JP3395811B2 - Manufacturing method of flat magnetite fine particle powder - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention
Of fine magnetite particles
Particles, and the particles are individual
Of flat magnetite particles that are non-porous
The present invention relates to a method for producing fine magnetite particles.
You. [0002] Flat magnetite fine particles according to the present invention
The main applications are for electromagnetic wave absorption, shielding, and rust prevention paint.
For materials, toner, vibration damping, soundproofing, magnetic recording, etc.
It is. 2. Description of the Related Art Magnetites having a plate-like or flat shape
Particle powder uses its characteristics such as morphology and magnetism.
Thus, it is expected to be used in various technical fields. This fact is described, for example, in JP-B-63-418.
No. 53, entitled "‥‥ Use one or more flake-shaped magnetic iron oxide particles.
Is a magnetic tape, card or
The potential for use in magnetic recording supports such as discs is open.
You. ‥‥ ”,“ ‥‥ magnetite or maghemite
Other applications for hexagonal flake iron oxide with a crystalline structure
is there.極 め て Extremely pronounced parallelism of individual particles in the coating material
Orientation occurs. Therefore, ‥‥ obtain extremely high packing density
Possible, resulting in increased corrosion protection, for example.
And effective shielding against electromagnetic interference fields, and
Conductivity increases. ‥‥ ”. Further, Japanese Patent Application Laid-Open No. 61-138959 discloses
"‥‥ Small flat or scale as a magnetic component of one-component toner
When using flaky magnetizable particles, toner color is determined
It depends on the original color of the magnetic component itself.
It is mainly due to the strong colorant added.
Was found. ‥‥ ”,“ ‥‥ These particles are easily
No special dispersing energy can be consumed just by stirring.
Good content in the binder or binder solution
It can be immediately converted to a scattered state.な る ”
It is as stated. [0006] By the way, magnetite particle powder is generally used.
In addition, it can be used as a paint by dispersing and mixing in a vehicle,
Alternatively, it is kneaded and dispersed in resin, molded and used as a molded product.
Have been used. Therefore, a vehicle of magnetite particle powder is used.
When mixing and dispersing into resin and kneading and dispersing into resin,
Particles with excellent dispersibility as much as possible in terms of improvement and work efficiency
There is a strong demand that there be magneta
That the particle powder has a plate-like or flat shape
Of course, fine particles and individual particles
And must be non-porous. Conventionally, plate-like or flat magnetite particles
Powder production methods include, for example, ferric hydroxide or gator
The alkaline suspension containing the site using an autoclave
Plate-like hematite grains from aqueous solution by hydrothermal treatment
And generate the plate-like hematite particles in a reducing gas.
Heat reduction method (JP-A-51-28700,
(Japanese Patent Publication No. 63-41853), including ferrous hydroxide.
Suddenly oxidize alkaline suspensions with strong oxidants
Or ferric and alkali in the presence of certain additives
And react in an aqueous medium to produce ferric hydroxide,
By subjecting the ferric hydroxide to a hydrothermal treatment,
Generating plate-like goethite particles;
After heat dehydration as necessary, heat reduction in reducing gas
(Japanese Patent Application Laid-Open No. 61-26631,
JP-A-5-104923) and a plate-like mask directly from an aqueous solution.
Method for producing powder of gnetite particles (JP-A-62-3)
No. 4141, JP-A-3-75228).
Have been. [0009] The fine particles, plate-like
Or a flat shape, and each particle is one by one.
Separated, non-porous magnetite particle powder
Is currently the most requested, but mentioned above
In the case of using a known method, these characteristics are sufficiently satisfied.
No particles have yet been obtained. That is, from an aqueous solution, a plate-like or flat hemata
By generating particles and heating and reducing the particles
In the case of heat reduction process, sintering between particles and particles
Occurs, resulting in dispersion in the vehicle or resin.
It will be difficult. Further, a plate-shaped or flat-shaped gator is prepared from an aqueous solution.
To produce particles, and after heating and dehydrating the particles as necessary,
In the case of the heat reduction method, a plate-shaped or flat
Moisture in goethite crystal particles is removed during heating of tight particles.
