Bonded magnet manufacturing method and bonded magnet

Abstract

To provide a method for manufacturing a bonded magnet that can produce a flat bonded magnet with a high magnetic powder filling rate, and a flat bonded magnet with a high magnetic powder filling rate.SOLUTION: A method for manufacturing a bonded magnet includes a molding step of compression-molding a magnetic powder mixture, which is a mixture of magnetic powder and a first thermosetting composition, to form a flat molded body, and a magnetic field orientation step, which is carried out during the molding step, to magnetically orient the magnetic powder, and the molded body has a thickness of 1 mm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a bonded magnet and to a bonded magnet. [Background technology]

[0002] Magnets include cast magnets, which have been used for a long time, sintered magnets made by sintering magnetic powder, and bonded magnets made by molding magnetic powder with a resin binder.

[0003] Patent Document 1 discloses a method for manufacturing a bonded magnet and the bonded magnet itself. This bonded magnet manufacturing method includes a first compression step in which magnetic powder with an average particle size of 10 μm or less is compressed while magnetically oriented to obtain a first compact; a second compression step in which the first compact is contacted with a thermosetting resin with a viscosity of 200 mPa·s or less and then compressed to obtain a second compact; and a heat treatment step in which the second compact is heat-treated. It is said that bonded magnets manufactured using this bonded magnet manufacturing method have improved magnetic properties due to the high filling rate and orientation rate of the magnetic powder. Patent Document 1 also discloses an example of molding a bonded magnet estimated to be several millimeters thick.

[0004] Patent Document 2 discloses a method for manufacturing a magnetic green body and a method for manufacturing an anisotropic bonded magnet. This method for manufacturing a magnetic green body includes a supplying step of supplying a compound containing magnetic powder, a thermosetting resin, and wax into a mold; a molding step of compressing the compound in the mold heated to a molding temperature Tm while applying a magnetic field to the compound in the mold to form a green body from the compound and removing the wax from the green body; a demagnetizing step of demagnetizing the green body after the molding step; and a thermosetting step of heating the green body at a temperature equal to or higher than the thermosetting temperature of the thermosetting resin to obtain a magnetic green body. In this method for manufacturing a magnetic green body, the magnetic powder includes an Sm-Fe-N permanent magnet, and the molding temperature Tm is equal to or higher than the dropping point of the wax but lower than the thermosetting temperature of the thermosetting resin. This method for manufacturing an anisotropic bonded magnet further includes a magnetizing step of magnetizing the magnetic green body to obtain an anisotropic bonded magnet. In this method for manufacturing a magnetic compact and anisotropic bonded magnet, the molding temperature Tm is above the wax dropping point, so the wax in the compound is liquefied during the molding process. The lubricating properties of this liquefied wax make it easier for the magnetic particles to slide against each other, facilitating the rotation of each magnetic particle magnetized by the magnetic field, which aligns the easy axis of magnetization of the magnetic domains in each magnetic particle along the magnetic field. Therefore, the bonded magnet manufactured by this manufacturing method is said to have excellent residual magnetic flux density and mechanical strength. Patent Document 2 also discloses an example of molding a bonded magnet estimated to be several millimeters thick.

[0005] Patent Document 3 discloses a compound for rare earth bonded magnets, a rare earth bonded magnet, and methods for manufacturing them. Patent Document 3 discloses that bonded magnets obtained by molding a compound containing magnetic powder and a resin binder into a predetermined shape can easily be produced in complex or thin shapes. Patent Document 3 also discloses that the use of vulcanized rubber (thermosetting resin) requires complex processes for manufacturing sheet-shaped bonded magnets, resulting in problems such as increased costs and reduced throughput, and that the use of vulcanized rubber reduces flexibility.

[0006] Patent Document 4 discloses a thermoplastic elastomer composition that can be highly filled with magnetic powder. Patent Document 4 also discloses that magnetic force, which is the most important characteristic of a rubber magnet, is roughly proportional to the amount of magnetic powder mixed in, so in order to increase the magnetic force, it is necessary to mix more magnetic powder, but that if the amount of magnetic powder mixed in is increased, problems arise such as a decrease in processability due to an increase in the viscosity of the rubber compound and an increase in the hardness of the molded product, as well as a loss of flexibility, which is one of the advantages of rubber magnets. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2020-109840 [Patent Document 2] Patent No. 7298804 [Patent Document 3] Japanese Patent Application Laid-Open No. 2006-135201 [Patent Document 4] Japanese Patent Application Laid-Open No. 2007-16057 Summary of the Invention [Problem to be solved by the invention]

[0008] For example, motors for electric vehicles (EVs) require precise magnetic control. For example, precise magnetic control can be achieved by devising the shape of the magnet inside the motor. In such cases, it may be necessary to mold the magnet into a complex shape or control its magnetic properties to achieve precise magnetic control. However, molding sintered magnets into complex shapes is generally not easy.

[0009] For example, as disclosed in Patent Documents 3 and 4, it is possible to create bonded magnets that are easy to shape. However, bonded magnets generally have inferior magnetic properties to cast magnets and sintered magnets. If one were to try to improve the magnetic properties of a bonded magnet, as disclosed in Patent Document 4, it would be necessary to increase the amount of magnetic powder mixed in, which would make it difficult to take advantage of the shape-processability that is one of the advantages of bonded magnets.

[0010] For example, the bonded magnet manufacturing methods and bonded magnets disclosed in Patent Documents 1 and 2 are said to produce bonded magnets with high filling rates and good magnetic properties, but it is thought that the bonded magnet's characteristic of good shape processability is difficult to utilize. Also, as disclosed in Patent Document 3, the use of thermosetting resins poses the problem of reduced flexibility of bonded magnets, and because the bonded magnets disclosed in Patent Documents 1 and 2 use thermosetting resins, it is thought that the bonded magnets disclosed in Patent Documents 1 and 2 also have difficulty utilizing their characteristic of good shape processability from this perspective as well.

[0011] As described above, it has been difficult to achieve both freedom of shape, such as moldability and shaping processability, and improved magnetic properties in magnets.

[0012] Another idea for providing a magnet that combines ease of shape processability and magnetic properties is to consider a magnet manufacturing method in which thin, flat, bonded magnets with a high magnetic powder filling rate are used as units and these are stacked to form magnets of any shape. Furthermore, in addition to the use of forming magnets of any shape, another method of manufacturing a magnet can be considered in which thin, flat, bonded magnets are used as units and these are stacked or arranged to form magnets with any magnetic properties.

[0013] However, for example, Patent Documents 1 and 2 only disclose bonded magnets that are several millimeters or thicker. Therefore, it is desirable to provide a flat bonded magnet with a high magnetic powder filling rate that is suitable for build-up magnet manufacturing methods, in which magnets of any shape and magnetic properties are constructed by lamination and arrangement.

