JPS60138002A - Magnetic metallic particle powder consisting essentially of iron having spindle shape and its production - Google Patents

Abstract

PURPOSE:To obtain titled powder having a uniform grain size and large satd. magnetization by incorporating a specific amt. of water soluble silicate into the reaction soln. of an aq. ferrous salt and alkali carbonate and subjecting the goethite particles formed by oxidation to reduction under heating. CONSTITUTION:An aq. ferrous salt soln. (FeSO4, etc.) and alkali carbonate (K2CO3, etc.) are brought into reaction with each other at about 40-80 deg.C and about 7-11pH to form an aq. soln. contg. FeCO3. Water soluble silicate (silicate of Na, etc.) is added to the aq. soln. so as to be incorporated therein at 0.1- 10atom% in terms of Si by the atom% of Fe. A gas contg. oxygen is passed through such soln. to oxidize the soln., thereby forming the goethite particles having a spindle shape. The particles are dehydrated by heating and are subjected to reduction under heating in a reducing gas. The magnetic metallic particle powder which consists essentially of the iron having the spindle shape, has <=3:1 long axis: short axis, contains 0.1-10atom% Si by the atom% of Fe and has 500-1,000Oe coercive force is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides magnetic particle powder for high-density recording, in particular, which has a uniform particle size that is optimal for short wavelength recording, does not contain dendritic particles, and has an axial ratio ( The long axis: short axis) is small and 3:l or less, especially 2=1 or less, and the coercive force is 500 to 10,000.
The present invention relates to a spindle-shaped metal magnetic particle powder mainly composed of iron and a method for producing the same.

In recent years, as magnetic recording and reproducing equipment has become longer recording time and has become smaller and lighter, there has been an increase in the performance and high density recording of both these magnetic recording and reproducing equipment and magnetic recording media such as magnetic tapes and magnetic disks. Demand is increasing.

In order to improve the performance and high density recording of magnetic recording media, improvements in dispersibility, filling properties, residual magnetic flux density Brs coercive force 11c, saturation magnetization σS, improvement in tape surface smoothness, and thin coating film are required. It is necessary to This fact is evidenced by, for example, the Development of Magnetic Materials and Highly Dispersed Magnetic Powder Technology (1999) published by the General Technology Center.
(1982), page 140, [Higher recording density...
In order to ensure a constant output, it is necessary to increase Br. In order to increase T3r, it is necessary to increase not only the magnetic field orientation but also the filling rate of the magnetic powder. '', page 15 of the same document, [An important index representing performance in magnetic recording is...recording density. Until now, this increase has been achieved primarily by improving magnetic heads and recording media. To summarize the direction of improvements to date in this field: Recording media: Emphasis has been placed on realizing a thin magnetic layer with high coercive force (tic). ” on page 141 of the same document, “For high-density recording, thinning of the coating film is the most important factor.” On page 312 of the same document, “High-density recording in coated tape The conditions for this are that high output characteristics can be maintained with low noise for short wavelength signals, but in order to do so, the coercive force Hc and residual magnetization Br must both be large in a balanced manner, and the coating film must be large. "The flying height of the head is the controlling factor for high-density recording" on page 143 of the same document in the case of a floating head type such as a rigid disk. , it is possible to increase the density by reducing this. When the flying height is lowered, if the surface of the disk is poor, the reproduction output will decrease due to head chipping, and the stable flying will be disturbed, resulting in hendokurasosh. Occurs. Therefore...
High-precision finishing of the coating surface is important. It is clear from the statement ``.

These characteristics of magnetic recording media are closely related to the magnetic particles used in magnetic recording media, and there is a strong desire to improve the characteristics of magnetic particles.

The relationship between the various characteristics of the magnetic recording medium and the characteristics of the magnetic particles used will now be detailed as follows.

First, the residual magnetic flux density Br of the magnetic recording medium depends on the dispersibility of the magnetic particles in the vehicle, the orientation and filling properties in the coating film.

In order to improve the dispersibility in the vehicle, the orientation and filling properties in the coating film, the particle size of the magnetic particles dispersed in the vehicle must be uniform and dendritic particles should not be mixed. As a result, a high bulk density is required.

Next, in order to improve the surface properties of magnetic recording media, dispersibility,
A magnetic particle powder with good orientation and a small particle size is preferable, and such a magnetic particle powder should have a uniform particle size, no dendritic particles mixed, and, as a result, a large bulk density. required.

