JP2690390B2 - Rare earth bonded magnet manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a rare earth bonded magnet used in various devices such as rotating electric machines.

(Prior Art) Conventionally, various types of relatively inexpensive and powerful permanent magnets have been developed. For example, Japanese Unexamined Patent Publication No. 59-211549 proposes a bonded magnet in which rare earth-iron-boron magnetic powder is solidified with an adhesive, and Japanese Unexamined Patent Publication No. 61-1
Japanese Patent No. 74364 proposes a plastic magnet obtained by mixing Misch metal-transition metal-boron magnetic powder with a binder.

Such a rare earth bonded magnet is one in which magnetic powder containing a rare earth and a transition metal is dispersed in a binder resin by kneading, and the production method thereof is, for example, JP-A-60-1.
It is described in Japanese Patent No. 64313. A mixing roll is used in the kneading step of the production method disclosed in the above publication, and the kneading is performed while mixing the rare earth magnetic powder and the silane coupling agent little by little in the binder resin. The obtained kneaded product is crushed and then rolled.

(Problems to be Solved by the Invention) Here, when kneading the magnetic powder containing a rare earth and a transition metal, there is a risk of ignition, and there is also a risk of production failure due to ignition. Therefore, when kneading a magnetic powder containing a rare earth and a transition metal by a conventional method,
Massive and continuous processing has become impossible.

Further, the method for producing a magnet disclosed in Japanese Patent Laid-Open No. 60-164313 uses samarium-cobalt type magnetic powder, and the magnetic characteristics are not so good for the price. Therefore, even if this is used in a rotating electric machine or the like, the rotating electric machine becomes expensive and it is not possible to obtain good characteristics for the price, and the range of use is extremely limited.

Therefore, the present invention provides a method for producing a rare earth bonded magnet capable of continuously kneading a large amount of magnetic powder containing a rare earth and a transition metal and having good magnetic properties. The purpose is to

(Means and Actions for Solving the Problems) In order to achieve the above object, the method for producing a rare earth bonded magnet according to claim 1, wherein a magnetic powder containing a rare earth and a transition metal is dispersed in a binder resin. In the method for producing a rare earth bonded magnet according to the above, at least (a) an inert gas is injected into a mixing device having a sealable mixing tank, and the air in the mixing device is changed into a gas having an oxygen concentration of 0.08 to 3%. The step of substituting, and (b) the magnetic powder containing a rare earth and a transition metal, the epoxy resin and the rust preventive agent are put into the mixing device after the gas replacement and mixed to form an oxide film, an epoxy resin film and an anti-corrosion agent. A mixing step of forming a rust coating on the magnetic powder, and (c) kneading the mixture obtained by the kneading step and the binder resin under a temperature condition of 95 ° C. or lower,
And a kneading step of dispersing magnetic powder containing a rare earth and a transition metal in a binder resin.

The method for producing a rare earth bonded magnet according to claim 2 is the method for producing a rare earth bonded magnet according to claim 1, wherein the magnetic powder containing rare earth and a transition metal is a boron-containing magnetic powder. Become.

In the means having such a configuration, first, the air in the mixing device having the mixing tank which can be sealed is gas-exchanged by the inert gas so that the oxygen concentration becomes non-ignitable, and then the rare earth and the transition metal are mixed. The magnetic powder containing is mixed with the epoxy resin film and the rust preventive film to form a film on the magnetic powder. That is, in this mixing step, the inflow of oxygen, which causes ignition, is blocked by gas replacement.

By the mixing step, an epoxy resin film and a rust preventive film are formed on the magnetic powder, and an oxide film is formed by a slight amount of oxygen remaining. Then, after such an oxide film, an epoxy resin film and a rust preventive film are formed, the magnetic powder is kneaded and dispersed with the binder resin.

