MXPA99003590A - Multiple layer pearl light pigment based on an op substrate - Google Patents

Abstract

The present invention relates to multi-layered pigments based on a platelet-shaped, absorbent substrate, which is coated with alternating layers of a low refractive material and a high refractive material, or with a metal, in where the difference of the refractive indices is at least 0

Description

MULTI-LAYER PEARL LIGHT PIGMENT BASED ON AN OPAQUE SUBSTRATE DESCRIPTION OF THE INVENTION The present invention relates to a multilayer interference pigment consisting of alternating layers of a low refractive index material and a high refractive index material or a metal, on an absorbent substrate in the form of a platelet. which is opaque or semi-opaque. Multilayer pigments with alternating layers of a high refractive index material and a low refractive index material are known. Most of them comprise metallic oxides. Alternatively, the high refractive index material can be replaced by a semitransparent metallic material. The metal oxide layers are prepared either by a wet technique, by precipitating the metal oxide hydrates of a metal salt solution on a carrier material, or by vapor deposition or vacuum dispersion. For example, the North American Patent .No. 4,434,010 discloses a multilayer interference pigment consisting of a central layer of a reflecting material (aluminum) and alternating layers of two transparent and electrical materials of high and low index of REF .: 29683 refraction, for example titanium dioxide and silicon dioxide, on either side of the central layer of aluminum. In another embodiment of the pigment, the layers following the aluminum core layer are formed of magnesium chloride and chromium. This pigment is used to print securities or stocks. Japanese Patent JP H7-159 (A) describes a multi-layered interference pigment having metallic luster. This consists of a substrate coated with alternating layers of titanium dioxide and silicon dioxide. The substrate is formed of aluminum, gold or silver flakes, or of mica flakes and glass, which are coated with metal. All types of pigment that have an opaque metallic layer as a central layer, have the disadvantage that all wavelengths are reflected in this reflection layer, with the effect that, although a high luster is obtained, the interference color real is exceeded at the same time. European Patent EP 0,753,545 discloses goniocro attic luster pigments based on mica pigments coated with titanium dioxide whose content of Ti02 is partially reduced. Due to the sub-oxides of titanium, titanium oxynitrides and titanium nitrides formed during the reduction, the titanium dioxide layer has a blue to violet coloration. All the multilayer interference pigments referred to are based on a transparent substrate or on an opaque reflecting metal layer as the middle layer. All pigments with a multilayer structure on a transparent substrate, examples being mica, Si02 flakes and Ti02 flakes, have the disadvantage that, in the case of coated materials, it is often necessary to add absorption pigments to these pigments, in order to obtain adequate hiding power. However, when absorption pigments are mixed, the color drop of the interference pigment is greatly attenuated. All pigments with multilayer structure in a central metal layer have the disadvantage that all wavelengths are reflected in this reflection layer. In order to reduce this effect, these pigments of high hiding power are also mixed with absorption pigments, resulting in a possible attenuation of the color drop. German Patent DE 197,07,805, not published in the priority date of the present invention, discloses multilayer interference pigments having an absorbent middle layer, which are prepared by vapor deposition or dispersion of individual layers over a continuous band that is provided with a release layer. These pigments have the disadvantage that during the detachment of the dry film from the band, and due to the subsequent crushing, particles with broken edges are produced. Since these broken edges form scattering centers for the incident light, the pigment luster is reduced, which can cause the interference effect to disappear. The object of the present invention is to provide an interference pigment having strong interference colors, a high angular dependence of the interference colors and a high covering power. This object is achieved in accordance with the present invention, by means of a pearlescent pigment based on non-metallic, platelet-shaped substrates, of multiple opaque or semi-opaque coatings and having at least a) a first layer comprising a metal oxide of high refractive index or a metal, b) a second layer comprising a metal oxide of low refractive index, c) a third layer comprising a metal oxide of high refractive index or a metal, and, if desired, ) a subsequent coating.

