JPS59222903A - Magnetic grain powders of needle crystal iron alloy for magnetic recording and method of manufacturing the same - Google Patents

Abstract

PURPOSE:To obtain grains having uniform grain size without mixing of tree- like grains or without grain crossing, by a method wherein aqueous solution of ferrous salt and aqueous solution of alkali are reacted and oxidation is performed by gas passing, and needle crystal including Si, Cr and Ni is produced. CONSTITUTION:Aqueous solution of ferrous salt and aqueous solution of alkali are reacted thereby suspension including Fe(OH)2 in pH 11 or more is obtained. Gas including oxygen passes through the suspension and oxidation is performed thereby needle crystal alpha-FeOOH grains are produced. Water-soluble silicate of 0.1-1.7atom% in Si equivalent to Fe, water-soluble chrome salt of 0.1-5.0 atom% in Cr equivalence to Fe and water-soluble nickel salt of 0.1-7.0atom% in Ni equivalence to Fe are added to the liquid previously. The grains are separated from the mother liquor and then suspended in water. Phosphate salt and water-soluble silicate are added in the suspension state of pH 8 or more, and then the pH value is adjusted thereby grains including Si, Cr and Ni are obtained in coated state by P compound and Si compound. Grains of alpha- Fe2O3 are made and then heated and reduced thereby magnetic grains of needle crystal iron alloy are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a magnetic material for magnetic recording of audio, video, etc., which has acicular crystals that are most suitable as a magnetic material for video, has uniform particle size, and has dendritic particles mixed therein. There is no entanglement of particles, and as a result, the bulk density is large, and the particles are fine and have a large specific surface area, and the degree of crystallinity on the particle surface and inside the particles is increased, resulting in a substantially high density. The present invention relates to an acicular iron alloy magnetic particle powder containing sl, Or, I.11, and P, which has a high coercive force Ha and a large saturation magnetization σS, and a method for producing the same.

When manufacturing magnetic recording media, S obtained by the present invention
i, Or, When using acicular iron alloy magnetic particle powder containing Ni and P, it has acicular crystals, the particle size is uniform, there are no dendritic particles mixed, and the particle size is small. There is no entanglement, etc., and as a result, the bulk density is large, and the specific surface area of the grains is large, and the degree of crystallinity on the particle surface and inside the particles is increased, and the density is substantially high. Moreover, due to the high coercive force Hc and large saturation magnetization σB, the dispersibility of the magnetic particles in the vehicle, the orientation and filling properties in the coating film are extremely excellent, and the recording properties of the magnetic tape are improved. An excellent magnetic recording medium with low noise level during reproduction and high output characteristics can be obtained.

In recent years, magnetic recording and reproducing equipment for video and audio has become increasingly compact and lightweight.
The spread of VTRs (video tape recorders) in Korea is remarkable.1. VTRs are being actively developed with the aim of recording for longer periods of time and being smaller and lighter.On the other hand, there is an increasing demand for higher performance and higher recording density for magnetic tape, which is a magnetic recording medium. .

That is, magnetic recording media are required to have high image quality, high output characteristics, especially improved frequency characteristics, and lowered raise levels. It is necessary to improve the filling property and the smoothness of the tape surface, and there is an increasing demand for an improvement in the S/N ratio.

These characteristics of magnetic recording media are closely related to the magnetic materials used in the magnetic recording media, and for example, Nikkei Electronics (1976) May 6th issue, pages 82-1.
In the document ``Recent Advances in Video and Audio Magnetic Tapes'' published on page 05, ``Among the image quality of video tape recorders, the main characteristics that change depending on the tape are as described on pages 83-84. ■SZN ratio, ■Chroma noise, and ■Video frequency characteristics.

--- These quantities representing image quality are determined by the electromagnetic conversion characteristics of the tape and head system, and the electromagnetic conversion characteristics have a correlation with the physical characteristics of the tape. Furthermore, the physical properties of the tape are largely determined by the magnetic material. It is clear from the statement, etc.

As mentioned above, the characteristics of magnetic recording media, such as high image quality, are closely related to the magnetic materials used, and there is a strong desire to improve the characteristics of magnetic materials.

The following is a detailed explanation of the relationship between the characteristics of the magnetic recording medium and the characteristics of the magnetic material used.

In order to obtain high image quality as a magnetic recording medium for video,
As is clear from the above-mentioned Nikkei Electronics description, improvements in ■video S/N ratio, ■chroma noise, and ■video frequency characteristics are required.

In order to improve the video S/N ratio, it is necessary to make the magnetic particles finer, improve their dispersibility in the vehicle, improve their orientation and filling properties in the coating film, and improve the surface of the magnetic recording medium. It is important to improve the smoothness of the surface.

This fact is based on the aforementioned Nikkei Electronics, p. 85, ``The physical quantities of the tape that are related to the SN ratio (ON ratio) of the luminance signal are the average number of particles per unit volume, their dispersion state (dispersibility), and the surface If the surface properties and dispersibility are constant, the S/N ratio will improve in proportion to the square root of the average number of particles, so magnetic powders with small particle volumes and high packing are advantageous. It is clear from the descriptions such as.

That is, as one method for improving the video S/N, it is important to reduce the noise level caused by the magnetic recording medium, and for this purpose, as is clear from the above description, it is necessary to reduce the noise level caused by the magnetic recording medium. It is known that a method of reducing the particle size of acicular magnetic particles is effective.

The value of the specific surface area of the magnetic particles is often used as a general method of expressing the particle size of the magnetic particles, but the noise level caused by the magnetic recording medium tends to decrease as the specific surface area of the magnetic particles increases. This is also generally known.

This phenomenon can be seen, for example, in IEICE technical research report MR81.
-11, page 27, 26-9, "rlg, ro" etc. "Fig. 3" is a diagram showing the relationship between the specific surface area of particles and the noise level in CO-coated ml-shaped maghemite particle powder, and the noise level decreases linearly as the specific surface area of the particles increases. .

This relationship holds true for the acicular iron magnetic particles and the all monomorphic alloy magnetic particles.

In order to improve the dispersibility of the magnetic particles in the vehicle, the orientation and filling properties in the coating film, it is necessary that the magnetic particles dispersed in the vehicle have acicular crystals and have a uniform particle size.
It is required that dendritic particles are not mixed, there is no entanglement of particles, etc., and as a result, the bulk density is high.

Next, in order to improve chroma noise, it is important to improve the surface properties of magnetic recording media.
Magnetic particle powder with good orientation is preferred, and such magnetic particle powder has acicular crystals, uniform particle size, no dendritic particles are mixed, there is no entanglement of particles, etc., and as a result, , high bulk density is required.

This fact is explained in the aforementioned Nikkei Electronics, p. 85 [Chroma noise is caused by relatively long-period roughness of the tape surface and is closely related to coating technology. Powders with good dispersibility and orientation are easier to improve surface properties. It is clear from the statements such as ".

Furthermore, in order to improve the video frequency characteristics, the magnetic recording medium must have a high coercive force Hc and a saturated residual magnetic flux density B.
It is necessary that r be large.

