JPH02219206A - Manufacture of bonded magnetic substance - Google Patents

Abstract

PURPOSE:To improve dimensional stability and corrosion resistance by compression molding a mixture principally composed of magnetic powder and a thermosetting resin, coating the surface of the compact thus obtained with a photosetting resin, curing the same by radiation of curing light and then curing the thermosetting resin. CONSTITUTION:Mixture principally composed of magnetic powder and a thermosetting resin is compression molded into a compact having a desired shape. Then, the surface of the compact is coated with a photosetting resin. After the photosetting resin is cured, the thermosetting resin is cured. In this manner, it is possible to distribute stress relaxation uniformly over the surface of the compact by constraint of the cured photosetting resin layer and to ensure high shape-retaining property of the compact. The magnetic powder, if it is of an alloy easy to corrode, can be protected against deterioration due to oxygen or water contained in the ambient atmosphere because it is shielded from the ambient atmosphere by the cured photosetting resin layer.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for producing a bonded magnetic material obtained by compression molding a mixture of magnetic powder and a thermosetting resin, and particularly relates to a method for producing a bonded magnetic material obtained by compression molding a mixture of a magnetic powder and a thermosetting resin. This invention relates to improving dimensional stability and preventing deterioration when using magnetic powder that is prone to deterioration due to corrosion.

[Prior Art] Demand for bonded magnetic materials has increased significantly in recent years because they have the following characteristics that cannot be obtained with sintered magnetic materials.

1. Complex thin shapes can be easily obtained.

2. A hard magnetic material with radial anisotropy can be easily obtained.

3. Less brittle than sintered magnetic materials.

As a method for manufacturing the above-mentioned bonded magnetic material, for example, a mixture of 2 to 4 parts by weight of thermosetting resin such as epoxy resin added to magnetic powder is filled into a required mold and molded by compression molding. There is a method of curing the thermosetting resin by heating or the like after forming the thermosetting resin into a body.

[Problems to be Solved by the Invention] However, in the conventional bonded magnetic material manufacturing method described above, the thermosetting resin of the molded product after compression molding is uncured, so the mechanical strength of the molded product is low. Therefore, there was a problem that the product was easily deformed during handling after compression molding, and the dimensional stability of the product was poor.

Furthermore, neodymium (Nd) is used as magnetic powder.

When using alloys that are easily corroded, such as iron (Fe) and boron (B) 1, the magnetic powder is corroded by oxygen and moisture adhering to it from the surrounding atmosphere, causing the thermosetting resin to deteriorate even after curing. There was a drawback that the deterioration of the magnetic powder progressed and the surface condition of the bonded magnetic material produced, as well as the reliability of the magnetic properties, were lacking.

In order to solve these problems, it is an object of the present invention to provide a method for manufacturing a bonded magnetic material that can improve the dimensional stability and corrosion resistance of the bonded magnetic material.

[Means for Solving the Problems] According to the present invention, after a mixture containing magnetic powder and a thermosetting resin as main components is formed into a molded body into a desired shape by compression molding, light is applied to the surface of the molded body. A method for manufacturing a bonded magnetic material is obtained, which comprises applying a curable resin, curing the photocurable resin by irradiating it with curing light, and then curing the thermosetting resin.

In a method for producing a bonded magnetic material, after compression molding a mixture of magnetic powder and thermosetting resin, the molded body removed from a compression mold is generally larger in size than the compression mold. This phenomenon is understood to be similar to the expansion associated with springback that is observed during compression molding of general metal powder.

In other words, the expansion associated with springback is thought to occur when the compressive stress generated inside the molded object during compression molding is released from the pressure during compression molding, and the expansion described above is caused by the compression stress generated inside the molded object during compression molding. It can be assumed that this will continue until heat curing is completed.

