JP2021009930A - Dust core - Google Patents

Abstract

To provide a high-density and high-strength dust core containing magnetic nanoparticles.SOLUTION: A dust core contains magnetic nanoparticles having an average particle size of 1-300 nm, at least one thermosetting resin selected from the group consisting of a phenol resin and an epoxy resin, and a fatty acid with 12-30 carbon atoms. In the dust core, the thermosetting resin is preferably a phenol resin, and it is preferable that, with respect to the total amount of the magnetic nanoparticles, the thermosetting resin and the fatty acid, the content of the thermosetting resin is 0.01-4.99 mass%, the content of the fatty acid is 0.01-4.99 mass%, and the total amount of the thermosetting resin and the fatty acid is 0.02-5 mass%.SELECTED DRAWING: Figure 1

Description

The present invention relates to a dust core, and more particularly to a powder core using magnetic nanoparticles.

The dust core is obtained by compression-molding magnetic particles whose surface is covered with an insulating film, such as a transformer, an electric motor, a generator, a speaker, an induction heater, and various actuators. It is used in various products that utilize the electromagnetics of. As such a dust core, for example, the surface of iron-based particles is coated with an insulating film formed of an organic acid containing a metal such as titanium, and the surface of the insulating film is further coated with a thermoplastic resin or heat. A dust core obtained by pressure-molding a soft magnetic material coated with an insulating film formed of at least one of a curable resin and a higher fatty acid salt and heat-treating it (Japanese Patent Laid-Open No. 2009-57586). Documents 1)) are known.

On the other hand, since the magnetic nanoparticles are extremely small in size, they exhibit properties different from those of bulk magnetic materials. For example, in the range where the particle size exceeds about 100 nm, the coercive force increases as the particle size decreases, and the particles The coercive force is maximized when the diameter is around 100 nm, but when the particle size is about 20 nm or less, a supernormal magnetic phenomenon occurs and the holding power becomes extremely small. Therefore, in a powder magnetic core using magnetic nanoparticles having a particle size of about 20 nm or less, it is considered that the hysteresis loss can be extremely reduced. Further, in a powder magnetic core using insulating magnetic nanoparticles or conductive magnetic nanoparticles having an insulating coating on the surface, by using magnetic nanoparticles having a particle size of about 300 nm or less, an eddy current path at a high frequency is used. Is limited, and it is considered that the eddy current loss can be reduced. In particular, it is considered that the eddy current loss can be extremely reduced by using magnetic nanoparticles having a particle size of about 20 nm or less. As described above, the dust core using magnetic nanoparticles having a particle size of about 20 nm or less is expected as a transcore material for power supply use because the hysteresis loss and the eddy current loss are extremely small.

JP-A-2009-57586

However, in the conventional dust core using magnetic microparticles, the magnetic microparticles are greatly deformed by pressure molding and the particles are intricately entangled with each other, so that the mechanical strength is improved, but the pressure using magnetic nanoparticles is improved. In the powder magnetic core, since the deformation of the magnetic nanoparticles due to pressure molding is small, the particles are difficult to entangle with each other, and the contact area between the magnetic nanoparticles is also small, so that it is difficult to sufficiently improve the mechanical strength. ..

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide a high-density and high-strength powder magnetic core containing magnetic nanoparticles.

As a result of diligent research to achieve the above object, the present inventors have made magnetic nanoparticles into at least one thermosetting resin selected from the group consisting of phenol resin and epoxy resin, and has 12 to 30 carbon atoms. It has been found that a high-density and high-strength dust core containing magnetic nanoparticles can be obtained by compression molding by adding the above-mentioned fatty acid, and the present invention has been completed.

That is, the dust core of the present invention contains magnetic nanoparticles having an average particle size of 1 to 300 nm, at least one thermosetting resin selected from the group consisting of phenol resin and epoxy resin, and having 12 to 12 carbon atoms. It is characterized by containing 30 fatty acids. In such a dust core, the thermosetting resin is preferably a phenol resin, and the thermosetting property is obtained with respect to the total amount of the magnetic nanoparticles, the thermosetting resin, and the fatty acid. The resin content is 0.01 to 4.99% by mass, the fatty acid content is 0.01 to 4.99% by mass, and the total amount of the thermosetting resin and the fatty acid is 0. It is preferably 02 to 5% by mass.

