JP2002033209A - Rare earth bonded magnet composition, rare earth bonded magnet and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rare earth element which can be cured at a low temperature, has high fluidity, and can be filled into a mold without impairing conventional moldability, magnetic properties, mechanical strength, heat resistance, corrosion resistance, etc. System bond magnet,
A composition for a rare earth-based bonded magnet capable of obtaining such a magnet and a method for producing a rare-earth bonded magnet are provided. SOLUTION: (A) A binder resin comprising a polymerizable compound in which 10% or more and less than 90% of epoxy groups in an epoxy compound are partially vinyl-esterified with an unsaturated monobasic acid, (B) a thermal radical polymerization initiator And (C) an epoxy curing agent, and (D) a rare earth alloy powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a composition for a rare earth-based bonded magnet, a rare earth-based bonded magnet, and a method for producing the same.

[0002]

2. Description of the Related Art Rare earth magnets have been applied in a wide range of fields from home appliances, communications, audio equipment, medical equipment and general industrial equipment due to their excellent magnetic properties. Among them, bonded magnets are superior in moldability compared to sintered magnets because they combine a binder resin with alloy powder, can be made into complex shapes or can be integrally molded, are resistant to cracking, and have dimensions. Due to advantages such as good accuracy, it has been particularly noticed in recent years, and its industrial use has been widened. Above all, HDD, CD
-The market for high magnetic property bonded magnets using Nd-Fe-B based rare earth magnet materials for small motors such as spindle motors and stepping motors for ROMs, STPs, etc. is growing rapidly.

[0003] Rare-earth bonded magnets are manufactured by pressing a mixture of a rare-earth alloy powder and a binder resin into a desired magnet shape, and the molding methods include a compression molding method and an injection molding method. And an extrusion molding method. For example, in a compression molding method, a rare earth alloy powder and a thermosetting binder resin are mixed, a compound as a mixture thereof is filled in a press mold, and the mixture is compression molded under a predetermined pressure to form a molded body. And then heating to cure the binder resin to produce a magnet. The compression molding method is advantageous in improving the magnetic properties because the molding is possible with a smaller amount of the binder resin than other methods.

[0004] Binder resins used in the compression molding process include epoxy resins, phenol resins,
Examples include thermosetting resins such as urea resins, melamine resins, polyimide resins, silicone resins, unsaturated polyester resins, and polyurethane resins, which are used alone or in combination of two or more. At present, epoxy resins are most commonly used in consideration of workability, fluidity during filling, mechanical strength of magnets, and the like. Conventionally, as a device that meets the conflicting demands of improving the magnetic properties and mechanical strength of a magnet, a binder resin that can maintain a high mechanical strength even if the mixing ratio of the resin is kept low has been selected. , And hardening conditions are set strictly.

[0005]

However, when the Nd-Fe-B-based rare earth alloy powder showing a large growth rate in the market is used as the magnet material, the deterioration of the magnetic properties due to the heat history due to the high temperature at the time of thermosetting. Concerns have been raised that the binder resin should be cured at as low a temperature as possible. When a conventional epoxy resin is cured at a low temperature below 150 ° C,
Since the required mechanical strength of the magnet cannot be obtained due to insufficient curing, the curing temperature is 150 to 200
The temperature is set to a high temperature of ° C., and the excellent magnetic properties of the angle Nd—Fe—B are not sufficiently exhibited. Also,
As magnets have become smaller and thinner, there has been an increasing demand for improved fluidity and fillability in a mold for a bonded magnet compound obtained by kneading a binder resin with magnet powder. If the fluidity of the bonded magnet compound is poor, the compound may harden during storage or distribution and may not be usable.On the other hand, since the filling property of the mold is poor, not only can the weighing by directly filling the mold be impossible, In a severe case, there is a problem that the mold is broken due to uneven thickness, and the magnetic properties of the resulting bonded magnet vary.

Accordingly, an object of the present invention is to provide a rare earth type bond which can be cured at a low temperature and has high fluidity and filling properties without impairing the conventional moldability, magnetic properties, mechanical strength, heat resistance, corrosion resistance and the like. An object of the present invention is to provide a magnet composition, a rare-earth bonded magnet, and a method for producing the same.

[0007]

Means for Solving the Problems As a result of intensive studies, the present inventors have achieved the above object. That is, the present invention relates to (A) 10% of the epoxy groups in the epoxy compound.
A binder resin comprising a polymerizable compound in which at least 90% is partially vinyl-esterified with an unsaturated monobasic acid,
(B) a thermal radical polymerization initiator, (C) an epoxy curing agent,
And (D) a composition for a rare earth-based bonded magnet comprising a rare earth-based alloy powder.

[0008] The present invention also provides the composition for a bonded rare earth magnet, wherein the softening point of the epoxy compound in the component (A) is 60 ° C or higher.

The present invention also provides the above composition for a bonded rare earth magnet, wherein the epoxy compound in the component (A) is a cresol novolak type epoxy compound.

[0010] The present invention also provides the above composition for a rare earth bonded magnet, wherein the epoxy compound in the component (A) is a phenol novolak type epoxy compound.

