JPH02204332A - Manufacturing method of hexagonal ferrite magnetic powder - Google Patents

Abstract

PURPOSE:To refine the average grain diameter and to improve the dispersibility and magnetic characteristic by partly or wholly removing the solute in the liq. mixture of a precipitate and the solute, then drying and calcining the liq. mixture. CONSTITUTION:An aq. <=10mol/l soln. contg. >=1 kind of metallic ion selected from Ba, Ca, Sr and Pb, and Fe ion and Si ion in the molar ratio of (0.5-6.0):(8-14):(0.05-5.0) and an aq. soln. contg. <=25mol/l of alkali metal ion or ammonium ion are mixed to control the pH to >=6, and a precipitate is formed. The solute is removed from the liq. mixture contg. the precipitate and solute so that 0.01-100wt.% precipitate remains along with the precipitate. The 0.01-10 pts.wt., based on the magnetic powder to be obtained, of a flux (e.g. NaCl) is then added, if necessary, to the liq. mixture contg. the remaining precipitate and solute. The mixture is dried, and then calcined for >=0.2hr to obtain Si-contg. hexagonal ferrite magnetic powder having <=0.1mum average grain diameter.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a hexagonal ferrite magnetic powder, and more specifically, to a hexagonal ferrite magnetic powder that has a fine average particle size, excellent dispersibility, and excellent magnetic properties. The present invention relates to a method for manufacturing hexagonal ferrite containing hexagonal ferrite with high productivity.

The hexagonal ferrite magnetic powder obtained by the production method of the present invention is suitable for applications such as magnetic powder for magnetic recording media, sintered magnets, rubber, and plastic magnets, and is particularly suitable as magnetic powder for magnetic recording media. It is.

[Prior Art J] In recent years, with the demand for higher density magnetic recording, a perpendicular magnetic recording method that records a magnetic field in the thickness direction of a magnetic recording medium has been attracting attention.

By the way, hexagonal ferrite such as barium ferrite has -axis magnetization anisotropy, and magnetic properties such as coercive force can be controlled by replacing some of the trivalent Fe ions with other metal ions. Therefore, it is known that the magnetic powder can be suitable for the perpendicular magnetic recording method.

Hexagonal ferrite suitable for perpendicular magnetic recording has a coercive force (Hc) of 200 to 2000 Oe, a suitable value, a high saturation magnetization (σS), and a small average grain size. (- Generally it is desirable that it is 0.3 μm or less, more preferably 0.1 μm or less)
Furthermore, it is desired that the magnetic powder be a uniform powder with no agglomeration or sintering of the 5 particles, and with good dispersibility.

Conventionally, a precipitation method (co-precipitation method) has been used as a method for producing hexagonal ferrite magnetic powder with a relatively small average particle size, for example, as disclosed in JP-A-56-60001 and JP-A-56-60002.
No. 1, JP-A-58-2223, JP-A-60-1
This method is disclosed in Japanese Patent Application Laid-open No. 15203, Japanese Patent Application Laid-open No. 11.5204/1980, and the like.

The production method of hexagonal ferrite magnetic powder such as barium ferrite using an alkali coprecipitation method or a precipitation method involves the uniform and quantitative production of various metal ions such as titanium and cobalt, which are added in small amounts for coercive force control and other purposes. It has many advantages, such as the ability to obtain uniform ferrite because it can be co-precipitated, and the fact that the precipitate (co-precipitate) is a microcrystalline powder, so it can be turned into ferrite at a relatively low temperature. .

However, in the conventional precipitation method, the average particle size of the obtained magnetic powder is relatively large, at least 0.12 μm (for example, JP-A-61-17411.8, JP-A-63-1
59224, etc.), sintering of particles tends to progress during the firing process, and as a result, the dispersibility of magnetic powder is poor. It has points.

In addition, in the conventional production method of hexagonal ferrite magnetic powder using the precipitation method, if alkali metal ions, etc. remain in the precipitate, it will cause deterioration of the powder properties and magnetic properties of the magnetic powder. In the precipitate washing step (dissolved substance removal step), which is one of the main steps, it was necessary to sufficiently remove the alkali content (for example,
0-157718, JP-A-61-174118, etc.), and therefore a large amount of washing water is required (for example, JP-A-60-115203, JP-A-60-115204, etc.). ), 10 for washing with water
00 hours or more may be required (for example,
(See Japanese Unexamined Patent Publication No. 58-2223).

