HK1206769B - Titanium dioxide-containing and carbonate-containing composite pigments and method for producing same - Google Patents

Description

Composite pigment containing titanium dioxide and carbonate and method for producing the same

Technical Field

The present invention relates to composite pigments containing titanium dioxide and carbonate, a method for their preparation and their use in improving the light scattering efficiency of pigments in coatings, plastics and laminates.

Background Art

Inorganic pigments, particularly titanium dioxide, are commonly added to various matrices as brighteners, colorants, or opacifiers. Due to its high refractive power, titanium dioxide scatters light very efficiently, making it a key white pigment in applications such as coatings and paints, plastics, paper, and fibers. Light scattering efficiency decreases when titanium dioxide particles are distributed within a matrix at a distance less than half the wavelength of light, i.e., at intervals of 0.20 to 0.25 μm. Light scattering efficiency is typically measured by the hiding power or tinting strength of the titanium dioxide pigment within the matrix.

On the other hand, titanium dioxide is a significant cost factor, and solutions have long been sought to reduce the amount of titanium dioxide used without significantly reducing hiding power.

Titanium dioxide particles can be combined with suitable fillers to conserve their use, acting as spacers between the _TiO₂ particles as so-called "extender particles." Known methods range from simple mixing of the components to bonding the _TiO₂ particles to the extender particles using a precipitated binder, or by in-situ precipitation of the extender onto the surface of the titanium dioxide particles. Also known are methods for distributing fine titanium dioxide particles onto coarser filler particles.

The following are only some of the documents selected from a large number of existing technologies.

For example, WO 1999/035193 A1 describes the production of pigment mixtures from titanium dioxide with inorganic extenders ("spacers") such as SiO ₂ or CaCO ₃ for use in papermaking.

DE 10 057 294 C5 proposes a pigment mixture consisting of titanium dioxide and talc for use in decorative base paper.

EP 0 861 299 B1 discloses a titanium dioxide pigment coated with inorganic nanoparticles (e.g., colloidal silicic acid) and a layer composed of an inorganic oxide (e.g., aluminum oxide, silicon oxide, or zinc oxide), wherein the inorganic oxide layer is either arranged between the titanium dioxide surface and the nanoparticles or forms an outer covering coating. The inorganic nanoparticles are SiO ₂ , Al ₂ O ₃ , or CaCO ₃ .

DE 10 2006 012 564 A1 discloses titanium dioxide pigment particles having hollow microspheres and an aluminum oxide-aluminum phosphate coating on the surface.

In the process proposed in EP 0 956 316 B1, pigment particles are mixed with precipitated calcium carbonate (PCC) in an aqueous phase to produce a composite pigment in which carbonate particles with a particle size of 30 to 100 nm adhere to the surface of the pigment particles. The composite pigment contains 30 to 90% by weight of precipitated calcium carbonate.

WO2009/109705 A1 proposes a composite pigment, wherein pigment particles are surrounded by mutually bonded nano-calcium carbonate particles.

DE 1 792 118 A1 proposes the in situ precipitation of calcium carbonate in a titanium dioxide pigment suspension by mixing a calcium chloride solution with a sodium carbonate solution, wherein one of the solutions contains the titanium dioxide pigment. This produces calcium carbonate-titanium dioxide composite particles.

WO 2000/001771 A1 proposes a composite pigment comprising inorganic particles with a particle size of approximately 1 to 10 μm, with titanium dioxide pigment particles adhered to the surfaces of these inorganic particles in reverse order of surface charge. Production is carried out in an aqueous phase. The inorganic particles are selected from commonly used fillers such as kaolin, clay, talc, mica, or carbonates.

WO 2013/023018 A1 proposes a pigment mixture consisting of carrier particles, pigment particles and colloidal spacer particles, wherein the spacer particles are located on the surface of the pigment particles, and the pigment particles with the spacer particles are dispersed on the surface of the carrier particles.

