Bonded magnet, vehicle-use main motor and oil pump including bonded magnet, curable composition for bonded magnet, and method for producing bonded magnet

Abstract

Provided is a bonded magnet which can be suitably used for applications in which it is immersed or brought into contact with oil, the bonded magnet comprising a cured product of a curable composition, the curable composition comprising: a magnetic powder; at least one or more of a novolak phenol-type epoxy resin, a cresol novolak-type epoxy resin, or a triphenylmethane-type epoxy resin having an epoxy equivalent of 250 g / eq or less; and a curing agent having a hydroxyl equivalent of 150 g / eq or less and being at least one or more of a novolak-type phenol resin, a cresol novolak-type phenol resin, or a triphenylmethane-type phenol resin.

Description

Technical Field

[0001] One aspect of the present invention relates to a bonded magnet and an on-board main motor and oil pump comprising the bonded magnet. Another aspect of the present invention relates to a curing composition for a bonded magnet and a method for manufacturing a bonded magnet. Background Technology

[0002] Previously, the use of bonded magnets, which are made by bonding ferrite powder, Sm-Co, Nd-Fe-B, Sm-Fe-N and other rare earth magnetic powders with adhesive resins, has been studied in various applications.

[0003] For bonded magnets, good magnetic properties are required, and depending on the application, excellent heat resistance is sometimes also necessary. In applications requiring heat resistance, thermosetting resins, such as epoxy resins, are being investigated as adhesive resins for bonded magnets.

[0004] For example, Patent Document 1 discloses a composite for bonding magnets and a bonded magnet manufactured by compression molding of the composite for bonding magnets. The composite for bonding magnets can produce a molded body for bonding magnets with excellent compressive strength at room temperature and high temperature. The composite for bonding magnets contains magnetic powder, epoxy resin, phenolic resin curing agent and other curing agents, and a resin composition containing a coupling agent having a functional group that can react with glycidyl groups. The composite for bonding magnets contains the epoxy resin and the curing agent in such a way that the amount of hydroxyl groups per 1g of cured product [= curing agent content [g] × 1000 / (hydroxyl equivalent of curing agent × (epoxy resin content [g] + curing agent content [g]))] is 3.0 mmol / g or more.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2022-17908 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] In recent years, research has been conducted on the application of bonded magnets in automotive main motors, oil pumps, and other components that are immersed in or in contact with oil, and, depending on the circumstances, in applications involving immersion in or contact with relatively high-temperature oils. Therefore, bonded magnets with excellent oil resistance, in addition to heat resistance, are also required.

[0010] In addition, in applications such as automotive main motors and oil pumps, bonded magnets with relatively complex shapes are sometimes required. Beyond applications involving immersion or contact with oil, bonded magnets with complex shapes are sometimes also required in other applications.

[0011] However, when epoxy resin, which is a thermosetting resin, is used as the adhesive resin, in the past, adhesive magnets were manufactured by compression molding, as described in Patent Document 1. However, the amount of adhesive resin used in compression molding is usually small (usually less than 5% by mass), making it difficult to manufacture magnets with complex shapes.

[0012] Methods for manufacturing bonded magnets with relatively complex shapes include injection molding and transfer molding. Injection molding utilizes commercially available large molding machines with built-in magnetic field coils, which can be easily applied to the manufacture of relatively large bonded magnet molded products suitable for applications such as electric motors. Furthermore, injection molding generally offers faster production speeds than transfer molding, making it suitable for mass production. However, in injection molding, from the perspective of continuous molding, it is generally difficult to use thermosetting resins such as epoxy resins as binder resins to manufacture bonded magnets. On the other hand, while epoxy resin can be used as a binder resin in transfer molding, there are concerns about difficulties in controlling the curing reaction, deterioration of shelf life, and decreased fluidity within the mold, sometimes making it difficult to manufacture bonded magnets satisfactorily.

[0013] One embodiment of the present invention aims to provide a bonding magnet that has excellent heat resistance and oil resistance, and is suitable for use in automotive main motors, oil pumps, and other applications that are immersed in or in contact with oil.

[0014] Furthermore, one embodiment of the present invention aims to provide a vehicle-mounted main motor with excellent performance. Another embodiment of the present invention aims to provide an oil pump with excellent performance.

[0015] Another embodiment of the present invention provides a curable composition for bonding magnets, which can produce a bonded magnet with high shape freedom and excellent heat resistance and oil resistance, or provides a curable composition for bonding magnets, which can produce a bonded magnet that can be applied to injection molding or transfer molding and has excellent heat resistance and oil resistance.

[0016] Furthermore, another objective of this invention is to provide a method for manufacturing bonded magnets that can effectively produce bonded magnets with high shape freedom and excellent heat resistance and oil resistance.

[0017] Problem Solving Methods

[0018] One embodiment of the present invention provides a bonding magnet for use in impregnation or contact with oil, and comprises a cured product of a curing composition, said curing composition comprising magnetic powder; at least one of a phenolic varnish-type epoxy resin, a cresol-phenolic varnish-type epoxy resin, or a triphenylmethane-type epoxy resin having an epoxy equivalent of 250 g / eq or less; and a curing agent having a hydroxyl equivalent of 150 g / eq or less and being at least one of a phenolic varnish-type phenolic resin, a cresol-phenolic varnish-type phenolic resin, or a triphenylmethane-type phenolic resin. In another embodiment of the present invention, the bonding magnet further comprises a phosphate ester.

[0019] One embodiment of the present invention provides a vehicle-mounted main motor comprising the aforementioned bonded magnet. Additionally, one embodiment of the present invention provides an oil pump comprising the aforementioned bonded magnet.

[0020] Another embodiment of the present invention provides a curing composition for bonding magnets comprising: magnetic powder; at least one of a phenolic varnish-type epoxy resin, a cresol-phenolic varnish-type epoxy resin, or a triphenylmethane-type epoxy resin having an epoxy equivalent of 250 g / eq or less; a curing agent having a hydroxyl equivalent of 150 g / eq or less and being at least one of a phenolic varnish-type phenolic resin, a cresol-phenolic varnish-type phenolic resin, or a triphenylmethane-type phenolic resin; and a phosphate ester.

[0021] Another embodiment of the present invention provides a method for manufacturing a bonded magnet that includes a step of injection molding or transfer molding of the bonded magnet with a curable composition and then curing it.

[0022] The effects of the invention

[0023] According to one embodiment of the present invention, a bonding magnet with excellent heat resistance and oil resistance can be provided, and it can be suitable for use in applications such as vehicle-mounted main motors and oil pumps that are immersed in or in contact with oil.

[0024] Furthermore, according to one embodiment of the present invention, a vehicle-mounted main motor with excellent performance can be provided. Additionally, according to one embodiment of the present invention, an oil pump with excellent performance can be provided.

[0025] In addition, according to another embodiment of the present invention, a curing composition for bonding magnets can be provided, which can produce a bonded magnet with high shape freedom and excellent heat resistance and oil resistance; or a curing composition for bonding magnets can be provided, which can be applied to injection molding or transfer molding and can produce a bonded magnet with excellent heat resistance and oil resistance.

[0026] Furthermore, according to another embodiment of the present invention, a method for manufacturing a bonded magnet can be provided, which can effectively manufacture a bonded magnet with high shape freedom and excellent heat resistance and oil resistance. Attached Figure Description

[0027] Figure 1 The graph shows the loss tangent (tanδ) of the bending strength test pieces (cured products of the curing composition for bonding magnets) of Example 1 and Comparative Example 1. Detailed Implementation

[0028] The embodiments of the present invention will now be described in detail. The embodiments shown below are merely examples to embody the technical concept of the present invention and do not limit the present invention to the following content. It should be noted that, in this specification, the numerical range represented by "~" indicates the range in which the values ​​before and after "~" are respectively the minimum and maximum values.

[0029] <Curing Composition for Bonding Magnets>

[0030] One embodiment of the curing composition for bonding magnets comprises: magnetic powder; at least one of phenolic varnish-type epoxy resin, cresol phenolic varnish-type epoxy resin, or triphenylmethane-type epoxy resin with an epoxy equivalent of 250 g / eq or less; a curing agent with a hydroxyl equivalent of 150 g / eq or less and being at least one of phenolic varnish-type phenolic resin, cresol phenolic varnish-type phenolic resin, or triphenylmethane-type phenolic resin; and a phosphate ester.

[0031] By using an epoxy resin with an epoxy equivalent of 250 g / eq or less, comprising at least one of phenolic varnish-type epoxy resin, cresol-phenolic varnish-type epoxy resin, or triphenylmethane-type epoxy resin as the main agent, and using at least one of the same phenolic varnish-type phenolic resin, cresol-phenolic varnish-type phenolic resin, or triphenylmethane-type phenolic resin as the curing agent, bonded magnets with excellent heat resistance and oil resistance can be obtained. While epoxy resins generally exhibit excellent heat resistance, this combination of epoxy resin (main agent) and curing agent achieves both excellent heat resistance and particularly excellent oil resistance. Furthermore, compared to others, the curable composition for bonded magnets containing this combination of epoxy resin (main agent) and curing agent exhibits good moldability.

[0032] Furthermore, the curing composition for bonded magnets in this embodiment, in addition to the above-described combination of epoxy resin (main agent) and curing agent, also contains phosphate ester, thereby achieving further improved moldability. The curing composition for bonded magnets containing phosphate ester in addition to the above-described combination of epoxy resin (main agent) and curing agent can be applied to injection molding and transfer molding methods, and bonded magnets with relatively complex shapes can be easily obtained. Furthermore, by adding phosphate ester, the magnetic powder can be highly filled, or sometimes the orientation of the magnetic powder can be improved, thereby increasing the remanent magnetic flux density (Br).

[0033] Therefore, the curing composition for bonded magnets of this embodiment can produce bonded magnets with excellent heat resistance and oil resistance that can be applied to injection molding or transfer molding. Furthermore, it can produce bonded magnets with high shape freedom and excellent heat resistance and oil resistance. It should be noted that the curing composition for bonded magnets of this embodiment is not limited to the combination of the epoxy resin (main agent) and curing agent described above. For the epoxy resin as a whole, the addition of phosphate esters tends to improve moldability, particularly in injection molding and transfer molding. This effect is significant when the epoxy resin is multifunctional, and even more so when it is the combination of the epoxy resin (main agent) and curing agent described above.

