Mixture, varnish, bonded magnet, and motor

Abstract

A mixture which contains an epoxy resin (A), magnetic particles (C) and a curing agent (D), and in differential scanning calorimetry, when the exothermic peak temperature of a heat curve at a temperature rise rate of 2 DEG C / min of the mixture is represented by (X) and the exothermic peak temperature of a heat curve at a temperature rise rate of 2 DEG C / min after the mixture is pressurized at 200 MPa for 5 minutes is represented by (Y), the exothermic peak temperature of a heat curve at a temperature rise rate of 2 DEG C / min is represented by (X). (X) and (Y) satisfy formula (1) and formula (2). 100 < = (X) < = 200 (1) (X)-(Y) > = 3 (2).

Description

Technical Field

[0001] This invention relates to mixtures, varnishes, bonded magnets, and motors. Background Technology

[0002] A molded body obtained by mixing magnetic particles with binder materials such as resin and processing them into a specified shape is called a bonded magnet. Because bonded magnets contain resin, they have a high degree of shape freedom and superior formability compared to sintered magnets. Therefore, their applications are expanding in motors used in automobiles, general household appliances, communication and audio equipment, medical equipment, and general industrial equipment.

[0003] On the other hand, for these motors, it is predicted that the motor speed will increase when high output is required, and there is a tendency to require high fixation strength of metal components for the bonded magnets subjected to strong centrifugal forces.

[0004] Patent Document 1 discloses a resin mixture for bonding magnets, which contains epoxy resin, curing agent, curing accelerator and magnetic powder. The accelerator has borane structure and borate structure, thereby maintaining excellent stability and mechanical strength.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent No. 6606908 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] The molding methods for bonded magnets are divided into compression molding and injection molding. Both methods involve applying heat and / or pressure to a composite material "compound" obtained by mixing magnetic particles and resin components as binders. Compression molding mixtures use thermosetting resins as resin components, resulting in excellent heat resistance. However, the resin components also undergo curing reactions during storage, often leading to issues with storage stability. Furthermore, compression molding requires heating to promote the curing reaction of the thermosetting resin, but the magnetic particles in the mixture are not heat-resistant. Under heating conditions, the surface of the magnetic particles oxidizes, easily leading to a decrease in magnetic properties.

[0010] Therefore, there is a requirement for a mixture that exhibits high fixing strength for metal parts even when thermosetting resins are reacted under low-temperature conditions (e.g., below 150°C).

[0011] In contrast, mixtures containing curing accelerators with borane and borate structures, as described in the aforementioned literature, while having some effect on storage stability, offer room for improvement in the fixing strength of metal parts when thermosetting resins are cured at lower temperatures.

[0012] The problem to be solved by the present invention is to provide a mixture that has excellent storage stability and exhibits high fixation strength for metal parts when thermosetting resins are cured at low temperatures.

[0013] Solution for solving the problem

[0014] In order to solve the above-mentioned problems, the inventors have repeatedly conducted in-depth research and found that by using a mixture containing epoxy resin, magnetic particles and curing agent and whose heat curve obtained by differential scanning calorimetry meets the specified relationship, the problems of the prior art can be solved, and thus the present invention is completed.

[0015] The present invention includes the following methods.

[0016] <1> A compound comprising epoxy resin (A), magnetic particles (C), and a curing agent (D),

[0017] In differential scanning calorimetry, the exothermic peak temperature of the heat curve of the mixture at a heating rate of 2°C / min is set as (X).

[0018] When the exothermic peak temperature of the heat curve of the mixture after being pressurized at 200 MPa for 5 minutes and heated at a rate of 2 °C / min is set as (Y),

[0019] (X) and (Y) satisfy the following equations (1) and (2).

[0020] 100≤(X)≤200…(1)

[0021] (X)-(Y)≥3…(2)

[0022] <2> according to <1> The mixture wherein the curing agent (D) comprises a capsule-type curing agent.

[0023] <3> according to <1> or <2> The mixture wherein, relative to 100 parts by weight of the epoxy resin (A), the content of the curing agent (D) is 0.1 parts by weight or more and 15.0 parts by weight or less.

[0024] <4> according to <2> or <3> The mixture wherein the core component of the curing agent (D) is a solid.

[0025] <5> according to <1> ~ <3> The mixture in any one of the following methods, wherein the curing agent (D) comprises an amine-epoxy adduct.

[0026] <6> according to <5> The mixture, wherein the amine-epoxy adduct class comprises an adduct of an imidazole compound and a bisphenol A type epoxy resin.

[0027] <7> according to <1> ~ <6> The mixture in any one of the above statements further comprises a curing agent (B).

[0028] <8> according to <7> The mixture wherein the curing agent (B) comprises a curing agent that is solid at room temperature, and the content of the curing agent that is solid at room temperature is 50% by mass or more relative to the total amount of the curing agent (B).

[0029] <9> according to <1> ~ <8> The mixture in any one of the following methods, wherein the epoxy resin (A) comprises the structure represented by the following formula (A1).

[0030]

[0031] (In formula (A1), R1 to R3 are each independently a hydrogen atom, an alkyl group, an aromatic group, a substituent containing a heteroatom, or a substituent containing a halogen atom. At least one of R1 to R3 contains a reactive group that reacts with the curing agent (D). R1 ​​to R3 may be the same or different from each other.)

[0032] <10> according to <1> ~ <9> The mixture in any one of the following methods, wherein the epoxy resin (A) comprises the structure represented by the following formula (A2),

[0033]

[0034] (In formula (A2), R) 1 R 2 It is an alkyl group with 1–12 carbon atoms, where m and n are each an independent integer greater than or equal to 1. G 1 and G 2 It is selected from the group consisting of hydrogen atoms, alkyl groups, aromatic groups, substituents containing heteroatoms, and substituents containing halogen atoms. G 1 and G 2 (They can choose to be the same or different from each other.)

[0035] <11> according to <1> ~ <10> The mixture in any one of the following methods, wherein the epoxy resin (A) comprises an epoxy resin that is solid at room temperature, and the content of the epoxy resin that is solid at room temperature is 50% by mass or more relative to the total amount of the epoxy resin (A).

[0036] <12> according to <1> ~ <11> The mixture in any one of the following methods, wherein the magnetic particles (C) are rare earth magnetic particles.

[0037] <13> A mixture comprising epoxy resin (A), magnetic particles (C), and a curing agent (D), wherein the curing agent (D) is a capsule-type curing agent.

[0038] <14> according to <13> The mixture further comprises a curing agent (B).

[0039] <15> according to <13> or <14> The mixture wherein the core component of the curing agent (D) is a solid, and the curing agent (D) comprises amine-epoxy adducts, wherein the amine-epoxy adducts comprise adducts of imidazole compounds and bisphenol A type epoxy resins.

[0040] <16> A varnish comprising an epoxy resin (A), a curing agent (B), a curing agent (D), and an organic solvent (E), wherein the curing agent (D) comprises a capsule-type curing agent, the core component of the curing agent (D) is solid, the curing agent (D) comprises an amine-epoxy adduct, wherein the amine-epoxy adduct comprises an adduct of an imidazole compound and a bisphenol A type epoxy resin.

[0041] <17> A type of bonded magnet, which is used to make <1> ~ <15> The mixture described in any one of the above is formed and cured.

[0042] <18> A motor comprising <17> The aforementioned bonded magnet.

[0043] The effects of the invention

[0044] According to the present invention, a mixture with excellent storage stability and high fixation strength to metal parts is provided when the thermosetting resin is cured at low temperature. Attached Figure Description

[0045] Figure 1 A diagram showing a test piece with a fixed strength. Detailed Implementation

[0046] Hereinafter, a detailed description will be given of the method for carrying out the present invention (hereinafter referred to as "this embodiment").

[0047] The following embodiments are illustrative of the present invention and are not intended to limit the present invention to the following content.

[0048] This invention can be implemented with appropriate modifications within the scope of its spirit.

[0049] "mixture"

[0050] The mixture in this embodiment includes Embodiment A and Embodiment B.

[0051] The following describes each implementation method.

[0052] Implementation Method A

[0053] The mixture in embodiment A comprises epoxy resin (A), magnetic particles (C), and curing agent (D).

[0054] In differential scanning calorimetry, the exothermic peak temperature of the heat curve of the mixture at a heating rate of 2℃ / min is set as (X).

