JPS5978930A - Manufacture of hydrated ferric oxide - Google Patents

Abstract

PURPOSE:To obtain fine-grained hydrated ferric oxide having a small ratio of major axis size/minor axis size and suitable for use in the manufacture of magnetic powder by adding a dibasic acid (salt) having double bond to a suspension contg. Fe(OH)2 and by blowing a gas contg. oxygen to carry out oxidation. CONSTITUTION:An aqueous ferrous salt soln. is reacted with an aqueous alkali soln. to form ferrous hydroxide, and to the resulting suspension contg. ferrous hydroxide is added a dibasic acid having double bond such as maleic acid or a salt thereof such as sodium maleate by about 0.001-0.1mole per 1l water. A gas contg. oxygen is then blown into the suspension to form the desired hydrated ferric oxide particles by oxidation. The hydarted ferric oxide particles having about 0.1mum length and about 3 ratio of major axis size/minor axis size are stably obtd. The ferric oxide particles are suitable for use as a starting material for magnetic powder for a magnetic recording system in which a vertically magnetizable component is effectively utilized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing hydrated ferric oxide, which is a raw material for ferromagnetic powder for magnetic recording materials. In particular, the present invention relates to a method for producing hydrated ferrous oxide, which is used as a raw material for magnetic powder having a small major axis/minor axis ratio and which is fine particles suitable for magnetic recording methods that effectively utilize all of the perpendicular magnetization components.

Conventionally, as magnetic powder for magnetic recording materials, average particle length/,
Highly acicular particles having a diameter of 2 to 00 μμ and a long axis/short axis ratio of about 7 to 20 are widely used. The reason for this is that a relatively high coercive force can be obtained due to the shape anisotropy of the particles, and the effect of magnetic field orientation due to the coincidence of the shape anisotropy with the magnetic anisotropy. By making the length very small, the noise suitability after being made into a tape improves, making it more attractive. However, if the particles are made too small, it becomes difficult to disperse them in a binder when preparing a magnetic coating material, so from the viewpoint of dispersibility, it has been recommended that the particle size is preferably 0.1 μm or more.

In contrast to these conventional magnetic tape magnetic recording systems using magnetic powder, ■EEE TRANSACTIONS ON MAGNETI
CS no VOL, MAG-/j, A6. i Y
b t~t Page 963 November, 7th, a magnetic recording system that effectively utilizes the perpendicular component has been reported. It is said that when recording with a narrow gap head using a magnetic tape coated on a base, the input/output characteristics are particularly high in the short wavelength region.

As a result of various studies based on the above information, the inventors of the present invention found that when using a narrow gap spatula, the magnetic powder is 0.4/
Fine particles with a particle size of -μ or less are more likely to produce reproduction output in the short wavelength region, and a smaller major axis/minor axis ratio is a magnetic powder that is advantageous for magnetic recording methods that effectively utilize the perpendicular magnetization component. I discovered that.

The reason for this is that when the long axis/short axis ratio is smaller, when applied as a magnetic paint onto a base, it is difficult to achieve particle orientation in the in-plane direction.
It lies in the fact that it exists.

In general, as a method for producing all of the fine sword-shaped hydrated ferric oxide particles, there is a known method in which the reaction is carried out by stirring, aeration of oxygen-containing gas by 1", changing the concentration of the reaction solution, etc., and increasing the oxidation efficiency. However, it is very difficult to control the conditions, and problems include problems with the uniformity of the shape of the generated hydrous ferrous oxide particles, problems with increased equipment costs due to the installation of high-speed stirring equipment, and problems such as low yields. Also, hydrous oxidized secondary
It is also known that when ions of a different metal other than Fe are added to the aqueous solution of the first iron oxide, which is the original iron oxide, during the production of iron particles, the hydrated ferrous oxide generally becomes extremely small. However, the hydrous ferric oxide particles that are produced tend to grow in the long direction, making it difficult to obtain particles with a small long axis/wisdom axis ratio that the present inventors are aiming for.

Therefore, an object of the present invention is to provide a method for effectively producing microscopic hydrated ferrous oxide having a small major axis/minor axis ratio and serving as a raw material for magnetic powder suitable for perpendicular magnetic recording.

The inventors of the present invention have made extensive studies and have found that the above objects of the present invention can be achieved by coexisting an ion of a dicarboxylic acid having a double bond such as maleic acid.

Specifically, the method of the present invention is to completely react a ferrous salt aqueous solution with an alkaline aqueous solution to obtain f'l-7c Fe (OH
) 2 in a suspension containing Fe(
The main feature is that a linear dicarboxylic acid ion having a double bond is added to the suspension containing OH)21c before passing the oxygen-containing gas through the suspension.

