JP2022035048A - Method for manufacturing rare-earth bond magnet - Google Patents

Abstract

To provide a method for manufacturing a rare-earth bond magnet having a high magnet strength with excellent manufacturing efficiency.SOLUTION: A method for manufacturing a rare-earth bond magnet includes: a step S1 of preparing rare-earth alloy magnet powder; a step S2 of preparing a resin composition for molding containing a resin for molding; a step S3 of kneading the rare-earth alloy magnet powder and the resin composition for molding, and manufacturing a compound for a rare-earth bond magnet; a step S4 of compressing the compound for the rare-earth bond magnet, and manufacturing a compression molding; a step S5 of heat treating the compression molding, and manufacturing a bond magnet molding; a step S7 of impregnating the bond magnet molding with a resin composition for impregnation, and manufacturing an impregnation molding; a step S8 of immersing the immersion molding in a curing agent, and curing a resin for impregnation of a surface layer part of the impregnation molding; and a step S9 of heating the impregnation molding after the resin for impregnation of the surface layer part has been cured, and curing the resin for impregnation.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing a rare earth-based bonded magnet having high magnet strength.

Rare earth permanent magnets have high magnetic properties and are used in various fields today. Rare earth permanent magnets are roughly classified into sintered magnets and bonded magnets depending on the raw material powder used and the manufacturing method. Rare earth bonded magnets (hereinafter referred to simply as bonded magnets) are compared with rare earth sintered magnets. It has a large degree of freedom in shape, and has an advantage of high electrical resistance because a resin that is an insulator exists between the magnet powders. However, since the bonded magnet has a structure in which magnet powder is bonded with a resin binder, the magnet strength has to be lower than that of a rare earth-based sintered magnet, and it is difficult to use it in applications requiring high magnet strength.

International Publication No. 2012/118001 (Patent Document 1) states that a compound for a bonded magnet produced by keeping the amount of resin added at the time of kneading and the amount of organic solvent within a certain range is strongly compressed to obtain a high molded body density and high molding density. A method for manufacturing a bonded magnet having magnetic properties is disclosed. However, the magnet strength is limited to those for applications that do not require particularly high strength.

Japanese Patent Application Laid-Open No. 2017-34097 (Patent Document 2) discloses a molding resin that can be used for ordinary compression bond magnets and the strong compression bond magnets described in Patent Document 1 and has excellent mechanical strength at high temperatures. Although the mechanical strength is improved to some extent by adopting such a resin, it cannot be said that it is sufficient for applications requiring higher strength such as a motor that rotates at high speed.

On the other hand, Japanese Patent Application Laid-Open No. 4-27102 (Patent Document 3) forms a rare earth magnet powder with a binder 1 containing a solid epoxy resin, a curing agent, and a curing accelerator at room temperature, and heat-cures the binder 1. Disclosed is a method for producing a bonded magnet by vacuum-impregnating a binder 2 containing an epoxy resin and a curing agent (imidazole compound) with the molded body and thermally curing the impregnated binder 2. According to the method described in Patent Document 3, a molded product molded with an epoxy resin having excellent strength and thermosetting is impregnated with an epoxy resin having further excellent strength in the voids existing in the molded product, and then heated. Since it is cured, the voids are filled with epoxy resin, and a significant improvement in magnet strength can be expected. However, the impregnated resin composition (binder 2) contains an impregnated resin (epoxy resin) and a curing agent (imidazole compound), and the curing gradually starts even at room temperature in the resin tank of the vacuum impregnating device. It has a pot life, and it is necessary to frequently replace the impregnated resin and clean the vacuum impregnated device, resulting in poor production efficiency.

International Publication No. 2012/118001 JP-A-2017-34097 Japanese Unexamined Patent Publication No. 427102

In the method described in Patent Document 3, as a method of using the impregnated resin without considering the pot life, instead of using the impregnated resin composition containing the impregnated resin (epoxy resin) and the curing agent (imidazole compound), the impregnated resin is used. A method is conceivable in which the molded body is first impregnated with only (epoxy resin) and then impregnated with a curing agent (imidazole compound). However, this method does not contain a curing agent at the time when the impregnated resin is impregnated into the molded body, so that there may be a problem that the impregnated resin flows out from the molded body before it is cured.

Further, a method of prolonging the pot life at room temperature by using dicyandiamide known as a latent curing agent as a curing agent is also conceivable. However, when the impregnated resin composition containing dicyandiamide is impregnated into the molded body and heated to cure the impregnated resin in the molded body, the impregnated resin composition becomes less viscous from the molded body before the impregnated resin is cured. It turned out that there was a problem such as flowing out.