[0014] The present disclosure has been made in consideration of such circumstances, and its purpose is to provide a method for manufacturing a bonded magnet that has a high magnetic powder filling rate and can produce a flat-shaped bonded magnet, and to provide a flat-shaped bonded magnet that has a high magnetic powder filling rate. [Means for solving the problem]

[0015] In order to achieve the above object, the bonded magnet manufacturing method and bonded magnet according to the present disclosure are as follows.

[0016] [1] A molding step of compressing and molding a magnetic powder mixture, which is a mixture of magnetic powder and a first thermosetting composition, to form a flat-plate-shaped molded body; a magnetic field orientation step that is carried out during the molding step and magnetically orients the magnetic powder, A method for producing a bonded magnet, wherein the molded body has a thickness of 1 mm or less.

[0017] The above manufacturing method allows for the production of flat bonded magnets with a high magnetic powder filling rate. Such bonded magnets are suitable for build-up magnet manufacturing methods, in which magnets of any shape and magnetic properties can be constructed by laminating or arranging the magnets.

[0018] [2] The method further comprises an impregnation step of impregnating the molded body with a second thermosetting composition, The method for producing a bonded magnet according to [1] above, wherein the second thermosetting composition has a viscosity of 200 mPa·s or less.

[0019] According to the above manufacturing method, it may be possible to increase the mechanical strength of the bonded magnet.

[0020] [3] The method for producing a bonded magnet according to [2] above, wherein the second thermosetting composition is a norbornene-based monomer.

[0021] According to the above manufacturing method, it may be possible to further increase the mechanical strength of the bonded magnet.

[0022] [4] The method for producing a bonded magnet according to [3] above, wherein the first thermosetting composition is the same as the second thermosetting composition.

[0023] The above manufacturing method may provide a bonded magnet that is less prone to defects such as cracks.

[0024] [5] A method for producing a bonded magnet according to any one of [1] to [4] above, wherein in the magnetic field orientation step, a magnetic field is applied in a direction perpendicular to the surface of the magnetic powder mixture during the molding process.

[0025] According to the above manufacturing method, a bonded magnet can be obtained that is suitable for manufacturing magnets that are laminated to form magnets of any shape.

[0026] [6] A flat-plate-shaped molded body including magnetic powder and a first thermosetting resin, The molded body is A powder compact having a thickness of 1 mm or less, The filling rate of the magnetic powder is 65% by volume or more, The magnetic powder is a bonded magnet that is magnetically oriented.

[0027] This bonded magnet is suitable for a build-up magnet manufacturing method, in which magnets of any shape and magnetic properties are constructed by laminating and arranging.

[0028] [7] The bonded magnet according to [6] above, wherein the molded body further contains a second thermosetting resin.

[0029] The bonded magnet has higher mechanical strength.

[0030] [8] The bonded magnet according to [7] above, wherein the second thermosetting resin is a norbornene-based resin.

[0031] The bonded magnet has higher mechanical strength.

[0032] [9] The bonded magnet according to [8] above, wherein the first thermosetting resin is the same as the second thermosetting resin.

[0033] The bonded magnet is less likely to develop defects such as cracks.

[0034]

[10] The bonded magnet according to any one of [6] to [9] above, wherein the magnetization direction is perpendicular to the surface.

[0035] The bonded magnet is suitable for the manufacturing method of a magnet in which magnets of any shape are formed by laminating them. [Brief explanation of the drawings]

[0036] [Figure 1] FIG. 1 is a perspective view showing a schematic configuration of a bonded magnet according to an embodiment of the present invention. [Figure 2] FIG. [Figure 3] FIG. 2 is an explanatory diagram of a magnetic hysteresis curve. DETAILED DESCRIPTION OF THE INVENTION

[0037] A bonded magnet manufacturing method and a bonded magnet according to an embodiment of the present disclosure will be described with reference to the drawings. First, an overview of the bonded magnet manufacturing method and the bonded magnet according to an embodiment of the present disclosure will be described.

[0038] The method for producing a bonded magnet according to this embodiment includes a molding step in which a magnetic powder mixture, which is a mixture of magnetic powder and a first thermosetting composition, is compression-molded to form a plate-shaped compact, and a magnetic field orientation step, which is carried out during the molding step, to magnetically orient the magnetic powder. The compact has a thickness of 1 mm or less.

[0039] According to the manufacturing method of the bonded magnet of this embodiment, it is possible to realize a bonded magnet that includes a flat molded body containing magnetic powder and a first thermosetting resin, where the molded body is a pressed powder body having a thickness of 1 mm or less, where the filling rate of the magnetic powder is 65 volume % or more, and where the magnetic powder is magnetically oriented, i.e., the bonded magnet of this embodiment.

[0040] The bonded magnet according to this embodiment is suitable for a build-up magnet manufacturing method in which a magnet with any shape or magnetic properties can be constructed by laminating or arranging.

[0041] The bonded magnet according to this embodiment comprises a flat-plate-shaped compact containing magnetic powder and a first thermosetting resin. This compact is a green compact with a thickness of 1 mm or less, and the magnetic powder filling rate is 65% by volume or more. In this bonded magnet, the magnetic powder is magnetically oriented.

[0042] The bonded magnet and the manufacturing method of the bonded magnet according to this embodiment will be described in detail below.

[0043] 1 shows an example of a bonded magnet 100 according to this embodiment. Bonded magnet 100 comprises a flat plate-shaped compact 1 containing magnetic powder and a first thermosetting resin.

[0044] The molded body 1 is a flat-plate-shaped green compact obtained by compression molding a magnetic powder mixture, which is a mixture containing at least a magnetic powder and a first thermosetting composition, and then curing the first thermosetting composition to form a first thermosetting resin. By including the first thermosetting resin in the molded body 1, the molded body 1 is less likely to crack and has a strength sufficient to allow it to be formed into a thin, flat plate.

[0045] The molded body 1 may further contain a second thermosetting resin in addition to the magnetic powder and the first thermosetting resin. In this case, the molded body 1 is a flat, green compact obtained by compression-molding a magnetic powder mixture containing the magnetic powder, the first thermosetting composition, and the second thermosetting composition, and then curing the first thermosetting composition and the second curable composition to form the first thermosetting resin and the first thermosetting resin. In this embodiment, "thermosetting" refers to the property of being hardened by heating more than before heating. Hereinafter, the hardening of a thermosetting composition by heating more than before heating may be simply referred to as "thermosetting." In this embodiment, the first thermosetting resin is the first thermosetting composition that is thermoset. Similarly, the second thermosetting resin is the second thermosetting composition that is thermoset. Details of the magnetic powder, the first thermosetting composition, the first thermosetting resin, the second thermosetting composition, and the second thermosetting resin will be described later.

[0046] Compacted body 1 has a flat plate thickness d of 1 mm or less, preferably 500 μm or less. With compacted body 1 having such a thickness d, bonded magnet 100 is suitable for a build-up magnet manufacturing method (hereinafter simply referred to as the build-up method) in which magnets of unit structures such as flat plates are stacked or arranged to form magnets of any shape or magnetic properties.

