Thermally conductive resin composition and molding

Abstract

To provide a thermally conductive resin composition from which a molding excellent in thermal conductivity and mechanical strength such as flexural elasticity can be produced.SOLUTION: The thermally conductive resin composition contains: a thermally conductive filler which contains plate-like alumina particles containing molybdenum, and boron nitride; and a thermoplastic resin. The plate-like alumina particles have an average particle diameter of 1-50 μm, an average thickness of 0.01-5 μm, and an aspect ratio represented by the ratio of the average particle diameter to the average thickness of 2-100. The boron nitride has an average particle diameter of 0.1-100 μm. The content of the plate-like alumina particles is 15-25 vol.%. The content of the boron nitride is 5-15 vol.%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a thermally conductive resin composition and a molded article. [Background technology]

[0002] Demand is expected to grow for heat-resistant compounds, such as thermally conductive resin compositions in which thermally conductive fillers (heat-dissipating fillers) are kneaded into resin, and for heat-dissipating adhesive insulating sheets formed from such resin compositions, in heat countermeasure applications for electric vehicles, etc. Among these, highly crystalline alumina has been extensively studied for its applicability, as it has good heat dissipation properties and can be produced inexpensively.

[0003] For example, polygonal plate-shaped alumina particles containing molybdenum within the particles have been proposed as useful thermally conductive fillers (Patent Document 1). Also, plate-shaped alumina containing silicon and a resin composition containing this plate-shaped alumina and a thermoplastic resin have been proposed as useful heat-dissipating materials (Patent Document 2). Furthermore, aluminum oxide containing molybdenum and a heat-dissipating resin composition containing this aluminum oxide and a resin have been proposed (Patent Document 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-123664 [Patent Document 2] International Publication No. 2019 / 194160 [Patent Document 3] Japanese Patent Application Laid-Open No. 2016-166374 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventional alumina particles and the like proposed in Patent Documents 1 to 3, etc., have good thermal conductivity, and resin compositions obtained using these alumina particles and the like exhibit relatively high thermal conductivity. However, considering the rapid technological developments in recent years, the thermal conductivity of these resin compositions is not necessarily sufficient. Furthermore, increasing the content of alumina particles in an attempt to further improve thermal conductivity tends to reduce the moldability of the resulting resin composition, making it difficult to mold it into a desired shape. Furthermore, thermally conductive molded bodies that simultaneously have improved mechanical strength, such as bending elasticity, as well as improved thermal conductivity, and resin compositions capable of producing such molded bodies have not yet been discovered.

[0006] The present invention has been made in view of the problems of the prior art, and an object of the present invention is to provide a thermally conductive resin composition capable of producing a molded article having excellent mechanical strength such as bending elasticity and excellent thermal conductivity. Another object of the present invention is to provide a molded article having excellent mechanical strength such as bending elasticity and excellent thermal conductivity. [Means for solving the problem]

[0007] That is, according to the present invention, there is provided the following thermally conductive resin composition. [1] A thermally conductive resin composition comprising: a thermally conductive filler containing molybdenum-containing plate-like alumina particles and boron nitride; and a thermoplastic resin, wherein the plate-like alumina particles have an average particle size of 1 to 50 μm, an average thickness of 0.01 to 5 μm, and an aspect ratio expressed as the ratio of the average particle size to the average thickness of 2 to 100; the boron nitride has an average particle size of 0.1 to 100 μm; the plate-like alumina particles are contained in an amount of 15 to 25% by volume; and the boron nitride is contained in an amount of 5 to 15% by volume. [2] The thermally conductive resin composition according to [1], wherein the thermoplastic resin is at least one selected from the group consisting of polypropylene resin, polycarbonate resin, acrylonitrile-butadiene-styrene copolymer resin, polyester resin, polyamide resin, and polyphenylene sulfide resin. [3] The thermally conductive resin composition according to [1] or [2], wherein a test piece obtained by mold press molding the thermally conductive resin composition has a thermal conductivity in the plane direction of 2.0 W / (m·K) or more, and a test piece obtained by injection molding the thermally conductive resin composition has a flexural modulus in three-point bending of 300% or more based on the flexural modulus in three-point bending of a test piece obtained by injection molding the thermoplastic resin alone.