The present invention also provides that the epoxy compound in the component (A) is a cresol novolak type or phenol novolak type epoxy compound obtained by subjecting a maximum of 30% of the epoxy group to a polyaddition reaction with a bisphenol compound. It is another object of the present invention to provide a rare earth-based bonded magnet composition described above.

The present invention also provides the above composition for a bonded rare earth magnet, wherein the amount of the component (A) is 1 to 10% by weight based on the composition for a bonded rare earth magnet. Is what you do.

Further, according to the present invention, the component (D) comprises Nd-Fe
It is another object of the present invention to provide the composition for a rare earth-based bonded magnet, wherein the composition is a -B-based alloy powder.

In the present invention, the component (D) is preferably Sm-Co
It is another object of the present invention to provide the composition for a rare earth-based bonded magnet described above, which is a system-based alloy powder.

The present invention also relates to a method for producing a composition for a bonded rare earth magnet, comprising:
It is an object of the present invention to provide a method comprising the steps of dispersing the component and the component (C) in an organic solvent in advance, kneading the obtained dispersion with the component (D), and removing the solvent.

The present invention also provides a composition obtained by the above-mentioned production method, which is molded by a cold or warm compression molding method at a molding pressure of ^{2 to} 8 t / cm ² at a temperature of 100 to 200 ° C. An object of the present invention is to provide a method for producing a rare-earth bonded magnet including a step of curing the composition by heating.

The present invention also provides a rare earth bonded magnet obtained by the above-mentioned manufacturing method.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

(A) Binder Resin The (A) binder resin used in the present invention is a polymerizable polymer in which 10% or more and less than 90% of epoxy groups in an epoxy compound are partially vinyl-esterified with an unsaturated monobasic acid. It is a compound and can be obtained by adding a predetermined amount of unsaturated monobasic acid to an epoxy compound by a vinyl esterification reaction. Manufacturing conditions and the like may be selected according to a known method. As the epoxy compound which is one of the raw materials in the component (A), cresol having a large number of epoxy groups as a crosslinking point represented by the following structural formula (I) is used in order to obtain mechanical strength as a rare-earth bonded magnet described below. Those which are novolak-type and / or phenol novolak-type epoxy compounds are preferred.

[0020]

Embedded image

(Wherein, Ar represents a divalent aromatic phenol residue having a substituent selected from a hydrogen atom, a halogen atom or a hydrocarbon having 1 to 12 carbon atoms which may contain an ether bond)

As the epoxy compound, commercially available epoxy compounds can be used. For example, in the case of the cresol novolak type, epicron N660, N670, N680, N690, N69 is used.
5, Epicoat E180H65 (trade name, manufactured by Yuka Shell Epoxy), EOCN102S, EOCN103S, EOCN
104S, EOCN1020 (trade name, manufactured by Nippon Kayaku) and ESCN195X (trade name, manufactured by Sumitomo Chemical Co., Ltd.), and phenol novolak type, Epicron N770, N775,
N865 (trade names, both manufactured by Dainippon Ink and Chemicals)
And Epicoat E157H70 (trade name, made of Yuka Shell Epoxy), and Epicoat E1 for other novolak types
032 (trade name, made of Yuka Shell Epoxy), EOCN5
01 (manufactured by Nippon Kayaku) and DCE400 (manufactured by Sanyo Kokusaku Pulp).

The softening point of the epoxy compound is 60 ° C.
Or more, more preferably 80 ° C. or more. When the softening point is lower than 60 ° C., the fluidity of the compound, that is, the filling property into a mold, and the storage stability of the compound tend to be inferior. To improve the softening point of the epoxy compound,
It is preferable that a phenol compound is previously subjected to a polyaddition reaction with an epoxy group of the epoxy compound. Epoxy compounds suitable in the present invention have a maximum of 30
% Of a phenolic novolak type or a phenol novolak type epoxy compound obtained by performing a polyaddition reaction with a bisphenol compound. As bisphenol compounds,
Bisphenol A and the like are preferably used. Specific polyaddition reaction conditions and the like are known, but there is no problem even if the reaction is carried out using an alkali as a catalyst, and the following solvents are preferably used alone or in combination for the purpose of improving the homogeneity of the reaction. can do.

Specific examples of the solvent include ketones such as methyl ethyl ketone and MIBK; aromatic hydrocarbons such as benzene, toluene, xylene and tetramethylbenzene; glycol ethers such as methyl cellosolve acetate and butyl cellosolve acetate; Esters such as butyl acetate and acetic acid ester compounds of glycol ethers; alcohols such as ethanol, propanol, ethylene glycol and propylene glycol; and the like, having good compatibility with epoxy compounds and having a boiling point of 100 to 160 ° C. Those in the range are preferred. Also,
Reactive solvents used in the following vinyl ester reaction can also be preferably used.

On the other hand, unsaturated monobasic acids are monobasic acids having one carboxyl group and one or more polymerizable unsaturated bonds, and specific examples include acrylic acid, methacrylic acid, crotonic acid, Cinnamic acid, sorbitan acid, acrylic acid dimer, monomethyl malate, monopropyl malate,
Carboxyl group-containing polyfunctional which is a reaction product of monobutyl maleate, a polyfunctional (meth) acrylate having one hydroxyl group and one or more (meth) acryloyl groups and a dibasic acid among polybasic anhydrides (Meth) acrylates and the like may be mentioned, and these may be used alone or in combination of two or more. Among them, methacrylic acid and the like can be preferably used.

