Composition for bonded magnet, bonded magnet, rotor for water pump, and method for manufacturing bonded magnet

Abstract

To provide a composition for a bonded magnet capable of obtaining a bonded magnet having a good appearance even when molded at a relatively low temperature, and to provide a bonded magnet having a sufficient residual magnetic flux density (Br) and a good appearance.SOLUTION: The present invention relates to a composition for a bonded magnet containing rare earth magnetic powder, a polyarylene sulfide resin, and paramagnetic or diamagnetic inorganic particles containing at least one metal element selected from the group consisting of zinc, copper, and manganese, and a bonded magnet obtained from the composition for a bonded magnet.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a bonded magnet composition, a bonded magnet, a rotor for a water pump, and a method for manufacturing the bonded magnet. [Background technology]

[0002] Rare earth magnets such as Sm-Fe-N magnets have excellent magnetic properties, and in recent years their use has been investigated in a variety of applications, including automotive motors and actuators. For example, they are also used in motors used in water pumps and other motors used in aqueous environments. Patent Document 1 discloses a bonded magnet that contains phosphate-coated Sm-Fe-N anisotropic magnetic powder with a phosphate content of more than 0.5% by mass and polypropylene, and that retains at least 95% of its total flux after 1000 hours of immersion in hot water at 120°C. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2022 / 107462 Summary of the Invention [Problem to be solved by the invention]

[0004] Polyarylene sulfide resins (hereinafter referred to as PAS resins) such as polyphenylene sulfide resins (hereinafter referred to as PPS resins) have excellent heat resistance, so depending on the application, it may be desirable to use PAS resins as the resin material for bonded magnets. While rare earth magnets generally have good magnetic properties, they tend to be easily oxidized and deteriorated at high temperatures, so it is desirable to mold them into bonded magnets at relatively low temperatures. Sm-Fe-N magnets in particular tend to be easily thermally deteriorated. However, when PAS resins such as PPS resin are used, molding at low temperatures causes them to solidify quickly inside the mold due to their high melting point, making it difficult for a skin layer to appear on the surface of the molded product (bonded magnet), which can result in a poor appearance.In particular, from the perspective of achieving excellent magnetic properties, bonded magnets preferably contain a large amount of metal filler (magnetic powder) with high thermal conductivity compared to general resin products, which means that heat is easily dissipated inside the mold during injection molding and they tend to solidify quickly.

[0005] One embodiment of the present invention aims to provide a bonded magnet composition that can produce a bonded magnet with good appearance even when molded at a relatively low temperature. Another embodiment of the present invention aims to provide a bonded magnet that has sufficient remanence (Br) and good appearance, and a method for manufacturing the bonded magnet. A further embodiment of the present invention aims to provide a rotor for a high-performance water pump. [Means for solving the problem]

[0006] A bonded magnet composition according to one embodiment of the present invention comprises a rare earth magnetic powder, a polyarylene sulfide resin, and paramagnetic or diamagnetic inorganic particles containing at least one metal element selected from the group consisting of zinc, copper, and manganese.

[0007] Moreover, a bonded magnet according to another embodiment of the present invention is obtained from the above-mentioned composition for a bonded magnet.

[0008] Furthermore, a rotor for a water pump according to a further embodiment of the present invention includes the above-described bonded magnet.

[0009] Moreover, a method for producing a bonded magnet according to one embodiment of the present invention includes a step of injection molding the above-described bonded magnet composition. [Effects of the Invention]

[0010] According to one embodiment of the present invention, it is possible to provide a bonded magnet composition that can produce a bonded magnet with good appearance even when molded at a relatively low temperature. Also, according to another embodiment of the present invention, it is possible to provide a bonded magnet that has sufficient remanence (Br) and good appearance, and a method for manufacturing such a bonded magnet. Furthermore, according to one embodiment of the present invention, it is possible to provide a rotor for a high-performance water pump. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a photograph of the side of the bonded magnet molded product of Example 4, taken from the side opposite the gate. [Figure 2] FIG. 2 is a photograph of the side surface of the bonded magnet molded product of Comparative Example 1, opposite the gate portion. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described in detail. However, the embodiments described below are examples for embodying the technical concept of the present invention, and the present invention is not limited to the following. In this specification, the term "process" includes not only an independent process, but also a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved. Furthermore, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively.

[0013] <Composition for bonded magnets> A bonded magnet composition according to one embodiment of the present invention includes a rare earth magnetic powder, a polyarylene sulfide resin, and an additive (solidification retarder) that coordinates with the resin to delay solidification. The bonded magnet composition according to one embodiment of the present invention includes a rare earth magnetic powder, a polyarylene sulfide resin, and paramagnetic or diamagnetic inorganic particles containing at least one metal element selected from the group consisting of zinc, copper, and manganese. It is believed that these inorganic particles function as an additive (solidification retarder) that delays solidification by coordinating with the polyarylene sulfide resin. By adding paramagnetic or diamagnetic inorganic particles containing at least one metal element selected from the group consisting of zinc, copper, and manganese, or a solidification retarder to a bonded magnet composition containing a polyarylene sulfide resin as the resin material, it is possible to obtain a bonded magnet with a good appearance even when molded at a relatively low temperature. This also makes it possible to obtain a bonded magnet with sufficient remanence (Br) and a good appearance.

[0014] [Content of each ingredient] The content of rare earth magnetic powder in the bonded magnet composition is preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, more preferably 75% by mass or more, more preferably 80% by mass or more, and even more preferably 85% by mass or more, in order to obtain good magnetic properties. As the content of rare earth magnetic powder increases, the thermal conductivity of the composition increases, which accelerates solidification and tends to deteriorate the appearance of the molded product (bonded magnet). However, according to this embodiment, even if the content of rare earth magnetic powder is within the above range, a bonded magnet with good appearance can be obtained. Furthermore, in terms of fluidity during molding, the content of rare earth magnetic powder in the bonded magnet composition is usually preferably 95% by mass or less.

[0015] From the viewpoint of fluidity during molding, the content of polyarylene sulfide resin in the bonded magnet composition is usually preferably 3% by mass or more, more preferably 5% by mass or more. Also, the content of polyarylene sulfide resin in the bonded magnet composition is usually preferably 50% by mass or less, more preferably 40% by mass or less, more preferably 30% by mass or less, more preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less.

[0016] The content of paramagnetic or diamagnetic inorganic particles containing at least one metal element selected from the group consisting of zinc, copper, and manganese in the bonded magnet composition is preferably 0.01% by mass or more, more preferably 0.03% by mass or more, more preferably 0.05% by mass or more, more preferably 0.08% by mass or more, and more preferably 0.1% by mass or more. Furthermore, in terms of fluidity during molding and the magnetic properties of the resulting bonded magnet, the content of paramagnetic or diamagnetic inorganic particles containing at least one metal element selected from the group consisting of zinc, copper, and manganese in the bonded magnet composition is usually preferably 15% by mass or less, more preferably 11% by mass or less, more preferably 8% by mass or less, more preferably 5% by mass or less, and more preferably 3% by mass or less.