Furthermore, in order to make the coating film of a magnetic recording medium thinner, it is necessary to refer to page 141 of the above-mentioned document, ``Thinning the coating film reduces the size of the magnetic powder and improves the orientation in the thickness direction of the coating film. Forming a thin coating film ultimately means using magnetic powder with low oil absorption to create a magnetic paint with good coating properties, as mentioned in 2.3. As is clear from the description, magnetic particle powder with good dispersibility and orientation is preferred, and as mentioned above, such magnetic particle powder has uniform particle size and does not contain dendritic particles. things are required.

As mentioned above, the coercive force Hc of the magnetic recording medium needs to be as high as possible for high-density recording.
It is necessary that c be as high as possible.

Currently, acicular magnetite particles or acicular maghemite particles are mainly used as magnetic particles for magnetic recording. These generally have a coercive force 11c 25
It has about 0 to 3500e.

It is known that the coercive force can be improved by adding cobalt to the above-mentioned acicular magnetophyte particles or acicular maghemite particles, and these have a coercive force of about 11c 400 to 8000e. However, since the saturation magnetization σS is 70 to 85' e+nu/g, the Bm when coated as a magnetic recording medium is at most 20
Only about 0.00 Gauss can be obtained.

In order to increase the density of magnetic recording media, it is necessary for magnetic particles to have a high coercive force llc and a large saturation magnetization σS. Metallic magnetic particles containing as a main component are attracting attention and are being put into practical use.

The saturation magnetization σS of currently available iron magnetic particles or metal magnetic particles mainly composed of iron is 110 to 170e.
It is about mu/g, and the coercive force 11c is 1000
~15,000e, and further efforts are being made to improve the coercive direction.

These iron magnetic particles or metal magnetic particles whose main component is iron are generally made from acicular hydrated ferric oxide particles, acicular ferric oxide particles, or a different metal other than iron as a starting material. It is obtained by heating and reducing the substance contained in a reducing gas.

On the other hand, there is a close relationship between the coercive force Hc of the magnetic recording medium and the performance of the magnetic head, and if the coercive force llc of the magnetic recording medium is too high, the write current will increase, so the current amount is also widely used. It is known that in a ferrite head, the core becomes magnetically saturated due to insufficient saturation magnetic flux density Bm of the hend core, making it impossible to sufficiently magnetize the magnetic recording medium.

This fact is evidenced by, for example, the Institute of Electronics and Communication Engineers technical research report MR8.
2-19 (1982), page 19 [...These high 11c tapes (llc 1000-15000e)
In order to record on high 11c tapes, a video head using a core with a high saturation magnetic flux density εBm is required, and with conventional ones using MnZn ferrite, magnetic saturation of the head core occurs due to lack of Bm, and high 11c tapes cannot be sufficiently magnetized. There are concerns. It is clear from the statement "...".

As mentioned above, there is a close relationship between the coercive force Ilc of the magnetic recording medium and the performance of the magnetic head, and for this reason, acicular magnetite particles, acicular maghemite particles, and their surface layers are modified with Co. Ferrite heads are used in magnetic recording and reproducing equipment for magnetic recording media manufactured using magnetic particles having a coercive force Hc of 10,000 s or less, such as acicular iron oxide particles.

On the other hand, Sendust is used for magnetic recording and reproducing equipment compatible with magnetic recording media manufactured using magnetic particles having a coercive force TLC of 10,000e or more, such as iron magnetic particles or metal magnetic particles containing iron as a main component. Heads, such as amorphous heads and thin film heads, are made of materials with a high saturation magnetic flux density for the head core.

However, heads using these materials have new problems that have not been a problem with ferrite heads, such as head abrasion due to contact between the magnetic recording medium and the recording and reproducing heads. Therefore, the saturation magnetization σS
Magnetic recording W using a large ferrite head and a ferrite head
There is a demand for iron magnetic particles or metal magnetic particles containing iron as a main component that have an appropriate coercive force 11c that can be used in raw equipment.

