JP3430686B2 - COMPOUND FOR HIGH CORROSION RESISTANCE BOND MAGNET, BOND MAGNET, AND PROCESS FOR PRODUCING THEM - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare earth-based bonded magnet excellent in corrosion resistance, its raw material compound, and a method for producing them.

[0002]

2. Description of the Related Art Bonded magnets produced by molding rare earth magnet powders having excellent magnetic properties using a thermoplastic or thermosetting synthetic resin as a binder contain a resin, so that conventional sintered magnets are used. Although the magnetic performance is lower than that of, it still has sufficiently high magnetic performance. In addition, because it has features not found in sintered magnets, such as complicated thin-walled magnets and radial anisotropic magnets, which are easily obtained, it is often used in small motors such as spindle motors and stepping motors, and demand has increased in recent years. is doing.

Although the rare earth magnet powder as a raw material has high magnetic properties, for example, one or more elements selected from R-Fe-B series (R is a rare earth element containing Y, especially
In the case of Nd) magnet powder, the active rare earth element and iron occupy most of the composition, so they are susceptible to air oxidation and corrosion.

Therefore, in the production of bonded magnets,
First, the surface of the rare earth magnet powder is mixed with a liquid binder resin to prepare a raw material powder called a compound, the powder surface of which is coated with a resin, and the compound is injection molded or compression molded, and the binder is a thermosetting resin. In this case, the product is obtained by further heating to cure the resin. However, even if the magnet powder is coated with the resin as described above, there is a problem that the oxidation and the corrosion proceed rapidly especially in a high temperature and high humidity environment, and the magnetic performance is deteriorated accordingly.

As means for improving the corrosion resistance (oxidation resistance) of bond type magnets, JP-A-1-102901 and JP-A-3-102901.
As disclosed in Japanese Patent No. 74810, it is known that the surface of a rare earth magnet powder is treated with a coupling agent such as a silane coupling agent before mixing with a binder resin. It was insufficient.

JP-A-3-191501 discloses that after a rare earth magnet powder is surface-treated with a coupling agent, an organic resin film is further formed on the powder surface by a plasma polymerization method utilizing glow discharge, and then a binder is used. There has been proposed a method for producing a bonded magnet, which is mixed with a resin and molded. However, this method requires two kinds of treatments, namely, a surface treatment with a coupling agent and a plasma polymerization before mixing with a resin, which complicates the process and, as shown in Examples,
Since it takes a long time of 40 minutes to form a resin film by plasma polymerization, it is not suitable for industrialization.

[0007]

In the bonded magnet, the magnet powder is covered with the magnet, and it is considered that the oxidation resistance is not a problem, but in reality, the adhesiveness between the resin and the powder is poor. In some cases, the coating was partly peeled off during molding and the surface of the magnet powder was partially exposed in many cases, and water and oxygen entered the interface of the magnet powder / resin, and oxidation sometimes proceeded. In particular, when used at high temperatures, the oxidation proceeded rapidly, and the magnetic performance was greatly reduced.

Since the present invention has an active surface, it is corrosion resistant.
(Oxidation resistance) R-Fe-B based rare earth magnet powders with poor heat resistance, while maintaining high initial magnetic characteristics, with a corrosion resistant and heat resistant compound for bonded magnets and this compound It is an object of the present invention to provide bonded magnets, and manufacturing methods thereof.

[0009]

The inventors of the present invention have noticed that a uniform resin film can be formed by a vapor deposition polymerization method at a relatively high film forming rate, and this resin film is used for surface treatment of rare earth magnet powder. As a result, they found that the oxidation resistance of the magnet powder can be remarkably enhanced, and completed the present invention.

Here, the gist of the present invention is that the rare earth magnet powder surface has an inner layer resin film formed by a vapor deposition polymerization method and a thermosetting or thermoplastic outer layer resin film. It is a compound for corrosion resistant bonded magnets.

This compound for a highly corrosion-resistant bonded magnet is obtained by vacuum-depositing vapors of two or more kinds of polycondensable monomers on the surface of rare earth magnet powder, and polymerizing on the surface of the powder to form an inner layer resin film, It can be produced by mixing the powder with a thermosetting or thermoplastic synthetic resin liquid to form an outer resin film on the inner resin film.

