Bonded magnet manufacturing method and bonded magnet compound

Abstract

To provide an additive for a bond magnet which can improve flowability of a compound for a bond magnet containing a thermoplastic resin, and mechanical characteristics of a bond magnet, and a compound for a bond magnet which improves these characteristics, and a method for manufacturing a bond magnet.SOLUTION: An additive for a bond magnet containing a thermoplastic resin contains a cured product of a thermosetting resin, and a curing agent having a ratio of the number of reactive groups to the number of reactive groups of the thermosetting resin of 2 or more and 11 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an additive for a bonded magnet and a method for producing a compound for a bonded magnet. [Background technology]

[0002] Patent Documents 1 and 2 disclose methods for producing bonded magnets in which a thermoplastic resin and SmFeN particles are melt-kneaded, then compression-molded to produce a compound, which is then injection-molded.

[0003] On the other hand, Patent Document 3 discloses a bonded magnet that uses NdFeB magnetic powder, epoxy resin, and an amine-based curing agent as a curing agent for the epoxy resin. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-43804 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-115921 [Patent Document 3] Japanese Patent Application Laid-Open No. 2010-232468 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention aims to provide an additive for bonded magnets that can improve the fluidity of bonded magnet compounds containing thermoplastic resins and the mechanical properties of bonded magnets, as well as a method for manufacturing bonded magnet compounds and bonded magnets with improved properties. [Means for solving the problem]

[0006] An additive for bonded magnets containing a thermoplastic resin according to one embodiment of the present invention contains a cured product of a thermosetting resin and a curing agent in which the ratio of the number of reactive groups to the number of reactive groups of the thermosetting resin is 2 or more and 11 or less.

[0007] A method for manufacturing a bonded magnet compound according to one embodiment of the present invention includes a step of thermally curing a thermosetting resin and a curing agent in which the ratio of the number of reactive groups to the number of reactive groups of the thermosetting resin is 2 or more and 11 or less to obtain a bonded magnet additive, and a kneading step of kneading the bonded magnet additive, magnetic material, and thermoplastic resin.

[0008] A method for manufacturing a bonded magnet according to one embodiment of the present invention includes a step of thermally curing a thermosetting resin and a curing agent in which the ratio of the number of reactive groups to the number of reactive groups in the thermosetting resin is 2 or more and 11 or less to obtain an additive for the bonded magnet; a kneading step of kneading the additive for the bonded magnet, a magnetic material, and a thermoplastic resin; and an injection molding step of injection molding the obtained compound for the bonded magnet. [Effects of the Invention]

[0009] According to the above embodiment, it is possible to improve the flowability of the bonded magnet compound containing the thermoplastic resin, and the mechanical properties of the bonded magnet. DETAILED DESCRIPTION OF THE INVENTION

[0010] 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 term "process" includes not only an independent process, but also a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved.

[0011] The additive for bonded magnets containing thermoplastic resins of the present invention is characterized by containing a cured product of a thermosetting resin and a curing agent in which the ratio of the number of reactive groups to the number of reactive groups in the thermosetting resin is 2 or more and 11 or less. Conventionally, when producing bonded magnets containing thermoplastic resins, injection molding a mixture of thermoplastic resins and thermosetting resins can result in a decrease in the fluidity of the resin and poor moldability due to reaction between the reactive groups in the thermosetting resin (e.g., glycidyl groups in the case of epoxy resin) and the reactive groups in the thermoplastic resin (e.g., amide groups in the case of nylon 12). In the cured product of the thermosetting resin and a curing agent in which the ratio of the equivalent weight to the equivalent weight of the thermosetting resin is 2 or more and 11 or less, the reactive groups in the thermosetting resin are sufficiently deactivated by the reactive groups in the curing agent (e.g., amino groups in the case of DDS (diaminodiphenylsulfone)), making them less likely to react with the reactive groups in the thermoplastic resin and suppressing a decrease in the fluidity of the resin. Therefore, the additive can be used as an additive for bonded magnets containing thermoplastic resins. Furthermore, when a bonded magnet is produced by injection molding using a bonded magnet compound made with the bonded magnet additive containing the thermoplastic resin of this embodiment, the injection pressure can be reduced, thereby improving the mechanical properties of the resulting bonded magnet.

