JPS61219720A - Production of particulate magnet plumbite-type ferrite - Google Patents

Abstract

PURPOSE:To produce easily the titled ferrite having a small particle diameter by treating hydrothermally iron compounds and a compound containing Ba, Sr or Pb in the presence of Sn(IV) or Sn(IV)-M(II) in an alkaline aqueous solution. CONSTITUTION:At least one kind of iron compound among hydrated iron compound, iron hydroxide or the substance which produces a hydrated iron compound and iron hydroxide by reaction, and a compound containing >=1 kinds of elements selected from Ba, Si and Pb are added into the mixture mixed so as to obtain 4-6 molar ratio of Fe2O3/M (M is Ba, Sr or Pb) and further 0.2-5mol Sn(IV) or Sn(IV)-M(II) (example: sodium stannate) against 12mol Fe(III) is added into said mixture to make a total mixture, which is treated hydrothermally at 80-360 deg.C in the alkaline aqueous solution having >=50wt% concentration. Thus, the titled particulate magnet plumbite-type ferrite having <=0.3mum particle diameter and being useful as magnetic powder for vertical magnetic recording is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing hexagonal plate-shaped or plate-shaped magnetoblanbite type ferrite fine particles.
The purpose is to provide an economical and stable method for producing magnetoblanbite type ferrite fine particles having a small particle size and particularly suitable as magnetic powder for perpendicular magnetic recording.

In recent years, in response to the demand for higher density magnetic recording, a perpendicular magnetic recording method that is capable of recording at a density several times higher than that of the conventional method (longitudinal recording method) has been proposed and is being put into practical use.

Unlike conventional methods, the magnetic recording medium used in this perpendicular magnetic recording method must have an axis of easy magnetization perpendicular to the magnetic tape or magnetic tape surface. Recording media are broadly classified into the following two types.

l) Sputtering, vapor deposition film (Co - (3r system)) 2) Coated film (Ba-ferrite) Among these, the coated film using Ba-ferrite, which is a typical example of magneto-1 lambite ferrite, is easy to mass-produce, It is said to be superior in terms of stability and economy. The characteristics required of Ba-ferrite powder for perpendicular magnetic recording are: - Be as fine as possible without becoming superparamagnetic.

2) Particles with good dispersibility, narrow particle size distribution, and easy orientation.

3) If the 8 diameter is small and the coercive force is, for example, 3,000 (Oc
t) Appropriately low.

etc.

Among these, the first is as fine and uniform as possible.
It is said that it is most important to produce No. 7 elite.

The present invention is a wet method for producing magnetobrambite-type ferrite fine particles having a fine and uniform hexagonal plate shape or plate shape that can be used as such a coated perpendicular magnetic recording medium.

(Prior Art) The conventional method for producing magnetoblanbite type ferrite is to use an iron compound containing Ba (nl) ions and Ba.

The so-called dry method is a well-known method in which a compound containing one or more elements of 5r1Pb is mixed and reacted by dry heating and sintering.On the other hand, the wet method involves mixing the above raw materials as an alkaline suspension. A hydrothermal treatment method was known. However, the ferrite obtained by these dry methods is polycrystalline with a particle size of several micrometers, and although it can be finely powdered to about 1 micrometer by crushing, it has poor dispersibility when made into a paint, which is required for perpendicular magnetization recording. ．．
It was far from 0.01 to 0.3 μm. On the other hand, ferrite obtained by the wet method usually has a hexagonal plate shape, and although the particle size and magnetic properties vary depending on the production conditions, it has been extremely difficult to obtain fine particle ferrite of 0.2 μm or less.

(Problems to be Solved by the Invention) The present invention provides a method for easily producing ultrafine ferrite particles of 0.3 μm or less in a wet method magneto-lambite ferrite production method using a simple method. and
This solves the difficulties in manufacturing particulate ferrite.

(Means for Solving the Problems) The present inventors have previously developed a method for producing magnetobrambite ferrite (Fe1Oa, (FeO), Fe1O).
(0 < They discovered that fine particles could be achieved by adding an agent and filed an application. (Special application 1986-13
(No. 6812) As a result of continued intensive study by the present inventors on the production method of fine magnetogra/pi-disc 7 elite particles,
Hydrous iron oxide, iron hydroxide, iron compounds that produce iron hydroxide or hydrate iron oxide by reaction are used as iron raw materials, and during hydrothermal treatment, 5n (fV) or 8n (IV '')-
It was discovered that extremely fine magnetobrambite-type 7-elite B particles can be obtained by adding the M(11) compound, and the present invention has been completed.

That is, the present invention provides a compound containing at least lff1 of hydrous iron oxide, iron hydroxide, or a compound that produces hydrous iron oxide and iron hydroxide by reaction, and Ba% 8r.

5n (IV
) or an(IV)-M(...) is provided.

The iron raw materials used in the method of the present invention include α-FeOOH (goethite) as hydrous iron oxide, F′e(on), , re (OH)z as δ-PeOOH1 iron hydroxide, and
Further, as the compound which produces iron hydroxide or hydrated iron oxide by reaction, iron chloride, iron nitrate, iron sulfate, etc. can be commonly used.

On the other hand, barium, strontium, and lead compounds as auxiliary raw materials can be used as long as they exhibit a relatively low solubility under -6 reaction conditions. For this reason, usually
Chlorides, nitrates and hydroxides are commonly used. Carbonates and sulfates are generally poorly soluble and undesirable.