In order to increase the coercive force Hc of the magnetic recording medium, it is required that the coercive force Ha of the magnetic particles be as high as possible.

The saturated residual magnetic flux density Br is the saturation magnetization σB of the magnetic particle powder.
is as large as possible and depends on the dispersibility of the magnetic particles in the vehicle, orientation and filling properties in the coating film.

This fact is based on the above-mentioned Nikkei Electronics, pages 84-85, ``The maximum output depends on the saturation residual magnetic flux precision Br and Ha of the tape.''
, and the effective interval.

If Br is large, more magnetic flux enters the reproducing head and the output increases.・・・・・・・・・・・・As Hc increases, self-demagnetization decreases and output increases.・・・・・・
....

To increase the Br of the tape, the magnetic material must be in a perfect state (
For example, the amount of saturation magnetization 8 (σ
8) is large.

・・・・・・・・・・・・Even if the material is the same...
- Br also changes depending on the degree of filling, which indicates the proportion of magnetic powder. Furthermore, since it is proportional to the squareness ratio (amount of residual magnetization/amount of saturation magnetization), this is required to be large.・・・・・・
.... In order to increase the squareness ratio, it is advantageous to use magnetic powder that has uniform particle sizes, a large acicular ratio, and excellent magnetic field orientation. It is clear from the descriptions such as ``...'' etc. 0 As detailed above, improvements in high image quality, high output characteristics, especially frequency characteristics, and noise level of magnetic recording media In order to meet the demands for higher performance, such as lowering the It is free from entanglement, has a large specific surface area, has a high degree of crystallinity on the particle surface and inside the particle, and has a substantially high density, and has a high coercive force Hc and a large saturation magnetization of 0 days. is necessary.

By the way, the magnetic materials conventionally used in magnetic recording media are magnetic powders such as magnetite, magnetite, and chromium dioxide, and these magnetic powders have a saturation magnetization of σ87.
It has a coercive force Ha of 0 to 85 emu/g and a coercive force Ha of 250 to 5000 e.

In particular, the σS of the oxide magnetic particles is at most 85θmu
Generally speaking, σs is about 70 to QQemu/g, which is the main reason for limiting the reproduction output and recording density.

Furthermore, Co-magnetite and CO-maghemite magnetic particles containing CO are also used, but these magnetic particle powders have a high coercive force Hc of 400 to 8000θ, but on the other hand, saturation magnetization σB is 60~
It is as low as 8Q emu/g.

Recently, there has been active development of magnetic particles with characteristics suitable for high output and high density recording, that is, magnetic particles with large saturation magnetization σB and high coercive force. Powders are generally acicular crystalline hydrated iron oxide particles, acicular crystalline iron oxide particles, or those containing different metals other than iron, heated at 350°C in a reducing gas.
It is an acicular crystal iron magnetic particle powder or an acicular crystal alloy magnetic particle powder obtained by heating and reducing the powder to a certain extent.

These acicular iron magnetic particles or acicular alloy magnetic particles have a higher saturation magnetization σB than conventionally used magnetic iron oxide particles and Co-containing magnetic iron oxide particles.
It has the characteristics of extremely large Br and high coercive force Ha, and when coated as a magnetic recording medium, it has a large residual magnetic flux density Br and a high coercive force Ha, making it suitable for high-density recording.
It has attracted attention because of its high output characteristics, and has been put into practical use in recent years.

As described above, the acicular iron magnetic particles or the acicular alloy magnetic particles having a high coercive force 1 (c) and a large saturation magnetization σB have acicular crystals, uniform particle size, and dendritic particles. It is necessary that there be no mixture of particles or entanglement of particles, and in order to obtain magnetic particle powder with such characteristics, first the starting material, acicular α-Felon
It is necessary for the particles to be uniform in particle size and free from dendritic particles, and then how to maintain and inherit these excellent properties while reducing heat to produce acicular ferromagnetic particles or acicular ferromagnetic particles. The big question is how to make crystal alloy magnetic particles.

Conventionally, needle-like α-FeOO is produced in the alkaline region with a pH of 11 or higher.
The most typical known method for producing H particles is
Acicular α-FθOOH particles are obtained by oxidizing an aqueous solution containing Fe(oH)2 obtained by adding an equivalent or more amount of alkaline solution to a ferrous salt aqueous solution at a temperature of 80°C or less at pH 11jJ. This is what you get.

The acicular α-FeOOH particles obtained by this method have a needle-like shape with a length of about 0.5 to 1.5 μm, but they are coarse with dendritic particles mixed in, and in terms of particle size. , it is difficult to say that the powder has a uniform particle size. The reason why acicular α-FeOOH particles having asymmetric particle sizes and dendritic particles are generated will be discussed below.

Generally, the generation of acicular α-FeOOH particles consists of two steps: the generation of φ(-shaped α-FeOOH nuclei and the growth of the acicular α-FeOOH nuclei.
H nuclei are generated by the reaction between Fe(OH)2 obtained by reacting a ferrous salt aqueous solution with an alkali and dissolved oxygen, but the contact reaction with dissolved oxygen is partial and non-uniform. Therefore, the generation of acicular α-FeOOH nuclei and the acicular α-Fe
Growth of OOH nuclei occurs simultaneously, and α-FeOO
Since many new nuclei are generated until the H production reaction is completed, the obtained acicular α-FeOOH particles are considered to have asymmetric particle sizes and to have a strong mixture of dendritic particles.

In addition, the reactive iron (Fe”) in the reaction aqueous solution in the above method
) 9 degrees is usually about 0.2 mol/B, and force)
First, it takes a long time to generate acicular α-FeOOH particles. - That is, according to the above method, the particle size is asymmetric even at a dilute reaction iron concentration of about 3.2 mob/l,
Acicular α-I+'eOOH particles containing dendritic particles were likely to be produced.

