Bonded magnet, method for manufacturing a bonded magnet, and composition used for manufacturing a bonded magnet.

Abstract

To provide a novel method for manufacturing bonded magnets. [Solution] A method for manufacturing a bonded magnet, comprising the steps of: impregnating a porous molded body containing magnetic particles and a binder resin having glycidyl groups with a composition containing a monomer having a functional group that can react with a glycidyl group; polymerizing the monomer impregnated in the molded body; and reacting the glycidyl group with the functional group.

Description

Technical Field

[0001] The present disclosure relates to bonded magnets, a method for manufacturing bonded magnets, and a composition used for manufacturing bonded magnets.

Background Art

[0002] Bonded magnets containing magnetic particles and a binder resin are advantageous in terms of a high degree of freedom in shape and a high electrical resistance due to the presence of the binder resin, compared with sintered magnets. For example, Patent Document 1 discloses a method for manufacturing a rare earth-based bonded magnet having high magnetic strength with excellent production efficiency.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present disclosure is to provide a novel bonded magnet, a method for manufacturing the same, and a composition used for manufacturing the bonded magnet.

Means for Solving the Problems

[0005] The present disclosure includes the following aspects. [1] A method for manufacturing a bonded magnet, comprising a step of impregnating a porous molded body containing magnetic particles and a binder resin having a glycidyl group with a composition containing a monomer having a functional group capable of reacting with the glycidyl group, a step of polymerizing the monomer impregnated in the molded body, and a step of reacting the glycidyl group with the functional group. [2] The manufacturing method according to [1], wherein the functional group is at least one selected from the group consisting of a phenolic hydroxy group, a carboxy group, and an amino group. [3] The method for producing the product according to [1], wherein the monomer is a (meth)acrylate having a phenolic hydroxyl group. [4] The method of production according to [1], wherein the monomer is (meth)acrylic acid. [5] The method for producing the product according to [1], wherein the monomer is a (meth)acrylate having an amino group.

[0006] [6] A composition used for manufacturing a bonded magnet by impregnating a porous molded body containing magnetic particles and a binder resin having glycidyl groups, the composition containing a monomer having a functional group that can react with glycidyl groups. [7] The composition according to [6], wherein the functional group is at least one selected from the group consisting of a phenolic hydroxyl group, a carboxyl group, and an amino group. [8] The composition according to [6], wherein the monomer is a (meth)acrylate having a phenolic hydroxyl group. [9] The composition according to [6], wherein the monomer is (meth)acrylic acid.

[10] The composition according to [6], wherein the monomer is a (meth)acrylate having an amino group.

[0007]

[11] A bonded magnet comprising magnetic particles, a binder resin that binds the magnetic particles together, and a polymer bonded to the binder resin via a linking group, wherein the linking group is a group formed by the reaction of a glycidyl group with a functional group that can react with the glycidyl group.

[12] The bond magnet according to

[11] , wherein the functional group is at least one selected from the group consisting of a phenolic hydroxyl group, a carboxyl group and an amino group.

[13] The bond magnet according to

[11] , wherein the functional group is derived from a (meth)acrylate having a phenolic hydroxyl group.

[14] The bond magnet according to

[11] , wherein the functional group is derived from (meth)acrylic acid.

[15] The bond magnet according to

[11] , derived from a (meth)acrylate having an amino group as a functional group. [Effects of the Invention]

[0008] This disclosure provides a novel bonded magnet, a method for manufacturing the same, and a composition used for manufacturing the bonded magnet. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic cross-sectional view showing one embodiment of a porous molded body. [Figure 2] Figure 2 is a schematic cross-sectional view showing one embodiment of a bonded magnet. [Modes for carrying out the invention]

[0010] Embodiments will be described below with reference to the drawings. In the following, "(meth)acrylate" means either acrylate or methacrylate, or both acrylate and methacrylate. "(meth)acryloyl group" means either acryloyl group or methacryloyl group, or both acryloyl group and methacryloyl group.

[0011] One embodiment is a method for manufacturing a bonded magnet, comprising: step S1 impregnating a porous molded body containing magnetic particles and a binder resin having glycidyl groups with a composition (monoma composition) containing a monomer having a functional group that can react with a glycidyl group; step S2 polymerizing the monomer impregnated in the molded body; and step S3 reacting the glycidyl groups of the binder resin with the functional groups of the monomer.