The addition of a dibasic acid such as maleic acid or its additive (I) is preferably o, oo, o, t mol per 11 of water, and o, oos to 0j mono 1 per 1 mol of Fe. This 1.
Ra no Misaki, the less the surrounding area, the lower the effect obtained, and 1
1. If the amount exceeds these ranges, the acid will be excessive and will be wasted, or the reaction time will be prolonged, which is not a good idea.

Dibasic acids used in the present invention include maleic acid and hydrophilic maleate salts.

Examples of maleic e+M include sodium salt, caritas salt, and ammonium salt.

According to the present invention; n, u: Addition of dibasic acid (compared to the case without ~, the additive force is 11 C/Effect in this case d1 is the hydrous oxidized 1 Q'): The particle length of the particle size is Miniaturized, long axis/
The minor axis ratio can also be obtained easily and with good reproducibility.

Figure 7 shows the concentration of an aqueous solution of ferrous salt in water lI! Ferrous salt per serving 0. J, the trace of addition of maleic acid and the particle length and length of the generated hydrous ferric oxide particles when the amount is 5 mol IIQll/
It is a graph showing the relationship with the minor axis ratio.

From Figure 1, when no maleic acid is contained, θ,
Particles of about 4 Iμ were obtained, whereas when maleic acid was added, particles of 0.2μ were obtained. especially,
On the side where the maleic acid concentration is low, there is a tendency for particles to become smaller in proportion to the concentration, and the particle length can be controlled by n1 maleic acid. As the particle length becomes smaller, the long axis/short axis ratio also becomes smaller.

Furthermore, when the force of malein M is increased, the particle length of the hydrous ferric oxide particles that are produced becomes saturated, and the particle length o, or
Hydrous ferric oxide particles with a major axis/minor axis ratio of 3 are stably produced in a wide range of conditions.

In addition, according to the method of the present invention, a high concentration of first iron bunker 1 is used.
．． Even in such a reaction, small particles with a small major axis/minor axis ratio can be stably obtained.

The 21st graph is a graph showing the relationship between the degree of aqueous solution of ferrous salt and the particle length and major axis/minor axis ratio of the generated hydrous λ iron oxide particles. When maleic acid is not added, the particle length is not sufficiently small and becomes seven lengths @ 1 (when the minor axis ratio is large), whereas when maleic acid is added, the ferrous salt concentration Both the particle length and the long axis/short axis ratio of the hydrous ferric oxide particles produced can be made small regardless of the height of the particles.

The manufacturability of the hydrous ferric oxide particles of the present invention is also excellent in the following points.
There is a way.

In other words, when the oxidation reaction rate of hydrous ferric oxide particles that are normally produced becomes slower (i.e., the reaction takes longer), they tend to become rice grains, but the reaction according to the present invention Even if it lasts for a long time, the oxidation rate becomes fine particles, and there is no need to precisely control the oxidation rate.

If maleic acid is not used, to generate hydrous ferric oxide with a particle length of approximately O1qμ! When adding maleic acid, the particle length is about 0. Hydrous J iron oxide particles of Orμ could be obtained in 2 hours.

Furthermore, the use of maleic acid for the first iron wall was increased to 1~
When the concentration of the aqueous solution was increased by a factor of ψ, the reaction time reached a time ratio of /31 hours;
The 7-axis length of the iron is approximately 0.7μ, and the length/minor axis ratio is approximately 3. That is, when maleic acid is added, the trapping effect is remarkable, and the particle length can be reduced even though the reaction time is greatly different.

Another advantage of the hydrous ferric oxide ladle produced by the present invention is that it has a uniform particle size and is less likely to produce dendritic particles.

Example / In a jl beaker with a stirring screw and an air blowing vibrator, put 1 water and BLK into it.
It was seven days ago.

Bide, / , 4 < g of water F e S 0200-7
Take an aqueous solution containing j moles of F; l'l; add 0 while adding L, stir, and bring the liquid temperature to yo0c:I and blow air 31/
The reaction was carried out by blowing at a rate of 1.5 min. The reaction solution was blue at first, but it gradually became oxidized by air. It turned yellowish brown. When this pH became below lt9, the entire reaction was considered complete.
The time required to complete the reaction was 2 hours, and as a result of observing the particles, the particle length was 0. The particles were hydrated ferric oxide particles with a long axis/short axis ratio of approximately 3. The particle length and major axis/minor axis ratio of the hydrous ferric oxide produced with the maleic acid-added particles are shown in FIG.

