EP1994098A2

EP1994098A2 - Titanium dioxide pigment coated with hollow bodies, and production method

Info

Publication number: EP1994098A2
Application number: EP07711855A
Authority: EP
Inventors: Lydia Drews-Nicolai; Siegfried Bluemel
Original assignee: Kronos International Inc
Current assignee: Kronos International Inc
Priority date: 2006-03-16
Filing date: 2007-03-08
Publication date: 2008-11-26
Also published as: DE102006012564A1; AU2007224748A1; KR20080102198A; JP5199894B2; AU2007224748B2; UA94075C2; MY151114A; WO2007104465A3; SA07280100B1; RU2008140369A; RU2443737C2; JP2009529613A; WO2007104465A2; CN101389714A; CN101389714B; DE102006012564B4; TW200740928A; BRPI0708985A2

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

Hollow coated titanium dioxide film and method of manufacture

Field of the invention

The invention relates to a titanium dioxide pigment with high opacity, a process for the preparation and its use in decorative paper or decorative films.

Technological background of the invention

Decorative paper or decorative films are part of a decorative, thermosetting coating material, which is preferably used for finishing furniture surfaces, for laminate flooring and interior design. Laminates are laminates in which, for example, several impregnated, laminated papers or papers and hardboard or chipboard are pressed together. The use of special resins results in extremely high scratch, impact, chemical and heat resistance of the laminates.

The use of decor papers (which shall be understood below also always decorative films) allows the production of decorative surfaces, the decorative paper not only as a cover paper for e.g. unattractive wood-based surfaces, but also serves as a support for the resin. The requirements for a decorative paper include, but are not limited to: Opacity (hiding power), light fastness (graying stability), color fastness, wet strength, impregnability and printability.

The economic efficiency of the production process of decorative papers is determined inter alia by the opacity of the pigment in the paper. To achieve the required opacity of the decorative paper, a pigment based on titanium dioxide is in principle outstandingly suitable. In papermaking, a titanium dioxide pigment or a titanium dioxide pigment suspension is usually mixed with a pulp suspension. In addition to the feedstock pigment and pulp generally also auxiliaries such. As wet strength agents and optionally other additives used. The interactions of the individual components (pulp, pigment, auxiliaries and additives, water) contribute to each other Paper formation and determine the retention of the pigment. Retention means the retention capacity of all inorganic substances in the paper during manufacture.

It is known that an improvement of the opacity can be achieved by special surface treatments on the titanium dioxide pigment.

In US 5,942,281 A and US 5,665,466 A a surface treatment is described in which a first layer of alumina phosphate is applied at an acidic pH of 4 to 6 and a second layer of alumina in a pH range of 3 to 10, preferably at pH is about 7 like. An improvement in retention is achieved by a third layer of magnesium oxide such that the pigment produced is characterized by successive layers of alumina phosphate, alumina and magnesia. US Pat. No. 6,962,622 discloses a titanium dioxide pigment mixture which comprises a pigment having high graying stability (type A of pigments) and a pigment having a coating which has an increased SiO ₂ and Al ₂ O ₃ content in flocculent precipitation (pigment type B) ,

No. 6,143,064 A describes a coating of pigment particles with precipitated calcium carbonate, the calcium carbonate particles being between 30 and 100 nm in size. The calcium carbonate-coated titanium dioxide achieves a higher opacity in the paper. The calcium particles take over the function of a spacing, so that the pigment particles have a better distribution in the paper. The minimum distance between the pigment particles should correspond approximately to the pigment particle size. US 5,886,069 A and US 5,650,002 describe TiO ₂ pigment particles which have both a continuous inorganic coating and a coating of inorganic individual particles with a diameter of 5 to 100 nm. The order of the surface coverage is arbitrary, as is the shape of the individual particles. The preparation is carried out by mixing a colloidal suspension of the individual particles with a TiO ₂ slurry. US 2003 0024437 A1 discloses a pigment mixture with pigment particles, on the surface of which spherical particles, such as calcium carbonate, silicon oxide, aluminum oxide, zirconium oxide or titanium oxide, have been precipitated in situ.

Task and summary of the invention

The object of the invention is to provide an alternative titanium dioxide pigment with good Opacity and good retention for use in decor papers. The object of the invention is further the provision of a method for producing such a titanium dioxide pigment.

The object is achieved by a titanium dioxide pigment which contains titanium dioxide particles and wherein on the particle surface a layer containing aluminum phosphate,

Alumina and hollow body is located.

