JPS6242858B2 - - Google Patents
Info
- Publication number
- JPS6242858B2 JPS6242858B2 JP53129865A JP12986578A JPS6242858B2 JP S6242858 B2 JPS6242858 B2 JP S6242858B2 JP 53129865 A JP53129865 A JP 53129865A JP 12986578 A JP12986578 A JP 12986578A JP S6242858 B2 JPS6242858 B2 JP S6242858B2
- Authority
- JP
- Japan
- Prior art keywords
- cobalt
- magnetic powder
- iron oxide
- salt
- powder
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 claims description 84
- 239000006247 magnetic powder Substances 0.000 claims description 49
- 239000010941 cobalt Substances 0.000 claims description 40
- 229910017052 cobalt Inorganic materials 0.000 claims description 40
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 40
- 150000001868 cobalt Chemical class 0.000 claims description 23
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims description 22
- 239000000843 powder Substances 0.000 claims description 14
- 239000003513 alkali Substances 0.000 claims description 11
- 229910001566 austenite Inorganic materials 0.000 claims description 10
- 239000006185 dispersion Substances 0.000 claims description 10
- 238000004519 manufacturing process Methods 0.000 claims description 4
- 230000005294 ferromagnetic effect Effects 0.000 claims description 3
- 238000000034 method Methods 0.000 description 11
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 9
- 230000005291 magnetic effect Effects 0.000 description 9
- 239000007864 aqueous solution Substances 0.000 description 8
- 239000007858 starting material Substances 0.000 description 6
- 238000007796 conventional method Methods 0.000 description 4
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 2
- 239000012670 alkaline solution Substances 0.000 description 2
- 229940044175 cobalt sulfate Drugs 0.000 description 2
- 229910000361 cobalt sulfate Inorganic materials 0.000 description 2
- KTVIXTQDYHMGHF-UHFFFAOYSA-L cobalt(2+) sulfate Chemical compound [Co+2].[O-]S([O-])(=O)=O KTVIXTQDYHMGHF-UHFFFAOYSA-L 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 235000003891 ferrous sulphate Nutrition 0.000 description 2
- 239000011790 ferrous sulphate Substances 0.000 description 2
- 229910000359 iron(II) sulfate Inorganic materials 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000003973 paint Substances 0.000 description 2
- 239000012266 salt solution Substances 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- MQIUGAXCHLFZKX-UHFFFAOYSA-N Di-n-octyl phthalate Natural products CCCCCCCCOC(=O)C1=CC=CC=C1C(=O)OCCCCCCCC MQIUGAXCHLFZKX-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- NTIZESTWPVYFNL-UHFFFAOYSA-N Methyl isobutyl ketone Chemical compound CC(C)CC(C)=O NTIZESTWPVYFNL-UHFFFAOYSA-N 0.000 description 1
