JPH0470692B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field and Object] The present invention relates to a metal magnetic powder suitable for use in magnetic recording media and a processing method thereof, and an object thereof is to provide a metal magnetic powder with excellent oxidation stability. [Background technology] Metal magnetic powders such as iron, nickel, and cobalt have superior magnetic properties compared to conventional oxide-based magnetic powders. It has the disadvantage that it is extremely susceptible to oxidation, lacks oxidation stability, and its saturation magnetization decreases over time. In order to improve these drawbacks, conventional methods have been to oxidize the particle surface of metal magnetic powder to form an oxide film (Japanese Patent Publication No. 56-28961), or to use higher aliphatic acids, carboxylic acids, metal soaps, and sulfonates. acid,
These coatings are formed by treatment with organic anticorrosive agents such as amines, phosphate esters, and esters (Special Publication Act 1983-
The oxidation stability has been improved by methods such as Japanese Patent No. 54485). However, in the method of achieving oxidation stability by oxidizing the particle surface of metal magnetic powder, in order to ensure sufficient oxidation stability, the thickness of the oxide film on the particle surface must be increased. In particular, the finer the magnetic powder, the more remarkable the decrease in magnetization due to surface oxidation, which poses the problem that the high magnetization characteristic of fine metal magnetic powder cannot be maintained. In addition, in the method of treating the particle surface of metal magnetic powder with organic anticorrosive agents, the binding strength of these organic anticorrosive agents with metal ions is not very strong, so sufficient anticorrosive effects cannot be exerted, and sufficient oxidation stability is still not achieved. Not obtained. [Summary of the Invention] In view of the current situation, the present invention has been made based on various studies and has been made based on the results that, when metal magnetic powder is treated with a chelating agent and the chelating agent is deposited on the particle surface, attack by oxygen gas, etc. is prevented. A metal magnetic powder with excellent oxidation stability can be obtained by strongly preventing oxidation, and if the particle surface of the metal magnetic powder is once oxidized and then treated with a chelating agent to coat the particle surface with the chelating agent. This method was developed based on the discovery that oxidation on the particle surface was even better prevented and a metal magnetic powder with even better oxidation stability could be obtained. The method is characterized in that the chelating agent is coated on the surface of the particles of the metal magnetic powder by treatment in a solution in which the chelating agent is dissolved or in vapor of the chelating agent obtained by evaporating the chelating agent. The chelating agent used in this invention is
A compound with a chelate group or chelate ring in which two or more polydentate ligands are coordinated, and it bonds well with metal ions. Therefore, when metal magnetic powder is treated with this chelating agent, the chelating agent chelates with the metal ions on the particle surface of the metal magnetic powder and is firmly adhered to the particle surface, and the particle surface becomes a solidly bound chelate. coated with the hydrophobic part of the curing agent. As a result, the chelating agent sufficiently exhibits its antioxidant effect without reducing the amount of magnetization of the metal magnetic powder, and a metal magnetic powder with excellent oxidation stability can be obtained. In particular, if the surface of the metal magnetic powder particles is once oxidized and then treated with a chelating agent, a large amount of metal ions will be present on the surface of the metal magnetic powder particles, allowing the chelating agent to adhere even better and leaving less room for oxidation. Therefore, the oxidation-preventing effect of the chelating agent becomes even better, and a metal magnetic powder with even better oxidation stability can be obtained. In addition,
If the particle surface of the metal magnetic powder is coated with a polar metal compound, a large amount of metal ions will be present on the particle surface, similar to when the particle surface of the metal magnetic powder is oxidized, and the chelating agent will adhere more easily. Therefore, the particle surface of the metal magnetic powder may be coated with a polar metal compound in advance, and the same effect as when the metal magnetic powder is oxidized in advance can be obtained. As such a chelating agent, any of those commonly used as a chelating agent can be used, and for example, the following are preferably used. general formula (However, in the formula, R ₁ and R ₂ have 1 to 1 carbon atoms.
24 alkyl or aryl groups, R ₃ is the same as H or R ₁ ; ) β-diketones having at least one methylene hydrogen between carbonyl groups, such as acetylacetone, methylacetylacetone, ethylacetylacetone, propylacetylacetone, phenylacetylacetetone, propionylacetone, dipropionylmethane, benzoylacetone, dibenzoyl Methane, methylbenzoylacetone, methyldibenzoylmethane, etc. General formula (However, in the formula, R ₁ and R ₂ have 1 to 1 carbon atoms.
The alkyl group or aryl group of 2, R ₃ is the same as H or R ₁ . ) β-ketocarboxylic acid esters having at least one methylene hydrogen between the keto and carboxyl groups, such as methyl acetoacetate, ethyl acetoacetate, propyl acetoacetate, isopropyl acetoacetate, butyl acetoacetate, Isobutyl acetoacetate, t-butyl acetoacetate, amyl acetoacetate, hexyl acetoacetate, nonyl acetoacetate, decyl acetoacetate, etc. Aromatic o-oxyketones, such as o-oxyacetophenone o-oxy Aldehydes, e.g. salicylaldehyde Schiff bases of the above carbonyl compounds with amines, e.g. acetylacetanyl, bisacetylacetone ethylenediamine, bis-salicylaldehyde ethylenediamine, bis-salicylaldehyde-o-phenylenediamine, bis-salicylaldehyde propylenediamine , bis-acetylacetone-o-phenylenediamine general group

