JP6750492B2 - Pressing method and composite material sheet manufacturing method - Google Patents

Description

The present invention relates to a pressing method and a method for manufacturing a composite material sheet. More specifically, the present invention relates to a method for pressing composite material particles and a method for manufacturing a composite material sheet.

In recent years, a sheet-shaped member (composite material sheet) using a composite material containing a resin and an inorganic material, which has characteristics such as thermal conductivity, has been used for various purposes.

Here, the composite material sheet is, for example, in order to impart desired anisotropy of physical properties such as thermal conductivity and conductivity, a primary sheet is once prepared, and a laminated body obtained by laminating the primary sheets is sliced. It may be manufactured by

For example, in Patent Document 1, a pre-heat conductive sheet having a thickness of 0.3 mm, which is obtained by pressure-molding particles obtained by crushing a composition containing an acrylic resin and a carbon material in the production of the heat conductive sheet. (Primary sheet) is used. In Patent Document 1, 200 sheets of the pre-heat conductive sheet are stacked in the thickness direction, and the obtained pre-heat conductive sheet is sliced in the stacking direction to orient the carbon material in a desired direction. There is.

International Publication No. 2016/129257

However, in the conventional method described in Patent Document 1 and the like, there is a problem that it is necessary to stack a large number of primary sheets, and work efficiency is poor when manufacturing a composite material sheet such as a heat conductive sheet.

With respect to the above problems, the inventors of the present invention improve the production efficiency of a composite material sheet by increasing the thickness of the primary sheet itself to reduce the number of laminated primary sheets, even when using a laminate. Focused on getting. However, when pressure-forming particles composed of a composition containing a resin and an inorganic material to prepare a primary sheet, an attempt to increase the thickness of the primary sheet may give sufficient pressure to the particles during pressure-forming. However, it was difficult to satisfactorily form the particles into a sheet.

Therefore, the present invention can form a thickened primary composite material sheet, and for example, even when a composite material sheet is produced using a laminate of primary composite material sheets, the composite material sheet can be efficiently produced. It is an object of the present invention to provide a method for pressurizing particles of a composite material, which is possible.
Another object of the present invention is to provide a method for manufacturing a composite material sheet, which can efficiently manufacture the composite material sheet.

The present inventors have earnestly studied to achieve the above object. Then, the present inventors sandwich the particles of the composite material containing the resin and the inorganic material between the sheet base materials and pressurize them to form the primary composite material sheet, and the blocking property of the particles of the composite material and the sheet base material. Focusing on the peelability of the material. The present inventors have found that the particles of the composite material have a certain degree of stickiness, and the blocking resistance (powder fluidity) is suppressed within a predetermined range, and at least one of the sheet base materials. It has been found that a thickened primary composite material sheet can be satisfactorily obtained if the peeling force is within a predetermined range. Then, the present inventors have found that a composite material sheet can be efficiently produced by stacking and slicing the above-mentioned primary composite material sheet, and completed the present invention.
In the present invention, “blocking” means that the particles of the composite material stick to each other to form a lump by stickiness due to the resin in the particles of the composite material.

That is, the present invention has an object to advantageously solve the above-mentioned problems, and a pressing method of the present invention provides particles of a composite material containing a resin and an inorganic material between two sheet base materials. A pressurizing method of performing primary pressurization in a sandwiched state, wherein a blocking resistance of particles of the composite material is 0% or more and 80% or less, and at least one sheet base material of the two sheet base materials is used. The peeling force is 0.03 N/cm or more and less than 4.0 N/cm. Thus, in sandwiching the particles of the composite material containing the resin and the inorganic material with the sheet base material and performing the pressure molding, the blocking resistance of the particles of the composite material is suppressed within the predetermined range, and When at least one peeling force is within the above-mentioned predetermined range, it is possible to favorably obtain a thickened primary composite material sheet.
In the present invention, the "blocking resistance" and the "peeling force" can be measured by the methods described in Examples of this specification.

Further, in the pressing method of the present invention, it is preferable that at least one of the two sheet base materials has a peeling force of 0.30 N/cm or more and 3.00 N/cm or less. This is because if the peeling force of at least one of the sheet base materials is within the above range, the thickness of the primary composite material sheet can be further increased.

Further, in the pressing method of the present invention, it is preferable that the thickness of the primary composite material sheet obtained by the primary pressing is 1.0 mm or more. This is because, if the thickness of the primary composite material sheet is increased in this manner, for example, the composite material sheet can be efficiently manufactured using the primary composite material sheet.

Further, the present invention has an object to advantageously solve the above problems, and a method for producing a composite material sheet of the present invention comprises a step of obtaining a primary composite material sheet according to any one of the pressing methods described above. A step of stacking a plurality of the primary composite material sheets in the thickness direction or folding or winding the primary composite material sheet to obtain a laminated body, and the laminated body being 45° or less with respect to the laminating direction. And obtaining a composite material sheet by slicing at an angle of. As described above, since the thickened primary composite material sheet can be obtained according to any one of the pressing methods described above, the composite material sheet can be efficiently manufactured using the primary composite material sheet. .. If the laminate of the primary composite material sheet is sliced in the stacking direction, the inorganic material in the composite material sheet is oriented in a desired direction such as the thickness direction, and the composite material sheet exhibits desired properties such as thermal conductivity. Can be made.

Further, the method for producing a composite material sheet of the present invention further includes a step of obtaining a compressed laminate by subjecting the laminate to a secondary pressure in a laminating direction to obtain a compressed laminate, and in the step of obtaining the composite material sheet, the compression is performed. It is preferable to obtain a composite material sheet by slicing the laminate at an angle of 45° or less with respect to the laminating direction. By using a compression laminate obtained by subjecting the laminate to a secondary pressure in the lamination direction, the inorganic material in the composite material sheet is better oriented in a desired direction such as the thickness direction, and the composite material sheet has a desired heat conductivity or the like. This is because the characteristics can be exhibited more effectively.

Further, in the method for producing a composite material sheet of the present invention, it is preferable that the reduction rate of the height of the laminate due to the secondary pressure is 1% or more and 30% or less. When the reduction rate of the height of the laminate due to the secondary pressure is within the above range, the inorganic material in the composite material sheet is better oriented in a desired direction such as the thickness direction, and the composite material sheet has thermal conductivity in the thickness direction. This is because it is possible to further exhibit desired characteristics such as.
In the present invention, the “ratio of decrease in height of laminated body” is expressed by the following formula (1):
Decrease in stack height (%) =
(Height of laminate before secondary pressing (mm)-Height of compression laminate after secondary pressing (mm))
/Height of laminated body before secondary pressing (mm)×100 (1)
Can be calculated according to. Here, the height of the laminate and the compression laminate can be measured by the method described in the examples of the present specification.

Further, the method for producing a composite material sheet of the present invention preferably further includes the step of subjecting the composite material sheet obtained by any one of the above-mentioned production methods to tertiary compression in the thickness direction to compress. By subjecting the composite material sheet to tertiary pressure in the thickness direction, the surface smoothness of the composite material sheet can be improved. Therefore, for example, when the composite material sheet is used in contact with an adherend such as a heating element and a radiator, the adhesion between the composite material sheet and the adherend is increased, and the composite material sheet is desired to have a desired thermal conductivity. This is because the characteristics of can be exhibited more effectively.

Further, in the method for producing a composite material sheet of the present invention, it is preferable that the reduction rate of the sheet thickness due to the third pressurization is 1% or more and 40% or less. By tertiary pressing the composite material sheet so that the reduction rate of the sheet thickness is within the above-mentioned predetermined range, while ensuring good orientation of the inorganic material in the composite material sheet, the surface smoothness of the composite material sheet is improved. This is because the composite material sheet can be further enhanced to exhibit desired properties such as thermal conductivity.
In the present invention, the “rate of decrease in sheet thickness” is defined by the following formula (2):
Reduction rate of sheet thickness (%) =
(Thickness (mm) of composite material sheet before tertiary pressing-thickness (mm) of composite material sheet after tertiary pressing)/thickness (mm) of composite material sheet before tertiary pressing*100 (2 )
Can be calculated according to. Here, the thickness of the composite material sheet before and after the third pressurization can be measured by the method described in Examples of the present specification.

According to the present invention, a thickened primary composite material sheet can be formed. For example, even when a composite material sheet is manufactured using a laminate of the primary composite material sheets, the composite material sheet can be efficiently manufactured. It is possible to provide a method of pressing the particles of the composite material.
Further, according to the present invention, it is possible to provide a method for manufacturing a composite material sheet, which can efficiently manufacture the composite material sheet.

