Bonded magnet, automotive main motor and oil pump containing a bonded magnet, curable composition for bonded magnet, and method for manufacturing a bonded magnet.

Abstract

The present invention provides a bonded magnet that exhibits excellent heat resistance and oil resistance, making it suitable for applications where it is immersed in or in contact with oil, such as in automotive main motors and oil pumps. [Solution] A bonded magnet for use in applications involving immersion in or contact with oil, comprising a cured product of a curable composition containing magnetic powder, an epoxy resin which is at least one of phenol novolac type epoxy resin, cresol novolac type epoxy resin, or triphenylmethane type epoxy resin, and a phenol resin curing agent which is at least one of novolac type phenol resin, cresol novolac type phenol resin, or triphenylmethane type phenol resin.

Description

Technical Field

[0001] One aspect of the present invention relates to bonded magnets, in-vehicle main motors including the bonded magnets, and oil pumps. Another aspect of the present invention relates to a curable composition for bonded magnets and a method for manufacturing bonded magnets.

Background Art

[0002] Conventionally, bonded magnets in which magnetic powders such as ferrite powders and rare earth magnetic powders such as Sm-Co-based, Nd-Fe-B-based, and Sm-Fe-N-based are bound with a binder resin have been considered for use in various applications.

[0003] Bonded magnets have good magnetic properties, and depending on their applications, they may also be required to have excellent heat resistance. In applications where heat resistance is required, the use of a thermosetting resin, such as an epoxy resin, as the binder resin for the bonded magnet has been considered.

[0004] For example, Patent Document 1 discloses a compound for a bonded magnet that can obtain a molded body for a bonded magnet having excellent crushing strength at room temperature and high temperature. The compound for a bonded magnet includes a magnetic powder, a curing agent such as an epoxy resin and a phenolic resin curing agent, and a resin composition containing a coupling agent having a functional group capable of reacting with a glycidyl group. The epoxy resin and the curing agent are included such that the amount of hydroxyl groups per 1 g of the cured product [= curing agent content [g] × 1000 / (hydroxyl equivalent of the curing agent × (epoxy resin content [g] + curing agent content [g]))] is 3.0 mmol / g or more. A bonded magnet manufactured by compression molding this compound for a bonded magnet is also disclosed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] In recent years, bonded magnets have been considered for use in applications where they are immersed in or in contact with oil, such as in automotive main motors and oil pumps, and in some cases, in oil at relatively high temperatures. Therefore, there is a need for bonded magnets that are not only heat resistant but also have excellent oil resistance.

[0007] Furthermore, in applications such as automotive main motors and oil pumps, bonded magnets with relatively complex shapes are sometimes required. Complex shapes are not limited to applications where the magnets are immersed in or in contact with oil; they may also be required in other applications.

[0008] However, when using epoxy resin, a thermosetting resin, as the binder resin, bonded magnets have conventionally been manufactured by compression molding, as described in Patent Document 1. However, with compression molding, the amount of binder resin used is generally small (usually 5% by mass or less), making it difficult to manufacture magnets with complex shapes.

[0009] Methods for manufacturing bonded magnets with relatively complex shapes include injection molding and transfer molding. Of these, injection molding is readily available as large molding machines with built-in magnetic field coils are commercially available, making it easy to manufacture relatively large bonded magnet molded products suitable for use in motors and the like. Furthermore, injection molding generally has a faster production speed than transfer molding and tends to be suitable for mass production. However, in injection molding, it is usually difficult to manufacture bonded magnets using thermosetting resins such as epoxy resin as the binder resin due to limitations in continuous molding. On the other hand, while epoxy resin can be used as the binder resin in transfer molding, controlling the curing reaction is difficult, and there are concerns about deterioration of pot life and decreased fluidity in the mold, making it difficult to manufacture bonded magnets well in some cases.

[0010] One embodiment of the present invention aims to provide a bonded magnet that has excellent heat resistance and oil resistance and can be suitably used in applications where it is immersed in or in contact with oil, such as in a vehicle's main motor or oil pump.

[0011] Furthermore, one embodiment of the present invention aims to provide an in-vehicle main motor having excellent performance. Another embodiment of the present invention aims to provide an oil pump having excellent performance.

[0012] Another embodiment of the present invention aims to provide a curable composition for bonded magnets that can produce bonded magnets with high degree of freedom in shape and excellent heat resistance and oil resistance, or a curable composition for bonded magnets that can produce bonded magnets with excellent heat resistance and oil resistance that can be applied to injection molding or transfer molding methods.

[0013] Furthermore, another embodiment of the present invention aims to provide a method for manufacturing bonded magnets that can successfully produce bonded magnets with a high degree of freedom in shape and excellent heat resistance and oil resistance. [Means for solving the problem]

[0014] A bonded magnet according to one embodiment of the present invention comprises a magnetic powder, a cured product of a curable composition comprising an epoxy resin which is at least one of a phenol novolac type epoxy resin, a cresol novolac type epoxy resin, or a triphenylmethane type epoxy resin, and a phenol resin curing agent which is at least one of a novolac type phenol resin, a cresol novolac type phenol resin, or a triphenylmethane type phenol resin, and is used for applications in which it is immersed in or in contact with oil. In a further embodiment of the present invention, the bonded magnet further comprises a phosphate ester in the curable composition.

[0015] An in-vehicle main motor according to one embodiment of the present invention includes the above-mentioned bonded magnet. Furthermore, an oil pump according to one embodiment of the present invention also includes the above-mentioned bonded magnet.

[0016] A curable composition for bonded magnets according to another embodiment of the present invention comprises magnetic powder, an epoxy resin which is at least one of phenol novolac type epoxy resin, cresol novolac type epoxy resin, or triphenylmethane type epoxy resin, a phenol resin curing agent which is at least one of novolac type phenol resin, cresol novolac type phenol resin, or triphenylmethane type phenol resin, and a phosphate ester.

[0017] A method for manufacturing a bonded magnet according to another embodiment of the present invention includes the steps of injection molding or transfer molding the above-mentioned curable composition for bonded magnets and curing it. [Effects of the Invention]

[0018] According to one embodiment of the present invention, a bonded magnet is provided that has excellent heat resistance and oil resistance and can be suitably used in applications where it is immersed in or in contact with oil, such as in a vehicle's main motor or oil pump.

[0019] Furthermore, according to one embodiment of the present invention, it is possible to provide an in-vehicle main motor with excellent performance. Also, according to one embodiment of the present invention, it is possible to provide an oil pump with excellent performance.

[0020] Furthermore, according to another embodiment of the present invention, it is possible to provide a curable composition for bonded magnets that can produce bonded magnets with a high degree of freedom in shape and excellent heat resistance and oil resistance, or a curable composition for bonded magnets that can produce bonded magnets with excellent heat resistance and oil resistance that can be applied to injection molding or transfer molding methods.

[0021] Furthermore, according to another embodiment of the present invention, it is possible to provide a method for manufacturing bonded magnets that have a high degree of freedom in shape and excellent heat resistance and oil resistance. [Brief explanation of the drawing]

[0022] [Figure 1] FIG. 1 is a graph of the loss tangent (tan δ) of the bending strength test pieces (cured products of the curable composition for bonded magnets) of Example 1 and Comparative Example 1.

BEST MODE FOR CARRYING OUT THE INVENTION

[0023] Hereinafter, embodiments of the present invention will be described in detail. However, the embodiments shown below are examples for embodying the technical idea of the present invention, and the present invention is not limited to the following. In this specification, the numerical range indicated by "~" indicates a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively.

[0024] <Curable Composition for Bonded Magnet> The curable composition for bonded magnets according to one aspect of the present embodiment includes magnetic powder, an epoxy resin which is at least one or more of a phenol novolak type epoxy resin, a cresol novolak type epoxy resin, or a triphenylmethane type epoxy resin, a phenolic resin curing agent which is at least one or more of a novolak type phenol resin, a cresol novolak type phenol resin, or a triphenylmethane type phenol resin, and a phosphate ester. The phenol novolak type epoxy resin, the cresol novolak type epoxy resin, or the triphenylmethane type epoxy resin preferably has an epoxy equivalent of 250 g / eq or less. The novolak type phenol resin, the cresol novolak type phenol resin, or the triphenylmethane type phenol resin preferably has a hydroxyl equivalent of 150 g / eq or less.

[0025] By using at least one of the following as the main epoxy resin, preferably with an epoxy equivalent of 250 g / eq or less: a phenol novolac type epoxy resin, a cresol novolac type epoxy resin, or a triphenylmethane type epoxy resin; and by using at least one of the following as the curing agent, preferably with a hydroxyl group equivalent of 150 g / eq or less: a novolac type phenol resin, a cresol novolac type phenol resin, or a triphenylmethane type phenol resin; a bonded magnet with excellent heat resistance and oil resistance can be obtained. Epoxy resins generally have excellent heat resistance, but this combination of epoxy resin (main component) and curing agent can achieve excellent heat resistance as well as particularly excellent oil resistance. Moreover, the curable composition for bonded magnets containing this combination of epoxy resin (main component) and curing agent has better moldability compared to others.

[0026] Furthermore, the curable composition for bonded magnets of this embodiment achieves even better moldability by including a phosphate ester in addition to the above-mentioned combination of epoxy resin (main component) and curing agent. The curable composition for bonded magnets containing a phosphate ester in addition to the above-mentioned combination of epoxy resin (main component) and curing agent is applicable to injection molding and transfer molding methods, and bonded magnets with relatively complex shapes can be easily obtained. Moreover, by adding a phosphate ester, it may be possible to achieve a higher filling rate of magnetic powder or improve the orientation of the magnetic powder, potentially improving the residual magnetic flux density (Br).

[0027] Therefore, the curable 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 methods, and can also produce bonded magnets with a high degree of freedom in shape and excellent heat resistance and oil resistance. Here, a high degree of freedom in shape means that bonded magnets of various shapes, from simple to relatively complex, can be easily manufactured. It should be noted that, not limited to the above combination of epoxy resin (main component) and curing agent contained in the curable composition for bonded magnets of this embodiment, adding phosphate esters to epoxy resins in general tends to improve moldability, especially in injection molding and transfer molding. However, this effect is particularly pronounced in the case of polyfunctional epoxy resins, and even more pronounced in the above combination of epoxy resin (main component) and curing agent.

[0028] The content of magnetic powder in the curable composition for bonded magnets is not particularly limited, as long as the desired fluidity during molding can be ensured. In one embodiment of this invention, the content of magnetic powder in the curable composition for bonded magnets is preferably less than 95% by mass, and more preferably 93% by mass or less. When the content of magnetic powder in the curable composition for bonded magnets is less than 95% by mass, more preferably 93% by mass or less, it can usually be easily molded by injection molding or transfer molding. Furthermore, although the content of magnetic powder in the curable composition for bonded 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, and more preferably 85% by mass or more.