The present inventors focused on the expansion of the dimensions of the molded body mentioned above,
The present invention has been achieved by applying a photocurable resin to the surface of a molded body obtained by compression molding and curing it, so that the above-mentioned stress relaxation can be achieved by restraining the cured layer of the photocurable resin. We discovered that it is possible to improve the dimensional stability of molded products by uniformly dispersing it on the surface, and we also discovered that the photocurable resin cured layer has high shape retention even when it is deformed during handling. It is something that

In addition, even when the magnetic powder is made of an alloy that is easily corroded, such as neodymium, iron, boron, etc., the magnetic powder is shielded from the surrounding atmosphere by the photocurable resin hardening layer. The present invention was completed based on the discovery that deterioration of the magnetic powder due to oxygen, moisture, etc. contained in the atmosphere can be prevented, and the reliability of the surface condition and magnetic properties of the bonded magnetic material can be maintained.

In the present invention, the magnetic powder includes not only Nd-Fe-B powder but also other magnetic abrasive powders, such as hard magnetic materials such as barium ferrite, strontium ferrite, and rare earth cobalt, and soft magnetic materials such as manganese zinc ferrite and permalloy. There are basically no particular limitations as long as the material is a magnetic material that can be obtained as a powder.

Although the particle size of the magnetic powder is not particularly limited, it is preferably 200 μm or less in consideration of workability such as mixing and molding, and the appearance of the bonded magnetic material.

Further, as the thermosetting resin, an epoxy resin or the like can be used, but it is not limited thereto, and it goes without saying that unsaturated polyester resins, phenol resins, etc. can also be used.

Furthermore, it goes without saying that photocurable resins are applicable as long as they basically contain an unsaturated resin and a photopolymerization initiator as main components and are crosslinked and cured by light of a specific wavelength.

[Example] Next, the present invention will be explained in more detail using examples.

Example 1 Nd, electrolytic iron, and ferroboron with a purity of 95% or more were prepared, melted and cast by high-frequency heating in an argon atmosphere, and 31.1 wt%N d -67.9 wt% Fe1,
An alloy ingot having a composition of Owt%B was obtained. Next, the ingot was remelted by high-frequency heating in an argon atmosphere, and then sprayed onto the surface of a copper roll rotating at a circumferential speed of 35 m/sec to obtain an alloy ribbon with an average thickness of 30 μm, which was ground to an average particle size of 50 μm. It was made into a powder.

Next, the powder, bisphenol A system, and epoxy resin were weighed so that the weight ratio was 97/3, and the mixture was mixed and kneaded to obtain a mixture.

Next, the mixture was compression molded using a mold with an outer diameter of 30 mm and an inner diameter of 27 + n + n at a pressure of 3 Lon/c/.
0 ring-shaped molded bodies were obtained.

Next, after applying an ultraviolet curable acrylic resin to the surface of the ring-shaped molded body, the ultraviolet curable acrylic resin was cured with ultraviolet rays from a low-pressure mercury lamp, and then the ring-shaped molded body was heated at 100° C. for 120 minutes. A bonded magnet was obtained by heating and curing.

The outer diameter and inner diameter of these molded bodies were measured, and the average value, range, and standard deviation calculated from the measured values are shown in Table 1.

Thereafter, 10 bonded magnets obtained in the above-mentioned process were cut and the cross section was observed, and the average thickness of the cured layer of the ultraviolet curable acrylic resin was 7 μm.

In addition, 10 of the remaining bonded magnets were heated at 60℃95%RH.
No changes such as rust were observed on the surface of the bonded magnet even after 500 hours when it was kept in a high temperature and high humidity environment.

Comparative Example 1 A mixture of Nd-Fe-B powder and epoxy resin prepared in the same manner as in Example 1 was heated at a pressure of 3 ton/c using a mold with an outer diameter of 30 mm and an inner diameter of 27 mm. Compression molding was performed to obtain 50 ring-shaped molded products.

Next, the ring-shaped molded body was heated at 100° C. for 120 minutes to cure it, thereby obtaining a bonded magnet.