Hereinafter, embodiments of the present invention will be described in detail.
The pressing method of the present invention can be used, for example, to obtain a primary composite material sheet that can be used to manufacture a composite material sheet having desired properties such as thermal conductivity. Further, the method for producing a composite material sheet of the present invention can be used to efficiently obtain a composite material sheet by using the primary composite material sheet obtained according to the above pressing method.
Then, according to the pressurizing method of the present invention, at the time of press-molding the particles of the composite material having a blocking resistance suppressed within a predetermined range in a state of being sandwiched between the sheet base materials, at least one of the sheet base materials Since the sheet base material having the peeling force within the predetermined range is used, it is possible to increase the thickness of the obtained primary composite material sheet. Further, according to the method for producing a composite material sheet of the present invention, since the primary composite material sheet is used, the composite material sheet can be produced efficiently.

The composite material sheet obtained according to the method for producing a composite material sheet of the present invention is, for example, sandwiched between the heating element and the radiator when attaching the radiator to the heating element to allow good heat dissipation from the heating element, It can be suitably used as a heat conductive sheet. When the composite material sheet obtained according to the production method of the present invention is used as a heat conductive sheet, the thermal conductivity in the thickness direction of the composite material sheet is, for example, 0.1 MPa or less, preferably 0.06 MPa or less. When sandwiched and used at a relatively low pressure, it can be more effectively improved.

(Pressurizing method)
In the pressing method of the present invention, particles of a composite material containing a resin and an inorganic material and having a blocking resistance suppressed within a predetermined range are primarily pressed while being sandwiched between two sheet base materials. At least one of the sheet base materials is a sheet base material having a peeling force within a predetermined range. When the particles of the composite material are sandwiched between the sheet base materials and pressure-molded, the blocking resistance of the particles of the composite material is within the predetermined range, and the peeling force of at least one of the sheet base materials is within the predetermined range. However, the primary composite material sheet described later cannot be formed into a thick film and formed well.
Further, the pressing method of the present invention may further include other steps such as a step of obtaining particles of the composite material prior to the above-mentioned primary pressing.

<Process of obtaining particles of composite material>
In the step of obtaining particles of the composite material that the pressurizing method of the present invention may optionally include, for example, a resin, an inorganic material, and an optional additive are mixed, and the composite mixture prepared by kneading is used as it is for the composite material. It may be obtained as particles. When the composite mixture has a non-particulate shape such as an agglomerate, in the step of obtaining particles of the composite material, for example, the composite mixture is further crushed and pulverized by an arbitrary method to form a particle shape. May be obtained as particles of the composite material. Among them, from the viewpoint of enhancing the handling property of the particles of the composite material, it is preferable to crush and pulverize the composite mixture to obtain particles of the composite material in the step of obtaining the particles of the composite material.
In the pressing method of the present invention, for example, the particles of the composite material obtained as described above can be primarily pressed.

<<Composite Material Particles>>
The particles of the composite material include a resin and an inorganic material, and have a blocking resistance suppressed within a predetermined range. In addition to the resin and the inorganic material, the particles of the composite material may optionally further contain an additive. Then, as the particles of the composite material, for example, particles of the composite material obtained according to the step of obtaining the particles of the composite material described above may be used, or a commercially available product may be used.

[resin]
The resin is not particularly limited and, for example, a thermoplastic resin or 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 as the resin, for example, particles of the composite material in which the respective components are uniformly mixed can be easily obtained by mixing the resin and the inorganic material while heating. Further, it is because the particles of the obtained composite material are excellent in formability, for example, the surface of the sheet can be made smooth by pressurizing (heating press) while heating to form a sheet.
Examples of the thermoplastic resin include a liquid thermoplastic resin at room temperature and atmospheric pressure, and a solid thermoplastic resin at room temperature and atmospheric pressure.

− Thermoplastic resin that is liquid under normal temperature and pressure −
Among them, as the resin, it is preferable to use at least a liquid thermoplastic resin at room temperature and atmospheric pressure, and more preferably to use only a liquid thermoplastic resin at room temperature and atmospheric pressure. This is because if a thermoplastic resin that is liquid at least under normal temperature and normal pressure is used as the resin, the particles of the composite material are provided with appropriate stickiness, and the blocking resistance can be more easily suppressed. Then, for example, by using the particles of the composite material, it becomes easier to form a thicker primary composite material sheet. Further, if a thermoplastic resin that is liquid at least under normal temperature and normal pressure is used as the resin, it is easy to obtain more uniform particles of the composite material.
In addition, in this specification, "normal temperature" refers to 23° C., and "normal pressure" refers to 1 atm (absolute pressure).

Further, examples of the thermoplastic resin that is liquid at room temperature and normal pressure include fluororesins, silicone resins, acrylic resins, epoxy resins, and the like. These may be used alone or in combination of two or more. Above all, it is preferable to use a thermoplastic fluororesin that is liquid under normal temperature and normal pressure as the thermoplastic resin that is liquid under normal temperature and normal pressure. If a thermoplastic fluororesin that is liquid at room temperature and normal pressure is used, in addition to the above effects, heat resistance, oil resistance, and chemical resistance of composite material particles and composite material sheets obtained using composite material particles, etc. It is because it can improve.

The viscosity of the thermoplastic resin which is liquid at room temperature and atmospheric pressure is not particularly limited, but from the viewpoint of good kneading property, fluidity, crosslinking reactivity and excellent moldability, the viscosity at a temperature of 105° C. is 500 mPas. -S to 30000 mPa-s is preferable, and 550 mPa-s to 25000 mPa-s is more preferable.

-A thermoplastic resin that is solid under normal temperature and pressure-
Examples of the solid thermoplastic resin at room temperature and atmospheric pressure include poly(2-ethylhexyl acrylate), a copolymer of acrylic acid and 2-ethylhexyl acrylate, polymethacrylic acid or its ester, polyacrylic acid or Acrylic resins such as esters; silicone resins; fluororesins; polyethylene; polypropylene; ethylene-propylene copolymers; polymethylpentene; polyvinyl chloride; polyvinylidene chloride; polyvinyl acetate; ethylene-vinyl acetate copolymers; polyvinyl alcohol Polyacetal; Polyethylene terephthalate; Polybutylene terephthalate; Polyethylene naphthalate; Polystyrene; Polyacrylonitrile; Styrene-acrylonitrile copolymer; Acrylonitrile-butadiene copolymer (nitrile rubber); Acrylonitrile-butadiene-styrene copolymer (ABS resin); Styrene-butadiene block copolymer or hydrogenated product thereof; Styrene-isoprene block copolymer or hydrogenated product thereof; Polyphenylene ether; Modified polyphenylene ether; Aliphatic polyamides; Aromatic polyamides; Polyamideimide; Polycarbonate; Polyphenylene sulfide Polysulfone; polyethersulfone; polyethernitrile; polyetherketone; 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-
Furthermore, 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, hydrogenated nitrile rubber, chloroprene rubber, ethylene propylene rubber, chlorinated polyethylene, chlorosulfonated polyethylene, butyl rubber, halogenated butyl rubber, and 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; To be These may be used alone or in combination of two or more.

[[Resin content ratio]]
The content ratio of the resin in the particles of the composite material is not particularly limited and is preferably 35% by mass or more, more preferably 55% by mass or more, and 95% by mass or less. preferable. This is because if the content ratio of the resin is at least the above lower limit, the particles of the composite material are made to have a suitable stickiness, and the blocking resistance can be more easily suppressed. And, for example, by using the particles of the composite material, it is easy to form a primary composite material sheet having excellent flexibility and a thick film. Further, if the content ratio of the resin is not more than the above upper limit, for example, a composite material sheet obtained by using particles of the composite material can easily exhibit desired characteristics.

[Inorganic material]
The inorganic material is not particularly limited and may be, for example, any inorganic material that can exhibit desired characteristics to be imparted to a composite material sheet obtained by using particles of the composite material. Examples of such inorganic materials include carbon materials, boron nitride, aluminum nitride, titanium oxide, and the like. Furthermore, examples of the carbon material include a particulate carbon material and a fibrous carbon material.
Then, for example, when imparting high thermal conductivity to the composite material sheet, among the above, the inorganic material is preferably a particulate carbon material, a fibrous carbon material, boron nitride and aluminum nitride, and at least particles It is more preferable to include a particulate carbon material, and it is even more preferred to include a particulate carbon material and a fibrous carbon material. In addition, for example, in the case of imparting high light reflectivity to the composite material sheet, the inorganic material is preferably titanium oxide among the above.

The above-mentioned inorganic materials may be used alone or in combination of two or more. Further, in the present invention, when the inorganic material has a particle shape, it may be referred to as “inorganic particle”.
Hereinafter, an example of using a composite material sheet using particles of the composite material obtained according to the pressing method of the present invention as a heat conductive sheet may be described, but the present invention is not limited to this example.

