Thermally conductive composition and method for manufacturing a thermally conductive member using said composition

Abstract

To provide a thermally conductive composition capable of preventing battery cells from being broken when exposed to extremely high temperatures by reducing the cohesive force of a thermally conductive member itself.SOLUTION: A thermally conductive composition contains: a component (A) that is a diorganopolysiloxane having an alkenyl group bonded to a silicon atom; a component (B) that is a diorganopolysiloxane having a hydrogen atom bonded to a silicon atom; a component (C) that is expandable graphite; a component (D) that is a thermally conductive filler; and a component (E) that is an addition reaction catalyst, wherein a content of the component (C) is 0.5 pts.mass or more and 5 pts.mass or less relative to 100 pts.mass of a total amount of the components (A) and (B), a content of the component (D) is 300 pts.mass or more and 2,000 pts.mass or less relative to 100 pts.mass of the total amount of the components (A) and (B), and the thermally conductive composition is applied in a liquid state to a substrate before curing.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a curable thermally conductive silicone composition containing a thermally conductive filler and expandable graphite, and a method for producing a thermally conductive member using said composition. [Background technology]

[0002] As electronic components become smaller, more powerful, and more powerful, the amount of heat energy released increases, causing temperatures in the electronic components to rise. Furthermore, with the recent spread of environmentally friendly electric vehicles, the development of high-performance batteries is progressing. Against this background, many heat-dissipating silicone products have been developed to transfer heat generated by heat-generating elements such as electronic components and batteries to heat sinks and other heat-dissipating components.

[0003] Heat-dissipating silicone products include those provided in sheet form, such as heat-dissipating sheets, and those provided in liquid form, such as gap fillers. The heat dissipation sheet is a flexible, highly thermally conductive silicone rubber sheet made by curing a thermally conductive silicone composition into a sheet. As a result, it is easy to install and has the advantage of adhering closely to the surface of components, enhancing heat dissipation. Gap fillers, on the other hand, are obtained by applying a liquid or paste-like thermally conductive silicone composition directly to a heat-generating or heat-dissipating body and then curing it after application. This has the advantage that they can fill gaps even when applied to complex, uneven shapes, and provide a high heat dissipation effect.

[0004] In light of this, many compositions have been developed for forming heat dissipation sheets and gap fillers that have improved adhesion to battery cells or modules. For example, Patent Document 1 discloses a thermally conductive silicone adhesive composition that provides good adhesion to organic resins. US Pat. No. 5,649,493 describes a gap filler that hardens rapidly. US Pat. No. 5,629,999 describes a thermally conductive polyurethane adhesive with an excellent combination of mechanical properties. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-224189 [Patent Document 2] Special Publication No. 2021-523965 [Patent Document 3] Special Publication No. 2021-507067 Summary of the Invention [Problem to be solved by the invention]

[0006] The compositions described in the above documents all harden strongly, so they cannot be expected to accommodate expansion of battery cells at abnormally high temperatures, which can cause deformation and destruction of the battery cells. In the event of abnormally high temperatures or fire, the battery cell may expand due to heat generation. However, even in the event of such expansion, the battery cell may be made of a flexible material such as PET film, which provides elasticity against thermal expansion.

[0007] However, if the adhesive strength between the thermally conductive material, such as a heat dissipation sheet or gap filler, and the skin is too strong, it may not be able to keep up with the expansion and contraction of the skin due to the expansion of the battery cell, potentially destroying the cell's skin. Furthermore, if the adhesive strength of the thermally conductive material is too strong, when a battery cell that has been exposed to abnormally high temperatures undergoes some kind of impact, the battery cell or skin may be destroyed in the same way. If the battery cell is destroyed, the liquid inside the battery may leak, causing the battery cell to explode, which could have a significant impact on the safety of users and others.

[0008] In light of the above background, an object of the present invention is to provide a thermally conductive member that has good adhesion and bonding properties to substrates such as heat generating bodies and heat dissipating bodies, has high thermal conductivity, and therefore has excellent heat dissipation properties, and that is capable of reducing deformation of the substrate at abnormally high temperatures by reducing its adhesion to the substrate. [Means for solving the problem]

[0009] The present inventors discovered that the problems of the present invention can be solved by blending a thermally conductive filler and expandable graphite in a silicone composition containing an organopolysiloxane, and thus completed the present invention.

[0010] The thermally conductive composition according to the present invention comprises: (A) a diorganopolysiloxane having alkenyl groups bonded to silicon atoms; (B) a diorganopolysiloxane having hydrogen atoms bonded to silicon atoms; (C) Expanded graphite; (D) a thermally conductive filler; (E) an addition catalyst; the content of the (C) component is 0.5 parts by mass or more and 5 parts by mass or less when the total amount of the (A) component and the (B) component is 100 parts by mass; The content of the component (D) is 300 parts by mass or more and 2,000 parts by mass or less when the total amount of the components (A) and (B) is 100 parts by mass.

[0011] The thermally conductive composition of the present invention (hereinafter also simply referred to as the composition) may be any composition for forming a thermally conductive member, and examples of the thermally conductive member include a heat dissipation sheet and a gap filler. In the case of a heat dissipation sheet, the thermally conductive composition is cured into a sheet to form a heat dissipation sheet, which is then used by being closely attached to a heat generating body (substrate) such as a battery cell or module. In the case of a gap filler, the thermally conductive composition is applied to a substrate in a liquid state, and after application to the substrate, the thermally conductive composition is cured by a crosslinking reaction to obtain the gap filler.

[0012] Here, the thermally conductive member and the substrate exhibit high adhesion due to interactions such as hydrogen bonding between the alkenyl groups and SiOH groups contained in the thermally conductive composition and the carbonyl groups and OH groups on the surface of the substrate. The thermally conductive composition contains 300 parts by mass or more of the thermally conductive filler (D) when the total amount of the components (A) and (B) is taken as 100 parts by mass. Therefore, the thermal conductivity of the thermally conductive member is sufficiently high, and the high thermal conductivity and adhesion result in high heat dissipation properties.

[0013] Furthermore, when the total amount of components (A) and (B) is taken as 100 parts by mass, the content of the expanded graphite (component (C)) is in the low content range of 0.5 parts by mass to 5 parts by mass. This allows the resulting thermally conductive material to have high insulating properties and be useful as a thermally conductive material for electronic components. Furthermore, by adjusting the amount of expanded graphite to fall within this range, the mixed viscosity of the thermally conductive composition (the viscosity when all components of the thermally conductive composition are mixed) can be maintained low, allowing the thermally conductive composition to be injected into even minute voids. This makes the thermally conductive composition particularly useful as a thermally conductive gap filler composition for forming gap fillers. This also allows for the production of gap fillers with high adhesion to substrates and good thermal conductivity.

[0014] When the thermally conductive material is exposed to high temperatures after curing (for example, when it is left at temperatures of 250°C or higher for one hour or more), the heat causes the intercalation materials such as sulfuric acid inserted between the layers of the expanded graphite (component (C)) to decompose and gasify, and the pressure of the gasification causes each layer to expand vertically, simultaneously causing cohesive failure of the thermally conductive material itself or severing the hydrogen bonds between the substrate and gap filler. Before exposure to high temperatures, the expanded graphite had a small specific surface area and was resistant to cohesive failure, which resulted in high adhesion of the thermally conductive member to the substrate. However, after exposure to high temperatures, cohesive failure occurs, reducing the cohesive strength of the thermally conductive member itself and the adhesion between the thermally conductive member and the substrate. This phenomenon causes the thermally conductive member, which had been in close contact with the substrate, to peel off from the surface of the substrate. The above mechanism makes it possible to reduce damage or deformation of the skin or battery cell caused by adhesion of the thermally conductive member, even when the battery cell expands due to high temperatures or the skin of the battery cell expands or contracts.

[0015] Here, the amount of expandable graphite is low, ranging from 0.5 parts by mass to 5 parts by mass, so the volume expansion of the thermal conductive material itself is small. Furthermore, since the cured thermal conductive material has a cross-linked structure and is highly acid-resistant, deterioration of the thermal conductive material itself is limited even when gaseous acid is generated at high temperatures. Therefore, even at high temperatures, there is little risk of damage to the battery cell or the surface due to deformation of the thermal conductive material. Furthermore, even after high temperature exposure, if the thermal conductive material is physically pressed against the substrate, it can still exhibit heat dissipation properties, although the effect is less than that achieved by adhesion through hydrogen bonding. [Effects of the Invention]

[0016] The thermally conductive composition according to the present invention provides a thermally conductive member that has good adhesion to a substrate before exposure to high temperatures and that is easily peeled from the substrate after exposure to high temperatures. Therefore, the thermally conductive composition is useful as a gap filler or a heat dissipation sheet that can prevent damage to a battery cell or its surface due to adhesion of the gap filler to the battery cell or its surface. DETAILED DESCRIPTION OF THE INVENTION

[0017] The thermally conductive composition, the method for producing the composition, and the method for producing a thermally conductive member using the composition according to the present invention will be described in detail below. In this specification, the thermally conductive filler is also simply referred to as a filler or a packing material.

[0018] The thermally conductive composition according to the present invention (A) a diorganopolysiloxane having alkenyl groups bonded to silicon atoms; (B) a diorganopolysiloxane having hydrogen atoms bonded to silicon atoms; (C) Expanded graphite; (D) a thermally conductive filler; (E) an addition catalyst; the content of the (C) component is 0.5 parts by mass or more and 5 parts by mass or less when the total amount of the (A) component and the (B) component is 100 parts by mass; When the total amount of components (A) and (B) is taken as 100 parts by mass, the amount of component (D) is 300 parts by mass or more and 2,000 parts by mass or less.

