INORGANIC POWDER COATING, INORGANIC POWDER TREATMENT AGENTS, AND METHODS FOR PRODUCING INORGANIC POWDER COATING USING THESE AGENTS

Abstract

The invention proposes a coated inorganic powder with superior dielectric properties and exhibiting superior fluidity and water resistance. A film containing Zr, N, and Si with N / Si molar ratios and Zr / Si molar ratios within predetermined ranges, respectively, is formed on the surface of the inorganic powder. The invention also proposes an inorganic powder treatment agent and a method for producing a coated inorganic powder using this agent.

Description

Inorganic powder, its manufacturing method, and powder processing agent usable in the manufacturing method

[0001] The present invention relates to an inorganic powder having excellent insulating properties, water resistance and flowability, which is useful for all industrial products that use inorganic powder, such as electronic devices and electronic components, a method for producing the same, and a powder treating agent that can be used in the production method.

[0002] In recent years, with the miniaturization and high functionality of electronic and electrical devices, the electronic components used therein are required to have excellent magnetic properties. Therefore, inorganic powders used in electronic components must have high insulating properties. In addition to insulating properties, they must also have fluidity during powder compaction and water resistance of the coating to enable long-term use in various environments. Therefore, inorganic powders having a coating on their surface that combines these properties have been developed.

[0003] For example, Patent Document 1 discloses a powder for powder cores having a first coating on the surface of the magnetic powder and a second coating on the first coating, the first coating being made of an organoalkoxysilane partial hydrolyzate and / or a precursor thereof, and the second coating being made of alkali-silicate glass.

[0004] Patent Document 2 discloses a particle coating-forming treatment liquid containing at least one silicon compound having an alkoxysilyl group, an alkoxysilylene group, and a siloxane bond, an organometallic compound, and a metal salt.

[0005] Japanese Patent No. 4436172 Japanese Patent Application Laid-Open No. 2019-157189

[0006] However, the powder for dust cores described in Patent Document 1 has a two-layer coating, which may result in insufficient fluidity, or insufficient water resistance, which may make it unsuitable for maintaining long-term performance in various environments. Furthermore, the particle coating treatment solution described in Patent Document 2 may not provide sufficient fluidity. Therefore, an object of the present invention is to provide a coated inorganic powder that has excellent insulation properties, as well as excellent fluidity and water resistance, a method for producing the same, and a powder treatment agent that can be used in the production method.

[0007] As a result of intensive research to solve the above problems, the present inventors have found that by using a predetermined powder treatment agent to form a coating on the surface of an inorganic powder, which contains Zr, N, and Si and has N / Si and Zr / Si molar ratios each within a predetermined range, an inorganic powder with excellent insulation properties, flowability, and water resistance can be obtained, and have completed the present invention.

[0008] That is, the present invention provides: (1) a coated inorganic powder having an inorganic powder and a coating on the surface of the inorganic powder, the coating containing at least Zr, N, and Si, wherein the N / Si molar ratio is in the range of 0.010 to 1.000 and the Zr / Si molar ratio is in the range of 0.10 to 10.00; (2) the coated inorganic powder according to (1) above, wherein the coating further contains C, and the C / Si molar ratio in the coating is in the range of 0.20 to 20.00; (3) the coated inorganic powder according to (1) above or (2), wherein the coating does not contain at least one element selected from P, Ti, and Cr; (4) A powder processing agent that is a mixed solution containing at least zirconium ions, an alkoxysilane compound, and an aqueous medium, wherein the alkoxysilane compound contains a nitrogen-containing alkoxysilane, the zirconium ions are in the range of 4 parts by mass to 400 parts by mass, and the aqueous medium is in the range of 100 parts by mass to 5,000 parts by mass, per 100 parts by mass of the alkoxysilane compound; (5) The inorganic powder processing agent according to (4), wherein the free acidity (pt) of the inorganic powder processing agent is in the range of 1.0 point to 100.0 points; (6) The inorganic powder processing agent according to (4) or (5), wherein the alkoxysilane compound contains a tetraalkoxysilane and a silane coupling agent having an amino group; (7) The inorganic powder processing agent according to any one of (4) to (6), wherein the alkoxysilane compound comprises a tetraalkoxysilane and a silane coupling agent having an epoxy group, and the amount of the silane coupling agent having an epoxy group is in the range of 2 to 200 parts by mass per 100 parts by mass of the alkoxysilane compound other than the silane coupling agent having an epoxy group; (8) A method for producing a coated inorganic powder, comprising the step of heating a composition containing an inorganic powder and the inorganic powder processing agent according to any one of (4) to (7), to evaporate volatile matter in the composition and form a coating on the surface of the inorganic powder; and the like.