As described above, the coercive force 11c of the magnetic recording medium needs to be well-balanced in consideration of both high-density recording and the material of the magnetic head. Magnetic recording media used in magnetic recording and reproducing equipment incorporating ferrite heads, which are currently widely available, are capable of high-density recording and require appropriate maintenance to avoid magnetic saturation of the ferrite heads. Magnetic force llc, i.e. 500~1
0000e is required. In order to obtain a magnetic recording medium with a coercive force Hc of about 500 to 10,000 e, it is necessary that the magnetic particles dispersed in the vehicle have a coercive force of 500 to 10,000 e.

In view of the above, the present inventor has determined that the grain size is uniform, the dendritic particles are not mixed, and the coercive force is 500 to 10.
As a result of various studies, we have arrived at the present invention.

That is, the present invention has an axial ratio (long axis: short axis) of 321 or less, contains 0.1 to 10 at% of Si relative to Fe, and has a coercive force of 500 to 10,000 e. Fe obtained by reacting a spindle-shaped metal magnetic particle with iron as a main component and an aqueous ferrous salt solution with an alkali carbonate.
In producing spindle-shaped goethite particles by passing an oxygen-containing gas through an aqueous solution containing C0@ to oxidize it, the ferrous salt aqueous solution, the alkali carbonate, and the oxygen-containing gas are passed through to carry out the oxidation reaction. The above F before performing
By adding water-soluble silicate to any of the aqueous solutions containing eCO, from 0.1 to 10 atomic % in terms of Si with respect to Fe, spindle-shaped goethite particles containing St are generated, The Si-containing spindle-shaped goethite particles, the Si-containing spindle-shaped hematite particles obtained by heating and dehydrating the Si-containing goethite particles, or the Si-containing spindle-shaped goethite particles are non-reducible. A spindle-shaped hematite particle containing substantially high-density Si obtained by heat treatment at 400°C to 600°C in an atmosphere is reduced by heating in a reducing gas. This is a method for producing metal magnetic particles containing iron as a main component, which are made of metal magnetic particles containing iron as a main component.

Next, the configuration of the present invention will be described.

The present inventor has found that magnetic particle powder that enables high-density recording and avoids magnetic saturation of the ferrite head has uniform particle size, does not contain dendritic particles, and I learned that it is necessary to use metal magnetic particles whose main component is iron and which has a coercive force of about 500 to 10,000 e and a high saturation magnetization. In order to obtain a magnetic particle powder with a uniform particle size and no dendritic particles mixed in, it is necessary that the starting material goethite particles have a uniform particle size and no dendritic particles mixed therein. .

Conventionally, the most typical known method for producing goethite particles is to add a solution containing ferrous hydroxide particles obtained by adding an equivalent or more alkaline solution to a ferrous salt solution, and
Goethite particles are obtained by performing an oxidation reaction at a temperature of i or higher and 80° C. or lower. The goethite particles obtained by this method are particles with an acicular shape with an axial ratio (major axis: short axis) of 10:1 or more, with dendritic particles mixed, and in terms of particle size. , it is difficult to say that the particles have a uniform particle size.

Therefore, the present inventor proposed a method for producing goethite particles by passing an oxygen-containing gas through an aqueous solution containing FeC0@ obtained by reacting an aqueous solution of ferrous salt with an alkali carbonate to oxidize it (Japanese Patent Laid-Open No. -80999).

When this method is used, a powder consisting of spindle-shaped goethite particles with uniform particle size and no dendritic particles is obtained. Metal magnetic particles whose main component is iron obtained by heat reduction using spindle-shaped goethite particles with no dendritic particles as a starting material are also uniform in particle size and have dendritic particles. The coercive force 11c is 1000.
It ends up being 0e or more. This fact is true, for example,
This is clear from the description of "Example 3" in Publication No. 3-10100. That is, the method described in "Example 3" of JP-A-53-10100 involves passing an oxygen-containing gas through an aqueous solution containing FeC0@ obtained by reacting an aqueous ferrous salt solution with an alkali carbonate. Metal magnetic particles containing iron as a main component are obtained by thermally reducing goethite particles exhibiting a spindle shape obtained by oxidation.The coercivity of the metal magnetic particles containing iron as a main component is 1020-116
It is 50e.

