JP2002198211A - Method of manufacturing high weather-resistant magnet powder, and product obtained by use of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing iron magnet powder which contains rare earth elements and has superior weather-resistant properties and a high coercive force in important environmental conditions in practice, such as high humidity, high weather-resistant magnet powder obtained through the above manufacturing method, a bonded magnet resin composition containing the same, and to provide a bonded magnet. SOLUTION: In a method of manufacturing an iron magnet powder, that is coated with low-melting metal and contains rare earth elements, iron magnetic coarse powder of grain diameter 150 μm or smaller is mixed into a low-melting metal powder, the mixture is subjected to thermal treatment at temperatures of 200 to 600 deg.C, in an atmosphere of nitrogen gas and/or hydrogen gas and then ground into iron magnet powder containing rare earth elements.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a highly weatherable magnet powder and a product obtained therefrom.
The present invention relates to a method for producing an iron-based magnet powder containing a rare earth element having excellent weather resistance, a highly weather-resistant magnet powder obtained by the method, a resin composition for a bonded magnet containing the same, and a bonded magnet.

[0002]

2. Description of the Related Art Conventionally, ferrite magnets, alnico magnets, rare earth magnets, and the like have been used for various applications including motors. However, since these magnets are mainly manufactured by a sintering method, they have a problem that they are generally brittle, and it is difficult to obtain a thin or complicated one. In addition, since shrinkage during sintering is as large as 15 to 20%, a product having high dimensional accuracy cannot be obtained, and post-processing such as polishing is required to increase accuracy. .

On the other hand, bonded magnets have been developed in recent years in order to solve these problems of the sintering method and to open up new applications. However, usually, bonded magnets are usually made of polyamide resin, polyphenylene sulfide resin. It is manufactured by filling a thermoplastic resin such as a binder with a magnet powder. However, among these bonded magnets, particularly, bonded magnets using an iron-based magnet powder containing a rare earth element are liable to generate rust and deteriorate magnetic properties in a high-temperature and high-humidity atmosphere. Rust can be suppressed by forming a coating film of a curable resin or the like, or as described in Japanese Patent Application Laid-Open No. 2000-208321, the surface of a molded product is subjected to a coating treatment with a phosphate-containing paint. However, it is not satisfactory in terms of magnetic characteristics such as hard rusting characteristics and coercive force.

[0004] Incidentally, when an iron-based magnet powder containing a rare-earth element is kneaded with a resin and used as a bond magnet, it is necessary to grind the magnetic coarse powder to several μm in order to obtain high magnetic properties. The grinding of the magnetic coarse powder is usually carried out in an inert gas or in a solvent, but the magnet powder after grinding is extremely active. However, there is a problem that the magnetic properties deteriorate due to rapid progress.

[0005] In order to solve this problem, for example, a magnetic coarse powder is pulverized to several μm and then a slight amount of oxygen is introduced into an inert atmosphere to gradually oxidize the magnet powder. As disclosed in Japanese Unexamined Patent Publication, a coating treatment by copper-zinc plating is performed on a magnet powder after pulverization. However, the magnet powder obtained after the pulverization is agglomerated with each other by its magnetic force, and even if the surface of the agglomerated powder is protected by a film, the protection of the individual magnet powder is not sufficient. Although the powder has improved weather resistance in a dry environment,
There is a problem that the weather resistance in a humid environment, which is important for practical use, has not been improved satisfactorily.

Under these circumstances, in recent years, bond magnets used in small motors, audio equipment, OA equipment, and the like have been required to have excellent magnetic properties in order to reduce the size of the equipment. The magnetic properties of bonded magnets obtained from iron-based magnet powders containing iron are insufficient for these applications, and the weather resistance of iron-based magnet powders containing rare earth elements is improved early, and the magnetic properties of bonded magnets are improved. It was strongly desired to improve the quality.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, an object of the present invention is to provide an iron containing rare earth element which has excellent weather resistance, and particularly has a high coercive force in a humidity environment which is important for practical use. An object of the present invention is to provide a method for producing a system magnet powder, a highly weather-resistant magnet powder obtained by the method, a resin composition for a bonded magnet containing the same, and a bonded magnet.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, in a method for producing an iron-based magnet powder containing a rare earth element coated with a low melting point metal, a rare earth element Is mixed with a low-melting metal powder, heat-treated in a nitrogen gas and / or a hydrogen gas, and then pulverized to obtain a desired, excellent weather resistance and excellent humidity. The present inventors have found that a magnetic powder in which a decrease in coercive force is suppressed can be obtained, and have completed the present invention.

