JPS5919963B2 - Manufacturing method of metal magnetic powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing metal magnetic powder mainly composed of iron, cobalt, and nickel.

More specifically, the present invention relates to a method for producing metal magnetic powder that has uses as high-density magnetic recording bodies such as magnetic tapes, magnetic drums, and magnetic disks. Up to now, various studies have been made regarding the manufacturing method of metal magnetic powder.
For example, Japanese Patent Publication No. 53-11512 or U.S. Pat. A method is described in which the material is then heated and reduced. However, this method essentially uses a solution of silicone oil in an organic solvent, and due to the use of an organic solvent, (1) the solvent cost is high, (2) the equipment cost for safety measures is high.
(3) There are problems such as the high cost of processing waste solvents,
Conversion to water solvent was desired. An improvement on this method is the invention described in Japanese Patent Publication No. 11515/1983.

In this method, a metal oxide is dispersed in an aqueous n-alkyltrimethylenediaminecarboxylic acid solution, and an aqueous silicone oil solution emulsified with an oleate salt is added thereto. This method uses water as a solvent, and although the drawbacks of the method described in Japanese Patent Publication No. 53-11512 are improved, since oleate is used as an emulsifier,
If the hydrogen index (PH) is biased towards the acidic side or if different types of metal salts are present, the emulsifying power of silicone oil will be weakened and silicone oil will precipitate, making it impossible to obtain metal powder with excellent magnetic properties. There were flaws. An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a method for easily producing metal magnetic powder having excellent magnetic properties.

In order to achieve the above object, the method for producing metal magnetic powder according to the present invention includes: i) starting material powder consisting of a compound of a metal mainly containing at least one element selected from the group consisting of iron, cobalt, and nickel; Step 11 of immersing in a silicone oil aqueous solution emulsified with a surfactant.
) heating the powder in a reducing atmosphere, and 11
1) It has a step of cooling the powder reduced in the previous step 11).

The present inventors have found that by using the method configured as described above, the problems of the prior art described above are solved, the method is inexpensive, and
It has been found that variations in properties due to pH variations and the presence or absence of different metal salts are extremely small, and metal magnetic powder with good properties can be obtained. The present invention has been made based on this discovery. The metal compound to be used may be any metal compound containing at least one of iron, cobalt, and nickel, such as oxide, acid hydroxide, oxalate, and formate. Alternatively, since acid hydroxide releases fewer atoms during thermal reduction, the particle shape is less likely to break, making it effective for producing metal powder with excellent magnetic properties. In addition, the shape of the metal compound is
Acicular compounds having a ratio of major axis to minor axis of 3 or more are effective for producing metal powder with excellent magnetic properties. Among the above-mentioned iron, cobalt, and nickel, iron is particularly useful as a material for magnetic recording media.

In order to improve the corrosion resistance and magnetic properties of metal magnetic powder, Cu, Cr, P, B, Sn, Aj, Mg are used as the starting materials.
, Ti, Si, W, Zn, or the like may be used. The nonionic surfactants used include polyethylene glycol higher fatty acid ester [RCOO(CH2CH2O)NH], polyoxyethylene alkyl phenolate [RC6H4O(CH2
CH2O)NH], polyoxypropylene alkyl phenolate [RC6H,O(CH2CH2CH2O)NH
], polyoxyethylene alcoholate [RO(CH2C
H2O)NH], polyoxypropylene alcoholate [
RO(CH2CH2CH2O)NH], polyoxyethylene sorbitan monophate ester [H(0CH2C
H2) NOCH2・C4O3H6CH2OOC-R],
Polyoxyethylene sorbitan diphate ester [H
(0CH2CH2)NOCH2・C3O2H4CHOO
CR'CH2OOCR], polyoxyethylene sorbitan triphate ester [H(0CH2CH2)NOC
H2・C2OH2・CHOOCR〃・CHOOCR′・
Any compound containing polyoxyalkylene compounds such as CH2OOCR] and at least one derivative thereof may be used.

