JP3303896B2 - Spindle-shaped iron-based metal magnetic particle powder and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to fine particles, and
The particle size is uniform and dendritic particles are not mixed, and the coercive force, especially the coercive force Hc is 1700 to 220
The iron exhibited fusiform is 0Oe relates metallic magnetic particles Powder production methods mainly.

[0002]

2. Description of the Related Art In recent years, long-time recording, miniaturization and lightening of magnetic recording / reproducing devices for video and audio have been promoted. In particular, VTRs (video tape recorders) have been remarkably popularized recently. 2. Description of the Related Art VTRs aiming at time recording and reduction in size and weight have been actively developed.
On the other hand, there is a demand for higher performance and higher density recording of a magnetic tape as a magnetic recording medium.

[0003] That is, the magnetic recording medium is required to have high image quality, high output characteristics, and especially improvement in frequency characteristics.
Improvement of residual magnetic flux density Br, high coercive force and dispersibility,
It is necessary to improve the filling property and the smoothness of the tape surface.
An improvement in the N ratio is required.

[0004] These characteristics of the magnetic recording medium have a close relationship with the magnetic particle powder used in the magnetic recording medium, but in recent years, these properties are higher than those of the conventional iron oxide magnetic particle powder. Attention has been paid to metal magnetic particle powder mainly composed of iron having a magnetic force and a large saturation magnetization, and has been put to practical use in magnetic recording media such as digital audio tape (DAT), 8 mm video tape, and Hi-8 tape. However, it is strongly desired to further improve the properties of these metal magnetic particle powders containing iron as a main component.

Now, the relationship between the characteristics of the magnetic recording medium and the characteristics of the magnetic particle powder used will be described in detail as follows.

In order to obtain high image quality as a magnetic recording medium for video, "Nikkei Electronics" (1976)
As is clear from the record of No. 133, pp. 82-105,
Improvements in video S / N ratio, chroma S / N ratio, and video frequency characteristics are required.

In order to improve the video S / N ratio and the chroma S / N ratio, it is necessary to improve the dispersibility of the magnetic particle powder in a vehicle, the orientation and the filling property in a coating film, and It is important to improve the surface smoothness of the magnetic recording medium, and such magnetic particles are fine particles, and have a uniform particle size, do not contain dendritic particles, and It is required that the axial ratio (major axis diameter / minor axis diameter-the same applies hereinafter) is large.

On the other hand, as one method for improving the video S / N ratio, it is important to reduce the noise level caused by the magnetic recording medium. It is known that there is a relationship also with the X-ray particle size of the powder.

[0009] This phenomenon is described in, for example, “Magnetic Recording Medium Comprehensive Data Collection” published by Sogo Electronic Research (August 15, 1985).
Sun), page 123, FIG. 38, etc. "Figure 3
FIG. 8 "is a diagram showing the correlation between the X-ray particle size of particles and noise in a magnetic tape obtained by using metal magnetic particle powder containing iron as a main component. It has become.

Therefore, in order to reduce the noise level caused by the magnetic recording medium, it is also effective to reduce the X-ray particle size of the metal magnetic particles as much as possible. In order to improve the noise level and reduce the noise level, it is required that the X-ray particle size of the metal magnetic particles be small.

Next, in order to improve the video frequency characteristics, it is necessary that the magnetic recording medium has a high coercive force and a high residual magnetic flux density Br. In order to increase the coercive force of a magnetic recording medium, it is required that the magnetic particles have as high a coercive force as possible.

Since the coercive force of magnetic particle powder generally occurs due to its shape anisotropy, a high coercive force can be obtained by making the particles as fine as possible or increasing the axial ratio of the particles. . For example, Japanese Patent Publication No. 1-18961 states that “‥‥ coercive force increases as the axial ratio increases, while coercive force is affected by the particle size, and is larger than the particle size at which superparamagnetism appears. Therefore, the target coercive force is
It can be obtained by appropriately selecting the particle size and its axial ratio. ‥‥ ”.

Recently, home high definition VTRs have been developed, and the VTR tape W-VH has been developed.
Finer particles are required for the iron-based metal magnetic particle powder used for the S tape.

For example, it is described in “Nikkei Materials & Technology” (1993) No. 128, pp. 14-15, “‥‥ Home Hi-Vision VTR System“ W-VH ”.
We have developed a VTR tape for the "S" standard. ‥‥ thickness 0.2
An upper layer of a metal (iron-based) magnetic material of about 0.4 μm,
It has a two-layer structure consisting of a lower layer of a non-magnetic material having a thickness of μm. ‥‥ The point of successful development is to make the metal magnetic layer as thin as possible. (4) In a high-definition VTR that records and reproduces a high-definition image, it is required to record and reproduce a recording signal with low noise in order to perform high-density recording.改善 We also improved the metal magnetic powder in the magnetic layer. ‥‥ The particles are further refined to improve coercive force and saturation magnetic flux density. (4) The magnetic particles are needle-shaped, but (4) the major axis is 0.1 μm, which is about half the length of the magnetic material for S-VHS. ‥‥ ”.

The metal magnetic particle powder containing iron as a main component generally requires goethite particles as a starting material, hematite particles obtained by heating and dehydrating the particles, or particles containing a dissimilar metal other than iron in these particles. , And then heat-reduced in a reducing gas.

Conventionally, as a method for producing goethite particle powder as a starting material, a suspension containing ferrous hydroxide colloid obtained by adding an equivalent amount or more of an aqueous alkali hydroxide solution to an aqueous ferrous salt solution has a pH of 11 or less. A method of producing acicular goethite particles by conducting an oxidation reaction by passing an oxygen-containing gas at a temperature of 80 ° C. or lower (Japanese Patent Publication No. 39-5)
No. 610, etc., hereinafter referred to as iron hydroxide-based goethite particles. -) And an oxygen-containing gas is passed through a suspension containing FeCO ₃ or an iron-containing precipitate obtained by reacting an aqueous solution of ferrous salt with an aqueous solution of alkali carbonate or a mixed aqueous solution of alkali carbonate and alkali hydroxide to carry out an oxidation reaction. To form spindle-shaped goethite particles by performing
0-80999, JP-A-2-51429, etc.-Hereinafter, iron carbonate-based goethite particles. -) And the like are known.

As a prior art for obtaining metal magnetic particles containing iron as a main component using goethite particles such as iron hydroxide-based goethite particles and iron carbonate-based goethite particles as starting material particles, Japanese Patent Publication No. 55-29577, Tokuhei 1
-18961, JP-B-2-57122, JP-B-3-43323, JP-A-63-222404
JP, JP-A-4-63210, JP-A-5-62
166 and JP-A-5-98321.

[0018]

The iron hydroxide-based goethite particles have a large axial ratio, in particular, acicular goethite particles of 10 or more, but contain dendritic particles.
Further, it cannot be said that the particle size is uniform, and for example, it is produced by air oxidation of a hydrolyzate of ferrous salt with an alkali hydroxide in Japanese Patent Application Laid-Open No. 5-62166. According to the method, in order to refine the goethite particles, in the reaction system, for example, a water-soluble silicate is added. ‥‥ Branches are easily generated in the particles. ‥‥ The particle size distribution of the metal magnetic powder spreads. The above-mentioned alkali hydroxide method has a limit in trying to make the goethite particles as fine as possible and to achieve a uniform particle size distribution.