There are many catalysts used for the vinyl esterification reaction between the epoxy compound and the unsaturated monobasic acid, but when roughly classified, tertiary amines, quaternary ammonium salts,
Phosphines, metal salts and the like. For example, Li methacrylate, potassium carbonate, magnesium oxide, zinc chloride,
Boron fluoride, aluminum chloride, tin chloride, N, N-benzyldimethylamine, N, N-dimethylphenylamine,
Triethylamine, trimethylbenzylammonium chloride, N-phenylnaphthylamine, N, N-dimethylethanolamine, dimethylaminoacrylate,
Examples include triphenylphosphine, tributylphosphine, vanadium chloride, phenothiazine, chromium oxide, chromium organic acid salts, iron chloride, and iron hydroxide. It is important to select a catalyst according to the type of the epoxy compound and the unsaturated monobasic acid so that there are few side reactions other than vinyl esterification and the vinyl ester can be smoothly converted to the end point of the reaction. Among them, tertiary amines and organic acid chromium salts are preferred as the vinyl esterification catalyst, and the amount used is usually in the range of 0.05 to 2% by weight based on the resin.

The vinyl esterification reaction can be performed without using a solvent, but may be diluted with a solvent such as xylene or toluene. For dilution, the following polymerizable monomers may be used. For example, styrene, vinyl toluene, vinyl based such as methacrylic acid; diallyl phthalate,
Allyls such as diallyl isophthalate and triallyl isocyanurate; phenoxyethyl (meth) acrylate, 1,6-hexanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, 2-hydroxyethyl (meth) acrylate and the like And acrylic acid esters such as vinylpyrrolidone and phenylmaleimide.

In some cases, a polymerization inhibitor is used to stabilize the storage of the product. As the polymerization inhibitor, for example,
p-benzoquinone, anthraquinone, naphthoquinone, phenanthraquinone, p-xyloquinone, p-toluquinone, 2,6-dichloroquinone, 2,5-diphenyl-p
-Benzoquinone, 2,5-diatoquinone-p-benzoquinone, 2,5-dicaproxy-p-benzoquinone,
Quinones such as 2,5-diasiloxy-p-benzoquinone; hydroquinone, pt-butylcatechol,
5-di-t-butylhydroquinone, mono-t-butylhydroquinone, monomethylhydroquinone, 2,5-
Hydroquinones such as di-t-amylhydroquinone;
Phenols such as di-t-butylparacresol, hydroquinone monomethyl ether, α-naphthol; organic and inorganic cupric acids such as copper naphthenate; phenyl-β-naphthylamine, parabenzylaminophenol, di-β
Amines such as naphthylparaphenylenediamine, dibenzylhydroxylamine, phenylhydroxylamine, diethylhydroxylamine; dinitrobenzene,
Nitro compounds such as trinitrotoluene and picric acid; oximes such as quinone dioxime and cyclohexanone oxime; phenothiazine and cupron. Among them, hydroquinone and the like can be preferably used.
The amount of polymerization inhibitor used is usually 0.005 to
0.05% by weight.

As described above, the vinyl esterification of the epoxy group in the epoxy compound with the monobasic acid is in the range of 10% or more and less than 90% with respect to the epoxy group. To ensure the mechanical strength of the binder, preferably 20%
The content is preferably from 80% to 80%, more preferably from 20% to 50%. When the vinyl esterification is less than 10%, the number of crosslinking points due to a radical reaction is small, which is disadvantageous in low-temperature curing. When the vinyl esterification is 90% or more,
The number of crosslinking points due to epoxy groups is small, and the mechanical strength is low. The amount of the component (A) is 1 to 10% by weight, preferably 1 to 5% by weight, based on the composition of the rare-earth bonded magnet.

(B) Thermal Radical Polymerization Initiator As the (B) thermal radical polymerization initiator used in the present invention, an organic peroxide and / or an azobis-based curing agent which is a radical polymerization initiator is useful. For example, as the organic peroxide, benzoyl peroxide, lauroyl peroxide, methyl isobutyl ketone peroxide, t-butyl peroxide benzoate, dicumyl peroxide, and the like can be used, and may be appropriately selected and used. As the azobis-based curing agent, 2,2-
Azobis [N- (2-propenyl) -2-methylpropionamide], 2,2-azobis (N-cyclohexyl-2-methylpropionamide), 1,1-azobis (cyclohexane-1-carbonitrile), 2, 2-azobis {2-methyl-N- [2- (1-hydroxybutyl)]} propionamide or the like can be used, and may be appropriately selected and used. When lower temperature curing is required, it may be used in combination with various accelerators. (B) The thermal radical polymerization initiator is preferably soluble in a solvent, and the compounding amount is (A)
It can be used in an amount of 0.1 to 10% by weight, preferably 0.5 to 5% by weight, based on the binder resin.