Plate-shaped or flat magnetite particles obtained because they are watered
At the same time as there are many vacancies on the particle surface and inside the particles
Sintering occurs between particles and particles. [0012] Such a porous plate-shaped or flat-shaped magne
When tight particle powder is dispersed in vehicle or resin
If the surface magnetic poles are generated, other fine particles
And as a result a large number of
Agglomerates are formed, which makes dispersion difficult. On the other hand, ferrous hydroxide particles and ferrous hydroxide
Of suspension containing manganese to produce granular magnetite particles
(Japanese Unexamined Patent Publication No. 5-32422, Japanese Unexamined Patent Publication No. 5-3
No. 39010 is also known. These hydrous secondary
Iron particles are mainly lipid crocite particles.
However, in the above-mentioned Japanese Patent Application Laid-Open No. 5-32422,
Note that goethite particles are used in addition to
It is listed. [0014] Including ferrous hydroxide particles and ferrous hydroxide
Heating the suspension to produce magnetite particles
Production method of ferric hydroxide particles as precursor particles and
The spindle shape described in JP-B-63-13941
And a method for producing a goethite particle powder exhibiting the following. This is a ferrous salt aqueous solution and an alkali carbonate aqueous solution.
The reaction with the liquid _Three And a suspension containing
Water-soluble silicate is added to the suspension to oxidize the suspension, and acid
Spindle by carrying out oxidation reaction by passing oxygen-containing gas
This is a method of producing goethite particles in a shape.
In the case of the method of the above, the axial ratio (long axis diameter / short axis diameter-below,
Simply referred to as "axial ratio". -) Is about 1.5 to 1.0
-Tight particles are obtained, but the particle size is still 0.15
It is about μm or more. Incidentally, Japanese Patent Publication No. 51-12318,
JP-A-51-16039, JP-B-51-21639
And Japanese Patent Publication No. 51-21640.
Goethite particles are spindle-shaped particles having an axial ratio of 5 or less.
Fine particles having an average particle diameter of 50 to 200 ° are obtained.
However, each embodiment described in each gazette
Are spindle-shaped particles with an axial ratio of about 3.
You. Also, as a granular goethite particle powder,
Are fine-grained particles described in JP-A-60-141625.
Α-iron oxyhydroxide (applicant's note:
You. ), Water-soluble silicate, ammonium carbonate
Oxidation of aqueous ferrous salt solution in the presence of
By carrying out the reaction, “Example 2” and “
In Example 3, granular goethite fine particles of “0.1 μ or less”
The child has been obtained. However, in the "Example 1" of the publication,
As shown in Fig. 1, the particle size distribution is uneven.
It is. In addition, ferric hydroxide particles and ferrous hydroxide particles
Of suspension containing manganese to produce granular magnetite particles
In the method, plate-shaped or flat magnetite particles are still
Not obtained. Therefore, the present invention relates to fine particles,
The T surface area is as large as possible, and one particle
Plate-shaped or flat-shaped magnet that is discrete and non-porous
It is a technical problem to obtain tight fine particle powder. [0020] The above technical problems are as follows.
This can be achieved by the method according to the invention. That is, the present invention provides an aqueous ferrous salt solution comprising
Fe in aqueous solution of iron salt ²⁺ More than 1.0 equivalent
Reaction with aqueous solution of alkali carbonate under non-oxidizing atmosphere
A suspension containing the iron-containing precipitate, and this suspension is non-oxidizing
30 to 3 in the temperature range of 50 to 65 ° C under the atmosphere
Maintain stirring for 60 minutes, then add water-soluble
The phosphate in the aqueous ferrous salt solution ²⁺ Against Si
After adding 0.5 to 5.0 atomic% in total,
Oxidation reaction is performed by passing oxygen-containing gas through the liquid in the temperature range.
This produces granular goethite fine particles,
In a non-oxidizing atmosphere, a ferrous salt aqueous solution
An aqueous alkali hydroxide solution is added and reacted to form the granular
PH containing goethite fine particles and ferrous hydroxide colloid
An alkaline suspension having a value of more than 11 is used.
Heat in a non-oxidizing atmosphere at a temperature of 40 to 100 ° C.
Flat magnetite particles are produced by thermal stirring.
