JP7387528B2 - Powder magnetic core and its manufacturing method - Google Patents
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- 239000000843 powder Substances 0.000 title claims description 79
- 238000004519 manufacturing process Methods 0.000 title claims description 9
- 239000002122 magnetic nanoparticle Substances 0.000 claims description 86
- 229920002554 vinyl polymer Polymers 0.000 claims description 76
- 125000002887 hydroxy group Chemical group [H]O* 0.000 claims description 47
- 125000002777 acetyl group Chemical group [H]C([H])([H])C(*)=O 0.000 claims description 39
- 239000002245 particle Substances 0.000 claims description 26
- 239000000203 mixture Substances 0.000 claims description 15
- 229910052751 metal Inorganic materials 0.000 claims description 11
- 239000002184 metal Substances 0.000 claims description 11
- 238000010438 heat treatment Methods 0.000 claims description 7
- 229910044991 metal oxide Inorganic materials 0.000 claims description 7
- 150000004706 metal oxides Chemical class 0.000 claims description 7
- 238000002156 mixing Methods 0.000 claims description 7
- 238000000034 method Methods 0.000 claims description 5
- 229910052742 iron Inorganic materials 0.000 claims description 2
- 239000011162 core material Substances 0.000 description 85
- 230000007423 decrease Effects 0.000 description 26
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 19
- 239000002105 nanoparticle Substances 0.000 description 19
- 230000000052 comparative effect Effects 0.000 description 16
- 238000000465 moulding Methods 0.000 description 16
- 239000000428 dust Substances 0.000 description 15
- 239000008188 pellet Substances 0.000 description 11
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 description 9
- 239000000314 lubricant Substances 0.000 description 9
- 239000002082 metal nanoparticle Substances 0.000 description 7
- 229910045601 alloy Inorganic materials 0.000 description 5
- 239000000956 alloy Substances 0.000 description 5
- 235000014113 dietary fatty acids Nutrition 0.000 description 5
- 239000000194 fatty acid Substances 0.000 description 5
- 229930195729 fatty acid Natural products 0.000 description 5
- 239000006249 magnetic particle Substances 0.000 description 5
- 229920003023 plastic Polymers 0.000 description 5
- 229910000859 α-Fe Inorganic materials 0.000 description 5
- 235000021355 Stearic acid Nutrition 0.000 description 4
- 239000011248 coating agent Substances 0.000 description 4
- 238000000576 coating method Methods 0.000 description 4
- 150000004665 fatty acids Chemical class 0.000 description 4
- QIQXTHQIDYTFRH-UHFFFAOYSA-N octadecanoic acid Chemical compound CCCCCCCCCCCCCCCCCC(O)=O QIQXTHQIDYTFRH-UHFFFAOYSA-N 0.000 description 4
- OQCDKBAXFALNLD-UHFFFAOYSA-N octadecanoic acid Natural products CCCCCCCC(C)CCCCCCCCC(O)=O OQCDKBAXFALNLD-UHFFFAOYSA-N 0.000 description 4
- 229920002037 poly(vinyl butyral) polymer Polymers 0.000 description 4
- 229920005989 resin Polymers 0.000 description 4
- 239000011347 resin Substances 0.000 description 4
- 150000003839 salts Chemical class 0.000 description 4
- 239000008117 stearic acid Substances 0.000 description 4
- 229910002555 FeNi Inorganic materials 0.000 description 3
- 238000000748 compression moulding Methods 0.000 description 3
- 239000000470 constituent Substances 0.000 description 3
- HGPXWXLYXNVULB-UHFFFAOYSA-M lithium stearate Chemical compound [Li+].CCCCCCCCCCCCCCCCCC([O-])=O HGPXWXLYXNVULB-UHFFFAOYSA-M 0.000 description 3
- 239000000696 magnetic material Substances 0.000 description 3
- 229920002050 silicone resin Polymers 0.000 description 3
- 239000002904 solvent Substances 0.000 description 3
- ZTQSAGDEMFDKMZ-UHFFFAOYSA-N Butyraldehyde Chemical group CCCC=O ZTQSAGDEMFDKMZ-UHFFFAOYSA-N 0.000 description 2
- 229910003962 NiZn Inorganic materials 0.000 description 2
- -1 fatty acid esters Chemical class 0.000 description 2
- 239000004519 grease Substances 0.000 description 2
- 230000006698 induction Effects 0.000 description 2
- 239000004570 mortar (masonry) Substances 0.000 description 2
- 229910000889 permalloy Inorganic materials 0.000 description 2
- 230000035699 permeability Effects 0.000 description 2
- 229920001296 polysiloxane Polymers 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- WRIDQFICGBMAFQ-UHFFFAOYSA-N (E)-8-Octadecenoic acid Natural products CCCCCCCCCC=CCCCCCCC(O)=O WRIDQFICGBMAFQ-UHFFFAOYSA-N 0.000 description 1
- LQJBNNIYVWPHFW-UHFFFAOYSA-N 20:1omega9c fatty acid Natural products CCCCCCCCCCC=CCCCCCCCC(O)=O LQJBNNIYVWPHFW-UHFFFAOYSA-N 0.000 description 1
- QSBYPNXLFMSGKH-UHFFFAOYSA-N 9-Heptadecensaeure Natural products CCCCCCCC=CCCCCCCCC(O)=O QSBYPNXLFMSGKH-UHFFFAOYSA-N 0.000 description 1
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 229910000976 Electrical steel Inorganic materials 0.000 description 1
- 229910002546 FeCo Inorganic materials 0.000 description 1
- 229910005347 FeSi Inorganic materials 0.000 description 1
- 229910001030 Iron–nickel alloy Inorganic materials 0.000 description 1
- ZQPPMHVWECSIRJ-UHFFFAOYSA-N Oleic acid Natural products CCCCCCCCC=CCCCCCCCC(O)=O ZQPPMHVWECSIRJ-UHFFFAOYSA-N 0.000 description 1
- 239000005642 Oleic acid Substances 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- 239000011354 acetal resin Substances 0.000 description 1
- DHKHKXVYLBGOIT-UHFFFAOYSA-N acetaldehyde Diethyl Acetal Natural products CCOC(C)OCC DHKHKXVYLBGOIT-UHFFFAOYSA-N 0.000 description 1
- DTOSIQBPPRVQHS-PDBXOOCHSA-N alpha-linolenic acid Chemical compound CC\C=C/C\C=C/C\C=C/CCCCCCCC(O)=O DTOSIQBPPRVQHS-PDBXOOCHSA-N 0.000 description 1
- 235000020661 alpha-linolenic acid Nutrition 0.000 description 1
- 150000001491 aromatic compounds Chemical class 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000001506 calcium phosphate Substances 0.000 description 1
- 229910000389 calcium phosphate Inorganic materials 0.000 description 1
- 235000011010 calcium phosphates Nutrition 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 239000004205 dimethyl polysiloxane Substances 0.000 description 1
- 235000013870 dimethyl polysiloxane Nutrition 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 150000002148 esters Chemical class 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 239000000017 hydrogel Substances 0.000 description 1
- CPSYWNLKRDURMG-UHFFFAOYSA-L hydron;manganese(2+);phosphate Chemical compound [Mn+2].OP([O-])([O-])=O CPSYWNLKRDURMG-UHFFFAOYSA-L 0.000 description 1
- 150000002484 inorganic compounds Chemical class 0.000 description 1
- 229910010272 inorganic material Inorganic materials 0.000 description 1
- 229910000398 iron phosphate Inorganic materials 0.000 description 1
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 description 1
- QXJSBBXBKPUZAA-UHFFFAOYSA-N isooleic acid Natural products CCCCCCCC=CCCCCCCCCC(O)=O QXJSBBXBKPUZAA-UHFFFAOYSA-N 0.000 description 1
- 229960004488 linolenic acid Drugs 0.000 description 1
- KQQKGWQCNNTQJW-UHFFFAOYSA-N linolenic acid Natural products CC=CCCC=CCC=CCCCCCCCC(O)=O KQQKGWQCNNTQJW-UHFFFAOYSA-N 0.000 description 1
- 230000001050 lubricating effect Effects 0.000 description 1
- 239000006247 magnetic powder Substances 0.000 description 1
- 230000005389 magnetism Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 229910001463 metal phosphate Inorganic materials 0.000 description 1
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 1
- LAQFLZHBVPULPL-UHFFFAOYSA-N methyl(phenyl)silicon Chemical compound C[Si]C1=CC=CC=C1 LAQFLZHBVPULPL-UHFFFAOYSA-N 0.000 description 1
- ZQPPMHVWECSIRJ-KTKRTIGZSA-N oleic acid Chemical compound CCCCCCCC\C=C/CCCCCCCC(O)=O ZQPPMHVWECSIRJ-KTKRTIGZSA-N 0.000 description 1
- 235000021313 oleic acid Nutrition 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 150000003013 phosphoric acid derivatives Chemical class 0.000 description 1
- 229920000435 poly(dimethylsiloxane) Polymers 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 229920006324 polyoxymethylene Polymers 0.000 description 1
- 230000008707 rearrangement Effects 0.000 description 1
- 235000003441 saturated fatty acids Nutrition 0.000 description 1
- 150000004671 saturated fatty acids Chemical class 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000001694 spray drying Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- QORWJWZARLRLPR-UHFFFAOYSA-H tricalcium bis(phosphate) Chemical compound [Ca+2].[Ca+2].[Ca+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O QORWJWZARLRLPR-UHFFFAOYSA-H 0.000 description 1
- LRXTYHSAJDENHV-UHFFFAOYSA-H zinc phosphate Chemical compound [Zn+2].[Zn+2].[Zn+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O LRXTYHSAJDENHV-UHFFFAOYSA-H 0.000 description 1
- 229910000165 zinc phosphate Inorganic materials 0.000 description 1
- XOOUIPVCVHRTMJ-UHFFFAOYSA-L zinc stearate Chemical compound [Zn+2].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O XOOUIPVCVHRTMJ-UHFFFAOYSA-L 0.000 description 1
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- Powder Metallurgy (AREA)
- Soft Magnetic Materials (AREA)
Description
本発明は、圧粉磁心及びその製造方法に関し、より詳しくは、磁性ナノ粒子を用いた圧粉磁心及びその製造方法に関する。 The present invention relates to a powder magnetic core and a manufacturing method thereof, and more particularly to a powder magnetic core using magnetic nanoparticles and a manufacturing method thereof.
