MXPA98010149A - Aperl glass - Google Patents

Abstract

A pearlescent or pearly pigment is present which consists of glass flakes C, which have a layer formed of rutile titanium dioxide or iron oxide thereon. A hydrated layer of titanium dioxide or iron oxide is formed on the glass flakes and subsequently coated with absorbing pigments.

Description

APERLADO GLASS BACKGROUND OF THE INVENTION This is a continuation in part of the patent application Series N °. 08 / 657,311, filed June 3, 1996. The imparting pearlescent luster, metallic luster and / or multicolored effects approaching iridescence can be achieved using a pearlescent or pearlescent pigment consisting of a foil coated with metal oxide. These pigments were described for the first time in U.S. Patent 3,087,828 and 3,087,829 and a description of their properties can be found in Pigment Handbook, Vol. I, Second Edition, p.829-858, John Wiley & Sons, N.Y. 1988. The oxide coating is in the form of a thin film deposited on the surface of the lamellae. At present, the most widely used oxide is titanium dioxide. The one that continues in use extension is iron oxide and other usable oxides include tin, chromium and zirconium oxides, as well as mixtures or combinations of oxides. The coating of the metal oxide on the foil should be smooth and uniform to achieve the optimum pearlescent appearance. If the surface that is formed is P1710 / 98MX irregular, light scattering occurs and the coated foil will no longer function as a pearlescent pigment. The metal oxide coating must also be strongly adhered to the lamella, otherwise it will separate during the process, resulting in considerable breakage and loss of gloss and luster. During the preparation of these coatings on the lamellae particles that are not bound to them can be formed. These small particles cause light scattering and impart opacity to the pigment. If too many small particles are present, the pearlescent appearance can be reduced or lost. The addition of these metal oxides to the foil so that the luster, the color and the homogeneity of the color are maintained is a very complex process, and to date the only laminated substrate that has achieved a significant use in commerce is mica. A wide variety of other laminates have been proposed to be used as substrates to make these pearlescent pigments. These include non-soluble inorganic materials such as glass, enamel, kaolin, porcelain, natural stones and other siliceous substances, metal objects and polymeric organic materials such as polycarbonates. See, for example, United States Patents 3,123,485, 3,219,734, 3,616,100, 3,444,987, P1710 / 98MX 4,552,593 and 4,735,869. While glass has been mentioned many times as a possibility, for example in US Pat. No. 3,331,699 commercial pearlescent products are not manufactured using glass and experience has shown that products made using glass as a substrate laminate have more poor quality Said US Pat. No. 3,331,699 teaches that glass flakes can be coated with a translucent layer of particles of a metal oxide having a high refractive index, such as titanium dioxide, as long as it is first deposited on the glass flakes. a nucleating substance that is insoluble in the acid solution from which the translucent layer of metal oxide is deposited. The patent does not mention the need for a smooth transparent film or particles for the quality of the interference pigments to be developed. The patent shows that the nature of glass is not critical, but that the presence of a nucleated surface is. It is further stated that there is only a small number of metal oxides which are insoluble in the acid solution and capable of forming a nucleated surface on the glass flakes; tin oxide and alumina monohydrate to the fibrous boehmite form are the only two materials that are exposed. As P1710 / 98MX is demonstrated below in the examples, the products prepared according to the teachings of this patent are of poor quality. The United States Patent 5No. 436,077 discloses a glass flake substrate having a covering layer of metal on which a dense protective protective layer of a metal oxide such as titanium dioxide is formed. In this patent, the nature of the glass is not important, the metal coating provides the desired appearance and the metal oxide coating is present to protect the metal layer from corrosive environments. It has now been determined that there is a method for preparing uniform and smooth coatings of metal oxides on glass flakes, which adhere to these to give high quality pearlescent pigments and it is therefore the object of the present invention to provide such a method and to provide such pearlescent pigments of glass flakes coated with metal oxide resulting from that method. It is also possible to make combination pigments containing absorption pigments which are not soluble in water and which can not be formed in place from reagents or water soluble reagents.

