JPS5864303A - Production of magnetic particle powder of needle crystal alloy consisting essentially of fe-mg-ni - Google Patents

Abstract

PURPOSE:To obtain titled powder having high coercive force and large satd. magnetization by covering needle crystal alpha-FeOOH particle powder contg. Mn and Ni with a P compd. and an Si compd. then oxidizing the same with an O2-contg. gas and further treating the same in a reducing gas under heating. CONSTITUTION:Water soluble Mg and water soluble Ni salt are added respectively at prescribed ratios with respect to Fe into a suspension of >=1 pH contg. Fe(OH)2 obtd. by reaction of an ag. ferrous salt and alkali. The resultant needle crystal alpha-FeOOH particles contg. Mg and Ni of >=20:1 long axis to short axis ratio are separated. Phosphate and water soluble silicate are added in an aq. suspension of said particles having >=8pH to control the pH to 3-7. The above- described resultant particles coated with a P compd. and an Si compd. are heated to 500-900 deg.C in a nonreducing atmosphere whereby the needle crystal alpha- Fe2O3 particles contg. Mg and Ni are produced. The particles are reduced by heating at 350-600 deg.C in a reducing gas, whereby the intended magnetic particle powder of the needly crystal alloy consisting essentially of Fe-Mg-Ni is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an acicular crystal IF having a higher coercive force Ha and a large saturation magnetization σ8, which is particularly suitable as a magnetic material for magnetic recording.
The present invention relates to a method for producing e-Mg-Ni alloy magnetic particles.

In detail, the average value is long axis α2 ~ 2.0 μm, uniaxial ratio 20:
Acicular crystal α-IFs00H particles containing magnesium and nickel having excellent needle crystals of 1 or more are obtained, and the acicular crystal α-F containing magnesium and nickel is obtained.
Magnesium and nickel coated with P compound and 81 compound are obtained by coating eOOH particles with P compound and 81 compound, and then heat-treating in a non-reducing atmosphere at a temperature range of 500°C to 900°C to make the powder densified. Acicular crystals containing α-? After reducing the size to 80g, the particles are heated and reduced in a reducing gas to maintain excellent needle-like crystals.
In addition, substantially high-density IFe has no entanglement of particles and has an increased degree of crystallinity on the particle surface and inside the particle.
An object of the present invention is to obtain an acicular alloy magnetic particle powder containing Mg-Ni as a main component.

In recent years, as magnetic recording and reproducing equipment has become smaller and lighter, there has been an increasing need for higher performance recording media. That is, high-density recording, high output characteristics, and especially improvement in frequency characteristics are required.

The characteristics of a magnetic material suitable for satisfying the above requirements for magnetic recording media are that it has a high coercive force and a large saturation magnetization.

By the way, the magnetic materials conventionally used in magnetic recording media are magnetic powders such as magnesium, maghemite, and sulfur PM dioxide, and these magnetic powders have a saturation magnetization σa7
0 to 85@m trout, and has a coercive force HQ of 250 to 5000e.

In particular, the maximum σB of the oxide magnetic particles is about 850 mga, and generally σ870 to 8Q emu,/e, which is the main reason for limiting the reproduction output and recording density. Furthermore, CO-Σgnetite and 00-maghemite magnetic powders containing 00 are also used, but these magnetic particle powders have a coercive force He of 400 to 8.
000e, but on the other hand, the saturation magnetization σB is as low as 60 to 800 mVg.

Recently, there has been active development of magnetic particles with characteristics suitable for high-output and high-density recording, that is, magnetic particles with high coercive force and large saturation magnetization. Acicular crystal iron magnetism obtained by heating and reducing acicular crystal hydrated iron oxide particles, acicular crystal iron oxide particles, or those containing different metals other than iron in a reducing gas at about 350°C. It is a particulate powder or an acicular alloy magnetic particulate powder.

The coercive force of the acicular ferromagnetic particles and acicular alloy magnetic particles currently used for magnetic recording is largely dependent on the shape anisotropy. The acicular crystal structure of the acicular crystal alloy magnetic particle powder is one of the most important properties.

In addition, the output characteristics and sensitivity characteristics of magnetic recording media such as magnetic tapes and magnetic disks depend on the residual magnetic flux density Br, which is determined by the dispersibility of magnetic particles in the vehicle and the orientation in the coating film. and filling properties.

In order to improve the orientation and filling properties in the coating film, it is required that the magnetic particles dispersed in the vehicle have needle crystals as excellent as possible.

As mentioned above, acicular iron magnetic particles and acicular alloy magnetic particles having excellent acicular crystals are currently in greatest demand, and acicular iron magnetic particles with such characteristics are currently in high demand. In order to obtain magnetic particle powder and acicular crystal alloy magnetic particle powder, first, the starting material acicular crystal α-FeOOH
It is necessary that the particles have good acicular crystals, and then
How can we preserve and inherit these excellent needle-like crystals while heating and reducing them to produce needle-like iron magnetic particles or needle-like alloy magnetic particles?
The big issue is how to make it into a child powder.

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 a solution containing ferrous hydroxide particles obtained by adding an equivalent amount or more of an alkaline solution to a ferrous salt solution at p) 111 or higher and 80°C or lower. By carrying out the oxidation reaction at a temperature of , acicular α-FeOOH particles are produced in the reaction solution.

The acicular α-11'eoon powder obtained by this method has a needle-like shape with a length of about 0.5 to 15μ, but the axial ratio (long axis: short axis) is at most The ratio is about 10:1, and it is difficult to say that the particles have excellent acicular crystals.

In this way, needle-like crystals a-yeooH with an axial ratio of about 10:1
When the particles are made into acicular ferromagnetic particles through a reduction process, the axial ratio of the obtained acicular ferromagnetic particles is approximately 2:1 at most because the particles shrink during the reduction process. turn into.

On the other hand, the present inventor has been developing needle-like crystals a-'Fe0O for many years.
This is involved in the production and development of H particle powder, and in the process, Fe is added to the ferrous salt aqueous solution, which is the raw material iron salt, during the production of acicular α-FeOOH particles.
It has been discovered that when certain types of dissimilar metal ions are added, the particles generally grow more easily in the longitudinal direction of the particles, and σ-IFeOOH particles with a large axial ratio can be obtained.

