A method for recycling rare earth bonded magnets, a method for manufacturing rare earth bonded magnets, and rare earth bonded magnets

Abstract

The goal is to recycle rare-earth bonded magnets at a low cost while minimizing the degradation of their magnetic properties during recycling. [Solution] The method for recycling rare earth bonded magnets comprises: a grinding step of grinding a rare earth bonded magnet, which is made by binding rare earth magnetic powder with a thermosetting resin binder; a kneading step of kneading the ground rare earth bonded magnet with a thermosetting resin composition containing a thermosetting resin and its curing agent; a compression molding step of compressing the kneaded material obtained in the kneading step; and a thermosetting step of heating the molded body obtained in the compression molding step to thermoset the thermosetting resin.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for recycling rare earth bonded magnets using a thermosetting resin, a method for producing a rare earth bonded magnet, and a rare earth bonded magnet, and particularly to a method for recycling a rare earth bonded magnet, a method for producing a rare earth bonded magnet, and a rare earth bonded magnet that can recycle rare earth bonded magnets at low cost and reduce the degradation of magnetic properties caused by recycling. BACKGROUND ART

[0002] Compared with sintered magnets, bonded magnets have superior formability, enabling forming into complex shapes and integral forming with other members, thus featuring high design freedom, good dimensional accuracy, excellent mechanical properties, and being less prone to cracking and chipping. Therefore, bonded magnets are widely used in various fields such as automobiles, home appliances, communication and audio equipment, medical equipment, and general industrial equipment. In addition, bonded magnets can be easily manufactured by forming a mixture of magnetic powder and a binder component such as an organic resin into a predetermined magnet shape and magnetizing it to obtain predetermined magnetic properties, and have good workability and productivity. Therefore, in recent years, the demand for bonded magnets has increased in many fields, and new application development has been carried out. In particular, rare earth bonded magnets using rare earth alloys as magnetic powder, for example, rare earth bonded magnets using neodymium (Nd), samarium (Sm), especially rare earth iron-based alloys represented by NdFeB-based alloys and SmFeN-based alloys as magnetic powder, have been put into practical use in various fields due to their excellent magnetic properties, and are used, for example, in on-board motors for electric vehicles, hybrid vehicles and the like.

[0003] However, neodymium (Nd) and samarium (Sm), which are contained in the magnetic powder of these rare-earth bond magnets, are rare metals (rare earth elements), and their mining and refining have a significant environmental impact. Furthermore, they are produced in limited countries and are expensive. In addition, with the expected further proliferation of next-generation vehicles such as electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid vehicles (PHVs), and fuel cell vehicles (FCVs), as well as motors for hard disk drives and robots, demand is soaring, raising concerns about supply instability. Therefore, from the perspective of effective resource utilization and reduction of environmental impact, it would be desirable to recycle the rare earth magnetic powder contained in discarded rare earth bonded magnets, that is, used rare earth bonded magnets or rare earth bonded magnets that have become defective during the manufacturing process.

[0004] Therefore, attempts have been made to separate, extract, and recover magnetic powder from used or defective rare-earth bonded magnets during the manufacturing process. Patent documents 1 to 3 describe methods for recovering rare-earth magnetic powder from rare-earth bonded magnets. Patent Document 1 discloses a method for recovering magnetic powder from a rare earth bonded magnet, which is made by adding a resin binder to magnetic powder made of a rare earth alloy and solidifying it into a predetermined shape, comprising: (a) a grinding step of grinding the rare earth bonded magnet; (b) a thermal decomposition step of heating the ground material in a sealed container in a non-oxidizing atmosphere with an oxygen concentration of 0.1% or less to a temperature above the thermal decomposition start temperature of the resin binder to thermally decompose the resin binder and remove the resin binder from the magnetic powder; (c) a cooling step of cooling the inside of the container after the thermal decomposition step; (d) a deoxidation step of supplying oxygen to the container after the cooling step to maintain a low-oxygen state in which the oxygen concentration inside the container is higher than the oxygen concentration in the thermal decomposition step and lower than the oxygen concentration in the atmosphere, and deoxidizing the surface layer of the magnetic powder; and (e) a magnetic powder removal step of opening the container to the atmosphere after the deoxidation step and removing the magnetic powder from the inside of the container. Patent Document 2 discloses a method for recovering magnet powder from a rare earth bonded magnet, comprising a resin dissolution and removal step of dissolving and removing the binder resin of the rare earth bonded magnet in a solvent, and a magnet powder recovery step of recovering the magnet powder thereafter, characterized in that the method includes a heating step of heating the rare earth bonded magnet before the resin dissolution and removal step. Patent Document 3 discloses a method for recovering magnetic material from a bonded magnet in powder form, comprising: a first step of decomposing the plastic component in the bonded magnet by contacting an oxide semiconductor with the surface of the bonded magnet and heating the bonded magnet and the oxide semiconductor to a temperature in which the oxide semiconductor becomes an intrinsic semiconductor in the presence of oxygen; and a second step of recovering the magnetic material as powdered fine particles by contacting the bonded magnet, which has had the plastic component removed and is in a sintered state as magnetic material powder particles, with a dilute acid and dissolving the particle interface with the acid to release the sintered state.

[0005] Furthermore, Patent Documents 4 and 5 describe technologies for recycling rare-earth bonded magnets using thermoplastic resins. Patent Document 4 describes a method for recycling rare earth bonded magnets by utilizing the fact that thermoplastic resins become soft when heated, making them suitable for re-injection molding. Patent Document 5 describes a method for producing rare earth magnets by mixing crushed powder of bonded magnet scrap, in which ultra-rapidly cooled powder of rare earth alloy is bonded with a thermosetting resin, with a thermosetting resin in which the thermosetting resin content is 0.2 to 5.0% by weight, the rare earth alloy content is 19.5% by weight or more, and the thermoplastic resin content is 5% by weight or more, and the total of the thermosetting resin, rare earth alloy, and thermoplastic resin is 100% by weight, and then molding and magnetizing the mixture. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2011-124394 [Patent Document 2] Japanese Patent Publication No. 2014-199887 [Patent Document 3] Japanese Patent Publication No. 2015-95470 [Patent Document 4] Japanese Patent Application Publication No. 59-136907 [Patent Document 5] Patent No. 3380870 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, rare-earth bonded magnets are manufactured by molding a mixture of magnetic powder and a binder such as an organic resin into a predetermined shape. The resin binder, such as a thermosetting resin like epoxy resin used in rare-earth compression-molded bonded magnets, or a thermoplastic resin like polyamide resin or PPS resin used in rare-earth injection-molded bonded magnets, firmly adheres to the magnetic powder. Therefore, in order to remove the resin binder from the rare-earth bonded magnet, Patent Document 1 describes thermal decomposition of the resin component of the recovered rare-earth bonded magnet under an anaerobic atmosphere, Patent Document 2 describes eluting the resin component of the recovered rare-earth bonded magnet in a solvent, and Patent Document 3 describes contacting the surface of the recovered rare-earth bonded magnet with an oxide semiconductor and heating it. These are complicated processes that require time and effort, resulting in high recovery costs. Furthermore, the process of removing the resin binder can adversely affect the magnetic particles, leading to a decrease in the magnetic properties of the magnetic powder. Furthermore, as described in Patent Documents 4 and 5, the bonded magnets intended for recycling are injection-molded bonded magnets containing thermoplastic resin. This requires high-temperature heating (over 250°C) to melt the thermoplastic resin, and this high-temperature heating causes oxidative degradation of the magnetic powder. Additionally, injection molding prevents a high filling rate of the magnetic powder, significantly reducing the magnetic properties of the powder. In particular, the magnetic powder of rare-earth magnets is prone to oxidative degradation, and this degradation significantly reduces coercivity and prismaticity (Hk / Hcj). Furthermore, as described in Patent Document 4, the lack of affinity between the thermosetting resin and the thermoplastic resin also prevents a high filling rate of the magnetic powder, resulting in low magnetic properties.

[0008] Therefore, the present invention provides a method for recycling rare earth bonded magnets that can recycle them at low cost and minimize the deterioration of their magnetic properties due to recycling, a method for manufacturing rare earth bonded magnets, and rare earth bonded magnets. [Means for solving the problem]

[0009] The method for recycling a rare earth bonded magnet according to claim 1 is a method for recycling a rare earth bonded magnet in which rare earth magnetic powder is bound with a thermosetting resin binder, comprising: a grinding step of grinding the rare earth bonded magnet; a kneading step of kneading the ground rare earth bonded magnet with a thermosetting resin composition containing a thermosetting resin and its curing agent; a compression molding step of compression molding the kneaded product obtained in the kneading step; and a thermosetting step of heating the molded body obtained in the compression molding step to thermoset the thermosetting resin.

[0010] Here, the rare-earth bonded magnets, which are made by bonding the rare-earth magnetic powder with a thermosetting resin binder, are rare-earth compression-molded bonded magnets made by mixing magnetic powder containing rare earth elements such as neodymium (Nd) and samarium (Sm) with a thermosetting resin binder (binding agent) and compressing and molding them into a predetermined shape. Examples include NdFeB-based bonded magnets and SmFeN-based bonded magnets, and magnets that have been used from the market or recovered as defective products (scrap) in the manufacturing process are eligible for recycling.

[0011] The above crushing process involves crushing the rare earth bonded magnets to be recycled without removing the thermosetting resin, thereby producing rare earth bonded magnet powder. The above kneading process involves kneading pulverized rare earth bond magnets with a thermosetting resin composition containing a thermosetting resin and its curing agent to produce a compound of pulverized rare earth bond magnets and a thermosetting resin composition containing a thermosetting resin and its curing agent. The above compression molding process involves compressing a mixture of crushed rare-earth bond magnets and a thermosetting resin composition containing a thermosetting resin and its curing agent to produce a rare-earth bond magnet molded body. The above thermosetting process involves heating the rare-earth bonded magnet molded body and thermosetting the thermosetting resin contained therein to solidify the rare-earth bonded magnet molded body, thereby obtaining a recycled rare-earth bonded magnet.

