Spherical metal oxide particle material and method for producing same, inorganic filler, resin composition, and slurry composition

Abstract

To provide a method for producing a spherical metal oxide particle material capable of reducing the content of aggregates and unburned metal by subjecting a spherical metal oxide produced by deflagration to wet sorting and wet removal of unburned metal. A problem was discovered to be that, when a wet operation is performed, particles aggregate in a subsequent drying step and become very hard. The problem was that it is possible to crush the aggregates to primary particles by a crusher or the like, but foreign matter may become admixed due to equipment wear, adequate crushing may be difficult, etc.　When the causes of aggregation during drying were studied, it was understood that bonding of adjacent particles occurs due to surface tension when liquid water dries. Therefore, it was discovered that aggregation can be suppressed by removing liquid water by stirring, substituting an organic solvent, freeze-drying, etc. when carrying out the drying step, and the present invention was completed.

Description

Spherical metal oxide particle material and its manufacturing method, inorganic filler, resin composition, and slurry composition

[0001] The present invention relates to a spherical metal oxide particle material having an extremely small amount of coarse particles and a low content of metal impurities, a method for producing the same, an inorganic filler, a resin composition, and a slurry composition.

[0002] To improve the physical properties of encapsulants that encapsulate electronic components such as semiconductor devices that make up electronic equipment, substrates on which electronic components are mounted, and other precision components, resin compositions are sometimes used in which inorganic fillers, which are made from inorganic materials and have superior thermal and mechanical properties compared to resin materials, are dispersed in the resin material, and these components are formed by molding and solidifying the resin composition into a molded product.

[0003] In recent years, electronic devices such as mobile terminals have become increasingly dense and precise, and the components used in these devices are also required to be dense and precise. Therefore, the size of inorganic fillers contained in resin compositions constituting encapsulants, substrates, etc. can have a significant impact on the performance of molded products, so the content of coarse particles, i.e., particles with a particle size greater than a certain value, is limited. A commonly used method for limiting the content of coarse particles is classification. For example, in Patent Document 1, coarse particles with a particle size of 50 μm or more are separated and removed by dry sieving.

[0004] JP 2004-269636 A JP 2014-101239 A

[0005] However, dry classification has low classification efficiency, making it difficult to sufficiently remove agglomerates. Therefore, wet classification, which has high classification efficiency, was considered. When performing wet classification, we also attempted to remove impurities consisting of metals remaining in the inorganic filler.

[0006] One method for producing particulate material made of metal oxide is to introduce raw particulate material made of metal into a high-temperature oxidizing atmosphere and cause it to deflagrate (the so-called VMC method). In the VMC method, the reaction to oxidize the metal does not proceed completely, and unburned metal remains in the form of particles, etc., which is unavoidable in principle. Since there is a method for removing unburned metal by immersion in a basic aqueous solution (Patent Document 2), we investigated the removal of unburned metal by a wet method in addition to wet classification.

[0007] The present invention was completed in consideration of the above-mentioned circumstances, and its problem to be solved is to provide a spherical metal oxide particle material and a method for producing the same, which can reduce the content of agglomerates and unburned metals by performing wet classification operations and wet removal of unburned metals on spherical metal oxides produced by the VMC method.

[0008] The present inventors have conducted extensive research to solve the above problems and have discovered that when wet processing is performed, particles aggregate and become very hard in the subsequent drying process. Although it is possible to break down these aggregates into primary particles using a crusher or the like, there are problems such as contamination with foreign matter due to equipment wear and difficulty in achieving sufficient break down.

[0009] When we investigated the cause of aggregation during drying, we found that when liquid water dries, surface tension causes adjacent particles to bond together. Therefore, we found that aggregation can be suppressed by replacing the liquid water that comes into contact with the surface of the particulate material with a substance other than water and / or by removing the water during the drying process, and we have completed the following invention.

[0010] That is, the method for producing a spherical metal oxide particulate material of the present invention, which solves the above-mentioned problems, comprises: a raw particle material preparation step of preparing a raw particle material composed of a metal material consisting of metallic aluminum and / or metallic silicon; a deflagration and spheroidization step of introducing the raw particle material into a high-temperature oxidizing atmosphere to deflagrate it, followed by rapid cooling and spheroidization to prepare a spherical metal oxide raw particle material; an unburned metal material removal step of contacting the spherical metal oxide raw particle material with a basic aqueous solution to remove unburned material from the metal material to prepare a spherical metal oxide particulate material, and preparing a slurry composition in which the spherical metal oxide particulate material is dispersed in a dispersion medium; a drying step of removing the dispersion medium from the slurry composition to obtain a dry spherical metal oxide particulate material; and a classification step of removing some or all of particles having at least a predetermined particle size or larger by a classification operation in the presence of a liquid dispersion medium after the deflagration and spheroidization step and before the drying step, wherein the drying step is carried out while replacing contact water, which is liquid water in contact with the surface of the spherical metal oxide particulate material, with other substances and / or removing it.