In view of the foregoing, the present inventors have found a material that has acicular crystals, uniform particle size, no dendritic particles, no intertwining of particles, etc., and a large specific surface area and a particle surface. In addition, various studies have been carried out to obtain acicular alloy magnetic particles that have a substantially high density with an increased degree of crystallinity inside the particles, and also have a high coercive force Ha and a large saturation magnetization σB. It's here. Then, the present inventor discovered that Fe obtained by reacting a ferrous salt aqueous solution and an alkaline aqueous solution
When generating acicular α-FeOOH particles by passing an oxygen-containing gas through a suspension containing (OH)2 and having a pH of 11 or higher, the oxidation reaction is carried out by passing the alkaline aqueous solution and oxygen-containing gas through the suspension. A water-soluble silica salt is added to any of the above suspensions before the S reaction to Fe.
The suspension and the oxygen-containing gas have been added with 0.1 to 17 atoms in terms of 1, and the ferrous salt aqueous solution, the alkaline aqueous solution, and the oxygen-containing gas are passed through the suspension to perform an oxidation reaction. A water-soluble chromium salt is added to Fe in any of the reaction solutions in which the oxidation reaction is carried out by aeration.
01 to 50 atoms and water-soluble nickel salt in terms of Fe
By adding 0.1 to ZO atoms in terms of N1 to the acicular crystal α-Fe containing Sl, Or and N1,
OOH particles are generated, and the acicular α-FθOOH particles containing S1, Or, and N1 are separated from the mother liquor, and then suspended in water.
To the acicular α-FeOOH particles containing r and Ni, 0.1-2 wt% (in terms of po) of phosphate was added, followed by 0.1-ZQwt% (in terms of S102).
After adding the water-soluble silicate, the pH value of the suspension was adjusted to 6.
Acicular α-FeO containing Sl, Or and N1 coated with P compound and 81 compound by preparing ~7
OH particles are obtained, the particles are separated from P, dried, and then heat treated in a non-reducing atmosphere to obtain acicular α-Fe20 containing sl, Or and N1 coated with P and 81 compounds.
After forming s particles, the particles are heated and reduced in a reducing gas to have needle-like crystals, uniform particle size, no dendritic particles mixed, no entanglement of particles, etc. , an acicular crystal alloy magnetic particle powder having a large specific surface area, a substantially high density with an increased degree of crystallinity on the particle surface and inside the particle, and also having a high coercive force He and a large saturation magnetization σ8. The present invention was completed by discovering that the following can be obtained.

That is, the present invention provides an acicular iron alloy magnetic particle powder for magnetic recording comprising acicular iron alloy magnetic particles containing Sl, 0rXNi and P, which is obtained by reacting an aqueous ferrous salt solution with an aqueous alkaline solution. The aqueous alkali solution and oxygen-containing gas are oxidized by passing an oxygen-containing gas through a suspension of Fe(OH) having a critical pH of 11 or higher to produce acicular crystal α-Fe00) particles. A water-soluble silicate is added in an amount of 01 to 1.7 atomic % based on Fe in terms of S1 to any one of the suspensions before the oxidation reaction is carried out, and the first In any one of the iron salt aqueous solution, the alkaline aqueous solution, the suspension before an oxidation reaction is carried out by passing an oxygen-containing gas through it, and the reaction solution before an oxidation reaction is carried out by passing an oxygen-containing gas through it. 01 to 500r and N1 in terms of Or for Fe with water-soluble chromium salt
The acicular α-FeOOH particles containing S1, Or and N1 are separated from the mother liquor and then suspended in water, and the p of the suspension is
I (0.1 to 2 wt% relative to acicular α-FeOOH particles containing 81, Or, and N1 with a value of 8 or more)
01-7.
After adding a water-soluble silicate other than 0wt (in terms of 5to2), the pH value of the suspension was adjusted to 3 to 7 to remove Si, -Or and Nj coated with P compound and 81 compound. Acicular α-FeOOH particles containing P are obtained, the particles are separated from P, dried, and then heat treated in a non-reducing atmosphere to contain Sl, Or and Ni coated with P and 81 compounds. After forming acicular α-F0203 particles,
The particles are heated and reduced in a reducing gas to form Si, Or, N
This is a method for producing acicular iron alloy magnetic particles for magnetic recording by obtaining acicular iron alloy magnetic particles containing i and P.

Next, the technical background that led to the completion of the present invention and the configuration of the present invention will be described.

As described above, the acicular α-FeOOH particles produced by the conventional method in the alkaline region of pH 11 or higher have asymmetric particle sizes and contain dendritic particles.

The present inventor has been involved in the production and development of acicular α-FeOOH particles for many years, and in the process, the inventor has developed acicular α-FeOOH particles with uniform particle size and no dendritic particles. We have already established a technology that allows us to obtain crystalline α-FeOOH particles.

1i1J, acicular α-FeOOH particles with uniform particle size and no dendritic particles are Fe(oH)2 obtained by reacting a ferrous salt aqueous solution with an alkaline aqueous solution.
In the method of producing acicular α-FeOOH particles by passing an oxygen-containing gas through a suspension containing the aqueous alkali solution and oxidizing it, In any of the turbid liquids,
It can be obtained by adding water-soluble silicate to Fe in an amount of 01 to 17 atoms calculated as Si (Japanese Patent Publication No. 8461/1983, Japanese Patent Publication No. 32652/1983).

Conventionally, acicular crystals α obtained in an alkaline region with a pH of 11 or higher
-FeOOH particles generally have asymmetric particle sizes and a mixture of dendritic particles, but this is because the flocs of F61(OH)2, the precursor of acicular α-FeOOH particles, are asymmetric and , the particles of he(oH) constituting the floc of ye(oH)2 are themselves asymmetric;
Furthermore, acicular crystals α-F are obtained from an aqueous solution containing Fe(oH).
eOOE (This is due to the fact that the generation of core particles and the growth of the acicular α-FeOOH core particles occur simultaneously, and new nuclei are generated many times over until the α-FeOOH production reaction is completed.

As mentioned above, acicular crystals α-F are formed by passing an oxygen-containing gas through a suspension containing F e (OH)2 obtained by reacting a ferrous salt aqueous solution with an alkaline aqueous solution to oxidize it.
In producing eOOH particles, water-soluble silicate is added to any of the suspensions before the alkali aqueous solution and oxygen-containing gas are passed through to perform the oxidation reaction.
When added in an amount of o1 to 1.7 atomic % calculated as s1 to The ye(oH)2 particles themselves can be made into sufficiently fine and uniform particles, and furthermore, the water-soluble silicate can be made into acicular crystals α-7 from an aqueous solution containing Fe(oH)2.
Because it has the effect of suppressing the oxidation reaction when generating eOOH particles, it is possible to generate acicular α-FeOOH core particles and grow the acicular α-FeOOH core particles in stages. Therefore, it is possible to obtain acicular α-FeOOH particles with uniform particle size and without dendritic particles mixed therein.

The filtrate soluble silicates used in the above method include sodium and potassium silicates.

The amount of water-soluble silicate added to the alkaline aqueous solution is Fe
01 to 1.7 atoms in terms of Si.

Almost all of the added water-soluble silicate was formed into acicular crystals α-
Contained in the FeOOH particles, as shown in Table 2G below, the obtained acicular α-F1300H particles contain 0206 to 106 atoms in terms of S1 to Fe, which is approximately the same as the amount added. are doing.

The amount of water-soluble tiate salt added is 01 in terms of S1 relative to Fe.
If the particle size is subatomic or less, the effect of obtaining acicular grains with uniform grain size and no dendritic grains is not sufficient;
If it is more than 17 atoms, granular magnetite particles will be mixed in.

All monomorphic alloy magnetic particle powder obtained by using the above-mentioned acicular α-FθOOH particles with uniform particle size and no dendritic particles as a starting material and heating and reducing the starting material is also used. The particle size is uniform and dendritic powder is not mixed, but as a result, the bulk density is large and
Dispersibility when forming into a paint (it has the characteristics of good filling properties in the paint film and a large residual magnetic flux density Br, but the specific surface area is at most 20'
/g.

