Alumina particles, resin composition, molded article, and method for producing alumina particles

Abstract

To provide alumina particles containing molybdenum and controlled in shape.SOLUTION: Alumina particles contain phosphorus and molybdenum. The alumina particles are preferably plate-like or card-house-like. The phosphorus is preferably distributed unevenly on a surface layer of the alumina particles. A resin composition contains the alumina particles and a resin. A molded product is formed by molding the resin composition. A method for producing the alumina particles includes a step of firing the aluminum compound in the presence of a molybdenum compound and a phosphorus compound.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to alumina particles containing phosphorus and molybdenum, a resin composition containing the alumina particles, and a molded body. The present invention also relates to a method for producing alumina particles containing phosphorus and molybdenum.

Background Art

[0002] Alumina is a chemically stable compound and is therefore difficult to react with molecules on the skin surface and has low irritation, so it is widely used in applications such as cosmetics and biological materials. In addition, since it is also difficult to react with external contaminants, it is also adopted for applications such as paints, coatings, or optical materials. In these applications, it is preferable to contain alumina α-crystals that are highly chemically and physically stable. Particularly as a brilliant pigment, since the area of the surface that can efficiently reflect light is large, a shape with a higher aspect ratio than the typically known icosahedron is required.

[0003] The general and most inexpensive method for producing conventional α-alumina is the Bayer process using bauxite as a raw material. In the Bayer process, aluminum hydroxide (gibbsite) or transition alumina is produced from the raw material bauxite, and then α-alumina powder is produced by firing these in the atmosphere. However, the α-alumina obtained by the Bayer process is an aggregate of amorphous particles, and it was difficult to control the particle shape by this method.

[0004] On the other hand, it has been disclosed that it is possible to produce plate-like alumina particles containing molybdenum and containing alumina α-crystals by using a molybdenum compound as a fluxing agent and a silicon or silicon compound as a shape control agent (Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] However, in fluxing methods that use molybdenum compounds as fluxing agents, there is still room for investigation regarding shape-controlling agents other than silicon or silicon compounds that can enable shape control of alumina particles.

[0007] This invention was made to solve the above-mentioned problems, and aims to provide alumina particles containing molybdenum and with a controlled shape. Furthermore, the present invention aims to provide a method for producing the alumina particles. [Means for solving the problem]

[0008] As a result of diligent research to solve the above problems, the present inventors have discovered that by using phosphorus as a shape control agent in a flux method using a molybdenum compound as a flux agent, it is possible to obtain alumina particles with a high aspect ratio, such as plate-shaped or card-house-shaped particles, and have completed the present invention. In other words, the present invention has the following aspects.

[0009] (1) Alumina particles containing phosphorus and molybdenum. (2) Alumina particles as described in (1) above, wherein the α-crystallization rate is 90% by weight or more. (3) Alumina particles as described in (1) or (2) above, which are in the form of a plate. (4) D 50 Alumina particles as described in (3) above, wherein the particle size is 2 to 100 μm. (5) The alumina particles according to (3), wherein the average particle diameter of the primary particles of the alumina particles is 5 to 200 μm, and the aspect ratio obtained by dividing the average particle diameter of the primary particles of the alumina particles by the thickness is 2 to 100. (6) Alumina particles as described in (1) or (2) above, which are in the shape of a cardhouse. (7) D 50 Alumina particles as described in (6) above, wherein the particle size is 3 to 300 μm. (8) Alumina particles according to (6), wherein the alumina particles contain plate-shaped alumina having an average particle diameter of 5 to 200 μm, and the aspect ratio obtained by dividing the average particle diameter of each plate-shaped alumina by its thickness is 2 to 100. (9) Alumina particles according to any one of (1) to (8) above, wherein the pH at which the zeta potential is the isoelectric point is 0 to 3. (10) Specific surface area measured by the BET method is 0.1 to 10 m² 2 Alumina particles according to any one of (1) to (9) above, wherein the weight is / g. (11) Alumina particles according to any one of (1) to (10), wherein the molybdenum is unevenly distributed on the surface of the alumina particles. (12) Alumina particles according to any one of (1) to (11), wherein the phosphorus is unevenly distributed on the surface of the alumina particles. (13) Alumina particles according to any one of (1) to (12) above, wherein the molar ratio [P] / [Al] of phosphorus concentration to aluminum concentration measured by X-ray photoelectron spectroscopy (XPS) is 0.001 or greater. (14) A resin composition containing alumina particles as described in any one of (1) to (13) above, and a resin. (15) A molded article obtained by molding the resin composition described in (14) above. (16) A method for producing alumina particles according to any one of (1) to (13), comprising the step of calcining an aluminum compound in the presence of a molybdenum compound and a phosphorus compound. (17) A method for producing alumina particles according to (16), comprising the step of calcining a mixture of a molybdenum compound, a phosphorus compound, and an aluminum compound. (18) A method for producing alumina particles according to (16), comprising the step of calcining a mixture of a molybdenum-containing aluminum compound and a phosphorus compound. (19) A method for producing alumina particles according to (16), comprising the step of calcining a mixture of a phosphorus-containing aluminum compound and a molybdenum compound. (20) A method for producing alumina particles according to (16), comprising the step of calcining a mixture of a phosphorus-containing molybdenum compound and an aluminum compound. (21) A method for producing alumina particles according to any one of (16) to (20), wherein the firing temperature is 900 to 1600°C. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide alumina particles with controlled shape that contain phosphorus and molybdenum. [Brief explanation of the drawing]

[0011] [Figure 1] This is an SEM image of the alumina particles from Example 1. [Figure 2] This is an SEM image of the alumina particles from Example 2. [Figure 3] This is an SEM image of the alumina particles from Example 3. [Figure 4] This is an SEM image of the alumina particles from Example 4. [Figure 5] This is an SEM image of the alumina particles from Example 5. [Figure 6] This is an SEM image of the alumina particles from Example 6. [Figure 7] This is an SEM image of alumina particles from Comparative Example 1. [Figure 8] This is an SEM image of alumina particles from Comparative Example 2. [Figure 9] This is the X-ray diffraction (XRD) pattern of the alumina particles in the example. [Figure 10] This is a schematic diagram showing an example of the structure of alumina particles having a cardhouse structure. [Figure 11] This is a schematic diagram illustrating another example of the composition of alumina particles having a cardhouse structure. [Modes for carrying out the invention]

[0012] The following describes embodiments of the alumina particles and the method for producing the alumina particles according to the present invention.

[0013] <Alumina particles> The alumina particles of this embodiment contain phosphorus and molybdenum. The alumina particles of this embodiment contain molybdenum and have excellent properties such as catalytic activity derived from molybdenum.

[0014] The alumina particles of the embodiment may contain molybdenum derived from a molybdenum compound used in the manufacturing method described later.

[0015] The alumina particles of the embodiment further contain phosphorus. The alumina particles may contain phosphorus or phosphorus derived from a phosphorus compound used as a shape-controlling agent in the manufacturing method described later. The shape-controlling agent plays an important role in plate-like crystal growth.

[0016] (alumina) In this specification, "alumina" refers to aluminum oxide (Al2O3). The alumina particles of the embodiments are not particularly limited in their crystalline form, as long as they contain phosphorus and molybdenum. For example, they may be transition alumina in various crystalline forms such as γ, δ, θ, κ, or they may contain alumina hydrate within the transition alumina. The α crystalline form is basically preferred in terms of superior mechanical strength or thermal conductivity.

[0017] The α-crystallization rate of alumina particles can be determined by XRD analysis. For example, using a wide-angle X-ray diffraction (XRD) instrument (e.g., Rigaku Ultima IV), the prepared sample is placed in a sample holder and measured under the conditions of Cu / Kα rays, 40kV / 40mA, scan speed 2° / min, and scanning range 10-70°. The α-crystallization rate can then be determined by the RIR (reference intensity ratio) method from the intensity ratio of the peaks of α-alumina and other alumina species relative to the baseline. The α-crystallization rate varies depending on the firing conditions and the raw materials used. From the viewpoint of improving the crushing strength and fluidity of alumina particles, an α-crystallization rate of 90% by weight or more is preferable, and more preferably 95% by weight or more. Alumina particles having the above-mentioned α-crystallization rate are preferable because they have a dense α-crystal structure, resulting in high strength and resistance to cracking even in plate-like or card-house-like shapes with a high aspect ratio.

[0018] (molybdenum) The alumina particles of this embodiment contain molybdenum. The alumina particles may contain molybdenum in their surface layer. By utilizing the properties of molybdenum contained in the alumina particles, they can be applied to applications such as oxidation reaction catalysts and optical materials.

[0019] The molybdenum contained in the alumina particles of the embodiment is not particularly limited, but may be molybdenum metal, molybdenum oxide, a partially reduced molybdenum compound, a molybdate salt, etc. Molybdenum may be contained in the plate-like alumina particles in any polymorph or combination of the molybdenum compound, and may be contained in the plate-like alumina particles as α-MoO3, β-MoO3, MoO2, MoO, molybdenum cluster structure, etc.

[0020] The form in which molybdenum is included is not particularly limited; it may be included in a form attached to the surface of plate-like alumina particles, in a form where it replaces some of the aluminum in the alumina crystal structure, or a combination of these.

[0021] (Lin) The alumina particles of this embodiment contain phosphorus. Furthermore, the alumina particles may contain phosphorus on their surface. Although it varies depending on the raw materials used, alumina particles contain phosphorus or phosphorus compounds, such as elemental phosphorus (P) and phosphorus oxide (P4O4). 10 , P2O5), aluminum phosphate (AlPO4), aluminum dihydrogen phosphate (Al(H2PO4)3), aluminum trihydrogen phosphate (AlH2(P3O 10 )), Phosphorus molybdate (H3(MoO3) 12It may contain at least one selected from the group consisting of PO4, etc., organophosphorus compounds such as trialkylphosphines, triarylphosphines, phosphine oxides, phosphinates, phosphates, and phospholanes; phosphates such as organic amine phosphates; compounds such as phosphoric acid, organophosphoric acid and polyphosphoric acid derivatives, and oxides or hydrates thereof, and the above substances may be contained in the surface layer. The alumina particles of the embodiment may contain aluminum phosphate (AlPO4), and may contain aluminum phosphate (AlPO4) on their surface. Furthermore, the "phosphorus or phosphorus compound" contained in the alumina particles according to this embodiment and the "raw material phosphorus compound" used as a shape control agent for the raw material may be the same type of phosphorus compound.

