JPH0463210A - Manufacture of metal magnetic granular powder having fusiform and iron as essential component - Google Patents

Abstract

PURPOSE:To improve the productivity of metal magnetic granular powder by heat-treating fusiform hematite particles coating-treated with metallic compound under non-reducing atmosphere at the specific temp. and heat-reducing under reducing gas. CONSTITUTION:Fusiform goethite particles are produced by adding zinc compound into suspension containing FeCO3. The above particles or the fusiform hematite particles obtd. by heat-dehydrating this, are coating-treated with one or more kinds of metallic compounds selected among Ni, Al, Si, P, Co, Mg, B and Zn. Successively, the fusiform hematite particles obtd. by heat-treating the particles under the non-reducing atmosphere at 300-800 deg.C, are heat-reduced under the reducing gas to obtain the metal magnetic particles having the fusiform and the iron as the essential component. By this method, the metal magnetic granular powder having the large axial ratio of fusiform and the iron as the component can be obtd. as profitable to industry and economy.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to magnetic particles having uniform particle size, which are optimal as magnetic particles having high output characteristics for high-density recording.
There are no dendritic particles mixed in, and the axial ratio (major axis diameter:
The present invention aims to provide industrially and economically advantageous spindle-shaped metal magnetic particle powder mainly composed of iron, which has a large minor axis diameter) and a high coercive force.

[Conventional technology]

In recent years, magnetic recording and playback devices for video and audio have become increasingly compact and lightweight. VTRs are being actively developed with the aim of making them smaller and lighter. On the other hand, demands for higher performance and higher recording density for magnetic tape, which is a magnetic recording medium, are increasing.

In other words, it is necessary to improve the image quality, high output characteristics, and especially the frequency characteristics of magnetic recording media, and for this purpose, it is necessary to improve the residual magnetic flux density Br, increase the coercive force, and improve the dispersibility, filling property, and tape surface. It is necessary to improve the smoothness, and there is an increasing demand for an improvement in the S/N ratio.

These characteristics of magnetic recording media are closely related to the magnetic particles used in magnetic recording media, but
In recent years, metal magnetic particles mainly composed of iron, which have higher coercive force and larger saturation magnetization than conventional iron oxide magnetic particles, have attracted attention, and have been widely used in Digital Audio Chive (DAT), 81 Video Tape, Hl. It has been put to practical use in magnetic recording media such as -8 tapes and video floppies. However, there is a strong desire to further improve the characteristics of these metal magnetic particles whose main component is iron.

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.

In order to obtain high image quality as a magnetic recording medium for video,
Nikkei Electronics (1976) May 3rd issue No. 82
~105 As is clear from the true description, ■Video S/N
Improvements are required in the ratio, (1) chroma S/N ratio, and (2) video frequency characteristics.

In order to improve the video S/N ratio and chroma S/N ratio, it is necessary to improve the dispersibility of magnetic particles in the vehicle, the orientation and filling properties in the coating film, and the magnetic recording medium. It is important to improve the surface smoothness of the magnetic particles. diameter) is required.

Next, in order to improve the video frequency characteristics, 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 He of magnetic recording media, it is required that the coercive force Hc of magnetic particles is as high as possible. The coercive force of the magnetic particle powder used in
About 13000e to 17000s is required.

Since the coercive force of magnetic particles is generally caused by its shape anisotropy, the coercive force tends to increase as the axial ratio (long axis diameter: short axis diameter) of the particles increases.

Metal magnetic particles containing iron as a main component are generally produced by combining goethite particles as a starting material, hematite particles obtained by heating and dehydrating these particles, or particles containing a different metal other than iron in a reducing gas. It is obtained by heating reduction.

Conventionally, as a method for producing goethite particle powder as a starting material, a suspension containing ferrous hydroxide obtained by adding an equivalent amount or more of an aqueous alkali hydroxide solution to an aqueous ferrous salt solution is mixed at a pH of 11 or higher to 80%. A method of producing acicular goethite particles by performing an oxidation reaction by passing oxygen-containing gas at a temperature below °C, and a method of reacting a ferrous salt aqueous solution with an alkali carbonate aqueous solution or an alkali carbonate/alkali hydroxide aqueous solution. A method is known in which spindle-shaped goethite particles are produced by carrying out an oxidation reaction by passing an oxygen-containing gas through a suspension containing PeC0 or Fe-containing precipitate obtained by this process.

