JPH0227804B2 - - Google Patents
Info
- Publication number
- JPH0227804B2 JPH0227804B2 JP55119026A JP11902680A JPH0227804B2 JP H0227804 B2 JPH0227804 B2 JP H0227804B2 JP 55119026 A JP55119026 A JP 55119026A JP 11902680 A JP11902680 A JP 11902680A JP H0227804 B2 JPH0227804 B2 JP H0227804B2
- Authority
- JP
- Japan
- Prior art keywords
- cobalt
- magnetic
- coercive force
- iron oxide
- iron
- 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 - Lifetime
Links
- 230000005291 magnetic effect Effects 0.000 claims description 46
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 claims description 41
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 41
- 239000010941 cobalt Substances 0.000 claims description 40
- 229910017052 cobalt Inorganic materials 0.000 claims description 40
- 239000000843 powder Substances 0.000 claims description 15
- 238000006243 chemical reaction Methods 0.000 claims description 8
- 238000004519 manufacturing process Methods 0.000 claims description 7
- 239000000243 solution Substances 0.000 claims description 7
- 239000003513 alkali Substances 0.000 claims description 6
- 150000001869 cobalt compounds Chemical class 0.000 claims description 6
- 239000012670 alkaline solution Substances 0.000 claims description 4
- 229910021503 Cobalt(II) hydroxide Inorganic materials 0.000 claims description 3
- ASKVAEGIVYSGNY-UHFFFAOYSA-L cobalt(ii) hydroxide Chemical compound [OH-].[OH-].[Co+2] ASKVAEGIVYSGNY-UHFFFAOYSA-L 0.000 claims description 3
- 235000014413 iron hydroxide Nutrition 0.000 claims description 3
- NCNCGGDMXMBVIA-UHFFFAOYSA-L iron(ii) hydroxide Chemical compound [OH-].[OH-].[Fe+2] NCNCGGDMXMBVIA-UHFFFAOYSA-L 0.000 claims description 3
- 239000002244 precipitate Substances 0.000 claims description 3
- 238000001556 precipitation Methods 0.000 claims description 3
- 239000000084 colloidal system Substances 0.000 claims description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 26
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 21
- 239000013078 crystal Substances 0.000 description 18
- 235000013980 iron oxide Nutrition 0.000 description 18
- 238000000034 method Methods 0.000 description 18
- 239000006247 magnetic powder Substances 0.000 description 14
- 229910052742 iron Inorganic materials 0.000 description 12
- 239000011259 mixed solution Substances 0.000 description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 9
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 8
- 235000011121 sodium hydroxide Nutrition 0.000 description 7
- 238000003756 stirring Methods 0.000 description 7
- 239000006185 dispersion Substances 0.000 description 6
- 150000002505 iron Chemical class 0.000 description 6
- 150000001868 cobalt Chemical class 0.000 description 5
- 238000010907 mechanical stirring Methods 0.000 description 5
- 229940044175 cobalt sulfate Drugs 0.000 description 4
- 229910000361 cobalt sulfate Inorganic materials 0.000 description 4
- KTVIXTQDYHMGHF-UHFFFAOYSA-L cobalt(2+) sulfate Chemical compound [Co+2].[O-]S([O-])(=O)=O KTVIXTQDYHMGHF-UHFFFAOYSA-L 0.000 description 4
- 235000003891 ferrous sulphate Nutrition 0.000 description 4
- 239000011790 ferrous sulphate Substances 0.000 description 4
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 4
- 229910000359 iron(II) sulfate Inorganic materials 0.000 description 4
