JP5905205B2 - Metallic magnetic powder and method for producing the same - Google Patents
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本発明は金属磁性粉末およびその製造方法に関し、特に、塗布型磁気記録媒体に使用される強磁性金属粉末およびその製造方法に関する。 The present invention relates to a metal magnetic powder and a method for producing the same, and more particularly to a ferromagnetic metal powder used for a coating type magnetic recording medium and a method for producing the same.
塗布型磁気記録媒体などの情報記録媒体は、音声情報や映像情報などの情報を記録および保存するために使用されており、近年の音声情報や映像情報のデジタル化やハイエンド化に伴って、情報記録媒体に記録および保存する情報量が増加する傾向にある。そのため、情報記録媒体の高容量化が指向されており、従来から高容量の磁気記録媒体として広く利用されてきた塗布型磁気記録媒体は、情報容量に対する単価の低廉性や、長期間の保管に耐え得る保管安定性から、益々重要性が高まっている。 Information recording media such as coating-type magnetic recording media are used for recording and storing information such as audio information and video information, and the information has become digital and high-end in recent years. There is a tendency that the amount of information recorded and stored in a recording medium increases. For this reason, an increase in the capacity of information recording media has been aimed at, and coating type magnetic recording media that have been widely used as high-capacity magnetic recording media have been used for low unit prices for information capacity and for long-term storage. The importance of storage stability that can withstand is increasing.
代表的な塗布型磁気記録媒体である磁気テープでは、１巻当たりの巻き数を増加させることによって高容量化する方法があるが、磁気テープの容器の容積やベースフィルムなどの他の部材の影響のために、巻き数の増加による高容量化には限界がある。一方、磁気記録媒体の小さい面積に多くの情報を書き込めるようにすることによって高容量化する方法もあり、この方法は極めて効果的な方法である。また、磁気記録媒体に情報を書き込むための記録波長を短くすることによって高容量化する方法もある。 There is a method to increase the capacity by increasing the number of windings per roll in a magnetic tape which is a typical coating type magnetic recording medium, but the influence of the volume of the container of the magnetic tape and other members such as a base film. For this reason, there is a limit to increasing the capacity by increasing the number of windings. On the other hand, there is a method of increasing the capacity by allowing a large amount of information to be written in a small area of the magnetic recording medium, and this method is extremely effective. There is also a method of increasing the capacity by shortening the recording wavelength for writing information on the magnetic recording medium.
磁気記録媒体の小さい面積に多くの情報を書き込めるようにすることによって高容量化する方法では、磁気記録媒体の限られた空間に金属磁性粉末の粒子をより多く存在させる必要があり、金属磁性粉末の粒子を微細化（低体積化）することが要求されている。また、磁気記録媒体に情報を書き込むための記録波長を短くする方法では、金属磁性粉末の粒子が情報の書き込みに耐えられる程度に微細化される、すなわち、記録波長よりも微細化されることが要求されている。このように、いずれの方法でも金属磁性粉末の粒子を微細化することが要求されている。 In the method of increasing the capacity by allowing a large amount of information to be written in a small area of the magnetic recording medium, it is necessary to have more particles of the metal magnetic powder in a limited space of the magnetic recording medium. It is demanded to reduce the size of the particles. Further, in the method of shortening the recording wavelength for writing information on the magnetic recording medium, the metal magnetic powder particles can be made fine enough to withstand the writing of information, that is, finer than the recording wavelength. It is requested. Thus, in any method, it is required to make the metal magnetic powder particles fine.
しかし、金属磁性粉末の粒子の微細化（低体積化）に伴って、比表面積が大きくなり、焼成および加熱還元の際に粒子間の焼結が生じ易くなり、粒子間の凝集が生じ易くなる。また、金属磁性粉末の粒子が焼結せずに粒子同士の凝集が抑制されて粒子の独立性が高くなっていなければ、微細化した金属磁性粉末を使用して磁性塗料を作製する際に分散性が悪くなり、磁性塗料中の磁性粒子の配向性が悪くなる。特に、金属磁性粉末の粒子が長軸長５０ｎｍ以下の微粒子になると、粒子間の焼結を完全に防止することが困難になり、磁性塗料を作製する際の分散性を向上させるのが困難になり、磁性塗料中の磁性粒子の配向性が向上させるのが困難になる。 However, as the particles of metal magnetic powder become finer (lower volume), the specific surface area increases, and sintering between particles is likely to occur during firing and heat reduction, and aggregation between particles is likely to occur. . In addition, if the particles of the metal magnetic powder are not sintered and aggregation of the particles is suppressed and the independence of the particles is not increased, the particles are dispersed when the magnetic paint is made using the miniaturized metal magnetic powder. And the orientation of the magnetic particles in the magnetic coating is deteriorated. In particular, when the particles of the metal magnetic powder become fine particles having a major axis length of 50 nm or less, it becomes difficult to completely prevent the sintering between the particles, and it becomes difficult to improve the dispersibility when producing the magnetic paint. Thus, it becomes difficult to improve the orientation of the magnetic particles in the magnetic paint.
塗布型磁気記録媒体に使用される金属磁性粉末である（鉄を主成分として含有する）鉄系磁性粉体の粒子を微細化する方法として、焼結防止剤を含有するオキシ水酸化鉄（α−ＦｅＯＯＨ）を焼成し、加熱還元して金属磁性粉末を得た後に、不要になった焼成防止剤に由来する非磁性成分を溶出させる方法が提案されている（例えば、特許文献１参照）。 An iron oxyhydroxide (α) containing an anti-sintering agent is used as a method of refining particles of an iron-based magnetic powder (containing iron as a main component) that is a metal magnetic powder used in a coating type magnetic recording medium. (FeOOH) is calcined and heat-reduced to obtain a metal magnetic powder, and then a method of eluting nonmagnetic components derived from the firing inhibitor that has become unnecessary is proposed (for example, see Patent Document 1).
また、金属磁性粉末を使用して磁性塗料を作製する際の分散性を向上させるために、ゲーサイト粒子を含む固形分濃度５０重量％以下の含液物を真空凍結乾燥した後に加熱脱水して得られたヘマタイト粒子を加熱還元して、ほぐれ易く分散性に優れた金属磁性粉末を製造する方法が提案されている（例えば、特許文献２参照）。 In addition, in order to improve the dispersibility when producing a magnetic coating using a metal magnetic powder, a liquid-containing material containing goethite particles and having a solid content concentration of 50% by weight or less is vacuum-lyophilized and then heat-dehydrated. A method has been proposed in which the obtained hematite particles are reduced by heating to produce a metal magnetic powder that is easily loosened and excellent in dispersibility (see, for example, Patent Document 2).
しかし、特許文献１の方法では、焼成および加熱還元の際に粒子間の焼結を防止することができるが、非磁性成分の少なくとも１種以上と錯体を形成し得る錯化剤が添加された液中において還元剤を作用させて非磁性成分を液中に溶出させる必要があり、金属磁性粉末の表面の特性が変化して磁性塗料中の磁性粒子の分散性が悪化する場合がある。 However, in the method of Patent Document 1, although sintering between particles can be prevented during firing and heat reduction, a complexing agent capable of forming a complex with at least one nonmagnetic component is added. It is necessary to cause a reducing agent to act in the liquid to elute the nonmagnetic component into the liquid, and the characteristics of the surface of the metal magnetic powder may change to deteriorate the dispersibility of the magnetic particles in the magnetic paint.
また、特許文献２の方法では、真空凍結乾燥という特殊な乾燥工程がボトルネックになって、大量生産には適していない。また、特許文献２の方法で得られる金属磁性粉末は、嵩密度が０．２５ｇ／ｃｍ３以下と低いため、容器に詰めたときに詰まり難い粒子になって、必ずしも高密度磁気記録に適した粒子ではない。
In the method of
したがって、本発明は、このような従来の問題点に鑑み、粒子を小さくしても粒子同士の凝集を抑制して粒子の独立性を高くすることができ、磁性塗料に使用した場合に分散性を向上させることができるとともに、嵩密度を高くすることができる、金属磁性粉末およびその製造方法を提供することを目的とする。 Therefore, in view of such a conventional problem, the present invention can increase the independence of the particles by suppressing the aggregation of the particles even if the particles are small, and the dispersibility when used in the magnetic coating material. An object of the present invention is to provide a metal magnetic powder and a method for producing the same, which can improve the bulk density and increase the bulk density.
本発明者らは、上記課題を解決するために鋭意研究した結果、オキシ水酸化鉄の粒子の表面に焼結防止成分を被着させる前に、オキシ水酸化鉄のスラリーを湿式粉砕してオキシ水酸化鉄の粒子の凝集をほぐすことにより、焼結防止成分がより均一にオキシ水酸化鉄の粒子の表面を被覆して粒子間の焼結を抑制することができるようにすれば、金属磁性粉末の粒子を小さくしても粒子同士の凝集を抑制して粒子の独立性を高くすることができ、磁性塗料に使用した場合に分散性を向上させることができるとともに、嵩密度を高くすることができることを見出し、本発明を完成するに至った。 As a result of diligent research to solve the above-mentioned problems, the inventors of the present invention performed wet pulverization of the iron oxyhydroxide slurry by wet grinding the iron oxyhydroxide slurry before depositing the sintering inhibiting component on the surface of the iron oxyhydroxide particles. By reducing the aggregation of iron hydroxide particles, the anti-sintering component can more uniformly coat the surface of the iron oxyhydroxide particles and suppress the sintering between the particles. Even if the particle size of the powder is reduced, it is possible to increase the independence of the particles by suppressing the aggregation of the particles, and to improve the dispersibility when used in the magnetic paint, and to increase the bulk density. As a result, the present invention has been completed.
