Method for manufacturing bonded magnets, bonded magnets, and curable composition for bonded magnets

Abstract

The present invention provides a method for manufacturing bonded magnets that can efficiently produce bonded magnets containing epoxy resin as a binder resin, a curable composition for bonded magnets that can efficiently produce bonded magnets containing epoxy resin as a binder resin, and a bonded magnet with high degree of freedom in shape and excellent properties. [Solution] A method for manufacturing a bonded magnet according to one aspect of this embodiment includes the step of heating and softening a curable composition for bonded magnets, which comprises magnetic powder, a trifunctional or polyfunctional epoxy resin, and an amine-based curing agent having a cyano group, and then injecting or pouring it into the cavity of a heated mold to cure it.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a bonded magnet, a bonded magnet, and a curable composition for a bonded magnet.

Background Art

[0002] Conventionally, ferrite magnets and rare earth magnets such as Sm-Co-based, Nd-Fe-B-based, and Sm-Fe-N-based magnets have been used in various applications. Magnets are required to have good magnetic properties, but depending on their applications, they are also required to be excellent in other properties such as heat resistance and durability, and may also be required to have a thin or complex shape.

[0003] As a conventional method for manufacturing magnets, for example, a sintering method can be mentioned. However, in the sintering method, it is generally difficult to manufacture a magnet with a thin or complex shape. Further, as a method for manufacturing a bonded magnet using a binder resin, a compression molding method can be mentioned. However, in the compression molding method, the amount of the binder resin used is small (usually 5% by mass or less), and similar to the sintering method, it is difficult to manufacture a magnet with a complex shape.

[0004] As methods capable of manufacturing a bonded magnet with a relatively complex shape, an injection molding method and a transfer molding method can be mentioned. Among these, for the injection molding method, a large-sized molding machine equipped with a magnetic field coil is commercially available, and it can be easily applied to the manufacture of a relatively large-sized bonded magnet molded product suitable for use in a motor or the like. Further, the injection molding method generally has a higher production speed than the transfer molding method and tends to be suitable for mass production. On the other hand, in the injection molding method, it is generally difficult to use a thermosetting resin as the binder resin in terms of continuous moldability, and usually, a thermoplastic resin is used.

[0005] Patent documents 1 to 3 disclose a method for manufacturing bonded magnets (resin-bonded magnets) by injection molding using a thermosetting resin as the binder resin. This method involves injecting a resin-bonded magnet composition, comprising a magnetic powder surface-coated with a specific compound and a binder component containing a thermosetting resin, wherein the binder component has a kinematic viscosity of 500 mPa·s to 3000 mPa·s at a temperature of -20°C to 150°C, into a mold at 150°C or below, and subsequently heating and curing the composition in the mold at 150°C or below. Furthermore, Patent documents 1 to 3 describe, as Comparative Example 3, an example in which a resin-bonded magnet composition (compound) consisting of Nd-Fe-B alloy magnetic powder, bisphenol A type solid epoxy resin (thermosetting resin), and dicyandiamide (curing agent) is injected into a mold at 180°C using an injection molding machine, and subsequently heat-cured in the mold maintained at 180°C to produce a resin-bonded magnet (bonded magnet). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 11-126710 [Patent Document 2] Japanese Patent Application Publication No. 11-126711 [Patent Document 3] Japanese Patent Application Publication No. 11-135314 [Overview of the project] [Problems that the invention aims to solve]

[0007] For example, in applications requiring heat resistance (durability and resistance to deformation at high temperatures), such as automotive drive motors, auxiliary motors, and various pumps like oil pumps, it is sometimes desirable to use a thermosetting resin as the binder resin for bonded magnets. In particular, epoxy resin is sometimes preferable because it possesses a good balance of the physical properties required for bonded magnets, including heat resistance, durability, mechanical strength, chemical resistance, fluidity during molding, and bonding properties with magnetic powder.

[0008] However, it is generally difficult to manufacture bonded magnets by injection molding using epoxy resin, a thermosetting resin, as the binder resin. In injection molding, a curable composition for bonded magnets, containing magnetic powder, epoxy resin, and a curing agent, is heated and softened (melted) in a screw cylinder, and then injected into the cavity of a heated mold to cure. At this time, it is necessary to suppress the rapid progress of the curing reaction and maintain the fluidity of the curable composition for bonded magnets during the softening phase before injection into the mold, while at the same time, it is necessary to allow the curing reaction to proceed rapidly during the curing phase after injection into the mold. Achieving control of these conflicting curing reaction processes is not easy. In addition, the temperature at which the curable composition for bonded magnets is cured can affect the heat resistance of the resulting bonded magnets; a lower curing temperature tends to result in lower heat resistance of the resulting bonded magnets.

[0009] As described above, in the methods described in Patent Documents 1 to 3, a curable composition for bonded magnets containing a thermosetting resin as a binder resin is injected into a mold at 150°C or below and heat-cured at 150°C or below. However, because the curing temperature is low, the resulting bonded magnets tend to have insufficient heat resistance. Furthermore, in Comparative Example 3 of Patent Documents 1 to 3, a curable composition for bonded magnets containing a bisphenol A type solid epoxy resin as a binder resin and dicyandiamide as a curing agent is heat-cured at 180°C. However, with this combination of binder resin and curing agent, the curing reaction proceeds slowly and takes a long time, making it difficult to manufacture (molde) bonded magnets with the productivity normally required.

[0010] On the other hand, in the transfer molding method, a thermosetting resin can be used as the binder resin. Therefore, it is possible to manufacture bonded magnets using epoxy resin as the binder resin according to the transfer molding method. However, from the viewpoint of productivity, in the transfer molding method as in the injection molding method, it is desirable to suppress the hardening of the bonded magnet curable composition when it is softened before being injected into the mold cavity, and to harden the bonded magnet curable composition in a short time after it has been injected into the mold cavity.

[0011] One embodiment of the present invention aims to provide a method for manufacturing bonded magnets that can efficiently produce bonded magnets containing epoxy resin as a binder resin. Furthermore, another embodiment of the present invention aims to provide a bonded magnet with a high degree of freedom in shape and excellent properties. A further embodiment of the present invention aims to provide a bonded magnet with a high degree of freedom in shape and excellent magnetic properties and heat resistance. Furthermore, another embodiment of the present invention aims to provide a curable composition for bonded magnets that can efficiently manufacture bonded magnets containing an epoxy resin as a binder resin. A further embodiment of the present invention aims to provide a curable composition for bonded magnets that contains an epoxy resin as a binder resin and is applicable to injection molding or transfer molding methods. [Means for solving the problem]

[0012] A method for manufacturing a bonded magnet according to one embodiment of the present invention includes the step of heating and softening a curable composition for bonded magnets, which comprises magnetic powder, a trifunctional or polyfunctional epoxy resin, and an amine-based curing agent having a cyano group, and then injecting or pouring it into the cavity of a heated mold to cure it. A bonded magnet according to another embodiment of the present invention is manufactured by the method for manufacturing a bonded magnet described above. Furthermore, a bonded magnet according to another embodiment of the present invention comprises a magnetic powder and a cured product of a curable composition containing an epoxy resin and an amine-based curing agent having a cyano group, wherein the content of the magnetic powder is 80% by mass or more and less than 95% by mass. A curable composition for bonded magnets according to a further embodiment of the present invention comprises magnetic powder, a polyfunctional epoxy resin with three or more functions, and an amine-based curing agent having a cyano group, wherein the content of the magnetic powder is 80% by mass or more and less than 95% by mass. Here, "bonded magnets" refer to what are commonly known as "magnets," or permanent magnets. Once a permanent magnet is magnetized, it can maintain its magnetic force for a long period of time even after the external magnetic field is removed. [Effects of the Invention]

[0013] According to one embodiment of the present invention, a method for manufacturing bonded magnets containing epoxy resin as a binder resin can be provided that enables productive manufacturing of bonded magnets. According to another embodiment of the present invention, a bonded magnet with a high degree of freedom in shape and excellent properties can be provided. Furthermore, according to yet another embodiment of the present invention, a bonded magnet with a high degree of freedom in shape and excellent magnetic properties and heat resistance can be provided. Furthermore, according to another embodiment of the present invention, a curable composition for bonded magnets that allows for the productive manufacture of bonded magnets containing an epoxy resin as a binder resin, or a curable composition for bonded magnets that contains an epoxy resin as a binder resin and is applicable to injection molding or transfer molding methods, etc., can be provided. [Modes for carrying out the invention]

[0014] Hereinafter, embodiments of the present invention will be described in detail. However, the embodiments shown below are merely examples for embodying the technical idea of the present invention, and the present invention is not limited to the following. In this specification, a numerical range indicated by using "~" indicates a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively.

[0015] <Method for manufacturing bonded magnet> A method for manufacturing a bonded magnet according to an embodiment of the present invention includes a step of heating a curable composition for a bonded magnet (hereinafter, also simply referred to as "composition for bonded magnet") containing magnetic powder, a trifunctional or higher polyfunctional epoxy resin, and an amine-based curing agent having a cyano group to soften it, and then injecting or pouring it into a cavity of a heated mold to cure it (hereinafter, also referred to as "curing and molding step"). Here, the cavity of the mold is a hollow portion formed by the mold. In one aspect of this embodiment, it is preferable that the curable composition for a bonded magnet contains a polyfunctional phenolic curing agent in addition to the amine-based curing agent having a cyano group.

[0016] An amine-based curing agent having a cyano group such as dicyandiamide is a latent curing agent, which stably exists in the epoxy resin at room temperature and does not function as a curing agent. When heated to a high temperature, it dissolves and decomposes in the epoxy resin, and the curing reaction starts. However, an amine-based curing agent having a cyano group such as dicyandiamide generally has a slow progress of its curing reaction and tends to require a long time for curing. On the other hand, by using a trifunctional or higher polyfunctional epoxy resin containing a large number of epoxy groups, which are reactive groups, as the main epoxy resin, once the curing reaction starts, the curing reaction can proceed more rapidly, and curing can be completed in a relatively short time. When the composition for a bonded magnet contains a polyfunctional phenolic curing agent in addition to the amine-based curing agent having a cyano group, similarly, the curing reaction does not start until heated to a high temperature, but in some cases, curing can be completed in a shorter time after the start of the curing reaction.

[0017] That is, by manufacturing (molding) a bonded magnet using a composition for a bonded magnet containing magnetic powder, a polyfunctional epoxy resin having three or more functional groups, and an amine-based curing agent having a cyano group such as dicyandiamide, or a composition for a bonded magnet containing magnetic powder, a polyfunctional epoxy resin having three or more functional groups, an amine-based curing agent having a cyano group such as dicyandiamide, and a polyfunctional phenolic curing agent, before injecting or pouring the composition for a bonded magnet into the cavity of a mold, the curing reaction of the composition for a bonded magnet can be suppressed, and while maintaining its fluidity, the composition for a bonded magnet can be heated and softened. After injecting or pouring the composition for a bonded magnet into the cavity of a mold, the curing reaction can proceed rapidly, and the composition for a bonded magnet can be cured in a short time. As a result, a bonded magnet containing an epoxy resin as a binder resin can be produced with high productivity. Moreover, since the composition for a bonded magnet is suppressed from curing and solidifying in the space for softening the composition for a bonded magnet or in the passage to the cavity of the mold, the bonded magnet can be stably and continuously molded.