This objective is achieved in accordance with the present invention, by a process for preparing the pigments of the present invention by suspending the substrate in water and alternately coating it with a high-refractive metal oxide hydrate and a low-metal oxide hydrate. refraction, by the addition and hydrolysis of the corresponding water-soluble metal compounds, establishing the pH required for the precipitation of the respective metal oxide hydrates and keeping it constant by the simultaneous addition of an acid or a base, and subsequently the material is separated from the vehicle coated with the aqueous suspension, dried and, if desired, calcined. The present invention further provides the use of the pigments of the present invention for pigmented paints, printing inks, plastics, glazes for ceramics and glass, and cosmetics. The present invention further provides the use of the pigments of the invention for pigmenting stock or stock securities and documents and packaging, and for laser marking of polymeric materials and papers. For this purpose, they can be used with mixtures with normal commercial pigments, of which the organic and inorganic absorption pigments, pigments of metallic effects and pigments LCP are examples. The high refractive index material used comprises metal oxides or mixtures of metal oxides with or without absorbent properties, and also metals. TÍO2 Zr? 2, Fe2? 3, Cr? 3, ZnO or (SnSb)? 2 / or thin metal layers, for example of nickel or aluminum. The low refractive index material used comprises metal oxides, for example AI2O3 or SiO2, or mixtures thereof. The thickness of the layers of high and low refractive index materials is essential for the optical properties of the pigment. Since a product that has strong interference colors is required, the thickness of the layers must be established with respect to each other. If n is the refractive index of a layer and d is its thickness, the interference color of a thin layer is given by the product of n and d, i.e. the optical thickness. The colors of such films that are produced in reflected light with a perpendicular incidence of light, are the result of an intensification of the wavelength? = -. "D and by the attenuation of the wavelength of the 2N - 1 light? = 2 -. "D where N is a positive integer. The N color variation that occurs as the thickness of the film increases, is a consequence of the intensification or attenuation of certain wavelengths through interference. For example, a 115 nm thick film of titanium dioxide with a Refractive Index of 1.94, has an optical thickness of 115 X 1.94 = 223 nm and light of wavelength 2 X 223 nm = 446 nm (blue) it is attenuated in the reflection, in such a way that the reflected light is yellow. In the case of multi-layer pigments, the interference color is determined by the intensification of certain wavelengths and if two or more layers in a multi-layer pigment have the same optical thickness, the color of the reflected light becomes more full and it becomes more intense, as the number of layers increases. In addition to this, it is possible, through an appropriate selection of the layer thicknesses, to achieve a particularly strong variation of the color as a function of the observation angle. A pronounced color drop develops, which may be desirable for the pigments according to the present invention. The thickness of the individual layers, irrespective of their refractive index, is from 10 to 300 nm, preferably from 20 to 200 nm in the case of materials with a high refractive index. The thickness of the metal layers is from about 5 to 35 nm. In the case of materials with a low refractive index, the thickness of the layer for pigments with intense interference colors, it is preferably from 2 to 300 nm, preferably from 40 to 150 nm and for pigments having a pronounced color drop, it is from 2 to 800 nm, preferably from 200 to 600 nm. The difference of the refractive indexes between a layer comprising a material of high refractive index and a layer comprising a material of low refractive index is at least 0.1. The substrate materials used for the pigments of the present invention are platelet-shaped materials that absorb some or all of the incident light. Examples of full absorption substrates are graphite platelets and graphite-based pigments, such as those described in greater detail in US Pat. No. 5,228,911. The graphite platelets are heated to a temperature of 200 to 500 ° C in an atmosphere containing oxygen. As a result, carboxyl groups and phenolic hydroxyl groups are formed on the graphite surface, which improves the adhesion of the metal oxide layer. Preferably, titanium dioxide is used. The titanium dioxide is deposited by known techniques. Graphite platelets are available in the market. Other suitable fully absorbent substrates are ilmenite pigments and iron oxide pigments, such as those described in US Pat. No. 4,867,793. These are interference pigments that consist of mica and a layer of magnetite (FeO • Fe2Ü3) or ilmenite (FeTi? 3). The magnetite layer is obtained by depositing the iron oxide from a salt solution of iron (II) in the presence of an oxidizing agent or by exposing a layer of Fe203, deposited by the known techniques, to a reductive atmosphere at elevated temperatures. If the layer of Fß2? 3 is deposited on a layer of titanium dioxide and the product is calcined in a reductive atmosphere at more than 800 ° C, a layer of iron titanate (FeTi? 3) is formed, which is known as ilmenite. In addition, the substrate used, for purposes of the present invention, can also be mica coated with pseudobroke, the precipitation of which is described in US Pat. No. 5,009,711. Other suitable substrates are interference pigments according to US Pat. No. 5,693,134, which consist of a substrate in the form of a platelet, a first layer of titanium dioxide and a second outer layer of a mixed oxide of copper and manganese, the General Formula CuxMn3-x04. As an additional opaque substrate, it is possible to use mica coated with graphite or mica pigments coated with graphite. Its preparation is described in US Pat. No. 5,271,771. The mica or mica coated with metal oxides is exposed to the flow of a volatile gaseous hydrocarbon at a temperature of 400 to 1000 ° C, or a liquid or solid carbon compound is applied to the raw material and the system is subsequently pyrolyzed, both variants taking place in the absence of oxygen. In both cases the product comprises platelet-shaped particles coated with a thin layer of graphite. Regardless of the thickness of the layer, a product is obtained that completely absorbs, and therefore is opaque, or that only partially absorbs, and therefore is semitransparent. This material is also suitable as a substrate for the pigments of the present invention. As partially absorbing substrates, it is also possible to use pigments with carbon inclusions in accordance with German Patent DE 195 02 231. These multilayer pigments comprise carbon black in the outer layer of titanium dioxide or in the underlying metal oxide layer . They are obtained by calcining the substrate in the form of a coated platelet at a temperature of 500 to 1000 ° C under an atmosphere of an inert gas.

