JP3428351B2 - Spindle-shaped metal magnetic particles containing iron as a main component and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a uniform particle size, no dendritic particles are mixed, and an appropriate particle shape and a large axial ratio (major axis diameter / minor axis diameter, hereinafter the same). And a spindle-shaped metal magnetic particle powder containing iron as a main component, which has a high coercive force and an excellent coercive force distribution obtained by using the spindle-shaped hematite particle powder It is about.

[0002]

2. Description of the Related Art In recent years, magnetic recording / reproducing devices for video and audio have been intensified for long-time recording and have been reduced in size and weight. In particular, the spread of VTRs (video tape recorders) has been remarkable recently. The development of VTRs aiming at long-time recording and reduction in size and weight is being actively conducted. On the other hand, there is an increasing demand for higher performance and higher density recording of magnetic tapes, which are magnetic recording media.

That is, it is required to improve the high image quality, high output characteristics, especially frequency characteristics of the magnetic recording medium.
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, and the S / N ratio is required to be improved more and more. These various 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, they have a high coercive force and a large coercive force as compared with the conventional iron oxide magnetic particle powder. Attention has been paid to powdered metal magnetic particles containing iron as a main component, which has saturation magnetization, and digital audio tape (DA
T), 8 mm video tapes, Hi-8 tapes, and magnetic recording media such as video floppies. However, it is strongly desired to further improve the properties of the metal magnetic particle powder containing iron as a main component.

Now, the relationship between various characteristics of the magnetic recording medium and the characteristics of the magnetic particle powder used will be described in detail below. In order to obtain high image quality as a magnetic recording medium for video, as is clear from the record of Nikkei Electronics (1976) May 3, issue, pages 82 to 105, (1)
Improvements in video S / N ratio, (2) chroma S / N ratio, and (3) video frequency characteristics are required.

In order to improve the video S / N ratio and the chroma S / N ratio, the dispersibility of the magnetic particle powder in the vehicle, the orientation in the coating film and the filling property are improved, and It is important to improve the surface smoothness of the magnetic recording medium.As such a magnetic particle powder, the particle size is uniform, dendritic particles are not mixed, and the particle shape and axis are suitable. It is required to be a ratio.

Next, in order to improve the video frequency characteristics, it is necessary for the magnetic recording medium to have a high coercive force Hc and a large residual magnetic flux density Br. In order to increase the coercive force Hc of the magnetic recording medium, the coercive force Hc of the magnetic particle powder is required to be as high as possible. Since the coercive force of magnetic particle powder is generally caused by its shape anisotropy, the coercive force tends to increase as the particle axial ratio increases.

In order to increase the output of the magnetic recording medium,
Japanese Unexamined Patent Publication No. 63-26821 shows "FIG. 1 is a diagram showing the relationship between the SFD measured on the above-mentioned magnetic disk and the recording / reproducing output. As is clear from Fig. 1, the relationship between the recording and reproducing output is a straight line, which means that the recording and reproducing output can be increased by using a ferromagnetic powder having a small SFD. In order to increase the recording / reproducing output, it is desirable that the SFD is small, and in order to obtain an output higher than usual, it is 0.6
The following S. F. D. is necessary. As stated,
The S. F. D. (Switching F
It is necessary that the field distribution, that is, the coercive force distribution be small. For that reason, it is required that the particle size of the magnetic particle powder be as uniform as possible and that the dendritic particles are not mixed.

As described above, the particle size is uniform, the dendritic particles are not mixed, the particles have an appropriate particle shape and axial ratio, and moreover, they have a high coercive force and an excellent coercive force distribution. Currently, the metal magnetic particle powder containing iron as a main component is the most demanded at present.

Generally, metal magnetic particle powders containing iron as a main component include goethite particles as a starting material, hematite particles obtained by heating and dehydrating the goethite particles, or each of the above particles containing a different metal other than iron. If necessary, the particles or the like are heat-treated in a non-reducing atmosphere, and then heat-reduced in a reducing gas atmosphere. Therefore, the metal magnetic particle powder mainly composed of iron inherits the shape of the goethite particle powder as the starting material in a similar manner,
It is known that the higher the axial ratio of the goethite particles is, the higher the axial ratio of the metal magnetic particles is, and in obtaining the metal magnetic particle powder containing iron as a main component having the above-mentioned characteristics, the particle size is uniform. Therefore, dendritic particles are not mixed,
Moreover, it is necessary to use a goethite particle powder having an appropriate particle shape and an axial ratio, and it is necessary to retain and inherit the particle shape and the uniform particle size in the subsequent heat treatment step. .

Conventionally, various methods are known as a method for producing goethite particle powder which is a starting material of metal magnetic particle powder containing iron as a main component. In particular, Co, which has an effect of improving magnetic properties when made into a metal magnetic particle powder, and a metal compound such as Al, which has an excellent shape-retaining property because it has an effect of preventing sintering when made into a metal magnetic particle powder, are The following is known as a method of adding in advance in the production process. For example, a suspension containing a ferrous hydroxide colloid obtained by adding an equivalent amount or less of an alkali hydroxide aqueous solution to a ferrous salt aqueous solution in the presence of a cobalt compound is subjected to an oxygen-containing gas at 50 ° C. by aeration with an oxygen-containing gas to carry out an oxidation reaction. To generate needle-shaped goethite particles, and further carry out a growth reaction (JP-A-7-11310),
Oxidation is carried out by passing an oxygen-containing gas through a suspension containing FeCO ₃ obtained by reacting a ferrous salt aqueous solution containing an Al acidic salt compound and an alkaline carbonate aqueous solution containing an Al basic salt compound. A method of producing spindle-shaped goethite particles by carrying out a reaction (JP-A-6-22861).
No. 4), a mixed aqueous solution of a ferric salt and a Co compound is neutralized with an aqueous alkali hydroxide solution, and goethite seed crystal particles obtained by hydrolysis are dissolved in an aqueous ferric salt solution containing an Al compound. A method in which a growth reaction is carried out by a hydrolysis reaction by neutralizing an aqueous alkali hydroxide solution (JP-A-58-17).
6902), a suspension containing a ferrous iron-containing precipitate obtained by reacting an aqueous solution of an alkali carbonate with an aqueous solution of a ferrous salt is aged in a non-oxidizing atmosphere, and then in the suspension. In producing spindle-shaped goethite particles by carrying out an oxidation reaction by aerating an oxygen-containing gas into
In a liquid of any one of the ferrous salt aqueous solution, the suspension containing the ferrous iron-containing precipitate, and the suspension containing the aged ferrous iron-containing precipitate before performing an oxidation reaction, , C
o compound is present, and F in the aqueous solution of the ferrous salt is further added.
During the oxidation reaction developing liquid in the range of 50-90% with respect to e ^2+, under the same conditions and the oxidation reaction, Al, Si,
The total sum of the compounds added to an aqueous solution of one or more compounds selected from rare earth elements such as Ca, Mg, Ba, Sr, and Nd with respect to Fe ²⁺ in the ferrous salt aqueous solution. Is known to be added in an amount of 0.1 to 5.0 mol% (JP-A-7-126704).

