Manufacturing method for bonded magnets

Abstract

This invention provides a novel manufacturing method for bonded magnets using a thermosetting resin that can be cured in a shorter time than conventional methods. [Solution] A method for manufacturing a bonded magnet comprises the steps of: preparing a main component containing magnetic particles including an Sm-Fe-N permanent magnet and an epoxy resin; preparing a curing agent containing magnetic particles including an Sm-Fe-N permanent magnet and a diamine; preparing a compound by mixing the main component and the curing agent; supplying the compound into a mold; and obtaining a molded body from the compound by heating and compressing the compound in the mold.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing bonded magnets.

Background Art

[0002] Sm-Fe-N-based permanent magnets (samarium-iron-nitrogen-based permanent magnets) can be manufactured from cheaper raw materials compared to other rare-earth magnets such as Nd-Fe-B-based permanent magnets (neodymium-iron-boron-based permanent magnets), and have excellent magnetic properties. However, since the crystal structure of Sm-Fe-N-based permanent magnets is liable to deteriorate at high temperatures (about 500°C), it is difficult to manufacture sintered magnets from Sm-Fe-N-based permanent magnets. Therefore, Sm-Fe-N-based permanent magnets are used as raw materials for bonded magnets that can be manufactured by heating at a low temperature at which the crystal structure is maintained (thermosetting of the thermosetting resin mixed with magnetic particles).

[0003] As a raw material for bonded magnets, a compound containing magnetic particles and a thermosetting resin is used (for example, Patent Document 1). Further, Patent Document 2 discloses a resin particle mixture that can be used as a molding material for bonded magnets and the like and has an excellent pot life. More specifically, a bonded magnet manufactured from a resin particle mixture containing epoxy resin particles and phenol resin particles containing a curing accelerator and Sm-Fe-N powder is disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the manufacture of bonded magnets, a compound is supplied into a mold, heated, and compressed to produce a bonded magnet made from a cured compound. If the thermosetting resin in the molded body formed in the mold is not sufficiently cured, the molded body is prone to deformation or breakage when removed from the mold. Therefore, it would be useful to use a thermosetting resin that can be cured in a shorter time than conventional resins.

[0006] This disclosure aims to provide a novel method for manufacturing bonded magnets. [Means for solving the problem]

[0007] This disclosure provides, for example, the following [1] to [8].

[0008] [1] A step of preparing a main component containing magnetic particles including an Sm-Fe-N permanent magnet and an epoxy resin, and a curing agent containing magnetic particles including an Sm-Fe-N permanent magnet and a diamine, The process involves mixing the main component and the curing agent to prepare a compound, and supplying the compound into a mold. A method for manufacturing a bonded magnet, comprising the steps of: heating and compressing the compound in the mold to obtain a molded body from the compound. [2] The manufacturing method according to [1], wherein the diamine comprises an aromatic diamine. [3] The manufacturing method according to [1] or [2], further comprising the step of storing the main component and the curing agent. [4] The manufacturing method according to any one of [1] to [3], wherein the heating and compression of the compound is carried out while a magnetic field is applied to the compound. [5] The manufacturing method according to [4], which does not include a step of demagnetizing the molded body. [6] The magnetic particles in the main component are coated with the epoxy resin, The manufacturing method according to any one of [1] to [5], wherein the magnetic particles in the curing agent are coated with the diamine. [7] Coated particles comprising magnetic particles and a diamine coating the magnetic particles. [8] Coated particles as described in [7], used for the manufacture of bonded magnets. [Effects of the Invention]

[0009] This disclosure provides a novel method for manufacturing bonded magnets. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic cross-sectional view showing an example of a bonded magnet. [Modes for carrying out the invention]

[0011] Embodiments of the present disclosure are described below. However, the following embodiments are illustrative for the purpose of illustrating the present disclosure and are not intended to limit the present disclosure to the following. In this specification, numerical ranges indicated by the symbol "~" include lower and upper limits. That is, a numerical range indicated by "x~y" means x or greater and y or less.

[0012] Unless otherwise specified, the materials exemplified herein may be used individually or in combination of two or more. The content of each component in a composition means the total amount of any multiple substances present in the composition, unless otherwise specified, if there are multiple substances corresponding to each component in the composition.

