JPH02133323A - Production of magnetic powder of magnetoplumbite type ferrite - Google Patents

Abstract

PURPOSE:To obtain fine uniform magnetic powder of magnetoplumbite type ferrite having a hexagonal plate shape by dissolving compds. of the constituent components of magnetic powder in water, adding alkali hydroxide to form a precipitate, hydrothermally treating the resulting slurry, adding an anionic surfactant to the treated slurry, drying and calcining the slurry. CONSTITUTION:Compds. of the constituent components of magnetic powder having a compsn. represented by the formula [where A is Ba, Sr, Ca or Pb, M is Co, Ni, Cu, Zn, Mg, Mn, In, Ti, Zr, Sn, Ge, Nb, V, Sb, Ta, Mo or W, n is 0.8-1.2, x is 0.1-5, y=(3-m)x/2 and m is the average valence of M] are dissolved in water to prepare a soln. Alkali hydroxide is added to the soln. to form a precipitate and the resulting slurry is hydrothermally treated at 120-300 deg.C. An anionic surfactant such as benzenesulfonic acid is added to the treated slurry and this slurry is dried and calcined at 700-950 deg.C to obtain magnetic powder of magnetoplumbite type ferrite.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing magnetoplumbite-type ferrite magnetic powder that has a uniform particle shape and excellent dispersibility.

In recent years, with the demand for higher density magnetic recording, development of perpendicular magnetic recording systems using magnetoplumbite-type ferrite magnetic powder as a magnetic recording medium has been progressing.

The magnetoplumbite type ferrite magnetic powder used in high-density magnetic recording media has fine particles that are well aligned and -
It is desired that each piece be separated into beautiful hexagonal plate shapes.

(Prior art and its problems) Conventionally, various methods have been known as methods for producing magnetoplumbite type ferrite magnetic powder, and regarding the hydrothermal synthesis method, for example, JP-A-59-175707;
Special Publication No. Sho 60-12973, Special Publication No. Sho 60-1557
This method has been proposed in Publication No. 6, Japanese Unexamined Patent Publication No. 137002/1980, and the like.

However, even in the above manufacturing method, the particle distribution may be wide or the shape may not be hexagonal plate-like.
Therefore, there were problems in that the dispersibility and orientation of the ink and tape were deteriorated, and the magnetic properties of the coating medium were also deteriorated.

(Object of the Invention) The object of the present invention is to solve the above-mentioned problems and provide a method for producing magnetoplumbite-type ferrite magnetic powder that has fine particles that are well-aligned, each piece is separate, and has a beautiful hexagonal plate shape. It's about doing.

(Means for solving the problems) The present invention solves the problem using the general formula A O-n (Fe12-XMXO+5
-y) (where A is Ba, Sr, Ca and Pb
M represents at least one element selected from C01
Ni, Cu, Zll, MgSMn, In, Ti
,, Zr, Sn, Ge, Nb, V, Sb, Ta
, no, and W (both represent one type of element, n = 0.8 to 1.2, x = 0.1 to 5.
O, y=(3-m)x/2, m represents the average valence of M.

) are dissolved in water, alkali hydroxide is added thereto to form a precipitate, and the slurry containing the precipitate is heated at 120 to 300°C. After hydrothermal treatment, an anionic surfactant was added to the resulting precipitate slurry, and after drying,
The present invention relates to a method for producing magnetoplumbite-type ferrite magnetic powder represented by the above general formula, which is characterized by firing at a temperature of ~950°C.

In the general formula of the present invention, A is Ba, Sr, C
At least - type of element selected from a and Pb, M is Co5Ni, Cu, Zn, Mg, Mn
,,In5Ti,,Zr.

At least one element selected from Sn, Ge5Nb, ■, Sb, Ta, Mo, and W. The substitution Mtx of M is 0.1 to 5.0, preferably 1.0 to 4.0. Further, y is represented by (3-m)x/2, but is usually -0, 5 to 2, and m is the average valence of M.