- UIHCLUNTQKBZGK-UHFFFAOYSA-N Methyl isobutyl ketone Natural products CCC(C)C(C)=O UIHCLUNTQKBZGK-UHFFFAOYSA-N 0.000 description 1
- 229920002433 Vinyl chloride-vinyl acetate copolymer Polymers 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- BJQHLKABXJIVAM-UHFFFAOYSA-N bis(2-ethylhexyl) phthalate Chemical compound CCCCC(CC)COC(=O)C1=CC=CC=C1C(=O)OCC(CC)CCCC BJQHLKABXJIVAM-UHFFFAOYSA-N 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- GVPFVAHMJGGAJG-UHFFFAOYSA-L cobalt dichloride Chemical compound [Cl-].[Cl-].[Co+2] GVPFVAHMJGGAJG-UHFFFAOYSA-L 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 229960002089 ferrous chloride Drugs 0.000 description 1
- 229910001448 ferrous ion Inorganic materials 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 1
- NMCUIPGRVMDVDB-UHFFFAOYSA-L iron dichloride Chemical compound Cl[Fe]Cl NMCUIPGRVMDVDB-UHFFFAOYSA-L 0.000 description 1
- 230000005415 magnetization Effects 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229920006267 polyester film Polymers 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
Landscapes
- Hard Magnetic Materials (AREA)
- Compounds Of Iron (AREA)
Description
この発明は、磁気記録媒体用の記録素子として
有用なコバルト含有酸化鉄強磁性粉末を製造法に
関する。
コバルトを含有する酸化鉄強磁性粉末は、従来
汎用されているγ−Fe2O3粉末などのコバルトを
含まない酸化鉄磁性粉末に比べて高保磁力を有し
ており、これを磁気記録媒体に使用すると高密度
記録ができる、高周波領域における感度が高いな
ど種々の利点がある。
このようなコバルト含有酸化鉄を製造する方法
としてはこれまで種々の方法が提案されており、
その中でも有用な方法のひとつとして、この発明
者らは既にγ−Fe2O3粉末もしくはこれを部分還
元してなる酸化鉄磁性粉末をコバルト塩と第一鉄
との混合水溶液中に分散させ、この分散液中のコ
バルト塩と第一鉄塩との総量に対して当量もしく
はそれ以上の量のアルカリを加え、加熱しながら
溶液中の第一鉄イオンが空気による酸化を殆んど
受けることのないような条件下で処理して酸化鉄
磁性粉末表面にコバルトを含む酸化鉄層を形成す
ることによりコバルト含有酸化鉄磁性粉末を製造
する方法を提案した。
これら従来の製造法においては、コバルトを含
有させるための加熱処理をできるだけ高い温度で
行なう方が保磁力を高める上で望ましいとされ、
いずれの方法においても実際上50℃以上で沸点近
くの温度での処理が行なわれているが、この発明
者らが引き続き行なつた研究の結果、磁性粉末中
に含ませようとするコバルトの量が比較的少ない
量でよい場合には、むしろ50℃より低い温度条件
下で処理を行なつた方が保磁力を高めるのに有利
であり、しかも高温処理の場合に比べて分散性お
よび配向性に優れるコバルト含有酸化鉄磁性粉末
が得られるという知見を得、この発明をなすに至
つた。
すなわちこの発明は、γ−Fe2O3粉末およびこ
れを部分還元してなる酸化鉄磁性粉末から選ばれ
る磁性粉末と、コバルト塩と、第一鉄塩と、前記
コバルト塩と第一鉄塩との総量に対して当量以上
のアルカリとを含む分散液を50℃より低い温度に
保持しながら処理することにより、前記磁性粉末
に対して２重量％以下のコバルトを含む酸化鉄層
を前記磁性粉末上に形成することを特徴とするも
のである。
この発明における最も重量な点は、コバルトの
含有量を出発原料の磁性粉末に対して２重量％以
下とし、かつ処理温度を50℃より低い温度とした
ことである。コバルトの含有量が２％以下の場合
には、第１図に示されるように、低温で処理を行
なうと従来法における高温処理を施した場合に比
べて保磁力の高い磁性粉末が得られる。
第１図は、コバルト含有酸化鉄磁性粉末のコバ
ルト含有量（但し、出発原料たる酸化鉄磁性粉末
に対する重量％で表わしたもの）とこの磁性粉末
の保磁力との関係を処理温度をパラメーターとし
て示した図であり、同図中、実線は出発原料とし
てγ−Fe2O3粉末を使用し、アルカリ（NaOH）
添加量をコバルト塩と第一鉄塩との総量に対して
３当量とし、処理温度30℃、処理時間６時間の条
件下にこの発明方法を実施して得られたコバルト
含有酸化鉄磁性粉末の場合であり、点線は処理温
度を100℃とした以外は上記の処理条件と全く同
一の条件下で製造したコバルト含有酸化鉄磁性粉
末の場合を示す。
この図から明らかなように、処理温度が高いほ
ど得られるコバルト含有酸化鉄磁性粉末の保磁力
が高くなるという従来の一般的通念とは逆に、コ
バルト含有量がほぼ２重量％以下の範囲では低温
処理によるものの方が保磁力が高くなつている。
この効果は処理温度が低くなるほど大きくなつ
ており、これは第２図からも明らかである。第２
図は、コバルト含有量を出発原料（γ−Fe2O3粉