The above-mentioned respective publications also describe metallic magnetic particle powders containing iron as a main component and obtained by using the respective goethite particle powders described in the respective publications as starting materials.

The ratio of the X-ray crystal grain size of the hematite particles is specified as follows:
The ratio D ₁₀₄ / D ₁₁₀ of the X-ray crystal grain size D ₁₀₄ and the X-ray crystal grain size D _{110 in} the direction perpendicular to the (110) plane is in the range of 1 to 2,
There are fine acicular α-ferric oxide particles having a specific surface area of 40 to 50 m ² / g (JP-A-7-206446).

[0013]

[Problems to be Solved by the Invention] The particle size is uniform, dendritic particles are not mixed, and it has an appropriate particle shape and a high axial ratio, and also has a high coercive force and an excellent coercive force distribution. The spindle-shaped metal magnetic particle powder containing iron as a main component having and is currently most demanded, but a metal obtained when each goethite particle powder described in the above publications is used as a starting material. It is hard to say that the magnetic particle powder is one that fully satisfies these various characteristics.

That is, according to the production method described in the above-mentioned JP-A-7-11310, needle-shaped goethite particles having an axial ratio of 10 or more in which Co atoms are present in the goethite particles are formed. Particles are mixed, and in terms of particle size, it cannot be said that the particles have a uniform particle size.

In the case of the production method described in JP-A-6-228614, the method for adding Al to goethite particles having no uniform dendritic particles and having a uniform particle size is devised. However, it is still insufficient in terms of axial ratio.

In the manufacturing method described in Japanese Patent Laid-Open No. 7-126704, Al is added in the middle stage of the oxidation reaction. In the middle stage of the oxidation reaction, Co ions remain in the solution, and when Co is present in the solution, A
When l was added and residual ferrous ions were oxidized to grow goethite particles, remarkable growth in the minor axis direction was observed,
The present inventor has found that the axial ratio is lowered as described later. Therefore, it is difficult to produce spindle-shaped goethite particles having a large axial ratio, particularly 13 or more.

The production method described in JP-A-58-176902 mentioned above uses trivalent iron as a starting material, and the reaction mechanism is hydrolysis, not oxidation, and the secondary reaction is 1
The hydrothermal treatment is performed at a high temperature exceeding 00 ° C, which is different from the reaction in the present invention.

The metal magnetic particle powder containing iron as a main component, which is obtained by using the goethite particle powder obtained by the production method described in the above-mentioned publications as a starting material, also has a uniform particle size and contains dendritic particles. However, it is hard to say that it has a large axial ratio.

The needle-shaped α-ferric oxide particles described in the above-mentioned JP-A-7-206446 have a ratio D of X-ray crystal grain size.
₁₀₄ / D ₁₁₀ is in the range of 1-2, and X in the present invention is
The linear crystal grain size ratio D ₁₀₄ / D ₁₁₀ does not fall within a specific range, but rather D ₁₁₀ is smaller than D ₁₀₄ , so that the crystallinity is completely different. Moreover, the acicular α-ferric oxide particles are obtained by hydrothermal reaction. On the other hand, as a comparative example, a hematite particle obtained by heating and dehydrating goethite particle powder having an X-ray crystal grain size ratio D ₁₀₄ / D ₁₁₀ of 0.7 is described. It does not fall within the specific range of the ratio of the crystal grain size.

Therefore, according to the present invention, a spindle-shaped hematite particle powder having a uniform particle size, containing no dendritic particles and having an appropriate particle shape and axial ratio is obtained. A technical problem is to obtain a spindle-shaped metallic magnetic particle powder containing iron as a main component, which has a high coercive force and an excellent coercive force distribution, using a hematite particle powder as a starting material.

[0021]

The above technical problems can be achieved by the method of the present invention as follows.

That is, in the present invention, the average major axis diameter is 0.05 to.
It is a spindle-shaped particle of 1.0 μm, and a compound of a rare earth element as a rare earth element on the surface of the particle is 0.5 to 1 with respect to all Fe
It contains 5 atomic% and consists of a hematite seed crystal portion and a hematite surface layer portion. The seed crystal portion contains Co in an amount of 0.5 to 25 atomic% with respect to the total Fe, and the surface layer portion contains Is 0.5 to 15 atom% of Al based on the total Fe.
Contains X-ray crystal grain size D ₁₀₄ and D
_The average major axis diameter obtained using the spindle-shaped hematite particle powder composed of hematite particles having a ratio D ₁₀₄ / D _{110 of 110} in the range of 0.20 to 0.65 is 0.05 to 0.
Spindle-shaped particles of 5 μm, containing Co to all Fe
0.5 to 25 atomic% is contained, and Al is 0.
5 to 15 atomic% and contains rare earth elements in all Fe
The main component is iron containing 0.5 to 15 atom%.
Featuring iron as a main component characterized by being composed of metallic magnetic particles
It is a spindle-shaped metal magnetic particle powder.

The present invention also non-oxidizes an aqueous suspension containing a ferrous iron-containing precipitate obtained by reacting a mixed alkaline aqueous solution of an alkaline carbonate aqueous solution and an alkaline hydroxide aqueous solution with a ferrous iron salt aqueous solution. After aging in a sexual atmosphere,
An oxygen-containing gas is passed through the water suspension to generate spindle-shaped goethite seed crystal particles, and then a mixed alkaline aqueous solution of alkali carbonate and alkali hydroxide is added to the water suspension containing the seed crystal particles. And a ferrous salt aqueous solution are newly added and mixed, and an oxygen-containing gas is aerated to grow a goethite layer on the particle surface of the spindle-shaped goethite seed crystal particles to generate spindle-shaped goethite particles, After treating the surface of the spindle-shaped goethite particles with a sintering inhibitor, in obtaining the spindle-shaped hematite particles by heating and dehydration, in the reaction of producing the seed crystal particles, a ferrous salt aqueous solution, a ferrous iron-containing precipitate In a water suspension containing the above, a water suspension containing a ferrous iron-containing precipitate during aging before the start of the oxidation reaction, or a water suspension during the formation reaction,
With respect to Co, 0.5 to 25 atomic% of Co compound is added, and during the growth reaction of the goethite layer,
Total Fe is added to each of the aqueous alkali solution to be added, the aqueous ferrous salt solution, the aqueous suspension containing the spindle-shaped goethite seed crystal particles before the start of the oxidation reaction and the ferrous iron-containing precipitate, or the aqueous suspension during the growth reaction. 0.5 to 15 atomic% of Al compound in terms of Al is added, and a compound of a rare earth element as the sintering inhibitor is added as a rare earth element to 0.5 to 15 with respect to all Fe.
Atomic% is added, and the heat dehydration is performed in the range of 400 to 850 ° C. to obtain a spindle-shaped hematite particle powder ,
Spindle-shaped hematite particles powder in reducing gas 400-6
Mainly iron, which is characterized by being heated and reduced within the range of 00 ° C
It is a method for producing a spindle-shaped metal magnetic particle powder as a component.

