JP7346985B2 - Method for manufacturing rare earth bonded magnet compound and method for manufacturing rare earth bonded magnet - Google Patents

Description

The present disclosure relates to a compound for a rare earth bonded magnet and a method of manufacturing the same, and a rare earth bonded magnet and a method of manufacturing the same.

Compounds containing metal powder and resin compositions are used as raw materials for various industrial products such as inductors, electromagnetic shields, and bonded magnets, depending on the physical properties of the metal powder (see Patent Documents 1 to 3 below). ).

Among these, rare earth magnets using rare earth magnet powder as metal powder have high magnetic properties and are used in various fields today. Rare earth magnets are broadly classified into rare earth sintered magnets and rare earth bonded magnets, depending on the raw material powder used, manufacturing method, etc. Rare earth sintered magnets undergo large dimensional changes during the sintering process, and there are restrictions on the shape that require post-processing. On the other hand, rare earth bonded magnets have little dimensional change during thermosetting, can maintain high dimensional accuracy, and can be shaped into irregular shapes without machining, so they have a high degree of freedom in shape. Furthermore, rare earth bonded magnets have the advantage of high electrical resistance because resin, which is an insulator, is present between the magnet powders.

Because rare earth bonded magnets contain a resin binder, the compact density is lower than the alloy true density (for example, the alloy true density of neodymium iron boron bonded magnet powder is 7.6 g/cm ³ ), and generally the binder is relatively low. Even if a compressed bonded magnet has a small amount of carbon, its magnetic properties will be lower than that of a sintered magnet. On the other hand, rare earth bonded magnets are increasingly being used in a wide range of environments, taking advantage of their features such as freedom of shape, dimensional accuracy, and the ability to be integrally molded with other components.

Japanese Patent Application Publication No. 8-273916 Japanese Patent Application Publication No. 2001-214054 Japanese Patent Application Publication No. 2004-31786

Rare earth bonded magnets are required to have high mechanical strength to withstand use in a wide range of environments. Therefore, it is desired to develop rare earth bonded magnets that have better mechanical strength.

Therefore, the present disclosure provides a method for manufacturing a compound for a bonded rare earth magnet, a method for manufacturing a bonded rare earth magnet, a compound for a bonded rare earth magnet, and a bonded rare earth magnet that can produce a bonded rare earth magnet having excellent mechanical strength. The purpose is to

In order to achieve the above object, the present disclosure provides a resin composition containing an epoxy resin, a phenolic resin, and a hardening accelerator, and a rare earth magnet powder, in a solvent that can dissolve the epoxy resin, the phenolic resin, and the hardening accelerator. and a mixing step of obtaining a mixture by mixing in the presence of a substance capable of donating protons, and a drying step of drying the mixture, wherein the amount of the substance capable of donating protons added in the mixing step is , the amount of the solvent and the proton-donating substance is 1 to 10% by mass based on the total amount of the compound for a bonded rare earth magnet.

According to the method for manufacturing a compound for rare earth bonded magnets, in the mixing step, a solvent that dissolves an epoxy resin, a phenol resin, and a hardening accelerator, and a substance capable of donating a specific amount of protons are used to generate protons. The crushing strength of a molded article (rare earth bonded magnet) using the obtained compound can be improved compared to the case where no substance capable of providing is added. Furthermore, a rare earth bonded magnet using the compound obtained by the above manufacturing method can suppress a decrease in crushing strength at high temperature relative to the crushing strength at room temperature.

Normally, it is recognized that it is preferable to avoid contact with water, oxygen, etc. as much as possible for rare earth magnet powder, from the perspective of preventing rust, etc., and it is recommended to handle it in a manner that avoids contact with water, such as by controlling humidity. It had been done. Therefore, the idea of adding a substance capable of donating protons, such as water, when mixing the rare earth magnet powder and the resin composition was unprecedented. However, as a result of extensive research, the present inventors surprisingly found that by adding a specific amount of a substance capable of donating protons during mixing, it was possible to produce a rare earth bonded magnet using the resulting compound. It has been found that strength can be improved. Although the reason for this effect is not clear, the present inventors speculate as follows. That is, the phenolic resin, the curing accelerator, and the substance capable of donating protons form a complex with the rare earth magnet powder, and the presence of this complex causes the binder resin (epoxy resin, phenol resin, etc.) and the rare earth magnet powder to form a complex. This is thought to be due to the increased adhesive strength between the two.

In the above manufacturing method, the curing accelerator may contain a phosphorus-containing compound. By using a phosphorus-containing compound as a hardening accelerator, the mechanical strength of a rare earth bonded magnet using the obtained compound can be further improved. In addition, the substance capable of donating protons acts on the phosphorus-containing compound, and in the resulting compound, the phenol resin, the phosphorus-containing compound, and the substance capable of donating protons form a complex with the rare earth magnet powder, The adhesive strength between the binder resin and the rare earth magnet powder can be further improved. As a result, superior mechanical strength of the resulting rare earth bonded magnet can be achieved.

In the above manufacturing method, the curing accelerator may contain at least one of a borate salt and a borane compound. By using at least one of a borate salt and a borane compound as a hardening accelerator, in the resulting compound, the phenol resin, at least one of the borate salt and the borane compound, and the substance capable of donating protons are combined into rare earth magnet powder. By forming a complex between the binder resin and the rare earth magnet powder, the adhesive strength between the binder resin and the rare earth magnet powder can be further improved. As a result, superior mechanical strength of the resulting rare earth bonded magnet can be achieved.

In the above production method, the substance capable of donating protons may contain at least one selected from the group consisting of water, benzoic acid, phthalic acid, and acetic acid. Thereby, the mechanical strength of the rare earth bonded magnet using the obtained compound can be further improved.

In the drying step of the production method, the mixture may be dried at a temperature of 20 to 80°C. Thereby, the compound can be produced without proceeding with the curing of the epoxy resin.

The present disclosure also provides a manufacturing method for a rare earth bonded magnet, comprising a step of manufacturing a compound for a rare earth bonded magnet by the method for manufacturing a compound for a rare earth bonded magnet of the present disclosure, and a molding step of compression molding the compound for a rare earth bonded magnet. A manufacturing method is provided. According to such a method for manufacturing a rare earth bonded magnet, a rare earth bonded magnet having excellent mechanical strength can be manufactured.

The present disclosure also provides a compound for a bonded rare earth magnet manufactured by the method for producing a compound for a bonded rare earth magnet of the present disclosure. According to such a compound for rare earth bonded magnets, it is possible to manufacture rare earth bonded magnets having excellent mechanical strength.

The present disclosure further provides a bonded rare earth magnet formed using the compound for a bonded rare earth magnet of the present disclosure. Such rare earth bonded magnets have excellent mechanical strength.

According to the present disclosure, a method for producing a compound for a bonded rare earth magnet, a method for producing a bonded rare earth magnet, a compound for a bonded rare earth magnet, and a bonded rare earth magnet are provided, which can produce a bonded rare earth magnet having excellent mechanical strength. can do.

Hereinafter, preferred embodiments of the present disclosure will be described. However, the present disclosure is not limited to the following embodiments.

<Compound>
The rare earth bonded magnet compound (also simply referred to as "compound" herein) according to the present embodiment includes a resin composition containing an epoxy resin, a phenol resin, and a hardening accelerator, and rare earth magnet powder. Each component constituting the compound will be explained in detail below.

