JP7201578B2 - Bonded magnet manufacturing method and bonded magnet - Google Patents

Description

The present invention relates to a method for manufacturing a bonded magnet and a bonded magnet.

Patent Literature 1 discloses a bonded magnet comprising rare earth magnetic powder and a binder comprising a thermoplastic resin and a thermosetting resin. After manufacturing a molded body that binds magnetic powder with a small amount of thermoplastic resin that retains its shape, the gaps between the molded body are impregnated with a liquid thermosetting resin to reduce the resin component content compared to conventional methods. In addition, a bonded magnet having a high filling rate of magnetic powder without a decrease in strength is obtained.

However, magnetic powders with an average particle size of 10 μm or more are targeted, and only magnetic powders with a particle size as large as 150 μm are used in the examples. When the particle size is so large, it is not a big problem that the filling rate of the magnetic powder becomes low. No improvement is expected.

JP 2014-146655 A

An object of the present invention is to provide a bonded magnet having excellent magnetic properties and a method for producing the same.

A method for producing a bonded magnet according to an aspect of the present invention includes a first compression step of compressing magnetic powder having an average particle size of 10 μm or less while magnetically orienting the magnetic powder to obtain a first molded body;
A second compression step of contacting the first molded body with a thermosetting resin having a viscosity of 200 mPa S or less and then compressing to obtain a second molded body;
A heat treatment step of heat-treating the second compact is included.

A bonded magnet according to an aspect of the present invention contains magnetic powder having an average particle size of 10 μm or less and a cured product of a thermosetting resin having a viscosity of 200 mPa·S or less, and has an impregnation depletion rate of 1% or less.

According to the method for producing a bonded magnet of the present invention, a bonded magnet with improved magnetic properties can be obtained by increasing the filling rate and the orientation rate of the magnetic powder.

4 is a diagram showing a cross section of the bond magnet in Example 1. FIG. FIG. 10 is a diagram showing a cross section of a bond magnet in Example 4;

Embodiments of the present invention will be described in detail below. However, the embodiment shown below is an example for embodying the technical idea of the present invention, and the present invention is not limited to the following. In this specification, the term "process" refers not only to an independent process, but also to the term if the intended purpose of the process is achieved even if it cannot be clearly distinguished from other processes. included.

The manufacturing method of the bonded magnet of this embodiment includes:
A first compression step of compressing a magnetic powder having an average particle size of 10 μm or less while magnetically orienting it to obtain a first molded body, and bringing the first molded body into contact with a thermosetting resin having a viscosity of 200 mPa·S or less. It is characterized by comprising a second compression step of obtaining a second molded body by compressing after it is compressed, and a heat treatment step of heat-treating the second molded body. A first molded body obtained by compressing magnetic powder while magnetically orienting it is brought into contact with a thermosetting resin having a viscosity of 200 mPa S or less, and then compressed and heat-treated to harden the thermosetting resin. , the packing rate and the orientation rate of the magnetic powder are increased, and the magnetic properties of the bonded magnet are considered to be improved.

<First compression step>
In the first compression step, magnetic powder having an average particle size of 10 μm or less is compressed while being magnetically oriented to obtain a first compact. The first compression step may be performed not only once but also multiple times.

The material of the magnetic powder is not particularly limited, and examples thereof include SmFeN-based, NdFeB-based, and SmCo-based rare earth magnetic materials. Among them, SmFeN-based magnetic powder is preferable in that it has heat resistance and does not contain rare metals. Examples of SmFeN-based magnetic powders include nitrides composed of rare earth metal Sm, iron Fe, and nitrogen N, which have a Th ₂ Zn ₁₇ -type crystal structure and are represented by the general formula Sm _x Fe _100-xy N _y . be done. Here, it is preferable that x is 8.1 atomic % or more and 10 atomic % or less, y is 13.5 atomic % or more and 13.9 atomic % or less, and the balance is mainly Fe.

SmFeN magnetic powder can be produced by the method disclosed in Japanese Patent Application Laid-Open No. 11-189811. The NdFeB magnetic powder can be produced by the HDDR method disclosed in International Publication No. 2003/85147. The SmCo-based magnetic powder can be produced by the method disclosed in JP-A-08-260083.

The average particle size of the magnetic powder is 10 μm or less, preferably 6 μm or less, more preferably 4 μm or less, from the viewpoint of magnetic properties. If it exceeds 10 μm, the coercive force of the magnetic powder tends to decrease significantly due to the increase in crystal grain size. The average particle diameter is measured as a particle diameter corresponding to 50% of volume accumulation from the small particle diameter side in the particle size distribution.

The magnetic powder can be phosphated. Phosphoric acid treatment forms a passivation film having PO bonds on the surface of the magnetic powder.

