Composite whitening agent for ceramic glaze and preparation method thereof

Abstract

The application belongs to the technical field of ceramics, and discloses a composite whitening agent for ceramic glaze and a preparation method thereof. The raw material components of the composite whitening agent include, by weight fraction, 100 parts of aluminum hydroxide, 1-10 parts of nano-zirconium sol, 1-5 parts of nano-silicon sol, 0.1-2 parts of a dispersing agent, and 0.1-3 parts of a mineralizing agent. The solid content of the nano-zirconium sol is 10-20 wt%, and the solid content of the nano-silicon sol is 25-35 wt%. In the preparation process of the composite whitening agent, the aluminum hydroxide is subjected to low-temperature heat treatment to generate porous and high-specific-surface-area γ-Al2O3, the nano-zirconium sol and the nano-silicon sol are coated with zirconium oxide and silicon dioxide films on the surface and pores of the γ-Al2O3 through impregnation, and the composite whitening agent containing zirconium silicate and polymorphic aluminum oxide and having low ɑ-Al2O3 is obtained through high-temperature calcination. The specific composition and crystal structure endow the composite whitening agent with excellent whitening effect.

Description

Technical Field

[0001] This invention belongs to the field of ceramic technology, specifically relating to a composite whitening agent for ceramic glaze and its preparation method. Background Technology

[0002] With the rapid development of the building and sanitary ceramics and daily-use ceramics industries, high-grade raw materials are becoming increasingly scarce, and large quantities of inferior raw materials or industrial waste are being widely used in ceramic bodies. Therefore, it is necessary to widely use whitening agents with strong covering power to improve the whiteness and quality of the glaze, thereby increasing the added value of the products.

[0003] In existing technologies, zirconium silicate is commonly used as a whitening agent in ceramic glazes. Due to its high refractive index, zirconium silicate exhibits excellent opacifying effects in the glaze layer. However, zirconium silicate is generally introduced from zircon sand, which contains small amounts of radioactive substances that are difficult to separate. Its associated mineral, monazite, is also radioactive, and the mineral contains trace amounts of radioactive decay products such as thorium, which can pose certain radioactive hazards to the human body. Furthermore, zircon sand is expensive, and the addition of high-content zircon sand significantly increases the production cost of the glaze. Other whitening agents for glazes, such as zirconium dioxide, titanium dioxide, tin oxide, cerium oxide, and antimony pentoxide, also suffer from resource scarcity and high prices, resulting in limited use in actual production. Based on these reasons, researchers have proposed some composite whitening agents, but their effects in practical applications have been less than satisfactory. Phosphate-based whitening agents, for example, mainly achieve the purpose of whitening through liquid-liquid phase separation, but the room for improvement in whiteness is limited by liquid phase turbidity; another example is calcium-titanium-based whitening agents, because titanium dioxide is not resistant to high temperatures, at higher firing temperatures (above 900℃), rutile titanium dioxide will precipitate in the glaze, making the glaze white with a yellowish tinge, resulting in a poor visual effect.

[0004] Therefore, existing whitening agents for ceramic glazes cannot achieve the whitening effect of zirconium silicate as an opacifier. There is an urgent need to develop a new whitening agent for glazes that can achieve or approach the whitening effect of zirconium silicate while maintaining low production costs and ensuring glaze performance. Summary of the Invention

[0005] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention proposes a composite whitening agent for ceramic glaze and its preparation method. This composite whitening agent can achieve a whitening effect comparable to that of zirconium silicate while significantly reducing the zirconium silicate content in the glaze.

[0006] The inventive concept of this invention is as follows: Using aluminum hydroxide as the main raw material, and adding a certain amount of nano-zirconium sol, nano-silica sol, and additives, the aluminum hydroxide is first subjected to low-temperature heat treatment to obtain porous γ-Al₂O₃ powder with a high specific surface area. Then, nano-zirconium sol and nano-silica sol films are successively coated onto the surface and pores of the γ-Al₂O₃ powder using an impregnation method. Finally, calcination is performed to generate alumina powder partially coated with zirconium silicate. Simultaneously, the zirconium silicate coating to a certain extent prevents the transformation of γ-Al₂O₃ to α-Al₂O₃, thereby obtaining a polycrystalline composite whitening agent with low α-Al₂O₃ content. Adding it to ceramic glazes provides excellent whitening effects without negatively impacting the performance of the glaze slurry or the quality of the glaze surface.

