JP2003183025A - Fe2O3 AND METHOD FOR PRODUCING THE SAME - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide Fe<SB>2</SB>O<SB>3</SB>containing smaller amount of Cl, SO<SB>4</SB><SP>2-</SP>, Na, K, Ca and Mg among unavoidable impurities, and to provide a method for producing the same. <P>SOLUTION: The Fe<SB>2</SB>O<SB>3</SB>consisting of Fe<SB>2</SB>O<SB>3</SB>and unavoidable impurities comprises a content of Cl of 300 ppm or less, a content of S converted to SO<SB>4</SB><SP>2-</SP>of 300 ppm or less and a total content of Na, K, Ca and Mg of less than 100 ppm. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to high-purity Fe ₂ O ₃ suitable for small magnetic elements such as chip inductors and a method for manufacturing the same.

[0002]

2. Description of the Related Art With the spread of portable electronic devices such as mobile phones, chip components such as chip inductors are widely used. The miniaturization of chip parts, which are compatible with higher functionality and smaller size and lighter weight of electronic devices, is also progressing. Multilayer chip inductors are manufactured by stacking and sintering a ferrite layer molded using the printing method and the doctor blade method, and an internal electrode molded using the printing method. It is performed by the method of connecting using. Such a multilayer chip inductor is disclosed in, for example, Japanese Patent Application Laid-Open No. 4-180610. Such a laminated type chip inductor is advantageous for miniaturization, and since it has an outer iron structure, it has a small leakage magnetic flux and is suitable for high-density mounting.

The ferrite raw material forming the chip inductor is a mixture of Fe ₂ O ₃ , NiO, ZnO, CuO, etc.
It is obtained by calcination and crushing. Fe ₂ O ₃ contains iron chloride (F
eCl ₂₎ and iron chloride Fe ₂ O ₃ in which the raw material, there are iron sulfate group Fe ₂ O ₃ in which the ferrous sulfate (FeSO ₄₎ as a raw material. Of these, iron chloride Fe ₂ O ₃ contains a large amount of Cl originating from iron chloride, and iron sulfate Fe ₂ O ₃ contains
It contains a large amount of SO ₄ ²⁻ derived from iron sulfate. For example, iron chloride-based Fe ₂ O ₃ produced by the spray roasting method usually contains 1000 ppm or more of Cl originating from the raw material.
Even if Fe ₂ O ₃ was washed with water after roasting, Cl was 500.
About ppm remains. On the other hand, about 2000 ppm of SO ₄ ²⁻ originating from the raw material remains in the iron sulfate-based Fe ₂ O ₃ . Therefore, in the conventional manufacturing method of Fe ₂ O ₃ ,
It was not possible to simultaneously reduce Cl and SO ₄ ²⁻ contained in the produced Fe ₂ O ₃ .

Cl and SO ₄ were added to the Fe ₂ O ₃ produced.
^{Even when 2-} is contained in the above amount, when calcination is performed at a high temperature (about 1000 ° C.) as in the production of Mn-Zn ferrite, Cl or SO ₄ contained in Fe ₂ O ₃ is used.
^{Since 2-} is almost volatilized, Cl and SO ₄ ^2- remaining after the calcination are extremely small, and there is almost no influence in the subsequent steps. However, Ni-Cu-Z, which is often used in small magnetic elements such as chip inductors
In the production of n-type ferrite, calcination is often performed at a lower temperature (about 700 ° C.) than that of Mn-Zn type. For this reason, Cl and SO ₄ ²⁻ remain in the ferrite calcined powder, which adversely affects the subsequent steps. For example, when a large amount of Cl or SO ₄ ²⁻ remains in the manufactured ferrite, when a structure in which an electrode such as Ag and the ferrite are laminated is adopted, Cl or SO ₄ ²⁻ contained in the ferrite reacts with Ag, Problems such as disconnection of electrodes are likely to occur. As miniaturization of the small magnetic element progresses, the thickness of the ferrite layer and the electrode layer also becomes thinner, so that problems such as disconnection of the electrode are more likely to occur. Therefore, Fe ₂ O ₃ containing both Cl and SO ₄ ^{2- in} a small amount is required.

Fe ₂ O ₃ for small magnetic elements such as chip inductors has a low temperature (about 700 ° C.) so that a high sintering density and high magnetic properties can be obtained even if firing is performed at a temperature of about 900 ° C. It is required to suppress grain growth by calcination in order to reduce the grain size by simple pulverization.
However, when Fe ₂ O ₃ contains a large amount of Na, K, Ca and Mg originating from an alkaline solution such as NaOH, Ca (OH) ₂ used in the neutralization step of the wet method,
There are problems that it cannot be calcined at a low temperature, the sintering density does not increase when fired at a temperature of about 900 ° C., or high magnetic properties cannot be obtained. Therefore Na, K, C
Fe containing as little a and Mg as possible
₂ O ₃ is required.

