WO2007077602A1

WO2007077602A1 - Anticorrosive rare earth magnet

Info

Publication number: WO2007077602A1
Application number: PCT/JP2005/024087
Authority: WO
Inventors: Hiroshi Kobayashi
Original assignee: Aisin Seiki Kabushiki Kaisha
Priority date: 2005-12-28
Filing date: 2005-12-28
Publication date: 2007-07-12
Also published as: JPWO2007077602A1

Abstract

For providing an anticorrosive rare earth magnet that not only realizes prevention of corrosion of rare earth magnet but also excels in impact resistance, the rare earth magnet is coated with a layer of rubber having gas permeation resistance.

Description

Corrosion resistant rare earth magnet

Technical field

The present invention relates to a corrosion-resistant rare earth magnet that prevents corrosion of a rare earth magnet.

Background art

[0002] A rare earth magnet is generally a Re-B-Fe system or a Re-Tm-B system (Re is one type selected from rare earth element force, and Tm is one type selected from transition elements. And is known to have magnetic properties superior to conventional alloy magnets and ferrite magnets.

[0003] Since such rare earth magnets are formed of an active metal material, in order to improve the magnetic properties particularly immediately after the main phase, many rare earth elements and transition elements are required not only in the main phase but also in the grain boundary phase. Become. Therefore, corrosion is an inevitable problem in rare earth magnets. For example, a so-called neo-composition in which the main phase, which is a kind of Re-B-Fe rare earth magnet, consists of Nd Fe B

2 14

In the case of di-m magnets, the Nd-Fe phase, which contains a large amount of neodym, is formed as a grain boundary phase! Then, this phase is oxidized or reacted with water vapor to produce oxides (Nd 0) and water.

Since 2 3 oxides (Nd (OH) 2) are formed and the volume of the grain boundary phase expands, the grain boundary fracture of the sintered body

3

Can happen.

On the other hand, on the surface of the main phase, the presence of oxygen and water vapor causes Fe 0 · Η water

There is a problem that a 2 3 hydrate is formed and the magnetic properties of the rare earth magnet are degraded.

Such a problem is a problem common to rare earth magnets, and the same corrosion phenomenon as neodymium magnets also occurs in Pr Fe B, a Re-Tm-B hot-work rare earth magnet.

2 14

[0004] To solve the above problems, as a method of preventing corrosion of the rare earth magnet, there is a method of forming a resin film on the surface of the rare earth magnet by injection molding, extrusion molding, transfer molding, etc. There is known a method of forming a film by applying a solution of resin on the surface of the film.

In addition, the surface of the rare earth magnet is subjected to chemical conversion treatment such as phosphate treatment or chromate treatment to form an oxidation resistant chemical conversion film (see, for example, Patent Document 1), or Zn or A1 is deposited, or Method of applying electroless Ni plating (see, for example, Patent Document 2), performing protection with rare earth magnets A method of binding an additive with a binder resin (see, for example, Patent Document 3) is also examined.

Furthermore, as a method of forming a diacidic acid protective film or a caictic acid protective film on the surface of a rare earth magnet, a technique of forming a resin film on the protective film (see, for example, Patent Document 4) A technique for bonding a rare earth magnet and a protective film with a resin binder (see, for example, Patent Document 5) has been proposed.

Patent Document 1: Japanese Patent Application Laid-Open No. 64-14902

Patent Document 2: Japanese Patent Application Laid-Open No. 64-15301

Patent Document 3: Japanese Patent Application Laid-Open No. 1-147806

Patent Document 4: Japanese Patent Application Laid-Open No. 62-152107

Patent Document 5: JP-A-8-111306

Disclosure of the invention

Problem that invention tries to solve

However, according to the conventional method of forming a resin film on the surface of a rare earth magnet by injection molding or the like, the film usually formed has a thickness of 0.5 mm or more. There is a problem that the amount of leakage flux is greatly reduced and the loss of magnetic energy is large. On the other hand, when the thickness of the film is less than 0.5 mm, defects such as voids inside the film are easily destroyed by thermal stress such as temperature impact, so the rare earth magnet is corroded. There was a risk of In addition, when a solution of resin is applied to the surface of a rare earth magnet, the force to form a film with a thickness of 30 to 40 m by applying a solution multiple times. Such a film has defects such as voids inside. The use environment conditions under which the film is susceptible to damage such as thermal shock due to thermal shock were limited.

[0006] In the method of surface treating a rare earth magnet as described in Patent Documents 1 to 3, in order to eliminate defects in the film, the film thickness of the film may be increased, or the film may be repeated multiple times to form a multilayer. It was necessary to form. Also, it is difficult to completely eliminate the defects in the film, and it is difficult to completely shut off the surface of the rare earth magnet from the external oxygen and water vapor forces, so the rare earth magnet was corroded.

[0007] In addition, a method of forming a carbon dioxide protective film or a cyanate protective film on the surface of a rare earth magnet In the method, it is difficult to form a uniform, dense and strong protective film on the surface because rare earth magnets have various sizes and shapes and the surface of rare earth magnets is often not flat.

In particular, the technology described in Patent Document 4 uses a reactive silyl isocyanate, but it is difficult to achieve uniform film growth, and it is easy to form a film having irregularities. In addition, it was impossible to form a strong film with weak bonding strength only by physically adsorbing the silicate to the irregularities of the rare earth magnet surface. Although the technology described in Patent Document 5 discloses a technology for forming a protective film by sol-gel reaction or plasma particle chemical vapor deposition using ethyl silicate, it forms a uniform, dense and strong protective film. I could not do it.

