JPS5941453A - Needle crystal iron alloy magnetic particulate powder for magnetic recording and preparation thereof - Google Patents

Abstract

PURPOSE:To provide the titled needle crystal iron alloy magnetic particulate powder uniform in a particle size, having no dendritic particle mixed therein, large in a specific surface area and having high coercive force and large saturation magnetization, comprising a needle crystal iron alloy magnetic particle containing Si, Cr and Ni. CONSTITUTION:O2-containing gas is passed through a suspension with a pH of 11 or more containing Fe(OH)2 obtained by reacting a ferrous salt (e.g. ferrous sulfate) and an alkali aqueous solution containing NaOH or the like to form a needle crystal alpha-FeOOH particle by oxidation. IN this case, either one of the alkali aqueous solution and the aforementioned suspension pripor to performing the aforementioned oxidation reaction, water soluble silicate (e.g., sodium silicate) is added in an amount of 0.1-1.7atom% as Si to Fe. In addition, water soluble Cr salt (e.g., chromium sulfate) is further added to the liquid prior to or during the aforementioned oxidation reaction in an amount of 0.1-5.0atom% as Cr to Fe and water soluble Ni salt (e.g., nickel sulfate) in an amount of 0.1-7.0 atom% as Ni. By this method, an objective needle crystal alpha-FeOOH particle containing Si, Cr and Ni is 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. I haven't done it,
As a result, it has a large bulk density, fine particles, and a large specific surface area, as well as a high coercive force Hc and a large saturation magnetization σ.
The present invention relates to an acicular iron alloy magnetic particle powder containing S, Qr, and N1, and a method for producing the same.

When manufacturing magnetic recording media, S obtained by the present invention
When using acicular iron alloy magnetic particle powder containing l, Or and Ni, it has acicular crystals and has uniform particle size,
Because there are no dendritic particles mixed in, as a result, the bulk density is large, and the particles are fine and have a large specific surface area, they also have a high coercive force Ha and a large saturation magnetization σS. To obtain an excellent magnetic recording medium that has extremely excellent dispersibility in a vehicle, orientation and filling properties in a coating film, has a low noise level generated during recording and reproduction of magnetic tape, and can obtain high output characteristics. be able to.

In recent years, magnetic recording and playback equipment for video and audio has become increasingly compact and lightweight. V aimed at reducing weight
TR is being actively developed, and on the other hand, demands for higher performance and higher density recording of magnetic tape, which is a magnetic recording medium, are increasing.

That is, magnetic recording media are required to have high image quality, high output characteristics, especially improved frequency characteristics, and lower noise 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 magnetic recording media, and for example, Nikkei Electronics (1976) May 6th issue, p. 82~
In the document ``Recent Advances in Video and Audio Magnetic Tapes'' published on page 105, ``Among the image quality of video tape recorders that change depending on the tape, the main characteristics described on pages 86 to 84 are: ■1 from S/N
■Chroma noise, ■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 special 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 relationship between the magnetic properties of the magnetic recording medium and the properties of the magnetic material used will now be detailed as follows.

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 sy 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 video S/N, it is important to reduce the noise level caused by magnetic recording media, and for this purpose, as is clear from the above description, it is necessary to reduce the noise level caused by the magnetic material used. 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 to express 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 the Institute of Electronics and Communication Engineers Technical Research Institute report MR8.
1-11, page 27, 26-9, 'Fig 3J etc. rFigs 3J is a diagram showing the relationship between the specific surface area of the particles and the noise level in CO-coated acicular maghemite particle powder. The noise level decreases linearly as the specific surface area increases.

This relationship holds true for the acicular iron magnetic particles and the acicular 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 therein, 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, and does not contain dendritic particles, and as a result, has a large bulk density. required.

This fact is based on the above-mentioned Nikkei Electronics, page 85: ``Chroma noise is caused by the relatively long-period roughness of the tape surface, and is closely related to coating technology. It is clear from the statement, "It is easier to improve the surface properties."

Furthermore, in order to improve the video frequency characteristics, it is necessary that the magnetic recording medium has a high coercive force 1 (c) and a high saturation residual magnetic flux density Br.

In order to increase the coercive force Hc of the magnetic recording medium, it is required that the coercive force Hc 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, which states, ``The maximum output depends on the saturation residual magnetic flux density Br and Hc 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.・・・－・・・
....