[0013] One embodiment of a method for manufacturing bonded magnets comprises: step S1 of preparing a main component containing magnetic particles including an Sm-Fe-N permanent magnet and an epoxy resin, and a curing agent containing magnetic particles including an Sm-Fe-N permanent magnet and a diamine; step S2 of mixing the main component and the curing agent to prepare a compound and supplying the compound into a mold; and step S3 of heating and compressing the compound in the mold to obtain a molded body from the compound.

[0014] In the conventional method for manufacturing bonded magnets, for example, a phenolic epoxy curing agent is used. In this case, the curing of the epoxy resin proceeds relatively slowly, and it is also possible to mix magnetic powder, epoxy resin, and epoxy curing agent in advance and store them as a composite. On the other hand, since curing takes time, there is a limit to improving the productivity of bonded magnets. In contrast, in the above-described method for manufacturing bonded magnets, a method of separately preparing a main agent and a curing agent is adopted, and by including a diamine, which is considered to have a relatively fast curing progress as a curing agent, it is possible to shorten the curing time as a composite. For this reason, it is possible to shorten the time for retaining the molded body in the mold, and the productivity of bonded magnets can be improved.

[0015] The magnetic particles used in step S1 include Sm-Fe-N-based permanent magnets. The Sm-Fe-N-based permanent magnet may be an alloy containing samarium (Sm), iron (Fe), and nitrogen (N). The Sm-Fe-N-based permanent magnet can have anisotropy. That is, in the powder composed of magnetic particles that are Sm-Fe-N-based permanent magnets, the magnetic domains in each magnetic particle can have an easy axis of magnetization (crystal axis) extending in one direction. The particle size of the magnetic particles may be, for example, 20 μm or more or 40 μm or more, and may be 300 μm or less or 250 μm or less.

[0016] As long as the magnetic particles contain Sm-Fe-N-based permanent magnets, they may further contain other permanent magnets. Other magnetic particles may include, for example, samarium-cobalt (Sm-Co) based alloy magnets, neodymium-iron-boron (Nd-Fe-B) based alloy magnets, iron-cobalt (Fe-Co) based alloy magnets, and Al-Ni-Co based alloy magnets (alnico magnets).

[0017] The epoxy resin used in step S1 may be a polyfunctional epoxy resin having two or more 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.

[0018] In the main component, the content of magnetic particles may be, for example, 90% by mass or more, or 95% by mass or more. The main component may contain other components in addition to magnetic particles and epoxy resin, but the main component does not have to contain diamine. The main component may consist of magnetic particles and epoxy resin.

[0019] The main agent contains magnetic particles and an epoxy resin, and its form is not limited. The magnetic particles in the main agent may be coated with the epoxy resin. The main agent may be an aggregate (powder) of coated particles in which the surface of the magnetic particles is coated with a coating layer (first coating layer) containing the epoxy resin. In this case, weighing is easy and the handleability is also excellent. Further, when the magnetic particles are covered with a coating layer containing the epoxy resin, a plurality of magnetic particles are likely to be firmly bonded by the curing of the epoxy resin in step S3. As a result, the bulk density, mechanical strength, and residual magnetic flux density of the bonded magnet produced from the compound are likely to increase. Furthermore, the electrical insulation of the compound is likely to be improved, and the electrical resistivity of the bonded magnet produced from the compound is likely to increase. The coated particles can be prepared by dissolving the epoxy resin in a solvent, bringing it into contact with the surface of the magnetic particles, and then removing the solvent. As the solvent, for example, a ketone solvent such as methyl ethyl ketone can be used.

[0020] The diamine used in step S1 is preferably a compound that is solid at 25°C. The diamine may contain an aromatic diamine and may be an aromatic diamine. Examples of the aromatic diamine include 4,4'-diaminodiphenylmethane, 3,3'-dichloro-4,4'-diaminodiphenylmethane, trimethylenebis(4-aminobenzoate), and 4,4'-methylenebis(2-ethyl-6-methylaniline).