[0022] By including phosphorus on the surface of alumina particles, the surface properties of the alumina particles can be made more acidic compared to when phosphorus is absent, which can improve the affinity with basic organic compounds and various binders and matrices. The alumina particles of this embodiment can be suitably used, for example, as a resin composition containing the alumina particles and a resin. For example, the affinity between basic dispersants, such as organic amine compounds that may be blended into the resin composition, and the acidic phosphorus portion on the surface of the alumina particles can be improved. The surface state of the alumina surface can be easily controlled by the phosphorus atoms and / or phosphorus compounds on the surface of the alumina particles.

[0023] The alumina particles of the embodiment are shape-controlled alumina particles. In this specification, shape-controlled alumina particles mean alumina particles whose particle shape is not amorphous. Alumina particles of one embodiment, manufactured by the manufacturing method of the embodiment, may have a distinctive self-shape, such as a plate-like or card-house-like form, as shown in the examples described later.

[0024] <Plate-shaped alumina particles> The alumina particles in the embodiment may have a plate-like shape. The median diameter D of the plate-shaped alumina particles of the embodiment, calculated by laser diffraction and scattering. 50 The particle size is preferably 2 to 100 μm, more preferably 5 to 40 μm, and even more preferably 10 to 20 μm.

[0025] The median diameter D of the plate-shaped alumina particles in the embodiment 50、 This is calculated by laser diffraction and scattering. Specifically, using an aggregate (powder) of alumina particles as a sample, the particle size distribution can be measured dry using a laser diffraction particle size analyzer (e.g., HELOS (H3355) & RODOS, R3: 0.5 / 0.9-175 μm, manufactured by Nippon Laser Co., Ltd.) under conditions of dispersion pressure of 3 bar and suction pressure of 90 mbar.

[0026] The average particle size of the primary particles of the plate-shaped alumina particles in the embodiment may be 5 to 200 μm, 5 to 50 μm, or 10 to 40 μm.

[0027] The average particle diameter of primary particles in plate-like alumina particles is determined by imaging the plate-like alumina particles with a scanning electron microscope (SEM) and taking the average of the maximum distance between two points on the contour line of 50 randomly selected primary particles, which are the smallest units of particles constituting the aggregates in the two-dimensional image (i.e., primary particles).

[0028] The thickness of the primary particles of the plate-shaped alumina particles in the embodiment may be less than 5 μm, 0.1 to 4 μm, 0.3 to 3 μm, or 0.5 to 2 μm.

[0029] The primary particle thickness of plate-shaped alumina particles is determined by taking images of the alumina particles with a scanning electron microscope (SEM) and using the average value of the thicknesses of 50 randomly selected primary particles, which are the smallest units of particles constituting the aggregates in the two-dimensional image (i.e., primary particles).

[0030] In this specification, "plate-like" refers to alumina particles in which the aspect ratio obtained by dividing the average particle diameter of the primary particles by the thickness is 2 or more. The aspect ratio of the primary particles of plate-like alumina particles is preferably 2 to 100, more preferably 5 to 50, and even more preferably 6 to 30. An aspect ratio above the lower limit is preferable because it allows for good heat dissipation due to a high specific surface area. An aspect ratio below the upper limit is preferable because it results in superior mechanical strength.

[0031] The average particle diameter and aspect ratio values ​​of the plate-shaped alumina particles exemplified above can be freely combined. As an example of plate-shaped alumina particles in the embodiment, plate-shaped alumina particles can be exemplified in which the average particle diameter of the primary particles is 5 to 200 μm, and the aspect ratio obtained by dividing the average particle diameter of the primary particles of the alumina particles by the thickness is 2 to 100.

[0032] The specific shape of the plate-like alumina particles can be, for example, a hexahedron in three dimensions, with a two-dimensional projection plane that is a typical quadrilateral with four corners (a quadrilateral plate), or a two-dimensional projection plane that is a polygon with five or more corners (the latter may be referred to as a polygonal plate). They may also be circular or elliptical plates.

[0033] The aggregate (powder) of alumina particles may contain alumina particles of any shape other than plate-like particles. The content of plate-like alumina particles is preferably 80% or more by weight or number, more preferably 90% or more, and even more preferably 95% or more, relative to the total amount of the aggregate (powder) of alumina particles.

[0034] <Card-house shaped alumina particles> The alumina particles of the embodiment may have a cardhouse structure in which multiple plate-like alumina particles are fixed together. Specifically, the alumina particles of the embodiment may be formed from three or more plate-like alumina particles, and have a cardhouse structure in which the plate-like alumina particles are fixed together (see, for example, Figure 10). By having a cardhouse structure, the specific surface area of ​​the alumina particles can be increased compared to spherical alumina particles of the same particle size. In this specification, alumina particles having a cardhouse structure may be referred to as cardhouse-like alumina particles.

[0035] The morphology of alumina particles can be confirmed by scanning electron microscopy (SEM). A cardhouse structure may be, for example, a structure in which plate-like alumina is arranged randomly without being oriented in a specific direction. For example, it may be a structure in which three or more plate-like alumina sheets intersect and aggregate at two or more locations, and the planes of the intersecting plate-like alumina sheets are arranged randomly (see Figure 11). The intersecting positions may be any positions on the plate-like alumina sheets. A random arrangement means that there are no restrictions on the direction in which the planes intersect each other, in terms of the X, Y, or Z axes, and the angle at which the planes intersect each other may be any angle.

[0036] Although it varies depending on the particle size of the alumina particles, the number of plate-like alumina particles contained in one cardhouse-shaped alumina particle is preferably, for example, 3 to 10,000, and more preferably 10 to 5,000, and especially 15 to 3,000, both in terms of performance and ease of manufacture.

[0037] The intersection of plate-like alumina occurs when three or more plate-like alumina particles interact with each other, for example, by bonding and assembling during the crystal formation process of the firing stage. As a result, it may appear as a penetration type. The strong bonding of the plate-like alumina particles to each other increases the strength of the cardhouse structure.

[0038] Furthermore, "intersection" refers to two or more surfaces meeting at a single point, and there are no restrictions on the position, diameter, area, etc., of the intersecting surfaces. Also, the number of orientations of the surfaces starting from the point of intersection can be three, four or more, or any number of orientations.

[0039] Furthermore, the major axis, minor axis, and thickness of the plate-like alumina particles contained within the cardhouse-shaped alumina particles can be of any size. It is also acceptable to include plate-like alumina of multiple sizes.

[0040] As described above regarding plate-shaped alumina particles, the plate-shaped alumina may be either square-shaped or polygonal-shaped. Within a single card-house-shaped alumina particle, either square-shaped or polygonal-shaped alumina may be present, or both may be present, and there are no restrictions on their ratio.

[0041] Furthermore, the aggregate (powder) of alumina particles may contain, in addition to the cardhouse structure, particles in a roughly X-shape (sometimes called twinned alumina particles), a roughly T-shape, a roughly L-shape, or a single sheet of plate-like alumina, in any form. To obtain excellent fluidity, it is preferable that the content of these is low. The content of alumina particles having a cardhouse structure formed by three or more sheets of plate-like alumina, where the plate-like alumina particles are fixed to each other, is preferably 80% or more by weight or number, more preferably 90% or more, and even more preferably 95% or more. The content of twinned particles and single sheet-like alumina can be easily adjusted by general classification operations such as sieving classification and wind classification.

[0042] Alumina particles with a card house structure have extremely high crushing strength due to their unique structure and are not easily crushed even when external stress is applied. Therefore, poor fluidity based on the anisotropy of the alumina particles themselves is unlikely to occur. Thus, not only can the inherent functions of the alumina particles be fully utilized, but even if they are mixed and used together with plate-shaped alumina particles, it is possible to make the plate-shaped alumina particles, which tend to be oriented in the longitudinal direction, exist in random directions. As a result, excellent mechanical strength can be exhibited not only in the longitudinal direction but also in the thickness direction.

[0043] Due to its unique structure, card house-shaped alumina particles have excellent fluidity as a powder, and it is possible to improve the discharge efficiency of supply machines used during mechanical conveyance, such as hoppers and feeders, for application as industrial products. Since card house-shaped alumina particles have voids inside due to their unique structure, their bulk specific gravity does not differ significantly from that of plate-shaped alumina particles. However, compared with plate-shaped alumina particles, they have a high sphericity and, as described above, high crushing strength and are difficult to break. Therefore, it is presumed that they have a high effect on the ease of conveyance by the rolling of the alumina particles.

[0044] The median diameter D of the card house-shaped alumina particles of the embodiment, calculated by the laser diffraction / scattering method 50 is preferably 3 to 300 μm, more preferably 5 to 100 μm, and even more preferably 5 to 40 μm.

[0045] The median diameter D of the card house-shaped alumina particles of the embodiment 50、 is calculated by the laser diffraction / scattering method, similar to the above-mentioned plate-shaped alumina particles.

[0046] Also, the maximum particle diameter of the card house-shaped alumina particles measured by the laser diffraction / scattering method is not particularly limited, but is usually 3000 μm or less, preferably 1000 μm or less, and more preferably 500 μm or less.

[0047] The cardhouse-shaped alumina particles of the embodiment may contain plate-shaped alumina with an average particle diameter of 5 to 200 μm, or plate-shaped alumina with an average particle diameter of 5 to 50 μm, or plate-shaped alumina with an average particle diameter of 5 to 20 μm.

[0048] The cardhouse-shaped alumina particles of the embodiment may contain plate-shaped alumina with a thickness of 0.1 to 5 μm, or plate-shaped alumina with a thickness of 0.2 to 2 μm, or plate-shaped alumina with a thickness of 0.3 to 1 μm.

[0049] The aspect ratio obtained by dividing the average particle diameter of the plate-shaped alumina by its thickness is preferably 2 to 100, more preferably 5 to 50, and even more preferably 10 to 40. An aspect ratio above the lower limit is preferable because it allows for good heat dissipation due to a high specific surface area. An aspect ratio below the upper limit is preferable because it results in superior mechanical strength.

[0050] The average particle diameter and aspect ratio values ​​of the plate-shaped alumina exemplified above can be freely combined. As an example of card-house-shaped alumina particles in the embodiment, card-house-shaped alumina particles can be exemplified that contain plate-shaped alumina with an average particle diameter of 5 to 200 μm, and the aspect ratio obtained by dividing the average particle diameter of each plate-shaped alumina by its thickness is 2 to 100.

[0051] The average particle diameter and thickness values ​​of the plate-like alumina constituting the cardhouse-shaped alumina particles refer to values ​​measured and calculated from images obtained by scanning electron microscope (SEM) of any 100 plate-like alumina particles.

[0052] Furthermore, a method for determining the average particle size of plate-like alumina is to observe card-house-shaped alumina particles with a scanning electron microscope (SEM), and for plate-like alumina located in the center of at least 50 randomly selected card-house-shaped alumina particles on a two-dimensional image, determine the maximum distance between two points on the contour line. The average value of these distances is taken as the average particle size of the plate-like alumina in the card-house-shaped alumina particles. Alternatively, if equivalent results can be obtained, a method of measuring the maximum length of a single piece obtained by wind classification of the card-house-shaped alumina particles with an SEM may be used. Or, a method of obtaining a single piece by dismantling the card-house structure through some mechanical process under conditions that do not destroy the plate-like alumina itself, and then measuring the maximum length with an SEM may be used.