本発明による金属磁性粉末の製造方法は、オキシ水酸化鉄（α−ＦｅＯＯＨ）のスラリーを湿式粉砕して得られたオキシ水酸化鉄の粒子の表面に焼結防止成分を被着させた後にオキシ水酸化鉄を還元することを特徴とする。 The method for producing a metal magnetic powder according to the present invention comprises the steps of depositing an anti-sintering component on the surface of iron oxyhydroxide particles obtained by wet-grinding an iron oxyhydroxide (α-FeOOH) slurry, and It is characterized by reducing iron hydroxide.
この金属磁性粉末の製造方法において、オキシ水酸化鉄のスラリーを湿式粉砕する際に、オキシ水酸化物のスラリーに分散剤を添加するのが好ましい。また、分散剤がカルボキシル基を有する化合物であるのが好ましい。さらに、焼結防止成分として（イットリウムを含む）希土類元素から選ばれる１種以上を含む焼結防止成分を使用してもよい。 In this metal magnetic powder manufacturing method, it is preferable to add a dispersant to the oxyhydroxide slurry when wet grinding the iron oxyhydroxide slurry. Moreover, it is preferable that a dispersing agent is a compound which has a carboxyl group. Further, a sintering preventing component containing one or more selected from rare earth elements (including yttrium) may be used as the sintering preventing component.
また、本発明による金属磁性粉末は、鉄または鉄とコバルトを主成分とする金属磁性相を有する粒子からなり、平均長軸長が１０〜５０ｎｍであり、水銀圧入法により測定した細孔分布において細孔径が２００ｎｍ以上の範囲の累積細孔容積が０．７５ｍＬ／ｇ以下であり、ゆるめ嵩密度が０．３５ｇ／ｃｃ以上で且つ固め嵩密度が０．４０ｇ／ｃｃ以上であることを特徴とする。 The metal magnetic powder according to the present invention is composed of particles having a metal magnetic phase mainly composed of iron or iron and cobalt, and has an average major axis length of 10 to 50 nm, in a pore distribution measured by a mercury intrusion method. The cumulative pore volume with a pore diameter in the range of 200 nm or more is 0.75 mL / g or less, the loose bulk density is 0.35 g / cc or more, and the consolidated bulk density is 0.40 g / cc or more. To do.
この金属磁性粉末では、金属磁性粉末の粒子の表面に焼結防止成分が被着してもよく、焼結防止成分として（イットリウムを含む）希土類元素から選ばれる１種以上を含む焼結防止成分を使用してもよい。 In this metal magnetic powder, an anti-sintering component may be deposited on the surface of the particles of the metal magnetic powder, and the anti-sintering component containing one or more selected from rare earth elements (including yttrium) as the anti-sintering component May be used.
本発明によれば、オキシ水酸化鉄の粒子の表面に焼結防止成分を被着させる前に、オキシ水酸化鉄のスラリーを湿式粉砕することにより、オキシ水酸化鉄の粒子の凝集をほぐすことができるので、焼結防止成分がより均一にオキシ水酸化鉄の粒子の表面を被覆することができ、金属磁性粉末の粒子を小さくしても粒子同士の凝集を抑制して粒子の独立性を高くすることができ、磁性塗料に使用した場合に分散性を向上させることができるとともに、嵩密度を高くすることができる。 According to the present invention, the iron oxyhydroxide slurry is wet pulverized to loosen the iron oxyhydroxide particles before the anti-sintering component is deposited on the surface of the iron oxyhydroxide particles. Therefore, the sintering prevention component can more uniformly coat the surface of the iron oxyhydroxide particles, and even if the particles of the metal magnetic powder are made smaller, the aggregation of the particles is suppressed and the independence of the particles is increased. When it is used for a magnetic paint, the dispersibility can be improved and the bulk density can be increased.
本発明による金属磁性粉末の製造方法の実施の形態では、オキシ水酸化鉄（α−ＦｅＯＯＨ）のスラリーを湿式粉砕して得られたオキシ水酸化鉄の粒子の表面に焼結防止成分を被着させた後にオキシ水酸化鉄を還元する。 In the embodiment of the method for producing metal magnetic powder according to the present invention, an anti-sintering component is deposited on the surface of iron oxyhydroxide particles obtained by wet-grinding an iron oxyhydroxide (α-FeOOH) slurry. Then, iron oxyhydroxide is reduced.
出発材料として使用するオキシ水酸化鉄は、Ｆｅの一部が他の元素で置換されたオキシ水酸化鉄でもよく、従来の一般的な湿式法によって製造することができる。このオキシ水酸化鉄の粒子は、長軸長が２０〜１５０ｎｍであるのが好ましく、２０〜１００ｎｍであるのがさらに好ましい。オキシ水酸化鉄の粒子がこの範囲の長軸長であれば、還元工程や安定化工程などの各工程の後でその体積が十分に小さくなり、より微粒子で高密度磁気記録に適した磁性粉末になる。 The iron oxyhydroxide used as a starting material may be iron oxyhydroxide in which a part of Fe is substituted with another element, and can be produced by a conventional general wet method. The major axis length of the iron oxyhydroxide particles is preferably 20 to 150 nm, and more preferably 20 to 100 nm. If the iron oxyhydroxide particles have a long axis length in this range, the volume is sufficiently small after each step such as the reduction step and the stabilization step, and the magnetic powder is finer and suitable for high-density magnetic recording. become.
オキシ水酸化鉄のスラリーの湿式粉砕は、分散容器内で回転翼の付いた回転軸を高速で回転させる回転剪断型撹拌機、分散メディアを含む分散容器内で回転翼の付いた回転軸を高速で回転させるアトライタおよびサンドミル、超音波分散機、高圧噴霧衝突式分散機などの様々な湿式粉砕装置を使用して行うことができる。この湿式粉砕装置にオキシ水酸化鉄のスラリーを通す回数は一回でもよいが、複数回にすれば、さらに独立性の高い粒子を得ることができる。 Wet grinding of iron oxyhydroxide slurry is a rotating shear type agitator that rotates a rotating shaft with rotating blades in a dispersion vessel at high speed, and a rotating shaft with rotating blades in a dispersion vessel containing dispersion media at high speed. It can be performed using various wet pulverizers such as an attritor and sand mill rotated at a high speed, an ultrasonic disperser, and a high-pressure spray impingement disperser. The number of times the iron oxyhydroxide slurry is passed through the wet pulverizer may be one, but if it is set to a plurality of times, particles with higher independence can be obtained.
オキシ水酸化鉄のスラリーの湿式粉砕は、効率的に粒子を処理するとともに粒子の独立性をさらに高めるために、スラリーに分散剤を添加して行うのが好ましい。この分散剤として、様々な分散剤を使用することができるが、最終製品として得られる金属磁性粉末の特性が劣化するのを防止するために、後工程において分解し得る炭素、窒素および酸素などによって構成された分散剤を使用するのが好ましい。特に、オキシ水酸化鉄の粒子の表面に作用して湿式粉砕効率を高めることができるカルボキシル基を有する化合物からなる分散剤を使用するのが好ましい。このようなカルボキシル基を有する化合物からなる分散剤として、（例えば、ライオン株式会社製のポリティＡ５３０、Ａ５４０、Ａ５５０、Ｎ−１００Ｋ、ＰＳ−１９００、サンノプコ株式会社製のＳＮディスパーザント５４６８、花王株式会社製のポイズ５２０、５３０、５３２Ａ、カオーセラ２０００などの）市販の分散剤を使用することができる。
The wet pulverization of the iron oxyhydroxide slurry is preferably performed by adding a dispersant to the slurry in order to efficiently process the particles and further increase the independence of the particles. Various dispersants can be used as this dispersant, but in order to prevent deterioration of the properties of the metal magnetic powder obtained as a final product, carbon, nitrogen, oxygen, etc., which can be decomposed in a later step, are used. It is preferred to use a structured dispersant. In particular, it is preferable to use a dispersant made of a compound having a carboxyl group that can act on the surface of the iron oxyhydroxide particles to increase the wet grinding efficiency. Examples of the dispersant composed of such a compound having a carboxyl group (for example, Polyty A530, A540, A550, N-100K, PS-1900 manufactured by Lion Corporation, SN Dispersant 5468 manufactured by San Nopco Corporation, Kao Corporation Commercially available dispersants (such as Poise 520, 530, 532A,
オキシ水酸化鉄の粒子の表面に被着させる焼結防止成分は、（イットリウム（Ｙ）を含む）希土類元素（Ｒ）から選ばれる１種以上を含むのが好ましい。このような焼結防止成分を被着させることにより、オキシ水酸化鉄の脱水および加熱還元時の焼結を防止することができる。なお、焼結防止成分を被着させる前にオキシ水酸化鉄のスラリーを湿式粉砕することにより、オキシ水酸化鉄の粒子の凝集をほぐすことができるので、焼結防止成分がより均一にオキシ水酸化鉄の粒子の表面を被覆することができる。 The sintering preventing component to be deposited on the surface of the iron oxyhydroxide particles preferably contains one or more selected from rare earth elements (R) (including yttrium (Y)). By adhering such an anti-sintering component, it is possible to prevent dehydration of iron oxyhydroxide and sintering during heat reduction. In addition, since the iron oxyhydroxide slurry is wet-pulverized before depositing the sintering preventing component, the aggregation of the iron oxyhydroxide particles can be loosened, so that the sintering preventing component is more uniformly distributed in the oxywater solution. The surface of the iron oxide particles can be coated.
