JP2882111B2 - Method for producing acicular metal magnetic particle powder containing iron as a main component - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a uniform particle size, no mixture of dendritic particles, a large axial ratio (major axis diameter / minor axis diameter), and 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, which is excellent.

[0002]

2. Description of the Related Art In recent years, long-time recording, miniaturization and lightening of magnetic recording / reproducing devices for video and audio have been intensified. In particular, VTR (video tape recorder) has been remarkably popularized in recent years. 2. Description of the Related Art VTRs aiming at long-term recording and reduction in size and weight have been actively developed.
On the other hand, demands for higher performance and higher density recording of magnetic tapes, which are magnetic recording media, are increasing. That is, high image quality and high output characteristics of the magnetic recording medium, especially improvement of the frequency characteristics are required. For that purpose, improvement of the residual magnetic flux density Br, high coercive force, and dispersibility, filling property,
It is necessary to improve the smoothness of the tape surface, and the S / N ratio is increasingly required to be improved.

[0003] These characteristics of a magnetic recording medium have a close relationship with the magnetic particle powder used in the magnetic recording medium, but in recent years, they have higher preservation than conventional iron oxide magnetic particle powder. Attention has been focused on needle-like metal magnetic particles mainly composed of iron having magnetic force and large saturation magnetization, and has been used in magnetic recording media such as digital audio tape (DAT), 8 mm video tape, Hi-8 tape, and video floppy. Has been However, it is strongly desired to further improve the characteristics of these needle-like metal magnetic particles containing iron as a main component.

Now, the relationship between the characteristics of the magnetic recording medium and the characteristics of the magnetic particle powder used will be described in detail as follows. In order to obtain high image quality as a magnetic recording medium for video, as is clear from the description of Nikkei Electronics (1976), May 3, Issue No. 82-105, the video S / N ratio and the chroma S / N ratio Therefore, it is required to improve video frequency characteristics.

[0005] 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 a vehicle, the orientation and the filling property in a coating film, and It is important to improve the surface smoothness of a magnetic recording medium. Such magnetic particles have a uniform particle size, do not contain dendritic particles, and have an axial ratio (long axis diameter). / Short axis diameter) is required to be large.

Next, in order to improve video frequency characteristics, it is necessary that the coercive force Hc of the magnetic recording medium be high and the residual magnetic flux density Br be high. In order to increase the coercive force Hc of the magnetic recording medium, it is required that the coercive force Hc of the magnetic particle powder be as high as possible, and is currently used for video floppy, DAT, 8 mm video, and Hi-8. The coercive force of the magnetic particle powder is 1300 Oe or more.
About 1800 Oe is required. Since the coercive force of the magnetic particle powder generally occurs due to its shape anisotropy, the coercive force tends to increase as the axial ratio (major axis diameter / minor axis diameter) of the particles increases.

In order to increase the output of a magnetic recording medium,
FIG. 1 of JP-A-63-26821 shows the relationship between the SFD measured for the above magnetic disk and the recording / reproducing output. 1, the relationship between the recording and reproduction output becomes a straight line, which indicates that the recording and reproduction output can be increased by using a ferromagnetic powder having a small SFD. In order to increase the recording / reproducing output, it is desirable that the SFD is small.
The following S. F. D. is necessary. "
S. of magnetic recording medium F. D. (Switching F
It is necessary that the field distribution is small, and for that purpose, the distribution width of the coercive force of the magnetic particle powder needs to be small.

[0008] The acicular metal magnetic particles containing iron as a main component generally include goethite particles as a starting material, hematite particles obtained by heating and dehydrating the particles, or particles containing a dissimilar metal other than iron. It is obtained by heat reduction in a reducing gas.

As described above, the particle size is uniform, dendritic particles are not mixed, and the large axial ratio (long axis diameter /
Needle-like magnetic metal particles mainly composed of iron and having a short axis diameter) and excellent coercive force distribution are currently the most demanded. In order to obtain the acicular magnetic metal particle powder as the main component, the goethite particle powder, which is the starting material, has a uniform particle size, does not contain dendritic particles, and has a large axial ratio (long axis diameter / (Short axis diameter) is required.