[0011] The spherical metal oxide particle material of the present invention, which solves the above problems, comprises as a main component an oxide of a metal material made of metallic aluminum and / or metallic silicon having a volume average particle size of 0.1 μm to 1.5 μm, and when 2 g of the dispersion dispersed in 30 mL of a dispersion medium is passed through a mesh with an opening of 20 μm, the number of particles / aggregates remaining on the mesh is 500 or less, the number of coarse particles having a circularity of 0.9 or more and a particle diameter of 3 μm or more contained in 99.1 μL of a 0.01 mass % aqueous dispersion is 500 or less, and the number of magnetic foreign matter is 0.5 mm or less. ２ / 20g or less.

[0012] The spherical metal oxide particle material and its manufacturing method of the present invention will be described in detail below based on the following embodiments. The numerical ranges "x to y" described in this specification include the lower limit x and the upper limit y. Furthermore, new numerical ranges can be formed by arbitrarily combining these upper and lower limits, as well as the numerical values ​​listed in the specification or examples. The new numerical range can also be a range that excludes one or both of the upper and lower limits. Furthermore, numerical values ​​arbitrarily selected from any of the above numerical ranges can be used as the upper and lower limits of the new numerical range. (Spherical Metal Oxide Particle Material and Inorganic Filler) The spherical metal oxide particle material of this embodiment is composed of an inorganic material primarily composed of an oxide of a metal material. The spherical metal oxide particle material of this embodiment can be used as the inorganic filler of this embodiment. The inorganic filler is dispersed in a resin material and can be used as an encapsulant, filler, underfill, substrate material, etc. for semiconductor devices. Examples of resin materials that can be used include epoxy resins, urea resins, acrylic resins, and their precursors.

[0013] The metal material may contain both metallic aluminum and metallic silicon, or may contain either alone, or may contain other metal elements. Metallic aluminum is particularly preferred. The inorganic material is primarily composed of an oxide of a metal material, and the term "primarily composed" here means that the inorganic material contains 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, 95% or more, 99% or more, or 100% of the spherical metal oxide particle material by mass.

[0014] The spherical metal oxide particle material preferably has a circularity of 0.8 or more, more preferably 0.9 or more, particularly preferably 0.95 or more, and even more preferably 0.99 or more. The circularity in this specification is measured by taking a photograph with an SEM and calculating the circularity from the area and perimeter of the observed particle, as follows: (circularity) = {4π × (area) ÷ (perimeter)} ２ The closer it is to 1, the closer it is to a perfect sphere.

[0015] The metallic element content of the spherical metal oxide particle material is 1 ppm or less, preferably 0.5 ppm or less, and more preferably 0.1 ppm or less. The metallic element content is measured using the method described below. <Method for measuring metallic element content> Approximately 50 g of sample was accurately weighed and placed in a 500 mL Erlenmeyer flask. 220 mL of 2 M sodium hydroxide solution was then added, and the flask was quickly sealed with a silicone stopper. Stirring was then initiated at 1000-1200 rpm using a magnetic stirrer. The temperature at the start of stirring, T1, was then measured.

[0016] Stirring was continued in a sealed state for approximately 15 minutes, until the reaction between the metallic metal elements and sodium hydroxide was thought to have completed. The generated hydrogen was collected in an Erlenmeyer flask. Immediately after stirring was stopped, a hydrogen detector tube (Kitagawa Gas Detector Tube Hydrogen 137U, manufactured by Komyo Rikagaku Kogyo Co., Ltd.) was inserted into the silicone stopper, and a detector tube gas sampler (Kitagawa Gas Sampler AP-20, manufactured by Komyo Rikagaku Kogyo Co., Ltd.) was attached. 50 mL of gas was drawn from the sealed Erlenmeyer flask, and the hydrogen concentration was measured.

[0017] The detector tube and gas sampler were removed, a rod-shaped thermometer was inserted into the silicone stopper, and the temperature in the Erlenmeyer flask, T3, was measured. The stopper was then removed, water was poured into the Erlenmeyer flask using a measuring cylinder, and the volume of the water in the Erlenmeyer flask was used to measure the volume of the space in the Erlenmeyer flask, V.