The outer diameter and inner diameter of these molded bodies were measured, and the average value, range, and standard deviation calculated from the measured values are shown in Table 1.

Furthermore, 10 of the bonded magnets were heated at 60°C, 95% RH.
1 after 48 hours when kept in a high temperature and high humidity environment.
Visually visible rust was found on the surfaces of all 0 pieces.

Below is a margin Example 2 A mixture of Nd-Fe-B powder and epoxy resin prepared in the same manner as in Example 1 was compression molded at a pressure of 3Lon/c+IT using a mold with an outer diameter of 20 mm and an inner diameter of 18 mm. 50 ring-shaped molded bodies were obtained.

Next, after applying an ultraviolet curable acrylic resin to the surface of the ring-shaped molded body, the ultraviolet curable acrylic resin was cured with ultraviolet rays from a low-pressure mercury lamp, and then the ring-shaped molded body was heated at 100'C for 120 minutes. The bonded magnet was cured by heating for a minute.

The outer diameter and inner diameter of these molded bodies were measured, and the average value, range, and standard deviation calculated from the measured values are shown in Table 2.

Thereafter, 10 bonded magnets obtained in the above-mentioned process were cut and the cross section was observed, and it was found that the average thickness of the cured layer of the ultraviolet curable acrylic resin was 6 μm.

In addition, 10 of the remaining bonded magnets were heated at 60℃95%RH.
When the bonded magnet was kept in a high temperature and high humidity environment, no changes such as rust were observed on the surface of the bonded magnet even after 5°0 hours.

Comparative Example 2 A mixture of Nd-Fe-B powder and epoxy resin prepared in the same manner as in Example 1 was heated at a pressure of 3 ton/cd using a mold with an outer diameter of 20 mm and an inner diameter of 18 mm in the same manner as in Example 2. Compression molding was performed to obtain 50 ring-shaped molded bodies.

Next, the ring-shaped molded body was heated at 100° C. for 120 minutes to cure it, thereby obtaining a bonded magnet.

The outer diameter and inner diameter of these molded bodies were measured, and the average value, range, and standard deviation calculated from the measured values are shown in Table 2.

Furthermore, 10 of the bonded magnets are 60°095%R.
When kept under the high temperature and high humidity environment of H, visible rust was observed on the surfaces of all 10 pieces after 48 hours.

Although the embodiments of the present invention have been described in detail in the space provided below, including comparison with conventional methods, the present invention is not limited to the above-mentioned embodiments, and various modifications can be made without departing from the gist of the present invention. .

[Effects of the Invention] As described above, the method for producing a bonded magnetic material of the present invention involves compression molding a mixture containing magnetic powder and a thermosetting resin as main components into a molded product having a desired shape, and then molding the mixture into a molded product having a desired shape. Since a photocurable resin is applied to the surface of the molded object, and then the thermosetting resin is cured after the photocurable resin is cured, the stress relaxation of the molded object is suppressed by the restraint of the photocurable resin cured layer. Since it can be uniformly dispersed on the surface and can have high shape retention, it has the effect of providing a bonded magnet with excellent dimensional stability.

Furthermore, in the case of alloys where the magnetic powder is easily corroded, the hardened layer of photocurable resin shields the magnetic powder from the surrounding atmosphere, which prevents deterioration of the magnetic powder due to oxygen, moisture, etc. contained in the surrounding atmosphere. Therefore, there is also the effect that the reliability of the surface condition and magnetic properties of the bonded magnetic material can be maintained.

Therefore, the method for producing a bonded magnetic material of the present invention greatly contributes to improving the quality stability of the bonded magnetic material, and is extremely useful industrially.

Claims (1)

[Claims] 1. After compression molding a mixture containing magnetic powder and thermosetting resin as main components into a molded body into a desired shape, a photocurable resin is applied to the surface of the molded body, and the photocurable resin is used for curing. A method for producing a bonded magnetic material, which comprises curing the thermosetting resin after curing it by irradiating it with light.