[0047] Compact 1 has a magnetic powder filling rate of 65% by volume or more. This gives bonded magnet 100 a high residual magnetic flux density, i.e., a magnet with strong magnetic force. Furthermore, bonded magnet 100 is suitable for the build-up method.

[0048] Furthermore, compact 1 is magnetically oriented. This results in bonded magnet 100 having a high residual magnetic flux density, i.e., a magnet with strong magnetic force. Furthermore, bonded magnet 100 is suitable for the build-up method. The method of magnetically oriented compact 1 will be described later.

[0049] As described above, the method for producing a bonded magnet according to this embodiment includes a molding step of compression-molding a magnetic powder mixture, which is a mixture of magnetic powder and a first thermosetting composition, to form a flat-plate-shaped compact, and a magnetic field orientation step carried out during the molding step to magnetically align the magnetic powder, as well as an impregnation step of impregnating the compact with a second thermosetting composition and a curing step of curing the first thermosetting composition and the second thermosetting composition. Furthermore, the bonded magnet produced by this method for producing a bonded magnet according to this embodiment may be further magnetized, if necessary, apart from the magnetic field orientation.

[0050] The magnetic powder mixture may contain additives other than the magnetic powder and the first thermosetting composition. For example, the magnetic powder mixture may contain a surface treatment agent for the magnetic powder. For example, the surface treatment agent may be mixed with the magnetic powder in advance. In other words, the magnetic powder mixture may contain magnetic powder that has been surface-treated in advance with a surface treatment agent.

[0051] The magnetic powder mixture may be one in which the first thermosetting composition is dispersed to an extent that it covers the entire particle surface of the magnetic powder. The magnetic powder mixture may be one in which the first thermosetting composition is mixed with or impregnated (penetrated) into the magnetic powder. The first thermosetting composition may be dispersed into the magnetic powder by, for example, manual mixing using a mortar and pestle or mixing using a stirring device, or by a dispersion method in which the first thermosetting composition is made into a liquid with low viscosity and then impregnated (penetrated) into the magnetic powder.

[0052] The viscosity of the first thermosetting composition is preferably 200 mPa·s or less, more preferably 100 mPa·s or less, more preferably 50 mPa·s or less, even more preferably 15 mPa·s or less, and most preferably 10 mPa·s or less. When the viscosity of the first thermosetting composition is 200 mPa·s or less, the first thermosetting composition is dispersed more uniformly in the magnetic powder.

[0053] When the viscosity of the first thermosetting composition is 200 mPa·s or less, it can be sufficiently dispersed by impregnation.

[0054] Furthermore, if the viscosity of the first thermosetting composition is 200 mPa·s or less, the particles in the magnetic powder become more mobile in the magnetic field orientation step described below, and magnetic field orientation becomes easier.

[0055] The molding step is a step of compression-molding a magnetic powder mixture to obtain a green body. The molding step can be realized, for example, by a die unit 4 shown in FIG. 2. FIG. 2 is a schematic cross-sectional view (explanatory diagram) illustrating the structure of the die unit 4. In the die unit 4, a magnetic powder mixture 2 can be compression-molded to produce a green compact that becomes the green body 1 (see FIG. 1).

[0056] The die unit 4 includes, for example, a cylindrical molding die 41, a cylindrical lower punch 42 (lower punch), and a cylindrical upper punch 44 (upper punch). The die unit 4 may be formed of, for example, iron or an iron alloy. The die unit 4 is preferably formed of a non-magnetic material. The space inside the cylinder of the molding die 41 is a space (cavity) into which the magnetic powder mixture 2 is filled and molded. In the die unit 4, the magnetic powder mixture 2 charged in the cavity is compressed by the lower punch 42 and the upper punch 44 to mold a green compact (green body 1).

[0057] There are no particular restrictions on the magnitude of the molding pressure in the molding step (the pressure applied by the upper punch 44 and the lower punch 42 to compress the magnetic powder mixture 2). In order to manufacture a bonded magnet 100 (see FIG. 1) with a sufficiently high magnetic powder filling rate, the molding pressure should be 1 t / cm 2 More than 11t / cm 2 Less than 1t / cm 2 More than 5t / cm 2 More preferably, 2 t / cm or less 2 More than 5t / cm 2or less. By setting the molding pressure within this range, the filling rate of the magnetic powder in bonded magnet 100 may be increased. It may also increase the strength of bonded magnet 100. It may also make it easier to obtain a good bonded magnet 100 without cracks. Furthermore, when the green compact is impregnated with the second thermosetting composition to form molded body 1, setting the molding pressure within this range may increase the impregnation of the second thermosetting composition, which may increase the strength of bonded magnet 100.

[0058] Compression in the molding process may be performed two or more times. For example, the mold may be compressed at a first pressure as a preliminary compression, and then a second pressure greater than the first pressure may be used as a finishing compression to compress the molded body. This may increase the strength of the molded body 1. It may also be possible to suppress the occurrence of cracks and make it possible to mold the green compact (molded body).

[0059] During the molding process, a magnetic field orientation process is carried out to magnetically orient the magnetic powder. This causes the particles in the magnetic powder to move so that the easy magnetization axis of the magnetic powder aligns in the direction of the magnetic field (magnetic field) during compression molding, resulting in magnetic field orientation. The magnitude of the external magnetic field (magnetic field magnitude) applied during magnetic field orientation is not particularly limited, but is preferably 0.5 T or more, and more preferably 1 T or more. An external magnetic field magnitude of 10 T is usually sufficient. By setting the external magnetic field magnitude to be between 0.5 T and 10 T, the magnetic powder can be appropriately magnetically oriented during compression molding. In this embodiment, magnetic field orientation refers to aligning the easy magnetization axis of the magnetic powder in the bonded magnet in a certain direction (increasing the degree of orientation).

[0060] As described above, if the viscosity of the first thermosetting composition is 200 mPa s or less, magnetic field orientation may be facilitated in this magnetic field orientation step. This is thought to be because, when the first thermosetting composition has a low viscosity of 200 mPa s or less, it serves as a lubricant that reduces the frictional force between particles when magnetically orienting the magnetic powder, thereby facilitating the movement of the particles in the magnetic powder and facilitating magnetic field orientation.

[0061] The direction of the magnetic field in the magnetic field orientation step is preferably perpendicular to the surface of the magnetic powder mixture in the molding process (see direction Z in Figure 2). This makes it possible to obtain a bonded magnet that is more suitable for the build-up method.

[0062] The impregnation step is a step of impregnating the powder compact with the second thermosetting composition. In other words, the impregnation step refers to the penetration of the liquid second thermosetting composition into the voids between particles inside the powder compact.

[0063] In the impregnation step, the powder compact may be impregnated with the second thermosetting composition by immersing the powder compact in the second thermosetting composition, or the powder compact may be impregnated with the second thermosetting composition by dropping the second thermosetting composition onto the powder compact and allowing it to penetrate. When impregnating the powder compact with the second thermosetting composition, for example, vacuuming may be performed to promote penetration.

