Coated aluminum oxide particles, method for manufacturing same, and use thereof

Abstract

Provided are coated aluminum oxide particles having sufficient electric conductivity, and a method for manufacturing same.　An antimony-doped tin oxide is contained in the surfaces of the aluminum oxide particles, such that the contained amount of an antimony component with respect to a tin component is 26-45 mass% when expressed as oxides as (Sb2O3 / SnO2). To a dispersion liquid containing aluminum oxide particles and a solvent, an alkali and a hydrochloric acid solution, containing an antimony component and a tin component such that the components are contained at an amount of 26-45 mass% when expressed as oxides as (Sb2O3 / SnO2), are mixed to cause a tin hydroxide that contains the antimony component to be deposited on the surfaces of the aluminum oxide particles. Then, the aluminum oxide particles are baked at a temperature of 400-800°C so as to be coated with an antimony-doped tin oxide.

Description

Coated aluminum oxide particles, their manufacturing method, and uses

[0001] The present invention relates to aluminum oxide particles coated with antimony-doped tin oxide, a method for producing the same, and a conductive material, a solvent composition, a resin composition, a coating composition, and a coating film containing the particles.

[0002] Conductive materials, which consist of a titanium dioxide particle substrate coated with a conductive substance such as antimony-doped tin oxide, are used as fillers in antistatic paints for floors and walls, primer paints for electrostatic painting of automobiles, and as external toner additives for electrophotography to adjust the charge and fluidize the toner.

[0003] In recent years, the International Agency for Research on Cancer (IARC) has changed the ranking of titanium dioxide particles from Group 3 (cannot be classified as carcinogenic to humans) to Group 2B (possibly carcinogenic to humans) in its "List of Carcinogenic Risk Information." This raises concerns that conductive materials using titanium dioxide particles may no longer be certified under some environmental protection certification systems.

[0004] Under these circumstances, aluminum oxide particles are one candidate for a substitute material for titanium dioxide particles. For example, Patent Document 1 discloses a white conductive powder in which the surface of a base powder is coated with an oxide of the elements antimony and tin, and the content of antimony doped in the tin oxide is 8 to 25% by weight as antimony relative to the tin oxide. In the examples, Sb / SnO ２ is 0.14 (oxide equivalent (Sb ２ O ３ / SnO ２ ) to a concentration of 16.7% by mass, and the surfaces of aluminum oxide particles are coated with a conductive layer of antimony-doped tin oxide. Patent Document 2 also discloses conductive particles having a coating layer made of conductive tin oxide containing a dopant element on the surface of a core material, and the dopant element is contained in the entire coating layer in an amount of 0.01 mol to 0.60 mol per 1 mol of tin, and in the examples, ２ O ３The amount of dopant to 1 mol of Sn in the substrate was 0.01 mol (oxide equivalent (Sb ２ O ３ / SnO ２ ) 1.0 mass %. ２ O ３ / SnO ２ ")" refers to the content of antimony and tin, respectively, as Sb ２ O ３ Content as antimony component (Sb ２ O ３ (also referred to as the converted value) and SnO ２ Content as tin component (SnO ２ The ratio of the content of the antimony component to the content of the tin component is calculated as SnO ２ Sb content as ２ O ３ expressed as a percentage of the content of Sb ２ O ３ The content as SnO ２ The value is expressed as mass %.

[0005] Japanese Patent Application Laid-Open No. 9-249820 International Publication No. 2015 / 060232

[0006] The conductive materials produced by the above-mentioned conventional techniques still do not have the desired level of conductivity, and further improvement in conductivity is required to replace conductive materials made of titanium dioxide particles. Furthermore, when used as a conductive white pigment, further improvement in conductivity is required while maintaining sufficient whiteness. Furthermore, depending on the application, excellent crushability may be required.

[0007] The inventors have found through their studies that the desired conductivity cannot be obtained by simply applying the conductive treatment technology for titanium dioxide particles to aluminum oxide particles. Therefore, the inventors have conducted extensive research and found that the desired conductivity can be achieved even when aluminum oxide particles are used as a substrate by optimizing the antimony-doped tin oxide coating treatment in accordance with the properties of the aluminum oxide particles, thereby completing the present invention.

[0008] That is, the present invention includes the following inventions (1) to (19): (1) An aluminum oxide particle having antimony-doped tin oxide on the surface thereof, wherein the content of the antimony component is 1 / 2 of the content of the tin component in terms of oxide (Sb ２ O ３ / SnO ２ (2) Coated aluminum oxide particles having antimony-doped tin oxide on the surface of the aluminum oxide particles, the content of the antimony component being 26% by mass or more and 45% by mass or less in terms of oxide (Sb ２ O ３ / SnO ２ (3) The content of the antimony-doped tin oxide is 30% by mass or more and 45% by mass or less in terms of oxide (Sb ２ O ３ and SnO ２ (4) The coated aluminum oxide particles according to (1) or (2), wherein the sodium content is 10% by mass or more and 40% by mass or less in terms of oxides (total amount of Na ２(1) The coated aluminum oxide particles according to any one of (1) to (3), having a particle size distribution (amount of ionic liquid) of 0.3 mass% or less in terms of the total particle size. (5) The coated aluminum oxide particles according to any one of (1) to (4), having a cumulative frequency of particles having a particle size of more than 1 μm of 21% or less in a volume-based particle size distribution. (6) The coated aluminum oxide particles according to any one of (1) to (4), having a cumulative frequency of particles having a particle size of more than 1 μm of 20% or less in a volume-based particle size distribution. (7) The coated aluminum oxide particles according to any one of (1) to (6), having a powder L value of 70 or more. (8) A conductive material comprising the coated aluminum oxide particles according to any one of (1) to (7). (9) A solvent composition comprising the coated aluminum oxide particles according to any one of (1) to (7) and a solvent. (10) A resin composition comprising the coated aluminum oxide particles according to any one of (1) to (7) and a resin. (11) A coating composition comprising the coated aluminum oxide particles according to any one of (1) to (7) and a coating resin. (12) A coating film comprising the coating composition according to (11). (13) A dispersion comprising aluminum oxide particles and an aqueous dispersion medium, wherein the proportion of antimony components in terms of oxide (Sb ２ O ３ / SnO ２ (14) A method for producing coated aluminum oxide particles, comprising mixing an alkali with a hydrochloric acid solution containing the antimony component and the tin component so that the ratio of the antimony component to the tin component in terms of oxide (Sb ２ O ３ / SnO ２ (15) A method for producing coated aluminum oxide particles, comprising: mixing an alkali with a hydrochloric acid solution containing the antimony component and the tin component so that the antimony component and the tin component are present in an amount of 30% by mass or more and 45% by mass or less in terms of oxide (Sb ), thereby precipitating tin hydroxide containing the antimony component on the surfaces of the aluminum oxide particles; and then baking the particles at a temperature of 400°C or more and 800°C or less to coat the surfaces with antimony-doped tin oxide. ２ O３ and SnO ２ (16) The method for producing coated aluminum oxide particles according to any one of (13) to (15), wherein the temperature of the dispersion is kept at 50°C or more and 95°C or less while mixing the hydrochloric acid solution containing the tin component and the antimony component with the alkali. (17) The method for producing coated aluminum oxide particles according to any one of (13) to (15), wherein the temperature of the dispersion is kept at 50°C or more and 90°C or less while mixing the hydrochloric acid solution containing the tin component and the antimony component with the alkali. (18) The method for producing coated aluminum oxide particles according to any one of (13) to (17), wherein the pH of the dispersion is kept at 4 or more and 10 or less while mixing the hydrochloric acid solution containing the tin component and the antimony component with the alkali. (19) The method for producing coated aluminum oxide particles according to any one of (13) to (18), wherein the alkali is sodium hydroxide.