[Resin composition]
The resin composition used in the compound of this embodiment has a function as a binding material for rare earth bonded magnets. The resin composition is produced by blending an epoxy resin, a phenol resin, and a curing accelerator.

(Epoxy resin)
The epoxy resin is, for example, an epoxy resin having two or more epoxy groups in one molecule. Such epoxy resins include, for example, biphenyl-type epoxy resins, stilbene-type epoxy resins, diphenylmethane-type epoxy resins, sulfur atom-containing epoxy resins, novolak-type epoxy resins, dicyclopentadiene-type epoxy resins, salicylaldehyde-type epoxy resins, Copolymerized epoxy resins of naphthols and phenols, epoxidized aralkyl phenol resins, bisphenol epoxy resins, glycidyl ether epoxy resins of alcohols, glycidyl ether epoxy resins of paraxylylene and/or metaxylylene modified phenolic resins, Glycidyl ether type epoxy resin of terpene modified phenol resin, cyclopentadiene type epoxy resin, glycidyl ether type epoxy resin of polycyclic aromatic ring modified phenol resin, glycidyl ether type epoxy resin of naphthalene ring-containing phenolic resin, glycidyl ester type epoxy resin, glycidyl type or methylglycidyl type epoxy resin, alicyclic type epoxy resin, halogenated phenol novolac type epoxy resin, hydroquinone type epoxy resin, trimethylolpropane type epoxy resin, and olefin bond obtained by oxidizing with peracid such as peracetic acid. Examples include linear aliphatic epoxy resins. These may be used alone or in combination of two or more.

The biphenyl-type epoxy resin is not particularly limited as long as it has a biphenyl skeleton, and is, for example, an alkyl-substituted or unsubstituted biphenol epoxy resin.

The stilbene type epoxy resin is not particularly limited as long as it has a stilbene skeleton, but for example, it is a diglycidyl ether type epoxy resin such as stilbene type phenols.

The diphenylmethane type epoxy resin is not particularly limited as long as it has a diphenylmethane skeleton.

A novolak-type epoxy resin is a resin obtained by epoxidizing a novolak resin, and is obtained by condensing or co-condensing phenols and/or naphthols with a compound having an aldehyde group under an acidic catalyst. Examples of phenols include phenol, cresol, xylenol, resorcinol, catechol, bisphenol A, and bisphenol F. Examples of naphthols include α-naphthol, β-naphthol, and dihydroxynaphthalene. Examples of compounds having an aldehyde group include formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde, and salicylaldehyde. Examples of the novolac type epoxy resin include phenol novolac type epoxy resin and orthocresol novolac type epoxy resin. These may be used alone or in combination of two or more.

The dicyclopentadiene type epoxy resin is not particularly limited as long as it is an epoxy resin obtained by epoxidizing a compound having a dicyclopentadiene skeleton as a raw material.

The salicylaldehyde type epoxy resin is not particularly limited as long as it is an epoxy resin made from a compound having a salicylaldehyde skeleton.

The copolymerized epoxy resin of naphthols and phenols is not particularly limited as long as it is an epoxy resin made from a compound having a naphthol skeleton and a compound having a phenol skeleton.

Examples of epoxidized products of aralkyl-type phenolic resins include epoxidized products of phenol aralkyl resins and naphthol aralkyl resins. These may be used alone or in combination of two types.

Examples of bisphenol-type epoxy resins include bisphenol A, bisphenol F, and bisphenol S. These may be used alone or in combination of two or more.

Examples of the glycidyl ether type epoxy resin of alcohols include glycidyl ether type epoxy resins such as butanediol, polyethylene glycol, and polypropylene glycol. These may be used alone or in combination of two or more.

The glycidyl ester type epoxy resin is, for example, a glycidyl ester type epoxy resin of carboxylic acids such as phthalic acid, isophthalic acid, and tetrahydrophthalic acid. These may be used alone or in combination of two or more.

The glycidyl type or methylglycidyl type epoxy resin is, for example, a glycidyl type or methylglycidyl type epoxy resin in which the active hydrogen bonded to the nitrogen atom of aniline and isocyanuric acid is substituted with a glycidyl group.

Alicyclic epoxy resins include, for example, vinylcyclohexene diepoxide obtained by epoxidizing olefin bonds in the molecule, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, and 2-(3,4- epoxy)cyclohexyl-5,5-spiro(3,4-epoxy)cyclohexane-m-dioxane and the like. These may be used alone or in combination of two or more.

Among the above epoxy resins, from the viewpoint of water resistance, solvent resistance, and oil resistance, biphenyl type epoxy resin, stilbene type epoxy resin, diphenylmethane type epoxy resin, sulfur atom-containing type epoxy resin, and aralkyl type phenol resin epoxy resin compounds are more preferred. The sulfur atom-containing epoxy resin is not particularly limited as long as it contains a sulfur atom. More preferable epoxidized aralkyl phenol resins include, for example, epoxidized aralkyl phenol resins such as phenol aralkyl resins, naphthol aralkyl resins, and biphenyl phenol aralkyl resins. This epoxidized aralkyl-type phenol resin is synthesized from phenol and phenols such as cresol and/or naphthols such as naphthol and dimethylnaphthol, and dimethoxyparaxylene, bis(methoxymethyl)biphenyl, and derivatives thereof. There are no particular limitations as long as the epoxy resin is made from a phenol resin. These may be used alone or in combination of two or more.

Among the above epoxy resins, from the viewpoint of high-temperature mechanical strength, novolac-type epoxy resins, dicyclopentadiene-type epoxy resins, salicylaldehyde-type epoxy resins, and copolymerized epoxy resins of naphthols and phenols are more preferable. More preferable novolak-type epoxy resins include, for example, epoxy resins obtained by epoxidizing novolak-type phenolic resins such as phenol novolak, cresol novolac, and naphthol novolak using a technique such as glycidyl etherification. These may be used alone or in combination of two or more.

Furthermore, from the viewpoint of heat resistance, an epoxy resin having a naphthalene structure may be used. Examples of epoxy resins having a naphthalene structure include those in which a glycidyl group is bonded to a naphthalene skeleton. The epoxy resin having a naphthalene structure may be bifunctional, trifunctional, or tetrafunctional. The number of naphthalene skeletons in the epoxy resin having a naphthalene structure can be one or more, but preferably two or more. Furthermore, the upper limit of the number of naphthalene skeletons can be eight. By including the epoxy resin having a naphthalene structure in the resin composition, it is possible to suppress a decrease in the mechanical strength of the rare earth bonded magnet at high temperatures.

Epoxy resins having a naphthalene structure include naphthalene diepoxy compounds, naphthylene ether type epoxy resins, naphthalene novolak type epoxy resins, and methylene-bonded dimers of naphthalene diepoxy compounds, from the viewpoint of superior mechanical strength at room temperature and high temperature. , a methylene bond of a naphthalene monoepoxy compound and a naphthalene diepoxy compound, and the like. Specifically, examples of epoxy resins having a naphthalene structure include HP-4032, HP-4032D, HP-4700, HP-4750, EXA-7311-G4, EXA-7734-G4, EXA-9540 (all of which are DIC stock (manufactured by a company, product name), etc. These may be used alone or in combination of two or more.