[0024]

[0025]

The structure of the present invention will be described in more detail as follows. First, we describe the spindle-shaped goethite particles as a precursor of the spindle-shaped hematite particles which definitive to the present invention.

The spindle-shaped goethite particles as a precursor have an average major axis diameter of 0.05 to 1.0 μm, preferably 0.05 to 1.0 μm.
It is 0.5 μm. Its shape is spindle-shaped, and the axial ratio (major axis diameter / minor axis diameter) is 10 to 15, preferably 13 to 15.

The spindle-shaped goethite particle powder as a precursor has a BET specific surface area of 50 to 180 m ² / g, preferably 60 to 150 m ² / g.

The particles constituting the spindle-shaped goethite particle powder as a precursor are formed of a seed crystal portion and a surface layer portion. The seed crystal portion refers to a goethite seed crystal particle portion formed by oxidizing all of the ferrous salt added first. Specifically, it is a part of the weight ratio determined by the ratio with the ferrous salt added in the growth reaction, preferably 50 to 80% by weight, more preferably 55 to 75% by weight from the inner center of the seed crystal particles. It is the part by weight. Co contained in the goethite seed crystal particles of the seed crystal portion is 0.5 to 25 atom%, preferably 1.0 to 20 atom% with respect to the total Fe.
Is. If it is less than 0.5 atom%, the effect of improving magnetic properties cannot be obtained. If it exceeds 25 atom%, a high axial ratio cannot be obtained. The surface layer portion means a goethite layer grown on the surface of the goethite seed crystal particles by oxidizing all of the ferrous salt added in the growth reaction. Specifically, it is 20 to 50% by weight, preferably 25 to 45% by weight from the outermost surface of the particle. Al contained in the goethite layer in the surface layer is 0.5 to 1 with respect to all Fe.
It is 5 atom%, preferably 1.0 to 10 atom%. 0.
If it is less than 5 atomic%, the effect of preventing sintering cannot be obtained. 1
When it exceeds 5 atomic%, it is difficult to obtain a high axial ratio.

Next, the spindle-shaped hematite particle powder according to the present invention will be described.

The particles constituting the spindle-shaped hematite particle powder according to the present invention have an average major axis diameter of 0.05 to 1.0 μm,
It is preferably 0.05 to 0.5 μm. Its shape is spindle-shaped, and the axial ratio (major axis diameter / minor axis diameter) is 10 to 15, preferably 11 to 15.

The spindle-shaped hematite particles which definitive to the present invention, BET specific surface area of 30~140m ² / g, preferably from 35~100m ² / g.

The particles constituting the spindle-shaped hematite particles definitive to the present invention is formed from the seed crystal part and the surface layer portion. The seed crystal portion is a seed crystal portion of the precursor goethite particles which is changed as it is, and preferably 50 to 80% by weight, more preferably 55 to 75% by weight from the inner center of the seed crystal particle. It is a part. Co contained in the hematite seed crystal particles in the seed crystal portion is 0.5 to 25 atom%, preferably 1.0 to 20 atom% with respect to the total Fe. If it is less than 0.5 atom%, the effect of improving magnetic properties cannot be obtained. If it exceeds 25 atom%, a high axial ratio cannot be obtained. The surface layer portion is a portion in which the surface layer portion of the precursor goethite particles is changed as it is, and is preferably 20 to 50% by weight, more preferably 25 to 45% by weight from the outermost surface of the particle. Al contained in the surface hematite layer is 0.5 with respect to the total Fe.
-15 atom%, preferably 1.0-10 atom%.
If it is less than 0.5 atom%, the effect of preventing sintering cannot be obtained. When it exceeds 15 atomic%, it is difficult to obtain a high axial ratio.

The particles constituting the spindle-shaped hematite particles definitive to the invention, 0.5 to 15 atomic% of a compound of a rare earth element on the surface of the particles based on the total Fe as the rare earth element, preferably 1.0 to 12. Contains 0 atom%. If it is less than 0.5 atom%, the effect of preventing sintering in the dehydration step from goethite to hematite is not sufficient, particle growth occurs, and further, a coercive force distribution is exhibited when the powder is made into metallic magnetic particles. SFD becomes high. When it exceeds 15 atomic%, the saturation magnetization value decreases. As the rare earth element, yttrium, lanthanum, cerium, praseodymium, neodymium, samarium and the like can be particularly preferably used. The compound of the rare earth element on the particle surface is an oxide, a hydroxide, a hydrous oxide or the like.

The particles constituting the spindle-shaped hematite particles definitive to the present invention, the ratio _D 104 _{/ D 110} of the X-ray crystallite size _{D 110} and _{D 104} is in a range of 0.20 to 0.65, Preferably, the following inequality regarding the content x (atomic%) with respect to the total Fe as a rare earth element of the compound of the rare earth element on the particle surface: 0.5 ≦ x ≦ 10, 0.500−0.03x ≦ D ₁₀₄ / D ₁₁₀ ≤ 0.6
For 65-0.03x 10 <x ≦ 15, are intended to be within the range satisfying _{0.20 ≦ D 104 / D 110 ≦} 0.365. This range is as shown in FIG. 1 below. X-ray grain size ratio D
_In both cases where ₁₀₄ / D ₁₁₀ is less than 0.20 and more than 0.65, the SFD (protection of the metal magnetic particle powder obtained by reducing the spindle-shaped hematite particle powder when formed into a sheet) Magnetic force distribution) deteriorates.

Next, a method for producing a spindle-shaped goethite particle powder which is a precursor of the spindle-shaped hematite particle powder according to the present invention will be described.

The spindle-shaped hematite particles which definitive to the present invention may be after produce spindle-shaped goethite particles as a precursor, obtained by heating and dehydrating the spindle-shaped goethite particles obtained.

The spindle-shaped goethite particles as a precursor of the particles constituting the spindle-shaped hematite particles definitive to the present invention, first, to produce spindle-shaped goethite seed crystal particles, then the goethite layer on seed crystal particle surface It is obtained by performing a growth reaction to grow.

The spindle-shaped goethite seed crystal particles are an aqueous suspension containing a ferrous iron-containing precipitate obtained by reacting a mixed aqueous alkaline solution of an aqueous alkali carbonate solution and an aqueous alkali hydroxide solution with an aqueous ferrous salt solution. After aging under a non-oxidizing atmosphere, oxygen-containing gas is aerated in the water suspension to generate spindle-shaped goethite seed crystal particles, an aqueous ferrous salt solution and a ferrous iron-containing precipitate are added. 0.5 to 25 atoms in terms of Co with respect to total Fe in the water suspension containing the same, the water suspension containing the ferrous iron-containing precipitate during aging before the start of the oxidation reaction, or the water suspension during the formation reaction. It is obtained by adding% Co compound.

In the reaction for producing the spindle-shaped goethite seed crystal particles, an aqueous ferrous salt solution, an aqueous ferrous chloride solution, or the like can be used as the aqueous ferrous salt solution. The ferrous iron concentration of the aqueous solution of ferrous salt is, in an aqueous suspension containing the ferrous iron-containing precipitate after the reaction with the mixed alkaline aqueous solution,
Fe ²⁺ is 0.1 to 1.0 mol / l, preferably 0.2 to 0.8 mol / l. If it is less than 0.1 mol / l, the yield is low and it is not industrial. 1.0 m
When it exceeds ol / l, the particle size distribution becomes large, which is not preferable.