Therefore, it is difficult to completely block oxygen, water vapor, etc. by the film, and the film itself is also easily peeled off. As a result, the rare earth magnet is corroded.

Further, since the rare earth magnet is manufactured by sintering, the volume of the magnet shrinks during force sintering, so that when manufacturing the rare earth magnet, dimensional accuracy is secured by machining. However, on the surface processed by such a machine tool, there are many physical defect layers, and the defect layers are in a state of being easily detached. Therefore, in the conventional method of forming a film on a rare earth magnet, since the bonding strength between the film itself and the bonding strength between the film and the rare earth magnet is weak, the physical defect layer on the surface of the rare earth magnet is barreled before forming the film. It had to be dropped off due to polishing, etc., and extra cost was strong.

Furthermore, since the rare earth magnet is a sintered body that is fragile to mechanical stress, there is also a problem that it is easy to be damaged and difficult to handle when it is dropped or the like. And regarding this, even if the rare earth magnet is formed with the above-mentioned conventional film, the impact resistance can not be improved.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a corrosion-resistant rare earth magnet capable of preventing corrosion of a rare earth magnet and having excellent impact resistance. Means for

[0011] A first feature of the corrosion-resistant rare earth magnet according to the present invention for achieving the above object is that the rare earth magnet is coated with a gas-permeable rubber layer. That is, according to this configuration, the rare earth magnet can also be shielded from external force, and corrosion of the rare earth magnet by water vapor, oxygen, etc. can be prevented.

Since the rubber layer covering the rare earth magnet has elasticity, when mechanical stress is applied to the corrosion resistant rare earth magnet from the outside, the rubber can be elastically deformed to relieve the stress. Therefore, the impact resistance of the rare earth magnet can be enhanced.

Examples of the rubber having gas permeability resistance include at least one rubber selected from butyl rubber, fluororubber, epichlorohydric acid, and nitrile rubber.

[0015] A second characterizing feature of the corrosion-resistant rare earth magnet according to the present invention is that the rubber layer is bonded to the rare earth magnet via a silane coupling agent.

That is, according to this configuration, the bonding strength between the rare earth magnet and the rubber layer can be enhanced, and the rare earth magnet force can also make the rubber layer difficult to peel off. Furthermore, when the bond strength between the rare earth magnet and the rubber layer is added to the covalent bond force based on the rubber net cake structure, the physical defect layer of the rare earth magnet also becomes difficult to come off, so when covering the rubber layer It is possible to omit the polishing process or the like for dropping off the physical defect layer of the above.

[0017] A third characterizing feature of the corrosion-resistant rare earth magnet according to the present invention is that the silane coupling agent has at least one of a methacryl group and a mercapto group.

That is, according to this configuration, since these functional groups can be particularly firmly bonded to rubber, the bonding strength between the rare earth magnet and the rubber layer can be further strengthened.

[0019] A fourth characterizing feature of the corrosion-resistant rare earth magnet according to the present invention is that in the rare earth magnet, a silane compound having an imidazolyl group and an alkoxysilyl group is at least one of the compound and the silane coupling agent. It is coated with a film formed by bonding to one side, and the film is connected to the rare earth magnet.

That is, according to the configuration, the silane compound having an imidazole group and an alkoxysilyl group is a dense molecular film having a net network structure of siloxane on the surface of a rare earth magnet due to a condensation polymerization reaction of a silanol group. Form Therefore, the corrosion resistance can be further improved by providing a rubber layer having gas permeability resistance to the rare earth magnet having such a molecular film.

In addition, a silane compound having an imidazole group and an alkoxysilyl group is a rare earth magnet The silanol group formed by hydrolysis of the alkoxysilyl group is hydrogen bonded to the surface of the rare earth magnet, or the nitrogen of the imidazole group is coordinated to the alloy forming the active phase of the rare earth magnet and then covalently bonded. It binds by forming a complex. Therefore, a film formed of a silane compound having an imidazole group and an alkoxysilyl group can be made difficult to peel off from the rare earth magnet.

Furthermore, the imidazole group can act as a catalyst for forming a network structure of siloxane, as well as bonding itself to a rare earth magnet, and thus the hydrolyzable silyl group of the silane coupling agent On the other hand, hydrolysis is promoted, and a siloxane network is formed by silane couplings or silane coupling compounds having an imidazole group and an alkoxysilyl group. For this reason, the bond strength between the rare earth magnet and the rubber layer is further enhanced.

[0023] A fifth characterizing feature of the corrosion-resistant rare earth magnet according to the present invention is that the rare earth magnet has a film of a magnetic ionic liquid or a polar group, and the rare earth magnet has a polar basic force coupling agent. At the point where it is coated with a film of oil that is bound to it.