As a result, the conventional method of manufacturing hexagonal ferrite magnetic powder using the precipitation method inevitably requires a batch-type manufacturing method, which has low productivity because continuous production cannot be performed. Since the characteristic values of the magnetic powder obtained tend to fluctuate, when producing large batches of magnetic powder of the same quality on an industrial scale, it is difficult to control variations between batches within an acceptable range. ing.

[Problem to be solved by the invention]

An object of the present invention is to provide a method for producing with high productivity hexagonal ferrite magnetic powder having a fine and uniform average particle size, excellent dispersibility, and excellent magnetic properties.

The present inventors have found that it is necessary to solve the above-mentioned problems in the conventional precipitation method (as a result of intensive research), when producing hexagonal ferrite magnetic powder containing SL, it is necessary to solve the above-mentioned problems in the conventional precipitation method. Instead of filtering the precipitate obtained in the process and washing it with a large amount of water, when removing the dissolved substance from the mixture containing the precipitate and dissolved substance, a considerable amount of the dissolved substance remains. We have discovered that magnetic powder with a small average particle size and excellent magnetic properties can be obtained with good reproducibility. Conventionally, in the precipitation method,
This is surprising since water-soluble substances such as alkali metal ions had to be thoroughly removed. And according to this method,
This method is suitable as an industrial manufacturing method for hexagonal ferrite magnetic powder because the conventional cleaning process, which requires a large amount of water and a long time, can be omitted or simplified, and continuous production is possible.

The present invention has been completed based on these findings.

[Means to solve the problem]

(According to the present invention, a hexagonal ferrite magnetic powder containing Si is mixed with an aqueous solution containing various metal ions constituting the hexagonal ferrite and an alkaline aqueous solution by a precipitation method to form a precipitate. During production through the precipitation step (A), the step (B) of removing dissolved substances that dissolve in water from the mixed liquid obtained in the precipitation step, the drying step (C) of the precipitate, and the calcination step (D), In the step (B) of removing the substance, from the mixed liquid containing the precipitate and the dissolved substance obtained in the precipitation step (A), 0.01% by weight or more but less than 100% by weight of the dissolved substance remains together with the precipitate. Provided is a method for producing Si-containing hexagonal ferrite magnetomagnetic material, which comprises removing dissolved substances, then drying a mixed solution containing precipitates and remaining dissolved substances, and firing the obtained solid substance. .

Further, according to the present invention, it is possible to obtain fine and uniform Si-containing hexagonal ferrite magnetic powder having an average particle size of 0.3 μm or less, preferably 0.1 μm or less.

As described above, according to the manufacturing method of the present invention, the manufacturing process of hexagonal ferrite magnetic powder is greatly simplified. Also,
Magnetic powder with a much finer average particle size than that obtained by conventional precipitation methods, a narrow particle size distribution, and good monodispersity can be produced with good reproducibility. The obtained magnetic powder also has excellent magnetic properties such as saturation magnetization.

When magnetic recording media such as floppy disks and video tapes are manufactured using the hexagonal ferrite magnetic powder obtained by the manufacturing method of the present invention, compared to those using magnetic powder obtained by the conventional method, , input/output characteristics, frequency characteristics, S
A product with significantly improved C/N ratio, C/N ratio, etc. can be obtained.

The present invention will be explained in detail below.

(Metal ion) In the present invention, 1 selected from Ba, Ca, Sr and pb
Species or more of metal ions, Fe ions and Si ions,
．． An aqueous solution having a molar ratio of 5 to 6.0:8 to 14:0.05 to 5.0 is used.

In addition, various metal ions such as Mg, Sc, Y, V, Ta, Mo,
W, Re, Ru, Os, Rh, Ir%Pd, Pt, Ag
, Hg, Ga%Ge, As%Te, Co%Ni, Mn,
Zn, Ti, In, Nd, Zr, Cr, La, Cu%C
d, A1. TI, Sn, P, Sb, Bi, Ss, Ce,
1 selected from Pr, Tb, Gd, Yb, Th, U, etc.
A small amount of more than one metal ion can be added, and in that case, the content ratio of these various metal ions is desirably 6 or less in terms of the above molar ratio.

