Modified fluorphlogopite powder, method for preparing the same, and silver-white mica titanium pearl pigment, method for preparing the same and application

Abstract

This invention provides a modified fluorophlogopite powder and its preparation method, as well as a silvery-white mica titanium pearlescent pigment and its preparation method and applications, relating to the field of inorganic pigment technology. The preparation method of the modified fluorophlogopite powder provided by this invention includes the following steps: sequentially subjecting the fluorophlogopite powder to calcination activation, alkali activation, acid activation, water washing, and drying to obtain the modified fluorophlogopite powder. This invention also provides a silvery-white mica titanium pearlescent pigment, comprising the modified fluorophlogopite powder and a rutile titanium dioxide layer coating the modified fluorophlogopite powder. This invention uses the modified fluorophlogopite powder as a substrate and coats its surface with a rutile titanium dioxide layer, forming a silvery-white mica titanium pearlescent pigment with excellent high-temperature stability. It can maintain the integrity of its layered structure and the optical stability of the coating layer above 1000℃, showing great application potential in high-temperature fields such as ceramics.

Description

Technical Field

[0001] This invention relates to the field of inorganic pigment technology, and in particular to a modified fluorophlogopite powder and its preparation method, and a silvery-white mica titanium pearlescent pigment and its preparation method and application. Background Technology

[0002] Pearlescent pigments are optical effect pigments that surpass inorganic pigments and dyes in both color and gloss. They also possess advantages not found in metallic or organic pigments, such as superior weather resistance, high thermal stability, low toxicity, and low electrical conductivity. Therefore, they are gradually replacing some traditional pigments in automotive coatings, architectural coatings, plastics, inks, product packaging, ceramics, and cosmetics. Furthermore, due to their conductivity, magnetism, and sensitivity to laser and infrared reflection, they are used in special processes and magnetic wave shielding. The pearlescent effect of pearlescent pigments originates from the physical interaction of their unique layered structure with light; the core mechanism is the synergistic effect of multilayer reflection and thin-film interference. These pigments typically use a flake-like substrate (such as natural mica or fluorophlogopite) as the core, coated with one or more layers of high-refractive-index metal oxides (such as TiO2), forming a core-shell structure of "substrate-coating layer," known as mica titanium pearlescent pigments. When natural light shines on the pigment surface, the light undergoes multiple reflections at the air / coating layer interface and the coating layer / substrate interface. Simultaneously, the coating layer (typically 50-100 nm thick) acts as a thin film for light, selectively interfering with different wavelengths of visible light. When the coating layer thickness satisfies the condition that the optical path difference is an integer multiple of half the wavelength, light of specific wavelengths (such as the 400-700 nm visible light band) is enhanced due to constructive interference, while other wavelengths are weakened due to destructive interference. For silvery-white pearlescent pigments, the TiO2 coating layer thickness is controlled at 70-90 nm to balance the interference enhancement effect across all visible light bands, ultimately resulting in a soft and uniform silvery-white pearlescent luster.

[0003] Currently, the mainstream silvery-white mica titanium pearlescent pigments are usually anatase phase TiO2 coated on the surface of mica substrate. However, they have significant performance shortcomings in high-temperature applications (such as ceramic glaze firing, ≥800℃). The pearlescent luster will decrease sharply or even disappear completely. The core problem is the destruction of the pearlescent mechanism at high temperatures: (1) The anatase phase TiO2 coating layer will undergo a crystal transformation above 800℃, and the grain size will coarsen from 20~50nm to more than 100nm, which will destroy the light interference conditions; (2) The substrate and the coating layer will undergo element interdiffusion at high temperatures (such as Al in natural mica). 3+(Diffusion into TiO2) generates low-refractive-index impurities (such as Al2TiO5, refractive index 1.89), further weakening light reflection and interference effects. Rutile TiO2 has a stable crystal structure and is not easily decomposed or undergoes phase transformation at high temperatures. Coating the surface of mica substrate with rutile TiO2 is expected to improve the high-temperature resistance of mica titanium pearlescent pigments. However, rutile TiO2 needs to be prepared at temperatures above 800℃, and during this process, the mica substrate will inevitably undergo structural damage: the critical heat resistance temperature of natural mica substrates such as muscovite is 450℃, and that of phlogopite is slightly higher at about 650℃. Due to the presence of water of crystallization, interlayer dehydration and lattice collapse occur at 600~800℃, resulting in a pearlescent luster attenuation rate of more than 50%, or even no luster. In contrast, fluorophlogopite has a natural structural advantage as a synthetic mica, with the chemical formula KMg3(AlSi3O) 10 F2, which contains no water of crystallization, has layers bonded by strong ionic and covalent bonds. Its theoretical upper limit for high temperature resistance can reach 1000℃, far exceeding that of natural mica (600~700℃). However, it still exhibits interlayer K+ at high temperatures. + Thermal migration, surface F - Issues such as leakage lead to a loss of lamellar integrity. These problems limit the application of silvery-white mica titanium pearlescent pigments prepared using mica as a substrate in fields such as high-temperature ceramic decoration. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a modified fluorophlogopite powder and its preparation method, as well as a silvery-white mica titanium pearlescent pigment and its preparation method and application. The modified fluorophlogopite powder prepared by this invention has excellent high-temperature stability, and the silvery-white mica titanium pearlescent pigment formed by coating it with rutile titanium dioxide can maintain the integrity of its layered structure and the optical stability of the coating layer at temperatures above 1000℃.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing modified fluorophlogopite powder, comprising the following steps: The modified fluorophlogopite powder was obtained by sequentially subjecting it to calcination activation, alkali activation, acid activation, water washing, and drying. The calcination activation temperature is 800~900℃, and the holding time is 1~2h; the alkali activation uses NaOH solution with a concentration of 3mol / L, the alkali activation temperature is 85~90℃, and the time is 0.5~2h; the acid activation uses sulfuric acid with a concentration of 0.5mol / L, the acid activation temperature is 85~90℃, and the time is 0.5~2h.

[0006] Preferably, the average particle size of the fluorophlogopite powder is 10~60μm.

[0007] The present invention provides modified fluorophlogopite powder prepared by the preparation method described in the above technical solution.

[0008] This invention provides a silvery-white mica titanium pearlescent pigment, comprising the modified fluorophlogopite powder described above and a rutile titanium dioxide layer encapsulating the modified fluorophlogopite powder.

[0009] Preferably, the chromaticity parameter of the silvery-white mica titanium pearlescent pigment is: L =93~97, a =-0.5~0.5, b =1.0~4.5, whiteness WI-CIE≥60.

[0010] This invention provides a method for preparing the silvery-white mica titanium pearlescent pigment described in the above technical solution, comprising the following steps: The modified fluorophlogopite powder, titanium source, and tin tetrachloride were respectively mixed with water to obtain a fluorophlogopite powder dispersion, a titanium source solution, and a tin tetrachloride solution. A titanium source solution and a tin tetrachloride solution are simultaneously added dropwise to the fluorophlogopite powder dispersion, with the addition of the titanium source solution and the tin tetrachloride solution completed at the same time. The resulting mixture is then subjected to a deposition reaction to obtain a pearlescent pigment precursor solution. During the dropwise addition, the system temperature is controlled at 60-80°C, and the pH value is 0.5-2. The deposition reaction includes a first deposition reaction and a second deposition reaction performed sequentially. The temperature of the first deposition reaction is 60-80°C, and the holding time is 0.5-1.5 h. The temperature of the second deposition reaction is 90-110°C, and the holding time is 0.5-2 h. The pearlescent pigment precursor solution was subjected to static standing, solid-liquid separation, water washing and drying in sequence to obtain pearlescent pigment precursor powder. The pearlescent pigment precursor powder was calcined to obtain the silvery-white mica titanium pearlescent pigment.

[0011] Preferably, the ratio of modified fluorophlogopite powder to water in the fluorophlogopite powder dispersion is 1g:15~40mL; the titanium source includes one or more of titanium oxysulfate, titanium tetrachloride, and tetrabutyl titanate, and the concentration of the titanium source solution is 0.5~3mol / L; the concentration of the tin tetrachloride solution is 0.05~0.15mol / L; the molar ratio of tin in the tin tetrachloride solution to titanium in the titanium source solution is 1:(4~14); and the molar ratio of modified fluorophlogopite powder to titanium in the titanium source solution in the fluorophlogopite powder dispersion is 1:(1~4).

[0012] Preferably, the calcination treatment temperature is 600~800℃, and the holding time is 1~4h.

[0013] This invention provides the application of the silvery-white mica titanium pearlescent pigment described in the above technical solutions or the silvery-white mica titanium pearlescent pigment prepared by the above technical solutions in ceramics.

[0014] The present invention also provides a ceramic pearlescent glaze, which is made by firing raw materials including transparent glaze and pearlescent pigment at high temperature. The pearlescent pigment is the silver-white mica titanium pearlescent pigment described in the above technical solution or the silver-white mica titanium pearlescent pigment prepared by the preparation method described in the above technical solution. The high temperature firing temperature is above 1000℃.

