JP2965606B2 - Method for producing metal magnetic powder - Google Patents

Description

The present invention relates to a method for producing a magnetic material for a high-density magnetic recording medium, and more particularly, to a high-density magnetic recording medium such as an 8 mm video tape or a commercial metal tape. The present invention relates to a method for producing a metal magnetic powder having an optimum coercive force as a magnetic material for use, excellent dispersibility and orientation in a medium, and a high squareness ratio.

[Conventional technology and its problems]

Conventionally, γ-Fe ₂ O ₃ , C
o-containing γ-Fe ₂ O ₃ , CrO _2, etc. have been used, but with the recent advances in the size and weight of magnetic recording devices, there is a demand for higher performance in magnetic recording media such as magnetic tapes and magnetic disks. Is also getting bigger.

As a magnetic material that meets this demand, a metal magnetic powder mainly composed of iron has been developed.
Used for metal tape for video, floppy disk for video, etc., with the recent digitization of audio, development of high-band 8mm video, development of floppy for high density memory, etc. The development of magnetic powders is strongly desired.

A general method for producing metal magnetic powder mainly composed of iron is as follows.
Acicular iron oxyhydroxide or other metals (eg, Ni, Co, Mn, Zn, Cr, Al, Si, B, P, Ca, Mg,
Ba, Ti, Zr, etc.) is a method in which doping or deposition is used as a raw material to control magnetic properties and prevent shape change due to heat of particles during reduction, and reduce this with a reducing gas. . Many proposals have been made for this manufacturing method, but none of them satisfy the characteristics required of recent high-density magnetic recording media, and further improvements are desired.

Densification of a magnetic recording medium is achieved by high output characteristics and a reduction in noise level. These various characteristics of the magnetic recording medium are closely related to the characteristics of the magnetic material used for the magnetic recording medium, and the following items can be mentioned as the characteristics that the magnetic powder for the high-density magnetic recording medium should have.

a. Have an appropriate coercive force (Hc).

b. High saturation magnetic flux density (σs).

c. The squareness ratio (σr / σs) is large.

d. The particle size must be small and uniform.

e. It must have a dense structure and be easily dispersed.

f. After being made into a medium, it should be rich in weather resistance.

In order to obtain high output characteristics as a magnetic recording medium, items a, b, c, and e are particularly required for magnetic materials.

It is necessary to control the coercive force of item a to a value suitable for the purpose of use of the magnetic recording medium. As a method for controlling the coercive force, the particle size of iron oxyhydroxide as a starting material is mainly controlled.

The characteristic of metal magnetic powder is that the saturation magnetic flux density of b is large, but metal magnetic powder as it is reduced has a large activity, and when it is taken out to the atmosphere, it reacts rapidly with oxygen, It changes to α-iron oxide without any. Therefore, before contacting the atmosphere, the reduced metal magnetic powder is treated to form a dense oxide film on the surface of the particles so that the particles can be safely handled in the atmosphere. However, the magnetism of the oxide film is small, and when the ratio of the oxide film per unit particle increases, the saturation magnetic flux density decreases. In particular, when the size of the metal magnetic powder is reduced for the purpose of reducing the noise of the magnetic recording medium, the saturation magnetic flux density is remarkably reduced.

In order to increase the squareness ratio of item c, it is important to increase the needle ratio (length 1 / thickness d) of the raw material iron oxyhydroxide and make the particle size uniform. Is controlled in consideration of the relationship with the coercive force of item a. Further, to improve the squareness ratio, it is important how to prevent collapse of the particle shape, particle cutting and sintering during reduction.

Item e is desired to be a metal magnetic powder particle which is dense without voids and has good surface smoothness.