On the other hand, the iron carbonate-based goethite particles mentioned above have a uniform particle size, and spindle-shaped particles in which dendritic particles are not mixed are formed. On the other hand, the axial ratio is about 7 at most. However, there is a drawback that particles having a large axial ratio are difficult to be produced. For example, the method described in Japanese Patent Application Laid-Open No. 5-62166 (1) is obtained by hydrolyzing a ferrous salt with an alkali carbonate, followed by air oxidation. Spindle-type goethite particles are refined and the particle size distribution is homogenized. This goethite generally has a small axial ratio and is considered to be difficult to achieve a high coercive force due to shape anisotropy. " It is.

Therefore, the present inventor has sought to obtain metal magnetic particle powder containing iron as a main component using the above-mentioned iron hydroxide-based goethite particles as a starting material particle, and to obtain iron using the aforementioned iron carbonate-based goethite as a starting material particle. The case where metal magnetic particle powder as a main component was obtained was examined in detail by the above-mentioned prior arts.

The technique described in JP-B-55-29577 described above produces acicular goethite containing Co uniformly (applicant's note: iron hydroxide-based goethite particles).
This is a method of obtaining Fe-Co alloy needle-shaped particles by hydrogen reduction. In Examples 3 and 4, when Co was added in an amount of 20 mol% and 25 mol%, respectively, the major axis diameter was 0.2 μm. , 0.1 μm, but the coercive force Hc is at most 1120 Oe,
It is as low as 00 Oe, and the coercive force decreases as the amount of Co added increases.

The technique described in Japanese Patent Publication No. 1-18961 has a major axis diameter of 0.05 to 0.3 μm and a minor axis diameter of 0.0 to 0.3 μm.
By using a spindle type goethite having an axis ratio of 3 to 15 and an axis ratio of 3 to 15 (applicant's note: iron carbonate-based goethite particles), the major axis diameter is 0.05 to 0.2 μm and the axis ratio is 15 to 0.04 μm. 4 to 8, a method in which a metal magnetic powder having a coercive force Hc of 1300 Oe or more is obtained, but the coercive force Hc of the obtained metal magnetic particle powder is only 1700 Oe or less from the examples. .

The technique described in Japanese Patent Publication No. 2-57122 mentioned above is characterized in that the surface of an oxide or hydrated oxide of a metal mainly composed of iron or iron and containing other elements such as Ni and Co is added.
attaching a water soluble salt of l, Cr, Ce or Nd as well as a water soluble borate or perborate compound;
In this method, iron or a magnetic metal powder mainly containing iron is produced by reducing the powder in a reducing gas. In Examples 1 to 3, 1840 Oe was obtained with the highest coercive force Hc. However, all of them use iron hydroxide-based goethite particles. The ones described in Examples 4 and 5 use iron carbonate-based goethite particles and have a coercive force Hc of 1430 to 1600.
Oe.

The technique described in the above-cited Japanese Patent Publication No. 3-43323 discloses a method in which sodium carbonate and water-soluble C are added to an aqueous ferrous salt solution.
An aqueous solution containing at least one compound selected from the group consisting of o, Ni, and Cu compounds is mixed, and air is blown into the mixture to form α-FeO.
In this method, OH is generated (applicant's note: iron carbonate-based goethite particles) and then reduced to produce metal magnetic powder. The coercive force Hc of the obtained metal magnetic particles is 7%.
It is 00 to 1200 Oe.

The invention described in the above-mentioned JP-A-63-222404 is disclosed in Japanese Patent Publication No. 2-57122 (JP-A-61-222122).
186410), but it is not clear which method is used to generate goethite particles, since no specific method is described. However, when iron carbonate-based goethite particles are used as a starting material, JP-B-1-18961 and JP-B-3-43323 cited above.
Coercive force Hc is 1700O
Since no metal magnetic particle powder exceeding e is obtained, the use of iron hydroxide-based goethite particles reduces
It can be estimated that a coercive force Hc of 900 Oe or more is obtained.

According to the technique described in JP-A-4-63210, FeCO ₃ or FeCO ₃ obtained by reacting an aqueous solution of ferrous salt with an aqueous solution of an alkali carbonate and an aqueous solution of an alkali hydroxide in combination as an aqueous alkali solution. When a zinc compound is present in the suspension containing the contained precipitate, the axial ratio can be further improved. In particular, spindle-shaped goethite particles having an axial ratio of 15 or more (application Human injection: iron carbonate-based goethite particles.)
The coercive force of the obtained metal magnetic particle powder can be increased.
Although those exceeding 00 Oe have been obtained, the major axis diameter is not more than 0.
It is as large as 23 to 0.33 μm.

JP-A-5-62166 discloses a precipitate formed by hydrolyzing a ferrous salt and a metal salt selected from the group consisting of Ni, Co, Zn and Mn with an alkali carbonate. Spindle-type metal magnetic powder starting from a spindle-type goethite containing an additional metal (applicant's note: iron carbonate-based goethite particles) produced by air oxidation of the slurry. In each case, the additive metal is only Ni, and the coercive force Hc is 1700 Oe or less even though the long axis diameter of the obtained metal magnetic powder is as small as 0.10 to 0.20 μm.

Japanese Patent Application Laid-Open No. 5-98321 discloses a seed crystal mainly composed of iron oxyhydroxide obtained by blowing an oxidizing gas into an aqueous suspension obtained by mixing a ferrous salt and an alkali. During the oxidation reaction, an aqueous solution of a rare earth element compound and / or a silicon compound was added to the suspension under a non-oxidizing atmosphere during the oxidation reaction, and the suspension was aged at a temperature higher than the oxidation reaction temperature, and then an oxidizing gas was blown again. Is a metal magnetic powder obtained by growing a ferrous oxyhydroxide crystal, coating a shape-retaining agent, heating, and reducing by heating with a reducing gas. Examples 1 to 8
The goethite particles described in (1) are all iron hydroxide-based goethite particles, and the goethite particles described in Example 9 are iron carbonate-based goethite particles. Unlike the case where Si is coated and the compound is added during the oxidation to cause a growth reaction, the coercive force Hc of the obtained metal magnetic powder is also 1602 Oe.

From the above results, it is possible to obtain a high coercive force exceeding 1700 Oe in the iron-based metal magnetic particle powder obtained using iron hydroxide-based goethite particles as a starting material. In the case where is used as a starting material, it can be said that metal magnetic particle powder mainly composed of fine iron particles having a coercive force Hc of more than 1700 Oe has not been obtained.

Therefore, the present invention is based on iron carbonate-based goethite particles, which are fine particles, have a uniform particle size, do not contain dendritic particles, and have a high coercive force, A technical object is to obtain spindle-shaped iron-based metal magnetic particle powder having a coercive force Hc of 1700 to 2200 Oe.

