JPS609969B2 - Production method of raw material powder for red iron oxide pigment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a raw material powder for red iron oxide pigments, and more specifically, the present invention relates to a method for producing a raw material powder for red iron oxide pigments, and more specifically, even when a by-product ferrous salt containing Mn ions as an impurity is used as a starting material, a red color with excellent definition can be produced. The present invention relates to a new production method capable of producing raw material powder with an extremely low Mn content from which iron oxide pigments can be obtained.

As is well known, the raw material powder for red iron oxide pigments is mainly made from iron sulfate crystals (FeS047, 20) obtained from pickling waste liquid by-produced in the steel industry or iron sulfate waste liquid by-product during the production of titanium white. It is produced 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, cubic Fe304 particles are formed mainly by selecting the oxidation temperature. A precipitate consisting of

The precipitate was filtered through a furnace, washed with water, and dried to produce a cubic Fe304 particle powder, which is Q-Fe, which is used as a red iron oxide pigment.
It is suitable as a starting material for 203. in this case,
The degree of red color and brightness of the red iron oxide pigment depend on the particle size distribution and size of the cubic Pe3Q particle powder that is the starting material. According to the inventor's certainty, the cubic Fe304 particle powder used as the starting material for the iron oxide pigment exhibiting a clear red color has: Something.

■Narrow particle size distribution. ■Contains as few specific impurities as possible. Three points are required. The generation mechanism of Fe304 particles will now be described 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 required to completely precipitate Fe20 in the solution as Fe(OH)2, it becomes neutral (p
A white suspension 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 LQ-Fe○(OH) or Fe304 increases. Fe(OH)2 is completely Q-Fe○(OH) or F
Even if the oxidation reaction is continued after changing to e304, there is almost no chemical change in the precipitate. On the other hand, when the above-mentioned neutral suspension is oxidized, a gray-blue non-ferromagnetic precipitate is produced regardless of the oxidation temperature.

This precipitate consists of hexagonal plate-shaped gelatin particles. This precipitate is gradually oxidized to ferromagnetic black (Fe304) or non-ferromagnetic yellow-brown (Q or Sea Fe○ (OH)) particles depending on whether the temperature of the neutral renal solution is high or low. When greenmst is completely oxidized, the suspension becomes acidic. The generation of Fe304 is suitable when the oxidation temperature is 6000 or higher, but when the oxidation temperature is 900 or higher, the effect of promoting grain growth by heating is small.

In view of the production mechanism of Fe304 particles as described above, the present inventor combined various conditions to obtain numerous types of Fe304 particles.As a result of comparative observation of these using an electron microscope, the following findings were made. Obtained.

(1) The particle size of Fe304 particles increases as the amount of the Fe304 particles produced (=the amount of Fe(OH)2 in the starting suspension) increases.

(b) The effect of the production amount on the increase in Fe304 particle size is particularly influenced by the pH of the suspension (alkaline or neutral).

(m) Fe304 particles obtained from an alkaline suspension have a significantly narrower particle size distribution than the product from a neutral suspension.

(W) Neutral suspension produces granular Fe304; alkaline suspension easily produces cubic Fe304 particles.

Comparing the results of (1) to (W) above with the results of ■ to ■ above, it can be seen that the particle size distribution of the iron oxide pigment as a starting material, which exhibited a bright red color, was significantly narrowed, and the desired average particle size of cubic Fe30 was obtained.
An alkaline suspension appears to be advantageous for obtaining a 4-grain powder.

Next, iron sulfate crystals obtained from pick ljing waste liquid by-produced in the steel industry and iron sulfate crystals obtained from sulfuric acid waste liquid by-produced during titanium white manufacturing were used as starting materials, and ferrous salts of each Using an alkaline suspension in which more than an equivalent amount of alkali is added to the solution, Fe30
When obtaining 4-particle powder, according to the experiments of the present inventor, it is easy to obtain cubic Fe304 particle powder, which is the starting material for iron oxide pigment, which has a bright red color in the case of iron sulfate crystals from pickling waste liquid. However, in the case of iron sulfate crystals from iron sulfate waste liquid that is destroyed during the production of titanium white, "no matter how much you adjust the reaction conditions to produce Fe304 particles of various sizes, the pick Compared to the cubic Fe304 particle powder when iron sulfate crystals from ring waste liquid are used, the cubic Fe304 particle powder exhibits a bright red color and is inferior to the cubic Fe304 particle powder used as the starting material for iron oxide pigments. Koto Rikishu Han U revealed.