[0012] Figure 1 is a schematic cross-sectional view showing one embodiment of a porous molded body used in process S1. As shown in Figure 1, the porous molded body 10 in one embodiment includes a plurality of magnetic particles 1 and a binder resin 2 that binds the plurality of magnetic particles 1 together. The surface of each magnetic particle 1 may be covered with the binder resin 2. A plurality of voids (pores) 3 are formed inside the molded body 10. The voids 3 may be formed between adjacent plurality of magnetic particles 1. Each void 3 may be a space surrounded by the binder resin 2 covering each magnetic particle 1. The plurality of voids 3 may be in communication with each other. Each void 3 formed inside the molded body 10 may be in communication with the outside of the molded body 10.

[0013] The size of the voids 3 in the molded body 10 (pore diameter) may be less than or equal to the particle size of the magnetic particles. The size of the voids 3 in the molded body 10 (pore diameter) may be 0.1 μm or larger, and may be 100 μm or smaller.

[0014] The magnetic particle 1 may be composed of a permanent magnet. The permanent magnet may be a samarium-cobalt (Sm-Co) alloy magnet, a neodymium-iron-boron (Nd-Fe-B) alloy magnet, a samarium-iron-nitrogen (Sm-Fe-N) alloy magnet, an iron-cobalt (Fe-Co) alloy magnet, or an Al-Ni-Co alloy magnet (Alnico magnet). If the magnetic particle 1 is composed of a permanent magnet, the particle size of the magnetic particle 1 may be, for example, 20 μm or more or 40 μm or more, and 300 μm or less or 250 μm or less.

[0015] The magnetic particles 1 may be composed of a soft magnetic material. The soft magnetic material may contain at least one metal selected from the group consisting of pure iron and alloys containing iron. The alloy containing iron may be, for example, at least one selected from the group consisting of Fe-Cr alloys (stainless steel), Fe-Ni-Cr alloys (stainless steel), Fe-Si alloys, Fe-Si-Al alloys (sendust), Fe-Ni alloys (permalloy), Fe-Cu-Ni alloys (permalloy), Fe-Co alloys (permenjule), Fe-Cr-Si alloys (electromagnetic stainless steel), and Fe-Ni-Mn-C alloys (invar). The soft magnetic material may be amorphous. The soft magnetic material may be an Fe amorphous alloy. The magnetic particles 1 composed of a soft magnetic material may be composed of amorphous iron or carbonyl iron. When composed of the magnetic particles 1, the particle size of the magnetic particles 1 may be 60 μm or more and may be 150 μm or less.

[0016] The magnetic particles 1 may contain a plurality of metal elements. In addition to the above elements, the magnetic particles 1 may further contain at least one element selected from the group consisting of base metal elements, noble metal elements, transition metal elements, and rare earth elements. The magnetic particles 1 may further contain at least one element selected from the group consisting of copper (Cu), titanium (Ti), manganese (Mn), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), tin (Sn), chromium (Cr), barium (Ba), strontium (Sr), lead (Pb), silver (Ag), oxygen (О), beryllium (Be), phosphorus (P), boron (B), and silicon (Si).

[0017] The molded body 10 may contain one kind of magnetic particles or may contain a plurality of kinds of magnetic particles. The molded body 10 may contain a plurality of kinds of magnetic particles that differ in average particle size (for example, the median diameter (D50) measured by a laser diffraction particle size distribution measuring device). The shape of the magnetic particles 1 is not particularly limited. The magnetic particles 1 may be, for example, spherical, flat, or needle-shaped.

[0018] The binder resin 2 may be an epoxy resin having glycidyl groups. Examples of such epoxy resins include biphenyl-type epoxy resins, stilbene-type epoxy resins, diphenylmethane-type epoxy resins, sulfur atom-containing epoxy resins, novolac-type epoxy resins, dicyclopentadiene-type epoxy resins, salicylaldehyde-type epoxy resins, copolymer epoxy resins of naphthols and phenols, epoxidized aralkyl-type phenol resins, bisphenol-type epoxy resins, glycidyl ether-type epoxy resins of alcohols, glycidyl ether-type epoxy resins of paraxylylene and / or metaxylylene-modified phenol resins, glycidyl ether-type epoxy resins of terpene-modified phenol resins, cyclopentadiene-type epoxy resins, glycidyl ether-type epoxy resins of polycyclic aromatic ring-modified phenol resins, glycidyl ether-type epoxy resins of naphthalene ring-containing phenol resins, glycidyl ester-type epoxy resins, halogenated phenol novolac-type epoxy resins, orthocresol novolac-type epoxy resins, hydroquinone-type epoxy resins, thioether-type epoxy resins, and trimethylolpropane-type epoxy resins.

