JPH11130439A - Fusiform goethite particle powder and its production, fusiform hematite particle powder and its production and fusiform metallic magnetic particle powder consisting essentially of iron and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fusiform goethite particle powder, a fusiform hematite particle powder and a fusiform metallic magnetic particle powder. SOLUTION: In the formation of the fusiform goethite particle by aging a water suspension containing a ferrous salt-containing precipitate obtained by allowing a mixed alkali aq. solution of an alkali carbonate aq. solution with an alkali hydroxide aq. solution to react with a ferrous salt aq. solution, passing the oxygen-containing gas to form a fusiform goethite seed crystal particle, passing the oxygen-containing gas through the water suspension containing the seed crystal particle to grow a goethite layer on the surface of the seed crystal particle, the fusiform goethite particle powder having Co existing ratio of 50:50 to 95: 5 and powder of Al existing only on the surface layer part is obtained by adding 10-45 atom% Co compound at the time of forming, performing an oxidation reaction in the range of 30-80% of total Fe<2+> , making the space velocity of an oxygen-containing gas at the time of growing >=2 times that at the time of forming and adding 5-20 atom% Al compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a spindle-shaped goethite particle powder, a spindle-shaped hematite particle powder, and a spindle-shaped goethite particle powder which are fine particles and have a good size distribution (standard deviation / average major axis diameter). It has high coercive force, excellent powder coercive force distribution (SFDr), high saturation magnetization value and excellent oxidation stability obtained by using spindle-shaped hematite particles as a starting material, and has good dispersibility in binder resin. The present invention relates to a spindle-shaped metal magnetic particle powder containing iron as a main component and having a good squareness ratio (Br / Bm) in a sheet due to goodness.

[0002]

2. Description of the Related Art In recent years, magnetic recording / reproducing devices for audio, video, and computers have become increasingly compact and lightweight, long-time recording, high-density recording, or increased storage capacity. Demands for higher performance and higher density recording of magnetic tapes and magnetic disks as recording media are increasing more and more.

[0003] That is, the magnetic recording medium is required to have high image quality, high output characteristics, and especially improvement in frequency characteristics.
Improvements in the residual magnetic flux density Br and high coercive force have been demanded.

[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 magnetic force and large saturation magnetization. Digital audio tape (DAT), 8 mm video tape, Hi
-8 tape and video floppy, further used for high-definition W-VHS tape and other magnetic recording media,
Recently, a digital recording type DVC system has been put to practical use. However, it is strongly desired to further improve the properties of these metal magnetic particle powders containing iron as a main component.

[0005] Regarding the relationship between the characteristics of the magnetic recording medium and the characteristics of the magnetic particle powder used, it is generally required that the magnetic particles be fine particles and have a good size distribution in order to achieve high density recording. Is done. Also, in order to obtain high image quality as a video magnetic recording medium, it is necessary that the magnetic recording medium has a high coercive force Hc and a high residual magnetic flux density Br. In order to increase the coercive force Hc of the magnetic recording medium and increase the residual magnetic flux density Br, the coercive force Hc of the magnetic particle powder is as high as possible, and the powder coercive force distribution (SFDr)
And a high saturation magnetization.

In order to increase the output of a magnetic recording medium,
FIG. 1 of JP-A-63-26821 shows the relationship between the SFD measured for the above magnetic disk and the recording / reproducing output. 1, the relationship between the recording and reproduction output becomes a straight line, which indicates that the recording and reproduction 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.
The following S. F. D. is necessary. "
S. of magnetic recording medium F. D. (Switching F
field distribution), that is, the coercive force distribution of the sheet is required to be small.
It is required that the magnetic particles have a good size distribution of the particle size and that no dendritic particles are present.

The metal magnetic particles containing iron as a main component have a very high surface activity as the particles become finer, and the oxidation reaction proceeds even in air due to oxygen, resulting in a significant decrease in magnetic properties. It is not possible to obtain the desired metal magnetic particle powder mainly composed of iron having high coercive force and high saturation magnetization. Therefore, metal magnetic particle powders containing iron as a main component and having excellent oxidation stability are required.

As described above, the particles are fine, have a good size distribution, do not contain dendritic particles, and
Iron-based metal magnetic particles having high coercive force, excellent powder coercive force distribution (SFDr), large saturation magnetization and excellent oxidation stability are currently in the most demanding place. is there. On the other hand, when the metal magnetic particles containing iron as the main component are made finer, and when the medium becomes a medium with a higher saturation magnetization, kneading with a binder in an organic solvent, in the process of dispersion, the attractive force between the particles is reduced. An increase or an increase in magnetic cohesion easily causes problems such as deterioration of dispersibility, and as a result, the magnetic properties of the medium, particularly the squareness ratio (Br / Bm), are likely to be inferior. Is desired.

Generally, metal magnetic particle powder containing iron as a main component is prepared by adding goethite particles as a starting material, hematite particles obtained by heating and dehydrating the goethite particles, or dispersing a foreign metal other than iron into each of the above particles. The particles are obtained by heat-treating particles and the like in a non-reducing atmosphere, if necessary, and then reducing them by heating in a reducing gas atmosphere. Accordingly, it is known that iron-based metal magnetic particle powder similarly inherits the shape of goethite particle powder, which is a starting material thereof, and that iron-based metal In obtaining the particle powder, it is necessary to use goethite particle powder which is fine particles, has a good size distribution, does not contain dendritic particles, and has an appropriate particle shape. It is necessary that the size distribution and the like be retained and inherited in the subsequent heat treatment step.

Conventionally, various methods have been known as methods for producing goethite particle powder, which is a starting material for metal magnetic particle powder containing iron as a main component. In particular, when a metal magnetic particle powder is used as Co, which has an effect of improving magnetic properties, and when a metal magnetic particle powder is used, a metal compound such as Al which has an excellent shape retention property has an effect of preventing sintering. 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 oxidation reaction by passing an oxygen-containing gas at 50 ° C. A method of producing acicular goethite particles by conducting a growth reaction (Japanese Unexamined Patent Publication (Kokai) No. 7-1310).
An oxygen-containing gas is passed through a suspension containing FeCO ₃ obtained by reacting an aqueous ferrous salt solution to which an acidic salt compound of Al is added with an aqueous alkali carbonate solution to which a basic salt compound of Al is added to oxidize the suspension. A method of producing spindle-shaped goethite particles by performing a reaction (Japanese Patent Laid-Open No. 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 the goethite seed crystal particles obtained by hydrolysis are dispersed in an aqueous ferric salt solution in which an Al compound is present. 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)
No. 6902), a suspension containing a ferrous-containing precipitate obtained by reacting an aqueous solution of an alkali carbonate and an aqueous solution of ferrous salt is aged in a non-oxidizing atmosphere. In producing goethite particles having a spindle shape by performing an oxidation reaction by passing an oxygen-containing gas through the
In any one of the aqueous solution of ferrous salt, the suspension containing the ferrous-containing precipitate, and the suspension containing the aged ferrous-containing precipitate before the oxidation reaction, , C
o compound in the aqueous solution of ferrous salt.
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 aqueous solution of one or more compounds selected from rare earth elements such as Ca, Mg, Ba, Sr and Nd is added to Fe ²⁺ in the aqueous ferrous salt solution in terms of each element. (JP-A-7-126704), so that the amount is in the range of 0.1 to 5.0 mol% with
In the formation of goethite particles, a method of adding Si, a rare earth element, or the like in advance, then adding a Co compound, and adding an Al compound at a maximum of 6 atomic% during the oxidation reaction (Japanese Patent Laid-Open No. 8-165501, Kaihei 8-165117
Publication), a ferrous salt is neutralized with an alkali hydroxide and / or an alkali carbonate, and a rare earth element and an alkaline earth element are doped near the surface of the iron oxyhydroxide in the middle of the oxidation reaction. Al and / or
Or a method of depositing a hydroxide of Si (Japanese Patent Laid-Open No. 6-14 / 1994)
No. 0222) is known.