In other words, according to this configuration, the magnetic ionic liquid does not dissolve various gases which are less hygroscopic, and therefore, small molecules such as water vapor and hydrogen gas can transmit gas, . In addition, the magnetic ionic liquid does not react with liquids other than strongly acidic and strongly alkaline, and has almost no vapor pressure even at high temperatures which are difficult to corrode, and the heat resistance which is difficult to evaporate is also close to 300 ° C. For this reason, the magnetic ionic liquid can be used in a wide range of environments. Furthermore, since the magnetic ionic liquid is a paramagnetic substance, the film of the magnetic ionic liquid can be magnetically adsorbed to the rare earth magnet, and the rare earth magnet force can also be made difficult to peel off. Therefore, by providing a layer of rubber having gas resistance to a rare earth magnet coated with a magnetic ionic liquid, the rare earth magnet can be shielded from the outside to further improve the corrosion resistance.

As the magnetic ionic liquid, 1-ethyl 3-methylimidazolium, 1-butyl-3-methylimidazolium, 1-octyl-3-methylimidazolium, 1-tert-ethyl-3-methylimidazolium as a cation Salt, sodium borate (III) acid with FeCl

Four

1-Ethyl 3-methyl imidazolium, 1-butyl 3- (methyl) imidazole (iron) chloride, 3-methyl imidazolium chloride (III) 1-octyl 3-methyl-imidazolium, sodium chloride (III) 1—De Syl-1 3-methylimidazolium and the like are preferred.

Further, when the rare earth magnet is covered with a film of oil, the whole surface of the rare earth magnet is covered with the film of oil, so that permeation of water vapor and various gases is prevented. Can. In addition, since the polar group of oil can be bonded to the rare earth magnet through the coupling agent, the bonding strength between the oil and the rare earth magnet becomes strong, and the oil film can not be easily peeled off from the rare earth magnet. it can. Therefore, by providing a rubber layer having resistance to gas permeability to a rare earth magnet coated with a film of oil, the rare earth magnet can be shielded from the outside world to further improve the corrosion resistance.

A characterizing feature of the fixing structure of the magnet according to the present invention is that the corrosion-resistant rare earth magnet is adhered to a supporting member for supporting the magnet via an adhesive.

That is, according to this configuration, even when the temperature of the use environment changes and the volume of the rare earth magnet is largely changed, the volume change can be followed by the elastic deformation of the rubber. Therefore, it is possible to prevent the problems caused by the disturbed volume change of the rare earth magnet.

BEST MODE FOR CARRYING OUT THE INVENTION

The corrosion resistant rare earth magnet according to the present invention, as shown in FIG. 1, is a rare earth magnet coated with a gas-permeable rubber layer. As a result, the rare earth magnet can be shielded from the outside, and corrosion of the rare earth magnet due to water vapor, oxygen, etc. can be prevented.

[0030] Since the rubber layer covering the rare earth magnet has elasticity, when mechanical stress is externally applied to the corrosion resistant rare earth magnet, the rubber can be elastically deformed to relieve the stress. Therefore, the impact resistance of the rare earth magnet can be enhanced.

The rubber constituting the rubber layer of the corrosion resistant rare earth magnet according to the present invention is not particularly limited as long as it has gas permeability resistance, and examples thereof include butyl rubber, fluororubber, epichlorohydrin rubber, nitrile rubber and the like. Force At least one rubber selected is preferably applicable. Among them, butyl rubber is particularly preferred, and the permeability of hydrogen gas at 25 ° C. is about 10, assuming that the natural rubber is 100. For this reason, hydrogen gas, oxygen gas, water vapor, etc. are transmitted 1 and corrosion and expansion and destruction caused by contact with these rare earth magnets are prevented. can do. Butyl rubber has a heat resistant limit temperature of 140 ° C and is resistant to thermal degradation at high temperatures, so it is also excellent in heat resistance.

The thickness of the rubber layer is not particularly limited and can be set arbitrarily, but is preferably 10 m or more from the viewpoint of preventing damage when dropped. On the other hand, if the rubber layer becomes too thick, the amount of leakage flux from the surface of the rare earth magnet tends to decrease, and if it becomes too thin, it becomes difficult to interrupt the surface of the rare earth magnet. About zm to several hundreds / zm is more preferable.

The rubber layer of the corrosion resistant rare earth magnet according to the present invention is preferably bonded to the rare earth magnet via a silane coupling agent. As a result, the bonding strength between the rare earth magnet and the rubber layer can be increased, and the rare earth magnet force can also make the rubber layer difficult to peel off. Furthermore, when the bonding force between the rare earth magnet and the rubber layer is added to the covalent bond force based on the rubber network structure, the physical defect layer of the rare earth magnet also becomes difficult to come off, so when covering the rubber layer Abrasive treatment etc. to drop off the physical defect layer of

The silane coupling agent used in the present invention can be selected according to the type of rubber used, etc., and is not particularly limited. For example, as a functional group capable of binding to rubber, boule group, epoxy Those having a group, a methacryl group, an amino group, a mercapto group and the like are applicable. Among them, it is preferable to have at least one of a methacryl group and a mercapto group. Since these functional groups can be particularly firmly bonded to rubber, the bonding between the rare earth magnet and the rubber layer can be further strengthened. Further, as the silane coupling agent, one having a hydrolyzable silyl group can be applied, and as the hydrolyzable group, for example, a chloro group, an alkoxy group, an acetoxy group, an isopropenoxy group and the like are exemplified. These hydrolyzable silyl groups are hydrolyzed to form silanol groups, which can be bonded to a rare earth magnet.

