JP2012199462A - Rare earth bond magnet, rare earth magnet powder and manufacturing method therefor, and compound for rare earth bond magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide rare earth magnet powder for obtaining such as a bond magnet having excellent resistance to environment.SOLUTION: Rare earth magnet powder of the invention has coated magnet particles comprising: basic magnet particles being an aggregation of RTMBtype crystals which are tetragon compounds of rare earth elements (R), boron (B), and transition elements (TM); and thermoset resin coats generated by thermal hardening of thermoset resin coating surfaces of the basic magnet particles. A bond magnet manufactured by using the rare earth magnet powder: has excellent resistance to environment, because the bond magnet is composed of the coated magnet particles coated with the thermoset resin coats having excellent oxidation resistance; and has a magnetic characteristic which is hardly deteriorated even when being exposed under severe environment. Thereby, the bond magnet having extremely excellent resistance to environment can be obtained by using the rare earth magnet powder of the invention.

Description

  The present invention relates to a rare earth bonded magnet excellent in oxidation resistance, a rare earth magnet powder, a method for producing the same, and a compound for a rare earth bonded magnet using the rare earth magnet powder.

  Since rare earth magnets exhibit extremely high magnetic properties, they are being used in various appliances such as electric appliances and automobiles that are required to be energy-saving and lightweight. A rare earth magnet includes a dense magnet made of a sintered body of a rare earth magnet powder (referred to as “magnet powder” as appropriate) or a dense molded body, and a bonded magnet in which the magnet powder is bound with a binder resin by compression molding or injection molding. There is. Recently, bond magnets having a high degree of freedom in molding and suitable for manufacturing light and thin parts tend to be frequently used.

  Since the magnet powder constituting this bonded magnet contains iron and rare earth elements as main components, it is easily oxidized by oxygen and moisture during the manufacturing process, transportation, and use of the bonded magnet. Among them, the rare earth magnet powder obtained by the hydrogenation treatment is easy to break because it contains a large number of fine cracks (microcracks), and a new surface to be newly oxidized is likely to appear. In particular, when the magnet powder that is the raw material of the bond magnet is compression-molded, the magnet particles are often cracked, and the magnet particles constituting the bond magnet are more easily oxidized. In any case, since such oxidation deteriorates the magnetic properties of the magnet particles and thus the bonded magnets with time, various oxidation suppression measures have been proposed.

  For example, the surface of the bond magnet may be coated with a resin or plating. However, such a coating is expensive and does not necessarily have a sufficient oxidation inhibiting effect.

  In addition, the following patent document proposes a method for suppressing oxidation caused by cracking of magnet particles that occurs during compression molding. Specifically, a magnet powder (fine powder) having a small particle size and a binder resin are added to a magnet powder (coarse powder) having a large particle size that is obtained by hydrogenation (d-HDDR), and a fine powder. And a ferromagnetic buffer (or ferromagnetic fluidized bed) made of a binder resin. This ferromagnetic buffer prevents direct contact between the magnet particles constituting the coarse powder or stress concentration on the magnet particles, reduces cracking of the magnet particles, and consequently suppresses the oxidation. .

Japanese Patent No. 3731597

  Certainly, according to the method of Patent Document 1, a bonded magnet having excellent weather resistance can be obtained, but this reduces the surface area of the magnet particles to be oxidized and indirectly improves the oxidation resistance of the bonded magnet. Is. That is, it does not directly or positively improve the oxidation resistance of the magnet particles themselves.

  It is also conceivable to prevent oxidation of the surface of the magnet particles by mixing a rust preventive material or the like with the magnet powder. However, such a rust-preventing film is cracked during molding of the bonded magnet, and ultimately does not improve the oxidation resistance of the magnet particles themselves in the bonded magnet. The same applies to magnet particles in a bonded magnet formed using a conventional rare earth bonded magnet compound (hereinafter referred to as “compound” as appropriate). The magnet particles in the conventional compound are in a state of being coated with a binder resin before thermosetting, and when only the state is observed, the oxidation resistance of the magnet particles is expected to be improved. However, when the magnet particles in the bonded magnet actually formed using the compound were observed, the surface was not completely covered with the resin coating, and the surface of the magnet particles was oxidized.

  The present invention has been made under such circumstances. That is, an object of the present invention is to provide a rare earth magnet powder that can improve the oxidation resistance of the magnet particles themselves and provide a bonded magnet having excellent weather resistance. Moreover, it aims at providing the manufacturing method of the magnet powder, the compound and bond magnet using the rare earth magnet powder together.

  As a result of intensive research and trial and error to solve this problem, the present inventor has come up with the idea that a thin thermoset resin film is formed on the surface of the magnet particle, and in fact, such a film is formed on the surface of the magnet particle. Succeeded in forming. And it confirmed that the bond magnet which consists of a magnet particle coat | covered with this resin film exhibits the outstanding weather resistance (environment resistance). By further developing this result, the present invention described below has been completed.

<Rare earth magnet powder>
(1) The rare earth magnet powder of the present invention is a basic magnet particle which is an aggregate of R ₂ TM ₁₄ B ₁ type crystals which are tetragonal compounds of rare earth elements (R), boron (B) and transition elements (TM). And a thermosetting resin film formed by thermosetting a thermosetting resin that coats the surfaces of the basic magnet particles.

