WO2019159799A1

WO2019159799A1 - Composite particle, powder, resin composition, and molded article

Info

Publication number: WO2019159799A1
Application number: PCT/JP2019/004303
Authority: WO
Inventors: 康二安賀; 一隆石井
Original assignee: パウダーテック株式会社
Priority date: 2018-02-13
Filing date: 2019-02-06
Publication date: 2019-08-22
Also published as: TW201935491A; JPWO2019159799A1; TWI814778B

Abstract

The present invention provides a composite particle comprising: a mother particle composed of Mn ferrite and a covering layer composed of a material including at least one selected from the group consisting of Au, Ag, Pt, Ni, and Pd; a powder characterized by comprising a plurality of the composite particles; a resin composition characterized by comprising the powder and the resin material; and a molded article characterized by being produced using a material containing the powder and the resin material.

Description

Composite particles, powder, resin composition and molded body

The present invention relates to composite particles, powder, a resin composition, and a molded body.

With recent downsizing and weight reduction of electronic devices (for example, smartphones), electronic components (including modules, substrates, etc.) mounted on electronic devices are also reduced in size and high density. It is often mounted inside the body and operated at a high frequency.

By being mounted in a high density in the housing, the electronic components are close to each other and are easily affected by electromagnetic noise generated from the electronic circuit, and the heat generated from the electronic components is difficult to escape. Therefore, an electronic component that operates at a higher temperature and a material that can suppress electromagnetic noise are desired. Furthermore, electric vehicles and hybrid vehicles are also being electrically equipped, and there is a need for noise suppression materials around parts that operate at high temperatures for a long time.

It is known to use silver powder as an electromagnetic shielding material (see, for example, Patent Document 1).
However, when silver powder is used, there is a problem that sufficient shielding properties against electromagnetic waves cannot be obtained.

Japanese Unexamined Patent Publication No. 2016-076444

An object of the present invention is to provide composite particles and powder excellent in electromagnetic wave shielding properties, to provide a molded body excellent in electromagnetic wave shielding properties, and a resin composition that can be suitably used for producing the molded body. To provide things.

Such an object is achieved by the present invention described below.

[1]
Mother particles composed of Mn ferrite;
A composite particle comprising: a coating layer made of a material containing at least one selected from the group consisting of Au, Ag, Pt, Ni, and Pd.

[2]
The Mn ferrite has a composition in which the Mn content is 3.5% by mass or more and 20.0% by mass or less, and the Fe content is 50.0% by mass or more and 70.0% by mass or less [1]. The composite particles according to 1.

[3]
The composite particle according to [1] or [2], in which the Curie point of the Mn ferrite is 200 ° C. or higher and 500 ° C. or lower.

[4]
The composite particle according to any one of [1] to [3], wherein the coating layer has a thickness of 10 nm to 500 nm.
[5]
The composite particle according to any one of [1] to [4], wherein the mother particle has a true spherical shape.

[6]
A powder comprising a plurality of composite particles according to any one of [1] to [5].
[7]
The powder according to [6], wherein the composite particles have a volume average particle diameter of 1.0 μm or more and 20 μm or less.

[8]
[6] A resin composition comprising the powder according to [7] and a resin material.
[9]
A molded article produced using a material containing the powder according to [6] or [7] and a resin material.

According to the present invention, it is possible to provide composite particles and powder excellent in electromagnetic wave shielding properties, to provide a molded body excellent in electromagnetic wave shielding properties, and a resin composition that can be suitably used for producing the molded body. Things can be provided.

2 is a cross-sectional SEM image of the composite particles of Example 1. FIG. 3 is a cross-sectional SEM image of the composite particles of Example 2. 6 is a cross-sectional SEM image of the composite particles of Example 3. It is a graph which shows the evaluation result of the electromagnetic wave shielding effect by KEC method.

Hereinafter, preferred embodiments of the present invention will be described in detail.
<Composite particles and powder>
First, the composite particles and powder of the present invention will be described.

The composite particle of the present invention includes a mother particle composed of Mn ferrite and a coating layer composed of a material containing at least one selected from the group consisting of Au, Ag, Pt, Ni and Pd. .

The powder of the present invention contains a plurality of the composite particles of the present invention.
Thereby, the composite particle and powder excellent in the shielding property of electromagnetic waves can be provided. Such an excellent effect can be obtained by providing the mother particles having excellent electromagnetic wave absorbability and the coating layer having excellent electromagnetic wave reflectivity so that they act synergistically.

Also, by providing the mother particles composed of Mn ferrite, the weight can be reduced compared to the case where the particles composed only of the metal material as described above are used. Therefore, for example, it can be suitably applied to mobile terminals such as mobile phones, smartphones, and tablets.

Also, the amount of expensive metal used can be suppressed, and the overall cost can be reduced.

In addition, since the mother particles are composed of Mn ferrite among various ferrites, not only is the resistance low, but the ionic radius of Mn is close to that of Fe, so that it is easily incorporated into the crystal structure regularly. Even if it is exposed to a plating solution, an acid or an alkali solution used when forming the layer, an effect that Mn is hardly eluted over a relatively long time can be obtained. Further, since the mother particles are composed of Mn ferrite, the adhesion between the mother particles and the coating layer described in detail later can be improved, and the effects of the present invention described in the present specification can be prolonged. It can be obtained stably over a period of time.

Also, the composite particles and powder can be adjusted to a color tone other than black. More specifically, by providing a coating layer composed of a material containing Au, the color tone of the composite particles and powder can be adjusted to gold. In addition, by providing a coating layer made of a material containing at least one selected from the group consisting of Ag, Pt, Ni, and Pd, the color tone of the composite particles and powder is suitably adjusted to a color tone of white to silver. be able to. Thereby, for example, not only can the color tone of the molded product containing composite particles and powder be suitably adjusted to a white to silver color tone, but also the molded product can contain a colorant (including providing a printing layer). Thereby, a molded object can be adjusted to a desired color tone.

Also, the conductivity of the composite particles, powders, and compacts containing these can be made excellent. In particular, it is mixed with resin and applied while controlling an external magnetic field during molding, and by orienting the particles along the magnetic field lines, a conductive path (path) is selectively formed in a specific direction, and a resin molded body The resistance can be anisotropic.

Also, for example, in a molded body produced using the powder of the present invention, particles (composite particles) can be suitably joined under relatively mild conditions. Thereby, the shielding property and electromagnetic strength of the electromagnetic wave about a molded object can be made compatible at a higher level.

Further, the frequency characteristics of the magnetic permeability of the composite particles can be controlled by controlling the thickness of the coating layer made of a material containing a highly conductive noble metal.

