JPH02103906A - Resin coupled type magnet excellent in corrosion resistance - Google Patents

Abstract

PURPOSE:To prevent oxidation deterioration and rust generation by forming a synthetic resin film wherein zinc powder is mixed and dispersed at the surface of a permanent magnet which is obtained by a compression molding method. CONSTITUTION:A permanent magnet is constituted of scalelike intermetallic compound magnetic powder, which is mainly composed of rare earth metal being expressed by R-Fe-B (R is Nd and/or Pr or the one that some of them are replaced with one or more kinds of rare earth elements) and transition metal and whose average grain diameter is below 200mum and thickness is 10-30mum, and synthetic resin as a binder, and is obtained by an compression molding method. A synthetic resin film wherein zinc powder is mixed and dispersed is formed at the surface of this permanent magnet. Hereby, uniform film forming action by synthetic resin and electrochemical anticorrosive actions of zinc powder and R-Fe-B alloy magnetic powder act synergetically whereby oxidation deterioration and rust generation can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a resin-bonded magnet, and more particularly to a resin-bonded magnet that prevents oxidative deterioration during the manufacturing process and during use.

[Prior art and problems]

Alloy magnets whose main components are rare earth metals and transition metals (hereinafter referred to as rare earth magnets) have superior magnetic properties compared to conventional ferrite and alnico magnets.
In recent years, it has been used in a variety of fields, mainly in small motors.

Plastic magnets in which such rare earth magnetic powder is fixed with binder resin are exposed to high temperatures during kneading with resin or molding, but rare earth magnetic powder is very easily oxidized.
Oxidized during the manufacturing process of plastic magnets. As a result, the magnetic properties of the resulting rare earth plastic magnet are significantly degraded, and the occurrence of rust becomes noticeable. In addition, oxidation may progress rapidly during manufacturing, and ignition may occur.

Therefore, it may be possible to manufacture the product using a compression molding method that minimizes exposure to high temperatures during manufacturing, but even in this case, if the product is used near the heat-resistant temperature of the binder resin, oxidative deterioration during use can be avoided. First, there is a problem in that the magnetic properties gradually deteriorate.

In order to overcome this problem, Japanese Patent Application Laid-Open No. 61-25330
No. 2 proposes a method in which rare earth magnetic powder is brought into contact with a phosphorus compound having an active proton with p) (a being 4 or less) and exposed to an oxygen-containing atmosphere.
No. 04 discloses a method of coating rare earth magnetic powder with a polymer resin.

However, although all of the above-mentioned methods have been found to be effective in preventing oxidative deterioration, they cannot be said to be fully satisfactory in practical terms.

[Means for solving problems]

The present inventors were aware of this situation, and as a result of intensive research, the reason why the above conventional technology cannot obtain sufficient effects is that the coated magnetic powder is destroyed during compression molding, and the magnetic powder is easily oxidized. They discovered that this is due to the fact that the body surface is exposed. Therefore, as a result of intensive research to obtain a resin-bonded magnet with better oxidation resistance, the present inventors formed a synthetic resin coating mixed and dispersed with zinc powder on the surface of the magnet after compression molding. The uniform film-forming effect of the synthetic resin and the electrochemical anticorrosion effect of the zinc powder and R-Fe-B alloy magnetic powder act synergistically to achieve prevention of oxidative deterioration and rust generation. The heading completes the invention.

That is, the present invention provides R-Fe-B (R is Nd and/or Pr
, or a part of these is replaced with one or more rare earth elements), an intermetallic compound magnetic powder whose main components are a rare earth metal and a transition metal, and a synthetic resin as a binder. A permanent magnet obtained by a compression molding method, characterized in that a synthetic resin coating in which zinc powder is mixed and dispersed is formed on the surface of the permanent magnet. .

The intermetallic compound magnetic powder mainly composed of rare earth metals and transition metals used in the present invention is R-Fe3 type (R is Nd
and/or P r % or a part thereof is replaced with rIl by one or more rare earth elements, and ^1, Co, Ga, Dy, etc. are added to improve the magnetic properties. T-alloy magnetic powder mainly composed of the iron element represented by
More preferably, the thickness is about 10 to 150 μm. When the average particle size is less than 10 μm, the surface area of the magnetic powder increases, causing significant oxidation, which adversely affects magnetic performance.

