JPH0533018A - Production of iron-based acicular magnetic metal powder - Google Patents

Abstract

PURPOSE:To industrially produce iron-based acicular magnetic metal powder contg. no dendritic particles and having uniform particle size, high axial ratio (major axis size/minor axis size) and excellent coercive force distribution. CONSTITUTION:An aq. ferrous salt soln. is allowed to react with less than an equiv. of an aq. alkali soln. and oxygen-contg. gas is blown into the resulting soln. to form core particles of acicular goethite. An aq. alkali carbonate soln. is then added to the core particles-contg. soln. by an equiv. or more basing on the amt. of Fe<2+> in the soln. and oxygen-contg. gas is blown into the soln. to grow the core particles. Formed acicular goethite particles or acicular hematite particles obtd. by dehydrating the goethite particles by heating are reduced to obtain iron-based acicular magnetic metal powder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a uniform particle size, does not contain dendritic particles, has a large axial ratio (major axis diameter / minor axis diameter), and has a coercive force distribution. It is an object of the present invention to provide an acicular metal magnetic particle powder containing iron as a main component.

[0002]

2. Description of the Related Art In recent years, magnetic recording / reproducing devices for video and audio have become increasingly long-time recording, and have become smaller and lighter. 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 of the magnetic recording medium, the high output characteristics, especially the frequency characteristics. For that purpose, the residual magnetic flux density Br is improved, the coercive force is increased, and the dispersibility, filling property,
The smoothness of the tape surface is required to be improved, and the S / N ratio is required to be improved more and more.

Although these various characteristics of the magnetic recording medium have a close relationship with the magnetic particle powder used in the magnetic recording medium, in recent years, they have been kept higher than the conventional iron oxide magnetic particle powder. Needle-like metal magnetic particle powder containing iron as a main component having magnetic force and large saturation magnetization has attracted attention and is used in magnetic recording media such as digital audio tape (DAT), 8 mm video tape, Hi-8 tape and video floppy. Has been converted. However, further improvement in characteristics is strongly desired for these acicular metal magnetic particle powders 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, it is clear from the description on pages 82 to 105 of May 3, Nikkei Electronics (1976), that the video S / N ratio and the chroma S / N ratio are , Improvement of video frequency characteristics is required.

In order to improve the video S / N ratio and the chroma S / N ratio, it is necessary to improve the dispersibility of the magnetic particle powder in the vehicle, the orientation and the filling property in the coating film, and It is important to improve the surface smoothness of the magnetic recording medium.As such magnetic particle powder, the particle size is uniform, dendritic particles are not mixed, and the axial ratio (major axis diameter) / Minor axis diameter) is required to be large.

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. Currently, it is used for video floppy, DAT, 8 mm video, and Hi-8. The coercive force of the magnetic particle powder is 1300 Oe
About 1800 Oe is required. 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 (major axis diameter / minor axis diameter) 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
The field distribution is required to be small, and for this reason, the coercive force distribution width of the magnetic particle powder is required to be small.

The acicular metal magnetic particle powder containing iron as a main component is generally composed of goethite particles as a starting material, hematite particles obtained by heating and dehydrating the particles, or particles containing a different metal other than iron. It is obtained by heating and reducing in a reducing gas.

As described above, the particle size is uniform, dendritic particles are not mixed, and a large axial ratio (major axis diameter /
The acicular magnetic metal particle powder containing iron as the main component, which has a short axis diameter) and has an excellent coercive force distribution, is currently most demanded, and iron having such characteristics is required. In order to obtain the acicular magnetic metal particle powder as the main component, the starting material, goethite particle powder, has a uniform particle size and no dendritic particles are mixed, and a large axial ratio (long axis diameter / (Minor axis diameter) is required.