On the other hand, the above-described excellent effects cannot be obtained with particles having no structure as described above.

For example, particles that do not have a coating layer as described above (simply ferrite particles) cannot sufficiently obtain the effect of electromagnetic wave reflection as described above, and have sufficiently excellent electromagnetic wave shielding properties as a whole. It can not be. Further, when a molded body as a sintered body is produced using a composition containing powder, it is usually necessary to make the temperature higher than the Curie temperature of ferrite in order to sufficiently improve the bonding strength of the particles. For this reason, it is difficult to exhibit sufficient characteristics in the finally obtained molded body. Moreover, when the sintering process is performed at a temperature lower than the Curie temperature, the strength of the molded body becomes insufficient. Further, since the color tone of the particles is black with low brightness, it is difficult to adjust the color tone of the molded body containing the powder. In addition, the conductivity of the particles, powders, and compacts containing them cannot be made sufficiently excellent.

Even when a coating layer is provided on the surface of the Mn ferrite particles, if the constituent material of the coating layer is not as described above, the effect of reflecting electromagnetic waves as described above can be sufficiently obtained. Therefore, the shielding property of the electromagnetic wave as a whole cannot be made sufficiently excellent.

In addition, when simple metal particles (particles that do not have mother particles composed of Mn ferrite) are used, the electromagnetic wave absorption effect as described above cannot be sufficiently obtained, and the electromagnetic wave shielding property as a whole is reduced. It cannot be made good enough. In addition, the specific gravity of the whole particle increases, and it is difficult to reduce the weight of the powder and the molded body. In general, the production cost of the powder and the molded body increases.

In addition, if the mother particles are composed of other ferrites instead of Mn ferrite, the volume resistance tends to be higher than that of Mn ferrite particles, and even if a coating layer is provided, the resistance is difficult to decrease, or eddy current The electromagnetic wave shielding effect at a low frequency due to loss is reduced.

(Mother particles)
The mother particle is composed of Mn ferrite.
And Mn ferrite is generally soft ferrite.
Thereby, the permeability can be easily controlled in a wide frequency range (for example, 1 MHz to 1 GHz) by adjusting the thickness of the coating layer and the like.

In particular, the Mn ferrite constituting the mother particles has a composition in which the Mn content is from 3.5% by mass to 20.0% by mass and the Fe content is from 50.0% by mass to 70.0% by mass. It is preferable.

As a result, the volume resistance is low, and an electromagnetic wave shielding effect due to eddy current loss is easily obtained even in a low frequency region.

On the other hand, when the Mn content is less than 3.5% by mass, although depending on the manufacturing conditions, not only is it easy to oxidize but the magnetization tends to decrease, and the volume resistance increases, resulting in eddy current loss. There is a possibility that the electromagnetic wave shielding effect at a low frequency is reduced.

In addition, when the Mn content is higher than 20.0 mass%, the Fe content is relatively decreased, the volume resistance is likely to be increased, and the electromagnetic wave shielding effect at low frequencies caused by eddy current loss can be reduced. There is sex.

Further, when the Fe content is less than 50.0% by mass, the volume resistance tends to be high, and the electromagnetic wave shielding effect at low frequencies caused by eddy current loss may be reduced. .

Further, when the Fe content is larger than 70.0% by mass, although depending on the manufacturing conditions, it is easy to oxidize and the magnetization is not only easily lowered, but also the volume resistance is increased, so low frequency due to eddy current loss. There is a possibility that the electromagnetic wave shielding effect in is reduced.

In the Mn ferrite, the Mn content is preferably 3.5% by mass or more and 20.0% by mass or less, more preferably 5.0% by mass or more and 19.0% by mass or less. More preferably, it is 4 mass% or more and 18.0 mass% or less.
Thereby, the effect mentioned above is exhibited more notably.

In the Mn ferrite, the Fe content is preferably 50.0% by mass or more and 70.0% by mass or less, more preferably 51.0% by mass or more and 66.0% by mass or less, More preferably, it is 52.0 mass% or more and 65.0 mass% or less.
Thereby, the effect mentioned above is exhibited more notably.

The content of metal elements (Fe, Mn, etc.) constituting the mother particles is measured as follows.

That is, 0.2 g of mother particles were weighed, 60 ml of pure water was added with 20 ml of 1N hydrochloric acid: 20 ml and 1N nitric acid: 20 ml to prepare an aqueous solution in which ferrite particles were completely dissolved, and ICP analysis By performing measurement using an apparatus (ICPS-1000IV, manufactured by Shimadzu Corporation), the content of the metal element can be obtained.

The Mn ferrite preferably contains only Fe and Mn as metal components. From the above viewpoint, it is desirable that the content of all components (elements) other than Fe, Mn, and O contained in the Mn ferrite does not exceed the amount of impurities.
Specifically, the content of all components (elements) other than Fe, Mn, and O contained in the Mn ferrite is preferably less than 0.1% by mass, and less than 0.05% by mass. More preferably, the content is less than 0.01% by mass.

The Curie point (also referred to as Curie temperature) of the Mn ferrite constituting the mother particle is preferably 200 ° C. or higher and 500 ° C. or lower, and more preferably 250 ° C. or higher and 480 ° C. or lower.

As a result, the heat resistance of the composite particles and the molded body produced using the composite particles can be made excellent, and for example, it can be suitably applied to a molded body used in a high temperature environment.

On the other hand, if the Curie temperature is too low, the heat resistance of the composite particles or a molded body produced using the composite particles is lowered, and there is a possibility that applicable parts, members, places, and the like are limited.

Also, although the Curie temperature itself is not too high, there is no problem, but the Curie point of the ferrite is determined by the composition, and usually the above ferrite composition does not exceed 500 ° C.

The above Curie point is obtained from measurement of change in magnetization of ferrite powder due to temperature change using a vibrating sample magnetometer (VSM) (VSM-5 manufactured by Toei Kogyo Co., Ltd.). In the obtained temperature change curve of magnetization, the temperature when the tangent of the curve crosses the line where the magnetization becomes 0 from the low temperature side immediately before the magnetization becomes 0 can be set as the Curie point.

Also, ferrite can be measured for magnetic properties such as saturation magnetization, remanent magnetization, coercive force, etc. using a vibration sample type magnetometer.

The above magnetic characteristics are obtained as follows. That is, first, ferrite powder to be measured was packed in a cell having an inner diameter of 5 mm and a height of 2 mm, and set in a vibration sample type magnetometer (VSM-C7-10A manufactured by Toei Kogyo Co., Ltd.). Next, an applied magnetic field was applied, sweeped to 5 kOe, and then the applied magnetic field was reduced to create a hysteresis curve. Thereafter, the saturation magnetization, residual magnetization and coercive force of the ferrite powder were determined from the data of this curve. The powder as an aggregate of composite particles described later was obtained in the same manner.