[0029] [Epoxy resin (main component)] The curable composition for bonded magnets according to this embodiment contains at least one epoxy resin (main component) from the following: a phenol novolac type epoxy resin, a cresol novolac type epoxy resin, or a triphenylmethane type epoxy resin. These epoxy resins may be used individually or in combination of two or more.

[0030] The phenol novolac type epoxy resin contains repeating units represented by the following formula (1-1), and may also contain one or more other types of repeating units. In the phenol novolac type epoxy resin, the content of the repeating units represented by the following formula (1-1) is preferably 50 mol% or more, and more preferably 60 mol% or more, of the total repeating units. The repeating units other than those represented by formula (1-1) are not particularly limited and can be selected as appropriate.

[0031] [ka]

[0032] The cresol novolac type epoxy resin contains repeating units represented by the following formula (1-2), and may also contain one or more other types of repeating units. In the cresol novolac type epoxy resin, the content of the repeating units represented by the following formula (1-2) is preferably 50 mol% or more, and more preferably 60 mol% or more, of the total repeating units. The repeating units other than those represented by formula (1-2) are not particularly limited and can be selected as appropriate.

[0033] [ka]

[0034] The triphenylmethane-type epoxy resin contains repeating units represented by the following formula (1-3), and may also contain one or more other types of repeating units. In the triphenylmethane-type epoxy resin, the content of the repeating units represented by the following formula (1-3) is preferably 50 mol% or more, and more preferably 60 mol% or more, of the total repeating units. The repeating units other than those represented by formula (1-3) are not particularly limited and can be selected as appropriate.

[0035] [ka]

[0036] In this embodiment, the epoxy resin (main component) is preferably composed of one or more of the repeating units represented by formula (1-1), formula (1-2), and formula (1-3), in which case the content of each repeating unit in the total repeating units may be 50 mol% or less. Among these, a phenol novolac type epoxy resin consisting only of the repeating units represented by formula (1-1), a cresol novolac type epoxy resin consisting only of the repeating units represented by formula (1-2), and a triphenylmethane type epoxy resin consisting only of the repeating units represented by formula (1-3) are preferred, a cresol novolac type epoxy resin consisting only of the repeating units represented by formula (1-2) and a triphenylmethane type epoxy resin consisting only of the repeating units represented by formula (1-3) are more preferred, and a triphenylmethane type epoxy resin consisting only of the repeating units represented by formula (1-3) is even more preferred.

[0037] In this embodiment, the epoxy equivalents of the phenol novolac type epoxy resin, cresol novolac type epoxy resin, and triphenylmethane type epoxy resin are preferably 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, from the standpoint of high curing speed, excellent moldability, and high heat resistance and oil resistance of the resulting bonded magnets. The lower limit of the epoxy equivalents of these epoxy resins is not particularly limited, but is usually around 140 g / eq.

[0038] From the viewpoint of moldability, the epoxy resin (main component) is generally preferably softened at 100°C or lower, and more preferably at 85°C or lower. While there is no particular lower limit to the softening point of the epoxy resin (main component), it is preferably 40°C or higher from the viewpoint of storage stability at room temperature.

[0039] Commercially available phenol novolac epoxy resins, cresol novolac epoxy resins, and triphenylmethane epoxy resins with an epoxy equivalent of 250 g / eq or less can also be used. Examples of commercially available phenol novolac epoxy resins with an epoxy equivalent of 250 g / eq or less include EPICLON N-740, N-770, and N-775 (all manufactured by DIC Corporation). Examples of commercially available cresol novolac epoxy resins with an epoxy equivalent of 250 g / eq or less include N-660, N-673, and N-695 (all manufactured by DIC Corporation), and YDCN-700-7 and YDCN-704A (all manufactured by Nippon Steel Chemical & Material Co., Ltd.). Examples of commercially available triphenylmethane epoxy resins with an epoxy equivalent of 250 g / eq or less include EPPN-501H and EPPN-502H (both manufactured by Nippon Kayaku Co., Ltd.).

[0040] The curable composition for bonded magnets of this embodiment preferably contains only phenol novolac type epoxy resin, cresol novolac type epoxy resin, and triphenylmethane type epoxy resin as the main epoxy resin, with an epoxy equivalent of preferably 250 g / eq or less (however, these epoxy resins may be one type or two or more types). However, it may also contain other epoxy resins or epoxy compounds (monomers, etc.) that cure to form epoxy resins. For example, it may contain biphenyl aralkyl type epoxy resin. In the curable composition for bonded magnets of this embodiment, the content (percentage) of other epoxy resins or epoxy compounds relative to the total epoxy resin (main component) is preferably 5% by mass or less, more preferably 1% by mass or less, and particularly preferably 0% by mass.

[0041] [Hardening agent] The curable composition for bonded magnets according to this embodiment contains at least one of the following as a curing agent: a novolac-type phenolic resin, a cresol novolac-type phenolic resin, or a triphenylmethane-type phenolic resin. These phenolic resin-based curing agents may be used individually or in combination of two or more.

[0042] The novolac-type phenolic resin contains repeating units represented by the following formula (2-1), and may also contain one or more other types of repeating units. In the novolac-type phenolic resin, the content of the repeating units represented by the following formula (2-1) is preferably 50 mol% or more, and more preferably 60 mol% or more, of the total repeating units. The repeating units other than those represented by formula (2-1) are not particularly limited and can be selected as appropriate.

[0043] [ka]

[0044] The cresol novolac type phenolic resin contains repeating units represented by the following formula (2-2), and may also contain one or more other types of repeating units. In the cresol novolac type phenolic resin, the content of the repeating units represented by the following formula (2-2) is preferably 50 mol% or more, and more preferably 60 mol% or more, of the total repeating units. The repeating units other than those represented by formula (2-2) are not particularly limited and can be selected as appropriate.

[0045] [ka]

[0046] The triphenylmethane-type phenolic resin contains repeating units represented by the following formula (2-3), and may also contain one or more other types of repeating units. In the triphenylmethane-type phenolic resin, the content of the repeating units represented by the following formula (2-3) is preferably 50 mol% or more, and more preferably 60 mol% or more, of the total repeating units. The repeating units other than those represented by formula (2-3) are not particularly limited and can be selected as appropriate.

[0047] [ka]

[0048] In this embodiment, the curing agent is preferably composed of one or more of the repeating units represented by formula (2-1), formula (2-2), and formula (2-3), in which case the content of each repeating unit in the total repeating units may be 50 mol% or less. Among these, a novolac-type phenolic resin consisting only of the repeating unit represented by formula (2-1), a cresol novolac-type phenolic resin consisting only of the repeating unit represented by formula (2-2), and a triphenylmethane-type phenolic resin consisting only of the repeating unit represented by formula (2-3) are preferred, and a novolac-type phenolic resin consisting only of the repeating unit represented by formula (2-1) is even more preferred.

[0049] In one embodiment of this invention, a combination of a triphenylmethane-type epoxy resin (main component) consisting only of repeating units represented by formula (1-3) above and a novolac-type phenolic resin (curing agent) consisting only of repeating units represented by formula (2-1) above may be particularly preferred.

[0050] In this embodiment, the hydroxyl group equivalent of the novolac-type phenolic resin, cresol-novolac-type phenolic resin, and triphenylmethane-type phenolic resin is preferably 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, from the standpoint of high curing speed, excellent moldability, and high heat resistance and oil resistance of the resulting bonded magnets. The lower limit of the hydroxyl group equivalent of these phenolic resin curing agents is not particularly limited, but is usually around 70 g / eq.

[0051] From the viewpoint of moldability, phenolic resin curing agents generally have a softening point of 100°C or lower, and more preferably 85°C or lower. While there is no particular lower limit to the softening point of phenolic resin curing agents, from the viewpoint of storage stability at room temperature, it is preferable that it be 40°C or higher.

[0052] Commercially available novolac-type phenolic resins, cresol novolac-type phenolic resins, and triphenylmethane-type phenolic resins with a hydroxyl equivalent of 150 g / eq or less can also be used. Examples of commercially available novolac-type phenolic resins with a hydroxyl equivalent of 150 g / eq or less include TD-2131 and TD-2106 (both manufactured by DIC Corporation). Examples of commercially available cresol novolac-type phenolic resins with a hydroxyl equivalent of 150 g / eq or less include KA-1160, KA-1163, and KA-1165 (both manufactured by DIC Corporation). Examples of commercially available triphenylmethane-type phenolic resins with a hydroxyl group equivalent of 150 g / eq or less include MEH-7500 (manufactured by UBE Corporation), S-TPM-130, S-TPM-113 (both manufactured by JFE Chemical Corporation), and KAYAHARD KTG-105 (manufactured by Nippon Kayaku Co., Ltd.).

[0053] The curable composition for bonded magnets of this embodiment preferably contains only novolac-type phenolic resin, cresol novolac-type phenolic resin, and triphenylmethane-type phenolic resin as curing agents, with a hydroxyl group equivalent of preferably 150 g / eq or less (however, there may be one or more of these phenolic resin-based curing agents). However, it may also contain other curing agents. For example, it may contain at least one phenolic resin-based curing agent other than novolac-type phenolic resin, cresol novolac-type phenolic resin, and triphenylmethane-type phenolic resin. In the curable composition for bonded magnets of this embodiment, the content (percentage) of other curing agents to the total curing agent is preferably 5% by mass or less, more preferably 1% by mass or less, and particularly preferably 0% by mass.

[0054] The content of novolac-type phenolic resin, cresol novolac-type phenolic resin, and triphenylmethane-type phenolic resin (curing agent) in the curable composition for bonded magnets, which preferably has a hydroxyl group equivalent of 150 g / eq or less, 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 novolac-type phenolic resin, cresol novolac-type phenolic resin, and triphenylmethane-type phenolic resin in the curable composition for bonded magnets, which preferably has a hydroxyl group equivalent of 150 g / eq or less, is preferably 30 to 90 parts by mass, and more preferably 40 to 65 parts by mass, per 100 parts by mass of epoxy resin (main component).

[0055] [Curing accelerator] The curable composition for bonded magnets according to this embodiment may further contain a curing accelerator. The inclusion of a curing accelerator in the curable composition for bonded magnets may lower the molding temperature (curing temperature of the composition) or shorten the molding time (curing time of the composition). The curing accelerator may be used alone or in combination of two or more types.

[0056] The curing accelerator is not particularly limited, but examples include urea-based curing accelerators such as dimethylurea, tertiary amine-based curing accelerators, imidazole-based curing accelerators, and aromatic amine-based curing accelerators.

