Thermally conductive silicone composition

Abstract

This invention provides a thermally conductive silicone composition that satisfies both weight reduction and storage stability, even when using aluminum hydroxide fillers. [Solution] The thermally conductive silicone composition is a thermally conductive filler selected from (A) a diorganopolysiloxane containing alkenyl groups bonded to silicon atoms, (B) a diorganopolysiloxane having hydrogen atoms bonded to silicon atoms, and (C) aluminum oxide (C1) with an average particle size of less than 5 μm and a hot water extracted sodium oxide content of less than 300 ppm, as quantified by atomic absorption spectrometry, and aluminum hydroxide with an average particle size of less than 5 μm and a hot water extracted sodium oxide content of less than 70 ppm, as quantified by atomic absorption spectrometry. The material comprises: (D) a first thermally conductive filler in the amount of 30 to 220 parts by mass per 100 parts by mass of the total of component (A) and component (B); (E) a second thermally conductive filler in the amount of 400 to 950 parts by mass per 100 parts by mass of the total of component (A) and component (B), wherein the hot water extracted sodium oxide content is less than 70 ppm as quantified by atomic absorption spectrometry, and the average particle size is 5 μm to 100 μm; and (E) an addition catalyst in the amount of 0.2 to 1.0 part by mass per 100 parts by mass of the total of component (A) and component (B).

Description

[Technical Field]

[0001] This disclosure relates to a thermally conductive silicone composition. [Background technology]

[0002] Thermally conductive silicone compositions, such as gap fillers, are directly applied to heat-generating or heat-sinking elements, such as batteries in electric vehicles or semiconductors in electronic devices, and have the function of transferring the heat they generate to heat-dissipating components such as heat sinks. In recent years, with the spread of environmentally friendly electric vehicles, the development of high-performance batteries has progressed. Against this backdrop, many thermally conductive silicone products have been developed to transfer the heat generated by heat-generating elements such as electronic components and batteries to heat-dissipating components such as heat sinks. Furthermore, since automobiles require weight reduction, it is desirable that the components installed in automobiles have a low specific gravity. The thermally conductive silicone composition for gap fillers described in Patent Document 1 uses only aluminum hydroxide filler. However, since Patent Document 1 uses an alkoxy catalyst having Si bonds as a condensation catalyst, the adhesion is insufficient.

[0003] Furthermore, Patent Document 2 discloses a silicone composition for gap fillers with improved adhesion. This silicone composition uses a Ti·Zr alkoxy compound as a condensation catalyst and an addition catalyst in combination. In gap filler applications, there is a desire for further weight reduction while maintaining thermal conductivity and adhesion. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 6339761 [Patent Document 2] International Publication No. WO2023-053760 [Overview of the project] [Problems that the invention aims to solve]

[0005] In adhesive, thermally conductive silicone compositions, aluminum hydroxide fillers with low specific gravity are sometimes used to reduce weight. However, using aluminum hydroxide fillers results in poor storage stability, and there are concerns that curing inhibition of the silicone composition may occur after storage for a certain period, or that the adhesiveness and hardness of the cured product obtained by curing the silicone composition may decrease. This is thought to be due to the increased basicity caused by the Na2O component contained in the aluminum hydroxide filler, which promotes hydrolysis reactions of the Si-H bonds in the silicone chain by moisture in the air and OH bonds in the silicone chain and on the filler surface. The same is thought to be true when aluminum oxide is used.

[0006] This disclosure provides a thermally conductive silicone composition that can suppress the reduction in hardness and adhesiveness during storage and satisfy storage stability, even when using aluminum oxide or aluminum hydroxide fillers. In particular, the disclosure provides a thermally conductive silicone composition that can also achieve weight reduction by using aluminum hydroxide. Furthermore, this disclosure provides a thermally conductive silicone composition that, despite having a low specific gravity, exhibits good storage stability, maintains good adhesion to heat-generating and heat-sinking elements even under vibrational conditions, possesses appropriate fluidity, and has high thermal conductivity, thereby providing a thermal conductive member (gap filler) with excellent heat dissipation characteristics. [Means for solving the problem]

[0007] The thermally conductive silicone composition of this disclosure, (A) A diorganopolysiloxane containing an alkenyl group bonded to a silicon atom, (B) A diorganopolysiloxane having a hydrogen atom bonded to a silicon atom, (C) At least one thermally conductive filler selected from aluminum oxide (C1) with an average particle size of less than 5 μm and a hot water extracted sodium oxide (Na2O) content of less than 300 ppm, as quantified by atomic absorption spectrometry, and aluminum hydroxide (C2) with an average particle size of less than 5 μm and a hot water extracted sodium oxide (Na2O) content of less than 70 ppm, as quantified by atomic absorption spectrometry, wherein the first thermally conductive filler is present in an amount of 30 parts by mass or more and 220 parts by mass or less per 100 parts by mass of the total of components (A) and (B), (D) An aluminum hydroxide filler with an average particle size of 5 μm to 100 μm, wherein the sodium oxide (Na2O) content quantified by atomic absorption spectrometry is less than 70 ppm, and the filler comprises 400 parts by mass to 950 parts by mass of a second thermally conductive filler (aluminum hydroxide filler) per 100 parts by mass of the total of components (A) and (B), (E) An addition catalyst in an amount of 0.2 parts by mass or more and 1.0 part by mass or less per 100 parts by mass of the total of component (A) and component (B), Includes.

[0008] The hot water-extracted sodium oxide (Na2O) is derived, for example, from an aqueous sodium hydroxide solution used in the manufacturing process of aluminum oxide or aluminum hydroxide. Sodium oxide (Na2O) extracted with hot water is obtained, for example, by placing aluminum oxide (C1) or aluminum hydroxide (C2) in hot water at a temperature of 80°C to 150°C in a pressure vessel, and after 4 to 30 hours, the dissolved sodium oxide (Na2O) in the hot water is quantified by atomic absorption spectrometry. In a thermally conductive silicone composition (for example, in both or either of the first and second liquids of a thermally conductive silicone composition), it is thought that hot water-extractable sodium oxide (Na2O) will leach out over time.

[0009] The first thermally conductive filler of component (C1 or C2) and / or the second thermally conductive filler of component (D) may be surface-treated.

[0010] The ratio of component (A) to component (B) may be within the range of SiH / SiVi, which is between 0.5 and 1.5.

[0011] The aforementioned component (A) may include an organopolysiloxane having a viscosity of 10 mPa·s or more and 7,000 mPa·s or less at 25°C.

[0012] The aforementioned component (B) may include an organopolysiloxane having two or more hydrogen atoms in one molecule and having a viscosity of 10 mPa·s or more and 7,000 mPa·s or less at 25°C.

[0013] The thermal conductivity of the thermally conductive silicone composition or its cured product may be 2.0 W / m·k or higher.