- 230000001590 oxidative effect Effects 0.000 description 4
- 229910000859 α-Fe Inorganic materials 0.000 description 4
- 238000007796 conventional method Methods 0.000 description 3
- VBMVTYDPPZVILR-UHFFFAOYSA-N iron(2+);oxygen(2-) Chemical class [O-2].[Fe+2] VBMVTYDPPZVILR-UHFFFAOYSA-N 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 239000002253 acid Substances 0.000 description 2
- 229910001566 austenite Inorganic materials 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 239000007771 core particle Substances 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 230000005294 ferromagnetic effect Effects 0.000 description 2
- 230000004907 flux Effects 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 2
- 239000000696 magnetic material Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 239000003973 paint Substances 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 238000009736 wetting Methods 0.000 description 2
- QVYYOKWPCQYKEY-UHFFFAOYSA-N [Fe].[Co] Chemical class [Fe].[Co] QVYYOKWPCQYKEY-UHFFFAOYSA-N 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000011162 core material Substances 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 229910052598 goethite Inorganic materials 0.000 description 1
- AEIXRCIKZIZYPM-UHFFFAOYSA-M hydroxy(oxo)iron Chemical compound [O][Fe]O AEIXRCIKZIZYPM-UHFFFAOYSA-M 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 229910052596 spinel Inorganic materials 0.000 description 1
- 239000011029 spinel Substances 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- 229910006540 α-FeOOH Inorganic materials 0.000 description 1
Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/62—Record carriers characterised by the selection of the material
- G11B5/68—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
- G11B5/70—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
- G11B5/706—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material
- G11B5/70626—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material containing non-metallic substances
- G11B5/70642—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material containing non-metallic substances iron oxides
- G11B5/70647—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the composition of the magnetic material containing non-metallic substances iron oxides with a skin
Landscapes
- Health & Medical Sciences (AREA)
- Dermatology (AREA)
- General Health & Medical Sciences (AREA)
- Compounds Of Iron (AREA)
- Paints Or Removers (AREA)
- Magnetic Record Carriers (AREA)
- Hard Magnetic Materials (AREA)
Description
本発明は磁気記録媒体用材料として好適なコバ
ルト被覆針状磁性酸化鉄粉末の製造法に関するも
のである。特に本発明は高保磁力で保磁力分布の
良好な高密度記録に適したコバルト被覆針状磁性
酸化鉄粉末の製造に適した方法に関するものであ
る。
昨今、各種の磁気記録用材料は益々高密度化の
傾向にあり、この高密度化を満すためには磁気記
録材料として使用される磁性酸化鉄の保磁力を高
くするとともに磁気テープとした場合の転写並び
に消去特性に大きく影響する保磁力分布を小さく
することが必要とされている。従来より磁性酸化
鉄の保磁力を高くする手段として各種針状酸化鉄
に各種のスピネル化合物を含有させる方法が種々
提案され、とりわけビデオ用磁気記録テープ等高
密度磁気記録に適した高保磁力針状磁性酸化鉄を
製造する手段としては各種の針状酸化鉄にコバル
トを含有させる方法が提案されている。
コバルト含有針状酸化鉄はコバルトの加え方に
より大略次の２つに類別出来る。
(1) 針状α−FeOOH、α−Fe2O3、γ−Fe2O3及
びFeO−Fe2O3等にコバルト塩あるいは鉄塩と
コバルト塩を添加し適当なアルカリ、例えば苛
性ソーダ等で水酸化物あるいは酸化雰囲気では
コバルトフエライトとして沈着せしめ、それを
水洗別、乾燥後コバルトが芯晶内部へ拡散し
うる温度、例えば300〜400℃で加熱処理しコバ
ルト均一拡散型（ドープ型ともいう）針状磁性
酸化鉄粉末を製造する方法。（例えば特公昭42
−6113号、特公昭47−27719号等の方法）
(2) 針状γ−Fe2O3、FeO・Fe2O3又は（FeO）
Ｘ・Fe2O3（０＜Ｘ＜１）等にコバルト塩あるい
は鉄塩とコバルト塩を添加しアルカリをともな
つた湿式工程で、それらの針状芯晶上にコバル
ト、コバルトフエライトあるいは他のコバルト