In order to reduce the noise of the magnetic recording medium, it is important to reduce the size of the metal magnetic powder to increase the number of particles per unit volume of the magnetic recording medium. That is, `` Tamakawa, Nakabachi Journal of the Japan Society of Applied Magnetics Vol.7, No.3, 1983 P 204 '' states that `` Generally, the S / N of the tape is the particle size, dispersibility, filling property, and It depends on the smoothness of the tape surface.If the surface property and dispersibility are constant, S / N
Is known to be proportional to the square root of the average number of particles per unit volume. Therefore, it can be said that the magnetic powder having the smallest possible particle size and having higher filling properties is more advantageous. "
It is described.

However, the miniaturization of the metal magnetic powder particles tends to increase the cohesiveness of the particles due to the increase in the specific surface area, making it difficult to disperse and orient the particles.

As described above, in order to achieve a higher density of the magnetic recording medium, there is a demand for a metal magnetic powder which is finer, has excellent dispersibility, has a high squareness ratio, and has a large saturation magnetic flux density, in order to achieve a higher density of the magnetic recording medium. However, a magnetic metal powder satisfying these many requirements has not been manufactured so far.

[Object of the invention]

The present invention has been made in order to solve the problems of the conventional technology as described above, and has an optimal coercive force according to the type of magnetic recording medium and a fine but excellent dispersibility, and when the medium is used. It is intended to produce a metal magnetic powder having a high squareness ratio.

[Means for solving the problem]

The present invention is to neutralize the aqueous ferrous chloride solution with an alkali to adjust the pH.
= 10 or more alkaline suspension, and the oxygen-containing gas is passed through the suspension to oxidize it to produce needle-like α-FeOOH particles, the ferrous chloride aqueous solution Alternatively, a water-soluble barium salt is added to the alkaline suspension before passing the oxygen-containing gas, and then the oxygen-containing gas is passed to generate α-FeOOH having excellent needle-like properties containing barium, Next, a silica compound and / or an aluminum compound was deposited on the needle compound α-FeOOH particles containing the barium compound, with or without the nickel compound and / or the cobalt compound deposited on the surface of the particles. Thereafter, filtration, washing with water, drying, and then heat treatment in a non-reducing atmosphere, followed by heat reduction in a temperature range of 300 to 600 ° C. under a hydrogen stream, to produce a metal magnetic powder. It is the law.

Ferrous salts include ferrous chloride, ferrous nitrate, and ferrous sulfate, and ferrous chloride is used in the present invention. Ferrous nitrate is not economical, and in the case of ferrous sulfate, barium sulfate microcrystals may be formed and mixed with the α-FeOOH crystal, which is not preferable.

The alkali used in the present invention is an alkali hydroxide such as KOH or NaOH, an alkali carbonate such as K ₂ CO ₃ or Na ₂ CO ₃ ,
An aqueous solution of H _{3 or} the like can be used, but any of these can be essentially selected to implement the present invention.

As the water-soluble barium salt used in the method of the present invention, barium chloride, barium nitrate, barium chlorate, barium perchlorate, barium salts of lower carboxylic acids and the like can be used.
The addition amount of the water-soluble barium salt is preferably 0.2 to 5.0 atomic% in terms of barium with respect to iron, more preferably 0.3 to 5.0 atomic%.
3.0 atomic%. With an addition amount of less than 0.2 atomic%, there is no addition effect, and α-FeOOH having excellent needle-like properties cannot be obtained. Also
Adding more than 5.0 atomic% has no further effect.