[0018] In addition, the method for manufacturing a bonded magnet and the curable composition for a bonded magnet of the present embodiment can also be applied to injection molding methods, transfer molding methods, etc. that can easily manufacture bonded magnets of various shapes from simple shapes to relatively complex shapes. Therefore, it is possible to obtain a bonded magnet with a high degree of freedom in shape and excellent characteristics.

[0019] Note that a curable composition for a bonded magnet containing an amine-based curing agent (latent curing agent) having a cyano group such as dicyandiamide tends to be able to be stored at room temperature for a relatively long time.

[0020] <<Curable Composition for Bonded Magnet>> The curable composition for bonded magnets according to this embodiment (also simply referred to as "composition for bonded magnets") comprises magnetic powder, a polyfunctional epoxy resin with three or more functions, and an amine-based curing agent having cyano groups. The composition for bonded magnets may also contain curing agents other than the amine-based curing agent having cyano groups, or curing accelerators, and may also contain a bifunctional epoxy resin. Here, the polyfunctional epoxy resin with three or more functions and the bifunctional epoxy resin are the main components of the epoxy resin and react with the curing agent to form a cured product. The epoxy resin with three or more functions has three or more epoxy groups in one molecule, and the bifunctional epoxy resin has two epoxy groups in one molecule. Furthermore, the epoxy resin may be any epoxy compound such as a monomer that hardens to form an epoxy resin.

[0021] The content of magnetic powder in the bonded magnet composition is not particularly limited, as long as the desired fluidity during molding can be ensured. In one embodiment of this invention, the content of magnetic powder in the bonded magnet composition is preferably less than 95% by mass, and more preferably 93% by mass or less. When the content of magnetic powder in the bonded magnet composition is less than 95% by mass, and more preferably 93% by mass or less, it can usually be easily molded by injection molding or transfer molding. Furthermore, although the content of magnetic powder in the bonded magnet composition is not particularly limited, from the viewpoint of the magnetic properties of the resulting bonded magnet, it is preferably 80% by mass or more, and more preferably 85% by mass or more.

[0022] [Epoxy resin (main component)] The bonded magnet composition according to this embodiment includes a polyfunctional epoxy resin with three or more functions as the epoxy resin (main component), and may also include a bifunctional epoxy resin. The polyfunctional epoxy resin with three or more functions and the bifunctional epoxy resin may be used individually or in combination of two or more.

[0023] In the bonded magnet composition of this embodiment, the content (percentage) of the trifunctional or polyfunctional epoxy resin relative to the total epoxy resin (main component) is preferably 10 to 100% by mass, more preferably 40 to 100% by mass, and even more preferably 60 to 100% by mass. In one embodiment of this embodiment, from the viewpoint of productivity or stability during molding, the content (percentage) of the trifunctional or polyfunctional epoxy resin relative to the total epoxy resin (main component) may be 60 to 95% by mass, and even more preferably 70 to 90% by mass.

[0024] Polyfunctional epoxy resins with three or more functions, and bifunctional epoxy resins, are not particularly limited and can be appropriately selected according to the desired physical properties. Examples of polyfunctional epoxy resins with three or more functions include novolac-type epoxy resins, glycidylamine-type epoxy resins, cresol novolac-type epoxy resins, trisphenolmethane-type epoxy resins, dicyclopentadiene-type epoxy resins, naphthalene-type epoxy resins, phenol biphenylene-type epoxy resins, biphenyl aralkyl-type epoxy resins, and triglycidyl isocyanurates. Examples of bifunctional epoxy resins include bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, brominated epoxy resins, glycidyl ethers such as biphenyl-type glycidyl ethers, glycidyl esters such as hydrophthalic acid-type glycidyl esters and dimer acid-type glycidyl esters, and alicyclic epoxy resins. Modified epoxy resins can also be used. As a polyfunctional epoxy resin with three or more functions, it is generally preferable to have one or more repeating units containing one or more epoxy groups, but it may also contain one or more repeating units that do not contain epoxy groups.

[0025] As for polyfunctional epoxy resins with three or more functions, those containing biphenyl structures are preferred in terms of the balance between the heat resistance of the resulting bonded magnets and other properties, and those containing unsubstituted biphenyl structures are more preferred, and among these, phenol aralkyl type epoxy resins or polyfunctional phenol aralkyl type epoxy resins containing unsubstituted biphenyl structures are preferred. Here, the (polyfunctional) phenol aralkyl type epoxy resin containing unsubstituted biphenyl structures may contain one or more repeating units in which one epoxy group is bonded to a benzene ring via oxygen (-O-), and one or more repeating units in which two or more epoxy groups are bonded to a benzene ring via oxygen (-O-).

[0026] For polyfunctional epoxy resins with three or more functions, the epoxy equivalent is usually preferably 290 g / eq or less, more preferably 280 g / eq or less, more preferably 250 g / eq or less, more preferably 230 g / eq or less, and even more preferably 220 g / eq or less, from the viewpoint of curability during molding. The lower limit of the epoxy equivalent of polyfunctional epoxy resins with three or more functions is not particularly limited, but is usually around 150 g / eq.

[0027] Commercially available polyfunctional epoxy resins with three or more functions can also be used. Examples of commercially available polyfunctional epoxy resins include NC-3000, NC-3500, EPPN-502H (all manufactured by Nippon Kayaku Co., Ltd.), jER 1031S, jER 1032H60, jER 154, and FAE 2500 (all manufactured by Mitsubishi Chemical Corporation).

[0028] As described above, the bond magnet composition of this embodiment may also contain a bifunctional epoxy resin in addition to a polyfunctional epoxy resin with three or more functions. As the bifunctional epoxy resin, a crystalline epoxy resin is preferred in terms of the fluidity and retention stability of the bond magnet composition during molding. In one embodiment of this embodiment, a crystalline epoxy resin containing a biphenyl structure (crystalline biphenyl epoxy resin) is more preferred in terms of the fluidity and retention stability of the bond magnet composition during molding, as well as the excellent properties of the resulting bond magnet, such as heat resistance, and a crystalline biphenyl epoxy resin containing a biphenyl structure substituted with one or more alkyl groups (preferably methyl groups) or unsubstituted is even more preferred.

[0029] The epoxy equivalent of the bifunctional epoxy resin is not particularly limited, but is generally preferred to be 220 g / eq or less, and more preferably 200 g / eq or less. The lower limit of the epoxy equivalent of the bifunctional epoxy resin is also not particularly limited, but is generally around 140 g / eq.

[0030] The melting or softening point of a bifunctional epoxy resin is generally preferably 140°C or lower, and more preferably 110°C or lower, from the viewpoint of fluidity during molding. The lower limit of the melting or softening point of a bifunctional epoxy resin is not particularly limited, but from the viewpoint of storage stability at room temperature, it is preferably 60°C or higher, and more preferably 70°C or higher.

[0031] Commercially available bifunctional epoxy resins can also be used. Examples of commercially available bifunctional epoxy resins include YX4000, YX4000K, YX8800, YL6677 (all manufactured by Mitsubishi Chemical Corporation), and YSLV-70XY, YSLV-80XY (both manufactured by Nippon Steel Chemical & Material Co., Ltd.).

[0032] [Hardening agent] The bonded magnet composition according to this embodiment includes a cyano group-containing amine curing agent as a curing agent. The bonded magnet composition may further include curing agents for other epoxy resins. The cyano group-containing amine curing agent and the curing agents for other epoxy resins may be used individually or in combination of two or more types.

[0033] In the bonded magnet composition of this embodiment, the content (percentage) of the amine-based curing agent having a cyano group relative to the total curing agent is preferably 30 to 100% by mass, more preferably 35 to 100% by mass, and even more preferably 40 to 100% by mass. In one embodiment of this embodiment, from the viewpoint of productivity, the content (percentage) of the amine-based curing agent having a cyano group relative to the total curing agent may be more preferably 40 to 90% by mass, more preferably 40 to 80% by mass, and even more preferably 40 to 75% by mass.

[0034] The amine-based curing agent having a cyano group is not particularly limited, but an example is dicyandiamide. Dicyandiamide is usually included in the bond magnet composition in a solid state such as powder, but a small particle size is preferred from the viewpoint of speed of curing in the mold and the amount of unreacted components remaining in the reaction-cured product. In one embodiment of this product, the particle size (D50) of dicyandiamide is preferably several tens of μm or less, and more preferably several μm to several tens of nm. Here, D50 is the particle size corresponding to 50% of the cumulative value of the particle size distribution based on the volume of the particles. D50 can be measured under dry conditions using a laser diffraction particle size distribution analyzer.

[0035] Other curing agents besides amine-based curing agents having a cyano group are not particularly limited, but include, for example, phenol-based curing agents, hydrazide-based curing agents, acid anhydride-based curing agents, aromatic polyamine-based curing agents, alicyclic polyamine-based curing agents, tertiary amine-based curing agents, and imidazole-based curing agents.

[0036] Other curing agents besides amine-based curing agents containing cyano groups are preferred, from the viewpoint of stability during molding, those with a relatively high curing temperature, such as phenol-based curing agents. More preferably, from the viewpoint of productivity, stability during molding, and physical properties such as heat resistance of the resulting bonded magnets, polyfunctional phenol-based curing agents are preferred. A polyfunctional phenol-based curing agent is one that has three or more phenolic hydroxyl groups in one molecule.

[0037] While not particularly limited, polyfunctional phenolic curing agents include phenolic resins such as cresol novolac type phenolic resins, trisphenolmethane type phenolic resins, dicyclopentadiene type phenolic resins, naphthalene type phenolic resins, and phenol biphenylene type phenolic resins, with trisphenolmethane type phenolic resins being more preferred. Trisphenolmethane type phenolic resins are commercially available, and a specific example of a commercially available product is MEH-7500 (manufactured by UBE Corporation).

[0038] The melting or softening point of curing agents other than amine-based curing agents containing cyano groups, preferably phenol-based curing agents (phenol resins), is generally preferably 140°C or lower, and more preferably 110°C or lower, from the viewpoint of fluidity during molding. The lower limit of the melting or softening point of curing agents other than amine-based curing agents containing cyano groups is not particularly limited, but from the viewpoint of storage stability at room temperature, it is preferably 60°C or higher, and more preferably 70°C or higher.

[0039] The content of amine-based curing agents having cyano groups, such as dicyandiamide, and the content of other curing agents in the bonded magnet composition can be appropriately selected depending on the type of epoxy resin, curing agent, and curing accelerator used, and is not particularly limited. In one embodiment of this present invention, the content of amine-based curing agents having cyano groups (such as dicyandiamide) in the bonded magnet composition can be, for example, 5 to 20 parts by mass per 100 parts by mass of epoxy resin (main component), and the content of other curing agents other than amine-based curing agents having cyano groups can be, for example, 0 to 20 parts by mass per 100 parts by mass of epoxy resin (main component).