化合物を被覆せしめ針状磁性酸化鉄粉末を製造
する方法。（例えば特公昭37−4825号、特公昭
49−49475号の方法）
(1)の方法の場合、利点として熱によりコバルト
が拡散されるため芯晶粒子個々に対してコバルト
の均一分配が行なわれ易く、又単位芯晶粒子自体
へのコバルトの拡散も容易になるため、保磁力分
布を好ましい方向に導くことが出来る反面、これ
らの磁性粉末を用いて作成された磁気記録テープ
等はコバルトが固溶しているため保磁力の経年変
化が大きく、又転写や消去劣化等に不都合が生じ
ることが明らかになつている。
一方(2)の方法により製造した磁性粉末を磁気テ
ープ等に用いた場合、前述の保磁力の経年変化、
転写及び消去劣化特性等は好ましい方向に改善さ
れるが(1)の方法に比べ保磁力分布が劣る欠点を有
しているため、転写や消去特性は未だ不充分で高
密度磁気記録用磁性材料としては満足出来るもの
ではない。そこで本発明者は(2)の方法が(1)の方法
に比べ保磁力分布が劣る原因を検討した結果(2)の
方法で製造した磁性粉末は単位芯晶粒子へコバル
トが均一に分配されていないという事実を発見し
た。
本発明者は単位芯晶粒子あたりへのコバルトの
均一分配又は単位芯晶粒子表面層へのコバルト化
合物の均一被覆化を達成せしめるための方法を
種々検討した結果、製造工程中、アルカリを加え
て水酸化鉄及び水酸化コバルトが沈殿するに必要
なPHとした後希硫酸等の希薄な酸によりPHを一旦
降下させて大部分の沈殿を解膠させて均一なコロ
イド状にし、しかる後に再びアルカリを加えてそ
のコロイド状核を成長させればコバルトが均一に
分配された磁性粉末を製造することが出来ること
を発見し、又これらにより得られた磁性粉末が従
来のものに比べ高保磁力でかつ保磁力分布が著し
く改善されたものであることを発見し本発明を完
成した。
次に本発明のコバルト被覆磁性酸化鉄粉末の製
造法について説明する。
本発明はまず鉄塩及びコバルト塩を用いて鉄と
コバルトの混合溶液をつくり、これに針状の強磁
性酸化鉄粉末の芯晶を加え強力な機械的撹拌を加
え芯晶を分散させる。この段階ではアルカリを加
えていないために強力な分散力を与えてもコバル
トフエライト等の反応が進行しないことを利用し
鉄とコバルト及び芯晶懸濁液をその強力な撹拌力
により芯晶の分散はもとより同時に個々の芯晶表
面に充分なるコバルトと鉄のぬれを与える。次に
ぬれの効果を与えられた鉄、コバルト包含芯晶分
散液に苛性ソーダ等のアルカリを加え水酸化鉄及
び水酸化コバルトが沈殿するに必要なPH12〜13と
し、しかる後希硫酸等の希薄酸によりPHを３〜５
に降下して沈殿を均一なコロイド状とし、良質で
均一なコバルトフエライト等を誘発する核とな
し、しかる後再びその核を成長させるために充分
なアルカリを加え、その後よく知られたコバルト
が芯晶内部へ拡散しない範囲の熱を加え、大気中
下で極めてゆるい撹拌を行ないながら個々の芯晶
粒子に対して均一に、かつ単位芯晶表面に均一に
コバルト化合物等を析出被覆せしめることを特徴
とする高保磁力で保磁力分布の良好なコバルト被
覆針状磁性酸化鉄粉末を製造する方法である。
本発明に於いて個々の芯晶表面に充分なコバル
トと鉄のぬれを与えるための撹拌機としてはジユ
ースミキサー、ホモミキサー等の高速回転翼型撹
拌分散機或いは超音波ホモジナイザー、ジエツト
式分散機等の強力分散機が用いられる。
本発明によつて得られる磁性粉末は高保磁力で
かつ保磁力分布が良好であるので高密度磁気記録
用磁性材料として最適なものである。
ここでいう保磁力分布は、得られたコバルト被
覆針状磁性粉末を次の条件で磁気テープ化し、こ
のテープを磁気測定機にかけ強磁性体磁気ヒステ
リシス曲線の△Ｂ／△Ｈから成る微分波形の半価
巾をその磁気テープの保磁力で除した値で示した
ものである。IEEE、Vol1、MAG8、No.３（1972
年９月）第426頁並びにIEEE、Vol1、MAG11、
No.５（1975年９月）第1200頁に詳しく記載されて
いるように保磁力分布（IEEE、Vol1、MAG11、
No.５（1975年９月）第1200頁では、スイツチン
グ・フイールド・デイストリビユーシヨン
（Switching field distribution）と表現されてい
る。）は磁気テープの感度を高める上において重
要であり、又保磁力分布の内高保磁力成分の一部
は、磁気テープの消去特性を悪くし、低保磁力成
分の一部は磁気テープの転写を悪くするので、保
磁力分布を改良することにより磁均テープの感度
を高め、かつ消去特性や転写を向上することが出
来る。
磁気テープ化は下記組成でレツドデビル社製ペ
イントコンデイシヨナーにより塗料化を行い、以
後よく知られた方法で磁気テープを作製した。
The present invention relates to a method for producing cobalt-coated acicular magnetic iron oxide powder suitable as a material for magnetic recording media. In particular, the present invention relates to a method suitable for producing cobalt-coated acicular magnetic iron oxide powder suitable for high-density recording with high coercive force and good coercive force distribution. In recent years, there has been a trend toward higher densities in various magnetic recording materials, and in order to satisfy this higher density, it is necessary to increase the coercive force of magnetic iron oxide used as magnetic recording materials and to make magnetic tapes. There is a need to reduce the coercive force distribution, which greatly affects the transfer and erasing characteristics of the magnetic disk. As a means of increasing the coercive force of magnetic iron oxide, various methods have been proposed in which various spinel compounds are incorporated into various acicular iron oxides. As a means for producing magnetic iron oxide, a method of incorporating cobalt into various acicular iron oxides has been proposed. Cobalt-containing acicular iron oxides can be roughly classified into the following two types depending on how cobalt is added. (1) Cobalt salt or iron salt