Thermally conductive silicone composition and cured product thereof

Abstract

To provide a thermally conductive silicone composition and a cured product thereof having superior insulation, thermal conductivity, and processability.SOLUTION: A thermally conductive silicone composition comprising: (A) 100 pts.mass of an organopolysiloxane having at least two alkenyl groups per molecule, the component (A) consisting of components (A-1) and (A-2), wherein the ratio (A-1) / (A-2) is 70 / 30 to 0 / 100 by mass ratio; components (A-1) and (A-2) being two types of alkenyl group-containing organopolysiloxanes each having a main chain composed of repeating diorganosiloxane units, differing in average degree of polymerization and kinematic viscosity at 25°C; (B) an organohydrogenpolysiloxane having at least two hydrogen atoms each directly bonded to a silicon atom; (C) a thermally conductive filler consisting of components (C-1) to (C-4); (D) a platinum group metal-based curing catalyst; and (E) an addition reaction inhibitor.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a thermally conductive silicone composition and a cured product thereof. [Background technology]

[0002] In recent years, electronic components such as CPUs, driver ICs, and memory used in electronic devices such as smartphones, personal computers, and car navigation systems have become more powerful, smaller, and more highly integrated, resulting in the generation of large amounts of heat at high densities. With conventional technologies, these components can become so hot that they malfunction or fail. For this reason, many heat dissipation methods have been proposed to suppress temperature increases in electronic devices and components, and various heat-dissipating materials for use in these methods have been developed. In recent years, there has been a growing demand for heat-dissipating materials with excellent thermal conductivity.

[0003] Conventionally, in electronic devices, etc., heat sinks made of metal plates with high thermal conductivity such as aluminum or copper are used to suppress the temperature rise of chips during operation. These heat sinks conduct heat generated by the chips and release the heat from their surfaces due to the temperature difference with the outside air. Furthermore, in order to efficiently transfer the heat generated by the heat-generating components to the heat sink, the heat sink needs to be in close contact with the heat-generating components. However, due to differences in the height of each component and tolerances due to assembly processing, flexible sheets or grease are placed between the components and the heat sink, and heat is conducted to the heat sink via these materials.

[0004] There are many different types of heat dissipation materials, and many different materials have been proposed, including heat dissipation grease and flexible heat dissipation sheets. Sheet-type materials are sandwiched between release films, and are easy to handle as they do not require heating during use. For example, an insulating composition has been disclosed in which 100 parts by mass of synthetic rubber such as silicone rubber is blended with at least one metal oxide selected from beryllium oxide, aluminum oxide, hydrated aluminum oxide, magnesium oxide, and zinc oxide (Patent Document 1).

[0005] Flexible heat dissipation sheets are easier to handle than grease, and thermally conductive sheets are used in a variety of fields.

[0006] Silicone is known as a material that is particularly excellent in heat resistance, weather resistance, and flame retardancy, and a silicone-based thermally conductive silicone rubber sheet with a thermal conductivity of 5.5 W / m·K or more has been proposed (Patent Document 2).

[0007] These high thermal conductive silicone rubber sheets are made by curing a composition consisting of a thermally conductive filler and silicone and molding it into a sheet, but if the viscosity of the composition is too high, the composition will not spread sufficiently during press molding, and will not spread to the standard sheet size.On the other hand, if the rubber elasticity of the composition is low, the release properties will be poor when the sheet is made, and the cured product will adhere to the release film when it is peeled off.

[0008] One way to solve this problem is to increase the amount of plasticizer, but adding too much plasticizer reduces the sheet strength and processability. It also increases the risk of oil bleeding, leaving oil on the release film. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 47-032400 [Patent Document 2] Japanese Patent Publication No. 2022-174600 Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been made to solve the above problems, and has as its object to provide a thermally conductive silicone composition and a cured product thereof that have excellent insulating properties, thermal conductivity, and processability, and in particular, a cured product thereof that has excellent film releasability. [Means for solving the problem]

[0011] In order to solve the above problems, the present invention provides a thermally conductive silicone composition containing the following components, and a cured product thereof.