[0012] The rare earth bonded magnet in the recycling method for rare earth bonded magnets of the invention of claim 2 has a residual magnetic flux density Br of preferably 0.50 [T] or more, more preferably 0.52 [T] or more, and even more preferably 0.55 [T] or more, and a coercivity Hcj of preferably 15.0 [kOe] or more, and more preferably 16.0 [kOe] or more. The above-mentioned remanent magnetic flux density Br and coercivity Hcj are calculated from the BH characteristics (demagnetization curve) measured using a BH curve tracer measuring device. Furthermore, for commercially available products, the upper limit of the remanent magnetic flux density Br is approximately 0.90 [T], and the upper limit of the coercivity Hcj is approximately 25.0 [kOe].

[0013] The rare earth bonded magnet of the recycling method for rare earth bonded magnets according to claim 3 is characterized in that the mixing ratio of the rare earth magnetic powder and the thermosetting resin binder is preferably within the range of rare earth magnetic powder:thermosetting resin binder = 100:4.0 to 100:8.0, more preferably magnetic powder:thermosetting resin binder = 100:4.5 to 100:7.5, and even more preferably magnetic powder:thermosetting resin binder = 100:5.0 to 100:7.0.

[0014] The pulverized rare earth bonded magnet in the method for recycling rare earth bonded magnets of the invention of claim 4 has a particle size preferably in the range of 2.5 to 1100 [μm], more preferably in the range of 3.5 to 750 [μm], and even more preferably in the range of 5.0 to 500 [μm].

[0015] In the recycling method for a rare-earth bonded magnet according to the invention of claim 5, the thermosetting resin contained in the thermosetting resin composition to be kneaded with the pulverized rare-earth bonded magnet is an epoxy resin or a phenol resin.

[0016] In the kneading step of the recycling method for a rare-earth bonded magnet according to the invention of claim 6, the mixing ratio of the pulverized rare-earth bonded magnet to be kneaded and the thermosetting resin contained in the thermosetting resin composition is preferably within the range of pulverized rare-earth bonded magnet : thermosetting resin = 100:1.0 to 100:5.0, more preferably within the range of pulverized rare-earth bonded magnet : thermosetting resin binder = 100:1.5 to 100:4.5, and still more preferably within the range of pulverized rare-earth bonded magnet : thermosetting resin binder = 100:2.0 to 100:4.0.

[0017] The method for producing a rare-earth bonded magnet according to the invention of claim 7 comprises: a pulverization step of pulverizing a rare-earth bonded magnet obtained by binding rare-earth magnetic powder with a thermosetting resin binder; a kneading step of kneading the pulverized rare-earth bonded magnet and a thermosetting resin composition containing a thermosetting resin and a curing agent thereof; a compression molding step of compression-molding the kneaded product obtained in the kneading step; and a thermosetting step of heating the molded body obtained in the compression molding step to thermally cure the thermosetting resin.

[0018] The rare-earth bonded magnet according to the invention of claim 8 is a recycled rare-earth bonded magnet comprising rare-earth magnetic powder and a thermosetting resin binder as a binder for the rare-earth magnetic powder, wherein, based on 100% by mass of the rare-earth bonded magnet, the content of the thermosetting resin binder is 3.0% by mass or more and 10.0% by mass or less, and preferably 4.0% by mass or more and 7.0% by mass or less.

[0019] The rare earth bonded magnet of the invention according to claim 9 preferably has a residual magnetic flux density Br of 0.48 [T] or more, more preferably 0.49 [T] or more, still more preferably 0.50 [T] or more, and preferably has a coercive force Hcj of 15.0 [kOe] or more, more preferably 16.0 [kOe] or more. The upper limit of the residual magnetic flux density Br is approximately 0.85 [T], and the upper limit of the coercive force Hcj is approximately 24.0 [kOe]. Effect of the Invention

[0020] According to the method for recycling a rare earth bonded magnet according to the invention of claim 1, in the crushing step, a rare earth bonded magnet formed by binding rare earth magnetic powder with a thermosetting resin binder is crushed; in the kneading step, the crushed rare earth bonded magnet is kneaded with a thermosetting resin composition containing a thermosetting resin and a curing agent thereof; in the compression molding step, the kneaded product obtained in the kneading step is compression molded; and in the thermosetting step, the molded product obtained in the compression molding step is heated to cure the thermosetting resin, whereby the original rare earth bonded magnet is recycled as a rare earth bonded magnet again.

[0021] Therefore, according to the rare earth bond magnet recycling method of the invention of claim 1, the original rare earth bond magnet is crushed without removing the thermosetting resin contained in the original rare earth bond magnet and attached to the magnetic powder, mixed with a new thermosetting resin composition, the mixture is compressed and molded, and then heated to thermoset the thermosetting resin, thereby recycling it as a new rare earth bond magnet. This method does not require chemical treatment to remove the thermosetting resin contained in the original rare earth bond magnet and attached to the magnetic powder, and because the binder of the magnetic powder is only thermosetting resin, high-temperature heating is not required. Furthermore, because the magnetic powder can be filled with a high filling rate by compression molding rather than injection molding, the deterioration of the magnetic properties of the magnetic powder due to chemical treatment or high heat is suppressed, and by enabling high filling of the magnetic powder by compression molding, the original rare earth bond magnet can be regenerated at low cost without significantly reducing its magnetic properties such as coercivity Hcj and prismaticity (Hk / Hcj). In other words, rare-earth bonded magnets can be recycled at low cost, and the degradation of their magnetic properties due to recycling can be minimized.

[0022] According to the method for recycling rare earth bonded magnets of the invention of claim 2, the rare earth bonded magnet has a residual magnetic flux density Br of preferably 0.50 [T] or more, more preferably 0.52 [T] or more, and even more preferably 0.55 [T] or more, and a coercivity Hcj of preferably 15.0 [kOe] or more, more preferably 16.0 [kOe] or more. Therefore, in addition to the effects described in claim 1, it is possible to obtain a rare earth bonded magnet with high magnetic properties as a recycled product, and even recycled rare earth bonded magnets can be used in a wide range of applications and fields.

[0023] According to the method for recycling rare earth bonded magnets of the invention of claim 3, the mixing ratio of the magnetic powder and the thermosetting resin binder of the rare earth bonded magnet is preferably within the range of rare earth magnetic powder:thermosetting resin binder = 100:4.0 to 100:8.0, more preferably magnetic powder:thermosetting resin binder = 100:4.5 to 100:7.5, and even more preferably magnetic powder:thermosetting resin binder = 100:5.0 to 100:7.0. Therefore, in addition to the effects described in claim 1, the moldability is also good, and the resulting recycled rare earth bonded magnet can have the desired magnetic properties.

[0024] According to the method for recycling rare earth bonded magnets of claim 4, the pulverized rare earth bonded magnets are preferably in the range of 2.5 to 1100 [μm], more preferably in the range of 3.5 to 750 [μm], and even more preferably in the range of 5.0 to 500 [μm]. Therefore, in addition to the effects described in claim 1, rust is less likely to occur because the magnetic powder particles are not pulverized, and the packing ability of the magnetic powder can be increased, and the orientation can be improved, thereby increasing the magnetic properties of the recycled rare earth bonded magnets.

[0025] According to the method for recycling rare earth bonded magnets of claim 5, the thermosetting resin contained in the thermosetting resin composition kneaded with the crushed rare earth bonded magnets is an epoxy resin or a phenolic resin. Therefore, in addition to the effects described in claim 1, the packing efficiency of the magnetic powder can be increased, thereby improving the magnetic properties of the recycled rare earth bonded magnets.

[0026] According to the method for recycling rare earth bonded magnets of claim 6, the mixing ratio of the crushed rare earth bonded magnets kneaded in the kneading step and the thermosetting resin contained in the thermosetting resin composition is preferably in the range of crushed rare earth bonded magnets:thermosetting resin = 100:1.0 to 100:5.0, more preferably crushed rare earth bonded magnets:thermosetting resin binder = 100:1.5 to 100:4.5, and even more preferably crushed rare earth bonded magnets:thermosetting resin binder = 100:2.0 to 100:4.0. Therefore, in addition to the effects described in claim 1, the moldability is also good, and the resulting recycled rare earth bonded magnets can have the desired magnetic properties.

[0027] According to the method for manufacturing a rare earth bonded magnet according to claim 7, a rare earth bonded magnet, which is made by binding rare earth magnetic powder with a thermosetting resin binder, is crushed in a crushing step; the crushed rare earth bonded magnet is kneaded with a thermosetting resin composition containing a thermosetting resin and its curing agent in a kneading step; the kneaded mixture obtained in the kneading step is compressed and molded in a compression molding step; and the molded body obtained in the compression molding step is heated to cure the thermosetting resin in a thermosetting step, thereby obtaining a recycled rare earth bonded magnet.