The object is further achieved by a method for producing a coated

Titanium dioxide pigments containing the steps a) providing an aqueous suspension of uncoated titanium dioxide particles, b) adding an aluminum component and a phosphorus component, c) adding hollow bodies, d) adjusting the pH of the suspension to a value in the range between about 4 and 9.

Further advantageous variants of the invention are described in the subclaims.

Description of the invention

Here and below, the term "oxide" should also be understood to mean the corresponding hydrous oxides or hydrates.All of the details disclosed below with regard to pH, temperature, concentration in% by weight or% by volume etc. are to be understood as follows in that all values which are within the range of the respective measuring accuracy known to those skilled in the art are included The term "significant amount" or "significant proportion" in the context of the present patent denotes the minimum quantity of a component above which the properties of the mixture in the context of Measuring accuracy can be influenced.

The titanium dioxide pigment of the invention is characterized by the use of hollow bodies. The hollow bodies also include hollow spheres, micro hollow bodies or hollow microspheres. The hollow bodies are used according to the invention in the aftertreatment. The hollow bodies are deposited on the particle surface and act as spacers between the individual pigment particles. The hollow bodies may be inorganic and organic in nature. They preferably have an average diameter of 5 to 1000 nm. The hollow bodies are characterized by the inclusion of air, the air inclusion may not be until after the drying of the Pigments is present.

Organic hollow bodies are used, for example, as fillers in paints. The hollow bodies act as spacers between the pigment particles and lead by their air pockets to a higher hiding power taking advantage of the favorable

Refractive index difference between pigment and air ("Quality improvement RopaqueTM Opaque polymer to improve the quality of paints and coatings", phenomenon color 2/98, 1/99). For the production of organic hollow bodies, the publication "Hollow latex particles: synthesis and applications" ( McDonald et al., Advances in Colloid and Interface Science 99 (2002) 181-213). The production of inorganic hollow spheres is described by way of example in "Nanoengineering of Inorganic and Hybrid Hollow Spheres by Colloidal Templating" (Caruso et al., Science 1998, Vol 282, p 1111. WO 02/074431 A1 discloses the preparation of inorganic Hollow bodies and their application in catalysis and in photonics.

In the method according to the invention, a layer of aluminum-phosphorus compounds in the mixture with hollow bodies and optionally with aluminum oxide is deposited on the TiO ₂ particle surface. The composition depends on the amounts of aluminum and phosphorus components used. In the following, this layer will be referred to simply as alumina phosphate hollow sphere layer.

The aftertreatment process on which the invention is based is based on an aqueous and preferably wet-milled TiO ₂ suspension (step a). The wet grinding is optionally carried out in the presence of a dispersant. The TiO ₂ are uncoated TiO ₂ particles, ie, TiO ₂ bulk particles prepared by the sulfate (SP) or chloride (CP) method. The main bodies are usually stabilized, in the CP process by addition of aluminum in the amount of 0.3 to 3 wt .-% calculated as Al ₂ O ₃ and an excess of oxygen in the gas phase in the oxidation of titanium tetrachloride to titanium dioxide of 2% - % and in the SP method by doping with eg Al, Sb, Nb or Zn.

Preference is given to using TiO ₂ particles produced by the chloride process. The

Process is carried out at a temperature of below 80 ^C C, preferably at 55 to 65 ⁰ C.

The suspension in step a) can be adjusted both alkaline and acidic with a pH preferably> 9 or <4. In a step b), an aluminum component and a phosphorus component are added.

Suitable aluminum components for the invention

Surface treatment methods are alkaline or acidic water soluble

Salts, for example, sodium aluminate, aluminum sulfate, aluminum nitrate, aluminum chloride, aluminum acetate, etc. This selection is not intended to be limiting. The

Aluminum component should in an amount of 1, 0 to 5.0 wt .-%, preferably 1, 5 to 4.5

Wt .-%, in particular 2.0 wt .-% calculated as Al ₂ O ₃ and based on the TiO ₂ particles are added.

Suitable phosphorus components are inorganic compounds such as alkali phosphates, ammonium phosphate, polyphosphates, phosphoric acid, etc. This selection is not as

To understand limitation. Particularly suitable are disodium hydrogen phosphate or

Phosphoric acid. The phosphorus component is in a concentration of 1, 0 to 5.0

Wt .-%, preferably 1, 5 to 4.0 wt .-% in particular 2.0 to 3.0 wt .-% calculated as P ₂ O ₅ based on the TiO ₂ particle added. The AI and P components may be added to the suspension in any order one at a time or simultaneously.

