Epoxy resin composition for metal powder binders, and the bonded magnet thereof.

Abstract

To provide an epoxy resin composition for a metal powder binder that provides excellent mechanical strength at a room temperature and a high temperature.SOLUTION: An epoxy resin composition for a metal powder binder contains 70 to 75 weight% of a trisphenolmethane type epoxy resin, 20 to 25 weight% of diaminodiphenylsulfone, 0.5 to 1 weight% of triphenylphosphine, 0.3 to 1 weight% of 2-phenyl-4-methylimidazole, and 1 to 3 weight% of 3-aminopropyltriethoxysilane.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an epoxy resin composition for a metal powder binder, a resin solution obtained by diluting the resin with an organic solvent, a solid obtained by curing a mixture of the epoxy resin composition for a metal powder binder and a metal powder, and a resin-bonded magnetic material and a bonded magnet obtained by curing a mixture of the epoxy resin composition for a metal powder binder and a magnetic metal powder.

Background Art

[0002] In recent years, rare earth magnets have excellent magnetic properties, and thus are applied in a wide range of fields such as rotating devices such as motors, general household appliances, audio equipment, medical equipment, and general industrial equipment. In particular, rare earth bonded magnets obtained by appropriately mixing rare earth magnet powder and a binder resin represented by an epoxy resin or the like have a high degree of freedom in shape, are widely used in the above-mentioned devices, and contribute to the miniaturization and high performance of the devices. Conventionally, ferrite magnets have been used as in-vehicle permanent magnets. However, ferrite magnets have a lower spontaneous magnetization than rare earth magnets, and there is a problem in that the magnet volume becomes large in order to obtain the required magnetic flux. Therefore, due to demands such as higher output and miniaturization, rare earth magnets having a small size and high spontaneous magnetization have been widely used instead of ferrite magnets.

[0003] Patent Document 1 discloses a coated rare earth bonded magnet in which a film containing a cured product of a second epoxy resin adheres to the surface of a rare earth bonded magnet containing rare earth magnet particles and a cured product of a first epoxy resin, and the glass transition point of the cured product of the second epoxy resin is higher than the glass transition point of the cured product of the first epoxy resin.

[0004] Patent Document 2 describes a Sm-Fe-N-based magnet material and a Sm-Fe-N-based bonded magnet.

[0005] Patent Document 3 discloses a rare earth bonded magnet comprising rare earth magnet particles, a first binder resin cured product, and a second binder resin cured product, wherein the glass transition temperature (Tg) of the first binder resin cured product is 150°C or higher, and the glass transition temperature (Tg) of the second binder resin cured product is less than 150°C. Patent Document 4 discloses an epoxy resin composition for a metal powder binder containing a trisphenolmethane type epoxy resin, a bisphenol A type epoxy resin, and a curing agent. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2019-096752 [Patent Document 2] Japanese Patent Publication No. 2018-046222 [Patent Document 3] Japanese Patent Publication No. 2019-054205 [Patent Document 4] Japanese Patent Application Publication No. 8-109244 [Overview of the project] [Problems that the invention aims to solve]

[0007] Rare earth bonded magnets, when used for extended periods in high-temperature environments, are prone to issues such as magnet failure due to resin degradation caused by oxidation, leading to the shedding of magnet powder. In particular, motors and actuators used in engine compartments require stable mechanical strength even when exposed to high temperatures of 150°C or higher for extended periods. Furthermore, while the epoxy resin composition described in Patent Document 4 contains bisphenol A type epoxy resin, bisphenol A is a concern for its effects on the human body. Therefore, it is preferable not to use resins derived from bisphenol A, or to reduce their usage.

