Thermally conductive resin composition and high-temperature high-thermal-conductivity sheet

Abstract

To provide a thermally conductive material with reduced deterioration of thermal conductivity at high temperatures and with the capability of forming good contact under a low-temperature process of 150°C or lower.SOLUTION: A thermally conductive resin composition comprising the following components (A) and (B). (A): polymer (A1) and polymer (A2), where (A1) is a halogen-containing polymer having a melting point of 150°C or higher and (A2) is a polymer incompatible with the polymer (A1). (B): at least one thermally conductive filler selected from the group consisting of metals, metal oxides, metal hydroxides, metal nitrides, metal carbides, and carbon allotropes, in an amount of 1 to 99 mass% relative to the total composition, wherein the polymer (A1) and the polymer (A2) have a sea-island structure, with the polymer (A2) being the island phase.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a thermally conductive resin composition. More specifically, the present invention relates to a thermally conductive resin composition used in a heat conducting part for cooling electronic parts, for example, a heat sink for temperatures of 150°C or higher. [Background technology]

[0002] Computers (central processing units: CPU), transistors, light-emitting diodes (LEDs), and other semiconductors generate heat during use, and this heat can reduce the performance of electronic components. For this reason, heat-generating electronic components are usually fitted with heat sinks.

[0003] Traditionally, metals with high thermal conductivity have been used for such heat sinks. However, in recent years, thermally conductive resin compositions, which offer a high degree of freedom in shape selection and facilitate lightweight and compact design, have begun to be used (Patent Documents 1 and 2). To improve thermal conductivity, such thermally conductive resin compositions must contain a large amount of thermally conductive inorganic filler in the binder resin. Even thermally conductive resin compositions that exhibit high thermal conductivity at room temperature often exhibit reduced thermal conductivity under the high-temperature conditions encountered during actual operation due to the properties of the binder resin and thermally conductive inorganic filler (Non-Patent Documents 1 to 3). Furthermore, when high-melting-point materials are used, the contact at the interface decreases, resulting in a decrease in thermal conductivity (Patent Document 3).

[0004] Increasing the amount of thermally conductive inorganic filler is effective in increasing thermal conductivity at high temperatures, but simply increasing the amount of thermally conductive inorganic filler is known to cause various problems. For example, increasing the amount increases the viscosity of the resin composition, significantly reducing contact with the adherend and increasing contact thermal resistance. Furthermore, because there is a limit to the amount of inorganic filler that can be added, the resulting resin composition often does not have sufficient thermal conductivity. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2005-255867 [Patent Document 2] Patent Publication No. 2010-65064 [Patent Document 3] Japanese Patent Application Publication No. 11-233696 [Non-patent literature]

[0006] [Non-Patent Document 1] Tokyo Metropolitan Industrial Technology Research Center Research Report, No. 7, 2012 [Non-patent document 2] Sumika Chemical Analysis Center, Ltd. Technical News TN522 [Non-patent document 3] Chemicals Evaluation and Research Institute: Thermal conductivity measurement example of heat dissipation sheet Summary of the Invention [Problem to be solved by the invention]

[0007] However, in Patent Document 1, although flexibility is imparted to the island phase of a polymer blend having a sea-island phase separation structure, the thermally conductive filler is uniformly dispersed in the sea phase, resulting in the problem of being unable to precisely control the heat transfer path at high temperatures. In Patent Document 2, the thermally conductive filler is unevenly distributed in one of the polymer phases, but because of the co-continuous structure, the polymer phase where the thermally conductive filler is unevenly distributed expands at high temperatures, resulting in a decrease in thermal conductivity at high temperatures. Furthermore, as described in Patent Document 3, contact with high-melting-point materials is reduced, resulting in a decrease in thermal conductivity.

[0008] The present invention has been made in view of these problems, and aims to provide a thermally conductive material that exhibits little decrease in thermal conductivity at high temperatures and is capable of forming a good contact state in a low-temperature process at 150°C or less. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention provides: The following components (A) and (B): (A) the following (A1) polymer and (A2) polymer: (A1) Halogen-containing polymer with a melting point of 150°C or higher (A2) a polymer incompatible with the (A1) polymer (B) at least one thermally conductive filler selected from the group consisting of metals, metal oxides, metal hydroxides, metal nitrides, metal carbides, and allotropes of carbon: an amount of 1 to 99% by mass based on the total mass of the composition wherein the (A1) polymer and the (A2) polymer have a sea-island structure, with the (A2) polymer forming an island phase.

[0010] Such a thermally conductive resin composition can provide a thermally conductive material that exhibits little decrease in thermal conductivity at high temperatures and can form a good contact state in a low-temperature process at 150°C or less.