Therefore, the present inventor conducted various tests on methods for improving the specific surface area of acicular iron alloy magnetic particles containing Sl, which have a uniform particle size and do not contain dendritic particles, and found that the particle size In order to generate acicular α-FθOOH particles containing Sl, which are uniform and do not contain dendritic particles, a ferrous salt aqueous solution, an alkaline aqueous solution, and an oxygen-containing gas are passed through the oxidation reaction. A water-soluble chromium salt is added to either of the Fe(on)2 suspension and the reaction solution in which an oxidation reaction is carried out by passing oxygen-containing gas, and the resulting Si and Or containing Acicular crystal α-FθOO
It has been found that when H particles are thermally reduced, the specific surface area of Si-containing acicular iron alloy magnetic particles can be improved.

This phenomenon will be explained by extracting some of the many experimental examples conducted by the present inventors as follows.

FIG. 1 is a diagram showing the relationship between the amount of water-soluble chromium salt added and the specific surface area of acicular iron alloy magnetic particles containing Si and Or and acicular iron alloy magnetic particles containing Or.

That is, ferrous sulfate aqueous solution 6001 containing 1.2 mol/l of Fe was prepared in advance in a reactor with sodium silicate prepared in advance at a ratio of 0 to 10 atoms in terms of S1 to Fe, and chromium sulfate to Fe. In addition to NaOH aqueous solution 4001 obtained by adding 0 to 5.0 atomic ratio in terms of Or,
3.8, a suspension containing re(on)2 was obtained, and the suspension was aerated with air at a rate of 10,001 per minute at a humidity of 45°C to perform an oxidation reaction. Acicular crystalline iron alloy magnetic particle powder containing Sl and Or obtained by producing crystalline α-FeOOH particles and then heating and reducing the particles at 430° C. for 4.0 hours; and acicular crystalline iron alloy magnetic particle powder containing Or. This figure shows the relationship between the specific surface area of crystalline alloy magnetic particles and the amount of chromium sulfate added.

In the figure, curve a is for the case where no S1 is added, and curves S and C are for the case where the amount of Si added is 0.35 atomic % and 10 atomic %, respectively.

As shown in curve c, when 81 and Or are added in combination, the specific surface area of the obtained acicular iron alloy magnetic particles containing Sl and Or can be significantly improved, and in this case , the specific surface area tends to increase as the amount of chromium sulfate added increases.

Since this phenomenon appears more markedly than when Or alone is added, as indicated by mMa in FIG. 1, the inventors believe that this phenomenon is due to the synergistic effect between Or and Or.

As mentioned above, the acicular iron/alloy magnetic particle powder containing 81 and Or has uniform particle size, does not contain dendritic particles, and has a large specific surface area.
On the other hand, there was a tendency that the coercive force decreased as the amount of Or added increased.

Therefore, the present inventors have proposed a method for improving the coercive force of acicular iron alloy magnetic particles containing $1 and Or.
As a result of various studies, we found that ferrous salt aqueous solution,
Water is present in either the alkaline aqueous solution, the Fe(OH)2 suspension before an oxidation reaction is carried out by passing an oxygen-containing gas through it, or the reaction solution in which an oxidation reaction is carried out by passing an oxygen-containing gas through the solution. By adding soluble nickel salt, the obtained Sl, Cr
When acicular α-FeOOH particles containing N1 and N1 were thermally reduced, 81
It has been found that the coercive force of acicular iron alloy magnetic particles containing and Or can be improved.

This phenomenon will be explained as follows by extracting some of the many experimental examples conducted by the present inventor.

FIG. 2 is a diagram showing the relationship between the amount of water-soluble nickel powder added and the coercive force of acicular iron alloy magnetic particles containing 81, Or, and N1.

That is, ferrous sulfate aqueous solution 6001 containing Fe2 + 1.2 mo170 was prepared in advance in a reactor with sodium silicate prepared in advance at 0.65 atoms in terms of S1 for Fe, and chromium sulfate in terms of Or for Fe. In addition to NaOH aqueous solution 4001 obtained by adding nickel sulfate to 7e to contain 0 to 7.0 at% in terms of N1, a suspension containing Fe(on)2 at pH 14.0 was added. A suspension was obtained and the suspension was subjected to I C!/min at a temperature of 45°C. 00
Sl
, Or and Nj obtained by producing acicular α-FθOOH particles containing , Or and N1, and then heating and reducing the particles at 420°C for 4.0 hours.

This figure shows the relationship between the coercive force of acicular iron alloy magnetic particles containing nickel sulfate and the amount of nickel sulfate added.

As shown in FIG. 2, the coercive force of the acicular iron alloy magnetic particles containing Sl, Or, and N1 tends to increase as the amount of nickel sulfate added increases.

This phenomenon of increasing coercive force while maintaining a large specific surface area is due to the fact that Si, C! Since it cannot be obtained even if either r or Ni is removed, the inventors of the present invention
This is thought to be due to the synergistic effect of , Or, and N1.

Next, various conditions for implementing the present invention will be described.

The filtrate soluble chromium salts used in the present invention include:
Chromium sulfate and chromium chloride can be used.

Regarding the timing of addition of the water-soluble chromium salt, in the present invention, it is necessary to make chromium present during the formation reaction of button-shaped α-FeOOH particles. , in a suspension containing Fe(OH)2, or after the start of aeration of oxygen-containing gas, acicular crystals α-FθO
The OH particles may be added to any part of the reaction solution that is being produced.

Furthermore, even if water-soluble chromium salt is added at the stage when the formation of acicular α-FeOOH particles has been completely completed, chromium does not enter the particles, so the effect of chromium addition in the present invention cannot be obtained. do not have.

The amount of water-soluble chromium salt added in the present invention is 0.1 to 5.0 atomic % in terms of Fe and Or.

Almost all of the water-soluble chromium salt added was formed into needle-shaped α- crystals.
Contained in the FθOOH particles, as shown in Table 2 below, the obtained acicular α-FeOOH particles contain 0296 to 298 atomic heads in terms of Or for approximately the same amount of Fe as the added amount. ing.

The amount of water-soluble chromium salt added is 0.0 in terms of Or to Fe.
If it is less than 1 atomic ratio, the effect of increasing the specific surface area of the obtained monomorphic gold iron alloy magnetic particles cannot be obtained.

If the content is 5.0 atomic % or more, the effect of increasing the specific surface area of the obtained acicular iron alloy magnetic particles can be obtained, but the coercive force and saturation magnetization decrease, which is not preferable.

As the water-soluble nickel salt used in the present invention, nickel sulfate, nickel chloride, nickel nitrate, etc. can be used.

Regarding the timing of addition of the water-soluble nickel salt, in the present invention, it is necessary to make nickel present during the formation reaction of acicular α-FeOOH particles, and for this purpose, it is necessary to add nickel in the ferrous iron salt aqueous solution, in the alkaline aqueous solution. Medium, Fllll(OH),
or into a reaction solution in which acicular α-FeOOH particles are being formed after the start of aeration of oxygen-containing gas.

