JP2016192517A - Bond magnet and manufacturing method of bond magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bond magnet of which the magnetic characteristics are improved and which is improved in productivity and recyclability, and a manufacturing method of the bond magnet.SOLUTION: The present invention relates to a bond magnet in which a magnet powder is coupled by a binder resin. In the bond magnet, the binder resin is a baroplastic. The manufacturing method of the bond magnet includes: a preparation step for preparing a mixture containing the magnet powder and the baroplastic; a molding step for molding the mixture by applying a pressure of 10 MPa or more and 100 MPa or less to the mixture and softening the baroplastic; and a solidification step for solidifying the mixture by returning the pressure to an ordinary pressure after molding and hardening the baroplastic.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a bonded magnet and a manufacturing method of the bonded magnet. In particular, the present invention relates to a bonded magnet having high magnetic properties and excellent productivity and reusability.

A bonded magnet (resin-bonded bonded magnet) in which magnet powder and a binder resin are mixed and molded and solidified, and the magnet powder is bonded with a binder resin is known. Magnet powders include oxide magnets such as ferrite magnets, metal magnets such as Fe—Al—Ni—Co magnets, Sm—Co (SmCo ₅ , Sm ₂ Co ₁₇ etc.) magnets, Nd—Fe—B, and the like. Rare earth magnets such as a system (Nd ₂ Fe ₁₄ B) magnet and a Sm—Fe—N system (Sm ₂ Fe ₁₇ N ₃ ) magnet are used. Generally, a thermoplastic resin and a thermosetting resin are used for the binder resin. A thermoplastic resin softens when heated, melts and exhibits fluidity, and cures (solidifies) when cooled. When the thermosetting resin is heated, the organic compound contained in the resin is polymerized and cured (solidified). Once the thermosetting resin is cured, it is difficult to break the molecular chain of the organic compound and return it to its original state. For example, Patent Documents 1 and 2 disclose techniques related to bonded magnets.

  A conventional bonded magnet is basically manufactured as follows. When using a thermoplastic resin, the mixture of magnet powder and thermoplastic resin is heated to soften the resin, molded by applying pressure, and then cooled to cure the resin. On the other hand, when using a thermosetting resin, after pressing and molding the mixture of magnet powder and a thermosetting resin, it heat-processes (cure process) by hardening resin. Furthermore, when using anisotropic magnet powder in the production of bonded magnets, anisotropy is imparted to the magnet by molding while applying a magnetic field (molding in a magnetic field) and orienting the magnet powder. The magnetic properties (particularly, remanent magnetization) are improved.

  Patent Document 3 proposes a technique of using a baroplastic having a pressure-induced transformation from hard to soft as a binder with respect to a method for producing a cemented carbide or cermet aggregate. Baroplastic is a polymer multiphase material that transitions from a solid phase (phase separation) state to a molten (compatibility) state under pressure, and is a solid at normal temperature and pressure. Baroplastics undergo phase transition and become compatible when a pressure above a certain level is applied, soften and show fluidity even at room temperature without applying heat, and return to atmospheric pressure to phase separation and lose fluidity. And become solid.

JP 2004-349337 A JP 2006-128170 A JP 2008-31552 A

  In the conventional bond magnet, since a thermoplastic resin or a thermosetting resin is used for the binder resin, there are the following problems.

-Decrease in magnetic properties When using either a thermoplastic resin or a thermosetting resin, the magnet powder is exposed to a high temperature because it needs to be heated in the manufacturing process. In general, the magnetic properties of the magnet powder deteriorate at a high temperature, so that the magnet may not exhibit the predetermined magnetic properties. In particular, rare earth magnets are vulnerable to high temperatures, and when heated, their magnetic properties tend to deteriorate, which tends to cause a decrease in magnetic properties. Further, when the magnetic powder is heated to a high temperature, the oxidation is promoted, and there is a possibility that the magnetic properties are deteriorated.

  Furthermore, when a thermoplastic resin is used, if a magnetic field is applied at the time of heat forming to orient the magnet powder, the magnetic force of the magnet powder is reduced by heating, so that the magnet powder cannot be sufficiently oriented. Therefore, there is a possibility that the degree of orientation decreases and sufficient magnetic properties cannot be obtained.

-Productivity is inferior As described above, since heating is required when any resin is used, a heating device is required, and the energy consumption for heating is large, which may increase the manufacturing cost. There is. In addition, the magnetic properties of the magnet may deteriorate due to the oxidation of the magnet powder by heating. Therefore, in order to suppress oxidation, it is conceivable to subject the magnet powder to a surface treatment or a heat treatment in a non-oxidizing atmosphere, but this may lead to a decrease in productivity and an increase in cost. In particular, when a thermosetting resin is used, a curing process is required, and it takes time for the thermosetting, so that productivity is low.