[0006]

In order to solve the above problems, the present invention provides Fe ₂ O ₃ containing a small amount of Cl, SO ₄ ²⁻ , Na, K, Ca and Mg, and a method for producing the same. The task is to do.

[0007]

[Means for Solving the Problems] The above problems will be described below.
It is achieved by the present invention. (1) SO with a Cl content of 300 ppm or less_Four ^2-
S content of 300ppm or less in conversion and total content
With less than 100 ppm of Na, K, Ca and Mg,
Fe containing₂O₃. (2) Mixing an aqueous solution containing an iron salt and an alkaline aqueous solution, medium
And a neutralization step of producing a solution containing iron hydroxide,
By oxidizing iron hydroxide in the solution, Fe₃O_FourGenerate particles
Fe₃O_FourManufacturing process and Fe₃O_FourContains particles
Adjust the pH of the solution to 2-6.5 by adding acid to the solution
And a pH adjustment step of
From the solution adjusted to 6.5, Fe₃O_FourMin the particles
The separation step of separating and the Fe separated in the separation step
₃O_FourFe by heating and oxidizing the particles₂O₃Fe manufacturing₂
O₃Fe with manufacturing process₂O₃Is a manufacturing method of
In the neutralization step, the alkaline aqueous solution and the
Between the aqueous solution containing the iron salt, the following formula (1) and (2)
Fe characterized by the fact that the relationship expressed by the equation holds ₂O
₃Manufacturing method.

[Equation 2] (In the formula (1), [OH^-] Is water in the alkaline aqueous solution
Acid group mol number, [Fe ²⁺] Is in an aqueous solution containing the iron salt
Fe²⁺Mol number of [Fe³⁺] Is a water solution containing the iron salt
Fe in liquid³⁺Shows the mol number of. )

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below. Fe ₂ O ₃ of the present invention has a Cl content of 300 pp.
m or less, and SO ₄ ^{2 -} content of S in terms 30
It is characterized by being 0 ppm or less. If the Cl content and / or the S content in terms of SO ₄ ²⁻ exceeds 300 ppm, the content of Cl and / or SO ₄ ^{2− in} the manufactured ferrite will increase, and the electrode such as Ag and the ferrite will be In the case of a laminated structure, Cl and / SO ₄ ^2- contained in ferrite react with Ag, so that a problem such as disconnection of the electrode is likely to occur. Further, when Cl and / or SO ₄ ²⁻ is contained in a large amount, there is a problem that the sintered density of ferrite does not increase sufficiently when calcined at a low temperature. Fe ₂ O ₃ of the present invention is C
and S content in terms of SO ₄ ^2- is 300p each
Since it is pm or less, the above-mentioned problem of electrode disconnection and the problem of sintered density of ferrite are solved. Cl and S
The content of S in terms of O ₄ ²⁻ is more preferably 200 ppm or less, and particularly preferably less than 100 ppm.

Fe of the present invention₂O₃Is mainly in the wet method
Na, K, which originates from the alkaline solution used in Japanese
The content of Ca and Mg is low.
The total content is less than 100 ppm.
If the content of Na, K, Ca and Mg is high,
Is the calcination process when the total content is 100 ppm or more
Therefore, the temperature required to turn ferrite into
There is a problem that calcination cannot be performed at high temperatures. Also about 900 ℃
Sintering density does not rise sufficiently when firing at low temperature
Or problems such as high magnetic properties are not obtained
It Fe of the present invention ₂O₃Is Na, K, Ca and Mg
Is low because the total content of
Calcination at high temperature is possible, and the ferrite sintering process is also possible.
Since sintering starts at a lower temperature in
Even if it is fired at a high temperature, the sintered density is high, and it shows a high initial permeability.
It is possible to obtain a cerite sintered body. Na, K, Ca
And the total content of Mg is preferably less than 80 ppm
Yes, more preferably less than 50 ppm, 30
Most preferably, it is less than ppm.

Fe ₂ O ₃ of the present invention preferably has a specific surface area of 6 to 60 m ² / g. Fe ₂ O ₃ having a specific surface area of less than 6 m ² / g cannot sufficiently reduce the calcination time. Therefore, grain growth proceeds in the calcination step, and it is necessary to lengthen the crushing time. It is not suitable for a small magnetic element because it also increases the contamination. On the other hand, with Fe ₂ O ₃ having a specific surface area of more than 60 m ² / g, the calcination temperature can be lowered but the reactivity becomes high, so that grain growth is likely to proceed in the calcination step. For this reason, the crushing time also becomes long, and the contamination from the crushing equipment increases, which is not suitable for a small magnetic element. F
When the specific surface area of e ₂ O ₃ is 6 to 60 m ² / g, the grain growth does not proceed excessively in the calcination step, and as a result, it is possible to pulverize to a predetermined grain size in a short time. Therefore, it is particularly suitable as a ferrite powder for small magnetic elements. The more preferable specific surface area of Fe ₂ O ₃ is 10 to 40 m ² / g.