Furthermore, even if a water-soluble nickel salt is added at a stage when the formation of acicular α-FeOOH particles has been completely completed, the effect of nickel addition in the present invention cannot be obtained because nickel does not enter the particles. .

The amount of water-soluble nickel salt added in the present invention is 0.1 to 70 atoms per FQ in terms of N1.

Almost all of the added water-soluble nickel salt is formed into needle-shaped α crystals.
-FeOOH particles, and as shown in Table 2 below, the obtained acicular α-FeOOH particles have 2.05 to 7.00 atoms in terms of Nj for approximately the same amount of FQ added. Contains attack.

The amount of water-soluble nickel salt added is 0 in terms of N1 compared to FQ.
If it is less than 1 atomic ratio, the effect of increasing the coercive force of the obtained acicular iron alloy magnetic particles cannot be obtained.

Although it is possible to achieve the object of the present invention in the case where the particle size is larger than that of ZO atoms, it is not preferable because foreign substances other than needle crystals are mixed in when α-FθOOH particles are generated.

Next, regarding the thermal reduction process, the acicular α-FeOOH particles containing Sl, Or, and N1, which are uniform in particle size and do not contain dendritic particles, are thermally reduced to form an acicular iron alloy magnetic material. When obtaining powder particles, the higher the reduction temperature, the greater the saturation magnetization. The deformation of the crystal grains and the sintering between the grains and the grains become significant, and the coercive force of the obtained acicular iron alloy magnetic particles is extremely reduced.

In particular, the shape of particles is easily affected by the heating temperature, and especially when the atmosphere is reducing, particle growth is significant, and a single particle grows to exceed the size of a skeleton particle. gradually disappears, causing deformation of the particle shape and sintering of the particles and each other. As a result, the coercive force decreases.

The causes of the deformation of the acicular crystal particles and the sintering of the particles and their mutual particles during the thermal reduction process will be explained below.

In general, acicular α-F'203 particles obtained by heating and dehydrating acicular α-FθOOH particles at a humidity of around 300°C retain and inherit the acicular crystals, but on the other hand, the particles There are many pores generated by dehydration on the surface and inside the particles, and the growth of single particles is insufficient, so the degree of crystallinity is very small.

When thermal reduction is performed using such acicular α-Fe, O, particles, uniform particle growth of a single particle occurs because the physical change is rapid, and the growth of a single particle occurs. <,
Therefore, it is considered that in the portion where the grain growth of a single grain has rapidly occurred, sintering of grains and grains occurs, and the grain shape is likely to be distorted.

Furthermore, in the thermal reduction process, rapid volumetric contraction from the oxide to the metal occurs, making the particle shape more likely to collapse.

Therefore, in order to prevent particle shape deformation and sintering between particles during the thermal reduction process, it is necessary to prepare acicular α-F8203 particles containing Sl, Cr and N1 before the thermal reduction process. Needle-shaped α-FeOOH particles with substantially high density and containing Sl, Or, and N1 have an increased degree of crystallinity by achieving sufficient and uniform particle growth of single particles. Acicular crystal α-Fe20. It is necessary to keep it as a particle.

As a method for obtaining substantially high-density acicular α-Fe203 particles with an increased degree of crystallinity, gold monomorphic α-Fe203 particles are used.
A method is known in which -FeOOH particles are heat-treated in a non-reducing atmosphere.

Generally, acicular α-F Q20. is obtained by heating and dehydrating acicular α-FeOOH particles. The higher the temperature at which the particles are heat-treated in a non-reducing atmosphere, the more effectively single particles can grow, and therefore the degree of crystallinity can be increased. Processing temperature is 65
It is known that when the temperature exceeds 0°C, sintering progresses and the acicular crystal grains collapse.

Therefore, in order to obtain acicular α-Fe208 particles that have a substantially high density with an increased degree of crystallinity and retain and inherit the acicular crystals of the acicular α-FθOOH particles, A method is known in which the surface of acicular α-FeOOH particles is coated with an organic compound or inorganic compound having an anti-sintering effect prior to heat treatment in a non-reducing atmosphere.

The present inventor has been engaged in the production and development of acicular magnetic particles for many years, and in the course of his research, he discovered acicular crystal magnetic particles coated with a Si compound that has a sintering prevention effect. A method for producing crystalline α-FeOOH particles has already been developed.

For example, as described below.

That is, the acicular α-FθooH17 powder containing Sl, Or and N1 coated with P compound and 81 compound is
σ toroidal α-Fe containing Sl, Or and N1 produced by a wet reaction between a ferrous salt aqueous solution and an alkaline aqueous solution
After the OOH particles are separated from the mother liquor, they are suspended in water, and when the pH value of the suspension is 8 or more, 01 to 2 wt.
% (calculated as PO3) by adjusting the pH value to 3-7.

The differences in explanation regarding the above method are as follows.

Generally, acicular α-Fe containing 5iXOr and N1
OOH particles are quite tightly entangled and bonded together during the crystal growth process in the reaction mother liquor during wet reaction, forming a group of particles that are intertwined and bonded to each other.
If a particle group of acicular α-FeOOH particles containing l, Or, and Ni is directly coated with a sintering inhibitor, further sintering is prevented, and the process of crystal growth in the reaction mother liquor is prevented. Since the entanglements and bonds that occurred in
Acicular crystal alloy magnetic particles obtained by heat-treating acicular α-FeOOH particles containing r and N1 in a non-reducing atmosphere and then thermally reducing the particles are also entangled and bonded together. becomes.

Such particles have a high dispersibility in the vehicle.1. It cannot be said that the orientation and filling properties in the coating film are sufficient.

Therefore, acicular crystals α-'F containing Sl, Or and N1
Before coating the e0OH particles with the 81 compound, it is necessary to disentangle the entanglements and bonds generated during the crystal growth process in the reaction mother liquor.

Acicular α-7eOOH containing Si, , Or and N1
After the particles are separated from the mother liquor, they are suspended in water, and when the pH value of the suspension is 8 or higher, 0.1 to 2 wt% ( p
By adding phosphate (converted to o3), Sl,
It is possible to disentangle the entanglements and bonds of the acicular α-Fe00H particles containing Or and N1.

Acicular α-FeOOH particles containing Sl, Or and N1 are acicular α-FeOOH particles containing Sl, Or and N1.
After the OH particles are generated, the reaction mother liquor may be separated from the reaction mother liquor by a conventional method and washed with water.

The concentration of the suspension is preferably 20 wt% or less based on water. When the amount is 20 wt% or more, the viscosity of the suspension becomes too high, and the effect of disentangling entanglements caused by the addition of the phosphate becomes insufficient.

If the amount of phosphate added is 01 to 2 wt% in terms of Po3 to the acicular crystals and α-FθOOH particles containing sl, Qr, and N1 in the suspension, entanglement of the particles, etc. can be loosened and particles can be uniformly dispersed.

The added phosphate is adsorbed on the surface of the acicular α-FθOOH particles, and as shown in Table 6 below, the obtained acicular α-FeOOH particles have a Fe ratio of 0158 to 1 in terms of P.
．． It contains 737 extra atoms.

