JPH0226833A - Manufacture of magnetoplumbite-type ferrite magnetic powder - Google Patents

Abstract

PURPOSE:To obtain a magnetic powder comprising hexagonal fine particles excellent in dispersiveness by subjecting a hydroxide of the component of the magnetoplumbite-type ferrite powder as shown in general formula to some treatments such as hydrothermal treatment, sintering and extraction with an organic solvent under specified conditions. CONSTITUTION:The component of the magnetic powder is represented in general formula (wherein A is an element selected from Ba, Sr, Ca and Pb, M is an element selected from Co, Ni, Cu, Zn, Mg, Mn, etc., (n) is 0.8-1.2, x is 0.1-5, y satisfies (3-m)x/2, and (m) is the average valence of M). A hydroxide of this component is produced and then subjected to hydrothermal treatment at 120-300 deg.C to produce fine particles of ferrite precursor. The fine particles are mixed with a flux and is sintered at 700-950 deg.C. Then the sintered material is covered with a surfactant and extracted in an organic solvent which does not dissolve in water.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing magnetoplumbite-type ferrite magnetic powder with 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, there is a problem that when the particles are made finer, the dispersibility and orientation deteriorate.

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

(Means for Solving the Problems) The present invention provides a general formula A O' n(Fe+z-XMxO+
5-y) (where A is Ba5Sr, Ca and Pb
M represents at least one element selected from Co,
Ni, Cu, ZnSMg, Mn5In, Ti,
Zr, Sn, Ge, Nb, V, sb.

Indicates at least one element selected from Ta, Mo and W, n = 0.8-1.2, 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 at
A magnet expressed by the above general formula, characterized in that it is fired at 950°C, the resulting fired product is washed, then coated with a surfactant, and extracted into an organic solvent that is sparingly soluble in water. The present invention relates to a method for producing plumbite-type ferrite magnetic powder.

In the general formula of the present invention, A is Ba, Sr, C
At least one element selected from a and Pb, M is Co, Ni, CuXZn, Mg, MnX
In5Ti, Zr.

Sn, Ge, Nb, V, Sb, Ta, Mo
and at least one element selected from W. M
The substitution lx is 0.1 to 5.0, preferably 1.0 to 4.
It is 0. Also, y is expressed as (3-m)x/2,
It is usually -0.5 to 2, and m is the average valence of M.

In the present invention, the element or combination of elements of M can be freely selected, but in particular C01Ni, Zn and T
When i is adopted and the average valence m is smaller than 3, the saturation magnetization is significantly improved, the temperature change in coercive force is small, and the anisotropic magnetic field distribution is sharp.

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.

As the compound A, nitrates, chlorides, hydroxides, etc. are used. 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/2.

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/l or more, particularly in the range of 4 to 8 mol/l. 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 use too much alkali hydroxide.

Next, by hydrothermally treating the slurry containing the precipitate,
Fine crystals of ferrite precursor are formed and precipitated. The temperature of hydrothermal treatment is 120 to 300°C, preferably 130 to
It is 280°C. If the temperature is too low, crystal formation will not be sufficient, and if the temperature is too high, the final ferrite powder will have a large particle size, which is undesirable.The hydrothermal treatment time is usually 0.5 to 20 hours. An autoclave is usually used for 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 a flux is mixed with the fine ferrite precursor particles. 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 180% by weight, especially 30 to 180% by weight, based on the ferrite precursor.
120% by weight is preferred.

Next, the resulting mixture is fired to completely crystallize the ferrite. Firing temperature is 700-9
50°C, preferably 750 to 930°C. If the temperature is too low, crystallization will not proceed and the saturation magnetization will become low. Furthermore, if the temperature is too high, the particles become large and sintering occurs, which is not preferable.

Appropriate firing time is about 10 minutes to 30 hours.

Next, the obtained baked product is washed. 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.

Cleaning liquids include water, inorganic acids such as nitric acid and hydrochloric acid, acetic acid,
Organic acids such as propionic acid can be used.

Next, the obtained ferrite fine powder is coated with a surfactant. At this time, it is preferable to coat the ferrite fine powder with silicon or aluminum oxide and/or hydroxide in advance.

Coating with silicon or aluminum oxide and/or hydroxide is generally carried out in the following manner. After dispersing fine ferrite powder in water and dissolving the compound of the element in the water, the particle surface is coated with the oxide and/or hydroxide of the element by adjusting the pH of the aqueous solution.

As the compound of the element to be coated, silicic acid, colloidal silica, sodium silicate, silicate ester, silicon halide, aluminum nitrate, aluminate ester, aluminum trichloride, etc. are used.

The amount of the oxide and/or hydroxide of the element coated on the particle surface is preferably 0.5 to 10% by weight in terms of oxide based on the ferrite fine powder.

As the surfactant, cationic ones are preferable, and for example, aliphatic amine salts, quaternary ammonium salts, aromatic quaternary ammonium salts, etc. are used.

When coating with silicon or aluminum oxide and/or hydroxide is not performed, anionic ones are preferred.

The coating amount of the surfactant is 0.0.
5 to 30% heavy background is preferable.

The fine ferrite powder coated with a surfactant is extracted into an organic solvent that is sparingly soluble in water. Is it a machine that is poorly soluble in water? As a medium, benzene, toluene, p-xylene, ethylbenzene, cyclohexane, n-hexane, n-hebutane, n-
Non-polar solvents such as -octane and methylcyclopenkune, and polar solvents such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone are used. The fine ferrite powder extracted into the organic solvent is separated by evaporation to dryness, filtration, etc. By extracting into an organic solvent in this manner, individual particles are separated, and agglomeration of particles during the drying process is less likely to occur, resulting in excellent dispersibility. Furthermore, since water-soluble impurities such as sodium are removed, dispersibility during application is also improved.

