WO2020013268A1 - Highly thermally conductive material having flexing properties - Google Patents

Abstract

Provided is a highly thermally conductive material having flexing properties which comprises a resin and an alumina fiber sheet comprising continuous alumina fibers, wherein the alumina fiber sheet is contained in an amount of 30-80 mass% of the highly thermally conductive material.

Description

Highly thermally conductive material with flexibility

The present invention relates to a highly heat conductive material having flexibility.

In recent years, electronic equipment has been reduced in size and weight in the automotive and electrical industries. On the other hand, thermal runaway, thermal fatigue, and the like due to an increase in the amount of generated heat have become problems. Metals such as aluminum have high thermal conductivity, but have problems in terms of weight and electrical insulation. The high heat conductive resin material is superior to the high heat conductive metal material in terms of weight reduction and electric insulation, and is expected to be replaced. Therefore, improvement of the thermal conductivity of a resin by combining a high thermal conductive and electrically insulating filler with the resin has been widely studied.

電子 In addition, electronic devices to be mounted are becoming smaller and more highly integrated, and their shapes are becoming more complicated. When the temperature of the heat-generating component is high, the shape of the heat-generating component is often deformed such as warpage. When a high heat conductive material is used as a heat dissipation material, it is important to follow the deformation of the heat-generating component due to the temperature and maintain the close contact. Therefore, the high thermal conductive material also requires flexibility. By containing the inorganic filler at a high concentration, high thermal conductivity can be achieved. However, since the inorganic substance is brittle, there is a problem in that the high thermal conductivity and the flexibility are inconsistent when the composite is contained at a high concentration, whereby the flexibility of the composite is lost.

In order to maintain the advantages of light weight and processability of the resin, it is important to add a small amount of a thermally conductive filler and efficiently form a heat conduction path. From such a viewpoint, a particle-like, plate-like or fibrous shape has been studied as the shape of the thermally conductive filler. For example, Patent Document 1 discloses a thermoplastic resin composition in which three highly thermally conductive alumina particles having different particle diameters are combined. Patent Literature 2 discloses a thermoplastic resin composition in which high thermal conductive inorganic fibers and high thermal conductive inorganic powder are combined. Further, Patent Document 3 describes high thermal conductivity and flexibility of a thermal conductive material in which woven alumina fibers are coated with silicone rubber. However, no specific embodiment is disclosed.

The present inventors have reported the use of alumina fibers as a fibrous heat conductive filler (Non-Patent Document 1). The spinning solution in which boehmite particles are dispersed in an aqueous polyvinyl alcohol solution is subjected to electrostatic spinning, and the alumina fiber is obtained by removing the polyvinyl alcohol by firing. Then, a sheet in which alumina fibers are combined with a polyurethane sheet is used as a highly conductive material. However, its flexibility was not reported.

JP-A-5-132576 JP-A-8-283456 Japanese Patent No. 4343355

Koji Nakane et al., `` Thermal Conductivity of Polyurethane Sheets containing Alumina Nanofibers '', SENI GAKKAISHI Vol. 71, No.1, 67 (2015)

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a highly heat-conductive material having flexibility and including an alumina fiber sheet and a resin.

The present inventors have conducted intensive studies in order to achieve the above object, and as a result, a composite obtained by combining a high heat conductive alumina fiber sheet made of continuous alumina fibers with a resin in an appropriate amount has sufficient heat conductivity. In addition, they have found that the thermal conductivity is excellent and the thermal conductivity after bending is excellent, and the present invention has been completed.

That is, the present invention provides the following high thermal conductive material.
1. A highly heat-conductive material having flexibility, comprising an alumina fiber sheet made of continuous alumina fibers and a resin, wherein the alumina fiber sheet is contained in an amount of 30 to 80% by mass in the high heat-conductive material.
2. 1. The high thermal conductivity material according to 1, wherein the alumina fiber sheet is contained in an amount of 40 to 70% by mass in the high thermal conductivity material.
3. 1 or 2, wherein the alumina continuous fiber has an aspect ratio of 100 or more.
4. 3. The high thermal conductive material having an aspect ratio of 1,000 or more.
5. The high thermal conductive material according to any one of 1 to 4, wherein the alumina fiber sheet is made of at least one selected from non-woven alumina continuous fibers and alumina continuous fibers oriented in a certain direction.
6. The high thermal conductive material according to any one of 1 to 5, wherein the alumina fiber sheet contains α-alumina.
7. 6. The high thermal conductive material according to 6, wherein the α-alumina is contained in the alumina fiber sheet in an amount of 50% by mass or more.
8. 8. The high thermal conductive material according to any one of 1 to 7, wherein the alumina continuous fiber has an average fiber diameter of 50 to 2,000 nm.
9. 8. The high heat conductive material according to 8, wherein the average fiber diameter of the continuous alumina fibers is 100 to 1,000 nm.
10. 10. The high thermal conductive material according to any one of 1 to 9, wherein the high thermal conductive material is a sheet.
11. 10. The high thermal conductive material according to 10, wherein the high thermal conductive material is in the form of a sheet and has a thickness of 20 to 2,000 μm.
12. 11. The high thermal conductive material according to 11, wherein the high thermal conductive material is in the form of a sheet and has a thickness of 40 to 1,500 μm.
13. 13. The high thermal conductive material according to any one of 1 to 12, wherein the resin is at least one selected from the group consisting of polyvinyl alcohol, polyurethane resin, epoxy resin, polyimide resin, polyvinylidene fluoride resin, polystyrene and silicone resin.
14． 14. The high thermal conductive material according to any one of 1 to 13, which has a thermal conductivity of 5 W / mK or more.
15. 15. The high thermal conductive material according to any one of 1 to 14, wherein the thermal conductivity after bending 10 times with a curvature of 5 mm in diameter maintains 80% or more.
16. The high thermal conductive material according to any one of 1 to 15, wherein the high thermal conductive material is electrically insulating.
17. 17. The high thermal conductive material according to any one of 1 to 16, wherein the surface thermal resistance of the high thermal conductive material is 1 × 10 ¹¹ Ω / □ or more.

高 The high thermal conductive material of the present invention has excellent thermal conductivity because it contains an appropriate amount of continuous alumina fiber, and also has good thermal conductivity after bending.

It is a schematic explanatory view showing the electrospinning method in the present invention. 4 is a scanning electron micrograph of the alumina fiber sheet A obtained in Production Example 1. FIG. 2 is an X-ray diffraction diagram of the alumina fiber sheet A obtained in Production Example 1. 1 is a scanning electron micrograph of a composite A obtained in Example 1-1. 5 is a scanning electron micrograph of a composite B1 obtained in Example 1-2. 9 is a scanning electron micrograph of a composite D2 obtained in Comparative Example 1-2.

[High thermal conductive material]
The high thermal conductive material of the present invention includes an alumina fiber sheet made of alumina continuous fiber (hereinafter, also referred to as alumina fiber) and a resin.