According to the present invention, there is also provided a highly corrosion resistant bonded magnet produced from the above compound, and a method for producing a highly corrosion resistant bonded magnet including the steps of extruding, injecting or compression molding the above compound. .

[0013]

The present invention will be described in detail below. The magnet powder used in the present invention may be any conventionally known rare earth magnet powder, for example, rare earth / iron magnet and rare earth / cobalt alloy magnet powder. A typical example of the rare earth / iron-based alloy is an alloy having an R-Fe-B-based or R-Fe-N-based composition. Here, R is one or more elements selected from rare earth elements including Y, and is preferably Nd or a mixture of Nd and one or more other rare earth elements. Fe
A part of may be replaced by Co. A typical example of rare earth / cobalt alloy is Sm-Co alloy. These may be manufactured by known methods or may be commercially available products. Further, the magnet powder may be either magnetic isotropic or magnetic anisotropy.

According to the present invention, inner and outer two-layer resin coatings are formed on the surface of the raw material rare earth magnet powder. The inner layer is a thin resin film formed by vapor deposition polymerization and functions as a protective film for the magnet powder. The outer layer is a resin film formed by mixing with a binder resin as in the conventional case, and also has a binder function.

The vapor deposition polymerization method for forming the inner layer resin film is usually carried out by placing vapors (gas phase monomers) of two or more polycondensation-polymerizable monomers consisting of an acid component and a base (amine) component in a vacuum chamber. By vapor-depositing on a substrate and then heating the substrate, or by heating the substrate during vacuum vapor deposition, the vaporized monomer is polymerized on the substrate to form a resin film made of a condensation-polymerized polymer on the substrate. Is the way.

The resin film formed by the vapor deposition polymerization method is
It has high adhesion strength to the magnetic powder of the substrate, high purity and denseness, smooth surface, and excellent film thickness uniformity. Therefore, a thin film having a thickness of several μm or less, for example, 1 μm can sufficiently protect the substrate from oxidation. Further, in the vapor deposition polymerization method, the rate of formation of the vapor deposited film is relatively high at 1 μm / min, so that the required resin film can be formed in about several minutes.

Examples of monomers applicable to the vapor deposition polymerization method include terephthaloyl chloride, 4,
4'-biphenyldicarbonyl chloride, pyromellitic dianhydride, 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride, trimellitic anhydride chloride, terephthalaldehyde, 4,4'-diphenylmethane diisocyanate Etc. As the base component, 4,4'-diaminodiphenyl ether, p-phenylenediamine, 4,4'-diaminodiphenylmethane, 3,3'-diaminobenzophenone, 3,3 '
-Dimethylbenzidine, N, N'-bis (trimethylsilyl) bis (4-aminophenyl) ether, N, N'-bis
(Trimethylsilyl) -p-phenylenediamine and the like are exemplified. The resin formed by these acid and base components is polyamide, polyimide, polyamideimide, polyazomethine, polyurea or the like.

Among them, aromatic polyamides have low oxygen permeability (for example, J. Appl. Polym. Sci., 25, 1391 (198
(See (0)) and the temperature of the substrate (rare earth magnet powder in the case of the present invention) is relatively low (generally 200 ° C. or lower, for example, 100 ° C. or lower).
Polymerization occurs at (° C. or lower), so that there is no deterioration of magnetic properties due to heating of the magnet powder as a base, which is particularly preferable.

According to the vapor deposition polymerization method, after the gas phase monomer reaches the surface of the magnet powder of the substrate, the reaction occurs while moving around the surface of the powder to cause polymerization. Therefore, the polymer film is formed by penetrating even minute cracks on the surface of the magnet powder.
In addition, since each of the gas phase monomers has a polar functional group such as a carboxylic acid group or its derivative group, or an amino group, it has excellent affinity with the surface of the magnet powder.
It also has excellent compatibility with synthetic resins formed on vapor-deposited polymer films.