・ Inferior reusability Once a thermosetting resin is cured, it will never return to its original state, so a bonded magnet using a thermosetting resin cannot be reused. Therefore, even if product scraps or defective magnets are generated, they cannot be crushed and used again as raw materials. In the case of a thermosetting resin, it is conceivable to collect and reuse only magnet powder from product waste and defective products. However, since the resin is firmly fixed to the magnet powder, it is not easy to remove the resin from the magnet powder and collect only the magnet powder. Patent Document 2 discloses a method of recovering magnet powder from a magnet, but the process is complicated, and it is expected that a lot of time and cost are required. On the other hand, the thermoplastic resin can be used repeatedly, and the bonded magnet using the thermoplastic resin can be reused. Therefore, it is possible to manufacture magnets by crushing product scraps and defective magnets, using them again as raw materials, and heat-molding them again. However, there is a problem that it is difficult to reuse, for example, magnetic properties are deteriorated by repeated heating.

  Accordingly, there is a demand for the development of bonded magnets that have high magnetic properties and are excellent in productivity and reusability.

  Accordingly, one of the objects of the present invention is to provide a bonded magnet and a magnet having high magnetic properties and excellent productivity and reusability. Another object of the present invention is to provide a bonded magnet manufacturing method capable of producing bonded magnets that are excellent in productivity and reusability.

  The bonded magnet according to one embodiment of the present invention is a bonded magnet in which magnet powder is bonded with a binder resin. In the bonded magnet, the binder resin is a baroplastic.

The manufacturing method of the bonded magnet which concerns on 1 aspect of this invention is equipped with the following preparatory processes, a formation process, and a solidification process.
In the preparation step, a mixture containing magnet powder and baroplastic is prepared.
In the molding step, a pressure of 10 MPa or more and 100 MPa or less is applied to the mixture to soften the baroplastic and mold the mixture.
In the solidification step, after molding, the pressure is returned to normal pressure, the baroplastic is cured, and the mixture is solidified.

  The bonded magnet has high magnetic properties and is excellent in productivity and reusability. The manufacturing method of the said bonded magnet can produce the bonded magnet which is high in a magnetic characteristic and excellent in productivity and reusability.

It is a mimetic diagram showing an example of a bonded magnet concerning an embodiment. It is a figure explaining an example of the manufacturing method of the bonded magnet which concerns on embodiment. It is a figure explaining another example of the manufacturing method of the bonded magnet which concerns on embodiment.

[Description of Embodiment of the Present Invention]
The present inventor has found that the above problem can be solved by using baroplastic as a binder resin in a bonded magnet, and has completed the present invention. First, embodiments of the present invention will be listed and described.

  (1) The bonded magnet which concerns on 1 aspect of this invention is a bonded magnet with which magnetic powder was couple | bonded with binder resin. In the bonded magnet, the binder resin is a baroplastic.

  According to the bonded magnet, since the binder resin is a ballo plastic, unlike the thermoplastic resin or the thermosetting resin, it is not necessary to heat in the manufacturing process. Specifically, since Baroplastic is used for the binder resin, the resin can be softened by pressurization and molded at room temperature, and after molding, the resin can be cured by solidification and solidified. it can. Therefore, the magnet powder is not exposed to high temperatures in the manufacturing process, and the oxidation of the magnet powder can be suppressed, so that it is possible to avoid the deterioration of the magnetic characteristics. Further, since molding at normal temperature is possible and there is no decrease in magnetic force of the magnet powder due to heating when molding in a magnetic field, the magnet powder can be easily oriented and the degree of orientation can be increased. The residual magnetization is improved by increasing the degree of orientation of the magnet powder. Therefore, magnetic characteristics can be improved as compared with conventional bonded magnets.

  Furthermore, since there is no need to heat in the manufacturing process, a heating device is not required, and the curing process can be omitted. For example, the manufacturing cost can be reduced and the lead time of the manufacturing process can be shortened, resulting in excellent productivity. . In addition, since a molten plastic and a solidified state are reversibly changed by applying pressure to the ballo plastic and can be repeatedly used, a bonded magnet using the ballo plastic can be reused. Therefore, it is possible to produce magnets by pulverizing product scraps and defective magnets, using them again as raw materials, and press-molding them again, and the reusability is excellent.

  (2) As one aspect of the bonded magnet, the baroplastic contains a polymer of a hard component and a soft component. And as a hard component of the polymer, at least one selected from polystyrene, poly (butyl methacrylate), poly (caprolactone), poly (ethyl methacrylate), poly (methyl methacrylate) and poly (hexyl methacrylate) is contained. . The soft component of the polymer may contain at least one selected from poly (butyl acrylate), poly (methyl acrylate), poly (ethyl acrylate), poly (ethyl hexyl acrylate), and poly (caprolactone). Can be mentioned.