[0057] Commercially available curing accelerators can also be used. Examples of commercially available urea-based curing accelerators include U-cat 3512T, U-cat 3513N (both manufactured by Sunapro Co., Ltd.), Dyhard UR200, and UR300 (both manufactured by AlzChem). Examples of commercially available imidazole-based curing accelerators include Curesol 2E4MZ-A and 2PHZ-PW (both manufactured by Shikoku Chemicals Co., Ltd.).

[0058] The content of the curing accelerator in the curable composition for bonded 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 product, the content of the curing accelerator in the curable composition for bonded magnets can be, for example, 0.5 to 5 parts by mass per 100 parts by mass of epoxy resin (main component).

[0059] The curing accelerator may be included in the curable composition for bonded magnets before the curing and molding process of the curable composition for bonded magnets, or it may be added to the curable composition for bonded magnets during the curing and molding process of the curable composition for bonded magnets, immediately before heating and softening the composition, or it may be added to the curable composition for bonded magnets at any point while heating and softening the composition.

[0060] [Phosphate esters] The curable composition for bonded magnets according to this embodiment further comprises a phosphate ester. The phosphate ester may be used alone or in combination of two or more types. As described above, by adding a phosphate ester, the rapid progression of the curing reaction of the epoxy resin can be suppressed, especially in injection molding and transfer molding, and even better moldability can be obtained. Furthermore, while Sm-Fe-N magnetic powder is preferable to other rare-earth magnetic powders in terms of magnetic properties, the effect of improving moldability by adding a phosphate ester tends to be more pronounced when Sm-Fe-N magnetic powder is used as the magnetic powder. Note that even if the curable composition does not contain a phosphate ester, bonded magnets can be obtained by, for example, compression molding, although the moldability of the bonded magnets is inferior, and the resulting bonded magnets have excellent heat resistance and oil resistance.

[0061] As for the phosphate ester, alkyl ether phosphate esters are preferred due to their high effectiveness in improving moldability, polyoxyethylene alkyl ether phosphate is more preferred, and polyoxyethylene alkyl ether phosphate represented by the following formula (3-1) is even more preferred.

[0062] [ka] (In the formula, R represents an alkyl group, n represents an integer of 1 or more, and m represents an integer between 1 and 3.)

[0063] The alkyl group contained in alkyl ether phosphate and polyoxyethylene alkyl ether phosphate may be linear or branched, and its carbon number is not particularly limited, but is preferably 8 or more, and more preferably 8 to 24.

[0064] In formula (3-1), R is preferably a linear or branched alkyl group having 8 or more carbon atoms, and more preferably a linear or branched alkyl group having 8 to 24 carbon atoms.

[0065] In equation (3-1), n ​​represents an integer greater than or equal to 1, preferably between 1 and 4, and more preferably between 1 and 2.

[0066] In formula (3-1), m represents an integer between 1 and 3. That is, the polyoxyethylene alkyl ether phosphate represented by formula (3-1) may be a monophosphate ester, a diphosphate ester, or a triester phosphate. Furthermore, one type of polyoxyethylene alkyl ether phosphate may be used, or a mixture of two or more types may be used.

[0067] As the phosphate ester, preferably polyoxyethylene alkyl ether phosphate, commercially available products can also be used. Examples of commercially available polyoxyethylene alkyl ether phosphates include phosphanol RS-410, RS-610, RS-710 (all manufactured by Toho Chemical Industry Co., Ltd.), lauryl EO2 acid phosphate, oleyl EO2 acid phosphate (both manufactured by Johoku Chemical Industry Co., Ltd.), and the like.

[0068] The content of phosphate ester in the curable composition for bonded 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 present invention, the content of phosphate ester in the curable composition for bonded magnets is preferably 0.05 to 1 part by mass, and more preferably 0.1 to 0.6 parts by mass, per 100 parts by mass of magnetic powder.

[0069] [Magnetic powder] In the curable composition for bonded magnets of this embodiment, the magnetic powder is not particularly limited, and any known type, such as ferrite powder or rare earth magnetic powder, can be suitably used. The magnetic powder may be used alone or in combination of two or more types.

[0070] In one embodiment of this model, rare earth magnetic powders are preferred due to their excellent magnetic properties. Examples of rare earth magnetic powders include Sm-Co, Nd-Fe-B, and Sm-Fe-N systems. In this embodiment, there are no particular limitations, and any rare earth magnetic powder can be suitably used, but Sm-Fe-N magnetic powders are particularly preferred in terms of the magnetic properties, heat resistance, oil resistance, and moldability of the resulting bonded magnets. Sm-Fe-N magnetic powders have high heat resistance due to a high anisotropic magnetic field exceeding 260 kOe (20.7 MA / m), as well as high corrosion resistance, and exhibit excellent heat resistance and oil resistance. Rare earth magnetic powders may be used individually or in combination of two or more types.

[0071] Sm-Co magnetic powder can be produced, for example, by the method disclosed in Japanese Patent Publication No. 08-260083. Nd-Fe-B magnetic powder can be produced, for example, by the HDR method disclosed in International Publication No. 2003 / 85147. Sm-Fe-N magnetic powder can be produced, for example, by the method disclosed in Japanese Patent Publication No. 11-189811.

[0072] As described above, in one embodiment of this embodiment, the rare earth magnetic powder is preferably an Sm-Fe-N type magnetic powder. As an example of an Sm-Fe-N type magnetic powder, Th2Zn 17 It has a crystal structure of type Sm x Fe 100-x-y N y Examples include nitrides composed of the rare earth metal samarium (Sm), iron (Fe), and nitrogen (N), represented by . Here, it is preferable that x is between 8.1 atomic% and 10 atomic%, y is between 13.5 atomic% and 13.9 atomic%, and the remainder is mainly Fe.

[0073] Rare earth magnetic powder can be used as is, but it can also be used after surface treatment with a silane coupling agent, for example. Surface treatment with a silane coupling agent can be carried out, for example, by the method disclosed in Japanese Patent Application Publication No. 2017-43804.

[0074] Furthermore, in the case of Sm-Fe-N magnetic powder, a phosphate coating formed on the surface, i.e., phosphate-coated Sm-Fe-N magnetic powder, can also be used. Phosphate-coated Sm-Fe-N magnetic powder can be manufactured, for example, by methods disclosed in International Publication No. 2022 / 107462, Japanese Patent Publication No. 2023-96735, Japanese Patent Publication No. 2024-51932, etc.

[0075] The average particle size of rare earth magnetic powder can be appropriately selected depending on its type and is not particularly limited. In the case of Sm-Co magnetic powder, the average particle size is usually preferably between 10 μm and 250 μm. In the case of Nd-Fe-B magnetic powder, the average particle size is usually preferably between 10 μm and 250 μm. In the case of Sm-Fe-N magnetic powder, the average particle size is usually preferably between 2 μm and 5 μm, and more preferably between 2.5 μm and 4.8 μm. By setting the average particle size to 2 μm or more, the amount of Sm-Fe-N magnetic powder packed into the bonded magnet can be increased, which may improve magnetization. Also, by setting the average particle size to 5 μm or less, the intrinsic coercivity of the bonded magnet may be improved. Here, the average particle size is the particle size measured under dry conditions using a laser diffraction particle size distribution analyzer.

[0076] For Sm-Fe-N magnetic powders, particle size D50 is preferably 2.5 μm to 5 μm, and more preferably 2.7 μm to 4.8 μm. Particle size D10 is preferably 1 μm to 3 μm, and more preferably 1.5 μm to 2.5 μm. Particle size D90 is preferably 3 μm to 7 μm, and more preferably 4 μm to 6 μm. Here, D50 is the particle size corresponding to 50% of the cumulative volume-based particle size distribution of the Sm-Fe-N magnetic powder. D10 is the particle size corresponding to 10% of the cumulative volume-based particle size distribution of the Sm-Fe-N magnetic powder. D90 is the particle size corresponding to 90% of the cumulative volume-based particle size distribution of the Sm-Fe-N magnetic powder.

[0077] The span defined below for Sm-Fe-N magnetic powders: Span = (D90 - D10) / D50 From the viewpoint of the coercivity of the bonded magnet, a value of 2 or less is preferable, and a value of 1.5 or less is more preferable.

[0078] The circularity of Sm-Fe-N magnetic powder is not particularly limited, but it is preferably 0.5 or higher, and more preferably 0.6 or higher. If the circularity is less than 0.5, the fluidity will be poor, and stress will be placed between particles during molding, which may reduce the magnetic properties. Here, the circularity is measured by binarizing SEM images taken at 3000x magnification using image processing, and the circularity is determined for each particle. The circularity defined here refers to the average value of the circularity obtained by measuring approximately 1000 to 10000 particles. Generally, the circularity increases as there are more particles with smaller particle sizes, so the circularity is measured for particles of 1 μm or larger. The definition formula for measuring circularity is: Circularity = (4πS / L 2 ) is used, where S is the two-dimensional projected area of ​​the particle and L is the two-dimensional projected perimeter.

[0079] [Sm-Fe-N magnetic powder] In one embodiment of this product, the Sm-Fe-N magnetic powder is preferably anisotropic from the viewpoint of the magnetic properties of the resulting bonded magnet. Furthermore, the Sm-Fe-N magnetic powder may be preferably coated with a phosphate on its surface from the viewpoint of improving coercivity, heat resistance, and oil resistance.

[0080] The following describes an example of a method for producing the Sm-Fe-N anisotropic magnetic powder and the phosphate-coated Sm-Fe-N anisotropic magnetic powder according to this embodiment. However, the method is not limited to the following embodiment and can also be produced by other methods.

[0081] [Method for producing Sm-Fe-N anisotropic magnetic powder] The Sm-Fe-N anisotropic magnetic powder is not particularly limited, but for example, A step of mixing a solution containing Sm and Fe with a precipitating agent to obtain a precipitate containing Sm and Fe (precipitation step), The aforementioned precipitate is calcined to obtain an oxide containing Sm and Fe (oxidation step), A step of obtaining a partial oxide by heat-treating the aforementioned oxide in a reducing gas-containing atmosphere (pretreatment step), A step of reducing the aforementioned partial oxide (reduction step), and A process of nitriding the alloy particles obtained in the reduction process (nitriding process). It can be manufactured by a method that includes [a specific component].

[0082] (Precipitation process) In the precipitation process, the Sm and Fe raw materials are dissolved in a strongly acidic solution to prepare a solution containing Sm and Fe. (Sm2Fe) 17 When obtaining N3 as the main phase, the molar ratio of Sm to Fe (Sm:Fe) is preferably 1.5:17 to 3.0:17, and more preferably 2.0:17 to 2.5:17. Raw materials such as La, W, Co, Ti, Sc, Y, Pr, Nd, Pm, Gd, Tb, Dy, Ho, Er, Tm, and Lu may be added to the solution.

