JPS609968B2 - Method for producing raw material powder for magnetic memory materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a raw material powder for a magnetic memory material, and more specifically, a magnetic memory material with excellent magnetic properties can be produced using a by-product ferrous salt containing Mn ions as an impurity as a raw material. The present invention relates to a new manufacturing method capable of manufacturing the obtained raw material powder.

As is well known, the raw material powder for magnetic memory materials is mainly iron sulfate crystals (F
It is manufactured using eS047 Day 20) as a starting material.
That is, when a suspension containing Fe(OH)2 obtained by adding an equivalent or more amount of alkali to a ferrous salt solution, which is an aqueous solution of the starting iron salt, is oxidized, acicular Q- A precipitate consisting of Fe○(OH) particles is obtained.

This precipitate was filtered through a furnace, washed with water, and dried into acicular Q-Fe○ (OH
) The powder particles are acicular y-
This is the starting material for Fe203. In this case, the magnetic properties of acicular y-Fe203 are
-Fe○(OH) particles It depends on the particle shape and size of the powder. According to the research of the present inventor, acicular Q can be used as a starting material for acicular y-Fe203 with excellent magnetic properties.
-The Fe○(OH) particle powder should have a large acicularity.

■The average volume of the acicular particles is approximately 0.0004A.
■Narrow shape and particle size distribution. ■Contains as few specific impurities as possible. Four points are required. Now, Q-Fe○
The generation mechanism of (OH) particles is as follows.

When an alkali such as NaOH, such as NaOH, is added to an aqueous solution of FeSO in an amount less than or more than the amount necessary to completely precipitate Fe20 in the solution as Fe(OH)2, it becomes neutral (F
A white enamel solution containing either Fe(OH)2 (H7-8) or alkaline (pH>11) is obtained.

When the above alkaline suspension is oxidized, either a yellow non-ferromagnetic Q-Fe○(OH) precipitate or a black ferromagnetic Fe304 precipitate is produced depending on the reaction temperature.

As the oxidation reaction progresses, the amount of Fe(OH)2 decreases and the amount of Q-Fe○(OH) or Fe304 increases. Fe(OH)2 is completely Q-Fe0(OH) or Fe
Even if the oxidation reaction is continued after changing to 304, there is almost no chemical change in the precipitate. On the other hand, when the above neutral suspension is oxidized, a fatty blue non-ferromagnetic precipitate Z is formed regardless of the oxidation temperature.This precipitate has a hexagonal plate shape.
It consists of eenr female T particles.

This precipitate is gradually oxidized to ferromagnetic black (Fe304) or non-ferromagnetic tan (Q or y-Fe0(OH)) particles depending on whether the temperature of the neutral suspension is high or low. gr
When completely oxidized, the liquid becomes acidic. Q-Fe○(OH) is generated at an oxidation temperature of 460
The following cases are suitable, but if it is less than 35 qo, the promotion of grain growth becomes extremely small.

2 The inventors have obtained Q-F as described above.
Considering the generation mechanism of e○(OH) particles, we obtained many types of Q-Fe○(OH) particles by combining various conditions and comparatively observed them using an electron microscope. As a result, we made the following findings. Obtained. 2(i)Q-
The particle size of Fe○(OH) particles increases as the amount of production (= amount of Fe(OH)2 in the starting suspension) increases. (ii) Q-FeO(OH) depending on the amount of production
The effect on the increase in fleas depends particularly on the pH of the suspension (alkaline 3 or neutral).

(iii) Q-F obtained from alkaline suspension
The e○(OH) particles have a significantly narrower particle size distribution than those produced from neutral suspensions.

OW It is easy to obtain Q-Fe○(OH) particle powder from the alkaline suspension, which has significantly greater acicularity and narrower shape distribution than the product from the neutral suspension 3.

Comparing the results of (i) to (M) above with (■ to
It can be seen that an alkaline suspension is advantageous in order to obtain acicular Q-Fe○(OH) particle powder as a material.

Next, iron sulfate crystals obtained from pickling waste liquid produced as a by-product in the steel industry and iron sulfate crystals obtained from iron sulfate waste liquid produced during the production of titanium white were used as starting materials, and the respective ferrous salt solutions were prepared. Using an alkaline suspension containing an equivalent or more alkali, Q-Fe
According to the inventor's experiments, when obtaining ○(OH) particle powder, iron sulfate crystals from pickling waste liquid have excellent magnetic properties. Q-Fe○(OH) particles can be easily obtained, but in the case of iron sulfate crystals from iron sulfate waste liquid, which is a by-product during the production of titanium white, how can the reaction conditions be adjusted to obtain various forms? , even when we tried producing water-like acicular Q-Fe○(OH) particles, the results were compared to acicular Q-Fe○(OH) particles using iron sulfate crystals from pickling waste liquid. It was found that it was difficult to obtain acicular Q-Fe○(OH) particles as a starting material for acicular y-Fe203 having excellent magnetic properties.