[0017] The content of the paramagnetic or diamagnetic inorganic particles containing at least one metal element selected from the group consisting of zinc, copper, and manganese per 100 parts by mass of polyarylene sulfide resin is usually preferably 0.02 parts by mass or more, more preferably 0.06 parts by mass or more, more preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, more preferably 0.6 parts by mass or more, more preferably 0.8 parts by mass or more, and more preferably 1 part by mass or more. Furthermore, the content of the paramagnetic or diamagnetic inorganic particles containing at least one metal element selected from the group consisting of zinc, copper, and manganese per 100 parts by mass of polyarylene sulfide resin is usually preferably 30 parts by mass or less, more preferably 26 parts by mass or less, more preferably 22 parts by mass or less, more preferably 18 parts by mass or less, more preferably 14 parts by mass or less, and more preferably 11 parts by mass or less.

[0018] [Polyarylene sulfide resin] Polyarylene sulfide resins are polymers containing one or more repeating units of a structure in which an aromatic ring (preferably a benzene ring) which may have a substituent is bonded to a sulfur atom, and are not particularly limited and can be selected appropriately depending on the physical properties required of the bonded magnet. Polyarylene sulfide resins may also contain one or more repeating units other than the repeating unit of a structure in which an aromatic ring which may have a substituent is bonded to a sulfur atom. Furthermore, polyarylene sulfide resins may be used alone or in combination of two or more. Examples of polyarylene sulfide resins include polyphenylene sulfide resins. Among polyphenylene sulfide resins, those containing the following structure in which the bond to the aromatic ring (benzene ring) of the repeating unit is at the para position are preferred in terms of heat resistance, etc. [ka]

[0019] In general, the polyarylene sulfide resin preferably has a weight-average molecular weight of 5,000 or more, more preferably 10,000 or more, from the viewpoint of strength of molded products, and preferably has a weight-average molecular weight of 50,000 or less, more preferably 30,000 or less, from the viewpoint of flowability during molding.

[0020] As the polyarylene sulfide resin, commercially available polyphenylene sulfide resins can also be used, such as TORELINA (Toray Industries, Inc.), DICPPS (DIC Corporation), TOYOBO PPS (Toyobo Co., Ltd.), and FORTRON (Polyplastics Co., Ltd.).

[0021] [Inorganic particles] The bonded magnet composition of this embodiment contains paramagnetic or diamagnetic inorganic particles (hereinafter simply referred to as "inorganic particles") containing at least one metal element selected from the group consisting of zinc, copper, and manganese. One type of inorganic particle may be used alone, or two or more types may be used in combination.

[0022] Zinc, copper, and manganese have standard electrode potentials (in other words, ionization tendencies) within an appropriate range, so that when the bonded magnet is molded, the metal element moieties present on the inorganic particle surfaces in the molten bonded magnet composition act as coordinate bonds with the unshared electron pairs of the sulfide groups (-S-) of the polyarylene sulfide resin, delaying solidification and making it possible to obtain a bonded magnet with a good appearance even when molded at a relatively low temperature. Furthermore, because zinc, copper, and manganese do not exhibit ferromagnetic properties between room temperature and the melting temperature of the bonded magnet composition, it is believed that their effects can be obtained without significantly affecting the magnetic properties of the rare earth magnet.

[0023] In terms of the magnetic properties of the resulting bonded magnet, inorganic particles containing at least one metal element selected from the group consisting of zinc, copper, and manganese are desirably paramagnetic or diamagnetic. Here, paramagnetic or diamagnetic inorganic particles containing at least one metal element selected from the group consisting of zinc, copper, and manganese refer to particles made of a substance that exhibits paramagnetism or diamagnetism at temperatures between room temperature and the melting temperature of the bonded magnet composition, for example. Paramagnetic or diamagnetic inorganic particles are those in which, when magnetic imaging of the cross section of a bonded magnet composition or bonded magnet is performed using a magnetic force microscope (MFM) or a Kerr effect microscope, no smallest region in which the magnetic moment characteristic of ferromagnetic materials is aligned in one direction, known as a magnetic domain, is observed within the inorganic particles when an external magnetic field is applied. Whether or not a particle is an inorganic particle containing at least one metal element selected from the group consisting of zinc, copper, and manganese can be confirmed using SEM-EDX or other methods. Examples of substances that exhibit paramagnetism or diamagnetism include, but are not limited to, zinc metal, copper metal, manganese metal, and alloys such as bronze and brass. Paramagnetic or diamagnetic inorganic particles containing at least one metal element selected from the group consisting of zinc, copper, and manganese may be used in a form supported on a carrier.Particles in a form in which the surface is coated with a paramagnetic or diamagnetic inorganic substance (preferably a simple metal) containing at least one metal element selected from the group consisting of zinc, copper, and manganese can also be used.

[0024] In this embodiment, the paramagnetic or diamagnetic inorganic particles containing at least one metal element selected from the group consisting of zinc, copper, and manganese preferably have at least one metal selected from the group consisting of zinc, copper, and manganese exposed on at least a portion of their surfaces. Therefore, it is preferable that the inorganic particles are not subjected to a treatment that coats their surfaces, for example, a surface treatment with a silane coupling agent or the like.

[0025] In this embodiment, the paramagnetic or diamagnetic inorganic particles containing at least one metal element selected from the group consisting of zinc, copper, and manganese preferably consist essentially of at least one metal (single metal or alloy) selected from the group consisting of zinc, copper, and manganese, more preferably consist essentially of zinc, copper, or a zinc-copper alloy, and even more preferably consist essentially of zinc. The total content of zinc, copper, and manganese in the inorganic particles is, for example, preferably 80% by mass or more, more preferably 90% by mass or more. Such particles (metal particles) essentially consisting of at least one metal selected from the group consisting of zinc, copper, and manganese may be particles whose main component is metal, and may, for example, have an oxide coating or the like on at least a portion of their surface.

[0026] The particle size D50 of paramagnetic or diamagnetic inorganic particles containing at least one metal element selected from the group consisting of zinc, copper, and manganese is typically preferably 100 μm or less. Furthermore, because the surface area per mass of the particles is large, a small amount of addition can provide a high effect, so 50 μm or less is more preferred, 20 μm or less is more preferred, and 10 μm or less is even more preferred. The lower limit of the particle size D50 of paramagnetic or diamagnetic inorganic particles containing at least one metal element selected from the group consisting of zinc, copper, and manganese is not particularly limited, but is typically about 0.01 μm. Here, D50 refers to the particle size at which the integrated value of the particle size distribution based on the particle volume is 50%. D50 can be measured under dry conditions using a laser diffraction particle size distribution analyzer.

[0027] The shape of the paramagnetic or diamagnetic inorganic particles containing at least one metal element selected from the group consisting of zinc, copper, and manganese is not particularly limited, and may be any shape, such as spherical, flat, plate-like, disk-like, conical, cylindrical, rectangular, polyhedral, needle-like, linear, fibrous, scale-like, or dendritic.

