JP2003309031A - Rare-earth bonded magnet and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rare-earth bonded magnet with excellent corrosion resistance and its manufacturing method. <P>SOLUTION: This magnet has a coat comprising a triazine dithiol compound on the surface of a rare-earth bonded magnet that is formed by kneading the powder of a rare-earth alloy with a resin and an oxidation-resistant resin layer on this coat. The coat on the surface of the magnet is formed by an electrolytic treatment in the solution of the triazine-base compound comprising a mercapto group. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare earth bonded magnet having improved oxidation resistance and a method for manufacturing the same.

[0002]

2. Description of the Related Art With the development of electric appliances in recent years, the demand for rare earth bonded magnets as high-performance magnets that can be reduced in weight and size is increasing, and further improvement in performance is required. A typical rare earth magnet having high characteristics is an Nd-Fe-B magnet. However, this magnet alloy contains an Nd-Fe alloy phase that is extremely easily oxidized in the structure, and further, Nd ₂ F
Since the e ₁₄ B phase is also easily oxidized, the deterioration and variation of the magnetic characteristics due to the oxidation of the magnet are larger than that of the Sm—Co based magnet. 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 contaminate peripheral parts.

[0003]

As a method for solving this problem, JP-A-60-54406 and JP-A-60-54406 are available.
No. 63903 has been proposed. However,
The oxidation-resistant coatings proposed in these publications use a large amount of water in the coating forming step, so that the magnet material is oxidized in the treatment step and a trace amount of water remains even after the treatment. In many cases, it is oxidized as a cause, and it cannot be said that the oxidation resistance is sufficient.

In addition, in the coating method which is a general method of rust preventive surface treatment of metal, since the base material of the coating material is an organic polymer, the affinity with the metal is insufficient, and the magnet is used in the process of forming parts or during use. It is easy for cracks and peeling to occur, and in the case of reaction-curable coatings, the change over time in traces of unreacted functional groups may cause rusting. At present, the properties are insufficient and the applications are limited.

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 magnet, 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 corrosion resistance cannot be expected.

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 corrosion resistance and a method for producing the same.

[0007]

According to the present invention, a powder of a rare earth alloy is kneaded and molded with a resin, and a triazine compound containing at least one mercapto group represented by Chemical formula 2 on the surface (provided that M ₁ And M ₂ is H, an alkali metal or an alkaline earth metal, R is NHR ₁ , NR ₁ R ₂ or S
H and R ₁ and R ₂ are rare earth bonded magnets characterized by having a coating film made of H, an alkyl group or a phenyl group) and an oxidation resistant resin layer on the coating film.

[0008]

[Chemical 2]

The present invention is also the above-mentioned method for producing a rare earth bonded magnet, characterized in that a coating film is formed on the surface by electrolytic treatment in a solution of the triazine compound.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention suppresses oxides formed on the surface of a rare earth bonded magnet, so that a strong and stable triazine compound containing a mercapto group on the surface (hereinafter referred to as a triazine compound) is used. After providing the oxidation resistant coating, the oxidation resistant resin layer is laminated.

As a method for coating the oxidation resistant coating, an organic solvent solution of a triazine compound is used as an electrolytic solution, a magnet is used as an anode, a liquid temperature is 0 to 80 ° C., a voltage is 20 V or less, and a current density is 10 mA / dm ^2. 10 seconds at 0.1 A / dm ²
Electrolyze for 10 minutes.

In the above-mentioned electrolytic solution, the triazine ring dissociates into negative ions, so when a triazine compound containing two mercapto groups is electrolyzed, the triazinedithiol compound is electrodeposited on the metal surface of the anode to form a film. .

The film formed from the triazine-based compound on the surface of the magnet has extremely high corrosion resistance as compared with conventional chemical conversion coatings.
It has excellent durability and has a strong bond with the metal surface. Furthermore, since water repellency and lubricity are imparted, it is possible to prevent water landing, ice landing and the like.

The triazine-based compound is a compound represented by the following chemical formula 3.

[0015]

[Chemical 3]

As the binder resin, olefin resins such as polyethylene and polypropylene, polyamide resins such as nylon 6 and nylon 12, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, ethylene-vinyl acetate copolymer, Ethylene-ethyl acrylate copolymer, polyphenylene sulfide, and modified types of these resins are used.

The electrolytic solution can be prepared by dissolving a triazine compound in an organic solvent. As the organic solvent, almost any organic solvent can be used as long as it has a low viscosity in the temperature range of 0 to 80 ° C. For example, alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, ethyl cellosolve, acetone, ketones such as methyl ethyl ketone, amides such as dimethylformamide, ethers such as ethyl acetate, furan such as tetrahydrofuran, benzene, toluene. Aromatic hydrocarbons such as can be used. The concentration of the triazinedithiol compound is 1 × 10 ⁻¹ to 1 × 10 ⁻⁶ mol / l,
It is preferably 5 × 10 ^{−2 to} 5 × 10 ⁻⁴ mol / l.

