JP6988074B2 - Powder composition containing composite particles and method for producing the same - Google Patents

Description

The present invention relates to a powder composition containing composite particles and a method for producing a powder composition containing composite particles.

In recent years, sheet-like members (composite material sheets) using composite materials containing resins and inorganic particles, which have properties such as thermal conductivity, have been used for various purposes.

Here, the composite material sheet is usually formed into a sheet by using a composite mixture containing an inorganic material and a resin capable of exhibiting desired properties such as thermal conductivity and conductivity. Manufactured. Further, when forming the composite mixture into a sheet shape, the composite mixture is crushed and pulverized in advance so that the composite mixture has a good powder shape and powder fluidity suitable for sheet formation, and the composite particles are formed. It may be formed into a sheet shape.

For example, in Patent Document 1, a composition obtained by mixing a carbon material as an inorganic material and an acrylic resin is put into a crusher to be crushed, and the crushed composition is rolled and molded to obtain a heat conductive sheet. Forming a sheet for.

International Publication No. 2016/129257

However, in the conventional method described in Patent Document 1 and the like, even when a composition (composite mixture) containing a resin or the like is crushed or the like, it is composited due to stickiness caused by the resin in the obtained composite particles. It has been clarified that the powder fluidity as a composite particle may be inferior because the particles are stuck together to form a lump (blocking). Such a mass usually has a size of about several cm to several tens of cm. Therefore, when the composite particles are blocked, the handleability of the composite particles deteriorates, and for example, when forming a composite material sheet using the composite particles, it becomes difficult to uniformly supply the composite particles. As a result, if the blocking resistance of the composite particles is low, it is difficult to obtain a good composite material sheet. The problem of blocking composite particles is, for example, when a highly adhesive resin is used or the amount of the resin is increased to give the composite material sheet further adhesiveness and / or flexibility. In addition, it is thought that it can become more apparent.

Therefore, the present invention provides a method for producing a powder composition containing composite particles, which is excellent in blocking resistance and handleability and can obtain composite particles capable of forming a good composite material sheet. The purpose.
Another object of the present invention is to provide a powder composition containing composite particles which are excellent in blocking resistance and handleability and can form a good composite material sheet.

The present inventors have made diligent studies to achieve the above object. Then, the present inventors include composite particles obtained by adding inorganic particles that are the same as or different from the inorganic particles contained in the composite mixture when pulverizing the composite mixture containing the resin and the inorganic particles. Attention was paid to further addition at different timings so that the powder composition and the powder composition satisfy a predetermined relationship. Then, the present inventors have found that if the inorganic particles are further added to the composite mixture in this way, blocking of the composite particles can be suppressed and good handleability can be realized, and a good composite material sheet can be formed. , The present invention has been completed.

That is, the present invention aims to advantageously solve the above problems, and the method for producing a powder composition containing composite particles of the present invention crushes a composite mixture containing a resin and inorganic particles A. A method for producing a powder composition containing composite particles, which comprises a crushing step of obtaining a powder composition containing the composite particles.
{(Specific surface area of inorganic particles B x mass of the inorganic particles B) /
(Specific surface area of the powder composition × mass of the powder composition)} × 100 ... (1)
The inorganic particles B are added so as to satisfy the relationship that the value represented by is 40% or more and 90% or less. As described above, if the composite mixture is pulverized by adding the inorganic particles B so as to satisfy the above lower limit or higher relationship, blocking of the composite particles contained in the obtained powder composition is suppressed and excellent handling is achieved. Can give sex. Further, if the relationship when the inorganic particles B are added is set to be equal to or less than the above upper limit, for example, a good composite material sheet can be obtained by using the composite particles contained in the obtained powder composition.
In the present invention, the inorganic particles A and the inorganic particles B may be the same as each other or may be different from each other.
Further, in the present invention, the "specific surface area" can be determined according to the method described in the examples of the present specification.

Further, in the method for producing a powder composition containing composite particles of the present invention, it is preferable that the amount of the inorganic particles B added is 80% by mass or more and 500% by mass or less of the content of the inorganic particles A. This is because if the amount of the inorganic particles B added is at least the above lower limit, the blocking resistance and handleability of the composite particles contained in the obtained powder composition can be further improved, and a better composite material sheet can be obtained. .. Further, if the amount of the inorganic particles B to be added is set to the above upper limit or less, for example, good strength can be given to the composite material sheet formed by using the composite particles contained in the obtained powder composition. be.

Further, in the method for producing a powder composition containing composite particles of the present invention, the amount of the inorganic particles B added is 30% by mass or more of 80% by mass or more of the total amount of the content of the inorganic particles A and the amount of the inorganic particles B added. It is preferably mass% or less. This is because if the amount of the inorganic particles B added is at least the above lower limit, the blocking resistance and handleability of the composite particles contained in the obtained powder composition can be further improved, and a better composite material sheet can be obtained. .. Further, if the amount of the inorganic particles B to be added is set to the above upper limit or less, for example, good strength can be given to the composite material sheet formed by using the composite particles contained in the obtained powder composition. be.

In the method for producing a powder composition containing composite particles of the present invention, it is preferable that the inorganic particles A and the inorganic particles B are particulate carbon materials. When both the inorganic particles A and the inorganic particles B are particulate carbon materials, the composite particles contained in the obtained powder composition are excellent in thermal conductivity and conductivity, and for example, the composite particles are excellent in thermal conductivity. This is because it can be suitably used for forming a heat conductive sheet.

Further, the present invention is intended to advantageously solve the above problems, and the powder composition containing the composite particles of the present invention contains composite particles containing a resin, inorganic particles A and inorganic particles B. In the powder composition, the inorganic particles A are unevenly distributed inside the composite particles, and the inorganic particles B are unevenly distributed on the surface layer portion of the composite particles, and the following formula (2):
{(Specific surface area of the inorganic particles B x mass of the inorganic particles B) /
(Specific surface area of the powder composition × mass of the powder composition)} × 100 ... (2)
It is characterized in that the coverage by the inorganic particles B represented by is 40% or more and 90% or less. When the coverage with the inorganic particles B is at least the above lower limit, it is possible to suppress the occurrence of blocking in the composite particles contained in the powder composition and to provide excellent handleability. Further, when the coverage with the inorganic particles B is at least the above lower limit, a good composite material sheet can be obtained by using the composite particles contained in the powder composition, for example.
In the present invention, the "coverage ratio" is a value (%) calculated by the above formula (2).

According to the present invention, it is possible to provide a method for producing a powder composition containing composite particles, which is excellent in blocking resistance and handleability and can obtain composite particles capable of forming a good composite material sheet. can.
Further, according to the present invention, it is possible to provide a powder composition containing composite particles which are excellent in blocking resistance and handleability and can form a good composite material sheet.

Hereinafter, embodiments of the present invention will be described in detail.
The method for producing a powder composition containing composite particles of the present invention can be used to provide composite particles that can be used, for example, for forming a molded body such as a composite material sheet having desired properties. can. The composite material sheet formed by using the composite particles contained in the powder composition obtained according to the production method of the present invention is, for example, sandwiched between the heating element and the heating element when the radiator is attached to the heating element. It can be used as a heat conductive sheet that radiates heat well from a heating element.
Further, the powder composition containing the composite particles of the present invention can be produced, for example, according to the method for producing a powder composition containing the composite particles of the present invention, and can be used for the same purposes as described above.

