JPH01319919A - Manufacture of bond magnet - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is directed to the productivity and productivity of bonded magnets obtained by compression molding a mixture of magnetic material powder and thermosetting resin and then curing the resin. This is related to improving quality stability.

BACKGROUND OF THE INVENTION In general, demand for bonded magnets has increased significantly in recent years because they have the following characteristics that cannot be obtained with sintered magnets.

(1) Excellent dimensional stability as there is no shrinkage due to sintering.

(2) Less brittle than sintered magnets.

(3) A radially anisotropic magnet can be easily obtained.

A typical manufacturing method for this magnet is to add 2 to 4% by weight of a thermosetting resin such as epoxy resin to the magnetic material powder, then mix and knead the mixture into a mold of the desired shape. The resin is charged into a compression molded body, and the resin is cured by heating or other operations to produce a product.

[Problems to be Solved by the Invention] The resin used in this manufacturing process should have a low viscosity as much as possible in consideration of the workability of mixing and kneading, but in this case, the surface of the magnetic powder is in a wet state. Therefore, the fluidity of the mixture is low, and there is a drawback that it becomes conical when charged into a mold. child. As a countermeasure to this drawback, there are cases where a finely powdered resin is used, which is solid even before heat curing. Because they are small, they are fragile and often difficult to link by hand.

In view of these drawbacks, the present invention has been devised, and its technical problems are to improve the workability of charging the mixture into the mold, to improve the mechanical strength of the molded product before curing, and to solve the above-mentioned drawbacks. The object of the present invention is to provide a method for manufacturing bonded magnets that reduces variations in product quality.

Means for Solving the Problem] According to the present invention, in the manufacturing method of manufacturing a bonded magnet by compression molding a mixture of magnetic powder and a thermosetting resin and then curing the thermosetting resin, the above-mentioned method is provided. A method for manufacturing a bonded magnet is obtained, which is characterized in that the mixture is granulated in advance and then compression molded.

According to the present invention, in the method for manufacturing the bonded magnet,
A method for producing a bonded magnet is obtained, in which the thermosetting resin 1 has a viscosity of 500 C1)S or more at room temperature.

Here, in the present invention, compression molding can be performed either in a magnetic field or in no magnetic field.

The present inventors have discovered that in order to improve the strength of the molded product before curing, it is necessary to use a high viscosity type thermosetting resin with high adhesive strength as the mixed thermosetting resin. As a result of our study to improve the difficulty of filling the mold that inevitably occurs when using this method, we found that by granulating the mixture by compressing and solidifying it in advance and then re-pulverizing it, it is possible to fill it into the mold. The present invention was based on the discovery that filling can be made easier.

Furthermore, according to the present invention, if the mixture is made into granules with approximately the same density as the product by granulation, it is possible to significantly reduce the variation in density in the pressing direction during molding, and it is possible to achieve uniform Quality products can be produced efficiently.

The reason why the mixture obtained by this method can be easily filled into a mold is because the magnetic material powder is coated with a thermosetting resin through granulation, and the wet surface area is significantly reduced. be understood.

As the magnetic material used in the present invention, any material that has been conventionally used in bonded magnets can be used; for example,
Examples include strontium ferrite, rare earth cobalt, neodymium-iron-boron, and examples of thermosetting resins include epoxy resins, unsaturated polyester resins, and phenol resins, but are not limited to these.

The mixture obtained by mixing and kneading the above materials can be granulated by compression molding with a normal press machine and then pulverizing it until the desired particle size is obtained. However, for continuous production, twin rolls are used. A method may be adopted in which the material is compressed between rolls and then pulverized, or if rolls are used, the pulverization step can be omitted if the roll surface is appropriately embossed.

In addition, in order to improve the mechanical strength of the molded product before heat curing, it is necessary to use a high viscosity resin to increase the adhesive force between the magnetic material powders. cps or more is desirable.0 However, when such a high viscosity resin is used, the workability of mixing and kneading with the magnetic powder may decrease, but in this case, dissolve and dilute the resin with an appropriate solvent. In the present invention, the granules are molded into a molded body in a magnetic field or in the absence of a magnetic field.