[0008] Furthermore, according to the present invention, there is provided the following molded article. [4] A molded article obtained by molding the thermally conductive resin composition according to any one of [1] to [3] above. [Effects of the Invention]

[0009] According to the present invention, a thermally conductive resin composition capable of producing a molded article having excellent mechanical strength such as bending elasticity and excellent thermal conductivity can be provided. Also, according to the present invention, a molded article having excellent mechanical strength such as bending elasticity and excellent thermal conductivity can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0010] <Thermal conductive resin composition> Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments. One embodiment of the thermally conductive resin composition of the present invention contains a thermally conductive filler containing molybdenum-containing plate-like alumina particles and boron nitride, and a thermoplastic resin. The plate-like alumina particles have an average particle size of 1 to 50 μm, an average thickness of 0.01 to 5 μm, and an aspect ratio represented by the ratio of the average particle size to the average thickness of 2 to 100. The boron nitride has an average particle size of 0.1 to 100 μm. The thermally conductive resin composition contains 15 to 25% by volume of the plate-like alumina particles and 5 to 15% by volume of the boron nitride particles. The thermally conductive resin composition of this embodiment will be described in detail below.

[0011] (thermal conductive filler) The thermally conductive filler includes platelet-like alumina particles and boron nitride. The thermally conductive filler may further include fillers other than the platelet-like alumina particles and boron nitride.

[0012] [Plate-shaped alumina particles] The plate-like alumina particles are polygonal plate-like particles containing molybdenum (Mo) within the particles. The plate-like alumina particles may contain trace amounts of impurities derived from the raw materials, shape control agents, etc. used during production.

[0013] The average particle diameter of the plate-shaped alumina particles (D 50 The average particle diameter (D ) of the tabular alumina particles is 1 to 50 μm, preferably 2 to 40 μm. The average thickness (T) of the tabular alumina particles is 0.01 to 5 μm, preferably 0.1 to 1 μm. The ratio of the average particle diameter (D ) to the average thickness (T) of the tabular alumina particles is 50 ) ratio (D 50 The aspect ratio, represented by (x / T), is 2 to 100. Plate-like alumina particles having an aspect ratio of 2 or more are preferred because they have two-dimensional blending properties. Furthermore, by using plate-like alumina particles having an aspect ratio of 100 or less, the mechanical strength, such as bending elasticity, of the thermally conductive resin composition can be improved. Furthermore, by using plate-like alumina particles having an aspect ratio of 5 to 90, the thermal conductivity of the thermally conductive resin composition can be further improved, which is preferable.

[0014] In this specification, the "average particle size" refers to the cumulative 50% particle size (median diameter; D) on a volume basis measured by a laser diffraction / scattering particle size distribution analyzer. 50 ) The "average thickness" of the plate-like alumina particles is the average value of the thicknesses of 50 randomly selected particles measured using a scanning electron microscope (SEM). The average particle size, average thickness, and aspect ratio of the plate-like alumina particles can be controlled by appropriately adjusting and selecting the proportions of the molybdenum compound, aluminum compound, and shape control agent used in the production method described below, the type of shape control agent, and the state of existence of the shape control agent and aluminum compound, etc.

[0015] The plate-like alumina particles may be produced by any method as long as they contain molybdenum (Mo). Among these, those obtained by a production method (flux method) in which an aluminum compound is fired in the presence of a molybdenum compound and a shape control agent are preferred, in terms of higher aspect ratios, excellent dispersibility, and good productivity. According to the flux method, aluminum molybdate formed by a high-temperature reaction between a molybdenum compound and an aluminum compound decomposes into alumina and molybdenum oxide under higher temperature conditions, easily forming plate-like alumina particles incorporating the molybdenum compound. In this process, the sublimated molybdenum oxide can be recovered and reused.