[0034] The content of magnetic powder in the curable composition for bonding magnets is not particularly limited, as long as it ensures the desired flowability during molding. In one embodiment, the content of magnetic powder in the curable composition for bonding magnets is preferably less than 95% by mass, more preferably less than 93% by mass. A content of less than 95% by mass, more preferably less than 93% by mass, in the curable composition for bonding magnets generally allows for easy molding by injection molding or transfer molding. Furthermore, while the content of magnetic powder in the curable composition for bonding magnets is not particularly limited, from the viewpoint of the magnetic properties of the resulting bonded magnet, it is preferably 80% by mass or more, more preferably 85% by mass or more.

[0035] [Epoxy resin (main agent)]

[0036] The curing composition for bonding magnets in this embodiment comprises at least one of the following epoxy resins (main agent): phenolic varnish-type epoxy resin, cresol-phenolic varnish-type epoxy resin, or triphenylmethane-type epoxy resin, with an epoxy equivalent of 250 g / eq or less. These epoxy resins may be used alone or in combination of two or more.

[0037] Phenolic varnishes made of phenolic epoxy resin contain repeating units represented by the following formula (1-1), and may also contain one or more repeating units other than those shown below. It should be noted that repeating units other than those shown in formula (1-1) are not particularly limited and can be selected appropriately.

[0038] [Chemical Formula 1]

[0039]

[0040] Cresol phenolic resin clear varnish type epoxy resin contains repeating units as shown in formula (1-2) below, and may contain more than one other repeating unit. It should be noted that there are no particular limitations on repeating units other than formula (1-2), and they can be selected appropriately.

[0041] [Chemical Formula 2]

[0042]

[0043] Triphenylmethane-type epoxy resins contain repeating units as shown in formulas (1-3) below, and may contain more than one type of repeating unit other than those shown. It should be noted that there are no particular limitations on the repeating units other than formulas (1-3), and they can be selected appropriately.

[0044] [Chemical Formula 3]

[0045]

[0046] In this embodiment, the epoxy resin (main agent) generally preferably contains one or more of the repeating units shown in formula (1-1), formula (1-2), and formula (1-3) above. More preferably, it is a phenolic varnish-type epoxy resin containing only the repeating units shown in formula (1-1), a cresol phenolic varnish-type epoxy resin containing only the repeating units shown in formula (1-2), or a triphenylmethane-type epoxy resin containing only the repeating units shown in formula (1-3). More preferably, it is a cresol phenolic varnish-type epoxy resin containing only the repeating units shown in formula (1-2) or a triphenylmethane-type epoxy resin containing only the repeating units shown in formula (1-3). Even more preferably, it is a triphenylmethane-type epoxy resin containing only the repeating units shown in formula (1-3).

[0047] In this embodiment, from the viewpoint of high curing speed, excellent moldability, and high heat resistance and oil resistance of the resulting bonded magnet, the epoxy equivalent of the phenolic varnish-type epoxy resin, cresol phenolic varnish-type epoxy resin, and triphenylmethane-type epoxy resin is 250 g / eq or less, more preferably 230 g / eq or less, more preferably 220 g / eq or less, and even more preferably 210 g / eq or less. The lower limit of the epoxy equivalent of these epoxy resins is not particularly limited, but is typically around 140 g / eq.

[0048] From a molding point of view, epoxy resin (main agent) is generally preferred to have a softening point below 100°C, more preferably below 85°C. It should be noted that the lower limit of the softening point of epoxy resin (main agent) is not particularly limited, but from the viewpoint of storage stability at room temperature, it is preferably above 40°C.

[0049] Commercially available products can also be used as phenolic varnish phenolic epoxy resins, cresol phenolic varnish epoxy resins, and triphenylmethane epoxy resins with an epoxy equivalent of 250 g / eq or less. Examples of commercially available phenolic varnish phenolic epoxy resins with an epoxy equivalent of 250 g / eq or less include EPICLON N-740, N-770, and N-775 (and above, manufactured by DIC Corporation). Examples of commercially available cresol phenolic varnish epoxy resins with an epoxy equivalent of 250 g / eq or less include N-660, N-673, and N-695 (and above, manufactured by DIC Corporation), YDCN-700-7, and YDCN-704A (and above, manufactured by Nippon Steel Chemical & Material Co., Ltd.). Triphenylmethane-type epoxy resins with an epoxy equivalent of 250 g / eq or less, such as EPPN-501H and EPPN-502H (and above, manufactured by Nippon Kayaku Co., Ltd.), are commercially available products.

[0050] The curable composition for bonding magnets in this embodiment preferably contains only epoxy resins with an epoxy equivalent of 250 g / eq or less, such as phenolic varnish phenolic epoxy resin, cresol phenolic varnish epoxy resin, and triphenylmethane epoxy resin as the main agent. It may contain other epoxy resins besides these, or epoxy compounds (monomers, etc.) that form epoxy resins upon curing. It may also contain at least one of, for example, phenolic varnish phenolic epoxy resin, cresol phenolic varnish epoxy resin, or triphenylmethane epoxy resin with an epoxy equivalent exceeding 250 g / eq. Additionally, it may contain, for example, biphenyl aralkyl epoxy resin. In the curable composition for bonding magnets in this embodiment, the content (proportion) of other epoxy resins or epoxy compounds relative to all epoxy resins (main agent) is preferably 5% by mass or less, more preferably 1% by mass or less, and particularly preferably 0% by mass.

[0051] [Curing agent]

[0052] The curing composition for bonding magnets in this embodiment comprises at least one of the following as a curing agent: a phenolic varnish-type phenolic resin, a cresol phenolic varnish-type phenolic resin, or a triphenylmethane-type phenolic resin, with a hydroxyl equivalent of 150 g / eq or less. These phenolic resin curing agents can be used alone or in combination of two or more.

[0053] Phenolic varnish-type phenolic resins contain repeating units as shown in formula (2-1) below, and may contain more than one other type of repeating unit. It should be noted that repeating units other than formula (2-1) are not particularly limited and can be selected appropriately.

[0054] [Chemical Formula 4]

[0055]

[0056] Cresol phenolic resin for varnish contains repeating units as shown in formula (2-2), and may contain more than one other type of repeating unit. It should be noted that there are no particular limitations on repeating units other than formula (2-2), and they can be selected appropriately.

[0057] [Chemical Formula 5]

[0058]

[0059] Triphenylmethane-type phenolic resins contain repeating units as shown in formula (2-3) below, and may contain more than one other type of repeating unit. It should be noted that there are no particular limitations on repeating units other than formula (2-3), and they can be selected appropriately.

[0060] [Chemical Formula 6]

[0061]

[0062] In this embodiment, the curing agent is generally preferably a phenolic varnish-type phenolic resin containing only the repeating units shown in formula (2-1), a cresol phenolic varnish-type phenolic resin containing only the repeating units shown in formula (2-2), or a triphenylmethane-type phenolic resin containing only the repeating units shown in formula (2-3). More preferably, it is a phenolic varnish-type phenolic resin containing only the repeating units shown in formula (2-1). In one embodiment, a combination of a triphenylmethane-type epoxy resin (main agent) containing only the repeating units shown in formula (1-3) and a phenolic varnish-type phenolic resin (curing agent) containing only the repeating units shown in formula (2-1) is sometimes particularly preferred.

[0063] In this embodiment, from the viewpoint of high curing speed, excellent moldability, and high heat resistance and oil resistance of the resulting bonded magnet, the hydroxyl equivalent of phenolic varnish-type phenolic resin, cresol phenolic varnish-type phenolic resin, and triphenylmethane-type phenolic resin is 150 g / eq or less, more preferably 140 g / eq or less, more preferably 130 g / eq or less, and even more preferably 120 g / eq or less. The lower limit of the hydroxyl equivalent of these phenolic resin-based curing agents is not particularly limited, and is typically around 70 g / eq.

[0064] From a molding perspective, the softening point of phenolic resin curing agents is generally preferably below 100°C, and more preferably below 85°C. It should be noted that there is no particular limitation on the lower limit of the softening point of phenolic resin curing agents; however, from the perspective of storage stability at room temperature, it is preferably above 40°C.

[0065] Commercially available phenolic resins, including phenolic varnish type, cresol phenolic varnish type, and triphenylmethane type phenolic resins, can be used as phenolic varnish type resins with a hydroxyl equivalent of 150 g / eq or less. Examples of commercially available phenolic varnish type phenolic resins with a hydroxyl equivalent of 150 g / eq or less include TD-2131 and TD-2106 (and above, manufactured by DIC Corporation). Examples of commercially available cresol phenolic varnish type phenolic resins with a hydroxyl equivalent of 150 g / eq or less include KA-1160, KA-1163 / KA-1165 (and above, manufactured by DIC Corporation). Examples of commercially available triphenylmethane-type phenolic resins with a hydroxyl equivalent of 150 g / eq or less include: MEH-7500 (manufactured by UBE Corporation), S-TPM-130, S-TPM-113 (and above, manufactured by JFEC Chemical Corporation), and KAYAHARD KTG-105 (manufactured by Nippon Kayaku Co., Ltd.).

[0066] Regarding the curing composition for bonding magnets according to this embodiment, the curing agent preferably contains only phenolic varnish-type phenolic resin, cresol phenolic varnish-type phenolic resin, and triphenylmethane-type phenolic resin with a hydroxyl equivalent of 150 g / eq or less. Other curing agents besides these may also be included. It may also contain, for example, phenolic resin-based curing agents other than phenolic varnish-type phenolic resin, cresol phenolic varnish-type phenolic resin, and triphenylmethane-type phenolic resin, or at least one of phenolic varnish-type phenolic resin, cresol phenolic varnish-type phenolic resin, or triphenylmethane-type phenolic resin with a hydroxyl equivalent exceeding 150 g / eq. In the curing composition for bonding magnets according to this embodiment, the content (proportion) of other curing agents relative to all curing agents is preferably 5% by mass or less, more preferably 1% by mass or less, and particularly preferably 0% by mass.

[0067] The content of phenolic varnish-type phenolic resin, cresol phenolic varnish-type phenolic resin, and triphenylmethane-type phenolic resin (curing agent) with a hydroxyl equivalent of 150 g / eq or less in the curing composition for bonding magnets can be appropriately selected according to the type of epoxy resin, curing agent, and curing accelerator used, and is not particularly limited. In one embodiment of this invention, the content of phenolic varnish-type phenolic resin, cresol phenolic varnish-type phenolic resin, and triphenylmethane-type phenolic resin with a hydroxyl equivalent of 150 g / eq or less in the curing composition for bonding magnets relative to 100 parts by weight of epoxy resin (main agent) is preferably 30 to 90 parts by weight, and more preferably 40 to 65 parts by weight.