[0053] The same applies to the method for determining the thickness of plate-like alumina. For example, a method can be used in which cardhouse-shaped alumina particles are observed with a scanning electron microscope (SEM), the maximum thickness of the plate-like alumina located in the center of at least 50 randomly selected cardhouse-shaped alumina particles on a two-dimensional image is measured, and the average value is calculated. Alternatively, if equivalent results can be obtained, a method can be used in which the thickness of a single piece obtained by wind classification of cardhouse-shaped alumina particles is measured with an SEM. Or, a method can be used in which the cardhouse structure is broken down by some mechanical process under conditions that do not destroy the plate-like alumina itself, a single piece is obtained, and its thickness is measured with an SEM.

[0054] The alumina particles of the embodiment may include α-alumina (α-Al2O3). α-Al2O3 content in alumina particles (R A The α-Al2O3 content (R) per 100 wt% of the alumina particles is determined by XRD analysis. The alumina particles of the embodiment are determined by the RIR (Reference Intensity Ratio) method from spectral data obtained by XRD analysis of the alumina particles. A The amount is preferably 70.0 to 99.9% by weight, more preferably 75.0 to 99.7% by weight, and even more preferably 80.0 to 99.5% by weight.

[0055] The alumina particles of the embodiment may contain aluminum phosphate (AlPO4). AlPO4 content in alumina particles (R B The AlPO4 content (R) per 100 wt% of the alumina particles is determined by XRD analysis. The alumina particles of the embodiment are determined by the RIR (Reference Intensity Ratio) method from spectral data obtained by XRD analysis of the alumina particles. B The amount is preferably 0.01 to 30.0% by weight, more preferably 0.05 to 25.0% by weight, and even more preferably 0.1 to 20.0% by weight.

[0056] The alumina particles of the embodiment contain aluminum. The aluminum content in the alumina particles can be measured by XRF analysis. In the embodiment, the alumina particles preferably have an Al2O3 content (A1) of 70.0 to 99.5 mass%, more preferably 85.0 to 99.5 mass%, and even more preferably 89.0 to 99.0 mass%, as determined by XRF analysis of the alumina particles.

[0057] The alumina particles of the embodiment contain molybdenum. The alumina particles of the embodiment preferably have a MoO3 content (M1) of 0.01 to 20.0 mass%, more preferably 0.05 to 5.0 mass%, and even more preferably 0.1 to 3.0 mass%, relative to 100 mass%, as determined by XRF analysis of the alumina particles.

[0058] In the alumina particles of the embodiment, the upper and lower limits of the Al2O3 content (A1) and MoO3 content (M1) exemplified above can be freely combined. Furthermore, the numerical values ​​of the Al2O3 content (A1) and MoO3 content (M1) can also be freely combined with each other.

[0059] As an example of alumina particles in the embodiment, alumina particles having an Al2O3 content (A1) of 70.0 to 99.5 mass% and a MoO3 content (M1) of 0.01 to 20.0 mass% can be cited.

[0060] The alumina particles of the embodiment contain phosphorus. The phosphorus content of the alumina particles of the embodiment is preferably such that the P2O4 content (P1) per 100% by mass of the alumina particles, determined by XRF analysis of the alumina particles, is 0.01 to 15% by mass, more preferably 0.1 to 10% by mass, and even more preferably 0.5 to 6% by mass.

[0061] In the alumina particles of the embodiment, the upper and lower limits of the Al2O3 content (A1), MoO3 content (M1), and P2O4 content (P1) exemplified above can be freely combined. Furthermore, the numerical values ​​of the Al2O3 content (A1), MoO3 content (M1), and P2O4 content (P1) can also be freely combined with each other.

[0062] As an example of alumina particles in the embodiment, alumina particles having an Al2O3 content (A1) of 70.0 to 99.5 mass%, a MoO3 content (M1) of 0.01 to 20.0 mass%, and a P2O4 content (P1) of 0.01 to 15 mass% can be exemplified.

[0063] The above Al2O3 content (A1), MoO3 content (M1), and P2O4 content (P1) can be measured by XRF analysis using an X-ray fluorescence analyzer (for example, Primus IV, manufactured by Rigaku Corporation).

[0064] Al2O3 content (A1) refers to the value obtained by analyzing alumina particles using XRF (X-ray fluorescence) and using a pre-determined Al2O3 calibration curve, where Al is expressed as the Al2O3 content relative to 100% mass of alumina particles. MoO3 content (M1) refers to the value obtained by analyzing alumina particles using XRF (X-ray fluorescence) and using a pre-determined MoO3 calibration curve to determine the Mo content as the MoO3 content relative to 100% mass of alumina particles. P2O4 content (P1) refers to the value obtained by analyzing alumina particles using XRF (X-ray fluorescence) and using a pre-determined P2O4 calibration curve, representing the P content as the P2O4 content per 100 mass% of alumina particles.

[0065] The aluminum content in the surface layer of alumina particles can be measured by XPS (X-ray photoelectron spectroscopy) surface analysis. In the embodiment, the alumina particles preferably have an Al2O3 content (A2) of 50 to 95% by mass, more preferably 55 to 90% by mass, and even more preferably 70 to 90% by mass, relative to 100% by mass of the surface layer of the alumina particles, as determined by XPS surface analysis of the alumina particles.

[0066] The alumina particles of the embodiment preferably have a MoO3 content (M2) of 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, and even more preferably 1 to 7% by mass, relative to 100% by mass of the surface layer of the alumina particles, as determined by XPS surface analysis of the alumina particles.

[0067] In the alumina particles of the embodiment, the upper and lower limits of the Al2O3 content (A2) and MoO3 content (M2) exemplified above can be freely combined. Furthermore, the numerical values ​​of the Al2O3 content (A2) and MoO3 content (M2) can also be freely combined with each other.

[0068] As an example of alumina particles in the embodiment, alumina particles having an Al2O3 content (A2) of 50 to 95% by mass and a MoO3 content (M2) of 0.1 to 20% by mass can be exemplified.

[0069] The alumina particles of the embodiment may contain phosphorus in their surface layer. The alumina particles of the embodiment preferably have a P2O4 content (P2) of 0.1 to 40% by mass, more preferably 1 to 30% by mass, and even more preferably 5 to 20% by mass, relative to 100% by mass of the surface layer of the alumina particles, as determined by XPS surface analysis of the alumina particles.

[0070] In the alumina particles of the embodiment, the upper and lower limits of the Al2O3 content (A2), MoO3 content (M2), and P2O4 content (P2) exemplified above can be freely combined. Furthermore, the numerical values ​​of the Fe2O3 content (F2), MoO3 content (M2), and P2O4 content (P2) can also be freely combined.

[0071] As an example of alumina particles in the embodiment, alumina particles having an Al2O3 content (A2) of 50 to 95 mass%, a MoO3 content (M2) of 0.1 to 20 mass%, and a P2O4 content (P2) of 0.1 to 40 mass% can be exemplified.

[0072] The Al2O3 content (A2) mentioned above refers to the value obtained by performing X-ray photoelectron spectroscopy (XPS) surface analysis on an alumina particle sample to acquire the abundance ratio (atom%) of each element, and then converting the aluminum content to oxide equivalent, thereby determining the Al2O3 content relative to 100 mass% of the surface layer of the alumina particles.

[0073] The above MoO3 content (M2) refers to the value obtained by performing XPS surface analysis of alumina particle samples using X-ray photoelectron spectroscopy to acquire the abundance ratio (atom%) of each element, and then converting the molybdenum content to oxide equivalent, thereby determining the MoO3 content relative to 100 mass% of the surface layer of the alumina particles.

[0074] The P2O4 content (P2) mentioned above refers to the value obtained by performing XPS surface analysis of alumina particle samples using X-ray photoelectron spectroscopy to acquire the abundance ratio (atom%) of each element, and then converting the phosphorus content to oxide equivalent, thereby determining the P2O4 content relative to 100% by mass of the surface layer of the alumina particles.

[0075] XPS surface analysis can be performed using a scanning X-ray photoelectron spectroscopy (XPS) analyzer (e.g., QUANTERA SXM from ULVAC-PHI), with a monochromatic Al-Kα X-ray source.

[0076] In this specification, when alumina particles are analyzed using the above-mentioned X-ray photoelectron spectroscopy (XPS) apparatus, the sample can be pressed and fixed onto double-sided tape, and compositional analysis can be performed under the following conditions. • X-ray source: Monochromatic Al-Kα, beam diameter 100 μmφ, output 25W • Measurement: Area measurement (1000 μm square), n=3 • Charge correction: C1s = 284.8eV

[0077] In the alumina particles of the embodiment, it is preferable that the molybdenum is unevenly distributed on the surface of the alumina particles.

[0078] In the alumina particles of the embodiment, it is preferable that the phosphorus is unevenly distributed on the surface of the alumina particles.

[0079] Herein, in this specification, "surface layer" refers to the area within 10 nm from the surface of the alumina particles in the embodiment. This distance corresponds to the detection depth of the XPS used for measurement in the example.

[0080] Here, "molybdenum being concentrated in the surface layer" means that the mass of molybdenum or molybdenum compounds per unit volume in the surface layer is greater than the mass of molybdenum or molybdenum compounds per unit volume in areas other than the surface layer.

[0081] In the alumina particles of this embodiment, the uneven distribution of molybdenum on the surface of the alumina particles can be confirmed by the fact that the MoO3 content (M2) relative to 100% by mass of the surface of the alumina particles, as determined by XPS surface analysis of the alumina particles, is greater than the MoO3 content (M1) relative to 100% by mass of the alumina particles, as determined by XRF (X-ray fluorescence) analysis of the alumina particles.

[0082] In the alumina particles of the embodiment, as an indicator that molybdenum is unevenly distributed on the surface of the alumina particles, the surface distribution ratio (M2 / M1) of the MoO3 content (M2) to the MoO3 content (M1) is preferably greater than 1 and 20 or less, more preferably 1.05 to 17, and even more preferably 1.5 to 5.

[0083] By unevenly distributing molybdenum or molybdenum compounds on the surface, superior properties such as catalytic activity can be efficiently imparted compared to cases where molybdenum or molybdenum compounds are uniformly present not only on the surface but also in other layers (inner layers).

[0084] Here, "predominance of phosphorus in the surface layer" means a state in which the mass of phosphorus or phosphorus compounds per unit volume in the surface layer is greater than the mass of phosphorus or phosphorus compounds per unit volume in areas other than the surface layer.