If the applied electric current is less than 0.1 wt%, the effect of addition is not sufficient.

On the other hand, when the amount added is 2 wt % or more, the particles can be dispersed, but since the particles are uniformly and strongly dispersed in the liquid, separation by p from the liquid is strictly prohibited, which is not appropriate.

Examples of the phosphate to be added include sodium metaphosphate and sodium birophosphate.

The pH value of the suspension to which the phosphate is added must be greater than or equal to 8.

If the pH value is 8 or less, 2 wt% or more of phosphate must be added to disperse the particles, and if 2 wt% or more of phosphate is added, as mentioned above, it will be difficult to separate by p. This is not preferable because alignment occurs.

Next, acicular α-FeO containing Sl, Or and N1
Regarding the Sl compound film formed on the particle surface of the OH particles, the formation of the Sl compound film is always performed using acicular crystals α-Fθ containing Sl, Or, and N1 by phosphate.
○This must be done after disentangling the OH particles.

The pH value of the suspension when adding the water-soluble silicate is preferably 8 or higher.

If a water-soluble silicate is added at a pH value of 8 or less, it will precipitate independently as solid 5iC12 at the same time it is added, and it cannot be efficiently formed as a thin film on the particle surface.

Therefore, 1. Add water-soluble silicate when the pH value of the suspension is 8 or higher, and after uniformly mixing it into the suspension, the pH value
If the value is adjusted to the range in which 5in2 precipitates, that is, the pH value is adjusted to 3 to 7, 5in2 precipitates on the surface of the particles to form a film.

The amount of water-soluble silicate added is 01 to 7.0 wt% based on the acicular α-FeOOH particles containing Sl, Or, and N1 in terms of 5in2.

If it is less than 0.1 wt%, the effect of addition is not noticeable, and if it is more than 7.0 wt%, it is possible to obtain acicular crystal alloy magnetic particles having excellent acicular crystals. However, due to the decrease in purity, the saturation magnetic flux density decreases, which is not preferable.

The added water-soluble silicate is precipitated and adsorbed on the surface of the acicular α-FθOOH particles, and as shown in Table 3 below, the obtained acicular α-Fe00H particles are acicular α-FeOOH particles.
06 in total with the amount of Si contained during the reaction generation of OH particles.
Contains 5 to 7.05 at%.

Note that examples of the water-soluble silicate to be added include sodium silicate and potassium silicate.

Next, acicular α-FeO containing Sl, Or and N1
The conditions for forming a film on the OH particles with the P compound and the 31 compound and then separating the particles by P from the suspension will be described.

When using ordinary p-separate means, if the particles are uniformly and strongly dispersed in the liquid, for example, P, t'P leakage, or p
Clogging of the fabric and various other transient efficiencies are also factors that cause stratification.

In order to increase the transient efficiency, it is necessary that the particles dispersed by the addition of the phosphate described above should be appropriately aggregated.

When the amount of phosphate added is within the range of 0.1 to 2 wt%, if the pH value of the suspension is set to 7 or less, the viscosity of the suspension increases, particle aggregation occurs, and the can be easily done.

Furthermore, even when the pH value of the suspension is 3 or less, Sl, O
Although it is possible to agglomerate acicular α-FeOOH particles containing r and N1, adsorb phosphate, and form the 5102 film described above, there are equipment problems and quality problems (dissolution, etc.). This is not desirable because it occurs.

In addition, in order to adjust the pH to 3 to 7, acetic acid, sulfuric acid, phosphoric acid, etc. can be used.

The P compound obtained as explained above and 81
Acicular α-7 containing Si, Or and N1 obtained by heat-treating compound-coated acicular α-FeOOH particles containing Si, Or and N1 in a non-reducing atmosphere
The %Os particles are substantially dense with an increased degree of crystallinity, and retain and inherit excellent acicular crystals without particle entanglement or bonding.

The temperature range of heat treatment in a non-reducing atmosphere is 500℃.
It is preferable that it is -900 degreeC.

When the heat treatment temperature in a non-reducing atmosphere is 500°C or less, Sl and O coated with P and 81 compounds
It is hard to say that the acicular α-Fe203 particles containing r and N1 are substantially high-density particles with an increased degree of crystallinity, and if the temperature is 900°C or higher, the acicular crystal particles may be deformed. This causes sintering of the particles and between particles. Furthermore, it requires highly accurate equipment and advanced technology, and is not industrially economical.

It is coated with the P compound and the 81 compound, which has a substantially high density with an increased degree of crystallinity as described above, and retains excellent acicular crystals without particle entanglement or bonding. Acicular α-Fe20 containing Sl, Or and N1
．． The acicular iron alloy magnetic particle powder containing Sl, Or, Ni, and P obtained by heating and reducing particles in a reducing gas also has a substantially increased degree of crystallinity on the particle surface and inside the particle. It has a high density and retains excellent acicular crystals with no entanglement or bonding of particles.

The obtained acicular iron alloy magnetic particle powder containing $1, Or, Ni, and P has 0.65 to 7.04 atoms of Sl in terms of S1 to Fe, as shown in Table 5 below.多、Or
is 0.296 to 2.99 atoms in Or conversion to Fe,
2.02 to 7.00 atomic% of N1 to Fe in terms of N1
It contains 0.157 to 1.737 at% of P in terms of P based on Fe, which is almost the entire amount added.

The temperature range of thermal reduction in reducing gas is 650°
C to 600°C is preferred.

When the temperature is 650°C or lower, the reduction reaction progresses slowly and requires a long time.

Furthermore, if the temperature is 600° C. or higher, the reduction reaction proceeds rapidly, causing deformation of the acicular crystal particles and sintering of the particles and the particles themselves.

The present invention configured as described above has the following effects.

That is, according to the present invention, it has acicular crystals, has uniform particle size, has no dendritic particles mixed therein, has no entanglement of particles, etc., and, as a result, has a large bulk density. and,
It is substantially dense with a large specific surface area and an increased degree of crystallinity on the particle surface and inside the particle, and
sl with high coercive force Ha and large saturation magnetization 0 days,
Since it is possible to obtain acicular iron alloy magnetic particles containing Or, Ni, and P, it can be used as magnetic particles for high image quality, high output, high sensitivity, and high recording density, which are currently most required. Can be done.

Furthermore, in the production of magnetic paint, the above 81, Or, N
When acicular iron alloy magnetic particles containing i and P are used, the noise level is low, and the dispersibility in the vehicle, the orientation and filling properties in the coating film are excellent, and it is preferable. A magnetic recording medium can be obtained.

Moreover, since the acicular iron alloy magnetic particles containing sl, Or, lJ4, and P obtained by the present invention are not ultrafine particles, they are relatively easy to handle when forming into a paint.

Next, the present invention will be explained with reference to Examples and Comparative Examples.

In addition, the specific surface area of the particles in the above experimental examples, the following examples, and comparative examples were measured by the IT method,
The axial ratio (long axis x short axis) and long axis of the particles are both shown as average values of values measured from electron micrographs.

