Method for manufacturing coated metal magnetic particles, magnetic cores, and inductors

Abstract

The present invention aims to provide a photosensitive composition that can form a film with good storage stability, heat shock resistance, and resolubility, and that is less prone to developing stains and has excellent solvent resistance after the low-temperature curing process. [Solution] A method for producing coated metal magnetic particles, comprising heating a mixture containing metal magnetic particles, a silane compound, a pyrolytic ammonium salt, and water, in the presence of ammonia produced by heating, in which case the silane compound reacts and coats the metal magnetic particles. The decomposition temperature of the pyrolytic ammonium salt is preferably 40 to 120°C.

Description

[Technical Field]

[0001] This invention relates to coated metal magnetic particles. [Background technology]

[0002] Conventionally, inductors and powdered magnetic cores have used metallic magnetic particles as the magnetic material constituting the core. Since core loss occurs when electrical conductivity occurs between metallic magnetic particles, it is common practice to form an insulating coating on the surface of the metallic magnetic particles before use.

[0003] The formation of the insulating coating can be achieved, for example, by chemical treatment with phosphate, by spray treatment with a silane compound, or by wet sol-gel reaction of a silane compound.

[0004] Among these methods, the method of wet sol-gel reaction of silane compounds involves sequentially reacting silane compounds in a solvent to form a coating layer on the particle surface, resulting in a homogeneous coating layer with easy control of film thickness. However, this method is known to involve a side reaction in which silica nanoparticles precipitate independently in parallel with the formation of the coating layer, resulting in a problem of low utilization efficiency of the silane compound (efficiency of forming the insulating coating layer).

[0005] Patent Document 1 discloses a method for forming a silica film on the surface of a soft magnetic powder mainly composed of iron, stating that a silica film can be formed by controlling the concentrations of tetraethoxysilane and water, pH, etc., in a hydrolysis solution containing tetraethoxysilane, an organic solvent, an alkali, and water. Patent Document 2 discloses a technique for coating rare earth magnetic powder with silica, stating that a homogeneous silica coating layer can be formed by using ammonia, ethylenediamine, ammonium carbonate, etc., as a hydrolysis catalyst for silicon alkoxide and by sufficiently slowing down the addition rate of silicon alkoxide. [Prior art documents] [Patent Documents]

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, the method of Patent Document 1 had insufficient insulation because the surface of the soft magnetic powder was coarsely coated. Also, the method of Patent Document 2 had a long coating treatment time and poor production efficiency.

[0008] An object of the present invention is to provide a method for producing coated metal magnetic particles that can coat metal magnetic particles relatively uniformly in a shorter time than conventional methods.

Means for Solving the Problems

[0009] The present invention relates to a method for producing coated metal magnetic particles in which a silane compound reacts and coats metal magnetic particles in the presence of ammonia generated by heating a mixture containing metal magnetic particles, a silane compound, a thermally decomposable ammonium salt, and water.

Effects of the Invention

[0010] According to the present invention, a method for producing coated metal magnetic particles that can coat metal magnetic particles relatively uniformly in a shorter time than conventional methods can be provided. Also, the present invention can provide a method for producing magnetic cores and inductors.

Modes for Carrying Out the Invention

[0011] The terms used in this specification are defined. "(Meth)acryl" means "acryl and / or methacryl". Also, the numerical range specified using "~" in this specification shall include the numerical values described before and after "~" as the range of the lower limit value and the upper limit value.

[0012] Hereinafter, the present disclosure will be described in detail. The present disclosure is not limited to the specific embodiments listed below.

[0013] The present invention is a method for producing coated metal magnetic particles in which a silane compound reacts in the presence of ammonia generated by heating a mixture containing metal magnetic particles, a silane compound, a thermally decomposable ammonium salt, and water to coat the metal magnetic particles.

[0014] The mechanism by which the present invention can solve the problems is speculated as follows. Generally, the reaction rate of the silane compound increases according to the strength of the basicity of the base. Therefore, when a strong base is used in the reaction to coat the metal magnetic particles with the silane compound, the reaction rate becomes excessive, and foreign substances due to the self-reaction of the silane compound are generated, resulting in a decrease in the utilization efficiency of the silane compound for the coating. In addition, the formed coating layer tends to be non-uniform. On the other hand, when a weak base is used, the reaction rate is slow and it takes a long time for the coating. In the present invention, by using a thermally decomposable ammonium salt and gradually generating ammonia by heating, the reaction rate of the silane compound and the rate of coating the metal magnetic particles can be adjusted to an appropriate rate. Thereby, generation of foreign substances due to the self-reaction of the silane compound can be suppressed, and coated metal magnetic particles having a more homogeneous coating layer than before can be produced in an appropriate time.

[0015] [Metal magnetic particles] The metal magnetic particles are particles of a magnetic metal. From the viewpoint of magnetic properties, particles containing 20% by mass or more of iron are preferable for the metal magnetic particles. Further, the iron content is more preferably 50% by mass or more, even more preferably 80% by mass or more, particularly preferably 85% by mass or more, and most preferably 90% by mass or more. Incidentally, there is no limit to the upper limit value of the iron content, but it is preferably 99.8% by mass or less, and more preferably 99.5% by mass or less.

[0016] The average primary particle diameter of the metallic magnetic particles is preferably 0.1 to 100 μm. More preferably, the average primary particle diameter is 0.5 μm or more, and even more preferably 1 μm or more. More preferably, it is 60 μm or less, even more preferably 50 μm or less, and particularly preferably 35 μm or less. The average primary particle diameter can be obtained by selecting approximately 20 arbitrary particles from a magnified image of 1000x using a scanning electron microscope, measuring their particle diameters, and calculating the arithmetic mean. If the particle image is, for example, elliptical, the average of the lengths of the major and minor axes is used.

[0017] The shape and average primary particle diameter of the metallic magnetic particles can be appropriately set according to the shape and average primary particle diameter of the coated metallic magnetic particles being manufactured.

[0018] Metallic magnetic particles may have a coating on their surface. Examples of coatings include native oxide films, metal films, carbon films, chemiadsorption films, and silane compound films. A native oxide film can be formed, for example, by oxidizing metallic magnetic particles in the atmosphere. A metal film can be formed, for example, by calcining metallic magnetic particles. A chemiadsorption film can be formed, for example, by spraying an adsorbate solution onto metallic magnetic particles. A silane compound film can be formed by spraying a silane compound or by a wet sol-gel reaction. In this specification, a good coating layer can be formed even when these coatings are formed on the surface of metallic magnetic particles.