The present inventor has investigated the cause of this problem, and found that iron sulfate crystals from iron sulfate waste liquid, which is a by-product during the production of titanium white, mainly contain M.
There are n ions, which are obtained in the acicular Q-Fe0(O
H) It is also contained in particles, and even when this acicular Q-Fe○(OH) is made into acicular y-Fe203, the acicular y-Fe2
I learned that the cause is that approximately several percent of Mn forms a hard lacquer in 03.

However, when iron sulfate crystals from iron sulfate waste liquid, which is a by-product during the production of titanium white, are used as a neutral suspension liquid,
Since the Mn ions in the water part are dissolved in the suspension liquid phase, Q-Fe0(OH) with a low Mn content can be obtained, but as mentioned above, it can be obtained by oxidizing the neutral suspension. The Q-Fe○(OH) particles produced have a very wide particle size distribution and shape distribution, so they have an acicular shape with excellent magnetic properties.
-It does not serve as a starting material for Fe203.

In view of the above, the inventors of the present invention used iron sulfate crystals containing Mn ions as a starting material, such as iron sulfate crystals from iron sulfate waste liquid by-produced during the production of titanium white, and used them in an alkaline suspension. The method of the present invention was arrived at as a result of pursuing a method capable of producing acicular Q-Fe○(OH) particles containing as little Mn ions as possible. That is, in the present invention, an alkaline white suspension containing Fe(OH)2 and Mn(OH)2 obtained by adding an equivalent or more amount of alkali to a ferrous salt solution containing Mn ions as an impurity is added to a ferrous salt solution containing Mn ions as an impurity. By blowing an oxidizing gas into the liquid while maintaining the temperature at 45°C to carry out an oxidation reaction, a yellow non-ferromagnetic precipitate consisting of acicular Q-Fe○(OH) particles is generated in the liquid, and the precipitate is filtered through a furnace and washed with water. , dry and needle-like Q
- In the method for producing a raw material powder for magnetic memory material to obtain yellow non-ferromagnetic particle powder consisting of FeO(OH) particles, the amount of Fe(OH)2 in the liquid is at least as low as the amount of Mn(OH)2. The oxidation reaction is stopped until the volume doubles, and the remaining Fe(OH)2 and Mn(OH)2 in the solution are dissolved by acid treatment, and then the acicular Q remaining in the solution is dissolved. One Fe○
The yellow non-ferromagnetic precipitate consisting of (OH) particles is filtered through an oven, washed with water,
This is a method for producing a raw material powder for a magnetic memory material, which comprises drying to obtain a yellow non-ferromagnetic particle powder consisting of acicular Q-Fe0(OH) particles.

Next, the configuration and effects of the method of the present invention will be explained in detail.

First, the Mn removal mechanism in the present invention will be explained. Mn
In an alkaline white suspension obtained by adding more than an equivalent amount of NaOH to an aqueous solution of iron sulfate crystals containing ions, almost all metal ions are precipitated as hydroxides.

When this alkaline white suspension is oxidized while being maintained at a temperature of 45 oo or less, as the oxidation time elapses,
The amount of hydroxides (Fe(OH)2, Mn(OH)2) in the liquid decreases, and acicular Q-Fe○(OH) particles grow.
The amount will also increase. In this case, acicular Q-Fe○(
The dissolution rate of OH) particles is very small compared to the dissolution rate of hydroxide. Therefore, the Mn content in the residual hydroxide and the oxidation reaction product can be estimated using the difference in dissolution rate as the oxidation time progresses. For example, if you collect an alkaline white suspension that is in the process of oxidation,
Add the precipitate to 1 t% acetic acid aqueous solution and
If the solution is allowed to stand for 0 minutes, most of the hydroxide will dissolve and oxidation reaction products will remain.

This oxidation reaction product is separated into a furnace, and the M in the oxidation reaction product is
If the amount of n and the amount of Mn in the furnace solution are known, the Mn content of the oxidation reaction product and the Mn content of the residual hydroxide can be determined depending on the oxidation time. As a result of conducting numerous experiments using the method described above, the present inventor found that (1) as the amount of oxidation reaction products increases due to the progress of the oxidation reaction, the amount of Mn in the remaining hydroxide increases.
content increases.