ア ル ミ ナ The alumina fiber preferably contains α-alumina. By including α-alumina, higher thermal conductivity can be obtained. The α-alumina is preferably contained in the alumina fiber in an amount of 50% by mass or more, more preferably 90% by mass or more, and even more preferably 99% by mass or more. Although α-alumina may be contained in 100% by mass, it is usually 99.9% by mass or less.

The alumina fiber may contain components other than α-alumina. Components other than α-alumina include γ-alumina, δ-alumina, θ-alumina, amorphous alumina and the like. When a component other than α-alumina is contained, its content in the alumina fiber is preferably 50% by mass or less, more preferably 10% by mass or less, and even more preferably 1% by mass or less.

The alumina fiber is a continuous fiber, and the aspect ratio represented by the fiber length / fiber diameter is preferably 100 or more, more preferably 1,000 or more. Further, since the fiber length is long, both ends cannot be distinguished, and it is more preferable that the continuous fiber is not required to have an aspect ratio.

ア ル ミ ナ The alumina fiber preferably has an average fiber diameter of 50 to 2,000 nm, more preferably 100 to 1,000 nm. When the average fiber diameter is in the above range, the composite with the resin is easily achieved. In the present invention, the average fiber diameter is a value obtained by using image analysis software from a scanning micrograph of an alumina fiber. Further, the alumina fiber is preferably non-porous.

The alumina fiber sheet is preferably formed into a sheet in a state where the alumina fibers are non-woven or oriented in a certain direction. Since the step of weaving into a woven form is not required, it can be easily manufactured.

Examples of the resin contained in the high thermal conductive material of the present invention include polyurethane resins such as polyvinyl alcohol (PVA), polyvinyl acetate, polyvinyl butyral, polyvinyl pyrrolidone, polyurethane elastomer, epoxy resin, polyimide resin, silicone resin, and polyfluoride. Polyolefin resins such as vinylidene (PVDF), (meth) acrylic resins such as polymethyl methacrylate, polyester resins such as polyethylene succinate / adipate, polystyrene, high impact polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene copolymer Polystyrene resin such as polymer, styrene-butadiene-styrene copolymer, methyl methacrylate-styrene copolymer, polyamide resin, polyethylene, poly Propylene, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene-ethyl acrylate copolymer, polycarbonate resin, vinyl chloride resin, polyacrylonitrile, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, Polybutylene naphthalate, polylactic acid, poly-3-hydroxybutyric acid, polycaprolactone, polybutylene succinate, polyethylene oxide, polyphenylene ether resin, polyacetal resin, polyether sulfone resin, polysulfone resin, polyphenylene sulfide resin, polyglycolic acid And modified starch, cellulose derivatives such as cellulose acetate and cellulose triacetate, chitin, chitosan, lignin and the like. Among them, PVA, polyurethane resin, epoxy resin, polyimide resin, silicone resin and the like are preferable. The resins may be used alone or in combination of two or more.

下限 The lower limit of the content of the alumina fiber sheet in the high heat conductive material of the present invention is 30% by mass, preferably 40% by mass, and more preferably 50% by mass. The upper limit is 80% by mass, preferably 75% by mass, and more preferably 70% by mass. By including the alumina fiber sheet in the above range, high thermal conductivity and high flexibility can be obtained.

高 The high thermal conductive material of the present invention has high thermal conductivity. Specifically, the thermal conductivity can be 5 W / mK or more, preferably 10 W / mK or more, and more preferably 15 W / mK or more.

高 The high thermal conductive material of the present invention has high flexibility. Specifically, after bending 10 times with a curvature of 5 mm or more in diameter, the thermal conductivity preferably maintains 70% or more, more preferably 80% or more, and even more preferably 90% or more.

高 The highly thermally conductive material of the present invention can include electrically insulating highly thermally conductive particles. High thermal conductive particles include, for example, alumina, silica, boron nitride, silicon nitride, aluminum nitride, magnesium oxide, silicon carbide, boron carbide, and diamond. The high thermal conductive particles may be used alone or in combination of two or more.

高 The high thermal conductive material of the present invention can include inorganic fibers other than alumina. Examples of the inorganic fibers include glass fibers, silica fibers, ceramic fibers, and rock fibers. The inorganic fibers may be used alone or in combination of two or more.

Further, the highly heat conductive material of the present invention is preferably electrically insulating. Specifically, the surface resistance value can be 1 × 10 ¹¹ Ω / □ or more, preferably 1 × 10 ¹² Ω / □ or more, more preferably 1 × 10 ¹³ Ω / □ or more. it can.

[Production method of high thermal conductive material]
The high thermal conductive material of the present invention,
(1) a step of preparing an alumina fiber sheet by electrostatic spinning using a dispersion containing an alumina source and a water-soluble polymer as a spinning material;
It can be manufactured by a method including (2) a step of firing the produced alumina fiber sheet, and (3) a step of impregnating the fired alumina fiber sheet with a resin solution.

[Step (1)]
Step (1) is a step of preparing a fiber sheet containing an alumina source by electrostatic spinning using a dispersion containing an alumina source and a water-soluble polymer as a spinning material.

As the alumina source, alumina hydrate, aluminum nitrate, aluminum sulfate, aluminum acetate, aluminum chloride, aluminum hydroxide, alumina and the like are preferable, and alumina monohydrate is particularly preferable. As the alumina source, boehmite particles, alumina sol particles and the like can be suitably used. The boehmite particles are not particularly limited. For example, "DISPERAL" and "DISPAL" manufactured by Sasol, "Serasur" (registered trademark) manufactured by Kawai Lime Co., Ltd., and "Boehmite Powder" manufactured by Daimei Chemical Co., Ltd. And the like. The alumina sol particles are not particularly limited, for example, Nissan Chemical Co., Ltd. alumina sol "AS-200", "AS-550", "AS-520", Kawaken Fine Chemical Co., Ltd. alumina sol "10A" , "10C", "10D", "A2", "CSA-110A", "F-1000", "F-3000", Taki Chemical Co., Ltd., Bailar (registered trademark) "Al-L7", " Al-ML15 "," Al-C20 "," AS-l10 "and the like. When boehmite particles or alumina sol particles are used as the alumina source, the primary particle diameter is preferably from 2 to 200 nm, more preferably from 5 to 100 nm, from the viewpoint of dispersion stability in the spinning solution and sinterability during firing. preferable. In the present invention, the primary particle diameter is a value measured by a laser diffraction method. The alumina source may be used alone or in combination of two or more. The content of the alumina source in the dispersion is preferably 1 to 40% by mass, more preferably 2 to 30% by mass, and still more preferably 3 to 20% by mass.