[0015] This invention provides a method for preparing modified fluorophlogopite powder. Compared with the prior art, this invention has the following advantages: This invention employs a modification process for fluorophlogopite powder, involving calcination activation, alkali activation, acid activation, and water washing, to progressively optimize the physicochemical properties of the fluorophlogopite powder surface, laying the foundation for uniform coating of TiO2. This activation sequence is based on a progressive action of physical purification, chemical etching, regulation and optimization, and final cleaning. High-temperature calcination ensures the absence of surface impurities, and its enhanced lattice stability guarantees the structural stability of the mica substrate when encapsulating rutile TiO2, making the resulting pigment less prone to cracking when calcined above 1000℃. The rough structure and hydroxyl groups formed by alkali activation provide physical anchors and chemical bonding sites for the coating. Acid activation eliminates alkaline interference and refines the surface; the hydroxyl groups introduced in these two steps can form chemical bonds with the coating (TiO2 layer), improving the pigment's corrosion resistance in acidic and alkaline environments and organic solvents. Finally, water washing ensures uniform deposition of the TiO2 coating precursor. After these four steps, the coating thickness deviation can be controlled within ±5nm, and color consistency is significantly improved. This four-step activation process targets the chemical composition and surface characteristics of fluorophlogopite. Through precise sequential design, it achieves full-process control from "substrate purification" to "interface optimization," specifically addressing the shortcomings of fluorophlogopite's high-temperature stability and ensuring the high gloss, high stability, and high uniformity of fluorophlogopite-based pearlescent pigments.

[0016] This invention also provides a silvery-white mica titanium pearlescent pigment, which exhibits excellent high-temperature stability, maintaining the integrity of its layered structure and the optical stability of its coating layer above 1000℃. Furthermore, this silvery-white mica titanium pearlescent pigment is a green, environmentally friendly, and non-toxic colorant, greatly meeting the environmental requirements of ceramic colorants in practical use and achieving sustainable development. Example results show that the silvery-white mica titanium pearlescent pigment provided by this invention remains white after calcination at 600~1100℃ in air, with a whiteness value WI-CIE≥60; it does not change color after soaking in 12mol / L concentrated hydrochloric acid for 24 hours; and after heat treatment at room temperature to 1300℃, the mass change is <8wt%, with no significant thermal effect.

[0017] The present invention provides a method for preparing the silver-white mica titanium pearlescent pigment described in the above technical solution: (1) In the present invention, tin tetrachloride and titanium source are added to the experimental system at the same time. The hydrolysis rate of the two can be synchronized by adjusting the concentration at a specific pH and temperature. The precursor generated by hydrolysis is nucleated and co-deposited on the surface of fluorophlogopite. At this time, due to the reduction of the growth energy barrier of TiO2 coating, TiO2 is more likely to spread along the mica surface to form a continuous and dense coating layer, reducing coating defects. At the same time, the crystal form and grain size of TiO2 can be controlled simultaneously (promoting the formation of rutile at a lower temperature), making the coating closer to the "ideal smooth interface" - the synergistic effect of co-deposition of tin tetrachloride and titanium source. The comprehensive performance of fluorophlogopite@TiO2 silver-white pearlescent pigment is optimized from four dimensions: coating structure (uniformity, density), crystal form and grain (stability, size), optical performance (reflectivity, gloss) and interface bonding force. This is crucial to the gloss (dependent on the light reflection of the smooth surface) and weather resistance (resistance to the penetration of corrosive media) of the pearlescent pigment. (2) This invention employs a two-step liquid-phase deposition method to prepare silvery-white mica titanium pearlescent pigment. Under liquid-phase conditions, a uniformly distributed crystal nucleus is preferentially formed at a low temperature, resulting in nanoparticles with a particle size of approximately 10-35 nm. This stage avoids agglomeration caused by rapid nucleation at high temperatures. Then, the reaction temperature is increased to allow the coating layer to form non-uniform nucleation, filling the coating pores through ion diffusion and improving density. This results in a more uniform coating on the fluorophlogopite surface, overcoming the technical bottleneck of existing mica titanium pearlescent pigments for ceramics. This method enables the mica titanium pearlescent pigment to retain its pearlescent effect after calcination at 1000℃, maintaining its original crystal structure without decomposition, and exhibiting superior high-temperature resistance. Through synergistic precursor combination and two-step temperature control, the pearlescent gloss can be increased to over 92%, while the coating adhesion is increased by over 25%, achieving dual optimization of crystal form and structure. (3) The silver-white mica titanium pearlescent pigment prepared by the liquid phase method of this invention is carried out in a liquid phase deposition reaction system. The raw material mixing reaches the molecular or atomic level, with high encapsulation efficiency, uniform and dense encapsulation. The resulting pigment product has fine particle size and uniform distribution, which greatly enhances the color effect of the pigment and can meet higher practical application requirements. In the core-shell type coating structure formed, the dense titanium dioxide coating layer can not only isolate the external strong acid corrosion, but also prevent the invasion of O2 at high temperature, ensuring that the core substrate fluorophlogopite is not oxidized at high temperature, thereby greatly improving the high temperature stability and acid corrosion resistance of the pigment and greatly expanding its application field. (4) The preparation method of this invention is simple and easy to control, requires simple equipment, and has low cost, which is conducive to industrial production promotion and application. Attached Figure Description

[0018] Figure 1 The XRD patterns of the fluorophlogopite-based core-shell silvery-white mica titanium pearlescent pigment obtained by calcination at different temperatures (600~1100℃) in air for 2 hours in Example 2 are shown. Figure 2 XRD patterns of samples obtained by acidifying fluorophlogopite directly with sulfuric acid of different concentrations and then washing with deionized water. Figure 3 The images show the FTIR spectra of fluorophlogopite samples after acidification with sulfuric acid of different concentrations. Figure 3 In (a), fluorophlogopite acidified with 0.1 mol / L H₂SO₄ was subjected to oxidation at 800–1200 cm⁻¹. -1 The deconvolutioned FTIR absorption spectra within the range, (b) are those of fluorinated phlogopite acidified with 0.5 mol / L H2SO4 in the range of 800–1200 cm⁻¹. -1 Deconvolutional FTIR absorption spectra within the range, (c) are fluorophlogopite acidified with 1 mol / L H2SO4 in the range of 800~1200 cm⁻¹. -1 The deconvolutioned FTIR absorption spectra within the range are shown in (d), which is the FTIR spectrum of fluorophlogopite acidified with three concentrations of H2SO4, and (e) is the Q spectrum obtained after peak separation of fluorophlogopite acidified with three concentrations of H2SO4. 2 Q 3 Q 4 Area ratio diagram of Si-O-Al / Mg; Figure 4 TEM images and elemental distribution analysis of the fluorine-phlogopite-based core-shell silvery-white mica titanium pearlescent pigment for ceramics in Example 2. Figure 4 (a) and (b) are TEM images of fluorophlogopite@TiO2 nanoparticles, (c) is an HRTEM image of fluorophlogopite@TiO2 nanoparticles, and (d) is the corresponding elemental diagram of fluorophlogopite@TiO2 nanoparticles. Figure 5 This is a SEM image of the fluorophlogopite-based core-shell silvery-white mica titanium pearlescent pigment for ceramics in Example 2. Figure 5 (a) and (b) are SEM images at different scales; Figure 6 XRD patterns of fluorophlogopite-based core-shell silvery-white mica titanium pearlescent pigments prepared by fluorophlogopite with different activation methods; Figure 7 The results of colorimetric and pearlescent index tests on fluorophlogopite-based core-shell silvery-white mica titanium pearlescent pigment samples prepared by fluorophlogopite with different activation methods. Figure 8 These are SEM images of the fluorophlogopite before and after activation in Example 2. Figure 8 (a) is the SEM image before activation, and (b) is the SEM image after activation; Figure 9 The image shows a photograph of the fluorophlogopite-based core-shell silvery-white mica titanium pearlescent pigment prepared using fluorophlogopite before and after activation as the substrate in Example 2. Figure 9(a) is a photograph of a fluorophlogopite-based core-shell silver-white mica titanium pearlescent pigment prepared using unactivated fluorophlogopite as a substrate, and (b) is a photograph of a fluorophlogopite-based core-shell silver-white mica titanium pearlescent pigment prepared using activated fluorophlogopite as a substrate. Figure 10 The XRD patterns of the fluorophlogopite-based core-shell silvery-white mica titanium pearlescent pigment samples prepared in Example 1 without the addition of synergistic regulator (SnCl4) and with the addition of synergistic regulator (calcined at 600℃ for 2h) are shown. Figure 11 SEM images and particle size distributions of fluorinated phlogopite-based core-shell silvery-white mica titanium pearlescent pigments prepared under different liquid-phase deposition reaction conditions. Figure 11 In (a) 70℃-2h, (b) 80℃-2h, (c) 80℃-1h, 100℃-1h, (d) 90℃-2h, (e) 100℃-2h, (f) 70℃-1h, 100℃-1h, (g) 90℃-1h, 100℃-1h; Figure 12 The TG-DTA curve of the pearlescent pigment precursor powder before calcination in Example 2; Figure 13 The effect of adding silvery-white mica titanium pearlescent pigment to transparent glaze in Example 2 and firing it at different temperatures (800℃, 850℃, 950℃, 1050℃, 1100℃) is shown. Detailed Implementation

[0019] This invention provides a method for preparing modified fluorophlogopite powder, comprising the following steps: The modified fluorophlogopite powder was obtained by sequentially subjecting it to calcination activation, alkali activation, acid activation, water washing, and drying. The calcination activation temperature is 800~900℃, and the holding time is 1~2h; the alkali activation uses NaOH solution with a concentration of 3mol / L, the alkali activation temperature is 85~90℃, and the time is 0.5~2h; the acid activation uses sulfuric acid with a concentration of 0.5mol / L, the acid activation temperature is 85~90℃, and the time is 0.5~2h.