As a certain type of foreign metal ion other than Pe, for example, 00. Ni, Or, Mn, Cd, etc. 0 However,
It is known that the addition of different metal ions other than IFe generally causes the acicular α-FeOOH particles to become extremely fine, and this tendency becomes more pronounced as the number of additions increases. It is being

In view of the above-mentioned prior art, the present inventor has conducted various studies in order to improve the axial ratio of the acicular a-FθOOH particles obtained in the alkaline region of pH 11 or higher without causing ultra-fineness. As a result, p containing Fe(OH) obtained by reacting a ferrous salt aqueous solution and an alkaline aqueous solution.
Acicular crystals a-IFe are formed in the reaction solution by passing an oxygen-containing gas through the H11 or higher suspension to carry out an oxidation reaction.
In order to generate OOH particles, a water-soluble magnesium salt was added to the above suspension in advance in nfJ, which is acidified by passing oxygen-containing gas, to Fe in terms of Mg equivalent to 0.5 to 20.
．． If 10L of 0 atomic % is added, needle crystal a-1
It is possible to improve the axial ratio without causing ultra-fineness of FeOOH particles, and the average value of the long axis is 0.3 to 2.0.
μm, axial ratio (major axis: minor axis), 20: We have already completed a rounding technology that can obtain H particles in gold monomorphic α-Woo containing magnesium of 1 or more (patent application). 1972
-75512).

This technology is explained as follows. - The production reaction of acicular α-FeOOH particles containing magnesium includes the steps of generation of acicular α-F'eOOH core particles containing magnesium from a Fe(oH)2 suspension containing magnesium; Needle crystals a containing the magnesium
- It consists of two steps: the growth of PeOOH core particles, and the acid is grown by aeration of an oxygen-containing gas. If a water-soluble magnesium salt is added in advance to the suspension containing II'5(OH)2, the magnesium ions will form acicular crystals containing magnesium α-IFeO.
At the stage of generation of OH core particles, acicular crystal α-IFeOOH core particles containing magnesium with an excellent axial ratio are generated, and further, acicular crystals α-]J'eOO containing the magnesium are generated.
At the growth stage of H core particles, growth in the short axis direction of the particles is suppressed and growth in the long axis direction of the particles is promoted.
particles can be obtained. Theoretical elucidation of the action of water-soluble magnesium salts in this phenomenon'
Although the research has not been conducted sufficiently, the present inventor has found that the magnesium ion is a magnesium-containing needle crystal α-IF.
eOO1 (at the growth stage of the core particle, magnesium ions have the effect of suppressing the growth of the particle in the direction of the short axis and promoting growth in the direction of the long axis of the particle). The force (-) is considered to be due to the fact that it is easier to adsorb on a surface parallel to the long axis than on a surface perpendicular to the surface.

The above-mentioned 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 magnesium salt added and the axial ratio of acicular α-P'eOOH particles containing magnesium.

That is, Fe(OH)2 with a pH of 13 was prepared using a ferrous sulfate 10+noJ,4 aqueous solution obtained by adding magnesium sulfate to Fe so as to contain 0.1 to 200 atoms in terms of Mg, and a caustic soda aqueous solution. of acicular α-peoOH particles containing magnesium, obtained by passing 1004 air per minute into the suspension at a temperature of 45°C to carry out an oxidation reaction. This figure shows the relationship between the axial ratio and the amount of magnesium sulfate added.

As shown in Figure 1, as the amount of water-soluble magnesium salt added increases, the magnesium-containing needle crystal a-Fe
The axial ratio of OOH particles shows a tendency to improve. Figure 2 shows the amount of water-soluble magnesium salt added and the acicular crystals of α-FeOOH containing magnesium produced under the same reaction conditions as in Figure 1. This shows the relationship with the long axis of the particle.

As shown in Figure 2, when the amount of water-soluble magnesium salt added is up to 2,000 meters in terms of Mg compared to Fe, as the amount of water-soluble magnesium salt increases, acicular crystals containing magnesium (α-Peso) (particles The long axis of indicates an increasing trend.

When the amount of water-soluble magnesium salt added exceeds 2 atomic % in terms of Mg based on pe, the long axis gradually decreases.

This phenomenon is thought to be due to the increase in the amount of water-soluble magnesium salt added, which caused magnesium ions to be adsorbed also on the plane perpendicular to the long axis of the particles, thereby suppressing growth in the long axis direction of the particles.

However, at the same time, adsorption of magnesium ions also increases on the plane parallel to the long axis of the particle, so growth in the short axis direction is further suppressed. Therefore, the axial ratio of the particle itself is As shown, even if the amount of water-soluble magnesium salt added exceeds 2 atomic % in terms of Mg with respect to Fe, u% does not decrease. Electron micrograph of acicular α-IPeOOH particle powder containing magnesium obtained when magnesium sulfate was added to contain .0 at% (
X20000).

As is clear from FIG. 3, the acicular α-FeOOH particles containing magnesium have excellent acicular crystals.

Conventionally, the Powder and Powder Metallurgy Association (Showa 49) added magnesium in the production of α-FeOOH particles.
There is a method described on page 108 of the 2018 Spring Conference Lecture Summary Collection.

The reaction system of this method uses alkali carbonate as the alkali to produce a-IFeOOH particles in the pH range of 7 to 11, and the resulting particles have a spindle shape.

In this reaction system, "a sodium salt such as hexametaphosphoric acid, hyrophosphoric acid, tartaric acid, etc. is added to an alkali carbonate, or ZnX0u, Mg is added to a ferrous salt.

When a sulfate such as Mn10rXA1 is added in an amount of 02 to 2% by weight based on ferrous iron, the reaction product has a fine particle size.
It is stated that it will be.

For example, in this reaction system, the long axis of α-FeOOH particles obtained at a temperature of 50″c is about 1 μm on average, but when 2% sodium hexamethalin is added, the average value is about 0.15 μm. becomes.

Therefore, in this reaction system, when the above-mentioned additive is added, particles become finer, which is completely different from the effect of the water-soluble magnesium salt in the present invention.

The coercive force of the acicular Fa-Mg alloy magnetic particle powder having excellent acicular crystals obtained using the magnesium-containing acicular α-PeOOH particle powder having excellent acicular crystals described above is high. However, in recent years there has been no end to the demand for higher performance in recording media, and there is also a demand for acicular iron magnetic particles or acicular alloy magnetic particles having higher coercive force.