[0068] [Curing Accelerator]

[0069] The curing composition for bonding magnets according to this embodiment may further include a curing accelerator. By including a curing accelerator, the curing composition for bonding magnets can sometimes reduce the molding temperature (curing temperature of the composition) or shorten the molding time (curing time of the composition). A single curing accelerator may be used alone, or two or more may be used in combination.

[0070] As a curing accelerator, there are no particular limitations, 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.

[0071] Commercially available products can be used as curing accelerators. Examples of commercially available urea-based curing accelerators include: U-cat3512T, U-cat 3513N (and above, manufactured by San-apro Co., Ltd.), Dyhard UR200, UR300 (and above, manufactured by AlzChem Co., Ltd.). Examples of commercially available imidazole-based curing accelerators include: Curezol 2E4MZ-A, 2PHZ-PW (and above, manufactured by Shikoku Chemical Co., Ltd.).

[0072] The content of the curing accelerator in the curing composition for bonding magnets 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 invention, the content of the curing accelerator in the curing composition for bonding magnets can be, for example, 0.5 to 5 parts by weight relative to 100 parts by weight of epoxy resin (main agent).

[0073] The curing accelerator can be included in the curing composition for bonding magnets before the curing process, or it can be added to the curing composition for bonding magnets during the curing process, just before the curing composition for bonding magnets is heated to soften it, or it can be added to the curing composition for bonding magnets at any time when the curing composition for bonding magnets is heated to soften it.

[0074] [Phosphate ester]

[0075] The curing composition for bonding magnets in this embodiment further comprises phosphate esters. Phosphate esters can be used alone or in combination of two or more. As mentioned earlier, by adding phosphate esters, particularly in injection molding and transfer molding, the vigorous curing reaction of the epoxy resin can be suppressed, resulting in further improved formability. Furthermore, from the viewpoint of magnetic properties, Sm-Fe-N based magnetic powders preferably have a smaller average particle size than other rare-earth magnetic powders; however, when using Sm-Fe-N based magnetic powders as the magnetic powder, the improvement in formability resulting from the addition of phosphate esters tends to become more significant.

[0076] From the viewpoint of improving formability, alkyl ether phosphate is preferred as a phosphate ester, more preferably polyoxyethylene alkyl ether phosphate, and even more preferably polyoxyethylene alkyl ether phosphate as shown in formula (3-1) below.

[0077] [Chemical Formula 7]

[0078]

[0079] (In the formula, R represents an alkyl group, n represents an integer greater than or equal to 1, and m represents an integer from 1 to 3.)

[0080] The alkyl groups contained in alkyl ether phosphates and polyoxyethylene alkyl ether phosphates can be linear or branched, and the number of carbon atoms is not particularly limited, but preferably 8 or more, more preferably 8 or more and 24 or less.

[0081] In formula (3-1), R is preferably a straight-chain or branched alkyl group with 8 or more carbon atoms, and more preferably a straight-chain or branched alkyl group with 8 or more and 24 or less carbon atoms.

[0082] In equation (3-1), n ​​represents an integer greater than or equal to 1, preferably greater than or equal to 1 and less than or equal to 4, and more preferably greater than or equal to 1 and less than or equal to 2.

[0083] In formula (3-1), m represents an integer from 1 to 3. That is, the polyoxyethylene alkyl ether phosphate shown in formula (3-1) can be a monophosphate, a diester, or a triphosphate. It should be noted that one type of polyoxyethylene alkyl ether phosphate can be used, or a mixture of two or more types can be used.

[0084] Phosphate esters, preferably polyoxyethylene alkyl ether phosphate esters, can be commercially available. Examples of commercially available polyoxyethylene alkyl ether phosphate esters include: Phosphhanol RS-410, RS-610, RS-710 (and above, manufactured by Tohoku Chemical Industry Co., Ltd.), Lauryl EO2 acid phosphate, and Oleyl EO2 acid phosphate (and above, manufactured by Johoku Chemical Industry Co., Ltd.).

[0085] The content of phosphate ester in the curing composition for bonding magnets can be appropriately selected depending on the type of magnetic powder, epoxy resin, and curing agent used, and is not particularly limited. In one embodiment of this invention, the content of phosphate ester in the curing composition for bonding magnets is preferably 0.05 to 1 part by weight, and more preferably 0.1 to 0.6 parts by weight, relative to 100 parts by weight of magnetic powder.

[0086] [Magnetic powder]

[0087] In the curing composition for bonding magnets of this embodiment, the magnetic powder is not particularly limited; any known magnetic powder, such as ferrite powder or rare earth magnetic powder, may be used. One type of magnetic powder may be used alone, or two or more may be used in combination.

[0088] In one embodiment of this invention, rare-earth magnetic powders are preferred from the viewpoint of superior magnetic properties. Examples of rare-earth magnetic powders include Sm-Co, Nd-Fe-B, and Sm-Fe-N series magnetic powders. In this embodiment, there is no particular limitation, and any type of rare-earth magnetic powder can be used appropriately. However, from the viewpoint of the magnetic properties, heat resistance, oil resistance, and formability of the resulting bonded magnet, Sm-Fe-N series magnetic powders are particularly preferred. Sm-Fe-N series magnetic powders possess heat resistance and high corrosion resistance due to a highly anisotropic magnetic field exceeding 260 kOe (20.7 MA / m), and exhibit excellent heat resistance and oil resistance. One type of rare-earth magnetic powder can be used alone, or two or more types can be combined.

[0089] Sm-Co magnetic powders can be manufactured by methods disclosed, for example, in Japanese Patent Application Publication No. 08-260083. Nd-Fe-B magnetic powders can be manufactured by the HDDR method disclosed, for example, in International Patent Application Publication No. 2003 / 85147. Sm-Fe-N magnetic powders can be manufactured by methods disclosed, for example, in Japanese Patent Application Publication No. 11-189811.

[0090] As described above, in one embodiment of this invention, the rare-earth magnetic powder is preferably an Sm-Fe-N based magnetic powder. Examples of Sm-Fe-N based magnetic powders include those containing Th₂Zn. 17 It has a crystalline structure of type Sm and the general formula is Sm x Fe 100-x-y N y The nitride shown comprises rare earth metals samarium (Sm), iron (Fe), and nitrogen (N). Here, x is preferably 8.1 atomic percent or more and 10 atomic percent or less, y is 13.5 atomic percent or more and 13.9 atomic percent or less, and the remainder is mainly Fe.

[0091] Rare earth magnetic powders can be used directly, or they can be powders that have undergone surface treatment with, for example, silane coupling agents. Surface treatment with silane coupling agents can be performed using, for example, the method disclosed in Japanese Patent Application Publication No. 2017-43804.

[0092] Alternatively, in the case of Sm-Fe-N based magnetic powder, powder with a phosphate coating formed on its surface can also be used; that is, phosphate-coated Sm-Fe-N based magnetic powder can also be used. Phosphate-coated Sm-Fe-N based magnetic powder can be manufactured by methods disclosed, for example, in International Publication No. 2022 / 107462, Japanese Patent Application Publication No. 2023-96735, and Japanese Patent Application Publication No. 2024-51932.

[0093] The average particle size of rare-earth magnetic powders can be appropriately selected depending on their type, and is not particularly limited. In the case of Sm-Co based magnetic powders, the average particle size is generally preferably 10 μm or more and 250 μm or less. In the case of Nd-Fe-B based magnetic powders, the average particle size is generally preferably 10 μm or more and 250 μm or less. In the case of Sm-Fe-N based magnetic powders, the average particle size is generally preferably 2 μm or more and 5 μm or less, more preferably 2.5 μm or more and 4.8 μm or less. By setting the average particle size to 2 μm or more, the filling amount of Sm-Fe-N based magnetic powder in the bonded magnet can be increased, and sometimes magnetization can be improved. Furthermore, by setting the average particle size to 5 μm or less, the intrinsic coercivity of the bonded magnet can sometimes be improved. Here, the average particle size is the particle size measured under dry conditions using a laser diffraction particle size distribution measuring device.

[0094] In the case of Sm-Fe-N based magnetic powder, the particle size D50 is preferably 2.5 μm or more and 5 μm or less, more preferably 2.7 μm or more and 4.8 μm or less. The particle size D10 is preferably 1 μm or more and 3 μm or less, more preferably 1.5 μm or more and 2.5 μm or less. Furthermore, the particle size D90 is preferably 3 μm or more and 7 μm or less, more preferably 4 μm or more and 6 μm or less. Here, D50 means that the cumulative value of the volume-based particle size distribution of the Sm-Fe-N based magnetic powder is equivalent to 50% of the particle size. D10 means that the cumulative value of the volume-based particle size distribution of the Sm-Fe-N based magnetic powder is equivalent to 10% of the particle size. D90 means that the cumulative value of the volume-based particle size distribution of the Sm-Fe-N based magnetic powder is equivalent to 90% of the particle size.

[0095] From the viewpoint of the coercivity of bonded magnets, the span of Sm-Fe-N magnetic powder is defined as follows ( ): Span = (D90-D10) / D50 is preferably 2 or less, more preferably 1.5 or less.

[0096] The sphericity of Sm-Fe-N magnetic powder is not particularly limited, but is preferably 0.5 or higher, more preferably 0.6 or higher. When the sphericity is below 0.5, the flowability deteriorates, thus generating stress between particles during molding, sometimes leading to a decrease in magnetic properties. Here, in determining the sphericity, the SEM image taken at 3000x magnification is binarized by image processing, and the sphericity is calculated for each particle. The sphericity defined in this invention refers to the average sphericity obtained by measuring approximately 1000 to 10000 particles. Generally, the more particles with smaller diameters, the higher the sphericity; therefore, the sphericity is measured for particles larger than 1 μm. The definition used in the sphericity measurement is: sphericity = (4πS / L) 2 Where S is the two-dimensional projected area of ​​the particle, and L is the two-dimensional projected perimeter.

[0097] [Sm-Fe-N based magnetic powder]

[0098] In one embodiment of this invention, from the viewpoint of the magnetic properties of the resulting bonded magnet, the Sm-Fe-N based magnetic powder is preferably anisotropic. Furthermore, from the viewpoint of improved coercivity, heat resistance, and oil resistance, the Sm-Fe-N based magnetic powder is sometimes preferably a magnetic powder with a phosphate coating on its surface.

[0099] The following describes an example of the manufacturing method of the Sm-Fe-N anisotropic magnetic powder and the phosphate-coated Sm-Fe-N anisotropic magnetic powder of this embodiment. It is not limited to the following method and can be manufactured by other manufacturing methods.