[[Particulate carbon material]]
The particulate carbon material that can be used as the inorganic particles is not particularly limited, and examples thereof include artificial graphite, flake graphite, exfoliated graphite, natural graphite, acid-treated graphite, expansive graphite, expansive graphite and the like graphite; Carbon black; etc. can be used. These may be used alone or in combination of two or more.
Above all, expanded graphite is preferably used as the particulate carbon material. This is because if the expanded graphite is used, the thermal conductivity of the composite material sheet can be further improved.

-Expanded graphite-
Here, expanded graphite that can be suitably used as the particulate carbon material is, for example, expandable graphite obtained by chemically treating graphite such as flake graphite with sulfuric acid or the like, heat-treated and expanded, and then finely divided. Can be obtained. And as commercially available expanded graphite, for example, EC-1500, EC-1000, EC-500, EC-300, EC-100, EC-50 (all are trade names) manufactured by Ito Graphite Industry Co., Ltd. Can be mentioned.

[[Particle size of inorganic particles]]
Here, the particle size of the inorganic particles such as the particulate carbon material is preferably 100 μm or more in volume average particle size, more preferably 150 μm or more, preferably 300 μm or less, and 250 μm or less. Is more preferable. This is because, if the particle size of the inorganic particles is not less than the above lower limit, for example, a composite material sheet using the particles of the composite material can be provided with desired properties such as good thermal conductivity and strength. In addition, if the particle size of the inorganic particles is not more than the above upper limit, for example, the ease of mixing when mixing the resin and the inorganic particles and the moldability when forming the particles of the composite material into a sheet are excellent.
In the present specification, the “volume average particle diameter” represents a particle diameter (D50) at 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 particle size distribution measuring device.

Here, in the present invention, the aspect ratio (major axis/minor axis) of the inorganic particles 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 the inorganic particles is obtained by observing the inorganic particles with a SEM (scanning electron microscope), and for any 50 inorganic particles, the maximum diameter (major axis) and the maximum diameter are orthogonal to each other. It can be determined by measuring the particle size in the direction (minor axis) and calculating the average value of the ratio of the major axis to the minor axis (major axis/minor axis).
When measuring the volume average particle size and aspect ratio of the inorganic particles, for example, the resin is dissolved using a good solvent for the resin contained in the particles of the composite material and the composite material sheet, or The inorganic particles can be taken out by an arbitrary method such as thermal decomposition.

[[Content ratio of inorganic particles]]
The content ratio of the inorganic particles in the particles of the composite material is not particularly limited and is preferably 5% by mass or more, preferably 65% by mass or less, and 45% by mass or less. More preferable. This is because, if the content ratio of the inorganic particles is at least the above lower limit, for example, a composite material sheet obtained by using the particles of the composite material can exhibit desired characteristics and can have better strength. Further, if the content ratio of the inorganic particles is not more than the above upper limit, the particles of the composite material are more likely to have a suitable stickiness and the blocking resistance can be more easily suppressed. Then, for example, by using the particles of the composite material, it becomes easy to favorably form a thicker primary composite material sheet.

[[Fibrous carbon material]]
The fibrous carbon material that can be used as the inorganic material is not particularly limited, and examples thereof include carbon nanotubes (hereinafter sometimes referred to as “CNT”), vapor-grown carbon fibers, and organic fibers obtained by carbonization. It is possible to use the carbon fibers to be produced, and cut products thereof. These may be used alone or in combination of two or more.
Among the above, as the fibrous carbon material, it is preferable to use a fibrous carbon nanostructure such as CNT, and it is more preferable to use a fibrous carbon nanostructure containing CNT. This is because, if a fibrous carbon nanostructure such as CNT is used, for example, the thermal conductivity and strength of the composite material sheet obtained by using the particles of the composite material can be further improved.

-Fibrous carbon nanostructure containing CNT-
Here, the fibrous carbon nanostructure containing CNT, which can be preferably used as the fibrous carbon material, may be composed of only CNT, or CNT and a fibrous carbon nanostructure other than CNT. It may be a mixture of.
Then, the preferable properties of the fibrous carbon nanostructure containing CNT can be the same as the properties of CNT described in JP-A-2016-054113, for example.
Moreover, the fibrous carbon nanostructure containing CNT can be efficiently prepared by the super growth method, for example, according to the description of International Publication WO 2006/011655.

[Content ratio of inorganic material]
The content ratio of the inorganic material in the particles of the composite material is not particularly limited and is preferably 5% by mass or more, preferably 65% by mass or less, and 45% by mass or less. More preferable. When the content ratio of the inorganic material is at least the above lower limit, for example, the composite material sheet obtained by using the particles of the composite material can further exhibit desired properties such as thermal conductivity, and can further enhance the strength. Is. Further, if the content ratio of the inorganic material is at most the above upper limit, the particles of the composite material will be made to have a suitable stickiness, and the blocking resistance will be more easily suppressed. Then, for example, by using the particles of the composite material, it becomes easier to form a thicker primary composite material sheet.

[Additive]
Examples of the additives that the particles of the composite material may optionally include include the same additives as those described in JP-A-2015-227411.

[Blocking resistance of composite material particles]
The blocking resistance of the particles of the composite material needs to be 0% or more and 80% or less. Further, the blocking resistance of the particles of the composite material is more preferably 50% or more, further preferably 70% or more. When the blocking resistance is not more than the above upper limit, the particles of the composite material exhibit appropriate stickiness, so that the particles of the composite material sandwiched between the two sheet base materials and the two sheet base materials. The friction between them increases and the particles of the composite material can be subjected to a sufficiently high force during primary pressing (so-called slippage is less likely to occur). Therefore, it is easy to form a thickened primary composite material sheet, and a composite material sheet using a laminate of the primary composite material sheet can be efficiently manufactured. Here, in the case of forming a thickened primary composite material sheet, in general, since the particles of the composite material are difficult to receive the force of the primary pressure sufficiently, the inorganic material contained in the particles of the composite material is directed in a desired direction. It is difficult to achieve good orientation. However, if the blocking resistance is not more than the above upper limit, as described above, the particles of the composite material can receive a large force at the time of primary pressing, so that the inorganic material can be applied in a desired direction such as an in-plane direction of the primary composite material sheet. Can be well oriented in the direction.
Further, if the blocking resistance is equal to or more than the above lower limit, the handling property of the particles of the composite material is more excellent, and the reason is not clear, but the surface roughness of the composite material sheet using the particles of the composite material is excellent, and the composite This is because the material sheet can be provided with a smooth surface. In addition, if the blocking resistance is at least the above lower limit, the effect of reducing the thermal resistance value when the composite material sheet, which will be described later in detail, is tertiary-pressurized is large, and a composite material sheet having superior thermal conductivity can be obtained. Is. Here, it is not clear why the effect of reducing the thermal resistance when the composite material sheet is subjected to the third pressurization becomes large when the blocking resistance is equal to or higher than the above lower limit. However, in the above case, the composite material sheet using the particles of the composite material having an appropriate powder fluidity does not receive an excessive force from the tertiary pressurization, while maintaining a good orientation of the inorganic material. It is assumed that the surface smoothness can be improved as described above.

In addition, in order to adjust the blocking resistance of the particles of the composite material within the above-mentioned predetermined range, the timing of adding the inorganic material can be shifted in the preparation of the particles of the composite material without any particular limitation. Specifically, for example, in the preparation of particles of a composite material, a part of the inorganic material (hereinafter, sometimes referred to as “inorganic particle A”) is mixed and added at the time of kneading, and the remaining inorganic material (hereinafter, “Inorganic particles B” may be referred to)) can be added at the time of crushing and crushing. Here, “mixing and kneading” may be before mixing, kneading may be started, may be during mixing, kneading, and may be continuous time before starting mixing, kneading to mixing, kneading. It may be. Similarly, "crushing and crushing" may be before crushing and crushing, may be crushing and crushing, and may be crushing and crushing before starting-crushing and crushing. May be continuous time.
When the inorganic material is charged with the timing shifted as described above, the inorganic material is preferably inorganic particles from the viewpoint of workability. In addition, when the materials are charged at different timings, the inorganic material and the inorganic particles may be the same or different.
Further, in order to adjust the blocking resistance of the particles of the composite material within the above-mentioned predetermined range, the kind and content ratio of the above-mentioned resin can be appropriately adjusted in the preparation of the particles of the composite material.

[Particle size of composite material particles]
The particle size of the particles of the composite material is preferably 100 μm or more, more preferably 500 μm or more, more preferably 1000 μm or less, and further preferably 850 μm or less in terms of volume average particle size. This is because if the particle size of the particles of the composite material is not less than the above lower limit, it is easy to form a thicker primary composite material sheet when the particles of the composite material are primarily pressed. In addition, if the particle size of the particles of the composite material is equal to or more than the above lower limit, the reason is not clear, but for example, the effect of reducing the thermal resistance value when the composite material sheet described below is tertiary-pressurized is large, This is because a composite material sheet having higher thermal conductivity can be obtained. Further, if the particle diameter of the composite material is equal to or less than the above upper limit, the handling property of the particles of the composite material is more excellent.