[0012] That is, the present invention provides: A thermally conductive silicone composition comprising: (A) 100 parts by mass of an organopolysiloxane having at least two alkenyl groups per molecule, which comprises the following components (A-1) and (A-2), with a mass ratio of (A-1) / (A-2) of 70 / 30 to 0 / 100: (A-1) The main chain consists of repeating diorganosiloxane units, the average degree of polymerization is 145 to 220, and the kinematic viscosity at 25°C is 400 to 1,000 mm 2 / s alkenyl group-containing organopolysiloxane, (A-2) The main chain consists of repeating diorganosiloxane units, the average degree of polymerization is 450 to 1,100, and the kinematic viscosity at 25°C is 5,000 to 100,000 mm 2 / s alkenyl group-containing organopolysiloxane, (B) an organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to silicon atoms: an amount such that the number of moles of hydrogen atoms directly bonded to silicon atoms is 0.1 to 5.0 times the number of moles of alkenyl groups derived from component (A); (C) 3,900 to 6,000 parts by mass of a thermally conductive filler consisting of the following components (C-1) to (C-4): (C-1) Spherical alumina filler having an average particle size of more than 65 μm and not more than 135 μm: 1,400 to 3,000 parts by mass, (C-2) Spherical alumina filler having an average particle size of more than 30 μm and not more than 65 μm: 500 to 1,500 parts by mass, (C-3) Spherical alumina filler having an average particle size of more than 4 μm and not more than 30 μm: 300 to 900 parts by mass, (C-4) Irregular shaped alumina filler having an average particle size of more than 0.4 μm and not more than 4 μm: 1,000 to 1,900 parts by mass, (D) a platinum group metal curing catalyst: 0.1 to 2,000 ppm by mass of platinum group metal element relative to the component (A), and (E) addition reaction inhibitor: 0.005 to 2.0 parts by mass, The thermally conductive silicone composition is characterized by comprising:

[0013] Such a thermally conductive silicone composition can provide a thermally conductive silicone composition and a cured product thereof that are excellent in insulating properties, thermal conductivity, processability, and film releasability.

[0014] The thermally conductive silicone composition further contains, as component (F), (F-1) an alkoxysilane compound represented by the following general formula (1), and R 1 a R 2 b Si(OR 3 ) 4-a-b (1) (In the formula, R 1 are independently alkyl groups having 6 to 15 carbon atoms, and R 2 are independently unsubstituted or substituted monovalent hydrocarbon groups having 1 to 12 carbon atoms, and R 3 are independently an alkyl group having 1 to 6 carbon atoms, a is an integer of 1 to 3, and b is an integer of 0 to 2, with the proviso that a+b is an integer of 1 to 3. (F-2) a dimethylpolysiloxane represented by the following general formula (2) in which one molecular chain terminal is blocked with a trialkoxysilyl group: [ka] (In the formula, R 4 are independently alkyl groups having 1 to 6 carbon atoms, and c is an integer of 5 to 100. It is preferable that at least one selected from the group consisting of the following is contained in an amount of 0.01 to 300 parts by mass per 100 parts by mass of the component (A).

[0015] In such a thermally conductive silicone composition, the thermally conductive filler (component (C)) is uniformly dispersed within the matrix made of component (A), and oil separation is not induced.

[0016] The thermally conductive silicone composition of the present invention preferably has a viscosity at 23°C of 1,000 Pa·s or less.

[0017] Such a thermally conductive silicone composition exhibits excellent processability.

[0018] The present invention also provides a cured thermally conductive silicone product, which is a cured product of the thermally conductive silicone composition described above.

[0019] The cured product of the thermally conductive silicone composition of the present invention is a thermally conductive silicone cured product that exhibits excellent insulating properties, thermal conductivity, processability, and mold releasability.

[0020] The thermally conductive silicone composition of the present invention preferably has a thermal conductivity at 23°C of 5.5 W / m·K or greater.

[0021] Such thermally conductive silicone cured products have particularly excellent thermal conductivity and are suitable as heat dissipation materials, etc.

[0022] The thermally conductive silicone cured product of the present invention preferably has a breakdown voltage of 10 kV / mm or more at a thickness of 1 mm.

[0023] Such a thermally conductive silicone cured product can ensure stable insulation during use.

[0024] The thermally conductive silicone cured product of the present invention is preferably in the form of a sheet.

[0025] The thermally conductive silicone cured product of the present invention is preferably used in the form of a sheet.

[0026] The thermally conductive silicone cured product preferably has a hardness of 3 to 40 as measured with an Asker C hardness tester.

[0027] Such a thermally conductive silicone cured product deforms to fit the shape of the object to be heat dissipated, and exhibits good heat dissipation properties without applying stress to the object to be heat dissipated. [Effects of the Invention]

[0028] As described above, the thermally conductive silicone composition of the present invention can provide a thermally conductive silicone cured product that exhibits excellent insulating properties, thermal conductivity, and processability. It can also provide a thermally conductive silicone cured product that exhibits excellent mold releasability. Furthermore, it can provide a composition that deforms to fit the shape of a heat-dissipating object and exhibits good heat dissipation properties without applying stress to the heat-dissipating object. It can also provide a composition that is easy to handle, has good low-temperature properties, and is resistant to oil separation. It can also provide a composition that causes little wear to the reaction vessel or stirring blades during production. DETAILED DESCRIPTION OF THE INVENTION

[0029] As described above, there has been a need for the development of a thermally conductive silicone composition and cured product that exhibits excellent insulating properties, thermal conductivity, processability, and mold releasability.