If the average particle size exceeds 200 μm, although the problem of oxidation of the magnetic powder is reduced, the fluidity of the powder during compression molding deteriorates, which is not preferable in terms of productivity. More preferable magnetic powder has an average particle size of 200 μm or less,
It is a scale-like substance with a thickness of 10 to 30 μm.

Examples of the synthetic resin used as a binder in the present invention include phenolic resin, epoxy resin, melamine resin, and other thermosetting resins, as well as polyamide, polyolefin, polyphenylene sulfide, and other thermoplastic resins, but the resins are kept at high temperatures. A thermosetting resin that does not soften or deform in a heated state is preferable.

In the present invention, a plasticizer is used as necessary, but
Plasticizers used in the present invention include polyester plasticizers, phthalate plasticizers, epoxidized oil plasticizers, fatty acid ester plasticizers, and others, and are selected depending on the type of resin used. In particular, when using phenolic resin, adipic acid polyester plasticizer,
Phthalate polyester plasticizers, phosphate ester plasticizers, dibutyl phthalate, epoxidized soybean oil, and the like are extremely suitable.

The mixing ratio of the rare earth magnetic powder and the synthetic resin is preferably 50 to 5 parts by volume of the synthetic resin to 50 to 95 parts by volume of the magnetic powder. If the amount of the magnetic powder is less than 50 parts by volume, it is difficult to obtain the desired magnetic properties, while if it exceeds 95 parts by volume, a decrease in mechanical strength appears. The plasticizer is used in an amount of 0 to 10 parts by volume, and commonly used additives such as lubricants, heat stabilizers, and other modifiers can also be added. The resin magnet composition as described above is compression molded by a conventional method, and then the binder is cured to obtain a molded permanent magnet.

A synthetic resin coating containing zinc powder mixed and dispersed is formed on the surface of the permanent magnet molded body obtained as described above. A suitable method for forming the synthetic resin coating is to prepare an impregnating treatment liquid in advance and impregnating and coating the surface of the magnet molded body with the impregnating treatment liquid. The impregnating treatment liquid can be prepared by mixing and dispersing zinc powder in a reactive synthetic resin as a binder, for example, to obtain a predetermined solid content concentration. Obtained by diluting with l solvent. The synthetic resin used as the binder is preferably a reactive synthetic resin that does not soften or deform when kept at high temperatures, such as phenol resin, epoxy resin, acrylic silicone resin, or melamine resin. Also, as zinc powder, the average particle size is 30
It is preferably less than .mu.m, more preferably 5 to 10 .mu.m. If the thickness is less than 5 μm, oxidation of the zinc powder itself progresses rapidly, and the original electrochemical effect cannot be exerted. Moreover, if the thickness exceeds 30 μm, the thickness will be close to that of the film, and the final finished state will be extremely uneven, which not only spoils the aesthetics (also, it becomes difficult to uniformly disperse zinc powder into the synthetic resin as a binder, and The rust prevention effect due to chemical action cannot be exerted.The mixing ratio of zinc powder and synthetic resin is 5 to 20 parts by weight of zinc powder to 100 parts by weight of synthetic resin.If the zinc powder is less than 5 parts by weight, zinc The effect of adding the powder is not sufficient, and if the amount exceeds 20 parts by weight, the strength of the film formed will drop significantly, resulting in falling off of the zinc powder and cracking of the film.As the organic solvent used in the present invention, , methyl ethyl ketone, toluene, ethanol, methanol, etc., and these may be used alone or in combination.

Examples of the method for impregnating and coating the surface of the permanent magnet molded body with the above-mentioned impregnation treatment solution include a dipping method, a spraying method, a brush coating method, etc., and the dipping method is particularly suitable. The impregnated permanent magnet molded body is dried in a drying process, or the resin is cured simultaneously with drying.