[0007] The whitening mechanism of the composite whitening agent of this invention mainly includes the following aspects: First, high-content alumina itself has a good opacifying and whitening effect; second, the high-refractive-index zirconium silicate generated by high-temperature calcination of zirconium sol and silica sol has an excellent opacifying and whitening effect; at the same time, zirconium silicate forms a coating layer on alumina, preventing alumina from reacting with other glaze components, further enhancing the opacifying and whitening effect of alumina; third, zirconium silicate has an inhibitory effect on the transformation of γ-Al2O3 to α-Al2O3 crystal form, reducing the content of α-Al2O3 and effectively enhancing the opacifying and whitening effect of alumina.

[0008] To solve the above-mentioned technical problems, the first aspect of the present invention provides a composite whitening agent, the raw material components of which, by weight, include: 100 parts aluminum hydroxide, 1-10 parts nano-zirconium sol, 1-5 parts nano-silica sol, 0.1-2 parts dispersant, and 0.1-3 parts mineralizer; wherein the solid content of the nano-zirconium sol is 10-20 wt%, and the solid content of the nano-silica sol is 25-35 wt%.

[0009] In some embodiments of the present invention, the aluminum hydroxide is fine enough to pass through an 80-325 mesh sieve.

[0010] In some embodiments of the present invention, the aluminum hydroxide is fine enough to pass through a 100-200 mesh sieve.

[0011] In some embodiments of the present invention, the dispersant is selected from at least one of sodium polyacrylate and polyvinylpyrrolidone, wherein the sodium polyacrylate has a weight-average molecular weight of 2000-4000 g / mol and the polyvinylpyrrolidone has a weight-average molecular weight of 8000-10000. These dispersants have relatively low molecular weights, resulting in less ash production during the heating synthesis process, which is beneficial for improving synthesis efficiency, ensuring the purity of the synthesized material, and thus improving the whiteness of the whitening agent.

[0012] In some embodiments of the present invention, the mineralizing agent is selected from at least one of sodium fluoride, calcium fluoride, and magnesium fluoride.

[0013] In some embodiments of the present invention, the raw material components of the composite whitening agent include, by weight: 100 parts aluminum hydroxide, 3-9 parts nano-zirconium sol, 1-3 parts nano-silica sol, 0.1-0.5 parts dispersant, and 0.1-0.5 parts mineralizer; the solid content of the nano-zirconium sol is 10-20 wt%, and the solid content of the nano-silica sol is 25-35 wt%.

[0014] A second aspect of the present invention provides a method for preparing the composite whitening agent described in the first aspect of the present invention, comprising the following steps: (1) Heat treatment of aluminum hydroxide to prepare porous γ-Al2O3 powder; (2) Disperse γ-Al2O3 powder and nano-zirconium sol in water, dry, and form a zirconia film on the surface of γ-Al2O3 powder to obtain powder A; (3) Disperse the aqueous solution of powder A, nano silica sol and mineralizer in water, dry it, and form a silica film on the surface of powder A to obtain powder B; (4) The powder B is calcined to obtain the composite whitening agent.

[0015] Specifically, in the preparation of the composite whitening agent of the present invention, aluminum hydroxide is first subjected to low-temperature heat treatment to generate γ-Al2O3 powder with porous structure and high specific surface area; then, the γ-Al2O3 powder is subjected to adsorption treatment by impregnation method, so that nano-zirconium sol enters the pores of the porous γ-Al2O3, and after drying, it is adsorbed on the surface of γ-Al2O3 to form a zirconium oxide film, obtaining γ-Al2O3 powder coated with zirconium oxide film, i.e., powder A; then, powder A is mixed with nano-silica sol and a mineralizing agent, the nano-silica sol enters the pores of the porous γ-Al2O3, and after drying, it is adsorbed on the surface of the zirconium oxide film to form a silica film, and... γ-Al2O3 is coated to obtain γ-Al2O3 powder with a double-layer film of zirconium oxide and silica, namely powder B. Finally, powder B is calcined at high temperature, and γ-Al2O3 is converted into α-Al2O3 and β-Al2O3. Zirconium oxide and silica react to form zirconium silicate and coat the surface of alumina, thereby preventing the complete crystal transformation of γ-Al2O3 to α-Al2O3, while retaining some β-Al2O3 and γ-Al2O3. Thus, a composite whitening agent containing both zirconium silicate and polycrystalline alumina with low α-Al2O3 is obtained. This specific composition and crystal structure endow it with excellent whitening effect.