Fe ₂ O ₃ of the present invention is
As long as it does not adversely affect the physical properties of the ₂ O _3, it may contain the usual content of known elements or compounds as unavoidable impurities Fe ₂ O _3. For example, unavoidable impurities include Si, Mn, Al, Cr, Ni, Co, P, B and oxides thereof.

Next, the method for producing Fe ₂ O ₃ of the present invention will be described. In the present invention, the so-called wet method is used for Fe ₂
The production of O _3. That is, an aqueous solution containing an iron salt such as iron chloride or iron sulfate is neutralized with an alkaline aqueous solution to obtain iron hydroxide, which is then oxidized to produce Fe ₃ O ₄ , which is further heated. In the method for producing Fe ₂ O ₃ of the present invention, which produces Fe ₂ O ₃ by oxidation, first, an alkaline aqueous solution is mixed with an aqueous solution containing an iron salt to neutralize the solution. As a result, Fe ²⁺ (ferrous iron ion) and Fe ³⁺ (ferric ion) produced by dissociation of the iron salt in the aqueous solution are converted into Fe (OH) ₂ (ferrous hydroxide), Fe (OH ) ₃ (ferric hydroxide) is produced. The raw iron salt is ferrous chloride,
It may be any of ferric chloride, ferrous sulfate and ferric sulfate, or a combination of any two or more thereof.

Above all, when Fe ²⁺ and Fe ³⁺ are present in the aqueous solution, the produced Fe ₃ O ₄ (magnetite) can be reduced in particle size. Also, in Fe ₃ O ₄ , Na, K, C
It becomes easy to take in a and Mg. Therefore, it is preferable to use an aqueous solution containing Fe ²⁺ and Fe ³⁺ . In addition,
When an aqueous solution containing Fe ²⁺ and Fe ³⁺ is used, the Fe ²⁺ concentration in the solution is preferably higher than the Fe ³⁺ concentration. More preferably, the Fe ³⁺ concentration in the solution is
It is 2 to 50% with respect to the total concentration of Fe ²⁺ and Fe ³⁺ .
If the content ratio of Fe ²⁺ and Fe ³⁺ in the solution is in such a range, the particle size of Fe ₃ O ₄ produced in the intermediate step can be controlled to be small, the particle size distribution is sharp, and the dispersion is good. Fe ₃ O ₄ having excellent properties can be obtained. When such Fe ₃ O ₄ is heated and oxidized, the specific surface area becomes 6
~60m ² / g, more preferably it is possible to obtain a Fe ₂ O ₃ of 10 to 40 m ² / g.

Examples of the alkaline aqueous solution include hydroxides of alkali metals or alkaline earth metals such as sodium hydroxide, potassium hydroxide, calcium hydroxide and magnesium hydroxide, and alkali metals or alkaline earth carbonates such as sodium carbonate. It is possible to use an aqueous solution of a metal carbonate or a general alkaline aqueous solution such as an aqueous ammonia solution. However, in the production method of the present invention, as described later in detail, since it is necessary to once incorporate the alkali metal or the alkaline earth metal into the produced Fe ₃ O ₄ ,
An aqueous solution of an alkali metal or alkaline earth metal hydroxide or carbonate is preferred to an aqueous ammonia solution.

In the method for producing Fe ₂ O ₃ of the present invention, in the neutralization step, the relationship represented by the following formulas (1) and (2) is established between the alkaline aqueous solution and the aqueous solution containing the iron salt. Holds.

[Equation 3] (In the formula (1), [OH^-] Is water in the alkaline aqueous solution
Acid group mol number, [Fe ²⁺] Is in an aqueous solution containing the iron salt
Fe²⁺Mol number of [Fe³⁺] Is a water solution containing the iron salt
Fe in liquid³⁺Shows the mol number of. )

Fe of the present invention₂O₃In the manufacturing method of
Hydroxyl Concentration of Potassium Aqueous Solution and Iron Ion of Aqueous Solution Containing Iron Salt
Since the relationship shown by the above equation holds between the concentrations,
Fe produced in a later step₃O_FourUsed in the neutralization step
Na, K, Ca derived from the alkaline aqueous solution used
And Mg are easily taken in. Fe of the present invention₂O ₃
Fe produced in the manufacturing method of₃O_Four, Na,
It is because it takes in K, Ca and Mg once.
Fe produced by₃O_FourCl or SO_Four ^2-Is captured
Because it becomes difficult. As a result, Fe produced₃O
_FourCl and SO in_Four ^2-The content of is kept low.
Fe produced₃O_FourWith Na, K, Ca and Mg
If not taken in, Fe₃O_FourCl and SO in_Four
^2-Content of Fe is higher, and thus Fe produced₂O₃
Cl and SO at_Four ^2-Higher content of the above mentioned
Have problems.