The epoxy resin may include epoxy resins other than the more preferred epoxy resins mentioned above. However, in order to fully exhibit the performance of the more preferred epoxy resin described above, the content of the more preferred epoxy resin in the epoxy resin is preferably 30% by mass or more based on the mass of the entire epoxy resin. , more preferably 50% by mass or more.

The biphenyl type epoxy resin is more preferably an epoxy resin represented by the following general formula (II). Commercially available epoxy resins represented by the following general formula (II) include, for example, YX-4000H (manufactured by Mitsubishi Chemical Corporation, trade name, ^R8 , where the oxygen atom is substituted). A compound in which the 3, 3', 5, and 5' positions are methyl groups and the others are hydrogen atoms) and YL-6121H (manufactured by Mitsubishi Chemical Corporation, trade name, all R ⁸ 4,4'-bis(2,3-epoxypropoxy)biphenyl in which is a hydrogen atom, and 3,3',5 when the positions where oxygen atoms are substituted in ^R8 are the 4 and 4' positions. , a mixture with a compound having a methyl group at the 5' position and a hydrogen atom at the other positions).

(In formula (II), R ⁸ represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group having 4 to 18 carbon atoms, each of which may be the same or different, and n is an average value. , indicates an integer from 0 to 20, a decimal number, or a mixed decimal number.)

The stilbene type epoxy resin is more preferably an epoxy resin represented by the following general formula (III). Among the commercially available epoxy resins represented by the following general formula (III), for example, ESLV-210 (manufactured by Sumitomo Chemical Co., Ltd., trade name, R ⁹ is substituted with an oxygen atom) A compound in which the 3,3', 5,5' positions when set to the 4 and 4' positions are methyl groups and the others are hydrogen atoms, and all of ^R10 are hydrogen atoms; Three of the 5'-positions are methyl groups, one is a tert-butyl group, and the others are hydrogen atoms, and a mixture with a compound in which all of R ¹⁰ are hydrogen atoms).

(In formula (III), R ⁹ and R ¹⁰ each independently represent a hydrogen atom or a monovalent organic group having 1 to 18 carbon atoms, and each may be the same or different, and n is the average (value, indicating an integer, decimal, or mixed decimal number from 0 to 20)

"A monovalent organic group having 1 to 18 carbon atoms" refers to an aliphatic hydrocarbon group, an aromatic hydrocarbon group, an aliphatic hydrocarbon group having 1 to 18 carbon atoms, and which may be substituted or unsubstituted. It means containing at least one type selected from the group consisting of group hydrocarbon oxy groups, aromatic hydrocarbon oxy groups, carbonyl groups, oxycarbonyl groups, and carbonyloxy groups.

Examples of the aliphatic hydrocarbon oxy groups include methoxy group, ethoxy group, propoxy group, isopropoxy group, n-butoxy group, sec-butoxy group, tert-butoxy group, cyclopropyloxy group, cyclohexyloxy group, and cyclopentyl group. An oxy group having a structure in which an oxygen atom is bonded to the above-mentioned aliphatic hydrocarbon group such as an oxy group, an allyloxy group, and a vinyloxy group; Examples include things that have been replaced. The aromatic hydrocarbon oxy group has a structure in which an oxygen atom is bonded to the above-mentioned aromatic hydrocarbon group, such as phenoxy group, methylphenoxy group, ethylphenoxy group, methoxyphenoxy group, butoxyphenoxy group, and phenoxyphenoxy group. and those substituted with an alkyl group, an alkoxy group, an aryl group, an aryloxy group, an amino group, a halogen atom, and the like.

Examples of the carbonyl group include aliphatic hydrocarbon carbonyl groups such as formyl group, acetyl group, ethylcarbonyl group, butyryl group, cyclohexylcarbonyl group, and allylcarbonyl group, and aromatic hydrocarbon groups such as phenylcarbonyl group and methylphenylcarbonyl group. Examples include carbonyl groups, and those substituted with alkyl groups, alkoxy groups, aryl groups, aryloxy groups, amino groups, halogen atoms, and the like.

Examples of the oxycarbonyl group include aliphatic hydrocarbonoxycarbonyl groups such as methoxycarbonyl group, ethoxycarbonyl group, butoxycarbonyl group, allyloxycarbonyl group and cyclohexyloxycarbonyl group, phenoxycarbonyl group and methylphenoxycarbonyl group. Examples include aromatic hydrocarbon oxycarbonyl groups, and those substituted with alkyl groups, alkoxy groups, aryl groups, aryloxy groups, amino groups, and halogen atoms.

Examples of the carbonyloxy group include aliphatic hydrocarbon carbonyloxy groups such as methylcarbonyloxy group, ethylcarbonyloxy group, butylcarbonyloxy group, allylcarbonyloxy group, and cyclohexylcarbonyloxy group, phenylcarbonyloxy group, and methylphenyl group. Examples include aromatic hydrocarbon carbonyloxy groups such as carbonyloxy groups, and those substituted with alkyl groups, alkoxy groups, aryl groups, aryloxy groups, amino groups, and halogen atoms.

Regarding R ⁸ to R ²¹ and R ³⁷ to R ⁴¹ in general formulas (II) to (III) and the following general formulas (IV) to (XI), "all of them may be the same or different" , for example, means that all 8 to 168 R ⁸ 's in formula (II) may be the same or different. This means that the numbers of the other R ⁹ to R ²¹ and R ³⁷ to R ⁴¹ included in the formula may be the same or different. Furthermore, R ⁸ to R ²¹ and R ³⁷ to R ⁴¹ may be the same or different. For example, all of R ⁹ and R ¹⁰ may be the same or different. Further, in this specification, other portions of "all may be the same or different" mean the same as above.

The diphenylmethane type epoxy resin is more preferably an epoxy resin represented by the following general formula (IV). Among the commercially available epoxy resins represented by the following general formula (IV), for example, YSLV-80XY (manufactured by Nippon Steel Chemical & Materials Co., Ltd., trade name, R ¹¹ is all hydrogen atoms, R Compounds in which the 3, 3', 5, and 5' positions are methyl groups and the other positions are hydrogen atoms, when the 4 and 4' positions are substituted with oxygen atoms in ¹² .

(In formula (IV), R ¹¹ and R ¹² each independently represent a hydrogen atom or a monovalent organic group having 1 to 18 carbon atoms, and each may be the same or different, and n is the average (value, indicating an integer, decimal, or mixed decimal number from 0 to 20)

More preferably, the sulfur atom-containing epoxy resin is an epoxy resin represented by the following general formula (V). Commercially available epoxy resins represented by the following general formula (V) include, for example, YSLV-120TE (manufactured by Nippon Steel Chemical & Materials Co., Ltd., trade name, ^R13 in which oxygen atoms are substituted). Examples include compounds in which the 3 and 3' positions are tert-butyl groups, the 6 and 6' positions are methyl groups, and the other positions are hydrogen atoms.

(In formula (V), R ¹³ represents a hydrogen atom or a monovalent organic group having 1 to 18 carbon atoms, each of which may be the same or different, n is an average value, and is an integer of 0 to 20. , indicating a decimal or mixed decimal)

The epoxy resin obtained by epoxidizing a novolac type phenol resin such as phenol novolak, cresol novolak, or naphthol novolak using a method such as glycidyl etherification is more preferably an epoxy resin represented by the following general formula (VI). . Commercially available epoxy resins represented by the following general formula (VI) include, for example, ESCN-190 and ESCN-195 (manufactured by Sumitomo Chemical Co., Ltd., trade names; both R ¹⁴ are hydrogen). atom, R ¹⁵ is a methyl group, and i=1).