Conventionally, as a method of producing goethite particle powder as a starting material, a suspension containing ferrous hydroxide colloid obtained by adding an equivalent amount or more of an aqueous solution of alkali hydroxide to an aqueous solution of ferrous salt has a pH of 11. As described above, a method of forming needle-shaped goethite particles by carrying out an oxidation reaction by passing an oxygen-containing gas at a temperature of 80 ° C. or lower (Japanese Patent Publication No. 39-39
No. 5610), a suspension containing FeCO ₃ obtained by reacting an aqueous solution of ferrous salt and an aqueous solution of alkali carbonate is passed through an oxygen-containing gas to carry out an oxidation reaction to obtain spindle-shaped goethite particles. Method of generating
-80999) and a ferrous salt aqueous solution containing an equivalent amount or less of an aqueous solution of an alkali hydroxide or an aqueous solution of an alkali carbonate, and an oxygen-containing gas is added to a ferrous hydroxide colloid obtained by adding the ferrous hydroxide colloid or iron carbonate. Needle-shaped goethite core particles are generated by performing an oxidation reaction by aeration, and then, in a ferrous salt aqueous solution containing the needle-shaped goethite core particles, an equivalent amount or more based on the amount of Fe ^{2+ in} the ferrous salt aqueous solution. Method of growing the acicular goethite nucleus particles by adding an aqueous solution of alkali hydroxide and then aerating an oxygen-containing gas (Japanese Patent Publication No. 59-487).
66, JP-A-59-128293, JP-A-59-128294, and JP-A-59-128295.
Japanese Patent Laid-Open No. 60-21818) and the like are known.

[0011]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention Dendritic particles do not coexist evenly in particle size, and have a large axial ratio (major axis diameter / minor axis diameter) and excellent coercive force distribution. The acicular metal magnetic particle powder containing iron as a main component is currently most demanded, but in the case of the above-described method for producing the goethite particle powder as the starting material, the axial ratio (long axis (Diameter / minor axis diameter) is large, especially 10 or more needle-shaped goethite particles are generated, but dendritic particles are mixed,
In terms of particle size, it cannot be said that the particles have a uniform particle size.

In the case of the above-mentioned method, particles having a uniform particle size and having a spindle shape in which dendritic particles are not mixed are produced. On the other hand, the axial ratio (major axis diameter / minor axis) is used. Diameter)
Is about 7 at most, and there is a drawback that particles with a large axial ratio (major axis diameter / minor axis diameter) are difficult to be generated. In particular, this phenomenon becomes more remarkable as the major axis diameter of generated particles becomes smaller. There is a tendency. Various attempts have been made to increase the axial ratio (major axis diameter / minor axis diameter) of spindle-shaped goethite particles, but the method is at most about 17 to 18, which is not yet sufficient.

The above-mentioned method includes various characteristics of needle-shaped goethite particles obtained by the above-mentioned method,
That is, although the purpose is to improve the particle size, the axial ratio (major axis diameter / minor axis diameter), the presence or absence of dendritic particles, etc., goethite particle powders having sufficiently satisfactory properties have not yet been obtained.

The acicular metal magnetic particle powders containing iron as a main component and obtained from these acicular goethite particle powders as starting raw material particles are also uniform in particle size, do not contain dendritic particles, and are large. It is hard to say that it has an axial ratio (major axis diameter / minor axis diameter).

Therefore, according to the present invention, the particle size is uniform, the dendritic particles are not mixed, and the large axial ratio (major axis diameter / minor axis diameter) is provided, and the coercive force distribution is excellent. It is a technical subject to obtain acicular metal magnetic particle powder containing iron as a main component.

[0016]

The above technical problems can be achieved by the present invention as follows. That is, the present invention is obtained by reacting an aqueous solution of a ferrous salt with an aqueous solution of an alkali hydroxide or an aqueous solution of an alkali carbonate or an aqueous solution of an alkali hydroxide / alkali carbonate which is less than an equivalent to Fe ²⁺ in the aqueous solution of the ferrous salt. The ferrous hydroxide colloid or the iron-containing precipitate colloid is bubbled through the ferrous salt reaction solution containing the ferrous hydroxide colloid or the iron-containing precipitate colloid to oxidize the ferrous hydroxide colloid or the iron-containing precipitate colloid. After generating the goethite core particles, the ferrous salt reaction solution containing the needle-shaped goethite core particles or the ferrous salt reaction solution containing the needle-shaped goethite core particles was kept at a temperature of 75 ° C. or higher if necessary. After that, the reaction solution is cooled to 60 ° C or lower, or if necessary, the reaction solution is kept at 60 ° C or lower in a non-oxidizing atmosphere, or if necessary, the temperature is kept at 75 ° C or higher and then lowered to 60 ° C or lower, and then continued. , The reaction solution was kept under a non-oxidizing atmosphere, and passing an oxygen-containing gas after the addition of more equivalents of aqueous alkali carbonate solution to Fe ²⁺ in the reaction solution, the growth reaction of the acicular goethite nucleus particles To produce acicular goethite particles by performing, then acicular hematite particles obtained by heating and dehydrating the acicular goethite particles or the particles, or if necessary, the particle surface is a Ni compound, an Al compound, a Si compound, The goethite particles or the hematite particles coated with one or more metal compounds selected from P compounds, Co compounds, Mg compounds, B compounds and Zn compounds are heated and reduced in a reducing gas. This is a method for producing a needle-shaped metal magnetic particle powder containing iron as a main component, which comprises obtaining needle-shaped metal magnetic particles containing iron as a main component.

