MXPA00008193A - Pearlescent pigments containing ferrites - Google Patents

Abstract

A pearlescent pigment which is a ferrite-coated iron oxide-coated platy substrate in which the ferrite is substantially free of crystallites is obtained by adding metal ions to a slurry of hydrous iron compound and platy particles and then co-calcining in the metal and iron.

Description

PEARL PIGMENTS OÜ? THEY CONTAIN ERRI ^ l. DESCRIPTION OF THE INVENTION There are many known pearlescent or nacred pigments that are based on micaceous substrates or other lamellae that have been covered with a layer of metal oxide. As a result of reflection and refraction to light, these pigments show a pearl-like finish, depending on the thickness of the metal oxide layer, may show interference color effects. A good description of this type of pigment can be found: US Patent No. 3,087,828 and 3,087,829. The pearlescent pigments most frequently found in commercial bases are coated titanium dioxide mica pigments and coated oxide mica. It is also known that the metal oxide layer can be dust jacket. For example, the '-'cent No. 3,087,828 describes deposition fe O, in a Ti02 layer while the North American Patent Mo. 3,711,308 discloses a pigment in which there is a mixed layer of titanium and iron oxides in the mica which is coated with titanium dioxide and / or zirconium dioxide. The oxide cover is in the form of a layer of tin deposited on the mica particle surfaces.