末）に対して１重量％と一定にした場合の処理温
度と保磁力との関係を示す図である。
この発明方法を実施するには、まずγ−Fe2O3
粉末またはγ−Fe2O3粉末を適宜の手段、たとえ
ば水素などの還元性気体中で部分還元して得られ
た酸化鉄磁性粉末をコバルト塩と第一鉄塩との混
合水溶液中に分散させる。
ここで用いられるコバルト塩としては、塩化コ
バルト、硫酸コバルトなどを挙げることができ
る。このコバルト塩の使用量については生成する
コバルト含有酸化鉄磁性粉末のコバルト含有量が
出発原料に対して２重量％以下の所望の値となる
ように適宜選定すればよい。
コバルト塩とともに使用される第一鉄塩として
は、塩化第一鉄、硫酸第一鉄などが好ましく用ら
れる。この第一鉄塩をコバルト塩とともに使用す
るのは、コバルト塩のみの場合よりも第一鉄塩を
共存させた場合の方が生成するコバルト含有酸化
鉄磁性粉末の保磁力が大きく増大するからであ
り、特に第一鉄塩とコバルト塩とをそのモル比が
１：１〜５：１となるような割合で用いたときに
好ましい結果が得られる。
次に、上記の分散液中のコバルト塩と第一鉄塩
との総量に対して当量もしくは当量以上のアルカ
リ、たとえば水酸化ナトリウムを添加し、分散液
の温度を50℃より低い温度、好ましくは30℃以下
の温度に保持したままで処理を行なうことによつ
てコバルトを含む酸化鉄層をγ−Fe2O3粉末また
はこれを部分還元してなる酸化鉄磁性粉末上に形
成させる。
コバルトを含む酸化鉄層の形成は系中のアルカ
リ濃度に大きく影響され、アルカリ添加量を系中
に含まれるコバルト塩と第一鉄塩との総量に対し
て当量以上とするとき、良好な結果が得られる。
このようにして得られたコバルト含有酸化鉄磁
性粉末は、出発原料に対して２重量％以下のコバ
ルトを含有するものであつて、従来法における比
較的高温での処理を施すことによつて得られた同
一のコバルト含有量の磁性粉末に比べて保磁力が
高いものとなつている。その上、この発明方法に
よつて得られたコバルト含有酸化鉄磁性粉末は、
従来法によるものに比べて分散性および配向性に
優れているため、磁気記録媒体の記録素子として
非常に有用である。
なお、この発明において酸化鉄磁性粉末をコバ
ルト塩と第一鉄塩で変成処理する場合に、酸化鉄
磁性粉末と、コバルト塩と、第一鉄塩と、アルカ
リとを含む分散液の調製方法としては、酸化鉄磁
性粉末をコバルト塩と、第一鉄塩との水溶液に分
散させ、これにアルカリ溶液を加えて調製する方
法、酸化鉄磁性粉末を、コバルト塩と第一鉄塩の
水溶液とアルカリの水溶液の混合液に分散させて
調製する方法、酸化鉄磁性粉末を水に分散させ、
これにコバルト塩および第一鉄塩溶液とアルカリ
溶液とを添加する方法、あるいは酸化鉄磁性粉末
をアルカリ水溶液に分散させ、これにコバルト塩
および第一鉄塩の溶液を添加する方法など、必要
に応じて適宜の方法を採用することができ、要
は、酸化鉄磁性粉末と、コバルト塩と、第一鉄塩
と、アルカリとを含む分散液を調製したのち、所
定の加熱処理を施すことが肝要である。
次に、この発明の実施例を記載する。
実施例
硫酸第一鉄1.53モルと硫酸コバルト0.51モルを
溶解させた水溶液10中に、粒径約0.3μ、軸比
約10、保磁力（以下、Hcという）330エルステツ
ド、飽和磁化（以下、σsという）74emu／ｇの
針状γ−Fe2O3粉末３Kgを加え、充分に分散させ
た後、これに12.2モルのNaOHを溶解させた水溶
液10を加えた。この分散液を30℃に保持したま
ま６時間撹拌を続けた。次いで、この分散液を
過して磁性粉末を取り出した後、充分に水洗を行
なつて反応溶液を除去し、乾燥した。このように
して得られたコバルト含有酸化鉄磁性粉末のHc
は400エルステツド、σsは74.5emu／ｇであつ
た。また、この磁性粉末のコバルト含有量（γ−
Fe2O3粉末に対する重量割合）は0.95重量％であ
つた。
比較例
実施例における処理温度を100℃とした以外は
実施例と全く同様にしてコバルト含有酸化鉄磁性
粉末を製造した。得られた磁性粉末のHcは375エ
ルステツド、σsは74.6emu／ｇ、コバルト含有
量は0.95重量％であつた。
上記実施例および比較例で得られたコバルト含
有酸化鉄磁性粉末を使用して下記組成からなる磁
性塗料を調製した。
コバルト含有酸化鉄磁性粉末 75重量部
塩化ビニル−酢酸ビニル共重合体 25 〃
ジオクチルフタレート ５ 〃
トルエン 100 〃
メチルイソブチルケトン 100 〃
この磁性塗料を厚さ12μのポリエステルフイル
ム上に乾燥厚が約６μとなるように塗布、乾燥し
た後、所定の幅に裁断して磁気テープを作成し
た。
得られた各磁気テープの保磁力（Hc）、角型比
（Br／Bs）、テープの長手方向の角型比と幅方向
の角型比との比〔（Ｂｒ／Ｂｓ）〃／（Ｂｒ／Ｂｓ）⊥
〕および周波数特性
（12.5KHz）を調べた結果は次表に示されるとお
りであつた。
The present invention relates to a method for producing cobalt-containing iron oxide ferromagnetic powder useful as a recording element for magnetic recording media. Iron oxide ferromagnetic powder containing cobalt has a higher coercive force than iron oxide magnetic powder that does not contain cobalt, such as the conventionally widely used γ-Fe 2 O 3 powder, and is used in magnetic recording media. When used, it has various advantages such as high-density recording and high sensitivity in the high frequency range. Various methods have been proposed to date to produce such cobalt-containing iron oxide.
