JP3473677B2 - Magnetic powder for rare earth bonded magnet, composition for rare earth bonded magnet, and rare earth bonded magnet - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic powder for a rare earth bonded magnet, which contains R (R is a rare earth element), Fe or Fe and Co, and N as main constituents, and the magnetic powder and a resin binder as main components. The present invention relates to a composition for a rare earth bond magnet, and a rare earth bond magnet formed by molding the composition into a magnet shape. Particularly, a magnetic powder for a rare earth bond magnet having a small irreversible demagnetization rate and excellent heat resistance, and a rare earth bond magnet. And a rare earth bonded magnet.

[0002]

2. Description of the Related Art In recent years, R-Fe- produced by introducing nitrogen into an intermetallic compound having a rhombohedral or hexagonal crystal structure.
N (R is a rare earth element) -based magnetic material has attracted attention because it has excellent magnetic properties, especially as a permanent magnet material.
For example, in Japanese Patent Laid-Open No. 2-57663, R-Fe-N-H having a hexagonal or rhombohedral crystal structure.
A magnetic anisotropic material represented by (R: at least one of rare earth elements including yttrium) is disclosed.

As a rare earth bond magnet composed of the R-Fe-N magnetic powder and a resin binder, an Sm-Fe-N injection-molded bond magnet using polyamide (nylon) as a resin binder is known. For example, "Developme
nt of high-energy product Sm ₂ Fe ₁₇ N ₃ bonded mag
nets "(Proc. Int. Conf. MRS, Tokyo, 1993, L7-1) discloses an Sm-Fe-N-based injection-molded bond magnet having a coercive force HcJ of 5 to 7 kOe. -29
5805 or JP-A-6-295816 discloses an Sm-Fe-N based injection-molded bond magnet having a coercive force HcJ of less than 6 kOe.

[0004]

By the way, these conventional R-Fe-N system injection-molded bonded magnets have a problem that the heat resistance of magnetic properties is poor.

That is, in a magnetic circuit incorporating a magnet, since the magnetic flux generated by the magnet is used, it is required that the required magnetic flux can be stably obtained without depending on the temperature history, that is, good heat resistance. .

As an index of this heat resistance, the magnet is heated at a predetermined temperature for a predetermined time and the rate of change in magnetic flux before and after that (irreversible demagnetization rate) is evaluated. In addition, the irreversible demagnetization rate after heating for one hour may be referred to as the initial demagnetization rate at the heating temperature. In all cases, the closer it is to 0, the better the heat resistance.

In the conventional R-Fe-N injection-molded bond magnet, the heating temperature at which the initial demagnetization rate is 5% is 80%.
It was below ℃. For example, above "Development of high-ene
According to "rgyproduct Sm ₂ Fe ₁₇ N ₃ bonded magnets", Sm-Fe-N based injection-molded bonded magnets at 50 ° C, S
The m- (Fe, Co) -N injection-molded bond magnet had a temperature of 80 ° C.

However, it is required that a small motor for OA equipment or AV equipment, which is a main application of the rare earth bonded magnet, can be used up to at least 80 ° C.,
Furthermore, heat resistance exceeding 100 to 125 ° C. is required for automobile applications.

Therefore, it cannot be said that the conventional R-Fe-N injection-molded bonded magnet, which is demagnetized by 5% or more at 80 ° C., has sufficient heat resistance.

The present invention was made by paying attention to such problems, and the problem is that the initial demagnetization rate is 5%.
To provide a magnetic powder for rare-earth bonded magnets, a composition for rare-earth bonded magnets, and a rare-earth bonded magnet, which have excellent heat resistance at a heating temperature of over 80 ° C.

[0011]

In order to solve such a problem, the inventors of the present invention tried to develop a magnetic powder for a rare earth bonded magnet with reference to the following prior art.

First, reference is made to JP-A-4-157705.
Japanese Patent Laid-Open Publication No. 2003-242242 discloses a material having an average particle size in the range of 0.1 to 30 μm and a particularly excellent moldability and surface smoothness with respect to the particle size of the R—Fe—N magnetic powder for bonded magnets. In that case, it is disclosed that the average particle size is preferably 1 to 10 μm, and the like.
Japanese Unexamined Patent Publication No. 12 discloses that the magnetic property of the magnetic powder containing the R—Fe—N system is improved by making the content of particles having a particle diameter of 1 μm or less 10% or less on a volume basis. These conventional techniques are methods for defining the average value of the particle size and the fine particle side of the particle size distribution, and there is no knowledge of the coarse particle side of the particle size distribution.

