Method for producing phosphate-coated SmFeN-based anisotropic magnetic powder and phosphate-coated SmFeN-based anisotropic magnetic powder

Abstract

The present invention provides: a phosphate-coated SmFeN-based anisotropic magnetic powder that has excellent coercivity; and a production method for the phosphate-coated SmFeN-based anisotropic magnetic powder. The present invention relates to a production method for a phosphate-coated SmFeN-based anisotropic magnetic powder that includes a step for adding an inorganic acid to a slurry that includes an SmFeN-based anisotropic magnetic powder, water, and a phosphate compound and adjusting the pH of the slurry to 1–4.5 to obtain an SmFeN-based anisotropic magnetic powder that is coated with phosphate.

Description

[Technical Field]

[0001] The present invention relates to a method for producing phosphate-coated SmFeN-based anisotropic magnetic powder and to phosphate-coated SmFeN-based anisotropic magnetic powder. [Background technology]

[0002] It is known that the coercivity of SmFeN-based anisotropic magnetic powder is improved when its surface is coated with phosphate. For example, Patent Document 1 discloses a method for coating the surface of SmFeN-based anisotropic magnetic powder with phosphate by adding a pH-adjusted phosphate treatment solution containing orthophosphoric acid to a slurry containing SmFeN-based anisotropic magnetic powder in a water solvent.

[0003] Patent Document 2 discloses a method for adjusting the particle size of SmFeN-based anisotropic magnetic powder by adding a pH-adjusted phosphoric acid treatment solution to a slurry containing SmFeN-based anisotropic magnetic powder with large particle sizes in an organic solvent, and then grinding the SmFeN-based anisotropic magnetic powder, as well as coating the surface with phosphate.

[0004] Patent Document 3 discloses that the coercivity of a phosphate-coated SmFeN-based anisotropic magnetic powder is increased by oxidizing the SmFeN-based anisotropic magnetic powder. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-056101 [Patent Document 2] Japanese Patent Publication No. 2017-210662 [Patent Document 3] Japanese Patent Publication No. 2014-160794 [Overview of the project] [Problems that the invention aims to solve]

[0006] The present invention aims to provide a phosphate-coated SmFeN-based anisotropic magnetic powder having excellent coercivity, and a method for producing the same. [Means for solving the problem]

[0007] A method for producing phosphate-coated SmFeN-based anisotropic magnetic powder according to one aspect of the present invention includes a phosphate treatment step in which an inorganic acid is added to a slurry containing SmFeN-based anisotropic magnetic powder, water, and a phosphate compound to adjust the pH of the slurry to 1 or more and 4.5 or less, thereby obtaining SmFeN-based anisotropic magnetic powder with a phosphate coating on its surface.

[0008] Furthermore, the phosphate-coated SmFeN-based anisotropic magnetic powder according to one aspect of the present invention has an exothermic onset temperature of 170°C or higher in DSC, and a phosphate content greater than 0.5% by mass. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a phosphate-coated SmFeN-based anisotropic magnetic powder having excellent coercivity. [Brief explanation of the drawing]

[0010] [Figure 1] The cross-sectional SEM image of the magnetic powder from Example 2 is shown. [Figure 2] The cross-sectional SEM image of the magnetic powder of Comparative Example 1 is shown. [Figure 3] The SEM image of the magnetic powder from Example 2 is shown. [Figure 4] The SEM image of the magnetic powder of Comparative Example 3 is shown. [Figure 5] The particle size distribution of the magnetic powders in Example 2 and Comparative Example 3 is shown. [Figure 6] The STEM-EDX mapping analysis results for the magnetic powders of Example 2 and Comparative Example 1 are shown. [Figure 7] The results of the EDX line analysis of the magnetic powder in Example 2 are shown. [Figure 8]The results of the EDX line analysis of the magnetic powder of Comparative Example 1 are shown.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described in detail. However, the embodiments shown below are merely examples for embodying the technical idea of the present invention, and the present invention is not limited to the following. In this specification, the term "step" includes not only an independent step but also a step that cannot be clearly distinguished from other steps as long as the intended purpose of the step is achieved. Also, the numerical range indicated by "~" indicates a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively.

[0012] <Method for Producing Phosphate-Coated SmFeN-Based Anisotropic Magnetic Powder> The method for producing a phosphate-coated SmFeN-based anisotropic magnetic powder according to this embodiment includes a phosphating step of adding an inorganic acid to a slurry containing a SmFeN-based anisotropic magnetic powder, water, and a phosphate compound, and adjusting the pH of the slurry to 1 or more and 4.5 or less to obtain a SmFeN-based anisotropic magnetic powder having a phosphate coating on its surface.

[0013] [Phosphating Step] In the phosphoric acid treatment step, an inorganic acid is added to a slurry containing SmFeN-based anisotropic magnetic powder, water, and a phosphoric acid compound, and the pH of the slurry is adjusted to 1 or more and 4.5 or less, whereby SmFeN-based anisotropic magnetic powder coated with phosphate on the surface is obtained. The phosphate-coated SmFeN-based anisotropic magnetic powder is formed by the reaction of the metal components (e.g., iron and samarium) contained in the SmFeN-based anisotropic magnetic powder and the phosphate component contained in the phosphoric acid compound, resulting in the precipitation of phosphate (e.g., iron phosphate, samarium phosphate) on the surface of the SmFeN-based anisotropic magnetic powder. According to the present embodiment, by adding an inorganic acid and adjusting the pH of the slurry to 1 or more and 4.5 or less, the precipitation amount of phosphate can be increased compared to the case where no inorganic acid is added, and a phosphate-coated SmFeN-based anisotropic magnetic powder with a thick coating portion can be obtained, so it is considered that the coercive force (iHc) is improved. Also, according to the present embodiment, by using water as the solvent, phosphates with smaller particle sizes precipitate compared to the case where an organic solvent is used as the solvent, so a phosphate-coated SmFeN-based anisotropic magnetic powder with a dense coating portion can be obtained, and it is considered that the coercive force (iHc) is improved.

[0014] The method for producing a slurry containing SmFeN-based anisotropic magnetic powder, water, and a phosphoric acid compound is not particularly limited. For example, it can be obtained by mixing a phosphoric acid aqueous solution containing SmFeN-based anisotropic magnetic powder and a phosphoric acid compound with water as the solvent. The content of the SmFeN-based anisotropic magnetic powder in the slurry is, for example, 1% by mass or more and 50% by mass or less, and preferably 5% by mass or more and 20% by mass or less from the viewpoint of productivity. The content of the phosphate component (PO4) in the slurry is, in terms of PO4 conversion amount, for example, 0.01% by mass or more and 10% by mass or less, and preferably 0.05% by mass or more and 5% by mass or less from the viewpoints of the reactivity between the metal component and the phosphate component and productivity.

[0015] A phosphoric acid aqueous solution is obtained by mixing a phosphoric acid compound with water. Examples of phosphoric acid compounds include phosphates such as orthophosphoric acid, sodium dihydrogen phosphate, sodium monohydrogen phosphate, ammonium dihydrogen phosphate, ammonium monohydrogen phosphate, zinc phosphate, and calcium phosphate, as well as inorganic phosphoric acids such as hypophosphorous acid, hypophosphite, pyrophosphoric acid, and polyphosphoric acid, and organic phosphoric acids. These may be used individually or in combination of two or more. In addition, to improve the water resistance and corrosion resistance of the coating and the magnetic properties of the magnetic powder, oxo salts such as molybdate, tungstate, vanadate, and chromate, oxidizing agents such as sodium nitrate and sodium nitrite, and chelating agents such as EDTA can be used as additives.

[0016] The concentration of phosphoric acid (in PO4 equivalent) in the aqueous phosphoric acid solution is, for example, 5% by mass or more and 50% by mass or less, and is preferably 10% by mass or more and 30% by mass or less from the viewpoint of solubility of phosphoric acid compounds, storage stability, and ease of chemical treatment. The pH of the aqueous phosphoric acid solution is, for example, 1 or more and 4.5 or less, and is preferably 1.5 or more and 4 or less from the viewpoint of being able to easily control the precipitation rate of phosphates. The pH can be adjusted with dilute hydrochloric acid, dilute sulfuric acid, etc.

[0017] In the phosphoric acid treatment process, the pH of the slurry is adjusted to between 1 and 4.5 by adding an inorganic acid, but it is preferable to adjust it to between 1.6 and 3.9, and more preferably between 2 and 3. Below pH 1, the phosphate-coated SmFeN-based anisotropic magnetic powders tend to aggregate, starting from locally precipitated phosphates, and the coercivity tends to decrease. Above pH 4.5, the amount of phosphate precipitated decreases, resulting in insufficient coating and a tendency for the coercivity to decrease. Examples of inorganic acids to be added include hydrochloric acid, nitric acid, sulfuric acid, boric acid, and hydrofluoric acid. During the phosphoric acid treatment process, inorganic acids are added as needed to maintain the pH within the above range. Inorganic acids are used from the viewpoint of wastewater treatment, but organic acids can be used in combination depending on the purpose. Examples of organic acids include acetic acid, formic acid, and tartaric acid.

[0018] The phosphoric acid treatment step may be carried out such that the lower limit of the phosphate content in the resulting phosphate-coated SmFeN-based anisotropic magnetic powder is greater than 0.5% by mass. The lower limit of the phosphate content in the phosphate-coated SmFeN-based anisotropic magnetic powder obtained in the phosphoric acid treatment step is preferably 0.55% by mass or more, and particularly preferably 0.75% by mass or more. The upper limit of the phosphate content is preferably 4.5% by mass or less, more preferably 2.5% by mass or less, and particularly preferably 2% by mass or less. When the phosphate content is 0.5% by mass or less, the effect of coating with phosphate tends to be small, and when it exceeds 4.5% by mass, the phosphate-coated SmFeN-based anisotropic magnetic powders tend to aggregate and the coercivity tends to decrease. The phosphate content of the magnetic powder is expressed in terms of PO4 molecules, measured using ICP emission spectrometry (ICP-AES).