(Method for producing powder composition containing composite particles)
The method for producing a powder composition containing composite particles of the present invention is a method having a crushing step of crushing a composite mixture containing a resin and inorganic particles A to obtain a powder composition containing the composite particles. Occasionally, the inorganic particles B are added to the composite mixture under predetermined conditions. Further, the method for producing a powder composition containing composite particles of the present invention may further include, for example, other steps such as a kneading step described later before the crushing step. Unless the method for producing composite particles has the above-mentioned crushing step and the inorganic particles B are added under predetermined conditions during the crushing step, blocking of the composite particles contained in the obtained powder composition cannot be satisfactorily suppressed. That is, it is not possible to give good blocking resistance to the composite particles and improve the handling property, and it is not possible to obtain a good composite material sheet.

<Kneading process>
In the kneading step that the method for producing a powder composition containing composite particles of the present invention may optionally have, for example, the resin, the inorganic particles A, and any fibrous carbon material and additives are kneaded prior to the pulverization step described later. To obtain a composite mixture. Further, the composite mixture obtained in the kneading step can be used in the pulverization step described later.
The resin, inorganic particles A, and any fibrous carbon material and additives used in the kneading step can follow the resin, inorganic particles A, and any fibrous carbon materials and additives described later in the pulverization step.

Here, the kneading method is not particularly limited, and can be performed using a kneading device such as a kneader, a roll, a Henschel mixer, a hobart mixer, a high-speed mixer, or a twin-screw kneader. Further, the kneading may be carried out in the presence of a solvent such as ethyl acetate or methyl ethyl ketone. The kneading temperature can be, for example, 5 ° C. or higher and 150 ° C. or lower.

<Crushing process>
The method for producing a powder composition containing composite particles of the present invention includes a crushing step of crushing a composite mixture containing a resin and inorganic particles A to obtain a powder composition containing the composite particles. Then, at the time of the pulverization step, it is necessary to add the inorganic particles B to the composite mixture so as to satisfy a predetermined relationship.

<< Complex Mixture >>
The composite mixture comprises the resin and the inorganic particles A and may optionally further comprise a fibrous carbon material and additives. Then, as the composite mixture, for example, the composite mixture obtained according to the above-mentioned kneading step may be used, or a commercially available product may be used.

[resin]
The resin is not particularly limited, and for example, a thermoplastic resin and a thermosetting resin can be used.

[[Thermoplastic resin]]
Above all, it is preferable to use a thermoplastic resin as the resin. This is because if a thermoplastic resin is used, for example, by mixing the resin and the inorganic particles A while heating, it is easy to obtain a uniformly mixed composite mixture. Further, for example, when the obtained composite particles are pressurized (heat-pressed) while being heated to form a composite material sheet, the smoothness of the sheet surface can be improved, and the formability is excellent. Normally, composite particles containing a thermoplastic resin are easily blocked by heating. However, in the production method of the present invention, the inorganic particles B are added under the above-mentioned predetermined conditions during the pulverization step of the composite mixture, so that heat is generated. Even composite particles containing a plastic resin can satisfactorily suppress blocking.
Examples of the thermoplastic resin include a solid thermoplastic resin under normal temperature and pressure, and a liquid thermoplastic resin under normal temperature and pressure.

-Liquid thermoplastic resin under normal temperature and pressure-
Above all, as the resin, it is preferable to use a liquid thermoplastic resin at least under normal temperature and pressure. This is because if a liquid thermoplastic resin is used under normal temperature and pressure, for example, when the resin and the inorganic particles A are mixed to obtain a composite mixture, it is easy to mix them more uniformly. Normally, composite particles containing a liquid thermoplastic resin under normal temperature and pressure are particularly liable to be blocked by heating. However, in the production method of the present invention, the inorganic particles B are formed under the above-mentioned predetermined conditions during the crushing step of the composite mixture. Since it is added, blocking can be satisfactorily suppressed even for composite particles containing a liquid thermoplastic resin under normal temperature and pressure.
Here, in the present specification, "normal temperature" means 23 ° C., and "normal pressure" means 1 atm (absolute pressure).

Examples of the thermoplastic resin that is liquid under normal temperature and pressure include fluororesins, silicone resins, acrylic resins, and epoxy resins. These may be used alone or in combination of two or more. Above all, as the liquid thermoplastic resin under normal temperature and pressure, it is preferable to use a liquid thermoplastic fluororesin under normal temperature and pressure. In addition to the above effects, the use of a liquid thermoplastic fluororesin under normal temperature and pressure improves the heat resistance, oil resistance, and chemical resistance of composite particles and, for example, a composite material sheet obtained by using composite particles. Because it can be done.

The viscosity of the liquid thermoplastic resin under normal temperature and pressure is not particularly limited, but the viscosity at a temperature of 105 ° C. is 500 mPa from the viewpoint of good kneading property, fluidity, cross-linking reactivity and excellent moldability. It is preferably s to 30,000 mPa · s, and more preferably 550 mPa · s to 25,000 mPa · s.

-Solid thermoplastic resin under normal temperature and pressure-
The composite mixture can also contain a solid thermoplastic resin under normal temperature and pressure. Examples of the thermoplastic resin that is solid under normal temperature and pressure include poly (2-ethylhexyl acrylate), a copolymer of acrylic acid and 2-ethylhexyl acrylate, polymethacrylic acid or an ester thereof, and polyacrylic acid or an ester thereof. Acrylic resin such as; silicone resin; fluororesin; polyethylene; polypropylene; ethylene-propylene copolymer; polymethylpentene; polyvinyl chloride; polyvinylidene chloride; polyvinylacetate; ethylene-vinyl acetate copolymer; polyvinyl alcohol; polyacetal Polyethylene terephthalate; Polybutylene terephthalate; Polyethylene naphthalate; Polystyrene; Polyacrylonitrile; Stylo-acrylonitrile copolymer; Acrylonitrile-butadiene copolymer (nitrile rubber); Acrylonitrile-butadiene-styrene copolymer (ABS resin); Butadiene block copolymer or its hydrogen additive; styrene-isoprene block copolymer or its hydrogen additive; polyphenylene ether; modified polyphenylene ether; aliphatic polyamides; aromatic polyamides; polyamideimide; polycarbonate; polyphenylene sulfide; polysulphon Polyether sulfone; polyether nitrile; polyether ketone; polyketone; polyurethane; liquid crystal polymer; ionomer; and the like. These may be used alone or in combination of two or more.
In the present invention, rubber is included in "resin".