[0019] By blending (C) expandable graphite with a composition containing the above components (A), (B), (D), and (E), it is possible to impart to the thermally conductive member obtained after curing the composition the property of maintaining high adhesion to the substrate before exposure to high temperatures, while allowing the thermally conductive member to be easily peeled from the substrate after exposure to high temperatures.

[0020] The thermally conductive composition of the present invention may be any composition for forming a thermally conductive member, and examples of the thermally conductive member include a heat dissipation sheet and a gap filler. The thermally conductive composition of the present invention may be a thermally conductive gap filler composition that is applied to a substrate in a liquid state before curing, and then cured after application to obtain a gap filler.

[0021] (Component (A)) Component (A) is the base component of the thermally conductive composition and is a diorganopolysiloxane having alkenyl groups bonded to silicon atoms. The viscosity and degree of polymerization of component (A) are not particularly limited and can be selected depending on the required mixed viscosity of the thermally conductive composition, for example, the viscosity at 25°C may be 10 mPa·s or more and 1,000,000 mPa·s or less. The diorganopolysiloxane can be used alone or in appropriate combination of two or more. This is the main component of the thermally conductive composition and has an average of at least 1, preferably 2 to 50, and more preferably 2 to 20 alkenyl groups bonded to silicon atoms per molecule.

[0022] The molecular structure of component (A) is not particularly limited and may be, for example, a linear structure, a linear structure with some branching, a branched structure, a cyclic structure, or a cyclic structure with branching. Of these, component (A) is preferably a substantially linear organopolysiloxane, and specifically may be a linear diorganopolysiloxane whose molecular chain is primarily composed of repeating diorganosiloxane units and whose molecular chain ends are capped with triorganosiloxy groups. Some or all of the molecular chain ends, or some of the side chains, may be Si-OH groups.

[0023] The position of the alkenyl group bonded to the silicon atom in component (A) is not particularly limited, and component (A) may be a diorganopolysiloxane having an alkenyl group bonded to a silicon atom at both molecular chain terminals. Organopolysiloxanes having one alkenyl group at each molecular chain terminal have fewer alkenyl groups that serve as reaction sites for crosslinking reactions, which has the advantage of increasing the flexibility of the gap filler obtained after curing and further improving adhesion to the substrate.

[0024] The alkenyl group may be bonded to either a silicon atom at a molecular chain terminal or a silicon atom at a non-terminal position (in the middle of the molecular chain), or to both. Furthermore, the component (A) may be a polymer made up of a single siloxane unit, or a copolymer made up of two or more types of siloxane units.

[0025] The viscosity of component (A) at 25°C is from 10 mPa·s to 1,000,000 mPa·s, preferably from 20 mPa·s to 100,000 mPa·s, and more preferably from 30 mPa·s to 2,000 mPa·s.

[0026] The components to be blended into the thermally conductive composition can be stored separately as two or more liquid compositions, and then mixed at the time of use to obtain the thermally conductive composition. In this case, the components can be separated into a first liquid composition containing components (A), (C), (D), and (E), and a second liquid composition containing components (A), (B), (C), and (D). The viscosity range described above can prevent components (C) and (D) from settling in the resulting liquid composition due to an excessively low viscosity of component (A). This allows for the production of a thermally conductive composition with excellent long-term storage stability. Furthermore, the viscosity range described above provides the resulting thermally conductive composition with adequate fluidity, resulting in high dischargeability and increased productivity.

[0027] In order to adjust the viscosity (mixed viscosity) of the thermally conductive composition obtained by mixing the liquid compositions before curing, two or more types of alkenyl group-containing diorganopolysiloxanes with different viscosities can also be used. To achieve both long-term storage stability and appropriate fluidity, it is more preferable that the composition does not contain diorganopolysiloxanes with a viscosity of 100,000 mPa·s or more at 25°C, and it is even more preferable that the composition does not contain diorganopolysiloxanes with a viscosity of 10,000 mPa·s or more.

[0028] The mixed viscosity of the thermally conductive composition before curing, as measured with a rotational viscometer at a temperature of 25°C and a shear rate of 10 / s, may be in the range of 10 to 1,000 Pa·s, more preferably in the range of 20 to 500 Pa·s, and even more preferably in the range of 30 to 300 Pa·s. If the viscosity is within the above range, the workability when applying the thermally conductive composition to a substrate is good. In order to ensure that the mixed viscosity falls within the above range, the viscosity of each of component (A) and component (B) at 25°C may be set to, for example, 10 mPa·s or more and 2,000 mPa·s or less.

[0029] The thermally conductive member obtained by curing the thermally conductive composition may be in any shape, such as a sheet, liquid, block, or cylinder, but is preferably in a sheet or liquid form. When the thermally conductive member is a gap filler, the liquid thermally conductive composition having a mixed viscosity within the above range can be applied to a substrate by being extruded from a container such as a cartridge, ribbon, dispenser, syringe, or tube, resulting in good workability. It is preferable to apply the composition to a substrate using a dispenser equipped with an L-shaped nozzle / needle or the like. Here, the substrate refers to a heat-dissipating part or a heat-generating part. The silicone composition may be applied to the heat-dissipating part and then the heat-generating part is arranged so as to sandwich the silicone composition, or the silicone composition may be applied to the heat-generating part and then the heat-dissipating part is arranged so as to sandwich the silicone composition, or the silicone composition may be poured into the gap between the heat-generating part and the heat-dissipating part. The thermally conductive composition can also be cured into a sheet having a thickness of 0.01 to 50 mm, preferably 0.1 to 5 mm, to obtain a heat dissipation sheet. The sheet-like form includes not only a sheet consisting of a single sheet, but also a layer formed by laminating it on another member, or a thin film formed by coating it on another member by application or the like. The heat dissipation sheet, which is a thermally conductive member formed into a sheet, may be placed on the surface of a battery cell by, for example, adhering it.

[0030] Specifically, the average composition formula of component (A) is represented by the following general formula (1). R 1 a SiO (4-a) / 2 (1) (However, in formula (1), R 1 are the same or different, unsubstituted or substituted monovalent hydrocarbon groups having 1 to 18 carbon atoms. a is 1.7 to 2.1. Furthermore, a is preferably 1.8 to 2.5, more preferably 1.95 to 2.05, and this organopolysiloxane is substantially linear, but may be branched to the extent that the properties of the thermally conductive member after curing are not impaired.

[0031] In one embodiment, the R 1At least two of the monovalent hydrocarbon groups represented by the formula (I) are selected from alkenyl groups such as vinyl, allyl, propenyl, isopropenyl, butenyl, isobutenyl, hexenyl, and cyclohexenyl, and the remaining groups are substituted or unsubstituted monovalent hydrocarbon groups having 1 to 18 carbon atoms, specifically alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, 2-ethylhexyl, heptyl, octyl, nonyl, decyl, and dodecyl; It is selected from cycloalkyl groups such as cyclopentyl, cyclohexyl, and cycloheptyl; aryl groups such as phenyl, tolyl, xylyl, biphenyl, and naphthyl; aralkyl groups such as benzyl, phenylethyl, phenylpropyl, and methylbenzyl; and halogen-substituted or cyano-substituted alkyl groups in which some or all of the hydrogen atoms in these hydrocarbon groups have been substituted with halogen atoms, cyano groups, or the like, such as chloromethyl, 2-bromoethyl, 3,3,3-trifluoropropyl, 3-chloropropyl, and cyanoethyl.

[0032] R 1 In selecting R, the alkenyl group required to be two or more is preferably a vinyl group, and other groups are preferably a methyl group, a phenyl group, or a 3,3,3-trifluoropropyl group. 1 It is preferable that 70 mol % or more of the copolymer contains methyl groups in terms of the physical properties of the cured product and economic efficiency, and generally, copolymers containing 80 mol % or more of methyl groups are used.

[0033] The molecular structure of component (A) is as follows: dimethylpolysiloxane terminated at both molecular chain ends with dimethylvinylsiloxy groups; dimethylsiloxane-methylphenylsiloxane copolymer terminated at both molecular chain ends with dimethylvinylsiloxy groups; dimethylsiloxane-methylvinylsiloxane copolymer terminated at both molecular chain ends with dimethylvinylsiloxy groups; dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymer terminated at both molecular chain ends with dimethylvinylsiloxy groups; dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymer terminated at both molecular chain ends with trimethylsiloxy groups; formula: (CH3)2ViSiO 1 / 2 Siloxane units represented by the formula: (CH3)3SiO 1 / 2 Siloxane units represented by the formula: SiO 4 / 2 (where Vi represents a vinyl group), organopolysiloxanes in which some or all of the methyl groups of these organopolysiloxanes have been substituted with alkyl groups such as ethyl groups, propyl groups, etc.; aryl groups such as phenyl groups, tolyl groups, etc.; or halogenated alkyl groups such as 3,3,3-trifluoropropyl groups, and mixtures of two or more of these organopolysiloxanes. However, from the viewpoint of increasing the elongation at break of the cured product by increasing the molecular chain length, linear diorganopolysiloxanes having vinyl groups at both molecular chain terminals are preferred.

[0034] These diorganopolysiloxanes may be commercially available products, or may be produced by methods known to those skilled in the art.

[0035] In the thermally conductive composition of the present invention, when the total amount of component (A) and component (B) is taken as 100 parts by mass, the content of the organopolysiloxane of component (A) is preferably from 2 to 90 parts by mass, and more preferably from 10 to 80 parts by mass. Within this range, the viscosity of the thermally conductive composition as a whole becomes appropriate, the composition has excellent long-term storage stability, is able to suppress outflow after application to a substrate, and has appropriate fluidity, making it possible to maintain high thermal conductivity in the resulting thermally conductive member.