The present inventor has discovered that acicular crystal Fe having the above-mentioned excellent acicular crystals
The present invention was achieved as a result of repeated studies to further improve the coercive force of -rig alloy magnetic particles.

That is, the present invention provides an oxidation reaction by passing an oxygen-containing gas through a suspension containing Fe(OH) obtained by reacting an aqueous ferrous salt solution with an aqueous alkaline solution and having a pH of 11 or more. In producing acicular α-FeOOH particles in the reaction solution, the ferrous salt aqueous solution, the alkaline aqueous solution, and any of the suspensions before an oxygen-containing gas is passed through the suspension to perform an oxidation reaction. Water-soluble magnesium salt in the liquid is 15 to 20.0 at% in terms of Mg based on re.
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. A water-soluble nickel salt is added to any of the above reaction solutions. By adding 0.5 to &0 atomic % in terms of N1 to e, the average value of the major axis is 03 to 2.
Acicular α-FθOOH particles containing magnesium and nickel with an axial ratio (long axis: short axis) of 0 μm or more of 20:1 are produced, and the acicular α-FθOOH particles containing magnesium and nickel 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, acicular crystals containing magnesium and nickel α-? After adding 01 to 2 wt% (in terms of POa) of phosphate to the eOOH particles, and then adding 0.1 to 7.0 vrt% (in terms of S102) of water-soluble silicate, suspension By adjusting the pH value of the liquid to 3 to 7, acicular crystals containing magnesium and nickel coated with P compound and 81 compound α-■? θOOH particles are obtained, the particles are separated by f, dried, and then heat treated in a non-reducing atmosphere at a temperature range of 500°C to 900°C to obtain needles containing magnesium and nickel coated with P compound and 81 compound. α-Fe, 03
Fe-Mg- obtained by forming particles into acicular crystal alloy magnetic particles having We-Mg-Ni as a main component by heating and reducing the particles in a reducing gas in a temperature range of 350°C to 600°C.
This is a method for producing acicular alloy magnetic particles containing Ni as a main component.

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

The present inventor has produced magnesium-containing acicular α-FeOOH particles having excellent acicular crystals without causing ultra-fine acicular α-FθOOH particles, and A different species other than Fθ that further improves the coercive force of the acicular Fe-Mg alloy magnetic particle powder having excellent acicular crystals obtained by heating and reducing acicular α-1 eQOH particle powder φ As a result of repeated studies on the type of metal ion, the amount of addition, and the timing of addition in the reaction system, we found that a suspension with a pH of 11 or higher containing he (oH\) obtained by reacting a ferrous salt aqueous solution with an aqueous alkali solution was Acicular crystals (1-FeOOH) are produced in the reaction solution by passing an oxygen-containing gas through the solution to carry out an oxidation reaction.
6, before oxidizing by passing in an oxygen-containing gas, a water-soluble magnesium salt was added to the Fe(oH)2-containing suspension in advance in an amount of 0.5 to 20.0 in terms of Mg relative to Fe.
If 05 to 60 atomic % of water-soluble nickel salt is added in advance to the above reaction solution in terms of N1, ultra-fine acicular α-FeOOH particles can be obtained. The average value of the long axis is 0.5 to 0.5 without causing
2.0 μm uniaxial ratio (long axis: short axis) 20:, acicular crystal a-IFe containing magnesium and nickel having a ratio of 1 or more
A novel finding that the acicular Fθ-Mg-N1 alloy magnetic particle powder obtained by using the acicular α-FeOOH particle powder containing magnesium and nickel, which can generate OOH, has a higher coercive force. I gained knowledge.

As mentioned above, when nickel is present alone in the production of acicular a-FeOOH particles, acicular a-FeOOH particles are produced.
It is known that FeOOH particles become extremely fine, and this tendency becomes more and more pronounced as the amount of nickel increases, but in the case of the present invention, nickel does not cause ultra-fineness. , it is possible to obtain acicular α-FeOOH particles containing magnesium and nickel having excellent acicular crystals.

Furthermore, it has been conventionally known that acicular Fe--Ni alloy magnetic particles to which nickel is added tend to have a lower coercive force than acicular iron magnetic particles.

This phenomenon can be seen, for example, in Japanese Unexamined Patent Publication No. 55-62105 [
...For example, if you want to increase the coercive force of metallic iron powder alone, it depends on the content, but usually cobalt salt etc. is used to increase the coercive force and saturation magnetization proof to a certain degree. It is clear from the description that if you want to lower the amount, use nickel salts, chromium salts, zinc salts, etc.].

However, the present inventor has found that when a water-soluble nickel salt is added in the production of magnesium-containing acicular a-PeOOH particles, the coercive force of the acicular Fe-Mg alloy magnetic particles can be further improved. We obtained new knowledge that was completely unexpected given the conventional understanding that it is possible to do this.

Although it is not yet clear why the presence of nickel can improve the coercive force of the acicular Fe--Mg alloy magnetic particles, the inventor believes that it is due to the synergistic effect of magnesium and nickel.

Next, the acicular α-PeOOH particles containing magnesium and nickel having excellent acicular crystals obtained by the method detailed above are thermally reduced while retaining the acicular crystals. The question is whether to use acicular Fe--Mg--Ni alloy magnetic particles.

Magnesium and nickel 350- with excellent needle crystals
Acicular crystals F' are produced by heating reduction at a humidity of 1@C to 600-C.
When obtaining an e-Mg-Ni alloy magnetic particle powder, when the heating temperature becomes high, the deformation of the acicular crystal grains of this lPe-Mg-Ni alloy magnetic particle powder and the sintering of the particles i and each other become significant. The coercive force of the obtained Fe-Mg-Ni alloy magnetic particles will be extremely reduced.

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

The deformation of the particle shape and the sintering of the particles and their mutual particles in a reducing gas occur when acicular α-Fe00H particles containing magnesium and nitrogen are heated and dehydrated. The acicular crystals (1-Fe, O, particles) containing magnesium and nickel are not sufficiently grown, and therefore, due to the small crystallinity of the particles, single grain growth occurs in the thermal reduction process, i.e. Because the physical changes are rapid, uniform grain growth of single grains is difficult to occur. Therefore, in areas where grain growth of single grains occurs rapidly, sintering of grains and grains occurs, resulting in changes in grain shape. It is thought that it becomes easier to collapse.