[The rIli particle size that the invention seeks to solve is uniform, dendritic particles are not mixed, and the axial ratio (major axis diameter: minor axis diameter) is large and has a high coercive force. Currently, metal magnetic particles whose main component is iron are most in demand, but the acicular goethite particles obtained by the former known method described above have an axial ratio (major axis diameter: short axis diameter). Although the acicular goethite particles have a large axis diameter of 10 or more, they contain dendritic particles, and in terms of particle size, it is difficult to say that the particles have a uniform particle size.The acicular goethite particles are heated and reduced. The metal magnetic particles obtained using iron as the main component have a high coercive force due to their large axial ratio (major axis diameter: minor axis diameter), but they also contain dendritic particles. , it is difficult to say that the particle size is uniform.

The spindle-shaped goethite particles obtained by the latter method among the above-mentioned known methods have uniform particle size, and
Although these particles do not contain dendritic particles, they have the disadvantage that it is difficult to generate particles with a large axial ratio (long axis diameter: short axis diameter). There is a tendency that the smaller the value, the more noticeable it becomes. The metal magnetic particles whose main component is iron obtained by heating and reducing these spindle-shaped goethite particles have uniform particle size, and
Although the absence of dendritic particles allows for excellent dispersibility in the vehicle, orientation and filling properties in the coating film, the small axial ratio (major axis diameter: minor axis diameter) results in high retention. It has the disadvantage that it is difficult to obtain particles with magnetic force.

Conventionally, in order to obtain spindle-shaped metallic magnetic particles mainly composed of iron, which have uniform particle size, do not contain dendritic particles, and have high coercive force, spindle-shaped goethite particles have been used. Various methods have been attempted to increase the axial ratio (major axis diameter: minor axis diameter).
922, JP 60-21307, JP 60-21819, JP 60-36603, JP 62458801, and JP 2-51
There is a method described in Japanese Patent No. 429, but the axial ratio (major axis diameter: minor axis diameter) of spindle-shaped goethite particles obtained by these methods is still not sufficiently large. It is also difficult to say that metal magnetic particles whose main component is iron obtained by heating reduction have a sufficiently large axial ratio (long axis diameter: short axis diameter), and therefore it is difficult to say that they have a high coercive force. It was difficult.

The present inventor conducted various studies in order to obtain goethite particle powder that has a uniform particle size, does not contain dendritic particles, and has a spindle shape with a large axial ratio (major axis diameter: minor axis diameter). After aging a suspension containing FeCO3 obtained by reacting an aqueous alkali carbonate solution and an aqueous ferrous salt solution in a non-oxidizing atmosphere, an oxygen-containing gas is bubbled into the suspension containing FeCO3. In producing spindle-shaped goethite particles by oxidation, the amount of the alkali carbonate aqueous solution is set to 1.5 to 3.5 times the equivalent of Fe in the ferrous salt aqueous solution, and the The aging temperature during aging is 40-60°C and the aging time is 50-60°C.
In the case of 100 minutes, the major axis diameter is 0.05 to 0.8
It has already been found that it is possible to obtain goethite particle powder consisting of spindle-shaped goethite particles that are μ- and have an axial ratio (major axis diameter: minor axis diameter) of 11 or more.
(Patent Application No. 63-330532).

However, in this method, the reaction concentration is at most 0.
It was about 45 moI/l, and it was still far from being sufficient in terms of productivity such as the amount of alkali used and the amount of energy.

Therefore, in order to obtain spindle-shaped goethite particles with a large axial ratio (major axis diameter: minor axis diameter) through a resource-saving and energy-saving reaction, various studies were conducted to obtain industrially and economically advantageous goethite particles using an aqueous alkali carbonate solution and A suspension containing FeCOx obtained by reacting with an aqueous iron salt solution is aged in a non-oxidizing atmosphere, and then an oxygen-containing gas is passed through the suspension containing FeCO3 to oxidize it, thereby changing the spindle shape. When an alkali hydroxide aqueous solution is used in combination with the alkali carbonate aqueous solution to produce the goethite particles shown above, a high concentration reaction is possible and the ratio of expensive alkaline aqueous solution to iron can be reduced. It is possible to do so, and we have already obtained knowledge that it is possible to save energy in the ripening process (Japanese Patent Laid-Open No. 2-514).
No. 29).