On the other hand, Japanese Patent Application Laid-Open No. 5-175022 referred to
In the publication, by setting the standard deviation of the magnetic powder particle diameter to 1.0 μm or less, Hk (the square shape of the demagnetization curve by the demagnetizing field when the magnetization J decreases to 90% of the residual magnetic flux density Br as described later) It is said that it is possible to manufacture a bonded magnet having high property). However, when it is applied to a resin-bonded magnet, it is only described that the average particle diameter of the magnetic powder is “crushed to a particle diameter of a single magnetic domain, for example, 0.5 to 10 μm”. Similar to the above-mentioned prior art, there is no knowledge of the coarse particle side of the particle size distribution. In addition, although the examples also have the magnetic properties of the powder, the magnetic properties and heat resistance of the bonded magnet are not specifically described.

Therefore, according to these conventional techniques for defining the fine particle side of the particle size distribution, the average particle size of the magnetic powder or 1
Various studies were conducted on the particle size distribution control on the fine particle side of less than μm,
Increasing the squareness and coercive force of the magnetic powder has not necessarily improved the heat resistance of the bonded magnet. In particular, the presence of particles having a particle size of less than 1 μm is reported in JP-A-5-308012.
It was confirmed that, unlike the case of the magnetic powder described in the publication, it did not significantly affect the squareness of the demagnetization curve and the coercive force after it was made into a bonded magnet.

From the above analysis, the magnetic powder as the raw material is exposed to 50 to 50 during the process of producing the bonded magnet.
The temperature history of 330 ° C. impairs the magnetic properties of small particles having a particle size of less than 1 μm, and the final magnetic properties of the bonded magnet are affected by the magnetic powder of 1 μm or more that survives without impairing the magnetic properties. The reasoning came to be guided. In other words, when a rare-earth bonded magnet with excellent heat resistance is sought, it is difficult to achieve it even with the conventional method of defining the fine particle side of the particle size distribution. We came to the idea that a method is needed.

Based on such inference, the effect of the particle size on the coarse particle side, which has not been found so far, on the heat resistance of the bonded magnet was examined in detail. The content rate of all magnetic powder of 0.0 μm or more is
It has been found that the squareness of the demagnetization curve and the coercive force are strongly influenced, and as a result, the heat resistance is influenced. The present invention has been completed based on such technical findings.

That is, the invention according to claim 1 is R (R
Is a rare earth element), Fe or Fe and Co, and N as main constituents, and magnetic powder for rare earth bonded magnets having a Th ₂ Zn ₁₇ type crystal structure is premised, and the particle diameter is 1.0 μm.
Whether the content of the total magnetic powder having a particle diameter of 5.0 μm or more with respect to the total magnetic powder of m or more is 2.5% or less on a number basis .
The particle size for all magnetic powders with a particle size of 1.0 μm or more
The total magnetic powder content of 4.0 μm or more is 0% on a number basis.
Is more than 4.5% and the particle size is 1.0 μm or less.
Total magnetism of particle size 3.2μm or more for the above total magnetic powder
It is characterized in that the powder content is more than 0% and 10% or less on a number basis .

[0018]

Next, the invention according to claim 2 presupposes a composition for a rare earth bonded magnet used for producing a rare earth bonded magnet having a heat resistance at which the heating temperature at which the initial demagnetization rate becomes 5% exceeds 80 ° C. In addition, the magnetic powder for rare earth bonded magnet according to claim 1 and a resin binder are main components, and the invention according to claim 3 is based on a rare earth bonded magnet, and the rare earth according to claim 2 above. It is characterized in that it is formed by molding the composition for a bonded magnet into a magnet shape and has heat resistance at which the heating temperature at which the initial demagnetization rate is 5% exceeds 80 ° C.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below.