[0018] From the above measured values, the concentration of the metal element in the metallic state is measured using the following equation, which uses the equation of state for an ideal gas and Boyle's law: (Concentration of metal element in the metallic state: ppm) = Hydrogen concentration (%) x (273 (K) + T1 (°C)) x (V (mL) + Gas intake volume (mL)) / {V (mL) x (273 (K) + T3 (°C))} x 10,000 x V (mL) / 1,000 x 1 / {22.4 (L) x (273 (K) + T1 (°C)) / 273 (K)} x (Reaction molar ratio of metal element in the metallic state to hydrogen) x Atomic weight of metal element in the metallic state x 1 / Amount of sample used (g) Here, (Reaction molar ratio of metal element in the metallic state to hydrogen) is a value indicating how many moles of hydrogen are produced per mole of metal element in the metallic state, and is 1.5 when the metal element in the metallic state is aluminum.

[0019] The inorganic material preferably has a low content of impurities such as alkali metals such as Na and K, and alkaline earth metals such as Mg and Ca. The content of impurities is in a range such that the electrical conductivity of the extracted water is 5.0 μS / cm or less.

[0020] The electrical conductivity of the extracted water is measured as follows. 3.5 g of spherical metal oxide particle material and 35 mL of ion-exchanged water are weighed and mixed in a 50 mL centrifuge tube. The mixture is shaken for 30 minutes using a shaker, and then the sample is precipitated using a centrifuge. The collected supernatant is measured using an EC meter, and the resulting value is taken as the electrical conductivity of the extracted water. Examples of upper limits for the electrical conductivity of the extracted water include 4.5 μS / cm, 3.0 μS / cm, and 2.0 μS / cm.

[0021] The spherical metal oxide particle material preferably has a small amount of U and Th. For example, the total amount of U and Th is 300 ppb or less, with the upper limit being preferably 200 ppb, 100 ppb, 50 ppb, 10 ppb, or 5 ppb.

[0022] The spherical metal oxide particle material has a volume average particle size of 0.1 μm to 1.5 μm. In particular, it is preferable that the upper limit is 1.4 μm, 1.3 μm, 1.2 μm, 1.1 μm, 1 μm, 0.9 μm, or 0.8 μm, and the lower limit is 0.1 μm, 0.15 μm, or 0.2 μm, and these upper and lower limit values ​​can be combined in any desired manner.

[0023] The spherical metal oxide particle material is preferably dispersed into primary particles or can be easily dispersed into primary particles by external force. Instead of determining whether it is dispersed into primary particles, it can also be determined that the number of aggregates falls within the range described below.

[0024] The number of agglomerates of the spherical metal oxide particle material is preferably 500 or less, with the upper limit being 400 or 300. The number of agglomerates is measured by passing a dispersion obtained by dispersing 2 g of the spherical metal oxide particle material in 30 mL of a dispersion medium through a mesh with an opening of 20 μm and counting the number of particles remaining on the mesh.

[0025] The spherical metal oxide particle material has a circularity of 0.9 or more and a particle diameter of 3 μm or more, and the number of coarse particles contained in 99.1 μL of a 0.01% by mass aqueous dispersion is 500 or less, with the upper limit being preferably 300, 200, or 150. The number of coarse particles is measured using an image processing device (Seishin Enterprise Co., Ltd.: PITA-04). First, a dispersion is prepared by dispersing the particles in water to a concentration of 0.01% by mass, and the particles are individually photographed and analyzed using the image processing device. The particle size is measured as the circle equivalent diameter.

[0026] The spherical metal oxide particle material has magnetic foreign matter of 0.5 mm ２ / 20g or less, 0.3mm ２ / 20g or less, 0.1mm ２ / 20g or less is preferable. <Method for measuring magnetic foreign matter> 1. 20g of sample and 80g of dispersion medium are weighed into a container and made into a slurry. 2. A magnet for recovering magnetic foreign matter (magnetic flux density: 0.5T) is set outside the container. 3. The magnetic foreign matter is adsorbed and collected by the magnet for recovering magnetic foreign matter. 4. The area of ​​the collected magnetic foreign matter is measured.

[0027] The spherical metal oxide particulate material may be surface-treated with a surface treatment agent. The surface treatment agent is appropriately selected depending on the application of the spherical metal oxide particulate material. When the spherical metal oxide particulate material is used as an inorganic filler to be filled in a resin material, it is preferable to use a surface treatment agent that can introduce functional groups that have high affinity with the resin material.