For the cathode, an insoluble material is used in order to prevent the eluate from the cathode from being mixed in the coating film. Examples of such a material include platinum, titanium, stainless steel, carbon, graphite and the like. Electrolysis for liquid temperature 0
Adjusted to 80 ℃, voltage 20V or less, current density 10mA
/ Dm ^{2 to} 10 A / dm ² for 0.1 seconds to 10 minutes.
When the liquid temperature is lower than 0 ° C, it takes a long time to form a coating film, and when the liquid temperature is higher than 80 ° C, it becomes difficult to control the thickness of the coating film. It forms unevenly on the metal surface. Furthermore, if the current density is less than 10 mA / dm ² ,
No coating is formed, and if it is larger than 10 A / dm ² ,
The coating film becomes uneven. The electrolysis time is 0.1
If it is less than a ^second , even if the current density is 10 A / dm ² ,
If a coating cannot be formed on the entire metal surface and it exceeds 10 minutes,
The coating becomes an insulator, making electrolysis difficult.

As the oxidation resistant resin layer laminated on the surface of the oxidation resistant coating, synthetic resin for paint such as epoxy resin, thermosetting acrylic resin, alkyd resin, melamine resin, silicone resin or a composite resin of these resins is used. The above resin may contain a rust-preventive pigment such as zinc oxide, zinc chromate, and red lead, or benzotriazole It may be contained.

Further, in the present invention, as a method for coating the surface of the permanent magnet with the oxidation resistant resin, a method of coating after applying it by a general coating method such as a brush coating method, a spray method, a dipping method, an electrodeposition method or the like is used. However, the resin layer may have a thickness of 5 μm or more, and if it exceeds 25 μm, it becomes difficult to obtain the dimensional accuracy of the product.

[0021]

EXAMPLES The present invention will be described below with reference to examples.

Example 1 Nd was used as a rare earth alloy powder.
A powder having a composition of 31 wt% -B1.1 wt% -the balance of Fe was prepared. Nylon 12 is mixed with this powder, and compression molding is performed by a press machine to obtain 10 mm x 10 mm x 10 mm.
A bonded magnet having the dimensions of was prepared.

Next, the concentrations of 2-dibutylamino-4,6-dithiol-S-triazine and LiClO ₄ (supporting electrolyte) were 5 × 10 ⁻² mol / l and 5 respectively.
An ethyl alcohol electrolyte solution having a ^{concentration of} × 10 ^-4 mol / l was prepared. Using this electrolytic solution, the acetone-washed Nd-Fe-B bonded magnet sample piece was used as an anode and a stainless steel plate (SUS304) was used as a cathode, and the liquid temperature was 25 to 30 ° C.
At a current density of 1.0 to 2.0 A / dm ² for 10 to 240 seconds to form an oxidation resistant film.

Thereafter, a paint of polyamideimide resin and acrylic resin was spray applied to this sample piece,
It heated at 100-200 degreeC for 20 minutes, and obtained the rare earth bond magnet which has a transparent resin layer on the sample piece surface.

The generated film thickness was 5 μm at the minimum and 15 μm at the maximum. However, the film thickness can be arbitrarily set depending on the number of sprays.

Example 2 A test prepared in the same manner as in Example 1.
Using a test piece, 2-oleylamino-4,6 as an electrolytic solution
-Concentration of dimercapto-S-triazine monosodium
Is 5 × 10^-4Mol / l, LiClO_FourCost of supporting electrolyte
LiBF used instead_FourConcentration of 5 × 10 ^-4Mol / l
Electrolyzed under the same conditions as in Example 1, using
A protective coating was obtained.

Thereafter, a paint of polyamideimide resin and acrylic resin was spray applied to this sample piece,
It heated at 100-200 degreeC for 20 minutes, and obtained the rare earth bond magnet which has a transparent resin layer on the sample piece surface.

Table 1 shows the results of the 72-hour 5% saline spray test and the goose eye test of the test pieces thus obtained and untreated test pieces for comparison.

[0029]

[Table 1]

From Table 1, no rust was found on the surfaces of Examples 1 and 2, but rust was found in Comparative Examples in which no oxidation resistant film was formed. It can be seen that, in both Example 1 and Example 2, good results were obtained in the results of the salt spray test and the goose eye test.

[0031]

As described above, since the rare earth bonded magnet according to the present invention has the oxidation resistant coating and the oxidation resistant resin layer sequentially laminated on the surface, it has excellent corrosion resistance and durability and stable characteristics. It is extremely effective in improving reliability and reliability.

Claims (2)

[Claims] 1. A triazine-based compound (provided that M ₁ and M ₂ are formed by kneading and molding a rare earth alloy powder with a resin and containing at least one mercapto group represented by Chemical formula 1 on the surface.
Is H, alkali metal or alkaline earth metal, R is NH
A rare earth bonded magnet, characterized in that it has a coating made of R ₁ , NR ₁ R ₂ or SH, and R ₁ and R ₂ are H, an alkyl group or a phenyl group, and an oxidation resistant resin layer on the coating. [Chemical 1] 2. The method for producing a rare earth bonded magnet according to claim 1, wherein a coating film is formed on the surface by performing an electrolytic treatment in a solution of the triazine-based compound.