Inorganic powder, production method thereof, and usable powder treatment agent for production thereof

Abstract

To provide a coated inorganic powder with good insulation properties, fluidity, and water resistance.SOLUTION: The inorganic powder is coated with a film containing Zr, N, and Si. The molar ratios of N / Si and Zr / Si fall within predetermined ranges.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an inorganic powder having excellent insulation properties, water resistance and flowability and 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. [Background technology]

[0002] In recent years, with the miniaturization and high functionality of electronic devices and electrical devices, electronic components used therein are required to have excellent magnetic properties. Therefore, inorganic powders used in electronic components need to have high insulation properties. In addition to insulation properties, they also need to have fluidity during powder molding and water resistance of the coating that allows long-term use in various environments. Therefore, inorganic powders having a coating on the surface that has both of the above properties have been developed.

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

[0004] Patent Document 2 discloses a particle coating treatment liquid that contains at least one silicon compound having an alkoxysilyl group, an alkoxysilylene group, and a siloxane bond, an organometallic compound, and a metal salt. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4436172 [Patent Document 2] JP 2019-157189 A Summary of the Invention [Problem to be solved by the invention]

[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 long-term performance maintenance in various environments. In addition, the particle coating forming treatment liquid of Patent Document 2 may not provide sufficient fluidity. Therefore, an object of the present invention is to provide a coated inorganic powder that is excellent in insulation, fluidity, and water resistance, a method for producing the same, and a powder treatment agent that can be used in the production method. [Means for solving the problem]

[0007] As a result of intensive research to solve the above problems, the present inventors have found that by using a specified powder processing agent to form a coating containing Zr, N and Si, with N / Si and Zr / Si molar ratios each falling within a specified range, on the surface of an inorganic powder, it is possible to obtain an inorganic powder having excellent insulation properties, fluidity and water resistance, and have completed the present invention.

[0008] That is, the present invention provides: (1) A coated inorganic powder comprising an inorganic powder and a coating on the 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 to 1.000, and the Zr / Si molar ratio being in the range of 0.10 to 10.00; (2) The inorganic powder with a coating according to (1) above, wherein the coating further contains C and the C / Si molar ratio in the coating is within the range of 0.20 or more and 20.00 or less; (3) The inorganic powder with a coating according to (1) or (2) above, wherein the coating does not contain at least one selected from P, Ti, and Cr; (4) A powder processing agent which is a mixed liquid containing at least zirconium ions, an alkoxysilane compound, and an aqueous medium, the alkoxysilane compound containing a nitrogen-containing alkoxysilane, the zirconium ions being in the range of 4 parts by mass or more and 400 parts by mass or less, and the aqueous medium being 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 (4) above, 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 (4) or (5) above, 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 contains 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 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 a step of heating a composition containing an inorganic powder and the inorganic powder processing agent according to any one of (4) to (7) above to evaporate volatile matters in the composition and form a coating on the surface of the inorganic powder; etc. Effect of the Invention

[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. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The 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, since it is useful, for example, as a material for electronic components. The magnetic inorganic powder is preferably one containing iron. The inorganic powder is also preferably a conductor, for example, one having an electrical conductivity of 1×10 6 S / m or more, and 1×10 5 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, Fe amorphous, etc. Examples of other inorganic powders include inorganic compounds such as metal oxides, nitrides, borides, etc. Examples of inorganic metal compounds include barium titanate (BaTiO3), boron nitride (BN), ferrite (MFe2O4; M represents a divalent metal element), lead zirconate titanate {Pb(Zr,Ti)O3}, aluminum oxide (Al2O3), silicon carbide (SiC), zinc oxide (ZnO), zirconia (ZrO2), zircon (ZrO2·SiO2), forsterite (2MgO·SiO2), mullite (3Al2O3·2SiO2), steatite (MgO·SiO2), cordierite (2MgO·2Al2O3·5SiO2), aluminum nitride (AlN), and silicon nitride (Si3N4).

[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 the 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 a value obtained by randomly selecting 100 inorganic powders in an image analysis using a scanning electron microscope, measuring the longest and shortest diameters of each inorganic powder, and averaging the measured lengths for the 100 inorganic powders.

[0013] The coating of the inorganic powder with coating 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 an ion source containing zirconium, which will be described later. However, it is preferable that the coating does not contain at least one selected from P, Ti, and Cr. Here, "does not contain" means that the coating does not substantially contain any of the elements, and does not exclude the presence of trace amounts of the elements.