圧粉磁心は、表面が絶縁被膜で覆われた磁性粒子を圧縮成形することによって得られるものであり、変圧器（トランス）、電動機（モータ）、発電機、スピーカ、誘導加熱器、各種アクチュエータ等の電磁気を利用した様々な製品に用いられている。このような圧粉磁心としては、例えば、軟磁性材料からなる粒径５～２００μｍの粉末の表面を、シリコーン樹脂で被覆し、さらに、ステアリン酸又はその金属塩からなる高級脂肪酸潤滑剤で被覆した軟磁性粉末をプレス成形し、熱処理することによって得られる磁心（特開２０００－２２３３０８号公報（特許文献１））、金属磁性粒子と、その表面を取り囲む、リン酸金属塩及び金属酸化物のうちの少なくとも一方を含む絶縁被膜と、この絶縁被膜の表面を取り囲む、ステアリン酸等の金属塩からなる金属石鹸を含む潤滑剤被膜とを有する複合磁性粒子を備える圧粉磁心（特開２００５－１２９７１６号公報（特許文献２））、表面にリン酸塩からなる絶縁被膜を有する平均粒径が３０～５００μｍの鉄基粉末と、ＯＨ基を有する脂肪酸のエステルを含む潤滑剤とを備える軟磁性材料を加圧成形し、熱処理することによって得られる圧粉磁心（特開２００７－２１１３４１号公報（特許文献３））、絶縁被膜を備える平均粒径が２００～４５０μｍの被覆鉄粉と、脂肪酸アミドからなる潤滑剤とを含む圧粉磁心（特開２０１６－１２６８８号公報（特許文献４））が知られている。 Powder magnetic cores are obtained by compression molding magnetic particles whose surfaces are covered with an insulating film, and are used in transformers, electric motors, generators, speakers, induction heaters, various actuators, etc. It is used in various products that utilize electromagnetism. Such a dust core may be made of, for example, a powder made of a soft magnetic material with a particle size of 5 to 200 μm, the surface of which is coated with a silicone resin, and further coated with a higher fatty acid lubricant made of stearic acid or its metal salt. A magnetic core obtained by press-molding soft magnetic powder and heat treating it (Japanese Unexamined Patent Publication No. 2000-223308 (Patent Document 1)), metal magnetic particles, and metal phosphate salts and metal oxides surrounding the surface thereof. A powder magnetic core comprising composite magnetic particles having an insulating coating containing at least one of Publication (Patent Document 2)) describes a soft magnetic material comprising an iron-based powder having an insulating coating made of phosphate on the surface and having an average particle size of 30 to 500 μm, and a lubricant containing an ester of a fatty acid having an OH group. A powder magnetic core obtained by pressure molding and heat treatment (Japanese Unexamined Patent Publication No. 2007-211341 (Patent Document 3)), consisting of coated iron powder with an insulating coating and an average particle size of 200 to 450 μm, and fatty acid amide A powder magnetic core (Japanese Unexamined Patent Publication No. 2016-12688 (Patent Document 4)) containing a lubricant is known.
一方、磁性ナノ粒子は、そのサイズが極めて小さいため、バルクの磁性材料とは異なる性質を示し、例えば、粒径が約１００ｎｍを超える範囲では、粒径が小さくなるにつれて保磁力が大きくなり、粒径が約１００ｎｍ付近で保磁力が最大となるが、粒径が約２０ｎｍ以下になると、超常磁性現象が発現して保持力が極めて小さくなる。このため、粒径が約２０ｎｍ以下の磁性ナノ粒子を用いた圧粉磁心においては、ヒステリシス損を極めて小さくすることが可能になると考えられる。また、絶縁性の磁性ナノ粒子や表面に絶縁被膜を有する導電性の磁性ナノ粒子を用いた圧粉磁心において、粒径が約３００ｎｍ以下の磁性ナノ粒子を用いることによって、高周波において渦電流の経路が制限され、渦電流損を小さくすることが可能になると考えられ、特に、粒径が約２０ｎｍ以下の磁性ナノ粒子を用いることによって、渦電流損を極めて小さくすることができると考えられる。このように、粒径が約２０ｎｍ以下の磁性ナノ粒子を用いた圧粉磁心は、ヒステリシス損や渦電流損が極めて小さくなるため、電源用途のトランスコア材として期待されている。 On the other hand, since magnetic nanoparticles are extremely small in size, they exhibit properties different from those of bulk magnetic materials. For example, in a particle size range exceeding about 100 nm, the coercive force increases as the particle size decreases; The coercive force is maximum when the particle size is around 100 nm, but when the particle size is less than about 20 nm, a superparamagnetic phenomenon occurs and the coercive force becomes extremely small. For this reason, it is thought that in a dust core using magnetic nanoparticles having a particle size of about 20 nm or less, it is possible to make the hysteresis loss extremely small. In addition, in powder magnetic cores using insulating magnetic nanoparticles or conductive magnetic nanoparticles with an insulating coating on the surface, by using magnetic nanoparticles with a particle size of approximately 300 nm or less, it is possible to create a path for eddy currents at high frequencies. It is thought that this makes it possible to reduce the eddy current loss, and in particular, by using magnetic nanoparticles with a particle size of about 20 nm or less, the eddy current loss can be made extremely small. As described above, a dust core using magnetic nanoparticles having a particle size of about 20 nm or less has extremely low hysteresis loss and eddy current loss, and is therefore expected to be used as a transformer core material for power supply applications.
また、ポリビニルホルマール樹脂やポリビニルアセトアセタール樹脂、ポリビニルブチラール樹脂等のポリビニルアセタール樹脂は、ボンド磁石の樹脂バインダーとして知られている（特開平５－３２６２３１号公報（特許文献５））。 Furthermore, polyvinyl acetal resins such as polyvinyl formal resin, polyvinyl acetoacetal resin, and polyvinyl butyral resin are known as resin binders for bonded magnets (Japanese Patent Laid-Open No. 5-326231 (Patent Document 5)).
しかしながら、ステアリン酸等又はそれらの金属塩、脂肪酸エステル、或いは脂肪酸アミド等の従来の潤滑剤と磁性ナノ粒子とを混合し、従来の成形条件（例えば、成形温度：１５０℃、成形圧力：１．４ＧＰａ）で圧縮成形しても、得られる圧粉磁心の密度は必ずしも十分に高いものではなかった。これは、磁性粒子がナノサイズまで小さくなると、磁性粒子の塑性変形強度が高くなり、従来の成形条件では磁性ナノ粒子が十分に塑性変形しなかったためと考えられる。そこで、成形温度を高くすることによって、磁性ナノ粒子を十分に塑性変形させることが可能になると考えられるが、成形温度を高くしすぎると、金型の強度が低下するという問題があった。 However, when magnetic nanoparticles are mixed with conventional lubricants such as stearic acid or their metal salts, fatty acid esters, or fatty acid amides, conventional molding conditions (for example, molding temperature: 150°C, molding pressure: 1. 4 GPa), the density of the powder magnetic core obtained was not always sufficiently high. This is thought to be because the plastic deformation strength of the magnetic particles increases when the magnetic particles are reduced to nano-size, and the magnetic nanoparticles were not sufficiently plastically deformed under conventional molding conditions. Therefore, it is thought that increasing the molding temperature makes it possible to sufficiently plastically deform the magnetic nanoparticles, but if the molding temperature is made too high, there is a problem that the strength of the mold decreases.
本発明者らは、金属ナノ粒子の融点がバルクの金属の融点よりも低下することに着目し、金属ナノ粒子の塑性変形強度が低くなる温度もバルクの金属の塑性変形強度が低くなる温度よりも低下すると考え、従来の成形温度よりも高い温度であっても、磁性ナノ粒子の塑性変形強度が低くなり、かつ、金型の強度が低下しない温度範囲が存在し、この範囲内の温度で磁性ナノ粒子を加熱することによって、磁性ナノ粒子を十分に塑性変形させることが可能であり、高密度の圧粉磁心を得ることができると考えた。 The present inventors focused on the fact that the melting point of metal nanoparticles is lower than that of bulk metal, and the temperature at which the plastic deformation strength of metal nanoparticles becomes lower is also lower than the temperature at which the plastic deformation strength of bulk metal becomes lower. Even if the temperature is higher than the conventional molding temperature, there is a temperature range in which the plastic deformation strength of the magnetic nanoparticles is low and the strength of the mold is not reduced. We thought that by heating the magnetic nanoparticles, it would be possible to sufficiently plastically deform the magnetic nanoparticles and obtain a high-density dust core.