[0019] The pH of the metal magnetic particles is preferably 7 to 10, more preferably 8 to 10, and even more preferably 8.5 to 10. The pH of the metal magnetic particles is measured using a pH meter at a liquid temperature of 25°C after preparing a suspension by adding 1 g of metal magnetic particles to 9 g of deionized water and treating it in an ultrasonic cleaner for 10 minutes.

[0020] The specific surface area of ​​metallic magnetic particles ranges from 0.01 to 20 m². 2 / g is preferable. Also, the specific surface area is 10m². 2 More preferably less than / g, 5m 2 It is even more preferable to be less than / g, 1m2 / g or less is particularly preferred, and 0.5m 2 It is most preferable that the amount is less than or equal to / g. Furthermore, the specific surface area is 0.05m². 2 More preferably 0.1m / g or more, 2 A value of 1 / g or higher is even more preferable. The specific surface area can be measured using Macsorb HM model-1220 (Mountech) and analyzed using the BET single-point method to obtain the BET specific surface area by nitrogen gas adsorption method.

[0021] Examples of metallic magnetic particles include pure iron powder particles such as iron powder and carbonyl iron particles; metal alloy particles such as iron-silicon alloy particles, iron-chromium alloy particles, iron-nickel alloy particles, iron-manganese alloy particles, iron-silicon-aluminum alloy particles, and iron-silicon-chromium alloy particles; and metal oxide particles such as ferrite. Among these, pure iron powder particles or metal alloy particles are particularly good at providing insulation and weather resistance in addition to magnetism.

[0022] Examples of commercially available metal magnetic particles include BASF's carbonyl iron powder (soft grade) and carbonyl iron powder (hard grade).

[0023] Examples of metallic magnetic particles include spherical and nearly spherical particles; and non-spherical particles such as flakes, scales, and filaments. Among these, spherical particles are preferred from the viewpoint of handling and manufacturing cost. Nearly spherical particles are generally spherical and may include elliptical shapes, and may have irregularities on their surface.

[0024] [Silane compounds] Silane compounds are compounds that have hydrolyzable groups bonded to silicon atoms. Silane compounds form a coating layer on the surface of metal magnetic particles through hydrolysis reactions. These hydrolyzable groups are hydrolyzed by water to produce silanol groups, and these silanol groups further undergo condensation reactions to produce high molecular weight products or crosslinked products (reaction products of silane compounds). By coating metal magnetic particles with reaction products of silane compounds, a coating layer with good insulation and weather resistance can be formed. Furthermore, it is possible to achieve a high level of balance between the magnetic properties, insulation, and weather resistance of the coated metal magnetic particles.

[0025] Examples of the hydrolyzable group include alkoxy groups and aryloxy groups. Among these, alkoxy groups are preferred. Among alkoxy groups, methoxy groups or ethoxy groups are preferred, and ethoxy groups are more preferred.

[0026] From the viewpoint of forming a coating layer, the silane compound preferably contains a tetrafunctional silane compound. The content of the tetrafunctional silane compound is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably substantially 100% by mass, of the silane compound.

[0027] Tetrafunctional silane compounds are compounds having four hydrolyzable groups, and examples include tetraalkoxysilane compounds such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane. Among these, tetramethoxysilane or tetraethoxysilane are preferred from the viewpoint of availability and reactivity, and tetraethoxysilane is more preferred.

[0028] Silane compounds other than tetrafunctional silane compounds include trifunctional silane compounds and difunctional silane compounds. Examples of trifunctional silane compounds include trialkoxysilane compounds having one functional group other than a hydrolyzable group. Examples of difunctional silane compounds include dialkoxysilane compounds having two functional groups other than a hydrolyzable group. Functional groups other than hydrolyzable groups in silane compounds include, for example, alkyl groups, substituted alkyl groups, alkenyl groups, aryl groups, styryl groups, and phenyl groups. Furthermore, substituents on substituted alkyl groups can include, for example, amino groups, alkoxy groups, (meth)acrylic groups, epoxy groups, mercapto groups, ureido groups, acid anhydride groups, isocyanate groups, isocyanurate groups, and so on.

[0029] The amount of silane compound used is preferably 0.1 to 10% by mass, more preferably 0.2% by mass or more, even more preferably 0.5% by mass or more, and particularly preferably 0.7% by mass or more, based on 100% by mass of metal magnetic particles. Furthermore, the amount of silane compound used is more preferably 7.5% by mass or less, even more preferably 5% by mass or less, and particularly preferably 4% by mass or less.

[0030] The amount of coating by components derived from silane compounds is preferably 0.1 to 10% by mass per 100% by mass of metal magnetic particles. Furthermore, the amount of coating by components derived from silane compounds is preferably 0.2% or more, more preferably 0.5% or more, and even more preferably 0.7% by mass or more. Moreover, it is preferably 7.5% by mass or less, more preferably 5% by mass or less, and even more preferably 4% by mass or less.

[0031] [Thermolytic ammonium salts] Pyrolytic ammonium salts are compounds that decompose upon heating to produce ammonia and function as reaction catalysts for silane compounds. Examples of pyrolytic ammonium salts include ammonium carbonate, ammonium bicarbonate, and ammonium carbamate. The acid produced along with ammonia after thermal decomposition of pyrolytic ammonium salts slows the reaction rate of the hydrolyzable groups of silane compounds, thereby suppressing the reaction between silane compounds. As a result, it is hypothesized that silane compounds can coat the surface of metal magnetic particles more uniformly than before by gradually coating them.

[0032] The thermal decomposition temperature of the pyrolytic ammonium salt is preferably 40°C or higher, more preferably 50°C or higher, and even more preferably 55°C or higher, from the viewpoint of optimizing the amount of ammonia supplied to the reaction system and the reaction rates of hydrolysis and condensation of the silane compound. Furthermore, the thermal decomposition temperature is preferably 120°C or lower, more preferably 100°C or lower, even more preferably 80°C or lower, and particularly preferably 65°C or lower.

[0033] The molecular weight of the pyrolytic ammonium salt is preferably 200 or less, more preferably 150 or less, and even more preferably 100 or less, from the viewpoint of the amount of ammonia supplied to the reaction system.