First, the magnetic powder for rare earth bonded magnets, the composition for rare earth bonded magnets, and the magnetic powder used in the rare earth bonded magnets according to the present invention are, for example, JP-A-2-
Melt casting method according to Japanese Patent No. 0576663, or Japanese Patent No. 1702544 or Japanese Patent Laid-Open No. 9-15780.
R-F manufactured by the reduction diffusion method disclosed in Japanese Patent No.
It can be obtained by nitriding an e-based alloy or an R- (Fe, Co) -based alloy and then finely pulverizing it. R is a rare earth element, but preferably contains Sm in an amount of 40% by weight or more. C
Addition of o improves the saturation magnetization of the magnet and the temperature coefficient of magnetic flux density. Further, R, Fe or Fe which is a main constituent component
In addition to Co and N, C, Al, Si, P, Ti,
V, Cr, Mn, Ni, Cu, Zn, Ga, Zr, N
b, Mo, Ag, In, Sn, Hf, Ta, W, Re,
If one or more of Os, Ir, Pt, and Au is added to the magnetic powder in an amount of 3% by weight or less, heat resistance can be further improved.
The fine pulverization can be carried out by a known technique such as a jet mill, a vibrating ball mill, a rotary ball mill, etc., but when the magnetic powder for a bonded magnet, the composition for a bonded magnet and the bonded magnet are produced, the total particle size is 1.0 μm or more. The content ratio of all magnetic powders of 5.0 μm or more to the magnetic powder is 2.5% or less on a number basis, preferably 1.0% or less.
It is necessary to control the crushing conditions and use a classifier together (Claims 1, 2 and 3 ). 5.0 μm here
When the content of the above total magnetic powder exceeds 2.5% on the number basis, the squareness of the demagnetization curve and the coercive force of the magnet decrease, and the heat resistance deteriorates. Further, the content ratio of the total magnetic powder having a particle diameter of 4.0 μm or more to the total magnetic powder having a particle diameter of 1.0 μm or more is more than 0% and 4.5% or less on the basis of the number (claim 1, claim 1
2 , claim 3 ), and further, the content ratio of the total magnetic powder having a particle diameter of 3.2 μm or more to the total magnetic powder having a particle diameter of 1.0 μm or more is set to more than 0% and 10% or less based on the number (claim 1). According to claims 2 and 3 , the squareness of the demagnetization curve and the coercive force are further improved, and the heat resistance is improved.

Next, in the magnetic powder for rare-earth bonded magnets, the composition for rare-earth bonded magnets, and the rare-earth bonded magnet according to the present invention, the particle size of the magnetic powder is evaluated and defined as follows. A cross-section of the above-mentioned magnetic powder for rare-earth bonded magnets embedded in a resin, a composition for rare-earth bonded magnets, or a rare-earth bonded magnet is polished, and one or more fields of view are taken for one sample with an optical microscope or a scanning electron microscope. Take a picture. A plurality of parallel straight lines are drawn on the obtained photograph so as not to overlap the same magnetic powder. At this time, the distance between the intersections of one magnetic powder and a straight line is defined as the particle diameter of the magnetic powder. Further, in evaluating the particle size distribution, the particle size of 100 or more, preferably 200 or more magnetic powders is measured. From the obtained data, a magnetic powder having a particle diameter of less than 1 μm is excluded, and a particle size distribution on a number basis with respect to the logarithm of the particle diameter is calculated for the magnetic powder having a particle diameter of 1 μm or more to obtain the content of the magnetic powder having a particle diameter of 5.0 μm or more.

In order to improve handling property such as prevention of ignition of finely pulverized magnetic powder, for example, Japanese Patent Laid-Open No.
-54998, JP-A-59-170201, JP-A-60-128202, JP-A-3-211203, or JP-A-46-7153, JP-A-56-5.
5503, JP-A-61-154112, JP-A-3-
It is possible to form a slow oxidation film on the surface of the magnetic powder by a wet or dry process as disclosed in Japanese Patent No. 126801.

[0024] Further, JP-A-5-230501, JP-A-5-234729, JP-A-8-143913, JP-A-7-268632 and summary of lectures of the Japan Institute of Metals (1996 Spring Conference, No. 446, p.184) and other methods for forming a metal film,
JP-B-6-17015, JP-A-1-234502,
JP-A-4-21702, JP-A-5-213601,
JP-A-7-326508, JP-A-8-153613
When the magnetic powder is subjected to one or more surface treatments such as a method of forming an inorganic film according to Japanese Patent Laid-Open No. 8-183601, the coercive force of the magnetic powder, the composition and the bond magnet is improved and the heat resistance is further improved. To do.