[[Thermosetting resin]]
Further, a thermosetting resin may be used as the resin as long as the effect of the present invention is not significantly impaired. Examples of the thermosetting resin include natural rubber; butadiene rubber; isoprene rubber; nitrile rubber; hydride nitrile rubber; chloroprene rubber; ethylene propylene rubber; chlorinated polyethylene; chlorosulfonated polyethylene; butyl rubber; halogenated butyl rubber; polyisobutylene. Rubber; epoxy resin; polyimide resin; bismaleimide resin; benzocyclobutene resin; phenol resin; unsaturated polyester; diallyl phthalate resin; polyimide silicone resin; polyurethane; thermosetting polyphenylene ether; thermosetting modified polyphenylene ether; etc. Be done. These may be used alone or in combination of two or more.

[[Resin content]]
The content ratio of the resin in the composite mixture is not particularly limited, and is preferably 35% by mass or more, and preferably 95% by mass or less. This is because when the content ratio of the resin is at least the above lower limit, the composite particles are more flexible, and for example, the workability when molding the composite particles into a composite material sheet or the like is excellent. Further, when the content ratio of the resin is not more than the above upper limit, blocking of the composite particles can be further suppressed and the handling property can be further improved.

[Inorganic particles A]
The inorganic particles A contained in the composite mixture are not particularly limited, and may be, for example, any inorganic particles capable of exhibiting desired properties to be imparted to the composite material sheet obtained by using the composite particles. Examples of such inorganic particles include particulate carbon material, boron nitride, aluminum nitride, titanium oxide and the like. Then, for example, in the case of imparting high thermal conductivity to the composite material sheet, it is preferable that the inorganic particles A are a particulate carbon material, boron nitride, and / or aluminum nitride, among the above-mentioned ones. Further, for example, when imparting high light reflectivity to a composite material sheet, it is preferable that the inorganic particles A are titanium oxide among the above-mentioned ones.
Hereinafter, an example in which a composite material sheet using composite particles contained in a powder composition obtained according to the production method of the present invention is used as a heat conductive sheet may be described, but the present invention is limited to this example. No.

[[Particulate carbon material]]
The particulate carbon material is not particularly limited, and for example, artificial graphite, scaly graphite, flaky graphite, natural graphite, acid-treated graphite, expandable graphite, graphite such as expanded graphite; carbon black; and the like can be used. Can be used. These may be used alone or in combination of two or more.
Above all, it is preferable to use expanded graphite as the particulate carbon material. This is because the thermal conductivity of the composite material sheet can be improved by using expanded graphite.

-Expanded graphite-
Here, the expanded graphite that can be suitably used as a particulate carbon material is, for example, expandable graphite obtained by chemically treating graphite such as scaly graphite with sulfuric acid or the like, heat-treated to expand it, and then finely divided. It can be obtained by converting it to graphite. Examples of commercially available expanded graphite include EC1500, EC1000, EC500, EC300, EC100, and EC50 (all trade names) manufactured by Ito Graphite Industry Co., Ltd.

[[Particle diameter of inorganic particle A]]
Here, the particle size of the inorganic particles A is preferably 100 μm or more, more preferably 150 μm or more, preferably 300 μm or less, and more preferably 250 μm or less in terms of volume average particle size. This is because if the particle size of the inorganic particles A is at least the above lower limit, better strength can be given to, for example, a composite material sheet using composite particles. Further, when the particle diameter of the inorganic particles A is not more than the above upper limit, for example, the ease of mixing when mixing the resin and the inorganic particles A and / or the formability when forming the composite particles into a sheet are excellent. be.
In the present specification, the "volume average particle diameter" represents a particle diameter (D50) in which the cumulative volume calculated from the small diameter side in the particle diameter distribution (volume basis) measured by the laser diffraction method is 50%. , It can be measured using a laser diffraction / scattering type particle size distribution measuring device.

Further, in the present invention, the aspect ratio (major axis / minor axis) of the inorganic particles A is preferably 1 or more and 10 or less, and more preferably 1 or more and 5 or less.
Further, in the present invention, the "aspect ratio of inorganic particles" such as inorganic particles A is determined by observing the inorganic particles with an SEM (scanning electron microscope) and determining the maximum diameter (major diameter) of any 50 inorganic particles. It can be obtained by measuring the particle diameter (minor diameter) in the direction orthogonal to the maximum diameter and calculating the average value of the ratio of major axis to minor axis (major axis / minor axis).
Here, when measuring the volume average particle diameter and the aspect ratio of the inorganic particles A, for example, the resin is dissolved by using a good solvent for the resin contained in the composite mixture, or the resin is thermally decomposed. Inorganic particles A can be extracted from the composite mixture using any of the above techniques.

[[Content ratio of inorganic particles A]]
The content ratio of the inorganic particles A in the composite mixture is not particularly limited, and is preferably, for example, 5% by mass or more, and preferably 50% by mass or less. This is because when the content ratio of the inorganic particles A is not more than the above lower limit, for example, a composite material sheet using composite particles can further exhibit desired properties and can be given better strength. Further, when the content ratio of the inorganic particles A is not more than the above upper limit, it is possible to impart even better flexibility to the composite particles and, for example, the composite material sheet made of the composite particles.

[Fibrous carbon material]
The fibrous carbon material that can be further contained in the composite mixture is not particularly limited, and for example, carbon nanotubes, vapor-grown carbon fibers, carbon fibers obtained by carbonizing organic fibers, and cut products thereof are used. be able to. These may be used alone or in combination of two or more.
For example, if the composite mixture further contains the fibrous carbon material, the thermal conductivity of the composite material sheet obtained by using the composite particles can be further improved, and the powder of the particulate carbon material can be prevented from falling off. You can also do it. Although it is not clear why the fibrous carbon material can be blended to prevent the particulate carbon material from falling off, the fibrous carbon material forms a three-dimensional network structure, so that it has thermal conductivity. It is presumed that this is because it prevents the desorption of the particulate carbon material while increasing the strength.

Among the above, as the fibrous carbon material, it is preferable to use a fibrous carbon nanostructure such as carbon nanotube, and it is more preferable to use a fibrous carbon nanostructure containing carbon nanotube. This is because the use of fibrous carbon nanostructures such as carbon nanotubes can further improve the thermal conductivity and strength of composite material sheets that can be obtained using composite particles, for example.

[[Fibrous carbon nanostructures containing carbon nanotubes]]
-Characteristics-
Here, the fibrous carbon nanostructure containing carbon nanotubes that can be suitably used as a fibrous carbon material may be composed of only carbon nanotubes (hereinafter, may be referred to as “CNT”). However, it may be a mixture of CNTs and fibrous carbon nanostructures other than CNTs.

Further, the CNT in the fibrous carbon nanostructure is not particularly limited, and single-walled carbon nanotubes and / or multi-walled carbon nanotubes can be used, but the CNT is a carbon nanotube from a single layer to five layers. , And more preferably single-walled carbon nanotubes. This is because the use of single-walled carbon nanotubes can further improve the thermal conductivity and strength of the composite material sheet that can be obtained by using composite particles, as compared with the case of using multi-walled carbon nanotubes.
RBM does not exist in the Raman spectrum of the fibrous carbon nanostructure composed of only three or more layers of multi-walled carbon nanotubes. Therefore, fibrous carbon nanostructures containing CNTs preferably have a Radial Breathing Mode (RBM) peak when evaluated using Raman spectroscopy.