[0040] [Curing accelerator] The bonded magnet composition according to this embodiment may further contain a curing accelerator. The inclusion of a curing accelerator in the bonded magnet composition may lower the molding temperature (curing temperature of the composition) or shorten the molding time (curing time of the composition). The curing accelerator may be used alone or in combination of two or more types.

[0041] The curing accelerator is not particularly limited, but examples include urea-based curing accelerators such as dimethylurea, tertiary amine-based curing accelerators, imidazole-based curing accelerators, and aromatic amine-based curing accelerators.

[0042] As a curing accelerator, urea-based curing accelerators are preferred in terms of curability during molding and productivity, and among them, urea-based curing accelerators containing an aromatic ring (preferably a benzene ring) (aromatic urea-based curing accelerators) are more preferred in terms of their excellent reactivity with amine-based curing agents having a cyano group and the physical properties of the resulting bonded magnets, such as heat resistance. Commercially available urea-based curing accelerators can also be used, and specific examples of commercially available products include U-cat 3512T and U-cat 3513N (both manufactured by Sunapro Co., Ltd.).

[0043] The content of the curing accelerator in the bonded magnet composition can be appropriately selected depending on the type of epoxy resin, curing agent, and curing accelerator used, and is not particularly limited. In one embodiment of this product, the content of the curing accelerator in the bonded magnet composition can be, for example, 0.5 to 5 parts by mass per 100 parts by mass of epoxy resin (main component).

[0044] The curing accelerator may be included in the bond magnet composition before the curing and molding process, or it may be added to the bond magnet composition immediately before heating and softening it during the curing and molding process, or it may be added to the bond magnet composition at any point while heating and softening it.

[0045] [Magnetic powder] In the bonded magnet composition of this embodiment, the magnetic powder is not particularly limited as long as it is a material that, once magnetized by an external magnetic field, retains its magnetization even after the external magnetic field is removed; in other words, a so-called hard magnetic material. Any known material, such as ferrite powder or rare earth magnetic powder, can be suitably used. The magnetic powder may be used alone or in combination of two or more types.

[0046] In one embodiment of this model, rare earth magnetic powders are preferred due to their excellent magnetic properties. Examples of rare earth magnetic powders include Sm-Co, Nd-Fe-B, and Sm-Fe-N systems. In this embodiment, there are no particular limitations, and any rare earth magnetic powder can be suitably used. One type of rare earth magnetic powder may be used alone, or two or more types may be used in combination.

[0047] Sm-Co magnetic powder can be produced, for example, by the method disclosed in Japanese Patent Publication No. 08-260083. Nd-Fe-B magnetic powder can be produced, for example, by the HDR method disclosed in International Publication No. 2003 / 85147. Sm-Fe-N magnetic powder can be produced, for example, by the method disclosed in Japanese Patent Publication No. 11-189811.

[0048] In one embodiment of this invention, the rare earth magnetic powder is preferably an Sm-Fe-N type magnetic powder. As an example of an Sm-Fe-N type magnetic powder, Th2Zn 17 It has a crystal structure of type Sm x Fe 100-x-y N y Examples include nitrides composed of the rare earth metal samarium (Sm), iron (Fe), and nitrogen (N), represented by . Here, it is preferable that x is between 8.1 atomic% and 10 atomic%, y is between 13.5 atomic% and 13.9 atomic%, and the remainder is mainly Fe.

[0049] Rare earth magnetic powder can be used as is, but it can also be used after surface treatment with a silane coupling agent, for example. Surface treatment with a silane coupling agent can be carried out by methods disclosed, for example, in Japanese Patent Application Publication No. 2017-43804. Furthermore, in the case of Sm-Fe-N magnetic powder, a phosphate coating formed on the surface, i.e., phosphate-coated Sm-Fe-N magnetic powder, can also be used. Phosphate-coated Sm-Fe-N magnetic powder can be manufactured, for example, by methods disclosed in International Publication No. 2022 / 107462, Japanese Patent Publication No. 2023-96735, Japanese Patent Publication No. 2024-51932, etc.

[0050] The average particle size of rare earth magnetic powder is usually preferably between 0.1 μm and 250 μm. In the case of Sm-Co magnetic powder, the average particle size is usually more preferably between 10 μm and 250 μm. In the case of Nd-Fe-B magnetic powder, the average particle size is usually more preferably between 10 μm and 250 μm. In the case of Sm-Fe-N magnetic powder, the average particle size is usually more preferably between 2 μm and 5 μm, and even more preferably between 2.5 μm and 4.8 μm. By setting the average particle size to 2 μm or more, the amount of Sm-Fe-N magnetic powder packed into the bonded magnet can be increased, which may improve magnetization. Also, by setting the average particle size to 5 μm or less, the intrinsic coercivity of the bonded magnet may be improved. Here, the average particle size is the particle size measured under dry conditions using a laser diffraction particle size distribution analyzer.

[0051] For Sm-Fe-N magnetic powders, particle size D50 is preferably 2.5 μm to 5 μm, and more preferably 2.7 μm to 4.8 μm. Particle size D10 is preferably 1 μm to 3 μm, and more preferably 1.5 μm to 2.5 μm. Particle size D90 is preferably 3 μm to 7 μm, and more preferably 4 μm to 6 μm. Here, D50 is the particle size corresponding to 50% of the cumulative volume-based particle size distribution of the Sm-Fe-N magnetic powder. D10 is the particle size corresponding to 10% of the cumulative volume-based particle size distribution of the Sm-Fe-N magnetic powder. D90 is the particle size corresponding to 90% of the cumulative volume-based particle size distribution of the Sm-Fe-N magnetic powder.

[0052] The span defined below for Sm-Fe-N magnetic powders: Span = (D90 - D10) / D50 From the viewpoint of the coercivity of the bonded magnet, a value of 2 or less is preferable, and a value of 1.5 or less is more preferable.

[0053] The circularity of Sm-Fe-N magnetic powder is not particularly limited, but it is preferably 0.5 or higher, and more preferably 0.6 or higher. If the circularity is less than 0.5, the fluidity will be poor, and stress will be placed between particles during molding, which may reduce the magnetic properties. Here, the circularity is measured by binarizing SEM images taken at 3000x magnification using image processing, and the circularity is determined for each particle. The circularity defined here refers to the average value of the circularity obtained by measuring approximately 1000 to 10000 particles. Generally, the circularity increases as there are more particles with smaller particle sizes, so the circularity is measured for particles of 1 μm or larger. The definition formula for measuring circularity is: Circularity = (4πS / L 2 ) is used, where S is the two-dimensional projected area of ​​the particle and L is the two-dimensional projected perimeter.

[0054] [Sm-Fe-N magnetic powder] In one embodiment of this product, the Sm-Fe-N magnetic powder is preferably anisotropic from the viewpoint of the magnetic properties of the resulting bonded magnet. Furthermore, the Sm-Fe-N magnetic powder may be preferably coated with a phosphate on its surface from the viewpoint of improving coercivity and heat resistance.

[0055] The following describes an example of a method for producing the Sm-Fe-N anisotropic magnetic powder and the phosphate-coated Sm-Fe-N anisotropic magnetic powder according to this embodiment. However, the method is not limited to the following embodiment and can also be produced by other methods.

[0056] [Method for producing Sm-Fe-N anisotropic magnetic powder] The Sm-Fe-N anisotropic magnetic powder is not particularly limited, but for example, A step of mixing a solution containing Sm and Fe with a precipitating agent to obtain a precipitate containing Sm and Fe (precipitation step), A step of calcining the aforementioned precipitate to obtain an oxide containing Sm and Fe (oxidation step), A step of obtaining a partial oxide by heat-treating the aforementioned oxide in a reducing gas-containing atmosphere (pretreatment step), A step of reducing the aforementioned partial oxide (reduction step), and A process of nitriding the alloy particles obtained in the reduction process (nitriding process). It can be manufactured by a method that includes [a specific component].

[0057] (Precipitation process) In the precipitation process, the Sm and Fe raw materials are dissolved in a strongly acidic solution to prepare a solution containing Sm and Fe. (Sm2Fe) 17 When obtaining N3 as the main phase, the molar ratio of Sm to Fe (Sm:Fe) is preferably 1.5:17 to 3.0:17, and more preferably 2.0:17 to 2.5:17. Starting materials such as La, W, Co, Ti, Sc, Y, Pr, Nd, Pm, Gd, Tb, Dy, Ho, Er, Tm, and Lu may be added to the solution.

[0058] The Sm and Fe raw materials are not limited as long as they can dissolve in a strongly acidic solution. For example, in terms of availability, samarium oxide can be used as the Sm raw material and FeSO4 as the Fe raw material. The concentration of the solution containing Sm and Fe can be adjusted as appropriate within the range in which the Sm and Fe raw materials are substantially soluble in the acidic solution. In terms of solubility, sulfuric acid can be used as an acidic solution.

[0059] An insoluble precipitate containing Sm and Fe is obtained by reacting a solution containing Sm and Fe with a precipitating agent. Here, the solution containing Sm and Fe only needs to be a solution containing Sm and Fe when reacted with the precipitating agent. For example, the raw materials containing Sm and Fe may be prepared as separate solutions, and each solution may be added dropwise to react with the precipitating agent. Even when preparing the raw materials as separate solutions, they should be adjusted appropriately so that each raw material is substantially soluble in the acidic solution. The precipitating agent is not limited as long as it is an alkaline solution that reacts with a solution containing Sm and Fe to produce a precipitate, and examples include aqueous ammonia and caustic soda, with caustic soda being preferred.

[0060] For the precipitation reaction, a method is preferred in which a solution containing Sm and Fe and a precipitant are added dropwise to a solvent such as water, as this allows for easy adjustment of the particle properties of the precipitate. By appropriately controlling the supply rate of the solution containing Sm and Fe and the precipitant, the reaction temperature, the concentration of the reaction solution, and the pH during the reaction, a precipitate with a homogeneous distribution of constituent elements, a sharp particle size distribution, and a well-formed powder shape can be obtained. Using such a precipitate improves the magnetic properties of the final magnetic powder product. The reaction temperature is preferably 0 to 50°C, and more preferably 35 to 45°C. The concentration of the reaction solution is preferably 0.65 mol / L to 0.85 mol / L, and more preferably 0.7 mol / L to 0.84 mol / L, as the total concentration of metal ions. The reaction pH is preferably 5 to 9, and more preferably 6.5 to 8.

[0061] The particle powder obtained in the precipitation process roughly determines the particle size, shape, and particle size distribution of the final magnetic powder. When the particle size of the obtained particles is measured using a laser diffraction wet particle size analyzer, it is preferable that the size and distribution of the entire powder fall approximately within the range of 0.05 to 20 μm, preferably 0.1 to 10 μm. Furthermore, the average particle size is measured as the particle size corresponding to 50% of the volume cumulative from the small particle size side in the particle size distribution, and it is preferable that it falls within the range of 0.1 to 10 μm.