[0085] In the alumina particles of this embodiment, the uneven distribution of phosphorus on the surface of the alumina particles can be confirmed by the fact that the P2O5 content (P2) relative to 100% by mass of the surface of the alumina particles, as determined by XPS surface analysis of the alumina particles, is greater than the P2O5 content (P1) relative to 100% by mass of the alumina particles, as determined by XRF (X-ray fluorescence) analysis of the alumina particles.

[0086] In the alumina particles of the embodiment, as an indicator that phosphorus is unevenly distributed on the surface of the alumina particles, the surface distribution ratio (P2 / P1) of the P2O5 content (P2) to the P2O5 content (P1) is preferably greater than 1 and 20 or less, more preferably between 1.1 and 17, and even more preferably between 1.5 and 15.

[0087] By causing phosphorus or phosphorus compounds to be unevenly distributed on the surface, it is possible to efficiently impart superior properties, such as improved dispersibility in resins containing basic functional groups, compared to cases where phosphorus or phosphorus compounds are uniformly distributed not only on the surface but also in other layers (inner layers).

[0088] The alumina particles of the embodiment may further contain lithium, potassium, or sodium in addition to molybdenum and the phosphorus mentioned above.

[0089] The alumina particles of the embodiment may further contain silicon, which is known to be usable as a shape-controlling agent, in addition to the phosphorus mentioned above. However, since good shape control of the alumina particles is possible even without using silicon, the alumina particles of the embodiment may substantially not contain silicon.

[0090] The alumina particles of the embodiment may contain phosphorus on their surface. The molar ratio of P to Al [P] / [Al], measured by XPS analysis, is preferably 0.001 or higher, more preferably 0.01 or higher, even more preferably 0.02 or higher, and particularly preferably 0.1 or higher. The upper limit of the molar ratio [P] / [Al] value in the aforementioned XPS analysis is not particularly limited, but it may be 0.5 or less, 0.4 or less, or 0.3 or less.

[0091] The alumina particles are preferably such that the molar ratio of P to Al [P] / [Al] obtained by XPS analysis is between 0.001 and 0.9, more preferably between 0.01 and 0.8, and even more preferably between 0.02 and 0.7. Having the molar ratio of P to Al within the above range, as obtained by XPS analysis, results in a particularly strong acidity on the surface, which lowers the isoelectric point of the zeta potential. This is preferable because it allows for suitable dispersibility when mixed with compounds, for example, those having basic functional groups.

[0092] The alumina particles of this embodiment contain molybdenum and phosphorus, and therefore, compared to alumina particles that do not contain these elements, their isoelectric point of zeta potential is shifted to the acidic side, resulting in superior dispersibility. Furthermore, by utilizing the properties of molybdenum contained in the alumina particles, it may be possible to apply them to oxidation reaction catalysts and optical materials.

[0093] The pH at the isoelectric point where the zeta potential of the alumina particles in the embodiment is 0 (zero) is preferably in the range of 0 to 3, and more preferably in the range of 0 to 2.

[0094] The specific surface area of ​​the alumina particles in this embodiment, as determined by the BET method, is 0.1 to 10 m². 2 It may also be / g, 0.1~2m 2 It may also be / g, 0.3~1m 2 / g is also acceptable.

[0095] The alumina particles of this embodiment have a controlled shape and can be suitably used for a variety of applications. The alumina particles of this embodiment contain α-alumina crystals and can have a plate-like or card-house-like shape with a high aspect ratio. Due to their large specific surface area and high brightness, such alumina particles can be suitably used as a thermally conductive filler, a high-brightness pigment, an automotive exterior paint, a cosmetic, an abrasive, a conductive powder substrate, and a lubricant for resin films.

[0096] <Resin composition> The alumina particles of the embodiment can be used as a resin composition by being compounded with a resin. As one embodiment, a resin composition containing the alumina particles of the embodiment and a resin is provided. There are no particular limitations on the resin; it may be a polymer, oligomer, or monomer. It may be a thermosetting resin or a thermoplastic resin.

[0097] (thermosetting resin) Thermosetting resins are resins that have the property of becoming substantially insoluble and infusible when cured by heating or by means such as radiation or catalysts. For example, they may be well-known and conventional resins used in molding materials, etc. Specifically, examples include novolac-type phenolic resins such as phenol novolac resins and cresol novolac resins; phenolic resins such as unmodified resol phenolic resins and oil-modified resol phenolic resins modified with tung oil, linseed oil, walnut oil, etc.; bisphenol-type epoxy resins such as bisphenol A epoxy resins and bisphenol F epoxy resins; novolac-type epoxy resins such as fatty acid chain-modified bisphenol-type epoxy resins, novolac epoxy resins, and cresol novolac epoxy resins; epoxy resins such as biphenyl-type epoxy resins and polyalkylene glycol-type epoxy resins; resins having a triazine ring such as urea resins and melamine resins; vinyl resins such as (meth)acrylic resins and vinyl ester resins; unsaturated polyester resins, bismaleimide resins, polyurethane resins, diallyl phthalate resins, silicone resins, resins having a benzoxazine ring, cyanate ester resins, etc., and they may be polymers, oligomers, or monomers.

[0098] The thermosetting resins described above may be used together with a curing agent. The curing agent used in this case can be a combination of the thermosetting resin and a known and commonly used curing agent. For example, if the thermosetting resin is an epoxy resin, any of the compounds commonly used as curing agents can be used, such as amine compounds, amide compounds, acid anhydride compounds, and phenolic compounds. Specifically, amine compounds include diaminodiphenylmethane, diethylenetriamine, triethylenetetramine, diaminodiphenylsulfone, isophoronediamine, imidazole, BF3-amine complex, and guanidine derivatives. Amide compounds include dicyandiamide and polyamide resins synthesized from a linolenic acid dimer and ethylenediamine. Acid anhydride compounds include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, maleic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, and methylhexahydrophthalic anhydride. Phenolic compounds include phenol novolac resins, cresol novolac resins, aromatic hydrocarbon formaldehyde resin-modified phenolic resins, dicyclopentadienephenol addition resins, phenol aralkyl resins (Zyloc resins), polyvalent phenol novolac resins synthesized from polyvalent hydroxy compounds and formaldehyde, such as resorcinol novolac resins, naphthol aralkyl resins, trimethylol methane resins, tetraphenyloleethane resins, naphthol novolac resins, naphthol-phenol copolymer novolac resins, and naphthol-C Examples of polyhydric phenol compounds include resol-co-condensed novolac resins, biphenyl-modified phenol resins (polyhydric phenol compounds in which the phenol nucleus is linked by a bismethylene group), biphenyl-modified naphthol resins (polyhydric naphthol compounds in which the phenol nucleus is linked by a bismethylene group), aminotriazine-modified phenol resins (polyhydric phenol compounds in which the phenol nucleus is linked by melamine, benzoguanamine, etc.), and alkoxy-group-containing aromatic ring-modified novolac resins (polyhydric phenol compounds in which the phenol nucleus and alkoxy-group-containing aromatic ring are linked by formaldehyde). These curing agents may be used alone or in combination of two or more types.

[0099] In the resin composition of the embodiment, the proportions of the thermosetting resin and the curing agent are not particularly limited. However, for example, when the curable resin is an epoxy resin, it is preferable to use an amount such that the amount of active groups in the curing agent is 0.7 to 1.5 equivalents for every 1 equivalent of epoxy groups in the epoxy resin, in order to obtain a product with good curing properties.

[0100] Furthermore, if necessary, a curing accelerator can be appropriately used in combination with the thermosetting resin in the resin composition of the embodiment. For example, when the curable resin is an epoxy resin, various curing accelerators can be used, such as phosphorus compounds, tertiary amines, imidazoles, organic acid metal salts, Lewis acids, and amine complex salts.

[0101] Furthermore, if necessary, a curing catalyst can be used in combination with the thermosetting resin as appropriate, such as known and conventional thermal polymerization initiators and activated energy ray polymerization initiators.

[0102] (thermoplastic resin) Examples of thermoplastic resins that may be used in the resin composition of the embodiment include well-known and commonly used resins for molding materials, etc. Specifically, examples include polyethylene resin, polypropylene resin, polymethyl methacrylate resin, polyvinyl acetate resin, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, polyvinyl chloride resin, polystyrene resin, polyacrylonitrile resin, polyamide resin, polycarbonate resin, polyacetal resin, polyethylene terephthalate resin, polyphenylene oxide resin, polyphenylene sulfide resin, polysulfone resin, polyethersulfone resin, polyetheretherketone resin, polyallylsulfone resin, thermoplastic polyimide resin, thermoplastic urethane resin, polyaminobismaleimide resin, polyamideimide resin, polyetherimide resin, bismaleimide triazine resin, polymethylpentene resin, fluorine resin, liquid crystal polymer, olefin-vinyl alcohol copolymer, ionomer resin, polyarylate resin, acrylonitrile-ethylene-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-styrene copolymer, and the like. At least one type of thermoplastic resin can be selected and used, but it is also possible to use a combination of two or more thermoplastic resins depending on the purpose.

[0103] The resin composition of the embodiment may contain other compounds as needed, and to the extent that the effects of the invention can be obtained, external lubricants, internal lubricants, antioxidants, flame retardants, light stabilizers, ultraviolet absorbers, silane-based, titanate-based, or aluminate-based coupling agents, reinforcing materials such as glass fibers or carbon fibers, fillers, various colorants, etc. may be added. Furthermore, stress-reducing agents (stress-relaxing agents) such as silicone oil, liquid rubber, rubber powder, butadiene copolymer rubbers such as methyl acrylate-butadiene-styrene copolymer and methyl methacrylate-butadiene-styrene copolymer, and silicone compounds can also be used.

[0104] The resin composition of the embodiment is obtained by mixing the alumina particles of the embodiment, a resin, and other compounding materials as needed. The mixing method is not particularly limited and can be done by known and conventional methods.

[0105] When the resin is a thermosetting resin, a general method is to thoroughly mix the thermosetting resin, the alumina particles of the embodiment, and other components as needed using a mixer, etc., and then knead it with a three-roll press or the like to obtain a fluid liquid composition, or to thoroughly mix a predetermined amount of thermosetting resin, the alumina particles of the embodiment, and other components as needed using a mixer, etc., then melt-knead it with a mixing roll, extruder, etc., and then cool it to obtain a solid composition. When a curing agent or catalyst is included, it is preferable that the curable resin and these components are thoroughly and uniformly mixed, and it is even more preferable that the alumina particles of the embodiment are uniformly dispersed and mixed.