[0021] In the curing agent, the content of the magnetic particles may be, for example, 90% by mass or more or 95% by mass or more. The curing agent may contain other components in addition to the magnetic particles and the diamine, but the curing agent does not have to contain an epoxy resin. The curing agent may consist of magnetic particles and a diamine.

[0022] The curing agent contains magnetic particles and a diamine, and its form is not limited. The magnetic particles in the curing agent may be coated with a diamine. The curing agent can also be described as a curing agent comprising magnetic particles and a diamine coating the magnetic particles. The curing agent can be stored alone as a curing agent used for the manufacture of bonded magnets. The curing agent may be an aggregate (powder) of coated particles in which the surface of the magnetic particles is coated with a coating layer (second coating layer) containing a diamine. In this case, it is easy to measure and easy to handle. The coated particles can be prepared by dissolving the diamine in a solvent, then bringing it into contact with the surface of the magnetic particles and removing the solvent. As the solvent, for example, a ketone solvent such as methyl ethyl ketone can be used.

[0023] In step 2, the compound is prepared and supplied into the mold. In the compound used in this embodiment, curing of the epoxy resin begins relatively quickly when the curing agent containing diamine is brought into contact with the main component; therefore, the compound is prepared immediately before being supplied into the mold. On the other hand, in the manufacturing method according to this disclosure, the main component and the curing agent are prepared separately and can be stored as compound raw materials as needed. Therefore, the above manufacturing method may further include a step of storing the main component and the curing agent after step S1 and before step S2. The storage of the main component and the curing agent may be, for example, in a sealed container or under an inert gas atmosphere.

[0024] The main component and the curing agent may be mixed, for example, by mixing without a solvent (dry mixing) or by stirring in a solvent (wet mixing), but dry mixing is preferred. If a solvent is used, a solvent in which the epoxy resin and diamine do not dissolve should be selected. Examples of such solvents include n-hexane and n-heptane.

[0025] In the compound prepared in step S2, the mixing ratio of the main component and the curing agent may be adjusted so that the amount of diamine is 20 parts by mass or more, or 300 parts by mass or less, per 100 parts by mass of epoxy resin.

[0026] The compound contains a main component and a hardener, but may also contain additives. Examples of additives include hardening accelerators (hardening catalysts), coupling agents (e.g., silane coupling agents), waxes (lubricants), reactive diluents, and flame retardants.

[0027] In step S3, a molded body is obtained by heating and compressing the compound. For example, the compound in the mold heated at molding temperature T may be compressed. Molding temperature T may be equal to or higher than the thermosetting temperature of the epoxy resin and the diamine. In this specification, thermosetting temperature is the temperature at which the thermosetting of the epoxy resin begins.

[0028] In step S3, heating and compression of the compound may be carried out while applying a magnetic field to the compound. For example, the compound in the mold may be compressed while a magnetic field is applied to the compound in the mold that has been heated at the molding temperature T. Each magnetic particle in the compound is magnetized and rotated by the magnetic field H, and the easy magnetization axis of the magnetic domain in each magnetic particle is oriented along the magnetic field. In other words, each magnetic particle 3 in the compound 2 is oriented such that its magnetization direction m is approximately parallel to the magnetic field H (see Figure 1). If each magnetic particle 3 is a single crystal grain (single magnetic domain), the magnetization direction m of each magnetic particle 3 is the same as the direction in which the easy magnetization axis of each magnetic particle 3 extends.

[0029] In step S3, the thermal curing of the epoxy and diamine forms a molded body 2A containing a plurality of magnetic particles oriented along the magnetic field H and a cured epoxy resin. In other words, a molded body 2A made of a cured compound 2 is formed. The magnetization direction M of the entire molded body 2A is substantially or perfectly parallel to the direction of the magnetic field H applied to the compound in step S3.

[0030] The molded body 2A obtained in step S3 may be an anisotropic bonded magnet. The overall magnetization direction of the anisotropic bonded magnet is substantially or perfectly parallel to the direction of the magnetic field H applied to the compound in step S3, the overall magnetization direction M of the molded body 2A, and the magnetization direction m of each magnetic particle 3 in the bonded magnet. The anisotropic bonded magnet can have a high residual magnetic flux density due to the excellent orientation of the magnetic powder. Furthermore, the compression of the compound in step S3 (i.e., the increase in the filling rate of magnetic powder in the molded body) and the thermal curing of the compound increase the mechanical strength and residual magnetic flux density of the anisotropic bonded magnet.