[0009] The aluminum oxide particles coated with antimony-doped tin oxide of the present invention have sufficient conductivity and can be suitably used as a substitute for conductive titanium dioxide particles. Furthermore, by adjusting the whiteness, they can be used as a conductive white pigment. It is also possible to provide aluminum oxide particles coated with antimony-doped tin oxide that have excellent crushability.

[0010] The particle size distributions of Sample 1 and Sample 11 were measured using a laser diffraction / scattering particle size distribution measuring device.

[0011] The coated aluminum oxide particles of the present invention are obtained by using aluminum oxide particles as a substrate and coating the surface of the substrate with antimony-doped tin oxide.

[0012] In the coated aluminum oxide particles of the present invention, aluminum oxide is used as the substrate. ２ O ３It is a compound represented by the formula: and is also called alumina. Aluminum oxide has crystal structures such as trigonal (α-alumina) and cubic (γ-alumina), but either crystal structure is acceptable.

[0013] The aluminum oxide particles preferably have a cumulative 50% diameter (D50) in a volume-based particle size distribution of 0.1 μm or more and 1.0 μm or less, and more preferably 0.1 μm or more and 0.5 μm or less. The use of such aluminum oxide particles can improve the whiteness of the coated aluminum oxide particles. The cumulative 50% diameter (D50) is calculated from the particle size distribution obtained when aluminum oxide particles dispersed in a solvent are measured using a laser diffraction / scattering particle size distribution analyzer. Examples of laser diffraction / scattering particle size distribution analyzers that can be used include the LA-950 series and LA-960 series (both manufactured by Horiba, Ltd.) and the MT-3300 (manufactured by Microtrackbell Corporation).

[0014] The aluminum oxide particles may contain various impurities that are unavoidable during production. Examples of impurities include iron, silicon, calcium, gallium, chromium, nickel, zinc, zirconium, magnesium, copper, and sodium. As will be described later, sodium reduces the electrical conductivity of the coated aluminum oxide particles of the present invention, and therefore, the sodium component (Na ２ The content of impurities (calculated as O) is preferably 500 ppm or less, more preferably 100 ppm or less, and even more preferably 50 ppm or less, based on the mass of aluminum oxide. The content of impurities is measured, for example, by ICP emission spectroscopy, atomic absorption spectroscopy, X-ray fluorescence spectroscopy, or the like.

[0015] The aluminum oxide particles may have their particle surfaces coated with other inorganic compounds. Known inorganic surface treatment materials can be used as the coating material, such as an oxide or hydroxide of at least one of zinc, silicon, titanium, aluminum, zirconium, tin, and cerium. The term "coated" as used herein means that the inorganic compound coats the entire aluminum oxide particle in a layer, or that the coating has holes in some parts, such as a discontinuous coating where the inorganic compound is present in island-like patterns on the surface of the aluminum oxide particle; the coating state is not particularly limited.

[0016] The aluminum oxide particles can be synthesized by a known method. Various commercially available aluminum oxide particles can also be used. Examples of commercially available aluminum oxide particles include SMM-22 (manufactured by Nippon Light Metal Co., Ltd.), AKP-15, AKP-20, AKP-30, AKP-50, AKP-53, AKP-700, AKP-3000, AL-41-01, AL-43A, and AL-420A (all manufactured by Sumitomo Chemical Co., Ltd.), APA-0.5 and AHPA-0.5 (all manufactured by SASOL), and SAO-020A, SAO-020E, and SAO-020N (all manufactured by SINOCERA).

[0017] The coated aluminum oxide particles of the present invention have a coating of antimony-doped tin oxide on the surface of a substrate aluminum oxide particle. The coating referred to here may be a state in which the antimony-doped tin oxide particles coat the entire aluminum oxide particle in a layer, or a state in which holes are formed in part of the coating, for example, a discontinuous coating in which the antimony-doped tin oxide is present in the form of islands on the surface of the aluminum oxide particle. There are no particular restrictions on the state of the coating, but from the viewpoint of electrical conductivity, a state in which the antimony-doped tin oxide particles coat the entire aluminum oxide particle in a layer is desirable. Antimony-doped tin oxide is a solid solution of antimony inside tin oxide crystals, which can impart electrical conductivity to the tin oxide.

[0018] The coated aluminum oxide particles of the present invention have an antimony component content in the coating of antimony-doped tin oxide of 0.5 to 1.0% by oxide equivalent (Sb ２ O ３ / SnO ２ ) is 26 mass % or more and 45 mass % or less, preferably 30 mass % or more and 45 mass % or less. ２ O ３ / SnO ２ ")" refers to the content of antimony and tin components, respectively, as described above. ２ O ３ and SnO ２ The ratio of the content of the antimony component to the content of the tin component is calculated as SnO ２ Sb content as ２ O ３ expressed as a percentage of the content of Sb ２ O ３ The content as SnO ２ The value is expressed in mass %. Therefore, the content of the antimony component in the above range is the ratio of the SnO content of the tin component contained in the antimony-doped tin oxide that coats the aluminum oxide particles to the total content of the antimony component in the antimony-doped tin oxide. ２ The Sb content of the antimony component contained in the antimony-doped tin oxide relative to the converted amount ２ O ３The antimony content refers to the ratio (mass %) of the amount converted to the antimony component. The reason for the above content of the antimony component is as follows. The inventors' studies have revealed that when aluminum oxide is used as the substrate, it is more difficult to ensure the conductivity of the conductive material than when titanium dioxide is used as the substrate. Although the mechanism is unclear, it is presumed that a portion of the aluminum component contained in the substrate migrates to the antimony-doped tin oxide coating, adversely affecting the conductivity. Therefore, when aluminum oxide is used as the substrate, the content of the antimony component, which contributes to the development of conductivity, must be higher than when titanium dioxide is used as the substrate. Therefore, from the perspective of conductivity, it is important that the content of the antimony component, in terms of oxide, relative to the content of the tin component be 26% by mass or more. On the other hand, although there is no particular upper limit for the content of the antimony component from the perspective of conductivity, since an improvement in conductivity cannot be expected even if the content exceeds 45% by mass, an antimony component content of 45% by mass, in terms of oxide, relative to the content of the tin component, is sufficient.

[0019] When the coated aluminum oxide particles of the present invention are used as a white conductive material, the content of the antimony component is preferably 45 mass % or less, calculated as oxide, relative to the content of the tin component, from the viewpoint of whiteness.

[0020] The content of antimony relative to the content of tin is based on the oxide (antimony: Sb ２ O ３ , tin component: SnO ２ ) and the content of the antimony component is divided by the content of the tin component. The content of the antimony component relative to the content of the tin component calculated in this manner is referred to as "oxide equivalent (Sb ２ O ３ / SnO ２ ) or "Sb ２ O ３ / SnO ２ "It is sometimes written as ".