しかしながら、従来の潤滑剤と磁性ナノ粒子とを混合して圧縮成形しても、従来の潤滑剤であるステアリン酸又はそれらの金属塩等が低分子量であるため、十分に高い分子間結合力が得られず、十分に高い機械的強度を有する圧粉磁心は得られなかった。 However, even if conventional lubricants and magnetic nanoparticles are mixed and compression-molded, the intermolecular bond strength is sufficiently high because conventional lubricants such as stearic acid or their metal salts have low molecular weights. Therefore, a powder magnetic core having sufficiently high mechanical strength could not be obtained.
本発明は、上記従来技術の有する課題に鑑みてなされたものであり、３００℃以上の温度で成形され、密度及び機械的強度が高い圧粉磁心を提供することを目的とする。 The present invention has been made in view of the above-mentioned problems of the prior art, and aims to provide a powder magnetic core that is molded at a temperature of 300° C. or higher and has high density and mechanical strength.
本発明者らは、上記目的を達成すべく鋭意研究を重ねた結果、磁性ナノ粒子にアセトアセタール化度、アセチル基含有率、水酸基含有率及びアセトアセタール基数とアセチル基数と水酸基数との合計が特定の範囲内にあるポリビニルアセトアセタールを添加して圧縮成形することによって、３００℃以上の温度で成形した場合でも、密度及び機械的強度が高い圧粉磁心が得られることを見出し、本発明を完成するに至った。 As a result of intensive research to achieve the above object, the present inventors found that magnetic nanoparticles have a degree of acetoacetalization, acetyl group content, hydroxyl group content, and the total number of acetoacetal groups, acetyl groups, and hydroxyl groups. It was discovered that by adding polyvinyl acetoacetal within a specific range and compression molding, a powder magnetic core with high density and mechanical strength could be obtained even when molded at a temperature of 300°C or higher, and the present invention was developed. It has been completed.
すなわち、本発明の圧粉磁心は、平均粒径が１～３００ｎｍの磁性ナノ粒子と、
下記式（１）：
That is, the powder magnetic core of the present invention comprises magnetic nanoparticles with an average particle size of 1 to 300 nm,
The following formula (1):
で表され、前記式（１）中のｉ、ｊ及びｋにより求められる、
アセトアセタール化度〔ｉ／（ｉ＋ｊ＋ｋ）〕が０．５０～０．６９９９の範囲内にあり、アセチル基含有率〔ｊ／（ｉ＋ｊ＋ｋ）〕が０．０００１～０．０５の範囲内にあり、
水酸基含有率〔ｋ／（ｉ＋ｊ＋ｋ）〕が０．３０～０．４９９９の範囲内にあり、
アセトアセタール基数とアセチル基数と水酸基数との合計〔ｉ＋ｊ＋ｋ〕が１００～１００００の範囲内にあるポリビニルアセトアセタールと、
を含有することを特徴とするものである。
is expressed by i, j and k in the above formula (1),
The degree of acetoacetalization [i/(i+j+k)] is within the range of 0.50 to 0.6999, the acetyl group content [j/(i+j+k)] is within the range of 0.0001 to 0.05,
The hydroxyl group content [k/(i+j+k)] is within the range of 0.30 to 0.4999,
polyvinyl acetoacetal in which the sum of the number of acetoacetal groups, the number of acetyl groups, and the number of hydroxyl groups [i+j+k] is within the range of 100 to 10,000;
It is characterized by containing.
本発明の圧粉磁心においては、前記ポリビニルアセトアセタールの含有量が圧粉磁心全体に対して０．０１～５質量％であることが好ましく、また、前記磁性ナノ粒子が、Ｆｅ含有金属磁性ナノ粒子、Ｆｅ含有金属酸化物磁性ナノ粒子、及び表面に絶縁層を備えるＦｅ含有金属磁性ナノ粒子からなる群から選択される少なくとも１種であることが好ましい。 In the powder magnetic core of the present invention, the content of the polyvinyl acetoacetal is preferably 0.01 to 5% by mass based on the entire powder magnetic core, and the magnetic nanoparticles are Fe-containing metal magnetic nanoparticles. The material is preferably at least one selected from the group consisting of particles, Fe-containing metal oxide magnetic nanoparticles, and Fe-containing metal magnetic nanoparticles having an insulating layer on the surface.
本発明の圧粉磁心の製造方法は、平均粒径が１～３００ｎｍの磁性ナノ粒子と、下記式（１）： The method for producing a powder magnetic core of the present invention includes magnetic nanoparticles having an average particle size of 1 to 300 nm and the following formula (1):
で表され、前記式（１）中のｉ、ｊ及びｋにより求められる、
アセトアセタール化度〔ｉ／（ｉ＋ｊ＋ｋ）〕が０．５０～０．６９９９の範囲内にあり、アセチル基含有率〔ｊ／（ｉ＋ｊ＋ｋ）〕が０．０００１～０．０５の範囲内にあり、
水酸基含有率〔ｋ／（ｉ＋ｊ＋ｋ）〕が０．３０～０．４９９９の範囲内にあり、
アセトアセタール基数とアセチル基数と水酸基数との合計〔ｉ＋ｊ＋ｋ〕が１００～１００００の範囲内にあるポリビニルアセトアセタールとの混合物を加圧しながら３００℃以上の温度で加熱することを特徴とする特徴とする方法である。
is expressed by i, j and k in the above formula (1),
The degree of acetoacetalization [i/(i+j+k)] is within the range of 0.50 to 0.6999, the acetyl group content [j/(i+j+k)] is within the range of 0.0001 to 0.05,
The hydroxyl group content [k/(i+j+k)] is within the range of 0.30 to 0.4999,
A feature characterized by heating a mixture with polyvinyl acetoacetal in which the sum of the number of acetoacetal groups, the number of acetyl groups, and the number of hydroxyl groups [i+j+k] is within the range of 100 to 10,000 at a temperature of 300° C. or higher while pressurizing the mixture. It's a method.
本発明の圧粉磁心の製造方法においては、前記磁性ナノ粒子と前記ポリビニルアセトアセタールとの混合比率が質量比（磁性ナノ粒子／ポリビニルアセトアセタール）で９９．９９／０．０１～９５／５であることが好ましく、また、３００～６００℃の範囲内の温度で加熱することが好ましく、５００ＭＰａ～３ＧＰａの範囲内の圧力で加圧することが好ましい。 In the method for producing a dust core of the present invention, the mixing ratio of the magnetic nanoparticles and the polyvinyl acetoacetal is 99.99/0.01 to 95/5 in terms of mass ratio (magnetic nanoparticles/polyvinylacetoacetal). Preferably, the temperature is within the range of 300 to 600° C., and the pressure is preferably within the range of 500 MPa to 3 GPa.
なお、前記磁性ナノ粒子に前記ポリビニルアセトアセタールを添加することによって、３００℃以上の温度で成形した場合でも、前記磁性ナノ粒子を含有し、密度及び機械的強度が高い圧粉磁心が得られる理由は必ずしも定かではないが、本発明者らは以下のように推察する。 The reason why a powder magnetic core containing the magnetic nanoparticles and having high density and mechanical strength can be obtained even when molded at a temperature of 300° C. or higher by adding the polyvinyl acetoacetal to the magnetic nanoparticles. Although it is not necessarily certain, the present inventors speculate as follows.
すなわち、ポリビニルアセトアセタールは、アセトアセタール化度が高くなると、機械的強度及び柔軟性が向上し、クラックの発生が抑制される。また、水酸基含有率が高くなると、磁性ナノ粒子との間で強い結合力が得られ、磁性ナノ粒子間の結合力を向上させることができる。しかしながら、前記アセトアセタール化度と前記水酸基含有率は相反関係にあるため、アセトアセタール化度が高くなると、相対的に水酸基含有率が低くなり、ポリビニルアセトアセタールと磁性ナノ粒子との間の結合力が低下し、磁性ナノ粒子間の結合力が低下する。また、水酸基含有率が高くなると、相対的にアセトアセタール化度が低くなり、ポリビニルアセトアセタールの機械的強度及び柔軟性が低下してクラックが発生する。 That is, when the degree of acetoacetalization of polyvinyl acetoacetal increases, mechanical strength and flexibility improve, and the occurrence of cracks is suppressed. Furthermore, when the hydroxyl group content is high, a strong bonding force can be obtained between the magnetic nanoparticles and the bonding force between the magnetic nanoparticles can be improved. However, since the degree of acetoacetalization and the hydroxyl group content are in a reciprocal relationship, as the degree of acetoacetalization increases, the hydroxyl group content decreases relatively, and the bonding force between polyvinyl acetoacetal and magnetic nanoparticles increases. decreases, and the bonding force between magnetic nanoparticles decreases. Furthermore, when the hydroxyl group content becomes high, the degree of acetoacetalization becomes relatively low, and the mechanical strength and flexibility of polyvinyl acetoacetal decreases, causing cracks to occur.
本発明においては、アセトアセタール化度及び水酸基含有率がそれぞれ特定の範囲内にあるポリビニルアセトアセタールを用いているため、ポリビニルアセトアセタールと磁性ナノ粒子との間における強い結合力による磁性ナノ粒子間の強い結合力と、ポリビニルアセトアセタールの高い機械的強度及び高い柔軟性の両特性がバランスよく得られ、その結果、密度及び機械的強度に優れた圧粉磁心が得られると推察される。 In the present invention, since polyvinyl acetoacetal whose degree of acetoacetalization and hydroxyl group content are within specific ranges is used, the strong bonding force between the polyvinyl acetoacetal and the magnetic nanoparticles causes It is presumed that strong bonding force and both the high mechanical strength and high flexibility properties of polyvinyl acetoacetal can be obtained in a well-balanced manner, and as a result, a powder magnetic core with excellent density and mechanical strength can be obtained.