In order to increase the Br of the tape, the magnetic material has a perfect shape M (
For example, the saturation magnetization S (σ
First of all, it is basic that S) 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. Further, since it is proportional to the squareness (amount of residual magnetization/amount of saturation magnetization), it is required that this is large.・・・・・・
.... In order to increase the squareness ratio, it is advantageous to use magnetic powder that has uniform particle sizes, a high acicularity ratio, and excellent magnetic field orientation. It is clear from the descriptions such as "...".

As detailed above, in order to meet the demands for high performance such as high image quality and high output characteristics of magnetic recording media, especially improved frequency characteristics, and lower noise levels, the magnetic The characteristics of the powder particles include acicular crystals, uniform particle size, no dendritic particles, large specific surface area, high coercive force Hc, and large saturation magnetization σ.
It is necessary to have S.

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 σs
70' -85emu/g, coercive force Hc250-500
0e.

In particular, the σB of the above oxide magnetic particles is at most 85θmu
/g, generally σ870~80 emu/9
This is the main reason for limiting the reproduction output and recording density.

Furthermore, CO-magnetite and C containing Co.

-Maghemite magnetic powder is also used, but these magnetic particles have a high coercive force Hc of 400 to 8000e, but on the other hand, the saturation magnetization σB is 6
It is as low as 0 to 80 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 σS 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 significantly higher saturation magnetization (6 days) than conventionally used magnetic iron oxide particles and Co-containing magnetic iron oxide particles, and have a coercive force. It is characterized by high Ha, and when coated as a magnetic recording medium, it has a large residual magnetic flux density Br and a high coercive force Hc, 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 crystal iron magnetic particles or acicular crystal alloy magnetic particles having a high coercive force Hc and a large saturation magnetization of 6 days have acicular crystals, uniform particle size, and dendritic particles. In order to obtain a magnetic particle powder with such characteristics, it is necessary that the starting material acicular α-FeOOH particles have uniform particle size and that dendritic particles are not mixed. It is necessary that you do not.

Conventionally, acicular crystal α-FeO was produced in the alkaline region with pH 11 or higher.
The most typical known method for producing OH particles is to add an equivalent or more alkaline solution to an aqueous ferrous salt solution to prepare an aqueous solution containing Fe(oH)2 at a pH of 11 or higher and a temperature of 80'C or lower. Acicular α-FeOOH particles are obtained by carrying out an oxidation reaction.

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 also contain dendritic particles, and it is difficult to tell from the particle size. It is difficult to say that these particles have 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 formation of acicular α-FeOOH particles is caused by the formation of acicular α-FeOOH particles.
It consists of two steps: generation of -FeOOH nuclei and growth of the acicular α-FeOOH nuclei. The acicular α-FθOOH nucleus is obtained by reacting a ferrous salt aqueous solution with an alkali.
It is produced by the reaction between e(oH)2 and dissolved oxygen, but because the contact reaction with dissolved oxygen is partial and non-uniform,
Generation of acicular α-FeOOH nuclei and the acicular α-11re
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 contain dendritic particles.

In addition, the reaction iron (1i
e2+ ) concentration is usually about 0.2 mol/l, and it takes a long time to generate acicular α-FeOOH particles.

That is, according to the above method, even at a dilute reaction iron concentration of about 0.2 mol/l, the particle size is asymmetric,
Acicular α-FeOOH particle powder containing dendritic particles was more likely to be produced.