[0034] The amount of pyrolytic ammonium salt added is preferably 5 to 50 parts by mass, more preferably 5 to 35 parts by mass, and even more preferably 5 to 25 parts by mass, per 100 parts by mass of the silane compound. The reaction rate of the silane compound can be controlled more gently by the amount added.

[0035] [water] Water is the reaction solvent and also reacts with silane compounds to produce silanol groups. The amount of water added is preferably 80 to 200 parts by mass, more preferably 100 to 180 parts by mass, and even more preferably 115 to 150 parts by mass, per 100 parts by mass of the silane compound. By adding 80 to 200 parts by mass of water, it is possible to achieve a high degree of balance between the rate of silanol group formation and the rate of the condensation reaction. This allows the coating of the metal magnetic particles to proceed efficiently.

[0036] [organic solvent] In this specification, an organic solvent may be used in combination with water. The organic solvent is preferably a water-soluble organic solvent that is miscible with water. The boiling point of the organic solvent at atmospheric pressure (1013 hPa) is preferably 50°C to 150°C, more preferably 70°C to 120°C, and even more preferably 70°C to 100°C, from the viewpoint of heatability and volatility.

[0037] Examples of water-soluble organic solvents include alcohol-based solvents (methanol, ethanol, 1-propanol, isopropanol, butanols, benzyl alcohol, etc.), polyhydric alcohol-based solvents (alkylene glycols, dialkylene glycols, polyalkylene glycols, glycerin, etc.), polyhydric alcohol ether-based solvents (alkylene glycol monoalkyl ethers, dialkylene glycol monoalkyl ethers, etc.), amine-based solvents (ethanolamine, diethanolamine, triethanolamine, N-ethyldiethanolamine, etc.), amide-based solvents (N-methyl-2-pyrrolidone (NMP), etc.), heterocyclic solvents (γ-butyrolactone, etc.), and lower ketone-based solvents (acetone, methyl ethyl ketone, etc.). Among these water-soluble organic solvents, alcohol-based solvents are more preferred from the viewpoint of availability, boiling point, and volatility, with ethanol, 1-propanol, isopropanol, and butanols being even more preferred, and ethanol, 1-propanol, and isopropanol being particularly preferred.

[0038] <Manufacturing of coated metal magnetic particles> The present invention's method for producing coated metal magnetic particles (hereinafter also referred to as "this production method") involves heating a mixture containing metal magnetic particles, a silane compound, a pyrolytic ammonium salt, and water, and in the presence of ammonia produced by this heating, the silane compound reacts to coat the metal magnetic particles. A mixture containing metallic magnetic particles, a silane compound, a pyrolytic ammonium salt, and water (hereinafter also referred to as "this mixture") is prepared and heated to generate ammonia from the pyrolytic ammonium salt. This ammonia functions as a catalyst for the hydrolysis and condensation reactions of the silane compound. The silane compound then undergoes hydrolysis and condensation to produce high molecular weight materials and crosslinked materials (reaction products of the silane compound), which coat the metallic magnetic particles. This manufacturing method allows for temperature-controlled supply of the reaction catalyst (ammonia), resulting in a reaction atmosphere more suitable for coating metal magnetic particles with silane compounds. Specifically, it is expected that milder reaction conditions can be obtained compared to using strong bases as catalysts, thereby suppressing the deposition of silica nanoparticles as a side reaction in coating layer formation, and improving the coating efficiency of metal magnetic particles with silane compounds. Furthermore, compared to methods that control the reaction rate by dropwise adding catalysts and silane compounds, this method allows the coating reaction to be carried out without a dropwise addition step, enabling the production of metal magnetic particles more efficiently and in a shorter time.

[0039] [Preparation of this mixture] This mixture can be prepared, for example, by mixing metallic magnetic particles with water, then adding a silane compound and a pyrolytic ammonium salt, and stirring the mixture. Alternatively, the mixture can be further prepared by adding an organic solvent.

[0040] From the viewpoint of fluidity, the content of metal magnetic particles in 100% by mass of this mixture is preferably 60 to 95% by mass, more preferably 75 to 95% by mass, and even more preferably 80 to 90% by mass.

[0041] The temperature at which this mixture is prepared is preferably 50°C or lower, more preferably 40°C or lower, and particularly preferably 30°C or lower, from the viewpoint of reaction control. There is no particular limit to the lower temperature, but from the viewpoint of water handling, it is preferably 0°C or higher, and more preferably 10°C or higher.

[0042] There is no limit to the stirring and mixing time for preparing this mixture; for example, it can be 10 to 60 minutes.

[0043] Examples of equipment used for stirring and mixing include dispersers, anchor mixers, planetary mixers, trimixes, homogenizer mixers, kneaders, and other kneading and mixing devices, as well as tumbler mixers, attritors, roll mills, and rotational and revolving mixers. The stirring and mixing equipment used can be appropriately configured according to the handling requirements of the mixture.

[0044] [Heating of this mixture] When this mixture is heated, it produces ammonia from the pyrolytic ammonium salt. The ammonia produced by heating accelerates the hydrolysis of the silane compound, and further condensation reactions occur between the hydrolyzed products of the silane compound.

[0045] The heating temperature is preferably above the thermal decomposition temperature of the thermally decomposable ammonium salt. For example, a heating temperature of 50°C or higher is more preferable, 65°C or higher is even more preferable, and 80°C or higher is particularly preferable. Furthermore, a temperature of 200°C or lower is more preferable, 150°C or lower is even more preferable, and 120°C or lower is particularly preferable. By setting the heating temperature in this way, it is possible to achieve a high degree of balance between the supply of ammonia and the reaction rates of hydrolysis and condensation of silane compounds, thereby effectively coating the metal magnetic particles.

[0046] One embodiment of heating this mixture is to heat it to 50°C or higher, and then to a temperature at least 10°C higher than that initial heating temperature.

[0047] There are no particular restrictions on the heating time of this mixture, but from the viewpoint of production time, for example, 1 to 10 hours, and more preferably 2 to 8 hours.

[0048] [Drying of coated metal magnetic particle solution] After coating, the coated metal magnetic particle solution is dried to obtain powdered coated metal magnetic particles. Drying can be done directly, or after filtering with a filter or the like. From the viewpoint of drying efficiency, it is preferable to filter with a filter or the like before drying.