It is also possible to use Si02 flakes with carbon black incorporated as partially absorbing substrates. In accordance with International Application WO 93/08237, the Si02 flakes are prepared in a continuous web by hydrolysis and solidification of a silicate solution (water glass). In the process of this procedure, the carbon black is incorporated into the matrix that is formed. The metal oxide layers are preferably chemically wet applied, making it possible to use wet chemical coating techniques developed to prepare pearlescent pigments; techniques of this type are described, for example, in German Patent DE 14 67 468; DE 19 59 988; DE 20 09 566; DE 22 14 545; DE 22 15 191; DE 22 44 298; DE 23 13 331; DE 25 22 572; DE 31 37 808; DE 31 37 809; DE 31 51 343; DE 31 51 354; DE 31 51 355; DE 32 11 602; DE 32 35 017; or other patents and other publications. For the coating operation, the substrate particles are suspended in water and one or more hydrolysable metals are added to a pH suitable for hydrolysis, wherein this pH is selected so that metal oxides or metal oxide hydrates precipitate directly on the particles, without any risk of secondary precipitation. The pH is normally kept constant by the simultaneous measured addition of an acid or a base. Subsequently, the pigments are separated, washed and dried and, if desired, calcined, it being possible to optimize the calcination temperature with respect to the particular coating present. If desired, after the application of the individual coatings, the pigments can be separated, dried and, if desired, calcined before being resuspended for the application of the other layers by precipitation. In addition, the coating can also be carried out by a gas phase process in a fluidized bed reactor, it being possible to apply accordingly, for example, the techniques proposed in European Patent EP 0,045,851 and EP 0,106,235 to prepare pigments with pearl luster. The metal oxide of high refractive index used, preferably is titanium dioxide and the metal oxide of low refractive index used, preferably is silicon dioxide. For the application of the titanium dioxide layers, preference is given to the technique described in US Pat. No. 3,553,001. An aqueous solution of titanium salt is slowly added to a suspension, heated to a temperature of about 50 to 100 ° C, especially 70 to 80 ° C, of the material to be coated, and to a substantially constant pH of about 0.5 to 5. , in particular from about 1.5 to 2.5, which is maintained by the simultaneous measured addition of a base, for example an aqueous solution of ammonia or an aqueous solution of an alkali metal hydroxide. As soon as the desired layer thickness of TiO2 precipitated on the substrate has been reached, the addition of both the titanium salt solution and the base is stopped. This technique, which is also called titration technique, is notable for the fact that it avoids an excess of titanium salt. This is achieved by supplying for each unit of time, only that amount of titanium salt solution that is required for a uniform coating with the hydrated TiO2 and that can be received, per unit of time, by the available surface area of the particles. of substrate that are being coated. As a result, no particles of hydrated titanium dioxide are produced that have not precipitated on the surface by being coated. For the application of silicon dioxide layers, the following technique can be used: a sodium silicate aqueous solution (glass of water) is added in a measured manner to a suspension heated to a temperature of about 50 to 100 ° C, especially 70 to 100 ° C. 80 ° C, of the material to be coated. The pH is kept constant at a value of 4 to 10, preferably 6.5 to 8.5, by the simultaneous addition of 10% hydrochloric acid. After the addition of the sodium silicate solution, the batch is stirred for another 30 minutes. Additionally, it is possible to alter the color of the pigment powder by applying other layers, such as colorful metal oxides or Prussian Blue, transition metal compounds such as, for example, Fe, Cu, Ni, Co, Mn, or Cr, or organic compounds such as dyes or lacquers. - It is also possible to subject the finished pigment to a post-coating or post-treatment process, which increases light stability, weathering stability and chemical stability, or also facilitates handling of the pigment, especially its incorporation into different means. Suitable post-coating or post-treatment techniques include those described, for example, in German Patent DE-C 22 15 191; DE-A 31 51 354; DE-A 32 35 017 or DE-A 33 34 598. The substances additionally applied comprise only about 0.1 to 5% by weight, preferably about 0.5 to 3% by weight of the overall pigment. The pigment of the present invention, additionally, can be coated with organic or inorganic dyes of low solubility, which adhere firmly. The use of lacquers is preferred, especially aluminum lacquers. For this purpose, a layer of aluminum hydroxide is applied by precipitation and, in a second step, it is lacquered with a lacquer pigment. The technique is described in greater detail in German Patents DE 29 29 762 and DE 29 28 287. Additional coatings with complex salt pigments, especially cyanoferrate complexes such as, for example, Prussian Blue and Turnbull Blue, are also preferred. , as described in the patents EP 0,141,173 and DE 23 13 332. The pigment according to the present invention can also be coated with organic dyes and, in particular, with dyes of phthalocyanine or phthalocyanine metal and / or indanthrene, in accordance with German Patent DE 40 09 567. For this purpose, a suspension of the pigment is prepared in a solution of the dye and this suspension is then mixed with a solvent in which the dye is sparingly soluble or insoluble at all. In addition, metal chalcogenides or metal chalcogenide hydrates and carbon black can also be used as an additional coating. The pigment can be used in a conventional manner for pigmented paints, inks for printing, plastics, cosmetics, and glazes for ceramics and glass. The pigments of the present invention possess a high hiding power and exhibit a pronounced color drop. This means that the interface colors are highly dependent on the angle of observation. Due to these properties, the absorption pigments must be added only in small quantities, if they are added, when the pigments of the present invention are used, for example, in automotive finishes. As a result, the color drop is retained in its entirety. The examples presented below are intended to illustrate the present invention in greater detail, without restricting it. EXAMPLE 1 100 g of graphite platelets are suspended in 2 l of deionized water and the suspension is heated to 75 ° C with continuous stirring. The pH is adjusted to 2.2 with concentrated hydrochloric acid (37%). 550 ml of an aqueous solution of TÍCI4 (400 g of TÍCI4 / I) are added to this suspension over the course of 280 minutes. During the addition, the pH is kept constant at 2.2 with a 32% NaOH solution. After the addition is complete, the precipitation is completed by stirring at 75 ° C for another 45 minutes. The pH of the suspension is raised to 7.5 with 32% NaOH and 210 g of a sodium silicate solution (13.5% by weight of SiO2) are added over the course of 40 minutes. During this addition, the pH is kept constant at 7.5 with 10% hydrochloric acid. After the addition is complete, the precipitation is completed by stirring at 75 ° C for another 45 minutes. The pH of the suspension is lowered to 2.2 with 10% hydrochloric acid. 630 ml of an aqueous solution of TÍCI4 are added (400 g of TÍCI4 / I) in the course of 320 minutes.