[0019] The phosphoric acid treatment step is preferably carried out such that the phosphate coating on the surface of the resulting SmFeN-based anisotropic magnetic powder has a region (high Sm concentration region) where the Sm atom concentration is higher than the Sm atom concentration in the SmFeN-based anisotropic magnetic powder. The Sm atom concentration in the high Sm concentration region can be 1.02 times or more than the Sm atom concentration in the SmFeN-based anisotropic magnetic powder, preferably 1.05 times or more, more preferably 1.1 times or more, and even more preferably 1.2 times or more. Furthermore, the Sm atom concentration in the high Sm concentration region is preferably 3 times or less than the Sm atom concentration in the SmFeN-based anisotropic magnetic powder. Here, the high Sm concentration region is the region that includes the layer showing the maximum peak of P (phosphorus) in the STEM-EDX line analysis of the phosphate-coated SmFeN-based anisotropic magnetic powder. The thickness of the high Sm concentration region can be, for example, 5 nm or more, and is preferably 10 nm to 200 nm. The atomic concentration (atm%) of each element in the high-concentration Sm region can be determined by averaging the atomic concentrations (atm%) in the phosphate coating area in STEM-EDX line analysis.

[0020] It is preferable to adjust the slurry containing SmFeN-based anisotropic magnetic powder, water, and a phosphate compound to a pH range of 1 to 4.5 for at least 10 minutes, and more preferably for at least 30 minutes from the viewpoint of reducing areas with thin coating thickness. Initially, the pH rises rapidly, so the interval between adding the inorganic acid for pH control is short. However, as the coating progresses, the pH fluctuations gradually slow down, and the interval between adding the inorganic acid lengthens, allowing the reaction endpoint to be determined.

[0021] [Oxidation process after phosphoric acid treatment] The phosphate-coated SmFeN-based anisotropic magnetic powder may be subjected to oxidation treatment as needed. By oxidizing the phosphate-coated SmFeN-based anisotropic magnetic powder, the surface of the SmFeN-based anisotropic magnetic powder of the base material coated with phosphate is oxidized, forming an iron oxide layer, which improves the oxidation resistance of the phosphate-coated SmFeN-based anisotropic magnetic powder. Furthermore, oxidation can suppress undesirable oxidation-reduction reactions, decomposition reactions, and alterations that occur on the surface of SmFeN particles when the phosphate-coated SmFeN-based anisotropic magnetic powder is exposed to high temperatures during bond magnet fabrication, resulting in the acquisition of magnets with high magnetic properties, particularly high intrinsic coercivity (iHc).

[0022] The oxidation treatment is carried out by heat-treating the SmFeN-based anisotropic magnetic powder after phosphoric acid treatment in an oxygen-containing atmosphere. The reaction atmosphere preferably contains oxygen in an inert gas such as nitrogen or argon. The oxygen concentration is preferably 3% to 21%, and more preferably 3.5% to 10%. During the oxidation reaction, it is preferable to exchange the gas at a flow rate of 2 L / min to 10 L / min per kg of magnetic powder.

[0023] The oxidation treatment temperature is preferably between 150°C and 250°C, and more preferably between 170°C and 230°C. Below 150°C, the formation of the iron oxide layer is insufficient, and the oxidation resistance tends to be low. Above 250°C, the iron oxide layer is formed excessively, and the coercivity tends to decrease. The reaction time is preferably between 3 hours and 10 hours.

[0024] <Phosphate-coated SmFeN-based anisotropic magnetic powder> The phosphate-coated SmFeN-based anisotropic magnetic powder of this embodiment is characterized by having an exothermic onset temperature of 170°C or higher in DSC and a phosphate content greater than 0.5% by mass.

[0025] The phosphate-coated SmFeN-based anisotropic magnetic powder has an exothermic start temperature in DSC of 170°C or higher, and more preferably 200°C or higher. The exothermic start temperature in DSC is a comprehensive evaluation of the density, thickness, and oxidation resistance of the phosphate coating, and high coercivity is obtained when it is 170°C or higher. The exothermic start temperature in DSC can be measured under the conditions described in the examples. The phosphate content of the phosphate-coated SmFeN-based anisotropic magnetic powder is as described in the phosphate treatment process above.

[0026] In the XRD diffraction pattern, the phosphate-coated SmFeN-based anisotropic magnetic powder has a ratio (I) / (II) of 2.0 × 10⁻¹⁰ of the diffraction peak intensity (I) of the (110) plane of αFe to the peak intensity (II) of the (300) plane of the SmFeN-based magnetic powder. -2 Preferably, it is 1.0 × 10 -2 The following is more preferable: The diffraction peak intensity (I) of the (110) plane of αFe represents the amount of αFe present as an impurity, and the aforementioned ratio (I) / (II) is 2.0 × 10⁻⁶. -2 High coercivity can be obtained when the following conditions are met. Note that the diffraction peak intensity in the XRD diffraction pattern can be measured under the conditions described in the examples.

[0027] The phosphate-coated SmFeN-based anisotropic magnetic powder preferably has a carbon content of 1000 ppm or less, and more preferably 800 ppm or less. The carbon content indicates the amount of organic impurities in the phosphate. If the carbon content exceeds 1000 ppm, the organic impurities decompose when the phosphate-coated SmFeN-based anisotropic magnetic powder is exposed to high temperatures during the process of manufacturing bonded magnets, causing defects in the coating and a tendency for the coercivity to decrease. The carbon content can be measured by the TOC method.

[0028] The thickness of the phosphate coating in phosphate-coated SmFeN-based anisotropic magnetic powder is preferably between 10 nm and 200 nm, from the viewpoint of the coercivity of the phosphate-coated SmFeN-based anisotropic magnetic powder. The thickness of the phosphate coating can be measured by performing compositional analysis by line analysis using EDX in a cross-section of the phosphate-coated SmFeN-based anisotropic magnetic powder.

[0029] The phosphate coating on the surface of the SmFeN-based anisotropic magnetic powder preferably has a region (high-Sm concentration region) where the Sm atom concentration is higher than the Sm atom concentration in the SmFeN-based anisotropic magnetic powder. The Sm atom concentration in the high-Sm concentration region can be 1.02 times or more the Sm atom concentration in the SmFeN-based anisotropic magnetic powder, preferably 1.05 times or more, more preferably 1.1 times or more, and even more preferably 1.2 times or more. Furthermore, the Sm atom concentration in the high-Sm concentration region can be, for example, 3 times or less the Sm atom concentration in the SmFeN-based anisotropic magnetic powder. Here, the high-Sm concentration region is the region that includes the layer showing the maximum peak of P (phosphorus) in the STEM-EDX line analysis of the phosphate-coated SmFeN-based anisotropic magnetic powder. The thickness of the high-Sm concentration region can be, for example, 5 nm or more, preferably 10 nm to 200 nm, and more preferably 10 nm to 100 nm. The atomic concentration (atm%) of each element in the high-concentration Sm region can be determined by averaging the atomic concentrations (atm%) in the phosphate coating area in STEM-EDX line analysis.

[0030] In the high-Sm concentration region, the Sm atom concentration is more preferably 0.5 times or more the Fe atom concentration in the high-Sm concentration region, and even more preferably 1 time or more. The Sm atom concentration in the high-Sm concentration region is preferably 4 times or less the Fe atom concentration in the high-Sm concentration region. The Sm atom concentration in the high-Sm concentration region is preferably higher than the Fe atom concentration. When the relationship between the Sm atom concentration and Fe atom concentration in the high-Sm concentration region is within the above range, the Fe atom concentration near the surface of the SmFeN-based anisotropic magnetic powder tends to be lower, resulting in improved water resistance.

[0031] When molybdate is added to the reaction slurry during the phosphate treatment process, the phosphate coating may contain Mo. Preferably, the amount of Mo in the phosphate coating increases gradually from the outermost surface of the SmFeN-based anisotropic magnetic powder to the surface of the phosphate coating. Preferably, the Mo atom concentration on the surface of the phosphate coating is 1.2 times or more, and more preferably 1.5 times or more, than the Mo atom concentration on the outermost surface of the SmFeN-based anisotropic magnetic powder. When the Mo atom concentrations on the surface of the phosphate coating and the outermost surface of the SmFeN-based anisotropic magnetic powder are within the above-mentioned range, the Mo atom concentration becomes higher closer to the surface of the phosphate coating, which may contribute to enhanced corrosion resistance.

[0032] Furthermore, the Fe atom concentration in the phosphate coating is preferably lower than the Fe atom concentration in the base material, SmFeN-based anisotropic magnetic powder. More preferably, the Fe atom concentration in the phosphate coating is 0.3 times or less the Fe atom concentration in the base material, SmFeN-based anisotropic magnetic powder, and even more preferably 0.1 times or less. In addition, the Fe atom concentration in the phosphate coating can be, for example, 0.05 times or more the Fe atom concentration in the base material, SmFeN-based anisotropic magnetic powder.

[0033] [Silica treatment process] The SmFeN-based anisotropic magnetic powder after phosphoric acid treatment may be subjected to silica treatment as needed. The oxidation resistance can be improved by forming a silica thin film on the magnetic powder. The silica thin film can be formed, for example, by mixing an alkyl silicate, a phosphate-coated SmFeN-based anisotropic magnetic powder, and an alkaline solution.

[0034] [Silane coupling treatment process] The magnetic powder after silica treatment may be further treated with a silane coupling agent. By treating the magnetic powder on which a silica thin film has been formed with silane coupling, a coupling agent film is formed on the silica thin film, improving the magnetic properties of the magnetic powder, as well as improving its wettability with the resin and the strength of the magnet.Silane coupling agents are not particularly limited and should be selected according to the type of resin, but examples include 3-aminopropyltriethoxysilane, γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane hydrochloride, γ-glycidoxypropyltrimethoxysilane, and γ-methyl Captopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, vinyltriacetoxysilane, γ-chloropropyltrimethoxysilane, hexamethylenedisilazane, γ-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, octadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, γ-chloropropylmethyldimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, vinyl Trichlorosilane, vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, N-β(aminoethyl)γ-aminopropyltrimethoxysilane, N-β(aminoethyl)γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, oleidopropyltriethoxysilane, γ-isocyanatetopropyltriethoxy Silane coupling agents include silane, polyethoxydimethylsiloxane, polyethoxymethylsiloxane, bis(trimethoxysilylpropyl)amine, bis(3-triethoxysilylpropyl)tetrasulfan, γ-isocyanatetopropyltrimethoxysilane, vinylmethyldimethoxysilane, 1,3,5-N-tris(3-trimethoxysilylpropyl)isocyanurate, t-butylcarbamatetrialkoxysilane, and N-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propanamine.These silane coupling agents may be used alone or in combination of two or more. The addition amount of the silane coupling agent is preferably 0.2 parts by weight or more and 0.8 parts by weight or less, more preferably 0.25 parts by weight or more and 0.6 parts by weight or less, based on 100 parts by weight of the magnetic powder. If it is less than 0.2 parts by weight, the effect of the silane coupling agent is small, and if it exceeds 0.8 parts by weight, the magnetic properties of the magnetic powder and the magnet tend to deteriorate due to the aggregation of the magnetic powder.