[0030] As a result of extensive research into achieving the above object, the inventors discovered that by reducing the proportion of oil with a low average degree of polymerization and low kinetic viscosity and increasing the proportion of oil with a high average degree of polymerization and high kinetic viscosity, the rubber elasticity of the cured thermally conductive silicone product is increased, the film releasability of the cured silicone product is improved, and the transfer of materials to the release film can be prevented, leading to the completion of the present invention.

[0031] A thermally conductive silicone composition comprising: (A) 100 parts by mass of an organopolysiloxane having at least two alkenyl groups per molecule, which comprises the following components (A-1) and (A-2), with a mass ratio of (A-1) / (A-2) of 70 / 30 to 0 / 100: (A-1) The main chain consists of repeating diorganosiloxane units, the average degree of polymerization is 145 to 220, and the kinematic viscosity at 25°C is 400 to 1,000 mm 2 / s alkenyl group-containing organopolysiloxane, (A-2) The main chain consists of repeating diorganosiloxane units, the average degree of polymerization is 450 to 1,100, and the kinematic viscosity at 25°C is 5,000 to 100,000 mm 2 / s alkenyl group-containing organopolysiloxane, (B) an organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to silicon atoms: an amount such that the number of moles of hydrogen atoms directly bonded to silicon atoms is 0.1 to 5.0 times the number of moles of alkenyl groups derived from component (A); (C) 3,900 to 6,000 parts by mass of a thermally conductive filler consisting of the following components (C-1) to (C-4): (C-1) Spherical alumina filler having an average particle size of more than 65 μm and not more than 135 μm: 1,400 to 3,000 parts by mass, (C-2) Spherical alumina filler having an average particle size of more than 30 μm and not more than 65 μm: 500 to 1,500 parts by mass, (C-3) Spherical alumina filler having an average particle size of more than 4 μm and not more than 30 μm: 300 to 900 parts by mass, (C-4) Irregular shaped alumina filler having an average particle size of more than 0.4 μm and not more than 4 μm: 1,000 to 1,900 parts by mass, (D) a platinum group metal curing catalyst: 0.1 to 2,000 ppm by mass of platinum group metal element relative to the component (A), and (E) addition reaction inhibitor: 0.005 to 2.0 parts by mass, and a cured product thereof.

[0032] The present invention will be described in detail below, but the present invention is not limited thereto.

[0033] [Thermal conductive silicone composition] (A) 100 parts by mass of an organopolysiloxane having at least two alkenyl groups per molecule, which comprises the following components (A-1) and (A-2), with a mass ratio of (A-1) / (A-2) of 70 / 30 to 0 / 100: (A-1) The main chain consists of repeating diorganosiloxane units, the average degree of polymerization is 145 to 220, and the kinematic viscosity at 25°C is 400 to 1,000 mm 2 / s alkenyl group-containing organopolysiloxane, (A-2) The main chain consists of repeating diorganosiloxane units, the average degree of polymerization is 450 to 1,100, and the kinematic viscosity at 25°C is 5,000 to 100,000 mm 2 / s alkenyl group-containing organopolysiloxane, (B) an organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to silicon atoms: an amount such that the number of moles of hydrogen atoms directly bonded to silicon atoms is 0.1 to 5.0 times the number of moles of alkenyl groups derived from component (A); (C) 3,900 to 6,000 parts by mass of a thermally conductive filler consisting of the following components (C-1) to (C-4): (C-1) Spherical alumina filler having an average particle size of more than 65 μm and not more than 135 μm: 1,400 to 3,000 parts by mass, (C-2) Spherical alumina filler having an average particle size of more than 30 μm and not more than 65 μm: 500 to 1,500 parts by mass, (C-3) Spherical alumina filler having an average particle size of more than 4 μm and not more than 30 μm: 300 to 900 parts by mass, (C-4) Irregular shaped alumina filler having an average particle size of more than 0.4 μm and not more than 4 μm: 1,000 to 1,900 parts by mass, (D) a platinum group metal curing catalyst: 0.1 to 2,000 ppm by mass of platinum group metal element relative to the component (A), and (E) addition reaction inhibitor: 0.005 to 2.0 parts by mass, As an essential component, the composition may also contain other components such as (F) a surface treatment agent. Each component will be described in detail below.

[0034] [(A) Organopolysiloxane having an alkenyl group] Component (A) is an alkenyl group-containing organopolysiloxane, which forms the base component of the thermally conductive silicone composition of the present invention. Component (A) contains at least two silicon-bonded alkenyl groups per molecule.

[0035] Examples of functional groups other than alkenyl groups bonded to silicon atoms include the monovalent hydrocarbon groups exemplified below. Examples include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, heptyl, octyl, nonyl, decyl, and dodecyl; cycloalkyl groups such as cyclopentyl, cyclohexyl, and cycloheptyl; aryl groups such as phenyl, tolyl, xylyl, naphthyl, and biphenylyl; and aralkyl groups such as benzyl, phenylethyl, phenylpropyl, and methylbenzyl. Among these monovalent hydrocarbon groups, those having 1 to 10 carbon atoms, and more preferably 1 to 6 carbon atoms, are preferred. Among these, alkyl groups having 1 to 3 carbon atoms, such as methyl, ethyl, and propyl, and phenyl groups are preferred. Furthermore, the functional groups other than alkenyl groups bonded to silicon atoms do not necessarily have to be the same.