During the addition, the pH is maintained, constant at 2.2 with a 32% NaOH solution. At the conclusion of the addition, the precipitation is completed by stirring at 75 ° C for another 45 minutes. Subsequently, the mixture is cooled to room temperature and the resulting pigment is filtered, washed with deionized water free of salts and dried at 110 ° C. Subsequently, the pigment is calcined at 700 ° C in an N2 atmosphere for 30 minutes. The resulting pigment exhibits a dark green powder color with an intense green interference color. EXAMPLE 2 100 g of graphite platelets are suspended in 2 1 of deionized water and the suspension is heated to 80 ° C with continuous stirring. The pH is adjusted to 2.0 with concentrated hydrochloric acid (37%). 100 ml of a 3% SnCl 4 solution are added to this suspension over the course of 25 minutes. During this time, the pH remains constant at 2.0 with a 32% NaOH solution. After a subsequent 15 minute stirring period, the pH is brought to 1.8 with 10% hydrochloric acid and 600 ml of an aqueous solution of TÍCI4 (400 g of TÍCI4 / I) are added over the course of 300 minutes. During the addition, the pH is kept constant at 1.8 with a 32% NaOH solution. After the addition is complete, the precipitation is completed by stirring at 80 ° C for another 15 minutes. The pH of the suspension is raised to 7.5 with a 32% NaOH solution and 430 g of a sodium silicate solution (13.5% by weight of SIO2) are added over a course of 216 minutes. During this addition, the pH is kept constant at 7.5 with 10% hydrochloric acid. After the addition is complete, the precipitation is completed by stirring at 80 ° C for another 15 minutes. The pH of the suspension is lowered to 2.0 with 10% hydrochloric acid. 100 ml of a 3% SnClj solution is added over the course of 25 minutes. During this time, the pH remains constant at 2.0 with a 32% NaOH solution. After a subsequent 15 minute stirring period, the pH is lowered to 1.8 with 10% hydrochloric acid and 590 ml of an aqueous solution of TÍCI4 (400 g of TiCl 4 / l) are added in the course of 296 minutes. During the addition, the pH is kept constant at 1.8 with a 32% NaOH solution. After the addition is complete, the precipitation is completed by stirring at 80 ° C for another 15 minutes. Subsequently, the mixture is cooled to room temperature and the resulting pigment is filtered, washed with deionized water free of salts and dried at 110 ° C. Subsequently, the pigment is calcined at 700 ° C in an N2 atmosphere for 30 minutes. This produces a dark green powder color pigment with a pronounced color drop. EXAMPLE 3 100 g of Iriodin® 602, which is a mica pigment with a coating of Ti02 and ilmenite, are suspended in 2 1 of deionized water and the suspension is heated to 75 ° C with continuous stirring. The pH is adjusted to 2.2 with concentrated hydrochloric acid (37%). 690 ml of an aqueous solution of TiCl 4 (400 g of TiCl 4 / l) are added to this suspension over the course of 350 minutes. During the addition, the pH is kept constant at 2.2 with a 32% NaOH solution. After the addition is complete, the precipitation is completed by stirring at 75 ° C for another 45 minutes. The pH of the suspension is raised to 7.5 with a 32% NaOH solution and 260 g of a sodium silicate solution (13.5% by weight of SiO) are added over the course of 50 minutes. During this addition, the pH is kept constant at 7.5 with 10% hydrochloric acid. After the addition is complete, the precipitation is completed by stirring at 75 ° C for another 45 minutes. The pH of the suspension is lowered to 2.2 with 10% hydrochloric acid. 790 ml of an aqueous solution of TÍCI4 are added (400 g of TÍCI4 / I) in the course of 400 minutes. During the addition, the pH is kept constant at 2.2 with a 32% NaOH solution. After concluding the addition, the precipitation is completed by stirring at 75 ° C for another 45 minutes. Subsequently, the mixture is cooled to room temperature and the resulting pigment is filtered, washed with deionized water free of salts and dried at 110 ° C. Subsequently, the pigment is calcined at 850 ° C in an atmosphere of N2 for 30 minutes.The resulting pigment exhibits a grayish-green powder color with an intense green interference color EXAMPLE 4 100 g of Iriodin® 602 are suspended. It is a mica pigment with a coating of UNCLE and ilmenite, in 2 1 of deionized water and the suspension is heated to 80 ° C with continuous agitation.The pH is adjusted to 2.0 with concentrated hydrochloric acid (37%). 100 ml of a 3% solution of SnCl 4 is added over the course of 25 minutes, during which time the pH remains constant at 2.0 with a 32% NaOH solution, after a subsequent period of agitation. minutes, the pH is brought to 1.8 with 10% hydrochloric acid and 750 ml of an aqueous solution of TiCl 4 (400 g of TÍCI 4 / I) are added to this suspension over the course of 375 minutes. During the addition, the pH is kept constant at 1.8 with a 32% NaOH solution. After the addition is complete, the precipitation is completed by stirring at 80 ° C for another 15 minutes. The pH of the suspension is raised to 7.5 with a 32% NaOH solution and 533 g of a sodium silicate solution (13.5% by weight of SIO2) are added over the course of 270 minutes. During this addition, the pH is kept constant at 7.5 with 10% hydrochloric acid.