[0036] (Component (B)) Component (B) is a diorganopolysiloxane having hydrogen atoms bonded to silicon atoms. The viscosity and degree of polymerization of component (B) are not particularly limited and can be selected depending on the required mixed viscosity of the thermally conductive composition, etc. For example, the viscosity at 25°C may be 10 mPa·s or more and 1,000,000 mPa·s or less. Component (B) is a diorganopolysiloxane containing one or more hydrogen atoms bonded to silicon atoms in each molecule, and is a component that functions as a crosslinking agent for curing the thermally conductive composition of the present invention. The number of hydrogen atoms bonded to silicon atoms is not particularly limited as long as it is at least 1, and may be 2 to 4. The linear component (B) may have one hydrogen atom bonded to a silicon atom at each end, and the number of hydrogen atoms bonded to silicon atoms in the molecule may be 2.

[0037] Component (B) may be any organohydrogenpolysiloxane containing one or more hydrogen atoms bonded to silicon atoms (SiH groups) per molecule, such as methylhydrogenpolysiloxane, dimethylsiloxane-methylhydrogensiloxane copolymer, methylphenylsiloxane-methylhydrogensiloxane copolymer, cyclic methylhydrogenpolysiloxane, and copolymers containing dimethylhydrogensiloxy units and SiO 4 / 2 The component (B) may be a copolymer of one type alone or a combination of two or more types.

[0038] The molecular structure of component (B) is not particularly limited and may be, for example, a linear, branched, cyclic, or three-dimensional network structure. Specifically, the structure represented by the following average composition formula (2) can be used. R 3 p H q SiO (4-p-q) / 2 (2) (In the formula, R 3is an unsubstituted or substituted monovalent hydrocarbon group excluding aliphatic unsaturated hydrocarbon groups. p is a positive number that satisfies the range of 0 to 3.0, preferably 0.7 to 2.1, q is a positive number that satisfies the range of 0.0001 to 3.0, preferably 0.001 to 1.0, and p+q is a positive number that satisfies the range of 0.5 to 3.0, preferably 0.8 to 3.0.

[0039] R in equation (2) 3 Examples of the alkyl group include unsubstituted or halogen-substituted monovalent hydrocarbon groups typically having 1 to 10 carbon atoms, preferably about 1 to 8 carbon atoms, excluding aliphatic unsaturated bonds, such as alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl, tert-butyl, and cyclohexyl; aryl groups such as phenyl, tolyl, and xylyl; aralkyl groups such as benzyl and phenethyl; and halogenated alkyl groups such as 3-chloropropyl and 3,3,3-trifluoropropyl. Preferred are methyl, ethyl, propyl, phenyl, and 3,3,3-trifluoropropyl, and particularly preferred is methyl.

[0040] Specific examples of component (B) include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane-dimethylsiloxane cyclic copolymer, tris(dimethylhydrogensiloxy)methylsilane, tris(dimethylhydrogensiloxy)phenylsilane, dimethylsiloxane-methylhydrogensiloxane copolymer terminated at both molecular chain ends with dimethylhydrogensiloxy groups, methylhydrogenpolysiloxane terminated at both molecular chain ends with dimethylhydrogensiloxy groups, and trimethylsiloxane terminated at both molecular chain ends. Siloxy-capped methylhydrogenpolysiloxane, dimethylpolysiloxane capped at both molecular chain ends with dimethylhydrogensiloxy groups, dimethylsiloxane-diphenylsiloxane copolymer capped at both molecular chain ends with dimethylhydrogensiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymer capped at both molecular chain ends with trimethylsiloxy groups, dimethylsiloxane-diphenylsiloxane-methylhydrogensiloxane copolymer capped at both molecular chain ends with trimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymer capped at both molecular chain ends with dimethylhydrogensiloxy groups, H(CH3)2SiO 1 / 2 Copolymer of SiO2 units and H(CH3)2SiO 1 / 2 Units and (CH3)3SiO 1 / 2 Examples include copolymers of SiO2 units and SiO2 units, and mixtures of two or more of these organohydrogensiloxanes.

[0041] The content of component (B) in the composition is preferably in a range such that the ratio of the number of SiH groups in component (B) to the number of alkenyl groups in component (A) is 1 / 5 to 7, more preferably 1 / 2 to 2, and even more preferably 3 / 4 to 5 / 4. Within the above ranges, the thermally conductive composition cures sufficiently, and the hardness of the entire thermally conductive composition falls within a more suitable range, making it less susceptible to cracking when used as a thermally conductive member such as a gap filler or heat dissipation sheet. Furthermore, when the thermally conductive member is a gap filler, the thermally conductive composition can maintain its vertical position even when the substrate is arranged vertically.

[0042] The SiH groups in component (B) may be located at the molecular chain terminals, in side chains, or both at the molecular chain terminals and in side chains. An organohydrogenpolysiloxane having SiH groups only at the molecular chain terminals and an organohydrogenpolysiloxane having SiH groups only in the molecular chain side chains may be mixed and used.

[0043] Component (B) may be a diorganopolysiloxane having hydrogen atoms bonded to silicon atoms only at both ends of the molecular chain. Organopolysiloxanes having one SiH group at each end of the molecular chain have the advantage of having a low SiH group content, which increases the flexibility of the thermally conductive member obtained after curing and further improves adhesion to the substrate. Organohydrogenpolysiloxanes having SiH groups only at the molecular chain terminals have the advantage of being highly reactive due to less steric hindrance, while organohydrogenpolysiloxanes having SiH groups in the side chains have the advantage of improving strength by contributing to network construction through crosslinking reactions.To impart flexibility to the thermally conductive member after curing, it is preferable to use organohydrogenpolysiloxanes having SiH groups only at the molecular chain terminals.

[0044] From the viewpoint of improving adhesiveness and heat resistance, component (B) is an organohydrogenpolysiloxane having trimethylsiloxy groups at both ends of the molecular chain and may also contain an organohydrogenpolysiloxane containing at least one aromatic group per molecule. For economic reasons, the aromatic group is preferably a phenyl group.

[0045] The viscosity of the organohydrogenpolysiloxane of component (B) at 25°C is from 10 mPa·s to 1,000,000 mPa·s, preferably from 20 mPa·s to 100,000 mPa·s, and more preferably from 30 mPa·s to 2,000 mPa·s. To adjust the viscosity of the final thermally conductive composition, two or more hydrogen-containing diorganopolysiloxanes with different viscosities can be used. The mixed viscosity of the gap filler composition may be in the range of 10 to 1,000 Pa·s, more preferably 20 to 500 Pa·s, and even more preferably 30 to 250 Pa·s.

[0046] In the thermally conductive composition of the present invention, when the total amount of components (A) and (B) is taken as 100 parts by mass, the content of the organohydrogenpolysiloxane of component (B) is preferably from 10 to 98 parts by mass, and more preferably from 20 to 90 parts by mass. Within this range, the hardness of the thermally conductive composition after curing will be in an appropriate range, and the thermally conductive member after curing will have flexibility and robustness.

[0047] (Component (C)) The expanded graphite of component (C) is added to make the thermally conductive member more likely to peel off from the substrate when exposed to high temperatures. The (C) expandable graphite is not particularly limited, and known expandable graphite can be used as appropriate. Here, the expandable graphite may be any graphite that expands when heated, and graphite (e.g., natural flaky graphite, pyrolytic graphite, kish graphite, etc.) with a compound inserted between its layers can be suitably used. Examples of compounds inserted between the graphite layers include acids such as sulfuric acid and nitric acid, mixtures of these acids, nitrates, potassium dichromate, potassium chlorate, potassium permanganate, ammonium peroxodisulfate, sodium peroxodisulfate, hydrogen peroxide, and potassium permanganate. As such expanded graphite, commercially available products can be used as appropriate, such as the EXP-50 series and EXP-80 series manufactured by Fuji Graphite Industries Co., Ltd.; the 953240 series, 9550 series, and 9510 series manufactured by Ito Graphite Industries Co., Ltd.; the 5099SS-3 and 60CA-60 manufactured by Coal Chemical Co., Ltd.; and the SMF, EMF, SFF, and SS manufactured by Chuetsu Graphite Industries Co., Ltd.

[0048] The expansion start temperature at which (C) expandable graphite expands is typically preferably 100 to 300°C, and more preferably 150 to 300°C. The expansion start temperature can be controlled by, for example, the type of intercalated compound. If the expansion start temperature is within the above range, the expansion of the expandable graphite begins when abnormal heat generation occurs in the battery, and the thermally conductive member quickly peels off from the substrate, thereby reducing damage and deformation of the battery cell and skin. Furthermore, even if the battery temperature rises to a certain extent, if there is no abnormal heat generation (for example, if the temperature is below 100°C), expansion does not begin, thereby preventing the thermally conductive member from peeling off from the substrate during normal heat generation, thereby reducing the heat dissipation characteristics.

[0049] (C) Expandable graphite expands while generating a gaseous inorganic acid at a temperature of 100° C. or higher and 300° C. or lower. The inorganic acid may be one or more selected from the group consisting of sulfuric acid, nitric acid, and hydrochloric acid.