また、本発明においては、前記ポリビニルアセトアセタールが高分子であることから、分子間の絡み合いが大きく、分子同士の結合力が強いため、密度及び機械的強度がより高い圧粉磁心が得られると推察される。 In addition, in the present invention, since the polyvinyl acetoacetal is a polymer, the entanglement between molecules is large, and the bonding force between molecules is strong, so that a powder magnetic core with higher density and mechanical strength can be obtained. It is inferred.
さらに、本発明においては、前記ポリビニルアセトアセタールが高温での揮発や分解が起こりにくいため、３００℃以上の温度で成形しても、高い密度及び高い機械的強度が維持された圧粉磁心が得られると推察される。 Furthermore, in the present invention, since the polyvinyl acetoacetal is difficult to volatilize or decompose at high temperatures, a powder magnetic core that maintains high density and high mechanical strength even when molded at temperatures of 300°C or higher can be obtained. It is presumed that
本発明によれば、３００℃以上の温度で成形した場合でも、密度及び機械的強度が高い圧粉磁心を得ることが可能となる。 According to the present invention, it is possible to obtain a powder magnetic core with high density and mechanical strength even when molded at a temperature of 300° C. or higher.
以下、本発明をその好適な実施形態に即して詳細に説明する。 Hereinafter, the present invention will be explained in detail based on its preferred embodiments.
先ず、本発明の圧粉磁心について説明する。本発明の圧粉磁心は、平均粒径が１～３００ｎｍの磁性ナノ粒子と、下記式（１）： First, the powder magnetic core of the present invention will be explained. The powder magnetic core of the present invention comprises magnetic nanoparticles having an average particle size of 1 to 300 nm and the following formula (1):
で表され、前記式（１）中のｉ、ｊ及びｋにより求められる、
アセトアセタール化度〔ｉ／（ｉ＋ｊ＋ｋ）〕が０．５０～０．６９９９の範囲内にあり、アセチル基含有率〔ｊ／（ｉ＋ｊ＋ｋ）〕が０．０００１～０．０５の範囲内にあり、
水酸基含有率〔ｋ／（ｉ＋ｊ＋ｋ）〕が０．３０～０．４９９９の範囲内にあり、
アセトアセタール基数とアセチル基数と水酸基数との合計〔ｉ＋ｊ＋ｋ〕が１００～１００００の範囲内にあるポリビニルアセトアセタールと、
を含有するものである。
is expressed by i, j and k in the above formula (1),
The degree of acetoacetalization [i/(i+j+k)] is within the range of 0.50 to 0.6999, the acetyl group content [j/(i+j+k)] is within the range of 0.0001 to 0.05,
The hydroxyl group content [k/(i+j+k)] is within the range of 0.30 to 0.4999,
polyvinyl acetoacetal in which the sum of the number of acetoacetal groups, the number of acetyl groups, and the number of hydroxyl groups [i+j+k] is within the range of 100 to 10,000;
It contains.
本発明に用いられる磁性ナノ粒子としては圧粉磁心に用いられるものであれば特に制限はないが、例えば、Ｆｅナノ粒子、Ｆｅ含有金属ナノ粒子、Ｆｅ含有金属酸化物ナノ粒子が挙げられる。また、前記Ｆｅナノ粒子及び前記Ｆｅ含有金属ナノ粒子は、表面に絶縁層を備えていてもよい。これらの磁性ナノ粒子は１種を単独で使用しても２種以上を併用してもよい。これらの中でも、Ｆｅ含有金属ナノ粒子、Ｆｅ含有金属酸化物ナノ粒子、表面に絶縁層を備えるＦｅ含有金属ナノ粒子が好ましく、ヒステリシス損及び渦電流損を低減でき、かつ、飽和磁束密度を比較的大きくでき、高温での特性劣化も比較的少ないという観点から、表面に絶縁層を備えるＦｅ含有金属ナノ粒子が特に好ましい。 The magnetic nanoparticles used in the present invention are not particularly limited as long as they can be used in powder magnetic cores, and examples thereof include Fe nanoparticles, Fe-containing metal nanoparticles, and Fe-containing metal oxide nanoparticles. Further, the Fe nanoparticles and the Fe-containing metal nanoparticles may have an insulating layer on their surfaces. These magnetic nanoparticles may be used alone or in combination of two or more. Among these, Fe-containing metal nanoparticles, Fe-containing metal oxide nanoparticles, and Fe-containing metal nanoparticles having an insulating layer on the surface are preferable, as they can reduce hysteresis loss and eddy current loss, and have relatively low saturation magnetic flux density. Fe-containing metal nanoparticles having an insulating layer on the surface are particularly preferred from the viewpoint that they can be made large and exhibit relatively little property deterioration at high temperatures.
前記Ｆｅ含有合金ナノ粒子としては圧粉磁心に用いられるものであれば特に制限はないが、例えば、ＦｅＮｉ合金ナノ粒子（パーマロイＢナノ粒子等）、ＦｅＳｉ合金ナノ粒子（ケイ素鋼ナノ粒子等）、ＦｅＣｏ合金ナノ粒子（パーメンジュールナノ粒子等）、ＮｉＦｅ合金ナノ粒子（パーマロイＣナノ粒子等）が挙げられる。また、前記Ｆｅ含有金属酸化物ナノ粒子としては圧粉磁心に用いられるものであれば特に制限はないが、例えば、ＮｉＺｎフェライトナノ粒子、ＭｎＺｎフェライトナノ粒子等のフェライト系ナノ粒子が挙げられる。 The Fe-containing alloy nanoparticles are not particularly limited as long as they are used in powder magnetic cores, but include, for example, FeNi alloy nanoparticles (permalloy B nanoparticles, etc.), FeSi alloy nanoparticles (silicon steel nanoparticles, etc.), Examples include FeCo alloy nanoparticles (permendur nanoparticles, etc.) and NiFe alloy nanoparticles (permalloy C nanoparticles, etc.). Further, the Fe-containing metal oxide nanoparticles are not particularly limited as long as they can be used in powder magnetic cores, and examples thereof include ferrite nanoparticles such as NiZn ferrite nanoparticles and MnZn ferrite nanoparticles.
前記絶縁層としては、例えば、ＳｉＯ２、Ａｌ２Ｏ３、Ｆｅ２Ｏ３、Ｆｅ３Ｏ４、ＮｉＺｎフェライト、ＭｎＺｎフェライト等の金属酸化物からなる絶縁層；脂肪酸（例えば、デカン酸、ラウリン酸、ステアリン酸、オレイン酸、リノレン酸）、シリコーン系有機化合物（例えば、メチルシリコーン樹脂、メチルフェニルシリコーン樹脂、ジメチルポリシロキサン、シリコーンハイドロゲル）等の有機化合物からなる絶縁層；リン系化合物（例えば、リン酸カルシウム、リン酸鉄、リン酸亜鉛、リン酸マンガン）等の無機化合物からなる絶縁層が挙げられる。 Examples of the insulating layer include an insulating layer made of a metal oxide such as SiO 2 , Al 2 O 3 , Fe 2 O 3 , Fe 3 O 4 , NiZn ferrite, and MnZn ferrite; , stearic acid, oleic acid, linolenic acid), silicone-based organic compounds (e.g., methyl silicone resin, methylphenyl silicone resin, dimethyl polysiloxane, silicone hydrogel); Examples include insulating layers made of inorganic compounds such as calcium phosphate, iron phosphate, zinc phosphate, and manganese phosphate.
また、本発明に用いられる磁性ナノ粒子の平均粒径は１～３００ｎｍである。磁性ナノ粒子の平均粒径が前記下限未満になると、粒子表面の影響が大きく、磁性ナノ粒子自体の磁気特性が低下する。他方、磁性ナノ粒子の平均粒径が前記上限を超えると、渦電流損が増大して磁心損失が大きくなる。また、超常磁性現象が発現して保磁力が極めて小さくなり、ヒステリシス損を極めて小さくすることが可能となり、また、高周波において渦電流の経路が制限され、渦電流損を極めて小さくすることが可能となるという観点から、磁性ナノ粒子の平均粒径としては、１～１００ｎｍが好ましく、１～２０ｎｍがより好ましい。なお、磁性ナノ粒子の平均粒径は、ＴＥＭ観察において１００個の粒子の粒径を測定し、その平均値として求めることができる。 Further, the average particle size of the magnetic nanoparticles used in the present invention is 1 to 300 nm. When the average particle size of the magnetic nanoparticles is less than the lower limit, the influence of the particle surface is large, and the magnetic properties of the magnetic nanoparticles themselves are degraded. On the other hand, if the average particle size of the magnetic nanoparticles exceeds the upper limit, eddy current loss increases and magnetic core loss increases. In addition, a superparamagnetic phenomenon occurs and the coercive force becomes extremely small, making it possible to make hysteresis loss extremely small.In addition, the path of eddy current is restricted at high frequencies, making it possible to make eddy current loss extremely small. In view of this, the average particle size of the magnetic nanoparticles is preferably 1 to 100 nm, more preferably 1 to 20 nm. Note that the average particle size of the magnetic nanoparticles can be determined by measuring the particle size of 100 particles in TEM observation and taking the average value.