Therefore, the present inventor conducted various studies on a method for controlling the coercive force of iron-based metal magnetic particles with uniform particle size and no dendritic particles to about 500" 10,000e. In producing spindle-shaped goethite particles by passing an oxygen-containing gas through an aqueous solution containing peck@ obtained by reacting a ferrous salt aqueous solution and an alkali carbonate to oxidize the ferrous salt aqueous solution and an alkali carbonate, A water-soluble silicate is added to either the aqueous salt solution, the aqueous solution containing the FeC0B and the alkali carbonate, and the aqueous solution containing the FeC0B before performing the oxidation reaction by passing through the alkali carbonate and oxygen-containing gas.
By adding 1 to 0 atomic percent of St, spindle-shaped goethite particles containing Si are generated, and the spindle-shaped goethite particles containing St or those obtained by heating and dehydration are produced. Substantially high-density Si obtained by heat-treating spindle-shaped hematite particles containing St or spindle-shaped goethite particles containing St in a non-reducing atmosphere at 400°C to 600°C. When spindle-shaped hematite particles that contain We have obtained the knowledge that it is possible to obtain metal magnetic particles with the following properties.

Why is the coercive force of metal magnetic particles whose main component is iron 500~?
Although it is not yet clear whether it can be controlled to about 10,000e, the present inventor believes that this is due to the fact that the shape anisotropy of metal magnetic particles whose main component is iron has become smaller.

That is, in producing goethite particles exhibiting a spindle shape as a starting material, the FeC before an oxidation reaction is carried out by passing through an aqueous ferrous salt solution, an alkali carbonate, and an oxygen-containing gas.
When a water-soluble silicate is added to any of the aqueous solutions containing 0@, the axial ratio (long axis; short axis) of the spindle-shaped goethite particles produced can be reduced, and the axial ratio Iron-based metal magnetic particles obtained by heat reduction using spindle-shaped goethite particles with a small (long axis: short axis) as a starting material also have a small axis ratio (long axis: short axis). We believe that this results in a reduction in shape anisotropy.

This phenomenon will be explained as follows by extracting some of the many experimental examples conducted by the present inventor.

FIG. 1 is a diagram showing the relationship between the amount of water-soluble silicate added and the axial ratio of spindle-shaped goethite particles containing Si.

That is, a ferrous sulfate aqueous solution 3.0β containing F (1" 1.Omol/j!) was prepared in advance by adding sodium silicate prepared in a reactor to a concentration of O to 10 atomic % in terms of Si relative to Fe.
In addition to the 2.0β aqueous solution of soda carbonate obtained by adding
A suspension containing FeC0B was obtained at a pH of about 10, and an oxidation reaction was carried out by passing air through the suspension at a rate of 15β per minute at a temperature of 50°C. This figure shows the relationship between the axial ratio (long axis: short axis) of goethite particles and the amount of water-soluble silicate added.

As is clear from FIG. 1, the axial ratio (long axis:short axis) tends to decrease as the amount of water-soluble silicate added increases.

FIG. 2 shows the relationship between the amount of water-soluble silicate added and the bulk density of spindle-shaped goethite particles containing SL obtained in the same manner as in FIG.

As is clear from FIG. 2, the bulk density tends to increase as the amount of water-soluble silicate added increases.

Figure 3 shows the amount of water-soluble silicate added and S obtained by thermal reduction of spindle-shaped goethite particles containing SL.
FIG. 2 is a diagram showing the relationship between the axis ratio (long axis: short axis) of spindle-shaped metal magnetic particles containing iron as a main component;

In other words, less than 5°0% Co in Go terms with respect to Fe'+
"Containing cobalt sulfate and Fe" 1.0 mol/I2
Sodium carbonate aqueous solution 2 obtained by adding O to 10 atomic % in terms of Si with respect to Fe to sodium silicate prepared in advance in a reactor to ferrous sulfate aqueous solution 3601 containing
．． 04 and a suspension containing FeC01 at pi1 of about 10 was obtained, and the suspension was heated at 15 min.
Substantially high-density Si obtained by heating spindle-shaped goethite particles containing Si and Co at 500°C in air, which were obtained by performing an oxidation reaction by passing β air through the air. Axial ratio (long axis:
This figure shows the relationship between the short axis) and the amount of water-soluble silicate added.

As is clear from FIG. 3, as the amount of water-soluble silicate added increases, the axial ratio (long axis:short axis) of the metal magnetic particles containing iron as a main component tends to decrease.