As a method for adding the water-soluble barium salt, it is common to mix the aqueous solution of ferrous chloride and neutralize the mixed solution with an alkali. Various methods are conceivable, such as a method of adding to an alkaline suspension of ferrous chloride which has been finished, or a method of adding an alkali excess suspension of a neutralized water-soluble barium salt to an aqueous solution of ferrous chloride for neutralization. However, any method may be used. By blowing an oxidizing gas into an alkaline suspension of ferrous chloride in the presence of barium ions, α-FeOO with excellent acicularity
Although H is obtained, the size of the particles can be controlled by the addition amount of the water-soluble barium salt, the temperature of the suspension, the oxygen concentration in the gas to be blown, and the flow rate. In addition, a reduction accelerator or a magnetic property control agent in the suspension,
Sintering inhibitor during reduction, additives for improving oxidation resistance (for example, Ni, Co, Zn, Cu, Mn, Cr, Al, Zr,
B, Ca, Mg, Ti, etc.)
Needle-like α-FeOOH containing these metal compounds can also be obtained. When the nickel compound and / or the cobalt compound is deposited on the surface of the needle-like crystals α-FeOOH containing the barium compound thus produced, the type of the nickel and cobalt compound to be added is chloride,
Nitrate is suitable, and it is better to avoid sulfate or the like containing a sulfate group since it reacts with barium ions to produce barium sulfate crystals insoluble in water. The method of deposition is such that an aqueous solution of a nickel compound and / or a cobalt compound is added dropwise to a needle-like crystal α-FeOOH suspension containing a barium compound, and after sufficient stirring, alkali is added dropwise to adjust the pH of the suspension. 7-9
The method of applying and adjusting to the range of, or the method of inverting the dropping order, or the needle crystal α containing a barium compound
-An aqueous solution of a nickel compound and / or a cobalt compound and an alkali are simultaneously dropped into the FeOOH suspension to form a suspension.
The present invention can be carried out by any method, such as a method in which the pH is kept constant in the range of 7 to 9 and a drop is continuously applied. The amount of the nickel compound and / or the cobalt compound to be deposited is preferably in the range of 0.3 to 30 at%, more preferably 0.5 to 20 at%, based on iron. Both nickel and cobalt have a function as a reduction promoter and a function as a control agent for magnetic properties.If the amount is too small, the reduction reaction does not proceed easily. The desired magnetic properties cannot be obtained due to the decrease in density and the decrease in coercive force. In particular, a decrease in the saturation magnetic flux density is a significant negative factor in manufacturing a high-output magnetic recording medium.
In the case of cobalt, assuming that it is alloyed with iron, theoretically the saturation magnetic flux density will increase up to 30 atomic%, but adding a large amount will maintain the particle shape during reduction and There is a problem with economy.

Next, the silica compound and / or the aluminum compound is applied. As the silica compound and the aluminum compound used in the present invention, any water-soluble or colloidal one can be used. Preferred examples of the compound include aluminum chloride, aluminum nitrate, water glass, colloidal silica, sodium aluminate, and alumina sol.

The deposition method is performed by adding a barium-containing suspension of α-FeOOH containing nickel compound and / or cobalt compound (or not having undergone the deposition process) to a silica compound and / or an aluminum compound. Is added dropwise, and if the added compound is acidic, an alkali is added. If the added compound is alkaline, an acid (eg, hydrochloric acid, nitric acid, etc.) is added dropwise, and the pH of the suspension is adjusted to 7 to 9. It is sufficient to neutralize and adhere so as to fall within the range. When both the silica compound and the aluminum compound are applied, a method of applying two kinds of compounds so as to overlap each other and a case of applying the two kinds of compounds at the same time can be considered. There is no hindrance to the implementation of the present invention.

The amount of the silica compound and the amount of the aluminum compound to be applied are each preferably 0.5 to 20 atomic%, more preferably 1.0 to 15 atomic%, based on iron. The purpose of the deposition of the silica compound and / or the aluminum compound is to prevent sintering of the particles at the time of reduction, and the amount of deposition is too small to have the effect of preventing sintering. Since aluminum does not have magnetism, the magnetism is diluted in proportion to the addition amount, and the saturation magnetic flux density decreases. Also, the reduction becomes extremely difficult, probably due to the formation of a hardly reducible substance by the sintering inhibitor and iron.