[0028] According to the method for manufacturing a rare-earth bonded magnet of the invention of claim 7, the original rare-earth bonded magnet is pulverized without removing the thermosetting resin attached to the magnetic powder contained in the original rare-earth bonded magnet, kneaded with a new thermosetting resin composition, the kneaded product is compression molded, and then heated to thermosetting the thermosetting resin, thereby recycling the original rare-earth bonded magnet to manufacture a new rare-earth bonded magnet. This method does not require chemical treatment to remove the thermosetting resin attached to the magnetic powder contained in the original rare-earth bonded magnet, and because the binder of the magnetic powder is only a thermosetting resin, high-temperature heating is not required. Furthermore, because the magnetic powder can be filled with a high filling rate by compression molding rather than injection molding, the deterioration of the magnetic properties of the magnetic powder due to chemical treatment or high heat is suppressed, and by enabling high filling of the magnetic powder by compression molding, the original rare-earth bonded magnet can be regenerated at low cost without significantly degrading its magnetic properties such as coercivity Hcj and prismaticity (Hk / Hcj). In other words, recycled rare-earth bonded magnets can be obtained at low cost, and the degradation of magnetic properties due to recycling can be minimized.

[0029] The rare earth bond magnet according to claim 8 is a recycled rare earth bond magnet containing rare earth magnetic powder and a thermosetting resin binder as a binder for the rare earth magnetic powder, wherein the thermosetting resin binder is contained in 3.0% by mass or more and 10.0% by mass or less, preferably 4.0% by mass or more and 7.0% by mass or less, per 100% by mass of the rare earth bond magnet.

[0030] In a rare-earth bonded magnet, where the binder binding the rare-earth magnetic powder is a thermosetting resin binder, a rare-earth bonded magnet is pulverized, a small amount of new thermosetting resin containing a thermosetting resin and its curing agent is added and kneaded, the kneaded mixture is compressed and molded, and the thermosetting resin in the molded product is thermoset to regenerate the rare-earth bonded magnet. As a result of adding new thermosetting resin to the thermosetting resin content in the original rare-earth bonded magnet, the thermosetting resin content is higher than in the original rare-earth bonded magnet. In 100% by mass of the rare-earth bonded magnet, the thermosetting resin binder is contained at a rate of 3.0% by mass or more and 10.0% by mass or less, preferably 4.0% by mass or more and 7.0% by mass or less.

[0031] Therefore, a rare earth bonded magnet containing 3.0% to 10.0% by mass, preferably 4.0% to 7.0% by mass, of thermosetting resin binder in 100% by mass of rare earth bonded magnet is a recycled product obtained by recovering a rare earth bonded magnet using thermosetting resin and separately adding thermosetting resin to create a new rare earth bonded magnet. Because the binder consists only of thermosetting resin, oxidative degradation of the magnetic powder due to high-temperature heating to melt it, as occurs when thermoplastic resin is used, does not occur. Furthermore, because the magnetic powder can be molded with high filling by compression molding rather than injection molding, the magnetic properties such as the coercivity Hcj and prismaticity (Hk / Hcj) of the original rare earth bonded magnet are hardly reduced, and it is recycled at low cost.

[0032] The rare earth bonded magnet according to claim 9 preferably has a T of 0.48 or higher, more preferably 0.49 or higher, and even more preferably 0.50 or higher, and a coercivity Hcj preferably 15.0 kOe or higher, more preferably 16.0 kOe or higher. Therefore, in addition to the effects described in claim 8, it can be used in a wide range of applications and fields for recycled rare earth bonded magnets. [Brief explanation of the drawing]

[0033] [Figure 1]Figure 1 is a flowchart showing a method for recycling rare earth bonded magnets according to an embodiment of the present invention. [Modes for carrying out the invention]

[0034] Embodiments of the present invention will be described below. First, a recycling method (manufacturing method) for rare earth bonded magnets according to an embodiment of the present invention will be described. The method for recycling (manufacturing) rare earth bond magnets according to an embodiment of the present invention comprises: a crushing step (step S10) in which the recovered rare earth bond magnets are crushed; a kneading step (step S20) in which the crushed rare earth bond magnets are kneaded with a thermosetting resin composition containing a thermosetting resin and its curing agent; a compression molding step (step S30) in which the kneaded mixture of the crushed rare earth bond magnets and the thermosetting resin composition is compressed and molded to form a rare earth bond magnet molded body; a thermosetting step (step S40) in which the thermosetting resin in the rare earth bond magnet molded body is thermoset to form a pre-magnetized rare earth bond magnet; and a magnetization step (step S50) in which the pre-magnetized rare earth bond magnet is magnetized to form a magnetized rare earth bond magnet.

[0035] In this embodiment, first, a crushing process (step S10) is performed to crush the recovered rare earth bond magnets to be recycled. The material to be crushed in the crushing process (step S10) is used rare earth bonded magnets, or waste materials that have become defective in the magnet manufacturing process, that is, rare earth bonded magnets recovered from the market or recovered as scrap in the manufacturing process. These recycled rare earth bonded magnets, which are the material to be crushed, are made by binding rare earth magnetic powder with a thermosetting resin binder, that is, by kneading rare earth magnetic powder with a thermosetting resin binder, compressing and molding it into a predetermined shape, and then thermosetting the thermosetting resin binder by heating. Furthermore, magnetized materials are demagnetized before being crushed. This prevents the crushed magnet powder from re-aggregating due to magnetism or adhering to equipment and jigs in subsequent processes, thus improving handling. Unmagnetized materials are crushed as is.

[0036] The rare earth magnetic powder (hereinafter sometimes simply referred to as "magnetic powder") used in the crushed rare earth bond magnets is not particularly limited, but commercially available products, for example, use rare earth-transition metal magnetic powder containing both rare earth elements and transition metal elements. Examples of rare earth elements include lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), while examples of transition metal elements include iron (Fe), cobalt (Co), nickel (Ni), manganese (Mn), chromium (Cr), vanadium (V), and copper (Cu). From the perspective of performance and cost, samarium-iron-nitrogen (SmFeN) magnetic powder (Sm2Fe) has great value for recycling. 17 N3, etc.) or neodymium-iron-boron (NdFeB) magnetic powder (Nd2FeB) 14 B, etc.) Furthermore, the rare earth bond magnets to be crushed should have a thermosetting resin binder that holds the magnetic powder together, and among these, epoxy resin or phenolic resin is preferred from the viewpoint of being able to achieve a high packing density of magnetic powder.

[0037] Furthermore, the rare earth bonded magnet to be crushed has a mixing ratio (weight ratio) of magnetic powder and thermosetting resin binder that constitutes it, preferably in the range of magnetic powder:thermosetting resin binder = 100:4.0 to 100:8.0, more preferably in the range of magnetic powder:thermosetting resin binder = 100:4.5 to 100:7.5, and even more preferably in the range of magnetic powder:thermosetting resin binder = 100:5.0 to 100:7.0. If the ratio of thermosetting resin binder to magnetic powder is too high, the resulting recycled rare-earth bonded magnet will have poor magnetic properties. Conversely, if the ratio of thermosetting resin binder to magnetic powder is too low, moldability will decrease, making the magnetic powder more prone to falling off, cracking, and chipping, resulting in reduced strength. If the mixing ratio of the magnetic powder and thermosetting resin binder in the rare earth bonded magnet is within the above range, the moldability will be good, and the strength will be such that powder shedding, cracking, and chipping will not occur easily, and the resulting recycled rare earth bonded magnet will have the desired magnetic properties. The mixing ratio (weight ratio) of the original rare-earth bonded magnet's magnetic powder to the thermosetting resin binder can be calculated by crushing the recovered original rare-earth bonded magnet, measuring the weight of the crushed powder, dissolving the resin with methyl ethyl ketone or the like, and measuring the weight of the magnetic powder separated from the resin. The weight of the thermosetting resin binder can then be calculated from the difference between the weight of the crushed powder and the weight of the magnetic powder, thus determining the weight ratio of the original rare-earth bonded magnet's magnetic powder to the thermosetting resin binder.

[0038] The rare earth bond magnets to be crushed have a residual magnetic flux density Br of preferably 0.50[T] or higher, more preferably 0.52[T] or higher, and even more preferably 0.55[T] or higher, and a coercivity Hcj of preferably 15.0[kOe] or higher, more preferably 16.0[kOe] or higher. The residual magnetic flux density Br and coercivity Hcj are based on 23°C. If the magnetic properties of the recycled rare-earth bonded magnets fall within the above range, the magnetic properties of the recycled rare-earth bonded magnets can be improved, making them suitable for a wide range of applications and fields. For example, they become suitable for use in small motors with relatively low output, such as auxiliary motors. While there are no upper limits on the residual magnetic flux density (Br) and coercivity (Hcj) of recycled rare-earth bonded magnets, market products typically have a residual magnetic flux density of around 0.90 [T] and a coercivity of around 25.0 [kOe].

[0039] In the grinding step (step S10), the rare earth bond magnets to be recycled are ground without pretreatment, and the particle size is preferably in the range of 2.5 to 1100 [μm]. More preferably, it is in the range of 3.5 to 750 [μm], and even more preferably, in the range of 5.0 to 500 [μm]. If the particle size is made too fine, the magnetic powder particles will be crushed, making them prone to rusting and reducing their magnetic properties. On the other hand, if the particle size is too large, the packing and orientation of the magnetic powder will decrease, reducing its magnetic properties, as well as its moldability, making it prone to powder shedding, cracking, and chipping, thus reducing its strength. If the particle size of the crushed rare-earth bonded magnet is within the above range, rust is less likely to occur because the magnetic powder particles are not crushed. Furthermore, the filling and orientation of the magnetic powder are good, suppressing the deterioration of magnetic properties. In addition, it has good moldability and strength that makes it resistant to powder shedding, cracking, and chipping. This adjustment of particle size range can be achieved by classification using a sieve with a predetermined mesh size.

[0040] For example, the pulverization of rare earth bonded magnets for recycling can be carried out using a ball mill, ring mill, vibratory mill, gas jet mill, high-speed mixer, grinder, jet mill, etc. Thus, in the crushing process (step S10), the rare earth bonded magnets to be recycled are crushed, and crushed rare earth bonded magnet material is obtained.