When the axial ratio (long axis: short axis) of metal magnetic particles containing iron as the main component is 3:1 or less, the coercive force 11c is set to 500 to 10,000.
e, and the axial ratio (long axis: short axis) is 2:1.
In the following cases, the coercive force Hc can be controlled to 500 to 8500e.

The invention described in "Example 3" of the above-mentioned Japanese Patent Application Publication No. 53-10100 uses spindle-shaped goethite particles with an axial ratio (long axis: short axis) of 5:l as a starting material. As is clear from Figure 3 (B) of the same publication, the axial ratio (long axis: short axis) of the metal magnetic particles whose main component is iron, which is obtained by thermally reducing the particles by 1q, is 5, which is the same as that of the goethite particles that are the starting material. :1, and as a result, it is thought that only those with a coercive force of 10,000e or more were obtained.

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

Examples of the ferrous salt aqueous solution used in the present invention include a ferrous sulfate aqueous solution and a ferrous chloride aqueous solution.

As the alnocarbonate used in the present invention, sodium carbonate, potassium carbonate, and ammonium carbonate may be used alone, or in combination with an alkali hydrogen carbonate such as sodium hydrogen carbonate, potassium hydrogen carbonate, or ammonium hydrogen carbonate. can be used.

The reaction temperature in the present invention is 40 to 80°C.

If the temperature is below 40°C, it is impossible to obtain spindle-shaped goethite particles. When the temperature is 80° C. or higher, granular Fe@04 is mixed.

pl+ in the present invention is 7-11. If it is 7 or less or 11 or more, goethite particles exhibiting a spindle shape cannot be obtained.

The oxidation means in the present invention is carried out by passing an oxygen-containing gas (for example, air) into the liquid.

The water-soluble silicates used in the present invention include sodium and potassium silicates.

The water-soluble silicate in the present invention is involved in the axis ratio (major axis: short axis) of spindle-shaped goethite particles to be produced, and therefore, the production reaction of spindle-shaped goethite particles starts. It is necessary to have it present before the oxidation reaction is carried out, and it can be added to either the ferrous salt aqueous solution, the aqueous solution containing FeCO, before the oxidation reaction is carried out by aerating the alkali carbonate and oxygen-containing gas. can.

The amount of water-soluble silicate added in the present invention is 0.1 to 10% or less based on Fe in terms of Si.

If it is 0.1% or less, the effect of reducing the axis ratio (long axis: short axis) of spindle-shaped metal magnetic particles mainly composed of iron can be sufficiently achieved. I can't.

If the content is 10 atomic % or more, it is not preferable because the saturation magnetization of metal magnetic particles containing iron as a main component obtained by heating and reducing the resulting powder consisting of spindle-shaped goethite particles is undesirable.

Axial ratio of spindle-shaped metal magnetic particles mainly composed of iron (
When considering long axis: short axis) and saturation magnetization, 0.3 to 8
Atomic % is preferred.

Almost the entire amount of the added water-soluble silicate is contained in the produced goethite particles, and as shown in Table 1 below, the obtained goethite particles contain almost the same amount of F as the added amount.
Metal magnetic particles containing 0.10 to 10.02 at% in terms of St based on e and containing iron as a main component obtained by thermal reduction of the particles are also shown in Table 3 below. street,
o, ioo~ in terms of St for almost the same amount of Fe as the added amount
Contains 10.00 at%.

Next, regarding the thermal reduction process, spindle-shaped metal magnetic particles mainly composed of iron are produced by thermally reducing spindle-shaped goethite particles with uniform particle size and no dendritic particles. The higher the reduction temperature, the more spindle-shaped iron-based metal magnetic particles with larger saturation magnetization can be obtained. The deformation of the component metal magnetic particles and the sintering between the particles and the particles become significant.

The causes of deformation of particles and sintering between particles and particles in the thermal reduction process will be explained below.

In general, spindle-shaped hematite particles obtained by heating and dehydrating spindle-shaped goethite particles at a temperature around 300°C retain and inherit the particle shape of the goethite particles, but on the other hand, the particle surface In addition, there are many pores generated by dehydration inside the particles, and the growth of a single particle is insufficient, so the degree of crystallinity is very small.

When thermal reduction is performed using hematite particles exhibiting such a spindle shape, uniform particle growth of a single particle is difficult to occur because the particle growth of a single particle, that is, the physical change is rapid, and therefore, It is thought that sintering between particles and particles occurs in a portion where the particle growth of a single particle occurs rapidly, and the particle shape becomes easily distorted.