A preferable range of the saturation magnetization of the mother particles is 70 to 95 emu / g, a preferable range of the residual magnetization is 0.5 to 10 emu / g, and a preferable range of the coercive force is 10 to 80 Oe.
The preferable range of the saturation magnetization of the powder (composite particles) as an aggregate of the composite particles is 30 to 90 emu / g, the preferable range of the residual magnetization is 0.5 to 9 emu / g, and the preferable range of the coercive force is 10 ~ 80 Oe.

The shape of the mother particle is not particularly limited, but is preferably a true sphere.
Thereby, in the molded object manufactured using the powder which concerns on this invention, the filling rate of powder can be made higher and the shielding property (absorbency, reflectivity) of electromagnetic waves can be improved more.

In this specification, the term “spherical” means a true sphere or a shape that is sufficiently close to a true sphere, and specifically means that the shape factor SF-1 is 100 or more and 120 or less.

Further, the shape factor SF-1 of the mother particles is preferably 100 or more and 120 or less, and more preferably 100 or more and 115 or less.

The shape factor SF-1 of the particles is obtained as follows.
First, using a scanning electron microscope (FE-SEM (SU-8020, manufactured by Hitachi High-Technologies Corporation)) and an energy dispersive X-ray analyzer (EDX) (E-MAX manufactured by Horiba, Ltd.), particles can be seen in one field of view. The magnification is set so that about 3 to 50 pieces are included (for example, 1000 to 2000 times in the examples and comparative examples described later), and the equivalent particle diameter, outer circumference, Automatically measure 1000 or more particles of length, width and area.

Among the obtained data, the particles clearly overlap each other (peripheral length is more than 1.8 times the perimeter calculated from the equivalent circle diameter) and fine powder (the equivalent circle diameter is less than 1 μm). (Small one) is excluded, the maximum length (horizontal ferret diameter) R of the particles and the area is the projected area S, and the value of SF-1 is calculated by the following formula. The closer the particle shape is to a spherical shape, the closer to 100.

SF-1 = (R ² / S) × (π / 4) × 100 (where R is the maximum particle length (horizontal ferret diameter) (μm), and S is Area (projection area, unit μm ² ) Is shown.)

SF-1 can be calculated as 200 or more particles per particle, and the average value can be used as the SF-1 of the powder.

The mother particle constituting the single composite particle may be composed of, for example, a single particle, or a joined body (including aggregates) of a plurality of fine particles.

(Coating layer)
The coating layer covers at least a part of the mother particles. And the coating layer is comprised with the material containing at least 1 sort (s) selected from the group which consists of Au, Ag, Pt, Ni, and Pd.

The above metal elements (Au, Ag, Pt, Ni, Pd) may be included in the coating layer as a single metal or may be included as a constituent component of the alloy.

The coating layer only needs to be made of a material containing at least one selected from the group consisting of Au, Ag, Pt, Ni, and Pd. Among them, as the constituent material of the coating layer, at least Au and Ag are used. One is preferred.

Au and Ag are composite particles having a relatively low melting point among the metals constituting the group, even when sintered at a relatively low temperature in the production of a molded body as a sintered body. They can be suitably joined together. Moreover, the frequency characteristic of the magnetic permeability of the composite particles can be more suitably controlled by controlling the thickness of the coating layer.

The sum of the content ratios of Au and Ag in the coating layer is preferably 80% by mass or more, and more preferably 90% by mass or more.
Thereby, the effects as described above are more remarkably exhibited.

The thickness of the coating layer is not particularly limited, but is preferably 10 nm or more and 500 nm or less, more preferably 10 nm or more and 400 nm or less, and further preferably 10 nm or more and 300 nm or less.

Thereby, electromagnetic waves can be reflected more effectively while suppressing the amount of metal used.
The thickness of the coating layer can be determined by the following method.
That is, after embedding the particles in a resin, cross-section processing of the particles was performed using an ion milling device, and the obtained sample for photographing was produced.
The obtained sample for photographing is photographed with FE-SEM, and the length of the scale included in the image analysis software or the image (value described), and the actual measurement value of the scale in the SEM image and the coating layer It can be calculated using an actual measurement value by a thickness ruler. As the Fe-SEM, Hitachi High-Technologies SU-8020 was used. IM-4000 manufactured by Hitachi High-Technologies was used as the ion milling device. Epoxy resin was used as the embedding resin.

When the particle diameter of the composite particles is D [μm] and the thickness of the coating layer is T [μm], it is preferable to satisfy the relationship of 0.0010 ≦ T / D ≦ 0.10, and 0.0030 ≦ T It is more preferable to satisfy the relationship of /D≦0.080, and it is even more preferable to satisfy the relationship of 0.0050 ≦ T / D ≦ 0.050.
The particle size of the composite particle is a volume average particle size. The volume average particle diameter can be measured by the method described later.

Thereby, the balance between electromagnetic wave absorption and electromagnetic wave reflection can be made more suitable, and the overall electromagnetic wave shielding effect can be made particularly excellent.

The composite particles of the present invention may have any structure as long as they include the mother particles and the coating layer as described above.

For example, the composite particle may have at least one intermediate layer between the mother particle and the coating layer.

In addition, a coating layer made of a material other than Au, Ag, Pt, Ni, and Pd may be provided on the surface of the coating layer described above. Examples of such a coating layer include a surface treatment layer using various coupling agents such as a silane coupling agent.

In addition to the coating layer (first coating layer) made of a material containing at least one selected from the group consisting of Au, Ag, Pt, Ni and Pd on the surface of the mother particle, Au, Another coating layer (second coating layer) made of a material other than Ag, Pt, Ni, and Pd may be provided.

The volume average particle size of the composite particles is preferably 1.0 μm or more and 20 μm or less, more preferably 1.5 μm or more and 18 μm or less, and further preferably 2.0 μm or more and 15 μm or less.

This makes it easy to create a state in which the gap between the particles is reduced and the magnetic substance (mother particles) are densely packed when the composite particle and the resin are mixed to form the formed body.

The volume average particle diameter is determined by the following measurement. That is, first, 10 g of powder as a sample and 80 ml of water are placed in a 100 ml beaker, and two drops of a dispersant (sodium hexametaphosphate) are added. Next, dispersion is performed using an ultrasonic homogenizer (UH-150, manufactured by SMT Co. LTD.). At this time, the output level of the ultrasonic homogenizer is set to 4, and dispersion is performed for 20 seconds. Thereafter, bubbles formed on the surface of the beaker are removed, and introduced into a laser diffraction particle size distribution measuring device (SALD-7500 nano manufactured by Shimadzu Corporation) to perform measurement. The measurement conditions at this time were pump speed 7, refractive index 1.70-0.50i, and internal ultrasonic irradiation time 30.