[0031]

The above technical objects can be achieved by the present invention as described below.

[0032]

The present invention also relates to a method for producing a suspension containing FeCO ₃ or an iron-containing precipitate obtained by reacting an aqueous alkali carbonate solution and an aqueous ferrous salt solution, followed by aging in a non-oxidizing atmosphere. In producing the spindle-shaped goethite particles by performing an oxidation reaction by passing an oxygen-containing gas through the suspension, the alkali carbonate aqueous solution and the FeCO ₃ or iron-containing precipitate before aging are included. The total amount of the aqueous alkali carbonate solution and the aqueous alkali hydroxide solution is obtained by adding an aqueous solution of an alkali hydroxide having a molar ratio of 0.2 to 1.0 with respect to the aqueous alkali carbonate solution to any of the suspensions 1.3 to 1.8 equivalents to Fe ^{2+ in the} ferrous salt aqueous solution, the temperature range for the aging is 40 to 60 ° C., the aging time is 2 to 7 hours, Salt solution, before A suspension containing the FeCO ₃ or iron-containing precipitate and the aged FeC prior to performing the oxidation reaction;
In any of the suspensions containing O ₃ or the iron-containing precipitate, 1.0 mol% or more and less than 8.0 mol% in terms of Co with respect to Fe ^{2+ in the} ferrous salt aqueous solution in advance. while the Co compound is present in an amount in the range of
By setting the temperature range of the oxidation reaction to 40 to 60 ° C., goethite particles having a spindle shape are generated or, if necessary, the oxidation rate of the oxidation reaction is reduced to Fe ²⁺ in the ferrous salt aqueous solution. On the other hand, under the same conditions as in the oxidation reaction, Al,
An aqueous solution of one or more compounds selected from rare earth elements such as Si, Ca, Mg, Ba, Sr and Nd, or an aqueous solution of an Al compound, and Si, Ca, Mg, Ba,
An aqueous solution of one or more compounds selected from rare earth elements such as Sr and Nd is mixed with an aqueous solution of the ferrous salt aqueous solution.
e ²⁺ is 0.1
To an amount in the range of ~ 5.0 mol%,
Spindle-shaped goethite particles are generated by any of the above, and the spindle-shaped goethite particles or spindle-shaped hematite particles obtained by heating and dehydrating the spindle-shaped goethite particles are reduced. This is a method for producing spindle-shaped iron-based metal magnetic particle powder by heating and reducing in a neutral gas.

Next, conditions for implementing the present invention will be described.

The aqueous ferrous salt solution used in the present invention includes an aqueous ferrous sulfate solution, an aqueous ferrous chloride solution and the like.

Examples of the aqueous alkali carbonate solution used in the present invention include an aqueous sodium carbonate solution, an aqueous potassium carbonate solution, an aqueous ammonium carbonate solution and the like.

Examples of the aqueous alkali hydroxide solution used in the present invention include sodium hydroxide and potassium hydroxide.

In the present invention, an aqueous solution of an alkali carbonate and an aqueous solution of an alkali hydroxide are used in combination. When an aqueous alkali carbonate solution is used alone, goethite particles having a large axial ratio cannot be obtained, and it is difficult to obtain metal magnetic particles containing iron having a large coercive force Hc as a main component. In addition, when an aqueous alkali hydroxide solution is used alone, it is difficult to obtain fine goethite particles, and it is difficult to say that the particle size is uniform.
In addition, since dendritic particles may be present in some cases, it is difficult to obtain metal magnetic particle powder containing iron as a main component and having a uniform particle size.

For the aqueous alkali hydroxide solution, an aqueous alkali hydroxide solution having a molar ratio of 0.2 to 1.0 with respect to the aqueous alkali carbonate solution is added. If it is less than 0.2, goethite particles having a large axial ratio cannot be obtained as in the case of using an aqueous alkali carbonate solution alone, and thus metal magnetic particles mainly containing iron having a large coercive force Hc can be obtained. It is hard to be. 1.0
If it exceeds, as in the case where the aqueous alkali hydroxide solution is used alone, it is difficult to obtain fine goethite particles, and it is difficult to say that the particle size is uniform. In addition, dendritic particles may be mixed, and granular particles may be mixed. Therefore, it is difficult to obtain metal magnetic particle powder containing iron as a main component, which is a fine particle having a uniform particle size.

The total amount of the aqueous alkali carbonate solution and the aqueous alkali hydroxide solution is 1 to Fe ²⁺ in the aqueous ferrous salt solution.
When it is 3 to 1.8 equivalents and less than 1.3 equivalents, it is difficult to obtain goethite particles having a large axial ratio, and granular particles may be mixed. If it exceeds 1.8 equivalents, it is difficult to obtain goethite particles having a large axial ratio.

Therefore, the pH value of the reaction solution is 7.0 to 1 similarly to the usual reaction for producing iron carbonate-based goethite particles.
1.0, and a more preferred pH value is 8.0-1.
0.0.

In the present invention, the aqueous alkali hydroxide solution is added at the timing of adding the aqueous alkali carbonate solution and the above-mentioned F before aging.
In any liquid of a suspension containing eCO ₃ or an iron containing precipitate. Particularly, it is preferable to add the compound to an aqueous alkali carbonate solution.

The aging in the present invention is carried out in a non-oxidizing atmosphere at a temperature range of 40 to 60 ° C. and an aging time of 2.0 to 2.0.
It is performed within a range of 7.0 hours. If the temperature is lower than 40 ° C,
Although the size of the goethite particles is small, it is difficult to obtain one having a large axial ratio, and if it exceeds 60 ° C., it is difficult to obtain small goethite particles.

When the aging time is less than 2.0 hours, it is difficult to obtain goethite particles having a small particle size. When the aging time exceeds 7.0 hours, the goethite particles intended for the present invention can be obtained. There is no point in making it longer.

The non-oxidizing atmosphere can be formed by passing an inert gas (such as N ₂ gas) through the reaction vessel of the suspension.

Examples of the Co compound used in the present invention include cobalt sulfate, cobalt chloride, and cobalt nitrate.

The Co compound is at least 1.0 mol% to 8.0 mol% in terms of Co with respect to Fe ²⁺ in the aqueous ferrous salt solution.
Amounts in the range less than . If it is less than 0.1 mol%, goethite particles having a large axial ratio are difficult to obtain. 8.0
In the case of mol% or more , fine goethite particles can be obtained, but the axial ratio becomes small.

The time of addition of the Co compound is determined by the aqueous ferrous salt solution, the suspension containing the FeCO ₃ or iron-containing precipitate, and the suspension containing the aged FeCO ₃ or iron-containing precipitate before the oxidation reaction. In any of the liquids. In particular, it is preferable to add it during 15 minutes before the oxidation reaction is started or immediately before it.