[0083] The Sm and Fe raw materials are not limited as long as they can be dissolved in a strongly acidic solution. For example, in terms of availability, samarium oxide can be used as the Sm raw material, and FeSO4 can be used as the Fe raw material. The concentration of the solution containing Sm and Fe can be adjusted as appropriate within the range in which the Sm and Fe raw materials are substantially soluble in the acidic solution. In terms of solubility, sulfuric acid can be used as an acidic solution.

[0084] An insoluble precipitate containing Sm and Fe is obtained by reacting a solution containing Sm and Fe with a precipitating agent. Here, the solution containing Sm and Fe only needs to be a solution containing Sm and Fe when it reacts with the precipitating agent. For example, the raw materials containing Sm and Fe may be prepared as separate solutions, and each solution may be added dropwise to react with the precipitating agent. Even when preparing the raw materials as separate solutions, they should be adjusted appropriately so that each raw material is substantially soluble in the acidic solution. The precipitating agent is not limited to alkaline solutions that react with a solution containing Sm and Fe to obtain a precipitate, and examples include aqueous ammonia and caustic soda, with caustic soda being preferred.

[0085] For the precipitation reaction, a method is preferred in which a solution containing Sm and Fe and a precipitant are added dropwise to a solvent such as water, as this allows for easy adjustment of the properties of the precipitate particles. By appropriately controlling the supply rate of the solution containing Sm and Fe and the precipitant, the reaction temperature, the concentration of the reaction solution, and the pH during the reaction, a precipitate with a homogeneous distribution of constituent elements, a sharp particle size distribution, and a well-formed powder shape can be obtained. Using such a precipitate improves the magnetic properties of the final magnetic powder product. The reaction temperature is preferably 0 to 50°C, and more preferably 35 to 45°C. The concentration of the reaction solution is preferably 0.65 to 0.85 mol / L, and more preferably 0.7 to 0.84 mol / L, as the total concentration of metal ions. The reaction pH is preferably 5 to 9, and more preferably 6.5 to 8.

[0086] The particle powder obtained in the precipitation process roughly determines the particle size, shape, and particle size distribution of the final magnetic powder. When the particle size of the obtained particles is measured using a laser diffraction wet particle size analyzer, it is preferable that the size and distribution of the entire powder fall approximately within the range of 0.05 to 20 μm, more preferably 0.1 to 10 μm. Furthermore, the average particle size is measured as the particle size corresponding to 50% of the volume cumulative from the small particle size side in the particle size distribution, and it is preferable that it falls within the range of 0.1 to 10 μm.

[0087] After separating the precipitate, it is preferable to desolvent the separated material to prevent the precipitate from redissolving in the remaining solvent during the subsequent oxidation heat treatment, which can lead to aggregation of the precipitate, changes in particle size distribution, powder particle size, etc., as the solvent evaporates. Specifically, a method for desolvation is to dry the material in an oven at 70-200°C for 5-12 hours, for example, when water is used as the solvent.

[0088] The process may include a step of separating and washing the precipitate after the precipitation step. The washing step is performed when the conductivity of the supernatant solution is 5 mS / m 2Continue as needed until the following is achieved. For example, to separate the precipitate, a solvent (preferably water) can be added to the obtained precipitate and mixed, after which filtration, decantation, or the like can be used.

[0089] (oxidation process) The oxidation process involves calcining the precipitate formed in the precipitation process to obtain an oxide containing Sm and Fe. For example, the precipitate can be converted into an oxide by heat treatment. When heat treating the precipitate, it must be done in the presence of oxygen, for example, in an atmospheric environment. Furthermore, because it must be done in the presence of oxygen, it is preferable that the nonmetallic portion of the precipitate contains oxygen atoms.

[0090] The heat treatment temperature in the oxidation process (hereinafter also referred to as the oxidation temperature) is not particularly limited, but is preferably 700 to 1300°C, and more preferably 900 to 1200°C. Below 700°C, oxidation may be insufficient, and above 1300°C, it tends to be difficult to obtain the desired shape, average particle size, and particle size distribution of the magnetic powder. The heat treatment time is also not particularly limited, but is preferably 1 to 3 hours.

[0091] The resulting oxides exhibit sufficient microscopic mixing of Sm and Fe within the oxide particles, and the precipitate shape, particle size distribution, and other characteristics are reflected in the oxide particles.

[0092] (Pre-treatment process) The pretreatment step is a process in which an oxide containing Sm and Fe is heat-treated in a reducing gas atmosphere to obtain a partial oxide in which a portion of the oxide has been reduced.

[0093] Here, a partially oxide refers to an oxide in which a portion of the oxide has been reduced. The oxygen concentration of the oxide is not particularly limited, but it is preferably 10% by mass or less, and more preferably 8% by mass or less. If it exceeds 10% by mass, the exothermic reaction with Ca during the reduction process increases, and the firing temperature rises, which tends to result in the formation of particles with abnormal particle growth. The oxygen concentration of the partially oxide can be measured by non-dispersive infrared absorption spectroscopy (ND-IR).

[0094] The reducing gas can be appropriately selected from hydrocarbon gases such as hydrogen (H2), carbon monoxide (CO), and methane (CH4), but hydrogen gas is preferred in terms of cost. The gas flow rate is appropriately adjusted within a range that does not cause oxide dispersion. The heat treatment temperature in the pretreatment step (hereinafter also referred to as the pretreatment temperature) is preferably in the range of 300 to 950°C, more preferably 400°C or higher, particularly preferably 750°C or higher, and more preferably less than 900°C. When the pretreatment temperature is 300°C or higher, the reduction of oxides containing Sm and Fe proceeds efficiently. When the temperature is 950°C or lower, particle growth and segregation of oxide particles are suppressed, and the desired particle size can be easily maintained.

[0095] (Reduction process) The reduction step is a step in which the partial oxide obtained in the pretreatment step is reduced to alloy particles by heat treatment, for example, in the presence of a reducing agent, preferably at 920 to 1200°C. For example, reduction is carried out by contacting the partial oxide with calcium molten material or calcium vapor. From the viewpoint of magnetic properties, the heat treatment temperature is preferably 950 to 1150°C, and more preferably 980 to 1100°C. From the viewpoint of suppressing non-uniform particle growth, the heat treatment time is preferably less than 120 minutes, and more preferably less than 90 minutes. Furthermore, from the viewpoint of carrying out the reduction reaction more uniformly, the heat treatment time is preferably 10 minutes or more, and more preferably 30 minutes or more.

[0096] Metallic calcium is used, for example, in granular or powder form, with a particle size of 10 mm or less being preferable. This allows for more effective suppression of aggregation during the reduction reaction. Furthermore, metallic calcium can be added in a ratio of 1.1 to 3.0 times the reaction equivalent (the stoichiometric amount required to reduce Sm oxide, and including the amount required to reduce Fe if it is in oxide form), with 1.5 to 2.0 times being preferable.

[0097] In the reduction process, a disintegration accelerator can be used as needed, along with the reducing agent, metallic calcium. This disintegration accelerator is used as appropriate to promote the disintegration and granulation of the product during the washing process described later, and examples include alkaline earth metal salts such as calcium chloride and alkaline earth metal oxides such as calcium oxide. These disintegration accelerators are used, for example, in a ratio of 1 to 30% by mass, preferably 5 to 28% by mass, per Sm oxide used as the Sm source.

[0098] (Nitriding process) The nitriding process is a step in which Sm-Fe-N anisotropic magnetic powder is obtained by nitriding the alloy particles obtained in the reduction process. In this method, the porous mass containing alloy particles obtained in the reduction process can be immediately heat-treated in a nitrogen atmosphere without pulverization, thereby allowing for uniform nitriding.

[0099] The heat treatment temperature (hereinafter also referred to as the nitriding temperature) for nitriding alloy particles is preferably 300 to 600°C, and particularly preferably 400 to 550°C, and the treatment is carried out by replacing the atmosphere with a nitrogen atmosphere within this temperature range. The heat treatment time should be set to ensure that the nitriding of the alloy particles is sufficiently uniform.

[0100] The product obtained after the nitriding process may contain not only magnetic particles (Sm-Fe-N anisotropic magnetic powder) but also by-products such as CaO and unreacted metallic calcium, which may form a sintered mass. In this case, the product can be immersed in cooling water to separate the CaO and metallic calcium from the magnetic particles as a calcium hydroxide (Ca(OH)2) suspension. Furthermore, the magnetic particles may be washed with acetic acid or the like to thoroughly remove any remaining calcium hydroxide.

[0101] [Method for producing phosphate-coated Sm-Fe-N anisotropic magnetic powder] The phosphate-coated Sm-Fe-N anisotropic magnetic powder is not particularly limited, but for example, A phosphoric acid treatment step is performed to obtain Sm-Fe-N anisotropic magnetic powder coated with phosphate on its surface by adding an inorganic acid to a slurry containing Sm-Fe-N anisotropic magnetic powder, water, and a phosphoric acid compound, thereby adjusting the pH of the slurry to preferably 1 to 4.5, and Oxidation process: Heat treatment of phosphate-coated Sm-Fe-N anisotropic magnetic powder in an oxygen-containing atmosphere, preferably at 200-330°C. It can be manufactured by a method that includes [a specific component].

[0102] (Phosphating treatment process) In the phosphate treatment step, an inorganic acid is added to a slurry containing Sm-Fe-N anisotropic magnetic powder, water, and a phosphate compound to adjust the pH of the slurry to preferably 1 to 4.5, thereby obtaining Sm-Fe-N anisotropic magnetic powder coated with phosphate on its surface. The phosphate-coated Sm-Fe-N anisotropic magnetic powder is formed when the metal components (e.g., iron or samarium) contained in the Sm-Fe-N anisotropic magnetic powder react with the phosphate components contained in the phosphate compound, causing phosphates (e.g., iron phosphate, samarium phosphate) to precipitate on the surface of the Sm-Fe-N anisotropic magnetic powder. By adding an inorganic acid to adjust the pH of the slurry to 1 to 4.5, the amount of phosphate precipitated can be increased compared to when no inorganic acid is added, and a phosphate-coated Sm-Fe-N anisotropic magnetic powder with a thicker coating tends to be obtained. Furthermore, by using water as the solvent, smaller particle size phosphates tend to precipitate compared to when an organic solvent is used, resulting in a densely coated phosphate-coated Sm-Fe-N anisotropic magnetic powder.

[0103] The method for preparing a slurry containing Sm-Fe-N anisotropic magnetic powder, water, and a phosphoric acid compound is not particularly limited, but for example, it can be obtained by mixing Sm-Fe-N anisotropic magnetic powder with an aqueous phosphoric acid solution containing a phosphoric acid compound using water as a solvent. The content of Sm-Fe-N anisotropic magnetic powder in the slurry is preferably, for example, 1 to 50% by mass, and more preferably 5 to 20% by mass from the viewpoint of productivity. The content of the phosphoric acid component (PO4) in the slurry is preferably, for example, 0.01 to 10% by mass in terms of PO4 equivalent, and more preferably 0.05 to 5% by mass from the viewpoint of the reactivity of the phosphoric acid component and productivity.

