JPS619553A - Magnetic powder and its manufacture - Google Patents

Abstract

PURPOSE:To obtain magnetic powder having coercive force and saturation magnetic flux density suitable for high density recording and showing a significant erasing effect by manufacturing Fe-base magnetic powder contg. specified mol% of Ni and Cu and having specified coercive force. CONSTITUTION:An Ni compound and a Cu compound are stuck, adsorbed or precipitated on iron oxyhydroxide or iron oxide having 0.5-3mum average major axis size and 0.01-0.5mum average minor axis size. The iron compound may contain 0.5-5wt% metal other than iron such as Mn, Ni, Ti or Bi. The treated iron compound is dried and reduced to manufacture magnetic powder contg. 20- 70mol% Ni and 0.5-10mol% Cu basing on the amount of Fe and having 700- 1,200Oe coercive force.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a ferromagnetic metal powder and a method for producing the same. This article relates to a magnetic powder that has a coercive force and saturation magnetic flux density suitable for high-density recording and has a strong erasing effect, and a method for manufacturing the same.[Prior art] The magnetic recording media currently in use are extremely They are diverse, and the properties required of the ferromagnetic powders used are also different. As a ferromagnetic powder conventionally used in magnetic recording media.

γ-Fe20. , Co-containing 7-11'e 20s
, Fev, Ox, Co-containing Fe, 04. F
e, 01l-γ-Fe, 0. , 0r02, etc.

Since these ferromagnetic powders have limitations in coercive force, saturation magnetic flux density, etc., ferromagnetic metal powder (metal powder) has recently attracted attention because of its high coercive force, saturation magnetic flux density, etc.

[Problem that the invention seeks to solve”]

However, for audio equipment, video equipment, digital equipment, etc., conventional ferromagnetic metal powder has a drawback that its coercive force is too high and cannot be used in audio equipment, video equipment, digital equipment, etc. other than those compatible with existing metals. . Therefore, conventional audio equipment eliminates this drawback by having a low coercive force, a high saturation magnetic flux density, and a high erasing effect.

Although the emergence of ferromagnetic metal powder that can be used in video equipment, digital equipment, etc. is desired, ferromagnetic metal powder that satisfies these characteristics is not yet known.

[Means for solving problems]

The present inventors have conducted intensive research to produce ferromagnetic metal powder with the characteristics described above, and have determined that the average major axis length is 0.5 to 5.
m, average short axis length of 0.01 to 0.5 m, iron oxyhydroxide, iron oxide, or Mn, Ni.

Ni obtained by attaching, adsorbing or precipitating Ni compounds and Ou compounds to iron oxide containing preferably 0.5 to 5 wt% of metals other than iron such as Ti, Bi, Mo, Ag, etc., and reducing after drying. A ferromagnetic metal powder containing 20 to 70 M% of Cu (M% means mol%. The same applies hereinafter) and 0.5 to 10 M% of Cu (all based on F'e) is The present invention was completed by discovering that the ferromagnetic metal powder has a lower coercive force, a higher saturation magnetic flux density, and a higher erasing effect than metal powder, and also has the characteristics of # and metal powder.

The magnetic recording medium using the ferromagnetic metal powder obtained by the present invention can of course be used in metal-compatible audio equipment, video equipment, and digital equipment, but it can also be used in existing non-metal audio equipment, video equipment, and digital equipment. The following methods have been considered for producing 0 ferromagnetic metal powder that can be used in industrial equipment, etc.

(1) A method of thermally decomposing metal organic acid salts (mainly oxalates) and reducing them with a reducing gas.

(2) Method 0 of reducing iron oxyhydroxide, or iron oxyhydroxide containing other metals, or iron oxide or ferrite composition monoxide with a reducing gas (3) Ferromagnetic metal salt gold in an inert gas (4) Method of decomposing metal carbonyl compounds.

(5) A method of electrodepositing ferromagnetic metal powder using mercury electrolysis to separate nine particles. (6) Wet reduction of ferromagnetic metal salts with sodium borohydride, sodium hypophosphite, etc. in the solution. how to.

(7) A method of generating ferromagnetic metal powder by am-emission through a large impact current.

Among these production methods, the method (2) of dry reduction of iron oxyhydroxide or iron oxide with a reducing gas is the most promising in terms of magnetic properties, industrial efficiency, and economic efficiency υ1, and the method of the present invention is also It belongs to this manufacturing method.

According to the present invention, Ni is 20-70M% and Cu is 0.
Contains 5 to IOM% (both relative to Fe).