[0008] This invention has been made in view of the above circumstances, and aims to provide an epoxy resin composition for metal powder binders that provides excellent mechanical strength at room temperature and high temperatures, and a resin-bonded magnetic material and bonded magnet obtained by curing a mixture consisting of the epoxy resin composition for metal powder binders and magnetic metal powder. [Means for solving the problem]

[0009] In other words, the present invention relates to the following [1] to [5]. In this application, "(numerical value 1) to (numerical value 2)" indicates that upper and lower limits are included. [1] An epoxy resin composition for metal powder binders, comprising 70-75% by weight of trisphenolmethane-type epoxy resin, 20-25% by weight of diaminodiphenylsulfone, 0.5-1% by weight of triphenylphosphine, 0.3-1% by weight of 2-phenyl-4-methylimidazole, and 1-3% by weight of 3-aminopropyltriethoxysilane, in total weight. [2] A resin solution containing the epoxy resin composition for metal powder binder and an organic solvent as described in the preceding paragraph [1]. [3] A solid obtained by curing a mixture consisting of the epoxy resin composition for metal powder binder and metal powder described in the preceding paragraph [1]. [4] A resin-bonded magnetic material obtained by curing a mixture consisting of the epoxy resin composition for metal powder binder and magnetic metal powder described in the preceding paragraph [1]. [5] A bonded magnet obtained by curing a mixture consisting of the epoxy resin composition for metal powder binder described in the preceding paragraph [1] and rare earth magnet powder. [Effects of the Invention]

[0010] The epoxy resin composition for metal powder binders of the present invention has excellent mechanical strength at room temperature and high temperatures. [Modes for carrying out the invention]

[0011] The present inventors, through diligent research to achieve the aforementioned objectives, have discovered that an epoxy resin composition for metal powder binders containing trisphenolmethane-type epoxy resin, diaminodiphenylsulfone, triphenylphosphine, 2-phenyl-4-methylimidazole, and 3-aminopropyltriethoxysilane exhibits excellent processability, dimensional stability, and high-temperature strength when metal powder is added and cured, thus completing the present invention. Specifically, the present invention provides an epoxy resin composition for metal powder binders, a solid obtained by curing a mixture consisting of the epoxy resin composition for metal powder binders and metal powder, a resin-bonded magnetic material obtained by curing a mixture consisting of the epoxy resin composition for metal powder binders and magnetic metal powder, and a bonded magnet. There are no particular restrictions on the magnetic metal powder as long as it can impart magnetism, but Nd-based and Sm-based rare earth magnet powders with high-performance magnetic properties are preferred for bonded magnets.

[0012] In this invention, trisphenolmethane type epoxy resin is contained in a total amount of 70-75% by weight of the epoxy resin composition for metal powder binder, from the viewpoint of the heat distortion temperature of the cured material and the mechanical strength at high temperatures. Examples of trisphenolmethane type epoxy resins include EPPN-501H, EPPN-501HY, EPPN-502H, and EPPN-503 (trade names, manufactured by Nippon Kayaku Co., Ltd.). The epoxy equivalent of the trisphenolmethane type epoxy resin is preferably 160-210 g / eq., more preferably 160-190 g / eq., and most preferably 160-170 g / eq. The softening point of the trisphenolmethane type epoxy resin is preferably 50-100°C, more preferably 50-95°C, and most preferably 50-70°C. Furthermore, the hydrolyzable chlorine content in the trisphenolmethane-type epoxy resin is preferably 100 to 1500 ppm, more preferably 100 to 1000 ppm, and most preferably 100 to 750 ppm. When the hydrolyzable chlorine content is within the above range, the epoxy group content increases, making it easier to exhibit excellent heat resistance.

[0013] The epoxy resin composition for metal powder binders of the present invention contains 20 to 25% by weight of diaminodiphenylsulfone as a curing agent for the epoxy resin, based on the total amount of the epoxy resin composition for metal powder binders. The diaminodiphenylsulfone content is preferably such that the ratio (α / β), obtained by dividing the epoxy equivalent (α) of the epoxy resin used by the active hydrogen equivalent (β: 62.1 g / eq.) of diaminodiphenylsulfone, is 0.7 to 1.0, more preferably 0.8 to 1.0, and most preferably 0.85 to 0.95. If (α / β) exceeds the upper limit of the above range, the epoxy resin undergoes partial anionic polymerization (self-polymerization) due to the basicity of the amino group itself, resulting in the retention of unreacted diaminodiphenylsulfone. If (α / β) is below the lower limit of the above range, there is a risk of retained unreacted epoxy resin.