[0020] Unless otherwise specified, all raw materials involved in this invention are commercially available products well known in the art.

[0021] In this invention, the fluorophlogopite powder is in flake form, and the average particle size is preferably 10~60µm.

[0022] In this invention, the calcination activation (also known as high-temperature calcination activation or thermal activation) temperature is 800~900℃, which can be 800, 850 or 900℃. The heating rate to the calcination activation temperature is preferably 5~10℃ / min, and the holding time for calcination activation is 1~2h. The calcination activation is preferably carried out in a fluoropolymer furnace in an air atmosphere. After calcination activation, the material is cooled. In this invention, the function of calcination activation is to remove physically adsorbed organic matter on the surface of the fluorophlogopite powder, while simultaneously causing local rearrangement of the surface lattice due to thermal vibration, resulting in lattice distortion, thus providing a more uniform reaction substrate for subsequent chemical activation.

[0023] In this invention, the alkaline reagent used for alkali activation is NaOH solution. Specifically, calcined and activated fluorophlogopite powder is added to the NaOH solution. The concentration of the NaOH solution is 3 mol / L, and the preferred solid-liquid ratio (i.e., the ratio of calcined and activated fluorophlogopite powder to the NaOH solution) is 1 g:(30~40) mL, or 1 g:35 mL. In this invention, the alkali activation temperature is 85~90℃, or 85, 86, 87, 88, 89, or 90℃, and the activation time is 0.5~2 h, or 1 h. The alkali activation is preferably carried out under stirring conditions. This invention uses a strong alkali to etch the surface of the calcined and activated fluorophlogopite powder, dissolving some lattice ions, such as F... - K + The introduction of hydroxyl groups (-OH) leads to the hydrolysis of some Si-O-Si bonds under strong alkaline conditions, forming Si-OH groups with the hydroxyl groups (-OH). These groups provide chemical bonding sites for subsequent acid activation and coating. Without alkaline activation, the fluorophlogopite powder surface is chemically inert, making subsequent acid activation difficult and resulting in insufficient surface active sites. After alkaline activation, the obtained fluorophlogopite powder is preferably washed with deionized water until neutral, then filtered, dried, and subjected to acid activation.

[0024] In this invention, the acid reagent used for acid activation is sulfuric acid (H2SO4), specifically, alkali-activated fluorophlogopite is added to sulfuric acid. In this invention, the concentration of sulfuric acid is 0.5 mol / L, and the preferred solid-liquid ratio (i.e., the ratio of alkali-activated fluorophlogopite powder to sulfuric acid) is 1 g:(30~40) mL, or 1 g:35 mL; the acid activation temperature is 85~90℃, or 85, 86, 87, 88, 89, or 90℃, and the time is 0.5~2 h, or 1 h. The acid activation is preferably carried out under stirring conditions. This invention uses acid activation to eliminate the physical barrier layer formed by excess OH- and metal hydroxide precipitates remaining on the surface of the alkali-activated fluorophlogopite powder; SO4 2- As a bidentate ligand, it interacts with Mg in the fluorophlogopite octahedron. 2+ Al 3+ The formation of stable chelates avoids excessive damage to the layered structure, while building a uniform hydroxyl network on the surface, further improving surface activity and enhancing the physical anchoring effect on the coating.

[0025] In this invention, the water washing preferably includes a first water wash and a second water wash performed sequentially. In this invention, the first water wash preferably involves washing the acid-activated fluorophlogopite powder with deionized water at room temperature until neutral; after the first water wash, the powder is filtered and dried, and then subjected to a second water wash. In this invention, the second water wash preferably involves adding the fluorophlogopite powder after the first water wash to deionized water and washing it at 85-95°C (90°C is acceptable); the washing time is preferably 1 hour, and the washing is preferably performed under stirring. During the second water wash, the water temperature is kept constant to avoid thermal stress cracking caused by sudden temperature changes. In this invention, the second water wash is also referred to as a fine wash. This fine wash dilutes the residual acid solution, removes residual acids, alkalis, salts, and micro-debris from the surface of the fluorophlogopite, completely terminates the etching reaction, maintains the layered structure, reduces the conductivity to below 5 μS / cm, and ensures a clean surface for the fluorophlogopite. After the fine wash, the powder is filtered and dried to obtain the modified fluorophlogopite powder.

[0026] Currently available mica titanium pearlescent pigments have significant drawbacks when used in high-temperature environments (≥800℃): Natural mica, due to the presence of crystal water and impurities, is prone to interlayer dehydration and lattice collapse at high temperatures, resulting in a pearlescent gloss reduction rate exceeding 50%, or even complete loss of gloss. These defects severely limit its application in high-temperature glazes (1000~1300℃) in ceramics. In contrast, fluorophlogopite, as a synthetic mica, has a natural structural advantage; its chemical formula is KMg3(AlSi3O3). 10 F2, anhydrous, has layers bonded by strong ionic and covalent bonds, theoretically capable of withstanding temperatures up to 1000℃, far exceeding that of natural mica (600~700℃). However, it still exhibits interlayer K+ at high temperatures. + Thermal migration, surface F - Issues such as leakage lead to loss of lamellar integrity. Based on these problems, this invention addresses the high-temperature stability limitation of fluorophlogopite through a synergistic process of high-temperature thermal activation, alkali activation, and acid activation: high-temperature heat treatment (800~900℃, calcination for 1~2h) promotes lattice rearrangement; alkali activation (3mol / L NaOH) facilitates the release of OH-. - Selective etching of the surface layer to introduce Na +The interlayer bonding is strengthened and the interlayer bonding energy is improved. Acid activation (0.5 mol / L H2SO4) constructs a surface hydroxyl network, providing a large number of chemical bonding sites, while retaining interlayer vacancies to buffer thermal stress. After the above modification treatment, the performance of fluorophlogopite is significantly improved, laying the foundation for the preparation of high-temperature stable pearlescent pigments.

[0027] This invention provides modified fluorophlogopite powder prepared by the preparation method described above. The modified fluorophlogopite powder provided by this invention has excellent high-temperature stability and can achieve the encapsulation of rutile titanium dioxide on the surface of a mica substrate, forming a silvery-white mica titanium pearlescent pigment that can maintain the integrity of its layered structure and the optical stability of the coating layer above 1000℃.

[0028] This invention provides a silvery-white mica titanium pearlescent pigment, comprising the modified fluorophlogopite powder described above and a rutile titanium dioxide layer encapsulating the modified fluorophlogopite powder.

[0029] The silvery-white mica titanium pearlescent pigment provided by this invention is a core-shell type. Therefore, in the embodiments of this invention, the silvery-white mica titanium pearlescent pigment is also referred to as a fluorophlogopite-based core-shell type silvery-white mica titanium pearlescent pigment (represented as fluorophlogopite@TiO2 pearlescent pigment). In this invention, the average particle size of the modified fluorophlogopite powder is preferably 10~60μm, and the average particle size of the titanium dioxide grains in the rutile titanium dioxide layer is preferably 20~40nm. In this invention, the chromaticity parameters of the silvery-white mica titanium pearlescent pigment are preferably... L =93~97, a =-0.5~0.5, b =1.0~4.5, whiteness WI-CIE≥60.

[0030] The silvery-white mica titanium pearlescent pigment provided by this invention is a functional pigment that combines high thermal stability with a silvery-white pearlescent effect. The silvery-white mica titanium pearlescent pigment provided by this invention remains white after calcination at 600~1100℃ in air, with a whiteness value WI-CIE≥60; it does not change color after soaking in 12mol / L concentrated hydrochloric acid for 24h; and after heat treatment at room temperature~1300℃, the mass change is <8%, with no significant thermal effect.

[0031] This invention provides a method for preparing the silvery-white mica titanium pearlescent pigment described above, comprising the following steps: The modified fluorophlogopite powder, titanium source, and tin tetrachloride were respectively mixed with water to obtain a fluorophlogopite powder dispersion, a titanium source solution, and a tin tetrachloride solution. A titanium source solution and a tin tetrachloride solution are simultaneously added dropwise to the fluorophlogopite powder dispersion, with the addition of the titanium source solution and the tin tetrachloride solution completed at the same time. The resulting mixture is then subjected to a deposition reaction to obtain a pearlescent pigment precursor solution. During the dropwise addition, the system temperature is controlled at 60-80°C, and the pH value is 0.5-2. The deposition reaction includes a first deposition reaction and a second deposition reaction performed sequentially. The temperature of the first deposition reaction is 60-80°C, and the holding time is 0.5-1.5 h. The temperature of the second deposition reaction is 90-110°C, and the holding time is 0.5-2 h. The pearlescent pigment precursor solution was subjected to static standing, solid-liquid separation, water washing and drying in sequence to obtain pearlescent pigment precursor powder. The pearlescent pigment precursor powder was calcined to obtain the silvery-white mica titanium pearlescent pigment.