[0100] [Method for manufacturing Sm-Fe-N based anisotropic magnetic powder]

[0101] Sm-Fe-N anisotropic magnetic powder is not particularly limited, and can be manufactured, for example, by a method including the following steps:

[0102] The process of mixing a solution containing Sm and Fe with a precipitant to obtain a precipitate containing Sm and Fe (precipitation process);

[0103] The process of calcining the above precipitate to obtain an oxide containing Sm and Fe (oxidation process);

[0104] The process of heat-treating the above oxides in a reducing gas atmosphere to obtain partial oxides (pretreatment process);

[0105] The process of reducing some of the oxides mentioned above (reduction process); and

[0106] The process of nitriding alloy particles obtained in the reduction process (nitriding process).

[0107] (Sedimentation process)

[0108] In the precipitation process, Sm and Fe raw materials are dissolved in a strongly acidic solution to prepare a solution containing Sm and Fe. This yields Sm₂Fe₂. 17 When N3 is the main phase, the molar ratio of Sm to Fe (Sm:Fe) is preferably 1.5:17 to 3.0:17, more preferably 2.0:17 to 2.5:17. Raw materials such as La, W, Co, Ti, Sc, Y, Pr, Nd, Pm, Gd, Tb, Dy, Ho, Er, Tm, and Lu can be added to the solution.

[0109] As raw materials for Sm and Fe, there are no limitations as long as they can dissolve in strongly acidic solutions. For example, from the viewpoint of ease of acquisition, samarium oxide can be used as a raw material for Sm, and FeSO4 can be used as a raw material for Fe. The concentration of the solution containing Sm and Fe can be appropriately adjusted within the range where the Sm and Fe raw materials are substantially soluble in acidic solutions. From the viewpoint of solubility, sulfuric acid can be used as an acidic solution.

[0110] By reacting a solution containing Sm and Fe with a precipitating agent, an insoluble precipitate containing Sm and Fe is obtained. Here, the solution containing Sm and Fe need only be able to react with the precipitating agent to form a solution containing Sm and Fe. For example, the raw materials containing Sm and Fe can be prepared as separate solutions, and each solution can be added dropwise to react with the precipitating agent. When preparing the solutions as separate solutions, the raw materials are appropriately adjusted to be substantially soluble in acidic solutions. The precipitating agent is not limited as long as it can react with the solution containing Sm and Fe in an alkaline solution to obtain a precipitate; examples include ammonia, sodium hydroxide, etc., with sodium hydroxide being preferred.

[0111] From the viewpoint that the particle properties of the precipitate can be easily adjusted, the precipitation reaction is preferably carried out by adding a solution containing Sm and Fe and a precipitant dropwise to a solvent such as water. By appropriately controlling the supply rates 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 uniform distribution of constituent elements, narrow particle size distribution, and regular powder shape can be obtained. By using such a precipitate, the magnetic properties of the magnetic powder as the final product are improved. The reaction temperature is preferably set to 0~50°C, more preferably 35~45°C. Regarding the concentration of the reaction solution, the total concentration of metal ions is preferably set to 0.65~0.85 mol / L, more preferably 0.7~0.84 mol / L. The reaction pH is preferably set to 5~9, more preferably 6.5~8.

[0112] Based on the anisotropic magnetic powder particles obtained in the precipitation process, the particle size, shape, and particle size distribution of the final magnetic powder can be roughly determined. When the particle size is measured using a laser diffraction wet particle size analyzer, it is preferable that the entire powder has a size and distribution approximately 0.05 to 20 μm, more preferably within the range of approximately 0.1 to 10 μm. Furthermore, the average particle size of the anisotropic magnetic powder particles is measured as the volumetric accumulation of 50% of the particle size from the smallest particle size side of the particle size distribution, and is preferably within the range of 0.1 to 10 μm.

[0113] After separating the precipitate, in order to prevent the precipitate from redissolving in the residual solvent during the subsequent oxidation heat treatment, and to prevent the precipitate from agglomerating during solvent evaporation, causing changes in particle size distribution and powder particle size, it is preferable to pre-desolventize the separated material. Specifically, a desolventizing method can be, for example, drying in an oven at 70–200°C for 5–12 hours when using water as the solvent.

[0114] Following the precipitation process, a step of separating / washing the resulting precipitate may be included. The washing process should continue until the conductivity of the supernatant reaches 5 mS / m. 2The following are examples of steps for separating precipitates. For instance, after adding a solvent (preferably water) to the obtained precipitate and mixing it, filtration, decantation, or other methods can be used.

[0115] (Oxidation process)

[0116] The oxidation process refers to the process of obtaining oxides containing Sm and Fe by calcining the precipitate formed in the precipitation process. For example, the precipitate can be converted into oxides by heat treatment. When heat treating the precipitate, it needs to be carried out in the presence of oxygen, for example, in an atmospheric atmosphere. In addition, since it needs to be carried out in the presence of oxygen, it is preferable that the non-metallic portion of the precipitate contains oxygen atoms.

[0117] The heat treatment temperature (hereinafter also referred to as oxidation temperature) in the oxidation process is not particularly limited, but is preferably 700~1300℃, more preferably 900~1200℃. At temperatures below 700℃, oxidation may be insufficient, and if the temperature exceeds 1300℃, it tends to be difficult to obtain the desired shape, average particle size, and particle size distribution of the target magnetic powder. The heat treatment time is not particularly limited, but is preferably 1~3 hours.

[0118] The resulting oxides are oxide particles in which Sm and Fe are fully mixed at the microscopic level within the oxide particles, and reflect the shape, particle size distribution, etc. of the precipitate.

[0119] (Pre-processing step)

[0120] The pretreatment process refers to the process of heat-treating oxides containing Sm and Fe in a reducing gas atmosphere to obtain a partially reduced oxide.

[0121] Here, "partial oxide" refers to oxides in which a portion has been reduced. The oxygen concentration of the oxide is not particularly limited, but is preferably 10% by mass or less, more preferably 8% by mass or less. If it exceeds 10% by mass, the exothermic reduction with Ca during the reduction process increases, resulting in a higher firing temperature and a tendency for abnormal particle growth to occur. Here, the oxygen concentration of the partial oxide can be determined by non-dispersive infrared absorption spectrometry (ND-IR).

[0122] The reducing gas is appropriately selected from hydrocarbon gases such as hydrogen (H2), carbon monoxide (CO), and methane (CH4), with hydrogen being preferred from a cost perspective. The gas flow rate is appropriately adjusted within a range that prevents oxide dispersion. The heat treatment temperature (hereinafter also referred to as the pretreatment temperature) in the pretreatment process is preferably set in the range of 300~950°C, more preferably 400°C or higher, particularly preferably 750°C or higher, and more preferably below 900°C. If the pretreatment temperature is 300°C or higher, the reduction of oxides containing Sm and Fe is carried out efficiently. In addition, if it is below 950°C, the particle growth and segregation of oxide particles are suppressed, and the desired particle size can be easily maintained.

[0123] (Restoration process)

[0124] The reduction process refers to a process in which, for example, a portion of the oxides obtained in the pretreatment process are heat-treated and reduced in the presence of a reducing agent, preferably at 920 to 1200°C, to obtain alloy particles. For example, reduction is performed by contacting the portion of the oxides with calcium melt or calcium vapor. From the viewpoint of magnetic properties, the heat treatment temperature is preferably 950 to 1150°C, more preferably 980 to 1100°C. From the viewpoint of suppressing uneven particle growth, the heat treatment time is preferably less than 120 minutes, more preferably less than 90 minutes. Furthermore, from the viewpoint of conducting the reduction reaction more uniformly, the heat treatment time is preferably 10 minutes or more, more preferably 30 minutes or more.

[0125] Metallic calcium is used, for example, in granular or powder form, with a particle size preferably less than 10 mm. This allows for more effective suppression of aggregation during the reduction reaction. Furthermore, metallic calcium can be added, for example, in a ratio of 1.1 to 3.0 times the reaction equivalent (the stoichiometric amount required to reduce Sm oxides, which, in the case of Fe oxides, includes the amount required for their reduction), preferably 1.5 to 2.0 times.

[0126] In the reduction process, a disintegration accelerator may be used together with metallic calcium as a reducing agent, as needed. This disintegration accelerator is a substance appropriately used during the subsequent washing process to promote the disintegration and granulation of the product; examples include alkaline earth metal salts such as calcium chloride and alkaline earth metal oxides such as calcium oxide. These disintegration accelerators are used, for example, at a ratio of 1 to 30% by mass, preferably 5 to 28% by mass, relative to the Sm oxide used as a Sm source.

[0127] (Nitriding process)

[0128] The nitriding process refers to the process of nitriding alloy particles obtained through the reduction process to obtain Sm-Fe-N anisotropic magnetic powder. In this method, the porous, blocky product containing alloy particles obtained in the reduction process is directly heat-treated in a nitrogen atmosphere without pulverization, which allows for nitriding of the alloy particles and ensures uniform nitriding.

[0129] The heat treatment temperature (hereinafter also referred to as nitriding temperature) in the nitriding treatment of alloy particles is preferably 300~600℃, and particularly preferably 400~550℃, by replacing the atmosphere with a nitrogen atmosphere within this temperature range. The heat treatment time is set to a level that ensures sufficient and uniform nitriding of the alloy particles.

[0130] The product obtained after the nitriding process contains not only magnetic particles (Sm-Fe-N anisotropic magnetic powder), but also byproducts such as CaO and unreacted metallic calcium, sometimes forming a sintered mass of these composites. In this case, immersing the product in cooling water allows the CaO and metallic calcium to be separated from the magnetic particles as calcium hydroxide (Ca(OH)2) suspension. Furthermore, washing the magnetic particles with acetic acid or similar substances can effectively remove residual calcium hydroxide.

[0131] [Method for manufacturing phosphate-coated Sm-Fe-N anisotropic magnetic powder]

[0132] There are no particular limitations on phosphate-coated Sm-Fe-N anisotropic magnetic powders. For example, they can be manufactured by the following method, which includes: adding an inorganic acid to a slurry containing Sm-Fe-N anisotropic magnetic powder, water, and a phosphoric acid compound, adjusting the pH of the slurry to preferably 1 to 4.5, to obtain Sm-Fe-N anisotropic magnetic powder coated with phosphate on the surface, in a phosphoric acid treatment step; and an oxidation step of heat-treating the phosphate-coated Sm-Fe-N anisotropic magnetic powder in an oxygen-containing atmosphere, preferably at 200 to 330°C.