Therefore, the resin film of the inner layer formed by the vapor deposition polymerization method seals the defective portion of the magnet powder and, at the same time, directly bonds to the magnet surface of the base and the resin film of the outer layer. As a result, the inner layer resin film has significantly higher adhesion to the magnet powder than the resin film formed by simply mixing the magnet powder and resin, peels off from the magnet powder surface during molding, and water and oxygen penetrate into the interface. Therefore, it was found that it is very effective in improving the corrosion resistance (oxidation resistance) and heat resistance of the magnet powder.

Also, unlike the method described in the above-mentioned Japanese Patent Laid-Open No. 3-191501, there is no need for surface treatment with a coupling agent before forming the inner layer resin film, and the vapor deposition polymerization method has a high film forming rate. The inner layer resin film can be formed in a relatively short time. The thickness of the resin film of the inner layer formed by the vapor deposition polymerization method is appropriately determined in consideration of the required degree of corrosion resistance and economical efficiency, but the preferable thickness is 0.5 to 20 μm, and more preferably 0.5 to 5 μm. As shown in the examples, a thin film having a thickness of 1 μm can sufficiently provide the magnet powder with corrosion resistance and heat resistance.

After the vapor deposition polymerization, a thermoplastic or thermosetting synthetic resin is coated on the resin film of the formed inner layer as in the conventional compound for bonded magnets to form a resin film of the outer layer. The resin type of the outer layer coating is not particularly limited,
As the thermoplastic resin, polyamide resin, polypropylene resin, polyphenylene sulfide resin, etc. can be used,
As thermosetting resin, epoxy resin, phenol resin,
A polyester resin or the like is suitable. In the case of a thermosetting resin, a curing agent and a curing accelerator are used together if necessary.

The resin coating of the outer layer can be carried out by mixing magnet powder having an inner layer resin film formed by vapor deposition polymerization with a thermosetting or thermoplastic synthetic resin liquid. As the synthetic resin liquid, a resin which is liquid at the coating temperature may be used as it is, or a solution, suspension or emulsion in which a solid or liquid resin is dissolved, suspended or emulsified in an appropriate organic solvent. Good. If desired, a small amount of additives such as a lubricant and a silane coupling agent may be added to the resin liquid.

After the above magnet powder is thoroughly mixed with the synthetic resin solution and dried if necessary to remove the solvent, an outer resin film is formed on the inner resin film, and the compound for a bonded magnet of the present invention is obtained. can get.

The compound of the present invention having a resin film of two layers inside and outside is molded by extrusion, injection, or compression molding as in the conventional case. When the raw rare earth magnet powder has magnetic anisotropy, when a magnetic field is applied during molding, an orientation occurs in which the easy magnetization directions of the magnet powders are aligned in the same direction, and the magnetic properties are Since it is possible to obtain an improved permanent magnet, it is preferable to perform molding under the application of a magnetic field.

In general, extrusion molding and injection molding require the flow of the compound during molding, so that it is applied when the outer layer resin is a thermoplastic resin, and it is necessary to form the resin film of the outer layer relatively thick. . The coating amount of the outer layer resin is appropriately in the range of 5 to 20% by weight based on the raw material magnet powder.

On the other hand, since the flow of the compound is not required in the compression molding, a thermosetting resin having excellent heat resistance can be used as the outer layer resin. A thermosetting resin that is solid at room temperature is preferably used as the outer layer resin in order to facilitate the introduction into the mold. In the case of compression molding, the coating amount of the outer layer resin may be as small as 1 to 4% by weight based on the magnet powder. Therefore, the compression molding can increase the filling amount of the magnet powder, and a bonded magnet having more excellent magnetic performance can be obtained.

After molding, particularly when the outer layer resin is a thermosetting resin, the resin is cured by heating if necessary. The heating atmosphere at this time is to avoid oxidation of the magnet powder,
An inert atmosphere is preferable. When molding at a high temperature such as extrusion or injection molding, it is preferable to carry out molding in an inert atmosphere. If necessary, the obtained bonded magnet may be subjected to surface treatment such as painting or plating according to a conventional method.

[0029]

The present invention will be described in more detail with reference to the following examples. In the examples, parts are parts by weight unless otherwise specified.