In addition, in the present invention, before mixing the ferrite precursor fine particles with a flux and firing, the ferrite precursor fine particles are coated with the silicon or aluminum oxide and/or hydroxide and/or with a surfactant. Processing may be performed. This prevents particles from adhering to each other and sintering due to firing, and further improves dispersibility.

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.

Furthermore, dispersants, lubricants, hardeners, abrasives, etc. may be added. Dispersants include lecithin, lubricants include higher fatty acids, fatty acid esters, etc., and hardeners include, for example, Examples of abrasives such as bifunctional or more functional isocyanate compounds include Crz(h, A
RzOx, (X-FezOs, 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
) 3 ・9HzO] 1287.6g, cobalt nitrate [Co(NO3)z・6HzO] 53.5g, nickel nitrate [Ni (NOs)z・6HzO] 17.8g,
Zinc nitrate [Zn(NOz)z・6HzO] 36.5g
and titanium tetrachloride [TiCL] 23.2g were dissolved,
Separately, barium hydroxide [Ba
(OH) 2 ・8H20]145. 1480 g of Og and caustic soda (NaOtl) were dissolved and the re-solutions were mixed to form a precipitate.

The resulting slurry containing the precipitate was placed in an autoclave;
Hydrothermal treatment was performed at 145°C for 8 hours. Next, the obtained precipitate was thoroughly washed with water, filtered and dried, and a mixture of NaCf1 and Ba (J2/2H20 in a weight ratio of 1:1) was added as a flux at 100% by weight based on the precipitate. This mixture was baked at 860°C for 2 hours. After thoroughly washing the obtained baked product with water, 200 ml of a 5 wt % sodium silicate aqueous solution was added and thoroughly stirred to adjust the pH.
After adjusting the barium ferrite fine powder to around 9, 100 ml of a 5 wt% oleylamine acetate aqueous solution was further added to make the barium ferrite fine powder hydrophobic. 1000 toluene in this slurry
d was added to extract barium ferrite fine powder into the toluene layer. Next, it was 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 magnetic powder was found to be BaO・(Fed, 4
cO0,6Nio, 2Zno, 4Tio, aO+
q, 6), and was of the magnetoplumbite type.

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: 70 parts by weight cyclohexanone The obtained magnetic coating material 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.

Examples 2-3 In Example 1, sodium silicate was changed to sodium aluminate (NaAi'Oz) (Example 2), and oleylamine acetate was changed to stearylamine acetate (
Example 3) Barium ferrite magnetic powder was obtained in the same manner as in Example 1 except for the above.

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 4 Deionized water 130 (ld) containing ferric nitrate [Fe (NO
3) 3・9HzO] 1287.6g, cobalt nitrate [C0(NO3)z・61zoko 53.5g, nickel nitrate [N1(No:+)z・6H20ko 17.8g
, zinc nitrate [Zn(NOz)z・6HzO] 36.5g
Dissolve 23.2 g of titanium tetrachloride [T1Cf4] and barium hydroxide [Ba
(OH)z-8HzO] and 1480 g of caustic soda (NaOH) were dissolved and the solutions were mixed again to form a precipitate.

The resulting slurry containing the precipitate was placed in an autoclave;
Hydrothermal treatment was carried out at 145"C for 8 hours. Next, the obtained precipitate was thoroughly washed with water, and 200 mf of a 5 wt % sodium silicate aqueous solution was added and thoroughly stirred, and the pH was adjusted to around 9. Furthermore, 100 inches of a 5 wt % oleylamine acetate aqueous solution was added to make the barium ferrite precursor hydrophobic.To this slurry, 1000 d of toluene was added to extract the barium ferrite precursor into the toluene layer.

Next, after filtration and drying, a mixture of NaCl1 and Ba1J2.2+1□0 in a weight ratio of 1:1 as a flux was added thereto in an amount of 100% by weight based on the precipitate and mixed. This mixture was fired at 860"C for 2 hours. After thoroughly washing the resulting fired product with water, a 54% sodium silicate aqueous solution 2
00mj! After stirring thoroughly and adjusting the pH to around 9, add 5 wt% oleylamine acetate aqueous solution 1
The barium ferrite fine powder was made hydrophobic by adding 0.00%. 1000 d of toluene was added to this slurry to extract barium ferrite fine powder into the toluene layer. Next, it was filtered and dried to obtain barium ferrite magnetic powder.

As a result of X-ray powder diffraction spectrum and compositional analysis, the obtained barium ferrite magnetic powder was found to contain BaO.(Fe+ 0.
4COO, Jio12Zna, aTio, 401? ,
6), it was a magnetoplumbite type.

Further, regarding this barium ferrite magnetic powder, Example 1
Table 1 shows the results of measuring the magnetic properties, etc. in the same manner as above.

Comparative Example 1 In Example 1, the barium ferrite fine powder after firing was thoroughly washed with water, and then filtered and dried to obtain barium ferrite magnetic powder.

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.

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, a fluxing agent is mixed with the generated ferrite precursor fine particles, and the mixture is
A magnetopran represented by the above general formula, which is characterized by firing at 50°C, washing the obtained fired product, coating it with a surfactant, and extracting it into an organic solvent that is sparingly soluble in water. A method for producing bite-type ferrite magnetic powder.