Epoxy resin composition for magnetic metal powder binder

Abstract

To provide a technique for obtaining a green compact which is excellent in mechanical strength and heat resistance and is less prone to strength deterioration due to high-temperature storage.SOLUTION: An epoxy resin composition for a magnetic metal powder binder contains component (A): a phenol biphenylaralkyl type epoxy resin, component (B): a phenol biphenylaralkyl resin, component (C): a curing accelerator, and (D): an organic solvent.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an epoxy resin composition for a magnetic metal powder binder.

Background Art

[0002] As a technique for improving the characteristics of electronic components that utilize magnetism, such as inductors, there is one described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2017-107935). In this document, as a technique for providing a compressed powder magnetic core having high magnetic permeability and high breakdown voltage, and a coil-built-in magnetic element including the compressed powder magnetic core, it is described that the binder of the compressed powder magnetic core has a configuration including a specific epoxy resin having an ether skeleton.

[0003] Further, Patent Document 2 (Japanese Patent Application Laid-Open No. 2020-174179) describes a soft magnetic resin composition containing flat soft magnetic particles and a resin component containing an epoxy resin, a phenol resin, and an acrylic resin, wherein the epoxy resin consists only of an epoxy resin having three or more functional groups, the phenol resin consists only of a phenol resin having three or more functional groups, the content ratio of the acrylic resin in the resin component is 25% by mass or more, the epoxy resin having three or more functional groups is a tris(hydroxyphenyl)methane type epoxy resin, and the phenol resin having three or more functional groups is a phenol novolak resin. And according to this document, it is said that the soft magnetic film of the present invention obtained from the above soft magnetic resin composition is excellent in magnetic properties and can suppress the generation of voids inside the soft magnetic film.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

[0005] However, when the inventor studied the technology described in the above literature, there was room for improvement in terms of obtaining excellent mechanical strength when forming a compacted powder body and suppressing the strength deterioration due to high-temperature storage of the formed body.

[0006] The present invention provides a technology for obtaining a compacted powder body that is excellent in mechanical strength and heat resistance and has suppressed strength deterioration due to high-temperature storage. [Means for Solving the Problems]

[0007] According to the present invention, an epoxy resin composition for a magnetic metal powder binder containing the following components (A) to (D) is provided. (A) Phenol biphenyl aralkyl type epoxy resin (B) Phenol biphenyl aralkyl resin (C) Curing accelerator (D) Organic solvent

[0008] Also, according to the present invention, a solid obtained by curing a composition containing the epoxy resin composition for a magnetic metal powder binder in the present invention, magnetic metal powder, is provided. [Effects of the Invention]

[0009] According to the present invention, it is possible to obtain a compacted powder body that is excellent in mechanical strength and heat resistance and has suppressed strength deterioration due to high-temperature storage. [Modes for Carrying Out the Invention]

[0010] Hereinafter, embodiments will be described. In the present embodiment, the composition can contain each component alone or in combination of two or more. Also, "~" representing a numerical range represents "above" and "below", and includes both the upper limit value and the lower limit value.

[0011] (Epoxy resin composition for magnetic metal powder binder) The epoxy resin composition for magnetic metal powder binder (hereinafter, also simply referred to as "resin composition" as appropriate) contains the following components (A) to (D). (A) Phenol biphenyl aralkyl type epoxy resin (B) Phenol biphenyl aralkyl resin (C) Curing accelerator (D) Organic solvent

[0012] (Component (A)) Component (A) is a phenol biphenyl aralkyl type epoxy resin. Specifically, examples of component (A) include those represented by the following general formula (1).

[0013] [Chemical formula]

[0014] In the above general formula (1), m is a number from 1 to 20. From the viewpoint of improving heat resistance and suppressing strength deterioration during high-temperature storage, m is preferably 1.5 or more, more preferably 2 or more. Also, from the viewpoint of improving dissolution stability in component (D) and moldability, m is preferably 10 or less, more preferably 5 or less.