[0035] After the phosphoric acid treatment step, after the oxidation step, after the silica treatment, or after the silane coupling treatment, the SmFeN-based anisotropic magnetic powder can be filtered, dehydrated, and dried by a conventional method.

[0036] <SmFeN-based anisotropic magnetic powder> The SmFeN-based anisotropic magnetic powder used in the phosphoric acid treatment step is not particularly limited. For example, a step of mixing a solution containing Sm and Fe with a precipitating agent to obtain a precipitate containing Sm and Fe (precipitation step), a step of firing the precipitate to obtain an oxide containing Sm and Fe (oxidation step), a step of heat-treating the oxide in an atmosphere containing a reducing gas to obtain a partial oxide (pretreatment step), a step of reducing the partial oxide (reduction step), and a step of nitriding the alloy particles obtained in the reduction step (nitriding step) manufactured by a method including can be preferably used.

[0037] [Precipitation step] In the precipitation step, a Sm raw material and an Fe raw material are dissolved in a strongly acidic solution to prepare a solution containing Sm and Fe. When obtaining Sm2Fe 17 N3 as the main phase, the molar ratio of Sm and Fe (Sm:Fe) is preferably 1.5:17 to 3.0:17, more preferably 2.0:17 to 2.5:17. Raw materials such as La, W, Co, Ti, Sc, Y, Pr, Nd, Pm, Gd, Tb, Dy, Ho, Er, Tm, Lu may be added to the aforementioned solution.

[0038] The Sm and Fe raw materials are not limited as long as they can dissolve in a strongly acidic solution. For example, in terms of availability, samarium oxide can be used as the Sm raw material and FeSO4 as the Fe raw material. The concentration of the solution containing Sm and Fe can be adjusted as appropriate within the range in which the Sm and Fe raw materials are substantially soluble in the acidic solution. In terms of solubility, sulfuric acid can be used as the acidic solution.

[0039] An insoluble precipitate containing Sm and Fe is obtained by reacting a solution containing Sm and Fe with a precipitating agent. Here, the solution containing Sm and Fe only needs to be a solution containing Sm and Fe when reacted with the precipitating agent. For example, the raw materials containing Sm and Fe may be prepared as separate solutions, and each solution may be added dropwise to react with the precipitating agent. Even when preparing the raw materials as separate solutions, they should be adjusted appropriately so that each raw material is substantially soluble in the acidic solution. The precipitating agent is not limited as long as it is an alkaline solution that reacts with a solution containing Sm and Fe to produce a precipitate, and examples include aqueous ammonia and caustic soda, with caustic soda being preferred.

[0040] For the precipitation reaction, a method is preferred in which a solution containing Sm and Fe and a precipitant are added dropwise to a solvent such as water, as this allows for easy adjustment of the particle properties of the precipitate. By appropriately controlling the supply rate of the solution containing Sm and Fe and the precipitant, the reaction temperature, the concentration of the reaction solution, and the pH during the reaction, a precipitate with a homogeneous distribution of constituent elements, a sharp particle size distribution, and a well-formed powder shape can be obtained. Using such a precipitate improves the magnetic properties of the final magnetic powder product. The reaction temperature can be 0 to 50°C, and is preferably 35 to 45°C. The concentration of the reaction solution is preferably 0.65 mol / L to 0.85 mol / L as the total concentration of metal ions, and more preferably 0.7 mol / L to 0.84 mol / L. The reaction pH is preferably 5 to 9, and more preferably 6.5 to 8.

[0041] The anisotropic magnetic powder particles obtained in the precipitation process roughly determine the particle size, shape, and particle size distribution of the final magnetic powder. When the particle size of the obtained particles is measured using a laser diffraction wet particle size analyzer, it is preferable that the size and distribution of the entire powder fall approximately within the range of 0.05 to 20 μm, preferably 0.1 to 10 μm. Furthermore, the average particle size of the anisotropic magnetic powder particles is measured as the particle size corresponding to 50% of the volume cumulative from the small particle size side in the particle size distribution, and it is preferable that it falls within the range of 0.1 to 10 μm.

[0042] After separating the precipitate, it is preferable to desolvent the separated material to prevent the precipitate from redissolving in the remaining solvent during the subsequent oxidation heat treatment, which can lead to aggregation of the precipitate, changes in particle size distribution, powder particle size, etc., as the solvent evaporates. Specifically, a method for desolvation is to dry the material in an oven at 70-200°C for 5-12 hours, for example, when water is used as the solvent.

[0043] The process may include a step of separating and washing the precipitate after the precipitation step. The washing step is performed when the conductivity of the supernatant solution is 5 mS / m 2 Continue as needed until the following is achieved. For example, to separate the precipitate, a solvent (preferably water) can be added to the obtained precipitate and mixed, after which filtration, decantation, or the like can be used.

[0044] [Oxidation process] The oxidation process involves calcining the precipitate formed in the precipitation process to obtain an oxide containing Sm and Fe. For example, the precipitate can be converted into an oxide by heat treatment. When heat treating the precipitate, it must be done in the presence of oxygen, for example, in an atmospheric environment. Furthermore, because it must be done in the presence of oxygen, it is preferable that the nonmetallic portion of the precipitate contains oxygen atoms.

[0045] The heat treatment temperature in the oxidation process (hereinafter referred to as the oxidation temperature) is not particularly limited, but is preferably 700 to 1300°C, and more preferably 900 to 1200°C. Below 700°C, oxidation is insufficient, and above 1300°C, the desired shape, average particle size, and particle size distribution of the magnetic powder tend not to be obtained. The heat treatment time is also not particularly limited, but is preferably 1 to 3 hours.

[0046] The resulting oxides exhibit sufficient microscopic mixing of Sm and Fe within the oxide particles, and the shape and particle size distribution of the precipitate are reflected in the oxide particles.

[0047] [Pre-treatment process] The pretreatment step is a process in which an oxide containing Sm and Fe is heat-treated in a reducing gas atmosphere to obtain a partial oxide in which a portion of the oxide has been reduced.

[0048] Here, a partially oxide refers to an oxide in which a portion of the oxide has been reduced. The oxygen concentration of the oxide is not particularly limited, but it is preferably 10% by mass or less, and more preferably 8% by mass or less. If it exceeds 10% by mass, the exothermic reaction with Ca during the reduction process increases, and the firing temperature rises, which tends to result in particles with abnormal particle growth. The oxygen concentration of the partially oxide can be measured by non-dispersive infrared absorption spectroscopy (ND-IR).

[0049] The reducing gas can be appropriately selected from hydrocarbon gases such as hydrogen (H2), carbon monoxide (CO), and methane (CH4), but hydrogen gas is preferred in terms of cost, and the gas flow rate is appropriately adjusted within a range where oxides do not scatter. The heat treatment temperature in the pretreatment step (hereinafter referred to as the pretreatment temperature) is in the range of 300°C to 950°C, preferably 400°C or higher, more preferably 750°C or higher, and preferably less than 900°C. When the pretreatment temperature is 300°C or higher, the reduction of oxides containing Sm and Fe proceeds efficiently. When the temperature is 950°C or lower, particle growth and segregation of oxide particles are suppressed, and the desired particle size can be maintained. Furthermore, when hydrogen is used as the reducing gas, it is preferable to adjust the thickness of the oxide layer used to 20 mm or less, and to adjust the dew point in the reaction furnace to -10°C or lower.

[0050] [Reduction Process] The reduction process is a process of obtaining alloy particles by heat-treating the partial oxide in the presence of a reducing agent at a temperature of 920°C to 1200°C. For example, reduction is carried out by contacting the partial oxide with a calcium melt or calcium vapor. The heat treatment temperature is preferably 950°C to 1150°C, and more preferably 980°C to 1100°C, from the viewpoint of magnetic properties. The heat treatment time is preferably less than 120 minutes, more preferably less than 90 minutes, from the viewpoint of carrying out the reduction reaction more uniformly, and the lower limit of the heat treatment time is preferably 10 minutes or more, and more preferably 30 minutes or more.

[0051] Metallic calcium is used in granular or powder form, but its particle size is preferably 10 mm or less. This allows for more effective suppression of aggregation during the reduction reaction. Furthermore, metallic calcium can be added in an amount of 1.1 to 3.0 times the reaction equivalent (the stoichiometric amount required to reduce Sm oxide, and including the amount required to reduce Fe if it is in oxide form), with 1.5 to 2.0 times being preferable.

[0052] In the reduction process, a disintegration accelerator can be used as needed together with metallic calcium as the reducing agent. This disintegration accelerator is appropriately used to promote the disintegration and granulation of the product during the water washing process described later. Examples thereof include alkaline earth metal salts such as calcium chloride and alkaline earth metal oxides such as calcium oxide. These disintegration accelerators are used at a ratio of 1 to 30% by mass, preferably 5 to 28% by mass, based on the Sm oxide used as the Sm source.

[0053] [Nitriding process] The nitriding process is a process of obtaining anisotropic magnetic particles by subjecting the alloy particles obtained in the reduction process to a nitriding treatment. Since the particulate precipitate obtained in the precipitation process described above is used, porous massive alloy particles are obtained in the reduction process. As a result, heat treatment can be immediately performed in a nitrogen atmosphere for nitriding without performing a pulverization treatment, so that nitriding can be performed uniformly.

[0054] The heat treatment temperature (hereinafter referred to as the nitriding temperature) in the nitriding treatment of the alloy particles is preferably 300 to 600 ° C, particularly preferably 400 to 550 ° C, and this temperature range is performed by replacing the atmosphere with a nitrogen atmosphere. The heat treatment time may be set to such an extent that the nitriding of the alloy particles is sufficiently uniform.