[Coverage of particles of composite material]
Further, in the preparation of particles of the composite material, as described above, when the inorganic particles A are charged at the time of mixing and kneading and the inorganic particles B are charged at the time of crushing and crushing, the following formula (3):
{(Specific surface area of inorganic particles B x mass of inorganic particles B)/
(Specific surface area of particles of composite material×mass of particles of composite material)×100 (3)
The coverage calculated by is preferably 20% or more, more preferably 30% or more, preferably 90% or less, and more preferably 60% or less. This is because the particles of the composite material having the coverage of the inorganic particles B equal to or higher than the lower limit described above suppress excessive stickiness and are more excellent in handling property. In addition, for the particles of the composite material in which the coverage of the inorganic particles B is not more than the above upper limit, the reason is not clear, but for example, due to the surface roughness of the composite material sheet using the particles of the composite material, the composite material sheet This makes it possible to provide a smooth surface. In addition, if the coverage of the inorganic particles B is less than or equal to the above upper limit, the reason is not clear, but for example, the effect of reducing the thermal resistance value when the composite material sheet, which will be described in detail later, is subjected to tertiary pressing is large, This is because a composite material sheet having higher conductivity can be obtained.
In addition, when the timing of adding the inorganic particles is shifted when preparing the particles of the composite material, the particles of the composite material in which all of the inorganic particles B are attached to the surface layer portion of the particle body containing the resin and the inorganic particles A are obtained. There is a case (I) and a case (II) where a powder composition containing the particles of the composite material and the inorganic particles B is obtained without adhering a part of the inorganic particles B to the surface layer portion of the particle body. Then, in the present specification, in the above case (II), the “specific surface area of particles of the composite material” and the “mass of particles of the composite material” used in the calculation of the coverage are “ratio as a composite composition”. It can be determined as "average surface area" and "average mass of composite composition".

<<Preparation Method of Composite Material Particles>>
The particles of the composite material are not particularly limited and can be prepared, for example, according to the same method as the step of obtaining the particles of the composite material described above.

Here, the mixing and kneading methods are not particularly limited and can be performed using a kneader, a roll, a Henschel mixer, a Hobart mixer, a high speed mixer, a biaxial kneader, or the like. The mixing and kneading may be carried out in the presence of a solvent such as ethyl acetate and methyl ethyl ketone. Furthermore, the mixing and kneading temperature can be, for example, 5° C. or higher and 150° C. or lower.

The crushing and crushing methods are not particularly limited, and include cutter mills, hammer mills, bead mills, vibration mills, meteor type ball mills, sand mills, ball mills, roll mills, triple roll mills, jet mills, high-speed rotary crushers, etc. Can be done using. Above all, it is desirable to use a cutter mill or a hammer mill.
Then, the crushing conditions may be adjusted as appropriate such as a crushing device and a crushing strength according to a desired particle size after crushing.

Furthermore, when preparing the particles of the composite material, for example, when using the above-described inorganic particles A and B as the inorganic material, the addition ratio of the inorganic particles B is the content of the inorganic particles A and the addition of the inorganic particles B. The total amount is preferably 10% by mass or more, more preferably 20% by mass or more, preferably 60% by mass or less, more preferably 50% by mass or less, and 35% by mass or less. Is more preferable. This is because when the addition ratio of the inorganic particles B is at least the above lower limit, the particles of the composite material can be prevented from being excessively sticky, and the handling properties of the particles of the composite material can be further improved. Further, if the addition ratio of the inorganic particles B is equal to or less than the above upper limit, for example, a composite material sheet obtained by using the particles of the composite material can exhibit desired properties such as thermal conductivity more.
Note that it is not clear why the particles of the composite material can be prevented from being excessively sticky by setting the addition ratio of the inorganic particles B to the above lower limit or more. However, when the composite mixture containing the resin and the inorganic particles A is crushed and crushed, the inorganic particles B are lagging behind the inorganic particles A, and particularly, the particles are added during crushing and crushing to obtain particles of the composite material. It is presumed that the reason is that the inorganic particles B are in a state of covering the surface layer portion of the particle body containing the resin and the inorganic particles A well.

<Sheet base material>
At least one of the sheet base materials used in the pressing method of the present invention needs to have a peeling force within a predetermined range. In sandwiching the particles of the above-mentioned predetermined composite material between the sheet base materials and performing the primary pressure, if at least one of the sheet base materials does not have a peeling force within a predetermined range, the thickened primary composite material sheet is favorably processed. Cannot be formed. Then, the composite material sheet cannot be efficiently manufactured using the laminate of the primary composite material sheet.

<<Peeling force of sheet base material>>
As for the peeling force of the sheet base material, the peeling force of at least one sheet base material among the two sheet base materials that sandwich the particles of the composite material described above at the time of primary pressing is 0.03 N/cm or more and 4.0 N/ Must be less than cm. Further, the peeling force of the sheet base material is preferably 0.30 N/cm or more, and 3.00 N/cm or less, when at least one of the two sheet base materials has a peeling force. It is preferable. Furthermore, in the sheet base material, both of the two sheet base materials sandwiching the particles of the composite material described above are more preferably 0.03 N/cm or more, further preferably less than 4.0 N/cm, More preferably, it is not more than 3.00 N/cm.
When the peeling force of at least one of the sheet base materials is equal to or more than the above lower limit, friction between the sheet base material and the particles of the composite material sandwiched between the sheet base materials increases, and the sheet base material is subjected to the primary pressurization. The material can exert a sufficiently large force on the particles of the composite material (so-called slippage does not easily occur). Therefore, it is easy to form a thickened primary composite material sheet, and a composite material sheet using a laminate of the primary composite material sheet can be efficiently manufactured. Here, in the case of forming a thickened primary composite material sheet, in general, since it is difficult for the sheet base material to give sufficient force to the particles of the composite material, the inorganic material contained in the particles of the composite material is directed in a desired direction. It is difficult to achieve good orientation. However, if the peeling force of at least one of the sheet base materials is equal to or more than the above lower limit, as described above, the sheet base material can give a large force to the particles of the composite material, so that the inorganic material is applied in the in-plane direction of the primary composite material sheet. Can be well oriented in a desired direction such as.
Further, if the peeling force of the sheet base material is equal to or less than the above upper limit, it is possible to sufficiently suppress the adhesion between the primary composite material sheet and the sheet base material when the sheet base material is peeled from the particles of the composite material that are primarily pressed. However, the primary composite material sheet can be satisfactorily obtained without damaging the sheet shape.
The material and the peeling force of the two sheet base materials may be the same or different.

<Primary pressure>
In the primary pressurization, the particles of the above-mentioned predetermined composite material are pressed in a state where at least one of the two particles is sandwiched between the sheet base materials having the above-mentioned predetermined peeling force. Then, by carrying out the primary pressure in this way, it is possible to favorably obtain the thickened primary composite material sheet.

<<Pressure method>>
The primary pressurization can be performed using a known pressurizing device such as a press machine or a roll machine without particular limitation. Above all, from the viewpoint of satisfactorily controlling the thickness of the primary composite material sheet, the primary pressurization is preferably performed by a roll machine.
The thickness of the primary composite material sheet can be well controlled by adjusting, for example, the pressure and the roll gap of the roll machine. For example, when the primary pressurization is performed using a roll machine, the roll linear pressure can be set to 10 kg/cm or more and 100 kg/cm or less.

<<Thickness of primary composite material sheet>>
The thickness of the primary composite material sheet obtained by primary pressing is preferably 1.0 mm or more, more preferably 1.2 mm or more, and 3.0 mm or less, preferably 2.0 mm or less. be able to. If the thickness of the primary composite material sheet is made thicker than the above lower limit, for example, when manufacturing a composite material sheet using a laminate of the primary composite material sheet, the number of layers of the primary composite material sheet in the laminate is Since it can be reduced, the manufacturing efficiency of the composite material sheet can be further increased. When the thickness of the primary composite material sheet is more than the above upper limit, the difficulty of forming the sheet is increased, and it is difficult to orient the inorganic material contained in the primary composite material sheet in a desired direction well. Also increases. Thus, in general, when a sheet is formed by pressing the particles of the composite material, the larger the thickness of the sheet, the more uniformly the particles of the composite material do not easily transmit a large pressing force, Sheet formation becomes difficult. However, in the present invention, the blocking resistance of the particles of the composite material is suppressed within a predetermined range, and the peeling force of at least one of the sheet base materials sandwiching the particles of the composite material is set within a predetermined range. For example, even when the thickness of the primary composite material sheet is set to 1.0 mm or more, which is relatively large, the primary composite material sheet can be satisfactorily formed.