本発明に用いられるポリビニルアセトアセタールは、前記式（１）で表される、アセトアセタール基を含有する構成単位とアセチル基を含有する構成単位と水酸基を含有する構成単位とを含むものである。このようなポリビニルアセトアセタールと前記磁性ナノ粒子とを含有する圧粉磁心は、高い密度及び高い機械的強度を有する。一方、アセトアセタール基を含有する構成単位の代わりに、ブチラール基を含有する構成単位を含むポリビニルブチラール又はホルマール基を含有する構成単位を含むポリビニルホルマールと、前記磁性ナノ粒子とを含有する圧粉磁心は、本発明の圧粉磁心に比べて、密度及び機械的強度が低くなる。また、前記ポリビニルホルマールと前記磁性ナノ粒子とを含有する圧粉磁心は、本発明の圧粉磁心に比べて、耐熱性に劣っている。 The polyvinyl acetoacetal used in the present invention contains a structural unit containing an acetoacetal group, a structural unit containing an acetyl group, and a structural unit containing a hydroxyl group, which are represented by the above formula (1). A dust core containing such polyvinyl acetoacetal and the magnetic nanoparticles has high density and high mechanical strength. On the other hand, a powder magnetic core containing polyvinyl butyral containing a butyral group-containing constituent unit or polyvinyl formal containing a formal group-containing constituent unit instead of the acetoacetal group-containing constituent unit, and the magnetic nanoparticles. has lower density and mechanical strength than the powder magnetic core of the present invention. Moreover, the powder magnetic core containing the polyvinyl formal and the magnetic nanoparticles has inferior heat resistance compared to the powder magnetic core of the present invention.
本発明に用いられるポリビニルアセトアセタールにおいては、前記式（１）中のｉ、ｊ及びｋにより求められるアセトアセタール化度〔ｉ／（ｉ＋ｊ＋ｋ）〕が０．５０～０．６９９９の範囲内にある。前記アセトアセタール化度が前記下限未満になると、ポリビニルアセトアセタールの機械的強度及び柔軟性が低下するため、得られる圧粉磁心に成形歪みによるクラックが発生し、得られる圧粉磁心の密度及び機械的強度が低下する。他方、前記アセトアセタール化度が前記上限を超えると、相対的に水酸基含有率が低下するため、磁性ナノ粒子との間における強い結合力が低下し、得られる圧粉磁心の密度が低下する。また、ポリビニルアセトアセタールの機械的強度及び柔軟性が向上してクラックの発生が抑制され、密度及び機械的強度がより高い圧粉磁心が得られるという観点から、前記アセトアセタール化度の下限としては０．６０以上が好ましい。他方、相対的に水酸基含有率が増大するため、磁性ナノ粒子との間における強い結合力が向上し、より高密度の圧粉磁心が得られるという観点から、前記アセトアセタール化度の上限としては０．６７９９以下が好ましい。 In the polyvinyl acetoacetal used in the present invention, the degree of acetoacetalization [i/(i+j+k)] determined by i, j, and k in the above formula (1) is within the range of 0.50 to 0.6999. . If the degree of acetoacetalization is less than the lower limit, the mechanical strength and flexibility of polyvinyl acetoacetal will decrease, causing cracks to occur in the resulting powder magnetic core due to molding distortion, and the density and mechanical properties of the resulting powder magnetic core will decrease. target strength decreases. On the other hand, when the degree of acetoacetalization exceeds the upper limit, the hydroxyl group content decreases relatively, so the strong bonding force with the magnetic nanoparticles decreases, and the density of the obtained dust core decreases. In addition, from the viewpoint of improving the mechanical strength and flexibility of polyvinyl acetoacetal, suppressing the occurrence of cracks, and obtaining a powder magnetic core with higher density and mechanical strength, the lower limit of the degree of acetoacetalization is 0.60 or more is preferable. On the other hand, the upper limit of the degree of acetoacetalization is It is preferably 0.6799 or less.
また、本発明に用いられるポリビニルアセトアセタールにおいては、前記式（１）中のｉ、ｊ及びｋにより求められるアセチル基含有率〔ｊ／（ｉ＋ｊ＋ｋ）〕が０．０００１～０．０５の範囲内にある。前記アセチル基含有率が前記上限を超えると、ポリビニルアセトアセタールの疎水性が高くなるため、磁性ナノ粒子との間における結合力が低下し、得られる圧粉磁心の密度が低下する。さらに、ポリビニルアセトアセタールの耐熱性が低下するため、得られる圧粉磁心の耐熱性も低下する。また、ポリビニルアセトアセタールの疎水性が低くなるため、磁性ナノ粒子との間における結合力が向上し、得られる圧粉磁心の密度が高くなり、さらに、ポリビニルアセトアセタールの耐熱性が向上するため、得られる圧粉磁心の耐熱性も向上するという観点から、前記アセチル基含有率の上限としては０．０３以下が好ましい。 Furthermore, in the polyvinyl acetoacetal used in the present invention, the acetyl group content [j/(i+j+k)] determined by i, j, and k in the formula (1) is within the range of 0.0001 to 0.05. It is in. When the acetyl group content exceeds the upper limit, the hydrophobicity of polyvinyl acetoacetal becomes high, so the bonding force with magnetic nanoparticles decreases, and the density of the obtained dust core decreases. Furthermore, since the heat resistance of polyvinyl acetoacetal decreases, the heat resistance of the obtained powder magnetic core also decreases. In addition, since the hydrophobicity of polyvinyl acetoacetal is lowered, the bonding force with magnetic nanoparticles is improved, the density of the obtained dust core is increased, and the heat resistance of polyvinyl acetoacetal is improved. From the viewpoint of improving the heat resistance of the powder magnetic core obtained, the upper limit of the acetyl group content is preferably 0.03 or less.
さらに、本発明に用いられるポリビニルアセトアセタールにおいては、前記式（１）中のｉ、ｊ及びｋにより求められる水酸基含有率〔ｋ／（ｉ＋ｊ＋ｋ）〕が０．３０～０．４９９９の範囲内にある。前記水酸基含有率が前記下限未満になると、磁性ナノ粒子との間における強い結合力が低下し、得られる圧粉磁心の密度が低下する。他方、前記水酸基含有率が前記上限を超えると、相対的にアセトアセタール化度が低下するため、ポリビニルアセトアセタールの機械的強度及び柔軟性が低下し、得られる圧粉磁心に成形歪みによるクラックが発生し、得られる圧粉磁心の密度及び機械的強度が低下する。また、磁性ナノ粒子との間における強い結合力が向上し、より高密度の圧粉磁心が得られるという観点から、前記水酸基含有率の下限としては０．３２以上が好ましい。他方、相対的にアセトアセタール化度が増大するため、ポリビニルアセトアセタールの機械的強度及び柔軟性が向上してクラックの発生が抑制され、密度及び機械的強度がより高い圧粉磁心が得られるという観点から、前記水酸基含有率の上限としては０．３９９９以下が好ましい。 Furthermore, in the polyvinyl acetoacetal used in the present invention, the hydroxyl group content [k/(i+j+k)] determined by i, j, and k in the above formula (1) is within the range of 0.30 to 0.4999. be. When the hydroxyl group content is less than the lower limit, the strong bonding force with the magnetic nanoparticles decreases, and the density of the obtained dust core decreases. On the other hand, when the hydroxyl group content exceeds the upper limit, the degree of acetoacetalization decreases relatively, so the mechanical strength and flexibility of the polyvinyl acetoacetal decreases, and the resulting powder magnetic core suffers from cracks due to molding distortion. The density and mechanical strength of the obtained powder magnetic core are reduced. Further, from the viewpoint of improving the strong bonding force with the magnetic nanoparticles and obtaining a powder magnetic core with higher density, the lower limit of the hydroxyl group content is preferably 0.32 or more. On the other hand, because the degree of acetoacetalization increases relatively, the mechanical strength and flexibility of polyvinyl acetoacetal are improved, the occurrence of cracks is suppressed, and a powder magnetic core with higher density and mechanical strength can be obtained. From this point of view, the upper limit of the hydroxyl group content is preferably 0.3999 or less.
また、本発明に用いられるポリビニルアセトアセタールにおいては、前記式（１）中のｉ、ｊ及びｋにより求められるアセトアセタール基数とアセチル基数と水酸基数との合計〔ｉ＋ｊ＋ｋ〕が１００～１００００の範囲内にある。前記アセトアセタール基数とアセチル基数と水酸基数との合計が前記下限未満のポリビニルアセトアセタールは分子量が小さすぎるため、得られる圧粉磁心の機械的強度が低下する。他方、前記アセトアセタール基数とアセチル基数と水酸基数との合計が前記上限を超えるポリビニルアセトアセタールは分子量が大きすぎるため、ポリビニルアセトアセタール中に前記磁性ナノ粒子を均一に分散させることが困難である。また、得られる圧粉磁心の機械的強度が向上するという観点から、前記アセトアセタール基数とアセチル基数と水酸基数との合計の下限としては２００以上が好ましい。他方、ポリビニルアセトアセタール中に前記磁性ナノ粒子を均一に分散させることができるという観点から、前記アセトアセタール基数とアセチル基数と水酸基数との合計の上限としては３０００以下が好ましい。 Furthermore, in the polyvinyl acetoacetal used in the present invention, the sum of the number of acetoacetal groups, the number of acetyl groups, and the number of hydroxyl groups [i+j+k] determined by i, j, and k in the above formula (1) is within the range of 100 to 10,000. It is in. Polyvinyl acetoacetal whose total number of acetoacetal groups, acetyl groups, and hydroxyl groups is less than the lower limit has a molecular weight that is too small, resulting in a decrease in the mechanical strength of the powder magnetic core obtained. On the other hand, polyvinyl acetoacetal in which the sum of the number of acetoacetal groups, the number of acetyl groups, and the number of hydroxyl groups exceeds the upper limit has too large a molecular weight, so it is difficult to uniformly disperse the magnetic nanoparticles in the polyvinyl acetoacetal. Further, from the viewpoint of improving the mechanical strength of the powder magnetic core obtained, the lower limit of the total number of acetoacetal groups, acetyl groups, and hydroxyl groups is preferably 200 or more. On the other hand, from the viewpoint that the magnetic nanoparticles can be uniformly dispersed in polyvinyl acetoacetal, the upper limit of the total number of acetoacetal groups, acetyl groups, and hydroxyl groups is preferably 3,000 or less.