Manufacture of raw material magnet powder Nd: 13%, Co: 12%, Ga: 1%, B: 6% by atomic fraction,
An alloy having a composition in which the balance was Fe was held in hydrogen gas at 970 to 1170 K and decomposed into Nd hydroxide, Fe ₂ B and Fe. Next, the hydrogen pressure was lowered in this temperature range to dissociate the hydrogen from the Nd hydroxide to prepare a magnet powder having a magnetic anisotropy composed of fine Nd ₂ Fe ₁₄ B crystals. The obtained magnet powder was further pulverized and classified, and powder having a particle size range of 63 to 297 μm was used as a raw material magnet powder.

(Example 1) A raw material magnet powder was placed in a vacuum chamber,
Two kinds of gas phase monomers generated by separately heating and evaporating both monomers of terephthaloyl chloride and 4,4'-diaminodiphenyl ether were introduced into a vacuum chamber, and under vacuum (achieved vacuum degree 8 × 10 ^-4 The inner layer resin film made of aromatic polyimide having a thickness of 1 μm was formed on the magnet powder surface by vapor deposition polymerization on the powder surface heated to 100 ° C.
The time required to form this inner layer film was about 1 minute.

On the other hand, 100 parts of a cresol novolac type epoxy resin which was solid at room temperature and 3 parts of a phenolic curing agent were dissolved in methyl ethyl ketone as a solvent to obtain a resin liquid. The above magnet powder coated with an inner layer resin by vapor deposition polymerization and the resin liquid were sufficiently mixed at a ratio of 97 parts of magnet powder: 3 parts of epoxy resin (solid content), and then methyl ethyl ketone was evaporated at room temperature to form a compound. It was made.

(Example 2) The raw material magnet powder was placed in a vacuum chamber,
Two kinds of gas phase monomers generated by separately heating and evaporating both monomers of terephthaloyl chloride and p-phenylenediamine were introduced into a vacuum chamber, and under vacuum (achieved vacuum degree 2
The inner layer resin film made of aromatic polyamide having a thickness of 1 μm was formed on the surface of the magnet powder by vapor deposition polymerization on the surface of the powder heated to × 10 ⁻³ torr) and 170 ° C. The time required to form this inner layer film was about 1 minute. The magnet powder thus coated with the inner layer resin was mixed with the epoxy resin solution in the same manner as in Example 1 to obtain a compound after solvent evaporation.

(Example 3) A raw material magnet powder was placed in a vacuum chamber,
Two kinds of gas phase monomers generated by separately heating and evaporating both monomers of terephthaloyl chloride and N, N'-bis (trimethylsilyl) bis (4-aminophenyl) ether were introduced into the vacuum chamber, and vacuum was generated. Lower (Ultimate vacuum degree 2 × 10 ^-3 tor
r), the inner surface resin film made of aromatic polyamide having a thickness of 1 μm was formed on the surface of the magnet powder by vapor deposition polymerization on the surface of the powder heated to 60 ° C. The time required to form this inner layer film was about 1 minute. The magnet powder thus coated with the inner layer resin was mixed with the epoxy resin solution in the same manner as in Example 1 to obtain a compound after solvent evaporation.

Comparative Example 1 100 parts of a cresol novolac type epoxy resin which was solid at room temperature and 3 parts of a phenolic curing agent were dissolved in methyl ethyl ketone as a solvent to obtain a resin solution.
After thoroughly mixing the raw material magnet powder and the resin liquid in the ratio of 97 parts of magnet powder: 3 parts of epoxy resin (solid content), methyl ethyl ketone was evaporated at room temperature to prepare a compound.

Comparative Example 2 100 parts of raw material magnet powder was mixed with 1 part of γ-glycidoxypropyltrimethoxysilane and an aqueous ethanol solution (water: ethanol was mixed at a volume ratio of 1: 9).
Mix well with 2 parts, then 2 at 80 ° C in a nitrogen atmosphere.
After drying for an hour, the magnet powder was surface-treated with a silane coupling agent.