(C) Epoxy curing agent As the (C) epoxy curing agent used in the present invention, for example, a single polyamine type curing agent, a modified polyamine type curing agent, an acid anhydride type curing agent, a polyphenol type curing agent And polymercaptan type curing agents, anionic polymerization type curing agents, cationic polymerization type curing agents, tertiary amines, imidazole and derivatives thereof, organic metal salts, chlorides, organic peroxides and the like. Various curing agents may be used in combination of two or more as necessary. The epoxy curing agent (C) is preferably soluble in a solvent, and the amount thereof is 0.1 to 10% by weight, preferably 0.1 to 10% by weight, based on the binder resin (A).
5 to 5% by weight can be used.

(D) Rare earth alloy powder The (D) rare earth alloy powder used in the present invention includes:
Although not particularly limited, an Nd-Fe-B-based material having high magnetic properties is preferable. The (D) rare earth alloy powder may be any one of a ground magnet powder, an isotropic magnet powder obtained by a liquid quenching method, and an anisotropic magnet powder obtained by a hydrogen treatment method. When an isotropic powder or an anisotropic magnet powder obtained by a hydrogen treatment method is used as a typical example of the alloy powder, which is likely to be deteriorated due to heat history, a further effect can be recognized. As the Nd-Fe-B alloy powder suitably used in the present invention, a commercially available product can be used. For example, isotropic MQP
-B powder (trade name, MAGNEQUENCH IN
TERNATIONAL, INC. And anisotropic MQA-T powder (trade name, manufactured by NEOMET). Generally, the raw powder of Nd—Fe—B rare earth alloy has an average particle size of about 150 μm, and there is no problem in using the powder as it is, but in order to further improve the packing density of the molded product, it is pulverized in advance. However, it is preferable to have an appropriate particle size distribution.

For use at high temperatures, Sm-Co
A system alloy powder can be particularly preferably used. As the alloy is two mainstream Sm-Co ₅ and Sm ₂ -Co _17, specifically, for example, it can be used RCo ₅ (trade name, Sumitomo Metal Mining Co., Ltd.) and the like. The average particle size of the alloy powder is relatively fine, 5 to 10 μm. The component (D) can be used in an amount of 85 to 99% by weight, preferably 92 to 98% by weight, based on the whole composition.

[0034]Other additives Ensuring the fluidity of the composition for a rare earth bonded magnet of the present invention
For this purpose, a lubricant can be added. Specific of lubricant
Examples include stearic acid, oleic acid, palmitin
Acid, linoleic acid, lauric acid, 1,2-oxystearyl
Fatty acids such as carboxylic acid and ricinoleic acid;
Amines such as thearylamine and laurylamine; glyci
, Alanine, aspartic acid, arginine, histidine
Amine acids such as zinc; zinc stearate, potassium stearate
Lucium, barium stearate, aluminum stearate
, Magnesium stearate, zinc laurate,
Calcium laurate, zinc ricinoleate, ricinol
Fatty acids such as calcium phosphate and zinc 2-ethylhexoate
Salts: stearic acid amide, hydroxystearic acid
Fatty acid salts such as amide and palmitic acid amide; Si_ThreeN_Four,
SiC, MgO, Al _TwoO_Three, TiC, Sb_TwoO_ThreeEtc. inorganic
Compound powder; silicone oil, silicone grease, silicone grease
Polysilicon such as corn resin and polysilane coupling agent
Siloxanes; fatty acid esters such as butyl stearate;
Alcohols such as Tylene glycol and stearyl alcohol
Le; paraffin wax, liquid paraffin, polyethylene
Len wax, polypropylene wax, ester wax
Wax, carnauba wax, micro wax, etc.
Cousins and the like. These are usually one or more
Can be used above.

If necessary, a known Si-based, Ti-based or Al-based coupling agent can be added. Typical examples are vinyltriethoxysilane, γ-aminopropyltriethoxysilane, N- (β
-Aminoethyl) -γ-aminopropylmethyldimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, isopropyltriisostearoyl titanate, isopropyltris (dioctylpyrophosphate) titanate, isopropyltri ( N-aminoethyl-aminoethyl) titanate, tetraoctylbis (ditridecylphosphite) titanate, isopropyltrioctanoyl titanate, isopropyltridecylbenzenesulfonyl titanate, acetoalkoxyaluminum diisopropylate, and the like. In general, when a large amount of a titanium-based coupling agent is added, the dispersibility is improved, and as a result, the orientation of the rare-earth alloy powder (D) is significantly improved, and a material having excellent magnetic properties is obtained. On the other hand, when a silicone-based coupling agent is used, there is an effect that (D) the orientation of the rare-earth alloy powder is improved and at the same time the mechanical strength is increased. By mixing these by, for example, a dry method, a wet method, an integral blend method, etc., the resulting rare earth-based bonded magnet not only has a rust-preventing effect on the magnet powder, but also has a (D) rare-earth alloy powder and (A) ) It is expected to be a material that improves the adhesion to the binder resin and has excellent magnetic and mechanical properties.

Further, in order to prevent (D) oxidation (deterioration and alteration) of the rare earth alloy powder and (A) oxidation of the binder resin (produced by the metal component of the rare earth alloy powder acting as a catalyst), the rare earth An antioxidant may be added to the composition for a system-based bonded magnet. This prevents (D) the oxidation of the rare earth alloy powder and contributes to the improvement of the magnetic properties of the magnet, and also contributes to the improvement of the thermal stability at the time of kneading and molding the composition. ) It is a preferable additive for securing good moldability with the amount of the binder resin. As the antioxidant, any antioxidant can be used as long as it can prevent or suppress the oxidation of (D) rare earth alloy powder and the like, for example, an amine compound, an amino acid compound,
A chelating agent that forms a chelating compound for metal ions such as nitrocarboxylic acids, hydrazine compounds, cyanide compounds, and sulfides, particularly Fe components, is preferably used. It goes without saying that the type, composition and the like of the antioxidant are not limited to these. The additive is, for example, for the entire composition of the rare earth-based bonded magnet,
0.1 to 5% by weight is used.