The magnetic nanoparticles are contained by adding at least one thermosetting resin selected from the group consisting of a phenol resin and an epoxy resin and a fatty acid having 12 to 30 carbon atoms to the magnetic nanoparticles. The reason why a high-density and high-strength dust core can be obtained is not always clear, but the present inventors speculate as follows. That is, when at least one thermosetting resin selected from the group consisting of phenol resin and epoxy resin is added to the magnetic nanoparticles, the density and strength of the compression molded product are improved. However, since the phenol resin and the epoxy resin do not have a sufficiently high affinity with the magnetic nanoparticles, it is difficult to mix them uniformly, and the fluidity of the magnetic nanoparticles during compression molding is not sufficiently improved. Therefore, the density and strength of the dust core containing the magnetic nanoparticles are not sufficiently improved. On the other hand, when the thermosetting resin and the fatty acid having 12 to 30 carbon atoms are added to the magnetic nanoparticles, the density and strength of the dust core containing the magnetic nanoparticles are sufficiently improved. The reason for this can be inferred as follows. That is, since the carboxy group of the fatty acid is easily adsorbed on the magnetic nanoparticles, the magneticity is caused by the synergistic effect of the adsorbed hydrocarbon chain of the fatty acid and the hydrocarbon chain of the free fatty acid existing between the magnetic nanoparticles. It is presumed that the lubricity of the nanoparticles is improved and the fluidity of the magnetic nanoparticles is improved. Further, it is presumed that the adsorbed hydrocarbon chain of the fatty acid improves the affinity and binding force between the thermosetting resin and the magnetic nanoparticles by the action of the fatty acid as a coupling agent. Due to the high fluidity of the magnetic nanoparticles and the high affinity between the thermosetting resin and the magnetic nanoparticles, the density of the dust core containing the magnetic nanoparticles is increased. It is inferred that. Further, it is presumed that the high strength of the thermosetting resin and the high bonding force between the thermosetting resin and the magnetic nanoparticles increase the strength of the powder magnetic core containing the magnetic nanoparticles. To.

According to the present invention, it is possible to obtain a high-density and high-strength dust core containing magnetic nanoparticles.

It is a graph which shows the density of the dust core obtained in Examples 1 to 4 and Comparative Examples 1 to 4, 6 to 10. It is a graph which shows the crack rate of the dust core obtained in Examples 1 to 4 and Comparative Examples 1 to 4, 6 to 10.

Hereinafter, the present invention will be described in detail according to its preferred embodiment.

The dust core of the present invention comprises magnetic nanoparticles having an average particle size of 1 to 300 nm, at least one thermosetting resin selected from the group consisting of phenol resin and epoxy resin, and having 12 to 30 carbon atoms. It contains a fatty acid.

The magnetic nanoparticles used in the present invention are not particularly limited as long as they are used for dust cores, and examples thereof include Fe nanoparticles, Fe-containing alloy nanoparticles, and Fe-containing metal oxide nanoparticles. Further, the Fe nanoparticles and the Fe-containing alloy nanoparticles may be provided with an insulating layer on the surface. These magnetic nanoparticles may be used alone or in combination of two or more. Among these, Fe nanoparticles having an insulating layer on the surface, from the viewpoints of being able to reduce hysteresis loss and eddy current loss, relatively increasing the saturation magnetic flux density, and relatively little deterioration of characteristics at high temperatures, are used on the surface. Fe-containing alloy nanoparticles provided with an insulating layer are preferred.

The Fe-containing alloy nanoparticles are not particularly limited as long as they are used for dust cores, and are, for example, FeNi alloy nanoparticles (Permalloy B nanoparticles, etc.), FeSi alloy nanoparticles (silicon steel nanoparticles, etc.), and the like. Examples thereof include FeCo alloy nanoparticles (permenzur nanoparticles and the like) and NiFe alloy nanoparticles (permalloy C nanoparticles and the like). The Fe-containing metal oxide nanoparticles are not particularly limited as long as they are used for dust cores, and examples thereof include ferrite nanoparticles such as NiZn ferrite nanoparticles and MnZn ferrite nanoparticles.

The insulating layer includes, for example, an insulating layer made of a metal oxide such as SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ , Fe ₃ O ₄ , NiZn ferrite, MnZn ferrite; and fatty acids (for example, decanoic acid and lauric acid). , Stearic acid, oleic acid, linolenic acid), an insulating layer composed of organic compounds such as silicone-based organic compounds (for example, methyl silicone resin, methylphenyl silicone resin, dimethylpolysiloxane, silicone hydrogel); phosphorus-based compounds (for example, An insulating layer made of an inorganic compound such as calcium phosphate, iron phosphate, zinc phosphate, manganese phosphate) can be mentioned.