[0014] It is preferable that the initial tensile shear bonding stress of the cured product of the thermally conductive silicone composition is 0.1 MPa or higher. The reduction rate of the tensile shear adhesive stress of the cured product of the thermally conductive silicone composition may be 30% or less, preferably 29% or less, and more preferably 28% or less. Tensile shear bond stress reduction rate = (Initial tensile shear bond stress - Tensile shear bond stress after 1 month of storage at 50°C and 50% relative humidity) / Initial tensile shear bond stress × 100 Tensile shear adhesion tests are performed on test specimens for tensile shear adhesion testing according to the method in accordance with JIS K6850, and an S-S curve graph is obtained. In the S-S curve graph, the maximum stress value is taken as the tensile shear adhesion stress of the cured silicone composition corresponding to each test specimen for tensile shear adhesion testing.

[0015] It is preferable that the initial Asker C hardness of the cured product of the thermally conductive silicone composition is in the range of 50 to 70. The reduction in Asker C hardness of the cured product of the thermally conductive silicone composition may be less than 20%. Hardness reduction rate = (Initial hardness - Hardness after 1 month of storage at 50°C and 50% relative humidity) / Initial hardness × 100 The hardness measurement complies with the Asker C method of the Japan Rubber Association Standard (SRIS 0101).

[0016] The thermally conductive silicone composition may be a two-component thermally conductive silicone composition having a first liquid and a second liquid packaged separately from each other, and the first liquid and the second liquid are mixed (for example, in a discharge device, under pressure) during use to form a thermally conductive silicone composition. The first liquid may contain (A), (C1 or C2), (D), and (E). The second liquid may contain (A), (B), (C1 or C2), and (D).

[0017] [First Liquid] Based on 100 parts by mass of the total amount of the first liquid, component (A) is 5 parts by mass or more and 20 parts by mass or less, component (C1 or C2) is 3 parts by mass or more and 22 parts by mass or less, component (D) is 60 parts by mass or more and less than 100 parts by mass, component (E) is 0.4 parts by mass or less, and it may be so. The first liquid may optionally further contain a silane coupling agent, a reaction inhibitor, an adhesion condensation catalyst, and / or a pigment.

[0018] [Second Liquid] Based on 100 parts by mass of the total amount of the second liquid, component (A) is 1 part by mass or more and 10 parts by mass or less, component (B) is 3 parts by mass or more and 15 parts by mass or less, component (C1 or C2) is 3 parts by mass or more and 22 parts by mass or less, component (D) is 60 parts by mass or more and less than 100 parts by mass, and it may be so. The second liquid may optionally further contain a silane coupling agent, a reaction inhibitor, and / or a pigment.

[0019] Based on 100 parts by mass of the total amount of the two-component thermally conductive silicone composition, the first liquid is 40 parts by mass or more and 60 parts by mass or less, The second liquid is present in amounts of 60 parts by mass or more and 40 parts by mass or less. But that's fine.

[0020] The method for producing the thermally conductive silicone composition of this disclosure is as follows: A first liquid manufacturing step involves mixing component (A), component (E), and an optional component, and then mixing component (C1 or C2) and component (D) to obtain the first liquid. The second liquid is manufactured by mixing component (A), component (B), and an optional component, and then mixing component (C1 or C2) and component (D) to obtain the second liquid. Includes. The aforementioned optional components include, for example, silane coupling agents, reaction inhibitors, adhesion condensation catalysts, and / or pigments.

[0021] The method for producing the aforementioned thermally conductive silicone composition is as follows: A first liquid packaging step in which the first liquid obtained in the first liquid manufacturing step is filled into a predetermined first packaging material, A second liquid packaging step in which the second liquid obtained in the second liquid manufacturing step is filled into a predetermined second packaging material, It may include.

[0022] The method for dispensing the thermally conductive silicone composition of this disclosure is as follows: The first liquid is introduced from the first packaging material into the first liquid channel of the dispenser. The second liquid is introduced from the second packaging material into the second liquid channel of the dispenser. The first liquid and the second liquid are introduced in a predetermined ratio into a merging channel where the first liquid channel and the second liquid channel merge. The process may include dispensing a mixture of the first liquid and the second liquid, which have been brought into contact in the aforementioned confluence channel, from the nozzle of a dispenser onto the substrate. The aforementioned "predetermined ratio" is the mixing ratio of the first liquid and the second liquid, and is set according to the specifications of the thermally conductive silicone composition. The predetermined ratio is, for example, 1:1.

[0023] The method for manufacturing a thermally conductive member according to this disclosure is: The process involves discharging the first liquid from the first liquid storage section to the mixing section, A step of discharging the second liquid from the second liquid storage section to the mixing section, The steps include: mixing the first liquid and the second liquid in the mixing section to obtain a thermally conductive silicone composition; The process involves dispensing and applying the aforementioned thermally conductive silicone composition to a substrate, The process may include a step of curing the thermally conductive silicone composition applied to the substrate to obtain a thermally conductive member.

[0024] In a method for manufacturing a thermally conductive member and a method for dispensing a thermally conductive silicone composition, the discharge pressure for dispensing the first liquid, the second liquid, and the thermally conductive silicone composition onto the substrate varies depending on the dispenser, but for example, the lower limit is 0.1 MPa, and preferably 0.2 MPa to 0.8 MPa.

[0025] (effect) In a configuration using a fine-particle aluminum oxide filler or aluminum hydroxide filler with an average particle size of less than 5 μm and a larger-particle aluminum hydroxide filler, even when not using a high-purity, low-Na2O grade filler, using a filler with a hot water-extracted sodium oxide (Na2O) content within the above numerical range provides a gap filler with good thermal conductivity, adhesion, fluidity, low specific gravity, and storage stability, resulting in a silicone composition. The aforementioned thermally conductive silicone composition is suitable for use as a gap filler due to its high thermal conductivity and excellent heat dissipation properties. Even when using a low-density aluminum hydroxide filler as the filler component, it can combine good adhesion to substrates such as heat dissipation pairs with appropriate fluidity and good storage stability. [Brief explanation of the drawing]

[0026] [Figure 1A] This figure shows the mixing ratio of the first and second liquids in the example. [Figure 1B] This figure shows the parts by mass of each component based on component A-1 of the first liquid in the example, and the parts by mass of each component based on the sum of A-1, A-2, and B-1 of the second liquid. [Figure 1C] This figure shows the mixing ratio of the example and the results for tensile shear bonding stress, hardness, and thermal conductivity. [Figure 1D] This figure shows the mass portion representation and the results of tensile shear bonding stress, hardness, and thermal conductivity for the example. [Figure 2A] This figure shows the mixing ratio of the first and second solutions in the comparative example. [Figure 2B] This figure shows the parts by mass of each component based on component A-1 of the first comparative solution, and the parts by mass of each component based on the sum of A-1, A-2, and B-1 of the second solution. [Figure 2C] This figure shows the mixing ratio of the comparative example and the results for tensile shear bonding stress, hardness, and thermal conductivity. [Figure 2D] This figure shows the mass portion representation and the results for tensile shear bonding stress, hardness, and thermal conductivity of the comparative example. [Modes for carrying out the invention]

[0027] The following describes the details of the thermally conductive silicone composition and the method for producing the thermally conductive silicone composition according to the present invention.