[0009] According to the present invention, it is possible to provide an inorganic powder having excellent insulating properties, fluidity and water resistance, a method for producing the same, and a powder treating agent that can be used in the production method.

[0010] A coated inorganic powder according to one embodiment of the present invention comprises an inorganic powder and a coating on the surface of the inorganic powder, the coating containing at least Zr, N, and Si, with an N / Si molar ratio in the range of 0.010 to 1.000 and a Zr / Si molar ratio in the range of 0.10 to 10.00. The inorganic powder used as the raw material is not particularly limited in terms of particle size, shape, composition, etc., as long as it is a powder made of an inorganic substance. The inorganic powder used as the raw material is preferably a magnetic inorganic powder, as it is useful, for example, as a material for electronic components. The magnetic inorganic powder preferably contains iron. The inorganic powder is also preferably a conductor, for example, with an electrical conductivity of 1×10 ６ S / m or more, and ５ It may be S / m or more.

[0011] Examples of inorganic powders containing iron include Fe (pure iron) and metal compounds such as Fe-Si, Fe-Si-Cr, Fe-Ni, Fe-Si-Al, Fe-Cr, Fe-Co, Fe-Nd, and amorphous Fe. Other examples of inorganic powders include inorganic compounds such as metal oxides, nitrides, and borides. Examples of inorganic metal compounds include barium titanate (BaTiO ３ ), boron nitride (BN), ferrite (MFe ２ O ４ ; M represents a divalent metal element), lead zirconate titanate {Pb(Zr,Ti)O ３}, aluminum oxide (Al ２ O ３ ), silicon carbide (SiC), zinc oxide (ZnO), zirconia (ZrO ２ ), zircon (ZrO ２ SiO ２ ), forsterite (2MgO.SiO ２ ), mullite (3Al ２ O ３ 2SiO ２ ), steatite (MgO.SiO ２ ), cordierite (2MgO 2Al ２ O ３ 5SiO ２ ), aluminum nitride (AlN), silicon nitride (Si３ N ４ ), etc.

[0012] The particle size of the inorganic powder is not particularly limited, and the 50 volume % particle size (D50) of the cumulative distribution is usually 0.1 μm or more, may be 0.5 μm or more, may be 1.0 μm or more, and usually 1000 μm or less, may be 500 μm or less, may be 300 μm or less, or may be 150 μm or less. The shape of the inorganic powder is also not particularly limited, and the aspect ratio is usually 50 or less, may be 20 or less, may be 10 or less, and is usually 1 or more. The aspect ratio of an inorganic powder is the value obtained by dividing the major axis by the minor axis. Here, the major axis and minor axis of the inorganic powder refer to the value obtained by randomly selecting 100 inorganic powders in image analysis using a scanning electron microscope, measuring the longest and shortest diameters of each inorganic powder, and averaging these measured lengths for the 100 inorganic powders.

[0013] The coating of the coated inorganic powder contains at least Zr, N, and Si, and may contain other elements. Examples of other elements include components contained in the inorganic powder. Other elements include H, O, and C derived from moisture and raw materials, and elements contained in the ion source containing zirconium, which will be described later. However, it is preferable that the powder does not contain at least one element selected from P, Ti, and Cr. Here, "free" means that the powder is substantially free of the elements, and does not exclude the inclusion of trace amounts.