The above formula (1) shows the equivalent ratio of hydroxyl group to iron ion. When the value of the formula (1) is less than 0.95, the amount of Cl and S incorporated into Fe ₃ O ₄ becomes too large, and the content of Cl and S in the finally obtained Fe ₂ O _{3 is} increased. Exceeds 300 ppm. When the value of the equation (1) is more than 1.5, the amount of the alkaline aqueous solution used is large, and a large amount of acid is required in the subsequent pH adjusting step, resulting in high cost. Further, phases other than Fe ₃ O ₄ are also generated depending on the type of alkaline aqueous solution used. The above formula (2) shows the ratio of the volume of the alkaline aqueous solution used for neutralization to the volume of the aqueous solution containing the iron salt. When the value of the formula (2) is less than 0.1, for example, in order to satisfy the formula (1), the concentration of the alkaline aqueous solution used becomes high, and the amount of solute (alkali component) in the solution is higher than the solubility. As the temperature rises, alkali components of the solution such as alkali metal salts and alkaline earth metal salts are more likely to be deposited. This tendency is remarkable in the case of an aqueous sodium hydroxide solution. When the value of the formula (2) is more than 3.5, the amount of Cl and S incorporated into Fe ₃ O ₄ becomes too large, and the content of Cl and S in the finally obtained Fe ₂ O _{3 is} increased. Exceeds 300 ppm.

In the method for producing Fe ₂ O ₃ of the present invention, the aqueous solution containing an iron salt is neutralized with an alkaline aqueous solution according to the above procedure,
After the iron hydroxide is produced, the oxygen-containing gas is bubbled in to oxidize the iron hydroxide in the solution to produce Fe ₃ O ₄ particles. In this case, air is usually used as the oxygen-containing gas used for the oxidation. The temperature of the aqueous solution during oxidation is 5
0-100 degreeC is preferable. If the temperature is lower than 50 ° C, acicular hydrous oxide is formed, which is not preferable. Also 100 ℃
Although it can be synthesized at a higher temperature than that, it is not industrially suitable due to the large equipment. This oxidation process ends when all the iron hydroxide in the solution has been consumed.

After the step of producing Fe ₃ O ₄ by this oxidation, Fe ₃ O ₄ is usually present in the solution in the form of slurry. In the method for producing Fe ₂ O ₃ of the present invention, an acid is added to a solution containing this slurry to adjust the pH of the solution to 2 to 6.
Adjust to 5. The pH of the solution is adjusted to 2 to 6.5 by adjusting Na, K, which is once incorporated into the produced Fe ₃ O ₄ ,
This is because Ca and Mg are eluted again from Fe ₃ O ₄ into the solution. In this step, ordinary acids such as hydrochloric acid, sulfuric acid, nitric acid and acetic acid can be used. It is also possible to use organic acids that are easily decomposed by heating. However, an acid that remains and adversely affects the ferrite characteristics is not preferable.

In this step, Na, K and Ca are extracted from Fe ₃ O _4.
By removing Mg and Mg, the total content of Na, K, Ca and Mg of Fe ₂ O ₃ produced in the subsequent step is kept below 100 ppm. This process is described in JP-A-8-
The cake obtained by dehydrating the precipitate of iron oxyhydroxide or magnetite disclosed in Japanese Patent No. 133742 is dispersed in water, and after adjusting the pH to 6 to 8, dehydration and washing are performed, and then the dehydrated cake is water-rehydrated again. Disperse in, and adjust the pH to 2 with acid.
Compared with the method of adjusting to the range of 5, the number of steps is small and the operation is easy. In this step, if the pH after addition of the acid is low, Na, K, Ca and Mg remaining in Fe ₃ O ₄ will remain.
However, when the pH is lower than ² , the residual components of acids such as Cl and SO ₄ ²⁻ increase,
It is not preferable because the manufacturing equipment is likely to be corroded. p
When H exceeds 6.5, Na, K, Mg and C
Since a cannot be sufficiently removed, F produced in a later step
e ₂ O ₃ has a total concentration of Na, K, Ca and Mg of 10
Exceeds 0 ppm.

The pH of the solution after addition of the acid in this step is more preferably 3 to 6.5, further preferably 4 to 6. The temperature of the solution when adding the acid is preferably 50 ° C. or higher. Compared to adjusting the pH at room temperature, by adding acid at 50 ° C or higher and adjusting the pH, Na, K, and
The removal rate of Ca and Mg is improved.