Examples of the water-soluble polymer include PVA, cellulose, cellulose derivatives, polyethylene glycol, polypropylene glycol, polyvinylpyrrolidone, poly (meth) acrylic acid, poly (meth) acrylate, polyvinyl acetate, polyvinylpyrrolidone, and the like. Can be These may be used alone or in combination of two or more. The content of the water-soluble polymer in the dispersion is preferably 5 to 40% by mass, more preferably 5 to 30% by mass, and even more preferably 5 to 20% by mass.

溶媒 As a solvent that can be used for the dispersion, water that can dissolve the water-soluble polymer and disperse the alumina source is preferable. Further, two or more solvents that dissolve in water may be mixed. Examples of solvents that can be mixed with water include acetone, methanol, ethanol, isopropyl alcohol, butanol, ethyl methyl ketone (MEK), isobutyl methyl ketone (MIBK), propylene glycol monomethyl ether (PGME), and propylene glycol monomethyl ether acetate ( PGMEA), propylene glycol monoethyl ether, butyl cellosolve, tetrahydrofuran (THF), 1,4-dioxane, N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone ( NMP), cyclohexanone, ethyl lactate, diethylene glycol monoethyl ether, γ-butyrolactone, formic acid, acetic acid, trifluoroacetic acid and the like. When other solvents are included, the content is not particularly limited as long as the water-soluble polymer can be dissolved.

FIG. 1 is a schematic explanatory view showing the electrospinning method in the present invention. In the electrostatic spinning method, a spinning solution is injected from a metal nozzle 2 to which a voltage is applied by a voltage supply device 1 to a grounded collector 3. In this method, the solvent is volatilized while the spinning solution is scattered, and the solid content is accumulated in the collector 3 in a fiber form. The electrostatic spinning method is also called an electrospinning method or an electrospinning method.

Electrostatic spinning can be performed with a commercially available device. The spinning conditions are appropriately selected. For example, the spinning distance 4 (distance between the metal nozzle and the fiber collecting collector) is 5 to 30 cm, the applied voltage between the metal nozzle and the fiber collecting collector is 5 to 50 kV, and the spinning liquid injection amount is 0. .1 to 5.0 mL / hour. A drum-shaped or flat-shaped fiber collecting collector can be used. When the drum-shaped fiber collecting collector is used, the fiber ejected from the metal nozzle is wound around the drum by rotating the drum at a high speed, and a sheet in which the fiber is oriented in a certain direction can be obtained. The rotation speed of the drum-shaped fiber collection collector is, for example, 50 to 5,000 rotations / minute. When a flat fiber collection collector is used, a non-woven sheet made of non-oriented fibers can be obtained.

[Step (2)]
Step (2) is a step of baking the fiber sheet containing the alumina source and the water-soluble polymer produced in step (1) to produce an alumina fiber sheet. The firing temperature is preferably 1,200 ° C or higher. When firing is performed at 1,200 ° C. or more, alumina in the obtained alumina fiber sheet changes to α-crystal, and higher thermal conductivity can be obtained. The upper limit of the firing temperature is not particularly limited, but is preferably not higher than the temperature at which alumina does not melt, more preferably not higher than 2,000 ° C.

(4) The fiber sheet containing the alumina source and the water-soluble polymer may be heated and pressed before firing to increase the number of contact portions between the fibers. The heating temperature is preferably from 25 to 160 ° C, more preferably from 40 to 120 ° C. The pressing pressure is preferably 1 MPa or more, more preferably 5 MPa or more. The upper limit of the pressing pressure is not particularly limited, but is preferably 50 MPa, more preferably 40 MPa.

Firing can be performed using a firing furnace such as an electric furnace or a gas furnace. The firing can be carried out in an air atmosphere or an oxygen atmosphere, but preferably under conditions in which the carbon component derived from PVA disappears.

The firing time is preferably 1 hour or more, more preferably 3 hours or more, and even more preferably 5 hours or more. The upper limit of the firing time is not particularly limited, but is preferably 10 hours, and more preferably 8 hours. When the calcination time is within the above range, the disappearance of the carbon component derived from PVA and the crystallization of α-crystal of alumina proceed. At this time, the α crystal crystallization ratio of alumina is preferably 50% by mass or more, more preferably 90% by mass or more, and even more preferably 99% by mass or more. The crystallinity of α-crystal is 100% by mass at the maximum, but is usually 99.9% by mass or less.

It is preferable to raise the temperature at a rate of 20 ° C./min or less until the firing temperature is reached. The heating rate is more preferably 15 ° C./min or less, and more preferably 10 ° C./min or less. When the heating rate is in the above range, the disappearance of the carbon component derived from PVA and the crystallization of α-crystal of alumina proceed.

(4) The average fiber diameter of the alumina fiber obtained by firing is preferably 50 to 2,000 nm, more preferably 100 to 1,000 nm. When the average fiber diameter is in the above range, the composite with the resin is easily achieved.

The thickness of the alumina fiber sheet is preferably from 10 to 2,000 μm, more preferably from 20 to 1,500 μm, and still more preferably from 40 to 1,000 μm.

[Step (3)]
Step (3) is a step of impregnating the alumina fiber sheet prepared in step (2) with a resin solution. By this step, a composite of the alumina fiber and the resin is formed, and a highly heat conductive material can be obtained. In addition, the alumina fiber sheet may include only one sheet in the composite, or may include a plurality of sheets.

、 In order for the obtained composite to exhibit high thermal conductivity, it is necessary to contain alumina fibers appropriately. The resin concentration in the resin solution is preferably 15% by mass or less, more preferably 10% by mass or less, still more preferably 7% by mass or less, and still more preferably 5% by mass or less. When the resin concentration exceeds 15% by mass, the content of the resin in the composite is large because the proportion of the resin in the resin solution is large, and the alumina fiber has a low content and may not show high thermal conductivity. The above-mentioned resins may be used alone or in combination of two or more.

溶媒 The solvent used for the resin solution is not particularly limited as long as it can dissolve the resin. For example, water, acetone, methanol, ethanol, isopropyl alcohol, butanol, MEK, MIBK, PGME, PGMEA, propylene glycol monoethyl ether, butyl cellosolve, THF, 1,4-dioxane, DMF, DMAc, NMP, cyclohexanone, ethyl lactate, Examples include diethylene glycol monoethyl ether, γ-butyrolactone, formic acid, acetic acid, trifluoroacetic acid and the like. The solvents may be used alone or as a mixture of two or more.

Examples of the method of impregnating the fired alumina fiber sheet with the resin solution include a method of dropping a solution in which a resin is dissolved, a method of dropping a solution in which a monomer is dissolved, and a method of reacting the monomer in a subsequent heating step. .

た After impregnating the fired alumina fiber sheet with the resin solution, the composite can be obtained by reducing the pressure and removing the solvent by heating and curing the resin. At this time, the pressure reduction is not necessary as long as the resin can be impregnated without gaps. However, when the pressure is reduced, it is preferably 1,000 Pa or less, more preferably 100 Pa or less. Heating is not particularly limited as long as the solvent can be removed and the resin can be cured, and the resin is not thermally decomposed, but is usually preferably at 100 to 150 ° C, more preferably at 100 to 140 ° C, It is even more preferred to carry out at 110 to 130 ° C. The heating time is usually preferably 30 minutes or more, and more preferably 1 hour or more.

