JPS5860630A - Preparation of cobalt-containing ferromagnetic iron oxide - Google Patents

Abstract

PURPOSE:To prepare a cobalt-containing ferromagnetic iron oxide, by treating a magnetic iron oxide with an alkali and an aqueous solution of a cobalt salt and a ferrous salt to effect the coating of the iron oxide with a cobalt-containing metallic compound, and carrying out the steam treatment and heat treatment of the product at a specific low temperature. CONSTITUTION:Magnetic iron oxide is treated with an aqueous solution of a Co salt and a ferrous salt and/or other metallic salt, and an alkali, at about <=50 deg.C to apply a Co-containing metallic compound to the surface of the iron oxide particle. The magnetic iron oxide s e.g. gamma-Fe2O3, etc., the Co salt is e.g. cobalt chloride, etc., and its amount is about 0.5-30wt% based on the iron oxide. The ferrous salt is e.g. ferrous chloride, etc., and its amount is about 1-30wt%. The other metallic salt is, e.g. an Mn salt, etc., and its amount about is 0-10wt%. The coated iron oxide is treated with steam at 60-200 deg.C, and then heat treated in an inert atmosphere at 100-250 deg.C. By this process, a Co-containing ferromagnetic iron oxide having high coercive force, and excellent square ratio, orientation, and saturated flux density can be obtained by low temperature treatments.

Description

【発明の詳細な説明】 本発明は、磁気記録媒体用材料として有用なコバルト含
有強磁性酸化鉄の製造方法に関する。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing cobalt-containing ferromagnetic iron oxide useful as a material for magnetic recording media.

コバルト含有磁性酸化鉄は高保磁力を有し、これを用い
て製作し九磁気テーグは高密度記録ができ、高周波領域
での感度にすぐれていて、近年ビデオテープなどの分野
でさかんに利用されている。磁性酸化鉄にコバルトを含
有させるために、多くの方法が提案されており、例えば
、（１）ｒ　−Ｆ−２０３粉末を第一鉄塩とコバルト塩
とを含む液中で、特定のＯＨ基濃度、高温、非酸化性雰
囲気中で処理する方法（％公昭５２−３６７５１）、（
２）コバルトイオンと鉄イオンの化合物によって強磁性
酸化鉄を被覆し友後、非酸化性雰囲気中で１２０〜２３
０℃の温度で熱処理をおこかう方法（特開昭５４−１２
４２９７　）　、（８＋磁性酸化鉄粉末を遷移金頃塩の
存在するアルカリ溶液中で水熱反応をおこなわせる方法
（特公昭４８−４４０４０）などがある。ところが、こ
れらの従来法で得られたコバルト含有磁性酸化鉄を用い
て磁気テープとし、た場合、十分圧高い保磁力が得にく
かったり、高保磁力のものが得られても角形比（Ｂｒ／
Ｂｍ）　、配向性（ＯＲ）、飽和磁束密度（Ｂｍ）ｉど
が劣ったシすることが多く、改良が望まれている。なお
、ここで言う配向性（ＯＲ）とは（Ｂｒ／／／Ｂｒ上）
を意味する。Cobalt-containing magnetic iron oxide has a high coercive force, and the nine magnetic tags manufactured using it are capable of high-density recording and have excellent sensitivity in the high frequency range, and have been widely used in fields such as videotapes in recent years. There is. Many methods have been proposed for incorporating cobalt into magnetic iron oxide. Concentration, high temperature, method of treatment in non-oxidizing atmosphere (% Kosho 52-36751), (
2) After coating ferromagnetic iron oxide with a compound of cobalt ions and iron ions, it was heated to 120 to 23% in a non-oxidizing atmosphere.
Method of performing heat treatment at a temperature of 0°C
4297), (Japanese Patent Publication No. 48-44040) in which 8+ magnetic iron oxide powder is subjected to a hydrothermal reaction in an alkaline solution containing a transition metal salt.However, cobalt obtained by these conventional methods When making a magnetic tape using magnetic iron oxide, it may be difficult to obtain a sufficiently high coercive force, or even if a high coercive force is obtained, the squareness ratio (Br/
Bm), orientation (OR), saturation magnetic flux density (Bm), etc. are often inferior, and improvements are desired. In addition, what is the orientation (OR) mentioned here (Br///Br on)
means.