(2) The rare earth magnet powder of the present invention (referred to as “magnet powder” as appropriate) is composed of coated magnet particles whose outer surface is coated with a thermosetting resin film formed by thermosetting a thermosetting resin. This magnet powder expresses high oxidation resistance, and is excellent in storage and handling properties, as well as greatly improving the oxidation resistance of the bonded magnet.

(3) By the way, the reason why the magnet powder of the present invention exhibits very high oxidation resistance is not necessarily clear, but at present, it is considered as follows. The thermosetting resin film formed on the surface of the basic magnet particles is formed by thermosetting the respective molecules of the thermosetting resin by three-dimensionally crosslinking. In addition to being dense and excellent in oxygen shielding properties, this thermosetting resin film has a very low water absorption rate, so that even a thin film effectively blocks contact between basic magnet particles and oxygen (or moisture). . As a result, it is considered that the oxidation resistance of the basic magnet particles is directly improved.

  Moreover, it is thought that a thermosetting resin film reinforces the outer surface of basic magnet particles and suppresses cracking of the basic magnet particles. Specifically, the basic magnet particles that have undergone the hydrogenation treatment have a large number of microcracks on the surface and inside thereof, but at the time of forming the thermosetting resin film, at least a part of the thermosetting resin (that is thermoset) Hereinafter referred to as “thermosetting resin”). Moreover, the surface (the whole) of the basic magnet particles is coated with the thermosetting resin, so that the stress applied to the magnet powder is absorbed by the elastic deformation of the thermosetting resin film. For this reason, the crack resistance of the basic magnet particles is increased (the crack sensitivity is reduced), and the generation of a new surface is reduced. As a result, it is considered that the oxidation surface area of the basic magnet particles is reduced and the oxidation resistance of the basic magnet particles is indirectly improved.

  In this way, the thermosetting resin coating blocks oxygen and moisture, which are oxidation factors, from the basic magnet particles and suppresses cracking of the basic magnet particles. It is considered that the chemical conversion has been remarkably improved. And it is thought that the bond magnet which expressed the outstanding environmental resistance and the long-term stable magnetic characteristic was obtained by using this basic magnet particle (covered magnet particle).

  In addition, since the thermosetting resin film is thin, there is little influence on the magnetic characteristics of the magnet powder and the bonded magnet. In addition, the coated magnet particles are excellent in fluidity and excellent in compatibility with the binder resin, adhesion, adhesiveness, and the like. For this reason, if the magnet powder of the present invention is used, a denser bonded magnet can be efficiently produced.

(4) The thermosetting resin film of the present invention may be any film thickness, resin composition, structure, and form. However, the film thickness is preferably 10 nm or more, 20 nm or more, 50 nm or more, or 100 nm or more in order to stably shield oxygen and the like without being peeled off in the manufacturing process of the bonded magnet. As described above, the increase in the film thickness is preferable from the viewpoint of the oxidation resistance of the magnet powder. On the other hand, the increase in the film thickness causes a decrease in the magnetic properties of the magnet powder and the bonded magnet. In particular, when the present inventor has intensively studied, when the film thickness increases beyond a certain range, the residual magnetic flux density (Br) of the bonded magnet rapidly decreases. Considering the case where the magnet powder is compression-molded with a constant binder resin amount, the total resin amount increases as the resin (coating resin) that becomes the thermosetting resin coating increases. If the amount of the binder resin is constant, the fluidity of the magnet powder at the time of compression molding is ensured, cracking of the magnet particles is suppressed, and a high filling rate of the bonded magnet is maintained and achieved. However, when the total resin amount increases, the resin part, which is a nonmagnetic part in the bonded magnet, increases, and the magnetic properties of the bonded magnet as a whole deteriorate. From such a viewpoint, the film thickness of the thermosetting resin film is preferably 700 nm or less, 600 nm or less, 500 nm or less, and further 400 nm or less.

  It is difficult to uniformly form a thermosetting resin film having a film thickness of 1200 nm or more on the surface of each magnet particle. Conversely, when such a thermosetting resin film is to be formed, the thermosetting resin film is likely to be formed on a magnet particle mass in which a plurality of magnet particles are aggregated.

  Various methods for specifying the “film thickness” of the thermosetting resin coating are conceivable. In this specification, JIS K 5600-1-7 No. The “film thickness” of the thermosetting resin coating was specified by applying 5A (coating film thickness measurement method, cross-sectional microscope observation). Specifically, as shown in FIG. 2, first, the surface of the magnet powder on which the thermosetting resin film is formed is observed with a scanning electron microscope (SEM). Next, the film thickness is measured at 10 points (points) in the field of view, and the arithmetic average of these measured values is defined as “film thickness”.

  The film thickness at each point was determined by measuring the thickness of the thermosetting resin film on the normal line set on the outermost surface (the surface that is not the crystal grain boundary) of the magnet particle itself. These points are selected on the surface of a smooth magnet particle that can draw a substantially unique tangent, and are further selected so that the linear distance between adjacent points is in principle 50 to 500 nm.

  Incidentally, the SEM image shown in FIG. 2 has a field of view of 30,000 times, and the film thickness in this case was 86.0 nm. Moreover, when it measured about the other visual field of the powder which carried out the same coating process, the film thickness was 87.2 nm. From these facts, it can be seen that according to the above method, the film thickness can be specified accurately and stably to some extent. Note that this measurement was performed using the sample No. in Examples described later. It went about 1-3.