[0014] The epoxy resin composition for metal powder binders of the present invention contains triphenylphosphine and 2-phenyl-4-methylimidazole as curing accelerators. Triphenylphosphine is present in an amount of 0.5 to 1% by weight of the total amount of the epoxy resin composition for metal powder binders, and 2-phenyl-4-methylimidazole is present in an amount of 0.3 to 1% by weight of the total amount of the epoxy resin composition for metal powder binders. If the amount of each curing accelerator added is less than the lower limit of the above range, the epoxy resin will not cure sufficiently, and when it becomes a solid, resin seepage may occur, and a uniform cured product may not be obtained. If the amount of each curing accelerator added is greater than the upper limit of the above range, the epoxy resin may cure during mixing of the epoxy resin composition and metal powder. In addition, since triphenylphosphine also has the effect of a compatibilizer, its use in combination with 2-phenyl-4-methylimidazole is preferred.

[0015] The epoxy resin composition for metal powder binders of the present invention contains 3-aminopropyltriethoxysilane as a coupling agent in an amount of 1 to 3% by weight of the total amount of the epoxy resin composition for metal powder binders. This is because sufficient interfacial adhesion between the resin and the metal powder is ensured within the above range.

[0016] The organic solvent used in the present invention is not particularly limited, but aromatic hydrocarbon-based organic solvents, ketone-based organic solvents, alcohol-based organic solvents, etc. are preferred. More preferably, polar organic solvents such as ketone-based organic solvents and alcohol-based organic solvents can be mentioned. Examples of aromatic hydrocarbon-based organic solvents include toluene, xylene, etc. Examples of ketone-based organic solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, etc. Examples of alcohol-based organic solvents include methanol, etc. These organic solvents can be used alone or in combination of two or more in any ratio. The amount of the organic solvent used can be any amount depending on the form of the adherent and the usage method. The solid content (residue after removing the organic solvent) when using the organic solvent is preferably 10 to 60% by weight, more preferably 20 to 50% by weight.

[0017] The resin solution containing the epoxy resin composition for the metal powder binder of the present invention can be obtained by adding an epoxy resin and a curing agent to a predetermined amount of an organic solvent, heating and dissolving if necessary, and then adding a coupling agent and a curing accelerator and stirring uniformly. In addition, materials other than those exemplified above can be added as needed. The epoxy resin composition for the metal powder binder of the present invention is obtained by removing the organic solvent from the above resin solution.

[0018] The solid of the present invention is obtained by curing a mixture composed of the epoxy resin composition of the present invention and metal powder. Specifically, a resin solution containing an epoxy resin composition and an organic solvent is uniformly mixed with metal powder or the like, the organic solvent is removed by an arbitrary method, and the obtained mixture is molded by a compression molding machine or the like, and cured at 100°C to 220°C, preferably 150°C to 200°C for 0.5 to 5 hours to obtain it. Here, examples of the metal powder include iron powder, nickel powder, aluminum powder, copper powder, Al-Ni alloy, magnetic metal powder, etc. Examples of the magnetic metal powder include soft magnetic iron powder, cast alloy magnet powder such as alnico, and magnetic metal powder of rare earth magnets. Examples of the magnetic metal powder of rare earth magnets include rare earth magnet powders such as 2-14-1 type rare earth magnet powder, 2-17 type rare earth magnet powder, 1-12 type rare earth magnet powder, 1-7, 2-17, 1-12 nitrogen-based rare earth magnet powders, Fe-Ni type magnet powder, Fe-N type magnet powder, etc. The mixing ratio of the metal powder and the epoxy resin composition of the present invention is preferably such that the epoxy resin composition of the present invention is 0.5 to 30% by weight, more preferably 1 to 30% by weight, as a solid content in the mixture.

[0019] The resin-bonded magnetic material composed of the epoxy resin composition of the present invention and magnetic metal powder is molded by a conventional method. If necessary, the magnetic metal powder may be oriented in an easy magnetization direction by molding in a magnetic field.