[0028] (Thermally conductive silicone composition) The thermally conductive silicone composition can be any composition for forming a thermally conductive member. Examples of thermally conductive members include heat-generating elements such as car batteries, substrates for electrical or electronic equipment, circuit chips, and heat dissipation members that are cured and formed. The thermally conductive silicone composition may be applied to the substrate in a liquid state before curing, and then cured to provide a thermally conductive member, or the cured thermally conductive member may be applied to the substrate.

[0029] The temperature and procedure for curing the thermally conductive silicone composition can be appropriately selected depending on the intended use of the resulting cured product, and are not limited to these.

[0030] The curing method for thermally conductive silicone compositions is preferably an addition reaction type. The main reasons for this are that curing can be controlled over a wide temperature range from room temperature to about 150°C, there is little volume change or desorption of gases, and it generally has good compatibility with thermally conductive fillers. Generally, a higher curing temperature results in faster curing, but in this invention, due to various constraints depending on the application, it is assumed that some or all of the steps of applying the thermally conductive silicone composition, curing, and subsequent steps must be performed at room temperature, and an appropriate curing temperature can be set accordingly.

[0031] In the case where the curing method of the thermally conductive silicone composition according to the present invention is an addition reaction type, each component of the thermally conductive silicone composition will be described in detail below.

[0032] [(A) component] Component (A) is the main component of the thermally conductive silicone composition and is a diorganopolysiloxane containing alkenyl groups bonded to silicon atoms. The alkenyl group-containing diorganopolysiloxane is preferably terminally Vi (vinyl group) in order to have appropriate hardness after curing. The alkenyl group-containing diorganopolysiloxane may also have OH groups at its ends. (A) The viscosity and degree of polymerization of component are not particularly limited and can be selected according to the required mixed viscosity of the thermally conductive silicone composition, for example, the viscosity at 25°C may be 10 mPa·s or more and 7,000 mPa·s or less. Diorganopolysiloxanes can be used individually or in appropriate combinations of two or more. They are the main component of thermally conductive silicone compositions and have at least two, preferably 2 to 50, and more preferably 2 to 20 alkenyl groups bonded to silicon atoms on average per molecule. When the total amount of the thermally conductive silicone composition is 100 parts by mass, component (A) is in the range of 3.0 parts by mass or more and 15.0 parts by mass or less, preferably 5.0 parts by mass or more and 11.0 parts by mass or less. Component (A) is preferably included in both the first liquid and the second liquid.

[0033] The molecular structure of component (A) is not particularly limited and may be, for example, a linear structure, a partially branched linear structure, a branched linear structure, a cyclic structure, or a branched cyclic structure. Component (A) is preferably a substantially linear diorganopolysiloxane, and more specifically, it may be a linear diorganopolysiloxane in which the molecular chain mainly consists of repeating diorganosiloxane units and both ends of the molecular chain are sealed with triorganosiloxy groups. Some or all of the ends of the molecular chain, or some of the side chains, may be silanol groups.

[0034] 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 alkenyl groups bonded to silicon atoms at both ends of the molecular chain. If the organopolysiloxane has one alkenyl group at each end of the molecular chain, it has the advantage of having a low content of alkenyl groups that serve as reaction sites for the crosslinking reaction, and thus increasing the flexibility of the gap filler obtained after curing.

[0035] The alkenyl group may be bonded to only one of the silicon atoms at the end of the molecular chain or to a silicon atom at the non-terminus (part of the molecular chain), or it may be bonded to both. Furthermore, component (A) may be a polymer consisting of a single siloxane unit, or a copolymer consisting of two or more siloxane units.

[0036] The viscosity of component (A) at 25°C is 10 mPa·s to 7,000 mPa·s, preferably 20 mPa·s to 5,000 mPa·s, more preferably 30 mPa·s to 3,000 mPa·s, even more preferably 40 mPa·s to 2,000 mPa·s, and even more preferably 50 mPa·s to 1,000 mPa·s. Within the viscosity range described above, the resulting thermally conductive silicone composition will have appropriate fluidity, resulting in high extrusion efficiency and increased productivity. Furthermore, it will be possible to increase the flexibility of the thermally conductive component obtained by curing the thermally conductive silicone composition.

[0037] To adjust the viscosity (mixed viscosity) of a thermally conductive silicone composition obtained by mixing liquid compositions before curing, diorganopolysiloxanes having two or more alkenyl groups with different viscosities can also be used.

[0038] Specifically, the average empirical formula of component (A) is represented by the following general formula (1). R 1 a SiO (4-a) / 2 (1) (However, in equation (1), R 1 These are unsubstituted or substituted monovalent hydrocarbon groups having 1 to 18 carbon atoms, either identical or different from each other. a is 1.7 to 2.1. Furthermore, a is preferably 1.8 to 2.5, and more preferably 1.95 to 2.05.

[0039] In one embodiment, the above R 1 Of the monovalent hydrocarbon groups represented by , at least two are selected from alkenyl groups such as vinyl, allyl, propenyl, isopropenyl, butenyl, isobutenyl, hexenyl, and cyclohexenyl groups, 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 groups. The hydrocarbon groups are selected from cycloalkyl groups such as cyclopentyl, cyclohexyl, and cycloheptyl groups; aryl groups such as phenyl, tolyl, xylyl, biphenyl, and naphthyl groups; aralkyl groups such as benzyl, phenylethyl, phenylpropyl, and methylbenzyl groups; and halogen-substituted alkyl groups and cyano-substituted alkyl groups such as chloromethyl, 2-bromoethyl, 3,3,3-trifluoropropyl, 3-chloropropyl, and cyanoethyl groups, in which some or all of the hydrogen atoms in these hydrocarbon groups are substituted with halogen atoms, cyano groups, etc.

[0040] R 1In the selection, as the alkenyl group(s) required in two or more numbers, vinyl group, allyl group, propenyl group, isopropenyl group, 2-methyl-1-propenyl group, 2-methylallyl group, 2-butenyl group are preferable, and vinyl group is particularly preferable. R other than the alkenyl group 1 is preferably a methyl group and a phenyl group, and particularly preferably a methyl group. Also, in all R 1 , it is preferable that 70 mol% or more is a methyl group in terms of physical properties and economic efficiency of the cured product, and usually those with 80 mol% or more of methyl group are used.