Since the oxide film is formed on the surface of the magnetic powder under an appropriate oxygen concentration (0.08 to 3%), the finished rare earth bonded magnet maintains very good magnetic characteristics. That is, in the magnet according to the present invention, the rate of change in the magnetic flux after magnetization becomes very small by the appropriate oxidation treatment, and the one without a rust preventive coating, the one without oxidation treatment, or the oxidation treatment being excessive. The rate of change of magnetic flux in the magnetic field is significantly higher than that of the product of the present invention.

In the kneading process, the activity of the magnetic powder surface is reduced by the oxide film, the epoxy resin film and the anticorrosive film, and the inflow of oxygen into the material is prevented as much as possible, and the temperature of the kneading process is the ignition point. It is regulated below 95 ℃. Therefore, even if a large amount of material is continuously kneaded, there is no risk of ignition.

The method for producing a rare earth bonded magnet according to the present invention is the first
It has the steps as shown in the figure.

First, a rare earth-transition metal magnetic powder is obtained by the ultraquenching method. An example of the super-quenching method is a jet casting method.

In the jet casting method, a rare earth-transition metal magnetic alloy formed in the shape of an ingot is contained in a saucer, and the alloy is melted by a high frequency wave or the like in an inert environment. The molten magnetic alloy is poured into a basin with a nozzle and dropped through a nozzle onto a rotating wheel. The rotating wheel is cooled by water, where rapid cooling takes place. The quenched magnetic alloy is solidified into ribbon-shaped magnetic powder, falls downward, and is collected in a container.

Here, one or more kinds of lanthanoids are used as the rare earths constituting the rare earth-transition metal magnetic powder, and one or more kinds of Fe, Co, Ni are used as the transition metal. In this rare earth-transition metal magnetic powder,
A rare earth-transition metal-boron-based magnetic powder can be obtained by incorporating boron. Specifically, Nd-Fe-B, Nd-Fe-C
o-B, Ce-La-Fe-Co-B, Sm-Co, Sm-Co-Fe, Sm-Co-Mn
Are used.

Next, the rare earth-transition metal magnetic powder is mixed with an epoxy main agent and a rust preventive to form an oxide film, an epoxy resin film and a rust preventive film (film forming step).

In forming the oxide film, the epoxy resin film, and the anticorrosive film, first, an inert gas is injected into the mixing device, and the air in the mixing device is replaced by gas so that the oxygen concentration becomes 0.08 to 3%. To be done. As the inert gas, argon gas (Ar), nitrogen gas (N _2), carbon dioxide (CO ₂₎
Are used.

Then, the rare earth-transition metal magnetic powder, the epoxy main agent and the rust preventive agent are charged into the mixing device in which the gas replacement has been performed, and the mixing is performed for about 2 hours.
At the time of this mixing, an oxide film is first formed on the surface of the magnetic powder by the oxygen slightly remaining in the mixing device, and an epoxy resin film and an anticorrosive film are further formed thereon. As the mixing device, a ball mill, a V-type blender, a double cone type blender, or the like is used. The oxygen concentration of 0.08 to 3% means that if the oxygen concentration is less than 0.08%, it becomes impossible to form an oxide film.
Alternatively, even if formed, it is only extremely thin, and if the oxygen concentration exceeds 3%, there is a danger of ignition by oxygen.

As the epoxy main agent, one or more of bisphenol-based, phenoxy-based, novolac-based, polyphenol-based, polyhydroxybenzene-based or derivatives thereof is used, and rust inhibitor sorbitan monooleate and mineral oil. Alternatively, a mixture of synthetic oils is used.

The magnetic powder on which the oxide film, the epoxy resin film, and the rust preventive film are formed is taken out, weighed, and then kneaded with a flexible binder resin by a pressure kneader for several minutes (kneading step). . At this time, a curing agent and a curing accelerator for the epoxy resin are added. The reason why the curing agent and the curing accelerator are added at this stage is to prevent the magnetic powder from being hardened immediately after the mixture of the magnetic powder is taken out. In this way, the rare earth-
The transition metal-based magnetic powder is almost uniformly dispersed in the flexible binder resin.