Next, various conditions for carrying out the method of the present invention will be described. As the aqueous ferrous salt solution used in the present invention, an aqueous ferrous sulfate solution, an aqueous ferrous chloride solution or the like can be used. As the alkali hydroxide aqueous solution used in the reaction for producing the acicular goethite particles of the present invention, a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, and the like, and as the alkali carbonate aqueous solution, a sodium carbonate aqueous solution, a potassium carbonate aqueous solution, ammonium carbonate, etc. Can be used.

The amount of the alkali hydroxide aqueous solution, the alkali carbonate aqueous solution, or the alkali hydroxide / alkali carbonate aqueous solution used is less than the equivalent amount to Fe ²⁺ in the ferrous salt aqueous solution. When the amount is equal to or more than the equivalent, goethite particles having an asymmetric particle size and mixed dendritic particles are obtained. Also,
Granular magnetite particles are mixed.

The amount of acicular goethite core particles in the present invention is 10 to 90 mol% with respect to the produced goethite particles.
Is preferred. If it is less than 10 mol%, the acicular goethite particles aimed at by the present invention cannot be obtained. If it exceeds 90 mol%, the ratio of iron carbonate to the acicular goethite nucleus particles decreases, so that the reaction becomes non-uniform and the obtained goethite particles have a non-uniform particle size.

In the present invention, the ferrous salt reaction solution containing acicular goethite core particles is kept at a temperature of 75 ° C. or higher and then cooled to 60 ° C. or lower, or if necessary, in a non-oxidizing atmosphere. A needle-like metal containing iron as a main component, which is obtained by keeping the temperature at 60 ° C or lower, or if necessary, keeping the temperature at 75 ° C or higher and then lowering the temperature to 60 ° C or lower, and subsequently holding it in a non-oxidizing atmosphere. The various properties of the magnetic particle powder can be further improved. The temperature for holding the ferrous salt reaction solution containing acicular goethite core particles is 75 ° C.
If the amount is less than the above, the effect of holding at high temperature is not sufficient, and it is not possible to obtain the acicular metal magnetic particle powder containing iron as the main component, which is superior in squareness and degree of orientation. When the temperature of holding the ferrous salt reaction solution containing acicular goethite core particles in a non-oxidizing atmosphere is higher than 60 ° C., a subsequent oxygen-containing gas is aerated to generate acicular goethite particles. Granular magnetite particles are mixed.

The amount of the aqueous alkali carbonate solution used in the growth reaction of the acicular goethite nucleus particles of the present invention is equal to or more than the amount of Fe ²⁺ in the residual aqueous ferrous salt solution. When the amount is less than the equivalent, the particle size of the obtained goethite particles becomes asymmetric, and spherical magnetite particles are mixed.

The oxidizing means in the present invention is carried out by aerating an oxygen-containing gas (for example, air) in the liquid, and may be accompanied by stirring by a mechanical operation or the like if necessary.

The reaction temperature in the present invention is usually 60 ° C. or lower at which goethite particles are formed. 6
If the temperature exceeds 0 ° C, granular magnetite particles are mixed in the acicular goethite particles. Incidentally, in the present invention, it is of course possible to carry out the production reaction of goethite nucleus particles and the growth reaction of the goethite nucleus particles using the same reaction tower, and even when using separate reaction towers, the intended goethite particles are can get.

In the present invention, starting materials are Ni compounds, Al compounds, Si compounds, P compounds, Co compounds, Mg compounds, and B in advance in order to prevent the shape of particles from being deformed and the sintering between particles during heating and reduction. It is preferable to perform the deposition treatment with one or more metal compounds selected from compounds and Zn compounds. These metal compounds not only have the effect of preventing sintering, but also have the function of controlling the reduction rate, so it is preferable to use them in combination as necessary.