このようにして焼結防止成分が表面に被着した針状粒子からなるオキシ水酸化鉄を先駆物質として得た後、酸化性雰囲気下において２５０〜６００℃で加熱脱水することによって鉄系酸化物（α−酸化鉄（α−Ｆｅ２Ｏ３））を得ることができる。なお、この加熱脱水時の雰囲気中に適量の水蒸気を添加してもよい。また、この酸化性雰囲気下における加熱脱水を省略して、鉄系酸化物を経由せずにオキシ水酸化鉄を直接加熱還元してもよい。 Thus, after obtaining iron oxyhydroxide which consists of acicular particle | grains which the anti-sintering component was adhere | attached on the surface as a precursor, it heat-dehydrates at 250-600 degreeC by oxidizing atmosphere, and iron-type oxide (Α-iron oxide (α-Fe 2 O 3 )) can be obtained. An appropriate amount of water vapor may be added to the atmosphere during the heat dehydration. Further, the heat dehydration in the oxidizing atmosphere may be omitted, and the iron oxyhydroxide may be directly heated and reduced without going through the iron-based oxide.
このようにして得られた鉄系酸化物を一酸化炭素、アセチレン、水素などの還元ガスにより２５０〜６００℃の温度範囲で還元する。この還元は、多段還元（設定された温度範囲において所定の温度で所定の時間保持することをその保持温度を変えて数回繰り返して還元すること）でもよい。この保持温度と保持時間を適正に制御することにより、金属磁性粉末の特性を変化させることができる。また、この還元処理の雰囲気として、還元ガスに水蒸気を添加した雰囲気を使用してもよい。 The iron-based oxide thus obtained is reduced in a temperature range of 250 to 600 ° C. with a reducing gas such as carbon monoxide, acetylene or hydrogen. This reduction may be multi-stage reduction (retaining for a predetermined time at a predetermined temperature within a set temperature range by repeating the reduction several times by changing the holding temperature). By appropriately controlling the holding temperature and the holding time, the characteristics of the metal magnetic powder can be changed. Moreover, you may use the atmosphere which added water vapor | steam to reducing gas as the atmosphere of this reduction process.
このように加熱還元して得られた金属磁性粉末は、そのまま大気中で取り扱うと発火のおそれがあるので、徐酸化工程によって金属磁性粉末の粒子の表面に非磁性酸化物層および９０ｅｍｕ／ｇ以下の磁性酸化物層の少なくとも一方の酸化物層を形成するのが好ましい。この徐酸化工程は、不活性ガスに添加する酸化性ガスの量を徐々に増加した雰囲気中において金属磁性粉末を２０〜３００℃の温度で所定時間保持して、金属磁性粉末の粒子の表面に酸化物層を形成する工程である。実際には、還元が終了した後の金属磁性粉末を徐酸化工程を行う温度まで冷却し、その温度で徐酸化を行うのが好ましく、この温度で弱酸化性ガスによって金属磁性粉末の粒子の表面に酸化物層を形成して安定化させるのが好ましい。 Since the metal magnetic powder obtained by heating and reducing in this manner may ignite if handled in the air as it is, a non-magnetic oxide layer and 90 emu / g or less are formed on the surface of the metal magnetic powder particles by a gradual oxidation process. It is preferable to form at least one of the magnetic oxide layers. In this gradual oxidation step, the metal magnetic powder is held at a temperature of 20 to 300 ° C. for a predetermined time in an atmosphere in which the amount of oxidizing gas added to the inert gas is gradually increased. This is a step of forming an oxide layer. In practice, it is preferable to cool the metal magnetic powder after the reduction is completed to a temperature at which the gradual oxidation process is performed, and to perform the gradual oxidation at that temperature, and at this temperature, the surface of the particles of the metal magnetic powder by the weak oxidizing gas. It is preferable to stabilize by forming an oxide layer.
上述した実施の形態の金属磁性粉末の製造方法により製造された金属磁性粉末は、鉄または鉄とコバルトを主成分とする金属磁性相を有する粒子からなる金属磁性粉末である。すなわち、金属磁性相を構成する磁性元素（例えば、鉄、コバルト、ニッケル）のうち、鉄または鉄とコバルトの合計の原子割合が５０％以上の金属磁性粉末である。 The metal magnetic powder produced by the method for producing a metal magnetic powder according to the above-described embodiment is a metal magnetic powder comprising particles having a metal magnetic phase mainly composed of iron or iron and cobalt. That is, among magnetic elements (for example, iron, cobalt, nickel) constituting the metal magnetic phase, it is a metal magnetic powder in which the total atomic ratio of iron or iron and cobalt is 50% or more.
この金属磁性粉末の表面に酸化膜を形成すると、鉄（Ｆｅ）とコバルト（Ｃｏ）を主成分として含有する金属磁性粉末では、「｛Ｃｏ含有量（ａｔ％）／Ｆｅ含有量（ａｔ％）｝×１００」で表される、Ｆｅに対するＣｏの原子割合（以下「Ｃｏ／Ｆｅ原子比」という）が、０〜５０ａｔ％であるのが好ましく、５〜４５ａｔ％であるのがさらに好ましく、１０〜４０ａｔ％であるのが最も好ましい。このような範囲であれば、安定した磁気特性が得られ易く、耐候性も良好になる。 When an oxide film is formed on the surface of the metal magnetic powder, the metal magnetic powder containing iron (Fe) and cobalt (Co) as main components is expressed as “{Co content (at%) / Fe content (at%). } × 100 ”, the atomic ratio of Co to Fe (hereinafter referred to as“ Co / Fe atomic ratio ”) is preferably 0 to 50 at%, more preferably 5 to 45 at%. Most preferred is ˜40 at%. Within such a range, stable magnetic characteristics can be easily obtained and weather resistance is also improved.
この金属磁性粉末にはＡｌが固溶しているのが好ましい。Ａｌが固溶することにより、耐候性が改善されるとともに、焼結防止の効果も得られる。しかし、Ａｌは非磁性成分であり、固溶量が多過ぎると磁気特性が希釈されて好ましくないので、金属磁性粉末全体に対するＡｌ含有量は、０．１〜１０質量％であるのが好ましく、０．５〜９質量％であるのがさらに好ましく、１〜８質量％であるのが最も好ましい。 It is preferable that Al is dissolved in the metal magnetic powder. When Al is dissolved, weather resistance is improved and an effect of preventing sintering is also obtained. However, Al is a non-magnetic component, and if the solid solution amount is too large, the magnetic properties are diluted, which is not preferable. Therefore, the Al content with respect to the entire metal magnetic powder is preferably 0.1 to 10% by mass, More preferably, it is 0.5-9 mass%, and it is most preferable that it is 1-8 mass%.
この金属磁性粉末には、還元時に焼結を抑制するための焼結防止成分が被着している。この焼結防止成分は、（イットリウム（Ｙ）やスカンジウム（Ｓｃ）を含む）希土類元素から選ばれる１種以上を含むのが好ましい。金属磁性粉末が微粒子の場合には、焼結が進み易いことから、加熱の際に金属磁性粉末の微粒子の表面に希土類元素からなる焼結防止成分が被着しているのが極めて有効である。しかし、希土類元素は非磁性成分であり、希土類元素の含有量が多過ぎると磁気特性が希釈され、また、この金属磁性粉末を使用して作製した磁気テープとヘッドの摺動時にヘッドの汚れとして付着する可能性もあるので好ましくない。そのため、金属磁性粉末全体に対する希土類元素の含有量は、０質量％より多く且つ２０質量％以下であるのが好ましく、０．１〜１７質量％であるのがさらに好ましく、０．５〜１５質量％であるのが最も好ましい。 This metal magnetic powder is coated with a sintering preventing component for suppressing sintering during reduction. This anti-sintering component preferably contains one or more selected from rare earth elements (including yttrium (Y) and scandium (Sc)). When the metal magnetic powder is a fine particle, sintering is easy to proceed. Therefore, it is extremely effective that a sintering preventing component made of a rare earth element is deposited on the surface of the fine particle of the metal magnetic powder during heating. . However, rare earth elements are non-magnetic components, and if the content of rare earth elements is too high, the magnetic properties are diluted. Since it may adhere, it is not preferable. Therefore, the content of the rare earth element with respect to the entire metal magnetic powder is preferably more than 0% by mass and 20% by mass or less, more preferably 0.1 to 17% by mass, and more preferably 0.5 to 15% by mass. % Is most preferred.
また、金属磁性粉末は、アルカリ土類金属を含んでもよい。アルカリ土類金属は意図的に添加してもよいが、原料の第一鉄塩、コバルト塩、アルミニウム塩、希土類塩から混入することもある。アルカリ土類金属の含有量が多過ぎると、時間の経過とともに周囲のバインダーなどと反応して塩を形成し、保存安定性を悪化させることがあり、特にアルカリ土類金属が水溶性の成分として含まれる場合にその影響が顕著に現れる可能性がある。そのため、金属磁性粉末全体に対するアルカリ土類金属の含有量は、０質量％より多く且つ０．５質量％以下であるのが好ましく、０．０１〜０．３質量％であるのがさらに好ましく、０．０１〜０．１質量％であるのが最も好ましい。 Moreover, the metal magnetic powder may contain an alkaline earth metal. The alkaline earth metal may be intentionally added, but may be mixed from the raw material ferrous salt, cobalt salt, aluminum salt or rare earth salt. When there is too much content of alkaline earth metal, it may react with surrounding binders over time to form a salt and deteriorate storage stability. Especially alkaline earth metal is a water-soluble component. If included, the effect may be noticeable. Therefore, the content of the alkaline earth metal with respect to the entire metal magnetic powder is preferably more than 0% by mass and 0.5% by mass or less, more preferably 0.01 to 0.3% by mass, Most preferably, it is 0.01-0.1 mass%.