The average diameter (Av) of the fibrous carbon nanostructures containing CNTs is preferably 0.5 nm or more, more preferably 1 nm or more, preferably 15 nm or less, and 10 nm or less. Is even more preferable. This is because when the average diameter (Av) of the fibrous carbon nanostructures is 0.5 nm or more, aggregation of the fibrous carbon nanostructures can be suppressed and the dispersibility of the carbon nanostructures can be enhanced. Further, when the average diameter (Av) of the fibrous carbon nanostructures is 15 nm or less, the thermal conductivity and strength of the composite material sheet obtained by using the composite particles can be sufficiently enhanced.

Further, as the fibrous carbon nanostructure containing CNT, the ratio (3σ / Av) of the value (3σ) obtained by multiplying the standard deviation (σ) of the diameter by 3 with respect to the average diameter (Av) is more than 0.20 0. It is preferable to use a carbon nanostructure of less than .60, more preferably a carbon nanostructure having a 3σ / Av of more than 0.25, and a carbon nanostructure having a 3σ / Av of more than 0.50. Is more preferable. If a fibrous carbon nanostructure containing CNTs having a 3σ / Av of more than 0.20 and less than 0.60 is used, a composite that can be obtained by using composite particles even if the amount of the fibrous carbon material is small. This is because the thermal conductivity and strength of the material sheet can be sufficiently increased. Therefore, the compounding of the fibrous carbon nanostructures containing CNTs suppresses the increase in hardness (that is, the decrease in flexibility) of the composite material sheet, and sufficiently improves the thermal conductivity and flexibility of the composite material sheet. This is because they can be arranged side by side at a high level.
The "average diameter of fibrous carbon nanostructures (Av)" and "standard deviation of diameter of fibrous carbon nanostructures (σ: sample standard deviation)" are randomly selected using a transmission electron microscope, respectively. It can be obtained by measuring the diameter (outer diameter) of 100 fibrous carbon nanostructures selected in 1. The average diameter (Av) and standard deviation (σ) of the fibrous carbon nanostructures containing CNTs may be adjusted by changing the manufacturing method and manufacturing conditions of the fibrous carbon nanostructures containing CNTs. However, it may be adjusted by combining a plurality of types of fibrous carbon nanostructures containing CNTs obtained by different production methods.

Further, the BET specific surface area of the fibrous carbon nanostructure containing CNT ^{is preferably 600 m 2} / g or more, more preferably 800 m ² / g or more, and preferably 2500 m ² / g or less. It is more preferably 1200 m ² / g or less. This is because when the BET specific surface area of the fibrous carbon nanostructure containing CNT is 600 m ² / g or more, the thermal conductivity and strength of the composite material sheet obtained by using the composite particles can be sufficiently enhanced. .. Further, when the BET specific surface area of the fibrous carbon nanostructure containing CNT is 2500 m ² / g or less, it is possible to suppress the aggregation of the fibrous carbon nanostructure and enhance the dispersibility of CNT in the composite material sheet. Because it can be done.
In the present invention, the "BET specific surface area" refers to the nitrogen adsorption specific surface area measured by the BET method.

-Preparation method-
Then, in the fibrous carbon nanostructure containing CNT having the above-mentioned properties, for example, a raw material compound and a carrier gas are supplied on a substrate having a catalyst layer for producing carbon nanotubes on the surface, and a chemical vapor phase is obtained. When CNTs are synthesized by the growth method (CVD method), a method of dramatically improving the catalytic activity of the catalyst layer by allowing a trace amount of an oxidizing agent (catalyst activator) to be present in the system (super growth method; It can be efficiently manufactured according to International Publication No. 2006/011655). In the following, the carbon nanotubes obtained by the super growth method may be referred to as "SGCNT".

Here, the fibrous carbon nanostructure containing CNT produced by the super growth method may be composed of only SGCNT, or in addition to SGCNT, for example, other carbon such as a non-cylindrical carbon nanostructure. Nanostructures may be included.

[[Content ratio of fibrous carbon material]]
The content ratio of the fibrous carbon material in the composite mixture can be 0% by mass, but is preferably 0.01% by mass or more, more preferably 0.05% by mass or more. It is preferably 1% by mass or less, and more preferably 0.2% by mass or less. When the content ratio of the fibrous carbon material is not less than the above lower limit, the thermal conductivity and strength of the composite material sheet obtained by using the composite particles can be further improved, and when used in combination with the particulate carbon material, it can be further improved. This is because it is possible to further prevent the particulate carbon material from falling off. Further, when the content ratio of the fibrous carbon material is not more than the above upper limit, it is possible to suppress the decrease in the flexibility of the composite mixture due to the blending of the fibrous carbon material.

[Additive]
The additives that may be further contained in the composite mixture are not particularly limited, and are, for example, plastic agents such as fatty acid esters; flame retardants such as red phosphorus flame retardants and phosphoric acid ester flame retardants; fluorooils (Daikin Industries, Ltd.). Additives that double as plasticizers and flame retardants, such as the company's Demnum series); toughness improvers such as urethane acrylates; hygroscopic agents such as calcium oxide and magnesium oxide; silane coupling agents, titanium coupling agents, acids Adhesive strength improvers such as anhydrides; wettability improvers such as nonionic surfactants and fluorosurfactants; ion trapping agents such as inorganic ion exchangers; and the like.
Further, the content ratio of the additive in the composite mixture can be arbitrarily selected according to the effect of the additive.

[Inorganic particles B]
In the pulverization step, for example, when the above-mentioned composite mixture is pulverized to obtain a powder composition containing the composite particles, the inorganic particles B are added to the composite mixture under predetermined conditions.
Examples of the inorganic particles B include particles similar to the above-mentioned inorganic particles A. Further, from the viewpoint of further exhibiting the desired properties in the composite particles and the composite material sheet using the composite particles, the inorganic particles A and the inorganic particles B are preferably the same particles. Further, for example, from the viewpoint of imparting excellent thermal conductivity to the composite particles and the composite material sheet using the composite particles, at least one of the above-mentioned inorganic particles A and B may be a particulate carbon material. It is preferable that at least the above-mentioned inorganic particles A are particulate carbon materials, and it is even more preferable that both the inorganic particles A and the inorganic particles B are particulate carbon materials. As the particulate carbon material, the same examples as those of the above-mentioned particulate carbon material for the inorganic particles A can be given.

[[Particle diameter of inorganic particle B]]
Here, the particle size of the inorganic particles B is preferably 100 μm or more, more preferably 150 μm or more, preferably 300 μm or less, and more preferably 250 μm or less in terms of volume average particle size. When the particle size of the inorganic particles B is not less than the above lower limit, the handling property is excellent, and when the composite mixture to which the inorganic particles B is added is pulverized, the inorganic particles B do not enter the inside of the composite mixture and are better in the surface layer portion. This is because it easily adheres to. Further, when the particle diameter of the inorganic particles B is equal to or less than the above upper limit, the value represented by the above formula (1) and the coverage represented by the formula (2) described later are further increased to further block the composite particles. This is because it can be suppressed.