[0011] Also, the (A1) polymer is a fluorine-containing polymer, The (A2) polymer is a crystalline polymer having a melting point 15°C or more lower than that of the (A1) polymer, and The thermally conductive filler (B) is preferably at least one thermally conductive filler selected from the group consisting of metals and allotropes of carbon.

[0012] Such a thermally conductive resin composition can more reliably provide a thermally conductive material that exhibits little decrease in thermal conductivity at high temperatures.

[0013] Furthermore, the thermally conductive resin composition of the present invention preferably has a thermal conductivity at 150°C that is within ±10% of the thermal conductivity at 25°C.

[0014] A composition with such properties is practically preferable.

[0015] The present invention also provides a high-temperature, high-thermal conductive sheet formed from the above-mentioned thermally conductive resin composition.

[0016] The thermally conductive resin composition of the present invention is particularly useful as a high-temperature, highly thermally conductive sheet. [Effects of the Invention]

[0017] The thermally conductive resin composition and high-temperature, high-thermal-conductivity sheet of the present invention use a polymer with a sea-island structure, with the sea phase made of a polymer having a melting point of 150°C or higher and the island phase made of a polymer having a melting point lower than that of the sea phase, and the thermally conductive filler is unevenly distributed, thereby suppressing the volume expansion of the island phase at high temperatures, thereby maintaining high contact at high temperatures and achieving high thermal conductivity.

[0018] The present invention provides a thermally conductive material that can form a good contact state in a low-temperature process, without requiring any special process, by dispersing a thermally conductive filler in a specific polymer blend, thereby allowing the filler to be spontaneously and selectively contained in a heat transfer path controlled by a phase separation structure, thereby precisely controlling the heat transfer path and minimizing the decrease in thermal conductivity at high temperatures. This reduces thermal damage to semiconductors such as computers (central processing units: CPUs), transistors, and light-emitting diodes (LEDs), and is also energy-efficient in terms of process temperatures. [Brief explanation of the drawings]

[0019] [Figure 1] 1 shows an SEM image and an EDS image of the thermally conductive resin composition obtained in Example 1. [Figure 2] 2 shows an SEM image and an EDS image of the thermally conductive resin composition obtained in Example 2. [Figure 3] 2 shows an SEM image and an EDS image of the thermally conductive resin composition obtained in Comparative Example 2. [Figure 4] 1 shows an SEM image and an EDS image of the thermally conductive resin composition obtained in Comparative Example 3. [Figure 5] 1 shows an SEM image and an EDS image of the thermally conductive resin composition obtained in Comparative Example 4. [Figure 6] 1 shows an SEM image and an EDS image of the thermally conductive resin composition obtained in Comparative Example 5. [Figure 7] 1 shows the results of DSC measurement of the thermally conductive resin composition obtained in Example 1. [Figure 8] 1 shows the results of DSC measurement of the thermally conductive resin composition obtained in Example 2. [Figure 9] 1 shows the results of DSC measurement of the thermally conductive resin composition obtained in Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0020] As mentioned above, there was a need to develop a thermally conductive material that would not lose much thermal conductivity at high temperatures and would be able to form good contact in low-temperature processes at temperatures below 150°C.

[0021] As a result of extensive research into achieving the above object, the inventors discovered that the above object can be achieved by unevenly dispersing a thermally conductive filler in a polymer matrix using a specific polymer blend system, and thus completed the present invention.

[0022] The present invention was made based on the above findings and provides a thermally conductive material having a structure in which a thermally conductive filler is dispersed in a polymer matrix, wherein the polymer forming the polymer matrix is ​​a polymer blend containing two or more polymer components, the polymer blend forms a sea-island type phase-separated structure, and due to the difference in melting points between the two polymer phases, the volume expansion of the low-melting-point island polymer phase is constrained by the high-melting-point sea polymer phase at high temperatures, and the thermally conductive filler is unevenly distributed in the island polymer phase. Note that "uneven distribution" as used here means that the thermally conductive filler is precipitated in a larger amount in one of the polymer phases, and does not necessarily mean that it is precipitated exclusively in one of the polymer phases.

[0023] The thermally conductive fillers include metals, metal oxides, metal hydroxides, metal nitrides, metal carbides, and allotropes of carbon.

[0024] The polymer blend contains, for example, two or more polymer components that differ in affinity with the thermally conductive filler. Examples of the polymer blend include a polymer blend containing a polymer component with a melting point of 150°C or higher.

