JP2002343623A - Plastic sheet magnet molded body and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polar anisotropic sheet magnet molded body, which is improved in flexibility and magnetic properties, enabling use for various kinds of products over a wider range of applications. SOLUTION: A polar anisotropic flexible sheet magnetic molded body is composed of thermoplastic resin and magnetic powder. Anisotropic rare earth magnetic powder containing at least rare earth iron nitrogen magnetic powder is used as the magnetic powder, so that a plastic sheet-like magnetic molded body, formed of the above magnetic powder, can be improved in flexibility and magnetic characteristics.

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, and more particularly to a flexible sheet-like magnet having excellent flexibility and magnetic properties and a method for producing the same.

[0002]

2. Description of the Related Art Motors are a typical application of permanent magnet materials. In particular, in a small motor having an output of several W or less, an annular permanent magnet is used as a field element. Particularly, bond magnets are excellent in moldability and workability, and are used as permanent magnets for the motor field element. In recent years, as a method of manufacturing this annular permanent magnet, a method has been proposed in which a sheet-like magnet molded body having flexibility is curled into an annular magnet. This has advantages such as easy assembly of the motor and is industrially useful.

[0003] For example, Japanese Patent Application Laid-Open No. 2000-331812 discloses a technique for suppressing a decrease in flexibility of a flexible sheet-like magnet formed using isotropic rare earth magnetic powder under long-term high-temperature storage. Proposed. Since the isotropic magnet molded body does not need to be subjected to magnetic field molding, it is easily molded as compared with the anisotropic magnet molded body, and has a characteristic that a desired magnetic pole pattern can be generated by magnetization. However, the isotropic magnet molded body has a smaller magnetic flux density than the anisotropic magnet molded body, and there is a limit to further improving the performance of the motor.

Japanese Patent Application Laid-Open No. 2000-341916 proposes a permanent magnet field type motor in which a flexible sheet-like magnet molded article having a magnetic field and made axially anisotropic is curled and mounted. . There is a feature that a higher magnetic flux density can be obtained as compared with an isotropic magnet molded body. However, when curled in a ring and mounted on a motor, the direction of anisotropy is the radial direction. For this reason, there is a problem that the leakage magnetic flux not used for driving the motor is large, and the high magnetic flux density of the rare earth magnetic powder cannot be sufficiently utilized.

A ring-shaped permanent magnet used as a motor includes a polar anisotropic magnet molded body in which magnetic poles are formed only on one of the ring-shaped inner and outer peripheral surfaces. This has a small leakage magnetic flux, and the highest magnetic flux density can be expected for the same size. Also, compared to axial anisotropy, polar anisotropy has a feature that a permeance coefficient can be increased because a longer magnetic path length can be secured. For example, Japanese Patent Application Laid-Open No. 7-250460 proposes a technique in which anisotropic ferrite powder and a flexible resin are mixed, extruded to form a polar anisotropic sheet-like magnet, curled, and inserted into a housing. Have been.

[0006]

However, according to the method disclosed in JP-A-7-250460, an Nd-Fe-B-based or Sm-Co-based anisotropic rare-earth magnetic powder is used to provide sufficient flexibility. It is difficult to form a polar anisotropic sheet-like magnet molded body having the following. Nd-Fe-B-based or Sm-Co-based anisotropic rare earth magnetic powders are not suitable for complicated orientation such as extremely anisotropic due to their large particle diameter. In addition, when the sheet-like magnet molded body is curled, coarse particles compete with each other, and the flexible resin connecting the particles is separated. For this reason, there was a problem that a crack was generated in the magnet molded body, and particles were precipitated from the magnet molded body, dropped off, and scattered.

[0007] Nd-Fe-B and Sm-Co anisotropic rare earth magnetic powders are generally produced using alloys as raw materials, and contain a large amount of fine particles in order to obtain a target particle size by grinding. When the number of fine particles is large, the specific surface area of the magnetic powder becomes large, so that the movement of the flexible resin at the interface between the particles and the flexible resin is restricted, and the flexibility of the sheet-like magnet molded body is reduced. There was a problem.