[0014] In this embodiment, it is particularly preferable that the molar ratio of N to Si (N / Si) in the coating is within a certain range, and that the molar ratio of Zr to Si (Zr / Si) in the coating is also within a certain range. By keeping these molar ratios within a certain range, it is possible to uniformly form the coating on the surface of the inorganic powder, which has superior fluidity, water resistance, and insulating properties.

[0015] The N / Si molar ratio is preferably in the range of 0.010 to 1.000, more preferably in the range of 0.020 to 0.700, and even more preferably in the range of 0.030 to 0.500. The Zr / Si molar ratio is preferably in the range of 0.10 to 10.00, more preferably in the range of 0.20 to 7.00, and even more preferably in the range of 0.40 to 4.00.

[0016] When the coating further contains C, the molar ratio of C to Si (C / Si) in the coating preferably falls within a certain range, preferably from 0.20 to 20.00, more preferably from 0.30 to 10.00, and particularly preferably from 0.50 to 5.00.

[0017] The contents of Zr, N, Si, and C in the coating can be determined by the following method. First, a mixture of the coated inorganic powder and a curable resin (which may be a composition of a resin and a curing agent) is cured. Next, the cured product is mechanically polished, and then a flake is prepared using ion milling. Next, the inorganic powder coating in the flake is subjected to elemental analysis using energy dispersive X-ray spectroscopy (EDS) attached to a field emission scanning electron microscope (FE-SEM). The content of each element can be calculated from the obtained elemental analysis value (intensity) of each element.

[0018] The thickness of the coating is not particularly limited, but is preferably in the range of 1 nm to 100 nm, more preferably in the range of 2 nm to 70 nm, and particularly preferably in the range of 5 nm to 50 nm.

[0019] The thickness of the coating can be measured by observing the prepared thin section with a field emission scanning electron microscope (FE-SEM) or a transmission electron microscope (TEM).

[0020] This embodiment also relates to a powder treatment liquid (inorganic powder treatment agent) capable of stably producing the coated inorganic powder (e.g., insulating magnetic powder) according to this embodiment. The powder treatment liquid is not particularly limited as long as it is a mixed liquid containing at least an alkoxysilane compound (the alkoxysilane compound includes a nitrogen-containing alkoxysilane), zirconium ions, and an aqueous medium, and may also contain other components. The zirconium ions contained in the powder treatment liquid are preferably in the range of 4 to 400 parts by mass, and more preferably in the range of 10 to 100 parts by mass, per 100 parts by mass of the alkoxysilane compound. Furthermore, the aqueous medium contained in the powder treatment liquid is preferably in the range of 100 to 5,000 parts by mass, and more preferably in the range of 300 to 3,000 parts by mass, per 100 parts by mass of the alkoxysilane compound. By using this powder treatment liquid, it is possible to more stably produce a coating having an N / Si molar ratio and a Zr / Si molar ratio in the ranges of 0.010 to 1.000 and 0.10 to 10.00, respectively. The powder treatment liquid may or may not contain a silicone resin and / or a pigment as an added component, but it is preferable that it does not contain them.

[0021] The powder treatment liquid according to the present embodiment contains at least a nitrogen-containing alkoxysilane compound as an alkoxysilane compound. Examples of the nitrogen-containing alkoxysilane compound include silane coupling agents having an amino group (organoalkoxysilanes having an amino group), such as N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, and N-phenyl-3-aminopropyltrimethoxysilane. These nitrogen-containing alkoxysilane compounds can be used alone or in combination of two or more.

[0022] As the alkoxysilane compound in the powder treatment solution according to the present embodiment, in addition to the nitrogen-containing alkoxysilane compound, various organoalkoxysilanes (silane coupling agents) may be used. Here, in order to adjust the N / Si molar ratio in the coating to an appropriate range, it is preferable to further use a tetraalkoxysilane in combination as a material that does not introduce N into the coating.

[0023] The tetraalkoxysilane is not particularly limited, and examples thereof include tetraethoxysilane (tetraethyl orthosilicate), tetramethoxysilane (tetramethyl orthosilicate), tetrabutoxysilane (tetrabutyl orthosilicate), tetraisopropoxysilane (tetraisopropyl orthosilicate), tetrapropoxysilane (tetrapropyl orthosilicate), etc. These tetraalkoxysilanes can be used alone or in combination of two or more.