[0028] [Rare earth magnetic powder] Examples of rare earth magnetic powders include Sm-Co, Nd-Fe-B, and Sm-Fe-N magnetic powders. In the present embodiment, there are no particular limitations, and any rare earth magnetic powder can be suitably used. The rare earth magnetic powders may be used singly or in combination of two or more.

[0029] Sm-Co based magnetic powder can be produced by the method disclosed in JP-A-08-260083, Nd-Fe-B based magnetic powder can be produced by the HDDR method disclosed in WO 2003 / 85147, and Sm-Fe-N based magnetic powder can be produced by the method disclosed in JP-A-11-189811.

[0030] In one aspect of this embodiment, the rare earth magnetic powder is preferably a Sm-Fe-N based magnetic powder. 17 It has a crystal structure of the type Sm x Fe 100-x-y N y Examples include nitrides of the rare earth metal samarium (Sm), iron (Fe), and nitrogen (N), represented by the formula: where x is preferably 8.1 atomic % or more and 10 atomic % or less, y is preferably 13.5 atomic % or more and 13.9 atomic % or less, and the remainder is preferably Fe.

[0031] The rare earth magnetic powder can be used as is, or can be surface-treated with, for example, a silane coupling agent, etc. Surface treatment with a silane coupling agent, etc. can be performed by, for example, the method disclosed in JP 2017-43804 A. In addition, in the case of Sm-Fe-N based magnetic powder, it is also possible to use one having a phosphate coating on the surface, i.e., a phosphate-coated Sm-Fe-N based magnetic powder. Phosphate-coated Sm-Fe-N based magnetic powder can be produced by the methods disclosed in, for example, WO 2022 / 107462, JP 2023-96735 A, JP 2024-51932 A, etc.

[0032] The average particle size of the rare earth magnetic powder is usually preferably 0.1 μm or more and 250 μm or less. In the case of Sm-Co based magnetic powder, the average particle size is usually more preferably 10 μm or more and 250 μm or less. In the case of Nd-Fe-B based magnetic powder, the average particle size is usually more preferably 10 μm or more and 250 μm or less. For Sm-Fe-N magnetic powder, the average particle size is usually preferably 2 μm or more and 5 μm or less, and even more preferably 2.5 μm or more and 4.8 μm or less. By making the average particle size 2 μm or more, the filling amount of Sm-Fe-N magnetic powder in the bonded magnet can be increased, which may improve magnetization. Furthermore, by making the average particle size 5 μm or less, the intrinsic coercivity of the bonded magnet can be improved. Here, the average particle size is a particle size measured under dry conditions using a laser diffraction particle size distribution measuring device.

[0033] In the case of Sm-Fe-N magnetic powder, the particle size D50 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. The particle size D10 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. The particle size D90 is preferably 3 μm or more and 7 μm or less, and more preferably 4 μm or more and 6 μm or less. Here, D50 is the particle size at which the integrated value of the particle size distribution on a volume basis of the Sm-Fe-N magnetic powder corresponds to 50%. D10 is the particle size at which the integrated value of the particle size distribution on a volume basis of the Sm-Fe-N magnetic powder corresponds to 10%. D90 is the particle size at which the integrated value of the particle size distribution on a volume basis of the Sm-Fe-N magnetic powder corresponds to 90%.

[0034] Sm-Fe-N magnetic powder span defined as follows: Span = (D90-D10) / D50 From the viewpoint of the coercive force of the bonded magnet, is preferably 2 or less, and more preferably 1.5 or less.

[0035] The circularity of the Sm-Fe-N magnetic powder is not particularly limited, but is preferably 0.5 or more, and more preferably 0.6 or more. A circularity of less than 0.5 may result in poor flowability, resulting in stress between particles during compaction, which may result in reduced magnetic properties. Here, to measure circularity, SEM images taken at 3000x magnification are binarized using image processing, and the circularity is determined for each particle. The circularity defined in this invention refers to the average circularity determined by measuring approximately 1000 to 10000 particles. Generally, the smaller the particle size, the higher the circularity, so the circularity is measured for particles of 1 μm or more. The circularity is measured using the following formula: circularity = (4πS / L2), where S is the two-dimensional projected area of ​​the particle, and L is the two-dimensional projected perimeter.

[0036] [Sm-Fe-N magnetic powder] In one aspect of this embodiment, the Sm-Fe-N magnetic powder is preferably anisotropic in terms of the magnetic properties of the resulting bonded magnet. In addition, it may be preferable for the Sm-Fe-N magnetic powder to be surface-coated with phosphate in terms of improving coercivity and heat resistance.

[0037] Below, an example of a method for producing the Sm-Fe-N based anisotropic magnetic powder according to this embodiment and the phosphate-coated Sm-Fe-N based anisotropic magnetic powder will be described, but the powders are not limited to the following form and can also be produced by other production methods.

[0038] [Method for producing Sm-Fe-N anisotropic magnetic powder] The Sm-Fe-N anisotropic magnetic powder is not particularly limited, but may be, for example: a step of mixing a solution containing Sm and Fe with a precipitant to obtain a precipitate containing Sm and Fe (precipitation step); a step of calcining 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 process of nitriding the alloy particles obtained in the reduction process (nitriding process) It can be produced by a method comprising:

[0039] (precipitation process) In the precipitation process, Sm and Fe raw materials are dissolved in a strongly acidic solution to prepare a solution containing Sm and Fe. 17 When N3 is obtained as the main phase, the molar ratio of Sm to Fe (Sm:Fe) is preferably 1.5:17 to 3.0:17, and 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, and Lu may be added to the solution.

[0040] The Sm raw material and the Fe raw material are not limited as long as they can be dissolved in a strongly acidic solution. For example, in terms of ease of availability, samarium oxide can be used as the Sm raw material, and FeSO4 can be used as the Fe raw material. The concentration of the solution containing Sm and Fe can be adjusted appropriately within a range in which the Sm raw material and the Fe raw material are substantially soluble in the acidic solution. In terms of solubility, sulfuric acid can be used as the acidic solution.

[0041] An insoluble precipitate containing Sm and Fe is obtained by reacting a solution containing Sm and Fe with a precipitant. The solution containing Sm and Fe may be any solution containing Sm and Fe upon reaction with the precipitant. For example, raw materials containing Sm and Fe may be prepared as separate solutions, and each solution may be added dropwise to react with the precipitant. Even when prepared as separate solutions, the concentrations of each raw material are adjusted appropriately so that they are substantially soluble in the acidic solution. The precipitant may be any alkaline solution that can react with the solution containing Sm and Fe to produce a precipitate, including aqueous ammonia and caustic soda, with caustic soda being preferred.

[0042] The precipitation reaction is preferably carried out by dropping a solution containing Sm and Fe and a precipitant into 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, the pH during the reaction, and other factors, a precipitate with a uniform distribution of constituent elements, a sharp particle size distribution, and a regular powder shape can be obtained. Using such a precipitate improves the magnetic properties of the final product, the magnetic powder. The reaction temperature is preferably 0 to 50°C, more preferably 35 to 45°C. The concentration of the reaction solution is preferably 0.65 mol / L to 0.85 mol / L, more preferably 0.7 mol / L to 0.84 mol / L, in terms of the total concentration of metal ions. The reaction pH is preferably 5 to 9, more preferably 6.5 to 8.