and cobalt salt are added to acicular α-FeOOH, α-Fe 2 O 3 , γ-Fe 2 O 3 and FeO-Fe 2 O 3 , etc., and then mixed with a suitable alkali such as caustic soda, etc. In a hydroxide or oxidizing atmosphere, it is deposited as cobalt ferrite, washed with water, dried, and then heat-treated at a temperature that allows cobalt to diffuse into the core crystal, e.g. 300 to 400°C, resulting in a cobalt uniform diffusion type (also called doped type). A method of producing acicular magnetic iron oxide powder. (For example, special public relations
(2) Acicular γ-Fe 2 O 3 , FeO・Fe 2 O 3 or (FeO)
By adding cobalt salt or iron salt and cobalt salt to X・Fe 2 O 3 (0 < A method for producing acicular magnetic iron oxide powder coated with a cobalt compound. (For example, Tokuko Shou 37-4825, Tokuko Sho No. 37-4825,
49-49475 method) In the case of method (1), the advantage is that cobalt is diffused by heat, so it is easy to uniformly distribute cobalt to each individual core crystal particle, and it is easy to distribute cobalt uniformly to each core crystal particle itself. This makes it easier to diffuse cobalt, leading to a favorable coercive force distribution. On the other hand, magnetic recording tapes made using these magnetic powders have cobalt dissolved in solid solution, so the coercive force changes over time. It has become clear that this is large, and that problems such as deterioration due to transfer and erasure occur. On the other hand, when the magnetic powder produced by method (2) is used in magnetic tape, etc., the above-mentioned aging change in coercive force,
Although the transfer and erasure deterioration characteristics are improved in a favorable direction, it has the disadvantage that the coercive force distribution is inferior to method (1), so the transfer and erase characteristics are still insufficient and it is difficult to use magnetic materials for high-density magnetic recording. As such, it is not satisfactory. Therefore, the present inventor investigated the reason why the coercive force distribution of method (2) is inferior to method (1), and found that the magnetic powder produced by method (2) has cobalt uniformly distributed in the unit core grains. I discovered that it is not. The present inventor investigated various methods for uniformly distributing cobalt per unit core particle or uniformly coating the surface layer of the unit core particle with a cobalt compound. After setting the pH required for iron hydroxide and cobalt hydroxide to precipitate, the pH is lowered with a dilute acid such as dilute sulfuric acid to peptize most of the precipitate and make it into a uniform colloid, and then alkali is added again. They discovered that it is possible to produce magnetic powder in which cobalt is evenly distributed by adding cobalt to grow the colloidal nuclei, and that the magnetic powder obtained by these methods has a higher coercive force and a higher coercive force than conventional ones. They discovered that the coercive force distribution was significantly improved and completed the present invention. Next, a method for producing the cobalt-coated magnetic iron oxide powder of the present invention will be explained. In the present invention, first, a mixed solution of iron and cobalt is prepared using an iron salt and a cobalt salt, and core crystals of