[0032] In this invention, the modified fluorophlogopite powder, titanium source, and tin tetrachloride (SnCl4) are mixed with water to obtain a fluorophlogopite powder dispersion, a titanium source solution, and a tin tetrachloride solution.

[0033] In this invention, the water is preferably deionized water; the ratio of modified fluorophlogopite powder to water in the fluorophlogopite powder dispersion is preferably 1g:15~40mL, or 1g:16~17mL; the titanium source preferably includes one or more of titanium oxysulfate (TiOSO4), titanium tetrachloride, and tetrabutyl titanate, and the concentration of the titanium source solution is preferably 0.5~3mol / L, or 0.5 or 1mol / L; the concentration of the tin tetrachloride solution is preferably 0.05~0.15 The concentration of tin in the tin tetrachloride solution is mol / L, which can be 0.1 mol / L; the molar ratio of tin to titanium in the titanium source solution is preferably 1:(4~14), which can be 1:(5~11), 1:5, 1:7, or 1:11; the molar ratio of modified fluorophlogopite powder to titanium in the titanium source solution is preferably 1:(1~4), which can be 1:(2~3); the molecular weight of the modified fluorophlogopite is based on the molecular weight of fluorophlogopite (chemical formula KMg3(AlSi3O3)). 10The molecular weight of F2 was calculated. In this embodiment of the invention, the fluorophlogopite powder dispersion, the titanium source solution, and the tin tetrachloride solution are referred to as solution A, solution B, and solution C, respectively. In this invention, tin tetrachloride acts as a synergistic regulator, specifically: (1) In the co-deposition stage, tin tetrachloride hydrolyzes to generate Sn(OH)4 colloid, which forms Ti-O-Sn bonds with Ti colloid through surface condensation, effectively inhibiting the aggregation of single colloids and coordinating the acidity of the solution to ensure the uniformity of the coating; (2) In the low-temperature dehydration stage of the calcination treatment, Sn achieves chemical anchoring of the coating with the fluorophlogopite substrate through Al-O-Sn and Ti-O-Sn bonds, while strengthening the internal structure of the coating; (3) In the medium-temperature crystallization stage of the calcination treatment, the Ti-O-Sn bond acts as a structural template for the rutile phase, significantly reducing the nucleation activation energy and guiding the amorphous precursor to directly transform into the rutile phase; (4) As the temperature increases, Sn evaporates completely in the form of gaseous oxide, ultimately forming a pure rutile phase TiO2 coating. In addition to being a precursor, SnCl4 is also a structure guiding agent + interface anchoring agent + stabilizer + catalyst, and its role runs through the entire preparation process, but it does not remain in the product in the end.

[0034] After obtaining the fluorophlogopite powder dispersion, titanium source solution, and tin tetrachloride solution, the present invention simultaneously adds the titanium source solution and tin tetrachloride solution to the fluorophlogopite powder dispersion, and the titanium source solution and tin tetrachloride solution are added dropwise at the same time. Then, the resulting mixture is subjected to a deposition reaction to obtain a pearlescent pigment precursor solution.

[0035] This invention employs a liquid-phase deposition method to prepare pearlescent pigment precursor solutions. In this invention, the temperature of the system during the dropwise addition is preferably 60-80°C, but can be 70 or 80°C, and the pH value is preferably 0.5-2, but can be 0.9, 1, 1.1, 1.3, 1.6, or 2. The preferred method for controlling the temperature and pH value of the system is as follows: the fluorophlogopite powder dispersion is thoroughly stirred and heated to 60-80°C, the pH value is adjusted to 0.5-2, and then a titanium source solution and a tin tetrachloride solution are simultaneously added dropwise. Simultaneously, a 3 mol / L NaOH solution is added dropwise to maintain the pH value of the reaction system at 0.5-2. This invention controls the dropping rate of the titanium source solution and the tin tetrachloride solution so that they are added simultaneously.

[0036] In this invention, the deposition reaction (also referred to as co-deposition) includes sequentially performing a first deposition reaction and a second deposition reaction. In this invention, the temperature of the first deposition reaction is 60~80℃, which can be 60, 70, or 80℃, and the holding time is 0.5~1.5h, which can be 0.5, 1, or 1.5h; the temperature of the second deposition reaction is 90~110℃, which can be 90, 100, or 110℃, and the holding time is preferably 0.5~2h, which can be 0.5, 1, 1.5, or 2h. After the second deposition reaction is completed, it is cooled to room temperature.

[0037] During the deposition reaction, taking titanium oxysulfate (TiOSO4) as the titanium source, the following reaction occurs: Under acidic conditions, TiOSO4 slowly hydrolyzes to generate TiO(OH)2 colloidal particles, as shown in the following reaction formula: The H2SO4 generated by hydrolysis maintains the acidity of the system, slows down the hydrolysis rate, and prevents Ti from... 4+ Aggregation is too rapid; while SnCl4 has higher hydrolytic activity than TiOSO4, and under the same conditions, it is more likely to hydrolyze to form Sn(OH)4 colloid, the reaction formula is: The HCl and H2SO4 generated during hydrolysis jointly regulate the hydrolysis equilibrium, ensuring that the formation rates of Sn(OH)4 and TiO(OH)2 are matched. Simultaneously, after the initial activation of fluorophlogopite, a large number of Si-OH (silanol) and Al-OH (aluminol) active sites are generated on its surface, becoming the dominant "anchor points" for chemical bonding with Sn(OH)4 and TiO(OH)2. 4+ Higher ionic potential and stronger binding force with Al-OH than Ti 4+It preferentially occupies the highly active sites on the surface of fluorophlogopite (Al-OH + HO-Sn≡→Al-O-Sn≡ +H₂O), forming "initial anchor sites"; subsequently, a portion of the -OH group of TiO(OH)₂ condenses with Si-OH (Si-OH + HO-Ti≡→Si-O-Ti≡). One part of the coating adheres to the anchored Sn(OH)4 via electrostatic attraction / hydrogen bonding (the two are extremely close in space, reaching the nanometer scale). The -OH groups of the two can directly undergo a condensation reaction to generate Ti-O-Sn bonds (Ti-OH (adsorbed state) + HO-Sn (adsorbed state) → Ti-O-Sn (bound state) + H2O). This process is the "in-situ reaction aggregation" of colloids on the mica surface. The chemical bonds formed by the two reactions intertwine to form a "three-dimensional network structure", which upgrades the bonding between the coating and mica from "single anchoring" to "double reinforcement". The chemical anchoring (Si-O-Ti / Al-O-Sn) on the mica surface is the foundation, and the colloid synergistic aggregation is the "core". Together, they constitute the complete mechanism of "directional deposition → uniform coating", which can avoid colloid agglomeration to the greatest extent and ultimately achieve the core performance of "high gloss, high adhesion, and high uniformity" of fluorophlogopite@TiO2 pearlescent pigment.

[0038] After obtaining the pearlescent pigment precursor solution, the present invention sequentially performs static standing, solid-liquid separation, water washing and drying on the pearlescent pigment precursor solution to obtain pearlescent pigment precursor powder.

[0039] In this invention, the settling time is preferably 10 minutes; the solid-liquid separation method can be high-speed centrifugation; the drying temperature can be 80°C, and the time can be 12~24 hours.

[0040] After obtaining the pearlescent pigment precursor powder, the present invention calcines the pearlescent pigment precursor powder to obtain the silvery-white mica titanium pearlescent pigment.

[0041] In this invention, the pearlescent pigment precursor powder is preferably ground uniformly and then placed in a fluoropolymer furnace for calcination. In this invention, the calcination temperature is preferably 600-800℃, which can be 600, 700, or 800℃; the holding time is preferably 1-4 hours, which can be 1.5, 2, or 2.5 hours; and the heating rate to the calcination temperature is preferably 3-5℃ / min. In this invention, the calcination is carried out in an air atmosphere.

[0042] During the calcination process, the Ti-O-Sn bond “interface strengthening” first occurs on the mica surface at a low temperature (200~400℃): (1) (2) The Ti-O-Sn bonds formed during the co-deposition stage increase in bond density during the low-temperature dehydration stage; subsequently, the Al-O-Sn bonds at the fluorophlogopite-coating interface link TiO(OH)2 through Ti-O-Sn bonds, achieving a chain bond of "fluorophlogopite → Sn → Ti". The Ti-O-Sn bonds at the interface chemically anchor the coating to the mica surface, preventing it from detaching at this stage. The Ti-O-Sn bonds within the coating provide a structural template for the subsequent direct formation of the rutile phase. During the intermediate-temperature crystallization stage (400~700℃), the surface Ti-O-Sn bonds lower the nucleation activation energy, allowing the amorphous TiO2 coating to skip the anatase phase and directly grow into rutile nuclei. In the later stages of crystallization, the Ti-O-Sn bonds on the surface break, leaving only the pure rutile phase: .