複合 By the above method, a composite of an alumina fiber sheet containing 30 to 80% by mass of an alumina fiber sheet and a resin can be produced. The thickness of the composite is preferably from 20 to 2,000 μm, more preferably from 40 to 1,500 μm.

The high heat conductive material of the present invention can be used as a heat radiating material. For example, a flexible heat radiating material for a heat radiating member such as a heat radiating sheet, a heat radiating tape, a heat radiating circuit board, a heat radiating housing, a heat radiating sealant, a heat sink, and a heat pipe. It can be suitably used as Further, these heat radiating members can be suitably used for devices such as LEDs, power semiconductors, CPUs, and lithium ion batteries. Furthermore, these heat dissipation devices can be used, for example, in digital home appliances such as mobile phones, smartphones, digital cameras, televisions, hard disk recorders, tablet PCs, notebook PCs, desktop PCs, hybrid vehicles, electric vehicles, and fuel cell vehicles. Suitable for next-generation lighting devices such as automobiles, home lighting, industrial lighting, and vehicle lighting, next-generation power generation devices such as solar cells, fuel cells, and geothermal power generation, and next-generation energy carrier manufacturing devices such as hydrogen production by water electrolysis. Available to

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. In addition, the used apparatus and the measurement conditions are as follows. The average fiber diameter of the alumina fiber is an average value obtained by measuring the fiber diameter at 10 points from a scanning microscope photograph of the alumina fiber using image analysis software “Adobe Photoshop CS3” or “Extract Mosaic”. The average fiber length of the alumina fiber is an average value obtained by measuring the fiber length at 10 locations from a scanning micrograph of the alumina fiber using image analysis software “Adobe Photoshop CS3” or “Extract Mosaic”. The aspect ratio of the alumina fiber was determined from the calculation of aspect ratio = fiber length / fiber diameter. In the examples, the apparatus and conditions used for sample preparation and physical property analysis are as follows.

(1) Electrostatic spinning method: Infusion pump (syringe pump): FP-1000 manufactured by Merquest, high voltage power supply: HR-40R0.75 manufactured by Matsusada Precision Co., Ltd. or antistatic made by MEC Corporation Device NANON-03
(2) Scanning electron microscope: VE-9800 manufactured by Keyence Corporation, Miniscope TM3000 manufactured by Hitachi High-Technologies Corporation
(3) X-ray diffractometer: Rigaku MiniFlex 2
(4) Thermogravimetric analyzer: TG-DTA 2000SA manufactured by BRUKER
(5) Thermal diffusivity measuring device: Thermo-wave analyzer TA-35 manufactured by Bethel Corporation

[1] Production of alumina fiber sheet [Production Example 1]
In 10.0 mass parts of a 10 mass% PVA (Fuji Film Wako Pure Chemical Industries, Ltd., average polymerization degree: 1,500, saponification degree: 99%) aqueous solution, boehmite powder (DISPERAL P2 manufactured by Sasol, Inc.) was used as an alumina source. 0.598 parts by mass of an alumina component (72%, primary particle size: 20 nm) was added and dispersed by stirring.
2 mL of the obtained aqueous dispersion was used as a spinning solution, and filled into a syringe having a metal nozzle attached to the tip. A rotating drum having a diameter of 15 cm was used as a collector for collecting fibers. The metal nozzle and the drum collector were electrically connected to a voltage supply. The voltage supply device applied a voltage of 20 kV to the metal nozzle side with the drum collector side as ground. The distance between the metal nozzle and the drum collector was adjusted to 15 cm. The drum collector was rotated at 4,000 revolutions per minute. By injecting a spinning solution from a syringe at an extrusion rate of 1.0 mL / h toward a rotating drum collector, fibers made of PVA and boehmite are formed on the rotating drum collector, and a fiber sheet containing an alumina source is formed. Obtained.

The fiber sheet containing the alumina source was placed in an electric furnace and heated at a heating rate of 10 ° C / min to a firing temperature of 1,200 ° C. After firing at 1,200 ° C. for 5 hours, the mixture was allowed to cool and cooled to room temperature to obtain an alumina fiber sheet A. FIG. 2 shows a scanning electron micrograph of the alumina fiber sheet A. The average fiber diameter of the alumina fibers in the alumina fiber sheet A was about 230 nm. Further, since the fiber length of the alumina fiber was long, both ends could not be identified, and the aspect ratio could not be calculated.
FIG. 3 shows an X-ray diffraction pattern (Ni filter, CuKα ray, 30 kV, 15 mA) of the alumina fiber sheet A. 3, the alumina fiber sheet A contained α-alumina, and the α-crystal crystallization ratio was 52.73%.

[Production Example 2]
In 10.0 mass parts of a 10 mass% PVA (Fuji Film Wako Pure Chemical Industries, Ltd., average polymerization degree: 1,500, saponification degree: 99%) aqueous solution, boehmite powder (DISPERAL P2 manufactured by Sasol, Inc.) was used as an alumina source. 0.598 parts by mass of an alumina component (72%, primary particle size: 20 nm) was added and dispersed by stirring.
2 mL of the obtained aqueous dispersion was used as a spinning solution, and filled into a syringe having a metal nozzle attached to the tip. A flat collector was used as a collector for collecting fibers. The metal nozzle and the flat collector were electrically connected to a voltage supply. The voltage supply device applied a voltage of 20 kV to the metal nozzle side with the flat collector side as ground. The distance between the metal nozzle and the flat collector was adjusted to 15 cm. By injecting the spinning solution from the syringe at an extrusion rate of 1.0 mL / h toward the flat plate collector, fibers composed of PVA and boehmite were formed on the flat plate collector, and a fiber sheet containing an alumina source was obtained. .

フ ァ イ バ ー The fiber sheet containing the alumina source was placed in an electric furnace, and the temperature was increased to 1,200 ° C. at a heating rate of 10 ° C./min. After firing at 1,200 ° C. for 5 hours, the mixture was allowed to cool and cooled to room temperature to obtain an alumina fiber sheet B. The average fiber diameter of the alumina fibers in the alumina fiber sheet B was about 143 nm. Further, since the fiber length of the alumina fiber was long, both ends could not be identified, and the aspect ratio could not be calculated.