In view of the above, the present inventor has found that the material has acicular crystals, has uniform particle size, does not contain dendritic particles, and
Various studies have been conducted to obtain acicular alloy magnetic particles having a large specific surface area, high coercive force Ha, and large saturation magnetization σS. 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 the oxygen-containing gas through the suspension. Water-soluble silicate is added to Fe in any of the above suspensions before the reaction is carried out.
o, 1 to 1.7 at. A water-soluble chromium salt is added to Fe in any of the reaction solutions in which the oxidation reaction is carried out by passing oxygen-containing gas.
01 to 5 atomic % in terms of r and water-soluble nickel salt to F
By adding 01 to ZO atomic % in terms of N1 to e, ml-shaped crystal α- containing sl, Or, and N1 can be obtained.
Acicular α-FeOOH particles containing S1, Cjr and N1 by generating FθOOH particles, or acicular α-FeOO3 particles containing Sl, Or and Ni obtained by heating and dehydrating the same By reducing , it has acicular crystals, uniform particle size, no dendritic particles, large specific surface area, high coercive force Hc, and large saturation magnetization σS. The present invention was completed by discovering that acicular crystal alloy magnetic particles could 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, Or, and N1, which is obtained by reacting an aqueous ferrous salt solution with an aqueous alkaline solution. In producing acicular α-FeOOH particles by passing an oxygen-containing gas through a suspension containing Fe(oH)2 and having a pH of 1'1 or higher, the aqueous alkaline solution and oxygen-containing gas are oxidized. Water-soluble silicate is added in any of the above suspensions before being aerated to carry out the oxidation reaction, in an amount of o, i to 1.7 atomic % in terms of FekJtLs1.
Adding the ferrous salt aqueous solution, the alkali aqueous solution, and the oxygen-containing gas to perform the oxidation reaction, the suspension and the oxygen-containing gas are aerated to perform the oxidation reaction. In either of the above reaction solutions, a water-soluble chromium salt is contained in an amount of 0.1 to 5 atomic % in terms of Or based on Fe, and a water soluble nickel salt is contained as 0.1 to 5 atomic % in terms of N1 based on Fe.
By adding 70 atom%, sl, Or and N
Acicular α-FeOOH particles containing Si, C! Acicular α-FeOOH containing r and N1
Acicular α-Fe203 particles containing Sl, Or, and N1 obtained by heating and dehydrating the particles are reduced by heating in a reducing gas in a temperature range of 300°C to 500°C to obtain Sl, Or, and This is a method for producing acicular iron alloy magnetic particles for magnetic recording, which is used to obtain acicular iron alloy magnetic particles containing N1.

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.

That is, the acicular α-FeOOH particles, which have a uniform particle size and do not contain dendritic particles, contain bee(oH)2 obtained by reacting a ferrous salt aqueous solution with an alkali aqueous solution. In a method of producing acicular α-FeOOH particles by passing an oxygen-containing gas through a suspension to oxidize it,
Water-soluble silicate is added to Fe in an amount of 0.1 to 1.7 atoms in terms of S1 in any of the suspensions before the aqueous alkaline solution and oxygen-containing gas are passed through to perform the oxidation reaction. % (Japanese Patent Publication No. 55-8461, Japanese Patent Publication No. 55-52652).

Conventionally, acicular crystals α obtained in an alkaline region with a pH of 11 or higher
-Fe00H particles generally have asymmetric particle sizes and are mixed with dendritic particles;
The Fe(OH)2 floc, which is the precursor of the particles, is asymmetric, and at the same time, the Fe(oH)2 particles themselves constituting the Fe(OH)2 floc are asymmetric; Acicular crystals α-F from an aqueous solution containing Fe(OH)
This is due to the fact that the generation of eOOH core particles and the growth of the acicular α-Fe00H core particles occur simultaneously, and new nuclei are generated many times until the α-FeOOH production reaction is completed.

As mentioned above, acicular α-IFe is produced by passing an oxygen-containing gas through a suspension containing Fe(OH)2 obtained by reacting a ferrous salt aqueous solution with an alkaline aqueous solution to oxidize it.
In producing oOH particles, a water-soluble silicate is added to the aqueous alkali solution and the suspension before the oxidation reaction is carried out by passing through the aqueous alkali solution and oxygen-containing gas, in terms of Fe and Si. When added at 1.7 at%, the Fe(oH)p flocs become sufficiently fine and uniform, and the Fe(OH)2 flocs are )2 particles themselves can be made into sufficiently fine and uniform particles, and furthermore, the water-soluble silicate can be made into needle-shaped α-
Due to the effect of suppressing the oxidation reaction when generating FeOOH particles, generation of acicular α-FeOOH core particles and growth of the acicular α-FeOOH core particles can be performed in stages. Therefore, it is possible to obtain acicular α-FeOOH particles with uniform particle size and without dendritic particles mixed therein.

The water-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
It is 01 to 1.7 atomic % in terms of S1.

The amount of water-soluble silicate added is 0.0% relative to Fe in terms of S1.
If it is 1 atomic % or less, the effect of obtaining acicular crystal grains with uniform particle size and no dendritic particles is not sufficient, and if it is 17 atomic % or more, granular magnetite particles are mixed in. come.