[expression] or (However, n is an integer of 1 or 2.) Aminoacetic acid or aminopropionic acid,
For example, ethylenediaminetetraacetic acid, ethylenediaminetetrapropionic acid, nitrilotriacetic acid, iminodiacetic acid, iminodipropionic acid, melamine hexaacetic acid, melamine hexapropionic acid or its alkali salt General group

[expression] or

[Formula] or

〔Example〕

Next, embodiments of the invention will be described. Example 1 5g of acicular fine particle metal iron magnetic powder (major diameter 0.3μ,
An axial ratio (major axis/minor axis) of 15/1, a coercive force of 1500 oersted, and a saturation magnetization of 150 emu/g) was added to 400 ml of toluene solution and stirred to thoroughly disperse it. Next, 10 ml of acetylacetone was added to this, and the mixture was further stirred to thoroughly disperse the mixture. Thereafter, it was filtered and dried at room temperature to obtain acicular fine particle metal iron magnetic powder whose surface was treated with acetylacetone. Example 2 Acicular fine particle metal iron magnetic powder surface-treated with methyl acetoacetate was obtained in the same manner as in Example 1 except that the same amount of methyl acetoacetate was used in place of acetylacetone. Example 3 Acicular fine particle metal iron magnetic powder surface-treated with n-butyl lactate was prepared in the same manner as in Example 1 except that the same amount of n-butyl lactate was used instead of acetylacetone. I got it. Example 4 Acicular fine particle metallic iron magnetic powder surface-treated with diethyl tartrate was obtained in the same manner as in Example 1 except that 5 ml of diethyl tartrate was used instead of acetylacetone. Example 5 The surface was treated with monoethanolamine in the same manner as in Example 1 except that 5 ml of monoethanolamine was used instead of acetylacetone and the same amount was used instead of toluene as the solvent. Acicular fine particle metallic iron magnetic powder was obtained. Example 6 Acetoethyl alcohol surface treatment was carried out in the same manner as in Example 1 except that the same amount of acetoethyl alcohol was used instead of acetylacetone and the same amount of ethanol was used instead of toluene as the solvent. Acicular fine particle metallic iron magnetic powder was obtained. Example 7 In the same manner as in Example 1, except that the same amount of malonic acid diethyl ester was used in place of acetylacetone, acicular fine particle metal iron magnetic powder surface-treated with malonic acid diethyl ester was obtained. Ta. Example 8 Acicular fine particle metallic iron surface-treated with o-oxyacetophenone was prepared in the same manner as in Example 1 except that the same amount of o-oxyacetophenone was used instead of acetylacetone. A magnetic powder was obtained. Example 9 Acicular fine particle metal iron magnetic powder surface-treated with salicylaldehyde was obtained in the same manner as in Example 1 except that the same amount of salicylaldehyde was used in place of acetylacetone. Example 10 Acicular fine particle metallic iron magnetic powder surface-treated with acetylacetanyl was obtained in the same manner as in Example 1 except that the same amount of acetylacetanyl was used in place of acetylacetone. Example 11 Acicular fine particle metal iron magnetic powder surface-treated with ethylenediaminetetraacetic acid was obtained in the same manner as in Example 1 except that the same amount of ethylenediaminetetraacetic acid was used in place of acetylacetone. Example 12 Acicular fine particle metallic iron magnetic powder surface-treated with dimethylglyoxime was obtained in the same manner as in Example 1 except that the same amount of dimethylglyoxime was used in place of acetylacetone. Example 13 A flask connected with a glass tube was charged with 3 g of the same acicular fine particle metal iron magnetic powder used in Example 1, and degassed using a vacuum pump. Next, air was gradually introduced to oxidize the particle surface of the metal iron magnetic powder. Thereafter, saturated vapor of acetylacetone contained in another flask was gradually introduced and adsorbed onto the particle surfaces to obtain acicular fine particles of metal iron magnetic powder surface-treated with acetylacetone. Examples 14-24 In Example 13, the surface was treated with each chelating agent in the same manner as in Example 13, except that saturated vapor of each chelating agent shown in Table 1 below was used instead of saturated vapor of acetylacetone. A treated acicular fine particle metal iron magnetic powder was obtained.