[0025] Examples of the polymer blend include crystalline polymers such as polyethylene, polypropylene, polycarbonate, and nylon, which have a melting point 15°C or more lower than that of the fluorine-containing polymer and undergo phase separation, as the main component of the island phases in which the thermally conductive filler is unevenly distributed when a sea-island phase-separated structure is formed.

[0026] Furthermore, the present invention can produce a high-temperature, highly thermally conductive sheet by first mixing and melting at a high temperature (A1) polymer and (A2) polymer that contain two or more polymer components and undergo phase separation to form a polymer blend, adding a thermally conductive filler, and rolling the polymer blend containing the thermally conductive filler into a sheet.

[0027] That is, the present invention provides a thermally conductive resin composition comprising the following components (A) and (B): (A) the following (A1) polymer and (A2) polymer: (A1) a halogen-containing polymer having a melting point of 150°C or higher, (A2) a polymer incompatible with the (A1) polymer, and (B) at least one thermally conductive filler selected from the group consisting of metals, metal oxides, metal hydroxides, metal nitrides, metal carbides, and carbon allotropes, in an amount of 1 to 99% by mass based on the total mass of the composition, wherein the (A1) polymer and the (A2) polymer form a sea-island structure, with the (A2) polymer forming an island phase.

[0028] The present invention will be described in detail below, but the present invention is not limited thereto.

[0029] <Thermal conductive resin composition> The thermally conductive resin composition of the present invention may be, for example, a thermally conductive resin composition having a structure in which a thermally conductive filler is unevenly distributed within a sea-island phase-separated polymer matrix. The polymer forming the phase-separated polymer matrix is ​​a polymer blend containing two or more polymer components, in which the sea phase is a polymer with a melting point of 150°C or higher, and the island phase has a lower melting point than the sea phase, and the thermally conductive filler can be unevenly distributed. Because the sea phase has a high melting point of 150°C or higher, there is no decrease in thermal conductivity even at temperatures above 150°C. Because the island phase has a lower melting point than the sea phase, there is good contact with the adherend. Although there is no decrease in thermal conductivity even when the sea phase has only a melting point of 150°C or higher, this is not practically suitable because it requires heating at temperatures above the melting point during use.

[0030] <Component (A)> The component (A) is (A1) a halogen-containing polymer having a melting point of 150° C. or higher, and (A2) a polymer incompatible with the polymer (A1).

[0031] (A1) Polymer The polymer (A1) (high-melting point polymer of the sea phase) used in the present invention is, for example, polyvinylidene fluoride, and basically any of the following fluorine-containing hydrocarbon polymers can be used. Those having the above-mentioned properties are preferably used.

[0032] The (A1) polymer is preferably a polymer having low affinity with metals, metal oxides, metal hydroxides, metal nitrides, metal carbides, and carbon allotropes, and is preferably a fluorine-containing hydrocarbon polymer containing fluorine in its molecular structure. Each of these is explained below.

[0033] Fluorine-containing hydrocarbon polymers that contain fluorine in their molecular structure include PTFE (melting point 327°C), FEP (285-295°C), PFA (302-310°C), PCTFE (212-217°C), PVDF (170-180°C), ETFE (265-275°C), and ECTFE (240-245°C).

[0034] Although thermoplastic resins are exemplified as the polymer (A1) used in the present invention, thermosetting resins such as fluorine-containing epoxy resin alone, epoxy resin-phenol resin, and epoxy resin-amine resin can also be selected.

[0035] Other polymers that can be selected as (A1) include halogen-containing (especially fluorine-containing) polyimide silicones and polyamic acids of polyimide silicones.

[0036] (A2) Polymer The (A2) polymer used in the present invention is not particularly limited as long as it is incompatible with the (A1) polymer, but it is preferably a polymer with a lower melting point than the (A1) polymer, and more preferably a crystalline polymer with a melting point at least 15°C lower than the (A1) polymer, such as polyethylene (e.g., HDPE), polypropylene, polycarbonate, nylon, etc. The melting point of the (A2) polymer can be 150°C or lower.

[0037] Other examples of the polymer (A2) that can be selected include an addition reaction product of an alkenyl group-containing organopolysiloxane and a hydrosilyl group-containing organopolysiloxane, and a condensation polymer of an alkoxysilane.

[0038] The phase-separated state of the (A1) polymer and the (A2) polymer must be such that the (A1) polymer forms a sea phase and the (A2) polymer forms an island phase.

[0039] Whether the (A1) polymer and the (A2) polymer form a sea-island structure or a co-continuous structure can be confirmed by observing the cross section of the thermally conductive resin composition using SEM / EDS and examining the distribution of fluorine atoms, for example. That is, in the SEM / EDS image, regions with a relatively high concentration of fluorine atoms represent the (A1) polymer phase, and regions with a relatively low concentration of fluorine atoms represent the (A2) polymer phase.