In the present invention, the element or combination of elements for M can be freely selected, but especially when Co, Ni, Zn, and Ti are used as M and the average valence m is less than 3, the saturation magnetization is significantly reduced. Moreover, it is possible to obtain a coercive force with a small temperature change and a sharp anisotropic magnetic field distribution.

In the present invention, first, the compounds of each component of the above general formula are dissolved in water, and alkali hydroxide is added thereto to form a precipitate.

Examples of compounds used include nitrates, chlorides, and hydroxides. In order to obtain hexagonal particles with good crystallinity, it is desirable that the amount of A used be such that the concentration is in the range of 0.03 to 0.50 mol/P.

As the iron compound, ferric nitrate, ferric chloride, etc. are used. The amount of iron used is 1 to 12 A per 1 gram atom.
It is a gram atom. If the amount of iron is too small, the amount of magnetoplumbite ferrite produced will be small and the crystallinity will be poor. Furthermore, if the amount of iron is too large, hematite may be formed as a by-product, and ferrite particles may become large, resulting in poor magnetic properties.

As the compound M, their chlorides, nitrates, etc. are used. The amount of M used per 12-x gram atom of iron is
It is an X gram atom.

As the alkali hydroxide, sodium hydroxide, potassium hydroxide, etc. are used. The amount of alkali hydroxide used is preferably such that the alkali hydroxide concentration in the solution after mixing the alkali hydroxide is 3 mol/1 or more, particularly in the range of 4 to 8 mol/2. If the amount of alkali hydroxide is too small, the particles will become large, the particle size distribution will become wide, and hematite will be formed. Also, it is not economical to increase the amount of alkali hydroxide excessively.

The method of adding alkali hydroxide to the aqueous solution of the above-mentioned constituent compounds may be either a continuous neutralization method or a punch neutralization method, but the continuous neutralization method is preferred in terms of immediately cooling the generated precipitate.

When the above-mentioned constituent compounds and alkali hydroxide are mixed to form a precipitate, excessive heat is generated, so that the temperature of the formed precipitate slurry usually rises to 50°C or higher. The generated precipitate generates minute nuclei, but when the temperature is high, particle growth of the generated nuclei is promoted at the same time as nucleation, so the precipitate becomes a mixture of generated and grown nuclei. It becomes uniform. Therefore, it is desirable to sufficiently remove heat during neutralization and not to carry out the reaction at too high a temperature.

Next, by hydrothermally treating the slurry containing the precipitate,
Fine crystals of ferrite precursor are formed and precipitated. The temperature of hydrothermal treatment is 140-300℃1 preferably 200-200℃
The temperature is 80°C. If the temperature is too low, crystal formation will not be sufficient, and if the temperature is too high, the particle size of the ferrite powder ultimately obtained will become large, which is not preferable. The hydrothermal treatment time is usually about 0.5 to 20 hours, and an autoclave is usually employed for the hydrothermal treatment.

Next, the precipitate of fine crystals of the ferrite precursor produced by the hydrothermal treatment is washed with water to remove free alkali, and then an anionic surfactant is added to the precipitate slurry of the ferrite precursor.

As the anionic surfactant, aromatic compounds having a sulfonic group are preferable, such as benzenesulfonic acids,
Examples include alkali metal salts such as naphthalene sulfonic acids and polystyrene sulfonic acids.

The amount of anionic surfactant added is preferably 0.1 to 20% by weight and 0.5 to 10% by weight based on the weight of the ferrite precursor. By adding an anionic surfactant, a slurry in which the ferrite precursor is uniformly dispersed can be obtained.

In the present invention, it is preferable that the content of the ferrite precursor be 10% by weight or more by concentrating the precipitate slurry of the ferrite precursor before adding the anionic surfactant. This makes it possible to shorten the subsequent drying process and simplify the dry powder recovery process.

Furthermore, in order to prevent particles from sintering or fusing during firing, it is desirable to add a flux to the precipitate slurry after adding the anionic surfactant.

As the flux, at least one of sodium chloride, barium chloride, potassium chloride, strontium chloride, and sodium fluoride is used.

The amount of flux used is 10 to 18 per ferrite precursor.
0% by weight, especially 30-120% by weight is preferred.