[Table] Examples 25 to 36 In each of Examples 13 to 24, acicular fine particle metallic iron was treated with the respective chelating agent in the same manner as in Examples 13 to 24, except that the oxidation in air was omitted. A magnetic powder was obtained. Examples 37 to 48 In each of Examples 1 to 12, before adding each chelating agent, oxidizing gas was blown into the dispersion of metal iron magnetic powder while heating it to change the particle surface of the metal iron magnetic powder. Acicular fine particle metal iron magnetic powder was obtained by oxidation to form an oxide film, and then treated with each chelating agent in the same manner as in Examples 1 to 12. Examples 49 to 60 The particle surface of metal iron magnetic powder was oxidized in the same manner as in Example 13, and then chelation treatment was performed in the same manner as in Examples 1 to 12, and the particles were treated with the respective chelating agents. Acicular fine particle metal iron magnetic powder was obtained. Example 61 In Example 1, instead of the acicular fine particle metallic iron magnetic powder, acicular fine particle metallic cobalt magnetic powder (major axis 0.5μ, axial ratio (major axis/minor axis) 10/1, coercive force 700) was used.
Acicular fine particle metal cobalt magnetic powder surface-treated with acetylacetone was obtained in the same manner as in Example 1, except that the same amount of Oersted, saturation magnetization 130 emu/g) was used. Example 62 In Example 13, instead of the acicular fine particle metallic iron magnetic powder, acicular fine particle metallic cobalt magnetic powder (major axis 0.5μ, axial ratio (major axis/minor axis) 10/1, coercive force 700) was used.
Acicular fine particle metal cobalt magnetic powder surface-treated with acetylacetone was obtained in the same manner as in Example 13, except that the same amount of Oersted, saturation magnetization 130 emu/g) was used. Example 63 In Example 25, instead of the acicular fine particle metallic iron magnetic powder, acicular fine particle metallic cobalt magnetic powder (major axis 0.5μ, axial ratio (major axis/minor axis) 10/1, coercive force 700) was used.
Acicular fine particle metallic cobalt magnetic powder surface-treated with acetylacetone was obtained in the same manner as in Example 25, except that the same amount of Oersted, saturation magnetization 130 emu/g) was used. Example 64 In Example 37, instead of the acicular fine particle metallic iron magnetic powder, acicular fine particle metallic cobalt magnetic powder (major axis 0.5μ, axial ratio (major axis/minor axis) 10/1, coercive force 700) was used.
Acicular fine particle metal cobalt magnetic powder surface-treated with acetylacetone was obtained in the same manner as in Example 37, except that the same amount of Oersted, saturation magnetization 130 emu/g) was used. Example 65 In Example 49, instead of the acicular fine particle metallic iron magnetic powder, acicular fine particle metallic cobalt magnetic powder (major axis 0.5μ, axial ratio (major axis/minor axis) 10/1, coercive force 700) was used.
Acicular fine particle metallic cobalt magnetic powder surface-treated with acetylacetone was obtained in the same manner as in Example 49, except that the same amount of Oersted, saturation magnetization 130 emu/g) was used. Example 66 In Example 1, instead of the acicular fine particle metallic iron magnetic powder, acicular fine particle metallic nickel magnetic powder (major axis 0.4μ, axial ratio (major axis/minor axis) 10/1, coercive force 480) was used.
Acicular fine particle metallic nickel magnetic powder surface-treated with acetylacetone was obtained in the same manner as in Example 1 except that the same amount of Oersted (saturated magnetization: 52 emu/g) was used. Example 67 In Example 13, acicular fine particle metal nickel magnetic powder (major axis 0.4μ, axial ratio (major axis/minor axis) 10/1, coercive force 480) was used instead of the acicular fine particle metal iron magnetic powder.
Acicular fine particle metallic nickel magnetic powder surface-treated with acetylacetone was obtained in the same manner as in Example 13, except that the same amount of Oersted (saturated magnetization: 52 emu/g) was used. Example 68 In Example 25, instead of the acicular fine particle metallic iron magnetic powder, acicular fine particle metallic nickel magnetic powder (major axis 0.4μ, axial ratio (major axis/minor axis) 10/1, coercive force 480) was used.