Although the starting material coated with the above metal compound can be directly reduced to obtain the target metal magnetic particle powder containing iron as a main component, control of magnetic properties and powder properties is possible. Further, in order to control the shape, it is preferable to perform a heat treatment in a non-reducing gas atmosphere in advance by a conventional method prior to the reduction.

The heat treatment in the non-reducing gas atmosphere is carried out under a flow of air, oxygen gas and nitrogen gas at 300 to 800.
It can be carried out in a temperature range of 0 ° C., and the heat treatment temperature is more preferably selected appropriately according to the kind of the metal compound used for the deposition treatment of the starting material particles. If it exceeds 800 ° C., deformation of particles and sintering between particles and each other are caused.

The temperature range of heat reduction in the present invention is 3
The temperature is preferably 00 to 550 ° C. When the temperature is lower than 300 ° C, the reduction reaction proceeds slowly and requires a long time. Also, 5
If the temperature exceeds 50 ° C., the reduction reaction will rapidly proceed, causing deformation of the particles and sintering between the particles and each other.

The metal 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 immersing it in an organic solvent such as toluene, and a metal magnetic particle containing iron after reduction as a main component. After the atmosphere of the powder is once replaced with an inert gas, the oxygen content in the inert gas is gradually increased and finally changed to air to gradually oxidize the powder.

In the present invention, in order to improve various properties of the metallic magnetic particle powder containing iron as a main component, Co compounds, Ni compounds, and Cr, which are usually added in producing goethite particles as a starting material, have been conventionally used. Compound, Zn compound, A
It is possible to add one kind or two kinds or more selected from a 1-compound, a Mn-compound, a P-compound, a Si-compound and a B-compound. In this case as well, the object particle size of the present invention is uniform, and It is possible to obtain a needle-shaped goethite particle powder which does not contain particle-shaped particles and has a large axial ratio (major axis diameter / minor axis diameter).

[0030]

First, the most important point in the present invention is an aqueous solution of ferrous salt and an aqueous solution of alkali hydroxide or an aqueous solution of alkali carbonate or an aqueous solution of alkali hydroxide / carbonic acid in an amount less than equivalent to Fe ²⁺ in the aqueous solution of ferrous salt. The ferrous hydroxide colloid or iron-containing colloid obtained by aeration of an oxygen-containing gas into a ferrous salt reaction solution containing a ferrous hydroxide colloid or an iron-containing precipitate colloid obtained by reacting with an alkaline aqueous solution. After oxidizing the precipitate colloid to generate acicular goethite nucleus particles, the ferrous salt reaction solution containing the acicular goethite nucleus particles is added in an amount of at least equivalent to Fe ²⁺ in the ferrous salt reaction solution. By aerating the oxygen-containing gas after adding the alkaline carbonate aqueous solution, when the growth reaction of the acicular goethite nucleus particles is performed, the particle size is uniform and the dendritic particles are not mixed, and, Axial ratio In particular, 20 or more acicular goethite particle powders having a large major axis / minor axis diameter are obtained, and the acicular goethite particles or acicular hematite particles obtained by heating and dehydrating the acicular goethite particles are used as starting material particles. The obtained acicular metal magnetic particles containing iron as a main component also have particles having a uniform particle size and no mixed dendritic particles, and having a large axial ratio (major axis diameter / minor axis diameter). can get. The fact is that the acicular magnetic iron oxide particles having these characteristics have an excellent coercive force distribution.

When an aqueous solution of alkali hydroxide was used in place of the aqueous solution of alkali carbonate in the growth reaction of goethite core particles, the objective particle size of the present invention was uniform and the dendritic particles were No acicular goethite particle powder having a large axial ratio (major axis diameter / minor axis diameter) is not obtained.

In the present invention, after the ferrous salt reaction solution containing acicular goethite core particles is maintained at a temperature of 70 ° C. or higher, 6
When the temperature is lowered to 0 ° C. or less, it is possible to obtain the acicular metal magnetic particle powder containing iron as the main component, which is more excellent in the degree of orientation and the squareness. When the ferrous salt reaction solution containing acicular goethite core particles is kept at 60 ° C. or lower in a non-oxidizing atmosphere,
It is possible to obtain the acicular metal magnetic particle powder containing iron as a main component, which has a better coercive force distribution. After holding the ferrous salt reaction solution containing acicular goethite core particles at a temperature of 75 ° C. or higher, 6
When the temperature is lowered to 0 ° C. or lower and subsequently kept in a non-oxidizing atmosphere, acicular metal magnetic particle powder having a better degree of orientation, squareness and coercive force distribution can be obtained.