Next, the slurry in which the ferrite precursor is uniformly dispersed is dried.

Examples of drying methods include spray drying, drum drying, fluidized drying, and the like.

Next, the dried material is fired to completely crystallize the ferrite. Firing temperature is 700-950℃1
Preferably it is 750-930°C.

If the temperature is too low, crystallization will not proceed and the saturation magnetization will become low. In addition, if the temperature is too high, the particles will become thick (or sintered), which is undesirable.The appropriate firing time is about 10 minutes to 30 hours.The firing atmosphere is not particularly limited, but
Generally an air atmosphere is convenient.

Next, by washing, filtering and drying the baked product,
Ferrite magnetic powder of the present invention is obtained.

The cleaning may be carried out by any method as long as impurities such as flux and excess barium in the fired product can be sufficiently removed. As the cleaning liquid, water, inorganic acids such as nitric acid and hydrochloric acid, and organic acids such as acetic acid and propionic acid can be used.

Furthermore, a magnetic recording medium can be obtained by applying ferrite magnetic powder together with a binder resin to the surface of a support.

As the binder resin, for example, vinyl chloride-vinyl acetate copolymer, cellulose derivative, polyurethane resin, epoxy resin, etc. are used. Further, as the support, for example, a polyethylene terephthalate film, a polyamide resin film, a polyimide resin film, etc. are used.

Further, a dispersant, a lubricant, a hardening agent, an abrasive, etc. can also be added. Examples of dispersants include lecithin, lubricants include higher fatty acids and fatty acid esters, hardeners include bifunctional or more functional isocyanate compounds, and abrasives include CrzO, .
I! 203, cr-FezO3, etc. are used.

The method for producing magnetic recording media is the usual method, for example, by kneading magnetic powder, binder resin, and additives with a solvent to produce a magnetic paint, applying this magnetic paint to a support, and then performing an orientation treatment and drying. Examples include methods of performing treatments and the like.

(Example) The present invention will be explained in more detail by showing Examples and Comparative Examples below.

Example 1 Ferric nitrate [Fe (NO3
) z ・9H20 1287.6g, cobalt nitrate [
C0(No3)z'68zO] 53.5g, nitric acid -'-
7 pieces/Lz [N1 (N(h)z・611zO] 17.8
g1 Zinc nitrate [Zn(NO3)z・611zO] 36.
Dissolve 5 g and 23.2 g of titanium tetrachloride [TiC1'4], separate 13 ml of deionized water, 145.0 g of barium hydroxide [Ba(OH)z.8H20] and 1480 g of caustic soda (Na011). Dissolved. Both solutions were then mixed by a continuous neutralization method to form a precipitate.

The resulting slurry containing the precipitate was placed in an autoclave;
Hydrothermal treatment was performed at 260°C for 2 hours. Next, the obtained precipitate was thoroughly washed with water and then concentrated to a solid content of 18
% cake by weight was obtained.

Next, 2% by weight of sodium naphthalene sulfonate based on the ferrite precursor was added to this cake and thoroughly mixed to obtain a slurry in which the ferrite precursor was uniformly dispersed.

Furthermore, NaCf1 and BaCj! as fluxing agents! □・2H2
A mixture having a weight ratio of 1:1 was added to the ferrite precursor in an amount of 50% by weight and thoroughly mixed, and the resulting slurry was dried at 200''C using a spray dryer.

Next, the obtained dried product was fired at 880° C. for 2 hours. The obtained fired product was thoroughly washed with water, filtered, and dried to obtain barium ferrite magnetic powder.

As a result of X-ray powder diffraction spectrum and composition analysis, the obtained barium ferrite powder was BaO.(Fel 0.
4COO, i+Nio, zZnolTio, 401
7.6) and was of the magnetoplumbite type.

This barium ferrite magnetic powder was observed with a transmission electron microscope, and the particle shape and distribution of 200 particles were measured. The results are shown in Table 1.

Table 1 shows the results of measuring the magnetic properties of this barium ferrite magnetic powder using a vibrating sample magnetometer and the specific surface area using the BET method.

Further, a magnetic paint having the following composition was prepared using this barium ferrite magnetic powder.