Furthermore, during 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 and particles in the thermal reduction process, it is necessary to prepare acicular α-P%Qa particles containing magnesium and nickel before the thermal reduction process. of a single particle, and
It has a substantially high density with a reduced degree of crystallinity by achieving uniform particle growth, and retains and inherits the acicular crystals of the acicular α-PeOOH particles containing magnesium and nickel. It is necessary to form particles into acicular crystals α-F~ containing magnesium and nickel.

As a method for obtaining substantially high-density acicular α-F-01 particles with an increased degree of crystallinity, the acicular α-F-01 particles are
-PeOOH particles at 500-900°C in a non-reducing atmosphere
A method is known in which heat treatment is performed in a temperature range of .

In general, the higher the temperature at which acicular α-F, OOH particles are heated and dehydrated, the more effectively single particles can be grown, and therefore the degree of crystallinity can be increased. 1. On the other hand, the heat treatment temperature was 650
It is known that when the temperature exceeds .degree. C., sintering progresses and the acicular crystal grains break down.

Therefore, in order to obtain acicular α-h^ particles that have an increased degree of crystallinity, are substantially dense, and retain and inherit the acicular crystals of the acicular a-★eooa particles. is a method in which the particle surface of acicular α-FeOOH particles is coated in advance with an organic compound or inorganic compound that has a sintering prevention effect prior to heat treatment at a temperature range of 500 to 900°C in a non-reducing atmosphere. It has been known.

The present inventor has been involved in the production and development of acicular magnetic particles for many years, and in the course of his research, he developed an acicular magnetic particle coated with an S1 compound that has an anti-sintering effect. A method for producing crystalline α-FeOOH particles has been extensively developed.

For example, as described below.

That is, the acicular α-FeOOH particle powder containing magnesium and nickel coated with the P4 compound and the 81 compound is the acicular α-FeOOH particle powder containing magnesium and nickel produced by a wet reaction between a ferrous salt aqueous solution and an alkaline aqueous solution. After the 1-FeOOH particles are separated from the mother liquor, they are suspended in water, and when the pH value of the suspension is 8 or higher, the acicular crystal a-FeOOH particles containing magnesium and nickel are mixed with 0. 1-2 vt% (po.

of phosphate (converted to 0.1 - ZOwt)
% (calculated in 5xcl) of water-soluble silicate by adjusting the pH value of the suspension to 3-7.

The above method will be explained as follows.

Generally acicular α containing magnesium and nickel
-PeOOH particles are quite strongly entangled during the crystal growth process in the reaction mother liquor during wet reaction, forming a group of particles that are bonded together, and contain magnesium and nickel that are entangled and bonded to each other. Needle crystals (1-
If a group of FeOOH particles is coated with an anti-sintering agent as it is, it only prevents further sintering, and the entanglements and bonds that occur during the crystal growth process in the reaction mother liquor remain as they are. Therefore, the acicular crystal α-F containing magnesium and nickel intertwined and bonded with each other.
The acicular crystal alloy magnetic particle powder mainly composed of Pa-Mg-Ni obtained by heat-treating eOOH particles in a non-reducing atmosphere and then thermal reduction also has particles entangled and bonded together. Become.

It cannot be said that such particles have sufficient dispersibility in a vehicle, orientation in a coating film, and filling properties.

Therefore, acicular crystals α containing magnesium and nickel
-Prior to coating the FeOOH 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 in advance.

Acicular crystals a-Ire containing magnesium and nickel
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 higher, 0.1 to 2 vt is added to the acicular crystal a-IPeOOH particles containing 1 ram and nickel. % (in terms of Pe8), it is possible to disentangle and untie the acicular a-FeOOH particles containing magnesium and nickel.

Acicular crystals α-? containing magnesium and nickel? eO
O)1 particles may be obtained by removing p from the reaction mother liquor and washing with water in a conventional manner after the formation of acicular α-IFeOOH particles containing magnesium and nickel.

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.

Addition of phosphate increases po3 to acicular α-FeOOH particles containing magnesium and nickel in suspension.
If the amount of k added is 0.1 to 2 wt% (converted to 0.1 to 2 wt%), it is possible to disentangle the particles and uniformly disperse the particles. The effect is not sufficient. On the other hand, when the addition lid is 2°wt% or more, particles can be dispersed, but since the particles are uniformly and strongly dispersed in the liquid, separation by p from the liquid is difficult. It is not suitable as a catalogue.

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

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

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

Next, acicular crystals containing magnesium and nickel α-
Regarding the S1 compound coating formed on the particle surface of FeOOH particles, the formation of the S1 compound coating always involves the following steps:
This must be done after disentangling the acicular α-FeOOH particles containing magnesium and nickel using a phosphate.

When adding water-soluble silicate, it is preferable that the pH value of the suspension is 8 or higher.If water-soluble silicate is added when the OpH value is 8 or lower, solid Sin , and cannot be efficiently formed as a thin film on the particle surface.

Therefore, the water-soluble silicate is added when the pH value of the suspension is 8 or higher, and after being uniformly mixed into the suspension, the pH value is adjusted to 810. If the range in which 5102 precipitates, that is, the pH value, is adjusted to a range of 3 to 7, 5102 precipitates on the surface of the particles to form a film.

The amount of water-soluble silicate to be added is acicular crystal α-FθO containing magnesium and nickel in terms of StO.
It is 0.1 to 7.0 wt% based on the OH particles.

If the amount is less than 0.1 wt%, the effect of addition is not noticeable, and if it is more than 7.0 wt%, the acicular crystals mainly composed of Fθ-Mg-IJi, which have excellent acicular crystals. Although it is possible to obtain crystalline alloy magnetic particles, the saturation magnetization decreases due to a decrease in purity, which is not preferable.

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

Next, acicular crystals containing magnesium and nickel α-
The conditions for forming a film on PeOOH particles with the P compound and the 81 compound and then separating the particles from the suspension will be described.

When using the usual Okibetsu method, if the particles are uniformly and strongly dispersed in the liquid, it may cause leakage of the P cloth, clogging of the P cloth, and other various transient efficiency problems. Become.

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 and particles agglomerate. In addition, almost all of the phosphate added for dispersion is adsorbed to the acicular crystal α-:jPeO'OH particles containing magnesium and nickel, causing wastewater pollution, etc. There is no need to worry about the @ problem occurring.