As mentioned above, there is an unstoppable demand for improving the properties of magnetic particles in recent years, and for this reason, the axial ratio (major axis diameter: minor axis diameter) of spindle-shaped goethite particles, which are the starting material particles, has been increasingly improved. requested.

Therefore, the technical problem of the present invention is to industrially and economically advantageously obtain spindle-shaped goethite particles with a large axial ratio (major axis diameter: minor axis diameter) through a resource-saving and energy-saving reaction. do.

[Means to solve problems]

The above technical problem can be achieved by the present invention as follows.

That is, in the present invention, a suspension containing FeCO2 obtained by reacting an aqueous alkali carbonate solution with an aqueous ferrous salt solution is aged in a non-oxidizing atmosphere, and then oxygen is added to the suspension containing pecks. In producing spindle-shaped goethite particle powder by aerating and oxidizing the contained gas, the above-mentioned aging is performed before aerating and oxidizing the alkali carbonate aqueous solution, the FeCO5-containing suspension, and the oxygen-containing gas. By adding an alkali hydroxide aqueous solution of 1 to 50% of the alkali carbonate aqueous solution into any of the suspensions containing FeCO3, the total amount of the alkali carbonate aqueous solution and alkali hydroxide aqueous solution can be Fe'' in the ferrous salt aqueous solution is 1.1 to 2.5 times equivalent, and the aging temperature in the aging is 30 to 60°C, the aging time is 10 to 100 minutes, and the alkali carbonate aqueous solution is , the presence of a zinc compound in advance in any of the ferrous salt aqueous solution, the FeCO3-containing suspension, and the FeCO3-containing suspension subjected to the aging process before being oxidized by passing an oxygen-containing gas through the aqueous solution; The spindle-shaped goethite particles or spindle-shaped hematite particles obtained by heating and dehydrating the spindle-shaped goethite particles are treated with Ni, Al5St'. , P, Co, Mg
, B and Zn, and then heat-treated the particles in a non-reducing atmosphere in a temperature range of 300 to 800°C. A method of producing spindle-shaped metal magnetic particles mainly composed of iron by heating and reducing spindle-shaped hematite particles in a reducing gas to obtain spindle-shaped metal magnetic particles mainly composed of iron. It is a manufacturing method.

Next, various conditions for implementing the method of 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.

In the reaction in the present invention, the reaction concentration is 1°0
1/j! It is possible to some extent.

As the aqueous alkali carbonate solution used in the present invention, aqueous solutions of sodium carbonate, potassium carbonate, ammonium carbonate, etc. can be used.

As the aqueous alkali hydroxide solution used in the present invention, an aqueous solution of sodium hydroxide, potassium hydroxide, etc. can be used.

In the present invention, even when the aging temperature is lowered by about 10°C compared to when an aqueous alkali carbonate solution is used alone,
Further, even when the aging time is shortened by about 40 minutes, goethite particles exhibiting a spindle shape with a desired axial ratio (major axis diameter: minor axis diameter) can be obtained.

The alkali hydroxide aqueous solution can be added to either an alkali carbonate aqueous solution, a suspension containing FeC0t, or a suspension containing FeC01 that has been aged before oxidation by aeration of oxygen gas. In any case,
Reactions that save resources and energy are possible.

The amount of alkali hydroxide added is 1 to 50% based on the standard value of alkali carbonate.

If it is less than 1%, it is difficult to achieve resource and energy saving reactions. If it exceeds 50%, granular magnetite particles will be mixed in spindle-shaped goethite particles.