さらに、本発明に用いられるポリビニルアセトアセタールにおいて、末端の構成単位は特に制限はないが、ポリビニルアセトアセタールの合成が容易であるという観点から、アセチル基を含有する構成単位が末端であることが好ましい。 Further, in the polyvinyl acetoacetal used in the present invention, the terminal structural unit is not particularly limited, but from the viewpoint of easy synthesis of polyvinyl acetoacetal, it is preferable that the terminal structural unit contains an acetyl group. .
本発明の圧粉磁心において、このようなポリビニルアセトアセタールの含有量としては、圧粉磁心全体に対して０．０１～５質量％が好ましく、０．１～２質量％がより好ましく、０．１～１質量％が更に好ましい。ポリビニルアセトアセタールの含有量が前記下限未満になると、前記磁性ナノ粒子をポリビニルアセトアセタール中に均一に分散させることができず、得られる圧粉磁心の密度が低下する傾向にあり、他方、前記上限を超えると、非磁性成分の割合が多くなり、得られる圧粉磁心の磁気特性が低下する傾向にある。 In the powder magnetic core of the present invention, the content of such polyvinyl acetoacetal is preferably 0.01 to 5% by mass, more preferably 0.1 to 2% by mass, and 0.01 to 5% by mass, more preferably 0.1 to 2% by mass, based on the entire powder magnetic core. More preferably 1 to 1% by mass. If the content of polyvinyl acetoacetal is less than the lower limit, the magnetic nanoparticles cannot be uniformly dispersed in the polyvinyl acetoacetal, and the density of the resulting powder magnetic core tends to decrease. If it exceeds , the proportion of non-magnetic components increases and the magnetic properties of the resulting powder core tend to deteriorate.
このような本発明の圧粉磁心の密度としては７．０ｇ／ｃｍ３以上が好ましく、７．２ｇ／ｃｍ３以上がより好ましい。このような高密度の圧粉磁心は高い比透磁率を有する。 The density of the powder magnetic core of the present invention is preferably 7.0 g/cm 3 or more, more preferably 7.2 g/cm 3 or more. Such a high-density dust core has high relative permeability.
本発明の圧粉磁心は、例えば、以下の方法により製造することができる。すなわち、先ず、前記磁性ナノ粒子と前記ポリビニルアセトアセタールとを所定の混合比率で混合する。前記磁性ナノ粒子と前記ポリビニルアセトアセタールとの混合物は均一性が高いため、後述する加圧成形において前記磁性ナノ粒子の流動性が確保され、高密度の圧粉磁心を得ることが可能となる。 The powder magnetic core of the present invention can be manufactured, for example, by the following method. That is, first, the magnetic nanoparticles and the polyvinyl acetoacetal are mixed at a predetermined mixing ratio. Since the mixture of the magnetic nanoparticles and the polyvinyl acetoacetal has high uniformity, the fluidity of the magnetic nanoparticles is ensured during pressure molding, which will be described later, and it becomes possible to obtain a high-density powder magnetic core.
前記磁性ナノ粒子と前記ポリビニルアセトアセタールとの混合比率としては、質量比（磁性ナノ粒子／ポリビニルアセトアセタール）で９９．９９／０．０１～９５／５が好ましく、９９．９／０．１～９８／２がより好ましい。磁性ナノ粒子／ポリビニルアセトアセタールが前記下限未満になると、前記磁性ナノ粒子をポリビニルアセトアセタール中に均一に分散させることができず、得られる圧粉磁心の密度が低下する傾向にあり、他方、前記上限を超えると、非磁性成分の割合が多くなり、得られる圧粉磁心の磁気特性が低下する傾向にある。 The mixing ratio of the magnetic nanoparticles and the polyvinyl acetoacetal is preferably from 99.99/0.01 to 95/5 in mass ratio (magnetic nanoparticles/polyvinylacetoacetal), and from 99.9/0.1 to 95/5. 98/2 is more preferred. When the amount of magnetic nanoparticles/polyvinylacetoacetal is less than the lower limit, the magnetic nanoparticles cannot be uniformly dispersed in the polyvinylacetoacetal, and the density of the resulting powder magnetic core tends to decrease. When the upper limit is exceeded, the proportion of non-magnetic components increases, and the magnetic properties of the obtained dust core tend to deteriorate.
前記磁性ナノ粒子と前記ポリビニルアセトアセタールとの混合方法としては特に制限はなく、例えば、ボールミルや乳鉢を用いて混合する方法、溶媒に前記磁性ナノ粒子と前記ポリビニルアセトアセタールとを分散・溶解させた後、乾燥等により溶媒を除去することによって混合する方法等が挙げられる。また、前記磁性ナノ粒子は再配列性に劣るため、溶媒に前記磁性ナノ粒子と前記ポリビニルアセトアセタールとを分散・溶解させた後、スプレードライ等により顆粒状の混合物を調製してもよい。これにより、圧縮成形時に顆粒状の混合物が崩れて前記磁性ナノ粒子が再配列しやすくなるため、圧粉磁心の密度が向上する。 There are no particular limitations on the method of mixing the magnetic nanoparticles and the polyvinyl acetoacetal, and examples include mixing using a ball mill or mortar, or dispersing and dissolving the magnetic nanoparticles and the polyvinyl acetoacetal in a solvent. Afterwards, the solvent may be removed by drying or the like, and the mixture may be mixed. Furthermore, since the magnetic nanoparticles have poor rearrangement properties, a granular mixture may be prepared by spray drying or the like after dispersing and dissolving the magnetic nanoparticles and the polyvinyl acetoacetal in a solvent. As a result, the granular mixture collapses during compression molding, making it easier for the magnetic nanoparticles to rearrange, thereby improving the density of the dust core.
次に、このようにして得られた前記磁性ナノ粒子と前記ポリビニルアセトアセタールとの混合物を金型に充填する。前記金型には必要に応じて潤滑剤が塗布されていてもよい。前記潤滑剤としては特に制限はなく、例えば、ステアリン酸リチウム、ステアリン酸亜鉛等の飽和脂肪酸の金属塩、潤滑グリース（例えば、株式会社ミスミ製「Ｍ－ＨＧＳＳＣ－Ｈ５００」）等が挙げられる。 Next, a mold is filled with the thus obtained mixture of the magnetic nanoparticles and the polyvinyl acetoacetal. A lubricant may be applied to the mold as necessary. The lubricant is not particularly limited, and examples thereof include metal salts of saturated fatty acids such as lithium stearate and zinc stearate, lubricating grease (for example, "M-HGSSC-H500" manufactured by Misumi Co., Ltd.), and the like.
次に、金型に充填した前記磁性ナノ粒子と前記ポリビニルアセトアセタールとの混合物を加圧成形する。これにより、本発明の圧粉磁心を得ることができる。成形温度としては、３００～６００℃が好ましく、３００～４００℃がより好ましい。成形温度が前記下限未満になると、磁性ナノ粒子の塑性変形強度が十分に低下せず、得られる圧粉磁性の密度が向上しにくい傾向にあり、他方、前記上限を超えると、金型の強度が低下し、金型の寿命が短くなる傾向にある。なお、金型は、設定温度（成形温度）に、前記磁性ナノ粒子と前記芳香族化合物との混合物を充填する前に昇温してもよいし、充填後に昇温してもよい。 Next, the mixture of the magnetic nanoparticles and the polyvinyl acetoacetal filled in the mold is pressure-molded. Thereby, the dust core of the present invention can be obtained. The molding temperature is preferably 300 to 600°C, more preferably 300 to 400°C. If the molding temperature is below the above-mentioned lower limit, the plastic deformation strength of the magnetic nanoparticles will not be sufficiently reduced, and the density of the resulting powder magnetism will tend to be difficult to improve.On the other hand, if the compaction temperature exceeds the above-mentioned upper limit, the strength of the mold There is a tendency for the life of the mold to decrease. Note that the mold may be heated to a set temperature (molding temperature) before being filled with the mixture of the magnetic nanoparticles and the aromatic compound, or may be heated after being filled.
成形圧力としては５００ＭＰａ～３ＧＰａが好ましく、８００ＭＰａ～２ＧＰａがより好ましい。成形圧力が前記下限未満になると、前記混合物が十分に圧縮されないため、圧粉磁心の密度が小さくなる傾向にあり、他方、前記上限を超えると、スプリングバック現象の影響が大きく、クラックが発生して圧粉磁心の密度が小さくなる傾向にある。 The molding pressure is preferably 500 MPa to 3 GPa, more preferably 800 MPa to 2 GPa. When the compacting pressure is less than the lower limit, the mixture is not compressed sufficiently, and the density of the powder magnetic core tends to decrease.On the other hand, when it exceeds the upper limit, the influence of springback phenomenon is large and cracks occur. As a result, the density of the powder magnetic core tends to decrease.
また、このようにして製造した圧粉磁心には、必要に応じて熱処理を施してもよい。これにより、加圧により圧粉磁心に生じた歪みを緩和し、磁気特性を改善することができる。このような熱処理の温度は通常５００～８００℃である。 Further, the powder magnetic core manufactured in this manner may be subjected to heat treatment as necessary. Thereby, the strain caused in the powder magnetic core due to pressurization can be alleviated, and the magnetic properties can be improved. The temperature of such heat treatment is usually 500 to 800°C.