Composite particles in which a coating layer is formed on mother particles composed of Mn ferrite are likely to aggregate in water and may not be able to be measured with high accuracy. In that case, the volume average particle diameter can be calculated using the above-described particle image analysis data.

That is, using the particle data used when calculating SF-1 in the particle analysis result, where the equivalent circle diameter of the i-th particle is d _i and the volume of the particle is V _i , V _i = 4/3 × π × ( V _i can be calculated as d _i / 2) ^{3 and} can be calculated as volume average diameter D ₅₀ = Σ (V _i · d _i ) / Σ (V _i ).

BET specific surface area of the powder (aggregate of composite particles) of the present invention is preferably equal to or less than ^{1 m} 2 / g or more ^9m 2 / g, more preferably not more than ^{1 m} 2 / g or more ^8m 2 / g, More preferably, it is 3 m ² / g or more and 8 m ² / g or less.

Thereby, while being able to improve the shielding property of electromagnetic waves more, the adhesiveness of the composite particles and the resin material in the molded body of the present invention can be further improved, and the durability of the molded body is particularly excellent. can do.

The BET specific surface area can be determined by measurement using a specific surface area measuring device (model: Macsorb HM model-1208 (manufactured by Mountec)).

The tap density of the powder (aggregate of composite particles) of the present invention is preferably 1.8 g / cm ³ or more and 3.0 g / cm ³ or less, and 2.0 g / cm ³ or more and 3.0 g / cm ³ or less. It is more preferable that
Thereby, it becomes easy to make high the filling rate of the composite particle in the molded object of this invention.

In addition, in this specification, a tap density means the density calculated | required by the measurement based on JISR1628.
As the tapping device, a USP tap density measuring device (Powder Tester PT-X, manufactured by Hosokawa Micron) can be used.

Electrical resistivity at 25 ° C. of the powder of the present invention (volume resistivity) is preferably equal to or less than 1.0 × ^{10 -5} or more 10Ω · cm, 1.0 × ^{10 -5} or more 1.0 × 10 ^{- It} is more preferably ¹ Ω · cm or less, and further preferably 1.0 × 10 ⁻⁵ or more and 1.0 × 10 ⁻² Ω · cm or less.

The electric resistivity (volume resistivity) of the mother particles of the present invention at 25 ° C. is preferably 1 × 10 ² to 5.0 × 10 ⁸ Ω · cm, and 1 × 10 ² to 1.0 × 10 ^7. More preferably, it is Ω · cm, and further preferably 1.0 × 10 ³ to 1.0 × 10 ⁶ Ω · cm.

This makes it easier to form a conductive path when the composite particles and the resin are mixed to form a molded body (depending on the mixing ratio with the resin), and the resistance of the resin molded body is more effectively reduced. Can be lowered.

The powder of the present invention only needs to contain a plurality of the composite particles of the present invention, and may further include particles other than the composite particles of the present invention.

In such a case, the content of particles other than the composite particles of the present invention in the powder of the present invention is preferably 10% by mass or less, more preferably 5.0% by mass or less, and 1.0% More preferably, it is at most mass%.
Thereby, the effect by this invention as mentioned above is exhibited more reliably.

<< Production method of composite particles >>
Next, the manufacturing method of the composite particle which concerns on this invention is demonstrated.

The composite particles of the present invention can be produced by forming a coating layer on the surface of Mn ferrite particles produced by a predetermined method by various plating methods.

Examples of the plating method for forming the coating layer include wet plating methods such as electrolytic plating and electroless plating, and dry plating methods such as vacuum deposition, sputtering, and ion plating. The wet plating method is preferable. The electroless plating method is more preferable.

The Mn ferrite particles to be the mother particles may be produced by any method, but can be suitably produced by, for example, the method described below.

For example, the Mn ferrite particles to be the mother particles can be suitably produced by thermally spraying a ferrite raw material prepared to a predetermined composition in the air and then rapidly solidifying it (first method).
In this method, a granulated material can be suitably used as the ferrite raw material.

The method for preparing the ferrite raw material is not particularly limited, and for example, a dry method or a wet method may be used. Moreover, you may use combining a dry type and a wet type.

An example of a method for preparing a ferrite raw material (granulated product) is as follows.
That is, a plurality of kinds of raw materials containing a metal element are weighed and mixed so as to correspond to the composition of Mn ferrite particles (mother particles) to be manufactured, and then water is added to pulverize to prepare a slurry. The prepared pulverized slurry is granulated with a spray dryer and classified to prepare a granulated product having a predetermined particle size.

Another example of the method for preparing the ferrite raw material (granulated product) is as follows.
That is, a plurality of raw materials containing metal elements are weighed and mixed so as to correspond to the composition of the Mn ferrite particles (mother particles) to be manufactured, and then dry pulverized to pulverize and disperse each raw material. Granulate with a granulator and classify to prepare a granulated product with a predetermined particle size.
The granulated material prepared as described above is sprayed in the atmosphere to be ferritized.

For thermal spraying, a mixed gas of combustion gas and oxygen can be used as a combustible gas combustion flame.

The volume ratio of the combustion gas and oxygen is preferably 1: 3.5 or more and 1: 6.0 or less.
Thereby, formation of the particle | grains with a comparatively small particle size by condensation of the volatilized material can be advanced suitably. Moreover, the shape of the obtained Mn ferrite particles (base particles) can be suitably adjusted. In addition, it is possible to omit or simplify the processing such as classification in the subsequent steps, and to further improve the productivity of the Mn ferrite particles (base particles). In addition, the proportion of particles to be removed by classification in a later step can be made smaller, and the yield of Mn ferrite particles (mother particles) can be further improved.

For example, it can be used in the following proportions oxygen 35 Nm ³ hr or 60 Nm ³ hr relative to the combustion gases 10 Nm ³ hr.

Examples of the combustion gas used for thermal spraying include propane gas, propylene gas, and acetylene gas. Of these, propane gas can be preferably used.

Moreover, in order to convey a granulated material in combustible gas, nitrogen, oxygen, air etc. can be used as a granulated material conveyance gas.
The flow rate of the granulated material to be conveyed is preferably 20 m / second or more and 60 m / second or less.

The thermal spraying is preferably performed at a temperature of 1000 ° C. or more and 3500 ° C. or less, more preferably 2000 ° C. or more and 3500 ° C. or less.

