JP2003092210A - Rare-earth bonded magnet having superior oxidation resistance, and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an oxidation-resistant coating on the surface of each particle of rare-earth alloy powder, and to improve the reliability of a bonded magnet obtained by using the resulting alloy powder. SOLUTION: On the surface of each particle of the alloy powder, a coating is formed obtained by reacting it and the derivative of triazinedithiol on each other. Specifically, after adding a solution of such compound as 2- dibuthylamino-4,6-dithiol-S-triazine of 1-3 pts.wt., which is obtained by dissolving it in an organic solvent, to the alloy powder 100 pts.wt. and fully agitating them, the solvent is removed to form an oxidation-resistant coating on the surface of each particle of the alloy powder. Thereafter, the alloy powder and a binder are kneaded and mixed with each other, to mold the resulting substance into the bonded magnet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare earth bond magnet obtained by molding a mixture obtained by kneading a rare earth alloy powder and a binder made of a polymer compound, and more particularly to a rare earth bond magnet having improved oxidation resistance. The present invention relates to a magnet and a manufacturing method thereof.

[0002]

2. Description of the Related Art As a high-performance magnet which is lightweight and can be miniaturized in response to the recent demand for miniaturization of electric and electronic equipment,
The demand for rare earth bonded magnets is increasing, and further improvement in performance is required. A typical rare earth magnet having high characteristics is an Nd-Fe-B magnet. This magnet alloy contains an Nd-Fe alloy phase which is extremely easy to oxidize in its structure, and further R ₂ Fe ₁₄ B is also easily oxidizable, so that Sm-
Compared to Co, the deterioration and variation of the magnetic characteristics due to the oxidation of the magnet are large.

Further, when incorporated in a device such as a magnetic circuit, there is a possibility that the oxides generated from the magnet may be scattered to cause contamination of peripheral parts.

As a method for solving this problem, it has been proposed to apply a plating film to the surface of the rare earth alloy powder or the surface of the molded magnet. However, the proposed oxidation resistant coating uses a large amount of water during the coating formation process,
In many cases, the magnet material is oxidized during the treatment process or is oxidized even after the treatment due to the residual of a small amount of water, and it is difficult to say that the oxidation resistance is sufficient.

Further, in the coating method, which is a general method of rust-proof surface treatment of metal, since the base material of the coating material is an organic polymer,
Insufficient affinity with metals, cracks and peeling are likely to occur during the process of making magnet parts and during use.In particular, in the case of reaction hardening type paint, traces of unreacted functional groups change over time with rust. In some cases, such an alloy system is currently unreliable and has limited applications. In addition, it is practically impossible to apply the coating treatment to the surface of the powder used as the raw material of the rare earth bonded magnet, because of the great difficulty in workability.

Further, in the oxidation prevention method by forming a metal film using sputtering or ion vapor deposition, it is difficult to uniformly coat the entire alloy powder, and the coating layer structure has a directivity in the direction perpendicular to the underlying surface. Therefore, there is a problem that a fine gap is generated in the coating layer and sufficient oxidation resistance cannot be expected.

[0007]

SUMMARY OF THE INVENTION Therefore, in view of the above-mentioned drawbacks, a technical object of the present invention is to provide a rare earth bonded magnet having more excellent oxidation resistance and a method for producing the same.

[0008]

The present invention is a conventional coating,
This was made as a result of studying a method for forming a stronger oxidation resistant coating on the surface of the rare earth alloy powder by using a method completely different from electrolytic plating, sputtering, ion vapor deposition and the like.

That is, the present invention relates to a rare earth alloy powder and a binder.
In a rare-earth bonded magnet obtained by kneading and forming
The earth alloy powder has 1,3,5-triazine on its surface.
-R at any one of positions 2, 4, and 6 and the rest at -SM [R
Is SH or NR₁R_TwoAnd R ₁, R_TwoIs hydrogen, alk
Group, phenyl group, M is hydrogen, alkali gold
Genus or alkaline earth metal, S for sulfur, N for nitrogen
At least the triazinedithiol derivative substituted with
Also has an oxidation-resistant coating formed of one type.
And a rare-earth bonded magnet.

The present invention also relates to the surface of rare earth alloy powder.
The position of 2,3,5-triazine
-R for the other, -SM for the rest [R is SH or NR₁R_Two
And R ₁, R_TwoIs hydrogen, alkyl group or phenyl group
Or M is hydrogen, alkali metal, or alkaline earth metal
Or S is sulfur and N is nitrogen]
Oxidation resistance of at least one dithiol derivative
Characterized by kneading and forming with a binder after forming a film
The method for producing a rare earth bonded magnet described above.

[0011]

The film formed from the triazinedithiol derivative on the surface of the alloy powder is extremely superior in corrosion resistance and durability as compared with the conventional chemical conversion film and has a large bonding force with the metal surface. Furthermore, since water repellency and lubricity are imparted, it is possible to prevent water, ice, etc. In addition, a thin film that is inexpensive and is difficult to peel off can be formed in a short time.

There are various methods for forming an oxidation resistant film obtained from a triazinedithiol derivative on the surface of a rare earth alloy powder, and typical methods are as follows.
A solution of the triazinedithiol derivative dissolved in an organic solvent is added to the alloy powder and mixed, and then the solvent is removed by drying.The alloy powder is put into a mixer and the inside of the mixer tank is filled with nitrogen or argon. There is a method of dropping and mixing the triazinedithiol derivative while maintaining the atmosphere of active gas.

