JPH07263213A - Molding method for soft magnetic material composition - Google Patents

Abstract

PURPOSE:To obtain a molded item in which the balance is improved between the strength, the dimensional accuracy and the magnetic characteristics while lessening the burden on a molding die by compression molding a soft magnetic material composition comprising a spinel ferrite magnetic powder, a liquid thermosetting resin containing a plasticizer, and a plasticizer and then thermosetting the composition. CONSTITUTION:A sintered item of Mn-Zn is ground to produce particles having particle size in the range of 0.6-0.8mm and 0.1-0.35mm, respectively, and 70wt.% of the former is mixed with 30wt.% of the latter. 70-95vol.% of material ferrite thus produced is mixed with 30-5vol.% of a resol type phenol resin containing plasticizer, obtained by adding 30-80 pts.wt. of adipic acid polyester plasticizer to 100 pts.wt. of solid content of resol type phenol resin, thus producing a mixture composition. The composition is molded with pressure in the range of 2-6t/cm<2> under normal temperature to produce a molded ring item. It is then subjected to thermosetting at 180 deg.C thus obtaining a sample of molded item.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention 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 soft magnetic materials used for magnetic cores and the like, spinel ferrites such as Mn-Zn ferrites, Ni-Zn ferrites and other sintered compacts with little loss in a high frequency region have been widely used. However, since these are manufactured by a powder metallurgy method, there are problems that the dimensional accuracy is poor due to shrinkage during firing, and it is difficult to obtain a molded product having a complicated shape. Furthermore, since it is a sintered body, it has the drawback of low impact strength.

In order to make up for these drawbacks, a so-called plastic soft magnetic material in which a soft magnetic material is bonded with a synthetic resin has been proposed in recent years. For example, Japanese Patent Publication No. 51-2835
No. 6 proposes a composition comprising spinel ferrite having a particle size in a specific range and a solid powder thermosetting resin. Since such a plastic soft magnetic material uses a synthetic resin, which is a non-magnetic substance, as a binder, it has a drawback in that the saturation magnetization and magnetic permeability of the molded magnetic core are inferior to those of the sintered body. Therefore, in order to improve the magnetic characteristics of the magnetic core using such a plastic soft magnetic material, the soft magnetic powder is increased by increasing the content of the soft magnetic powder and increasing the pressure during pressure molding. The packing density must be improved.

However, in the conventional plastic soft magnetic material, when the content of the soft magnetic material is increased, the strength of the molded product before hardening and solidification is low, and the molded product is liable to be damaged or deformed, or the mechanical strength of the molded product after hardening is high. There is a problem that is low. If the pressure is increased in order to further reduce the porosity, not only will the plastic be subjected to a large strain during compression molding, but also the magnetic properties of the magnetic core will be degraded due to the destruction of the soft magnetic particles, and The load on the mold is large and the mold is easily damaged.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned drawbacks, reduces the load on the molding die, and improves strength and strength.
The present invention provides a method for producing a molded product having a good balance of dimensional accuracy and magnetic properties.

[0006]

In view of the above-mentioned various problems, the inventors of the present invention reduce the adverse effect of strain due to a pressing force and at the same time improve the density of a molded body to improve the magnetic characteristics and the load of the molding die. In order to reduce the above-mentioned problem, and to improve the fixing strength of the molded product before curing to prevent breakage / deformation and achieve good dimensional accuracy, the inventors have conducted earnest researches and arrived at the present invention.

According to the present invention, 70 to 95% by volume of spinel ferrite magnetic powder obtained by mixing a fraction having a particle diameter of 0.1 to 0.35 mm and a fraction having a particle diameter of 0.6 to 0.8 mm and the balance of a plasticizer are used. And a plasticizer content of 30 to 100 parts by weight of the solid content of the liquid thermosetting resin.
A plastic-containing high-permeability soft magnetic material composition, characterized in that 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 is the molding method.

The spinel ferrite used in the present invention is, for example, Mn-Zn ferrite, Ni-Zn ferrite, M.
n-Mg ferrite and others, at least 1000
What was pulverized after baking at ℃ or more, for example, 1100 to 1300 ℃ is preferable. The spinel ferrite magnetic powder has a powder form, but its particle size distribution is important for obtaining good magnetic properties. That is, the particle size is 0.1 to 0.
A mixture of a 35 mm fraction and a 0.6 to 0.8 mm fraction is used. If the particle size is less than 0.1 mm, a molded product 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, or a phenol resin, especially a resol type resin. Phenolic resins are preferred. When a liquid thermosetting resin is used as a binder, the mixing of the binder and the soft magnetic material powder is significantly better than the case where a solid powder resin is used, and the binder itself has an adhesive force. The strength immediately after compression molding is excellent, there is no fear of damage or deformation before curing, and the strength after curing is also good.

