JP2677278B2 - Magnetic iron oxide powder for magnetic recording and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic powder for magnetic recording and a method for producing the same, and more particularly to a method for producing a cobalt-modified magnetic iron oxide powder capable of high density recording.

[0002]

2. Description of the Related Art Magnetic powders for magnetic recording are magnetic iron oxide particles (γ iron oxide particles, magnetite, or acicular magnetic iron oxide fine particles in an intermediate state, which have a high coercive force due to shape anisotropy. Powder) is used,
Further, cobalt-modified magnetic iron oxide particles obtained by modifying the above magnetic iron oxide particles with cobalt or cobalt and another element are used as magnetic powder for magnetic recording with high coercive force capable of high density recording.

Among these, various methods have been proposed so far as a method for producing the latter cobalt-modified magnetic iron oxide particles, and among them, as one of the useful methods, magnetic properties in an alkaline solution have been proposed. There is a method of dispersing iron oxide particles and adding a cobalt salt or other components such as a cobalt salt and a ferrous salt to obtain cobalt modified magnetic iron oxide particles.

Further, by the method (Japanese Patent Publication No. 62-17364) in which the Fe ²⁺ / Fe ³⁺ is in a molar ratio of 0.2 or less in the above-mentioned cobalt metamorphic atmosphere, it is more preferable than the simple metamorphism of cobalt alone. A method of further increasing the coercive force is also known.

[0005]

However, in the above method, the amount ratio of Fe ²⁺ / Fe ³⁺ is also limited, so that it cannot be applied to a wide range of high performance and high coercive force as a magnetic recording medium. The object of the present invention is to solve the above-mentioned drawbacks of the prior art, to eliminate the restriction of the Fe ²⁺ / Fe ³⁺ molar ratio with ^respect to magnetic iron oxide particles, to obtain a high coercive force, and to have a wide range as a magnetic recording medium. It is an object of the present invention to provide a method for obtaining magnetic iron oxide powder for magnetic recording, which can realize high performance.

[0006]

[Means for Solving the Problems] To achieve the above object, as a result of research conducted by the present inventors, a magnetic oxide for magnetic recording in which calcium, magnesium and silicon compounds coexist on the surface of cobalt-modified iron oxide magnetic powder. The surfaces of iron powder and cobalt-modified iron oxide magnetic powder are simultaneously treated in a solution in which calcium ions, magnesium ions, and silicon compounds coexist, and calcium ions, magnesium ions, and silicon compounds are formed on the iron oxide layer containing cobalt. The coercive force of the magnetic iron oxide particles obtained by subsequent drying is further increased as compared with the case where the ions alone or other elements are contained, and a wide range of high performance as a magnetic recording medium is achieved. The present invention has been accomplished by finding that the above can be realized.

Hereinafter, the present invention will be described in more detail. In the present invention, the steps until obtaining the cobalt-modified iron oxide magnetic powder are the same as in the conventional case, and first, the iron oxide magnetic powder is obtained. At this time, the composition can be continuously changed from γ-Fe ₂ O ₃ (Fe ²⁺ / Fe ³⁺ = 0) to Fe ₃ O ₄ (Fe ²⁺ / Fe ³⁺ = 0.5).

Subsequently, the iron oxide magnetic powder is subjected to cobalt conversion treatment in an alkaline aqueous solution according to a well-known method. The cobalt-modified iron oxide magnetic powder obtained by this cobalt modification treatment is dipped in a solution in which three kinds of water-soluble salts (calcium ion, magnesium ion and silicon compound) coexist, and is slurried to form 3 The seed salts (calcium, magnesium and silicon compounds) are simultaneously deposited on the cobalt-modified powder. The amount of calcium, magnesium and silicon compounds present is 0.05 to 1.0 in terms of Ca, Mg and Si, respectively, based on the total amount.
Preferably it is in the range of weight%. If the content of these is less than 0.05% by weight, the effect of increasing the coercive force becomes small. On the other hand, even if the content is more than 1.0% by weight, no further effect is obtained, and on the contrary, the additive adheres to the particle surface as a hydroxide or an oxide to lower the saturation magnetization value. In addition, the magnetic oxide is not preferable because it has adverse effects such as a decrease in dispersibility when formed into a tape.