P1710 / 98MX SUMMARY OF THE INVENTION The present invention relates to a pearlescent pigment and to a method for the production of such a pigment. The resulting pigment can be used in any application where pearlescent pigments have hitherto been used, as for example, in cosmetics, plastics, inks and coatings including solvent or aqueous type automotive paint systems.

DESCRIPTION OF THE INVENTION According to the present invention, a pearlescent pigment is formed by establishing a layer of hydrated film of titanium and / or iron oxides on glass flakes and then calcining the coated flakes, provided that the glass flakes used are C glass flakes and that when the hydrated layer is titanium, the process is a rutilization process. In industry, glass flakes are convenient because they are very elastic and can also be optically attractive. The glass is mainly composed of Si02 and A1203 and can also include ZnO, CaO, B203, Na20 and K20 as well as FeO and Fe203. The glass flakes are made by stretching molten glass to thin sheets, beads or glass tubes and then crushing the glass.

P1710 / 98MX glass flakes. Large hollow spheres can be produced and then solidification and crushing as well as a variety of other flake production methods. The leaflets have a size and shape that mimic the mica lamellae used in pearlescent mica pigments coated with Ti02 and Fe203 and, thus, have a particle size in the range between about 1 and 250 microns and a thickness of about 0.1-10 micras More cubic flakes having similar particle sizes and thicknesses of about 10-100 microns can be used, however, the pearlescent effect is considerably reduced due to the low dimensional relationship. The glass can be classified as glass A, glass C or glass E. Glass A is a glass of soda lime and is commonly used to make windows. It contains more sodium than potassium and also contains calcium oxide. Glass C is also known as chemical glass, it is a form of glass that is resistant to corrosion by acid and moisture. It frequently contains zinc oxide as well as other oxides that make the leaflets more resistant to chemical destruction. The glass E glass is, as the name implies, designed for electronic applications and, although it is very stable at high temperatures, it can be susceptible to chemical attack. The following table shows the percentage weight composition of P1710 / 98MX several commercial samples of glasses A, C and E. It is known that glass C as well as A and E have wide margins considering their chemical composition and in reality the compositions of glasses A and E can be very similar to the of glass C. TABLE 1 In the practice of the present invention, glass C or glass of chemical type is used in comparison with any other type. While metal oxide coatings can be prepared in glasses A or E, the resulting pigments do not have the quality of the products equal to that of glass C and, therefore, have a limited commercial value. When preparing products coated with TiO2, crystalline modifications of the rutile or anatase forms are possible. The pigments P1710 / 98MX higher quality and more stable pearlescents are obtained when Ti02 is in the rutile form. The glass used can also influence the crystalline form of the titanium dioxide in the coating. For example, when common E glass is used, the resulting crystalline phase is mainly anatase. To obtain rutile, an additive that can guide Ti02 to the rutile modification should be used. To coat the glass flakes with titanium dioxide or iron oxide, the processes known in the art for the formation of mica coated with Ti02 or iron oxide are generally followed. The mica orients to anatase and as it was observed before, most glasses seem to also orient the titanium dioxide coatings to the anatase crystalline form. At least some rutile training is needed to obtain higher quality and more stable products. In general, the process involves dispersing the particulate of glass flakes and combining that dispersion with a precursor that forms a hydrated coating film of titanium oxide or iron oxide on the flakes. In the coating process, the glass flakes are dispersed in water, which is preferably distilled. Preferably, the average particle size P1710 / 98MX used may vary between an average of about 3 microns and an average of about 150 microns and a flake thickness of 0.1-25 microns, although larger flakes may also be used if desired. The concentration of the glass flakes in water can vary between about 5% and 30% although in general the concentration that is preferred varies between about 10% and 