The average particle size of the magnetic nanoparticles used in the present invention is 1 to 300 nm. When the average particle size of the magnetic nanoparticles is less than the lower limit, the influence of the particle surface is large and the magnetic properties of the magnetic nanoparticles themselves are deteriorated. On the other hand, when the average particle size of the magnetic nanoparticles exceeds the upper limit, the eddy current loss increases and the magnetic core loss increases. In addition, the superparamagnetic phenomenon occurs and the coercive force becomes extremely small, making it possible to make the hysteresis loss extremely small, and the path of the eddy current is restricted at high frequencies, making it possible to make the eddy current loss extremely small. From the viewpoint of the above, the average particle size of the magnetic nanoparticles is preferably 1 to 100 nm, more preferably 1 to 20 nm. The average particle size of the magnetic nanoparticles can be obtained as an average value obtained by measuring the particle size of 100 particles in TEM observation.

The thermosetting resin used in the present invention is at least one selected from the group consisting of phenol resin and epoxy resin. By adding such a thermosetting resin to the magnetic nanoparticles in combination with a fatty acid having 12 to 30 carbon atoms, which will be described later, the affinity and bonding strength between the thermosetting resin and the magnetic nanoparticles can be improved. It is possible to improve and obtain a high-density and high-strength dust core. Further, among these thermosetting resins, a phenol resin is preferable from the viewpoint of further improving the density and strength of the dust core.

On the other hand, when a polyimide resin, an acrylic resin or a silicone resin is used instead of the phenol resin and the epoxy resin, the density and strength of the dust core are not sufficiently improved.

The content of the thermosetting resin is not particularly limited, but is preferably 0.01 to 5% by mass, preferably 0.01 to 5% by mass, based on the total amount of the magnetic nanoparticles, the thermosetting resin, and the fatty acid described later. 1 to 2% by mass is more preferable, and 0.1 to 1% by mass is particularly preferable. When the content of the thermosetting resin is less than the lower limit, the thermosetting resin does not sufficiently spread among the magnetic nanoparticles, so that the strength of the dust core tends to be difficult to improve, while the upper limit is mentioned. If it exceeds, the proportion of non-magnetic components increases, and the magnetic properties of the dust core tend to decrease.

The fatty acid used in the present invention is a fatty acid having 12 to 30 carbon atoms. By adding such a fatty acid to the magnetic nanoparticles in combination with the thermosetting resin, the affinity and binding force between the thermosetting resin and the magnetic nanoparticles are improved, and the density and strength are high. Powder magnetic core can be obtained. Further, such fatty acids may be saturated fatty acids or unsaturated fatty acids, and these may be used in combination.

Examples of the saturated fatty acids include lauric acid (12 carbon atoms), melissic acid (14 carbon atoms), pentadecylic acid (15 carbon atoms), palmitic acid (16 carbon atoms), margaric acid (17 carbon atoms), and stearic acid (carbon atoms). Number 18), arachidic acid (20 carbons), henicosylic acid (21 carbons), bechenic acid (22 carbons), lignoceric acid (24 carbons), cerotic acid (26 carbons), montanic acid (28 carbons) ), Melissic acid (30 carbon atoms). These saturated fatty acids may be used alone or in combination of two or more.