Therefore, an object of the present invention is to provide a method for producing a rare earth-based bonded magnet having high magnet strength with excellent production efficiency.

As a result of diligent studies in view of the above objectives, the present inventor has formed, for example, a rare earth-based bond magnet composition (including rare earth magnet powder, epoxy resin and curing agent) and thermally cured it in the process of manufacturing a rare earth bond magnet. The obtained molded product is impregnated with an impregnated resin composition containing an impregnated resin (epoxy resin) and a curing agent (dicyandiamide), and then the molded product is immersed in a liquid curing agent (for example, triethyltetramine). By curing the impregnated resin on the surface layer of the molded body, the impregnated resin composition impregnated in the molded body does not flow out from the surface of the molded body when the molded body is heated in a subsequent step. We have found that a rare earth-based bonded magnet having magnet strength can be manufactured with excellent production efficiency, and have arrived at the present invention.

That is, the method of the present invention for producing a rare earth-based bonded magnet is
The process of preparing rare earth alloy magnet powder and
The process of preparing a molding resin composition containing a molding resin, and
A step of kneading the rare earth alloy magnet powder and the molding resin composition to prepare a compound for a rare earth bond magnet.
The process of compressing the compound for rare earth-based bonded magnets to produce a compression molded product, and
The step of heat-treating the compression molded body to produce a bonded magnet molded body, and
A step of impregnating the bonded magnet molded product with an impregnating resin composition containing an impregnating resin to prepare an impregnated molded product.
A step of immersing the impregnated molded product in a liquid curing agent to cure the impregnating resin on the surface layer portion of the impregnated molded product.
It is characterized by including a step of heating the impregnated molded product after curing the impregnating resin on the surface layer portion to cure the impregnating resin inside the impregnated molded product.

The rare earth alloy magnet powder is preferably a rare earth quenching alloy magnet powder.

The molding resin is preferably a thermosetting epoxy resin.

The impregnating resin is preferably a liquid thermosetting epoxy resin.

The impregnating resin composition preferably contains the impregnating resin and a latent curing agent.

The latent curing agent is preferably dicyandiamide.

The liquid curing agent for immersing the impregnated molded product is preferably triethyltetramine.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a method for producing a rare earth-based bonded magnet having high magnet strength with excellent production efficiency.

It is a flowchart which shows the manufacturing method of the rare earth type bond magnet of this invention.

Hereinafter, an example of a method for manufacturing a rare earth-based bonded magnet according to the present invention will be described with reference to FIG.

(1) Process of preparing rare earth alloy magnet powder S1
First, a rare earth alloy magnet powder is prepared. There are no particular restrictions on the rare earth alloy magnet powder that can be used in the present invention. For example, a molten alloy having a predetermined composition is quenched by a roll quenching method such as a melt spinning method or a strip casting method to pulverize a quenching alloy strip produced. Suitable rare earth alloy magnet powders include, for example, Nd-Fe-B-based quenching alloy magnet powders described in US Pat. No. 4,409,31. The method of the present invention can also be applied to the production of bonded magnets using other magnetic powders, and for example, Sm-Fe-N-based magnetic powders can also be preferably used.

(2) Step of preparing the resin composition for molding S2
A molding resin composition containing a molding resin is prepared. The molding resin composition may contain a curing agent and an organic solvent, if necessary. A thermosetting resin is used as the molding resin. The thermosetting resin (molding resin) is not particularly limited, but it is preferable to use an epoxy resin. When an epoxy resin is used, for example, bisphenol A type epoxy or the like is desirable. The curing agent is not particularly limited, but dicyandiamide or the like known as a latent curing agent is preferable, and dicyandiamide is particularly preferable. As the mixing ratio of the molding resin and the curing agent, an appropriate amount may be selected depending on the type and combination of the molding resin and the curing agent.

As the organic solvent, a volatile organic solvent that becomes a gas at room temperature is preferable. Examples of the organic solvent that can be preferably used include acetone, methyl ethyl ketone, methyl isobutyl ketone, benzene, toluene, xylene and the like. From the viewpoint of safety and handleability, ketones such as methyl ethyl ketone are most preferable.

The molding resin composition may contain two or more types of epoxy resins, a curing agent, and the like. Examples of such a resin composition for molding include the resin composition described in Patent Document 2, Epicron 4050 manufactured by DIC Corporation, and JER7007P manufactured by Mitsubishi Chemical Corporation.