needle-shaped ferromagnetic iron oxide powder are added to the solution and strong mechanical stirring is applied to disperse the core crystals. At this stage, since no alkali is added, the reaction of cobalt ferrite etc. does not proceed even if a strong dispersion force is applied. Taking advantage of this fact, the iron, cobalt and core crystal suspension is dispersed by the strong stirring force. At the same time, sufficient cobalt and iron wetting is applied to the surface of each core crystal. Next, an alkali such as caustic soda is added to the iron and cobalt-containing core crystal dispersion that has been given a wetting effect to adjust the pH to 12 to 13, which is necessary for the precipitation of iron hydroxide and cobalt hydroxide, and then a dilute acid such as dilute sulfuric acid. PH 3-5
The precipitate is made into a uniform colloidal form, forming a core that induces good quality and uniform cobalt ferrite, etc., and then enough alkali is added to grow the core again, and then the well-known cobalt core is formed. It is characterized by applying heat in a range that does not diffuse into the inside of the crystal, and by performing extremely gentle stirring in the atmosphere, cobalt compounds etc. are precipitated and coated uniformly on each individual core crystal particle and uniformly on the surface of the unit core crystal. This is a method for producing cobalt-coated acicular magnetic iron oxide powder with high coercive force and good coercive force distribution. In the present invention, as a stirrer to sufficiently wet the surface of each core crystal with cobalt and iron, a high-speed rotary blade type stirring and dispersing machine such as a youth mixer or a homomixer, an ultrasonic homogenizer, a jet type dispersing machine, etc. are used. A powerful disperser is used. The magnetic powder obtained by the present invention has a high coercive force and a good coercive force distribution, and is therefore optimal as a magnetic material for high-density magnetic recording. The coercive force distribution here refers to the differential waveform consisting of △B/△H of the ferromagnetic magnetic hysteresis curve, which is obtained by converting the obtained cobalt-coated acicular magnetic powder into a magnetic tape under the following conditions, and applying the tape to a magnetic measuring machine. It is expressed as the value obtained by dividing the half width by the coercive force of the magnetic tape. IEEE, Vol1, MAG8, No.3 (1972
(September), page 426 and IEEE, Vol1, MAG11,
Coercive force distribution (IEEE, Vol1, MAG11,
No. 5 (September 1975), page 1200, it is expressed as switching field distribution. ) is important in increasing the sensitivity of magnetic tape, and part of the high coercive force component of the coercive force distribution deteriorates the erasing characteristics of the magnetic tape, and part of the low coercive force component impairs the transfer of the magnetic tape. Therefore, by improving the coercive force distribution, it is possible to increase the sensitivity of the magnetic tape and improve the erasing characteristics and transfer. To make a magnetic tape, the following composition was made into a paint using a paint conditioner manufactured by Red Devil Co., Ltd., and a magnetic tape was then produced by a well-known method.