[0106] A common method when the resin is a thermoplastic resin is to pre-mix the thermoplastic resin, the alumina particles of the embodiment, and other components as needed using various mixers such as a tumbler or Henschel mixer, and then melt-knead them using a mixer such as a Banbury mixer, rolls, brabender, single-screw compounding extruder, twin-screw compounding extruder, kneader, or mixing roll. The melt-kneading temperature is not particularly limited, but is generally in the range of 240 to 320°C.

[0107] When preparing the resin composition of the embodiment, the mixing ratio of the alumina particles of the embodiment to the non-volatile content of the resin is not particularly limited, but it is preferable to select from the range of 0.1 to 900 parts of alumina particles per 100 parts by mass of the non-volatile content of the resin.

[0108] <Molded body> A molded article can be obtained by molding the resin composition of the embodiment. As one embodiment, a molded article obtained by molding the resin composition of the embodiment is provided. The resin molded article can be obtained by known and conventional methods.

[0109] For example, if the resin contained in the resin composition is a thermosetting resin, the curing method should be the same as that for general thermosetting resin compositions such as epoxy resin compositions. For example, resin compositions in which the resin is epoxy resin can be cured by heat, and the heating temperature conditions should be appropriately selected depending on the type of curing agent used and the application, and heating within a temperature range of room temperature to about 250°C is sufficient. In the case of active energy ray curable resins, curing and molding can be performed by irradiating them with active energy rays such as ultraviolet rays or infrared rays.

[0110] Furthermore, even when the resin in the embodiment is a thermoplastic resin, the molded product can be produced using known and conventional molding methods. Examples include injection molding, ultra-high-speed injection molding, injection compression molding, two-color molding, hollow molding methods such as gas-assisted molding, molding methods using insulated molds, molding methods using rapidly heated molds, foam molding (including supercritical fluids), insert molding, IMC (in-mold coating) molding, extrusion molding, sheet molding, rotational molding, lamination molding, and press molding. Molding methods using a hot runner system can also be used. There are no restrictions on the shape, pattern, color, dimensions, etc. of the molded product; these can be arbitrarily set according to the intended use of the molded product.

[0111] <Method for manufacturing alumina particles> [Firing process] The alumina particles of this embodiment contain phosphorus and molybdenum. An example of a method for producing the alumina particles of this embodiment is to calcine an aluminum-containing compound in the presence of molybdenum and phosphorus.

[0112] As one embodiment, a method for producing alumina particles is provided, which includes a step of calcining an aluminum compound in the presence of a molybdenum compound and a phosphorus compound. Specifically, it is possible to produce them by a method including, for example, any of the following steps. 1) A process of calcining a mixture of a molybdenum compound, a phosphorus compound, and an aluminum compound. 2) A process of calcining a mixture of a molybdenum-containing aluminum compound and a phosphorus compound. 3) A process of calcining a mixture of a phosphorus-containing aluminum compound and a molybdenum compound. 4) A process of calcining a mixture of a phosphorus-containing molybdenum compound and an aluminum compound.

[0113] Here, in all cases, such as using the molybdenum-containing aluminum compound and phosphorus compound in 2), using the phosphorus-containing aluminum compound and molybdenum compound in 3), and using the phosphorus-containing molybdenum compound and aluminum compound in 4), the aluminum compound is considered to be calcined in the presence of the molybdenum compound and the phosphorus compound.

[0114] The state of the above compounds during calcination is not particularly limited, as long as they exist in the same space. Specifically, the mixture may be obtained by simple mixing of powders, mechanical mixing using a pulverizer, or mixing using a mortar and pestle, and the mixture may be obtained in a dry or wet state.

[0115] In any of the methods described in 1) to 4) above, alumina particles of the embodiment containing phosphorus and molybdenum can be obtained by calcining a mixture of the respective compounds.

[0116] During firing, aluminum atoms and molybdenum atoms react to form aluminum molybdate. This process is called the fluxing method, and the molybdenum-containing compound is called the fluxing agent.

[0117] The flux method is classified as a solution method. More specifically, the flux method is a crystal growth method that utilizes the fact that the two-component phase diagram of the crystal-flux system exhibits a eutectic type. The mechanism of the flux method is presumed to be as follows: When a mixture of solute and flux is heated, the solute and flux become liquid phases. At this time, since the flux is a flux, in other words, the two-component phase diagram of the solute-flux system exhibits a eutectic type, so the solute melts at a temperature lower than its melting point and forms a liquid phase. In this state, when the flux is evaporated, the concentration of the flux decreases, in other words, the effect of the flux on lowering the melting point of the solute is reduced, and crystal growth of the solute occurs with the evaporation of the flux as the driving force (flux evaporation method). Crystal growth in a liquid-phase flux is also a preferred method, and crystal growth of the solute can also be induced by cooling the liquid phase of the solute and flux (slow cooling method).

[0118] The flux method has several advantages, including the ability to grow crystals at temperatures far below the melting point, precise control of the crystal structure, and the formation of polyhedral crystals with their own shape.

[0119] In the flux method for producing alumina particles using a molybdenum compound as a flux, the mechanism is not entirely clear, but it is presumed to be as follows: When an aluminum compound is calcined in the presence of a molybdenum compound, aluminum molybdate is formed first. At this time, as can be understood from the explanation above, the aluminum molybdate grows alumina crystals at a temperature lower than the melting point of alumina. Then, through processes such as the decomposition of aluminum molybdate and the evaporation of the flux, crystal growth is accelerated, and alumina particles can be obtained. In other words, the molybdenum compound functions as a flux, and alumina particles are produced via an intermediate called aluminum molybdate.

[0120] Furthermore, phosphorus or phosphorus compounds play an important role in plate-like crystal growth as shape-controlling agents. In the commonly used molybdenum oxide flux method, molybdenum oxide reacts with an aluminum compound to form aluminum molybdate, and then the change in chemical potential during the decomposition of this aluminum molybdate acts as the driving force for crystallization, resulting in the formation of hexagonal bipyramidal polyhedral particles with well-developed euhedral planes (113). In the manufacturing method of the embodiment, it is thought that phosphorus or phosphorus compounds localize near the particle surface during the α-alumina growth process, significantly inhibiting the growth of euhedral planes (113). As a result, the growth of crystal orientations in the plane direction becomes relatively faster, the (006) plane grows, and a plate-like morphology can be formed.

[0121] It should be noted that the above mechanism is merely speculative, and even if the effects of the present invention are obtained by a mechanism different from the above mechanism, it is still within the technical scope of the present invention.

[0122] The flux method is preferably a reaction at a firing temperature of 700°C or higher, in which aluminum atoms and molybdenum atoms react to form aluminum molybdate. Furthermore, a firing temperature of 900°C or higher is preferable because it allows for the decomposition of aluminum molybdate and facilitates the efficient formation of plate-like shapes through the action of phosphorus, thus facilitating the production of plate-like or card-house-like particles. Alternatively, instead of using a molybdenum compound as a fluxing agent for an aluminum compound, the same effect can be obtained by directly using molybdenum-containing aluminum and firing it at a temperature of 700°C or higher.

[0123] Furthermore, as the firing temperature is increased, the alumina particles undergo crystal growth in the presence of molybdenum, resulting in a significant increase in the proportion of α-alumina crystals. A firing temperature of 900°C or higher is preferable because it results in an α-crystallization rate of 90% by weight or more of the alumina particles.

[0124] Generally, controlling the shape of α-alumina crystals obtained after firing requires high-temperature firing at over 2000°C, close to the melting point of α-alumina. However, this presents significant challenges for industrial use due to the strain on the firing furnace, limitations on the heat-resistant materials used in the furnace, and fuel costs.

[0125] The manufacturing method of the embodiment can be carried out even at high temperatures exceeding 2000°C, but the presence of molybdenum atoms makes it possible to form α-alumina particles that are plate-shaped or card-house shaped with a high α-crystallization rate and a high aspect ratio, regardless of the shape of the precursor, even at temperatures considerably lower than the melting point of α-alumina, such as 1600°C or below.

[0126] According to one embodiment of the present invention, even under conditions where the firing temperature is 900 to 1600°C, alumina particles with a high aspect ratio and an α-crystallization rate of 90% by weight or more can be formed at low cost and efficiently. Firing at a temperature of 950 to 1500°C is preferred, and firing at a temperature of 1000 to 1400°C is more preferred.

[0127] Regarding the firing time, it is preferable to raise the temperature to a predetermined firing temperature within a range of 15 minutes to 10 hours, and to hold the temperature at that temperature for 5 minutes or more, and more preferably within a range of 5 minutes to 100 hours. To efficiently form alumina particles, a firing and holding time of approximately 10 minutes to 15 hours is more preferable. By selecting firing temperatures of 900-1600°C and firing holding times of 10 minutes to 15 hours, alumina particles with an α-crystallization rate of 90% by weight or more can be easily obtained. By selecting firing temperatures of 1000-1400°C and firing holding times of 10 minutes to 15 hours, highly crystalline alumina particles can be easily obtained.

[0128] For firing, an oxygenated atmosphere such as air or oxygen, or an inert atmosphere such as nitrogen, argon, or carbon dioxide are preferred, and an air atmosphere is more preferable when considering cost.

[0129] The apparatus used for firing is not necessarily limited, and a so-called firing furnace can be used. Preferably, the firing furnace is made of a material that does not react with sublimated molybdenum oxide, and furthermore, it is preferable to use a highly sealed firing furnace so that molybdenum oxide can be utilized efficiently.

[0130] The above-mentioned alumina particles can be obtained by calcining an aluminum-containing compound in the presence of molybdenum and phosphorus. Furthermore, calcining in the presence of potassium is preferable because it allows for the stable acquisition of plate-shaped or card-house-shaped particles.

[0131] (Molybdenum compounds) Molybdenum compounds that can be used as raw materials function as fluxing agents in the α-crystal growth of alumina. While there are no particular limitations on the molybdenum compounds, molybdenum oxide and molybdenum metals can be used, as well as acid anions (MoO) formed by bonding with oxygen. x n- Examples of compounds containing ) include:

[0132] The aforementioned acid root anion (MoO x n- Compounds containing ) are not particularly limited, but include molybdic acid, sodium molybdate, potassium molybdate, lithium molybdate, and H3PMo 12 O 40 H3SiMo 12 O 40 NH4Mo7O 12 Examples include molybdenum disulfide, etc.

[0133] Of the molybdenum compounds mentioned above, molybdenum oxide is preferred from a cost standpoint. Furthermore, the molybdenum compounds mentioned above may be used individually or in combination of two or more.

[0134] Furthermore, the molybdenum-containing aluminum compounds and phosphorus-containing molybdenum compounds described later can also be used as molybdenum compounds because they contain molybdenum.