Accordingly, an object of the present invention has been made in view of the above circumstances. That is, an object of the present invention is to provide a flexible sheet-like magnet molded body using anisotropic rare-earth magnetic powder and having excellent flexibility and magnetic properties, and a method for producing the same.

[0009]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have conducted intensive studies on a polar anisotropic flexible sheet-like magnet formed using anisotropic rare earth magnetic powder, The inventors have found that the above-mentioned problems can be solved by using a rare earth iron-nitrogen based magnetic powder, and have completed the present invention.

That is, the objects of the present invention are as follows:
This can be achieved by the configuration of (5). (1) A polar anisotropic flexible sheet-like magnet formed from a flexible thermoplastic resin and magnetic powder, wherein the magnetic powder contains at least a rare earth iron-nitrogen-based magnetic powder. A flexible sheet-shaped magnet molded body, which is a rare earth magnetic powder.

(2) The molded flexible sheet magnet according to (1), wherein the anisotropic rare earth magnetic powder contains at least 50% by weight of rare earth iron-nitrogen based magnetic powder.

(3) The rare earth iron-nitrogen based magnetic powder has a Fisher diameter of 1.5 to 5.5 μm and a BET value of 0.1 to ⁵ m ² / g. Or the flexible sheet-like molded magnet according to (2).

(4) The flexible sheet-like magnet molded article according to any one of (1) to (3), wherein the flexibility α of the flexible sheet-like magnet molded article is 30 mm or less.
(However, when the flexible α is wound around a 1.5 mm-thick flexible sheet-shaped magnet formed around a cylindrical rod without discoloration, cracking, or cracking on the outer peripheral surface thereof, It is represented by the minimum diameter α of the cylindrical rod that can be formed.)

(5) In a method for producing a sheet-like magnet molded body having two main surfaces, which comprises molding a resin composition comprising a magnetic powder and a resin in a magnetic field, the magnetic powder comprises at least a rare earth iron-nitrogen based magnetic powder. Containing anisotropic rare earth magnetic powder, wherein the resin is a thermoplastic resin having flexibility,
The method of manufacturing a flexible sheet-like magnet according to any one of (1) to (4), wherein the forming in the magnetic field is performed such that a magnetic pole is generated only on the first main surface.

That is, the flexible sheet-like magnet molded article of the present invention can realize excellent magnetic properties and flexibility by using a rare earth iron-nitrogen based magnetic powder. In particular, the rare-earth iron-nitrogen based magnetic powder has a nucleation type in which the coercive force is developed, and the particle diameter is used as a single magnetic domain particle diameter.
For this reason, it is easy to orient the magnetic field, is excellent in molding workability, and obtains a practical level of flexibility. Even when used together with other anisotropic rare earth magnetic powders such as Nd-Fe-B and Sm-Co, excellent flexibility and moldability can be obtained. At this time, as described in the above (2), it is preferable to standardize the content of the rare earth iron-nitrogen based magnetic powder. Further, as described in the above (3), it is preferable to use a rare earth iron-nitrogen-based magnetic powder whose powder properties are standardized, and the flexibility of the sheet-like magnet molded body can be further improved.

In the above (4), BMG-3 of the Guidebook for Bonded Magnet Test Methods (Japan Bonded Magnet Industry Association)
According to the method described in 002, the flexibility of the magnet molded body is evaluated. A sheet-shaped magnet molded body having a thickness of 1.5 mm is wound around cylindrical rods having various outer diameters, and at this time, the outer peripheral surface of the sheet-shaped magnet molded body is visually observed for any discoloration, crack, or crack. The minimum value among the diameters of the cylindrical rods that can be wound around the outer peripheral surface of the sheet-shaped magnet molded body without causing deterioration is α, which is used as an index for evaluating flexibility.
In the present invention, the flexibility α is more preferably 30 mm or less.

[0017]

Next, the present invention will be described in detail. In the present invention the general formula _{R x Fe 100-x- y N} y (R
Uses one or more rare earth metals). The rare earth metal preferably contains Sm. When Sm is contained, magnetic anisotropy and saturation magnetization increase, and excellent magnetic properties can be obtained as a permanent magnet material. Further, Sm-Fe-N-based magnetic powder having a composition represented by Sm ₂ Fe ₁₇ N ₃ is most preferable,
Excellent magnetic properties can be obtained.