[Production Example 3]
5.0 parts by mass of nitric acid (manufactured by Junsei Chemical Co., Ltd.) and boehmite powder as alumina source (DISPERAL P2 manufactured by Sasol Chemicals Japan KK, alumina component 72%, primary particle diameter 20 nm) in 78.0 parts by mass of distilled water 22.0 parts by mass were added and dispersed by sonication. Further, 5.0 parts by mass of PVA (Gohsenol GM14L manufactured by Nippon Synthetic Chemical Co., Ltd.) was added, and the mixture was heated and stirred in an oil bath (70 ° C.) to obtain a spinning solution.
2 mL of the obtained spinning solution was filled in a syringe having a metal nozzle attached to the tip. The fiber was spun using an electrostatic spinning device NANON-03 (manufactured by MEC Corporation). A rotating drum having a diameter of 20 cm was used as a collector for collecting fibers. A voltage of 25 kV was applied to the metal nozzle side with the drum collector side as ground. The distance between the metal nozzle and the drum collector was adjusted to 12.5 cm. The drum collector was rotated at 2,000 revolutions per minute. By injecting a spinning solution from a syringe at an extrusion rate of 1.0 mL / h toward a rotating drum collector, fibers made of PVA and boehmite are formed on the rotating drum collector, and a fiber sheet containing an alumina source is formed. Obtained.

A fiber sheet (size 5 cm × 5 cm) containing the alumina source is sandwiched between Teflon (registered trademark) sheets, and at a temperature of 120 ° C. and a pressure of 20 MPa using a desktop test press (SA-302 manufactured by Tester Sangyo Co., Ltd.). The heating press was performed for 30 minutes. After cooling, it was peeled off from the Teflon (registered trademark) sheet, placed in an electric furnace, and heated at a heating rate of 10 ° C / min to a firing temperature of 1,300 ° C. After firing at 1,300 ° C. for 5 hours, the mixture was allowed to cool and cooled to room temperature to obtain an alumina fiber sheet C. The average fiber diameter of the alumina fibers in the alumina fiber sheet C was about 262 nm. Further, since the fiber length of the alumina fiber was long, both ends could not be identified, and the aspect ratio could not be calculated.

[2] Production of High Thermal Conductive Material [Example 1-1]
An aqueous solution (solid content: 5% by mass) was prepared by diluting a polyurethane emulsion (Superflex 300, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., solid content: 30% by mass) to 1/6. 22 parts by mass of the alumina fiber sheet A was impregnated with 159 parts by mass of the diluted aqueous solution. Removal of water and heating and curing of the polyurethane at 120 ° C. under a vacuum were performed to obtain a composite A of the alumina fiber sheet A and the polyurethane. The composite A was obtained in the form of a sheet and had a thickness of 48 μm.
About the composite A, the content of the alumina fiber sheet in the composite A was measured by raising the temperature to 500 ° C. at a rate of 10 ° C./min using a thermogravimetric analyzer. The content of the alumina fiber sheet A in the composite A was 73.4% by mass (46.0% by volume).
The scanning electron micrograph of the composite A is shown in FIG. In the composite A, the alumina fibers were composited with the long fibers oriented.

[Example 1-2]
An aqueous solution (solid content: 10% by mass) was prepared by diluting a polyurethane emulsion (Superflex 300, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., solid content: 30% by mass) to one third. 318 parts by mass of the diluted aqueous solution was impregnated into 25 parts by mass of the alumina fiber sheet B. Removal of water and heating and curing of the polyurethane at 120 ° C. under vacuum were performed to obtain a composite B1 of the alumina fiber sheet B and the polyurethane. The composite B1 was obtained in the form of a sheet, and had a thickness of 40 μm.
The content of the alumina fiber sheet in the composite B1 was measured by raising the temperature of the composite B1 to 500 ° C. at a rate of 10 ° C./min using a thermogravimetric analyzer. The content of the alumina fiber sheet B in the composite B1 was 44.0% by mass (19.5% by volume).
FIG. 5 shows a scanning electron micrograph of the composite B1. In the composite B1, the alumina fibers were composited in a state where the long fibers were not oriented (that is, in a nonwoven fabric shape).

[Example 1-3]
An aqueous solution (solid content: 10% by mass) of PVA (Fuji Film Wako Pure Chemical Industries, Ltd., average polymerization degree: 1,500, saponification degree: 99%) was prepared. 20 parts by mass of the alumina fiber sheet B was impregnated with 114 parts by mass of the aqueous solution. Removal of water and heating and curing of PVA were performed at 120 ° C. under vacuum to obtain a composite B2 of alumina fiber sheet B and PVA. The composite B2 was obtained in the form of a sheet, and the thickness was 33 μm.
The content of the alumina fiber sheet in the composite B2 was measured by raising the temperature of the composite B2 to 500 ° C. at a rate of 10 ° C./min using a thermogravimetric analyzer. The content of the alumina fiber sheet B in the composite B2 was 63.6% by mass (36.0% by volume).

[Example 1-4]
A silicone resin solution (KR-112 manufactured by Shin-Etsu Chemical Co., Ltd., solid content: 30% by mass) was diluted to one third with toluene (manufactured by Junsei Chemical Co., Ltd.) to prepare a solution (solid content: 10% by mass). . 20.0 parts by mass of the alumina fiber sheet C was impregnated with 300.0 parts by mass of the toluene diluted solution. The removal of toluene and the heat curing of the silicone resin were performed at 120 ° C. to obtain 50.0 parts by mass of a composite C1 of the alumina fiber sheet C and the silicone resin.
The composite C1 was obtained in the form of a sheet, and had a thickness of 87 μm. The content of the alumina fiber sheet in the composite C1 was calculated to be 40.0% by mass (15.4% by volume).

[Example 1-5]
18.0 parts by mass of PVDF (manufactured by Sigma-Aldrich) is added to 88.0 parts by mass of DMF (manufactured by Junsei Chemical Co., Ltd.), and the mixture is stirred in an oil bath (80 ° C.) to obtain a uniform solution (solid content: 12% by mass). Was prepared. 325.0 parts by mass of the DMF solution was impregnated into 26.0 parts by mass of an alumina fiber sheet C. DMF was removed at 160 ° C. to obtain 65.0 parts by mass of a composite C2 of the alumina fiber sheet C and PVDF.
The composite C2 was obtained in the form of a sheet, and had a thickness of 83 µm. The content of the alumina fiber sheet in the composite C2 was calculated to be 40.0% by mass (23.4% by volume).

[Example 1-6]
10.0 parts by mass of PVA (Gosenol GM14L manufactured by Nippon Synthetic Chemical Co., Ltd.) is added to 90.0 parts by mass of purified water and stirred in an oil bath (80 ° C.) to prepare a uniform solution (solid content: 10% by mass). did. 375.0 parts by mass of the aqueous solution was impregnated into 25.0 parts by mass of an alumina fiber sheet C. Water was removed at 100 ° C. to obtain 63.0 parts by mass of a composite C3 of the alumina fiber sheet C and PVA.
The composite C3 was obtained in the form of a sheet, and had a thickness of 62 μm. The alumina fiber sheet content in the composite C3 was calculated to be 40.0% by mass (17.6% by volume).