Regarding the oxidation rate during the reaction of forming goethite, a production method for producing goethite particles with a gas flow velocity within a specific range (JP-A-59-23922) is disclosed. A method for producing goethite particles by oxidizing at a specific oxidation rate and oxidizing the remaining Fe at an oxidation rate larger than the initial oxidation rate and twice or less (Japanese Patent Application Laid-Open No. 1-212232).
Etc. are known.

The above publications also describe metal magnetic particle powders containing iron as a main component and obtained using each goethite particle powder described in each publication as a starting material.

[0013]

The fine particles have a good size distribution, do not contain dendritic particles, have an appropriate particle shape, and have a high coercive force and excellent powder. It has a coercive force distribution (SFDr), a large saturation magnetization value and excellent oxidation stability, and has good squareness ratio (Br / Bm) in the sheet due to good dispersibility in the binder resin. The spindle-shaped metal magnetic particle powder as a main component is the most demanded at present, but the metal magnetic particle powder obtained when each goethite particle powder described in each of the above publications is used as a starting material has these various properties. It is hard to be satisfied with the above.

That is, according to the production method described in Japanese Patent Application Laid-Open No. Hei 7-11310, acicular goethite particles in which Co atoms are present in goethite particles are generated, but dendritic particles are mixed. Also, speaking of the particle size, it is hard to say that the particles have a uniform particle size. Also, the amount of Co, Al
It is difficult to obtain a large saturation magnetization and a high coercive force depending on the amount and its location in the goethite particles.

In the case of the production method described in the above-mentioned Japanese Patent Application Laid-Open No. 6-228614, goethite particles which do not contain dendritic particles and have a uniform particle size are devised by a method of adding Al. However, the Al content is at most 6 atom% with respect to Fe, and the surface of the goethite particles is coated with a Co compound, so that a large saturation magnetization and a high coercive force are obtained. Is difficult to obtain.

In the production method described in JP-A-7-126704, 1 to 8 atomic% of a Co compound is added.
Al compound is added at most 5 atomic% in the middle of the oxidation reaction, and it is difficult to obtain iron-based metal magnetic particle powder having high coercive force, large saturation magnetization and excellent oxidation stability. It is.

In the manufacturing methods described in JP-A-8-165501 and JP-A-8-165117,
The addition amount of Al is at most 6 atomic%, and it is difficult to obtain iron-based metal magnetic particle powder having high coercive force, large saturation magnetization and excellent oxidation stability. It is considered that the dispersibility becomes poor. In addition, when adding an Al compound in the middle of an oxidation reaction, it is necessary to continue under the same conditions as the initial oxidation reaction conditions.

The production method described in the above-mentioned JP-A-58-176902 uses trivalent iron as a starting material, the reaction mechanism is hydrolysis instead of oxidation, and the secondary reaction is one-step.
Hydrothermal treatment is performed at a high temperature exceeding 00 ° C.

In the production method described in the above-mentioned Japanese Patent Application Laid-Open No. 6-140222, metal magnetic particles having a large saturation magnetization and excellent oxidation stability cannot be obtained because Co is not added.

The above-mentioned Japanese Patent Application Laid-Open No. 59-23922 discloses that
There is no description about dissolving elements such as Al and Co which are effective in preventing sintering in goethite particles.
Further, there is no description about increasing the superficial velocity of the oxygen-containing gas during the oxidation.

In the production method described in Japanese Patent Application Laid-Open No. 1-212232, 30 mol% or more of the total iron is oxidized for the purpose of industrially producing in a short time, and then the oxidation rate is increased. It is still not enough that it is twice or less.
Further, this publication does not disclose that Co and Al, which are effective for magnetic properties when sintering is prevented and metal magnetic particles are used, are contained in goethite particles.

The iron-based metal magnetic particle powder obtained using the goethite particle powder obtained by the production methods described in the above-mentioned publications as starting materials is a fine particle and is not said to have a good size distribution. It is difficult to say that it does not contain dendritic particles. Further, it has a high coercive force, an excellent powder coercive force distribution (SFDr), a large saturation magnetization value, and an excellent oxidation stability. It is hard to say that the squareness ratio (Br / Bm) in the sheet is good due to the good dispersibility in the resin.

Accordingly, the present invention provides a spindle-shaped goethite particle powder which is fine particles, has a good size distribution, does not contain dendritic particles, and has an appropriate particle shape. High coercive force, excellent powder coercive force distribution (SFDr), starting from spindle-shaped goethite particles
A spindle-shaped metal mainly composed of iron, which has a large saturation magnetization value and excellent oxidation stability, and has a good squareness ratio (Br / Bm) in a sheet due to good dispersibility in a binder resin. It is a technical object to obtain magnetic particle powder.

[0024]

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

That is, according to the present invention, Co is added to all Fe
Mean major axis diameter 0.05-0.18 containing 0-45 atom% and containing 5-20 atom% of Al with respect to all Fe
μm spindle-shaped goethite particles, wherein the spindle-shaped goethite particles consist of a seed crystal part and a surface layer part, and the ratio of the seed crystal part to the surface layer part is 30:70 to 8
0:20, the abundance ratio of Co in the seed crystal part and the surface layer part is 50:50 to 95: 5, and Al is a particle present only in the surface layer part. Is a spindle-shaped goethite particle powder.

The present invention also provides a non-oxidizing aqueous suspension containing a ferrous-containing precipitate obtained by reacting a mixed alkali aqueous solution of an aqueous alkali carbonate solution and an aqueous alkali hydroxide solution with an aqueous ferrous salt solution. After aging in a sexual atmosphere,
An oxygen-containing gas is passed through the aqueous suspension to generate spindle-shaped goethite seed particles by an oxidation reaction, and then the oxygen-containing gas in the aqueous suspension containing the seed particles and the ferrous-containing precipitate. When a gas is passed and a goethite layer is grown on the particle surface of the seed crystal particles by an oxidation reaction to produce spindle-shaped goethite particles, during the generation of the seed crystal particles, during the ripening before the start of the oxidation reaction, 10 to 45 atomic% in terms of Co with respect to the total Fe in the aqueous suspension containing the ferrous-containing precipitate of
Of the total Fe ²⁺ by adding a Co compound of
0%, and during the growth of the goethite layer, the superficial velocity of aeration of the oxygen-containing gas into the aqueous suspension containing the seed crystal particles and the ferrous-containing precipitate was adjusted to the seed value. Producing a spindle-shaped goethite particle powder characterized in that the superficial velocity of aeration at the time of formation of the crystalline particles is twice or more and an Al compound of 5 to 20 atomic% in terms of Al is added to all Fe. It is.

In the present invention, the spindle-shaped goethite particles may be treated with a sintering inhibitor comprising a compound of a rare earth element, and then heat-treated at 400 to 850 ° C. in a non-reducing atmosphere. A method for producing spindle-shaped hematite particle powder characterized by the following.

The present invention also relates to a method of manufacturing a semiconductor device according to the present invention, which comprises 10 to 45 atomic% of Co based on the total Fe, 5 to 20 atomic% of Al based on the total Fe, and a rare earth element. A powder composed of spindle-shaped hematite particles having an average particle diameter of 0.05 to 0.17 μm containing 1 to 15 atomic% with respect to all Fe, wherein the spindle-shaped hematite particles are a seed crystal part, an intermediate layer part, and an outermost layer. And the ratio between the seed crystal portion and the intermediate layer portion is 30:70 to 80:20, and the ratio of Co in the seed crystal portion and the intermediate layer portion is 50:50 to 95: 5. There is a spindle-shaped hematite particle powder characterized in that Al is present only in the intermediate layer portion and rare earth elements are present only in the outermost layer portion.