[0104] A phosphoric acid aqueous solution is obtained by mixing a phosphoric acid compound with water. Examples of phosphoric acid compounds include phosphates such as orthophosphoric acid, sodium dihydrogen phosphate, sodium monohydrogen phosphate, ammonium dihydrogen phosphate, ammonium monohydrogen phosphate, zinc phosphate, and calcium phosphate; inorganic phosphoric acids such as hypophosphorous acid, hypophosphite, pyrophosphoric acid, and polyphosphoric acid; and organic phosphoric acids. These may be used individually or in combination of two or more. Furthermore, to improve water resistance and corrosion resistance through coating, and to improve the magnetic properties of magnetic powders, oxo salts such as molybdate, tungstate, vanadate, and chromate, oxidizing agents such as sodium nitrate and sodium nitrite, and chelating agents such as EDTA may be added.

[0105] The concentration of phosphoric acid (in PO4 equivalent) in the aqueous phosphoric acid solution is preferably, for example, 5 to 50% by mass, and more preferably 10 to 30% by mass from the viewpoint of solubility of phosphoric acid compounds, storage stability, and ease of chemical treatment. The pH of the aqueous phosphoric acid solution is preferably, for example, 1 to 4.5, and more preferably 1.5 to 4 from the viewpoint of being able to easily control the precipitation rate of phosphates. The pH can be adjusted with dilute hydrochloric acid, dilute sulfuric acid, etc.

[0106] In the phosphoric acid treatment process, the pH of the slurry is preferably adjusted to 1 to 4.5 by adding an inorganic acid, more preferably to 1.6 to 3.9, and even more preferably to 2 to 3. Below pH 1, the phosphate-coated Sm-Fe-N anisotropic magnetic powders may aggregate, starting from locally precipitated phosphates, which can reduce coercivity. Above pH 4.5, the amount of phosphate precipitated decreases, resulting in insufficient coating and potentially reducing coercivity. Examples of inorganic acids to be added include hydrochloric acid, nitric acid, sulfuric acid, boric acid, and hydrofluoric acid. During the phosphoric acid treatment process, inorganic acids are added as needed to maintain the pH within the above range. From the viewpoint of wastewater treatment, the use of inorganic acids is preferable, but organic acids can also be used in combination depending on the purpose. Examples of organic acids include acetic acid, formic acid, and tartaric acid. A mixture of inorganic and organic acids may also be used.

[0107] The phosphate content of the phosphate-coated Sm-Fe-N anisotropic magnetic powder obtained in the phosphoric acid treatment process is preferably greater than 0.5% by mass, more preferably 0.55% by mass or more, and particularly preferably 0.75% by mass or more. Furthermore, the phosphate content of the phosphate-coated Sm-Fe-N anisotropic magnetic powder is preferably 4.5% by mass or less, more preferably 2.5% by mass or less, and particularly preferably 2% by mass or less. When the phosphate content is 0.5% by mass or less, the effect of coating with phosphate tends to be reduced. When the phosphate content exceeds 4.5% by mass, the phosphate-coated Sm-Fe-N anisotropic magnetic powders may aggregate with each other, reducing the coercivity. The phosphate content of the magnetic powder is expressed in terms of PO4 molecules, measured using ICP emission spectrometry (ICP-AES).

[0108] The adjustment of the slurry containing Sm-Fe-N anisotropic magnetic powder, water, and a phosphate compound to a pH range of 1 to 4.5 is preferably carried out for 10 minutes or more, and more preferably for 30 minutes or more, in order to reduce the area where the coating is thin. Initially, the pH rises rapidly, so the interval between adding the inorganic acid for pH control is short, but as the coating progresses, the pH fluctuations gradually slow down, and the interval between adding the inorganic acid lengthens, allowing the reaction endpoint to be determined.

[0109] (Oxidation process after phosphoric acid treatment) In the oxidation step after phosphoric acid treatment, the Sm-Fe-N anisotropic magnetic powder coated with the phosphate obtained in the phosphoric acid treatment step is heat-treated in an oxygen-containing atmosphere, preferably at 200 to 330°C, thereby oxidizing the phosphate-coated Sm-Fe-N anisotropic magnetic powder. By heat-treating the phosphate-coated Sm-Fe-N anisotropic magnetic powder in an oxygen-containing atmosphere, preferably at a high temperature of 200 to 330°C, the surface of the phosphate-coated base material Sm-Fe-N anisotropic magnetic powder is oxidized, forming a thick iron oxide layer, which tends to improve the heat resistance and oil resistance of the phosphate-coated Sm-Fe-N anisotropic magnetic powder.

[0110] The oxidation step after phosphoric acid treatment is carried out by heat treatment of the phosphate-coated Sm-Fe-N anisotropic magnetic powder in an oxygen-containing atmosphere. The reaction atmosphere preferably contains oxygen in an inert gas such as nitrogen or argon. The oxygen concentration is preferably, for example, 3 to 21%, and more preferably 3.5 to 10%. During the oxidation reaction, it is preferable to exchange the gas at a flow rate of 2 to 10 L / min per 1 kg of magnetic powder.

[0111] The heat treatment temperature in the oxidation step after phosphoric acid treatment is preferably 200 to 330°C, more preferably 200 to 250°C, and even more preferably 210 to 230°C. Below 200°C, the formation of the iron oxide layer may be insufficient, and the effect of improving heat resistance and oil resistance may be reduced. Above 330°C, an excessive amount of iron oxide layer may be formed, and the coercivity may decrease. The heat treatment time is preferably, for example, 3 to 10 hours.

[0112] The oxidation step after phosphoric acid treatment is preferably carried out such that the phosphate coating on the surface of the Sm-Fe-N anisotropic magnetic powder has a first region, the Sm atom concentration in the first region is higher than the Sm atom concentration in the Sm-Fe-N anisotropic magnetic powder, and the Sm atom concentration in the first region is 0.5 times or more and 4 times or less than the Fe atom concentration in the first region. The Sm atom concentration in the first region can be, for example, 1.02 times or more than the Sm atom concentration in the Sm-Fe-N anisotropic magnetic powder, preferably 1.05 times or more, more preferably 1.1 times or more, and even more preferably 1.2 times or more. The Sm atom concentration in the first region can be, for example, 3 times or less than the Sm atom concentration in the Sm-Fe-N anisotropic magnetic powder. The Sm atom concentration in the first region is preferably 0.6 times or more and 3.5 times or less than the Fe atom concentration in the first region, and more preferably 0.7 times or more and 3 times or less. The atomic concentrations (atm%) of the Sm-Fe-N anisotropic magnetic powder and the first region are determined by averaging the atomic concentrations (atm%) in each region obtained from STEM-EDX line analysis.

[0113] (Silica treatment process) After phosphoric acid treatment, the Sm-Fe-N anisotropic magnetic powder (i.e., phosphate-coated Sm-Fe-N anisotropic magnetic powder) may be subjected to silica treatment as needed after the oxidation step described above. Forming a silica thin film on the magnetic powder can improve oxidation resistance. The silica thin film can be formed, for example, by mixing alkyl silicate, phosphate-coated Sm-Fe-N anisotropic magnetic powder, and an alkaline solution.

[0114] (Silane coupling treatment process) The magnetic powder after silica treatment may be further treated with a silane coupling agent. By treating the magnetic powder on which a silica thin film has been formed with silane coupling, a coupling agent film is formed on the silica thin film, which can improve the magnetic properties of the magnetic powder, as well as the wettability with resin and the strength of the magnet.

[0115] The silane coupling agent can be selected according to the type of resin and is not particularly limited, but examples include 3-aminopropyltriethoxysilane, γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane hydrochloride, γ-glycidoxypropyltrimethoxy Sisilane, γ-glycidoxyoctyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, vinyltriacetoxysilane, γ-chloropropyltrimethoxysilane, hexamethylenedisilazane, γ-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, octadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, γ-chloropropylmethyldimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, Methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, vinyltrichlorosilane, vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, N-β(aminoethyl)γ-aminopropyltrimethoxysilane, N-β(aminoethyl)γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyl Trimethoxysilane, oleidopropyltriethoxysilane, γ-isocyanatetopropyltriethoxysilane, polyethoxydimethylsiloxane, polyethoxymethylsiloxane, bis(trimethoxysilylpropyl)amine, bis(3-triethoxysilylpropyl)tetrasulfan, γ-isocyanatetopropyltrimethoxysilane, vinylmethyldimethoxysilane, 1,3,5-N-tris(3-trimethoxysilylpropyl)isocyanurate, t-butylcarbamatetrialkoxysilane, N-(1,Examples of silane coupling agents include 3-dimethylbutylidene)-3-(triethoxysilyl)-1-propanamine, octyltriethoxysilane, octyltrimethoxysilane, decyltriethoxysilane, decyltrimethoxysilane, octadecyltriethoxysilane, octadecyltrimethoxysilane, and docosyltriethoxysilane. These silane coupling agents may be used individually or in combination of two or more. The amount of silane coupling agent added is preferably 0.2 to 0.8 parts by mass, more preferably 0.25 to 0.6 parts by mass, per 100 parts by mass of magnetic powder. Below 0.2 parts by mass, the effect of the silane coupling agent tends to be small, and above 0.8 parts by mass, aggregation of the magnetic powder may occur, potentially reducing the magnetic properties of the magnetic powder and magnets.

[0116] Sm-Fe-N anisotropic magnetic powders that have undergone phosphoric acid treatment, oxidation, silica treatment, or silane coupling treatment can be filtered, dehydrated, and dried by conventional methods.

[0117] [Other ingredients] The curable composition for bonded magnets of this embodiment may further contain, as needed, various additives such as fillers (preferably inorganic fillers), lubricants, dispersants, antioxidants, heavy metal deactivators, nucleating agents, flame retardants, plasticizers, ultraviolet absorbers, antistatic agents, colorants, and mold release agents, as well as optional components such as thermosetting resins other than epoxy resins, thermoplastic resins, and thermoplastic elastomers.

[0118] Examples of lubricants and dispersants include waxes such as paraffin wax, polyethylene wax, and polypropylene wax; fatty acids such as stearic acid and their salts; metal soaps; fatty acid amides; urea compounds; fatty acid esters; polyethers; polysiloxanes such as silicone oil and silicone grease; fluorinated oils; fluorinated greases; and fluororesin powders. Lubricants and dispersants can be added individually or in combination of two or more.