The organic solvent is not particularly limited as long as it is a liquid having a low viscosity in the temperature range of 0 to 80 ° C., and most of them can be used. For example, alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, ethyl cellosolve, acetone, ketones such as methyl ethyl ketone, amides such as dimethylformamide, esters such as ethyl acetate, furan such as tetrahydrofuran, benzene, toluene. Aromatic hydrocarbons such as can be used.

The amount of the triazinedithiol derivative added is 0.1 to 5 parts by weight based on 100 parts by weight of the alloy. This amount is appropriately adjusted depending on the particle size of the alloy powder, the particle size distribution, the type of the triazinedithiol derivative, and the like.

As the polymer compound used as the binder, polyolefins such as polyethylene and polypropylene, polyamide resins such as nylon-6 and nylon-12, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, and ethylene-vinyl acetate. Copolymers, ethylene-ethyl acrylate copolymers, polyphenylene sulfide, and resins of these modified types are used.

Further, depending on the type of the triazinedithiol derivative, there are those which increase the affinity between the metal and the polymer compound, and those which suppress the corrosion of the metal and the decomposition of the polymer compound. Various properties may be improved by using a combination of two or more species.
Further, it is arguable that the oxidation resistance can be further improved by subjecting the magnet surface after molding to treatment such as electrolytic plating and painting.

[0017]

EXAMPLES Next, specific examples of the present invention will be described.

Example 1 As a rare earth alloy powder, an alloy having a composition of neodymium of 31% by weight, boron of 1.1% by weight, and the balance of iron was prepared by pulverizing to an average particle size of 50 μm. 100 parts by weight of this alloy powder is charged into a mixer, 3 parts by weight of 2-dibutylamino-4,6-dithiol-S-triazine is dissolved in isopropyl alcohol, and the mixture is stirred for 1 hour and then vacuum dried to obtain isopropyl. The alcohol was removed.

Next, with respect to 100 parts by weight of this powder, 9
By weight, nylon-12 was mixed and kneaded with a twin-screw extruder, and the resulting mixture was compression-molded by hot pressing to obtain a cubic bonded magnet having one side of 10 mm. A salt spray test was conducted on this bonded magnet under the condition that 5% saline was sprayed for 72 hours. In addition, a cross-cut test was also conducted. Table 1 shows the results of these tests.

[0020]

[Table 1]

(Example 2) A bonded magnet obtained under exactly the same conditions as in Example was subjected to electrolytic nickel plating. The same test as in Example 1 was conducted also for this, and the results are shown in Table 1 as in Example 1.

(Example 3) 2-dibutylamino-4,6
-A bonded magnet was obtained under exactly the same conditions except that the addition amount of dithiol-S-triazine was 1 part by weight with respect to 100 parts by weight of the rare earth alloy powder, the same test as in Example 1 was performed, and the results were carried out. The results are shown in Table 1 as in Example 1.

(Example 4) The bonded magnet of Example 3 was subjected to electrolytic nickel plating to obtain a bonded magnet, and the same test as in Example 1 was conducted. The results are shown in Table 1 as in Example 1.

Comparative Example For comparison, a bonded magnet obtained by using a rare earth alloy powder not surface-treated with a triazinedithiol derivative under the same conditions as in Example 1, and the above The same test as in Example 1 was performed on the sample in which the bonded magnet was subjected to electrolytic nickel plating, and the results are shown in Table 1 as in Example 1.

According to the results shown in Table 1, in the bonded magnet using the rare earth alloy powder which was not surface-treated with the triazinedithiol derivative, rust was observed without nickel plating. In contrast,
No rusting was observed in the bonded magnet obtained by subjecting the rare earth alloy powder to the surface treatment with the triazinedithiol derivative, regardless of the presence or absence of nickel plating.

[0026]

As described above, since the rare earth bonded magnet obtained by the present invention has the oxidation resistant coating on the surface of the rare earth alloy powder as the raw material, it is excellent in the oxidation resistance and the durability, and the conventional products. Compared with, the stability and reliability of the characteristics are improved.

Further, in the examples, an example was shown in which a thermoplastic polymer compound was used as a binder and compression molding was performed by hot pressing. However, injection molding type or thermosetting polymer compound was used for compression molding. For raw material powder used for bond magnets,
It was confirmed that the same excellent effect can be obtained even if an oxidation resistant film is formed with the triazinedithiol derivative.

Claims (2)

[Claims] 1. A rare earth alloy powder and a binder are kneaded and molded.
In the rare earth bonded magnet, the rare earth alloy powder
Is the 2,3,5-triazine 2,4,6 position on the surface.
-R for any of the positions and -SM for the rest [R is SH or N
R₁R_TwoAnd R ₁, R_TwoIs hydrogen, alkyl group, phenyl
Any of the groups, M is hydrogen, alkali metal, alkaline earth
Any of the metals, S for sulfur, N for nitrogen]
Formed by at least one riadine dithiol derivative
Rarely characterized by having an oxidation resistant coating formed
Earth bond magnet. 2. The surface of the rare earth alloy powder is 1,3,5-
-R at any of positions 2, 4, and 6 of triazine, balance
-SM [R is SH or NR₁R_TwoAnd R ₁, R_TwoIs
Hydrogen, an alkyl group, a phenyl group, M is hydrogen,
Alkali metal or alkaline earth metal, S is Io
C, N is nitrogen] substituted triazinedithiol derivative
After forming an oxidation resistant coating with at least one of
The kneading and molding with a binder, according to claim 1.
Manufacturing method of rare earth bonded magnet.