[0049] Drying equipment can include, for example, box-type dryers, vacuum dryers, spray dryers, and vibrating dryers. Drying is preferably performed to obtain a powder while thoroughly removing volatile components such as water and organic solvents. If the dried material is in block form, a metal ball or the like can be added to the dryer and stirred, or the material can be pulverized using a pulverizer after drying to obtain a fine powder. Alternatively, coarse particles can be removed from the obtained dried material by filtration or classification.

[0050] The drying temperature is preferably 70 to 300°C, more preferably 80 to 200°C, and particularly preferably 80 to 150°C, in order to control the formation state of the coating layer while removing volatile components.

[0051] The drying time is adjusted as appropriate depending on the equipment, reaction scale, type of solvent component, and ratio, but is preferably 1 to 20 hours, more preferably 1 to 10 hours, and particularly preferably 1 to 5 hours.

[0052] When using vacuum drying (reduced pressure drying), for example, drying at a pressure (absolute pressure) of 0.02 MPa or less will result in good drying.

[0053] <Coated metal magnetic particles> The coated metallic magnetic particles according to this disclosure have metallic magnetic particles and a coating layer formed on their surface. This coating layer mainly contains a silane compound or a reaction product thereof.

[0054] The coated metallic magnetic particles of this disclosure can be used in a variety of fields. Examples of applications include magnetic cores, inductors, electromagnetic wave absorbing materials, coils, and various electronic components that use them.

[0055] The coated metal magnetic particles of this disclosure can efficiently form a more homogeneous coating layer than conventional methods, thereby providing the metal magnetic particles with high insulation and weather resistance. The coating layer covers all or part of the metal magnetic particles to the extent that the problem is solved.

[0056] The average primary particle diameter of the coated metal magnetic particles is preferably 0.1 to 100 μm. Further, the average primary particle diameter is more preferably 0.5 μm or more, still more preferably 1 μm or more. Further, it is more preferably 60 μm or less, still more preferably 50 μm or less, and particularly preferably 35 μm or less. The average primary particle diameter can be obtained by selecting any about 20 particles from an enlarged image at a magnification of 1000 times of a scanning electron microscope, measuring the particle diameter, and calculating the arithmetic mean value. When the particle image is, for example, elliptical, the average value of the lengths of the major axis and the minor axis is used.

[0057] The specific surface area of the coated metal magnetic particles is preferably 0.01 to 20 m 2 / g. Further, the specific surface area is more preferably 10 m 2 / g or less, still more preferably 5 m 2 / g or less, still more preferably 1 m 2 / g or less, still more preferably 0.8 m 2 / g or less, and particularly preferably 0.05 m 2 / g or more, more preferably 0.1 m 2 / g or more. The specific surface area can be obtained by the same method as that for the metal magnetic particles.

[0058] The specific surface area of the coated metal magnetic particles is preferably 50 to 150% of the specific surface area of the metal magnetic particles before forming the coating layer, more preferably 80 to 120%, and still more preferably 80 to 110%. When the ratio of the specific surface area after forming the coating layer is 50 to 150%, coated metal magnetic particles efficiently coated can be obtained.

[0059] In 100% by mass of the coated metal magnetic particles, the coating layer is preferably 0.5 to 10% by mass, more preferably 0.5 to 5% by mass, still more preferably 0.5 to 3% by mass, and particularly preferably 0.5 to 2.5% by mass.

[0060] The average thickness of the coating layer on coated metal magnetic particles is preferably 0.5 to 100 nm from the viewpoint of insulation and weather resistance. More preferably, the average thickness is 50 nm or less, and even more preferably 30 nm or less. Furthermore, 1 nm or more is more preferable, and even more preferably 3 nm or more. The average thickness of the coating layer can be obtained by observing with a transmission electron microscope, selecting approximately 10 arbitrary particles, measuring the thickness of the coating layer, and calculating the arithmetic mean.

[0061] The particle size (average particle diameter of the powder) D50 of the coated metal magnetic particles is preferably 0.5 to 100 μm. More preferably, the particle size D50 is 60 μm or less, even more preferably 50 μm or less, and particularly preferably 35 μm or less. More preferably, it is 1 μm or more, even more preferably 1.5 μm or more, and particularly preferably 3 μm or more. The particle size D50 is measured dry using a laser diffraction particle size distribution analyzer SALD-2300 manufactured by Shimadzu Corporation, and the particle size (median diameter) at 50% of the cumulative mass can be calculated from the measurement results.

[0062] The particle size D50 of the coated metal magnetic particles is preferably 150% or less, more preferably 125% or less, and even more preferably 110% or less, of the particle size D50 of the metal magnetic particles before the coating layer is formed. There is no particular lower limit, but for example, 80% or more is preferred. When the ratio of the particle size D50 after the coating layer is formed is 150% or less, better coated metal magnetic particles with fewer aggregates can be obtained.

[0063] By keeping the average primary particle diameter, specific surface area, and powder particle size D50 within this range, a high level of balance between handling properties, insulation, and magnetic properties can be achieved.

[0064] The volume resistivity of coated metal magnetic particles is 1 × 10⁻⁶ 6 Preferably Ω·cm or more, 1 × 10 7 Ω·cm or larger is more preferable, 1 × 10 8 A value of Ω·cm or higher is even more preferable. Furthermore, while a higher upper limit for volume resistivity is preferable, if we were forced to name one, it would be 1 × 10⁻⁶. 11 It is less than or equal to Ω·cm. The volume resistivity of coated metal magnetic particles can be measured using a resistivity meter (Mitsubishi Chemical Analytec Highresta-UX MCP-HT800) and a powder resistance measurement system (Mitsubishi Chemical Analytec MCP-PD51, high-resistivity probe unit for powders MCP-PD522: double-ring electrode method, applied voltage 10V). 6g of coated metal magnetic particles are packed into a cylinder container with a radius of 1cm, compressed under a load of 63.7Mpa (20kN), and then measured by applying a voltage.

[0065] The apparent density of coated metal magnetic particles is 4-9 g / cm³. 3 Preferably, 6-8.5 g / cm³ 3 More preferably, 7-8 g / cm³ 3 That is even more preferable. Furthermore, the apparent density of the metal magnetic particles before the formation of the coating layer is preferably 90-99.9%, and more preferably 97-99.5%. The apparent density is measured using a true density analyzer BELPYCNO (manufactured by Microtrac-Bel) at an ambient temperature of 25°C and obtained as the apparent density by the gas displacement method.