[0035] In such a silane coupling agent having a mercapto group and an alkoxysilyl group, for example, when a rare earth magnet is made to form a butyl rubber layer, a mercapto group is present in the unsaturated bond portion of butyl rubber or in butyl rubber. It reacts with the radical of a vulcanizing agent such as sulfur and bonds with butyl rubber. On the other hand, alkoxysilyl groups were generated by hydrolysis The silanol group forms a hydrogen bond with the surface of the rare earth magnet, and the silanol groups form a network structure of siloxane. The silane coupling agent can thus bond the rare earth magnet and the rubber layer.

The corrosion resistant rare earth magnet according to the present invention is preferably applicable to a rare earth magnet having no toughness, and the type thereof is not limited, but it is preferable to apply to a rare earth magnet containing neodymium as a rare earth element. . A rare earth magnet containing neodym as a rare earth element can prevent corrosion to such a rare earth magnet which is particularly easily corroded among the rare earth magnets.

Such a method for producing a corrosion-resistant rare earth magnet can be produced, for example, by the following method. First, a reinforcing agent such as carbon black, a softener with oil, other processing aids and extenders are added to the rubber base and kneaded. Thereafter, it is extruded and vulcanized in the vulcanization step. Then, the obtained rubber is cut and added to the solvent divided into two containers so that the solid content of the rubber becomes about 15 mass% and about 20 mass%, respectively, and the viscosity is about 150 centioises each. Prepare two solutions that will give about 250 centi. At this time, it is advisable to add a slight amount of antifoaming agent to the solution. Furthermore, add 2 wt% of silane coupling agent to each solution and mix while vacuum degassing.

[0038] Of the two types of solutions thus obtained, first, the rare earth magnet is dipped in a solution having a viscosity of about 250 centistokes, and the entire vessel containing the solution is degassed under vacuum, and one minute later. Pull up and leave at 150 ° C. for 10 minutes to semi-dry the solution adhering to the surface of the rare earth magnet. Subsequently, the rare earth magnet is similarly immersed in a solution having a viscosity of about 150 centipoise, and after 1 minute, the magnet is pulled up, left at 160 ° C. for 30 minutes, dried, and a silane coupling agent is reacted. According to such a method, as shown in FIG. 1, it is possible to form a rubber layer of about 200 μm in thickness on a rare earth magnet, for example.

The reinforcing agents, processing aids such as softeners, processing aids such as softeners, and vulcanizing agents used in the method of producing the rubber described above are not particularly limited, and any conventionally known ones may be selected and used. Can.

Although the solvent for dissolving the rubber is not particularly limited in the method for producing the corrosion-resistant rare earth magnet according to the present invention, the solvent has a solubility parameter (hereinafter referred to as “SP value”) which the rubber has. It is preferable to dissolve with a solvent having a low SP value. For example, in the case of butyl rubber, the SP value is 7. 7-8. As solvents close to this SP value, bul monomer of SP value .8, isopentyl acetate, 2,6-dimethyl- 4-heptane, SP value .6 n-octane, jetyl ether of SP value 7.4, SP value: 3 n-hexane etc. may be mentioned. In view of dissolving the silane coupling agent, it is particularly preferable to use polar isopentyl acetate or 2,6-dimethyl-4-heptane as a solvent.

The rare earth magnet used for the corrosion resistant rare earth magnet according to the present invention is produced by a conventionally known method, for example, after making an ingot, adsorbing hydrogen, grinding it into particles of several microns, and applying a magnetic field. It can be manufactured by molding, sintering, and further aging treatment to remove distortion associated with sintering.

In the present invention, the rare earth magnet used is one coated with a film formed by bonding a silane compound having an imidazole group and an alkoxysilyl group to at least one of the compound and a silane coupling agent. It may be That is, a silane compound having an imidazole group and an alkoxysilyl group forms a dense molecular film having a siloxane network structure on the surface of a rare earth magnet by condensation polymerization reaction of a silanol group. Therefore, corrosion resistance can be further improved by providing a rubber layer having gas permeability resistance to the rare earth magnet having such a molecular film.

In the silane compound having an imidazole group and an alkoxysilyl group, the rare earth magnet is such that a silanol group formed by hydrolysis of the alkoxysilyl group is hydrogen-bonded to the surface of the rare earth magnet, or nitrogen of the imidazole group Are coordinated to the alloy forming the active phase of the rare earth magnet, and are bonded by forming a complex by covalent bonding. Therefore, a film formed of a silane compound having an imidazole group and an alkoxysilyl group can be made difficult to peel off from the rare earth magnet.

Furthermore, the imidazole group can act as a catalyst for forming a network structure of siloxane, as well as bonding itself to a rare earth magnet, and thus the hydrolyzable silyl group of the silane coupling agent On the other hand, hydrolysis is promoted, and a siloxane network is formed by silane couplings or silane coupling compounds having an imidazole group and an alkoxysilyl group. For this reason, the bond strength between the rare earth magnet and the rubber layer is stronger Become.

The silane compound having an imidazole group and an alkoxysilyl group is not particularly limited, but, for example, a silane compound as shown in the following formulas (I) and (Π) can be applied. In the following formulas (I) and (Π), various alkoxysilyl groups such as ethoxysilyl group, provoxy silyl group, butoxy silyl group, and the like which are not limited to the methoxy silyl group are exemplified. What you have is applied.