The present invention also relates to a method for treating the spindle-shaped goethite particles with a sintering inhibitor comprising a compound of a rare earth element and then reducing the same by heating in a reducing gas atmosphere at a temperature of 400 to 700 ° C. This is a method for producing a spindle-shaped metal magnetic particle powder containing iron as a main component.

In the present invention, the spindle-shaped goethite particles are treated with a sintering inhibitor comprising a compound of a rare earth element, and then heat-treated at 400 to 850 ° C. in a non-reducing atmosphere. Continued, in a reducing gas atmosphere,
This is a method for producing spindle-shaped metal magnetic particles containing iron as a main component, which is reduced by heating in the range of 400 to 700 ° C.

The present invention also provides a spindle-shaped metal magnetic particle powder containing iron as a main component, wherein the spindle-shaped hematite particle powder is reduced by heating in a reducing gas atmosphere within a range of 400 to 700 ° C. It is a manufacturing method of.

The present invention also relates to a method for manufacturing a semiconductor device, comprising the following steps:
And iron having an average major axis diameter of 0.05 to 0.15 μm containing 5 to 20 atomic% of the total Fe and 1 to 15 atomic% of the rare earth element with respect to the total Fe. Spindle-shaped metal magnetic particle powder containing iron as a main component, characterized in that the powder is made of metal magnetic particles.

The configuration of the present invention will be described in more detail as follows. First, the spindle-shaped goethite particles according to the present invention will be described.

The particles constituting the spindle-shaped goethite particles according to the present invention have an average major axis diameter of 0.05 to 0.18 μm,
Preferably, it is 0.05 to 0.16 μm, and its size distribution (standard deviation / average major axis diameter) is 0.24 or less.
The average minor axis diameter is from 0.010 to 0.025 μm, preferably from 0.010 to 0.023 μm. The shape is a spindle shape and the axial ratio (major axis diameter / minor axis diameter) is 4 to 8.

Spindle-shaped goethite particles according to The present invention, BET specific surface area of 100 to 250 m ² / g, preferably from 120~230m ² / g.

The particles constituting the spindle-shaped goethite particles according to the present invention contain 10 to 45 atomic% of Co with respect to all Fe and 5 to 20 atomic% of Al with respect to all Fe.

The particles constituting the spindle-shaped goethite particles according to the present invention are formed of a seed crystal part and a surface part. The seed portion is defined as Al ferrous salt among the added ferrous salts.
It refers to the goethite seed crystal particle portion formed by oxidation until the compound is added. Specifically, it is a portion having a weight ratio determined by the oxidation rate of Fe ²⁺ , preferably 30 to 80% by weight, more preferably 40 to 70% by weight from the inner center of the seed crystal particles. Co contained in the goethite seed particles in the seed portion is 50 to 9 with respect to the total Co.
5%, preferably 60 to 90%. If it is less than 50%, the effect of improving the magnetic properties cannot be obtained. If it exceeds 95%, it becomes difficult to maintain the shape at the time of reduction, and the magnetic properties are reduced.

The above-mentioned surface layer portion refers to Al in the growth reaction.
It refers to a goethite layer that has grown on the surface of the goethite seed particles after the compound has been added. Specifically, 20 to 70% by weight, preferably 30 to 6% by weight from the outermost surface of the particles.
0% by weight. The content of Co in the goethite layer in the surface layer is 5 to 50%, preferably 10 to 40%, based on the total Co. Al is present only in the surface layer, and 5 to 20 atomic% based on the total Fe. Preferably it is 6 to 15 atomic%, more preferably 7 to 12 atomic%. 5 atomic%
If it is less than the above, no sintering preventing effect can be obtained. 20 atomic%
When the value exceeds, the magnetic properties, particularly the saturation magnetization, decrease.

Next, a method for producing the spindle-shaped goethite particles according to the present invention will be described.

The particles constituting the spindle-shaped goethite particles according to the present invention are obtained by first forming spindle-shaped goethite seed crystal particles and then growing a goethite layer on the surface of the seed crystal particles.

The spindle-shaped goethite seed particles are an aqueous suspension containing a ferrous-containing precipitate obtained by reacting a mixed alkali aqueous solution of an aqueous alkali carbonate solution and an aqueous alkali hydroxide solution with an aqueous ferrous salt solution. After aging in a non-oxidizing atmosphere, an oxygen-containing gas is passed through the aqueous suspension to produce spindle-shaped goethite seed crystal particles by an oxidation reaction. The aqueous suspension containing the iron-containing precipitate was added to the total Fe in an amount of 10 to 4 in terms of Co.
It is obtained by adding a 5 atomic% Co compound.

It is preferable that the aging is carried out in a temperature range of usually 40 to 80 ° C. for the suspension under a non-oxidizing atmosphere. When the temperature is lower than 40 ° C., the axial ratio is small and it is difficult to obtain a sufficient aging effect. When the temperature is higher than 80 ° C., magnetite may be mixed. The aging time is 3
0-300 minutes. If the time is less than 30 minutes, the axial ratio cannot be sufficiently increased. Although it may be longer than 300 minutes, it does not mean that the time is longer than necessary.

To make 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 production reaction of the spindle-shaped goethite seed crystal particles, an aqueous ferrous salt solution may be an aqueous ferrous sulfate solution, an aqueous ferrous chloride solution, or the like.

The mixed alkaline aqueous solution used in the production reaction of the spindle-shaped goethite seed particles is obtained by mixing an alkaline carbonate aqueous solution and an alkaline hydroxide aqueous solution. In this case, as a mixing ratio (expressed as% in specified conversion), the ratio of the aqueous alkali hydroxide solution is 10 to 40% (normal conversion%), and preferably 15 to 35% (normal conversion%). If it is less than 10%, a sufficient axial ratio cannot be obtained, and if it exceeds 40%, particulate magnetite may be mixed.

As the aqueous alkali carbonate solution, an aqueous sodium carbonate solution, an aqueous potassium carbonate solution, an aqueous ammonium carbonate solution and the like can be used, and as the aqueous alkali hydroxide solution, sodium hydroxide, potassium hydroxide and the like can be used.

The amount of the mixed alkali aqueous solution used is 1.3 to 1.0 as an equivalent ratio to the total Fe in the ferrous salt aqueous solution.
3.5, preferably 1.5 to 2.5. If the ratio is less than 1.3, magnetite may be mixed.
If it exceeds 5, it is not industrially preferable.

The ferrous concentration after mixing the aqueous ferrous salt solution and the mixed aqueous alkaline solution is 0.1 to 1.0 mol / mol.
l, preferably 0.2 to 0.8 mol / l. 0.
If it is less than 1 mol / l, the yield is low and it is not industrial. If it exceeds 1.0 mol / l, the particle size distribution is undesirably large.

The pH value in the formation reaction of the spindle-shaped goethite seed particles is 8.0 to 11.5, preferably 8.
It is in the range of 5 to 11.0. When the pH is less than 8.0, a large amount of acid radicals are contained in the goethite particle powder and cannot be easily removed by washing. In this case, sintering of the particles is caused. If it exceeds 11.5, the desired high coercive force cannot be obtained when the metal magnetic particles are used.