In addition, even when the voice value of the 1viii suspension is 3 or less, acicular crystals containing magnesium and nickel α-p, oO
H particle aggregation and phosphate adsorption, as well as the aforementioned 81
0. Although it is possible to form a film, it is not preferable because it causes equipment problems and quality issues (dissolution, etc.).

Incidentally, in order to adjust the pH to 5 to 7, acetic acid, sulfuric acid, phosphoric acid, etc. can be used.

The P compound obtained as explained above and 81
Acicular crystal a-1F600H particles containing magnesium and nickel coated with a compound were heated at 50°C in a non-reducing atmosphere.
Acicular α-Fe20 containing magnesium and nickel obtained by heat treatment in a temperature range of 0°C to 900°C
The 3 particles have a substantially high density with an increased degree of crystallinity, and retain and inherit excellent acicular crystals without particle entanglement or bonding.

When the heat treatment temperature in a non-reducing atmosphere is below 504)'c, the degree of crystallinity of the particles changes to acicular crystals α-F~ containing magnesium and nickel coated with P compound and 81 compound. It cannot be said that the grains have an increased and substantially high density, and if the temperature is higher than 900'C, deformation of the acicular crystal grains and sintering of the grains and the grains among themselves will occur.

In addition, it requires highly accurate equipment and advanced technology, and is not industrially economical.Next, some of the numerous experimental examples conducted by the present inventor will be extracted and explained as follows. .

Generally, the particle size of the starting material acicular crystal α-Fθ001 (particle powder or a material containing a different metal other than Fe) and the acicular crystal iron magnetic particle powder or needles obtained by heating and reducing the starting material are determined. It is known that there is an inverse correlation with the coercive force of crystalline alloy magnetic particles.

That is, the smaller the particle size of the starting raw material, acicular α-FθOOH particles, or the powder containing a different metal other than Fe, the higher the acicular iron magnetism obtained by heating and reducing the starting raw material. The coercive force of particle powder or acicular crystal alloy magnetic particle powder tends to be improved.

FIG. 4 shows the particle size of acicular α-FeOOH particle powder, which is a starting material. In the figure, the particle size is expressed by the specific surface area by the BET method. ) and the coercive force of the obtained acicular alloy magnetic particle powder.

In Fig. 1, curve A shows the particle size of acicular α-FeOOH particles containing 5.0yA 1,000% magnesium based on Fe and the retention of the obtained acicular Fe-Mg alloy magnetic particles. This shows the relationship between magnetic force.

That is, ferrous sulfate 6J obtained by adding magnesium sulfate to Fe so as to contain S and O atomic % in terms of Mg.
pH 1 using mat/6 aqueous solution and caustic soda aqueous solution
A suspension containing Fe(OH) of 3 was obtained, and to the suspension,
The particle size of the acicular crystal a-FeOOH particles containing magnesium produced in the reaction solution by performing an oxidation reaction by passing air at a rate of 10,001 per minute at a temperature of 45 ° C. Acicular crystal α-F
The eOOH particles were mixed with a P compound (0.56 wt% in terms of pos).
) and 81 compound (3.4 wt% in terms of S10), followed by heat treatment at 700°C in air, and then heat reduction at 490°C in a reducing atmosphere. This figure shows the relationship between coercive force of alloy magnetic particles.

As shown in curve A, as the particle size of the magnesium-containing acicular α-FeOOH particles becomes smaller, the coercive force of the obtained acicular lFe-Mg alloy magnetic particles tends to increase. be.

In Figure 4, the song! BSO calculates the relationship between the particle size of acicular α-FeOOH particles containing magnesium and nickel and the coercive force of the obtained acicular F's-Mg-Ni alloy magnetic particle powder. ID is acicular crystal a containing nickel
-Particle size of PeOOH particles and obtained acicular Fe
- The relationship between the coercive force of the Ni alloy magnetic particles is shown.

That is, curve B was obtained by adding magnesium sulfate to Fe in an amount of 5.0 atomic % in terms of Mg, and adding nickel sulfate in an amount of 2.0 atomic % in terms of N1 to Fe. Ferrous sulfate Q, f3 mol/1 aqueous solution and caustic soda aqueous solution were used to obtain a suspension containing Fe (OH ~) with a pH of 13, and the suspension was heated at 1 min/min at a temperature of 45°C.
Acicular crystal α containing magnesium and nickel obtained by aerating the air of oooJ to perform an oxidation reaction
- The particle size of FeOOH particles and the acicular crystal α-Fe00H particles containing magnesium and nickel are calculated by curve A.
The acicular Fe obtained by coating with P compound and 81 compound in the same manner as in the case of
- The relationship between the coercive force of Mg-Ni alloy magnetic particles is shown.

The song IfilO shows that the added nickel sulfate is N compared to Fe.
Acicular crystals containing magnesium and nickel The particle size of α-Pe00H particles containing magnesium and nickel produced in the same manner as in the case of curve 11IB except for 5.0 atomic % in terms of 1 atomic %. The acicular shape obtained by coating α-FeOOH particles with P compound and 81 compound in the same manner as in the case of curve A, then heat-treating them in air at 700°C, and then heat-reducing them at 490°C in a reducing atmosphere. This figure shows the relationship between the coercive forces of crystalline Fe-Mg-Ni alloy magnetic particles.

Song 11D is straight B except that no magnesium is added.
The size of the nickel-containing acicular α-FeOOH particles produced in the same manner as in the case of nickel and the nickel-containing acicular α-FeOOH particles were determined in the same manner as in the case of curve IsA, and the P compound and the 81 compound were This figure shows the relationship between the magnetic force and the magnetic force.

As shown in FIG. 4, the acicular Pa-Mg-Ni alloy magnetic particle powder has acicular crystals a-? containing magnesium having the same size. The coercive force is further improved compared to the acicular lFe-Mg alloy magnetic particle powder obtained using eOOH particles.

In addition, as the amount of nickel added increases, the acicular crystal Fe-M
It is highly effective in improving the coercive force of the g-alloy magnetic particles.

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

Examples of the ferrous salt aqueous solution used in the present invention include a ferrous sulfate aqueous solution and a ferrous chloride aqueous solution.