この金属磁性粉末の粒子サイズは、平均長軸長が１０〜５０ｎｍであるのが好ましく、１０〜４０ｎｍであるのがさらに好ましい。平均長軸長が５０ｎｍを超えると、粒子体積が大きくなってしまい、磁気記録の高記録密度化に十分対応することが難しくなる。 As for the particle size of the metal magnetic powder, the average major axis length is preferably 10 to 50 nm, and more preferably 10 to 40 nm. When the average major axis length exceeds 50 nm, the particle volume becomes large, and it becomes difficult to sufficiently cope with the increase in recording density of magnetic recording.
この金属磁性粉末は、水銀圧入法により測定した細孔分布において細孔径が２００ｎｍ以上の範囲の累積細孔容積が０．７５ｍＬ／ｇ以下である。この累積細孔容積が０．７５ｍＬ／ｇより大きいと、金属磁性粉末にオキシ水酸化鉄の脱水および加熱還元時の粒子の焼結によるネッキングにより生じた粒子間の空孔が多く存在していることを示し、そのような金属磁性粉末は、粒子間の凝集が多くなり過ぎるため、高密度磁気記録に使用するには好ましくないからである。 This metal magnetic powder has a cumulative pore volume of 0.75 mL / g or less in a pore size range of 200 nm or more in a pore distribution measured by a mercury intrusion method. If the cumulative pore volume is larger than 0.75 mL / g, the metal magnetic powder has many voids between particles produced by necking by dehydration of iron oxyhydroxide and sintering of particles during heat reduction. This is because such a metal magnetic powder is not preferable for use in high-density magnetic recording because of excessive aggregation between particles.
この金属磁性粉末は、ゆるめ嵩密度が０．３５ｇ／ｃｃ以上で且つ固め嵩密度が０．４０ｇ／ｃｃ以上である。なお、本明細書中において、「ゆるめ嵩密度」とは、金属磁性粉末を自由落下させて容器に詰めたときの単位容積質量、「固め嵩密度」とは、金属磁性粉末１００ｃｃを容器に入れてタッピングを１８０回行った状態の単位容積質量をいい、これらの値から金属磁性粉末の単位体積当たりの詰まり易さがわかる。金属磁性粉末のゆるめ嵩密度が０．３５ｇ／ｃｃ以上で且つ固め嵩密度が０．４０ｇ／ｃｃ以上であれば、金属磁性粉末の粒子が詰まり易く、粒子が焼結せずに独立に存在する割合が高いため、磁気テープに使用したときに金属磁性粉末の単位体積当たりの保磁力が高くなることがわかった。なお、実用性を考慮すると、ゆるめ嵩密度は、好ましくは０．３５〜０．６５ｇ／ｃｃ、さらに好ましくは０．３５〜０．５５ｇ／ｃｃであり、固め嵩密度は、好ましくは０．４０〜０．６０ｇ／ｃｃ、さらに好ましくは０．４０〜０．５５ｇ／ｃｃである。 This metal magnetic powder has a loose bulk density of 0.35 g / cc or more and a hardened bulk density of 0.40 g / cc or more. In this specification, “loose bulk density” means the unit volume mass when the metal magnetic powder is freely dropped and packed in a container, and “hardened bulk density” means that 100 cc of the metal magnetic powder is put in the container. The unit volume mass in the state where tapping is performed 180 times is referred to, and the ease of clogging per unit volume of the metal magnetic powder can be understood from these values. If the loose bulk density of the metal magnetic powder is 0.35 g / cc or more and the solid bulk density is 0.40 g / cc or more, the particles of the metal magnetic powder are easily clogged and the particles exist independently without being sintered. Since the ratio was high, it was found that the coercive force per unit volume of the metal magnetic powder was high when used in a magnetic tape. In consideration of practicality, the loose bulk density is preferably 0.35 to 0.65 g / cc, more preferably 0.35 to 0.55 g / cc, and the hard bulk density is preferably 0.40. It is -0.60g / cc, More preferably, it is 0.40-0.55g / cc.
以下、本発明による金属磁性粉末およびその製造方法の実施例について詳細に説明する。 Examples of the magnetic metal powder and the method for producing the same according to the present invention will be described in detail below.
［実施例１］
Ｃｏ／Ｆｅ＝２０．１ａｔ％、Ａｌ／（Ｆｅ＋Ｃｏ）＝１０．４ａｔ％の組成を有する長軸長８８．１ｎｍのオキシ水酸化鉄（α−ＦｅＯＯＨ）を用意し、このオキシ水酸化鉄のスラリーを攪拌しながら、カルボキシル基を有する分散剤をオキシ水酸化鉄に対して２．５質量％になるように添加して１０分間熟成させた後、この熟成させたスラリーを図１に概略的に示す分散処理装置の処理タンク１に入れて分散処理（湿式粉砕処理）を施した。この分散処理では、スラリーが処理タンク１から分散機を通って処理タンク２に送液されるのを１パスとし、処理タンク２から分散機を通って処理タンク１に送液されるのを２パスとして、１０パス繰り返すことによって、オキシ水酸化鉄粒子を分散させた。なお、分散機としてアルティマイザーシステム（株式会社スギノマシン製のＨＪＰ−２００８４）を使用した。この湿式粉砕後のオキシ水酸化鉄の粒子の透過型電子顕微鏡（ＴＥＭ）写真を図７に示す。このＴＥＭ写真からわかるように、オキシ水酸化鉄のスラリーを湿式粉砕することにより、オキシ水酸化鉄の粒子の凝集がほぐれていることがわかる。
[Example 1]
An iron oxyhydroxide (α-FeOOH) having a composition of Co / Fe = 20.1 at% and Al / (Fe + Co) = 10.4 at% and having a major axis length of 88.1 nm is prepared, and this iron oxyhydroxide slurry 1 was added to a dispersant having a carboxyl group so as to be 2.5% by mass with respect to iron oxyhydroxide and aged for 10 minutes, and the aged slurry is schematically shown in FIG. Dispersion treatment (wet pulverization treatment) was performed in the treatment tank 1 of the dispersion treatment apparatus shown. In this dispersion treatment, the slurry is sent from the treatment tank 1 through the dispersion machine to the
このようにしてオキシ水酸化鉄粒子を分散させた液に（イットリウムとして２．０質量％含有する）酸化イットリウムの硫酸水溶液３００ｇを添加して、Ａｌが固溶するとともにイットリウムが表面に被着したオキシ水酸化鉄の粉末（ケーキ）を得た。このオキシ水酸化鉄のケーキを濾過し、水洗した後、１３０℃で乾燥させ、オキシ水酸化鉄の乾燥固形物を得た。 300 g of a sulfuric acid aqueous solution of yttrium oxide (containing 2.0 mass% as yttrium) was added to the liquid in which the iron oxyhydroxide particles were dispersed in this manner, so that Al was dissolved and yttrium was deposited on the surface. An iron oxyhydroxide powder (cake) was obtained. The iron oxyhydroxide cake was filtered, washed with water, and dried at 130 ° C. to obtain a dry solid of iron oxyhydroxide.
このオキシ水酸化鉄の乾燥固形物１０ｇをバケットに入れ、水の流量として１．０ｇ／分で水蒸気を添加しながら大気中において４００℃で焼成し、α−酸化鉄（α−Ｆｅ２Ｏ３）（ヘマタイト）を主成分とする鉄系酸化物を得た。 10 g of this dry iron oxyhydroxide solid was put into a bucket and fired at 400 ° C. in the atmosphere while adding water vapor at a flow rate of water of 1.0 g / min, and α-iron oxide (α-Fe 2 O 3 ) (Hematite) as a main component was obtained.
このα−酸化鉄を主成分とする鉄系酸化物を通気可能なバケット内に投入した後、バケットを貫通型還元炉内に装入し、水素ガスを４０Ｌ／分の流量で通気するとともに、水の流量として１．０ｇ／分で水蒸気を添加しながら、５００℃で６０分間還元処理を行った。この還元処理が終了した後、水蒸気の供給を停止し、水素雰囲気下において昇温速度１０℃／分で６００℃まで昇温させた。その後、水の流量として１．０ｇ／分で水蒸気を添加しながら６０分間高温還元処理を行い、（Ｆｅの一部がＣｏに置換された）金属鉄の粉末を得た。 After charging the iron-based oxide containing α-iron oxide as a main component into a bucket that can be ventilated, the bucket is charged into a through-type reduction furnace, and hydrogen gas is vented at a flow rate of 40 L / min. Reduction treatment was performed at 500 ° C. for 60 minutes while adding water vapor at a water flow rate of 1.0 g / min. After the reduction treatment was completed, the supply of water vapor was stopped, and the temperature was raised to 600 ° C. at a temperature rising rate of 10 ° C./min in a hydrogen atmosphere. Then, high-temperature reduction treatment was performed for 60 minutes while adding water vapor at a flow rate of water of 1.0 g / min, to obtain metallic iron powder (a part of Fe was replaced with Co).