[0031] The molding temperature T may be, for example, 80 to 180°C or 120 to 150°C. The heating time may be, for example, 15 minutes or less, 0.5 to 15 minutes, or 0.5 to 10 minutes. In the manufacturing method according to this disclosure, since the curing agent contains diamine, the curing of the molded article proceeds sufficiently even with a short heating time.

[0032] The molding pressure in process S3 may be 500-2000 MPa, 700-2000 MPa, or 980-2000 MPa.

[0033] The magnetic field applied to the compound in the mold may be a static magnetic field (a continuous, constant magnetic field). The magnetic field may also be a pulsed magnetic field (a pulsed magnetic field). The strength of the static magnetic field may be, for example, 0.5 to 2.5 Tesla, 1.0 to 2.5 Tesla, or 2.0 to 2.5 Tesla. The time for which the static magnetic field is applied to the compound in the mold may be, for example, 0.08 to 4 minutes, 0.5 to 4 minutes, or 1 to 4 minutes. The strength of the pulsed magnetic field may be, for example, 4 to 12 Tesla, or 8 to 12 Tesla. The number of times the pulsed magnetic field is applied to the compound may be one or more times.

[0034] The above manufacturing method may further include a step of storing the main agent and the curing agent as a step following step S1, and a cooling step, a demagnetization step, a thermosetting step, and a magnetization step as steps following step S3.

[0035] If the molded body does not harden sufficiently when step S3 is performed while applying a magnetic field to the compound, the magnetic particles may move in a direction that causes them to protrude from the surface of the molded body along the direction of the magnetic field generated in the molded body due to the alignment of the magnetization directions of the magnetic particles, which can lead to deformation of the molded body. Therefore, generally, from the viewpoint of suppressing this deformation, a method is taken to suppress the deformation of the molded body by performing a demagnetization treatment on the molded body when it is removed from the mold. In contrast, in the above manufacturing method, since a compound that hardens quickly is used, it is possible to harden the molded body appropriately when it is removed from the mold, and deformation of the molded body is suppressed, so a demagnetization step is not required.

[0036] From the viewpoint of further advancing the curing of the epoxy resin in the molded body obtained in step S3, a thermosetting step may be included. In the thermosetting step, the molded body is heated to a temperature above the thermosetting temperature of the epoxy resin. As a result, the thermosetting of the epoxy resin in the molded body progresses further, and the bulk density, mechanical strength, and residual magnetic flux density of the molded body (bonded magnet) tend to increase further.

[0037] When a demagnetization process is performed, a magnetization process may be further included as a subsequent step in order to manufacture an anisotropic bonded magnet.

[0038] The bonded magnet according to this disclosure includes a cured compound. The cured compound includes a plurality of magnetic particles and a crosslinked epoxy resin reaction product (binder resin) that binds the plurality of magnetic particles together. The bonded magnet may consist only of the cured compound. The bonded magnet may be an anisotropic bonded magnet. An anisotropic bonded magnet means, for example, a bonded magnet 2 in which a plurality of magnetic particles 3 are bound together by a binder resin 5, as shown in Figure 1, in which the magnetization direction m of each magnetic particle 3 is oriented along the magnetization direction M.

[0039] One embodiment of the coated particles comprises magnetic particles and a diamine coating the magnetic particles. The magnetic particles and the diamine can be adapted as described in the above-described method for manufacturing bonded magnets. The coated particles may also be used for manufacturing bonded magnets. [Examples]

[0040] (Preparation of the main ingredient) A predetermined amount of epoxy resin-containing solution (resin solution) and magnetic powder (aggregate of magnetic particles) were measured, stirred, and mixed. The organic solvent was removed by heating and drying the mixture of resin solution and magnetic particles. In this way, a powder (main component) was obtained in which the surface of each magnetic particle was covered with epoxy resin.