As the unsaturated fatty acid, myristoleic acid (14 carbons, 1 double bond), palmitreic acid (16 carbons, 1 double bond), sapienoic acid (16 carbons, 1 double bond), olein. Acid (18 carbons, 1 double bond), Elaidic acid (18 carbons, 1 double bond), Baxenoic acid (18 carbons, 1 double bond), Gadrain acid (20 carbons, double bond) Number of bonds 1), eicosenoic acid (20 carbons, 1 double bond), erucic acid (22 carbons, 1 double bond), nervonic acid (24 carbons, 1 double bond), linoleic acid (24 carbons, 1 double bond) 18 carbons, 2 double bonds), eikosazienoic acid (20 carbons, 2 double bonds), docosazienoic acid (22 carbons, 2 double bonds), linolenic acid (18 carbons, 2 double bonds) 3), pinolenic acid (18 carbons, 3 double bonds), eleostearic acid (18 carbons, 3 double bonds), meadic acid (20 carbons, 3 double bonds), dihomo-γ -Linolenic acid (20 carbons, 3 double bonds), Eikosatrienic acid (20 carbons, 3 double bonds), stearidonic acid (18 carbons, 4 double bonds), arachidonic acid (20 carbons) 20, double bond number 4), eikosatetraenoic acid (carbon number 20, double bond number 4), adrenoic acid (carbon number 22, double bond number 4), boseopentaenoic acid (carbon number 18, double bond number) Number 5), Eikosapentaenoic acid (20 carbons, 5 double bonds), Osbondic acid (22 carbons, 5 double bonds), Iwashicic acid (22 carbons, 5 double bonds), Tetracosapenta Examples thereof include enoic acid (24 carbon atoms, 5 double bonds), docosahexaenoic acid (22 carbon atoms, 6 double bonds), and heric acid (24 carbon atoms, 6 double bonds). These unsaturated fatty acids may be used alone or in combination of two or more.

On the other hand, when a fatty acid having 11 or less carbon atoms, a metal salt of a fatty acid, a fatty acid ester or a fatty acid amide is added to the magnetic nanoparticles, the density and strength of the dust core are not sufficiently improved.

Among the fatty acids, from the viewpoint of improving the fluidity of the magnetic nanoparticles and improving the density of the dust core, the entanglement with the thermosetting resin is increased, and the strength of the dust core is improved. From the viewpoint, those having 12 to 20 carbon atoms are preferable, and those having 15 to 20 carbon atoms are more preferable.

The fatty acid may be linear or branched, but from the viewpoint of improving the fluidity of the magnetic nanoparticles and improving the density of the dust core, the fatty acid may be linear or branched. A linear one is preferable, while a branched one is preferable from the viewpoint of increasing entanglement with the thermosetting resin and improving the strength of the dust core. Therefore, from the viewpoint that the density and strength of the dust core can be improved in a well-balanced manner, it is preferable to use a linear fatty acid and a branched fatty acid in combination.

Further, the unsaturated fatty acid preferably has two or more carbon-carbon double bonds from the viewpoint of relaxing stress during compression molding and suppressing the occurrence of cracks, and carbon-carbon double bonds. It is more preferable that the number of bonds is 3 or more.

The content of the fatty acid is not particularly limited, but is preferably 0.01 to 5% by mass, preferably 0.1 to 2% by mass, based on the total amount of the magnetic nanoparticles, the thermosetting resin, and the fatty acid. % Is more preferable, and 0.1 to 1% by mass is particularly preferable. When the content of the fatty acid is less than the lower limit, the fatty acid does not sufficiently spread among the magnetic nanoparticles, so that the fluidity of the magnetic nanoparticles in that portion becomes low and the density of the dust core tends to be difficult to improve. On the other hand, when the upper limit is exceeded, the proportion of non-magnetic components increases, and the magnetic properties of the dust core tend to decrease.

The content of the fatty acid is the amount of free fatty acid existing between the magnetic nanoparticles, and does not include the amount of fatty acid in which the surface of the magnetic nanoparticles is preliminarily modified. Since the hydrocarbon chain of the fatty acid having the surface of the magnetic nanoparticles preliminarily modified extends in the direction perpendicular to the surface of the magnetic nanoparticles, it also extends perpendicular to the sliding direction. The improvement of the fluidity of the magnetic nanoparticles is limited. On the other hand, if free fatty acids are present between the magnetic nanoparticles in addition to the fatty acids that pre-modify the surface of the magnetic nanoparticles, the free fatty acids are arranged parallel to the sliding direction. Therefore, the fluidity of the magnetic nanoparticles is greatly improved.

The total amount of the thermosetting resin and the fatty acid is 0.02 to 5% by mass (in this case, the said) with respect to the total amount of the magnetic nanoparticles, the thermosetting resin and the fatty acid. The content of the thermosetting resin is 0.01 to 4.99% by mass, and the content of the fatty acid is preferably 0.01 to 4.99% by mass), preferably 0.1 to 2% by mass (this). In this case, the content of the thermosetting resin is 0.1 to 1.9% by mass, and the content of the fatty acid is 0.1 to 1.9% by mass), more preferably 0.1 to 1%. Mass% (in this case, the content of the thermosetting resin is 0.1 to 0.9% by mass and the content of the fatty acid is 0.1 to 0.9% by mass) is particularly preferable. When the total amount of the thermosetting resin and the fatty acid is less than the lower limit, the thermosetting resin and the fatty acid are not sufficiently distributed between the magnetic nanoparticles, so that the density and strength of the dust core are improved. On the other hand, when the upper limit is exceeded, the proportion of non-magnetic components tends to increase, and the magnetic properties of the dust core tend to decrease.