To prepare aqueous solutions containing these metal ions, water-soluble metal salts of various metals, such as halides, nitrates,
Prizes include sulfates, acid anhydrides, salts of organic acids, and salts of free acids and condensed acids.

The concentration of the metal ion in the aqueous solution is usually preferably 10 mol/C or less.

(Aqueous alkaline solution) On the other hand, the alkaline component used in the aqueous alkaline solution for precipitating (co-precipitating) metal ions from the aqueous solution containing the metal ions may be any water-soluble one, such as alkali metal hydroxide or Prizes include carbonates (carbonates, bicarbonates), ammonia, ammonium carbonate, and organic alkalis.

Examples of the alkali used in the present invention include Na
OH, N a z COs N a HCO5KO
H, Kg Co,, K) (COI, NH40H1(N
H4) m COs, among others, combinations of hydroxide and carbonate, for example, NaOH and Na z C
Combination use with Os is preferred.

The concentration of the alkaline aqueous solution is usually such that the total amount of alkali metal ions and/or ammonium ions is 25 mol/C.
The following range is preferable.

In addition, when producing the above-mentioned aqueous solution of metal ions, the metal ions may be dissolved in an alkali aqueous solution if necessary. Therefore, the production method of the present invention can be used, for example, by dissolving some of the various metal ions in an alkali solution. This includes an embodiment in which they are used together as an alkaline aqueous solution. As a specific example, there is a mode in which Si ions are dissolved in an alkaline aqueous solution and used.

(Precipitation method) In the present invention, an aqueous solution containing the metal ions and an alkaline aqueous solution (which may contain some metal ions) are mixed to form a precipitate (co-precipitate). Generate. In this case, it is desirable to prepare an alkaline aqueous solution in advance so that the pH after the precipitation is preferably 6 or more, more preferably 9 or more, and the liquid temperature at the time of precipitation is 0 to 100. Can be arbitrarily selected within the range of °C. The mixing method is not particularly limited, and various methods can be employed, such as simply mixing both liquids and dropping an alkaline aqueous solution into an aqueous solution containing metal ions.

The resulting mixture contains the precipitate (co-precipitate), the water used as a solvent, and the dissolved substances that dissolve in water (i.e., substances that are dissolved in water, substances that are water-soluble but do not appear in the precipitate), and water that is used as a solvent. (substances mixed or adsorbed) are present.

9 5. Process B In the present invention, in the next step of removing dissolved substances that dissolve in water from the mixed liquid obtained in the precipitation step, the dissolved substances are reduced to o, oi% by weight or more. 0% by weight, preferably 0.03-90% by weight, more preferably 0.05-8% by weight
0% by weight remains with the precipitate and only the remaining dissolved material is removed.

The proportion of dissolved substances (wt%) is calculated by filtering the mixture containing the precipitate and dissolved substances obtained in the precipitation step, and adding the used washing water ( However, the total amount of washing water obtained by drying the washing water at 110℃ until the evaporation residue obtained is substantially eliminated is added, and the evaporation residue obtained by drying this mixed aqueous solution at 110℃. This is a value calculated based on the 100% by weight of the dissolved substance.

Regarding dissolved substances, when water-soluble components in the precipitation method were measured by various instrumental analyses, for example, in addition to carbonate ions, anions of metal compounds, alkali metal ions, and excess alkali components used in raw materials, Barium ions and strontium ions with relatively high solubility were observed even in the high pH region, and many complex ions containing Ba and Fe and complex ions with other metals were also observed.

As in conventional precipitation methods, the residual proportion of dissolved substances is 0.
When the magnetic powder is sufficiently removed to less than 0.1% by weight, the average particle size of the obtained magnetic powder exceeds 0.3μm, sintering is observed, and the saturation magnetization is 40emu/g.
As a result, the magnetic powder has insufficient characteristics as a magnetic powder for magnetic recording. In other words, when producing hexagonal ferrite magnetic powder containing SL by the precipitation method, the precipitate is thoroughly washed with water and dissolved substances are thoroughly removed to less than 0.01% by weight according to the conventional precipitation method. Then, the magnetic powder particles finally obtained tend to become coarser at the same time as sintering occurs.

On the other hand, even when Fii powder is produced with almost no dissolved substances removed (98% by weight remains), Si
The hexagonal ferrite magnetic powder containing the average particle size is 0.
In the present invention, almost the entire amount of dissolved substances (1
In this case, the average particle size of the magnetic powder is larger than 0.1 μm.