After the above deposition process is completed, the processed material is filtered,
Wash and dry thoroughly. Then, in a non-reducing atmosphere,
For example, the heat treatment is performed in air or an inert gas such as nitrogen. In this heat treatment, a dehydration reaction of α-FeOOH occurs, which changes to an oxide mainly composed of α-Fe ₂ O ₃ , and has an effect of preventing the shape of particles during reduction. The temperature of the heat treatment is preferably 500 to 850 ° C. If the temperature is low, there is no effect of the heat treatment, and if the temperature is too high,
The shape of the particles changes during the heat treatment, and the characteristics of the metal magnetic powder deteriorate.

Next, the treated product is charged into a reduction reactor, and reduced by a conventional method in a temperature range of 300 to 600 ° C. under a stream of hydrogen.If the reduction temperature is too low, the reaction time becomes longer,
Not economic. When the temperature is high, the reaction time is shortened, but the metal magnetic powder is sintered, the coercive force and the squareness ratio are reduced, and the noise level when the medium is used becomes high.

After reduction, the reduction reactor is cooled, and the metal magnetic powder is stabilized and taken out of the system by a conventional method such as flowing a mixed gas of nitrogen and air.

As described above, the needle-like property of the present invention is good, and the dispersibility is excellent.
A metal magnetic powder having a good squareness ratio is produced.

〔Example〕

 Next, the present invention will be described with reference to examples.

Example-1 In order to contain 1.0 atomic% of barium with respect to iron,
100 l of a 0.6 mol / l aqueous solution of ferrous chloride obtained by adding 146.6 g of barium chloride (BaCl ₂ .2H ₂ O) was added to 200 l of a 1.8 mol / l aqueous NaOH solution previously prepared in a reactor. A nitrogen gas was flowed into the mixture, and the mixture was added with stirring to carry out a reaction for forming an alkaline suspension.

At a temperature of 50 ° C., 100 liters of air per minute was passed through the suspension for 7 hours to obtain barium-containing acicular α-FeOOH.

This was separated by filtration and washed with water by a conventional method to obtain a wet cake (this was used as a raw material A).

As a result of electron microscopic observation, the barium-containing acicular α-FeOOH particles were found to have excellent acicularity with an average major axis of 0.55 μm and an average acicular ratio (major axis / minor axis) of 28. . The specific surface area of this product measured by the BET method was 68 m ² / g. The added barium was detected in α-FeOOH by X-ray fluorescence analysis, and it was confirmed that barium was dissolved in the needle crystal α-FeOOH.

500 g of this barium-containing acicular α-FeOOH (in terms of pure content) was put into 100 l of distilled water and dispersed well. An aqueous solution obtained by dissolving separately prepared 0.28 mol of each of nickel chloride and cobalt chloride in 1 distilled water was added thereto, followed by stirring for 30 minutes. Then, a 2N aqueous NaOH solution was added dropwise over 1 hour, and pH =
Neutralization to 8 and continued stirring for 1 hour. Next, an aqueous solution in which 0.34 mol of aluminum chloride was dissolved in 2 liters of distilled water was added, and the mixture was stirred well, and an aqueous solution in which 0.11 mol of water glass in terms of silica was dissolved in 2 liters of distilled water was added dropwise over 1 hour. . Thereafter, a 2N aqueous solution of NaOH was added dropwise until the pH of the suspension became 8, and stirring was continued for 1 hour. The α-FeOOH after the deposition process is filtered, washed with water, and dried to deposit a nickel and cobalt compound and an aluminum and silica compound.
-FeOOH was obtained.

Next, the deposited α-FeOOH is subjected to a heat treatment in an electric furnace at 650 ° C. for 2 hours.
Reduction at a temperature of 5 ° C. for 5 hours. After completion of the reduction, the gas in the reaction system was changed to nitrogen gas and cooled to room temperature, and then air was gradually fed in to stabilize the reduced product to obtain a metal magnetic powder.
Sample vibration type magnetometer (VSM manufactured by Toei Kogyo Co., Ltd.)
According to the measurement of the magnetic field at a maximum magnetic field of 10KG, the coercive force (Hc) = 1603 Oe and the saturation magnetic flux density (σs) = 137.0 emu /
g, squareness ratio (σr / σs) = 0.525. BET value is 56.5m
² / g. Observation of the particle morphology of the metal magnetic powder with a transmission electron microscope (TEM) revealed that the particles were excellent in needle-like properties without sintering.