As one of the most useful methods, the present inventors have already dispersed γ-Fe 2 O 3 powder or iron oxide magnetic powder obtained by partially reducing it in a mixed aqueous solution of cobalt salt and ferrous iron. An equivalent or more amount of alkali is added to the total amount of cobalt salt and ferrous salt in this dispersion, and while heating, the ferrous ion in the solution is almost oxidized by air. We proposed a method for producing cobalt-containing iron oxide magnetic powder by forming a cobalt-containing iron oxide layer on the surface of the iron oxide magnetic powder. In these conventional manufacturing methods, it is considered desirable to perform the heat treatment to incorporate cobalt at as high a temperature as possible in order to increase the coercive force.
In both methods, treatment is actually carried out at a temperature of 50°C or higher, close to the boiling point, but as a result of continued research by the inventors, it was found that the amount of cobalt that should be included in the magnetic powder If only a relatively small amount of The inventors have discovered that a cobalt-containing iron oxide magnetic powder with excellent properties can be obtained, leading to the creation of this invention. That is, this invention provides a magnetic powder selected from γ-Fe 2 O 3 powder and iron oxide magnetic powder obtained by partially reducing the same, a cobalt salt, a ferrous salt, and the cobalt salt and ferrous salt. By treating a dispersion containing at least an equivalent amount of alkali with respect to the total amount of alkali while maintaining the temperature below 50°C, an iron oxide layer containing 2% by weight or less of cobalt with respect to the magnetic powder is added to the magnetic powder. It is characterized by being formed on the top. The most important point in this invention is that the content of cobalt is 2% by weight or less based on the starting magnetic powder, and the processing temperature is lower than 50°C. When the cobalt content is 2% or less, as shown in FIG. 1, a magnetic powder with a higher coercive force can be obtained by performing the treatment at a low temperature than by performing the high temperature treatment in the conventional method. Figure 1 shows the relationship between the cobalt content of a cobalt-containing iron oxide magnetic powder (expressed in weight percent with respect to the starting material iron oxide magnetic powder) and the coercive force of this magnetic powder, using the processing temperature as a parameter. In the figure, the solid line indicates the case where γ-Fe 2 O 3 powder is used as the starting material and alkali (NaOH) is used.