The temperature range of the oxidation reaction in the present invention is 40.
６０60 ° C. When the temperature is lower than 40 ° C., fine goethite particles can be obtained, but the axial ratio becomes small. When the temperature is higher than 60 ° C., goethite fine particles as the object of the present invention can be obtained, but granular particles may be present in some cases.

Examples of the Al compound used in the present invention include aluminum sulfate, aluminum chloride, aluminum nitrate, sodium aluminate, potassium aluminate, and ammonium aluminate.

The aqueous solution of one or more compounds selected from rare earth elements such as Ca, Mg, Ba, Sr and Nd includes water-soluble salts such as sulfates, chlorides and nitrates of each element. Can be mentioned. In addition, about a Si compound, sodium silicate, potassium silicate, water glass, etc. can be used.

Examples of rare earth elements such as Nd include elements such as Y, La, Ce, Pr, and Tb in addition to Nd.

In the present invention, under the same conditions as in the oxidation reaction, A in an oxidizing solution in which the oxidation rate of the oxidation reaction is in the range of 50 to 90% with respect to Fe ²⁺ in the aqueous ferrous salt solution.
l, an aqueous solution of one or more compounds selected from rare earth elements such as Si, Ca, Mg, Ba, Sr and Nd, or Al and selected from rare earth elements such as Si, Ca, Mg, Ba, Sr and Nd. The aqueous solution of one or more kinds of compounds to be added is in the range of 0.1 to 5.0 mol% in terms of each element in terms of the total amount of the compounds added to Fe ²⁺ in the aqueous ferrous salt solution. It can be added as follows.

When the oxidation rate of the oxidation reaction is less than 50%, the formation of fine particles and spindle-shaped goethite particles having a large axial ratio is prevented. If it exceeds 90%, the formation of goethite particles is already near completion, and the added element may not form a solid solution with the particle surface of the goethite particles.
Further, granular particles may be mixed. Therefore, a preferable range is 70 to 85%.

When the amount of the compound to be added is less than 0.1 mol% in terms of each element, the effect of preventing sintering is not sufficient, and the oxidation in the case of using metal magnetic particles containing iron as a main component is not sufficient. The stability and coercive force are not sufficiently improved. 5.
If it exceeds 0 mol%, the reduction time may be prolonged, and the saturation magnetization may decrease.

In the present invention, it is preferable that Al is dissolved as a solid solution on the surface of the goethite particles, which is excellent in shape retention and oxidation stability when metal magnetic particles containing iron as a main component are used. In addition to this, when the magnetic recording medium is used, the affinity with the binder resin is improved, and the dispersibility and the durability are also excellent.
Therefore, it is preferable to use Al in combination with elements other than Al.

When the Si element is used, the effect of preventing sintering is particularly excellent, and when each of the elements Ca, Mg, Ba, and Sr is used, each element is a basic substance. -COOM used for the recording medium, -SO ₃ M
The dispersibility can be improved because it is well compatible with a binder resin having an acidic functional group such as (M is a metal).

Further, when a rare earth element such as Nd is used, the effect of preventing sintering can be exhibited, and since it is a basic substance, it is well compatible with the binder resin and the dispersibility can be improved.

Therefore, it is preferable to add the above-mentioned compounds in the present invention by appropriately combining the combination of the elements and the amount of addition according to the purpose within the range of the oxidation rate of the oxidation reaction being 50 to 90%. .

The oxidizing means in the present invention is carried out by passing an oxygen-containing gas (for example, air) through the liquid, and may be used in combination with mechanical stirring.

In the present invention, the produced spindle-shaped goethite particles are filtered, washed with water and dried by a conventional method to obtain a particle powder.

The spindle-shaped goethite particles obtained by the present invention have an average major axis diameter of 0.05 to 0.20.
μm, short axis diameter is 0.010-0.020 μm, axis ratio is 4
~ 15.

More preferable spindle-shaped goethite particles have an average major axis diameter of 0.05 to 0.17 μm.
m, minor axis diameter is 0.010 to 0.017 μm, axial ratio is 6 to
Twelve.

If necessary, spindle-shaped hematite particles obtained by heating and dehydrating spindle-shaped goethite particles can be used. Heat dehydration may be performed by a commonly used method. In this case, the heat dehydration temperature is 250.
５００500 ° C.

The obtained spindle-shaped goethite particle powder or, if necessary, the spindle-shaped hematite particle powder obtained by dehydrating the goethite particle powder, is suspended in water. The semi-synthetic starch or semi-synthetic cellulose soluble in water or hot water is 0.1 to 0.1 with respect to spindle-shaped goethite particles or spindle-shaped hematite particles.
After adding 5.0% by weight and stirring, the cake obtained by compression dehydration can be granulated and formed, and handling is easy in heat treatment such as heat treatment or reduction treatment in a non-reducing gas atmosphere. It is preferred.

In practicing the present invention, goethite particles or hematite particles are first added to Ni, Al, Si, P, Co, and Ca, Mg, Ba, S
It is desirable that a seed or two or more kinds of metal compounds selected from rare earth elements such as r, Bi, B, Zn and Nd be coated by a conventional method. Since these metal compounds not only have a sintering preventing effect but also have a function of controlling the reduction rate, they are preferably used in combination as needed.

The particle powder coated with the above metal compound can be reduced as it is to obtain the desired magnetic metal particle powder mainly composed of iron. For this purpose, it is preferable to perform a heat treatment in a non-reducing gas atmosphere in advance before the reduction.

The heat treatment in the non-reducing gas atmosphere is performed under a flow of air, oxygen gas, and nitrogen gas at 300 to 800
Annealing can be performed in a temperature range of ° C., and it is more preferable that the heat treatment temperature is appropriately selected according to the type of the metal compound used for the coating treatment of the particle powder. 800 ° C
In the case where it exceeds 3, deformation of the particles and sintering between the particles and the particles are caused.

The temperature range of the heat reduction in the present invention is 30.
0-550 ° C is preferred. When the temperature is lower than 300 ° C., the progress of the reduction reaction is slow, and a long time is required. 550 ° C
In the case of exceeding, the reduction reaction proceeds rapidly, causing deformation of the particles and sintering between the particles and the particles.

The metal magnetic particles containing iron as the main component after heat reduction in the present invention can be prepared by a known method, for example, by immersing the particles in an organic solvent such as toluene, or by reducing the metal magnetic particles containing iron as the main component after reduction. After the atmosphere of the powder is once replaced with an inert gas, it can be taken out into the air by a method of gradually oxidizing by gradually converting the inert gas into air while gradually increasing the oxygen content in the inert gas.

The spindle-shaped iron-based metal magnetic particle powder obtained by the present invention has an X-ray particle size of 120%.
Å160 °, and the average major axis diameter is 0.05〜0.4 mm.
18 μm, a minor axis diameter of 0.010 to 0.018 μm, an axial ratio of 4 to 15, a Co content of 1.0 to 7.5 wt%, and a coercive force Hc of 1700 to 2200 Oe. Spindle-shaped iron-based metal magnetic particle powder.