[0064] The viscosity of the second thermosetting composition may be, for example, 200 mPa·s or less. The viscosity of the second thermosetting composition is preferably 100 mPa·s or less, more preferably 50 mPa·s or less, even more preferably 15 mPa·s or less, and most preferably 10 mPa·s or less. If the viscosity of the second thermosetting composition is 200 mPa·s or less, impregnation in the impregnation step is carried out properly, and the strength of the bonded magnet after the curing step described below is likely to be increased.

[0065] The second thermosetting composition may be the same thermosetting composition as the first thermosetting composition.

[0066] The curing process is a process in which the first thermosetting composition and the second thermosetting composition (hereinafter, the first thermosetting composition and the second thermosetting composition may be collectively referred to simply as the thermosetting composition) in the powder compact are cured to increase the strength (mechanical strength) of the powder compact and turn it into a bonded magnet. If an impregnation process is performed, the curing process is performed after the impregnation process. The thermosetting composition in the curing process can be cured by subjecting the powder compact to a heat treatment in which the powder compact is heated. As the thermosetting composition in the powder compact hardens, a crosslinked structure of the thermosetting resin (first thermosetting resin, second thermosetting resin) is formed between the particles of the magnetic powder, fixing the positional relationship between these particles.

[0067] The magnetic powder particles and the thermosetting resin may be chemically bonded together or may be bonded together by surface force.

[0068] The heat treatment temperature for heating the powder compact is not particularly limited, but is preferably 100°C or higher and 150°C or lower, and more preferably 110°C or higher and 130°C or lower. If the temperature is lower than 100°C, the thermosetting composition may not cure sufficiently, resulting in a molded body 1 with insufficient strength. Furthermore, if greater strength is desired, secondary curing at 150°C or higher and 180°C or lower can be performed to achieve greater strength.

[0069] The heat treatment time is not particularly limited, but is preferably 1 minute to 120 minutes, more preferably 3 minutes to 60 minutes. If the time is less than 1 minute, the curing of the thermosetting composition will not proceed sufficiently, resulting in insufficient strength. If the secondary curing time is between 1 minute and 120 minutes, but exceeds 120 minutes, oxidation of the thermosetting composition by air will proceed, resulting in insufficient strength.

[0070] The bonded magnet, which is a compact obtained through the curing process, may be further magnetized, for example, to strengthen the magnetic force.

[0071] The magnetic powder, the first thermosetting composition, the first thermosetting resin, the second thermosetting composition, and the second thermosetting resin will be described in detail below.

[0072] There are no particular limitations on the magnetic powder, but examples of magnetic powder that can be used in the method for producing a bonded magnet according to this embodiment include rare earth magnetic materials such as SmFeN, NdFeB, and SmCo.

[0073] SmFeN magnetic powder can be produced by the method disclosed in JP-A-11-189811, NdFeB magnetic powder can be produced by the HDDR method disclosed in WO 2003 / 85147, and SmCo magnetic powder can be produced by the method disclosed in JP-A-08-260083.

[0074] The particle shape of the magnetic powder is preferably close to spherical. For example, the aspect ratio of the magnetic powder shape is preferably 3 or less. When the magnetic powder particle shape is spherical with an aspect ratio of 3 or less, it becomes easier to achieve a bonded magnet with a high magnetic powder filling rate.

[0075] In this embodiment, the aspect ratio of the magnetic powder can be determined by observing the magnetic powder with a scanning electron microscope (SEM), measuring the maximum diameter (major diameter) and the particle diameter (minor diameter) perpendicular to the maximum diameter for 50 random particles, and calculating the average ratio of the major diameter to the minor diameter (major diameter / minor diameter). The magnification ratio during SEM observation may be changed as appropriate depending on the particle diameter. The magnification ratio may be, for example, 100 to 1000 times.

[0076] The particle size of the magnetic powder is, for example, the median diameter (50% particle diameter, so-called D 50 ), the particle size may be 3 μm or more and 300 μm or less. In this embodiment, the particle size and particle size distribution of the magnetic powder can be determined as volume-based values ​​measured using a laser diffraction / scattering particle size distribution analyzer (manufactured by Horiba, Ltd., model "LA960"). For measurements using the laser diffraction / scattering particle size distribution analyzer, a suspension in which 1 g of the magnetic powder to be measured is dispersed in methyl ethyl ketone as a solvent may be used.

[0077] The magnetic powder may be treated with phosphate, which forms a passivation film having PO bonds on the surface of the magnetic powder.

[0078] Phosphating is carried out by reacting the magnetic powder with a phosphating agent, such as phosphates (e.g., orthophosphoric acid, sodium dihydrogen phosphate, potassium dihydrogen phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, zinc phosphate, calcium phosphate), inorganic phosphoric acids (e.g., hypophosphorous acid, hypophosphites, pyrophosphoric acid, polyphosphoric acid), organic phosphoric acids, and salts thereof.

[0079] The magnetic powder may be mixed with a surface treatment agent, that is, the magnetic powder used in the molding step may be surface-treated magnetic powder to which a predetermined amount of surface treatment agent has been added.

[0080] The surface treatment agent may be an additive that protects the surface or modifies the surface properties, such as preventing oxidation of the magnetic powder, compact, or bonded magnet, or improving wettability during the impregnation process of the linking body, or an additive that functions as a binder, improving the bonding strength between the particle surfaces of the magnetic powder in the compact. Examples of surface treatment agents include alkyl silicates that perform silica treatment on the particle surfaces of the magnetic powder, silane coupling agents that perform silane treatment, and surfactants such as nonionic surfactants. The surface treatment agent is not limited to one type, and two or more types may be used in combination.

[0081] The surface treatment agent is preferably mixed in an amount of 5 parts by mass or less, and more preferably 1 to 3 parts by mass, per 100 parts by mass of magnetic powder. This may increase the strength of the compact or bonded magnet. It may also improve the handleability of the compact.

[0082] The magnetic powder is preferably surface-treated with a coupling agent, preferably silane-treated, in order to improve the magnetic properties of the magnetic powder, improve wettability with the thermosetting composition in the impregnation step described below, and increase the mechanical strength of the bonded magnet. Note that a coupling agent is one that has two or more different groups in its molecule, one of which interacts with inorganic materials and the other with organic materials.

[0083] The coupling agent is not particularly limited, and examples of the coupling agent include a silane coupling agent that does not have an alkyl or alkenyl group having 8 to 24 carbon atoms, and a coupling agent that has an alkyl or alkenyl group having 8 to 24 carbon atoms.

[0084] Examples of coupling agents having an alkyl or alkenyl group having from 8 to 24 carbon atoms include silane coupling agents, phosphate coupling agents, and hydrogen phosphite coupling agents. These coupling agents may be used alone or in combination of two or more.