[0066] <Resin composition> The resin composition of this disclosure (hereinafter also referred to as "the resin composition") contains the coated metal magnetic particles and a binder resin. The resin composition may further contain other additives. In addition, the coated metal magnetic particles may be replaced with metal magnetic particles to the extent that the problem can be solved.

[0067] In this resin composition, the total content of coated metal magnetic particles and metal magnetic particles is preferably 50 to 99.5% by mass, more preferably 65% ​​or more by mass, even more preferably 80% or more by mass, and particularly preferably 90% or more by mass. There is no particular upper limit to the total content of coated metal magnetic particles and metal magnetic particles, but it is more preferably 99% or less by mass, and even more preferably 98% or less by mass. By keeping the total content of coated metal magnetic particles and metal magnetic particles within the above range, both handling properties and magnetic properties can be achieved.

[0068] In this resin composition, the content of coated metal magnetic particles is preferably 20 to 100% by mass, more preferably 50% by mass or more, and particularly preferably 80% by mass or more, out of the total amount of coated metal magnetic particles and metal magnetic particles as a whole (100% by mass).

[0069] [Binder resin] The binder resin is a component that binds coated metal magnetic particles or metal magnetic particles together, and synthetic resins and / or their precursors can be used. A synthetic resin precursor is a compound that reacts to produce a synthetic resin.

[0070] The binder resin content is preferably 0.5 to 50% by mass, more preferably 1 to 20% by mass, even more preferably 1 to 10% by mass, and particularly preferably 1 to 5% by mass, based on 100% by mass of the resin composition.

[0071] Examples of synthetic resins include (meth)acrylic resins, polyester resins, polyurethane resins, epoxy resins, phenoxy resins, polyamide resins, polyether resins, silicone resins, polyolefin resins, polystyrene resins, polyvinyl alcohol resins, polyvinyl ester resins, poly(meth)acrylic acid resins, polyvinylpyrrolidone resins, vinyl chloride resins, carbonate resins, unsaturated carboxylic acid resins, fluorine resins, and copolymers thereof. Among these, (meth)acrylic resin, polyester resin, polyurethane resin, epoxy resin, and phenoxy resin are preferred from the viewpoint of handling, availability, and weather resistance. Furthermore, (meth)acrylic resin or epoxy resin is more preferred, and epoxy resin is particularly preferred.

[0072] Examples of epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy resin, aliphatic type epoxy resin, and glycidylamine type epoxy resin.

[0073] Precursors of synthetic resins include monomers and oligomers having multiple reactive functional groups such as polymerizable unsaturated groups, epoxy groups, and oxetanyl groups. Examples of polymerizable unsaturated groups include vinyl groups, (meth)acryloyl groups, and (meth)allyl groups.

[0074] Examples of precursors for synthetic resins having multiple epoxy groups include glycidyl ethers such as glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, ethylene glycol diglycidyl ether, and polyethylene glycol diglycidyl ether.

[0075] Binder resins can be used in combination with curing agents depending on the application. The curing agent can be selected according to the reactive groups of the binder resin. Examples of curing agents include amine compounds, amide compounds, acid anhydride compounds, phenolic compounds, imidazole compounds, latent curing agents, and dibutyltin compounds.

[0076] [Other additives] Other additives include, for example, dispersants, organic solvents, leveling agents, defoamers, rheology modifiers, colorants, stabilizers such as antioxidants, flame retardants, plasticizers, and ion scavengers. These other additives can be used individually or in combination of two or more types.

[0077] [Manufacturing of resin compositions] The resin composition of this disclosure can be manufactured by charging coated metal magnetic particles and a binder resin and thoroughly stirring and mixing them.

[0078] One embodiment of a method for producing a resin composition involves mixing coated metal magnetic particles, a binder resin that dissolves in an organic solvent, and an organic solvent. This method can produce a paste-like resin composition.

[0079] One embodiment of a method for producing a resin composition involves mixing coated metal magnetic particles and a binder resin that is liquid at room temperature. This method can produce a paste-like resin composition.

[0080] One embodiment of a method for producing a resin composition involves using a thermoplastic resin as the binder resin and mixing coated metal magnetic particles and the binder resin at a temperature above the melting point of the binder resin. This method allows for obtaining a resin composition that is solid at room temperature, which can then be further processed, for example, into pellets for suitable use.

[0081] Examples of equipment used for stirring and mixing include dispersers, anchor mixers, planetary mixers, trimixes, homogenizer mixers, kneaders, and other kneading and mixing devices, as well as tumbler mixers, attritors, roll mills, and rotational and revolving mixers. The stirring and mixing equipment used can be appropriately configured according to the handling requirements of the resin composition.

[0082] <Cured product and method for producing the same> The cured products of the present disclosure can be obtained, for example, by coating a resin composition of the present disclosure onto a substrate and drying and / or curing it.

[0083] The method of coating the resin composition is not particularly limited, but it can be coated by various known methods such as die coating, dip coating, roll coating, doctor coating, gravure coating, and screen printing.

[0084] The method for drying the resin composition is not particularly limited, but it can be dried by various known methods, such as a forced-air dryer, a hot-air dryer, an infrared heater, or a far-infrared heater.

[0085] When further curing the resin composition, the curing method is not particularly limited, but methods include aging at room temperature or under heating. The aging period for the curing reaction is, for example, about 1 to 5 days at 40°C or about 10 hours at 180°C. Furthermore, if necessary, the curing reaction can be carried out in multiple temperature steps.

[0086] The type of substrate to which the resin composition is applied is not particularly limited, but various known substrates can be used, such as resin films, resin sheets, metal plates, and fillers for molds and castings.

[0087] <Manufacturing method for magnetic cores> The method for manufacturing a magnetic core according to this disclosure is a method for obtaining a magnetic core by coating or molding. The method for manufacturing a magnetic core by coating involves coating a coil with a resin composition. For example, the coil can be impregnated in a resin solution, removed, dried, and then coated. The coating is applied to a degree that allows it to be used as a magnetic core. Instead of impregnation, coating can also be done by printing or spraying.