<<Specific gravity of primary composite material sheet>>
Further, the specific gravity of the primary composite material sheet obtained by primary pressing is preferably 1.30 or more, more preferably 1.40 or more, and preferably 1.65 or less. If the specific gravity of the primary composite material sheet is equal to or more than the above lower limit, it can be said that the primary composite material sheet is formed while giving sufficient primary pressure force to the particles of the composite material. Therefore, it is possible to suppress the particles of the composite material from slipping during the primary pressurization, to better form a thicker composite material sheet, and to better align the inorganic material in the composite material sheet. This is because it can be done. Further, if the specific gravity of the primary composite material sheet is above the upper limit, it can be said that the particles of the composite material are excessively subjected to the force of the primary pressure, so that it is difficult to secure a large thickness of the composite material sheet.
In the present invention, the specific gravity of the primary composite material sheet can be appropriately adjusted by adjusting the conditions of primary pressurization such as roll gap and roll linear pressure.

And, in the obtained primary composite material sheet, since the inorganic material is favorably oriented in the in-plane direction, for example, when a particulate carbon material and a fibrous carbon material are used as the inorganic material, the primary composite material sheet It is inferred that the heat transfer paths of the particulate carbon material and the fibrous carbon are excellently formed in the in-plane direction. That is, it is presumed that the obtained primary composite material sheet has excellent thermal conductivity in the in-plane direction.

(Method of manufacturing composite material sheet)
The method for producing a composite material sheet of the present invention comprises a step of obtaining a primary composite material sheet according to the above-described pressing method, a step of obtaining a laminate of the obtained primary composite material sheet, and slicing the obtained laminate. And a step of obtaining a composite material sheet. By using the laminate of the primary composite material sheets obtained according to the above-described predetermined pressing method, the composite material sheet can be efficiently manufactured. Further, the method for producing a composite material sheet of the present invention further includes a step of subjecting the obtained laminate to a secondary pressurization to obtain a compressed laminate, prior to the step of obtaining the composite material sheet, to obtain a composite material sheet. It is preferable to slice the compressed laminate in the step. Further, it is preferable that the method for producing a composite material sheet of the present invention further includes a step of subjecting the obtained composite material sheet to a third pressurization and compression after the step of obtaining the composite material sheet.

<Step of obtaining primary composite material sheet>
In the step of obtaining the primary composite material sheet, the primary composite material sheet is obtained according to the pressing method described above. The thickness of the obtained primary composite material sheet can be set to the suitable thickness as described above in the paragraph of primary pressurization, and the same effect can be obtained.

<Process of obtaining laminated body>
In the step of obtaining a laminated body, a plurality of primary composite material sheets obtained in the step of obtaining the primary composite material sheet are laminated in the thickness direction, or the primary composite material obtained in the step of obtaining the primary composite material sheet The sheet is folded or rolled to obtain a laminate.

<<Stacking method>>
Formation of the laminated body by laminating the primary composite material sheets is not particularly limited, and may be performed using a laminating apparatus or may be performed manually. Further, the formation of the laminated body by folding the primary composite material sheet is not particularly limited and can be performed by folding the primary composite material sheet with a constant width using a folding machine. Further, the formation of the laminate by winding the primary composite material sheet is not particularly limited, by winding the primary composite material sheet around an axis parallel to the lateral direction or the longitudinal direction of the primary composite material sheet. It can be carried out.

Here, normally, in the step of obtaining a laminated body, the adhesive force between the surfaces of the primary composite material sheets is sufficiently obtained by the pressure when laminating the primary composite material sheets and the pressure when folding or winding the primary composite material sheets. However, when the adhesive strength is insufficient or when it is necessary to sufficiently suppress delamination of the laminate, the laminate may be formed with the surface of the primary composite material sheet slightly dissolved with a solvent. Then, the laminated body may be formed in a state in which an adhesive is applied to the surface of the primary composite material sheet or in a state in which an adhesive layer is provided on the surface of the primary composite material sheet.
The solvent used for dissolving the surface of the primary composite material sheet is not particularly limited, and a known solvent capable of dissolving the resin component contained in the primary composite material sheet can be used. The adhesive applied to the surface of the primary composite material sheet is not particularly limited, and a commercially available adhesive or tacky resin can be used. Further, the adhesive layer provided on the surface of the primary composite material sheet is not particularly limited, and a double-sided tape or the like can be used.

[Number of layers]
Then, in the step of obtaining a laminated body, when the thickened primary composite material sheet is used as described above, the number of laminated layers, the number of folds or the number of windings of the laminated body can be reduced, thus making the laminated body more efficient. Can be formed as desired. For example, if the thickness of the primary composite material sheet is doubled from 0.5 mm to 1.0 mm, the number of laminated layers can be generally halved, so that the laminated material and the composite material sheet are formed. Efficiency can be doubled.

In the laminate obtained by laminating, folding or winding the primary composite material sheets, it is presumed that the inorganic materials such as the particulate carbon material and the fibrous carbon material are oriented in a direction substantially orthogonal to the laminating direction. It

<Step of obtaining compressed laminate>
In the step of obtaining a compressed laminate that may be further included in the method for producing a composite material sheet of the present invention, the laminate obtained in the step of obtaining the laminate is secondarily pressed in the laminating direction and compressed to form a compressed laminate. obtain. If the laminate is further subjected to secondary pressure in this way, the inorganic material can be favorably oriented in the compression laminate in a direction substantially orthogonal to the laminating direction (in-plane direction of the primary composite material sheet). The sheet may provide desired properties such as better thermal conductivity.

<<Secondary pressure>>
In the secondary pressing, the above-mentioned laminated body of the primary composite material sheets is pressed in the laminating direction to compress the laminated body. The secondary pressurization of the laminate is not particularly limited, and can be performed by the same method as the above-described primary pressurization. Among them, it is preferable to use a press machine from the viewpoint of workability.
Here, from the viewpoint of suppressing delamination, for example, the press pressure of the secondary pressurization can be set to 0.05 MPa or more and 1.0 MPa or less, the pressing temperature is 20° C. or more and 150° C. or less, and the pressing time is Can be 1 minute or more and 30 minutes or less.

[Rate of stack height reduction]
Here, in the secondary pressurization, it is preferable that the reduction rate of the height from the laminated body to the compressed laminated body (the reduction rate of the laminated body height) calculated by the above formula (1) is 1% or more. It is more preferably 3% or more, further preferably 10% or more, more preferably 30% or less, and further preferably 20% or less. If the reduction rate of the laminate height is not less than the above lower limit, the laminated primary composite material sheets can be better adhered to each other to further suppress delamination, and the inorganic material is substantially orthogonal to the laminating direction of the laminate. Since it is more favorably oriented (in the in-plane direction of the primary composite material sheet), for example, a conductive path made of a particulate carbon material, a fibrous carbon material, or the like is more favorably formed. Therefore, it is possible to further impart anisotropy of physical properties such as thermal conductivity in a direction substantially orthogonal to the stacking direction of the stacked body. Further, if the reduction rate of the height of the laminate is not more than the upper limit, it is possible to maintain good thermal conductivity without excessively pressing the laminate to cut the conductive path of the inorganic material. ..

<Process of obtaining composite material sheet>
In the step of obtaining the composite material sheet, the laminate obtained in the step of obtaining the laminate is sliced at an angle of 45° or less with respect to the laminating direction to obtain a composite material sheet (“composite material sheet before tertiary pressing”). May be called)). Further, in the step of obtaining the composite material sheet, when slicing the laminated body, it is preferable to slice the compressed laminated body obtained in the step of obtaining the compressed laminated body at an angle of 45° or less with respect to the laminating direction.

<<Slicing method>>
The method for slicing a laminated body such as a compressed laminated body is not particularly limited, and examples thereof include a multi-blade method, a laser processing method, a water jet method, and a knife processing method. Among them, the knife processing method is preferable because it is easy to make the thickness of the composite material sheet uniform. Further, the cutting tool when slicing the laminated body such as the compressed laminated body is not particularly limited, a smooth board surface having a slit, and a slicing member having a blade portion protruding from the slit portion (for example, A planer or slicer with a sharp blade can be used.

From the viewpoint of enhancing desired properties such as thermal conductivity of the composite material sheet, the angle at which a laminated body such as a compressed laminated body is sliced is preferably 30° or less with respect to the laminating direction, and in the laminating direction. On the other hand, the angle is more preferably 15° or less, and preferably approximately 0° with respect to the stacking direction (that is, the direction along the stacking direction).
Further, from the viewpoint of easily slicing a laminated body such as a compressed laminated body, the temperature of the laminated body such as the compressed laminated body at the time of slicing is preferably −20° C. or higher and 40° C. or lower, and 10° C. or higher and 30° C. The following is more preferable. Further, from the viewpoint of easily slicing a laminated body such as a compressed laminated body, it is preferable to slice a laminated body such as a compressed laminated body while applying pressure in a direction (laminating side surface) orthogonal to the laminating direction. More preferably, slicing is performed while applying a pressure of 0.1 MPa or more and 0.5 MPa or less in a direction (stacking side surface) orthogonal to the stacking direction.