[0016] In some embodiments of the present invention, in step (1), the temperature of the heat treatment is 350-550°C and the time of the heat treatment is 2-4 hours.

[0017] In some embodiments of the present invention, in step (1), the heat treatment temperature is 450-550°C, and the heat treatment time is 2.5-3.5 hours. This heat treatment temperature allows for the complete removal of moisture from the aluminum hydroxide, generating γ-Al2O3 with a high specific surface area.

[0018] In some embodiments of the present invention, in step (2), the mass ratio of the nano-zirconium sol to water is 1:(20-30).

[0019] In some embodiments of the present invention, in step (3), the concentration of the mineralizing agent solution is 2-6 wt%, and the solvent in the mineralizing agent solution is water.

[0020] In some embodiments of the present invention, in step (3), the mass ratio of the nano-silica sol to water is 1:(30-40).

[0021] In some embodiments of the present invention, in step (4), the calcination temperature is 1100-1250°C and the calcination time is 2-4 hours.

[0022] In some embodiments of the present invention, in step (4), the heating rate of calcination is 5-8°C / min.

[0023] A third aspect of the present invention provides a glaze comprising the composite whitening agent described in the first aspect of the present invention.

[0024] In some embodiments of the present invention, the glaze raw material components, by weight, include: 30-60 parts feldspar, 6-18 parts quartz, 6-10 parts kaolin, 10-18 parts nepheline, 3-6 parts calcined talc, 5-15 parts calcined kaolin, 5-12 parts calcined alumina, 7-20 parts composite whitening agent, and 1-3 parts zirconium silicate. By adding a certain amount of the composite whitening agent of the present invention to the glaze, only a very small amount of zirconium silicate is needed to achieve the whitening effect of traditional high-zirconium silicate glazes.

[0025] A fourth aspect of the present invention provides a ceramic article comprising a glaze layer, wherein the raw materials for preparing the glaze layer include the glaze described in the third aspect of the present invention.

[0026] In some embodiments of the present invention, the ceramic products include building ceramics, sanitary ceramics, or daily-use ceramics.

[0027] Compared with the prior art, the above-described technical solution of the present invention has at least the following technical effects or advantages: (1) The composite whitening agent of the present invention uses aluminum hydroxide as the main raw material and adds a certain amount of nano-zirconium sol, nano-silica sol and additives. In the preparation process, aluminum hydroxide is subjected to low-temperature heat treatment to generate porous γ-Al2O3 with high specific surface area. The nano-zirconium sol and nano-silica sol are impregnated to form a zirconium oxide and silica film that coats the surface and pores of γ-Al2O3. After high-temperature calcination, a composite whitening agent containing both zirconium silicate and polycrystalline alumina with low α-Al2O3 is obtained. This specific composition and crystal structure endow it with excellent whitening effect.

[0028] (2) The main raw material of the composite whitening agent of the present invention is aluminum hydroxide. Compared with the traditional opacifier zirconium silicate, the raw material reserves are abundant and the cost is low. It is a good supplement to the scarce zirconium silicate resources and provides a feasible industrialization direction for developing low-cost glaze whitening agents. Attached Figure Description

[0029] Figure 1 The images show actual ceramic bricks prepared in Example 1 and Comparative Example 1 of this invention. Detailed Implementation

[0030] The present invention will now be described in detail with reference to embodiments to facilitate understanding of the invention by those skilled in the art. It is particularly important to note that the embodiments are merely illustrative of the invention and should not be construed as limiting the scope of protection of the invention. Non-essential improvements and adjustments made to the invention by those skilled in the art based on the above description should still fall within the scope of protection of the invention. Furthermore, all raw materials mentioned below, unless otherwise specified, are commercially available products; all process steps or preparation methods not mentioned in detail are process steps or preparation methods known to those skilled in the art.