Cobalt-containing iron oxide magnetic powder obtained by carrying out the method of the present invention at a treatment temperature of 30° C. and a treatment time of 6 hours, with the amount added being 3 equivalents based on the total amount of cobalt salt and ferrous salt. The dotted line indicates the case of cobalt-containing iron oxide magnetic powder produced under exactly the same processing conditions as above except that the processing temperature was 100°C. As is clear from this figure, contrary to the conventional wisdom that the higher the processing temperature, the higher the coercive force of the resulting cobalt-containing iron oxide magnetic powder, when the cobalt content is approximately 2% by weight or less, The coercive force is higher with the low-temperature treatment. This effect becomes larger as the processing temperature becomes lower, and this is also clear from FIG. 2. Second
The figure shows the relationship between processing temperature and coercive force when the cobalt content is constant at 1% by weight based on the starting material (γ-Fe 2 O 3 powder). To carry out the method of this invention, first γ-Fe 2 O 3
Iron oxide magnetic powder obtained by partially reducing powder or γ-Fe 2 O 3 powder in a reducing gas such as hydrogen by an appropriate means is dispersed in a mixed aqueous solution of cobalt salt and ferrous salt. . Examples of the cobalt salt used here include cobalt chloride and cobalt sulfate. The amount of cobalt salt to be used may be appropriately selected so that the cobalt content of the produced cobalt-containing iron oxide magnetic powder is a desired value of 2% by weight or less based on the starting material. As the ferrous salt used together with the cobalt salt, ferrous chloride, ferrous sulfate, etc. are preferably used. The reason why this ferrous salt is used together with a cobalt salt is that the coercive force of the cobalt-containing iron oxide magnetic powder that is produced increases more when a ferrous salt is present than when a cobalt salt is used alone. In particular, favorable results are obtained when the ferrous salt and cobalt salt are used in a molar ratio of 1:1 to 5:1. Next, an equivalent or more than equivalent amount of alkali, such as sodium hydroxide, is added to the total amount of cobalt salt and ferrous salt in the dispersion, and the temperature of the dispersion is lowered to below 50°C, preferably By carrying out the treatment while maintaining the temperature at 30° C. or lower, an iron oxide layer containing cobalt is formed on the γ-Fe 2 O 3 powder or the iron oxide magnetic powder obtained by partially reducing the same. The formation of an iron oxide layer containing cobalt is greatly affected by the alkali concentration in the system, and good results are obtained when the amount of alkali added is equal to or higher than the total amount of cobalt salt and ferrous salt contained in the system. is obtained. The cobalt-containing iron oxide magnetic powder thus obtained contains 2% by weight or less of cobalt based on the starting material, and can be obtained by processing at a relatively high temperature in the conventional method. The coercive force is higher than that of magnetic powder with the same cobalt content. Moreover, the cobalt-containing iron oxide magnetic powder obtained by the method of this invention is
Since it has superior dispersibility and orientation compared to conventional methods, it is very useful as a recording element for magnetic recording media. In this invention, when iron oxide magnetic powder is metamorphosed with cobalt salt and ferrous salt, as a method for preparing a dispersion containing iron oxide magnetic powder, cobalt salt, ferrous salt, and alkali. The method involves dispersing iron oxide magnetic powder in an aqueous solution of cobalt salt and ferrous salt and adding an alkaline solution to the dispersion, and dispersing iron oxide magnetic powder in an aqueous solution of cobalt salt and ferrous salt with alkali A method of preparing iron oxide magnetic powder by dispersing it in a mixture of aqueous solutions, dispersing iron oxide magnetic powder in water,
