JPH0772283B2 - Magnetic metal powder for magnetic recording - Google Patents

Description

TECHNICAL FIELD The present invention relates to a magnetic metal powder for magnetic recording, and more specifically, it significantly improves deterioration over time and other characteristics required as other magnetic recording materials. The present invention relates to a magnetic metal powder for magnetic recording, which maintains a high level and can sufficiently cope with miniaturization of the magnetic metal powder.

[Problems to be Solved by the Related Art and Invention] As a recent magnetic recording medium, a coating type magnetic recording medium using iron or a magnetic metal powder mainly containing iron for the purpose of improving magnetic recording density and reproducing output. Has been put to practical use.

However, although these magnetic metal powders have advantages such as high recording density, they have drawbacks such as large deterioration over time as compared with iron oxide magnetic powder.

Furthermore, with the recent trend toward higher recording densities, the magnetic metal powders are becoming finer, and along with that, deterioration over time and the like tend to decrease further.

In order to solve such problems, Al in the magnetic metal powder is
Various proposals have been made to incorporate various elements such as (JP-A-52-134858, JP-A-62-65307,
JP-A-64-52002, JP-A-64-33019, etc.).

However, in spite of these proposals, there is still a problem that deterioration with time is large.

The present invention has been made to solve the problems of these conventional techniques, and it is possible to significantly improve the deterioration over time, while maintaining other required characteristics such as magnetic characteristics and coating dispersibility at a high level, In particular, it is an object of the present invention to provide a magnetic metal powder for magnetic recording which can sufficiently cope with miniaturization of the magnetic metal powder.

[Means for Solving the Problem] The above object of the present invention is to provide iron, nickel, manganese,
This is achieved by a magnetic metal powder containing a certain amount of aluminum, phosphorus and / or silicon.

That is, the magnetic metal powder for magnetic recording of the present invention contains 10% iron.
When the atomic ratio is 0, nickel 1.0 to 5.0 atom%, manganese 0.1 to 5.0 atom%, aluminum 3.0 to 15 atom%,
It is characterized in that it is composed of 0.3 to 1.5 atomic% of phosphorus and / or silicon.

In the present invention, as described above, the content of nickel is 1.0 to 5.0 atom% in terms of atomic ratio when iron is 100. When the content of nickel is less than 1.0 atomic%, the saturation magnetization amount (σs) is small and the deterioration with time becomes large. Also
When it exceeds 5.0 atomic%, σs is satisfied, but deterioration with time is large.

The content of manganese is 0.1 in terms of atomic ratio when iron is 100.
~ 5.0 at%. When the content of manganese is less than 0.1 atom%, σs is satisfied, but deterioration with time is large. Also,
If it exceeds 5.0 atomic%, σs is small and deterioration with time becomes large.

The content of aluminum is 3.0 to 15 atom% in terms of atomic ratio when iron is 100. When the content of aluminum is less than 3.0 atomic%, σs is satisfied, but deterioration with time is large. On the other hand, if it exceeds 15 atom%, the deterioration with time is small, but σs becomes a remarkably small value.

The content of phosphorus and / or silicon is 0.3 to 1.5 atom% in terms of atomic ratio when iron is 100. When the content of phosphorus and / or silicon deviates from the above range, deterioration with time becomes large.

The magnetic metal powder of the present invention has an average major axis diameter of 0.10 to 0.35.
μm, average minor axis diameter 0.015 to 0.025 μm, major axis / minor axis ratio 5.0
-25 and a specific surface area of 50 to 70 m ² / g are preferably used.

The method for producing the magnetic powder for magnetic recording of the present invention is not particularly limited, but for example, the following [Method A] or [Method B] is adopted.

[Method A] In this manufacturing method, as the step I, a ferrous salt aqueous solution,
An aqueous solution of nickel salt and an aqueous solution of manganese salt and an excess aqueous solution of alkali are sufficiently mixed, stirred, and then oxidized to obtain needle-shaped α-iron oxyhydroxide (α-
FeOOH) slurry is obtained.