The present inventors investigated the cause of this problem and found that Mn ions are present in iron sulfate crystals from iron sulfate waste liquid that is a by-product during the production of titanium white, and that Mn ions are also contained in the cubic Fe304 particles obtained. Even when Fe304 is used as o-Fe203, it has been found that the main cause is that about several percent of Mn is dissolved in the Q-Fe203.

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,
Most of the Mn ions are dissolved in the suspended liquid phase.
Although it is possible to obtain Fe304 with a significantly lower content, Fe304 obtained by oxidizing a neutral suspension as described above
Since the 04 particles have a very wide particle size distribution, they are unsuitable as a starting material for an iron oxide pigment that exhibits a bright red color and has good dispersibility.

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 cubic Fe304 particles containing as little Mn ions as possible.

That is, the present invention contains Mn ions as impurities.
Fe obtained by adding more than equivalent amount of alkali to ferrous salt solution
An alkaline white resin solution containing (OH)2 and Mn(OH)2 is maintained at a molecular weight of 60 to 9000, and an oxidizing gas is blown into the solution to carry out an oxidation reaction, resulting in a black color consisting of cubic Fe304 particles in the solution. In a method for producing a raw material powder for red iron oxide pigments, a ferromagnetic precipitate is generated, and the precipitate is filtered, washed with water, and dried to obtain a black ferromagnetic particle powder consisting of cubic Fe304 particles. )2 amount is M
The oxidation reaction is stopped until the amount reaches at least twice the amount of n(OH)2, and the remaining Fe(OH)2 and M
After dissolving n(OH)2 by acid treatment, the black ferromagnetic precipitate consisting of cubic Fe304 particles remaining in the solution is heated in a furnace, washed with water, and dried to form a black ferromagnetic precipitate consisting of cubic Fe304 particles. This is a method for producing raw material powder for red iron oxide pigments by obtaining particulate powder. 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 liquid is oxidized while being maintained at a temperature of 6000°C or higher, as the oxidation time elapses, the amount of hydroxides (Fe(OH)2, Mn(OH)2) in the liquid decreases. Cubic Fe304 particles grow and their amount increases. In this case, the dissolution rate of the cubic Fe304 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, an alkaline white suspension in the process of oxidation is collected, and the precipitate is
When added to an aqueous solution of Wt% acetic acid and allowed to stand for 10 to 3 minutes, most of the hydroxide is dissolved and an oxidation reaction product remains. This oxidation reaction product is separated into furnaces, and if the amount of Mn in the oxidation reaction product and the amount of Mn in the furnace liquid are known, the Mn content of the oxidation reaction product and the Mn of the residual hydroxide depending on the oxidation time can be determined.
content can be determined. The inventors of the present invention have conducted numerous experiments using the method described above, and have found that (1) as the oxidation reaction progresses and the amount of oxidation reaction products increases, the Mn content of the residual hydroxide 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 1) is due to the fact that Mn ions are significantly less oxidized than Fe ions in the alkaline white suspension. From the above, Fe(OH)2 and Mn(OH)2, which are obtained by adding an equivalent or more alkali to a ferrous salt solution, which is an aqueous solution of iron sulfate crystals containing Mn ions,
) 2 and an alkaline white suspension solution at 60 to 90o.
A black ferromagnetic precipitate consisting of cubic Fe304 particles is produced in the liquid by blowing an oxidizing gas into the solution while the temperature is maintained at C. In order to obtain black ferromagnetic particles, the oxidation reaction is stopped before the Mn content in the black ferromagnetic precipitate consisting of cubic Fe304 particles, which is an oxidation product, increases significantly. Residual Fe(O
Fe(OH)2 and Mn(OH)2 by utilizing the difference in dissolution rate between H)2 and Mn(OH)2 and Fe304.
Mn is dissolved and the remaining Fe304 precipitate is collected.
It will be appreciated that a cubic Fe304 particle powder with as low a content as possible is obtained.