[0016] Shape control agents play an important role in the growth of platelet crystals. In the conventional flux method using molybdenum oxide, molybdenum oxide selectively adsorbs to the

[0113] plane of the alumina α crystal, making it difficult for crystalline components to be supplied to the

[0113] plane, completely suppressing the appearance of the

[0001] plane. This results in the formation of polyhedral particles based on a hexagonal bipyramidal shape. In contrast, the use of a shape control agent suppresses the selective adsorption of the fluxing agent, molybdenum oxide, to the

[0113] plane. This allows the formation of platelet particles with a well-developed

[0001] plane and a close-packed hexagonal lattice crystal structure, which is the thermodynamically most stable.

[0017] Furthermore, by using a molybdenum compound as a fluxing agent, it is possible to easily form molybdenum-containing plate-like alumina particles having a high α-crystallization rate, specifically an α-crystallization rate of 90% or more. The molybdenum-containing plate-like alumina particles have a high α-crystallization rate of alumina and are idiomorphic, resulting in excellent dispersibility. Therefore, by using the molybdenum-containing plate-like alumina particles, it is possible to obtain a thermally conductive resin composition having excellent mechanical strength and thermal conductivity.

[0018] [alumina] The alumina (aluminum oxide) constituting the plate-like alumina particles may be transition alumina of various crystal forms such as γ, δ, θ, and κ, or may contain alumina hydrate in these transition aluminas. Among these, α-crystal alumina is preferred because of its superior mechanical strength and thermal conductivity.

[0019] [molybdenum] By using molybdenum in the production method described below, plate-like alumina particles with a high aspect ratio and excellent dispersibility can be produced. Molybdenum includes metallic molybdenum, molybdenum oxide, and partially reduced molybdenum compounds. The state of molybdenum within the plate-like alumina particles may be in a state of being attached to the particle surface, a state of being substituted for part of the aluminum in the alumina crystal structure, or a combination of these states.

[0020] The molybdenum content in the plate-like alumina particles is preferably 10% by mass or less, more preferably 0.001 to 8% by mass, and particularly preferably 0.01 to 5% by mass, calculated as molybdenum trioxide. A molybdenum content (calculated as molybdenum trioxide) of 10% by mass or less is preferred because it improves the α single crystal quality of the alumina. The molybdenum content can be controlled by appropriately adjusting the firing temperature, firing time, and sublimation rate of the molybdenum compound.

[0021] [Method of manufacturing plate-shaped alumina particles] The plate-like alumina particles can be produced, for example, by a flux method using a molybdenum compound. The flux method is preferred because it allows plate-like alumina particles formed from alumina with a high α-crystallization ratio to be produced under lower temperature conditions.

[0022] (1) Firing process The flux method usually includes a step of calcining an aluminum compound in the presence of a molybdenum compound and a shape control agent (calcination step).

[0023] The aluminum compound is a component that serves as a raw material for the plate-like alumina particles. Examples of the aluminum compound that can be used include aluminum chloride, aluminum sulfate, basic aluminum acetate, aluminum hydroxide, boehmite, pseudo-boehmite, transition alumina (such as γ-alumina, δ-alumina, and θ-alumina), α-alumina, and mixed alumina having two or more crystal phases.

[0024] In the flux method, the shape of the aluminum compound used as a raw material is hardly reflected in the shape of the obtained plate-like alumina particles. Therefore, the shape of the aluminum compound is not limited, and may be any shape, such as spherical, amorphous, a shape with an aspect ratio (wire, fiber, ribbon, tube, etc.), or sheet-like. In addition, the particle diameter of the aluminum compound is not particularly limited, and solid aluminum compounds ranging from several nm to several hundred μm can be used.

[0025] (2) Shape control agent The shape control agent is a component that plays an important role in the growth of alumina plate crystals. The state of the shape control agent during firing may be such that it can come into contact with the aluminum compound. For example, a physical mixture of the shape control agent and the aluminum compound; a complex in which the shape control agent is uniformly or locally distributed on the surface or inside of the aluminum compound; or the like can be suitably used. The shape control agent may also be added to the aluminum compound, or may be contained in the aluminum compound as an impurity.

[0026] As the shape control agent, it is preferable to use a metal compound (excluding molybdenum compounds and aluminum compounds) from the viewpoint of being able to produce plate-like alumina particles having a higher aspect ratio and better dispersibility with good productivity. Among them, it is preferable to use a compound containing silicon, a compound containing a silicon atom, a compound containing sodium, or a compound containing a sodium atom.