[0024] The powder treatment liquid may contain an alkoxysilane other than the above-mentioned alkoxysilanes (nitrogen-containing alkoxysilanes and tetraalkoxysilanes). Examples of the alkoxysilane include silane coupling agents having a vinyl group, such as vinyltrimethoxysilane and vinyltriethoxysilane; and silane coupling agents having an epoxy group, such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycidoxypropyltriethoxysilane. These silane coupling agents may be used alone or in combination of two or more.

[0025] As described above, the powder treatment liquid according to the present embodiment essentially contains one or more nitrogen-containing alkoxysilane compounds as the alkoxysilane compound, and may also contain one or more other alkoxysilane compounds. For example, the powder treatment liquid may contain a tetraalkoxysilane and a silane coupling agent having an amino group, or a tetraalkoxysilane, a silane coupling agent having an amino group, and a silane coupling agent having an epoxy group. The alkoxysilane compound may also contain a hydrolyzate of an alkoxysilane compound. When the powder treatment liquid according to the present embodiment contains a silane coupling agent having an epoxy group, the content of the silane coupling agent having an epoxy group is preferably in the range of 2 to 200 parts by mass, more preferably in the range of 10 to 100 parts by mass, per 100 parts by mass of the alkoxysilane compound other than the silane coupling agent having an epoxy group. By using this powder treatment liquid, a coating having a C / Si molar ratio in the range of 0.20 to 20.00 can be more stably produced. Components other than Zr, N, and Si may or may not be included in the powder processing liquid according to the present embodiment. "Not included in the powder processing liquid" means that they are not intentionally blended, and does not exclude unavoidable inclusion. However, it is preferable that at least one of P, Ti, and Cr is not included in the powder processing liquid according to the present embodiment.

[0026] The powder treatment liquid according to the present invention contains zirconium ions. The water-soluble zirconium compound serving as the zirconium ion source is not particularly limited, and examples thereof include hexafluorozirconic acid, zirconium sulfate tetrahydrate, zirconyl nitrate dihydrate, zirconium chloride, and zirconyl acetate. These reagents may be used singly or in combination. The term "water-soluble" used herein means that 1 g or more of the compound can be dissolved in 1 L of water at 25°C.

[0027] The combination of the alkoxysilane compound and the water-soluble zirconium compound is not particularly limited, and examples thereof include a combination of tetrabutoxysilane, 3-glycidoxypropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, and zirconyl nitrate dihydrate; a combination of tetraisopropoxysilane, vinyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, and zirconium chloride; a combination of tetrapropoxysilane, vinyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, and zirconyl acetate; and a combination of tetraethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. a combination of tetramethoxysilane, 3-aminopropyltrimethoxysilane, and hexafluorozirconic acid; a combination of tetramethoxysilane, vinyltriethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-aminopropyltriethoxysilane, and zirconium sulfate tetrahydrate; a combination of tetrabutoxysilane, vinyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-triethoxysilyl-N-(1,4-dimethylbutylidene)propylamine, and zirconyl nitrate dihydrate; a combination of tetraisopropoxysilane, 3-glycidoxypropyltrimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, and zirconium chloride; a combination of tetrapropoxysilane, vinyltriethoxysilane, 2-(3,a combination of 4-epoxycyclohexyl)ethyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, and zirconyl acetate; a combination of tetraethoxysilane, vinyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, and hexafluorozirconic acid; a combination of tetramethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, and zirconium sulfate tetrahydrate; a combination of tetrabutoxysilane, vinyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, and zirconyl nitrate dihydrate; a combination of tetraisopropoxysilane and vinyltrimethoxysilane; a combination of silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-aminopropyltriethoxysilane, and zirconium chloride; a combination of tetrapropoxysilane, 3-glycidoxypropyltriethoxysilane, 3-triethoxysilyl-N-(1,4-dimethylbutylidene)propylamine, and zirconyl acetate; a combination of tetraethoxysilane, vinyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, and hexafluorozirconic acid; a combination of tetramethoxysilane, vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, and zirconium sulfate tetrahydrate; a combination of tetrabutoxysilane, 2-(3,a combination of 4-epoxycyclohexyl)ethyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, and zirconyl nitrate dihydrate; a combination of tetraisopropoxysilane, vinyltriethoxysilane, 3-glycidoxypropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, and zirconium chloride; a combination of tetrapropoxysilane, vinyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane, and zirconyl acetate; a combination of tetraethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and hexafluorozirconic acid; a combination of tetramethoxysilane, vinyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and 3-triethoxysilyl-N-(1,4-dimethylbutylidene ) a combination of propylamine and zirconium sulfate tetrahydrate, a combination of tetrabutoxysilane, vinyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, and zirconyl nitrate dihydrate, a combination of tetraisopropoxysilane, 3-glycidoxypropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, and zirconium chloride, a combination of tetrapropoxysilane, vinyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, and zirconyl acetate, a combination of tetraethoxysilane, vinyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, and hexafluorozirconic acid, and the like.