[0050] The expansion ratio of the (C) expandable graphite is preferably 100 to 300 cc / g, more preferably 150 to 250 cc / g. The expansion ratio (volume after high-temperature exposure / volume before high-temperature exposure) of the thermally conductive member obtained by curing the thermally conductive composition containing the (C) expandable graphite in the above-mentioned amount range may be 1.1 or less. If the expansion ratio is within the above-mentioned range, the thermally conductive member maintains its property of easy peeling from the substrate after high-temperature exposure while experiencing relatively little volumetric expansion, thereby reducing damage to the battery cell caused by the volumetric expansion of the thermally conductive member. Furthermore, even after peeling, although a decrease in heat dissipation properties due to a decrease in adhesion is observed, the thermal insulation properties of the thermally conductive member itself are small compared to when the expansion ratio is high, and it is possible to maintain a certain degree of heat dissipation properties by physically pressing the thermally conductive member against the substrate.

[0051] The amount of (C) expandable graphite is in the range of 0.5 to 5 parts by mass, where the total amount of component (A) and component (B) is 100 parts by mass. A range of 0.5 to 3 parts by mass is more preferable, and a range of 0.5 to 2 parts by mass is even more preferable. Within this range, the mixed viscosity of the thermally conductive composition can be maintained low. Particularly when the thermally conductive member is a gap filler, this has the advantage of allowing the thermally conductive composition to be injected into minute voids and providing excellent crushability. Furthermore, the hardness of the cured thermally conductive member can be maintained low, resulting in excellent displacement tracking ability during high-temperature exposure. Furthermore, the expansion ratio of the thermally conductive member after high-temperature exposure (volume after high-temperature exposure / volume before high-temperature exposure) can be maintained at 1.1 or less.

[0052] If the amount of expanded graphite is reduced, the expansion ratio of the thermally conductive member after exposure to high temperatures can be further reduced, and damage to the substrate and the like can be reduced, which is preferable. Further reducing the amount of expanded graphite to, for example, 2 parts by mass or less when the total amount of component (A) and component (B) is 100 parts by mass, makes it possible to further reduce the mixed viscosity, for example, to 95 Pa s or less at 25°C, which is more preferable. Furthermore, expanded graphite has a predetermined volume resistivity, and by limiting the blending amount within the above range, it is possible to obtain a thermally conductive member with high insulating properties.

[0053] The volume resistivity of the thermally conductive composition is not particularly limited and can be appropriately selected depending on the application and shape of the thermally conductive member. When a gap filler or a heat dissipation sheet is used in an electronic component, high insulation is preferred. For example, the thermally conductive composition has a volume resistivity of 1×10 before curing. 6 It is preferable that the resistivity is Ω·cm or more.

[0054] (Component (D)) The thermally conductive filler (D) is a filler component that improves the thermal conductivity and shape retention of the thermally conductive composition. Component (D) can be a thermally conductive filler containing at least one selected from the group consisting of metals, oxides, hydroxides, and nitrides. In order to obtain a thermally conductive member with high insulating properties suitable for use in electronic substrates and the like, it is preferable to use an inorganic material that has excellent not only thermal conductivity but also insulating properties as the thermally conductive filler of component (D).

[0055] The shape of component (D) is not particularly limited, and it may be spherical, amorphous, or fibrous. Examples of thermally conductive fillers include metal oxides such as aluminum oxide, zinc oxide, magnesium oxide, titanium oxide, silicon oxide, and beryllium oxide; metal hydroxides such as aluminum hydroxide and magnesium hydroxide; nitrides such as aluminum nitride, silicon nitride, and boron nitride; carbides such as boron carbide, titanium carbide, and silicon carbide; graphite and other graphite; metals such as aluminum, copper, nickel, and silver, and mixtures thereof.

[0056] In particular, when the thermally conductive member needs to have electrical insulation properties, it may be possible to select a non-conductive thermally conductive filler. It is preferably a metal oxide, metal hydroxide, nitride, or a mixture thereof, and may be an amphoteric hydroxide or amphoteric oxide. Specifically, it is preferable to use one or more selected from the group consisting of aluminum hydroxide, boron nitride, aluminum nitride, zinc oxide, aluminum oxide, magnesium oxide, and magnesium hydroxide, and it is more preferable to contain at least one selected from aluminum hydroxide and aluminum oxide. Aluminum oxide is an insulating material, has relatively good compatibility with components (A) and (B), is available in a wide industrial range of particle sizes, is readily available as a resource, and is available at a relatively low cost, making it suitable as a thermally conductive inorganic filler.

[0057] When aluminum oxide is used as component (D), it is preferable to use spherical or amorphous aluminum oxide. Spherical aluminum oxide is mainly α-alumina obtained by high-temperature spraying or by hydrothermal treatment of alumina hydrate. Here, "spherical" refers not only to a perfect sphere but also to a rounded shape.

[0058] The average particle size of component (D) is not particularly limited and may be, for example, in the range of 0.1 μm to 500 μm, more preferably 0.5 μm to 200 μm, and even more preferably 1.0 μm to 100 μm. If the average particle size is too small, the fluidity of the silicone composition will decrease, while if the average particle size is too large, the dispensability will decrease and the particles may get caught in the sliding parts of the application device, causing problems such as abrasion of the device. In the present invention, the average particle size of component (C) is the 50% particle size D50 (or median size) in the volume-based cumulative particle size distribution measured using a laser diffraction particle size analyzer.

[0059] As component (D), spherical fillers alone or amorphous fillers alone can be used, but they can also be used in combination. Using two or more fillers with different shapes in combination allows for a state of packing close to the closest possible, resulting in higher thermal conductivity. When spherical and amorphous fillers are used in combination, if the proportion of the spherical thermally conductive filler is 30% by mass or more, assuming the total amount of component (D) to be 100% by mass, it is possible to further increase thermal conductivity.

[0060] The BET specific surface area of ​​component (D) is not particularly limited. For example, in the case of a spherical filler, 2 / g or less is preferable, and 0.5 m 2 / g or less is more preferable. 2 / g or less is preferable, and 3 m 2 / g or less is more preferable. BET specific surface area is 5m 2 If only amorphous fillers exceeding 1 / g are blended, the viscosity of the thermally conductive composition will increase, and adhesion between the cured thermally conductive composition and the substrate will be poor, resulting in poor heat dissipation. Furthermore, high loadings of bulky fillers hinder the movement of silicone rubber molecules within the composition, resulting in poor recovery. In this invention, the BET specific surface area of ​​component (D) is calculated by measuring the amount of gas physically adsorbed on the particle surface when the particles are cooled.

[0061] At least a portion of the surface of the thermally conductive filler may be surface-treated or coated to improve dispersibility, increase filler loading, or reduce mixing viscosity. Any known surface treatment or coating may be suitable. When the thermally conductive member is applied to a resin substrate such as PET, the surface treatment or coating improves adhesion, but tends to slightly reduce peeling from the substrate after exposure to high temperatures.

[0062] In the thermally conductive composition of the present invention, the content of component (D) is preferably 300 parts by mass or more and 2,000 parts by mass or less, more preferably 400 parts by mass or more and 1,900 parts by mass or less, and even more preferably 500 parts by mass or more and 1,800 parts by mass or less, relative to 100 parts by mass of the total of components (A) and (B). Within the above range, the thermally conductive composition as a whole has sufficient thermal conductivity, is easy to mix during blending, maintains flexibility after curing, and does not have an excessively high specific gravity, making it more suitable as a thermally conductive composition for forming thermally conductive parts that require both thermal conductivity and lightweight design. If the content of component (D) is too low, it becomes difficult to sufficiently increase the thermal conductivity of the resulting cured product of the thermally conductive composition. On the other hand, if the content of component (D) is too high, the silicone composition will have a high viscosity, which may make it difficult to apply the thermally conductive composition uniformly, and problems such as increased thermal resistance and reduced flexibility may occur in the cured composition.

[0063] (Component (E)) The addition catalyst of component (E) is a catalyst known to those skilled in the art that promotes the addition curing reaction between the silicon-bonded alkenyl groups in component (A) and the silicon-bonded hydrogen atoms in component (B). Component (E) includes platinum group metals such as platinum, rhodium, palladium, osmium, iridium, and ruthenium, as well as those immobilized on a fine particle support material (e.g., activated carbon, aluminum oxide, or silicon oxide). Further examples of component (E) include platinum compounds such as platinum halides, platinum-olefin complexes, platinum-alcohol complexes, platinum-alcoholate complexes, platinum-vinylsiloxane complexes, dicyclopentadiene-platinum dichloride, cyclooctadiene-platinum dichloride, and cyclopentadiene-platinum dichloride.

[0064] From an economical viewpoint, metal compound catalysts other than the platinum group metals described above may also be used. For example, examples of hydrosilylation iron catalysts include iron-carbonyl complex catalysts, iron catalysts having a cyclopentadienyl group as a ligand, iron catalysts having a terpyridine-based ligand, iron catalysts having a terpyridine-based ligand and a bis(trimethylsilylmethyl) group, iron catalysts having a bisiminopyridine ligand, iron catalysts having a bisiminoquinoline ligand, iron catalysts having an aryl group as a ligand, iron catalysts having a cyclic or acyclic olefin group having an unsaturated group, and iron catalysts having a cyclic or acyclic olefin group having an unsaturated group. Other examples include hydrosilylation cobalt catalysts, vanadium catalysts, ruthenium catalysts, iridium catalysts, samarium catalysts, nickel catalysts, and manganese catalysts.

[0065] The amount of component (E) to be blended is an effective amount depending on the desired curing temperature and curing time depending on the application, but typically the concentration of the catalytic metal element relative to the total mass of the thermally conductive composition is preferably in the range of 0.5 to 1,000 ppm, more preferably 1 to 500 ppm, and even more preferably 1 to 100 ppm. If the blending amount is less than 0.5 ppm, the addition reaction will be significantly slowed, while if the blending amount exceeds 1,000 ppm, costs will increase and this is economically undesirable.