[0028] Examples of surface treatment agents include silane compounds and silazanes, and the silane compounds preferably have functional groups such as phenyl, amino, phenylamino, vinyl, epoxy, styryl, acrylic, alkyl, and methacrylic groups. An example of a silazanes is hexamethyldisilazane.

[0029] The amount of surface treatment agent used is not particularly limited, but it is preferable to use an amount of surface treatment agent equivalent to 50% or more, 75% or more, 100% or more, 150% or more, or 200% or more of the number of OH groups present on the surface. (Method for Producing Spherical Metal Oxide Particle Material) The method for producing spherical metal oxide particle material of this embodiment includes a raw particle material preparation step, a deflagration and spheroidization step, an unburned metal material removal step, a drying step, a classification step, and other steps selected as necessary. The spherical metal oxide particle material of this embodiment is a method that can suitably produce the spherical metal oxide particle material of this embodiment. Raw Particle Material Preparation Step The raw particle material preparation step is a step of preparing a raw particle material composed of a metal material. The metal material is a material composed of metallic aluminum and / or metallic silicon. The composition ratio of metal oxides (ratio of Al to Si) contained in the final spherical metal oxide particle material also changes depending on the abundance ratio of metallic aluminum and metallic silicon in the metal material.

[0030] Since the purity of the metal material directly affects the purity of the spherical metal oxide particle material produced, it is preferable that the impurity content be low. By keeping the total amount of U and Th below the content described for the spherical metal oxide particle material of this embodiment, the total amount of U and Th contained in the spherical metal oxide particle material produced can also be reduced. It is preferable that the total amount of alkali metals such as Na and K is 50 ppm or less, and the total amount of alkaline earth metals is 50 ppm or less.

[0031] The process for preparing raw material particles from a metal material is not particularly limited, but methods such as atomization and pulverization can be used. The particle size of the raw material particles is not particularly limited, but a particle size of approximately 0.1 μm to 30 μm can be used. Deflagration and Spheroidization Process The deflagration and spheroidization process is a process for preparing spherical metal oxide raw material particles by introducing raw material particles into a high-temperature oxidizing atmosphere to deflagrate them, and then rapidly cooling and spheroidizing them. The high-temperature oxidizing atmosphere can be a flame in which a flammable gas such as a hydrocarbon such as propane, ammonia, or hydrogen is mixed with a combustion-supporting gas such as air or oxygen.

[0032] A flame serving as a high-temperature oxidizing atmosphere can be formed in a furnace. After the raw material particles are introduced into the flame, they are converted into metal oxide by deflagration. The raw material particles are preferably dispersed in a carrier and introduced into the high-temperature oxidizing atmosphere. A gas such as air or a liquid such as water can be used as the carrier. The metal oxide is rapidly cooled by escaping the flame and becomes spherical metal oxide raw material particles. The spherical metal oxide raw material particles are recovered using a bag filter or cyclone. - Unburned Metal Material Removal Process The unburned metal material removal process involves contacting the spherical metal oxide raw material particles with a basic aqueous solution to remove unburned metal material, thereby preparing spherical metal oxide particles, and preparing a slurry composition in which the spherical metal oxide particles are dispersed in a dispersion medium. Here, removing unburned metal material with a basic aqueous solution means reacting the metal material with the basic aqueous solution to form a reactant, such as a metal oxide or metal hydroxide, which is a compound different from the original metal material, thereby reducing the amount of metal material present. If the reactant is soluble, it is preferable to dissolve and remove it.

[0033] As the dispersion medium, the basic aqueous solution may be used as it is, or may be replaced with another dispersion medium such as an organic solvent, water, etc. When replacing the basic aqueous solution with another dispersion medium, by performing this after the unburned metal material removal step, the unburned metal material can be effectively removed, and the basic substance contained in the basic aqueous solution can also be removed.

[0034] The basic aqueous solution is an aqueous solution in which a basic substance is dissolved in water. The basic substance contained in the basic aqueous solution is one or more compounds selected from inorganic bases and organic bases, and is preferably one or more compounds selected from ammonia, primary amines, secondary amines, tertiary amines, quaternary ammonium hydroxide, arylamines, silazanes, and hydrazines in terms of ease of volatilization. These compounds volatilize upon heating and can be easily removed.