To all Fe in the magnetite fine particles
Silicon compound of 0.5 to 5.0 atomic% in terms of Si
Is 0.02 to 0.1 μm, and the BET is
Specific surface area value is 50-85m ^Two / G and particles
Is a non-porous flat magnet
This is a method for producing fine particle powder. The structure of the present invention will be described in more detail.
It is on the street. First, the flat magnetite fine powder according to the present invention is used.
Granular goethite microparticles, which are precursor particles of
Below, it is simply referred to as “precursor particles”. )
Bell. Ferrous salt aqueous solution used in the present invention
Examples include ferrous sulfate aqueous solution and ferrous chloride aqueous solution.
I can do it. The amount of the aqueous ferrous salt solution is expressed as
It is in the range of 0.3 to 0.6 mol / l. 0.3mol
/ L, the reaction concentration is low and industrial
No. If it exceeds 0.6 mol / l, the obtained precursor
The particle size distribution of body particles becomes wider. Preferably 0.4 to 0.
5 mol / l. In the present invention, an aqueous ferrous salt solution and carbonic acid
Reaction with an alkaline aqueous solution in a non-oxidizing atmosphere
A suspension containing the precipitate is obtained. This is the precursor
Oxidation reaction before growth of particles in the short axis direction is not controlled
To avoid the occurrence of precursor particles.
You. To obtain a non-oxidizing atmosphere, the inside of the reaction vessel
Inert gas (N _Two Gas) or reducing gas (H _Two gas
Etc.) may be ventilated. Alkaline carbonate water used in the present invention
Solutions include sodium carbonate aqueous solution and potassium carbonate aqueous solution
Solutions and the like can be mentioned. Ammonium carbonate is
Maintain the suspension containing the iron-containing precipitate in a non-oxidizing atmosphere.
During stirring, ammonium carbonate reacts and decomposes to ammonia.
Um salt is NH _Three It is discharged as a gas outside the reaction system
I can not use it. The pH value of the reaction solution is set in an alkaline range.
So NH _Three Gas is CO _Two Discharged outside the system before gas
The chemical equilibrium in the reaction
The particle size distribution of the particles becomes uneven, especially when the temperature exceeds 50 ° C.
In some cases, particulate magnetite may be present. The amount of the aqueous alkali carbonate solution depends on the amount of the first
Fe in aqueous solution of iron salt ²⁺ More than 1.0 equivalent
is there. In the case of 1.0 equivalent or less, the target precursor particles
No flat particles are obtained and the flat magnetite fine particles according to the present invention
I can't get it. Preferably more than 1.0 equivalent and not more than 3.0 equivalents
Below. It may exceed 3.0 equivalents but excess alkali
There is no need to use. More preferably, 1.3 to 2.
5 equivalents. In this case, the reaction solution during the oxidation reaction
The pH value is in the range of 7.0 to 11.0, preferably
It is in the range of 8.0 to 10.0. The suspension containing the iron-containing precipitate is made non-oxidizable.
The temperature for maintaining and stirring under the atmosphere is in a temperature range of 50 to 65 ° C.
It is an enclosure. If the temperature is lower than 50 ° C., the CO
_Two Insufficient discharge of gas out of the reaction system
Therefore, sufficient suppression of growth of the precursor particles in the short axis direction
Rather, the atomization becomes insufficient. Exceeding 65 ° C
In this case, particulate magnetite particles are mixed in the precursor particles.
Sometimes. The preferred temperature range is 50-55 ° C.
You. The suspension containing the iron-containing precipitate is made non-oxidizable.
The time for maintaining and stirring under the atmosphere is 30 to 360 minutes.
You. If less than 30 minutes, the CO _Two Moth
Not be able to sufficiently discharge
Therefore, the suppression of growth of the precursor particles in the short axis direction is sufficient.
In addition, fine particles are insufficient. Even after more than 360 minutes
Good, but it doesn't have to be long. Preferred
The preferred range is 60 to 240 minutes. The non-oxidizing atmosphere is the same as the non-oxidizing atmosphere.
The same may be used. In addition, maintain stirring under a non-oxidizing atmosphere.
The growth of the precursor particles in the short axis direction
Therefore, maintain stirring under an oxidizing atmosphere.