[Formula 1]

[Formula 2]

Li CH 3) 3 (()

Such a corrosion-resistant rare earth magnet can be produced, for example, by the following method. As the molecular film, it is only necessary to form a film having a thickness of several tens to 100 mm, as long as the film does not allow water vapor and various gases to penetrate. For this reason, the rare earth magnet is immersed for about 30 minutes in a solution mixed with a solvent so that the concentration of a silane compound having an imidazole group and an alkoxysilyl group is about 0.5 wt% and the silane coupling agent is about 2 wt%. And adsorb the silane compound and the silane coupling agent on the magnet surface. After that, the rare earth magnet is pulled up and left at a temperature above the boiling point of the solvent for about 30 minutes to evaporate the solvent, thereby causing the silane compound and the silane coupling agent to form an atomic bond on the surface of the rare earth magnet. Form a siloxane network structure. Thereafter, the rare earth magnet is left under an atmosphere of 2 to 3 mmHg for about 1 hour to remove the solvent in the siloxane network structure. Then, after forming a molecular film on the rare earth magnet, a rubber layer is formed by the same procedure as the above method except that a silane coupling agent is added to the solution. In this way, the rare earth magnet can be coated with the molecular film and the rubber layer. In the method for producing a corrosion-resistant rare earth magnet according to the present invention, the solvent for dissolving the silane compound and the silane coupling agent is toluene, xylene, methyl ketone, ether, dichloromethane, alcohol From the viewpoint of strength and corrosion resistance which can be optionally selected, it is preferable to use one having no hygroscopic property such as toluene, xylene, methyl ketone, ether, dichloromethane or the like. In addition, for example, when using toluene as a solvent, if it processes at 130 degreeC for about 30 minutes, while evaporating toluene, condensation reaction reaction of a silanol group can be advanced.

Similarly, from the viewpoint of corrosion resistance, the silane compound is preferable because it has no hydroxyl group and the silane compound of the above formula (I) has no hygroscopicity. Furthermore, after the molecular film is produced, it is preferable to completely remove the solvent by the low pressure treatment as described above, which is preferable not to remain in the siloxane network structure.

Further, the rare earth magnet used in the present invention may be one coated with a film of a magnetic ionic liquid. The magnetic ionic liquid does not dissolve various hygroscopic materials, so it does not transmit small molecule gas such as water vapor and hydrogen gas. In addition, magnetic ionic liquids do not react with liquids other than strongly acidic and strongly alkaline, so they are not easily corroded, and even at high temperatures, they have almost no vapor pressure. Because of this, magnetic ionic liquids can be used in a wide range of environments. Furthermore, since the magnetic ionic liquid is a paramagnetic substance, the film of the magnetic ionic liquid can be magnetically adsorbed to the rare earth magnet, and the rare earth magnetic force can be made difficult to peel off. Therefore, as shown in FIG. 2, by providing a rubber layer having gas permeability resistance to the rare earth magnet coated with the magnetic ionic liquid, it is possible to block the external force of the rare earth magnet and to further improve the corrosion resistance.

Such a magnetic ionic liquid is not particularly limited, but [Fe M N C 1

An anionic anion represented by XYZ 4 Γ (where M and N are transition metal atoms and x + y + z = 1 and n are numbers determined by X, y and z) is selected. It is possible to use one with at least one anion. Specifically, as an anion, it has [FeCl 2] which is x = 1, y = z = 0, n = 1

4 as cation, 1-ethyl 3-methylimidazolium, 1-butyl 3-methylimidazolyl, 1-octyl 3-methylimidazolium, 1-decyl-3-methylimidazole as cation 1-acetyl 3- (methylimidazolium) chloride, ferric-chloride (III), 1-butyl 3-methylimidazolium chloride, ferric-chloride (III) acid 1-octyl-7-methylimidazole Examples thereof include 1-decyl-3-methylimidazolium of sodium oxalate (III). The alkyl group at the 1-position is not particularly limited, but the higher the carbon number is, the higher the degree of hydrophobicity is, and the alkyl group at the 1-position preferably has 6 to 20 carbon atoms.

The thickness of the magnetic ionic liquid film is not particularly limited, but preferably in the order of microns. That is, if the film has a thickness on the order of microns, the magnetic adsorptive power of the rare earth magnet to the magnetic ionic liquid is greater than the gravity of the magnetic ionic liquid, and the magnetic ionic liquid film is further difficult to peel off from the rare earth magnet. Become.

Such corrosion-resistant rare earth magnet can be manufactured, for example, by the following method.

That is, first, the rare earth magnet is immersed in the magnetic ionic liquid. In the case of the magnetic ion liquid exemplified above, when a rare earth magnet having a viscosity of 14 to 15111? & '3 at 30 is immersed, the magnetic attraction force in addition to the viscosity as the liquid is absorbed. As a result, it is possible to adsorb the magnetic ionic liquid with a thickness of more than 10 m even though it is a low viscosity liquid. Then, the rare earth magnet on which the magnetic ionic liquid is magnetically adsorbed is fixed to a rotating device and rotated, and a part of the magnetic ionic liquid is scattered by the centrifugal force to form a film having a thickness of, for example, about 5 m. In this case, the thickness of the magnetic ionic liquid can be set by considering the relationship between the centrifugal force acting on the magnetic ionic liquid and the magnitude of the magnetic attraction between the rare earth magnet and the magnetic ionic liquid. Then, after a magnetic ionic liquid is formed on the rare earth magnet, a rubber layer is formed by the same procedure as the above method. In this way, the rare earth magnet can be coated with the magnetic ionic liquid and the rubber layer. In addition, since the magnetic ionic liquid does not react with the silane coupling agent, the silane coupling agent may not be present in the rubber solution when forming the rubber layer.