  In this way, the “film thickness” per magnet particle (magnet particle unit) is specified. The “film thickness” of the magnet powder unit in which such magnet particles are gathered can be further specified as follows. That is, the above-mentioned “film thickness” is obtained for five particles randomly extracted from the target magnet powder, and the arithmetic average thereof is set as the “film thickness” of the magnet powder.

  Although some magnet particles in the magnet powder were examined, the fact that a very thin film of several tens of nanometers was formed is also the same for particles of various particle sizes observed from different fields of view of the same sample. Has been observed. However, the observation of such a thermosetting resin film needs to be observed at a considerably large magnification because the film thickness is very thin. Therefore, the number of magnet particles that can be observed in one visual field is naturally limited, and it is very difficult to observe many magnet particles at once. Therefore, it is difficult to unambiguously specify the film thickness of the thermosetting resin film in a strict sense, and it is not realistic. Therefore, in this specification, the film thickness is specified by the method described above.

(5) The usefulness of the thermosetting resin film according to the present invention is that when a compound used for compression molding or injection molding is manufactured, a bond magnet injection-molded or a compression-bonded bond magnet is manufactured using the compound. Furthermore, it appears in various situations, such as when transporting and transporting magnet powder. Here, as an example in which the magnet particles and the thermosetting resin coating are extremely harsh and the magnet particles are likely to be oxidized, a case where a bonded magnet is manufactured by heat compression molding will be described. Incidentally, a compression-molded bond magnet is required to have high magnetic properties and weather resistance, but has a small amount of binder resin, and therefore is more easily oxidized and deteriorated by oxygen and moisture in the atmosphere than an injection-molded bond magnet. Therefore, the compression-bonded bonded magnet is optimal for examining the true value of the thermosetting resin according to the present invention. Conversely, if the usefulness of thermosetting resin coatings is sufficient for compression-molded bonded magnets, both injection-molded bonded magnets and their raw materials can be transported over long distances and stored for long periods of time. It can be said that the thermosetting resin coating is sufficiently useful for the magnet powder itself that requires quality assurance or flammability countermeasures.

  First, the reason why magnet particles in a compression-bonded bonded magnet (hereinafter referred to as “compressed bonded magnet”) are likely to be oxidized is not clearly understood, but is considered as follows from the results. The compression bonded magnet is obtained by compression molding while heating the compound supplied to the cavity. At this time, the air introduced into the cavity seeks a escape field at the time of pressure molding and tries to escape from the mold at once through the gaps between the magnet particles. For this reason, the penetration path | route used as the passage of the air can be formed in the binder resin interposed between magnet particles.

  Next, the magnet particles in the conventional compound were in a state where the entire surface was coated with the binder resin. However, it seems that the magnet particles in the bonded magnet obtained by compression molding the compound had a portion not covered with the binder resin, that is, an exposed portion. The reason for this is considered that the binder resin on the surface of the magnet particles in the compound was uncured and was removed during the heat compression molding. This is because during heat compression molding, the binder resin reduces the viscosity of the fluid to facilitate the change in the orientation of the magnet particles, but on the other hand, the magnet is moved by the high-pressure air that escapes vigorously when the above-mentioned through path is formed. This is thought to be because the particles are easily peeled off from the surface of the particles.

  Conventionally, the heat compression molding is completed in such a state, and then the heat treatment (curing treatment) for thermosetting the binder resin has been completed. The bond magnet obtained in this way seems to have many fine penetrating paths communicating with the surface, and there were magnet particles with the surface partially exposed in or near the penetrating path. . As a result, in conventional bonded magnets composed of rare earth magnet powders and compounds, oxygen and moisture penetrate into the inside through the through path, oxidize the magnet particles constituting the bonded magnet, and thus reduce the weather resistance of the bonded magnet. It is thought.

  On the other hand, the magnet particle which comprises the rare earth magnet powder of this invention is coat | covered with the thermosetting resin film which the surface has already thermoset before compression molding. This thermosetting resin film is strong without being reversibly liquefied upon heating. For this reason, the thermosetting resin coating is not affected by the behavior of the air in the cavity and the binder resin during the heat compression molding, and hardly peels during the compression molding. The thermosetting resin film remains after covering almost the entire surface of the magnet particles even after compression molding.

  As a result, even if oxygen or moisture may enter the compression bonded magnet through a through-path or the like, each magnet particle is covered with a thermosetting resin film that is dense and blocks oxygen and moisture, so that the magnet is protected. The particles hardly undergo oxidative deterioration, and the bonded magnet can exhibit high weather resistance.

  In addition, although it is preferable that the whole surface of all the magnet particles which comprise rare earth magnet powder is coat | covered with the thermosetting resin film, the coating ratio by a thermosetting resin film is not ask | required in this invention. It may be determined based on the magnetic properties and weather resistance required for the bond magnet. And what is necessary is just to determine the amount of thermosetting resins to be used according to the coating ratio and film thickness of the desired thermosetting resin film.

《Rare earth magnet powder manufacturing method》
The present invention can also be grasped as a method for producing the rare earth magnet powder described above. That is, the present invention relates to a coupling treatment step in which a coupling agent is attached to the surface of basic magnet particles that are aggregates of R ₂ TM ₁₄ B ₁ type crystals that are tetragonal compounds of R, B, and TM; A resin adhesion step in which a thermosetting resin is adhered to the surface of the basic magnet particles after the ring treatment step, and the thermosetting resin is thermally cured on the surfaces of the basic magnet particles by heating the thermosetting resin. A method for producing a rare earth magnet powder, characterized in that a rare earth magnet powder comprising the above-described coated magnet particles is obtained.