When this occurs, the oxidation reaction starts and needle-like goethite particles are generated
By doing so, the suppression effect in the short axis direction becomes insufficient. The water-soluble silicic acid used in the present invention
Salts include sodium silicate and potassium silicate.
I can do it. The amount of the water-soluble silicate added is ferrous salt water.
Fe in solution ²⁺ 0.5 to 5.0 atoms in terms of Si
%. If less than 0.5 atomic%, the resulting precursor
The particle diameter of the body particles increases, and the BET specific surface area value is 30.
0m ^Two / G or more.
Tight fine particle powder cannot be obtained. Exceeds 5.0 atomic%
In such a case, the silicon compound is not contained in the obtained precursor fine particles.
It is not preferable because it will be present as an important salt.
In addition, it is difficult to form a uniform composition. The addition timing of the water-soluble silicate is maintained as described above.
This is from the end of stirring to the start of the oxidation reaction. Previous
As described above, the minor axis direction of the precursor particles generated by the maintenance stirring
Since the growth is suppressed, the agitation is stopped.
15 minutes before starting the oxidation reaction until just before the oxidation reaction starts
Is preferred. More preferably 5 minutes before the oxidation reaction
It is until just before the beginning. Added after oxidation reaction has started
In the case of
Needle particles are generated, and the obtained precursor particles are also granular.
Instead, the particles have a rice grain shape with an axial ratio. In addition, the water-soluble silicate is
When added and mixed in an alkaline aqueous solution,
Precursor particles generated by maintaining and stirring in a non-oxidizing atmosphere
It is difficult to obtain the effect of suppressing growth in the short axis direction,
Becomes insufficient. Incidentally, the water-soluble silicate is dissolved in water and dissolved in water.
The addition as a solution is quick and even in the suspension.
It is preferable because it is agitated and dispersed. The temperature during the oxidation reaction in the present invention is 50
-60 ° C. If the temperature is lower than 50 ° C.,
The crystallinity of the precursor particles is insufficient,
Cannot be obtained. 6
If the temperature exceeds 0 ° C., the obtained precursor particles have
Gunetite particles may be present. Preferably 50
The temperature range is ~ 55 ° C. In the present invention, the oxidizing means is an oxygen-containing gas.
(For example, air) is passed through the liquid. Ma
In addition, if necessary, mechanical stirring may be accompanied. Flat magnetite fine particle powder according to the present invention
The powder precursor particles have a BET specific surface area of 300 to
350m ^Two / G. 300m ^Two / G or less than 3
50m ^Two / G, the bias which is the object of the present invention
Flat magnetite fine particles cannot be obtained. Preferred range
The box indicates a BET specific surface area of 310 to 330 m. ^Two / G
And the average particle diameter is 0.003 to 0.008 μm. The precursor particles are composed of all F in the precursor particles.
Si of 0.5 to 5.0 atomic% in terms of Si with respect to e
Contains the compound. If less than 0.5 atomic%,
BET specific surface area value of the precursor particles is 300 m ^Two / G or more
Therefore, the flat magnetar target of the present invention
No fine particle powder is obtained. If it exceeds 5.0 atomic%
In the case, the silicon compound is unnecessary in the precursor particles obtained.
It is not preferred because it will be present as a salt. The precursor particles include filtration, washing and drying.
The dried goethite fine particle powder may be used. Next, the flat magnetite fine particles according to the present invention will be described.
The generation of the particle powder will be described. Flat magnetite fine particle powder according to the present invention
The precursor particles are used as the last raw material particles. As the ferrous salt aqueous solution in the present invention,
Ferrous sulfate and ferrous chloride used to produce the precursor particles
And the like. The amount of the aqueous ferrous salt solution added to the precursor particles
On the other hand, it is 17.0 to 38.0% by weight in terms of Fe.
If less than 17.0% by weight, sufficient magnetite
And blackness was insufficient, exceeding 38.0% by weight
Unreacted ferrous hydroxide colloid
Sometimes. The preferred range is 25.0-36.0% by weight.
It is. The aqueous alkali hydroxide solution of the present invention
Sodium hydroxide, potassium hydroxide, etc.
be able to. In the reaction solution containing the precursor particles in the present invention
, Ferrous salt aqueous solution and alkali hydroxide aqueous solution
Particles and ferrous hydroxide colloid
The suspension containing pH and pH is more than 11
It is. When the pH value is less than 11, the reaction time is long.