[0041] Next, a kneading step (step S20) is performed in which the rare earth bonded magnet (pulverized rare earth bonded magnet) pulverized in the pulverization step (step S10) is kneaded with a thermosetting resin composition containing a thermosetting resin and its curing agent. In the kneading process (step S20), the pulverized rare earth bond magnets are kneaded with a thermosetting resin composition containing a thermosetting resin and its curing agent. The thermosetting resin contained in the thermosetting resin composition is preferably an epoxy resin or a phenolic resin. If an epoxy resin or a phenolic resin is used, the amount of magnetic powder packed in can be increased to improve the magnetic properties. Among these, epoxy resins improve workability when kneading with crushed rare earth bonded magnets and fluidity when filling into molds, and they can also exhibit high mechanical strength in rare earth bonded magnets, making it possible to achieve both improved magnetic properties and mechanical strength. Furthermore, from the viewpoint of compatibility, it is preferable to use the same type of thermosetting resin that was used in the recycled rare earth bonded magnets.

[0042] Epoxy resins are generally compounds that have two or more epoxy groups (oxirane rings) in one molecule and yield a three-dimensional cured product when cured with a curing agent. For example, epoxy compounds having bisphenyl groups such as bisphenol A type, bisphenol F type, brominated bisphenol A type, hydrogenated bisphenol A type, bisphenol S type, bisphenol AD ​​type, bisphenol AF type, and biphenyl type; epoxy compounds such as polyalkylene glycol type and alkylene glycol type; epoxy compounds having naphthalene rings; epoxy compounds having fluorene groups; bifunctional glycidyl ether type epoxy resins; novolac type epoxy resins such as phenol novolac type and orthocresol novolac type; polyfunctional glycidyl ether type epoxy resins such as polyfunctional glycidyl ether and tetraphenyloleethane type; glycidyl ester type epoxy resins of synthetic fatty acids such as dimer acid; and N,N,N′,N′-tetraglycidyldiaminodiphenylmethane. Examples include aromatic epoxy resins having glycidylamino groups such as TGDDM, tetraglycidyl-m-xylylenediamine, triglycidyl-p-aminophenol, and N,N-diglycidylaniline; trishydroxyphenylmethane type epoxy resins; epoxy compounds having a tricyclodecane ring (for example, epoxy compounds obtained by a production method in which dicyclopentadiene is polymerized with cresols or phenols such as m-cresol, and then reacted with epichlorohydrin); trishydroxyphenylmethane type epoxy resins; sorbitol type epoxy resins; polyglycerol type epoxy resins; glycidyl ester type epoxy resins; heterocyclic epoxy resins; diarylsulfone type epoxy resins; pentaerythritol type epoxy resins; and trimethylolpropane type epoxy resins. Among these, epoxy resins such as bisphenol type epoxy resins, brominated epoxy resins, alicyclic epoxy resins, and novolac type epoxy resins are preferred, and in particular, bisphenol A type, which is a general-purpose epoxy resin, is generally preferred, and those that are liquid at room temperature are preferably used.

[0043] Any curing agent for epoxy resins that has an active group that reacts with epoxy groups is acceptable, for example, imidazole compounds such as dicyandiamide, polyaminoamide, 4,4'-diaminodiphenylsulfone, and 2-n-heptadecylimidazole; organic acid hydrazide compounds such as adipic acid dihydrazide, stearate dihydrazide, isophthalic acid dihydrazide, dibasic acid hydrazide, and isophthalic acid dihydrazide; urea compounds such as N,N-dialkylurea derivatives and N,N-dialkylthiourea derivatives; acid anhydrides such as tetrahydrophthalic anhydride; semicarbazide; cyanoacetamide; diaminodiphenylmethane. Examples include aliphatic and aromatic tertiary amines, polyamines, amine compounds such as isophorone diamine and m-phenylenediamine, aminotriazoles such as 3-amino-1,2,4-triazole, N-aminoethylpiperazine, melamines, guanamines such as acetoguanamine and benzoguanamine, guanidines, dimethylureas, boron trifluoride complex compounds, boron trichloride complex compounds, Lewis acid complexes, polymercaptans, liquid phenols such as trisdimethylaminomethylphenol, polythiols, triphenylphosphine, ketimine compounds, sulfonium salts, onium salts, and phenol resins such as phenol novolac resins. These can be used individually or in combination of two or more. Among these, from the viewpoint of moldability, dispersed latent curing agents such as dicyandiamide, imidazole compounds, and organic acid hydrazides, which do not chemically react with epoxy resins at room temperature but are activated by heat, are preferred. More preferably, from the viewpoint of storage stability, etc., when dispersed in a fine powder state in the epoxy resin, heat-soluble dicyandiamide (including derivatives such as polyepoxide addition modified products, amidation modified products, Mannichation modified products, Michael addition modified products, etc.) or imidazole compounds are used. If dicyandiamide is used, the curing agent component dissolves and is activated by heat, and the epoxy resin can be cured at a temperature of 160 to 180°C. The amount of curing agent to be blended is determined based on the amine equivalent and epoxy equivalent, for example, if amines such as dicyandiamide are used.

[0044] Furthermore, curing accelerators may be added to shorten the curing time or lower the curing temperature, thereby accelerating the chemical reaction between the epoxy resin and the curing agent. Examples of curing accelerators that can be used include urea-based (dimethylurea, etc.), imidazole-based (alkyl-substituted imidazole, benzimidazole, etc.), phosphorus-based, amine-based, and triphenylphosphine.

[0045] Examples of phenolic resins include novolac-type phenolic resins (polyfunctional phenolic resins), resol-type phenolic resins, aryl-type phenolic resins, aralkyl-type phenolic resins, alkyl-type phenolic resins, and (novolac-type phenolic resins), with novolac-type phenolic resins being preferred. Examples of novolac-type phenolic resins include cresol-novolac-type phenolic resins, xylenol-type phenolic resins, trisphenolmethane-type phenolic resins, dicyclopentadiene-type phenolic resins, naphthalene-type phenolic resins, and phenol biphenylene-type phenolic resins, with trisphenolmethane-type phenolic resins being more preferred. As curing agents for phenolic resins, amine-based curing agents such as hexamine and xamethylenetetramine are suitably used.

[0046] In the kneading process (step S20), the mixing ratio of the pulverized rare earth bonded magnet to the thermosetting resin is preferably in the range of pulverized rare earth bonded magnet:thermosetting resin = 100:1.0 to 100:5.0, more preferably in the range of pulverized rare earth bonded magnet:thermosetting resin = 100:1.5 to 100:4.5, and even more preferably in the range of pulverized rare earth bonded magnet:thermosetting resin = 100:2.0 to 100:4.0. If the proportion of thermosetting resin is too high relative to the crushed rare-earth bonded magnet, the magnetic properties of the recycled rare-earth bonded magnet will be low because the packing density of the magnetic powder will decrease relatively. If the proportion of thermosetting resin is too low, the moldability will decrease, making it prone to powder shedding, cracking, and chipping, resulting in reduced strength. If the mixing ratio of crushed rare-earth bonded magnets and thermosetting resin is within the above range, the moldability will be good, the strength will be such that powder shedding, cracking, and chipping will not occur easily, and the resulting recycled rare-earth bonded magnets will have the desired magnetic properties.

[0047] In the kneading process (step S20), for kneading the pulverized rare-earth bond magnets with the thermosetting resin composition containing the thermosetting resin and its curing agent, various mixers (kneaders) such as kneaders, rotary mixers, pulverizers, Banbury mixers, rolls, kneader extruders, single-screw extruders, twin-screw extruders, mills, V-type mixers, ribbon mixers, double-cone mixers, mixing shakers, tumbler mixers, Nauter mixers, rotary mixers, flash mixers, tumblers, Henschel mixers, and super mixers can be used. Among these, a kneader is preferred because its blades do not rotate at high speed, making it less likely to load (damage) the magnetic powder.

[0048] During the mixing process (step S20), an organic solvent may be added to the thermosetting resin composition to reduce its viscosity and improve its workability and fluidity during mixing. Examples of organic solvents that can be used to dilute the thermosetting resin composition include methyl ethyl ketone, acetone, methyl isobutyl ketone, benzene, toluene, and xylene. Among these, volatile organic solvents that become gaseous at room temperature are preferred from the viewpoint of workability, and methyl ethyl ketone is preferably used from the viewpoint of safety and ease of handling.

[0049] Thus, in the mixing process (step S20), the pulverized rare earth bond magnet (pulverized rare earth bond magnet) and a thermosetting resin composition containing a thermosetting resin and its curing agent are mixed together to produce a moist powdery compound of the pulverized rare earth bond magnet and the thermosetting resin composition containing a thermosetting resin and its curing agent.

[0050] Next, a compression molding process (step S30) is carried out in which the mixture of the pulverized rare earth bond magnet and the thermosetting resin composition obtained in the kneading process (step S20) is compressed and molded. In this case, if the thermosetting resin composition is diluted with an organic solvent in the kneading process (step S20), the organic solvent is evaporated by drying at a predetermined temperature (for example, within the range of room temperature to 120°C), and then compression molding is performed.

[0051] In the compression molding process (step S30), a mixture of crushed rare earth bond magnets and thermosetting resin composition is filled into the powder press mold of the compression molding apparatus and compressed. In this case, if the recycled rare-earth bonded magnets are to be anisotropic magnets, a magnetic field is applied in the mold before compression to orient the magnetic powder. Alternatively, compression molding is performed while applying an orientation magnetic field. That is, the material is placed in the mold of the molding section of a magnetic field compression molding apparatus (for example, a mechanical cold press), an orientation magnetic field application section installed around the mold applies a magnetic field to the mixture inside the mold, and then compression molding is performed by the molding section in that state.