20%. After the glass is dispersed in the water and placed in a suitable container, the appropriate titanium or iron source materials are introduced. The pH of the resulting dispersion is maintained at a suitable level during the addition of titanium or iron by the use of a suitable base such as sodium hydroxide to cause the precipitation of hydrated titanium dioxide or hydrous iron oxide on the glass chips . An aqueous acid can be used as hydrochloric acid to adjust the pH. If desired, the coated lamellae can be washed and dried before calcining to obtain the final pearlescent pigment. The iron source is preferably ferric chloride although any other source of iron known in the prior art can be employed. The titanium source is preferably titanium tetrachloride, although in the same way, other sources can be used P1710 / 98MX known in the art. If desired, layers of titanium and iron can be deposited successively. In the case of titanium dioxide, modifications of the aforementioned method to perform a rutilization procedure are known in the prior art. In a process, first a layer of hydrous tin oxide is deposited on the surface of the glass flakes and then a layer of hydrated titanium dioxide. When this combination of layers is processed and calcined, the titanium dioxide is oriented to the rutile form. The process is described in detail in U.S. Patent 4,038,099, which is incorporated herein by reference. An alternate process involves depositing the hydrated titanium dioxide on the glass flakes in the presence of iron and calcium, magnesium and / or zinc ions, without the use of tin. This is described in detail in U.S. Patent 5,433,779, the disclosure of which is hereby incorporated by reference. Combined pigments can be made in the same manner as described in U.S. Patent 4,755,229, the disclosure of which is incorporated herein by reference. Briefly, an aqueous dispersion of the colorful pigment containing an anionic polymer substance is P1710 / 98MX adds to a pigment suspension. The hydrous oxide of a polyvalent metal is then produced by the simultaneous addition of a solution of the metal salt and a basic solution. The dispersed pigment and polymer particles are deposited with the hydrous oxide of the polyvalent metal to form a smooth, adhesive and smooth coating on the pearlescent glass. To successfully use an insoluble absorption pigment in combination pigments, the insoluble pigment must be quite dispersed. A convenient starting point is to start from the dry pigment or, preferably, from an aqueous filtration cake of the pigment. After dilution with water or other liquid, such as alcohol, dispersion is achieved by any of the usual techniques, such as grinding, high shear mixing or ultrasonic energy application. The convenient degree of dispersion is similar to that conventionally used in formulations of paints and coatings. Preferably the anionic polymer is added before or during the dispersion step to aid the dispersion process. The polymer-pigment absorption dispersion is combined with a coated glass pigment suspension. The pH of the resulting suspension should be in the suitable range for the precipitation of the hydroxide of the polyvalent cation or of the hydrated oxide that is desired, P1710 / 98MX in general between about pH 1 and 11 and more frequently between about pH 2 and 8. A solution of the soluble salt of the polyvalent cation is then added to the suspension simultaneously with a basic material soluble in sufficient quantity to maintain the pH in the desired precipitation interval. The absorption pigment is deposited on the lamellae to form a uniform and smooth colorful coating. The suspension can then be filtered and the filter cake washed with water and dried, for example, at 120 ° C, to produce an easily dispersible powder of the combined pigment. The absorption pigments which are insoluble in water, transparent (for example, which do not cause light scattering practically) and which can not be formed in situ from water-soluble reagent (s), but which can be quite dispersed in water or in water-alcohol solution and containing anionic polymers, are suitable for the invention. These include, for example, carbon black and organic pigments of the following groups: azo compounds, anthraquinones, perinones, perylenes, quinacridones, thioindigos, dioxazines and phthalocyanines and their metal complexes. Depending on their color intensity, the pigments are used in a concentration range between about 0.01% and 30% based on the weight of the pigment, preferably between 0.1% and 10%.