[0015] The weight average molecular weight Mwa of component (A) may be, for example, 500 or more. From the viewpoint of improving heat resistance and suppressing strength deterioration during high-temperature storage, it is preferably 1500 or more, more preferably 1600 or more, still more preferably 2000 or more, even more preferably 2500 or more, and even more preferably 3000 or more. Also, from the viewpoint of improving dissolution stability in component (D) and moldability, the weight average molecular weight Mwa is preferably 20000 or less, more preferably 10000 or less, still more preferably 8000 or less, even more preferably 5000 or less, and even more preferably 4000 or less.

[0016] From the viewpoint of improving the granulation processability and heat resistance of the magnetic metal powder / resin composite, the softening point of component (A) is preferably 60°C or higher, more preferably 65°C or higher, still more preferably 70°C or higher, and even more preferably 75°C or higher. Also, from the viewpoints of compatibility with component (B) and component (C) and improvement in solubility in component (D), the softening point of component (A) may be, for example, 100°C or lower, preferably 90°C or lower, and more preferably 85°C or lower.

[0017] From the viewpoint of achieving lower moisture absorption, the epoxy equivalent of component (A) is preferably 200 g / eq or higher, more preferably 220 g / eq or higher, still more preferably 240 g / eq or higher, even more preferably 270 g / eq or higher, and even more preferably 300 g / eq or higher. Also, from the viewpoints of improving heat resistance and mechanical strength, the epoxy equivalent of component (A) is preferably 500 g / eq or lower, more preferably 450 g / eq or lower, still more preferably 400 g / eq or lower, and even more preferably 350 g / eq or lower.

[0018] From the viewpoints of improving molding processability and curability, the content of component (A) in the resin composition is preferably 20% by mass or more, more preferably 25% by mass or more, and still more preferably 28% by mass or more based on the total resin composition. Also, from the viewpoints of improving mechanical strength and heat resistance, the content of component (A) in the resin composition is preferably 50% by mass or less, more preferably 45% by mass or less, and still more preferably 40% by mass or less based on the total resin composition.

[0019] (Component (B)) Component (B) is a phenolic biphenyl aralkyl resin. Specific examples of component (B) include those represented by the following general formula (2).

[0020]

Chemical formula

[0021] In the general formula (2) above, n is a number from 1 to 10. From the viewpoint of improving heat resistance and suppressing strength deterioration during high-temperature storage, n is preferably 1.5 or more, more preferably 2 or more. Also, from the viewpoints of improving the dissolution stability in component (D) and the moldability, n is preferably 8 or less, more preferably 4 or less.

[0022] The weight-average molecular weight Mwb of component (B) is preferably 600 or more, more preferably 700 or more, still more preferably 800 or more, and even more preferably 900 or more from the viewpoints of improving heat resistance and suppressing strength deterioration during high-temperature storage. Also, from the viewpoints of improving heat resistance and mechanical strength, the weight-average molecular weight Mwb may be, for example, 4000 or less, preferably 3000 or less, more preferably 2000 or less, still more preferably 1500 or less, and even more preferably 1000 or less.

[0023] Also, from the viewpoints of improving heat resistance and suppressing strength deterioration during high-temperature storage, it is also preferable that the weight-average molecular weight Mwb of component (B) is 2000 or less and the weight-average molecular weight Mwa of component (A) is 1500 or more.

[0024] The ratio (Mwa / Mwb) of the weight-average molecular weight Mwa of component (A) to the weight-average molecular weight Mwb of component (B) may be, for example, 0.1 or more from the viewpoint of improving mechanical strength, preferably 1.0 or more, more preferably 1.5 or more. Also, from the viewpoint of improving the curing reactivity, the above ratio (Mwa / Mwb) is preferably 7.0 or less, more preferably 5.0 or less, still more preferably 4.5 or less, and even more preferably 4.0 or less.