The resulting pigment has the optical properties of the tin films and in this way the color reflected by the pigment raised from the interference of light which is dependent on the thickness of the cover. ? j that the o - _do c < = • Iron has an inherent red color, a single cubic-celestial oxide has a reflection color and an absorption color, the previous interference the last absorption of light. Reflection colors average from red to yellow and pigments are generally refl ",] d as" bronze, "" copper, "" red, "etc. Pigments are used for many purposes such as incorporation in plastics and cosmetics as well as exterior applications such as automotive paints Pearlescent pigments containing ferins are well known, for example, Morteamei patents 5,344,488 and DE 4120747 describe the deposition of zinc in the platelets. of mica that have been covered with iron oxide The American Patent sets out to evade the disadvantages of conventional zinc oxide / mica pigments, mainly the tendency to agglomerate, to obtain a pigment that has good compatibility to 1"'skin, antibacterial action , absorption properties _ > Favorable and a surface color, the oxide layer - z r.c is applied to the substrate similar to pre-prepared coated metal oxide plate. When the small, calcined needle-shaped crystals are randomly distributed in the surface layer so that the obtained zinc ferrite toa is not completely continuous. The patent states that the different substrates completely covered with zinc oxide in a continuous layer, the substrates covered with a crystallite-containing layer show only a slight tendency to agglomeration. The amount of a pearl pigment is generally dependent on the smoothness or continuity of the micaceous substrate cover. The amount of pigment decreases rapidly with the increased discontinuity in the coating. U.S. Patent 5,344,488 indicates that discontinuity is essential to avoid agglomeration. Therefore, the amount must be sacrificed to obtain a usable pigment. It is the object of the present invention to provide a ferrite-coated micaceous pigment which is substantially free of crystallites and, therefore, has high quality. These and other objects of the invention will be apparent to those of ordinary skill in the art in which: This invention relates to a pearl pigment which is a flat substrate of iron oxide coated with coated ferrite in which the ferrite is substantially free of crystallites. The pigment is obtained by the addition of metal ions to a mixture of an aqueous iron compound, composed of flat particles and then co-calcining the metal and the aqueous iron oxide. The metal can be added before or while simultaneously or after hydrolyzing the iron compound. The flat substrate can be natural mica, synthetic mica, vitreous flakes, Si02, A1203, mica covered with Ti02 and the like. According to the present invention, there is provided a pearl pigment which is a coated iron oxide micaceous pigment, of coated ferrite in which the coated ferrite is substantially free of crystallites. Ferrite is usual and completely free of crystallites and is a continuous layer, but the present invention does not exclude the existence of a misplaced crystallite or two. A ferrite is a double oxide of iron oxide and another metal oxide such as zinc oxide. Ferrites generally conform to the formula Mfe202 in which M is one or a mixture of metals that can exist in a divalent state such as calcium, strontium, barium, zinc, cadmium, manganese, magnesium, cobalt, nickel, copper and silica. '.s. The pearlescent pigment of that invention is obtained by combining a metal source M with an iron material and the flat substrate, preferably mica, provided that the iron and metal M deposit on the substrate and then co-calcining the iron and the metal M. The hydrolysis of the aqueous iron compound can be done before, preferably, while or after the metal source is agitated.The preparation of the micaceous pearlescent pigments of iron oxide covered is well known in the art and the process does not need to be described in any form here, in broad terms, an iron source is combined with the mica substrate to form an aqueous, aqueous, and reaction conditions. they are adjusted such that an aqueous iron compound is deposited on the mica substrate, followed by hydrolysis.Adjusting the pH of the system at a base value is usually achieved by means of the addition of a base to the mixture. the bases in •. sodium hydroxide and potassium hydroxide. This process can also be carried out, if desired, in the vapur phase. At any time prior to the calcination of the iron-coated mica, a metal source MI is combined with the reactants. Any metal source can be used as long as it does not interfere with the formation of an iron oxide or ferrite shell or cause the formation of crystallites. In this way, metal oxides, metal salts such as chloride or sulphate and the like or even metal complexes can be used. At those times, where the mica is present in the form of an aqueous mixture, the metal salt is preferably one that is soluble in water. The metal source is usually added to the metal deposit in the substrate after the aqueous iron compound has already been deposited. However, if desired, the metal can be added before the aqueous iron compound originates to deposit on the mica substrate. • After the iron and metal have been deposited, the covered substrate is washed and / or calcined in the conventional manner as if a mica pearl pigment covered with iron oxide has been prepared. As a result of the calcination, a covered dual layer is obtained with iron oxide adjacent to the mica substrate and a layer of ferrite in the upper part of the Fe .0-¿layer. The relative thickness of the two layers is a function of the amount of the metal relative to the amount of iron. In general, the Fe: M ratio can average from about 1-10, preferably about 2-5. When the Fe / M ratio is long, the Fe.