[0019] The molded article 10 may further contain other resins in addition to the binder resin 2 having glycidyl groups. Examples of other resins include phenolic resins, bismaleimide resins, polyimide resins, polyamideimide resins, polyphenylene sulfide resins, acrylic resins, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyethylene terephthalate, and silicone resins.

[0020] The molded body 10 may further contain additives in addition to the binder resin 2 and other resins. Examples of additives include curing agents, coupling agents (e.g., silane coupling agents), curing accelerators (curing catalysts), flame retardants, waxes (lubricants), and organic solvents.

[0021] The content of magnetic particles 1 in the molded body 10 may be 95 parts by mass or more, or 96 parts by mass or more, and 99.5 parts by mass or less, or 99 parts by mass or less, based on 100 parts by mass of the total mass of magnetic particles 1 and binder resin 2. The content of binder resin 2 in the molded body 10 may be 0.5 parts by mass or more, or 1 part by mass or more, and 5 parts by mass or less, or 4 parts by mass or less, based on 100 parts by mass of the total mass of magnetic particles 1 and binder resin 2.

[0022] The molded body 10 described above may be manufactured by the following method.

[0023] First, a resin solution is obtained by dissolving the binder resin in an organic solvent. Examples of organic solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, benzene, toluene, and xylene. Magnetic particles (magnetic powder, which is an aggregate of magnetic particles) are added to the resin composition to disperse the magnetic particles in the resin solution, and then the organic solvent is removed by vacuum distillation and drying. As a result, a compound (powder) is obtained in which the surface of each magnetic particle is coated with the binder resin. The compound may also be obtained by pulverizing the solid material after the organic solvent has been removed.

[0024] Although organic solvents are used in the compound preparation method described above, the compound may be prepared without using organic solvents. In other words, the compound may be prepared by dry mixing without the use of organic solvents. For example, magnetic particles and binder resin may be mixed in a sealed container.

[0025] The resulting compound is filled into a mold and compression molding is performed to obtain a molded body. The molding pressure may be 500 MPa or more or 700 MPa or more, and may be 2500 MPa or less or 2000 MPa or less. The compound may be molded such that the density of the molded body is 75% to 90% of the true density of the magnetic particles.

[0026] The resulting molded body may be heated to heat-cur the binder resin coating the surface of the magnetic particles. This allows the magnetic particles to bond firmly to each other with the binder resin, making it easier to obtain a molded body with high mechanical strength. The heating temperature may be 150°C or higher or 200°C or higher, and 450°C or lower or 350°C or lower. The heating time may be 5 minutes or higher or 15 minutes or higher, and 4 hours or lower or 3 hours or lower.

[0027] In step S1, the above-described molded body 10 is impregnated with the monomer composition. The monomer composition may be impregnated into each void 3 formed inside the molded body 10 through the voids 3 opened on the surface of the molded body 10. Specifically, for example, the monomer composition may be impregnated into the voids 3 in the porous molded body 10 by the following method.

[0028] The entire porous molded body 10 is immersed in a monomer composition contained in a container that can be depressurized. Subsequent depressurization of the container removes the gas present in the voids 3 within the molded body 10. After the gas is removed from the molded body 10, the pressure inside the container is returned to atmospheric pressure. In this way, the monomer composition is impregnated into the voids 3 of the porous molded body 10. The depressurization operation and release of atmospheric pressure inside the container may be performed only once. Multiple depressurization operations and releases of atmospheric pressure may be repeated alternately.

[0029] The monomer composition contains monomer X, which has polymerizable groups and functional groups that can react with the glycidyl groups of the binder resin 2. The monomer X may have ethylenically unsaturated groups as polymerizable groups, or it may have (meth)acryloyl groups.

[0030] A functional group that can react with a glycidyl group means a group that can react with a glycidyl group in step S3. This functional group may be at least one selected from the group consisting of a phenolic hydroxyl group, a carboxyl group, and an amino group.

[0031] When the functional group is a phenolic hydroxyl group, monoma X may be a (meth)acrylate having a phenolic hydroxyl group. An example of a (meth)acrylate having a phenolic hydroxyl group is 4-hydroxyphenyl (meth)acrylate.

[0032] When the functional group is a carboxyl group, examples of monomer X include (meth)acrylic acid, (meth)acrylic acid, carboxyethyl (meth)acrylate, and carboxypentyl (meth)acrylate.

[0033] When the functional group is an amino group, monoma X may be an amino group-containing (meth)acrylate. Examples of amino group-containing (meth)acrylates include N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, and N,N-diethylaminopropyl (meth)acrylate.