R, R' and r are alkyl groups. Furthermore, as the nonionic surfactant, compounds in which the value of n is 6 to 10 are generally often used, and this may be used in the present invention as well. The amount of nonionic surfactant used may be any amount as long as it can emulsify the silicone oil, but it is usually preferably 0.1 to 10 times the amount of silicone oil by weight.

The reason why the amount of nonionic surfactant was set in this range is that 0
．． This is because if the amount is less than 1 times the amount, the emulsifying power will be weak, and if the amount exceeds 10 times the amount, it will be unfavorable in terms of cost. The viscosity of the silicone oil may be any value, but a viscosity of 1 to 100,000 Cs is usually preferred.

The amount of silicone oil is 0% of the starting material metal compound.
．． It is preferably 5 to 20% by weight, more preferably 1 to 10%. The reason why this range is preferable is that if it is less than 0.5%, sintering between particles tends to occur during thermal reduction and it is difficult to obtain metal magnetic powder with excellent magnetic properties. This is because the saturation magnetization of the magnetic powder becomes smaller. The amount of water in the silicone aqueous solution is
The weight is preferably 3 to 100 times the weight of the metal compound as the starting material.

If it is less than 3 times, the dispersion of the raw material powder will not be sufficient, and the
If the number is more than double, manufacturing efficiency is not good.

The temperature at which the metal compound is immersed in the emulsified silicone oil aqueous solution may be any temperature above the melting point of the emulsified silicone oil aqueous solution (the melting point is below 0°C due to the presence of the surfactant). A temperature of ˜50° C. is practically preferred. The immersion time may be extremely short, but is preferably 10 minutes to 24 hours in practice.

It is also desirable to stir the silicone aqueous solution during this immersion. The metal compound after the immersion treatment may be taken out by drying after filtration or by drying the entire slurry, but drying after filtration is preferable due to equipment considerations. This drying process
If moisture is removed by natural drying in another step, it may be omitted.

The conditions for thermal reduction of the metal compound subjected to the above treatment are as follows.

The atmosphere for thermal reduction may be any atmosphere containing a reducing gas such as H2, CO, or city gas, but H2 and city gas are particularly preferred since they are easily available.

The reduction temperature is preferably in the range of 300 to 650°C.

The reason why a reduction temperature in this range is preferable is that if it is less than 30°C, reduction tends to be insufficient, and if it exceeds 650°C, sintering between particles tends to occur. In addition,
Optionally, prior to reduction, heat treatment can be carried out at a temperature of 300 to 10,000 C in an oxidizing gas or an inert gas. This heat treatment is for converting oxalates, formates, and acid hydroxides into oxides, and this treatment may facilitate the next reduction step. Further, after completion of the reduction, it is desirable to form an oxide layer on the particle surface to inactivate the surface of the metal magnetic powder.

Methods for forming an oxide layer on the particle surface include (1) a method of treating metal magnetic powder in an inert gas containing 100 to 5,000 degrees Celsius of oxygen at a temperature of 0 to 150 °C; There are known methods such as suspending the slurry in a solvent and blowing an oxidizing gas (e.g., air, an inert gas containing about 10% oxygen) into the slurry at a temperature of 0 to 150°C. good. Other manufacturing conditions are conventional technology,
Especially the production of metal magnetic powder using known silicone oil? You can follow the rules.

The magnetic properties were measured using a sample vibrating magnetometer in a magnetic field with a maximum magnetic field of 100,000 e.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited in any way by these. Example 1 Silicone oil 609 with a viscosity of 30 cs was added to water in 271, and mixture 1509, which was a mixture of polyethylene sorbitan monostearate and polyethylene nonyl phenolate at a ratio of 1:1, was added as an emulsifier to form a nonionic interface. An aqueous silicone oil solution emulsified with an activator was prepared.