Next, the metal magnetic powder was dispersed in a solution in which a vinyl chloride-vinyl acetate copolymer resin was dissolved together with a dispersing agent, a lubricant and an abrasive, and a urethane elastomer was added to the dispersion to sufficiently disperse. After adding a cross-linking agent to the dispersion paint and mixing well, a 14 μm PET by a gravure coater.
Apply on a film and leave the magnetic paint undried, 2500
The magnetic field orientation treatment was performed with a Gaussian magnet, and after drying, a super calender treatment was performed.
Millivideo tape was manufactured. The magnetic properties of the tape
When measured with VSM at a maximum magnetic field of 10KG, Hc = 1570 O
e, Br = 3420 G, Bm = 3931 G, Br / Bm = 0.87, indicating that the squareness ratio was extremely good.

Example-2 Barium-containing acicular crystal α- produced in Example-1
500 g of FeOOH (raw material A) (in terms of pure content) was put into 100 l of distilled water and dispersed well. An aqueous solution prepared by dissolving separately prepared 0.45 mol of nickel chloride and cobalt chloride in 1 distilled water was added thereto, followed by stirring for 30 minutes. Then, a 2N aqueous NaOH solution was added dropwise over 1 hour to neutralize to pH = 8, and stirring was continued for 1 hour. Next, 2 l of 0.26 mol water glass in terms of silica
An aqueous solution dissolved in distilled water was added thereto, and the mixture was sufficiently stirred. A 2N HCl aqueous solution was added dropwise thereto, and the mixture was neutralized to pH = 8 in 1 hour, and a silica compound was applied. After neutralization,
After stirring for 1 hour, the deposited α-FeOOH was filtered, washed with water, and dried to obtain α-FeOOH on which the nickel compound, the cobalt compound and the silica compound were deposited.

Next, the deposited α-FeOOH is heat-treated in an electric furnace at 600 ° C. for 2 hours, and then the heat-treated product is heated at 450 ° C. in a stream of hydrogen gas.
For 5 hours. After completion of the reduction, stabilization was performed in the same manner as in Example 1, and a metal magnetic powder was obtained. The magnetic properties of the metal magnetic powder were as follows: Hc = 1635 Oe, σs = 139.0 emu / g, σr / σ
s = 0.530. The BET value was 54.2 m ² / g. The magnetic properties when taped in the same manner as in Example 1 were Hc = 1590 O
e, Br = 3551 G, Bm = 4105 G, Br / Bm = 0.865, and excellent squareness ratio as in Example-1.

Example 3 Using the raw material A prepared in Example 1, a nickel compound of 0.5 atomic% (using nickel chloride) is applied in the same manner as in Example 1, and then 0.56 mol of aluminum chloride is added to 2 liters. An aqueous solution dissolved in distilled water was added and sufficiently stirred.
A 2N aqueous solution of NaOH was added dropwise over 1 hour, and the pH was adjusted to 8.5.
And stirring was continued for 1 hour. Then, it is filtered, washed with water, dried, and heat-treated in an electric furnace at 700 ° C. for 2 hours.
Reduced at 5 ° C for 5 hours. It was stabilized in the same manner as in Example 1 to obtain a metal magnetic powder. The magnetic property of the metal magnetic powder is Hc =
1545 Oe, σs = 128.0 emu / g, and σr / σs = 0.524. The BET value was 53.8m ² / g. The magnetic properties when taped were as in Example-1: Hc = 1530 Oe, Br = 3381
G, Bm = 3900 G, Br / Bm = 0.876, as in Examples 1-1 and 2, the squareness ratio was extremely good.