[0040] In addition, the sea-island structure of the thermally conductive resin composition of the present invention is such that the area of ​​each island phase of the (A2) polymer is 1 μm in the SEM / EDS image. 2 More than 25μm 2 Preferably, the area of ​​the island phases is less than this. For example, the average area of ​​10 randomly selected island phases can be used as the area of ​​the island phases. If the island phases of the (A2) polymer have this size, the effects of the (A2) polymer can be fully exerted, good contact can be reliably obtained, and the thermal expansion of the (A2) polymer can be reliably suppressed, thereby minimizing the decrease in thermal conductivity at high temperatures.

[0041] (B) Thermally conductive filler Next, the thermally conductive filler dispersed in the polymer matrix will be described. Examples of the thermally conductive filler dispersed in the polymer matrix of the thermally conductive resin composition of the present invention include metals (noble metals and base metals), metal oxides, metal hydroxides, metal nitrides, metal carbides, and carbon allotropes.

[0042] Examples of metals for such thermally conductive fillers include silver, copper, gold, aluminum, palladium, iron, chromium, nickel, manganese, tin, cobalt, titanium, magnesium, and lithium.

[0043] Examples of metal oxides include aluminum oxide, zinc oxide, and magnesium oxide.

[0044] Furthermore, an example of the metal hydroxide is magnesium hydroxide.

[0045] Examples of metal nitrides include silicon nitride, boron nitride, aluminum nitride, gallium nitride, chromium nitride, tungsten nitride, magnesium nitride, molybdenum nitride, and lithium nitride.

[0046] Examples of metal carbides include silicon carbide, boron carbide, aluminum carbide, titanium carbide, and tungsten carbide.

[0047] Examples of carbon allotropes include carbon black, furnace black, graphite, diamond, fullerene, carbon nanotube, carbon nanofiber, nanohorn, carbon microcoil, and nanocoil.

[0048] The average particle diameter of the thermally conductive filler (inorganic filler) is, for example, 0.1 to 100 μm, preferably 0.2 to 50 μm. The average particle diameter is the mass average value D 50 (or median diameter).

[0049] The thermal conductivity of the thermally conductive filler is, for example, 10 W / m·K or more, preferably 30 W / m·K or more, and usually 2000 W / m·K or less.

[0050] The thermally conductive filler preferably has a chemically modified surface. To chemically modify the inorganic material, a chemical modifier (surface modifier) ​​is reacted with the surface of the thermally conductive filler. Examples of such chemical modifiers include hydrophobicity-introducing compounds for hydrophobizing the surface of the thermally conductive filler, and hydrophilicity-introducing compounds for hydrophilizing the surface of the thermally conductive filler.

[0051] The hydrophobic introducing compound is a compound that has both a hydrophobic group and a functional group that reacts with hydroxyl groups present on the surface of the thermally conductive filler, and examples thereof include carboxylic acids such as hexanoic acid, decanoic acid, and oleic acid, amines such as hexylamine and decylamine, and aminocarboxylic acids such as aminohexanoic acid.

[0052] The hydrophilic introducing compound is a compound that has both a hydrophilic group and a functional group that reacts with hydroxyl groups or the like present on the surface of the thermally conductive filler, and examples thereof include p-hydroxybenzoic acid, 4-oxovaleric acid, 4-hydroxyphenylacetic acid, sebacic acid, 5-oxohexanoic acid, 3-(4-hydroxyphenyl)propionic acid, 3-(4-carboxyphenyl)propionic acid, 7-oxooctanoic acid, and 6-hydroxycaproic acid.

[0053] The mixing ratio of each component is, for example, 0.5 to 50 parts by weight, or preferably 1 to 25 parts by weight, of the chemical modifier relative to 100 parts by weight of the thermally conductive filler.

[0054] <Method for producing thermally conductive resin composition> Next, a method for producing the thermally conductive resin composition of the present invention will be described. First, in this method, the incompatible (A1) polymer and (A2) polymer are first hot-melt mixed, and then the thermally conductive filler (B) is blended with the hot-melt mixed incompatible polymer components and thoroughly stirred to prepare the thermally conductive resin composition. The prepared thermally conductive resin composition can then be melt-rolled to produce a thermoelectrically conductive sheet.