The coexistence mode may be either a mode in which calcium ions, magnesium ions and a silicon compound are added to the alkaline slurry obtained after the cobalt modification treatment, or a mode in which they are coexistent in the washing water. When the soluble salt is added to the slurry obtained after the cobalt conversion treatment, it may be added at any time after the cobalt conversion treatment. Even when three kinds of salts are added to the alkaline slurry obtained after the cobalt conversion treatment and the slurry is washed with pure water, the slurry after the cobalt conversion treatment is treated with 3 times.
In both cases where the treatment is carried out by washing with the washing water in which the seed salts are coexisted at the same time, it is preferable to finish the washing when the pH of the slurry is 8 or more in order to prevent dissolution of Ca, Mg and Si. Further, since Ca, Mg, and Si are contained in the above amounts, the addition amount of these calcium ion, magnesium ion, and silicon compound in the solution is a rough estimate of a single element ion. 0% by weight is preferred.

Here, as the calcium ion and the magnesium ion to be coexisted, any compounds soluble in water such as chloride, sulfate and nitrate may be used. Further, as the silicon compound, orthosilicic acid, metasilicic acid, sodium orthosilicate, sodium metasilicate, potassium metasilicate, calcium metasilicate, orthosilicate calcium, barium metasilicate, calcium orthosilicate, barium metasilicate, cobalt orthosilicate, etc. Silicate, silicon monoxide, silicon dioxide, colloidal silica,
Water glass etc. are mentioned.

[0011]

The effect of simultaneous addition of calcium ion, magnesium ion and silicon compound in the present invention is not clear, but it is considered to be due to surface magnetic anisotropy due to coexistence of calcium ion, magnesium ion and silicon compound.

According to the results of the elemental analysis conducted by the present inventor, the coercive force of the cobalt metamorphic magnetic particles becomes maximum only when the above-mentioned three additional elements coexist. Also, when taped,
It is possible to achieve high performance in a wide range of the composition and amount of the magnetic compound.

[0013]

Examples of the present invention will be described below. Example 1 γ-iron oxide powder manufactured by a conventional method (coercive force: 350 O
e, saturation magnetization: 74 emu / g) 400 g was added to 2.4 liters of 2.5N caustic soda aqueous solution and sufficiently dispersed, then the temperature of this dispersion was raised to 100 ° C. and a cobalt chloride solution was added, Allow to react for 7 hours, then chloride first
An iron solution was added and reacted for 1 hour to deposit Co (2) and Fe (2) on the surfaces of the γ iron oxide particles. Deposition amount is
Cobalt atoms are 2.5% by weight and iron atoms are 5.0% by weight with respect to γ-iron oxide. After the completion of the cobalt conversion treatment, 50 ml of an aqueous solution containing 0.5% by weight each of calcium, magnesium and silicon with respect to γ-iron oxide was added to the alkaline slurry. Here, calcium was added to the slurry as calcium chloride, magnesium as magnesium chloride, and the silicon compound as sodium metasilicate. The slurry was diluted with pure water, decanted, the supernatant was discarded, and the same operation was repeated, and the slurry was washed with water until the pH value was 9.0 or less. Then, this was filtered and dried at 60 ° C. for 12 hours to obtain a magnetic iron oxide powder.

Example 2 A magnetic iron oxide powder was obtained in the same manner as in Example 1 except that magnetite powder was used in place of γ iron oxide powder in Example 1.

Example 3 Bertride magnetic iron oxide powder (Fe ²⁺ / Fe ³⁺ = 0.2) was used in place of the γ iron oxide powder in Example 1,
Magnetic iron oxide powder was obtained in the same manner as in Example 1.