[0052] The magnetic field compression molding apparatus, for example, consists of a molding section equipped with a mold and punch for pressurizing and compressing a mixture of crushed rare earth bond magnets and a thermosetting resin composition; a supply section such as a quantitative feeder for filling the mixture into the mold; and an orientation magnetic field application section for applying an orientation magnetic field to the mixture filled in the mold. The orientation magnetic field application unit has magnetic poles for applying a magnetic field around the mold and a coil or permanent magnet swirled around the magnetic poles. It generates a magnetic field based on the current applied to the coil or permanent magnet, and this magnetic field orients the magnetic powder contained in the mixture inside the mold. The orientation of the magnetic powder can be controlled by controlling the magnetism of the magnetic poles and the direction and magnitude of the current applied to the coil or permanent magnet. To sufficiently orient the magnetic powder, an orientation magnetic field of, for example, 240 to 1600 kA / m, preferably 240 to 1200 kA / m, and more preferably 400 to 800 kA / m is applied. The magnetic field at this time may be a static magnetic field or a pulsed magnetic field. The mold for the molding section is designed according to the desired magnet shape, is made of a non-magnetic material, and allows a magnetic field to pass through.

[0053] The molding pressure used to compress the kneaded material filled into the mold is, for example, 50 to 1500 MPa, preferably 100 to 1000 MPa, and more preferably 150 to 400 MPa. Within this range, the filling rate of the magnetic powder can be increased, and the magnetic properties can be improved. The density of the compressed molded body at this time is the true density of the magnetic powder particles (for example, the true density of neodymium iron boron-based magnetic powder alloy is 7.6 g / cm³). 3 The ratio is preferably 70% or more, and more preferably 75% or more. This yields a rare-earth bonded magnet molded body with higher magnetic properties and higher mechanical strength. In this case, compression molding is preferably performed at room temperature (cold molding), but warm molding at a temperature lower than the curing start temperature of the thermosetting resin is also acceptable.

[0054] Thus, in the compression molding process (step S30), the mixture of crushed rare earth bond magnets and thermosetting resin composition is dried as appropriate, then placed in a mold and compressed to produce a molded rare earth bond magnet.

[0055] Next, a thermosetting process (step S40) is performed in which the rare earth bonded magnet molded body obtained in compression molding (step S30) is heated, and the thermosetting resin in the rare earth bonded magnet molded body is thermoset, thereby binding and solidifying the magnetic powder with the thermosetting resin.

[0056] In the thermosetting process (step S40), the rare-earth bonded magnet molded in the compression molding process (step S30) is removed from the mold and heated in an oven or the like to produce a pre-magnetized bonded magnet (demagnetized / demagnetized) in which the thermosetting resin has been heat-cured. The heating method used in this case is not particularly limited, but examples include ovens, electricity, infrared radiation, and high-frequency waves.

[0057] In the thermosetting step (step S40), if the thermosetting resin is an epoxy resin or a phenolic resin, it is preferably heated for 20 to 60 minutes in a range of 120°C or higher and less than 200°C, more preferably 150°C or higher and 190°C or lower. If the heating temperature is too low, the heat curing will be insufficient, causing the magnetic powder to fall off and making it prone to chipping and cracking, thus reducing its strength. On the other hand, if the heating temperature is too high, the magnetic properties of the magnetic powder will deteriorate, or the thermosetting resin will oxidize and degrade, causing the magnetic powder to fall off and reducing its strength. If the temperature at which the rare-earth bonded magnet molded body is heated is within the above range, the decrease in magnetic properties from the original rare-earth bonded magnet is effectively suppressed, and the moldability is good, resulting in strength that is resistant to powder shedding, cracking, and chipping.

[0058] In addition, to prevent oxidation of the magnetic powder, heating may be performed under reduced pressure (1 kPa or less) or in an inert gas atmosphere such as argon or nitrogen gas. For example, when using neodymium-iron-boron (NdFeB) type rapidly cooled alloy magnetic powder, which is easily oxidized, as a rare-earth type magnetic powder, the heat treatment atmosphere is preferably a reduced pressure atmosphere of 10 Pa or less, more preferably a vacuum of 1 Pa or less, or a non-oxidizing atmosphere such as an inert gas atmosphere such as argon or nitrogen gas.

[0059] Thus, in the thermosetting process (step S40), the rare earth bonded magnet molded body is heated to heat-cur the thermosetting resin contained therein, and the magnetic powder is bound and solidified by the thermosetting resin to produce a pre-magnetized rare earth bonded magnet in a demagnetized / demagnetized state.

[0060] Subsequently, the pre-magnetized rare-earth bond magnet obtained in the thermosetting process (step S40) is magnetized in a magnetic field, and the magnetization process (step S50) is carried out to obtain a magnetized rare-earth bond magnet, which is a recycled product. Magnetization in this case is performed by applying a magnetic field in the orientation direction using known methods such as an electromagnet that generates a static magnetic field or a capacitor magnetizer that generates a pulsed magnetic field. The magnetic field strength (strength of the magnetic field) for magnetization is set to, for example, 1.2 [MA / m] or more, preferably 2.4 to 4000 [MA / m], and the magnetic flux density is set to, preferably 1 to 36 [T], more preferably 1 to 12 [T], and even more preferably 3 to 8 [T]. Within this range, magnetization can be performed sufficiently without causing magnet cracking due to thermal shock or the like.

[0061] Thus, in this embodiment, rare earth bonded magnets (rare earth compression-molded bonded magnets) to be collected and recycled are crushed, a thermosetting resin composition containing a thermosetting resin such as epoxy resin and its curing agent is added and kneaded, the kneaded mixture is compressed and molded into a predetermined shape, the thermosetting resin is heat-cured, and then the magnetization is performed to produce rare earth bonded magnets (rare earth compression-molded bonded magnets) as recycled products. In other words, used or scrapped rare earth bonded magnets that have been collected are recycled again as rare earth bonded magnets.

[0062] In this embodiment, for rare-earth bonded magnets (rare-earth compression-molded bonded magnets) in which the binder binding the magnetic powder is a thermosetting resin binder, the original rare-earth bonded magnet is crushed, a new thermosetting resin composition is added, and it is compressed and molded again. Because the binder binding the magnetic powder is only a thermosetting resin, high-temperature heating for melting is not required, and compression molding is possible instead of injection molding. After compression molding, the thermosetting resin is heat-cured at a low temperature to function as a binder that binds the magnetic powder.

[0063] Therefore, without removing the thermosetting resin binder, the original rare-earth bonded magnet is crushed, a new thermosetting resin composition is added, and it is compressed and heat-cured again to recycle it as a rare-earth bonded magnet. Since this process does not require the complicated process and effort of removing the thermosetting resin binder, it can be recycled at a low cost. Furthermore, the reduction in the magnetic properties of the original magnetic powder associated with the removal of the thermosetting resin binder is suppressed. Additionally, because the binder binding the magnetic powder is solely thermosetting resin, high-temperature heating is not required. Moreover, compression molding is possible instead of injection molding, which improves the packing efficiency of the magnetic powder, further suppressing the reduction in the magnetic properties of the original magnetic powder. Therefore, it can be recycled as a rare-earth bonded magnet without causing a significant decrease in the magnetic properties of the original rare-earth compression-molded bonded magnet.

[0064] In this way, recycled rare-earth bonded magnets contain thermosetting resin in an amount of 3.0% to 10.0% by mass, preferably 4.0% to 7.0% by mass, per 100% by mass of rare-earth bonded magnet, and the filling rate of magnetic powder is preferably in the range of 40 to 90% by mass, more preferably 60 to 75% by mass. This makes it possible to suppress the decrease in coercivity Hcj of the magnetic properties to 5% without significantly degrading the magnetic properties of the original rare-earth bonded magnet, and makes them usable in a wide range of fields and applications. Specifically, recycled rare-earth bonded magnets have a residual magnetic flux density Br of preferably 0.48[T] or higher, more preferably 0.49[T] or higher, and even more preferably 0.50[T] or higher, and a coercivity Hcj of preferably 15.0[kOe] or higher, more preferably 16.0[kOe] or higher, and even more preferably 18.0[kOe] or higher. While there are no upper limits on the residual magnetic flux density Br and coercivity Hcj of recycled rare-earth bonded magnets, the residual magnetic flux density Br is approximately 0.85[T] and the coercivity Hcj is approximately 24.0[kOe]. If the magnetic properties are within the specified range, it can be used in a wide range of applications and fields, and is suitable for use in small motors with relatively low output, such as auxiliary motors.

[0065] In this way, the degradation of magnetic properties from the original rare-earth compression-molded bonded magnet can be minimized, making it possible to recycle high-performance rare-earth bonded magnets, such as those used in the main motors of electric vehicles, into low-cost and simple rare-earth bonded magnets that can withstand use in relatively low-power small motors and sensors, such as auxiliary motors, that do not require the high output of the main motors of electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid vehicles (PHVs), and fuel cell vehicles (FCVs).

[0066] In this embodiment, a rare earth bonded magnet, in which the binder to which magnetic powder is bound is a thermosetting resin binder, is crushed, a new thermosetting resin composition containing a thermosetting resin and its curing agent is kneaded into it, the kneaded mixture (compound) is compressed and molded, then heated to cure the thermosetting resin, and then magnetized to obtain a recycled rare earth bonded magnet. Specifically, a rare-earth bonded magnet, which has a thermosetting resin binder to which magnetic powder is bound, is crushed, a new thermosetting resin composition containing a thermosetting resin and its curing agent is kneaded into it, the kneaded mixture (compound) is compressed and molded, then heated to harden the thermosetting resin, and then magnetized to produce a recycled rare-earth bonded magnet.