Summary of the Invention

The object of the present invention is to provide an alternative composite pigment with a reduced titanium dioxide content, which achieves the same covering power as pure titanium dioxide, and a method for its production.

The present invention provides a solution for achieving the above-mentioned object, which is a composite pigment containing titanium dioxide and carbonate, comprising:

- titanium dioxide particles,

- at least one inorganic and/or organic filler, and

- calcium carbonate precipitated at least partially in situ in an amount of less than 30 wt. % (based on the composite pigment).

Another solution of the present invention for achieving the above-mentioned object is a method for producing composite pigment particles containing titanium dioxide and carbonate, using titanium dioxide, at least one inorganic and/or organic filler, and a soluble calcium source and a carbonate source as two reaction components, comprising the following steps:

a) preparing an aqueous suspension containing titanium dioxide particles, filler particles and the one reaction component,

b) adding the second reaction component and adjusting the pH value of the suspension to >8, preferably >8.5

c) separating the composite pigment particles from the suspension, wherein the amount of the added soluble calcium source, calculated as CaCO ₃ , is less than 30 wt % (based on the composite pigment).

Advantageous embodiments of the invention are given by the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a scanning electron micrograph of a composite pigment having the composition of Example 3 of the present invention.

DETAILED DESCRIPTION

All data provided below, i.e., size in units of μm, concentration in units of wt% or vol.%, and pH value, etc., include all values within the measurement accuracy range known to those skilled in the art.

The composite pigment particles according to the invention are characterized in that the titanium dioxide pigment particles are uniformly distributed on the surface of the inorganic or organic filler particles (extender) and that a strong bond is established between the extender particles and the titanium dioxide pigment particles by means of in situ precipitated calcium carbonate, which bond does not break during typical further processing by the user, for example, during dispersion in a dissolver or in-line disperser.

Compared to the corresponding composite particles or pigment mixtures in the prior art, in particular those having the compositions disclosed in WO 2009/109705 A1 and WO 2013/023018 A1, the composite pigment particles of the present invention differ in that the in situ precipitated calcium carbonate in the present invention primarily establishes a connection between the filler particles and the titanium dioxide particles, without covering the surface of the titanium dioxide particles and without interacting as a spacer for the titanium dioxide particles (see FIG. 1 ).

The titanium dioxide particles or titanium dioxide pigment particles in the present invention refer to particles having a size of about 100 nm to about 1 μm.

The composite pigment particles of the present invention contain pigment dispersed in a near-ideal manner, thereby improving the light scattering efficiency of the titanium dioxide pigment. This prevents the presence of non-ideally dispersed, "flocculated" portions of the pigment. These composite pigment particles can improve covering power in a user's system while maintaining the same pigment content, or reduce the pigment content in a user's system while maintaining the same covering power.

The composite pigment particles of the present invention are produced using titanium dioxide, at least one inorganic and/or organic filler, and as two reactive components a soluble calcium source and a carbonate source. The present invention involves producing an aqueous (especially well-dispersed) suspension containing titanium dioxide particles, inorganic and/or organic filler particles, and a reactive component. The second reactive component is added to the suspension and the pH is adjusted to >8, preferably >8.5. Finally, the composite particles are separated from the suspension. The amount of the added soluble calcium source, calculated as _CaCO₃ , is less than 30 wt% (based on the composite pigment).

In a first embodiment of the present invention, the composite pigment particles can be produced by preparing an aqueous suspension of titanium dioxide particles and calcium carbonate particles (as a soluble calcium source) and setting the pH to an acidic pH of less than 5, preferably less than 4.3 (optionally with the aid of an acid-reactive compound) to completely dissolve the calcium carbonate particles or to a solubility of at least 50%. Subsequently, a filler and a carbonate source are added to reprecipitate the calcium carbonate and establish connections between the titanium dioxide particles, the filler particles, and the calcium carbonate particles. The carbonate source is preferably an alkaline carbonate, such as sodium carbonate. Alternatively, the pH of the suspension can be adjusted to greater than 8, preferably greater than 8.5, by adding an alkaline compound, without adding an alkaline carbonate compound, and then carbon dioxide gas is introduced.