[0043] After the calcination process is completed, the mixture is cooled to room temperature in the furnace to obtain a silvery-white mica titanium pearlescent pigment.

[0044] This invention utilizes the modified fluorophlogopite powder to prepare a mica titanium pearlescent pigment precursor via liquid phase deposition. The precursor is then subjected to high-temperature calcination to obtain a core-shell mica titanium pearlescent pigment (with fluorophlogopite as the substrate and rutile titanium dioxide as the coating layer). The coating layer is uniform and dense, and the pigment particle size is uniform and controllable, significantly improving the high-temperature resistance, acid corrosion resistance, and color rendering properties of the mica titanium pearlescent pigment. The preparation method of this invention is simple and convenient, and the product performance is stable and controllable, which is conducive to industrial promotion and application.

[0045] This invention provides the application of the silvery-white mica titanium pearlescent pigment described in the above technical solutions or the silvery-white mica titanium pearlescent pigment prepared by the above preparation methods in ceramics. This invention does not impose any special requirements on the application method; any application method well-known to those skilled in the art can be used.

[0046] The silvery-white mica titanium pearlescent pigment provided by this invention exhibits excellent high-temperature stability, overcoming the performance bottleneck of existing silvery-white pearlescent pigments (especially the mainstream mica titanium system) in high-temperature environments. Their coating layers (such as anatase TiO2) often undergo crystal transformation, lattice oxygen escape, or substrate interface diffusion reactions above 800℃, leading to a sharp decline or even complete disappearance of pearlescent luster. This makes it difficult to meet the process requirements of ceramic glazes, high-temperature coatings, and other fields within a stable temperature range. The silvery-white mica titanium pearlescent pigment provided by this invention not only solves the key problem of insufficient high-temperature resistance limiting the application of existing mica titanium pearlescent pigments in high-temperature ceramic fields, but also promotes the large-scale application of environmentally friendly pearlescent pigments in high-temperature industrial scenarios, replacing traditional high-temperature pigments containing heavy metals such as lead and cadmium, thus contributing to the green upgrading of industries such as ceramics from a material perspective.

[0047] This invention provides a ceramic pearlescent glaze, which is made by firing raw materials including transparent glaze and pearlescent pigment at high temperature. The pearlescent pigment is the silver-white mica titanium pearlescent pigment described in the above technical solution or the silver-white mica titanium pearlescent pigment prepared by the preparation method described in the above technical solution. The high temperature firing temperature is above 1000℃.

[0048] This invention does not have any special requirements for the transparent glaze; any transparent glaze well-known to those skilled in the art can be used. In this invention, the mass of the silvery-white mica titanium pearlescent pigment is preferably 10% of the mass of the transparent glaze. In this invention, the high-temperature firing temperature can be 1050℃ or 1100℃.

[0049] The ceramic pearlescent glaze provided by this invention, which is fired at a high temperature of over 1000℃, still has a good silvery-white pearlescent effect.

[0050] To further illustrate the present invention, the modified fluorophlogopite powder and its preparation method, as well as the silver-white mica titanium pearlescent pigment and its preparation method and application, provided by the present invention are described in detail below with reference to examples. However, these should not be construed as limiting the scope of protection of the present invention.

[0051] Example 1 A method for preparing a fluorophlogopite-based core-shell type silvery-white mica titanium pearlescent pigment (fluorophlogopite@TiO2 silvery-white pearlescent pigment) for ceramics, comprising the following steps: (1) Modification treatment of the substrate fluorophlogopite High-temperature calcination (thermal activation): The purchased fluorophlogopite powder (particle size 10~60µm) is placed in a fluoropolymer furnace, heated to 850℃ at a heating rate of 10℃ / min, and held for 2 hours, and then cooled. Alkali activation: The thermally activated fluorophlogopite was added to a 3 mol / L NaOH solution with a solid-liquid ratio of 1:35 (g / mL), and the mixture was stirred at 85℃ for 1 h. After the reaction was completed, the mixture was washed with deionized water until neutral, filtered, and dried. Acid activation: Add the alkali-activated fluorophlogopite to 0.5 mol / L sulfuric acid at a solid-liquid ratio of 1:35 (g / mL) and stir at 85℃ for 1 h. After the reaction is complete, wash with deionized water until neutral, filter, and dry. Deionized water washing: Acid-activated fluorophlogopite was added to deionized water and stirred at 85°C for 1 hour. After washing, the mixture was filtered and dried to obtain modified fluorophlogopite powder.

[0052] (2) Preparation of pearlescent pigment precursor solution by liquid phase method Measure 6g of modified fluorophlogopite powder and 100mL of deionized water, mix them evenly and stir for 0.5h. The resulting dispersion is denoted as solution A. Measure 7.25g of TiOSO4 powder and add it to deionized water to prepare a 0.5mol / L TiOSO4 solution, which is denoted as solution B; Measure 13.03g of tin tetrachloride pentahydrate and prepare a 0.1mol / L tin tetrachloride pentahydrate solution, denoted as solution C; Take 60 mL of solution C and 60 mL of solution B and add them dropwise to solution A. Under the conditions of controlling the temperature of the reaction system at 70℃ and maintaining the pH value at 1~2, stir the reaction and control the dropping rate so that solution B and solution C are added dropwise at the same time. Then, perform liquid phase deposition at 80℃ for 1 h, followed by deposition at 100℃ for 1 h to obtain pearlescent pigment precursor solution.

[0053] (3) After the above pearlescent pigment precursor solution is left to stand for 10 minutes, it is centrifuged and washed with water, and then dried at 80°C for 24 hours to obtain pearlescent pigment precursor powder. The pearlescent pigment precursor powder is calcined in a muffle furnace at 700°C for 2 hours in an air atmosphere, and then cooled to room temperature with the furnace to obtain fluorine-phlogopite-based core-shell type silver-white mica titanium pearlescent pigment.

[0054] Example 2 A method for preparing a fluorophlogopite-based core-shell type silvery-white mica titanium pearlescent pigment (fluorophlogopite@TiO2 silvery-white pearlescent pigment) for ceramics, comprising the following steps: (1) Modification treatment of the substrate fluorophlogopite High-temperature calcination (thermal activation): The purchased fluorophlogopite powder (particle size 10~60µm) is placed in a fluoropolymer furnace, heated to 900℃ at a heating rate of 5℃ / min, and held for 1 hour, and then cooled. Alkali activation: The thermally activated fluorophlogopite was added to a 3 mol / L NaOH solution at a solid-liquid ratio of 1:40 (g / mL), and the mixture was stirred at 90℃ for 1 h. After the reaction was completed, the mixture was washed with deionized water until neutral, filtered, and dried. Acid activation: Add the alkali-activated fluorophlogopite to 0.5 mol / L sulfuric acid at a solid-liquid ratio of 1:40 (g / mL) and stir at 90℃ for 1 h. After the reaction is complete, wash with deionized water until neutral, filter, and dry. Deionized water washing: Acid-activated fluorophlogopite is added to deionized water and stirred at 90°C for 1 hour. After washing, it is filtered and dried to obtain modified fluorophlogopite powder.

[0055] (2) Preparation of pearlescent pigment precursor solution by liquid phase method Measure 6g of modified fluorophlogopite powder and 100mL of deionized water, mix them evenly and stir for 0.5h. The resulting dispersion is denoted as solution A. Measure 14.51g of TiOSO4 powder and add it to deionized water to prepare a 1mol / L TiOSO4 solution, which is denoted as solution B; Measure 13.03g of tin tetrachloride pentahydrate and prepare a 0.1mol / L tin tetrachloride pentahydrate solution, denoted as solution C; Take 30 mL of solution B and 42 mL of solution C and add them dropwise to solution A. Under the conditions of controlling the temperature of the reaction system at 80℃ and maintaining the pH at 0.9~1.1, stir the reaction and control the dropping rate so that solution B and solution C are added dropwise at the same time. Then, perform liquid phase deposition at 80℃ for 1 h, followed by deposition at 100℃ for 1 h to obtain pearlescent pigment precursor solution.

[0056] (3) After the above pearlescent pigment precursor solution is left to stand for 10 min, it is centrifuged and washed with water, and then dried at 80℃ for 12 h to obtain pearlescent pigment precursor powder. The pearlescent pigment precursor powder is calcined in a muffle furnace at 700℃ for 2 h in an air atmosphere, and then cooled to room temperature with the furnace to obtain fluorophlogopite-based core-shell type silver-white mica titanium pearlescent pigment.