This rare earth iron-nitrogen based magnetic powder is made of Nd-F
It has the same magnetic properties as the eB magnetic powder and has an average particle size of about several μm to 20 μm. For this reason, the orientation is excellent, and a sufficient orientation is possible even with a thin sheet-shaped magnet molded body. Furthermore, since it contains almost no coarse particles, an excellent flexible magnet molded body can be produced. In addition, since it is a nitride, it has excellent corrosion resistance, and it is not necessary to coat the produced magnet molded body with an epoxy resin or the like. Tables 1-3
As compared with the comparative example using no rare earth iron-nitrogen-based magnetic powder as shown in the above, the present example is excellent in both flexibility and rust prevention and has a high surface magnetic flux density.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

[Table 3]

In the present invention, the rare-earth iron-nitrogen-based magnetic powder is preferably used alone, but may be used together with another anisotropic rare-earth magnetic powder. Anisotropic rare earth magnetic powder that can be used together with rare earth iron-nitrogen based magnetic powder is, for example, SmC
o ₅ (1-5 _{system), Sm 2 (Co, Fe} , Zr, V)
₁₇ (2-17 type), such as Sm-Co type, Nd ₂ Fe _1
4 B, Nd ₂ (Fe, Co) ₁₄ B, (Nd, Dy) ₂
Nd-Fe-B system, such as Fe ₁₄ B, and Nd-Fe-
Ti-N type, Nd-Fe-VN type and the like can be mentioned.

For example, Nd represented by Nd ₂ Fe ₁₄ B
-Fe-B based magnetic powder is relatively inexpensive and has excellent magnetic properties. Therefore, by using the Nd-Fe-B-based magnetic powder together with the rare-earth iron-nitrogen-based magnetic powder, an inexpensive sheet-shaped magnet molded body having excellent magnetic properties, excellent flexibility, and excellent flexibility can be obtained. As described above, the anisotropic rare-earth magnetic powder used together with the rare-earth iron-nitrogen-based magnetic powder can be selected depending on the application and use conditions, and two or more kinds may be used. In order to further improve heat resistance and environmental resistance, the rare earth iron-nitrogen-based magnetic powder or the anisotropic rare-earth magnetic powder may be subjected to a surface treatment with a silane-based coupling agent or the like.

When the rare-earth iron-nitrogen-based magnetic powder is used together with the above-described anisotropic rare-earth magnetic powder, the rare-earth iron-nitrogen-based magnetic powder is preferably 50 parts by weight or more based on 100 parts by weight of the magnetic powder used. It is more preferably at least 70 parts by weight. As shown in FIG. 2, when the rare earth iron-nitrogen based magnetic powder is contained in an amount of 50 parts by weight or more, the surface magnetic flux density is improved. Further, as shown in Tables 1 to 3, it can be seen that the higher the content of the rare earth iron-nitrogen based magnetic powder, the higher the flexibility and the rust prevention.

In the present invention, the rare earth iron-nitrogen based magnetic powder has a Fischer diameter of 1.5 to 5.5 μm,
The ET value is preferably from 0.1 to 5 m ² / g. At this time, as shown in Table 4, it can be seen that the flexibility is improved. More preferably, the Fisher diameter is 2 to 4 μm, and the BET value is 0.5 to ² m ² / g. At this time, as shown in Table 4, the outer peripheral surface can be wound around a cylindrical rod having a diameter of 5 mm without causing discoloration, cracks, and cracks on the outer peripheral surface, and excellent flexibility can be obtained. I understand. Here, the Fischer diameter of the magnetic powder is an average particle diameter measured by an air permeation method using a Fischer sub-sieve sizer. The BET value is a specific surface area of the magnetic powder measured by an adsorption method using nitrogen gas.

[0026]

[Table 4]

The rare earth iron-nitrogen based magnetic powder to be used is
Preferably, it is produced without pulverization. This makes it possible to produce a sheet-like magnet molded body having excellent flexibility and magnetic properties without generation of fine particles due to pulverization and deterioration of magnetic properties due to changes in surface properties.