Phosphating is performed by reacting a phosphating agent with magnetic powder. Phosphating agents include, for example, phosphates such as orthophosphoric acid, sodium dihydrogen phosphate, potassium dihydrogen phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, zinc phosphate, and calcium phosphate; Inorganic phosphoric acids such as phosphoric acid, hypophosphite, pyrophosphoric acid and polyphosphoric acid, organic phosphoric acids and salts thereof.

The magnetic powder is preferably subjected to silica treatment with an alkyl silicate in order to protect it from oxidation during the production of the molded body and during use of the obtained molded body. Alkyl silicates are represented by the following general formula, and among them, methyl silicate or ethyl silicate is preferable.
Si _n O _(n−1) (OR) _(2n+2)
(R is an alkyl group and n is an integer of 1 to 10.)

Silica treatment can form a silica film by mixing the above-mentioned alkyl silicate with water necessary for hydrolyzing the silicate with magnetic powder and heat-treating in an inert gas atmosphere. Water necessary for hydrolyzing silicate includes acidic aqueous solutions such as acetic acid aqueous solution, sulfuric acid aqueous solution and phosphoric acid aqueous solution, and basic aqueous solutions such as ammonia water, sodium hydroxide aqueous solution and potassium hydroxide aqueous solution. The amount of the alkylsilicate to be mixed is preferably 1 to 4 parts by weight, more preferably 1.5 to 2.5 parts by weight, per 100 parts by weight of the magnetic powder.

The magnetic powder is preferably treated with a coupling agent because the magnetic properties of the magnetic powder can be improved, and the wettability with the resin and the strength of the magnet can be improved. It is preferable that the silica-treated magnetic powder is treated with a coupling agent.

The coupling agent is not particularly limited, but a silane coupling agent having no alkyl or alkenyl group having 8 to 24 carbon atoms or a coupling agent having an alkyl or alkenyl group having 8 or more to 24 carbon atoms or alkenyl group. agents. The number of carbon atoms in the alkyl group or alkenyl group is preferably 10 or more and 24 or less. Here, if the number of carbon atoms in the alkyl or alkenyl group is less than 8, lubricity is not sufficiently imparted, and if the number of carbon atoms is greater than 24, the viscosity of the treatment liquid increases significantly, making uniform coating difficult.

A silane coupling agent, a phosphate coupling agent, a hydrogen phosphite coupling agent, etc. are mentioned as a coupling agent which has a C8-C24 alkyl group or an alkenyl group. These coupling agents may be used alone or in combination of two or more. Here, the coupling agent has two or more different groups in the molecule, one of which has a group that acts with an inorganic material and the other has a group that acts with an organic material. .

Examples of the silane coupling agent having an alkyl or alkenyl group having 8 to 24 carbon atoms are represented by the following general formula. Specific examples include decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, octadecyltrimethoxysilane, octadecyltriethoxysilane, octyltriethoxysilane. Examples include silanes, among which octadecyltriethoxysilane and octyltriethoxysilane are preferred.
(R ¹ ) _x Si(OR ² ) _(4−x)
(R ¹ is an alkyl group represented by C _n H _2n+1 or an alkenyl group represented by C _n H _2n-1 , n is an integer of 8 to 24, and R ² is an alkyl represented by C _m H _2m+1 group, m is an integer of 1 to 4, and x is an integer of 1 to 3.)
In addition, the group that acts on the organic material in the silane coupling agent refers to, for example, one in which a silicon atom and a carbon atom are directly bonded, and in the above formula is R ¹ , and the group that acts on the inorganic material is OR ² . .

Phosphate coupling agents having an alkyl or alkenyl group having 8 to 24 carbon atoms include those represented by the following general formula. Specific examples include didecyl acid phosphate, isodecyl acid phosphate, isotridecyl acid phosphate, lauryl acid phosphate, oleyl acid phosphate, stearyl acid phosphate, isostearyl acid phosphate, and tetracosyl acid phosphate. However, oleyl acid phosphate is preferred.
(R ¹ O) _x PO(OH) _(3−x)
(R ¹ is an alkyl group represented by C _n H _2n+1 or an alkenyl group represented by C _n H _2n-1 , n is an integer of 8 to 24, and x is an integer of 1 to 2.)
In the above formula, the group that acts on the organic material in the phosphate coupling agent is R ¹ O, and the group that acts on the inorganic material is OH.

Hydrogen phosphite coupling agents having an alkyl or alkenyl group having 8 to 24 carbon atoms include those represented by the following general formula. Specific examples include didecyl hydrogen phosphite, dilauryl hydrogen phosphite, dioleyl hydrogen phosphite and the like, with dioleyl hydrogen phosphite being preferred.
( ^R1O ) _2POH
(R ¹ is an alkyl group represented by C _n H _2n+1 or an alkenyl group represented by C _n H _2n-1 , where n is an integer of 8 to 24.)
The group acting on the organic material in the hydrogen phosphite coupling agent is R ¹ O in the above formula, and the group acting on the inorganic material is OH.