<<Specific gravity of composite material sheet before tertiary pressing>>
Here, the specific gravity of the composite material sheet before the third pressurization described later is preferably 1.40 or more, more preferably 1.50 or more, and preferably 2.00 or less, It is more preferably 1.80 or less. If the specific gravity of the composite material sheet before the third pressurization obtained through the secondary pressurization and slicing of the laminate is equal to or more than the above lower limit, for example, the laminate is sufficiently given the force of the secondary pressurization. It can be said that the compressed laminate is used to form the composite material sheet. Therefore, a conductive path in which an inorganic material such as a particulate carbon material and a fibrous carbon material is oriented in the thickness direction is more favorably formed, and anisotropy of physical properties such as thermal conductivity in the thickness direction of the composite material sheet. This can be further imparted. In addition, when the specific gravity of the composite material sheet before the third pressure is above the above upper limit, the laminate receives the force of the second pressure excessively, the conductive path of the inorganic material is cut off, and the thermal conductivity of the composite material sheet, etc. This is because there is a possibility that the characteristics of will deteriorate.
In the present invention, the specific gravity of the composite material sheet before the third pressurization can be appropriately adjusted by adjusting the conditions of the second pressurization, for example.

In the obtained composite material sheet, the inorganic material is favorably oriented in the thickness direction, and it is speculated that the composite material sheet is particularly excellent in desired properties such as thermal conductivity in the thickness direction.

<Third pressurizing and compressing step>
In the step of tertiary pressurizing and compressing which may be further included in the method for producing a composite material sheet of the present invention, the composite material sheet obtained according to the above-mentioned producing method is further subjected to tertiary pressurization in the thickness direction to be compressed. By tertiary pressing the composite material sheet in this manner, the surface smoothness of the composite material sheet can be enhanced. Therefore, for example, when the composite material sheet is used by being attached to an arbitrary adherend, the adhesion between the composite material sheet and the adherend is enhanced, and the composite material sheet is made to exhibit desired properties such as thermal conductivity more. obtain.
The composite material sheet obtained through the step of applying the third pressurizing and compressing may be referred to as a “composite material sheet after the third pressurizing”.

<< tertiary pressurization >>
The third pressurization of the composite material sheet is not particularly limited and can be performed by the same method as the above-mentioned primary pressurization, and among them, it is preferable to use a press machine from the viewpoint of workability. For example, from the viewpoint of imparting good smoothness to the surface without impairing the physical properties of the composite material sheet, the conditions of the third pressurization are as follows: temperature 20° C. or higher and 100° C. or lower, press pressure 0.1 MPa or higher and 50 MPa or lower, press time. It can be 5 seconds or more and 5 minutes or less.

[Reduction rate of sheet thickness]
Here, in the tertiary pressurization, the reduction rate of the sheet thickness calculated by the above-mentioned formula (2) is preferably 1% or more, more preferably 5% or more, and 40% or less. Is preferable, 30% or less is more preferable, and 20% or less is further preferable. By tertiary pressing the composite material sheet at a reduction rate of the sheet thickness equal to or more than the above lower limit, the surface of the obtained composite material sheet can be smoothed. For example, the composite material sheet is attached to an adherend and used. In this case, the adhesion between the composite material sheet and the adherend is enhanced. As a result, the desired characteristics of the composite material sheet can be better exhibited. Further, if the reduction rate of the sheet thickness is suppressed to the above upper limit or less, for example, the orientation of the inorganic material that is favorably oriented in the thickness direction of the composite material sheet is maintained, and desired properties in the thickness direction of the composite material sheet are maintained. This is because it is possible to secure good.

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 "parts" representing amounts are based on mass unless otherwise specified.
Then, in Examples and Comparative Examples, the density, volume average particle size and specific surface area of the particles of the inorganic material and the composite material; the blocking resistance of the particles of the composite material; the peeling force of the sheet base material; Height; specific gravity of the primary composite material sheet and the composite material sheet before the tertiary pressurization; thickness of the primary composite material sheet and the composite material sheet before and after the tertiary pressurization; surface roughness Sz and heat of the composite material sheet before and after the tertiary pressurization The resistance value was measured or evaluated according to the following methods.

<Density>
The particle densities of the inorganic material and the composite material were measured for each using a true density measuring device (manufactured by Seishin Enterprise Co., Ltd., product name "MAT-7000"). The measurement temperature: 25° C., sample mass: 2 g, solvent: N-butanol, degassing time: 10 minutes. Here, regarding the density of the particles of the composite material, the total amount of the inorganic particles B used when preparing the particles of the composite material was included (that is, there are inorganic particles B that did not form the particles of the composite material. In this case, the average value (g/m ³ ) of the powder composition including the inorganic particles B was calculated.
And the obtained density was used for the calculation of the specific surface area mentioned later.

<Volume average particle size>
The volume average particle diameter (m) of the particles of the inorganic material and the composite material was measured using a laser diffraction/scattering type particle diameter distribution measuring device (manufactured by Nikkiso Co., Ltd., product name “Microtrac MT3300EX-II”). Specifically, the particle size distribution was obtained for the particles of the inorganic material and the composite material. Then, in each of the obtained particle size distributions (volume basis), the central particle size (D50) at which the cumulative volume calculated from the small diameter side is 50% was calculated as the volume average particle size of the particles of the inorganic material and the composite material. .. Regarding the volume average particle diameter of the particles of the composite material, the total amount of the inorganic particles B used when preparing the particles of the composite material was included (that is, the inorganic particles B that did not form the particles of the composite material were When it was present, it was calculated as an average value (m) of the entire powder composition including the inorganic particles B.
And the obtained volume average particle diameter was used for the calculation of the specific surface area mentioned later.

<Specific surface area>
The specific surface area of the particles of the inorganic material and the composite material is calculated by the following equation (4) using the values of the density and the volume average particle diameter calculated as described above:
Specific surface area (m ² /g)=
6/(density (g/m ³ )×volume average particle diameter (m)) (4)
Asked according to.
And the obtained specific surface area was used for calculation of the coverage represented by the above-mentioned formula (3).

<Blocking resistance>
The blocking resistance of the particles of the composite material was evaluated by the sieving method. Specifically, 80 g of particles of the composite material sieved with a mesh having an opening of 1.4 mm were charged into the beaker from the same height as the upper mouth of a 200 mL glass beaker without applying pressure. Next, a 400 g weight having the same inner diameter as the inner diameter of the beaker charged with the particles of the composite material was slowly placed on the particles of the composite material in the beaker. One minute after the weight was placed, the weight was removed, and the particles of the composite material attached to the outer bottom surface of the weight were removed into the beaker so that the particles of the composite material were not lost.
Then, on the upper mouth of the beaker containing the particles of the composite material, put a mesh having a wire diameter of 1.1 mm, an opening of 11.3 mm, and a size larger than the upper mouth (a square of 150 mm on a side), Further, a bat was placed on the mesh. Next, while fixing the beaker, mesh, and bat, the upper and lower surfaces were turned upside down, and the beaker was pulled up 15 cm from the mesh. Then, the mesh was slowly lifted by 5 cm, and 1 minute after the lifting, the particles of the composite material remaining on the mesh were transferred to another vat. If particles of the composite material do not almost drop from the bottom of the beaker even if the top and bottom are turned upside down, lightly tap the outside of the beaker with a spatula etc. without separating the beaker from the mesh. Was dropped on the mesh. Also, when the particles of the composite material adhered to the inside of the beaker when the beaker was pulled up, the outside of the beaker was lightly tapped with a spatula or the like to drop the particles of the composite material onto the mesh.
Then, the following equation (5):
Blocking resistance (%)=(mass of composite material particles passing through mesh (g))/(mass of composite material particles remaining on mesh (g)+mass of composite material particles passing through mesh ( g))×100% (5)
According to the above, the blocking resistance of the particles of the composite material was determined. The larger the calculated value is, the less sticky the particles of the composite material are, and the more difficult the blocking is.

<Peeling force>
The sheet base material was cut into a 25 mm×125 mm strip shape to obtain a test body. Next, a polyester pressure-sensitive adhesive tape (manufactured by Nitto Denko, trade name “No. 31B”) was attached to the surface of the test body that was in contact with the particles of the composite material. Then, the peeling force (N/cm) between the test body and the polyester adhesive tape attached to the test body was measured using a tensile tester (manufactured by Shimadzu Corporation, product name "Autograph AG-IS 20kN"). Then, in accordance with JIS Z-0237, the peeling speed was measured at 500 mm/min and the peeling angle was 180°.