[0088] The method for manufacturing a magnetic core by rolling involves filling a resin composition into a molding die and applying pressure using a hydraulic press or the like to obtain a magnetic core. This magnetic core is also called a compacted magnetic core. The aforementioned pressurization is preferably 50 MPa to 2000 MPa, and more preferably 400 to 1200 MPa. The pressurization time is, for example, about 1 minute. The obtained magnetic core can be heat-treated for about an hour at a temperature below the crystallization temperature of metallic magnetic particles, for example, 200°C or higher. This removes molding distortion and hardens the binder resin to obtain a compacted magnetic core. There are no particular restrictions on the shape of the obtained magnetic core, and it can be appropriately selected according to the purpose. Examples of magnetic core shapes include ring shapes (e.g., annular shapes, rectangular frame shapes, etc.) and rod shapes.

[0089] The magnetic core can be used in inductors, compacted magnetic cores, reactors, and the like.

[0090] The method for manufacturing an inductor according to this disclosure comprises the step of embedding the magnetic core in a coil. The coil is preferably a coil conductor formed by winding a strip of wire in a spiral shape. The coil conductor has lead-outs that can be electrically connected to the wiring of a circuit.

[0091] [Example of an embodiment] Examples of embodiments of the present invention are given below. The present invention is not limited to the following.

[0092] <1> The specified method for producing coated metal magnetic particles involves heating a mixture containing metal magnetic particles, a silane compound, a pyrolytic ammonium salt, and water, in which the silane compound reacts in the presence of ammonia produced by heating, thereby coating the metal magnetic particles. <2> The decomposition temperature of the aforementioned pyrolytic ammonium salt is 40 to 120°C. <1> A method for producing coated metal magnetic particles. <3> The mixture further contains an organic solvent. <1> or <2> A method for producing coated metal magnetic particles. <4> <1> ~ <3> A method for producing a resin composition, comprising mixing coated metal magnetic particles obtained by any of the manufacturing methods with a binder resin. <5> <4> A method for producing a magnetic core, comprising coating or molding a resin composition obtained by the method for producing a magnetic core. <6> <5> A method for manufacturing an inductor, comprising the step of embedding a magnetic core obtained by the manufacturing method into a coil. [Examples]

[0093] The present invention will be described below based on examples. However, the present invention is not limited to these examples. Unless otherwise specified, "parts" in the examples means "parts by mass" and "%" means "mass percent". In Table 3, "-" in the formulation means "the corresponding ingredient is not included," and "-" in the evaluation result means "the corresponding evaluation has not been performed."

[0094] <Metal magnetic particles> • Carbonyl iron powder, soft grade SQ (BASF): Pure iron powder particles. Average primary particle size 4 μm, BET specific surface area 0.3 m².2 / g, apparent density 7.9g / cm 3 Fe content 99.5% by mass, spherical shape. Hereinafter referred to as SQ. • Carbonyl iron powder, hard grade HQ (BASF): Pure iron powder particles. Average primary particle size 1.5 μm, BET specific surface area 0.6 m². 2 / g, apparent density 7.7g / cm³ 3 Fe content 98% by mass, spherical shape. Hereinafter referred to as HQ. ·Ultra-fine Iron Powder YX5 / 5S (manufactured by Jiangsu Tianyi Ultrafine Metal Powder Co.,Ltd): Pure iron powder particles. Average primary particle diameter 1.2μm, BET specific surface area 1.0m 2 / g, apparent density 7.7g / cm³ 3 Fe content 96% by mass, spherical shape. Hereinafter referred to as iron powder A. • Iron-silicon-chromium alloy particles: Metal alloy particles. Average primary particle diameter 4 μm, BET specific surface area 0.36 m². 2 / g, apparent density 7.5g / cm³ 3 ,spherical. Fe content: 90.5% by mass, Si content: 5.5% by mass, Cr content: 4% by mass. Hereinafter, it will be referred to as FeSiCr. • Iron-nickel-zinc ferrite particles: Ferrite. Average primary particle diameter 30 μm, BET specific surface area 0.11 m². 2 / g, apparent density 5.29 g / cm³ 3 Spherical in shape. Fe content: 44% by mass. Hereinafter referred to as FeNiZn.

[0095] <Silane compounds> Tetramethoxysilane. Hereinafter referred to as TMOS. Tetraethoxysilane. Hereinafter referred to as TEOS.

[0096] <Thermolytic ammonium salts> Ammonium carbonate. Thermal decomposition temperature: 58°C. Molecular weight: 96. Ammonium bicarbonate. Thermal decomposition temperature: 58°C. Molecular weight: 79. Ammonium carbamate. Thermal decomposition temperature: 59°C. Molecular weight: 78.

[0097] <Other catalysts> • Ammonia: 30% by mass of aqueous ammonia. Hereinafter referred to as aqueous ammonia. Triethanolamine Sodium bicarbonate

[0098] <Water> • Water: Ion-exchanged water

[0099] <organic solvents> ·ethanol Isopropyl alcohol. Hereinafter referred to as IPA. 1-propanol Methyl ethyl ketone. Hereinafter referred to as MEK.

[0100] <Binder resin> • Methyl methacrylate polymer (manufactured by Fujifilm Wako Pure Chemical Industries). (Meth)acrylic resin. Hereinafter, a 20% by mass solution of methyl ethyl ketone with methyl methacrylate polymer will be referred to as Acrylic A. • jER-806 (manufactured by Mitsubishi Chemical Corporation), bisphenol F type epoxy resin. Hereinafter referred to as Epoxy A. • Byron UR-4800 (manufactured by Toyobo Co., Ltd.). Polyurethane ester resin solution (32% by mass of non-volatile content, 34% by mass of methyl ethyl ketone, 34% by mass of toluene). Hereinafter referred to as Polyester A.

[0101] <Other additives> • 2-ethyl-4-methylimidazole. Imidazole-based curing agent. Hereinafter referred to as 2E4MZ.

[0102] <Manufacturing of coated metal magnetic particles (1)> [Example 1-1] A mixture was prepared by charging 89.43 parts of metal magnetic particles (SQ), 1.57 parts of tetraethoxysilane, 0.37 parts of ammonium carbonate, 2.19 parts of water, and 6.44 parts of IPA into a stainless steel container and stirring and mixing in a planetary mixer at 30°C for 10 minutes. Next, the mixture was transferred to a sealed stainless steel container and mixed for 2 hours at 65°C while stirring with an anchor mixer. After that, stirring was continued at 80°C for another 4 hours to form a coating layer on the surface of the metal magnetic particles. Subsequently, the mixture was vacuum-dried at 80°C under a reduced pressure of 0.01 MPa using a vacuum pump for 2 hours to completely evaporate the water and IPA, obtaining a dry powder. This powder was then sieved through a 125 μm mesh to obtain coated metal magnetic particles.