In a subsequent step c), the addition of organic or inorganic hollow bodies with an average diameter of 5 to 1000 nm, preferably from 400 to 600 nm.

As organic hollow spheres, for example, the product Ropaque ™ from Rohm & Haas comes into question. RopaqueTM is styrene / acrylic copolymer hollow spheres. Also suitable are other latex or polymer hollow spheres. However, this list is not to be understood as limiting the invention. On the contrary, in principle all organic hollow bodies which have the required particle diameter in the range from 5 to 1000 nm and which are stable at the occurring pH values are suitable. As inorganic Hohlkkörper both hollow glass spheres, and ceramic hollow spheres in general as well as in the special TiO ₂ hollow spheres are described in the prior art. It also applies here that all types of inorganic hollow bodies can be used in principle in the context of the invention, provided that they have the required mean

Have particle diameter of 5 to 1000 nm and if they are stable at the occurring pH values. The person skilled in the art will select the suitable hollow bodies due to boundary conditions such as processibility, costs, etc. The hollow bodies are added in an amount of 1 to 15 wt .-% based on the uncoated TiO ₂ particles. In a further step d), the pH of the suspension is adjusted to a value in the range from 4 to 9 by addition of a pH-adjusting component. The pH-adjusting component used may be an acid or an alkali. As the acid, for example, sulfuric acid, hydrochloric acid, phosphoric acid or another suitable acid can be used. Furthermore, instead of the acid, a corresponding acidic salt such as, for example, aluminum sulfate can also be used. Furthermore, it is possible to use an acidic metal salt solution of, for example, cerium, titanium or zirconium, so that a common precipitation takes place with the aluminum oxide phosphate hollow-sphere layer. Caustic soda is preferably used as the lye. Also suitable are alkaline salts. The skilled person is suitable pH-regulating

Known connections. The selection is therefore not to be understood as limiting the invention.

It has proved to be advantageous, in a subsequent step e) on the alumina phosphate hollow sphere layer to apply a layer of alumina such that by the parallel addition of an alkaline and an acidic aluminum component (eg sodium aluminate / aluminum sulfate) or by the Addition of an alkaline aluminum component such as sodium aluminate and an acid, for example sulfuric acid or hydrochloric acid or by the addition of an acidic aluminum component such as aluminum sulfate together with an alkali such as NaOH, the pH is maintained in the range of 4 to 9. In this case, the components can either be added so that the pH remains constant at a value in the range 4 to 9. Or the components are added in such a combination that the pH during the addition varies within the pH range 4 to 9. The person skilled in the art knows these procedures. For example, alkalis or acids (eg NaOH / H ₂ SO ₄ ) or alkaline or acidic salt solutions (eg sodium aluminate / aluminum sulfate) are suitable for adjusting the pH. It has proven particularly advantageous to carry out the treatment at the pH which was set in step d).

If required, then in a step f), a pH adjustment to 5 to 8, for example with alkalis / acids (eg NaOH / H ₂ SO ₄ or HCl) or with alkaline / acidic salt solutions such as sodium aluminate / aluminum sulfate.

The amount of aluminum compounds used in step d), e) and f), calculated as Al ₂ O _3, are to be taken into account for the amount of Al ₂ O ₃ already used in step b). The sum The aluminum compounds used in steps b) to f), calculated as Al ₂ O ₃ based on the uncoated TiO ₂ particle, is ideally from 1.0 to 9.0% by weight, preferably from 3.5 to 7.5% by weight. %, in particular 5.5% by weight. Likewise, the amount of the phosphorus component optionally used in steps d) and e), calculated as P ₂ O _{5, is} to be taken into account for the amount of P ₂ O ₅ used in step b). The sum of the phosphorus compounds used in steps b) to e) calculated as P ₂ O ₅ is thus ideally from 1, 0 to 5.0 wt .-%, preferably 1, 5 to 3.5 wt .-% and in particular 2 , 0 to 3.0 wt .-% calculated as P ₂ O ₅ based on the uncoated TiO ₂ particles.

Together with the AI and the P component can also in step b)

Metal salt solutions of z. As Ce, Ti, Si, Zr or Zn are added to the suspension, which are then precipitated in step d) together as phosphate or oxide in the alumina phosphate hollow sphere layer on the particle surface. Further, it is possible to apply, either before step e) or after step e), another inorganic layer as known in the art (e.g., Zn, Ti, Si containing compounds).