【表】
以下実施例により本発明を詳細に説明する。
実施例 １
市販の硫酸第１鉄20.4ｇと硫酸コバルト9.6ｇ
を600mlの水に溶解させ、鉄及びコバルトの混合
溶液とした。この鉄・コバルト混合溶液に長軸径
0.4μｍ、短軸径0.04μｍの針状ゲーサイトを常法
により処理して製造した黒色針状磁性酸化鉄粉末
（Fe2+／Fe3+＝0.16；保磁力3900e；残留磁束
（σr）39emu／ｇ；飽和磁束（σs）79emu／ｇ）
を芯晶として90ｇ加え、強力な機械的撹拌でよく
分散させた。その後600mlの水に苛性ソーダ34.2
ｇを溶解した調整アルカリ溶液を先の芯晶分散液
にPH＝13になるまで加えた。10分間放置後希硫酸
にてPH＝４とし、この状態で２時間放置した。し
かる後前述の苛性ソーダ調整液の残量をゆるい撹
拌を行ないながら添加し、そして90℃に昇温保持
して４時間の反応を行つた。その後反応終了液を
10℃／時の速度で室温まで降温しその後常法によ
り反応液を過、水洗、乾燥、粉砕してコバルト
被覆針状磁性酸化鉄粉末を得た。
得られた磁性粉末の磁気特性及び前記した方法
により作成した磁気テープの特性を第１表に示し
た。
比較例 １
市販の硫酸第１鉄20.4ｇと硫酸コバルト9.6ｇ
を600mlの水に溶解させ鉄及びコバルトの混合溶
液とした。この鉄、コバルト混合溶液に600mlの
水に苛性ソーダ34.2ｇを溶解した調整アルカリ溶
液を加えた。これに実施例１で使用した芯晶90ｇ
を加え機械的撹拌でよく分散させた後、ゆるい撹
拌を行いつつ90℃まで昇温し４時間の反応を行つ
た。
以下実施例１と同様に行つてコバルト被覆針状
磁性酸化鉄粉末を得た。得られた磁性粉末の磁気
特性及び磁気テープの特性を第１表に示した。
第１表から明らかなように本発明によるPHを一
旦降下させることによりコバルト化合物を被覆し
た磁性粉末は従来の方法によりコバルト化合物を
被覆した磁性粉末に比べ保磁力分布が改善されて
いることがわかる。又、第１図の曲線１に実施例
１に於ける降下PHと保磁力分布の関係を図示した
が、これによると降下PHは４附近の時が最も好ま
しい保磁力分布を示す磁性粉末が得られることが
わかる。
比較例 ２
市販の硫酸第一鉄20.4ｇと硫酸コバルト9.6ｇ
を600mlの水に溶解させ鉄及びコバルトの混合溶
液とした。この鉄コバルト混合溶液に実施例１で
使用した芯晶90ｇを加え、強力な機械的撹拌でよ
く分散させた。その後600mlの水に苛性ソーダ
34.2ｇを溶解した調整アルカリ溶液を先の芯晶分
散液にPH＝13になるまで加えた。10分間放置後希
硫酸にてPH＝４としこの状態で２時間放置した。
しかる後前述の苛性ソーダ調整液の残量をゆるい
撹拌を行ないながら添加し、そして90℃に昇温し
た。その後90℃で４時間ゆるい撹拌を行いながら
毎分３の空気を吹込み酸化反応を行なつた。
以下実施例１と同様に行つてコバルト被覆針状
磁性酸化鉄粉末を得た。得られた磁性粉末の磁気
特性及び磁気テープの特性を第１表に示した。
第１表から明らかなように本発明に於いて酸化
性ガスを吹き込んで酸化反応を行なわせたものは
機械的撹拌のみを行つたものより保磁力分布が劣
つているのがわかる。従つて本発明に於いては酸
化性ガスを吹き込んで酸化反応を行なわせること
は保磁力分布を逆に悪くするので好ましくない。
実施例 ２
市販の硫酸第一鉄20.4ｇと硫酸コバルト9.6ｇ
を600mlの水に溶解させ、鉄及びコバルトの混合
溶液とした。この鉄、コバルト混合溶液に実施例
１で使用した芯晶90ｇを加え超音波ホモジナイザ
ーでよく分散させた。以下実施例１と同様に行つ
てコバルト被覆針状磁性酸化鉄粉末を得た。得ら
れた磁性粉末の磁気特性及び磁気テープの特性を
第１表に示した。又、第１図の曲線２に本実施例
に於ける降下PHと保磁力分布の関係を図示した。
第１表及び第１図から明らかなように超音波ホ
モジナイザーを使用して分散を行つた場合もPHを
一旦降下させることにより改善されており、そし
てこの場合もPH４附近にしたものが最も好ましい
不磁力分布を示している。[Table] The present invention will be explained in detail with reference to Examples below. Example 1 Commercially available ferrous sulfate 20.4g and cobalt sulfate 9.6g
was dissolved in 600ml of water to form a mixed solution of iron and cobalt. This iron/cobalt mixed solution has a long axis diameter.