1 kg of needle-shaped goethite (α-FeOOH) was immersed and suspended in this silicone oil aqueous solution, and stirred for 1 hour using a homomixer. Next, the slurry thus obtained was suction filtered using a Buchna funnel, and then
It was dried at 100°C. This game site (α-FeOOH
) 0.59 was heated and reduced at 500° C. for 3 hours in a hydrogen atmosphere. After heating and reduction, the mixture was slowly cooled to 50°C, and the atmosphere was changed from hydrogen to nitrogen at 50°C. After the atmosphere has been changed, it is cooled to room temperature, and then N2 containing 1000PF1 oxygen is added.
Gas was introduced into the sample container, and surface oxidation treatment was performed overnight. The obtained sample was a metal magnetic powder whose surface was covered with iron oxide. This powder consists of acicular fine particles, and the acicular ratio (length of major axis/length of minor axis) of the particles is approximately 8.
The length of the long axis was 0.3 μm. The shape and size of this metal powder are determined by the shape of the goethite powder used as a raw material,
They were almost the same size. FIG. 1 shows the relationship between the magnetic properties of the metal magnetic powder obtained by the above method and the heating reduction temperature.

For comparison, the figure also shows a case where the above processing was not performed. In Figure 1, curves 1, 2, 3
are the coercive force (
Hc), saturation magnetization (σs), and squareness ratio (σr/σs).

Curves 4, 5, and 6 are the coercive force (Hc) of the metal magnetic powder obtained without emulsified silicone oil treatment, respectively.
Saturation magnetization (σs) and squareness ratio (σr/σs) are shown. As can be seen from the figure, when goethite (α-FeOOH) is immersed in an aqueous silicone oil solution emulsified with a nonionic surfactant and then heated and reduced, a metal magnetic powder with excellent coercive force and squareness ratio can be obtained. A metal magnetic powder with the best magnetic properties can be obtained at a reduction temperature of 300 to 650°C. Example 2 Metal magnetic powder was produced in the same manner as in Example 1, except that emulsified silicone oil having the viscosity shown in Table 1 was used.

The magnetic properties of the obtained metal magnetic powder are shown in Table 1. As shown in Table 1, no matter what viscosity silicone oil is emulsified with a nonionic surfactant,
A metal magnetic powder with excellent magnetic properties is obtained.

Further, the obtained metal powder was a fine particle with good acicularity, having an acicular ratio of 5 to 101 and a major axis length of about 0.3 μm. Example 3 Hydrogen index (PH) when acicular α-FeOOH is immersed
Metal magnetic powder was produced in the same manner as in Example 1, except that the conditions were as shown in Table 2.

For comparison, Table 2 also shows the case where sodium oleate was used as an emulsifier. The magnetic properties of the obtained metal magnetic powder are shown in Table 2. As shown in Table 2, if a nonionic surfactant is used, any P
Even when treated with H, there is no change in magnetic properties, and moreover, a metal magnetic powder with better properties than when sodium oleate is used as an emulsifier can be obtained. Example 4 Metal magnetic powder was produced in the same manner as in Example 1, except that polyethylene glycol ester of zorpic acid was used as the emulsifier and the raw materials listed in Table 3 were used.

The properties of the obtained metal magnetic powder are shown in Table 3. The * in the raw material column of Table 3 indicates α-Fe2O3 obtained by heat-treating α-FeOOH similar to that used in Example 1 at 300° C. for 2 hours in air. As shown in Table 3, metal magnetic powder having excellent magnetic properties can be obtained no matter which acid hydroxide or oxide is used.

Example 5 5 moles as raw material? α-FeOOH containing Ni was used, and silicone oil (viscosity: 30 cs) was used.
A metal powder was produced in the same manner as in Example 1 except that 309 was used as a nonionic surfactant.

The molar ratio of Fe and Ni in the obtained metal magnetic powder was 95:5.
The magnetic properties are as follows. In addition, the long axis length and acicular ratio of the metal magnetic powder are approximately 0.3 μMl, respectively.
It is 7.

As can be seen from this example, by the method of the present invention, Nl-containing metal magnetic powder with excellent magnetic properties can be obtained.

Example 6 5 moles as raw material? A metal magnetic powder was produced in the same manner as in Example 1 except that γ-Fe2O3 containing CO was used.

The magnetic properties of the obtained metal magnetic powder are as follows. In addition, the long axis length and acicular ratio of the metal magnetic powder are 0, respectively.
．． 4 μM l6.

As can be seen from this example, CO-containing metal magnetic powder with excellent magnetic properties can be obtained by the method of the present invention.