Coercive force is 700~12000θ, saturation magnetic flux density is 90~
A method is provided for producing a highly dispersed ferromagnetic metal powder with a ferromagnetic metal powder of 170 erΩu/'t. That is, before entering the reduction process, a compound of Ni and O is attached to the surface of oxywater-depleted iron or iron oxide (which may contain metals other than iron) whose particle size is regulated within a certain range. adsorption or precipitation;
After that, by dry reduction with reducing gas such as hydrogen to create an alloy with nickel and copper based on fine iron, shape collapse and sintering are prevented, and the desired coercive force and squareness ratio are achieved. It is possible to obtain a stable ferromagnetic metal powder with excellent dispersibility and suppressed ignitability.

In the method of the present invention, the coercive force and saturation magnetic flux density can be varied by varying the size of the starting material particles and the Ni and O contents in the ferromagnetic metal powder.

In other words, the coercive force ranges from as low as 500 oe to as low as 1500 oe.
However, since the Mononoke particles as low as 5oooθ are large, the noise characteristics deteriorate. Also, 1
Those as high as 300 Oe have poor erasing characteristics in existing non-metal audio equipment, video equipment, and digital equipment, and are not practical in any case. On the other hand, the saturation magnetic flux density is 60 to 20 Oemu/ It is possible to obtain ferromagnetic metal powders in the range of y, but 90 emu
If it is less than /r, the characteristics of metal powder, which is characterized by high output, are lost and it is not practical. Also% 171 emu /
Attempting to obtain a ferromagnetic metal powder with a ferromagnetic metal powder of more than 20% requires reduction at high temperatures for a long period of time, resulting in the shape being distorted and the squareness ratio being reduced, making it unusable.

From the above, the coercive force of ferromagnetic metal powder, which can be used for audio equipment, video equipment, digital equipment, etc. other than existing metal compatible and metal compatible equipment, is 700 to 1200.
Oe, the saturation magnetic flux density needs to be 90 to 170 emu/r.

The average major axis length and average minor axis length of the starting material in the method of the present invention are the average values of the major axis length and minor axis length when particles are randomly selected from electron micrographs of the starting material. be. The average major axis length is less than 0.5 μm and the average minor axis length is 0.01 μm.
If it is less than m, the coercive force will be higher than 1200 Oe.

In addition, the average major axis length is greater than 3 μm, and the average minor axis length is 0.
When it is larger than 5 μm, the coercive force becomes smaller than 700 Oe. Therefore, the starting material has an average major axis length of 0.5 μm to 3 μm.
sb and an average minor axis length of 0.01 μm to 0.5 μm are preferred.

The Ni and O contents in the ferromagnetic metal powder were determined by atomic absorption spectrometry, but if the Ni content in the ferromagnetic metal powder is less than 20 M% with respect to Fe, the coercive force is 1.
It becomes higher than 200 Oe.

Furthermore, if the Ni content is 70 M% or more relative to Fe, the coercive force will be as low as 700 Oe. Therefore, the Ni content in the ferromagnetic metal powder is required to be 20 to 70 M% with respect to ye. Furthermore, if O exceeds 10 M% relative to Fe, the coercive force will be as low as 700 Oe and the squareness ratio will also be low.

If O is less than 0.5 M% with respect to Fe, the erasing effect is not sufficient.

Preferred embodiments of the present invention will be described in more detail below. Starting materials of the present invention include α-FeOOH, β-F
oxyhydroxidation properties such as elon, 7-Fe1on, α-Fe20. , γ-F e20-,, Fe 50
Iron oxides such as 4sγ-Fe2O3/Fe2O rods (bertolide compound) and 0.5 to 5 wt% Mn to these
, Ni.

A material doped with one or more metals other than iron, such as Ti, Bi, Mo, and Ag, is suitable.

As the Ni and O compounds that can be used in the present invention, any soluble or colloidal compound can be used. The Ni compound which can be suitably used is 1n.
ch, , Ni(no,)2.1uso.

Water soluble salts such as ul(on)Xa7. −、、
Ni(OH)X(N05)2-X (x: o ”-
Examples include hydroxides, partial hydroxides, and colloidal compounds such as 2).

Also, as an Ou compound, OuOi2. au(No,)2
．． Water-soluble salts such as Ou(OR)x
S2-x, Ou (OR)x(No,)2-X(x
:O~2) hydroxides, partial hydroxides, colloidal compounds, etc. are exemplified. Two or more kinds of these compounds can also be used.

In the present invention, when using the water-soluble salts of Ni and O exemplified above, the above-mentioned iron oxyhydroxide or iron oxide is added to the solution and stirred for a certain period of time to ensure sufficient contact with the water-soluble salts. However, the most effective method is to disperse iron oxide with an acid such as hydrochloric acid, sulfuric acid, phosphoric acid, or nitric acid if the soluble salt is alkaline, or conversely, if the soluble salt is acidic. For example, it is completely or partially neutralized with an alkali such as sodium hydroxide, potassium hydroxide, or ammonia, and hydroxides or silicate oxides of Ni and O are attached, adsorbed, or precipitated to iron oxides to form a surface coating. This is a method of processing in such a way that Further, in this treatment, the effects of the present invention can be further improved by using a surfactant such as sodium oleate or sodium alginate in order to improve the dispersion of the iron oxyhydroxide or iron oxide.