[0021] The coated aluminum oxide particles of the present invention have a coating amount of antimony-doped tin oxide of aluminum oxide (Al ２ O ３) in terms of oxide (Sb ２ O ３ and SnO ２ The total amount of the antimony-doped tin oxide coating is preferably 10% by mass or more and 40% by mass or less, and more preferably 20% by mass or more and 35% by mass or less. A coating amount of 10% by mass or more is preferable because the mass ratio of the antimony-doped tin oxide coating relative to the base particle made of aluminum oxide is sufficient, and it is possible to more effectively avoid the situation where the desired conductivity cannot be obtained if the coating amount is insufficient. On the other hand, if the coating amount of the antimony-doped tin oxide is too large, an effective improvement in conductivity cannot be expected, so the coating amount is preferably 40% by mass or less. Note that the "oxide equivalent (Sb ２ O ３ and SnO ２ "The total amount of Sb" is used in the present application. ２ O ３ + SnO ２ ", which indicates the content of antimony and tin components, respectively. ２ O ３ and SnO ２ Therefore, the coating amount of antimony-doped tin oxide in the above range is the same as that of aluminum oxide (Al ２ O ３ ) particle content (i.e., Al in the coated aluminum oxide particles ２ O ３ The ratio of the antimony component Sb contained in the antimony-doped tin oxide coating the aluminum oxide particles to the content of the antimony component Sb ２ O ３ Equivalent amount and tin component SnO ２ It means the percentage (mass %) of the sum (total) of the converted amounts.

[0022] The coating amount of antimony-doped tin oxide is determined by the content of the antimony component and the tin component contained in the coated aluminum oxide particles of the present invention on an oxide basis (antimony component: Sb ２ O ３ , tin component: SnO ２), and the sum of the content of the antimony component and the content of the tin component is divided by the content of aluminum oxide to calculate the coating amount of antimony-doped tin oxide. ２ O ３ + SnO ２ ) / Al ２ O ３ "It is sometimes written as ".

[0023] The coated aluminum oxide particles of the present invention have a sodium content of 100% or less in terms of oxides (Na ２ The sodium content is preferably 0.3% by mass or less, more preferably 0.2% by mass or less, and even more preferably 0.01% by mass or less, as expressed by the formula (O). When the content of the sodium component is within the above range, a decrease in electrical conductivity due to the sodium component being contained in the coated aluminum oxide particles can be more effectively avoided. Therefore, it is preferable that the sodium component be within the above range.

[0024] The contents of the tin component, antimony component, sodium component, and aluminum oxide component contained in the coated aluminum oxide particles of the present invention are measured, for example, using an X-ray fluorescence analyzer. Examples of such an apparatus that can be used include ZSX Primus IV and RIX-2100 (manufactured by Rigaku Corporation).

[0025] The coated aluminum oxide particles of the present invention preferably have a cumulative 50% diameter (D50) in a volume-based particle size distribution measured by a laser diffraction / scattering method of 0.1 μm or more and 1.0 μm or less, and more preferably 0.1 μm or more and 0.5 μm or less. By adjusting the diameter to this range, the whiteness of the coated aluminum oxide particles is improved. Note that the increase in particle size due to the coating with antimony-doped tin oxide is extremely small, and the effect on the particle size of the aluminum oxide particles of the base material (raw material) is negligible, so the particle size of the aluminum oxide particles can be considered unchanged by the coating.

[0026] In the coated aluminum oxide particles of the present invention, in a volume-based particle size distribution measured by a laser diffraction / scattering method, the cumulative frequency of particles having a particle diameter larger than 1 μm is preferably 21% or less, more preferably 20% or less, and even more preferably 18% or less. It is believed that the particles larger than 1 μm are agglomerates of multiple coated aluminum oxide particles. By reducing the proportion of such agglomerates (i.e., coated aluminum oxide particles having a particle diameter larger than 1 μm), the time required to disintegrate the coated aluminum oxide particles to a desired particle size (disintegration time) can be shortened. The disintegration time is defined as the time required for the coated aluminum oxide particles to be disintegrated to a cumulative 50% diameter (D50) of 0.4 μm or less. In this indicator, a disintegration time of less than 20 minutes is preferred, and 15 minutes or less is more preferred. A disintegration time of the above-mentioned range can be considered to have good disintegrability. The proportion of particles larger than 1 μm is calculated from the particle size distribution obtained when the coated aluminum oxide particles of the present invention dispersed in a solvent are measured using a laser diffraction / scattering particle size distribution analyzer. The disintegration time was measured by weighing 5 g of coated aluminum oxide particles, 30 g of pure water, and 30 g of glass beads, placing them in a glass container, and disintegrating them with a disperser (Paint Shaker, manufactured by Red Devil), and measuring the time until the cumulative 50% diameter (D50) reached 0.4 μm or less.

[0027] The coated aluminum oxide particles of the present invention may be coated with an organic compound, if necessary. The amount of the organic compound coated can be appropriately set. Examples of the organic compound include: (1) organosilicon compounds ((a) organopolysiloxanes (dimethylpolysiloxane, methylhydrogenpolysiloxane, methylmethoxypolysiloxane, methylphenylpolysiloxane, dimethylpolysiloxanediol, dimethylpolysiloxanedihydrogen, etc., or copolymers thereof), (b) organosilanes (aminosilane, epoxysilane, methacrylsilane, vinylsilane, phenylsilane, mercaptosilane, chloroalkylsilane, alkylsilane, fluoroalkylsilane, etc., or hydrolysis products thereof), (c) organosilazanes (hexamethylsilazane, hexamethylcyclotrisilazane, etc.)), etc. (2) organometallic compounds ((a) organic titanium compounds (triisostearoyloxy-isopropoxy titanium, aminoalkoxy titanium, phosphate ester titanium, carboxylate ester titanium, sulfonate ester titanium, titanium chelate, phosphite ester titanium complex, etc.), (b) organic zirconium compounds (carboxylate ester zirconium, zirconium chelate, etc.)), (3) polyols (trimethylolpropane, trimethylolethane, pentaerythritol, etc.), (4) alkanolamines (monoethanolamine, diethanolamine, triethanolamine, monopropanolamine, dipropanolamine, tripropanolamine, etc.) or derivatives thereof (organic acid salts such as acetates, oxalates, tartrates, formates, benzoates, etc.), (5) higher fatty acids (stearic acid, lauric acid, oleic acid, etc.) or metal salts thereof (aluminum salts, zinc salts, magnesium salts, calcium salts, barium salts, etc.), (6) Higher hydrocarbons (paraffin wax, polyethylene wax, etc.) or derivatives thereof (perfluorinated products, etc.).

[0028] The method for producing coated aluminum oxide particles of the present invention is to add an antimony component in an amount equivalent to the oxide of the antimony component relative to the tin component (Sb ２ O ３ / SnO ２) containing the components in an amount of 26% by mass or more and 45% by mass or less, and an alkali, and then firing the mixture at a temperature of 400°C or more and 800°C or less.

[0029] First, a dispersion containing aluminum oxide particles and an aqueous dispersion medium (this dispersion is also referred to as "aluminum oxide dispersion") is prepared. The aluminum oxide particles may be those described above. The particle size of the aluminum oxide particles may be appropriately adjusted using a known classifier or grinder. Examples of classifiers that can be used include a vibrating sieve device, a gravity classifier, a hydraulic classifier, and a centrifugal classifier. Examples of grinders that can be used include wet grinders such as a bead mill or a sand mill, and dry grinders such as a hammer mill, a pin mill, a roller mill, and a jet mill.

[0030] The aqueous dispersion medium is one whose main component is water, i.e., one whose water content is 50% by mass or more. The water content of the aqueous dispersion medium is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. Examples of components other than water include various organic solvents that are soluble in water (e.g., methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, tetrahydrofuran, etc.).