Example-4 Barium chloride (BaCl ₂ .2) was added so that it contained 0.5 atomic% in terms of barium and 3.0 atomic% in terms of nickel with respect to iron.
H ₂ O) 73.3 g and nickel chloride (NiCl ₂ .6H ₂ O) 214 g obtained by adding 100 mol of an aqueous solution of ferrous chloride 0.6 mol / l,
1.8 mol / l NaOH previously prepared in the reactor
Nitrogen gas was flowed into 200 l of the aqueous solution, and the mixture was added with stirring to perform an alkaline suspension generation reaction. Temperature to the suspension
At 45 ° C., 100 l / min of air were passed through for 6 hours to obtain needle-like α-FeOOH containing barium and nickel. This was separated by filtration and washed with water by a conventional method to obtain a wet cake (this was used as raw material B). The needle-like α-FeOOH particles containing barium and nickel were found to have excellent needle-like properties with an average major axis value of 0.49 μm and an average needle-like ratio (major axis / minor axis) of 23 by electron microscopic observation. there were. The specific surface area of this product by the BET method was 63 m ² / g.

When barium and nickel in the α-FeOOH were analyzed with a fluorescent light, both elements were detected, and it was confirmed that barium and nickel were dissolved in the needle α-FeOOH.

Next, in the same manner as in Example 1, 0.28 mol of cobalt (using cobalt chloride) was applied to the α-FeOOH, and then 0.26 mol of silica (using water glass) was applied to the α-FeOOH, followed by filtration.
It was washed with water, dried and heat-treated at 600 ° C. for 2 hours in an electric furnace. The heat-treated product was reduced under a hydrogen stream at a temperature of 450 ° C. for 5 hours. After the reduction was completed, the powder was stabilized in the same manner as in Example 1 to obtain a metal magnetic powder. The magnetic properties of the metal magnetic powder are Hc
= 1647 Oe, σs = 134.0 emu / g, σr / σs = 0.331, and the BET value was 52.0 m ² / g. The magnetic properties of the tape manufactured by the same method as in Example 1 were as follows: Hc = 1604 Oe, Br = 347.
6 G, Bm = 4018 G, and Br / Bm = 0.865, indicating that the squareness ratio was excellent.

Example-5 The needle compound α-FeOOH containing the barium and nickel compounds produced in Example-4 (raw material B) was added with 1.8 atomic% of a silica compound and 9.0 atomic% of an aluminum compound with respect to iron to a silica compound. Was applied in the order of aluminum compounds by a neutralization method. After filtration, washing and drying, 650 ° C in an electric furnace
At 470 ° C. for 5 hours under a hydrogen stream.

Table 3 shows the magnetic properties of the obtained metal magnetic powder, the specific surface area measured by the BET method, and the magnetic properties when formed into a tape.

The raw material α-FeOO used in the following Examples and Comparative Examples
Table 1 summarizes the production conditions of H, the specific surface area of the product by the BET method, the average major axis dimension, and the average axial ratio. Similarly, Table 2 summarizes the types and amounts of metal compounds added for deposition in each of the examples and comparative examples, heat treatment conditions, and reduction conditions.

Example-6 In the same manner as in Example-1, barium was converted to iron.
Acicular α-FeOOH containing 3.0 atomic% barium compound
(This is referred to as raw material C).

This raw material C is coated with 15 atomic% of a nickel compound and 4.7 atomic% of a silica compound with respect to iron, filtered, washed with water,
After drying, it was heat-treated in an electric furnace at 600 ° C. for 2 hours and reduced at 440 ° C. for 5 hours under a hydrogen stream. Table 3 shows the magnetic properties of the obtained metal magnetic powder, the specific surface area measured by the BET method, and the magnetic properties when formed into a tape.