[[Specific surface area of inorganic particles B]]
The specific surface area of the inorganic particles B ^{is preferably 0.005 m 2} / g or more, more preferably 0.01 m ² / g or more, and preferably 0.1 m ² / g or less. It is more preferably 0.05 m ² / g or less. When the specific surface area of the inorganic particles B is not less than the above lower limit, the value represented by the above formula (1) and the coverage represented by the following formula (2) can be further increased, and the blocking of the composite particles can be further suppressed. Because. Further, when the specific surface area of the inorganic particles B is not more than the above upper limit, the handleability is further improved, and when the inorganic particles B are added and the composite mixture is crushed, the inorganic particles B do not enter the inside of the composite mixture and are surface layers. This is because it is easier to adhere to the portion even better.

[[Amount of Inorganic Particle B Added]]
The amount of the inorganic particles B added to the composite particles is preferably 30% by mass or more, preferably 50% by mass or more, which is the total of the above-mentioned content of the inorganic particles A and the amount of the inorganic particles B added. It is more preferably 90% by mass or less, more preferably 80% by mass or less, and further preferably 60% by mass or less. When the content ratio of the inorganic particles B is not less than the above lower limit, the value represented by the above formula (1) and the coverage represented by the following formula (2) can be further increased, and the blocking of the composite particles can be further suppressed. Because. Further, when the content ratio of the inorganic particles B is not more than the above upper limit, for example, the strength of the composite material sheet obtained by using the composite particles can be further improved.

<< Crushing method >>
The pulverization is not particularly limited as long as the composite mixture containing the above-mentioned resin, inorganic particles A and any fibrous carbon material and additives can be pulverized, and the pulverization is not particularly limited, and is a cutter mill, a hammer mill, a bead mill, a vibration mill, a meteor type. This can be performed using a ball mill, a sand mill, a ball mill, a roll mill, a three-roll mill, a jet mill, a high-speed rotary crusher, or the like. Above all, it is desirable to use a cutter mill or a hammer mill.
Further, as for the crushing conditions, the crushing device, the crushing strength, and the like may be appropriately adjusted according to the desired particle size after crushing. For example, the adjustment of the grinding strength can be made by adjusting the capacity of the grinding device; the type, properties, and content ratio of the resin, the inorganic particles A and any fibrous carbon material and the additive contained in the composite mixture; the type, properties, and addition of the inorganic particles B. Amount; size and shape of stirring blades provided in the crushing device; crushing conditions such as crushing temperature, crushing time, crushing speed (rotation speed of stirring blades, etc.); and many factors such as combinations thereof are controlled. This can be done by adjusting the energy applied to the object to be crushed. Above all, from the viewpoint of workability, it is preferable to adjust the crushing strength by controlling the crushing time and the crushing speed. For example, the crushing strength can be increased by increasing the crushing speed and / or the crushing time. ..

[Conditions for adding inorganic particles B]
Here, in the method for producing a powder composition containing composite particles of the present invention, the specific surface area and the amount (mass) of the inorganic particles B added during the pulverization step are determined by the following formula (1):
{(Specific surface area of inorganic particle B x mass of inorganic particle B) /
(Specific surface area of powder composition x mass of powder composition)} x 100 ... (1)
It is necessary to satisfy the relationship that the value represented by is 40% or more and 90% or less. If the amount of the inorganic particles B added does not satisfy the relationship within the above range, the powder fluidity of the composite particles contained in the obtained powder composition cannot be improved and blocking cannot be suppressed satisfactorily. Therefore, if the amount of the inorganic particles B added does not satisfy the relationship within the above range, the composite particles contained in the obtained powder composition are inferior in handleability due to the stickiness of the resin and the like.
The value represented by the above formula (1) is preferably 50% or more, more preferably 55% or more, and preferably 80% or less. When the addition amount of the inorganic particles B satisfies the relationship of the above lower limit or more, the added inorganic particles B adheres better to the surface layer portion of the composite mixture and sufficiently covers the surface. Therefore, it is possible to further suppress the occurrence of blocking in the obtained composite particles and to provide better handleability. Further, if the addition amount of the inorganic particles B satisfies the relationship of the above upper limit or less, the composite material sheet can be formed without excessive addition of the inorganic particles B, for example, when the composite material sheet is formed by using the composite particles. This is because the strength can be improved.

In the present invention, "during the crushing step" means before crushing the composite mixture; during crushing of the composite mixture; or during crushing from before crushing the composite mixture. Therefore, the addition of the inorganic particles B to the composite mixture is continuous before grinding the composite mixture; during the grinding of the composite mixture; or between before grinding the composite mixture and during the grinding. Or it can be done discontinuously. Further, the inorganic particles B may be added in a batch or gradually by adding the total amount of the inorganic particles B.

<< Powder composition containing composite particles >>
The powder composition obtained through the above-mentioned pulverization step contains composite particles, and may further contain, for example, a small amount of the added inorganic particles B in addition to the composite particles. Here, the slight amount (content) of the inorganic particles B that the powder composition may further contain in addition to the composite particles is preferably 10% by mass or less and 5% by mass or less of the total amount of the inorganic particles B added. Is more preferable, and 0% by mass is further preferable. That is, it is more preferable that the powder composition is composed of only composite particles, and all of the added inorganic particles B constitute composite particles.

[Composite particles]
Here, the composite particles contained in the powder composition include the above-mentioned resin, inorganic particles A, inorganic particles B, and any fibrous carbon material and additives. Further, in the composite particles, the inorganic particles A are usually unevenly distributed inside and the inorganic particles B are unevenly distributed on the surface layer portion, for example, like the composite particles contained in the powder composition of the present invention described later. More specifically, the composite particles usually have a structure in which the inorganic particles B cover the surface layer portion of the particle body containing the resin, the inorganic particles A, and any fibrous carbon material and additives. It is presumed that by covering the surface layer portion with the inorganic particles B in this way, the blocking resistance and handleability of the composite particles can be improved, and a good composite material sheet can be obtained.

[[Particle diameter of composite particles]]
The particle size of the composite particles is preferably 300 μm or more, more preferably 400 μm or more, preferably 1000 μm or less, and more preferably 750 μm or less in terms of volume average particle size. When the particle size of the composite particle is equal to or larger than the above lower limit, the value represented by the above formula (1) and the coverage represented by the formula (2) described later are better maintained, and the blocking of the composite particle is further improved. This is because it can be suppressed. Further, when the particle diameter of the composite particles is not more than the above upper limit, for example, when the composite material sheet is formed by using the composite particles, the strength of the composite material sheet can be improved.

[[Specific surface area of composite particles]]
The specific surface area of the composite particles, for example, is preferably 0.0040m ² / g or more, more preferably 0.0045m ² / g or more, is preferably from 0.01 m ² / g , 0.0090 m ² / g or less, more preferably. This is because if the specific surface area of the composite particles is not less than the above lower limit, the strength of the composite material sheet can be improved, for example, when the composite material sheet is formed using the composite particles. Further, when the specific surface area of the composite particles is equal to or less than the above upper limit, the value represented by the above formula (1) and the coverage represented by the formula (2) described later are further increased, and the blocking of the composite particles is further suppressed. Because it can be done.