The cubic Fe304 particle powder obtained in this way satisfies the requirements (1) to (3) above, and if this is used as a starting material and made into Q-Fe203 particle powder by a conventional method, it becomes a red color with excellent redness and sharpness. iron oxide pigments can be obtained.

Next, in carrying out the method of the present invention, the preparation of an alkaline white suspension solution, the temperature maintenance of the solution, the blowing of an oxidizing gas (for example, air), the filtration of the Fe304 precipitate, the washing with water, the drying, etc. are carried out in the usual manner. The important points are the timing of stopping the oxidation reaction and the Fe(OH)2 and Mn(O) in the liquid.
H) It is a means of dissolving and removing 2.

To explain the former, the Mn content in Fe304 increases significantly, and the production amount of Fe304 increases, in other words, F
The oxidation time at which the Mn content in e304 begins to increase significantly is difficult to specify strictly as it is slightly influenced by various factors, but The present inventor has confirmed through many experiments that the amount of Mn in the Fe304 precipitate increases significantly from the time when the amount becomes at least about twice the amount.

The amount of residual Fe(OH)2 in the alkaline suspension is M
If it is 0 times the amount of n(OH)2, the Mn content in the produced Fe304 is 5.1wt as shown in the later comparative example.
%, residual Fe in alkaline suspension (
The same applies when the amount is less than twice the amount of OH)2. For example, if an example is shown where the amount of residual Fe(OH)2 is 1.83 volume relative to Mn(OH)2, It is as follows. Experimental example oxidation time 9. When the oxidation reaction was carried out under exactly the same conditions as in the examples described later, except that the reaction was carried out immediately, 90% of the total iron content was precipitated as cubic Fe304 particles.

At this point, stop blowing air and heating the solution (remaining F
e(OH)2 is 0.072 hol, Mn(OH)
Since 2 is 0.039 hol, the remaining Fe(OH)2
is 1.85 times the amount of Mn(OH)2). Then, the muddy precipitate after furnace separation was treated with the same acid as in the example described later, and the black ferromagnetic precipitate consisting of cubic Fe304 particles in the acid solution was separated into furnaces, washed with water, and dried. Cubic Fe30
45 pieces of black ferromagnetic particle powder consisting of 4 particles is obtained. This powder is 0 according to an electron microscope.

It has a narrow particle size distribution consisting of cubic particles on the surface of Mn.
The content was 3.5 wt%.

Therefore, Mn ions existing as impurities, Fe304
Even considering the yield of precipitation, etc., residual Fe(OH)
If the oxidation reaction is stopped until the amount of Mn(OH)2 becomes at least twice that of Mn(OH)2, Fe30 with a significantly low Mn content can be produced.
4 precipitate can be obtained.

In addition, the Mn 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.
It 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.
H)2 can be easily removed by acid treatment. In the precipitate treatment, the amount of Fe(OH)2 in the liquid is reduced to Mn(
This is carried out by stopping the oxidation reaction until the amount reaches at least twice the amount of OH)2, and treating the precipitate separated from the L furnace with an appropriate amount of acid. A preferred acid treatment means is to add the precipitate taken up from the furnace to an aqueous acetic acid solution prepared to the required concentration. When the precipitate is added to the acetic acid aqueous solution, Fe(OH)2 and Mn(OH)2 in the solution are dissolved and the already formed Fe304 precipitate remains.

If this is separated in a furnace, washed with water, and dried in a conventional manner, it is possible to obtain Fe304 particles having a significantly low Mn content. Next, the method of the present invention will be specifically explained with reference to Examples. Example 1 FeS047 day 20200 evening and MnS049 day 209.
A ferrous sulfate salt solution containing Mn ions is prepared by dissolving 4 ml of ferrous sulfate in ice and 2 ml of ice.