[0055] When the exothermic peak temperature of the heat curve of the mixture after being pressurized at 200 MPa for 5 minutes and heated at a rate of 2 °C / min is set as (Y),

[0056] (X) and (Y) satisfy the following equations (1) and (2).

[0057] 100≤(X)≤200…(1)

[0058] (X)-(Y)≥3…(2)

[0059] The mixture in embodiment A comprises epoxy resin (A), magnetic particles (C), and curing agent (D).

[0060] The mixture of epoxy resin (A) and curing agent (D) (hereinafter referred to as the "resin composition") undergoes a curing reaction with heat treatment, which not only provides a strong bond with magnetic particles (C) but also exhibits high fixation strength for metal parts.

[0061] (Equation (1))

[0062] In differential scanning calorimetry, when the exothermic peak temperature of the heat curve of the mixture in embodiment A is set as (X) at a heating rate of 2°C / min, (X) satisfies the following equation (1).

[0063] 100≤(X)≤200…(1)

[0064] By satisfying the above-mentioned configuration, a mixture exhibiting excellent storage stability and high fixing strength to metal parts can be obtained even when the thermosetting resin is cured at low temperatures. The reasons for this are as follows.

[0065] The exothermic peak in differential scanning calorimetry originates from the heat of reaction of the resin composition during curing due to heating the mixture. Furthermore, the exothermic peak temperature (X) can serve as an indicator of the reactivity of the resin composition.

[0066] When the value of (X) is 100 or higher, the curing reaction of the resin composition will not occur during the storage of the mixture (usually below 40°C), and the storage stability of the mixture is improved. On the other hand, if the value of (X) is 200 or lower, the curing of the resin composition will be sufficient even under low-temperature heating (e.g., below 150°C), and the fixing strength to the metal parts will be improved. Therefore, the mixture is required to satisfy formula (1).

[0067] From the perspective of balancing storage stability and fixed strength during low-temperature curing, the value of the exothermic peak temperature (X) is preferably 110≤(X)≤190, more preferably 120≤(X)≤180, and particularly preferably 130≤(X)≤170.

[0068] As a method for controlling the exothermic peak temperature (X), one example is to adjust the exothermic peak temperature (X) by changing the type and amount of curing agent.

[0069] (Equation (2))

[0070] In differential scanning calorimetry (DSC) of the mixture in Embodiment A, the exothermic peak temperature of the heat curve at a heating rate of 2°C / min is set as (X).

[0071] When the exothermic peak temperature of the heat curve of the mixture after being pressurized at 200 MPa for 5 minutes and heated at a rate of 2 °C / min is set as (Y),

[0072] (X) and (Y) satisfy the following equation (2).

[0073] (X)-(Y)≥3…(2)

[0074] By satisfying the above-mentioned composition, a mixture exhibiting excellent storage stability and high fixing strength to metal parts can be obtained even when the thermosetting resin is reacted at low temperatures. The reasons for this are as follows.

[0075] The manufacturing process of the bonded magnet using thermosetting resin is carried out in the following order: (1) preparation and storage of the mixture, (2) compression molding of the mixture, and (3) thermosetting of the molded body.

[0076] By arbitrarily controlling the reactivity of the resin composition in each process, it is possible to achieve a high level of balance between storage stability and fixation strength during low-temperature curing.

[0077] Specifically, this can be achieved by: (1) suppressing the reactivity of the resin composition during the preparation and storage of the mixture; (2) compressing the mixture; and (3) increasing the reactivity of the resin composition during the thermosetting of the molded body.

[0078] As a method for arbitrarily controlling the reactivity of the resin composition, in the compression molding process of the mixture (2), the reactivity of the resin composition can be improved by utilizing the pressure (usually 200 MPa or more) applied to the mixture in the mold cavity.

[0079] The value of (X)-(Y) in equation (2) is an indicator of the change in the reactivity of the resin composition before and after the mixture is pressurized at 200 MPa for 5 minutes. The larger the value, the more reactive the resin composition becomes after pressurization. Therefore, the mixture in embodiment A is required to satisfy equation (2).

[0080] In embodiment A, the value of (X)-(Y) in formula (2) is preferably (X)-(Y)≥5 when comparing the same amount of magnetic particles, from the viewpoint of balancing storage stability and fixed strength during low-temperature curing. More preferably (X)-(Y)≥7, and even more preferably (X)-(Y)≥10.

[0081] As a method for controlling the value of (X)-(Y), as mentioned above, to improve reactivity under pressure, for example, the use of a capsule-type curing agent can be employed. Furthermore, the value can be adjusted depending on the type of epoxy resin and curing agent; for example, by including epoxy resin and solid components as curing agents, the value tends to increase. Additionally, by increasing the amount of magnetic particles added, the value tends to increase as well.

[0082] <Epoxy Resin (A)>

[0083] The mixture in Embodiment A contains epoxy resin.

[0084] As for epoxy resins, although not limited to the following, examples include biphenyl-type epoxy resins, stilbene-type epoxy resins, diphenylmethane-type epoxy resins, sulfur-containing epoxy resins, phenolic varnish-type epoxy resins, cresol-phenolic varnish-type epoxy resins, naphthol-phenolic varnish-type epoxy resins, dicyclopentadiene-type epoxy resins, salicylaldehyde-type epoxy resins, naphthol and phenol copolymer epoxy resins, epoxides of aralkyl-type phenolic resins, bisphenol-type epoxy resins, glycidyl ether-type epoxy resins of alcohols, and glycidyl ether-type epoxy resins modified with p-xylene and / or m-xylene. Epoxy resins include terpene-modified phenolic resins (glycidyl ether type), cyclopentadiene type epoxy resins, polycyclic aromatic ring-modified phenolic resins (glycidyl ether type), naphthalene-containing phenolic resins (glycidyl ether type), glycidyl ester type epoxy resins, glycidyl or methyl glycidyl type epoxy resins, alicyclic epoxy resins, halogenated phenolic varnish type epoxy resins, hydroquinone type epoxy resins, trimethylolpropane type epoxy resins, and linear aliphatic epoxy resins obtained by oxidizing olefin bonds using peracetic acid or other peracids, epoxy resins containing the structure represented by formula (A1), and epoxy resins containing the structure represented by formula (A2). They can be used alone or in combination of two or more types.

[0085]

[0086] (In formula (A1), R1 to R3 are each independently a hydrogen atom, an alkyl group, an aromatic group, a substituent containing a heteroatom, or a substituent containing a halogen atom, and at least one of R1 to R3 contains a reactive group that reacts with the curing agent (D). R1 ​​to R3 may be the same or different from each other.)

[0087]

[0088] (In formula (A2), R) 1 R 2 It is an alkyl group having 1 to 12 carbon atoms, where m and n are each an independent integer greater than or equal to 1. G 1 and G 2 It is selected from the group consisting of hydrogen atoms, alkyl groups, aromatic groups, substituents containing heteroatoms, and substituents containing halogen atoms. G 1 and G 2 (They can choose to be the same or different from each other.)

[0089] From the viewpoint of improving the mechanical strength of bonded magnets, the epoxy resin preferably comprises at least one selected from the group consisting of biphenyl type epoxy resin, o-cresol phenolic varnish type epoxy resin, phenolic varnish type epoxy resin, salicylaldehyde phenolic varnish type epoxy resin, naphthol phenolic varnish type epoxy resin, epoxy resin comprising the structure represented by the following formula (A1), and epoxy resin comprising the structure represented by the following formula (A2).

[0090]

[0091] (In formula (A1), R1 to R3 are each independently a hydrogen atom, an alkyl group, an aromatic group, a substituent containing a heteroatom, or a substituent containing a halogen atom, and at least one of R1 to R3 contains a reactive group that reacts with the curing agent (D). R1 ​​to R3 may be the same or different from each other.)

[0092]

[0093] (In formula (A2), R) 1 R 2 It is an alkyl group having 1 to 12 carbon atoms, where m and n are each an independent integer greater than or equal to 1. G 1 and G 2 It is selected from the group consisting of hydrogen atoms, alkyl groups, aromatic groups, substituents containing heteroatoms, and substituents containing halogen atoms. G 1 and G 2 (They can choose to be the same or different from each other.)