[0031] The aluminum oxide dispersion may be prepared by dispersing aluminum oxide particles in an aqueous dispersion medium using a known method. For example, a blade-type agitator, a disperser, a homomixer, or a wet grinding device such as a bead mill or a sand mill may be used, or a combination of these may be used. Furthermore, additives such as a dispersant, an emulsifier, a thickener, an antifoaming agent, a surface conditioner, an anti-settling agent, and a pH adjuster may be added as needed.

[0032] The concentration of aluminum oxide particles in the aluminum oxide dispersion is preferably 10% by mass or more and 40% by mass or less, and more preferably 15% by mass or more and 35% by mass or less. A concentration of 10% by mass or more is preferred in that it is possible to more effectively avoid a decrease in the amount of coated aluminum oxide particles produced. On the other hand, a concentration of 40% by mass or less is preferred in that it is possible to more effectively avoid a viscosity increase of the dispersion, which makes it difficult to form an antimony-doped tin oxide coating on the surface of the aluminum oxide particles.

[0033] The method may also include a step of coating the surfaces of the aluminum oxide particles with an inorganic compound. The coating method may be a known method, and for example, a compound of at least one element selected from zinc, silicon, titanium, aluminum, zirconium, tin, and cerium may be added to the aluminum oxide dispersion, and an acid and / or alkali may be added thereto to coat the surfaces of the aluminum oxide particles with the inorganic compound.

[0034] Next, a hydrochloric acid solution containing a tin component and an antimony component is prepared. Examples of the tin component include tin halides such as tin chloride, tin oxide, tin hydroxide, and inorganic tin salts (stannous salts, stannic salts) such as tin sulfate and tin nitrate, and these may be used alone or in combination of two or more. Among these, from the viewpoint of suppressing the inclusion of a sodium component in the coated aluminum oxide particles, it is preferable to use a tin compound that does not contain sodium, such as a tin halide, rather than a tin compound that contains sodium, such as sodium stannate.

[0035] Examples of the antimony component include antimony halides such as antimony chloride, antimony oxide, antimony hydroxide, and inorganic acid salts such as antimony sulfate, and these may be used alone or in combination of two or more. Among these, from the viewpoint of suppressing the content of sodium components in the coated aluminum oxide particles, it is preferable to use an antimony compound that does not contain sodium, such as an antimony halide, rather than an antimony compound that contains sodium, such as sodium antimonate.

[0036] The method for dissolving the tin component and the antimony component in the hydrochloric acid solution is not particularly limited. The tin component and the antimony component may be dissolved simultaneously in the hydrochloric acid solution. Alternatively, a solution of the tin component dissolved in hydrochloric acid and a solution of the antimony component dissolved in hydrochloric acid may be prepared separately and mixed. Alternatively, either the tin component or the antimony component may be dissolved in a hydrochloric acid solution, and the other component may be dissolved in the hydrochloric acid solution. Among these, dissolving the tin component in a hydrochloric acid solution containing the antimony component is preferred. This can suppress the precipitation of antimony compounds in the hydrochloric acid solution, thereby enabling the aluminum oxide particles to be uniformly coated with antimony-doped tin oxide. The concentration of hydrochloric acid in the hydrochloric acid solution is not particularly limited. Alternatively, the dissolution may be performed while stirring using a known stirrer, such as a blade stirrer, a disperser, or a homomixer.

[0037] When the tin component and the antimony component are dissolved in a hydrochloric acid solution, the tin component and the antimony component are dissolved in a hydrochloric acid solution such that the antimony component is converted to an oxide (Sb ２ O ３ / SnO ２ ), the content of the antimony component relative to the tin component in terms of oxide (Sb ２ O ３ / SnO ２ ) can be in the above-mentioned range, thereby improving the electrical conductivity of the coated aluminum oxide particles and allowing the coated aluminum oxide particles to have an appropriate whiteness.

[0038] Subsequently, a hydrochloric acid solution containing a tin component and an antimony component and an alkali are mixed with the aluminum oxide dispersion, and tin hydroxide containing an antimony component is precipitated on the surface of the aluminum oxide particles. The total amount of the tin component and the antimony component contained in the hydrochloric acid solution is adjusted to the ratio of the aluminum oxide (Al ２ O ３) component, oxide equivalent (Sb ２ O ３ and SnO ２ The total amount of antimony-doped tin oxide (Sb ) is preferably 10% by mass or more and 40% by mass or less, and more preferably 20% by mass or more and 35% by mass or less. By doing so, the coating amount of antimony-doped tin oxide on the aluminum oxide particles can be set within the above-mentioned range. ２ O ３ and SnO ２ "The total amount of Sb" is used in the present application. ２ O ３ + SnO ２ ", which indicates the content of antimony and tin components, respectively. ２ O ３ and SnO ２ Therefore, the ratio of the total amount of the tin component and the antimony component contained in the hydrochloric acid solution in the above range is calculated based on the total amount of aluminum oxide (Al ２ O ３ ) Sb of the antimony component in the hydrochloric acid solution relative to the amount of particles ２ O ３ Equivalent amount and tin component SnO ２ The total amount of the tin component and the antimony component contained in the hydrochloric acid solution is calculated by calculating the content of the antimony component and the content of the tin component on an oxide basis (antimony component: Sb ２ O ３ , tin component: SnO ２ ), and the sum (total) of the content of the antimony component and the content of the tin component was calculated as the aluminum oxide (Al ２ O ３ The total amount of tin and antimony contained in the hydrochloric acid solution calculated in this manner is referred to as "(Sb ２ O ３ + SnO ２ ) / Al ２ O ３". Examples of alkalis include hydroxides and carbonates of alkali metals such as sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate, and ammonia, and these may be used alone or in combination. The alkali may be used as a powder or as a solution by mixing with a solvent such as water. However, it is preferable to use the alkali as a solution because it can be uniformly mixed with the hydrochloric acid solution. In particular, it is preferable to use an alkali metal hydroxide, and sodium hydroxide is particularly preferable. The use of sodium hydroxide can reduce the specific surface area of ​​the tin hydroxide containing antimony component precipitated on the surface of the aluminum oxide particles, thereby suppressing aggregation of aluminum oxide particles coated with antimony-containing tin hydroxide (the aluminum oxide particles are referred to as "antimony-containing tin hydroxide-coated aluminum oxide particles"). As a result, aggregation is also suppressed in coated aluminum oxide particles obtained by calcining the particles, and the time required for disintegration to the desired particle size can be shortened.

[0039] However, there is a concern that the use of sodium hydroxide as the alkali may result in sodium components remaining in the coated aluminum oxide particles, which may result in a decrease in conductivity. To address this issue, the sodium components contained in the antimony-containing tin hydroxide-coated aluminum oxide particles can be removed by thoroughly washing the antimony-containing tin hydroxide-coated aluminum oxide particles with pure water or the like.