[0085] Examples of silane coupling agents having an alkyl or alkenyl group having from 8 to 24 carbon atoms include those represented by the following general formula: Specific examples include decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, octadecyltrimethoxysilane, octadecyltriethoxysilane, and octyltriethoxysilane, with octadecyltriethoxysilane and octyltriethoxysilane being preferred. (R 1 ) x Si(OR 2 ) (4-x) (R 1 is C n H 2n+1 or C n H 2n-1where n is an integer of 8 to 24, and R 2 is C m H 2m+1 where m is an integer of 1 to 4 and x is an integer of 1 to 3. The group in the silane coupling agent that reacts with the organic material refers to, for example, a group in which a silicon atom is directly bonded to a carbon atom, and in the above formula, R 1 and the group that interacts with inorganic materials is OR 2 is.

[0086] Examples of phosphate coupling agents having an alkyl or alkenyl group having from 8 to 24 carbon atoms include those represented by the following general formula: Specific examples include didecyl acid phosphate, isodecyl acid phosphate, isotridecyl acid phosphate, lauryl acid phosphate, oleyl acid phosphate, stearyl acid phosphate, isostearyl acid phosphate, and tetracosyl acid phosphate, with oleyl acid phosphate being preferred. (R 1 O) x PO(OH) (3-x) (R 1 is C n H 2n+1 or C n H 2n-1 where n is an integer of 8 to 24, and x is an integer of 1 or 2. In the above formula, the group in the phosphate coupling agent that interacts with the organic material is R 1 O, and the group that interacts with inorganic materials is OH.

[0087] The silane coupling agent, phosphate coupling agent or hydrogen phosphite coupling agent having an alkyl or alkenyl group having 8 to 24 carbon atoms may be used alone or in combination of two or more.

[0088] Treatment with a coupling agent having an alkyl or alkenyl group having from 8 to 24 carbon atoms can be carried out by mixing the above-mentioned coupling agent with the magnetic powder and heating it in air to form a coating of the coupling agent. Examples of water needed to hydrolyze the coupling agent include acidic aqueous solutions such as an aqueous acetic acid solution, sulfuric acid solution, and phosphoric acid solution, and basic aqueous solutions such as ammonia water, sodium hydroxide solution, and potassium hydroxide solution.

[0089] The amount of coupling agent having an alkyl or alkenyl group having 8 to 24 carbon atoms is preferably 0.01 to 1 part by mass, and more preferably 0.05 to 0.5 parts by mass, per 100 parts by mass of magnetic powder. If the amount is less than 0.01 part by mass, sufficient lubrication cannot be imparted to the magnetic powder, and if the amount is more than 1 part by mass, the mechanical strength of the resulting molded product is impaired.

[0090] Examples of silane coupling agents having 8 to 24 carbon atoms and no alkyl or alkenyl group include γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane hydrochloride, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, vinyltriacetoxysilane, γ-chloropropyltrimethoxysilane, hexamethylenedisilazane, γ-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, γ-chloropropylmethyldimethoxysilane, γ-mercaptopropyl Methyldimethoxysilane, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, vinyltrichlorosilane, vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, N-β(aminoethyl)γ-aminopropyltrimethoxysilane, N-β(aminoethyl)γ-aminopropylmethyldimethoxysilane, Examples include γ-aminopropyltriethoxysilane, ureidopropyltriethoxysilane, γ-isocyanatepropyltriethoxysilane, bis(3-triethoxysilylpropyl)tetrasulfane, γ-isocyanatepropyltrimethoxysilane, vinylmethyldimethoxysilane, 1,3,5-N-tris(3-trimethoxysilylpropyl)isocyanurate, and N-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propanamine.Furthermore, examples of silane coupling agents having a cyclic structure include coupling agents having an alicyclic structure such as a monocyclo ring or a bicyclo ring, or an aromatic ring as the cyclic structure. For example, coupling agents having a norbornene skeleton, which is a bicyclo ring, include 2-(bicyclo[2.2.1]hept-5-en-2-yl)ethyltrimethoxysilane, 2-(bicyclo[2.2.1]hept-5-en-2-yl)ethyltriethoxysilane, 2-(bicyclo[2.2.1]hept-5-en-2-yl)trimethoxysilane, 2-(bicyclo[2.2.1]hept-5-en-2-yl)triethoxysilane, 2-(bicyclo[2.2.1]hept-5-en-2-yl)triethoxysilane, 2-(bicyclo[2.2.1]hept-5-en-2-yl)ethyltrimethoxysilane, 2-(bicyclo[2.2.1]hept-5-en-2-yl)triethoxysilane, 2-(bicyclo[2.2.1]hept-5-en-2-yl)ethyl ... [2.2.1]hept-2-enyl)ethynyltrimethoxysilane, 2-(bicyclo[2.2.1]hept-2-enyl)ethynyltriethoxysilane, 2-(bicyclo[2.2.1]hept-5-en-2-yl)hexyltrimethoxysilane, 2-(bicyclo[2.2.1]hept-5-en-2-yl)hexyltriethoxysilane, and examples of coupling agents having an aromatic ring skeleton include N-phenyl-3-aminopropyltrimethoxysilane, N-aminoethylaminomethylphenyl-3-ethyltrimethoxysilane, p-styryltrimethoxysilane, and m-allylphenylpropyltriethoxysilane. These silane coupling agents may be used alone or in combination of two or more. Among these, in terms of wettability and compatibility with the thermosetting composition, lubricity of the magnetic powder particle surface, heat resistance, etc., silane coupling agents having a cyclic structure are preferred, silane coupling agents having a norbornene skeleton are more preferred, and 2-(bicyclo[2.2.1]hept-5-en-2-yl)ethyltrimethoxysilane and 2-(bicyclo[2.2.1]hept-5-en-2-yl)ethyltriethoxysilane are even more preferred.

[0091] Treatment with a silane coupling agent having no alkyl or alkenyl groups and having from 8 to 24 carbon atoms can be carried out by mixing the above-mentioned coupling agent with magnetic powder and heating it in air to form a coating of the silane coupling agent. Examples of water needed to hydrolyze the coupling agent include acidic aqueous solutions such as an aqueous acetic acid solution, sulfuric acid solution, and phosphoric acid solution, and basic aqueous solutions such as ammonia water, sodium hydroxide solution, and potassium hydroxide solution.

[0092] The amount of the silane coupling agent having 8 to 24 carbon atoms and no alkyl or alkenyl group mixed is preferably 0.1 to 2 parts by mass, and more preferably 0.2 to 1.2 parts by mass, per 100 parts by mass of the magnetic powder. If the amount is less than 0.1 part by mass, the effect of the coupling agent is small, and if it exceeds 2 parts by mass, the magnetic powder tends to aggregate and the magnetic properties tend to deteriorate.

[0093] The magnetic powder may be silica-treated with an alkyl silicate to protect it from oxidation during the molding process and during use of the resulting molded body. For example, silica treatment may be performed prior to treatment with the coupling agent. The alkyl silicate is represented by the following general formula, and methyl silicate or ethyl silicate is preferred. SinO (n-1) (OR) (2n+2) (R is an alkyl group, and n is an integer of 1 to 10.)