P1710 / 98MX Useful polymers are those that are capable of precipitating at suitable pH values with polyvalent cations. Thus polymers are usually anionic or like proteins that have both anionic and cationic groups. Useful polymers include albumin, gelatin, polyacrylamides, polyacrylic acids, polystyrene sulfonates, polyvinyl phosphonates, sodium carboxymethyl cellulose and polysaccharides such as xanthan gum, alginates and carrageenan. The polymer content is between about 0.01% and 20%, preferably between 0.05 and 10%, based on the weight of the mica pigment. Any polyvalent cation can be used which, under given pH conditions, forms a precipitate with the polymer. Such polyvalent cations are used in the form of a solution of the soluble salt. Thus, the cation can be, for example, one or more of the following Al (III), Cr (III), Zn (II), Mg (II), Ti (IV), Zr (IV), Fe (II) , Fe (III) and Sn (IV). Suitable anions include chloride, nitrate, sulfate and the like. The amount of polyvalent metal ion is between about 0.01% and 20%, preferably between about 0.05% and 10%, of the weight of the mica pigment. The pH range that is preferred for deposition depends on the particular cation that is used. For Al and Cr (III) it is between approximately 4.0 and 8.0. For Zr (IV) P1710 / 98MX is between approximately 1.0 and 4.0. The metal salt solution is usually acidic and the pH of the suspension is maintained in the convenient range with the addition of a soluble base, such as sodium hydroxide, potassium hydroxide or ammonia solution. When the desired precipitation pH is lower than that of the salt solution, a soluble acid such as HCl is added in the amount required. The purpose in each case is to deposit on the pigment lamellae a complex of metal hydroxide or hydrated oxide and polymer that carries with it the particles of the absorption pigment, to produce a pigment combined with a colorful adhesive film and smooth on the lamellae. After depositing, the film can be fixed by washing and drying the combined pigment. If desired, the colors can be adjusted by mixing combined pigments. In general, it is preferred to mix pigments of the same or similar reflection color, since the reflection colors are mixed additively and the color intensity is reduced when very different reflection colors are mixed. The pigment absorption components are mixed subtractively and the usual pigment mixing procedures are followed. To further illustrate the invention, they are exposed P1710 / 98MX below various non-limiting examples. In these, as well as throughout the remainder of this specification and claims, all parts and percentages are by weight and all temperatures are in degrees centigrade unless otherwise indicated.

E.IEMP OS 1 - 4 A procedure was adopted for coating, in which 100 grams of glass flakes C (RFC-140 of Nippon Sheet Glass) having an average particle size of approximately 140 microns (by laser light scattering) they were dispersed in 750 ml of water. Iron and zinc were introduced in the form of 1 ml of 39% aqueous solution of ferric chloride and 7 ml of 9% aqueous solution of zinc chloride. The pH of the paste was adjusted to 3.0 using a 35% aqueous solution of sodium hydroxide and heated to a temperature of 76 ° C. The pH was then lowered to 1.6 with the addition of hydrochloric acid and a 40% aqueous solution of titanium tetrachloride was added at a frequency of 100 ml / hour while the pH was maintained at 1.6 with the addition of sodium hydroxide. aqueous at 35%. The addition of titanium was continued until an appearance of pearl white or gold, red and blue interference colors was achieved. When the desired end point was achieved, the paste was filtered on a Buchner funnel and washed with additional water.

P1710 / 98MX Then the coated lamellae were dried and calcined at 600 ° C. The microscopic evaluation of the resulting pigment confirmed that the lamellae are coated with a homogeneous film layer of Ti02. In addition, the luster and color of the resulting pigments were evaluated visually and instrumentally using drag tests on a cover letter (Form 2-6 The Leneta Company's Opacity Chart), half of which is black and the other half white. . A coating over the black part of this chart shows the reflection color and luster when examined specularly, while the coating over the white portion shows the transmission color when viewed at non-specular angles. The drag tests were prepared by incorporating 12% pigment in a nitrocellulose lacquer and applying this suspension to the black and white chart with a Bird applicator film bar. When the charts were examined visually, pearlescent pigments with good luster and color intensity were observed. The appearance characteristics of these pigments were subsequently characterized by determination of the wavelength at which the reflectivity is at the maximum and minimum points and by the color described in terms of L * a * b. The data L * a * b P1710 / 98MX characterize the appearance of a product in terms of its luminosity-darkness component symbolized by L *, a red-green component represented by a * and a yellow-blue component symbolized by b *. These measurements were made using a gonioespectrophotometer (GK-111 from Datacolor, Inc.). In addition to the appearance measurements, three of the pigments were also analyzed by x-ray diffraction to determine the rutile and anatase content present in each sample. All these results were summarized in Table 2.