[0055] The product obtained after the nitriding process contains, in addition to the magnetic particles, by-produced CaO, unreacted metallic calcium, etc., and in some cases, these are in a sintered massive state in which they are combined. Therefore, in that case, this product can be put into cooling water to separate CaO and metallic calcium from the magnetic particles as a calcium hydroxide (Ca(OH)2) suspension. Further, the remaining calcium hydroxide may be sufficiently removed by washing the magnetic particles with acetic acid or the like.

[0056] The SmFeN-based anisotropic magnetic powder obtained by the above-described production method has a Th2Zn 17 type crystal structure, and the general formula is Sm x Fe 100-x-y N yThis nitride is composed of the rare earth metal samarium (Sm), iron (Fe), and nitrogen (N), represented by the formula shown. Here, it is preferable that x is between 8.1 atomic% and 10 atomic%, y is between 13.5 atomic% and 13.9 atomic%, and the remainder is mainly Fe.

[0057] The average particle size of the SmFeN-based anisotropic magnetic powder is preferably 2 μm to 5 μm, and more preferably 2.5 μm to 4.8 μm. Below 2 μm, the amount of magnetic powder filling the bonded magnet decreases, resulting in reduced magnetization, and above 5 μm, the coercivity of the bonded magnet tends to decrease. Here, the average particle size is the particle size measured under dry conditions using a laser diffraction particle size distribution analyzer.

[0058] The particle size D10 of the SmFeN-based anisotropic magnetic powder is preferably 1 μm or more and 3 μm or less, and more preferably 1.5 μm or more and 2.5 μm or less. If the particle size is less than 1 μm, the amount of magnetic powder filling the bonded magnet becomes small, resulting in a decrease in magnetization, while if it exceeds 3 μm, the coercivity of the bonded magnet tends to decrease. Here, D10 is the particle size that corresponds to 10% of the cumulative value of the volume-based particle size distribution of the SmFeN-based anisotropic magnetic powder.

[0059] The particle size D50 of the SmFeN-based anisotropic magnetic powder is preferably 2.5 μm or more and 5 μm or less, and more preferably 2.7 μm or more and 4.8 μm or less. If the particle size is less than 2.5 μm, the amount of magnetic powder filling the bonded magnet becomes small, resulting in a decrease in magnetization, and if it exceeds 5 μm, the coercivity of the bonded magnet tends to decrease. Here, D50 is the particle size that corresponds to 50% of the cumulative value of the volume-based particle size distribution of the SmFeN-based anisotropic magnetic powder.

[0060] The particle size D90 of the SmFeN-based anisotropic magnetic powder is preferably 3 μm to 7 μm, and more preferably 4 μm to 6 μm. Below 3 μm, the amount of magnetic powder filling the bonded magnet decreases, resulting in reduced magnetization, and above 7 μm, the coercivity of the bonded magnet tends to decrease. Here, D90 refers to the particle size corresponding to 90% of the cumulative value of the volume-based particle size distribution of the SmFeN-based anisotropic magnetic powder.

[0061] The span defined below for SmFeN-based anisotropic magnetic powders: Span = (D90 - D10) / D50 From the viewpoint of coercivity, the value is preferably 2 or less, and more preferably 1.5 or less. The particle size distribution of the magnetic powder used in the compound for bonded magnets is preferably monodisperse from the viewpoint of the angularity of the demagnetizing properties.

[0062] The circularity of SmFeN-based anisotropic magnetic powder is not particularly limited, but is preferably 0.5 or higher, and more preferably 0.6 or higher. Below 0.5, the fluidity deteriorates, causing stress between particles during molding and reducing magnetic properties. Here, the circularity is measured by binarizing SEM images taken at 3000x magnification using image processing, and determining the circularity for each individual particle. The circularity defined in this invention refers to the average value of the circularity obtained by measuring approximately 1000 to 10000 particles. Generally, the circularity increases as there are more particles with smaller particle sizes, so the circularity is measured for particles of 1 μm or larger. The defining formula for measuring circularity is: Circularity = (4πS / L2), where S is the two-dimensional projected area of ​​the particle and L is the two-dimensional projected perimeter.

[0063] The phosphate-coated SmFeN-based anisotropic magnetic powder of this embodiment can be used primarily as a bonded magnet.

[0064] The compound for bonded magnets is made from the magnetic powder of this embodiment and a resin. By including this magnetic powder, a compound for bonded magnets with high magnetic properties can be constructed.

[0065] The resin contained in the compound for bonded magnets may be a thermosetting resin or a thermoplastic resin, but a thermoplastic resin is preferred. Specific examples of thermoplastic resins include polyphenylene sulfide (PPS), polyether ether ketone (PEEK), liquid crystal polymer (LCP), polyamide (PA), polypropylene (PP), polyethylene (PE), and the like.

[0066] The weight ratio of magnetic powder to resin (resin / magnetic powder) when obtaining a compound for bonded magnets is preferably 0.08 to 0.15, and more preferably 0.09 to 0.13.

[0067] Bonded magnet compounds can be obtained, for example, by mixing magnetic powder and resin at 180-300°C using a kneader. For example, after mixing magnetic powder and resin powder in a mixer, the strand can be extruded using a twin-screw extruder, air-cooled, and then cut into pellets of several millimeters in size using a pelletizer to obtain bonded magnet compounds in pellet form.

[0068] Bonded magnets can be manufactured using a compound for bonded magnets and a suitable molding machine. Specifically, for example, a bonded magnet can be obtained by injecting a molten compound for bonded magnets in a mold with a magnetic field applied, aligning the easy magnetization axis (orientation step), cooling and solidifying it, and then magnetizing it with an air-core coil or magnetizing yoke (magnetization step).

[0069] The barrel temperature is selected according to the type of resin used, ranging from 160°C to 320°C, and similarly, the mold temperature can be, for example, 30°C to 150°C. The orientation magnetic field in the orientation process is generated using electromagnets or permanent magnets, with a magnetic field magnitude of 4 kOe or more, and more preferably 6 kOe or more. Furthermore, the magnetic field magnitude in the magnetization process is preferably 20 kOe or more, and more preferably 30 kOe or more.

[0070] The first method for manufacturing the compound for bonded magnets according to this embodiment is: A process to obtain an additive for bonded magnets by thermal curing a thermosetting resin and a curing agent having a ratio of the number of reactive groups to the number of reactive groups of the thermosetting resin of 2 or more and 11 or less, A kneading step to knead the additive for bonded magnets, the magnetic powder obtained by the method for producing the phosphate-coated SmFeN-based anisotropic magnetic powder, or the magnetic powder, and a thermoplastic resin to obtain a bonded magnet compound in which the filling rate of magnetic powder in the bonded magnet compound is 91.5% by mass or more. It is characterized by including.

[0071] When manufacturing bonded magnets containing thermoplastic resins, injection molding a mixture of thermoplastic resin and thermosetting resin can sometimes lead to a decrease in resin fluidity and poor moldability due to a reaction between the reactive groups of the thermosetting resin (e.g., glycyl groups in the case of epoxy resin) and the thermoplastic resin (e.g., amide groups in the case of nylon 12). In this embodiment, the cured product of a thermosetting resin and a curing agent with an equivalent ratio of 2 to 11 for the thermosetting resin is sufficiently deactivated by the reactive groups of the curing agent (e.g., amino groups in the case of DDS (diaminodiphenylsulfone)). Therefore, a reaction with the reactive groups of the thermoplastic resin is less likely to occur, suppressing a decrease in resin fluidity, and thus it can be used as an additive for bonded magnets containing thermoplastic resins. Furthermore, when manufacturing bonded magnets by injection molding using a bonded magnet compound made with the thermoplastic resin additive of this embodiment, the injection pressure can be reduced, improving the magnetic properties of the resulting bonded magnets.

[0072] Thermosetting resins are not particularly limited as long as they are thermosetting, and examples include epoxy resins, phenolic resins, urea resins, melamine resins, guanamine resins, unsaturated polyester resins, vinyl ester resins, diallyl phthalate resins, polyurethane resins, silicone resins, polyimide resins, alkyd resins, furan resins, dicyclopentadiene resins, acrylic resins, and allyl carbonate resins. Among these, epoxy resins are preferred in terms of mechanical properties and heat resistance. Thermosetting resins are preferably liquid at room temperature or solids that dissolve in a solvent to become liquid.

[0073] The curing agent is not particularly limited as long as it is capable of thermosetting the selected thermosetting resin. When the thermosetting resin is an epoxy resin, examples include amine-based curing agents, acid anhydride-based curing agents, polyamide-based curing agents, imidazole-based curing agents, phenol-based curing agents, polymercaptan-based curing agents, polysulfide-based curing agents, and organic acid hydrazide-based curing agents. Examples of amine-based curing agents include diaminodiphenylsulfone, metaphenylenediamine, diaminodiphenylmethane, diethylenetriamine, and triethylenetetramine.

[0074] The amount of curing agent is adjusted by the ratio of the number of reactive groups in the curing agent to the number of reactive groups in the thermosetting resin (the ratio of the equivalent amount of curing agent to the equivalent amount of thermosetting resin). The ratio of the number of reactive groups in the curing agent to the number of reactive groups in the thermosetting resin is between 2 and 11, but is preferably between 2 and 10, and more preferably between 2 and 7. The lower limit of the number of reactive groups is preferably greater than 2.5, and more preferably 3 or greater. If the ratio exceeds 11, the mechanical properties of the bonded magnet will deteriorate, and if it is less than 2, the ratio of reactive groups in the curing agent to the reactive groups in the thermosetting resin is small, so reactive groups of the thermosetting resin will remain. When kneaded with a thermoplastic resin in a subsequent process, the reactive groups of the thermoplastic resin react with the reactive groups of the remaining thermosetting resin, causing an increase in viscosity during injection molding, and the moldability of the bonded magnet and the mechanical properties of the resulting molded product will be worse than those of the thermoplastic resin alone. Here, the equivalent weight of the thermosetting resin species refers to the number of grams of resin containing 1 gram equivalent of reactive groups, and the equivalent weight of the curing agent species refers to the equivalent weight of active hydrogen.

[0075] The cured product can be obtained by mixing a curing agent with the aforementioned thermosetting resin and then heat-curing it. The temperature for heat curing can be set according to the properties of the thermosetting resin used, but from the viewpoint of curing performance, a temperature of 60°C to 250°C is preferred, and a temperature of 180°C to 220°C is more preferred.