Rare-Earth Bonded Magnet Composition Hereinafter, an example of the method for producing the rare-earth bonded magnet composition of the present invention will be described. After the binder resin (A) is uniformly dissolved in a solvent in advance, (B) a thermal radical polymerization initiator, (C) an epoxy curing agent, and other necessary additives are added thereto. The resin liquid and the (D) rare earth alloy powder are mixed, and the solvent is evaporated while uniformly mixing to obtain a rare earth bonded magnet composition.

The solvent used here may be any solvent such as protic or aprotic as long as it can dissolve the component (A). Specific examples include ethanol and n-propyl alcohol. Alcohols such as isopropyl alcohol, n-butanol and cellosolve; ketones such as acetone, methyl ethyl ketone and cyclohexanone; and hydrocarbon compounds such as tetrahydrofuran, cyclohexane, hexane, heptane, octane, mineral spirits, benzene, toluene and xylene. . It is desirable to select a solvent having a low boiling point because it is desired to dry as quickly as possible. However, for the poorly soluble (A) binder resin, a solvent having a high dissolving ability is selected.
For example, tetrahydrofuran or the like can be used.

The mixer is not particularly limited.
Examples include a ribbon mixer, a V-type mixer, a rotary mixer, a Henschel mixer, a flash mixer, a Nauta mixer, a super mixer, a tumbler, and the like. It is effective to use.

Method for Producing Rare-Earth Bonded Magnet The rare-earth bonded magnet composition obtained as described above may be used to form a rare-earth bonded magnet by compression molding as it is. ) And packing density (bulk density) can be improved by a granulation step. Improving the flowability eliminates uneven filling during filling of the composition, and has the effect of reducing variations in the magnetic properties of the magnet. Further, clogging of the compound in the hopper and the feeder during molding is reduced, and automation is facilitated. On the other hand, by increasing the bulk density, it is possible to produce a molded article having a large thickness with respect to the stroke of the punch when filling the mold during compression molding. The shape of the granulated rare earth-based bonded magnet composition is not particularly limited, and may be spherical, cylindrical, or pulverized, but preferably spherical.

The granulation method is not particularly limited, and may be a wet type or a dry type. For example, a spray dryer method as a spray granulation method, a centrifugal tumbling granulation method as a mixed granulation method, a stirring and mixing granulation method, a flow granulation method, an extrusion granulation method as a forced granulation method, and the like are exemplified. . Specifically, mechano mill, speed kneader, alexander roller compactor, spray dryer, spira coater, tilsonator, granulizer, new melmerizer,
A powder coater, a vertical granulator, a multiplex, or the like is used, but generally, a sieving type is preferably used.

At the time of granulation, a granulating agent, a dispersing agent and the like can be added as required. As the granulating agent, a water-soluble polymer such as polyvinyl alcohol or polybutyl alcohol is used, and as the dispersing agent, sodium polycarboxylate, ammonium polycarboxylate, sodium salt of condensed naphthalene sulfonic acid, condensed naphthalene sulfonic acid, Ammonium salt, cationic surfactant, anionic surfactant, nonionic surfactant, diamine surfactant, polyamine amine surfactant, amide surfactant, ester nonionic surfactant, polyfunctional Ester polymers and the like can be mentioned.

The method for producing a rare-earth bonded magnet is as follows. The obtained rare-earth bonded magnet composition is filled in a mold of a compression molding apparatus, and placed in a magnetic field (for example, an orientation magnetic field of 0.4 to 1.6).
MA / m, orientation direction can be vertical, horizontal or radial)
Alternatively, press molding is performed in the absence of a magnetic field. This compression molding may be either cold molding (molding at room temperature) or warm molding, but is preferably warm molding. That is, when the material temperature at the time of molding is increased to a temperature equal to or higher than the softening temperature of the binder resin (A), particularly by heating the molding die,
The fluidity of the molding material in the mold is improved, and molding with high dimensional accuracy at a low molding pressure becomes possible. In addition, warm forming facilitates forming, and mass-produces a shape with a thin portion such as a link, a flat plate, or a curved plate, or a long and long shape with good and stable shape and dimensions. Can be. In addition, by using warm forming, it is possible to increase the density of the magnet even at a low forming pressure. Furthermore, in warm compacting, the fluidity of the molding material in the mold is improved, the magnetic properties are improved, and (C) the holding power of the rare earth alloy powder during molding is reduced. Since an apparently high magnetic field is applied, the magnetic properties can be improved regardless of the orientation direction.