By satisfying the above conditions, formation of particles having a relatively small particle diameter due to condensation of the volatilized material can be further suitably advanced. Moreover, the shape of the obtained Mn ferrite particles (base particles) can be further suitably adjusted. In addition, it is possible to omit or simplify the processing such as classification in the subsequent steps, and to further improve the productivity of the Mn ferrite particles (base particles). In addition, the proportion of particles to be removed by classification in a later step can be made smaller, and the yield of Mn ferrite particles (mother particles) can be further improved.

The particles sprayed and ferritized in this way are rapidly solidified in water or in the atmosphere and collected by a cyclone and / or a filter.

Thereafter, the Mn ferrite particles collected by the cyclone and / or the collection filter are classified as necessary. As a classification method, the particle size is adjusted to a desired particle size using an existing air classification, mesh filtration method, sedimentation method, or the like. It is also possible to separate and collect the particles having a large particle size with a cyclone or the like.

Further, the Mn ferrite particles (mother particles) can be preferably produced by the method described below (second method).

That is, the Mn ferrite particles (mother particles) are, for example, pelletized a composition containing a ferrite raw material, pre-baked to obtain a pre-fired body, and after pulverizing and classifying the pre-fired body, Can be manufactured by a method having a main baking step of baking.

Thereby, the Mn ferrite particles used for manufacturing the composite particles having the shape and size as described above can be efficiently manufactured. Further, unlike the wet granulation method using acid or alkali in the production process, it is possible to effectively prevent impurities derived from acid or alkali from remaining in the Mn ferrite particles (mother particles). Further, the durability and reliability of the composite particles and the resin composition produced using the composite particles and the molded body can be further improved.
The production of the pellet can be suitably performed by using a pressure molding machine.

The heating temperature in the preliminary firing step is not particularly limited, but is preferably 600 ° C. or more and 1200 ° C. or less, more preferably 650 ° C. or more and 1000 ° C. or less, and more preferably 700 ° C. or more and 900 ° C. or less. preferable.

Thereby, a calcination of a temporary calcination object can be performed suitably and Mn ferrite particles used for manufacture of a composite particle of the shape and size as mentioned above can be manufactured more suitably.
In the temporary firing step, two or more stages of heat treatment (firing treatment) may be performed.

In the main firing step, an irregular-shaped temporary fired body that has been pulverized and / or a sintered body that has been pulverized (fired at a higher temperature) are provided.
The volume average particle size of the temporarily fired body and / or the sintered body to be subjected to the main firing step is preferably 0.5 μm or more and 30 μm or less, and more preferably 0.5 μm or more and 20 μm or less. Alternatively, when the particle size of the irregularly shaped temporary fired body and / or sintered body is small, it is preferable to use a granulated product obtained by aggregating a plurality of particles. When using the granulated product, the amount of the binder of the granulated product may be adjusted in order to easily disperse the raw material particles in the thermal spray frame.

Thereby, the Mn ferrite particles used for manufacturing the composite particles having the shape and size as described above can be manufactured more efficiently. In addition, it is possible to omit or simplify the processing such as classification in the subsequent steps, and to further improve the productivity of the Mn ferrite particles. Moreover, the ratio of the particles to be removed by classification in the subsequent step can be reduced, and the yield of the Mn ferrite particles can be further improved.

The main firing step is preferably performed, for example, on a granulated product obtained by granulating a powder of a temporarily fired body (powder obtained by pulverization and classification).

Thereby, the Mn ferrite particles used for manufacturing the composite particles having the shape and size as described above can be manufactured more efficiently. In addition, it is possible to omit or simplify the processing such as classification in the subsequent steps, and to further improve the productivity of the Mn ferrite particles. Further, the proportion of particles to be removed by classification in the subsequent step can be made smaller, and the yield of Mn ferrite particles can be further improved.

The main firing can be suitably performed by spraying the powder of the temporarily fired body in the air.
For thermal spraying, a mixed gas of combustion gas and oxygen can be used as a combustible gas combustion flame.

The volume ratio of the combustion gas and oxygen is preferably 1: 3.5 or more and 1: 6.0 or less.
Thereby, formation of Mn ferrite particles having a relatively small particle size due to condensation of the volatilized material can be suitably advanced. In addition, the shape of the obtained Mn ferrite particles can be further suitably adjusted. In addition, it is possible to omit or simplify the processing such as classification in the subsequent steps, and to further improve the productivity of the Mn ferrite particles. Further, the proportion of particles to be removed by classification in the subsequent step can be made smaller, and the yield of Mn ferrite particles can be further improved.

By satisfying the above conditions, the formation of Mn ferrite particles having a relatively small particle size due to condensation of the volatilized material can be further promoted. In addition, the shape of the obtained Mn ferrite particles can be further suitably adjusted. In addition, it is possible to omit or simplify the processing such as classification in the subsequent steps, and to further improve the productivity of the Mn ferrite particles. Further, the proportion of particles to be removed by classification in the subsequent step can be made smaller, and the yield of Mn ferrite particles can be further improved.

Subsequently, the Mn ferrite particles formed by the main firing by thermal spraying are rapidly cooled and solidified by being carried in an air stream by air supply in the atmosphere, and then Mn ferrite particles having a predetermined particle size range are collected and recovered. .

In the collection, the rapidly solidified Mn ferrite particles are transported in an air flow by air supply, and particles having a large particle size fall in the middle of the air current transport, while other particles are transported downstream. , And a method of collecting Mn ferrite particles having a desired particle size range by a cyclone and / or a filter provided on the downstream side of the airflow.

By setting the flow velocity at the time of air flow to 20 m / second or more and 60 m / second or less, particles having a large particle size can be dropped with particularly high selectivity, and Mn ferrite particles having a predetermined particle size range can be more efficiently obtained. It can be recovered. If the flow rate is too small, even particles with a relatively small particle size will fall in the middle of the air flow conveyance, so the average particle size of the Mn ferrite particles recovered downstream of the air flow will be too small, or The absolute amount of Mn ferrite particles recovered downstream of the airflow is reduced, and productivity is reduced. On the other hand, if the flow rate is too large, even particles having a relatively large particle size are conveyed downstream, so that the average particle size of the Mn ferrite particles recovered downstream of the airflow tends to be too large.
Thereafter, the recovered Mn ferrite powder may be classified as necessary.

<Resin composition>
Next, the resin composition of the present invention will be described.

The resin composition of the present invention contains the powder of the present invention described above and a resin material.
Thereby, the resin composition which can be used suitably for manufacture of the molded object which is excellent in the shielding property of electromagnetic waves can be provided.