Example 4 Iron oxide particles in which Co (2) was attached to γ-iron oxide were obtained by omitting the addition of ferrous chloride in Example 1, and then treated in the same manner as in Example 1 to obtain magnetic iron oxide. Got the powder.

Comparative Example 1 In the same manner as in Example 1, except that an aqueous solution containing only 0.5% by weight of calcium was used in Example 1,
A magnetic iron oxide powder was obtained.

Comparative Example 2 A magnetic iron oxide powder was obtained in the same manner as in Example 1, except that an aqueous solution containing only 0.5% by weight of magnesium was used in Example 1.

Comparative Example 3 A magnetic iron oxide powder was obtained in the same manner as in Example 1 except that an aqueous solution containing only 0.5% by weight of silicon was used in Example 1.

Comparative Example 4 A magnetic iron oxide powder was obtained in the same manner as in Example 1, except that an aqueous solution containing 0.5% by weight of each of calcium and silicon was used.

Comparative Example 5 In Example 1, magnesium and silicon were added to 0.5
Magnetic iron oxide powder was obtained in the same manner as in Example 1 using an aqueous solution containing wt%.

Comparative Example 6 A magnetic iron oxide powder was obtained in the same manner as in Example 1 except that an aqueous solution containing 0.5% by weight of each of calcium and magnesium was used.

Comparative Examples 7 to 12 The amounts of additives in Comparative Examples 1 to 6 were changed to 2.0% by weight in Comparative Examples 7 to 12 in the same manner as in Example 1,
A magnetic iron oxide powder was obtained.

Comparative Examples 13 and 14 In Comparative Examples 1 and 2, magnetite and bertride (Fe ²⁺ / Fe ³⁺ = 0.2) were used instead of the γ iron oxide powder.

Comparative Example 15 A magnetic iron oxide powder was obtained in the same manner as in Example 1, except that the pure aqueous solution containing no additive was used.

Comparative Example 16 A magnetic iron oxide powder was obtained in the same manner as in Example 1 except that strontium (SrCl ₂ ) was used in place of calcium (CaCl ₂ ) in Example 1.

With respect to the magnetic iron oxide powder obtained in each of the above Examples and Comparative Examples, the magnetic characteristics and the tape magnetic characteristics immediately after washing and drying were examined. Table 1 shows the results.
5 shows.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

[Table 3]

[0031]

[Table 4]

[0032]

[Table 5]

As is clear from Tables 1 to 5, it is found that the coercive force is maximized and the magnetic properties of the tape are improved when the calcium ion, the magnesium ion and the silicon compound of the Examples are coexistent.

[0034]

As described above in detail, according to the present invention, the cobalt-containing iron oxide powder obtained by forming the iron oxide layer containing cobalt on the surface of the iron oxide magnetic powder is used as calcium ion, magnesium ion and silicon. Only when the compounds are subjected to simultaneous coexistence treatment, it is possible to obtain a magnetic iron oxide powder for magnetic recording having a high coercive force and excellent tape magnetic characteristics.

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Claims (2)

(57) [Claims] 1. A calcium-, magnesium-, and silicon-containing compound Ca, M on the surface of the cobalt-modified iron oxide magnetic powder.
A magnetic iron oxide powder for magnetic recording, characterized in that 0.05 to 1.0% by weight in terms of g and Si coexist. 2. For cobalt-modified iron oxide magnetic powder
0.01-2.0% by weight of calcium and magnesium
In the solution in which Co-on and silicon compound coexist,
By bringing the formed iron oxide magnetic powder into contact, calcium ions, magnesium ions, and a silicon compound coexist on the surface of the cobalt-modified iron oxide magnetic powder in an amount of 0.05 to 1.0% by weight in terms of Ca, Mg, and Si. Thereafter, the cobalt-modified iron oxide magnetic powder is dried to produce a magnetic iron oxide powder for magnetic recording.