[0094] From the viewpoint of improving the fixing strength of metal parts, epoxy resin is further preferably an epoxy resin containing the structure represented by the following formula (A1) or an epoxy resin containing the structure represented by the following formula (A2).

[0095]

[0096] (In formula (A1), R1 to R3 are each independently a hydrogen atom, an alkyl group, an aromatic group, a substituent containing a heteroatom, or a substituent containing a halogen atom, and at least one of R1 to R3 contains a reactive group that reacts with the curing agent (D). R1 ​​to R3 may be the same or different from each other.)

[0097]

[0098] (In formula (A2), R) 1 R 2 It is an alkyl group having 1 to 12 carbon atoms, where m and n are each an independent integer greater than or equal to 1. G 1 and G 2It is selected from the group consisting of hydrogen atoms, alkyl groups, aromatic groups, substituents containing heteroatoms, and substituents containing halogen atoms. G 1 and G 2 (They can choose to be the same or different from each other.)

[0099] From the viewpoint of improving the flowability of the mixture, the epoxy resin preferably contains at least one crystalline epoxy resin. Crystalline epoxy resins have a melting point and do not soften in the temperature range below the melting point, thus exhibiting excellent flowability.

[0100] Examples of crystalline epoxy resins include hydroquinone-type epoxy resins, bisphenol-type epoxy resins, thioether-type epoxy resins, and biphenyl-type epoxy resins.

[0101] Commercially available crystalline epoxy resins include, for example, EPICLON 860, EPICLON 1050, EPICLON 1055, EPICLON 2050, EPICLON 3050, EPICLON 4050, EPICLON 7050, EPICLON HM-091, EPICLON HM-101, EPICLON N-730A, EPICLON N-740, EPICLON N-770, EPICLON N-775, EPICLON N-865, EPICLON HP-4032D, EPICLON HP-7200L, EPICLON HP-7200, EPICLON HP-7200H, EPICLON HP-7200HHH, EPICLON HP-7200HHH, EPICLON HP-4700, and EPICLON... HP-4710, EPICLON HP-4770, EPICLON HP-5000, EPICLON HP-6000 and N500P-2 (these are trade names manufactured by DIC Corporation), NC-3000, NC-3000-L, NC-3000-H, NC-3100, CER-3000-L, NC-2000-L, XD-1000, NC-7000-L, NC-7300-L, EPPN-501H, EPPN-501HY, EPPN-50 2H, EOCN-1020, EOCN-102S, EOCN-103S, EOCN-104S, CER-1020, EPPN-201, BREN-S, BREN-10S (the above are trade names manufactured by Nippon Kayaku Co., Ltd.), YX-4000, YX-4000H, YL4121H and YX-8800 (the above are trade names manufactured by Mitsubishi Chemical Co., Ltd.), etc.

[0102] The epoxy resin (A) in embodiment A preferably comprises an epoxy resin that is solid at room temperature.

[0103] The content of epoxy resin that is solid at room temperature is preferably 50% by mass or more, more preferably 75% by mass or more, and even more preferably 95% by mass or more, relative to the total amount of epoxy resin.

[0104] The content of epoxy resin that is solid at room temperature is preferably 100% by mass or less, more preferably 99% by mass or less, relative to the total amount of epoxy resin.

[0105] By satisfying the above composition with epoxy resin, the value of (X)-(Y) can be easily controlled within any range, which can improve the fixing strength during low-temperature curing and also suppress the adhesion of the mixture.

[0106] The epoxy resin content relative to the total volume of the mixture is preferably 1% by volume or more and 35% by volume or less, more preferably 3% by volume or more and 30% by volume or less, and even more preferably 5% by volume or more and 25% by volume or less. By satisfying the above range for the epoxy resin content, both the magnetic properties and mechanical strength of the bonded magnet can be taken into account.

[0107] The epoxy resin content relative to the total mass of the mixture is preferably 0.5% by mass or more and 20% by mass or less, more preferably 1% by mass or more and 15% by mass or less, and even more preferably 2% by mass or more and 10% by mass or less. By satisfying the above range for the epoxy resin content, both the magnetic properties and mechanical strength of the bonded magnet can be taken into account.

[0108] <Curing Agent (B)>

[0109] The mixture in embodiment A preferably contains a curing agent (B) that is different from the curing agent (D).

[0110] Curing agents are not limited to the following, but may include aliphatic polyamines, polyaminoamides, polythiols, aromatic polyamines, acid anhydrides, phenolic resins, and dicyandiamide (DICY).

[0111] From the viewpoint of improving the heat resistance of bonded magnets, aromatic polyamines, acid anhydrides, phenolic resins and dicyandiamide (DICY) are preferred curing agents, with phenolic resins being more preferred.

[0112] Examples of phenolic resins include aralkyl-type phenolic resins, dicyclopentadiene-type phenolic resins, salicylaldehyde-type phenolic resins, phenolic varnish-type phenolic resins, copolymers of benzaldehyde-type phenol and aralkyl-type phenol, p-xylene and / or m-xylene-modified phenolic resins, melamine-modified phenolic resins, terpene-modified phenolic resins, dicyclopentadiene-type naphthol resins, cyclopentadiene-modified phenolic resins, polycyclic aromatic ring-modified phenolic resins, biphenyl-type phenolic resins, and triphenylmethane-type phenolic resins. Phenolic resins can be copolymers composed of two or more of the above-mentioned types.

[0113] From the perspective of improving the heat resistance of bonded magnets, phenolic resin is preferably a phenolic varnish type phenolic resin.

[0114] Phenolic varnish-type phenolic resins include, for example, resins obtained by condensing or co-condensing phenols and / or naphthols with aldehydes under an acidic catalyst. Examples of phenols constituting phenolic varnish-type phenolic resins include phenol, cresol, xylenol, resorcinol, catechol, bisphenol A, bisphenol F, phenylphenol, and aminophenol. Examples of naphthols constituting phenolic varnish-type phenolic resins include α-naphthol, β-naphthol, and dihydroxynaphthol. Examples of aldehydes constituting phenolic varnish-type phenolic resins include formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde, and salicylaldehyde.

[0115] Curing agents can be, for example, compounds having two phenolic hydroxyl groups per molecule. Examples of compounds having two phenolic hydroxyl groups per molecule include: resorcinol, catechol, bisphenol A, bisphenol F, substituted or unsubstituted biphenols, etc.

[0116] One of the above-mentioned curing agents can be used alone, or two or more can be used in combination.

[0117] The ratio of the active groups (phenolic OH groups) in the curing agent that react with the epoxy groups in the epoxy resin to the epoxy groups in the epoxy resin is preferably 0.5 to 1.5 equivalents, more preferably 0.7 to 1.4 equivalents, and even more preferably 0.8 to 1.3 equivalents.

[0118] By ensuring that the ratio of active groups in the curing agent meets the above-mentioned range, the mechanical properties and heat resistance of the bonded magnet can be improved.

[0119] The curing agent (B) in embodiment A preferably comprises a curing agent that is solid at room temperature.

[0120] The content of the curing agent, which is solid at room temperature, relative to the total amount of curing agent (B) is preferably 50% by mass or more, more preferably 75% by mass or more, and even more preferably 95% by mass or more. By satisfying the above-described configuration of the curing agent (B), the values ​​of (X)-(Y) can be easily controlled within any range, which can improve the fixing strength during low-temperature curing and also suppress the adhesion of the mixture.

[0121] The content of the curing agent (B) relative to the total volume of the mixture is preferably 1% by volume or more and 35% by volume or less, more preferably 3% by volume or more and 30% by volume or less, and even more preferably 5% by volume or more and 25% by volume or less. By satisfying the above range for the content of the curing agent (B), the mechanical strength of the bonded magnet can be improved.

[0122] The content of the curing agent (B) relative to the total mass of the mixture is preferably 0.5% by mass or more and 20% by mass or less, more preferably 1% by mass or more and 15% by mass or less, and even more preferably 2% by mass or more and 10% by mass or less. By satisfying the above range for the content of the curing agent (B), the mechanical strength of the bonded magnet can be taken into account.

[0123] <Magnetic Particles (C)>

[0124] The mixture in Implementation Method A contains magnetic particles.

[0125] Magnetic particles can be used alone or in combination of two or more. When mixing two or more magnetic particles, two or more magnetic particles with different alloy compositions, particle sizes (particle size distributions), shapes, properties (isotropic or anisotropic), and surface treatments can be used together.