More preferred spindle-shaped metal magnetic particle powders have an average major axis diameter of 0.05 to 0.15 μm,
Short axis diameter is 0.010 to 0.015 μm, axis ratio is 5 to 10
And the coercive force Hc is 1800 to 2000O
e.

[0073]

The operation of the present invention having the above-described configuration is as follows.

As described above, the magnetic metal particles containing iron as a main component include goethite particles as a starting material, hematite particles obtained by heating and dehydrating the particles, or particles containing a dissimilar metal other than iron in these particles. Is heat-reduced in a reducing gas after heat treatment if necessary.

As a method for producing the goethite particle powder as a starting material, a method for obtaining iron hydroxide-based goethite particles and a method for obtaining iron carbonate-based goethite particles are known, and each has its own characteristics. That is, iron hydroxide-based goethite particles generate needle-like particles having a large axial ratio, but contain dendritic particles, and are hard to say that the particle size is uniform. The goethite particles are spindle-shaped particles having a uniform particle size and no mixture of dendritic particles, but are difficult to produce particles having a large axial ratio.

On the other hand, when it is intended to obtain metal magnetic particle powder mainly composed of iron having a high coercive force, as described above, the coercive force of the magnetic particle powder is generated due to its shape anisotropy. Therefore, it is necessary to make the particles as fine as possible or to increase the axial ratio of the particles. That is, when iron hydroxide-based goethite particles are used as a starting material, 1700O
Although metal magnetic particle powder mainly composed of iron having a high coercive force exceeding e is obtained, when iron carbonate-based goethite particles are used as a starting material, fine particles having a coercive force Hc of 17
Metal magnetic particle powder containing iron as a main component and having a high coercive force exceeding 00 Oe has not been obtained.

Therefore, the present inventor has made iron carbonate-based goethite particles from which fine particles and particles having a uniform particle size can be easily obtained as starting materials, and are fine particles having a uniform particle size and a mixture of dendritic particles. No, and high coercivity, especially
We worked on obtaining spindle-shaped iron-based metal magnetic particle powder having a coercive force Hc of 1700 to 2200 Oe.

For this purpose, first, when producing iron carbonate-based goethite particles, an element having an effect of making the iron carbonate-based goethite particles finer or an element capable of obtaining a large axial ratio is added to the goethite particles. Considering the formation of a solid solution, it was studied to add and present commonly used elements such as Co, Zn, and Ni in a reaction for producing iron carbonate-based goethite particles, and to conduct a reaction.

As described above, none of the above-mentioned prior arts has produced any fine particles of metal magnetic particles containing iron as a main component and obtained from iron carbonate goethite particles as a starting material and having a high coercive force. . However, as disclosed in
According to the method disclosed in Japanese Unexamined Patent Publication No. 63210/1994, in which an aqueous solution of an alkali carbonate and an aqueous solution of an alkali hydroxide are used in combination, a metal magnetic particle powder mainly composed of iron and having a high coercive force is obtained. However, the FeCO ₃
Alternatively, when a Zn compound is present in a suspension containing an iron-containing precipitate, spindle-shaped goethite particles having an axial ratio of 15 or more can be produced, and thus the obtained iron is obtained. Can increase the coercive force Hc of the metal magnetic particle powder whose main component is, but the major axis diameter is as large as 0.23 to 0.33 μm.

Therefore, the study by a reaction using an aqueous alkali carbonate solution and an aqueous alkali hydroxide solution in combination was further advanced.
As a result, as shown in Comparative Example 5 below, when the Ni compound was present in the iron-containing precipitate instead of the Zn compound,
Although the obtained spindle-shaped goethite particles are fine particles, only those having a small axial ratio can be obtained, and when the metal magnetic particle powder containing iron as a main component is used, Comparative Example 2 described later is used.
As shown in FIG. 3, it was confirmed that the coercive force Hc was as low as 1427 Oe.

Next, C was added to the suspension containing the iron-containing precipitate.
The effect of the presence of the o compound was examined. As a result, it is possible to obtain goethite particles which are fine particles and have a spindle shape having a relatively large axial ratio,
The coercive force Hc of the iron-based metal magnetic particles obtained by reducing the goethite particles as a starting material is 17%.
Large ones exceeding 00 Oe were obtained.

When the obtained spindle-shaped goethite particles were examined in detail by electron microscopic observation, the spindle-shaped goethite particles in which Co was dissolved were found to have fine particles and a small particle diameter in the short axis direction. Due to being small,
It was possible to confirm that the axial ratio was appropriately increased, and that the X-ray particle size by the X-ray diffraction method was also small. As a result, it is considered that the coercive force Hc of the metal magnetic particle powder containing iron as a main component obtained by the reduction is large, exceeding 1700 Oe.

The reason is that the formation of particles in the minor axis direction is suppressed by the presence of the aqueous alkali carbonate solution and the Co compound to form fine particles, and the particles grow in the major axis direction by the presence of the aqueous alkali hydroxide solution. The axial ratio increases, the particles are fine, the particle size is uniform, and
Spindle-shaped goethite particles having a moderately large axial ratio were obtained, and thus the coercive force Hc of the iron-based metal magnetic particle powder obtained by reducing the goethite particles was reduced.
Was higher than 1700 Oe. This is thought to be due to the synergistic effect of the combined use of the aqueous alkali carbonate solution and the aqueous alkali hydroxide solution and the addition of the Co compound.

Further, when the suspension containing the iron-containing precipitate was aged in a non-oxidizing atmosphere, as shown in Example 1,
The viscosity of the suspension measured by a Stormer viscometer after 2 hours from the start of ripening was 270 cps, and 5 hours after the start of ripening.
It has been found that by reducing the viscosity at the time when the time has elapsed to 205 cps, spindle-shaped goethite particles having finer particles, a uniform particle size, and a large axial ratio can be obtained. The reason is not yet known, but is the fact that finer goethite particles can be obtained after the viscosity has decreased compared to when the viscosity is high.

On the other hand, since the metal magnetic particle powder containing iron as a main component is more easily oxidized in the air as it is finer, it is oxidized to prevent the magnetic properties such as the coercive force Hc and the saturation magnetization from deteriorating. There is a need.

There are several methods for improving the oxidation stability using a compound such as Al. For example, as shown in JP-A-57-73105,
When Al is dissolved, the coercive force Hc of the obtained metal magnetic particle powder decreases. Also, for example, see JP-A-63-1
JP-A-03424, JP-A-63-171419 and JP-A-5-73898 disclose a method of coating Al on the particle surface. However, it is difficult to uniformly coat Al on the particle surface. And oxidation stability is not sufficient. Also, if a large amount of Al is used to sufficiently cover the particle surface, the magnetic properties such as the coercive force Hc deteriorate.

Therefore, in the present invention, in order to uniformly coat the particle surface, it is better to form a solid solution only on the particle surface, so that the particle surface can be more uniformly coated, and the shape retention and oxidation stability can be improved. I thought it could be improved.

As a prior art of the method, Japanese Patent Laid-Open Publication No.
No. 8321 discloses a technical means. In the same publication, a non-oxidizing atmosphere is formed during oxidation,
We considered whether it is necessary to ripen at a temperature higher than the oxidation reaction temperature.