Next, in the present invention, a thermoplastic resin having flexibility is used as the resin. In particular, it is preferable to use a thermoplastic elastomer which is a block copolymer of a hard segment and a soft segment. The thermoplastic elastomer exhibits a low melt viscosity in a temperature range of the melting point or higher because the hard segment is melted, and the magnetic particles easily flow during magnetic field molding. For this reason, molding can be performed even with a complicated magnetic field orientation such as polar anisotropy. Further, when the magnetic segment is cooled to a temperature equal to or lower than the melting point after the magnetic field is formed, the hard segment is crystallized, so that the magnetic powder can be fixed in a state of being polar anisotropically oriented.

In the present invention, for example, polyolefin resins such as polyethylene, polypropylene, polybutene, chlorinated polyethylene, and polystyrene; polyvinyl resins such as polyvinyl chloride and polyvinyl acetate; polystyrene resins; polyesters, polyamides, polyurethanes, and polyethylene acetate A thermoplastic elastomer having at least one type of structural unit having a thermoplastic segment such as a vinyl copolymer can be used. Two or more kinds of thermoplastic elastomers may be appropriately mixed and used.

The thermoplastic elastomer is formed by a molding method, an application,
Although it can be selected according to the use conditions, a thermoplastic elastomer whose hard segment is polybutylene terephthalate or polyamide is particularly preferable. At this time, when forming the magnetic field,
Particularly excellent fluidity is obtained, and the orientation is improved. For this reason, even when the magnetic powder is highly filled, or even in the form of a thin sheet, complicated polar anisotropy can be obtained, as shown in the results of using the amide-based thermoplastic elastomers in Tables 1 to 4. And excellent magnetic flux density can be realized. Further in the present invention, depending on the purpose of use, polyolefin resin, polyvinyl resin, polystyrene resin, polyester, polyamide,
A mixture of at least one resin binder selected from polyurethane and polyethylene vinyl acetate copolymer and a thermoplastic elastomer may be used.

In the present invention, first, the above-described anisotropic rare earth magnetic powder and a flexible thermoplastic resin are prepared at a predetermined compounding ratio, and mixed and kneaded using a mixer and a kneader to obtain a resin composition. I do. The compounding ratio can be appropriately set according to the type of the anisotropic rare earth magnetic powder to be used and the thermoplastic resin having flexibility, production conditions, and the like. In addition, in order to improve various properties such as moldability and flexibility of the molded product, it is preferable to appropriately use additives such as a lubricant, a plasticizer, and an antioxidant according to the purpose.

Next, the prepared resin composition is molded in a magnetic field to obtain a polar anisotropic sheet-like molded magnet. At this time, the magnetic field is formed such that a magnetic pole is generated only on one of the two main surfaces of the flat plate. The shape of the magnetic pole is not particularly limited, but when used as a motor field magnet, it is preferable to form the magnetic poles in a stripe shape. Also, when curled, it becomes a skewed magnetic pole,
A magnetic pole may be formed.

Here, the molding means is, for example, extrusion molding,
Compression molding and injection molding can be applied. Of these, injection molding is preferred. In molding, a magnet or a coil for generating a magnetic field is arranged in a die or a mold to generate an orientation magnetic field necessary for polar anisotropy to form a magnetic circuit. At this time, the strength of the magnetic field necessary for forming a polar anisotropic magnet is set according to the magnetic properties of the magnetic powder used and the fluidity of the resin.

In the injection molding, the produced resin composition is heated to be in a molten state and then injected into a mold. For this reason, at the time of magnetic field shaping, magnetic particles flow easily, and polar anisotropy can be easily formed. Further, since the mold is not heated, the resin composition injected into the mold is rapidly cooled and solidified in the orientation magnetic field. For this reason, the magnetic particles are completely oriented in the desired polar anisotropy, and a sheet-like magnet molded body having excellent magnetic properties can be obtained.