[0041] As the molecular structure of the component (A), dimethylvinylsiloxy group-terminated dimethylpolysiloxane at both ends of the molecular chain, dimethylvinylsiloxy group-terminated dimethylsiloxane·methylphenylsiloxane copolymer at both ends of the molecular chain, dimethylvinylsiloxy group-terminated dimethylsiloxane·methylvinylsiloxane copolymer at both ends of the molecular chain, dimethylvinylsiloxy group-terminated dimethylsiloxane·methylvinylsiloxane·methylphenylsiloxane copolymer at both ends of the molecular chain, trimethylsiloxy group-terminated dimethylsiloxane·methylvinylsiloxane copolymer at both ends of the molecular chain, formula: (CH3)2ViSiO 1 / 2 The siloxane unit represented by, formula: (CH3)3SiO 1 / 2 The siloxane unit represented by, formula: SiO 4 / 2 Organopolysiloxane composed of the siloxane unit represented by (where Vi in the formula represents a vinyl group), a part or all of the methyl groups of these organopolysiloxanes are replaced with an alkyl group such as an ethyl group or a propyl group; an aryl group such as a phenyl group or a tolyl group; a halogenated alkyl group such as a 3,3,3-trifluoropropyl group Organopolysiloxane, and mixtures of two or more of these organopolysiloxanes are exemplified. From the viewpoint of increasing the elongation until the cured product is cut by increasing the molecular chain length, a linear diorganopolysiloxane having vinyl groups at both ends of the molecular chain is preferable.

[0042] (A) Component may contain 1.0 part by mass or more and 9.0 parts by mass or less of an alkenyl group-containing diorganopolysiloxane having at least one silanol group at the end of the molecular chain. When storing the thermally conductive silicone composition of the present invention as a two-component type, a diorganopolysiloxane containing an alkenyl group having a silanol group may be incorporated into the first and / or second liquid.

[0043] These diorganopolysiloxanes may be commercially available or manufactured by methods known to those skilled in the art.

[0044] [(B) Component] Component (B) is a diorganopolysiloxane having hydrogen atoms bonded to silicon atoms. (B) The viscosity and degree of polymerization of component (B) are not particularly limited and can be selected according to the required mixed viscosity of the thermally conductive silicone composition, for example, it may contain an organopolysiloxane having two or more hydrogen atoms in one molecule and having a viscosity of 10 mPa·s or more and 7,000 mPa·s or less at 25°C.

[0045] The ratio of component (A) to component (B) may be within the range of SiH / SiVi, which is between 0.5 and 1.5. (A) The molar ratio [Si-H groups / alkenyl groups] of the total alkenyl groups bonded to silicon atoms in component A to the total Si-H groups contained in the entire thermally conductive silicone composition may be in the range of 0.5 or more and 1.5 or less.

[0046] The number of hydrogen atoms bonded to a silicon atom may be two or more, and the bonding site is not particularly limited. The hydrogen content (H content) of component (B) is not particularly limited, but in order to provide a thermally conductive member obtained by curing the thermally conductive silicone composition with sufficient elongation for practical use, the hydrogen content (H content) of component (B) is preferably 0.01 mmol / g or more and 4.0 mmol / g or less, more preferably 0.1 mmol / g or more and 2.0 mmol / g or less, and even more preferably 0.4 mmol / g or more and 1.0 mmol / g or less.

[0047] Component (B) may be an organohydrogenpolysiloxane. Component (B) forms a cured product by an addition reaction with an alkenyl group, and may have at least one hydrogen atom (hydrosilyl group) bonded to a silicon atom in the side chain of the molecule. Component (B) may function as a crosslinking agent. Preferably, the crosslinking agent has three or more hydrosilyl groups in one molecule, and may also have at least one hydrosilyl group in the side chain of the molecule. More preferably, the crosslinking agent is an organohydrogenpolysiloxane having five or more hydrosilyl groups, and may have 10 to 18 hydrosilyl groups. The organohydrogenpolysiloxane that is the crosslinking agent has at least two hydrosilyl groups in its side chain. The number of hydrosilyl groups at the end of the molecular chain can be zero to two, but two is economically preferable. 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 end of the molecular chain, off-terminus, or in the side chain. Other conditions, such as organic groups other than hydrosilyl groups, bond positions, degree of polymerization, and structure, are not particularly limited, and two or more organohydrogenpolysiloxanes may be used.

[0048] In the above-mentioned thermally conductive silicone composition, the content of component (B) is preferably in the range of 0.2 to 7, more preferably in the range of 0.3 to 2, and even more preferably in the range of 0.4 to 1.5, where the ratio of the number of hydrogen atoms (hydrosilyl groups) in component (B) to the number of alkenyl groups in component (A) is 0.2 to 7. Within this range, the thermally conductive silicone composition hardens sufficiently, the overall hardness of the cured product of the thermally conductive silicone composition becomes more suitable, and when used as a gap filler, it is less prone to cracking, and also has the advantage of combining flexibility and adhesiveness.

[0049] (B) The hydrogen atoms (hydrosilyl groups) in component (B) may be located at the molecular chain ends, at the side chains, or at both the molecular chain ends and the side chains. An organohydrogenpolysiloxane having hydrogen atoms (hydrosilyl groups) only at the molecular chain ends and an organohydrogenpolysiloxane having hydrogen atoms (hydrosilyl groups) only at the molecular chain side chains may be used in combination.

[0050] Component (B) may also contain an organohydrogenpolysiloxane having at least one aromatic group in its molecule, from the viewpoint of improving heat resistance. For economic reasons, a phenyl group is more preferable as the aromatic group. An aromatic group-containing organohydrogenpolysiloxane and an organohydrogenpolysiloxane without an aromatic group can also be used in mixture form.

[0051] The viscosity of component (B) at 25°C is 10 mPa·s or more and 7,000 mPa·s or less, preferably 20 mPa·s or more and 5,000 mPa·s or less, and more preferably 30 mPa·s or more and 500 mPa·s or less. To adjust the viscosity of the final product, the thermally conductive silicone composition, two or more diorganopolysiloxanes containing hydrogen atoms with different viscosities may be used. The mixed viscosity of the thermally conductive silicone composition may be in the range of 10 Pa·s to 1,000 Pa·s, more preferably in the range of 20 Pa·s to 500 Pa·s, and even more preferably in the range of 30 Pa·s to 200 Pa·s.

[0052] [(C) component] The first thermally conductive filler of component (C) is a filler component for improving the thermal conductivity of the thermally conductive silicone composition. In order to obtain a highly insulating gap filler for application to electronic substrates and the like, it is preferable to use a material for the first thermally conductive filler that is excellent not only in thermal conductivity but also in insulating properties. The first thermally conductive filler of component (C) is at least one thermally conductive filler selected from aluminum oxide (C1) and aluminum hydroxide (C2). The primary thermally conductive filler of component (C) is 30 parts by mass or more and 220 parts by mass or less per 100 parts by mass of the total of components (A) and (B).