And unreacted precursor particles may remain.
You. In addition, the reason for the alkaline
No ferrous oxide colloid is formed and ferrous salt remains
Not preferred. Preferred pH values are 12-13.
5 range. The precursor particles after the precursor particles have been formed
The reaction solution containing is washed once with water and remains in the reaction solution.
After removing the alkali carbonate, pour aqueous alkali hydroxide solution
Preferably. In addition, the remaining alkali carbonate
Alkali hydroxide aqueous solution can be added without removing
However, in this case, suspend a considerable amount of aqueous alkali hydroxide solution.
By pouring into a suspension, the pH value of the suspension is adjusted to 11
Can be exceeded. In the present invention, the suspension is prepared in an amount of 40 to 100.
Heat and stir in the temperature range of ° C. If the temperature is lower than 40 ° C,
The reactivity is not enough and it is difficult to make magnetite. 1
If the temperature exceeds 00 ° C, use an autoclave or other device.
Not industrial to need. When heating and stirring, the atmosphere is non-acidic.
Atmosphere. In the case of an oxidizing atmosphere,
Oxidation of ferrous colloid occurs and magnetite of precursor particles
May be inhibited. Incidentally, flat magnetite fine particle powder is obtained.
The filtration, washing and drying may be performed according to a conventional method. In addition, when the precursor particles are formed, the characteristics are improved.
P, Al, Zn, Ni, C usually added for the purpose
Add water-soluble salts such as u, Co, Mn and Cr
Can also. Both of these salts to be added are ferrous
Fe in salt solution ²⁺ From 1.0 to the elemental equivalent of each salt
The range is 20.0 atomic%. The operation of the present invention having the above-described configuration is as follows.
It is on the street. First, as the precursor particles, a granular goethite is used.
0.5 to 5.0 in terms of Si with respect to all Fe in the fine particles.
BET specific surface area value containing 3% by atomic silicon compound is 3
00-350m ^Two / G of granular goethite fine particles
You. And a granular goetie with an axial ratio of about 1.0 ± 0.2
Microparticles. Usually, the precursor particles obtained, ie, gator
Since the particles are needle-shaped or spindle-shaped,
Particles having an axial ratio of about 1.0 ± 0.2
In order to obtain the precursor particles, the particle diameter in the major axis direction and the minor axis
Unless both particle diameters in the
No. As a method for suppressing the particle diameter in the major axis direction,
The above-mentioned Japanese Patent Publication No. 63-13941 discloses an oxidation reaction.
Obtained by adding water-soluble silicate before
Growth of goethite particles in the major axis direction can be suppressed.
To suppress the particle diameter in the short axis direction.
No method is shown. Therefore, as a result of various investigations, it was found that an alkaline aqueous solution was used.
An aqueous solution of alkali carbonate is used as the liquid and ferrous salt
The suspension containing the iron-containing precipitate reacted by adding the aqueous solution
Under non-oxidizing atmosphere, in a temperature range of 50 to 65 ° C for a certain time
After maintaining and stirring, water-soluble silicate is added, and then
When an oxidation reaction is performed, the major axis of the precursor particles generated
It can be seen that growth in the short axis direction as well as growth in the
I put it out. It can be seen that F in suspension containing iron-containing precipitates
eCO _Three Fe (OH) for _Two The ratio of
An oxygen-containing gas was passed through the suspension to perform an oxidation reaction.
As a result, it has a spindle shape, which is characteristic of the alkali carbonate reaction.
The bulge on the short axis side of the goethite became smaller.
This is thought to be due to suppression of grain growth in the short axis direction.
You. As described above, the suspension is placed in a non-oxidizing atmosphere.
Of the precursor particles produced by the method of maintaining and stirring under
In addition to suppressing axial growth, the suspension after maintaining stirring
In the liquid, suppresses the growth of the generated precursor particles in the longitudinal direction
Oxidation reaction after adding water-soluble silicate
Thereby, the precursor particles according to the present invention could be obtained.