TABLE 2 In all cases, pearlescent pigments of glass flakes coated with titanium dioxide were obtained to the rutile form of high luster and high quality.

P1710 / 98MX E.JEMP O 5-11 One hundred grams of C glass chips having an average particle size of 140 μm (RCF-140 of Nippon Sheet Glass) were dispersed in 333 ml of distilled water. This dispersion was heated to 74 ° C and the pH adjusted to 1.6 using dilute hydrochloric acid. Then 7 ml of a 18% stannous chloride solution was added slowly. After the addition of the tin, an aqueous 40% titanium tetrachloride solution was added with a frequency of 100 ml / hour. The pH was maintained at 1.6 during the addition of tin and titanium with the simultaneous addition of an aqueous solution of dilute sodium hydroxide. The addition of titanium was continued until a pearl white was observed, golden, red, blue or green colorful interference. When the desired end point was reached, the pulp was filtered, washed with additional water and calcined at 600 ° C. The resulting products were examined microscopically to verify that the Ti02 was attached to the glass flakes in the form of a smooth and homogeneous film layer. When the drag tests are carried out, a series of vibrant, high-quality colors are observed. The results of the color and x-ray diffraction data for these products were summarized in Table 3. In each case, a pearlescent pigment of glass flakes coated with titanium dioxide was obtained.

P1710 / 98MX the rutile form of high luster and high quality.

TABLE 3 E-JEMPLOS 12-20 75 grams of glass flakes C having an average particle size of 100 μm were dispersed in 300 ml of distilled water. The dispersion was heated to 76 ° C and the pH adjusted to 3.2 with dilute hydrochloric acid. A solution of ferric chloride was added to the suspension at 0.2 ml / min while the pH was maintained at 3.2 using dilute sodium hydroxide. The addition of ferric chloride was continued until the desired color was observed. At the proper end point, the paste was filtered, washed with water P1710 / 98MX and calcined at 600 ° C to give glass flakes coated with Fe203. The resulting products were examined microscopically verifying that the Fe203 is attached to the glass flakes as a homogeneous and smooth film coating. Since Fe203 has an inherent red color, the glass flakes coated with this oxide have both the reflection color and the absorption color. The interference color comes from the luminous interference, while the absorption color is due to the absorption of the light. The color of reflection will change from gold to red to blue and green as the quantities of iron (III) that cover the glass flakes increase. While more iron (III) oxide is added, even thicker Fe203 coatings are obtained which give another set of interference colors known as second order observable interference colors. These second order colors have a color intensity even greater than those. first colors together with greater coverage. If the coating process is further continued, a third series of interference colors can be obtained. When these glass flakes coated with iron oxide were subjected to drag tests, a series of vivid high quality colors was observed. HE P1710 / 98MX obtained color data from these trawl tests and summarized in Table 4.

TABLE 4 EXAMPLES 21-23 The Ti02 coatings also produce a series of interference colors as the thickness of the Ti02 layer increases. The thin coatings of Ti02 produce a whitish reflection with pearly or silver appearance. As the Ti02 layer becomes thicker, interference colors of gold, red, blue and green are observed. As the layer becomes even thicker P1710 / 98MX a series of observable secondary colors is observed. These secondary colors have more intensity of color and concealment than the first colors described in the examples above. These secondary colors were prepared by dispersing 50 g of the glass flakes used in Examples 1-11 in 333 ml of distilled water. The pH was adjusted to 1.6 with dilute hydrochloric acid and the suspension was heated to 74 ° C. 7 ml of 18% stannous chloride was added and then 40% titanium chloride was added with a frequency of 0.33 ml / min. The pH was maintained at 1.6 by adding dilute sodium hydroxide simultaneously. The addition of titanium was continued until the "desired observable secondary color was observed. The pulp was filtered, washed with water and the resulting filter cake was calcined at 600 ° C to give glass flakes coated with Ti02. When subjected to drag test, the resulting products have greater color intensity and more coverage than their comparable first order observable interference colors. The color data of these drag tests are summarized in Table 5.