[0035] Particularly desirable basic substances are one or more compounds selected from ammonia, methylamine, ethylamine, propylamine, dimethylamine, diethylamine, pyrrolidine, trimethylamine, triethylamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, benzyltrimethylammonium hydroxide, methyltriamylammonium hydroxide, methyltributylammonium hydroxide, pyrrolidine, piperidine, pyridine, quinoline, imidazole, indole, pyrimidine, hexamethyldisilazane, and hydrazine.

[0036] When a volatilizable basic substance is used, it is preferable to adopt conditions in the drying step described below that allow the basic substance to volatilize. Furthermore, since volatilizable basic substances can be easily removed, it is preferable to increase the concentration of the basic substance contained in the basic aqueous solution to improve reactivity with the unburned metal.

[0037] The basic aqueous solution is preferably heated to improve its reactivity with unburned metal. The heating temperature is preferably 40°C or higher, more preferably 50°C or higher, and even more preferably 60°C or higher. Furthermore, ultrasonic irradiation or stirring can be performed during the reaction to promote the reaction. The reaction time for contact with the basic aqueous solution is not particularly limited, but is preferably a time required for the unburned metal material to undergo almost complete reaction, such as 20 hours or more, more preferably 30 hours or more, and particularly preferably 40 hours or more. For example, when ammonia water is used as the basic aqueous solution, the pH can be adjusted to 9 or higher. A pH of 9 or higher can be achieved by adding 1% or more of 28% ammonia water to the water by volume. By heating this ammonia water to 40°C, unburned metal material can be almost completely eliminated within a treatment time of 20 hours or more. Furthermore, by heating the ammonia water to 20°C, unburned metal material can be almost completely eliminated within a treatment time of 72 hours or more. Here, water with low conductivity (containing no ionic impurities) is used to prepare the basic aqueous solution. For example, it is desirable to use water with a viscosity of 2 μS / cm or less. Classification step The classification step is a step in which, after the deflagration and spheroidization step and before the drying step, some or all of the particles having a predetermined particle size or larger are removed by classification in the presence of a liquid dispersion medium. In other words, the classification step is a wet classification operation. Classification can be performed by passing the particles through a filter with a predetermined mesh size or by using the difference in sedimentation velocity due to centrifugal force or gravity.

[0038] The predetermined particle size is not particularly limited, but for example, if it is necessary to exclude particles with a particle size of 3 μm or more, the predetermined particle size is set to a value of 3 μm or less. By doing so, particles with a particle size larger than the predetermined particle size can be removed. - Drying process The drying process is a process in which the dispersion medium is removed from the slurry composition to obtain a dried spherical metal oxide particle material. The drying process can be performed by heating within a temperature range that does not deteriorate the spherical metal oxide particle material, or under reduced pressure.

[0039] When a volatile basic substance is used, the basic substance can be removed by heating together with the removal of the dispersion medium. Alternatively, the basic substance can be effectively removed by washing the slurry composition with an organic solvent or water that does not contain the basic substance.

[0040] The drying step is carried out by replacing the liquid water, which is in contact with the surface of the spherical metal oxide particle material, with other substances and / or removing it. If water is evaporated while in contact with the surface of the spherical metal oxide particle material, the surface tension of the water will cause aggregation of adjacent particles of the spherical metal oxide particle material. Therefore, drying is carried out by replacing the contact water with other substances or by removing the contact water.

[0041] Here, "other substances" refers to substances other than contact water (liquid water), such as solid water and organic solvents other than water. By solidifying the contact water and drying it under reduced pressure, a process known as freeze-drying, the progress of aggregation due to surface tension is suppressed even when the water evaporates.

[0042] Examples of preferred organic solvents include isopropyl alcohol (IPA), propylene glycol monomethyl ether (PGM), propylene glycol monomethyl ether acetate (PGMAC), and cyclohexanone. By using one or a mixture of two or more of these organic solvents, aggregation can be suppressed. In particular, by replacing all contact water with an organic solvent, aggregation can be effectively suppressed.

[0043] Furthermore, the organic solvent other than water is preferably an organic solvent that is miscible with water and evaporates simultaneously with or slower than water (e.g., PGM, PGMAC, cyclohexanone), because even if contact water remains, it volatilizes first, and ultimately the organic solvent remains, thereby suppressing the progression of aggregation due to drying.

[0044] The amount of organic solvent added is preferably more than 60% based on the sum of the masses of the organic solvent and water, and the lower limit of the amount of organic solvent added is preferably 65%, 70%, 75%, 80%, 85%, etc.

