JP2573168B2 - Molding method of soft magnetic material composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for molding a soft magnetic material composition comprising a soft magnetic material and a liquid thermosetting resin as a binder.

[0002]

2. Description of the Related Art Conventionally, as a soft magnetic material used for a magnetic core or the like, a spinel ferrite having a small loss in a high frequency region, for example, Mn-Zn ferrite, Ni-Zn ferrite or other sintered compact has been widely used. However, since these are manufactured by a powder metallurgy method, there are problems such as poor dimensional accuracy due to shrinkage during firing and difficulty in obtaining a molded article having a complicated shape. Furthermore, since it is a sintered body, it has a disadvantage that impact strength is low.

In order to compensate for these drawbacks, a so-called plastic soft magnetic material in which a soft magnetic material is bonded with a synthetic resin has recently been proposed. For example, Japanese Patent Publication No. 51-2835
No. 6 proposes a composition comprising spinel ferrite having a specific range of particle diameter and a solid powdery thermosetting resin. Since such a plastic soft magnetic material uses a synthetic resin, which is a non-magnetic substance, as a binder, there is a drawback that the saturation magnetization and the magnetic permeability of a molded magnetic core are inferior to those of a sintered body. Therefore, in order to improve the magnetic properties of a magnetic core using such a plastic soft magnetic material, the porosity is reduced by increasing the content of the soft magnetic powder and increasing the pressure at the time of pressing to reduce the porosity. Must be improved in packing density.

However, in the conventional plastic soft magnetic material, when the content of the soft magnetic material is increased, the strength of the molded body before being hardened and solidified is low, and it is easy to cause breakage and deformation, or the mechanical strength of the molded body after hardening. Is low. When the pressing force is increased to further reduce the porosity, a large strain is applied at the time of compression molding, and further, the soft magnetic material particles are destroyed and the magnetic properties of the magnetic core are lowered. The burden on the mold is large and the mold is likely to be damaged.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned disadvantages, reduces the burden on a molding die, and improves strength and strength.
An object of the present invention is to provide a method for producing a molded article having a good balance between dimensional accuracy and magnetic properties.

[0006]

SUMMARY OF THE INVENTION In view of the above-mentioned various problems, the present inventors have reduced the adverse effects of distortion due to pressurizing force, and at the same time, increased the density of the molded body to improve the magnetic characteristics and the burden on the molding die. The present inventors have conducted intensive studies to reduce the occurrence of the stiffness, and to enhance the fixing strength of the molded body before curing to prevent breakage and deformation and achieve good dimensional accuracy.

The present invention relates to a spinel ferrite magnetic powder containing 70 to 95% by volume of a mixture of a fraction having a particle size of 0.1 to 0.35 mm and a fraction having a particle size of 0.6 to 0.8 mm, and a balance comprising a plasticizer. Liquid thermosetting resin containing, and the plasticizer content is 30 to 100 parts by weight of the solid content of the liquid thermosetting resin
80 parts by weight of a soft magnetic material composition is compression-molded at room temperature, and then thermoset at the curing temperature of the liquid thermosetting resin. The content of the molding method is included.

The spinel ferrite used in the present invention is, for example, Mn-Zn ferrite, Ni-Zn ferrite, M
n-Mg ferrite or other, at least 1000
It is preferable that the powder is fired at a temperature of at least 1100C, for example, 1100 to 1300C, and then powdered. The spinel ferrite magnetic powder is in the form of a powder, but its particle size distribution is important for obtaining good magnetic properties. That is, the particle size is 0.1 to 0.1.
A mixture of a 35 mm fraction and a 0.6 to 0.8 mm fraction is used. When the particle diameter is less than 0.1 mm, a molded article having a high density and a high initial permeability cannot be obtained.

The liquid thermosetting resin used in the present invention is a liquid at room temperature, and is a phenol resin, an epoxy resin, a urea resin, a melamine resin, a furan resin, an unsaturated polyester resin, and other phenol resins, especially a resol type. Phenolic resins are preferred. When a liquid thermosetting resin is used as the binder, the mixing of the binder and the soft magnetic material powder is remarkably better compared to the case of using a solid powdery resin, and the binder itself has an adhesive force. The strength immediately after compression molding is excellent, there is no fear of breakage or deformation before curing, and the strength after curing is also good.

The composition used in the present invention comprises the above-mentioned magnetic powder 70
It is composed of a liquid thermosetting resin containing about 95% by volume and a balance of a plasticizer. If the soft magnetic material powder containing a plasticizer is less than 70% by volume, desired magnetic properties cannot be obtained. On the other hand, if it exceeds 95% by volume, breakage and deformation are likely to occur.

According to the present invention, since a liquid thermosetting resin containing plasticity is used as a binder, the binder has a low viscosity, which makes it easier to be more evenly distributed on the surface of the soft magnetic powder. Since the friction between the soft magnetic particles is reduced and a high packing density can be easily realized, both the density of the compact and the initial magnetic permeability are improved. Furthermore, when such a binder is used, even if the compression molding pressure is lowered, a desired level of high molded body density and initial magnetic permeability can be easily realized, and the load on the molding die can be reduced, which is extremely valuable from an industrial viewpoint. high.

The plasticizer used in the present invention is a polyester plasticizer, a phthalate ester plasticizer, an epoxidized oil plasticizer, a fatty acid ester plasticizer, or the like. Select and use according to your needs. Particularly when a phenol resin is used, adipic acid polyester plasticizer, phthalate polyester plasticizer, DB
P and epoxidized soybean oil are very suitable. When the amount of such a plasticizer is extremely small, the effect is not remarkable.On the other hand, when the plasticizer is used in excess of the solid content of the thermosetting resin as a binder, the mechanical strength of a molded body is reduced, so that the plasticizer is usually used. 30 to 80 with respect to 100 parts by weight of the solid content of the liquid thermosetting resin
A range of parts by weight is preferred.