[[Particle diameter of powder composition]]
The particle size of the powder composition containing the composite particles is preferably 300 μm or more, more preferably 400 μm or more, preferably 1000 μm or less, and more preferably 750 μm or less in terms of volume average particle size. preferable. When the particle size of the powder composition is equal to or larger than the above lower limit, the value represented by the above formula (1) and the coverage represented by the formula (2) described later are better maintained, and the blocking of the composite particles is maintained. This is because it can be more suppressed. Further, when the particle size of the powder composition is not more than the above upper limit, for example, when the composite material sheet is formed by using the composite particles, the strength of the composite material sheet can be improved.
The volume average particle size of the powder composition can be measured according to the method described in the examples of the present specification.

[Specific surface area of powder composition]
The specific surface area of the powder composition containing the composite particles is preferably 0.0040m ² / g or more, more preferably 0.0045m ² / g or more, 0.01 m ² / g or less It is preferably 0.0090 m ² / g or less, and more preferably 0.0090 m 2 / g or less. This is because if the specific surface area of the powder composition is at least the above lower limit, the strength of the composite material sheet can be improved, for example, when the composite material sheet is formed using composite particles. Further, when the specific surface area of the powder composition containing the composite particles is equal to or less than the above upper limit, the value represented by the above formula (1) and the coverage rate represented by the formula (2) described later are further increased to further increase the composite. This is because the blocking of particles can be further suppressed.
The specific surface area of the powder composition can be measured according to the method described in the examples of the present specification.

(Powder composition containing composite particles)
The powder composition of the present invention is characterized in that the coverage is within a predetermined range. Further, the composite particles contained in the powder composition of the present invention include at least a resin, inorganic particles A and inorganic particles B present in a predetermined portion, and optionally further contain a fibrous carbon material and additives. You may go out. Here, the resin, the inorganic particles A, the inorganic particles B, the fibrous carbon material and the additive which can be contained in the composite particles are the resin, the inorganic particles A, the inorganic particles B and the fibrous carbon material according to the above-mentioned production method of the present invention. And can be of the same type as the additive, and its suitable properties and content can also be the same.
Then, the powder composition containing the composite particles of the present invention can be produced, for example, according to the above-mentioned method for producing a powder composition containing the composite particles of the present invention.

Since the powder composition containing the composite particles of the present invention has the above-mentioned predetermined coverage, the composite particles contained in the powder composition of the present invention are excellent in blocking resistance and handleability. Further, a good composite material sheet can be obtained by using the composite particles contained in the powder composition of the present invention. Therefore, by using the composite particles contained in the powder composition of the present invention, for example, a composite material sheet having desired properties can be satisfactorily formed.

<Coverage>
The coverage to be satisfied by the powder composition containing the composite particles of the present invention is the following formula (2):
{(Specific surface area of inorganic particle B x mass of inorganic particle B) /
(Specific surface area of powder composition x mass of powder composition)} x 100 ... (2)
It can be expressed by, and it is required to be within the range of 40% or more and 90% or less. If the coverage is not equal to or higher than the above lower limit, the powder fluidity of the composite particles contained in the obtained powder composition cannot be improved and blocking cannot be suppressed satisfactorily. Therefore, if the coverage is not equal to or higher than the above lower limit, the composite particles are inferior in handleability due to the stickiness of the resin and the like. Further, if the coverage is not equal to or less than the above upper limit, for example, a good composite material sheet cannot be obtained by using the composite particles contained in the powder composition.
The coverage is preferably 50% or more, more preferably 55% or more, and preferably 80% or less. When the coverage is equal to or higher than the above lower limit, the inorganic particles B adhere better to the surface layer portion of the composite mixture and sufficiently cover the surface. Therefore, the blocking resistance and handleability of the composite particles can be further improved. Further, when the coverage is equal to or less than the above upper limit, the strength of the composite material sheet can be improved, for example, when the composite material sheet is formed by using the composite particles.

Further, the suitable particle size and specific surface area of the composite particles contained in the powder composition of the present invention are the same as the particle size and specific surface area of the above-mentioned composite particles, and the obtained effects are also the same.
Further, the suitable particle size and specific surface area of the powder composition of the present invention are the same as those of the above-mentioned powder composition, and the obtained effects are also the same.

The specific structure of the composite particles contained in the powder composition of the present invention is, for example, a surface layer portion of a particle body containing, for example, a resin and inorganic particles A, and optionally further containing a fibrous carbon material and an additive. The structure in which the inorganic particles B are unevenly distributed can be mentioned. From the viewpoint of further improving the blocking resistance and handleability of the composite particles, the inorganic particles B are preferably unevenly distributed only within a range of 10% or less of the radius of the composite particles from the surface of the composite particles. It is more preferable that the particles are unevenly distributed only within a range of 5% or less of the radius of the composite particles from the surface of the composite particles, and it is further preferable that they are attached to the surface of the particle body and do not exist inside the particle body. Further, from the viewpoint of further satisfactorily exhibiting the desired characteristics of the composite particles, it is preferable that the inorganic particles A do not exist on the surface of the composite particles.
The structure of the composite particle can be confirmed, for example, by observing the cross section of the composite particle using an SEM (scanning electron microscope).

Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. In the following description, "%" and "part" representing quantities are based on mass unless otherwise specified.
Then, in Examples and Comparative Examples, the density, volume average particle diameter and specific surface area of the inorganic particles and the powder composition; the blocking resistance of the composite particles; the strength of the composite material sheet; are measured or evaluated according to the following methods, respectively. did.

<Density>
^{The densities (g / m 3} ) of the inorganic particles and the powder composition were measured for each using a true density measuring instrument (manufactured by Seishin Enterprise Co., Ltd., product name "MAT-7000"). The conditions were such that the measurement temperature was 25 ° C., the sample mass was 2 g, the solvent was N-butanol, and the degassing time was 10 minutes. Here, the density of the powder composition was calculated as an average value including components other than the composite particles when the powder composition also contained components other than the composite particles (for example, inorganic particles B).
Then, the obtained density was used for the calculation of the specific surface area described later.

<Volume average particle size>
The volume average particle size (m) of the inorganic particles and the powder composition was measured using a laser diffraction / scattering type particle size distribution measuring device (manufactured by Nikkiso, product name "Microtrack MT3300EX-II"). Specifically, particle size distributions were obtained for the inorganic particles and the powder composition. Then, the central particle diameter (D50) at which the cumulative volume calculated from the small diameter side in each of the obtained particle diameter distributions (volume basis) is 50% was calculated as the volume average particle diameter of the inorganic particles and the composite particles. The volume average particle size of the powder composition was calculated as an average value including components other than the composite particles when the powder composition also contained components other than the composite particles (for example, inorganic particles B). ..
Then, the obtained volume average particle diameter was used for the calculation of the specific surface area described later.