[0036] Examples of alkenyl groups include those typically having about 2 to 8 carbon atoms, such as vinyl, allyl, propenyl, isopropenyl, butenyl, hexenyl, and cyclohexenyl groups, and among these, lower alkenyl groups such as vinyl and allyl are preferred, with vinyl being particularly preferred. Although two or more alkenyl groups are present in a molecule, it is preferred that they be bonded only to silicon atoms at the molecular chain terminals in order to improve the flexibility of the resulting cured product.

[0037] Component (A-1) has a main chain consisting of repeating diorganosiloxane units, an average degree of polymerization of 145 to 220, and a kinematic viscosity at 25°C of 400 to 1,000 mm 2 / s is an alkenyl group-containing organopolysiloxane. The average degree of polymerization of the component (A-1) is 145 to 220, preferably 150 to 200, and more preferably 160 to 190. If the average degree of polymerization is less than 145, the mold releasability of the cured product will be poor, and if it is more than 220, the viscosity of the composition will be high. The kinematic viscosity of component (A-1) at 25°C is 400 to 1,000 mm 2 / s, preferably 500 to 900 mm 2 / s, and more preferably 600 to 800 mm 2 / s. The kinematic viscosity is 400mm 2 If it is less than 1,000mm / s, the rubber elasticity will be low. 2 If it is greater than / s, the viscosity of the composition will be high. The component (A-1) may be used alone or in combination of two or more.

[0038] Component (A-2) has a main chain consisting of repeating diorganosiloxane units, an average degree of polymerization of 450 to 1,100, and a kinematic viscosity at 25°C of 5,000 to 100,000 mm 2 / s is an alkenyl group-containing organopolysiloxane. The average degree of polymerization of component (A-2) is 450 to 1,100, preferably 600 to 900, and more preferably 700 to 800. If the average degree of polymerization is less than 450, the mold releasability of the cured product will be poor, and if it is more than 1,100, the viscosity of the composition will be high. The kinematic viscosity of component (A-2) at 25°C is 5,000 to 100,000 mm 2 / s, preferably 10,000 to 70,000 mm 2 / s, and more preferably 20,000 to 50,000 mm 2 / s. The kinematic viscosity is 5,000mm 2 If it is less than 100,000 mm2 / s, the release properties of the cured product will be poor, and if it is more than 100,000 mm2 / s, the viscosity of the composition will be high. The component (A-2) may be used alone or in combination of two or more.

[0039] The mass ratio of (A-1) / (A-2) is 70 / 30 to 0 / 100, preferably 65 / 35 to 30 / 70, and more preferably 60 / 40 to 40 / 60. When the mass ratio of (A-1) / (A-2) is greater than 70 / 30, the resulting cured product has excellent compressibility and releasability.

[0040] In this specification, the average degree of polymerization can usually be determined by calculation from the weight-average degree of polymerization (or weight-average molecular weight) in terms of polystyrene measured by gel permeation chromatography (GPC) analysis using toluene as a developing solvent. [Measurement conditions] Developing solvent: toluene Flow rate: 1mL / min Detector: Refractive index detector (RI) Column: KF-805L x 2 (Shodex) Column temperature: 25℃ Sample injection volume: 30 μL (0.2% by mass toluene solution)

[0041] In this specification, the kinematic viscosity is a value measured at 25°C using a Cannon-Fenske viscometer according to the method described in JIS Z 8803:2011.

[0042] [(B) Organohydrogenpolysiloxane] The organohydrogenpolysiloxane of component (B) is an organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to silicon atoms. That is, it is an organohydrogenpolysiloxane having at least two, preferably 2 to 100, hydrogen atoms (hydrosilyl groups) directly bonded to silicon atoms per molecule, and it functions as a crosslinker for component (A). Specifically, the hydrosilyl groups in component (B) and the alkenyl groups in component (A) undergo addition via a hydrosilylation reaction promoted by the platinum group metal curing catalyst of component (D), described below, to form a three-dimensional network structure with a crosslinked structure. Note that if the number of hydrosilyl groups is less than two, the composition will not cure.

[0043] The organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to silicon atoms is represented by the following average structural formula (3), but is not limited thereto. [ka] (In the formula, R 5 are independently a hydrogen atom or a monovalent hydrocarbon group selected from an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, and an aralkyl group having 7 to 12 carbon atoms. However, there are two or more, preferably two to ten, R 5 is a hydrogen atom, and e is an integer of 1 or more, preferably an integer of 10 to 200.