The above-mentioned acicular α-FeOOH particles having uniform particle size and no dendritic particles or the acicular α-FeOO
Acicular crystal α-78203 particles obtained by heating and dehydrating H particles are used as a starting material, and the acicular crystal alloy magnetic particle powder obtained by heating and reducing the starting material also has a uniform particle size and a dendritic structure. As a result, it has a large bulk density and good dispersibility when made into a paint.
Moreover, it has the characteristics of high filling properties in the coating film and a large residual magnetic flux density Br, but the specific surface area is about 207f9 at most.

Therefore, the present inventor conducted various studies on a method for improving the specific surface area of acicular iron alloy magnetic particle powder containing Sl, which has uniform particle size and does not contain dendritic particles. To generate acicular α-FeOOH particles containing Sl with uniform particle size and no dendritic particles, an oxidation reaction is carried out by aerating a ferrous salt aqueous solution, an alkaline aqueous solution, and an oxygen-containing gas. A water-soluble chromium salt was added to either the previous Fe(OH)2 suspension or the reaction solution in which the oxidation reaction was carried out by passing oxygen-containing gas, and the resulting mixture contained Sl and Or. Needle crystal α-FeOO
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 as follows by extracting some of the numerous experimental examples conducted by the present inventor.

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 Or and acicular iron alloy magnetic particles containing Or.

That is, ferrous sulfate aqueous solution 3001 containing F♂ + 1.2 nag/6 was mixed with sodium silicate prepared in advance in a reactor, 0 to 1.0 atomic % calculated as S1 with respect to Fe, and chromium sulfate. In addition to NaOH aqueous solution 4001 obtained by adding 0 to 5.0 atomic % in terms of Or to Fe, PH1
! A suspension containing Fe(OH)2 was obtained in step 1.8, and acicular air containing Sl and Or was obtained by passing 10,001 air per minute into the suspension at a temperature 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 needles 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 S1 is not added, and curves S and c are for the case where the amount of S1 added is 0.65 atomic % and 1.0 atomic %, respectively.

As shown in curve b1c, when 81 and cr are added in combination, the specific surface area of the resulting acicular iron alloy magnetic particles containing Sl and Or can be significantly improved; in this case, sulfuric acid The specific surface area tends to increase as the amount of chromium added increases.

Since this phenomenon appears more markedly than when Or is added alone, as shown by curve a in FIG. 1, the present inventor believes that it is due to the synergistic effect of Sl and Or.

As mentioned above, the acicular iron alloy magnetic particles containing 81 and Or have uniform particle size, do not contain dendritic particles, and have a large specific surface area.
There was a tendency for the coercive force to decrease 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 Sl and Or.
As a result of various studies, we found that when producing acicular α-FeOOH particles containing Sl and Cjr, Fe(OH )2 A water-soluble nickel salt is added to either the suspension or the reaction solution in which an oxidation reaction is carried out by passing an oxygen-containing gas through the resulting Sl, O
When acicular α-FeOOH particles containing r and N1 are thermally reduced, S remains while maintaining a large specific surface area.
It has been found that the coercive force of acicular iron alloy magnetic particles containing i and Cr 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 salt added and the coercive force of acicular iron alloy magnetic particles containing 81, Or, and N1.

That is, a ferrous sulfate aqueous solution 3001 containing 1.2 mol/(l of Fe) was mixed with sodium silicate prepared in advance in a reactor at 0.65 atomic % based on S1, and chromium sulfate In addition to NaOH aqueous solution 4001 obtained by adding nickel sulfate so as to contain 0 to 0 to ZO atomic% in terms of N1 with respect to Fe,
Sl, Or
Acicular crystal iron containing Si, Or, and N1 obtained by producing acicular α-FeOOH particles containing Si, Or, and N1, and then reducing the particles by heating at 420°C for 4.0 hours. This figure shows the relationship between the coercive force of the alloy magnetic particles 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.

Since the phenomenon of improving the coercive force while maintaining a large specific surface area cannot be obtained by removing any of Si, Or, and Ni, the inventors of the present invention
It is believed that this is due to the synergistic effect between l, Or, and N1.

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

The water-soluble chromium salt used in the present invention includes:
Chromium sulfate and chromium chloride can be used.

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

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

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

The amount of water-soluble chromium salt added is 0.0% compared to Fe in terms of Cr.
If it is less than 1 atomic %, the effect of increasing the specific surface area of the obtained acicular 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 effluent soluble nickel salt used in the present invention, nickel sulfate, nickel chloride, nickel nitrate, etc. can be used.