In the prior art, the molding pressure is increased to 5 t / cm ² or more in order to improve the formability in compression molding, reduce the porosity in the magnet, and increase the density, and 8 t in order to further increase the density. / cm ² had to be increased. Therefore, the size of the compression molding machine becomes large, and the mold becomes severely worn. Further, there is a disadvantage that molding is disadvantageous in a magnetic field, and there is a problem that molding is inferior in ease. Further, even if the molding pressure is increased to some extent, there is a limit in reducing the porosity if the state of the molding composition and the manufacturing conditions are inappropriate. If the composition for a rare earth-based bonded magnet of the present invention is used, the molding pressure is 2 to 2.
Molding can be performed in the range of 8 t / cm ² , and a rare-earth bonded magnet having a sufficiently high density can be obtained even at a molding pressure of 5 t / cm ² or less.

The component (A) is cured by subjecting the molded article thus formed to a heat treatment.
Nd-Fe- having higher magnetic properties than m-Co alloy
B-based alloys have a large temperature coefficient, and their magnetic properties drop sharply at high temperatures. It is a major issue to lower the curing temperature (epoxy resin) which requires the current temperature of 150 ° C. or higher as much as possible. In the present invention, the thermosetting temperature is set at 10
Even if the temperature is lowered to 0 ° C., a rare-earth bonded magnet having sufficient mechanical strength can be obtained. Thereby, Nd-Fe-B
The system alloy powder is less likely to be degraded by heat, and it is possible to produce a higher performance rare earth bonded magnet. Suitable curing temperatures are between 100 and 200C.

Finally, the compact is magnetized in a magnetic field to obtain a rare-earth bonded magnet. Magnetization is performed by a commonly used method, for example, an electromagnet that generates a static magnetic field, a condenser magnetizer that generates a pulsed magnetic field, or the like. The magnetic field strength for sufficiently magnetizing is preferably 1.2 M
A / m or more, more preferably 2.4 MA / m or more.

[0047]

The binder resin used in the composition for a bonded rare earth magnet of the present invention comprises (A) a polymerizable compound in which 10% or more and less than 90% of epoxy groups in the epoxy compound are partially vinyl-esterified. However, while maintaining superior mechanical strength compared to currently used epoxy resin,
Since the curing temperature is relatively low, it is useful for (D) preventing deterioration of the rare earth alloy powder, and is particularly useful for anisotropic magnet powder having excellent magnetic properties, which will be greatly expected in the future. Further, since it shows the same heat resistance as epoxy resin, it is also promising as a binder for Sm-Co based bonded magnets. Since the binder resin (A) of the present invention is solid, a highly stable bonded magnet can be obtained without concern about volatility and the like. Further, the composition for a rare earth-based bonded magnet of the present invention has no adhesiveness to the composition itself, and exhibits good fluidity and workability.
It is useful as a rare-earth bonded magnet for a wide range of products and equipment, including medical equipment and general industrial equipment.

[0048]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples.

(Synthesis Example 1) 33.9 g of xylene was charged into a 0.5-liter four-neck separable flask equipped with a stirrer, a thermometer, a cooling condenser, a dropping device, and an inert gas inlet tube. A cresol novolak-type epiclone N-695 (trade name, manufactured by Dainippon Ink and Chemicals, epoxy equivalent 220 g / eq, softening point 95) used as an epoxy compound while heating and stirring at a temperature of 0 ° C.
(° C.) 214 g was added and dissolved. After complete dissolution,
0.1 g of hydroquinone as a polymerization inhibitor and 1.2 g of chromium naphthenate previously dissolved in 6.8 g of xylene as a polymerization initiation catalyst were added over 15 minutes, followed by uniform stirring. After a further 15 minutes, 42.7 g of methacrylic acid are added over 30 minutes, but at the same time air blowing is started.
Next, the reaction temperature was raised to 130 to 135 ° C., the temperature was maintained for about 3 hours, and the reaction was continued until the acid value became 4 or less. The solvent was removed from the obtained resin by vacuum drying. The melting point of the resin was 88 ° C.

(Synthesis Example 2) 241.5 g of xylene was placed in the same 1-liter four-neck separable flask as in Synthesis Example 1.
And 535 g of Epicron N-680 (trade name, manufactured by Dainippon Ink and Chemicals, epoxy equivalent 210 g / eq, softening point 85 ° C.), which is a cresol novolak type, used as an epoxy compound while heating and stirring at 130 ° C. After dissolving, then 28.5 g of bisphenol A
Was added and dissolved. After complete dissolution, once set the flask temperature to 8
The temperature was lowered to 0 ° C. or lower, 0.25 g of triethylamine (TEA) used as a catalyst was added, and the temperature was raised to 130 ° C. again. After a lapse of 5 hours, the bubble viscosity was measured, and the reaction was terminated when a constant point was reached. The softening point of the product was 95 ° C. This product was converted to a solid content of 214
g, transferred to another flask and heated to 110 ° C. After the temperature became constant, 0.1 g of hydroquinone as a polymerization inhibitor and 1.2 g of chromium naphthenate previously dissolved in xylene as a polymerization initiation catalyst were added over 15 minutes, followed by uniform stirring. After 15 minutes, 36.5 g of methacrylic acid
Was added over 30 minutes, and air blowing was started at the same time. Then, the reaction temperature was further increased to 130 to 135 ° C., and the temperature was maintained for about 3 hours. When the acid value became 4 or less, the reaction was terminated. The obtained resin was similarly dried in a vacuum to remove the solvent. The melting point of the resin was 92 ° C.