[0062] After separating the precipitate, it is preferable to desolvent the separated material to prevent the precipitate from redissolving in the remaining solvent during the subsequent oxidation heat treatment, which can lead to aggregation of the precipitate, changes in particle size distribution, powder particle size, etc., as the solvent evaporates. Specifically, a method for desolvation is to dry the material in an oven at 70-200°C for 5-12 hours, for example, when water is used as the solvent.

[0063] The process may include a step of separating and washing the precipitate after the precipitation step. The washing step is performed when the conductivity of the supernatant solution is 5 mS / m 2 Continue as needed until the following is achieved. For example, to separate the precipitate, a solvent (preferably water) can be added to the obtained precipitate and mixed, after which filtration, decantation, or the like can be used.

[0064] (oxidation process) The oxidation process involves calcining the precipitate formed in the precipitation process to obtain an oxide containing Sm and Fe. For example, the precipitate can be converted into an oxide by heat treatment. When heat treating the precipitate, it must be done in the presence of oxygen, for example, in an atmospheric environment. Furthermore, because it must be done in the presence of oxygen, it is preferable that the nonmetallic portion of the precipitate contains oxygen atoms.

[0065] The heat treatment temperature in the oxidation process (hereinafter also referred to as the oxidation temperature) is not particularly limited, but is preferably 700 to 1300°C, and more preferably 900 to 1200°C. Below 700°C, oxidation may be insufficient, and above 1300°C, it tends to be difficult to obtain the desired shape, average particle size, and particle size distribution of the magnetic powder. The heat treatment time is also not particularly limited, but is preferably 1 to 3 hours.

[0066] The resulting oxides exhibit sufficient microscopic mixing of Sm and Fe within the oxide particles, and the precipitate shape, particle size distribution, and other characteristics are reflected in the oxide particles.

[0067] (Pre-treatment process) The pretreatment step is a process in which an oxide containing Sm and Fe is heat-treated in a reducing gas atmosphere to obtain a partial oxide in which a portion of the oxide has been reduced.

[0068] Here, a partially oxide refers to an oxide in which a portion of the oxide has been reduced. The oxygen concentration of the oxide is not particularly limited, but it is preferably 10% by mass or less, and more preferably 8% by mass or less. If it exceeds 10% by mass, the exothermic reaction with Ca during the reduction process increases, and the firing temperature rises, which tends to result in particles with abnormal particle growth. The oxygen concentration of the partially oxide can be measured by non-dispersive infrared absorption spectroscopy (ND-IR).

[0069] The reducing gas can be appropriately selected from hydrocarbon gases such as hydrogen (H2), carbon monoxide (CO), and methane (CH4), but hydrogen gas is preferred in terms of cost. The gas flow rate is appropriately adjusted within a range that does not cause oxide dispersion. The heat treatment temperature in the pretreatment step (hereinafter also referred to as the pretreatment temperature) is preferably in the range of 300°C to 950°C, more preferably 400°C or higher, particularly preferably 750°C or higher, and more preferably less than 900°C. When the pretreatment temperature is 300°C or higher, the reduction of oxides containing Sm and Fe proceeds efficiently. Furthermore, when the temperature is 950°C or lower, particle growth and segregation of oxide particles are suppressed, and the desired particle size can be easily maintained. In addition, when hydrogen is used as the reducing gas, it is preferable to adjust the thickness of the oxide layer used to 20 mm or less, and further adjust the dew point in the reaction furnace to -10°C or lower.

[0070] (Reduction process) The reduction step is a step in which the partial oxide is reduced to alloy particles by heat treatment, for example, in the presence of a reducing agent, preferably at a temperature of 920°C to 1200°C. For example, reduction is carried out by contacting the partial oxide with a calcium melt or calcium vapor. From the viewpoint of magnetic properties, the heat treatment temperature is preferably 950°C to 1150°C, and more preferably 980°C to 1100°C. The heat treatment time is preferably less than 120 minutes, more preferably less than 90 minutes, and the lower limit of the heat treatment time is preferably 10 minutes or more, and more preferably 30 minutes or more, from the viewpoint of carrying out the reduction reaction more uniformly.

[0071] Metallic calcium is used, for example, in granular or powder form, with a particle size of 10 mm or less being preferable. This allows for more effective suppression of aggregation during the reduction reaction. Furthermore, metallic calcium can be added in an amount of 1.1 to 3.0 times the reaction equivalent (the stoichiometric amount required to reduce the Sm oxide, and including the amount required to reduce Fe if it is in oxide form), with 1.5 to 2.0 times being preferable.

[0072] In the reduction process, a disintegration accelerator can be used as needed, along with the reducing agent, metallic calcium. This disintegration accelerator is used as appropriate to promote the disintegration and granulation of the product during the washing process described later, and examples include alkaline earth metal salts such as calcium chloride and alkaline earth metal oxides such as calcium oxide. These disintegration accelerators are used in a ratio of 1 to 30% by mass, preferably 5 to 28% by mass, per Sm oxide used as the Sm source.

[0073] (Nitriding process) The nitriding process is a step in which Sm-Fe-N anisotropic magnetic powder is obtained by nitriding the alloy particles obtained in the reduction process. Since particulate precipitate obtained in the aforementioned precipitation process is used, porous, lumpy alloy particles are obtained in the reduction process. This allows for immediate heat treatment in a nitrogen atmosphere and nitriding without the need for grinding, thus enabling uniform nitriding.

[0074] The heat treatment temperature (hereinafter also referred to as the nitriding temperature) for nitriding alloy particles is preferably 300 to 600°C, and particularly preferably 400 to 550°C, and the treatment is carried out by replacing the atmosphere with a nitrogen atmosphere within this temperature range. The heat treatment time should be set to ensure that the nitriding of the alloy particles is sufficiently uniform.

[0075] The product obtained after the nitriding process may contain not only magnetic particles (Sm-Fe-N anisotropic magnetic powder) but also by-products such as CaO and unreacted metallic calcium, which may form a sintered mass. In this case, the product can be immersed in cooling water to separate the CaO and metallic calcium from the magnetic particles as a calcium hydroxide (Ca(OH)2) suspension. Any remaining calcium hydroxide may be thoroughly removed by washing the magnetic particles with acetic acid or the like.

[0076] [Method for producing phosphate-coated Sm-Fe-N anisotropic magnetic powder] The phosphate-coated Sm-Fe-N anisotropic magnetic powder is not particularly limited, but for example, A phosphoric acid treatment step to obtain Sm-Fe-N anisotropic magnetic powder coated with phosphate on its surface by adding an inorganic acid to a slurry containing Sm-Fe-N anisotropic magnetic powder, water, and a phosphoric acid compound to adjust the pH of the slurry to preferably 1 to 4.5, and Oxidation process: Heat treatment of phosphate-coated Sm-Fe-N anisotropic magnetic powder in an oxygen-containing atmosphere, preferably at 200°C to 330°C. It can be manufactured by a method that includes [a specific component].

[0077] (Phosphating treatment process) In the phosphate treatment step, an inorganic acid is added to a slurry containing Sm-Fe-N anisotropic magnetic powder, water, and a phosphate compound to adjust the pH of the slurry to preferably between 1 and 4.5, thereby obtaining Sm-Fe-N anisotropic magnetic powder coated with phosphate on its surface. The phosphate-coated Sm-Fe-N anisotropic magnetic powder is formed when the metal components (e.g., iron or samarium) contained in the Sm-Fe-N anisotropic magnetic powder react with the phosphate components contained in the phosphate compound, causing phosphates (e.g., iron phosphate, samarium phosphate) to precipitate on the surface of the Sm-Fe-N anisotropic magnetic powder. By adding an inorganic acid to adjust the pH of the slurry to between 1 and 4.5, the amount of phosphate precipitated can be increased compared to when no inorganic acid is added, and a phosphate-coated Sm-Fe-N anisotropic magnetic powder with a thicker coating tends to be obtained. Furthermore, by using water as the solvent, smaller particle size phosphates tend to precipitate compared to when an organic solvent is used, resulting in a densely coated phosphate-coated Sm-Fe-N anisotropic magnetic powder.

[0078] The method for preparing a slurry containing Sm-Fe-N anisotropic magnetic powder, water, and a phosphate compound is not particularly limited, but for example, it can be obtained by mixing Sm-Fe-N anisotropic magnetic powder and an aqueous phosphoric acid solution containing a phosphate compound with water as the solvent. The content of Sm-Fe-N anisotropic magnetic powder in the slurry is preferably, for example, 1% by mass or more and 50% by mass or less, and more preferably 5% by mass or more and 20% by mass or less from the viewpoint of productivity. The content of the phosphate component (PO4) in the slurry is preferably, for example, 0.01% by mass or more and 10% by mass or less in terms of PO4 equivalent, and more preferably 0.05% by mass or more and 5% by mass or less from the viewpoint of the reactivity of the phosphate component and productivity.

[0079] Aqueous phosphoric acid solutions are obtained by mixing a phosphoric acid compound with water. Examples of phosphoric acid compounds include phosphates such as orthophosphoric acid, sodium dihydrogen phosphate, sodium monohydrogen phosphate, ammonium dihydrogen phosphate, ammonium monohydrogen phosphate, zinc phosphate, and calcium phosphate; inorganic phosphoric acids such as hypophosphorous acid, hypophosphite, pyrophosphoric acid, and polyphosphoric acid; and organic phosphoric acids. These may be used individually or in combination of two or more. Furthermore, to improve water resistance, corrosion resistance, and the magnetic properties of magnetic powders through coating, oxo salts such as molybdate, tungstate, vanadate, and chromate, oxidizing agents such as sodium nitrate and sodium nitrite, and chelating agents such as EDTA may be added.

[0080] The concentration of phosphoric acid (in PO4 equivalent) in the aqueous phosphoric acid solution is preferably, for example, 5% by mass or more and 50% by mass or less, and more preferably 10% by mass or more and 30% by mass or less from the viewpoint of solubility of phosphoric acid compounds, storage stability, and ease of chemical treatment. The pH of the aqueous phosphoric acid solution is preferably, for example, 1 or more and 4.5 or less, and more preferably 1.5 or more and 4 or less from the viewpoint of being able to easily control the precipitation rate of phosphates. The pH can be adjusted with dilute hydrochloric acid, dilute sulfuric acid, etc.

[0081] In the phosphoric acid treatment process, the pH of the slurry is preferably adjusted to between 1 and 4.5 by adding an inorganic acid, more preferably between 1.6 and 3.9, and even more preferably between 2 and 3. Below 1 pH, the phosphate-coated Sm-Fe-N anisotropic magnetic powders may aggregate, starting from locally precipitated phosphates, which can reduce coercivity. Above 4.5 pH, the amount of phosphate precipitated decreases, resulting in insufficient coating and potentially reducing coercivity. Examples of inorganic acids to be added include hydrochloric acid, nitric acid, sulfuric acid, boric acid, and hydrofluoric acid. During the phosphoric acid treatment process, inorganic acids are added as needed to maintain the pH within the above range. From the viewpoint of wastewater treatment, the use of inorganic acids is preferable, but organic acids can also be used in combination depending on the purpose. Examples of organic acids include acetic acid, formic acid, and tartaric acid. A mixture of inorganic and organic acids may also be used.