[0126] There are no restrictions on the alloy composition of the magnetic particles as long as it does not reduce the curing properties of the resin composition.

[0127] Magnetic particles can be, for example, samarium-cobalt (Sm-Co) alloy particles (rare earth magnetic particles), neodymium-iron-boron (Nd-Fe-B) alloy particles (rare earth magnetic particles), samarium-iron-nitrogen (Sm-Fe-N) alloy particles (rare earth magnetic particles), iron-cobalt (Fe-Co) alloy particles, Al-Ni-Co alloy particles, or ferrite system magnetic particles, etc.

[0128] The magnetic particles in embodiment A are preferably rare earth magnetic particles.

[0129] Rare earth magnetic particles exhibit superior holding force and magnetic flux density compared to other magnetic particles, and can, for example, enhance the magnetic force of bonded magnets.

[0130] The shape of the magnetic particles is not particularly limited; spherical, flat, prismatic, and needle-shaped magnetic particles can be used individually or in combination. The shape of the magnetic particles can be evaluated by measuring the roundness coefficient using image processing of microscopic observations. The roundness coefficient is defined by the following formula; the higher the value, the more rounded and spherical the particles are. From the viewpoint that the magnetic particles are easy to rotate in magnetic field shaping and can improve orientation, it is preferable to include at least one type of magnetic particle with a roundness coefficient of 0.70 or higher.

[0131] The particle size (particle size distribution) of magnetic particles can be used alone or in combination, with coarse magnetic particles (hereinafter referred to as "coarse particles") and fine magnetic particles (hereinafter referred to as "microparticles").

[0132] The average particle size (D50) of the coarse particles is preferably 30 μm or more and 300 μm or less, more preferably 40 μm or more and 250 μm or less. The coarse particles have high magnetic properties, thus the magnetic properties of the bonded magnet can be adjusted according to the amount of coarse particles added.

[0133] The average particle size (D50) of the microparticles is preferably 0.5 μm or more and 30 μm or less, more preferably 1 μm or more and 20 μm or less. Microparticles can increase the filling amount of magnetic particles and improve magnetic properties.

[0134] The average particle size and particle size distribution of the magnetic particles were determined using a laser diffraction particle size distribution measuring device (HELOS manufactured by Japan Laser Corp.).

[0135] There are no particular limitations on the properties of magnetic particles; anisotropic and isotropic magnetic particles can be used individually or in combination. By using anisotropic magnetic particles to create mixtures and then shaping them using a magnetic field to orient the magnetic particles within the bonded magnet, the magnetic properties can be improved.

[0136] The magnetic particles are preferably treated with rust prevention. Rust prevention treatments include, for example, phosphoric acid treatment to form a phosphate compound layer, metal alkoxy oligomer treatment to form an organometallic compound layer, coupling treatment to form a coupling agent layer, and slow oxidation treatment to form an oxide coating. It should be noted that rust prevention treatments can be performed using a single type or in combination.

[0137] The content of magnetic particles relative to the total volume of the mixture is preferably 40% by volume or more and 95% by volume or less, more preferably 45% by volume or more and 90% by volume or less, and even more preferably 50% by volume or more and 85% by volume or less. By satisfying the above range for the content of magnetic particles, it becomes easier to control the value of (X)-(Y) in formula (2).

[0138] <Curing Agent (D)>

[0139] The mixture in embodiment A contains a curing agent (D).

[0140] As the curing agent (D), it is not limited to the following substances, for example, from the viewpoint of balancing storage stability and fixed strength during low-temperature curing, a latent curing agent is preferred.

[0141] As a latent curing agent, it is not limited to the following, but may include, for example, amine adducts such as imidazole compounds, amine-epoxy adducts, and amine-urea adducts, or encapsulated curing agents formed by coating them, or curing agents formed by adsorbing them onto porous bodies. From the viewpoint of balancing storage stability and reactivity, the curing agent (D) preferably contains amine-epoxy adducts, and more preferably contains adducts of imidazole compounds and bisphenol A type epoxy resins.

[0142] As a curing agent (D), it can be at least one selected from the group consisting of imidazole compounds and amine adduct compounds.

[0143] In the mixture of embodiment A, from the viewpoint of balancing storage stability and fixed strength during low-temperature curing, it is preferable that the curing agent (D) includes a capsule-type curing agent.

[0144] The encapsulated curing agent exhibits high stability by preventing the curing agent components from diffusing into the epoxy resin and curing agent during storage of the mixture, thanks to the shielding effect of the encapsulation membrane. Conversely, during the pressure molding process of the mixture, the capsule membrane is broken by the pressure applied to the mixture, allowing the curing agent components to diffuse into the epoxy resin. Therefore, the curing strength at low temperatures can be improved. The effect of this invention is achieved by multiple magnetic powder particles compressing the microcapsules and breaking the capsule membrane.

[0145] Encapsulated curing agents preferably have a structure in which the surface of a core containing the curing agent is covered with a shell comprising a synthetic resin and / or an inorganic oxide. From the viewpoint of the stability of the membrane constituting the shell and its susceptibility to damage under heating and pressure, the shell constituting the encapsulated curing agent preferably comprises a synthetic resin.

[0146] From the viewpoint of storage stability, the core is preferably solid at room temperature, but is not limited to the following. For example, solid imidazole compounds, amine-epoxy adducts, amine-urea adducts, and other amine adduct compounds can be used. Among these, from the viewpoint of balancing storage stability and reactivity, compounds containing amine-epoxy adducts are preferred, and compounds containing adducts of imidazole compounds and bisphenol A type epoxy resin are more preferred.

[0147] The synthetic resin contained in the shell is not limited to the following, but can include, for example, epoxy resins, phenolic resins, polyester resins, polyethylene resins, nylon resins, polystyrene resins, and urethane resins. Among these, from the viewpoint of balancing the stability of the membrane constituting the shell with the destructive effects of heating and pressurization, epoxy resins, phenolic resins, and urethane resins are preferred.

[0148] The epoxy resin used for the shell is not limited to the following, but may include, for example, epoxy resins having two or more epoxy groups, resins generated by reacting epoxy resins having two or more epoxy groups with compounds having two or more active hydrogen atoms, and reaction products of compounds having two or more epoxy groups with compounds having one active hydrogen atom and a carbon-carbon double bond. From a stability viewpoint, reaction products of compounds having two or more epoxy groups with compounds having two or more active hydrogen atoms are preferred, and reaction products of amine curing agents with epoxy resins having two or more epoxy groups are particularly preferred.

[0149] As a phenolic resin, it is not limited to the following, but may include, for example, phenol-formaldehyde condensate, cresol-formaldehyde condensate, resorcinol-formaldehyde condensate, bisphenol A-formaldehyde condensate, and polyethylene polyamine modified from phenol-formaldehyde condensate.

[0150] As a polyester resin, it is not limited to the following, but can include, for example, ethylene glycol-terephthalic acid-polypropylene glycol condensate, ethylene glycol-butanediol-terephthalic acid condensate, terephthalic acid-ethylene glycol-polyethylene glycol condensate, etc.

[0151] As a polyethylene-based resin, it is not limited to the following, but may include, for example, ethylene-propylene-vinyl alcohol copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-acrylic acid copolymer, etc.

[0152] As for nylon-based resins, they are not limited to the following, but can include, for example, adipic acid-hexamethylene diamine condensate, sebacic acid-hexamethylene diamine condensate, p-phenylenediamine-terephthalic acid condensate, etc.

[0153] As a polystyrene-based resin, it is not limited to the following, but may include, for example, styrene-butadiene copolymer, styrene-butadiene-acrylonitrile copolymer, acrylonitrile-styrene-divinylbenzene copolymer, styrene-propylene alcohol copolymer, etc.

[0154] As a urethane resin, it is not limited to the following, but may include, for example, butyl isocyanate, cyclohexyl isocyanate, octadecyl isocyanate, phenyl isocyanate, toluene diisocyanate, diphenylmethane diisocyanate, phenyl dimethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, bitoluidine diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, and other isocyanate monomers, or their condensates, or polymers thereof, with monohydric alcohols or polyhydric alcohols. Among these, urethane resins that are addition polymers obtained by adding monoisocyanates or polyisocyanates to monohydric alcohols or polyhydric alcohols are preferred.