On the other hand, 100 parts of a cresol novolac type epoxy resin which was solid at room temperature and 3 parts of a phenolic curing agent were dissolved in methyl ethyl ketone as a solvent to obtain a resin liquid. The magnet powder surface-treated with the above silane coupling agent and the resin liquid were thoroughly mixed in a ratio of 97 parts of magnet powder: 3 parts of epoxy resin (solid content), and then methyl ethyl ketone was evaporated at room temperature to prepare a compound. did.

Production of Bonded Magnets The compounds produced in each of the above Examples and Comparative Examples were compression-molded in a magnetic field of 12 kOe at a pressing force of 8 ton / cm ² . The molded body thus obtained was heated in an argon atmosphere at 150 ° C. for 1 hour to cure the resin and produce a bonded magnet.

Corrosion resistance tests were carried out on the compounds and bonded magnets produced in the above Examples and Comparative Examples. Corrosion resistance was evaluated using compounds and magnets 12
Leave it in the air at 0 ° C for 1000 hours.
This was done by examining the magnetic properties after standing for 1000 hours.

The magnetic characteristics of the compound were measured by VSM after orientation magnetization was performed immediately before the measurement. On the other hand, the magnetic characteristics of the bonded magnet were measured with a BH tracer after magnetization was performed immediately before the measurement. Moreover, the rust generation state of the bonded magnet was visually observed. The results are shown in Table 1.

[0041]

[Table 1]

As shown in Table 1, a compound for a bonded magnet, which was only coated with a resin by mixing with a resin liquid as in the conventional case (Comparative Example 1), or a compound which was further surface-treated with a silane coupling agent as a base (Comparative Example 2)
The bonded magnet produced from the above had a remarkable decrease in magnetic performance after being left in air at 120 ° C. for 1000 hours, and the magnet had visible rust.

On the other hand, the bonded magnet compound of the example having the protective resin film of the inner layer formed by the vapor deposition polymerization method according to the present invention and the bonded magnet produced from the compound were left to stand in air at 120 ° C. for 1000 hours. After that, there was almost no deterioration in magnetic performance. Therefore, it is clear that the compound and bonded magnet of the present invention have excellent corrosion resistance (oxidation resistance) and heat resistance.

[0044]

According to the present invention, the surface of the magnet powder is first coated with a dense thin film formed by vapor deposition polymerization and having excellent adhesive strength. Alternatively, by mixing with a thermosetting synthetic resin liquid, it is possible to obtain a compound for bonded magnets and a bonded magnet that are excellent in corrosion resistance (oxidation resistance) and heat resistance. During use, especially in high temperature and high humidity environments It is possible to effectively prevent deterioration of the magnetic performance of the bonded magnet inside, and it is possible to remarkably enhance the durability of the bonded magnet.

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-3-262104 (JP, A) JP-A-4-83306 (JP, A) JP-A-6-158104 (JP, A) JP-A-2- 248012 (JP, A) JP 6-306647 (JP, A) JP 1-98120 (JP, A) JP 59-1506 (JP, A) JP 7-130520 (JP, A) JP-A-3-112103 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01F 1/08 H01F 1/053 H01F 41/02 B22F C22C

Claims (4)

(57) [Claims] 1. An inner resin film made of one of polyamide, polyimide, polyamideimide, polyazomethine, and polyurea formed on the surface of a rare earth magnet powder by vapor deposition polymerization, and a thermosetting or thermoplastic outer resin. A compound for a highly corrosion-resistant bonded magnet, which has a coating. 2. A polycondensation-free 2 layer on the surface of the rare earth magnet powder.
After vapor-depositing vapors of at least one kind of monomer and polymerizing them on the surface of the powder, an inner layer resin film made of one kind of polyamide, polyimide, polyamideimide, polyazomethine, and polyurea is formed, and then the powder is thermosettable. Alternatively, a method for producing a compound for a high corrosion-resistant bonded magnet, which comprises forming an outer resin film on the inner resin film by mixing with a thermoplastic synthetic resin liquid. 3. A highly corrosion resistant bonded magnet manufactured from the compound of claim 1. 4. Extruding the compound according to claim 1,
A method for producing a highly corrosion-resistant bonded magnet, which comprises a step of injection or compression molding.