[0043] The anisotropic magnetic powder particles obtained in the precipitation step largely determine the particle size, shape, and particle size distribution of the final magnetic powder. When the particle sizes of the obtained particles are measured using a laser diffraction wet particle size distribution analyzer, it is preferable that the size and distribution of the entire powder is approximately in 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 cumulative volume from the small particle size side in the particle size distribution, and is preferably in the range of 0.1 to 10 μm.

[0044] After separating the precipitate, it is preferable to remove the solvent from the separated material in order to prevent the precipitate from redissolving in the remaining solvent during the heat treatment in the subsequent oxidation step, which may result in aggregation of the precipitate when the solvent evaporates, or changes in particle size distribution, powder particle size, etc. Specific examples of the method for removing the solvent include drying in an oven at 70 to 200°C for 5 to 12 hours when water is used as the solvent.

[0045] After the precipitation step, a step of separating and washing the resulting precipitate may be included. The washing step is carried out until the conductivity of the supernatant solution is 5 mS / m 2The process is continued as appropriate until the following is achieved: In the step of separating the precipitate, for example, a solvent (preferably water) is added to the obtained precipitate and mixed, followed by filtration, decantation, or the like.

[0046] (oxidation process) The oxidation step is a step of obtaining an oxide containing Sm and Fe by calcining the precipitate formed in the precipitation step. For example, the precipitate can be converted into an oxide by heat treatment. When the precipitate is heat treated, it must be performed in the presence of oxygen, for example, in the air atmosphere. Furthermore, since it must be performed in the presence of oxygen, it is preferable that the non-metallic part of the precipitate contains oxygen atoms.

[0047] The heat treatment temperature in the oxidation step (hereinafter also referred to as the oxidation temperature) is not particularly limited, but is preferably 700 to 1300°C, and more preferably 900 to 1200°C. If the temperature is less than 700°C, oxidation may be insufficient, and if the temperature exceeds 1300°C, it tends to be difficult to obtain the desired shape, average particle size, and particle size distribution of the magnetic powder. The heat treatment time is also not particularly limited, but is preferably 1 to 3 hours.

[0048] The oxide particles obtained are oxide particles in which Sm and Fe are thoroughly mixed microscopically within the oxide particles, and the shape, particle size distribution, etc. of the precipitates are reflected.

[0049] (Pretreatment process) The pretreatment step is a step in which an oxide containing Sm and Fe is heat-treated in a reducing gas atmosphere to obtain a partial oxide in which part of the oxide is reduced.

[0050] Here, the term "partial oxide" refers to an oxide in which a portion of an oxide has been reduced. The oxygen concentration of the oxide is not particularly limited, but is preferably 10% by mass or less, and more preferably 8% by mass or less. If the oxygen concentration exceeds 10% by mass, the heat generated by reduction with Ca increases during the reduction process, and the firing temperature increases, which tends to result in particles that have undergone abnormal particle growth. Here, the oxygen concentration of the partial oxide can be measured by non-dispersive infrared absorption (ND-IR) spectroscopy.

[0051] The reducing gas is suitably selected from hydrocarbon gases such as hydrogen (H), carbon monoxide (CO), and methane (CH), but hydrogen gas is preferred from a cost perspective. The gas flow rate is suitably adjusted within a range that does not cause oxides to scatter. The heat treatment temperature in the pretreatment step (hereinafter also referred to as the pretreatment temperature) is preferably in the range of 300°C to 950°C, more preferably 400°C or higher, particularly preferably 750°C or higher, and more preferably less than 900°C. When the pretreatment temperature is 300°C or higher, the reduction of oxides containing Sm and Fe proceeds efficiently. Furthermore, when the pretreatment temperature is 950°C or lower, particle growth and segregation of oxide particles are suppressed, making it easy to maintain the desired particle size. 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 further adjust the dew point in the reactor to -10°C or less.

[0052] (Reduction process) The reduction step is a step of reducing the partial oxide by, for example, heat treating it in the presence of a reducing agent, preferably at a temperature of 920°C to 1200°C, to obtain alloy particles. For example, the reduction is carried out by contacting the partial oxide with calcium melt or calcium vapor. From the viewpoint of magnetic properties, the heat treatment temperature is preferably 950°C to 1150°C, more preferably 980°C to 1100°C. From the viewpoint of carrying out the reduction reaction more uniformly, the heat treatment time is preferably less than 120 minutes, more preferably less than 90 minutes, and the lower limit of the heat treatment time is preferably 10 minutes or more, more preferably 30 minutes or more.

[0053] Metallic calcium is used in the form of, for example, granules or powder, with the particle size preferably being 10 mm or less. This allows for more effective suppression of aggregation during the reduction reaction. 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, including the amount required to reduce Fe when it is in the form of oxide), and preferably 1.5 to 2.0 times.

[0054] In the reduction step, a disintegration accelerator can be used as needed together with metallic calcium as a reducing agent. This disintegration accelerator is used as appropriate to promote disintegration and granulation of the product during the water washing step described below, and examples thereof include alkaline earth metal salts such as calcium chloride and alkaline earth oxides such as calcium oxide. These disintegration accelerators are used in a proportion of 1 to 30% by mass, preferably 5 to 28% by mass, based on the Sm oxide used as the Sm source.

[0055] (nitriding process) The nitriding process is a process for obtaining Sm-Fe-N anisotropic magnetic powder by nitriding the alloy particles obtained in the reduction process. Since the particulate precipitate obtained in the precipitation process is used, porous, agglomerated alloy particles are obtained in the reduction process. This allows for immediate nitriding by heat treatment in a nitrogen atmosphere without pulverization, ensuring uniform nitriding.

[0056] The heat treatment temperature (hereinafter also referred to as nitriding temperature) for the nitriding of the alloy particles is preferably 300 to 600°C, particularly preferably 400 to 550°C, and is performed by replacing the atmosphere with a nitrogen atmosphere within this temperature range. The heat treatment time may be set to a time sufficient to ensure that the nitriding of the alloy particles is sufficiently uniform.

[0057] The product obtained after the nitriding step may contain, in addition to the magnetic particles (Sm-Fe-N anisotropic magnetic powder), by-product CaO, unreacted metallic calcium, etc., which may form a composite sintered mass. In this case, the product can be poured into cooling water, and the CaO and metallic calcium can be separated from the magnetic particles as a calcium hydroxide (Ca(OH)2) suspension. Furthermore, the remaining calcium hydroxide can be thoroughly removed by washing the magnetic particles with acetic acid or the like.