[0066] In the gap filler composition, the components (A) and (B) undergo a crosslinking reaction in the presence of the (E) addition catalyst to produce a cured product (gap filler). The gap filler composition may have a thermal conductivity of 1 or greater, preferably 2 or greater. The specific gravity of the composition may be 1.5 or greater and 10 or less. Since there is a trend toward weight reduction for substrates to which the thermally conductive composition is applied or for components including a substrate to which the thermally conductive member is applied (e.g., electronic devices, batteries, etc.), the specific gravity of the composition is preferably 5.0 or less, more preferably 3.0 or less.

[0067] The method for producing the thermally conductive composition of the present invention can be any method known to those skilled in the art, and is not limited thereto. For example, the method may include a step of mixing components (A), (B), and (D), followed by adding component (C), and further mixing the mixture. For example, components (A), (B), and (D) can be mixed in advance in a mixer, or they can be kneaded uniformly in a high-shear mixer such as a two-roll mill, kneader mixer, pressure kneader mixer, or Ross mixer, or in an extruder or continuous extruder to prepare a silicone rubber base, and then component (C) can be added and blended to produce the silicone rubber base.

[0068] The thermally conductive composition of the present invention may further contain optional components other than components (A) to (E) described above, including conventional additives for silicone rubbers and gels, provided that the objectives of the present invention are not impaired. Examples of such additives include organosilicon compounds or organosiloxanes (also known as silane coupling agents) that generate silanols upon hydrolysis, crosslinking agents, condensation catalysts, adhesion promoters, pigments, dyes, cure inhibitors, heat resistance additives, flame retardants, antistatic agents, conductivity additives, airtightness improvers, radiation shielding agents, electromagnetic wave shielding agents, preservatives, stabilizers, organic solvents, plasticizers, and fungicides. These optional components may be used singly or in combination.

[0069] Silane coupling agents include organosilicon compounds or organosiloxanes containing an organic group such as an epoxy group, an alkyl group, or an aryl group and a silicon-bonded alkoxy group in one molecule. Examples of silane coupling agents include silane compounds such as octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, and dodecyltriethoxysilane. The silane compounds may not contain SiH groups and can be used alone or in combination. Treating the surface of a thermally conductive filler with the silane coupling agent improves its affinity with silicone polymers, reduces the viscosity of the composition, and improves the filler's packing. Therefore, incorporating a larger amount of filler can improve thermal conductivity. The silanols produced by hydrolysis can react and bond with condensable groups (e.g., hydroxyl groups, alkoxy groups, acid groups, etc.) present on the surface of metal substrates or organic resin substrates. The catalytic effect of the condensation catalyst described below causes the silanols and condensable groups to react and bond, thereby promoting adhesion of the thermally conductive member to various substrates. The amount of silane coupling agent to be blended with the filler is an effective amount depending on the desired curing temperature and curing time depending on the application. Normally, the optimum amount is 0.5 to 2 wt% relative to the thermally conductive filler, but as a guideline for the required amount, it can be calculated using the following formula and blended in an amount 1 to 3 times that amount. Required amount of silane coupling agent (g) = Filler weight (g) × Filler specific surface area (m 2 / g) ÷ specific minimum coverage area of ​​silane coupling agent (m 2 / g)

[0070] The crosslinking agent is an organohydrogenpolysiloxane that forms a cured product by addition reaction with alkenyl groups and may have at least three SiH groups in the molecule. The crosslinking agent of the present invention is preferably an organohydrogenpolysiloxane having five or more SiH groups, and may have from 10 to 15 SiH groups. The organohydrogenpolysiloxane used as the crosslinking agent has at least one SiH group in its side chain. The number of SiH groups at the molecular chain terminals can be from 0 to 2, but two is economically preferred. The molecular structure of the organohydrogenpolysiloxane may be linear, cyclic, branched, or a three-dimensional network structure. There are no particular restrictions on the position of the silicon atom to which the hydrogen atom is bonded, and it may be at the terminal or non-terminal of the molecular chain, or in a side chain. Other conditions, such as organic groups other than hydrogen groups, bonding positions, degree of polymerization, and structure, are not particularly limited, and two or more organohydrogenpolysiloxanes may be used.

[0071] If necessary, a condensation catalyst may be used together with the silane coupling agent. As the condensation catalyst, a compound of a metal selected from magnesium, aluminum, titanium, chromium, iron, cobalt, nickel, copper, zinc, zirconium, tungsten, and bismuth can be used. Preferred examples of the condensation catalyst include organic acid salts, alkoxides, and chelate compounds of aluminum trivalent, iron trivalent, cobalt trivalent, zinc divalent, zirconium tetravalent, and bismuth trivalent. Examples include organic acids such as octylic acid, lauric acid, and stearic acid, alkoxides such as propoxide and butoxide, and polydentate ligand chelate compounds such as catechol, crown ether, polycarboxylic acid, hydroxy acid, diketone, and keto acid, and multiple types of ligands may be bonded to one metal. In particular, compounds of zirconium, aluminum, and iron are preferred, as they tend to provide stable curing properties even when the formulation and conditions of use vary slightly, and more desirable structures are trivalent aluminum or iron chelate compounds in which zirconium butoxide, or malonic acid ester, acetoacetic acid ester, acetylacetone, or substituted derivatives thereof, etc., serve as polydentate ligands. Among trivalent aluminum and trivalent iron metal compounds, organic acids having 5 to 20 carbon atoms, such as octylic acid, can also be preferably used, and structures in which the above-mentioned polydentate ligand and organic acid are bonded to a single metal are also acceptable.

[0072] The substituted derivatives are those in which hydrogen atoms contained in the above compounds are substituted with alkyl groups such as methyl groups and ethyl groups, alkenyl groups such as vinyl groups and allyl groups, aryl groups such as phenyl groups, halogen atoms such as chlorine atoms and fluorine atoms, hydroxyl groups, fluoroalkyl groups, ester group-containing groups, ether-containing groups, ketone-containing groups, amino group-containing groups, amide group-containing groups, carboxylic acid-containing groups, nitrile group-containing groups, epoxy group-containing groups, or the like, and examples thereof include 2,2,6,6-tetramethyl-3,5-heptanedione and hexafluoropentanedione.

[0073] The adhesive aid preferably has an alkoxy group in the molecule, specifically tetraethoxysilane is preferred.Other examples include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, oligomers of 3-glycidoxypropyltrimethoxysilane, oligomers of 3-glycidoxypropyltriethoxysilane, or organic functional groups containing one or more selected from vinyl groups, methacryl groups, acrylic groups, and isocyanate groups, such as methacryloxysilanes (e.g., 3-methacryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane), 3-trimethoxysilylpropylsuccinic anhydride, and furandione (e.g., dihydro-3-(3-(triethoxysilyl)propyl)-2,5-furandione). The organic functional group may be bonded to the silicon atom via another group such as an alkylene group. In addition to the above, preferred are organosilicon compounds or organosiloxanes containing an organic group such as an epoxy group, alkyl group, or aryl group and a silicon-bonded alkoxy group per molecule. More preferred are organosilicon compounds or organosiloxanes containing at least one organic group such as an epoxy group, alkyl group, or aryl group and at least two silicon-bonded alkoxy groups. The epoxy group is preferably bonded to the silicon atom in the form of a glycidoxyalkyl group such as a glycidoxypropyl group, or an epoxy-containing cyclohexylalkyl group such as a 2,3-epoxycyclohexylethyl group or a 3,4-epoxycyclohexylethyl group, or a linear or branched alkyl group having 1 to 20 carbon atoms, or an organic group having an aromatic ring. In the case of epoxy groups, those containing 2 to 3 epoxy groups per molecule may be used. Preferred silicon-bonded alkoxy groups include methoxy, ethoxy, and propoxy groups, as well as alkyldialkoxysilyl groups such as methyldimethoxysilyl, ethyldimethoxysilyl, methyldiethoxysilyl, and ethyldiethoxysilyl. Furthermore, as functional groups other than those mentioned above, for example, functional groups selected from an alkenyl group such as a vinyl group, a (meth)acryloxy group, a hydrosilyl group (SiH group), and an isocyanate group may be used.

[0074] Examples of pigments include titanium oxide, alumina silicate, iron oxide, zinc oxide, calcium carbonate, carbon black, rare earth oxides, chromium oxide, cobalt pigment, ultramarine, cerium silanolate, aluminum oxide, aluminum hydroxide, titanium yellow, carbon black, barium sulfate, precipitated barium sulfate, and the like, and mixtures thereof. The amount of pigment to be blended is an effective amount depending on the desired curing temperature and curing time for the application, but typically the amount of pigment component blended is in the range of 0.001% to 5% of the total mass of the thermally conductive silicone composition. A range of 0.01% to 2%, and more preferably 0.05% to 1%, is preferred. If the blending amount is less than 0.001%, the coloring will be insufficient, making it difficult to visually distinguish between the first and second liquids. On the other hand, if the blending amount exceeds 5%, costs will increase and this is economically undesirable.

[0075] Curing inhibitors are capable of adjusting the curing rate of the addition reaction, and examples thereof include acetylene compounds, hydrazines, triazoles, phosphines, and mercaptans. Any curing inhibitor known in the art to have a curing inhibitory effect can be used. Examples of such compounds include phosphorus-containing compounds such as triphenylphosphine, nitrogen-containing compounds such as tributylamine, tetramethylethylenediamine, and benzotriazole, sulfur-containing compounds, acetylene compounds, compounds containing two or more alkenyl groups, hydroperoxy compounds, and maleic acid derivatives. Silane and silicone compounds containing an amino group may also be used. The amount of cure inhibitor used is an effective amount depending on the desired curing temperature and curing time for the application, but it is usually in the range of 0.1 to 15 parts by mass, assuming the total amount of components (A) and (B) is 100 parts by mass. The range is preferably 0.2 to 10 parts by mass, and more preferably 0.5 to 5 parts by mass. If the amount is less than 0.1 part by mass, the addition reaction will be significantly faster, and the curing reaction may progress during application, potentially worsening workability. On the other hand, if the amount exceeds 10 parts by mass, the addition reaction will be slower, potentially resulting in pump-out.

