JPS6148501A - Manufacture of metallic magnetic powder - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing iron or iron-based metal magnetic powder, which has excellent oxidation resistance and dispersibility and is suitable for use in magnetic recording media.

[Conventional technology]

Iron or iron-based metal magnetic powder (hereinafter referred to as iron-based magnetic powder).

Metal magnetic powder (abbreviated as metal magnetic powder) is generally made of iron oxyhydroxide or iron oxide, or metals other than iron, such as Ni, Co, and O.
It is obtained by heating and reducing iron oxyhydroxide or iron oxide containing metals such as r, Mn, Cu, Zn, Ti, and V with hydrogen gas.

The metal magnetic powder is conventional oxide magnetic powder 1, for example, γ-
Compared to Fe2O3, it provides higher coercive force and higher saturation magnetic moment, and is partly used for high-density recording.

However, metal magnetic powder has a high surface activity. There are major problems in that it is easily oxidized in the atmosphere, its saturation magnetization decreases over time, there is a risk of ignition or combustion, and it lacks storage stability.

Therefore, in order to suppress the ignition and combustion of the metal magnetic powder obtained by thermal reduction, so that it can be safely discharged into the atmosphere, and to improve the oxidation resistance, storage stability, etc., various manufacturing methods of metal magnetic powder have been developed. Alternatively, stabilization methods have been proposed.

For example, (1) a method in which a metal magnetic powder is immersed in an organic solvent such as toluene or xylene, and then the organic solvent is gradually evaporated to form an oxide film on the powder particle surface; (2) a method in which an oxide film is formed on the powder particle surface; A method of forming an oxide film by oxidizing with an oxygen-containing inert gas.

(3) A method of coating the surface of metal magnetic powder with a certain metal element, metal compound, resin, etc. has been proposed.

[Problem that the invention seeks to solve]

However, method (1) has the risk of combustion depending on conditions such as the evaporation rate of the organic solvent, and (2) the expected stabilizing effect and magnetic properties cannot be obtained. However, method (2) has the disadvantage that when the metal magnetic powder is made into fine particles in order to improve the recording density, the oxidation resistance deteriorates and the saturation magnetization decreases. In addition, in method (3), not only is it difficult to select a coating material, but even if oxidation resistance can be improved, there are often problems with dispersibility when forming an ink.

[Failure to solve the problem]

The present inventors have discovered that when metal magnetic powder is treated with a specific sulfur compound, the resulting metal magnetic powder has improved oxidation resistance, storage stability, etc., has good dispersibility when made into ink, and has excellent magnetic properties. The inventors discovered that the present invention has the following characteristics.

The present invention relates to a method for producing metal magnetic powder, which is characterized by treating metal magnetic powder with a disulfide compound represented by formula % (1) (wherein R1 and R2 represent an alkyl group).

The disulfide compound represented by formula (1) is as follows.

Di-n-amyl disulfide, di-n-hexyl disulfide, di-n-hebutyl disulfide.

Di-n-octyl disulfide, di-tert-octyl disulfide, di-n-nonyl disulfide, di-n
-Decyl disulfide, di-n-dodecyl disulfide, ')-tert-dodecyl disulfide, and other alkyl groups having 5 to 12 carbon atoms.

It is suitable in terms of oxidation resistance, dispersibility, economical efficiency, etc.

As a method for treating metal magnetic powder with a disulfide compound represented by formula (1), the disulfide compound is treated with water,
It is also possible to adopt a method of spraying a solution dissolved or dispersed in an organic solvent, etc. onto the metal magnetic powder, but a method of immersing the metal magnetic powder in an organic solvent in which a disulfide compound is dissolved or dispersed, and then drying it. It is preferable to adopt During the immersion process, the concentration of disulfide compounds in the organic solvent is usually 0.05 because if it is too high, it may have an adverse effect on the magnetic properties.
~10 parts by weight, preferably 0.1 to 5 parts by weight are suitable. Further, it is appropriate that the amount of the disulfide compound is 0.1 to 10% by weight based on the metal magnetic powder. The immersion treatment temperature is above room temperature.

Preferably about 30-80°C for 2 hours, 1-10 hours,
Preferably, about 2 to 7 hours is generally employed. After the immersion treatment, the metal magnetic powder is separated and obtained by a known separation method 2, such as filtration, and dried.
A metal magnetic powder whose particle surface is firmly coated with a disulfide compound is obtained. The drying method is air drying.

Drying under an inert gas atmosphere, vacuum drying, etc. is not particularly limited, but the drying temperature is about 50°C or lower.

Generally, a temperature between room temperature and 50°C is appropriate.

As the organic solvent, those commonly used as solvents for magnetic coatings, such as toluene, quinolene, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, acetone, dioxane, methyl cellosolve, ethyl alcohol, and tetrahydrofuran, can be used.