[0082] The phosphate content of the phosphate-coated Sm-Fe-N anisotropic magnetic powder obtained in the phosphoric acid treatment process is preferably greater than 0.5% by mass, more preferably 0.55% by mass or more, and particularly preferably 0.75% by mass or more. Furthermore, the phosphate content of the phosphate-coated Sm-Fe-N anisotropic magnetic powder is preferably 4.5% by mass or less, more preferably 2.5% by mass or less, and particularly preferably 2% by mass or less. When the phosphate content is 0.5% by mass or less, the effect of coating with phosphate tends to be reduced. When the phosphate content exceeds 4.5% by mass, the phosphate-coated Sm-Fe-N anisotropic magnetic powders may aggregate with each other, reducing the coercivity. The phosphate content of the magnetic powder is expressed in terms of PO4 molecules, measured using ICP emission spectrometry (ICP-AES).

[0083] The adjustment of a slurry containing Sm-Fe-N anisotropic magnetic powder, water, and a phosphate compound to a pH range of 1 to 4.5 is preferably carried out for 10 minutes or more, and more preferably for 30 minutes or more, in order to reduce the area where the coating is thin. Initially, the pH rises rapidly, so the interval between adding the inorganic acid for pH control is short, but as the coating progresses, the pH fluctuations gradually slow down, and the interval between adding the inorganic acid lengthens, allowing the reaction endpoint to be determined.

[0084] (Oxidation process after phosphoric acid treatment) In the oxidation step after phosphoric acid treatment, the Sm-Fe-N anisotropic magnetic powder coated with the phosphate obtained in the phosphoric acid treatment step is heat-treated in an oxygen-containing atmosphere, preferably at 200°C to 330°C, thereby oxidizing the phosphate-coated Sm-Fe-N anisotropic magnetic powder. By heat-treating the phosphate-coated Sm-Fe-N anisotropic magnetic powder in an oxygen-containing atmosphere, preferably at a high temperature of 200°C to 330°C, the surface of the phosphate-coated base material Sm-Fe-N anisotropic magnetic powder is oxidized, forming a thick iron oxide layer, which tends to improve the hot water resistance of the phosphate-coated Sm-Fe-N anisotropic magnetic powder.

[0085] The oxidation step after phosphoric acid treatment is carried out by heat treatment of the phosphate-coated Sm-Fe-N anisotropic magnetic powder in an oxygen-containing atmosphere. The reaction atmosphere preferably contains oxygen in an inert gas such as nitrogen or argon. The oxygen concentration is preferably 3% to 21%, and more preferably 3.5% to 10%. During the oxidation reaction, it is preferable to exchange the gas at a flow rate of 2 L / min to 10 L / min per 1 kg of magnetic powder.

[0086] The heat treatment temperature in the oxidation step after phosphoric acid treatment is preferably 200°C to 330°C, more preferably 200°C to 250°C, and even more preferably 210°C to 230°C. Below 200°C, the formation of the iron oxide layer may be insufficient, resulting in reduced resistance to hot water. Above 330°C, an excessive amount of iron oxide layer may be formed, potentially reducing coercivity. The heat treatment time is preferably 3 hours to 10 hours.

[0087] The oxidation step after phosphoric acid treatment is preferably carried out such that the phosphate coating on the surface of the Sm-Fe-N anisotropic magnetic powder has a first region, the Sm atom concentration in the first region is higher than the Sm atom concentration in the Sm-Fe-N anisotropic magnetic powder, and the Sm atom concentration in the first region is 0.5 times or more and 4 times or less than the Fe atom concentration in the first region. The Sm atom concentration in the first region can be 1.02 times or more than the Sm atom concentration in the Sm-Fe-N anisotropic magnetic powder, preferably 1.05 times or more, more preferably 1.1 times or more, and even more preferably 1.2 times or more. The Sm atom concentration in the first region can be 3 times or less than the Sm atom concentration in the Sm-Fe-N anisotropic magnetic powder. The Sm atom concentration in the first region is preferably 0.6 times or more and 3.5 times or less than the Fe atom concentration in the first region, and more preferably 0.7 times or more and 3 times or less. The atomic concentrations (atm%) of the Sm-Fe-N anisotropic magnetic powder and the first region are determined by averaging the atomic concentrations (atm%) in each region obtained from STEM-EDX line analysis.

[0088] (Silica treatment process) The Sm-Fe-N anisotropic magnetic powder after phosphoric acid treatment (i.e., phosphate-coated Sm-Fe-N anisotropic magnetic powder) may be subjected to silica treatment as needed. Forming a silica thin film on the magnetic powder can improve oxidation resistance. The silica thin film can be formed, for example, by mixing an alkyl silicate, phosphate-coated Sm-Fe-N anisotropic magnetic powder, and an alkaline solution.

[0089] (Silane coupling treatment process) The magnetic powder after silica treatment may be further treated with a silane coupling agent. By treating the magnetic powder on which a silica thin film has been formed with silane coupling, a coupling agent film is formed on the silica thin film, which can improve the magnetic properties of the magnetic powder, as well as the wettability with resin and the strength of the magnet. The silane coupling agent can be selected according to the type of resin and is not particularly limited, but examples include 3-aminopropyltriethoxysilane, γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane hydrochloride, γ-glycidoxypropyltrimethoxy Sisilane, γ-glycidoxyoctyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, vinyltriacetoxysilane, γ-chloropropyltrimethoxysilane, hexamethylenedisilazane, γ-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, octadecyl[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, N-phenyl-γ-aminopropyl Trimethoxysilane, oleidopropyltriethoxysilane, γ-isocyanatetopropyltriethoxysilane, polyethoxydimethylsiloxane, polyethoxymethylsiloxane, bis(trimethoxysilylpropyl)amine, bis(3-triethoxysilylpropyl)tetrasulfan, γ-isocyanatetopropyltrimethoxysilane, vinylmethyldimethoxysilane, 1,3,5-N-tris(3-trimethoxysilylpropyl)isocyanurate, t-butylcarbamatetrialkoxysilane, N-(1,Examples of silane coupling agents include 3-dimethylbutylidene)-3-(triethoxysilyl)-1-propanamine, octyltriethoxysilane, octyltrimethoxysilane, decyltriethoxysilane, decyltrimethoxysilane, octadecyltriethoxysilane, octadecyltrimethoxysilane, and docosyltriethoxysilane. These silane coupling agents may be used individually or in combination of two or more. The amount of silane coupling agent added is preferably 0.2 parts by weight or more and 0.8 parts by weight or less, and more preferably 0.25 parts by weight or more and 0.6 parts by weight or less, per 100 parts by weight of magnetic powder. Below 0.2 parts by weight, the effect of the silane coupling agent tends to be small, and above 0.8 parts by weight, aggregation of the magnetic powder may occur, potentially reducing the magnetic properties of the magnetic powder and magnets.

[0090] Sm-Fe-N anisotropic magnetic powders that have undergone phosphoric acid treatment, oxidation, silica treatment, or silane coupling treatment can be filtered, dehydrated, and dried by conventional methods.

[0091] [Other ingredients] In one embodiment of this product, the bonded magnet composition may further contain a filler, preferably an inorganic filler. Including a filler in the bonded magnet composition may suppress the generation of burrs during molding. The filler may be used alone or in combination of two or more types.

[0092] The material of the filler is not particularly limited, but examples include talc, silica, mica, urastonite, calcium carbonate, potassium titanate, and glass.

[0093] The shape of the filler is not particularly limited and may include, for example, spherical, flattened, plate-like, needle-like, fibrous, whisker-like, columnar, rod-like, or flaky shapes.

[0094] As fillers, it is preferable that they are relatively small in diameter and needle-shaped or fibrous in shape, as they disperse easily in the resin and have a high effect in suppressing burr formation. Although not particularly limited, the average major diameter (long axis diameter) of the filler is preferably 3 μm or more and 100 μm or less, the average minor diameter (short axis diameter) is preferably 0.1 μm or more and 3 μm or less, and the average aspect ratio (ratio of major diameter to minor diameter) is preferably 10 or more and 100 or less.

[0095] When a filler is included, the filler content in the bonded magnet composition is not particularly limited, but is generally preferably 0.5% by mass or more, and more preferably 1% by mass or more. Furthermore, from the viewpoint of the magnetic properties of the resulting bonded magnet, the filler content in the bonded magnet composition is generally preferably 5% by mass or less.

[0096] The bonded magnet composition of this embodiment may further contain, as needed, various additives such as lubricants, dispersants, antioxidants, heavy metal deactivators, crystal nucleating agents, flame retardants, plasticizers, ultraviolet absorbers, antistatic agents, colorants, and mold release agents, as well as optional components such as thermosetting resins other than epoxy resins, thermoplastic resins, and thermoplastic elastomers.

[0097] Examples of lubricants and dispersants include waxes such as paraffin wax, polyethylene wax, and polypropylene wax; fatty acids such as stearic acid and their salts; metal soaps; fatty acid amides; urea compounds; fatty acid esters; phosphate esters; polyethers; polysiloxanes such as silicone oil and silicone grease; fluorinated oils; fluorinated greases; and fluororesin powders. From the viewpoint of fluidity during molding, fatty acid esters and phosphate esters can be preferably used.

[0098] The resins added to the composition for bonded magnets are not particularly limited, but examples include thermosetting resins such as phenolic resins, unsaturated polyester resins, vinyl esters (epoxy acrylates), diallyl phthalate resins, urea resins, melamine resins, and urethane resins, and thermoplastic resins such as polyphenylene sulfide, polyamide, polyester, polycarbonate, polystyrene, ABS, polyethylene, polypropylene, polyether ether ketone, liquid crystal polymer, polyethylene terephthalate, polybutylene terephthalate, polyphenylene ether, cycloolefin polymer, and cycloolefin copolymer. These thermosetting resins and thermoplastic resins can be added individually or in combination of two or more.

[0099] The bonded magnet composition of this embodiment can be suitably applied to injection molding, transfer molding, and the like, and in that case, it is preferable that it does not contain water and organic solvents. Here, organic solvent means an organic compound capable of dissolving at least the entire amount of the main component epoxy resin (a polyfunctional epoxy resin with three or more functions and a bifunctional epoxy resin as an optional component).

[0100] <<Method for producing a curable composition for bonded magnets>> The curable composition for bonded magnets according to this embodiment (composition for bonded magnets) can be obtained, for example, by mixing and kneading magnetic powder, a polyfunctional epoxy resin with three or more functions, an amine-based curing agent having a cyano group, and other components added as needed (such as a bifunctional epoxy resin, a curing agent other than an amine-based curing agent having a cyano group, a curing accelerator, a filler, etc.).