If necessary, such as adding a cobalt salt and ferrous salt solution and an alkaline solution to this, or dispersing iron oxide magnetic powder in an alkaline aqueous solution and adding a cobalt salt and ferrous salt solution to this, An appropriate method can be adopted depending on the situation, and the point is that a dispersion containing iron oxide magnetic powder, cobalt salt, ferrous salt, and alkali is prepared and then subjected to a prescribed heat treatment. It is essential. Next, examples of this invention will be described. Example In an aqueous solution 10 in which 1.53 mol of ferrous sulfate and 0.51 mol of cobalt sulfate were dissolved, a particle size of about 0.3 μ, an axial ratio of about 10, a coercive force (hereinafter referred to as Hc) of 330 oersted, and a saturation magnetization (hereinafter referred to as σ After adding 3 kg of acicular γ-Fe 2 O 3 powder of 74 emu/g and thoroughly dispersing it, 10 of an aqueous solution in which 12.2 mol of NaOH was dissolved was added. Stirring was continued for 6 hours while maintaining this dispersion at 30°C. Next, the dispersion was filtered to remove the magnetic powder, and then thoroughly washed with water to remove the reaction solution and dried. Hc of the cobalt-containing iron oxide magnetic powder thus obtained
was 400 oersted, and σ s was 74.5 emu/g. In addition, the cobalt content (γ-
The weight ratio to Fe 2 O 3 powder was 0.95% by weight. Comparative Example A cobalt-containing iron oxide magnetic powder was produced in exactly the same manner as in the example except that the treatment temperature in the example was changed to 100°C. The obtained magnetic powder had an Hc of 375 oersted, a s of 74.6 emu/g, and a cobalt content of 0.95% by weight. A magnetic paint having the following composition was prepared using the cobalt-containing iron oxide magnetic powder obtained in the above Examples and Comparative Examples. Cobalt-containing iron oxide magnetic powder 75 parts by weight Vinyl chloride-vinyl acetate copolymer 25 〃 Dioctyl phthalate 5 〃 Toluene 100 〃 Methyl isobutyl ketone 100 〃 This magnetic paint was applied on a 12μ thick polyester film to a dry thickness of about 6μ. After coating and drying, the magnetic tape was cut to a predetermined width. The coercive force (Hc), squareness ratio (Br/Bs), and ratio of the squareness ratio in the longitudinal direction and the squareness ratio in the width direction of each magnetic tape obtained [(Br/Bs)/(Br /Bs)⊥
] and frequency characteristics (12.5KHz), the results are shown in the table below.
【表】
以上の結果から明らかなように、この発明方法
によつて得られたコバルト含有酸化鉄磁性粉末
は、従来法における高温処理を施すことにより得
られた比較例の磁性粉末に比べて保磁力が高く、
また上記表に示されているように、これを用いた
磁気テープの角型比や（Ｂｒ／Ｂｓ）〃／（Ｂｒ／Ｂｓ
）⊥が大きいことか
ら分散性および配向性に優れていることが判る。[Table] As is clear from the above results, the cobalt-containing iron oxide magnetic powder obtained by the method of this invention has better retention than the magnetic powder of the comparative example obtained by high-temperature treatment in the conventional method. High magnetic force,
Also, as shown in the table above, the squareness ratio of the magnetic tape using this and (Br/Bs)/(Br/Bs
) It can be seen that the dispersibility and orientation are excellent because ⊥ is large.
第１図は、コバルト含有酸化鉄磁性粉末のコバ
ルト含有量（出発原料たる酸化鉄磁性粉末に対す
る重量％）とこの磁性粉末の保磁力との関係を処
理温度をパラメーターとして示した図であり、同
図中、実線は処理温度が30℃の場合、点線は100
℃の場合である。第２図は、コバルト含有量を一
定にした場合の処理温度と得られたコバルト含有
酸化鉄磁性粉末の保磁力との関係を示す図であ
る。
FIG. 1 is a diagram showing the relationship between the cobalt content (wt% relative to the iron oxide magnetic powder as a starting material) of a cobalt-containing iron oxide magnetic powder and the coercive force of this magnetic powder using the processing temperature as a parameter. In the figure, the solid line indicates a processing temperature of 30°C, and the dotted line indicates a processing temperature of 100°C.