Next, the resin binder of the rare earth bonded magnet composition according to the present invention acts as a binder for the magnetic powder, and the applicable resin is not particularly limited, and examples thereof include thermoplastic resins. In case of, 6 nylon, 6, 6 nylon, 11 nylon, 12 nylon,
Polyamide resin such as 6,12 nylon, aromatic nylon, modified nylon obtained by partially modifying these molecules, linear polyphenylene sulfide resin, crosslinked polyphenylene sulfide resin, semi-crosslinked polyphenylene sulfide resin, low density polyethylene, wire 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 resin -Styrene copolymer resin, acrylonitrile-styrene copolymer resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyvinyl acetate resin, polyvinyl alcohol resin, polyvinyl butyral resin Polyvinyl formal resin, methacrylic resin, polyvinylidene fluoride resin, polytrifluorochloroethylene resin, tetrafluoroethylene-hexafluoropropylene copolymer resin, ethylene-tetrafluoroethylene copolymer resin, tetrafluoroethylene-perfluoro Alkyl 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, various elastomers and rubbers, and the like, random copolymers of these homopolymers and other kinds of monomers, block copolymers, Examples include graft copolymers and end group-modified products with other substances. Further, a system in a blend of two or more kinds of these thermoplastic resins is naturally included. The melt viscosity and the molecular weight of these thermoplastic resins are preferably as low as possible in the range where the desired mechanical strength can be obtained, and the shape is not particularly limited such as powder, beads, pellets, etc., but considering from the uniform mixing property with the magnetic powder. Powder is desirable.

In the case of a thermosetting resin, for example, epoxy resin, vinyl ester epoxy resin, unsaturated polyester resin, phenol resin, melamine resin, urea resin, benzoguanamine resin, bismaleimide triazine resin, diallyl phthalate resin. , Furan resin, thermosetting polybutadiene resin, polyimide resin, polyurethane resin, silicone resin, xylene resin, and the like. Of course, these basic compositions, other kinds of monomers, and systems in blends of two or more kinds of these resins are also included. included. The viscosity, molecular weight, properties, etc. of these thermosetting resins are not particularly limited as long as the desired mechanical strength and moldability can be obtained, but in view of uniform mixing with magnetic powder and moldability, powder or liquid Is desirable.

When the content of these resin binders is more than 100 parts by weight with respect to 100 parts by weight of magnetic powder, the magnetic flux density of the bonded magnet is significantly reduced. On the other hand, if the amount is less than 3 parts by weight, the moldability is remarkably reduced and a desired molded product cannot be obtained. Therefore, the mixing amount of these resins is
The amount is preferably 3 parts by weight or more and 100 parts by weight or less with respect to 100 parts by weight of the magnetic powder.

When a rare earth bonded magnet composition according to the present invention is produced, if a coupling agent, a lubricant, a stabilizer or the like is used as an additive, the heating fluidity of the composition is further improved and the moldability and magnetic properties are improved. The characteristics are improved. Examples of the coupling agent include silane coupling agents such as vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, β- (3,4epoxycyclohexylethyltrimethoxysilane), γ-glycidoxypropyltrimethoxysilane. Silane, γ-glycidoxymethyldiethoxysilane, N-β (aminoethyl) γaminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N -Phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, methyltrimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane,
Phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltrimethoxysilane, decyltrimethoxysilane, etc. are also titanium-based coupling agents such as isopropyltriisostearoyl titanate,
Isopropyltri (N-aminoethyl-aminoethyl)
Titanate, isopropyl tris (dioctyl pyrophosphate) titanate, tetraisopropyl bis (dioctyl phosphite) titanate, tetraisopropyl titanate, tetrabutyl titanate, tetraoctyl bis (ditridecyl phosphite) titanate, isopropyl trioctanoyl titanate, isopropyl tridodecylbenzene. Sulfonyl titanate, isopropyl tri (dioctyl phosphate) titanate, bis (dioctyl pyrophosphate) ethylene titanate, isopropyl dimethacryl isostearoyl titanate, tetra (2,2-diallyloxymethyl-1-butyl) bis (ditridecyl phosphite) titanate,
Isopropyl tricumyl phenyl titanate, bis (dioctyl pyrophosphate) oxyacetate titanate, isopropyl isostearoyl diacryl titanate, etc. are selected, and one or more of them are selected by selecting an appropriate one according to the type of resin binder. You can Examples of the lubricant include paraffin wax, liquid paraffin, polyethylene wax, polypropylene wax, ester wax, carnauba,
Waxes such as microwax, stearic acid, 1,
2-oxystearic acid, lauric acid, palmitic acid,
Fatty acids such as oleic acid, calcium stearate, barium stearate, magnesium stearate, lithium stearate, zinc stearate, aluminum stearate, calcium laurate, zinc linoleate,
Fatty acid salts (metal soaps) such as calcium ricinoleate, zinc 2-ethylhexoate, stearic acid amide, oleic acid amide, erucic acid amide, behenic acid amide, palmitic acid amide, lauric acid amide, hydroxystearic acid amide, methylenebisstearin. Acid amide, ethylene bisstearic acid amide, ethylene bislauric acid amide, distearyl adipic acid amide, ethylene bisoleic acid amide, dioleyl adipic acid amide, N-
Fatty acid amides such as stearyl stearic acid amide, fatty acid esters such as butyl stearate, alcohols such as ethylene glycol and stearyl alcohol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and polyethers composed of these modified products, dimethyl Polysiloxanes such as polysiloxane and silicon grease, fluorine-based oils, fluorine compounds such as fluorine-based grease and fluorine-containing resin powders, and inorganic compound powders such as silicon nitride, silicon carbide, magnesium oxide, alumina, silicon dioxide and molybdenum disulfide. Is mentioned. Further, 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]], 2- (3,5-di-tert-butyl-4-hydroxybenzyl) -2-n-butylmalonate bis (1,2,2,6,6-pentamethyl-4-piperidyl) In addition to hindered amine-based stabilizers such as the above, antioxidants such as phenol-based, phosphite-based, thioether-based and the like can be mentioned. As the lubricant, waxes such as paraffin wax, liquid paraffin, polyethylene wax, polypropylene wax, ester wax, carnauba and micro wax, stearic acid, 12
-Fatty acids such as oxystearic acid and lauric acid,
Zinc stearate, calcium stearate, barium stearate, aluminum stearate, magnesium stearate, calcium laurate, fatty acid salts such as zinc linoleate, calcium linoleate, 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 acid amide,
Distearyl adipic acid amide, ethylene bisoleic acid amide, dioleyl adipic acid amide, N-stearyl suric acid amide, N-oleyl stearic acid amide, N-stearyl erucic acid amide, methylol stearic acid amide, methylol behenic acid amide, etc. Fatty acid amides, fatty acid esters such as butyl stearate, alcohols such as ethylene glycol and stearyl alcohol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol and polyethers composed of these modified products, silicone oil, silicone grease, etc. Fluorine compounds such as polysiloxanes, fluorinated oils, fluorinated greases, fluorinated resin powders, silicon nitride, silicon carbide, magnesium oxide, alumina, silica gel How the inorganic compound powder and the like can be used alone or in combination.