<height>
The height (mm) of the laminate and the compression laminate was determined by visually measuring the height of the laminate with a ruler.

<Specific gravity>
The specific gravities of the primary composite material sheet and the composite material sheet before the third pressurization were measured using an automatic hydrometer (manufactured by Toyo Seiki Co., Ltd., product name “DENSIMETER-H”).

<Thickness>
The thicknesses of the primary composite material sheet and the composite material sheet before and after the third pressurization were measured by using a film thickness meter (manufactured by Mitutoyo, product name “Digimatic Indicator ID-C112XBS”). Then, the measurement was carried out at arbitrary 5 points on the surface of each sheet, and the average value of the measured values was taken as the thickness (mm) of each sheet.

<Surface roughness Sz>
The surface roughness Sz of the composite material sheet before and after the third pressurization was measured using a three-dimensional shape measuring instrument (manufactured by Keyence Corporation, product name "One Shot 3D Measuring Macroscope"). Here, each sheet cut into an approximately square having an arbitrary size of 1 cm square or more was used as a sample. Moreover, the analysis range was set to 1 cm×1 cm, and the three-dimensional shape of each surface (pressurized surface) of the sample was measured. Then, the measurement result of the three-dimensional shape was further filtered by software (2.5 mm) to remove the waviness component, thereby automatically extracting the surface roughness Sz (μm) component.
In the present invention, the “surface roughness Sz” is the maximum height (a distance in the height direction connecting the highest point and the lowest point on a certain surface) defined in International Standard ISO 25178, It is an index for evaluating the roughness state of the certain surface.

<Thermal resistance value>
The thermal resistance value of the composite material sheet before and after the third pressurization was measured by a stationary method using a thermal resistance measuring device (manufactured by Hitachi Technology and Service Co., Ltd., product name "resin material thermal resistance measuring device"). Here, each sheet cut into an approximately square of 1 cm square was used as a sample, and the thermal resistance value (°C/W) under a relatively low pressure of 0.05 MPa was measured. The sample temperature during measurement was 50°C. It is shown that the smaller the heat resistance value, the more excellent the thermal conductivity of the composite material sheet is, and, for example, the better the heat dissipation characteristic when the composite material sheet is interposed between the heat generating body and the heat dissipating body to form a heat dissipating device.

(Example 1)
<Preparation of fibrous carbon nanostructure containing CNT>
A fibrous carbon nanostructure containing CNTs was obtained by the supergrowth method according to the description in WO 2006/011655.
The resulting fibrous carbon nanostructure had a BET specific surface area of 800 m ² /g. The diameter of 100 randomly selected fibrous carbon nanostructures was measured using a transmission electron microscope. As a result, the average diameter (Av) was 3.3 nm, and the sample standard deviation (σ) of the diameter was 3 The value (3σ) multiplied by was 1.9 nm, and their ratio (3σ/Av) was 0.58. Moreover, the obtained fibrous carbon nanostructure was mainly composed of single-walled CNTs.

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

<Preparation of particles of composite material>
100 parts of a thermoplastic fluororesin that is liquid as a resin under normal temperature and pressure (manufactured by Daikin Industries, Ltd., trade name "Daiel G-101"), and expanded graphite as inorganic particles A among inorganic materials (Ito Graphite Industry Co., Ltd.) Ltd., trade name “EC-100”, volume average particle diameter: 190 μm) 30 parts, and 0.1 part of a readily dispersible aggregate of fibrous carbon nanostructures as a fibrous carbon material, It 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, 20 parts of the obtained composite mixture and expanded graphite (manufactured by Ito Graphite Industry Co., Ltd., trade name “EC-100”, volume average particle diameter: 190 μm) as the inorganic particles B among the inorganic materials, It was put into a free speed mill (manufactured by Ronect Co., Ltd., product name "FS20") all at once. Then, particles of the composite material were obtained by crushing for 60 seconds at a speed memory=100.
And about the particle|grains of the obtained composite material, the density, the volume average particle diameter, the specific surface area, and blocking resistance were measured according to the above-mentioned method. The results are shown in Table 1.

<Formation of primary composite material sheet>
Then, 100 g of the particles of the obtained composite material are sandwiched between two pieces of fluorine film (manufactured by Daikin Industries, Ltd., trade name “Neotron PFA film”, thickness: 50 μm, peeling force: 0.30 N/cm) as a sheet base material. It is. Then, the sandwiched composite material particles are roll-formed (primary pressure) under the conditions of a roll gap of 1500 μm, a roll temperature of 50° C., a roll linear pressure of 50 kg/cm, and a roll speed of 1 m/min to obtain a thickness of 1.449 mm. A primary composite material sheet having a specific gravity of 1.50 was obtained.
The releasability between the primary composite material sheet obtained by primary pressing and the sheet base material was good.
Then, the specific gravity and the thickness of the obtained primary composite material sheet were determined according to the method described above. The results are shown in Table 1.

<Formation of laminated body>
The obtained primary composite material sheet was cut into a length of 6 cm×width of 6 cm×thickness of 1.449 mm, and 33 sheets were laminated in the thickness direction to obtain a laminate having a height of 4.78 cm.
And about the obtained laminated body, the height was calculated|required according to the above-mentioned method.

<Formation of compressed laminate>
Next, the obtained laminated body is subjected to a secondary pressure (press) in the laminating direction at a temperature of 120° C. for 1 minute at a pressure of 0.1 MPa to be compressed, whereby a compressed laminated body having a height of about 4.16 cm. Got That is, the reduction rate of the height of the laminate due to the secondary pressure was 13%.
During the secondary pressurization, the pressure applied to the laminate does not escape in a direction orthogonal to the lamination direction, which is the pressure direction (in other words, the in-plane direction of the primary composite material sheet), so that the laminate does not escape. The four laminated side surfaces other than the pressing upper surface and the pressing bottom surface were surrounded by a resin cover. In this way, the laminated body was prevented from being deformed in the direction substantially orthogonal to the laminating direction due to the secondary pressure.
And about the obtained compression laminated body, the height was calculated|required according to the above-mentioned method. The results are shown in Table 1.

<Formation of composite material sheet before tertiary pressing>
Using the slicer for woodworking (manufactured by Marunaka Iron Works Co., Ltd., product name "Super Finishing Planer Super Mechanical S") while pressing the laminated side surface of the obtained compressed laminate with a pressure of 0.1 MPa. Sliced at an angle of 0 degree with respect to the direction (in other words, sliced in the direction normal to the main surface of the laminated primary composite material sheet), and the cubic of 6 cm in length × 6 cm in width × 147 μm and specific gravity of 1.47 A composite material sheet before pressing was obtained. Here, as a knife for a slicer for woodworking, two single blades are in contact with each other on the opposite sides of the cutting blades, and the tip end of the front edge is 0.10 mm higher than the tip end of the back edge, and the slit part A two-blade knife having a protrusion length of 0.16 mm and a front blade angle of 21° was used.
Then, the specific gravity, the thickness, the surface roughness Sz, and the thermal resistance value of the obtained composite material sheet before the third pressurization were measured according to the methods described above. The results are shown in Table 1.

<Formation of composite material sheet after tertiary pressing>
Using the press machine (manufactured by Shinto Kogyo Co., Ltd., product name "Precision Hot Press CYPT-20") obtained above, the composite material sheet before the third pressurization was carried out at a press plate temperature of 25° C. and a pressure of 5 MPa. The composite material sheet after the third pressurization was obtained by third pressurizing and compressing in the thickness direction under the condition of 30 seconds.
The thickness of the composite material sheet subjected to the third pressure was 126 μm, and the reduction rate of the sheet thickness due to the third pressure was 14.3%.
Then, with respect to the obtained composite material sheet after the third pressurization, the surface roughness Sz and the thermal resistance value were measured according to the methods described above. The results are shown in Table 1.

(Example 2)
In the preparation of the particles of the composite material, the amount of the expanded graphite which is the inorganic particle A was changed to 35 parts, the amount of the expanded graphite which was the inorganic particle B was changed to 15 parts, and the speed memory of the free speed mill was 40%. In the same manner as in Example 1 except for crushing for 30 seconds, particles of the composite material having the properties described in Table 1, primary composite material sheet, laminate, compression laminate, and composite material sheet before and after tertiary pressurization Was manufactured.
And it measured like Example 1. The results are shown in Table 1.

(Example 3)
In the formation of the primary composite material sheet, as a sheet base material, two sand matted sand mat pets (manufactured by Unitika, trade name "Emblet (registered trademark) PTHA-50", thickness: 75 μm, peeling force: 2 .3 N/cm) in the same manner as in Example 1 except that the particles of the composite material having the properties shown in Table 1, the primary composite material sheet, the laminate, the compression laminate, and the composite material before and after the tertiary pressurization are used. The sheet was manufactured.
And it measured like Example 1. The results are shown in Table 1.