[0067] In this method, rare earth bonded magnets, which have a thermosetting resin binder to which magnetic powder is bound, are crushed, a small amount of a new thermosetting resin composition containing a thermosetting resin and its curing agent is kneaded into the crushed magnet, the kneaded mixture is compressed and molded, the thermosetting resin in the compressed molded product is thermoset, and then the product is magnetized to produce recycled rare earth bonded magnets. This method does not involve removing the thermosetting resin attached to the magnetic powder contained in the original rare earth bonded magnet through chemical treatment or other means. The rare earth bonded magnet is crushed, a new thermosetting resin binder is added, and the mixture is compressed and thermoset to solidify the magnetic powder with the thermosetting resin and recycle it as a rare earth bonded magnet. Therefore, recycling is low-cost, and moreover, the magnetic properties of the original magnetic powder are not significantly reduced. In other words, rare earth bonded magnets are crushed without the need for chemical treatment to remove the thermosetting resin, a new thermosetting resin binder is added, and the mixture is compression molded and thermoset. Since the magnetic powder is solidified with thermosetting resin, high-temperature heating of 250°C or higher is not required, and because the magnetic powder is molded by compression molding rather than injection molding, it can be molded at high density. This allows for the recycling of rare earth bonded magnets at low cost without significantly reducing the magnetic properties of the original rare earth bonded magnet, such as coercivity (Hcj) and prismaticity (Hk / Hcj).

[0068] Thus, according to the rare-earth bonded magnet recycling method of this embodiment, a rare-earth bonded magnet in which the binder to which magnetic powder is bound is crushed, a small amount of thermosetting resin containing thermosetting resin and its curing agent is kneaded into it, the kneaded mixture is compressed and molded, and then heated to heat-cur the thermosetting resin in the compressed molded product, and then magnetized to obtain a recycled rare-earth bonded magnet. According to the rare-earth bond magnet recycling method of this embodiment, the original rare-earth bond magnet is pulverized without removing the thermosetting resin contained in it, and a new thermosetting resin composition is added and kneaded, compressed and molded, thermoset and magnetized to recycle it as a new rare-earth bond magnet. This method does not require chemical treatment to remove the thermosetting resin adhering to the magnetic powder contained in the original rare-earth bond magnet, and if the binder of the magnetic powder is only a thermosetting resin, it does not require high-temperature heating of 250°C or higher. Furthermore, since the magnetic powder can be filled with a high filling rate by compression molding rather than injection molding, the deterioration of the magnetic properties of the magnetic powder due to chemical treatment or high heat is suppressed, and the high filling rate of the magnetic powder by compression molding is enabled, allowing the original rare-earth bond magnet to be recycled as a rare-earth bond magnet at low cost without significantly reducing its magnetic properties such as coercivity Hcj and prismaticity (Hk / Hcj). Therefore, high-performance rare-earth bonded magnets, such as those used in the main motors of electric vehicles and high-speed rotating motors used in hard disk drives (HDDs), can be recycled at low cost and easily without much effort into magnets that are suitable for use in auxiliary motors of electric vehicles and small motors in sensors, where high magnetic performance is not required.

[0069] [Examples] Next, a method for recycling rare earth bonded magnets according to an embodiment of the present invention and examples of recycled rare earth bonded magnets will be described. In this embodiment, the magnets are first fabricated from recycled rare-earth bonded magnets. Specifically, 5.4 g of bisphenol A type liquid epoxy resin ("jER828" manufactured by Mitsubishi Chemical Corporation), 0.39 g of dicyandiamide (Omicure DDA10 manufactured by Chori GLEX Co., Ltd.) as a curing agent for the epoxy resin, and 0.21 g of an imidazole-based curing agent ("Curesol" manufactured by Shikoku Kasei Chemical Industry Co., Ltd.) were mixed to prepare a thermosetting epoxy resin composition. To 6 g of this thermosetting epoxy resin composition, 5 g of methyl ethyl ketone (MEK) was added as a solvent, and then kneaded with 100 g of SmFeN-based magnetic powder. Next, the kneaded mixture (compound) was dried in an air atmosphere at 100°C for 10 minutes, placed in a mold, and compression molding (press molding) was performed at 200 MPa in a magnetic field orientation of 2.5 [T]. After compression molding, the rare-earth bonded magnet molded body was removed from the mold and heated in an atmospheric environment at 170°C for 30 minutes to cause a crosslinking reaction of the epoxy resin in the molded body, thereby thermosetting it. From this, a rare-earth bonded magnet (unmagnetized) for recycling was produced with a weight ratio of magnetic powder to thermosetting resin = 100:6.

[0070] First, the rare-earth bonded magnets to be recycled were crushed using a mortar and pestle, and then classified through a predetermined mesh to obtain rare-earth bonded magnet powder (crushed rare-earth bonded magnet material). Specifically, first, a grinding process (step S10) was carried out to grind a rare-earth bonded magnet, which was made by binding SmFeN-based magnetic powder with an epoxy resin binder.

[0071] Next, to 100g of the pulverized rare earth bond magnet powder obtained in the pulverization process (step S10), a predetermined amount of bisphenol A type liquid epoxy resin ("jER828" manufactured by Mitsubishi Chemical Corporation) is added, along with dicyandiamide (manufactured by Chori GLEX Co., Ltd.) as a curing agent for the epoxy resin. 0.18 g of Omicure DDA10, 0.105 g of an imidazole-based curing agent ("Curesol" manufactured by Shikoku Chemicals Co., Ltd.), and 5 g of methyl ethyl ketone (MEK) as a solvent were added and kneaded. Specifically, a kneading step (step S20) was carried out in which crushed rare earth bond magnets, an epoxy resin composition containing epoxy resin, dicyandiamide, and an imidazole-based curing agent, and methyl ethyl ketone were kneaded together.

[0072] Next, the compound obtained in the kneading process (step S20) was dried in an air atmosphere at 100°C for 10 minutes, then placed in a mold and compressed and pressed at 200 MPa in a magnetic field orientation of 2.5 [T]. Specifically, a compression molding process (step S30) was carried out in which a mixture of crushed rare earth bond magnets and epoxy resin, along with an epoxy resin composition containing dicyandiamide and an imidazole-based curing agent, was dried and then compression molded to produce a rare earth bond magnet molded body.

[0073] Subsequently, the rare-earth bonded magnet molded body obtained in the compression molding process (step S30) was removed from the mold and heated in an atmospheric environment at 170°C for 30 minutes to heat-cur the epoxy resin in the rare-earth bonded magnet molded body. Specifically, a thermosetting process (step S40) was performed in which a rare-earth bonded magnet molded body was heated and an epoxy resin was heat-cured to create a pre-magnetized rare-earth bonded magnet. Subsequently, a magnetization process (step S50) was carried out to magnetize the pre-magnetized rare-earth bond magnet, thereby obtaining a recycled rare-earth bond magnet molded body.

[0074] In Example 1, rare earth bonded magnets were crushed and classified using a sieve with a mesh opening of 500 μm to obtain rare earth bonded magnet powder (powdered rare earth bonded magnet pulverized material) with a particle size of 500 μm or less. 3.0 g of bisphenol A type epoxy resin was mixed with 100 g of this rare earth bonded magnet powder with a particle size of 500 μm or less, resulting in a mixing ratio of rare earth bonded magnet to thermosetting resin of 100:3.0. In Example 2, rare earth bonded magnets were crushed and classified using a sieve with a mesh opening of 251 μm to obtain rare earth bonded magnet powder with a particle size of 251 μm or less. 3.0 g of bisphenol A type epoxy resin was mixed with 100 g of this rare earth bonded magnet powder with a particle size of 251 μm or less, resulting in a mixing ratio of rare earth bonded magnet to thermosetting resin of 100:3.0.

[0075] Example 3 involves crushing rare earth bonded magnets and classifying them using a sieve with a mesh opening of 500 μm to obtain rare earth bonded magnet powder with a particle size of 500 μm or less. 2.0 g of bisphenol A type epoxy resin is mixed with 100 g of this rare earth bonded magnet powder with a particle size of 500 μm or less, resulting in a mixing ratio of rare earth bonded magnet to thermosetting resin of 100:2.0. Example 4 involves crushing rare earth bonded magnets and classifying them using a sieve with a mesh opening of 500 μm to obtain rare earth bonded magnet powder with a particle size of 500 μm or less. 4.0 g of bisphenol A type epoxy resin is mixed with 100 g of this rare earth bonded magnet powder with a particle size of 500 μm or less, resulting in a mixing ratio of rare earth bonded magnet to thermosetting resin of 100:4.0.

[0076] Example 5 involves crushing rare earth bonded magnets and classifying them using a sieve with a mesh opening of 1.09 mm to obtain rare earth bonded magnet powder with a particle size of 1.09 mm or less. 3.0 g of bisphenol A type epoxy resin is mixed with 100 g of this rare earth bonded magnet powder with a particle size of 1.09 mm or less, resulting in a mixing ratio of rare earth bonded magnet to thermosetting resin of 100:3.0. Example 6 involves crushing rare earth bonded magnets and classifying them using a sieve with a mesh opening of 500 μm to obtain rare earth bonded magnet powder with a particle size of 500 μm or less. 5.0 g of bisphenol A type epoxy resin is mixed with 100 g of this rare earth bonded magnet powder with a particle size of 500 μm or less, resulting in a mixing ratio of rare earth bonded magnet to thermosetting resin of 100:5.0.