(In formula (VI), R ¹⁴ and R ¹⁵ each independently represent a hydrogen atom or a monovalent organic group having 1 to 18 carbon atoms, and each may be the same or different, and i is 0 Indicates an integer from ~3, n is the average value, and represents an integer, decimal, or mixed decimal number from 0 to 20, and i may be the same or different.)

More preferably, the dicyclopentadiene type epoxy resin is an epoxy resin represented by the following general formula (VII). Commercially available epoxy resins represented by the following general formula (VII) include, for example, HP-7200 (manufactured by DIC Corporation, trade name, compound where i=0).

(In formula (VII), R ¹⁶ represents a hydrogen atom or a monovalent organic group having 1 to 18 carbon atoms, each of which may be the same or different, i represents an integer of 0 to 3, and n represents It is an average value, and indicates an integer, decimal, or mixed decimal number from 0 to 20, and i may be the same or different.)

More preferably, the salicylaldehyde-type epoxy resin is an epoxy resin obtained by glycidyl etherifying a reaction product of a compound having a salicylaldehyde skeleton and a compound having a phenolic hydroxyl group (salicylaldehyde-type phenolic resin such as novolac-type phenol resin). It is a salicylaldehyde type epoxy resin, for example, an epoxy resin represented by the following general formula (VIII). Commercially available epoxy resins represented by the following general formula (VIII) include EPPN-502H (manufactured by Nippon Kayaku Co., Ltd., trade name), 1032H60 (manufactured by Mitsubishi Chemical Corporation, trade name), i=0, k=0) and EPPN-502H (manufactured by Nippon Kayaku Co., Ltd., trade name).

(In formula (VIII), R ¹⁷ and R ¹⁸ each independently represent a hydrogen atom or a monovalent organic group having 1 to 18 carbon atoms, and each may be the same or different, and i is 0 Indicates an integer of ~3, k represents an integer of 0 to 4, n is an average value, and represents an integer, decimal, or mixed decimal of 0 to 20, and i and k may be the same or different. .)

The copolymerized epoxy resin of naphthols and phenols is more preferably one obtained by glycidyl etherifying a novolak phenol resin using a compound having a naphthol skeleton and a compound having a phenol skeleton. This is an epoxy resin represented by (IX). Commercially available epoxy resins represented by the following general formula (IX) include, for example, NC-7300 (manufactured by Nippon Kayaku Co., Ltd., trade name, R ²¹ is a methyl group, i=1, j =0, k=0), and the like.

(In formula (IX), R ¹⁹ to R ²¹ each independently represent a hydrogen atom or a monovalent organic group having 1 to 18 carbon atoms, and each may be the same or different, and i is 0 Indicates an integer of ~3, j indicates an integer of 0 to 2, k indicates an integer of 0 to 4, p indicates an integer or decimal of 0 to 1 as an average value, and l and m each indicate an average value. An integer, decimal, or mixed decimal number from 0 to 21, (l+m) represents an integer or mixed decimal number from 1 to 21, and j and k may be the same or different.)

The epoxy resin represented by the above general formula (IX) includes a random copolymer randomly containing l structural units and m structural units, an alternating copolymer containing alternating units, a copolymer containing regularly containing them, Examples include block copolymers contained in block form, and any one of these may be used alone or two or more types may be used in combination.

Epoxidized products of aralkyl type phenol resins such as phenol aralkyl resins, naphthol aralkyl resins, and biphenyl type phenol aralkyl resins are preferably phenols such as phenol and cresol, and/or naphthols such as naphthol and dimethylnaphthol, and dimethoxyparaxylene, It is a glycidyl etherified phenol resin synthesized from bis(methoxymethyl)biphenyl and derivatives thereof, and is, for example, an epoxy resin represented by the following general formulas (X) and (XI). Commercially available epoxy resins represented by the following general formula (X) include, for example, NC-3000 (manufactured by Nippon Kayaku Co., Ltd., trade name, i=0, compound in which R ³⁸ is a hydrogen atom) and CER-3000 (manufactured by Nippon Kayaku Co., Ltd., trade name, i=0, an epoxy resin in which R ³⁸ is a hydrogen atom, and an epoxy resin in which all R ⁸ in general formula (II) are hydrogen atoms) A mixed product mixed at a ratio of 80:20), etc. Furthermore, commercially available epoxy resins represented by the following general formula (XI) include, for example, ESN-175 (manufactured by Nippon Steel Chemical & Materials Co., Ltd., trade name, i=0, j=0, k =0), and the like.

(In formulas (X) and (XI), R ³⁷ to R ⁴¹ each independently represent a hydrogen atom or a monovalent organic group having 1 to 18 carbon atoms, and each of them may be the same or different. , i represents an integer from 0 to 3, j represents an integer from 0 to 2, k represents an integer from 0 to 4, n represents an average value, and represents an integer from 0 to 20, a decimal, or a mixed decimal. , i, j, and k may be the same or different.)

In the above general formulas (II) to (XI), n is an average value, preferably an integer, decimal number, or mixed decimal number of 0 to 20. When n is 0 to 20, the melt viscosity of the epoxy resin can be reduced, and the viscosity of the compound for rare earth bonded magnets during melt molding can also be reduced, so deterioration of moldability due to high viscosity can be suppressed. be able to. More preferably, the average n in one molecule is set in the range of 0 to 10.

Among the epoxy resins represented by the above general formulas (II) to (XI), more preferred epoxy resins are the epoxy resins shown by the above general formulas (VI) to (VIII) from the viewpoint of high temperature mechanical strength. .

(phenolic resin)
Phenolic resin functions as a curing agent for epoxy resin. The phenolic resin is not particularly limited, but examples thereof include phenolic resins having two or more phenolic hydroxyl groups in one molecule, which are commonly used as curing agents. Examples of phenolic resins include compounds having two phenolic hydroxyl groups in one molecule, aralkyl-type phenolic resins, dicyclopentadiene-type phenolic resins, salicylaldehyde-type phenolic resins, novolak-type phenolic resins, benzaldehyde-type phenols, and aralkyl-type phenolic resins. Copolymerized phenolic resin with phenol, paraxylylene and/or metaxylylene modified phenolic resin, melamine modified phenolic resin, terpene modified phenolic resin, dicyclopentadiene type naphthol resin, cyclopentadiene modified phenolic resin, polycyclic aromatic ring modified phenolic resin, biphenyl Examples include a type phenol resin, a triphenylmethane type phenol resin, and a phenol resin obtained by copolymerizing two or more of these types. These may be used alone or in combination of two or more. In addition, examples of compounds having two phenolic hydroxyl groups in one molecule include resorcinol, catechol, bisphenol A, bisphenol F, and substituted or unsubstituted biphenol.

Among the above-mentioned phenolic resins, preferred are aralkyl-type phenol resins and copolymerized phenol resins of benzaldehyde-type phenol and aralkyl-type phenol from the viewpoint of water resistance, solvent resistance, and oil resistance. Among the above-mentioned phenolic resins, from the viewpoint of high-temperature mechanical strength, dicyclopentadiene-type phenolic resins, salicylaldehyde-type phenolic resins, and novolac-type phenolic resins are preferred. These aralkyl-type phenolic resins, dicyclopentadiene-type phenolic resins, salicylaldehyde-type phenolic resins, copolymerized phenolic resins of benzaldehyde-type phenol and aralkyl-type phenol, and novolak-type phenolic resins can be used alone or in two types. The above may be used in combination.