After the addition is complete, the precipitation is completed by stirring at 80 ° C for another 15 minutes. The pH of the suspension is lowered to 2.0 with 10% hydrochloric acid. 100 ml of an aqueous 3% SnCl 4 solution are added over the course of 25 minutes. During this time, the pH remains constant at 2.0 with a 32% NaOH solution. After a subsequent period of agitation of 15 minutes, the pH is lowered to 1.8 with 10% hydrochloric acid and 740 ml of an aqueous solution of TÍCI4 are added. (400 g of TÍCI4 / I) in the course of 370 minutes. During the addition, the pH is kept constant at 1.8 with a 32% NaOH solution. After the addition is complete, the precipitation is completed by stirring at 80 ° C for another 15 minutes. Subsequently, the mixture is cooled to room temperature and the resulting pigment is filtered, washed with deionized water free of salts and dried at 110 ° C. Subsequently, the pigment is calcined at 850 ° C in an N2 atmosphere for 30 minutes. This produces a grayish-green powder color pigment with a pronounced color drop.

EXAMPLE 5 100 g of mica are suspended with a graphite concealment coating and a particle size of 10 to 50 μm in 2 1 of deionized water and the suspension is heated to 75 ° C with continuous stirring. The pH is adjusted to 2.2 with concentrated hydrochloric acid (37%). To this suspension is added 690 ml of an aqueous solution of TÍCI4 (400 g of TÍCI4 / I) in the course of 350 minutes. During the addition, the pH is kept constant at 2.2 with a 32% NaOH solution. After the addition is complete, the precipitation is completed by stirring at 75 ° C for another 45 minutes. The pH of the suspension is raised to 7.5 with a 32% NaOH solution and 260 g of a sodium silicate solution (13.5% by weight of SiO2) are added over the course of 50 minutes. During this addition, the pH is kept constant at 7.5 with 10% hydrochloric acid. After the addition is complete, the precipitation is completed by stirring at 75 ° C for another 45 minutes. The pH of the suspension is lowered to 2.2 with 10% hydrochloric acid. 790 ml of an aqueous solution of TÍCI4 (400 g of TÍCI4 / I) are added in the course of 400 minutes.

During the addition, the pH is kept constant at 2.2 with a 32% NaOH solution. After the addition is complete, the precipitation is completed by stirring at 75 ° C for another 45 minutes. Subsequently, the mixture is cooled to room temperature and the resulting pigment is filtered, washed with deionized water free of salts and dried at 110 ° C. Subsequently, the pigment is calcined at 700 ° C in an N2 atmosphere for 30 minutes. The resulting pigment exhibits a dark green powder color with an intense green interference color. EXAMPLE 6 100 g of mica are suspended with a graphite concealment coating and a particle size of 10 to 50 μm in 2 1 of deionized water and the suspension is heated to 80 ° C with continuous agitation. The pH is adjusted to 2.0 with concentrated hydrochloric acid (37%). To this suspension is added 100 ml of an aqueous solution of SnCl 4 in the course of 25 minutes. During this time, the pH remains constant at 2.0 with a 32% NaOH solution. After a subsequent period of agitation of 15 minutes, the pH is brought to 1.8 with 10% hydrochloric acid and 750 ml of an aqueous solution of TÍCI4 (400 g of TÍCI4 / I) are added over the course of 375. During the addition, the pH is kept constant at 1.8 with an 32% NaOH solution. After the addition is complete, the precipitation is completed by stirring at 80 ° C for another 15 minutes. The pH of the suspension is raised to 7.5 with a 32% NaOH solution and 533 g of a sodium silicate solution (13.5% by weight of SIO2) are added over the course of 270 minutes. During this addition, the pH is kept constant at 7.5 with 10% hydrochloric acid. After the addition is complete, the precipitation is completed by stirring at 80 ° C for another 15 minutes. The pH of the suspension is lowered to 2.0 with 10% hydrochloric acid. 100 ml of an aqueous solution of SnCl 4 are added over the course of 25 minutes. During this time, the pH remains constant at 2.0 with a 32% NaOH solution. After a subsequent period of turmoil in minutes, the pH is lowered to 1.8 with 10% hydrochloric acid and 740 ml of an aqueous solution of TÍCI4 are added. (400 g of TiCl 4 / l) in the course of 370 minutes.

During the addition, the pH is kept constant at 1.8 with a 32% NaOH solution. After the addition is complete, the precipitation is completed by stirring at 80 ° C for another 15 minutes. Subsequently, the mixture is cooled to room temperature and the resulting pigment is filtered, washed with deionized water free of salts and dried at 110 ° C. Subsequently, the pigment is calcined at 700 ° C under a nitrogen atmosphere for 30 minutes. This produces a dark green powder color pigment with a pronounced color drop. EXAMPLE 7 105 g of a pigment including carbon having a blue interference color and a particle size of 10 to 50 μm are suspended in 2 1 of deionized water and the suspension is heated to 75 ° C with continuous stirring. The pigment contains a layer of TIO2 in which carbon has been incorporated. The pH of the suspension is raised to 7.5 with a 32% NaOH solution and 153 g of a sodium silicate solution (13.5% by weight of SiO2) are added over the course of 75 minutes. During this addition, the pH is kept constant at 7.5 with 10% hydrochloric acid.