一方、フェライトを形成すべき成分の共沈物、沈＃湿式
混合物、沈澱乾式渭金物を飽和水蒸気圧下で処理してフ
ェライトを生成させることが、「粉体および粉末冶金」
第１３巻ｇ３号、２０〜２５頁に報告されている・が、
磁性酸化鉄をコバルトを含む金属化合物で被覆して飽和
水蒸気圧下で処理した例及び飽和水蒸気圧下で処理し、
続いて不活性雰囲気中で熱処理した例はない。On the other hand, producing ferrite by processing coprecipitates, precipitated wet mixtures, and precipitated dry metal products under saturated steam pressure is called "powder and powder metallurgy".
It is reported in Vol. 13, No. g3, pages 20-25.
Examples of magnetic iron oxide coated with a metal compound containing cobalt and treated under saturated steam pressure;
There are no examples of subsequent heat treatment in an inert atmosphere.

本発明の方法は、コバルト被着磁性酸化鉄を飽和水蒸気
圧下で処理し、さらに不活性雰囲気中で熱処理する点で
、従来のいずれの方法とも異なっている。また、本方法
はコバルト被着処ｆ！Ｉ後において、水蒸気処理及び不
活性雰囲気中での熱処理のいずれも、従来考えられてい
るよりむしろ低い温度で行ない、荘られたものを用いて
製作した磁気テープは、高保磁力と同時に角形比、配向
性区飽和磁束密度に優れているという特長を有する。The method of the present invention differs from any conventional method in that cobalt-coated magnetic iron oxide is treated under saturated steam pressure and further heat-treated in an inert atmosphere. In addition, this method is suitable for cobalt deposition. After I, both steam treatment and heat treatment in an inert atmosphere were performed at lower temperatures than previously thought, and the magnetic tape produced using the processed material had high coercive force, squareness ratio, It has the feature of excellent orientation saturation magnetic flux density.

本発明は、磁性酸化鉄を、コバルト塩と第−鉄塩及び／
又はその他の金属塩との水溶液並びにアルカリで処理し
て粒子表面にコバルトを含水蒸気圧下で処理し、さらに
不活性雰囲気中で熱処理することを特徴とする、コバル
ト含有強磁性酸化鉄の製造方法である。The present invention combines magnetic iron oxide with cobalt salt, ferrous salt and/or magnetic iron oxide.
A method for producing cobalt-containing ferromagnetic iron oxide, which is characterized by treating the particle surface with cobalt under water-containing vapor pressure by treating with an aqueous solution with or other metal salts and an alkali, and further heat-treating in an inert atmosphere. be.

本発明に使用する磁性酸化鉄としては、γ−Ｆｅ２Ｏ３
、Ｆｅ３Ｏ４、又は７−Ｆｅ２Ｏ３を部分還元して得ら
れるベルト２イド化合物などがある。コバルト塩として
は、塩化コバルト、硫酸コバルト、酢酸コバルトなどが
、第一鉄塩としては、塩化第一鉄、硫酸第一鉄などが用
いられる。また必要に応じ用いられる他の金属塩ケ、マ
ンガン、亜鉛、クロム、ニッケルなど遷移金属の塩が適
宜選ばれる。The magnetic iron oxide used in the present invention includes γ-Fe2O3
, Fe3O4, or belt 2oid compounds obtained by partially reducing 7-Fe2O3. As the cobalt salt, cobalt chloride, cobalt sulfate, cobalt acetate, etc. are used, and as the ferrous salt, ferrous chloride, ferrous sulfate, etc. are used. In addition, other metal salts, salts of transition metals such as manganese, zinc, chromium, and nickel may be appropriately selected if necessary.