Examples of the ferrous iron, nickel, and manganese salts used here include sulfates, chlorides, nitrates, acetates, carbonates, and the like, but sulfates in consideration of economic efficiency and reaction stability are preferable. Used. The aqueous solution of each of these salts may be added as a mixed aqueous solution or as a single aqueous solution of each. The alkali is not particularly limited, and examples thereof include sodium hydroxide and potassium hydroxide, but sodium hydroxide is generally used.

In this step, the alkali needs to be in an excessive amount with respect to the total amount of the ferrous, nickel and manganese salts, and unreacted alkali remains in the obtained slurry. The unreacted alkali after the reaction is, for example, NaOH.
Is preferably 1.0 to 7.0 mol /.

By sufficiently mixing and stirring each of these components and then oxidizing them, a slurry having nickel- and manganese-containing acicular α-iron oxyhydroxide can be obtained. The oxidation method here is to blow air or oxygen into it.
It is desirable to carry out at 20-60 ° C.

Next, in a step II, the thus obtained slurry of α-iron oxyhydroxide containing nickel and manganese (hereinafter, sometimes referred to as α-iron oxyhydroxide forming a central layer) is added to An aluminum-containing α-oxy water is added to the surface of α-iron oxyhydroxide that forms a central layer by adding an aqueous solution of monoiron salt and an excess of an aqueous solution of aluminum salt or aluminate, thoroughly mixing and stirring, and then oxidizing. This is a step of coating iron oxide (hereinafter, referred to as α-iron oxyhydroxide forming an outer peripheral layer in some cases) and obtaining a slurry containing free aluminate ions. The oxidation method here is also preferably performed at 20 to 60 ° C. by blowing air or oxygen into it.

As the ferrous iron salt used here, the same ones as those used in the step I can be used, but the sulfate salt is also preferably used. Examples of the aluminum salt include aluminum sulfate, and examples of the aluminate include sodium aluminate and potassium aluminate. Also in this case, the aqueous solution of each salt may be added as a mixed aqueous solution or as a single aqueous solution of each. Here, it is necessary that an excessive amount of aluminum salt or aluminate is added and free aluminate ions remain in the obtained slurry.

The alkali concentration at the end of this step II is 0.5-5.0 mol /
And preferably 1.0 to 3.0 mol /.

The content ratio of aluminum in α-iron oxyhydroxide forming the outer peripheral layer is an atomic ratio when the total Fe (Fe in the first step and the second step) is set to 100, and Al is 2.0 to 10 atoms. % Is preferable.

The ratio of Fe in the α-iron oxyhydroxide forming the central layer to the total Fe is 30 to 90%. Therefore, the total
Fe in α-iron oxyhydroxide forming the outer peripheral layer for Fe
The ratio is 70 to 10%.

In the next Step III, the aqueous solution of phosphoric acid or a salt thereof and / or the aqueous solution of silicic acid or a salt thereof is added to the slurry on which the free aluminate ion obtained in Step II is stepped,
After thoroughly mixing and stirring, neutralize and age with sulfuric acid, etc.,
A salt of phosphoric acid and silicic acid used here, which is a step of obtaining a slurry in which aluminum and phosphorus and / or silicon are deposited on the outer surface of α-iron oxyhydroxide containing aluminum forming the outer peripheral layer. Examples of the sodium salt, potassium salt and the like.

These components are thoroughly mixed and stirred, and then neutralized and aged to show a predetermined amount of aluminum and phosphorus and / or silicon on the outer surface of the α-iron oxyhydroxide containing aluminum forming the outer peripheral layer. Be worn.

Further, in the step IV of this method, the slurry of α-iron oxyhydroxide thus obtained is washed, dried and calcined. This drying is carried out at 100 to 200 ° C. for about 12 hours, and the baking is carried out at 300 to 800 ° C., preferably 400 to 700 ° C. in the air or nitrogen atmosphere. Then, it is reduced in a reducing gas to further form an oxide film on the surface. This reduction is
400 to 5 in reducing gas such as hydrogen gas or carbon monoxide gas
It is carried out at 50 ° C, and to form an oxide film on the surface,
A method is preferred in which the oxidation concentration is gradually increased in a mixed gas of an inert gas and oxygen gas, and the magnetic metal powder finally obtained as the concentration of air is taken out.