After the addition is complete, the precipitation is completed by stirring at 75 ° C for another 45 minutes. The pH of the suspension is lowered to 2.2 with 10% hydrochloric acid. 330 ml of an aqueous solution of TÍCI4 are added (400 g of TiCl / l) in the course of 165 minutes.

During the addition, the -pH remains constant at 2.2 with a 32% NaOH solution. After the addition is complete, the precipitation is completed by stirring at 75 ° C for another 45 minutes. Subsequently, the mixture is cooled to room temperature and the resulting pigment is filtered, washed with deionized water free of salts and dried at 110 ° C. Subsequently, the pigment is calcined at 850 ° C in a nitrogen atmosphere for 30 minutes. This produces a pigment with blue-green mass tone with an intense blue interference color. EXAMPLE 8 126 g of a pigment including carbon having a blue interference color and a particle size of 10 to 50 μm are suspended in 2 1 of deionized water and the suspension is heated to 80 ° C with continuous stirring. The pigment contains a layer of TIO2 in which carbon has been incorporated. The pH of the suspension is raised to 7.5 with a 32% NaOH solution and 533 g of a sodium silicate solution (13.5% by weight of SiO2) are added over the course of 270 minutes. During this addition, the pH is kept constant at 7.5 with 10% hydrochloric acid. After the addition is complete, the precipitation is completed by stirring at 80 ° C for another 15 minutes. The pH of the suspension is lowered to 2.0 with 10% hydrochloric acid. 100 ml of a 3% SnCl 4 solution are added over the course of 25 minutes. During this time, the pH remains constant at 2.0 with a 32% NaOH solution. After a subsequent 15 minute stirring period, the pH is lowered to 1.8 with 10% hydrochloric acid and 740 ml of an aqueous solution of TÍCI4 (400 g of TÍCI4 / I) are added in the course of 370 minutes. During the addition, the pH is kept constant at 1.8 with a 32% NaOH solution. After the addition is complete, the precipitation is completed by stirring at 80 ° C for another 15 minutes. Subsequently, the mixture is cooled to room temperature and the resulting pigment is filtered, washed with deionized water free of salts and dried at 110 ° C. Subsequently, the pigment is calcined at 850 ° C in a nitrogen atmosphere for 30 minutes. The resulting pigment exhibits a grayish green mass tone with a pronounced color drop.

EXAMPLE 9 100 g of mica are suspended with a semitransparent coating of graphite and a particle size of 10 to 50 μm in 2 1 of deionized water and the suspension is heated to 75 ° C with continuous stirring. The pH is adjusted to 2.2 with concentrated hydrochloric acid (37%). To this suspension is added 690 ml of an aqueous solution of TÍCI4 (400 g of TÍCI4 / I) in the course of 350 minutes. During the addition, the pH is kept constant at 2.2 with a 32% NaOH solution. After the addition is complete, the precipitation is completed by stirring at 75 ° C for another 45 minutes. The pH of the suspension is raised to 7.5 with a 32% NaOH solution and 260 g of a sodium silicate solution (13.5% by weight of SiO2) are added over the course of 50 minutes. During this addition, the pH is kept constant at 7.5 with 10% hydrochloric acid. After the addition is complete, the precipitation is completed by stirring at 75 ° C for another 45 minutes. The pH of the suspension is lowered to 2.2 with 10% hydrochloric acid. 790 ml of an aqueous solution of TÍCI4 (400 g of TÍCI4 / I) are added in the course of 400 minutes.

During the addition, the pH is kept constant at 2.2 with a 32% NaOH solution. After the addition is complete, the precipitation is completed by stirring at 75 ° C for another 45 minutes. Subsequently, the mixture is cooled to room temperature and the resulting pigment is filtered, washed with deionized water free of salts and dried at 110 ° C. Subsequently, the pigment is calcined at 700 ° C in an N2 atmosphere for 30 minutes. The resulting pigment exhibits a grayish-green powder color with an intense green interference color. EXAMPLE 10 100 g of mica are suspended with a semitransparent coating of graphite and a particle size of 10 to 50 μm in 2 1 of deionized water and the suspension is heated to 80 ° C with continuous stirring. The pH is adjusted to 2.0 with concentrated hydrochloric acid (37%). To this suspension is added 100 ml of a 3% SnCl 4 solution in the course of 25 minutes. During this time, the pH remains constant at 2.0 with a 32% NaOH solution. After a subsequent period of agitation of 15 minutes, the pH is brought to 1.8 with 10% hydrochloric acid and to this suspension is added 750 ml of an aqueous solution of TiCl (400 g of TiCl 4 / l) over the course of 375 hours. minutes During the addition, the pH is kept constant at 2.0 with a 32% NaOH solution. After the addition is complete, the precipitation is completed by stirring at 80 ° C for another 15 minutes. The pH of the suspension is raised to .7.5 with a 32% NaOH solution and 533 g of a sodium silicate solution (13.5% by weight of SiO2) are added over the course of 270 minutes. During this addition, the pH is kept constant at 7.5 with 10% hydrochloric acid. After the addition is complete, the precipitation is completed by stirring at 80 ° C for another 15 minutes. The pH of the suspension is lowered to 2.0 with 10% hydrochloric acid. 100 ml of a 3% SnCl 4 solution are added over the course of 25 minutes. During this time, the pH remains constant at 2.0 with 32% NaOH. After a subsequent period of turmoil in minutes, the pH is lowered to 1.8 with 10% hydrochloric acid and 740 ml of an aqueous solution of TÍCI4 are added. (400 g of TÍCI4 / I) in the course of 370 minutes.