(3) Process for manufacturing a compound for rare earth-based bonded magnets S3
Subsequently, the rare earth alloy magnet powder prepared in step S1 and the molding resin composition prepared in step S2 are kneaded to prepare a compound for rare earth bond magnets. The molding resin composition used for kneading is a molding resin (epoxy resin) with respect to 100 parts by mass of the rare earth alloy magnet powder when the rare earth alloy magnet powder and the molding resin composition are mixed in a specified amount. ) Is preferably adjusted and mixed so as to contain 0.5 to 4.0 parts by mass and 3 to 7 parts by mass of the organic solvent.

If the proportion of the organic solvent is less than 3 parts by mass, the organic solvent may volatilize before the resin reaches the surface of the magnet powder during kneading, and uniform coating may not be possible. Further, if the proportion of the organic solvent exceeds 7 parts by mass, it takes time for the organic solvent to volatilize, which is not preferable from the viewpoint of productivity. By kneading at such a ratio and volatilizing the organic solvent during kneading to prepare a compound, it is possible to prepare a compound in which the surface of each powder particle is thinly and uniformly coated with a resin. In a preferred embodiment, the resin in the compound covers the magnet powder particles constituting the rare earth alloy magnet powder with a coverage of 90% or more, and the thickness of the resin is 0.1 μm or more and 1 μm or less. In such a compound, since the magnet powder particles are thinly and uniformly coated with a high coverage, it is difficult for the magnet powder particles to conduct even if they come into contact with each other, and finally a bonded magnet having a high electric resistance can be obtained. In order to reduce damage to the mold during compression molding in the subsequent process, a lubricant such as calcium stearate may be added or mixed with the compound. The rare earth alloy magnet powder and the molding resin may be blended and kneaded without diluting the molding resin with an organic solvent.

(4) Step of manufacturing a compression molded product S4
Next, the compound for rare earth-based bonded magnets is compressed to produce a compression molded product. In this compression molding step, it is preferable to compress the compound for rare earth bond magnets so that the density of the compression molded body is in the range of 70% or more and 90% or less of the true density of the rare earth alloy magnet powder, and the molding pressure is 80. The range is preferably in the range of ~ 2000 MPa, more preferably in the range of 200 to 1000 MPa. If the forming pressure is less than 80 MPa, it is difficult to obtain a high magnet density. Further, if it exceeds 2000 MPa, the load on the mold becomes too large, which is not preferable. Examples of the press device used for compression molding include a mechanical cold press machine and an ultra-high pressure powder press device described in Patent Document 1. The method of the present invention is not limited to the strong compression high-density magnet described in Patent Document 1, but is also applicable to general-purpose compression bond magnets, and is suitable for applications requiring high magnet strength such as high-speed rotary motors. Will be adopted.

(5) Step of heat-treating the compression molded body to produce a bonded magnet molded body S5
By heat-treating the compression-molded body as described above, the molding resin is cured to obtain a bonded magnet-molded body. The heat treatment conditions may be based on the curing conditions of the resin to be used, but are preferably 150 ° C. or higher and 300 ° C. or lower. When Nd-Fe-B-based quenching alloy magnet powder is used as the rare earth alloy magnet powder, it is particularly easily oxidized, so the heat treatment atmosphere is in a reduced pressure atmosphere of 10 Pa or less (especially in a vacuum of 1 Pa or less). A non-oxidizing atmosphere such as in an inert gas atmosphere such as Ar gas or nitrogen gas is preferable. Similarly, from the viewpoint of preventing oxidation, the heat treatment time (retention time in the above temperature range) is preferably 1 minute or more and 4 hours or less.

(6) Step of preparing the resin composition for impregnation S6
The impregnating resin composition is a composition containing the impregnating resin as a main component and, if necessary, a diluent, a curing agent, etc. of the impregnating resin. In the present application, the impregnating resin composition includes those composed only of the impregnating resin.

The impregnating resin is not limited as long as it is a thermosetting resin, but a thermosetting epoxy resin is particularly preferable. The thermosetting epoxy resin is not particularly limited, but for example, a bisphenol F type epoxy resin having a lower viscosity than the bisphenol A type epoxy resin is desirable. The impregnating resin composition containing a thermosetting epoxy resin may contain a resin other than the epoxy resin.

The impregnating resin composition needs to be in a liquid state having a relatively low viscosity so that the bonded magnet molded body can be quickly impregnated in the step S7 described later. Therefore, it is preferable to use a liquid resin as the impregnating resin. Even if it is a solid or a highly viscous liquid at room temperature, it may be in the form of a low-viscosity liquid at the time of impregnation by heating or diluting with a reactive diluent.