A silane coupling agent, a phosphate coupling agent or a hydrogen phosphite coupling agent having an alkyl or alkenyl group having 8 to 24 carbon atoms may be used alone or in combination of two or more. good too.

Treatment with a coupling agent having an alkyl or alkenyl group having 8 or more and 24 or less carbon atoms is performed by mixing the above-mentioned coupling agent with the magnetic powder together with water necessary for hydrolyzing the coupling agent, and making an inert A coating of the coupling agent can be formed by heat-treating in a gas atmosphere. Water necessary for hydrolyzing the coupling agent includes acidic aqueous solutions such as acetic acid aqueous solution, sulfuric acid aqueous solution and phosphoric acid aqueous solution, and basic aqueous solutions such as ammonia water, sodium hydroxide aqueous solution and potassium hydroxide aqueous solution. The amount of the coupling agent mixed is preferably 0.01 to 1 part by weight, more preferably 0.05 to 0.5 part by weight, per 100 parts by weight of the magnetic powder. If the amount is less than 0.01 part by weight, sufficient lubricity cannot be imparted to the magnetic powder.

As the treatment with a coupling agent, a silane coupling agent different from the above-mentioned silane coupling agent having an alkyl or alkenyl group having 8 to 24 carbon atoms (an alkyl or alkenyl group having 8 to 24 carbon atoms is used. silane coupling agent) may be used. Silane coupling agents other than silane coupling agents having an alkyl or alkenyl group having 8 to 24 carbon atoms include, for example, γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2 -aminoethyl)aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane/hydrochloric acid salt, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, vinyltriacetoxysilane, γ-chloropropyltrimethoxysilane, hexamethylenedisilazane, γ- anilinopropyltrimethoxysilane, vinyltrimethoxysilane, dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, γ-chloropropylmethyldimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, methyltrichlorosilane, dimethyldichlorosilane , trimethylchlorosilane, vinyltrichlorosilane, vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, β-(3,4 epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, N-β ( aminoethyl) γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, ureidopropyltriethoxysilane, γ-isocyanatopropyltriethoxysilane, bis( 3-triethoxysilylpropyl)tetrasulfane, γ-isocyanatopropyltrimethoxysilane, vinylmethyldimethoxysilane, 1,3,5-N-tris(3-trimethoxysilylpropyl)isocyanurate, N-(1,3 -dimethylbutylidene)-3-(triethoxysilyl)-1-propanamine and the like. Further, the silane coupling agent having a cyclic structure includes, as a cyclic structure, a coupling agent having an alicyclic structure such as a monocyclo ring or a bicyclo ring, or an aromatic ring, such as a bicyclo ring. 2-(bicyclo[2.2.1]hept-5-en-2-yl)ethyltrimethoxysilane and 2-(bicyclo[2.2.1]hept-5-ene as coupling agents having a norbornene skeleton -2-yl)ethyltriethoxysilane, 2-(bicyclo[2.2.1]hept-5-en-2-yl)trimethoxysilane, 2-(bicyclo[2.2.1]hept-5- En-2-yl)triethoxysilane, 2-(bicyclo[2.2.1]hept-2-enyl)ethynyltrimethoxysilane, 2-(bicyclo[2.2.1]hept-2-enyl ) ethynyltriethoxysilane, 2-(bicyclo[2.2.1]hept-5-en-2-yl)hexyltrimethoxysilane, 2-(bicyclo[2.2.1]hept-5-ene-2 -yl)hexyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-aminoethylaminomethylphenyl-3-ethyltrimethoxysilane, p-styryltriethoxysilane as a coupling agent having an aromatic ring skeleton; methoxysilane, m-allylphenylpropyltriethoxysilane, and the like. These silane coupling agents may be used alone or in combination of two or more. Among them, a silane coupling agent having a cyclic structure is preferred, and a silane coupling agent having a norbornene skeleton is more preferred, in terms of compatibility with thermosetting resins, lubricity on the magnetic powder surface, heat resistance, etc. 2- (bicyclo[2.2.1]hept-5-en-2-yl)ethyltrimethoxysilane, 2-(bicyclo[2.2.1]hept-5-en-2-yl)ethyltriethoxysilane More preferred.

The treatment with a silane coupling agent having no alkyl or alkenyl group and having 8 to 24 carbon atoms and having no alkenyl group is carried out by mixing the above-mentioned coupling agent with the water necessary for hydrolyzing the coupling agent into the magnetic powder. A film of the silane coupling agent can be formed by heat-treating in an inert gas atmosphere. Water necessary for hydrolyzing the coupling agent includes acidic aqueous solutions such as acetic acid aqueous solution, sulfuric acid aqueous solution and phosphoric acid aqueous solution, and basic aqueous solutions such as ammonia water, sodium hydroxide aqueous solution and potassium hydroxide aqueous solution. The amount of the silane coupling agent mixed is preferably 0.1 to 2 parts by weight, more preferably 0.2 to 1.2 parts by weight, per 100 parts by weight of the magnetic powder. If the amount is less than 0.1 part by weight, the effect of the coupling agent is small, and if it exceeds 2 parts by weight, the magnetic properties tend to deteriorate due to aggregation of the magnetic powder.

