JPH02162703A - Manufacture of metallic magnetic powder - Google Patents

Abstract

PURPOSE:To manufacture metal magnetic powder having excellent oxidation- resistant property in a good economical and efficient manner by a method wherein a metal complex is decomposed by heat, and the residue of the thermal decomposition is carried on the surface of metallic magnetic powder. CONSTITUTION:A metal hydroxide, containing at least a kind of Co, Ni and Cu, and a metal complex compound, consisting at least of a kind selected from a complexing agent and/or Co, Ni and Cu, are brought to come in contact with metallic magnetic powder, and they are dissolved by heat. Then, the pyrogenous residue of the above-mentioned metal complex is treated so that it is carried on the grain surface of the metallic magnetic powder. Moreover, the treated material is heat-treated in an inert atmosphere, then it is subjected to a slow oxidation treatment in an oxidizing atmosphere, and then a heat treatment is conducted thereon in an inert atmosphere. As a result, the metallic magnetic powder is marakedly improved in oxidation-resistant property and excellent magnetic characteristics can be maintained for a long period.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for producing a metal magnetic powder having excellent oxidation resistance and suitable for magnetic recording.

[Technical background of the invention and its problems]

In recent years, there has been an increasing trend toward miniaturization and higher performance of magnetic recording media due to higher recording densities.

In conjunction with this, iron or iron-based metal magnetic powders (hereinafter referred to as metal magnetic powders) are attracting attention as magnetic powders for magnetic recording, as they have larger saturation magnetization and are easier to increase coercive force than conventional iron oxide-based magnetic powders. It is now being put to practical use in digital audio tapes, 8 m/m video tapes, etc., but in recent years, it has been increasingly applied to high-performance recording media such as high-definition video tapes and high-density disks. It is expected.

By the way, such metal magnetic powder usually has a thickness of about 0.5μ.
Preferably, the particles are fine particles with a diameter of 1.5 m or less (longer diameter), and more preferably 0.3 μm or less, and have excellent dispersibility, orientation in a coating film, filling property, etc. when used as a magnetic coating. It is hoped that However, such fine particles have strong surface activity, and as a result, oxidation progresses over time, resulting in a decrease in magnetic properties such as saturation magnetization and coercive force, resulting in so-called stability over time (hereinafter referred to as oxidation resistance). ) may be unavoidable. In even more severe cases, if the oxidation reaction proceeds rapidly, spontaneous combustion may occur.
This can cause various problems in handling operations and process control, such as combustion.

Many proposals have already been made to improve these problems. For example, (1) the particle surface of the metal magnetic powder immediately after being produced by reduction may be slowly oxidized to form a thin oxide film, or (2) the particle surface of the metal magnetic powder may be coated with, for example, a silicon-based compound or a higher fatty acid-based compound. There are also known methods in which (3) a corrosion-resistant metal compound is deposited on the surface of the metal magnetic powder particles by various wet or dry methods. However, even with these methods, the oxidation resistance cannot be fully satisfied, and when trying to impart sufficient oxidation resistance, it is difficult to obtain the excellent magnetic properties of metal magnetic powder such as high saturation magnetization and high coercive force, or to make it into a paint. There are still many problems that need to be improved, such as the fact that the dispersibility of the liquid is easily impaired. In particular, in conjunction with the demand for higher S/N ratios and higher outputs, there is a trend toward finer particles of metal magnetic powder, and there is a strong desire to solve the above-mentioned problems.

[Purpose of the invention]

An object of the present invention is to solve the above-mentioned problems and provide a method for producing metal magnetic powder suitable for use in magnetic recording media with excellent oxidation resistance.

[Summary of the invention]

The present invention aims to solve the above-mentioned problems without impairing the inherent excellent properties of metal magnetic powder (we have been conducting various studies, and firstly, we have developed an acetylacetonate complex compound into a metal magnetic powder). It has been proposed to improve oxidation resistance by bringing the magnetic powder particles into contact with the surface and subjecting the particles to heat treatment to carry the thermal decomposition residue.

However, although the oxidation resistance of the metal magnetic powder can be improved by the supporting treatment, it is still easy to cause shape deformation due to dissolution of the surface of the metal magnetic powder particles by the complexing agent decomposed and liberated in the supporting treatment. , the cost increase due to the use of the complex compound is large, and therefore there is an urgent need to develop a supporting treatment method that can reduce the amount of treatment.