[0012] The thermosetting resin is not particularly limited as long as it is thermosetting, and examples thereof include epoxy resin, phenol resin, urea resin, melamine resin, guanamine resin, unsaturated polyester, vinyl ester resin, diallyl phthalate resin, polyurethane resin, silicone resin, polyimide resin, alkyd resin, furan resin, dicyclopentadiene resin, acrylic resin, and allyl carbonate resin. Among these, epoxy resin is preferred in terms of mechanical properties and heat resistance. The thermosetting resin is preferably a liquid at room temperature or a solid that dissolves in a solvent and becomes liquid.

[0013] The curing agent is not particularly limited as long as it can thermally cure the selected thermosetting resin, and when the thermosetting resin is an epoxy resin, examples of the curing agent include amine-based curing agents, acid anhydride-based curing agents, polyamide-based curing agents, imidazole-based curing agents, phenolic resin-based curing agents, polymercaptan resin-based curing agents, polysulfide resin-based curing agents, organic acid hydrazide-based curing agents, etc. Examples of the amine-based curing agents include diaminodiphenyl sulfone, metaphenylenediamine, diaminodiphenylmethane, diethylenetriamine, triethylenetetramine, etc.

[0014] The amount of curing agent blended is adjusted by the ratio of the number of reactive groups to the number of reactive groups in the thermosetting resin (the ratio of the equivalent weight of the curing agent to the equivalent weight of the thermosetting resin). The ratio of the number of reactive groups in the curing agent to the number of reactive groups in the thermosetting resin is 2 to 11, preferably 2 to 10, and more preferably 2 to 7. The lower limit of the number of reactive groups is preferably greater than 2.5, more preferably 3 or greater. If this ratio exceeds 11, the mechanical properties of the bonded magnet deteriorate. If it is less than 2, the ratio of reactive groups in the curing agent to the reactive groups in the thermosetting resin is small, so reactive groups from the thermosetting resin remain. When kneaded with a thermoplastic resin in a subsequent process, the reactive groups in the thermoplastic resin react with the remaining reactive groups in the thermosetting resin, causing an increase in viscosity during injection molding. This results in the moldability of the bonded magnet and the mechanical properties of the resulting molded product being worse than those of the thermoplastic resin alone. Here, the equivalent weight of the thermosetting resin species refers to the number of grams of resin containing 1 gram equivalent of reactive groups, and the equivalent weight of the curing agent species refers to the active hydrogen equivalent.

[0015] The cured product can be obtained by blending the aforementioned thermosetting resin with a curing agent and then thermally curing the mixture. The thermosetting temperature can be set according to the properties of the thermosetting resin used, but in order to suppress magnetic deterioration of the magnetic material due to heat and to achieve thermal curing, a temperature of 60°C or higher and 250°C or lower is preferred, and 180°C or higher and 220°C or lower is even more preferred.

[0016] The cured product can be pulverized as needed. The method for pulverizing the cured product is not particularly limited, and a sample mill, ball mill, stamp mill, mortar, mixer pulverization, or the like can be used. If necessary, the pulverized product can also be classified using a sieve or the like. The average particle size of the pulverized product is preferably 1000 μm or less, more preferably 500 μm or less, from the viewpoint of compatibility with the thermoplastic resin.

[0017] Bonded magnet additives can also be cured by blending a curing accelerator with the thermosetting resin and curing agent. Examples of curing accelerators include 1,8-diazabicyclo(5,4,0)-undecene-7, 1,5-diazabicyclo(4,3,0)-nonene-5, 1-cyanoethyl-2-ethyl-4-methylimidazole, 2-methyl-4-methylimidazole, triphenylphosphine, and sulfonium salts. The amount of curing accelerator added is not particularly limited, but is generally between 0.01% and 10% by mass of the total amount of thermosetting resin and curing agent.

[0018] The manufacturing method for the bonded magnet compound of this embodiment is characterized by including a step of thermally curing a thermosetting resin and a curing agent whose equivalent ratio to the equivalent weight of the thermosetting resin is 2 or more and 11 or less to obtain a bonded magnet additive, and a kneading step of kneading the bonded magnet additive, magnetic material, and thermoplastic resin.