[0044] In formula (3), R 5 are independently a hydrogen atom or a monovalent hydrocarbon group selected from an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, and an aralkyl group having 7 to 12 carbon atoms. 5Examples of monovalent hydrocarbon groups other than hydrogen atoms include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, heptyl, octyl, nonyl, decyl, and dodecyl; cycloalkyl groups such as cyclopentyl, cyclohexyl, and cycloheptyl; aryl groups such as phenyl, tolyl, xylyl, naphthyl, and biphenylyl; and aralkyl groups such as benzyl, phenylethyl, phenylpropyl, and methylbenzyl. Among these monovalent hydrocarbon groups, those having 1 to 10 carbon atoms are preferred, with those having 1 to 6 carbon atoms being particularly preferred. Of these, alkyl groups having 1 to 3 carbon atoms, such as methyl, ethyl, and propyl, and phenyl are preferred. Furthermore, R 5 The integers e are not necessarily all the same. Furthermore, e is an integer of 1 or more, preferably an integer of 10 to 200.

[0045] The amount of component (B) added is such that the number of hydrosilyl groups derived from component (B) is 0.1 to 5.0 moles per mole of alkenyl groups derived from component (A), i.e., such that the number of moles of hydrogen atoms directly bonded to silicon atoms is 0.1 to 5.0 times the number of moles of alkenyl groups derived from component (A), preferably 0.3 to 2.0 moles, and more preferably 0.5 to 1.0 moles. If the number of Si-H groups derived from component (B) is less than 0.1 mole per mole of alkenyl groups derived from component (A), the composition may not cure, or the strength of the cured product may be insufficient to maintain its shape as a molded product, making it difficult to handle. If the number of Si-H groups derived from component (B) is more than 5.0 moles, the cured product may lose flexibility and become brittle.

[0046] [(C) Thermally conductive filler] The thermally conductive filler, which is component (C), is composed of the following components (C-1) to (C-4). (C-1) Spherical alumina filler having an average particle size of more than 65 μm and not more than 135 μm; (C-2) Spherical alumina filler having an average particle size of more than 30 μm and not more than 65 μm; (C-3) Spherical alumina filler having an average particle size of more than 4 μm and not more than 30 μm; (C-4) irregular alumina filler having an average particle size of more than 0.4 μm and not more than 4 μm; In the present invention, the average particle size is a volume-based cumulative average particle size (median diameter) measured by a laser diffraction / scattering method using a particle size analyzer, Microtrac MT3300EX, manufactured by Nikkiso Co., Ltd.

[0047] The spherical alumina filler of component (C-1) can significantly improve thermal conductivity. The average particle size of the spherical alumina filler is more than 65 μm and not more than 135 μm, and preferably 70 to 120 μm. If the average particle size of the spherical alumina filler of component (C-1) is greater than 135 μm, wear of the reaction vessel and stirring blades becomes significant, and the insulating properties of the composition deteriorate. As the spherical alumina of component (C-1), one type or a combination of two or more types may be used. When two or more types are used in combination, it is sufficient that each satisfies the above-mentioned average particle size range.

[0048] The spherical alumina fillers of components (C-2) and (C-3) improve the thermal conductivity of the composition and also provide a barrier effect by preventing contact between the amorphous alumina filler and the reaction vessel or stirring blades, thereby reducing wear. The average particle size of component (C-2) is greater than 30 μm and not greater than 65 μm, preferably 35 to 60 μm, while that of component (C-3) is greater than 4 μm and not greater than 30 μm, preferably 7 to 25 μm. If the average particle size of the spherical alumina filler is 4 μm or less, the barrier effect decreases, and wear of the reaction vessel or stirring blades due to the amorphous particles becomes significant. The spherical alumina of components (C-2) and (C-3) may be used alone or in combination of two or more types. When two or more types are used in combination, it is sufficient that each satisfies the above-mentioned average particle size range.

[0049] The amorphous alumina filler (C-4) also plays a role in improving the thermal conductivity of the composition, but its main role is to adjust the viscosity of the composition, improve smoothness, and improve filling properties. The average particle size of component (C-4) is more than 0.4 μm and not more than 4 μm, and more preferably 0.6 to 3 μm, in order to achieve the above-mentioned properties.

[0050] The amount of component (C-1) blended is 1,400 to 3,000 parts by mass, and preferably 1,800 to 2,500 parts by mass, per 100 parts by mass of component (A). If the amount of component (C-1) blended is too small, it becomes difficult to improve thermal conductivity, while if it is too large, wear on the reaction vessel and stirring blades becomes significant, and the insulating properties of the composition decrease.

[0051] The amount of component (C-2) blended is 500 to 1,500 parts by mass, and preferably 600 to 1,300 parts by mass, per 100 parts by mass of component (A). If the amount of component (C-2) blended is too small, the irregular particles will cause significant wear on the reaction vessel and stirring blades, while if the amount is too large, the composition will lose its fluidity and its moldability will be impaired.