To this solution was added 76 g of NaOH, and the whole solution was diluted with water for 3 g to obtain an alkaline white suspension (pH 12.5). An oxidation reaction is carried out by blowing air into the alkaline white suspension at a rate of 300 k/hour while maintaining the alkaline white suspension at 7,000 kph.

After 4 hours, 50% of the total iron content was precipitated as cubic Fe304 particles.

At this point, air blowing and heating of the solution were stopped. (Residual Fe(OH)2 was 0.36 mol, Mn(OH)
)2 is 0.039 hol, so the residual Fe(OH)
2 is 9.23 times as much as Mn(OH)2. ) The muddy precipitate after the furnace separation is added to a 100% acetic acid aqueous solution of 1 OWt%, and the slurry is clarified. The pH value of the solution after the fly azusa was 4. Next, the black ferromagnetic precipitate consisting of cubic Fe304 particles in the acid suspension was separated in a furnace, washed with water, and dried to obtain black ferromagnetic particle powder 23 consisting of cubic Fe304 particles.

According to an electron microscope, this powder has a narrow particle size distribution consisting of cubic particles of 0.07 to 0.15 mounds, and has a BE of
The average particle size calculated from the measured T specific surface area was 0.08 mm, and the Mn content was 0.2 Wt% as a result of analysis. Further, when the oxidation reaction was carried out under the same conditions as above except that the oxidation time was 7 hours, 80% of the total iron content was precipitated as cubic Fe304 particles. After stopping the oxidation reaction (
The remaining Fe(OH)2 is 0.144 mol, and Mn(
Since OH)2 is 0.039 hol, the remaining Fe(O
The amount of H)2 is 3.69 times that of Mn(OH)2. )
After performing the same acid treatment as above, the black ferromagnetic precipitate consisting of cubic Fe304 particles in the acidic suspension was separated in a furnace, washed with water, and dried to obtain a black ferromagnetic particle powder consisting of cubic Fe304 particles. obtain. This powder consists of cubic particles with a diameter of 0.07 to 0.15 mm according to an electron microscope. The particle size distribution is narrow, and the average particle size calculated from the BET specific surface area measurement value is 0.09 French, and as a result of analysis,
The Mn content was 0.7 Wt%. Comparative Example For comparison, when the oxidation reaction was carried out under the same conditions as above except that the oxidation time was 2 feeding hours, all the iron content was precipitated into cubic Fe304 particles. After all the iron content has become cubic Fe304 particles, the oxidation reaction is stopped and the cubic Fe3 particles in the liquid are precipitated.
The black ferromagnetic particle precipitate consisting of Fe304 particles was separated in a furnace, washed with water, and dried to obtain a black ferromagnetic particle powder consisting of cubic Fe304 particles.

According to an electron microscope, this powder has a narrow particle size distribution consisting of cubic particles of 0.07 to 0.15 mm, and has a BE of
The average particle diameter calculated from the T specific surface area measurement value was 0.09 mm, but the Mn content was 5.1 Wt% as a result of analysis. The above three types of powders were each mixed in air at 500 to 80%
The color and sharpness of the powder obtained by heating at each temperature of 00°C for 2 hours are 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
Cubic Fe_3O is added to the alkaline white suspension containing Mn(OH)_2 by blowing an oxidizing gas into the solution while maintaining it at 60 to 90°C to carry out an oxidation reaction.
In a method for producing a raw material powder for red iron oxide pigment, a black ferromagnetic precipitate consisting of _4 particles is generated, and the precipitate is filtered, washed with water, and dried to obtain a black ferromagnetic particle powder consisting of cubic Fe_3O_4 particles. The amount of Fe(OH)_2 is M
The oxidation reaction is stopped until the amount reaches at least twice the amount of n(OH)_2, and the remaining Fe(OH)_2 in the liquid is removed.
After dissolving Mn(OH)_2 and Mn(OH)_2 by acid treatment, the black ferromagnetic precipitate consisting of cubic Fe_3O_4 particles remaining in the solution is filtered, washed with water, and dried to form cubic Fe_
A method for producing a raw material powder for a red iron oxide pigment, characterized by obtaining a black ferromagnetic particle powder consisting of 3O_4 particles.