[0076] The cured material can be pulverized as needed. The method of pulverizing the cured material is not particularly limited, and sample mills, ball mills, stamp mills, mortars, mixer mills, etc., can be used. If necessary, the pulverized material can also be classified using a sieve or the like. The average particle size of the pulverized material is preferably 1000 μm or less, and more preferably 500 μm or less, from the viewpoint of compatibility with thermoplastic resins.

[0077] Additives for bonded magnets can also be obtained by curing a thermosetting resin and a curing agent together with a curing accelerator. Examples of curing accelerators include 1,8-diazabicyclo(5,4,0)-undecene-7, 1,5-diazabicyclo(4,3,0)-nonene-5, 1-cyanoethyl-2-ethyl-4-methylimidazole, 2-methyl-4-methylimidazole, triphenylphosphine, and sulfonium salts. The content of the curing accelerator is not particularly limited, but generally it is added in an amount of 0.01% to 10% by mass relative to the total amount of thermosetting resin and curing agent.

[0078] In the compounding process, a bond magnet additive, magnetic powder, and thermoplastic resin are melt-mixed to produce a bond magnet compound for injection molding. The melt mixer is not particularly limited, but a single-screw mixer, twin-screw mixer, mixing roll, kneader, Banbury mixer, meshing twin-screw extruder, non-meshing twin-screw extruder, etc., can be used. The melt mixing temperature is not particularly limited and can be set according to the properties of the thermoplastic resin used, but 180°C to 250°C is preferred.

[0079] Thermoplastic resins are not particularly limited as long as they are injection-molded resins, but examples include nylon resin (polyamide); polyolefins such as polypropylene (PP) and polyethylene (PE); polyester; polycarbonate (PC); polyphenylene sulfide (PPS); polyether ether ketone (PEEK); polyacetal (POM); and liquid crystal polymer (LCP). Examples of nylon resins include polylactams such as nylon 6, nylon 11, and nylon 12; condensates of dicarboxylic acid and diamine such as nylon 6,6, nylon 6,10, and nylon 6,12; copolymer polyamides such as nylon 6 / 6,6, nylon 6 / 6,10, nylon 6 / 12, nylon 6 / 6,12, nylon 6 / 6,10 / 6,10, nylon 6 / 6,6 / 6,12, and nylon 6 / polyether; nylon 6T, nylon 9T, nylon MXD6, aromatic nylon, and amorphous nylon. Among these, nylon resin is preferred due to its low water absorption rate, moldability, and mechanical properties, and nylon 12 is particularly preferred.

[0080] In the first method for manufacturing a bonded magnet compound of this embodiment, the filling rate of magnetic powder in the bonded magnet compound is 91.5% by mass or more, preferably 91.8% by mass or more, and more preferably 92.2% by mass or more. There is no particular upper limit, but it is preferably 93.2% by mass or less, more preferably 92.8% by mass or less, and even more preferably 92.5% by mass or less. If it exceeds 93.2% by mass, the viscosity during injection molding increases, and the moldability decreases.

[0081] The content of the bond magnet additive in the first bond magnet compound of this embodiment is preferably 0.5% by mass or more and 4.2% by mass or less, more preferably 0.9% by mass or more and 3.5% by mass or less, and even more preferably 0.9% by mass or more and 1.2% by mass or less. If the content of the bond magnet additive exceeds 4.2% by mass, the residual magnetic flux density of the bond magnet will decrease, and if it is less than 0.5% by mass, the viscosity during injection molding will increase, which may reduce moldability.

[0082] The thermoplastic resin content in the first bonded magnet compound of this embodiment is preferably 8.0% by mass or less, and more preferably 6.5% by mass or less. The lower limit is not particularly limited, but is preferably 4.2% by mass or more, and more preferably 5.5% by mass or more. If the amount of thermoplastic resin added exceeds 8.0% by mass, the residual magnetic flux density of the bonded magnet will decrease, and if it is less than 4.2% by mass, the viscosity during injection molding will increase, resulting in reduced moldability.

[0083] The method for manufacturing the second compound for bonded magnets according to this embodiment is: A process to obtain an additive for bonded magnets by thermal curing a thermosetting resin and a curing agent having a ratio of the number of reactive groups to the number of reactive groups of the thermosetting resin of 2 or more and 11 or less, The process involves kneading the aforementioned additive for bonded magnets with a thermoplastic resin to obtain a resin composition for bonded magnets. The resin composition for bonded magnets and the magnetic powder obtained by the method for producing the phosphate-coated SmFeN-based anisotropic magnetic powder, or the magnetic powder, are kneaded together to obtain a compound for bonded magnets. It is characterized by including.

[0084] The process for obtaining additives for bonded magnets, and the thermosetting resin and curing agent used in this process, are as described above.

[0085] The kneading process for obtaining the resin composition for bonded magnets, and the thermoplastic resin used in this process, are as described above. A molten kneaded product is obtained by pre-melt kneading the thermosetting resin with a curing agent having a ratio of the number of reactive groups to the number of reactive groups of the thermosetting resin of 2 to 11, and the thermoplastic resin, before kneading with the magnetic powder. In the obtained kneaded product, the thermoplastic resin and the curing agent may be completely miscible, partially miscible, or miscible, as long as they have been pre-melt kneaded, but complete miscible is preferred.

[0086] In a resin composition for bonded magnets obtained by thoroughly kneading a cured product and a thermoplastic resin, the melting point and crystallization temperature are lower when the thermoplastic resin is a crystalline resin. As a result, the injection pressure of the bonded magnet compound is also reduced, improving the orientation and magnetic properties of the resulting bonded magnet, and also improving its coercivity. The melting point is preferably 3.0°C or more lower than the melting point of the thermoplastic resin, and more preferably 4.5°C or more lower. The crystallization temperature is preferably 2.0°C or more lower than the crystallization temperature of the thermoplastic resin, and more preferably 3.0°C or more lower.

[0087] When polyamide 12 is used as the thermoplastic resin, the melting point (peak top) of the resin composition for bonded magnets is preferably 160°C to 177°C, and more preferably 170°C to 175°C. Furthermore, the difference between the peak top of the melting peak and the final melting point is preferably greater than 5.0°C, and more preferably greater than 5.5°C. In addition, the heat energy of the melting peak is preferably 50 mJ / mg or more, and more preferably 55 mJ / mg or more.

[0088] The amount of additive for bonded magnets is preferably 5% to 50% by mass, and more preferably 10% to 20% by mass, in the resin composition consisting of the additive for bonded magnets and the thermoplastic resin. If it exceeds 50% by mass, the packing density of the magnetic powder decreases, and if it is less than 5% by mass, the effect of lowering the melting point and crystallization temperature of the molten mixture is small, making it impossible to sufficiently reduce the injection pressure during bonded magnet molding.

[0089] The process for obtaining the compound for bonded magnets, and the magnetic powder used in the process, are as described above.

[0090] In the second method for manufacturing a bonded magnet compound of this embodiment, the filling ratio of magnetic powder in the bonded magnet compound is preferably 75% by mass or more and 94% by mass or less, and more preferably 90% by mass or more and 93.5% by mass or less. If it exceeds 94% by mass, the viscosity during injection molding increases, reducing moldability, and if it is less than 75% by mass, the residual magnetic flux density of the bonded magnet becomes low.

[0091] The content of the resin composition for bonded magnets in the second compound for bonded magnets of this embodiment is preferably 6% by mass or more and 25% by mass or less, and more preferably 6.5% by mass or more and 10% by mass or less. If the content of the resin composition for bonded magnets exceeds 25% by mass, the residual magnetic flux density of the bonded magnet decreases, and if it is less than 6% by mass, the viscosity during injection molding increases, resulting in reduced moldability.

[0092] The compound for bonded magnets of this embodiment is obtained by the manufacturing method described above.

[0093] The first method for manufacturing a bonded magnet according to this embodiment is: A process to obtain an additive for bonded magnets by thermal curing a thermosetting resin and a curing agent having a ratio of the number of reactive groups to the number of reactive groups of the thermosetting resin of 2 or more and 11 or less, A kneading step to obtain a bonded magnet compound in which the magnetic powder obtained by the method for producing the bonded magnet additive, the magnetic powder obtained by the method for producing the phosphate-coated SmFeN-based anisotropic magnetic powder, or the magnetic powder, and a thermoplastic resin are kneaded together to obtain a bonded magnet compound in which the filling rate of magnetic powder in the bonded magnet compound is 91.5% by mass or more, An injection molding process in which the resulting compound for bonded magnets is injection molded. It is characterized by including.

[0094] The method for manufacturing the second bonded magnet of this embodiment is as follows: A process to obtain an additive for bonded magnets by thermal curing a thermosetting resin and a curing agent having a ratio of the number of reactive groups to the number of reactive groups of the thermosetting resin of 2 or more and 11 or less, The process involves kneading the aforementioned additive for bonded magnets with a thermoplastic resin to obtain a resin composition for bonded magnets. A kneading step to obtain a compound for bonded magnets by kneading the resin composition for bonded magnets and the magnetic powder obtained by the method for producing the phosphate-coated SmFeN-based anisotropic magnetic powder, or the magnetic powder, An injection molding process in which the resulting compound for bonded magnets is injection molded. It is characterized by including.

[0095] In these two methods for manufacturing bonded magnets, the steps for obtaining the additive for bonded magnets and the kneading step for obtaining the compound for bonded magnets are as described above.

[0096] In the injection molding process, the bond magnet compound is injection molded to obtain an injection-molded product. The cylinder temperature of the injection molding machine should be within the temperature range in which the bond magnet compound melts, and is preferably 260°C or lower to suppress magnetic degradation of the magnetic powder due to heat. The injection pressure should be any pressure at which the molten compound can be injected, but for example, when the cylinder temperature of the injection molding machine is 230°C and injection molding is performed on a cavity with a diameter of 10 mm and a thickness of 7 mm, it is preferable to be able to fully fill it at a pressure of less than 250 MPa from the viewpoint of moldability.