That is, according to the first aspect of the present invention, in a method for producing a rare earth element-containing iron-based magnet powder coated with a low melting point metal, the iron-based magnetic coarse powder containing a rare earth element having a particle size of 150 μm or less is used. The present invention provides a method for producing a rare earth element-containing iron-based magnet powder, which comprises mixing non-ferrous metal powder with a low-melting metal powder, heat-treating the powder in a nitrogen gas and / or a hydrogen gas at 200 to 600 ° C., and pulverizing the mixture. You.

Further, according to the second aspect of the present invention, the first aspect
In the invention, the low melting point metal powder is Zn, Sn, I
A method for producing an iron-based magnet powder containing a rare earth element, characterized by being a powder of at least one metal selected from the group consisting of n and Pb.

According to a third aspect of the present invention, in the first or second aspect, the low melting point metal powder has a particle size of 5
A method for producing an iron-based magnet powder containing a rare earth element, which is characterized in that the particle diameter is 0 μm or less.

On the other hand, according to the fourth aspect of the present invention, the first
An iron-based magnet powder containing a rare earth element, which is obtained by the production method according to any one of the third to third inventions, is provided.

According to the fifth aspect of the present invention, the fourth aspect
The present invention provides a resin composition for a bonded magnet, characterized by containing the iron-based magnet powder containing a rare earth element according to the invention as a main component.

Further, according to a sixth aspect of the present invention, there is provided a bonded magnet obtained by molding the resin composition for a bonded magnet of the fifth aspect.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

1. Magnetic coarse powder The magnetic coarse powder used in the present invention is not particularly limited as long as it is not an iron-based magnetic coarse powder containing at least a rare earth element. For example, rare-earth-iron-boron-based, rare-earth -Various magnetic coarse powders of iron-nitrogen system. Among these, Nd—Fe—B-based magnetic coarse powder by liquid quenching method, Sm—Fe—N-based magnetic coarse powder, Nd
-(Dy, Tb) -Fe-B based magnetic coarse powder, Sm-F
An e-Co-N-based magnetic coarse powder is particularly suitable. The particle size of the magnetic coarse powder is preferably 150 μm or less.

2. Method for Producing Highly Weatherable Magnet Powder In the present invention, before grinding the iron-based magnetic coarse powder containing a rare earth element having a particle size of 150 μm or less into a magnet powder having a particle size of several μm, Is coated with a low melting point metal.

As a method for coating a low melting point metal, first, a magnetic coarse powder is mixed with a low melting point metal powder, and a heat treatment is performed in a nitrogen gas and / or a hydrogen gas to form a metal coating layer on the non-surface of the magnet powder. .

The heat treatment temperature is usually from 200 to 600 ° C, preferably from 300 to 500 ° C. When the temperature is lower than 200 ° C., the reaction between the low melting point metal powder and the magnet powder does not proceed,
If the temperature exceeds ℃, the magnet powder may be decomposed.

The low-melting metal powder forming the coating layer can cover the surface of the magnetic coarse powder but can also repair the surface of the magnetic coarse powder. Is not limited as long as is formed, for example,
Zn powder, Sn powder having a melting point of 150 to 500 ° C.,
In powder, Pb powder and the like can be mentioned. Of these, Zn powder is particularly preferred.

The low melting point metal powder has a particle size of 5
It is preferable to use one having a size of 0 μm or less. Particle size 50
If it exceeds μm, the reaction does not proceed smoothly, and it is difficult to uniformly coat the surface of the magnet powder.

The amount of the low melting metal powder to be added is preferably in the range of 0.1 to 8% by mass based on the magnetic coarse powder. If the amount of the low-melting-point metal powder is less than 0.1% by mass, it is difficult to uniformly coat the surface of the magnet powder, and if it exceeds 8% by mass, the magnetic properties are degraded by the non-magnetic low-melting-point metal.