[0077] Thus, in Examples 1 to 6, rare earth compression-molded bonded magnets, to which SmFeN-based magnetic powder is bound, are crushed, kneaded with an epoxy resin composition containing epoxy resin, dicyandiamide, and an imidazole-based curing agent, compressed and molded the mixture, then heat-cured, and subsequently magnetized to obtain rare earth compression-molded bonded magnets that can be recycled. In contrast, as a comparative example, a rare-earth injection-molded bonded magnet was prepared, in which the binder to which SmFeN-based magnetic powder was bound was a thermoplastic resin. This was heated, then injection-molded again, and finally magnetized to produce a recycled rare-earth injection-molded bonded magnet.

[0078] The density of the rare-earth bonded magnets in these examples and comparative examples was calculated from their weight and dimensions, and their magnetic properties were evaluated using a BH curve tracer. Specifically, the residual magnetic flux density Br [T], coercivity Hcj [kOe], and Hk90 (magnetic field for 90% of Br) [kOe] were calculated from the BH characteristics (demagnetization curve) measured using a BH curve tracer measuring device.

[0079] If the residual magnetic flux density Br of a rare-earth bonded magnet is 0.50[T] or higher, it is judged to be suitable for a wide range of applications and fields, and is also suitable for practical use in small motors with relatively low output, such as auxiliary motors, and is rated as ◎. If it is between 0.48[T] and 0.50[T], it is judged to be at a level that can withstand use in small motors with relatively low output, such as auxiliary motors, and is rated as ○. If it is below 0.48[T], it is judged to be unsuitable for practical use and is rated as ×. Furthermore, if the coercivity Hcj of the rare-earth bonded magnet is 18.0 [kOe] or higher, it is judged to be suitable for practical use in small motors with relatively low output, such as auxiliary motors, and is rated as ◎. If it is between 15.0 [kOe] and 18.0 [kOe], it is judged to be at a level that can withstand use in small motors with relatively low output, such as auxiliary motors, and is rated as ○. If it is below 14.0 [kOe], it is judged to be unsuitable for practical use and is rated as ×. Hk90[kOe] is the external magnetic field required to reduce the magnetic flux density B to 90% of the residual magnetic flux density Br. This value is calculated for reference only. Preferably, Hk90[kOe] is 5.8kOe or higher, and more preferably 6.0kOe or higher. This suppresses the decrease in magnetism due to the external magnetic field, making it suitable for applications such as motors.

[0080] Similarly, for the original rare-earth bonded magnets that were recycled, the coercivity Hcj [kOe] was calculated from the BH characteristics (demagnetization curve) measured using a BH curve tracer. The retention rate of the coercivity Hcj of the recycled rare-earth bonded magnets was then calculated from the coercivity Hcj of the original rare-earth bonded magnets before recycling and the coercivity Hcj of the recycled rare-earth bonded magnets (retention rate of coercivity Hcj of recycled rare-earth bonded magnets [%] = coercivity Hcj [kOe] of recycled rare-earth bonded magnets / coercivity Hcj [kOe] of original rare-earth bonded magnets before recycling × 100). If the retention rate [%] of the coercivity Hcj of the recycled rare-earth bonded magnet was 95.0% or higher, it was judged that the coercivity Hcj of the original rare-earth bonded magnet before recycling had hardly decreased, and was evaluated as ◎. Even if it was 94.0% or higher but less than 95.0%, it was judged that a significant decrease in the coercivity Hcj of the original rare-earth bonded magnet before recycling had been suppressed, and was evaluated as ○. If it was less than 94.0%, it was judged that the coercivity Hcj of the original rare-earth bonded magnet before recycling had decreased significantly, and was evaluated as ×.

[0081] Furthermore, regarding the molding condition of the recycled rare earth bond magnets, we visually inspected them for cracks and chips, and checked whether powder flakes off when rubbed. Those without cracks, chips, or powder flakes were rated ○, while those with cracks, chips, or powder flakes were rated ×. Table 1 shows the evaluation results for each example and comparative example.

[0082] [Table 1]

[0083] As shown in Table 1, in Comparative Examples 1 and 2, the recycled rare-earth injection-molded bonded magnets, in which the binder to which the magnetic powder is bound is a thermoplastic resin, were heated and re-injected to recycle them as rare-earth injection-molded bonded magnets, showed a low coercivity Hcj (rated as ×) and a low retention rate of coercivity Hcj (rated as ×), indicating a significant decrease in the coercivity Hcj, a magnetic property, compared to the original rare-earth injection-molded bonded magnets. This is because, in the recycling methods of Comparative Examples 1 and 2, the target of recycling was rare-earth injection-molded bonded magnets in which the binder to which the magnetic powder is bound is a thermoplastic resin, and the high temperature of over 250°C used to melt the thermoplastic resin during injection molding caused the magnetic powder to oxidize and deteriorate.

[0084] In contrast, in Examples 1 to 6, in which a rare-earth compression-molded bonded magnet, to which magnetic powder is bound, is crushed, mixed with a thermosetting resin composition containing a thermosetting resin and its curing agent, the mixture is compressed, thermo-cured, and magnetized for recycling as a rare-earth compression-molded bonded magnet, the residual magnetic flux density Br, coercivity Hcj, and retention rate of coercivity Hcj are all rated as ◎ or 〇, indicating that the decrease in magnetic properties from the original rare-earth bonded magnet is small. This is because, in Examples 1 to 6, rare-earth compression-molded bonded magnets, in which the binder to which the magnetic powder is bound is a thermosetting resin binder, are crushed, a new thermosetting resin is added as the binder, and the magnets are recycled by compression molding. Unlike Comparative Examples 1 and 2, which recycle by melting thermoplastic resin, this method does not require high-temperature heating to melt the resin, and there is no oxidative degradation of the magnetic powder due to high-temperature heating. Furthermore, because the binder for the magnetic powder is only a thermosetting resin, compression molding is possible and the magnetic powder can be filled to a high degree.

[0085] As can be seen from the comparison between Examples 1-4 and Example 5, when the rare-earth bond magnet is crushed coarsely and the particle size is large, the retention rate of the coercivity Hcj decreases. This is thought to be because the packing efficiency of the magnetic powder decreases. On the other hand, if the particle size is too small, the particles of the magnetic material are crushed, making them prone to rusting, and the magnetic properties also deteriorate. According to experimental research by the present inventors, if the particle size of the pulverized rare-earth bond magnet is in the range of 2.5 to 1100 [μm], more preferably in the range of 3.5 to 750 [μm], and even more preferably in the range of 5.0 to 500 [μm], rust is less likely to occur because the magnetic powder particles are not finely pulverized, the packing of the magnetic powder can be increased, the orientation can be improved, and furthermore, the moldability is good and the strength is such that the magnetic powder is less likely to fall off or crack or chip.

[0086] Furthermore, as can be seen from the comparison between Examples 1, 3, and 4 and Example 6, when the amount of thermosetting resin added to the original rare-earth bonded magnet increases and the proportion of thermosetting resin binder increases, the residual magnetic flux density Br decreases. On the other hand, if too little thermosetting resin is added to the original rare-earth bonded magnet, molding defects, cracks, and chips will occur. According to experimental research by the present inventors, the mixing ratio of crushed rare-earth bonded magnet to added thermosetting resin is preferably in the range of crushed rare-earth bonded magnet:thermosetting resin = 100:1.0 to 100:5.0, more preferably in the range of crushed rare-earth bonded magnet:thermosetting resin = 100:1.5 to 100:4.5, and even more preferably in the range of crushed rare-earth bonded magnet:thermosetting resin = 100:2.0 to 100:4.0. When this ratio is used, the moldability is good, and recycled rare-earth bonded magnets can be given the desired magnetic properties.

[0087] As described above, the recycling method for rare earth bonded magnets according to the above embodiment comprises: a grinding step of grinding a rare earth bonded magnet, which is made by binding rare earth magnetic powder with a thermosetting resin binder; a kneading step of kneading the ground rare earth bonded magnet with a thermosetting resin composition containing a thermosetting resin and its curing agent; a compression molding step of compressing the kneaded material obtained in the kneading step; and a thermosetting step of heating the molded body obtained in the compression molding step to thermoset the thermosetting resin.

[0088] Therefore, according to the rare-earth bond magnet recycling method of the above embodiment, the original rare-earth bond magnet is crushed without removing the thermosetting resin contained in the original rare-earth bond magnet and attached to the rare-earth magnetic powder, mixed with a new thermosetting resin composition, the mixture is compressed and molded, and then heated to thermoset the thermosetting resin, thereby recycling it as a new rare-earth bond magnet. This method does not require chemical treatment to remove the thermosetting resin contained in the original rare-earth bond magnet and attached to the magnetic powder, and because the binder of the magnetic powder is only thermosetting resin, high-temperature heating is not required. Furthermore, because the magnetic powder can be filled with a high filling rate by compression molding rather than injection molding, the deterioration of the magnetic properties of the magnetic powder due to chemical treatment or high heat is suppressed, and by enabling high filling of the magnetic powder by compression molding, the original rare-earth bond magnet can be regenerated at low cost without significantly degrading its magnetic properties such as coercivity Hcj and prismaticity (Hk / Hcj). In other words, rare-earth bonded magnets can be recycled at low cost, and the degradation of their magnetic properties due to recycling can be minimized.

[0089] In the rare-earth bonded magnet recycling method of the above embodiment, if the rare-earth bonded magnet has a residual magnetic flux density Br of preferably 0.50[T] or higher, more preferably 0.52[T] or higher, and even more preferably 0.55[T] or higher, and a coercivity Hcj of preferably 15.0[kOe] or higher, and more preferably 16.0[kOe] or higher, then a rare-earth bonded magnet with high magnetic properties can be obtained as a recycled product, and even recycled rare-earth bonded magnets can be used in a wide range of applications and fields.