[0053] [(C1) component] Aluminum oxide (C1) is quantified by atomic absorption spectrometry, with a hot water extract sodium oxide (Na2O) content of less than 300 ppm and an average particle size of less than 5 μm. The amount of aluminum oxide (C1) is 30 parts by mass or more and 220 parts by mass or less per 100 parts by mass of the total of components (A) and (B), preferably 40 parts by mass or more and 200 parts by mass or less, and more preferably 60 parts by mass or more and 180 parts by mass or less. Even when using only one type of aluminum oxide, two or more types with different shapes may be combined. For example, spherical aluminum oxide and amorphous aluminum oxide may be combined.

[0054] The average particle size is D50, which is the 50% particle size in the volume-based cumulative particle size distribution measured by a laser diffraction particle size analyzer. The same measurement method is used below unless otherwise specified. The median diameter may also be used.

[0055] [(C2) component] Aluminum hydroxide (C2) is quantified by atomic absorption spectrometry, with a hot water extract sodium oxide (Na2O) content of less than 70 ppm and an average particle size of less than 5 μm. The amount of aluminum hydroxide (C2) is 30 parts by mass or more and 220 parts by mass or less, preferably 40 parts by mass or more and 210 parts by mass or less, per 100 parts by mass of the total of components (A) and (B). Even when using only one type of aluminum hydroxide, two or more types with different shapes may be combined. For example, spherical aluminum hydroxide may be combined with amorphous aluminum hydroxide.

[0056] The aluminum hydroxide filler may be surface-treated. Surface treatments include, for example, treatment with long-chain alkyl fatty acids, silane coupling treatment, and titanium coupling agent treatment.

[0057] [(D) component] The second thermally conductive filler of component (D) is a filler component for improving the thermal conductivity of the thermally conductive silicone composition. In order to obtain a highly insulating gap filler for application to electronic substrates and the like, it is preferable to use a material for the second thermally conductive filler that is excellent not only in thermal conductivity but also in insulating properties. The second thermally conductive filler of component (D) is aluminum hydroxide, which has a hot water extracted sodium oxide (Na2O) content of less than 70 ppm and an average particle size of 5 μm to 100 μm, as quantified by atomic absorption spectrometry.

[0058] The aluminum hydroxide component (D) is in an amount of 400 parts by mass or more and 950 parts by mass or less, preferably 400 parts by mass or more and 750 parts by mass or less, and more preferably 400 parts by mass or more and 600 parts by mass or less, based on 100 parts by mass of the total of components (A) and (B). Even when using only one type of aluminum hydroxide, two or more types with different shapes may be combined. For example, spherical aluminum hydroxide may be combined with amorphous aluminum hydroxide.

[0059] The aluminum hydroxide filler may be surface-treated. Surface treatments include, for example, treatment with long-chain alkyl fatty acids, silane coupling treatment, and titanium coupling agent treatment.

[0060] The shape of the thermal conductive fillers in components (C) and (D) is not particularly limited and may be spherical, amorphous, fine powder, fibrous, flaky, etc. In order to incorporate the amount of thermal conductive filler necessary to increase the thermal conductivity of the thermal conductive member, the shape of the thermal conductive filler is preferably spherical, and the average particle size may be 1 to 100 μm. Here, "spherical" does not only mean perfectly spherical, but also rounded.

[0061] When using spheroidal aluminum oxide as components (C) and (D), α-alumina obtained by high-temperature thermal spraying or hydrothermal treatment of alumina hydrate may be used.

[0062] To improve the packing density of the thermally conductive fillers in components (C) and (D), it is more preferable to use spherical thermally conductive fillers and non-spherical thermally conductive fillers. Using at least two types of thermally conductive fillers with different shapes in combination allows for packing in a state close to close packing, resulting in a higher thermal conductivity. Using spherical and non-spherical thermally conductive fillers (for example, amorphous thermally conductive fillers) in combination makes it possible to further increase thermal conductivity.

[0063] The thermally conductive fillers of components (C) and (D) preferably have a thermal conductivity of 10 W / m·K or higher. If the thermal conductivity is less than 10 W / m·K, the thermal conductivity of the thermally conductive silicone composition itself may be reduced. In particular, if electrical insulation is required for the thermally conductive component, it is advisable to select a non-conductive thermally conductive filler.

[0064] The thermal conductive fillers of components (C) and (D) only need to be included in amounts necessary to increase the thermal conductivity of the thermal conductive member (for example, to be 2.0 W / m·K or higher). For example, when the total thermal conductive silicone composition is 100 parts by mass, the content of the thermal conductive filler may be 70 parts by mass or more and 95 parts by mass or less. Within the above range, the thermally conductive silicone composition as a whole has sufficient thermal conductivity, is easy to mix during compounding, maintains flexibility after curing, and does not have an excessively high specific gravity, making it more suitable as a thermally conductive silicone composition for forming thermally conductive members where thermal conductivity and lightweight properties are required. If the thermally conductive filler content is too low, it becomes difficult to sufficiently increase the thermal conductivity of the cured thermally conductive silicone composition. On the other hand, if the thermally conductive filler content is too high, the thermally conductive silicone composition becomes highly viscous, which may make it difficult to apply the thermally conductive silicone composition uniformly, and problems such as an increase in the thermal resistance value and a decrease in flexibility of the cured thermally conductive silicone composition may occur.

[0065] [(E) component] Component (E) is an addition catalyst that promotes the addition hardening reaction between the alkenyl group bonded to the silicon atom in component (A) and the hydrogen atom bonded to the silicon atom in component (B). Addition catalysts are known to those skilled in the art. Component (E) may include platinum group metals such as platinum, rhodium, palladium, osmium, iridium, and ruthenium, or these metals immobilized on a particulate support material (e.g., activated carbon, aluminum oxide, silicon oxide). Furthermore, component (E) can include platinum compounds such as platinum halides, platinum-olefin complexes, platinum-alcohol complexes, platinum-alkoxide complexes, platinum-vinylsiloxane complexes, dicyclopentadiene-platinum dichloride, cyclooctadiene-platinum dichloride, and cyclopentadiene-platinum dichloride.

[0066] Furthermore, from an economic standpoint, metal compound catalysts other than the platinum group metals mentioned above may be used as component (E). For example, examples of hydrosilylated iron catalysts include iron-carbonyl complex catalysts, iron catalysts having a cyclopentadienyl group as a ligand, iron catalysts having a terpyridine ligand or a terpyridine ligand and a bistrimethylsilylmethyl 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 with an unsaturated group, and iron catalysts having a cyclic or acyclic olefinyl group with an unsaturated group. Other examples include hydrosilylated cobalt catalysts, vanadium catalysts, ruthenium catalysts, iridium catalysts, samarium catalysts, nickel catalysts, and manganese catalysts.