Therefore, in order to reduce the average particle size of the magnetic powder to about 0.1 μm or less, the proportion of dissolved substances coexisting with the precipitate (residual proportion) in the dissolved substance removal process should be 0.03 to 0.1 μm or less.
The content may be 90% by weight, more preferably 0.05 to 80% by weight.

This point will be explained with reference to FIG. 1st
The figure shows the relationship between the amount of dissolved substances (residual ratio) contained in the mixed liquid (slurry) containing the precipitate and remaining dissolved substances obtained after the dissolved substance removal step (B) and the average particle size of the obtained magnetic powder. It is a figure showing that there is a correlation between them. From FIG. 1, if the remaining proportion of dissolved substances is 0.01% by weight or more, magnetic powder with an average particle size of 0.3 μm or less can be obtained;
It can be seen that fine magnetic powder with an average particle size of 0.1 μm or less can be obtained in the range of 3 to 90% by weight, particularly 0.605 to 80% by weight. The above correlation indicates that the remaining proportion of the dissolved substance has extremely critical significance with respect to the average particle size of the magnetic powder.

Dissolved substances can be removed from a mixed solution containing precipitates by natural sedimentation, filtration, centrifugal dehydration (continuous type, batch type), etc. to separate them together with the solvent.

Examples include a method of separation using an adsorbent and a method of extraction and separation using a solvent.

In the second step, water may be added to the mixed liquid containing the precipitate at the beginning, if necessary, such as adjusting the viscosity or concentration of the mixed liquid. In addition, if the amount of dissolved substances removed is large,
Appropriate water washing may be performed within the range that provides the above-mentioned residual ratio. Furthermore, an acid such as hydrochloric acid, nitric acid, acetic acid, or oxalic acid may be added for the purpose of controlling the pH of the mixed solution containing the precipitate.

1 cup of the thus obtained mixed solution containing the dissolved substance within the above range (
The slurry precipitate) is dried in the presence or absence of a fluxing agent.

When processing is carried out in the presence of a flux, the types of flux are:
Usually NaC1, KCI, B a C1x, Nag
S04 Kg SO4, SrC1gBaSO45r
One or more compounds selected from Ci* LiC1 and LixSO+ are used. The amount of flux is 0.01 to 10 times the weight of the finally obtained magnetic powder, preferably 0.
．． It is added in an amount of 0.5 to 3 times the weight.

The general method for adding a flux is to add and mix the flux substance to a mixed solution containing a precipitate, but it is also possible to add an inorganic acid such as hydrochloric acid or sulfuric acid to a mixed solution containing a precipitate. There is also a method of reacting with the compound to produce a compound that becomes a fluxing agent.

In the drying step, water is removed from a mixed solution (slurry precipitate) containing a specific amount of dissolved substances.

As a method for removing moisture, for example, vacuum drying, heat drying, etc. are commonly used, and there are no particular limitations as long as the method does not remove dissolved substances.

1) The solid material containing the precipitate and dissolved substances thus dried is then calcined at 500-1200°C in a calcination step,
Here, the desired hexagonal ferrite magnetic powder is produced.

Examples of the firing apparatus include a tunnel furnace, a rotary furnace, and a fluidized fluidized firing furnace.

The firing time is usually 0.2 hours or more, but preferably 0.5 to 10 hours.

Further, the firing atmosphere may be a nitrogen atmosphere or an oxygen atmosphere, but it is usually preferable to perform the firing under an air atmosphere.

The fired product is washed as necessary. Any method can be used as the cleaning method as long as it can remove impurities remaining in the fired product. As a cleaning liquid, water, carbon number 1
-8 organic acids, nitric acid, hydrochloric acid, and sulfuric acid can be used.

The washed fired product is dried, but the drying method is as follows:
There are no particular limitations, and any method such as vacuum drying or heat drying can be employed.

(Thus, the desired hexagonal ferrite magnetic powder is obtained.

[Function] The present invention targets hexagonal ferrite magnetic powder containing Si, and when producing it by a precipitation method, the amount of o, oi, io or more by weight of the dissolved substance is io.