Generally, impurities adhere to the surface of the iron-based magnetic coarse powder containing a rare earth element, and geometric unevenness and the like are formed. It is presumed that, for example, they remain on the surface of the magnet particles even after nitriding, become nuclei that cause the generation of reverse magnetic domains, and reduce magnet properties including corrosion resistance and heat resistance. Therefore, in particular, if the magnetic coarse powder is coated with metal before milling, not after milling when the activity of the magnet powder becomes extremely high, surface defects such as protrusions are repaired at the time of film formation, and nuclei for generating reverse magnetic domains are reduced. Also, oxidation of the magnet powder and the like are suppressed. As a result, it is considered that a high coercive force is obtained, and heat resistance and corrosion resistance are also improved.

By the way, in the conventional method, in order to prevent oxidation of the magnet powder, it is necessary to carefully introduce a small amount of oxygen into an inert atmosphere during drying to perform slow oxidation.
For this reason, the drying time must be long, which is a factor of increasing the manufacturing cost. In addition, when the magnetic properties of the obtained magnet powder are changed over time, a relatively large coercive force is maintained in a dry state at 60 ° C., but about 50% when left in an environment of 60 ° C. and a relative humidity of 80% for 10 hours. Coercive force decreases.

On the other hand, in the method of the present invention, surface defects such as projections are repaired during the film formation, and the nuclei of the generation of reverse magnetic domains are reduced. As a result, the drying time can be reduced without requiring any special conditions other than performing the drying of the magnet powder in an inert gas or in a vacuum. Further, the coercive force of the obtained magnet powder hardly changes even when exposed to an environment of 60 ° C. and a relative humidity of 80% for 10 hours, and a significant improvement in weather resistance is achieved.

3. Bonded Magnet Resin Composition and Bonded Magnet The method for producing the bonded magnet resin composition and the bonded magnet using the highly weatherable magnet powder of the present invention is not particularly limited, and includes, for example, a known thermal method as shown below. It can be manufactured using a plastic resin or an additive.

(Thermoplastic resin) The thermoplastic resin serves as a binder for the magnet powder, and is not particularly limited.
Conventionally known ones can be used. As specific examples of the thermoplastic resin, 6 nylon, 6, 6 nylon, 11 nylon,
12 nylon, 6, 12 nylon, aromatic nylon,
Polyamide resin such as modified nylon partially modified from these molecules, linear polyphenylene sulfide resin, cross-linked polyphenylene sulfide resin, semi-cross-linked polyphenylene sulfide resin, low density polyethylene, linear low density polyethylene resin, high density polyethylene resin , Ultra high molecular weight polyethylene resin, polypropylene resin, ethylene-vinyl acetate copolymer resin, ethylene-ethyl acrylate copolymer resin, ionomer resin, polymethylpentene resin, polystyrene resin, acrylonitrile-butadiene-styrene copolymer resin, acrylonitrile-styrene copolymer Polymerized resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyvinyl acetate resin, polyvinyl alcohol resin, polyvinyl butyral resin, polyvinyl formal resin, methacrylic Resin, polyvinylidene fluoride resin,
Polytetrafluoroethylene chloride resin, ethylene tetrafluoride-propylene hexafluoride copolymer resin, ethylene-tetrafluoroethylene copolymer resin, ethylene tetrafluoride-perfluoroalkyl vinyl ether copolymer resin, polytetrafluoroethylene resin, Polycarbonate resin, polyacetal resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polyphenylene oxide resin, polyallyl ether allyl sulfone resin, polyether sulfone resin, polyether ether ketone resin, polyarylate resin, aromatic polyester resin, cellulose acetate resin, The above-mentioned respective resin-based elastomers and the like, such as random copolymers with these homopolymers and other monomers, block copolymers, graft copolymers, end-group modified products with other substances, and the like. It is.

It is desirable that the melt viscosity and the molecular weight of these thermoplastic resins be as low as possible so long as the desired mechanical strength of the resulting bonded magnet can be obtained. The shape of the thermoplastic resin is not particularly limited, such as a powder, a bead, a pellet, or the like, but a powder is desirable because it is uniformly mixed with the magnet powder. The blending amount of the thermoplastic resin is 100
5 to 100 parts by weight, preferably 5 to 100 parts by weight,
５０50 parts by weight. If the blending amount of the thermoplastic resin is less than 5 parts by weight, the kneading resistance (torque) of the composition becomes large, or the fluidity is reduced, making molding of the magnet difficult. Cannot be obtained.