[0019] The process for obtaining the additive for a bonded magnet of this embodiment is as described above.

[0020] In the kneading process, the bond magnet additive, magnetic material, and thermoplastic resin are melt-kneaded to produce a bond magnet compound to be used in injection molding. There are no particular limitations on the melt-kneading machine, but a single-screw kneader, twin-screw kneader, mixing roll, kneader, Banbury mixer, intermeshing twin-screw extruder, non-intermeshing twin-screw extruder, etc. can be used. There are no particular limitations on the melt-kneading temperature, and it can be set depending on the properties of the thermoplastic resin used, but a temperature of 180°C or higher and 250°C or lower is preferred.

[0021] The thermoplastic resin is not particularly limited as long as it is an injection-moldable resin, and examples thereof include nylon resin (polyamide resin), polyolefins such as polypropylene (PP) and polyethylene (PE), polyester, polycarbonate (PC), polyphenylene sulfide resin (PPS), polyether ether ketone (PEEK), polyacetal (POM), liquid crystal polymer (LCP), etc. Examples of nylon resins include polylactams such as nylon 6, nylon 11, and nylon 12, condensates of dicarboxylic acids and diamines such as nylon 6,6, nylon 6,10, and nylon 6,12, copolymer polyamides such as nylon 6 / 6,6 nylon, nylon 6 / 6,10 nylon, nylon 6 / 12 nylon, nylon 6 / 6,12 nylon, nylon 6 / 6,10 nylon / 6,10 nylon, nylon 6 / 6,6 nylon / 6,12 nylon, and nylon 6 / polyether, nylon 6T, nylon 9T, nylon MXD6, aromatic nylon, and amorphous nylon. Among these, nylon resin is preferred, and nylon 12 is particularly preferred, due to its low water absorption rate, moldability, and mechanical properties.

[0022] The magnetic material is not particularly limited, but examples include rare earth magnetic materials such as SmFeN, NdFeB, and SmCo. Among them, SmFeN is preferred because of its heat resistance and lack of rare metals. Examples of SmFeN magnetic materials include Th2Zn 17 It has a crystal structure of the type Sm x Fe 100-x-y N y It is a nitride composed of rare earth metal Sm, iron Fe, and nitrogen N, represented by the formula: where x is preferably 8.1 atomic % or more and 10 atomic % or less, y is preferably 13.5 atomic % or more and 13.9 atomic % or less, and the remainder is preferably Fe.

[0023] SmFeN magnetic materials can be produced by the method disclosed in Japanese Patent Laid-Open No. 11-189811. NdFeB magnetic materials can be produced by the HDDR method disclosed in International Publication No. 2003 / 85147. SmCo magnetic materials can be produced by the method disclosed in Japanese Patent Laid-Open No. 08-260083. Magnetic materials that have been surface-treated with a silane coupling agent by the method disclosed in Patent Document 1 can also be used.

[0024] The average particle size of the magnetic material is preferably 10 μm or less, more preferably 6 μm or less, and even more preferably 4 μm or less. The average particle size is measured as the particle size corresponding to 50% of the cumulative volume from the small particle size side in the particle size distribution. The particle size distribution of the magnetic material used in the bonded magnet compound is preferably monodisperse in terms of the squareness of the demagnetization characteristics.

[0025] The magnetic material can also be surface-treated with a silane coupling agent, which enhances the bond between the magnetic material and the resin, thereby preventing an increase in viscosity during injection molding.

[0026] The silane coupling agent is a compound represented by the general formula: X-Si-(OR) n (wherein X is an alkyl group having a polar group at the terminal, R is an alkyl group having 1 to 3 carbon atoms, and n is an integer of 1 to 3), and the polar group in X preferably has an amino group, ureido group, epoxy group, thiol group, or methacryloxy group. When using nylon resin as the thermoplastic resin, it is preferable to use a coupling agent having an amino group that has high affinity with nylon resin, and it is particularly preferable to use 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-(2-aminoethyl)aminopropyltrimethoxysilane, or 3-(2-aminoethyl)aminopropylmethyltriethoxysilane.