[Example 1-7]
In a glass container, 6.7 parts by mass of pyromellitic anhydride (manufactured by Tokyo Chemical Industry Co., Ltd.) and 2.7 parts by mass of paraphenylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.) 4,4 ″ -diamino- 1.6 parts by mass of p-terphenyl and 89 parts by mass of NMP (manufactured by Junsei Chemical Co., Ltd.) were added, and the mixture was stirred at 50 ° C. for 12 hours to prepare an NMP solution of polyamic acid having a solid content of 11% by mass. A total of 26 parts by mass of the alumina fiber sheet C was impregnated with 360 parts by mass of the NMP solution. The mixture was heated at 100 ° C. for 1 hour, and then heated at 400 ° C. for 2 hours under nitrogen to cure the polyamic acid, thereby obtaining 63.0 parts by mass of a composite C4 of an alumina fiber sheet and a polyimide resin.
The composite C4 was obtained in the form of a sheet, and the thickness was 49 μm. The magnesia fiber sheet content of the composite C4 was calculated to be 40.0% by mass (19.6% by volume).

[Example 1-8]
12.0 parts by mass of polystyrene (manufactured by Sigma-Aldrich) was added to 88.0 parts by mass of DMF (manufactured by Junsei Chemical Co., Ltd.), and the mixture was stirred in an oil bath (80 ° C.) to obtain a uniform solution (solid content: 12% by mass). Was prepared. 28.0 parts by mass of the alumina fiber sheet C was impregnated with 350.0 parts by mass of the DMF solution. DMF was removed at 160 ° C. to obtain 70.0 parts by mass of a composite C5 of an alumina fiber sheet C and polystyrene.
The composite C5 was obtained in the form of a sheet, and had a thickness of 63 μm. The content of the alumina fiber sheet in the composite C5 was calculated to be 40.0% by mass (15.3% by volume).

[Example 1-9]
In a glass container, 5.0 parts by mass of triglycidyl isocyanurate (TEPIC (registered trademark) manufactured by Nissan Chemical Industries, Ltd.), 5.2 parts by mass of phenol novolak resin (phenolic (registered trademark) TD2131 manufactured by DIC) and 92.0 parts by mass of NMP (manufactured by Junsei Chemical Co., Ltd.) was added, and the mixture was heated and stirred at 60 ° C. The NMP solution was cooled to room temperature, 0.050 parts by mass of 2-ethyl-4-methylimidazole (manufactured by Kanto Chemical Co., Ltd.) was added, and the mixture was stirred to prepare an NMP solution having a solid content of 10% by mass. . 330 parts by mass of the NMP solution were impregnated into 22.0 parts by mass of the alumina fiber sheet C. By heating at 100 ° C. for 5 minutes and then at 180 ° C. for 1 hour, 55.0 parts by mass of a composite C6 of an alumina fiber sheet and an epoxy resin was obtained.
The composite C6 was obtained in the form of a sheet, and had a thickness of 81 μm. The content of the alumina fiber sheet in the composite C6 was calculated to be 40.0% by mass (19.4% by volume).

[Comparative Example 1-1]
An aqueous solution (solid content: 20% by mass) was prepared by diluting a polyurethane emulsion (Superflex 300, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., solid content: 30% by mass) into two-thirds. The alumina fiber sheet A was impregnated with the diluted aqueous solution. Removal of water and heating and curing of the polyurethane were performed at 120 ° C. under vacuum to obtain a composite D1 of the alumina fiber sheet A and the polyurethane. The composite D1 was obtained in the form of a sheet, and had a thickness of 82 μm.
The content of the alumina fiber sheet in the composite C was measured by raising the temperature of the composite D1 to 500 ° C. at a rate of 10 ° C./min using a thermogravimetric analyzer. The content of the alumina fiber sheet in the composite D1 was 24.4% by mass (9.1% by volume).

[Comparative Example 1-2]
The alumina fiber sheet A and the polyurethane emulsion (Superflex 300, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., solid content: 30% by mass) are diluted with water so that the solid content is 9% by mass and the solid content is 11% by mass, respectively. The alumina fiber sheet was pulverized and dispersed by sonication to obtain a dispersion of alumina fiber and polyurethane. The obtained dispersion was dropped on a silicone sheet. After drying at room temperature overnight, water was removed at 120 ° C. and the polyurethane was cured by heating to obtain a composite D2 of alumina fiber and polyurethane. The composite D2 was obtained in the form of a sheet, and had a thickness of 90 μm.
The content of the alumina fiber sheet in the composite D2 was measured by raising the temperature of the composite D2 to 500 ° C. at a rate of 10 ° C./min using a thermogravimetric analyzer. The content of the alumina fiber sheet in the composite was 44.3% by mass (19.7% by volume).
FIG. 6 shows a scanning electron micrograph of the composite D2. In the composite D2, the alumina fibers were composited in a state of a short fiber. It is considered that the fibers became shorter when dispersed in water by ultrasonic waves. The aspect ratio was calculated as 37 from the fiber diameter and fiber length.

[Comparative Example 1-3]
An aqueous solution (solid content: 15% by mass) was prepared by diluting a polyurethane emulsion (Superflex 300, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., solid content: 30% by mass) by half. 115.0 parts by mass of the aqueous solution was added to 21.0 parts by mass of the alumina fiber sheet C, and the mixture was subjected to ultrasonic treatment for 1 minute to pulverize and disperse the alumina fiber sheet to obtain a dispersion of alumina fibers and polyurethane. The obtained dispersion was dropped on a silicone sheet. After drying at room temperature overnight, removal of water and heat curing of the polyurethane were performed at 120 ° C. to obtain 38.0 parts by mass of a composite D3 of alumina fiber and polyurethane.
The composite D3 was obtained in the form of a sheet, and had a thickness of 131 μm. The content of the alumina fiber sheet in the composite D3 was calculated to be 55.0% by mass (27.4% by volume). The alumina fiber aspect ratio in the composite D3 was calculated to be 109 from the fiber diameter and the fiber length.

[Comparative Example 1-4]
An aqueous solution (solid content: 15% by mass) was prepared by diluting a polyurethane emulsion (Superflex 300, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., solid content: 30% by mass) by half. 125.0 parts by mass of the diluted aqueous solution was added to 23.0 parts by mass of the alumina fiber sheet C, and ultrasonic treatment was performed for 30 seconds to pulverize and disperse the alumina fiber sheet to obtain a dispersion of alumina fibers and polyurethane. The obtained dispersion was dropped on a silicone sheet. After drying overnight at room temperature, removal of water and heat curing of the polyurethane were performed at 120 ° C. to obtain 42.0 parts by mass of a composite D4 of an alumina fiber and a polyurethane.
The composite D4 was obtained in the form of a sheet, and had a thickness of 163 μm. The content of the alumina fiber sheet in the composite D4 was calculated to be 55.0% by mass (27.4% by volume). The alumina fiber aspect ratio in the composite D4 was calculated to be 208 from the fiber diameter and the fiber length.