(Other Additives) The composition for a bonded magnet using the highly weather-resistant magnet powder of the present invention may contain other additives such as a lubricant for plastic molding and various stabilizers as long as the object of the present invention is not impaired. Additives can be blended.

Examples of the lubricant include waxes such as paraffin wax, liquid paraffin, polyethylene wax, polypropylene wax, ester wax, carnauba, microwax, stearic acid, 1,2-
Fatty acids such as oxystearic acid, lauric acid, palmitic acid, oleic acid, calcium stearate, barium stearate, magnesium stearate, lithium stearate, zinc stearate, aluminum stearate, calcium laurate, zinc linoleate, calcium ricinoleate Fatty acid salts (metal soaps) such as zinc 2-ethylhexoate, stearic acid amide, oleic acid amide, erucic acid amide, behenic acid amide, palmitic acid amide, lauric acid amide, hydroxystearic acid amide, methylenebisstearic acid amide, Ethylenebisstearic acid amide, ethylenebislauric amide, distearyladipamide, ethylenebisoleic amide, dioleyladipamide, N-stearylstearin Amides such as fatty acid amides, fatty acid esters, ethylene glycol and butyl stearate,
Alcohols such as stearyl alcohol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and polyethers composed of these modified products, dimethylpolysiloxane, polysiloxanes such as silicon grease, fluorine-based oil, fluorine-based grease,
Examples include fluorine compound such as fluorine-containing resin powder, and inorganic compound powder such as silicon nitride, silicon carbide, magnesium oxide, alumina, silicon dioxide, and molybdenum disulfide. These lubricants may be used alone or in combination of two or more. The compounding amount of the lubricant is usually 0.01 to 20 parts by weight, preferably 0.1 to 10 parts by weight based on 100 parts by weight of the magnet powder.

As the stabilizer, bis (2, 2,
6,6, -tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6, -pentamethyl-4-
Piperidyl) sebacate, 1- [2- {3- (3,5-
Di-tert-butyl-4-hydroxyphenyl) propionyloxy {ethyl] -4- {3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy}
-2,2,6,6-tetramethylpiperidine, 8-benzyl-7,7,9,9-tetramethyl-3-octyl-
1,2,3-triazaspiro [4,5] undecane-
2,4-dione, 4-benzoyloxy-2,2,6,
6-tetramethylpiperidine, dimethyl succinate-1-
(2-hydroxyethyl) -4-hydroxy-2,2,
6,6-tetramethylpiperidine polycondensate, poly [[6
-(1,1,3,3-tetramethylbutyl) imino-
1,3,5-triazine-2,4-diyl] [(2,
2,6,6-tetramethyl-4-piperidyl) imino]
Hexamethylene [[2,2,6,6-tetramethyl-4
-Piperidyl] imino]], bis (1,2,2,6,6-pentamethyl-4-piperidyl) 2- (3,5-di-tert-butyl-4-hydroxybenzyl) -2-n-butylmalonate ), Antioxidants such as phenolic, phosphite, thioether and the like. These stabilizers may be used alone or in combination of two or more. The amount of the stabilizer is usually 0.01 to 5 parts by weight, preferably 0.05 to 3 parts by weight, based on 100 parts by weight of the magnet powder.

The method of mixing the above components is not particularly limited. For example, a mixer such as a ribbon blender, a tumbler, a Nauter mixer, a Henschel mixer, a super mixer, or a Banbury mixer, a kneader,
It is carried out using a kneader such as a roll, a kneader-ruder, a single-screw extruder, a twin-screw extruder, or the like. The shape of the composition for a bonded magnet to be obtained is in the form of powder, beads, pellets, or a mixture thereof, but pellets are desirable from the viewpoint of easy handling.