(Synthesis Example 3) A phenol novolak-type epicron N-775 (trade name, manufactured by Dainippon Ink and Chemicals, epoxy equivalent 190 g / epoxy compound) was used as an epoxy compound.
eq, softening point of 75 ° C.)
Is the same as The softening point of the obtained resin was about 73 ° C.

(Synthesis Example 4) All procedures were the same as in Synthesis Example 1 except that the amount of methacrylic acid, which is an unsaturated monobasic acid used for vinyl esterification, was reduced to 21 g. The softening point of the obtained resin was 93 ° C.

(Comparative Synthesis Example 5) The amount of methacrylic acid which is an unsaturated monobasic acid used for vinyl esterification is 7.5.
Except for g, all are the same as in Synthesis Example 1. The softening point of the obtained resin was 95 ° C.

(Comparative Synthesis Example 6) The amount of methacrylic acid which is an unsaturated monobasic acid used for vinyl esterification was 84.
Except for 3 g, all are the same as Synthesis Example 1. The softening point of the obtained resin was 87 ° C.

Example 1 As a binder resin, 3 parts by weight of the partially vinyl esterified epoxy resin of Synthesis Example 1 was weighed and completely dissolved in 20 parts by weight of acetone, and then t-butyl was used as a thermal radical polymerization initiator. Perbutyl Z, a peroxybenzoate (trade name, manufactured by NOF Corporation) 0.0
6 parts by weight and 0.05 parts by weight of 2E4MZ (trade name, manufactured by Shikoku Chemicals) as an imidazole derivative-based epoxy curing agent were added. Then, MQP-B powder, which is an isotropic Nd-Fe-B alloy powder (trade name, MAGNEQUA)
ENCH INTERNATIONAL, INC. Made)
100 parts by weight were added to the above solution, mixed with stirring, and then depressurized (10 ^-2 kPa) at room temperature to completely evaporate the solvent acetone to obtain a rare earth-based bonded magnet composition.

The composition for a rare earth-based bonded magnet obtained above was supplied into a press die, and a molding surface pressure of 5 t / cm ² was applied at room temperature.
To obtain a die-shaped molded body of 10 mm long × 10 mm wide × 10 mm. Then, the sample is placed in the atmosphere 120.
Heat treatment was performed at 30 ° C. for 30 minutes to cure the binder resin to obtain a rare-earth bonded magnet, which was used as a sample for measurement.

Example 2 The binder resin was the same as Example 1 except that the partially vinyl esterified epoxy resin of Synthesis Example 2 was used.

(Example 3) The binder resin was the same as Example 1 except that the partially vinyl esterified epoxy resin of Synthesis Example 3 was used.

Example 4 As the binder resin, the same procedure as in Example 1 was carried out except that the partially vinyl esterified epoxy resin of Synthesis Example 4 was used.

Example 5 This is an example in which MQA-T powder (trade name, manufactured by MEOMET), which is an anisotropic Nd—Fe—B alloy powder, is used as the rare earth alloy powder.
As a molding method, first, the rare earth-based bonded magnet composition obtained in the same manner as in Example 1 was placed in a polypropylene container, and heated in a water bath heated to about 60 ° C. for 30 minutes. 1.5 MA / m while keeping this composition in a container
After magnetizing by applying a magnetic field of, this composition was disintegrated through a resin roll. The crushed composition was supplied into a press mold, and a transverse magnetic field of 1.6 MA / m was applied at room temperature. Then, the composition was press-molded at a molding surface pressure of 5 t / cm ^2. A shaped product was obtained. Next, the sample was heat-treated in the air at 120 ° C. for 30 minutes to cure the binder resin, thereby obtaining a measurement sample of this example.

Example 6 Sm was used as a rare earth alloy powder.
-Co based alloy powder, RCo ₅ alloy (manufactured by Sumitomo Metal Mining)
All are the same as Example 1 except for using.

(Example 7) The surface pressure of the press molding pressure was 2 t /
Except for molding in cm ² , all were the same as Example 1.

Comparative Example 1 The procedure was the same as in Example 1 except that the imidazole derivative epoxy curing agent 2E4MZ (trade name, manufactured by Shikoku Chemicals) was not used.

Comparative Example 2 The same procedure as in Example 1 was conducted except that the thermal radical polymerization initiator Perbutyl Z (trade name, manufactured by NOF Corporation) was not used.

(Comparative Example 3) The binder resin was the same as Example 1 except that the partially vinyl esterified epoxy resin of Comparative Synthetic Example 5 was used.

(Comparative Example 4) The binder resin was the same as Example 1 except that the vinyl esterified epoxy resin of Comparative Synthesis Example 6 was used.

(Comparative Example 5) A commercially available cresol novolak-type epicron N-695 as a binder resin
(Product name, manufactured by Dainippon Ink and Chemicals, epoxy equivalent 22
(0 g / eq, softening point 95 ° C.) 3 parts by weight, and the same as Example 1 except that 0.05 parts by weight of 2E4MZ was added as an imidazole derivative-based epoxy curing agent to the binder resin.