This is the case at °C. FIG. 2 is a diagram showing the relationship between the treatment temperature and the coercive force of the obtained cobalt-containing iron oxide magnetic powder when the cobalt content is kept constant.
Claims (1)
る酸化鉄磁性粉末から選ばれる磁性粉末と、コバ
ルト塩と、第一鉄塩と、前記コバルト塩と第一鉄
塩との総量に対して当量以上のアルカリとを含む
分散液を50℃より低い温度に保持しながら処理す
ることにより、前記磁性粉末に対して２重量％以
下のコバルトを含む酸化鉄層を前記磁性粉末上に
形成することを特徴とする強磁性粉末の製造法。1 Magnetic powder selected from γ-Fe 2 O 3 powder and iron oxide magnetic powder obtained by partially reducing the same, cobalt salt, ferrous salt, and the total amount of the cobalt salt and ferrous salt By treating a dispersion containing at least an equivalent amount of alkali at a temperature lower than 50°C, an iron oxide layer containing 2% by weight or less of cobalt based on the magnetic powder is formed on the magnetic powder. A method for producing ferromagnetic powder characterized by:
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12986578A JPS5556019A (en) | 1978-10-20 | 1978-10-20 | Production of ferromagnetic powder |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP12986578A JPS5556019A (en) | 1978-10-20 | 1978-10-20 | Production of ferromagnetic powder |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5556019A JPS5556019A (en) | 1980-04-24 |
| JPS6242858B2 true JPS6242858B2 (en) | 1987-09-10 |
Family
ID=15020184
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP12986578A Granted JPS5556019A (en) | 1978-10-20 | 1978-10-20 | Production of ferromagnetic powder |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5556019A (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6029646B2 (en) * | 1981-01-20 | 1985-07-11 | 堺化学工業株式会社 | Method for producing magnetic iron oxide powder |
| JPS5832027A (en) * | 1981-07-28 | 1983-02-24 | Ishihara Sangyo Kaisha Ltd | Preparation of ferromagnetic powder of cobalt-containing iron oxide |
| JPS5888122A (en) * | 1981-11-20 | 1983-05-26 | Ishihara Sangyo Kaisha Ltd | Production of cobalt-containing ferromagnetic iron oxide |
| JPS6081026A (en) * | 1983-10-06 | 1985-05-09 | Ishihara Sangyo Kaisha Ltd | Manufacture of magnetic iron oxide containing cobalt |
| JPH01194306A (en) * | 1988-01-29 | 1989-08-04 | Sony Corp | Manufacture of cobalt-contained iron oxide magnetic powder |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS4974399A (en) * | 1972-11-24 | 1974-07-18 | ||
| JPS5037668A (en) * | 1973-08-07 | 1975-04-08 | ||
| JPS5037667A (en) * | 1973-08-07 | 1975-04-08 | ||
| JPS53129895A (en) * | 1977-04-20 | 1978-11-13 | Hitachi Maxell | Method of manufacturing ferromagnetic powder for magnetic recording |
| JPS5556605A (en) * | 1978-10-20 | 1980-04-25 | Hitachi Maxell Ltd | Magnetic recording medium |
-
1978
- 1978-10-20 JP JP12986578A patent/JPS5556019A/en active Granted
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS4974399A (en) * | 1972-11-24 | 1974-07-18 | ||
| JPS5037668A (en) * | 1973-08-07 | 1975-04-08 | ||
| JPS5037667A (en) * | 1973-08-07 | 1975-04-08 | ||
| JPS53129895A (en) * | 1977-04-20 | 1978-11-13 | Hitachi Maxell | Method of manufacturing ferromagnetic powder for magnetic recording |
| JPS5556605A (en) * | 1978-10-20 | 1980-04-25 | Hitachi Maxell Ltd | Magnetic recording medium |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5556019A (en) | 1980-04-24 |
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