During the addition, the pH is kept constant at 1.8 with a 32% NaOH solution. After the addition is complete, the precipitation is completed by stirring at 80 ° C for another 15 minutes. Subsequently, the mixture is cooled to room temperature and the resulting pigment is filtered, washed with deionized water free of salts and dried at 110 ° C. Subsequently, the pigment is calcined at 700 ° C in an N2 atmosphere for 30 minutes. This produces a grayish-green powder color pigment with a pronounced color drop. EXAMPLE 11 75 g of colored SiO2 flakes are suspended by incorporation of carbon black and with a particle size of 10 to 50 μm in 1.5 1 of deionized water and the suspension is heated to 75 ° C with continuous agitation. The pH is adjusted to 2.2 with concentrated hydrochloric acid (37%). To this suspension is added 690 ml of an aqueous solution of TiCl4 (400 g of TÍCI4 / I) in the course of 350 minutes. During the addition, the pH is kept constant at 2.2 with a 32% NaOH solution. After the addition is complete, the precipitation is completed by stirring at 75 ° C for another 45 minutes. The pH of the suspension is raised to 7.5 with a 32% NaOH solution and 260 g of a sodium silicate solution (13.5% by weight of SIO2) are added over the course of 50 minutes. During this addition, the pH is kept constant at 7.5 with 10% hydrochloric acid. After the addition is complete, the precipitation is completed by stirring at 75 ° C for another 45 minutes. The pH of the suspension is lowered to 2.2 with 10% hydrochloric acid. 790 ml of an aqueous solution of TÍCI4 are added (400 g of TÍCI4 / I) in the course of 400 minutes. During the addition, the pH is kept constant at 2.2 with a 32% NaOH solution. After the addition is complete, the precipitation is completed by stirring at 75 ° C for another 45 minutes. Subsequently, the mixture is cooled to room temperature and the resulting pigment is filtered, washed with deionized water free of salts and dried at 110 ° C. Subsequently, the pigment is calcined at 700 ° C for 30 minutes. The resulting pigment exhibits a grayish-green powder color with an intense green interference color. EXAMPLE 12 100 g of colored Si02 flakes are suspended by means of carbon black incorporation and with a particle size of 10 to 50 μm in 2 l of deionized water and the suspension is heated to 80 ° C with stirring. keep going. The pH is adjusted to 2.0 with concentrated hydrochloric acid (37%). To this suspension is added 300 ml of a 3% SnCl solution in the course of 100 minutes. During this time, the pH remains constant at 2.0 with a 32% NaOH solution. After a subsequent period of turmoil in minutes, the pH is brought to 1.8 with 10% hydrochloric acid and 1020 ml of an aqueous solution of TÍCI4 (400 g of TÍCI4 / I) are added to this suspension over the course of 340 minutes. During the addition, the pH is kept constant at 1.8 with a 32% NaOH solution. After the addition is complete, the precipitation is completed by stirring at 80 ° C for another 15 minutes. The pH of the suspension is raised to 7.5 with a 32% NaOH solution and 704 g of a sodium silicate solution (13.5% by weight of SiO2) are added over the course of 230 minutes. During this addition, the pH is kept constant at 7.5 with 10% hydrochloric acid. After the addition is complete, the precipitation is completed by stirring at 80 ° C for another 15 minutes. The pH of the suspension is lowered to 2.0 with 10% hydrochloric acid. 300 ml of a 3% SnCl 4 solution is added over the course of 100 minutes. During this time, the pH remains constant at 2.0 with 32% NaOH.

After a subsequent period of turmoil in minutes, the pH is lowered to 1.8 with hydrochloric acid at % and 922 ml of an aqueous solution of TÍCI4 are added (400 g of TÍCI4 / I) in the course of 300 minutes. During the addition, the pH is kept constant at 1.8 with a 32% NaOH solution. After the addition is complete, the precipitation is completed by stirring at 80 ° C for another 15 minutes. Subsequently, the mixture is cooled to room temperature and the resulting pigment is filtered, washed with deionized water free of salts and dried at 110 ° C. Subsequently, the pigment is calcined at 700 ° C for 30 minutes. This produces a grayish-green powder color pigment with a pronounced color drop. EXAMPLE 13 105 g of a pigment with blue-green interference consisting of mica coated with titanium dioxide and also having an outer layer of a mixed oxide of the formula CuxMn 3 x 4, in 2 l of deionized water and the suspension are suspended. heat at 75 ° C with continuous agitation. The pH is adjusted to 7.5 and 153 g of a sodium silicate solution (13.5% by weight of SIO2) are added over the course of 75 minutes. During this addition, the pH is kept constant at 7.5 with 10% hydrochloric acid. After the addition is complete, the precipitation is completed by stirring at 75 ° C for another 45 minutes. The pH of the suspension is lowered to 2.2 with 10% hydrochloric acid. 330 ml of an aqueous solution of TiCl (400 g of TÍCI4 / I) are added over the course of 165 minutes.