As the colored water-soluble magnesium salt used in the present invention, magnesium tetraacid, magnesium chloride, magnesium nitrate, etc. can be used. Regarding the timing of addition of the water-soluble magnesium salt, in the present invention we It is necessary for magnesium to be present before a-FeOOH particle powder is produced by passing an oxygen-containing gas through the suspension to carry out an oxidation reaction. The water-soluble magnesium salt may be added to either an aqueous solution, an alkaline aqueous solution, or a suspension containing IPe(on) before oxygen-containing gas ventilation.

Note that even if the water-soluble magnesium salt is added at a stage when some needle-like α-FθOOH core particles have already been generated by the oxidation reaction after the oxygen-containing gas ventilation is started, a sufficient effect will not be obtained.

In the present invention, the amount of water-soluble magnesium salt added is
0.5 to 20.0 yJL% in terms of Mg' to Fe
It is.

'The water-soluble magnesium salt addition cap is α5111. in terms of Jg compared to Fe. child% or less. In some cases, the object of the present invention cannot be fully achieved.

Although the object of the present invention can be achieved even when the content is 200 atomic % or more, the obtained acicular α-FeOOH particles containing magnesium and nickel are combined with the P compound at 81%.
coated with a compound and then heated to 500°C in a non-reducing atmosphere
The acicular Fe--Mg--Ni alloy magnetic particles obtained by heat treatment in a temperature range of 900° C. and then thermal reduction are undesirable because the saturation magnetization is greatly reduced due to a decrease in purity.

When considering the saturation magnetization of the obtained acicular Fe-Mg-Ni alloy magnetic particles, the content is preferably 0.5 to 15.0 atomic %.

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, and for this purpose, it is necessary to add nickel in the ferrous salt aqueous solution, in the alkaline aqueous solution. During.

It may be added either to a suspension containing Fe(OH~) or to a reaction solution in which acicular α-FeOOH particles are being generated after the start of aeration of oxygen-containing gas.

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

The amount of water-soluble nickel salt added in the present invention is 0.5 to 60 atomic % based on FEI 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 5 atomic %, the object of the present invention cannot be fully achieved.

If it is 6.0 atomic % or more, unreacted nickel hydroxide remains, which is not preferable.

Acicular crystal α containing magnesium and nickel obtained
- p6oon particle powder has a long axis of 0.6 to 2.0 on average
The μIn1 axis ratio (long axis: short axis) is 20:1 or more.

If the long axis has an average value of 05 μm or less and 20 μm or more, it is not preferred as a starting material for magnetic recording.

Acicular α-FeO containing magnesium and nickel
O) If the axial ratio (long axis: short axis) of the f particle powder is 20:1 or less, the acicular α-FeOOH particle powder containing magnesium and nickel is coated with a P compound and an 81 compound. treatment and then at 500°C to 90°C in a non-reducing atmosphere.
The acicular lFe-Mg-Ni alloy magnetic particle powder obtained by heat treatment at a temperature range of 0°C and then heat reduction has an excellent axial ratio because the particles shrink in the heat reduction process. It is difficult to say, therefore, the acicular a-FeOO containing magnesium and nickel as a starting material for magnetic recording.
The axial ratio of the H particle powder is preferably 20:1 or more.

The heating reduction temperature in the present invention is 650 to 600°C.

If the temperature is 550°C or lower, the reduction reaction progresses slowly and requires a long time.

Further, 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 is possible to improve the axial ratio of the acicular α-IPeOOH particles obtained in the alkaline region of pH 11 or higher without causing ultra-fineness, and the average value of the long axis is 0.3 to 0.3. Acicular crystals containing magnesium and nickel (1-FeOOH particles) having excellent acicular crystals with an axial ratio (long axis: short axis) of 2.0 μm or more of 20:1 can be obtained, and the magnesium Acicular crystal α-FsO containing
Acicular crystal α-Fe203 particles containing magnesium and nickel coated with P compound and 81 compound, which are obtained by coating OH particle powder with P compound and 81 compound, and then heat-treating the coated particles in a non-reducing atmosphere. By heating and reducing the acicular crystal α-PeOOH particles containing magnesium and nickel, the excellent acicular crystal structure is maintained and inherited, and there is no entanglement of particles, and sufficient single particle size is obtained. In addition, substantially high-density Fe has an increased degree of crystallinity on the particle surface and inside the particle due to uniform particle growth.
Acicular alloy magnetic particles containing -Mg-Ni as a main component can be obtained.

The thus obtained acicular alloy magnetic particles mainly composed of Fe-Mg-Ni have magnetic properties such as higher coercive force and larger saturation magnetization in I and Z, and powder properties. Because it has high dispersibility, high orientation, and high filling property,
Currently, when using the most demanded alpine-Mg-Ni acicular alloy magnetic particle powder, it has extremely excellent orientation and filling properties in the coating film, and has a desirable magnetic property. A recording medium can be obtained.

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

In addition, the axial ratio (long axis: short axis) and long axis of the particles in the above experimental examples, the following examples, and comparative examples are all shown as average values of values measured from electron micrographs.

Further, the Mg content and Ni content in the particles were measured by fluorescence Xm analysis.

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

Production of acicular α-FeOOH particle powder> Example 1~
11 Comparative Examples 1 to 6; Example 1 Magnesium sulfate (MgSO4.7%O) 895 'I and Fe contained 2.0 at% in terms of N1 so as to contain 1.0 at% in terms of Mg with respect to Fe. Ferrous sulfate 0.80 m0//27 aqueous solution 4 obtained by adding nickel sulfate (N15O4, 6% O) 1922 f to contain
50 l of 4,05 liters previously prepared in the reactor
-N NaOH aqueous solution 4501, pH 13.4,
F containing magnesium and nickel at a temperature of 45°C
e(OH)2 suspension production reaction was carried out.

Air was passed through the Fe(OH)2 suspension containing magnesium and nickel at a rate of 1000 l/min for 98 hours at a temperature of 45''C to produce acicular α-FeOOH particles containing magnesium and nickel.

The end point of the oxidation reaction was determined by extracting a portion of the reaction solution and adjusting the acidity with salt, 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 washed with water in a conventional manner, and then a portion was dried and ground to obtain a sample for analysis and electron G microscopic observation.

The obtained acicular crystal α containing magnesium and nickel
-FeOOH particles were found to be α-IFeOO as a result of X-ray diffraction.
A diffraction pattern identical to the crystal structure of H particles was obtained. Furthermore, as a result of fluorescent X-ray analysis, Mg and N1 were detected.