Treatment with a coupling agent increases lubricity, reduces the frictional force acting between particles during compression molding, and allows the magnetic powder in the molded product to be highly filled. Alternatively, after treatment with a silane coupling agent having no alkenyl group, treatment with a coupling agent having an alkyl or alkenyl group having 8 to 24 carbon atoms is preferred.

The magnitude of the external magnetic field applied for magnetic orientation is not particularly limited, but is preferably 0.5 T or more, more preferably 1 T or more. If it is less than 0.5 T, there is a tendency that the magnet cannot be sufficiently oriented.

In the first compression step, the structure of the mold to be used is not particularly limited. A mold or the like configured with a spring for the purpose is mentioned. A mold with an inner plate is preferred to facilitate removal of excess thermosetting resin in the second compression step. Although the size of the mold is not particularly limited, it is preferable that the mold has a volume of 0.1 cm ³ or more and 10 cm ³ or less so that excess thermosetting resin can be easily removed.

The magnitude of the pressure applied to the mold is not particularly limited, but is preferably 0.1 ton/cm ² or more and less than 4 ton/cm ² , more preferably 0.5 ton/cm ² or more and less than 2 ton/cm ² . If it is less than 0.1 tons/cm ² , the rearrangement of the magnetic powder does not progress and the filling rate of the magnetic powder in the ^second compact tends to decrease. There is a tendency for molding defects to occur because sufficient impregnation cannot be achieved when the coating is applied.

<Second compression step>
In the second compression step, the first molded body is brought into contact with a thermosetting resin having a viscosity of 200 mPa·S or less and then compressed to obtain a second molded body. The magnetic powder used in the present invention has a very small average particle size of 10 μm or less and is bulky, so the packing rate is low. In the first compression step, after sufficiently magnetically oriented, it is brought into contact with a thermosetting resin and compressed, whereby excess thermosetting resin is removed and the filling rate and orientation rate of the magnetic powder are increased, resulting in a bond magnet. The magnetic properties of are improved.

The method of bringing the thermosetting resin into contact with the first molded body is not particularly limited, and for example, the thermosetting resin may be added and impregnated into the first molded body existing in the mold. Although the amount of the thermosetting resin to be brought into contact is not particularly limited, it is preferably 0.25 to 2 times the volume of the compact, more preferably 0.5 to 1.5 times. If it is less than 0.25 times, the thermosetting resin cannot be sufficiently impregnated into the first molded body, resulting in molding failure. At the same time there is a tendency to have to remove the overflowing material.

The viscosity of the thermosetting resin is 200 mPa·S or less, preferably 100 mPa·S or less, more preferably 50 mPa·S or less, still more preferably 15 mPa·S or less, and most preferably 10 mPa·S or less. If it exceeds 200 mPa·S, there is a tendency that impregnation cannot be performed sufficiently, resulting in poor molding.

The thermosetting resin is not particularly limited as long as it is thermosetting, and examples thereof include thermosetting monomers, thermosetting prepolymers, and thermosetting polymers. Examples of thermosetting monomers include norbornene-based monomers, epoxy-based monomers, phenol-based monomers, acrylic-based monomers, and vinyl ester-based monomers. Norbornene-based monomers include tricyclo[5.2.1.0 ^2,6 ] Deca-3,8-diene (dicyclopentadiene), tricyclo[5.2.1.0 ^2,6 ]decane-3-ene, bicyclo[2.2.1]hepta-2,5-diene (2 ,5-norbornadiene), bicyclo[2.2.1]hept-2-ene (2-norbornene), bicyclo[3.2.1]oct-2-ene, 5-ethylidene-2-norbornene, bicyclo[2 .2.1]hept-5-ene-2,3-dicarboxylic anhydride, 5-vinylbicyclo[2.2.1]hept-2-ene, tetracyclo[6.2.1.1 ^3,6 . 0 ^2,7 ]dodeca-4-ene and the like. Thermosetting prepolymers include epoxy resins, phenolic resins, melamine resins, guanamine resins, unsaturated polyesters, vinyl ester resins, diallyl phthalate resins, silicone resins, alkyd resins, furan resins, acrylic resins, urea resins, and allyl carbonate resins. etc. Thermosetting polymers include polyurethane resins, polyimide resins, polyester resins, and the like.