<Compound and bonded magnet>
(1) The present invention can also be grasped as a compound using the above-mentioned rare earth magnet powder. That is, the present invention may be a compound for a rare earth bonded magnet comprising the rare earth magnet powder described above and a binder resin capable of binding the coated magnet particles of the rare earth magnet powder.

(2) Moreover, this invention can be grasped | ascertained also as a bonded magnet which consists of the above-mentioned rare earth magnet powder and a compound. That is, the present invention may be a rare earth bonded magnet comprising the rare earth magnet powder described above and a binder resin that binds the coated magnet particles of the rare earth magnet powder.

(3) The conventional magnet particles constituting the compression-molded bonded magnet were easily oxidized despite being encapsulated by the binder resin, between the cured binder resin, such as oxygen This is thought to be due to the formation of minute air holes that serve as passages. Such a hole path can be inevitably formed in the manufacturing process of obtaining a bonded magnet by compression-molding a compound filled in the atmosphere of the mold cavity.

  According to the bonded magnet of the present invention, the thermosetting resin film formed on the surface of the coated magnet particle constituting the basic magnet and the oxygen, moisture, etc. passing through the air holes formed in the bonded magnet Block contact with the particles and protect the basic magnet particles from them. As a result, even in the presence of the above-described air holes, the basic magnet particles constituting the compression-bonded bonded magnet are suppressed from being oxidized, and the bonded magnet of the present invention exhibits high weather resistance.

<Others>
(1) The rare earth element referred to in this specification is one or more of yttrium (Y), lanthanoid and actinoid. Among them, lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium ( Typical examples are Er), thulium (TM element), and lutetium (Lu). These rare earth elements (R) may be one kind or two or more kinds.

  Here, as R, Nd is particularly representative, but Pr may also be included. This is because even if a part of Nd in the magnet raw material or the diffusion raw material is replaced with Pr, there is little influence on the magnetic properties, and a mixed rare earth raw material (zidymium) mixed with Nd and Pr is available at a relatively low cost. . In addition, since the coercive force improving element such as Dy, Tb, or Ho is a rare element and expensive, it is preferable to suppress the use. Therefore, it is preferable that the magnet raw material or the diffusion raw material used for manufacturing the magnet powder does not contain Dy, Tb and Ho.

  TM is particularly preferably one or more of 3d transition elements or 4d transition elements. The 3d transition element is atomic number 21 (Sc) to atomic number 29 (Cu), and the 4d transition element is atomic number 39 (Y) to atomic number 47 (Ag). Among them, TM is preferably any of group 8 iron (Fe), cobalt (Co), or nickel (Ni), and more preferably Fe. Further, a part of boron can be substituted with carbon (C).

(2) In addition to R, B and TM described above, the basic magnet particles may contain “modified elements” which are elements effective for improving the characteristics thereof. There are various kinds of modifying elements, the combination of each element is arbitrary, and the content thereof is usually very small. Of course, the rare earth magnet powder of the present invention may also contain “unavoidable impurities” that are difficult to remove due to cost or technical reasons.

(3) “Rare earth magnet powder” as used herein includes both anisotropic rare earth magnet powder and isotropic rare earth magnet powder. The term “magnet particles” may be basic magnet particles, coated magnet particles, or other particles. The same applies to the constituent particles when simply called “magnet powder”.

(4) The “average particle diameter” as used herein is specified by the volume sphere equivalent diameter (VMD) obtained by measuring the sample powder with a HELOS & RODOS laser diffraction particle size distribution measuring device.

(5) “x to y” in the present specification includes the lower limit value x and the upper limit value y unless otherwise specified. Further, a new numerical range such as “ab” can be configured by arbitrarily combining various lower limit values or upper limit values described in the present specification. Furthermore, any numerical value included in the numerical value range described in the present specification can be used as the upper limit value or the lower limit value constituting the new numerical value range.

It is the SEM photograph which observed the surface of the bonded magnet which concerns on a present Example. It is the SEM photograph which expanded a part of the bond magnet. Furthermore, it is the SEM photograph which expanded the part. It is explanatory drawing explaining the calculation method of the film thickness of the thermosetting resin film formed in the surface of a magnet particle.

  The present invention will be described in more detail with reference to embodiments of the invention. The contents described in this specification including the following embodiments can be applied not only to the rare earth magnet powder according to the present invention, but also to a manufacturing method thereof, a compound using the magnet powder, and a bonded magnet. One or more configurations arbitrarily selected from the present specification may be added to the configuration of the present invention described above. At this time, the structure related to the manufacturing method can be a structure related to an object if understood as a product-by-process. Note that which embodiment is the best depends on the target, required performance, and the like.

<Resin coating>
The thermosetting resin coating according to the present invention is preferably as uniform and thin as possible in order to achieve both the magnetic properties and oxidation resistance of the magnet powder and the bonded magnet at a high level. Therefore, as described above, the thermosetting resin film is made by attaching a coating resin (thermosetting resin, etc.) to the basic magnet particles subjected to the coupling process (coupling process) and curing the resin (resin adhesion process). It is good to form (film formation process). Hereinafter, these steps will be described in detail.

(1) First, a coupling agent is attached to the surface of the basic magnet particles by a coupling treatment step. This makes it easier for the coating resin to uniformly adhere to the metal surfaces of the basic magnet particles. The type and amount of the coupling agent are appropriately adjusted according to the type and amount of the coating resin used.