Conventionally, as a method for producing goethite particle powder as a starting material, a suspension containing ferrous hydroxide colloid obtained by adding an equivalent amount or more of an alkali hydroxide aqueous solution to a ferrous salt aqueous solution is used. A method of producing needle-like goethite particles by passing an oxygen-containing gas at a temperature of 80 ° C. or lower to carry out an oxidation reaction (Japanese Patent Publication No.
No. 5610), spindle-shaped goethite particles are formed by passing an oxygen-containing gas through a suspension containing FeCO ₃ obtained by reacting an aqueous ferrous salt solution and an aqueous alkali carbonate solution to carry out an oxidation reaction. Generation method (Japanese Unexamined Patent Publication No.
No. -80999) and an aqueous solution of ferrous salt to which an aqueous solution of an alkali hydroxide or an alkali carbonate is added in an amount equivalent to or less than an equivalent amount of ferrous hydroxide colloid or an aqueous solution of ferrous salt containing iron carbonate. Aeration is performed to generate an acicular goethite nucleus particle by performing an oxidation reaction, and then, to an aqueous ferrous salt solution containing the acicular goethite nucleus particle, an equivalent amount or more with respect to the amount of Fe ²⁺ in the aqueous ferrous salt solution. After adding an aqueous alkali hydroxide solution of the formula (1) to grow the needle-like goethite core particles by passing an oxygen-containing gas (Japanese Patent Publication No. 59-487).
No. 66, JP-A-59-128293, JP-A-59-128294, JP-A-59-128295
And Japanese Patent Application Laid-Open No. Sho 60-21818).

[0011]

The particle size is uniform, dendritic particles are not mixed, and a large axial ratio (long axis diameter / short axis diameter) is excellent, and the coercive force distribution is excellent. Needle-like metal magnetic particles containing iron as a main component are the most demanded at present, but in the case of the above-mentioned method for producing goethite particles as a starting material, the axial ratio (long axis) In particular, 10 or more needle-like goethite particles having a large diameter / short axis diameter) are generated, but dendritic particles are mixed.
Also, in terms of the particle size, it is difficult to say that the particles have a uniform particle size.

In the case of the above method, spindle-shaped particles having a uniform particle size and containing no dendritic particles are produced, while the axial ratio (major axis diameter / minor axis) Diameter)
Has a drawback that particles having a large axial ratio (major axis diameter / short axis diameter) are difficult to generate. In particular, this phenomenon becomes more pronounced as the major axis diameter of the formed particles decreases. There is a tendency. Various attempts have been made to increase the axial ratio (major axis diameter / minor axis diameter) of goethite particles having a spindle shape, but at most about 17-18, which is not yet satisfactory.

The above-mentioned method is characterized by various properties of the acicular goethite particles obtained by each of the above-mentioned methods and
That is, although it is intended to improve the particle size, the axial ratio (major axis diameter / minor axis diameter), and the presence or absence of dendritic particles, goethite particle powder having sufficiently satisfactory properties has not yet been obtained.

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

Therefore, the present invention provides a uniform particle size without dendritic particles, a large axial ratio (major axis diameter / minor axis diameter), and excellent coercive force distribution. It is a technical object to obtain acicular metal magnetic particle powder containing iron as a main component.

[0016]

The above technical objects can be achieved by the present invention as described below. That is, the present invention is obtained by reacting an aqueous solution of 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 the equivalent to Fe ²⁺ in the aqueous solution of a ferrous salt. The ferrous hydroxide colloid or the iron-containing precipitate colloid is oxidized by passing an oxygen-containing gas through the ferrous hydroxide reaction solution or the ferrous salt-containing reaction solution containing the iron-containing precipitate colloid. After forming the goethite core particles, the ferrous salt reaction solution containing the acicular goethite core particles or the ferrous salt reaction solution containing the acicular goethite core particles was maintained at a temperature of 75 ° C. or higher as necessary. After that, the reaction solution was cooled to 60 ° C or lower, or the reaction solution was maintained at 60 ° C or lower in a non-oxidizing atmosphere if necessary, or the temperature was lowered to 60 ° C or lower after maintaining the temperature at 75 ° C or higher as necessary. , 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 The axial ratio (major axis diameter / minor axis)
Diameter) to form acicular goethite particles of 20 to 32, and then the acicular goethite particles or acicular hematite particles obtained by heating and dehydrating the particles or, if necessary, the surface of the particles is a Ni compound, an Al compound, Si compound, P compound, C
o the goethite particles or the hematite particles coated with one or more metal compounds selected from the group consisting of an o compound, a Mg compound, a B compound, and a Zn compound are heat-reduced in a reducing gas to mainly reduce iron. This is a method for producing acicular metal magnetic particle powder containing iron as a main component, which comprises obtaining acicular metal magnetic particles as a component.