Next, the above composition for a bonded magnet is heated and melted at the melting temperature of the thermoplastic resin, and then formed into a magnet having a desired shape. At that time, as a molding method,
Various molding methods, such as injection molding, extrusion molding, injection compression molding, injection press molding, and transfer molding, which have been conventionally used for plastic molding, etc., can be mentioned. Among these, particularly injection molding is preferred. , Extrusion molding, injection compression molding, and injection press molding are preferred.

[0034]

EXAMPLES Examples and comparative examples of the present invention will be shown below, but the present invention is not limited to these examples. The details and evaluation methods of each component used in Examples and Comparative Examples are as follows.

(1) ComponentMagnet magnetic coarse powder  ・ Sm-Fe-N magnet alloy powder (Sumitomo Metal Mining Co., Ltd.)
Made)Zn powder  ・ Zn powder (Mitsui Metal Mining Co., Ltd.) Particle size: 325
Below mesh

(2) Evaluation method Evaluation of heat resistance The obtained magnet powder sample and 210 ° C. in a vacuum oven
The coercive force of the sample held for 1 hour was measured at room temperature with a vibration sample magnetometer (VSM-3 manufactured by Toei Kogyo Co., Ltd.). Evaluation of Corrosion Resistance The coercive force of a magnet powder sample left for 10 hours in an atmosphere of 60 ° C. and 80% relative humidity was measured at room temperature with the above-mentioned vibrating sample magnetometer.

(Examples 1 to 4, Comparative Example 1) Sm—Fe-based magnetic coarse powder obtained by the reduction diffusion method (Sm content: 2)
(5 wt%) was sieved to 100 μm or less, nitrided at 480 ° C. for 270 minutes in a hydrogen / ammonia mixed gas, and then cooled. Zn powder was added at a ratio shown in Table 1 to 1 kg of the obtained Sm-Fe-N-based magnetic coarse powder,
Mixed. Next, the mixture was maintained at 430 ° C. for 10 hours while supplying a nitrogen / hydrogen mixed gas at 11 / min, and then cooled to room temperature. Then, 200 ml in a solvent was prepared using an attritor.
After crushing at 60 rpm for 60 minutes, it was dried. Magnetic properties were measured using the dried magnet powder (average particle size: 4 to 5 μm). Table 1 shows the obtained results.

[0038]

[Table 1]

As is evident from Table 1, the magnet powder obtained by the manufacturing method of the present invention has a higher coercive force and remarkably high heat resistance and weather resistance as compared with the magnet powder manufactured by the conventional method. Has been improved.

As described above, in the magnetic powder obtained by the manufacturing method of the present invention, surface defects such as projections are repaired during the formation of a film, the nuclei for generating reverse magnetic domains are reduced, and the surface of the magnet powder is reduced. Is coated with a low-melting metal, so that it has excellent coercive force and remarkably improved heat resistance and corrosion resistance. In addition, since heat is not generated even when the aggregates after the magnet powder is dried are disintegrated, the handling of the powder when kneading with the resin is facilitated in the manufacturing process of the bonded magnet, and the magnetic properties due to the heat generation are improved. Degradation can be suppressed. The magnet powder obtained by the manufacturing method of the present invention makes it possible to manufacture a highly weather-resistant bonded magnet, and its industrial value is extremely large.

Claims (6)

[Claims] 1. A method for producing an iron-based magnet powder containing a rare-earth element coated with a low-melting-point metal, comprising mixing an iron-based magnetic coarse powder containing a rare-earth element with a particle size of 150 μm or less with the low-melting-point metal powder, 200 to 60 in nitrogen gas and / or hydrogen gas
A method for producing an iron-based magnet powder containing a rare-earth element, which is heat-treated at 0 ° C. and then pulverized. 2. The low melting point metal powder is Zn, Sn, In,
The method of claim 1, wherein the powder is at least one metal selected from the group consisting of Pb and Pb. 3. The method for producing an iron-based magnet powder containing a rare earth element according to claim 1, wherein the low melting point metal powder has a particle size of 50 μm or less. 4. An iron-based magnet powder containing a rare earth element, which is obtained by the production method according to claim 1. 5. A resin composition for a bonded magnet, comprising the iron-based magnet powder containing a rare earth element according to claim 4 as a main component. 6. A bonded magnet obtained by molding the resin composition for a bonded magnet according to claim 5.