[0155] As an inorganic oxide, it is not limited to the following, but may include boron compounds such as boron oxide and boron esters; silicon dioxide; calcium oxide, etc. Among them, from the viewpoint of the stability of the film constituting the shell and its susceptibility to damage upon heating, boron oxide is preferred.

[0156] Furthermore, from the viewpoint of balancing the storage stability and curability of the mixture in Embodiment A, the shell preferably contains a reaction product selected from the group consisting of isocyanate compounds, active hydrogen compounds, curing agents for epoxy resins, epoxy resins, and amine compounds.

[0157] As isocyanate compounds, they are not limited to the following, for example, aliphatic diisocyanates, alicyclic diisocyanates, aromatic diisocyanates, aliphatic triisocyanates, polyisocyanates, etc.

[0158] As an aliphatic diisocyanate, it is not limited to the following, but may include, for example, ethylene diisocyanate, propylene diisocyanate, butyl diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, etc.

[0159] As an alicyclic diisocyanate, it is not limited to the following, for example, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, norbornene diisocyanate, 1,4-isocyanate cyclohexane, 1,3-bis(isocyanate methyl)-cyclohexane, 1,3-bis(2-isocyanate prop-2-yl)-cyclohexane, etc.

[0160] As an aromatic diisocyanate, it is not limited to the following, for example, toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylene diisocyanate, 1,5-naphthalene diisocyanate, etc.

[0161] As an aliphatic triisocyanate, it is not limited to the following, for example, 1,6,11-undecane triisocyanate, 1,8-diisocyanate-4-isocyanate methyl octane, 1,3,6-triisocyanate methyl hexane, etc.

[0162] Polyisocyanates, while not limited to the following, may include polymethylene polyphenyl polyisocyanates, polyisocyanates derived from diisocyanate compounds, etc. Polyisocyanates derived from diisocyanate compounds may include isocyanurate-type polyisocyanates, biuret-type polyisocyanates, carbamate-type polyisocyanates, urethane-type polyisocyanates, carbodiimide-type polyisocyanates, etc.

[0163] The active hydrogen compounds are not limited to the following, but may include, for example, water, compounds having at least one primary amino group and / or a secondary amino group, compounds having at least one hydroxyl group, etc. These active hydrogen compounds may be used alone or in combination of two or more.

[0164] As a compound having at least one primary amino group and / or secondary amino group, although not limited to the following, examples include aliphatic amines, alicyclic amines, aromatic amines, etc.

[0165] As an aliphatic amine, it is not limited to the following, but may include, for example, alkylamines such as methylamine, ethylamine, propylamine, butylamine, and dibutylamine; alkylene diamines such as ethylenediamine, propylenediamine, butylenediamine, and hexamethylenediamine; polyalkylene polyamines such as diethylenetriamine, triethylenetetramine, and tetraethylenepentamine; and polyoxypropylenediamine and polyoxyethylenediamine, etc.

[0166] As alicyclic amines, they are not limited to the following, but can include, for example, cyclopropylamine, cyclobutylamine, cyclopentylamine, cyclohexylamine, isophorone diamine, etc.

[0167] As aromatic amines, they are not limited to the following, but may include, for example, aniline, toluidine, benzylamine, naphthylamine, diaminodiphenylmethane, diaminodiphenyl sulfone, etc.

[0168] Examples of compounds having at least one hydroxyl group include alcohols and phenols.

[0169] As an alcohol compound, it is not limited to the following, but may include, for example, methanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, undecanol, lauryl alcohol, dodecanol, stearyl alcohol, eicosanool, allyl alcohol, crotonol, propargyl alcohol, cyclopentanol, cyclohexanol, benzyl alcohol, cinnamyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monobutyl ether, and other monools; ethylene glycol, polyethylene glycol, etc.

[0170] Polyols such as propylene glycol, polypropylene glycol, 1,3-butanediol, 1,4-butanediol, hydrogenated bisphenol A, neopentyl glycol, glycerol, trimethylolpropane, pentaerythritol, etc.; and polyols such as compounds having two or more secondary hydroxyl groups in one molecule obtained by reacting a compound having at least one epoxy group with a compound having at least one hydroxyl, carboxyl, primary amino, secondary amino, or thiol group.

[0171] These alcohol compounds can be any of the primary, secondary, and tertiary alcohols.

[0172] As phenolic compounds, they are not limited to the following, but may include monophenols such as carbolic acid, cresol, xylenol, carvacrol, thymol, and naphthol; and polyphenols such as catechol, resorcinol, hydroquinone, bisphenol A, bisphenol F, pyrogallol, pyrogallol, 2-(dimethylaminomethyl)phenol, and 2,4,6-tris(dimethylaminomethyl)phenol.

[0173] From the viewpoints of latency and solvent resistance, polyols and polyphenols are preferred as compounds having at least one hydroxyl group, and polyols are more preferred.

[0174] The reaction conditions for preparing the reaction product contained in the shell constituting the capsule-type curing agent as described above, which is selected from the group consisting of isocyanate compounds, active hydrogen compounds, epoxy resin curing agents, epoxy resins, and amine compounds, are not particularly limited. For example, the reaction is usually carried out in a temperature range of -10°C to 150°C, and the reaction time is 10 minutes to 100 hours.

[0175] When using isocyanate compounds and active hydrogen compounds to prepare the reaction products contained in the shell, the mixing ratio of (isocyanate groups in the isocyanate compound): (active hydrogen in the active hydrogen compound) (equivalent ratio) is preferably in the range of 1:0.1 to 1:1000.

[0176] As imidazole compounds, the following are not limited to imidazoles: imidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 1-aminoethyl-2-methylimidazole, 1-(2-hydroxy-3-phenoxypropyl)-2-methylimidazole, 1-(2-hydroxy-3-phenoxypropyl)-2-ethyl-4-methylimidazole, 1-(2-hydroxy-3-butoxypropyl)-2-methylimidazole, 1-(2-hydroxy-3-butoxypropyl)-2-ethyl-4-methylimidazole, and compounds obtained by reacting these imidazoles with at least one of the groups consisting of carboxylic acid compounds, sulfonic acid compounds, urea compounds, isocyanate compounds, and epoxy resins.

[0177] Examples of amine adduct compounds include compounds obtained by reacting at least one of the groups selected from carboxylic acid compounds, sulfonic acid compounds, urea compounds, isocyanate compounds, and epoxy resins with an amine curing agent.

[0178] The above-mentioned curing agents can be used alone or in combination of two or more.

[0179] In the mixture of Embodiment A, the content of curing agent (D) is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, relative to 100 parts by mass of epoxy resin (A). By ensuring that the content of curing agent (D) meets the above range, it is easy to control the fixing strength during low-temperature curing within an appropriate range.

[0180] Furthermore, the content of the curing agent (D) is preferably 15.0 parts by weight or less, more preferably 12.0 parts by weight or less, and even more preferably 10.0 parts by weight or less, relative to 100 parts by weight of epoxy resin (A). By ensuring that the content of the curing agent (D) meets the above range, the storage stability of the mixture of Embodiment A can be easily controlled within an appropriate range.

[0181] Lubricant

[0182] The mixture in embodiment A may contain a lubricant. By including a lubricant in the mixture, the fluidity and formability of the mixture are improved, as is its release properties. As a result, the shape and dimensional accuracy of the bonded magnet are improved, and structural defects in the bonded magnet are more easily suppressed.