Therefore, magnesium and nickel are acicular α-PeO
It is thought that it is solidly dissolved in the OH particles.

This acicular crystal α-P containing magnesium and nickel
As a result of electron microscopic observation, the θOOH particles had an average long axis Q of 62 μM, an axial ratio (long axis: short axis) of 24:1, and were excellent in needle-like crystals.

Examples 2 to 11 Except that the type of ferrous salt aqueous solution, the concentration of NaOH aqueous solution, the type, amount, and timing of addition of water-soluble magnesium salt, and the type, amount, and timing of addition of water-soluble nickel salt were varied. Acicular α-FeOOH particles containing magnesium and nickel were produced in the same manner as in Example 1.

Table 1 shows the main manufacturing conditions and characteristics at this time.

As a result of electron microscopic observation, all of the acicular crystal α-FeOOH particle powders containing magnesium and nickel obtained in Examples 2 to 11 were found to have excellent acicular crystals.

Electron micrograph (X
20000) is shown in FIG.

Comparative Example 1 Acicular α-Fe00H was produced under the same conditions as Example 1 without adding magnesium sulfate and nickel sulfate.
A particulate powder was produced.

・Table 1 shows the main manufacturing conditions and characteristics at this time.

The obtained needle-like α-FθOOH particles had a long axis of 0.45 μm on average and a uniaxial ratio (long axis: short axis) of 9:1, indicating that the needle-like crystals were poor.

Comparative Example 2 Acicular α-FeOO containing nickel was produced under the same conditions as Example 1 without adding magnesium sulfate.
H particle powder was produced.

Table 1 shows the main manufacturing conditions and characteristics at this time.

The obtained nickel-containing acicular α-FeOOH particle powder had an average long axis of 0.48 μm and a uniaxial ratio (long axis:short axis) of 15:1.

Comparative Example 3 Particle powder was produced in the same manner as in Example 3, except that the addition lid of nickel sulfate was changed to zO primary atom color in terms of N1 with respect to Fe.

The obtained powder particles were a mixture of acicular crystal particles and irregularly shaped particles.

As a result of X-ray analysis, the acicular crystal particles and irregularly shaped particles were found to be unreacted nickel hydroxide with the acicular crystal α-FeOOH~ particles containing magnesium and nickel.

<Acicular crystal α-FθO coated with P compound and 81 compound
Production of OH particle powder> Examples 12 to 22 Comparative Example 4.5; Example 12 Acicular crystal a-FeOOH particles containing magnesium and nickel obtained in Example 1 and washed with water. This corresponds to approximately 2000'i of acicular α-FθOOH particles containing magnesium and nickel. )
was suspended in 6 og of water.

The voice value of the suspension at this time was 96.

Next, sodium hexametaphosphate 16 was added to the above suspension.
An aqueous solution containing soog/g (corresponding to 0.56 wt% as PO2 with respect to acicular α-FeOOH particles containing magnesium and nickel) was added and stirred for 30 minutes.

Next, IJum (No. 3 water glass) 2009 (corresponding to 28 wt% as 5in2 based on acicular α-FeOOH particles containing magnesium and nickel) was added to the above Mfti liquid and stirred for 60 minutes. After that, 10% acetic acid was added so that the pH value of the WaZ solution became 60, and then acicular α-FθOOH particles containing magnesium and nickel were separated by p, using a press filter.
After drying, acicular α-FeOOH particle powder containing magnesium and nickel coated with P compound and 81 compound was obtained.

Examples 13 to 22, Comparative Example 4.5 Various types of particles to be treated, pH of suspension when phosphate is added, amount of phosphate added, amount of water-soluble silicate added, and pH after adjustment , Acicular α-PeOOH particles containing magnesium and nickel coated with P compound and 81 compound, and Acicular α-IFeOOH particles containing nickel coated with P compound and 81 compound, except for the following changes: Alternatively, acicular crystal α-IPeOOH particle powder was obtained.

Table 2 shows the main manufacturing conditions at this time.

<Production of needle-shaped α-h^ particle powder> Examples 23 to 54 Comparative Examples 6 to 8; Example 25 Needles containing magnesium and nickel coated with the P compound obtained in Example 12 and the 81 compound Crystal (1-F
600 g of eOOH particle powder was heat-treated at 750°C in air to produce acicular crystals containing magnesium and nickel (
Z-Fe203 particle powder was obtained.

As a result of electron microscopy observation, the average value of these particles was 06 on the long axis.
The uniaxial ratio (long axis: short axis) of 0 μm was 23:1, and the crystals were excellent in needle-like crystals.

Examples 24-64, Comparative Examples 6-8 Acicular crystals α-Fθ00 coated with P compound and S1 compound
) Acicular crystal α-F'e containing magnesium and nickel was prepared in the same manner as in Example 23, except that the 1-particle powder of Yuzu 1, the heat treatment temperature and the type of non-reducing atmosphere were varied.
Acicular crystal α-Fe2o containing 2Q3 particle powder nickel
s particle powder or acicular α-'F e20s particle powder was obtained.

Table 5 shows the main manufacturing conditions and characteristics at this time.

Incidentally, the acicular α-F 01 particle powder containing magnesium and Niacel obtained in Comparative Example 8 had an average value of 0 and a long axis of 0.
The 47 μm uniaxial ratio (long axis: short axis) of 18:1 caused deformation of the particle shape and sintering of the particles and each other.

(Production of acicular crystal alloy magnetic particle powder containing IFe-Mg-Ni or Pe-N1 as the main component or acicular crystal metal magnetic particle powder containing iron as the main component) Examples 35 to 46 Comparative Example 9
~11; Example 35 Acicular crystal a-IF containing magnesium and nickel coated with the P compound obtained in Example 23 and the 81 compound
e. Pour 150 g of QJ particle powder into a retort container with one end open (51), and while driving and rotating, 4 gases were supplied per minute.
Aeration was carried out at a rate of b, and reduction was carried out at a reduction temperature of 490°C.

The acicular alloy magnetic particles mainly composed of Ii'e -Mg-Ni obtained by reduction are 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 alloy magnetic particles containing Pe--Mg--Ni as a main component had a single-phase diffraction pattern with a body-centered cubic structure similar to that of iron.