Regarding the timing of adding the water-soluble nickel salt, in the present invention, it is necessary to have nickel present during the formation reaction of acicular α-FeOOH particles. , Fe(OH), or after the start of aeration of the prime-containing gas, acicular crystals α-F
What is necessary is just to add it to any of the reaction solutions in which eloHQ molecules are being produced.

Note that even if water-soluble nickel salt is added at a stage when the formation of acicular α-FeOOH particles has been completely completed, nickel will not enter the particles, so the effect of nickel addition in the present invention cannot be obtained. I don't know.

The amount of water-soluble nickel salt added in the present invention is 0.1 to 70% based on Fe in terms of N1.

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

If the content is 10 atomic % or more, the object of the present invention can be achieved, but it is not preferable because foreign substances other than needle crystals are mixed in when α-FeOOH particles are generated.

The reduction temperature in the present invention is 600°C to 500°C. When the temperature is below 300°C, the reduction reaction progresses slowly;
It takes a long time.

Furthermore, if the temperature is 500° C. or higher, the reduction reaction rapidly progresses, resulting in deformation of the acicular crystal particles and sintering of the particles and each other.

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

That is, according to the present invention, the material has acicular crystals, has uniform particle size, does not contain dendritic particles, has a large bulk density, has a large specific surface area, and has a high 1/) coercive force Hc. 3i, , Or and N1. with large saturation magnetization σB. Acicular iron alloy magnetic particles containing acicular crystals can be obtained, so they can be used as magnetic particles for high image quality, high output, high sensitivity, and high recording density, which are currently most demanded. .

Furthermore, when the above-mentioned acicular iron alloy magnetic particle powder containing Si, Or, and N1 is used in the production of magnetic paint, the noise level is low, and the dispersibility in the vehicle and in the coating film are low. It is possible to obtain a preferred magnetic recording medium with extremely excellent orientation and filling properties.

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 previous experimental example, the following example, and the comparative example is based on the BIT method number. The axial ratio (long axis: 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 J Engineering S K 5101-1978 [
Measured according to pigment test method j.

The amount of 81, the amount of Or, and the amount of N1 in the particles were determined using a "fluorescent X-ray analyzer 30 (type 53M" (manufactured by Rigaku Denki Kogyo),
It was measured by performing fluorescence X-ray analysis in accordance with "General Rules for Fluorescence XM Analysis" of Engineering S.K. 0119-1979.

The magnetic tape characteristics are the results of measurements under an external magnetic field of 10 KOθ.

Production of acicular α-FeOOH particle powder> Examples 1 to 1
6. Comparative Example 1; Example 1 A ferrous sulfate aqueous solution 5001 containing Fe" 1.2 mol/(l) was prepared in advance in a reactor.
Sodium silicate (No. 3) containing 020 atomic% in terms of Si (5iQ22B, 55 wt%)
152 g, 644 g of chromium sulfate to contain 0.50 atomic% in terms of Or based on Fe, 3 in terms of N1 based on Fe.
．． In addition to 5,45-N NaOH aqueous solution 4001 obtained by adding nickel sulfate 28849 to contain 0 at%, Sl, Cjr were added at pH 14.0° and temperature 45°C.
A reaction was carried out to produce a Fe(OH)2 suspension containing N1 and N1.

The above Fe(oH)2 suspension containing S1, Or and N1 was aerated with air at a rate of 100 ol/min for 66 hours at a temperature of 50°C to form acicular crystals α-F containing Si, Or and N1.
eOOH particles were generated.

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

The resulting particles were separated by p, washed with water, dried, and crushed by a conventional method.

The obtained acicular crystal α-F containing Si, Car and N1
As a result of X-ray diffraction, the eOOH particles had the same diffraction pattern as the crystal structure of the α-Fe00H particles.

In addition, as a result of fluorescent X-ray analysis, Si was found to be 0204
atomic%, Or to Fe, o496496 atom 1 to Fe
The content was 3.02 atomic %.

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

This acicular crystal α-FeO0 containing Sl, Or and N1
1 (The particles are shown in the electron micrograph (X20000) shown in Figure 3.
As is clear from the above, the average value of the long axis was 0.50 pm, the axial ratio (long axis: short axis) was 28.21, and the particle size was uniform and dendritic particles were not mixed.