By allowing less than 0.03% by weight, preferably 0.03 to 90% by weight, more preferably 0.05 to 80% by weight, to remain with the precipitate, a magnetic powder with very excellent properties can be obtained. In hexagonal ferrite magnetic powder that does not contain Si, if 0.01% by weight or more of dissolved substances remain,
Only magnetic powder with inferior properties can be obtained.

The reason why the magnetic powder obtained by the production method of the present invention exhibits significantly superior properties is not yet clear, but by leaving the dissolved substances in a specific proportion, the SL ions and the remaining dissolved substances are absorbed in the drying process. It forms a complex compound that is appropriately mixed with the precipitate particles, and prevents the precipitate particles from sintering and coarsening due to particle growth during the sintering process, and
It is presumed that it embodies high-performance magnetic properties.

(The following is a blank space) [Examples] The present invention will be described below in more detail with reference to Examples, but the present invention is not limited to these Examples.

Methods for measuring physical properties, etc. The methods for measuring various physical properties, etc. in Examples are as follows.

Magnetism: Using VSM (vibrating magnetism measuring device), maximum applied magnetic field 10KOe, measurement temperature 28℃
It was measured with

i Standing plate 11: 40 from a photo taken with a transmission electron microscope
The maximum diameter of 0 particles was measured and calculated by arithmetic mean.

LUt: The maximum diameter and maximum thickness of 400 individual particles were measured and calculated by the arithmetic mean.

CN(7)l': Add 3 parts by weight of conductive carbon black, 10 parts by weight of cyclohexanone, 50 parts by weight of methyl ethyl ketone (MEK), and 30 parts by weight of toluene to 60 parts by weight of magnetic powder, mix well, and then add magnetic powder. Add 6 parts of tape binder (manufactured by Nippon Zeon@, trade name MR-110) and mix it further to make a magnetic paint. This is applied to a polyester film with a roll coater, smoothed with a calendar roll, and then magnetically coated. This magnetic recording medium was used as a 4 MHz carrier, and the tape speed was 4 m/min.
The measurement was carried out under the conditions of sec. Note that the OdB calm is a measured value of a commercially available metal tape.

・: The mixture containing the precipitate and dissolved substances obtained in the precipitation step is filtered, and the filtrate is added to the used washing water obtained by thoroughly washing the precipitate with water (however, the washing water is
The total amount of washing water obtained by washing until the evaporation residue obtained by drying at 110℃ is substantially eliminated, and the evaporation residue obtained by drying this mixed aqueous solution at 110℃ is added to the dissolved substance 10
It was set as 0% by weight, and calculations were made using this as a reference.

In addition, the empirical formula of the magnetic powder shown in the examples uses the atomic ratio of the metal at the time of raw material preparation, and the representation of oxygen in the hexagonal ferrite component is omitted for the sake of simplicity.

[Example 1] Barium chloride dihydrate 0.28 mol, titanium tetrachloride 0.28 mol.
191 mol of cobalt chloride hexahydrate, 0.191 mol of cobalt chloride hexahydrate, and 2.67 mol of ferric chloride hexahydrate were dissolved in 2.52 mol of pure water to form a solution A.

Sodium hydroxide 12.50 mol, sodium carbonate 3.
77 moles and 0.25 moles of sodium metasilicate nonahydrate were dissolved in 2.512 moles of pure water and this was used as liquid B.

While keeping both A and B at 40°C, mix both liquids,
A mixed solution containing a precipitate and a dissolved substance was obtained. The mixed liquid was separated from the filtrate using a centrifugal dehydrator to obtain a slurry (mixed liquid) containing a precipitate and 50% by weight of dissolved substances.

This slurry was dried at 110°C and then fired in an electric furnace at 900°C for 3 hours.

The obtained calcined product was washed with a 5% nitric acid aqueous solution until no soluble matter was removed, filtered, dried, and BaF810.5
275 g of Si-containing barium ferrite magnetic powder represented by C00,75T'0.75S' 1.0 was obtained.

The magnetic powder thus obtained has an average particle size of 0.050μ
m, the plate ratio was 4.06, the particles were separated one by one, and the particle size was uniform and in the shape of a clean hexagonal plate. When we measured the Mi magnetic properties, the coercive force was 555 (Oe), the saturation magnetization was 56.8 (e mu / g), and the C/
The N ratio was +4 dB.

The same operation was repeated five times, and magnetic powder having substantially the same characteristics was obtained with good reproducibility.