The total amount of the aqueous alkali carbonate solution and aqueous alkali hydroxide solution used in the present invention is 1.1 to 2.5 times equivalent to Fe in the ferrous salt aqueous solution, and the ratio of the alkaline aqueous solution to iron is reduced. Is possible. 1
．． If the amount is less than 1 equivalent, granular magnetite particles will be mixed in spindle-shaped goethite particles. When the amount exceeds 2.5 times the equivalent, the amount of expensive alkali used increases, which is not economical.

Aging in the present invention is carried out in an inert atmosphere by passing an inert gas such as N2 gas into the liquid, and is carried out while stirring using the aeration gas or mechanical operation.

The aging temperature in the present invention is 30 to 60°C. 30
If the temperature is less than °C, the axial ratio (long axis diameter: short axis diameter) becomes small, and goethite particles having a spindle shape with a large axial ratio (long axis diameter: short axis diameter) cannot be obtained. Even when the temperature exceeds 60°C, goethite particles having a spindle shape with a large axial ratio (major axis diameter: minor axis diameter) can be obtained, but there is no point in raising the ripening temperature more than necessary.

The aging time in the present invention is 10 to 100 minutes.

If the heating time is less than 10 minutes, goethite particles having a spindle shape with a large axis ratio (major axis diameter: minor axis diameter) cannot be obtained. Even if the heating time exceeds 100 minutes, goethite particles having a spindle shape with a large axial ratio (major axis diameter: short axis diameter) can be obtained, but there is no point in making the heating time longer than necessary.

As the zinc compound in the present invention, zinc sulfate, zinc chloride, etc. can be used.

The amount of zinc compound added is Z based on Fe in the ferrous salt aqueous solution.
It is 0.3 to 10 atomic % in terms of n. 0.3 atomic%
If it is less than that, it is impossible to obtain goethite particles exhibiting a spindle shape with a large axial ratio (major axis diameter: minor axis diameter). Even when the concentration exceeds 10.0 at%, spindle-shaped goethite particles with a large axial ratio (major axis diameter: minor axis diameter) can be obtained. The magnetization value of the metal magnetic particle powder, which is the main component, decreases. Axial ratio of spindle-shaped goethite particles (
Considering the long axis diameter: short axis diameter), 0.5 to 8.0 atomic % is preferable.

As shown in the Examples below, almost all of the added zinc compound is contained in the spindle-shaped goethite produced. Since the zinc compound is related to the axial ratio (major axis diameter: minor axis diameter) of the spindle-shaped goethite particles produced,
It is necessary to aerate an oxygen-containing gas into the suspension containing the Fe-containing precipitate to make it exist before oxidation. Either a suspension containing a Fe-containing precipitate or a suspension containing an Fe-containing precipitate that has been aged before passing through an oxygen-containing gas, and containing the Fe-containing precipitate that has been aged. It is most effective when added to a suspension.

The reaction temperature during oxidation of the present invention is 30 to 70°C. If the temperature is less than 30°C, it is impossible to obtain goethite particles having a spindle shape with a large axis ratio (major axis diameter: minor axis diameter). When the temperature exceeds 70''C, granular hematite particles are mixed in the spindle-shaped goethite particles.

p)l in the present invention is 7-11. If it is less than 7 or more than 11, spindle-shaped goethite particles cannot be obtained.

The oxidation means in the present invention is carried out by aerating an oxygen-containing gas (for example, air) into the liquid, and is carried out while stirring with the aerated gas or mechanical operation.

In the present invention, in order to prevent deformation of the particle shape and sintering between particles during thermal reduction, the starting material is made of Ni in advance.
, 8L Si, , P , Co, Mg, B and Zn
It is preferable to perform the adhesion treatment with one or more metal compounds selected from the following. 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.

The starting material coated with the above metal compound can be reduced as it is to obtain the desired metal magnetic particle powder whose main component is iron, but it is possible to control the magnetic properties and powder properties, and to control the shape. For control purposes, it is preferable to perform heat treatment in advance in a non-reducing gas atmosphere by a conventional method prior to reduction.

The heat treatment in the non-reducing gas atmosphere includes air,
The heat treatment can be carried out under a flow of oxygen gas or nitrogen gas at a temperature in the range of 300 to 800 °C, and the heat treatment temperature can be appropriately selected depending on the type of metal compound used for the deposition treatment of the starting material particles. preferable.