[0057] Example 3 A method for preparing a synthetic mica-based core-shell type silvery-white mica titanium pearlescent pigment (fluorophlogopite@TiO2 silvery-white pearlescent pigment) for ceramics, comprising the following steps: (1) Modification treatment of the substrate fluorophlogopite High-temperature calcination (thermal activation): The purchased fluorophlogopite powder (particle size 10~60µm) is placed in a fluoropolymer furnace, heated to 900℃ at a heating rate of 5℃ / min, and held for 1 hour, and then cooled. Alkali activation: The thermally activated fluorophlogopite was added to a 3 mol / L NaOH solution at a solid-liquid ratio of 1:40 (g / mL), and the mixture was stirred at 90℃ for 1 h. After the reaction was completed, the mixture was washed with deionized water until neutral, filtered, and dried. Acid activation: Add the alkali-activated fluorophlogopite to 0.5 mol / L sulfuric acid at a solid-liquid ratio of 1:40 (g / mL) and stir at 90℃ for 1 h. After the reaction is complete, wash with deionized water until neutral, filter, and dry. Deionized water washing: Acid-activated fluorophlogopite was added to deionized water and stirred at 90°C for 1 hour. After washing, the mixture was filtered and dried to obtain modified fluorophlogopite powder.

[0058] (2) Preparation of pearlescent pigment precursor solution by liquid phase method Measure 6g of modified fluorophlogopite powder and 100mL of deionized water, mix them evenly and stir for 0.5h. The resulting dispersion is denoted as solution A. Measure 14.51g of TiOSO4 solution and add it to deionized water to prepare a 1mol / L TiOSO4 solution, which is denoted as solution B; Measure 13.03g of tin tetrachloride pentahydrate and prepare a 0.1mol / L tin tetrachloride pentahydrate solution, denoted as solution C; Take 30 mL of solution B and 28 mL of solution C and add them dropwise to solution A. Under the conditions of controlling the temperature of the reaction system at 80℃ and maintaining the pH at 1.3~1.6, stir the reaction and control the dropping rate so that solutions B and C are added dropwise at the same time. Then, perform liquid phase deposition at 80℃ for 1 h, followed by deposition at 100℃ for 1 h to obtain the pearlescent pigment precursor solution.

[0059] (3) After the above pearlescent pigment precursor solution is left to stand for 10 min, it is centrifuged and washed with water, and then dried at 80℃ for 12 h to obtain pearlescent pigment precursor powder. The pearlescent pigment precursor powder is calcined in an air atmosphere in a muffle furnace at 800℃ for 2 h, and then cooled to room temperature with the furnace to obtain fluorine-phlogopite-based core-shell type silver-white mica titanium pearlescent pigment.

[0060] The chromaticity parameters and pearlescent index of the fluorophlogopite-based core-shell silver-white mica titanium pearlescent pigments for ceramics prepared in each embodiment are shown in Table 1.

[0061] Table 1. Colorimetric parameters and pearlescent index of the fluorophlogopite-based core-shell silvery-white mica titanium pearlescent pigments for ceramics prepared in each embodiment.

[0062] Table 1 presents the key performance indicators of the ceramic fluorophlogopite-based core-shell silvery-white mica titanium pearlescent pigments prepared in the three examples, and the lightness ( ) of the three examples. L The value is between 93 and 96, of which Example 2 L The highest value; Example 1 a The value was -0.38 (slightly greenish), Example 2 was -0.01 (nearly no red-green bias), and Example 3 was 0.07 (slightly redish); The three examples... b All values ​​are positive and all have a slight yellowish tint, with Example 2 having the lowest value; and Example 2 has the best whiteness (WI-CIE); the pearlescent index ΔE reflects the strength of the pearlescent effect of the pigment, with Example 1 having the highest value.

[0063] Table 2 shows the chromaticity and pearlescent index of the ceramic fluorophlogopite-based core-shell silver-white mica titanium pearlescent pigment obtained by calcining at different temperatures for 2 hours in air atmosphere in step (3) of Example 2 of the present invention. Commercial silver-white pearlescent pigments with mica as the base material are used as comparative examples.

[0064] Table 2. Colorimetric parameters and pearlescent index of the fluorine-phlogopite-based core-shell silvery-white mica titanium pearlescent pigments for ceramics obtained after calcination at different temperatures for 2 hours in the comparative examples and Example 2.

[0065] Table 2 shows the chromaticity parameters and pearlescent index of the ceramic fluorophlogopite-based core-shell silvery-white mica titanium pearlescent pigment after calcination at different temperatures for 2 hours in air atmosphere for the comparative example and Example 2. It focuses on the effect of calcination temperature on the performance of the pigment in Example 2 and the performance differences between the comparative example and the comparative example at the same calcination temperature. Specific details are as follows: (1) After calcination at 700℃, the comparative example… L The value is 92.04. a The value is 0.32 (slightly reddish). b The value was 3.82 (yellowish), the WI-CIE whiteness value was 63.02, and the pearlescent index ΔE was 2.144; under the same calcination conditions, Example 2 showed better performance in all aspects, purer color, significantly higher whiteness value than the comparative example, and slightly higher pearlescent index ΔE than the comparative example, with a more prominent pearlescent effect. (2) Effect of calcination temperature on the performance of pigments in Example 2: As the calcination temperature increased, L The values ​​showed a fluctuating upward trend, but remained above 95.0 overall, demonstrating stable performance. a The value fluctuates between -0.3 and 0.5, indicating good color stability; b The value gradually increases with increasing temperature. High temperatures exacerbate the yellowing tendency of the pigment, thus continuously reducing the WI-CIE whiteness. The pearlescent index ΔE is at its maximum at 700℃.

[0066] Figure 1 The XRD patterns of the fluorinated phlogopite-based core-shell silvery-white mica titanium pearlescent pigments obtained by calcining in air at different temperatures for 2 hours in step (3) of Example 2 are shown. Figure 1It can be observed that when the calcination temperature is 600℃, the TiO2 precursor directly crystallizes into the rutile phase without the anatase intermediate state, and the peak intensity is relatively weak at this time. As the calcination temperature continues to rise, the rutile phase further sintersulates and densifies, the crystallinity increases, and the grain size continues to increase. At 1100℃, the rutile phase remains stable, and the fluorophlogopite does not decompose. This indicates that the hydroxyl groups (-OH) on the surface of the activated fluorophlogopite react with the TiO2 precursor and form a tight interfacial bond through the "Ti-O-Si" covalent bond. This can directionally induce the hydrolysis product of the TiO2 precursor (amorphous TiO2) to preferentially form the lattice arrangement of the rutile phase during the dehydration and crystallization process (the

[110] crystal plane of rutile has a higher matching degree with the

[001] crystal plane of fluorophlogopite), rather than the

[101] crystal plane of anatase. This result demonstrates the precise control of TiO2 crystal structure by substrate activation, laying the foundation for the high-temperature stability of pearlescent pigments (rutile phase has better weather resistance than anatase).

[0067] Figure 2 XRD patterns of fluorophlogopite samples obtained by acidification with different concentrations of sulfuric acid (0.1 mol / L, 0.5 mol / L, 1 mol / L, and no acidification) followed by washing with deionized water. The figures show that all samples retained the fluorophlogopite crystal structure after acidification (PDF#16-0352). Significant changes in peak intensity, width, and position were observed near 2θ≈27°, with systematic peak shifts with increasing acid concentration indicating lattice adjustment. Although the sample treated with 1 mol / L H₂SO₄ exhibited a smaller full width at half maximum (FWHM), this sharpening was accompanied by a larger peak shift, attributed to the selective dissolution of defect-rich regions and partial structural interference under strong acid conditions. In contrast, treatment with 0.5 mol / L H₂SO₄ minimized lattice distortion while maintaining high crystallinity, demonstrating a more balanced activation strategy between preserving structural integrity and generating more surface-active sites.

[0068] Figure 3 The images show the FTIR spectra of fluorophlogopite samples after acidification with sulfuric acid solutions of different concentrations. Figure 3 In (a), fluorophlogopite acidified with 0.1 mol / L H₂SO₄ is at 800–1200 cm⁻¹ -1 The deconvolutioned FTIR absorption spectra within the range, (b) are those of fluorinated phlogopite acidified with 0.5 mol / L H2SO4 in the range of 800–1200 cm⁻¹. -1 Deconvolutional FTIR absorption spectra within the range, (c) are fluorophlogopite acidified with 1 mol / L H2SO4 in the range of 800~1200 cm⁻¹. -1 The deconvolutioned FTIR absorption spectra within the range are shown in (d), which is the FTIR spectrum of fluorophlogopite acidified with three concentrations of H2SO4, and (e) is the Q spectrum obtained after peak separation of fluorophlogopite acidified with three concentrations of H2SO4.2 Q 3 Q 4 (Q) 2 Refers to the fractured chain Si-O, Q 3 Terminal Si-O - Q 4 This refers to the area ratio diagram of structured Si-O-Si and Si-O-Al / Mg. As shown in the figure, the area ratio of fluorophlogopite acidified with different concentrations of H2SO4 is within the range of 800~1200 cm⁻¹. -1 All exhibit characteristic absorption bands of the silicate framework, indicating that the main layered silica-oxygen framework of fluorophlogopite still exists after acidification. However, with increasing H₂SO₄ concentration, the intensity of the main band, the shoulder structure, and the broadening of the peak shape change significantly. Figure 3 In the middle (a)~(c), the silicon-oxygen tetrahedral polymerization state (Q) induced by acidification is reflected. n The redistribution and environmental changes of Si-O-Al / Mg bonds. Comprehensive deconvolution results indicate that fluorophlogopite acidified with 0.5 mol / L H₂SO₄ improves Q while maintaining the integrity of the silicon-oxygen framework. 3 The components are more concentrated and have a higher proportion, while Q 4 The Si-O-Al / Mg ratio remains at a reasonable level, indicating that it can effectively introduce uniformly distributed surface active sites without excessively damaging the structure. In contrast, 0.1 mol / L is insufficient for activation, while 1 mol / L leads to excessive acid etching, increasing the risk of structural reconstruction / perturbation. Therefore, fluorophlogopite acidified with 0.5 mol / L H2SO4 provides the optimal surface chemistry and structural basis for subsequent TiO2 nucleation and continuous deposition.

