate. The resin-impregnated sheet is completely immersed in the melamine resin solution and then stretched between two doctor blades so that a specific amount of resin is applied, and then immediately precompressed in a recirculating air drying oven at 130 ° C. -condensing). The amount of resin applied was 120 to 140% of the weight of the sheet. The residual moisture content of the sheet was about 6% by weight. Compressed sheets were combined into a book containing phenolic resin impregnated core paper and black and white overlay paper.

Laminated structures used to test test pigments include decorative laminates, black and white shielding paper, heart paper, heart paper, heart paper, white shielding paper, heart paper, heart paper, heart paper, black and white heart paper, decorative laminates, A total of 11 floors were included.

The book was pressed for 300 seconds at a temperature of 140 ° C. and a pressure of 900 N / cm 2 using a Wickert Type 2742 lamination press.

The optical properties of the laminate were measured using a commercially available spectrophotometer.

3000 비색계를 사용하여 측정하였다. 불투명도는 종이의 광 투과율의 척도이다. 적층체의 불투명도의 척도로서, CIELAB L^* _흑색; 흑색 차폐지 위에서 측정한 적층체의 휘도; 및 흑색 차폐지 위에서 측정한 장식용 적층지의 Y 값(Y_흑색)과 백색 차폐지 위에서 측정한 Y 값(Y_백색)으로부터 측정한 불투명도 값 L[%] = Y_흑색/Y_백색 ×100와 같은 파라미터를 선택하였다.To test the optical properties of the laminate, the optical properties (CIELAB L ^* , a ^* , b ^* ) of the decorative laminates to DIN 6174 were tested on a black and white shielded paper.

Measurement was made using a 3000 colorimeter. Opacity is a measure of the light transmittance of a paper. As a measure of the opacity of the laminate, CIELAB L ^* _black ; Luminance of the laminate measured on the black shield paper; And the opacity value L [%] = Y _black / Y _white × 100 measured from the Y value (Y _black ) of the decorative laminated sheet measured on the black shield paper and the Y value (Y _white ) measured on the _white shield paper. Selected.

Test result

The following table shows the test results for laminates prepared using the pigments according to the invention (examples) and reference pigments (reference examples). Compared with reference pigments, the pigments according to the invention exhibit improved opacity.

[table]

Pigment Opacity Retention L ^* _black L [%] [%] Example 90.3 91.1 69 See Example 90.1 90.7 71

Claims (22)

A titanium dioxide pigment comprising titanium dioxide particles, wherein a coating containing aluminum phosphate, aluminum oxide and a hollow body is located on the surface of the particle. The titanium dioxide pigment according to claim 1, wherein the hollow body has an average diameter of 5 to 1,000 nm. Titanium dioxide pigment according to claim 1 or 2, characterized in that the aluminum content of the coating is 1.0 to 9.0% by weight, preferably 3.5 to 7.5% by weight, in particular 5.5% by weight, calculated as Al ₂ O ₃ . . The phosphorous content of the coating according to any one of claims 1 to 3, calculated as P ₂ O ₅ , is 1.0 to 5.0% by weight, preferably 1.5 to 3.5% by weight, in particular 2.0 to 3.0% by weight. Titanium dioxide pigment characterized by the above-mentioned. (a) providing an aqueous suspension of uncoated titanium dioxide particles, (b) adding an aluminum component and a phosphorus component, (c) adding a component comprising a hollow body, (d) setting the pH value of the suspension in the range of approximately 4-9. 6. The method of claim 5, wherein the pH value of the suspension is at least 10 in step (a) and the pH value of the suspension is maintained at 10 or more in step (b). 6. The method of claim 5, wherein in step (b) the pH value of the suspension is converted to less than 4. 8. A method according to any one of claims 5 to 7, characterized in that the average diameter of the hollow bodies is 5 to 1,000 nm. The method of claim 5, wherein in step (e) an additional aluminum coating is applied at a pH of approximately 4-9. The total amount of the aluminum compound to be added is 1.0 to 9.0% by weight, preferably 3.5 to 7.5% by weight, in particular 5.5% by weight, calculated as Al ₂ O ₃ . How to feature. The phosphorus compound according to any one of claims 5 to 9, wherein the total amount of the phosphorus compound is 1.0 to 5.0% by weight, preferably 1.5 to 3.5% by weight, in particular 2.0 to 3.0% by weight, calculated as P ₂ O ₅ . How to feature. The process according to any one of claims 5 to 11, wherein in step (b) an additional metal salt solution, for example Ce, Ti, Si, Zr or Zn, is added to the suspension together with the Al and P components. How to feature. 12. The method of claim 11, wherein in step (f) the final pH value of the suspension is set to approximately 5-8. The process according to claim 5, wherein in step (d) a solution of the acid metal salt of Ce, Ti or Zr is used for the adjustment of the pH value. 15. The process according to any one of claims 5 to 14, wherein in a subsequent step, the pigment particles are treated with nitrate such that the treated pigment contains 1.0 wt% or less of nitrate. The process according to claim 5, wherein the pigment particles are milled together with the organic material in a subsequent step. (a) providing an aqueous suspension of uncoated titanium dioxide particles, wherein the pH value of the suspension is at least 10, (b) adding an aluminum component and a phosphorus component and maintaining the pH value of the suspension at least 10, (c) adding a component comprising a hollow body, (d) setting the pH value of the suspension in the range of about 4 to 9, (e) applying a layer of aluminum oxide at a pH of 4-9. Titanium dioxide pigment particles prepared according to any one of claims 5 to 17. Use of the titanium dioxide pigment according to any one of claims 1, 2, 3, 4 or 18 in the manufacture of decorative laminated paper. A decorative laminated paper containing the titanium dioxide pigment according to any one of claims 1, 2, 3, 4 or 18. Use of decorative laminated paper containing the titanium dioxide pigment as described in any one of Claims 1, 2, 3, 4, or 18 in manufacture of a decorative coating material. A decorative covering comprising the decorative laminate according to claim 20.

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