The thickness of the synthetic resin coating mixed and dispersed with zinc powder is 5 to 5.
0 μm is preferable; if it is less than 5 μm, a sufficient antirust effect cannot be expected, and if it exceeds 50 μm, sagging of the coating immediately after impregnation coating cannot be ignored, which is not aesthetically pleasing.

〔Example〕

The present invention will be explained below with reference to Examples and Comparative Examples.
The present invention is not limited to these in any way.

Example Scale-shaped Nd- with an average particle size of 150 μm and a thickness of 20 μm.
After stirring and mixing 8% Fe-BTli powder and 20% by volume of resol-type phenolic resin, the resulting mixture was press-molded at room temperature, and the phenolic resin was cured at 180°C for 2 hours. -1 A ring-shaped molded body with an inner diameter of 6 mm and a height of 4 fl was obtained.

After that, the average particle size was 10μ for the acrylic silicone resin.
After mixing 17-tχ of zinc powder, the mixture was diluted with methyl ethyl ketone to prepare a low-viscosity impregnating solution, and the ring-shaped molded body was immersed in the impregnating solution and held for 1 minute.

Thereafter, the ring-shaped molded body was taken out from the impregnating treatment liquid and heat-treated at the curing temperature of the acrylic silicone resin to harden the resin.

The thickness of the coating formed on the surface of the molded product was 25 μm. 1O pole magnetization was performed using the pulse magnetization method, and a test sample was obtained.

The ring-shaped test sample obtained by the above procedure was heated at 60°C x 95°C.
The sample was placed in a constant temperature bath at %RH, and after 100 hours, the state of rust on the sample was observed and the rate of change in total magnetic flux was measured.

The total amount of magnetic flux was measured using a flux meter. As a result, no rust was observed, and the rate of change in total magnetic flux was -1.01%.

Comparative Example 1 Using a ring-shaped molded body whose surface was not coated,
The same operation as in the example was performed and the same test was conducted. As a result, the surface of the compact was covered with rust, and the rate of change in total magnetic flux was -1.8%.

Comparative Example 2 In the example, impregnation treatment was performed in the same manner as in the example except that zinc powder was not mixed, a coating film of 25 μm was formed on the surface of the compact, and the prepared impregnation treatment solution was subjected to the same operation as in the example. , conducted a test. As a result, rust on the surface of the molded product was reduced compared to Comparative Example 1, but mackerel was observed over the entire surface, especially around the edges. The rate of change in total magnetic flux is −
It was 1.4%.

[Action/Effect]

As described above, according to the present invention, a uniform coating of synthetic resin containing and dispersing zinc powder is formed on the surface of a permanent magnet, and the coating is hardened by impregnating into the porous portion of the surface of the permanent magnet, resulting in the so-called anchor effect. Since it is firmly fixed, it does not easily separate when handling or using the permanent magnet, and it is possible to obtain a permanent magnet that does not deteriorate magnetic performance due to oxidative deterioration or rust due to moisture.

Patent applicant Kanebuchi Chemical Industry Co., Ltd.

Claims (5)

[Claims] 1. A metal whose main components are a rare earth metal represented by R-Fe-B (R is Nd and/or Pr, or a part of these is substituted with one or more rare earth elements) and a transition metal. A permanent magnet made of an intermediate compound magnetic powder and a synthetic resin as a binder and obtained by a compression molding method, characterized in that a synthetic resin coating in which zinc powder is mixed and dispersed is formed on the surface of the permanent magnet. Resin bonded magnet. 2. 2. The resin-bonded magnet according to claim 1, wherein the intermetallic compound magnetic powder has a scale-like shape with an average particle size of 200 μm or less and a thickness of 10 to 30 μm. 3. Claim 1: The average particle size of the zinc powder is 30 μm or less.
Or the resin-bonded magnet according to 2. 4. 2. The resin-bonded magnet according to claim 1, wherein the mixing ratio of zinc powder is 5 to 20 parts by weight based on 100 parts by weight of the synthetic resin. 5. The thickness of the synthetic resin coating mixed and dispersed with zinc powder is 5.
The resin-bonded magnet according to claim 1, which has a diameter of 50 μm.