The present inventor has conducted a number of experiments. In the reaction for producing goethite particles according to the present invention, it was found that first the particles in the short axis direction of goethite particles were formed, and then the particles grew in the long axis direction. I found it. Therefore, when the oxidation rate of the oxidation reaction exceeds 50%, the operation of changing the reaction rate (for example, the reaction) is performed when the formation of the particles in the short axis direction has already been completed and the growth reaction of the particles has occurred. Temperature, oxygen flow, non-oxidizing atmosphere, etc.), uniform particle size cannot be obtained. Therefore, when an operation such as a temperature rise is performed, growth in the short axis direction occurs again, which has an unfavorable effect such that particles having a large axial ratio cannot be obtained.

In the present invention, a Co compound is formed into a solid solution inside the particles, and Al and S which are hardly oxidized in the air.
By uniformly dissolving one or more compounds selected from rare earth elements such as i, Ca, Mg, Ba, Sr and Nd on the particle surface, it is hardly affected by oxygen in the air, and is oxidatively stable. The magnetic metal particles mainly composed of spindle-shaped iron having excellent coercivity, being fine particles, having a uniform particle size, containing no dendritic particles, and having a high coercive force. can get.

The spindle-shaped iron-based metal magnetic particle powder according to the present invention may be made of Al
And the above-mentioned compounds in combination to form a solid solution uniformly on the particle surface, thereby improving the shape retention and oxidation stability of the iron-based metal magnetic particle powder. The resin has good dispersibility because of the good adaptability of the resin.

[0092]

Next, the present invention will be described with reference to examples and comparative examples. In addition, the major axis diameter and the axial ratio of the particles in the experimental examples described above, the following examples and comparative examples are all shown as average values of numerical values measured from electron micrographs, and the specific surface area of the particles was measured by the BET method. Indicated by value.

The X-ray particle size is a value obtained by expressing the size of a crystal particle measured by the X-ray diffraction method in the direction perpendicular to the (110) crystal plane. The value was calculated from the line profile of the diffraction line of the (110) plane using the following Scherrer equation.

D ₁₁₀ = Kλ / βcos θ where β = half-width of the true diffraction peak obtained by subtracting the mechanical width by the apparatus K = Scherrer constant (0.9) λ = characteristic X-ray wavelength θ = diffraction angle

The magnetic properties and coating properties of the metal magnetic particles containing iron as a main component are described in “Vibration sample magnetometer VSM-3S-
15 "(manufactured by Toei Industry Co., Ltd.) and an external magnetic field of 10K
It was measured over Oe.

The square shape of the coating film and S.T. F. D. The measurement of
This was performed using a sheet sample obtained by the method of Reference Example 1 described later. In addition, S.I. F. D. Is to obtain a differential curve of a demagnetization curve of a magnetic hysteresis curve using a differentiation circuit of the magnetometer, measure a half width of the curve, and divide this value by a coercive force of a peak value of the curve. Determined by

Incidentally, the viscosity of the suspension containing the iron-containing precipitate is as follows:
This is a value measured using a Stormer viscometer.

<Production of Goethite Particle Powder> Examples 1 to 15, Comparative Examples 1 to 10;

Example 1 ₂₀ l of an aqueous solution containing 25 mol of Na ₂ CO ₃ and 15 mol of NaOH were placed in a reaction vessel kept in a non-oxidizing atmosphere by flowing N ₂ gas at a rate of 100 l / min.
Aqueous solution containing 10 liters (0.6 mole ratio to Na ₂ CO ₃₎
Corresponds to. ) (The total amount of Na ₂ CO ₃ and NaOH corresponds to 1.63 equivalents to Fe ²⁺ ), and then 20 l of an aqueous ferrous sulfate solution containing 20 mol of Fe ²⁺ is added and mixed (Fe ²⁺ ). ^{The 2+} concentration corresponds to 0.4 mol / l) and an iron-containing precipitate was formed at a temperature of 47 ° C.

While continuously blowing N ₂ gas at a rate of 100 l / min into the suspension containing the iron-containing precipitate,
Maintained at a temperature of 47 ° C. for 5 hours (viscosity after 2 hours by passing N ₂ gas is 270 cps, viscosity after 5 hours is 205 cps)
cps. Then, an aqueous solution of cobalt sulfate was added so as to contain 3.0 mol% in terms of Co with respect to Fe ²⁺ , and the mixture was further aged for 10 minutes.

[0102] During liquid suspension containing the iron-containing precipitate after aging, was bubbled for 65 minutes of air per minute 180l at temperature 47 ° C., Fe ² where the oxidation rate of the oxidation reaction became 80% ^An aluminum sulfate aqueous solution was added so as to contain 3.0 mol% in terms of Al with respect to ^+, and the oxidation reaction was further continued for 35 minutes under the same conditions as the above oxidation reaction conditions to produce yellow-brown precipitate particles. The pH during air ventilation was 8.0 to 8.0.
9.5.

The yellow-brown precipitate particles were separated by filtration, washed with water, dried and pulverized by a conventional method. The obtained yellow-brown precipitate particles are goethite and have a major axis diameter of 0.126 μm and a minor axis diameter of 0.01 as shown in the electron micrograph (× 30000) of FIG.
5 μm, the axial ratio was 8.4, no dendritic particles were present at all, and the particle size was uniform. Further, the content of Co is 1.84 wt%, and the content of Al is 0.81 wt%.
wt%.

Examples 2 to 15 and Comparative Examples 1 to 10 In the reaction for producing a precipitate containing FeCO ₃ or iron, the amount of an aqueous alkali carbonate solution, the amount of an aqueous alkali hydroxide solution used, the timing of addition and the mixing ratio, and the temperature during mixing Example 1 except that the temperature and time in the aging step, the amount and timing of addition of the Co compound, the temperature in the oxidation step, the type of compound added during oxidation, the amount and timing of addition (oxidation rate) were variously changed. In the same manner as described above, goethite particles were generated.

In Comparative Example 10, a suspension containing an iron-containing precipitate after aging was added at a temperature of 47 ° C. for 180 minutes per minute.
1 of air for 70 minutes, the oxidation rate of the oxidation reaction is 80
%, A 100 l / min N ₂ gas was passed through to form a non-oxidizing atmosphere, the temperature was raised to 57 ° C., and then No. 3 water was added to contain 1.0 mol% of Fe ^{2+ in} terms of Si. The glass solution was added and held for 35 minutes. Then the temperature 5
The oxidation reaction was continued for 15 minutes at 7 ° C. while changing the N ₂ gas to 180 liters of air per minute to produce tan precipitated particles. The yellow-brown precipitate particles were separated by filtration, washed with water, dried and pulverized by a conventional method. The obtained yellow-brown precipitate particles are goethite, and FIG.
As shown in the electron micrograph (× 30000), the major axis diameter was 0.153 μm, the minor axis diameter was 0.023 μm, the axial ratio was 6.7, and the goethite particles were slightly larger. It was confirmed that axial growth occurred.