[0055] The blending ratio of the thermally conductive filler (B) in the thermally conductive resin composition of the present invention is an amount that is 1 to 99 mass % based on the total mass of the composition, but preferably the amount of the thermally conductive filler (B) is 10 to 2000 parts by weight, more preferably 50 to 1000 parts by weight, per 100 parts by weight of the incompatible polymer phase containing the (A1) polymer and the (A2) polymer.

[0056] In the thermally conductive resin composition of the present invention, it is preferred that the (A1) polymer is a fluorine-containing polymer, the (A2) polymer is a crystalline polymer having a melting point 15°C or more lower than that of the (A1) polymer, and the (B) thermally conductive filler is at least one thermally conductive filler selected from the group consisting of metals and carbon allotropes.

[0057] If necessary, the thermally conductive resin composition of the present invention may contain additives such as surfactants, antioxidants, ultraviolet absorbers, light stabilizers, pigments, dyes, rust inhibitors, flame retardants, etc. The surfactants are added to control the interfacial activity between the (A1) polymer phase and the (A2) polymer phase, and examples of such surfactants include anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants.

[0058] Anionic surfactants include, for example, carboxylates, alkyl sulfonates, Examples include alkyl aryl sulfonates, alkyl sulfates, sulfated oils, and sulfate esters.

[0059] Examples of cationic surfactants include amine salts, tetraalkyl quaternary ammonium salts, trialkylbenzyl quaternary ammonium salts, alkylpyridinium salts, and alkylsulfonium salts.

[0060] Examples of amphoteric surfactants include betaine, sulfobetaine, and sulfate betaine.

[0061] Examples of nonionic surfactants include fatty acid monoglycerin esters, fatty acid polyglycol esters, fatty acid sorbitan esters, fatty acid sucrose esters, fatty acid alkanolamides, fatty acid polyethylene glycol condensates, fatty acid amide polyethylene glycol condensates, alkylphenol polyethylene glycol condensates, and polypropylene glycol polyethylene glycol condensates.

[0062] These surfactants can be used alone or in combination of two or more. Among these surfactants, amphoteric surfactants are preferred.

[0063] The surfactant is added in an amount of 0.05 to 1 part by weight, preferably 0.1 to 0.5 parts by weight, per 100 parts by weight of the immiscible polymer phase containing the (A1) polymer and the (A2) polymer. If the surfactant amount is within the above range, the sea-island phase-separated structure can be formed more reliably.

[0064] Specifically, the thermally conductive resin composition (immiscible polymer-thermally conductive filler composition) of the present invention can be obtained, for example, as a sheet or bulk (lump) molded article. When the immiscible polymer-thermally conductive filler sheet or molded article thus obtained is used as a heat dissipating material, its thermal conductivity is, for example, 0.2 to 50 W / m K, preferably 0.5 to 30 W / m K.

[0065] The thermally conductive resin composition of the present invention forms a sea-island phase-separated structure, and due to the difference in melting points between the two polymer phases, the volume expansion of the low-melting-point island polymer phase is restricted by the high-melting-point sea polymer phase at high temperatures, thereby preventing a decrease in thermal conductivity at high temperatures. It is preferable that the thermal conductivity of the thermally conductive resin composition of the present invention is within ±10% of the thermal conductivity at 25°C at 150°C. A composition with such characteristics is practically preferable.

[0066] <High-temperature, high-thermal-conductivity sheet> The present invention also provides a high-temperature, highly thermally conductive sheet formed from the above-mentioned thermally conductive resin composition. The thermally conductive resin composition of the present invention is particularly useful as a high-temperature, highly thermally conductive sheet.

[0067] <Thermal conductive resin composition (another viewpoint)> The thermally conductive resin composition of the present invention can also be expressed as follows from the viewpoint of the volume ratio of the (A1) polymer to the (A2) polymer. The following components (A) and (B): (A) the following (A1) polymer and (A2) polymer: (A1) Halogen-containing polymer with a melting point of 150°C or higher (A2) a polymer incompatible with the (A1) polymer (B) at least one thermally conductive filler selected from the group consisting of metals, metal oxides, metal hydroxides, metal nitrides, metal carbides, and allotropes of carbon: an amount of 1 to 99% by mass based on the total mass of the composition and wherein the volume ratio of the (A1) polymer to the (A2) polymer is (A1):(A2) in the range of 72:28 to 95:5 (Vol% ratio).

[0068] In the thermally conductive resin composition of the present invention, the blending ratio of the (A1) polymer to the (A2) polymer is not particularly limited as long as the (A1) polymer and the (A2) polymer form a sea-island structure and the (A2) polymer forms an island phase. However, by setting the volume ratio of the (A1) polymer to the (A2) polymer as described above, it is possible to more reliably form such a sea-island structure.