[0025] The softening point of component (B) is preferably 50°C or more, more preferably 55°C or more, still more preferably 60°C or more, and even more preferably 65°C or more from the viewpoints of improving the granulation processability and heat resistance of the magnetic metal powder composition. Further, from the viewpoints of compatibility with component (B) and component (C) and improvement in solubility in component (D), the softening point of component (B) is preferably 120°C or lower, more preferably 100°C or lower, still more preferably 90°C or lower, and even more preferably 80°C or lower.

[0026] From the viewpoint of lower hygroscopicity, the hydroxyl equivalent of component (B) is preferably 180 g / eq or more, more preferably 190 g / eq or more, and still more preferably 200 g / eq or more. Also, from the viewpoints of improving heat resistance and mechanical strength, the hydroxyl equivalent of component (B) is preferably 300 g / eq or less, more preferably 250 g / eq or less, and still more preferably 220 g / eq or less.

[0027] From the viewpoint of improving curability, the content of component (B) in the resin composition is preferably 10% by mass or more, more preferably 15% by mass or more, and still more preferably 18% by mass or more based on the total resin composition. Also, from the viewpoint of improving mechanical strength, the content of component (B) in the resin composition is preferably 30% by mass or less, more preferably 25% by mass or less, and still more preferably 23% by mass or less based on the total resin composition.

[0028] (Component (C)) Component (C) is a curing accelerator. As the curing accelerator, for example, those that promote the curing reaction of a thermosetting resin such as component (A) can be used. Component (C) specifically includes organic phosphines such as triphenylphosphine, tris(4-methylphenyl)phosphine, and tris(4-methoxyphenyl)phosphine; tetraphenylphosphonium tetraphenylborate, tetraphenylphosphonium tetrakis(4-methylphenyl)borate, tetraphenylphosphonium bis(naphthalene-2,3-dioxy)phenyl silicate, molecular compounds of tetraphenylphosphonium and bisphenols, and complex salts of tetraphenylphosphonium and dihydroxynaphthalenes, etc., tetrasubstituted phosphonium compounds; phosphobetaine compounds such as 2-(triphenylphosphonium)phenolate, 3-(triphenylphosphonium)phenolate, and the adduct of triphenylphosphine and 1,4-benzoquinone, etc., phosphorus atom-containing compounds (phosphorus-based curing accelerators); imidazoles such as 2-methylimidazole, 2-phenylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-benzyl-2-phenylimidazole, and 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole (imidazole-based curing accelerators); amidines exemplified by 1,8-diazabicyclo[5.4.0]undecene-7 and 1,5-diazabicyclo[4.3.0]nonene-5, tertiary amines such as benzyldimethylamine and 2,4,6-tris(dimethylaminomethyl)phenol, and nitrogen atom-containing compounds such as quaternary salts of amidines and amines and organic acids, etc., and one or more selected from the group consisting thereof are mentioned.

[0029] From the viewpoint of improving the stability of mechanical properties during high-temperature storage, component (C) is preferably a phosphorus-based curing accelerator, and more preferably at least one selected from the group consisting of triphenylphosphine and the adduct of triphenylphosphine and benzoquinone.

[0030] From the viewpoint of improving curability, the content of component (C) in the resin composition is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, still more preferably 0.1% by mass or more, and even more preferably 0.3% by mass or more based on the whole resin composition. From the viewpoint of improving the moldability and storage stability, the content of component (C) in the resin composition is preferably 3% by mass or less, more preferably 2% by mass or less, and still more preferably 1.5% by mass or less, based on the total amount of the resin composition.