  The above-described baroplastic can be suitably used as a binder resin for bond magnets. Examples of the combination of the hard component and the soft component constituting the baroplastic include combinations of polystyrene and poly (butyl acrylate), poly (ethyl methacrylate) and poly (ethyl acrylate), polystyrene and poly (ethyl hexyl acrylate), and the like. . The hard component has a glass transition temperature higher than that of the soft component, and the difference in glass transition temperature is preferably 20 ° C. or more.

  (3) As one aspect | mode of the said bonded magnet, it is mentioned that content of the said baroplastic is more than 0.5 mass% and 2.0 mass% or less.

  When the content of the baroplastic is more than 0.5% by mass, the magnet powders are sufficiently bonded to each other to easily maintain the shape, and the magnet can be easily molded. On the other hand, when the content of the baroplastic is 2.0% by mass or less, the volume ratio (resin ratio) of the balloplastic in the magnet can be reduced, and the volume ratio (magnetic powder ratio) of the magnet powder can be increased. Increasing the magnetic powder ratio can improve the magnetic properties.

  (4) As one aspect of the bonded magnet, a lubricant is added, and the amount of the lubricant added is 0.1% by mass or less.

  Lubricants contribute to improving moldability and magnetic properties. By adding a lubricant, friction between the magnet powder and the binder resin (baroplastic) and between the magnet powder during pressure molding can be reduced, and the magnet density (magnet powder ratio) is improved and the magnetic properties are improved. improves. Further, the seizure with the mold can be reduced by the lubricant, and friction with the mold can be reduced when the magnet is taken out from the mold after molding, thereby improving the moldability. Furthermore, when the lubricant is added, when the magnetic powder is oriented by applying a magnetic field in the manufacturing process, the magnetic powder is easily rotated and oriented, and the degree of orientation can be increased.

  When the addition amount of the lubricant is 0.1% by mass or less, the reduction of the magnetic powder ratio can be suppressed and the magnetic characteristics can be improved. The lower limit of the addition amount of the lubricant is not particularly limited as long as the function as the lubricant can be exhibited, but is 0.01% by mass or more, for example.

(5) The manufacturing method of the bonded magnet which concerns on 1 aspect of this invention is equipped with the following preparatory processes, a formation process, and a solidification process.
In the preparation step, a mixture containing magnet powder and baroplastic is prepared.
In the molding step, a pressure of 10 MPa or more and 100 MPa or less is applied to the mixture to soften the baroplastic and mold the mixture.
In the solidification step, after molding, the pressure is returned to normal pressure, the baroplastic is cured, and the mixture is solidified.

  According to the method for manufacturing a bonded magnet, since a plastic material is used as the binder resin, unlike the thermoplastic resin or the thermosetting resin, no heat treatment is required in the manufacturing process. And by carrying out shaping | molding solidification at normal temperature without heating, since the fall of the magnetic characteristic of a magnet powder and the oxidation of a magnet powder can be suppressed, the fall of a magnetic characteristic can be avoided. Therefore, magnetic characteristics can be improved as compared with conventional bonded magnets. Furthermore, since no heat treatment is performed in the manufacturing process, a heating device is not required, and the curing process can be omitted. For example, the manufacturing cost can be reduced and the lead time of the manufacturing process can be shortened. Excellent. Moreover, the manufactured magnet and the defective product produced at the time of manufacture can be used again as a raw material. Specifically, a pulverized powder obtained by pulverizing a magnet once manufactured (including product scraps and defective products) can be used as a mixture of raw magnetic powder and baroplastic, and this is pressure-molded again. It is possible to manufacture a magnet. Therefore, the magnet manufactured by the manufacturing method of the said bonded magnet is excellent in reusability.

  By setting the molding pressure to 10 MPa or more, the baroplastic phase transitions to a compatible state, and molding at room temperature is easy. Moreover, the density (magnetic powder ratio) of a magnet can be raised and the improvement of a magnetic characteristic can be aimed at. By setting the molding pressure to 100 MPa or less, it is possible to suppress the occurrence of cracks in the magnet due to volume expansion due to the decompression after molding, or to reduce the pulling resistance when the magnet is taken out from the mold after molding. It becomes easy.

  (6) As one aspect of the method for producing the bonded magnet, at least one of before and during molding, performing a magnetic field orientation treatment for applying a magnetic field of 0.5 T or more to the mixture.

  By applying a magnetic field, the magnet powder can be oriented, and anisotropy can be imparted to the magnet to enhance magnetic properties (particularly, residual magnetization). In particular, in the method for manufacturing a bonded magnet, since pressure molding is performed at room temperature without heating, there is no decrease in magnetic force of the magnet powder due to heating even when molding in a magnetic field. The degree can be increased.

  By setting the applied magnetic field to 0.5 T or more, a magnet having a high degree of orientation (residual magnetization) can be obtained with sufficient orientation of the magnet powder. Although the upper limit of an applied magnetic field is not specifically limited, From a manufacturing viewpoint, for example, it may be 10T or less.