An initiator and a curing agent for the thermosetting resin can be blended together with the thermosetting resin. Examples of initiators include Grubbs catalysts, dihalogens, azo compounds and the like. Curing agents include amine curing agents, acid anhydride curing agents, polyamide curing agents, imidazole curing agents, phenolic resin curing agents, polymercaptan resin curing agents, polysulfide resin curing agents, and organic acid hydrazide curing agents. Curing agents, isocyanate-based curing agents, and the like are included. Amine-based curing agents include diaminodiphenylsulfone, metaphenylenediamine, diaminodiphenylmethane, diethylenetriamine, triethylenetetramine, and the like.

In the second compression step, the magnitude of the pressure to be applied is not particularly limited, but it is preferably equal to or higher than the compression pressure in the first compression step in order to produce a highly packed magnet. Specifically, it is preferably 4 tons/cm ² or more and 11 tons/cm ² or less, more preferably 6 tons/cm ² or more and 10 tons/cm ² or less. If it is less than 4 tons/cm ² , the filling rate of the magnetic powder cannot be sufficiently increased, and if it exceeds 11 tons/cm ² , the coercive force tends to decrease.

Also in the second compression step, magnetic orientation can be achieved in the same manner as in the first compression step. In the case of magnetic orientation, the magnitude of the external magnetic field to be applied is not particularly limited, and the magnitude of the external magnetic field in the first compression step can be applied as it is.

<Heat treatment process>
The heat treatment temperature is not particularly limited, but is preferably 100° C. or higher and 150° C. or lower, more preferably 110° C. or higher and 130° C. or lower. If the temperature is less than 100°C, the curing of the resin does not proceed sufficiently, resulting in insufficient strength.

The heat treatment time is not particularly limited, but is preferably 1 minute or more and 120 minutes or less, more preferably 3 minutes or more and 60 minutes or less. If the curing time is less than 1 minute, the strength tends to be insufficient due to insufficient curing of the resin.

After the heat treatment is finished, the inner plate and the punch are pulled out from the mold, the bonded magnet compact is taken out, and a pulse magnetic field is applied in the orientation direction to magnetize it.

The magnetizing magnetic field is preferably 1 T or more and 36 T or less, more preferably 3 T or more and 12 T or less. If it is less than 1 T, the magnet cannot be sufficiently magnetized and the residual magnetic flux density cannot be obtained. If it exceeds 36 T, the heat shock caused by the heat generated during magnetization is too large, and the magnet breaks.

The bonded magnet of the present embodiment is characterized by containing magnetic powder having an average particle size of 10 μm or less and a cured product of a thermosetting resin having a viscosity of 200 mPa·S or less, and having an impregnation depletion rate of 1% or less. The bonded magnet can be manufactured, for example, by the manufacturing method of the bonded magnet of the present invention described above. Here, the magnetic powder, thermosetting resin, average particle size, etc. of the bonded magnet are as described above.

In the bonded magnet manufacturing method and the bonded magnet of the present invention, the impregnation depletion rate of the bonded magnet refers to the ratio of the area that is actually not occupied by the resin to the area that should be occupied by the resin. The impregnation depletion rate is preferably 12% or less, more preferably 10% or less, even more preferably 5% or less, and most preferably 1% or less. If it exceeds 12%, the mechanical strength tends to decrease. The impregnation depletion rate is the area of the portion not impregnated with resin (resin deficient portion area) and the contour of the image observed with an optical microscope at the lowest magnification that includes the entire cut surface of the bonded magnet. The area of the entire cut surface (the area of the cut surface) was calculated by binarization analysis of brightness (BMPEdit), and the ratio of the area of the resin-deficient portion to the area of the cut surface was obtained. The cut surface of the bonded magnet is cut through the center of the resin-contacted surface of the obtained bonded magnet, perpendicular to the contact surface, and with the maximum cut area. make.

The ratio of the magnetic powder contained in the bonded magnet, that is, the filling rate is not particularly limited, but is preferably 71% by volume or more, more preferably 72% by volume or more. If it is less than 71% by volume, there is a tendency that a sufficient residual magnetic flux density cannot be obtained.

The coercive force of the bond magnet is not particularly limited, but is preferably 1020 kA/m or more, more preferably 1150 kA/m or more. If it is less than 1020 kA/m, demagnetization tends to occur when used in a powerful motor or the like.

Although the residual magnetic flux density of the bond magnet is not particularly limited, it is preferably 0.75 T or more, more preferably 0.8 T or more. If it is less than 0.75 T, there is a tendency that sufficient torque cannot be obtained when used in a motor or the like.

The magnetic flux orientation ratio of the bond magnet is preferably 80% or more, more preferably 81% or more. By setting it to 80 or more, the residual magnetic flux density increases. Here, the orientation ratio is obtained by dividing the residual magnetic flux density of the bonded magnet by the product of the residual magnetic flux density of the magnetic powder and the volume filling factor of the bonded magnet.