[0183] Lubricants may be, for example, at least one selected from the group consisting of saturated fatty acids, saturated fatty acid salts, and saturated fatty acid esters. Waxes may be, for example, selected from lauric acid, myristic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, arachidic acid, dodecanoic acid, behenic acid, tetracosanoic acid, wax acid, lignite, beeswax acid, calcium laurate, calcium myristicate, calcium pentadecanoate, calcium palmitate, calcium heptadecanoate, calcium stearate, calcium arachidate, calcium dodecanoate, calcium behenicate, calcium tetracosanoate, calcium wax acid, calcium lignite, calcium beeswax acid, barium laurate, etc. The mixture comprises at least one of the following groups: barium myristate, barium pentadecanoate, barium palmitate, barium heptadecanate, barium stearate, barium arachidate, barium dodecanoate, barium behenate, barium ceramide, barium ceramide, barium lignite, barium beeswax, laurate, myristate, pentadecanoate, palmitate, heptadecanate, stearate, arachidate, dodecanoate, behenate, tetracosinate, ceramide, lignite, and beeswax. The mixture may also contain waxes other than those listed above. For example, the wax may be selected from the group consisting of magnesium salts of the aforementioned saturated fatty acids, aluminum salts of the aforementioned saturated fatty acids, 12-hydroxystearic acid, calcium ricinoleate, stearamide, oleamide, erucamide, betaine, palmitamide, laurylamide, hydroxystearamide, methylene distearate, ethylene distearate, ethylene bislaurate, distearate adipamide, ethylene dioleate, dioleate adipamide, N-stearate stearamide, N-oleate stearamide, N-stearate erucamide, hydroxymethylstearamide, hydroxymethyl betaine, ethylene glycol, stearyl alcohol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, silicone oil, silicone grease, fluorinated oil, fluorinated grease, fluorinated resin powder, paraffin wax, polyethylene wax, amide wax, polypropylene wax, ester wax, carnauba wax, and microcrystalline wax. The mixture may contain one of the aforementioned lubricants. The mixture may contain a variety of the lubricants mentioned above.

[0184] Lubricants can also be mixed into the mixture, or the dispersion of the internal lubricant can be applied to the inner wall of the mold (the wall that contacts the punch) during mixing.

[0185] <Coupled Agent>

[0186] The mixture in Embodiment A may contain a coupling agent. By including a coupling agent, the adhesion between the resin composition and the surface of the magnetic particles can be further improved, and the strength of the bonded magnet can be further improved.

[0187] Examples of coupling agents include: coupling agents of silane compounds such as epoxy silanes, mercaptosilanes, aminosilanes, alkylsilanes, ureosilanes and vinylsilanes, coupling agents of titanium compounds, coupling agents of aluminum chelates, coupling agents of aluminum / zirconium compounds, etc.

[0188] <Flow aids>

[0189] The mixture of the present invention may contain inorganic fillers as flow aids. The inorganic fillers may consist of a single type of particle. Alternatively, the inorganic fillers may be a combination of two or more types of particles.

[0190] The average particle size (D50) of the inorganic filler is preferably 1 μm or less, more preferably 500 nm or less, and even more preferably 100 nm or less. This improves the space filling rate of the bonded magnet.

[0191] Inorganic fillers can include inorganic microparticles such as silica, alumina, calcium carbonate, kaolin, titanium dioxide, barium sulfate, zinc oxide, aluminum hydroxide, magnesium hydroxide, talc, and mica.

[0192] Flame retardants

[0193] The mixture in Embodiment A may contain a flame retardant. By containing a flame retardant, the fire resistance of the mixture can be improved. From the viewpoints of environmental safety, recyclability, processability, and low cost, the flame retardant is preferably at least one selected from the group consisting of brominated flame retardants, phosphorus-based flame retardants, hydrated metal compound flame retardants, organosilicon flame retardants, nitrogen-containing compounds, hindered amine compounds, organometallic compounds, and aromatic engineering plastics.

[0194] <Organic Solvents (E)>

[0195] In the process of manufacturing the mixture, a varnish, formed by dissolving the resin composition in an organic solvent, is produced and applied to the surface of each magnetic particle constituting the magnetic particles, thereby obtaining a homogeneous mixture. The organic solvent is not limited to any solvent capable of dissolving the resin composition. Examples of organic solvents include at least one solvent selected from the group consisting of acetone, methyl ethyl ketone, methyl isobutyl ketone, benzene, toluene, and xylene. For workability considerations, the organic solvent is preferably liquid at room temperature, and its boiling point is preferably 60°C or higher and 150°C or lower. Acetone and methyl ethyl ketone are preferred examples of such solvents.

[0196] Implementation Method B

[0197] The mixture in Embodiment B (hereinafter also referred to as the "mixture") is a mixture comprising epoxy resin (A), magnetic particles (C) and curing agent (D), wherein the curing agent (D) is a capsule-type curing agent.

[0198] The mixture in embodiment B preferably contains a curing agent (B) that is different from the curing agent (D).

[0199] The core component of the curing agent (D) is a solid, preferably containing amine-epoxy adducts.

[0200] The details of specific examples, preferred examples, preferred contents, preferred methods, etc. of epoxy resin (A), curing agent (B), magnetic particles (C), and curing agent (D) are the same as those of the specific examples, preferred examples, preferred contents, preferred methods, etc. of epoxy resin (A), curing agent (B), magnetic particles (C), and curing agent (D) in Embodiment A above.

[0201] The details of specific examples, preferred examples, preferred content, preferred method, etc. of the curing agent (D) are the same as those of the specific examples, preferred examples, preferred content, preferred method, etc. of the curing agent (D) in Embodiment A above.

[0202] Varnish

[0203] The varnish of this embodiment comprises epoxy resin (A), curing agent (B), curing agent (D), and organic solvent (E). The curing agent (D) comprises a capsule-type curing agent, and the core component of the curing agent (D) is a solid, comprising an amine-epoxy adduct. The varnish of this embodiment can be used for bonding magnets, or it can be used in the process of manufacturing the mixture for bonding magnets described later.

[0204] <Methods for preparing mixtures>

[0205] The method for manufacturing the mixture in this embodiment is not particularly limited. For example, methods for mixing resin compositions above the melting point (hereinafter referred to as "melt mixing") and methods for dissolving and mixing resin compositions in a solvent (hereinafter referred to as "dissolution mixing") can be cited.

[0206] Melt mixing can be carried out using the following methods.

[0207] By thoroughly mixing the raw materials (epoxy resin, curing agent, magnetic particles, and other additives) in a mixer, a mixed powder of the raw materials can be obtained. The obtained mixed powder of the raw materials is heated and mixed at a temperature above the softening temperature of the resin composition, and the solid matter is appropriately pulverized, thereby obtaining the mixture.

[0208] The heating and mixing temperature also depends on the type and amount of resin composition, preferably 40°C or higher and 140°C or lower, more preferably 60°C or higher and 120°C or lower. By heating and mixing within the above temperature range, the curing reaction of the resin composition can be suppressed and the dispersibility of the materials in the mixture can be improved.

[0209] There are no particular limitations on the mixing device; for example, a heated mixer can be used. In this case, the material dispersion can be controlled by changing the amount of raw materials added to the mixture.

[0210] Dissolution and mixing can be carried out using the following methods.

[0211] A solution of the resin composition (varnish) is obtained by dissolving raw materials such as epoxy resin and curing agent in an organic solvent. Magnetic particles are added to the resin composition solution to disperse the magnetic particles. The organic solvent is then removed from the solution containing the magnetic particles and the resin composition by vacuum distillation and drying. As a result, the surface of the magnetic particles is coated with the resin composition, yielding a mixture containing the magnetic particles and the resin composition.

[0212] In the process of removing organic solvent from a solution containing magnetic particles and a resin composition, it is preferable to use an evaporator to remove the organic solvent by vacuum distillation at room temperature while stirring the solution. The solid material obtained by vacuum distillation is further dried using a vacuum dryer or similar equipment, and then appropriately pulverized to obtain a mixture. Alternatively, instead of vacuum distillation, atmospheric distillation can be performed while stirring the solution using a kneader or similar equipment. As a drying method for the solid material obtained by distillation, the solid material can be dried by heating it to a temperature below 80°C, preferably below 60°C, and more preferably below 40°C.

[0213] <Manufacturing Methods of Bonded Magnets>

[0214] The bonded magnet in this embodiment is a bonded magnet formed by molding and curing a mixture.

[0215] A molded body is obtained by compressing the mixture filled into a mold. Higher molding pressure results in a higher density of the bonded magnet, but also makes the magnetic particles more prone to cracking. The molding pressure can be arbitrarily set according to the characteristics of the mixture and the bonded magnet.

[0216] By heat treating the molded body, the resin composition in the molded body is cured, and the magnetic particles in the molded body are bonded together by the cured resin composition, thus obtaining a bonded magnet. The heat treatment temperature of the molded body is preferably set to a temperature at which the resin composition is fully cured. Furthermore, from the viewpoint of suppressing oxidation of the surface of the magnetic particles, low-temperature curing and short-time curing are preferred. The curing temperature is preferably, for example, below 200°C, more preferably below 180°C, and even more preferably below 150°C. The curing time is preferably, for example, below 120 minutes, more preferably below 60 minutes, and even more preferably below 30 minutes.