Comparative Example 6 Epicoat 828 (trade name, commercially available bisphenol A type) as a binder resin
Oiled shell epoxy, epoxy equivalent 188g / eq)
All were the same as Comparative Example 5 except that was used. The normal state of Epicoat 828 is a liquid.

Evaluation of Fluidity 30 g of the composition for a bonded rare earth magnet obtained as described above is weighed out, and the bottom opening is covered with a funnel having a bottom diameter of 6.5 mm, and then put into the funnel. The measurement starts the stopwatch at the moment when the bottom of the funnel is opened, and reads the time when the above composition completely falls from the funnel. The measurement was repeated three times, and those having an average value of 5 seconds / 30 g or less were evaluated as having good fluidity, and those having an average value of more than 5 seconds / 30 g were evaluated as having poor fluidity.

Magnet Density Measurement Using a rare earth bonded magnet sample obtained as described above, a precision balance BP221S (Sartori) was used at room temperature.
us) and a micrometer (manufactured by Mitutoyo), and the weight and volume were measured, and the resulting value was taken as the density.

Measurement of Magnetic Properties The above sample (10 mm × 10 mm × 10 mm die-shaped molded product) was pulse-magnetized at room temperature at 1.2 MA / m.
The measurement was performed using a vibrating sample magnetometer Model BHV-5 (manufactured by Riken Denshi). The measured magnetic properties are representative values of the maximum energy product (BH) max (kJ /
m ³ ).

Measurement of Compressive Strength The above bonded magnet sample was prepared at 25 ° C. using Tensilon UTM-10T (manufactured by Orientec) equipped with a 10 t cell.
The compressive strength at the time of breaking was measured at a speed of 2 mm / min. Table 1 summarizes the obtained results.

[0073]

[Table 1]

[0074]

According to the present invention, low-temperature curing, high fluidity, and mold filling properties can be achieved without impairing conventional moldability, magnetic properties, mechanical strength, heat resistance, corrosion resistance, and the like. The present invention can provide a rare-earth bonded magnet having the same, a composition for a rare-earth bonded magnet capable of obtaining such a magnet, and a method for producing a rare-earth bonded magnet.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) C08K 5/00 C08K 5/00 C08L 63/10 C08L 63/10 H01F 1/053 H01F 41/02 G 41/02 1 / 04 HA (72) Inventor Son ▲ Ko ▼ 1019-1 Tomizuka-cho, Isesaki-shi, Gunma, Japan Showa Takahashi Co., Ltd. (72) Inventor Katsuhiko Muraguchi 1019-1 Tomizuka-cho, Isesaki-shi, Gunma, Japan Inside the Research Institute Co., Ltd. (72) Hideki Chiyo, Inventor 1019-1 Tomizuka-cho, Isesaki-shi, Gunma F-term in the Research Institute Co., Ltd. F-term (reference) 4J036 AF06 AF08 CA21 DB06 DB15 DB29 DC02 DC05 DC41 DD02 FA02 GA01 GA07 4K018 AA11 AA27 BA05 BA18 BD01 CA02 CA09 GA04 KA46 5E040 AA03 AA04 AA06 AA19 BB05 CA01 HB05 HB07 NN04 NN17 NN18 5E062 CD05 CE04

Claims (11)

[Claims] 1. A binder resin comprising a polymerizable compound in which 10% or more and less than 90% of epoxy groups in an epoxy compound are partially vinyl-esterified with an unsaturated monobasic acid, and (B) thermal radical polymerization initiation. A rare earth-based bonded magnet composition, comprising: an agent, (C) an epoxy curing agent, and (D) a rare earth-based alloy powder. 2. The composition for a rare-earth bonded magnet according to claim 1, wherein the softening point of the epoxy compound in the component (A) is 60 ° C. or higher. 3. The rare-earth bonded magnet composition according to claim 1, wherein the epoxy compound in the component (A) is a cresol novolak-type epoxy compound. 4. The composition for a rare-earth bonded magnet according to claim 1, wherein the epoxy compound in the component (A) is a phenol novolak type epoxy compound. 5. The epoxy compound in component (A) is a cresol novolak type or phenol novolak type epoxy compound obtained by subjecting a bisphenol compound to a polyaddition reaction of up to 30% with respect to an epoxy group. The composition for a bonded rare earth magnet according to any one of claims 1 to 4. 6. The rare earth element according to claim 1, wherein the amount of the component (A) is 1 to 10% by weight based on the composition of the rare earth bonded magnet. Composition for bonded magnets. 7. The rare earth-based bonded magnet composition according to claim 1, wherein the component (D) is an Nd—Fe—B-based alloy powder. 8. The composition for a rare-earth bonded magnet according to claim 1, wherein the component (D) is an Sm—Co-based alloy powder. 9. The method for producing a rare earth-based bonded magnet composition according to claim 1, wherein the components (A), (B) and (C) are previously dissolved in an organic solvent. A method comprising dispersing, kneading the obtained dispersion and the component (D), and then removing the solvent. 10. The composition obtained by the production method according to claim 9, which is molded by a cold or warm compression molding method at a molding pressure of ^{2 to} 8 t / cm ² , and in a temperature range of 100 to 200 ° C. A method for producing a rare earth-based bonded magnet, comprising a step of heating the composition to cure the composition. 11. A rare earth bonded magnet obtained by the production method according to claim 10.