コバルトを含む金属化合物を被着する方法としては、（
１）磁性酸化鉄を金属塩水溶液に分散させ、これにアル
カリ溶液を加える方法、（２）磁性酸化鉄を金属塩水溶
液とアルカリ溶液との混合液に分散させる方法、（８）
磁性酸化鉄を水に分散させ、これに金属塩水溶液とアル
カリ溶液とを添加する方法、（４）磁性酸化鉄をアルカ
リ水溶液に分散させ、これに金属塩水溶液を添加する方
法、（６）磁性酸化鉄を金属塩水溶液に分散させ、この
分散液をアルカリ溶液中に滴下添加する方法などがあシ
、またコバルト、第一鉄、その他の金属の一部又は全部
を同時に処理し九り、順次処理したり、適宜の方法を採
用することがでｔｋル。いずれにしても、アルカリ例え
ば水酸化ナトリウム或は、水酸化カリ、クムは分散液中
の金属塩に対して当量もしくは当量以上を添加する。The method of depositing a metal compound containing cobalt is (
1) A method of dispersing magnetic iron oxide in an aqueous metal salt solution and adding an alkaline solution thereto, (2) A method of dispersing magnetic iron oxide in a mixed solution of a metal salt aqueous solution and an alkaline solution, (8)
A method of dispersing magnetic iron oxide in water and adding a metal salt aqueous solution and an alkaline solution thereto, (4) A method of dispersing magnetic iron oxide in an alkaline aqueous solution and adding a metal salt aqueous solution thereto, (6) Magnetic There are methods such as dispersing iron oxide in a metal salt aqueous solution and adding this dispersion dropwise into an alkaline solution.Also, cobalt, ferrous iron, and some or all of other metals can be treated simultaneously or sequentially. You can process it or adopt an appropriate method. In any case, the alkali, such as sodium hydroxide, potassium hydroxide, or cum, is added in an amount equivalent to or more than the amount of the metal salt in the dispersion.

この処理は、沸点以下、望ましくは５０℃より低い温度
、さらに望ましくｔｉ３０℃よシ低い温度で、反応が終
了するまで攪拌して、磁性酸化鉄粒子表面にコバルトを
含む金属化合物を被着する。酸化鉄に対する重量基準の
値でコバルトの被着量Ｆｉｏ、　ｓ〜３０チ、好ましく
は１〜１０−１第一鉄は１〜３０％、好ましくは２〜２
０嗟、その他の金属は０〜１０チ程度である。In this treatment, the metal compound containing cobalt is deposited on the surface of the magnetic iron oxide particles by stirring at a temperature below the boiling point, preferably below 50°C, more preferably below 30°C, until the reaction is completed. The amount of cobalt deposited Fio, based on the weight relative to iron oxide, is ~30%, preferably 1~10-1, and ferrous iron is 1~30%, preferably 2~2%.
The amount of other metals is about 0 to 10 inches.

被着処理した磁性酸化鉄は、通常戸遇した後水洗し、湿
ケーキをそのまま加熱することによシ水蒸気処理する。The magnetic iron oxide that has been deposited is usually washed with water after being used, and the wet cake is heated as it is to be treated with steam.