<Specific surface area>
^{The specific surface area (m 2} / g) of the inorganic particles and the powder composition is determined by the following formula (3): using the values of the density and the volume average particle diameter calculated as described above, respectively.
Specific surface area (m ² / g) =
6 / (Density (g / m ³ ) x Volume average particle size (m)) ... (3)
Asked according to.
Then, the obtained specific surface area was used for calculating the value represented by the above-mentioned formula (1) and the coverage ratio represented by the above-mentioned formula (2).

<Blocking resistance>
The blocking resistance (powder fluidity) of the composite particles was evaluated by a sieving method. Specifically, 80 g of composite particles sieved with a mesh having an opening of 1.4 mm was put into the beaker from the same height as the upper opening of a 200 mL glass beaker without applying pressure. Next, a weight of 400 g having the same inner diameter as the inner diameter of the beaker into which the composite particles were charged was slowly placed on the composite particles in the beaker. One minute after the weight was placed, the weight was removed, and the composite particles attached to the outer bottom surface of the weight were wiped off into the beaker so that there was no loss of the composite particles.
Next, a mesh with a wire diameter of 1.1 mm, an opening of 11.3 mm, and a size larger than the above upper opening (a square with a side of 150 mm) is placed on the upper opening of the beaker containing the composite particles. A bat was placed on the mesh. Next, while fixing the beaker, mesh, and bat, the top and bottom surfaces were turned upside down, and the beaker was pulled up 15 cm directly above the mesh. Then, the mesh was slowly lifted by 5 cm, and one minute after lifting, the composite particles remaining on the mesh were transferred to another vat. If the composite particles hardly fall from the bottom inside the beaker even if the top and bottom surfaces are turned upside down, do not separate the beaker from the mesh and tap the outside of the beaker lightly with a spatula or the like to place the composite particles on the mesh. Dropped. Also, when the beaker was pulled up and the composite particles adhered to the inside of the beaker, the outside of the beaker was tapped lightly with a spatula or the like to drop the composite particles on the mesh.
Then, the following equation (4):
Blocking resistance (%) = (mass of composite particles that have passed through the mesh (g)) /
(Mass of composite particles remaining on the mesh (g) + Mass of composite particles passing through the mesh (g)) × 100% ・ ・ ・ (4)
Therefore, the blocking resistance of the composite particles was determined. The larger the obtained value, the more excellent the powder fluidity of the composite particles and the more difficult it is to block.

<Strength>
The strength of the composite material sheet was measured as the tensile strength (MPa) as follows. That is, in accordance with JIS K6251, the composite material sheet was punched and molded with dumbbell No. 2 to prepare a sample piece. Then, using a tensile tester (manufactured by Shimadzu Corporation, product name "AG-IS20kN"), pinch 1 cm from both ends of the sample piece, and at a temperature of 23 ° C, make a normal from the surface of the sample piece. The breaking strength (tensile strength) was measured by pulling at a tensile speed of 500 mm / min in the direction perpendicular to the normal direction.

(Example 1)
<Preparation of fibrous carbon nanostructures containing CNTs>
A fibrous carbon nanostructure containing SGCNT was obtained by the super growth method according to the description of International Publication No. 2006/011655.
The obtained fibrous carbon nanostructure had a BET specific surface area of 800 m ² / g. In addition, as a result of measuring the diameters of 100 randomly selected fibrous carbon nanostructures using a transmission electron microscope, the average diameter (Av) was 3.3 nm, and the sample standard deviation (σ) of the diameter was 3 The value multiplied by (3σ) was 1.9 nm, and their ratio (3σ / Av) was 0.58. Further, the obtained fibrous carbon nanostructures were mainly composed of single-walled CNTs (also referred to as "SGCNTs").

<Preparation of easily dispersible aggregates of fibrous carbon nanostructures>
[Preparation of dispersion]
400 mg of the fibrous carbon nanostructures obtained above as the fibrous carbon material was weighed, mixed in 2 L of methyl ethyl ketone as a solvent, and stirred with a homogenizer for 2 minutes to obtain a crude dispersion. Next, using a wet jet mill (manufactured by Tsunemitsu Co., Ltd., product name "JN-20"), the obtained crude dispersion liquid was passed through a 0.5 mm flow path of the wet jet mill for two cycles at a pressure of 100 MPa. The fibrous carbon nanostructures were dispersed in methyl ethyl ketone. Then, a dispersion liquid having a solid content concentration of 0.20% by mass was obtained.
[Removal of solvent]
Then, the dispersion obtained above was filtered under reduced pressure using Kiriyama filter paper (No. 5A) to obtain a sheet-like easily dispersible aggregate.

<Preparation of composition>
100 parts of thermoplastic fluororesin (manufactured by Daikin Industries, Ltd., trade name "Daiel G-101") that is liquid under normal temperature and pressure as a resin, and expanded graphite as a particulate carbon material that is inorganic particles A (Ito) 30 parts of Graphite Industry Co., Ltd., trade name "EC-100", volume average particle size: 190 μm), and 0.1 part of easily dispersible aggregate of fibrous carbon nanostructure as fibrous carbon material. Was put into a Hobart mixer (manufactured by Kodaira Seisakusho Co., Ltd., product name "ACM-5LVT type", capacity: 5 L). Then, the mixture was heated to 80 ° C. and stirred and mixed for 30 minutes to obtain a composite mixture.
Next, the obtained composite mixture and 20 parts of expanded graphite (manufactured by Ito Graphite Industry Co., Ltd., trade name "EC-100", volume average particle diameter: 190 μm) as a particulate carbon material which is inorganic particles B. Was put into a free speed mill (manufactured by Labonect Co., Ltd., product name "FS20") all at once. Then, the powder composition containing the composite particles was obtained by pulverizing at a stirring blade speed = 8400 rpm for 30 seconds (corresponding to the pulverization strength “weak” shown in Table 1).
At this time, the specific surface area of the added inorganic particles B was 0.0178 m ² / g. The specific surface area of the obtained powder composition containing the composite particles was 0.00583 m ² / g, and the coverage (or the value represented by the above formula (1)) was 41%.

<Formation of composite material sheet>
Next, 5 g of the obtained composite particles were sandwiched between a PET film (protective film) having a thickness of 50 μm subjected to sandblasting, and the conditions were that the roll gap was 550 μm, the roll temperature was 50 ° C., the roll linear pressure was 50 kg / cm, and the roll speed was 1 m / min. A composite material sheet having a thickness of 0.5 mm was obtained.

(Example 2)
In the preparation of the composition, the amount of expanded graphite as the particulate carbon material of the inorganic particles A is 20 parts, and the amount of the expanded graphite as the particulate carbon material of the inorganic particles B is 30 parts. A composite mixture, a powder composition containing composite particles, and a composite material sheet were produced in the same manner as in Example 1 except that the coverage of the particles was 71%. The specific surface area of the obtained powder composition containing the composite particles was 0.00498 m ² / g.
Then, the measurement was carried out in the same manner as in Example 1. The results are shown in Table 1.

(Example 3)
In the preparation of the composition, the amount of expanded graphite as the particulate carbon material of the inorganic particles A is 35 parts, and the amount of the expanded graphite as the particulate carbon material of the inorganic particles B is 15 parts. A composite mixture, a powder composition containing composite particles, and a composite material sheet were produced in the same manner as in Example 1 except that the coverage of the particles was 42%. The specific surface area of the obtained powder composition containing the composite particles was 0.00421 m ² / g.
Then, the measurement was carried out in the same manner as in Example 1. The results are shown in Table 1.