Subsequently, the treated iron oxyhydroxide or iron oxide is heated to a temperature not exceeding 600°C, preferably 500°C.
Reduce in a reducing atmosphere at the following temperatures: There is actually no lower limit for the reduction temperature, but since the reaction proceeds very slowly at low temperatures, the reaction time becomes longer, which is undesirable from a practical standpoint, so it is appropriate to carry out the reduction at a temperature of at least 250°C. .

After reduction, the reducer is cooled and filled with, for example, 1% air and 9% nitrogen.
A 9% mixed gas is introduced into the reducer, the air content is gradually increased, and after 4-5 hours it is switched to only air and the magnetic iron powder is taken out from the reducer. Then, the obtained ferromagnetic metal powder can be used as a magnetic tape or other magnetic recording medium. [Example] Next, the present invention will be explained in more detail with reference to Examples.
The scope of the present invention is not limited by these Examples.

Furthermore, in carrying out the present invention, Japanese Patent Application Laid-Open No. 52-13482
Simultaneous adhesion or adsorption of aluminum compounds and/or silicon compounds as described in Publication No. 8 causes precipitation 6
It is preferable to combine the principles.

Examples and Comparative Examples The average major axis length is 1 μm and the average minor axis length is 0.04 μm.
m needle a -Fe1on 178 t 10! Ni ('#2 aqueous solution and IMOVJ concentration of Ou O7
2 aqueous solution was added and neutralized with NaOH. Then 100f/
7 (Sio2 equivalent) A 100-proof aqueous solution of sodium silicate was added and neutralized with HO7. It was then filtered, washed and dried at a temperature not exceeding 150°C. The ex obtained in this way
-Fe1on 200 f was reduced in a hydrogen flow of 5 J/min at the temperature shown in Table 1 for 7 hours. After the reduction was completed, the reactor was cooled to room temperature, and a mixed gas of 1% air and 99% nitrogen was added. The amount of air in the mixed gas was increased stepwise at intervals of about 30 minutes, and after 5 hours, the mixture was switched to air only. Magnetic powder was taken out of the reactor and used as a sample. The magnetic properties were measured. Furthermore, magnetic tapes were made using these samples in the following manner, and the magnetic properties of the tapes were measured. The results are shown in Table 1.

Method for Measuring Tape Magnetic Characteristics The following ingredients were dispersed and kneaded for 112 hours in a ball mill.
A magnetic paint was prepared, and this paint was spread on a polyester film having a thickness of 14 μm so that the thickness after wire transfer was 4 μm, dried, calendered, and then heat treated at 50° C. for 96 hours. This film was cut into a predetermined width to obtain a magnetic tape.

・Sample 100 copies・vA
10 parts of eu (vinyl m-vinyl acetate copolymer, UOO product from the United States), 15 parts of Nilaboran 5033 (polyol manufactured by Nippon Polyurethane Co., Ltd.), 5 parts of Coronate L (polyincyanate manufactured by Nippon Polyurethane Co., Ltd.), antistatic agent
3 parts - 10 parts of K (methyl isobutyl ketone) from M toluene
100 copies In Table 1, A1-8 are examples, and A1-17 are comparative examples.

Comparing A1-8 and A9-13, A1 contains Ou.
8, the erasing effect is stronger and the effect of tCu can be seen. On the other hand, since A14 and A15 do not contain Ni, Hc is high and erasing performance is poor. In A16, O is 10M% of Fe.
At a station building that exceeds σr/σB, Rc becomes lower and B”
r/Bm also becomes low, which is not preferable. A1
7, when Ni exceeds 70M% of Fe, the coercive force decreases and the squareness ratio (σr/aB, Br
/Bm) also became low, showing unfavorable results.

〔Effect of the invention〕

According to the method of the present invention, a coercive force of 700 to 1200 Oe
Within this range, it is possible to easily obtain ferromagnetic metal powder that can be used for audio equipment, video equipment, digital equipment, etc. other than those compatible with existing metals.

Claims (1)

[Claims] 1 20 to 70 mol% Ni and 0.5 to 10 mol% Cu
(both relative to Fe), and has a coercive force (Hc) of 7
00-1200 Oe-based magnetic powder. 2. Attaching Ni compounds and Cu compounds to iron oxyhydroxide, iron oxide, or those containing metals other than iron,
consisting of adsorption or precipitation, reduction after drying,
20-70 mol% Ni and 0.5-10 mol% Cu
Contains (both relative to Fe) and has a coercive force of 700 to 12
A method for producing magnetic powder having an Oe rating of 00 Oe.