[0027] Examples of silicon-containing compounds and silicon atom-containing compounds include metallic silicon, artificially synthesized silicon compounds such as organosilanes, silicon resins, silica microparticles, silica gel, mesoporous silica, SiC, and mullite, and natural silicon compounds such as biosilica. Among these, organosilanes, silicon resins, and silica microparticles are preferably used from the viewpoint of achieving more uniform compounding and mixing with the aluminum compound.

[0028] The shape of the silicon-containing compound and the silicon atom-containing compound is not limited, and may be any shape, such as a sphere, an amorphous shape, a shape having an aspect ratio (such as a wire, a fiber, a ribbon, or a tube), or a sheet shape.

[0029] The amount of the silicon-containing compound and the silicon atom-containing compound used is preferably 0.0001 to 1 mol, more preferably 0.001 to 0.5 mol, per mol of aluminum metal (Al) in the aluminum compound. By setting the amount of the silicon-containing compound and the silicon atom-containing compound used within the above range, plate-like alumina particles with a higher aspect ratio and excellent dispersibility can be obtained.

[0030] Examples of compounds containing sodium and compounds containing sodium atoms include sodium carbonate, sodium molybdate, sodium oxide, sodium sulfate, sodium hydroxide, sodium nitrate, sodium chloride, metallic sodium, etc. Among these, it is preferable to use sodium carbonate, sodium molybdate, sodium oxide, and sodium sulfate because they are easily available industrially and easy to handle.

[0031] The shape of sodium or a compound containing sodium atoms is not limited, and may be any shape, such as spherical, amorphous, a shape with an aspect ratio (such as a wire, fiber, ribbon, or tube), or a sheet.

[0032] The amount of the sodium-containing compound and the sodium atom-containing compound used is preferably 0.0001 to 2 mol, more preferably 0.001 to 1 mol, per mol of aluminum metal (Al) in the aluminum compound. By setting the amount of the sodium-containing compound and the sodium atom-containing compound used within the above range, plate-like alumina particles with a higher aspect ratio and excellent dispersibility can be obtained.

[0033] (3) Molybdenum compounds Molybdenum compounds have a flux function that promotes the growth of α-crystals of alumina under lower temperature conditions. Molybdenum compounds include molybdenum oxide and the acid radical anion (MoO) in which metal molybdenum (Mo) is bonded to oxygen. x n- Compounds containing an acid radical anion (MoO) can be used. x n- ) compounds containing molybdic acid, sodium molybdate, potassium molybdate, lithium molybdate, H3PMo 12 O 40 , H3SiMo 12 O 40 , NH4Mo7O 12 and molybdenum disulfide.

[0034] The molybdenum compound may be a compound containing sodium (Na) or silicon (Si). The molybdenum compound containing sodium (Na) or silicon (Si) functions not only as a fluxing agent but also as a shape control agent. Among the above molybdenum compounds, it is preferable to use molybdenum oxide from the viewpoint of cost and the like.

[0035] The amount of the molybdenum compound used is preferably 0.01 to 3.0 mol, more preferably 0.03 to 0.7 mol, per mol of aluminum metal (Al) in the aluminum compound. By using the molybdenum compound in the above range, plate-like alumina particles having a higher aspect ratio and excellent dispersibility can be obtained.

[0036] (4) Firing The desired plate-like alumina particles can be obtained by calcining an aluminum compound in the presence of a molybdenum compound and a shape-controlling agent. When an aluminum compound is calcined in the presence of a molybdenum compound and a shape-controlling agent, the molybdenum compound first reacts with the aluminum compound to form aluminum molybdate. The formed aluminum molybdate then decomposes into alumina and molybdenum oxide under higher temperature conditions. During this process, the presence of the shape-controlling agent allows α-alumina plate-like crystals to grow efficiently, making it possible to easily obtain molybdenum-containing plate-like alumina particles.

[0037] When the firing temperature exceeds 700°C, the molybdenum compound reacts with the aluminum compound to form aluminum molybdate, and when the firing temperature reaches 900°C or higher, the aluminum molybdate decomposes and plate-like alumina particles are formed by the action of the shape control agent.