The ratio of the fatty acid to the total amount of the thermosetting resin and the fatty acid is not particularly limited, but is preferably 0.1 to 90% by mass, more preferably 1 to 50% by mass, and 20 to 50% by mass. % Is particularly preferable. When the ratio of the fatty acid is less than the lower limit, the strength of the dust core tends to be difficult to improve, while when the ratio exceeds the upper limit, the fluidity of the magnetic nanoparticles is lowered and the density of the dust core is improved. It tends to be difficult.

The density of the dust core of the present invention is 6.3 g / cm ³ or more, and has a high relative magnetic permeability. Further, from the viewpoint of having a higher relative magnetic permeability, the density of the dust core is preferably 6.5 g / cm ³ or more.

The method for producing the dust core of the present invention is not particularly limited as long as the magnetic nanoparticles, the thermosetting resin, and the fatty acid can be uniformly mixed. For example, the following method is used. The dust core of the present invention can be produced. That is, first, the magnetic nanoparticles and the fatty acid are mixed so as to have a predetermined content. The method for mixing the magnetic nanoparticles and the fatty acid is not particularly limited, and for example, a method of mixing using a ball mill or a dairy pot, a method of dispersing and dissolving the magnetic nanoparticles and the fatty acid in a solvent, and then drying and the like. Examples thereof include a method of mixing by removing the solvent.

Next, the thermosetting resin is mixed with the mixture of the magnetic nanoparticles and the fatty acid thus prepared so as to have a predetermined content. The method of mixing the mixture and the thermosetting resin is not particularly limited. For example, a method of mixing using a ball mill or a dairy bowl, after dispersing and dissolving the mixture and the thermosetting resin in a solvent, Examples thereof include a method of mixing by removing the solvent by drying or the like.

In the method for producing a dust core of the present invention, the mixing order of the magnetic nanoparticles, the thermosetting resin, and the fatty acid is not particularly limited, and the magnetic nanoparticles and the fatty acid are mixed as in the above method. After mixing, the thermosetting resin may be mixed, or the thermosetting resin and the fatty acid may be mixed, and then the magnetic nanoparticles may be mixed.

Since the mixture of the magnetic nanoparticles, the thermosetting resin, and the fatty acid prepared in this manner has high uniformity, the fluidity of the magnetic nanoparticles is ensured in the pressure molding described later, and the density and high density are high. It is possible to obtain a strong dust core.

Further, since the magnetic nanoparticles are inferior in rearrangement property, a mixture of the magnetic nanoparticles, the thermosetting resin and the fatty acid is dispersed and dissolved in a solvent, and then a granular mixture is prepared by spray drying or the like. You may. As a result, the granular mixture collapses during compression molding, and the magnetic nanoparticles are easily rearranged, so that the density of the dust core is improved.

Next, the mixture of the magnetic nanoparticles, the thermosetting resin, and the fatty acid thus obtained is filled in a mold coated with a lubricant. The lubricant is not particularly limited, and examples thereof include metal salts of saturated fatty acids such as lithium stearate and zinc stearate, and lubricating greases (for example, "M-HGSSC-H500" manufactured by Misumi Co., Ltd.).

Next, the dust core of the present invention can be obtained by pressure molding a mixture of the magnetic nanoparticles, the thermosetting resin, and the fatty acid packed in a mold. The molding temperature is not particularly limited, but is usually room temperature to 200 ° C., and from the viewpoint of ensuring the fluidity of the magnetic nanoparticles, a temperature equal to or higher than the melting point of the thermosetting resin and the fatty acid is preferable. When a metal salt of saturated fatty acid is applied to the mold as a lubricant, it is preferably pressure-molded at a temperature of 150 ° C. or higher. The molding pressure is preferably 700 MPa to 3 GPa, more preferably 1 GPa to 2 GPa. When the forming pressure is less than the lower limit, the mixture is not sufficiently compressed, so that the density of the dust core tends to decrease. On the other hand, when the molding pressure exceeds the upper limit, the effect of the springback phenomenon is large, and the powder magnetic core is affected. The density tends to decrease. In addition, the life of the mold tends to be shortened.