It is. This is because volatile alcohols such as ammonium carbonate
A method using an alkali carbonate aqueous solution containing no potassium component,
Method of maintaining stirring under non-oxidizing atmosphere and water-soluble silica
Due to the synergistic effect of the oxidation reaction
It can be said that. Next, the flat magnetite fine particles according to the present invention will be described.
The generation of particles will be described. From goethite particles to flat magnetite fine particles
Regarding the reaction to form particles, see, for example,
No. 32422, “‥‥ Repidoclosa with high reactivity”
The particles react to produce granular magnetite core particles,
Then, the less reactive goethite particles react and are already precipitated.
Formed on the surface of the granular magnetite core particles
Long reaction occurs. ”
Magnetite particles using only low-response goethite particles
I rarely spawned children. However, in the present invention, the BET specific surface area
Value is 300m ^Two / G or more,
"Pigment Dispersion Technology" published by Technical Information Association (1993)
Year) Page 18 "‥‥ The smaller the particle, the more ‥‥
The chemical activity of the particles increases. ‥‥ ”
Since precursor particles with high activity are used,
As shown in the examples, flat magnetite fine particles can be easily
You can create children. In the present invention, the precursor particles and the hydroxide
Flat magnets are produced by heating a suspension containing ferrous iron.
The reason why tight particles can be generated is not yet clear.
No. However, the precursor particles used in the present invention
BET specific surface area value is 300 ~ 350m ^Two / G and very
High reactivity due to fine surface area
That the precursor particles are formed by the alkali carbonate reaction.
The carbonate surface at a relatively high density on the particle surface.
In the process of transforming into magnetite
The flattening according to the present invention due to influencing the crystal growth
It is thought that it produces the shape-like particles. Next, the present invention will be explained with reference to Examples and Comparative Examples.
I will tell. BET specific surface area in Examples and Comparative Examples
Values are MONOSORB MS-11 type (QUATAC
(HROME). The particle diameter and the axial ratio of the particles (as a measure of sphericity,
Those with an axial ratio within 1.0 ± 0.2 are excellent in granular or spherical form
Suppose ) And the plate-like ratio of the flat particles are both
The average value of the numerical values measured from the electron micrograph was shown. [0071] Precursor particles or magnetite particles
The amount of Si, Al, etc., measured by X-ray fluorescence analysis
Was. X-ray particle size D of magnetite particles ₃₁₁ Is X
In the (311) crystal plane measured by X-ray diffraction
Is the diameter of the crystal grains.
The values were calculated using the error formula. D ₃₁₁ = Kλ / βcosθ, where β = true diffraction beam minus machine width
Λ = wavelength of characteristic X-ray θ = diffraction angle The adsorption capacity is shown in Examples, Comparative Examples and Reference Examples.
The obtained particle powder is pressed and crushed to 10 to 20 m
Approximately 0.4 g as a sample with uniform particle size
Is packed in a column and a circulating adsorption rate evaluation device (“Chemical Engineering
Business materials "vol. 20, No4, (1985) p. 14
Evaluation method described), and then the sulfur concentration of 5 ppm
Apply a Tedla bag containing 10 l of hydrogen-containing test gas.
Attached to the device. Then, the flow rate of 5 l / min
The test gas was circulated through the sample column by venting. Circulate
The test gas is sampled after 120 minutes and sampled.
Determine the concentration of hydrogen sulfide in the ring test gas by gas chromatography.
It was shown by the value measured by the tomography method. After 120 minutes
The smaller the adsorption capacity, the better the adsorption capacity. <Production of Precursor Particles> Examples 1 to 4, Comparative Examples 1 and 2; Example 1 N at a rate of 50 liters per minute _Two Flow gas to a non-oxidizing atmosphere
1.6 mol / l of Na was added to the held reaction vessel. _Two CO
_Three 25 l of aqueous solution (Na _Two CO _Three Is a ferrous salt aqueous solution
Fe in liquid ²⁺ 2.0 equivalents. ), Then
1.33 mol Fe ²⁺ Ferrous salt aqueous solution containing 15 l
(The reaction concentration corresponds to 0.5 mol / l.)
A suspension containing the iron-containing precipitate at a temperature of 50 ° C.
And The suspension containing the above-mentioned iron-containing precipitate was drawn into the suspension.
Followed by N _Two While blowing gas at a rate of 50 l per minute,
The temperature of the suspension was set at 51 ° C. and maintained for 150 minutes.