[0027] The amount of magnetic material added in the kneading step is preferably 93.2% by mass or less, and more preferably 75% to 92.5% by mass, in terms of the content of magnetic material in the bond magnet compound. If it exceeds 93.2% by mass, the viscosity during injection molding will increase, reducing moldability, while if it is less than 75% by mass, the residual magnetic flux density of the bond magnet will be low.

[0028] The amount of bond magnet additive added in the kneading step is preferably 0.1% by mass or more and 2.5% by mass or less, and more preferably 0.2% by mass or more and 2.0% by mass or less, in terms of the content of bond magnet additive in the bond magnet compound. If the content of bond magnet additive exceeds 2.5% by mass, the mechanical properties will deteriorate, and if it is less than 0.1% by mass, the effect of adding the bond magnet additive will be small.

[0029] The amount of thermoplastic resin added in the kneading step is preferably 6.3% by mass or more, and more preferably 7.0% by mass or more and 24.5% by mass or less, in terms of the content of thermoplastic resin in the bonded magnet compound. If the amount of thermoplastic resin added exceeds 24.5% by mass, the residual magnetic flux density will decrease, and if it is less than 6.3% by mass, the viscosity will increase during injection molding, reducing moldability.

[0030] The compound for bonded magnets of this embodiment is obtained by the manufacturing method described above.

[0031] The method for manufacturing the bonded magnet of this embodiment is as follows: a step of thermally curing a thermosetting resin and a curing agent having a ratio of the number of reactive groups to the number of reactive groups of the thermosetting resin of 2 or more and 11 or less to obtain an additive for a bonded magnet; a kneading step of kneading the bonded magnet additive, the magnetic material, and the thermoplastic resin; and an injection molding step of injection molding the resulting bonded magnet compound. The present invention is characterized by comprising:

[0032] The process for obtaining the additive for a bonded magnet and the kneading process are as described above.

[0033] In the injection molding process, the bond magnet compound is injection molded to obtain an injection-molded product. The cylinder temperature of the injection molding machine should be within the temperature range in which the bond magnet compound melts, and is preferably 260°C or less to prevent magnetic deterioration due to heat in the magnetic material. The injection pressure should be high enough to inject the molten compound, but for example, when the cylinder temperature of the injection molding machine is set to 260°C and injection molding is performed into a cavity 10 mm wide, 4 mm thick, and 80 mm long, it is preferable from the standpoint of moldability that the pressure be less than 162 MPa to completely fill the cavity.

[0034] The bonded magnet of this embodiment is obtained by the manufacturing method described above. [Example]

[0035] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[0036] In the examples and comparative examples, the following materials were used. Epoxy resin: biphenyl type (epoxy equivalent 186g / eq) Curing agent: DDS (diaminodiphenyl sulfone) (active hydrogen equivalent: 62.0 g / eq) Curing accelerator: TPP (triphenylphosphine) Magnetic material: Surface-treated SmFeN-based magnetic material (Average particle size 3 μm (particle size distribution is monodisperse), residual magnetic flux density Br of magnetic powder alone = 1.31 T)

[0037] Manufacturing Example 1 100 parts by mass of SmFeN-based magnetic material was surface-treated using 1.875 parts by mass of ethyl silicate and 0.4 parts by mass of 3-aminopropyltriethoxysilane (Z-6011 manufactured by Dow Corning Toray Co., Ltd.) to prepare a surface-treated SmFeN-based magnetic material.

[0038] Example 1 (Production of additives for bonded magnets) 12 parts by weight of epoxy resin, 8.9 parts by weight of curing agent, and 0.4 parts by weight of curing accelerator were dissolved and mixed in 100 parts by weight of acetone. After volatilizing the acetone, the mixture was cured in a tray dryer under a nitrogen atmosphere at 200°C for 6 hours. The resulting cured product was pulverized in a mixer and classified using a 500 μm mesh sieve to produce an additive for bonded magnets.

[0039] (Making compounds for bonded magnets) 100 parts by mass of the surface-treated SmFeN-based magnetic material prepared in Production Example 1 was mixed with 0.5 parts by mass of a bonded magnet additive and 8.8 parts by mass of polyamide 12, and the mixture was melt-extruded and mixed in a twin-screw mixer at 230°C to obtain a bonded magnet compound.