[0067] The amount of component (E) used depends on the desired curing temperature and curing time for the application, but is generally in the range of 0.5 ppm to 1,000 ppm, more preferably 1 ppm to 500 ppm, and even more preferably 1 ppm to 100 ppm, relative to the total mass of the thermally conductive silicone composition. If the amount is less than 0.5 ppm, the addition reaction becomes significantly slower, while if the amount exceeds 1,000 ppm, the cost increases, making it economically undesirable.

[0068] The addition catalyst of component (E) is 0.2 parts by mass or more and 1.0 part by mass or less, preferably 0.25 parts by mass or more and 0.9 parts by mass or less, and more preferably 0.3 parts by mass or more and 0.8 parts by mass or less, based on 100 parts by mass of the total of components (A) and (B).

[0069] In the thermally conductive silicone composition, to the extent that it does not impair the purpose of this disclosure, further optional components other than the above components (A) to (E) may be used, which are conventionally known additives to silicone rubber and gels. Examples of such additives include organosilicon compounds, crosslinking agents, adhesion aids, pigments, dyes, reaction inhibitors, curing inhibitors, heat-resistant agents, flame retardants, antistatic agents, conductivity-imparting agents, airtightness-improving agents, radiation shielding agents, electromagnetic shielding agents, preservatives, stabilizers, organic solvents, plasticizers, antifungal agents, or organopolysiloxanes containing one silicon-bonded hydrogen atom or alkenyl group per molecule and not containing other functional groups, or non-functional organopolysiloxanes not containing silicon-bonded hydrogen atoms or alkenyl groups. These further optional components may be used individually or in combination of two or more. The thermally conductive silicone composition of the present invention may contain one or more of the following: octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), dodecamethylcyclohexasiloxane (D6), tetradecamethylcycloheptasiloxane (D7), and hexadecamethylcyclooctasiloxane (D8). The total content of each of (D4), (D5), (D6), (D7), and (D8) may be less than 0.1 parts by mass (i.e., less than 1,000 ppm) when the total amount of the first liquid and / or the total amount of the second liquid is 100 parts by mass.

[0070] Examples of optional coupling agents include silane coupling agents. Examples of silane coupling agents include organosilicon compounds or organosiloxanes having an organic group with 3 or more carbon atoms in one molecule, such as an epoxy group, alkyl group, aryl group, vinyl group, styryl group, methacrylic group, acrylic group, amino group, isocyanurate group, ureido group, mercapto group, isocyanate group, or acid anhydride, and a silicon atom-bonded alkoxy group. Examples of silane coupling agents include silane compounds such as octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, tris-(trimethoxysilylpropyl)isocyanurate, 3-ureidopropyltrialkoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-isocyanatetopropyltriethoxysilane, and 3-trimethoxysilylpropyl succinic anhydride. The silane compounds may be compounds that do not have a hydrosilyl group, and can be used individually or in combination of two or more. By treating the surface of the thermally conductive filler with the silane coupling agent, the affinity with the silicone polymer is improved, the viscosity of the composition can be reduced, and the packing ability of the thermally conductive filler can be improved. Therefore, by incorporating more thermally conductive filler, it is possible to improve the thermal conductivity.

[0071] The optional reaction inhibitor has the ability to adjust the curing rate of the addition reaction, and examples include acetylene compounds, hydrazines, triazoles, phosphines, and mercaptans. Any curing inhibitor conventionally known in the art that has 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. Silanes and silicone compounds having an amino group may also be used. The amount of reaction inhibitor used depends on the desired curing temperature and curing time for the application, but generally, when the total amount of components (A) and (B) is 100 parts by mass, the range of 0.1 to 15 parts by mass is desirable. Preferably, the range is 0.2 to 10 parts by mass, and more preferably 0.3 to 5 parts by mass. If the amount is less than 0.1 parts by mass, the addition reaction will be significantly faster, and the curing reaction may proceed during the application process, potentially worsening workability. On the other hand, if it exceeds 10 parts by mass, the addition reaction will be slower, and there is a risk of pump-out.

[0072] The optional crosslinking agent can be an organohydrogenpolysiloxane. The crosslinking agent component forms a cured product by an addition reaction with an alkenyl group, and may have at least one hydrogen atom (hydrosilyl group) bonded to a silicon atom in the side chain of the molecule. Preferably, the crosslinking agent has three or more hydrosilyl groups in one molecule, and at least one hydrosilyl group in the side chain of the molecule. The crosslinking agent of the present invention is more preferably an organohydrogenpolysiloxane having five or more hydrosilyl groups, and may also have 10 to 15 hydrosilyl groups. The organohydrogenpolysiloxane that is the crosslinking agent has at least two hydrosilyl groups in its side chain. The number of hydrosilyl groups at the end of the molecular chain can be zero to two, but two is economically preferable. 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; it may be at the end of the molecular chain, a non-terminant, or a side chain. Other conditions, such as organic groups other than hydrosilyl groups, bond positions, degree of polymerization, and structure, are not particularly limited, and two or more organohydrogenpolysiloxanes may be used. The amount of crosslinking agent should be such that it is necessary to form a matrix containing components (A) and (B) by crosslinking. The amount of crosslinking agent component may be 0.1 parts by mass or more and 10 parts by mass or less, more preferably 0.2 parts by mass or more and 6 parts by mass or less, and even more preferably 0.4 parts by mass or more and 4 parts by mass or less, when the total amount of components (A) and (B) is 100 parts by mass.

[0073] The optional component adhesive condensation catalyst is an alkoxy compound, and is preferably an alkoxy compound containing Ti or Zr, for example. The adhesive condensation catalyst is in an amount of 0.1 parts by mass or more and 1.5 parts by mass or less, preferably 0.2 parts by mass or more and 1.2 parts by mass or less, and more preferably 0.3 parts by mass or more and 1.0 part by mass or less, per 100 parts by mass of the total of components (A) and (B). An "adhesion condensation catalyst" is a catalyst for condensation reactions that imparts adhesive properties.