The main manufacturing conditions at this time are shown in Tables 1 to 4.
The properties of the resulting goethite particles are shown in Tables 3 and 4.

[0106]

[Table 1]

[0107]

[Table 2]

[0108]

[Table 3]

[0109]

[Table 4]

<Production of Hematite Particle Powder> Examples 16 to 28, Comparative Examples 11 to 19;

Example 16 15 g of the press cake equivalent to 900 g of spindle-shaped goethite particles obtained in Example 1 and separated by filtration and washed with water was used.
suspended in 1 l of water. At this time, the pH of the suspension was 8.5.
Met.

Next, 90 g of cobalt acetate was added to the above suspension so as to be 10% by weight based on goethite particles, and boric acid was further added so as to be 15% by weight based on goethite particles, followed by stirring for 10 minutes. did. At this time, the pH of the suspension was 4.5.

Further, the pH was adjusted to 9.5 by adding an aqueous ammonia solution, followed by filtration with a filter press and drying to obtain goethite particles coated with Co and B compounds.

In the obtained goethite particles, Al, Co,
The content of B is 0.81% by weight as Al and C is
o was 3.95% by weight and B was 0.75% by weight.

900 g of goethite particle powder coated with Co and B compounds was heated in air at 400 ° C.
A spindle-shaped hematite particle powder coated with the B compound was obtained.

Examples 17 to 28 and Comparative Examples 11 to 19 Example 16 except that the kind of particles to be treated, the kind and amount of the compound containing the coating element, the amount of heat dehydration, the presence or absence of annealing and the temperature were variously changed. A coated hematite particle powder was obtained in the same manner as described above.

In Example 24, coated hematite particles were obtained in the same manner as in Example 16 except that the compound containing the coating element was coated, filtered, and washed with water.

The main processing conditions at this time are shown in Tables 5 and 6.

[0119]

[Table 5]

[0120]

[Table 6]

<Production of Metal Magnetic Particle Powder Mainly Containing Iron> Examples 29 to 41 and Comparative Examples 20 to 28;

Example 29 100 g of the spindle-shaped hematite particle powder coated with the Co and B compounds obtained in Example 16 and having an inner diameter of 72 mm
, And H ₂ gas was passed at a rate of 35 l / min to reduce at a reduction temperature of 420 ° C.

After completion of the reduction, the H ₂ gas was replaced with N ₂ gas once, and then the N ₂ gas was flown at 50 l / min and the temperature was reduced to 40 ° C.
Cooled down. Next, while maintaining the furnace temperature at 40 ° C.,
₂ gas 50l / min Air in gas 0.2l / mi
A mixed gas of air and N ₂ gas mixed at a ratio of n was ventilated. After an exothermic peak was observed by the oxidation reaction at the mixed gas ratio, the air amount was increased to 0.4 l / min, and the air ratio in the mixed gas was increased. In this way, after an exothermic peak due to the oxidation reaction at the mixed gas ratio is observed, the air mixing ratio is increased stepwise by a method of increasing the air ratio in the mixed gas, and finally, the air is mixed with 0.6 l of air. /
The oxidation treatment was continued with a mixed gas of 50 l / min of N ₂ gas and N ₂ gas, and the oxidation treatment was performed until the heat of the oxidation disappeared and the temperature of the product reached approximately 40 ° C. which was almost the same as the furnace temperature. During this time, the temperature of the article reached a maximum of 75 ° C.

Subsequently, the furnace temperature was set to 40 ° C. and the N ₂ gas flow rate was set to 50.
While maintaining 1 / min, the mixing ratio of air was gradually increased, and the air amount was finally set to 10 1 / min. During this time,
No fever was observed. Further, the mixture was cooled to room temperature while passing a mixed gas of N ₂ gas and air under the same conditions.

Once the air flow rate is set to 0 l / min, N
After the replacement with the _two gases, the thus-obtained spindle-shaped iron-based metal magnetic particle powder whose main component is an oxide film formed on the surface was recovered.

This spindle-shaped iron-based metal magnetic particle powder containing Co, Al, and B has an X-ray particle size of 146 °, and is shown by an electron micrograph (× 3000) in FIG.
As shown in 0), the average major axis diameter was 0.096 μm, the average minor axis diameter was 0.014 μm, the axial ratio was 6.9, the particle size was uniform, and there were few dendritic particles. The magnetic properties are as follows: coercive force Hc is 1847 Oe, saturation magnetization s is 121
The emu / g, the squareness ratio r / s were 0.508, the Co content was 5.65 wt%, Al was 1.16 wt%, and B was 1.07 wt%.

Examples 30 to 41, Comparative Examples 20 to 28 Metals containing iron as a main component in the same manner as in Example 29 except that the type of the particles to be treated and the reduction temperature in the reduction heating step were variously changed. Magnetic particle powder was obtained.

Tables 7 and 8 show the main production conditions and various characteristics at this time.

[0129]

[Table 7]

[0130]

[Table 8]

<Production of Coated Film> Reference Examples 1 to 9;

REFERENCE EXAMPLE 1 A strong polar function comprising 100 parts by weight of a spindle-shaped iron-based metal magnetic particle powder containing Co, Al and B obtained in Example 29 and a 30% by weight solution of cyclohexanone A kneaded product was obtained by kneading 50 parts by weight of a vinyl chloride copolymer resin MR-110 having a group (manufactured by Zeon Corporation) for 50 minutes using a 88 cc plastmill.

The kneaded material was placed in a 140 cc glass bottle at the following ratio and mixed and dispersed for 6 hours. A magnetic coating prepared by coating was applied to a 25 μm thick polyethylene terephthalate film to a thickness of 50 μm using an applicator. Next, the sample was dried in a magnetic field of 8 K Gauss to produce a coating film, thereby preparing a sheet sample.

Kneaded material 100 parts by weight 1 mmφ glass beads 530 parts by weight Cyclohexanone 50 parts by weight Methyl ethyl ketone 57 parts by weight Toluene 57 parts by weight

The coercive force Hc of the coating film obtained from this sheet sample piece was 1903 Oe, the degree of orientation SQ was 0.891, and
F. D. Was 0.440.

Reference Examples 2 to 9 Coating films were produced in the same manner as in Reference Example 1, except that the type of metal magnetic particle powder containing iron as a main component was variously changed.
Table 9 shows the properties of this coating film.

[0137]

[Table 9]

[0138]

According to the present invention, as shown in the previous embodiment, the particles are fine, the particle size is uniform, dendritic particles are not mixed, and the coercive force is high. Thus, it is possible to obtain spindle-shaped iron-based metal magnetic particle powder having a coercive force Hc of 1700 to 2200 Oe, so that high recording density, high sensitivity, and high output magnetic particle powder can be obtained. It is suitable.

[0139] Additionally, magnetic metal particles to the iron exhibited more resulting spindle-shaped to the present invention as a main component, in the production of magnetic coating, has good dispersibility in vehicle, the filling property is very Excellent, and the X-ray particle size is 120 to 1
Since it is as small as 60 °, the noise level is reduced and S
A preferable magnetic recording medium having a large / N ratio can be obtained.