[Details of the embodiment of the present invention]
Specific examples of the bonded magnet and the bonded magnet manufacturing method according to the embodiment of the present invention will be described below with reference to the drawings. In addition, this invention is not limited to these illustrations, is shown by the claim, and is intended that all the changes within the meaning and range equivalent to the claim are included.

<Bond magnet>
In the bonded magnet 10 shown in FIG. 1, magnet powder 11 is bonded with a binder resin 12. In the bonded magnet 10, the binder resin 12 is a baroplastic and contains magnet powder 11 and a baroplastic 12. The magnet powder 11 is composed of a plurality of magnet particles 11p. An arrow in the magnet particle 11p represents an easy magnetization axis (c axis).

(Magnet powder)
The magnet powder 11 includes a ferrite magnet, an Fe—Al—Ni—Co based magnet, an Sm—Co based (SmCo ₅ , Sm ₂ Co ₁₇ etc.) magnet, an Nd—Fe—B based (Nd ₂ Fe ₁₄ B) magnet, and an Sm. -fe-N system _{(Sm 2 Fe} 17 _{N 3)} is a magnetic powder such as a magnet. Among them, rare earth magnets such as Nd—Fe—B magnets are superior in magnetic properties as compared to ferrite magnets and the like, so that the performance of the magnet can be improved by using rare earth magnet powder for the magnet powder 11. In this example, the magnet powder 11 is a rare earth magnet powder, for example, an Nd—Fe—B magnet powder.

  The magnet powder (rare earth magnet powder) 11 may be either an anisotropic magnet powder or an isotropic magnet powder. If it is an anisotropic magnet powder, the magnet powder is oriented by aligning the easy magnetization axes. Anisotropy can be imparted to the magnetic properties (particularly remanent magnetization). In the case of rare earth magnet powders, those produced by rapid solidification methods such as the strip cast method and the melt span method, but also produced by the HDDR (Hydrogenation Deposition Recombination Recombination) method (So-called HDDR powder) may also be used.

  The volume ratio (magnetic powder ratio) of the magnet powder 11 in the bonded magnet 10 is preferably 60% by volume or more, more preferably 70% by volume or more, and more preferably 80% by volume or more. The higher the magnetic powder ratio, the higher the magnetic properties. As the magnetic powder ratio increases, the resin ratio decreases, leading to a decrease in the mechanical strength and moldability of the magnet. Therefore, the upper limit of the magnetic powder ratio is, for example, 90% by volume or less.

  The average particle size of the magnet powder 11 is, for example, 1 μm or more and 700 μm or less. When the average particle size of the magnet powder 11 is 1 μm or more, it is easy to suppress the oxidation of the magnet powder 11 (magnet particles 11p) in the manufacturing stage, and the handling becomes easy. When the average particle size of the magnet powder 11 is 700 μm or less, it is easy to increase the filling rate of the magnet powder 11 during molding, and it is easy to increase the density (magnet powder ratio) of the magnet. The average particle size of the magnet powder 11 is preferably 2 μm or more and 500 μm or less, and more preferably 300 μm or less. The “average particle size” as used herein refers to a particle size (D50: 50% by volume particle size) in which the cumulative volume is 50% from the small diameter side in the volume-based particle size distribution measured by the laser diffraction method.

(Binder resin)
The binder resin 12 is a baroplastic having a pressure-induced transformation from hard to soft, and transitions from a solid phase (phase separation) state to a molten (compatibility) state under pressure. The baroplastic 12 contains a polymer of a hard component and a soft component. Examples of the hard component of the polymer include at least one selected from polystyrene, poly (butyl methacrylate), poly (caprolactone), poly (ethyl methacrylate), poly (methyl methacrylate), and poly (hexyl methacrylate). . Examples of the soft component of the polymer include at least one selected from poly (butyl acrylate), poly (methyl acrylate), poly (ethyl acrylate), poly (ethyl hexyl acrylate), and poly (caprolactone). Examples of the combination of the hard component and the soft component include combinations of polystyrene and poly (butyl acrylate), poly (ethyl methacrylate) and poly (ethyl acrylate), polystyrene and poly (ethyl hexyl acrylate), and the like. The baroplastic 12 is preferably a block copolymer of a hard component and a soft component.

  Baroplastic 12 has a phase separation structure of a hard component and a soft component in which a hard component and a soft component are phase-separated at normal temperature and normal pressure. Examples of the phase separation structure include a core-shell structure, a lamella structure, and a sea-island structure. In the case of the core-shell structure, either the hard component or the soft component may be the core or the shell, but the shell side is preferably the hard component. In the case of a sea-island structure, either may be the sea or an island, but the sea side is preferably a hard component. Examples of the baroplastic 12 include those that are compatible and soften and flow under a pressure of 10 MPa to 50 MPa.