Examples 2 to 3 Hydrous ferric oxide particles were produced in the same manner as in Example 1, except that the maleic acid and acetic acid calories were changed to the values shown in the table. The results are shown in Table 1.

16 Maleic acid fS 7J[] if and the particle length and major axis/minor axis ratio of the produced hydrous ferric oxide are shown in Figure 1 ◇Example
SZ with stirring screw and air blowing pipe set
Pour water/67:f into a heater and dissolve mol of NaoHj in it. Then add F e S 04 to the water of i, pz
7 Dissolve 3 mol of H20 and make an aqueous solution,
, then add θ, ij moles of maleic acid as a powder,
While stirring, blow air into the liquid po0c 831! /min.

The progress of the reaction was monitored by inserting a pH electrode, and the reaction was terminated when the reaction solution turned yellowish brown and the pH became below t.

It took more than 73 hours to complete the reaction.

As a result of observing the obtained particles f'L, they were found to be hydrated ferric oxide particles with particle lengths o and iμ and a major axis/minor axis ratio of approximately 3.

It can be seen that maleic acid may be added after the neutralization reaction with alkali and ferrous ions has started.

Example j Heating a hydrous ferric oxide aqueous solution produced under the same conditions as Example 1! It was set as rO0C. After this, a NaOH aqueous solution was added and the remaining ferrous ions were removed by blowing air at a rate of 31/min while controlling the temperature below H4'.
! , a growth reaction was carried out on the surface of the produced hydrous ferric oxide particles. After the reaction has proceeded and no longer requires addition of NaOH aqueous solution to pH'7.

It was raised to 5 and ended. Observation of the obtained f'' particles revealed that they were particles with a particle length o and an iμ major axis/minor axis ratio of about 3.

The method of neutralizing the remaining Fe 2 ions by adding alkali treatment in this way facilitates the subsequent p overwater washing operation and is an effective means for reducing wastewater pollution.

Example 6 Under the same conditions as Example 1, all 72 additives listed in the table below were added. The results are summarized in the same table.

This result shows that dicarboxylic acids having double bonds are effective for the purpose of the present invention.

On the other hand, oxydicarboxylic acid reduces the size of particles, but rather than needle-like particles with a long axis/short axis ratio of λ ~ 3, it forms particles of a completely different shape, stably forming needles with a small long axis/short axis ratio. It is not suitable for the purpose of creating fine particles.

Comparative example l Set up the stirring screw and air blowing screw! Put water i and bz2 in a beaker and put Na0H (
7.75 mol was added and dissolved.

Separately, add F e S 047H20 (7, 7
Add the dissolved mole to the mixture that is being stirred, and the temperature of the liquid is 1.
The reaction was carried out at a rate of 31/min.

The reaction solution was dark blue at first, but gradually became yellow due to air oxidation. This progress '< pH was monitored by inserting a pole, and the time when the pH became below t was defined as the end. The time required to complete the reaction was 2 hours and 10 minutes. Asymmetric hydrated ferric oxide particles with attached thin dendritic particles having a particle length of o, about xiμ, and a long axis/short axis ratio of about lj are obtained.
``It's L.

Comparative Example 2 NaOH fluoride used 1. Hydrous ferric oxide particles were produced in the same manner as in Comparative Example 1, where j moles, F e S 0 7 I420 t k, ', ' moles were used. The time required to complete the reaction is approximately 5 hours, and the produced f'L7 particles have a particle length o, 6 μ long axis/short axis ratio/j
The particles were asymmetric hydrated ferrous oxide particles to which fine dendritic particles were attached.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the particle length and major axis/minor axis ratio of the produced hydrous ferric oxide particles with respect to the amount of maleic acid added. FIG. 2 is a graph showing the relationship between the particle length and major axis/minor axis ratio of the produced 1ζ hydrated ferric oxide particles with respect to the aqueous solution concentration of the ferrous salt. However, regarding the reaction of maleic acid addition, the molar ratio of maleic acid addition 7J11t to 1am is the same. Patent applicant: Fuji Photo Film Co., Ltd. Figure 1 pr-1ifc4 clear
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Claims (1)

[Claims] Hydrous ferric oxide particles are generated by passing an oxygen-containing gas through a suspension containing F e (OH) 2 '(r) obtained by reacting a 7-iron salt aqueous solution with an alkaline aqueous solution to oxidize it. A method for preparing hydrated ferric oxide characterized by adding a tribasic acid containing a double bond or a salt thereof before passing an oxygen-containing gas into the Fe(oH)2-containing suspension. Production method.