[0097] The first bonded magnet of this embodiment is obtained, for example, by the method for manufacturing the first bonded magnet of this embodiment described above, and is characterized by comprising a bonded magnet additive, magnetic powder, and thermoplastic resin, wherein the filling rate of the magnetic powder is 91.5% by mass or more. The first bonded magnet is manufactured at a low injection pressure by using a highly fluid bonded magnet compound containing a bonded magnet additive, so that magnetic degradation of the magnetic powder due to injection molding is suppressed, and the magnetic properties of the bonded magnet are improved.

[0098] In the first bonded magnet of this embodiment, the filling rate of magnetic powder in the bonded magnet is 91.5% by mass or more, preferably 91.8% by mass or more, and more preferably 92.2% by mass or more. There is no particular upper limit, but it is preferably 93.2% by mass or less, more preferably 92.8% by mass or less, and even more preferably 92.5% by mass or less. If it exceeds 93.2% by mass, the viscosity during injection molding increases, and the moldability decreases.

[0099] In the first bonded magnet of this embodiment, the content of the additive for bonded magnets in the bonded magnet is preferably 0.5% by mass or more and 4.2% by mass or less, more preferably 0.9% by mass or more and 3.5% by mass or less, and even more preferably 0.9% by mass or more and 1.2% by mass or less. If the content of the additive for bonded magnets exceeds 4.2% by mass, the residual magnetic flux density of the bonded magnet decreases, and if it is less than 0.5% by mass, the viscosity during injection molding increases, resulting in decreased moldability.

[0100] In the first bonded magnet of this embodiment, the content of thermoplastic resin in the bonded magnet is preferably 8.0% by mass or less, and more preferably 6.5% by mass or less. The lower limit is not particularly limited, but is preferably 4.2% by mass or more, and more preferably 5.5% by mass or more. If the amount of thermoplastic resin added exceeds 8.0% by mass, the residual magnetic flux density of the bonded magnet decreases, and if it is less than 4.2% by mass, the viscosity during injection molding increases, resulting in reduced moldability.

[0101] The orientation ratio in the first bonded magnet of this embodiment is not particularly limited, but is preferably 98.3% or higher, and more preferably 99% or higher.

[0102] The residual magnetic flux density in the first bonded magnet of this embodiment is not particularly limited, but when the magnetic powder is SmFeN-based, it is preferably 0.81T or higher, and more preferably 0.82T or higher. By using the resin additive for bonded magnets of this embodiment, a high residual magnetic flux density can be achieved.

[0103] The coercivity of the first bonded magnet of this embodiment is not particularly limited, but is preferably 1100 kA / m or more, and more preferably 1200 kA / m or more. High coercivity can be achieved by using the resin additive for bonded magnets of this embodiment.

[0104] In this embodiment, the first bonded magnet is manufactured by kneading a bonded magnet additive, magnetic powder, and thermoplastic resin, so the bonded magnet additive and the magnetic powder exist independently of each other.

[0105] The second bonded magnet of this embodiment is obtained, for example, by the method for manufacturing the second bonded magnet of this embodiment described above, and is characterized by comprising a resin composition for bonded magnets and magnetic powder. The second bonded magnet is manufactured at a low injection pressure by using a highly fluid compound for bonded magnets containing the resin composition for bonded magnets, so that magnetic degradation of the magnetic powder due to injection molding is suppressed, and the magnetic properties of the bonded magnet are improved.

[0106] In the second bonded magnet of this embodiment, the packing ratio of magnetic powder in the bonded magnet is preferably 75% by mass or more and 94% by mass or less, and more preferably 90% by mass or more and 93.5% by mass or less. If it exceeds 94% by mass, the viscosity during injection molding increases, reducing moldability, and if it is less than 75% by mass, the residual magnetic flux density of the bonded magnet becomes low.

[0107] In the second bonded magnet of this embodiment, the content of the resin composition for bonded magnets in the bonded magnet is preferably 6% by mass or more and 25% by mass or less, and more preferably 6.5% by mass or more and 10% by mass or less. If the content of the resin composition for bonded magnets exceeds 25% by mass, the residual magnetic flux density of the bonded magnet decreases, and if it is less than 6% by mass, the viscosity during injection molding increases, resulting in reduced moldability.

[0108] The orientation ratio in the second bonded magnet of this embodiment is not particularly limited, but is preferably 98.3% or higher, and more preferably 99% or higher.

[0109] The residual magnetic flux density in the second bonded magnet of this embodiment is not particularly limited, but when the magnetic powder is SmFeN-based, it is preferably 0.81T or higher, and more preferably 0.82T or higher. A high residual magnetic flux density can be achieved by using the resin composition for bonded magnets of this embodiment, which contains a cured product of a thermosetting resin and a curing agent and a molten kneaded product of a thermoplastic resin.

[0110] The coercivity of the second bonded magnet of this embodiment is not particularly limited, but is preferably 1150 kA / m or more, and more preferably 1200 kA / m or more. High coercivity can be achieved by using the resin composition for bonded magnets of this embodiment, which contains a cured product of a thermosetting resin and a curing agent and a molten kneaded product of a thermoplastic resin.

[0111] In this embodiment, the second bonded magnet is manufactured by kneading a resin composition for bonded magnets and magnetic powder, so the resin composition for bonded magnets and the magnetic powder exist independently of each other. [Examples]

[0112] Example 1 5.0 kg of FeSO4·7H2O was mixed and dissolved in 2.0 kg of pure water. Then, 0.49 kg of Sm2O and 0.74 kg of 70% sulfuric acid were added and the mixture was thoroughly stirred until completely dissolved. Next, pure water was added to the resulting solution to adjust the final concentration to 0.726 mol / L for Fe and 0.112 mol / L for Sm, thus obtaining the SmFe sulfuric acid solution.

[0113] [Precipitation process] The entirety of the prepared SmFe sulfuric acid solution was added dropwise to 20 kg of pure water maintained at 40°C, while stirring for 70 minutes from the start of the reaction. Simultaneously, 15% ammonia solution was added dropwise to adjust the pH to 7-8. This yielded a slurry containing SmFe hydroxide. The obtained slurry was washed with pure water by decantation, and then the hydroxide was separated into solid and liquid phases. The separated hydroxide was dried in an oven at 100°C for 10 hours.

[0114] [Oxidation process] The hydroxide obtained in the precipitation process was calcined in air at 1000°C for 1 hour. After cooling, red SmFe oxide was obtained as the raw material powder. [Pre-treatment process] 100 g of SmFe oxide was placed in a steel container to a thickness of 10 mm. The container was placed in a furnace, the pressure was reduced to 100 Pa, and then the temperature was raised to the pretreatment temperature of 850°C while introducing hydrogen gas, and it was held at that temperature for 15 hours. The oxygen concentration was measured by non-dispersive infrared absorption spectroscopy (ND-IR) (EMGA-820, Horiba, Ltd.) and found to be 5 mass%. This indicates that the oxygen bonded to Sm was not reduced, while 95% of the oxygen bonded to Fe was reduced, resulting in a black partial oxide.

[0115] [Reduction Process] 60 g of partial oxide obtained in the pretreatment process and 19.2 g of metallic calcium with an average particle size of approximately 6 mm were mixed and placed in the furnace. After evacuating the furnace, argon gas (Ar gas) was introduced. The temperature was raised to 1045°C and held for 45 minutes to obtain Fe-Sm alloy particles.

[0116] [Nitriding process] Subsequently, the furnace temperature was cooled to 100°C, then the chamber was evacuated, and the temperature was raised to 450°C while introducing nitrogen gas. This temperature was maintained for 23 hours to obtain a massive product containing magnetic particles.

[0117] [Water washing process] The lumpy product obtained in the nitriding process was added to 3 kg of pure water and stirred for 30 minutes. After standing, the supernatant was drained by decantation. The process of adding to pure water, stirring, and decanting was repeated 10 times. Next, 2.5 g of 99.9% acetic acid was added and stirred for 15 minutes. After standing, the supernatant was drained by decantation. The process of adding to pure water, stirring, and decanting was repeated twice, followed by dehydration and drying, and then mechanical crushing to obtain SmFeN-based anisotropic magnetic powder (average particle size 3 μm).

[0118] [Phosphating treatment process] As the phosphoric acid treatment solution, a mixture of 85% orthophosphoric acid, sodium dihydrogen phosphate, and sodium molybdate dihydrate in a weight ratio of 1:6:1 was prepared, and the pH was adjusted to 2 and the PO4 concentration to 20% by mass using pure water and dilute hydrochloric acid. 1000g of the SmFeN-based anisotropic magnetic powder obtained in the water washing step was stirred for 1 minute in dilute hydrochloric acid (hydrogen chloride:70g) to remove surface oxide film and contaminants. Then, the drainage and addition of water were repeated until the conductivity of the supernatant liquid was 100 μS / cm or less, to obtain a slurry containing 10% by mass of SmFeN-based anisotropic magnetic powder. While stirring the obtained slurry, 100g of the prepared phosphoric acid treatment solution was added entirely to the treatment tank, and the pH of the phosphoric acid treatment reaction slurry was controlled within the range of 2.0 ± 0.1 by adding 6% by weight hydrochloric acid as needed, and maintained for 30 minutes. Subsequently, suction filtration, dehydration, and vacuum drying were performed to obtain phosphate-coated SmFeN-based anisotropic magnetic powder.

[0119] Example 2 A phosphate-coated SmFeN-based anisotropic magnetic powder was obtained in the same manner as in Example 1, except that a phosphate treatment solution was prepared with a pH adjusted to 2.5, and the pH of the phosphate treatment reaction slurry was controlled within the range of 2.5 ± 0.1.

[0120] Example 3 A phosphate-coated SmFeN-based anisotropic magnetic powder was obtained in the same manner as in Example 1, except that a phosphate treatment solution was prepared with a pH adjusted to 3, and the pH of the phosphate treatment reaction slurry was controlled within the range of 3.0 ± 0.1.

[0121] Example 4 A phosphate-coated SmFeN-based anisotropic magnetic powder was obtained in the same manner as in Example 1, except that a phosphate treatment solution was prepared with a pH adjusted to 3.5, and the pH of the phosphate treatment reaction slurry was controlled within the range of 3.5 ± 0.1.

[0122] Example 5 A phosphate-coated SmFeN-based anisotropic magnetic powder was obtained in the same manner as in Example 1, except that a phosphate treatment solution was prepared with a pH adjusted to 1.5, and the pH of the phosphate treatment reaction slurry was controlled within the range of 1.5 ± 0.1.