次に、炉内雰囲気を水素から窒素に変換し、５０Ｌ／分の流量で窒素を導入しながら炉内温度を降温速度２０℃／分で８０℃まで降温させた。その後、窒素と純酸素をそれぞれ５０Ｌ／分および４００ｍＬ／分の流量で混合したガスを炉内に添加した後、水の流量として１．０ｇ／分で水蒸気を添加しながら、水蒸気と酸素と窒素の混合雰囲気中において、粉末の表面に酸化膜を形成し、空気の供給量を徐々に増加することによって、混合雰囲気中における酸素濃度を上昇させ、最終的な酸素の流量を２．０Ｌ／分にした。なお、炉内に導入されるガスの総量は、窒素の流量を調整することによってほぼ一定に保たれるようにし、この徐酸化処理は、約８０℃に維持される雰囲気下において行った。 Next, the furnace atmosphere was converted from hydrogen to nitrogen, and the furnace temperature was lowered to 80 ° C. at a temperature drop rate of 20 ° C./min while introducing nitrogen at a flow rate of 50 L / min. Then, after adding a gas in which nitrogen and pure oxygen were mixed at a flow rate of 50 L / min and 400 mL / min, respectively, and adding water vapor at a flow rate of 1.0 g / min, water vapor, oxygen and nitrogen were added. In the mixed atmosphere, an oxide film is formed on the surface of the powder, and by gradually increasing the supply amount of air, the oxygen concentration in the mixed atmosphere is increased, and the final oxygen flow rate is 2.0 L / min. I made it. The total amount of gas introduced into the furnace was kept almost constant by adjusting the flow rate of nitrogen, and this gradual oxidation treatment was performed in an atmosphere maintained at about 80 ° C.
このようにして得られた金属磁性粉末（表面に酸化膜を有する最終製品としての金属磁性粉末）の製造条件として、オキシ水酸化鉄の長軸長、分散機の種類、分散処理のパス数および分散剤の添加量を表１に示す。 The production conditions of the metal magnetic powder thus obtained (the metal magnetic powder as the final product having an oxide film on the surface) include the major axis length of iron oxyhydroxide, the type of disperser, the number of passes of the dispersion treatment, and The amount of dispersant added is shown in Table 1.
また、得られた金属磁性粉末について、金属磁性相と酸化膜を含む粒子全体の質量分析を行うことによって粉末の組成を求めた。なお、Ｃｏ、Ａｌおよび（Ｙを含む）希土類元素の定量は、日本ジャーレルアッシュ株式会社製の高周波誘導プラズマ発光分析装置ＩＣＰ（ＩＲＩＳ／ＡＰ）を使用し、Ｆｅの定量は、平沼産業株式会社製の平沼自動滴定装置（ＣＯＭＴＩＭＥ−９８０）を使用して行った。また、これらの定量結果は質量％として与えられるので、適宜原子％（ａｔ％）に換算して、原子比Ｃｏ／Ｆｅ、Ａｌ／（Ｆｅ＋Ｃｏ）、Ｙ／（Ｆｅ＋Ｃｏ）を求めた。その結果、Ｃｏ／Ｆｅ＝２０．４ａｔ％、Ａｌ／（Ｆｅ＋Ｃｏ）＝１０．３ａｔ％、Ｙ／（Ｆｅ＋Ｃｏ）＝９．８ａｔ％であった。 Moreover, about the obtained metal magnetic powder, the composition of the powder was calculated | required by performing mass spectrometry of the whole particle | grains containing a metal magnetic phase and an oxide film. Co, Al and rare earth elements (including Y) were quantified using a high frequency induction plasma emission spectrometer ICP (IRIS / AP) manufactured by Japan Jarrel Ash Co., and Fe was quantified by Hiranuma Sangyo Co., Ltd. This was carried out using a Hiranuma automatic titrator (COMTIME-980). Since these quantitative results are given as mass%, the atomic ratios Co / Fe, Al / (Fe + Co), and Y / (Fe + Co) were determined by appropriately converting to atomic% (at%). As a result, Co / Fe = 20.4 at%, Al / (Fe + Co) = 10.3 at%, and Y / (Fe + Co) = 9.8 at%.
また、得られた金属磁性粉末の粉体物理特性として、平均長軸長、平均短軸長、平均粒子体積、結晶子サイズＤｘおよびＢＥＴ比表面積を算出し、ゆるめ嵩密度および固め嵩密度を測定した。 In addition, as the powder physical properties of the obtained metal magnetic powder, the average major axis length, the average minor axis length, the average particle volume, the crystallite size Dx and the BET specific surface area are calculated, and the loose bulk density and the compacted bulk density are measured. did.
（平均長軸長および平均短軸長）
平均長軸長および平均短軸長は、透過型電子顕微鏡（日本電子株式会社製のＪＥＭ−１００ＣＸＭａｒｋ−ＩＩ型）を使用し、１００ｋＶの加速電圧で、明視野で金属磁性粉末を観察した像を（例えば、倍率５８０００倍で）写真撮影して（例えば、縦横の倍率を９倍に）拡大し、複数の写真から単分散している粒子をランダムに３００個選択して、各々の粒子について長軸長と短軸長を測定し、その平均値から求めた。
(Average major axis length and average minor axis length)
The average major axis length and the average minor axis length are obtained by using a transmission electron microscope (JEM-100CXMark-II type manufactured by JEOL Ltd.) and observing an image obtained by observing the metal magnetic powder in a bright field at an acceleration voltage of 100 kV. Take a picture (for example, at a magnification of 58000) and magnify it (for example, the vertical and horizontal magnification is 9 times), and randomly select 300 monodispersed particles from a plurality of photographs. The axial length and the short axis length were measured and obtained from the average value.
（平均粒子体積）
平均粒子体積は、金属磁性粉末の粒子を円柱形状に近似して、平均粒子体積＝π×平均長軸長×（平均短軸長／２）２から求めた。
(Average particle volume)
The average particle volume was determined from the average particle volume = π × average long axis length × (average short axis length / 2) 2 by approximating the particles of the metal magnetic powder to a cylindrical shape.
（ＢＥＴ比表面積）
ＢＥＴ比表面積は、ユアサイオニクス株式会社製の４ソーブＵＳを用いて、ＢＥＴ法により求めた。
(BET specific surface area)
The BET specific surface area was calculated | required by BET method using 4 Sorb US made from Your Scionics.
（結晶子サイズＤｘ）
結晶子サイズＤｘは、Ｘ線回折装置（株式会社リガク製のＵｌｉｔｉｍａｔｅ−ＩＩＩ）を使用して、測定範囲２θ＝４５〜６０°においてスキャンスピード５°／分で積算回数を５回としてＸ線回折パターンを測定し、シェラー式（結晶子サイズ＝Ｋλ／βｃｏｓθ）により求めた。このシェラーの式において、Ｋはシェラー定数０．９、λはＣｏ−Ｋα線波長、βはＦｅ（１１０）面の回折ピークの半価幅（ラジアン）、θは回折角（ラジアン）である。
(Crystallite size Dx)
The crystallite size Dx is determined by X-ray diffraction using an X-ray diffractometer (Ultimate-III manufactured by Rigaku Corporation) with a scanning speed of 5 ° / min and a number of integrations of 5 times in the measurement range 2θ = 45-60 °. The pattern was measured and determined by the Scherrer equation (crystallite size = Kλ / βcos θ). In this Scherrer equation, K is the Scherrer constant 0.9, λ is the Co-Kα ray wavelength, β is the half-value width (radian) of the diffraction peak of the Fe (110) plane, and θ is the diffraction angle (radian).
（ゆるめ嵩密度および固め嵩密度）
ゆるめ嵩密度および固め嵩密度は、粉体特性評価装置（ホソカワミクロン株式会社製のパウダーテスターＰＴ−Ｅ型）を使用して測定した。
(Loose bulk density and firm bulk density)
The loose bulk density and the hard bulk density were measured using a powder characteristic evaluation apparatus (Powder Tester PT-E type manufactured by Hosokawa Micron Corporation).
これらの結果を表２に示す。 These results are shown in Table 2.
（金属磁性粉末の磁気特性および耐候性の評価）
得られた金属磁性粉末の磁気特性として、東英工業株式会社製のＶＳＭ装置（ＶＳＭ−７Ｐ）を使用して、外部磁場１０ｋＯｅ（７９５．８ｋＡ／ｍ）で、保磁力Ｈｃ（ＯｅおよびｋＡ／ｍ）、飽和磁化σｓ（Ａｍ２／ｋｇ）、角形比ＳＱを測定した。また、金属磁性粉末の耐候性を評価する指標として、金属磁性粉末を設定温度６０℃、相対湿度９０％の恒温恒湿容器内に１週間保持したときの飽和磁化σｓの低下率Δσｓ（％）を測定した。これらの結果を表３に示す。
(Evaluation of magnetic properties and weather resistance of metallic magnetic powder)
As the magnetic properties of the obtained metal magnetic powder, using a VSM device (VSM-7P) manufactured by Toei Kogyo Co., Ltd., an external magnetic field of 10 kOe (795.8 kA / m) and a coercive force Hc (Oe and kA / m), saturation magnetization σs (Am 2 / kg), and squareness ratio SQ were measured. Further, as an index for evaluating the weather resistance of the metal magnetic powder, the decrease rate Δσs (%) of the saturation magnetization σs when the metal magnetic powder is kept in a constant temperature and humidity container at a set temperature of 60 ° C. and a relative humidity of 90% for one week. Was measured. These results are shown in Table 3.