[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 the molar ratio of Zr to Si (Zr / Si) in the coating is within a certain range. By keeping these molar ratios within a certain range, the coating having superior fluidity, water resistance, and insulating properties can be uniformly formed on the surface of the inorganic powder.

[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 is preferably within a certain range. The C / Si mass ratio is preferably within a range of 0.20 to 20.00, more preferably within a range of 0.30 to 10.00, and particularly preferably within a range of 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 inorganic powder with the coating 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 produced using ion milling. Next, the inorganic powder coating in the flake is subjected to elemental analysis using an 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 (strength) 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 coating thickness can be measured by observing the prepared thin piece 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 inorganic powder with a coating according to this embodiment (for example, insulating magnetic powder). 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 contains nitrogen-containing alkoxysilane), zirconium ions, and an aqueous medium, and may contain other components. The zirconium ions contained in the powder treatment liquid are preferably in the range of 4 parts by mass to 400 parts by mass, and more preferably in the range of 10 parts by mass to 100 parts by mass, relative to 100 parts by mass of the alkoxysilane compound. In addition, the aqueous medium contained in the powder treatment liquid is preferably in the range of 100 parts by mass to 5000 parts by mass, and more preferably in the range of 300 parts by mass to 3000 parts by mass, relative to 100 parts by mass of the alkoxysilane compound. By using this powder treatment liquid, a coating having a 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, can be more stably produced. 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 processing 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. The nitrogen-containing alkoxysilane compound can be used alone or in combination of two or more.

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

[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, tetraalkoxysilanes) as the alkoxysilane. For example, silane coupling agents having a vinyl group such as vinyltrimethoxysilane and vinyltriethoxysilane; silane coupling agents having an epoxy group such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycidoxypropyltriethoxysilane; and the like. 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 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 may contain a tetraalkoxysilane, a silane coupling agent having an amino group, and a silane coupling agent having an epoxy group. The alkoxysilane compound may 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 parts by mass to 200 parts by mass, more preferably in the range of 10 parts by mass to 100 parts by mass, relative to 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. In addition, 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 it is not intentionally mixed, and does not exclude unavoidable mixing. 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 embodiment contains zirconium ions. The water-soluble zirconium compound as the zirconium ion source is not particularly limited, and examples thereof include hexafluorozirconic acid, zirconium sulfate tetrahydrate, zirconyl nitrate dihydrate, zirconium chloride, zirconyl acetate, and the like. These reagents can be used alone or in combination of two or more. In this specification, the term "water-soluble" means that 1 g or more 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, a combination of tetraethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and combination of tetramethoxysilane, 3-aminopropyltrimethoxysilane, and hexafluorozirconium acid; combination of tetramethoxysilane, vinyltriethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-aminopropyltriethoxysilane, and zirconium sulfate tetrahydrate; combination of tetrabutoxysilane, vinyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-triethoxysilyl-N-(1,4-dimethyl-butylidene)propylamine, and zirconyl nitrate dihydrate; combination of tetraisopropoxysilane, 3-glycidoxypropyltrimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, and zirconium chloride; 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 hexafluorozirconium acid, a combination of tetramethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, and zirconium sulfate tetrahydrate, a combination of tetrabutoxysilane, vinyltriethoxysilane, and 3-glycidoxypropylmethyldimethoxysilane, and combination of glycidoxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, and zirconyl nitrate dihydrate; combination of tetraisopropoxysilane, vinyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-aminopropyltriethoxysilane, and zirconium chloride; combination of tetrapropoxysilane, 3-glycidoxypropyltriethoxysilane, 3-triethoxysilyl-N-(1,4-dimethyl-butylidene)propylamine, and zirconyl acetate; combination of tetraethoxysilane, vinyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and N-phenyl-3 -aminopropyltrimethoxysilane and hexafluorozirconate, tetramethoxysilane, vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane and zirconium sulfate tetrahydrate, tetrabutoxysilane and 2-(3,Combination of 4-epoxycyclohexyl)ethyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, and zirconyl nitrate dihydrate, combination of tetraisopropoxysilane, vinyltriethoxysilane, 3-glycidoxypropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, and zirconium chloride, combination of tetrapropoxysilane, vinyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane, and zirconyl acetate, combination of tetraethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and hexafluorozirconium acid, combination of tetramethoxysilane, vinyltriethoxysilane, and 2-(3,4-epoxycyclohexyl ) Ethyltrimethoxysilane, 3-triethoxysilyl-N-(1,4-dimethyl-butylidene)propylamine, and zirconium sulfate tetrahydrate; tetrabutoxysilane, vinyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, and zirconyl nitrate dihydrate; tetraisopropoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and N-2-(aminoethyl)-3-aminopropyltrimethoxysilane. Examples of the combination include a combination of silane and zirconium chloride, a combination of tetrapropoxysilane, vinyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, and zirconyl acetate, and a combination of tetraethoxysilane, vinyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, and hexafluorozirconium acid.