[0038] The state of the aluminum compound, shape control agent, and molybdenum compound during firing is not limited, as long as the molybdenum compound and shape control agent are present in the same space where they can interact with the aluminum compound. For example, these components can be mixed by simple mixing of powders of the molybdenum compound, shape control agent, and aluminum compound, mechanical mixing using a grinder, or mixing using a mortar. Furthermore, they may be mixed in either a dry state or a wet state.

[0039] The maximum temperature during calcination is usually 900°C or higher, which is the decomposition temperature of aluminum molybdate (Al2(MoO4)3). To control the shape of the resulting α-alumina, calcination is generally required at a high temperature of 2,000°C or higher, which is close to the melting point of α-alumina. However, calcination at high temperatures of 2,000°C or higher presents industrial challenges due to the burden on the calcination furnace and fuel costs. In contrast, the calcination process using the flux method can form plate-like alumina particles with a high α-crystallization rate and a high aspect ratio, regardless of the shape of the precursor, even at temperatures significantly lower than the melting point of α-alumina (e.g., 1,600°C or lower). Therefore, from the standpoint of industrial constraints and costs, the maximum temperature during calcination should be 900 to 1,600°C, preferably 950 to 1,500°C, and more preferably 1,000 to 1,400°C.

[0040] The time required to raise the temperature to the maximum temperature is preferably 15 minutes to 10 hours, and the time required to maintain the maximum temperature is preferably 5 minutes to 30 hours. To form plate-like alumina particles more efficiently, the firing maintenance time is preferably about 10 minutes to 15 hours. The firing atmosphere is preferably, for example, an oxygen-containing atmosphere or an inert atmosphere containing nitrogen or argon. Of these, firing in an air atmosphere is preferable from the viewpoint of cost. A so-called firing furnace can be used for firing. The firing furnace is preferably made of a material that does not react with sublimated molybdenum oxide. Furthermore, it is preferable to use a highly airtight firing furnace so that the sublimated molybdenum oxide can be efficiently reused.

[0041] (5) Molybdenum removal process The flux method for producing plate-like alumina particles may further include, after the firing step, a molybdenum removal step of removing at least a portion of the molybdenum, if necessary.

[0042] As mentioned above, molybdenum oxide sublimes during firing, so the molybdenum content contained in the plate-like alumina particles can be controlled by appropriately adjusting the firing time and firing temperature. However, molybdenum may adhere to the surface of the plate-like alumina particles. Molybdenum adhered to the surface of the plate-like alumina particles can be removed by washing with a cleaning solution such as water, an aqueous ammonia solution, an aqueous sodium hydroxide solution, or an acidic aqueous solution. The molybdenum content of the resulting plate-like alumina particles can be controlled by appropriately adjusting the concentration and amount of the cleaning solution used, the cleaning site, and the cleaning time. The plate-like alumina particles used in the examples described below were produced in accordance with the method described in International Publication No. 2020 / 021675.

[0043] [Boron nitride] Boron nitride (boron nitride particles) is usually scaly. While boron nitride has particularly good thermal conductivity in the orientation direction, it has low hardness (Mohs hardness 2). Therefore, when boron nitride is used alone as a thermally conductive filler, the mechanical strength of the resulting thermally conductive resin composition decreases. Furthermore, even if one attempts to knead only boron nitride into a thermoplastic resin, it is difficult to increase the loading amount. In contrast, the thermally conductive resin composition of this embodiment uses both plate-like alumina particles and boron nitride, thereby increasing the loading amount of boron nitride.

[0044] The average particle size of boron nitride (cumulative 50% particle size based on volume (D 50 )) is preferably 0.1 to 100 μm, and more preferably 1 to 80 μm. If the average particle size of boron nitride is less than 0.1 μm, it is likely to aggregate when kneaded into a thermoplastic resin, making kneading (filling) difficult and reducing the strength of the resulting molded body. On the other hand, if the average particle size of boron nitride is more than 100 μm, the thermal conductivity may decrease slightly due to a decrease in the contact surface and particle number. Furthermore, boron nitride may be more likely to be exposed, which may reduce the moldability and the surface condition of the resulting molded body.