[0069] That is, the volume ratio of the (A1) polymer to the (A2) polymer is preferably in the range of (A1):(A2)=72:28 to 95:5 (Vol% ratio), more preferably in the range of (A1):(A2)=75:25 to 92:8 (Vol% ratio), and even more preferably in the range of (A1):(A2)=77:23 to 90:10 (Vol% ratio).

[0070] Of course, all the other matters relating to the thermally conductive resin composition of the present invention described above also apply to this other viewpoint (defined by volume ratio). [Example]

[0071] EXAMPLES The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples and comparative examples.

[0072] In the examples and comparative examples, the thermally conductive resin compositions, the production of discs for measuring thermal conductivity, the measurement of thermal conductivity, the comparison of melting point peaks by DSC, and the observations under an electron microscope were carried out as follows: The extruder used to produce the thermally conductive resin compositions was a Labo Plastomill 4M150 manufactured by Toyo Seiki Seisaku-sho, Ltd., and the press was a tabletop hot press machine manufactured by Techno Supply Co., Ltd.

[0073] The raw materials used are as follows: PVDF: Kyner 720, manufactured by Arkema, MFR = 5.0 to 29.0 g / 10 min HDPE: Novatec HD HJ560, manufactured by Japan Polyethylene Co., Ltd., MFR = 7.0 g / 10 min Furnace Black: PM342, manufactured by Columbia Chemical Co.

[0074] [Example 1] 88.1 parts by weight (52.0 vol%) of PVDF and 11.9 parts by weight (13.0 vol%) of HDPE were melt-kneaded in an extruder at 200°C for 5 minutes at 60 rpm, and then 60.0 parts by weight (35 vol%) of furnace black was added, and the mixture was melt-kneaded in an extruder at 200°C for 5 minutes at 60 rpm to obtain a thermally conductive resin composition.

[0075] The obtained thermally conductive resin composition was placed in a mold measuring 100 mm x 100 mm x 1 mm, melted at 200°C for 20 minutes without pressure, then held at 200°C for 20 minutes under a pressure of 1.5 MPa, and cooled from 200°C to room temperature over 30 minutes.

[0076] The heated thermally conductive resin composition was filled into a 30mm diameter x 6mm thick mold, melted at 200°C for 20 minutes without pressure, then held at 200°C for 20 minutes under a pressure of 1.5 MPa, cooled from 200°C to 100°C over 120 minutes, and allowed to cool from 100°C to room temperature over 30 minutes. Using the above method, a 30mm diameter x 6mm thick disk-shaped sheet was obtained.

[0077] [Example 2] 94.3 parts by weight (58.5 vol%) of PVDF and 5.7 parts by weight (6.5 vol%) of HDPE were mixed by stirring in an extruder at 200°C for 5 minutes at 60 rpm, and then 57.1 parts by weight (35 vol%) of furnace black was added, and the mixture was melt-kneaded in an extruder at 200°C for 5 minutes at 60 rpm to obtain a thermally conductive resin composition.

[0078] The obtained thermally conductive resin composition was subjected to the same method as in Example 1 to obtain a disk-shaped sheet of 30 mm diameter x 6 mm thickness.

[0079] [Comparative Example 1] 100 parts by weight (65.0 vol%) of PVDF was stirred and mixed in an extruder at 200°C for 5 minutes at 60 rpm, and then 54.4 parts by weight (35 vol%) of furnace black was added, and the mixture was melt-kneaded in an extruder at 200°C for 5 minutes at 60 rpm to obtain a thermally conductive resin composition.

[0080] The obtained thermally conductive resin composition was placed in a mold measuring 100 mm x 100 mm x 1 mm, melted at 200°C for 20 minutes without pressure, then held at 200°C for 20 minutes under a pressure of 1.5 MPa, and cooled from 200°C to room temperature over 30 minutes.

[0081] The heated thermally conductive resin composition was filled into a 30mm diameter x 6mm thick mold, melted at 200°C for 20 minutes without pressure, then held at 200°C for 20 minutes under a pressure of 1.5 MPa, cooled from 200°C to 100°C over 120 minutes, and allowed to cool from 100°C to room temperature over 30 minutes. Using the above method, a 30mm diameter x 6mm thick disk-shaped sheet was obtained.

[0082] Comparative Example 2 81.5 parts by weight (45.5 vol%) of PVDF and 18.5 parts by weight (19.5 vol%) of HDPE were mixed in an extruder at 200°C for 5 minutes at 60 rpm, and then 63.5 parts by weight (35 vol%) of furnace black was added, and the mixture was melt-kneaded in an extruder at 200°C for 5 minutes at 60 rpm to obtain a thermally conductive resin composition.