[0119] The resins added to the curable composition for bonded magnets are not particularly limited, but examples include thermosetting resins such as phenolic resins, unsaturated polyester resins, vinyl esters (epoxy acrylates), diallyl phthalate resins, urea resins, melamine resins, and urethane resins, and thermoplastic resins such as polyphenylene sulfide, polyamide, polyester, polycarbonate, polystyrene, ABS, polyethylene, polypropylene, polyether ether ketone, liquid crystal polymer, polyethylene terephthalate, polybutylene terephthalate, polyphenylene ether, cycloolefin polymer, and cycloolefin copolymer. These thermosetting resins and thermoplastic resins can be added individually or in combination of two or more.

[0120] <Method for producing a curable composition for bonded magnets> The curable composition for bonded magnets according to this embodiment can be obtained, for example, by mixing and kneading magnetic powder with at least one of the following (main epoxy resin): preferably a phenol novolac type epoxy resin, a cresol novolac type epoxy resin, or a triphenylmethane type epoxy resin having an epoxy equivalent of 250 g / eq or less; preferably at least one of the following (phenol resin-based curing agent): preferably a novolac type phenol resin, a cresol novolac type phenol resin, or a triphenylmethane type phenol resin having a hydroxyl group equivalent of 150 g / eq or less; a phosphate ester; and other components added as needed (other epoxy resins and curing agents, curing accelerators, fillers, and other resins other than epoxy resins).

[0121] The mixing and kneading method and conditions are not particularly limited and can be appropriately selected by referring to known methods. For example, a mixture containing magnetic powder, the epoxy resin described above, the phenolic resin-based curing agent described above, and a phosphate ester, and optionally including other optional components, is kneaded using a kneader such as a single-screw kneader or a twin-screw kneader. The kneading temperature should be a temperature at which the progress of the curing reaction is suppressed, for example, 140°C or lower, preferably 60 to 110°C, and more preferably 60 to 85°C. The kneading time is also not particularly limited and can be appropriately determined, for example, it can be 1 to 10 minutes.

[0122] For example, a pellet-shaped curable composition for bonded magnets can be obtained by mixing and kneading magnetic powder, epoxy resin as described above, a phenolic resin-based curing agent as described above, a phosphate ester, and other optional components as needed, then extruding the strand with a twin-screw extruder, air-cooling it, and cutting it into the desired size (e.g., several millimeters) with a pelletizer. This pellet-shaped curable composition for bonded magnets can be suitably used in injection molding.

[0123] Furthermore, for example, a tablet-shaped curable composition for bonded magnets can be obtained by mixing and kneading magnetic powder, the epoxy resin described above, the phenolic resin-based curing agent described above, a phosphate ester, and other optional components as needed, then grinding the mixture using a ball mill, high-speed mill, etc., and compressing the resulting pulverized material (tabletization). Compression molding can be performed, for example, by filling a mold with the pulverized material and applying pressure at, for example, about 2 to 20 MPa. This tablet-shaped curable composition for bonded magnets can be suitably used in transfer molding.

[0124] <Method for manufacturing bonded magnets> A method for manufacturing a bonded magnet according to one embodiment of the present invention includes a step of injection molding or transfer molding and curing the above-described curable composition for bonded magnets (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, it is possible to manufacture bonded magnets with a high degree of freedom in shape and excellent properties such as heat resistance and oil resistance.

[0125] Furthermore, bonded magnets can also be manufactured from a curable composition for bonded magnets as described above, i.e., a curable composition for bonded magnets comprising magnetic powder, at least one of a phenol novolac type epoxy resin, a cresol novolac type epoxy resin, or a triphenylmethane type epoxy resin preferably having an epoxy equivalent of 250 g / eq or less, a phenol resin-based curing agent preferably having at least one of a novolac type phenol resin, a cresol novolac type phenol resin, or a triphenylmethane type phenol resin preferably having a hydroxyl group equivalent of 150 g / eq or less, and a phosphate ester, by molding methods other than injection molding and transfer molding, such as compression molding, extrusion molding, or potting. Depending on the molding method, or by appropriately controlling the molding conditions, the curable composition for bonded magnets may also be made free of phosphate esters.

[0126] As described above, in the method for manufacturing bonded magnets according to this embodiment, the curable composition for bonded magnets is injection molded or transfer molded and cured. More specifically, the curable composition for bonded magnets can be heated to soften it, and then injected or injected into the cavity (empty portion) of a heated mold to cure.

[0127] The temperature at which the curable composition for bonded magnets is softened can be appropriately selected depending on the type of magnetic powder, epoxy resin, and curing agent used, and is not particularly limited, but is generally preferably 140°C or lower, and more preferably 130°C or lower. In one embodiment of this embodiment, the temperature at which the curable composition for bonded magnets is softened is more preferably 120°C or lower, and even more preferably 100°C or lower. In one embodiment of this embodiment, the temperature at which the curable composition for bonded magnets is softened 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 curable composition for bonded magnets is softened is not particularly limited, but is generally preferably 60°C or higher. The heating time (softening time) for softening the curable composition for bonded magnets is not particularly limited and can be appropriately determined, for example, it can be 10 to 3600 seconds, but from the viewpoint of productivity, a relatively short time is preferred.

[0128] The temperature at which the curable composition for bonded magnets is cured (i.e., the temperature of the mold from which the curable composition for bonded 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. However, from the viewpoint of productivity and the heat resistance of the resulting bonded magnets, it is generally preferable to exceed 150°C, and more preferably 160°C or higher. In one embodiment of this product, the temperature at which the curable composition for bonded magnets is cured is particularly preferable to exceed 170°C, and even more preferably 175°C or higher, from the viewpoint of the heat resistance of the resulting bonded magnets. Furthermore, the upper limit of the temperature at which the curable composition for bonded magnets is cured is not particularly limited, but it is generally preferable to be 250°C or lower in order to suppress the decomposition of the material. The time (curing time) at which the curable composition for bonded magnets is held in the heated cavity of the mold to cure it can be appropriately selected from the viewpoint of the progress of the curing reaction and productivity. For example, it is preferable to hold it for 20 to 180 seconds.

[0129] In the case of transfer molding, the temperature at which the curable composition for bonded magnets softens is usually the same as the temperature at which it hardens. Even in this case, the temperature for softening and hardening the curable composition for bonded magnets, as well as the softening time and hardening time, can be appropriately selected depending on the type of magnetic powder, epoxy resin, and hardener used to form bonded magnets well.

[0130] In one embodiment of this invention, a bonded magnet can be manufactured by molding it using an injection molding method. For example, using an injection molding machine, a curable composition for bonded magnets is heated in a screw cylinder to soften and melt it, then injected into the cavity of a mold to which a magnetic field is applied, aligning (orienting) the easy magnetization axes of the magnetic powder, and curing it. The orientation magnetic field at that time can be generated using an electromagnet or a permanent magnet. The magnitude of the orientation magnetic field is not particularly limited, but is usually preferably 4 kOe or more, and more preferably 6 kOe or more. After that, the cured product is removed from the mold, and if necessary, a bonded magnet can be obtained by magnetizing it with an air-core coil or a magnetizing yoke. The magnitude of the magnetizing magnetic field is also not particularly limited, but is usually preferably 20 kOe or more, and more preferably 30 kOe or more.

[0131] In one embodiment of this invention, a bonded magnet can be manufactured by molding it using a transfer molding method. For example, using a transfer molding machine, the curable composition for bonded magnets is heated and softened in a mold pot, then injected into the mold cavity under a magnetic field to align (orient) the easy magnetization axes of the magnetic powder and harden. The orientation magnetic field can be generated using an electromagnet or a permanent magnet. The magnitude of the orientation magnetic field is not particularly limited, but is usually preferably 4 kOe or more, and more preferably 6 kOe or more. After that, the hardened material is removed from the mold, and if necessary, the bonded magnet can be obtained by magnetizing it with an air-core coil or a magnetizing yoke. The magnitude of the magnetizing magnetic field is also not particularly limited, but is usually preferably 20 kOe or more, and more preferably 30 kOe or more. The injection pressure when injecting the softened curable composition for bonded magnets into the mold cavity is not particularly limited, but is usually preferably 5 to 30 MPa, and more preferably 5 to 15 MPa.

[0132] As stated 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 and transfer molding. Although the degree of freedom in shape is reduced, any known method such as compression molding, extrusion molding, or potting can be used. The molding conditions in this case are also not particularly limited and can be set appropriately by referring to known methods. Furthermore, the temperature setting of the molding machine and the settings of the orientation magnetic field and magnetization magnetic field can be performed, for example, in the same manner as described above.

[0133] The bonded magnets obtained from the curable composition for bonded magnets according to this embodiment possess the excellent magnetic properties inherent to magnetic powder, and furthermore, because the binder resin is an epoxy resin, they have excellent heat resistance and mechanical strength, as well as particularly excellent oil resistance among various epoxy resins. Therefore, these bonded magnets can be used particularly suitably in applications where they are immersed in or in contact with oil, such as in automotive main motors, oil pumps, valve actuators, etc. These bonded magnets can also be suitably used in various applications where they are not immersed in or in contact with oil, such as in automotive auxiliary motors, electric water pumps, electric power steering motors, etc., where heat resistance and heat deformation resistance are required. In addition, the bonded magnets of this embodiment can be suitably used in applications where they may be immersed in or in contact with oil, such as in home appliance applications like air conditioner compressors, and in aviation applications such as drive motors for aerodynamic mobility devices like drones.

[0134] <Bonded Magnets> A bonded magnet according to one aspect of this embodiment comprises a cured product of a curable composition containing magnetic powder, an epoxy resin which is at least one of phenol novolac type epoxy resin, cresol novolac type epoxy resin, or triphenylmethane type epoxy resin, and a phenol resin curing agent which is at least one of novolac type phenol resin, cresol novolac type phenol resin, or triphenylmethane type phenol resin, and is used for applications involving immersion in or contact with oil. The phenol novolac type epoxy resin, cresol novolac type epoxy resin, or triphenylmethane type epoxy resin preferably has an epoxy equivalent of 250 g / eq or less. The novolac type phenol resin, cresol novolac type phenol resin, or triphenylmethane type phenol resin preferably has a hydroxyl group equivalent of 150 g / eq or less.

[0135] The curable composition may further contain a phosphate ester, and therefore, the cured product of the curable composition in the bonded magnet of this embodiment may be the cured product of the curable composition for bonded magnets as described above. The curable composition may contain epoxy resins other than phenol novolac type epoxy resin, cresol novolac type epoxy resin, and triphenylmethane type epoxy resin, and may also contain phenol resin-based curing agents other than novolac type phenol resin, cresol novolac type phenol resin, or triphenylmethane type phenol resin, and other curing agents.