[0045] Examples of methods for drying while removing contact water include a method of drying while stirring, or spray drying. By drying while stirring, the contact water is replaced by the atmospheric gas used for stirring, and drying progresses, thereby suppressing the progression of aggregation. Contact water can be removed by using a reduced pressure or vacuum atmosphere as the atmosphere used for stirring.

[0046] Instead of stirring, the slurry composition is sprayed into a high-temperature atmosphere, i.e., spray drying, whereby contact water is removed from the surface before the spherical metal oxide particle material aggregates, thereby suppressing aggregation. In particular, by replacing the dispersion medium with an organic solvent, a further aggregation suppression effect can be expected.

[0047] This process is preferably performed until the spherical metal oxide particle material obtained by this production method, which meets the definition of the spherical metal oxide particle material described above, is stored in a state that does not deviate from the definition of the spherical metal oxide particle material of this embodiment. Storage conditions include 10 days, 1 month, 3 months, etc. at room temperature. Alternatively, the end of this process can be determined when the moisture content, based on the total mass, reaches 1.0 mass% or less, 0.5 mass% or less, or 0.3 mass% or less. Other Processes: The spherical metal oxide particle material can be surface-treated with a surface treatment agent. Examples of surface treatment agents include those described above for the spherical metal oxide particle material. Surface treatment can be performed at any time after the deflagration and spheroidization process. After the surface treatment, heating can promote the reaction between the surface treatment agent and the spherical metal oxide particle material. (Resin Composition) The resin composition of this embodiment contains the inorganic filler of this embodiment and a resin material in which the inorganic filler is dispersed. The resin material is in a liquid or solid state. The resin material can be a polymeric material such as epoxy resin, urea resin, or acrylic resin, or a monomer that is a precursor to the polymeric material. This resin composition can be cured later and is suitable for use as an encapsulant for semiconductor elements and substrates.

[0048] The resin material can be one that can exhibit fluidity in the final resin composition. The resin material contains one or more compounds and may be either one that melts when heated to exhibit fluidity (such as a thermoplastic resin) or one that is initially liquid and solidifies upon reaction (such as a thermosetting resin). A preferred example of the resin material is a combination of an epoxy resin and a curing agent.

[0049] The mixing ratio of the inorganic filler and the resin material is not particularly limited. However, the improved fluidity due to the addition of the microparticle material makes it possible to incorporate a large amount of inorganic filler. For example, the filler can be incorporated at 60% or more, or even 75% or more, or 80% or more, based on the total mass. The upper limit is not particularly limited, but examples include approximately 95%, 90%, and 85%. These upper and lower limits can be combined arbitrarily. (Slurry Composition) The slurry composition of this embodiment contains the inorganic filler of this embodiment and a dispersion medium for dispersing the inorganic filler. The dispersion medium is a fluid substance such as a liquid. Examples of dispersion mediums include organic solvents such as IPA, PGM, PGMAC, cyclohexanone, toluene, and hexane, as well as the resin material before curing described above. The slurry composition is particularly free of moisture (for example, a moisture content of 0.1% by mass or less, based on the total mass). Taking advantage of its fluidity, this slurry composition can be used for applications in which it is mixed with other substances.

[0050] The mixing ratio of inorganic filler to dispersion medium is not particularly limited, but as a result of improving fluidity by mixing fine particle material, it is possible to incorporate a large amount of inorganic filler. For example, the filler can be incorporated in an amount of 60% or more, or even 75% or more, or 80% or more based on the total mass. The upper limit is not particularly limited, but examples include approximately 95%, 90%, and 85%. These upper and lower limit values ​​can be combined as desired.

[0051] The spherical metal oxide particle material and its manufacturing method of the present invention will be described in detail with reference to examples. (Preparation of spherical metal oxide raw particle material) A raw particle material was prepared using metallic aluminum as the metal material (raw particle material preparation step). The raw particle material was prepared by atomizing metallic aluminum melted under an inert atmosphere. The obtained raw particle material was charged into a heat-resistant furnace. The raw particle material was dispersed in air as a carrier and supplied. A flame was formed in the heat-resistant furnace by supplying propane gas as a combustible gas and air as a combustion-supporting gas. After deflagration, the raw particle material charged into the flame was rapidly cooled and solidified as it settled to the bottom of the heat-resistant furnace, becoming a spherical metal oxide raw particle material. The solidified spherical metal oxide raw particle material consisting of alumina was collected using a bag filter (deflagration and spheroidization step). (Example 1: Substitution with Organic Solvent and Drying) 100 g of the prepared spherical metal oxide raw particle material was immersed for 20 hours in 100 mL of a basic aqueous solution containing dimethylamine as a basic substance dissolved at a concentration of 0.5% by mass (weight basis) to obtain a spherical metal oxide particle material (unburned metal material removal step). The temperature of the basic aqueous solution was 25°C.