  The content of the baroplastic 12 is preferably more than 0.5% by mass and not more than 2.0% by mass. When the content of the baroplastic 12 is more than 0.5% by mass, the magnet powder 11 (magnet particles 11p) are sufficiently bonded to each other to easily maintain the shape, and the magnet can be easily molded. On the other hand, when the content of the baroplastic 12 is 2.0% by mass or less, the volume ratio (resin ratio) of the baroplastic 12 in the bonded magnet 10 can be reduced and the magnetic powder ratio can be increased. The content of the baroplastic 12 is 1.7% by mass or less, more preferably 1.5% by mass or less.

(lubricant)
A lubricant (not shown) may be added to the bond magnet 10. By adding the lubricant, it is possible to reduce friction between the magnet powder 11 and the ballo plastic 12 and between the magnet powder 11 (magnet particles 11p) in the molding process, and the density of the magnet (magnetic powder ratio) is improved. Further, the seizure with the mold can be reduced by the lubricant, and friction with the mold can be reduced when the magnet is taken out from the mold after molding, thereby improving the moldability. Furthermore, when a magnetic field is applied during the manufacturing process to orient the magnet powder 11 by adding a lubricant, the magnet powder 11 (magnet particles 11p) is easily rotated and oriented, thereby increasing the degree of orientation. Can do.

  The addition amount of the lubricant is preferably 0.1% by mass or less. When the addition amount of the lubricant is 0.1% by mass or less, the reduction of the magnetic powder ratio can be suppressed and the magnetic characteristics can be improved. The lower limit of the addition amount of the lubricant is not particularly limited as long as the function as the lubricant can be exhibited, but is 0.01% by mass or more, for example. The addition amount of the lubricant is more preferably 0.02% by mass or more and 0.08% by mass or less.

  Examples of the lubricant include organic compounds such as ester lubricants, amide lubricants, hydrocarbon lubricants, fatty acid lubricants, higher alcohol lubricants, metal soaps, and composite lubricants. Examples of the ester lubricant include stearic acid monoglyceride, pentaerythritol tetrastearate, hydrogenated castor oil, stearyl stearate and the like. Examples of the amide-based lubricant include stearic acid amide, oleic acid amide, erucic acid amide, methylene bis stearic acid amide, ethylene bis stearic acid amide, and ethylene bisolefinic acid amide. Examples of the hydrocarbon-based lubricant include paraffin wax, micro wax, and polyethylene wax. Examples of fatty acid lubricants include stearic acid, behenic acid, 1,2-hydroxystearic acid and the like. Examples of higher alcohol lubricants include stearyl alcohol. Examples of the metal soap include calcium stearate, zinc stearate, magnesium stearate, lead stearate and the like.

<Method for manufacturing bonded magnet>
The manufacturing method of a bonded magnet includes a preparation process, a molding process, and a solidification process. Hereinafter, an example of a method for manufacturing a bonded magnet will be described with reference to FIG.

(Preparation process)
The preparation step is a step of preparing a mixture containing the magnet powder 11 and the baroplastic 12 (see the first and second stages in FIG. 2). In the example shown in FIG. 2, the magnet powder 11 and the baroplastic 12 are blended at a predetermined ratio (first stage in FIG. 2), and mixed with the mixer 200, and the magnet powder 11 and the baroplastic as raw materials are mixed. 12 is prepared (second stage in FIG. 2). The magnet powder 11 shown in FIG. 2 is an anisotropic magnet powder, and the arrow in the magnet particle 11p represents an easy magnetization axis (c axis). As the mixer 200, for example, various mixers and mixers such as a ball mill and a V-type mixer can be used.

  Moreover, when blending the magnet powder 11 and the ballo plastic 12, a predetermined amount of lubricant (not shown) may be added. The blending amount (content) of the baroplastic 12 is preferably more than 0.5% by mass and 2.0% by mass or less, and the addition amount of the lubricant is preferably 0.1% by mass or less. The average particle size of the magnet powder 11 is preferably 1 μm or more and 700 μm or less, for example.

(Molding process)
The molding step is a step of applying pressure to the mixture to soften the baroplastic 12 and molding the mixture (see the third and fourth stages in FIG. 2). In the example shown in FIG. 2, the case where the mixture is pressure-formed by the compression molding machine 300 will be described as an example. The compression molding machine 300 includes a mold 30 having an upper punch 31, a lower punch 32, and a cylindrical die 33. Then, the mold 30 is filled with a mixture of the magnet powder 11 and the baroplastic 12.

  The compression molding machine 300 includes a magnetic field application device 34, and can apply a magnetic field to the mixture in the mold 30 in a direction perpendicular (perpendicular) to the compression direction of the compression molding machine 300. In the example shown in FIG. 2, a magnetic field orientation process is performed by applying a magnetic field to the mixture before molding (third stage in FIG. 2). Thereby, the magnet particles 11p rotate so that the easy magnetization axes of the magnet powder 11 (magnet particles 11p) are aligned with the application direction of the magnetic field, and the magnet powder 11 is oriented. In this example, the magnetic field application direction is a direction perpendicular (perpendicular) to the compression direction, but the magnetic field application direction may be parallel to the compression direction.