Examples 2 to 13 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, production of Fe(OH)2 suspension in Example 5 Acicular crystal α-Fe
OOH 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 particles have an average value of 045 μm on the long axis and an axial ratio (long axis: short axis) of 9:1. The particle size was asymmetric, and dendritic particles were mixed.

(Production of acicular α-Fe203 particles containing Si, Or and N1) Example 14 α-Fe containing Sl, Or and N1 obtained in Example 5
A 203-particle powder was obtained.

Obtained acicular crystal α-FQ20 containing Sl, Or and N1
As a result of fluorescent X-ray analysis, the 3-grain powder has a Sl content of 0 compared to Fe.
．． 256 at%, Or 0.499 at% with respect to Fe,
It contained 5.03 atom % of N1 based on Fe.

As a result of electron microscopy observation, the average value of these particles was 03 on the long axis.
The grain size was 8 μm, the axis ratio (long axis: short axis) was 30:1, the particle size was uniform, and dendritic particles were not mixed.゛゛〈Production of acicular iron or iron alloy magnetic particles〉 Example 15
~28 Comparative Example 2; Example 15 100 g of the acicular α-FeOOH particle powder containing Si, Car, and N1 obtained in Example 1 was put into a retort container No. 31 with one end open, and the container was rotated without being driven. H2 gas was passed through the reactor at a rate of 551/min, and the reduction was carried out at a reduction temperature of 390°C.

The acicular iron alloy magnetic particle powder containing Sl, Or, and N1 obtained by reduction is 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.

As a result of X-ray diffraction, the thus obtained acicular iron alloy magnetic particles containing Si, Or, and Ni had a single-phase diffraction pattern with a body-centered cubic structure similar to that of iron.

In addition, as a result of fluorescent X-ray analysis, Si was 0.20% higher than Fe.
It contained 3 atomic % of Cr, 0.498 atomic % of Cr based on Fe, and 3.02 atomic % of N1 based on Fe.

Therefore, it is considered that iron, 81, Or, and Ni are in solid solution.

This acicular iron alloy magnetic particle powder containing Sl, Cr, and N1 has an average long axis of 028μ〃7, an axial ratio (long axis: short axis) of 8:1, and a specific surface area of 5B, 6y〃? '/q, bulk density 0.43 g/l, coercive force 11300e, and saturation magnetization 164.5 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 16 to 28, Comparative Example 2 Acicular iron alloy magnetic particles or iron magnetic particles containing 5iXOr and Ni were prepared in the same manner as in Example 15, except that the type of starting materials and the reduction temperature were varied. Obtained.

In addition, in Example 28, the acicular crystal α-F'320 containing Si, Cr and Ni obtained in Example 14 was used as a starting material.
A 3-grain powder was used.

Table 3 shows the properties of the obtained particles.

As a result of electron microscopic observation, the acicular iron alloy magnetic particles containing Sl, Or, and N1 obtained in Examples 16 to 28 were found to have uniform particle size and no dendritic particles.

The ferromagnetic particles obtained in Comparative Example 2 had an average long axis of 0.
．． 20μm 1 axis ratio (long axis: short axis) 2:1, specific surface area 15
．． 8 m';A, bulk density 0.17 Q/ll, coercive cuff 040e, saturation magnetization 160. It was roemu/Q.

Moreover, this particle powder is shown in the electron micrograph (X2
0000), the particle size was asymmetric and the shape was greatly distorted.

<Manufacture of magnetic tape> Examples 29 to 42, comparative examples
6; Example 29 Using the xiphoid iron alloy magnetic particle powder containing Si, Or, and N1 obtained in Example 15, an appropriate amount of a dispersant, a vinyl chloride copolymer, a thermoplastic polyurethane resin, and toluene were added. After blending a mixed solvent consisting of , methyl ethyl ketone, and methyl isobutyl ketone to a certain composition,
The mixture was mixed and dispersed for a period of time to form 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 Hc of this magnetic tape is 10300e, the residual magnetic flux density Br is 720 Gauss, and the rectangular shape Br/
Bm was 0706 and the degree of orientation was 166.

Examples 30 to 42, Comparative Example 6: Magnetic tapes were manufactured in exactly the same manner as in Example 29, except that the type of acicular magnetic particles was varied.

Table 4 shows the characteristics of this magnetic tape.