Furthermore, the rare earth magnet used in the present invention may have a polar group, and the polar group may be bonded to the rare earth magnet through a coupling agent and coated with an oil film.ヽSince the entire surface of the rare earth magnet is covered with a film of oil, permeation of water vapor and various gases can be prevented. In addition, since the polar base force of oil can be bonded to the rare earth magnet through the coupling agent, the bonding strength between the oil and the rare earth magnet is enhanced, and the oil The film can be made difficult to peel off from the rare earth magnet. Therefore, by providing a layer of rubber having gas resistance to a rare earth magnet coated with an oil film, the external force of the rare earth magnet can be blocked to further improve the corrosion resistance. Also, since the polar groups of the oil can be bonded to the rubber layer via the coupling agent, the bond between the oil film and the rubber layer is also strong.

As the oil having a polar group, one having properties shown in Table 1 is preferable, and, for example, a polyol ester or the like can be applied.

As a polar group, in addition to the hydroxyl group and ester group which the said polyol ester has, an amide group, a carbonyl group, a cyano group, a urethane group etc. are illustrated, It does not specifically limit.

[Table 1]

The polyol ester is produced by an esterifying reaction in which a polyhydric alcohol having a neopentyl structure and a fatty acid are bonded. The hydrolysis resistance of the polyol ester depends on the type of fatty acid, and is not particularly limited. For example, as a fatty acid, valeric acid

It is possible to apply isovaleric acid, hexanoic acid, heptanoic acid, octanoic acid, isooctanoic acid, 2-ethylhexyl acid, pelargonic acid, isononanoic acid, decanoic acid and the like. Among them, 2-ethylhexyl acid is particularly preferable because it is excellent in hydrolysis resistance. Meanwhile, poly The viscosity of the all ester is determined depending on the type of polyhydric alcohol, and is not particularly limited. Examples of the polyhydric alcohol having a low viscosity include pentaerythritol, dipentaerythritol, neopentyl darylol and the like. If such a polyhydric alcohol is used, the viscosity of the polyol ester at normal temperature can be 40 to 50 cSt. Therefore, the rare earth magnet can be coated with a micron order film by the dicing method.

As the coupling agent for bonding the above-mentioned oil and the rare earth magnet, coupling agents such as titanium-based, aluminum-based and silane-based coupling agents can be used. As such a coupling agent which is preferably, for example, silane compounds of the above formulas (I) and (II) can be applied. As described above, the silane compound bonds to the rare earth magnet and to the film-forming oil by the interaction between the polar group of the oil and the silanol group.

A corrosion-resistant rare earth magnet using a polyol ester and the above-mentioned silane compound can be produced, for example, by the following method. That is, first, the rare earth magnet is dipped for about 30 minutes in a solution in which the silane compound is mixed with a solvent to a concentration of about 0.5 wt% and a silane coupling agent to a concentration of about 2 wt%. And the silane coupling agent are adsorbed on the magnet surface. Subsequently, the rare earth magnet is immersed in a polyol ester heated to 80 to 100 ° C. for about one hour, after which the solvent is evaporated and the polyol ester and the silane compound are mixed. The reaction is carried out to bond the polyol ester to the surface of the rare earth magnet via the silane compound. Thereafter, the rare earth magnet is allowed to stand under an atmosphere of 2 to 3 mmHg for about 1 hour to remove the solvent. Thus, a film of oil having a thickness of about 10 m can be formed on the rare earth magnet. Then, after a film of oil is formed on the rare earth magnet, a layer of rubber is formed through the silane coupling agent by the same procedure as the method described above. In this way, the rare earth magnet can be coated with a film of oil and a layer of rubber.

As in the case of producing the molecular film, the solvent for dissolving the silane compound is preferably a solvent having no hygroscopic property such as toluene, xylene, methyl ethyl ketone, ether, dichloromethane or the like. The compound is preferably one having no hygroscopicity as in the above formula (I). Yes. Also, it is preferable to remove the solvent as much as possible so as not to remain in the oil film.

In addition, after the oil film is formed, the above-mentioned mixture can be mixed with the rubber solution in forming the rubber layer. This makes it possible to produce a molecular film having a silica network structure also between the oil film and the rubber layer, thereby further improving the corrosion resistance. In this case, the silane compound may be mixed with the solution of rubber at about 0.5 wt%.

(Example)

Hereinafter, an embodiment in which a so-called neodymium magnet containing neodymium as a rare earth element is used as the rare earth magnet V will be described.

Example 1

Using a butyl rubber as the rubber, a corrosion resistant rare earth magnet was prepared by coating a neodymium magnet with a butyl rubber layer having a thickness of about 200 m by the above method as shown in FIG. 1, and the test shown in Table ² was conducted.

Example 2

A neodymium magnet was coated with a molecular film having a thickness of about 100 nm according to the above method using the silane compound shown in the above formula (I) and then covered with a butyl rubber layer in the same manner as in Example 1. Corrosion resistant rare earth magnets were prepared and the tests shown in Table 2 were conducted.