In addition, the charging ratio of these iron compounds and barium, strontium, and lead compounds, including barium, strontium, and lead compounds alone and in combination, is expressed as molar ratio (Fe/MO) (where M= Ba, S
r, Pb) is in the range of 4 to 6, preferably 5 to 6.

Generally, coercive force (tHe) increases as the grain size of magnetobrambite ferrite particles becomes finer, so it is desirable to reduce this appropriately. As such a method, it is known to replace part of the iron constituting the magnetobrambite ferrite with a different metal.

The dissimilar metals used in the dry method include co! +-T1
Although it is well known that metals such as 4+, Zn"-Ti'+, etc. are added, the addition of these metal elements is not necessarily effective in the wet method. cD cleft production (patent application 1973)
8-229185) is 5n (IV) or 5n (V)
We found that M(n) is valid.

In Japanese Patent Application No. 55-229185 under conditions of low alkali concentration, these different elements were useful in lowering the coercive force, but had no effect on refinement, and on the contrary, the grain size tended to increase.

However, under conditions of high alkali concentration, at least one of hydrated iron oxide, iron hydroxide, an iron compound that becomes hydrated iron oxide or iron hydroxide through reaction, and at least one of Ba%Sr%PB are used as raw materials. These 5n(IV) or an(IV)-M(11
) The present invention was completed based on the discovery that the addition of a compound has a remarkable effect on reducing the particle size.

Eln(IV) used in the present invention is sodium stannate, tin tetrachloride, M(n) is Fe, (3u,
Basically, it is a divalent metal compound having an ionic radius similar to Fe(III), such as Zn, co%N1, Mn%Mg, etc.

On the other hand, the addition ratio is 0.5n(IV) alone or in combination with M(...) per 12 moles of Fe(l[).
2 to 5 moles are used.

If it is less than 0.2 mol, the effect of refining is small, and if it is added in excess of 5 mol, the particle size will become coarser, which is not preferable.

The alkali used in the reaction is usually NaOH1KOH.
A caustic alkali such as the above is used, and although a high concentration is useful for micronization, addition of 50 wt % or more is not preferable because it may become insoluble. Generally, about 3 to 8 moles is preferable.

Hydrothermal treatment temperature is 80-360℃, preferably 220-360℃
30°C is recommended.

An oxidizing agent is not necessary when Fe (Ill) is used as the iron raw material, but it must be added at the same time when using Pe (River). Nitrate, chlorate, nitrite, perchlorate, Oxidizing agents such as hydrogen peroxide and oxygen are used.

Hereinafter, the present invention will be explained in detail with reference to Examples.

Example 1 100gj of ferric chloride aqueous solution (5 mol), 5% caustic soda in 21P1 barium chloride, 4.7F sodium stannate trihydrate
ay and water at 50F to co-precipitate iron hydroxide and barium hydroxide.

This mixed reaction solution was placed in an autoclave equipped with a stirrer, and at the same time, 95F caustic soda was added and water was added so that the total amount was 300 tJ. Then autoclave for 27
After reacting at 0° C. for 3 hours, the contents were filtered, washed, and dried to obtain a brown ferromagnetic powder.

As a result of X* diffraction and electron microscopy of this material, the average particle size was 0.
．． It was confirmed that it was a 2 μm hexagonal plate-shaped Ba-ferrite.

Comparative example! The same procedure as in Example 1 was carried out except that sodium stannate was not added. The particle size of the obtained Ba-ferrite was 0.8 μm.

Examples 2-3 To 4.7F of sodium stannate, add 4.72F of sodium stannate and 5.1F of cobalt nitrate hexahydrate, and then add 4.7Y of sodium stannate and 2.4F of zinc chloride. The same procedure as in Example 1 was carried out except for the above. The grain size of the obtained ferrite was 0.15 μm.

Examples 4 to 6 As an iron source, iron nitrate, iron sulfate,
The same procedure as in Example 2 was conducted except that α-FeOOH (goethite) was used and barium nitrate was used instead of barium chloride. The particle size of the obtained Ba-ferrite was 0.15 μm.

Example 7 The same procedure as in Example 1 was carried out except that fiK13.4F was added instead of 4.71 sodium stannate. The particle size of the obtained Ba-ferrite was 0.1 μm.

Example 8 The same procedure as in Example 1 was carried out except that strontium nitrate was added in place of barium chloride. The particle size of the obtained 5r-7 elite was 0.2 μm.

Comparative Examples 2-3 Instead of adding 4.71 sodium stannate, 0.62 and 4
The same procedure as in Example 5 was conducted except that 65E was added. The particle sizes of the obtained Ba-ferrite were 0.8 μm and 1.0 μm, respectively.
It was μm.

Table 1 shows the main manufacturing conditions of Examples 1 to 8 and Comparative Examples 1 to 5 and the physical properties of the produced 7-elite.

Claims (1)

[Claims] At least one type of hydrated iron oxide, iron hydroxide, and a compound that generates hydrated iron oxide or iron hydroxide by reaction, and Ba, Sr.
, and a compound containing at least one element among Pb in an alkaline aqueous solution to produce magnetobrambite type ferrite fine particles, Sn(IV) or Sn(IV)-M(II) A method for producing fine particulate magnetoblanbite type ferrite, characterized by adding.