[0031] (Component (D)) Component (D) is an organic solvent. Specific examples of component (D) include one or more solvents selected from the group consisting of acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone, toluene, ethyl acetate, cyclohexane, heptane, cyclohexane, cyclohexanone, tetrahydrofuran, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, ethylene glycol, cellosolves such as ethyl cellosolve, carbitols such as ethyl carbitol, anisole, and N-methylpyrrolidone. From the viewpoints of improving the solubility of components (A) to (C) and removing the solvent at low temperature, component (D) specifically includes ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, and more preferably includes methyl ethyl ketone.

[0032] The content of component (D) in the resin composition can be, for example, the remainder excluding the components other than component (D) in the resin composition. Also, from the viewpoint of improving the mixing workability with the magnetic metal powder, the content of component (D) is preferably 30% by mass or more, more preferably 35% by mass or more, still more preferably 40% by mass or more, and even more preferably 45% by mass or more, based on the total amount of the resin composition. Also, from the viewpoint of facilitating the removal of the solvent after mixing with the magnetic metal powder, the content of component (D) in the resin composition is preferably 65% by mass or less, more preferably 60% by mass or less, still more preferably 55% by mass or less, and even more preferably 50% by mass or less, based on the total amount of the resin composition.

[0033] The resin composition may contain components other than components (A) to (D). Examples of such components include one or more selected from the group consisting of a low stress agent, a coupling agent such as a silane coupling agent, an adhesion aid, a colorant, an antioxidant, a corrosion inhibitor, a dye, a pigment, a flame retardant, and non-magnetic particles such as silica. Also, from the viewpoint of reducing the adhesiveness between the magnetic metal powder and the resin, the resin composition preferably does not contain wax. Further, from the viewpoints of improving heat resistance and mechanical strength, it is also preferable that the resin composition does not contain a (meth)acrylic resin. Here, the (meth)acrylic resin means at least one of an acrylic resin and a methacrylic resin.

[0034] Next, a method for producing the resin composition will be described. The resin composition can be obtained, for example, by mixing components (A) to (D) and other raw material components as appropriate in a predetermined order. More specifically, a part of component (A) and component (D) are mixed to prepare a main agent (p), and a part of component (B) and (C) and component (D) are mixed to prepare a curing agent (q). Then, the resin composition can be obtained by mixing the main agent (p) and the curing agent (q) at a desired timing.

[0035] In the present embodiment, the resin composition is specifically suitably used as a magnetic metal powder binder. Also, in the present embodiment, the resin composition is suitably blended, for example, in a composition containing magnetic metal powder.

[0036] (Composition Containing Magnetic Metal Powder and Its Solid Matter) In the present embodiment, the composition containing magnetic metal powder includes, for example, the epoxy resin composition for magnetic metal powder binder in the present embodiment and magnetic metal powder. Also, in the present embodiment, the cured product is obtained by curing a composition containing the epoxy resin composition for magnetic metal powder binder and magnetic metal powder.

[0037] From the viewpoint of improving mechanical strength, the content of the resin composition in the composition containing magnetic metal powder is preferably 3% by mass or more, more preferably 5% by mass or more, still more preferably 8% by mass or more, and even more preferably 10% by mass or more with respect to the entire composition containing magnetic metal powder. Also, from the viewpoints of improving heat resistance and magnetic properties, the content of the resin composition in the composition containing magnetic metal powder is preferably 20% by mass or less, more preferably 18% by mass or less, and still more preferably 15% by mass or less with respect to the entire composition containing magnetic metal powder.

[0038] (Magnetic metal powder) From the viewpoint of improving magnetic properties, the magnetic metal powder preferably contains one or more elements selected from the group consisting of Fe, Cr, Co, Ni, Ag, and Mn as constituent elements.

[0039] Also, from the viewpoints of imparting preferable magnetic properties to the cured product and excellent cost and availability, the specific magnetic particles preferably contain soft magnetic particles, and more preferably contain iron-based particles. Here, soft magnetism refers to ferromagnetism with a small coercive force. Generally, ferromagnetism with a coercive force of 800 A / m or less is called soft magnetism.