[0058] [Method for producing phosphate-coated Sm-Fe-N anisotropic magnetic powder] The phosphate-coated Sm-Fe-N anisotropic magnetic powder is not particularly limited, but examples thereof include: a phosphate treatment step in which an inorganic acid is added to a slurry containing Sm-Fe-N anisotropic magnetic powder, water, and a phosphate compound to adjust the pH of the slurry to preferably 1 or more and 4.5 or less, thereby obtaining an Sm-Fe-N anisotropic magnetic powder whose surface is coated with phosphate; and An oxidation step in which the phosphate-coated Sm-Fe-N anisotropic magnetic powder is heat-treated in an oxygen-containing atmosphere, preferably at 200°C or higher and 330°C or lower. It can be produced by a method comprising:

[0059] (Phosphating process) In the phosphate treatment step, an inorganic acid is added to a slurry containing Sm-Fe-N anisotropic magnetic powder, water, and a phosphate compound to adjust the pH of the slurry to preferably 1 or more and 4.5 or less, thereby obtaining an Sm-Fe-N anisotropic magnetic powder whose surface is coated with phosphate. The phosphate-coated Sm-Fe-N anisotropic magnetic powder is formed by a reaction between a metal component (e.g., iron or samarium) contained in the Sm-Fe-N anisotropic magnetic powder and a phosphate component contained in the phosphate compound, resulting in the precipitation of phosphate (e.g., iron phosphate or samarium phosphate) on the surface of the Sm-Fe-N anisotropic magnetic powder. By adding an inorganic acid to adjust the pH of the slurry to 1 or more and 4.5 or less, the amount of phosphate precipitated can be increased compared to when the inorganic acid is not added, and a phosphate-coated Sm-Fe-N anisotropic magnetic powder with a thicker coating tends to be obtained. Furthermore, by using water as the solvent, phosphates with smaller particle sizes tend to precipitate, and phosphate-coated Sm-Fe-N anisotropic magnetic powder with a dense coating tends to be obtained compared to when an organic solvent is used as the solvent.

[0060] The method for preparing a slurry containing Sm-Fe-N anisotropic magnetic powder, water, and a phosphate compound is not particularly limited. For example, the slurry can be prepared by mixing Sm-Fe-N anisotropic magnetic powder with an aqueous phosphoric acid solution containing a phosphate compound using water as a solvent. The content of the Sm-Fe-N anisotropic magnetic powder in the slurry is preferably 1% by mass to 50% by mass, and more preferably 5% by mass to 20% by mass from the viewpoint of productivity. The content of the phosphate component (PO4) in the slurry is preferably 0.01% by mass to 10% by mass, calculated as PO4, and more preferably 0.05% by mass to 5% by mass from the viewpoint of the reactivity of the phosphate component and productivity.

[0061] The phosphoric acid aqueous solution can be obtained by mixing a phosphoric acid compound with water. Examples of phosphoric acid compounds include inorganic phosphoric acids such as orthophosphoric acid, sodium dihydrogen phosphate, sodium monohydrogen phosphate, ammonium dihydrogen phosphate, ammonium monohydrogen phosphate, zinc phosphate, and calcium phosphate, as well as organic phosphoric acids such as hypophosphorous acid, hypophosphite, pyrophosphoric acid, and polyphosphoric acid. These compounds may be used alone or in combination of two or more. Furthermore, for the purpose of improving the water resistance and corrosion resistance of the coating and the magnetic properties of the magnetic powder, oxoacid salts such as molybdate, tungstate, vanadate, and chromate, oxidizing agents such as sodium nitrate and sodium nitrite, and chelating agents such as EDTA may also be added.

[0062] The phosphoric acid concentration (PO4 equivalent) in the phosphoric acid aqueous solution is preferably, for example, 5% by mass or more and 50% by mass or less, and more preferably 10% by mass or more and 30% by mass or less from the viewpoints of the solubility of the phosphoric acid compound, storage stability, and ease of chemical conversion treatment. The pH of the phosphoric acid aqueous solution is preferably, for example, 1 to 4.5 or less, and more preferably 1.5 to 4 or less from the viewpoint of easy control of the precipitation rate of the phosphate. The pH can be adjusted with dilute hydrochloric acid, dilute sulfuric acid, or the like.

[0063] In the phosphate treatment step, the pH of the slurry is adjusted by adding an inorganic acid, preferably to between 1 and 4.5, more preferably between 1.6 and 3.9, and even more preferably between 2 and 3. At a pH below 1, the phosphate-coated Sm-Fe-N anisotropic magnetic powder may aggregate from locally deposited large amounts of phosphate, resulting in a decrease in coercivity. At a pH above 4.5, the amount of phosphate deposited decreases, resulting in insufficient coating and a decrease in coercivity. Examples of inorganic acids to be added include hydrochloric acid, nitric acid, sulfuric acid, boric acid, and hydrofluoric acid. During the phosphate treatment step, inorganic acids are added as needed to maintain the pH within the above range. From the perspective of wastewater treatment, the use of inorganic acids is preferred, but organic acids can also be used in combination depending on the purpose. Examples of organic acids include acetic acid, formic acid, and tartaric acid. A mixture of inorganic and organic acids may also be used.

[0064] The phosphate content of the phosphate-coated Sm-Fe-N anisotropic magnetic powder obtained in the phosphate treatment step is preferably greater than 0.5% by mass, more preferably 0.55% by mass or more, and particularly preferably 0.75% by mass or more. The phosphate content of the phosphate-coated Sm-Fe-N anisotropic magnetic powder is preferably 4.5% by mass or less, more preferably 2.5% by mass or less, and particularly preferably 2% by mass or less. If the phosphate content is 0.5% by mass or less, the effect of the phosphate coating tends to be reduced. If the phosphate content exceeds 4.5% by mass, the phosphate-coated Sm-Fe-N anisotropic magnetic powder may aggregate, resulting in a decrease in coercivity. The phosphate content of the magnetic powder is expressed in terms of the PO4 molecule amount measured using inductively coupled plasma atomic emission spectroscopy (ICP-AES).

[0065] The pH of a slurry containing Sm-Fe-N anisotropic magnetic powder, water, and a phosphate compound is adjusted to a range of 1 to 4.5, preferably for 10 minutes or more, and more preferably for 30 minutes or more to reduce areas where the coating is thin. In the early stages of pH maintenance, the pH rises quickly, so the intervals between additions of inorganic acid for pH control are short, but as coating progresses, the pH fluctuations gradually slow down and the intervals between additions of inorganic acid become longer, allowing the reaction endpoint to be determined.

[0066] (Oxidation process after phosphoric acid treatment) In the oxidation step after the phosphate treatment, the phosphate-coated Sm-Fe-N anisotropic magnetic powder obtained in the phosphate treatment step is heat-treated in an oxygen-containing atmosphere, preferably at a temperature of 200°C or higher and 330°C or lower, thereby subjecting the phosphate-coated Sm-Fe-N anisotropic magnetic powder to oxidation. By heat-treating the phosphate-coated Sm-Fe-N anisotropic magnetic powder in an oxygen-containing atmosphere, preferably at a high temperature of 200°C or higher and 330°C or lower, the surface of the phosphate-coated Sm-Fe-N anisotropic magnetic powder base material is oxidized to form a thick iron oxide layer, which tends to improve the hot water resistance of the phosphate-coated Sm-Fe-N anisotropic magnetic powder.

[0067] The oxidation step after the phosphoric acid treatment is carried out by heat treating the phosphate-coated Sm-Fe-N anisotropic magnetic powder 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%, more preferably 3.5% to 10%. During the oxidation reaction, the gas is preferably exchanged at a flow rate of 2 L / min to 10 L / min per 1 kg of magnetic powder.