Further, the dust core produced in this manner may be heat-treated if necessary. As a result, the strain generated in the dust core due to pressurization can be alleviated and the magnetic characteristics can be improved. The temperature of such heat treatment is usually 500 to 800 ° C.

Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

(Example 1)
4.925 g of FeNi alloy nanoparticles (manufactured by Aldrich) having an average particle size of 100 nm as magnetic nanoparticles and 0.025 g of lauric acid (manufactured by Wako Pure Chemical Industries, Ltd., 12 carbon atoms) which is a saturated fatty acid as a fatty acid are mixed. Further, the mixture was crushed and mixed in a dairy pot for 30 minutes. Next, as a thermosetting resin, a phenol resin adhesive (“110” manufactured by Cemedine Co., Ltd.) was weighed so that the resin component was 0.05 g, and this was dissolved in 10 ml of 2-methoxyethanol. A mixture of the FeNi alloy nanoparticles and lauric acid was added to the obtained solution, and the mixture was stirred using a rotation / revolution mixer. The obtained paste was vacuum dried at room temperature to remove the solvent, and then crushed and mixed in an air mortar for 30 minutes. The obtained crushed mixture was filled into a die for pellet test pieces coated with grease (“M-HGSSC-H500” manufactured by Misumi Co., Ltd.), and a manual heating press machine (“IMC-1946” manufactured by Imoto Seisakusho Co., Ltd. was modified. ”) And heating at 180 ° C. for 20 minutes while pressurizing to 1.4 GPa. After stopping the pressurization, the mixture was cooled to room temperature, and the obtained magnetic nanoparticle molded body (powder magnetic core pellet (outer diameter 3 mmφ)) was taken out from the mold. The densities of the obtained molded products are shown in Table 1 and FIG.

(Example 2)
Magnetic nanoparticles molded product in the same manner as in Example 1 except that 0.05 g of epoxy resin varnish (“Epiform R2400” manufactured by Somer Co., Ltd. and diaminodiphenylmethane added as a curing agent) was used as a thermosetting resin. (Powder magnetic core pellet (outer diameter 3 mmφ)) was prepared. The densities of the obtained molded products are shown in Table 1 and FIG.

(Example 3)
Magnetic nanoparticle compact (dust magnetic core pellet (outer diameter 3 mmφ)) in the same manner as in Example 1 except that 0.025 g of lignoceric acid (manufactured by Tokyo Chemical Industry Co., Ltd., 24 carbon atoms), which is a saturated fatty acid, was used as the fatty acid. ) Was prepared. The densities of the obtained molded products are shown in Table 1 and FIG.

(Example 4)
Magnetic nanoparticle molded body (dust magnetic core pellet (outer diameter 3 mmφ)) in the same manner as in Example 1 except that 0.025 g of linolenic acid (manufactured by Nacalai Tesque, Inc., 18 carbon atoms), which is an unsaturated fatty acid, was used as the fatty acid. ) Was prepared. The densities of the obtained molded products are shown in Table 1 and FIG.

(Comparative Example 1)
A magnetic nanoparticle molded product (powdered magnetic core pellet (outer diameter 3 mmφ)) was prepared in the same manner as in Example 1 except that the fatty acid and the thermosetting resin were not mixed. The densities of the obtained molded products are shown in Table 1 and FIG.

(Comparative Example 2)
A magnetic nanoparticle molded product (compact magnetic core pellet (outer diameter 3 mmφ)) was prepared in the same manner as in Example 1 except that the fatty acid was not mixed. The densities of the obtained molded products are shown in Table 1 and FIG.

(Comparative Example 3)
A magnetic nanoparticle molded product (compact magnetic core pellet (outer diameter 3 mmφ)) was prepared in the same manner as in Example 2 except that the fatty acid was not mixed. The densities of the obtained molded products are shown in Table 1 and FIG.

(Comparative Example 4)
A magnetic nanoparticle molded body (powder magnetic core pellet (outer diameter 3 mmφ)) was prepared in the same manner as in Example 1 except that 0.025 g of capric acid (manufactured by Wako Pure Chemical Industries, Ltd., 10 carbon atoms) was used as the fatty acid. did. The densities of the obtained molded products are shown in Table 1 and FIG.