In order to improve the above-mentioned problems, the present inventors conducted further studies and found that a specific metal hydroxide and a complexing agent or a specific metal complex compound that forms a specific organometallic compound, for example, The remaining complex compound is removed by heating and contacting the metal magnetic powder particles to generate a metal complex, thermally decomposing the generated metal complex, and supporting the thermal decomposition residue on the surface of the metal magnetic powder particles. , metal magnetic particles with excellent oxidation resistance can be produced economically and efficiently without substantially accompanying the decomposition and without causing shape deformation due to dissolution of the surface of the metal magnetic powder particles by the decomposed and liberated complexing agent. The present invention was completed based on the knowledge that powder could be produced.

That is, the first aspect of the present invention is to combine at least one metal hydroxide of Co, Ni, and Cu, and a complexing agent or/and at least one metal complex compound of Co, Ni, and Cu with a metal magnetic powder. A method for producing a metal magnetic powder, characterized by carrying the thermal decomposition residue of at least one metal complex of the constituent metals of the hydroxide on the particle surface of the metal magnetic powder by contacting and thermally decomposing the hydroxide. and the second
This is a method characterized by carrying the thermal decomposition residue of the metal complex on the surface of the metal magnetic powder particles according to the second invention, and then heat-treating the treated product in an inert atmosphere. is a method characterized by carrying the thermal decomposition residue of the metal complex obtained by the first invention on the surface of metal magnetic powder particles, and then subjecting the treated product to gradual oxidation treatment in an oxidizing atmosphere. A fourth method is characterized in that the slowly oxidized product obtained according to the third invention is heat-treated in an inert atmosphere.

In the present invention, the metal magnetic powder (hereinafter referred to as substrate constituent particles) used as the object to be processed is a metal magnetic powder of iron or an iron-based alloy mainly composed of iron, which is manufactured by various methods, and most For boat fishing, needle-shaped crystals are used, but in addition to the above-mentioned needle-shaped crystals, various other shapes such as spindle-shaped, rice-grain-shaped, spherical, rod-shaped, plate-shaped, dice-shaped, etc. are also used. be able to. Note that, prior to the supporting treatment, these substrate constituent particles may be subjected to a gradual oxidation treatment, for example, with an oxygen-containing gas, if necessary.

In the present invention, the metal hydroxides of Co, Ni, and Cu used include, for example, Co(Oll)g, Co(Oll)g, and Co(Oll)g.
tl)s.

N1(OH)z4.5Hzo, N1(OH)t, C
Examples include u(Otl)z. Examples of complexing agents include acetylacetone, ethylenediamine, ethylenediaminetetraacetic acid, hydroxyquinoline,
Tartaric acid, malonic acid, salicylic acid, alanine, glycine,
Triphenylphosphine, dithizone, etc. can be mentioned. Furthermore, examples of complex compounds of Co, Ni, and Cu include acetylacetone cobalt (■, II[), acetylacetone nickel, acetylacetone copper, ethylenediamine cobalt (I[, I), ethylenediamine nickel, ethylenediamine L ethylenediaminetetraacetic acid (EDTA), cobalt (III ), cobalt malonate (
(2), glycine cobalt (III), glycine nickel, 8-quinoline copper, and 1,10-zenatroline nickel.

In the present invention, in order to support the thermal decomposition residue of the metal complex on the surface of the base material particles, the base material powder is treated with at least one metal hydroxide of Co, Ni, and Cu in a liquid phase system. , a complexing agent or/and at least one metal complex compound of Co, Ni, and Cu are brought into contact and heat treated to generate a metal complex and thermally decompose the formed metal complex. be able to.

As the solvent used in the liquid phase treatment, various solvents can be used, such as aliphatic hydrocarbons, aromatic hydrocarbons, ketones, ethers, alcohols, and amines.

The treatment can be carried out by various methods, for example (a) Co.

At least one metal hydroxide of Ni and Cu and a complexing agent or/and at least one metal complex compound of Co, Ni and Cu are suspended in the solvent in advance, and the suspension is The above-mentioned base material constituent particles are added to the inside, and then heated and mixed as necessary while passing an inert gas such as nitrogen gas, or (bl Co
, at least one metal hydroxide of Ni and Cu;
The complexing agent is preheated in the solvent to, for example, 50° C. or higher while passing an inert gas such as nitrogen gas to form a complex compound of the metal, and then the base constituent particle powder is added, and then After that, the processed product of (a) and (b) is heat-treated at usually 80 to 300°C, preferably 90 to 280°C, more preferably 130 to 250°C, for 0.1 to 10 hours, preferably 0.5 to 5 hours. do. By this, C
The metal hydroxides of O, Ni, and Cu form a metal complex, which is thermally decomposed on the particle surface of the substrate-constituting particle powder, and the thermal decomposition residue is supported.

Note that the complexing agent such as acetylacetone produced by thermal decomposition of the produced metal complex is sequentially reacted with a predetermined amount of the metal hydroxide to produce a metal complex. Therefore, in the method of the present invention, the complexing agent and metal complex compound are used efficiently in the reaction treatment system, and as a result, the amount of complexing agent and metal complex compound used can be reduced, and processing costs can be reduced. It is.