[0052] The amount of component (C-3) blended is 300 to 900 parts by mass, and preferably 500 to 800 parts by mass, per 100 parts by mass of component (A). If the amount of component (C-3) blended is too small, the irregular particles will cause significant wear on the reaction vessel and stirring blades, while if the amount is too large, the composition will lose its fluidity and its moldability will be impaired.

[0053] The amount of component (C-4) blended is 1,000 to 1,900 parts by mass, preferably 1,100 to 1,500 parts by mass, per 100 parts by mass of component (A). If the amount of component (C-4) blended is too small, the composition loses its fluidity and its moldability is impaired. If the amount of component (C-4) blended is too large, significant wear of the reaction vessel and stirring blades occurs.

[0054] Furthermore, the blending amount of component (C) (i.e., the combined blending amount of components (C-1) to (C-4)) is 3,900 to 6,000 parts by mass, and preferably 4,000 to 5,500 parts by mass, per 100 parts by mass of component (A). If this blending amount is less than 3,900 parts by mass, the thermal conductivity of the resulting composition will be poor, and if it exceeds 6,000 parts by mass, the composition will lose its fluidity and its moldability will be impaired.

[0055] By using component (C) in the above blending ratio, the above-mentioned effects of the present invention can be achieved more advantageously and reliably.

[0056] [(D) Platinum group metal curing catalyst] The platinum group metal curing catalyst of component (D) is a catalyst for promoting the addition reaction between the alkenyl group derived from component (A) and the hydrosilyl group derived from component (B), and examples thereof include catalysts well known for use in hydrosilylation reactions. Specific examples include platinum group metals such as platinum (including platinum black), rhodium, and palladium; platinum chlorides such as HPtCl·nH2O, HPtCl·nH2O, NaHPtCl·nH2O, KaHPtCl·nH2O, NaPtCl·nH2O, KPtCl·nH2O, PCl·nH2O, PtCl·nH2O, PtCl2, and NaHPtCl·nH2O (wherein n is an integer of 0 to 6, preferably 0 or 6); chloroplatinic acid and chloroplatinic acid salts; and alcohol-modified chloroplatinic acid (disclosed in U.S. Pat. No. 3,220,972). see details), complexes of chloroplatinic acid and olefins (see U.S. Pat. Nos. 3,159,601, 3,159,662, and 3,775,452), platinum black, platinum group metals such as palladium supported on a support such as alumina, silica, or carbon, rhodium-olefin complexes, chlorotris(triphenylphosphine)rhodium (Wilkinson's catalyst), complexes of platinum chloride, chloroplatinic acid, or chloroplatinate with vinyl group-containing siloxanes, particularly vinyl group-containing cyclic siloxanes, and the like.

[0057] The amount of component (D) is 0.1 to 2,000 ppm, preferably 50 to 1,000 ppm, calculated as the mass of platinum group metal element relative to component (A). If the amount of component (D) is too small, the addition reaction will not proceed, while if it is too large, it is economically disadvantageous and therefore undesirable.

[0058] [(E) Addition reaction regulator] The addition reaction retarder of component (E) can be any known addition reaction retarder used in conventional addition reaction curable silicone compositions, including, for example, acetylene compounds such as 1-ethynyl-1-hexanol, 3-butyn-1-ol, and ethynylmethylidenecarbinol, various nitrogen compounds, organic phosphorus compounds, oxime compounds, and organic chloro compounds.

[0059] The amount of component (E) blended is 0.005 to 2.0 parts by mass, and preferably 0.1 to 1.2 parts by mass, per 100 parts by mass of component (A). If the amount of component (E) blended is too small, the addition reaction may proceed excessively, resulting in poor handleability of the composition. If the amount of component (E) blended is too large, the addition reaction may not proceed, resulting in impaired molding efficiency.

[0060] [(F) Surface treatment agent] The thermally conductive silicone composition of the present invention can be blended with a surface treatment agent (F) to hydrophobize the thermally conductive filler (C) during composition preparation, improving wettability with the alkenyl-containing organopolysiloxane (A), and uniformly dispersing the thermally conductive filler (C) within the matrix of component (A). Component (F) is not particularly limited, but components (F-1) and (F-2) shown below are particularly preferred.

[0061] The component (F-1) is an alkoxysilane compound represented by the following general formula (1). R 1 aR 2 bSi(OR 3 ) 4-a-b (1) (In the formula, R 1 are independently alkyl groups having 6 to 15 carbon atoms, and R2 are independently unsubstituted or substituted monovalent hydrocarbon groups having 1 to 12 carbon atoms, and R 3 are independently an alkyl group having 1 to 6 carbon atoms, a is an integer of 1 to 3, and b is an integer of 0 to 2, with the proviso that a+b is an integer of 1 to 3.