[0041] As for epoxy resins, biphenyl-type epoxy resin (YX-4000H manufactured by Mitsubishi Chemical Corporation) TM ) was used. The amount of epoxy resin used was 3.5g. Methyl ethyl ketone was used as the organic solvent. The relative mass of the organic solvent to 1 part by mass of epoxy resin was 50 parts by mass. As for magnetic powders, Sm2Fe 17 SmFeN powder (spherical magnetic powder) containing a main phase of N3 was used. The amount of magnetic powder added was 100g.

[0042] (Preparation of hardening agent) A predetermined amount of a solution containing diamine (diamine solution) and magnetic powder (aggregate of magnetic particles) were measured out, stirred, and mixed. The organic solvent was removed by heating and drying the mixture of diamine solution and magnetic powder. In this way, a powder (curing agent) was obtained in which the surface of each magnetic particle was covered with diamine.

[0043] As the diamine used, 4,4'-diaminodiphenylmethane (manufactured by Tokyo Chemical Industry Co., Ltd.) was used. The amount of diamine used was 4.0 g. Methyl ethyl ketone was used as the organic solvent. The relative mass of the organic solvent to 1 part by mass of diamine was 60 parts by mass. As for magnetic powder, Sm2Fe 17 SmFeN powder (spherical magnetic powder) containing a main phase of N3 was used. The amount of magnetic powder added was 100g.

[0044] (Compound preparation) 30g of the main component and 20g of the hardener were measured into a 100mL plastic bottle and mixed by shaking for 10 minutes. The resulting mixed powder was used as the compound.

[0045] [Manufacturing of bonded magnets] (Supply process) Approximately 2g of the compound obtained as described above was supplied into the mold of the molding apparatus (supply process). Here, the shape of the mold (cavity) was cubic, and the volume of the mold (cavity) was 7mm x 7mm x 7mm. The molding apparatus (hydraulic press apparatus) was a TM-MPH10525-10A2TM model manufactured by Tamagawa Seisakusho Co., Ltd. TM I used it.

[0046] (molding process) Next, the pressure acting on the compound in the mold (molding pressure) was maintained at 1800 MPa, and molding was carried out at room temperature for 10 minutes. Through this molding process, a molded body was formed from the compound. After molding, the bonded magnet was removed from the mold without cooling the mold. The dimensions of the molded body were 7 mm in length, 7 mm in width, and 7 mm in height. In other words, the molded body was a cube. Subsequently, the molded body was heated at 100°C for 30 minutes to harden it. In this way, a bonded magnet was manufactured. [Industrial applicability]

[0047] This disclosure provides a novel method for manufacturing bonded magnets. This manufacturing method allows for improved productivity of bonded magnets compared to conventional methods. [Explanation of Symbols]

[0048] 2...Bonded magnet, 2A...Molded body, 3...Magnetic particles, 5...Binder resin, m...Magnification direction of magnetic particles, M...Magnification direction of bonded magnet.

Claims

1. A process for preparing a main component containing magnetic particles including an Sm-Fe-N permanent magnet and an epoxy resin, and a curing agent containing magnetic particles including an Sm-Fe-N permanent magnet and a diamine, The process involves mixing the main component and the curing agent to prepare a compound, and supplying the compound into a mold. A method for manufacturing a bonded magnet, comprising the steps of: heating and compressing the compound in the mold to obtain a molded body from the compound.

2. The manufacturing method according to claim 1, wherein the diamine includes an aromatic diamine.

3. The manufacturing method according to claim 1 or 2, further comprising the step of storing the main component and the curing agent.

4. The manufacturing method according to claim 1 or 2, wherein the heating and compression of the compound are performed while a magnetic field is applied to the compound.

5. The manufacturing method according to claim 4, which does not include a step of demagnetizing the molded body.

6. The magnetic particles in the main component are coated with the epoxy resin. The manufacturing method according to claim 1 or 2, wherein the magnetic particles in the curing agent are coated with the diamine.

7. Coated particles comprising magnetic particles and a diamine coating the magnetic particles.

8. Coated particles according to claim 7, used for manufacturing bonded magnets.

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