[0083] The obtained thermally conductive resin composition was processed in the same manner as in Comparative Example 1 to obtain a disk-shaped sheet having a diameter of 30 mm and a thickness of 6 mm.

[0084] Comparative Example 3 73.9 parts by weight (39.0 vol%) of PVDF and 26.1 parts by weight (26.0 vol%) of HDPE were mixed in an extruder at 200°C for 5 minutes at 60 rpm, and then 66.9 parts by weight (35 vol%) of furnace black was added, and the mixture was melt-kneaded in an extruder at 200°C for 5 minutes at 60 rpm to obtain a thermally conductive resin composition.

[0085] The obtained thermally conductive resin composition was processed in the same manner as in Comparative Example 1 to obtain a disk-shaped sheet having a diameter of 30 mm and a thickness of 6 mm.

[0086] Comparative Example 4 65.3 parts by weight (32.5 vol%) of PVDF and 34.7 parts by weight (32.5 vol%) of HDPE were mixed in an extruder at 200°C for 5 minutes at 60 rpm, and then 71.0 parts by weight (35 vol%) of furnace black was added, and the mixture was melt-kneaded in an extruder at 200°C for 5 minutes at 60 rpm to obtain a thermally conductive resin composition.

[0087] The obtained thermally conductive resin composition was processed in the same manner as in Comparative Example 1 to obtain a disk-shaped sheet having a diameter of 30 mm and a thickness of 6 mm.

[0088] Comparative Example 5 55.5 parts by weight (26.0 vol%) of PVDF and 44.5 parts by weight (39.0 vol%) of HDPE were mixed in an extruder at 200°C for 5 minutes at 60 rpm, and then 75.6 parts by weight (35 vol%) of furnace black was added, and the mixture was melt-kneaded in an extruder at 200°C for 5 minutes at 60 rpm to obtain a thermally conductive resin composition.

[0089] The obtained thermally conductive resin composition was processed in the same manner as in Comparative Example 1 to obtain a disk-shaped sheet having a diameter of 30 mm and a thickness of 6 mm.

[0090] (Evaluation of Thermally Conductive Resin Composition) The thermally conductive resin compositions obtained in Examples 1 and 2 and Comparative Examples 1 to 5 were observed with an electron microscope, and their thermal conductivities and melting points were measured as described below.

[0091] (Electron microscope observation) Evaluation of the sea-island structure and bicontinuous structure by SEM cross-section observation was carried out using a JEOL JSM-6500F, and EDS was carried out using a JEOL JED-2200F. Data was acquired at an SEM accelerating voltage of 15 kV, a probe current of 11 μA, and an EDS integration count of 50. The SEM / EDX measurement results for Examples 1 and 2 and Comparative Examples 2 to 5 are shown in Figures 1 to 6. The evaluation results of the sea-island structure and bicontinuous structure are shown in Tables 1 and 2.

[0092] Although it is difficult to distinguish between a sea-island structure and a co-continuous structure by observing the cross section of a composition using an SEM photograph, this can be determined by analyzing the fluorine distribution using EDS measurement. In Examples 1 and 2 (Figs. 1 and 2), the areas surrounded by dotted lines are darker than the surrounding area. The dark areas (island phases) are isolated and phase-separated from the light areas (sea phases), indicating a sea-island structure, and the dark areas indicate that this island phase is an HDPE phase. In Comparative Examples 2 to 5 (Figs. 3 to 6), a large continuous phase (co-continuous phase) of 5 μm or more is present, and it is clear that the light areas are a PVDF phase and the dark areas are an HDPE phase.

[0093] (Measurement of thermal conductivity) To measure thermal conductivity, two disc-shaped sheets were prepared as described in Examples 1 and 2 and Comparative Examples 1 to 5. A thermal conductivity probe was sandwiched between the disc-shaped sheets. The thermal conductivity probe and the two disc-shaped sheets were further pressed with an aluminum plate and clips to ensure good contact between the disc-shaped sheets and the discs of the thermal conductivity probe. The disc-shaped sheets and the thermal conductivity probe were placed in a dryer at a specified temperature for 30 minutes, and the thermal conductivity was measured at 25°C, 50°C, 100°C, and 150°C to evaluate the thermal conductivity ratio (150°C / 25°C). A hot-disk thermal conductivity measuring device (TPA-501, Kyoto Electronics Co., Ltd.) was used. The results are shown in Tables 1 and 2.