In principle, surface-treated or untreated titanium dioxide pigment particles can be used. Untreated titanium dioxide bulk particles, in particular those produced in a chlorination process, are preferred. The titanium dioxide pigment particles may be doped, preferably with aluminum. A particularly advantageous solution in terms of economy is to use titanium dioxide bulk particles produced in a chlorination process that have not been sand-ground or dechlorinated. Alternatively, sand-ground and dechlorinated titanium dioxide bulk particles produced in a chlorination process may be used.

For example, calcium salts such as calcium chloride, calcium nitrate, or calcium hydroxide can be used as soluble calcium sources. Calcium carbonate in the form of commercially available calcium carbonate variants known to those skilled in the art can also be used. Advantageously, the calcium carbonate used has a high whiteness and a particle size of up to approximately 100 μm, preferably 1 to 40 μm, and in particular 1 to 20 μm. Natural calcium carbonate in the form of chalk or marble powder is preferred.

For example, inorganic acids such as hydrochloric acid or nitric acid can be used as acid-reactive compounds. In addition, acid-reactive salts whose cations do not interfere with the structure of the composite pigment particles and their subsequent use in the user system are also suitable. Particularly advantageously, acid-reactive compounds associated with the production of titanium dioxide, such as titanium oxychloride (titanium oxychloride), and, depending on the process, hydrochloric acid or hypochlorous acid associated with the chlorination process, are used. In the chlorination process, these acids are generated, for example, by dissolving chlorine when the pigment is transferred to the aqueous phase.

The acidic suspension of titanium dioxide and a soluble calcium source (e.g., calcium carbonate) can be prepared in different sequences. For example, an aqueous suspension of titanium dioxide particles and calcium carbonate particles at a pH of approximately neutral can be prepared first, followed by the addition of an acidic component. Alternatively, a bulk suspension of undechlorinated titanium dioxide, typically at a pH of 2.5 to 4, produced during the chlorination process can be used. After the addition of calcium carbonate, the pH can be adjusted to <5, preferably <4.3, by adding another acidic component as appropriate. As a rule of thumb, calcium carbonate dissolves at a pH <5.

In another embodiment of the present invention, calcium chloride, calcium nitrate or calcium hydroxide can be added to the titanium dioxide suspension as a soluble calcium source, and then the pH value of the suspension is adjusted to <5, preferably <4.3, by adding an acidic component as appropriate.

In principle, all commercially available inorganic or organic fillers known to those skilled in the art, including mixtures thereof, can be used as fillers. Suitable inorganic fillers include, for example, natural or precipitated calcium carbonate, calcium magnesium carbonate or magnesium carbonate, such as marble powder, chalk, precipitated calcium carbonate (PCC), dolomite, magnesite, hydromagnesite or magnesite. At this time, "carbonate" also includes carbonates containing hydroxyl groups and/or water of crystallization. In addition, suitable ones include: sulfates (such as barium sulfate and calcium sulfate), natural phosphates, hydroxides (such as magnesium hydroxide, aluminum hydroxide or hydrated aluminum oxide) and oxides (such as natural, ground, pyrolyzed or precipitated silicon dioxide, such as quartz powder, diatomaceous earth, etc.). In addition, silicates and aluminosilicates, such as talc, zeolite, kaolin, wollastonite, mica, unfired or fired clay minerals, are also suitable. Also suitable, for example, are pearlite and glass powder. Inorganic or organic fibers can also be used as fillers. In addition, suitable organic fillers include, for example, Ropague from Rohm & Haas.

White fillers are preferably used. Particularly preferred are calcium magnesium carbonate or magnesium carbonate, such as dolomite, spelterite, hydromagnesite or magnesite.

The filler particles generally have a particle size greater than 1 μm. Suitable particle sizes are at least 1 to 30 μm, preferably 2 to 10 μm.