[Method B] In the step I of this production method, the ferrous salt aqueous solution, the nickel salt aqueous solution, the manganese salt aqueous solution, the aluminum salt or aluminate aqueous solution and the excess alkaline aqueous solution are sufficiently mixed and stirred, and then oxidized. Α-iron oxyhydroxide (α-FeOO) containing nickel, nickel, manganese and aluminum
H) slurry is obtained.

That is, in the step I of the above [Method A], an aluminum salt or aluminate aqueous solution is further added.

The salts of ferrous iron, nickel, manganese, and alkali used here are not particularly limited, and the same ones as those in the above [Method A] are used. Examples of the aluminum salt include aluminum sulfate, and examples of the aluminate include sodium aluminate and potassium aluminate.

Also in this production method, the alkali needs to be in an excessive amount relative to the total amount of ferrous iron, nickel, manganese, aluminum, or aluminate, and unreacted alkali is present in the obtained slurry. To remain.

By sufficiently mixing and stirring each of these components and then oxidizing them, a slurry having acicular α-iron oxyhydroxide containing nickel, manganese, and aluminum can be obtained. The oxidation method here may be the same as the above-mentioned [Method A].

Next, in this method, the second step of [Method A] is omitted, and after washing the slurry containing the acicular α-iron oxyhydroxide,
As step III, aluminum and phosphorus and / or silicon are deposited. That is, an aqueous solution of an aluminum salt or an aluminate and an aqueous solution of phosphoric acid or a salt thereof and / or an aqueous solution of silicic acid or a salt thereof are added, and sufficiently mixed and stirred to form an outer surface of α-iron oxyhydroxide. It is used to deposit aluminum and phosphorus and / or silicon.

The aluminum salt or aluminate used here is the same as that used in the above step I, and examples of the salts of phosphoric acid and silicic acid include sodium salt and potassium salt.

Then, the following is the same as in the step IV of [Method A], drying,
A magnetic metal powder is obtained by firing and further reducing in a reducing gas to form an oxide film on the surface.

The method for producing the magnetic metal powder of the present invention is the same as the above-mentioned [Method A].
Any method may be adopted without being limited to the above-mentioned method and the method B, but in addition to the effect that the method A greatly improves the deterioration over time, the dispersibility of the coating material, especially the dispersion rising property and the magnetic property are improved. , Especially because it also has the effect of improving the coercive force,
It is particularly preferably adopted.

[Examples] Hereinafter, the present invention will be specifically described based on Examples and the like. The numerical values in Tables 1 and 2 are based on atomic% unless otherwise specified.

Example 1 FeSO ₄ 0.47 mol /, NiS in 7.8 mol / 1.8 NaOH aqueous solution 1.8
A mixed aqueous solution 2.5 consisting of O ₄ 0.024 mol / and MnSO ₄ 0.005 mol / was added, thoroughly mixed and diffused, and after dispersing each component, air was blown at 35 ° C. to oxidize the Ni-Mn mixture. A slurry containing the contained α-iron oxyhydroxide was obtained. As a result of observation with a TEM photograph, amorphous fine particles were not recognized, and all were completely α-iron oxyhydroxide.
In addition, the unreacted NaOH after the reaction was analyzed to be 2.5 mol /
Met.

The content ratios of nickel and manganese in this α-iron oxyhydroxide were 5.0 atomic% of Ni and 1.0 atomic% of Mn in terms of atomic ratio when Fe obtained here was 100.

0.5 mol / sodium aluminate aqueous solution 0.36 and 0.31 mol / FeSO ₄ aqueous solution 2.0 were added to this slurry. The added amount of Al was 29 atomic% of Al in terms of atomic ratio when Fe in step II was 100. After thoroughly mixing and diffusing this mixed solution and dispersing each component, air is blown in to oxidize the Ni-Mn-containing α-iron oxyhydroxide to the outer periphery, and
The contained α-iron oxyhydroxide was coated. As a result of taking a part of this slurry and analyzing the filtrate after filtration, about 30% of the added aluminate ions remained in a released state, and the NaOH concentration was 1.5 mol /.

The content ratio of Al in α-iron oxyhydroxide forming the outer peripheral layer was 7.0 atomic% of Al in terms of atomic ratio when the total amount of Fe was 100.

The ratio of Fe in α-iron oxyhydroxide forming the central layer was 65.5% with respect to the total amount of Fe.