[0028] The aqueous medium contained in the powder processing agent according to the present 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-based solvents such as acetone and methyl ethyl ketone; amide-based solvents such as N,N'-dimethylformamide and dimethylacetamide; alcohol-based solvents such as methanol, ethanol, and isopropanol; ether-based solvents such as ethylene glycol monobutyl ether and ethylene glycol monohexyl ether; and pyrrolidone-based 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 of them 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), distilled water, and the like.

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

[0030] Free acidity (pt) means that 10 ml of the powder processing agent is taken, 2 to 3 drops of "D-11" manufactured by Nihon Parkerizing Co., Ltd. are added, and then titrated with "T-11" manufactured by Nihon Parkerizing Co., Ltd., and the amount of "T-11" (ml) is expressed as a point (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. The lubricant may be further provided as a lubricating coating on the coating according to the present embodiment.

[0032] The inorganic powder with a coating according to the present embodiment can be produced by contacting the inorganic powder with the powder treatment agent, and then heating the powder treatment agent to evaporate the volatile content of the powder treatment agent, thereby forming a coating on the inorganic powder. More specifically, the inorganic powder with a coating can be produced by heating a composition containing the powder treatment agent and the inorganic powder, and evaporating the volatile content in the composition (the volatile content in the powder treatment agent). The contact between the powder treatment agent and the inorganic powder may be performed by a mixing method, or other contact methods may be adopted. In order to stably and efficiently produce the inorganic powder, it is preferable to heat the composition in air or an inert gas (nitrogen, carbon dioxide, helium, neon, argon, krypton, xenon, radon, etc.) and evaporate the volatile content in the composition. The evaporation of the volatile content can be performed, for example, using a spray dryer. After evaporating the volatile matter, a step of forming another film on the surface of the inorganic powder with a film, for example, a step of contacting the inorganic powder with a lubricant to form a lubricating film, may be further provided. The contact method is not particularly limited, and examples thereof include a method of immersing the inorganic powder in a lubricant and a method of mixing the inorganic powder with a lubricant. In addition, the production of the inorganic powder may further include a step of drying the surface of the inorganic powder with the lubricant after contacting the inorganic powder with the lubricant. The drying method is not particularly limited, and examples thereof include a method of heating in air or an inert gas. By the above production method, an inorganic powder with a film having a lubricating film 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 less, more preferably 300°C or less, and particularly preferably 200°C or less. 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 less, and more preferably 100°C or less.

[0034] The inorganic powder with a coating according to this embodiment is typically subjected to powder compaction when used as an industrial product (e.g., electronic components). The inorganic powder with a coating according to this embodiment has excellent insulating properties even as a thin film under a pressure condition of 13 MPa, and exhibits excellent fluidity when filled into a mold during powder compaction, and further exhibits excellent water resistance. Therefore, the inorganic powder with a coating 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 the 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, due to its excellent water resistance, it is possible to maintain performance in various environments, making it extremely useful in practical use. 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, etc.) between the inorganic powder and the coating. EXAMPLES

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

[0037] "Inorganic powder" Inorganic powders were produced as described below using a 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 an 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").