(Example 4)
In the preparation of the composition, the amount of expanded graphite as the particulate carbon material of the inorganic particles A is 20 parts, and the amount of the expanded graphite as the particulate carbon material of the inorganic particles B is 30 parts. The coverage of the particles was set to 60%. Further, the composite mixture, the powder composition containing the composite particles, and the composite material sheet were prepared in the same manner as in Example 1 except that the speed of the stirring blade of the free speed mill was changed to 16800 rpm (corresponding to the crushing strength "medium"). Manufactured. The specific surface area of the obtained powder composition containing the composite particles was 0.00588 m ² / g.
Then, the measurement was carried out in the same manner as in Example 1. The results are shown in Table 1.

(Example 5)
In the preparation of the composition, the amount of expanded graphite as the particulate carbon material which is the inorganic particles A is 10 parts, and the amount of the expanded graphite as the particulate carbon material which is the inorganic particles B is 40 parts. The coverage of the particles was set to 61%. Further, the powder composition containing the composite mixture and the composite particles was the same as in Example 1 except that the speed of the stirring blade of the free speed mill was changed to 25000 rpm and the crushing time was changed to 60 seconds (corresponding to the crushing strength "strong"). Manufactured materials and composite material sheets. The specific surface area of the obtained powder composition containing the composite particles was 0.00775 m ² / g.
Then, the measurement was carried out in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 1)
In the preparation of the composition, except that the amount of expanded graphite as the particulate carbon material which is the inorganic particles A was changed to 50 parts and the coverage of the composite particles was set to 0% without adding the inorganic particles B. A composite mixture, a powder composition containing composite particles, and a composite material sheet were produced in the same manner as in Example 1.
Then, the measurement was carried out in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 2)
In the preparation of the composition, the amount of expanded graphite as the particulate carbon material of the inorganic particles A is 35 parts, and the amount of the expanded graphite as the particulate carbon material of the inorganic particles B is 15 parts. The coverage of the particles was set to 36%. Further, the composite mixture, the powder composition containing the composite particles, and the composite material sheet were prepared in the same manner as in Example 1 except that the speed of the stirring blade of the free speed mill was changed to 16800 rpm (corresponding to the crushing strength "medium"). Manufactured. The specific surface area of the obtained powder composition containing the composite particles was 0.00500 m ² / g.
Then, the measurement was carried out in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 3)
In the preparation of the composition, the composite mixture and the composite particles were prepared in the same manner as in Example 1 except that the speed of the stirring blade of the free speed mill was changed to 25000 rpm and the crushing time was changed to 60 seconds (corresponding to the crushing strength “strong”). A powder composition containing the mixture and a composite material sheet were produced. The specific surface area of the obtained powder composition containing the composite particles was 0.0219 m ² / g.
Then, the measurement was carried out in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 4)
In the preparation of the composition, the amount of expanded graphite as the particulate carbon material of the inorganic particles A is 40 parts, and the amount of the expanded graphite as the particulate carbon material of the inorganic particles B is 10 parts. A composite mixture, a powder composition containing composite particles, and a composite material sheet were produced in the same manner as in Example 1 except that the coverage of the particles was 31%. The specific surface area of the obtained powder composition containing the composite particles was 0.00383 m ² / g.
Then, the measurement was carried out in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 5)
In the preparation of the composition, the amount of expanded graphite as the particulate carbon material of the inorganic particles A is 10 parts, and the amount of the expanded graphite as the particulate carbon material of the inorganic particles B is 40 parts. A composite mixture, a powder composition containing composite particles, and a composite material sheet were produced in the same manner as in Example 1 except that the coverage of the particles was 114%. The specific surface area of the obtained powder composition containing the composite particles was 0.00417 m ² / g.
Then, the measurement was carried out in the same manner as in Example 1. The results are shown in Table 1.

Here, the coverage with the inorganic particles B is only an approximate value based on the surface area of the added inorganic particles B and the surface area of the obtained composite particles, and may exceed 100%.

From Table 1, when the composite mixture containing the resin and the inorganic particles A was pulverized, the relationship (coverage) within a predetermined range was satisfied and the inorganic particles B were added. In Examples 1 to 5, the relationship is a predetermined relationship. Compared with Comparative Examples 1 to 5 in which the inorganic particles B were added in an amount less than or above a predetermined relationship, the composite particles contained in the powder composition had better blocking resistance and handleability, and the obtained composite material sheet had better properties. It can be seen that both strength and strength can be achieved.

According to the present invention, it is possible to provide a method for producing a powder composition containing composite particles, which is excellent in blocking resistance and handleability and can obtain composite particles capable of forming a good composite material sheet. can.
Further, according to the present invention, it is possible to provide a powder composition containing composite particles which are excellent in blocking resistance and handleability and can form a good composite material sheet.

Claims (4)

A method for producing a powder composition containing composite particles, which comprises a crushing step of crushing a composite mixture containing the resin and the inorganic particles A to obtain a powder composition containing the composite particles.
The resin is a liquid under normal temperature and pressure, and the viscosity of the resin at a temperature of 105 ° C. is 500 mPa · s to 30,000 mPa · s.
The inorganic particles A are expanded graphite, and the inorganic particles A are expanded graphite.
During the pulverization step, the following formula (1): is applied to the composite mixture.
{(Specific surface area of inorganic particles B x mass of the inorganic particles B) /
(Specific surface area of the powder composition × mass of the powder composition)} × 100 ... (1)
The inorganic particles B are added so as to satisfy the relationship that the value represented by is 40% or more and 90% or less , and the inorganic particles B are expanded graphite powders containing composite particles. Method for producing body composition. The method for producing a powder composition containing composite particles according to claim 1, wherein the amount of the inorganic particles B added is 80% by mass or more and 500% by mass or less of the content of the inorganic particles A. The composite particle according to claim 1 or 2, wherein the amount of the inorganic particles B added is 30% by mass or more and 80% by mass or less of the total of the content of the inorganic particles A and the amount of the inorganic particles B added. A method for producing a powder composition. A powder composition containing composite particles containing a resin, inorganic particles A and inorganic particles B.
The resin is a liquid under normal temperature and pressure, and the viscosity of the resin at a temperature of 105 ° C. is 500 mPa · s to 30,000 mPa · s.
The inorganic particles A and the inorganic particles B are expanded graphite, and the inorganic particles A and the inorganic particles B are expanded graphite.
The inorganic particles A are unevenly distributed inside the composite particles,
The inorganic particles B are unevenly distributed on the surface layer of the composite particles, and the inorganic particles B are unevenly distributed on the surface layer portion of the composite particles.
The following formula (2):
{(Specific surface area of the inorganic particles B x mass of the inorganic particles B) /
(Specific surface area of the powder composition × mass of the powder composition)} × 100 ... (2)
A powder composition containing composite particles, wherein the coverage with the inorganic particles B is 40% or more and 90% or less.