[0040] Iron-based particles refer to particles having iron atoms as the main component, that is, particles having the highest content mass of iron atoms in the chemical composition, and more specifically, iron alloys having the highest content mass of iron atoms in the chemical composition. More specifically, as the iron-based particles, particles showing soft magnetism and having an iron atom content rate of 85% by mass or more, more preferably 90% by mass or more can be used.

[0041] Examples of the constituent material of such particles include metal-containing materials having an iron content rate of 85% by mass or more as a constituent element. Metal materials having a high iron content rate as a constituent element show soft magnetism with relatively good magnetic properties such as magnetic permeability and magnetic flux density. Therefore, when molded, a composition showing good magnetic properties and its cured product can be obtained. Examples of the form of the above metal-containing material include, for example, simple substances, alloys such as solid solutions, eutectics, and intermetallic compounds. By using particles composed of such metal materials, it is possible to obtain a composition having excellent magnetic properties derived from iron, that is, magnetic properties such as high magnetic permeability and high magnetic flux density, and a cured product thereof.

[0042] In addition, the above metal-containing material may contain elements other than iron as constituent elements. Specific examples of elements other than iron include one or more elements selected from the group consisting of B, C, N, O, Al, Si, P, S, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Cd, In, and Sn.

[0043] Specific examples of the above metal-containing material include pure iron, silicon steel, iron-cobalt alloy, iron-nickel alloy, iron-chromium alloy, iron-aluminum alloy, carbonyl iron, stainless steel, and composite materials containing one or more of these. Carbonyl iron can be preferably used from the viewpoint of availability.

[0044] In addition, other examples of the magnetic particles include Ni-based soft magnetic particles, Co-based soft magnetic particles, and the like.

[0045] From the viewpoint of improving the granulation processability of the magnetic metal powder / resin composite, the average particle diameter of the magnetic particles is preferably 10 μm or more, more preferably 20 μm or more, and still more preferably 30 μm or more. From the viewpoint of improving the high-frequency characteristics of the magnetic metal powder / resin composite material, the average particle diameter of the magnetic particles is preferably 200 μm or less, more preferably 100 μm or less, and still more preferably 80 μm or less. Here, the average particle diameter of the magnetic particles is measured by a laser diffraction particle size distribution measuring device (dry method).

[0046] The circularity of the magnetic particles is preferably 0.6 or more, more preferably 0.7 or more, and still more preferably 0.8 or more, from the viewpoints of the melt fluidity of the magnetic metal powder / resin composite and the high filling of the magnetic powder. Specifically, the circularity of the magnetic particles is 1.0 or less. Here, the circularity of the magnetic particles is measured by an image analysis type particle size distribution measuring apparatus (dry method).

[0047] The content of the magnetic metal powder in the composition containing the magnetic metal powder can be, for example, the remainder obtained by excluding components other than the magnetic metal powder in the composition containing the magnetic metal powder. Also, the content of the magnetic metal powder is, for example, 80% by mass or more, preferably 82% by mass or more, more preferably 85% by mass or more, with respect to the entire composition containing the magnetic metal powder, and is, for example, 99% by mass or less, preferably 98% by mass or less, more preferably 97% by mass or less, still more preferably 95% by mass or less, even more preferably 92% by mass or less, and even more preferably 90% by mass or less.