In the reaction for producing the spindle-shaped goethite seed crystal particles, the aqueous alkali solution is an aqueous sodium carbonate solution, an aqueous potassium carbonate solution,
Sodium hydroxide, potassium hydroxide and the like can be used as an aqueous solution of alkali hydroxide mixed with an alkali carbonate such as an aqueous solution of ammonium carbonate.

The mixed alkaline aqueous solution used in the reaction for producing the spindle-shaped goethite seed crystal particles is obtained by mixing an alkaline carbonate aqueous solution and an alkaline hydroxide aqueous solution. As a mixing ratio in this case, the ratio of the aqueous alkali hydroxide solution is 5 to 35 mol%, preferably 10 to 3
5 mol%, more preferably 15-35 mol%
Is. If it is less than 5 mol%, a sufficient axial ratio cannot be obtained, and if it exceeds 35 mol%, granular magnetite may be mixed.

The amount of the mixed alkaline aqueous solution used is 1.3 to 10 as an equivalent ratio to all Fe in the aqueous ferrous salt solution.
It is 3.5, preferably 1.5 to 2.5. If it is less than 1.3, magnetite may coexist.
When it exceeds 5, it is not industrially preferable.

The pH value in the reaction for producing the spindle-shaped goethite seed crystal particles is 8.0 to 11.0, preferably 8.
It is in the range of 5 to 10.0. When the pH is less than 8.0, a large amount of acid radicals will be contained in the goethite particle powder and cannot be easily removed even by washing. Therefore, the metal magnetic particle powder containing iron as the main component was used. In some cases, it causes sintering of the particles. If it exceeds 11.0, the desired high coercive force cannot be obtained when the metal magnetic particle powder is used.

The oxidizing means in the reaction for producing the spindle-shaped goethite seed crystal particles is carried out by passing an oxygen-containing gas (for example, air) through the liquid.

The temperature in the reaction for producing the spindle-shaped goethite seed crystal particles is usually 80 at which goethite particles are produced.
It may be carried out at a temperature of ℃ or less. If the temperature exceeds 80 ° C,
Magnetite may be mixed in the spindle-shaped goethite particles. It is preferably in the range of 45 to 55 ° C.

In the reaction of forming the spindle-shaped goethite seed crystal particles, cobalt sulfate, cobalt chloride, cobalt nitrate or the like can be used as the Co compound. Co
The addition of the compound is carried out by adding the ferrous salt aqueous solution, the suspension containing the ferrous iron-containing precipitate, the suspension containing the ferrous iron-containing precipitate that has been aged before the oxidation reaction, or the production reaction. It can be added in any of the aqueous suspensions. Particularly, it is preferable to add it just before starting the oxidation reaction. The amount of the Co compound added is 0.5 to 25 atom%, preferably 1.0 to 20.0 atom% based on the total Fe in the spindle-shaped goethite particles as the final product. 0.
When it is less than 5 atom%, there is no effect of improving the magnetic properties when it is made into a metal magnetic particle powder, and when it exceeds 25 atom%, the axial ratio is lowered due to miniaturization.

In the water suspension containing the spindle-shaped goethite seed crystal particles, a mixed alkaline aqueous solution of an alkaline carbonate aqueous solution and an alkaline hydroxide aqueous solution and a ferrous iron salt aqueous solution are newly added and mixed to form an oxygen-containing gas. Aerated, in growing a goethite layer on the particle surface of the spindle-shaped goethite seed crystal particles, each alkaline aqueous solution to be added, ferrous iron salt aqueous solution, the spindle-shaped goethite seed crystal particles before the oxidation reaction and the first By adding an Al compound in an amount of 0.5 to 15 atomic% in terms of Al to the total Fe to the water suspension containing the iron-containing precipitate or the water suspension during the growth reaction, the objective spindle Goethite particle powder can be obtained.

Examples of the ferrous salt aqueous solution used in the growth reaction of the goethite layer include ferrous sulfate aqueous solution and ferrous chloride aqueous solution. The addition amount of the ferrous salt is 20 to 50 mol with respect to the total amount of the addition amount of the ferrous salt in the production reaction of the goethite seed crystal particles.
%, Preferably 25 to 45 mol%. 20 mol
If it is less than%, the growth reaction of the spindle-shaped goethite particles does not sufficiently occur, and the desired spindle-shaped goethite particle powder cannot be obtained. When it exceeds 50 mol%, new seed crystals of goethite particles are generated to generate dendritic particles, and the particle size of the generated goethite particles becomes asymmetric.

The alkaline aqueous solution used in the growth reaction of the goethite layer can be selected from those that can be used in the reaction of forming the spindle-shaped goethite seed crystal particles, and the addition amount is also selected from the same range. be able to. The growth reaction of the goethite layer is preferably performed under the same conditions as the reaction for producing the spindle-shaped goethite seed crystal particles as much as possible, and the proportion of the alkali hydroxide aqueous solution in the mixed alkaline aqueous solution and the ferrous salt aqueous solution It is more preferable to make the alkali equivalent ratio to all Fe the same.

PH in the growth reaction of the goethite layer
The value is 8.0 to 11.0, preferably 8.5 to 10.0.
Is the range. If the pH is less than 8.0, a large amount of acid radicals will be contained in the goethite particle powder and cannot be easily removed even by washing. Therefore, when the metal magnetic particle powder is used, the particles are burned together. It causes a conclusion. If it exceeds 11.0, the desired high coercive force cannot be obtained when the metal magnetic particle powder is used.

The pH value of the reaction solution during the reaction for producing the spindle-shaped goethite seed crystal particles and the pH value of the reaction solution during the reaction for growing the goethite layer are the pH values in the respective reaction solutions.
The value difference is within ± 0.5. The difference in pH value is ± 0.
When it exceeds 5, the coercive force of the metal magnetic particle powder is still insufficient. It is preferably ± 0.3, more preferably ± 0.1.

The oxidizing means in the growth reaction of the goethite layer is performed by passing an oxygen-containing gas (for example, air) through the liquid.

The temperature for the growth reaction of the goethite layer is usually 80 ° C. or lower at which goethite particles are formed. If it exceeds 80 ° C., magnetite may be mixed in the spindle-shaped goethite particles. It is preferably in the range of 45 to 55 ° C.

In the growth reaction of the goethite layer, A
As the l compound, an acid salt such as aluminum sulfate, aluminum chloride or aluminum nitrate, or an aluminate such as sodium aluminate, potassium aluminate or ammonium aluminate can be used. The timing of adding the Al compound is the ferrous salt aqueous solution added in the growth reaction,
It may be present in any of the aqueous alkali solution, the water suspension containing the spindle-shaped goethite seed crystal particles before the aeration of the oxygen-containing gas and the ferrous iron-containing precipitate, or the water suspension during the growth reaction. In particular, it is preferable to start the growth reaction of the goethite layer. Further, even if the Al compound is added in a divided manner, or continuously and intermittently, the effect of the present invention remains the same and can be improved rather. In this case, the Al compound is added in a state where no Co compound remains in the water suspension. When the Al compound is added in the presence of the Co compound, the axial ratio of the goethite particles produced is decreased, which is not preferable.