Black acicular magnetic iron oxide powder (Fe 2+ /Fe 3+ = 0.16; coercive force 3900e; residual magnetic flux (σ r )) produced by processing acicular goethite with a diameter of 0.4 μm and a short axis diameter of 0.04 μm using a conventional method. 39emu/g; saturation magnetic flux (σ s ) 79emu/g)
90 g of core crystals were added and well dispersed with strong mechanical stirring. Then caustic soda 34.2 in 600ml water
A prepared alkaline solution in which g was dissolved was added to the core crystal dispersion until pH=13. After being left for 10 minutes, the pH was adjusted to 4 with dilute sulfuric acid and left in this state for 2 hours. Thereafter, the remaining amount of the above-mentioned caustic soda adjustment solution was added with gentle stirring, and the temperature was raised and maintained at 90°C to carry out a reaction for 4 hours. After that, add the reaction finished solution.
The temperature was lowered to room temperature at a rate of 10° C./hour, and then the reaction solution was filtered, washed with water, dried, and pulverized by a conventional method to obtain a cobalt-coated acicular magnetic iron oxide powder. Table 1 shows the magnetic properties of the obtained magnetic powder and the properties of the magnetic tape prepared by the above method. Comparative example 1 Commercially available ferrous sulfate 20.4g and cobalt sulfate 9.6g
was dissolved in 600ml of water to obtain a mixed solution of iron and cobalt. A prepared alkaline solution prepared by dissolving 34.2 g of caustic soda in 600 ml of water was added to this iron and cobalt mixed solution. Add to this 90g of core crystal used in Example 1.
After adding and thoroughly dispersing with mechanical stirring, the temperature was raised to 90°C with gentle stirring, and reaction was carried out for 4 hours. Thereafter, the same procedure as in Example 1 was carried out to obtain a cobalt-coated acicular magnetic iron oxide powder. The magnetic properties of the obtained magnetic powder and the properties of the magnetic tape are shown in Table 1. As is clear from Table 1, the coercive force distribution of the magnetic powder coated with a cobalt compound by once lowering the pH according to the present invention is improved compared to the magnetic powder coated with a cobalt compound using the conventional method. . In addition, curve 1 in Figure 1 shows the relationship between the drop PH and the coercive force distribution in Example 1, and it shows that when the drop PH is around 4, a magnetic powder exhibiting the most preferable coercive force distribution can be obtained. I know that it will happen. Comparative example 2 Commercially available ferrous sulfate 20.4g and cobalt sulfate 9.6g
was dissolved in 600ml of water to obtain a mixed solution of iron and cobalt. 90 g of the core crystal used in Example 1 was added to this iron-cobalt mixed solution and well dispersed by strong mechanical stirring. Then add caustic soda to 600ml of water.
A prepared alkaline solution in which 34.2 g was dissolved was added to the core crystal dispersion until pH=13. After being left for 10 minutes, the pH was adjusted to 4 with dilute sulfuric acid and left in this state for 2 hours.