[0040] The method for mixing the aluminum oxide dispersion with the hydrochloric acid solution containing the tin and antimony components and the alkali is not particularly limited. The hydrochloric acid solution containing the tin and antimony components may be added to the aluminum oxide dispersion, followed by the addition of the alkali. Alternatively, the alkali may be added to the aluminum oxide dispersion, followed by the addition of the hydrochloric acid solution containing the tin and antimony components. Alternatively, the hydrochloric acid solution containing the tin and antimony components and the alkali may be added simultaneously. Among these, simultaneous addition of the hydrochloric acid solution containing the tin and antimony components and the alkali is preferred. This allows the aluminum oxide particles to be coated with antimony-containing tin hydroxide while maintaining the pH of the aluminum oxide dispersion within a certain range, thereby improving the conductivity of the antimony-doped tin oxide. Alternatively, the mixture may be mixed while stirring using a known stirrer such as a blade stirrer, a disperser, or a homomixer. The mixing time is not particularly limited, but the mixing time is preferably from 10 minutes to 120 minutes, as this allows the antimony-doped tin oxide particles to be completely coated on the aluminum oxide particles.

[0041] Furthermore, during the mixing of the aluminum oxide dispersion with the alkali and the hydrochloric acid solution containing the tin component and the antimony component, the aluminum oxide dispersion is preferably heated to a temperature of 50° C. or higher and 95° C. or lower, more preferably 55° C. or higher and 95° C. or lower, and even more preferably 60° C. or higher and 95° C. or lower. The aluminum oxide dispersion may be heated to a temperature of 50° C. or higher and 90° C. or lower, 55° C. or higher and 90° C. or lower, or 60° C. or higher and 90° C. or lower. When the temperature of the aluminum oxide dispersion is in the range of 50° C. or higher and 95° C., the deposition rate of tin hydroxide containing an antimony component is not slow, and the difference in deposition rates between antimony and tin is not large, so that the composition of the antimony-doped tin oxide coating becomes relatively uniform, and as a result, a decrease in electrical conductivity can be more effectively avoided, which is preferable.

[0042] Furthermore, during the mixing of the alkali and the hydrochloric acid solution containing the tin component and the antimony component with the aluminum oxide dispersion, the pH is preferably maintained at 4 or more and 10 or less, more preferably at 5 or more and 9 or less, and even more preferably at 6 or more and 8 or less. Within this pH range, aggregation of the aluminum oxide particles serving as the base material can be suppressed, thereby allowing a uniform antimony-doped tin oxide coating to be formed on the surfaces of the aluminum oxide particles, and improving conductivity more effectively.

[0043] The dispersion of antimony-containing tin hydroxide-coated aluminum oxide particles thus obtained may be subjected to an aging treatment, if necessary. The conditions for the aging treatment are not particularly limited, but the temperature condition is preferably 50°C or higher and 95°C or lower. Alternatively, heating may be performed at 60°C or higher and 80°C or lower. The aging time is preferably 10 minutes or higher and 120 minutes or lower. During the aging treatment, the pH is preferably maintained at 2 or higher and 8 or lower, more preferably 2 or higher and 5 or lower. By maintaining the pH within the above-mentioned range, the inclusion of sodium components in the coated aluminum oxide particles can be suppressed. If necessary, the pH of the dispersion of antimony-containing tin hydroxide-coated aluminum oxide particles may be adjusted using a known pH adjuster or the like. Alternatively, aging may be performed while stirring using a known stirrer such as a blade stirrer, a disperser, or a homomixer.

[0044] The dispersion of antimony-containing tin hydroxide-coated aluminum oxide particles may be subjected to solid-liquid separation as needed. A known filtration method can be used for solid-liquid separation, and examples of such methods include pressure filtration devices typically used in industry, such as rotary presses and filter presses, and vacuum filtration devices, such as Nutsche filters and Moore filters. Centrifugal separation can also be used. During the solid-liquid separation, the solid content may be washed using pure water or a known method.

[0045] The method may also include a step of drying the solid content obtained by solid-liquid separation. When the drying step is included, the drying temperature and drying time can be appropriately set. For example, the drying temperature is preferably 30°C or higher and 120°C or lower, and the drying time is preferably 0.5 hours or higher and 10 hours or lower. In the drying step, for example, a heating device such as a dryer, oven, or electric furnace can be used.

[0046] Next, the antimony-containing tin hydroxide-coated aluminum oxide particles thus obtained are subjected to a calcination step. In this way, the antimony-containing tin hydroxide-coated aluminum oxide particles become antimony-doped tin oxide-coated aluminum oxide particles. The calcination temperature in the calcination step is 400°C or higher and 800°C or lower, preferably 450°C or higher and 750°C or lower, and more preferably 500°C or higher and 700°C or lower. By maintaining the temperature within the above range, antimony-doped tin oxide-coated aluminum oxide particles having a desired particle size can be obtained. The calcination time is not particularly limited, but is preferably 30 minutes to 10 hours, more preferably 1 hour to 4 hours.

[0047] The firing atmosphere in the firing step is not particularly limited, but it is industrially preferable to perform firing in an air atmosphere.

[0048] The coated aluminum oxide particles produced by the above method may be subjected to appropriate particle size adjustment using a known grinder or classifier.

[0049] The coated aluminum oxide particles produced by the above method may also include a step of surface-treating the surface thereof with an inorganic and / or organic compound coating, such as an oxide or hydroxide of silicon, titanium, aluminum, zirconium, tin, or the like, or a phosphate thereof. In this case, the inorganic and / or organic compound may be any of those described above. The surface treatment method may be a conventional surface treatment method, such as a titanium dioxide pigment coating. Specifically, in the case of an inorganic compound coating, it is preferable to add an inorganic compound to a dispersion of coated aluminum oxide particles to coat them, and more preferably to neutralize and precipitate the inorganic compound in a slurry to coat them. In the case of an organic compound coating, it is preferable to add the organic compound to a powder of coated aluminum oxide particles to coat them, and more preferably to include a heating step. The conditions for the heating step can be appropriately set; for example, the heating temperature is preferably 50°C or higher and 200°C or lower, and the heating time is preferably 10 minutes or higher and 120 minutes or lower.

[0050] The coated aluminum oxide particles of the present invention can be used as a conductive material by utilizing their conductive properties, and their volume resistivity is preferably 50 Ω·cm or less, more preferably 30 Ω·cm or less, and even more preferably 15 Ω·cm or less. If the volume resistivity is within the above range, the particles can be used as a conductive material. The volume resistivity can be calculated from the volume resistance value measured using a known measuring device. For example, a digital multimeter (manufactured by Yokogawa Measurement Co., Ltd.) can be used as the measuring device.

[0051] Furthermore, the coated aluminum oxide particles of the present invention can be used as a white pigment by utilizing their whiteness. The whiteness can be evaluated from the L value and b value of the powder in the Lab color system. The coated aluminum oxide particles of the present invention preferably have an L value of 60 or more, more preferably 70 or more. Furthermore, the b value of the powder is preferably -4.0 or more and 0.3 or less, more preferably -2.0 or more and 0.0 or less. If the L value and b value of the powder are as described above, it can be used as a white pigment. The L value and b value of the powder can be measured using a colorimetric color difference meter, for example, a spectrophotometer SD5000 manufactured by Nippon Denshoku Industries Co., Ltd.

[0052] Furthermore, the coated aluminum oxide particles of the present invention can also be used as a white conductive material by utilizing the above-mentioned conductivity and whiteness. When used as a white conductive material, the coated aluminum oxide particles of the present invention may be used in combination with other colorants or conductive agents.