Magnetic powder 100 parts by weight Vinyl chloride-vinyl acetate copolymer 10 parts by weight Polyurethane resin 10 parts by weight Lecithin
2 parts by weight stearic acid
2 parts by weight methyl ethyl ketone
70 parts by weight methyl isobutyl ketone
70 parts by weight cyclohexanone 70 parts by weight The obtained magnetic paint was applied to the surface of a polyethylene terephthalate film and oriented in a magnetic field at 4 kOe.

Table 1 shows the results of measuring the magnetic properties of the resulting coating film.

Comparative Example 1 In Example 1, the precipitate slurry of the barium ferrite precursor after the hydrothermal treatment was concentrated to obtain a slurry with a solid content of 5% by weight.

Thereafter, barium ferrite magnetic powder was obtained in the same manner as in Example 1 without adding an anionic surfactant to this slurry.

The magnetic properties of this barium ferrite magnetic powder were measured in the same manner as in Example 1, and the results are shown in Table 1.

Example 2 1287.6 g of ferric nitrate in 1300 mf of deionized water
X cobal nitrate) 71.3g and titanium tetrachloride 46.
Separately, 145.0 g of barium hydroxide and 1480 g of caustic soda were dissolved in 1300 d of deionized water. Both solutions were then mixed by a continuous neutralization method to form a precipitate.

The resulting slurry containing the precipitate was placed in an autoclave;
Hydrothermal treatment was carried out at 260''C for 2 hours.Then, the obtained precipitate was thoroughly washed with water and subjected to ?a'4i''6 to obtain a cake with a solid content of 18% by weight.

Next, 2% by weight of sodium naphthalene sulfonate based on the ferrite precursor was added to this cake and thoroughly mixed to obtain a slurry in which the ferrite precursor was uniformly dispersed.

Furthermore, Na (J and BaCf!2・211□
A mixture having a weight ratio of 1:1 was added to the ferrite precursor in an amount of 50% by weight and thoroughly mixed, and the resulting slurry was dried at 200'C using a spray dryer.

Next, the obtained dried product was fired at 880''C for 2 hours.The obtained fired product was thoroughly washed with water, filtered, and dried to obtain barium ferrite magnetic powder.

As a result of compositional analysis of the obtained barium ferrite magnetic powder,
Bat) (FetolCoo, 5Tio, ao
+ a).

The magnetic properties of this barium ferrite magnetic powder were measured in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 2 In Example 2, the precipitate slurry of the barium ferrite precursor after the hydrothermal treatment was concentrated to obtain a slurry with a solid content of 5% by weight.

Thereafter, barium ferrite magnetic powder was obtained in the same manner as in Example 1 without adding an anionic surfactant to this slurry.

The magnetic properties of this barium ferrite magnetic powder were measured in the same manner as in Example 1, and the results are shown in Table 1.

Example 3 Barium ferrite magnetic powder was obtained in the same manner as in Example 1 except that sodium naphthalene sulfonate was replaced with sodium polystyrene sulfonate.

The magnetic properties of this barium ferrite magnetic powder were measured in the same manner as in Example 1, and the results are shown in Table 1.

Patent ratio: 191 people Ube Industries Co., Ltd.

Claims (1)

[Claims] General formula AO・n(Fe_1_2_−_xM_xO_1_
8_-_y) (A is Ba, Sr, Ca and P
represents at least one element selected from b, M is Co
, Ni, Cu, Zn, Mg, Mn, In, Ti, Zr,
Indicates at least one element selected from Sn, Ge, Nb, V, Sb, Ta, Mo and W, n = 0.8 to 1
．． 2, x=0.1~5.0, y=(3-m)x/2, m
represents the average valence of M. ) are dissolved in water, alkali hydroxide is added thereto to form a precipitate, and the slurry containing the precipitate is heated at 120 to 300°C. After hydrothermal treatment, an anionic surfactant was added to the resulting precipitate slurry, and after drying,
A method for producing magnetoplumbite-type ferrite magnetic powder represented by the above general formula, characterized by firing at a temperature of ~950°C.