この工程で水洗の彼、非酸化性雰凹気中でできるだけ像
源での乾燥を行なっても上く、水蒸気処理の加熱ｌ１度
は、普通６０〜２００℃、望ましくは９０〜１５０℃で
あり、この温度が低すぎると、所望の効果が得られず、
一方高すぎると、磁気テープとした場合角形比、配向性
が悪り麿り望まし、（３い。ここに水蒸気処理というの
は、密閉容器中において水蒸気の存在下で加熱する方法
の他に流動層中において加熱水蒸気を存在させて接触さ
せる方法などがあり、望ましくは、飽和水蒸気臣下での
処理がよく、９・０℃よシ低い温度ではさらに加圧する
のがよい。これらの場合において、少量の他の気体、例
えば空気、窒素ガス、塩化水素ガス、エチレンクロロヒ
ドリンなどを共存させたり、マイクロナイザーなどを用
いて粉砕も兼ねて処理したりすることもできる。In this step, it is best to dry the image source in a non-oxidizing atmosphere as much as possible after rinsing with water. , if this temperature is too low, the desired effect will not be achieved;
On the other hand, if the temperature is too high, the squareness ratio and orientation will be poor when used as a magnetic tape. There are methods such as making contact with heated steam in a fluidized bed. Preferably, treatment is carried out under saturated steam, and at temperatures lower than 9.0°C, it is better to further pressurize. In these cases, It is also possible to coexist with a small amount of other gas such as air, nitrogen gas, hydrogen chloride gas, ethylene chlorohydrin, etc., or to perform a process that also serves as pulverization using a micronizer or the like.

水蒸気処理の後、不活性雰囲気中で熱処理を行なって、
本発明でいうコバルト含有強磁性酸化鉄を得る。この熱
処理の前に通常の乾燥を行なってもよく、熱処理温度は
、普通１００〜２５０℃、望ましくは１５０〜２００℃
であり、この温度節回外であれば所望の効果が得られな
い　ここに不活性雰囲気というのは、例えば窒素、ヘリ
ウム、アルゴンなどの不活性ガスヲ用いた雰囲気をいう
。After steam treatment, heat treatment is performed in an inert atmosphere,
A cobalt-containing ferromagnetic iron oxide as used in the present invention is obtained. Conventional drying may be performed before this heat treatment, and the heat treatment temperature is usually 100 to 250°C, preferably 150 to 200°C.
Therefore, if the temperature exceeds supination, the desired effect cannot be obtained.The inert atmosphere herein refers to an atmosphere using an inert gas such as nitrogen, helium, or argon.

ここで得られたコ／＜ルＦ含有強磁性酸化鉄を用いて製
作した磁気テープは、高保磁力と同時に角形比、配向性
、飽和磁束密度に優れている。The magnetic tape manufactured using the ferromagnetic iron oxide containing C/< C/F obtained here has high coercive force and excellent squareness ratio, orientation, and saturation magnetic flux density.

この理ｒｌ】については充分明らかヤないが、（１）１
１＆性酸化鉄へのコバルトと第１鉄との金属化合物の被
着処理によって、この磁性蒙化鉄の表面ではＷ１鉄イオ
ンを含む均一なコバルトフェライト層が形成され、（２
）次いで、低温における水蒸気処理によって、とのコバ
ルトフェライト層において、コバルトフェライトの結晶
化反応力；ゆつくシと進行し、均一な結晶成長反応が促
進され、（３）さらに、不活性雰囲気中での低温におけ
るｉ％処理によって、コバルトイオンを磁性酸化鉄内部
に固溶させずに、コノくルトフエライト層中のコバルト
フェライト結晶をより安定化させるものと推定される。This theory is not clear enough, but (1) 1
A uniform cobalt ferrite layer containing W1 iron ions is formed on the surface of this magnetic iron monoxide by adhesion treatment of a metal compound of cobalt and ferrous iron to ferrous oxide (2
) Next, by steam treatment at a low temperature, the crystallization reaction force of cobalt ferrite progresses slowly in the cobalt ferrite layer, promoting a uniform crystal growth reaction, and (3) further, in an inert atmosphere. It is presumed that the i% treatment at a low temperature of 10.0% stabilizes the cobalt ferrite crystals in the conorthoferrite layer without solidly dissolving cobalt ions inside the magnetic iron oxide.