[0076] Specific examples include those containing various "ene-yne" systems such as 3-methyl-3-penten-1-yne and 3,5-dimethyl-3-hexen-1-yne; acetylenic alcohols such as 3,5-dimethyl-1-hexyn-3-ol, 1-ethynyl-1-cyclohexanol, and 2-phenyl-3-butyn-2-ol; maleates and fumarates, such as the well-known dialkyl, dialkenyl, and dialkoxyalkyl fumarates and maleates; and cyclovinylsiloxanes.

[0077] Examples of heat resistance imparting agents include cerium hydroxide, cerium oxide, iron oxide, fume titanium dioxide, and mixtures thereof.

[0078] The airtightness improver may be any substance that has the effect of reducing the breathability of the cured product, whether organic or inorganic. Specific examples include urethane, polyvinyl alcohol, polyisobutylene, isobutylene-isoprene copolymer, plate-like talc, mica, glass flakes, boehmite, various metal foils and metal oxide powders, and mixtures thereof.

[0079] The thermally conductive composition of the present invention may not contain an organosilicon compound having, in one molecule, at least one alkenyl group and at least one alkoxy group bonded to a silicon atom. When a compound having an alkenyl group and an alkoxy group bonded to a silicon atom is contained in the same molecule, the compound functions as a component that bonds the substrate and the gap filler. A composition of the present invention that does not contain such a component can further reduce deformation, damage, etc. of batteries and other devices when exposed to high temperatures and the thermally conductive member peels off from the substrate.

[0080] The present invention also provides (A) a diorganopolysiloxane having alkenyl groups bonded to silicon atoms; (B) a diorganopolysiloxane having hydrogen atoms bonded to silicon atoms; (C) Expanded graphite; (D) a thermally conductive filler; (E) an addition catalyst, The thermally conductive member obtained by curing the thermally conductive composition is a gap filler that has a thermal conductivity of 1 W / m·K or more at -30°C to 80°C and satisfies the following conditions (a) and (b): (a) The shear adhesive strength of the thermally conductive member before heating, as measured by the following test, is 0.1 MPa or more. (b) The shear adhesive strength of the thermally conductive member after heating at 250°C for 1 hour or more, as measured by the following test, is less than 0.1 MPa. Test: The thermally conductive composition is sandwiched between an aluminum plate and an electrodeposition-coated steel plate to a coating thickness of 1 mm, and left at room temperature for one day to harden. Then, using a tensile tester, a shear adhesion tensile test is performed at room temperature (23°C) at a tensile speed of 50 mm / min. The stress at break is measured.

[0081] Here, "before heating" refers to a state in which the thermally conductive composition has been cured to form a thermally conductive member and has not yet been exposed to a high temperature of 80°C or higher, and "after heating" refers to a state in which the thermally conductive composition has been exposed to a high temperature of 250°C or higher for one hour or more after being cured.

[0082] As mentioned above, before heating, the specific surface area of ​​the expanded graphite is small, and the cohesive force of the thermally conductive member is large, resulting in high adhesion to the substrate. The preferred shear bond strength varies depending on the properties and shape of the thermally conductive member. For example, when the thermally conductive member is a gap filler, the shear bond strength measured by the above test method is 0.10 MPa or more. The shear bond strength is more preferably 0.11 MPa or more, and even more preferably 0.12 MPa or more. When the thermally conductive member is a heat dissipation sheet, the shear adhesive strength may be lower than in the case of a gap filler. When the thermally conductive member is heated at 250°C for 1 hour or more, the cohesive strength of the thermally conductive member is reduced due to the action of the expandable graphite, making the thermally conductive member more likely to peel off from the base material or the heat-dissipating-sheet-forming substrate, and the shear bond strength measured by the above method is less than 0.1 MPa. The shear bond strength after heating is more preferably 0.09 MPa or less, and even more preferably 0.08 MPa or less.

[0083] The thermally conductive composition according to the present invention is an addition-curable composition, and may be a one-component composition or a two-component composition. In the case of a one-component composition, storage stability can be improved by, for example, using a composition that is cured by heat curing. In the case of a two-component composition, it is possible to further improve storage stability without these measures, and it is easy to create a composition that cures at room temperature (e.g., 25°C). In this case, the thermally conductive composition according to the present invention can be divided into a first component and a second component, for example, as follows: The first component is characterized by not containing component (B) but containing component (E), and the second component is characterized by containing component (B) but not containing component (E).

[0084] Therefore, the method for producing the two-component thermally conductive composition of the present invention is as follows: a first step of mixing (A) a diorganopolysiloxane having an alkenyl group bonded to a silicon atom, (C) expandable graphite, (D) a thermally conductive filler, and (E) an addition catalyst to obtain a first liquid; and a second step of mixing (A) a diorganopolysiloxane having an alkenyl group bonded to a silicon atom, (B) a diorganopolysiloxane having a hydrogen atom bonded to a silicon atom, (C) expandable graphite, and (D) a thermally conductive filler to obtain a second liquid.

[0085] The present invention also provides a method for producing a thermally conductive member, comprising: a mixing step of mixing the first and second liquids of the two-component thermally conductive composition; a coating step of coating the mixture of the first and second liquids obtained in the mixing step onto a substrate or a substrate for forming a heat dissipation sheet; and a curing step of curing the uncured mixture coated in the coating step.

[0086] The thermally conductive composition applied to the substrate in the application step forms a thermally conductive member that is a non-flowable cured product within approximately 120 minutes after application. The temperature at which the composition is cured after being applied to a substrate is not particularly limited, and may be, for example, 15°C or higher and 60°C or lower. To reduce thermal damage to the substrate, the temperature may be 15°C or higher and 40°C or lower. In the case of a thermosetting composition, the composition may be heated after being applied to a substrate, or may be cured by utilizing heat dissipation from a heat dissipation member. The temperature at which the composition is cured by heating may be, for example, 40°C or higher and 200°C or lower.

[0087] The substrate to which the gap filler or heat dissipation sheet is applied is not particularly limited, and examples include resins such as polyethylene terephthalate (PET), poly(1,4-butylene terephthalate) (PBT), and polycarbonate, ceramics, glass, and metals such as aluminum.

[0088] The thermally conductive component manufactured by the above method has good adhesion and bonding to the substrate, excellent heat dissipation properties, and can reduce damage and deformation of the substrate due to a decrease in adhesion to the substrate at abnormally high temperatures.Furthermore, by manufacturing from a two-component thermally conductive composition with high storage stability, there is an advantage that a high-quality thermally conductive component can be obtained even when using a thermally conductive composition that has been stored for a long period of time.

[0089] The present invention also provides (A) a diorganopolysiloxane having alkenyl groups bonded to silicon atoms; (B) a diorganopolysiloxane having hydrogen atoms bonded to silicon atoms; (D) a thermally conductive filler; (E) an addition catalyst; (C) A method for reducing the shear bond strength of the thermally conductive composition after curing, as measured by the following test method, to 0.8 times or less after heating at 250°C for 1 hour, by blending expanded graphite, In this method, when the total amount of the components (A) and (B) is 100 parts by mass, the amount of the component (C) is 0.5 parts by mass or more and 5 parts by mass or less. Test: The thermally conductive composition is sandwiched between an aluminum plate and an electrodeposition-coated steel plate so that the coating thickness is 1 mm, and left at room temperature for one day to harden. Then, using a tensile tester, a shear adhesion tensile test is performed at room temperature at a tensile speed of 50 mm / min. The stress at break is measured. Within the above range of magnification, the film exhibits the property of being easily peeled off from the substrate when exposed to high temperatures. [Example]

[0090] The present invention will be described in detail based on examples, but the present invention is not limited to the following examples. The compounding ratios of each component in the examples and comparative examples and the evaluation results are shown in Tables 1 and 2. The numerical values ​​of the compounding ratios shown in Tables 1 and 2 indicate parts by mass.

[0091] <Method for producing a cured product (thermal conductive member) of a thermally conductive composition> The first and second components shown in each of the examples and comparative examples were weighed out in a 1:1 ratio, thoroughly mixed in a stirrer, and then degassed using a vacuum pump to prepare each thermally conductive composition. These were then cured to prepare test pieces for each evaluation item, which were then used to prepare thermally conductive members.

[0092] <Hardness measurement method> The first and second liquids shown in the examples and comparative examples were weighed out in a 1:1 ratio, thoroughly mixed using a stirrer, and then degassed using a vacuum pump. The mixture was then poured into a cylindrical press mold measuring 30 mm in diameter and 6 mm in height, and cured at 100°C for 60 minutes to produce a cylindrical cured product. The Shore-OO hardness was measured in accordance with the JIS K6253 standard of the Society of Rubber Industry of Japan using a durometer hardness tester at a temperature of 23°C. Specifically, the durometer hardness tester was pressed directly above the surface of the cylindrical cured product, and the measured value obtained by bringing the pressed surface into close contact was used as the measurement value. The measurement was performed three times using the hardness tester, and the average of the measurement results was used. Generally, a lower Shore-OO hardness indicates higher flexibility. The Shore-OO hardness of the cured product is preferably in the range of 50 to 95. If the hardness is less than 50, the strength of the cured product is insufficient and sufficient shear strength cannot be obtained. On the other hand, if the hardness exceeds 95, the flexibility of the cured product is impaired, and it is presumed that the gap between the heating element and the heat sink will be filled and the follow-up to vibration after curing will be insufficient.