[0033]

The present invention will be described below with reference to Examples and Comparative Examples. The major axis diameter and the axial ratio (major axis diameter / minor axis diameter) of the particles in the following Examples and Comparative Examples are all shown as the average value of the numerical values measured from electron micrographs.

The particle size distribution of the particles is shown by the geometric standard deviation value (σg) obtained by the following method. That is, the major axis diameter of 350 particles shown in an electron micrograph at 120,000 times is measured, and the logarithmic normal is calculated from the actual major axis diameter and the number of particles calculated from the measured values according to a statistical method. The major axis diameter of the particles is plotted on the abscissa on the probability paper, and the cumulative number of particles belonging to each major axis section at equal intervals is plotted on the ordinate as a percentage. Then, the values of the major axis diameters corresponding to the particle numbers of 50% and 84.13% are read from this graph, and the major axis diameter (μm) when the number of particles is 50% is the number of 84.1.
The value was divided by the major axis diameter (μm) at 3%.

The magnetic properties and coating properties of the acicular metal magnetic particle powder containing iron as the main component are described in "Vibration Sample Magnetometer VSM-3".
S-15 "(manufactured by Toei Industry Co., Ltd.)
The measurement was performed up to 0 KOe. Square film and S.I. F.
D. Was measured using the sheet sample piece obtained by the method of Example 43 described later. Also, S. F. D. Is obtained by using the differential circuit of the magnetic measuring instrument to obtain the differential curve of the demagnetization curve of the magnetic hysteresis curve, and measuring the half width of this curve,
It was determined by dividing this value by the coercive force.

<Method for producing acicular goethite particle powders> Examples 1 to 14 and Comparative Examples 1 and 2; Example 1 Ferrous sulfate aqueous solution 1 containing Fe ²⁺ 1.50 mol / l 1
2.8 l and 0.44-N NaOH aqueous solution 30.2
1 (corresponding to 0.35 equivalent to Fe ²⁺ in the ferrous sulfate aqueous solution) is mixed to produce a ferrous sulfate aqueous solution containing Fe (OH) ₂ at pH 6.7 and temperature 38 ° C. Was done.

To the ferrous sulfate aqueous solution containing Fe (OH) ₂ above, at a temperature of 40 ° C., 130 l / min of air was added in an amount of 3.0.
It was aerated for a period of time to generate goethite nucleus particles. 7. A 5.4-N Na ₂ CO ₃ aqueous solution was added to the ferrous sulfate aqueous solution containing the above-described goethite core particles (the amount of goethite core particles present was 35 mol% with respect to the produced goethite particles).
0 l (1.5 for Fe ²⁺ in the residual ferrous sulfate aqueous solution)
It corresponds to the equivalent. ) Was added, and 130 l / min of air was aerated at pH 9.4 and a temperature of 42 ° C. for 4 hours to produce goethite particle powder. The produced goethite particles were filtered, washed with water and dried by a conventional method.

As a result of electron microscopic observation, the resulting goethite particle powder had a uniform σg of 0.801 and no dendritic particles mixed therein, and had a major axis of 0.33 μm and an axial ratio (major axis diameter). / Minor axis diameter) 25.

Examples 2 to 14 Type of ferrous salt aqueous solution, Fe ²⁺ concentration and amount used, type of alkaline aqueous solution in the production of goethite core particles,
Example 1 except that the concentration and usage amount, the type and amount of different elements, the reaction temperature, and the concentration and usage amount of the alkaline aqueous solution in the growth of goethite nucleus particles, the type and amount of different elements, and the reaction temperature were variously changed. Similarly, goethite particle powder was obtained. The main production conditions and various characteristics of the goethite particle powder at this time are shown in Tables 1 and 2. Examples 2-1
As a result of electron microscopic observation, the acicular goethite particle powders obtained in No. 4 were all uniform in particle size and did not contain dendritic particles. Electron micrographs (× 30) of the acicular goethite particle powders obtained in Examples 2, 10 and 14.
000) are shown in FIGS. 1 to 3, respectively.