To this slurry, 0.5 mol / phosphoric acid aqueous solution 0.03 was added, thoroughly mixed and stirred, then neutralized and aged, and the outer surface of the α-iron oxyhydroxide containing aluminum forming the outer peripheral layer was treated with aluminum. Said Rin. As a result of taking a part of this slurry and analyzing the filtrate and the solid content after filtration, all the free aluminate ions were α
-It was confirmed that it was dressed on the surface of iron oxyhydroxide.

The deposited amount of aluminum and phosphorus is the atomic ratio when the total amount of the magnetic metal powder finally obtained is 100.
The content was 10.0 at.% and P was 0.8 at.

The neutralized slurry was thoroughly washed and then dried overnight at 100 to 120 ° C. Then, after firing at 700 ° C. in air, reduction was performed at 500 ° C. in hydrogen gas to obtain a needle-shaped ferromagnetic metal powder.
Finally, a stable oxide film was formed on the surface of the reduced needle-shaped ferromagnetic metal powder, and then taken out into the air to obtain a magnetic metal powder for magnetic recording.

The amount of addition of each component and the alkali concentration in each of these steps were as shown in Table 1.

The composition of this magnetic metal powder is, as shown in Table 2,
The atomic ratio when Fe was 100 was Ni 3.3 at%, Mn 0.7 at%, Al 10.0 at%, and P 0.8 at%.

The properties are as shown in Table 2, the average major axis diameter.
0.26 μm, average minor axis diameter 0.02 μm, specific surface area 60 m ² / g.

The magnetic characteristics of this magnetic metal powder were evaluated. The magnetic characteristics were measured with respect to the saturation magnetization amount (σs), the saturation magnetization amount after 72 hours, and the magnetization deterioration rate (%). put it here,
The magnetization deterioration rate was calculated as follows.

Magnetization deterioration rate (%) = [(σs−σs after 72 hours) / σs] × 100 These results are shown in Table 2. FIG. 1 shows the relationship between the manganese content and the magnetization deterioration rate.

Examples 2 to 4 As shown in Table 1, the same method as in Example 1 except that the addition amount of manganese sulfate was changed in the step I.
Under the conditions, magnetic powder for magnetic recording having the composition shown in Table 2 was obtained.

The properties and characteristics of this magnetic powder were evaluated in the same manner as in Example 1, and the results are shown in Table 2 and FIG.

Example 5 As shown in Table 1, nickel sulfate, manganese sulfate and sodium aluminate were added in the step I to obtain a slurry containing α-iron oxyhydroxide containing nickel, manganese and aluminum. This slurry contained an excess of aluminate ions.

Next, the second step is omitted, and as the third step, after the slurry is washed, aluminum and phosphorus are further deposited. The following is the same method as in Example 1 for the magnetic recording having the composition shown in Table 2. A magnetic powder was obtained.

The properties and characteristics of this magnetic powder were evaluated in the same manner as in Example 1. The results are shown in Table 2 and the relationship between the manganese content and the magnetization deterioration rate is shown in FIG.

Examples 6 to 8 As shown in Table 1, the same method as in Example 5 except that the amount of manganese sulfate added was changed in the step I.
Under the conditions, magnetic powder for magnetic recording having the composition shown in Table 2 was obtained.

The properties and characteristics of this magnetic powder were evaluated in the same manner as in Example 1, and the results are shown in Table 2 and FIG.

Example 9 As shown in Table 1, Example 8 was repeated except that the additive element in the step III was changed from phosphorus to phosphorus and silicon.
Magnetic powders for magnetic recording having the compositions shown in Table 2 were obtained by the same method and conditions as described above.

The properties and characteristics of this magnetic powder were evaluated in the same manner as in Example 1, and the results are shown in Table 2.

Examples 10 to 11 As shown in Table 1, the same method as in Example 1 except that the addition amount of nickel sulfate was changed in the step I.
Under the conditions, magnetic powder for magnetic recording having the composition shown in Table 2 was obtained.

The properties and characteristics of this magnetic powder were evaluated in the same manner as in Example 1, and the results are shown in Table 2.

Examples 12 to 13 As shown in Table 1, magnetic recording having the composition shown in Table 2 was carried out under the same conditions and conditions as in Example 1, except that the addition amount of sodium aluminate was changed in the step II. A magnetic powder for use was obtained.