[0031] Some of the raw materials used in the following examples and comparative examples are as follows: Sodium polyacrylate: Rohm and Haas Corporation, USA, model ACUMER 9300, weight average molecular weight 2000-4000 g / mol; Polyvinylpyrrolidone: Guangdong Yuemei Chemical Co., Ltd., model K15, weight average molecular weight 8000-10000 g / mol; Polyethylene glycol: Jiangsu Aichuangde Chemical Technology Co., Ltd., model PEG20000, weight average molecular weight 18500-22000g / mol; Polyvinyl alcohol: Guangzhou Kete Chemical Co., Ltd., model 1788, weight average molecular weight 20000-120000g / mol.

[0032] Example 1 A composite whitening agent, the raw material components of which, by weight, include: 100 parts aluminum hydroxide, 3 parts nano zirconium sol, 2 parts nano silica sol, 0.3 parts sodium polyacrylate, and 0.2 parts sodium fluoride.

[0033] The solid content of the nano-zirconium sol is 15wt%, the solid content of the nano-silica sol is 30wt%, the fineness of the aluminum hydroxide is passing through a 150-mesh sieve, and the concentration of sodium fluoride is 4%.

[0034] The preparation method of the above-mentioned composite whitening agent includes the following steps: (1) Aluminum hydroxide was placed in a muffle furnace and heat-treated at 500°C for 3 hours, and then cooled naturally to obtain γ-Al2O3 powder.

[0035] (2) Add nano-zirconium sol and 50% sodium polyacrylate to water (the mass ratio of nano-zirconium sol to water is 3:70) and stir evenly; then add the γ-Al2O3 powder obtained in step (1) and continue to stir evenly; then dry in an oven at 150℃ to obtain powder A.

[0036] (3) Add nano silica sol and sodium fluoride to water (the mass ratio of nano zirconium sol to water is 2:70) and stir evenly; then add powder A obtained in step (2) and continue to stir evenly; then dry in an oven at 150°C to obtain powder B.

[0037] (4) Place the powder B obtained in step (3) in a muffle furnace, calcine it at 1150°C for 3 hours at a heating rate of 7°C / min, cool it naturally, crush it, and obtain the composite whitening agent of this embodiment.

[0038] A glaze, the raw material components of which, by weight, include: 38 parts feldspar, 11 parts quartz, 8 parts kaolin, 10 parts nepheline, 4 parts calcined talc, 8 parts calcined kaolin, 8 parts calcined alumina, 10 parts composite whitening agent, and 3 parts zirconium silicate.

[0039] Example 2 A composite whitening agent, the raw material components of which, by weight, include: 100 parts aluminum hydroxide, 5 parts nano zirconium sol, 2 parts nano silica sol, 0.15 parts polyvinylpyrrolidone, and 0.2 parts sodium fluoride.

[0040] The solid content of the nano-zirconium sol is 15wt%, the solid content of the nano-silica sol is 30wt%, the fineness of the aluminum hydroxide is passing through a 150-mesh sieve, and the concentration of sodium fluoride is 4%.

[0041] The preparation method of the above-mentioned composite whitening agent includes the following steps: (1) Aluminum hydroxide was placed in a muffle furnace and heat-treated at 550°C for 3 hours, and then cooled naturally to obtain γ-Al2O3 powder.

[0042] (2) Add nano-zirconium sol and 50% polyvinylpyrrolidone to water (the mass ratio of nano-zirconium sol to water is 3:70) and stir evenly; then add the γ-Al2O3 powder obtained in step (1) and continue to stir evenly; then put it in an oven and set it to 150℃ to dry to obtain powder A.