[0101] The mixing and kneading method and conditions are not particularly limited and can be appropriately selected by referring to known methods. For example, a mixture comprising magnetic powder, a polyfunctional epoxy resin with three or more functions, and an amine-based curing agent having a cyano group, and optionally including a bifunctional epoxy resin, a curing agent other than the amine-based curing agent having a cyano group, a curing accelerator, a filler, etc., is kneaded using a kneader such as a single-screw kneader or a twin-screw kneader. The kneading temperature should be a temperature at which the progress of the curing reaction is suppressed, for example, 140°C or lower, more preferably 60 to 110°C. The kneading time is also not particularly limited and can be appropriately determined, for example, 1 to 10 minutes.

[0102] For example, a bonded magnet composition in pellet form can be obtained by mixing and kneading magnetic powder, a polyfunctional epoxy resin with three or more functions, an amine-based curing agent having a cyano group, and optionally other components (such as a bifunctional epoxy resin, a curing agent other than an amine-based curing agent having a cyano group, a curing accelerator, or a filler), then extruding the strand with a twin-screw extruder, air-cooling it, and cutting it into the desired size (e.g., several millimeters) with a pelletizer. Alternatively, a bonded magnet composition in tablet form can be obtained by mixing and kneading magnetic powder, a polyfunctional epoxy resin with three or more functions, an amine-based curing agent having a cyano group, and optionally other components (such as a bifunctional epoxy resin, a curing agent other than an amine-based curing agent having a cyano group, a curing accelerator, or a filler), then grinding it using a ball mill, high-speed mill, etc., and compressing the resulting pulverized material (tabletization). Compression molding can be performed, for example, by filling a mold with the pulverized material and applying pressure at approximately 2 to 20 MPa.

[0103] <<Manufacturing method for bonded magnets (hardening and molding process)>> In the method for manufacturing bonded magnets according to this embodiment, a curable composition for bonded magnets (bonded magnet composition) containing magnetic powder, a trifunctional or polyfunctional epoxy resin, and an amine-based curing agent having a cyano group is heated to soften it, and then injected or poured into the cavity of a heated mold to cure it (curing molding step).

[0104] The temperature of the heating element for softening the bonded magnet composition, i.e., the temperature at which the bonded magnet composition is softened, can be appropriately selected depending on the type of epoxy resin, curing agent, and curing accelerator used, and is not particularly limited as long as the rapid curing reaction is suppressed and the fluidity of the bonded magnet composition is maintained, but is usually preferably 140°C or lower, and more preferably 130°C or lower. In one embodiment of this embodiment, the temperature of the heating element for softening the bonded magnet composition, i.e., the temperature at which the bonded magnet composition is softened, is more preferably 120°C or lower, and even more preferably 100°C or lower. In one embodiment of this embodiment, the temperature of the heating element for softening the bonded magnet composition, i.e., the temperature at which the bonded magnet composition is softened, can be higher, for example, 190°C or lower, and more preferably 180°C or lower. Furthermore, the temperature of the heating element for softening the bonded magnet composition, i.e., the lower limit of the temperature at which the bonded magnet composition is softened, is not particularly limited, but is generally preferably 60°C or higher in order to sufficiently soften the composition and ensure fluidity during molding. The heating time (softening time) for softening the bonded magnet composition is not particularly limited and can be determined as appropriate, for example, it can be 10 to 3600 seconds, but a relatively short time is preferred from the viewpoint of productivity.

[0105] The temperature of the mold in which the bonded magnet composition is injected or poured, i.e., the temperature at which the bonded magnet composition is cured, can be appropriately selected depending on the type of epoxy resin, curing agent, and curing accelerator used, and is not particularly limited. However, from the viewpoint of productivity and the heat resistance of the resulting bonded magnet, it is generally preferable to exceed 150°C, and more preferably 160°C or higher. In one embodiment of this example, the temperature of the mold in which the bonded magnet composition is injected or poured, i.e., the temperature at which the bonded magnet composition is cured, is particularly preferable to exceed 170°C, and even more preferably 175°C or higher, from the viewpoint of the heat resistance of the resulting bonded magnet. Furthermore, the upper limit of the temperature of the mold in which the bonded magnet composition is injected or poured, i.e., the temperature at which the bonded magnet composition is cured, is not particularly limited, but it is generally preferable to be 250°C or lower in order to suppress material decomposition. The time (curing time) for holding the bond magnet composition in the heated mold cavity to cure it can be appropriately selected from the viewpoint of the progress of the curing reaction and productivity, and is preferably 20 to 180 seconds.

[0106] For example, in injection molding, where the bond magnet composition is heated and softened in a separate component outside the curing mold (in the case of injection molding, inside a screw cylinder), and then injected or injected into the heated cavity of the mold to cure, it is preferable to set the temperature of the heating component for softening the bond magnet composition to 140°C or lower, and the temperature of the mold into which the bond magnet composition is injected or injected to a temperature exceeding 150°C.

[0107] On the other hand, in methods such as transfer molding, where the bond magnet composition is heated and softened in another cavity of the same mold (in the case of transfer molding, in the mold's pot), and then injected or injected into the mold's curing cavity to cure, the temperature at which the bond magnet composition softens may be the same as the temperature of the mold from which the bond magnet composition is injected or injected, i.e., the temperature at which the bond magnet composition cures. In such cases, the bond magnet can be successfully molded by appropriately selecting the mold temperature, i.e., the temperature at which the bond magnet composition softens and cures, as well as the softening time and curing time, depending on the type of epoxy resin, curing agent, and curing accelerator used.

[0108] In one embodiment of this invention, a bonded magnet can be manufactured by molding it using an injection molding method. For example, using an injection molding machine, the bonded magnet composition is heated and softened in a screw cylinder, then injected into the cavity of a mold to which a magnetic field is applied, aligning (orienting) the easy magnetization axes of the magnetic powder, and then cured. The orientation magnetic field at that time can be generated using an electromagnet or a permanent magnet. The magnitude of the orientation magnetic field is not particularly limited, but is usually preferably 4 kOe or more, and more preferably 6 kOe or more. After that, the cured product is removed from the mold, and if necessary, the bonded magnet can be obtained by magnetizing it with an air-core coil or a magnetizing yoke. The magnitude of the magnetizing magnetic field is also not particularly limited, but is usually preferably 20 kOe or more, and more preferably 30 kOe or more.

[0109] In one embodiment of this invention, a bonded magnet can be manufactured by molding it using a transfer molding method. For example, using a transfer molding machine, the bonded magnet composition is heated and softened in a pot, then injected into the cavity of a mold to which a magnetic field is applied, aligning (orienting) the easy magnetization axes of the magnetic powder, and then curing. The orientation magnetic field at that time can be generated using an electromagnet or a permanent magnet. The magnitude of the orientation magnetic field is not particularly limited, but is usually preferably 4 kOe or more, and more preferably 6 kOe or more. After that, the cured product is removed from the mold, and if necessary, the bonded magnet can be obtained by magnetizing it with an air-core coil or a magnetizing yoke. The magnitude of the magnetizing magnetic field is also not particularly limited, but is usually preferably 20 kOe or more, and more preferably 30 kOe or more. The injection pressure when injecting the softened bonded magnet composition into the cavity of the mold is not particularly limited, but is usually preferably 5 to 30 MPa, and more preferably 5 to 15 MPa.

[0110] In the manufacturing method of bonded magnets according to this embodiment, injection molding and transfer molding are preferred as molding methods because they allow for easy production of bonded magnets of various shapes, but the method is not limited to these, and any known method such as compression molding, extrusion molding, or potting can be used. The molding conditions are also not particularly limited and can be set as appropriate by referring to known methods. Furthermore, the temperature setting of the molding machine and the settings of the orientation magnetic field and magnetization magnetic field can be performed, for example, in the same manner as described above.

[0111] <Bonded Magnets> A bonded magnet according to one aspect of this embodiment is manufactured by the bonded magnet manufacturing method described above. A bonded magnet according to another embodiment of this embodiment comprises magnetic powder and a cured product of a curable composition containing an epoxy resin, preferably a trifunctional or polyfunctional epoxy resin, and an amine-based curing agent having a cyano group, wherein the magnetic powder content is 80% by mass or more and less than 95% by mass. In the bonded magnet of this embodiment, the curable composition may further contain a phenol-based curing agent, preferably a polyfunctional phenol-based curing agent, and the cured product of the curable composition may be a cured product of a curable composition containing an epoxy resin, an amine-based curing agent having a cyano group, and a phenol-based curing agent (preferably a polyfunctional phenol-based curing agent). In the bonded magnet of this embodiment as well, it is preferable that the epoxy resin contains a biphenyl structure from the viewpoint of excellent properties such as heat resistance of the resulting bonded magnet. The bonded magnet of this embodiment may, for example, contain a cured product of the above-mentioned curable composition for bonded magnets (composition for bonded magnets).

[0112] The bonded magnet of this embodiment possesses the excellent magnetic properties inherent to magnetic powder, and furthermore, because the binder resin is epoxy resin, it tends to excel in one or more properties such as mechanical strength, heat resistance, durability, and chemical resistance, or to have an excellent balance of these properties.

[0113] The bonded magnets of this embodiment can be manufactured by injection molding or transfer molding, and may have relatively complex shapes, but their shapes are not particularly limited and may have relatively simple shapes. Although molding is possible even if the epoxy resin contained in the curable composition is not a polyfunctional epoxy resin with three or more functions, it is preferable that the curable composition contains a polyfunctional epoxy resin with three or more functions in terms of mass production in injection molding or transfer molding.

[0114] The bonded magnet of this embodiment can be suitably used in a variety of applications. For example, it can be suitably used in applications requiring heat resistance (durability and resistance to deformation at high temperatures), such as in-vehicle drive motors, auxiliary motors, and various pumps such as oil pumps. Furthermore, the bonded magnet of this embodiment can be suitably used in home appliance applications such as air conditioner compressors, and in aviation applications such as drive motors for aerodynamic mobility devices such as drones.

[0115] An in-vehicle drive motor according to one aspect of this embodiment includes a bonded magnet as described above. An in-vehicle auxiliary motor according to one aspect of this embodiment includes a bonded magnet as described above. An in-vehicle pump according to one aspect of this embodiment includes a bonded magnet as described above. As described above, the bonded magnet of this embodiment has excellent properties, and the in-vehicle drive motor, auxiliary motor, and pump using it have excellent practical performance. [Examples]

[0116] Manufacturing example (Preparation of rare earth magnetic powder) [Precipitation process] 5.0 kg of FeSO4·7H2O was mixed and dissolved in 2.0 kg of pure water. Then, 0.49 kg of Sm2O and 0.74 kg of 70% sulfuric acid were added and the mixture was thoroughly stirred until completely dissolved. Next, pure water was added to the resulting solution to adjust the final concentration to 0.726 mol / L for Fe and 0.112 mol / L for Sm, thus obtaining the SmFe sulfuric acid solution.