Was. Then, 0.8 mol / l sodium silicate
0.5l (Fe in aqueous ferrous salt solution) ²⁺ For Si
This corresponds to 2.0 atomic%. ) And hold for 5 minutes
After that, 0.8 mol / l sodium aluminate
0.5l (Fe in aqueous ferrous salt solution) ²⁺ To Al conversion
Corresponds to 2.0 atomic%. ) Was added. Subsequently, the suspension was heated to a temperature of 52 ° C.
And aerated at 150 l / min for 75 min.
Particles were generated. The pH value during air ventilation is as follows:
9.3 to 9.5. The obtained tan particle powder was analyzed by X-ray diffraction.
As a result, it was goethite, and the electron micrograph (×
30000), the granules having an axial ratio of 1.0
Consisting of particles presented, with a particle size of 0.005 μm,
The quasi-deviation σg is 0.83, which is excellent in particle size distribution.
Was. The BET specific surface area value is 314 m ^Two / G,
0.63% by weight of Si contained in the precursor particle powder, Al
Was 0.60% by weight. Examples 2 to 4, Comparative Examples 1 and 2 The concentration of the aqueous ferrous salt solution, the type of the aqueous alkali carbonate solution and
Concentration, presence / absence of alkali hydroxide aqueous solution, type, concentration and usage
Dose, Fe in aqueous ferrous salt solution ²⁺ Alkali ratio to
Reaction concentration, temperature and maintenance stirring time, water-soluble silicate
Kind, addition amount, presence or absence of addition, addition of other metal compounds
Addition, presence of air flow and reaction temperature in oxidation reaction
Was changed in the same manner as in Example 1 except that
Particles were generated. The main manufacturing conditions and various characteristics at this time are shown in Table 1.
The results are shown in Table 3. [Table 1] [Table 2] [Table 3] The production conditions of Example 1 were further changed to hydroxyl.
Comparative Example 1 to which alkali halide was added, as shown in FIG.
203m ET specific surface area ^Two / G. Water soluble ke
Comparative Example 2 in which no formate was added had a spindle shape as shown in FIG.
The particles exhibit the following. <Production of magnetite particle powder> Examples 5 to 8, Comparative Examples 3 to 5; Example 5 The reaction solution containing the precursor particles obtained in Example 1 was added to the reaction vessel.
50 l of N per minute in the vessel _Two Non-oxidizing atmosphere by passing gas
And the yellowish brown precipitate (the amount of the precipitate is
1.78 kg. ) In the reaction solution containing
7.5 l of 3 mol / l ferrous sulfate aqueous solution (precursor particles
Corresponds to 50% by weight in terms of Fe. )
The liquid temperature was 85 ° C. Then, 10 mol / l NaO
2.5 l of H aqueous solution was added to adjust the pH value to 12.2, and
Ferrous bromide colloid, followed by 3 hours at 85 ° C
The mixture was stirred while heating to form a black precipitate. The formed black precipitate particles are filtered by a conventional method.
Separately, washed with water, dried and pulverized. The obtained black fine particle powder
Is magnetite as a result of X-ray diffraction, and is shown in FIG.
As is clear from the electron micrograph (× 60000)
Flat particles having a diameter of 0.07 μm and a plate-like ratio of 5
Was. Further, the BET specific surface area value is 56.3 m. ^Two / G
The Si contained in the flat magnetite fine particle powder is
0.49% by weight and Al was 0.47% by weight. Further, the flat magnetite fine particle powder can be maintained.
The magnetic force Hc is 121 Oe, and the saturation magnetization s is 55.6 emu.
/ G, and the adsorption capacity after 120 minutes is 0.18 ppm.
there were. Comparative Example 3 50 l of N per minute _Two Gas is vented to a non-oxidizing atmosphere
0.67 mol / l Fe in the reaction vessel ³⁺ Sulfuric acid containing
20 l of aqueous solution of diiron and 0.67 mol / l of Fe ²⁺ including
10 l aqueous ferrous sulfate solution (reaction concentration is 0.5 mol / l
And the molar ratio of Fe ³⁺ : Fe ²⁺ = 2: 1
You. ) And heated to 55 ° C. to dissolve the mixed iron ion solution.