In order to improve the properties of the composition used in the present invention, a small amount of a coupling agent, a lubricant, a heat stabilizer, or other modifying additives may be used.

The molding method of the composition described above includes:
Compression molding methods such as hot press and cold press can be used, but since a liquid binder containing a plasticizer is used, the strength of the molded body after compression molding and before curing is large, so there are various operational difficulties. There is no need to employ an accompanying hot press.
That is, when molding the composition of the present invention, the composition is compression-fixed at room temperature, and then cured and solidified at the curing temperature of the used thermosetting resin, so that the productivity is high and the dimensional accuracy is good. And a molded article having both magnetic properties.

The preferable pressure condition for compression molding is 2 to 6 tons.
/ Cm ² . In 2t / cm ² less than the pressure, sometimes packing density is also achieved by a composition I than in the present invention becomes insufficient, the longer packing density by applying pressure beyond 6t / cm ² No remarkable improvement can be expected, and on the contrary, there is a possibility that the magnetic properties may be deteriorated due to the destruction of the particles of the soft magnetic material powder used.

[0016]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto.

Examples 1 to 6 and Comparative Example 1 As a raw material ferrite, the initial permeability was 1000 to 3000.
Mn-Zn ferrite sintered product of the above was crushed, and the particle diameter was 0.
Particles having a fraction of 6 to 0.8 mm and a fraction of 0.1 to 0.35 mm were obtained, and a mixture of the former at 70% by weight and the latter at 30% by weight was used. 86% by volume of the raw material ferrite
And a ribbon containing 14 vol% of a plasticizer-containing resole phenol resin obtained by adding an adipic acid polyester plasticizer in the range of 0 to 80 parts by weight as shown in Table 1 with respect to 100 parts by weight of the solid content of the resole phenol resin. Each composition was mixed by a blender to obtain each composition. This composition was molded at room temperature under the pressures shown in Table 1 to obtain a 30 mmφ × 20 mmφ × 10 mm ring-shaped fixed molded product. The obtained molded body was easy to handle and did not have chipping or cracking. Thereafter, the molded body was cured by heating at 180 ° C. for 2 hours to obtain a molded body sample having a good appearance. Example 1 containing a plasticizer
In Comparative Examples 1 to 6, the density and initial magnetic permeability of the molded sample showed good values as shown in Table 1, but Comparative Example 1 containing no plasticizer was used.
Then, in any of density and initial magnetic permeability, Examples 1 to 6
Was inferior to

Examples 7 to 8 In Example 3, polyester phthalate or dibutyl phthalate was used instead of adipic acid polyester plasticizer.
A composition and a ring-shaped molded product were obtained in the same manner except that 0 parts by weight were used. The results were good as shown in Table 1, and the appearance was good without chipping or cracking.

Example 9 and Comparative Example 2 100 parts by weight of a novolak type phenol resin powder and 100 parts by weight of an aminosilane coupling agent are reacted at room temperature in 200 parts by weight of methanol. A liquid modified phenolic resin having the same was obtained. Example 1 using the modified phenolic resin thus obtained
In the same manner as in the above, a composition and a molded article were obtained. As shown in Table 1, the results of Example 9 containing the plasticizer were good, but Comparative Example 2 containing no plasticizer was poorer than Example 9.

Comparative Examples 3 and 4 Using novolak type phenol resin powder, compositions and molded articles were obtained in the same manner as in Example 1. In Comparative Example 3, the pressure was set at 2 t / cm ² , but the strength of the fixed molded product was extremely unsatisfactory, and a sample for evaluation of magnetic properties could not be obtained. On the other hand, Comparative Example 4 is a case where the pressure is 6 t / cm ² ,
The density and initial magnetic permeability of the molded product were extremely unsatisfactory.

[0021]

[Table 1]

Comparative Example 5 In Example 3, M having a particle size of 0.05 to 0.09 mm was used.
A composition and a molded article were obtained in the same manner except that n-Zn ferrite was used. As shown in Table 2, the density was rather small and the initial magnetic permeability was low.

Comparative Example 6 In Example 3, Mn having a particle diameter of 0.1 to 0.35 mm was used.
-A composition and a molded article were obtained in the same manner except that Zn ferrite was used. The results were inferior to Example 3 as shown in Table 2.

[0024]

[Table 2]

[0025]

As described above, according to the present invention, a high-permeability molded article having a high density, a large initial magnetic permeability, and excellent strength and dimensional accuracy can be obtained by reducing the burden on a molding die. It can be provided with good productivity. The molded article obtained by the present invention has a good balance of moldability, strength, dimensional accuracy, and magnetic properties, and can accurately correct a current magnetic field.

Claims (2)

(57) [Claims] 1. A 70% to 95% by volume spinel ferrite magnetic powder obtained by mixing a fraction having a particle size of 0.1 to 0.35 mm and a fraction having a particle size of 0.6 to 0.8 mm, with the balance containing a plasticizer. After compression molding a soft magnetic material composition comprising a liquid thermosetting resin and having a plasticizer content of 30 to 80 parts by weight based on 100 parts by weight of the solid content of the liquid thermosetting resin, A method of molding a plastic-containing high magnetic permeability soft magnetic material composition, wherein the composition is heat-cured and solidified at a curing temperature of the liquid thermosetting resin. 2. The molding method according to claim 1, wherein the compression molding is performed under a pressure of ² to 6 t / cm ² .