Further, all of the phenolic resin does not need to be the above-mentioned preferred phenolic resin, and a part of the phenolic resin may be the above-mentioned preferred phenolic resin. In this case, the content of the above-mentioned preferred phenol resin in the phenol resin is preferably 30% by mass or more based on the total mass of the phenol resin, more preferably, from the viewpoint of fully demonstrating its performance. It is 50% by mass or more.

The aralkyl type phenol resin is not particularly limited as long as it is a phenol resin synthesized from phenols and/or naphthols and dimethoxyparaxylene, bis(methoxymethyl)biphenyl, or derivatives thereof. The aralkyl type phenolic resin is preferably a phenolic resin represented by the following general formulas (XII) to (XIV).

(In formulas (XII) to (XIV), R ²² to R ²⁸ each independently represent a hydrogen atom or a monovalent organic group having 1 to 18 carbon atoms, and they may all be the same or different. , i represents an integer from 0 to 3, k represents an integer from 0 to 4, j represents an integer from 0 to 2, n represents an average value, and represents an integer from 0 to 20, a decimal, or a mixed decimal. , i, j, k and n may be the same or different.)

Among the phenolic resins represented by the above general formula (XII), commercially available ones include MEH-7851 (Meiwa Kasei Co., Ltd., trade name, i=0, a compound in which all R ²³ are hydrogen atoms), etc. can be mentioned.

Commercially available phenolic resins represented by the general formula (XIII) include, for example, XLC (manufactured by Mitsui Chemicals, Inc., trade name, compound where i=0, k=0), XL-225 (manufactured by Mitsui Chemicals Co., Ltd., trade name) and MEH-7800 (manufactured by Meiwa Kasei Co., Ltd., trade name).

Commercially available phenolic resins represented by the above general formula (XIV) include, for example, SN-170 (manufactured by Nippon Steel Chemical & Materials Co., Ltd., trade name, j=0, k=0 of ^R27 , Compounds in which k=0 in R ²⁸ ), etc. can be mentioned.

The dicyclopentadiene type phenol resin is not particularly limited as long as it is a phenol resin using a compound having a dicyclopentadiene skeleton as a raw material. The dicyclopentadiene type phenol resin is preferably a phenol resin represented by the following general formula (XV). Commercially available phenolic resins represented by the following general formula (XV) include, for example, DPP (manufactured by Nippon Petrochemical Co., Ltd., trade name, compound where i=0).

(In formula (XV), R ²⁹ represents a hydrogen atom or a monovalent organic group having 1 to 18 carbon atoms, each of which may be the same or different, i represents an integer of 0 to 3, and n represents It is an average value, and indicates an integer, decimal, or mixed decimal number from 0 to 20, and i may be the same or different.)

The salicylaldehyde type phenolic resin is not particularly limited as long as it is a phenolic resin using a compound having a salicylaldehyde skeleton as a raw material. The salicylaldehyde type phenol resin is preferably a phenol resin represented by the following general formula (XVI). Commercially available phenolic resins represented by the following general formula (XVI) include MEH-7500 (manufactured by Meiwa Kasei Co., Ltd., trade name, compound where i = 0, k = 0), etc. It will be done.

(In formula (XVI), R ³⁰ and R ³¹ each independently represent a hydrogen atom or a monovalent organic group having 1 to 18 carbon atoms, and each may be the same or different, and i is 0 Indicates an integer of ~3, k represents an integer of 0 to 4, n is an average value, and represents an integer, decimal, or mixed decimal of 0 to 20, and i and k may be the same or different. .)

The copolymerization type phenol resin of benzaldehyde type and aralkyl type is not particularly limited as long as it is a copolymerization type phenol resin of a phenol resin and aralkyl type phenol resin using a compound having a benzaldehyde skeleton as a raw material. The copolymerized phenol resin of benzaldehyde type and aralkyl type is preferably a phenol resin represented by the following general formula (XVII). Among the commercially available phenolic resins represented by the following general formula (XVII), for example, HE-510 (manufactured by Air Water Chemical Co., Ltd., trade name, i=0, k=0, q=0 Compounds that are

(In formula (XVII), R ³² to R ³⁴ each independently represent a hydrogen atom or a monovalent organic group having 1 to 18 carbon atoms, and each may be the same or different, and i is 0 -3 represents an integer, k represents an integer from 0 to 4, q represents an integer from 0 to 5, l and m each represent an integer, decimal, or mixed decimal number from 0 to 21 as an average value (l+m) represents a positive number from 1 to 21, and all i's may be the same or different.)

Novolak type phenolic resins include, for example, phenols such as phenol, cresol, xylenol, resorcinol, catechol, bisphenol A, bisphenol F, phenylphenol, and aminophenol, and/or naphthols such as α-naphthol, β-naphthol, and dihydroxynaphthalene. and aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde and salicylaldehyde under an acidic catalyst. The novolac type phenol resin is not particularly limited as long as it is a phenol resin obtained by condensing or co-condensing the above phenols and/or naphthols with the above aldehydes under an acidic catalyst. The novolac type phenol resin is preferably a phenol resin represented by the following general formula (XVIII). Among the commercially available phenolic resins represented by the following general formula (XVIII), for example, Tamanol 758 and 759 (manufactured by Arakawa Chemical Co., Ltd., trade name, i=0, R ³⁵ are all hydrogen atoms) HP-850N (manufactured by Hitachi Chemical Co., Ltd., trade name), etc.

(In formula (XVII), R ³⁵ and R ³⁶ each independently represent a hydrogen atom or a monovalent organic group having 1 to 18 carbon atoms, and each may be the same or different, and i is 0 k is an integer from 0 to 4, n is an average value, and represents an integer, decimal, or mixed decimal from 0 to 20, and i may be the same or different.)

In the above general formulas (XII) to (XVIII), n preferably ranges from 0 to 20. When n is in the range of 0 to 20, the melt viscosity of the phenol resin can be prevented from becoming too high, and the moldability of the compound can be improved. More preferably, the average n is in the range of 0 to 10.

In the rare earth bonded magnet compound of this embodiment, the blending ratio of epoxy resin and phenolic resin is the ratio of hydroxyl group equivalents of all phenolic resins to epoxy equivalents of all epoxy resins (number of hydroxyl groups in phenol resin/epoxy resin in epoxy resin). (radix), preferably from 0.5 to 2.0, more preferably from 0.7 to 1.5, even more preferably from 0.8 to 1.3. When the ratio is between 0.5 and 2.0, the epoxy resin will be sufficiently cured, and the cured product will have good heat resistance and mechanical strength.

(hardening accelerator)
The curing accelerator is not limited, for example, as long as it is a composition that reacts with the epoxy resin to promote curing of the epoxy resin. The curing accelerators may be used alone or in combination of two or more.