（磁気記録媒体の磁気特性）
得られた金属磁性粉末１００質量部に、塩化ビニル樹脂（日本ゼオン株式会社製のＭＲ−５５５）１５質量部、ポリウレタン樹脂（東洋紡株式会社製のＵＲ−８２００）１５質量部、ステアリン酸１質量部、アセチルアセトン１質量部、メチルエチルケトン１９０質量部、シクロヘキサノン８０質量部およびトルエン１１０質量部を加えた組成の磁性塗料をマイクロピペットで０．７００ｍＬ採取してポットに添加し、その直後にスチールボール（２φ）３０ｇとナイロンボール（８φ）１０個をポットに加えて、ポットの蓋を閉じて１０分間静置した。その後、ポットを遠心式ボールミル（ＦＲＩＴＳＨ Ｐ−６）にセットし、ゆっくりと回転数を上げて６００ｒｐｍに調整し、６０分間分散させた。遠心式ボールミルを停止した後、ポットを取り出し、予めメチルエチルケトンとトルエンを１：１で混合した調整液１．８００ｍＬをマイクロピペットで添加した。その後、再びポットを遠心式ボールミルにセットし、６００ｒｐｍで５分間分散させて、磁性塗料を作製した。
(Magnetic properties of magnetic recording media)
100 parts by mass of the obtained metal magnetic powder, 15 parts by mass of vinyl chloride resin (MR-555 manufactured by Nippon Zeon Co., Ltd.), 15 parts by mass of polyurethane resin (UR-8200 manufactured by Toyobo Co., Ltd.), 1 part by mass of stearic acid Then, 0.700 mL of a magnetic paint having a composition comprising 1 part by mass of acetylacetone, 190 parts by mass of methyl ethyl ketone, 80 parts by mass of cyclohexanone and 110 parts by mass of toluene was sampled with a micropipette and added to the pot. 30 g and 10 nylon balls (8φ) were added to the pot, and the pot lid was closed and allowed to stand for 10 minutes. Thereafter, the pot was set on a centrifugal ball mill (FRITSH P-6), and the number of rotations was slowly increased to 600 rpm and dispersed for 60 minutes. After stopping the centrifugal ball mill, the pot was taken out and 1.800 mL of a preliminarily mixed solution of methyl ethyl ketone and toluene at 1: 1 was added with a micropipette. Thereafter, the pot was set again on the centrifugal ball mill and dispersed at 600 rpm for 5 minutes to produce a magnetic paint.
次に、ポットの蓋を開けてナイロンボールを取り除き、スチールボールごと磁性塗料をアプリケータ（５５μｍ）に入れ、ベースフィルム（東レ株式会社製のポリエチレンフィルム１５Ｃ−Ｂ５００、膜厚１５μｍ）上に磁性塗料を塗布した後、迅速に５．５ｋＧの配向器のコイル中心に置いて磁場配向させた後、乾燥させて磁気テープを作製した。 Next, the pot lid is opened, the nylon balls are removed, the steel ball and the magnetic paint are put into an applicator (55 μm), and the magnetic paint is applied on the base film (polyethylene film 15C-B500 manufactured by Toray Industries, Inc., film thickness 15 μm). Was applied to the coil center of a 5.5 kG aligner and magnetically oriented, and then dried to produce a magnetic tape.
このようにして作製した媒体としての磁気テープについて、東英工業株式会社製のＶＳＭ装置（ＶＳＭ−７Ｐ）を使用して磁気測定を行い、保磁力Ｈｃｘ（ＯｅおよびｋＡ／ｍ）、金属磁性粉末の単位体積当たりの磁気テープの保磁力Ｈｃｘ／Ｖ（Ｏｅ／ｎｍ３）、保磁力分布ＳＦＤ、角形比ＳＱ、配向比ＯＲを求めた。これらの結果を表４に示す。 The magnetic tape as the medium thus produced was subjected to magnetic measurement using a VSM device (VSM-7P) manufactured by Toei Kogyo Co., Ltd., coercive force Hcx (Oe and kA / m), metal magnetic powder The coercive force Hcx / V (Oe / nm 3 ), coercive force distribution SFD, squareness ratio SQ, and orientation ratio OR of the magnetic tape per unit volume were determined. These results are shown in Table 4.
また、得られた金属磁性粉末のゆるめ嵩密度および固め嵩密度とその金属磁性粉末の単位体積当たりの磁気テープの保磁力との関係をそれぞれ図２および図３に示す。 Moreover, the relationship between the loose bulk density and the hard bulk density of the obtained metal magnetic powder and the coercive force of the magnetic tape per unit volume of the metal magnetic powder is shown in FIGS. 2 and 3, respectively.
また、得られた金属磁性粉末の粒子の焼結状態を確認するため、細孔分布ポロシメーター（Ｍｉｃｒｏｍｅｒｉｔｉｃｓ Ｉｎｓｔｒｕｍｅｎｔ社製のＡｕｔｏＰｏｒｅＩＶ ９５００
Ｖ１．０５）を用いて、水銀圧入法により細孔分布測定を行った。その結果、得られた細孔径と累積細孔容積の関係を図４に示す。また、得られた金属磁性粉末を用いて磁気テープを作製した際の金属磁性粉末の平均粒子体積と磁気テープの保磁力との関係を図５に示し、得られた金属磁性粉末の水銀圧入法により測定した細孔分布における細孔径２００ｎｍ以上の累積細孔容積とその金属磁性粉末を用いて作製した磁気テープの配向比との関係を図６に示す。
In addition, in order to confirm the sintered state of the particles of the obtained metal magnetic powder, a pore distribution porosimeter (AutoPore IV 9500 manufactured by Micromeritics Instruments) was used.
V1.05) was used to measure pore distribution by mercury porosimetry. As a result, the relationship between the obtained pore diameter and the cumulative pore volume is shown in FIG. FIG. 5 shows the relationship between the average particle volume of the metal magnetic powder and the coercive force of the magnetic tape when a magnetic tape is produced using the obtained metal magnetic powder, and a mercury intrusion method of the obtained metal magnetic powder. FIG. 6 shows the relationship between the cumulative pore volume having a pore diameter of 200 nm or more in the pore distribution measured by the above and the orientation ratio of the magnetic tape produced using the metal magnetic powder.
［実施例２〜３］
それぞれ長軸長７６．５ｎｍ（実施例２）および６６．４ｎｍ（実施例３）のオキシ水酸化鉄（実施例１とほぼ同じ組成）を使用した以外は実施例１と同様の方法により、金属磁性粉末を作製した。この金属磁性粉末の製造条件を表１に示す。
[Examples 2-3]
In the same manner as in Example 1, except that iron oxyhydroxides having a major axis length of 76.5 nm (Example 2) and 66.4 nm (Example 3) were used (substantially the same composition as Example 1), Magnetic powder was prepared. The production conditions for this metal magnetic powder are shown in Table 1.
また、得られた金属磁性粉末について、実施例１と同様の方法により粉体物理特性および磁気特性を測定した。これらの結果をそれぞれ表２および表３に示す。 The obtained metal magnetic powder was measured for powder physical properties and magnetic properties by the same method as in Example 1. These results are shown in Table 2 and Table 3, respectively.
また、得られた金属磁性粉末を使用して実施例１と同様の方法により作製した磁気テープについて、実施例１と同様の方法により磁気測定を行った。その結果を表４に示す。 In addition, magnetic measurement was performed on the magnetic tape produced by the same method as in Example 1 using the obtained metal magnetic powder by the same method as in Example 1. The results are shown in Table 4.
また、得られた金属磁性粉末のゆるめ嵩密度および固め嵩密度とその金属磁性粉末の単位体積当たりの磁気テープの保磁力との関係をそれぞれ図２および図３に示す。 Moreover, the relationship between the loose bulk density and the hard bulk density of the obtained metal magnetic powder and the coercive force of the magnetic tape per unit volume of the metal magnetic powder is shown in FIGS. 2 and 3, respectively.
さらに、得られた金属磁性粉末について、実施例１と同様の方法により細孔分布測定を行った。その結果、得られた細孔径と累積細孔容積の関係を図４に示す。また、得られた金属磁性粉末を用いて磁気テープを作製した際の金属磁性粉末の平均粒子体積と磁気テープの保磁力との関係を図５に示し、得られた金属磁性粉末の水銀圧入法により測定した細孔分布における細孔径２００ｎｍ以上の累積細孔容積とその金属磁性粉末を用いて作製した磁気テープの配向比との関係を図６に示す。 Furthermore, pore distribution measurement was performed on the obtained metal magnetic powder by the same method as in Example 1. As a result, the relationship between the obtained pore diameter and the cumulative pore volume is shown in FIG. FIG. 5 shows the relationship between the average particle volume of the metal magnetic powder and the coercive force of the magnetic tape when a magnetic tape is produced using the obtained metal magnetic powder, and a mercury intrusion method of the obtained metal magnetic powder. FIG. 6 shows the relationship between the cumulative pore volume having a pore diameter of 200 nm or more in the pore distribution measured by the above and the orientation ratio of the magnetic tape produced using the metal magnetic powder.
［実施例４］
長軸長９０．２ｎｍのオキシ水酸化鉄（実施例１とほぼ同じ組成）を使用し、分散剤の添加量を５．０質量％とした以外は実施例１と同様の方法により、金属磁性粉末を作製した。この金属磁性粉末の製造条件を表１に示す。
[Example 4]
In the same manner as in Example 1 except that iron oxyhydroxide having a major axis length of 90.2 nm (substantially the same composition as in Example 1) was used and the addition amount of the dispersant was 5.0% by mass, A powder was prepared. The production conditions for this metal magnetic powder are shown in Table 1.
また、得られた金属磁性粉末について、実施例１と同様の方法により粉体物理特性および磁気特性を測定した。これらの結果をそれぞれ表２および表３に示す。 The obtained metal magnetic powder was measured for powder physical properties and magnetic properties by the same method as in Example 1. These results are shown in Table 2 and Table 3, respectively.