Comparative Example 1 7.0 l of a 6.2-N NaOH aqueous solution was used in place of 7.0 l of a 5.4-N Na ₂ CO ₃ aqueous solution (based on Fe ²⁺ in the residual ferrous sulfate aqueous solution). It corresponds to 2.25 equivalents.)
Example 2 except that P compound was used and no P compound was added.
Goethite particle powder was obtained in the same manner as in. The obtained goethite particle powder is an electron micrograph (× 3000 of FIG. 4).
As shown in 0), σg was 0.635 and the particle size was asymmetric, and dendritic particles were mixed.

Comparative Example 2 In place of 7.0 l of a 5.4-N Na ₂ CO ₃ aqueous solution, 7.0 l of a 2.74-N NaOH aqueous solution (1 relative to Fe ²⁺ in the ferrous sulfate aqueous solution was added ^). (Corresponding to 0.0 equivalent) was used, a growth reaction was performed at 80 ° C. while adjusting the pH to 4.2, and a goethite particle powder was obtained in the same manner as in Example 2 except that the P compound was not added. It was As shown in the electron micrograph (× 30000) of FIG. 5, the obtained goethite particle powder had an asymmetric particle size of σg of 0.612 and contained dendritic particles.

<Production of Needle-Shaped Hematite Particle Powder> Example 15 The needle-shaped goethite particles obtained in Example 5 were heated in air for 300 times.
It was heated and dehydrated at ℃ to obtain needle-like hematite particles. As a result of electron microscope observation, the obtained acicular hematite particles had a major axis diameter of 0.20 μm and an axial ratio (major axis diameter / minor axis diameter) of 20.

<Deposition treatment of acicular goethite particle powder with a metal compound> Examples 16 to 28, Comparative Examples 3 to 4 Example 16 To 1000 g of filtered and washed needle-shaped goethite particles obtained in Example 1. The corresponding amount of presscake was suspended in 30 l of water. The pH of the suspension at this time was 9.3. Then, 300 ml of an aqueous solution in which 5 g of sodium hexametaphosphate was dissolved was added to the above suspension and dispersed by stirring for 15 minutes. Next, 120 g of sodium silicate (No. 3 water glass) was added to the above goethite dispersion suspension, and the mixture was stirred for 30 minutes. Further, an aqueous solution containing 40 g of a sodium aluminate solution was added to the above goethite dispersion suspension, and the mixture was stirred for 20 minutes.

Next, 10% concentration of acetic acid was added so that the pH of the suspension became 6.0, followed by filtration and washing with water to remove unnecessary salts. The goethite press cake filtered and washed with water was dried to obtain goethite particles coated with a P compound, a Si compound and an Al compound. The content of P, Si, and Al in the obtained goethite was 0.29 as P, respectively.
wt%, Si was 3.43 wt% as SiO ₂ , and Al was 0.36 wt%.

Examples 17, 21, and 26, Comparative Examples 3 to 4 The metal compound was deposited in the same manner as in Example 16 by changing the type of particles to be treated, the type of the adhered substance and the addition amount. Obtained needle-shaped goethite particles were obtained. Table 3 shows the main manufacturing conditions at this time.

Example 18 An amount of press cake corresponding to 1000 g of the needle-shaped goethite particles obtained by filtering in Example 4 and washed with water was suspended in 30 liters of water. The pH of the suspension at this time was 9.4. Next, 180% Al (NO ₃ ) ₃ .9H ₂ O was added to the above suspension so as to be 18.0% by weight with respect to goethite.
g, and further, 127 g of Co (CH ₃ COO) ₂ .4H ₂ O so that the content becomes 12.7% by weight with respect to goethite.
Zn to 5.0 wt% with respect to goethite
(CH ₃ COO) was added to ₂ · 4H ₂ O 50g 20
Stir for minutes. The pH of the suspension at this time was 4.15.

Next, 1 part of goethite was added to the above suspension.
A solution in which 130 g of H ₃ BO ₃ was dissolved was slowly added so as to be 3.0% by weight, and the mixture was stirred for 15 minutes. Further, ammonia water was added to adjust the pH to 9.5, and then filtered with a filter press and dried to obtain Al, Co,
A goethite coated with Zn and B compounds was obtained. The content of Al, Co, Zn, and B in the obtained goethite was 1.12 wt% as Al and 2.75 wt% Co, respectively.
%, Zn was 1.15 wt%, and B was 0.56 wt%.