[0028] The aqueous medium contained in the powder processing agent according to this embodiment is not particularly limited as long as it is water or a mixture of water and a water-miscible organic solvent (containing 50% or more by mass of water based on the volume of the aqueous medium). The water-miscible organic solvent is not particularly limited as long as it is miscible with water, and examples thereof include ketone solvents such as acetone and methyl ethyl ketone; amide solvents such as N,N'-dimethylformamide and dimethylacetamide; alcohol solvents such as methanol, ethanol, and isopropanol; ether solvents such as ethylene glycol monobutyl ether and ethylene glycol monohexyl ether; and pyrrolidone solvents such as 1-methyl-2-pyrrolidone and 1-ethyl-2-pyrrolidone. One of these water-miscible organic solvents may be mixed with water, or two or more may be mixed with water. The water is not particularly limited, and examples thereof include ion-exchanged water (electrical conductivity: 1 μS / cm or less) and distilled water.

[0029] The powder processing agent according to this embodiment preferably has a free acidity (pt) in the range of 1.0 to 100.0 points, more preferably 2.0 to 75.0 points, and even more preferably 3.0 to 50.0 points. The free acidity can be adjusted using a commercially available acidic or alkaline solution. Examples of acidic solutions include aqueous solutions of sulfuric acid, nitric acid, hydrochloric acid, acetic acid, formic acid, oxalic acid, and hydrofluoric acid. Examples of alkaline solutions include aqueous solutions of ammonia, ammonium bicarbonate, sodium hydroxide, and potassium hydroxide.

[0030] The free acidity (pt) is obtained by taking 10 ml of the powder treatment agent, adding 2 to 3 drops of "D-11" manufactured by Nihon Parkerizing Co., Ltd., and then titrating it with "T-11" manufactured by Nihon Parkerizing Co., Ltd., and expressing the amount of "T-11" (ml) as points (1 ml = 1 point).

[0031] Examples of the other components include additives such as surfactants and lubricants. These additive components may be included in the coating to the extent that they do not impair the effects of the present invention. In addition, a lubricant may be further provided as a lubricating coating on the coating of this embodiment.

[0032] The coated inorganic powder according to this embodiment can be produced by contacting the powder treatment agent with the inorganic powder, followed by heating to evaporate the volatile components of the powder treatment agent, thereby forming a coating on the inorganic powder. More specifically, the coated inorganic powder can be produced by heating a composition containing the powder treatment agent and the inorganic powder to evaporate the volatile components in the composition (the volatile components in the powder treatment agent). The contact between the powder treatment agent and the inorganic powder can be carried out by mixing, or other contact methods can be employed. For stable and efficient production of the inorganic powder, it is preferable to heat the composition in air or an inert gas (such as nitrogen, carbon dioxide, helium, neon, argon, krypton, xenon, or radon) to evaporate the volatile components in the composition. Evaporation of the volatile components can be carried out, for example, using a spray dryer. After evaporating the volatile components, a step of forming another coating on the surface of the coated inorganic powder, for example, a step of contacting the powder with a lubricant to form a lubricating coating, may be further included. The contacting method is not particularly limited, and examples thereof include immersion in a lubricant and mixing with a lubricant. Furthermore, the production of the inorganic powder may further include a step of drying the surface of the inorganic powder that has been contacted with the lubricant after contact with the lubricant. The drying method is not particularly limited, and examples thereof include heating in air or an inert gas. By the above-mentioned production method, a coated inorganic powder having a lubricating coating can be obtained.