The spindle-shaped goethite seed crystal particles are formed by an oxidation reaction in which an oxygen-containing gas (eg, air) is passed through the liquid. The superficial velocity of the oxygen-containing gas is 0.5
-3.5 cm / s, preferably 1.0-3.0 cm / s
It is. The superficial velocity is the amount of oxygen-containing gas permeated per unit cross-sectional area (it does not consider the bottom cross-sectional area of the column reactor, the hole diameter of the nest plate, and the number of holes), and the unit is cm / sec.
It is.

The temperature in the formation reaction of the spindle-shaped goethite seed crystal particles is usually set at 80 ° C.
It may be performed at a temperature of not more than ℃. If the temperature exceeds 80 ° C,
Magnetite may be mixed in the spindle-shaped goethite particles. Preferably it is in the range of 45 to 55 ° C.

In the formation reaction of the spindle-shaped goethite seed crystal particles, as the Co compound, cobalt sulfate, cobalt chloride, cobalt nitrate or the like can be used. Co
The compound is added to the suspension containing the ferrous-containing precipitate that has been aged before the oxidation reaction is performed.

The amount of the Co compound added is 10 to 4 with respect to the total Fe in the spindle-shaped goethite particles as the final product.
It is 5 atomic%, preferably 10 to 40 atomic%, more preferably 10 to 35 atomic%. If it is less than 10 atomic%, there is no effect of improving the magnetic properties of the metal magnetic particle powder, and if it exceeds 45 atomic%, the axial ratio decreases due to miniaturization.

PH in the growth reaction of the goethite layer
The value is between 8.0 and 11.5, preferably between 8.5 and 11.0.
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 by washing. It will cause the result. If it exceeds 11.5, the desired high coercive force cannot be obtained when the metal magnetic particles are used.

The growth reaction of the goethite layer is performed by an oxidation reaction in which an oxygen-containing gas (for example, air) is passed through the liquid. The superficial velocity of the oxygen-containing gas is set to be at least twice as high as that during the seed crystal particle formation reaction. Preferably 2-3.5
It is twice. If the ratio is less than twice, the viscosity of the water suspension increases when Al is added, growth in the short axis direction is promoted, and the axial ratio decreases. In addition, the superficial velocity is 1.0 to 7.0 cm /
s, preferably 2.0 to 6.0 cm / s.

The temperature in the growth reaction of the goethite layer may be usually at a temperature of 80 ° C. or less at which goethite particles are generated. When the temperature exceeds 80 ° C., magnetite may be mixed in the spindle-shaped goethite particles. Preferably it is in the range of 45 to 55 ° C.

In the growth reaction of the goethite layer, A
Examples of the compound include acid salts such as aluminum sulfate, aluminum chloride, and aluminum nitrate, and aluminates such as sodium aluminate, potassium aluminate, and ammonium aluminate.

The addition of the Al compound can be carried out at the same time as or after the aeration, with the superficial velocity of the oxygen-containing gas being twice or more that of the seed crystal particle formation reaction. Preferably, the addition is performed at the same time as the aeration in which the superficial velocity is twice or more. Further, when the Al compound is dividedly added or added continuously or intermittently, the sufficient effect of the present invention cannot be obtained.

The addition amount of the Al compound is 5 to 20 with respect to the total Fe in the spindle-shaped goethite particles as the final product.
Atomic%, preferably 6 to 15 atomic%, more preferably 7 to 12 atomic%. If it is less than 5 atomic%, there is no sintering prevention effect, and if it exceeds 20 atomic%, particles other than goethite are generated, and the magnetic properties, particularly the saturation magnetization, are reduced.

Before the growth reaction of the goethite layer, aging may be performed in a non-oxidizing atmosphere before the superficial velocity of the oxygen-containing gas is increased twice or more. Various conditions for the aging can be performed under the same conditions as the aging performed before the seed crystal particle formation reaction. In the present invention,
In order to improve various properties of the spindle-shaped metal magnetic particles containing iron as a main component, an Mg compound usually added during the spindle-like goethite particle formation reaction is used during the seed crystal particle formation reaction or during the seed crystal particle growth. It may be added during the reaction.

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

The particles constituting the spindle-shaped hematite particles according to the present invention have an average major axis diameter of 0.05 to 0.17 μm.
m, preferably 0.05 to 0.15 μm, and the size distribution (standard deviation / average major axis diameter) is 0.22 or less.
The average minor axis diameter is from 0.010 to 0.025 μm, preferably from 0.010 to 0.023 μm. The shape is a spindle shape and the axial ratio (major axis diameter / minor axis diameter) is 4 to 8.

The spindle-shaped hematite particles according to the present invention have a BET specific surface area of 30 to 150 m ² / g, preferably 50 to 120 m ² / g.

In the particles constituting the spindle-shaped hematite particles according to the present invention, Co is 10 to 45 at%, preferably 10 to 40 at%, more preferably 1 to 40 at% based on the total Fe.
0 to 35 atomic%, and Al is 5 to 20
Atomic%, preferably 6 to 15 atomic%, more preferably 7 to 12 atomic%, and the content of the rare earth element is
The content is 1 to 15 at%, preferably 5 to 12 at%, and more preferably 5 to 10 at% with respect to all Fe.

The particles constituting the spindle-shaped hematite particles according to the present invention are composed of a seed crystal part, an intermediate layer part and an outermost layer part. The seed crystal part is the one in which the seed crystal part of the goethite particles is changed as it is, and preferably 30 to 80% by weight, more preferably 40 to 70% by weight from the inner center of the seed crystal particles.

The amount of Co contained in the hematite seed crystal particles in the seed crystal portion is 50 to 95%, preferably 6%, of the total Co.
0 to 90%. The intermediate layer part is the one in which the surface layer part of the goethite particles is changed as it is, preferably 20 to 70% by weight from the outermost surface of the particle surface excluding the outermost layer made of a rare earth compound, more preferably 30 to 60% by weight. Co contained in the hematite layer in the intermediate layer portion is 5 to 50% of the total Co,
Preferably, it is 10 to 40%, and Al is contained only in the intermediate layer portion, and is 5 to 20 at%, preferably 6 to 15 at%, more preferably 7 to 12 at% based on the total Fe. If it is less than 5 atomic%, no sintering preventing effect can be obtained. If it exceeds 20 atomic%, the magnetic properties, especially the saturation magnetization, will be reduced. The outermost layer portion is made of a rare earth compound. The content of the rare earth element contained in the outermost layer portion is 1 to 15 atomic%, preferably 5 to 1 atomic% based on the total Fe.
It is 2 atomic%, more preferably 5 to 10 atomic%. 1
If it is less than atomic%, no sintering preventing effect can be obtained. 1
If it exceeds 5 atomic%, the saturation magnetization decreases.

Next, a method for producing the spindle-shaped hematite particles according to the present invention will be described.

In the present invention, the surface of the spindle-shaped goethite particles is coated with a sintering inhibitor to prevent sintering of the obtained spindle-shaped goethite particles prior to the heat dehydration treatment.

As the sintering inhibitor, a compound of a rare earth element is used.

As the rare earth element compound, one or more compounds such as scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, and samarium are preferable, and the rare earth element chlorides, sulfates, and nitrates are preferred. Etc. can be used. The treatment method may be either a dry method or a wet method, preferably a wet coating treatment. The amount used is preferably 1 to 15 relative to the total Fe.
Atomic%, more preferably 4 to 12 atomic%. If the number is less than 1 atom, the effect of preventing sintering is not sufficient, and the powder coercive force distribution (SFDr) deteriorates when the metal magnetic particles are used. If it exceeds 15 atomic%, the saturation magnetization value will be low.