[0103] [Examples 1-2 to 1-5, Comparative Examples 1-1 to 1-4] Except for changing the materials and quantities used in Example 1-1 as shown in Table 1A, coated metal magnetic particles for Examples 1-2 to 1-5 and Comparative Examples 1-1 to 1-4 were prepared in the same manner as in Example 1-1.

[0104] [Comparative Examples 1-5] A mixture was prepared by charging 84.45 parts of FeSiCr as metallic magnetic particles, 2.11 parts of tetraethoxysilane, 0.35 parts of ammonium carbonate, 2.96 parts of water, and 10.13 parts of IPA into a stainless steel container and stirring the mixture in a planetary mixer at 30°C for 10 minutes. The ammonium carbonate did not decompose, and no ammonia was produced. Next, the mixture was transferred to a sealed stainless steel container and mixed using an anchor mixer at 50°C for 6 hours. Subsequently, the mixture was vacuum-dried at 50°C under a reduced pressure of 0.01 MPa using a vacuum pump for 3 hours to completely evaporate the water and IPA, obtaining a dry powder. This powder was then sieved through a 125 μm mesh to obtain coated metal magnetic particles.

[0105] [Comparative Examples 1-6] In a stainless steel container, 80.50 parts of iron powder A, 3.62 parts of tetraethoxysilane, 0.24 parts of ammonium carbonate, 4.30 parts of water, and 11.34 parts of IPA were charged and mixed in a planetary mixer at 30°C for 10 minutes to prepare the mixture. The ammonium carbonate did not decompose, and no ammonia was produced. Next, the mixture was transferred to a sealed stainless steel container and mixed using an anchor mixer at 50°C for 6 hours. Subsequently, the mixture was vacuum-dried at 50°C under a reduced pressure of 0.01 MPa using a vacuum pump for 3 hours to completely evaporate the water and IPA, obtaining a dry powder. This powder was then sieved through a 125 μm mesh to obtain coated metal magnetic particles.

[0106] <Evaluation of coated metal magnetic particles (1)> The powder particle size D50, specific surface area, apparent density, and volume resistivity of the manufactured coated metal magnetic particles were evaluated using the following methods.

[0107] [Powder particle size D50] The particle size D50 of coated metal magnetic particles was measured dry using a Shimadzu Corporation SALD-2300 laser diffraction particle size distribution analyzer. The refractive index of the coated metal magnetic particles was set to the literature value of the refractive index of the metal magnetic particles used as raw materials; for example, for pure iron powder, the refractive index parameter was set to 2.9-0.10i for the analysis. From the measurement results, the particle size (median diameter) at 50% of the cumulative mass percentage was calculated and defined as the powder particle size D50. In the table, the powder particle size D50 ratio is the value obtained by dividing the powder particle size D50 of the coated metal magnetic particles by the powder particle size D50 of the metal magnetic particles before coating.

[0108] [Specific surface area] The specific surface area of ​​the coated metal magnetic particles was measured using a Macsorb HM model-1220 (Mountech), and obtained as the BET specific surface area by nitrogen gas adsorption. The specific surface area ratio in the table is the value obtained by dividing the specific surface area of ​​the coated metal magnetic particles by the specific surface area of ​​the metal magnetic particles before coating.

[0109] [Apparent Density] The apparent density of coated metal magnetic particles was measured using a BELPYCNO true density analyzer (Microtrac-Bel) at an ambient temperature of 25°C, and obtained as the apparent density by gas displacement method. Helium gas (G1 grade) was used for the measurement. The apparent density ratio in the table is the value obtained by dividing the apparent density of coated metal magnetic particles by the apparent density of the metal magnetic particles before coating.

[0110] [Volume resistivity] The volume resistivity of coated metal magnetic particles was obtained by using a resistivity meter (Mitsubishi Chemical Analytec Highresta-UX MCP-HT800) and a powder resistance measurement system (Mitsubishi Chemical Analytec MCP-PD51, high-resistivity probe unit for powders MCP-PD522: double-ring electrode method, applied voltage 10V). The measurement was performed under ambient temperature of 25°C and humidity of 60%, by filling a cylinder container with a radius of 1 cm, compressing it under a load of 63.7 MPa (20 kN), and applying a voltage. The evaluation criteria were as follows: ◎: Volume resistivity 1 × 10 8 Ω·cm or higher (particularly good). ○: Volume resistivity 1 × 10 7 Ω cm or more, 1×10 8 Less than Ω cm (good). △: Volume resistivity 1 × 10 6 Ω cm or more, 1×10 7 Less than Ω·cm (acceptable). ×: Volume resistivity 1 × 10 6 Less than Ω·cm (defective).

[0111] [Table 1A]

[0112] [Table 1B]

[0113] Table 1B shows that the coated metal magnetic particles of Examples 1-1 to 1-5 could be uniformly coated in a shorter manufacturing time than conventional methods, and exhibited high volume resistivity and good insulation properties. On the other hand, the coated metal magnetic particles of Comparative Examples 1-1 to 1-4 used a base as a catalyst, resulting in the formation of numerous silica fine particles within the same coating time as Examples 1-1 to 1-5. As a result, a coating layer with sufficient insulation properties for practical use could not be formed, and thus the volume resistivity was low. Furthermore, in Comparative Examples 1-5 to 1-6, the coating treatment was carried out in an atmosphere without catalyst, where the pyrolytic ammonium salt (ammonium carbonate) did not decompose. This resulted in insufficient reaction of the silane compound, and a coating layer with sufficient insulation properties for practical use could not be formed, resulting in low volume resistivity.