また、得られた金属磁性粉末を使用して実施例１と同様の方法により作製した磁気テープについて、実施例１と同様の方法により磁気測定を行った。その結果を表４に示す。 In addition, magnetic measurement was performed on the magnetic tape produced by the same method as in Example 1 using the obtained metal magnetic powder by the same method as in Example 1. The results are shown in Table 4.
また、得られた金属磁性粉末のゆるめ嵩密度および固め嵩密度とその金属磁性粉末の単位体積当たりの磁気テープの保磁力との関係をそれぞれ図２および図３に示す。 Moreover, the relationship between the loose bulk density and the hard bulk density of the obtained metal magnetic powder and the coercive force of the magnetic tape per unit volume of the metal magnetic powder is shown in FIGS. 2 and 3, respectively.
さらに、得られた金属磁性粉末について、実施例１と同様の方法により細孔分布測定を行った。その結果、得られた細孔径と累積細孔容積の関係を図４に示す。また、得られた金属磁性粉末を用いて磁気テープを作製した際の金属磁性粉末の平均粒子体積と磁気テープの保磁力との関係を図５に示し、得られた金属磁性粉末の水銀圧入法により測定した細孔分布における細孔径２００ｎｍ以上の累積細孔容積とその金属磁性粉末を用いて作製した磁気テープの配向比との関係を図６に示す。 Furthermore, pore distribution measurement was performed on the obtained metal magnetic powder by the same method as in Example 1. As a result, the relationship between the obtained pore diameter and the cumulative pore volume is shown in FIG. FIG. 5 shows the relationship between the average particle volume of the metal magnetic powder and the coercive force of the magnetic tape when a magnetic tape is produced using the obtained metal magnetic powder, and a mercury intrusion method of the obtained metal magnetic powder. FIG. 6 shows the relationship between the cumulative pore volume having a pore diameter of 200 nm or more in the pore distribution measured by the above and the orientation ratio of the magnetic tape produced using the metal magnetic powder.
［実施例５〜７］
それぞれ長軸長８６．５ｎｍ（実施例５）、７９．６ｎｍ（実施例６）および７０．７ｎｍ（実施例７）のオキシ水酸化鉄（実施例１とほぼ同じ組成）を使用し、分散機として超音波ホモジナイザー（株式会社日本精機製作所製のＵＳ−６００ＴＣＶＰ）を使用して１５時間処理した以外は実施例１と同様の方法により、金属磁性粉末を作製した。この金属磁性粉末の製造条件を表１に示す。
[Examples 5 to 7]
Dispersing machine using iron oxyhydroxide (substantially the same composition as in Example 1) having a major axis length of 86.5 nm (Example 5), 79.6 nm (Example 6) and 70.7 nm (Example 7), respectively. A metal magnetic powder was prepared in the same manner as in Example 1 except that the treatment was performed for 15 hours using an ultrasonic homogenizer (US-600TCVP manufactured by Nippon Seiki Seisakusho Co., Ltd.). The production conditions for this metal magnetic powder are shown in Table 1.
また、得られた金属磁性粉末について、実施例１と同様の方法により粉体物理特性および磁気特性を測定した。これらの結果をそれぞれ表２および表３に示す。 The obtained metal magnetic powder was measured for powder physical properties and magnetic properties by the same method as in Example 1. These results are shown in Table 2 and Table 3, respectively.
また、得られた金属磁性粉末を使用して実施例１と同様の方法により作製した磁気テープについて、実施例１と同様の方法により磁気測定を行った。その結果を表４に示す。また、得られた金属磁性粉末を用いて磁気テープを作製した際の金属磁性粉末の平均粒子体積と磁気テープの保磁力との関係を図５に示す。 In addition, magnetic measurement was performed on the magnetic tape produced by the same method as in Example 1 using the obtained metal magnetic powder by the same method as in Example 1. The results are shown in Table 4. FIG. 5 shows the relationship between the average particle volume of the metal magnetic powder and the coercivity of the magnetic tape when a magnetic tape is produced using the obtained metal magnetic powder.
［実施例８〜１０］
それぞれ長軸長８８．４ｎｍ（実施例８）、８０．２ｎｍ（実施例９）および７１．５ｎｍ（実施例１０）のオキシ水酸化鉄（実施例１とほぼ同じ組成）を使用し、分散機としてマイルダー（太平洋機工株式会社製のＭＤＮ３０３Ｖ）を使用してゼネレータの標準仕様により回転数１２０００ｒｐｍで処理した以外は実施例１と同様の方法により、金属磁性粉末を作製した。この金属磁性粉末の製造条件を表１に示す。
[Examples 8 to 10]
Dispersing machines using iron oxyhydroxides (substantially the same composition as in Example 1) having major axis lengths of 88.4 nm (Example 8), 80.2 nm (Example 9) and 71.5 nm (Example 10), respectively. A metal magnetic powder was prepared in the same manner as in Example 1 except that treatment was performed at 12000 rpm with a standard specification of the generator using Milder (MDN303V manufactured by Taiheiyo Kiko Co., Ltd.). The production conditions for this metal magnetic powder are shown in Table 1.
また、得られた金属磁性粉末について、実施例１と同様の方法により粉体物理特性および磁気特性を測定した。これらの結果をそれぞれ表２および表３に示す。 The obtained metal magnetic powder was measured for powder physical properties and magnetic properties by the same method as in Example 1. These results are shown in Table 2 and Table 3, respectively.
また、得られた金属磁性粉末を使用して実施例１と同様の方法により作製した磁気テープについて、実施例１と同様の方法により磁気測定を行った。その結果を表４に示す。また、得られた金属磁性粉末を用いて磁気テープを作製した際の金属磁性粉末の平均粒子体積と磁気テープの保磁力との関係を図５に示す。 In addition, magnetic measurement was performed on the magnetic tape produced by the same method as in Example 1 using the obtained metal magnetic powder by the same method as in Example 1. The results are shown in Table 4. FIG. 5 shows the relationship between the average particle volume of the metal magnetic powder and the coercivity of the magnetic tape when a magnetic tape is produced using the obtained metal magnetic powder.
［比較例１〜４］
それぞれ長軸長９１．１ｎｍ（比較例１）、８６．５ｎｍ（比較例２）、６７．０ｎｍ（比較例３）および９５．７ｎｍ（比較例４）のオキシ水酸化鉄（実施例１とほぼ同じ組成）を使用し、スラリーの分散処理を行わなかった以外は実施例１と同様の方法により、金属磁性粉末を作製した。この金属磁性粉末の製造条件を表１に示す。
[Comparative Examples 1-4]
Iron oxyhydroxides having a major axis length of 91.1 nm (Comparative Example 1), 86.5 nm (Comparative Example 2), 67.0 nm (Comparative Example 3) and 95.7 nm (Comparative Example 4), respectively (almost the same as Example 1) A metal magnetic powder was prepared in the same manner as in Example 1 except that the same composition was used and the slurry was not dispersed. The production conditions for this metal magnetic powder are shown in Table 1.
また、得られた金属磁性粉末について、実施例１と同様の方法により粉体物理特性および磁気特性を測定した。これらの結果をそれぞれ表２および表３に示す。 The obtained metal magnetic powder was measured for powder physical properties and magnetic properties by the same method as in Example 1. These results are shown in Table 2 and Table 3, respectively.
また、得られた金属磁性粉末を使用して実施例１と同様の方法により作製した磁気テープについて、実施例１と同様の方法により磁気測定を行った。その結果を表４に示す。 In addition, magnetic measurement was performed on the magnetic tape produced by the same method as in Example 1 using the obtained metal magnetic powder by the same method as in Example 1. The results are shown in Table 4.
また、得られた金属磁性粉末のゆるめ嵩密度および固め嵩密度とその金属磁性粉末の単位体積当たりの磁気テープの保磁力との関係をそれぞれ図２および図３に示す。 Moreover, the relationship between the loose bulk density and the hard bulk density of the obtained metal magnetic powder and the coercive force of the magnetic tape per unit volume of the metal magnetic powder is shown in FIGS. 2 and 3, respectively.
さらに、比較例１および比較例４で得られた金属磁性粉末について、実施例１と同様の方法により細孔分布測定を行った。その結果、得られた細孔径と累積細孔容積の関係を図４に示す。また、比較例１〜４で得られた金属磁性粉末を用いて磁気テープを作製した際の金属磁性粉末の平均粒子体積と磁気テープの保磁力との関係を図５に示し、比較例１および比較例４で得られた金属磁性粉末の水銀圧入法により測定した細孔分布における細孔径２００ｎｍ以上の累積細孔容積とその金属磁性粉末を用いて作製した磁気テープの配向比との関係を図６に示す。 Further, pore distribution measurement was performed on the metal magnetic powder obtained in Comparative Example 1 and Comparative Example 4 by the same method as in Example 1. As a result, the relationship between the obtained pore diameter and the cumulative pore volume is shown in FIG. Moreover, the relationship between the average particle volume of the metal magnetic powder and the coercive force of the magnetic tape when the magnetic tape was produced using the metal magnetic powder obtained in Comparative Examples 1 to 4 is shown in FIG. The relationship between the cumulative pore volume with a pore diameter of 200 nm or more in the pore distribution measured by the mercury intrusion method of the metal magnetic powder obtained in Comparative Example 4 and the orientation ratio of the magnetic tape produced using the metal magnetic powder is shown in FIG. It is shown in FIG.