(0) However, ultimately all the metal ions in the liquid become oxidation reaction products. The results of (1) and (0) were confirmed. (
The result of 1) is due to the fact that Mn ions are much more difficult to oxidize than Fe ions in an alkaline white suspension. From the above, Fe(OH)2 obtained by adding more than an equivalent amount of alkali to a ferrous salt solution, which is an aqueous solution of iron sulfate crystals containing Mn ions, and a small amount of Mn
An alkaline white suspension containing no(OH)2
Acicular Q-Fe○ (O
H) A yellow non-ferromagnetic precipitate consisting of particles is produced, and the precipitate is heated in a furnace, washed with water, and dried to obtain a yellow non-ferromagnetic particle powder consisting of acicular Q-Fe06(OH) particles. The oxidation reaction is stopped before the Mn content in the yellow non-ferromagnetic precipitate consisting of acicular Q-Fe○(OH) particles increases significantly, and the residual Fe(OH)2 and Utilizing the difference in dissolution rate between Mn(OH)20 and Q-Fe○(OH), Fe(OH)2 and Mn(OH)2
If the remaining Q-Fe○(OH) precipitate is collected, acicular Q-Fe○(OH) with the lowest Mn content can be obtained.
) It will be appreciated that a particulate powder is obtained.

The Q-Fe○(OH) particle powder obtained in this way satisfies the above-mentioned requirements, and if it is made into y-Fe203 particle powder using the usual method as a starting material, it will have magnetic properties. An excellent magnetic memory material can be obtained.

0 Next, in carrying out the method of the present invention, preparation of an alkaline white suspension solution, maintaining the temperature of the solution, blowing in an oxidizing gas (for example, air), and filtering the Q-Fe○(OH) precipitate in an oven,
Washing with water, drying, etc. can be carried out according to conventional methods, but the important points are the timing at the end of the oxidation reaction and the residual Fe (O
This is a means of dissolving and removing H)2 and Mn(OH)2. To explain the former, the Mn content in Q-Fe○(OH) begins to increase significantly.
The amount of production, in other words, the oxidation time at which the content of 0 Mn in Q-Fe○(OH) begins to increase significantly, is difficult to specify strictly as it depends on various factors. Residual Fe(O) in alkaline white suspension
The present inventor has conducted many experiments to find that the amount of Mn in the Q-Fe○(OH) precipitate increases significantly from the time when the amount of H)2 becomes at least twice the amount of Mn(OH)2. It has been confirmed by

The amount of residual Fe(OH)2 in the alkaline suspension is M
If the amount is 0 times the amount of n(OH)2, as shown in the comparative example below, the Mn in the produced acicular Q-Fe○(OH) particles is
The content is 4. The same is true when the amount of residual Fe(OH)2 in the alkaline suspension is less than twice the amount of Mn(OH)2.
An experimental example in which the amount of Mn(OH)2 is 1.6% is the following Z pattern. Experimental Example When the oxidation reaction was carried out under exactly the same conditions as in the example described later except that the oxidation time was 2 hours, 91% of the total iron content was acicular Q-
Fe○(OH) particles were precipitated.

At this point Z, stop blowing air and heating the solution (residual Fe(OH)2 is 0.0648 mol, Mn(O
H) Since 2 is 0.03 egg ol, residual Fe(OH)
2 has a volume of 1.6 needles for Mn(OH)2. )death,
The yellow precipitate after the furnace separation was subjected to the same acid treatment as in the example below, and then the yellow non-ferromagnetic precipitate consisting of acicular Q-Fe○(OH) particles in the acidic suspension was furnace separated and After washing with water and drying, yellow non-ferromagnetic particle powder 57 consisting of acicular Q-Fe○(OH) particles is obtained. According to an electron microscope, this powder is 0.4
It consisted of biacicular particles with ~0.7 mounds, and had a very narrow shape distribution and particle size distribution, and as a result of analysis, the Mn content was 3.3 Wt%.

Therefore, Mn ions existing as impurities, Q-Fe○
Even if the yield of (OH) precipitate is taken into account, residual F remains as shown in 3 above.
If the oxidation reaction is stopped until the amount of e(OH)2 becomes at least twice the amount of Mn(OH)2, a Q-Fe○(OH) precipitate with a significantly low Mn content can be obtained.