The curing accelerator may include, for example, a phosphorus-containing compound. The phosphorus-containing compound is preferably a phosphate, since a rare earth bonded magnet with better mechanical strength can be easily obtained. Further, the curing accelerator may contain, for example, at least one of a borate salt and a borane compound. The phosphorus-containing compound and the borate salt or borane compound may be a common compound. That is, the curing accelerator may contain at least one of a phosphorus-containing borate salt and a phosphorus-containing borane compound. A compound containing at least one of a borate salt and a borane compound as a curing accelerator has superior fluidity, storage stability, and moldability compared to compounds containing other curing accelerators (e.g., imidazoles). . Moreover, since it is easy to obtain a rare earth bonded magnet with better mechanical strength, it is more preferable that the curing accelerator contains a borate salt.

The borate salt used as a curing accelerator may be a compound represented by the following general formula (I-1).
X ⁺ B ^- (R) ₄ (I-1)
(In general formula (I-1), represents boron, and R represents at least one selected from the group consisting of an alkyl group, an aryl group, and a fluoro group.)

The borate salt represented by general formula (I-1) is, for example, tetrabutylphosphonium tetraphenylborate, tetraphenylphosphonium tetrakis(4-methylphenyl)borate, tetraphenylphosphonium tetraphenylborate tetraphenylphosphonium. Tetra-p-tolylborate, tri-tert-butylphosphonium tetraphenylborate, triphenylphosphine-benzoquinone tetraphenylphosphonium, tetraphenylphosphonium tetrakis(4-methylphenyl)borate, tetra(n-butyl)phosphonium tetra It may be at least one selected from phenylborate.

The borane compound used as a curing accelerator may be a compound represented by the following general formula (I-2).
Y・B(R) ₃ (I-2)
(In general formula (I-2), Y represents at least one selected from the group consisting of alkyl phosphine, arylphosphine, imidazole, imidazole derivatives and tertiary amine, B represents boron, and R represents an alkyl group, an aryl group, represents at least one selected from the group consisting of groups and fluoro groups.)

The borane compound represented by general formula (I-2) may be, for example, at least one selected from triphenylphosphinetriphenylborane, 2-methylimidazoletriphenylborane, and triethanolaminetriphenylphosphine.

The curing accelerator may include, for example, imidazoles. The imidazole used as a curing accelerator may be an alkyl group-substituted imidazole, benzimidazole, or the like. The activation temperature of imidazoles tends to be lower than that of the above-mentioned borate salts and borane compounds. Therefore, compounds containing imidazoles are easier to cure at lower temperatures in a shorter time than compounds containing borate salts or borane compounds. Therefore, imidazoles are suitable as curing accelerators when curing a molded article in a short time. The compound contains imidazole-based curing accelerators such as 1-cyanoethyl-2-undecylimidazole, 2-undecylimidazole, 2-heptadecyl imidazole, 2-ethyl-4-methylimidazole, and 1-cyanoethyl-2- It may contain at least one selected from phenylimidazoles. Commercially available imidazole curing accelerators include, for example, 2MZ-H, C11Z, C17Z, 1,2DMZ, 2E4MZ, 2PZ-PW, 2P4MZ, 1B2MZ, 1B2PZ, 2MZ-CN, C11Z-CN, 2E4MZ-CN, 2P. Z -CN, C11Z-CNS, 2P4MHZ, TPZ, and SFZ (the above are trade names manufactured by Shikoku Kasei Kogyo Co., Ltd.), and the like.

The amount of the curing accelerator to be blended is not particularly limited as long as it provides a curing accelerating effect. However, from the viewpoint of improving the curability and fluidity of the epoxy resin upon moisture absorption, the amount of the curing accelerator is preferably 0.1 to 30 parts by mass, more preferably 0.1 to 30 parts by mass, per 100 parts by mass of the epoxy resin. may be 1 to 15 parts by weight. The content of the curing accelerator is preferably 0.001 parts by mass or more and 5 parts by mass or less based on the total mass of the epoxy resin and the curing agent (for example, phenol resin). When the amount of the curing accelerator is less than 0.1 part by mass, it is difficult to obtain a sufficient curing accelerating effect. When the amount of the curing accelerator is 30 parts by mass or less, the storage stability of the compound tends to improve. However, even if the blending amount and content of the curing accelerator are outside the above range, the effects of the present disclosure can be obtained.

In the resin composition, the curing accelerator exists either in the structure when mixed with the epoxy resin and phenol resin, in the structure reacted with the epoxy resin and/or phenol resin, or as a mixture, and the structure is , nuclear magnetic resonance (NMR), and other methods.

(other ingredients)
The resin composition may contain components other than the above-mentioned epoxy resin, phenol resin, and curing accelerator, if necessary. Examples of other components include resins other than those mentioned above, coupling agents, elastomer modifiers, fillers, flame retardants, and the like.

(coupling agent)
A coupling agent may be added to the compound in order to improve the adhesion between the resin composition of the compound and the rare earth magnet powder. As coupling agents, known coupling agents such as silane compounds such as epoxysilane, mercaptosilane, aminosilane, alkylsilane, ureidosilane, and vinylsilane, titanium compounds, aluminum chelates, and aluminum/zirconium compounds are used. Can be mentioned.

(elastomer modifier)
The elastomer modifier may be added to the compound in order to increase the adhesion between the resin composition of the compound and the rare earth magnet powder, to toughen the resin composition, and to reduce the internal stress of the resin component. Examples of elastomer modifiers include liquid rubber modifiers, rubber particle size modifiers, core-shell particle size modifiers, silicone modifiers, and urethane prepolymer modifiers.

(filler)
Fillers may be added to the compound to improve water absorption, dimensional stability, chemical resistance, mechanical strength, thermal expansion coefficient, and the like. Examples of fillers include silica, calcium carbonate, kaolin clay, titanium oxide, barium sulfate, zinc oxide, aluminum hydroxide, magnesium hydroxide, talc, and mica.

(Flame retardants)
Flame retardants may be incorporated into the compound for environmental safety, recyclability, processability, and low cost. Examples of the flame retardant include brominated flame retardants, scale flame retardants, hydrated metal compound flame retardants, silicone flame retardants, nitrogen-containing compounds, hindered amine compounds, organometallic compounds, and aromatic engineering plastics.

[Rare earth magnet powder]
The rare earth magnet powder used in the compound of this embodiment is not particularly limited as long as it is a rare earth magnet powder. Examples of the rare earth magnet powder include samarium-cobalt rare earth magnet powder, neodymium iron boron rare earth magnet powder, and samarium iron nitrogen rare earth magnet powder. Among these, neodymium iron boron rare earth magnet powder is particularly preferred since the effects of the present disclosure can be easily obtained.

Rare earth magnet powder is manufactured, for example, by a rapid solidification method. In the rapid solidification method, the molten magnetic alloy is discharged onto the surface of a rotating water-cooled roll to rapidly cool and solidify the molten magnetic alloy, thereby producing a rapidly solidified alloy. Then, rare earth magnet powder is produced by pulverizing the rapidly solidified alloy. Alternatively, rare earth magnet powder produced by HDDR (Hydrogenation Disproportionation Desorption Recombination) method may be used.

The shape of each particle of a suitable rare earth magnet powder is preferably a flat shape (for example, the aspect ratio of the powder particle=minor axis/long axis is 0.3 or less). Examples of such powders include Ti-containing nanocomposite magnet powders described in International Publication No. 2006/064794 pamphlet and International Publication No. 2006/101117 pamphlet, rare earth-based powders described in US Patent No. 4802931, etc. Examples include rapidly solidified alloy powder. When rare earth magnet powder having a flat shape is used in a rare earth bonded magnet compound, the rare earth magnet powder is layered in a relatively orderly manner during compression molding. This makes it difficult for voids and resin pools to form between the rare earth magnet powders, making it easier to densely pack the rare earth magnet powders. Therefore, it is preferable that the rare earth magnet powder has a flat shape.