The mixture then needs to be thoroughly stirred or dispersed. Dispersing equipment known to those skilled in the art, such as a dissolver or various in-line dispersers, is preferably used. The intensity and duration of the dispersion operation will vary depending on the filler and pigment used and will correspond to the setup used in the manufacture of the dispersible coating. Such procedures are known to those skilled in the art.

Subsequently, an alkaline carbonate compound, such as sodium carbonate, is added to the suspension in an amount such that the pH of the suspension is raised to >8, preferably >8.5, and the dissolved calcium carbonate is reprecipitated.

Alternatively, instead of adding an alkaline carbonate compound, an alkaline compound may be added to adjust the pH of the suspension to greater than 8, preferably >8.5, and then carbon dioxide gas may be introduced to precipitate calcium carbonate.

As already mentioned above, in this case too, it is necessary to stir the suspension thoroughly during the precipitation.

Finally, the composite pigment particles are separated from the suspension by filtration, washed and dried.

In a second embodiment of the present invention, the composite pigment particles are produced as follows: an alkaline carbonate compound (e.g., sodium carbonate) is added as a first reaction component to an aqueous suspension of titanium dioxide particles, which may have an alkaline pH. Subsequently, at least one inorganic and/or organic filler is added to the suspension. Suitable fillers are listed above. Subsequently, a soluble calcium source is added as a second reaction component, and optionally an alkaline-reactive compound is added to adjust the pH of the suspension to >8, preferably >8.5. For example, _CaCl₂ , Ca( _NO₃ ) _₂ , or Ca(OH) _₂ can be used as the soluble calcium source. Alternatively, CaCl₂, Ca( _NO₃ ) _₂ , or Ca(OH) _₂ can be used as the first reaction component, wherein the pH of the suspension is adjusted to >8, preferably >8.5. In this case, the carbonate source in the form of an alkaline carbonate compound, or _in the form of a combination of _CO₂ gas and an alkaline compound, is added as the second reaction component.

As mentioned above, the suspension needs to be stirred well during precipitation.

Finally, the composite pigment particles are separated from the suspension by filtration, washed and dried.

In the present invention, the amount of the added soluble calcium source, calculated as CaCO ₃ , is less than 30 wt%, preferably 10 to 25 wt% (based on the composite pigment particles). The composite pigment particles preferably contain up to 70 wt% TiO ₂ , in particular up to 50 wt% TiO ₂ , and in particular 30 wt% TiO ₂ .

The efficiency of titanium dioxide can be optimized depending on the desired quality of the coating or paint produced using the composite pigment particles. This more efficient use of the composite pigment particles results in pigment savings, which can be advantageous compared to using extenders and pigment separately. For equivalent optical properties, the composite pigment particles produced by the present invention can achieve pigment savings of up to 30%, preferably 15 to 30%, when used in a user's system.

The composite pigment of the present invention can be combined with pure _TiO2 , or the _TiO2 required in the user's system can be added by completely replacing it with the composite pigment of the present invention.

Another advantage is that the _TiO₂ is already well distributed on the composite pigment particles, saving energy required for dispersion in the paint system. Coarser extender particles and composite pigment particles require less dispersion energy, grinding energy, and dispersant. This makes the use of these composites advantageous for paint manufacturers.

In another embodiment of the method of the present invention, the composite pigment particles of the present invention may be additionally treated with phosphoric acid or sodium silicate to enhance the acid resistance of the product.

The composite pigment particles of the present invention can also be treated with inorganic compounds commonly used in the manufacture of titanium dioxide. The corresponding compounds and treatment methods are known to those skilled in the art.

In a particular embodiment of the method according to the present invention, an organic additive in an amount of 0.05 to 30 wt. %, preferably 0.5 to 10 wt. %, based on the pigment-extender mixture, can be added to the mixing device. The organic additive can be either solid or liquid. Commercially available waxy additives, with or without additional chemical effects, are suitable as organic additives. Known dispersing additives or other auxiliary materials commonly used in paint technology, such as those for rheological, defoaming, and wetting effects, are also suitable.