Further, as a result of fluorescent XS analysis, predetermined amounts of Mg and N1 were detected. Therefore, it is considered that iron, magnesium, and nickel are in solid solution.

Table 4 shows the characteristics of this acicular crystal alloy magnetic particle powder mainly composed of Fe-Mg-Ni.

Examples 36-46, Comparative Examples 9-11 Acicular α-Fe20 coated with P compound and 81 compound
Acicular crystal alloy magnetic particle powder mainly composed of Fe-Mg-Ni and acicular crystal alloy magnetic particle powder mainly composed of Fe-Ni were prepared in the same manner as in Example 35 except that the type of s-particle powder and the reduction temperature were varied. A crystalline alloy magnetic particle powder or an acicular crystalline metal magnetic particle powder containing iron as a main component was obtained.

Table 4 shows the properties of this particulate powder.

In Examples 36-46, obtained: EPe-Mg-Ni
As a result of electron microscopy, all of the acicular crystal alloy magnetic particles containing li'e-Mg-Ni obtained in Example 67 as the main component were found to have excellent acicular crystals. Electron micrograph (X2000
0) is shown in FIG.

The acicular metal magnetic particles mainly composed of iron obtained in Comparative Example 9 had a coercive force of 126,400, and as a result of electron microscopy observation, the average value was 03 μM on the long axis and the uniaxial ratio (long axis: short axis).
The ratio was 6:1, and the needle crystals were poor.

The coercive force of the acicular crystal alloy magnetic particle powder mainly composed of Pe-Ml obtained in Comparative Example 10 is 11800e, and the coercive force of the acicular crystal metal magnetic particle powder mainly composed of iron obtained in Comparative Example 9 ←It was even lower than that.

The average long axis of the acicular alloy magnetic particles mainly composed of lFe-Mg-Ni obtained in Comparative Example 11 was 0.55 μm.
Deformation of particle shape with a uniaxial ratio (long axis: short axis) of 9:1, and between particles and grains). Pull sintering, Kiyu L, Th'b (7)
-Manufacture of magnetic tape> Examples 47 to 58 Comparative Example 12
．． 13i Example 47 Using the acicular alloy magnetic particle powder mainly composed of lFe-Mg-Ni obtained in Example 35, appropriate amounts of a dispersant, a vinyl chloride-vinyl acetate copolymer, a thermoplastic polyurethane resin, and toluene, 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 level, and the mixture was coated on a polyester resin film by a conventional method and dried to produce a magnetic tape. The coercive force Ha of this magnetic tape is 15030s, the residual magnetic flux density Br is 3457 Gauss, and the square type Br/
B and n were o, 796, and the degree of orientation was 2.34.

Examples 48 to 58, Comparative Examples 12 to 15 Magnetic tapes were manufactured in the same manner as in Example 47, except that the type of acicular magnetic particles was varied. Table 5 shows the characteristics of this magnetic tape.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the addition cap of a water-soluble magnesium salt and the axial ratio of acicular crystal a-F'aOOH particles containing magnesium. FIG. 2 is a diagram showing the relationship between the water-soluble magnesium salt addition cap and the long axis of the magnesium-containing acicular α-IFeOOH particles produced under the same reaction conditions as in FIG. @3 is acicular crystal α-FθOOH containing magnesium
It is an electron micrograph (X20000) of particle powder. FIG. 4 is a diagram showing the relationship between the particle size of the acicular crystal α-FeOOH particle powder, which is a starting material, and the coercive force of the obtained acicular crystal alloy magnetic particle powder. In FIG. 4, curve A is acicular crystal Pa-Mg alloy magnetic particle powder (Mg content 5 at%), curve 1 [B is acicular crystal Fe-M
g-Ni alloy magnetic particle powder (Mg content 5 at%, N1
content 2%), curve 0 is needle crystal? e-Mg-Ni alloy magnetic particle powder (Mg content 5 atom%, Ni content 5 atom%), the curve is in the case of acicular crystal Ire-Ni alloy magnetic particle powder (in content @2 atom%) be. 5 and 6 are electron micrographs (X2000
0 ), FIG. 5 shows the acicular α-FeOOH particle powder containing magnesium and nickel obtained in Example 3, and FIG. 6 shows the acicular crystal fI'e-Mg- obtained in Example 37.
This is Ni alloy magnetic particle powder. Patent applicant Toda Kogyo Co., Ltd. Representative Matsui Gobe 13 Hamaka" Renko 2) 11 Na 7 aiclr, +Z) Mouth 4 d-Fe00HJ Honi Kaku (m〃)

Claims (1)

[Claims] 1. Oxygen-containing gas is passed through a suspension containing Fe(OH) obtained by reacting an aqueous ferrous salt solution with an aqueous alkaline solution and having a pH of 11 or more to carry out an oxidation reaction. In order to produce acicular α-FeOOH particles in the reaction solution, any of the ferrous salt aqueous solution, the alkaline aqueous solution, and the suspension before the oxygen-containing gas is passed through the suspension to perform the oxidation reaction. Add a water-soluble magnesium salt to the solution.
05 to 20.0 atomic % in terms of Mg is added to
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. Water-soluble nickel salt I in either solution
Contains magnesium and nickel with an average long axis of 0.3 to 2.0 μm and a uniaxial ratio (long axis: short axis) of 20:1 or more by adding α5 to 60 atoms in terms of N1 to Fe. The acicular a-FeOOH particles containing magnesium and nickel are produced, and the acicular a-? eO
After the OH particles are separated from the mother liquor, they are suspended in water, and when the pH value of the suspension is 8 or higher, 0.0% is added to the acicular crystal 11-1F600H particles containing magnesium and nickel.
After adding 1-2 wt% (in terms of PO) of phosphate and then 0.1-70 wt% (in terms of S1O2) of water-soluble silicate, the pH value of the suspension was 3-7
Acicular α-Fe containing magnesium and nickel coated with P compound and 81 compound by adjusting
00H particles were obtained, the particles were separated from P, dried, and then heat treated in a non-reducing atmosphere at a temperature range of 500 to 900°C to obtain acicular particles containing magnesium and nickel coated with P compound and 81 compound. Akira α-'I! A Pe-Mg- A method for producing acicular crystal alloy magnetic particles containing Ni as a main component. 2. A water-soluble magnesium salt added to a suspension containing Fe(OH)2 has a ratio of 0.5 to Fe in terms of Mg.