[Brief explanation of the drawing]

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 Or and acicular iron alloy magnetic particles containing Or. FIG. 2 is a diagram showing the relationship between the amount of water-soluble nickel salt added and the coercive force of acicular iron alloy magnetic particles containing 81, Or, and Ni. 6 and 6 are electron micrographs (X2000
0), and FIG. 6 shows the acicular α-FeOOH particle powder containing Sl, Or, and N1 obtained in Example 1, and FIG. 4 shows the acicular α-FeOOH particle powder obtained in Comparative Example 1. , FIG. 5 shows the acicular iron alloy magnetic particles containing Si, Or, and N1 obtained in Example 15, and FIG. 6 shows the iron magnetic particles obtained in Comparative Example 2. Patent applicant: Toda Kogyo Co., Ltd. Representative: Gobe Matsui 0/2 34! ; Figure 3 May 31, 1980 Commissioner of the Japan Patent Office 1. Indication of the case 1982 Patent Application No. 151467 2. Name of the invention Acicular iron alloy magnetic particle powder for magnetic recording and its manufacturing method 3. Amendment Relationship with the case of a person who does 1-1.
It is 7 atom%. '' followed by ``Almost the entire amount of the added water-soluble silicate was contained in the produced acicular α-FeOO11 particles, and as shown in Table 2 below, the resulting acicular α-
Fe00H particles have St
Contains 0.203 to 1.03 at% in terms of conversion. ”
I will insert. (2) “... 0.1 to 5” on page 26, line 18 of the specification
．． It is 0 atom%. '' followed by ``Almost the entire amount of the water-soluble chromium salt added was contained in the produced acicular α-FeOOH particles, and as shown in Table 2 below, the resulting acicular α-FeOOH particles
FeOOH particles contain almost the same amount of Fe as the added amount of Cr.
Contains 0.296 to 2.99 at% in terms of conversion. ”
I will insert. (3) "... 0.1 to 7." on page 28, line 4 of the specification.
It is 0 atom%. '' followed by ``Almost the entire amount of the water-soluble nickel salt added was contained in the produced acicular α-Fe0011 particles, and as shown in Table 2 below, the resulting acicular α-Fe0011 particles
-Felon particles contain approximately the same amount of Fe as the added amount of N.
It contains 2.05 to 5.04 atomic % in terms of i. ”
I will insert. (4) On page 28 of the specification, lines 11 and 12, after "Undesirable", "The obtained acicular iron alloy magnetic particles containing Si, Cr and Ni are listed in Table 3 below. As shown, Si is 0.202 to 1.02 atomic % relative to Fe in terms of Si, and Cr is 0.297 to 2.9 in terms of Cr relative to Fe.
9 atomic% and Ni converted to Fe from 2.01 to 5
．． It contains 0.3 at%, which is almost the entire amount added. ” will be inserted. (5) On page 29, line 15 of the specification, after “can be”, “in addition, Si, Cr and N
Since the acicular iron alloy magnetic particles containing i are not extremely fine particles, they are relatively easy to handle when forming into a paint. ” will be inserted. that's all

Claims (1)

[Claims] 1) Acicular iron alloy magnetic particle powder for magnetic recording comprising acicular iron alloy magnetic particles containing Sl, Or, and N1. 2) Acicular crystals α-F are produced by passing an oxygen-containing gas through a suspension containing Fe(OH)2 and having a pH of 11 or higher 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 Fe in any of the suspensions before the aqueous alkali solution and oxygen-containing gas are passed through to perform the oxidation reaction. .1 to 1.7 atomic % is added, and the ferrous salt aqueous solution, the alkali aqueous solution,
Adding a water-soluble chromium salt to Fe in either the suspension before an oxidation reaction is carried out by passing an oxygen-containing gas through it, or the reaction solution before an oxidation reaction is carried out by passing an oxygen-containing gas through the solution. On the other hand, by adding 01 to 5.0 atomic % in terms of Or and a water-soluble nickel salt to Fe (1,1 to 5.0 atomic % in terms of N1), the acicular crystals α containing Si, Or, and N1 are added. -FeOOH particles are generated, and the S1, O
Acicular α-FθOOH particles containing r and N1 or acicular α-Fe20. Particles in reducing gas 301
]' sl, Or by heating reduction in the temperature range of Q~500℃
A method for producing acicular iron alloy magnetic particles for magnetic recording, the method comprising obtaining acicular iron alloy magnetic particles containing N1 and N1.