[0034] The monomer composition may further contain monomers other than monomer X. The other monomers may be other (meth)acrylates that do not have the above-mentioned functional groups. The other (meth)acrylates may be monofunctional (meth)acrylates having one (meth)acryloyl group, or polyfunctional (meth)acrylates having two or more (meth)acryloyl groups.

[0035] Examples of monofunctional (meth)acrylates include alkyl (meth)acrylates, hydroxyalkyl (meth)acrylates, alkoxypolyalkylene glycol (meth)acrylates, and phenoxypolyalkylene glycol (meth)acrylates. In alkyl (meth)acrylates, the number of carbon atoms in the alkyl group may be 1 or more and 18 or less. In hydroxyalkyl (meth)acrylates, the number of carbon atoms in the hydroxyalkyl group may be 1 or more and 4 or less. In alkoxypolyalkylene glycol (meth)acrylates, the number of carbon atoms in the alkoxy group may be 1 or more and 4 or less. In alkoxypolyalkylene glycol (meth)acrylates and phenoxypolyalkylene glycol (meth)acrylates, the number of carbon atoms in the oxyalkylene group may be 1 or more and 4 or less, and the number of oxyalkyl groups may be 1 or more and 4 or less.

[0036] Examples of polyfunctional (meth)acrylates include pentaerythritol tetra(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl di(meth)acrylate, methoxydiethylene glycol di(meth)acrylate, methoxytetraethylene glycol di(meth)acrylate, and methoxydiethylene glycol di(meth)acrylate.

[0037] In one embodiment, the monomer composition does not contain monomers having a glycidyl group, such as glycidyl (meth)acrylate. For example, since glycidyl methacrylate is designated as a hazardous substance, a monomer composition that does not contain glycidyl methacrylate is preferable in that it does not use a hazardous substance.

[0038] The monomer composition may further contain a polymerization initiator. The polymerization initiator may be a thermal radical polymerization initiator. The thermal radical polymerization initiator may be at least one selected from the group consisting of azo compounds and organic peroxides, and is preferably an organic peroxide. The organic peroxide may preferably be a liquid at room temperature. Examples of organic peroxides include benzoyl peroxide, t-butyl peroxy-2-ethylhexanoate, and lauryl peroxide.

[0039] The amount of monoma X in the monoma composition may be 1% by mass or more, 5% by mass or more, or 10% by mass or more, and may be 80% by mass or less, 60% by mass or less, or 50% by mass or less, based on the total mass of the monoma composition.

[0040] The total content of monoma X and other monomas in the monoma composition may be 95% by mass or more, or 98% by mass or more, and 99.9% by mass or less, or 99% by mass or more, based on the total mass of the monoma composition.

[0041] The amount of polymerization initiator in the monomer composition may be 0.1% by mass or more, or 1% by mass or more, or 2% by mass or less, or 5% by mass or more, based on the total mass of the monomer composition.

[0042] The viscosity of the monomer composition at 25°C may be 1 mPa·s or more, 10 mPa·s or more, or 20 mPa·s or more, and may be 200 mPa·s or less, 100 mPa·s or less, or 90 mPa·s or less.

[0043] Formula (1): Rm=(M B -M A ) / M B ×100 (1) The impregnation amount Rm of the monomer composition represented by formula (1) may be 0.1% by mass or 0.5% by mass or more, and may be 5% by mass or less or 2% by mass or less. B M is the mass of the molded body impregnated with the monomer composition. AThis is the mass of the porous molded body before it is impregnated with the monomer composition.

[0044] The monomer composition described above is suitable as a composition used to manufacture bonded magnets by impregnating a porous molded body containing magnetic particles and a binder resin having glycidyl groups. That is, one embodiment of the present disclosure is a composition used to manufacture bonded magnets by impregnating a porous molded body containing magnetic particles and a binder resin having glycidyl groups, and contains monomer X having a functional group that can react with a glycidyl group.

[0045] Following step S1, step S2 is carried out. In step S2, monomer X (and other monomers used as needed) polymerizes by heating, for example. The heating temperature and heating time are set appropriately according to the polymerization initiator (thermal radical polymerization initiator). The heating temperature may be 40°C or higher, 60°C or higher, or 80°C or higher, and may be 120°C or lower, 110°C or lower, or 100°C or lower. The heating time may be 30 minutes or more, and may be 2 hours or less.