In a preferred embodiment of the method according to the invention is based on an alkaline TiO ₂ suspension. For this purpose, in step a) the suspension is first adjusted to a pH of at least 10 with suitable alkaline compounds, eg NaOH. This happens, if a wet grinding takes place, ideally before the grinding.

In step b), an aluminum component and a phosphorus component are subsequently added to the suspension in the form of an aqueous solution. During the addition of the components, the pH of the suspension is maintained at least 10, preferably at least 10.5 and more preferably at least 11. As the alkaline aluminum component is particularly suitable sodium aluminate. If it is an acidic compound, for example aluminum sulfate, which would reduce the pH to less than 10 upon addition, it has proved to be advantageous to compensate for this effect by adding a suitable alkaline compound such as NaOH. The person skilled in the art, the appropriate alkaline compounds and the necessary amounts to keep the pH at least 10, familiar.

In the case of phosphorus components, the addition of which would lower the pH below 10, it has also been found advantageous to compensate for this effect by adding a suitable alkaline compound, such as NaOH. The person skilled in the appropriate alkaline compounds and the necessary amounts to the pH at to keep at least 10, common.

The AI and P components may be added to the suspension in any order one at a time or simultaneously.

In the subsequent step c), the addition of the organic or inorganic hollow body having an average diameter of 5 to 1000 nm, preferably from 400 to 600 nm, wherein the pH of the suspension is not less than 10, preferably not less than 10.5 in particular not below 11 drops.

In the subsequent step d), the addition of the pH-regulating component takes place so that a pH in the range of 4 to 9 is established.

In an alternative embodiment of the method according to the invention, the surface treatment according to the invention is started from the acidic pH range.

In this case, in step b), such aluminum and phosphorus components are added that the pH of the suspension is below a value below 4. It is up to the person skilled in the art whether he already lowers the pH in step a) with a suitable acid or whether in step b) he lowers the pH to below 4 by adding a suitable combination of the components. For example, the combinations phosphoric acid / sodium aluminate or disodium hydrogen phosphate / aluminum sulfate are suitable. The components may be added to the suspension in any order one at a time or simultaneously. In step c) only hollow bodies are used which are stable at an acidic pH. In step d), in turn, a pH-regulating component is added, which sets a pH of 4 to 9.

The surface-treated TiO ₂ pigment is separated from the suspension by methods of filtration known to those skilled in the art, and the resulting filter cake is washed to remove the soluble salts. The washed filter paste can be used to improve the light fastness of the pigment in the laminate before or during the subsequent drying a nitrate-containing compound, for example KNO ₃ , NaNO ₃ , Al (NO ₃ ) ₃ in an amount of 0.05 to 0.5% calculated as NO ₃ , to be mixed. In the subsequent grinding, for example with a steam mill, an organic compound can be added to the pigment from the series of those which are commonly used in the preparation of TiO ₂ pigments and which are known in the art such as polyhydric alcohol (trimethylolpropane). Alternatively to the addition of the nitrate-containing compounds before or during the drying, the addition of such substances can also take place during the grinding.

The pigment produced by this process exhibits improved opacity over the comparative pigments and is ideally suited for use in decorative paper or in decorative coating materials.

The surface treatment method according to the invention is usually carried out in batch mode. However, it is also possible to carry out the treatment continuously, whereby a suitable mixing must be guaranteed by suitable mixing elements, as are known to those skilled in the art.

Working Example

In the following, the invention is described by way of example, without any intention to limit the invention.

For example, a sand-milled _TiO2 suspension from the chloride process with a TiO ₂ concentration of 350 g / l was set at 60 ⁰ C with NaOH to a pH of 10th With stirring, 2.0% by weight of Al ₂ O ₃ as a sodium aluminate solution was added to the suspension. After a stirring time of 15 minutes, 2.4% by weight of P ₂ O _{5 were added} as disodium hydrogen phosphate solution. It was followed by another stirring time of 15 minutes. Subsequently, 30% Ropque Ultra Emulsion (hollow polymer spheres Rohm & Haas) according to a

Active substance content styrene / acrylic copolymer of 2 wt .-% based on TiO ₂ added and stirred for a further 15 minutes. The suspension was adjusted to a pH of 5 in the next step by addition of aluminum sulfate solution corresponding to 2.6% by weight of Al ₂ O ₃ . Subsequently, 0.7% by weight of Al ₂ O ₃ in the form of a parallel addition of sodium aluminate and aluminum sulfate solution was mixed in such a way that the pH was kept at 5.