In order to improve the sintering prevention effect, other elements such as Al, Si, B, Ca, Mg,
One or more compounds of elements selected from Ba, Sr and the like may be used. These compounds not only have the effect of preventing sintering but also have the function of controlling the reduction rate, and thus may be used in combination as necessary. The total amount used in this case is preferably 1 to 15 atomic% as the total amount of the compound of the rare earth element used as the sintering inhibitor with respect to all Fe of the spindle-shaped goethite particles. A small amount is not enough to prevent sintering,
If the amount is too large, the saturation magnetization decreases when the metal magnetic particles are used. Therefore, the optimum amount may be appropriately selected depending on the type of the combination.

By coating in advance with the above-mentioned sintering inhibitor or the like, sintering between the particles and the particles is prevented, and spindle-shaped hematite particles which retain and inherit the particle shape and axis ratio of the spindle-shaped goethite particles. A powder can be obtained, which makes it easier to obtain spindle-shaped metal magnetic particle powders that retain the above-mentioned shape and the like and are individually independent and mainly composed of iron.

The spindle-shaped goethite particles coated with the above-mentioned sintering inhibitor are subjected to a 400-
Heat treatment is performed within the range of 850 ° C. to obtain spindle-shaped hematite particles.

The hematite after the heat treatment may be washed to remove impurity salts such as Na ₂ SO ₄ .
In this case, it is preferable to remove unnecessary impurities by performing washing under conditions where the coated sintering inhibitor does not elute. Specifically, the pH can be increased to remove the cationic impurities, and the pH can be reduced to remove the anionic impurities, whereby the washing can be performed more efficiently.

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

In the present invention, the spindle-like goethite particle powder according to the present invention is subjected to sintering prevention treatment with the above-mentioned sintering inhibitor and directly heated and reduced, or the spindle-like hematite particle powder according to the present invention is used. Can be used to obtain spindle-shaped metal magnetic particles containing iron as a main component. After the spindle-shaped goethite particles according to the present invention have been subjected to the sintering prevention treatment with the sintering inhibitor, the heat treatment in a non-reducing atmosphere and the heat reduction in a reducing atmosphere are successively performed to reduce iron. Spindle-shaped metal magnetic particle powder containing as a main component can also be obtained.

The spindle-shaped goethite particle powder coated with the sintering inhibitor can be directly reduced to obtain the desired spindle-shaped metal magnetic particle powder containing iron as a main component. In order to control the powder characteristics and the shape, it is preferable to perform a heat treatment in a non-reducing gas atmosphere in advance by a conventional method before the reduction.

The non-reducing gas atmosphere can be one or more gas flows selected from air, oxygen gas, nitrogen gas and the like. Heat treatment temperature is 400-850 ° C
The heat treatment temperature is more preferably appropriately selected according to the type of the compound used for the coating treatment of the spindle-shaped goethite particles. When the temperature exceeds 850 ° C., 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 4
00-700 degreeC is preferable. When the temperature is lower than 400 ° C., the progress of the reduction reaction is slow, and a long time is required. Also, 7
If the temperature exceeds 00 ° C., the reduction reaction proceeds rapidly, causing deformation of the particles and sintering between the particles.

The spindle-shaped magnetic metal particles containing iron as a main component after heat reduction according to the present invention can be obtained by a known method, for example, a method of immersing the particles in an organic solvent such as toluene, and a method of using a spindle containing iron as a main component after reduction. Method of once replacing the atmosphere of the metallic magnetic particle powder with an inert gas and then gradually increasing the oxygen content in the inert gas to finally produce air, or using a mixed gas of oxygen and water vapor Then, it can be taken out into the air by a method such as slow oxidation.

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

The particles constituting the spindle-shaped metal magnetic particles mainly composed of iron according to the present invention have an average major axis diameter of 0.05.
0.15 μm, preferably 0.05 to 0.13 μm, and the size distribution (standard deviation / average major axis diameter) is 0.20.
It is as follows. The average short axis diameter is 0.010 to 0.02.
It is 2 μm, preferably 0.010 to 0.020 μm. The shape is spindle shape and the axial ratio (major axis diameter / minor axis diameter)
Is 4 to 7.

The spindle-shaped metal magnetic particles containing iron as a main component according to the present invention have a BET specific surface area of 35 to 65 m ² /
g, preferably 40 to 60 m ² / g.

The particles constituting the spindle-shaped metal magnetic particles containing iron as a main component according to the present invention contain Co in an amount of 10 to 45 atomic%, preferably 10 to 40 atomic%, more preferably 10 to 40 atomic% based on the total Fe. ３５35 atomic%. Further, Al is contained in an amount of 5 to 20 atomic%, preferably 6 to 15 atomic%, more preferably 7 to 12 atomic%, based on the total Fe. Further, the rare earth element is contained at 1 to 15 at%, preferably 4 to 12 at% with respect to the total Fe.

The spindle-shaped metal magnetic particles containing iron as a main component according to the present invention have a coercive force Hc of 1800 to 2500O.
e, preferably 1900 to 2500 Oe. Also,
The saturation magnetization s is 110 to 160 emu / g, preferably 120 to 160 emu / g. The powder coercive force distribution SFDr obtained from the remanence (DC erase residual magnetization) curve is 0.72 or less.

The X-ray crystal grain size D ₁₁₀ of the particles constituting the spindle-shaped metal magnetic particles containing iron as a main component according to the present invention is:
12.0-17.0 nm, preferably 13.0-16.
0 nm.

The spindle-shaped metal magnetic powder containing iron as a main component according to the present invention has a saturation magnetization σs after one week of an accelerated aging test in an environment of a temperature of 60 ° C. and a relative humidity of 90%.
Is not more than 15% as an absolute value, preferably not more than 10%.

The spindle-shaped metal magnetic particles mainly composed of iron according to the present invention have a squareness ratio (Br / B
m) is at least 0.85, preferably at least 0.86;
The sheet SFD of the coercive force distribution is 0.44 or less, preferably 0.42 or less.

[0089]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A typical embodiment of the present invention is as follows.

The average major axis diameter and the axial ratio of the particles constituting the particle powder were all indicated by the average values of the numerical values measured from electron micrographs.

The specific surface area of the particle powder is “Monosorb MS”.
-11 "(manufactured by Cantachrome Co., Ltd.) and the value measured by the BET method.

The X-ray crystal grain size (D _{110 of} metal magnetic particles containing iron as a main component) is determined by changing the size of the crystal particles measured by the X-ray diffraction method to ( 110)
It represents the thickness of a crystal grain in a direction perpendicular to each of the crystal planes, and is represented by a value calculated from the diffraction peak curve for each crystal plane using the following Scherrer equation.

D ₁₁₀ = Kλ / βcos θ where β = half-width (in radians) of a true diffraction peak corrected for the machine width due to the apparatus K = Scherrer constant (= 0.9) λ = wavelength of X-ray ( Fe Kα ray 0.1935 nm) θ = diffraction angle (corresponding to the diffraction peak on the (110) plane)

The magnetic properties of the metal magnetic particles containing iron as a main component were measured using a “vibrating sample magnetometer VSM-3S-15” (manufactured by Toei Kogyo Co., Ltd.) under an external magnetic field of 10 kOe.