Examples of the resin material constituting the resin composition include epoxy resins, urethane resins, acrylic resins, silicone resins, various modified silicone resins (acrylic modified, urethane modified, epoxy modified, fluorine), polyamide resins, polyimide resins, and polyamideimides. Resins, fluorine, polyvinyl alcohol and the like can be mentioned, and one or more selected from these can be used in combination.

Moreover, the resin composition may contain components (other components) other than the powder and resin material of the present invention.

Examples of such components include solvents, fillers (organic fillers, inorganic fillers), plasticizers, antioxidants, dispersants, colorants such as pigments, heat conductive particles (particles with high heat conductivity). ) And the like.

The ratio (content ratio) of the powder of the present invention to the total solid content in the resin composition is preferably 50% by mass to 95% by mass, and more preferably 80% by mass to 95% by mass.

As a result, a molded body produced using the resin composition while having excellent dispersion stability of the powder of the present invention in the resin composition, storage stability of the resin composition, moldability of the resin composition, and the like. The mechanical strength, shielding properties of electromagnetic waves, and the like can be further improved.

The ratio (content ratio) of the resin material to the total solid content in the resin composition is preferably 5% by mass or more and 50% by mass or less, and more preferably 5% by mass or more and 20% by mass or less.

<Molded body>
Next, the molded product of the present invention will be described.
The molded body of the present invention is manufactured using a material containing the powder of the present invention and a resin material.
Thereby, the molded object which is excellent in the shielding property of electromagnetic waves can be provided.

The shaped product of the present invention may be of any use, but is preferably an electromagnetic shielding material.
Thereby, the effect by this invention as mentioned above is exhibited more notably.

The molded product of the present invention can be suitably produced using the resin composition of the present invention as described above.

Examples of the molding method of the molded body include compression molding, extrusion molding, injection molding, blow molding, calendar molding, various coating methods, and the like. The molded body may be formed by, for example, directly applying a resin composition on a member on which the molded body is to be formed, or a target member (for example, a printed wiring) after being separately manufactured. It may be installed on a substrate or a metal foil (such as a copper foil).

The powder according to the present invention may be used without mixing and dispersing in a resin or the like without performing a process such as firing. For example, the powder is molded, granulated, or coated into a desired shape. After the firing, firing may be performed (at a relatively low temperature so that the coating layer of the composite particles does not change), and the compact may be used as a sintered body.

In addition, the molded object of this invention should just contain the composite particle which concerns on this invention in the at least one part, for example, may have the area | region which does not contain a composite particle.

The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments.

For example, in the method for producing composite particles of the present invention, other steps (pretreatment step, intermediate step, post-treatment step) may be included in addition to the steps described above, if necessary.

Further, the composite particles of the present invention are not limited to those manufactured by the method as described above, and may be manufactured by any method.

In the above-described embodiment, the composite particles, powder, and resin composition of the present invention have been representatively described for use in the production of an electromagnetic shielding material. You may use for manufacture other than an electromagnetic wave shielding material. For example, the composite particles and powder of the present invention may be used as magnetic core materials or fillers (particularly magnetic fillers).

Moreover, the composite particles and powders of the present invention have a property that can be suitably detected by a metal detector.
Therefore, the composite particle, powder, resin composition and molded product of the present invention may be used for the purpose of detection with a metal detector.

In particular, according to the present invention, as described above, the composite particles and powder can be adjusted to a color tone other than black (for example, white to silver color tone). Thereby, for example, the color tone of the molded product containing composite particles and powder is adjusted to a color tone other than black (for example, white to silver color tone) corresponding to the composite particles and powder, or a colorant is included in the molded product. (Including providing a printing layer), the molded product can be adjusted to a desired color tone. As a result, it can be suitably applied to various molded bodies applied to metal detectors.

When the molded body of the present invention is applied to a metal detector, the molded body is provided on, for example, a base formed using a material other than the resin composition of the present invention and the surface of the base. And a surface layer formed using the resin composition of the present invention.

When the molded body of the present invention is applied to a metal detector, the molded body preferably includes composite particles at least near the surface thereof.
More specifically, the compact preferably contains composite particles in a region within 1.0 mm in the thickness direction from the surface, and the composite particles in a region within 0.5 mm in the thickness direction from the surface. It is more preferable that it contains.

When the molded product of the present invention is applied to a metal detector, the molded product can be used for, for example, food production, processing, packaging (including packaging, the same applies hereinafter), cosmetics, and pharmaceuticals. Production of quasi-drugs, processing, packaging sites, pharmaceutical manufacturing, processing, packaging sites, other products manufacturing, processing, packaging sites, medical sites, cell culture, tissue culture, organ culture In-situ use for biological treatment such as genetic recombination, and on-site use for chemical treatment such as compound synthesis. Especially, it is preferable that it is used in the manufacture of food, processing, and packaging sites.

Foods are required to have high safety, but are generally manufactured, processed, and packaged in an environment where foreign substances are easily mixed. Therefore, by applying the present invention to an article used in the field of food production, processing, and packaging, a part of the article is separated, or at least a part of the article is mixed with another article. Etc. can be suitably detected.

In addition, in this specification, in addition to solid form and semi-solid form (gel form of jelly, pudding, etc.), the form of food includes liquid, and the concept of food includes drinks and the like. Food additives and supplements (health supplements) are also included in the concept of food. In addition to natural products such as animal-derived meat, seafood, plant-derived vegetables, fruits, seeds, grains, beans, seaweed, and processed products thereof, artificial sweeteners, artificial seasonings such as artificial seasonings, etc. New products are also included in the concept of food.

Examples of molded products used in the production and processing of food include cooking appliances, cooking utensils, cooking utensils, tableware, clothing (articles worn on the human body), and packaging members used for food packaging And articles used in association therewith, as well as articles used for maintenance and repair of these.

More specifically, for example, hot plate, stove, gas burner, oven, toaster, microwave oven, dishwasher, dish dryer, scale (scale), kitchen timer, thermometer, water purifier, water purification filter (cartridge) Cooking equipment such as pans, pans, kettles, lids, knives, scissors, ladle, spatula, peeler, slicer, mixer, chopper, masher, rolling pin, mudler, whisk, pestle, bowl, drainer Bowl, cutting board, mat, rice paddle, mold, die cutting, lye removal, grater (food grader), frying (turner), pick, drainer, sieve, mill, drop lid, ice tray, grill, tongs, egg slicer Cooking utensils such as bowls, measuring cups, measuring spoons; towels, kitchen paper, towels, towels, paper towels Cooking utensils such as draining sheets, wrap film, oven paper, squeezed bags, virtues, pans, etc .; dishes, cups, bowls, chopsticks (including chopsticks), spoons, forks, knives, shellfish thigh legs Tableware such as take-out appliances (crab spoon, crab fork); Apron, lab coat, mask, gloves, shoes, socks, underwear, hat, glasses, etc. (articles worn on the human body); food laminate film, etc. Food packaging films, packaging tubes, food storage bottles, plastic sealed containers, and other food packaging materials; dried fish nets, hoses, chopping boards, tableware, sponges, scourers, detergent containers, grindstones, sharpeners These constituent members and the like can be mentioned, but are not limited thereto.