Example -7 A nickel compound of 3.0 atomic% with respect to iron and a cobalt compound of 12.0 atomic% with respect to iron were applied to the raw material C, and a silica compound was further applied to iron in the same manner as in Example-1. On the other hand, 2.0 atomic% of the aluminum compound and 6.0 atomic% of the aluminum compound were applied. Hereinafter, processing was performed under the conditions shown in Table-2. Magnetic properties of the obtained metal magnetic powder and specific surface area value by BET method,
Table 3 shows the magnetic properties of the tape.

Example -8 The material C was coated with a cobalt compound at 3.0 atomic% based on iron, and a mixed aqueous solution of water glass and sodium aluminate was added to the coated α-FeOOH suspension, and the mixture was sufficiently stirred. A 2N HCl aqueous solution was added dropwise to adjust the pH to 8.0, and the silica compound and the aluminum compound were deposited on 2.0 atomic% and 5.0 atomic% of iron, respectively. Hereinafter, processing was performed under the conditions shown in Table-2. Table 3 shows the magnetic properties of the obtained metal magnetic powder, the specific surface area measured by the BET method, and the magnetic properties when formed into a tape.

Comparative Example-1 In order to contain 3.0 atomic% in terms of nickel with respect to iron,
Aqueous NaOH solution 200l of 1.8 mol / l that had been prepared in advance reactor solution 100l of ferrous chloride 0.6 mol / l, obtained by adding nickel _{(NiCl 2 · 6H 2 O)} 214g chloride Nitrogen gas was flowed and the mixture was added with stirring to carry out a reaction for forming an alkaline suspension. Air was passed through the suspension at a temperature of 45 ° C. at a rate of 100 l / min for 6 hours to obtain needle-like crystals α-FeOOH containing a nickel compound (this is referred to as “raw material D”).

Next, acicular crystals containing this nickel compound α-FeOO
On the surface of H, a cobalt compound was deposited at 5.0 atomic% on iron in the same manner as in the example, and then a silica compound was deposited at 4.7 atomic% on iron. Hereinafter, processing was performed under the conditions shown in Table-2. Magnetic properties and BE of the obtained metal magnetic powder
Table 3 shows the specific surface area by the T method and the magnetic properties of the tape.

This can be compared with Example-4 as the metal composition of the metal magnetic powder, and the squareness ratio of the tape is not a bad value. However, it is inferior to the examples.

Comparative Example-2 Nickel was formed on the surface of the raw material D in the same manner as in Example-1.
Cobalt, silica, and aluminum compounds were deposited at 2.0, 5.0, 2.0, and 6.0 atomic percent, respectively, on iron. Less than,
Processing was performed under the conditions shown in Table-2. Table 3 shows the magnetic properties of the obtained metal magnetic powder, the specific surface area measured by the BET method, and the magnetic properties when formed into a tape.

This was comparable to the metal composition of Example 1 and the metal magnetic powder, but the tape squareness ratio was inferior.

Comparative Example-3 Nickel was applied on the surface of the raw material D in the same manner as in Example-2.
Cobalt, silica compounds, iron, 5.0, 8.0, 4.7
Atomic% deposited. Hereinafter, processing was performed under the conditions shown in Table-2. Table 3 shows the magnetic properties of the obtained metal magnetic powder, the specific surface area value by the BET method, and the magnetic properties when a tape was formed.
It was shown to.

This was comparable to Example-2 as the metal composition of the metal magnetic powder, but the tape squareness ratio was inferior.

Comparative Example-4 0.5 mol / l of an aqueous solution of ferrous chloride obtained by adding nickel chloride and zinc chloride so as to contain 3.0 atomic% in terms of nickel and 2.5 atomic% in terms of zinc with respect to iron. 100l
1.8 mol / l NaO previously prepared in the reactor
Nitrogen gas is flowed into 200 liters of H aqueous solution and added with stirring.
An alkaline suspension formation reaction was performed. Air was passed through the suspension at a temperature of 45 ° C. at 100 l / min for 6 hours to obtain needle-like α-FeOOH containing nickel and zinc compounds. This was separated by filtration and washed with water by a conventional method to obtain a wet cake (this was used as raw material E).