Next, conditions for implementing 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. The aqueous solution of alkali hydroxide used in the production reaction of the acicular goethite particles of the present invention includes an aqueous solution of sodium hydroxide, an aqueous solution of potassium hydroxide, and the like, and the aqueous solution of alkali carbonate includes an aqueous solution of sodium carbonate, an aqueous solution of potassium carbonate, ammonium carbonate, and the like. Can be used.

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

The abundance of the acicular goethite core particles in the present invention is 10 to 90 mol% based on the produced goethite particles.
Is preferable. If the content is less than 10 mol%, the needle-like goethite particles intended for the present invention cannot be obtained. If the content exceeds 90 mol%, the ratio of iron carbonate to the acicular goethite core particles becomes small, so that the reaction becomes nonuniform and the particle size of the obtained goethite particles becomes uneven.

In the present invention, if necessary, the ferrous salt reaction solution containing acicular goethite core particles is maintained at a temperature of 75 ° C. or higher and then cooled to 60 ° C. or lower, or optionally in a non-oxidizing atmosphere. A needle-like metal mainly composed of iron obtained by maintaining the temperature at 60 ° C. or lower, or, if necessary, maintaining the temperature at 75 ° C. or higher, and then lowering the temperature to 60 ° C. or lower, and subsequently maintaining the non-oxidizing atmosphere. Various properties of the magnetic particle powder can be further improved. The temperature at which the ferrous salt reaction solution containing acicular goethite core particles is held is 75 ° C.
If it is less than 1, the effect of maintaining the temperature at a high temperature is not sufficient, and it is not possible to obtain needle-like metal magnetic particles containing iron as a main component and having a more excellent squareness and orientation degree. If the temperature at which the ferrous salt reaction solution containing the acicular goethite nucleus particles is maintained in a non-oxidizing atmosphere exceeds 60 ° C., the oxygen-containing gas is then passed through 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 at least equivalent to Fe ²⁺ in the remaining aqueous ferrous salt solution. When the amount is less than the equivalent, the particle size of the obtained goethite particles becomes uneven, and spherical magnetite particles are mixed.

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

The reaction temperature in the present invention may be usually at a temperature of 60 ° C. or less at which goethite particles are formed. 6
When the temperature exceeds 0 ° C., granular magnetite particles are mixed in the acicular goethite particles. In the present invention, not only the formation reaction of goethite nucleus particles and the growth reaction of the goethite nucleus particles can be performed using the same reaction tower, but also when the target goethite particles are used even when separate reaction towers are used. can get.

In the present invention, in order to prevent the deformation of the particle shape and the sintering between the particles during the heat reduction, the starting materials are Ni compound, Al compound, Si compound, P compound, Co compound, Mg compound, It is preferable to perform the deposition treatment with one or more metal compounds selected from a compound and a Zn compound. Since these metal compounds not only have a sintering preventing effect but also have a function of controlling the reduction rate, they are preferably used in combination as needed.

The starting material that has been subjected to the deposition treatment with the above-mentioned metal compound can be directly reduced to obtain the desired metal magnetic particle powder containing iron as a main component. In order to control the shape and shape, it is preferable to perform a heat treatment in a non-reducing gas atmosphere in advance by a conventional method before the reduction.

The heat treatment in the non-reducing gas atmosphere is performed under a flow of air, oxygen gas, and nitrogen gas at 300 to 800.
It can be performed in a temperature range of ° C., and it is more preferable that the heat treatment temperature is appropriately selected according to the type of the metal compound used for the deposition treatment of the starting material particles. When the temperature exceeds 800 ° C., deformation of the particles and sintering between the particles and the particles are caused.

The temperature range of the heat reduction in the present invention is 3
00-550 degreeC is preferable. When the temperature is lower than 300 ° C., the progress of the reduction reaction is slow and a long time is required. Also, 5
If the temperature exceeds 50 ° C., the reduction reaction proceeds rapidly, causing deformation of the particles and sintering between the particles.