[0045] (thermoplastic resin) The thermoplastic resin is a component used as the base resin of the thermally conductive resin composition of this embodiment. By using a thermoplastic resin as the base resin, it is possible to increase the affinity with thermally conductive fillers such as plate-like alumina particles and boron nitride by molding methods such as extrusion molding and injection molding, thereby improving thermal conductivity. In addition, it is possible to increase the fluidity during molding processing.

[0046] The type of thermoplastic resin is not particularly limited, and any common thermoplastic resin can be used. Among them, the thermoplastic resin is preferably at least one selected from the group consisting of polypropylene resin, polycarbonate resin, acrylonitrile-butadiene-styrene copolymer resin, polyester resin, polyamide resin, and polyphenylene sulfide resin.

[0047] (Other ingredients) The thermally conductive resin composition of this embodiment may further contain other components in addition to the plate-like alumina particles, boron nitride, and thermoplastic resin. Examples of other components include external lubricants, internal lubricants, antioxidants, flame retardants, light stabilizers, UV absorbers, reinforcing materials such as glass fiber and carbon fiber, fillers, and various colorants. The composition may also contain stress-reducing agents (stress relaxation agents) such as silicone oil, liquid rubber, rubber powder, butadiene copolymer rubbers such as methyl acrylate-butadiene-styrene copolymers and methyl methacrylate-butadiene-styrene copolymers, and silicone compounds.

[0048] (Thermal conductive resin composition) The content of the plate-like alumina particles in the thermally conductive resin composition is 15 to 25% by volume, preferably 20 to 25% by volume. If the content of the plate-like alumina particles is less than 15% by volume, the thermal conductivity will be insufficient. On the other hand, if the content of the plate-like alumina particles exceeds 25% by volume, the adhesive strength will be insufficient, for example, when the thermally conductive resin composition is used as a material for bonding substrates such as metals. This may result in significant warping of electronic components, cracking or peeling under thermal cycling, or peeling at the adhesive interface. Furthermore, the viscosity of the thermally conductive resin composition may increase excessively, which may lead to reduced applicability and workability.

[0049] The thermally conductive resin composition contains 5 to 15% by volume of boron nitride, preferably 10 to 15% by volume. If the content of boron nitride is less than 5% by volume, the thermal conductivity will be insufficient. On the other hand, if the content of boron nitride is more than 15% by volume, the mechanical strength such as bending elasticity will decrease.

[0050] It is also preferable to use thermally conductive fillers with different average particle sizes in combination. When thermally conductive fillers with different average particle sizes are used in combination, the thermally conductive fillers with smaller particle sizes fill the voids formed by the thermally conductive fillers with larger particle sizes, resulting in a more densely packed structure, which can further increase the thermal conductivity.

[0051] The thermally conductive resin composition of this embodiment can be obtained by further mixing other components, which are used as needed, in addition to the plate-like alumina particles, boron nitride, and thermoplastic resin. The mixing method is not particularly limited, and mixing can be performed by a known or commonly used method. As a filler other than the plate-like alumina particles and boron nitride, known or commonly used aluminas such as acicular, spherical, and polyhedral alumina can also be used in combination.

[0052] The thermally conductive resin composition of this embodiment can be used to produce molded articles that are excellent in mechanical strength, such as bending elasticity, and thermal conductivity. More specifically, the thermal conductivity of a test piece obtained by mold press molding the thermally conductive resin composition of this embodiment is preferably 2.0 W / (m·K) or more, and more preferably 2.2 W / (m·K) or more in the in-plane direction. Furthermore, the bending modulus of a test piece obtained by injection molding the thermally conductive resin composition of this embodiment, as measured by three-point bending, is preferably 300% or more, and more preferably 350% or more, based on the bending modulus of a test piece obtained by injection molding a thermoplastic resin alone (i.e., a base resin only that does not contain a thermally conductive filler).

[0053] The thermally conductive resin composition of the present embodiment is suitable as a material that is interposed between substrates to bond them and improve the thermal conductivity at the interface, i.e., a so-called thermal interface material (TIM). In addition, by molding the thermally conductive resin composition of the present embodiment into a desired shape, it can be used as a molded product such as a heat dissipation member.