Examples are described below. "%" is based on weight unless otherwise specified.

Production example 1
[Alkylsilicate treatment step]
300 g of SmFeN magnetic powder (average particle size: 3 μm) and 7.5 g of ethyl silicate (Si ₅ O ₄ (OEt) ₁₂ ) were put into a mixer and mixed for 5 minutes in a nitrogen atmosphere. Subsequently, 0.8 g of ammonia water having a pH of 11.7 was added, mixed for 5 minutes, and heat-treated at 180° C. for 10 hours under reduced pressure to obtain SmFeN-based anisotropic magnetic powder with a silica thin film formed on the surface. .

[Surface treatment step 1]
300 g of silica-treated magnetic powder and 1.5 g of an acetic acid aqueous solution having a pH of 4 were put into a mixer and mixed for 5 minutes under a nitrogen atmosphere. Subsequently, as a silane coupling agent A, 2-(bicyclo[2.2.1]hept-5-en-2-yl)ethyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., silane coupling agent X-88-351 ) was added and mixed for 5 minutes under a nitrogen atmosphere. The mixture was taken out and heat-treated at 100° C. for 5 hours under reduced pressure to obtain a magnetic powder having a coating layer formed of coupling agent A on a silica film.

[Surface treatment step 2]
300 g of SmFeN magnetic powder having a coating layer formed from coupling agent A and 1.5 g of an acetic acid aqueous solution having a pH of 4 were put into a mixer and mixed for 5 minutes under a nitrogen atmosphere. Subsequently, a mixed solution of 0.5 g of octadecyltriethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.) and 0.5 g of ethanol was added as coupling agent B and mixed for 5 minutes under a nitrogen atmosphere. Heat treatment was performed at 100° C. for 5 hours under reduced pressure to obtain SmFeN anisotropic magnetic powder (Magnetic powder 1) having a coating layer formed of coupling agent A and coupling agent B on the surface.

Production example 2
Coupling agent A was applied to the surface in the same manner as in Production Example 1, except that octyltriethoxysilane was used as coupling agent B in place of octadecyltriethoxysilane in surface treatment step 2 of Production Example 1. An SmFeN-based anisotropic magnetic powder (magnetic powder 2) having a coating layer formed from agent B was obtained.

Production example 3
In the same manner as in Production Example 1, except that oleyl acid phosphate was used as the coupling agent B in place of octadecyltriethoxysilane in the surface treatment step 2 of Production Example 1, the coupling agent A and the coupling agent were applied to the surface. A SmFeN-based anisotropic magnetic powder (magnetic powder 3) having a coating layer formed of B was obtained.

Production example 4
In the same manner as in Production Example 1, except that dioleyl hydrogen phosphite was used as the coupling agent B in place of octadecyltriethoxysilane in the surface treatment step 2 of Production Example 1, the surface was coated with the coupling agent A. A SmFeN-based anisotropic magnetic powder (magnetic powder 4) having a coating layer formed from ring agent B was obtained.

Example 1
In the first compression step, 0.8 g of the SmFeN-based anisotropic magnetic powder having the coating layers A and B formed on the surface, which was produced in Production Example 1, was placed in a non-magnetic cemented carbide mold having a cavity of 5 mm square. After filling, upper and lower punches were attached, and compression was performed in an oriented magnetic field of 1 T at a compression pressure of 1 ton/cm ² to obtain a first compact.

Second compression step Subsequently, the upper punch was removed, and dicyclopentadiene monomer (viscosity of 3 mPa·s, density of 1.02 g/cc) and dichloro[1,3-bis(2,2, 0.1 g of a mixed solution of 6-isopropylphenyl)-2-imidazolidinylidene](2-isopropylphenylmethylene)ruthenium (III) was added dropwise and maintained for 30 seconds. The upper punch was attached again, and the mixture was compressed at a compression pressure of 8 tons/cm ² in an oriented magnetic field of 1 T to impregnate the dicyclopentadiene monomer and discharge excess liquid mixture components to obtain a second compact. .

Heat Treatment Step The second compact was then heated at 120° C. for 15 minutes while still compressed to obtain a bond magnet. The density, volume filling factor, coercive force, residual magnetic flux density, impregnation depletion rate, and orientation rate of the obtained bonded magnet were measured by the following methods. Table 1 shows the results.

<Density and volume filling factor>
The density of the bonded magnet was calculated by dimensional and gravimetric measurements. The volume filling ratio was calculated by applying the density calculated from a calibration curve between the magnetic powder filling ratio and the magnet density prepared based on the densities of the magnetic powder and the resin.