Hereinafter, the present invention will be described in detail based on examples and comparative examples, but the present invention is not limited thereto. In the following description, treatments and measurements that do not particularly indicate temperature conditions were performed at room temperature (25 ° C.).

<< 1 >> Manufacture of Composite Particles and Powders Composite particles and powders of Examples and Comparative Examples were manufactured as follows.

Example 1
First, Fe ₂ O ₃ and Mn ₃ O ₄ as raw materials were mixed at a predetermined ratio and mixed for 15 minutes with a Henschel mixer.

The mixture thus obtained was pelletized using a roller compactor, and then pre-fired using a rotary kiln at 1000 ° C. for 5 hours in the air.

After calcination, the mixture was pulverized with a ball mill to obtain a powdery calcination body (calcination powder) having a volume average particle size of 1.8 μm.

Next, using the obtained powdery calcined body, propane: oxygen ⁼ 10 Nm 3 / hr: it was sprayed at a flow rate of 40 m / sec in the combustible gas combustion flame of 35 Nm ³ / hr. At this time, since the granulated material was sprayed while continuously flowing, the particles after spraying and quenching were independent without being bound to each other. Subsequently, the cooled particles were collected by a cyclone provided on the downstream side of the airflow. This obtained the ferrite powder (Mn ferrite powder) (volume average particle diameter: 27.5 micrometers) which consists of several Mn ferrite particles. The obtained ferrite powder was air-flow classified to obtain a volume average particle size of 4.7 μm.

The volume average particle size of the powder was determined by the following measurement. That is, first, 10 g of powder as a sample and 80 ml of water were placed in a 100 ml beaker, and two drops of a dispersant (sodium hexametaphosphate) were added. Subsequently, dispersion was performed using an ultrasonic homogenizer (UH-150 type manufactured by SMT Co Ltd). At this time, the output level of the ultrasonic homogenizer was set to 4, and dispersion was performed for 20 seconds. Thereafter, bubbles formed on the surface of the beaker were removed and introduced into a laser diffraction particle size distribution measuring apparatus (SALD-7500 nano manufactured by Shimadzu Corporation) for measurement. The measurement conditions at this time were pump speed 7, refractive index 1.70-0.50i, and internal ultrasonic irradiation time 30. In addition, it calculated | required similarly about the other Example and comparative example which are mentioned later.

The average value of SF-1 of the ferrite powder was 106.

The shape factor SF-1 was determined as follows.
That is, first, using a scanning electron microscope (FE-SEM (SU-8020, manufactured by Hitachi High-Technology)) and an energy dispersive X-ray analyzer (EDX) (E-MAX manufactured by Horiba, Ltd.), a magnification of 1000 times And the equivalent circle diameter, outer circumference, length, width and area were automatically measured automatically using a particle analysis function which is a function attached to EDX.

Among the obtained data, the particles clearly overlap each other (peripheral length is more than 1.8 times the perimeter calculated from the equivalent circle diameter) and fine powder (the equivalent circle diameter is less than 1 μm). The value of SF-1 was calculated by the above formula, excluding the small ones), the maximum length (horizontal ferret diameter) R of the particles and the area as the projected area S.

SF-1 was calculated for each particle, and an average value of 200 particles or more was defined as SF-1 of the ferrite powder. In addition, it calculated | required similarly about the other Example and comparative example which are mentioned later.

Moreover, the BET specific surface area of the obtained ferrite powder was 0.68 m < ² > / g.
The BET specific surface area was determined by measurement using a specific surface area measuring device (model: Macsorb HM model-1208 (manufactured by Mountec)). More specifically, about 5 g of the measurement sample was put in a standard sample cell dedicated to a specific surface area measurement apparatus, accurately weighed with a precision balance, the sample (ferrite powder) was set in the measurement port, and measurement was started. The measurement was performed by a one-point method, and the BET specific surface area was automatically calculated when the weight of the sample was input at the end of the measurement. As a pretreatment before the measurement, about 20 g of the measurement sample was placed on the medicine wrapping paper, then degassed to −0.1 MPa with a vacuum dryer, and it was confirmed that the degree of vacuum had reached −0.1 MPa or less. Then, it heated at 200 degreeC for 2 hours. The measurement environment was temperature: 10-30 ° C., humidity: 20-80% relative humidity, and no condensation.

Further, when the ferrite powder was measured using a vibration sample type magnetometer, the saturation magnetization was 87.1 emu / g, the residual magnetization was 2.8 emu / g, and the coercive force was 42 Oe.

The above magnetic properties were obtained as follows. That is, first, ferrite powder to be measured was packed in a cell having an inner diameter of 5 mm and a height of 2 mm, and set in a vibration sample type magnetometer (VSM-C7-10A manufactured by Toei Kogyo Co., Ltd.). Next, an applied magnetic field was applied, sweeped to 5 kOe, and then the applied magnetic field was reduced to create a hysteresis curve. Thereafter, the saturation magnetization, residual magnetization and coercive force of the ferrite powder were determined from the data of this curve. The powder as an aggregate of composite particles described later was obtained in the same manner. Moreover, it calculated | required similarly about the other Example and comparative example which are mentioned later.

0.2 g of the obtained ferrite powder was weighed, 60 ml of pure water added with 20 ml of 1N hydrochloric acid and 20 ml of 1N nitric acid was heated to prepare an aqueous solution in which the ferrite powder was completely dissolved, and an ICP analyzer (Shimadzu) The contents of Fe, Mn, Mg and Sr were measured using ICPS-1000IV manufactured by Seisakusho. Moreover, it calculated | required similarly about the other Example and comparative example which are mentioned later.

Thereafter, electroless plating was performed on the obtained ferrite powder to obtain a powder containing a plurality of composite particles having a coating layer composed of Ag on the surface of the mother particle composed of Mn ferrite. .

(Examples 2 and 3)
In the production of Mn ferrite particles (ferrite powder) used as mother particles, the ratio of raw materials, pre-firing conditions, thermal spraying treatment conditions, classification conditions, and the formation conditions of the coating layer can be adjusted to adjust the powder (multiple The powder (aggregate of a plurality of composite particles) was produced in the same manner as in Example 1 except that the conditions of the aggregates of the composite particles were as shown in Tables 1 and 2.