[0135] The amount of molybdenum compound used is not particularly limited, but the molar ratio of molybdenum to aluminum (Mo / Al) in the entire raw material compound (e.g., the mixture to be calcined) is preferably 0.005 to 10, more preferably 0.007 to 5, and even more preferably 0.01 to 3. Furthermore, when the flux method is employed and a molybdenum compound is used as the fluxing agent, the alumina particles will contain molybdenum, which can be used as evidence to identify the manufacturing method by which the unknown alumina particles were produced.

[0136] (Phosphorus compounds) Phosphorus or phosphorus compounds that can be used as raw materials include elemental phosphorus (P), phosphorus oxide (P4O4O4O4). 10 , P2O5), aluminum phosphate (AlPO4), aluminum dihydrogen phosphate (Al(H2PO4)3), aluminum trihydrogen phosphate (AlH2(P3O 10 )), Phosphorus molybdate (H3(MoO3) 12 Examples include PO4, organophosphorus compounds such as trialkylphosphines, triarylphosphines, phosphine oxides, phosphinates, phosphates, and phospholanes; phosphates such as organic amine phosphates; compounds such as phosphoric acid, organophosphoric acid and polyphosphoric acid derivatives, and oxides or hydrates thereof, and at least one selected from the group. Among these, phosphorus oxide (P4O) is preferred. 10 These are P2O5, aluminum phosphate (AlPO4), aluminum dihydrogen phosphate (Al(H2PO4)3), and phosphomolybdate hydrate. Phosphorus or phosphorus compounds can be used as shape control agents. These shape control agents contribute to the plate-like crystal growth of alumina by calcining the alumina compound in the presence of a molybdenum compound.

[0137] There are no particular limitations on the amount of phosphorus compound used, but the molar ratio of phosphorus to aluminum (P / Al) in the entire raw material compound (for example, the aforementioned mixture to be calcined) is preferably 0.0001 to 3.0, more preferably 0.0005 to 0.5, and even more preferably 0.001 to 0.1 for good productivity and favorable crystal growth. When the amount of phosphorus compound used is within the above range, it is preferable because plate-shaped alumina particles with a high aspect ratio and excellent dispersibility, or cardhouse-shaped alumina particles made of plate-shaped alumina, are easily obtained.

[0138] Furthermore, the phosphorus-containing molybdenum compounds described later can also be used as phosphorus compounds because they contain phosphorus.

[0139] (Aluminum compounds) The aluminum compounds that can be used as raw materials are not particularly limited as long as they can be converted into alumina by calcination. For example, aluminum chloride, aluminum sulfate, basic aluminum acetate, aluminum hydroxide, boehmite, pseudoboehmite, transition alumina (γ-alumina, δ-alumina, θ-alumina, etc.), α-alumina, and mixed alumina having two or more crystalline phases can be used. The physical form of these precursor aluminum compounds, such as shape, particle size, and specific surface area, is not particularly limited.

[0140] The aluminum compound can be suitably used in any form, such as spherical, amorphous, or aspect-defined structures (wires, fibers, ribbons, tubes, etc.), or sheets.

[0141] Similarly, for aluminum compounds, solid aluminum compounds with particle sizes ranging from a few nanometers to several hundred micrometers can be suitably used.

[0142] The specific surface area of ​​the aluminum compound is not particularly limited. A larger specific surface area is preferable because the molybdenum atoms act more effectively, but by adjusting the firing conditions and the amount of molybdenum atoms used, compounds with any specific surface area can be used as raw materials.

[0143] Furthermore, the phosphorus-containing aluminum compounds described later can also be used as aluminum compounds because they contain aluminum.

[0144] (Molybdenum-containing aluminum compound) Examples of molybdenum-containing aluminum compounds that can be used as raw materials include aluminum molybdate.

[0145] (Phosphorus-containing aluminum compound) Examples of phosphorus-containing aluminum compounds that can be used as raw materials include aluminum phosphate (AlPO4), aluminum dihydrogen phosphate (Al(H2PO4)3), and aluminum tridihydrogen phosphate (AlH2(P3O 10 Examples include:

[0146] (Phosphorus-containing molybdenum compound) Examples of phosphorus-containing molybdenum compounds that can be used as raw materials include phosphomolybdic acid and phosphomolybdic acid hydrate.

[0147] (metal compound) As described later, the metal compound may have the function of promoting the crystal growth of alumina. The metal compound may be used during calcination if desired. However, since the metal compound may have the function of promoting the crystal growth of α-alumina, it is not essential for the production of alumina particles according to the present invention.

[0148] The metal compound is not particularly limited, but it is preferable to include at least one selected from the group consisting of Group II metal compounds and Group III metal compounds.

[0149] Examples of the aforementioned Group II metal compounds include magnesium compounds, calcium compounds, strontium compounds, and barium compounds.

[0150] Examples of the aforementioned Group III metal compounds include scandium compounds, yttrium compounds, lanthanum compounds, and cerium compounds.

[0151] The above-mentioned metal compounds refer to oxides, hydroxides, carbonides, and chlorides of metal elements. For example, yttrium compounds include yttrium oxide (Y2O3), yttrium hydroxide, and yttrium carbonate. Of these, the metal compound is preferably an oxide of a metal element. These metal compounds also include isomers.

[0152] Of these, it is preferable that the metal compounds are of the third period elements, the fourth period elements, the fifth period elements, and the sixth period elements; more preferably that they are of the fourth period elements and the fifth period elements; and even more preferably that they are of the fifth period elements. Specifically, it is preferable to use magnesium compounds, calcium compounds, yttrium compounds, and lanthanum compounds; more preferably that magnesium compounds, calcium compounds, and yttrium compounds are used; and particularly preferably that yttrium compounds are used.

[0153] The addition rate of the metal compound is preferably 0.02 to 20% by mass, and more preferably 0.1 to 20% by mass, relative to the total mass of aluminum atoms in the raw material compound (for example, the mixture to be calcined). An addition rate of 0.02% by mass or more of the metal compound is preferable because it allows for favorable crystal growth of α-alumina containing molybdenum. On the other hand, an addition rate of 20% by mass or less of the metal compound is preferable because it allows for the production of alumina particles with a low content of impurities derived from the metal compound.

[0154] In the firing process, a potassium compound or a sodium compound may be used in combination with the molybdenum compound as a fluxing agent.

[0155] (Potassium compounds) The potassium compound is not particularly limited, but examples include potassium chloride, potassium chlorite, potassium chlorate, potassium sulfate, potassium bisulfate, potassium sulfite, potassium bisulfite, potassium nitrate, potassium carbonate, potassium bicarbonate, potassium acetate, potassium oxide, potassium bromide, potassium bromate, potassium hydroxide, potassium silicate, potassium phosphate, potassium hydrogen phosphate, potassium sulfide, potassium hydrogen sulfide, potassium molybdate, potassium tungstate, etc. In this case, the potassium compound includes isomers, as in the case of molybdenum compounds. Of these, potassium carbonate, potassium bicarbonate, potassium oxide, potassium hydroxide, potassium chloride, potassium sulfate, and potassium molybdate are preferred, and potassium carbonate, potassium bicarbonate, potassium chloride, potassium sulfate, and potassium molybdate are more preferred. The potassium compounds mentioned above may be used individually or in combination of two or more.

[0156] Of the above, potassium molybdate contains molybdenum and therefore may also function as a molybdenum compound as described above. When potassium molybdate is used as a flux, it can produce the same effects as when molybdenum compounds and potassium compounds are used as fluxes.

[0157] (Sodium compounds) The sodium compound is not particularly limited, and known compounds can be used. Specific examples include sodium carbonate, sodium molybdate, sodium oxide, sodium sulfate, sodium hydroxide, sodium nitrate, sodium chloride, and metallic sodium. Of these, sodium carbonate, sodium molybdate, sodium oxide, and sodium sulfate are preferred from the viewpoint of easy industrial availability and handling. The sodium compound may be used alone or in combination of two or more.

[0158] Of the above, sodium molybdate contains molybdenum and therefore may also function as a molybdenum compound as described above. When sodium molybdate is used as a flux, it can produce the same effects as when molybdenum compounds and sodium compounds are used as fluxes.

[0159] As potassium or sodium compounds used during raw material preparation or produced during the heating process of calcination, water-soluble potassium or sodium compounds, such as potassium molybdate, do not vaporize even in the calcination temperature range and can be easily recovered by washing after calcination. This reduces the amount of molybdenum compounds released outside the calcination furnace, and significantly reduces production costs.

[0160] When using molybdenum and potassium compounds as fluxing agents, the molar ratio of molybdenum to potassium (Mo / K) in the entire raw material compound (for example, the mixture to be calcined) is preferably 5 or less, more preferably 0.01 to 3, and even more preferably 0.5 to 1.5, as this can further reduce production costs. It is preferable that the molar ratio (Mo / K) is within the above range because it can yield alumina particles with a larger particle size.

[0161] Similarly, when using molybdenum compounds and sodium compounds as fluxing agents, the molar ratio of molybdenum to sodium (Mo / Na) in the entire raw material compound (for example, the aforementioned mixture to be calcined) is preferably 5 or less, more preferably 0.01 to 3, and even more preferably 0.5 to 1.5, as this can further reduce production costs. A molar ratio (Mo / Na) within the above range is preferable because it can yield alumina particles with a larger particle size.

[0162] (Manufacturing conditions for card-house-shaped alumina particles) As an example of conditions for efficiently producing cardhouse-shaped alumina particles, in the process of calcining an aluminum compound in the presence of a molybdenum compound and a phosphorus compound, (1) Using a raw material aluminum compound with a specific average particle size, (2) Limit the amount of molybdenum compound used as a raw material to a specific range. (3) Limit the amount of phosphorus compounds used in raw materials to a specific range. These are some examples. Of the conditions (1) to (3), it is preferable that at least condition (2) is met, that conditions (2) and (3) are met, and that all conditions (1) to (3) are met.

[0163] Specifically, for example, (1-1) As the raw material aluminum compound, an aluminum compound corresponding to the particle size of the desired cardhouse-shaped alumina particles is used, preferably with an average particle size of 3 to 300 μm, more preferably 5 to 100 μm. (2-1) The molar value of molybdenum element (Mo / Al) per mole of aluminum element in the entire raw material compound is preferably 0.005 to 0.24 moles, and more preferably 0.03 to 0.2 moles. (3-1) The molar value of phosphorus element per mole of aluminum element in the entire raw material compound (P / Al) is preferably 0.003 to 0.09, and more preferably 0.004 to 0.02.

[0164] Furthermore, alumina particles having a cardhouse structure can have their average particle size and shape arbitrarily adjusted through the crushing and classification processes described later.

[0165] [Cooling process] The method for producing alumina particles may include a cooling step. This cooling step is a step of cooling the alumina particles that have undergone crystal growth in the firing step.