As the flexible binder resin at this time,
Natural rubber (NR), isoprene rubber (IR), budadiene rubber (BR), styrene-butadiene rubber (SBR), butyl rubber (IIR), ethylene-propylene rubber (EPR), ethylene-vinyl acetate rubber (EVA), nitrile rubber ( NBR), acrylic rubber (AR), urethane rubber (UR), etc. are used alone or in combination of two or more.

That is, the binder resin in this embodiment is composed of so-called ternary rubber and has a non-polar rubber component (for example, II
R) and a highly polar rubber component (eg NBR) are mixed well via a halogen-containing rubber component (eg CR).

Non-polar rubber components have difficulty in oil resistance and weather resistance,
A rubber component having a strong polarity is very hard and requires the addition of an extender oil or a plasticizer. Therefore, if both rubber components are mixed through a rubber component containing halogen, rubber components that complement the difficulties of each rubber component are easily mixed with each other, and oil resistance and weather resistance are improved. is there.

As the rubber component containing halogen, one containing chlorine, such as chloroprene rubber (CR), hypalon (CSM), chlorinated polyethylene, or the like is used, or two or more thereof are used. In this case, the halogen-containing rubber component is preferably set to 15% by weight or less based on the total weight of the binder resin. If the rubber component containing halogen exceeds 15 wt% of the total weight of the binder resin, chlorine gas (Cl ₂ ) or hydrochloric acid gas (HCl) will be generated. For example, in the case of a motor, a commutator This is because it causes corrosion, rust of magnets, and core rust.

Examples of the curing agent include polyamines such as aliphatic polyamines and aromatic polyamines, acid anhydrides such as phthalic anhydride, polyamide resins, polysulfide resins, amine complexes such as boron trifluoride, and synthetic resin precondensates such as phenol resins. Alternatively, one or more of these derivatives are used. As the curing accelerator, amines such as trisdimethylaminomethylphenol, 1-isobutyl-
One or more imidazoles such as 2-methylimidazole or derivatives thereof are used.

In this kneading step, the pressure kneader is cooled, and the kneading is carried out at a temperature of 95 ° C or lower, preferably 50 to 60 ° C. This temperature setting avoids the risk of ignition in the kneading process. In other words, if kneading is performed at over 95 ° C, there is a danger of ignition due to heat generation.
Below 40 ° C, plasticization of rubber does not proceed and sufficient kneading cannot be performed.

The magnet material as a kneaded material obtained by the above kneading step is taken out from the pressure kneader and immediately divided into small lots of 10 kg or less. Each magnet material is divided into
Each of them is enclosed and stored in an airtight container, and is left as it is until the temperature of the magnet material drops to room temperature (preservation step). The danger of ignition is avoided by the heat radiation in this storage step.

The magnet material as a kneaded material, which has been sufficiently radiated by the storage step, is taken out and crushed into a predetermined size (crushing step). This crushing process uses argon gas (A
r), nitrogen gas (N ₂ ), carbon dioxide gas (CO ₂ ), and the like under cooling by the flow of an inert gas, and the temperature condition is set to 95 ° C. or lower. A rotary blade or the like is used for crushing. That is, in this pulverization step, air cooling with an inert gas is performed, so that pulverization in the atmosphere is possible.

Then, the pulverized product obtained in the pulverization step is rolled by a roll or the like to obtain a sheet-shaped bond magnet (sheet forming step).

After that, a predetermined heat treatment is performed and the product is cut into appropriate dimensions. At this time, since the magnetic powder is subjected to anticorrosion treatment, the cut surface of the sheet-shaped bond magnet also has sufficient anticorrosion ability, and it is not necessary to perform anticorrosion treatment such as coating after cutting.

Through this process, the maximum energy product is 9.0 [M
It is possible to obtain a sheet-shaped rare-earth bonded magnet having a GOe] of less than. When the maximum energy product is 9.0 [MGOe] or more, the amount of magnetic particles becomes too large with respect to the amount of binder and the flexibility is lost, which is not suitable for practical use. Also, the optimum maximum energy product for use in various rotating electrical machines is 3.0 [MGOe] or higher,
If the maximum energy product is less than 3.0 [MGOe], the characteristics of the rotating electrical machine cannot be improved for the price of the magnet.