[0043] (3) Add nano silica sol and sodium fluoride to water (the mass ratio of nano zirconium sol to water is 2:70) and stir evenly; then add the powder A obtained in step (2) and continue to stir evenly; then put it in an oven and set it to 150℃ to dry, and obtain powder B.

[0044] (4) Place the powder B obtained in step (3) in a muffle furnace, calcine it at 1150°C for 3 hours at a heating rate of 7°C / min, cool it naturally, crush it, and obtain the composite whitening agent of this embodiment.

[0045] A glaze, the raw material components of which, by weight, include: 38 parts feldspar, 11 parts quartz, 8 parts kaolin, 10 parts nepheline, 4 parts calcined talc, 8 parts calcined kaolin, 8 parts calcined alumina, 10 parts composite whitening agent, and 3 parts zirconium silicate.

[0046] Example 3 A composite whitening agent, the raw material components of which, by weight, include: 100 parts aluminum hydroxide, 7 parts nano zirconium sol, 2.5 parts nano silica sol, 0.15 parts sodium polyacrylate, and 0.2 parts sodium fluoride.

[0047] The solid content of the nano-zirconium sol is 15wt%, the solid content of the nano-silica sol is 30wt%, the fineness of the aluminum hydroxide is passing through a 150-mesh sieve, and the concentration of sodium fluoride is 4%.

[0048] The preparation method of the above-mentioned composite whitening agent includes the following steps: (1) Aluminum hydroxide was placed in a muffle furnace and heat-treated at 450°C for 3 hours, and then cooled naturally to obtain γ-Al2O3 powder.

[0049] (2) Add nano-zirconium sol and 50% sodium polyacrylate to water (the mass ratio of nano-zirconium sol to water is 3:70) and stir evenly; then add the γ-Al2O3 powder obtained in step (1) and continue to stir evenly; then dry in an oven at 150℃ to obtain powder A.

[0050] (3) Add nano silica sol and sodium fluoride to water (the mass ratio of nano zirconium sol to water is 2:70) and stir evenly; then add powder A obtained in step (2) and continue to stir evenly; then dry in an oven at 150°C to obtain powder B.

[0051] (4) Place the powder B obtained in step (3) in a muffle furnace, calcine it at 1150°C for 3 hours at a heating rate of 7°C / min, cool it naturally, crush it, and obtain the composite whitening agent of this embodiment.

[0052] A glaze, the raw material components of which, by weight, include: 38 parts feldspar, 11 parts quartz, 8 parts kaolin, 10 parts nepheline, 4 parts calcined talc, 8 parts calcined kaolin, 8 parts calcined alumina, 10 parts composite whitening agent, and 3 parts zirconium silicate.

[0053] Example 4 A composite whitening agent, the raw material components of which, by weight, include: 100 parts aluminum hydroxide, 9 parts nano zirconium sol, 3 parts nano silica sol, 0.15 parts sodium polyacrylate, and 0.2 parts sodium fluoride.

[0054] The solid content of the nano-zirconium sol is 15wt%, the solid content of the nano-silica sol is 30wt%, the fineness of the aluminum hydroxide is passing through a 150-mesh sieve, and the concentration of sodium fluoride is 4%.

[0055] The preparation method of the above-mentioned composite whitening agent includes the following steps: (1) Aluminum hydroxide was placed in a muffle furnace and heat-treated at 500°C for 3 hours, and then cooled naturally to obtain γ-Al2O3 powder.

[0056] (2) Add nano-zirconium sol and 50% sodium polyacrylate to water (the mass ratio of nano-zirconium sol to water is 3:70) and stir evenly; then add the γ-Al2O3 powder obtained in step (1) and continue to stir evenly; then put it in an oven and set it to 150℃ to dry to obtain powder A.

[0057] (3) Add nano silica sol and sodium fluoride to water (the mass ratio of nano zirconium sol to water is 2:70) and stir evenly; then add the powder A obtained in step (2) and continue to stir evenly; then put it in an oven and set it to 150℃ to dry, and obtain powder B.

[0058] (4) Place the powder B obtained in step (3) in a muffle furnace, calcine it at 1150°C for 3 hours at a heating rate of 7°C / min, cool it naturally, crush it, and obtain the composite whitening agent of this embodiment.