[0136] The magnetic powder contained in the bonded magnet of this embodiment, preferably with an epoxy equivalent of 250 g / eq or less, is at least one of a phenol novolac type epoxy resin, a cresol novolac type epoxy resin, or a triphenylmethane type epoxy resin (main component), and preferably with a hydroxyl group equivalent of 150 g / eq or less, is at least one of a novolac type phenol resin, a cresol novolac type phenol resin, or a triphenylmethane type phenol resin (phenol resin curing agent). The same materials as those contained in the above-mentioned curable composition for bonded magnets are included, and the preferred materials are also the same. The phosphate ester is also the same material as those contained in the above-mentioned curable composition for bonded magnets, and the preferred materials are also the same.

[0137] The preferred range for the content of each component in the bonded magnet is the same as the preferred range for the content of each component in the curable composition for bonded magnets described above. The magnetic powder content in the bonded magnet is preferably less than 95% by mass, and more preferably 93% by mass or less. Furthermore, the magnetic powder content in the bonded magnet is preferably 80% by mass or more, and more preferably 85% by mass or more.

[0138] Furthermore, similar to the curable composition for bonded magnets described above, the bonded magnet of this embodiment may also further contain other components such as other resins and curing agents, curing accelerators, and additives, as needed.

[0139] The bonded magnet of this embodiment can be manufactured by curing the curable composition described above. The curing method and curing conditions are not particularly limited and can be appropriately selected depending on the type of epoxy resin, curing agent, and curing accelerator used.

[0140] The bonded magnet of this embodiment can be manufactured, for example, by the method for manufacturing bonded magnets as described above. A bonded magnet according to one aspect of this embodiment may be obtained from a curable composition that does not contain phosphate esters. In this case, the moldability is poor, making it difficult to control the molding conditions. However, a transfer molding method can be used, for example, to manufacture the bonded magnet from the curable composition in the same manner as the method for manufacturing bonded magnets described above.

[0141] The bonded magnets of this embodiment can be manufactured by injection molding or transfer molding, and may have relatively complex shapes, but their shapes are not particularly limited and may have relatively simple shapes. The molding method is also not limited to injection molding or transfer molding.

[0142] The bonded magnet of this embodiment is used for applications involving immersion in or contact with oil. The bonded magnet of this embodiment uses a binder resin formed by a reaction between an epoxy resin main component containing at least one of phenol novolac type epoxy resin, cresol novolac type epoxy resin, or triphenylmethane type epoxy resin, and a curing agent containing at least one of novolac type phenol resin, cresol novolac type phenol resin, or triphenylmethane type phenol resin, resulting in excellent heat resistance and excellent oil resistance.

[0143] More specifically, the bonded magnet of this embodiment can be used particularly suitably in vehicle-mounted main engine motors, oil pumps, valve actuators, and the like.

[0144] An on-board main motor according to one aspect of this embodiment includes a bonded magnet as described above. An oil pump according to one aspect of this embodiment also includes a bonded magnet as described above. An on-board main motor and oil pump using a bonded magnet having the above-described excellent heat resistance and oil resistance have excellent performance and are highly practical. [Examples]

[0145] Manufacturing example (Preparation of rare earth magnetic powder) [Precipitation process] 5.0 kg of FeSO4·7H2O was mixed and dissolved in 2.0 kg of pure water. Then, 0.49 kg of Sm2O and 0.74 kg of 70% sulfuric acid were added and the mixture was thoroughly stirred until completely dissolved. Next, pure water was added to the resulting solution to adjust the final Fe concentration to 0.726 mol / L and the Sm concentration to 0.112 mol / L, thus obtaining the SmFe sulfuric acid solution.

[0146] The entirety of the prepared SmFe sulfuric acid solution was added dropwise to 20 kg of pure water maintained at 40°C, while stirring for 70 minutes from the start of the reaction. Simultaneously, 15% ammonia solution was added dropwise to adjust the pH to 7-8. This yielded a slurry containing SmFe hydroxide. The precipitate (SmFe hydroxide) was separated from the obtained slurry by decantation, washed with pure water, and then the hydroxide was separated by solid-liquid separation. The separated hydroxide was dried in an oven at 100°C for 10 hours.

[0147] [Oxidation process] The hydroxide obtained in the precipitation process was calcined in air at 1000°C for 1 hour. After cooling, red SmFe oxide was obtained as the raw material powder.

[0148] [Pre-treatment process] 100 g of SmFe oxide obtained in the oxidation process was placed in a steel container to a thickness of 10 mm. The container was placed in a furnace, the pressure was reduced to 100 Pa, and then the temperature inside the furnace was raised to 850°C while introducing hydrogen gas, and maintained at that temperature for 15 hours. This yielded a partial oxide in which a portion of the oxide was reduced.

[0149] [Reduction Process] 60 g of partial oxide obtained in the pretreatment process and 19.2 g of metallic calcium with an average particle size of approximately 6 mm were mixed and placed in the furnace. After evacuating the furnace, argon gas (Ar gas) was introduced. Subsequently, the temperature inside the furnace was raised to 1045°C and held for 45 minutes to obtain Sm-Fe alloy particles.

[0150] [Nitriding process] Subsequently, the temperature inside the furnace was cooled to 100°C, then the furnace was evacuated, and while introducing nitrogen gas, the temperature was raised to 450°C and maintained at that temperature for 23 hours to obtain a massive product containing Sm-Fe-N magnetic particles.

[0151] [Water washing process] The lumpy product obtained in the nitriding process was added to 3 kg of pure water and stirred for 30 minutes. After standing, the supernatant was drained by decantation. The process of adding to pure water, stirring, and decanting was repeated 10 times. Next, 3 kg of pure water and 2.5 g of 99.9% acetic acid were sequentially added to the slurry after decantation and stirred for 15 minutes. After standing, the supernatant was drained by decantation. The process of adding to 3 kg of pure water, stirring, and decanting was repeated twice, followed by dehydration and drying, and then mechanical crushing to obtain Sm-Fe-N magnetic powder (average particle size (D50) approximately 3 μm).

[0152] [Phosphating treatment process] As the phosphoric acid treatment solution, a mixture of 85% orthophosphoric acid, sodium dihydrogen phosphate, and sodium molybdate dihydrate in a mass ratio of 1:6:1 was prepared, and the pH was adjusted to 2.5 and the PO4 concentration to 20% by mass using pure water and dilute hydrochloric acid. 1000 g of Sm-Fe-N magnetic powder obtained in the water washing step was stirred for 1 minute in 10 L of dilute hydrochloric acid containing 0.7% by mass of hydrogen chloride to remove surface oxide film and contaminants. Then, the draining and adding of water was repeated until the conductivity of the supernatant liquid was 100 μS / cm or less, to obtain a slurry containing 10% by mass of Sm-Fe-N magnetic powder. While stirring the obtained slurry, 100 g of the prepared phosphoric acid treatment solution was added entirely to the treatment tank, and then 6% by mass of hydrochloric acid was added as needed to control the pH of the phosphoric acid treatment reaction slurry within the range of 2.5 ± 0.1, and this was maintained for 30 minutes. Next, the mixture was subjected to suction filtration, dehydration, and vacuum drying to obtain a phosphate-coated Sm-Fe-N magnetic powder (residual magnetic flux density Br: 13.0 kG, coercivity iHc: 19.8 kOe, average particle size 3.32 μm, D10: 1.59 μm, D50: 3.24 μm, D90: 5.15 μm, particle size distribution 1.10).

[0153] [Oxidation treatment process after phosphoric acid treatment] 1000 g of the obtained phosphate-coated Sm-Fe-N magnetic powder was gradually heated from room temperature in a nitrogen and air mixed gas atmosphere (oxygen concentration 4%, flow rate 5 L / min), and heat-treated at a maximum temperature of 230°C for 8 hours to obtain oxidized phosphate-coated Sm-Fe-N magnetic powder.

[0154] Examples 1-3 and Comparative Examples 1-2 According to the formulations listed in Table 1, magnetic powder, epoxy resin, curing agent, dispersant, and curing accelerator were weighed and mixed. Subsequently, the mixture was kneaded in a laboplast mill (10 rpm, test volume 40 cc, residence time 6 minutes) to obtain a curable composition for bonded magnets. The kneading temperature was set to 85°C for Examples 1-3 and 110°C for Comparative Examples 1-2, according to the softening point of the resin.

[0155] The components used in the examples and comparative examples are as follows:

[0156] <Magnetic powder> SmFeN-based magnetic powder prepared according to the manufacturing example.

[0157] <Epoxy resin main component> Main component 1: EPPN-501H (manufactured by Nippon Kayaku Co., Ltd., triphenylmethane-based polyfunctional epoxy resin (thermosetting oligomer), number of epoxy groups in repeating structural units: 2, epoxy equivalent weight: 166 g / eq, softening point: 53°C) Main component 2: NC-3500 (manufactured by Nippon Kayaku Co., Ltd., biphenyl-based polyfunctional epoxy resin (thermosetting oligomer), number of epoxy groups in repeating structural units: 1 or 2, epoxy equivalent: 210 g / eq, softening point: 73°C) Main component 3: YX4000K (manufactured by Mitsubishi Chemical Corporation, biphenyl-based crystalline epoxy resin, melting point 105°C, number of epoxy groups per molecule 2, epoxy equivalent 186 g / eq)

[0158] <Hardening agent> Hardener 1: PHENOLITE TD-2131 (manufactured by DIC Corporation, novolac-type phenolic resin, hydroxyl group equivalent 104 g / eq, softening point 80°C) Hardener 2: MEH-7500 (manufactured by UBE Corporation, triphenylmethane-based phenolic resin (hardener oligomer), hydroxyl group equivalent 98 g / eq, softening point 111°C) Hardening agent 3: Dicyandiamide (DICY) (manufactured by Tokyo Chemical Industry Co., Ltd., melting point 209.5℃, functional group equivalent 21g / eq)

[0159] <Dispersant> Dispersant 1: Phosphanol RS-410 (manufactured by Toho Chemical Co., Ltd., polyoxyethylene tridecyl ether phosphate) Dispersant 2: BYK-W9010 (manufactured by Bic Chemie, phosphate polyester)

[0160] <Curing accelerator> Curing accelerator 1: Ucat3512T (manufactured by Sunapro Co., Ltd., aromatic dimethylurea-based curing accelerator) Curing accelerator 2: Curazole 2PHZ-PW (manufactured by Shikoku Chemicals Co., Ltd., imidazole-based curing accelerator)

[0161] [Table 1]

[0162] The curable compositions for bonded magnets obtained in Examples 1-3 and Comparative Examples 1-2 were evaluated as follows. The evaluation results are shown in Table 2.