  Examples of such a coupling agent include a titanate coupling agent containing Ti, a silane coupling agent containing Si, and an aluminate coupling agent containing Al. Among these, titanate coupling agents are preferred because they greatly improve the wettability of the coating resin on the surface of the basic magnet particles.

  By using an appropriate solvent or dispersion medium, the coupling agent can be efficiently and uniformly attached to the surfaces of the basic magnet particles. Examples of such a solvent or dispersion medium include nonpolar organic solvents such as hexane, nonane, decane, benzene, toluene, and xylene, and polar organic solvents such as ethanol, methanol, propanol, and methyl ethyl ketone. Since the coupling agent only needs to extend uniformly and thinly on the surface of the basic magnet particles, it may be 0.1 to 1.0% by mass with respect to 100% by mass of the powder (processed powder) made of the basic magnet particles. . In particular, in order to mix uniformly, it is preferable to stir using a stirrer such as a magnetic stirrer after putting the coupling agent and the organic solvent of the dispersion medium into a container.

(2) Next, in the resin attaching step, a coating resin that is a raw material for the thermosetting resin coating is attached to the surface of the coupling-treated basic magnet particles. The type and amount of the coating resin are appropriately adjusted according to the desired type and thickness of the thermosetting resin coating. A thermoplastic resin is also considered as such a coating resin, but considering the denseness, thermosetting, and subsequent heat history (heat kneading during compound production, thermoforming during bond magnet production, etc.), etc., thermosetting Is preferred. Examples of such thermosetting resins include epoxy resins, polyamide resins, polyimide resins, polyamideimide resins, and urea resins.

  The coating resin may be the same as or different from the binder resin of the bond magnet. However, if the coating resin and the binder resin are of the same type, it is easy to improve the adhesion and adhesion between them. In addition, if these resins are the same type, the productivity of bonded magnets can be improved and the cost can be reduced.

  The term “resin” as used herein includes both the case of using only the main agent and the case of containing various additives such as a curing agent and a curing accelerator in addition to the main agent. The main agent may be a single species or a plurality of species. The above-mentioned coating resin and binder resin may be the same type of main agent and different additives. By appropriately selecting the additive, the softening temperature, glass transition point, curing temperature, degree of curing and the like of each resin can be adjusted.

  By using an appropriate solvent or dispersion medium, the coating resin can be uniformly and efficiently attached to the surface of the coupled basic magnet particles. Examples of such a solvent or dispersion medium include methyl ethyl ketone (MEK), acetone, and methyl ether. The amount of the coating resin is adjusted according to the desired film thickness of the thermosetting resin coating. For example, 0.1 to 1.0% by mass, 0.2 to 0.8% with respect to 100% by mass of the powder to be processed. It is preferable to set it as the mass% further 0.3-0.7 mass%. In particular, in order to mix uniformly, it is preferable to stir using a stirrer such as a magnetic stirrer after putting the resin and the organic solvent of the dispersion medium in a container.

(3) In order to make the thermosetting resin adhered to the surface of the basic magnet particles into a thermosetting resin film, a heat treatment for thermosetting the thermosetting resin is required (film forming process). The heat pattern at this time is appropriately selected according to the type and amount of the coating resin. For example, the processing temperature (coating curing temperature) is about 70 to 200 ° C., further about 90 to 150 ° C., and the processing time is 0. About 5 to 3 hours, more preferably about 0.75 to 2 hours are preferable.

  The film curing temperature may be the same as or different from the temperature at which the binder resin of the bonded magnet is thermally cured (binder curing temperature). Further, the resin (coating resin) in the thermosetting resin film may be further cured during the curing heat treatment for curing the binder resin of the bonded magnet. In this case, the film curing temperature in the previous step may be set lower than the binder curing temperature in the subsequent step.

《Basic magnet particles》
(1) Basic magnet particles for forming a thermosetting resin film are composed of an aggregate of fine R ₂ TM ₁₄ B ₁ type crystals, and particles obtained by subjecting a magnet alloy (mother alloy) to hydrogenation treatment (hydrogen treatment) Or particles after diffusion treatment (diffusion treatment particles) in which a diffusion raw material is diffused.

(2) The hydrogenation treatment includes a disproportionation step in which a magnet alloy (mother alloy) absorbs hydrogen to cause a disproportionation reaction, and recombination that dehydrogenates and recombines the mother alloy after the disproportionation step. Process. Examples of this hydrogenation treatment include the HDDR method (hydrogenation-decomposition (or decomposition) -deposition-recombination), the d-HDDR method (dynamic-HDDR), and the like. According to the d-HDDR method, a magnet powder having particularly high magnetic properties can be obtained.

  The d-HDDR method comprises a low temperature hydrogenation process, a high temperature hydrogenation process, a controlled exhaust process, and a forced exhaust process. The above-mentioned disproportionation process is a high temperature hydrogenation process, and the recombination process is a controlled exhaust process. Correspond. By the way, in the low-temperature hydrogenation process, the hydrogen pressure is reduced in the low temperature range below the temperature at which the hydrogenation / disproportionation reaction occurs so that the hydrogenation / disproportionation reaction in the next process (high-temperature hydrogenation process) proceeds slowly. This is a step for sufficiently dissolving hydrogen. The high-temperature hydrogenation step is a step of causing a hydrogenation / disproportionation reaction to the magnet alloy. The controlled exhaust process is a process in which a tissue that has undergone three-phase decomposition in a high-temperature hydrogenation process is subjected to a recombination reaction. The forced exhaust process is a process for removing hydrogen remaining in the magnet alloy and completing the dehydrogenation process. Details of these steps are described in JP-A-2006-28602.