The amount of the Al compound added is 0.5 to 0.5 based on the total Fe in the spindle-shaped goethite particles as the final product.
It is 15 atom%, preferably 1.0 to 10 atom%.
If it is less than 0.5 atom%, there is no sintering prevention effect and 1
If it exceeds 5 atomic%, the axial ratio will decrease.

In the reaction for producing the spindle-shaped goethite seed crystal particles, it is preferable to carry out so-called aging, in which the suspension containing the ferrous iron-containing precipitate is maintained and stirred under a non-oxidizing atmosphere. In that case, it is preferable that the aging is carried out in the temperature range of 40 to 80 ° C. for the suspension under a non-oxidizing atmosphere. When the temperature is lower than 40 ° C, it is difficult to obtain a sufficient aging effect because the axial ratio is small, and when the temperature exceeds 80 ° C, magnetite may be mixed. The aging time is 30 to 300 minutes. If it is less than 30 minutes, the axial ratio cannot be sufficiently increased. Thirty
It may exceed 0 minutes, but there is no point in making it longer than necessary. Further, aging may be performed during the growth reaction of the goethite layer.

In order to establish the non-acidic atmosphere, an inert gas (such as nitrogen gas) or a reducing gas (such as hydrogen gas) may be passed through the reaction vessel of the suspension.

In the present invention, in order to improve various characteristics of the spindle-shaped metallic magnetic particle powder containing iron as a main component, Mg which is usually added during the reaction for producing the spindle-shaped goethite particles.
One kind or two or more kinds of compounds, compounds of rare earth elements and the like may be added during the reaction of forming seed crystal particles or during the reaction of growing seed crystal particles.

Next, the process for producing the spindle-shaped hematite particles which definitive to the present invention.

In the present invention, the above-obtained spindle-shaped goethite particle powder is mixed with a compound of a rare earth element which is a sintering inhibitor for preventing sintering prior to the heat dehydration treatment, and optionally other elements. The surface of the spindle-shaped goethite particles is coated with a compound.

As the compound of the rare earth element, one or more compounds such as yttrium, lanthanum, cerium, praseodymium, neodymium and samarium are suitable, and chlorides, sulfates, nitrates and the like of the rare earth element are preferable. Can be used. The method of use may be dry or wet, preferably wet coating. The amount of the rare earth element used is 0.5 to 15 atom%, preferably 1.0 to 12.0 atom% with respect to the total Fe. 0.5
If it is less than atomic%, the effect of preventing sintering is not sufficient, and the SFD (coercive force distribution) is deteriorated when the metal magnetic particle powder is used. When it exceeds 15 atomic%, the saturation magnetization value becomes low.

If necessary, other elements such as Al, Si, B, Ca and M are added in order to improve the effect of preventing sintering.
You may use 1 type (s) or 2 or more types of the compound of the element selected from g, Ba, Sr, etc. These compounds not only have the effect of preventing sintering, but also have the function of controlling the reduction rate, so they may be used in combination as necessary. In this case, the total amount used is 1 to 15 atom% as the total amount with the rare earth element with respect to the total Fe in the spindle-shaped goethite particle powder. If the amount is small, the effect of improving the sintering prevention is not sufficient, and if the amount is too large, the saturation magnetization value decreases. Therefore, the optimum amount may be appropriately selected depending on the combination.

Spindle-shaped hematite particles which have been pre-coated with the above-mentioned sintering inhibitor or the like to prevent sintering between particles and particles, and further retain and succeed the particle shape and axial ratio of the spindle-shaped goethite particles. It is possible to obtain a powder, which facilitates obtaining a spindle-shaped metallic magnetic particle powder that retains and inherits the above-mentioned shape and the like and that is independent and has iron as a main component.

The spindle-shaped goethite particle powder thus obtained can be heat-treated in the range of 400 to 850 ° C. in a non-reducing atmosphere to obtain a spindle-shaped hematite particle powder. The temperature of the heat treatment in this case can be appropriately selected so that the ratio D ₁₀₄ / D ₁₁₀ of the X-ray crystal grain size of the hematite particles is within a specific range.

Next, a method for producing the spindle-shaped metallic magnetic particle powder containing iron as a main component according to the present invention will be described.

The heat reduction in the present invention is carried out by circulating a reducing gas such as hydrogen. Examples of the reducing gas include hydrogen and carbon monoxide, with hydrogen being preferred. The temperature range of heat reduction is preferably 400 to 600 ° C. Four
When the temperature is lower than 00 ° C, the reduction reaction proceeds slowly and requires a long time. On the other hand, if the temperature exceeds 600 ° C., the reduction reaction rapidly progresses, causing deformation of the particles and sintering between the particles.

The spindle-shaped metallic magnetic particle powder containing iron as a main component after heat reduction in the present invention is a well-known method, for example, a method of dipping in an organic solvent such as toluene and a spindle containing iron after reduction as a main component. After once replacing the atmosphere of the powdery metallic magnetic particles with an inert gas, gradually increasing the oxygen content of the inert gas and finally turning it into air to take out into the air by a method such as gradual oxidation. You can

Next, the spindle-shaped metal magnetic particle powder containing iron as a main component according to the present invention will be described.

The particles constituting the spindle-shaped metallic magnetic particle powder containing iron as a main component according to the present invention have an average major axis diameter of 0.05.
˜0.50 μm, preferably 0.06 to 0.3 μm. Its shape is spindle-shaped and the axial ratio (major axis diameter / minor axis diameter)
Is 9 or more, preferably 9.5 or more.

The spindle-shaped metal magnetic particle powder containing iron as a main component according to the present invention has a BET specific surface area of 30 to 80 m ² /
g, preferably 35 to 60 m ² / g.

The particles constituting the spindle-shaped metallic magnetic particle powder containing iron as a main component according to the present invention contain Co in an amount of 0.5 to 25 atom%, preferably 1.0 to 20 atom%, based on the total Fe. To do. Further, Al is contained in an amount of 0.5 to 15 atom%, preferably 1.0 to 10 atom% with respect to the total Fe. Further, the rare earth element is contained in an amount of 0.5 to 15 atom%, preferably 1.0 to 12.0 atom% with respect to the total Fe.

The spindle-shaped metal magnetic particle powder containing iron as a main component according to the present invention has a coercive force Hc of 95.49 to 175.0.
7 kA / m 2 , preferably 119.37-159.15 k
A / m . In addition, the saturation magnetization σs is 110 Am ² / k
It is g or more, preferably 120 Am ² / kg or more.

The spindle-shaped metallic magnetic particle powder containing iron as the main component according to the present invention has a coercive force distribution (SF
D) is 0.50 or less, preferably 0.45 or less.