[0163] <90°C residence stabilization time (A)> The torque of a curable composition for bonded magnets, obtained using a laboplast mill, was monitored during kneading at 90°C, a rotation speed of 10 rpm, and a test volume of 40 cc. The time it took for the torque to rise to 1.3 times the initial value was measured and defined as the 90°C residence stabilization time (A). The measurement time for time (A) was limited to 3600 seconds, at which point the measurement was terminated. Therefore, the upper limit of time (A) is 3600 seconds. A longer time (A) suppresses the thickening due to material hardening in the cylinder during injection molding, allowing for the maintenance of high fluidity over a longer period.

[0164] <180℃ curing time (B)> The time it took for 2.0 g of the resulting curable composition for bonded magnets to completely harden while being kneaded on a hot plate heated to 180°C was measured and defined as the 180°C curing time (B). A shorter time (B) indicates that the material hardens more rapidly in the mold, thus shortening the mold closing time and reducing the cycle time. From a productivity standpoint, a time (B) of 90 seconds or less is desirable.

[0165] <Cycle stability of injection molding (A / B)> The cycle stability (A / B) of injection molding was calculated by dividing the residence stabilization time at 90°C (A) by the curing time at 180°C (B). A larger (A / B) indicates that continuous cycle molding is more advantageous. The results are shown in Table 2.

[0166] [Table 2]

[0167] The curable compositions for bonded magnets in Examples 1-3 exhibit relatively high 90°C retention stability and relatively short 180°C curing times, resulting in excellent cycle stability. On the other hand, the curable compositions for bonded magnets in Comparative Examples 1 and 2 increase viscosity relatively quickly, have low 90°C retention stability, and have relatively long 180°C curing times, making them unsuitable for injection molding.

[0168] <Bending strength> For each of the curable compositions for bonded magnets in Example 1 and Comparative Examples 1 and 2, the material was placed in the hopper of a Japan Steel Works injection molding machine with the cylinder temperature set to Zone 1: 50°C and Zone 2: 85°C, and the mold temperature set to 200°C. The material was weighed to a predetermined weighing position at a screw rotation speed of 20 rpm, and the material was injected into the mold under the conditions of injection speed of 10 mm / s, injection pressure of 30 MPa, and orientation magnetic field of 9 kOe. After 90 seconds, the mold was opened to prepare a long test specimen measuring 100 mm in length, 12 mm in width, and 4 mm in height. The obtained long test specimen was annealed in a 200°C oven for 1 hour, and then a three-point bending test (support distance: 50 mm, speed: 2 mm / min) was performed on a multi-purpose strength testing machine to measure the bending strength. The results are shown in Table 3.

[0169] <Degradation resistance> A 7mm wide x 7mm long x 4mm high evaluation specimen was cut by milling from a 100mm long x 12mm wide x 4mm high long test specimen, prepared in the same manner as the bending strength evaluation described above. After subjecting the specimens to the durability test described below, they were sequentially embedded in epoxy resin, cross-sectioned, and polished with alumina abrasive. The degradation resistance was evaluated by observing the surface of the specimens using SEM-EDS. The durability test conditions were 500 hours of exposure to air at 180°C and 1000 hours of immersion in commercially available ATF at 150°C. Specimens showing discoloration, a decrease in carbon (C) concentration, or an increase in oxygen (O) concentration on the surface were classified as "degraded." The results are shown in Table 3.

[0170] <Magnetic properties (BH) max> A rectangular parallelepiped magnet measuring 7 mm wide x 7 mm long x 4 mm high was cut from a long test specimen measuring 100 mm in length x 12 mm in width x 4 mm in height, prepared in the same manner as the bending strength evaluation described above, by milling. The resulting rectangular parallelepiped was then pulse-magnetized with 60 kOe, and its magnetic properties (BH)max at room temperature was measured using a BH curve tracer manufactured by RIKEN Electron Co., Ltd. The results are shown in Table 3.

[0171] <Glass transition temperature (Tg)> Dynamic viscoelasticity (DMA) measurements were performed on the bending strength test specimens obtained from Example 1 and Comparative Example 1 in a three-point bending measurement mode in the range from room temperature to 300°C to measure the storage modulus (E', G'), loss modulus (E'', G''), and loss tangent (tanδ = E'' / E'). The glass transition temperature (Tg) was evaluated by reading the peak position of the loss tangent graph. The loss tangent graph is shown in Figure 1.

[0172] [Table 3]

[0173] The curable composition for bonded magnets in Example 1 exhibits high retention stability, and the resulting bonded magnets (cured products) have excellent flexural strength, magnetic properties, and decomposition resistance. On the other hand, the bonded magnets (cured products) obtained in Comparative Examples 1 and 2 have poor flexural strength, decomposition resistance, and magnetic properties. Furthermore, as shown in Figure 1, the cured product of the curable composition of Comparative Example 1 showed a Tg of approximately 176°C, while the cured product of the curable composition of Example 1 showed two Tgs of approximately 186°C and approximately 231°C. This confirms that the cured products of the examples, i.e., the bonded magnets, have high heat resistance.

[0174] The embodiments relating to this disclosure may include, for example, the following embodiments: [Section 1] The curable composition comprises magnetic powder, an epoxy resin which is at least one of phenol novolac type epoxy resin, cresol novolac type epoxy resin, or triphenylmethane type epoxy resin, and a phenol resin curing agent which is at least one of novolac type phenol resin, cresol novolac type phenol resin, or triphenylmethane type phenol resin, and includes a cured product of the curable composition. Bonded magnets used for applications involving immersion in or contact with oil. [Section 2] The bonded magnet according to item 1, wherein the epoxy equivalent of the epoxy resin is 250 g / eq or less, and the hydroxyl group equivalent of the phenolic resin curing agent is 150 g / eq or less. [Section 3] The cured product of a curable composition comprising magnetic powder, at least one of phenol novolac type epoxy resin, cresol novolac type epoxy resin, or triphenylmethane type epoxy resin having an epoxy equivalent of 250 g / eq or less, and at least one of phenol resin-based curing agents having a hydroxyl group equivalent of 150 g / eq or less, which is a novolac type phenol resin, cresol novolac type phenol resin, or triphenylmethane type phenol resin, is included. Bonded magnets used for applications involving immersion in or contact with oil. [Section 4] The bonded magnet according to any one of claims 1 to 3, wherein the curable composition further comprises a phosphate ester. [Section 5] The bonded magnet according to item 4, wherein the phosphate ester is polyoxyethylene alkyl ether phosphate. [Section 6] A bonded magnet according to any one of claims 1 to 5, wherein the content of the magnetic powder is 80% by mass or more and less than 95% by mass. [Section 7] A bonded magnet according to any one of items 1 to 6, wherein the magnetic powder is an Sm-Fe-N type magnetic powder. [Section 8] A bonded magnet as described in any one of items 1 to 7, used in a vehicle's main motor or oil pump. [Section 9] Automotive main motor containing a bonded magnet as described in any one of items 1 to 7. [Section 10] An oil pump containing a bonded magnet as described in any one of items 1 to 7. [Section 11] A curable composition for bonded magnets comprising magnetic powder, an epoxy resin which is at least one of phenol novolac type epoxy resin, cresol novolac type epoxy resin, or triphenylmethane type epoxy resin, a phenol resin-based curing agent which is at least one of novolac type phenol resin, cresol novolac type phenol resin, or triphenylmethane type phenol resin, and a phosphate ester. [Section 12] The curable composition for bonded magnets according to item 11, wherein the epoxy equivalent of the epoxy resin is 250 g / eq or less, and the hydroxyl group equivalent of the phenolic resin curing agent is 150 g / eq or less. [Section 13] A curable composition for bonded magnets comprising magnetic powder, at least one of the following having an epoxy equivalent of 250 g / eq or less: a phenol novolac type epoxy resin, a cresol novolac type epoxy resin, or a triphenylmethane type epoxy resin, at least one of the following having a hydroxyl group equivalent of 150 g / eq or less: a phenol resin-based curing agent, at least one of the following having a hydroxyl group equivalent of 150 g / eq or less: a novolac type phenol resin, a cresol novolac type phenol resin, or a triphenylmethane type phenol resin, and a phosphate ester. [Section 14] The curable composition for bonded magnets according to any one of claims 11 to 13, wherein the phosphate ester is polyoxyethylene alkyl ether phosphate. [Section 15] A curable composition for bonded magnets according to any one of claims 11 to 14, wherein the content of the magnetic powder is 80% by mass or more and less than 95% by mass. [Section 16] The curable composition for bonded magnets according to any one of claims 11 to 15, wherein the magnetic powder is an Sm-Fe-N type magnetic powder. [Section 17] A method for manufacturing a bonded magnet, comprising the steps of injection molding or transfer molding a curable composition for bonded magnets described in any one of items 11 to 16, and curing it.

Claims

1. The cured product of a curable composition comprising magnetic powder, an epoxy resin which is at least one of phenol novolac type epoxy resin, cresol novolac type epoxy resin, or triphenylmethane type epoxy resin, and a phenol resin curing agent which is at least one of novolac type phenol resin, cresol novolac type phenol resin, or triphenylmethane type phenol resin, Bonded magnets used for applications involving immersion in or contact with oil.

2. The bonded magnet according to claim 1, wherein the epoxy equivalent of the epoxy resin is 250 g / eq or less, and the hydroxyl group equivalent of the phenolic resin curing agent is 150 g / eq or less.

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

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

5. The bonded magnet according to claim 1 or 2, wherein the content of the magnetic powder is 80% by mass or more and less than 95% by mass.

6. The bonded magnet according to claim 1 or 2, wherein the magnetic powder is an Sm-Fe-N type magnetic powder.

7. A bonded magnet according to claim 1 or 2, used in a vehicle's main motor or oil pump.

8. An in-vehicle main motor comprising a bonded magnet according to claim 1 or 2.

9. An oil pump comprising a bonded magnet according to claim 1 or 2.

10. A curable composition for bonded magnets comprising magnetic powder, an epoxy resin which is at least one of phenol novolac type epoxy resin, cresol novolac type epoxy resin, or triphenylmethane type epoxy resin, a phenol resin curing agent which is at least one of novolac type phenol resin, cresol novolac type phenol resin, or triphenylmethane type phenol resin, and a phosphate ester.

11. The curable composition for bonded magnets according to claim 10, wherein the epoxy equivalent of the epoxy resin is 250 g / eq or less, and the hydroxyl group equivalent of the phenolic resin curing agent is 150 g / eq or less.

12. The curable composition for bonded magnets according to claim 10 or 11, wherein the phosphate ester is polyoxyethylene alkyl ether phosphate.

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

14. The curable composition for bonded magnets according to claim 10 or 11, wherein the magnetic powder is an Sm-Fe-N type magnetic powder.

15. A method for manufacturing a bonded magnet, comprising the steps of injection molding or transfer molding and curing the curable composition for bonded magnets according to claim 10 or 11.

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