If the temperature exceeds 800''C, deformation of the particles and sintering of the particles and the particles among themselves will occur.

The temperature range of thermal reduction in the present invention is 300 to 550
°C is preferred.

If the temperature is lower than 300°C, the reduction reaction progresses slowly;
It takes a long time.

Furthermore, if the temperature exceeds 550° C., the reduction reaction rapidly progresses, causing deformation of the particles and sintering of the particles and each other.

In the present invention, the metal magnetic particle powder mainly composed of iron after thermal reduction can be prepared by a well-known method, for example, by immersing it in an organic solvent such as toluene, and in the atmosphere of the metal magnetic particle powder mainly composed of iron after reduction. After replacing the inert gas with -H inert gas, the inert gas can be taken out into the air by gradual oxidation by gradually increasing the oxygen content in the inert gas and finally converting it into air.

In the present invention, in order to improve various properties of metal magnetic particles whose main component is iron, Co5Ni, which is usually added when producing goethite particles as a starting material,
Different metals other than Fe such as Cr, Zn, Al, and sn can be added, and even in this case, the particle size that is the object of the present invention is uniform, dendritic particles are not mixed, and , it is possible to obtain goethite particle powder exhibiting a spindle shape with a large axial ratio (long axis diameter: short axis diameter).

[For production]

First, the most important point in the present invention is that FeCO obtained by reacting an aqueous alkali carbonate solution with an aqueous ferrous salt solution
) is aged in a non-oxidizing atmosphere, and then oxygen-containing gas is passed through the FeCO3-containing suspension to oxidize it to produce spindle-shaped goethite particles. 1 of the alkali carbonate aqueous solution, the FeC0y-containing suspension, and the FeCO3-containing suspension subjected to the aging process before oxidation by passing an oxygen-containing gas through the alkali carbonate aqueous solution. By adding ~50% aqueous alkali hydroxide solution, the total amount of aqueous alkali carbonate solution and aqueous alkali hydroxide solution relative to Fe'' in the aqueous ferrous salt solution],
1 to 2.5 times the weight equivalent, the aging temperature in the aging is 30 to 60°C, the aging time is 10 to 100 minutes, and the alkali carbonate aqueous solution, the ferrous salt aqueous solution, and the FeCO3 are included. FeC0 subjected to the aging before oxidation by passing through the suspension and oxygen-containing gas.
If a zinc compound is previously present in any of the suspensions containing 1, the axial ratio (major axis diameter: short axis diameter) can be increased between layers. Shaft diameter: short shaft diameter)
It is possible to produce spindle-shaped goethite particles having 15 or more, and the spindle-shaped hematite particles obtained by heating and dehydrating the spindle-shaped goethite particles or the spindle-shaped goethite particles are treated with Ni, Al
, St, P, Co, FIG, B, and Zn.
The particles or particles are then heated in a non-reducing atmosphere for 30
When spindle-shaped hematite particles obtained by heat treatment in the temperature range of 0 to 800°C are heat-reduced in a reducing gas, the particle shape deforms and sintering between particles occurs during heat-reduction. By preventing this, the particle shape and axial ratio (major axis diameter: minor axis diameter) of the starting material particles can be maintained and inherited, resulting in uniform particle size and no dendritic particles. Moreover, it is a fact that spindle-shaped metal magnetic particle powder mainly composed of iron can be obtained, which has a large axial ratio (major axis diameter: minor axis diameter) and has a high coercive force.

In the present invention, the reason why goethite particles exhibiting a spindle shape with a large axis ratio (major axis diameter: minor axis diameter) is obtained is explained by the present inventors, as shown in the reference examples and comparative examples described later. The effects of the present invention cannot be obtained in either case where the aging is not carried out or in the case where a zinc compound is not present in the reaction for producing spindle-shaped goethite particles according to the present invention. We believe this is due to a synergistic effect.

Some of the numerous experimental examples conducted by the present inventor will be explained below.

FIGS. 1 and 2 respectively show the relationship between the amount of zinc sulfate present and the long sleeve and axis ratio (long axis diameter: short axis diameter) of spindle-shaped goethite particles.