The powder SFDr was measured using a torque / vibration sample magnetometer (manufactured by Digital Measurement Systems). The measurement was performed as follows. First, the capsule is filled with metal magnetic particle powder containing iron as a main component, and an external magnetic field of 10 kOe is applied (the initial application direction is set to a positive direction). After measuring (0), an external magnetic field of 100 Oe is applied in the opposite direction (negative direction) to that previously applied, and then the remanent magnetization σr (100) is measured with the magnetic field set to zero. Next, after applying an external magnetic field of 10 kOe in the positive direction again, measuring the remanent magnetization σr (0) with the magnetic field being zero, applying an external magnetic field of 200 Oe in the negative direction, and then setting the magnetic field to zero and setting the remanent magnetization σr ( 200). Less than,
After applying an external magnetic field of 10 kOe in the positive direction, the magnitude of the magnetic field applied in the negative direction is increased in steps of 100 Oe, and the residual magnetization σr (100 × n) is measured, and plotted according to the magnitude of the external magnetic field in the negative direction. The obtained remanence (DC erase residual magnetization) curve is obtained, and the value of the external magnetic field at which the residual magnetization becomes 0 is obtained by interpolation, and is defined as Hr. The half width of the peak of the differential curve of the remanence curve was ΔHr, and was calculated by the following equation. SFDr = ΔHr / Hr

The amount of Co, the amount of Al, the amount of rare earth elements and the contents of other metal elements in the spindle-shaped goethite particle powder and the spindle-shaped metal magnetic particle powder containing iron as a main component are determined by the inductively coupled plasma emission spectrometer SPS4000. (Manufactured by Seiko Electronic Industry Co., Ltd.).

[0097] The following components were used in 100 cc
The magnetic paint prepared by putting the mixture in the following ratio in a polybin at the following ratio and mixing and dispersing for 8 hours with a paint shaker (manufactured by Red Devil Co., Ltd.) was applied to a polyethylene terephthalate film having a thickness of 25 μm using an applicator.
And then dried in a magnetic field of 5 kGauss. 3 mmφ steel ball 800 parts by weight Spindle-shaped metal magnetic particle powder mainly composed of iron 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.

Δσs, which is the evaluation of the oxidation stability of the saturation magnetization value σs of the powder, and ΔBm, which is the evaluation of the oxidation stability of the saturation magnetic flux density Bm of the sheet, are a temperature of 60 ° C. and a relative humidity of 90%.
After the accelerated aging test in which the powder or sheet-shaped sample piece is allowed to stand for one week in a constant temperature bath, the saturation magnetization value of the powder and the saturated magnetic flux density of the sheet were measured, respectively, and σs and Bm and the accelerated aging before the test were started. The difference (absolute value) between σs ′ and Bm ′ one week after the test was calculated as Δσs and ΔBm, respectively.

30 l of a mixed alkali aqueous solution containing 25 mol of sodium carbonate and 20 mol of an aqueous sodium hydroxide solution (sodium hydroxide corresponds to 28.6 mol% in terms of a specified conversion with respect to the mixed alkali) are charged into a bubble column. The temperature is adjusted to 47 ° C. while passing nitrogen gas at a superficial velocity of 2.21 cm / s. Next, 20 mo as Fe ²⁺
20 l of an aqueous ferrous sulfate solution containing 1 l (a mixed alkaline aqueous solution with respect to ferrous sulfate corresponds to 1.75 equivalents in terms of a specified conversion) in a bubble column, aged for 30 minutes, and then cooled with Co.
⁴ l of an aqueous solution of cobalt sulfate containing 4.0 mol of ²⁺ (total Fe
Corresponds to 20 atomic% in terms of Co. )
After further aging for 4 hours and 30 minutes, the air was superficially superposed at a speed of 1.
Ventilation was performed at 32 cm / s to carry out an oxidation reaction until the oxidation rate of Fe ²⁺ reached 40%, thereby producing goethite seed crystal particles. In addition,
A water suspension containing goethite seed particles oxidized to an oxidation rate of Fe ²⁺ of 40% is fractionated, quickly washed with a dilute acetic acid aqueous solution, filtered, and washed with water. Analysis showed that Fe was 49.54.
% Of Co and 6.43% by weight of Co.

Next, the air flow rate was adjusted to the superficial velocity of 3.31.
cm / s, and then 1 liter of an aluminum sulfate aqueous solution containing 2.4 mol of Al ³⁺ (1
It corresponds to 2 atomic%. ) Was added at a rate of 3 ml / sec or less to carry out an oxidation reaction, followed by washing with a filter press to an electric conductivity of 60 μS to obtain a press cake.

A goethite particle powder obtained by drying and pulverizing a part of the cake by a conventional method has a particle shape shown in FIG.
As shown in the transmission electron micrograph of the above, has a BET specific surface area of 180.3 m ² / g, an average major axis diameter of 0.130 μm, and σ (standard deviation) of 0.0251.
μm, size distribution (standard deviation / major axis diameter) is 0.193,
It has an average minor axis diameter of 0.0173 μm, an axial ratio of 7.5, has no dendritic particles, and has an Fe content of 44.5.
Wt%, Co 9.39 wt%, Al 2.58 wt%
By comparison with the analysis values of goethite seed particles,
The Co content of the seed crystal portion is 12.3 atomic% based on the total Fe.
And the abundance in the seed portion is 6 with respect to all Co.
The content of Co was 1.5%, and the Co content of the whole particles was 20 atomic% based on the total Fe, and the Al content was 12 atomic% based on the total Fe. Al was present only in the surface layer.

Then, a press cake containing 1000 g of spindle-shaped goethite particles (7.88 mol as Fe) obtained here was sufficiently dispersed in 40 l of water, and then dispersed.
2 l of an aqueous yttrium nitrate solution containing 45 g of yttrium nitrate hexahydrate (corresponding to 8 atomic% as Y with respect to all Fe in the goethite particle powder) was added, and the mixture was stirred.
Then, an aqueous solution of sodium carbonate having a concentration of 25.0% by weight was added as a precipitant to adjust the pH to 9.5, and then washed with a filter press, and the obtained press cake was molded using a compression molding machine on a molding plate having a pore size of 3 mm. Extruded to 120
The resultant was dried at ℃ to obtain a goethite particle powder coated with the Y compound. The content of Co in the obtained goethite particles was 20 atomic% with respect to the total Fe, the content of Al was 12 atomic% with respect to the total Fe, and the content of Y was 8 atomic% with respect to the total Fe. there were. Al is present only in the intermediate layer, and Y
Was present only in the outermost layer.

The spindle-shaped goethite particles coated with the Y compound were heated and dehydrated in air at 600 ° C. to obtain spindle-shaped hematite particles comprising spindle-shaped hematite particles having an outermost layer of the Y compound.

The obtained spindle-shaped hematite particles had an average major axis diameter of 0.121 μm, a (standard deviation) of 0.0223 μm, as shown in the transmission electron micrograph of FIG.
The size distribution (standard deviation / average major axis diameter) is 0.184, the average minor axis diameter is 0.0166 μm, the axial ratio is 7.3, the BET specific surface area is 87.3 m ² / g, and the Co content in the particles is Was 20 atomic% based on the total Fe, the Al content was 12 atomic% based on the total Fe, and the Y content was 8 atomic% based on the total Fe.

[0105] After the Y spindle-shaped hematite particles 100g having an outermost layer made of a compound was placed in a fixed bed reduction apparatus having an inner diameter of 72 mm, bubbled with H ₂ gas per minute 35l, and thermally reduced in a reducing temperature 600 ° C. After switching to nitrogen gas and cooling to 80 ° C., the oxygen partial pressure was gradually increased while passing water vapor to form a stable oxide film on the particle surface at the same ratio as air.