In the present invention, the amount of the thermal decomposition residue supported varies depending on the shape, size, specific surface area, etc. of the metal magnetic powder particles constituting the base body particles, and although it cannot be generalized, it is based on the weight of the base body particles. 0.1 to 30%, preferably 1 to 30%
It is 20%. If the supported amount is too small than the above range, the desired effect will not be produced, and if the supported amount is too large, magnetic properties such as saturation magnetization, dispersibility when forming into a paint, etc. may be easily impaired. The metal magnetic powder that has been treated to support the thermal decomposition residue may be further heat-treated on the particle surface in a nitrogen-containing gas atmosphere, or slowly oxidized in an oxidizing gas atmosphere, if necessary. By doing so, the oxidation resistance can be made even more preferable.

In the present invention, at least one of Co, Ni and Cu
The thermal decomposition residue of a metal complex using a seed metal hydroxide refers to the thermal decomposition residue of a metal complex of Co, Ni, and Cu.
It refers to a surface layer of a corrosion-resistant metal or a metal compound thereof, which is formed on the surface of the metal magnetic powder of the base material particles and is substantially made of the constituent metal components of the hydroxides of Co, Ni, and Cu. Although the mechanism by which the extremely excellent properties such as oxidation resistance of the present invention are brought about by the above-mentioned supporting treatment of thermal decomposition residues has not yet been fully elucidated, It is presumed that this is because a corrosion-resistant film is easily formed. Furthermore, the oxidation resistance of the metal magnetic powder can be further increased by heat-treating the metal magnetic powder that has been treated to support the thermal decomposition residue in an oxidizing gas atmosphere or an inert gas atmosphere such as nitrogen gas. The reason seems to be that the corrosion-resistant film on the surface of the substrate constituent particles becomes more dense, and that a more stable oxide film is formed.

The metal magnetic powder produced according to the method of the present invention described above can be made of various binder resins, such as vinyl chloride-vinyl acetate copolymer resins, polyurethane resins, polyester resins, acrylic resins, cellulose resins, etc. A magnetic paint is prepared by adding a binder component and various additives, such as a dispersant, a lubricant, an abrasive, an antistatic agent, etc., and applied onto various non-magnetic supports such as polyethylene terephthalate film and acetate film. A magnetic recording medium such as a magnetic tape can be obtained by applying the magnetic layer to a thickness (usually 2 to 5 μm thick after drying) and drying after orientation treatment to form a magnetic layer, followed by calendering and slitting. In addition, the magnetic tape may be provided with a so-called back coat layer on the opposite surface of the support from the magnetic layer side in order to further improve antistatic properties, running stability, etc., if necessary.

The present invention will be further explained by giving examples and comparative examples below.

[Example of the present invention]

Example 1 A ferrous sulfate aqueous solution was neutralized with a sodium hydroxide aqueous solution,
Further, an oxidizing gas is introduced and oxidized to produce αPe0OH, which is then heated and dehydrated to produce α-Fe, 0. and then heated and reduced in a hydrogen stream to obtain acicular metallic iron magnetic powder (specific surface area (BET) 50 m''/g, average major axis particle diameter 0.i6u, average axial ratio 9, coercive force 1). .250
0e, saturation magnetization 186 emu/g, squareness ratio 0.48
7) as the base constituent particles (sample M), 20g of this material
was suspended in 400 ml of ethylene glycol.

This suspension was placed in a fourth flask equipped with a stirrer, and while nitrogen gas was introduced to maintain a non-oxidizing atmosphere, cobalt hydroxide (Co(OH)z) was added under stirring.
3.33g and 0.64g of ethylenediamine were added, and then the temperature was raised to 190°C at a rate of 4°C/min, and at this temperature 1
The mixture was maintained for a certain period of time and then thermally decomposed. After cooling to room temperature, the suspension was filtered and washed with ethanol and then with toluene. The resulting cake was air-dried to obtain the desired metal magnetic powder (Sample A).

Example 2 Sample A log obtained in Example 1 was heat-treated at 300° C. for 2 hours while passing nitrogen gas in a tubular electric furnace to obtain the desired metal magnetic powder (Sample B).

Example 3 In Example 1, the amount of ethylenediamine added was 6.4
After treatment in the same manner as on the same side except that the amount was 5 g, heat treatment was performed in nitrogen gas as in Example 2 to obtain the desired metal magnetic powder (Sample C).

Example 4 The desired metal magnetic powder was obtained in the same manner as in Example 1 except that 1.56 g of hydroxyquinoline was used instead of 0.64 g of ethylenediamine (Sample D).
).