[0052] The obtained spherical metal oxide particle material was subjected to a centrifugal classifier multiple times to separate particles having a particle size of 3 μm or less, thereby obtaining a slurry composition in which spherical metal oxide particle material, from which particles exceeding 3 μm had been removed, was dispersed in a basic aqueous solution (classification process).

[0053] 100 mL of organic solvent (IPA) was added to the resulting slurry composition, and then 200 mL of the dispersion medium was removed by centrifugation. This process was repeated three times, replacing the basic aqueous solution with the organic solvent. The mixture was then dried at 90°C for 5 hours to obtain a test sample of this example (drying process). (Example 2: Drying with Stirring) The test sample of this example was obtained in the same manner as Example 1, except that the drying process in Example 1 involved stirring with a stirrer and drying at 100°C for 5 hours while reducing the pressure to 4 kPa. (Example 3: Freeze-Drying) The test sample of this example was obtained in the same manner as Example 1, except that the drying process in Example 1 involved cooling to -40°C in a refrigerator, freezing the composition, reducing the pressure to 2 MPa, and drying for 2 hours (freeze-drying). (Example 4: Adding PGM and Drying with Stirring) The test sample of this example was obtained in the same manner as Example 1, except that the drying process in Example 1 involved adding PGM to the slurry composition to a concentration of 80% by mass, and then drying at 130°C for 10 hours while stirring with a stirrer. (Comparative Example 1: Static Drying) The test sample of this comparative example was obtained in the same manner as in Example 1, except that the drying step involved drying the slurry composition in a static state at 200°C for 10 hours, followed by crushing to a primary particle state using a crusher. (Comparative Example 2: Dry Classification) The test sample of this comparative example was obtained in the same manner as in Example 1, except that the unburned metal material removal step was not performed. (Test Example 1: Omission of the Classification Step of Example 1) The test sample of this test example was obtained in the same manner as in Example 1, except that particles of 5 μm or larger were removed instead of the classification step of Example 1. (Test Example 2: Omission of the Unburned Metal Material Removal Step and Classification Step of Example 1) The test sample of this test example was obtained in the same manner as in Example 1, except that Test Example 2 was obtained without the unburned metal material removal step and classification step of Example 1. (Evaluation) The test samples of each Example, Comparative Example, and Test Example were evaluated for volume average particle size, amount of metallic aluminum, electrical conductivity of the extracted water, magnetic foreign matter, number of particles of 3 μm or more, and number of aggregates of 20 μm or more using the test methods described in the embodiments. The results are shown in Table 1.

[0054] As is clear from Table 1, the test samples obtained in each Example contained low amounts of magnetic foreign matter, particles larger than 3 μm, aggregates larger than 20 μm, and unburned aluminum as unburned metal. In contrast, the test sample of Comparative Example 1, which underwent a drying process in a stationary state, was crushed to roughly primary particles, but magnetic foreign matter originating from the crusher was observed. Furthermore, the test sample of Comparative Example 2, which did not undergo wet classification or removal of unburned metal, contained a small number of aggregates (aggregates larger than 20 μm), but a large number of particles larger than 3 μm. Furthermore, because dry classification was performed, it was presumed that friction with the sieve caused a large amount of magnetic foreign matter to be mixed in.

[0055] Furthermore, as in Test Example 1, it was found that by changing the classification point in the classification process from 3 μm in Example 1 to 5 μm, the number of particles 3 μm or larger naturally increased. In this way, it was found that the amount of coarse particles can be controlled by changing the classification point. Furthermore, it was found that the amount of agglomerates (aggregates 20 μm or larger) was small, as in Example 1.

[0056] Furthermore, it was found that the test sample not subjected to the classification step, such as Test Example 2, had a larger amount of coarse particles of 3 μm or more than that of Test Example 1. Also, it was found that the number of aggregates (aggregates of 20 μm or more) was small, as in Example 1.