[0093] <Method for measuring specific gravity> The first and second liquids shown in the examples and comparative examples were weighed out in a 1:1 ratio, thoroughly mixed in a mixer, and then degassed using a vacuum pump. The mixture was then poured into a sheet-shaped press mold measuring approximately 10 cm in length, 10 cm in width, and 2 mm in thickness, and cured at 100°C for 60 minutes to produce a cured product. The specific gravity (density) (g / cm) of the cured products obtained in the examples and comparative examples was measured in accordance with JIS K 6249. 3 ) was measured. For applications where weight reduction is important, a specific gravity of 3.0 or less is preferable. Furthermore, when the same test piece is exposed to 250°C for 1 hour and then its specific gravity is measured using the same method, if the specific gravity is lower than before heating, it can be confirmed that the expandable raw material has expanded after heating. The specific gravity of the test piece after heating is preferably 0.95 to 0.99 times the specific gravity of the test piece before heating, and more preferably 0.97 to 0.99 times.

[0094] <Method for measuring thermal conductivity> The first and second components shown in the examples and comparative examples were weighed out in a 1:1 ratio, thoroughly mixed using a mixer, and degassed using a vacuum pump. The mixture was then poured into a cylindrical press mold measuring 30 mm in diameter and 6 mm in height and cured at 100°C for 60 minutes to produce a cylindrical cured product. The thermal conductivity of the cured product was measured using a hot disc measuring machine (TPS-500, manufactured by Kyoto Electronics Manufacturing Co., Ltd.) in accordance with ISO 22007-2. A sensor was placed between two of the cylindrical cured products, and the thermal conductivity was measured using the same device. The thermal conductivity is preferably 2.0 W / m·k or more.

[0095] <Method for measuring shear bond strength> Shear bond strength was measured as shear tensile strength in accordance with JIS K6850. The substrates were an aluminum plate approximately 60 cm long, 25 cm wide, and 2 mm thick, and an electrodeposited steel plate. The gap filler was applied to the first substrate in an area approximately 25 mm long and 25 mm wide, with a thickness of approximately 1 mm. The gap filler was then sandwiched between the other substrate and cured at room temperature for 24 hours. Measurements were taken using a Shimadzu autograph at 23°C. The first and second substrates were then pulled in the shear direction at a speed of 50 mm / min, and the stress at which the two substrates peeled was taken as the shear bond strength. Before exposure to high temperatures, the shear bond strength is preferably 0.1 MPa or more because adhesion to the substrate is required. On the other hand, after preparing a test piece in the same manner, it is exposed to 250°C for 1 hour, and when the shear bond strength is measured, it is required that the shear bond strength should be easy to peel off. Therefore, the shear bond strength after exposure to high temperatures should be less than 0.1 MPa, and preferably 0.08 MPa or less.

[0096] <Method for measuring mixed viscosity> The first and second parts shown in the examples and comparative examples were weighed out in a 1:1 ratio and thoroughly mixed with a stirrer, and the viscosity at 25°C was measured in accordance with JIS K 7117-2. Specifically, the uncured thermal conductive composition was placed between parallel plates with a diameter of 25 mm, and the viscosity was measured with an Anton Paar Physica MR 301 at a shear rate of 10 (1 / s) and a gap of 0.5 mm. A viscosity of 500 Pa·s or less can be said to have good application workability.

[0097] <Volume resistivity measurement method> The volume resistivity of the thermal conductive composition of the present invention was measured by a method in accordance with IEC 60093. 6 It is preferable that the resistance is Ω·cm or more, and 1×10 7 Within this range, the composition of the present invention can ensure its insulating properties.

[0098] <Method for producing a cured product of the curable silicone composition> Example 1 The first and second liquids shown in the examples and comparative examples were prepared according to the compositions shown in the tables by the following procedure. The blending ratios of each component shown in the tables are in parts by mass.

[0099] [First liquid of Examples 1 to 7] Component (A) was a diorganopolysiloxane having alkenyl groups, and component (D) was a platinum-divinyltetramethyldisiloxane complex. Optional silane coupling agents included n-octyltriethoxysilane and Momentive Corporation's A-137, a cure inhibitor containing 3-methyl-3-penten-1-yne, tetra-n-butyl zirconate as a condensation catalyst, and Stan-Tone 50SP01 Green as a pigment. These components were then weighed and added, and the mixture was kneaded at room temperature for 30 minutes using a planetary mixer. Component (A) is a linear dimethylpolysiloxane with alkenyl groups at both ends only and a viscosity of 150 mPa·s. As component (C), half the amount of spherical alumina having an average particle size of 45 μm and amorphous alumina having an average particle size of 3 μm, which are thermally conductive fillers, was added and kneaded using a planetary mixer at room temperature for 15 minutes. Then, half of the silane coupling agent, component (C) spherical thermally conductive filler and half of the amorphous thermally conductive filler, and component (E) expanded graphite were added and kneaded at room temperature for 15 minutes using a planetary mixer to prepare the first liquid. As the spherical alumina, spherical alumina DAM-45 (average particle size 45 μm) manufactured by Denka Co., Ltd. was used. As the amorphous alumina, fine alumina AL-S43B (average particle size 3 μm) manufactured by Sumitomo Chemical Co., Ltd. was used. The expanded graphite used was EXP-50HO (expandable graphite, expansion ratio 200 cc / g, expansion start temperature 220°C) manufactured by Fuji Graphite Industries Co., Ltd. In Examples 1 to 7, the blending amount of expanded graphite was varied from 0.5 parts by mass to 5 parts by mass.

[0100] [Second liquid of Examples 1 to 7] Component (A) was a diorganopolysiloxane with the same alkenyl group as in Liquid 1, and component (B) was a linear diorganopolysiloxane with two hydrogen atoms at both ends and a viscosity of 100 mPa·s. Optional components included a crosslinker, a silane coupling agent, and an adhesive aid, and these were all weighed and added, and the mixture was kneaded at room temperature for 30 minutes using a planetary mixer. The optional crosslinker was a dimethylpolysiloxane with a viscosity of 200 mPa·s, containing silicon-bonded hydrogen atoms only in the side chains. The optional adhesion promoter was tetraethoxysilane. Then, half of the optional silane coupling agent and half of the thermally conductive filler (component (C)) of spherical alumina with an average particle size of 45 μm and amorphous alumina with an average particle size of 3 μm) were added and mixed at room temperature for 15 minutes using a planetary mixer. Then, half the amount of the silane coupling agent, the same spherical thermally conductive filler as component (C) as in liquid 1 and half the amount of the amorphous thermally conductive filler, and expanded graphite as component (E) were added, and the mixture was kneaded at room temperature for 15 minutes using a planetary mixer to prepare liquid 2. In Examples 1 to 7, the amount of expanded graphite blended was varied from 0.5 parts by mass to 5 parts by mass.

[0101] Example 9 The first and second liquids were prepared in the same manner as in Example 3, except that EXP-50S160 (expandable graphite, expansion ratio 300 cc / g, expansion start temperature 160°C) manufactured by Fuji Graphite Industries Co., Ltd. was used as the expandable graphite.

[0102] Example 10 The first and second liquids were prepared in the same manner as in Example 1, except that the amounts of spherical alumina and amorphous alumina were increased.

[0103] Example 11 The first and second liquids were prepared in the same manner as in Example 1, except that aluminum hydroxide was blended in place of amorphous alumina. As the aluminum hydroxide, BW103 (average particle size 10 μm) manufactured by Nippon Light Metal Co., Ltd. was used.

[0104] (Comparative Example 1) The first and second liquids were prepared in the same manner as in Example 1, except that the expanded graphite of component (E) was not included.

[0105] (Comparative Example 2) The first and second liquids were prepared in the same manner as in Example 6, except that microballoons were used instead of the expanded graphite of component (E). FN-190D (expansion starting temperature 190°C) manufactured by Matsumoto Oil & Fat Industries Co., Ltd. was used as the microballoons.

[0106] (Comparative Example 3) Except for blending expanded graphite instead of the expanded graphite of component (E), the first and second liquids were prepared in the same manner as in Example 3. AED-50 manufactured by Fuji Graphite Industries Co., Ltd. was used as the expanded graphite.

[0107] Comparative Example 4 The first and second liquids were prepared in the same manner as in Example 6, except that expanded graphite was used instead of the expanded graphite of component (E).

[0108] (Comparative Example 5) The first and second liquids were prepared in the same manner as in Example 1, except that the blending amount of expanded graphite as component (E) was changed to 20 parts by mass.

[0109] The evaluation results are shown in Tables 1 and 2. In Examples 1 to 7, 0.5 to 5 parts by mass of EXP-50HO (expandable graphite, expansion onset temperature 220°C) was blended as the expanded graphite of component (E). In all cases, the shear bond strength before high-temperature exposure was 0.1 MPa or more, and the shear bond strength after 1 hour of exposure to 250°C was less than 0.1 MPa (0.08 MPa or less). It was confirmed that while good adhesion was maintained under normal conditions, the material easily peeled from the substrate after high-temperature exposure. In addition, all of the materials had a thermal conductivity of 2.0 W / m·k or more, demonstrating good thermal conductivity. The volume resistivity was 10 7 The electrical insulation was also good, with a resistance of Ω·cm or more. In Examples 6 and 7, 3 parts by mass and 5 parts by mass of expanded graphite were blended, respectively. The viscosity increased, but was within an acceptable range.