During the addition, the pH is kept constant at 2.2 with a 32% NaOH solution. After the addition is complete, the precipitation is completed by stirring at 75 ° C for another 45 minutes. Subsequently, the mixture is cooled to room temperature and the resulting pigment is filtered, washed with deionized water free of salts and dried at 110 ° C. Subsequently, the pigment is calcined at 600 ° C for 30 minutes. The resulting pigment exhibits a green powder color with an intense green interference color. EXAMPLE 14 126 g of a pigment with blue-green interference consisting of mica coated with titanium dioxide and also having an outer layer of a mixed oxide of the formula CuxMn3_x? 4, in 2 l of deionized water and the suspension are suspended. heat at 80 ° C with continuous stirring. The pH is adjusted to 7.5 and 533 g of a sodium silicate solution (13.5% by weight of SIO2) are added in the course of 270 minutes. During this addition, the pH is kept constant at 7.5 with 10% hydrochloric acid. After the addition is complete, the precipitation is completed by stirring at 80 ° C for another 15 minutes. The pH of the suspension is lowered to 2.0 with 10% hydrochloric acid. 100 ml of a 3% SnCl solution is added over the course of 25 minutes. During this time, the pH remains constant at 2.0 with a 32% NaOH solution. After a subsequent 15 minute stirring period, the pH is lowered to 1.8 with 10% hydrochloric acid and 740 ml of an aqueous solution of TÍCI4 (400 g of TÍCI4 / I) are added over the course of 370 minutes. During the addition, the pH is kept constant at 1.8 with a 32% NaOH solution. After the addition is complete, the precipitation is completed by stirring at 80 ° C for another 15 minutes. Subsequently, the mixture is cooled to room temperature and the resulting pigment is filtered, washed with deionized water free of salts and dried at 110 ° C. Subsequently, the pigment is calcined at 600 ° C for 30 minutes. This produces a green powder color pigment with a pronounced color drop.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (14)

2. Having described the invention as an antecedent, what is contained in the following is claimed as property. A pearlescent pigment characterized in that it is based on platelet-shaped non-metallic substrates, with multiple coatings, which are opaque or semi-opaque and has at least a) a first layer comprising a metal oxide of high refractive index or a metal, b) a second layer comprising a metal oxide of low refractive index, c) a third layer comprising a metal oxide of high refractive index or a metal, and, if desired, d) a subsequent coating. 2. A pearlescent pigment according to claim 1, characterized in that the platelet-shaped substrate consists of graphite platelets, platelet-shaped carrier materials coated with ilmenite, magnetite, CuxMn3-x? 4 or graphite, pigments. including carbon or Si02 flakes with incorporated carbon black.
3. 3. A pearl-gloss pigment according to any of claims 1 or 2, characterized in that the material with high refractive index is Ti02 / Zr02, FeU3, (SnSb) 02, Fe3? 4, Cr2? 3, ZnO, a mixture of these oxides, nickel or aluminum.
4. 4. A pigment with pearl luster according to any of claims 1 to 3, characterized in that the. Low refractive index material is SiO2, AI2O3 or a mixture thereof.
5. 5. A process for preparing the pearlescent pigment according to any of claims 1 to 4, characterized in that the substrate is suspended in water and alternatively coated with a metal oxide hydrate of high refractive index and an oxide hydrate. metal of low refractive index, by the addition and hydrolysis of the corresponding water-soluble metal compounds, wherein the pH required for the precipitation of the respective metal oxide hydrate is established and kept constant by the simultaneous addition of an acid or a base, and subsequently the coated substrate is separated from the aqueous suspension, dried and, if desired, calcined.
6. 6. The process according to claim 5, characterized in that the substrate in the form of absorbent platelets consists of graphite platelets, platelet-shaped carrier materials coated with ilmenite, magnetite, CuxMn3_x? or graphite, pigments including carbon or flakes of SÍO2 with incorporated carbon black. The process according to any of claims 5 or 6, characterized in that the metal oxide hydrate of high refractive index is a hydrate of titanium oxide, zirconium, iron, chromium, zinc, tin and antimony, or a mixture of these oxide hydrates. 8. The process according to any of claims 5 to 7, characterized in that the metal oxide hydrate of low refractive index is a hydrate of silicon oxide, aluminum, or a mixture thereof. 9. The process for preparing the pearlescent pigment according to any of claims 1 to 4, characterized in that the metal oxides are applied by CVD in a fluidized bed reactor. 10. The use of the pigments according to any of claims 1 to 4, for pigmented paints, inks for printing, plastics, cosmetics and glazes for ceramics and glass. 11. Use in accordance with the claim 10, characterized in that the pigments are used mixed with the conventional pigments and with other effect pigments. 12. The use of the pigments according to any of claims 1 to 4, for pigmenting securities and documents and packaging, and for laser marking of polymeric materials and papers. 13. Paints, inks for printing, plastics, cosmetics, ceramics and glasses pigmented with a pigment according to any of claims 1 to 4. 14. Polymeric materials marked by laser and papers, value txtulos and documents and packaging, characterized because they comprise the pigments according to any of claims 1 to 4.