(3) The diffusion treatment is performed by mixing a mixed raw material (mixed powder) obtained by mixing a magnetic raw material (powder made of hydrogen-treated particles) with a diffusion raw material, for example, an antioxidation atmosphere (vacuum atmosphere or 400 to 900 ° C. or even 600 to 850 ° C. For example, an inert atmosphere).

  It is preferable to use an R—Cu alloy, an R—Cu—Al alloy, or the like as the diffusion raw material. Thereby, the coercive force of the magnet powder can be increased while suppressing the use of rare elements such as Dy and Ga. Specifically, when the diffusion raw material is 100 at% as a whole, it is preferable that Cu is 1 to 47 at%, further 6 to 39 at%, the remaining rare earth element, and inevitable impurities. When the diffusion raw material contains Al, it is preferable that Cu is 5 to 27 at%, Al: 20 to 55 at%, the remaining rare earth element, and inevitable impurities when the entire diffusion raw material is 100 at%.

  The diffusion raw material may include Co, Ni, Si, Mn, Cr, Mo, Ti, V, Ga, Zr, Ge, Fe, or the like instead of Al or together with Al. The total amount of these elements is preferably 5 to 64 at% with respect to 100 at% of the entire diffusion raw material.

  By the way, it is preferable that the magnet raw material subjected to the diffusion treatment has a theoretical composition. Specifically, R is 11.6 to 12.7 at%, 11.7 to 12.5 at%, 11.8 to 12.4 at%, or 11.9 to 12.3 at%, and B is 5. It is preferable in it being 5-7 at% and also 5.9-6.5 at%. By using a magnet raw material having a theoretical composition, a magnet powder with high magnetization (residual magnetic flux density) can be obtained. Accordingly, if a magnetic material having a theoretical composition is subjected to a diffusion treatment, a magnet powder having high magnetization and high coercive force can be obtained.

  The hydrogen-treated particles (diffusion-treated particles) after such diffusion treatment are Cu: 0.05-2 at%, 0.05-1 at%, 0.05-0.8 at%, It is preferable that it is 0.2 to 0.8 at%, more preferably 0.3 to 0.7 at%. Moreover, when the whole diffusion treated particle is 100 at%, Al is preferably 0.1 to 5 at%, and more preferably 0.5 to 3.0 at%.

(4) The basic magnet particles are titanium (Ti), vanadium (V), zirconium (Zr), niobium (Nb), nickel (Ni), chromium (Cr), which are TM as modifying elements such as coercive force, In addition to manganese (Mn), molybdenum (Mo), hafnium (Hf), tungsten (W), tantalum (Ta), etc., aluminum (Al), gallium (Ga), silicon (Si), zinc (Zn), tin ( Sn) or the like may be included. These modifying elements are preferably 3 at% or less in total when the entire basic magnet particle is 100 at%.

  Among the modifying elements, Ga is an element that is particularly effective for improving the coercive force, and therefore 0.05 to 1 at% Ga may be included when the entire basic magnet particle is 100 at%. Moreover, since Nb is an element effective in improving the residual magnetic flux density, 0.05 to 0.6% Nb may be included when the entire basic magnet particle is taken as 100 at%. Of course, it is more preferable that both are included at the same time. Co is an element effective for improving the magnetic powder or the Curie point of the magnet, and hence the heat resistance thereof, and therefore 0.1 to 10 at% Co may be included when the entire basic magnet particle is 100 at%. .

<Compound and bonded magnet>
(1) A compound as a raw material for a bonded magnet can be obtained by heat-kneading the magnetic powder of the present invention with a binder resin. If this compound is compression molded or injection molded, a bonded magnet can be obtained.

  In the case of injection molding, the binder resin is preferably a thermoplastic resin such as polyphenylene sulfide (PPS) or polyamide (PA) such as nylon. In the case of compression molding, the binder resin is preferably a thermosetting resin, such as an epoxy resin, or a binder resin.

(2) The magnet powder constituting the compound or bonded magnet may be a mixed magnet powder obtained by mixing a plurality of types of magnet powder. For example, the magnet powder of the present invention may be a composite rare earth magnet powder obtained by mixing a magnet powder having a large average particle diameter (coarse powder) and a magnet powder having a small average particle diameter (fine powder). For example, it is preferable that the coarse powder is R-TM-B type anisotropic magnet powder and the fine powder is Sm-Fe-N type anisotropic magnet powder.

<Application>
The permanent magnet (bonded magnet or the like) according to the present invention is excellent in environmental resistance and can stably exhibit high magnetic properties. For this reason, it is suitable not only for equipment used in a normal temperature range but also for equipment used in a severe environment of high temperature and humidity.

The present invention will be described more specifically with reference to examples.
<Production of sample>
Each sample shown in Table 1 was manufactured as follows.

(1) Magnet raw material The magnetic raw material shown in Table 1 was prepared as follows. Magnet alloys prepared with the composition of the magnet raw materials shown in Table 1 were obtained by the strip cast (SC) method. This magnet alloy was held in an Ar gas atmosphere at 1140 ° C. for 10 hours to homogenize the structure (homogenization heat treatment step). After cooling this to room temperature, hydrogen pulverization was performed in a hydrogen atmosphere at a hydrogen pressure of 0.13 MPa to obtain a mother alloy powder.