[0062] In the above general formula (1), R 1 Examples of the alkyl group represented by R include a hexyl group, an octyl group, a nonyl group, a decyl group, a dodecyl group, and a tetradecyl group. 1 When the number of carbon atoms in the alkyl group represented by the formula (I) is in the range of 6 to 15, the wettability of the component (A) is improved sufficiently, the handling property is good, and the low-temperature properties of the composition are good.

[0063] R 2 The unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms represented by the formula (I) is preferably a group selected from an alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 12 carbon atoms, and an aralkyl group having 7 to 12 carbon atoms. Examples of the alkyl group having 1 to 5 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, and a neopentyl group. Examples of the aryl group having 6 to 12 carbon atoms include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and a biphenylyl group. Examples of the aralkyl group having 7 to 12 carbon atoms include a benzyl group, a phenylethyl group, a phenylpropyl group, and a methylbenzyl group. Among these, alkyl groups having 1 to 3 carbon atoms, such as a methyl group, an ethyl group, and a propyl group, and a phenyl group are preferred. R 3 Examples of the alkyl group having 1 to 6 carbon atoms represented by the formula include a methyl group, an ethyl group, a propyl group, a butyl group, and a hexyl group.

[0064] Component (F-2) is a dimethylpolysiloxane represented by the following general formula (2) in which one molecular chain end is blocked with a trialkoxysilyl group. [ka] (In the formula, R 4 are independently alkyl groups having 1 to 6 carbon atoms, and c is an integer of 5 to 100.

[0065] R 4 Examples of the alkyl group having 1 to 6 carbon atoms represented by the formula (I) include the above-mentioned R 3 Examples of the alkyl group include the same alkyl groups as those exemplified by the alkyl groups shown in the formula (1). c is an integer of 5 to 100, preferably 5 to 70, and particularly preferably 10 to 50. Among these, the component (F-2) represented by the general formula (2) is an alkyl group represented by the formula (1) shown in the formula (1). 4 is a methyl group, and c is an integer of 10 to 50.

[0066] As the surface treatment agent of the component (F), at least one selected from the group consisting of the components (F-1) and (F-2) can be blended. When component (F) is blended, the blending amount is preferably 0.01 to 300 parts by mass, and more preferably 0.1 to 200 parts by mass, per 100 parts by mass of component (A). If the blending amount of component (F) is below the upper limit, oil separation will not be induced. On the other hand, if it is above the lower limit, the effect will be exhibited.

[0067] [Other ingredients] The thermally conductive silicone composition of the present invention may further contain other components depending on the purpose and effects of the present invention. For example, optional components such as heat resistance improvers such as iron oxide and cerium oxide, viscosity modifiers such as organopolysiloxanes with a kinematic viscosity of 10 to 100,000 mm / s, colorants, and mold release agents may be added.

[0068] [Viscosity of the thermally conductive silicone composition] The viscosity (absolute viscosity) of the thermally conductive silicone composition of the present invention at 23°C is preferably 1,000 Pa·s or less, and more preferably 700 Pa·s or less. There are no particular restrictions on the lower limit of the viscosity, but it can be, for example, 100 Pa·s or more. A viscosity of 1,000 Pa·s or less provides excellent processability for the composition. In the present invention, this viscosity is measured using a rheometer viscometer.

[0069] [Preparation of Thermally Conductive Silicone Composition] The thermally conductive silicone composition of the present invention can be prepared by uniformly mixing the above-mentioned components in accordance with conventional methods.

[0070] [Thermal conductive silicone cured product] The thermally conductive silicone cured product of the present invention is obtained by curing the above-mentioned thermally conductive silicone composition of the present invention in accordance with a conventional method. There are no particular restrictions on the shape of the thermally conductive silicone cured product of the present invention, but a sheet shape is preferred.

[0071] [Method for producing a thermally conductive silicone cured product] The curing conditions for molding the thermally conductive silicone composition may be the same as those for known addition reaction curing silicone rubber compositions. For example, the composition will cure sufficiently at room temperature, but heating may be used if necessary. Preferably, the composition is added and cured at 100 to 120°C for 8 to 12 minutes. The thermally conductive silicone cured product of the present invention obtained in this manner has excellent thermal conductivity.

[0072] [Thermal conductivity of cured thermally conductive silicone] The thermal conductivity of the thermally conductive silicone cured product of the present invention, measured at 23°C, is preferably 5.5 W / m K or more, and more preferably 6.0 W / m K or more. The higher the thermal conductivity, the better, and there is no particular upper limit, but it can be set to, for example, 8.0 W / m K or less. In the present invention, thermal conductivity is based on measurements using the hot disc method (ISO 22007-2:2008).