[Comparative Example 1-5]
An aqueous solution (solid content: 15% by mass) was prepared by diluting a polyurethane emulsion (Superflex 300, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., solid content: 30% by mass) by half. 83.0 parts by mass of the diluted aqueous solution was added to 15.0 parts by mass of the alumina fiber sheet C, and ultrasonic treatment was performed for 10 seconds to pulverize and disperse the alumina fiber sheet to obtain a dispersion of alumina fibers and polyurethane. The obtained dispersion was dropped on a silicone sheet. After drying at room temperature overnight, water was removed at 120 ° C. and the polyurethane was cured by heating to obtain 42.0 parts by mass of a composite D5 of alumina fiber and polyurethane.
The composite D5 was obtained in the form of a sheet, and had a thickness of 272 μm. The content of the alumina fiber sheet in the composite D5 was calculated to be 55.0% by mass (27.4% by volume). The alumina fiber aspect ratio in the composite D5 was calculated to be 657 from the fiber diameter and the fiber length.

[Comparative Example 1-6]
An aqueous solution (solid content: 1.5% by mass) prepared by diluting a polyurethane emulsion (Superflex 300, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., solid content: 30% by mass) to 1/20 was prepared. The diluted aqueous solution was impregnated. Removal of water and heating and curing of the polyurethane were performed at 120 ° C. under vacuum to obtain a composite D6 of the alumina fiber sheet A and the polyurethane. Composite D6 was obtained in the form of a sheet, and had a thickness of 82 µm.
The content of the alumina fiber sheet in the composite D6 was measured by raising the temperature of the composite D6 to 500 ° C. at a rate of 10 ° C./min using a thermogravimetric analyzer. The content of the alumina fiber sheet B in the composite D6 was 84.7% by mass (63.1% by volume).

[Comparative Example 1-7]
An aqueous solution (solid content: 20% by mass) prepared by diluting a polyurethane emulsion (Superflex 300, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., solid content: 30% by mass) was prepared and dropped onto a silicone sheet. After drying at room temperature overnight, water was removed at 120 ° C. and the polyurethane was cured by heating to obtain a polyurethane sheet containing no alumina fiber sheet. The thickness of the sheet was 110 μm.

[Comparative Example 1-8]
A silicone resin solution (KR-112 manufactured by Shin-Etsu Chemical Co., Ltd., solid content: 30% by mass) was diluted to one third with toluene (manufactured by Junsei Chemical Co., Ltd.) to prepare a solution (solid content: 10% by mass). , And dropped on a silicone sheet. After drying at room temperature overnight, the removal of toluene and the heat curing of silicone were performed at 120 ° C. to obtain a silicone sheet containing no alumina fiber sheet. The thickness of the sheet was 160 μm.

[Comparative Example 1-9]
Add 12.0 parts by mass of PVDF (manufactured by Sigma-Aldrich) to 88.0 parts by mass of DMF (manufactured by Junsei Chemical Co., Ltd.) and stir in an oil bath (80 ° C.) to prepare a uniform solution (solid content: 12% by mass). And dropped on a silicone sheet. After drying at room temperature overnight, DMF was removed at 150 ° C. to obtain a PVDF sheet containing no alumina fiber sheet. The thickness of the sheet was 102 μm.

[Comparative Example 1-10]
10.0 parts by mass of PVA (Gohsenol GM14L manufactured by Nippon Synthetic Chemical Co., Ltd.) was added to 90.0 parts by mass of purified water, and stirred in an oil bath (80 ° C.) to prepare a uniform solution (solid content: 10% by mass). , And dropped on a silicone sheet. After drying at room temperature overnight, water was removed at 100 ° C. to obtain a PVA sheet containing no alumina fiber sheet. The thickness of the sheet was 97 μm.

[Comparative Example 1-11]
In a glass container, 6.7 parts by mass of pyromellitic anhydride (manufactured by Tokyo Chemical Industry Co., Ltd.) and 2.7 parts by mass of paraphenylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.) 4,4 ″ -diamino- 1.6 parts by mass of p-terphenyl and 89 parts by mass of NMP (manufactured by Junsei Chemical Co., Ltd.) were added, and the mixture was stirred at 50 ° C. for 12 hours to prepare an NMP solution of polyamic acid having a solid content of 11% by mass. The NMP solution was dropped on a silicone sheet. After drying at room temperature overnight, the mixture was heated at 100 ° C. for 1 hour. The polyamic acid was cured by peeling off from the silicone sheet and heating at 400 ° C. for 2 hours under nitrogen to obtain a polyimide sheet containing no alumina fiber sheet. The thickness of the sheet was 40 μm.

[Comparative Example 1-12]
12.0 parts by mass of polystyrene (manufactured by Sigma-Aldrich) was added to 88.0 parts by mass of DMF (manufactured by Junsei Chemical Co., Ltd.), and the mixture was stirred in an oil bath (80 ° C.) to obtain a uniform solution (solid content: 12% by mass). Was prepared and dropped on a silicone sheet. After drying at room temperature overnight, DMF was removed at 150 ° C. to obtain a polystyrene sheet containing no alumina fiber sheet. The thickness of the sheet was 140 μm.

[Comparative Example 1-13]
In a glass container, 5.0 parts by mass of triglycidyl isocyanurate (TEPIC (registered trademark) manufactured by Nissan Chemical Co., Ltd.), 5.2 parts by mass of phenol novolak resin (fenolite (registered trademark) TD2131 manufactured by DIC Corporation), And 92.0 parts by mass of NMP (manufactured by Junsei Chemical Co., Ltd.), and the mixture was heated and stirred at 60 ° C. The NMP solution was cooled to room temperature, and 0.050 parts by mass of 2-ethyl-4-methylimidazole (manufactured by Kanto Chemical Co., Ltd.) was added and stirred to prepare an NMP solution having a solid content of 10% by mass. The NMP solution was dropped on a silicone sheet. After drying at room temperature overnight, the mixture was heated at 100 ° C. for 5 minutes and then at 180 ° C. for 1 hour to obtain an epoxy resin sheet containing no alumina fiber sheet. The thickness of the sheet was 231 μm.

[3] Evaluation of High Thermal Conductivity Material The thermal diffusivity was measured using a thermal diffusivity measuring device. From the thermal diffusivity to the thermal conductivity, the specific gravity of alumina is 3,890 kg / m ³ , the specific heat of alumina is 750 J / kg ° C., the specific gravity of polyurethane resin is 1,200 kg / m ³ , and the specific heat of polyurethane resin is 1,900 J / kg. ° C, specific gravity of silicone resin 1,060 kg / m ³ , specific heat of silicone resin 1,200 J / kg ° C, specific gravity of PVDF resin 1,780 kg / m ³ , specific heat of PVDF resin 1,200 J / kg ° C, specific gravity of PVA resin 1,250 kg / m ³ , specific heat of PVA resin 1,680 J / kg ° C., specific gravity of polyimide resin 1,420 kg / m ³ , specific heat of polyimide resin 1,100 J / kg ° C., specific gravity of polystyrene 1,055 kg / m ³ , Specific heat 1,340J / kg ℃ polystyrene, density 1,400 kg / m ³ of epoxy resin, using a specific heat 1,400J / kg ℃ epoxy resin, respectively It was performed by calculating the specific gravity and specific heat of the complex from the content.