Acicular fine particle metallic nickel magnetic powder surface-treated with acetylacetone was obtained in the same manner as in Example 25, except that the same amount of Oersted (saturated magnetization: 52 emu/g) was used. Example 69 In Example 37, acicular fine particle metal nickel magnetic powder (major axis 0.4μ, axial ratio (major axis/minor axis) 10/1, coercive force 480) was used instead of the acicular fine particle metal iron magnetic powder.
Acicular fine particle metallic nickel magnetic powder surface-treated with acetylacetone was obtained in the same manner as in Example 37, except that the same amount of Oersted (saturated magnetization: 52 emu/g) was used. Example 70 In Example 49, instead of the acicular fine particle metallic iron magnetic powder, acicular fine particle metallic nickel magnetic powder (major axis 0.4μ, axial ratio (major axis/minor axis) 10/1, coercive force 480) was used.
Acicular fine particle metallic nickel magnetic powder surface-treated with acetylacetone was obtained in the same manner as in Example 49, except that the same amount of Oersted (saturated magnetization: 52 emu/g) was used. Comparative Example 1 Comparative Example 1 was obtained by omitting the chelation treatment in Example 1. Comparative Example 2 Example 13 except that the chelation treatment with saturated acetylacetone vapor was omitted in Example 13.
Acicular fine particle metal iron magnetic powder was obtained in the same manner as above. Comparative Example 3 Acicular fine particle metal iron magnetic powder was obtained in the same manner as in Example 37, except that the addition of acetylacetone was omitted. Comparative Example 4 5 g of the same acicular fine particle metal iron magnetic powder used in Example 1 was immersed in a solution of 500 mg of calcium lanophosphate dissolved in 300 ml of toluene, and stirred and mixed for 30 minutes. Thereafter, it was filtered and dried at room temperature to obtain acicular fine particle metal iron magnetic powder whose particle surface was coated with calcium lanophosphate. Comparative Example 5 Comparative Example 5 was obtained by omitting the chelation treatment in Example 61. Comparative Example 6 Example 62 except that the chelation treatment with saturated steam of acetylacetone was omitted.
Acicular fine particle metallic cobalt magnetic powder was obtained in the same manner as above. Comparative Example 7 Acicular fine particle metallic cobalt magnetic powder was obtained in the same manner as in Example 64, except that the addition of acetylacetone was omitted. Comparative Example 8 Comparative Example 4 was carried out in the same manner as in Comparative Example 4, except that the same amount of acicular fine particle metal cobalt magnetic powder as used in Example 61 was used in place of the acicular fine particle metal iron magnetic powder. Acicular fine particle metal cobalt magnetic powder whose particle surface was coated with calcium lanophosphate was obtained. Comparative Example 9 Comparative Example 9 was obtained by omitting the chelation treatment in Example 66. Comparative Example 10 Example 67 except that the chelation treatment with saturated steam of acetylacetone was omitted.
Acicular fine particle metallic nickel magnetic powder was obtained in the same manner as above. Comparative Example 11 Acicular fine particle metallic nickel magnetic powder was obtained in the same manner as in Example 69, except that the addition of acetylacetone was omitted. Comparative Example 12 Comparative Example 4 was carried out in the same manner as in Comparative Example 4, except that the same amount of acicular fine particle metal nickel magnetic powder as used in Example 66 was used in place of the acicular fine particle metal iron magnetic powder. Acicular fine particle metallic nickel magnetic powder whose particle surface was coated with calcium lanophosphate was obtained. The acicular fine particle metal magnetic powder obtained in each Example and each Comparative Example was tested for oxidation stability.
The oxidation stability test was conducted by measuring the oxidation acceleration temperature (ignition point) of each acicular fine particle metal iron magnetic powder in air using a differential thermal analyzer. Table 2 below shows the results.