  The applied magnetic field is 0.5T or more. By setting the applied magnetic field to 0.5 T or more, it is easy to sufficiently orient the magnet powder, and the degree of orientation (residual magnetization) can be increased. Although the upper limit of an applied magnetic field is not specifically limited, For example, it is mentioned as 10T or less. The applied magnetic field is more preferably 1T or more and 7T or less.

  After performing the magnetic field orientation treatment, pressure is applied to the mixture to form the mixture (fourth stage in FIG. 2). Molding is performed only by pressing at room temperature without heating the mixture. By applying pressure to the mixture, the baroplastic 12 is compatible and softened into a molten state, and can be molded at room temperature without heating.

  The molding pressure may be 10 MPa or more and 100 MPa or less. By setting the molding pressure to 10 MPa or more, the baroplastic 12 undergoes phase transition and becomes a compatible state, and molding at room temperature is easy. Moreover, the density (magnetic powder ratio) of a magnet can be raised and the improvement of a magnetic characteristic can be aimed at. By setting the molding pressure to 100 MPa or less, it is possible to suppress the occurrence of cracks in the magnet due to volume expansion due to the decompression after molding, or to reduce the pulling resistance when the magnet is removed from the mold 30 after molding. Becomes easy. The molding pressure is preferably 15 MPa or more, and more preferably 20 MPa or more.

  In the example shown in FIG. 2, the case where the magnetic field orientation process is performed before molding has been described, but the magnetic field orientation process can also be performed during molding. The magnetic field orientation treatment may be performed either before molding or during molding, or may be performed both before molding and during molding.

  By adding a lubricant to the mixture, friction between the magnet powder 11 (magnet particles 11p) and the baroplastic 12 and between the magnet powder 11 (magnet particles 11p) during pressure molding can be reduced, and the density of the magnet (Magnetic powder ratio) can be increased. Further, the seizure with the mold 30 can be reduced by the lubricant, or the friction with the mold can be reduced when the magnet is taken out from the mold 30 after molding, and the moldability is improved. Furthermore, when the magnetic field orientation treatment is performed, the magnet particles 11p are easily rotated by the lubricant, so that the degree of orientation of the magnet powder 11 is easily increased. The lubricant remains in the magnet without being removed by the molding process or the subsequent solidification process.

(Solidification process)
The solidification step is a step of returning the pressure to normal pressure after molding to cure the baroplastic 12 and solidifying the mixture. By removing the pressure, the baroplastic 12 is phase-separated and hardens and solidifies at room temperature without being heated. After solidification, the bonded magnet 10 containing the magnet powder 11 and the baroplastic 12 is completed by taking out from the mold 30 (see the fifth stage in FIG. 2).

  Next, another example of the method for manufacturing a bonded magnet will be described with reference to FIG. The example shown in FIG. 3 is a case where the bonded magnet 10 once manufactured by the manufacturing method shown in FIG. 2 is used again as a raw material. Hereinafter, the difference from the manufacturing method shown in FIG. 2 will be mainly described, and description of similar points will be omitted.

(Preparation process)
In the example shown in FIG. 3, pulverized powder 15 obtained by pulverizing the bond magnet 10 is prepared as a mixture of the magnet powder 11 and the baroplastic 12 as raw materials (see the first and second stages in FIG. 3). For the pulverization, a known pulverizer such as a jaw crusher, a brown mill, a pin mill, a disk mill, a jet mill, or a ball mill can be used.

  As shown in FIG. 3, the pulverized powder 15 may be in a state where the baroplastic 12 is attached to the magnet powder 11 (magnet particles 11 p), or may be in a state where a plurality of magnet particles 11 p are bonded by the baroplastic 12. Since the magnet powder 11 is oriented in the bond magnet 10 before pulverization, the magnetized axes of the individual magnet particles 11p are also aligned in the pulverized powder 15 in which the plurality of magnet particles 11p are combined. The average particle size of the pulverized powder 15 is, for example, 3 μm or more and 700 μm or less.

(Molding process)
As in the manufacturing method shown in FIG. 2, the pulverized powder 15 is filled in the mold 30 and a magnetic field orientation process is performed by applying a magnetic field to the pulverized powder 15 before molding (see the third stage in FIG. 3). Thereby, the pulverized powder 15 rotates so that the easy magnetization axes of the magnet particles 11p in the pulverized powder 15 are aligned with the application direction of the magnetic field, and the magnet powder 11 is oriented. In the case of the pulverized powder 15 in a state where a plurality of magnet particles 11p are combined, the easy magnetization axes of the individual magnet particles 11p are aligned, and therefore, the magnetized particles 11p in the pulverized powder 15 are easily affected by the magnetic field. The pulverized powder 15 is easy to rotate so as to be aligned in the magnetic field application direction.