実施例１゜ 針状γ−Ｆｅ　２０３　（保磁力（Ｈｅ）：３４１０ｅ
〕１００ｇを水１１に分散させてスラリーとし、水酸化
ナトリウム５壬ル／ｌ溶液８８１を加えたＬ液中にＮ２
　　ガスを吹込みながら、攪拌して硫酸コバルト１千ル
／ｌ溶液６０ｍ１と硫酸第一鉄１モル／ｌ溶液１２５ｍ
Ｊとの混合液を１時間にわたって加えた。その後室温（
２８Ｃ）で５時間攪拌′を続けた。反応後のスラリーを
ろ過、水洗し７、得られた湿ケーキを容器に入れ、別の
容器に入れた水と共にオートクレーブ中に密閉して、１
２５℃で１２時間飽和水蒸気圧下で処理した。この後処
理物を管状炉に入れ、Ｎｔガスを吹き込みながら、１５
０℃で２時間加熱処理を行ない、目的のコバルト含有強
磁性酸化鉄（Ａ）を得念。Example 1 acicular γ-Fe 203 (coercive force (He): 3410e
] 100g was dispersed in 11 parts of water to make a slurry, and N2
While blowing gas and stirring, add 60 ml of cobalt sulfate 1,000 l/l solution and 125 ml of ferrous sulfate 1 mol/l solution.
The mixture with J was added over 1 hour. Then room temperature (
Stirring was continued for 5 hours at 28C). The slurry after the reaction was filtered and washed with water 7. The resulting wet cake was placed in a container and sealed in an autoclave with water in another container.
The mixture was treated at 25° C. for 12 hours under saturated steam pressure. This post-treated product was placed in a tube furnace, and while blowing Nt gas, it was heated for 15 minutes.
Heat treatment was performed at 0°C for 2 hours to obtain the desired cobalt-containing ferromagnetic iron oxide (A).

実施例２ 飽和水蒸気圧での処理の後、６０℃で１２時間乾燥し、
さらにこの処理物をＮ、ガスを吹き込みながら、１７０
℃で２時間加熱処理する以外は前記実施例１の場合と同
様にして、目的のコバルト含有強磁性酸化鉄（Ｂ）を得
た。Example 2 After treatment with saturated steam pressure, drying at 60°C for 12 hours,
Further, while blowing N and gas into this treated material, 170
The desired cobalt-containing ferromagnetic iron oxide (B) was obtained in the same manner as in Example 1 except that the heat treatment was performed at ℃ for 2 hours.

比較例Ｌ Ｍ記実施例Ｉ　において得られた反応後のスラリーを濾
過、水洗し、得られたケーキを大気中において６０℃で
１２時間乾燥した彼、Ｎ冨ガス雰囲気中で２３０℃、１
時間の熱処理を行ない　コバルト含有強磁性酸化鉄（Ｃ
）を得九〇比較例２゜ 前記実施例１において得られ九反応後のスラリーをオー
トクレーブに入れて、１２０℃、３時間の水熱処理を行
なグた後、濾過、水洗し大気中において６０℃で１２時
間乾燥してコノ（ルト含有磁性酸化鉄（Ｄ）を得た。Comparative Example L The slurry after the reaction obtained in Example I was filtered and washed with water, and the resulting cake was dried in the atmosphere at 60°C for 12 hours.
Cobalt-containing ferromagnetic iron oxide (C
) Comparative Example 2 The slurry obtained in Example 1 after the reaction was placed in an autoclave, subjected to hydrothermal treatment at 120°C for 3 hours, filtered, washed with water, and left in the atmosphere for 60 minutes. It was dried at ℃ for 12 hours to obtain rut-containing magnetic iron oxide (D).