A curing agent is not always necessary, but it is preferably used to accelerate thermal curing. As the curing agent, it is preferable to use dicyandiamide or the like known as a latent curing agent. By using the latent curing agent, a long pot life can be secured, the cycle of resin replacement and resin tank cleaning in the vacuum impregnation device is long, and the production efficiency is high.

(7) Step of impregnating the impregnating resin composition to prepare an impregnated molded product S7
Subsequently, the bonded magnet molded body prepared in step S5 is impregnated with the impregnating resin composition prepared in step S6 to prepare an impregnated molded body. As a method of impregnation, a vacuum pressurization method, a vacuum method, a pressurization method, an immersion method, a centrifugal method or the like can be adopted, but impregnation by the vacuum pressurization method is particularly preferable. When the impregnation treatment is performed by these methods, it is preferable to heat the impregnating resin composition and / or the bonded magnet molded body in order to facilitate the impregnation of the impregnating resin composition into the bonded magnet molded body.

(8) Step of immersing the impregnated molded product in a liquid curing agent S8
Next, the impregnated molded product prepared in step S6 is immersed in a liquid curing agent. The curing agent used here is not particularly limited as long as it is liquid and can cure the impregnating resin at room temperature, but TETA (triethylenetetramine) or the like is desirable. The viscosity of the liquid curing agent is preferably 80 P (8 Pa · s) or less at 25 ° C, and more preferably 50 P (5 Pa · s) or less. By immersing the impregnated molded product in a liquid curing agent, the impregnating resin on the surface layer of the impregnated molded product is cured, and as a result, the impregnating resin impregnated inside the molded product is applied to the surface of the molded product by the heat treatment in the next step. You can prevent it from seeping out.

(9) Step of heat-treating the impregnated molded body to produce a rare earth-based bonded magnet S9
Subsequently, the impregnated molded body produced in step S8 is heat-treated to cure the impregnating resin inside the molded body to produce a rare earth-based bonded magnet. When Nd-Fe-B-based quenching alloy magnet powder is used as the rare earth alloy magnet powder, it is particularly easily oxidized, so that the heat treatment atmosphere is preferably a non-oxidizing atmosphere similar to that in step S5.

When an impregnating resin composition containing a curing agent is used as in Patent Document 3, curing of the impregnating resin gradually starts even at room temperature. Therefore, the resin composition for impregnation has a pot life, and if the pot life is short, it is necessary to frequently replace the resin or clean the resin tank. Therefore, it is preferable to use a resin having a pot life as long as possible. Since the resin has a long curing time and a high curing temperature, the production efficiency is poor and the magnetic properties may be deteriorated. As described above, when the impregnating resin composition containing a curing agent is used, it is difficult to achieve both pot life, production efficiency and deterioration rate of magnetic properties.

On the other hand, in the method of the present invention, since the surface layer portion of the impregnated molded product is cured with a liquid curing agent in step S8, even when an impregnating resin composition having a long pot life is used, step S9 Since the impregnated resin for impregnation does not seep out to the surface of the molded product during the heat treatment, the heat treatment at a high temperature is possible, and the pot life, production efficiency, deterioration rate of magnetic properties, and magnet strength are all affected. Can be solved.

A processing process of the bonded magnet molded body may be added between the process S5 and the process S6. That is, the bonded magnet molded body may be processed, and the processed bond magnet molded body may be impregnated with the impregnating resin composition prepared in step S6. Further, a processing step may be added after the step S9. That is, the bond magnet produced in step S9 may be processed into a finished product. Further, various surface treatments may be performed after step S9. As described above, the order of the steps S1 to S9 is as described above, but other steps may be added after each step.

In the above embodiment, steps S1 (step of preparing rare earth alloy magnet powder) to step S9 (step of heat-treating the impregnated molded body to produce a rare earth-based bonded magnet) have been described. It is not limited to the embodiment.

For example, a bonded magnet molded product obtained by compressing and heat-treating a kneaded product obtained by kneading a rare earth alloy magnet powder, an epoxy resin and a curing agent is obtained, and the impregnated molded product is impregnated with an impregnating resin composition. (Step S7), the impregnated molded product is immersed in a liquid curing agent (Step S8), and heat-treated (Step S9) to obtain a rare earth-based bonded magnet.

As a rare earth alloy magnet powder, Nd-Fe-B quenching alloy magnet powder (MQP-13-9 manufactured by Magnequench) obtained by the melt spinning method was prepared.