  After performing the magnetic field orientation treatment, pressure is applied to the pulverized powder 15 to form the pulverized powder 15 (see the fourth stage in FIG. 3). By applying pressure to the pulverized powder 15, the ballo plastic 12 is compatible and softened into a molten state, which can be remolded.

(Solidification process)
A solidification process is performed after shaping | molding (refer the 5th stage of FIG. 3). The solidification process is the same as the manufacturing method shown in FIG.

  In the example illustrated in FIG. 3, the case where the pulverized powder 15 obtained by pulverizing the bond magnet 10 is used as a raw material has been described. But you can. Moreover, when using the pulverized powder 15 as a raw material, you may mix | blend magnet powder and baroplastic as needed, and may add a lubricant further as needed.

[Example 1]
Samples of bonded magnets were manufactured by changing the manufacturing conditions, and the bonded magnets were evaluated.

As a magnet powder, an Nd—Fe—B rare earth magnet powder having an Nd ₂ Fe ₁₄ B alloy as a main phase was prepared. This magnet powder is an anisotropic magnet powder subjected to HDDR treatment. The average particle size (D50) of the magnet powder is 100 μm. Further, as a binder resin, baroplastic, phenol resin, and nylon 12 (polyamide 12) were prepared. The prepared baroplastic is a block copolymer of polystyrene and poly (ethylhexyl acrylate). This balloplastic is solid at room temperature and pressure, and has a lamellar structure in which polystyrene and poly (ethylhexyl acrylate) are phase-separated. As the lubricant, stearamide was used.

(Sample No. 1-1)
The above-described magnet powder, baroplastic powder, and lubricant were mixed to prepare a mixture as a raw material. The blending amount of the baroplastic powder was 1.5% by mass of the whole mixture, and the addition amount of the lubricant was 0.05% by mass of the whole mixture. The average particle size (D50) of the baroplastic powder is 15 μm.

  The prepared mixture was filled into a mold of a compression molding machine, and the mixture was compressed at a molding pressure of 80 MPa while applying a 1.6 T magnetic field from a magnetic field generator, and molded into 11 mm × 11 mm × 10 mm. Molding was performed at room temperature (25 ° C.). After molding, return to normal pressure at room temperature and remove from the mold. 1-1 bonded magnet was manufactured.

(Sample Nos. 1-2 to 1-5)
Except for changing the blending amount (content) of baroplastic powder as shown in Table 1, sample No. In the same manner as the bonded magnet 1-1, sample No. 1-2 to 1-5 bonded magnets were produced.

(Sample Nos. 2-1 to 2-4)
Except for changing the molding pressure during pressure molding as shown in Table 1, sample No. In the same manner as the bonded magnet 1-1, sample No. 2-1 to 2-4 bonded magnets were produced.

(Sample Nos. 3-1 to 3-4)
Except for changing the addition amount of the lubricant as shown in Table 1, Sample No. In the same manner as the bonded magnet 1-1, sample No. 3-1 to 3-4 bonded magnets were manufactured.

(Sample No. 4)
Sample No. 4 sample No. 4 The bonded magnet manufactured under the same conditions as 1-1 was pulverized to prepare pulverized powder. And sample no. Was used except using this pulverized powder as a raw material. Sample No. 1-1 was molded in a magnetic field as in 1-1. 4 bonded magnets were produced.

(Sample No. 5)
Sample No. In No. 5, the above-mentioned magnet powder and a phenol resin which is a thermosetting resin were mixed to prepare a mixture as a raw material. Sample No. In No. 5, the blending amount of the phenol resin is 1.5% by mass, and no lubricant is added. And this mixture is referred to as Sample No. After molding in a magnetic field under the same conditions as in 1-1, a curing process was performed at 160 ° C. for 3 hours in an Ar gas atmosphere. 5 bonded magnets were produced.

(Sample Nos. 6-1 and 6-2)
Sample No. In 6-1 and 6-2, the above-described magnet powder and nylon 12 which is a thermoplastic resin were mixed to prepare a mixture as a raw material. Sample No. In 6-1 and 6-2, the blending amount of nylon 12 is 1.5 mass%, and no lubricant is added. And sample no. In Sample No. 6-1, this mixture was subjected to sample no. A bonded magnet was manufactured by molding in a magnetic field under the same conditions as in 1-1. On the other hand, sample no. In Sample No. 6-2, Sample No. was changed except that the molding temperature during pressure molding was changed to 200 ° C. A bonded magnet was manufactured in the same manner as in 6-1.

  About the manufactured bonded magnet of each sample, the magnet density and remanent magnetization were evaluated.