[0074] (base material) The substrate may be one or more selected from glass, metal, ceramics, and resin. The metal substrate to which the thermally conductive silicone composition adheres is preferably a metal substrate selected from aluminum, magnesium, iron, nickel, titanium, stainless steel, copper, lead, zinc, molybdenum, and silicon. The ceramic substrate to which the thermally conductive silicone composition adheres is preferably made of aluminum oxide, aluminum nitride, alumina zirconia, zirconium oxide, zinc oxide, barium titanate, lead zirconate titanate, beryllium oxide, silicon nitride, silicon carbide, or other oxides, carbides, or nitrides. The resin substrate to which the thermally conductive silicone composition hardens and adheres is preferably a resin substrate selected from polyester, epoxy, polyamide, polyimide, ester, polyacrylamide, acrylonitrile-butadiene-styrene (ABS), styrene, polypropylene, polyacetal, acrylic, polycarbonate (PC), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyetheretherketone (PEEK), polymethyl methacrylate (PMMA), and silicone. When the heat-conductive member obtained by curing a heat-conductive silicone composition is a gap filler for a battery unit, the battery unit housing, which is the substrate to be bonded, may have an iron surface on which at least a portion is covered by cationic electrodeposition coating, or it may have an aluminum surface as a heat sink. The thermally conductive silicone composition is injected to fill the gap between the iron surface and the aluminum surface, which are coated by cationic electrodeposition coating, and hardens to provide a gap filler.

[0075] Electrical and electronic equipment are not particularly limited and include, for example, mobile phones, smartphones, tablets, smartwatches, computers, semiconductor package substrates, electronic circuit boards, LED package substrates, sensor substrates, image sensor substrates, liquid crystal substrates, organic EL substrates, etc.

[0076] <Examples> Examples will be described below, but the invention is not limited to these examples. The viscosities described herein are values ​​measured using a rotational viscometer (JIS K7117-2) at 25°C and a shear rate of 10 / s.

[0077] The first and second solutions shown in the examples and comparative examples were prepared, respectively. Figure 1A shows the mixing ratio of the first and second solutions for Examples 1 to 12, and Figure 1B shows the parts by mass of each component based on component (A) of the first solution and the parts by mass of each component based on the sum of components (A) and (B) of the second solution. Figure 2A shows the mixing ratio of the first and second solutions for Comparative Examples 1 to 8, and Figure 2B shows the parts by mass of each component based on component (A) of the first solution and the parts by mass of each component based on the sum of components (A) and (B) of the second solution.

[0078] [1st liquid] The following were weighed and added: (A) a diorganopolysiloxane having an alkenyl group, (E) a platinum-divinyltetramethyldisiloxane complex, hexadecyltrimethoxysilane as a silane coupling agent for any (F1) component, (F4) a condensation catalyst, and (F5) a pigment. The mixture was then kneaded at room temperature for 30 minutes using a planetary mixer. Component (A) is a linear dimethylpolysiloxane (A-1) having one alkenyl group at each end and a viscosity of 120 mPa·s. Subsequently, half of the amounts of component (C) and component (D) relative to the total amount of the composition were added and mixed using a planetary mixer at room temperature for 15 minutes to prepare the first liquid.

[0079] [Second liquid] As component (A), a diorganopolysiloxane (A-1) having the same alkenyl groups as in the first solution, and a linear dimethylpolysiloxane (A-2) with a viscosity of 1,000 mPa·s were added. As component (B), a linear diorganopolysiloxane with a viscosity of 70 mPa·s having one hydrogen atom at each end, for a total of two hydrogen atoms (hydrogen content is 0.5 mmol / g) was added. As optional components, an oligomer which is a hydrolysis product of tetraethoxysilane, a silane coupling agent (F1), a reaction inhibitor (F2) which is a diorganosiloxane with a viscosity of 50 mPa·s having two or more alkenyl groups, and a crosslinking agent (F3) were weighed and added, and mixed at room temperature for 30 minutes using a planetary mixer. The silane coupling agent (F1) is the same as in the first solution. The crosslinking agent (F3) is a dimethylpolysiloxane with a viscosity of 200 mPa·s, having 12 to 18 hydrogen atoms bonded to silicon atoms in its side chains. Subsequently, the same thermally conductive fillers (C) and (D) as in the first solution were added and mixed using a planetary mixer at room temperature for 15 minutes to prepare the second solution. The surface treatment of aluminum oxide or aluminum hydroxide is a hydrophobic treatment using long-chain alkyl fatty acids.

[0080] <Method for measuring tensile shear bond stress> A thermally conductive silicone composition is sandwiched between an aluminum test piece and a cationic electrodeposited iron test piece, with a coating area of ​​25 mm x 25 mm and a thickness of 0.8 mm. The mixture is then cured at 23°C for 24 hours to obtain a test piece for tensile shear adhesion testing. The aforementioned tensile shear adhesion test specimens are subjected to a tensile shear adhesion test in accordance with JIS K6850, and an S-S curve graph is obtained. In the S-S curve graph, the maximum stress value is taken as the tensile shear adhesion stress of the cured silicone composition corresponding to each tensile shear adhesion test specimen.

[0081] <Method for measuring thermal conductivity> The first and second liquids shown in the examples and comparative examples were measured in a 1:1 ratio, thoroughly mixed with a stirrer, and then degassed with a vacuum pump. This mixture was poured into a cylindrical press mold with a diameter of 30 mm and a height of 6 mm, 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 machine [TPS-500, manufactured by Kyoto Electronics Manufacturing Co., Ltd.] that measures by the hot disk method in accordance with ISO 22007-2. Sensors were placed between the two cylindrical cured products prepared above, and the thermal conductivity was measured using the above apparatus. The thermal conductivity is preferably 2.0 W / m·k or higher.

[0082] <Method for measuring viscosity> These values ​​were measured at 25°C, with a shear rate of 10 / s and a gap of 0.5 mm, using a rotational viscometer (JIS K7117-2).

[0083] <Method for measuring Asker C hardness> The first and second liquids shown in the examples and comparative examples were measured in a 1:1 ratio, thoroughly mixed with a stirrer, and then degassed with a vacuum pump. This mixture was then poured into a cylindrical press mold with a diameter of 30 mm and a height of 6 mm, and cured at 100°C for 60 minutes to produce a cylindrical cured product. Asker C hardness was measured in accordance with the Asker C method of the Japan Rubber Association standard (SRIS 0101), using a hardness tester (manufactured by Polymer Instruments Co., Ltd., product name "ASKER CL-150LJ") at a temperature of 23°C. Specifically, the damper height was adjusted so that the distance between the obtained cylindrical hardened material and the pointer was 15 mm, and the damper drop speed was adjusted so that the time it took for the pointer to reach the surface of the test specimen was 5 seconds. The maximum value when the pointer hit the test specimen was taken as the measured value of Asker C hardness. Three measurements were taken using the above hardness tester, and the average value of the measurement results was adopted. Generally, a lower Asker C hardness indicates higher flexibility. The Asker C hardness of the hardened material is preferably in the range of 50 to 70.

[0084] <Ingredients> (A-1) A linear dimethylpolysiloxane having one alkenyl group at each end and a viscosity of 120 mPa·s. (A-2) A linear dimethylpolysiloxane having at least one alkenyl group and a viscosity of 1,000 mPa·s. (B-1) A linear diorganopolysiloxane with a viscosity of 70 mPa·s, having one hydrogen atom at each end and a total of two hydrogen atoms.