[0046] In one embodiment, step S3 is carried out following step S2. In step S3, for example, the glycidyl groups of the binder resin are reacted with the functional groups derived from monomer X (functional groups possessed by the polymer produced by polymerization in step S2) by heating. The heating temperature may be 150°C or higher or 180°C or higher, and 210°C or lower or 200°C or lower. The heating time may be 10 minutes or higher, and 1 hour or lower.

[0047] In another embodiment, steps S2 and S3 may be carried out simultaneously. For example, steps S2 and S3 may be carried out simultaneously if the heating temperature and heating time for polymerizing monomer X (and other monomers as may be used) are similar to the heating temperature and heating time for reacting the glycidyl groups of the binder resin with the functional groups derived from monomer X.

[0048] As step S3 is performed, the binder resin and the polymer containing monomer X (and other monomers used as necessary) as monomer units are bonded together. This results in a bonded magnet. Figure 2 is a schematic cross-sectional view showing one embodiment of a bonded magnet. As shown in Figure 2, the bonded magnet 20 in one embodiment comprises a plurality of magnetic particles 1, a binder resin 2 that bonds the plurality of magnetic particles 1 together, and a polymer 4 that exists between adjacent plurality of magnetic particles 1 (the space surrounded by the binder resin 2 covering each magnetic particle 1).

[0049] In this bonded magnet 20, polymer 4 is bonded to binder resin 2 via a linking group. This linking group is formed by the reaction of a glycidyl group with a functional group that can react with the glycidyl group (a functional group derived from monomer X). In this linking group, the structure derived from the glycidyl group is located on the binder resin 2 side, and the structure derived from the functional group is located on the polymer 4 side. That is, in the bonded magnet 20, the structure (binder resin 2)-(structure derived from glycidyl group)-(structure derived from functional group)-(polymer 4) is formed, and the linking group refers to the part -(structure derived from glycidyl group)-(structure derived from functional group)-.

[0050] In one embodiment, the bonded magnet has the above-described structure (a structure in which the binder resin and polymer are bonded together), which allows the polymer to crosslink the binder resins in a mesh-like manner, and allows the magnetic particles to bond more strongly to each other. As a result, the heat resistance of the bonded magnet is improved, and the mechanical strength of the bonded magnet tends to improve even at high temperatures. [Explanation of Symbols]

[0051] 1...Magnetic particles, 2...Binder resin, 3...Void, 4...Polymer, 10...Porous molded body, 20...Bonded magnet.

Claims

1. A step of impregnating a porous molded body containing magnetic particles and a binder resin having glycidyl groups with a composition containing a monomer having a functional group that can react with the glycidyl groups, A step of polymerizing the monomer impregnated in the molded body, A step of reacting the glycidyl group with the functional group, A method for manufacturing bonded magnets, comprising the following:

2. The manufacturing method according to claim 1, wherein the functional group is at least one selected from the group consisting of a phenolic hydroxyl group, a carboxyl group, and an amino group.

3. The manufacturing method according to claim 1, wherein the monomer is a (meth)acrylate having a phenolic hydroxyl group.

4. The manufacturing method according to claim 1, wherein the monomer is (meth)acrylic acid.

5. The manufacturing method according to claim 1, wherein the monomer is a (meth)acrylate having an amino group.

6. A composition used for manufacturing bonded magnets by impregnating a porous molded body containing magnetic particles and a binder resin having glycidyl groups, A composition containing a monomer having a functional group that can react with the glycidyl group.

7. The composition according to claim 6, wherein the functional group is at least one selected from the group consisting of a phenolic hydroxyl group, a carboxyl group, and an amino group.

8. The composition according to claim 6, wherein the monomer is a (meth)acrylate having a phenolic hydroxyl group.

9. The composition according to claim 6, wherein the monomer is (meth)acrylic acid.

10. The composition according to claim 6, wherein the monomer is a (meth)acrylate having an amino group.

11. Magnetic particles and, A binder resin that binds the magnetic particles together, The binder resin comprises a polymer bonded to the binder resin via a linking group, A bonded magnet in which the linking group is a group formed by the reaction of a glycidyl group with a functional group that can react with the glycidyl group.

12. The bond magnet according to claim 11, wherein the functional group is at least one selected from the group consisting of a phenolic hydroxyl group, a carboxyl group, and an amino group.

13. The bond magnet according to claim 11, wherein the functional group is derived from a (meth)acrylate having a phenolic hydroxyl group.

14. The bond magnet according to claim 11, wherein the functional group is derived from (meth)acrylic acid.

15. The bonded magnet according to claim 11, wherein the functional group is derived from a (meth)acrylate having an amino group.

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