The composite pigment particles of the present invention are particularly suitable for use in interior or exterior dispersion coatings and other water-based paint systems. The composite pigment particles of the present invention can also be used in plastics and laminates.

Examples

The present invention is described in detail below with the help of several examples, which do not limit the scope of protection of the present invention in any way.

The composite pigment particles are prepared using the following ingredients:

Pigment: Unground and undechlorinated titanium dioxide produced during the chlorination process

Supplement 1: Minelco Ultracarb 1250 (calcite-hydromagnesite blend)

Supplement 2: Omyacarb 5GU (calcium carbonate) from Omya

Additive: Calgon N (sodium hexametaphosphate)

Pure titanium dioxide pigments KRONOS 2190 and KRONOS 2310 were used in the comparative examples.

The composition of the composite pigment particles is as follows (given in mass ratio):

The composite pigment particles of the present invention (Examples 1, 2, and 3) were prepared as follows:

425 g of an aqueous suspension of unground, undechlorinated titanium dioxide bulk particles, with a _TiO2 solids concentration of 42.3 wt% and a pH of 3.7, was placed in a suitable container. 180 g of Omyacarb 5GU (calcium carbonate) and 150 g of water were then added with stirring. The pH was adjusted to approximately 4.3 by slowly adding a total of 430 ml of 25% HCl and stirred at this pH for approximately 30 minutes. The additives (0.5 wt%, based on the total solids including all fillers) were then added. 240 g of Ultracarb 1250 (a blend of magnesite and hydromagnesite) was then added to the suspension with vigorous stirring and dispersed at 4000 rpm using a suitable toothed disc for approximately 30 minutes. Following dispersion, 1050 ml of 20% sodium carbonate solution was added with stirring at a pH of approximately 8.5 to reprecipitate the calcium carbonate. Subsequently, the suspension was filtered, rinsed with about 5 1 of deionized water, and dried in a drying cabinet at 120° C. for about 16 hours.

Figure 1 is a scanning electron micrograph of a composite pigment of the present invention having the composition of Example 3. The equiaxed particles are titanium dioxide, the flat particles of different sizes are the filler, and the fine polycrystals are precipitated calcium carbonate.

The composite pigment particles and the commercially available TiO ₂ pigments KRONOS 2190 (Comparative Example 1) and KRONOS 2310 (Comparative Example 2) were tested for lightness (PLV L*) and yellow color shift (PLV b*). The measurement results are summarized in Table 1.

Table 1: Optical properties of the composite pigment particles of the present invention

Subsequently, the composite pigment particles were added to an internal dispersion paint having the formulation given in Table 2, wherein up to 20 wt% of the _TiO2 pigment (based on the _TiO2 pigment) was replaced with the composite pigment particles of the present invention. The pigment volume concentration (PVK) of the internal dispersion paint was 78%.

For comparison, the commercially available TiO ₂ pigment KRONOS 2190 (Comparative Example 1) and the commercially available TiO 2 pigment KRONOS 2310 (Comparative Example 2) were also used to produce internal dispersion coatings.

Table 2: Formulation of white internal dispersion paint (test paint)

The test coatings were examined for contrast ratio (KV). The measurement results are summarized in Table 3.

Table 3: White interior dispersion paint

Test Method

The lightness (L*) and color shift (b*) of the composite pigment particles compared to the pure pigment were determined using a HUNTERLAB tristimulus colorimeter on the corresponding powder compacts (PLV test) according to the following procedure:

Before producing the compacts, the pigment powder is ground. To do this, 100 g of powder is added to a commercial mixer (manufacturer: Braun, model: MX 2050) and ground 12 times for 5 seconds each. Between each grinding step, the mixer is opened and the powder is stirred again. To produce the powder compact, a sheet of matte white paper, both sides of which are flat, is placed on a base with a circular indentation. A metal ring (4 cm high, 2.4 cm diameter) is pressed into the indentation using a press. Approximately 25 g of ground powder is fed into the ring while gently shaking and tapping. The powder is pressed together using a pressure of 2–3 kN. This pressing process is repeated until the desired working pressure of 15 kN is reached. The ring is carefully rotated and pulled to remove it from the base. The paper between the base and the ring is removed. The compact is now located in the ring for measurement on a HUNTERLAB colorimeter. The measured values L* and b* are read directly on the colorimeter.