The suspension was adjusted to a pH of about 5.8 after a stirring time of 30 minutes with the aid of an alkaline sodium aluminate solution, filtered and freed from the water-soluble salts by washing. The washed filter paste was dried in a spray dryer with the addition of 0.25 wt .-% NO ₃ in the form of NaNO ₃ and then steam-milled. A transmission electron micrograph of the example pigment in FIG. 1 shows the hollow bodies deposited on the pigment surface.

Comparative Example: A sand-milled _TiO2 suspension from the chloride process with a TiO ₂ concentration of 350 g / l was set at 60 ⁰ C with NaOH to a pH of 10th With stirring, 2.0% by weight of Al ₂ O ₃ as a sodium aluminate solution was added to the suspension. After a stirring time of 15 minutes, 2.4% by weight of P ₂ O _{5 were added} as disodium hydrogen phosphate solution. It was followed by another stirring time of 15 minutes. The suspension was adjusted to a pH of 5 in the next step by addition of aluminum sulfate solution corresponding to 2.6% by weight of Al ₂ O ₃ . Subsequently, 0.8% by weight of Al ₂ O ₃ in the form of a parallel addition of sodium aluminate and aluminum sulfate solution was admixed so that the pH was kept at 5. The suspension was adjusted to a pH of about 5.8 after a stirring time of 30 minutes with the aid of an alkaline sodium aluminate solution, filtered and freed from the water-soluble salts by washing. The washed filter paste was dried in a spray dryer with the addition of 0.25 wt .-% NO ₃ in the form of NaNO ₃ and then steam-milled.

Test methods and test results

test methods

For the assessment of the optical properties of the decorative papers and thus the quality of the titanium dioxide pigment, it is important that decorative papers of the same ash content are compared. Decorative paper sheets having a sheet weight of about 80 g / m ² and an ash content of about 30 g / m ² were prepared. The procedure and the auxiliaries used are known to the person skilled in the art. The titanium dioxide content (ash) of a leaf and the retention of the pigment were then determined.

a) ash content

To determine the titania content of a defined weight of the produced paper was ashed with a rapid incinerator at 900 ⁰ C. The weight of the residue gave the mass fraction of TiO ₂ (ash) in% by weight. For calculating The ash content was based on the following formula: ash content [g / m ² ] = (ash [wt.%] x basis weight [g / m ² ]) / 100 [%].

b) Retention Retention refers to the retention capacity of all inorganic substances in the

Paper sheet on the screen of the paper machine. The so-called one-pass retention, which has been determined here, indicates the percentage that is retained in the one-time feeding process of the paper machine. The percentage of ash based on the mass fraction of the pigment used in the total solids of the suspension gives the retention:

Retention [%] = ash f% l x (weight of pigment [gl + weight of pulp [gl)]

Weight of pigment [g]

b) Optical Properties The optical properties of the pigments were determined in laminates.

For this purpose, the decorative paper was impregnated with a modified melamine impregnating resin and pressed into laminates. The sheet to be sealed was completely immersed in the melamine resin solution, then drawn between 2 squeegee to ensure a certain resin application, and immediately precondensed in a convection oven at 130 ⁰ C. The resin coverage was 120 to 140% of the sheet weight. The sheet had a residual moisture of about 6 wt .-%. The condensed sheets were combined with phenolic resin impregnated core papers and white / black underlay paper into press packages. For the evaluation of the test pigments, the laminate structure consisted of 11 layers: decorative paper, white / black underlay, core paper, core paper, core paper, white underlay, core paper, core paper, core paper, white / black underlay, decorative paper. The packages are pressed by means of a Wickert type 2742 laminate press at a temperature of 140 ^° C. and a pressure of 900 N / cm ² for a pressing time of 300 seconds. The measurement of the optical properties of the laminates was carried out using a commercially available spectrophotometer.

To evaluate the optical properties of the laminates, the color values of the decor papers were (CIELAB L *, a *, b ^*) according to DIN 6174 is determined using the ELREPHO ^® 3000 calorimeter over white and black underlay. The opacity is a measure of the translucence or transmission of the paper. The following sizes were chosen as a measure of the opacity of the laminates: CIELAB L ^* _SC hwarz _> the brightness of the laminates measured over black underlay paper, and the opacity value L [%] = (Yblack / Yweiu) ^{x 10} °. determined from the Y value of the decor papers measured over black Unterlay paper (Y _black) and the Y value measured over a white underlay paper (Y _wh ite) -

Testerqebnisse

The table shows the test results for laminates made with the pigment according to the invention (example) and with a comparative pigment (comparison). The pigment of the invention has improved opacity over the comparative pigment.