[0020] Also, the solid of the present invention can be obtained by applying the resin solution to the surface of a metal molded product such as a can or a metal sheet such as a label, or impregnating the resin solution into a metal molded product or a metal sheet, etc., then removing the organic solvent by an arbitrary method, and bonding this to another metal article and curing it. Such a cured product of the present invention has excellent mechanical strength and excellent reliability of mechanical strength even at high temperatures. The bonded magnet of the present invention is obtained by curing a mixture composed of the above epoxy resin composition for metal powder binder and rare earth magnet powder.

Examples

[0021] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0022] [Example 1, Comparative Examples 1-4] An epoxy resin composition containing epoxy resin, curing agent, accelerator, and coupling agent in the proportions shown in Table 1 was dissolved in the amount of solvent shown in Table 1 and mixed to obtain a diluted solution (resin solution) of the epoxy resin composition of the present invention. 5 g of the obtained diluted epoxy resin composition solution was added to 100 g of Nd-based magnet powder and stirred in a mixer for about 30 minutes. After standing at room temperature for 2 hours, the solvent was distilled off to obtain 102 g of Nd-Fe-B magnet powder containing about 2% by weight of resin. 3.4 g of this Nd-based magnet powder was filled into a predetermined mold and press-molded in a uniaxial pressure molding machine at a molding load of 700 MPa. This was then heated at 170°C for 1 hour to obtain a cured product of the present invention (diameter about 10 mm, height about 7 mm). The measurement results of each physical property are shown in Table 1.

[0023] Strength evaluation was performed in accordance with the compression test specified in JIS K 6911, section 5.19.1. At a temperature of 23°C, the load (kN) at which the sample fractured when compressed in the same direction as the uniaxial compression molding direction was measured was defined as the fracture strength.

[0024] The demagnetization rate was calculated by using the total magnetic flux measurement of the magnet at room temperature before evaluation as a baseline, and then measuring the magnetic flux reduction rate from the total magnetic flux measurement after heating at 150°C for 1000 hours.

[0025] Moldability was assessed by checking for resin seepage after press molding and heating at 170°C for 1 hour. The criteria for evaluation are as follows: • If there is no resin seepage: ○ • If there is resin seepage: ×

[0026] [Table 1]

[0027] • Trisphenolmethane type epoxy resin: EPPN-501H (manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent: 166 g / eq., softening point: 53.5°C) • Dicyclopentadiene type epoxy resin: XD-1000 (manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent: 251 g / eq., softening point: 74.2°C) • Bisphenol A type epoxy resin (epoxy equivalent: 946 g / eq. softening point: 100°C) • Diaminodiphenyl sulfone (manufactured by Tokyo Chemical Industry Co., Ltd.) • Triphenylphosphine (manufactured by Tokyo Chemical Industry Co., Ltd.) • 2-phenyl-4-methylimidazole: 2P4MZ (manufactured by Shikoku Chemicals Co., Ltd.) • 3-aminopropyltriethoxysilane (manufactured by Tokyo Chemical Co., Ltd.) • 3-Glycidyloxypropyltrimethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0028] The present invention provides an epoxy resin composition that is excellent in moldability and mechanical strength, and also in mechanical strength reliability even at high temperatures, for use as a binder for metal powders, magnetic metal powders, and especially rare earth magnet powders.

Claims

1. An epoxy resin composition for metal powder binders, comprising 70-75% by weight of trisphenolmethane-type epoxy resin, 20-25% by weight of diaminodiphenyl sulfone, 0.5-1% by weight of triphenylphosphine, 0.3-1% by weight of 2-phenyl-4-methylimidazole, and 1-3% by weight of 3-aminopropyltriethoxysilane, in total weight.

2. A resin solution containing the epoxy resin composition for metal powder binder and an organic solvent as described in claim 1.

3. A solid obtained by curing a mixture consisting of the epoxy resin composition for metal powder binder and metal powder described in claim 1.

4. A resin-bonded magnetic material obtained by curing a mixture consisting of the epoxy resin composition for metal powder binder and magnetic metal powder described in claim 1.

5. A bonded magnet obtained by curing a mixture consisting of the epoxy resin composition for metal powder binder described in claim 1 and rare earth magnet powder.

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