Extrusion molding is characterized by excellent productivity because magnetic field molding can be performed continuously. While kneading the anisotropic rare earth magnetic powder and the flexible thermoplastic resin with a kneader, the resulting resin composition may be extruded into a die and subjected to magnetic field molding. Further, as in the injection molding, after kneading with a kneading machine, a granular resin composition may be formed and heated again with a molding machine to form a predetermined magnet molded body.

In the compression molding, the magnetic field can be oriented in a polar anisotropic manner by increasing the mold temperature and decreasing the viscosity of the thermoplastic resin having flexibility. Then, by cooling the mold while applying the orientation magnetic field, the magnetic particles oriented in the polar anisotropy can be fixed.

As shown in Tables 1 to 5, the flexible sheet-like molded magnet of the present invention obtained as described above has excellent flexibility with a flexibility α of less than 30 mm. I understand.

[0038]

Hereinafter, embodiments of the present invention will be described.
The present invention is not limited to only specific examples. [Example 1] Samarium oxide having a purity of 99.9% and an average particle diameter of 1.2 µm, and a samarium oxide having a purity of 99.9% and an average particle diameter of 1.3 µm
The mixed raw material consisting of m. iron oxide was calcined at 600 ° C. for 20 hours while passing hydrogen gas through the furnace to reduce a part of the iron oxide to iron.

Next, granular metal Ca was added, put into a mild steel crucible, fired at 1100 ° C. for 3 hours in an Ar gas atmosphere, and subjected to a reduction diffusion treatment. Then, the inside of the furnace was gradually cooled to 100 ° C., and calcined at 450 ° C. for 10 hours in a nitrogen atmosphere to perform a nitriding treatment.

The obtained nitrided product was put into pure water, and decantation was repeated several times. Next, the mixture was stirred in an aqueous acetic acid solution having a pH of 4.0 to remove Ca. The slurry was subjected to solid-liquid separation and vacuum-dried at 80 ° C. to obtain an Sm—Fe—N-based magnetic powder. This Sm—Fe—N magnetic powder had a Fisher diameter of 3 μm and a BET value of 1.4 m ² / g.

89 parts by weight of Sm-Fe-N type magnetic powder surface-treated with an amino type silane coupling agent, 10 parts by weight of an amide type thermoplastic elastomer, 0.6 parts by weight of a phenolic antioxidant, zinc stearate as a lubricant And 0.4 parts by weight were uniformly mixed with a mixer. Next, the obtained mixture was kneaded at a heating temperature of 220 ° C. with a twin-screw extruder,
A pellet-shaped resin composition was obtained.

This pellet-shaped resin composition was magnetically molded by an injection molding machine at a heating temperature of 230 ° C. and an orientation magnetic field of 4 kOe or more, and the polar anisotropy shown in FIG.
m, a sheet-like magnet molded body having a thickness of 1.5 mm. At this time, the magnetic poles were striped, and four poles were formed so as to be parallel to the width direction of the sheet-like magnet molded body. Then, it was magnetized with a magnetic field of 20 kOe along the formed pole anisotropy to form a magnetic pole.

Examples 2 to 10 and Comparative Examples 1 to 3 HD
Nd-Fe-B based magnetic powder (average particle diameter 50 μm), Sm-Co (2-17 based) magnetic powder (average particle diameter 40 μm), Sm-Co (1-5 based) magnetic obtained by DR treatment Using a powder (average particle diameter of 10 μm) and mixing with the Sm—Fe—N-based magnetic powder at the weight ratios shown in Tables 1 to 3, a sheet-like magnet molded body was produced in the same manner as in Example 1 except that it was used. Produced.

[Examples 11 to 23] By changing the particle size characteristics of raw materials such as samarium oxide and iron oxide, the temperature of reduction diffusion treatment, and the temperature of nitriding treatment, the Fischer diameter and BET shown in Table 4 were changed. A Sm-Fe-N-based magnetic powder having a specific value was produced. Next, in the same manner as in Example 1, a sheet-like magnet molded body was produced.

Examples 24 and 25 and Comparative Example 4 A sheet-like magnet molded body was produced in the same manner as in Example 1 except that the resin binder shown in Table 5 was used instead of the amide-based thermoplastic elastomer. .