The particle size of the rare earth magnet powder is preferably 20 to 300 μm, more preferably 40 to 250 μm, accounting for 80% by mass or more of the total. In this specification, the particle size of the rare earth magnet powder is a value measured using a low-tap type sieve shaker (manufactured by Iida Seisakusho Co., Ltd.).

The content of rare earth magnet powder in the compound is 90% by mass or more and less than 100% by mass, 93% by mass or more and 99.5% by mass or less, 94% by mass or more and 99.5% by mass or less, based on the total solid content of the compound. Alternatively, it may be 96% by mass or more and 99.5% by mass or less. As the content of rare earth magnet powder increases, the relative magnetic permeability of the compound tends to increase. On the other hand, as the content of rare earth magnet powder increases, the fluidity of the compound tends to decrease. The content of the rare earth magnet powder in the compound may be translated into the filling rate of the rare earth magnet powder in the compound. The filling factor of the rare earth magnet powder in the compound may be translated as the space factor of the rare earth magnet powder in the compound. The content of the resin composition in the compound is greater than 0 mass% and less than or equal to 10 mass%, 0.5 mass% or more and less than or equal to 7 mass%, 0.5 mass% or more and less than or equal to 6 mass%, based on the mass of the entire compound. Alternatively, it may be 0.5% by mass or more and 4% by mass or less.

In a preferred embodiment, the resin composition in the compound coats the rare earth magnet powder particles with a coverage of 90% or more. If the coverage is less than 90%, particles of the rare earth magnet powder that are not covered with the resin composition will come into contact with each other and become electrically conductive, increasing the probability that a high electrical resistance value will not be obtained. The upper limit of coverage is 100%.

The compound described above is manufactured by the method for manufacturing a rare earth bonded magnet compound according to the present embodiment, which will be described below.

<Compound manufacturing method>
In the method for manufacturing a rare earth bonded magnet compound of the present embodiment, first, an epoxy resin, a phenol resin, a curing accelerator, and other components as necessary are blended to produce a resin composition (blending step). Also, prepare rare earth magnet powder. Next, after diluting the resin composition with a solvent, the rare earth magnet powder and the resin composition diluted with the solvent are mixed in the presence of a substance capable of donating protons to obtain a mixture (mixing step). In the mixing step, part of the solvent may be evaporated (dryed) during mixing. Further, when the substance capable of donating protons is a liquid, a part of the substance capable of donating protons may be volatilized (drying) in the mixing step. Thereafter, the mixture is dried (drying process), and if necessary, the dried product is crushed into a desired size (crushing process), thereby forming the rare earth magnet powder and the resin composition that coats the rare earth magnet powder. A compound for a rare earth bonded magnet can be produced containing the following.

The solvent used in the mixing step is a solvent that can dissolve the epoxy resin, phenol resin, and hardening accelerator. Furthermore, in the mixing step, a substance capable of donating protons (also referred to herein as a "proton donor") is used together with the solvent. In the mixing step, the amount of proton donor added is 1 to 10% by mass based on the total amount of solvent and proton donor.

From the viewpoint of workability, the solvent is preferably a volatile organic solvent that becomes a gas at room temperature. Examples of solvents that can be suitably used include acetone, methyl ethyl ketone, methyl isobutyl ketone, benzene, toluene, and xylene. Among these, methyl ethyl ketone is preferred from the viewpoint of safety and ease of handling. These may be used alone or in combination of two or more.

Examples of proton donors include water, benzoic acid, phthalic acid, acetic acid, and the like. As the proton donor, water is particularly preferred from the viewpoint of being soluble in solvents and having low reactivity with epoxy resins. These may be used alone or in combination of two or more. Note that in this specification, a substance that has the properties of both a solvent that can dissolve an epoxy resin, a phenol resin, and a hardening accelerator, and a substance that can donate protons is classified as a substance that can donate protons.

The amount of the proton donor added in the mixing step is 1 to 10% by mass based on the total amount of the solvent and the proton donor, but may be 2 to 8% by mass, and may be 4 to 6% by mass. There may be. When the amount of the proton donor added is within the above range, the mechanical strength of the rare earth bonded magnet using the obtained compound can be improved. If the amount of the proton donor added is less than 1% by mass, the effect of improving the mechanical strength of the rare earth bonded magnet will not be sufficiently achieved, and if it exceeds 10% by mass, it will hinder the dissolution of the epoxy resin and phenolic resin, It may not be possible to uniformly coat the resin component onto the magnet powder.

The solvent is capable of dissolving the mixed material of epoxy resin, phenol resin, and curing accelerator blended in the composition ratio constituting the compound at a concentration of 10% by mass or more, 8% by mass or more, or 6% by mass or more. It is preferable. Thereby, it is easy to uniformly coat the rare earth magnet powder with the resin component, and a homogeneous compound tends to be easily obtained.

In the mixing step, the proton donor may be used as a solution in which the proton donor is dissolved in a solvent in advance, or may be added separately from the solvent. When adding the proton donor separately from the solvent, the proton donor may be added after diluting the resin composition with the solvent and before adding the rare earth magnet powder; The proton donor may be added after adding the rare earth magnet powder. In either case, the materials may be mixed to some extent before the proton donor is added, but are further mixed after the proton donor is added.

The temperature during mixing in the mixing step is not particularly limited, but may be 20 to 80°C or 30 to 60°C from the viewpoint of uniformly dissolving in a predetermined time and preventing the reaction of the epoxy resin from proceeding. .

After the mixing step, a drying step is performed to dry the obtained mixture. In the drying step, the solvent contained in the mixture is removed. Furthermore, at least a portion of the proton donor may be removed in the drying step. The drying step may be performed at room temperature without heating, or may be performed while heating. The drying temperature in the drying step may be 20 to 80°C, 30 to 80°C, 40 to The temperature may be 60°C. Further, the drying step may be performed under reduced pressure from the viewpoint of sufficiently reducing residual volatile matter. When drying under reduced pressure, for example, a vacuum dryer can be used.

<Manufacturing method of rare earth bond magnet>
The method for manufacturing a rare earth bonded magnet according to the present embodiment includes a step of manufacturing a compound using the method for manufacturing a compound described above, and a molding step of compression molding the compound. Further, the method for manufacturing a rare earth bonded magnet of the present embodiment may further include a heat treatment step of heat treating the compression molded body obtained in the molding step.

In the step of compression molding the compound (molding step), the compound is compression molded preferably at a pressure of 500 to 2,500 MPa, more preferably at a pressure of 1,400 to 2,000 MPa to produce a compression molded product of the compound. When the pressure when compressing the compound is 500 to 2500 MPa, the rare earth bonded magnet can be made dense, practical magnetic properties can be obtained, and the burden on the mold can be reduced. The density of the compression molded body is preferably 75% or more and 86% or less, more preferably 80% or more and 86% or less of the true density of the rare earth magnet powder. When the density of the compression molded compound is 75% or more and 86% or less, a rare earth bonded magnet with good magnetic properties and high mechanical strength can be manufactured.