In the method for producing Fe ₂ O ₃ of the present invention, Fe ₃ O ₄ is separated by adjusting the pH of the solution to the above range and then dehydrating (filtering) the solution. PH 2 in the previous step
By adjusting to ~ 6.5, Na, K, Ca and Mg
Since There has been eluted into the solution from Fe ₃ O _4, Fe ₃ O ₄ and Na by dehydration (filtration), K, can be completely separate the Ca and Mg, high purity Fe ₃
O ₄ particles are obtained. In the present invention, the pH of the solution is 2
It may be adjusted to ~ 6.5 until the time of filtration, and after the filtration, even if the pH rises to 6.5 or higher, the N in Fe ₃ O ₄ is increased.
The concentrations of a, K, Ca and Mg do not increase. As a filtration method, a usual method such as a filter press can be used. The Fe ₃ O ₄ cake obtained by filtration is
High-purity Fe ₃ O ₄ powder can be obtained by washing with water (desalting), drying and crushing by a usual method.

[0023] In the manufacturing method of the Fe ₂ O ₃ of the present invention, by heating and oxidation Thus the Fe ₃ O ₄ particles obtained by, obtain Fe ₂ O _3. At this time, the heating oxidation temperature is 2
Maghemite (γ-
Fe ₂ O ₃ ) is obtained, and hematite (α-Fe ₂ O ₃ ) is obtained at a temperature of 300 ° C. or higher and about 500 ° C. or lower. Both of them are suitable for small magnetic elements when ferrite is used, and maghemite or hematite can be selectively obtained by adjusting the heating oxidation temperature according to the required conditions, application, etc. it can. The Fe ₂ O ₃ thus obtained is mixed with nickel oxide, zinc oxide, copper oxide, manganese oxide and the like and calcined to obtain ferrite powder. The ferrite powder can be used, for example, as a laminated chip inductor or a planar inductor after forming a magnetic material layer by a printing method or a doctor blade method after mixing a binder to form a paste. Alternatively, a ferrite powder and a binder such as polyvinyl alcohol (PVA) or a small amount of an additional element may be added, granulated and molded, and then fired to obtain a ferrite core.

[0024]

EXAMPLES Hereinafter, the method of the present invention will be further explained with reference to Examples.
Reveal In the examples, Fe₂O₃And fe
The light was evaluated by the following method.Iron oxide analysis Specific surface area: BET analysis Cl, SO_Four ^2-: Fluorescent X-ray analysis Na, K, Ca and Mg: ICP (inductively coupled plasma
Atomic fluorescence analysis) Evaluation of ferrite Calcinable temperature: Spinelization rate of 90% or more by XRD
Minimum temperature

(Examples 1 to 4) The ferrous chloride solution and the ferric chloride solution contained in the solution had an Fe ³⁺ concentration of Fe ³⁺ / Total-
The mixture was mixed so that Fe = 8%, and water was added to prepare a total Fe concentration of 0.58 mol / l and a solution amount of 25.75 liters. 8 mol / l N in a container with an internal volume of 40 liters
4.25 liters of aOH solution was put therein, and the above iron chloride solution was mixed with nitrogen gas by agitating the solution. The temperature of this solution was raised to 90 ° C in a nitrogen atmosphere, and the pH was adjusted to 1
Air is maintained at 0.2 ± 0.1 while air is supplied at 10 l / min
Fe ₃ O ₄ particles were synthesized by aeration and oxidation. After the reaction was completed, sulfuric acid was added to the reaction solution at 90 ° C. to adjust the pH shown in Table 1. Then, desalting, filtration, drying and crushing were performed to obtain Fe ₃ O ₄ powder. 450 this powder
Iron oxide (hematite: α-Fe)
₂ O ₃ ). Next, a ferrite powder was produced using this iron oxide. The ferrite powder was trial-produced by using the obtained iron oxide and Fe ₂ O ₃ : NiO: ZnO: CuO = 49:
It was weighed to be 11:30:10, mixed with a ball mill for 1 hour, and then dried. 600 of this powder
It was calcined at a temperature of not less than ° C to obtain NiCuZn ferrite powder.
The calcination was performed by XRD for 2 hours at the lowest temperature at which the spinelization rate was 90% or more. Further, it was pulverized with a ball mill and continued until the specific surface area became 6 m ² / g or more. The obtained pulverized powder was dried, mixed with a PVA solution for granulation, and then press-molded into a toroidal shape. The obtained molded body is 900
A sintered body was obtained by firing at ℃. The sintered density was calculated from the weight and size of the sintered body. The initial permeability is 9 using the LCR meter.
The measurement was performed on cores fired at 00 ° C. The results are shown in Table 1.