[0133] (Phosphoric acid treatment process)

[0134] In the phosphoric acid treatment process, an inorganic acid is added to a slurry containing Sm-Fe-N anisotropic magnetic powder, water, and a phosphoric acid compound. By adjusting the pH of the slurry to a preferred value of 1 to 4.5, Sm-Fe-N anisotropic magnetic powder with a phosphate coating is obtained. The phosphate-coated Sm-Fe-N anisotropic magnetic powder is formed by reacting the metal components (e.g., iron, samarium) contained in the Sm-Fe-N anisotropic magnetic powder with the phosphoric acid components contained in the phosphoric acid compound, thereby precipitating phosphates (e.g., ferric phosphate, samarium phosphate) on the surface of the Sm-Fe-N anisotropic magnetic powder. Adjusting the pH of the slurry to 1 to 4.5 by adding an inorganic acid increases the amount of phosphate precipitation compared to the case without adding an inorganic acid, and tends to result in phosphate-coated Sm-Fe-N anisotropic magnetic powder with a thick coating. Furthermore, by using water as the solvent, compared to using an organic solvent, the precipitation of smaller phosphate particles tends to result in phosphate-coated Sm-Fe-N anisotropic magnetic powders with denser coatings.

[0135] The method for preparing a slurry comprising Sm-Fe-N anisotropic magnetic powder, water, and a phosphoric acid compound is not particularly limited. For example, it can be prepared by mixing an aqueous solution of phosphoric acid containing Sm-Fe-N anisotropic magnetic powder and a phosphoric acid compound, using water as a solvent. The content of Sm-Fe-N anisotropic magnetic powder in the slurry is preferably 1 to 50% by mass, and more preferably 5 to 20% by mass from a production point of view. The content of phosphoric acid (PO4) in the slurry, in terms of PO4 equivalent, is preferably 0.01 to 10% by mass, and more preferably 0.05 to 5% by mass from a reactivity and production point of view.

[0136] Phosphoric acid aqueous solution can be obtained by mixing a phosphoric acid compound with water. Examples of phosphoric acid compounds include: orthophosphoric acid, sodium dihydrogen phosphate, sodium monohydrogen phosphate, ammonium dihydrogen phosphate, ammonium monohydrogen phosphate, zinc phosphate, calcium phosphate, and other phosphate-based, hypophosphoric acid-based, hypophosphoric acid-based, pyrophosphoric acid-based, polyphosphoric acid-based, and organic phosphoric acid compounds. Only one type of these can be used, or two or more can be combined. Furthermore, to improve the water resistance, corrosion resistance, and magnetic properties of the magnetic powder resulting from the coating, oxyacid salts such as molybdates, tungstates, vanadates, and chromates can be added; oxidizing agents such as sodium nitrate and sodium nitrite; and chelating agents such as EDTA.

[0137] The concentration of phosphoric acid (PO4 equivalent) in the phosphoric acid aqueous solution is preferably 5-50% by mass, and more preferably 10-30% by mass from the viewpoint of facilitating the solubility, storage stability, and chemical conversion of phosphoric acid compounds. The pH of the phosphoric acid aqueous solution is preferably 1-4.5, and more preferably 1.5-4 from the viewpoint of facilitating the control of phosphate precipitation rate. The pH can be adjusted using dilute hydrochloric acid, dilute sulfuric acid, etc.

[0138] In the phosphoric acid treatment process, the pH of the slurry is preferably adjusted to 1-4.5, more preferably 1.6-3.9, and even more preferably 2-3 by adding an inorganic acid. When the pH is below 1, starting with the localized large-scale precipitation of phosphate, the Sm-Fe-N anisotropic magnetic powder coated with phosphate aggregates, sometimes resulting in a decrease in coercivity. If the pH exceeds 4.5, the amount of phosphate precipitation decreases, the coating is insufficient, and sometimes the coercivity decreases. Examples of added inorganic acids include hydrochloric acid, nitric acid, sulfuric acid, boric acid, and hydrofluoric acid. Inorganic acids are added as needed during the phosphoric acid treatment process to achieve the above-mentioned pH range. From the viewpoint of wastewater treatment, inorganic acids are preferred, 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 can be prepared for use.

[0139] 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 coating effect of the phosphate tends to decrease. If the phosphate content exceeds 4.5% by mass, the phosphate-coated Sm-Fe-N anisotropic magnetic powder aggregates together, sometimes resulting in a decrease in coercivity. It should be noted that the phosphate content of the magnetic powder is expressed as the PO4 molecular weight equivalent determined using ICP-AES.

[0140] The pH adjustment time for the slurry containing Sm-Fe-N anisotropic magnetic powder, water, and phosphoric acid compound to a range of 1 to 4.5 is preferably 10 minutes or more, and more preferably 30 minutes or more from the viewpoint of reducing the thin parts of the coating. In the initial stage of pH maintenance, the pH rises rapidly, so the interval between the addition of inorganic acid for pH control is short; as coating progresses, the pH fluctuation becomes more gradual, and the interval between the addition of inorganic acid becomes longer, so the reaction endpoint can be determined.

[0141] (Oxidation process after phosphoric acid treatment)

[0142] In the oxidation process following phosphoric acid treatment, the phosphate-coated Sm-Fe-N anisotropic magnetic powder obtained in the phosphoric acid treatment process is heat-treated in an oxygen-containing atmosphere, preferably at 200~330°C, to oxidize 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 200~330°C, the surface of the phosphate-coated Sm-Fe-N anisotropic magnetic powder is oxidized, forming a thick iron oxide layer. This tends to improve the heat resistance and oil resistance of the phosphate-coated Sm-Fe-N anisotropic magnetic powder.

[0143] The oxidation process following phosphoric acid treatment involves heat treatment of 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, for example, 3-21%, more preferably 3.5-10%. During the oxidation reaction, it is preferable to exchange the gas at a flow rate of 2-10 L / min per kg of magnetic powder.

[0144] The heat treatment temperature in the oxidation process after phosphoric acid treatment is preferably 200~330℃, more preferably 200~250℃, and even more preferably 210~230℃. Below 200℃, the formation of the iron oxide layer is insufficient, and sometimes the effect of improving heat resistance and oil resistance is diminished. If the temperature exceeds 330℃, an excessive amount of iron oxide layer forms, and sometimes the coercivity decreases. The heat treatment time is preferably, for example, 3~10 hours.

[0145] The oxidation process following phosphoric acid treatment is preferably carried out in the following manner: the phosphate-coated portion present on the surface of the Sm-Fe-N anisotropic magnetic powder has a first region, the Sm atom concentration in the first region being higher than the Sm atom concentration in the Sm-Fe-N anisotropic magnetic powder, and the Sm atom concentration in the first region being 0.5 times or more and 4 times or less of the Fe atom concentration in the first region. The Sm atom concentration in the first region can be, for example, set to 1.02 times or more of 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, for example, set to 3 times or less of 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 of the Fe atom concentration in the first region, more preferably 0.7 times or more and 3 times or less. It should be noted that the atomic concentration (atm%) of the Sm-Fe-N anisotropic magnetic powder and the first region was obtained by averaging the atomic concentration (atm%) in each region during STEM-EDX line analysis.

[0146] (Silica treatment process)

[0147] Phosphoric acid-treated Sm-Fe-N anisotropic magnetic powder (i.e., phosphate-coated Sm-Fe-N anisotropic magnetic powder) can be subjected to silica treatment as needed after the above-mentioned oxidation process. Oxidation resistance can sometimes be improved by forming a silica film on the magnetic powder. The silica film can be formed, for example, by mixing alkyl silicates, phosphate-coated Sm-Fe-N anisotropic magnetic powder, and an alkaline solution.

[0148] (Silane coupling process)

[0149] The magnetic powder treated with silica can be further processed using a silane coupling agent. By subjecting the magnetic powder with the silica film to silane coupling treatment, a coupling agent film is formed on the silica film, which improves the magnetic properties of the magnetic powder and can sometimes improve its wettability with resin and the strength of the magnet.

[0150] The silane coupling agent can be selected based on the type of resin and is not particularly limited. Examples include: 3-aminopropyltriethoxysilane, γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropylmethyldimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, γ-methacryloyloxypropylmethyldimethoxysilane, N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane hydrochloride, γ-glycidyl etheroxypropyltrimethoxysilane, and γ-glycidyl etheroxyoctyltrimethoxysilane. Silane, γ-mercaptopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, vinyltriacetoxysilane, γ-chloropropyltrimethoxysilane, hexamethylenedisilazane, γ-anilinepropyltrimethoxysilane, vinyltrimethoxysilane, octadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, γ-chloropropylmethyldimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, vinyltrichlorosilane, vinyltri(β-methoxyethoxy)silane, vinyl Triethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidyl etheroxypropylmethyldiethoxysilane, N-β(aminoethyl)γ-aminopropyltrimethoxysilane, N-β(aminoethyl)γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, ureapropyltriethoxysilane, γ-isocyanate propyltriethoxysilane, polyethoxydimethylsiloxane, polyethoxymethylsiloxane, bis(trimethoxysilylpropyl)amine, bis(3-triethoxy) Silane coupling agents include propyl(3-trimethoxypropyl)tetrasulfide, γ-isocyanate propyltrimethoxysilane, vinylmethyldimethoxysilane, 1,3,5-N-tris(3-trimethoxysilylpropyl)isocyanurate, tert-butylcarbamate trimekoxysilane, N-(1,3-dimethylbutylene)-3-(triethoxysilyl)-1-propane, octyltriethoxysilane, octyltrimethoxysilane, decyltriethoxysilane, decyltrimethoxysilane, octadecyltriethoxysilane, octadecyltrimethoxysilane, and docosyltriethoxysilane. These silane coupling agents can be used alone or in combination of two or more. The amount of silane coupling agent added relative to 100 parts by weight of magnetic powder is preferably 0.2 to 0.8 parts by weight, more preferably 0.25 to 0.6 parts by weight. When the amount is below 0.2 parts by mass, the effect of the silane coupling agent tends to be small. If it exceeds 0.8 parts by mass, the magnetic properties of the magnetic powder and magnet may decrease due to the aggregation of magnetic powder.

[0151] After phosphoric acid treatment, oxidation, silica treatment, or silane coupling treatment, Sm-Fe-N anisotropic magnetic powder can be filtered, dehydrated, and dried using conventional methods.

[0152] [Other ingredients]

[0153] The curable composition for bonding magnets in this embodiment may further include, as needed, various additives such as fillers (preferably inorganic fillers), lubricants, dispersants, antioxidants, heavy metal deactivators, crystallizing nucleating agents, flame retardants, plasticizers, ultraviolet absorbers, antistatic agents, colorants, and release agents, as well as any components such as thermosetting resins other than epoxy resins, thermoplastic resins, and thermoplastic elastomers.