These magnetic powder and resin binder, etc.,
For example, a mixer such as a ribbon blender, a tumbler, a Nauter mixer, a Henschel mixer, a super mixer, a planetary mixer, and a kneading machine such as a Banbury mixer, a kneader, a roll, a kneader ruder, a single screw extruder, and a twin screw extruder. The composition for a rare earth bonded magnet according to the present invention can be obtained by mixing and kneading using.

The rare earth bonded magnet according to the present invention can be obtained by, for example, injection molding the composition for a rare earth bonded magnet according to the present invention. Alternatively, although it is not an injection-molded bonded magnet, a similar rare-earth bonded magnet having excellent heat resistance can be manufactured by an extrusion molding method as disclosed in JP-A-6-236807 and JP-A-7-249538. At this time, if it is molded in a magnetic field, it is possible to manufacture an anisotropic high-performance rare earth bonded magnet having a high magnetic flux density in which the easy directions of magnetization of the magnetic powder are aligned.

By performing one or more of the following seven items in these kneading / molding steps, the heat resistance of the bonded magnet can be further improved.

That is, 1. The kneading temperature of the resin binder and the magnetic powder is 240 ° C. or less when a thermoplastic resin is used, preferably 22
The temperature may be 0 ° C or lower. When the kneading temperature exceeds 240 ° C., the magnetic properties of the rare earth bonded magnet composition and the bonded magnet, particularly the squareness and the coercive force are deteriorated.

2. The atmosphere to be kneaded may be a non-oxidizing atmosphere such as nitrogen gas, argon gas or helium gas, and the residual oxygen concentration may be 10% by volume or less, preferably 1% by volume or less. At this time, it is particularly effective to set the above-mentioned non-oxidizing atmosphere in the raw material feeding hopper of the kneading machine, the inside of the cylinder, and the vicinity of the die which is the exit of the kneaded molten composition. Further, when a thermoplastic resin is used, it is desirable that the atmosphere before the composition for a rare earth bonded magnet that has passed through the die is cooled to room temperature is also the non-oxidizing atmosphere. If the residual oxygen concentration exceeds 10% by volume, the magnetic properties of the composition and the bonded magnet, particularly the squareness and the coercive force, deteriorate.

3. When using a thermoplastic resin, the cooling time of the composition passing through the die to room temperature should be as fast as possible, and the composition discharged from the die should be air-cooled with a fan or a refrigerant such as liquid nitrogen or water. It is good to throw it in. If the cooling time is long, the magnetic properties of the composition and the bonded magnet, particularly the squareness and the coercive force are deteriorated.