In the present invention, the metal magnetic particle powder containing iron as a main component after heat reduction can be obtained by a known method, for example, a method of immersing the powder in an organic solvent such as toluene, or a metal magnetic particle containing iron as a main component after reduction. After the atmosphere of the powder is once replaced with an inert gas, it can be taken out into the air by a method such as gradually oxidizing by gradually increasing the oxygen content in the inert gas into air while gradually increasing the oxygen content.

In the present invention, a Co compound, a Ni compound, a Cr compound, which are usually added when producing goethite particles as a starting material, in order to improve various properties of the metal magnetic particles containing iron as a main component. Compound, Zn compound, A
One or two or more compounds selected from the group consisting of a compound 1, a Mn compound, a P compound, a Si compound and a B compound can be added. It is possible to obtain a goethite particle powder having no needle-like particles and having an acicular shape having a large axial ratio (major axis diameter / minor axis diameter).

[0030]

First, the most important point in the present invention is that an aqueous solution of ferrous salt and an aqueous solution of alkali hydroxide or an aqueous solution of alkali carbonate or alkali hydroxide / carbonate which are less than equivalent to Fe ²⁺ in the aqueous solution of ferrous salt are used. An oxygen-containing gas is passed through the ferrous hydroxide colloid or iron-containing precipitate colloid containing a ferrous hydroxide colloid or an iron-containing precipitate colloid obtained by reacting with an alkaline aqueous solution. After the precipitate colloid is oxidized to form acicular goethite nucleus particles, the ferrous salt reaction solution containing the acicular goethite nucleus particles is added to the ferrous salt reaction solution in an amount equivalent to or more than Fe ²⁺ in the ferrous salt reaction solution. When the growth reaction of the acicular goethite nucleus particles is performed by passing the oxygen-containing gas after the addition of the aqueous alkali carbonate solution, the particle size is uniform and dendritic particles are not mixed, and Axle ratio Major axis diameter / minor axis diameter) is large, in particular, 20 acicular goethite particles of ~ 32 is obtained, starting material particles acicular hematite particles were heated dehydrated acicular goethite particles or acicular goethite particles The needle-like metal magnetic particles containing iron as a main component obtained as the above are also particles having a uniform particle size, no mixture of dendritic particles, and having a large axial ratio (major axis diameter / minor axis diameter). Is obtained. The fact is that acicular magnetic iron oxide particles having these various properties have excellent coercive force distribution.

When an aqueous alkali hydroxide solution is used in place of the aqueous alkali carbonate solution in the growth reaction of the goethite core particles, as shown in the comparative examples described below, the target particle size of the present invention is uniform and dendritic particles are formed. Needle-like goethite particle powder that is not mixed and has a large axial ratio (major axis diameter / short axis diameter) cannot be 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 more, 6
When the temperature is lowered to 0 ° C. or lower, needle-like metal magnetic particles containing iron as a main component and having a more excellent degree of orientation and squareness can be obtained. When the ferrous salt reaction solution containing acicular goethite core particles is kept at 60 ° C. or lower under a non-oxidizing atmosphere,
Needle-like metal magnetic particles having iron as a main component and having a better coercive force distribution can be obtained. After maintaining 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 the sample is kept in a non-oxidizing atmosphere, needle-like metal magnetic particles having better orientation, squareness and coercive force distribution can be obtained.

[0033]

Next, the present invention will be described with reference to examples and comparative examples. In addition, 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 average values of the numerical values measured from electron micrographs.

The particle size distribution of the particles was represented by a geometric standard deviation (σg) obtained by the following method. That is, the major axis diameter of 350 particles shown in a 120,000-fold electron micrograph was measured, and the logarithmic normal was calculated from the actual major axis diameter and the number of particles calculated from the measured value according to a statistical method. The horizontal axis on the probability paper plots the major axis diameter of the particles, and the vertical axis plots the cumulative number of particles belonging to each of the major axis diameter sections at equal intervals in percentage. Then, the value of the major axis diameter corresponding to 50% and 84.13% of the number of particles was read from this graph, and the major axis diameter (μm) when the number of particles was 50% was counted to 84.1%.
It was shown by the value divided by the major axis diameter (μm) at 3%.

The magnetic properties and coating properties of the acicular metal magnetic particles containing iron as a main component are described in "Vibration sample magnetometer VSM-3".
S-15 "(manufactured by Toei Industry Co., Ltd.)
The measurement was performed over 0KOe. Squareness of coating film and S.I. F.
D. Was measured using a sheet sample obtained by the method of Example 43 described later. Also, S.I. F. D. Using the differentiating circuit of the magnetometer, obtain the differential curve of the demagnetization curve of the magnetic hysteresis curve, measure the half width of this curve,
It was determined by dividing this value by the coercive force.