-03 layer adjacent to the mica substrate is relatively thick and the detritus layer is relatively thin. As the ratio decreases, the relative amount of the iron oxide layer decreases and the relative thickness of the ferrite layer increases as the overall thickness of the cover increases. _ Considering, for example, a coated iron oxide mica pigment in which the absorbance and reflectance is red. The layer covered at this time is approximately 80 nm thick and is 100% ferrite oxide. When the zinc is deposited at a Fe: Zn ratio of 11.4, the total thickness of the cover increases to 38 nm of which about 75% is ferric oxide and 25% is zinc ferrite. The absorbance and reflectance of this pigment is orange-reddish. In a Fe: Zn ratio of 5.2, the thickness of the cover has increased to 95 nm of which approximately 50% is ferric oxide and 50% is zinc ferrite. In a ratio e: Zn of 3.1, the thickness of the cover has increased to. 105.8 nm of which approximately 25% is ferric oxide and 75 '- is zinc ferrite. As the thickness of the total cover increases, the absorbance and reflectance, which initially are the same, progressively diverge. For example, when the Fe: Zn ratio was 11.4, the absorbance and reflectance were orange / reddish but when the ratio increased to 7.1, the absorbance was orange-yellow while the reflectance was red. In this way, the effects o-- JO Lor unique can be obtained. To further illustrate the present invention, several examples are set forth in the following. In the e-grades, as throughout this specification and claims, all temperatures are in degrees centigrade and parts and percentages are by weight unless indicated otherwise. EXAMPLE 1 A mixture in which 50 g of mica (average particle size of 20 μm) previously covered with 39 FeCl; a bronze color was heated to 74 ° and the pri was adjusted to 8.5 by adding. Aqueous NaOH. An aqueous solution of ZnCl was added over the course of about 1 hour to deposit aqueous zinc oxide in the aqueous iron oxide coated mica while the pH was maintained with aOH. An aqueous solution of ZnCl was added over the course of about 1 hour to deposit aqueous zinc oxide in aqueous iron oxide coated mica while the pH was maintained with HaOH. é.mque Zn was added to achieve a Fe / Zn ratio of 4.5. The mixture was then filtered, washed and calcined at 900 ° C yielding a lustrous pearl pigment with an immense golden bronze color. EXAMPLE 2 (COMPARATIVE) A mixture of 78 g of a mica pigment coated with calcined iron oxide and a bronze color equivalent to 50 g of mica) in 50u ml of distilled water heated to 74 ° C and the pH was adjusted to 8.5 with aqueous NaOH. An aqueous solution of ZnCl2 was added over the course of about 1 hour to aqueous zinc oxide deposited in the iron oxide coated mica while the pH was maintained with NaOH. Although Zn was added to achieve a Fe / Zn ratio of 4.5. The mixtures were then filtered, washed and calcined at 900 ° C giving a bronze colored pearl pigment. EXAMPLE 3 The general procedure of Example 1 was guided, except that the aqueous iron oxide had a copper color. The product obtained a lustrous pearl pigment with an intense golden orange color. EXAMPLE 4 (COMPARATIVE) The general procedure of Example 2 was followed except that the calcined pigment had a copper color. The product obtained was an orange colcreated pearl pigment. EXAMPLE 5 The general procedure of Example 1 was followed except that the aqueous iron oxide had a yellowish brown color and the Fe / Zn ratio was 5.4. The product obtained was a lustrous pearl pigment with an intense orange color. The SEM photomicrograph (Figure 1) at 71,000 amplifications showed a smooth continuous layer of ZnFe204"which was formed by co-alkylation of the aqueous iron and zinc oxides EXAMPLE 6 (COMPARATIVE) The general procedure of Example 2 was followed except that the Calcined iron oxide had a yellowish brown color and the Fe / Zn ratio was 5.4 The product obtained was a colored reddish orange pearl pigment The SEM photomicrograph (Figure 2) has 71,000 amplifications showed discontinuous needle cover as ZnFe20 crystallites which was formed by two prior art stage processes EXAMPLE 7 The data L * a * b * of the pigments obtained in Examples 1-6 were measured using a spectrometer and listed in Table 1. See "The Measurement" of Appearance ", 2nd Edition, edited by Hunter and Harold Bryant John Wiley &Sons, 1987. The CIELab measures characterize the appearance of the product in terms of subcomponent d e clarity-darkness, symbolized by L *, a red-green compoentne represented by a * and a yellow-blue component represented by b *. Two additional parameters can be supplied from the data L * a * b *; the chromium (c) that is, [(a *) 2+ (b *)] 1 ^ and the hue (h) that is, arctan (tangent arc) (b * / a *). Chroma refers to the intensity or diversity of the color and the hue of the product's color probe. The data in Table 1 compare the chroma and hue obtained by the present invention and by the prior art in pairs, where each pair is a particular iron content and the Fe / Zn ratio. One can clearly see that the pigments of the present invention have higher chroma and hue that have more significant changes in the color of the original ferric oxide than those prepared by the prior art. These differences represent the smooth continuous layer of a ferrite formed by the present invention compared to the discontinuous layer of the crystallites in the prior art.