[0114] <Manufacturing of coated metal magnetic particles (2)> [Example 2-1] 85.01 parts of FeSiCr metal magnetic particles, 1.70 parts of tetramethoxysilane, 0.35 parts of ammonium carbonate, 2.74 parts of water, and 10.20 parts of ethanol were charged into a stainless steel container, and the mixture was stirred and mixed in a planetary mixer at 30°C for 10 minutes to prepare the mixture. Next, the mixture was transferred to a sealed stainless steel container and mixed for 2 hours at 65°C while stirring with an anchor mixer. After that, stirring was continued at 80°C for another 4 hours to form a coating layer on the surface of the metal magnetic particles. Subsequently, the mixture was vacuum-dried at 80°C under a reduced pressure of 0.01 MPa using a vacuum pump for 2 hours to completely evaporate the water and ethanol, obtaining a dry powder. This powder was then sieved through a 125 μm mesh to obtain coated metal magnetic particles.

[0115] [Examples 2-2 to 2-5] The coated metal magnetic particles of Examples 2-2 to 2-5 were prepared in the same manner as in Example 2-1, except that the materials and their quantities were changed as shown in Table 2A.

[0116] <Evaluation of coated metal magnetic particles (2)> The powder particle size D50, specific surface area, apparent density, and volume resistivity of the manufactured coated metal magnetic particles were evaluated. The evaluation method was the same as that described in Evaluation of Coated Metal Magnetic Particles (1).

[0117] [Table 2A]

[0118] [Table 2B]

[0119] As shown in Table 2B, the coated metal magnetic particles of Examples 2-1 to 2-6 could be uniformly coated in a shorter manufacturing time than conventional methods, and exhibited good volume resistivity.

[0120] <Manufacturing of resin compositions> [Example 3-1] According to the composition shown in Table 3, 82.76 parts of the coated metal magnetic particles prepared in Example 1-1 and 17.24 parts of Acrylic A (a 20% by mass methyl ethyl ketone solution of methyl methacrylate polymer) were placed in a plastic container. Then, the mixture was stirred and kneaded for 2 minutes at room temperature using a foaming mixer (manufactured by Shinki Co., Ltd., 2000 rpm) to prepare the resin composition. The evaluation results are shown in Table 3.

[0121] [Example 3-2] The coated metal magnetic particles of Example 3-2 were prepared in the same manner as in Example 3-1, except that the materials and their quantities were changed as shown in Table 3.

[0122] [Example 3-3] According to the composition shown in Table 3, 82.76 parts of coated metal magnetic particles prepared in Example 1-1, 10.78 parts of polyester A as a binder resin, and 6.46 parts of MEK as an organic solvent were placed in a plastic container. Then, the mixture was stirred and kneaded for 2 minutes at room temperature using a foaming mixer (manufactured by Shinki Co., Ltd., 2000 rpm) to prepare a resin composition. The evaluation results are shown in Table 3.

[0123] [Examples 3-4] The coated metal magnetic particles of Example 3-4 were prepared in the same manner as in Example 3-3, except that the materials and their quantities were changed as shown in Table 3.

[0124] [Examples 3-5] According to the composition shown in Table 3, 86.36 parts of coated metal magnetic particles prepared in Example 1-1, 3.64 parts of epoxy A as a binder resin, 0.91 parts of 2E4MZ as a curing agent, and 9.09 parts of MEK as an organic solvent were placed in a plastic container. Then, the mixture was stirred and kneaded for 2 minutes at room temperature using a foaming kneader (manufactured by Shinky Co., Ltd., 2000 rpm) to prepare a resin composition. The evaluation results are shown in Table 3.

[0125] [Examples 3-6] The resin composition of Example 3-6 was prepared in the same manner as in Example 3-5, except that the materials and their quantities were changed as shown in Table 3.

[0126] <Evaluation of resin compositions> The viscosity and coating properties of the obtained resin compositions were evaluated.

[0127] [viscosity] The viscosity of the resin composition was measured immediately after stirring and mixing the resin composition for 30 seconds using an Awatori Rentaro (Sinky Co., Ltd., 2000 rpm), using a Brookfield type viscometer (Eiko Seiki Co., Ltd., "HB", spindle SC4-14), at a sample temperature of 25°C, a spindle rotation speed of 50 rpm, and a measurement time of 1 minute. The evaluation criteria for the obtained resin composition are as follows. ○: Viscosity is between 0 Pa·s and 200 Pa·s (good) ×: Viscosity exceeds 200 Pa·s and cannot be measured (not possible)

[0128] [Coating properties (1)] The resin compositions obtained in Examples 3-1 to 3-4 were coated onto corona-discharge-treated polyethylene terephthalate (PET) films using an applicator to achieve a dry thickness of 50 μm. The cured products were then dried in a 120°C oven for 5 minutes, and their appearance was visually evaluated according to the following criteria. The visual evaluation criteria for the obtained cured products are as follows: ○: No defects such as gaps or aggregates (good) ×: Contains a large amount of aggregates (defective)

[0129] [Coating properties (2)] The resin compositions obtained in Examples 3-5 to 3-6 were coated onto corona-discharge-treated polyethylene terephthalate (PET) films using an applicator to a dry thickness of 50 μm, and then dried in an oven at 120°C for 5 minutes. The curing reaction was then completed by heating in an oven at 110°C for 3 hours to produce cured products, whose appearance was visually evaluated according to the following criteria. The visual evaluation criteria for the obtained cured products are as follows. ○: No defects such as gaps or aggregates (good) ×: Contains a large amount of aggregates (defective)

[0130] [Table 3]

[0131] The results in the table show that the resin compositions of Examples 3-1 to 3-6 had low viscosity and good coating properties. This allows for proper coating of coils and the like.

Claims

1. A method for producing coated metal magnetic particles, comprising heating a mixture containing metal magnetic particles, a silane compound, a pyrolytic ammonium salt, and water, in the presence of ammonia produced by heating, in which the silane compound reacts to coat the metal magnetic particles.

2. The method for producing coated metal magnetic particles according to claim 1, wherein the decomposition temperature of the pyrolytic ammonium salt is 40 to 120°C.

3. The method for producing coated metal magnetic particles according to claim 1, wherein the mixture further comprises an organic solvent.

4. A method for producing a resin composition, comprising mixing coated metal magnetic particles obtained by the manufacturing method described in any one of claims 1 to 3 with a binder resin.

5. A method for producing a magnetic core, comprising coating or molding a resin composition obtained by the manufacturing method of claim 4 to obtain a magnetic core.

6. A method for manufacturing an inductor, comprising the step of embedding a magnetic core obtained by the manufacturing method of claim 5 into a coil.

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