<Method for Producing Acicular Goethite Particle Powder> Examples 1 to 14, Comparative Examples 1 and 2 Example 1 Ferrous sulfate aqueous solution 1 containing 1.50 mol / l of Fe ²⁺
2.8 l and 0.44-N NaOH aqueous solution 30.2
1 (corresponding to 0.35 equivalents to Fe ²⁺ in the aqueous ferrous sulfate solution) to form an aqueous ferrous sulfate solution containing Fe (OH) ₂ at a pH of 6.7 and a temperature of 38 ° C. Was performed.

At a temperature of 40 ° C., 130 l of air per minute was added to the aqueous ferrous sulfate solution containing Fe (OH) ₂ at a rate of 3.0 l / min.
Vent for a period of time to produce goethite core particles. To a ferrous sulfate aqueous solution containing the above goethite core particles (the abundance of goethite core particles corresponds to 35 mol% based on the produced goethite particles), a 5.4-N aqueous solution of Na ₂ CO ₃ 7.
0 l (1.5 ^% for Fe ²⁺ in the residual aqueous ferrous sulfate solution)
It corresponds to the equivalent. ) Was added, and 130 l / min of air was passed through at pH 9.4 and a temperature of 42 ° C. for 4 hours to produce goethite particle powder. The produced goethite particles were separated by filtration, washed with water and dried by a conventional method.

Observation by an electron microscope revealed that the resulting goethite particle powder had a uniform σg of 0.801, a uniform particle size, no dendritic particles mixed, a long axis of 0.33 μm, and an axial ratio (long axis diameter). (Short axis diameter) was 25.

Examples 2 to 14 In the production of goethite core particles, the type of ferrous salt aqueous solution, the concentration and amount of Fe ²⁺ used, the type of alkaline aqueous solution,
Example 1 except that the concentration and amount used, the type and amount of the different element, the reaction temperature, and the concentration and amount of the alkaline aqueous solution in growing the goethite core particles, the type and amount of the different element, and the reaction temperature were variously changed. In the same manner, goethite particle powder was obtained. Tables 1 and 2 show the main production conditions and various properties of the goethite particle powder at this time. Examples 2-1
As a result of observation with an electron microscope, the acicular goethite particle powder obtained in 4 was uniform in particle size and did not contain dendritic particles. Electron micrographs (× 30) of the acicular goethite particles obtained in Examples 2, 10 and 14
000) is shown in FIGS.

COMPARATIVE EXAMPLE 1 7.0 l of a 6.2-N NaOH aqueous solution (based on Fe ²⁺ in the residual ferrous sulfate aqueous solution) instead of 7.0 l of a 5.4-N aqueous Na ₂ CO ₃ solution This corresponds to 2.25 equivalents.)
Example 2 was repeated except that no P compound was added.
In the same manner as in Example 1, goethite particle powder was obtained. The obtained goethite particle powder was obtained by an electron microscope photograph (× 3000) shown in FIG.
As shown in (0), the σg was 0.635 and the particle size was uneven, and dendritic particles were mixed.

COMPARATIVE EXAMPLE 2 7.0 l of a 2.74-N NaOH aqueous solution (1 liter of Fe ²⁺ in an aqueous ferrous sulfate solution) was used in place of 7.0 l of a 5.4-N aqueous Na ₂ CO ₃ solution. 2.0 equivalents) and a growth reaction was performed at 80 ° C. while adjusting the pH to 4.2, and goethite particle powder was obtained in the same manner as in Example 2 except that the P compound was not added. Was. As shown in the electron micrograph (× 30000) of FIG. 5, the obtained goethite particle powder had an uneven particle size of σg of 0.612 and a mixture of dendritic particles.

<Production of Acicular Hematite Particle Powder> Example 15 The acicular goethite particles obtained in Example 5 were placed in air for 300 hours.
The resultant was dehydrated by heating at ℃ to obtain acicular hematite particles. As a result of observation with an electron microscope, 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.