4. Also in the step of crushing the obtained composition after kneading into pellets, the atmosphere is, for example, nitrogen gas,
A non-oxidizing atmosphere such as argon gas or helium gas may be used, and the residual oxygen concentration may be 10% by volume or less, preferably 1% by volume or less. If the residual oxygen concentration exceeds 10% by volume, the magnetic properties of the composition and the bonded magnet, particularly the squareness and the coercive force, deteriorate.

5. When a thermoplastic resin is used, the temperature of the molding machine cylinder when molding the bonded magnet is 250 ° C. or lower, preferably 230 ° C. or lower. When a thermoplastic resin or a thermosetting resin is used, the mold temperature may be 140 ° C or lower, preferably 120 ° C or lower. If the cylinder temperature exceeds 250 ° C. or the mold temperature exceeds 140 ° C., the magnetic properties of the composition and the bonded magnet, particularly the squareness and the coercive force, deteriorate. However, it is desirable that the cylinder temperature and the mold temperature are set as described above within a range that does not impair the orientation of the magnetic powder when formed in a magnetic field.

6. The atmosphere for molding is, for example, a non-oxidizing atmosphere such as nitrogen gas, argon gas, helium gas or reduced pressure vacuum, and the residual oxygen concentration may be 10% by volume or less, preferably 1% by volume or less. At this time,
Especially inside the raw material input hopper of the molding machine, inside the cylinder,
It is effective to perform molding after the vicinity of the mold cavity is set to the non-oxidizing atmosphere. Furthermore, it is desirable that the atmosphere until the molded product is cooled to room temperature is also the non-oxidizing atmosphere. If the residual oxygen concentration exceeds 10% by volume, the magnetic properties of the rare earth bonded magnet composition and the bonded magnet, particularly the squareness and the coercive force, deteriorate.

7. The time taken to cool the molded product taken out of the mold to room temperature should be as quick as possible, and the molded product should be air-cooled with a fan or put into a refrigerant such as liquid nitrogen, dry ice or water. When the cooling time is long, the magnetic properties of the rare earth bonded magnet composition and the bonded magnet, particularly the squareness and the coercive force are deteriorated.

8. When a thermosetting resin is used and a resin curing step is required after molding, the temperature is 140 ° C or lower,
It is preferably 80 ° C. or lower. The higher the curing temperature is, the shorter the curing time can be. However, if the curing temperature exceeds 140 ° C., the magnetic properties, particularly the squareness and the coercive force of the rare earth bonded magnet composition and the bonded magnet deteriorate. Further, the hardening atmosphere may be a non-oxidizing atmosphere such as nitrogen gas, argon gas, helium gas or reduced pressure vacuum, and the residual oxygen concentration may be 10% by volume or less, preferably 1% by volume or less. If the residual oxygen concentration exceeds 10% by volume, the magnetic properties of the rare earth bonded magnet composition and the bonded magnet, particularly the squareness and the coercive force, deteriorate.

[0040]

EXAMPLES Examples of the present invention will be described below.
The invention is not limited to these examples.

Electrolytic Fe powder having a purity of 99.9% by weight and a particle size of 150 mesh (Tyler standard, the same applies below) 2.25
kg, purity 99% by weight, oxidized Sm powder having an average particle size of 325 mesh 1.01 kg, granular metal Ca 0.44 kg with a purity 99% by weight, anhydrous Ca chloride powder 0.05 kg
And were mixed using a V blender. The mixture obtained here was placed in a stainless steel container and placed under an argon atmosphere.
The mixture was heated at 50 ° C. for 8 hours to cause reduction diffusion reaction.

Then, the reaction product was cooled and then put into water to disintegrate. The obtained slurry was washed with water and then with acetic acid to remove unreacted Ca and CaO by-produced. The obtained slurry was filtered, replaced with ethanol, and then vacuum dried to obtain about 3 kg of Sm—Fe alloy powder having a particle size of 150 μm or less.

Next, this powder was loaded into a tubular furnace and heated (nitriding treatment) at 465 ° C. for 6 hours in an ammonia-hydrogen mixed gas atmosphere with an ammonia partial pressure of 0.35, and then,
Heating at 465 ° C for 2 hours in argon gas (annealing treatment)
Then, Sm-Fe-N based magnetic powder of 24.6 wt% Sm-3.6 wt% N-71.8 wt% Fe was obtained.