以下、実施例及び比較例に基づいて本発明をより具体的に説明するが、本発明は以下の実施例に限定されるものではない。 EXAMPLES Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.
（実施例１）
磁性ナノ粒子として平均粒径が１００ｎｍのＦｅＮｉナノ粒子（アルドリッチ社製）４．９７５ｇと、ポリビニルアセトアセタールとしてアセトアセタール化度が０．６６、アセチル基含有率が０．０１、水酸基含有率が０．３３、アセトアセタール基数とアセチル基数と水酸基数との合計が１６４０のポリビニルアセトアセタール（積水化学工業株式会社製「エスレック」）０．０２５ｇとを混合し、さらに、酢酸エチル２ｇを添加した。得られた混合物に超音波を印加して酢酸エチル中にＦｅＮｉナノ粒子を分散させた後、自転公転ミキサーを用いて更に混合した。得られた混合ペーストを真空乾燥させて酢酸エチルを除去し、得られた固形物を乳鉢で３０分間破砕混合した。得られた破砕混合物を、グリース（株式会社ミスミ製「Ｍ－ＨＧＳＳＣ－Ｈ５００」）を塗布したペレット試験片用金型に充填し、手動油圧真空加熱プレス機（株式会社井元製作所製「ＩＭＣ－１９４６型改」）を用いて真空中、１．４ＧＰａに加圧しながら３５０℃で１分間加熱した。加圧を停止した後、室温まで冷却して、得られた磁性ナノ粒子成形体（圧粉磁心ペレット（外径３ｍｍφ））を金型から取り出した。得られた成形体の質量と体積から密度を求めた。その結果を表１に示す。
(Example 1)
4.975 g of FeNi nanoparticles (manufactured by Aldrich) with an average particle size of 100 nm as magnetic nanoparticles, and polyvinyl acetoacetal with a degree of acetoacetalization of 0.66, an acetyl group content of 0.01, and a hydroxyl group content of 0. .33, 0.025 g of polyvinyl acetoacetal ("S-LEC" manufactured by Sekisui Chemical Co., Ltd.) having a total number of acetoacetal groups, acetyl groups, and hydroxyl groups of 1640 was mixed, and further, 2 g of ethyl acetate was added. After applying ultrasonic waves to the obtained mixture to disperse FeNi nanoparticles in ethyl acetate, the mixture was further mixed using a rotation-revolution mixer. The obtained mixed paste was vacuum dried to remove ethyl acetate, and the obtained solid was crushed and mixed in a mortar for 30 minutes. The resulting crushed mixture was filled into a mold for pellet test pieces coated with grease ("M-HGSSC-H500" manufactured by Misumi Co., Ltd.), and a manual hydraulic vacuum heating press machine ("IMC-1946" manufactured by Imoto Seisakusho Co., Ltd.) was used. The mixture was heated at 350° C. for 1 minute while pressurizing it to 1.4 GPa in a vacuum using a vacuum cleaner. After stopping the pressurization, it was cooled to room temperature, and the obtained magnetic nanoparticle molded body (powder magnetic core pellet (outer diameter 3 mmφ)) was taken out from the mold. The density was determined from the mass and volume of the obtained molded body. The results are shown in Table 1.
（実施例２）
ポリビニルアセトアセタールとして、アセトアセタール化度が０．６１、アセチル基含有率が０．０２、水酸基含有率が０．３７、アセトアセタール基数とアセチル基数と水酸基数との合計が２５０のポリビニルアセトアセタール（積水化学工業株式会社製「エスレック」）０．０２５ｇを用いた以外は実施例１と同様にして磁性ナノ粒子成形体（圧粉磁心ペレット（外径３ｍｍφ））を作製し、その密度を求めた。その結果を表１に示す。
(Example 2)
Polyvinyl acetoacetal has a degree of acetoacetalization of 0.61, an acetyl group content of 0.02, a hydroxyl group content of 0.37, and a total of the number of acetoacetal groups, the number of acetyl groups, and the number of hydroxyl groups of 250 ( A magnetic nanoparticle molded body (powder magnetic core pellet (outer diameter 3 mmφ)) was prepared in the same manner as in Example 1 except that 0.025 g of “S-LEC” manufactured by Sekisui Chemical Co., Ltd. was used, and its density was determined. . The results are shown in Table 1.
（実施例３）
ポリビニルアセトアセタールとして、アセトアセタール化度が０．５３、アセチル基含有率が０．０１、水酸基含有率が０．４６、アセトアセタール基数とアセチル基数と水酸基数との合計が８３０のポリビニルアセトアセタール（積水化学工業株式会社製「エスレック」）０．０２５ｇを用いた以外は実施例１と同様にして磁性ナノ粒子成形体（圧粉磁心ペレット（外径３ｍｍφ））を作製し、その密度を求めた。その結果を表１に示す。
(Example 3)
Polyvinyl acetoacetal has a degree of acetoacetalization of 0.53, an acetyl group content of 0.01, a hydroxyl group content of 0.46, and a total of the number of acetoacetal groups, the number of acetyl groups, and the number of hydroxyl groups of 830 ( A magnetic nanoparticle molded body (powder magnetic core pellet (outer diameter 3 mmφ)) was prepared in the same manner as in Example 1 except that 0.025 g of “S-LEC” manufactured by Sekisui Chemical Co., Ltd. was used, and its density was determined. . The results are shown in Table 1.
（比較例１）
ポリビニルアセトアセタールを混合しなかった以外は実施例１と同様にして磁性ナノ粒子成形体（圧粉磁心ペレット（外径３ｍｍφ））を作製し、その密度を求めた。その結果を表１に示す。
(Comparative example 1)
A magnetic nanoparticle molded body (powder core pellet (outer diameter 3 mmφ)) was produced in the same manner as in Example 1 except that polyvinyl acetoacetal was not mixed, and its density was determined. The results are shown in Table 1.
（比較例２）
ポリビニルアセトアセタールとして、アセトアセタール化度が０．７４、アセチル基含有率が０．０１、水酸基含有率が０．２５、アセトアセタール基数とアセチル基数と水酸基数との合計が１６４０のポリビニルアセトアセタール（積水化学工業株式会社製「エスレック」）０．０２５ｇを用いた以外は実施例１と同様にして磁性ナノ粒子成形体（圧粉磁心ペレット（外径３ｍｍφ））を作製し、その密度を求めた。その結果を表１に示す。
(Comparative example 2)
Polyvinyl acetoacetal has a degree of acetoacetalization of 0.74, an acetyl group content of 0.01, a hydroxyl group content of 0.25, and a total of the number of acetoacetal groups, the number of acetyl groups, and the number of hydroxyl groups of 1640 ( A magnetic nanoparticle molded body (powder magnetic core pellet (outer diameter 3 mmφ)) was prepared in the same manner as in Example 1 except that 0.025 g of “S-LEC” manufactured by Sekisui Chemical Co., Ltd. was used, and its density was determined. . The results are shown in Table 1.
（比較例３）
ポリビニルアセトアセタールとして、アセトアセタール化度が０．３０、アセチル基含有率が０．０３、水酸基含有率が０．６７、アセトアセタール基数とアセチル基数と水酸基数との合計が１２６０のポリビニルアセトアセタール（積水化学工業株式会社製「エスレック」）０．０２５ｇを用いた以外は実施例１と同様にして磁性ナノ粒子成形体（圧粉磁心ペレット（外径３ｍｍφ））を作製し、その密度を求めた。その結果を表１に示す。
(Comparative example 3)
Polyvinyl acetoacetal has a degree of acetoacetalization of 0.30, an acetyl group content of 0.03, a hydroxyl group content of 0.67, and a total of the number of acetoacetal groups, the number of acetyl groups, and the number of hydroxyl groups of 1260 ( A magnetic nanoparticle molded body (powder magnetic core pellet (outer diameter 3 mmφ)) was prepared in the same manner as in Example 1 except that 0.025 g of “S-LEC” manufactured by Sekisui Chemical Co., Ltd. was used, and its density was determined. . The results are shown in Table 1.
（比較例４）
ポリビニルアセトアセタールの代わりに、下記式（２）：
(Comparative example 4)
Instead of polyvinyl acetoacetal, the following formula (2):
で表され、前記式（２）中のｉ、ｊ及びｋにより求められる、ブチラール化度〔ｉ／（ｉ＋ｊ＋ｋ）〕が０．６５、アセチル基含有率〔ｊ／（ｉ＋ｊ＋ｋ）〕が０．０１、水酸基含有率〔ｋ／（ｉ＋ｊ＋ｋ）〕が０．３４、ブチラール基数とアセチル基数と水酸基数との合計〔ｉ＋ｊ＋ｋ〕が６７０のポリビニルブチラール（和光純薬工業株式会社製）０．０２５ｇを用いた以外は実施例１と同様にして磁性ナノ粒子成形体（圧粉磁心ペレット（外径３ｍｍφ））を作製し、その密度を求めた。その結果を表１に示す。 The degree of butyralization [i/(i+j+k)] determined by i, j, and k in the above formula (2) is 0.65, and the acetyl group content [j/(i+j+k)] is 0.01. , 0.025 g of polyvinyl butyral (manufactured by Wako Pure Chemical Industries, Ltd.) with a hydroxyl group content [k/(i+j+k)] of 0.34 and a total number of butyral groups, acetyl groups, and hydroxyl groups [i+j+k] of 670 was used. Except for this, a magnetic nanoparticle molded body (powder magnetic core pellet (outer diameter 3 mmφ)) was produced in the same manner as in Example 1, and its density was determined. The results are shown in Table 1.