[0094] The silica treatment can be carried out by mixing the above-mentioned alkyl silicate with the magnetic powder and heating it in air to form a silica coating. Examples of water needed to hydrolyze the silicate include acidic aqueous solutions such as acetic acid, sulfuric acid, and phosphoric acid, and basic aqueous solutions such as ammonia water, sodium hydroxide, and potassium hydroxide. The amount of alkyl silicate mixed is preferably 1 to 4 parts by weight, more preferably 1.5 to 2.5 parts by weight, per 100 parts by weight of the magnetic powder.

[0095] It is preferable that a surfactant such as a nonionic surfactant be added to the magnetic powder in order to improve wettability with the first thermosetting composition and the second thermosetting composition described below.

[0096] Examples of nonionic surfactants include polyoxyethylene alkyl ethers such as laureth-4, laureth-7, laureth-9, laureth-21, laureth-23, ceteth-10, ceteth-20, steareth-2, steareth-20, steareth-21, steareth-25, beheneth-20, beheneth-30, oleth-2, and oleth-10. Other examples include polyoxyethylene fatty acid esters such as PEG-25 stearate, PEG-40 stearate, PEG-45 stearate, PEG-55 stearate, PEG-75 stearate, PEG-100 stearate, PEG-150 stearate, and PEG-150 distearate. Other examples include glycerin fatty acid esters such as glyceryl myristate, glyceryl stearate, glyceryl isostearate, glyceryl oleate, glyceryl dioleate, and glyceryl distearate. Other examples include polyglycerin fatty acid esters such as polyglyceryl-10 stearate, polyglyceryl-10 distearate, polyglyceryl-10 tristearate, polyglyceryl-10 pentastearate, polyglyceryl-10 oleate, polyglyceryl-10 isostearate, polyglyceryl-10 myristate, polyglyceryl-10 laurate, polyglyceryl-4 stearate, polyglyceryl-6 stearate, and polyglyceryl-2 stearate. Other examples include polyoxyethylene glycerin fatty acid esters such as PEG-6 glyceryl isostearate, PEG-20 glyceryl triisostearate, PEG-20 glyceryl tristearate, and PEG-7 glyceryl coconut oil fatty acid. Further examples include sorbitan fatty acid esters such as sorbitan laurate, sorbitan palmitate, sorbitan stearate, sorbitan isostearate, sorbitan oleate, sorbitan sesquistearate, sorbitan sesquiisostearate, sorbitan sesquioleate, sorbitan trioleate, sorbitan tristearate, sorbitan olivary oil fatty acid, and sorbitan coconut oil fatty acid.Other examples include polyoxyethylene sorbitan fatty acid esters such as POE(20) sorbitan laurate, POE(20) sorbitan stearate, POE(20) sorbitan oleate, and POE(20) sorbitan isostearate.

[0097] The first thermosetting composition is not particularly limited as long as it is thermosetting, and may contain a thermosetting monomer, a thermosetting prepolymer, a thermosetting polymer, or the like.

[0098] Examples of thermosetting monomers include norbornene-based monomers, epoxy-based monomers, phenol-based monomers, acrylic-based monomers, and vinyl ester-based monomers. Examples of norbornene-based monomers include tricyclo[5.2.1.0 2,6 ]Deca-3,8-diene (dicyclopentadiene), tricyclo[5.2.1.0 2,6 ]decane-3-ene, bicyclo[2.2.1]hepta-2,5-diene (2,5-norbornadiene), bicyclo[2.2.1]hept-2-ene (2-norbornene), bicyclo[3.2.1]oct-2-ene, 5-ethylidene-2-norbornene, bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic anhydride, 5-vinylbicyclo[2.2.1]hept-2-ene, tetracyclo[6.2.1.1 3,6 .0 2,7 ]dodec-4-ene, etc. Examples of thermosetting prepolymers include epoxy resins, phenolic resins, melamine resins, guanamine resins, unsaturated polyesters, vinyl ester resins, diallyl phthalate resins, silicone resins, alkyd resins, furan resins, acrylic resins, urea resins, and allyl carbonate resins. Examples of thermosetting polymers include polyurethane resins, polyimide resins, and polyester resins.

[0099] The first thermosetting composition may contain a polymerization initiator and a curing agent. Examples of initiators include Grubbs' catalyst (ruthenium carbene complex), dihalogens, and azo compounds. Examples of curing agents include amine-based curing agents, acid anhydride-based curing agents, polyamide-based curing agents, imidazole-based curing agents, phenolic resin-based curing agents, polymercaptan resin-based curing agents, polysulfide resin-based curing agents, organic acid hydrazide-based curing agents, and isocyanate-based curing agents. Examples of amine-based curing agents include diaminodiphenyl sulfone, metaphenylenediamine, diaminodiphenylmethane, diethylenetriamine, and triethylenetetramine.

[0100] The second thermosetting composition is described in accordance with the description of the first thermosetting composition. The second thermosetting composition is not particularly limited as long as it is thermosetting. The second thermosetting composition may contain a thermosetting monomer, a thermosetting prepolymer, a thermosetting polymer, or the like. [Example]

[0101] The bonded magnet and the manufacturing method of the bonded magnet according to this embodiment will be described below based on examples.

[0102] Example 1 The bonded magnet according to Example 1 was manufactured and evaluated as follows: The purpose of the bonded magnet according to Example 1 was to manufacture a bonded magnet with a magnetic field oriented in the perpendicular direction (having anisotropy).

[0103] (Preparation of magnetic powder) In a mortar, magnetic filler with the composition NdFe 14 B(True density: 7.6g / cm 3A magnetic powder (product name: MF15P, manufactured by Aichi Steel Corporation) was prepared, which is a powder of a magnetic material of 120 μm in diameter (hereinafter referred to as HDDR powder). The particle size of this magnetic powder was a median diameter of 120 μm. The aspect ratio of this magnetic powder was 1.3. The magnification of the SEM observation when measuring the aspect ratio was 100 times. 2-(bicyclo[2.2.1]hept-5-en-2-yl)ethyltrimethoxysilane (model: X-88-351, manufactured by Shin-Etsu Chemical Co., Ltd.) was prepared as a silane coupling agent. Furthermore, fatty acid ester-type sorbitan trioleate (manufactured by Kao Corporation, model: Rheodor SP-O30V) was prepared as a nonionic surfactant.

[0104] Then, 300 g of this magnetic powder was placed in a stirring container (mortar), and 3 g of the silane coupling agent was added to the magnetic powder in the container and stirred with a pestle for 5 minutes. After this stirring was completed, the container was left open for 30 minutes and dried at room temperature. After that, 3 g of the nonionic surfactant was added and stirred with a pestle for 5 minutes. After this stirring was completed, the container was left open for 30 minutes to obtain surface-treated magnetic powder.