A bisphenol A type epoxy resin JER1004 manufactured by Mitsubishi Chemical Corporation and a curing agent DICY7 (dicyandiamide) manufactured by Mitsubishi Chemical Corporation were dissolved in methyl ethyl ketone (MEK) at a mass ratio of 100: 1.5 to prepare a resin composition for molding. The amount of MEK was adjusted to 4.5 parts by mass with respect to 100 parts by mass of the quenching alloy magnet powder to be kneaded.

A molding resin composition was mixed with 100 parts by mass of Nd-Fe-B-based quenching alloy magnet powder so that the amount of resin excluding MEK (total of epoxy resin and curing agent) was 2.0 parts by mass. The mixture was kneaded until the MEK in the solution was completely volatilized. 0.07 parts by mass of calcium stearate was mixed with the obtained kneaded product to prepare a compound for rare earth-based bonded magnets.

A compression molded product was produced by compression molding the obtained compound for rare earth bond magnets at a molding pressure of 6 ton / cm ² (588 MPa). This molded product was heat-treated at a temperature of 150 ° C. for 2 hours in a vacuum atmosphere to prepare a bonded magnet molded product.

Subsequently, Mitsubishi Chemical's bisphenol F type epoxy resin jER806, Mitsubishi Chemical's reactive diluent YED216D, and Mitsubishi Chemical's curing agent DICY7 were mixed at a mass ratio of 85.5: 9.5: 5.0 to form a liquid. A resin composition for impregnation was prepared.

The impregnated resin composition was impregnated into a bonded magnet molded product by a vacuum pressurization method to prepare an impregnated molded product. The impregnation was performed by immersing the bonded magnet molded product in the resin composition for impregnation for 30 minutes in a vacuum state (1 kPa). Subsequently, this impregnated molded product was immersed in a liquid curing agent [TETA; viscosity 15 P (1.5 Pa · s)] at 25 ° C. for 3 hours. By immersing in a curing agent, the epoxy resin on the surface layer of the impregnated molded product was cured. When the impregnated molded body having the surface layer portion cured was cut and the cross section was observed with an optical microscope, the epoxy resin inside the impregnated molded body was not cured.

The impregnated molded product after curing the epoxy resin on the surface layer was heated at 160 ° C. for 2 hours to prepare a rare earth-based bonded magnet of the present invention. When the obtained rare earth-based bond magnet was cut and the cross section was observed with an optical microscope, it was confirmed that the impregnated epoxy resin was cured to the inside.

According to the present invention, it is possible to obtain a method for producing a rare earth-based bonded magnet having high magnet strength with excellent production efficiency.

Claims (7)

The process of preparing rare earth alloy magnet powder and
The process of preparing a molding resin composition containing a molding resin, and
A step of kneading the rare earth alloy magnet powder and the molding resin composition to prepare a compound for a rare earth bond magnet.
The process of compressing the compound for rare earth-based bonded magnets to produce a compression molded product, and
The step of heat-treating the compression molded body to produce a bonded magnet molded body, and
A step of impregnating the bonded magnet molded product with an impregnating resin composition containing an impregnating resin to prepare an impregnated molded product.
A step of immersing the impregnated molded product in a liquid curing agent to cure the impregnating resin on the surface layer portion of the impregnated molded product.
A rare earth-based bond magnet comprising a step of heating the impregnated molded body after curing the impregnating resin on the surface layer portion to cure the impregnating resin inside the impregnated molded body. Manufacturing method. In the method for manufacturing a rare earth-based bonded magnet according to claim 1,
A method for producing a rare earth-based bonded magnet, wherein the rare-earth-based alloy magnet powder is a rare-earth-based quenching alloy magnet powder. In the method for manufacturing a rare earth-based bonded magnet according to claim 1 or 2.
A method for producing a rare earth-based bonded magnet, wherein the molding resin is a thermosetting epoxy resin. In the method for manufacturing a rare earth-based bonded magnet according to any one of claims 1 to 3.
A method for producing a rare earth-based bonded magnet, wherein the impregnating resin is a liquid thermosetting epoxy resin. In the method for manufacturing a rare earth-based bonded magnet according to any one of claims 1 to 4.
A method for producing a rare earth-based bonded magnet, wherein the impregnating resin composition contains the impregnating resin and a latent curing agent. In the method for manufacturing a rare earth-based bonded magnet according to claim 5.
A method for producing a rare earth-based bonded magnet, wherein the latent curing agent is dicyandiamide. In the method for manufacturing a rare earth-based bonded magnet according to any one of claims 1 to 6.
A method for producing a rare earth-based bonded magnet, wherein the liquid curing agent for immersing the impregnated molded product is triethyltetramine.

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