(Comparative Example 1)
In this comparative example, an aggregate including a plurality of particles composed of Mn—Mg—Sr ferrite was used as a target powder as it was. That is, the particles constituting the powder of this comparative example were composed of Mn—Mg—Sr ferrite and were not provided with a coating layer.

(Comparative Example 2)
A powder was produced in the same manner as in Example 1 except that instead of particles composed of Mn ferrite, particles composed of Mn—Mg—Sr ferrite were used as mother particles. That is, in this comparative example, the composite particles constituting the powder had mother particles composed of Mn—Mg—Sr ferrite and a coating layer composed of Ag provided on the surface thereof. It was.

(Comparative Example 3)
A powder was produced in the same manner as in Example 1 except that the formation of the coating layer on the ferrite powder was omitted. That is, in this comparative example, the ferrite powder was used as a target powder as it was.

Tables 1 and 2 collectively show the configurations of the powders of the Examples and Comparative Examples.
The color tone of the powders of the above Examples was white to silver, whereas the color tone of the powders of Comparative Examples 1 and 3 was black.

In each of the above Examples and Comparative Example 2, the content of components other than ferrite in the mother particles was 0.1% by mass or less.

Further, in each of the above Examples and Comparative Example 2, the content of components other than Ag in the coating layer was 0.1% by mass or less. The content of Ag in the coating layer was determined by measurement using fluorescent X-rays. That is, 100 parts by mass of ferrite particles serving as mother particles were mixed with Ag powder at a ratio of 0.1 part by mass, 0.5 part by mass, and 1 part by mass with a ball mill (100 rpm) for 30 minutes, and then X-ray fluorescence After measuring the intensity of Ag with a measuring device (ZSX100s manufactured by Rigaku Corporation) and creating a calibration curve, X-ray fluorescence measurement was performed on the powders (aggregates of a plurality of composite particles) of each of the above Examples and Comparative Example 2. The intensity | strength of Ag was measured with the apparatus and Ag content was computed.

In each of the above Examples and Comparative Example 2, the content of the component outside the composite particles in the powder was 0.1% by mass or less.

In addition, the volume average particle diameter, magnetic properties, and SF-1 values of the powders of the respective Examples and Comparative Examples were determined by the same method as that for the ferrite powder described above.

Moreover, the tap density was measured using a USP tap density measuring device (Powder Tester PT-X, manufactured by Hosokawa Micron Corporation) in accordance with JIS R1628.

The true density was measured using a fully automatic true density measuring device Macpycno manufactured by Mountec Co., Ltd. according to JIS Z 8807: 2012.
The Curie temperature and the thickness T of the coating layer in Table 1 were measured by the above methods.

1 shows a cross-sectional SEM image of the composite particle of Example 1, FIG. 2 shows a cross-sectional SEM image of the composite particle of Example 2, and FIG. 3 shows a cross-sectional SEM image of the composite particle of Example 3. showed that.

<< 2 >> Evaluation of Electromagnetic Shielding Ability by KEC Method A 10% by mass PVA aqueous solution was prepared so that 70 parts by mass of the powder and binder resin (PVA) obtained in each of the Examples and Comparative Examples were 30 parts by mass as a solid content. Each was weighed and dispersed and mixed for 5 minutes with a rotation and revolution mixing device.

The obtained mixed liquid was poured into a mold for molding, and water was evaporated to produce a sheet-like molded body having a thickness of 1 mm.

The electromagnetic wave shielding ability (attenuation rate) of the magnetic field of the obtained sheet-like molded body was measured by the KEC method. The electromagnetic wave shielding ability (attenuation rate) of the magnetic field was measured in the range of 0.1 MHz to 1 GHz.

<< 3 >> Electric resistivity Using the powders obtained in the above Examples and Comparative Examples, the electric resistivity was evaluated as follows.

First, after filling powder as a sample in a fluororesin cylinder with a cross-sectional area of 4 cm ² to a height of 4 mm, electrodes were attached to both ends, and a weight of 1 kg was placed on top of the electrode, and the electrical resistance was measured. did. The electrical resistance was measured by applying a measurement voltage of 1 V with a 2182A nanovolt meter manufactured by Keithley Co., Ltd., measuring the resistance after 60 seconds, and calculating the volume resistance.

For each example and each comparative example, the evaluation results of the electromagnetic shielding effect by the KEC method are shown in FIG. 4, and the results of electrical resistivity are shown in Table 3.

As is clear from FIG. 4, in the present invention, it was confirmed that the frequency dependency of the electromagnetic wave shielding ability (attenuation rate) was shifted to the lower frequency side by the thickness of the coating layer, and Mn ferrite particles (mother particles) While it was confirmed that the electromagnetic wave was shielded by the metal coating (coating layer) existing on the surface, in Comparative Examples 1 and 3, satisfactory results could not be obtained because there was no metal coating. In Comparative Example 2, not only the rising of the electromagnetic wave shielding ability was shifted to the high frequency side, but also the electromagnetic wave shielding ability was inferior to that of Example 1.

The present invention can provide composite particles and powder excellent in electromagnetic wave shielding properties, can provide a molded body excellent in electromagnetic wave shielding properties, and can be suitably used for producing the molded body. A resin composition can be provided.

Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
This application is based on a Japanese patent application filed on Feb. 13, 2018 (Japanese Patent Application No. 2018-023566), the contents of which are incorporated herein by reference.

Claims

Mother particles composed of Mn ferrite;
A composite particle comprising: a coating layer made of a material containing at least one selected from the group consisting of Au, Ag, Pt, Ni, and Pd.
The Mn ferrite has a composition in which a Mn content is 3.5% by mass or more and 20.0% by mass or less, and a Fe content is 50.0% by mass or more and 70.0% by mass or less. The composite particles according to 1.
The composite particle according to claim 1, wherein the Mn ferrite has a Curie point of 200 ° C. or more and 500 ° C. or less.
The composite particle according to any one of claims 1 to 3, wherein the coating layer has a thickness of 10 nm to 500 nm.
The composite particle according to any one of claims 1 to 4, wherein the mother particle has a true spherical shape.
A powder comprising a plurality of the composite particles according to any one of claims 1 to 5.
The powder according to claim 6, wherein the composite particles have a volume average particle diameter of 1.0 μm or more and 20 μm or less.
A resin composition comprising the powder according to claim 6 or 7 and a resin material.
A molded body produced by using a material containing the powder according to claim 6 or 7 and a resin material.