That is, under the reaction conditions of Example I described below, the long axis and axis ratio (long axis diameter: short axis diameter) of spindle-shaped goethite particles obtained when the amount of zinc sulfate was limited to 0 to 10% by weight. The vertical axis represents the shaft diameter, and the horizontal axis represents the amount of zinc sulfate present.

As shown in Figures 1 and 2, the long axis of the spindle-shaped goethite particles produced is little affected by the presence of zinc sulfate, and the axial ratio (long axis diameter: short axis diameter) is smaller than that of zinc sulfate. It tends to become larger as the abundance increases.

From this, it is thought that the zinc compound has the effect of suppressing the growth of spindle-shaped goethite particles that are produced in the minor axis direction.

In addition, there is a method disclosed in Japanese Patent Publication No. 59-48768, for example, in which a suspension containing FeCO3 is aged in a non-oxidizing atmosphere. F produced as 1.06 times the amount
By treating an aqueous solution containing eCO3 at room temperature in a non-oxidizing atmosphere for 120 to 240 minutes, goethite particle powder having a uniform particle size and a spindle shape is obtained,
It is not possible to obtain goethite particles having a spindle shape with a large axis ratio (major axis diameter: minor axis diameter).

Incidentally, the axial ratio (major axis diameter: minor axis diameter) of the spindle-shaped goethite particles obtained by the method described in the above-mentioned Japanese Patent Publication No. 59-48768 is "Example 1" and "Example 2". In each example, it is about 4.

〔Example〕

Next, the present invention will be explained with reference to Examples and Comparative Examples.

In addition, the major axis diameter of the particles in the following examples and comparative examples,
The axial ratio (major axis diameter/minor axis diameter) was expressed as an average value of values measured from electron micrographs.

Moreover, the zinc content was shown as a value measured by fluorescent X-ray analysis.

Example 1 In a reaction vessel maintained in a non-oxidizing atmosphere by flowing N gas at a rate of 3.40 -
ol/l NazCOi aqueous solution 5581 and 6.5 m
ol/12 NaOH aqueous solution 42.01 (NazC
This corresponds to 25.3% of O*. ) was added (NazC
The total amount of O3 and NaOH corresponds to 1.5 times equivalent to Fe. ), 300 i of ferrous sulfate aqueous solution containing 1.5 mol/l of Fe was added and mixed (Fe" if
! r! j corresponds to 0.50 sol/l. ) and produced a Fe-containing precipitate at a temperature of 50°C.

While continuously blowing N2 gas into the suspension containing the Fe-containing precipitate at a rate of 3.4 cm/sec,
Hold at °C for 70 min, then Zn versus Fe 3.
After adding an aqueous zinc sulfate solution so as to contain 0 atom %, the solution was held for an additional 10 minutes. Air was passed through the aged suspension containing the Fe-containing precipitate at a rate of 4.0 cm/sec for 6.7 hours at a temperature of 50°C to generate yellowish brown precipitate particles. In addition, po during air ventilation was 8.7 to 9.8.

The yellow-brown precipitated particles were separated in a furnace, washed with water, dried, and pulverized by a conventional method.

As a result of X-ray diffraction, the obtained yellow-brown particles were found to be goethite, and the electron micrograph shown in Figure 3 (x 30,000
), it consists of spindle-shaped particles with an average major axis diameter of 0°29 μm and an axial ratio (major axis diameter: minor axis diameter) of 17.6, and the particle size is uniform and dendritic particles are not mixed. Met. Further, the zinc content was 3.0 atomic % of Zn with respect to Fe.

Examples 2 to 5, Comparative Examples 1 to 4, Reference Example 1, Type, concentration, and usage amount of alkali carbonate aqueous solution in production reaction of Fe-containing precipitate or FeCO3, Type, concentration, usage amount, and mixing of alkali hydroxide aqueous solution Proportion and timing of addition, type, concentration and usage amount of Fe''° aqueous solution, reaction (Fe'') concentration, temperature during mixing, temperature and time in the aging process, type of Zn compound, amount and timing of addition, and temperature in the oxidation process. Yellowish brown particles were obtained in the same manner as in Example 1, except that the air flow rate was varied.