The obtained metal magnetic particle powder containing iron as a main component containing Co, Al and Y has an average major axis diameter of 0.108 μm as shown in the transmission electron micrograph of FIG.
σ (standard deviation) 0.0171 μm, size distribution (standard deviation / major axis diameter) 0.158, average minor axis diameter 0.0158 μm
m, axial ratio 6.8, BET specific surface area 47.0 m ² / g,
X-ray crystallite size of D ₁₁₀ consists particles 15.2 nm,
It had a spindle shape, uniform particle size, and few dendritic particles. Further, the content of Co in the particles was 2 to the total Fe.
0 atomic%, the content of Al is 12 atomic% with respect to all Fe,
The content of Y was 8 atomic% based on the total Fe. Also,
The magnetic properties of the metal magnetic particle powder are as follows.
10 Oe and a saturation magnetization σs of 141.0
The emu / g, the squareness ratio (σr / σs) is 0.535, the SFD of the powder is 0.710, and the oxidation stability Δσs of the saturation magnetization is 8.6% (actual measurement value -8.6%) as an absolute value. The sheet characteristics were such that the sheet Hc was 2365 Oe and the sheet squareness ratio (Br / Bm, where Bm was 3901 G) was 0.87.
0, sheet SFD was 0.395, and ΔBm was 6.0%.

[0107]

Conventionally, in order to improve the shape and the like of goethite particles as a starting material of metal magnetic particles containing iron as a main component, various metal salts have been added. Among them, it is known that Co forms a solid solution with iron when it is made into metal magnetic particles, increases the magnetization, increases its coercive force Hc, and contributes to oxidation stability. ing. Al contributes to prevention of sintering when used as metal magnetic particles, has excellent shape retention, and has a bond having a functional group of sodium sulfonate, which is generally used in a medium using metal magnetic particles. It is known that the dispersibility in the resin is improved.

Regarding the existence state of Co, when the metal magnetic particles are introduced into the inside of the goethite particles, a larger saturation magnetization is obtained, and when the existence state of Al is coated on the surface of the goethite particles, the coercive force is increased. It is known that the solid solution in the surface layer of the particles improves the shape retention and oxidation stability because the magnetic properties of the particles decrease.

In addition, in the reaction for forming goethite particles, when alkali carbonate and alkali hydroxide are used together and Co is dissolved, fine particles are obtained and the particle diameter in the minor axis direction is small. Therefore, it is known that goethite particles having an appropriately large axial ratio can be obtained. It is also known that Al has a crystal growth control effect, and the axial ratio greatly differs depending on the timing and amount of addition. However, there has been no known method of fine particles, having an appropriate axial ratio, excellent particle size distribution, and effectively containing a large amount of Co and Al in goethite particles.

The present inventor has conducted intensive studies, and as a result, has separated the formation reaction of goethite particles into a seed crystal generation reaction and a growth reaction, and has a Co fine particle-forming effect and an effect of appropriately improving the axial ratio. Is added at the time of ripening before the formation reaction of seed crystal particles,
Co is solid-dissolved in the goethite seed crystal particles with a concentration gradient higher than that of the surface layer portion. Further, in the growth reaction of the goethite seed crystal particles, the superficial velocity of the oxygen-containing gas is set to be twice or more that in the generation reaction of the seed crystal particles. At the same time as the ventilation, or by adding Al having an effect of preventing sintering thereafter, even if a large amount of Al is added, the axial ratio is not reduced, and the particles are fine particles, and the axial ratio is appropriately maintained. It has been found that a spindle-shaped goethite particle powder composed of goethite particles having excellent distribution and containing a large amount of Co and Al can be effectively obtained.

The inventor of the present invention has been able to obtain spindle-shaped goethite particle powder comprising goethite particles containing a large amount of Co and Al because the addition of Al during the growth reaction of seed crystal particles has a long axis. Although the crystal growth in the direction is moderately suppressed, when a large amount of Al is added, the growth in the short axis direction occurs excessively due to the increase in the viscosity of the aqueous suspension containing the seed crystal particles. Although the ratio decreased and the particle size distribution deteriorated, there were problems such as the superficial velocity of the oxygen-containing gas being twice or more that of the seed crystal particle formation reaction, so that the water suspension containing the seed crystal particles was It is considered that the effect was obtained by obtaining the viscosity reducing effect of the liquid and forming the surface layer portion more uniformly on the surface of the seed crystal particles.

Further, as a result of various studies, the present inventor has found that when the goethite particle powder is dehydrated and reduced to obtain a metal magnetic particle powder containing iron as a main component, the spindle-shaped goethite particle powder is treated. By using a rare earth element compound as an anti-caking agent, it has excellent particle size distribution, dendritic particles are not mixed, has an appropriate particle shape and axial ratio, and has high coercive force and excellent powder. Spindle-shaped metal magnetic particles containing iron as a main component and having both coercive force distribution (powder SFDr), large saturation magnetization and excellent oxidation stability can be obtained. The obtained metal magnetic particles and sulfonic acid can be obtained. When a sheet is formed with a binder resin having sodium as a functional group, the squareness ratio (Br
/ Bm) and the sheet SFD (coercive force distribution) can be improved, and the present invention has been completed.

[0113]

Next, examples and comparative examples will be described.

Examples 1 to 7 and Comparative Examples 1 to 5 <Production of Spindle-shaped Goethite Particle Powder> Examples 1 to 7 and Comparative Examples 1 to 5 Spindle-shaped goethite particles were obtained in the same manner as in the embodiment of the present invention except that the conditions of and the growth reaction were variously changed as shown in Table 1. Table 2 shows properties of the obtained spindle-shaped goethite particles. FIG. 4 shows an electron micrograph showing the particle morphology of the goethite particle powder obtained in Example 2.

Comparative Example 1 Except that the superficial velocity of the oxygen-containing gas during the growth reaction of the goethite seed crystal particles at the time of the formation reaction of the goethite particles was 1.32 cm / sec, which was the same as that at the time of the formation reaction of the seed crystal particles. A production reaction of goethite particle powder was performed in the same manner as in the embodiment of the present invention. In the obtained goethite particle powder, as shown in the transmission electron micrograph of FIG. 4, the short axis grew, and as a result, the axial ratio was reduced and the size distribution was poor.

Comparative Example 2 The superficial velocity of the oxygen-containing gas during the growth reaction of the goethite seed crystal particles during the reaction for the formation of goethite particles was 1.98 cm / sec, which is 1.5 times that during the reaction for forming the seed crystals. A production reaction of goethite particle powder was carried out in the same manner as in the embodiment of the present invention except for the above. In the obtained goethite particle powder, the short axis grew, and as a result, the axial ratio was reduced, and the size distribution was poor.

[0117] Comparative Example 3 Goethite addition time of oxidation rate of 100% of Fe ²⁺ of Al compound added in the growth reaction during production reaction of the particles, i.e., the embodiment except that the state of Fe ²⁺ unreacted absent A goethite particle powder generation reaction was performed in the same manner as in the example. In the obtained goethite particle powder, the major axis grew and the axial ratio was improved, but the size distribution was poor.

Comparative Example 4 The reaction of forming goethite particles was carried out under the conditions shown in Table 1 with the addition amount of the Co compound being 5 atomic% with respect to Fe and the addition amount of the Al compound being 3 atomic% with respect to Fe. Was. In the obtained goethite particle powder, the major axis grew and the axial ratio was improved, but the size distribution was poor.

Then, 2.4 mol of aluminum sulfate
(Al / Fe equivalent to 8 atomic%) was added, and air was passed at a superficial velocity of 4.42 cm / sec to perform a growth reaction of seed crystal particles. In the obtained goethite particle powder, the major axis grew and the axial ratio improved to 10, but the size distribution was insufficient.

[0120]

[Table 1]

[0121]

[Table 2]

<Production of Spindle-Shaped Hematite Particle Powder> Examples 1 to 6, Comparative Examples 1 to 5 The type of spindle-shaped goethite particle powder as a precursor, the type and amount of coating used for sintering prevention treatment, heating Dehydration temperature, except for changing the temperature of the subsequent heat treatment,
Spindle-shaped hematite particle powder was obtained in the same manner as in the embodiment. Table 3 shows the conditions and various properties of the obtained spindle-shaped hematite particles. FIG. 5 shows a transmission electron micrograph showing the particle morphology of the hematite particle powder obtained in Example 2.