[0068] The heat treatment temperature in the oxidation step after the phosphate treatment is preferably 200°C or higher and 330°C or lower, more preferably 200°C or higher and 250°C or lower, and even more preferably 210°C or higher and 230°C or lower. If the temperature is lower than 200°C, the iron oxide layer may not be formed sufficiently, resulting in reduced hot water resistance. If the temperature exceeds 330°C, the iron oxide layer may be formed in excess, resulting in reduced coercivity. The heat treatment time is preferably 3 hours or higher and 10 hours or lower.

[0069] The oxidation step after the phosphoric acid treatment is preferably carried out so that the phosphate coating portion present on the surface of the Sm-Fe-N based anisotropic magnetic powder has a first region, the Sm atomic concentration of the first region is higher than the Sm atomic concentration in the Sm-Fe-N based anisotropic magnetic powder, and the Sm atomic concentration of the first region is 0.5 to 4 times the Fe atomic concentration of the first region. The Sm atomic concentration of the first region can be 1.02 times or more, preferably 1.05 times or more, more preferably 1.1 times or more, and even more preferably 1.2 times or more, of the Sm atomic concentration in the Sm-Fe-N based anisotropic magnetic powder. The Sm atomic concentration of the first region can be 3 times or less of the Sm atomic concentration in the Sm-Fe-N based anisotropic magnetic powder. The Sm atomic concentration of the first region is preferably 0.6 to 3.5 times, more preferably 0.7 to 3 times, of the Fe atomic concentration in the first region. The atomic concentrations (atm %) of the Sm-Fe-N based anisotropic magnetic powder and the first region are determined by averaging the atomic concentrations (atm %) in each region in STEM-EDX line analysis.

[0070] (Silica treatment process) The phosphoric acid-treated Sm-Fe-N anisotropic magnetic powder (i.e., phosphate-coated Sm-Fe-N anisotropic magnetic powder) may be silica-treated if necessary. Forming a thin silica film on the magnetic powder can improve oxidation resistance. The thin silica film can be formed, for example, by mixing alkyl silicate, phosphate-coated Sm-Fe-N anisotropic magnetic powder, and an alkaline solution.

[0071] (Silane coupling treatment process) The magnetic powder after silica treatment may be further treated with a silane coupling agent. By subjecting the magnetic powder on which a thin silica film has been formed to a silane coupling treatment, a coupling agent film is formed on the thin silica film, which improves the magnetic properties of the magnetic powder and may also improve wettability with resin and the strength of the magnet. The silane coupling agent may be selected depending on the type of resin, and is not particularly limited. Examples of the silane coupling agent 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 Mercaptopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, vinyltriacetoxysilane, γ-chloropropyltrimethoxysilane, hexamethylenedisilazane, γ-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, octadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, γ-chloropropylmethyldimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, vinyl Vinyltrichlorosilane, 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, oleopropyltriethoxysilane, γ-isocyanatopropyltriethoxysilane Examples of silane coupling agents include silane, polyethoxydimethylsiloxane, polyethoxymethylsiloxane, bis(trimethoxysilylpropyl)amine, bis(3-triethoxysilylpropyl)tetrasulfane, γ-isocyanatepropyltrimethoxysilane, 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 amount of silane coupling agent added is preferably 0.2 to 0.8 parts by weight, more preferably 0.25 to 0.6 parts by weight, per 100 parts by weight of magnetic powder. If the amount is less than 0.2 parts by weight, the effect of the silane coupling agent tends to be small, and if the amount is more than 0.8 parts by weight, the magnetic powder may aggregate, resulting in a decrease in the magnetic properties of the magnetic powder and magnet.

[0072] After the phosphoric acid treatment step, oxidation step, silica treatment, or silane coupling treatment, the Sm-Fe-N based anisotropic magnetic powder can be filtered, dehydrated, and dried by conventional methods.

[0073] [Other ingredients] In one aspect of this embodiment, the bonded magnet composition may further include a lubricant. Examples of lubricants include waxes such as paraffin wax, polyethylene wax, and polypropylene wax; fatty acids such as stearic acid and salts thereof; metal soaps, fatty acid amides, urea compounds, fatty acid esters, polyethers, polysiloxanes such as silicone oil and silicone grease; fluorine-based oils, fluorine-based greases, and fluororesin powders.

[0074] The lubricant is not particularly limited, but examples thereof include polyethylene wax and polypropylene wax. The polyethylene wax is not particularly limited, but examples thereof include branched low-density polyethylene wax, branched medium-density polyethylene wax, branched high-density polyethylene wax, linear low-density polyethylene wax, linear medium-density polyethylene wax, linear high-density polyethylene wax, and ultra-low-density polyethylene wax. The polypropylene wax is not particularly limited, but examples thereof include isotactic polypropylene, syndiotactic polypropylene, and atactic polypropylene. The polyethylene wax and polypropylene wax may be modified (modified polyethylene wax and modified polypropylene wax).

[0075] When a lubricant is included, the content of the lubricant in the bonded magnet composition is generally preferably 2% by mass or less, more preferably 1% by mass or less, and even more preferably 0.5% by mass or less.

[0076] The bonded magnet composition of this embodiment may further contain various additives such as antioxidants, heavy metal deactivators, nucleating agents, flame retardants, plasticizers, ultraviolet absorbers, antistatic agents, colorants, and release agents, as well as optional components such as thermoplastic resins other than polyarylene sulfide resins, thermosetting resins, and thermoplastic elastomers, if necessary.

[0077] Resins that can be added to the bonded magnet composition are not particularly limited, but examples include thermoplastic resins such as polyamide, polyester, polycarbonate, polystyrene, ABS, polyethylene, polypropylene, polyether ether ketone, liquid crystal polymer, polyethylene terephthalate, polybutylene terephthalate, polyphenylene ether, cycloolefin polymer, cycloolefin copolymer, etc. These thermoplastic resins can be added alone, or two or more thermoplastic resins can be combined and used as a polymer alloy.

[0078] <Method for producing a bonded magnet composition> The bonded magnet composition of this embodiment can be obtained, for example, by kneading rare earth magnetic powder, polyarylene sulfide resin, and paramagnetic or diamagnetic inorganic particles containing at least one metal element selected from the group consisting of zinc, copper, and manganese. If necessary, other optional components may also be added and kneaded to obtain the bonded magnet composition.

[0079] The kneading method and conditions are not particularly limited and can be appropriately selected with reference to known methods. For example, a mixture containing a rare earth magnetic powder, a polyarylene sulfide resin, and inorganic particles (which may also contain other optional components) is kneaded using a kneader such as a single-screw kneader or a twin-screw kneader, preferably at 280°C to 330°C. For example, the rare earth magnetic powder, the polyarylene sulfide resin powder, the inorganic particles, and optional components, if necessary, are mixed in a mixer, and then extruded into strands using a twin-screw extruder. The strands are air-cooled, and then cut into pieces several millimeters in size using a pelletizer, thereby obtaining a pellet-shaped bonded magnet composition.