The magnet alloy powder was subjected to hydrogenation (d-HDDR) to obtain a rare earth anisotropic magnet powder (magnet raw material). This hydrogenation treatment was performed as follows. First, 15 g of the magnet alloy powder was placed in a processing furnace and exposed to a room temperature × 0.1 MPa low temperature hydrogen atmosphere for 1 hour (low temperature hydrogenation step). Subsequently, the powder after the low-temperature hydrogenation step was exposed to a high-temperature hydrogen atmosphere of 780 ° C. × 0.03 MPa for 30 minutes (high-temperature hydrogenation step). Thereafter, the atmosphere was heated to 840 ° C. over 5 minutes, and the powder of the high-temperature hydrogenation process was exposed to a high-temperature hydrogen atmosphere of 840 ° C. × 0.03 MPa for 60 minutes (structure stabilization process). Thus while adjusting the reaction rate, to obtain a powder that caused decompose order transformation into a three-phase _{(α-Fe, RH 2,} Fe 2 B) ( disproportionation step). Thereafter, hydrogen is continuously exhausted from the inside of the processing furnace, and the inside of the processing furnace is placed in an atmosphere of 840 ° C. × 5 to 1 kPa for 90 minutes to generate R ₂ TM ₁₄ B type ₁ crystals in the alloy after forward transformation. The reverse transformation was generated (controlled exhaust process / recombination process).

  The powder thus obtained was quenched (first cooling step). This powder was crushed in an inert gas atmosphere in a mortar and then adjusted in particle size to obtain a magnet raw material (powder composed of hydrogen-treated particles) having an average particle size of 122 μm.

(2) Diffusion Raw Material A diffusion raw material having the composition shown in Table 1 was prepared as follows. A raw material alloy (ingot) prepared to the composition of the diffusion raw material shown in Table 1 was obtained by a book mold method. This raw material alloy was pulverized with hydrogen and further pulverized with a dry ball mill to obtain a powdery diffusion raw material (hydride powder) having an average particle size of 6 μm.

(3) Diffusion treatment A diffusion raw material was added to the magnet raw material and mixed in an inert gas atmosphere to obtain a mixed raw material (mixing step). The mixing ratio shown in Table 1 is the mass ratio of the diffusion raw material when the entire mixed raw material is 100 mass%. This mixed raw material was heated in a vacuum atmosphere of 10 ⁻¹ Pa at 800 ° C. for 1 hour (diffusion process). Following this, the mixed raw material was rapidly cooled (second cooling step). In this way, diffusion magnet powder (powder composed of diffusion treated particles) was obtained. In the case of this example, the diffusion treated particles correspond to the basic magnet particles in the present invention, and the diffusion magnet powder becomes the powder to be treated.

(4) Resin coating (formation of thermosetting resin film)
A coupling solution in which 0.33 g of titanate coupling agent was uniformly dispersed in 0.65 g of hexane was prepared. The coupling liquid and 130 g of the diffusion magnet powder were mixed, then evacuated and dried (coupling process step). Thereby, a powder composed of particles coated with a coupling agent was obtained.

  Next, a coating solution was prepared by dissolving 0.39 g of epoxy resin in 1.56 g of methyl ethyl ketone (MEK). Incidentally, the glass transition point (Tg) of the epoxy resin was about 150 ° C.

  This coating solution was added to the coupled diffusion magnet powder (130 g), mixed, and then evacuated and dried. The amount of the coating liquid added to the diffusion magnet powder was adjusted so that the amount of the epoxy resin became the “amount of coating resin” shown in Table 1 with respect to the total amount of the diffusion magnet powder and the amount of the epoxy resin.

  The dried powder was further heated in vacuum at 100 ° C. for 2 hours. Thus, a powder (first magnet powder) made of diffusion-treated particles (coated magnet particles) whose surface was uniformly coated with a thermally cured epoxy resin coating (thermosetting resin coating) was obtained (Sample No. 1-1 to 1-1). 1-7). This powder corresponds to the rare earth (anisotropic) magnet powder in the present invention.

  For comparison, a powder that does not thermally cure the coated epoxy resin (that is, a powder made of diffusion-treated particles coated with an uncured resin film) was also prepared (Sample Nos. 2-1 to 2-6).

  In Table 1, the magnet powder having a coating resin amount of zero is a sample not subjected to resin coating. For convenience, a powder having a coating resin amount of zero and a powder in which the coating resin is uncured are also referred to as a first magnet powder.

<Production of compound>
124 g of first magnet powder, 21.9 g of rare earth magnet powder (second magnet powder) made of SmFeN and 4.1 g of epoxy (solid) resin are mixed by a small rocking mixer,
The obtained mixture was pressure-heated and kneaded (110 ° C.) for 10 minutes with a Laboplast mill (manufactured by Toyo Seiki). After cooling to room temperature, the particle size was adjusted to obtain a compound.

  The glass transition point (Tg) of the epoxy resin (binder resin) used here was about 200 ° C. The amount of the binder resin (epoxy resin amount) in this example was 2.75% by mass when the entire compound was 100% by mass.

  Unlike the coating resin, a small amount of zinc stearate was added to the binder resin. This is for reducing the output force (knockout load) generated between the bond magnet and the inner wall of the mold when the compound is compression molded to produce the bond magnet.