[0117] The entirety of the prepared SmFe sulfuric acid solution was added dropwise to 20 kg of pure water maintained at 40°C, while stirring for 70 minutes from the start of the reaction. Simultaneously, 15% ammonia solution was added dropwise to adjust the pH to 7-8. This yielded a slurry containing SmFe hydroxide. The obtained slurry was washed with pure water by decantation, and then the hydroxide was separated into solid and liquid phases. The separated hydroxide was dried in an oven at 100°C for 10 hours.

[0118] [Oxidation process] The hydroxide obtained in the precipitation process was calcined in air at 1000°C for 1 hour. After cooling, red SmFe oxide was obtained as the raw material powder.

[0119] [Pre-treatment process] 100 g of SmFe oxide was placed in a steel container to a thickness of 10 mm. The container was placed in a furnace, the pressure was reduced to 100 Pa, and then the temperature was raised to the pretreatment temperature of 850°C while introducing hydrogen gas, and it was held at that temperature for 15 hours. The oxygen concentration was measured by non-dispersive infrared absorption spectroscopy (ND-IR) (EMGA-820, Horiba, Ltd.) and found to be 5 mass%. This indicates that the oxygen bonded to Sm was not reduced, while 95% of the oxygen bonded to Fe was reduced, resulting in a black partial oxide.

[0120] [Reduction Process] 60 g of partial oxide obtained in the pretreatment process and 19.2 g of metallic calcium with an average particle size of approximately 6 mm were mixed and placed in the furnace. After evacuating the furnace, argon gas (Ar gas) was introduced. The temperature was raised to 1045°C and held for 45 minutes to obtain Fe-Sm alloy particles.

[0121] [Nitriding process] Subsequently, the furnace temperature was cooled to 100°C, then the chamber was evacuated, and the temperature was raised to 450°C while introducing nitrogen gas. This temperature was maintained for 23 hours to obtain a massive product containing magnetic particles.

[0122] [Washing process] The lumpy product obtained in the nitriding process was added to 3 kg of pure water and stirred for 30 minutes. After standing, the supernatant was drained by decantation. The process of adding to pure water, stirring, and decantation was repeated 10 times. Next, 2.5 g of 99.9% acetic acid was added and stirred for 15 minutes. After standing, the supernatant was drained by decantation. The process of adding to pure water, stirring, and decantation was repeated twice, followed by dehydration and drying, and then mechanical crushing to obtain SmFeN-based magnetic powder (average particle size (D50) approximately 3 μm).

[0123] [Phosphating treatment process] As the phosphoric acid treatment solution, a mixture of 85% orthophosphoric acid, sodium dihydrogen phosphate, and sodium molybdate dihydrate in a weight ratio of 1:6:1 was prepared, and the pH was adjusted to 2.5 and the PO4 concentration to 20% by mass using pure water and dilute hydrochloric acid. 1000g of SmFeN-based magnetic powder obtained in the water washing step was stirred for 1 minute in 10L of 0.7% dilute hydrochloric acid to remove surface oxide film and contaminants. Then, the draining and adding of water was repeated until the conductivity of the supernatant liquid was 100 μS / cm or less, to obtain a slurry containing 10% by mass of SmFeN-based magnetic powder. While stirring the obtained slurry, 100g of the prepared phosphoric acid treatment solution was added entirely to the treatment tank, and then 6% by mass hydrochloric acid was added as needed to control the pH of the phosphoric acid treatment reaction slurry within the range of 2.5 ± 0.1 and maintained for 30 minutes. Next, the mixture was subjected to suction filtration, dehydration, and vacuum drying to obtain a phosphate-coated SmFeN-based magnetic powder (residual magnetic flux density Br: 13.0 kG, coercivity iHc: 19.8 kOe, average particle size 3.32 μm, D10: 1.59 μm, D50: 3.24 μm, D90: 5.15 μm, particle size distribution 1.10).

[0124] [Silica treatment process] The phosphate-coated SmFeN magnetic powder obtained above, ethyl silicate 40, and 12.5% ​​by weight of aqueous ammonia were mixed in a mixer in a weight ratio of 97.8:1.8:0.4. The mixture was heated in a vacuum at 200°C to obtain SmFeN magnetic powder (silica-treated magnetic powder) on which a thin silica film was formed on the particle surface.

[0125] [Silane coupling treatment process] The magnetic powder on which a thin silica film was formed on the surface obtained as described above was mixed with 12.5% ​​by weight of aqueous ammonia in a mixer. Then, a 50% by weight ethanol solution of octadecyltriethoxysilane and a 50% by weight ethanol solution of γ-glycidoxypropyltriethoxysilane were sequentially mixed in the mixer. The weight ratio of the magnetic powder with the thin silica film formed, 12.5% ​​by weight of aqueous ammonia, a 50% by weight ethanol solution of octadecyltriethoxysilane, and a 50% by weight ethanol solution of γ-glycidoxypropyltriethoxysilane was 99.1:0.3:0.2:0.4. The mixture was dried at 120°C under a nitrogen atmosphere for 10 hours to obtain silane-coupled magnetic powder (magnetic powder after coupling treatment).

[0126] Examples 1-12, Comparative Examples 1-3, and Reference Example 1 According to the formulations shown in Table 1, magnetic powder (magnetic powder after coupling treatment), epoxy resin, curing agent, and curing accelerator were weighed and kneaded. Subsequently, the mixture was kneaded in a laboplast mill (110°C, 10 rpm, test volume 40 cc, residence time 6 minutes) to obtain a curable composition for bonded magnets.

[0127] The components used in the examples, comparative examples, and reference examples are as follows.

[0128] <Magnetic powder> SmFeN-based magnetic powder (magnetic powder after coupling treatment) prepared according to the manufacturing example.

[0129] <Filler> Filler: Tismo D-102 (manufactured by Otsuka Chemical Co., Ltd., potassium titanate fiber, fiber length 10-20 μm, fiber diameter 0.3-0.6 μm)

[0130] <Epoxy resin main component> Main component 1: NC-3500 (manufactured by Nippon Kayaku Co., Ltd., biphenyl-based polyfunctional epoxy resin (thermosetting oligomer), number of epoxy groups in repeating structural units: 1 or 2, epoxy equivalent: 210 g / eq) Main component 2: YX4000K (manufactured by Mitsubishi Chemical Corporation, biphenyl-based crystalline epoxy resin, melting point 105°C, number of epoxy groups per molecule 2, epoxy equivalent 186 g / eq) Main component 3: EPICLON 850-S (manufactured by DIC Corporation, bisphenol A type epoxy resin, 2 epoxy groups per molecule, epoxy equivalent 188 g / eq)

[0131] <Hardening agent> Hardener 1: Dicyandiamide (DICY) (manufactured by Tokyo Chemical Industry Co., Ltd., melting point 209.5℃, functional group equivalent 21g / eq) Hardener 2: MEH-7500 (manufactured by UBE Corporation, triphenylmethane-based phenolic resin (hardener oligomer), hydroxyl group equivalent 98g / eq)

[0132] <Curing accelerator> Curing accelerator 1: Ucat3512T (manufactured by Sunapro Co., Ltd., aromatic dimethylurea-based curing accelerator) Curing accelerator 2: Curazole 2PHZ-PW (manufactured by Shikoku Chemicals Co., Ltd., imidazole-based curing accelerator)

[0133] [Table 1]

[0134] The curable compositions for bonded magnets obtained in Examples 1-12, Comparative Examples 1-3, and Reference Example 1 were evaluated as follows. The evaluation results are shown in Table 2.

[0135] <90°C residence stabilization time (A)> The torque of a curable composition for bonded magnets, obtained using a laboplast mill, was monitored during kneading at 90°C, a rotation speed of 10 rpm, and a test volume of 40 cc. The time it took for the torque to rise to 1.3 times the initial value was measured and defined as the 90°C residence stabilization time (A). The measurement time for time (A) was limited to 3600 seconds, at which point the measurement was terminated. Therefore, the upper limit of time (A) is 3600 seconds. A longer time (A) suppresses the thickening due to material hardening in the cylinder during injection molding, allowing for the maintenance of high fluidity over a longer period.

[0136] <180℃ curing time (B)> The time it took for 2.0 g of the resulting curable composition for bonded magnets to completely harden while being kneaded on a hot plate heated to 180°C was measured and defined as the 180°C curing time (B). The shorter the time (B), the more rapidly the material hardens in the mold, which shortens the mold closing time and thus the cycle time. From a productivity standpoint, it is desirable for (B) to be 90 seconds or less.

[0137] <Cycle stability of injection molding (A / B)> The cycle stability (A / B) of injection molding was calculated by dividing the residence stabilization time at 90°C (A) by the curing time at 180°C (B). A larger (A / B) indicates that continuous cycle molding is more advantageous. The results are shown in Table 2.

[0138] [Table 2]

[0139] In Comparative Example 1, which did not contain an amine-based curing agent having a cyano group, cured quickly at 180°C, but also quickly at 90°C. In Comparative Examples 2-3 and Reference Example 1, which consisted of a non-polyfunctional epoxy resin main component and an amine-based curing agent having a cyano group, curing did not occur for a relatively long time at 90°C, but required a long time to cure at 180°C. In all of these compositions, the cycle stability (A / B) of thermosetting injection molding was low, in the range of 15-36. On the other hand, in Examples 1-12, which contained a polyfunctional epoxy resin and an amine-based curing agent having a cyano group, curing did not occur for a relatively long time at 90°C, but cured quickly at 180°C. In all of these compositions, the cycle stability (A / B) of thermosetting injection molding was high, in the range of 40-89. Therefore, the curable compositions for bonded magnets of this disclosure can be injection molded despite the fact that the resins they contain are not thermoplastic resins.

[0140] <Bar flow length> The obtained curable composition for bonded magnets was pulverized using a high-speed mill, and the composition powder was filled into a mold and compressed at 0.5 MPa to produce tablets (shape: 14 mm in diameter x 40 mm in height). After preheating the tablets in an oven heated to 100°C for 10 minutes, they were placed in a pot inside a mold heated to 180°C in a transfer molding machine. The material was injected into a cavity with a volume of 70 mm in length x 10 mm in width x 3 mm in height at a plunger pressure of 9.9 MPa, an injection speed of 20 mm / s, and an orientation magnetic field of 6 kOe. After 180 seconds, corresponding to the cure time (CT) from the start of pressurization, the mold was opened to obtain a long test specimen. The bar flow length was evaluated by measuring the longitudinal dimension of the long test specimen using a ruler. Comparative Example 2 showed poor curing at a CT of 180 seconds, so the long test specimen was obtained at 300 seconds. Furthermore, since Comparative Example 3 and Reference Example 1 showed poor curing at CT300 seconds, the long test specimens were obtained at 600 seconds. Fluidity was evaluated by measuring the longitudinal dimension of the obtained molded product. The conditions for this curing process were selected to allow the long test specimens to be obtained without problems using the composition of Comparative Example 1. For example, when the preheating temperature was 130°C or 150°C, or even 180°C (the same as the pot in the mold of the molding machine), the long test specimens could be obtained without problems using the compositions of Examples 1 to 12, but it was difficult with the composition of Comparative Example 1. In terms of time, when the tablets were preheated in a 100°C oven for 30 minutes, molding was difficult with the composition of Comparative Example 1. Based on the above, the preheating temperature was set to 100°C and the preheating time to 10 minutes as preheating conditions that allowed the composition of Comparative Example 1 to be molded.