[0080] <Bonded Magnets and Manufacturing Methods of Bonded Magnets> The bonded magnet according to one aspect of this embodiment is obtained from the composition for a bonded magnet described above. That is, the bonded magnet according to this embodiment is obtained from a composition for a bonded magnet that includes a rare earth magnetic powder, a polyarylene sulfide resin, and paramagnetic or diamagnetic inorganic particles containing at least one metal element selected from the group consisting of zinc, copper, and manganese.

[0081] The bonded magnet of this embodiment uses a rare earth magnet with good magnetic properties, and the resin material for the bonded magnet is a polyarylene sulfide resin with excellent heat resistance and water resistance, making it suitable for a variety of applications. For example, it can be used as a driving source for vehicle motors, such as fuel pumps, oil pumps, and water pumps in automobiles and motorcycles. The bonded magnet of this embodiment can also be used as a driving source for vehicle actuators and motors for home appliances such as air conditioner compressors.

[0082] An example of a method for manufacturing the bonded magnet according to this embodiment will be described below, but the method is not limited to the following embodiment and can also be manufactured by other manufacturing methods.

[0083] A bonded magnet can be manufactured by using a bonded magnet composition and an appropriate molding machine. The molding method is not particularly limited, and the bonded magnet of this embodiment can be manufactured by any known method such as injection molding or extrusion molding. The molding conditions are also not particularly limited, and can be set appropriately with reference to known methods.

[0084] A method for manufacturing a bonded magnet according to one aspect of this embodiment includes the step of injection molding a bonded magnet composition. For example, the bonded magnet composition is molten in the barrel of a molding machine and then injection molded into a mold to which a magnetic field is applied (injection molding step), the axis of easy magnetization is aligned (orientation step), and after cooling and solidifying, the composition is magnetized with an air-core coil or a magnetizing yoke (magnetization step), thereby obtaining a bonded magnet.

[0085] The barrel temperature during injection molding can be appropriately selected depending on the type of resin used and is preferably set to, for example, 280°C to 350°C.Similarly, the mold temperature is preferably set to, for example, 90°C to 150°C.The orienting magnetic field in the orienting step can be generated using an electromagnet or permanent magnet, and the strength of the magnetic field is usually preferably 4 kOe or more, more preferably 6 kOe or more.Furthermore, the strength of the magnetizing magnetic field in the magnetizing step is usually preferably 20 kOe or more, more preferably 30 kOe or more.

[0086] When a bonded magnet is produced from a bonded magnet composition by a method other than injection molding, the temperature settings of the molding machine and the magnitudes of the aligning magnetic field and magnetizing magnetic field can be set in the same manner as above.

[0087] <Water pump rotor> The rotor for a water pump of this embodiment includes the bonded magnet described above. The bonded magnet of this embodiment has good magnetic properties and is also excellent in heat resistance and water resistance, making it suitable for use in rotors for water pumps. A rotor for a water pump can be manufactured by providing an impeller and the like to a bonded magnet using a known method. [Example]

[0088] [Measurement and evaluation methods] The particle size D50 of the Zn powder used in the examples and comparative examples, the residual magnetic flux density (Br) of the bonded magnet molded products obtained in the examples and comparative examples, and the percentage of visually defective area were measured and evaluated as follows. (Zn powder particle size D50) The particle size D50 of the Zn powder was measured under dry conditions using a laser diffraction particle size distribution analyzer. Here, D50 is the particle size at which the integrated value of the particle size distribution based on the volume of the Zn powder corresponds to 50%.

[0089] (Residual magnetic flux density (Br) of bonded magnet molded products) The residual magnetic flux density Br(T) of the bonded magnet molded product was measured using a BH tracer.

[0090] (Percentage of defective areas in bonded magnet molded products) The proportion of the area with poor appearance was calculated using the following formula. (Percentage of visually defective area) = (area of ​​visually defective area) / (area of ​​molded product) x 100 (%) Here, the defective appearance refers to a portion of the molded product surface where the skin layer is not visible. The skin layer is a glossy surface layer that is formed when the molded product comes into contact with the mold cavity and is rapidly cooled during injection molding. The molded product area is the two-dimensional projected area on the side opposite the gate. The bonded magnet molded product produced is cylindrical with a diameter of 10 mm and a height of 7 mm, so the molded product area is 10 x 7 = 70 mm. 2 is. The area of ​​the visually defective part was determined by taking a photograph of the surface corresponding to the above-mentioned molded product area (the side opposite the gate) and binarizing it using image analysis software to extract areas that differ in appearance from the surrounding skin layer, and then calculating the area.

[0091] Example 1 (Manufacturing surface-treated SmFeN magnetic powder) The composition is Sm2Fe 17 SmFeN magnetic powder (average particle size 3 μm) as N3 was produced by a conventional method. [Phosphating process] The phosphate treatment solution was prepared by mixing 85% orthophosphoric acid, sodium dihydrogen phosphate, and sodium molybdate dihydrate in a weight ratio of 1:6:1, and adding pure water and dilute hydrochloric acid to adjust the pH to 2 and the PO4 concentration to 20% by mass. To a slurry made by mixing 1,000 g of SmFeN-based magnetic powder and 10,000 g of pure water, 70 g of 6 mass % diluted hydrochloric acid (equivalent to hydrogen chloride) was added, and the mixture was stirred for 1 minute to remove surface oxide films and contaminants. After that, the water was repeatedly drained and poured in, to obtain a slurry containing 10 mass % SmFeN-based magnetic powder. While stirring the resulting slurry, 100 g of the prepared phosphate treatment solution was poured into the treatment tank, and then 6 wt% hydrochloric acid was added from time to time to control the pH of the slurry within the range of 2.5±0.1. The slurry was stirred for 30 minutes, after which it was suction filtered and vacuum dried to obtain phosphate-coated SmFeN-based magnetic powder. [Oxidation treatment process] 1000 g of the obtained phosphate-coated SmFeN-based magnetic powder was gradually heated from room temperature in an atmosphere of a mixed gas of nitrogen and air (oxygen concentration 4 vol%, flow rate 5 L / min), and heat-treated at a maximum temperature of 230°C for 8 hours to obtain an oxidized phosphate-coated SmFeN-based magnetic powder. [Silica treatment process] The oxidized phosphate-coated SmFeN magnetic powder, ethyl silicate 40, and 12.5 wt% ammonia water were mixed in a weight ratio of 97.8:1.8:0.4. The resulting mixture was heated in a vacuum at 200°C for 5 hours to obtain SmFeN magnetic powder with a thin silica film formed on the particle surfaces. [Silane coupling treatment] The SmFeN magnetic powder with a thin silica film formed on the particle surface was mixed with 12.5 wt% ammonia water and a 50 wt% ethanol solution of 3-aminopropyltriethoxysilane in a weight ratio of 99:0.2:0.8. The resulting mixture was dried at 100°C for 10 hours under a nitrogen atmosphere to obtain a silane-coupling-treated SmFeN magnetic powder.