(Example 4)
In the formation of the primary composite material sheet, a release-treated PET film (manufactured by Toray Film Co., Ltd., trade name “Serapeal (registered trademark) BX8”, thickness: 75 μm, peeling force: 0.03 N, as a sheet base material on the upper surface. /Cm), and sand blasted sand mat pet as a sheet base material for the lower surface (Unitika, trade name "Emblet (registered trademark) PTHA-50", thickness: 75 μm, peeling force: 2.3 N/ cm) was used in the same manner as in Example 2 to produce particles of a composite material having the properties shown in Table 1, a primary composite material sheet, a laminate, a compression laminate, and a composite material sheet before and after tertiary pressing. did. Note that, for convenience, the sheet base material arranged on the upper side of the particles of the composite material at the time of primary pressurization is referred to as the “upper surface”, and the sheet base material arranged on the lower side of the particles of the composite material is referred to as the “lower surface”. In achieving the effect of the present invention, there is no particular distinction between the upper surface and the lower surface.
And it measured like Example 1. The results are shown in Table 1.

(Example 5)
In the formation of the primary composite material sheet, as a sheet base material, two sand matted sand mat pets (manufactured by Unitika, trade name "Emblet (registered trademark) PTHA-50", thickness: 75 μm, peeling force: 2 .3 N/cm) in the same manner as in Example 2 except that the particles of the composite material having the properties shown in Table 1, the primary composite material sheet, the laminate, the compression laminate, and the composite material before and after the tertiary pressurization were used. The sheet was manufactured.
And it measured like Example 1. The results are shown in Table 1.

(Comparative example 1)
In the formation of the primary composite material sheet, as the sheet base material, two PET films subjected to a release treatment (manufactured by Fujiko Co., Ltd., a release film, thickness: 50 μm, release force: 0.02 N/cm) were used. In the same manner as in Example 1 except for the above, particles of the composite material having the properties shown in Table 1 were prepared. Then, an attempt was made to form a primary composite material sheet in the same manner as in Example 1, but it could not be formed into a sheet.
And it measured like Example 1. The results are shown in Table 1.

(Comparative example 2)
In the formation of the primary composite material sheet, as the sheet base material, two PET films subjected to a release treatment (manufactured by Fujiko Co., Ltd., a release film, thickness: 50 μm, release force: 0.02 N/cm) were used. In the same manner as in Example 2 except for the above, particles of the composite material having the properties shown in Table 1 were prepared. Then, an attempt was made to form a primary composite material sheet in the same manner as in Example 1, but it could not be formed into a sheet.
And it measured like Example 1. The results are shown in Table 1.

(Comparative example 3)
In the formation of the primary composite material sheet, as the sheet base material, two PET films subjected to a release treatment (manufactured by Fujiko Co., Ltd., release film, thickness: 50 μm, release force: 0.02 N/cm) are used, By changing the roll gap to 500 μm, a primary composite material sheet having a thickness of 0.447 mm and a specific gravity of 1.67 was obtained. Further, in forming the laminate, the number of laminated primary composite material sheets was changed to 100. Furthermore, the same as Example 2 except that the formation of the compression laminate (secondary pressing of the laminate) was not performed, and the formation of the composite material sheet after the third pressing (third pressing of the composite material sheet) was not performed. Thus, particles of the composite material having the properties shown in Table 1, a primary composite material sheet, a laminate, and a composite material sheet before the third pressing were manufactured.
And it measured like Example 1. The results are shown in Table 1.

(Comparative example 4)
In the preparation of the particles of the composite material, the particles of the composite material having the properties shown in Table 1 were prepared in the same manner as in Example 1 except that the particles of the composite material were obtained by the following method. Then, an attempt was made to form a primary composite material sheet in the same manner as in Example 1, but it could not be formed into a sheet.
And it measured like Example 1. The results are shown in Table 1.
<Preparation of particles of composite material>
As a resin, 45 parts of a thermoplastic fluororesin that is liquid under normal temperature and normal pressure (manufactured by Daikin Industries, Ltd., trade name "DAIEL G-101") and a thermoplastic fluororesin that is solid under normal temperature and normal pressure (manufactured by Daikin Industries, Ltd., 40 parts of trade name "DAIEL G-704BP") and expanded graphite as a particulate carbon material which is the inorganic particles A (manufactured by Ito Graphite Industry Co., Ltd., trade name "EC-50", volume average particle diameter: 250 μm) ), and 0.1 part of an easily dispersible aggregate of fibrous carbon nanostructures as a fibrous carbon material, and sebacate ester as a plasticizer (manufactured by Daihachi Chemical Industry Co., Ltd., trade name " 5 parts of DOS") was stirred and mixed for 5 minutes using a Hobart mixer (manufactured by Kodaira Manufacturing Co., Ltd., product name "ACM-5LVT type") in the presence of 100 parts of ethyl acetate as a solvent. Next, the mixture in the Hobart mixer was vacuum degassed for 30 minutes, and ethyl acetate was removed simultaneously with the degassing. Then, the mixture from which the ethyl acetate was removed was crushed for 10 seconds using a crusher (free speed mill described above) without adding the inorganic particles B to obtain particles of the composite material.

(Comparative example 5)
In the formation of the primary composite material sheet, as the sheet base material, two PET films which are not surface-treated (manufactured by Toyobo, trade name "TOYOBO Ester (registered trademark) film E5000", thickness: 50 μm, peeling force: 4. Particles of the composite material having the properties shown in Table 1 were prepared in the same manner as in Example 1 except that 0 N/cm) was used. Then, when a primary composite material sheet was formed in the same manner as in Example 1, the primary composite material sheet was not properly separated from the sheet base material, and the primary composite material sheet was broken.
And it measured like Example 1. The results are shown in Table 1.

From Table 1, the particles of the composite material containing the resin and the inorganic material and having the blocking resistance of 0% or more and 80% or less have a peeling force of at least one sheet base material of 0.03 N/cm or more and 4.0 N/ In Examples 1 to 5 sandwiched between sheet base materials having a size of less than cm and subjected to primary pressure, Comparative Examples 1 and 2 and Comparative Example 5 in which two sheet base materials are out of the above-described predetermined ranges, and a blocking resistance rate is predetermined. It can be seen that the thickened primary composite material sheet can be favorably formed as compared with Comparative Example 4, which is out of the range.
On the other hand, in Comparative Example 3, which can be formed into a sheet of a primary composite material sheet but has a small thickness, a laminated body is formed with about three times as many laminated layers as in Examples 1 to 5 in which the thickness of the primary composite material sheet is increased. Therefore, it can be seen that it takes time to manufacture the composite material sheet.

According to the present invention, a thickened primary composite material sheet can be formed. For example, even when a composite material sheet is manufactured using a laminate of the primary composite material sheets, the composite material sheet can be efficiently manufactured. It is possible to provide a method of pressing the particles of the composite material.
Further, according to the present invention, it is possible to provide a method for manufacturing a composite material sheet, which can efficiently manufacture the composite material sheet.

Claims (8)

A pressurizing method in which particles of a composite material containing a resin and an inorganic material are first pressed while being sandwiched between two sheet base materials,
The blocking resistance of the particles of the composite material is 0% or more and 80% or less,
A pressing method, wherein the peeling force of at least one of the two sheet base materials is 0.03 N/cm or more and less than 4.0 N/cm. The pressurizing method according to claim 1, wherein at least one of the two sheet base materials has a peeling force of 0.30 N/cm or more and 3.00 N/cm or less. The pressing method according to claim 1, wherein the thickness of the primary composite material sheet obtained by the primary pressing is 1.0 mm or more. Obtaining a primary composite material sheet according to the pressing method according to any one of claims 1 to 3,
Stacking a plurality of the primary composite material sheets in the thickness direction, or folding or winding the primary composite material sheet to obtain a laminate,
And a step of obtaining a composite material sheet by slicing the laminate at an angle of 45° or less with respect to the laminating direction. The method further includes the step of obtaining a compressed laminated body by subjecting the laminated body to a secondary pressure in the laminating direction to compress the laminated body,
The method for producing a composite material sheet according to claim 4, wherein in the step of obtaining the composite material sheet, the composite laminate sheet is obtained by slicing the compressed laminate at an angle of 45° or less with respect to the laminating direction. The method for producing a composite material sheet according to claim 5, wherein the reduction rate of the height of the laminate due to the secondary pressure is 1% or more and 30% or less. A method for producing a composite material sheet, further comprising the step of subjecting the composite material sheet obtained by the production method according to any one of claims 4 to 6 to tertiary pressure in the thickness direction to compress the composite material sheet. The method for producing a composite material sheet according to claim 7, wherein the reduction rate of the sheet thickness due to the third pressing is 1% or more and 40% or less.