[0217] When the magnetic particles are oriented, a magnetic field can be applied before molding compression, during molding compression, and during the heat treatment of the molded body.

[0218] The bonded magnet of this embodiment is preferably used in a motor. The motor of this embodiment includes the bonded magnet of this embodiment.

[0219] Example

[0220] The present invention will be specifically described below with examples and comparative examples, but the present invention is not limited to the following examples and comparative examples.

[0221] It should be noted that, unless otherwise specified, "parts" and "%" are the quality standards below.

[0222] [Bonded Magnet Mixture]

[0223] (Epoxy resin (A-1)~(A-7))

[0224] The epoxy resins (A-1) to (A-7) used in the various embodiments and comparative examples are shown in Table 1.

[0225] [Table 1]

[0226]

[0227] (Curing agents (B-1)~(B-3))

[0228] The epoxy resins (B-1) to (B-3) used in each embodiment and comparative example are shown in Table 2.

[0229] [Table 2]

[0230]

[0231] (Magnetic particles (C-1)~(C-2))

[0232] The magnetic particles (C-1) to (C-2) used in each embodiment and comparative example are shown in Table 3.

[0233] [Table 3]

[0234]

[0235] (Curing agent (D-1)~(D-5))

[0236] The magnetic particles (D-1) to (D-5) used in each embodiment and comparative example are shown in Table 4.

[0237] [Table 4]

[0238]

[0239] <Example of manufacturing curing agent (D-1)>

[0240] One equivalent of epoxy resin (A-3) and one equivalent of 2-methylimidazole (converted to active hydrogen) were reacted in a 1:1 mixture of n-butanol and toluene at 80°C. Then, excess amine was removed by distillation along with the solvent under reduced pressure to obtain a block curing agent 1 that is solid at 25°C.

[0241] The block-shaped curing agent 1 was coarsely crushed to approximately 0.1–2 mm using a ROTOPLEX pulverizer (manufactured by Hosokawa Micron Co., Ltd.), and then further pulverized using an air jet mill (manufactured by NISSHIN ENGINEERING Co., Ltd., model CJ25). Next, the pulverized material was classified using an air classifier (manufactured by NISSHIN ENGINEERING Co., Ltd.) to obtain curing agent (D-1) that is solid at 25°C.

[0242] <Example of manufacturing curing agent (D-2)>

[0243] 100 parts by weight of epoxy resin (A-3), 100 parts by weight of epoxy resin (A-4), 100 parts by weight of curing agent (D-1), and 10 parts by weight of encapsulating agent (manufactured by Nippon Polyurethane Co., Ltd.: MR-200) were added, dispersed and mixed, and reacted at 25°C to 55°C for 5 hours and at 60°C for 48 hours to obtain encapsulated curing agent (D-2) dispersed in epoxy resin.

[0244] [Preparation of a bonded magnet mixture]

[0245] (Example 1)

[0246] 4.0 g of epoxy resin (A-1), 3.17 g of curing agent (B-1), 0.3 g of curing agent (D-2), and 33.0 g of methyl ethyl ketone were mixed in a 300 mL round-bottom flask and stirred for 30 minutes to prepare a solution of the resin composition (resin solution). The curing agent (D-2) used contained 0.1 g of encapsulated curing agent, 0.1 g of epoxy resin (A-3), and 0.1 g of epoxy resin (A-4).

[0247] 67.5 g of magnetic particles (C-1) were added to a flask containing the above resin solution and stirred at 25°C for 30 minutes. Then, the pressure in the evaporator was reduced to below 0.1 MPa to completely distill off the solvent in the flask. During the solvent removal process, to ensure thorough removal, the pressure in the flask was repeatedly reduced, the pressure was restored to atmospheric pressure, and the accumulated contents in the flask were disassembled several times. After solvent removal by distillation, the mixture of resin composition and magnetic particles was recovered from the flask and spread on a flat plate. The mixture on the plate was dried in a vacuum dryer at room temperature for 8 hours. After drying, the accumulated mixture was coarsely pulverized to obtain the bonded magnet mixture (CPD-1).

[0248] The following evaluation was conducted using the obtained bonded magnet mixture.

[0249] (Examples 2-17, Comparative Examples 2-10)

[0250] Except for changing the formulation to the formulation described in Table 5, bonded magnet mixtures (CPD-2) to (CPD-17) and (CPD-19) to (CPD-27) were obtained in the same manner as in Example 1.

[0251] The evaluation was conducted in the same manner as in Example 1.

[0252] (Comparative Example 1)

[0253] 4.10g of epoxy resin (A-3), 3.10g of curing agent (B-2) and 0.1g of curing agent (D-1) were placed in a plastic mixing container and mixed using a rotary mixer (THINKY Co., Ltd. "ARE-310") to obtain a resin composition.

[0254] 65.5 g of magnetic particles (C-1) were added to the above resin composition and stirred and mixed using a rotation-revolution mixer to obtain a bonded magnet mixture (CPD-17).

[0255] The evaluation was conducted in the same manner as in Example 1.

[0256] [evaluate]

[0257] (Exothermic peak temperatures (X) and (Y) in differential scanning calorimetry)

[0258] For the bonded magnet mixtures obtained in the examples and comparative examples, a DSC measuring device (TA Instruments Q2000) was used to measure the thermal profiles at 25–250°C at a rate of 2°C / min. The temperature at which the exothermic peak reaches its maximum was designated as (X) for the obtained thermal profiles.

[0259] Similarly, thermal profiles were obtained for samples of the bonded magnet mixtures obtained in the Examples and Comparative Examples, which were pressurized at 200 MPa for 5 minutes. The exothermic peak temperature at which the exothermic heat reaches its maximum was set as (Y). The pressurization of the bonded magnet mixture used a diameter... The powder forming process was performed using a mold (manufactured by Labonect Co., Ltd.) to break down the resulting granules, thereby obtaining a test sample. The thickness of the granules was 1.0 mm.

[0260] (Relative to the fixed strength of the steel plate)

[0261] In diameter The adhesive magnet mixtures of each embodiment and comparative example were filled into a powder molding die (manufactured by Labonect Co., Ltd.), and granules with a thickness of 1.0 mm were formed by applying pressure of 200 MPa for 1 minute.

[0262] The obtained granules were sandwiched between two standard test plates (SPCC-SB, 1.6mm × 25mm × 100mm, manufactured by Nippon Testpanel Co., Ltd.) and hot-pressed using a TM-10 hydroforming machine (manufactured by Toho Machinery Co., Ltd.) to produce test pieces. The heating conditions of the hydroforming machine were 150°C for 30 minutes, and the compression conditions were 200MPa. The fixed position of the granules relative to the test pieces is shown below. Figure 1 .

[0263] The obtained test pieces were tested using an Autograph testing machine (AGX-5kNX, manufactured by Shimadzu Corporation). The maximum load at which the test piece separated due to the fracture of the fixed surface was measured using a force sensor at a speed of 5kN and 5mm / min. The maximum load of separation was divided by the bonded area to obtain the fixed strength.

[0264] Set grades A, B, and C as qualified.

[0265] <Evaluation Criteria>

[0266] A: Fixed strength is 1200 N / mm 2 above.

[0267] B: Fixed strength is 1000 N / mm 2 Above and below 1200 N / mm 2 .

[0268] C: Fixed strength is 800 N / mm 2 Above and below 1000 N / mm 2 .

[0269] D: Fixed strength is 600 N / mm2 Above and below 800 N / mm 2 .

[0270] E: Fixed strength less than 600 N / mm 2 .

[0271] (Storage stability)

[0272] The bonded magnet mixture (CPD-1) was placed at 40°C for 7 days. After placement, the bonding strength of the bonded magnet mixture (CPD-1) to the steel plate was measured. Based on the bonding strength to the steel plate before and after placement, the rate of decrease in bonding strength was calculated by the following formula (3) as an indicator of storage stability.

[0273] Fixed strength reduction rate = Fixed strength of steel plate after 7 days at 40℃ / Fixed strength of steel plate × 100…(3)

[0274] Set grades A, B, and C as qualified.

[0275] <Evaluation Criteria>

[0276] A: The reduction rate of fixed strength relative to the steel plate is less than 10.0%.