In addition, the bulk density is determined by JIS K 51o1-1978 "
Measured according to the Pigment Test Method.

The amount of Si, amount of Or, NiM and pil in the particles can be determined using the "Fluorescence xiIiIi! Analyzer 3063 M type J (Rigaku t
(manufactured by 1M Kogyo), : rkos K 0119-19
It was measured by performing fluorescence X-ray analysis in accordance with ``General Rules for Fluorescence X-ray Analysis''.

The magnetic tape characteristics were measured under an external magnetic field of 10 KOe.

Production of acicular α-FeOOH particle powder> Examples 1 to 1
4. Comparative Example 1; Example 1 Ferrous sulfate aqueous solution 3 containing 1.2 m017 g of Fe”
Sodium silicate (No. 3) (5ic228.55 wt%) 1529 was added to contain 00β in advance in an amount of 0.20 at% in terms of S1 based on the Fe prepared in the reactor.
, 644 g of chromium sulfate to contain 0.50 atomic % in terms of Or for Fe, and 6.0 at% in terms of N1 for In
5,45-N NaOH aqueous solution 4001 obtained by adding 2884 g of nickel sulfate to contain p
H14,0, 81 at temperature 45°C, Or and N1
Fe(oH) containing.

A suspension production reaction was performed.

The above ye(on)2 suspension containing S1, Or and N1 was blown with 10,004 air per minute at a temperature of 50°C for 6,3
Needle crystal α- containing Sl, Or and N1 by aeration for a time
FeOOH particles were produced.

The end point of the oxidation reaction was determined by extracting a portion of the reaction solution and acidifying it with hydrochloric acid, and then using a red blood salt solution to determine the presence or absence of a blue coloring reaction of Fe2+.

The generated particles were separated from P and washed with water in a conventional manner.

A part of the acicular α-FeOOH particles containing Si, Or, and N1, which had been washed with water according to p, was dried and pulverized to obtain a sample for evaluating the characteristics.

The obtained acicular α-Fe containing Sl, Or and N1
As a result of X-ray diffraction, the OOH particles had the same diffraction pattern as the crystal structure of the α-FeOOH particles.

In addition, as a result of fluorescent Xi analysis, Sl was 0204 compared to Fe.
atomic%, Or is 0.496 extra atoms for Fe, N1 is F
It contained 502 atomic proportions per e.

Therefore, it is considered that Sl, Or, and N1 are solidly dissolved in the acicular α-FeOOH particles.

This acicular α-FeOO containing Sl, Or and N1
As is clear from the electron micrograph (X20000) shown in Figure 6, the H particles have an average value of long axis of 050 μπ and an axial ratio (long axis
short axis) was 28:1.

Examples 2 to 14 Type and concentration of ferrous salt aqueous solution, concentration of NaOH aqueous solution,
Acicular crystals α containing Sl, Or, and N1 were prepared in the same manner as in Example 1, except that the types, amounts, and times of addition of the water-soluble silicate, water-soluble chromium salt, and water-soluble nickel salt were varied. -FeOOH particles were generated.

The main manufacturing conditions at this time are shown in Table 1, and the characteristics are shown in Table 2.

In addition, the production reaction of Fe(oH)2 suspension in Example 5 was carried out at 40°C, and the production reaction of acicular α-FeOOH was carried out at 40°C.
The temperature was 5°C.

Comparative Example 1 Acicular crystal α-F was produced in the same manner as in Example 1, except that sodium silicate, chromium sulfate, and nickel sulfate were not added.
An eOOH particle powder was produced.

The main manufacturing conditions at this time are shown in Table 1, and the characteristics are shown in Table 2.

As is clear from the electron micrograph (X20000) shown in FIG. 4, the obtained acicular α-FeOOH particle powder has an average value of 045 μm on the long axis and a uniaxial ratio (long axis: short axis) of 9:1. , the particle size was asymmetric, and dendritic particles were mixed.

Acicular α-FeO coated with P compound and 81 compound
Production of OH particle powder> Examples 15 to 28 Comparative Example 2: Example 15 Separate p obtained in Example 1, water washed Si, Or and N1
A paste of acicular α-FeOOH particles containing 3oo
o g(acicular crystals containing st, Or and N1 (1-F
This corresponds to approximately 10,009 eOOH particles. ) was suspended in 606 water.

The pH value of the suspension at this time was 97.

Next, 300 d of an aqueous solution containing 8 g of sodium hexametaphosphate was added to the above suspension (0.5 as PO for acicular α-FeOOH particles containing Si, Cr, and N1).
This corresponds to 6 wt%. ) and stirred for 30 minutes.

Next, sodium silicate (No. 3 water glass) was added to the above suspension.
148g (acicular crystal α-F containing Si, Or and N1
This corresponds to 4.2 wt% of SiQ with respect to eOOH particles. ) and stirred for 60 minutes, the pH of the suspension
After adding 100 grams of acetic acid to give a value of 5.8, the acicular α-FeOOH particles containing Si, Or, and N1 were separated using a press tweeter and dried to form P compounds and S.
Acicular α-FeOOH particle powder containing 8, Or and N1 coated with a compound was obtained.

The obtained acicular α-Fe containing Sl, Or and N1
Table 3 shows the properties of the OOH particles.

Examples 16 to 2B, Comparative Example 2 Type of particles to be treated, p)i of suspension when phosphate is added,
Sl, Or, and N1 coated with P compound and 81 compound were prepared in the same manner as in Example 15, except that the amount of IJ phosphate, the amount of water-soluble silicate, and the adjusted pH were varied. Acicular α-FθOOH particles or acicular α-FθOOH particles containing acicular α-FθOOH were obtained.

Table 6 shows the main manufacturing conditions and characteristics at this time.

<Sl, Or and N coated with P and Sl compounds
Production of acicular α-Fe208 particle powder containing 1>
Examples 29 to 42 Comparative Example 5 Example 29 Acicular α-FeOOH containing Sl, Or and N1 coated with the P compound obtained in Example 15 and the 81 compound
Particle powder 10009 was heat treated at 750°C in air to form Sl, Or and N coated with P compound and Sl compound.
Acicular crystal α-Fe203 particle powder containing 1 was obtained.

As a result of electron microscopy observation, the average value of these particles was 04 on the long axis.
The crystal had an 8 μm uniaxial ratio (long axis: short axis) of 26:1, and had excellent acicular crystals.

Examples 30 to 42, Comparative Example 3 Si, Or and N1 coated with P compound and Sl compound
sl, Or, and N1 coated with the P compound and the 81 compound in the same manner as in Example 29, except that the type of the acicular α-FeOOH particle powder, the heat treatment temperature, and the non-reducing atmosphere were varied. Acicular crystal α-Fe containing 20.
A particulate powder was obtained.

Table 4 shows the main manufacturing conditions and characteristics at this time.

The acicular α-F111203 particles coated with the P compound and the 81 compound obtained in Comparative Example 6 had an average long axis of 044 μm and an axial ratio (long axis:short axis) of 9:1.