Furthermore, in the thermal reduction process, rapid volumetric contraction from the oxide to the metal occurs, making the particle shape more likely to collapse.

- Therefore, in order to prevent particle shape deformation and sintering between particles and particles during the thermal reduction process, it is necessary to prepare a sufficient number of single particles of hematite particles that have a spindle shape in advance, and , spindle-shaped hematite particles that have a substantially high density with an increased degree of crystallinity by achieving uniform particle growth, and that retain and inherit the particle shape of spindle-shaped goethite particles. It is necessary to keep it as

As a method for obtaining substantially high-density spindle-shaped hematite particles with an increased degree of crystallinity, spindle-shaped goethite particles are heated at 400° C. in a non-reducing atmosphere.
The method of heat treatment at 600°C is - When reducing tight particles or spindle-shaped hematite particles containing St obtained by heating and dehydrating the tight particles, the reduction temperature is 300°C.
~450°C is preferred.

If the temperature is 300°C or lower, the reduction reaction progresses slowly and requires a long time. Further, if the temperature is 450° C. or higher, the reduction reaction rapidly progresses, causing deformation of the particle morphology and sintering of the particles and each other.

In the present invention, the reduction temperature when reducing spindle-shaped goethite particles containing substantially high-density Si is 3.
00°C to 500°C is preferred. The reason is the same as in the case of thermally reducing Si-containing spindle-shaped goethite particles or St-containing spindle-shaped hematite particles obtained by heating and dehydrating the goethite particles.

The present invention configured as described above has the following effects.

That is, according to the present invention, the particle size is uniform, dendritic particles are not mixed, and the coercive force is 500 to 10,000 e.
Since it is possible to obtain iron-based metal magnetic particles having a spindle shape of a certain degree, it is suitable as a magnetic particle powder for high recording density, which is currently most required.

In addition, the spindle-shaped metal magnetic particles containing St and mainly composed of iron obtained by the present invention have an axial ratio (long axis:
Since the short axis) is small, 3:l or less, especially 2:1 or less, it is suitable as a magnetic particle powder for short wavelength recording.

The fact that magnetic particles with a small axial ratio (long axis: short axis) are suitable as magnetic particle powder for short wavelength recording can be seen, for example, in JP-A-57-183626, "The present invention is based on the above-mentioned prior art. The major axis used in technology is 0.4 to 2μ or 0.3
Instead of regular acicular particles with ~1μ and a length/width ratio (axis ratio) of 5 to 20, the particle size is as small as 0.3μ or less, and...
By making it a short shape with an aspect ratio of more than 1 and less than 3, we can lower the noise level due to discontinuity of magnetization caused by the particle size, and by reducing the aspect ratio... It is characterized by suppressing the tendency of the particles to be oriented lying in the plane and, if necessary, actively giving them a tendency to be easily oriented perpendicular to the plane, so that a large residual magnetization perpendicular to the plane can be obtained. be. ” and “As described in the examples, the magnetic recording medium thus obtained has a high output in a short recording wavelength range, for example 1μ, and has low noise, so as a result, the S/N is low.
It is possible to obtain an excellent ratio. It is clear from the statement ``.

Furthermore, when the spindle-shaped iron-based metal magnetic particle powder containing St obtained according to the present invention is used in the production of magnetic paint, it is well dispersed in the vehicle, and the filling process is improved. It is possible to obtain a preferable magnetic recording medium with extremely excellent properties.

The above-mentioned effects of the present invention can be obtained by adding Co, ng, .
AI% Crs Zns Nis Ti, Mn, Sn
It also works effectively when a different metal other than Fe, such as sPb, is added.

In addition, the axial ratio (major axis - short axis) and major axis of the particles in the above experimental examples, the following examples, and comparative examples are determined from electron micrographs of two or more fields of view magnified at least 100,000 times.
It is shown as the average value of the values measured for 0 or more particles, and the bulk density was measured according to "JIS K 5101r Pigment Test Method".

The amounts of Si, C01Zn, and Ni in the particles were measured using a fluorescent It was measured by performing line analysis.