[0053] The coated aluminum oxide particles of the present invention and conductive materials containing the same can be mixed with a solvent to form a solvent composition (dispersion or suspension). Examples of solvents used in the solvent composition include aqueous solvents, non-aqueous solvents such as alcohols (e.g., methanol, ethanol, butanol, isopropyl alcohol, ethylene glycol), esters (e.g., ethyl acetate), ethers (e.g., butyl cellosolve, propylene glycol-1-monomethyl ether), ketones (e.g., acetone, methyl ethyl ketone), aromatic hydrocarbons (e.g., toluene, xylene, mineral spirits), and aliphatic hydrocarbons, as well as mixtures thereof. The solvent composition may contain additives such as dispersants, emulsifiers, antifreeze agents, pH adjusters, thickeners, and antifoaming agents, as needed. The solids concentration of such solvent compositions can be appropriately set.

[0054] A known mixer can be used in the mixing step when preparing the solvent composition. Furthermore, degassing may be performed during the mixing, if necessary. Examples of mixers include those typically used industrially, such as a two-shaft mixer, a three-roll mill, a sand mill, and a planetary mixer. For laboratory scale applications, a stirrer, a hybrid mixer, a homogenizer, or a paint shaker may be used. In this case, grinding media containing glass, alumina, zirconia, zirconium silicate, or the like may be used, if necessary.

[0055] The coated aluminum oxide particles of the present invention can be mixed with a resin to form a resin composition. Examples of resins used in the resin composition include thermoplastic resins, thermosetting resins, and thermoplastic elastomers. Examples of thermoplastic resins include: (1) general-purpose plastic resins (e.g., (a) polyolefin resins (polyethylene, polypropylene, etc.), (b) polyvinyl chloride resins, (c) acrylonitrile butadiene styrene resins, (d) polystyrene resins, (e) methacrylic resins, and (f) polyvinylidene chloride resins); (2) engineering plastic resins (e.g., (a) polycarbonate resins, (b) polyethylene terephthalate resins, (c) polyamide resins, (d) polyacetal resins, (e) modified polyphenylene ethers, and (f) fluororesins); (3) Super engineering plastic resins (for example, (a) polyphenylene sulfide resin (PP), (b) polysulfone resin (PSF), (c) polyethersulfone resin (PES), (d) amorphous polyarylate resin (PAR), (e) liquid crystal polymer (LCP), (f) polyetheretherketone resin (PEEK), (g) polyamideimide resin (PAI), (h) polyetherimide resin (PEI), etc.) are exemplified.

[0056] Examples of thermosetting resins include (a) epoxy resins, (b) phenolic resins, (c) unsaturated polyester resins, (d) polyurethane resins, (e) melamine resins, and (f) silicone resins.

[0057] Examples of thermoplastic elastomers include styrene-based, olefin / alkene-based, vinyl chloride-based, urethane-based, and amide-based elastomers.

[0058] Furthermore, the above-mentioned resin composition may contain, as necessary, various additives such as a lubricant, a light stabilizer, an antistatic agent, a bactericide, a dispersant, a filler, a flame retardant, an antifreeze agent, a pH adjuster, a thickener, an ultraviolet absorber, an antioxidant, etc. The concentration of the coated aluminum oxide particles in such a resin composition may be appropriately set, and a high-concentration masterbatch may also be prepared.

[0059] The resin composition can be obtained by blending the coated aluminum oxide particles of the present invention with a molten resin using a kneader, which may be a commonly used kneader, such as a single-screw extruder, a twin-screw extruder, an intensive mixer such as a Banbury mixer, or a roll molding machine.

[0060] The coated aluminum oxide particles of the present invention and conductive materials containing the same can be mixed with a paint resin to form a paint composition. The paint resin is not particularly limited as long as it is one that is commonly used in paint applications, and various paint resins can be used, such as phenolic resins, alkyd resins, acrylic alkyd resins, acrylic resins, acrylic emulsion resins, polyester resins, polyester urethane resins, polyether resins, polyolefin resins, polyurethane resins, acrylic urethane resins, epoxy resins, modified epoxy resins, silicone resins, acrylic silicone resins, fluororesins, ethylene vinyl acetate copolymers, acrylic-styrene copolymers, amino resins, methacrylic resins, polycarbonate resins, and polyvinyl chloride resins.

[0061] The coating composition of the present invention can contain various additives, solvents, etc. as needed. Examples of additives include various commonly used dispersants, emulsifiers, antifreeze agents, pH adjusters, thickeners, antifoaming agents, film-forming aids, etc. Examples of solvents include aqueous solvents, non-aqueous solvents such as alcohols (e.g., methanol, butanol, ethylene glycol), esters (e.g., ethyl acetate), ethers, ketones (e.g., acetone, methyl ethyl ketone), aromatic hydrocarbons (e.g., toluene, xylene, mineral spirits), and aliphatic hydrocarbons, as well as mixtures thereof. The concentration of the coated aluminum oxide particles in such a coating composition can be appropriately set.

[0062] The mixing step with the resin can be carried out using the same method as the mixing step in producing the solvent composition.

[0063] The solvent composition or coating composition of the present invention can be applied to a substrate and cured to form a coating film, which can be used as a white coating film, a conductive coating film, or a white conductive coating film.

[0064] The solvent composition or coating composition of the present invention can be applied by any conventional method, such as spin coating, spray coating, roller coating, dip coating, flow coating, knife coating, electrostatic coating, bar coating, die coating, brush coating, or dropwise application, without limitation. The tool used to apply the solvent dispersion or coating composition can be appropriately selected from known tools such as a spray gun, roller, brush, bar coater, or doctor blade. A coating film can be obtained by drying and curing the coating after application. Baking may also be performed after drying. The baking conditions can be appropriately set, but for example, baking can be performed in an oxidizing atmosphere at a temperature ranging from 40°C to 200°C for a time period of approximately 1 minute to 120 minutes. Setting these conditions allows for sufficient baking in the drying furnace of a coil coating line.

[0065] Examples of substrates to which the solvent composition or coating composition is applied include ceramic products, glass products, metal products, plastic products, and paper products.

[0066] The present invention will be described in detail with reference to examples and comparative examples, but the present invention is not limited to these.

[0067] <Measurement of Chemical Composition> Measurement was performed using a ZSX Primus IV X-ray fluorescence analyzer (manufactured by Rigaku Corporation). 10 g of each sample obtained in the Examples and Comparative Examples was weighed out and crushed for 10 minutes using a crusher. This was packed into an aluminum ring (outer diameter 38 mm, inner diameter 34 mm, thickness 5 mm) and pressure-molded at 15 tf using a hydraulic press. The measurement was performed using the resulting sample.

[0068] <Particle size distribution> 10 g of the samples obtained in the examples and comparative examples were weighed out and crushed for 10 minutes using a crusher. Pure water was added to the sample, and the mixture was dispersed using an ultrasonic cleaner to prepare a dispersion. The particle size distribution of the dispersion was measured using a laser diffraction / scattering particle size distribution measuring device LA-950 (manufactured by Horiba, Ltd.) under the following conditions: Sample refractive index: 1.66 (aluminum oxide) Solvent refractive index: 1.33 (pure water) Circulation speed: 3 Ultrasonic intensity: 4 Ultrasonic duration: 4 minutes 30 seconds Stirring intensity: 3

[0069] <Cumulative frequency of particles having a particle diameter of greater than 1 μm in volume-based particle size distribution> This was calculated from the particle size distribution obtained as described above.