[0048] The cured product of the composition containing the magnetic metal powder is specifically obtained by compacting the composition containing the magnetic metal powder. Since the cured product contains the resin composition in the present embodiment, it can be made to have excellent mechanical strength and heat resistance, and also excellent suppression effect of strength deterioration due to high-temperature storage. Also, the cured product of the composition containing the magnetic metal powder is used, for example, in electronic components that utilize magnetism, and more specifically, can be suitably used as a material for inductors such as power inductors. Examples of reference embodiments are appended below. 1. An epoxy resin composition for a magnetic metal powder binder, containing the following components (A) to (D). (A) A phenol biphenyl aralkyl type epoxy resin (B) A phenol biphenyl aralkyl resin (C) A curing accelerator (D) An organic solvent 2. The epoxy resin composition for a magnetic metal powder binder according to 1., wherein the weight average molecular weight Mwa of the component (A) is 1500 or more. 3. The epoxy resin composition for a magnetic metal powder binder according to 1. or 2., wherein the weight average molecular weight Mwb of the component (B) is 2000 or less and the weight average molecular weight Mwa of the component (A) is 1500 or more. 4. The epoxy resin composition for a magnetic metal powder binder according to any one of 1. to 3., wherein the ratio (Mwa / Mwb) of the weight average molecular weight Mwa of the component (A) to the weight average molecular weight Mwb of the component (B) is 1.0 or more and 7.0 or less. 5. The epoxy resin composition for a magnetic metal powder binder according to any one of 1. to 4., wherein the component (C) is a phosphorus-based curing accelerator. 6. A solid obtained by curing a composition comprising the epoxy resin composition for a magnetic metal powder binder according to any one of 1. to 5., magnetic metal powder, and.

Example

[0049] Hereinafter, this embodiment will be described in detail with reference to Examples and Comparative Examples. Note that this embodiment is not limited to the descriptions of these Examples at all.

[0050] (Example 1) According to the formulation shown in Table 1, an epoxy resin composition for a magnetic metal powder binder and a composition containing magnetic metal powder were prepared by the following procedure.

[0051] (Preparation of epoxy resin composition for magnetic metal powder binder) 61.6 g of a phenol biphenyl aralkyl type epoxy resin (Epoxy Resin 1: NC-3000-FH-75M, manufactured by Nippon Kayaku Co., Ltd., a methyl ethyl ketone solution with a solid content of 75%, epoxy equivalent per solid content of 325 g / eq) was added with methyl ethyl ketone as a solvent so as to be 50% by mass, and stirred and dissolved to obtain a main agent (p). Next, 38.4 g of a phenol biphenyl aralkyl type phenol resin (Phenol Resin 1: MEHC-7851SS, manufactured by Meiwafosis Co., Ltd., hydroxyl equivalent of 203 g / eq), 2.0 g of triphenylphosphine as a curing accelerator, and methyl ethyl ketone as a solvent were added so as to be 50% by mass, and stirred and dissolved to obtain a curing agent (q).

[0052] Next, the above main agent (p) and the above curing agent (q) were mixed in total amount to obtain an epoxy resin composition (mixed solution) for a magnetic metal powder binder of this example. The equivalent ratio calculated by epoxy group / phenolic hydroxyl group in the mixed solution was 1.0, and the content of the curing accelerator was 1% by mass based on the total mass of the epoxy resin and the phenol resin.

[0053] (Preparation of composition containing magnetic metal powder) 200 g of magnetic powder (magnetic metal powder 1: manufactured by Epson Atmix Corporation, KUAMET6B2, average particle diameter 50 μm, roundness 0.85) and 25.4 g of the above-mentioned epoxy resin composition (mixed solution) for magnetic metal powder binder were mixed and stirred well to disperse the epoxy resin sufficiently in the magnetic powder, and a slurry was produced. The mixing ratio of the magnetic powder is about 94% by mass based on the total mass (solid content) of the slurry. Next, this slurry was spread out in a sheet shape, placed in a constant temperature bath, and dried at about 50 °C for 90 minutes to evaporate methyl ethyl ketone, and a solidified sheet was produced. Subsequently, the sheet was pulverized, and particles were obtained by passing through a mesh with an opening of 500 μm. The obtained particles were placed in a vacuum constant temperature bath, and dried under reduced pressure at 50 °C and 40 Torr for 60 minutes to evaporate the remaining methyl ethyl ketone and size the particles, and granulated powder of the composition containing magnetic metal powder was obtained.