(Production of spindle-shaped goethite particles) Examples 1 to 1
2. Comparative Example 1; Example I Fe” 1. Ferrous sulfate aqueous solution containing Omol/β 30
ρ is S for the Fe prepared in the reactor in advance.
Sodium silicate (3
In addition to 3,53 mol of Na C,0 @ aqueous solution 20β obtained by adding 12.7 g of (SiO PECO* was generated.

The temperature of the aqueous solution containing PeC0@ containing Si is 50.
St-containing goethite particles were produced by blowing air at 1301/min for 6.5 hours at .

The end point of the oxidation reaction was determined by taking out a portion of the reaction solution and adjusting the acidity with hydrochloric acid, and then using a red blood salt solution to determine the presence or absence of a blue coloring reaction of Fe2+.

The produced particles were separated by filtration, washed with water, dried, and pulverized by a conventional method.

As a result of electron microscopy observation, this St-containing goethite particle powder has an average long axis of 0.38 μm and an axial ratio (long axis/
It consisted of spindle-shaped particles with a ratio of 2.5:1 (minor axis), uniform particle size, and no dendritic particles.

Further, as a result of fluorescent X-ray analysis, this spindle-shaped goethite particle powder contained 0.19 atomic % of St relative to Pe, and its bulk density was 0.41 g/cc.

Examples 2 to 12 Same as Example 1 except that the type of Fe2+ aqueous solution, the type and concentration of alkali carbonate, the type, amount and timing of addition of water-soluble silicate, the type, amount and temperature of metal ions were varied. Goethite particles exhibiting a spindle shape were produced in the same manner.

Table 1 shows the main manufacturing conditions and characteristics of the produced goethite particles.

Comparative Example 1 Goethite particles were produced in the same manner as in Example 1 except that sodium silicate was not added.

As a result of electron microscopic observation, the obtained goethite particles had an average value of 0.55 μm on the long axis and a uniaxial ratio (long axis: short axis) of 7:
1, and the bulk density was 0.33 g/cc.

(Production of substantially high-density spindle-shaped hematite particles) Examples 13 to 20; Example 13 700 g of spindle-shaped goethite particles containing St obtained in Example 1 were dissolved in air at 500 g. A spindle-shaped hematite particle powder containing substantially high-density St was obtained by heat treatment at .degree.

As a result of electron microscopy observation, the average value of these particles was 0.
The particle size was 38 μm, the axis ratio (long axis: short axis) was 2.5:1, the particle size was uniform, and dendritic particles were not mixed.

Examples 14 to 20 A spindle-shaped material containing substantially high-density St was prepared in the same manner as in Example 13, except that the type of goethite particles to be treated, the heat treatment temperature, and the type of non-reducing atmosphere were variously changed. A hematite particle powder with the following properties was obtained.

Table 2 shows the main manufacturing conditions and various characteristics at this time.

As a result of electron microscopy, the obtained spindle-shaped hematite particles containing substantially high-density St were found to have uniform particle size and no dendritic particles were present.

<Production of spindle-shaped hematite particles> Example 21 700 g of spindle-shaped goethite particles containing St obtained in Example 8 were heated and dehydrated in air at 300°C to produce spindle-shaped particles containing St. A hematite particle powder exhibiting the following properties was obtained.

As a result of electron microscopy observation, the average value of these particles was 0.
The particle size was 23 μm, the axis ratio (long axis: short axis) was 2:1, the particle size was uniform, and there were no dendritic particles mixed.

In addition, as a result of fluorescent X-ray analysis, St was 1.49 for Pe.
It contains atomic percent, and its bulk density is 0. '50
g/cc.

Production of iron-based metal magnetic particles exhibiting a spindle shape> Examples 22 to 33, Comparative Example 3; Example 22 Goethite particles exhibiting a spindle shape containing St obtained in Example 13 150 g of the powder was put into a No. 31 retort reduction container, and while driving and rotating, HQ gas was passed through at a rate of 35β per minute, and reduction was carried out at a reduction temperature of 300°C.

The spindle-shaped iron-based metal magnetic particles containing St obtained by the reduction were first immersed in a toluene solution to prevent rapid oxidation when taken out into the air. By evaporating this, a safe oxide film was formed on the particle surface.

As a result of fluorescent X-ray analysis, the spindle-shaped metal magnetic particles containing St and mainly composed of iron contained 0.194 atomic % of Si relative to Fe. As a result of electron microscope observation, the long axis was 0.35 μm, the axial ratio (long axis: short axis) was 2.5:1, the particle size was uniform, and dendritic particles were not mixed.