実施例３゜ 針状γ−Ｆ＊２０３　（Ｈｃ３４１０・）１００ｇを水
１１に分散させてスラリーとし、液中にＮ２ガスを吹込
みながら硫酸コノくルト１モル／ｌ溶液を６０ｍ１加え
、さらに水酸化ナトリウム５壬ル／ｌ溶液３８８ｍＪを
１時間にわたって加えて攪拌した。次いで硫酸第−鉄−
ル／溶液１２５ｍ／を１時間にわたって加え、室温（２
８℃）で５時間攪拌を続けた。反応後のスラリーをろ過
、水洗し、得られたケーキを容器に入れ、別の容器に入
れた水と共にオートクレーブ中に密閉して１００℃で２
４時間飽和水蒸気圧下で処理し７た。この後処理物を管
状炉に入れ、Ｎ２ガスを吹き込みながら、１７０℃で２
時間加熱処畑を行ない、目的のコバルト含有強磁性酸化
鉄（Ｅ）を得た。Example 3 100 g of acicular γ-F*203 (Hc3410. 388 mJ of a 5 l/l solution of sodium oxide was added over 1 hour and stirred. Then ferrous sulfate
125 m/solution was added over 1 hour at room temperature (2
Stirring was continued for 5 hours at 8°C. The slurry after the reaction was filtered and washed with water, and the resulting cake was placed in a container, sealed in an autoclave with water in another container, and incubated at 100°C for 2 hours.
The mixture was treated under saturated steam pressure for 4 hours. This post-treated product was placed in a tube furnace and heated at 170℃ for 2 hours while blowing N2 gas.
A time heating treatment was performed to obtain the desired cobalt-containing ferromagnetic iron oxide (E).

比較例３゜ 飽和水蒸気圧下での処理を、２３０Ｔｌ：で１時間に代
える以外は前記実施例３の場合と同様にし、て、コバル
ト含有強磁性酸化鉄（Ｆ）を得九。Comparative Example 3 A cobalt-containing ferromagnetic iron oxide (F) was obtained in the same manner as in Example 3 except that the treatment under saturated steam pressure was changed to 230 Tl for 1 hour.

比較例４゜ Ｎ、ガスを吹き込みながらの加熱処理を　３００℃で１
時間に代える以外は、前記実施例３の場合と同様にして
、コバルト含有強磁性酸化鉄（Ｇ）を得た。Comparative Example 4: Heat treatment at 300°C while blowing gas at 1°N.
Cobalt-containing ferromagnetic iron oxide (G) was obtained in the same manner as in Example 3 except that the time was changed.

比較例５゜ 実施例３で得られ九ケーキを、大気中において６０℃で
１２時間乾燥し、この乾燥物を管状炉に入れ、Ｎｔガス
を吹き込みながら、１００℃で２４時間加熱処理を行な
い、コバルト含有強磁性酸化鉄（Ｈ）を得た。Comparative Example 5 The nine cakes obtained in Example 3 were dried in the atmosphere at 60°C for 12 hours, and the dried product was placed in a tube furnace and heat-treated at 100°C for 24 hours while blowing Nt gas. Cobalt-containing ferromagnetic iron oxide (H) was obtained.

比較例６゜ 飽和水蒸気圧下での処理の後、管状炉での熱処理を大気
中での６０℃、１２時間の乾燥に代える以外Ｆｉ前記実
施例３の場合と同様にして、コバルト含有強磁性酸化鉄
（Ｉ）を得た。Comparative Example 6 A cobalt-containing ferromagnetic oxide was prepared in the same manner as in Example 3 above, except that after the treatment under saturated steam pressure, the heat treatment in the tube furnace was replaced with drying at 60° C. for 12 hours in the air. Iron(I) was obtained.

前記実施例１〜３並びに比較例１〜６で得られた酸化鉄
ム〜Ｉについて、通常の方法により保磁力を測定し、さ
らに下記の配合割合に従つノて、配合物を調整し、ボー
ルミルで混練して磁性塗料を製造した。The coercive force of the iron oxide particles I obtained in Examples 1 to 3 and Comparative Examples 1 to 6 was measured by a conventional method, and the mixture was further adjusted according to the following blending ratio, A magnetic paint was produced by kneading in a ball mill.