To determine the contrast ratio, the white internal dispersion coating (test coating) produced according to the recipe was applied to a Morest contrast chart (Kontrastkarte) using an automated laminating system with a gap doctor blade (80–125 μm) at a speed of 12.5 mm/s. The color values Y (Y) on a black background (Y _(Schwarz) ) and Y (Y _(Weiβ) ) on a white background were then measured three times using a Color-View spectrophotometer. The contrast ratio was calculated using the following formula:

KV[%]＝Y _(schwarz) /Y _(weiβ) ×100

in conclusion

The composite pigment particles of the invention, consisting of an extender and titanium dioxide pigment, make it possible to reduce the pigment dosage, depending on the selected combination, without compromising the optical properties, or only slightly. Alternatively, even with an equal pigment content, it is possible to improve the values, particularly in terms of tinting strength.

Claims (25)

1. A composite pigment containing titanium dioxide and carbonate, said composite pigment being composed of the following substances: Titanium dioxide particles, At least one inorganic filler selected from the group consisting of calcium carbonate, calcium magnesium carbonate or magnesium carbonate, sulfates, natural phosphates, oxides, hydrated oxides, silicates, aluminosilicates, pearlites and glass powders, and, The amount of the relative complex pigment is less than 30% by weight and is at least locally precipitated in situ; The titanium dioxide particles are uniformly distributed on the surface of the inorganic filler, and a strong connection is established between the inorganic filler particles and the titanium dioxide particles by means of in-situ precipitated calcium carbonate. The composite pigment is manufactured by following these steps using titanium dioxide, at least one inorganic filler, and soluble calcium and soluble carbonate sources as two reactants: a) Prepare an aqueous suspension containing titanium dioxide particles and a soluble calcium source as the first reactant component, wherein the pH of the aqueous suspension is adjusted to <5, such that the soluble calcium source is dissolved by more than 50%, and the aqueous suspension is thoroughly stirred or dispersed. b) Add the inorganic filler and the second reactive component, a soluble carbonate source, and adjust the pH of the suspension to >8. The suspension is then thoroughly stirred to ensure that the titanium dioxide particles are uniformly distributed on the surface of the inorganic filler particles. Furthermore, the in-situ precipitated calcium carbonate establishes a strong bond between the inorganic filler particles and the titanium dioxide particles. c) Separating the composite pigment particles from the suspension, wherein, when calculated as _CaCO3 , the amount of the added soluble calcium source relative to the composite pigment is less than 30% by weight. 2. The composite pigment according to claim 1, wherein the titanium dioxide particles are surface-treated or untreated titanium dioxide pigment particles. 3. The composite pigment according to claim 1, characterized in that, The inorganic filler is selected from the group consisting of dolomite, calcium magnesium carbonate, magnesite, and hydromagnesite. 4. The composite pigment according to claim 1, characterized in that, In step b), the pH of the suspension is adjusted to >8.5. 5. The composite pigment according to claim 1, characterized in that, In step a), _CaCO3 is used as a soluble calcium source, and the pH of the suspension is adjusted to <5. 6. The composite pigment according to claim 5, characterized in that, In step a), the pH value of the suspension is adjusted to <4.3. 7. The composite pigment according to claim 1, characterized in that, Step a) includes the following steps: Provides aqueous suspensions of titanium dioxide particles. Add calcium carbonate, and, if necessary, at least one acid-reactive compound, wherein the pH of the suspension is <5. Add at least one of the inorganic fillers, Furthermore, the soluble carbonate source is added in step b). 8. The composite pigment according to claim 7, characterized in that, The pH of the suspension is less than 4.3. 9. The composite pigment according to claim 7, characterized in that, The acid reaction compound is selected from the group consisting of hydrochloric acid, nitric acid, titanium oxychloride, and hydrochloric acid and hypochlorous acid, which are produced as a byproduct of the chlorination process used to manufacture titanium dioxide. 