[0090] In the rare-earth bonded magnet recycling method of the above embodiment, if the mixing ratio of the rare-earth magnetic powder and the thermosetting resin binder is preferably within the range of rare-earth magnetic powder:thermosetting resin binder = 100:4.0 to 100:8.0, more preferably rare-earth magnetic powder:thermosetting resin binder = 100:4.5 to 100:7.5, and even more preferably rare-earth magnetic powder:thermosetting resin binder = 100:5.0 to 100:7.0, the moldability is good, and the recycled rare-earth bonded magnet can have the desired magnetic properties.

[0091] In the rare earth bond magnet recycling method of the above embodiment, if the crushed rare earth bond magnet has particles in the range of 2.5 to 1100 [μm], more preferably in the range of 3.5 to 750 [μm], and even more preferably in the range of 5.0 to 500 [μm], rust is less likely to occur because the particles of the rare earth magnetic powder are not crushed, and the packing and orientation of the rare earth magnetic powder can be improved, thereby improving the magnetic properties of the recycled rare earth bond magnet.

[0092] In the rare earth bonded magnet recycling method of the above embodiment, if the thermosetting resin contained in the thermosetting resin composition kneaded with the crushed rare earth bonded magnet is an epoxy resin or a phenolic resin, the packing capacity of the rare earth magnetic powder can be increased, thereby improving the magnetic properties of the recycled rare earth bonded magnet.

[0093] In the rare-earth bonded magnet recycling method of the above embodiment, if the temperature at which the rare-earth bonded magnet molded body is heated in the thermosetting process is within the range of 120°C or higher and less than 200°C, the rare-earth magnetic powder will not oxidize and degrade, and the magnetic properties of the recycled rare-earth bonded magnet can be improved.

[0094] In the rare earth bond magnet recycling method of the above embodiment, the mixing ratio of the crushed rare earth bond magnet and the thermosetting resin contained in the thermosetting resin composition, which is kneaded in the kneading step, is preferably in the range of crushed rare earth bond magnet:thermosetting resin = 100:1.0 to 100:5.0, more preferably in the range of crushed rare earth bond magnet:thermosetting resin = 100:1.5 to 100:4.5, and even more preferably in the range of crushed rare earth bond magnet:thermosetting resin = 100:2.0 to 100:4.0. This ensures good moldability and allows the recycled rare earth bond magnet to have the desired magnetic properties.

[0095] Furthermore, the above description of the embodiment can also be interpreted as a method for manufacturing a rare earth bonded magnet comprising: a grinding step of grinding a rare earth bonded magnet in which rare earth magnetic powder is bound with a thermosetting resin binder; a kneading step of kneading the ground rare earth bonded magnet with a thermosetting resin composition containing a thermosetting resin and its curing agent; a compression molding step of compressing the kneaded mixture obtained in the kneading step; and a thermosetting step of heating the molded body obtained in the compression molding step to thermoset the thermosetting resin.

[0096] According to the manufacturing method for rare-earth bonded magnets of the above embodiment, the original rare-earth bonded magnet is pulverized without removing the thermosetting resin contained in the original rare-earth bonded magnet and attached to the rare-earth magnetic powder, kneaded with a new thermosetting resin composition, the kneaded product is compression molded, and then heated to thermoset the thermosetting resin, thereby recycling the original rare-earth bonded magnet and manufacturing a new rare-earth bonded magnet. This method does not require chemical treatment to remove the thermosetting resin contained in the original rare-earth bonded magnet and attached to the magnetic powder, and because the binder of the magnetic powder is only thermosetting resin, high-temperature heating is not required. Furthermore, because the magnetic powder can be filled with a high filling rate by compression molding rather than injection molding, the deterioration of the magnetic properties of the magnetic powder due to chemical treatment or high heat is suppressed, and by enabling high filling of the magnetic powder by compression molding, the original rare-earth bonded magnet can be regenerated at low cost without significantly degrading its magnetic properties such as coercivity Hcj and prismaticity (Hk / Hcj). In other words, recycled rare-earth bonded magnets can be obtained at low cost, and the degradation of magnetic properties due to recycling can be minimized.

[0097] Furthermore, the above description of the embodiment can also be interpreted as an invention of a rare earth bonded magnet that is a recycled product containing rare earth magnetic powder and a thermosetting resin binder as a binder for the rare earth magnetic powder, wherein the thermosetting resin binder is contained in an amount of 3.0% by mass or more and 10.0% by mass or less, preferably 4.0% by mass or more and 7.0% by mass or less, per 100% by mass of the rare earth bonded magnet.

[0098] In a rare-earth bonded magnet, where the binder binding the rare-earth magnetic powder is a thermosetting resin binder, a rare-earth bonded magnet is produced by crushing the magnet, adding a small amount of new thermosetting resin containing a thermosetting resin and its curing agent, kneading the mixture, compressing and molding the kneaded mixture, and then thermosetting the thermosetting resin in the molded product. As a result of adding new thermosetting resin to the thermosetting resin content in the original rare-earth bonded magnet, the thermosetting resin content is higher than in the original rare-earth bonded magnet. Specifically, the thermosetting resin binder is contained in 3.0% by mass or more and 10.0% by mass or less, preferably 4.0% by mass or more and 7.0% by mass or less, per 100% by mass of the rare-earth bonded magnet.

[0099] Therefore, a rare earth bonded magnet containing 3.0% to 10.0% by mass, preferably 4.0% to 7.0% by mass, of thermosetting resin binder in 100% by mass of rare earth bonded magnet is a recycled product obtained by recovering a rare earth bonded magnet using thermosetting resin and separately adding thermosetting resin to create a new rare earth bonded magnet. Because the binder consists only of thermosetting resin, oxidative degradation of the magnetic powder due to high-temperature heating to melt it, as occurs when thermoplastic resin is used, does not occur. Furthermore, because the magnetic powder can be molded with high filling by compression molding rather than injection molding, the magnetic properties such as the coercivity Hcj and prismaticity (Hk / Hcj) of the original rare earth bonded magnet are hardly reduced, and it is recycled at low cost.

[0100] Recycled rare-earth bonded magnets are preferably 0.48[T] or higher, more preferably 0.49[T] or higher, and even more preferably 0.50[T] or higher, and their coercivity Hcj is preferably 15.0[kOe] or higher, more preferably 16.0[kOe] or higher, making them suitable for a wide range of applications and fields.

[0101] When implementing the present invention, the recycling method and manufacturing method of the rare earth bonded magnet, as well as the composition, components, blending amounts, and manufacturing methods of other parts of the rare earth bonded magnet, are not limited to the embodiments described above. Furthermore, not all of the numerical values ​​given in the embodiments and examples of the present invention represent critical values; some values ​​represent suitable values ​​for implementation. Therefore, slightly changing the above numerical values ​​does not negate the possibility of implementation.

Claims

1. A grinding process for grinding rare earth bonded magnets, which are made by binding rare earth magnetic powder with a thermosetting resin binder, A kneading step in which the pulverized rare earth bond magnet and a thermosetting resin composition containing a thermosetting resin and its curing agent are kneaded together, A compression molding step is performed to compress and mold the kneaded material obtained in the kneading step, A thermosetting step is performed by heating the molded body obtained in the compression molding step to heat-cur the thermosetting resin. A method for recycling rare earth bonded magnets, characterized by comprising the following:

2. The method for recycling a rare earth bonded magnet according to claim 1, characterized in that the rare earth bonded magnet has a residual magnetic flux density Br of 0.50 [T] or more and a coercivity Hcj of 15.0 [kOe] or more.

3. The method for recycling a rare earth bonded magnet according to claim 1, characterized in that the mixing ratio of the rare earth magnetic powder and the thermosetting resin binder is within the range of rare earth magnetic powder:thermosetting resin binder = 100:4.0 to 100:8.

0.

4. The method for recycling rare earth bonded magnets according to claim 1, characterized in that the crushed rare earth bonded magnets have a particle size in the range of 2.5 to 1100 [μm].

5. The method for recycling rare earth bonded magnets according to claim 1, characterized in that the thermosetting resin contained in the thermosetting resin composition kneaded with the pulverized rare earth bonded magnets is an epoxy resin or a phenolic resin.

6. The method for recycling rare earth bonded magnets according to claim 1, characterized in that the mixing ratio of the crushed rare earth bonded magnets and the thermosetting resin contained in the thermosetting resin composition, which are kneaded in the kneading step, is within the range of crushed rare earth bonded magnets: thermosetting resin = 100:1.0 to 100:5.

0.

7. A grinding process for grinding rare earth bonded magnets, which are made by binding rare earth magnetic powder with a thermosetting resin binder, A kneading step in which the pulverized rare earth bond magnet and a thermosetting resin composition containing a thermosetting resin and its curing agent are kneaded together, A compression molding step is performed to compress and mold the kneaded material obtained in the kneading step, A thermosetting step is performed by heating the molded body obtained in the compression molding step to heat-cur the thermosetting resin. A method for manufacturing rare earth bond magnets, characterized by comprising the following:

8. A recycled rare earth bond magnet comprising rare earth magnetic powder and a thermosetting resin binder as a binder for the rare earth magnetic powder, A rare earth bonded magnet characterized in that the thermosetting resin binder is contained in 100% by mass of the rare earth bonded magnet in an amount of 3.0% by mass or more and 10.0% by mass or less.

9. The rare earth bond magnet according to claim 8, characterized in that the rare earth bond magnet has a residual magnetic flux density Br of 0.48 [T] or more and a coercivity Hcj of 15.0 [kOe] or more.

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