(Comparative Examples 1 and 2) Samples were prepared and evaluated under the same conditions as in Examples 1 to 4 except that sulfuric acid was added to the solution after the reaction to adjust the pH to the value shown in Table 3. Carried out. The results are shown in Table 3.

(Embodiment 5) The ferrous chloride solution and the ferric chloride solution contained in the solution had an Fe ³⁺ concentration of Fe ³⁺ / Total-Fe.
= 1.5%, and water was added to adjust the total Fe concentration to 0.71 mol / l and the solution amount to 25.25 liters. 8 mol / l N in a container with an internal volume of 40 liters
4.75 liters of aOH solution was put therein, and the above iron chloride solution was mixed with nitrogen gas by agitating the solution. The temperature of this solution was raised to 80 ° C. in a nitrogen atmosphere and the pH was adjusted to 8.
While maintaining at 5 ± 0.2, air was blown at 10 l / min for oxidation to synthesize Fe ₃ O ₄ particles. After the reaction was completed, the reaction solution was cooled to 55 ° C., and hydrochloric acid was added to adjust the pH to 4.0. Then, desalting, filtration, drying and crushing were performed to obtain Fe ₃ O ₄ powder. This powder at 230 ℃ 3
Iron oxide (maghemite: γ-Fe ₂ O)
₃ ) and. The evaluation was performed in the same manner as in Examples 1 to 4. Table 1
The results are shown in.

(Example 6) A ferrous chloride solution and a ferric chloride solution were mixed so that the Fe ³⁺ concentration in the solution was Fe ³⁺ / Total-Fe.
= 6.5%, and water was added to adjust the total Fe concentration to 0.71 mol / l and the solution amount to 25.25 liters. 8 mol / l N in a container with an internal volume of 40 liters
4.75 liters of aOH solution was put therein, and the above iron chloride solution was mixed with nitrogen gas by agitating the solution. Thereafter, a sample was prepared and evaluated under the same conditions as in Example 5. The results are shown in Table 1.

(Embodiment 7) The ferrous chloride solution and the ferric chloride solution have Fe ³⁺ concentration in the solution of Fe ³⁺ / Total-Fe
^The mixture was mixed so that ^{3 +} = 12%, and water was added to adjust the total Fe concentration to 0.72 mol / l and the solution amount to 25 liters.
8 mol / l NaOH in a container with an internal volume of 40 liters
5 liters of the solution was put therein, and the above iron chloride solution was mixed while agitating nitrogen gas and stirring it. Thereafter, a sample was prepared and evaluated under the same conditions as in Example 5. The results are shown in Table 1.

(Embodiment 8) The ferrous chloride solution and the ferric chloride solution have Fe ³⁺ concentration in the solution of Fe ³⁺ / Total-Fe.
= 24%, and water was added to adjust the total Fe concentration to 0.72 mol / l and the solution amount to 25 liters.
8 mol / l NaOH in a container with an internal volume of 40 liters
5 liters of the solution was put therein, and the above iron chloride solution was mixed while agitating nitrogen gas and stirring it. Thereafter, a sample was prepared and evaluated under the same conditions as in Example 5. The results are shown in Table 1.

(Example 9) The ferrous chloride solution and the ferric chloride solution had Fe ³⁺ concentration in the solution of Fe ³⁺ / Total-Fe
= 32%, and water was added to adjust the total Fe concentration to 0.72 mol / l and the solution amount to 24.5 liters. 8 mol / l Na in a container with an internal volume of 40 liters
5.5 L of an OH solution was added, and the above iron chloride solution was mixed with nitrogen gas by agitating the solution. Thereafter, a sample was prepared and evaluated under the same conditions as in Example 5. The results are shown in Table 1.

(Embodiment 10) The ferrous chloride solution and the ferric chloride solution contained in the solution had an Fe ³⁺ concentration of Fe ³⁺ / Total-F.
The mixture was mixed so that e = 46%, and water was added to adjust the total Fe concentration to 0.73 mol / l and the solution amount to 24 liters.
8 mol / l NaOH in a container with an internal volume of 40 liters
5.5 liters of the solution was added thereto, and nitrogen gas was bubbled through the solution to mix the above iron chloride solution with stirring. Thereafter, a sample was prepared and evaluated under the same conditions as in Example 5. The results are shown in Table 1.