[0110] Example 8 is a formulation that does not contain an adhesion promoter or a condensation catalyst. Before exposure to high temperatures, the shear bond strength is low, but after exposure to high temperatures, the shear bond strength becomes even lower due to the inclusion of expanded graphite.

[0111] In Example 9, the expanded graphite EXP-50S160, which has an expansion starting temperature of 160°C, was blended. It was confirmed that while good adhesion was maintained under normal conditions, it easily peeled off from the substrate after exposure to high temperatures. In addition, the thermal conductivity was 2.0 W / m·k or more, indicating good thermal conductivity. The volume resistivity was 10 6 The electrical insulation was also good, with a resistance of Ω·cm or more.

[0112] In Example 10, when the amount of alumina, the thermally conductive filler (component (C)), was increased, a high thermal conductivity of 2.8 W / m·k was achieved, but the viscosity rose to 150 Pa·s, which is thought to have resulted in poor application properties. However, it was confirmed that while good adhesion was maintained under normal conditions, the adhesive easily peeled off from the substrate after exposure to high temperatures.

[0113] In Example 11, aluminum hydroxide was used instead of amorphous alumina, and although the thermal conductivity decreased slightly, the specific gravity was reduced to 2.88, which contributed to weight reduction. Furthermore, it was confirmed that while good adhesion was maintained under normal conditions, it peeled easily from the substrate after exposure to high temperatures.

[0114] Comparative Example 1 did not contain expanded graphite, but it had good adhesion under normal conditions and high shear bond strength even after being exposed to 250°C for 1 hour. This is thought to be why it does not peel easily from the substrate at high temperatures. In Comparative Example 2, microballoons that expand at 160°C were blended with expanded graphite. Like expanded graphite, microballoons also expand when heated, so it was confirmed that while they maintain good adhesion under normal conditions, they easily peel off from the substrate after being exposed to high temperatures. However, because the microballoons are hollow, their own thermal conductivity is low, resulting in a low thermal conductivity of 1.9 W / m·k as a gap filler. In Comparative Examples 3 and 4, expanded graphite was blended in place of expanded graphite. Because expanded graphite is graphite that has already been expanded, it has low cohesive strength in its normal state and therefore low shear adhesive strength in its normal state, resulting in insufficient adhesion to the substrate. In Comparative Example 5, 20 parts by mass of expanded graphite was blended, and it was confirmed that while good adhesion was maintained under normal conditions, the adhesive easily peeled off from the substrate after exposure to high temperatures. However, because the amount of conductive graphite was large, the volume resistivity decreased and sufficient insulation properties could not be obtained.

[0115] [Table 1]

[0116] A part or all of the above-described embodiments can be described as in the following supplementary notes, but are not limited to the following descriptions.

[0117] (Appendix 1) (A) a diorganopolysiloxane having alkenyl groups bonded to silicon atoms; (B) a diorganopolysiloxane having hydrogen atoms bonded to silicon atoms; (C) Expanded graphite; (D) a thermally conductive filler; (E) an addition catalyst; the content of the (C) component is 0.5 parts by mass or more and 5 parts by mass or less when the total amount of the (A) component and the (B) component is 100 parts by mass, A thermally conductive composition, wherein the content of the component (D) is 300 parts by mass or more and 2,000 parts by mass or less when the total amount of the component (A) and the component (B) is 100 parts by mass.

[0118] (Appendix 2) 2. The thermally conductive composition of claim 1, wherein the thermally conductive composition is a thermally conductive gap filler composition that is applied to a substrate in a liquid state before curing and then cured to form a gap filler.

[0119] (Appendix 3) 3. The thermally conductive composition according to claim 1, wherein the component (A) is a diorganopolysiloxane having alkenyl groups bonded to silicon atoms at both molecular chain terminals.

[0120] (Appendix 4) 4. The thermally conductive composition according to any one of claims 1 to 3, wherein the component (B) is a diorganopolysiloxane having hydrogen atoms bonded to silicon atoms at both molecular chain terminals.

[0121] (Appendix 5) 5. The thermally conductive composition according to any one of claims 1 to 4, wherein the thermally conductive composition has a viscosity before curing in the range of 10 to 1,000 Pa s at a temperature of 25°C and a shear rate of 10 / s, as measured with a rotational viscometer.

[0122] (Appendix 6) The thermally conductive composition has a volume resistivity of 1×10 before curing. 6 6. The thermally conductive composition according to any one of claims 1 to 5, having a resistivity of Ω·cm or more.

[0123] (Appendix 7) 7. The thermally conductive composition according to claim 1, wherein the thermally conductive member obtained by curing the composition has an expansion ratio (volume after high-temperature exposure / volume before high-temperature exposure) of 1.1 or less.

[0124] (Appendix 8) 8. The thermally conductive composition according to any one of claims 1 to 7, wherein the component (C) is expandable graphite that generates an inorganic acid at a temperature of 100°C or higher and 300°C or lower.

[0125] (Appendix 9) 9. The thermally conductive composition according to claim 8, wherein the inorganic acid is one or more selected from the group consisting of sulfuric acid, nitric acid, and hydrochloric acid.

[0126] (Appendix 10) 10. The thermally conductive composition according to any one of claims 1 to 9, wherein the (D) thermally conductive filler is a non-conductive thermally conductive filler.

[0127] (Appendix 11) 11. The thermally conductive composition according to any one of claims 1 to 10, wherein the (D) thermally conductive filler contains at least one selected from aluminum hydroxide and aluminum oxide.

[0128] (Appendix 12) 12. The thermally conductive composition according to any one of claims 1 to 11, characterized in that it does not contain an organosilicon compound having, in one molecule, at least one alkenyl group and at least one alkoxy group bonded to a silicon atom.

Claims

1. (A) a diorganopolysiloxane having alkenyl groups bonded to silicon atoms; (B) a diorganopolysiloxane having hydrogen atoms bonded to silicon atoms; (C) Expanded graphite; (D) a thermally conductive filler; (E) an addition catalyst; A thermally conductive composition comprising an organosilicon compound or organosiloxane (also called a silane coupling agent) that generates silanol upon hydrolysis, the content of the (C) component is 0.5 parts by mass or more and 3 parts by mass or less when the total amount of the (A) component and the (B) component is 100 parts by mass, the content of the (D) component is 300 parts by mass or more and 2000 parts by mass or less when the total amount of the (A) component and the (B) component is 100 parts by mass, The amount of silane coupling agent to be mixed with the filler is 1 to 3 times the amount calculated by the following formula: Required amount of silane coupling agent (g) = Filler weight (g) × Filler specific surface area (m2 / g) ÷ Specific minimum coverage area of ​​silane coupling agent (m2 / g) A thermally conductive composition, wherein the thermally conductive member obtained by curing the composition has an expansion ratio (volume after high-temperature exposure at 250°C for 1 hour / volume before high-temperature exposure) of 1.1 or less.

2. 10. The thermally conductive composition according to claim 1, wherein the thermally conductive composition is a thermally conductive gap filler composition that is applied to a substrate in a liquid state before curing and then cured to form a gap filler.

3. 3. The thermally conductive composition according to claim 1, wherein the component (A) is a diorganopolysiloxane having alkenyl groups bonded to silicon atoms at both molecular chain terminals.

4. 3. The thermally conductive composition according to claim 1, wherein the component (B) is a diorganopolysiloxane having hydrogen atoms bonded to silicon atoms at both molecular chain terminals.

5. 3. The thermally conductive composition according to claim 1, wherein the thermally conductive composition has a viscosity before curing in the range of 10 to 1,000 Pa s at a temperature of 25°C and a shear rate of 10 / s, as measured with a rotational viscometer.

6. 3. The thermally conductive composition according to claim 1, wherein the thermally conductive composition has a volume resistivity of 1×10 6 Ω·cm or more before curing.

7. 3. The thermally conductive composition according to claim 1, wherein the component (C) is expanded graphite that generates an inorganic acid at a temperature of 100°C or higher and 300°C or lower.

8. 8. The thermally conductive composition according to claim 7, wherein the inorganic acid is one or more acids selected from the group consisting of sulfuric acid, nitric acid, and hydrochloric acid.

9. 3. The thermally conductive composition according to claim 1, wherein the thermally conductive filler (D) is a non-conductive thermally conductive filler.

10. 3. The thermally conductive composition according to claim 1, wherein the thermally conductive filler (D) contains at least one selected from aluminum hydroxide and aluminum oxide.

11. 3. The thermally conductive composition according to claim 1, wherein the composition does not contain an organosilicon compound having, in one molecule, at least one alkenyl group and at least one alkoxy group bonded to a silicon atom.

12. A thermally conductive member obtained by curing the thermally conductive composition according to claim 1, wherein the thermally conductive member has a thermal conductivity of 1 W / m K or more at -30°C to 80°C and satisfies the following conditions (a) and (b): (a) The shear adhesive strength of the thermally conductive member before heating, as measured by the following test, is 0.1 MPa or more. (b) The shear adhesive strength of the thermally conductive member after heating at 250°C for 1 hour or more is less than 0.1 MPa, as measured by the following test: Test: The thermally conductive composition was sandwiched between an aluminum plate and an electrodeposition-coated steel plate to a coating thickness of 1 mm, and left at room temperature for one day to harden. Then, a shear adhesion tensile test was performed at room temperature using a tensile tester at a tensile speed of 50 mm / min. The stress at break was measured.

13. The thermally conductive member of claim 12 , wherein the thermally conductive member is a gap filler.

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