[0033] The composition may be heated gradually to reach a predetermined temperature, or may be heated stepwise to finally reach a predetermined temperature. The upper limit of the predetermined temperature is not particularly limited, but is preferably 400°C or lower, more preferably 300°C or lower, and particularly preferably 200°C or lower. The drying temperature on the surface of the coated inorganic powder in contact with the lubricant is not particularly limited, but is preferably 200°C or lower, more preferably 100°C or lower.

[0034] The coated inorganic powder according to this embodiment is typically subjected to powder compaction when used as an industrial product (e.g., electronic components). The coated inorganic powder according to this embodiment has excellent insulating properties even when formed as a thin film under a pressure of 13 MPa, exhibits excellent fluidity when filled into a mold during powder compaction, and also exhibits excellent water resistance. Therefore, the coated inorganic powder according to this embodiment is useful as a material for all industrial products that use inorganic powder, such as various electronic devices and electronic components manufactured by pressure compaction.

[0035] In particular, due to its excellent insulating properties and fluidity, the use of the coated inorganic powder of this embodiment makes it possible to realize miniaturization and high performance of various electronic devices and electronic components such as inductors, capacitors, thermistors, varistors, etc., and in addition, its excellent water resistance allows it to maintain its performance in a variety of environments, making it extremely useful in practice. Note that the coated inorganic powder of this embodiment includes not only inorganic powders having a coating on the surface thereof, but also inorganic powders having one or more coatings (e.g., oxide films) between the inorganic powder and the coating.

[0036] Next, the effects of the present invention will be specifically explained by showing examples and comparative examples of actual treatments, but the examples do not limit the present invention in any way.

[0037] "Inorganic Powder" Commercially available atomized pure iron powder (manufactured by Höganäs, ABC100.29, volume average particle size (D50) = 106 μm, hereinafter referred to as "pure iron powder") or Fe-5.5%Si-4%Cr atomized powder (soft magnetic powder manufactured by Nippon Atomize Processing Co., Ltd., volume average particle size (D50) = 10 μm, hereinafter referred to as "alloy powder") was used to produce inorganic powders as described below.

[0038] (Preparation of powder treatment liquid) As shown in Table 1, each component and pure water were mixed in a predetermined amount to prepare powder treatment agents according to Examples 1 to 23 and Comparative Examples 3 to 9. The free acidity was adjusted using sulfuric acid, sodium hydroxide, etc. The symbols shown in the "Component symbol" column in Table 1 are as follows: 1: Hexafluorozirconium acid 2: Zirconium sulfate tetrahydrate 3: Zirconyl nitrate dihydrate 4: Zirconium chloride 5: Zirconyl acetate 6: N-2-(aminoethyl)-3-aminopropyltrimethoxysilane 7: N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane 8: N-2-(aminoethyl)-3-aminopropyltriethoxysilane 9: 3-aminopropyltrimethoxysilane 10: 3-aminopropyltriethoxysilane 11: 3-triethoxysilyl-N-(1,4-dimethyl-butylidene)propylamine 12: N-phenyl-3-aminopropyltrimethoxysilane 13: Vinyltrimethoxysilane 14: Vinyltriethoxysilane 15: 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane 16: 3-glycidoxypropyltrimethoxysilane 17: 3-glycidoxypropylmethyldimethoxysilane 18: 3-glycidoxypropyltriethoxysilane 19: Tetraethoxysilane 20: Tetramethoxysilane 21: Tetrabutoxysilane 22: Tetraisopropoxysilane 23: Tetrapropoxysilane A: 67.5% nitric acid B: 85% phosphoric acid

[0039] Value A: parts by mass of zirconium ions per 100 parts by mass of alkoxysilane compound. Value B: parts by mass of aqueous medium per 100 parts by mass of alkoxysilane compound. Value C: parts by mass of silane coupling agent having an epoxy group per 100 parts by mass of alkoxysilane compound other than silane coupling agent having an epoxy group.