[0070] <Volume Resistivity> 10 g of each sample obtained in the Examples and Comparative Examples was weighed out and crushed for 10 minutes using a crusher. The crushed sample was compression molded under a pressure of 9.8 MPa, and the volume resistivity was measured using a digital multimeter DM7560 (manufactured by Yokogawa Measurement Corporation). The volume resistivity was calculated using the following formula (1): Volume resistivity (Ω cm) = Volume resistivity (Ω) × Electrode area (cm ２ ) / sample thickness (cm) Equation (1)

[0071] <Evaluation of Whiteness> 5 g of each of the samples obtained in the Examples and Comparative Examples was weighed out, filled into an aluminum ring (outer diameter 38 mm, inner diameter 34 mm, thickness 5 mm), and press-molded at 10 tf using a pressure molding machine. The L value and b value of the powder were measured using a spectrophotometer SD5000 manufactured by Nippon Denshoku Industries Co., Ltd.

[0072] Example 1 200 g of aluminum oxide particles (AKP-30, manufactured by Sumitomo Chemical Co., Ltd.) were dispersed in 1 L of pure water using a stirrer to obtain an aluminum oxide dispersion liquid with a pH of 7 to 8. This dispersion liquid was heated to 70°C while being stirred with the stirrer. The liquid temperature of the aluminum oxide dispersion liquid was maintained until the end of the aging step. In addition, 20.7 g of antimony trichloride was dissolved in 118 g of 35% by mass hydrochloric acid, and 138.3 g of a 50% by mass aqueous solution of tin tetrachloride was mixed therewith to obtain a hydrochloric acid solution. In the hydrochloric acid solution, Sb ２ O ３ / SnO ２ = 33.0 mass%, (Sb ２ O ３ + SnO ２ ) / Al ２ O ３ = 26.6% by mass. Next, the pH of the aluminum oxide dispersion was maintained at 7 to 8, the liquid temperature at 70°C, and the hydrochloric acid solution and the sodium hydroxide aqueous solution were simultaneously added to the aluminum oxide dispersion over 60 minutes while stirring the aluminum oxide dispersion with a stirrer, yielding a dispersion of antimony-containing tin hydroxide-coated aluminum oxide particles. Next, as an aging step, 35% by mass of hydrochloric acid was added to the dispersion of antimony-containing tin hydroxide-coated aluminum oxide particles, the pH was adjusted to 4, and the mixture was stirred at 70°C for 20 minutes. The dispersion obtained by the aging step was filtered, and the solid content was washed with pure water until the specific conductivity of the filtrate reached 50 μS / cm, and then dried at 110°C for 24 hours. The dried solid content was calcined in air at 600°C for 1 hour using an electric furnace (manufactured by Kyoei Electric Furnace Manufacturing Co., Ltd.), yielding Sample 1 of Example 1. For sample 1, the cumulative frequency of particles having a particle size of more than 1 μm was calculated to be 12.5%.

[0073] Example 2 In Example 1, Sb in a hydrochloric acid solution ２ O ３ / SnO ２ 33.3 mass%, (Sb ２ O ３ + SnO ２ ) / Al ２ O ３Sample 2 was obtained in the same manner as in Example 1, except that the content of the cellulose acetate stearate was changed to 33.3 mass%. For Sample 2, the cumulative frequency of particles having a particle size of more than 1 μm was calculated and found to be 13.8%.

[0074] Example 3 In Example 1, Sb in a hydrochloric acid solution ２ O ３ / SnO ２ 35.0 mass% (Sb ２ O ３ + SnO ２ ) / Al ２ O ３ Sample 3 was obtained in the same manner as in Example 1, except that the content of the cellulose acetate stearate was changed to 33.0 mass %. For Sample 3, the cumulative frequency of particles having a particle size of more than 1 μm was calculated and found to be 20.1%.

[0075] Example 4 In Example 1, Sb in a hydrochloric acid solution ２ O ３ / SnO ２ 40.0 mass% (Sb ２ O ３ + SnO ２ ) / Al ２ O ３ Sample 4 was obtained in the same manner as in Example 1, except that the content of the cellulose acylate was changed to 28.0 mass %. For Sample 4, the cumulative frequency of particles having a particle size of more than 1 μm was calculated and found to be 19.8%.

[0076] Example 5 In Example 1, Sb in a hydrochloric acid solution ２ O ３ / SnO ２ 29.7% by mass, (Sb ２ O ３ + SnO ２ ) / Al ２ O ３ Sample 5 was obtained in the same manner as in Example 1, except that the content of the cellulose acylate was changed to 19.5 mass %. For Sample 5, the cumulative frequency of particles having a particle size of more than 1 μm was calculated and found to be 16.3%.

[0077] Example 6 Sample 6 was obtained in the same manner as in Example 1, except that the pH in the aging step was changed to 5. For Sample 6, the cumulative frequency of particles having a particle size of more than 1 μm was calculated and found to be 15.5%.

[0078] Example 7 Sample 7 was obtained in the same manner as in Example 1, except that the pH in the aging step was changed to 6. For Sample 7, the cumulative frequency of particles having a particle size of more than 1 μm was calculated and found to be 16.2%.

[0079] Example 8 Sample 8 was obtained in the same manner as in Example 1, except that the pH in the aging step was changed to 7. For Sample 8, the cumulative frequency of particles having a particle size of more than 1 μm was calculated and found to be 15.8%.

[0080] Example 9 Sample 9 was obtained in the same manner as in Example 1, except that the temperature of the aluminum oxide dispersion was changed to 90° C. and maintained at that temperature until the aging step was completed.

[0081] Example 10 Sample 10 was obtained in the same manner as in Example 1, except that the liquid temperature of the aluminum oxide dispersion was changed to 50°C and maintained at that temperature until the aging step was completed. For Sample 10, the cumulative frequency of particles having a particle size of more than 1 µm was calculated and found to be 10.5%.

[0082] Comparative Example 1 300 g of aluminum oxide particles (AKP-30, manufactured by Sumitomo Chemical Co., Ltd.) were dispersed in 2 L of pure water using a stirrer to obtain a dispersion liquid with a pH of 8. This aluminum oxide dispersion liquid was heated to 70°C while being stirred with the stirrer. Next, 18.1 g of antimony trichloride was dissolved in 779.8 g of 2.4 N hydrochloric acid, and 160.5 g of tin tetrachloride pentahydrate was dissolved therein to obtain a hydrochloric acid solution. In the hydrochloric acid solution, Sb ２ O ３ / SnO ２= 16.7% by mass. One-fifth of the hydrochloric acid solution and an aqueous ammonia solution were added simultaneously over 60 minutes while maintaining the pH of the aluminum oxide dispersion at 8, and then the remaining four-fifths of the hydrochloric acid solution and the aqueous sodium hydroxide solution were added simultaneously over 120 minutes while maintaining the pH at 8, to obtain a dispersion of antimony-containing tin hydroxide-coated aluminum oxide particles. The aluminum oxide dispersion was stirred with a stirrer while each solution was added to the aluminum oxide dispersion. Next, in the aging step, 2.4 N hydrochloric acid was added to the dispersion of antimony-containing tin hydroxide-coated aluminum oxide particles to adjust the pH to 4, and the mixture was stirred at 70°C for 60 minutes. The dispersion obtained by the aging step was filtered, and the solid content was washed with pure water until the specific conductivity of the filtrate reached 50 μS / cm, and the solid content was dried at 110°C for 24 hours. The dried solid content was fired in air at 700°C for 1 hour using an electric furnace (manufactured by Kyoei Electric Furnace Manufacturing Co., Ltd.) to obtain Sample 11 of Comparative Example 1. For Sample 11, the cumulative frequency of particles having a particle diameter of more than 1 µm was calculated and found to be 21.6%.