[0040] (Production of bonded magnets) The bonded magnet compound was injection molded at a cylinder temperature of 260°C, a mold temperature of 90°C, and an injection pressure of 152 MPa to obtain a bonded magnet strength test piece measuring 10 mm wide, 4 mm thick, and 116 mm long.

[0041] Comparative Example 1 100 parts by mass of the surface-treated SmFeN-based magnetic material was mixed with 9.2 parts by mass of polyamide 12, and the mixture was melt-extruded and kneaded in a twin-screw kneader at 230°C to obtain a bonded magnet compound. Subsequently, a bonded magnet was produced using the obtained bonded magnet compound in the same manner as in Example 1. The bending strength was measured. The injection pressure during injection molding is shown in Table 1.

[0042] Examples 2 and 3 and Comparative Example 2 A compound for a bonded magnet and a bonded magnet were obtained in the same manner as in Example 1, except that the blending when preparing the additive for a bonded magnet was changed as shown in Table 1.

[0043] In the examples and comparative examples, the injection pressure used during injection molding of the bonded magnets is shown in Table 1. The bending strength of the bonded magnets was measured using an Instron universal testing machine, and the results are shown in Table 2.

[0044] [Table 1]

[0045] As can be seen from Table 1, the compositions of Examples 1 to 3 had lower injection pressures than the compositions of Comparative Examples 1 and 2, which shows that compositions containing additives for bonded magnets that contain a cured product of a thermosetting resin and a curing agent whose equivalent weight ratio to the equivalent weight of the thermosetting resin is within a specific range improve the fluidity of the bonded magnet compound.

[0046] [Table 2]

[0047] As can be seen from Table 2, the bonded magnets of Examples 1 to 3 have higher bending strength than the bonded magnets of Comparative Examples 1 and 2, and it was therefore confirmed that the mechanical properties of bonded magnets made from compositions containing additives for bonded magnets, which contain a cured product of a thermosetting resin and a curing agent whose equivalent weight ratio to the equivalent weight of the thermosetting resin is within a specific range, are also improved. [Industrial Applicability]

[0048] The bonded magnet additive of the present invention significantly improves the flowability of the bonded magnet compound and also improves the mechanical properties of the resulting bonded magnet. The resulting bonded magnet can be suitably used as a composite material and a bonded magnet in applications such as motors.

Claims

1. A process for obtaining a bonded magnet compound having fluidity that can be filled into a cavity 10 mm wide, 4 mm thick, and 80 mm long at an injection pressure of less than 162 MPa when the cylinder temperature of an injection molding machine is set to 260°C by mixing an additive for a bonded magnet containing a hardened product of a thermosetting resin and a hardener, a magnetic material, and a thermoplastic resin; and injection molding the bonded magnet compound.

2. 2. The method for producing a bonded magnet according to claim 1, wherein the injection molding step involves setting the cylinder temperature of the injection molding machine to 260° C. or less.

3. 3. The method for producing a bonded magnet according to claim 1, wherein the additive is a cured product of a biphenyl-type epoxy resin and diaminodiphenyl sulfone as a curing agent.

4. The method for producing a bonded magnet according to any one of claims 1 to 3, wherein the thermoplastic resin is a nylon resin.

5. The method for producing a bonded magnet according to any one of claims 1 to 4, wherein the magnetic material is a SmFeN-based rare earth magnetic material.

6. A bonded magnet additive containing a cured product of a thermosetting resin and a curing agent, a magnetic material, and a thermoplastic resin, A compound for bonded magnets that has the fluidity to fill a cavity 10 mm wide, 4 mm thick, and 80 mm long with an injection pressure of less than 162 MPa when the cylinder temperature of the injection molding machine is 260°C.

7. 7. A compound for bonded magnets according to claim 6, wherein said additive is a cured product of a biphenyl type epoxy resin and diaminodiphenyl sulfone as a curing agent.

8. 8. A compound for bonded magnets according to claim 6 or 7, wherein said thermoplastic resin is a nylon resin.

9. 9. A compound for bonded magnets according to claim 6, wherein the magnetic material is a rare earth magnetic material of SmFeN system.

Images