Example 5 10 g of the sample obtained in Example 4 was heat-treated in nitrogen gas in the same manner as in Example 2 to obtain the desired metal magnetic powder (sample, E).

Example 6 In Example 1, Co(
OH)z 2.83g and Co(CslltOz)z・
The desired metal magnetic powder was obtained in the same manner except that 1.57 g of 28zo was used (sample F).

Example 7 10 g of Sample F obtained in Example 6 was heat-treated in nitrogen gas in the same manner as in Example 2 to obtain the desired metal magnetic powder (Sample G).

Example 8 The same process as in Example 7 was carried out except that kerosene was used instead of ethylene glycol.
The desired metal magnetic powder was obtained (sample H).

Example 9 The cake on which the thermal decomposition residue of the metal complex obtained in Example 7 was supported was dried in a nitrogen atmosphere, and 10 g of this dried product was dried.
in a fluidized bed reactor (inner diameter 40III + Iφ, height 200
mm) at 70°C, Ox/Nz = 1/99 (
A mixed gas (volume ratio) was aerated at a flow rate of 41/min for 30 minutes, and then dry air was changed to air for 120 minutes to carry out slow oxidation treatment to obtain the desired metal magnetic powder (Sample I).

Example 10 Sample ① obtained by slow oxidation treatment in Example 9 was subjected to the slow oxidation treatment in Example 2.
Further treatment was carried out under a nitrogen atmosphere in the same manner as in the case of Example 1 to obtain the desired metal magnetic powder (Sample J).

Comparative Example 1 A metal magnetic powder was obtained in the same manner as in Example 1 except that cobaltous hydroxide and ethylenediamine were not added (Sample K).

Comparative Example 2 A metal magnetic powder was obtained in the same manner as in Example 2, except that cobaltous hydroxide and ethylenediamine were not added (Sample L).

Using the metal magnetic powder samples of the Examples and Comparative Examples and the samples of ', H, 1, J and M among the samples, the following blended composition was mixed and dispersed to prepare a magnetic paint, and then the above-mentioned Apply magnetic paint on polyester film to a dry film thickness of 10
The saturation magnetization (σs H
ea+u/g), coercive force (Hc:Oe), saturation magnetic flux density (Bm: Gauss), squareness ratio (Rs, SQ)
Orientation (OR) and reversal magnetic field distribution (S F D) were measured. In addition, in order to evaluate the oxidation stability, the σ5SHCS was left for 4 weeks at a temperature of 60°C and a relative humidity of 80%.
Accelerated changes over time were measured for R5% Bm, and saturation magnetization deterioration rates ΔσS (%) and ΔBm (%) were determined using the following formulas.

These results are shown in Table 1 (powder properties) and Table 2 (tape properties).

Magnetic powder 5 Weight part dispersant
0.25 Polyurethane resin (30
% melt? 2.96 "Mixed solvent"
13.4 〃1 toluene/MEK/cyclohexanone (4,5/4.5/1)Bm'-B
m (In the formula, Bm' is Bm before aging, and Bm' is Bm after aging.) (In the formula, σs6 is σS before aging, and σS is σS after aging.) [Invention [Effect] The metal magnetic powder supporting the thermal decomposition residue of the metal complex obtained by the present invention has significantly improved oxidation resistance, and therefore can maintain excellent magnetic properties for a long period of time, and is Excellent storage stability, easy handling,
It is extremely preferable in terms of process control, and has good dispersibility into the medium, making it extremely suitable for producing high-output, high-recording-density magnetic media. Furthermore, the present invention is of great industrial significance, as it allows magnetic powder with excellent performance to be produced economically and advantageously using relatively simple means.

Claims (1)

[Claims] 1) At least one metal hydroxide of CO, Ni and Cu and a complexing agent or/and at least one metal complex compound of Co, Ni and Cu are combined into a metal magnetic powder. A method for producing a metal magnetic powder, which comprises contacting and thermally decomposing the hydroxide to carry a thermal decomposition residue of at least one metal complex of the constituent metals on the particle surface of the metal magnetic powder. . 2) A method for producing a metal magnetic powder, which comprises carrying the thermal decomposition residue of the metal complex on the surface of the metal magnetic powder particles according to claim 1, and then heat-treating the treated product in an inert atmosphere. 3) A method for producing metal magnetic powder, which comprises carrying the thermal decomposition residue of the metal complex on the surface of the metal magnetic powder particles according to claim 1, and then subjecting the treated product to gradual oxidation treatment in an oxidizing atmosphere. 4) A method for producing a metal magnetic powder, characterized in that the product subjected to the slow oxidation treatment according to claim 3 is then heat treated in an inert atmosphere.