[0038] (Preparation of Powder Processing Solution) As shown in Table 1, each component and pure water were mixed in a given amount to prepare powder processing 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: Hexafluorozirconate 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] [Table 1] A value: parts by mass of zirconium ion relative to 100 parts by mass of alkoxysilane compound B value: parts by mass of aqueous medium relative to 100 parts by mass of alkoxysilane compound C value: Alkoxysilane compounds other than silane coupling agents having epoxy groups Parts by weight of silane coupling agent having an epoxy group per 100 parts by weight

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

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

[0042] (Insulation evaluation) Using Nitto Seiko Analytech Co., Ltd. (formerly Mitsubishi Chemical Analytech Co., Ltd.) powder resistivity measurement system MCP-PD51 and Hiresta-UX or Loresta GX, pressure was applied to a specified amount of inorganic powder with a coating to measure the volume resistivity (Ω·cm). The pressure was 13 MPa, and the volume resistivity was measured at the specified pressure. The evaluation criteria were as follows: Compared to the volume resistivity of the pure iron powder without a coating (Comparative Example 1) at a pressure of 13 MPa, the volume resistivity of the pure iron powder with a coating at a pressure of 13 MPa was 1.0×10 4 More than double is marked as "◎"; 1.0×10 3 More than 1.0×10 4 Less than double is marked as "〇", 1.0×10 2 More than 1.0×10 3 Less than double is marked as "△" 1.0×10 2 Anything less than double was marked as "X". Compared to the volume resistivity of the alloy powder without a coating (Comparative Example 2) at a pressure of 13 MPa, the volume resistivity of the alloy powder with a coating at a pressure of 13 MPa was 1.0×10 6 More than double is marked as "◎"; 1.0×10 5 More than 1.0×106 Less than double is marked as "〇", 1.0×10 4 More than 1.0×10 5 Less than double is marked as "△" 1.0×10 4 The results are shown in Table 2. Furthermore, "◯" or "◎" was judged to be at a practical level.

[0043] (Liquidity assessment) The evaluation was conducted in accordance with JIS Z 2502:2020. However, the inner diameter of the outlet side of the Hall Flow Meter used was Φ4.5mm. The evaluation criteria were as follows: The outflow time is less than 1.1 times longer than that of inorganic powder without a coating, and the rating is "◎". A rating of "good" indicates that the outflow time is 1.1 to 1.2 times longer than that of inorganic powder without a coating. The outflow time is 1.2 to 1.3 times longer than that of inorganic powder without a coating, and is marked as "△". The flow time was marked as "X" when it was 1.3 times or more longer than that of an inorganic powder that did not form a coating. The results are shown in Table 2. Incidentally, "◯" or "◎" was judged to be at a practical level.

[0044] (Water resistance evaluation) 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, and the mixture was stirred using a glass rod so that the inorganic powder would fly up. The stirring time was 1 minute. After that, the mixture was left to stand for 3 minutes, and the supernatant liquid after the inorganic powder had settled was collected, 20 g of 35% hydrochloric acid was added, and the mixture was stirred for 30 minutes, and then the mixture was made up to 100 ml with DI water. A quantitative analysis of Si, one of the film components, was performed using ICP emission spectroscopy (iCAP7400 manufactured by Thermo Ficher Scientific). The evaluation criteria were as follows. Less than 0.3mg / L is marked as "◎"; 0.3mg / L or more but less than 0.7mg / L is marked as "○"; 0.7mg / L or more but less than 1.0mg / L is marked as "△"; Levels of 1.0 mg / L or higher were marked as "X". The results are shown in Table 2. Incidentally, "◯" or "◎" was judged to be at a practical level.

[0045] [Table 2] [Industrial Applicability]

[0046] The inorganic powder with a coating according to the embodiment of the present invention has excellent insulating properties, fluidity, and water resistance, and can be applied to any application where these properties are required. In addition, by using the powder processing 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. In this way, the powder processing agent according to the embodiment of the present invention is useful for producing inorganic powder that can be applied to various applications.

Claims

1. An inorganic powder; 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; The coated inorganic powder has the following properties:

2. 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 or more and 20.00 or less.

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

4. A mixed liquid containing at least zirconium ions, an alkoxysilane compound, and an aqueous medium, the alkoxysilane compound comprises a nitrogen-containing alkoxysilane; the zirconium ion is 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, relative to 100 parts by mass of the alkoxysilane compound.

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

6. 5. 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 alkoxysilane compound contains a tetraalkoxysilane and a silane coupling agent having an epoxy group, The inorganic powder processing agent according to claim 4, wherein 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 the steps of: heating a composition containing an inorganic powder and the inorganic powder treatment agent according to any one of claims 4 to 7 to evaporate volatile matter in the composition and form a coating on a surface of the inorganic powder.

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