[0094] It was confirmed that Examples 1 and 2 had a high thermal conductivity ratio (150°C / 25°C) (i.e., a small decrease in thermal conductivity at high temperatures). This is because Examples 1 and 2 formed a sea-island structure. On the other hand, it was confirmed that Comparative Examples 2 to 5 had a low thermal conductivity ratio (150°C / 25°C) (i.e., a large decrease in thermal conductivity at high temperatures). This is because, when the blending ratio of the (A2) polymer reaches a certain level, the sea-island structure changes to a co-continuous structure. However, since the thermally conductive filler is present in the (A2) polymer phase and the co-continuous structure allows the volume expansion of the (A2) polymer to occur without restraint, direct contact between the thermally conductive particles is reduced, resulting in a significant decrease in thermal conductivity at high temperatures.

[0095] (Melt point measurement) Melting point measurements based on DSC peaks were performed using the thermally conductive resin compositions described in Examples 1 and 2 and Comparative Examples 1 to 5, using a Hitachi High-Tech Science Corporation high-sensitivity differential scanning calorimeter (DSC7000X) at a temperature rise rate of 10°C / min in the temperature range of 25°C to 300°C. DSC profiles of Examples 1 and 2 and Comparative Example 1 are shown in Figures 7 to 9. Tables 1 and 2 also show whether or not there was a peak below 150°C in Examples 1 and 2 and Comparative Examples 1 to 5.

[0096] 7 and 8, two melting point peaks, HDPE and PVDF, were observed in Examples 1 and 2, with the HDPE melting point peak at around 135°C and the PVDF melting point peak at around 170°C, indicating that a good contact state was obtained at a process temperature of around 150°C, which brings the adherend and the thermally conductive resin into contact, resulting in a thermally conductive resin sheet with good contact.On the other hand, as shown in Figure 9, only the PVDF melting point peak was observed in Comparative Example 1, indicating that good contact could not be obtained unless a process temperature of 170°C or higher was used.

[0097] [Table 1]

[0098] [Table 2]

[0099] From the above results of Examples 1 and 2 and Comparative Examples 1 to 5, it can be seen that the present invention has little decrease in thermal conductivity at high temperatures and can form a good contact state in a low-temperature process at 150° C. or less.

[0100] This specification includes the following inventions.

[0101] [1]: A thermally conductive resin composition comprising the following components (A) and (B): (A) the following (A1) polymer and (A2) polymer: (A1) a halogen-containing polymer having a melting point of 150°C or higher, (A2) a polymer incompatible with the (A1) polymer, and (B) at least one thermally conductive filler selected from the group consisting of metals, metal oxides, metal hydroxides, metal nitrides, metal carbides, and carbon allotropes, in an amount of 1 to 99% by mass based on the total mass of the composition, wherein the (A1) polymer and the (A2) polymer form a sea-island structure, with the (A2) polymer forming an island phase.

[0102] [2]: The thermally conductive resin composition according to the above [1], wherein the (A1) polymer is a fluorine-containing polymer, the (A2) polymer is a crystalline polymer having a melting point 15°C or more lower than that of the (A1) polymer, and the (B) thermally conductive filler is at least one thermally conductive filler selected from the group consisting of metals and allotropes of carbon.

[0103] [3]: The thermally conductive resin composition according to [1] or [2] above, characterized in that the thermal conductivity at 150°C is within ±10% of the thermal conductivity at 25°C.

[0104] [4]: A high-temperature, highly thermally conductive sheet characterized by being formed from the thermally conductive resin composition according to any one of the above [1] to [3].

[0105] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention.

Claims

1. The following components (A) and (B): (A) The following (A1) polymer and (A2) polymer: (A1) Halogen-containing polymer with a melting point of 150°C or higher (A2) A polymer incompatible with the polymer (A1) (B) at least one thermally conductive filler selected from the group consisting of metals, metal oxides, metal hydroxides, metal nitrides, metal carbides, and allotropes of carbon: in an amount of 1 to 99% by mass based on the total mass of the composition wherein the (A1) polymer and the (A2) polymer have a sea-island structure, and the (A2) polymer forms an island phase.

2. the polymer (A1) is a fluorine-containing polymer, The (A2) polymer is a crystalline polymer having a melting point 15°C or more lower than that of the (A1) polymer, and 2. The thermally conductive resin composition according to claim 1, wherein the thermally conductive filler (B) is at least one thermally conductive filler selected from the group consisting of metals and allotropes of carbon.

3. 2. The thermally conductive resin composition according to claim 1, wherein the thermal conductivity at 150°C is within ±10% of the thermal conductivity at 25°C.

4. A high-temperature, highly thermally conductive sheet formed from the thermally conductive resin composition according to any one of claims 1 to 3.

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