(Example) Hereinafter, an example of the present invention will be described in detail.

Example 1 As the magnetic powder, MQP manufactured by General Motors Co., Ltd. was pulverized in advance by a wet mixing device and its particle size was adjusted. Moreover, the above-mentioned magnetic powder has a grain size of 2 m if it is formed by the ultra-quenching method.
Since it is a magnetic powder of m or less, it was pulverized to have a particle size of 78 μm or less. As the rust preventive agent, Leodol SP-10 manufactured by Kao Corporation was used, and as the epoxy main agent, Epicoat 828 manufactured by Yuka Shell Co. was used.

Then, the magnetic powder, the epoxy main agent, the rust preventive agent and the alumina balls are put in the container of the mixing apparatus, and the air in the container is filled with N ₂
After the gas was replaced with a gas so that the oxygen concentration became 1.2%, mixing was performed for one hour to form an oxide film, an epoxy resin film, and a rust prevention film on the surface of the magnetic powder.

Next, the above mixture and a rubber binder were kneaded with a curing agent and a curing accelerator in a pressure kneader for 7 minutes. As the above curing agent and curing accelerator, YH-302 and IBMI-12 manufactured by Yuka Shell Co., Ltd. were used. The temperature during this kneading was maintained at about 55 ° C.

The obtained kneaded material was subdivided into small lots of 4 kg each and placed in a plastic bag. After that, the kneaded product was taken out from the closed container by leaving it for an appropriate time, crushed by a crusher, and rolled to obtain a sheet. As the crusher, a U-140 rotary blade type made by Horai Iron Works was used.

Then, the sheet was heated to about 170 ° C. to vulcanize the rubber binder and then cut into a predetermined size to obtain a flexible magnet.

 The composition in this example is shown in the following table.

IIR-NBR-CR in the above table is set to 60 for NBR (nitrile rubber) and 15 for CR (chloroprene rubber) with respect to 100 IIR (butyl rubber).

In the kneading step of this example, the air in the kneading apparatus was gas-substituted by an inert gas so that the concentration of oxygen could not be ignited, and the inflow of oxygen causing ignition was blocked by gas substitution. . Therefore, there was almost no risk of ignition in the mixing process.

Also, in the next kneading step, it was confirmed that the activity of the magnetic powder surface was reduced by the oxide film, epoxy resin film and anticorrosive film formed in advance, and that the inflow of oxygen into the material was prevented as much as possible. Was done. Further, in this kneading step, in addition to the above oxygen blocking action, temperature regulation by cooling was performed below the ignition point. Therefore, even if a large amount of material is continuously kneaded, there is no risk of ignition.

In this way, under a given oxygen concentration (0.08-3%),
A rare earth bonded magnet having an oxide film formed on the surface of magnetic powder maintains very good magnetic properties. Suwanachi second
In the magnet according to the present invention shown by a solid line, the rate of change in magnetic flux (vertical axis) with respect to the time (horizontal axis) after magnetization (left at 85 ° C.) is very small, while the rust preventive coating is not used. The rate of change in magnetic flux of the product with excessive oxidation treatment (dashed line) is slightly larger than that of the product of the present invention, and the magnetic flux of the product with an anticorrosive coating but not subjected to oxidation treatment (broken line) The rate of change is significantly higher than that of the product of the present invention.

The magnetic characteristics of the obtained magnet are Br = 5.5 [KG], iHc
= 9.9 [kOe], bHc = 4.5 [kOe], (BH) _max = 6.2 [MGO
e].

Further, when the obtained magnet was left in an atmosphere of 60 ° C. and 90% RH for 80 hours, no rust was observed on the surface. When used as a driving magnet for a brushed DC motor,
No corrosion occurred in the brush material (Ag-Pd) and commutator material (Ag-Cd) even after continuous rotation for 200 hours at ℃.