また、比較例１のオキシ水酸化鉄の粒子（湿式粉砕処理を行わないオキシ水酸化鉄の粒子）の透過型電子顕微鏡（ＴＥＭ）写真を図８に示す。このＴＥＭ写真から、湿式粉砕処理を行わないオキシ水酸化鉄の粒子は凝集しているのがわかる。 Moreover, the transmission electron microscope (TEM) photograph of the iron oxyhydroxide particle | grains (Iron oxyhydroxide particle | grains which do not perform a wet grinding process) of the comparative example 1 is shown in FIG. From this TEM photograph, it can be seen that the iron oxyhydroxide particles that are not wet pulverized are aggregated.
［比較例５］
長軸長８９．６ｎｍのオキシ水酸化鉄（実施例１とほぼ同じ組成）を使用し、スラリーの分散処理を行わなかった以外は実施例１と同様の方法により、Ａｌが固溶するとともにイットリウムが表面に被着したオキシ水酸化鉄の乾燥固形物を得た。
[Comparative Example 5]
Al was dissolved in the same manner as in Example 1 except that iron oxyhydroxide having a major axis length of 89.6 nm (substantially the same composition as in Example 1) was used and the slurry was not dispersed. Gave a dry solid of iron oxyhydroxide deposited on the surface.
このオキシ水酸化鉄の乾燥固形物１０ｇをバケットに入れ、水の流量として１．０ｇ／分で水蒸気を添加しながら大気中において４００℃で焼成し、α−酸化鉄（α−Ｆｅ２Ｏ３）（ヘマタイト）を主成分とする鉄系酸化物を得た。 10 g of this dry iron oxyhydroxide solid was put into a bucket and fired at 400 ° C. in the atmosphere while adding water vapor at a flow rate of water of 1.0 g / min, and α-iron oxide (α-Fe 2 O 3 ) (Hematite) as a main component was obtained.
このα−酸化鉄を主成分とする鉄系酸化物を通気可能なバケット内に投入した後、バケットを貫通型還元炉内に装入し、水素ガスを４０Ｌ／分の流量で通気しながら、水の流量として１．０ｇ／分で水蒸気を添加しながら、４００℃で３０分間焼成させて還元処理を行った。この還元処理が終了した後、水蒸気の供給を停止し、水素雰囲気下において昇温速度１０℃／分で６００℃まで昇温させた。その後、水の流量として１．０ｇ／分で水蒸気を添加しながら６０分間高温還元処理を行い、鉄系合金粉末（α−鉄）（中間製品としての金属磁性粉末）を得た。 After putting this iron-based oxide containing α-iron oxide as a main component into a bucket that can be ventilated, the bucket was charged into a through-type reduction furnace, and hydrogen gas was vented at a flow rate of 40 L / min. While water vapor was added at a flow rate of 1.0 g / min, the reduction treatment was performed by baking at 400 ° C. for 30 minutes. After the reduction treatment was completed, the supply of water vapor was stopped, and the temperature was raised to 600 ° C. at a temperature rising rate of 10 ° C./min in a hydrogen atmosphere. Thereafter, a high temperature reduction treatment was performed for 60 minutes while adding water vapor at a flow rate of 1.0 g / min to obtain an iron-based alloy powder (α-iron) (metal magnetic powder as an intermediate product).
次に、この粉末の溶出処理を行うために使用する処理液として、純水９００ｍＬに対して、錯化剤として酒石酸ナトリウムを０．０５モル／Ｌ、緩衝剤として硫酸アンモニウムを０．１モル／Ｌになるように混合し、ＮＨ３でｐＨ＝９に調整した処理液を用意した。この処理液に還元処理後の中間製品としての金属磁性粉末１０ｇを投入して３０℃に保持した後、還元剤として水素化ホウ素ナトリウムを０．３モル／Ｌになるよう添加し、３０℃で３０分間攪拌しながら熟成させ、スラリーを得た。このスラリーを固液分離して固形分と濾液を回収した。 Next, as a treatment liquid used for the elution treatment of the powder, 0.05 mol / L of sodium tartrate as a complexing agent and 0.1 mol / L of ammonium sulfate as a buffering agent are applied to 900 mL of pure water. Then, a treatment liquid adjusted to pH = 9 with NH 3 was prepared. After adding 10 g of metal magnetic powder as an intermediate product after the reduction treatment to this treatment liquid and keeping it at 30 ° C., sodium borohydride was added as a reducing agent to 0.3 mol / L, and at 30 ° C. The slurry was aged with stirring for 30 minutes to obtain a slurry. This slurry was subjected to solid-liquid separation to recover a solid content and a filtrate.
回収した固形分を水洗し、濾過し、乾燥した後、実施例１と同様の方法により酸化処理を行って（表面に酸化膜を有する最終製品としての）金属磁性粉末を得た。この金属磁性粉末の製造条件を表１に示す。 The collected solid content was washed with water, filtered, dried, and then oxidized in the same manner as in Example 1 to obtain a metal magnetic powder (as a final product having an oxide film on the surface). The production conditions for this metal magnetic powder are shown in Table 1.
また、得られた金属磁性粉末について、実施例１と同様の方法により粉体物理特性および磁気特性を測定した。これらの結果をそれぞれ表２および表３に示す。 The obtained metal magnetic powder was measured for powder physical properties and magnetic properties by the same method as in Example 1. These results are shown in Table 2 and Table 3, respectively.
また、得られた金属磁性粉末を使用して実施例１と同様の方法により作製した磁気テープについて、実施例１と同様の方法により磁気測定を行った。その結果を表４に示す。 In addition, magnetic measurement was performed on the magnetic tape produced by the same method as in Example 1 using the obtained metal magnetic powder by the same method as in Example 1. The results are shown in Table 4.
さらに、得られた金属磁性粉末について、実施例１と同様の方法により細孔分布測定を行った。その結果、得られた細孔径と累積細孔容積の関係を図４に示す。また、得られた金属磁性粉末を用いて磁気テープを作製した際の金属磁性粉末の平均粒子体積と磁気テープの保磁力との関係を図５に示し、得られた金属磁性粉末の水銀圧入法により測定した細孔分布における細孔径２００ｎｍ以上の累積細孔容積とその金属磁性粉末を用いて作製した磁気テープの配向比との関係を図６に示す。 Furthermore, pore distribution measurement was performed on the obtained metal magnetic powder by the same method as in Example 1. As a result, the relationship between the obtained pore diameter and the cumulative pore volume is shown in FIG. FIG. 5 shows the relationship between the average particle volume of the metal magnetic powder and the coercive force of the magnetic tape when a magnetic tape is produced using the obtained metal magnetic powder, and a mercury intrusion method of the obtained metal magnetic powder. FIG. 6 shows the relationship between the cumulative pore volume having a pore diameter of 200 nm or more in the pore distribution measured by the above and the orientation ratio of the magnetic tape produced using the metal magnetic powder.
図５に示すように、実施例１〜１０の金属磁性粉末を用いて磁気テープを作製した場合、比較例１〜５の同程度の平均粒子体積の金属磁性粉末を用いて磁気テープを作製した場合と比べて、磁気テープの保磁力が高くなっている。したがって、実施例１〜１０の金属磁性粉末は、比較例１〜５の金属磁性粉末と比べて、磁気テープに使用したときに磁性粉末の単位体積当たりの磁気テープの保磁力を高くすることができるので、高密度磁気記録に適していることがわかる。 As shown in FIG. 5, when magnetic tapes were produced using the metal magnetic powders of Examples 1 to 10, magnetic tapes were produced using the same average particle volume metal magnetic powders of Comparative Examples 1 to 5. Compared to the case, the coercive force of the magnetic tape is higher. Therefore, the metal magnetic powders of Examples 1 to 10 can increase the coercive force of the magnetic tape per unit volume of the magnetic powder when used in the magnetic tape as compared with the metal magnetic powders of Comparative Examples 1 to 5. It can be seen that it is suitable for high-density magnetic recording.
また、図６に示すように、実施例１〜４で得られた金属磁性粉末は、比較例１、４および５で得られた金属磁性粉末と比べて、水銀圧入法により測定した細孔分布における細孔径２００ｎｍ以上の累積細孔容積が非常に小さく、その金属磁性粉末を用いて作製した磁気テープの配向比が非常に高くなっている。これらの結果から、実施例１〜４で得られた金属磁性粉末は、比較例１、４および５で得られた金属磁性粉末と比べて、粒子の焼結によって生じる粒子間の空孔が少なく、粒子の焼結が抑制されていることがわかる。なお、「細孔径２００ｎｍ以上の累積細孔容積」としたのは、それより小さい細孔径も含めると、粒子の表面に存在する「脱水により生じた細孔」なども含んでしまうので、粒子の焼結によって生じる粒子間の空孔を正確に把握することができなくなるからである。 In addition, as shown in FIG. 6, the metal magnetic powders obtained in Examples 1 to 4 were compared with the metal magnetic powders obtained in Comparative Examples 1, 4 and 5, and the pore distribution measured by the mercury intrusion method. The cumulative pore volume with a pore diameter of 200 nm or more in is very small, and the orientation ratio of the magnetic tape produced using the metal magnetic powder is very high. From these results, the metal magnetic powders obtained in Examples 1 to 4 have fewer voids between particles produced by particle sintering than the metal magnetic powders obtained in Comparative Examples 1, 4 and 5. It can be seen that the sintering of the particles is suppressed. Note that the term “cumulative pore volume with a pore diameter of 200 nm or more” includes the pores smaller than that, including “pores generated by dehydration” existing on the surface of the particles. This is because it becomes impossible to accurately grasp the voids between particles generated by sintering.
本発明による金属磁性粉末を使用すれば、高密度磁気記録に適した磁気記録媒体を製造することができる。 If the metal magnetic powder according to the present invention is used, a magnetic recording medium suitable for high-density magnetic recording can be produced.
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