P17X0 / 98 X TABLE 5 EXAMPLES 24-28 For comparison purposes, several examples of the aforementioned U.S. Patent 3,331,699 were repeated. First, examples 1 and 2 of the patent in which the glass was first treated with tin and then with titanyl sulfate were reproduced using E glass (REF-140 from Nippon Sheet Glass). The resulting products were examined using an optical microscope. The coatings were not smooth and in reality very little Ti02 was attached to the surface of the glass flakes. When subjected to the drag test in the black and white letters, the resulting products had little luster and did not present a real interference effect. Example 1 of the patent indicates that if a small portion of a dry sample is resuspended in water, it could P1710 / 98MX present a lustrous flash. Consequently, small amounts of the samples were redispersed in distilled water. The sample reproduced from Example 1 showed nothing except a milky suspension while the sample from Example 2 showed pale purple flakes. The product reproduced from Example 1 was calcined and a mixture of titanium dioxide in the anatase and rutile forms was observed, but the quality of the product was poor. Example 6 of Patent 3,331,699 was also reproduced twice and resulted in a sequence of pigments with interference colors. In one reproduction, the leaflets were of glass C (RCF-140 of Nippon Sheet Glass) and in the other reproduction were of glass E (REF-140 of Nippon Sheet Glass). When the pigments produced in these two examples were examined microscopically, some of the flakes were uncoated and for those flakes that were coated, the coatings were rough, contained many fractures and in some cases detached from the glass surface. The pigments produced on glass C were superior to their counterparts produced on glass E. Glass products C had approximately 30% rutile and 70% anatase while E glass products had anatase almost exclusively.

P1710 / 98MX Example 12 of Patent 3,331,699 in which the glass flakes were treated with tin and then with iron, was repeated using E glass (REF-140 of Nippon Sheet Glass). The resulting product was a rust-colored powder that first exhibited an absorption color effect. When a drag test was prepared, the product exhibited very little luster and reflectivity. The products prepared in examples 12-20 above were much superior.

EXAMPLES 29-30 The procedure of Example 5-11 was repeated except that a glass E replaced a glass C. The coating of Ti02 that was made showed a white, pearly appearance. The resulting glass product E had a coating of titanium dioxide that was mainly anatase while the C glass products had coatings of 100% rutile titanium dioxide and were products of much higher quality. The color data are presented in Table 6.

P1710 / 98 X TABLE 6 EXAMPLE 31 An aqueous filter cake of quinacridone red (Sunfast Red 19, Sun Chemical Co., 23.7% pigment) is diluted with water to 0.50% pigment. TO 250 g of this suspension is added 0.1 g of xanthan gum (Kelzan, microbiological polysaccharide containing glucuronic acid, Kelco Division). Ultrasonic energy is applied by means of a Sonifier® Model 350 (Branson Sonic Power Co.) Device for 30 minutes to disperse the pigment. The pearlescent glass substrate is constituted by 50 g of the blue reflective pigment of Example 4, which is suspended with stirring in 400 g of water. The pH value of the suspension is 9.0 and is adjusted to 6.0 with 0.1 N HCl. This suspension was combined with the quinacridone red dispersion. A solution of 2.64 g of CrCl3.6H20 in 165 g of water was added with a uniform frequency P1710 / 98MX while the pH was maintained at 6.0 with 3.5% NaOH (by weight). A uniform and smooth red coating is achieved. The suspension was filtered and the filter cake was washed with water. The filter cake was dried at 120 ° C for 1 hour. It was incorporated at 3% by weight in a paint as a vehicle, with the following composition: 50% NV thermoset acrylic resin 51.78 Melamine Parts, 60% NV 16.83 Parts Solvent, xylene 30.29 Parts The combined pigment gives a two-color paint, which When coating a surface, it has a blue tint on a red background.