[Comparative example 1] (Do not let A) In Example 1, the precipitate obtained was filtered.

Furthermore, the precipitate was thoroughly washed with water and filtered. The residual ratio of dissolved substances was less than 0.0005% by weight, and substantially no dissolved substances remained in the precipitate after washing.

The obtained precipitate was dried at 110° C., then calcined and washed with water in exactly the same manner as in Example 1 to obtain magnetic powder.

The magnetic powder obtained in this way has an average particle size of 0.54 μm and a plate ratio of 6.04, and not only are most of the particles aggregated, but the particle size of each particle ranges from 1.38 μm to 0.01 μm or less. It was very heterogeneous, including many things. When the magnetic properties were measured, the coercive force was 340 (Oe) and the saturation magnetization was 36.8 (e mu / g). Also, C
/N ratio was -2 dB.

The same operation was repeated five times, but the characteristic values of the magnetic powders obtained were different each time, and all of them were as bad as above.

[Comparative Example 2J (Si Not Made A) In Example 1, sodium metasilicate nonahydrate 0.
Magnetic powder was obtained in exactly the same manner as in Example 1 except that 25 mol was not added.

The magnetic powder thus obtained has an average particle size of 0.73 μm and a platelet ratio of 8.25, and not only are most of the particles aggregated, but the particle size of each particle ranges from 2.45 μm to 0.01 μm or less. When we measured the 0Mi characteristics, which were extremely nonuniform and included even particles, we found that the coercive force was 238 (Oe), the saturation magnetization was 4Q.4 (emu/g), and the C/N ratio was -2d.
It was B.

[Example 2] In Example 1, 80% of the mixture containing the obtained precipitate was added.
Magnetic powder was obtained in the same manner as in Example 1, except that pure water of C was added, and then the filtrate was separated using a centrifugal dehydrator to form a slurry containing the precipitate and 3% by weight of dissolved substances. .

The magnetic powder thus obtained has an average particle size of 0.063 μm.
, the plate ratio is 4.24, the particles are separated one by one,
The particle size was uniform and had a clean hexagonal plate shape. When the magnetic properties were measured, the coercive force was 524 (Oe) and the saturation magnetization was 55.7 (emu/g).

[Example 3] In Example 1, p was added to the mixed solution containing the obtained precipitate.
Magnetic powder was obtained in the same manner as in Example 1, except that 0.25 ml of 12N hydrochloric acid was added to adjust H, and then a centrifugal dehydrator was used.

The magnetic powder thus obtained has an average particle size of 0.058 μm.
, the plate ratio was 4.11, each particle was separated one by one, and the particle size was uniform and in the shape of a clean hexagonal plate. When the magnetic properties were measured, the coercive force was 496 (Oe) and the saturation magnetization was 55.3 (emu/g).

[Examples 4 to 7] The same procedure as in Example 1 was carried out except that the substances listed in Table 1 were added as a flux to the slurry containing the obtained precipitate and 50% by weight of dissolved substances, and the materials were thoroughly mixed. Magnetic powder was obtained in exactly the same manner as in Example 1. The average particle size, platelet ratio, coercive force, and saturation magnetization of the magnetic powder thus obtained are shown in Table 1. Incidentally, each of the obtained magnetic powders had individual particles, and the particle size was uniform and in the shape of a clean hexagonal plate.

(Left below) [Example 8] In Example 1, the residual ratio of dissolved substances was reduced to 0 using a centrifugal dehydrator from the mixed solution containing the precipitate obtained in the precipitation step.
．． 01% by weight, 0.04% by weight.

Magnetic powder was produced in exactly the same manner as in Example 1, except that the powder was adjusted to 1.5% by weight, 20% by weight, 70% by weight, 90% by weight, and 98% by weight.

Note that the remaining proportion of dissolved substances is 0.01% by weight and 0.04% by weight.
% by weight and 1.5% by weight magnetic powder were prepared by adding water to the precipitate and centrifuging it.

The average particle diameter of the magnetic powder thus obtained is shown in FIG. Incidentally, each of the obtained magnetic powders had individual particles, and the particle size was uniform and in the shape of a clean hexagonal plate.