(Comparative Example 5)
A magnetic nanoparticle compact was prepared in the same manner as in Example 1 except that 0.025 g of ethylene bisstearic acid amide (manufactured by Wako Pure Chemical Industries, Ltd., 38 carbon atoms), which is a saturated fatty acid amide, was used instead of the fatty acid. However, the density could not be measured because the magnetic nanoparticle molded body cracked when it was taken out from the mold.

(Comparative Example 6)
Magnetic nanoparticle molded body (powder magnetic core) in the same manner as in Example 1 except that 0.025 g of glycerol monostearate (manufactured by Wako Pure Chemical Industries, Ltd., 21 carbon atoms) which is a saturated fatty acid ester was used instead of fatty acid. Pellets (outer diameter 3 mmφ)) were prepared. The densities of the obtained molded products are shown in Table 1 and FIG.

(Comparative Example 7)
Magnetic nanoparticle compact (dust magnetic core) in the same manner as in Example 1 except that 0.025 g of zinc laurate (manufactured by Wako Pure Chemical Industries, Ltd., 12 carbon atoms), which is a saturated fatty acid metal salt, was used instead of the fatty acid. Pellets (outer diameter 3 mmφ)) were prepared. The densities of the obtained molded products are shown in Table 1 and FIG.

(Comparative Example 8)
Magnetic nanoparticle molded body (dust magnetic core pellet (outer powder magnetic core pellet (outside)) in the same manner as in Example 1 except that 0.05 g of polyimide resin varnish (“SPIXAREA” manufactured by Somer Co., Ltd.) was used as a resin component instead of the phenol resin adhesive. A diameter of 3 mmφ)) was produced. The densities of the obtained molded products are shown in Table 1 and FIG.

(Comparative Example 9)
A magnetic nanoparticles molded product (in the same manner as in Example 1) except that 0.05 g of an acrylic resin adhesive (“WORLD ROCK” manufactured by Kyoritsu Chemical Industry Co., Ltd.) was used as a resin component instead of the phenol resin adhesive. Phenol formaldehyde pellets (outer diameter 3 mmφ)) were prepared. The densities of the obtained molded products are shown in Table 1 and FIG.

(Comparative Example 10)
Magnetic nanoparticle molded body (compact magnetic core) in the same manner as in Example 1 except that 0.05 g of a silicone resin adhesive (“Super X” manufactured by Cemedine Co., Ltd.) was used as a resin component instead of the phenol resin adhesive. Pellets (outer diameter 3 mmφ)) were prepared. The densities of the obtained molded products are shown in Table 1 and FIG.

<Crack rate>
The dust core pellets obtained in Examples 1 to 4 and Comparative Examples 1 to 4, 6 to 9 are cut and polished on a plane parallel to the longitudinal direction of the pellet, and the cross section thereof is observed using a scanning electron microscope. did. The length of the crack was measured in the image acquired at a magnification of 50 times, and the value obtained by dividing the length of the crack by the area of the observed cross section was obtained as the crack ratio (unit: cm / cm ² ). This measurement was performed at 4 points for one pellet, and the average value was calculated. The results are shown in Table 1 and FIG. Since the magnetic nanoparticle molded product obtained in Comparative Example 5 cracked when it was taken out from the mold, the crack ratio could not be measured.

As shown in Table 1 and FIG. 1, the magnetic nanoparticles and the phenol resin (Comparative Example 2) or the epoxy resin (Comparative Example 3) were mixed as compared with the case consisting of only the magnetic nanoparticles (Comparative Example 1). In some cases, the density of the dust core becomes high, and when the saturated or unsaturated fatty acids of carbons 12 to 24 are further mixed (Examples 1 to 4), the density of the dust core becomes higher (6). .3 g / cm ³ or more) was found. Further, it was found that when the phenol resin was mixed (Example 1), a higher density dust core was obtained as compared with the case where the epoxy resin was mixed (Example 2). On the other hand, when the magnetic nanoparticles and the saturated fatty acid having 10 carbon atoms (Comparative Example 4), the saturated fatty acid ester (Comparative Example 6) or the saturated fatty acid metal salt (Comparative Example 7) and the phenol resin are mixed, the magnetic nanoparticles The density of the dust core was higher than that of the case consisting of only (Comparative Example 1), but it was less than 6.3 g / cm ³ , and the magnetic nanoparticles and the saturated or unsaturated fatty acids of carbons 12 to 24 were used. It was lower than that when the phenol resin or the epoxy resin was mixed (Examples 1 to 4). Further, when the magnetic nanoparticles, the saturated fatty acid having 12 carbon atoms, and the polyimide resin (Comparative Example 8), the acrylic resin (Comparative Example 9), or the silicone resin (Comparative Example 10) are mixed, the density of the dust core becomes high. It was equal to or higher than the case consisting of only magnetic nanoparticles (Comparative Example 1), but less than 6.3 g / cm ³ , and the magnetic nanoparticles and saturated or unsaturated fatty acids of carbons 12 to 24 and phenol resin or It was lower than that when mixed with the epoxy resin (Examples 1 to 4). From these results, it was confirmed that the density of the dust core was further improved by blending the magnetic nanoparticles with the fatty acid having 12 to 30 carbon atoms and the phenol resin or the epoxy resin.