An X-ray analysis of this magnetic powder revealed that the diffraction line (Sm ₂ Fe _{17) of the} rhombohedral Th ₂ Zn ₁₇ type crystal structure was used.
N ₃ intermetallic compound).

Next, the above magnetic powder was finely pulverized under the conditions shown in Table 1 below to prepare magnetic powders for rare earth bonded magnets according to Examples 1-2 , Comparative Examples and Reference Examples 1-2 .

[0046]

[Table 1] In each of the magnetic powders for rare-earth bonded magnets according to Examples 1 to 2, Comparative Examples and Reference Examples 1 to 2, 8 parts by weight of 12-polyamide resin and 1 part by weight of ethylenebisstearic acid amide were used with respect to 100 parts by weight of the magnetic powder. , Paraffin wax 1
Parts by weight were mixed and kneaded with a Labo Plastomill. The kneading temperature is 220 to 240 ° C, and the atmosphere in the kneading tank is 8% by volume.
O ₂ —N ₂ and the composition taken out after kneading were cooled by air.

Obtained Examples 1-2, Comparative Examples and References
The rare earth bonded magnet compositions according to Examples 1 and 2 were crushed by a plastic crusher to obtain pellets for molding. From this pellet, a cylindrical bonded magnet of φ20 × 13 mm was
It was manufactured by injection molding while applying an orientation magnetic field of 4 kOe in the mm direction. Cylinder temperature is 190-250 ° C, mold temperature is 110 ° C, atmosphere inside the raw material hopper / cylinder of the injection molding machine is 8% by volume O ₂ -N ₂ , atmosphere near the mold cavity is atmospheric air, and molding taken out. The cooling method of the product was air cooling.

Obtained Examples 1-2, Comparative Examples and References
After polishing the end faces of each molded product (bonded magnet) according to Examples 1 and 2 , a scanning electron microscope was used to take 2000 times magnification photographs in 3 fields of view. Next, a plurality of straight lines were drawn on the photograph at 6 μm intervals, and the particle size of the magnetic powder was measured by the method described above. Particles having a size of 1 μm or more were extracted from the obtained data, and the number-based particle size distribution with respect to the logarithm of the particle diameter was obtained. The number of extracted magnetic powder particles is 200 or more. From this data, the content ratio of the magnetic powder having a particle size of 5.0 μm, 4.0 μm, 3.2 μm or more was examined. 1 to 3
Shows the number-based cumulative particle size distribution of Example 1, Comparative Example, and Example 2 obtained from electron micrographs.

The obtained Examples 1 and 2, Comparative Examples and
And Hk and coercive force HcJ of each bonded magnet according to Reference Examples 1 and 2
Was magnetized with a pulsed magnetic field of 50 kOe in the direction of 13 mm and then measured with a self-recording magnetometer. Here, Hk is a demagnetizing field when the magnetization J is reduced to 90% of the residual magnetic flux density Br, and represents the squareness of the demagnetization curve.

The results are shown in Table 2.

[0051]

[Table 2] However, in Table 2, the content rate 1 indicates a magnetic powder content rate of 5.0 μm or more, the content rate 2 indicates a magnetic powder content rate of 4.0 μm or more, and the content rate 3 indicates a magnetic powder content rate of 3.2 μm or more. ing.

Next, Examples 1 and 2, Comparative Examples and Reference Examples
Each bonded magnet according to 1-2 is processed into φ10 × 7 mm (7 mm direction is the orientation direction), magnetized in the orientation direction with a magnetic field of 50 kOe, and then in a constant temperature bath set to each temperature in the range of 50 to 125 ° C. Heated for 1 hour. The irreversible demagnetization rate (initial demagnetization rate) was evaluated by measuring the total amount of magnetic flux at room temperature before and after heating and dividing the difference by the total amount of magnetic flux before heating. A digital flux meter was used to measure the total amount of magnetic flux. From the heating temperature dependence of the initial demagnetization rate, the temperature at which the initial demagnetization of 5% occurs (referred to as heat resistant temperature) was obtained and shown in Table 2 above.

[Evaluation] In Examples 1 and 2, the particle diameter was 5.0 μm, 4.0 μm and 3.2 μ with respect to the total magnetic powder having a particle diameter of 1.0 μm or more.
When the content of all magnetic powders of m or more is 2.5%, 4.5%, or 10% or less on a number basis (all conditions of claim 1 are satisfied), the demagnetization curve has a square shape. It can be confirmed that the properties and coercive force are improved and the heat resistance temperature is 100 ° C. or more, which is the most excellent.