[0141] <Magnetic properties (BH) max> 10.0 g of the curable composition for bonded magnets was preheated for 10 minutes in an oven heated to 100°C. Then, it was placed in a pot in a mold with a surface temperature of 180°C, set in a 120-ton transfer molding machine (manufactured by Apic Yamada Co., Ltd.). Pressurization was then applied with a plunger pressure of 9.9 MPa and an orientation magnetic field of 6 kOe. After 180 seconds, corresponding to the cure time (CT), the mold was opened to obtain a cylindrical test specimen with a diameter of 10 mm and a height of 7 mm. Comparative Example 2 showed poor curing at 180 seconds, so the cylindrical test specimen was obtained at 300 seconds. Similarly, Comparative Example 3 and Reference Example 1 also showed poor curing at 300 seconds, so the cylindrical test specimen was obtained at 600 seconds. After pulse magnetization of the obtained cylindrical test specimens with 60 kOe, the magnetic properties (BH)max at room temperature was measured using a BH curve tracer manufactured by RIKEN Electron Co., Ltd. As with the above, the conditions for this curing process were selected to allow the long test specimens to be obtained without problems using the composition of Comparative Example 1. For example, when the preheating temperature was 130°C or 150°C, or even 180°C (the same as the pot in the mold of the molding machine), the long test specimens could be obtained without problems using the compositions of Examples 1 to 12, but this was difficult with the composition of Comparative Example 1. In terms of time, when the tablets were preheated in a 100°C oven for 30 minutes, molding was difficult with the composition of Comparative Example 1. Based on the above, the preheating temperature was set to 100°C and the preheating time to 10 minutes as preheating conditions that would allow the composition of Comparative Example 1 to be molded. The results are shown in Table 3.

[0142] [Table 3]

[0143] Comparative Examples 2-3 and Reference Example 1, which consisted of an epoxy resin main component that was not polyfunctional and an amine-based curing agent having a cyano group, could not be cured within a curing time of 180 seconds. Furthermore, the bar flow length of Comparative Examples 2-3 and Reference Example 1 was 42 mm or less, which was lower than that of Examples 1-11, which did not contain fillers. Compared to Examples 1-11, Comparative Examples 2-3 and Reference Example 1 showed poor fluidity, as the reaction between the main component and curing agent was slower, making the resin more prone to separation as burrs during molding. In addition, Comparative Example 1, which did not contain an amine-based curing agent having a cyano group in its composition, could only be molded under limited conditions of a preheating temperature of 100°C and a preheating time of 10 minutes, compared to Examples 1-11. Because it was difficult to control the preheating conditions for the tablets, it was difficult to transition to mass production molding.

[0144] <Number of injection molding cycles> For the curable compositions for bonded magnets of Example 7, Example 8, and Reference Example 1, the materials were placed in the hopper of a Japan Steel Works injection molding machine with the cylinder temperature set to Zone 1: 50°C and Zone 2: 85°C, and the mold temperature set to 180°C. The material was weighed to a predetermined metering position at a screw rotation speed of 20 rpm, and the material was injected into the mold under the conditions of injection speed of 10 mm / s, injection pressure of 30 MPa, holding pressure of 20 MPa (2.5 seconds), and orientation magnetic field of 9 kOe. After 90 seconds, the mold was opened to produce a long test piece measuring 100 mm in length, 12 mm in width, and 4 mm in height. The curable compositions for bonded magnets of Example 7 and Example 8 were able to undergo 50 cycles of continuous molding, but the bonded magnet molded product of Reference Example 1 was insufficiently cured and broke immediately upon mold opening, making further molding impossible.

[0145] <(BH)max of injection molded products> From the long test pieces obtained in Examples 7 and 8, rectangular magnets measuring 7 mm wide x 7 mm wide x 4 mm high were cut out by milling. After the resulting rectangular magnets were pulse-magnetized with 60 kOe, the magnetic properties (BH)max at room temperature were measured using a BH curve tracer manufactured by RIKEN Electron Co., Ltd. The results are shown in Table 4.

[0146] [Table 4]

[0147] While Reference Example 1 could not be injection molded and therefore could not obtain magnetic properties, the curable compositions for bonded magnets in Examples 7 and 8 allowed for continuous molding of 50 shots or more, achieving a magnetic flux of 118-124 kJ / m². 3 We were able to obtain injection-molded bonded magnets with excellent magnetic properties (BH)max of (14.8~15.6 MGOe).

[0148] The embodiments relating to this disclosure may include, for example, the following embodiments: [Section 1] A method for manufacturing a bonded magnet, comprising the steps of heating and softening a curable composition for bonded magnets containing magnetic powder, a trifunctional or polyfunctional epoxy resin, and an amine-based curing agent having a cyano group, and then injecting or pouring the composition into the cavity of a heated mold to cure it. [Section 2] The temperature of the heating element used to soften the curable composition for the bonded magnet is 140°C or lower. The method for manufacturing a bonded magnet according to item 1, wherein the temperature of the mold used to inject or pour the curable composition for bonded magnets exceeds 150°C. [Section 3] The method for producing a bonded magnet according to item 1 or 2, wherein the amine-based curing agent is dicyandiamide. [Section 4] A method for producing a bonded magnet according to any one of claims 1 to 3, wherein the epoxy equivalent of the polyfunctional epoxy resin is 290 g / eq or less. [Section 5] A method for producing a bonded magnet according to any one of claims 1 to 4, wherein the curable composition for bonded magnets comprises a polyfunctional phenolic curing agent. [Section 6] A method for producing a bonded magnet according to any one of claims 1 to 5, wherein the curable composition for bonded magnets includes a curing accelerator. [Section 7] The method for producing a bonded magnet according to item 6, wherein the curing accelerator is a urea-based curing accelerator. [Section 8] A method for producing a bonded magnet according to any one of claims 1 to 7, wherein the polyfunctional epoxy resin contains a biphenyl structure. [Section 9] A bonded magnet manufactured by the method for manufacturing a bonded magnet described in any one of items 1 to 8. [Section 10] The invention includes a cured product of a curable composition comprising magnetic powder and an epoxy resin and an amine-based curing agent having a cyano group. A bonded magnet having a magnetic powder content of 80% by mass or more and less than 95% by mass. [Section 11] The bonded magnet according to claim 10, wherein the cured product is a cured product of a curable composition comprising an epoxy resin, an amine-based curing agent having a cyano group, and a phenol-based curing agent. [Section 12] The bonded magnet according to item 10 or 11, wherein the epoxy resin comprises a biphenyl structure. [Section 13] It comprises magnetic powder, a polyfunctional epoxy resin with three or more functions, and an amine-based curing agent having a cyano group. A curable composition for bonded magnets, wherein the magnetic powder content is 80% by mass or more and less than 95% by mass. [Section 14] The curable composition for bonded magnets according to item 13, wherein the amine-based curing agent is dicyandiamide. [Section 15] The curable composition for bonded magnets according to item 13 or 14, wherein the epoxy equivalent of the polyfunctional epoxy resin is 290 g / eq or less. [Section 16] A curable composition for bonded magnets according to any one of claims 13 to 15, further comprising a polyfunctional phenolic curing agent. [Section 17] A curable composition for bonded magnets according to any one of claims 13 to 16, further comprising a curing accelerator. [Section 18] The curable composition for bonded magnets according to item 17, wherein the curing accelerator is a urea-based curing accelerator. [Section 19] The curable composition for bonded magnets according to any one of claims 13 to 18, wherein the polyfunctional epoxy resin comprises a biphenyl structure. [Section 20] An in-vehicle drive motor or auxiliary motor or pump containing a bonded magnet as described in any one of items 9 to 12.

Claims

1. A method for manufacturing a bonded magnet, comprising the steps of heating and softening a curable composition for bonded magnets containing magnetic powder, a trifunctional or polyfunctional epoxy resin, and an amine-based curing agent having a cyano group, and then injecting or pouring it into the cavity of a heated mold to cure it.

2. The temperature of the heating element used to soften the curable composition for bonded magnets is 140°C or lower. The method for manufacturing a bonded magnet according to claim 1, wherein the temperature of the mold used to inject or pour the curable composition for bonded magnets exceeds 150°C.

3. The method for producing a bonded magnet according to claim 1 or 2, wherein the amine-based curing agent is dicyandiamide.

4. The method for manufacturing a bonded magnet according to claim 1 or 2, wherein the epoxy equivalent of the polyfunctional epoxy resin is 290 g / eq or less.

5. The method for producing a bonded magnet according to claim 1 or 2, wherein the curable composition for bonded magnets comprises a polyfunctional phenolic curing agent.

6. The method for producing a bonded magnet according to claim 1 or 2, wherein the curable composition for bonded magnets includes a curing accelerator.

7. The method for manufacturing a bonded magnet according to claim 6, wherein the curing accelerator is a urea-based curing accelerator.

8. The method for producing a bonded magnet according to claim 1 or 2, wherein the polyfunctional epoxy resin contains a biphenyl structure.

9. A bonded magnet manufactured by the method for manufacturing a bonded magnet according to claim 1 or 2.

10. The invention includes a cured product of a curable composition comprising magnetic powder and an epoxy resin and an amine-based curing agent having a cyano group. A bonded magnet having a magnetic powder content of 80% by mass or more and less than 95% by mass.

11. The bonded magnet according to claim 10, wherein the cured product is a cured product of a curable composition comprising an epoxy resin, an amine-based curing agent having a cyano group, and a phenol-based curing agent.

12. The bonded magnet according to claim 10 or 11, wherein the epoxy resin comprises a biphenyl structure.

13. It comprises magnetic powder, a polyfunctional epoxy resin with three or more functions, and an amine-based curing agent having a cyano group. A curable composition for bonded magnets, wherein the magnetic powder content is 80% by mass or more and less than 95% by mass.

14. The curable composition for bonded magnets according to claim 13, wherein the amine-based curing agent is dicyandiamide.

15. The curable composition for bonded magnets according to claim 13 or 14, wherein the epoxy equivalent of the polyfunctional epoxy resin is 290 g / eq or less.

16. The curable composition for bonded magnets according to claim 13 or 14, further comprising a polyfunctional phenolic curing agent.

17. A curable composition for bonded magnets according to claim 13 or 14, further comprising a curing accelerator.

18. The curable composition for bonded magnets according to claim 17, wherein the curing accelerator is a urea-based curing accelerator.

19. The curable composition for bonded magnets according to claim 13 or 14, wherein the polyfunctional epoxy resin comprises a biphenyl structure.

20. An in-vehicle drive motor, auxiliary motor, or pump comprising a bonded magnet as described in claim 9 or 10.

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