The present invention will be explained below with reference to Examples.

<Example> A predetermined amount of Nd, electrolytic iron, and ferroboron with a purity of 95% or more was weighed, melted by high-frequency heating in an argon atmosphere, and cast to yield 31.1 wt% Nd-67, 9 wt% Fe-1, O.
After obtaining an alloy ingot with a composition of wt%B, this zero-order ingot was remelted by high-frequency heating in an argon atmosphere, and then sprayed onto the surface of a roll made of #J rotating at a circumferential speed of 35 M/sec to a thickness of approx. A 30 μl alloy ribbon was obtained and ground to an average particle size of 50 μm to form a powder. A mixture of this powder, a bisphenol A-based epoxy resin, and a polyamine-based curing agent was weighed and mixed and kneaded with a liquid whose viscosity was adjusted to 2,600 cps so that the weight ratio was 97/3. During kneading, 10 wt % of acetone was added so that the powder was uniformly coated with resin. The mixture thus obtained was vacuum dried to sufficiently remove acetone, rolled with twin copper rolls with a gap of 0.3 m to form a plate, and pulverized to a size of 28 mesh or less. A raw material mixture for bonded magnets was obtained. This mixture was charged into a mold, a pressure of 3 tons/- was applied, and the outer diameter:
A compression molded body having a shape of 23 cities, an inner diameter of 20 cities, and a height of 12 cities was obtained. 2mm/1lin in the height direction of this molded body
When a compressive strength test was performed at a constant strain rate at a rate of 9.6K (+), the product broke.

In addition, after sufficiently heating and curing this molded body, Fig. 1 (b)
) and (c), samples 1 to 12 were obtained by cutting into 12 equal pieces each having one width in the height direction. The densities of Samples 1 to 12 were measured, and the results are shown in curve 11 in FIG. 1(a). Looking at FIG. 1(a), the bonded magnet according to the example shows almost no change in density in the height direction.

Comparative Example> Powder produced in the same manner as in the example was mixed with a liquid containing a bisphenol A-based epoxy resin and a polyamine curing agent, the viscosity of which was adjusted to 350 cps, at a weight ratio of 97/
The mixture was weighed and mixed and kneaded. This mixture was put into a mold as it was and a pressure of 3jOn/cJ was applied to obtain a molded article having the same shape as in the example. When this molded article was subjected to a compressive strength test in the same manner as in the examples, it broke under a load of 3.9 KCI.

In addition, after sufficiently curing this molded body by heating, it was cut and the density was measured in the same manner as in the example. The results are shown in Figure 1.
It is shown in curve 22. As shown in FIG. 1, in the bonded magnet according to the comparative example, a difference in density was observed between the pressurized surface and the opposite surface.

[Effects of the Invention] As explained in detail above, according to the method for manufacturing a bonded magnet of the present invention, a raw material mixture for bonded magnets with extremely excellent pressability can be obtained, improving the productivity of bonded magnets and improving products. It greatly contributes to improving the stability of quality and is extremely useful industrially.

[Brief explanation of the drawing]

Figure 1(a) is a diagram showing the density of the bonded magnet in the height direction, Figure 1(b) is a plan view showing the shape of the sample for density measurement of the bonded magnet in Figure 1(a), (c) is Figure 1(b)
In the front view, each number indicated by G in the figure is 0 corresponding to the sample number. Figure 1 Density (CL) inside the molded body Procedural corrector (voluntary) 8th month of 1995

Claims (1)

[Scope of Claims] 1. A manufacturing method of manufacturing a bonded magnet by compression molding a mixture of magnetic powder and a thermosetting resin and then curing the thermosetting resin, wherein after the mixture is granulated in advance, A method for manufacturing a bonded magnet, characterized by compression molding. 2. The method for manufacturing a bonded magnet according to claim 1, wherein the thermosetting resin has a viscosity of 500 cps or more at room temperature.