[0075]

BEST MODE FOR CARRYING OUT THE INVENTION A typical embodiment of the present invention is as follows.

The average major axis diameter and the axial ratio of the particle powder are shown by the average of the numerical values measured from electron micrographs.

The specific surface area of the particle powder is "monosorb MS".
-11 "(manufactured by Kantachrome Co., Ltd.) was used, and the value was measured by the BET method.

X-ray crystal grain size (D in the case of hematite particles
₁₀₄ or D ₁₁₀ , D of metallic magnetic particles mainly composed of iron
₁₁₀ ) is the crystal grain size measured by X-ray diffractometry, and is the (104) crystal plane or (1
10) Crystal face, (11) of metallic magnetic particles containing iron as a main component
0) It shows the thickness of crystal grains in the direction perpendicular to each of the crystal planes, and is the value calculated from the diffraction peak curve for each crystal plane using the Scherrer's formula below. .

D ₁₀₄ or D ₁₁₀ = Kλ / β cos θ where β = half width of true diffraction peak (radian unit) in which the machine width due to the apparatus is corrected K = Scherrer constant (= 0.9) λ = X-ray Wavelength (Fe Kα ray 0.1935 nm) θ = diffraction angle (corresponding to the diffraction peaks of the (104) plane and the (110) plane)

The magnetic characteristics of the metallic magnetic particle powder containing iron as a main component were measured by using an "oscillating sample magnetometer VSM-3S-15" (manufactured by Toei Industry Co., Ltd.) and an external magnetic field of 795.8 kA / m.
It was measured at.

The amount of Co, the amount of Al, and the content of other metal elements in the spindle-shaped hematite particle powder and the spindle-shaped metallic magnetic particle powder containing iron as the main component are determined by "inductively coupled plasma emission spectroscopy analyzer SPS4000" (Seiko Denshi). Industry Co., Ltd.
Manufactured) was used.

The sheet-like sample piece contains 100 cc of the following components.
Then, the magnetic paint prepared by mixing and dispersing in a polybin of No. 1 at the following ratio with a paint shaker (manufactured by Red Devil Co.) for 8 hours was applied on a polyethylene terephthalate film having a thickness of 25 μm using an applicator to give a thickness of 50 μm.
To a thickness of 0.5 T and then dried in a magnetic field of 0.5 T. 3 mmφ steel ball 800 parts by weight Spindle-shaped metal magnetic particle powder containing iron as a main component 100 parts by weight Polyurethane resin having sodium sulfonate group 20 parts by weight Cyclohexanone 83.3 parts by weight Methyl ethyl ketone 83.3 parts by weight Toluene 83.3 parts by weight The magnetic properties of the obtained sheet-shaped sample piece were measured.

3.7 l of a 6.5N aqueous Na ₂ CO ₃ solution was introduced into a reactor under a non-oxidizing atmosphere by passing N ₂ gas.
30.3 l of 0.374 N NaOH aqueous solution (NaOH corresponds to 33.3 mol% with respect to the mixed alkali)
To give a mixed solution, and then Fe ²⁺ 1.5 mol /
13.3 l of ferrous sulfate aqueous solution containing 1 l (alkaline aqueous solution corresponds to 1.5 equivalents of ferrous sulfate) was heated to 47 ° C. and maintained for 130 minutes, and then the suspension. Cobalt sulphate 396g (total Fe in the reaction of seed crystal particle formation)
7% by atom in terms of Co (7% by atom in terms of Co) for all Fe in the seed crystal particle formation reaction and the growth reaction described later.
It corresponds to 7 atom%. )) Was dissolved in 1 l of pure water, added, and mixed with stirring. Further, after so-called aging, which is maintained for 170 minutes in a non-oxidizing atmosphere at pH 9.5, 70 l of air per minute was aerated for 60 hours at a temperature of 47 ° C. to produce spindle-shaped goethite seed crystal particle powder. Was generated.

The needle-shaped goethite seed crystal particle powder obtained by partially extracting a slurry containing the produced spindle-shaped goethite seed crystal particle powder, filtering, washing with water, and drying has an average major axis diameter of 0.27 μm and an axis. Ratio 13, BET specific surface area 81m ² / g
The dendritic particles were not mixed at all, and the particle size was uniform. Further, when the filtrate obtained by solid-liquid separation of the extracted slurry and the spindle-shaped goethite seed crystal particle powder were analyzed, Co ions were not detected in the filtrate. On the other hand, in the spindle-shaped goethite seed crystal particle powder, as Co, 7 atomic% in terms of Co with respect to all Fe in the seed crystal particles (Co with respect to all Fe in the goethite particles after the growth reaction of the seed crystal particles was performed. It corresponds to 4.7 atomic% in terms of conversion), and the added Co ions are 100%.
It was adsorbed.

Next, 1.85 l of a 6.5N aqueous Na ₂ CO ₃ solution was added to a suspension containing spindle-shaped goethite seed crystal particle powder in which the reactor was made a non-oxidizing atmosphere by passing N ₂ gas.
To a mixed solution of 2.0 L of 3.0 N NaOH aqueous solution (NaOH corresponds to 33.3 mol% with respect to mixed alkali) and 6.66 L of ferrous sulfate aqueous solution containing Fe ²⁺ 1.5 mol / l. (The alkaline aqueous solution corresponds to 1.5 equivalents to ferrous sulfate.), The temperature was raised to 47 ° C. and maintained for 20 minutes, and the pH was adjusted to 9.6 (pH at the time of the production reaction of goethite seed crystal particles). The difference with the value is 0.1.) Sodium aluminate (Al ₂ O ₃ content 19
(Wt%) 483 g (corresponding to 6.0 atom% in terms of Al with respect to total Fe) was added and mixed with stirring, and after aging,
A growth reaction of the spindle-shaped goethite seed crystal particles was carried out by bubbling 150 l / min of air at a temperature of 50 ° C. for 2.0 hours.

After completion of the growth reaction, the needle-shaped goethite particle powder obtained by filtering, washing with water, drying and pulverizing by a conventional method has a spindle shape, an average major axis diameter of 0.28 μm, and an axial ratio of 1
3.5, particles having a BET specific surface area of 95 m ² / g,
The dendritic particles were not mixed at all, and the particle size was uniform. In addition, Co is converted to Co for all Fe.
7 atomic% is contained, and Al is 6.0 in terms of Al with respect to all Fe.
It was contained at atomic%.

An amount of press cake corresponding to 2500 g (25.1 mol as Fe) of the spindle-shaped goethite particle powder which had been separated by filtration and washed with water was suspended in 40 l of water. The pH of the suspension at this time was 7.9. Then, (corresponding to 3.0 atomic% of Al with respect to the total Fe in the goethite particles in the powder.) The _{Al (NO 3) 3 · 9H} 2 O in the suspension 281.5g stirring added to 10 min After that, 2 mol /
375.5 ml of an aqueous solution of neodymium nitrate (corresponding to 3.0 atom% as Nd with respect to all Fe in the goethite particle powder) was added and stirred for 10 minutes.