<Impregnation Deficiency Rate>
The obtained bonded magnet is cut through the center of the surface in contact with the dicyclopentadiene monomer, perpendicular to the contact surface, and cut so that the cut area is maximized, and the cut surface is sandpapered. Polished. FIG. 1 shows an image of the cut surface observed with an optical microscope (magnification of 25 times). From the image, the resin was uniformly contained in the entire cross section, and no impregnated deficient portion could be observed.

<Residual magnetic flux density, coercive force and orientation ratio>
SmFeN magnetic powder is packed in a sample container together with paraffin wax, and after the paraffin wax is melted with a dryer, its easy magnetization magnetic domains are aligned with an aligning magnetic field of 2T. This magnetically oriented sample is pulse-magnetized with a magnetizing magnetic field of 6T, and the residual magnetic flux density (T) and coercive force iHc (kA/m) are measured using a VSM (vibrating sample magnetometer) with a maximum magnetic field of 2T. As a result, the SmFeN magnetic powder had a residual magnetic flux density of 1.317 T and a coercive force of 1300 kA/m. In addition, when the residual magnetic flux density (T) and coercive force iHc (kA/m) of the manufactured bonded magnet were measured using a BH tracer, the residual magnetic flux density of the magnet was 0.85 T and the coercive force was 1190 kA/m. there were. Therefore, the orientation ratio was 0.85(T)/(0.751*1.317(T))*100=85.9%.

Examples 2-5
A bond magnet was produced in the same manner as in Example 1, except that the compression pressure in the first compression step was changed to the conditions shown in Table 1. FIG. 2 shows an image of a cross-section of the impregnation depletion rate of Example 4 as in Example 1 (magnification: 25 times). From FIG. 2, a resin-deficient portion was confirmed at the center of the cut surface, and the area of the resin-deficient portion and the area of the cut surface were calculated by binarization analysis (BMPEdit), and the impregnation depletion rate was 11.1%. rice field.

Examples 6-8
A bonded magnet was produced in the same manner as in Example 1, except that the magnetic powder was changed to one shown in Table 1.

Comparative example 1
A bonded magnet was produced in the same manner as in Example 1, except that in the first compression step the magnet was compressed without being magnetically oriented.

Comparative example 2
0.8 g of the SmFeN magnetic powder prepared in Production Example 1, 0.05 g of a dicyclopentadiene monomer (viscosity/25° C.: 3 mPa·s, density: 1.02 g/cc) as a binder component, and dichloro[1] as a reaction initiator. ,3-bis(2,6-isopropylphenyl)-2-imidazolidinylidene](2-isopropylphenylmethylene)ruthenium (III) (0.002 g) was mixed in a mortar. After filling this mixture into a non-magnetic cemented carbide mold provided with a 5 mm square cavity, while applying an aligning magnetic field of 1 T, the mold is compressed by applying a compression pressure of 8 tons/cm ² in the vertical direction. At the same time, an excess binder component was discharged, and the bonded magnet was obtained by heating at 120° C. for 15 minutes in this state. Table 1 shows the density, volume filling factor, coercive force, residual magnetic flux density, impregnation depletion rate, and orientation rate of the obtained bonded magnet.

From Table 1, it was confirmed that the inclusion of the first compression step and the second compression step increased the filling rate and improved the magnetic properties as compared to Comparative Example 2. In addition, it was confirmed that the magnetic properties were improved by compressing the magnetic powder while magnetically orienting the magnetic powder in the first compression step, as compared with Comparative Example 1.

Example 9
In the second compression step, a low-viscosity epoxy resin (Bond E205 manufactured by Konishi Co., Ltd., viscosity / 25 ° C.: 100 mPa s, density: 1.10 g cc) instead of a mixed solution of dicyclopentadiene monomer and a reaction initiator The procedure was carried out in the same manner as in Example 1, except that 0.1 g of a mixed solution of a curing agent (E205, manufactured by Konishi Co., Ltd.) was added dropwise. Table 2 shows the density, volume filling factor, coercive force, residual magnetic flux density, impregnation depletion rate, and orientation rate of the obtained bonded magnet.

Comparative example 3
In the second compression step, low-viscosity epoxy resin bond E206SS (manufactured by Konishi Co., Ltd., viscosity / 25 ° C.: 450 mPa s, density: 1.15 g / cc) instead of the mixed solution of dicyclopentadiene monomer and reaction initiator The procedure of Example 1 was repeated except that 0.1 g of a mixture of a curing agent (manufactured by Konishi Co., Ltd., E206SS) was added dropwise, but molding was not possible.

Comparative example 4
In the second compression step, liquid epoxy resin YDF-170 (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd., viscosity 2000 mPa s, density 1.19 g / cc) and curing instead of the mixed solution of dicyclopentadiene monomer and reaction initiator The procedure of Example 1 was repeated except that 0.1 g of a mixed agent (E205, manufactured by Konishi Co., Ltd.) was added dropwise, but molding was not possible.