(Magnet density)
The magnet density (% by volume) was calculated by the following formula.
Formula: [(A−B) / (C−B)] × 100
A: Density of bonded magnet. A value obtained by measuring the actual size and weight of a bonded magnet and calculating the weight / volume.
B: The true density of the binder resin. A value calculated by weight / volume after solidifying only the resin.
C: True density of magnet powder. The value calculated from the composition of the magnet powder.

(Residual magnetization)
The residual magnetization (T) was obtained from a BH curve obtained by measuring a BH curve using a BH tracer (DCBH tracer manufactured by Riken Denshi Co., Ltd.).

  Sample No. shown in Table 1 From the comparison results of 1-1 to 1-5, sample Nos. In the range where the blending amount (content) of the baroplastic is more than 0.5% by mass and not more than 2.0% by mass. 1-1, 1-3, and 1-4 are sample Nos. Out of this range. Compared to 1-5, it is excellent in terms of magnet density and residual magnetization, and has high magnetic properties. Sample No. From the comparison with 1-5, when industrial productivity is taken into consideration, it is considered that the blending amount of baroplastic is preferably more than 0.5% by mass.

  Sample No. shown in Table 1 1-1 and sample no. From the comparison results of 2-1 to 2-4, sample Nos. In which the molding pressure during pressure molding is in the range of 10 MPa to 100 MPa. 1-1, 2-2, and 2-3 are sample Nos. Out of this range. Compared to 2-1, 2-4, industrial production is sufficiently possible, and magnetic properties are also high. Further, from this result, it is considered that the molding pressure is preferably 10 MPa or more and 100 MPa or less in consideration of industrial productivity.

  Sample No. shown in Table 1 1-1 and sample no. From the comparison results of 3-1 to 3-4, it can be seen that, by adding a lubricant, particularly the residual magnetization can be increased among the magnet density and the residual magnetization. Sample No. in which the amount of lubricant added is in the range of 0.1% by mass or less. 1-1, 3-2 and 3-3 are sample Nos. Out of this range. Compared to 3-4, it is excellent in terms of magnet density and residual magnetization, and has high magnetic properties.

  Sample No. shown in Table 1 1-1 and Sample No. From the result of comparison with Sample No. 4, Sample No. using the pulverized powder obtained by pulverizing the bond magnet as a raw material again. No. 4 shows that the magnet density and the residual magnetization are sample Nos. It is equivalent to 1-1. Therefore, bond magnets using baroplastics can be reused as raw materials after pulverizing bond magnets once manufactured, and since magnetic properties are not significantly reduced, reusability is excellent. I can say that.

  Sample No. using phenolic resin No. 5 requires a curing process in the manufacturing process, so the lead time is long and the productivity is low.

  Sample No. using nylon 6-1 and 6-2, the sample No. with a molding temperature of room temperature (25 ° C.). In 6-1, the resin was not softened and could not be molded. On the other hand, Sample No. with a molding temperature of 200 ° C. Although 6-2 could be molded, the magnet density and remanent magnetization were low, and sufficient magnetic properties were not obtained.

  The bonded magnet of the present invention can be used for a permanent magnet used for a motor, a generator or the like. The method for manufacturing a bonded magnet of the present invention can be used for manufacturing a bonded magnet.

10 Bond magnet 11 Magnet powder (rare earth magnet powder)
11p Magnet particles 12 Binder resin (Baroplastic)
15 Pulverized powder 200 Mixer 300 Compression molding machine 30 Mold 31 Upper punch 32 Lower punch 33 Die 34 Magnetic field applying device

Claims (6)

A bonded magnet in which magnet powder is bonded with a binder resin,
A bonded magnet in which the binder resin is baroplastic. The baroplastic contains a polymer of a hard component and a soft component,
The hard component of the polymer contains at least one selected from polystyrene, poly (butyl methacrylate), poly (caprolactone), poly (ethyl methacrylate), poly (methyl methacrylate) and poly (hexyl methacrylate),
The soft component of the polymer contains at least one selected from poly (butyl acrylate), poly (methyl acrylate), poly (ethyl acrylate), poly (ethyl hexyl acrylate) and poly (caprolactone). The bonded magnet described.   The bonded magnet according to claim 1 or 2, wherein a content of the baroplastic is more than 0.5 mass% and not more than 2.0 mass%. Lubricant is added,
The bonded magnet according to any one of claims 1 to 3, wherein an amount of the lubricant added is 0.1 mass% or less. Preparing a mixture containing magnet powder and baroplastic; and
A molding step of applying a pressure of 10 MPa or more and 100 MPa or less to the mixture to soften the balloplastic and molding the mixture;
A solidifying step of returning the pressure to normal pressure after molding to cure the baroplastic and solidifying the mixture.   The method for producing a bonded magnet according to claim 5, wherein a magnetic field orientation process is performed to apply a magnetic field of 0.5 T or more to the mixture before molding and during molding.

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