[0054] (Examples 2 to 12 and Comparative Examples 1 to 4) The compositions were prepared according to Example 1, except that the formulations of the main agent (p), the curing agent (q), the epoxy resin composition for magnetic metal powder binder, and the composition containing magnetic metal powder were as described in Table 1 or Table 2, respectively.

[0055] In Table 1 and Table 2, the amounts of the respective components are the active amounts. Also, the details of each component in Table 1 and Table 2 are as follows. "Equivalent weight" is the epoxy equivalent weight for epoxy resin and the hydroxyl equivalent weight for phenol resin. (Epoxy resin) (A) Epoxy resin 1: Phenol biphenyl aralkyl type epoxy resin, manufactured by Nippon Kayaku Co., Ltd., NC-3000-FH-75M, softening point 80 °C, epoxy equivalent weight 325 g / eq, weight average molecular weight 3380 (A) Epoxy resin 2: Phenol biphenyl aralkyl type epoxy resin, manufactured by Nippon Kayaku Co., Ltd., NC-3000-H, softening point 70 °C, epoxy equivalent weight 290 g / eq, weight average molecular weight 1780 (A) Epoxy Resin 3: Phenol Biphenyl Aralkyl Type Epoxy Resin, manufactured by Nippon Kayaku Co., Ltd., NC-3100, softening point 95°C, epoxy equivalent 260 g / eq, weight average molecular weight 660 Epoxy Resin 4: Bisphenol A Type Epoxy Resin, manufactured by Mitsubishi Chemical Corporation, Jer-1004, softening point 97°C, epoxy equivalent 925 g / eq, weight average molecular weight 3300 Epoxy Resin 5: Ortho-Cresol Novolak Type Epoxy Resin, manufactured by Nippon Kayaku Co., Ltd., EOCN-102S, softening point 65°C, epoxy equivalent 210 g / eq, weight average molecular weight 1480 Epoxy Resin 6: Phenol Aralkyl Type Epoxy Resin, manufactured by Nippon Kayaku Co., Ltd., NC-2000-L, softening point 52°C, epoxy equivalent 235 g / eq, weight average molecular weight 1730 (Phenolic Resin) (B) Phenolic Resin 1: Phenol Biphenyl Aralkyl Resin, manufactured by Meiwa Kasei Co., Ltd., MEHC-7851SS, softening point 66°C, hydroxyl equivalent 203 g / eq, weight average molecular weight 970 (B) Phenolic Resin 2: Phenol Biphenyl Aralkyl Resin, manufactured by Meiwa Kasei Co., Ltd., MEHC-7851H, softening point 85°C, hydroxyl equivalent 216 g / eq, weight average molecular weight 1620 (B) Phenolic Resin 3: Phenol Biphenyl Aralkyl Resin, manufactured by Nippon Kayaku Co., Ltd., KAYAHARD GPH-103, softening point 102°C, hydroxyl equivalent 230 g / eq, weight average molecular weight 3240 Phenolic Resin 4: Phenol Novolak Resin, manufactured by Sumitomo Bakelite Co., Ltd., PR-51714, softening point 95°C, hydroxyl equivalent 104 g / eq, weight average molecular weight 1670 Phenolic Resin 5: Phenol Aralkyl Resin, manufactured by Meiwa Kasei Co., Ltd., MEHC-7800-4S, softening point 62°C, hydroxyl equivalent 168 g / eq, weight average molecular weight 1130 (Curing Accelerator) (C) Triphenylphosphine: PP-360, manufactured by K.I. Kasei Co., Ltd. (C) Adduct of Triphenylfin and 1,4-Benzoquinone: TPP-BQ, manufactured by K.I. Kasei Co., Ltd. (C) 2-Phenylimidazole: 2PZ, manufactured by Shikoku Chemicals Corporation (C) 1-Cyanoethyl-2-phenylimidazole: 2PZ-CN, manufactured by Shikoku Chemicals Corporation (Magnetic metal powder) Magnetic metal powder 1: manufactured by Epson Atmix Corporation, KUAMET6B2, average particle diameter 50 μm, circularity 0.85

[0056] (Weight-average molecular weight) The weight-average molecular weights of the epoxy resin and the phenolic resin were measured by gel permeation chromatography (GPC) and calculated based on the calibration curve prepared using polystyrene standard substances.

