JPS63250808A - Manufacture of resin magnet - Google Patents

Abstract

PURPOSE:To make it possible to give the required anisotropy completely to the title resin magnet by a method wherein the mixture mainly composed of thermoplastic resin and magnetic powder is fused by heating, it is projected into a molding mold, an isotropic molded body is formed, it is placed in a substantially same molding mold in which a magnetic field is applied, and it is brought into an anisotropic state by fusing it again by heating. CONSTITUTION:An isotropic molded body is formed by heat-fusing the mixture mainly composed of thermoplastic resin and magnetic powder and filled it by injection into a molding mold. Then, said molded body is placed in the molding mold, in which a magnetic field is applied, having the molding cavity substantially same as that of the above-mentioned molding mold, the molded body is fused by heating again, and it is brought in an anisotropic state. Consequently, there is no restriction by an injection-molding machine and the like in this anisotropic treatment, an ideal magnetic field orientation can be obtained, and the quality and efficiency of a resin magnet can be improved sharply.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for manufacturing a resin magnet by heating and melting a mixture mainly consisting of a thermoplastic resin and magnetic powder, and injecting the mixture into a mold. This is related to the improvement of.

[Conventional technology]

Conventional resin magnets are made from a mixture of thermoplastic resins such as polyamide resin and polyethylene, and magnetic powders such as hard ferrite powder and rare earth cobalt powder (including additives such as lubricants, dispersants, and plasticizers). In other words, the most common method of manufacturing is to use an injection molding method in which a compound formed into granules with a size of 3 to 51 square meters is supplied to the cylinder of an injection molding machine, heated and melted, and then injected into the mold. It's a method. In this case, a magnetic field is usually applied to a mold to make the powder anisotropic, that is, to align the axes of easy magnetization of the magnetic powder. The resin magnets molded in this way have the advantage of being thin, with high dimensional accuracy, and can be made into complex shapes, making them lightweight. Applications are expanding in various fields where miniaturization and the like are required.

[Problem that the invention seeks to solve]

When manufacturing a resin magnet by the above-mentioned magnetic field injection molding means, the material constituting the molding die is required to be a material with high magnetic permeability in order to effectively apply magnetic flux to the molded body. However, since the magnetic powder 1, for example, ferrite t+> that constitutes the resin magnet, has extremely high hardness, the molding die is subject to extremely high wear, and therefore has a short lifespan.
There are problems in that it requires frequent replacement or repair, resulting in low productivity and increased costs. On the other hand, materials with high wear resistance, such as cemented carbide, have a low magnetic permeability and therefore cannot be used as mold materials for molding in a magnetic field. Furthermore, since the structure is such that a predetermined magnetic field is applied to the molding cavity, it is difficult to produce a large number of magnets, which also causes an increase in the cost of the magnet. Furthermore, depending on the shape of the magnet, there are structural constraints on the injection molding machine and/or the molding die, and there is also the problem that it is impossible to provide the required anisotropy sufficiently. are doing.

The present invention solves the problems existing in the above-mentioned prior art, has less wear on the molding die, extremely high productivity, and
The object of the present invention is to provide a method for manufacturing a resin magnet that can completely impart the required anisotropy.

C. Means for Solving Problems] In order to solve the problems existing in the above-mentioned prior art, the present invention has the following features.

A. A method of manufacturing a resin magnet made of thermoplastic resin and magnetic powder using a mold.

B. An isotropic molded body is formed by heating and melting a mixture mainly consisting of a thermoplastic resin and magnetic powder and injecting the mixture into a mold.

C1: The molded article is placed into a mold having a molding cavity substantially the same as the molding mold and to which a magnetic field is applied.

D. This molded body is heated and melted again to make it anisotropic.

This technical method was adopted.

〔Example〕

Sr ferrite (Sr0 ・6Fez
03) A compound was prepared by kneading 90 parts by weight of powder and 10 parts by weight of polyamide resin at 250°C using a kneader, and then pulverizing the mixture into pellets of 3 to 5 mm square.

Using this compound, an outer diameter of 2
An isotropic molded body having an inner diameter of 16 nm and a length of 20 mm was obtained. The molding die was made of cemented carbide, and the heating and melting temperature of the compound was 270°C.

The injection pressure was 800 kg/cJ. Next, this molded body is charged into a mold having a molding cavity substantially the same as the mold, and heated and melted again (approximately 270°C),
Anisotropy was achieved by applying a magnetic field of about 5000 G. The material constituting the mold used for reheating the molded body to make it anisotropic is preferably a material with a high magnetic index of 33, such as an iron-nickel alloy.

In this example, an example was shown in which Sr ferrite was used as the magnetic powder, but the present invention is not limited to this, and RCo5. R
Even if other magnetic powders such as zCo+ (R is a rare earth metal element) are used, the effect is the same. In addition to polyamide resins such as nylon, polyethylene is used as a thermoplastic resin as a binder.

Of course, other thermoplastic resins such as ethylene/vinyl acetate/copolymers can be used.

The pressure applied to the mold for further anisotropy treatment is 1
Although the pressure is usually atmospheric, a slight pressure may be applied to prevent the molded body from swelling. Although a ring-shaped magnet has been described as an example of a resin magnet, the object of the present invention is not limited to the above-mentioned embodiments, and is naturally applicable to magnets of other shapes.

〔Effect of the invention〕

Since the method for manufacturing a resin magnet of the present invention has the structure and operation as described above, the following effects can be expected.

+1+ The material constituting the mold for injection molding to form an isotropic molded body does not necessarily have to be a high magnetic permeability material, but rather a material with high corrosion resistance or wear resistance (for example, cemented carbide). ) can be freely selected, and the life of the mold can be significantly extended.

(2) As a result of (11) above, the frequency of replacing or repairing molds is significantly reduced, making it possible to improve productivity and reduce costs.

(3) Because multiple pieces can be molded in injection molding.

Not only can the yield be improved, but mass production is also possible.

(4) The process of anisotropy treatment in a magnetic field is performed with only atmospheric pressure or a slight pressure applied;
There is less wear on the molding die caused by the magnetic powder, so the frequency of maintenance is significantly reduced, making it possible to reduce costs.

(5) Since the anisotropy treatment is not restricted by injection molding machines, ideal magnetic field orientation is possible, and the quality and performance of the resin magnet can be greatly improved.

Claims (1)

[Claims] In a method of manufacturing a resin magnet made of a thermoplastic resin and magnetic powder using a mold, a mixture mainly consisting of a thermoplastic resin and magnetic powder is heated and melted and then injected and filled into the mold. A tropic molded body is formed, the molded body is charged into a mold having a molding cavity substantially the same as that of the mold and to which a magnetic field is applied, and the molded body is heated and melted again. A method for producing a resin magnet characterized by being anisotropic.