10. The composite pigment according to claim 1, characterized in that, _CaCl2 , Ca( _NO3 ) ₂ , or Ca(OH) ₂ can be used as soluble calcium sources. 11. The composite pigment according to claim 1, characterized in that, A basic carbonate compound can be used as a soluble carbonate source, or carbon dioxide gas can be used together with a basic compound as a soluble carbonate source. 12. The composite pigment according to any one of claims 1 to 11, characterized in that, Finally, the composite pigment particles are treated with phosphoric acid or sodium silicate. 13. A method for manufacturing composite pigment particles containing titanium dioxide and carbonate, using titanium dioxide, at least one inorganic filler, and a soluble calcium source and a soluble carbonate source as two reactants, comprising the following steps: a) To manufacture an aqueous suspension containing titanium dioxide particles and a soluble calcium source as the first reactant, wherein the pH of the aqueous suspension is adjusted to <5, such that the soluble calcium source is dissolved by more than 50%, and the aqueous suspension is thoroughly stirred or dispersed. The inorganic filler is selected from the group consisting of calcium carbonate, calcium magnesium carbonate or magnesium carbonate, sulfate, natural phosphate, oxides, hydrated oxides, silicates, aluminosilicates, pearlites, and glass powder. b) Add the inorganic filler and the second reactive component, a soluble carbonate source, and adjust the pH of the suspension to >8. The suspension is then thoroughly stirred to ensure that the titanium dioxide particles are uniformly distributed on the surface of the inorganic filler particles. Furthermore, the in-situ precipitated calcium carbonate establishes a strong bond between the inorganic filler particles and the titanium dioxide particles. c) Separating the composite pigment particles from the suspension, wherein, when calculated as _CaCO3 , the amount of the added soluble calcium source relative to the composite pigment is less than 30% by weight. 14. The method according to claim 13, wherein in step b), the pH value of the suspension is adjusted to >8.5. 15. The method according to claim 13, Step a) includes the following steps: Provides aqueous suspensions of titanium dioxide particles. Add calcium carbonate, and, if necessary, at least one acid-reactive compound, wherein the pH of the suspension is <5. Add at least one filler. Furthermore, a soluble carbonate source is added in step b). 16. The method according to claim 15, characterized in that, In step a), the pH value of the suspension is <4.3. 17. The method according to claim 13, characterized in that, _CaCl2 , Ca( _NO3 ) ₂ , or Ca(OH) ₂ can be used as soluble calcium sources. 18. The method according to claim 13, characterized in that, In step a), _CaCO3 is used as a soluble calcium source, and the pH of the suspension is adjusted to <5. 19. The method according to claim 18, wherein the pH value of the suspension is adjusted to <4.3. 20. The method according to claim 13, characterized in that, A basic carbonate compound can be used as a soluble carbonate source, or carbon dioxide gas can be used together with a basic compound as a carbonate source. 21. The method according to claim 13, characterized in that, Titanium dioxide pigment particles, whether surface-treated or untreated, are used as titanium dioxide particles. 22. The method according to claim 13, characterized in that, The inorganic filler is selected from the group consisting of dolomite, calcium magnesium carbonate, magnesite, and hydromagnesite. 23. The method according to claim 15, characterized in that, The acid reaction compound is selected from the group consisting of hydrochloric acid, nitric acid, titanium oxychloride, and hydrochloric acid and hypochlorous acid, which are produced as a byproduct of the chlorination process used to manufacture titanium dioxide. 24. The method according to any one of claims 13 to 23, characterized in that, Alternatively, the composite pigment particles can be treated with phosphoric acid or sodium silicate. 25. The use of a composite pigment particle as described in any one of claims 1 to 12 in laminated materials, coatings and plastics.