In the step of heat treating the compression molded body (heat treatment step), the compression molded body is heat treated preferably at a temperature of 150 to 400°C, more preferably at a temperature of 175 to 350°C. When the compression molded body is heat-treated at a temperature of 150 to 400°C, it is possible to produce a rare earth bonded magnet in which the resin composition is sufficiently cured. Further, the heat treatment time is preferably 1 minute to 4 hours, more preferably 5 minutes to 3 hours.

<Rare earth bond magnet>
The rare earth bonded magnet of this embodiment is manufactured by the method of manufacturing a rare earth bonded magnet of this embodiment.

In the rare earth bonded magnet, the glass transition temperature of the cured resin composition formed by curing the resin composition is preferably 150°C or higher, more preferably 175°C or higher, and still more preferably 200°C or higher. When the glass transition temperature of the cured resin composition formed by curing the resin composition in the rare earth bonded magnet is 150° C. or higher, a rare earth bonded magnet with excellent heat resistance can be obtained. Note that the glass transition temperature is, for example, the temperature at which tan δ reaches a peak in dynamic viscoelasticity measurement.

The ratio of the elastic modulus of the rare earth bonded magnet at 150° C. to the elastic modulus of the rare earth bonded magnet at 50° C. is preferably 70% or more, more preferably 80% or more, and still more preferably 90% or more. When the ratio of the elastic modulus is 70% or more, a rare earth bonded magnet with excellent heat resistance can be obtained. In addition, methods for measuring the elastic modulus include a method of measuring a three-point bending test at temperatures of 50 ° C. and 150 ° C., a method of measuring the elastic modulus at 50 ° C. and 150 ° C. by dynamic viscoelasticity measurement, etc. .

The relative density of the rare earth bonded magnet is preferably 70% or more, more preferably 80%, and even more preferably 90% or more of the true density of the rare earth magnet powder. When the relative density of the rare earth bonded magnet is 70% or more of the true density of the rare earth magnet powder, a rare earth bonded magnet having excellent magnetic properties can be obtained. Further, the density of the rare earth bonded magnet is preferably 95% or less of the true density of the rare earth magnet powder.

The crushing strength of the rare earth bonded magnet at a temperature of 120° C. is preferably 100 MPa or more, more preferably 150 MPa, and still more preferably 160 MPa or more. When the crushing strength of the rare earth bonded magnet at a temperature of 120° C. is 100 MPa or more, it is possible to obtain a rare earth bonded magnet with high mechanical strength at high temperatures.

EXAMPLES Hereinafter, the present disclosure will be described in more detail with reference to examples, but the scope of the present disclosure is not limited by the examples shown below.

(Example 1)
In a 500 mL eggplant-shaped flask, add 2.45 g of epoxy resin (salicylaldehyde type epoxy resin, brand name: EPPN-502H, manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent: 168 g/eq), phenol resin (novolac type phenol resin, brand name). : HP-850N, manufactured by Hitachi Chemical Co., Ltd., hydroxyl equivalent: 108 g/eq) 1.55 g, and curing accelerator (tetrabutylphosphonium tetraphenylborate, trade name: PX-4PB, manufactured by Hokuko Chemical Co., Ltd.) 0 .118 g was weighed out and dissolved in 6 g of methyl ethyl ketone (MEK, manufactured by Wako Pure Chemical Industries, Ltd., trade name). After dissolving, 0.3 g of water (4.8% by mass based on the total amount of solvent and proton donor) was added to the flask, and after stirring, 196 g of NdFeB powder (rare earth magnet powder, manufactured by Hitachi Metals, Ltd.) was added to the flask. The mixture was added and mixed for 30 minutes (mixing step). Thereafter, MEK and water were distilled off under reduced pressure using an evaporator at room temperature (25°C). The resulting mixture was spread on a vat and dried in a vacuum dryer at room temperature (25° C.) for 24 hours. The obtained dried product was crushed to obtain a compound having a rare earth magnet powder content (space factor) of 98% by mass.

(Examples 2-3)
A compound was obtained in the same manner as in Example 1 except that the amount of water added in the mixing step was changed to the amount shown in Table 1.

(Example 4)
A compound was obtained in the same manner as in Example 1, except that a biphenyl-type epoxy resin (trade name: YX-4000H, manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 192 g/eq) was used as the epoxy resin.

(Comparative example 1)
A compound was obtained in the same manner as in Example 1 except that 0.3 g of water was not added in the mixing step.

(Comparative Examples 2-3)
A compound was obtained in the same manner as in Example 1 except that the amount of water added in the mixing step was changed to the amount shown in Table 1. However, in Comparative Example 3, the resin precipitated and a uniform compound could not be obtained, making it difficult to produce a rare earth bonded magnet.

<Production of rare earth bonded magnet>
The compounds obtained in the Examples and Comparative Examples were filled into a predetermined mold and molded using a hydraulic press at a molding pressure of 2000 MPa to produce a cylindrical molded body with a diameter of 11.3 mm and a height of 8 mm. Thereafter, the molded body was heat-treated in a dryer at a temperature of 200° C. for 10 minutes to harden the resin composition in the compound, and a rare earth bonded magnet (cylindrical test piece) was produced. The obtained rare earth bonded magnets had the same magnetic flux density and coercive force in all Examples and Comparative Examples.

<Measurement of crushing strength>
Using a universal compression testing machine (AG-10TBR, manufactured by Shimadzu Corporation), compressive pressure was applied from the height direction of the cylindrical test piece at a crosshead speed of 0.5 mm/min in the atmosphere, and the cylindrical test was performed. The maximum value of the compression pressure when the piece broke was defined as the crushing strength (MPa). The crushing strength was measured using a cylindrical test piece at room temperature (25° C.) and heated at 120° C. for 10 minutes in a constant temperature bath. The results are shown in Table 1.

According to the method for producing a compound for a bonded rare earth magnet according to the present disclosure, a compound for a bonded rare earth magnet that can produce a bonded rare earth magnet having excellent mechanical strength can be obtained, and its industrial value is high.

Claims (7)

A resin composition containing an epoxy resin, a phenol resin, and a curing accelerator and rare earth magnet powder are mixed in the presence of a solvent capable of dissolving the epoxy resin, the phenol resin, and the curing accelerator, and a substance capable of donating protons. a mixing step to obtain a mixture;
a drying step of drying the mixture;
Equipped with
A method for producing a compound for a rare earth bonded magnet, wherein the amount of the proton-donating substance added in the mixing step is 1 to 10% by mass based on the total amount of the solvent and the proton-donating substance. The manufacturing method according to claim 1, wherein the curing accelerator includes a phosphorus-containing compound. The manufacturing method according to claim 1 or 2, wherein the curing accelerator contains at least one of a borate salt and a borane compound. The production method according to any one of claims 1 to 3, wherein the substance capable of donating protons contains at least one selected from the group consisting of water, benzoic acid, phthalic acid, and acetic acid. The manufacturing method according to any one of claims 1 to 4, wherein the rare earth magnet powder includes neodymium iron boron rare earth magnet powder. The manufacturing method according to any one of claims 1 to 5, wherein in the drying step, the mixture is dried at a temperature of 20 to 80°C. A step of manufacturing a compound for a rare earth bonded magnet by the method for manufacturing a compound for a bonded rare earth magnet according to any one of claims 1 to 6, and a molding step of compression molding the compound for a rare earth bonded magnet, Method for manufacturing rare earth bonded magnets.