Then, pure water was added while adjusting the pH to 9.5 by adding an aqueous solution of sodium hydroxide, and the total amount was adjusted to 50.
After stirring for 10 minutes, the mixture was filtered with a filter press, washed with water, passed through a molded plate having a diameter of 4 mm and dried to obtain a goethite particle powder coated with an Al compound and an Nd compound. The content of Co in the obtained goethite particle powder was 4.7 atomic% based on the total Fe, the content of Al was 9.0 atomic% relative to the total Fe, and the content of Nd was based on the total Fe. It was 3.0 atom%.

400 g of the spindle-shaped goethite particle powder coated with the Al compound and the Nd compound was 770 ° C. in air.
To obtain a spindle-shaped hematite particle powder coated with an Al compound and an Nd compound.

The spindle-shaped hematite particle powder thus obtained had an average major axis diameter of 0.25 μm, an axial ratio of 12.6, a BET specific surface area of 41.1 m ² / g, and an X-ray crystal grain size D ₁₀₄ of 1.
2.8nm, D ₁₁₀ is 25.7nm, the ratio D
₁₀₄ / D ₁₁₀ is 0.50, and the content of Co in the particles is 4.7 atomic% with respect to the total Fe.
The content of Fe was 9.0 atomic% with respect to the total Fe, and the content of Nd was 3.0 atomic% with respect to the total Fe.

100 g of the spindle-shaped hematite particle powder coated with the Al compound and the Nd compound was put into a fixed-bed reducing device having an inner diameter of 72 mm, and 35 l of H ₂ gas was passed through for reduction at a reducing temperature of 500 ° C.

The metal magnetic particle powder containing iron, which contains Co, Al, and Nd as a main component, obtained by reduction, is initially ventilated with nitrogen only so as not to cause rapid oxidation when taken out into the air. After that, a mixed gas of air and nitrogen was used, and a stable oxide film was formed on the surface while increasing the ratio of air with time.

The obtained iron-based metal magnetic particle powder containing Co, Al and Nd had an average major axis diameter of 0.1.
7 μm, axial ratio 10.5, BET specific surface area 43.8 m ²
/ G, an X-ray crystal grain size of D ₁₁₀ was 15.5 nm, and the particles were spindle-shaped and had a uniform grain size and few dendritic particles. Further, the Co content in the particles is 4.7 atomic% with respect to the total Fe, the Al content is 9.0 atomic% with respect to the total Fe, and the Nd content is 3. It was 0 atomic%. The magnetic properties of this metallic magnetic particle powder are as follows: coercive force Hc is 133.69 kA / m , saturation magnetization σs is 144.9 Am ² / kg , and squareness ratio (σr / σ).
s) is 0.518, and the sheet characteristic is that the sheet Hc is
It was 128.12 kA / m 2 , the sheet squareness ratio (Br / Bm) was 0.855, and the SFD was 0.450.

[0094]

In the past, various metal salts have been tried to be added in order to improve the shape and the like of goethite particles as a starting material for powdered metal magnetic particles containing iron as a main component. Among them, Co is known to have a function of forming a solid solution with iron when it is made into metal magnetic particle powder, increasing the magnetization, and increasing the coercive force Hc thereof. Further, it is known that Al contributes to prevention of sintering when it is made into metal magnetic particles and is excellent in shape retention.

However, in the formation reaction of goethite particles, when Co is dissolved in solid solution, fine particles are obtained and the particle size in the minor axis direction of the particles is small, so that the axial ratio is appropriately large. It is known that particles are obtained. On the other hand, since it is extremely finely divided, it is difficult to obtain a material suitable for use. Further, it is known that Al has a crystal growth control effect and the axial ratio greatly varies depending on the addition timing and the addition amount. For example, if an Al compound is added during the formation of goethite particles, the axial ratio may be reduced. Is expected. The present inventor has found that the axial ratio is most reduced when the reaction for producing goethite particles is performed while Al compounds are present in the presence of Co as divalent ions.

Therefore, as a result of extensive studies, the present inventor separated the formation reaction of goethite particles into a seed crystal formation reaction and a growth reaction, and made Co seed particles having an appropriate effect of improving the axial ratio. In the growth reaction which is added during the production reaction of, Co is dissolved in the goethite seed crystal particles, and the ferrous salt aqueous solution and the mixed alkaline aqueous solution are further added, Co is not present in the solution, By adding Al having a sintering preventing effect and allowing Al to exist only during the growth reaction,
It was found that it is possible to prepare particles having the axial ratio required for the seed crystal particle formation reaction, and to obtain spindle-shaped goethite particles having a large axial ratio of the seed crystal particles and an appropriate particle shape even in the growth reaction.

By using as a starting material a powder composed of spindle-shaped goethite particles in which Co is dissolved in the goethite seed particles of the seed crystal portion and Al is dissolved in the goethite layer of the surface layer portion, Mainly iron, which has a uniform particle size, is not mixed with dendritic particles, has an appropriate particle shape and a large axial ratio, and has a high coercive force and an excellent coercive force distribution. It is possible to obtain a spindle-shaped metal magnetic particle powder as a component.

Further, as a result of various investigations, the present inventor carried out a sintering prevention treatment on the spindle-shaped goethite particle powder in advance using a sintering inhibitor of a compound of a rare earth element, and then carried out the sintering prevention treatment. When the ratio D ₁₀₄ / D ₁₁₀ of the rare earth element content of the spindle-shaped hematite particles obtained by dehydrating the spindle-shaped goethite particle powder and the X-ray crystal grain diameter within a specific range, heat reduction is performed thereafter. The inventors have found that the SFD (coercive force distribution), which is a sheet characteristic of the metal magnetic particle powder obtained by performing the test, is good, and completed the present invention.

That is, as shown in the examples described later, when a rare earth element is used as a sintering inhibitor to be processed into spindle-shaped goethite particle powder, it can be obtained by appropriately selecting the heating dehydration temperature. The ratio D ₁₀₄ / D ₁₁₀ of the X-ray crystal grain size of the spindle-shaped hematite particles can be set within a specific range, whereby the sheet properties of the iron-based metal magnetic particle powder obtained by heat reduction can be obtained. A certain SFD (coercive force distribution) could be improved. On the other hand, as shown in Comparative Examples below, even if a compound of a rare earth element is used as a sintering inhibitor, if the ratio D ₁₀₄ / D ₁₁₀ of the X-ray crystal grain size of the hematite particles is not within a specific range, it is subjected to heat reduction. The SFD (coercive force distribution) which is the sheet property of the obtained iron-based metal magnetic particle powder is not sufficient.

[0100]

EXAMPLES Next, examples and comparative examples will be given.

Examples 1 to 7 and Comparative Examples 1 to 5 <Production of spindle-shaped goethite particle powders> Examples 1 to 7 and Comparative Examples 1 to 5 Table 2 shows various characteristics of the goethite seed crystal particles obtained by various extractions under various conditions as shown in Table 1. Further, spindle-shaped goethite particle powder was obtained in the same manner as in the embodiment of the present invention, except that various conditions for the growth reaction of the goethite seed crystal particles were changed as shown in Table 3. Table 4 shows various properties of the obtained spindle-shaped goethite particle powder.