[0154] Examples of lubricants and dispersants include: solid paraffin wax, polyethylene wax, polypropylene wax, and other waxes; stearic acid and other fatty acids and their salts; metal soaps, fatty acid amides, urea compounds, fatty acid esters, polyethers, silicone oils, silicone greases, and other polysiloxanes; fluorinated oils, fluorinated greases, fluoropolymer powders, etc. One lubricant or dispersant can be added alone, or two or more can be used in combination.

[0155] The resins added to the curing composition for bonding magnets are not particularly limited, and 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, polyetheretherketone, liquid crystal polymers, polyethylene terephthalate, polybutylene terephthalate, polyphenylene ether, cyclic olefin polymers, and cyclic olefin copolymers. These thermosetting and thermoplastic resins can be added individually or in combination of two or more.

[0156] <Method for manufacturing a curing composition for bonding magnets>

[0157] The curable composition for bonding magnets according to this embodiment can be obtained by mixing / kneading the following components: for example, magnetic powder; at least one of the following: phenolic varnish-type epoxy resin, cresol phenolic varnish-type epoxy resin, or triphenylmethane-type epoxy resin with an epoxy equivalent of 250 g / eq or less (epoxy resin as the main agent); at least one of the following: phenolic varnish-type phenolic resin, cresol phenolic varnish-type phenolic resin, or triphenylmethane-type phenolic resin with a hydroxyl equivalent of 150 g / eq or less (curing agent); phosphate ester; and other components added as needed (epoxy resins and curing agents other than those mentioned above, curing accelerators, fillers, etc., resins other than epoxy resins, etc.).

[0158] There are no particular limitations on the mixing / mixing method and conditions; any appropriate method can be selected by referring to known methods. A mixing mill such as a single-screw mixer or a twin-screw mixer is used to mix, for example, a mixture containing magnetic powder, the epoxy resin described above, the phenolic resin-based curing agent described above, phosphate esters, and any other components as needed. The mixing temperature is only required to inhibit the curing reaction, for example, below 140°C, preferably 60~110°C, and more preferably 60~85°C. The mixing time is not particularly limited and can be appropriately determined, for example, it can be set to 1~10 minutes.

[0159] For example, after mixing / kneading magnetic powder, the epoxy resin as described above, the phenolic resin-based curing agent as described above, phosphate ester, and any other components as needed, the mixture is extruded into a filament using a twin-screw extruder, air-cooled, and then cut into desired sizes (e.g., several millimeters) using a granulator, thereby obtaining a granular curable composition for bonding magnets. It should be noted that this granular curable composition for bonding magnets is suitable for injection molding.

[0160] Furthermore, by mixing / kneading, for example, magnetic powder, epoxy resin as described above, phenolic resin-based curing agent as described above, phosphate ester, and any other components as needed, and then pulverizing the mixture using a ball mill, high-speed rolling mill, etc., and compressing the resulting pulverized material (pressing), a tablet-shaped curable composition for bonded magnets can be obtained. Compression molding can be performed, for example, by filling the pulverized material into a mold and applying pressure at, for example, around 2 to 20 MPa. It should be noted that this tablet-shaped curable composition for bonded magnets can be suitably used for transfer molding.

[0161] <Manufacturing Methods of Bonded Magnets>

[0162] One embodiment of the present invention provides a method for manufacturing a bonded magnet that includes a step of injection molding or transfer molding the bonded magnet as described above with a curable composition, followed by curing (hereinafter also referred to as the "curing molding step"). By employing injection molding or transfer molding, bonded magnets of various shapes, from simple to relatively complex, can be easily manufactured. Therefore, bonded magnets with high shape freedom and excellent properties such as heat resistance and oil resistance can be well manufactured.

[0163] It should be noted that the bonded magnet can be manufactured from the curing composition for bonding magnets described above by molding methods other than injection molding and transfer molding, such as compression molding, extrusion molding, and casting. The curing composition for bonding magnets comprises magnetic powder; at least one of phenolic varnish-type epoxy resin, cresol phenolic varnish-type epoxy resin, or triphenylmethane-type epoxy resin with an epoxy equivalent of 250 g / eq or less; a curing agent with a hydroxyl equivalent of 150 g / eq or less and being at least one of phenolic varnish-type phenolic resin, cresol phenolic varnish-type phenolic resin, or triphenylmethane-type phenolic resin; and a phosphate ester.

[0164] As described above, in the method for manufacturing the bonded magnet according to this embodiment, the bonded magnet is injection molded or transfer molded using a curing composition and then cured. More specifically, the curing composition for the bonded magnet can be softened by heating, then injection molded or injected into the cavity (hollow portion) of a heated mold and cured.

[0165] The temperature at which the curing composition for bonding magnets softens can be appropriately selected depending on the type of magnetic powder, epoxy resin, and curing agent used, and is not particularly limited. Generally, 140°C or lower is preferred, and more preferably 130°C or lower. In one embodiment, the temperature at which the curing composition for bonding magnets softens is more preferably 120°C or lower, and sometimes further preferably 100°C or lower. In one embodiment, the temperature at which the curing composition for bonding magnets softens can be higher, for example, 190°C or lower, and more preferably 180°C or lower. Furthermore, the lower limit of the temperature at which the curing composition for bonding magnets softens is not particularly limited, but is generally preferably 60°C or higher. The heating time (softening time) for softening the curing composition for bonding magnets is not particularly limited and can be appropriately determined; for example, it can be set to 10 to 3600 seconds, but from a production point of view, a relatively short time is preferred.

[0166] The curing temperature of the curing composition for bonding magnets (i.e., the temperature of the mold into which the curing composition for bonding magnets is injected or poured) can be appropriately selected depending on the type of magnetic powder, epoxy resin, and curing agent used, and is not particularly limited. Generally, from the viewpoint of productivity and the heat resistance of the resulting bonded magnets, it is preferable to exceed 150°C, and more preferably 160°C or higher. In one embodiment of this invention, particularly from the viewpoint of the heat resistance of the resulting bonded magnets, the curing temperature of the curing composition for bonding magnets is more preferably 170°C or higher, and sometimes even more preferably 175°C or higher. Furthermore, the upper limit of the curing temperature of the curing composition for bonding magnets is not particularly limited, but generally from the viewpoint of suppressing material decomposition, it is preferably 250°C or lower. The time (curing time) for holding the self-heated mold cavity in place for curing the curing composition for bonding magnets can be appropriately selected depending on the progress of the curing reaction and productivity, and is preferably set to 20 to 180 seconds, for example.

[0167] It should be noted that, in the case of transfer molding, the softening temperature of the curing composition for bonding magnets is usually the same as the curing temperature of the curing composition for bonding magnets. In this case, the softening and curing temperatures, softening times, and curing times of the curing composition for bonding magnets can be appropriately selected according to the type of magnetic powder, epoxy resin, and curing agent used, so that the bonded magnets can be well molded.

[0168] In one embodiment of the method for manufacturing a bonded magnet, the bonded magnet can be formed and manufactured by injection molding. For example, using an injection molding machine, the bonded magnet is softened / melted by heating a curing composition in a screw barrel, and then injected into the cavity (hollow portion) of a mold after a magnetic field is applied, so that the easy magnetization axis of the magnetic powder is aligned (oriented), and then cured. The orientation magnetic field at this time can be generated by an electromagnet or a permanent magnet. The magnitude of the orientation magnetic field is not particularly limited, but it is generally preferred to be 4 kOe or more, and more preferably 6 kOe or more. Thereafter, the cured material is removed from the mold, and the bonded magnet can be obtained by magnetizing it with a hollow coil or a magnetized yoke as needed. The magnitude of the magnetization magnetic field is not particularly limited, but it is generally preferred to be 20 kOe or more, and more preferably 30 kOe or more.

[0169] In one embodiment of the method for manufacturing a bonded magnet, the bonded magnet can be manufactured by transfer molding. For example, the bonded magnet is softened by heating a curing composition in a mold using a transfer molding machine, and then injected into the cavity (hollow portion) of the mold to which a magnetic field is applied, so that the easy magnetization axis of the magnetic powder is aligned (oriented), and then cured. The orientation magnetic field at this time can be generated by an electromagnet or a permanent magnet. The magnitude of the orientation magnetic field is not particularly limited, but is generally preferably 4 kOe or more, and more preferably 6 kOe or more. Subsequently, the cured material is removed from the mold, and the bonded magnet can be obtained by magnetizing it with a hollow coil or a magnetized yoke as needed. The magnitude of the magnetization magnetic field is not particularly limited, but is generally preferably 20 kOe or more, and more preferably 30 kOe or more. It should be noted that the injection pressure when injecting the softened bonded magnet into the cavity of the mold with the curing composition is not particularly limited, but is generally preferably 5 to 30 MPa, and more preferably 5 to 15 MPa.

[0170] It should be noted that, as mentioned above, the molding method for manufacturing bonded magnets using the curable composition for bonded magnets according to this embodiment is not limited to injection molding or transfer molding. Although the degree of shape freedom is low, any of the known methods such as compression molding, extrusion molding, or casting can be used. The molding conditions are not particularly limited and can be appropriately set by referring to known methods. Furthermore, the temperature setting of the molding machine, and the magnitudes of the orientation magnetic field and magnetizing magnetic field are set in the same manner as described above.

[0171] The bonded magnet obtained from the curable composition for bonded magnets of this embodiment possesses the excellent magnetic properties inherent in magnetic powders. Furthermore, since the adhesive resin is an epoxy resin, it not only exhibits excellent heat resistance and mechanical strength, but also demonstrates particularly excellent oil resistance among various epoxy resins. Therefore, this bonded magnet is particularly suitable for applications involving immersion in or contact with oil, such as automotive main motors, oil pumps, and valve actuators. Additionally, this bonded magnet is also suitable for various applications where immersion in or contact with oil is not required, such as automotive auxiliary motors, electric water pumps, and electric power steering motors, where heat resistance / heat deformation resistance is required. Moreover, the bonded magnet of this embodiment is also suitable for applications in household appliances such as air conditioner compressors, and aviation applications such as drive motors for aerial mobile vehicles like drones, where immersion in or contact with oil is possible.

[0172] <Bonded Magnets>

[0173] One embodiment of the adhesive magnet is used for impregnation or contact with oil and includes a cured product of a curing composition comprising: magnetic powder; at least one of a phenolic varnish-type epoxy resin, a cresol-phenolic varnish-type epoxy resin, or a triphenylmethane-type epoxy resin with an epoxy equivalent of 250 g / eq or less; and a curing agent having a hydroxyl equivalent of 150 g / eq or less and being at least one of a phenolic varnish-type phenolic resin, a cresol-phenolic varnish-type phenolic resin, or a triphenylmethane-type phenolic resin. The curing composition may further contain a phosphate ester; therefore, the cured product of the curing composition in the adhesive magnet of this embodiment can be a cured product of the curing composition for adhesive magnets as described above.