Thereafter, the remaining amount of the above caustic soda adjustment solution was added with gentle stirring, and the temperature was raised to 90°C. Thereafter, the mixture was heated at 90° C. for 4 hours with gentle stirring, and air was blown in at a rate of 3 per minute to carry out an oxidation reaction. Thereafter, the same procedure as in Example 1 was carried out to obtain a cobalt-coated acicular magnetic iron oxide powder. The magnetic properties of the obtained magnetic powder and the properties of the magnetic tape are shown in Table 1. As is clear from Table 1, the coercive force distribution of the present invention in which the oxidizing reaction was carried out by blowing in an oxidizing gas was inferior to that in which only mechanical stirring was performed. Therefore, in the present invention, it is not preferable to blow in an oxidizing gas to cause an oxidation reaction because it adversely affects the coercive force distribution. Example 2 Commercially available ferrous sulfate 20.4g and cobalt sulfate 9.6g
was dissolved in 600ml of water to form a mixed solution of iron and cobalt. 90 g of the core crystals used in Example 1 were added to this iron and cobalt mixed solution and well dispersed using an ultrasonic homogenizer. Thereafter, the same procedure as in Example 1 was carried out to obtain a cobalt-coated acicular magnetic iron oxide powder. The magnetic properties of the obtained magnetic powder and the properties of the magnetic tape are shown in Table 1. Further, curve 2 in FIG. 1 illustrates the relationship between the drop PH and the coercive force distribution in this example. As is clear from Table 1 and Figure 1, dispersion using an ultrasonic homogenizer is also improved by lowering the pH, and in this case as well, a pH around 4 is the most preferable. Shows magnetic force distribution.
第１図は水酸化物析出後の降下PHと保磁力分布
の関係を示す特性図で曲線１は分散を機械的に行
つた場合、曲線２は超音波ホモジナイザーを用い
た場合である。
FIG. 1 is a characteristic diagram showing the relationship between the PH drop after hydroxide precipitation and the coercive force distribution. Curve 1 is the case when dispersion is performed mechanically, and curve 2 is the case when an ultrasonic homogenizer is used.
Claims (1)
及びコバルト塩を含有する混合溶液に分散させ
て、これらの化合物を含有した針状黒色磁性酸化
鉄粉末を製造する方法において、鉄水酸化物及び
コバルト水酸化物が沈殿するに必要なアルカリ溶
液を加えた後、反応溶液のPHを降下させて得られ
た沈殿を解膠してコロイド状となし、その後再び
アルカリを加えてコバルト化合物を均一に被覆さ
せることを特徴とするコバルト被覆針状磁性酸化
鉄粉末の製造法。 ２ 反応溶液のPHを降下させた時のPHが３〜５の
範囲である特許請求の範囲第１項記載のコバルト
被覆針状磁性酸化鉄粉末の製造法。[Claims ] 1 ( FeO ) In the method for producing iron oxide powder, after adding an alkaline solution necessary for precipitation of iron hydroxide and cobalt hydroxide, the pH of the reaction solution is lowered and the resulting precipitate is peptized to form a colloid. A method for producing cobalt-coated acicular magnetic iron oxide powder, which comprises adding alkali again to coat the cobalt compound uniformly. 2. The method for producing cobalt-coated acicular magnetic iron oxide powder according to claim 1, wherein the PH of the reaction solution is in the range of 3 to 5 when the PH is lowered.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP55119026A JPS5745206A (en) | 1980-08-30 | 1980-08-30 | Manufacture of acicular powder of magnetic iron oxide covered with cobalt |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP55119026A JPS5745206A (en) | 1980-08-30 | 1980-08-30 | Manufacture of acicular powder of magnetic iron oxide covered with cobalt |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5745206A JPS5745206A (en) | 1982-03-15 |
| JPH0227804B2 true JPH0227804B2 (en) | 1990-06-20 |
Family
ID=14751138
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP55119026A Granted JPS5745206A (en) | 1980-08-30 | 1980-08-30 | Manufacture of acicular powder of magnetic iron oxide covered with cobalt |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5745206A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0604849B1 (en) * | 1992-12-29 | 1996-10-16 | Ishihara Sangyo Kaisha, Ltd. | Cobalt-containing magnetic iron oxide and process for producing the same |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS525494A (en) * | 1975-07-02 | 1977-01-17 | Fuji Photo Film Co Ltd | Ferromagnetic grit manufacturing process |
-
1980
- 1980-08-30 JP JP55119026A patent/JPS5745206A/en active Granted
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS525494A (en) * | 1975-07-02 | 1977-01-17 | Fuji Photo Film Co Ltd | Ferromagnetic grit manufacturing process |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5745206A (en) | 1982-03-15 |
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