[0059] A glaze, the raw material components of which, by weight, include: 38 parts feldspar, 11 parts quartz, 8 parts kaolin, 10 parts nepheline, 4 parts calcined talc, 8 parts calcined kaolin, 8 parts calcined alumina, 10 parts composite whitening agent, and 3 parts zirconium silicate.

[0060] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that ultra-white calcined alumina (whiteness: 72) was used instead of the composite whitening agent in Example 1.

[0061] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that an equal amount of polyethylene glycol dispersant was used instead of sodium polyacrylate in Example 1.

[0062] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that an equal amount of polyvinyl alcohol, the dispersant, was used instead of sodium polyacrylate in Example 1.

[0063] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that zirconium silicate is used instead of the composite whitening agent in Example 1.

[0064] Comparative Example 5 A composite whitening agent, the raw material components of which, by weight, include: 100 parts calcined alumina, 3 parts nano-zirconium sol, 2 parts nano-silica sol, 0.3 parts sodium polyacrylate, and 0.2 parts sodium fluoride.

[0065] The solid content of the nano-zirconium sol is 15wt%, the solid content of the nano-silica sol is 30wt%, the fineness of the aluminum hydroxide is passing through a 150-mesh sieve, and the concentration of sodium fluoride is 4%.

[0066] The preparation method of the above-mentioned composite whitening agent includes the following steps: (1) Add nano-zirconium sol and 50% sodium polyacrylate to water (the mass ratio of nano-zirconium sol to water is 3:70) and stir evenly; then add calcined alumina powder and continue to stir evenly; then dry in an oven at 150℃ to obtain powder A.

[0067] (2) Add nano silica sol and sodium fluoride to water (the mass ratio of nano zirconium sol to water is 2:70) and stir evenly; then add the powder A obtained in step (1) and continue to stir evenly; then dry in an oven at 150°C to obtain powder B.

[0068] (3) Place the powder B obtained in step (2) in a muffle furnace, calcine it at 1150°C for 3 hours at a heating rate of 7°C / min, cool it naturally, crush it, and obtain the composite whitening agent of this comparative example.

[0069] A glaze, the raw material components of which, by weight, include: 38 parts feldspar, 11 parts quartz, 8 parts kaolin, 10 parts nepheline, 4 parts calcined talc, 8 parts calcined kaolin, 8 parts calcined alumina, 10 parts composite whitening agent, and 3 parts zirconium silicate.

[0070] Performance testing 1. Component analysis Semi-quantitative phase analysis was performed on the composite whitening agent prepared in Example 1 and the calcined alumina used in Comparative Example 1. The results are shown in Table 1 and Table 2, respectively.

[0071] Table 1:

[0072] Table 2:

[0073] As shown in Tables 1-2, the composite whitening agent prepared in Example 1 has a lower α-Al2O3 content than conventional calcined alumina, which is more conducive to the opacification and whitening of glazes.

[0074] 2. Glaze properties Using the glazes prepared in Examples 1-4 and Comparative Examples 1-5 as raw materials, the same amount of water was added and the glazes were ground into glaze slurries. The flow rate of the glaze slurry was tested using a Cotton-4 cup, and then applied to the brick blank. A layer of polishing glaze was then applied, and after drying, the samples were fired at 1180℃ for 50 minutes to obtain ceramic tile samples. The gloss and whiteness of each ceramic tile were tested, and the glaze quality was recorded. The results are shown in Table 3 and... Figure 1 As shown.

[0075] The raw material components for polishing glaze, by weight, include: 43 parts feldspar, 5 parts quartz, 5 parts barium carbonate, 4 parts strontium carbonate, 5 parts calcined talc, 5 parts calcined zinc oxide, 10 parts dolomite, 10 parts washed clay, and 3 parts wollastonite.

[0076] Table 3:

[0077] Table 3 shows that the composite whitening agents prepared in Examples 1-4 all exhibit good whitening effects, with glaze whiteness reaching 65.4-66.4°, comparable to the expensive zirconium silicate sample used in Comparative Example 4. Furthermore, the glaze slurry demonstrates good fluidity and exhibits excellent glaze color and surface quality. Figure 1 .