Example 3

A neodymium magnet is coated with a film of a magnetic ionic liquid having a thickness of about 5 m according to the above method using a magnetic ionic liquid 1-oxtyl-3-ethylimidazolium chloride (III) as the magnetic ionic liquid, and then the example is further described. A corrosion resistant rare earth magnet as shown in FIG. 2 coated with a butyl rubber layer in the same manner as 1 was prepared, and the test shown in Table 2 was conducted.

Example 4

Using a polyol ester as an oil having a polar group and using an imidazole silane compound shown in the above formula (I) as a coupling agent, a neodymium magnet is formed into an oil film of about 10 m thickness by the above method After coating with the above, a corrosion-resistant rare earth magnet covered with a butyl rubber layer was prepared in the same manner as in Example 1, and the test shown in Table 2 was performed. Example 5

Using a polyol ester as an oil having a polar group and using an imidazole silane compound shown in the above formula (I) as a coupling agent, a neodymium magnet is formed into an oil film of about 10 m thickness by the above method In the same manner as in Example 2, a corrosion-resistant rare earth magnet coated with a molecular film and a butyl rubber layer was prepared, and the test shown in Table 2 was performed.

The surface strength test is an index indicating the ease of handling of the rare earth magnet. For evaluation after the drop impact test, examine the degree of damage to the drop impact by the supersaturated steam test 1 shown in Table 2 in addition to visual confirmation.

[0067] The compactness test is an indicator of the blocking performance in an environment using a rare earth magnet. In the temperature-humidity cycle test, assuming that rare earth magnets are used in the dew condensation state, the rare earth magnets are heated from 25 ° C to 85 ° C for 0.25 hours under the conditions of humidity 85% RH, After holding at 85 ° C. for 6 hours, cool to −30 ° C. for 0.5 hours, hold at −30 ° C. for 3 hours, and further heat to 25 ° C. for 0.25 hours It is to evaluate the blocking performance when it is exposed to the environment of the temperature and humidity cycle of holding at 25 ° C for 2 hours. In the boiling test, the permeability of water vapor is evaluated on the assumption that the rare earth magnet is immersed in the cooling water of the automobile's radiator and is shaken. In the supersaturated steam test, the permeability of high-pressure water vapor is evaluated, and in the hydrogen gas permeation test, the permeability resistance of high-pressure hydrogen gas is evaluated, assuming a motor used for a fuel cell. is there. Since hydrogen gas is the smallest and molecule, the permeation resistance of the film is sufficient by examining the permeability of hydrogen gas.

[0068] The reactivity is to determine whether or not the rare earth magnet reacts to destroy the surface. The salt water immersion test evaluates the corrosion resistance to salt water. In the pressurized oxygen LLC solution immersion test, it is assumed that the rare earth magnet is used by being immersed in the cooling water of the automobile's radiator, and the antifreeze liquid (LLC solution) in the cooling water is oxidized. The reaction with the forcibly oxidized LLC solution is evaluated by forcibly introducing oxygen gas and treating it at a temperature of 100 ° C. or more for a predetermined time. In the ionic liquid immersion test, a rare earth magnet is used by being immersed in cooling water of a car's radiator, the radiator itself is corroded, and metal ions and acid ions are mixed in the LLC solution and found to be damaged. Assuming that the metal ion is Cu ²⁺ ion, the acid ion is C 1 − ion and SO 2

Four

The use of ions is used to evaluate the reactivity to an aqueous solution in which each ion is dissolved at a predetermined concentration.

[Table 2]

The results are as shown in Table 3.

In the drop impact test, no damage was found in all the examples. It was found that the mechanical strength is improved by coating the rare earth magnet with a 200 m thick butyl rubber layer.

In the boiling test 2, supersaturated steam test 2, hydrogen gas permeability test 2, pressurized oxygen LLC solution immersion test 2, and the ionic liquid immersion test 2, changes were observed on the surface of the magnet of Example 1. In Example 2, a slight change in the magnet surface is observed in boiling test 2 and supersaturated steam test 2, and hydrogen gas permeability test 2, pressurized oxygen LLC solution immersion test 2, ionic liquid immersion test 2 in magnet There was a change in the surface. Further, in Example 4, a slight change in the magnet surface was observed in the pressurized oxygen LLC solution immersion test 2, and the ionic liquid immersion test In the case of No. 2, a slight change in the magnet surface was observed. With respect to the other tests, the corrosion-resistant rare earth magnet in any of the examples did not particularly change.

[Table 3]

Thus, the elastic rare earth magnet according to the present invention can be used as a conventional rare earth magnet even in the case of misplacement. It is necessary to improve the corrosion resistance and the impact resistance as compared with the earth-earth magnet. And, among the corrosion-resistant rare earth magnets according to the present invention, whether to use a corrosion-resistant rare earth magnet with V deviation

And may be appropriately selected depending on the application. For example, when used under an environment where hydrogen gas resistance, acid solution, and high corrosion resistance to ionic liquids are not required, Example 1 can be used.