[0174] The magnetic powder, at least one of the following (main agent): phenolic varnish-type epoxy resin, cresol phenolic varnish-type epoxy resin, or triphenylmethane-type epoxy resin, containing an epoxy equivalent of 250 g / eq or less, and at least one of the following (curing agent): phenolic varnish-type phenolic resin, cresol phenolic varnish-type phenolic resin, or triphenylmethane-type phenolic resin, containing a hydroxyl equivalent of 150 g / eq or less, can be examples of substances identical to those contained in the curing composition for bonding magnets described above; preferably, the same substances are also included. Phosphate esters can also be examples of substances identical to those contained in the curing composition for bonding magnets described above; preferably, the same substances are also included.

[0175] The preferred ranges for the content of each component in the bonded magnet are the same as those for the content of each component in the curable composition for bonded magnets described above. The content of magnetic powder in the bonded magnet is preferably less than 95% by mass, more preferably less than 93% by mass. Furthermore, the content of magnetic powder in the bonded magnet is preferably 80% by mass or more, more preferably 85% by mass or more.

[0176] It should be noted that, similar to the curing composition for bonding magnets described above, the bonding magnet of this embodiment may further contain other resins and curing agents, curing accelerators, additives and other components as needed.

[0177] The bonded magnet of this embodiment can be manufactured by curing the curable composition described above. The curing method and conditions are not particularly limited and can be appropriately selected depending on the type of epoxy resin, curing agent, and curing accelerator used.

[0178] The bonded magnet of this embodiment can be manufactured by, for example, the bonded magnet manufacturing method described above. In one embodiment, the bonded magnet can be obtained from a curable composition that does not contain phosphate esters. In this case, the formability is poor, and therefore the molding conditions are difficult to control. For example, a transfer molding method can be used to manufacture the bonded magnet from a curable composition, similar to the bonded magnet manufacturing method described above.

[0179] The bonded magnet of this embodiment can be formed by injection molding or transfer molding, and can be made into a material with a relatively complex shape. The shape is not particularly limited and can also be relatively simple. The molding method is not limited to injection molding or transfer molding.

[0180] The adhesive magnet of this embodiment is used for impregnation or contact with oil. The adhesive magnet of this embodiment uses a reaction product comprising at least one epoxy resin main agent selected from phenolic varnish-type epoxy resin, cresol-phenolic varnish-type epoxy resin, or triphenylmethane-type epoxy resin with an epoxy equivalent of 250 g / eq or less, and a curing agent comprising at least one phenolic varnish-type phenolic resin, cresol-phenolic varnish-type phenolic resin, or triphenylmethane-type phenolic resin with a hydroxyl equivalent of 150 g / eq or less as an adhesive resin. It exhibits excellent heat resistance and excellent oil resistance.

[0181] More specifically, the bonding magnet of this embodiment is particularly suitable for use in vehicle-mounted main motors, oil pumps, valve actuators, etc.

[0182] One embodiment of the vehicle-mounted main motor includes the bonded magnet as described above. One embodiment of the oil pump includes the bonded magnet as described above. The vehicle-mounted main motor and oil pump using the bonded magnet having the excellent heat resistance and oil resistance described above exhibit excellent performance and high practicality.

[0183] Example

[0184] Manufacturing example (Preparation of rare earth magnetic powders)

[0185] [Sedimentation Process]

[0186] 5.0 kg of FeSO4·7H2O was dissolved in 2.0 kg of pure water. Additionally, 0.49 kg of Sm2O3 and 0.74 kg of 70% sulfuric acid were added and stirred thoroughly until completely dissolved. Then, pure water was added to the resulting solution to adjust the final Fe concentration to 0.726 mol / L and the Sm concentration to 0.112 mol / L, thus preparing an SmFe sulfuric acid solution.

[0187] In 20 kg of pure water maintained at 40°C, the entire volume of the prepared SmFe sulfuric acid solution was added dropwise while stirring over the first 70 minutes of the reaction, along with 15% ammonia solution, to adjust the pH to 7-8. This yielded a slurry containing SmFe hydroxide. The precipitate (SmFe hydroxide) was separated from the slurry by decantation, washed with pure water, and then the hydroxide was separated into solid and liquid components. The separated hydroxide was dried in an oven at 100°C for 10 hours.

[0188] [Oxidation Process]

[0189] 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.

[0190] [Pre-processing steps]

[0191] 100g of SmFe oxide obtained in the oxidation process was added to a steel container, resulting in a buildup thickness of 10mm. The container was placed in a furnace, and after the pressure was reduced to 100Pa, hydrogen gas was introduced while the furnace temperature was raised to 850℃ and maintained at this temperature for 15 hours. This yielded a partially reduced oxide.

[0192] [Restoration Process]

[0193] 60g of the oxide obtained in the pretreatment process was mixed with 19.2g of metallic calcium with an average particle size of approximately 6mm and added to the furnace. After evacuating the furnace, argon gas (Ar gas) was introduced. Subsequently, the temperature inside the furnace was raised to 1045℃ and maintained for 45 minutes, thereby obtaining Sm-Fe alloy particles.

[0194] [Nitriding process]

[0195] Next, after cooling the temperature inside the furnace to 100°C, vacuum exhaust was performed, and nitrogen gas was introduced while the temperature was raised to 450°C. This state was maintained for 23 hours to obtain a blocky product containing Sm-Fe-N magnetic particles.

[0196] [Washing Process]

[0197] 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 discharged by decantation. The process of adding pure water, stirring, and decantation was repeated 10 times. Next, 3 kg of pure water and 2.5 g of 99.9% acetic acid were added to the decanted slurry sequentially and stirred for 15 minutes. After standing, the supernatant was discharged by decantation. The process of adding 3 kg of pure water, stirring, and decantation was repeated twice. After dehydration and drying, the product was mechanically pulverized to obtain Sm-Fe-N magnetic powder (average particle size (D50) approximately 3 μm).

[0198] [Phosphoric acid treatment process]

[0199] As the phosphoric acid treatment solution, the following liquid was prepared: 85% orthophosphoric acid:sodium dihydrogen phosphate:sodium molybdate dihydrate = 1:6:1 by mass. The pH was adjusted to 2.5 with pure water and dilute hydrochloric acid, and the PO4 concentration was adjusted to 20% by mass. 1000g of Sm-Fe-N magnetic powder obtained in the water washing process was stirred in 10L of dilute hydrochloric acid with 0.7% by mass hydrogen chloride for 1 minute to remove the surface oxide film and contaminants. The process of draining and adding water was repeated until the conductivity of the supernatant reached below 100 μS / cm, resulting in a slurry containing 10% by mass Sm-Fe-N magnetic powder. While stirring the obtained slurry, 100g of the prepared phosphoric acid treatment solution was added to the treatment tank. Then, by adding 6% by mass hydrochloric acid at any time, the pH of the phosphoric acid treatment reaction slurry was controlled within the range of 2.5 ± 0.1 for 30 minutes. Next, phosphate-coated Sm-Fe-N magnetic powder was obtained by suction filtration, dehydration, and vacuum drying (remanent 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).

[0200] [Oxidation treatment process following phosphoric acid treatment]

[0201] 1000g of the obtained phosphate-coated Sm-Fe-N magnetic powder was slowly heated from room temperature in a mixed gas atmosphere of nitrogen and air (oxygen concentration 4%, flow rate 5L / min) for 8 hours at a maximum temperature of 230℃ to obtain oxidized phosphate-coated Sm-Fe-N magnetic powder.

[0202] Examples 1-3 and Comparative Examples 1-2

[0203] According to the formulation described in Table 1, magnetic powder, epoxy resin, curing agent, dispersant, and curing accelerator were weighed and mixed. Then, the mixture was kneaded using a laboratory plasticizer (10 rpm, test volume 40 cc, residence time 6 minutes) to obtain a curable composition for bonding magnets. The mixing temperature was set according to the softening point of the resin; 85°C for Examples 1-3 and 110°C for Comparative Examples 1-2.

[0204] It should be noted that the components used in the embodiments and comparative examples are as follows.

[0205] <Magnetic Powder>

[0206] SmFeN-based magnetic powder produced by the manufacturing example

[0207] <Epoxy Resin Main Agent>

[0208] Main agent 1: EPPN-501H (manufactured by Nippon Kayaku Co., Ltd., a triphenylmethane-based multifunctional epoxy resin (thermosetting oligomer), with 2 epoxy groups in the repeating structural unit, epoxy equivalent of 166 g / eq, and softening point of 53℃)

[0209] Main agent 2: NC-3500 (manufactured by Nippon Kayaku Co., Ltd., a biphenyl-based multifunctional epoxy resin (thermosetting oligomer), with 1 or 2 epoxy groups in the repeating structural unit, epoxy equivalent 210 g / eq, softening point 73℃)

[0210] Main agent 3: YX4000K (manufactured by Mitsubishi Chemical Co., Ltd., a biphenyl-based crystalline epoxy resin, melting point 105℃, number of epoxy groups in 1 molecule 2, epoxy equivalent 186g / eq)

[0211] <Curing agent>

[0212] Hardener 1: PHENOLITE TD-2131 (manufactured by DIC Co., Ltd., a phenolic resin for phenolic varnishes, hydroxyl equivalent 104 g / eq, softening point 80℃)

[0213] Curing agent 2: MEH-7500 (manufactured by UBE Corporation, triphenylmethane-based phenolic resin (curing agent oligomer), hydroxyl equivalent 98 g / eq, softening point 111℃)

[0214] Curing agent 3: Dicyandiamide (DICY) (manufactured by Tokyo Chemical Industry Co., Ltd., melting point 209.5℃, functional group equivalent 21g / eq)

[0215] <Dispersant>

[0216] Dispersant 1: Phosphanol RS-410 (manufactured by Toho Chemical Co., Ltd., polyoxyethylene tridecyl ether phosphate)

[0217] Dispersant 2: BYK-W9010 (manufactured by BYK-Chemie, phosphate polyester)

[0218] <Curing Accelerator>

[0219] Curing accelerator 1: Ucat3512T (manufactured by San-apro Co., Ltd., aromatic dimethylurea-based curing accelerator)

[0220] Curing accelerator 2: Curezol 2PHZ-PW (manufactured by Shikoku Kasei Corporation, imidazole-based curing accelerator)

[0221]

[0222] The curable compositions for bonding magnets obtained in Examples 1-3 and Comparative Examples 1-2 were evaluated as follows. The evaluation results are shown in Table 2.