Further, in Reference Example 1 , when the content ratio of the total magnetic powder having a particle diameter of 5.0 μm or more is 2.5% or less on the number basis (the content ratio of the total magnetic powder of 4.0 μm or more is the number basis. It is 5.2%, and the content ratio of the total magnetic powder of 3.2 μm or more is 12% on the number basis (not satisfying the conditions of claim 1 ), and it can be confirmed that the heat resistance temperature exceeds 80 ° C. .

In Reference Example 2 , the particle diameter is 5.0 μm, 4.0.
μm or more of the total magnetic powder content is 2.5% on a particle number basis, respectively, according to claim 1 when 4.5% or less (3.2 .mu.m or more of the total magnetic powder content is 11% by number basis It can be confirmed that the heat resistant temperature is 90 ° C. or higher. That is, it can be confirmed that the heat resistance is slightly inferior to Examples 1 and 2, but is superior to Reference Example 1 .

On the other hand, in the comparative example, the particle diameter is 5.0 μm,
The total magnetic powder content of 4.0 μm and 3.2 μm or more is
It can be confirmed that the heat-resistant temperature does not reach 80 ° C., in the cases of exceeding 2.5%, 4.5%, and 10% on the number basis, respectively.

As a matter of course, the particle size distribution of the magnetic powder contained in each of these bonded magnets is exactly the same in each rare earth bonded magnet composition before molding.

[0058]

According to the inventions according to claims 1, 2 and 3 ,
4. Particle size for all magnetic powder having a particle size of 1.0 μm or more.
The total magnetic powder content of 0 μm or more is 2.5% on a number basis.
All magnetic powder having a particle size of 1.0 μm or more
Content of the total magnetic powder having a particle diameter of 4.0 μm or more
The number of particles is more than 0% and 4.5% or less, and particles
Particle diameter 3.2μ for all magnetic powders with diameter 1.0μm or more
The total magnetic powder content of m or more exceeds 0% on a number basis and is 1
Since it is set to 0% or less , the temperature at which the initial demagnetization rate becomes 5% exceeds 80 ° C, and R-Fe excellent in heat resistance is excellent.
-It has the effect of providing a magnetic powder for an N-based bonded magnet (rare earth bonded magnet), a composition for a rare earth bonded magnet, and a rare earth bonded magnet.

[Brief description of drawings]

FIG. 1 is a graph showing a number-based cumulative particle size distribution of magnetic powder with respect to a logarithm of a particle size of 1 μm or more in Example 1 of the present invention.

FIG. 2 is a graph showing a number-based cumulative particle size distribution of magnetic powder with respect to a logarithm of a particle size of 1 μm or more in a comparative example.

FIG. 3 is a graph showing a cumulative particle size distribution based on the number of magnetic powders with respect to a logarithm of a particle size of 1 μm or more in Example 2 of the present invention.

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-5-308012 (JP, A) JP-A-5-226132 (JP, A) JP-A-10-41116 (JP, A) JP-A-9- 97732 (JP, A) JP 7-302725 (JP, A) JP 5-339683 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01F 1/00-1 / 117 B22F 1/00 C22C 38/00 303

Claims (3)

(57) [Claims] 1. R (R is a rare earth element) and Fe or Fe
In addition, in the magnetic powder for a rare earth bonded magnet having Co and N as main constituents and having a Th ₂ Zn ₁₇ type crystal structure, the particle diameter of all magnetic powder having a particle diameter of 1.0 μm or more is 5.
The total magnetic powder content of 0 μm or more is 2.5% on a number basis.
All magnetic powder having a particle size of 1.0 μm or more
Content of the total magnetic powder having a particle diameter of 4.0 μm or more
The number of particles is more than 0% and 4.5% or less, and particles
Particle diameter 3.2μ for all magnetic powders with diameter 1.0μm or more
The total magnetic powder content of m or more exceeds 0% on a number basis and is 1
A magnetic powder for a rare earth bonded magnet, which is 0% or less . 2. The heating temperature at which the initial demagnetization rate is 5% is 80 ° C.
A rare earth bond magnet composition for use in the production of a rare earth bond magnet having a heat resistance exceeding 60 ° C., characterized in that the magnetic powder for a rare earth bond magnet according to claim 1 and a resin binder are the main components. Composition for magnets. 3. The composition for a rare earth bonded magnet according to claim 2 , which is formed into a magnet shape and has an initial demagnetization rate of 5.
% Rare-earth bonded magnet having a heat resistance exceeding 80 ° C.