[0078] Compared to Example 1, Comparative Example 1 used ultra-white calcined alumina, and the whiteness of the sample decreased by 10° compared to Example 1, and pinholes were present on the glaze surface.

[0079] Compared to Example 1, Comparative Examples 2-3 used other dispersants, which resulted in varying degrees of decrease in the whiteness and quality of the glaze. The reason for this is that polyethylene glycol and polyvinyl alcohol are both high-molecular-weight dispersants, which have more ash content after firing, affecting the synthesis of the material and reducing the whitening effect of the material.

[0080] Comparative Example 5, compared to Example 1, uses calcined alumina instead of aluminum hydroxide, and the specific surface area of ​​the calcined alumina is 1-5 m². 2 / g, while the specific surface area of ​​active γ-Al2O3 treated with aluminum hydroxide at 500℃ is as high as 100-500m².2 / g, its synthesis process has higher reactivity, the resulting material is more perfect, and the whitening effect is better.

[0081] For those skilled in the art, several simple deductions or substitutions can be made without departing from the inventive concept, without requiring creative effort. Therefore, any simple improvements made to this invention by those skilled in the art based on the disclosure of this invention should be within the scope of protection of this invention. The above embodiments are preferred embodiments of this invention, and all processes similar to this invention and equivalent changes should fall within the scope of protection of this invention.

Claims

1. A composite whitening agent, characterized in that, The raw material components, by weight, include: 100 parts aluminum hydroxide, 1-10 parts nano-zirconium sol, 1-5 parts nano-silica sol, 0.1-2 parts dispersant, and 0.1-3 parts mineralizer; the solid content of the nano-zirconium sol is 10-20 wt%, and the solid content of the nano-silica sol is 25-35 wt%.

2. The composite whitening agent according to claim 1, characterized in that, The aluminum hydroxide has a fineness that passes through an 80-325 mesh sieve.

3. The composite whitening agent according to claim 1, characterized in that, The dispersant is selected from at least one of sodium polyacrylate and polyvinylpyrrolidone; and / or the mineralizer is selected from at least one of sodium fluoride, calcium fluoride, and magnesium fluoride.

4. A method for preparing the composite whitening agent as described in any one of claims 1-3, characterized in that, Includes the following steps: (1) Heat treatment of aluminum hydroxide to prepare porous γ-Al2O3 powder; (2) Disperse γ-Al2O3 powder and nano-zirconium sol in water, dry, and form a zirconia film on the surface of γ-Al2O3 powder to obtain powder A; (3) Disperse the powder A, nano silica sol and mineralizing agent solution in water, dry them, and form a silica film on the surface of powder A to obtain powder B; (4) The powder B is calcined to obtain the composite whitening agent.

5. The method for preparing the composite whitening agent according to claim 4, characterized in that, In step (1), the temperature of the heat treatment is 350-550℃ and the time of the heat treatment is 2-4 hours.

6. The method for preparing the composite whitening agent according to claim 4, characterized in that, In step (2), the mass ratio of the nano-zirconium sol to water is 1:(20-30). In step (3), the concentration of the mineralizing agent solution is 2-6 wt%, and the mass ratio of the nano silica sol to water is 1:(30-40).

7. The method for preparing the composite whitening agent according to claim 4, characterized in that, In step (4), the calcination temperature is 1100-1250℃ and the calcination time is 2-4 hours.

8. A glaze, characterized in that, The glaze includes the composite whitening agent as described in any one of claims 1-3.

9. The glaze according to claim 8, characterized in that, The glaze raw material components, by weight, include: 30-60 parts feldspar, 6-18 parts quartz, 6-10 parts kaolin, 10-18 parts nepheline, 3-6 parts calcined talc, 5-15 parts calcined kaolin, 5-12 parts calcined alumina, 7-20 parts composite whitening agent, and 1-3 parts zirconium silicate.

10. A ceramic product, characterized in that, The ceramic product includes a glaze layer, and the raw materials for preparing the glaze layer include the glaze material as described in claim 8 or 9.

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