[0057] (Evaluation) (Preparation of test specimens) Test specimens for measuring the flexural strength, the flexural strength after heat treatment, and the glass transition temperature were prepared by powder pressing molding method according to the following procedure. That is, the granulated powder of the composition containing the magnetic metal powder obtained in each example was compression molded at a pressure of 60 MPa for 30 minutes in a test specimen mold at 160 °C to obtain a molded product with a width of 10 mm, a thickness of 4 mm, and a length of 80 mm. The obtained molded product was post-cured at 200 °C for 1 hour to prepare a test specimen.

[0058] (Flexural strength) The flexural strength (MPa) at 25 °C of the obtained test specimen was measured in accordance with JIS K 6911.

[0059] (Flexural strength after heat treatment) The obtained test specimen was heat-treated at 200 °C for 1000 hours, cooled to room temperature, and the flexural strength (MPa) at 25 °C was measured in accordance with JIS K 6911.

[0060] (Strength retention rate) From the above-mentioned flexural strength and the flexural strength after heat treatment, the strength retention rate was determined by the following formula. Strength retention rate (%) = flexural strength / flexural strength after heat treatment × 100

[0061] (Glass transition temperature) The above test piece was cut into a size of 40 mm × 10 mm × 1 mm using a precision cutting machine to obtain a test piece for measuring the glass transition temperature. Subsequently, for the obtained test piece, a dynamic viscoelasticity measurement was performed using a thermomechanical analyzer (manufactured by Seiko Instruments Inc., DMS6100) under the conditions of a measurement temperature range of 25°C to 300°C, a heating rate of 5°C / min, and a frequency of 1 Hz. The temperature (°C) at the peak value of tanδ was defined as the glass transition temperature.

[0062]

Table 1

[0063]

Table 2

[0064] From Table 1 and Table 2, in each example, the balance of the heat resistance (glass transition temperature), flexural strength, and strength retention rate after heat treatment of the cured product of the composition containing magnetic metal powder was excellent.

Claims

1. An epoxy resin composition for a magnetic metal powder binder, comprising the following components (A) to (D), wherein the epoxy resin in the epoxy resin composition for a magnetic metal powder binder is the following component (A), and the epoxy resin composition for a magnetic metal powder binder does not contain non-magnetic particles. (A) Phenol biphenyl aralkyl type epoxy resin (B) Phenol biphenyl aralkyl resin (C) Curing accelerator (D) Organic solvent

2. The epoxy resin composition for a magnetic metal powder binder according to Claim 1, wherein the weight average molecular weight Mwa of the component (A) is 1500 or more.

3. The epoxy resin composition for a magnetic metal powder binder according to Claim 1 or 2, wherein the weight average molecular weight Mwb of the component (B) is 2000 or less and the weight average molecular weight Mwa of the component (A) is 1500 or more.

4. The epoxy resin composition for a magnetic metal powder binder according to any one of Claims 1 to 3, wherein the ratio (Mwa / Mwb) of the weight average molecular weight Mwa of the component (A) to the weight average molecular weight Mwb of the component (B) is 1.0 or more and 7.0 or less.

5. The epoxy resin composition for a magnetic metal powder binder according to any one of Claims 1 to 4, wherein the component (C) is a phosphorus-based curing accelerator.

6. A method for producing a cured product, comprising curing a composition containing the epoxy resin composition for a magnetic metal powder binder according to any one of Claims 1 to 5 and magnetic metal powder by powder compression molding to obtain a cured product.

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