（比較例５）
ポリビニルアセトアセタールの代わりに、下記式（３）：
(Comparative example 5)
Instead of polyvinyl acetoacetal, the following formula (3):
で表され、前記式（３）中のｉ、ｊ及びｋにより求められる、ホルマール化度〔ｉ／（ｉ＋ｊ＋ｋ）〕が０．６６、アセチル基含有率〔ｊ／（ｉ＋ｊ＋ｋ）〕が０．０２、水酸基含有率〔ｋ／（ｉ＋ｊ＋ｋ）〕が０．３２、ホルマール基数とアセチル基数と水酸基数との合計〔ｉ＋ｊ＋ｋ〕が１３６０のポリビニルホルマール（和光純薬工業株式会社製）０．０２５ｇを用いた以外は実施例１と同様にして磁性ナノ粒子成形体（圧粉磁心ペレット（外径３ｍｍφ））を作製し、その密度を求めた。その結果を表１に示す。 The formalization degree [i/(i+j+k)] is 0.66, and the acetyl group content [j/(i+j+k)] is 0.02, which is expressed by i, j, and k in the formula (3) above. , 0.025 g of polyvinyl formal (manufactured by Wako Pure Chemical Industries, Ltd.) with a hydroxyl group content [k/(i+j+k)] of 0.32 and a total of the number of formal groups, acetyl groups, and hydroxyl groups [i+j+k] of 1360 was used. Except for this, a magnetic nanoparticle molded body (powder magnetic core pellet (outer diameter 3 mmφ)) was produced in the same manner as in Example 1, and its density was determined. The results are shown in Table 1.
表１に示したように、アセトアセタール化度、アセチル基含有率、水酸基含有率、及びアセトアセタール基数とアセチル基数と水酸基数との合計が特定の範囲内にあるポリビニルアセトアセタールを用いた場合（実施例１～３）には、いずれも高密度（７．０ｇ／ｃｍ３以上）の圧粉磁心が得られることがわかった。 As shown in Table 1, when using polyvinyl acetoacetal whose degree of acetoacetalization, acetyl group content, hydroxyl group content, and the sum of the number of acetoacetal groups, the number of acetyl groups, and the number of hydroxyl groups are within specific ranges ( It was found that powder magnetic cores with high density (7.0 g/cm 3 or more) were obtained in all of Examples 1 to 3).
一方、ポリビニルアセトアセタールを用いなかった場合（比較例１）、アセトアセタール化度が特定の範囲より高いポリビニルアセトアセタールを用いた場合（比較例２）、水酸基含有率が特定の範囲より高いポリビニルアセトアセタールを用いた場合（比較例３）、ポリビニルアセトアセタールの代わりにポリビニルブチラールを用いた場合（比較例４）、並びにポリビニルアセトアセタールの代わりにポリビニルホルマールを用いた場合（比較例５）には、得られる圧粉磁心はいずれも低密度（７．０ｇ／ｃｍ３未満）になることがわかった。 On the other hand, when polyvinyl acetoacetal was not used (Comparative Example 1), when polyvinyl acetoacetal was used with a degree of acetoacetalization higher than the specific range (Comparative Example 2), when polyvinyl acetoacetal was used with a hydroxyl group content higher than the specific range, When acetal was used (Comparative Example 3), when polyvinyl butyral was used instead of polyvinyl acetoacetal (Comparative Example 4), and when polyvinyl formal was used instead of polyvinyl acetoacetal (Comparative Example 5), It was found that the resulting dust cores all had low density (less than 7.0 g/cm 3 ).
（比較例６）
ポリビニルアセトアセタールの代わりに、ステアリン酸リチウム（東京化成工業株式会社製）０．０２５ｇを用いた以外は実施例１と同様にして磁性ナノ粒子成形体（圧粉磁心ペレット（外径３ｍｍφ））を作製し、その密度を求めた。その結果を表２に示す。
(Comparative example 6)
A magnetic nanoparticle molded body (powder magnetic core pellet (outer diameter 3 mmφ)) was prepared in the same manner as in Example 1 except that 0.025 g of lithium stearate (manufactured by Tokyo Kasei Kogyo Co., Ltd.) was used instead of polyvinyl acetoacetal. It was prepared and its density was determined. The results are shown in Table 2.
＜破壊強度＞
実施例１、比較例１及び比較例６で得られた磁性ナノ粒子成形体（圧粉磁心ペレット（外径３ｍｍφ））をロードセル付油圧加圧機（株式会社井元製作所製「ＩＭＣ－１８２３型改」）に設置し、圧力を徐々に増加させながら成形体の平坦面の両側から圧縮し、成形体が破壊された時点の印加圧力を破壊力とし、これを圧力印加面積で割ることによって破壊強度を求めた。その結果を表２に示す。
<Breaking strength>
The magnetic nanoparticle molded bodies (powder magnetic core pellets (outer diameter 3 mmφ)) obtained in Example 1, Comparative Example 1, and Comparative Example 6 were processed using a hydraulic pressure machine with a load cell (“IMC-1823 type modified” manufactured by Imoto Seisakusho Co., Ltd.). ), compress the compact from both sides of the flat surface while gradually increasing the pressure, take the applied pressure at the time the compact breaks as the breaking force, and calculate the breaking strength by dividing this by the pressure applied area. I asked for it. The results are shown in Table 2.
表２に示したように、特定のポリビニルアセトアセタールを配合した場合（実施例１）には、ポリビニルアセトアセタールを配合しなかった場合（比較例１）や低分子潤滑剤（ステアリン酸リチウム）を配合した場合（比較例６）に比べて、得られた圧粉磁心の破壊強度が高くなることがわかった。 As shown in Table 2, when a specific polyvinyl acetoacetal was blended (Example 1), when polyvinyl acetoacetal was not blended (Comparative Example 1), and when a low molecular lubricant (lithium stearate) was blended, It was found that the fracture strength of the powder magnetic core obtained was higher than that in the case of blending (Comparative Example 6).
以上説明したように、本発明によれば、３００℃以上の温度で成形した場合でも、密度及び機械的強度が高い圧粉磁心を得ることが可能となる。したがって、本発明の圧粉磁心は、比透磁率が高く、ヒステリシス損や渦電流損が小さくなるため、変圧器（トランス）、電動機（モータ）、発電機、スピーカ、誘導加熱器、各種アクチュエータ等の電磁気を利用した製品のコア材などとして有用である。 As explained above, according to the present invention, it is possible to obtain a powder magnetic core with high density and mechanical strength even when molded at a temperature of 300° C. or higher. Therefore, the powder magnetic core of the present invention has high relative permeability and low hysteresis loss and eddy current loss, so it can be used in transformers, electric motors, generators, speakers, induction heaters, various actuators, etc. It is useful as a core material for products that utilize electromagnetism.
Claims (7)
下記式（１）：
アセトアセタール化度〔ｉ／（ｉ＋ｊ＋ｋ）〕が０．５０～０．６９９９の範囲内にあり、アセチル基含有率〔ｊ／（ｉ＋ｊ＋ｋ）〕が０．０００１～０．０５の範囲内にあり、
水酸基含有率〔ｋ／（ｉ＋ｊ＋ｋ）〕が０．３０～０．４９９９の範囲内にあり、
アセトアセタール基数とアセチル基数と水酸基数との合計〔ｉ＋ｊ＋ｋ〕が１００～１００００の範囲内にあるポリビニルアセトアセタールと、
を含有することを特徴とする圧粉磁心。 Magnetic nanoparticles with an average particle size of 1 to 300 nm,
The following formula (1):
The degree of acetoacetalization [i/(i+j+k)] is within the range of 0.50 to 0.6999, the acetyl group content [j/(i+j+k)] is within the range of 0.0001 to 0.05,
The hydroxyl group content [k/(i+j+k)] is within the range of 0.30 to 0.4999,
polyvinyl acetoacetal in which the sum of the number of acetoacetal groups, the number of acetyl groups, and the number of hydroxyl groups [i+j+k] is within the range of 100 to 10,000;
A powder magnetic core characterized by containing.
アセトアセタール化度〔ｉ／（ｉ＋ｊ＋ｋ）〕が０．５０～０．６９９９の範囲内にあり、アセチル基含有率〔ｊ／（ｉ＋ｊ＋ｋ）〕が０．０００１～０．０５の範囲内にあり、
水酸基含有率〔ｋ／（ｉ＋ｊ＋ｋ）〕が０．３０～０．４９９９の範囲内にあり、
アセトアセタール基数とアセチル基数と水酸基数との合計〔ｉ＋ｊ＋ｋ〕が１００～１００００の範囲内にあるポリビニルアセトアセタールとの混合物を加圧しながら３００℃以上の温度で加熱することを特徴とする圧粉磁心の製造方法。 Magnetic nanoparticles with an average particle size of 1 to 300 nm and the following formula (1):
The degree of acetoacetalization [i/(i+j+k)] is within the range of 0.50 to 0.6999, the acetyl group content [j/(i+j+k)] is within the range of 0.0001 to 0.05,
The hydroxyl group content [k/(i+j+k)] is within the range of 0.30 to 0.4999,
A powder magnetic core characterized in that a mixture with polyvinyl acetoacetal whose total number of acetoacetal groups, acetyl groups, and hydroxyl groups [i+j+k] is within the range of 100 to 10,000 is heated at a temperature of 300° C. or higher while pressurizing it. manufacturing method.
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