[0040] (Method for producing coated inorganic powder) 50 g of each of the inorganic powders shown in Table 1 was weighed out, powder treatment agents according to Examples 1 to 23 and Comparative Examples 3 to 8 shown in Table 1 were prepared, and the amounts of treatment liquid shown in Table 1 were weighed out and added to the inorganic powder, followed by stirring at 25°C for 5 minutes. Next, as a drying step, the stirred mixture was left to stand in an incubator maintained at 120°C for 30 minutes, yielding coated inorganic powders 1 to 31. Note that inorganic powders 24 and 25 did not form a coating and were left as the inorganic powder material.

[0041] (Measurement of N / Si molar ratio, Zr / Si molar ratio, C / Si molar ratio, and film thickness) After preparing a potting resin using an Epomount A Set (27-770, manufactured by Refine Tech Co., Ltd.), the potting resin was mixed with the coated inorganic powder according to the examples and comparative examples. This mixture was poured into a mold and allowed to harden. The cured product was mechanically polished, and then a flake was prepared using ion milling (IM-4000, manufactured by Hitachi High-Technologies Corporation). Elemental analysis of the coating of the coated inorganic powder in the flake was performed using an EDS attached to a field emission scanning electron microscope (FE-SEM, JEOL Ltd., JSM-F100). From the obtained elemental analysis values ​​of each element, the content of each element was determined, and the molar ratios of N / Si, Zr / Si, and C / Si were calculated. Film thickness was also measured by observation using the FE-SEM. These results are shown in Table 2.

[0042] (Evaluation of Insulation Properties) A ​​powder resistivity measuring system MCP-PD51 manufactured by Nitto Seiko Analytech Co., Ltd. (formerly Mitsubishi Chemical Analytech Co., Ltd.) and a Hiresta-UX or Loresta GX were used to apply pressure to a predetermined amount of coated inorganic powder to measure its volume resistivity (Ω cm). The pressure was set to 13 MPa, and the volume resistivity was measured at the predetermined pressure. The evaluation criteria were as follows: - The volume resistivity of the coated pure iron powder at a pressure of 13 MPa was 1.0 x 10 compared to the volume resistivity of the uncoated pure iron powder (Comparative Example 1) at a pressure of 13 MPa. ４ More than double is marked with "◎", 1.0 x 10 ３ More than twice 1.0×10 ４ Less than double is marked as "〇", 1.0 x 10 ２ More than twice 1.0×10 ３ Less than 1.0 x 10 is marked as "△"２ The volume resistivity of the alloy powder with a coating at a pressure of 13 MPa was 1.0×10 or less compared to the volume resistivity of the alloy powder without a coating (Comparative Example 2) at a pressure of 13 MPa. ６ More than double is marked with "◎", 1.0 x 10 ５ More than twice 1.0×10 ６ Less than double is marked as "〇", 1.0 x 10 ４ More than twice 1.0×10 ５ Less than 1.0 x 10 is marked as "△" ４ The results are shown in Table 2. The results were judged to be at a practical level when they were marked "Good" or "Excellent."

[0043] (Evaluation of fluidity) Evaluation was made in accordance with JIS Z 2502:2020. However, the inner diameter of the outlet side of the Hall flow meter used was Φ4.5 mm. The evaluation criteria were as follows: "◎" indicates an outflow time less than 1.1 times that of an inorganic powder not formed with a coating; "〇" indicates an outflow time that is 1.1 to 1.2 times that of an inorganic powder not formed with a coating; "△" indicates an outflow time that is 1.2 to 1.3 times that of an inorganic powder not formed with a coating; and "×" indicates an outflow time that is 1.3 times or more that of an inorganic powder not formed with a coating. These results are shown in Table 2. "〇" or "◎" was determined to be at a practical level.