〔Effect of the invention〕

As is clear from the above table, the acicular fine particle metal magnetic powders obtained by the present invention (Examples 1 to 70) have lower ignition points than the conventional acicular fine particle metal magnetic powders (Comparative Examples 1 to 12). The temperature rises by about 15°C or more, which indicates that the metal magnetic powder obtained by the present invention has excellent oxidation stability.

Claims (1)

[Claims] 1. A metal magnetic powder formed by coating a chelating agent on the surface of powder particles. 2. A method for treating metal magnetic powder, which comprises dispersing metal magnetic powder in a solution containing a chelating agent and depositing the chelating agent on the particle surface of the metal magnetic powder. 3. A method for treating metal magnetic powder, which comprises exposing the metal magnetic powder to vapor in which a chelating agent has been evaporated to deposit the chelating agent on the particle surface of the metal magnetic powder. 4 Oxidize the particle surface of the metal magnetic powder, then
A method for treating metal magnetic powder, which comprises dispersing the chelating agent in a solution and depositing the chelating agent on the oxidized particle surface of the metal magnetic powder. 5 Oxidize the particle surface of the metal magnetic powder, then
1. A method for treating metal magnetic powder, which comprises exposing the chelating agent to vapor that has evaporated it to deposit the chelating agent on the oxidized particle surface of the metal magnetic powder. 6. In oxidizing the particle surface of the metal magnetic powder, the metal magnetic powder is dispersed in a solvent, and an oxidizing gas is blown into this dispersion to oxidize the particle surface of the metal magnetic powder. A method of processing metal magnetic powder. 7. The method for treating metal magnetic powder according to claim 4, wherein the metal magnetic powder is exposed to an oxidizing gas atmosphere to oxidize the particle surface of the metal magnetic powder. 8. In oxidizing the particle surface of the metal magnetic powder, the metal magnetic powder is dispersed in a solvent, and an oxidizing gas is blown into this dispersion to oxidize the particle surface of the metal magnetic powder. A method of processing metal magnetic powder. 9. The method for treating metal magnetic powder according to claim 5, wherein in oxidizing the particle surface of the metal magnetic powder, the metal magnetic powder is exposed to an oxidizing gas atmosphere to oxidize the particle surface of the metal magnetic powder.