TABLE

Pigment opacity retention

L ^* black L [%] [%]

Example 90.3 91, 1 69 Comparison 90.1 90, 7 71

Claims

1. titanium dioxide pigment containing titanium dioxide particles, wherein on the particle surface is a coating containing aluminum phosphate, alumina and hollow body.

2. titanium dioxide pigment according to claim 1, characterized in that the hollow bodies have an average diameter of 5 to 1000 nm.

3. Titanium dioxide pigment according to claim 1 or 2, characterized in that the aluminum content of the coating 1, 0 to 9.0 wt .-%, preferably 3.5 to 7.5 wt .-%, in particular about 5.5 wt. % calculated as Al ₂ O ₃ .

4. Titanium dioxide pigment according to one or more of claims 1 to 3, characterized in that the phosphorus content of the coating 1, 0 to 5.0 wt .-%, preferably 1, 5 to 3.5 wt .-%, in particular 2.0 to 3.0 wt .-% calculated as P ₂ O ₅ .

5. A process for producing coated titanium dioxide pigment particles comprising the steps a) providing an aqueous suspension of uncoated titanium dioxide particles b) adding an aluminum component and a phosphorus component c) adding a component containing hollow bodies, d) adjusting the pH of the Suspension to a value in the range of about 4 to 9.

6. The method according to claim 5, characterized in that in step a) the pH of the suspension is at least 10 and in step b) the pH of the suspension is maintained at least 10.

7. The method according to claim 5, characterized in that adjusts a pH of the suspension below 4 in step b).

8. The method according to any one of claims 5, 6 or 7, characterized in that the hollow bodies have an average diameter of 5 to 1000 nm.

9. The method according to one or more of claims 5 to 8, characterized in that in a step e) at a pH of about 4 to 9, a further aluminum oxide layer is applied.

10. The method according to one or more of claims 5 to 9, characterized in that the sum of the added aluminum compounds 1, 0 to 9.0 wt .-%, preferably 3.7 to 7.5 wt .-%, in particular about 5.5 wt .-% calculated as Al ₂ O ₃ .

11. The method according to one or more of claims 5 to 9, characterized in that the sum of the added phosphorus compounds 1, 0 to 5.0 wt .-%, preferably 1, 5 to 3.5 wt .-%, in particular 2.0 to 3 , 0 wt .-% calculated as P ₂ O ₅ .

12. The method according to one or more of claims 5 to 11, characterized in that in step b) together with the AI and the P-component further metal salt solutions of e.g. Ce, Ti, Si, Zr or Zn are added to the suspension.

13. The method according to claim 1 1, characterized in that in a step f) the final pH of the suspension is adjusted to about 5 to 8.

14. The method according to one or more of claims 5 to 13, characterized in that in step d) an acidic metal salt solution of Ce, Ti or Zr is used for adjusting the pH.

15. The method according to one or more of claims 5 to 14, characterized in that in a subsequent step, the pigment particles are treated with nitrate, so that the finished pigment contains up to 1, 0 wt .-% nitrate.

16. The method according to one or more of claims 5 to 15, characterized in that in a subsequent step, the pigment particles are ground with an organic substance.

17. A process for the preparation of coated titanium dioxide pigment particles comprising the steps of a) providing an aqueous suspension of uncoated titanium dioxide particles, wherein the pH of the suspension is at least 10 b) adding an aluminum and a phosphorus component, wherein the pH C) adding component containing hollow body, d) adjusting the pH of the suspension to a value in the range of about 4 to 9. e) applying an alumina layer at a pH from about 4 to 9.

18. titanium dioxide pigment particles prepared by a process according to one or more of claims 5 to 17.

19. Use of the titanium dioxide pigment according to one or more of claims 1, 2, 3, 4, 18 in the production of decorative paper.

20. decorative paper containing a titanium dioxide pigment according to one or more of claims 1, 2, 3, 4, 18.

21. Use of decorative paper, which contains a titanium dioxide pigment according to one or more of claims 1, 2, 3, 4, 18, for the production of decorative coating materials.

22. Decorative coating material containing decorative paper according to claim 20.