The main manufacturing conditions and characteristics at this time are shown in Tables 1 and 2.

The spindle-shaped goethite particles obtained in Examples 2 to 5 all had uniform particle sizes and did not contain dendritic particles.

Further, the particles obtained in Comparative Example 1 and Comparative Example 2 are shown in electron micrographs (X 3000
0) and X-ray diffraction results showed that granular magnetite particles were mixed in spindle-shaped goethite particles.

As shown in the electron micrograph (X30000) shown in FIG. 6, the spindle-shaped L7 goethite particles obtained in Comparative Example 3 all had small axial ratios (major axis diameter: minor axis diameter). .

<Adhesion treatment of spindle-shaped goethite particles with metal compound> Examples 6 to 10, Comparative Examples 5 to 6, Reference Example 2
Example 6 In addition to the press cake obtained in Example 1, an amount equivalent to 1000 g of water-washed spindle-shaped goethite particles was added to 3
It was suspended in 01 t of water. The pH of the suspension at this time was 9.
．． It was 4.

Next, 13.0% by weight of goethite was added to the suspension.
So that ＾1 (NOz) s・9■20 becomes 130
Co(CHzCOO)z ・4Hz0 21
1 g was added and stirred for 10 minutes. p of the suspension at this time
H was 4.54.

Next, 18.0% by weight of goethite was added to the suspension.
A solution in which 180 g of HsBOs was dissolved was slowly added and stirred for 15 minutes.

Furthermore, after adding ammonia water and adjusting the pH to 9.5, it was separated in a furnace using a filter press and dried to obtain A1, Co,
Goethite coated with compound B was obtained.

The content of ^l, Co, and B in the obtained goethite was 70.81wtX for AI, and 4.0wtX for Co.
34@tL B and 0.73wtχ.

Examples 7-1O1 Comparative Examples 5-6, Reference Example 2 Types of particles to be treated, ^1. Si, P, Ni, Mg, Co
, B, and Zn compounds and the amounts added were varied in the same manner as in Example 6 to obtain spindle-shaped goethite particles coated with metal compounds.

Table 3 shows the main processing conditions at this time.

<Production of spindle-shaped metal magnetic particle powder mainly composed of iron> Examples 11 to 17, Comparative Examples 7 to 8, Reference Example 3; Example 11 Old, Co, B compound obtained in Example 6 700 g of spindle-shaped goethite particles coated with
After heat treatment at 00°C, spindle-shaped hematite particles coated with ^l, Co, and B compounds were obtained.

Above ^1. 100 g of spindle-shaped hematite particles coated with Co, B compounds were placed in a rotating retort reducing container with a volume of about 101 cm, and the H8 was heated without being driven and rotated.
Gas is aerated at a rate of 501/min and the reduction temperature is 410°C.
I returned it with

When the metal magnetic particle powder mainly composed of iron containing Al, Co, and B obtained by reduction is taken out into the air, 2. It was immersed in toluene and taken out to prevent severe oxidation.

A portion was taken out and a stable oxide film was formed on the surface while toluene was evaporated.

This^1. The metal magnetic particle powder mainly composed of iron containing Co and B is shown in the electron micrograph (X 3
0000), the average long axis is 0424 μm,
The axial ratio (major axis diameter: minor axis diameter) was 15.1:1, and the particle size was uniform and fine without any dendritic particles.

Further, the magnetic properties were a coercive force He of 17500e, a saturation magnetization σs of 15B, and 3 emu/g.

Examples 12 to 17, Comparative Examples 7 to 8, Reference Example 3 Example 11 except that the type of starting material, heat treatment temperature, type of non-reducing atmosphere, reduction temperature and H2 flow rate were variously changed.
In the same manner as above, spindle-shaped metal magnetic particles mainly composed of iron were obtained.

Table 4 shows the main manufacturing conditions and characteristics at this time.

All of the spindle-shaped metal magnetic particle powders containing iron as a main component obtained in Examples 12 to 17 had uniform particle size and did not contain any dendritic particles.