[0092] (Manufacturing bonded magnet molded products) [Mixing process] Silane-coupling-treated SmFeN magnetic powder, commercially available polyphenylene sulfide resin (H-1G manufactured by DIC Corporation), and spherical Zn powder with a particle size D50 of 4.07 μm were mixed in a mass ratio of 87.0:12.9:0.1 and kneaded in a twin-screw extruder to obtain a bonded magnet composition. The kneading temperature was 295°C. [Molding process] This bonded magnet composition was heated to 310°C in the barrel of an injection molding machine, and the molten composition was injection molded into a mold whose temperature was controlled at 150°C while applying a magnetic field of 9 kOe, resulting in a cylindrical bonded magnet molded product with a diameter of 10 mm and a height of 7 mm. The Br and the percentage of the area with visual defects of the obtained bonded magnet molded products were measured and evaluated, and the results are shown in Table 1.

[0093] <Example 2> A cylindrical bonded magnet molded product was obtained in the same manner as in Example 1, except that silane coupling-treated SmFeN magnetic powder, polyphenylene sulfide resin, and spherical Zn powder with a particle size D50 of 4.07 μm were mixed in a mass ratio of 87.0:12.8:0.2. The Br and the percentage of the area with visual defects of the obtained bonded magnet molded products were measured and evaluated, and the results are shown in Table 1.

[0094] Example 3 A cylindrical bonded magnet molded product was obtained in the same manner as in Example 1, except that silane coupling-treated SmFeN magnetic powder, polyphenylene sulfide resin, and spherical Zn powder with a particle size D50 of 4.07 μm were mixed in a mass ratio of 87.0:12.7:0.3. The Br and the percentage of the area with visual defects of the obtained bonded magnet molded products were measured and evaluated, and the results are shown in Table 1.

[0095] Example 4 A cylindrical bonded magnet molded product was obtained in the same manner as in Example 1, except that silane coupling-treated SmFeN magnetic powder, polyphenylene sulfide resin, and spherical Zn powder with a particle size D50 of 4.07 μm were mixed in a mass ratio of 87.0:12.6:0.4. The results of measuring and evaluating the Br and the percentage of the visually defective area of ​​the obtained bonded magnet molded product are shown in Table 1. Also, Fig. 1 shows a photograph of the side surface opposite the gate of the bonded magnet molded product of Example 4, taken to determine the percentage of the visually defective area.

[0096] <Example 5> A cylindrical bonded magnet molded product was obtained in the same manner as in Example 1, except that silane coupling-treated SmFeN magnetic powder, polyphenylene sulfide resin, and spherical Zn powder with a particle size D50 of 4.07 μm were mixed in a weight ratio of 87.2:11.9:0.9. The Br and the percentage of the area with visual defects of the obtained bonded magnet molded products were measured and evaluated, and the results are shown in Table 1.

[0097] Example 6 A cylindrical bonded magnet molded product was obtained in the same manner as in Example 4, except that spherical Zn powder having a particle size D50 of 4.49 μm was used instead of the spherical Zn powder having a particle size D50 of 4.07 μm. The Br and the percentage of the area with visual defects of the obtained bonded magnet molded products were measured and evaluated, and the results are shown in Table 1.

[0098] Example 7 A cylindrical bonded magnet molded product was obtained in the same manner as in Example 4, except that flat Zn powder with a particle size D50 of 6.29 μm was used instead of the spherical Zn powder with a particle size D50 of 4.07 μm. The Br and the percentage of the area with visual defects of the obtained bonded magnet molded products were measured and evaluated, and the results are shown in Table 1.

[0099] <Comparative Example 1> A cylindrical bonded magnet molded product was obtained in the same manner as in Example 1, except that no Zn powder was used and a bonded magnet compound was obtained by mixing and kneading silane-coupling-treated SmFeN magnetic powder and polyphenylene sulfide resin in a weight ratio of 86.9:13.1. The results of measuring and evaluating the Br and the percentage of the visually defective area of ​​the obtained bonded magnet molded product are shown in Table 1. Also, Fig. 2 shows a photograph of the side surface opposite the gate of the bonded magnet molded product of Comparative Example 1, taken to determine the percentage of the visually defective area.

[0100] [Table 1]

[0101] Embodiments of the present disclosure may include, for example, the following aspects. [Section 1] Rare earth magnetic powder; a polyarylene sulfide resin; Paramagnetic or diamagnetic inorganic particles containing at least one metal element selected from the group consisting of zinc, copper, and manganese; A composition for a bonded magnet comprising: [Section 2] Item 2. A bonded magnet composition according to item 1, wherein the content of the rare earth magnetic powder is 50% by mass or more. [Section 3] 3. A bonded magnet composition according to item 1 or 2, wherein the content of the inorganic particles is 0.01% by mass or more and 15% by mass or less. [Section 4] 4. The composition for a bonded magnet according to any one of items 1 to 3, wherein the content of the inorganic particles is 0.02 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the polyarylene sulfide resin. [Section 5] 5. A composition for a bonded magnet according to any one of items 1 to 4, wherein the inorganic particles have a particle size D50 of 100 μm or less. [Section 6] 6. A composition for a bonded magnet according to any one of items 1 to 5, wherein the inorganic particles are essentially made of at least one metal selected from the group consisting of zinc, copper, and manganese. [Section 7] 7. A bonded magnet composition according to any one of items 1 to 6, wherein the rare earth magnetic powder is a Sm-Fe-N based magnetic powder. [Section 8] 8. A bonded magnet obtained from the composition for a bonded magnet according to any one of items 1 to 7. [Section 9] Item 9. A rotor for a water pump including the bonded magnet according to item 8. [Section 10] 8. A method for producing a bonded magnet, comprising the step of injection molding the bonded magnet composition according to any one of items 1 to 7.

Claims

1. Rare earth magnetic powder; a polyarylene sulfide resin; Paramagnetic or diamagnetic inorganic particles containing at least one metal element selected from the group consisting of zinc, copper, and manganese; A composition for a bonded magnet comprising:

2. 2. The bonded magnet composition according to claim 1, wherein the content of said rare earth magnetic powder is 50% by mass or more.

3. 2. The bonded magnet composition according to claim 1, wherein the content of said inorganic particles is 0.01% by mass or more and 15% by mass or less.

4. 2. The bonded magnet composition according to claim 1, wherein the content of said inorganic particles is 0.02 parts by mass or more and 30 parts by mass or less per 100 parts by mass of said polyarylene sulfide resin.

5. 2. The bonded magnet composition according to claim 1, wherein the inorganic particles have a particle size D50 of 100 μm or less.

6. 2. The bonded magnet composition according to claim 1, wherein said inorganic particles consist essentially of at least one metal selected from the group consisting of zinc, copper, and manganese.

7. 2. The bonded magnet composition according to claim 1, wherein the rare earth magnetic powder is a Sm--Fe--N magnetic powder.

8. A bonded magnet obtained from the bonded magnet composition according to any one of claims 1 to 7.

9. A rotor for a water pump comprising the bonded magnet according to claim 8.

10. A method for producing a bonded magnet, comprising the step of injection molding the bonded magnet composition according to any one of claims 1 to 7.

Images