The properties and characteristics of this magnetic powder were evaluated in the same manner as in Example 1, and the results are shown in Table 2.

Examples 14 to 15 As shown in Table 1, the magnetic recording magnetic compositions having the compositions shown in Table 2 were prepared under the same conditions and conditions as in Example 1, except that the amount of phosphorus added was changed in the step III. A powder was obtained.

The properties and characteristics of this magnetic powder were evaluated in the same manner as in Example 1, and the results are shown in Table 2.

Examples 16 to 17 All are the same as in Example 1 except that in the step I, the temperature conditions for blowing air for oxidation were changed to 45 ° C. (Example 16) and 25 ° C. (Example 17), respectively. The magnetic powder for magnetic recording having the composition shown in Table 2 was obtained by the method and conditions.

The properties and characteristics of this magnetic powder were evaluated in the same manner as in Example 1, and the results are shown in Table 2.

Comparative Example 1 As shown in Table 1, magnetic powder for magnetic recording having the composition shown in Table 2 was obtained under the same conditions and conditions as in Example 1 except that manganese sulfate was not added in the step I. .

The properties and characteristics of this magnetic powder were evaluated in the same manner as in Example 1, and the results are shown in Table 2 and FIG.

Comparative Example 2 As shown in Table 1, the same method as in Example 1 was used except that the addition amount of manganese sulfate was changed in the step I.
Under the conditions, magnetic powder for magnetic recording having the composition shown in Table 2 was obtained.

The properties and characteristics of this magnetic powder were evaluated in the same manner as in Example 1, and the results are shown in Table 2 and FIG.

Comparative Example 3 As shown in Table 1, magnetic powder for magnetic recording having the composition shown in Table 2 was obtained under the same conditions and conditions as in Example 5, except that manganese sulfate was not added in the step I. .

The properties and characteristics of this magnetic powder were evaluated in the same manner as in Example 1, and the results are shown in Table 2 and FIG.

Comparative Example 4 As shown in Table 1, the same method as in Example 5 was used except that the amount of manganese sulfate added was changed in the step I.
Under the conditions, magnetic powder for magnetic recording having the composition shown in Table 2 was obtained.

The properties and characteristics of this magnetic powder were evaluated in the same manner as in Example 1, and the results are shown in Table 2 and FIG.

Comparative Examples 5 to 6 All were the same as Comparative Example 1 except that the temperature conditions at the time of blowing air to oxidize were changed to 45 ° C. (Comparative Example 5) and 25 ° C. (Comparative Example 6), respectively. The magnetic powder for magnetic recording having the composition shown in Table 2 was obtained by the method and conditions.

The properties and characteristics of this magnetic powder were evaluated in the same manner as in Example 1, and the results are shown in Table 2.

As shown in the magnetic characteristics of Table 2, the magnetic metal powders of Examples 1 to 17 are extremely remarkable in the effect of improving deterioration over time as compared with the magnetic metal powders of Comparative Examples 1 to 6. Further, FIGS. 1 and 2 show the effect of manganese content on the deterioration with time of the obtained magnetic metal powder for each manufacturing method, but a certain amount of manganese should be contained in spite of the difference in the manufacturing method. It can be seen that there is an effect of improving deterioration over time. The magnetic metal powders of Examples 11 to 17 were in the range that satisfied other required characteristics as a magnetic recording material.

[Effects of the Invention] As described above, the magnetic metal powder for magnetic recording of the present invention containing a certain amount of nickel, manganese, aluminum, phosphorus and / or silicon significantly improves the deterioration over time, and The various properties required as a magnetic recording material can be maintained at a high level, and the magnetic metal powder can be sufficiently miniaturized.

[Brief description of drawings]

1 and 2 are graphs showing the relationship between the manganese content and the magnetization deterioration rate in Examples and Comparative Examples, respectively.

Claims (1)

[Claims] 1. The atomic ratio of iron to 100 is nickel.
1.0-5.0 atomic%, manganese 0.1-5.0 atomic%, aluminum 3.0-15 atomic%, phosphorus and / or silicon 0.3-1.5
A magnetic metal powder for magnetic recording, which is characterized by comprising at%.