EXAMPLE 32 A load of 50 g of the blue reflective pigment of Example 4 in 800 ml of water was stirred at 60 ° C and the pH was adjusted to 2 with hydrochloric acid solution. A charge of approximately 64.7 grams of blue Sunfast dye (7.5 g of solids) was added and stirred for 30 minutes while the pH was adjusted to 6.0 with 3.5% NaOH. 2.4 aqueous solution of aluminum chloride hexahydrate was then added at a frequency of 1.5 ml / min and the pH was maintained at 6.0 with the NaOH solution. The pH was raised to 7 and stirring was continued for a further 15 minutes. The product was recovered by filtration and the P1710 / 98MX wet cake was washed five times with 500 ml of water, then dried overnight at 90 ° C.

EXAMPLES 33-36 Example 32 was repeated four times using green Sunfast dye on glass coated with titanium dioxide to the green rutile form (Example 33), green Sunfast dye and the blue reflective pigment of Example 4 (Example 34) , carbon black and copper coated pigment (Example 35) and carbon black in a pearlescent violet glass (Example 36). All the resulting products were very attractive.

P1710 / 98MX

Claims (14)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following CLAIMS is claimed as property: 1. A pearlescent pigment comprising glass flakes C (chemical glass) having on they are a first coating consisting of iron oxide or titanium dioxide in the rutile form.
2. 2. The pearlescent pigment of claim 1, wherein the first coating consists of titanium dioxide in the rutile form.
3. 3. The pearlescent pigment of claim 1, wherein the first coating consists of iron oxide.
4. 4. The pearlescent pigment of claim 1, coated with a second layer comprising hydrated oxide or hydroxide of a polyvalent cation, the precipitate of said polyvalent cation and an anionic polymeric substance and a water-insoluble colorful pigment, the percentages of said cation , substance and pigment, based on the weight of said pearlescent pigment, are 0.01-20, 0.01-20 and 0.01-30 respectively.
5. 5. The pearlescent pigment of claim 4,
6. P1710 / 98MX in which the first coating consists of titanium dioxide in the rutile form.
7. 7. A method for forming a pearlescent pigment that consists in forming a first layer of hydrated titanium dioxide that is oriented to rutile or hydrous iron oxide, on the glass flakes C and calcining said flakes with layers.
8. 8. A method according to claim 7, wherein a first layer of hydrous titanium dioxide that is rouylike is deposited.
9. 9. A method according to claim 8, wherein the layer is formed by precipitating tin oxide hydrate on the surface of the glass flakes and then depositing a layer of hydrous titanium dioxide thereon.
10. A method according to claim 7, in which the hydrated titanium dioxide is deposited on the glass flakes in the presence of iron and at least one member selected from the group consisting of calcium, magnesium and zinc ions.
11. 11. A method according to claim 7, wherein a first layer of hydrous iron oxide is deposited.
12. 12. A method according to claim 7, which consists of combining an aqueous suspension of the flaked flakes with an aqueous suspension of colorful pigment

    P1710 / 98MX insoluble in water, containing an anionic polymeric substance, combine the resulting suspension with an acid aqueous solution of a polyvalent cation that forms a precipitate of hydrous oxide or hydroxide and a precipitate, with said substance at a specific pH and with an amount of a pH adjusting agent to provide said specific pH and recover the resulting colorful pigment.
13. 13. A method according to claim 12, wherein a first layer of hydrous titanium dioxide is deposited which orientates rutile.
14. 14. A method according to claim 12, wherein a first layer is formed by precipitating tin oxide hydrate on the surface of the glass flakes and then depositing a layer of hydrous titanium dioxide thereon.

    P1710 / 98MX