Examples 19, 20, 22 to 25, 27, 2
8 Needle-shaped goethite particles coated with a metal compound were obtained in the same manner as in Example 18 by changing the type of the particles to be treated, the type of the substance to be treated and the addition amount. Table 3 shows the main manufacturing conditions at this time.

<Production of acicular metal magnetic particle powder containing iron as a main component> Examples 29 to 42, Comparative Examples 5 to 6; Example 29 P, Si and Al compounds obtained in Example 16 were deposited. 800 g of the obtained needle-shaped goethite particle powder was heat-treated in air at 750 ° C. to obtain a needle-shaped hematite particle powder coated with P, Si, and Al compounds. Approximately 1 g of 100 g of the acicular hematite particles powder coated with the P, Si and Al compounds
A rotary retort reduction container having a volume of 0 l was charged, and while being driven and rotated, H ₂ gas was aerated at a rate of 50 l / min,
Reduction was carried out at a reduction temperature of 420 ° C.

The metal magnetic particle powder containing P, Si, and Al and containing iron as a main component, which was obtained by reduction, was immersed in a toluene solution so as not to cause rapid oxidation when taken out into the air. I took it out. A part was taken out and a stable oxide film was formed on the surface while evaporating toluene.

As a result of electron microscopic observation, the metal magnetic particle powder containing iron as a main component containing P, Si and Al was
The average major axis was 0.27 μm and the axial ratio (major axis diameter / minor axis diameter) was 21, and the particle size was uniform and the number of dendritic particles was small.
The magnetic properties were a coercive force Hc 1560 Oe and a saturation magnetization σs 159.6 emu / g.

Examples 30 to 42, Comparative Examples 5 to 6 The same as Example 29 except that the type of starting material, the heat treatment temperature, the type of non-reducing atmosphere, the reducing temperature and the H ₂ flow rate were variously changed. A needle-like metal magnetic particle powder containing iron as a main component was obtained. Table 4 shows the main manufacturing conditions and various characteristics at this time. All of the acicular metal magnetic particle powders containing iron as the main component obtained in Examples 30 to 42 had a uniform particle size and did not contain dendritic particles. Examples 30, 3
8 and 42 and the electron micrographs of the acicular metal magnetic particle powders containing iron as the main component obtained in Comparative Examples 5 and 6 (× 30
000) are shown in FIGS. 6 to 10, respectively.

<Manufacture of Coating Films> Examples 43 to 56, Comparative Examples 7 to 8; Example 43 P-, Si- and Al-containing acicular metal magnetic particles containing P, Si and Al obtained in Example 29 as a main component. Using a powder, a suitable amount of a dispersant, a vinyl chloride-vinyl acetate copolymer, a thermoplastic polyurethane resin, and a mixed solvent of toluene, methyl ethyl ketone, and methyl isobutyl ketone are mixed in a given composition, and then mixed and dispersed with a paint conditioner for 9 hours. Magnetic coating. The above-mentioned mixed solvent was added to the obtained magnetic paint to adjust it to an appropriate paint viscosity, which was applied on a polyester film by a usual method, oriented in a magnetic field, and dried to produce a coating film. This coating film was measured by VSM under an external magnetic field of 10 KOe. As a result, the coercive force Hc was 1580 Oe, the residual magnetic flux density Br was 3440 Gauss, the square Br / Bm was 0.86, and the S.I. F. D. Was 0.496.

Examples 44 to 56, Comparative Examples 7 to 8 Coating films were produced in exactly the same manner as in Example 43 except that the kind of the acicular metal magnetic particle powder containing iron as the main component was changed variously. Table 5 shows various characteristics of this coating film.

[0055]

[Table 1]

[0056]

[Table 2]

[0057]

[Table 3]

[0058]

[Table 4]

[0059]

[Table 5]

[0060]

EFFECTS OF THE INVENTION According to the method for producing an acicular metal magnetic particle powder containing iron as a main component according to the present invention, as shown in the above Examples, the particle size is uniform and the dendritic particles are mixed. No,
Moreover, it has a large axial ratio (major axis diameter / minor axis diameter), and
Since the acicular metal magnetic particle powder containing iron as a main component having an excellent coercive force distribution can be obtained, it is suitable as a magnetic particle powder for high recording density, high sensitivity and high output.