<Manufacture of coating film> Examples 18 to 24, Comparative Examples 9 to 10, Reference Example 4; Example 18 The main component is spindle-shaped iron containing Al, Co, and B obtained in Example 11. Using metal magnetic particles, an appropriate amount of dispersant, vinyl chloride/vinyl acetate copolymer, thermoplastic polyurethane resin, and a mixed solvent consisting of toluene, methyl ethyl ketone, and methyl isobutyl ketone were blended to a certain composition, and then mixed with a paint conditioner for 8 hours. The mixture was mixed and dispersed to make a magnetic paint.

The above-mentioned mixed solvent was added to the obtained magnetic paint to adjust the viscosity of the paint to an appropriate paint viscosity, and the mixture was coated on a polyester film in a conventional manner, oriented in a magnetic field, and dried to produce a coating film.

This coated film was measured by VSH under an external magnetic field of 10 KOeO, and as a result, the coercive force Hc was 17200e, the residual magnetic flux density Br was 3490 Gauss, and the square shape Br/Bm was 0.90.

Examples 19-24, Comparative Examples 9-10, Reference Example 4 Coating films were produced in the same manner as in Example 18, except that the type of spindle-shaped magnetic particles was varied.

Table 5 shows the properties of this coating film.

Table [Effects of the Invention] According to the method for producing spindle-shaped metal magnetic particle powder mainly composed of iron according to the present invention, as shown in the above-mentioned example,
High concentration reaction is possible, the ratio of alkaline aqueous solution to iron can be reduced, and productivity can be increased due to the ability to save energy in the ripening process. By making it possible to obtain spindle-shaped goethite particles with a large axial ratio (long axis diameter: short axis diameter) through a resource-saving and energy-saving reaction, the spindle-shaped particles have a large axial ratio (long axis diameter: short axis diameter). Metal magnetic particles containing iron as a main component can be obtained industrially and economically advantageously.

[Brief explanation of drawings]

FIGS. 1 and 2 respectively show the relationship between the amount of zinc sulfate present and the long axis and axis ratio (long axis diameter: short axis diameter) of spindle-shaped goethite particles. 3 and 6 are electron micrographs (X30000) showing the particle structure of spindle-shaped goethite particles obtained in Example 1 and Comparative Example 3, respectively. FIGS. 4 and 5 are electron micrographs (x 30,000 ). FIG. 7 is an electron micrograph (X 30
000). Patent source: Toda Kogyo Co., Ltd. In/Fe(IJt) lλ 3Q<)00n

Claims (1)

[Claims] (1) After aging a suspension containing FeCO_3 obtained by reacting an aqueous alkali carbonate solution and an aqueous ferrous salt solution in a non-oxidizing atmosphere, an oxygen-containing gas is added to the suspension containing FeCO_3. In producing spindle-shaped goethite particles by aeration and oxidation, the alkali carbonate aqueous solution, the suspension containing FeCO_3, and the oxygen-containing gas are aerated to perform the aging before oxidation. By adding an alkali hydroxide aqueous solution of 1 to 50% of the alkali carbonate aqueous solution into any of the suspensions containing FeCO_3, the total amount of the alkali carbonate aqueous solution and the alkali hydroxide aqueous solution becomes the ferrous iron aqueous solution. The amount is 1.1 to 2.5 times equivalent to Fe^2^+ in the salt aqueous solution, and the ripening temperature is set at 30 to 60°C.
, the aging time is 10 to 100 minutes, and the alkali carbonate aqueous solution, the ferrous salt aqueous solution, the FeCO_3
goethite that has a spindle shape by pre-existing a zinc compound in either the suspension containing FeCO_3 or the suspension containing FeCO_3 which is aged before being oxidized by passing an oxygen-containing gas through the suspension. Ni, Al, Si, P, Co, Mg, B
and Zn, and then the particles were heated in a non-reducing atmosphere for 30
Hematite particles exhibiting a spindle shape obtained by heat treatment in a temperature range of 0 to 800°C are thermally reduced in an ubiquitous gas to obtain spindle-shaped metal magnetic particles mainly composed of iron. A method for producing metal magnetic particles whose main component is iron and which exhibits a spindle shape.