[0223] <Stability time at 90℃ (A)>

[0224] The torque of the curable composition for bonded magnets, obtained using a laboratory plasticizer, was monitored during mixing 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 its initial value was measured and defined as the residence time (A) at 90°C. The measurement of time (A) was set to 3600 seconds, at which point the measurement ended. Therefore, the upper limit of time (A) is 3600 seconds. A longer time (A) can better suppress the thickening caused by material solidification in the barrel during injection molding, and can maintain high fluidity for a longer period of time.

[0225] <Curing time at 180℃ (B)>

[0226] 2.0 g of the obtained adhesive magnet curing composition was placed on a hot plate heated to 180°C, and kneaded while measuring the time until complete curing. This time was taken as the curing time (B) at 180°C. The shorter the time (B), the faster the material cures in the mold, thus shortening the mold closing time and cycle time. From a productivity point of view, a time (B) of less than 90 seconds is desired.

[0227] <Cyclic stability of injection molding (A / B)>

[0228] The cyclic stability (A / B) of injection molding was calculated by dividing the residence time at 90°C (A) by the curing time at 180°C (B). It can be determined that a higher (A / B) ratio is more beneficial for continuous cyclic molding. The results are shown in Table 2.

[0229]

[0230] The curable compositions for bonding magnets in Examples 1-3 exhibit relatively high 90°C retention stability and relatively short 180°C curing time, demonstrating excellent cycle stability. On the other hand, the curable compositions for bonding magnets in Comparative Examples 1 and 2 show a viscosity increase in a relatively short time and low 90°C retention stability, making them unsuitable for injection molding.

[0231] <Bending Strength>

[0232] For the curable compositions for bonding magnets of Examples 1, 1, and 2, the compositions were respectively placed into the hopper of an injection molding machine manufactured by Nippon Steel Works, with the barrel temperature set to zone 1: 50°C, zone 2: 85°C, and the mold temperature set to 200°C. The material was weighed to the given metering position at a screw rotation speed of 20 rpm. The material was injected into the mold at an injection speed of 10 mm / s, an injection pressure of 30 MPa, and an orientation magnetic field of 9 kOe. After 90 seconds, the mold was opened, and a strip test piece with a length of 100 mm × width of 12 mm × height of 4 mm was produced. The obtained strip test piece was annealed in an oven at 200°C for 1 hour, and then a three-point bending test (distance between support points: 50 mm, speed: 2 mm / min) was performed using a multi-functional strength testing machine to determine the bending strength. The results are shown in Table 3.

[0233] <Resistance to Decomposition>

[0234] The following durability test was conducted on evaluation test pieces, prepared in the same manner as the bending strength evaluation, cut from a 100mm long × 12mm wide × 4mm high strip test piece by milling, with a width of 7mm × length of 7mm × height of 4mm. Then, for test pieces that underwent sequential processes including embedding in sealing epoxy resin, section removal machining, and grinding with alumina abrasive, the surface of the test pieces was observed using SEM-EDS to evaluate decomposition resistance. The durability test conditions were atmospheric exposure at 180°C for 500 hours and immersion in commercially available ATF at 150°C for 1000 hours. Test pieces showing discoloration, a decrease in carbon (C) concentration, and an increase in oxygen (O) concentration on the surface were classified as "decomposing". The results are shown in Table 3.

[0235] <Magnetic property (BH)max>

[0236] A rectangular magnet measuring 7mm wide × 7mm long × 4mm high was cut from a strip test piece (100mm long × 12mm wide × 4mm high) prepared in the same manner as the bending strength evaluation described above. The resulting cuboid was then pulse-magnetized with 60kOe, and its magnetic property (BH)max at room temperature was measured using a BH curve tracker manufactured by Riken Electronics Co., Ltd. The results are shown in Table 3.

[0237] <Glass transition point (Tg)>

[0238] For the flexural strength test specimens of Example 1 and Comparative Example 1, DMA (Dynamic Viscoelasticity) measurements were performed in a three-point bending test mode within a range of room temperature to 300°C. The storage modulus (E', G'), loss modulus (E”, G”), and loss tangent (tanδ = E” / E') were measured. The glass transition point (Tg) was evaluated by reading the peak position of the loss tangent graph. The loss tangent graph is shown in... Figure 1 .

[0239]

[0240] The curable composition for bonding magnets in Example 1 exhibits high retention stability, and the resulting bonded magnets (cured products) demonstrate excellent flexural strength, magnetic properties, and decomposition resistance. Conversely, the bonded magnets (cured products) obtained in Comparative Examples 1 and 2 lack flexural strength, decomposition resistance, and magnetic properties. Furthermore, according to… Figure 1 The cured product of the curable composition of Comparative Example 1 showed a Tg of about 176°C, while the cured product of the curable composition of Example 1 showed two Tgs of about 186°C and about 231°C. This confirms that the cured product of the example, i.e. the bonded magnet, has high heat resistance.

[0241] Implementations of this disclosure may include, for example, the following methods.

[0242] [Item 1]

[0243] A bonding magnet comprising a cured product of a curing composition, wherein,

[0244] The curable composition comprises:

[0245] Magnetic powder;

[0246] At least one of the following: phenolic varnish epoxy resin, cresol phenolic varnish epoxy resin, or triphenylmethane epoxy resin, with an epoxy equivalent of 250 g / eq or less; and

[0247] The curing agent has a hydroxyl equivalent of less than 150 g / eq and is at least one of phenolic resins selected from phenolic varnish type, cresol phenolic varnish type, or triphenylmethane type.

[0248] The adhesive magnet is intended for use in immersion or contact with oil.

[0249] [Item 2]

[0250] According to the bonded magnet described in item 1, wherein...

[0251] The curable composition further comprises a phosphate ester.

[0252] [Item 3]

[0253] According to the bonded magnet described in item 2, wherein...

[0254] The phosphate ester is a polyoxyethylene alkyl ether phosphate ester.

[0255] [Item 4]

[0256] The bonded magnet according to any one of items 1 to 3, wherein,

[0257] The content of the magnetic powder is 80% or more by mass and less than 95% by mass.

[0258] [Item 5]

[0259] The bonded magnet according to any one of items 1 to 4, wherein,

[0260] The magnetic powder is an Sm-Fe-N based magnetic powder.

[0261] [Item 6]

[0262] The adhesive magnet according to any one of items 1 to 5 is used for a vehicle-mounted main motor or oil pump.

[0263] [Item 7]

[0264] A vehicle-mounted main motor, comprising any one of items 1 to 5, a bonded magnet.

[0265] [Item 8]

[0266] An oil pump comprising the bonded magnet described in any one of items 1 to 5.

[0267] [Item 9]

[0268] A curing composition for bonding magnets, comprising:

[0269] Magnetic powder;

[0270] At least one of the following: phenolic varnish phenolic epoxy resin, cresol phenolic varnish epoxy resin or triphenylmethane epoxy resin with an epoxy equivalent of less than 250 g / eq.

[0271] The curing agent has a hydroxyl equivalent of less than 150 g / eq and is at least one of phenolic resins selected from phenolic varnish type, cresol phenolic varnish type, or triphenylmethane type; and

[0272] Phosphate esters.

[0273] [Item 10]

[0274] According to item 9, the curing composition for bonding magnets, wherein...

[0275] The phosphate ester is a polyoxyethylene alkyl ether phosphate ester.

[0276] [Item 11]

[0277] The curing composition for bonding magnets according to item 9 or 10, wherein...

[0278] The content of the magnetic powder is 80% or more by mass and less than 95% by mass.

[0279] [Item 12]

[0280] The curing composition for bonding magnets according to any one of items 9 to 11, wherein,

[0281] The magnetic powder is an Sm-Fe-N based magnetic powder.

[0282] [Item 13]

[0283] A method for manufacturing a bonded magnet, comprising:

[0284] The process of injection molding or transfer molding the adhesive magnet described in any one of items 9 to 11 with a curing composition and then curing it.

Claims

1. A bonded magnet comprising a cured product of a curing composition, wherein, The curable composition comprises: Magnetic powder; An epoxy resin with an epoxy equivalent of 250 g / eq or less, wherein the epoxy resin is at least one of phenolic varnish-type epoxy resin, cresol-phenolic varnish-type epoxy resin, or triphenylmethane-type epoxy resin; and The curing agent has a hydroxyl equivalent of less than 150 g / eq and is at least one of phenolic resins selected from phenolic varnish type, cresol phenolic varnish type, or triphenylmethane type. The adhesive magnet is intended for use in immersion or contact with oil.

2. The bonded magnet according to claim 1, wherein, The curable composition further comprises a phosphate ester.

3. The bonded magnet according to claim 2, wherein, The phosphate ester is a polyoxyethylene alkyl ether phosphate ester.

4. The bonded magnet according to any one of claims 1 to 3, wherein, The content of the magnetic powder is 80% or more by mass and less than 95% by mass.

5. The bonded magnet according to any one of claims 1 to 3, wherein, The magnetic powder is an Sm-Fe-N based magnetic powder.

6. The bonded magnet according to any one of claims 1 to 3, used in a vehicle-mounted main motor or oil pump.

7. A vehicle-mounted main motor comprising the bonded magnet as described in any one of claims 1 to 3.

8. An oil pump comprising the bonded magnet according to any one of claims 1 to 3.

9. A curing composition for bonding magnets, comprising: Magnetic powder; An epoxy resin with an epoxy equivalent of 250 g / eq or less, wherein the epoxy resin is at least one of phenolic varnish phenolic epoxy resin, cresol phenolic varnish epoxy resin or triphenylmethane epoxy resin. The curing agent has a hydroxyl equivalent of less than 150 g / eq and is at least one of phenolic resins selected from phenolic varnish type, cresol phenolic varnish type, or triphenylmethane type; and Phosphate esters.

10. The curable composition for bonding magnets according to claim 9, wherein, The phosphate ester is a polyoxyethylene alkyl ether phosphate ester.

11. The curing composition for bonding magnets according to claim 9 or 10, wherein, The content of the magnetic powder is 80% or more by mass and less than 95% by mass.

12. The curing composition for bonding magnets according to claim 9 or 10, wherein, The magnetic powder is an Sm-Fe-N based magnetic powder.

13. A method for manufacturing a bonded magnet, comprising: The process of injection molding or transfer molding the adhesive magnet of claim 9 or 10 with a curable composition and then curing it.

Images