The metal magnetic powder to be coated in the present invention is as follows.

These are metallic iron magnetic powder and gold magnetic powder whose main component is iron. Metals other than iron in the gold magnetic powder mainly composed of iron include Ni, Co, and C!, which are conventionally used in this type of magnetic recording magnetic powder. Examples include r, Mn, Cu, Zn, Ti, and V. These metal magnetic powders may be produced by any method, but generally they are iron oxyhydroxides containing or not containing metals other than the above-mentioned iron, which are obtained by various conventionally known methods.

Iron oxide etc. in a reducing gas atmosphere such as hydrogen 00~5
Those manufactured by a method of thermal reduction at a temperature of about 00'C are used.

〔Example〕

The evaluation of oxidation resistance [o″S retention rate @)] on each side is as follows:
] After leaving the treated metal magnetic powder in air at 60°C and 90% R for one week, the saturation magnetization S(emu/f)
was measured and expressed as a percentage of the saturation magnetization before standing.

In addition, the evaluation of dispersibility [filtration rate @)] was performed by using the treated metal magnetic powder to create a magnetic paint with the binder composition shown in Table 1, and applying the magnetic paint using a filter with a sieve size of 1μ. Filtered and judged by the degree to which the magnetic paint passes through a 74/letter (
When the entire amount passed through, the filtration rate was 100% by weight).

Table 1 *1) Vinyl chloride-vinyl acetate copolymer *2) Coronate (trade name) Example 1 Di-n-amyl disulfide 0.5f)/Renin 20
In this treatment solution, needle-shaped metallic iron magnetic powder (long axis 0.2 μm, axial ratio 8-10, specific surface area 5 am”
/f) Immerse 10 tons and stir thoroughly.

After dispersing and holding at a temperature of 80 °C for 2 hours.

The treatment solution is lowered to room temperature, and the metal iron magnetic powder is filtered out.
A treated metal iron magnetic powder whose particle surface was coated with di-n-amyl disulfide was obtained by vacuum drying at a temperature of 40°C. FT-IR, E of the surface structure of treated metal iron magnetic powder
As a result of analysis using SOA etc., a strong bond between iron and sulfur was observed.

Table 2 shows the measurement results of the magnetic properties (coercive force He and saturation magnetization O''S) and the evaluation results of oxidation resistance and dispersibility of the treated metal iron magnetic powder.

Examples 2 to 9 Using a disulfide compound in the amount listed in Table 2 in place of di-n-amyl disulfide in Example 1 as a disulfide compound, and using a solvent listed in Table 2 as an organic solvent, Metallic iron magnetic powder was treated in the same manner as in Example 1.

The magnetic properties and evaluation results of the treated metal iron magnetic powder are shown in Table 2.

Comparative Example 1 Acicular metal iron magnetic powder similar to Example 1 (long axis 0.2μ
m, axial ratio 8-10. Specific surface area 50tr? #) 102 was suspended in 200 d of toluene, and air was blown in at a rate of 350 m6 per minute for 5 hours at room temperature under stirring and dispersion to form a thin oxide film on the surface of the iron pot particles. After removing the supernatant toluene, the toluene was evaporated by air drying to obtain treated metal iron magnetic powder. The magnetic properties and evaluation results of the treated metal iron magnetic powder are shown in Table 2.

Comparative Example 2 Acicular metal iron magnetic powder similar to Example 1 (long axis 0.2p
mr axial ratio 8. -10. Specific surface area 50R/g) 10g to 0
．． Immersed in a toluene solution containing 5% by weight silicone oil,
After stirring and dispersing for 5 hours at room temperature, the supernatant toluene solution was removed and the toluene was evaporated by air drying to obtain treated metal iron magnetic powder. The magnetic properties and evaluation results of the treated metal iron magnetic powder are shown in Table 2.

〔Effect of the invention〕

When metal magnetic powder is treated with a disulfide compound represented by formula (1) according to the present invention, oxidation resistance, storage stability, etc. are improved, and metal magnetic powder with good dispersibility and excellent magnetic properties can be obtained.

Claims (2)

[Claims] (1) Iron or iron-based metal magnetic powder is treated with a disulfide compound represented by the formula R^1-S-S-R^2 (wherein R^1 and R^2 represent an alkyl group). A method for producing metal magnetic powder characterized by processing. (2) Treatment with a disulfide compound transforms iron or iron-based metal magnetic powder into a compound with the formula R^1-S-S-R^2 (wherein R^1 and R^2 have a carbon number of 5 to 12 The method for producing a metal magnetic powder according to claim 1, which is carried out by immersion treatment in an organic solvent in which a disulfide compound represented by (representing an alkyl group) is dissolved or dispersed, and then dried.