[0054] <Molded body> One embodiment of the molded article of the present invention is obtained by molding the above-described thermally conductive resin composition. That is, by molding the above-described thermally conductive resin composition into a desired shape, it is possible to obtain the molded article of this embodiment, which is useful as a heat dissipation member or the like and has excellent mechanical strength such as bending elasticity and thermal conductivity. The shape of the molded article is not particularly limited, and can be formed according to the application. For example, it can be formed into various shapes such as a film, a sheet, or a fiber. The molded article of this embodiment can be produced by molding and processing the above-described thermally conductive resin composition according to a known and commonly used method. [Example]

[0055] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[0056] <Preparing ingredients> The following thermoplastic resins and thermally conductive fillers were prepared. Both plate-like alumina particles A and B were produced in accordance with the method described in International Publication No. 2020 / 021675. All thermally conductive fillers other than plate-like alumina particles A and B were commercially available.

[0057] (thermoplastic resin) PP (polypropylene resin, product name "Novatec PP" series, manufactured by Japan Polypropylene Corporation) ABS (acrylonitrile-butadiene-styrene copolymer resin, product name "Techno ABS" series, manufactured by Techno UMG) PC (polycarbonate resin, product name "Panlite" series, manufactured by Teijin) PET (polyethylene terephthalate resin, product name "Unitika Polyester" series, manufactured by Unitika Ltd.) PBT (polybutylene terephthalate resin, product name "NovaDuran" series, manufactured by Mitsubishi Chemical Corporation) PA (polyamide resin, product name "Trogamid" series, manufactured by Polypla-Evonik) PPS (polyphenylene sulfide resin, product name "MA-505", manufactured by DIC Corporation)

[0058] (thermal conductive filler) Boron nitride A Boron nitride B Boron nitride C Plate-shaped alumina particles A Plate-shaped alumina particles B Lumped alumina ·talc

[0059] <Measurement of physical properties of thermally conductive fillers> The physical properties of the prepared thermally conductive filler were measured according to the methods described below. The results are shown in Table 1.

[0060] (Average particle diameter (D 50 )) Using a laser diffraction particle size distribution analyzer (product name "HELOS (H3355) &RODOS", manufactured by Nippon Laser Co., Ltd., R3: 0.5 / 0.9-175 μm), the average particle diameter (volume-based cumulative 50% particle diameter (median diameter; D 50 The average particle diameter (volume-based cumulative 50% particle diameter (median diameter; D )) of the thermally conductive filler other than the tabular alumina particles was also measured. 50 )) was measured using a dry laser diffraction scattering particle size distribution measuring device (manufactured by Spectris).

[0061] (average thickness) The thickness of 50 randomly selected pieces of each of the plate-like alumina particles and the block alumina was measured using a scanning electron microscope (SEM), and the average value was taken as the average thickness.

[0062] (aspect ratio) The aspect ratio of the plate-like alumina particles was calculated using the following formula (1). The major and minor axes of 50 aggregated alumina particles were measured using a scanning electron microscope (SEM) to calculate the aspect ratio. The average value of the aspect ratios of the 50 aggregated alumina particles was then used as the aspect ratio of the aggregated alumina. Aspect ratio = average particle diameter (D 50 (μm)) / average thickness (μm) (1)

[0063] (Mo content) Approximately 70 mg of plate-like alumina particles were placed on filter paper, covered with PP film, and subjected to composition analysis using an X-ray fluorescence analyzer (product name "Primus IV", manufactured by Rigaku Corporation). From the amount of molybdenum (Mo) determined from the XRF analysis results, the amount of Mo (mass%) based on the entire plate-like alumina particles was calculated as a molybdenum trioxide equivalent value.

[0064] TIFF2025160656000001.tif57170

[0065] <Production of Thermally Conductive Resin Composition> Example 1 A mixture was obtained by mixing 75 parts by volume of polypropylene resin, 15 parts by volume of plate-like alumina particles A, and 10 parts by volume of boron nitride A. The resulting mixture was melt-kneaded at 190°C for 3 minutes using a lab kneader (trade name "Labo Plastomill 10M100 type", manufactured by Toyo Seiki Seisakusho, Ltd.) to produce a thermally conductive resin composition.