Further, as shown in Table 1 and FIG. 2, the magnetic nanoparticles and the phenol resin (Comparative Example 2) or the epoxy resin (Comparative Example 3) are compared with the case where only the magnetic nanoparticles are composed (Comparative Example 1). When mixed, the crack ratio of the dust core becomes smaller, and when the saturated or unsaturated fatty acids of carbons 12 to 24 are further mixed (Examples 1 to 4), the crack ratio of the dust core further increases. It turned out to be smaller. Further, it was found that when the phenol resin was mixed (Example 1), the crack rate of the dust core was smaller than that when the epoxy resin was mixed (Example 2). On the other hand, when the magnetic nanoparticles and the saturated fatty acid having 10 carbon atoms (Comparative Example 4), the saturated fatty acid ester (Comparative Example 6) or the saturated fatty acid metal salt (Comparative Example 7) and the phenol resin are mixed, the magnetic nanoparticles The crack rate of the dust core was smaller than that of the case consisting of only (Comparative Example 1), but the magnetic nanoparticles, saturated or unsaturated fatty acids of carbons 12 to 24, and phenol resin or epoxy resin were mixed. It was higher than the case (Examples 1 to 4). Further, when the magnetic nanoparticles, the saturated fatty acid having 12 carbon atoms and the polyimide resin are mixed (Comparative Example 8), the crack ratio of the dust core is higher than that in the case of containing only the magnetic nanoparticles (Comparative Example 1). Has become higher. Further, when the magnetic nanoparticles, the saturated fatty acid having 12 carbon atoms and the acrylic resin (Comparative Example 9) or the silicone resin (Comparative Example 10) are mixed, the crack ratio of the dust core consists only of the magnetic nanoparticles. It was equal to or less than that of (Comparative Example 1), but compared with the case where magnetic nanoparticles, saturated or unsaturated fatty acids having 12 to 24 carbons and a phenol resin or epoxy resin were mixed (Examples 1 to 4). It got higher. From these results, it was found that the crack rate of the dust core was further reduced by blending the magnetic nanoparticles with a fatty acid having 12 to 30 carbon atoms and a phenol resin or an epoxy resin. Therefore, it was confirmed that the dust core of the present invention has a high strength because cracks occur when the strength of the molded body is smaller than the force for alleviating the molding strain.

As described above, according to the present invention, it is possible to obtain a high-density and high-strength dust core containing magnetic nanoparticles. Therefore, the dust core of the present invention has a high relative permeability and a small hysteresis loss and eddy current loss. Therefore, a transformer, an electric motor, a generator, a speaker, an induction heater, various actuators, etc. It is useful as a core material for products that utilize electromagnetic currents.

Claims (3)

It is characterized by containing magnetic nanoparticles having an average particle size of 1 to 300 nm, at least one thermosetting resin selected from the group consisting of phenol resin and epoxy resin, and fatty acids having 12 to 30 carbon atoms. Powder magnetic core. The dust core according to claim 1, wherein the thermosetting resin is a phenol resin. The content of the thermosetting resin is 0.01 to 4.99% by mass with respect to the total amount of the magnetic nanoparticles, the thermosetting resin and the fatty acid, and the content of the fatty acid is 0. The dust core according to claim 1 or 2, wherein the amount is 01 to 4.99% by mass, and the total amount of the thermosetting resin and the fatty acid is 0.02 to 5% by mass.