[0057] In summary, we found that the wet classification process can reduce the amount of coarse particles with a particle size above the classification point compared to a dry classification process. Furthermore, the amount of unburned aluminum metal can be reduced by removing unburned metals using a wet process. Furthermore, we found that actively reducing the amount of contact water in the drying process can suppress the formation of agglomerates, eliminating the need for a crushing process or allowing for more lenient crushing conditions in the crushing process, thereby reducing the amount of foreign matter (especially magnetic foreign matter) that gets mixed in during the crushing process. Amount of Organic Solvent (Test Examples 3 to 6) The test samples of this example were obtained in the same manner as in Example 1, except that the drying step in Example 1 involved adding PGM to the slurry composition to a concentration of 75% by mass (organic solvent:water = 3:1, Test Example 3), 71.4% by mass (organic solvent:water = 2.5:1, Test Example 4), 66.7% by mass (organic solvent:water = 2:1, Test Example 5), or 60% by mass (organic solvent:water = 2:1, Test Example 6), followed by drying at 130°C for 10 hours while stirring with a stirrer. (Evaluation) The amount of aggregates was evaluated for each of the test samples of Example 4 and Test Examples 3 to 6 using the method described above. The results are shown in Table 2.

[0058] As is clear from the table, it was found that the amount of aggregates was small and that it was preferable to add an organic solvent in an amount of more than 71.4% in Example 4 and Test Examples 3 and 4. In particular, it was found that Example 4 and Test Example 3, in which the amount of organic solvent added was 75% or more, were even more preferable.

Claims

1. The main component is an oxide of a metal material made of metallic aluminum and / or metallic silicon with a volume average particle size of 0.1 μm to 1.5 μm, and when 2 g of the dispersion dispersed in 30 mL of dispersion medium is passed through a mesh with openings of 20 μm, the number of particles / aggregates remaining on the mesh is 500 or less, the circularity is 0.9 or more and the number of coarse particles with a particle diameter of 3 μm or more contained in 99.1 μL of a 0.01 mass% aqueous dispersion is 500 or less, and the magnetic foreign matter is 0.5 mm ２ / 20g or less of spherical metal oxide particulate material.

2. The spherical metal oxide particle material according to claim 1, wherein the content of said metal material is 1 ppm or less.

3. A spherical metal oxide particle material according to claim 1 or 2, wherein the total amount of U and Th is 300 ppb or less based on the total mass.

4. The spherical metal oxide particle material according to any one of claims 1 to 3, wherein the electrical conductivity of extracted water is 5.0 μS / cm or less.

5. The spherical metal oxide particle material according to any one of claims 1 to 4, which has been surface-treated with a surface treatment agent.

6. A method for producing a spherical metal oxide particulate material, comprising: a raw particle material preparation step for preparing a raw particle material composed of a metallic material consisting of metallic aluminum and / or metallic silicon; a deflagration and spheroidization step for introducing the raw particle material into a high-temperature oxidizing atmosphere to deflagrate it, followed by rapid cooling and spheroidization to prepare a spherical metal oxide raw particle material; an unburned metal material removal step for contacting the spherical metal oxide raw particle material with a basic aqueous solution to remove unburned material from the metallic material to prepare a spherical metal oxide particulate material, and preparing a slurry composition in which the spherical metal oxide particulate material is dispersed in a dispersion medium; a drying step for removing the dispersion medium from the slurry composition to obtain a dry spherical metal oxide particulate material; and a classification step for removing part or all of particles having at least a predetermined particle size or larger by classification in the presence of a liquid dispersion medium after the deflagration and spheroidization step and before the drying step, wherein the drying step is carried out while replacing liquid water, which is contact water that is in contact with the surface of the spherical metal oxide particulate material, with a substance other than the liquid water and / or removing it.

7. The method for producing a spherical metal oxide particle material according to claim 6, wherein the drying step is carried out while the contact water is replaced with atmospheric gas by stirring.

8. The method for producing a spherical metal oxide particle material according to claim 6 or 7, wherein the drying step is carried out while the contact water is in a frozen state.

9. A method for producing a spherical metal oxide particle material according to any one of claims 6 to 8, wherein the drying step is carried out by spray drying, in which the contact water is replaced with a high-temperature atmospheric gas.

10. A method for producing a spherical metal oxide particle material described in any one of claims 6 to 9, wherein the drying step is carried out while replacing the contact water with an organic solvent that is miscible with water and evaporates simultaneously with or slower than water, and / or after replacing the contact water.

11. An inorganic filler comprising the spherical metal oxide particle material according to any one of claims 1 to 5.

12. A resin composition comprising the inorganic filler according to claim 11 and a resin material in which the inorganic filler is dispersed.

13. A slurry composition comprising: the inorganic filler according to claim 11; and a dispersion medium for dispersing the inorganic filler.

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