[0123] Example 6 A phosphate-coated SmFeN-based anisotropic magnetic powder was obtained in the same manner as in Example 1, except that a phosphate treatment solution was prepared with a pH adjusted to 4, and the pH of the phosphate treatment reaction slurry was controlled within the range of 4.0 ± 0.1.

[0124] Comparative Example 1 Magnetic powder was obtained by carrying out the water washing step in the same manner as in Example 1. As the phosphoric acid treatment solution, a mixture of 85% orthophosphoric acid, sodium dihydrogen phosphate, and sodium molybdate dihydrate in a weight ratio of 1:6:1 was prepared, and the pH was adjusted to 2.5 and the PO4 concentration to 20% by mass with pure water and dilute hydrochloric acid. 1000g of the SmFeN-based anisotropic magnetic powder obtained in the water washing step was stirred for 1 minute in dilute hydrochloric acid with hydrogen chloride:70g to remove surface oxide film and contaminants. Then, the drainage and addition of water were repeated until the conductivity of the supernatant liquid was 100 μS / cm or less, to obtain a slurry containing 10% by mass of SmFeN-based anisotropic magnetic powder. While stirring the obtained slurry, 100g of the prepared phosphoric acid treatment solution was added entirely to the treatment tank. The pH of the phosphoric acid treatment reaction slurry rose from 2.5 to 6 over 5 minutes. After stirring for 15 minutes, the material was filtered by suction, dehydrated, and vacuum dried to obtain a phosphate-coated SmFeN-based anisotropic magnetic powder.

[0125] Comparative Example 2 A phosphate-coated SmFeN-based anisotropic magnetic powder was obtained in the same manner as in Comparative Example 1, except that the pH of the phosphate treatment solution was adjusted to 3.5. Here, the pH of the phosphate treatment reaction slurry increased from 3.5 to 6 over 15 minutes.

[0126] Comparative Example 3 [Reduction Process 2] A crucible filled with a mixed powder of 52.5 g of iron powder with an average particle size (D50) of approximately 50 μm, 21.3 g of samarium oxide powder with an average particle size (D50) of 3 μm, and 10.5 g of metallic calcium was placed in a furnace. After evacuating the furnace, argon gas (Ar gas) was introduced. Fe-Sm alloy particles were obtained by raising the temperature to 1150°C and holding it for 5 hours.

[0127] [Nitriding Process 2] Next, the Fe-Sm alloy particles were heat-treated in an ammonia-hydrogen mixed gas at 420°C for 23 hours to obtain a massive product containing magnetic particles.

[0128] [Washing process 2] The lumpy product obtained in the nitriding process was added to 3 kg of pure water and stirred for 30 minutes. After standing, the supernatant was drained by decantation. The process of adding to pure water, stirring, and decantation was repeated 10 times. Next, 2.5 g of 99.9% acetic acid was added and stirred for 15 minutes. After standing, the supernatant was drained by decantation. The process of adding to pure water, stirring, and decantation was repeated twice. Subsequently, dehydration and drying treatment were performed to obtain SmFeN-based anisotropic magnetic powder (average particle size 30 μm).

[0129] [Phosphating treatment process 2] 15 g of the obtained magnetic powder was placed in a glass bottle with 0.44 g of 85% orthophosphoric acid aqueous solution, 100 ml of isopropanol (IPA), and 200 g of 10 mm diameter alumina beads, and the mixture was ground in a vibrating ball mill for 120 minutes. After filtering the slurry, it was vacuum-dried at 100°C to obtain phosphate-coated SmFeN-based anisotropic magnetic powder (average particle size 1.5 μm).

[0130] [Magnetic powder evaluation] (Residual magnetic flux density (Br), coercivity (iHc) of magnetic powder) The magnetic properties (remanent magnetization σr, intrinsic coercivity iHc) of the phosphate-coated SmFeN-based anisotropic magnetic powders obtained in Examples 1 to 6 and Comparative Examples 1 to 3 were measured using a VSM (vibrating sample magnetometer, RIKEN Electronics Corporation; model: BHV-55). Furthermore, the remanent magnetization σr (unit: emu / g) was calculated using the formula (Br = 4 × π × ρ × σr, ρ: density = 7.66 g / cm³). 3 The residual magnetic flux density Br (unit: kG) was calculated using ). The results are shown in Table 1.

[0131] (DSC fever onset temperature) 20 mg of the phosphate-coated SmFeN-based anisotropic magnetic powder obtained in Examples 1 to 6 and Comparative Examples 1 to 3 was weighed and analyzed using a high-temperature differential scanning thermal analyzer (DSC6300, Hitachi High-Tech Science Corporation) under the following conditions: air atmosphere (200 mL / min), room temperature to 400°C (heating rate: 20°C / min), and reference: alumina (20 mg). The exothermic onset temperature was measured. The DSC results are shown in Table 1. A high exothermic onset temperature indicates that heat generation due to oxidation is less likely to occur, meaning that the phosphate coating is more densely formed.

[0132] (α-Fe peak height ratio) The phosphate-coated SmFeN-based anisotropic magnetic powders obtained in Examples 1 to 6 and Comparative Examples 1 to 3 were subjected to XRD pattern measurement using a powder X-ray crystal diffractometer (Rigaku Corporation, X-ray wavelength: CuKa1). The α-Fe peak height ratio was determined by dividing the diffraction peak intensity of the (110) plane of α-Fe by the peak intensity of the (300) plane of Sm2Fe17N3 and multiplying by 10,000. The results are shown in Table 1. A low α-Fe peak height ratio indicates a low content of α-Fe, which is an impurity.

[0133] (PO4 adhesion amount) The P concentration in the phosphate-coated SmFeN-based anisotropic magnetic powders obtained in Examples 1 to 6 and Comparative Examples 1 to 3 was measured using ICP emission spectroscopy (ICP-AES), and the amount of PO4 attached was determined by converting it to PO4 molecular weight. The results are shown in Table 1.

[0134] (Total carbon content) The total carbon (TC) content in the phosphate-coated SmFeN-based anisotropic magnetic powders obtained in Examples 1 to 6 and Comparative Examples 1 to 3 was measured using a combustion catalyst oxidation type total organic carbon (TOC) meter (Shimadzu Corporation; Model: SSM-5000A). The results are shown in Table 1.

[0135] [Table 1]

[0136] Table 1 shows that Examples 1 to 6, in which pH adjustment was performed in an aqueous solvent during phosphoric acid treatment, had higher coercivity (iHc) compared to Comparative Examples 1 and 2, in which pH adjustment was not performed in an aqueous solvent. Comparative Example 3, in which pH adjustment was not performed in an isopropanol solvent, had the lowest coercivity.

[0137] (SEM analysis) Cross-sectional SEM images of the magnetic powders obtained in Example 2 and Comparative Example 1 are shown in Figures 1 and 2. In Example 2, a thicker phosphate coating was formed on the surface of the SmFeN-based anisotropic magnetic powder compared to Comparative Example 1.

[0138] SEM images of the magnetic powders obtained in Example 2 and Comparative Example 3 are shown in Figures 3 and 4. The particle size of the magnetic powder was also measured under dry conditions using a laser diffraction particle size distribution analyzer, and the results are shown in Figure 5. The vertical axis in Figure 5 shows the volume-based frequency distribution. In Comparative Example 3, the uniformity of the particle size distribution was poor because grinding was performed in parallel with the phosphoric acid treatment. In Example 2, a magnetic powder with uniform particle size was obtained.

[0139] (STEM-EDX mapping) The magnetic powders obtained in Example 2 and Comparative Example 1 were dispersed in epoxy resin and solidified. Cross-sections were then prepared using a cross-section polisher to obtain cross-sectional samples for measurement. STEM images (acceleration voltage 200kV) were measured on the obtained samples using a scanning transmission electron microscope (STEM; JEOL) and an energy-dispersive X-ray spectrometer (EDX; JEOL). Figure 6 shows the STEM-EDX mapping analysis results (elements: P, Fe, Sm, Mo).

[0140] (STEM-EDX line analysis) Figures 7 and 8 show the EDX line analysis corresponding to the arrows at the phosphate coating / SmFeN-based anisotropic magnetic powder interface for the magnetic powders obtained in Example 2 and Comparative Example 1. In Figure 7, for the magnetic powder of Example 2, a region is observed from a distance of 65 nm to 80 nm where the atomic ratio of Sm and N is almost the same, which is thought to correspond to the base material, SmFeN-based anisotropic magnetic powder. A distribution of P is observed from a distance of 10 nm to 65 nm, and this region is thought to correspond to the phosphate coating (metals = Sm, Fe, Mo). Furthermore, within the region corresponding to the phosphate coating, a region with a particularly high concentration of Sm was observed from a distance of 30 nm to 65 nm. In this region, the proportion of Sm among the metal elements is the highest, and the main component is presumed to be samarium phosphate. In addition, Mo has a peak at a position of around 65 nm, which corresponds to the outermost surface region of the SmFeN-based anisotropic magnetic powder, and gradually increases towards the surface of the phosphate coating. Thus, it was confirmed that the phosphate coating in Example 2 was mainly composed of samarium phosphate and had a lower Fe atom concentration compared to Comparative Example 1.

[0141] In Figure 8, for the magnetic powder of Comparative Example 1, a distribution of P is observed over a distance of approximately 50 nm to 70 nm, and this region corresponds to the phosphate coating (metal = Sm, Fe, Mo). In this region, the proportion of Fe is the highest, and it is presumed that the main component is iron phosphate. Furthermore, the shape of the graph for Mo is similar to that of P, and unlike the magnetic powder of Example 2, the Mo / P ratio is present at a nearly constant composition.

[0142] Example 7 [Oxidation process after phosphoric acid treatment] 1000 g of the phosphate-coated SmFeN-based anisotropic magnetic powder obtained in Example 2 was gradually heated from room temperature in a nitrogen and air mixed gas atmosphere (oxygen concentration 4%, 5 L / min), and heat-treated at a maximum temperature of 170°C for 8 hours to obtain oxidized SmFeN-based anisotropic magnetic powder.

[0143] Example 8 Except for changing the heat treatment temperature in the oxidation process from 170°C to 200°C, the same procedure as in Example 7 was followed to obtain an oxidized SmFeN-based anisotropic magnetic powder.