Acicular crystals α-Fe containing nickel and zinc compounds
Observation of OOH by an electron microscope revealed that very fine particles were bundled. The average major axis length of the bundled particles was about 0.44 μm. Since the particles were bundled, the short axis length could not be measured, but the particles had good needle-like properties. Also
The specific surface area by the BET method was 70.0 m ² / g, and the particles were fine.

Next, on the surface of the α-FeOOH, a cobalt compound of 5.0 atomic% and a silica compound of 4.7 atomic% with respect to iron were applied. Hereinafter, processing was performed under the conditions shown in Table-2. Table 3 shows the magnetic properties of the obtained metal magnetic powder, the specific surface area measured by the BET method, and the magnetic properties when formed into a tape.

The metal composition of the metal magnetic powder was comparable to that of Example-4, and showed a good squareness ratio due to the effect of zinc, but was below the numerical value of the example.

Comparative Example-5 A raw material E was provided with a 1.8 atomic% silica compound with respect to iron,
9.0 atomic% of an aluminum compound was deposited in the same manner as in Example-5. Hereinafter, processing was performed under the conditions shown in Table-2.
Table 3 shows the magnetic properties of the obtained metal magnetic powder, the specific surface area measured by the BET method, and the magnetic properties when formed into a tape.

Although the metal composition of the metal magnetic powder was comparable to that of Example-5, the squareness ratio of the tape was inferior to that of Example.

[Effects of the Invention] As is clear from the examples and comparative examples, the metal magnetic powder produced by the method of the present invention, while being fine, has excellent dispersibility and orientation, and has a squareness ratio when formed into a tape. It is very good.

────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Ei Endo 425 Kanai, Shibukawa-shi, Gunma Research and Development Center, Kanto Denka Kogyo Co., Ltd. (56) References JP-A-57-5802 (JP, A) JP-A-58-159313 (JP, A) JP-A-58-159312 (JP, A) JP-B 1-222204 (JP, B2) JP-B-58-37363 (JP, A) B2) (58) Field surveyed (Int.Cl. ⁶ , DB name) B22F 9/22 G11B 5/842 H01F 1/06

Claims (2)

(57) [Claims] 1. A ferrous chloride aqueous solution is neutralized with an alkali to obtain a pH value.
= 10 or more alkaline suspension, and the oxygen-containing gas is passed through the suspension to oxidize it to produce needle-like α-FeOOH particles, the ferrous chloride aqueous solution Alternatively, a water-soluble barium salt is added to the alkaline suspension before passing the oxygen-containing gas, and then the oxygen-containing gas is passed to generate α-FeOOH having excellent needle-like properties containing barium, Next, after a silica compound and / or an aluminum compound are applied to the surface of the needle-like α-FeOOH particles containing the barium compound,
A method for producing a metal magnetic powder, which comprises performing filtration, washing with water, and drying, followed by heat treatment in a non-reducing atmosphere, and subsequently heating and reducing in a hydrogen stream at a temperature in the range of 300 to 600 ° C. 2. The ferrous chloride aqueous solution is neutralized with an alkali to obtain a pH value.
= 10 or more alkaline suspension, and the oxygen-containing gas is passed through the suspension to oxidize it to produce needle-like α-FeOOH particles, the ferrous chloride aqueous solution Alternatively, a water-soluble barium salt is added to the alkaline suspension before passing the oxygen-containing gas, and then the oxygen-containing gas is passed to generate α-FeOOH having excellent needle-like properties containing barium, Next, a nickel compound and / or a cobalt compound are applied to the surface of the needle-like α-FeOOH particles containing the barium compound, and a silica compound and / or an aluminum compound are applied thereon, followed by filtration and washing with water. Drying, followed by heat treatment in a non-reducing atmosphere, followed by heat reduction in a hydrogen stream at a temperature in the range of 300 to 600 ° C.