[0105] Next, a first thermosetting composition was prepared by mixing 100 parts by weight of dicyclopentadiene monomer (viscosity: 3 mPa·s, density: 1.02 g / cc) with 0.3 parts by weight of dichloro[1,3-bis(2,6-isopropylphenyl)-2-imidazolidinylidene](2-isopropylphenylmethylene)ruthenium(III) as a reaction initiator.

[0106] (molding process and magnetic field orientation process) Next, the first thermosetting composition was added to the surface-treated magnetic powder as follows to form a magnetic powder mixture, which was then compression-molded while being magnetically oriented to obtain a flat-plate-shaped green compact (molded body).

[0107] For compression molding, a mold unit conforming to the shape shown in Figure 2 was used. The mold unit was made of austenitic stainless steel, which is a non-magnetic material. The cavity of the molding die of the mold unit had a cylindrical shape with a circular cross section perpendicular to the axial direction. The diameter of the cavity cross section was 30 mm.

[0108] A lower punch was attached to the molding die to adjust the cavity height to 3 mm, and 2.0 g of surface-treated magnetic powder was charged into the cavity. The amount of magnetic powder charged was set so that the thickness of the bonded magnet after the curing process described below would be approximately 500 μm. 0.04 g of the first thermosetting composition was then dropped onto the charged surface-treated magnetic powder to impregnate it, producing a magnetic powder mixture.

[0109] The upper punch was then attached to the molding die. The lower punch and upper punch were compressed together while applying a magnetic field (static magnetic field) to the magnetic powder mixture (magnetic field orientation step), thereby compressing the magnetic powder mixture to obtain a flat green compact (molding step). The pressure used to compress the lower punch and upper punch, i.e., the molding pressure, was 3 t / cm. 2 To produce a bonded magnet with anisotropy in the perpendicular direction, a magnetic field was applied perpendicular to the surface of the flat compact (the axial direction of the cylindrical cavity). The magnetic flux density of the applied magnetic field was 5T.

[0110] (Impregnation process) Next, the green compact was removed from the cavity and placed in a metal container for heat treatment, and 1.0 g of a second thermosetting composition was dropped into the green compact in the metal container to impregnate it. In this example, the same second thermosetting composition as the first thermosetting composition was used.

[0111] (hardening process) Next, the powder compact was heated to harden the thermosetting composition, yielding a bonded magnet (molded body) according to this example. The bonded magnet according to this example has a circular, flat plate shape (i.e., a disk shape). The powder compact was heated at 120°C for 15 minutes while still contained in the metal container. The bonded magnet was cooled to below 30°C in an indoor environment and then removed from the metal container.

[0112] The bonded magnets obtained as described above were subjected to the following evaluations. First, the density and strength (mechanical strength) of the bonded magnets were measured. The bonded magnets were also visually inspected to check for the presence of cracks. Based on the results of these measurements, the filling rate of the magnetic powder in the bonded magnets was calculated. The state of magnetic field orientation of the bonded magnets was also evaluated (evaluation of the degree of orientation of the axis of easy magnetization). The results of these evaluations, along with an overview of the manufacturing conditions, are shown in Table 1.

[0113] [Table 1]

[0114] The density of the bonded magnet was measured using an automatic hydrometer (manufactured by Toyo Seiki Seisakusho, product name "DENSIMETER-H"). 3 If this is the case, the filling rate of the magnetic powder in the bonded magnet is sufficiently high and is judged to be good.

[0115] The packing ratio of the magnetic powder in the bonded magnet was calculated by multiplying the density measured by the above method by the true density (7.6 g / cm) of the magnetic powder used in the production of the bonded magnet. 3 ) and multiplied by 100. If the filling rate is 64% or higher, the filling rate of the magnetic powder in the bonded magnet is sufficiently high and is considered to be good.

[0116] In this example, compressive strength was measured as the strength of the bonded magnet. Compressive strength was measured using a precision universal testing machine (Shimadzu Corporation, model: Autograph AG-IS 20kN). Specifically, using the testing machine, pressure was applied from one side of the bonded magnet plate toward the other side (i.e., downward) at a pressing speed of 500 mm / min, and the applied pressure was determined when the bonded magnet cracked, and this was taken as the compressive strength (MPa).

[0117] The presence or absence of cracks was ranked according to the following criteria. The fewer structural defects such as cracks a bonded magnet has, the better. Therefore, magnets in which no cracks were visible through visual observation were rated as Rank A (good). Furthermore, magnets in which cracks less than 1 mm in length were visible through visual observation were rated as Rank B (good). Finally, magnets in which cracks 1 mm or longer were visible through visual observation were rated as Rank C (poor). Table 1 shows the results of this ranking of the presence or absence of cracks as the "appearance evaluation rank."

[0118] To evaluate the state of magnetic field orientation of the bonded magnet, a magnetic hysteresis curve (BH curve, hysteresis loop) was obtained, and based on this, the ratio of residual magnetic flux density to saturation magnetic flux density (residual magnetic flux density / saturation magnetic flux density) was calculated.

[0119] The magnetic hysteresis curve was obtained using a vibrating sample magnetometer (VSM) ("VSM-7P" manufactured by Toei Industry Co., Ltd.) Specifically, while applying a magnetic field (external magnetic field) in the direction perpendicular to the surface of the bonded magnet, the magnetic flux density was measured by changing the magnetic field strength from 0 kOe to 20 kOe, -20 kOe, and 20 kOe in that order, and the magnetic hysteresis curve was obtained. The orientation was evaluated by comparing the shapes of these hysteresis loops.

[0120] FIG. 3 shows an explanatory diagram of a magnetic hysteresis curve. In the figure, curve H represents the magnetic hysteresis curve. Point a represents the value of saturation magnetic flux density. Point b represents the residual magnetic flux density. Explaining this according to the present embodiment, when the magnetic field strength is changed in the order of 0 kOe to 20 kOe, -20 kOe, and 20 kOe, the measured magnetic flux density forms a loop curve that starts at 0 (zero), passes through points A, B, C, and D, and returns to point A, i.e., forms a magnetic hysteresis curve (curve H).

[0121] In Table 1, the ratio of the residual magnetic flux density to the saturation magnetic flux density is shown as the "VSM evaluation result." In this evaluation, the closer the ratio of the residual magnetic flux density to the saturation magnetic flux density when measured with a magnetic field applied in the perpendicular direction to the surface is to 1, the higher the ease of magnetization in the perpendicular direction, and the more the magnetic field is oriented in the perpendicular direction. Therefore, in this evaluation, the closer the ratio of the residual magnetic flux density to the saturation magnetic flux density when measured with a magnetic field applied in the perpendicular direction to the surface is to 1, the more preferable it is.

[0122] The state of magnetic field orientation was ranked as follows based on the value of the ratio of residual magnetic flux density. When the ratio of residual magnetic flux density to saturation magnetic flux density was 0.60 or more and 1.0 or less, it was evaluated as rank A (good). When this ratio was 0.53 or more and less than 0.60, it was evaluated as rank B (good). When this ratio was less than 0.53, it was evaluated as rank C (poor). In Table 1, the results of this ranking are shown as "VSM rank."