20 liters of 2.665N NaOH aqueous solution at 85 ° C. (N
aOH is Fe ³⁺ And Fe ²⁺ Corresponds to one equivalent. )
And stirring, and then, under the non-oxidizing atmosphere,
Generate black precipitate particles by heating and stirring at a reaction temperature of 80 ° C for 1 hour.
I let it. The formed black precipitate particles are filtered by a conventional method.
Separately, washed with water, dried and pulverized. The obtained black fine particle powder
Is magnetite as a result of X-ray diffraction, and is shown in FIG.
As is clear from the electron micrograph (× 50000), the axis
It consists of granular particles having a ratio of 1.0 and a particle diameter of 0.1.
011 μm and a BET specific surface area of 98.5 m ^Two /
g. Examples 6 to 8, Comparative Examples 4 and 5 Types of particles to be treated, amount of aqueous ferrous salt used,
PH value of the suspension when adding the aqueous solution of Lucari and
Same as Example 5 except that the reaction temperature was variously changed.
To produce magnetite particles. Table 4 shows the main manufacturing conditions and various characteristics at this time.
Show. [Table 4] In Comparative Examples 4 and 5, the purpose was
No flat magnetite particles were obtained. The magnetite fine particle powder according to the present invention
Has a flat shape as shown in the previous embodiment.
BET specific surface area of 30 to 85 m ^Two / G and large
Crisp and produced directly from aqueous solution
Because of this, the particles are individual and
High packing density in the vehicle or resin
Excellent in dispersibility and orientation, and the contact ratio between particles
High, electromagnetic wave absorption, shielding, rust-proof coating
Materials for materials, toner, vibration suppression, soundproofing, magnetic recording, etc.
It is suitable as a raw material powder.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an electron micrograph (× 30000) showing the particle structure of the granular goethite fine particle powder obtained in Example 1. FIG. 2 is an electron micrograph (× 6000) showing the particle structure of the flat magnetite fine particle powder obtained in Example 5.
0). FIG. 3 is an electron micrograph (× 50000) showing the particle structure of the granular goethite particle powder obtained in Comparative Example 1. FIG. 4 is an electron micrograph (× 30000) showing the particle structure of the spindle-shaped goethite particles obtained in Comparative Example 2. FIG. 5 is an electron micrograph (× 50000) showing the particle structure of the granular magnetite particles obtained in Comparative Example 3. FIG. 6 is an electron micrograph (× 30000) showing the particle structure of the granular magnetite particles obtained in Comparative Example 4. FIG. 7 is an electron micrograph (× 50000) showing the particle structure of the granular magnetite particles obtained in Comparative Example 5.

Claims (1)

(57) [Claim 1] An aqueous solution of a ferrous salt and an aqueous solution of an alkali carbonate in an amount exceeding 1.0 equivalent to Fe ²⁺ in the aqueous solution of a ferrous salt are non-oxidizing. The suspension is reacted under an atmosphere to form a suspension containing the iron-containing precipitate, and the suspension is stirred under a non-oxidizing atmosphere at a temperature of 50 to 65 ° C. for 30 to 360 minutes. The water-soluble silicate in the liquid is 0.5 to 0.5 in terms of Si with respect to Fe ²⁺ in the ferrous salt aqueous solution.
After the addition of 5.0 atomic%, an oxygen-containing gas is passed through the liquid at a temperature in the range of 50 to 60 ° C. to perform an oxidation reaction to generate particulate goethite fine particles. An aqueous ferrous salt solution and an aqueous alkali hydroxide solution are charged into the solution and reacted to form an alkaline suspension containing the particulate goethite fine particles and the ferrous hydroxide colloid having a pH value exceeding 11, and the suspension is prepared. The flat magnetite fine particles are formed by heating and stirring the liquid in a non-oxidizing atmosphere at a temperature in the range of 40 to 100 ° C., wherein the total Fe in the magnetite fine particles is 0.5 to 5. The average plate surface diameter containing 0 atomic% of the silicon compound is 0.02 to 0.1 μm
m, a BET specific surface area value of 50 to 85 m ² / g, and a method of producing flat magnetite fine particle powder in which each particle is discrete and non-porous.