Example 2 As the magnetic powder, an alloy having a composition of MM ₁₄ (Fe ₀ .9 Co ₀ .1) ₇₉ B ₇ was used as an ultra-quenched ribbon by the single roll method, and the particle size was adjusted by crushing with a wet mixing device. As the rust preventive agent, a mixed liquid of Leodol SP-10 manufactured by Kao Co. and Anderol 456 manufactured by Teneco Chemical Co. of the United States was used. Thereafter, a sheet-like flexible magnet was obtained in the same manner as in Example 1 described above.

Also in the kneading process according to this example, the inflow of oxygen, which causes ignition, was blocked by gas replacement. Therefore, there was almost no risk of ignition in the mixing process.

It was also confirmed that in the kneading step, the activity of the magnetic material was lowered by the oxide film, the epoxy resin film and the rust preventive film, and the inflow of oxygen into the magnetic material was almost completely prevented. Further, the cooling in the kneading step was sufficiently performed, and even if a large amount of the materials were kneaded continuously, there was almost no risk of ignition in the kneading step.

Furthermore, since an oxide film was formed on the surface of the magnetic powder, very good magnetic characteristics were maintained.

The magnetic characteristics of the magnet obtained in Example 2 are
Br = 4.6 [KG], iHc = 7.0 [kOe], bHc = 3.1 [kOe],
(BH) _max = 4.0 [MGOe].

Furthermore, when the obtained magnet was left in an atmosphere of 60 ° C. and 90% RH for 80 hours, no rust was observed on the surface. When used as a driving magnet for a brushed DC motor,
No corrosion occurred on the brush material (Ag-Pd) and commutator material (Ag-Cd) even after continuous rotation at 60 ° C for 200 hours.

As described above, it was confirmed that the sheet-shaped rare earth bonded magnet according to the present invention is preferably attached to a rotating electric machine and used.

If a metal powder having a high magnetic permeability such as an iron powder or an iron alloy is used instead of the permanent magnet powder, a flexible high magnetic permeability material can be formed.

(Effects of the Invention) As described above, in the method for producing a rare earth bonded magnet according to the present invention, the surface activity of the magnetic powder containing the rare earth and the transition metal is controlled in the mixing device in which the gas replacement with the inert gas is performed. After forming an oxide film, an epoxy resin film and an anticorrosive film to reduce the temperature, each step of kneading and crushing is carried out to prevent oxygen from flowing into the magnetic material, and at a predetermined temperature below the ignition point in the kneading step. Since it is decided to perform cooling, it is possible to avoid the risk of ignition in the kneading step, it is possible to continuously knead a large amount of magnetic powder containing a rare earth and a transition metal, the magnetic powder to a predetermined Good magnetic characteristics can be obtained by providing the oxide film.

[Brief description of the drawings]

FIG. 1 is a flow chart showing a manufacturing process of a rare earth bonded magnet according to the present invention, and FIG. 2 is a diagram showing a magnetic flux change characteristic of a magnet in an embodiment of the present invention.

Claims (2)

(57) [Claims] 1. A method for producing a rare earth bonded magnet, wherein magnetic powder containing a rare earth and a transition metal is dispersed in a binder resin, which comprises at least the following steps. Method. (A) A gas replacement step of injecting an inert gas into the mixing device and replacing the air in the mixing device with a gas having an oxygen concentration of 0.08 to 3%. (B) A magnetic powder containing a rare earth and a transition metal, an epoxy resin and an anticorrosive agent are charged into the mixing device after the gas replacement and mixed to form an oxide film, an epoxy resin film and an anticorrosive film with the above magnetic property. Mixing process to form powder. (C) A kneading step of kneading the mixture obtained by the above mixing step and the binder resin under a temperature condition of 95 ° C. or lower to disperse magnetic powder containing a rare earth and a transition metal in the binder resin. 2. The method for producing a rare earth bonded magnet according to claim 1, wherein the magnetic powder containing a rare earth and a transition metal contains boron.