[Example 2-1]
About the composite A, the thermal diffusivity was measured using the thermal diffusivity measuring apparatus. The thermal conductivity was calculated by multiplying the thermal diffusivity by the specific gravity and specific heat of the composite.

屈曲 Furthermore, a bending test was performed on the composite A whose thermal diffusivity was measured. The composite sheet was wound around a metal rod having a diameter of 5 mm and a length of 5.5 cm so that the fiber orientation direction was bent, and then returned to a flat state. This was repeated 10 times. After that, the thermal diffusivity was measured and the thermal conductivity was calculated by the method described above. The maintenance rate of the thermal conductivity was expressed as a percentage of the thermal conductivity after the bending test with respect to the thermal conductivity before the bending test.

[Example 2-2]
The thermal diffusivity of the composite B1 was measured using a thermal diffusivity measuring device. The thermal conductivity was calculated by multiplying the thermal diffusivity by the specific gravity and specific heat of the composite.

(4) A bending test was performed on the composite B2 whose thermal diffusivity was measured. The composite sheet was wound around a metal rod having a diameter of 5 mm and a length of 5.5 cm, and then returned to a flat state. This was repeated 10 times. After that, the thermal diffusivity was measured and the thermal conductivity was calculated by the method described above. The maintenance rate of the thermal conductivity was expressed as a percentage of the thermal conductivity after the bending test with respect to the thermal conductivity before the bending test.

[Example 2-3]
For the composite B2, the measurement of the thermal diffusivity, the calculation of the thermal conductivity, and the bending test were performed in the same manner as in Example 2-2.

[Examples 2-4 to 2-9]
For the composites C1 to C6, the measurement of the thermal diffusivity, the calculation of the thermal conductivity, and the flexibility test were performed in the same manner as in Example 2-1.

[Comparative Examples 2-1 and 2-2]
For the composites D1 and D2, the measurement of the thermal diffusivity, the calculation of the thermal conductivity, and the bending test were performed in the same manner as in Example 2-1.

[Comparative Examples 2-3 to 2-5]
For the composites D3 to D5, the measurement of the thermal diffusivity and the calculation of the thermal conductivity were performed in the same manner as in Example 2-1.

[Comparative Example 2-6]
For the composite D6, the measurement of the thermal diffusivity and the calculation of the thermal conductivity were performed in the same manner as in Example 2-1. A bending test was performed in the same manner as in Example 2-1, except that the sample was broken by the first bending. It was considered that the sample was brittle because of the high alumina content.

[Comparative Examples 2-7 to 2-13]
The thermal diffusivity of the sheets prepared in Comparative Examples 1-7 to 1-13 without the alumina fiber sheet was measured using a thermal diffusivity measuring apparatus. The calculation from the thermal diffusivity to the thermal conductivity and the flexibility test were performed in the same manner as in Example 2-1.

Tables 1 to 4 show that the thermal conductivity in the direction parallel to the oriented fiber (average value at four places), the thermal conductivity in the perpendicular direction to the aligned oriented fiber (average value at four places), and the non-oriented fiber are composited. The thermal conductivity in the plane direction (average at four locations) and the thermal conductivity in the thickness direction of the sheet (average value at six locations) are shown.

よ り From the results shown in Tables 1 and 2, the high thermal conductive material of the present invention exhibited a high thermal conductivity of 5 W / mK or more, and was maintained at 80% or more even after the bending test. On the other hand, from the results shown in Table 3, the material of Comparative Example 2-1 had a low alumina fiber content and a low thermal conductivity. The materials of Comparative Examples 2-2 to 2-5 had low thermal conductivity because the alumina fibers were shortened. The material of Comparative Example 2-6 had a high alumina fiber content and had no flexibility. From the results shown in Table 4, since the materials of Comparative Examples 2-7 to 2-13 did not contain alumina fibers, the thermal conductivity was low.

1 voltage supply device 2 metal nozzle 3 drum type collector 4 spinning distance

Claims (17)

(4) A highly heat-conductive material having flexibility and comprising an alumina fiber sheet made of continuous alumina fibers and a resin, wherein the alumina fiber sheet is contained in an amount of 30 to 80% by mass in the high heat-conductive material. 高 The high heat conductive material according to claim 1, wherein the alumina fiber sheet is contained in the high heat conductive material in an amount of 40 to 70% by mass. The high thermal conductivity material according to claim 1 or 2, wherein the alumina continuous fiber has an aspect ratio of 100 or more. (4) The highly thermally conductive material according to (3), wherein the aspect ratio is 1,000 or more. The high thermal conductive material according to any one of claims 1 to 4, wherein the alumina fiber sheet is made of at least one selected from non-woven alumina continuous fibers and alumina continuous fibers oriented in a certain direction. (6) The high thermal conductive material according to any one of (1) to (5), wherein the alumina fiber sheet contains α-alumina. 7. The high thermal conductive material according to claim 6, wherein the α-alumina is contained in the alumina fiber sheet in an amount of 50% by mass or more. The high thermal conductive material according to any one of claims 1 to 7, wherein the alumina continuous fiber has an average fiber diameter of 50 to 2,000 nm. The high thermal conductive material according to claim 8, wherein the average fiber diameter of the alumina continuous fibers is 100 to 1,000 nm. The high thermal conductive material according to any one of claims 1 to 9, wherein the high thermal conductive material is in a sheet shape. The high thermal conductive material according to claim 10, wherein the high thermal conductive material is sheet-like and has a thickness of 20 to 2,000 μm. (12) The highly thermally conductive material according to (11), wherein the highly thermally conductive material has a sheet shape and a thickness of 40 to 1,500 μm. The high heat according to any one of claims 1 to 12, wherein the resin is at least one selected from the group consisting of polyvinyl alcohol, polyurethane resin, epoxy resin, polyimide resin, polyvinylidene fluoride resin, polystyrene and silicone resin. Conductive material. (14) The high thermal conductive material according to any one of (1) to (13), which has a thermal conductivity of 5 W / mK or more. The high thermal conductivity material according to any one of claims 1 to 14, wherein the thermal conductivity after bending 10 times with a curvature having a diameter of 5 mm maintains 80% or more. The high thermal conductivity material according to any one of claims 1 to 15, wherein the high thermal conductivity material is electrically insulating. The high heat conductive material according to any one of claims 1 to 16, wherein a surface resistance value of the high heat conductive material is 1 × 10 ¹¹ Ω / □ or more.

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