[0069] Figure 4 TEM images and elemental distribution analysis of the fluorine-phlogopite-based core-shell silvery-white mica titanium pearlescent pigment for ceramics prepared in Example 2. Figure 4 In the image, (a) and (b) are TEM images of fluorophlogopite@TiO2 nanoparticles, (c) is an HRTEM image of fluorophlogopite@TiO2 nanoparticles, and (d) is the corresponding elemental diagram of fluorophlogopite@TiO2 nanoparticles. Figure 4 As shown in (a) and (b), TEM images of fluorophlogopite@TiO2 nanoparticles reveal their uniform morphology. HRTEM images of fluorophlogopite@TiO2 nanoparticles ( Figure 4 In (c), the TiO2 coating layer exhibits clear and continuous lattice fringes with a crystal plane spacing of d = 0.3241 nm, corresponding to the

[110] crystal plane of the rutile phase TiO2. There are no broken or blurred fringes, indicating that TiO2 is a highly crystalline single rutile phase without amorphous regions or impurities such as anatase. The

[110] crystal plane of the rutile phase is the closest packing plane, with an atomic packing density as high as 9.6 × 10⁻⁶. 14 atoms / cm2 The lattice gaps are extremely small (<0.1nm), which can effectively block H. + The penetration of O2 molecules (0.01 nm ionic radius) and O2 molecules (0.34 nm kinetic diameter) is limited. Furthermore, at the interface, the lattice fringes of the fluorophlogopite

[003] crystal plane (d=0.330 nm) and the rutile

[110] crystal plane are continuously connected, with no obvious dislocation lines or concentrated areas of lattice distortion. This reflects the coordination of atomic arrangement at the interface, enhances the interfacial bonding force, reduces the risk of interfacial cracking, and thus prevents O2 or other corrosive media from penetrating through interfacial cracks. Figure 4 Mapping of the (d) fluorophlogopite@TiO2 nanoparticles shows that the Ti element (TiO2 coating layer) is distributed in a continuous closed loop, completely encapsulating the Si, Al, Mg, K, and F elements (fluorophlogopite core) in the central region, with no areas lacking Ti element. This proves that the TiO2 coating layer achieves complete encapsulation of the fluorophlogopite, with no exposed substrate. This complete structure is a prerequisite for isolating external corrosive media and high-temperature O2. Figure 4 The results show that the encapsulated pigment prepared by the present invention has a core-shell structure, with nano-sized TiO2 particles coated on the outside of the synthetic mica base.

[0070] Figure 5 This is a SEM image of the fluorine-phlogopite-based core-shell silvery-white mica titanium pearlescent pigment for ceramics prepared in Example 2 of this invention. Figure 5 (a) and (b) are SEM images at different scales. Figure 5 It can be observed that the surface of fluorophlogopite is completely covered by a continuous, unbroken TiO2 coating layer, without obvious pores, cracks or protrusions. This proves that the TiO2 particles form a dense structure through close packing. For high-temperature O2, the non-porous structure avoids the formation of gas diffusion channels.

[0071] Table 3 shows the color parameters and pearlescent index of the ceramic fluorophlogopite-based core-shell silvery-white mica titanium pearlescent pigment prepared by calcination at 700℃ for 2 hours in Example 2 of this invention, after being soaked in 12mol / L HCl and 3mol / L NaOH solutions for 24 hours respectively.

[0072] Table 3. Color parameters and pearlescent index of the silvery-white mica titanium pearlescent pigment prepared in Example 2 after soaking in 12 mol / L HCl and 3 mol / L NaOH solutions for 24 h, respectively.

[0073] Table 3 reflects the effects of acid and alkali soaking on pigment properties. Both acid and alkali soaking... L A slight decrease, but the reduction is small (≤0.7), and the overall brightness remains at a high level; after acid and alkali soaking. a Slightly greenish, with minimal change in red-green hue, and the purity of the color is basically unaffected; after acid and alkali soaking... b All values ​​decreased, with a slight reduction in yellow tone; WI-CIE whiteness also showed only minor fluctuations, with overall whiteness performance remaining good; the pearlescent index ΔE decreased slightly after the pigments were soaked in acid and alkali, but the decrease was ≤0.1, and the pearlescent effect remained at a high level.

[0074] Figure 12 The TG-DTA curve of the pearlescent pigment precursor powder before calcination in step (3) of Example 2 shows the thermal behavior of fluorophlogopite@TiO2 silver-white pearlescent pigment in the range of room temperature to 1300℃: (1) For the TG curve, in the range of room temperature to 530℃, the thermogravimetric loss is -4.81%. This stage is mainly the removal process of physically adsorbed water and surface hydroxyl groups in the pigment, which belongs to the typical low-temperature dehydration and desorption weight loss range; in the range of 530℃ to 1221.1℃, the thermogravimetric loss is... The weight loss was -0.95% (cumulative weight loss -5.76%). The weight loss in this stage was relatively gradual and may be related to the breaking of some weak chemical bonds and the crystal transformation of the TiO2 coating (a slight weight loss accompanied by the transformation from amorphous to rutile). The thermal behavior was relatively stable. In the 1221.1~1300℃ stage, the thermogravimetric loss was -1.58% (cumulative weight loss -7.34%). The weight loss in this stage may be due to the high-temperature decomposition of the fluorine phlogopite crystal structure (such as the escape of fluorine and the destruction of the layered structure). (2) Corresponding to the DTA curve, in the range of room temperature to about 600℃, the DTA curve shows a weak endothermic signal, which corresponds to the -4.81% weight loss of the TG curve. This is attributed to the endothermic process during the physical adsorption of water and the removal of hydroxyl groups. In the range of about 600℃ to 1221.1℃, there are no obvious endothermic or exothermic peaks, indicating that the thermal behavior of the pigment in this temperature range is mainly due to the weak interaction of chemical bonds, and there is no obvious chemical reaction heat effect during the phase transition. Above 1221.1℃, there are also no obvious endothermic or exothermic peaks, indicating that the decomposition of fluorophlogopite may be a non-synergistic thermal effect. However, the TG weight loss clearly shows that its structure has undergone irreversible decomposition and evolution at high temperature.

[0075] Figure 13 To demonstrate the effect of adding the silvery-white mica titanium pearlescent pigment prepared in Example 2 to a transparent glaze and firing it at different temperatures (800℃, 850℃, 950℃, 1050℃, 1100℃), the amount of silvery-white mica titanium pearlescent pigment added was 10% of the mass of the transparent glaze. Figure 13 It can be observed that when the firing temperature reaches 1100℃, the sample still has a distinct silvery-white pearlescent effect.

[0076] As can be seen from the above embodiments, the fluorophlogopite-based core-shell type silvery-white mica titanium pearlescent pigment prepared by the present invention has excellent high-temperature resistance.

[0077] Comparison of Activation Methods in Comparative Example 1 The activation methods for fluorophlogopite were as follows: ① alkalization with 3 mol / L NaOH solution at 90℃ for 1 h; ② acidification with 0.5 mol / L H2SO4 solution at 90℃ for 1 h; ③ thermal activation at 900℃ for 1 h, with a heating rate of 5℃ / min; ④ fine washing with deionized water at 90℃. Based on different treatment methods and their order, a total of 16 substrates were prepared, numbered A to P, as shown in Table 4. The subsequent preparation method for fluorophlogopite-based core-shell silvery-white mica titanium pearlescent pigments was the same as in Example 2 (Note: the pH of the liquid phase deposition in Example 2 was adjusted to 2.4-2.6).

[0078] Table 4 Different activation methods of fluorophlogopite

[0079] Figure 6 The image shows the XRD pattern of a fluorophlogopite-based core-shell silvery-white mica titanium pearlescent pigment (fluorophlogopite@TiO2 pearlescent pigment) prepared using fluorophlogopite (designated AP) as the substrate. Figure 7 The colorimetric (whiteness WI-CIE) and pearlescent index test results of fluorophlogopite-based core-shell silvery-white mica-titanium pearlescent pigments (fluorophlogopite@TiO2 pearlescent pigments) prepared by different activation methods are presented. Rutile has a refractive index of 2.70, and anatase has a refractive index of 2.55. To obtain fluorophlogopite@TiO2 pearlescent pigments with a high pearlescent index, it is desirable to coat the fluorophlogopite surface with rutile. Figure 6 It can be seen that the fluorophlogopite@TiO2 pearlescent pigment prepared using fluorophlogopite activated by group O as the substrate has a sharper rutile diffraction peak at the same calcination temperature. At the same time, its pearlescent index and whiteness are the highest in the same group of experiments. Therefore, group O treatment method was selected, which is to first activate it at 900℃ for 1h, then alkalize it with 3mol / L NaOH solution at 90℃ for 1h, then acidify it with 0.5mol / L H2SO4 solution at 90℃ for 1h, and finally wash it with deionized water at 90℃ for 1h and then dry it to obtain fluorophlogopite for the experiment.