[0046]

[Table 5]

Comparative Example 5 A sheet-like magnet molded body was produced in the same manner as in Example 1 except that the magnetic field was molded in an axial direction by an injection molding machine.

The obtained sheet-like magnet molded body was evaluated for surface magnetic flux density, flexibility and rust prevention by the following methods. (Measurement of Surface Magnetic Flux Density) The Hall element was moved in the longitudinal direction of the sheet-like magnet molded body, and measured with a Gauss meter, and the maximum and minimum values of the surface magnetic flux density were recorded.

(Evaluation of Flexibility) A sheet-like magnet molded body was wound around a cylindrical rod having an outer diameter of 5 to 40 mm. At this time, the outer peripheral surface of the sheet-like magnet molded body was visually inspected for discoloration, cracks, and cracks. Was observed. Among the diameters of the columnar rods that can be wound without causing deterioration on the outer peripheral surface of the magnet molded body, the minimum value was α, which was used as an index for evaluating flexibility. The smaller the value of the flexibility α, the better the flexibility,
This shows that curling can be performed even with a small diameter.

(Evaluation of Rust Prevention Property)
% Salt solution at 25 ° C. for 24 hours, and visually inspected for rust on the sheet-like magnet molded body. A state in which no rust was confirmed and the rust resistance was good was indicated by "O". The state where rust was observed at several places was indicated by “△”, and the state where many rusts were generated was indicated by “×”.

Tables 1 to 5 and FIG. 2 show the surface magnetic flux density, flexibility and rust prevention of the obtained sheet-like magnet molded product.

[0052]

As described above, the flexible sheet-like magnet molded article of the present invention has excellent flexibility and high magnetic flux density. The flexible sheet-like magnet molded article of the present invention can be used as a magnet for a motor field by, for example, being curled and formed into a ring shape. Particularly, since it is excellent in flexibility, it can be mounted on a small-diameter motor, and a highly anisotropic and high surface magnetic flux density can be obtained. Further, according to the production method of the present invention, it is possible to provide a flexible sheet-like molded magnet having excellent magnetic properties.

[Brief description of the drawings]

FIG. 1 is a schematic view of a flexible sheet-like magnet molded article of the present invention showing formed polar anisotropic magnetic poles.

FIG. 2 is a graph showing the relationship between the maximum value of the surface magnetic flux density of the sheet-like magnet molded body and the content of rare earth iron-nitrogen-based magnetic powder in the magnetic powder.

Claims (5)

[Claims] 1. A molded article made of a polar anisotropic flexible magnet made of a thermoplastic resin having flexibility and magnetic powder, wherein the magnetic powder contains at least a rare earth iron-nitrogen based magnetic powder. A flexible sheet-shaped magnet molded product, which is an isotropic rare earth magnetic powder. 2. The flexible sheet-like molded magnet according to claim 1, wherein the anisotropic rare earth magnetic powder contains at least 50% by weight of a rare earth iron-nitrogen based magnetic powder. 3. The rare earth iron-nitrogen based magnetic powder has a Fischer diameter of 1.5 to 5.5 μm and a BET value of 0.5.
3. It is 1 to 5 m ² / g.
3. The flexible sheet-like magnet molded product according to item 1. 4. The flexibility α of the flexible sheet-like magnet molded body.
Is not more than 30 mm.
3. The flexible sheet-like magnet molded product according to item 1. (However, when the flexible α is wound around a 1.5 mm-thick flexible sheet-shaped magnet formed around a cylindrical rod without discoloration, cracking, or cracking on the outer peripheral surface thereof, It is represented by the minimum diameter α of the cylindrical rod that can be formed.) 5. A method for producing a sheet-shaped magnet molded body having two main surfaces, wherein a resin composition comprising a magnetic powder and a resin is molded in a magnetic field, wherein the magnetic powder contains at least a rare earth iron-nitrogen based magnetic powder. Anisotropic rare earth magnetic powder,
The flexible resin according to any one of claims 1 to 4, wherein the resin is a thermoplastic resin having flexibility, and the molding in the magnetic field is performed such that a magnetic pole is generated only on the first main surface. Method for producing conductive sheet-shaped magnet molded body.