<Production of U-shaped crystalline iron or iron alloy magnetic particles> Example 46
~56 Comparative Example 4; Example 43 Acicular crystal α-F'1120 containing Sl, Or, and Ni coated with the P compound obtained in Example 29 and the 81 compound
120 g of the 3-particle powder was put into a 34 retort reduction container, and while the container was being driven and rotated, H2 gas was passed through the container at a rate of 401/min, and reduction was carried out at a reduction temperature of 440'C.

The acicular iron alloy magnetic particle powder containing Sl, Or, Ni, and P obtained by reduction was once immersed in a toluene solution to prevent rapid oxidation when taken out into the air. By evaporating this, a stable oxide film was formed on the particle surface.

The button-like iron alloy magnetic particles containing Sl, Or, Ml, and P thus obtained had a single-phase diffraction pattern with a body-centered cubic structure similar to that of iron as a result of X-Iwa diffraction.

In addition, as a result of fluorescent X-ray analysis, Sl was 4.70 compared to Fe.
Atomic section, Or is 0495 atomic rice for Fe, Ni is for Fe.
It contained 301 atoms of P compared to Fe, and 0,661 atoms of P to Fe.

Therefore, it is considered that iron, Si, Or, IJi, and P are in solid solution.

This acicular iron alloy magnetic particle powder containing Sl, Or, Ni, and P has an average long axis of 030 μm, an axial ratio (long axis: short axis) of 12:1, a specific surface area of 47.1 m/l, and a bulk. The density was 0.479/d, the coercive force was 14200e, and the saturation magnetization was 165.2 emu/g.

Moreover, this particle powder is shown in the electron micrograph (X
20000), the particle size was uniform and dendritic particles were not mixed.

Examples 44 to 56, Comparative Example 4 Acicular iron alloy magnetic particles or iron containing Sl, Or, Ni, and P were prepared in the same manner as in Example 46, except that the type of starting materials and the reduction temperature were varied. Magnetic particle powder was obtained.

Table 5 shows the properties of the obtained powder particles.

As a result of electron microscopic observation, the acicular iron alloy magnetic particles containing Sl, Or, Ni, and P obtained in Examples 44 to 56 were found to have uniform particle size and no dendritic particles. Ta.

The ferromagnetic particles obtained in Comparative Example 4 had an average long axis of 0.
4 μm, axial ratio (long axis: short axis) 5:1, specific surface area 19.3
n//9, bulk density 0.19'/ml, coercive force 1
0130θ, and the saturation magnetization was 166.4 emu/g.

Moreover, this particle powder is shown in the electron micrograph (X2
0000), the particle size was asymmetric and the axial ratio was poor.

Manufacturing of magnetic tape> Examples 57 to 70, Comparative Example 5; Example 57 Using the acicular iron alloy magnetic particle powder containing Sl, OrXNi, and P obtained in Example 43, an appropriate amount of dispersant was added. ,
A PVC copolymer, a thermoplastic polyurethane resin, and a mixed solvent consisting of toluene, methyl ethyl ketone, and methyl isobutyl ketone were blended to a certain composition, and then mixed and dispersed in a ball mill for 8 hours to obtain a magnetic paint.

The above-mentioned mixed solvent was added to the obtained magnetic paint to adjust the paint viscosity to an appropriate paint viscosity, and the mixture was coated on a polyester resin film and dried in a conventional manner to produce a magnetic tape.

The coercive force Ha of this magnetic tape is 16450e, the residual magnetic flux density Br is 3910 Gauss, and the square shape B r
/Bm was 0790, and the degree of orientation was 2.02.

Examples 58 to 70, Comparative Example 5: Magnetic tapes were produced in exactly the same manner as in Example 57, except that the type of acicular magnetic particles was varied.

Table 6 shows the characteristics of this magnetic tape.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the amount of water-soluble chromium salt added and the specific surface area of acicular iron alloy magnetic particles containing 81 and Cr and acicular iron alloy magnetic particles containing Or. Figure 2 shows the amount of water-soluble nickel salt added and Si. FIG. 3 is a relationship diagram of coercive force of chain crystal iron alloy magnetic particle powder containing Or and N1. Figures 6 to 4 are all electron micrographs (X2000
0), and FIG. 3 shows the acicular iron alloy magnetic particles containing Sl obtained in Example 1, and FIG. 6 shows the iron magnetic particles obtained in Comparative Example 2. Patent applicant: Toda Kogyo Co., Ltd. Figure 3 (X 20600) Note 4 (X 26000)

Claims (1)

[Claims] 1) An acicular iron alloy magnetic particle powder for magnetic recording comprising acicular iron alloy magnetic particles containing Sl, Or, Ni, and P. 2) Oxygen-containing gas is passed through a suspension containing he(oH) obtained by reacting a ferrous salt aqueous solution and an alkaline aqueous solution and has a pH of 11 or more to oxidize it to produce needle-shaped α-F.
In producing eOOH particles, a water-soluble silicate is added to any of the suspensions before the alkali aqueous solution and oxygen-containing gas are passed through to perform the oxidation reaction.
Add 01 to 1.7 atoms in S1 terms to e,
and the ferrous salt aqueous solution, the alkaline aqueous solution, the suspension before an oxidation reaction is carried out by passing an oxygen-containing gas through the solution, and the reaction solution in which an oxidation reaction is carried out by passing an oxygen-containing gas through the suspension. Add water-soluble chromium salt to Ir in either solution.
0.1 to 5.0 atomic % in terms of Or to e and 01 to 7.0 IJ7 in terms of N1 to Fe and water-soluble nickel salt
．． By adding Si, Si. Acicular α-FeOOH particles containing Cr and N1 are produced, and acicular α-F containing Si, Or and N1 are produced.
After the eOOH particles are separated from the mother liquor, they are suspended in water, and when the pH value of the suspension is 8 or more, 0.1-2
wt% (calculated as PO2) of phosphate was added, then 0
After adding 1~ZOwt% (calculated in 5IQI) of water-soluble silicate, Si, Or and N1 coated with P and Sl compounds were prepared by adjusting the pH value of the suspension to 3~7. Acicular α-FeOOH particles containing acicular crystals were obtained, the particles were separated from P, dried, and then heat-treated in a non-reducing atmosphere to obtain Sj,,Or
After forming acicular α-Fe203 particles containing N1 and N1, the particles are heated and reduced in a reducing gas to form Sl, Or, N
A method for producing acicular iron alloy magnetic particles for magnetic recording, the method comprising obtaining acicular iron alloy magnetic particles containing i and P. 6) The temperature range of heat treatment in a non-reducing atmosphere is 5.
The method for producing acicular iron alloy magnetic particles for magnetic recording according to claim 2, wherein the temperature is 00°C to 900°C. 4) Temperature range of thermal reduction in reducing gas is 350
The method for producing acicular iron alloy magnetic particles for magnetic recording according to claim 2, wherein the temperature is from .degree. C. to 600.degree.