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

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

The plasticizers used in the present invention include polyester plasticizers, phthalate ester plasticizers, epoxidized oil plasticizers, fatty acid ester plasticizers, etc., depending on the type of liquid thermosetting resin used. Select and use accordingly. Especially when a phenolic resin is used, adipic acid polyester plasticizer, phthalic acid polyester plasticizer, DB
P and epoxidized soybean oil are very suitable. When the amount of such a plasticizer added is extremely small, the effect is not remarkable. On the other hand, when it is used in excess of the solid content of the thermosetting resin as a binder, the mechanical strength of the molded product is lowered, and therefore it is usually 30-80 with respect to 100 parts by weight of the solid content of the liquid thermosetting resin
A range of parts by weight is preferred.

Further, 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 and other modifying additives may be added and used.

As a method of molding the composition described above,
Compression molding methods such as hot pressing and cold pressing 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 great, so it is troublesome in various operations. There is no need to employ the accompanying hot press.
That is, in molding the composition of the present invention, it is compression-fixed and molded at room temperature and then cured and solidified at the curing temperature of the thermosetting resin used, resulting in high productivity and good dimensional accuracy. It is possible to obtain a molded product having both magnetic properties.

Suitable pressure conditions for compression molding are 2 to 6 t.
/ Cm ² . At a pressure of less than 2 t / cm ^{2, the} packing density achieved with the composition of the present invention may be insufficient, and even if a pressure of more than 6 t / cm ² is applied, the packing density is no longer sufficient. A remarkable improvement cannot be expected, and on the contrary, there is a possibility that the magnetic properties may be deteriorated due to the particle destruction 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 the raw material ferrite, the initial permeability is 1000 to 3000.
The Mn-Zn ferrite sintered product of No. 1 was pulverized to have a particle diameter of 0.
Particles having a fraction of 6 to 0.8 mm and a fraction of 0.1 to 0.35 mm were obtained, and the former was mixed at a ratio of 70% by weight and the latter at a ratio of 30% by weight. 86% by volume of the above raw material ferrite
And 14% by volume of a plasticizer-containing resol-type phenolic resin in which a polyester adipic acid plasticizer is added in the range of 0 to 80 parts by weight as shown in Table 1 to 100 parts by weight of the solid content of the resol-type phenolic resin. Each composition was obtained by mixing with a blender. This composition was molded at room temperature under the pressure shown in Table 1 to give a ring-shaped fixed molded body of 30 mmφ × 20 mmφ × 10 mm. The obtained molded body was easy to handle and was free from chipping and cracking. Then, the molded body was heat-cured at 180 ° C. for 2 hours to obtain a molded body sample having a good external shape. Example 1 containing a plasticizer
6 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.
Then, in any of the density and the initial magnetic permeability, Examples 1 to 6
Was inferior to.

Examples 7 to 8 In Example 3, a polyester phthalate or dibutyl phthalate 6 was used instead of the adipic polyester plasticizer.
A composition and a ring-shaped molded body were obtained in the same manner except that 0 part by weight was used. The results were good as shown in Table 1, and the appearance was also good with no cracks or cracks.

Example 9, Comparative Example 2 100 parts by weight of a novolac type phenolic resin powder and 100 parts by weight of an aminosilane coupling agent were reacted in 200 parts by weight of methanol at room temperature, and the silane terminal in a viscous state was evaporated after the methanol was volatilized. A liquid modified phenolic resin having Example 1 using the modified phenolic resin thus obtained
A composition and a molded body were obtained in the same manner as in. The results, as shown in Table 1, were good in Example 9 containing a plasticizer, but were poor in Comparative Example 2 containing no plasticizer as compared with Example 9.

Comparative Examples 3 to 4 Compositions and molded products were obtained in the same manner as in Example 1 using the novolac type phenolic resin powder. In Comparative Example 3, the pressure was set to 2 t / cm ² , but the strength of the fixed molded body was extremely unsatisfactory, and a sample for magnetic property evaluation 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 body 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 product were obtained in the same manner except that n-Zn ferrite was used. As shown in Table 2, the results were that the density was slightly small and the initial magnetic permeability was low.

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

[0024]

[Table 2]

[0025]

As described above, according to the present invention, it is possible to provide a high-permeability molded article which reduces the load on the molding die, has a high density and a large initial magnetic permeability, and is excellent in strength and dimensional accuracy. It can be provided with good productivity. The molded product obtained by the present invention has a good balance of moldability, strength, dimensional accuracy, and magnetic characteristics, and it is possible to precisely correct the current magnetic field.

Claims (2)

[Claims] 1. 70 to 95% by volume of 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, and 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 with respect to 100 parts by weight of the solid content of the liquid thermosetting resin at room temperature, A method for molding a plastic-containing high-permeability soft magnetic material composition, which comprises thermosetting and solidifying the liquid thermosetting resin at a curing temperature. 2. The molding method according to claim 1, wherein the compression molding is performed under a pressure condition of ² to 6 t / cm ² .