[0083] Comparative Example 2 In Example 1, Sb in the hydrochloric acid solution ２ O ３ / SnO ２ 20.0 mass% (Sb ２ O ３ + SnO ２ ) / Al ２ O ３ Sample 12 of Comparative Example 2 was obtained in the same manner as in Example 1, except that the content of the hydroxybenzoate was changed to 24.0 mass%.

[0084] Comparative Example 3 In Example 1, Sb in the hydrochloric acid solution ２ O ３ / SnO ２ 50.0 mass% of (Sb ２ O ３ + SnO ２ ) / Al ２ O ３ Sample 13 of Comparative Example 3 was obtained in the same manner as in Example 1, except that the content of the hydroxybenzoate was changed to 30.0 mass %.

[0085] The ratio of the antimony content (Sb ２ O３ / SnO ２ ), the total content of the tin component and the antimony component relative to the aluminum oxide particles ((Sb ２ O ３ + SnO ２ ) / Al ２ O ３ ), sodium content (Na ２ The analytical values ​​of Sb and O and the volume resistivity are shown in Table 1. ２ O ３ / SnO ２ (mass%) and (Sb ２ O ３ + SnO ２ ) / Al ２ O ３ It should be noted that the values ​​(mass %) are analytical values ​​of the final products, Samples 1 to 13, and do not represent values ​​in hydrochloric acid solution.

[0086]

[0087] From Table 1, Sb ２ O ３ / SnO ２ It can be seen that Samples 1 to 10, which were produced with Sb in an amount of 26% by mass or more and 45% by mass or less, have a volume resistivity of 50 Ω·cm or less, and have sufficient conductivity. It can also be seen that the same samples have an L value of 60 or more and a b value of 0.3 or less, and have sufficient whiteness. ２ O ３ / SnO ２ When Sb is less than 26 mass % (samples 11 and 12), the volume resistivity exceeds 50 Ω cm, and it is found that the electrical conductivity is insufficient. ２ O ３ / SnO ２ When the b value exceeds 45% by mass (sample 13), it is found that the b value exceeds 0.3 and the whiteness is insufficient.

[0088] <Evaluation of disintegration ability> 5 g each of Sample 1 and Sample 11 was weighed into a 100 ml mayonnaise bottle. Next, 30 g of pure water and 30 g of glass beads (Unibeads (registered trademark) UB-2224LN, manufactured by Unitika Ltd.) were weighed into each mayonnaise bottle. For each mayonnaise bottle, a disperser (paint shaker, manufactured by Red Devil) was used to measure the time required for the cumulative 50% diameter (D50) in the volume-based particle size distribution to become 0.4 μm or less, and this was taken as the disintegration time.

[0089] For sample 1, the cumulative 50% diameter (D50) was 0.4 μm or less after 15 minutes of crushing treatment. On the other hand, for sample 11, the cumulative 50% diameter (D50) was 0.4 μm or less after 20 minutes of crushing treatment. This shows that when the cumulative frequency of particles having a particle diameter of 1 μm or more is 21% or less, excellent crushability is achieved. Furthermore, samples 2 to 8 and sample 10 were confirmed to have excellent crushability, similar to sample 1.

[0090] According to the present invention, coated aluminum oxide particles having sufficient conductivity can be obtained. Such a material can be used as an alternative to conductive materials made of titanium dioxide particles. Furthermore, since the material has sufficient whiteness, it can also be used as a white conductive material. Furthermore, it can also be used as coated aluminum oxide particles with excellent crushability.

Claims

1. The surface of the aluminum oxide particles is coated with antimony-doped tin oxide, and the content of the antimony component is in an oxide equivalent (Sb ２ O ３ / SnO ２ ) is 26 mass % or more and 45 mass % or less.

2. The surface of the aluminum oxide particles is coated with antimony-doped tin oxide, and the content of the antimony component is in an oxide equivalent (Sb ２ O ３ / SnO ２ ) is 30 mass % or more and 45 mass % or less.

3. The content of the antimony-doped tin oxide is expressed as an oxide equivalent (Sb ２ O ３ and SnO ２ 3. The coated aluminum oxide particles according to claim 1, wherein the total amount of the above (amount of the above) is 10% by mass or more and 40% by mass or less.

4. The sodium content is calculated as an oxide equivalent (Na ２ 3. The coated aluminum oxide particles according to claim 1, wherein the total amount of the aluminum oxide particles is 0.3 mass % or less.

5. 3. The coated aluminum oxide particles according to claim 1, wherein in a volume-based particle size distribution, the cumulative frequency of particles having a particle diameter of more than 1 μm is 21% or less.

6. 3. The coated aluminum oxide particles according to claim 1, wherein in a volume-based particle size distribution, the cumulative frequency of particles having a particle diameter of more than 1 μm is 20% or less.

7. 3. The coated aluminum oxide particles according to claim 1 or 2, wherein the powder L value is 70 or more.

8. A conductive material comprising the coated aluminum oxide particles according to claim 1 or 2.

9. A solvent composition comprising the coated aluminum oxide particles according to claim 1 or 2 and a solvent.

10. A resin composition comprising the coated aluminum oxide particles according to claim 1 or 2 and a resin.

11. A coating composition comprising the coated aluminum oxide particles according to claim 1 or 2 and a coating resin.

12. A coating comprising the coating composition of claim 11.

13. In a dispersion containing aluminum oxide particles and an aqueous dispersion medium, the antimony component is added in an amount equivalent to the oxide of the tin component (Sb ２ O ３ / SnO ２ % by mass or more and 45% by mass or less of the antimony component and the tin component, and then calcining the mixture at a temperature of 400°C or more and 800°C or less.

14. In a dispersion containing aluminum oxide particles and an aqueous dispersion medium, the antimony component is added in an amount equivalent to the oxide of the tin component (Sb ２ O ３ / SnO ２ a hydrochloric acid solution containing the antimony component and the tin component in an amount of 30% by mass or more and 45% by mass or less based on the total mass of the aluminum oxide particles, and an alkali to precipitate tin hydroxide containing the antimony component on the surfaces of the aluminum oxide particles; and then calcining the particles at a temperature of 400°C or more and 800°C or less to coat the aluminum oxide particles with antimony-doped tin oxide.

15. The total amount of the tin component and the antimony component contained in the hydrochloric acid solution is calculated as an oxide equivalent (Sb ２ O ３ and SnO ２ The method for producing coated aluminum oxide particles according to claim 13 or 14, wherein the total amount of the above (amount of the above) is 10 mass % or more and 40 mass % or less.

16. 15. The method for producing coated aluminum oxide particles according to claim 13 or 14, wherein the temperature of the dispersion is kept at 50° C. or higher and 95° C. or lower while the hydrochloric acid solution containing the tin component and the antimony component and the alkali are mixed.

17. 15. The method for producing coated aluminum oxide particles according to claim 13 or 14, wherein the temperature of the dispersion is kept at 50°C or higher and 90°C or lower while the hydrochloric acid solution containing the tin component and the antimony component and the alkali are mixed.

18. 15. The method for producing coated aluminum oxide particles according to claim 13 or 14, wherein the pH of the dispersion is maintained at 4 or more and 10 or less during mixing of the hydrochloric acid solution containing the tin component and the antimony component with the alkali.

19. The method for producing coated aluminum oxide particles according to claim 13 or 14, wherein the alkali is sodium hydroxide.