[Brief description of the drawings]

FIG. 1 is an electron micrograph (× 3000) showing the particle structure of the spindle-shaped goethite particle powder obtained in Example 1.
0).

FIG. 2 is an electron micrograph (× 3000) showing the particle structure of the goethite particle powder having a spindle shape obtained in Example 3.
0).

FIG. 3 is an electron micrograph (× 3000) showing the particle structure of the spindle-shaped goethite particles obtained in Example 9.
0).

FIG. 4 is an electron micrograph (× 30000) showing the particle structure of the granular goethite particles obtained in Comparative Example 3.

FIG. 5 is an electron micrograph (× 3000) showing the particle structure of spindle-shaped goethite particles obtained in Comparative Example 4.
0).

FIG. 6 is an electron micrograph (× 3000) showing the particle structure of the spindle-shaped goethite particles obtained in Comparative Example 5.
0).

FIG. 7 is an electron micrograph (× 300) showing the particle structure of the goethite particle powder having a spindle shape obtained in Comparative Example 10.
00).

FIG. 8 is an electron micrograph (× 30000) showing the particle structure of a spindle-shaped iron-based metal magnetic particle powder obtained in Example 29 and having a spindle shape.

Claims (3)

(57) [Claims] 1. A suspension containing an FeCO ₃ or iron-containing precipitate obtained by reacting an aqueous alkali carbonate solution and an aqueous ferrous salt solution is aged in a non-oxidizing atmosphere, and then the suspension is subjected to aging. In order to produce spindle-shaped goethite particles by performing an oxidation reaction by passing an oxygen-containing gas through the alkali carbonate aqueous solution and the FeCO before aging.
₃ or any of the suspensions containing the iron-containing precipitate in a molar ratio of 0.2 to 1.0 with respect to the aqueous alkali carbonate solution.
The total amount of the aqueous alkali carbonate solution and the aqueous alkali hydroxide solution is adjusted to 1.3 to 1.8 equivalents to Fe ²⁺ in the aqueous ferrous salt solution by adding And the aging time is in the range of 2 to 7 hours. The ferrous salt aqueous solution, the suspension containing the FeCO ₃ or the iron-containing precipitate, and the aged F before the oxidation reaction are performed.
In any of the suspensions containing eCO ₃ or the iron-containing precipitate, 1.0 mol% or more and less than 8.0 mol% in terms of Co with respect to Fe ^{2+ in the} ferrous salt aqueous solution in advance. While the amount of the Co compound is present in the range, by setting the temperature range of the oxidation reaction to 40 to 60 ° C., spindle-shaped goethite particles are generated, and the spindle-shaped goethite particles or The spindle-shaped hematite particles obtained by heating and dehydrating the spindle-shaped goethite particles are reduced by heating in a reducing gas. A method for producing metal magnetic particle powder as a component. 2. A suspension containing FeCO ₃ or an iron-containing precipitate obtained by reacting an aqueous alkali carbonate solution and an aqueous ferrous salt solution is aged in a non-oxidizing atmosphere, and then the suspension is subjected to aging. In order to produce spindle-shaped goethite particles by performing an oxidation reaction by passing an oxygen-containing gas through the alkali carbonate aqueous solution and the FeCO before aging.
₃ or any of the suspensions containing the iron-containing precipitate in a molar ratio of 0.2 to 1.0 with respect to the aqueous alkali carbonate solution.
The total amount of the aqueous alkali carbonate solution and the aqueous alkali hydroxide solution is adjusted to 1.3 to 1.8 equivalents to Fe ²⁺ in the aqueous ferrous salt solution by adding And the aging time is in the range of 2 to 7 hours. The ferrous salt aqueous solution, the suspension containing the FeCO ₃ or the iron-containing precipitate, and the aged F before the oxidation reaction are performed.
In any of the suspensions containing eCO ₃ or the iron-containing precipitate, 1.0 mol% or more and less than 8.0 mol% in terms of Co with respect to Fe ^{2+ in the} ferrous salt aqueous solution in advance. While the amount of the Co compound is present in the range, the temperature range of the oxidation reaction is 40 to 60 ° C., and the oxidation rate of the oxidation reaction is Fe ^{2+ in the} aqueous ferrous salt solution.
Al, Si, C under the same conditions as in the above oxidation reaction in the oxidation reaction solution in the range of 50 to 90%
a, Mg, Ba, Sr, and an aqueous solution of one or more compounds selected from rare earth elements such as Nd are added to Fe ²⁺ in the aqueous ferrous salt solution in terms of each element in total. To form a spindle-shaped goethite particle, or the spindle-shaped goethite particle or the spindle-shaped goethite particle. 3. Spindle-shaped hematite particles obtained by heating and dehydrating the particles are heat-reduced in a reducing gas. Manufacturing method of metal magnetic particle powder. 3. A suspension containing FeCO ₃ or an iron-containing precipitate obtained by reacting an aqueous alkali carbonate solution and an aqueous ferrous salt solution is aged in a non-oxidizing atmosphere, and then the suspension is subjected to aging. In order to produce spindle-shaped goethite particles by performing an oxidation reaction by passing an oxygen-containing gas through the alkali carbonate aqueous solution and the FeCO before aging.
₃ or any of the suspensions containing the iron-containing precipitate in a molar ratio of 0.2 to 1.0 with respect to the aqueous alkali carbonate solution.
The total amount of the aqueous alkali carbonate solution and the aqueous alkali hydroxide solution is adjusted to 1.3 to 1.8 equivalents to Fe ²⁺ in the aqueous ferrous salt solution by adding And the aging time is in the range of 2 to 7 hours. The ferrous salt aqueous solution, the suspension containing the FeCO ₃ or the iron-containing precipitate, and the aged F before the oxidation reaction are performed.
In any of the suspensions containing eCO ₃ or the iron-containing precipitate, 1.0 mol% or more and less than 8.0 mol% in terms of Co with respect to Fe ^{2+ in the} ferrous salt aqueous solution in advance. With a range of amounts of Co compound present,
The temperature range of the oxidation reaction is 40 to 60 ° C., and the oxidation rate of the oxidation reaction is Fe ^{2+ in the} aqueous ferrous salt solution.
In an oxidation reaction solution in the range of 50 to 90%, an aqueous solution of an Al compound and a rare earth element such as Si, Ca, Mg, Ba, Sr and Nd are selected under the same conditions as the oxidation reaction. And an aqueous solution of one or more compounds to be added to Fe ²⁺ in the aqueous ferrous salt solution in an amount in the range of 0.1 to 5.0 mol% in terms of each element in terms of the total of the compounds added. As a result, spindle-shaped goethite particles are generated, and the spindle-shaped goethite particles or the spindle-shaped hematite obtained by heating and dehydrating the spindle-shaped goethite particles are obtained. 3. The method of claim 2, wherein the particles are reduced by heating in a reducing gas.