[0277] B: The reduction rate of fixed strength relative to the steel plate is greater than 10.0% but less than 15.0%.

[0278] C: The reduction rate of fixed strength relative to the steel plate is greater than 15.0% but less than 20.0%.

[0279] D: The reduction rate of fixed strength relative to the steel plate is greater than 20.0% but less than 25.0%.

[0280] E: The reduction rate of fixed strength relative to the steel plate is more than 25.0%.

[0281] (Adhesiveness)

[0282] The bonded magnet mixture (CPD-1) was placed at 40°C for 7 days to evaluate the change in particle size of the mixture before and after placement.

[0283] Set grades A and B as qualified.

[0284] <Evaluation Criteria>

[0285] A: No change in particle size was observed in the mixture.

[0286] B: The mixture was observed to coalesce, but it dispersed when touched with a finger.

[0287] C: The mixture was observed to coalesce, and it did not disperse even when touched with a finger.

[0288] D: The mixture is combined into a block.

[0289] The compositions of the bonded magnet mixtures (CPD-1 to CPD-17) of [Examples 1 to 17] and the bonded magnet mixtures (CPD-18 to CPD-27) of [Comparative Examples 1 to 10] are shown in Table 5 below, and the evaluation results are shown in Table 6 below.

[0290] [Table 5]

[0291]

[0292] [Table 6]

[0293]

[0294] As shown in Tables 5 and 6, the examples using the following mixture exhibit excellent storage stability and high fixation strength for metal parts when the thermosetting resin is cured at low temperatures. The aforementioned mixture contains epoxy resin (A), magnetic particles (C), and curing agent (D). In differential scanning calorimetry, when the exothermic peak temperature of the heat curve of the mixture at a heating rate of 2°C / min is set as (X) and the exothermic peak temperature of the heat curve of the mixture after being pressurized at 200MPa for 5 minutes at a heating rate of 2°C / min is set as (Y), (X) and (Y) satisfy equations (1) and (2).

[0295] On the other hand, comparative examples with (X)-(Y) less than 3 showed poor storage stability and poor fixation strength of metal parts when the thermosetting resin was cured at low temperatures.

[0296] The present invention may include the following embodiments.

[0297] <1> A bonding magnet mixture comprising epoxy resin (A), a curing agent (B), magnetic particles (C), and a curing accelerator (D),

[0298] In differential scanning calorimetry, the exothermic peak temperature of the heat curve of the bonded magnet mixture at a heating rate of 2°C / min is set as (X).

[0299] When the exothermic peak temperature of the heat curve of the bonded magnet mixture after being pressurized at 200 MPa for 5 minutes and heated at a rate of 2 °C / min is set as (Y),

[0300] (X) and (Y) satisfy the following equations (1) and (2).

[0301] 100≤(X)≤200…(1)

[0302] (X)-(Y)≥3…(2)

[0303] <2> according to <1> The adhesive magnet mixture, wherein the epoxy resin (A) comprises an epoxy resin that is solid at room temperature.

[0304] The content of the epoxy resin is 50% by mass or more relative to the total amount of epoxy resin.

[0305] <3> according to <1> or <2> The bonding magnet mixture, wherein the curing agent (B) comprises a curing agent that is solid at room temperature,

[0306] The content of the curing agent is more than 50% by mass relative to the total amount of curing agent.

[0307] <4> according to <1> ~ <3> The bonded magnet mixture according to any one of the following, wherein the content of magnetic particles (C) is 40% or more and 95% or less relative to the total volume of the bonded magnet mixture.

[0308] <5> according to <1> ~ <4> The bonded magnet mixture according to any one of the following methods, wherein the magnetic particles (C) are rare earth magnetic particles.

[0309] <6> according to <1> ~ <5> The bonding magnet mixture according to any one of the following, wherein the curing accelerator (D) comprises a microencapsulated latent accelerator.

[0310] <7> according to <1> ~ <6> The bonding magnet mixture according to any one of the following methods, wherein the content of the curing accelerator (D) is 0.1 parts by mass or more and 15.0 parts by mass or less relative to 100 parts by mass of the epoxy resin (A).

[0311] <8> A bonding magnet mixture comprising epoxy resin (A), a curing agent (B), magnetic particles (C), and a curing accelerator (D),

[0312] The curing accelerator (D) is a microencapsulated latent accelerator.

[0313] The publication of Japanese Patent Application No. 2020-106880, filed on July 13, 2023, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as those specifically and separately described and incorporated herein by reference.

[0314] Industrial availability

[0315] The mixture of the present invention is industrially available as a material for various bonded magnets.

[0316] Explanation of reference numerals in the attached figures

[0317] 1 granular material

[0318] 2 steel plates

Claims

1. A mixture comprising epoxy resin (A), magnetic particles (C), and a curing agent (D), In differential scanning calorimetry, the exothermic peak temperature of the heat curve of the mixture at a heating rate of 2°C / min is set as (X). When the exothermic peak temperature of the heat curve of the mixture after being pressurized at 200 MPa for 5 minutes and heated at a rate of 2 °C / min is set as (Y), (X) and (Y) satisfy the following equations (1) and (2), 100≤(X)≤200…(1) (X)-(Y)≥3…(2).

2. The mixture according to claim 1, wherein, The curing agent (D) comprises a capsule-type curing agent.

3. The mixture according to claim 1, wherein, The content of the curing agent (D) is 0.1 parts by weight or more and 15.0 parts by weight or less, relative to 100 parts by weight of the epoxy resin (A).

4. The mixture according to claim 2, wherein, The core component of the curing agent (D) is solid.

5. The mixture according to claim 1, wherein, The curing agent (D) comprises amine-epoxy adducts.

6. The mixture according to claim 5, wherein, The amine-epoxy adducts include adducts of imidazole compounds and bisphenol A type epoxy resins.

7. The mixture according to claim 1, further comprising a curing agent (B).

8. The mixture according to claim 7, wherein, The curing agent (B) comprises a curing agent that is solid at room temperature. The content of the curing agent, which is solid at room temperature, is 50% by mass or more relative to the total amount of the curing agent (B).

9. The mixture according to claim 1, wherein, The epoxy resin (A) comprises the structure represented by the following formula (A1). In formula (A1), R1 to R3 are each independently a hydrogen atom, an alkyl group, an aromatic group, a substituent containing a heteroatom, or a substituent containing a halogen atom. At least one of R1 to R3 contains a reactive group that reacts with the curing agent (D). R1 ​​to R3 may be the same or different from each other.

10. The mixture according to claim 1, wherein, The epoxy resin (A) comprises the structure represented by the following formula (A2). In equation (A2), R 1 R 2 It is an alkyl group having 1 to 12 carbon atoms, where m and n are each an independent integer greater than or equal to 1; G 1 and G 2 It is selected from one of the group consisting of hydrogen atoms, alkyl groups, aromatic groups, substituents containing heteroatoms, and substituents containing halogen atoms; G 1 and G 2 They can choose to be the same or different from each other.

11. The mixture according to claim 1, wherein, The epoxy resin (A) comprises an epoxy resin that is solid at room temperature. The content of the epoxy resin that is solid at room temperature is 50% by mass or more relative to the total amount of the epoxy resin (A).

12. The mixture according to claim 1, wherein, The magnetic particles (C) are rare earth magnetic particles.

13. A mixture comprising epoxy resin (A), magnetic particles (C), and a curing agent (D), The curing agent (D) is a capsule-type curing agent.

14. The mixture according to claim 13, further comprising a curing agent (B).

15. The mixture according to claim 13, wherein, The core component of the curing agent (D) is a solid. The curing agent (D) comprises amine-epoxy adducts. The amine-epoxy adducts include adducts of imidazole compounds and bisphenol A type epoxy resins.

16. A varnish comprising an epoxy resin (A), a curing agent (B), a curing agent (D), and an organic solvent (E), The curing agent (D) comprises a capsule-type curing agent. The core component of the curing agent (D) is a solid. The curing agent (D) comprises amine-epoxy adducts. The amine-epoxy adducts include adducts of imidazole compounds and bisphenol A type epoxy resins.

17. A bonded magnet, which is formed and cured by molding the mixture according to any one of claims 1 to 15.

18. A motor comprising the bonded magnet of claim 17.

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