[0166] The cooling rate is not particularly limited, but is preferably 1 to 1000°C / hour, more preferably 5 to 500°C / hour, and even more preferably 50 to 100°C / hour. A cooling rate of 1°C / hour or higher is preferable because it can shorten the manufacturing time. On the other hand, a cooling rate of 1000°C / hour or lower is preferable because the firing container is less likely to crack due to thermal shock and can be used for a longer period.

[0167] The cooling method is not particularly limited; it may be natural cooling or a cooling device may be used.

[0168] [Post-processing steps] The embodiment of the method for producing alumina particles may include a post-treatment step. This post-treatment step is a post-treatment step for the alumina particles and is a step of removing excess molybdenum. The post-treatment step may be performed after the calcination step described above, or after the cooling step described above, or after both the calcination step and the cooling step. Furthermore, it may be repeated two or more times as necessary.

[0169] Post-treatment methods include washing and high-temperature treatment. These can be performed in combination.

[0170] The aforementioned cleaning method is not particularly limited, but excess molybdenum can be removed by cleaning with water, an aqueous ammonia solution, an aqueous sodium hydroxide solution, or an acidic aqueous solution.

[0171] In this process, the molybdenum content in the alumina particles can be controlled by appropriately changing the concentration and amount of water, ammonia solution, sodium hydroxide solution, and acidic solution used, as well as the washing area and washing time.

[0172] Another method of high-temperature treatment is to raise the temperature above the sublimation point or boiling point of the molybdenum compound.

[0173] [Grinding process] In calcined products obtained through the calcination process, alumina particles may aggregate and fail to meet the suitable particle size range for the intended application. Therefore, the alumina particles may be crushed as needed to meet the suitable particle size range.

[0174] The method of grinding the calcined material is not particularly limited, and conventional known grinding methods such as ball mills, jaw crushers, jet mills, disc mills, spectromills, grinders, and mixer mills can be applied.

[0175] [Classification process] The calcined material containing alumina particles obtained through the calcination process may be subjected to classification as appropriate to adjust the range of particle sizes. "Classification" refers to the operation of grouping particles according to their size. Classification can be either wet or dry, but dry classification is preferred from a productivity standpoint. Dry classification methods include sieving and wind classification, which uses the difference between centrifugal force and fluid drag. From the standpoint of classification accuracy, wind classification is preferred and can be performed using classifiers such as airflow classifiers utilizing the Coanda effect, swirling airflow classifiers, forced vortex centrifugal classifiers, and semi-free vortex centrifugal classifiers. The grinding and classification processes described above can be carried out at the necessary stage. By choosing whether or not to perform these grinding and classification processes, and by selecting their conditions, for example, the average particle size of the resulting alumina particles can be adjusted.

[0176] Alumina particles of the embodiment, or alumina particles obtained by the manufacturing method of the embodiment, that exhibit little or no aggregation are preferable because they exhibit their inherent properties more easily, are easier to handle, and have superior dispersibility when dispersed in a dispersion medium.

[0177] The method for producing alumina particles according to the above embodiment makes it possible to easily produce alumina particles with little or no aggregation. Therefore, it has the excellent advantage that alumina particles with the desired excellent properties can be produced with high productivity without having to perform the above-mentioned grinding and classification steps. [Examples]

[0178] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to the following examples.

[0179] [Example 1] A mixture of 15.6g of aluminum hydroxide (FR-3801 from Hefei Zhongke Flame Retardant New Material), 0.72g of molybdenum trioxide (manufactured by Nippon Inorganic Chemical Co., Ltd.), and 1.41g of phosphorus pentoxide (manufactured by Kanto Chemical Co., Ltd.) was shaken and mixed for 10 minutes. This mixture was placed in an alumina crucible (BA-1 from Tokyo Glassware Co., Ltd.) and covered. This crucible was then heated in a high-speed electric furnace (SC-2045D-SP from Motoyama Co., Ltd.) at a heating rate of 5 degrees / min and a maximum temperature of 1100°C. After firing at the maximum temperature for 10 hours, the mixture was allowed to cool naturally to room temperature, and the resulting powder was collected. Next, the powder obtained above was dispersed in 150 mL of 0.5% ammonia water. The dispersion solution was stirred at room temperature (25-30°C) for 0.5 hours, the ammonia water was removed by filtration, and the remaining molybdenum on the particle surface was removed by washing with water and drying to obtain the powder of Example 1.

[0180] [Example 2] A mixture of 10.2g of aluminum oxide (AO9999 from Hefei Zhongke Flame Retardant New Material) and 43.2g of molybdenum trioxide (manufactured by Nippon Inorganic Chemical Co., Ltd.) was shaken and mixed for 10 minutes. This mixture was divided into five equal portions and placed in an alumina crucible (BA-1, manufactured by Tokyo Glassware Co., Ltd.), which was then covered. These five crucibles were then heated in a high-speed electric furnace (SC-2045D-SP, manufactured by Motoyama Co., Ltd.) at a heating rate of 5°C / min and a maximum temperature of 700°C. After firing at the maximum temperature for 10 hours, the furnace was allowed to cool naturally to room temperature, and aluminum molybdate was quantitatively recovered as an intermediate. A mixture of 5.5 g of aluminum molybdate and 0.07 g of phosphorus pentoxide (manufactured by Kanto Chemical) was shaken and mixed for 10 minutes. This mixture was placed in an alumina crucible (BA-1, manufactured by Tokyo Glassware) and covered. The crucible was then heated in a high-speed electric furnace (SC-2045D-SP, manufactured by Motoyama) at a heating rate of 5°C / min and a maximum temperature of 1100°C. After firing at the maximum temperature for 10 hours, the mixture was allowed to cool naturally to room temperature, and the resulting powder was collected. Next, the powder obtained above was dispersed in 150 mL of 0.5% ammonia water. The dispersion solution was stirred at room temperature (25-30°C) for 0.5 hours, the ammonia water was removed by filtration, and the remaining molybdenum on the particle surface was removed by washing with water and drying to obtain the powder of Example 2.

[0181] [Example 3] The powder of Example 3 was obtained in the same manner as in Example 1, except that instead of the mixture of Example 1, a mixture of 7.8 g of aluminum hydroxide (FR-3801 from Hefei Zhongke Flame Retardant New Material) and 3.9 g of phosphomolybdate hydrate (manufactured by Kanto Chemical Co., Ltd.) was used, which was shaken and mixed for 10 minutes.

[0182] [Example 4] The powder of Example 4 was obtained in the same manner as in Example 3, except that the amount of phosphomolybdate hydrate used was changed to 15.6 g and the maximum firing temperature was set to 1300°C.

[0183] [Example 5] The powder of Example 5 was obtained in the same manner as in Example 1, except that instead of the mixture of Example 1, a mixture of 10.2 g of transition alumina particles (AO9999, manufactured by CHALCO, with an average particle size of 45 μm) and 1.6 g of phosphomolybdate hydrate was used as the alumina source, and the mixture was shaken and mixed for 10 minutes.

[0184] [Example 6] The powder of Example 6 was obtained in the same manner as in Example 1, except that instead of the mixture of Example 1, a mixture of 10.2 g of transition alumina particles (AO9999, manufactured by CHALCO, with an average particle size of 45 μm) and 3.9 g of phosphomolybdic acid, which were shaken and mixed for 10 minutes, was used as the alumina source.

[0185] [Comparative Example 1] The powder of Comparative Example 1 was obtained in the same manner as in Example 1, except that a mixture of 15.6 g of aluminum hydroxide (FR-3801 from Hefei Zhongke Flame Retardant New Material) and 1.56 g of molybdenum trioxide (manufactured by Nippon Inorganic Chemical Co., Ltd.) was used, which was shaken and mixed for 10 minutes, instead of the mixture of Example 1.

[0186] [Comparative Example 2] The powder of Comparative Example 2 was obtained in the same manner as in Example 1, except that a mixture of 15.6 g of aluminum hydroxide (FR-3801 from Hefei Zhongke Flame Retardant New Material), 0.72 g of molybdenum trioxide (manufactured by Nippon Inorganic Chemical Co., Ltd.), and 0.16 g of silicon dioxide (special grade, manufactured by Kanto Chemical Co., Ltd.) was used, shaken and mixed for 10 minutes, instead of the mixture of Example 1.

[0187] <Rating> The powders produced in the above examples and comparative examples were used as samples, and the following evaluations were performed. The measurement methods are shown below.

[0188] [Particle size distribution measurement] The particle size distribution of the sample powder was measured dry using a laser diffraction dry particle size analyzer (HELOS (H3355) & RODOS, manufactured by Nippon Laser Co., Ltd.) under conditions of dispersion pressure of 3 bar and suction pressure of 90 mbar. The particle size at the point where the volume integrated % distribution curve intersects the horizontal axis at 10% from the smallest particle side was defined as D. 10 The particle size at the point where it intersects the horizontal axis at 50% is defined as D. 50 As such, the particle diameter at the point where the horizontal axis intersects with the 90% side from the small particle side is D. 90 They were calculated accordingly.

[0189] [Size measurement of plate-shaped alumina particles] The sample powder was imaged using a scanning electron microscope (SEM) (VE9800 from Keyence Corporation or JCM-7000 from JEOL Ltd.). For the smallest unit particles constituting the aggregates on the two-dimensional image (i.e., primary particles), the average of the maximum distances between two points on the contour lines of 50 randomly selected primary particles was defined as the average particle diameter of the plate-like alumina particles. The thickness was determined by using a scanning electron microscope (SEM) to measure the thickness of 50 plate-shaped alumina particles, and then using the average value. The aspect ratio was calculated using the following formula. Aspect ratio = Average particle diameter of plate-shaped alumina particles / Thickness of plate-shaped alumina particles

[0190] [Size measurement of plate-like alumina particles in card-house-shaped alumina particles] The sample powder was imaged using a scanning electron microscope (SEM), and for 50 randomly selected card-house-shaped alumina particles in the two-dimensional image, the maximum distance between two points on the contour line of the plate-like alumina located in the center of the alumina particle was determined. The average value of these distances was defined as the average particle diameter of the plate-like alumina in the card-house-shaped alumina particles. The thickness was determined by using a scanning electron microscope (SEM) to measure the thickness of 50 plates of alumina in the same manner, and then adopting the average value. The aspect ratio was calculated using the following formula. Aspect ratio = Average particle size of plate-like alumina / Thickness of plate-like alumina

[0191] [Crystal structure analysis: XRD (X-ray diffraction) method] The sample powder was packed into a 0.5 mm deep sample holder, which was then placed in a wide-angle X-ray diffraction (XRD) system (Ultima IV, manufactured by Rigaku Corporation). Measurements were performed using Cu / Kα rays, 40 kV / 40 mA, a scan speed of 2° / min, and a scanning range of 10-70°.