[0085] (C1-1) Aluminum oxide with a sodium oxide (Na2O) concentration of less than 300 ppm extracted with hot water. (C1-2) Aluminum oxide with a sodium oxide (Na2O) concentration of less than 300 ppm extracted with hot water. (C1-3) Aluminum oxide with a sodium oxide (Na2O) concentration of 300 ppm or higher extracted with hot water.

[0086] (C2-1) Aluminum hydroxide with a sodium oxide (Na2O) concentration of less than 70 ppm extracted with hot water. (C2-2) Aluminum hydroxide with a sodium oxide (Na2O) concentration of less than 70 ppm extracted with hot water. (C2-3) Aluminum hydroxide with a sodium oxide (Na2O) concentration of less than 70 ppm extracted with hot water. (C2-4) Aluminum hydroxide with a sodium oxide (Na2O) concentration of 70 ppm or higher, extracted with hot water. (C2-5) Aluminum hydroxide with a sodium oxide (Na2O) concentration of 70 ppm or higher, extracted with hot water.

[0087] (D1-1) Aluminum hydroxide with a sodium oxide (Na2O) concentration of less than 70 ppm extracted with hot water. (D1-2) Aluminum hydroxide with a sodium oxide (Na2O) concentration of less than 70 ppm extracted with hot water. (D1-3) Aluminum hydroxide with a sodium oxide (Na2O) concentration of less than 70 ppm extracted with hot water. (D1-4) Aluminum hydroxide with a sodium oxide (Na2O) concentration of less than 70 ppm extracted with hot water. (D1-5) Aluminum hydroxide with a sodium oxide (Na2O) concentration of less than 70 ppm extracted with hot water. (D1-6) Aluminum hydroxide with a sodium oxide (Na2O) concentration of 70 ppm or higher extracted with hot water. (D1-7) Aluminum hydroxide with a sodium oxide (Na2O) concentration of 70 ppm or higher extracted with hot water.

[0088] (E) Platinum-divinyltetramethyldisiloxane complex (F1) Silane coupling agent (hexadecyltrimethoxysilane) (F2) Reaction inhibitor (diorganosiloxane with a viscosity of 50 mPa·s and containing two or more alkenyl groups) (F3) Crosslinking agent (dimethylpolysiloxane with a viscosity of 200 mPa·s, having 12 to 18 hydrogen atoms bonded to silicon atoms in its side chains) (F4) Alkoxy group-containing titanium chelate compound (F5) Pigment

[0089] (evaluation) Figure 1C shows the mixing ratios and measurement results for Examples 1 to 12, in which the first and second solutions were integrated, and Figure 1D shows the parts by mass data and measurement results based on components (A) and (B). Figure 2C shows the mixing ratios and measurement results for Comparative Examples 1 to 8, in which the first and second solutions were integrated, and Figure 2D shows the parts by mass data and measurement results based on components (A) and (B). The measurement results show the tensile shear bonding stress (initial), the rate of decrease in tensile shear bonding stress, hardness (initial), the rate of decrease in hardness, thermal conductivity, and viscosity (when the first and second liquids were mixed before curing). The following measurement items were considered to have yielded favorable results. Tensile shear bonding stress (initial): 0.1 MPa or higher Tensile shear bond stress reduction rate: 30% or less Asker C Hardness (Initial): Range of 50 to 70 Asker C hardness reduction rate: 20% or less Thermal conductivity: 2.0 W / m·k or higher Viscosity: 50-200Pa·s

[0090] Table 1 shows the particle size of the filler, the conditions for the range of Na2O concentration extracted with hot water, and the evaluation results for Examples 1 to 12, and Table 2 shows the conditions for Comparative Examples 1 to 8. Examples 1 to 12 performed well in all evaluation items. On the other hand, Comparative Examples 1 to 8 showed higher-than-standard rates of decrease in both tensile shear adhesive stress and hardness. Comparative Examples 7 and 8 had viscosity outside the evaluation criteria.

[0091] [Table 1]

[0092] [Table 2]

Claims

1. (A) A diorganopolysiloxane containing an alkenyl group bonded to a silicon atom, (B) A diorganopolysiloxane having a hydrogen atom bonded to a silicon atom, (C) At least one thermally conductive filler selected from aluminum oxide (C1) with an average particle size of less than 5 μm and a hot water extracted sodium oxide content of less than 300 ppm, as quantified by atomic absorption spectrometry, and aluminum hydroxide (C2) with an average particle size of less than 5 μm and a hot water extracted sodium oxide content of less than 70 ppm, as quantified by atomic absorption spectrometry, wherein the first thermally conductive filler is present in an amount of 30 parts by mass or more and 220 parts by mass or less per 100 parts by mass of the total of components (A) and (B), (D) An aluminum hydroxide filler having an average particle size of 5 μm to 100 μm, wherein the sodium oxide content extracted with hot water is less than 70 ppm, as quantified by atomic absorption spectrometry, and comprising 400 parts by mass to 950 parts by mass of a second thermally conductive filler per 100 parts by mass of the total of components (A) and (B), (E) An addition catalyst in an amount of 0.2 parts by mass or more and 1.0 part by mass or less per 100 parts by mass of the total of component (A) and component (B), A thermally conductive silicone composition containing [a specific substance].

2. The thermally conductive silicone composition according to claim 1, wherein the ratio of component (A) to component (B) is in the range of SiH / SiVi, which is between 0.5 and 1.

5.

3. The thermally conductive silicone composition according to claim 1, wherein component (A) comprises an organopolysiloxane having a viscosity of 10 mPa·s or more and 7,000 mPa·s or less at 25°C.

4. The thermally conductive silicone composition according to claim 1, wherein component (B) comprises an organopolysiloxane having two or more hydrogen atoms in one molecule and having a viscosity of 10 mPa·s or more and 7,000 mPa·s or less at 25°C.

5. The thermally conductive silicone composition according to claim 1, further comprising an adhesive condensation catalyst, wherein the adhesive condensation catalyst is an alkoxy compound containing Ti or Zr.

6. The thermally conductive silicone composition according to claim 1, wherein the thermal conductivity of the thermally conductive silicone composition or its cured product is 2.0 W / m·k or higher.

7. The thermally conductive silicone composition according to claim 1, wherein the rate of reduction in tensile shear adhesive stress of the cured product of the thermally conductive silicone composition is 30% or less.

8. The thermally conductive silicone composition according to claim 1, wherein the rate of decrease in hardness of the cured product of the thermally conductive silicone composition is 20% or less.

9. The aforementioned thermally conductive silicone composition, The thermal conductive silicone composition according to claim 1, comprising a first liquid and a second liquid packaged separately from each other, wherein the first liquid and the second liquid are mixed at the time of use to form a thermal conductive silicone composition.

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