The corrosion-resistant rare earth magnet according to the present invention can be applied to a fixing structure of a magnet fixed to a support member supporting the magnet via an adhesive. That is, in general, in the rare earth magnet, the coefficient of linear expansion differs between the direction of the easy axis of magnetization and the direction perpendicular thereto. For example, in the case of neodymium 'iron' boron magnet, the linear expansion coefficient in the direction of easy magnetization axis is 5.2 × 10 ⁶ / ° C., and the linear expansion coefficient in the direction perpendicular thereto is − 0.8 X 10 ⁶ / ° It is C. Thus, the thermal expansion differs in the direction of the easy axis of magnetization and in the direction perpendicular thereto, and in such a magnet, the direction of the easy axis expands due to the temperature rise. Reduce in the vertical direction. For this reason, when the permanent magnet is thermally expanded or thermally shrunk after the rare earth magnet is fixed to the support member by the adhesive, the movement of the rare earth magnet is suppressed by the adhesive, and stress may be generated to cause a failure. . Therefore, if the corrosion resistant rare earth magnet according to the present invention is applied to the fixing structure of the magnet, even if the volume of the rare earth magnet changes due to a change in temperature of the use environment, the volume change due to elastic deformation of rubber. Can follow. Therefore, by preventing the volume change of the rare earth magnet, it is possible to prevent the occurrence of problems.

Hereinafter, an embodiment of a magnet fixing structure to which the corrosion resistant rare earth magnet according to the present invention is applied will be described with reference to the drawings. Here, a case where it is applied to a direct current motor (hereinafter referred to as “motor”) 1 as shown in FIG. 3 will be described as an example.

The motor 1 includes a housing 2 as a support member, a corrosion-resistant rare earth magnet 3 of the present invention attached to the housing 2, and a rotor 4 inserted inside the housing 2. The motor 4 is provided with a shaft 5 serving as a rotation shaft when the rotor 4 rotates, and a coil 6 for flowing an electric current to magnetize the mouth 4 !. The housing 2 doubles as a yoke, and the housing 2 and the corrosion-resistant rare earth magnet 3 are bonded by an adhesive. In addition, the corrosion-resistant rare earth magnet 3 has a rare earth magnet 8 coated with a layer 7 of butyl rubber The butyl rubber layer 7 is bonded to the rare earth magnet 8 via a silane coupling agent.

The thickness of the corrosion resistant rare earth magnet 3 is set in accordance with the circumferential direction etching accuracy of the housing 2 and the corrosion resistant rare earth magnet 3. For example, if the machining accuracy is ± 50 m, the maximum tolerance of both is 100 m. In order to fix the corrosion resistant rare earth magnet 3 to the housing 2 while the rubber is elastically deformed, the thickness of the rubber layer is at least about 200 μm. do it.

Here, when an example of an assembly process of the motor 1 is shown, first, the corrosion resistant rare earth magnet 3 is inserted into the housing 2 and bonded with an adhesive to fix the corrosion resistant rare earth magnet 3 to the housing 2. Then, the housing member comprising the housing 2 and the corrosion-resistant rare earth magnet 3 is provided with the rotor 4, the shaft 5 and the coil 6, and the sub-assembled rotor member and the sub-assembled end bell cup member (not shown) Insert and secure to the housing member. The other configuration of the motor 1 is the same as that of the conventionally known one.

As described above, by applying the corrosion-resistant rare earth magnet 3 according to the present invention to the motor 1, for example, even if the motor 1 is used in an automobile etc. and the temperature changes widely, the butyl rubber layer 7 Since the shape change is possible, the volume change of the rare earth magnet 8 can be followed, and no trouble occurs in the motor 1. In addition, since the butyl rubber layer 7 is strongly bonded to the rare earth magnet 8 via the silane coupling agent, even if the motor 1 operates, the butyl rubber layer 7 is peeled off by the centrifugal force. There is nothing to do.

In addition, the corrosion-resistant rare earth magnet 3 according to the present invention can be arbitrarily set, such as the type and thickness of the rubber of the rubber layer, in accordance with the application of the motor 1 and the use environment. It is also possible to form the above-mentioned molecular film, magnetic ionic liquid film, oil film and the like.

Industrial applicability

Since the corrosion resistant rare earth magnet according to the present invention has excellent corrosion resistance and impact resistance, various applications, such as conventional rare earth magnets, as well as applications to which rare earth magnets can not be applied, can be used. Can be applied to various applications.

Brief description of the drawings

[FIG. 1] A schematic view of the cross section of the corrosion resistant rare earth magnet according to the present invention [2] A schematic view of the cross section of the corrosion resistant rare earth magnet according to the present invention [3] A cross section showing the configuration of the motor according to the present embodiment

Claims

The scope of the claims

[1] A corrosion-resistant rare earth magnet in which the rare earth magnet is coated with a layer of gas-permeable rubber

[2] The corrosion resistant rare earth magnet according to claim 1, wherein the rubber layer is bonded to the rare earth magnet via a silane coupling agent.

[3] The corrosion resistant rare earth magnet according to claim 2, wherein the silane coupling agent has at least one of a methacryl group and a mercapto group.

[4] The rare earth magnet is a silane compound having an imidazole group and an alkoxysilyl group.

The corrosion-resistant rare earth magnet according to claim 2, coated with a film formed by bonding with at least one of the compound and the silane coupling agent, and the film is bonded with the rare earth magnet.

[5] The rare earth magnet is coated with a film of a magnetic ionic liquid or a film of oil having a polar group, and the polar group is bonded to the rare earth magnet via a coupling agent. Corrosion resistant rare earth magnet as described in.

[6] A fixing structure of a magnet in which the corrosion resistant rare earth magnet according to any one of claims 1 to 5 is bonded to a supporting member for supporting the magnet via an adhesive.