[Comparative Example 3] (A) In Example 1, water was added to the mixed solution containing the precipitate,
Using a centrifugal dehydrator, the remaining percentage of dissolved substances is reduced to 0.000.
Magnetic powder was produced in exactly the same manner except that 5% by weight was added. The average particle size of the magnetic powder thus obtained is also shown in Figure 1.It should be noted that the particles were not only aggregated, but also varied in size from 1 μm or more to 0.050 μm or less. Ta.

[Comparative Example 41 (゛, 6 ta A) 50% by weight of the dissolved substance obtained in Example 1 was added to the slurry-like precipitate obtained in Comparative Example 1 which was substantially free of dissolved substances.
B so that the composition of each element component of the slurry containing
a ion, Fe ion, CO ion, Ti ion, Si
ions, Na ions and Cl ions were added.

The slurry-like precipitate thus obtained was produced in exactly the same manner as in Example 1 to obtain magnetic powder.

The obtained magnetic powder had an average particle size of 0.63 μm, a plate ratio of 8,
3. Coercive force 598 (Oe) and saturation magnetization 22.6 (
emu/g).

From this result, it is inferred that the effects of the present invention are not simply due to individual elemental ions contained in the dissolved substance, but are due to complex compounds produced during the drying process.

[Example 9] Sr1.1 F810.5C00 was prepared in exactly the same manner as in Example 1 except that strontium chloride hexahydrate was used instead of barium chloride dihydrate used in Example 1.
, 75T' 0.75S11.0 was obtained.

The thus obtained magnetic powder had an average diameter of 0.061 μm, a plate-like ratio of 4.49, and the particles were separated one by one, and the particle size was in the shape of a neat hexagonal plate.

When we measured the magnetic properties, the coercive force was 637 (Os),
The saturation magnetization was 55.9.

(Left below) [Effects of the invention] In the conventional precipitation method, washing the precipitate requires a large amount of water and a long time, and therefore the production of hexagonal ferrite magnetic powder has to be done in a batch process, which requires a large amount of It was unsuitable for production, and it was difficult to stabilize the quality. However, the present invention greatly simplifies the washing process, making it possible to continuously produce hexagonal ferrite magnetic powder, which can be expected to significantly reduce production costs, and significantly stabilize the quality of magnetic powder. effective.

In addition, the hexagonal ferrite magnetic powder obtained by the present invention has good dispersibility and excellent magnetic properties, and further has fine and uniform particle size and good reproducibility.

When the magnetic powder obtained by the production method of the present invention is used as magnetic powder for magnetic recording media such as floppy disks, audio tapes, and video tapes, for example,
Compared to those using magnetic powder obtained by conventional methods,
Input/output characteristics, frequency characteristics, S/N ratio, C/N ratio, etc. are significantly improved.

Further, the Si-containing hexagonal ferrite magnetomagnetic material obtained by the production method of the present invention is also suitable for applications such as sintered magnets, rubber, and plastic magnets.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the remaining proportion of dissolved substances and the average particle size of the obtained Si-containing barium ferrite magnetic powder.

Claims (5)

[Claims] (1) A precipitation step (A) in which Si-containing hexagonal ferrite magnetic powder is mixed with an aqueous solution containing various metal ions constituting the hexagonal ferrite and an alkaline aqueous solution to form a precipitate. ), a step (B) of removing dissolved substances that dissolve in water from the mixed liquid obtained in the precipitation step;
In the step (B) of removing dissolved substances during production through the precipitate drying step (C) and firing step (D),
The dissolved substances are removed from the mixed solution containing the precipitate and dissolved substances obtained in the precipitation step (A) so that 0.01% by weight or more and less than 100% by weight of the dissolved substances remain together with the precipitates, and then the precipitates and Si, which is characterized by drying the mixed liquid containing the remaining dissolved substance and firing the obtained solid substance.
A method for manufacturing hexagonal ferrite magnetic powder. (2) The method according to claim 1, wherein the Si-containing hexagonal ferrite is barium ferrite and/or strontium ferrite containing Si. (3) The method according to claim 1 or 2, wherein the proportion of the dissolved substances remaining together with the precipitate is 0.05 to 80% by weight of the dissolved substances present in the precipitation step (A). (4) Si-containing hexagonal ferrite magnetic powder obtained by the method according to claim 1. (5) The Si-containing hexagonal ferrite magnetic powder according to claim 4, which has an average particle size of 0.1 μm or less.