Note that the 3Mn content in iron sulfate crystals obtained from iron sulfate waste liquid, which is generally a by-product during the production of titanium white, is not constant, but does not exceed 10% at most. Next, the means for dissolving Fe(OH)2 and Mn(OH)2 in the latter liquid will be explained.
OH)2 can be easily removed by acid treatment4.

In the acid treatment, the oxidation reaction is stopped until the amount of Fe(OH)2 in the liquid becomes at least twice the amount of Mn(OH)2, and the precipitate separated in the furnace is mixed with an appropriate amount. This is done by treatment with acid. A preferred acid treatment means is to add the filtered precipitate to an aqueous acetic acid solution prepared to the required concentration. When a precipitate is added to an acetic acid aqueous solution, Fe(
OH)2 and Mn(OH)2 are dissolved, leaving behind the already formed Q-Fe0(OH) precipitate.

If this is separated in a furnace, washed with water, and dried in a conventional manner, it is possible to obtain Q-Fe○(OH) particle powder with a significantly low Mn content. Next, the method of the present invention will be specifically explained using examples.

Example 1FeS047 day 20200 evening and MnS049
A ferrous sulfate salt solution containing Mn ions was prepared by dissolving 209.4 yen in water.

Add 127 ml of NaOH to this solution and dilute the total volume with water to 1 ml.
alkaline white suspension liquid (pH 13.2)
get. An oxidation reaction is carried out by blowing air into the above alkaline white suspension at a rate of 4000 ml per hour at a rate of 500 ml per hour.

After 18 hours, 80% of the total iron content was acicular Q-Fe0(OH
) Particles precipitated.

At this point, air blowing and solution humidification were stopped (residual Fe(OH)2 was 0.144 mol, Mn(OH)
)2 is 0.039 hol, so the remaining Fe(O
H)2 has a volume of 3.6 needles for Mn(OH)2. )
The yellow precipitate separated by furnace was added to 0.8 g of a 15 wt% acetic acid aqueous solution and stirred. The pH value of the liquid at this time was 4. Next, the needle-like Q-Fe○ (
The yellow non-ferromagnetic precipitate consisting of OH) particles is separated in a furnace, washed with water and dried to obtain yellow non-ferromagnetic particle powder consisting of acicular Q-Fe○(OH) particles.

According to an electron microscope, this powder consists of acicular particles with a length of 0.4 to 0.7 mm, and the shape distribution and particle size distribution are extremely narrow.As a result of analysis, the Mn content is 1.2 Wt. %
Met. Comparative Example For comparison, using the same alkaline white suspension liquid as above, the liquid temperature was kept at 4000°C and air was blown in at 500°C per hour so that all the iron content was acicular Q-Fe○(OH).
The oxidation reaction was continued until particles precipitated.

After 50 hours, all the iron content became acicular Q-Fe○(OH) particle precipitates.

Next, the yellow non-ferromagnetic precipitate consisting of acicular Q-Fe○(OH) particles in the liquid is separated in a furnace, washed with water, and dried to form acicular Q-Fe○.
Yellow non-ferromagnetic particle powder 67 consisting of (OH) particles was obtained. According to an electron microscope, this powder also has a length of 0.4 to 0.7
Although the shape distribution and particle size distribution were very narrow, consisting of acicular particles, the analysis revealed that the Mn content was 4.8W.
It was t%. The above two powders were each mixed in air for 4 hours.
After dehydration for 2 hours at each temperature of 00 to 800℃,
The Hc value of the y-Fe203 powder obtained by reducing at 0oo and heating again in air at 200qo for 2 hours was as shown in the following table.

Claims (1)

[Claims] 1 Fe(OH)_2 obtained by adding an equivalent or more amount of alkali to a ferrous salt solution containing Mn ions as impurities
Acicular α-FeO(
OH) particles are produced, and the precipitates are filtered, washed with water, and dried to obtain a yellow non-ferromagnetic particle powder consisting of acicular α-FeO(OH) particles. In the manufacturing method, residual Fe(OH)_2 in the liquid
The oxidation reaction is stopped until the amount of Mn(OH)_2 becomes at least twice the amount of Mn(OH)_2, and the remaining Fe(O
H) Acicular α-FeO(OH) remaining in the solution after dissolving _2 and Mn(OH)_2 by acid treatment
A method for producing a raw material powder for a magnetic memory material, which comprises filtering a yellow non-ferromagnetic precipitate consisting of particles, washing with water, and drying to obtain a yellow non-ferromagnetic particle powder consisting of acicular α-FeO(OH) particles.