Example 7 As raw materials, 5 mol% of Cr and 0.5 mol of Cu? A metal magnetic powder was produced in the same manner as in Example 1 except that α-FeOOH contained in the powder was used.

The magnetic properties of the obtained metal magnetic powder are as follows. VJL/ VO' ν● Li υ 0 Also, the long axis length and acicular ratio of the metal magnetic powder are each 0.35μMl
It is 7.

As can be seen from this example, a metal magnetic powder containing Cr and Cu with excellent magnetic properties can be obtained by the method of the present invention.

Example 8 100,000 Cs silicone oil was used as the silicone oil, and after treatment with emulsified silicone oil, α-Fe
Except that OOH was preheat-treated at 600°C in air.
Metal magnetic powder was produced in the same manner as in Example 1.

The magnetic properties of the obtained metal magnetic powder are as follows.
Further, the length of the long axis and the acicular ratio of the obtained metal magnetic powder were each 0.3 μMl9.

As can be seen from this example, metal magnetic powder with excellent magnetic properties can be obtained by the method of the present invention.

[Brief explanation of drawings]

FIG. 1 is a curve diagram showing the relationship between the magnetic properties of a metal magnetic powder obtained by thermal reduction of α-FeOOH immersed in a silicone oil aqueous solution emulsified with a nonionic surfactant and the thermal reduction temperature. . 1, 2, 3... When treated with a silicone oil aqueous solution emulsified with a nonionic surfactant, 4, 5, 6
...When treatment with silicone oil aqueous solution is not performed.

Claims (1)

[Claims] 1 i) A starting material powder consisting of a metal compound mainly containing at least one element selected from the group consisting of iron, cobalt and nickel is added to an aqueous silicone oil solution emulsified with a nonionic surfactant. A method for producing metal magnetic powder, comprising the steps of immersing the powder, ii) heating the powder in a reducing atmosphere, and iii) cooling the powder reduced in the previous step ii). 2. The method for producing metal magnetic powder according to claim 1, wherein a step of drying the powder is inserted between the step i) and the step ii). 3. The method for producing metal magnetic powder according to claim 1 or 2, wherein the metal is iron. 4. Claim 1, wherein the compound is at least one compound selected from the group consisting of oxalates, formates, oxides, and acid hydroxides of the metal.
A method for producing a metal magnetic powder according to item 1, 2 or 3. 5 The raw materials further include Cu, Cr, P, B, Sn, A
The metal magnetic powder according to any one of claims 1 to 4, characterized in that it contains at least one element selected from the group consisting of L, Mg, Ti, Si, W, and Zn. manufacturing method. 6 The nonionic surfactant is polyethylene glycol higher fatty acid ester, polyoxyethylene alkyl phenolate, polyoxypropylene alkyl phenolate, polyoxyethylene alcoholate, polyoxypropylene alcoholate, polyoxyethylene sorbitan monofatty ester, Claim 1 characterized in that it is at least one selected from the group consisting of polyoxyethylene sorbitan diphate ester and polyoxyethylene sorbitan triphate ester.
A method for producing a metal magnetic powder according to any one of Items 1 to 5. 7 The silicone oil aqueous solution contains water in an amount of 3 to 100 times the weight of the starting material powder, and 0.5 times the weight of the starting material powder.
Any one of claims 1 to 6, characterized in that it consists of ~20% by weight of silicone oil and a nonionic surfactant in an amount of 0.1 to 10 times the weight of the silicone oil. The method for producing the metal magnetic powder described in 2. 8 The amount of the silicone oil is 1 of the starting material powder.
8. The method for producing metal magnetic powder according to claim 7, wherein the amount is 10% by weight. 9 The heating temperature of the powder in a reducing atmosphere is 300~
The method for producing metal magnetic powder according to any one of claims 1 to 8, characterized in that the temperature is 650°C. 10 Prior to the step of heating the powder in a reducing atmosphere, the powder is heated in an oxidizing gas or an inert gas for 30 minutes.
The method for producing metal magnetic powder according to any one of claims 1 to 9, characterized in that the metal magnetic powder is heated to a temperature of 0 to 1000°C.