[0102]

[Table 1]

[0103]

[Table 2]

[0104]

[Table 3]

[0105]

[Table 4]

<Production of Spindle-shaped Hematite Particle Powder> Examples 1 to 7 and Comparative Examples 1 to 5 Type of spindle-shaped goethite particle powder as a precursor, type and addition amount of coating used for sintering prevention treatment, heating Other than changing the dehydration temperature and the temperature of the subsequent heat treatment variously,
Spindle-shaped hematite particles were obtained in the same manner as in the embodiment. Table 5 shows the conditions and various characteristics of the obtained spindle-shaped hematite particles.

The total Fe of the rare earth elements in the spindle-shaped hematite particles obtained in the above-mentioned embodiments, examples and comparative examples.
Ratio of content x (atomic%) to X-ray crystal grain size to D ₁₀₄
The relationship with / D ₁₁₀ is ○ in the above-mentioned embodiment and example,
A comparative example is shown by ● in FIG. Here, the straight line A is 0.5
D ₁₀₄ / D ₁₁₀ = 0.500-0 in the case of ≦ x ≦ 10.
03 × x, and the straight line A ′ is D ₁₀₄ / D ₁₁₀ = 0.20 when 10 <x ≦ 15. The straight line B is 0.5 ≦
D ₁₀₄ / D ₁₁₀ = 0.665-0.0 when x ≦ 10
3 × x and the straight line B ′ is D when 10 <x ≦ 15
₁₀₄ / D ₁₁₀ = 0.365. The value of the ratio D ₁₀₄ / D ₁₁₀ of the X-ray crystal grain size of the particles constituting the spindle-shaped hematite particle powder according to the present invention is in the range of 0.20 to 0.65, preferably the straight line in FIG. A, straight line B, straight line A ',
It is within the range surrounded by the straight line B ′, x = 0.5 and x = 15.

[0108]

[Table 5]

<Production of Metallic Magnetic Particle Powder Containing Iron as Main Component> Examples 1 to 7 and Comparative Examples 1 to 5 of the present invention except that the type of particles to be treated and the reduction temperature in the heating reduction step were variously changed. Metal magnetic particle powder containing iron as a main component was obtained in the same manner as in the embodiment. Table 6 shows the reducing conditions at this time and various characteristics of the obtained metal magnetic particle powder containing iron as a main component.

[0110]

[Table 6]

[0111]

The spindle-shaped hematite particle powder according to the present invention has a uniform particle size and does not contain dendritic particles.
Consisting of particles with proper particle shape and axial ratio,
Is also effective by adding the rare earth element and Al together.
It is suitable because of the balance between sintering prevention and grain growth.
X-ray crystal grain size D ₁₀₄ and D
The ratio of ₁₁₀ , D ₁₀₄ / D ₁₁₀ is 0.20 to 0.65
To produce a spindle-shaped hematite particle powder within the range of
You can The spindle-shaped metallic magnetic particle powder containing iron as a main component, which is obtained by using the spindle-shaped hematite particle powder as a starting material, has a uniform particle size and does not contain dendritic particles, as shown in the above Examples. Moreover, since it is composed of particles having an appropriate particle shape and an axial ratio, it has a high coercive force and an excellent coercive force distribution, and has high recording density, high sensitivity, and high output as a magnetic particle powder. It is suitable.

[Brief description of drawings]

FIG. 1 is a ratio D of the content (atomic%) of the compound of the rare earth element contained in the spindle-shaped hematite particles of the embodiment of the present invention, the example and the comparative example to the total Fe as a rare earth element and the X-ray crystal grain size. _It shows the relationship with ₁₀₄ / D ₁₁₀ .

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI // C01G 49/00 H01F 1/06 L (58) Fields investigated (Int.Cl. ⁷ , DB name) B22F 1/00 B22F 9/22 G11B 5/62-5/82 H01F 1/00-1/375 C01G 49/00-49/08

Claims (2)

(57) [Claims] 1. Spindle-shaped particles having an average major axis diameter of 0.05 to 1.0 μm, wherein a compound of a rare earth element is contained on the particle surface as a rare earth element in an amount of 0.5 to 15 atomic% with respect to all Fe. In addition, it is composed of a hematite seed crystal portion and a hematite surface layer portion, the seed crystal portion contains Co in an amount of 0.5 to 25 atomic% with respect to the total Fe, and the surface layer portion has A.
0.5 to 15 atomic% with respect to the total Fe,
Moreover, the ratio of the X-ray crystal grain size D ₁₀₄ to D ₁₁₀ , D ₁₀₄
/ D ₁₁₀ obtained by using a fusiform hematite particle powder composed of hematite particles having a range of 0.20 to 0.65
Particles having an average major axis diameter of 0.05 to 0.5 μm
And the rare earth element is 0.5 to 15
% Of Co, 0.5 to 25 atomic% of Co based on total Fe
0.5 to 15 atoms containing Al and total Al
%, Consisting of metallic magnetic particles containing iron as the main component
Spindle-shaped metallic magnetic particles containing iron as a main component
Powder. 2. An aqueous suspension containing a ferrous iron-containing precipitate obtained by reacting a mixed alkaline aqueous solution of an alkaline carbonate aqueous solution and an alkaline hydroxide aqueous solution with a ferrous salt aqueous solution under a non-oxidizing atmosphere. After aging, an oxygen-containing gas was passed through the water suspension to generate spindle-shaped goethite seed crystal particles, and the water suspension containing the seed crystal particles was treated with an alkali carbonate and an alkali hydroxide. A new mixed alkaline aqueous solution and ferrous salt aqueous solution are added and mixed, and an oxygen-containing gas is aerated, and a goethite layer is grown on the particle surface of the spindle-shaped goethite seed crystal particles to form spindle-shaped goethite particles. And treating the surface of the spindle-shaped goethite particles with a sintering inhibitor, followed by heating and dehydration to obtain spindle-shaped hematite particles, in the reaction of generating the seed crystal particles, a ferrous iron salt aqueous solution, Including iron A water suspension containing a precipitate, a water suspension containing a ferrous iron-containing precipitate that was being aged before the start of the oxidation reaction, or a water suspension that was being used in the formation reaction, was added as Co. 5-25 atomic% of a Co compound is added, and at the time of the growth reaction of the goethite layer, each alkaline aqueous solution, ferrous iron salt aqueous solution, spindle-shaped goethite seed crystal particles and ferrous iron before the start of the oxidation reaction are added. In the water suspension containing the contained precipitate or the water suspension during the growth reaction,
0.5 to 15 atomic% of the Al compound is added, and further, a compound of a rare earth element is added as the sintering inhibitor to the total Fe in an amount of 0.5 to 15 atomic%.
Spindle performing the thermal dehydration in the range of 400 to 850 ° C.
-Shaped hematite particle powder was obtained, and then the spindle-shaped hematite particles were obtained.
Particle powder in reducing gas within the range of 400-600 ° C
Spindle composed mainly of iron characterized by being heated and reduced with
For producing powdery magnetic metal particles.