<Manufacture of bonded magnets>
The compound was placed in the mold cavity in the atmosphere and warm compression molded (120 ° C. × 1 t / cm ² (98 MPa) × 10 seconds) in an oriented magnetic field (1.5 T). As a result, a 14 mm square cubic compact was obtained. The molded body was heated in an Ar gas at 150 ° C. for 1 hour (curing treatment) to thermally cure the epoxy resin as a binder resin. This was magnetized in a 4.5 T pulse magnetic field to obtain a bonded magnet.

<< Surface observation >>
Sample No. The photograph which observed the surface of the bonded magnet which consists of 1-3 magnet powder by SEM was shown to FIG. 1A-FIG. 1C. In the SEM observation, the observation surface was pretreated with an argon shower in advance. In the photograph, the black part is the binder resin part, and the gray part is the coated magnet particle or the basic magnet particle. When FIG. 1C in which the vicinity of the surface of the particle is enlarged is observed, a white to gray thin layer can be clearly confirmed between the particle surface and the binder resin. The white thin layer formed in close contact with the particle surface and densely corresponds to the thermosetting resin film referred to in the present invention.

<Measurement>
(1) Magnetic characteristics The residual magnetic flux density (Br) of each first magnet powder was measured using a pulse BH tracer. The results are shown in Table 1.

(2) Deterioration with time of magnetic characteristics The change with time in the magnetic flux of each bonded magnet was measured using a flux meter. Specifically, first, an initial magnetic flux amount (flux) φ0 of the bonded magnet was measured. Next, the bonded magnet was placed in a constant temperature and humidity state of 80 ° C. and 95% humidity for 1000 hours and then cooled to room temperature, and the magnetic flux amount φt of the bonded magnet was measured again. The ratio ((φ0−φt) / φ0) of the demagnetization amount (φ0−φt) to the initial magnetic flux amount φ0 is expressed as a percentage, and is defined as the demagnetization rate (Flux-loss:%) after 1000 hours. Table 1 also shows the demagnetization rates of various bonded magnets.

  Further, the demagnetization rate of the bonded magnet after 1000 hours in an air atmosphere at 120 ° C. was measured in the same manner, and the results are also shown in Table 1.

<Evaluation>
(1) Thermosetting resin film Sample No. shown in Table 1 1-1 and Sample No. As is clear from comparison with 1-2 to 1-7, when a magnet powder made of magnet particles coated with a thermosetting resin film is used, the demagnetization rate of the bonded magnet is drastically improved and the weather resistance is improved. I understand that. In addition, the amount of the coating resin was about 0.1% by mass for improving the demagnetization rate. On the contrary, even if the amount of the coating resin increased, the improvement of the demagnetization rate could not be expected so much and the residual magnetic flux density (Br) decreased. In particular, when the amount of the coating resin was a certain value (for example, 1% by mass or more), the residual magnetic flux density (Br) was suddenly lowered. Therefore, it was found that the amount of the coating resin was preferably 0.1 to 1% by mass, and more preferably 0.2 to 0.8% by mass with respect to 100% by mass of the powder to be treated.

In addition, the improvement of the demagnetization factor by the thermosetting resin film was significantly larger at 80 ° C. × 95% RH than at 120 ° C. The reason is considered that the thermosetting resin film according to the present invention not only has a high oxygen shielding property but also has a very low water absorption rate. Therefore, it can be seen that by using the magnet powder coated with the thermosetting resin film, an excellent weather-resistant bonded magnet can be obtained not only in a high temperature environment but also in a severe high humidity environment.
(2) Uncured resin film Sample No. shown in Table 1 2-1 to 2-6 and Sample No. As is clear from comparison with 1-1 to 1-7, the demagnetization rate of the bonded magnet made of the magnet powder whose resin film is not thermally cured is the same level as the case where the resin film is not provided, and the improvement is very slight. Met. This tendency was the same even when the amount of the coating resin increased and the test environment was different.

Claims (7)

A basic magnet which is an aggregate of R ₂ TM ₁₄ B type ₁ crystals which are tetragonal compounds of rare earth elements (hereinafter referred to as “R”), boron (B) and transition elements (hereinafter referred to as “TM”). Particles,
A thermosetting resin film formed by thermosetting a thermosetting resin covering the surfaces of the basic magnet particles;
A rare earth magnet powder comprising coated magnet particles comprising:   The rare earth magnet powder according to claim 1, wherein the thermosetting resin film is formed on a surface of the basic magnet particle to which a coupling agent is applied.   The rare earth magnet powder according to claim 2, wherein the coupling agent is a titanate coupling agent containing titanium (Ti). A coupling treatment step of attaching a coupling agent to the surface of the basic magnet particles that are aggregates of R ₂ TM ₁₄ B type ₁ crystals, which are tetragonal compounds of R, B, and TM;
A resin attachment step of attaching a thermosetting resin to the surface of the basic magnet particles after the coupling treatment step;
A film forming step of heating the thermosetting resin to form a thermosetting resin film formed by thermosetting the thermosetting resin on the surfaces of the basic magnet particles;
A rare earth magnet powder comprising the coated magnet particles according to claim 1 is obtained. The rare earth magnet powder according to any one of claims 1 to 3,
A binder resin capable of binding the rare earth magnet powder;
A rare earth bonded magnet compound characterized by comprising: The rare earth magnet powder according to any one of claims 1 to 3,
A binder resin to which the rare earth magnet powder is bound;
A rare earth bonded magnet characterized by comprising:   The rare earth bonded magnet according to claim 6, wherein the rare earth magnet powder is a composite rare earth magnet powder composed of two or more kinds having different average particle diameters.