Also, specific surface area 30.5rrr/g, bulk density 0.64
g/cc, and the magnetism has a coercive force of 8700e
, the saturation magnetization was 150.2 emu/g.

Examples 23 to 33, Comparative Example 3 Spindle-shaped metal magnetic particles containing iron as a main component were obtained in the same manner as in Example 22, except that the type of starting material and the reduction temperature were varied.

Table 3 shows the main manufacturing conditions and characteristics at this time.

As a result of electron microscopy observation, the spindle-shaped iron-based metal magnetic particle powders containing St obtained in Examples 23 to 33 were found to have uniform particle size and a mixture of dendritic particles. It was something I wouldn't do.

FIGS. 4 and 5 are electron micrographs (X20.000) of spindle-shaped iron-based metal magnetic particles containing St obtained in Example 23 and Example 27, respectively.
Shown below. In addition, an electron micrograph (X
20.000) is shown in FIG.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the amount of water-soluble silicate added and the axial ratio of spindle-shaped goethite particles containing Si. FIG. 2 shows the relationship between the amount of water-soluble silicate added and the Kerr density of spindle-shaped goethite particles containing Si. FIG. 3 is a diagram showing the relationship between the amount of water-soluble silicate added and the axial ratio of spindle-shaped metal magnetic particles containing St and mainly composed of iron. Figures 4 to 6 are all electron micrographs (×20.0
00), and FIGS. 4 and 5 show Example 23 and FIG.
6 is a spindle-shaped metal magnetic particle powder mainly composed of iron containing Si obtained in Example 27, and FIG.
This is spindle-shaped metal magnetic particle powder mainly composed of iron obtained in Comparative Example 3. Patent applicant Toda Kogyo Co., Ltd. Representative Matsui Gobe 1 0 0, I 1. OIQ, Q しょう e (atomic

Claims (1)

[Claims] +11 The axial ratio (major axis: minor axis) is 3:1 or less, and S
Iron-based metal magnetic particles containing spindle-shaped iron-based metal magnetic particles containing 0.1 to 10 at% of t based on Fe and having a coercive force of 500 to 10,000 s. Metal magnetic particle powder as an ingredient. (2) The axial ratio (long axis: short axis) is 2:1 or less, and Si
From spindle-shaped metal magnetic particles containing iron as a main component and having a coercive force of 500 to 8,500 e and having a coercive force of 500 to 8,500 e. (3) A spindle-shaped metal magnetic particle powder whose main component is iron. In order to generate goethite particles exhibiting By adding 0.1 to 10 at% in terms of St to Fe, spindle-shaped goethite particles containing Si are generated, and the spindle-shaped goethite particles containing Si or this Iron is produced by heating and reducing spindle-shaped hematite particles containing Si obtained by heating and dehydrating in a reducing gas. A method for producing a metal magnetic particle powder containing mainly spindle-shaped iron as described in claim 3, wherein the amount of water-soluble silicate added is 0.3 to 8 at%. A method for producing metal magnetic particle powder containing iron as a main component, consisting of metal magnetic particles as a component. (5) Oxygen-containing gas is added to an aqueous solution containing FeC0@ obtained by reacting a ferrous salt aqueous solution and an alkali carbonate. In producing spindle-shaped goethite particles by aerating and oxidizing, the aqueous solution containing FeC0° before performing an oxidation reaction by aerating the ferrous salt aqueous solution, the alkali carbonate, and the oxygen-containing gas. By adding 0.1 to 10 atomic % of water-soluble silicate to either Fe in terms of St, spindle-shaped goethite particles containing Si are generated, and the St-containing Goethite particles exhibiting a spindle shape are heated at 400°C to 600°C in a non-reducing atmosphere.
A spindle-shaped hematite particle containing substantially high-density St obtained by heat treatment at ℃ is heated and reduced in a reducing gas, and the main component is spindle-shaped iron. A method for producing metal magnetic particle powder whose main component is iron, which is composed of metal magnetic particles. (6) Iron-based material consisting of spindle-shaped iron-based metal magnetic particles according to claim 5, wherein the amount of water-soluble silicate added is 0.3=8% or less. A method for producing metal magnetic particle powder.