[0123]

[Table 3]

<Production of Metal Magnetic Particle Powder Containing Iron as Main Component> Examples 1 to 7, Comparative Examples 1 to 5 Types of particles to be treated, type and amount of coating used for sintering prevention treatment, heating temperature A metal magnetic particle powder containing iron as a main component was obtained in the same manner as in the embodiment of the present invention except that the reduction temperature in the heat reduction step was variously changed. Table 4 shows the reduction conditions and various properties of the obtained metal magnetic particle powder containing iron as a main component. FIG. 6 is a transmission electron micrograph showing the particle morphology of the metal magnetic particle powder containing iron as a main component obtained in Example 2. FIG. 8 shows a transmission electron micrograph showing the particle morphology of the metal magnetic particle powder containing iron as a main component obtained in Comparative Example 1.

Example 7 Spindle-shaped goethite particles were subjected to a sintering prevention treatment, and then directly reduced by heating at 600 ° C. in hydrogen to obtain spindle-shaped metal magnetic particles containing iron as a main component. Table 4 shows the manufacturing conditions and various properties of the obtained iron-based metal magnetic particle powder.

[0126]

[Table 4]

[0127]

The spindle-shaped goethite particle powder and spindle-shaped hematite particle powder according to the present invention are fine particles, have a good size distribution, do not contain dendritic particles, and have an appropriate particle shape. Since the spindle-shaped goethite particle powder or the spindle-shaped hematite particle powder obtained from the particles having the iron-based spindle-shaped metal magnetic particle powder obtained using the spindle-shaped hematite particle powder as a starting material, as described in the above Examples, Since the particles are fine and have a good size distribution, do not contain dendritic particles, and are composed of particles having an appropriate particle shape, a high coercive force and an excellent powder coercive force distribution ( SFDr) has a high saturation magnetization value and excellent oxidation stability, and has a high recording density because of its good squareness ratio (Br / Bm) in the sheet due to its good dispersibility in the binder resin. , High Degrees, are suitable as magnetic particles for high output.

[Brief description of the drawings]

FIG. 1 is a transmission electron micrograph (300) showing the particle shape of spindle-shaped goethite particles obtained in an embodiment of the invention.
00)

FIG. 2 is a transmission electron micrograph (300) showing the particle shape of spindle-shaped hematite particles obtained in the embodiment of the invention.
00)

FIG. 3 is a transmission electron micrograph (× 30000) showing the particle shape of spindle-shaped metal magnetic particles containing iron as a main component and obtained in an embodiment of the present invention.

FIG. 4 is a transmission electron micrograph (× 30000) showing the particle shape of spindle-shaped goethite particles obtained in Example 2.

FIG. 5 is a transmission electron micrograph (× 30000) showing the particle shape of spindle-shaped hematite particles obtained in Example 2.

FIG. 6 is a transmission electron micrograph (× 30000) showing the particle shape of spindle-shaped metal magnetic particles containing iron as a main component and obtained in Example 2.

FIG. 7 is a transmission electron micrograph (× 30000) showing the particle shape of spindle-shaped goethite particles obtained in Comparative Example 1.

FIG. 8 is a transmission electron micrograph (× 30000) showing the particle shape of spindle-shaped metal magnetic particles containing iron as a main component and obtained in Comparative Example 1.

Claims (8)

[Claims] 1. Co is present in an amount of 10 to 45 atomic% with respect to all Fe.
5-20 atomic% of Al with respect to all Fe
A powder comprising spindle-shaped goethite particles having an average major axis diameter of 0.05 to 0.18 μm, wherein the spindle-shaped goethite particles comprise a seed crystal part and a surface layer part. The ratio is 30:70 to 80:20, and the existence ratio of Co in the seed crystal portion and the surface layer portion is 5
0:50 to 95: 5, and spindle-shaped goethite particle powder, wherein Al is present only in the surface layer portion. 2. An aqueous suspension containing a ferrous-containing precipitate obtained by reacting a mixed alkali aqueous solution of an aqueous alkali carbonate solution and an aqueous alkali hydroxide solution with an aqueous ferrous salt solution under a non-oxidizing atmosphere. After aging, an oxygen-containing gas is passed through the aqueous suspension to generate spindle-shaped goethite seed crystal particles by an oxidation reaction, and then an aqueous suspension containing the seed crystal particles and a ferrous precipitate. When an oxygen-containing gas is passed through the liquid to grow a goethite layer on the particle surface of the seed crystal particles by an oxidation reaction to produce spindle-shaped goethite particles, the oxidation reaction starts when the seed crystal particles are generated. The aqueous suspension containing the ferrous-containing precipitate during the previous aging was added to the total F
The oxidation reaction is performed in the range of 30 to 80% of the total Fe ²⁺ by adding a Co compound of 10 to 45 atomic% in terms of Co with respect to e, and the seed crystal particles are grown during the growth of the goethite layer. The superficial velocity of aeration of the oxygen-containing gas into the aqueous suspension containing the ferrite-containing precipitate and the ferrous precipitate is set to be at least twice the superficial velocity of the aeration at the time of generation of the seed crystal particles, and 2. The method for producing spindle-shaped goethite particles according to claim 1, wherein 5 to 20 atomic% of an Al compound in terms of Al is added. 3. After the spindle-shaped goethite particles according to claim 1 are treated with a sintering inhibitor comprising a compound of a rare earth element, heat treatment is performed in a non-reducing atmosphere at a temperature in the range of 400 to 850 ° C. A method for producing spindle-shaped hematite particle powder, comprising: 4. C obtained by the production method according to claim 3.
Average particle size containing 10 to 45 atomic% of o with respect to all Fe, 5 to 20 atomic% of Al with respect to total Fe, and 1 to 15 atomic% of rare earth element with respect to total Fe A powder comprising spindle-shaped hematite particles of 0.05 to 0.17 μm, wherein the spindle-shaped hematite particles comprise a seed crystal part, an intermediate layer part, and an outermost layer part. A ratio of 30:70 to 80:20, an existence ratio of Co in the seed crystal portion and the intermediate layer portion of 50:50 to 95: 5, and Al existing only in the intermediate layer portion; A spindle-shaped hematite particle powder, wherein the rare earth element is a particle existing only in the outermost layer. 5. A method of treating the spindle-shaped goethite particle powder according to claim 1 with a sintering inhibitor comprising a compound of a rare earth element, followed by heat reduction at 400 to 700 ° C. in a reducing gas atmosphere. A method for producing spindle-shaped metal magnetic particles containing iron as a main component. 6. After treating the spindle-shaped goethite particles according to claim 1 with a sintering inhibitor comprising a compound of a rare earth element, a heat treatment is performed in a non-reducing atmosphere at a temperature of 400 to 850 ° C., Next, in a reducing gas atmosphere, 40
A method for producing spindle-shaped metal magnetic particles containing iron as a main component, wherein the powder is heated and reduced in a range of 0 to 700 ° C. 7. A spindle-shaped metal magnetic particle powder comprising iron as a main component, wherein the spindle-shaped hematite particle powder according to claim 4 is heat-reduced in a reducing gas atmosphere at a temperature of 400 to 700 ° C. Manufacturing method. 8. The composition according to claim 5, which contains Co in an amount of 10 to 45 at% based on the total Fe, Al in an amount of 5 to 20 at% based on the total Fe, and An average major axis diameter of 0.05 to 0.15 mainly composed of iron containing a rare earth element in an amount of 1 to 15 atomic% based on all Fe
A spindle-shaped metal magnetic particle powder containing iron as a main component, comprising metal magnetic particles of μm.