[0061]

[Brief description of drawings]

FIG. 1 is an electron micrograph (× 30000) showing the particle structure of the acicular goethite particle powder obtained in Example 2.

2 is an electron micrograph (× 30000) showing the particle structure of the acicular goethite particle powder obtained in Example 10. FIG.

FIG. 3 is an electron micrograph (× 30000) showing the particle structure of the acicular goethite particle powder obtained in Example 14.

4 is an electron micrograph (× 30000) showing the particle structure of the goethite particle powder obtained in Comparative Example 1. FIG.

5 is an electron micrograph (× 30000) showing the particle structure of the goethite particle powder obtained in Comparative Example 2. FIG.

6 is an electron micrograph (× 3) showing the particle structure of the acicular metal magnetic particle powder containing iron as a main component obtained in Example 30. FIG.
0000).

FIG. 7 is an electron micrograph (× 3) showing the particle structure of the acicular metal magnetic particle powder containing iron as a main component obtained in Example 38.
0000).

8 is an electron micrograph (× 3) showing the particle structure of the acicular metal magnetic particle powder containing iron as a main component obtained in Example 42. FIG.
0000).

9 is an electron micrograph (× 30) showing the particle structure of the acicular metal magnetic particle powder containing iron as a main component obtained in Comparative Example 5. FIG.
000).

10 is an electron micrograph (× 3) showing the particle structure of the acicular metal magnetic particle powder containing iron as a main component obtained in Comparative Example 6. FIG.
0000).

Claims (5)

[Claims] 1. Obtained by reacting an aqueous solution of ferrous salt with an aqueous solution of alkali hydroxide or an aqueous solution of alkali carbonate or an aqueous solution of alkali hydroxide / alkali carbonate with ^respect to Fe ²⁺ in the aqueous solution of ferrous salt. The ferrous hydroxide colloid or the iron-containing precipitate colloid is oxidized by passing an oxygen-containing gas through a ferrous salt reaction solution containing the ferrous hydroxide colloid or the iron-containing precipitate colloid to oxidize the needle-shaped colloid. After generating goethite core particles, an aqueous solution of an alkali carbonate equivalent to or more than Fe ²⁺ in the ferrous salt reaction solution is added to the ferrous salt reaction solution containing the needle-shaped goethite core particles, and then oxygen is contained. The needle-shaped goethite particles are generated by aeration of gas to carry out the growth reaction of the needle-shaped goethite core particles, and then the needle-shaped goethite particles or the needle-shaped hematite obtained by heating and dehydrating the particles. A method for producing acicular metal magnetic particle powder containing iron as a main component, characterized in that the acicular metal magnetic particle containing iron as a main component is obtained by heating and reducing the magnetic particles in a reducing gas. 2. An acicular goethite particle or an acicular hematite particle obtained by heating and dehydrating the particle to obtain a Ni compound, Al.
The iron-based needle-shaped material according to claim 1, wherein the deposition treatment is performed with one or more metal compounds selected from compounds, Si compounds, P compounds, Co compounds, Mg compounds, B compounds and Zn compounds. Manufacturing method of metal magnetic particle powder. 3. The ferrous salt reaction solution containing acicular goethite core particles before the addition of the alkali carbonate aqueous solution is heated to a temperature of 75 ° C.
The method for producing an acicular metal magnetic particle powder containing iron as a main component according to claim 1 or 2, wherein the temperature is lowered to 60 ° C or lower after being kept above. 4. The iron according to claim 1 or 2, wherein the ferrous salt reaction solution containing acicular goethite core particles before the addition of the aqueous alkali carbonate solution is kept at 60 ° C. or lower in a non-oxidizing atmosphere. A method for producing a powder of acicular metal magnetic particles as a component. 5. The ferrous salt reaction solution containing acicular goethite nucleus particles before the addition of the aqueous alkali carbonate solution is heated to a temperature of 75 ° C.
The method for producing an acicular metal magnetic particle powder containing iron as a main component according to claim 1 or 2, wherein the temperature is lowered to 60 ° C or lower after being kept above, and subsequently kept in a non-oxidizing atmosphere.