<Attachment Treatment of Acicular Goethite Particle Powder with Metal Compound> Examples 16 to 28, Comparative Examples 3 to 4; Example 16 1000 g of the filtered and water-washed acicular goethite particles obtained in Example 1 was added to 1000 g of the particles. The corresponding amount of presscake was suspended in 30 l of water. At this time, the pH of the suspension was 9.3. Next, 300 ml of an aqueous solution in which 5 g of sodium hexametaphosphate was dissolved was added to the above suspension, and the mixture was stirred and dispersed for 15 minutes. Then, 120 g of sodium silicate (No. 3 water glass) was added to the goethite dispersion suspension, followed by stirring for 30 minutes. Further, an aqueous solution containing 40 g of a sodium aluminate solution was added to the goethite dispersion suspension, followed by stirring for 20 minutes.

Next, acetic acid having a concentration of 10% 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 washed by filtration 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 and 4 The metal compound was deposited in the same manner as in Example 16 by changing the type of particles to be processed, the type of the material to be processed, and the amount of addition. Needle-like goethite particles were obtained. Table 3 shows the main manufacturing conditions at this time.

Example 18 An amount of press cake equivalent to 1000 g of filtered and washed needle-like goethite particles obtained in Example 4 was suspended in 30 l of water. At this time, the pH of the suspension was 9.4. Next, 180 parts by weight of Al (NO ₃ ) ₃ .9H ₂ O was added to the above suspension so as to be 18.0% by weight of goethite.
g of Co (CH ₃ COO) ₂ .4H ₂ O in an amount of 12.7% by weight based on goethite.
With Zn so as to be 5.0% by weight based on goethite.
(CH ₃ COO) was added to ₂ · 4H ₂ O 50g 20
Stirred for minutes. At this time, the pH of the suspension was 4.15.

Next, 1 g 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, the pH was adjusted to 9.5 by adding aqueous ammonia, followed by filtration with a filter press, drying and drying of Al, Co,
Goethite to which Zn and B compounds were applied was obtained. The contents of Al, Co, Zn, and B in the obtained goethite were 1.12 wt% as Al and 2.75 wt% of Co, respectively.
%, Zn was 1.15 wt%, and B was 0.56 wt%.

Examples 19, 20, 22 to 25, 27, 2
8 The needle-like goethite particles to which the metal compound was adhered were obtained in the same manner as in Example 18 by variously changing the type of the particles to be treated, the type of the object to be treated, and the amount of addition. Table 3 shows the main manufacturing conditions at this time.

<Production of Acicular Metal Magnetic Particle Powder Containing Iron as Main Component> Examples 29 to 42, Comparative Examples 5 to 6; Example 29 The P, Si, and Al compounds obtained in Example 16 were adhered. 800 g of the obtained needle-like goethite particle powder was heated at 750 ° C. in the air to obtain a needle-like hematite particle powder on which P, Si, and Al compounds were adhered. About 100 g of the acicular hematite particle powder on which the P, Si,
Into a rotary retort reduction container having a volume of 0 l, and while driving and rotating, aeration of H ₂ gas was performed at a rate of 50 l / min.
The reduction was performed at a reduction temperature of 420 ° C.

The metal magnetic particle powder mainly containing iron containing P, Si, and Al obtained by reduction is 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 observation with an electron microscope, the metal magnetic particle powder containing iron as a main component containing P, Si and Al has the following properties:
The average major axis was 0.27 μm, the axial ratio (major axis diameter / minor axis diameter) was 21, the particle size was uniform, and there were few dendritic particles.
The magnetic properties were a coercive force Hc 1560 Oe and a saturation magnetization s 159.6 emu / g.

Examples 30 to 42, Comparative Examples 5 to 6 The same procedures as in Example 29 were carried out except that the types of the starting materials, the heat treatment temperature, the type of the non-reducing atmosphere, the reduction temperature and the H ₂ flow rate were variously changed. Acicular 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. The acicular metal magnetic particles containing iron as a main component and obtained in Examples 30 to 42 were all uniform in particle size and free of dendritic particles. Examples 30 and 3
8 and 42, and electron micrographs (× 30) of the acicular metallic magnetic particles containing iron as a main component and obtained in Comparative Examples 5 and 6.
000) are shown in FIGS. 6 to 10, respectively.