[0144] Example 9 Except for changing the heat treatment temperature in the oxidation process from 170°C to 230°C, the procedure was carried out in the same manner as in Example 7 to obtain an oxidized SmFeN-based anisotropic magnetic powder.

[0145] Comparative Example 4 [Oxidation process after phosphoric acid treatment] 1000 g of the phosphate-coated SmFeN-based anisotropic magnetic powder obtained in Comparative Example 1 was gradually heated from room temperature in a nitrogen and air mixed gas atmosphere (oxygen concentration 4%, 5 L / min), and heat-treated at a maximum temperature of 170°C for 8 hours to obtain oxidized SmFeN-based anisotropic magnetic powder.

[0146] Comparative Example 5 [Oxidation process after phosphoric acid treatment] 15 g of the phosphate-coated SmFeN-based anisotropic magnetic powder obtained in Comparative Example 3 was gradually heated from room temperature in a nitrogen and air mixed gas atmosphere (oxygen concentration 4%, 5 L / min), and heat-treated at a maximum temperature of 150°C for 8 hours to obtain oxidized SmFeN-based anisotropic magnetic powder.

[0147] [Magnetic powder evaluation] (Coercive force (iHc)) The magnetic properties (intrinsic coercivity iHc) of the oxidized SmFeN-based anisotropic magnetic powders obtained in Examples 7 to 9 and Comparative Examples 4 and 5 were measured using a VSM (vibrating sample magnetometer). The results are shown in Table 2.

[0148] [Silica treatment process] The oxidized SmFeN-based anisotropic magnetic powders obtained in Examples 7 to 9 and Comparative Examples 4 and 5, ethyl silicate 40, and 12.5% ​​by weight of aqueous ammonia were mixed in a mixer in a weight ratio of 97.8:1.8:0.4, respectively. The mixture was heated in a vacuum at 200°C to obtain SmFeN-based anisotropic magnetic powders on which a thin silica film was formed on the particle surface.

[0149] Furthermore, the unoxidized SmFeN-based anisotropic magnetic powders obtained in Example 2 and Comparative Examples 1 and 3 were also treated under the same conditions to obtain SmFeN-based anisotropic magnetic powders with a silica thin film formed on the particle surface (these are designated as Example 10, Comparative Example 6, and Comparative Example 7, respectively).

[0150] [Silane coupling treatment process] SmFeN-based anisotropic magnetic powder with a silica thin film formed on it was mixed with 12.5% ​​by weight of aqueous ammonia in a mixer, and then mixed with 50% by weight of 3-aminopropyltriethoxysilane in ethanol solution in the mixer. The weight ratios of the SmFeN-based anisotropic magnetic powder with the silica thin film formed on it, 12.5% ​​by weight of aqueous ammonia, and 50% by weight of 3-aminopropyltriethoxysilane in ethanol solution were 99:0.2:0.8, respectively. The mixture was dried at 100°C under a nitrogen atmosphere for 10 hours to obtain silane-coupled SmFeN-based anisotropic magnetic powder.

[0151] [Mixing and molding process] A compound for bonded magnets was obtained by mixing silane-coupled SmFeN-based anisotropic magnetic powder, 12-nylon resin, and an antioxidant in a weight ratio of 91:8.5:0.5, and kneading the mixture in a twin-screw extruder. The kneading temperature at this time was 210°C.

[0152] [Molding process] The bonded magnet compound was heated to 240°C in the barrel of an injection molding machine. The molten bonded magnet compound was then injection molded into a mold maintained at 90°C while applying a magnetic field of 9 kOe, yielding a cylindrical bonded magnet molded product with a diameter (Φ) of 10 mm and a height (t) of 7 mm for water resistance evaluation.

[0153] [Magnet Evaluation Process] (Magnet iHc, iHc reduction rate) The bonded magnet molded articles obtained in Examples 7, 8, 9, and 10 and Comparative Examples 4, 5, 6, and 7 were placed in an air-core coil and magnetized with a magnetization magnetic field of 60 kOe. After magnetization, the magnetic properties (intrinsic coercivity iHc of the magnet after molding) were measured using a BH tracer. The iHc reduction rate during the magnetization process was calculated using the formula: (iHc of the magnetic powder after oxidation - iHc of the magnet after molding) ÷ iHc of the magnetic powder after oxidation × 100. For Examples 10 and Comparative Examples 6 and 7, the iHc reduction rate was calculated using the value of the magnetic powder iHc before oxidation instead of the iHc of the magnetic powder after oxidation. The results are shown in Table 2.

[0154] [Table 2]

[0155] Table 2 shows that the bonded magnets obtained in Examples 7, 8, 9, and 10 had higher coercivity than the bonded magnets obtained in Comparative Examples 4, 5, 6, and 7. Furthermore, the bonded magnets obtained in Examples 7, 8, and 9, which underwent oxidation treatment after phosphate coating, had even higher coercivity than those in Example 10. In Comparative Example 4, the magnetic powder was not pH adjusted during phosphate coating formation, so even after oxidation treatment, the improvement in coercivity of the bonded magnet was only slight compared to Comparative Example 6. Similarly, in Comparative Example 5, the improvement in coercivity of the bonded magnet was only slight compared to Comparative Example 7. From this, it was confirmed that the effect of oxidation treatment is significant for SmFeN-based magnetic powder treated with phosphate under predetermined conditions. [Industrial applicability]

[0156] According to the manufacturing method of the present invention, a phosphate-coated SmFeN-based anisotropic magnetic powder with excellent coercivity can be obtained. The obtained magnetic powder can be used as a sintered magnet or a bonded magnet.

Claims

1. A method for producing phosphate-coated SmFeN-based anisotropic magnetic powder, comprising a phosphoric acid treatment step to obtain SmFeN-based anisotropic magnetic powder coated with phosphate on its surface, by adding an inorganic acid as needed to a slurry containing SmFeN-based anisotropic magnetic powder, water, and an inorganic phosphoric acid compound to adjust the pH of the slurry to 1 or more and 4.5 or less.

2. A method for producing a phosphate-coated SmFeN-based anisotropic magnetic powder according to claim 1, wherein the phosphate content in the phosphate-coated SmFeN-based anisotropic magnetic powder is greater than 0.5% by mass.

3. A method for producing a phosphate-coated SmFeN-based anisotropic magnetic powder according to claim 1 or 2, wherein the phosphate coating present on the surface of the SmFeN-based anisotropic magnetic powder has a region in which the Sm atom concentration is higher than the Sm atom concentration in the SmFeN-based anisotropic magnetic powder.

4. A method for producing a phosphate-coated SmFeN-based anisotropic magnetic powder according to any one of claims 1 to 3, comprising performing the adjustment for 10 minutes or more in the phosphate treatment step.

5. A method for producing a phosphate-coated SmFeN-based anisotropic magnetic powder according to any one of claims 1 to 4, wherein the pH is adjusted to 1.6 or more and 3.9 or less in the phosphate treatment step.

6. A method for producing phosphate-coated SmFeN-based anisotropic magnetic powder according to any one of claims 1 to 5, comprising an oxidation step of heat-treating the phosphate-coated SmFeN-based anisotropic magnetic powder in an oxygen-containing atmosphere at 150°C to 250°C after a phosphoric acid treatment step.

7. A step of obtaining a phosphate-coated SmFeN-based anisotropic magnetic powder by a manufacturing method described in any one of Claims 1 to 6, A process to obtain an additive for bonded magnets by thermal curing a thermosetting resin and a curing agent having a ratio of the number of reactive groups to the number of reactive groups of the thermosetting resin of 2 or more and 11 or less, A kneading step to knead the aforementioned additive for bonded magnets, the aforementioned phosphate-coated SmFeN-based anisotropic magnetic powder, and a thermoplastic resin to obtain a bonded magnet compound in which the filling rate of magnetic powder in the bonded magnet compound is 91.5% by mass or more. A method for manufacturing a compound for bonded magnets that includes [the specified substance].

8. A step of obtaining a phosphate-coated SmFeN-based anisotropic magnetic powder by a manufacturing method described in any one of Claims 1 to 6, A process to obtain an additive for bonded magnets by thermal curing a thermosetting resin and a curing agent having a ratio of the number of reactive groups to the number of reactive groups of the thermosetting resin of 2 or more and 11 or less, The process involves kneading the aforementioned additive for bonded magnets with a thermoplastic resin to obtain a resin composition for bonded magnets. A kneading step to obtain a compound for bonded magnets by kneading the resin composition for bonded magnets and the phosphate-coated SmFeN-based anisotropic magnetic powder. A method for manufacturing a compound for bonded magnets that includes [the specified substance].

9. A method for manufacturing a compound for bonded magnets according to claim 7 or 8, wherein the thermoplastic resin is a nylon resin.

10. The method for producing a compound for bonded magnets according to any one of claims 7 to 9, wherein the magnetic powder has a monodisperse particle size distribution.

11. A step of obtaining a phosphate-coated SmFeN-based anisotropic magnetic powder by a manufacturing method described in any one of Claims 1 to 6, A process to obtain an additive for bonded magnets by thermal curing a thermosetting resin and a curing agent having a ratio of the number of reactive groups to the number of reactive groups of the thermosetting resin of 2 or more and 11 or less, A kneading step to knead the aforementioned additive for bonded magnets, the aforementioned phosphate-coated SmFeN-based anisotropic magnetic powder, and a thermoplastic resin to obtain a bonded magnet compound in which the filling rate of magnetic powder in the bonded magnet compound is 91.5% by mass or more, An injection molding process in which the resulting compound for bonded magnets is injection molded. A method for manufacturing bonded magnets containing [a specific material].

12. A step of obtaining a phosphate-coated SmFeN-based anisotropic magnetic powder by a manufacturing method described in any one of Claims 1 to 6, A process to obtain an additive for bonded magnets by thermal curing a thermosetting resin and a curing agent having a ratio of the number of reactive groups to the number of reactive groups of the thermosetting resin of 2 or more and 11 or less, The process involves kneading the aforementioned additive for bonded magnets with a thermoplastic resin to obtain a resin composition for bonded magnets. A kneading step to obtain a compound for bonded magnets by kneading the resin composition for bonded magnets and the phosphate-coated SmFeN-based anisotropic magnetic powder, An injection molding process in which the resulting compound for bonded magnets is injection molded. A method for manufacturing bonded magnets containing [a specific material].

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