Comparative Example 3 A sample was prepared and evaluated under the same conditions as in Example 5, except that hydrochloric acid was added to the solution after the reaction to adjust the pH to 1.7. The results are shown in Table 3. (Comparative Example 4) Hydrochloric acid was added to the solution after completion of the reaction to adjust the pH.
A sample was prepared and evaluated under the same conditions as in Example 5, except that the sample was adjusted to 7.2. The results are shown in Table 3. (Comparative Example 5) The mixing conditions of the solution in the neutralization step were changed under the conditions of Example 7. That is, the ferrous chloride solution and the ferric chloride solution have an Fe ³⁺ concentration of Fe ³⁺ / Total-
The mixture was mixed so that Fe = 12%, and water was added to adjust the total Fe concentration to 3.0 mol / l and the solution amount to 6 liters. In a container with an internal volume of 40 liters, 1.67 mol / l Na
24 liters of OH solution was put therein, and the above iron chloride solution was mixed with nitrogen gas by agitating. Thereafter, a sample was prepared and evaluated under the same conditions as in Example 5. The results are shown in Table 3.
It was shown to.

(Examples 11 to 14) 8.1 mol in a container
4 liter of NaOH solution of 1 / l was introduced, and 26 liter of 0.62 mol / l ferrous sulfate solution was mixed with nitrogen gas while stirring. The temperature of this solution was raised to 85 ° C. in a nitrogen atmosphere, and while adjusting the pH to 8.5 ± 0.2, air was blown at 10 l / min to oxidize Fe.
₃ O ₄ particles were synthesized. After the reaction was completed, sulfuric acid was added to the reaction solution at a temperature of 85 ° C. to adjust the pH to a predetermined value.
Then, desalting, filtration, drying and crushing were performed to obtain Fe ₃ O ₄ powder. The obtained Fe ₃ O ₄ was heated and oxidized at 400 ° C. for 1 hour to form iron oxide (hematite: α-Fe ₂ O ₃ ) and the same evaluation as in Example 1 was performed. The results are shown in Table 2.

Comparative Example 6 In Comparative Example 6, after the formation of Fe ₃ O ₄ , the pH of the solution was adjusted to ₂ to 6.5 and Fe ₂
O ₃ was produced. 2.8 mol / l NaOH solution 1
4 liters and 14 liters of ferrous sulfate solution having Fe ²⁺ concentration of 1.5 mol / l were mixed. The temperature of this solution was raised to 90 ° C. in a nitrogen atmosphere, and while controlling the pH at 6.8 ± 0.1, air was passed through at 10 l / min to oxidize Fe ₃
O ₄ particles were synthesized. Then, desalting, filtration, drying and crushing were performed to obtain Fe ₃ O ₄ powder. The Fe ₃ O ₄ obtained is 40
Iron oxide (hematite: α-Fe ₂
O ₃ ). The Fe ₂ O ₃ obtained was evaluated under the same conditions as in the examples. The results are shown in Table 3.

(Comparative Example 7) Evaluation was carried out under the same conditions as in Examples 1 to 4 using iron oxide produced by a spray roasting method using a ferrous chloride solution and not washed with water. The results are shown in Table 3. (Comparative Example 8) Examples 1 to 4 using iron oxide produced by the spray roasting method as in Comparative Example 3 and subjected to a washing treatment after roasting.
Evaluation was performed under the same conditions as above. The results are shown in Table 3.

(Examples 15 to 18) A ferrous sulfate solution and a ferric sulfate solution were ^mixed so that the Fe ³⁺ concentration in the solution was Fe ³⁺ / Tot.
Mix so that al-Fe = 5%, add water and add all F
e The concentration was adjusted to 0.82 mol / l and the solution amount was adjusted to 25.5 liters. 10 mol / in a container with an internal volume of 30 liters
4.5 liters of NaOH solution (1 liter) was put therein, and the above iron sulfate solution was mixed with nitrogen gas by agitating the solution.
The temperature of this solution was raised to 75 ° C. in a nitrogen atmosphere, and while maintaining the pH at 10.3 ± 0.1, air was supplied at 10 l / mi.
Fe ₃ O ₄ particles were synthesized by carrying out oxidation by passing n. After the reaction was completed, the reaction solution was cooled to 60 ° C. and hydrochloric acid was added to adjust the pH to a predetermined value. Then, desalting, filtration, drying and crushing were performed to obtain Fe ₃ O ₄ powder. 250 this powder
Iron oxide (maghemite: γ-F)
e ₂ O ₃ ). The evaluation was performed under the same conditions as in Examples 1 to 4. The results are shown in Table 3.