<Production of Coating Film> Examples 43 to 56, Comparative Examples 7 to 8; Example 43 Acicular metal magnetic particles containing P, Si, and Al obtained in Example 29 and containing iron as a main component. Using a powder, an appropriate amount of a dispersant, a vinyl chloride-vinyl acetate copolymer, a thermoplastic polyurethane resin and a mixed solvent composed of toluene, methyl ethyl ketone, and methyl isobutyl ketone are blended into a fixed composition, and then mixed and dispersed with a paint conditioner for 9 hours. Magnetic paint. The mixed solvent was added to the obtained magnetic paint to adjust the paint viscosity to an appropriate value, and applied on a polyester film by a conventional method, magnetically oriented, and dried to produce a coated film. The coating film was measured by a 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.V. F. D. Was 0.496.

Examples 44 to 56 and Comparative Examples 7 to 8 Coated films were produced in exactly the same manner as in Example 43 except that the type of the acicular metal magnetic particles containing iron as a main component was variously changed. Table 5 shows the properties of this coating film.

[0055]

[Table 1]

[0056]

[Table 2]

[0057]

[Table 3]

[0058]

[Table 4]

[0059]

[Table 5]

[0060]

According to the method for producing acicular metal magnetic particles containing iron as a main component according to the present invention, as shown in the preceding embodiment, the particle size is uniform and dendritic particles are mixed. No
Moreover, it has a large axis ratio (long axis diameter / short axis diameter), and
Since needle-like metal magnetic particles having iron as a main component and having excellent coercive force distribution can be obtained, they are suitable as magnetic particles for high recording density, high sensitivity and high output.

[0061]

[Brief description of the drawings]

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

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

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

FIG. 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.
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).

FIG. 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.
0000).

FIG. 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.
000).

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

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-128295 (JP, A) JP-A-50-80999 (JP, A) JP-A-60-21307 (JP, A) 42438 (JP, B2) JP-B-58-53688 (JP, B2) JP-B-59-32523 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) B22F 9/22 C22C 38 / 00 303

Claims (5)

(57) [Claims] 1. An aqueous solution of a ferrous salt obtained by reacting an aqueous solution of a ferrous salt with an aqueous solution of an alkali hydroxide, an aqueous solution of an alkali carbonate or an aqueous solution of an alkali hydroxide / alkali carbonate, which is less than the equivalent of Fe ²⁺ in the aqueous solution of a ferrous salt. The ferrous hydroxide colloid or the iron-containing precipitate colloid is oxidized by passing oxygen-containing gas through the ferrous hydroxide reaction solution containing the ferrous hydroxide colloid or the iron-containing precipitate colloid. After the formation of goethite core particles, an aqueous solution of 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 acicular goethite core particles, and then oxygen-containing. A gas is passed to allow a growth reaction of the acicular goethite nucleus particles to be performed, so that the axial ratio (major axis diameter / short axis diameter) is 20 to 32.
Then, the acicular goethite particles or the acicular hematite particles obtained by heating and dehydrating the acicular goethite particles are heated and reduced in a reducing gas to obtain an acicular metal having iron as a main component. A method for producing acicular metal magnetic particle powder containing iron as a main component, characterized by obtaining magnetic particles. 2. An acicular goethite particle or an acicular hematite particle obtained by heating and dehydrating the particle, a Ni compound, an Al
2. The needle-like iron-based component according to claim 1, wherein the at least one metal compound is selected from the group consisting of a compound, a Si compound, a P compound, a Co compound, a Mg compound, a B compound, and a Zn compound. Manufacturing method of metal magnetic particle powder. 3. A ferrous salt reaction solution containing needle-like goethite core particles before adding an aqueous alkali carbonate solution is heated to a temperature of 75 ° C.
The method for producing needle-like magnetic metal particles containing iron as a main component according to claim 1 or 2, wherein the temperature is lowered to 60 ° C or less after the temperature is maintained as described above. 4. The method according to claim 1, wherein the ferrous salt reaction solution containing the acicular goethite core particles before the addition of the aqueous alkali carbonate solution is maintained at a temperature of 60 ° C. or lower in a non-oxidizing atmosphere. A method for producing acicular metal magnetic particle powder as a component. 5. A ferrous salt reaction solution containing needle-like goethite core particles before adding an aqueous alkali carbonate solution is heated to a temperature of 75 ° C.
The method for producing needle-like magnetic metal particles containing iron as a main component according to claim 1 or 2, wherein the temperature is lowered to 60 ° C or lower after the above-mentioned holding, and the temperature is subsequently kept in a non-oxidizing atmosphere.