[0066] (Examples 2 to 16, Comparative Examples 1 to 11) Thermally conductive resin compositions were produced in the same manner as in Example 1 above, except that the formulations shown in Tables 2-1 to 2-3 were used and the temperature during melt-kneading was appropriately adjusted depending on the type of thermoplastic resin used.

[0067] (Reference examples A~E) Reference Examples A to E were a simple thermoplastic resin containing no thermally conductive filler and a mixture of two types of thermoplastic resins.

[0068] <Preparation of molded body (test piece)> (Preparation of test specimens for measuring thermal conductivity) Using a compression molding machine equipped with a mold measuring 20 mm in length, 20 mm in width, and 6 mm in height, each of the produced thermally conductive resin compositions was compression molded (mold press molding) under appropriate temperature conditions to prepare test pieces for measuring thermal conductivity. The compression molding machine used was an "SFA Type Single-Action Compression Molding Machine" (manufactured by Shinto Metal Industries Co., Ltd.). Note that the thermally conductive resin composition of Comparative Example 5 could not be molded.

[0069] (Preparation of test specimens for measuring flexural modulus) Using an injection molding machine equipped with a mold for tensile test pieces based on ISO-527-2-5A, each of the produced thermally conductive resin compositions was injection molded under appropriate temperature conditions to prepare test pieces for measuring flexural modulus. The injection molding machine used was a "Minijet Pro" (manufactured by ThermoFisher Scientific). It should be noted that the thermally conductive resin composition of Comparative Example 5 could not be molded.

[0070] <Evaluation> (Measurement of thermal conductivity) The thermal conductivity (in all directions and in the plane direction) of the prepared test pieces was measured using a thermal property measuring device (product name "TPS-2500S", manufactured by Kyoto Electronics Manufacturing Co., Ltd.) The results are shown in Tables 2-1 to 2-3.

[0071] (Measurement of flexural modulus) A three-point bending test was performed using a mechanical property measuring device (product name "Precision Universal Testing Machine Autograph AG-XD plus", manufactured by Shimadzu Corporation) with a support span of 40 mm and a test speed of 2 mm / min to measure the flexural modulus of the prepared test specimens. Furthermore, from the measured flexural modulus values, the rate of change (%) of flexural modulus was calculated based on the flexural modulus of the test specimen obtained by injection molding the resin alone. The results are shown in Tables 2-1 to 2-3.

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[0073] TIFF2025160656000003.tif179170

[0074] TIFF2025160656000004.tif177170 [Industrial Applicability]

[0075] The thermally conductive resin composition of the present invention is suitable as a material that is interposed between substrates to bond them and improve the thermal conductivity at the interface, i.e., a so-called thermal interface material (TIM), and is also useful as a material for constructing various molded articles such as heat dissipation members that are required to have high thermal conductivity.

Claims

1. The composite material comprises a thermally conductive filler containing molybdenum-containing plate-like alumina particles and boron nitride, and a thermoplastic resin; the plate-like alumina particles have an average particle size of 1 to 50 μm, an average thickness of 0.01 to 5 μm, and an aspect ratio, which is the ratio of the average particle size to the average thickness, of 2 to 100; The average particle size of the boron nitride is 0.1 to 100 μm, The content of the plate-like alumina particles is 15 to 25% by volume, The thermally conductive resin composition has a boron nitride content of 5 to 15% by volume.

2. The thermoplastic resin is at least one selected from the group consisting of polypropylene resin, polycarbonate resin, acrylonitrile-butadiene-styrene copolymer resin, polyester resin, polyamide resin, and polyphenylene sulfide resin. The thermally conductive resin composition according to claim 1.

3. a test piece obtained by mold press molding the thermally conductive resin composition has a thermal conductivity in the plane direction of 2.0 W / (m K) or more; 2. The thermally conductive resin composition according to claim 1, wherein a test piece obtained by injection molding the thermally conductive resin composition has a flexural modulus in three-point bending of 300% or more based on the flexural modulus in three-point bending of a test piece obtained by injection molding the thermoplastic resin alone.

4. A molded article obtained by molding the thermally conductive resin composition according to any one of claims 1 to 3.

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