[0192] α-Al2O3 content (R A ) and AlPO4 content (R B The baseline value (I0) at 2θ = 15.0 ± 0.2° and the RIR value (K) of α-alumina were determined by the RIR (Reference Intensity Ratio) method from spectral data obtained by XRD analysis. A ), and the intensity of the peak around 2θ = 35.1 ± 0.2° that is attributed to the (10⁴) plane of α-alumina (I A ), as well as the RIR value of AlPO4 (K B ), and the intensity of the peak around 2θ = 21.7 ± 0.2° that is attributed to the (111) plane of AlPO4 (I B ) and the following equation (1 A ) and (1 B ) was derived from this. R A (wt%)=((I A -I0) / K A ) / (Σ((I-I0) / K))×100···(1 A ) R B (wt%)=((I B -I0) / K B ) / (Σ((I-I0) / K))×100···(1 B ) Furthermore, if other trace amounts of transition alumina (β, θ, κ, etc.) peaks are observed, the I of each strongest peak should be measured. X and the corresponding RIR value K X When using (where X represents the component of each transition alumina), the value of the above Σ((I-I0) / K) is I A , I B , and I X Each component and K A , K B, and K X This is a value described using each component of . In the analysis in this embodiment, I X The spectra of each component were below the detection limit.

[0193] The α-crystallization rate of alumina was determined by the RIR (Reference Intensity Ratio) method from spectral data obtained by XRD analysis. The baseline value (I0) at 2θ = 15.0 ± 0.2°, and the RIR value (K) of α-alumina were used. A ), and the intensity of the peak around 2θ = 35.1 ± 0.2° that is attributed to the (10⁴) plane of α-alumina (I A ) and the following equation (1 C ) was derived from this. α-crystallization rate of alumina (weight %) = ((I A -I0) / K A ) / (Σ((I-I0) / K))×100···(1 C ) Furthermore, if other trace amounts of transition alumina (β, θ, κ, etc.) peaks are observed, the I of each strongest peak should be measured. X and the corresponding RIR value K X When using (where X represents the component of each transition alumina), the value of the above Σ((I-I0) / K) is I A , each I X Each component and K A , each K X It is described using each component of . That is, equation (1 C The term added by the summation in the denominator of equation (1) is A (I B -I0) / K B This excludes the term ). In the analysis in this embodiment, I X The spectra of each component were below the detection limit.

[0194] The RIR values ​​used were those listed in the ICSD database, and the analysis was performed using the Integrated Powder X-ray Spectroscopy (PDXL) software (manufactured by Rigaku).

[0195] [XRF (X-ray fluorescence) analysis] Using a PrimusIV X-ray fluorescence analyzer (manufactured by Rigaku Corporation), approximately 70 mg of sample powder was placed on filter paper, covered with a PP film, and XRF (X-ray fluorescence) analysis was performed under the following conditions. Measurement conditions EZ Scan Mode Measuring elements: F~U Measurement time: Standard Measurement diameter: 10mm Residue (balancing components): None

[0196] By converting the aluminum and molybdenum content of alumina particles obtained by XRF analysis into oxide equivalents, the Al2O3 content (A1), MoO3 content (M1), and P2O5 content (P1) per 100% by mass of alumina particles were obtained.

[0197] [XPS surface analysis] Surface elemental analysis of the sample powder was performed using X-ray photoelectron spectroscopy (XPS) with an ULVAC-PHI QUANTERA SXM. Area measurements were taken in a 1000 μm square area, and the average value of n=3 measurements was obtained as atom% for each element. • X-ray source: Monochromatic Al-Kα, beam diameter 100 μmφ, output 25W • Measurement: Area measurement (1000 μm square), n=3 • Charge correction: C1s = 284.8eV

[0198] By converting the aluminum content and molybdenum content of the surface layer of alumina particles obtained by XPS analysis into oxide equivalents, the Al2O3 content (A2) (mass%), MoO3 content (M2) (mass%), P2O5 content (P2), and [P] / [Al] molar ratio per 100 mass% of the surface layer of alumina particles were determined.

[0199] [Isoelectric point measurement of alumina particles] Zeta potential measurements of alumina particles were performed using a zeta potential analyzer (Malvern, Zetasizer Nano ZSP). 20 mg of the sample and 10 mL of 10 mM KCl aqueous solution were stirred for 3 minutes in a foam remover (Sinky, ARE-310) in stirring / defoaming mode, and the supernatant after standing for 5 minutes was used as the measurement sample. Using an automatic titrator, 0.1 N HCl was added to the sample, and zeta potential measurements were performed in the pH range up to 2 (applied voltage 100 V, Monomodl mode), and the pH at the isoelectric point where the potential was 0 (zero) was determined.

[0200] [Measurement of specific surface area of ​​alumina particles] The specific surface area of ​​alumina particles was measured using a specific surface area meter (BELSORP-mini, manufactured by Microtrac-Bel Co., Ltd.), and the surface area per gram of sample, measured from the amount of nitrogen gas adsorbed by the BET method, was defined as the specific surface area (m²). 2 It was calculated as ( / g).

[0201] <Result> Table 1 shows the values ​​obtained from the above evaluation. "ND" stands for "not detected," indicating that no detection was found.

[0202] [Table 1]

[0203] Figures 1-8 show SEM images of the powders from the above examples and comparative examples, obtained by scanning electron microscopy (SEM). In each of the examples and comparative examples, plate-like or card-house-like particles were observed. Furthermore, the powders obtained in the examples were found to have few aggregates and excellent handling properties.

[0204] The results of the XRD analysis are shown in Figure 9. Peaks originating from α-alumina (α-Al2O3) were observed in the samples of each example. In addition, peaks originating from AlPO4 were observed in the samples of each example. Sharp peak scattering originating from α-alumina was observed, and no alumina crystal system peaks other than the α-crystalline structure were detected. From the ratio of the strongest peak heights of α-alumina and transition alumina, it was confirmed that the α-crystallization rate of the alumina particles in the examples was 99% by weight or more, indicating that they possess a dense crystalline structure.

[0205] The α-Al2O3 content (R) per 100 wt% of alumina particles, as determined by XRD analysis. A ) and AlPO4 content (R B The results are shown in Table 1. In this example, no peaks corresponding to molybdenum compounds were detected in the alumina particles analyzed by XRD (they were below the detection limit). It is thought that the molybdenum contained in these alumina particles did not grow as crystals but was attached to the surface of the alumina particles as amorphous material, which is why no peaks were detected in the XRD analysis.

[0206] From the results of the above SEM observation and XRD analysis, it was confirmed that the powders obtained in the examples and comparative examples were alumina particles containing alumina.

[0207] The alumina particles obtained in the examples and comparative examples are shown in Table 1 as D 50 It had average particle diameter, thickness, aspect ratio, and BET specific surface area.

[0208] The results from each example demonstrate that plate-shaped or card-house-shaped alumina particles can be produced by calcining an aluminum compound in the presence of a molybdenum compound and a phosphorus compound.

[0209] Furthermore, it was demonstrated that even at a relatively low firing temperature of 1100°C, it is possible to fire alumina particles with controlled shape and a high α-crystallization rate.

[0210] The plate-like alumina particles and the plate-like alumina constituting the card house-like alumina particles had a high aspect ratio as shown in Table 1. This indicates that in the flux method using a molybdenum compound as a fluxing agent, phosphorus can exhibit excellent functions as a shape control agent related to the growth of plate-like crystals.

[0211] The values of the above Al2O3 content (A1), MoO3 content (M1), P2O5 content (P1), Al2O3 content (A2), MoO3 content (M2), and P2O5 content (P2) are shown in Table 1.

[0212] From the results of the MoO3 content (M1) and the MoO3 content (M2), it can be expected that the alumina particles of Examples 1 to 6 contain molybdenum in the surface layer and various actions due to molybdenum, such as catalytic activity, will be exhibited.

[0213] From the results of the P2O5 content (P1) and the P2O5 content (P2), it can be expected that the alumina particles of Examples 1 to 6 contain phosphorus in the surface layer, can make the surface properties of the alumina particles more acidic, and various actions due to phosphorus will be exhibited, such as improving the affinity with basic organic compounds, various binders, and matrices.

[0214] Also, it was confirmed that the alumina particles obtained in the examples and comparative examples had the pH values of the isoelectric points shown in Table 1. It is推测 that the inclusion of molybdenum and phosphorus in the surface layer of the alumina particles shifts the pH value of the isoelectric point to the acidic side and the dispersibility is excellent.

[0215] Each configuration and their combinations in each embodiment are examples, and additions, omissions, substitutions, and other changes of the configuration are possible without departing from the gist of the present invention. Also, the present invention is not limited by each embodiment and is only limited by the scope of the claims.

Claims

1. Alumina particles containing phosphorus and molybdenum, The phosphorus is contained in the surface layer, or in both the surface and inner layers. The molybdenum is present in a form that adheres to the surface of the alumina particles and / or in a form that replaces some of the aluminum in the crystalline structure of the alumina. Alumina particles having a molar ratio [P] / [Al] of phosphorus concentration to aluminum concentration of 0.001 or higher, as measured by X-ray photoelectron spectroscopy (XPS), and having a plate-like shape.

2. D ５０ Alumina particles according to claim 1, wherein the diameter is 2 to 100 μm.

3. The alumina particle according to claim 2, wherein the average particle diameter of the primary particles of the alumina particle is 5 to 200 μm, and the aspect ratio obtained by dividing the average particle diameter of the primary particles of the alumina particle by its thickness is 2 to 100.

4. Alumina particles containing phosphorus and molybdenum, The phosphorus is contained in the surface layer, or in both the surface and inner layers. The molybdenum is present in a form that adheres to the surface of the alumina particles and / or in a form that replaces some of the aluminum in the crystalline structure of the alumina. Alumina particles having a molar ratio [P] / [Al] of phosphorus concentration to aluminum concentration of 0.001 or higher, as measured by X-ray photoelectron spectroscopy (XPS), and having a card-house-like shape.

5. D ５０ Alumina particles according to claim 4, wherein the diameter is 3 to 300 μm.

6. Alumina particles according to claim 4, comprising plate-shaped alumina having an average particle diameter of 5 to 200 μm, wherein the aspect ratio obtained by dividing the average particle diameter of each plate-shaped alumina by its thickness is 2 to 100.

7. A resin composition containing alumina particles according to any one of claims 1 to 6 and a resin.

8. A molded article obtained by molding the resin composition described in claim 7.

9. A method for producing alumina particles according to any one of claims 1 to 6, comprising the step of calcining an aluminum compound in the presence of a molybdenum compound and a phosphorus compound by a flux method.

10. The method for producing alumina particles according to claim 9, wherein the aluminum compound is solid.

11. A method for producing alumina particles according to claim 9, wherein the firing temperature is 900 to 1600°C.

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