[0044] (Evaluation of Water Resistance) In an environment at room temperature of 25°C, 2 g of inorganic powders 1 to 31 were weighed out and placed in a 100 ml beaker containing 50 g of pure water. The mixture was stirred using a glass rod to raise the inorganic powder. The stirring time was 1 minute. After 3 minutes of standing, the inorganic powder settled, and the supernatant was collected. 20 g of 35% hydrochloric acid was added, and the mixture was stirred for 30 minutes, followed by distilled water to make the total volume 100 ml. Quantitative analysis of Si, one of the coating components, was performed using ICP atomic emission spectroscopy (iCAP7400, manufactured by Thermo Fisher Scientific). The evaluation criteria were as follows: less than 0.3 mg / L was designated "◎", 0.3 mg / L to less than 0.7 mg / L was designated "◯", 0.7 mg / L to less than 1.0 mg / L was designated "△", and 1.0 mg / L or more was designated "X". The results are shown in Table 2. "Good" or "Excellent" was judged to be at a practical level.

[0045]

[0046] The coated inorganic powder according to the embodiment of the present invention has excellent insulating properties, fluidity, and water resistance, and can be used in any application where these properties are required. Furthermore, by using the powder treatment agent according to the embodiment of the present invention, a coating containing Zr, N, and Si can be formed on the surface of the inorganic powder, and the properties of the coating (insulating properties, fluidity, and water resistance) can be imparted to the inorganic powder. Thus, the powder treatment agent according to the embodiment of the present invention is useful for producing inorganic powders that can be used in a variety of applications. CROSS-REFERENCE TO RELATED APPLICATIONS

[0047] This application claims priority based on Japanese Patent Application No. 2023-182923, filed with the Japan Patent Office on October 25, 2023, the entire disclosure of which is incorporated herein by reference in its entirety.

Claims

1. A coated inorganic powder comprising: an inorganic powder; and a coating on a surface of the inorganic powder, the coating containing at least Zr, N and Si, the N / Si molar ratio being in the range of 0.010 or more and 1.000 or less, and the Zr / Si molar ratio being in the range of 0.10 or more and 10.00 or less.

2. The coated inorganic powder according to claim 1, wherein the coating further contains C, and the C / Si molar ratio in the coating is within the range of 0.20 to 20.

00.

3. The coated inorganic powder according to claim 1 or 2, wherein the coating does not contain at least one element selected from the group consisting of P, Ti and Cr.

4. An inorganic powder treatment agent, which is a mixed liquid containing at least zirconium ions, an alkoxysilane compound, and an aqueous medium, wherein the alkoxysilane compound contains a nitrogen-containing alkoxysilane, and the zirconium ions are in the range of 4 parts by mass or more and 400 parts by mass or less, and the aqueous medium is in the range of 100 parts by mass or more and 5,000 parts by mass or less, per 100 parts by mass of the alkoxysilane compound.

5. The inorganic powder processing agent according to claim 4, wherein the inorganic powder processing agent has a free acidity (pt) within the range of 1.0 point or more and 100.0 point or less.

6. The inorganic powder processing agent according to claim 4, wherein the alkoxysilane compound comprises a tetraalkoxysilane and a silane coupling agent having an amino group.

7. The inorganic powder treatment agent according to claim 4, wherein the alkoxysilane compound comprises a tetraalkoxysilane and a silane coupling agent having an epoxy group, and the amount of the silane coupling agent having an epoxy group is within the range of 2 parts by mass or more and 200 parts by mass or less per 100 parts by mass of the alkoxysilane compound other than the silane coupling agent having an epoxy group.

8. A method for producing a coated inorganic powder, comprising a step of heating a composition containing an inorganic powder and the inorganic powder treatment agent described in any one of claims 4 to 7 to evaporate volatile matter in the composition and form a coating on the surface of the inorganic powder.