Comparative example 5
0.8 g of the SmFeN magnetic powder prepared in Production Example 1, a low-viscosity epoxy resin (Bond E205 manufactured by Konishi Co., Ltd., viscosity/25° C.: 100 mPa·s, density: 1.10 g·cc) as a binder component, and a curing agent. (manufactured by Konishi Co., Ltd., E205) was mixed in a mortar. After filling this mixture into a non-magnetic cemented carbide mold provided with a 5 mm square cavity, the mold was compressed by applying a compression pressure of 8 tons/cm ² in the vertical direction while applying an oriented magnetic field of 1 T. Excessive binder components were discharged, and in this state, the product was heated at 120° C. for 15 minutes and molded by thermosetting. Table 2 shows the density, volume filling factor, coercive force, residual magnetic flux density, impregnation depletion rate, and orientation rate of the obtained bonded magnet.

From Table 2, it was confirmed that molding cannot be performed when the viscosity exceeds 200 mPa·S. In addition, by bringing a thermosetting resin having a viscosity of 200 mPa S or less into contact with the first molded body, the filling rate and the orientation rate are higher than in Comparative Example 5, and the magnetic properties are improved. Confirmed to do.

According to the method for producing a bonded magnet of the present invention, a bonded magnet having a high magnetic powder content and excellent magnetic properties can be obtained.

1: resin deficient part

Claims (20)

A first compression step of compressing a magnetic powder having an average particle size of 10 μm or less while magnetically orienting it in a mold to obtain a first compact;
After contacting the first molded body with a thermosetting resin having a viscosity of 200 mPa S or less in the mold , it is compressed to impregnate the thermosetting resin and remove excess thermosetting resin. a second compression step of obtaining a second molded body by
including a heat treatment step of heat-treating the second compact,
The method for producing a bonded magnet, wherein the first compact does not contain resin . A first compression step of compressing a magnetic powder having an average particle size of 10 μm or less while magnetically orienting it in a mold to obtain a first compact;
The first compact is brought into contact with a thermosetting resin having a viscosity of 200 mPa S or less in the mold and then compressed to obtain a second compact having a magnetic powder ratio of 69% by volume or more. process and
Heat treatment step of heat-treating the second compact
including
The method for producing a bonded magnet, wherein the first compact does not contain resin. 3. The method for producing a bonded magnet according to claim 1, wherein the thermosetting resin is a thermosetting monomer or a thermosetting prepolymer. The method for producing a bonded magnet according to any one of claims 1 to 3, wherein the compression pressure in the second compression step is equal to or higher than the compression pressure in the first compression step. The method for producing a bonded magnet according to any one of claims 1 to 4 , wherein the compression pressure in the first compression step is less than 4 tons/ ^cm2 . The method for producing a bonded magnet according to any one of claims 1 to 5 , wherein the impregnation depletion rate of the bonded magnet is 1% or less. The method for producing a bonded magnet according to any one of claims 3 to 6 , wherein the thermosetting monomer is a norbornene-based monomer. 8. The method for producing a bonded magnet according to claim 7 , wherein the norbornene-based monomer is dicyclopentadiene. The method for producing a bonded magnet according to any one of claims 1 to 8 , wherein the magnetic powder content of the bonded magnet is 71% by volume or more. The method for producing a bonded magnet according to any one of claims 1 to 9 , wherein the magnetic powder is SmFeN magnetic powder. The method for producing a bonded magnet according to any one of claims 1 to 10 , wherein the magnetic powder is magnetic powder treated with a coupling agent having an alkyl or alkenyl group having 8 to 24 carbon atoms. 12. The method for producing a bonded magnet according to claim 11 , wherein the coupling agent is a silane coupling agent, a phosphate coupling agent or a hydrogen phosphite coupling agent. A bonded magnet containing magnetic powder having an average particle size of 10 μm or less and a cured product of a thermosetting resin, wherein the ratio of the magnetic powder contained in the bonded magnet is 69% by volume or more and the orientation ratio is 80% or more. 14. A bonded magnet according to claim 13 , wherein the thermosetting resin is a thermosetting monomer or a thermosetting prepolymer. 15. A bonded magnet according to claim 14 , wherein the thermosetting monomer is a norbornene-based monomer. 16. The bonded magnet according to claim 15 , wherein the norbornene-based monomer is dicyclopentadiene. The bonded magnet according to any one of claims 13 to 16 , wherein the magnetic powder content of the bonded magnet is 71% by volume or more. The bonded magnet according to any one of claims 13 to 17 , wherein the magnetic powder is SmFeN magnetic powder. The bonded magnet according to any one of claims 13 to 18 , wherein the magnetic powder is magnetic powder treated with a coupling agent having an alkyl or alkenyl group having 8 to 24 carbon atoms. The bonded magnet according to any one of claims 13 to 19 , having an impregnation depletion rate of 1% or less.

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