TABLE 1 EXAMPLE 8 A mixture wherein 50 g of mica (average particle size 20 μm) previously covered with 39% FeCl 3 to a yellowish brown color was heated to 75 ° C and the pH was left unadjusted approximately 3. Although the CnCl 2 solution was added over the course of approximately 20 minutes with unregulated pH to achieve a Fe / Zn ratio of 4.5. The pH was then slowly raised to 8 by the addition of aqueous NaOH to deposit aqueous zinc oxide in the aqueous iron oxide coated mica. The mixture was then filtered, washed and calcined at 900 ° C producing a pearlescent or lustrous colored orange pigment. EXAMPLE 9 A mixture of 50 g of mica (average particle size 20 μm) previously covered with 39% FeCl 3 to a yellowish brown color was filtered, washed and remeasured before heating to 74 ° C and the pH was adjusted to 9.5. A solution of ZnCl2 was added during the body of approximately 20 minutes to deposit aqueous zinc oxide in mica coated with aqueous iron oxide while the pH was maintained with NaOH. Although Zn was added to achieve a Fe / Zn ratio of 5.4. The mixture was then filtered, washed and calcined at 900 ° C producing a lustrous pearl pigment with an intense orange color.

EXAMPLE 10 A mixture of 50 g of mica (average particle size 15 μm) previously covered with 33% FeCl 3 to a yellowish brown color was heated to 75 ° C and the pH adjusted to 8 with aqueous NaOH. An aqueous solution of ZnCl2 was added over the course of about -40 minutes to deposit aqueous zinc oxide in the aqueous iron oxide shell while the pH was maintained with NaOH. Although Zn was added to "achieve a Fe / Zn ratio of 3.6, the mixture was then filtered, washed and calcined at 900 ° C producing a lustrous pearl pigment with an intense orange color EXAMPLE 11 A mixture of 50 g of mica (size of 20 μm average particle previously covered with 39% FeCl3 to a yellowish brown color was heated to 75 ° C and the pH was adjusted to 9.5 with aqueous NaOH An aqueous solution of MnCl2 was added over the course of approximately 40 minutes to deposit oxide of aqueous magnesium in the mica covered with aqueous iron oxide while the pH was maintained with NaOH, although Mn was added to achieve an Fe / Mn ratio of 4. The mixture was then filtered and calcined at 900 ° C and gave a pearly pigment glossy with a dark purple color EXAMPLE 12 A mixture of 50 g of mica (average particle size 20 μm) previously covered with 39% FeCl 3 to a bronze color was heated to 75 ° C and the pH was adjusted to 9 with aqueous NaOH An aqueous solution CuCl 2 was added over the course of about 1 h to deposit aqueous copper oxide in the aqueous iron oxide coated mica while the pH was maintained with NaOH. Although Cu was added to achieve a Fe / Cu ratio of 2. The mixture was then filtered, washed and calcined at 900 ° C and gave a lustrous brown colored pearl pigment. EXAMPLE 13 A mixture of 50 g of mica (average particle size 20 μm) previously covered with 39% FeCl 3 to a bronze color was heated to 75 ° C and the pH was adjusted to 9 with aqueous NaOH. An aqueous MgCl 2 solution was added over the course of about 2 h to deposit magnesium oxide in the aqueous iron oxide coated mica while the pH was maintained with NaOH. Although Mg was added to achieve an Fe / Mg ratio of 2. The mixture was then filtered, washed and calcined at 900 ° C and gave a yellow / lustrous brown pearl pigment. EXAMPLES 14-18 Following the procedure of Example 1, a series of pearlescent pigments were prepared wherein the Fe / Zn ratio varied and the characteristic color of those products was evaluated by means of data L * a * b * against a card of black and white reduction using spectrophotometer. The data L * a * b * measured on the black and white portions of the reduction card were established in Tables 2 and 3 below. TABLE 2 Increased Zn level, interference color on black TABLE 3 Increased Zn level, absorbance color on white Note that the hue measured on the black portion of the black reduction portion increased from a reddish shade of orange to a yellow orange with increased amounts of zinc, and then it reverted to a reddish orange with high levels of zinc. The fluctuation of the interference color is indicative that it has two layers, Fe203 and the other ZnFe204. With low zinc levels, the pigment is closer to a pure Fe203 layer, which in this example had a red interference color. More zinc was added, the zinc ferrite layer grew at the cost of ferric oxide, so at one level the ferrite oxide layer is effectively thinner with an orange interference color while the zinc ferrite is thick but also has an orange interference color (presumptive). Where more zinc is added, the ZnFe20 layer increases the thickness although it has a red interference color. The hue measured on the white portion of the card read the color absorption shown that the matrix became more yellow as the yellow-orange zinc ferrite replaced the red ferric oxide. EXAMPLE 19 A mixture of 50 g of glass sheets (average particle size 100 μm) previously covered with 39% FeCl 3 to a yellowish brown color was heated to 74 ° C and the pH was adjusted to 9.5 by the addition of NaOH. An aqueous solution of ZnCl 2 was added over the course of about 20 minutes to deposit aqueous zinc oxide on the glass sheets coated with aqueous iron oxide while the pH was maintained with NaOH. Although Zn was added to achieve a Fe / Zn ratio of 10. The mixture was then filtered, washed and calcined at 700 ° C. The resulting product was a lustrous pearl with an intense orange color. EXAMPLE 20 A mixture wherein 100 g of titanium dioxide-coated mica with a pearl color (average particle size 20 μm) in 500 ml of distilled water was dropped to 75 ° C, and the pH was adjusted to 4.3. the mixture is added: or an aqueous solution of FeCl3 and ZnCl? where the ratio Fc / '. n was 2. The pH remained constant during the addition with aqueous MaOH. The mixture was then filtered, washed and calcined at 900 ° C giving a pearl pigment colored bright glossy orange. EXAMPLES 21-27 The procedure of Example 1 was followed where the zinc was replaced with cobalt, nickel, calcium, barium, strontium, cadmium and lead, respectively. Various changes and modifications can be made in the process and products of the present invention without departing from the spirit and scope thereof. Various embodiments that have been set forth herein were for purposes of further illustration of the invention but are not intended to limit it.