（１）コバルト含有強磁性酸化鉄　１００重量部（２）
大豆レシチン　　　　　　　　　ＩＩ（３）界面活性剤
　　　　　　　　　　　４１（４）塩ビー酢ビ共重合樹
脂　　　　１５重量部（５）ジオクチルフタレー）　　
　　　　　５１（６）メチルエチルケトン　　　　１１
１１（７）トルエン　　　　　　　　　１２２　。(1) 100 parts by weight of cobalt-containing ferromagnetic iron oxide (2)
Soy lecithin II (3) Surfactant 41 (4) Vinyl chloride vinyl acetate copolymer resin 15 parts by weight (5) Dioctylphthalate)
51(6) Methyl ethyl ketone 11
11(7) Toluene 122.

次いで各々の磁性塗料をポリエステルフィルムに通常の
方法によ）塗布、配向した後乾燥して、約９μ厚の磁性
塗膜を有する磁気テープを作成した。それぞれのテープ
について通常の方法により、保磁力（Ｈｃ）、角形比（
Ｂｒ／Ｂａ）、配向性（ＯＲ）及び飽和磁束密ｗ、（Ｂ
ｍ）を測定ｊ１第１表の結果を得た。Next, each magnetic coating material was applied to a polyester film using a conventional method, oriented and dried to produce a magnetic tape having a magnetic coating film approximately 9 microns thick. For each tape, the coercive force (Hc) and squareness ratio (
Br/Ba), orientation (OR) and saturation magnetic flux density w, (B
m) was measured and the results shown in Table 1 were obtained.

第１表 ′￥、続補正丼（自発） 特許庁長官　島　　１）　春　　０１　　　　殿２、　
発明の名称　　コバルト含有強磁性酸化鉄の製造方法３
、補正をする者 事件との関係　　特許出願人 住所　　〒５５０　大阪市西区江戸堀−丁ｒ１３番２２
号５、補ＩＸ：、の内容　　別紙のとおり別　　紙 発明の詳細な説明 （目　明細書中、第３真第１行・−第２行、第５行へ第
６行、第６行に記載の［飽和水蒸気圧Ｔ：１を［水蒸気
圧下Ｊと訂正する。Table 1 '￥, Continued correction bowl (spontaneous) Commissioner of the Patent Office Shima 1) Spring 01 Tono 2,
Title of the invention Method for producing cobalt-containing ferromagnetic iron oxide 3
, Relationship with the case of the person making the amendment Patent applicant address 13-22 Edobori-chome, Nishi-ku, Osaka 550
No. 5, Supplement IX: Contents of Attachment Detailed explanation of the invention as shown in the attached document Correct [saturated water vapor pressure T:1] to [water vapor pressure below J].

（２）同、第４頁、第１行−第２行の［飽和水蒸気圧下
で処理しＪを［６０〜２００°Ｃの温疫で水蒸気処理し
］と訂正する。(2) Same, page 4, lines 1 and 2, [processed under saturated steam pressure] and corrected J to [processed with steam at a temperature of 60 to 200°C].

に（）同、同頁第３行の［熱処理」を［ｉ　（１０〜２
５　（１’Ｑの温度で熱処理ｊと訂正する。(), same page, line 3, [heat treatment] [i (10 to 2
5 (Corrected as heat treatment j at a temperature of 1'Q.

Claims (1)

【特許請求の範囲】[Claims] 磁性酸化鉄を、コバルト塩と第−鉄塩及び／又はその他
の金属塩との水溶液並びにアルカリで処理して粒子表面
にコバルトを含む金属化合１００〜２５０℃の温度で熱
処理することを特徴とする、コバルト含有強磁性酸化鉄
の製造方Magnetic iron oxide is treated with an aqueous solution of cobalt salt and ferrous salt and/or other metal salts and an alkali to form a metal compound containing cobalt on the particle surface.It is characterized by heat treatment at a temperature of 100 to 250°C. , method for producing cobalt-containing ferromagnetic iron oxide