Examples 19 to 22 and Comparative Example 9 A mixed solution of a ferrous chloride solution and a ferric chloride solution under the conditions shown in Table 4 and a sodium carbonate solution were prepared. Inner volume 4
An alkaline solution was put into a 0 liter container, and nitrogen gas was bubbled through the alkaline solution to mix the iron chloride solution with stirring. The temperature of this solution was raised to 85 ° C., and without adjusting the pH, air was blown at 10 l / min for oxidation to synthesize Fe ₃ O ₄ particles. After the reaction was completed, the reaction solution was cooled to 60 ° C. and hydrochloric acid was added to adjust the pH to a predetermined value. Then, desalting, filtration, drying and crushing were performed to obtain Fe ₃ O ₄ powder. This powder was heated at 430 ° C. for 2 hours to form iron oxide (hematite: α-Fe ₂ O ₃ ). Evaluation is made in Examples 1 to 4.
I went under the same conditions. The results are shown in Table 4. From the results in Table 4, the equivalent ratio of the alkaline solution and the solution containing the iron salt was 0.9.
It can be seen that the range of 5 to 1.5 is preferable.

(Examples 23 to 26, Comparative Example 10) A mixed solution of a ferrous iron chloride solution and a ferric chloride solution under the conditions shown in Table 5 and a potassium hydroxide solution were prepared. An alkaline solution was put into a container having an internal volume of 40 liters, and nitrogen gas was bubbled through the container to mix the iron chloride solution with stirring. The temperature of this solution was raised to 80 ° C., and without adjusting pH, air was blown at 10 l / min to oxidize Fe ₃
O ₄ particles were synthesized. After the reaction is completed, add 6 to the reaction solution.
After cooling to 0 ° C., hydrochloric acid was added to adjust the pH to a predetermined level. Then, desalting, filtration, drying and crushing were performed to obtain Fe ₃ O ₄ powder. This powder was heated at 430 ° C. for 2 hours to form iron oxide (hematite: α-Fe ₂ O ₃ ). The evaluation was performed under the same conditions as in Examples 1 to 4. The results are shown in Table 5. From the results of Examples 23 to 26, Comparative Example 5, and Comparative Example 10, the volume ratio of the alkaline solution and the solution containing the iron salt was 0.1 to 3.5.
It can be seen that the range is preferable.

From the examples and comparative examples, the Cl content is 300 ppm or less, and the SO ₄ ^2- equivalent S content is 300.
F of less than 100 ppm, total content of K, Na, Ca and Mg less than 100 and specific surface area of 6 to 60 m ² / g
When making ferrite using e ₂ O ₃ , 700 ℃
It can be confirmed that calcination is possible at about low temperature, and high sintering density and initial magnetic permeability can be obtained even by firing at low temperature of 900 ° C. or lower.

[0041]

According to the production method of the present invention, Cl and SO ₄ ^2- contained in Fe ₂ O ₃ produced can be reduced at the same time regardless of whether iron chloride or iron sulfate is used as a raw material. To be done. This is particularly effective when Fe ₂ O ₃ is produced using a raw material in which iron chloride and iron sulfate are mixed. When producing ferrite using Fe ₂ O ₃ of the present invention,
It can be calcined at a low temperature, and even if it is fired at a low temperature of 900 ° C, a high sintered density and an initial magnetic permeability can be obtained. Further, the above-mentioned Fe ₂ O ₃ can be obtained by the production method of the present invention.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

[0045]

[Table 4]

[0046]

[Table 5]

Continued front page    (72) Inventor Koji Ikeda             1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Made in Kawasaki             Chiba Steel Works, Ltd. (72) Inventor Yukio Makiishi             1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Made in Kawasaki             Chiba Steel Works, Ltd. F-term (reference) 4G002 AA03 AB02 AE02

Claims (2)

[Claims] 1. Fe ₂ containing Cl with a content of 300 ppm or less, S with a content of SO ₄ ²⁻ of 300 ppm or less, and Na, K, Ca, and Mg with a total content of less than 100 ppm. O ₃ . 2. An aqueous solution containing an iron salt and an alkaline aqueous solution are mixed.
Neutralization process to produce a solution containing iron hydroxide
When, By oxidizing the iron hydroxide in the solution, Fe₃O_FourMake particles
Fe formed₃O_FourManufacturing process, Fe₃O_FourAn acid is added to a solution containing particles, and the solution is added.
PH adjusting step of adjusting the pH of the solution to 2 to 6.5, The pH is adjusted to 2 to 6.5 in the pH adjusting step.
From solution, Fe₃O_FourA separation step for separating the particles, The Fe separated in the separation step₃O_FourAcid heating particles
Turn Fe₂O₃Fe manufacturing₂O₃With manufacturing process
Fe₂O₃The manufacturing method of In the neutralization step, the alkaline aqueous solution and the iron salt
In the following formulas (1) and (2),
Fe characterized in that the relationship expressed by the above holds ₂O₃of
Production method. [Equation 1] (In the formula (1), [OH^-] Is water in the alkaline aqueous solution
Acid group mol number, [Fe ²⁺] Is in an aqueous solution containing the iron salt
Fe²⁺Mol number of [Fe³⁺] Is a water solution containing the iron salt
Fe in liquid³⁺Shows the mol number of. )