Claims (10)

1. CLAIMS 1. A pearl pigment comprising a silver pigment covered with ferrite iron oxide covered in which the ferrite shell is substantially lite-e crystallites.
2. 2. The pearlescent pigment according to claim 1, characterized in that the ferrite is of the formula Mfe20 in which M is a divalent metal or mixture of divalent metals and the Fe / M ratio is approximately ia 10.
3. 3. The pearl pigment according to claim 2, characterized in that M is selected from the group consisting of calcium, strontium, barium, zinc, cadmium, manganese, cobalt, magnesium, nickel and copper and the Fe / M ratio is approximately 2 to 5.
4. The pearl pigment according to claim 3, characterized in that the ferrite shell is free of crystals
5. 5. The pearl pigment according to claim 4, characterized in that M is Zn
6. 6. The pearl pigment according to claim 1, characterized in that the flat substrate of the flat pigment is selected from the group consisting of mica, glass, metal oxide covered mica and metal oxide coated sheets.
7. 7. A method of manufacturing pearl pigment according to claim 1, characterized in that it comprises depositing one or more mixtures of captal-. , d form a ferrite and a compound of aqueous iron and flat particles and calcine the resulting combination.
8. 8. The method according to claim 7, characterized in that the metal is selected from the group consisting of calcium, strontium, barium, zinc, manganese, magnesium, cobalt, nickel and copper, and in the and iron to the metal ratio of about _-lC where the flat particle is selected from the group consisting of mica, glass, metal oxide covered mica /! i.dri coated metal oxide cover.
9. 9. The method according to claim 8, characterized in that the iron to metal ratio is d approximately 2-5 and in which the metal is zinc.
10. 10. The method according to claim 9, characterized in that the iron-to-metal ratio is approximately 2-5 and in which the elective compound is deposited in the particles before it is deposited therein. .