[0123] <Example 2> This example differs from Example 1 in that 1.0 g of surface-treated magnetic powder was charged into the cavity during the molding process, but otherwise the bonded magnet was obtained in the same manner as Example 1. Evaluations were also carried out in the same manner as Example 1. The results of evaluations and the outline of the manufacturing conditions for Example 2 are shown in Table 1. The amount of magnetic powder charged in this example was set so that the thickness of the bonded magnet after the curing process would be approximately 300 μm.

[0124] Example 3 This example differs from Example 1 in that the first thermosetting composition was changed to one prepared by mixing 100 parts by weight of low-viscosity epoxy resin bond E206SS (manufactured by Konishi Co., Ltd., viscosity: 450 mPa·s (25°C), density: 1.15 g / cc) and 0.3 parts by weight of curing agent (manufactured by Konishi Co., Ltd., E206SS). Otherwise, a bonded magnet was obtained in the same manner as in Example 1. Evaluations and the like were also carried out in the same manner as in Example 1. The results of evaluations and the like of Example 3, together with an outline of the manufacturing conditions, are shown in Table 1.

[0125] <Comparative Example 1> A bonded magnet was obtained in the same manner as in Example 1, except that the application of a magnetic field when compression-molding the magnetic powder mixture and the subsequent demagnetization were omitted. Evaluations were also performed in the same manner as in Example 1. The results of evaluations and other aspects of Comparative Example 1, along with an overview of the manufacturing conditions, are shown in Table 1.

[0126] <Comparative Example 2> A bonded magnet was obtained in the same manner as in Example 1, except that only the first thermosetting composition was not used. Evaluations were also carried out in the same manner as in Example 1. The results of evaluations and the like for Comparative Example 2, along with an outline of the manufacturing conditions, are shown in Table 1.

[0127] As shown in Table 1, compared to the bonded magnets of the comparative examples, the bonded magnets of the examples generally received a higher appearance evaluation rank, exhibiting fewer structural defects, and also received a higher VSM rank, indicating that the internal magnetic powder is well oriented in the magnetic field. Furthermore, the bonded magnets of the examples achieved a thickness of 500 μm or less, making them thin, flat bonded magnets of less than 1 mm. Furthermore, the bonded magnets of the examples ensure a necessary and sufficient compressive strength of 25 MPa or more.

[0128] A comparison of the Examples and Comparative Examples shows that the type and presence of the first thermoplastic composition, and the presence or absence of a magnetic field orientation process, do not have a significant effect on the density and packing ratio of the bonded magnet. Focusing particularly on the results of Example 2, it is suggested that the packing ratio may decrease slightly if the thickness of the flat bonded magnet is reduced.

[0129] Comparing the VSM rank and VSM evaluation results between the Example and Comparative Example 1, it can be seen that when magnetic field orientation was performed during the compression molding of the powder compact (see Example), the VSM rank was high and a bonded magnet with magnetic field orientation in the perpendicular direction (anisotropy) was produced. Therefore, in order to produce a magnetically oriented bonded magnet, it is necessary to carry out a magnetic field orientation process.

[0130] Regarding the VSM evaluation results, a comparison of Examples 1 to 3 shows that there is not much difference in the VSM evaluation results, and it is believed that there is not much difference in the state of magnetic field orientation for the bonded magnets under any of the conditions.

[0131] Comparing the appearance ranking results between Examples and Comparative Examples, it can be seen that when the first thermosetting composition is not used (see Comparative Example 2), the appearance ranking is low and cracks are more likely to occur. This is thought to be because the bonding strength between the magnetic powder particles in the bonded magnet is not sufficiently high when the first thermosetting composition is not used. Therefore, in order to obtain a flat bonded magnet without structural defects such as cracks, it is thought that it is necessary to manufacture the bonded magnet using the first thermosetting composition and for the bonded magnet to contain the first thermosetting resin.

[0132] As described above, the bonded magnet according to the embodiment is a thin, flat, plate-shaped magnet less than 1 mm thick, with a high magnetic powder filling rate and magnetically oriented. Such bonded magnets are suitable for build-up magnet manufacturing methods, in which magnets of any shape and magnetic properties are constructed by stacking and arranging. In other words, they are suitable as unit structures when constructing magnets of any shape and magnetic properties by stacking and arranging. For example, by stacking flat bonded magnets in the perpendicular direction, a cylindrical bonded magnet can be constructed. By arranging flat bonded magnets adjacent to each other in the in-plane direction, a large-area, plate-shaped bonded magnet can be constructed.

[0133] In this way, it is possible to provide a method for manufacturing a bonded magnet that can produce a flat bonded magnet with a high magnetic powder filling rate, and a flat bonded magnet with a high magnetic powder filling rate.

[0134] It should be noted that the embodiments disclosed in this specification are merely examples, and the embodiments of the present disclosure are not limited to these, and can be modified as appropriate within the scope of the purpose of the present disclosure. [Industrial Applicability]

[0135] The present disclosure is applicable to bonded magnets and methods for manufacturing bonded magnets. [Explanation of symbols]

[0136] 1: Molded body 100: Bonded magnet 2:Magnetic powder mixture 4: Mold unit 41: Molding mold 42: Lower pestle 44: Upper pestle d: thickness H: Curve (magnetic hysteresis curve) Z: Direction

Claims

1. a molding step of compressing and molding a magnetic powder mixture, which is a mixture of magnetic powder and a first thermosetting composition, to form a plate-shaped molded body; a magnetic field orientation step that is carried out during the molding step and magnetically orients the magnetic powder, A method for producing a bonded magnet, wherein the molded body has a thickness of 1 mm or less.

2. The method further comprises an impregnation step of impregnating the molded body with a second thermosetting composition, 2. The method for producing a bonded magnet according to claim 1, wherein the second thermosetting composition has a viscosity of 200 mPa·s or less.

3. The method for producing a bonded magnet according to claim 2, wherein the second thermosetting composition is a norbornene-based monomer.

4. The method for producing a bonded magnet according to claim 3 , wherein the first thermosetting composition is the same as the second thermosetting composition.

5. 5. The method for producing a bonded magnet according to claim 1, wherein the magnetic field orientation step applies a magnetic field perpendicular to the surface of the magnetic powder mixture during the molding process.

6. a flat-plate-shaped compact containing magnetic powder and a first thermosetting resin; The molded body is A powder compact having a thickness of 1 mm or less, The filling rate of the magnetic powder is 65% by volume or more, The magnetic powder is a bonded magnet that is magnetically oriented.

7. The bonded magnet according to claim 6 , wherein the compact further comprises a second thermosetting resin.

8. 8. The bonded magnet according to claim 7, wherein the second thermosetting resin is a norbornene-based resin.

9. 9. The bonded magnet of claim 8, wherein the first thermosetting resin is the same as the second thermosetting resin.

10. 10. The bonded magnet according to claim 6, wherein the magnetization direction is perpendicular to the surface.

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