[0080] Figure 8 These are SEM images of the fluorophlogopite before and after activation in Example 2. Figure 8 Image (a) is the SEM image before activation, and image (b) is the SEM image after activation. Figure 8 As can be seen in (a), the surface of unactivated fluorophlogopite exhibits obvious irregular protrusions, depressions, and step-like structures, with fine particles of varying sizes distributed on the surface; Figure 8 As can be seen in (b), the irregular protrusions and depressions of the original fluorophlogopite after the four-step activation treatment almost disappeared, and the surface showed a continuous and uniform "mirror-like" appearance. There were no obvious attached particles on the surface, and the small particles that were originally distributed were basically removed, presenting an overall clean state of "no foreign matter".

[0081] Figure 9 The image shows a photograph of the fluorophlogopite@TiO2 silver-white pearlescent pigment prepared using fluorophlogopite before and after activation as a substrate, as shown in Example 2. Figure 9 Image (a) shows a photograph of fluorophlogopite@TiO2 silver-white pearlescent pigment prepared using unactivated fluorophlogopite as a substrate, and image (b) shows a photograph of fluorophlogopite@TiO2 silver-white pearlescent pigment prepared using activated fluorophlogopite as a substrate. Figure 9 As can be seen, the fluorophlogopite@TiO2 silver-white pearlescent pigment prepared using fluorophlogopite activated in four steps as a substrate is brighter. This may be because the activated fluorophlogopite enhances the light reflection efficiency of the pearlescent pigment from multiple dimensions through smoothing to enhance specular reflection, cleaning the surface to reduce light loss, and homogenizing the coating to optimize the interference effect, thus resulting in a brighter appearance.

[0082] Comparative Example 2: Comparison of the effects of adding or not adding the synergistic regulator (tin tetrachloride) Figure 10 The images show the XRD patterns of the fluorophlogopite@TiO2 silver-white pearlescent pigment samples prepared in Example 1 with and without the addition of the synergistic regulator (calcined at 600℃ for 2h).

[0083] like Figure 10 As shown, both the fluorophlogopite@TiO2 silver-white pearlescent pigments prepared with and without the synergistic regulator exhibit rutile XRD characteristic peaks at 2θ = 27.1, 40.9, 54.0, and 56.2°, while the fluorophlogopite@TiO2 silver-white pearlescent pigment prepared without the synergistic regulator shows anatase characteristic peaks at 2θ = 25.1, 36.946, and 55.060°. The sample without SnCl4, after calcination at 600℃ for 2 h, follows the conventional crystallization path (anatase nucleation barrier is lower) and is dominated by the anatase phase, further confirming the rutile-induced effect of its "template synergistic regulation".

[0084] Comparative Example 3: Comparison of Different Liquid Phase Deposition Reaction Conditions Figure 11 SEM images and particle size distributions of fluorophlogopite@TiO2 pearlescent pigments prepared under different liquid-phase deposition reaction conditions. Figure 11 (a) 70℃-2h, (b) 80℃-2h, (c) 80℃-1h, 100℃-1h (i.e., first deposit at 80℃ for 1h, then at 100℃ for 1h), (d) 90℃-2h, (e) 100℃-2h, (f) 70℃-1h, 100℃-1h, (g) 90℃-1h, 100℃-1h. Figure 11 In the text (a) to (g), we can refer to different liquid phase deposition conditions. The rest of the methods for preparing pearlescent pigments are the same as in Example 2.

[0085] When the reaction time was fixed at 2 hours and the reaction temperature was relatively low (70℃, 80℃), Ti 4+ The slow hydrolysis rate results in a large distance between the colloidal particles dispersed in the solution and the mica, insufficient for electrostatic adsorption. This leads to aggregation between crystal nuclei, forming nucleation centers and resulting in a significant number of free metatitanic acid particles. Furthermore, the nucleation rate and number of metatitanic acid particles deposited on the mica substrate are very small, affecting the pearlescent effect. When the reaction temperature increases to above 90℃, a large amount of metatitanic acid is generated instantaneously. As the reaction proceeds, the newly formed metatitanic acid deposits on the free particles, gradually increasing in size and exhibiting a somewhat loose structure. When a two-step deposition reaction is used, from... Figure 11 In (f), (c), and (g), it can be observed that the obtained sample particles have uniform size and good density. As the temperature of the first-step deposition reaction increases from 70℃ to 80℃, the average particle size of the sample decreases from 27.33nm to 21.77nm, and the particle arrangement gradually becomes denser. However, as the deposition reaction temperature is further increased, the average particle size gradually increases, and even agglomeration intensifies, while the pearlescent index also decreases. Therefore, the optimal deposition reaction conditions are to react at 80℃ for 1 hour first, followed by increasing the reaction temperature to 100℃ for 1 hour, resulting in sample particles with uniform size and good density.

[0086] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing modified fluorophlogopite powder, characterized in that, Includes the following steps: The modified fluorophlogopite powder was obtained by sequentially subjecting it to calcination activation, alkali activation, acid activation, water washing, and drying. The calcination activation temperature is 800~900℃, and the holding time is 1~2h; the alkali activation uses NaOH solution with a concentration of 3mol / L, the alkali activation temperature is 85~90℃, and the time is 0.5~2h; the acid activation uses sulfuric acid with a concentration of 0.5mol / L, the acid activation temperature is 85~90℃, and the time is 0.5~2h.

2. The preparation method according to claim 1, characterized in that, The average particle size of the fluorophlogopite powder is 10~60μm.

3. The modified fluorophlogopite powder prepared by the preparation method according to claim 1 or 2.

4. A silvery-white mica titanium pearlescent pigment, characterized in that, It includes the modified fluorophlogopite powder as described in claim 3 and a rutile titanium dioxide layer encapsulating the modified fluorophlogopite powder.

5. The silvery-white mica titanium pearlescent pigment according to claim 4, characterized in that, The chromaticity parameters of the silvery-white mica titanium pearl pigment are as follows: L =93~97, a =-0.5~0.5, b =1.0~4.5, whiteness WI-CIE≥60.

6. The method for preparing the silvery-white mica titanium pearlescent pigment according to claim 4 or 5, characterized in that, Includes the following steps: The modified fluorophlogopite powder, titanium source, and tin tetrachloride were respectively mixed with water to obtain a fluorophlogopite powder dispersion, a titanium source solution, and a tin tetrachloride solution. A titanium source solution and a tin tetrachloride solution are simultaneously added dropwise to the fluorophlogopite powder dispersion, with the addition of the titanium source solution and the tin tetrachloride solution completed at the same time. The resulting mixture is then subjected to a deposition reaction to obtain a pearlescent pigment precursor solution. During the dropwise addition, the system temperature is controlled at 60-80°C, and the pH value is 0.5-2. The deposition reaction includes a first deposition reaction and a second deposition reaction performed sequentially. The temperature of the first deposition reaction is 60-80°C, and the holding time is 0.5-1.5 h. The temperature of the second deposition reaction is 90-110°C, and the holding time is 0.5-2 h. The pearlescent pigment precursor solution was subjected to static standing, solid-liquid separation, water washing and drying in sequence to obtain pearlescent pigment precursor powder. The pearlescent pigment precursor powder was calcined to obtain the silvery-white mica titanium pearlescent pigment.

7. The preparation method according to claim 6, characterized in that, The modified fluorophlogopite powder to water ratio in the fluorophlogopite powder dispersion is 1g:15~40mL; the titanium source includes one or more of titanium oxysulfate, titanium tetrachloride, and tetrabutyl titanate, and the concentration of the titanium source solution is 0.5~3mol / L; the concentration of the tin tetrachloride solution is 0.05~0.15mol / L; the molar ratio of tin in the tin tetrachloride solution to titanium in the titanium source solution is 1:(4~14); the molar ratio of modified fluorophlogopite powder to titanium in the titanium source solution in the fluorophlogopite powder dispersion is 1:(1~4).

8. The preparation method according to claim 6, characterized in that, The calcination treatment is carried out at a temperature of 600~800℃ and a holding time of 1~4h.

9. The application of the silvery-white mica titanium pearlescent pigment according to claim 4 or 5, or the silvery-white mica titanium pearlescent pigment prepared by the preparation method according to any one of claims 6 to 8, in ceramics.

10. A ceramic pearlescent glaze, characterized in that, The ceramic pearlescent glaze is made from raw materials including transparent glaze and pearlescent pigment through high-temperature firing. The pearlescent pigment is the silver-white mica titanium pearlescent pigment of claim 4 or 5 or the silver-white mica titanium pearlescent pigment prepared by the preparation method of any one of claims 6 to 8. The high-temperature firing temperature is above 1000°C.

Images