[0073] [Breakdown voltage of cured thermally conductive silicone] The breakdown voltage of the thermally conductive silicone cured product of the present invention is the measured value of the breakdown voltage of a 1 mm thick cured product measured in accordance with JIS K 6249:2003, and is preferably 10 kV / mm or more, more preferably 12 kV / mm or more. The upper limit of the breakdown voltage is not particularly limited, but can be, for example, 30 kV / mm or less. A cured product with a breakdown voltage of 10 kV / mm or more can ensure stable insulation during use. This breakdown voltage can be adjusted by adjusting the type and purity of the filler.

[0074] [Hardness of cured thermally conductive silicone] The hardness of the thermally conductive silicone cured product of the present invention, measured at 23°C using an Asker C hardness tester, is preferably 3 to 40, and more preferably 3 to 20. When the hardness is 40 or less, the product will deform to fit the shape of the heat-dissipating object, exhibiting good heat-dissipating properties without applying stress to the heat-dissipating object. This hardness can be adjusted by changing the ratio of components (A) and (B) to control the crosslink density. [Example]

[0075] EXAMPLES The present invention will be specifically explained below using examples and comparative examples, but the present invention is not limited to these.

[0076] The kinematic viscosity was measured at 25°C using a Canon-Fenske viscometer. The average particle size is the cumulative average particle size (median diameter) on a volume basis measured by the laser diffraction / scattering method using a particle size analyzer, Microtrac MT3300EX, manufactured by Nikkiso Co., Ltd.

[0077] Components (A) to (F) used in the following examples and comparative examples are shown below. Component (A): The following two types of organopolysiloxanes having alkenyl groups: (A-1): Kinematic viscosity of 600 mm as shown in the following formula (4) 2 / s organopolysiloxane (wherein X is a vinyl group and f=180). (A-2): Kinematic viscosity 30,000 mm as shown in the following formula (4) 2 / s organopolysiloxane (wherein X is a vinyl group and f=745). [ka]

[0078] (B) Component: The following two types of organohydrogenpolysiloxane. (B-1): Organohydrogenpolysiloxane represented by the following formula (5-1). [ka] (In the formula, g is 27, h is 3, and the arrangement order of the siloxane units in the parentheses is unspecified.) (B-2): Organohydrogenpolysiloxane represented by the following formula (5-2). [ka] (wherein g is 18).

[0079] Component (C): Spherical alumina and amorphous alumina having the following average particle sizes: (C-1): Spherical alumina with an average particle size of 88.6 μm. (C-2): Spherical alumina with an average particle size of 48.7 μm. (C-3): Spherical alumina with an average particle size of 16.7 μm. (C-4): Irregular alumina with an average particle size of 1.7 μm. Component (D): 5% by mass solution of chloroplatinic acid in 2-ethylhexanol. (E) Component: Ethynylmethylidene carbinol.

[0080] Component (F): A dimethylpolysiloxane represented by the following formula (6) having an average degree of polymerization of 30 and one end blocked with a trimethoxysilyl group. [ka]

[0081] [Examples 1 to 5, Comparative Examples 1 and 2] In Examples 1 to 5 and Comparative Examples 1 and 2, thermally conductive silicone compositions were prepared as described below using the above components (A) to (F) in the specified amounts shown in Table 1 below, and the viscosity of the thermally conductive silicone compositions was measured according to the methods described below. The thermally conductive silicone compositions were molded and cured, and the thermal conductivity, breakdown voltage, and hardness of the resulting cured thermally conductive silicone products were measured according to the methods described below. The results are shown in Table 1.

[0082] [Preparation of Thermally Conductive Silicone Composition] Components (A), (C), and (F) were added in the prescribed amounts shown in Examples 1 to 5 and Comparative Examples 1 to 2 in Table 1 below, and kneaded for 60 minutes with a planetary mixer. Component (D) was then added in the prescribed amount shown in Examples 1 to 5 and Comparative Examples 1 to 2 in Table 1 below, and an effective amount of KF-54, a phenyl-modified silicone oil manufactured by Shin-Etsu Chemical Co., Ltd., was added as an internal release agent to promote release from the release film, and the mixture was kneaded for 30 minutes. Components (B) and (E) were then added to the mixture in the amounts shown in Examples 1 to 5 and Comparative Examples 1 and 2 in Table 1 below, and the mixture was kneaded for 30 minutes to obtain a thermally conductive silicone composition.

[0083] [Evaluation method] Viscosity of the thermally conductive silicone composition: The viscosity of the thermally conductive silicone compositions obtained in Examples 1 to 5 and Comparative Examples 1 and 2 was measured at 23°C using a rheometer viscometer at a rotation speed of 10 (1 / s). The measuring device used was a HAAKE MARS40 manufactured by Thermo Scientific.

[0084] Thermal Conductivity: The thermally conductive silicone compositions obtained in Examples 1 to 5 and Comparative Examples 1 and 2 were cured in a press molding machine at 120°C for 10 minutes into 6 mm thick sheets. Using two of these sheets, the thermal conductivity of the sheets was measured using a thermal conductivity meter (product name: TPS-2500S, manufactured by Kyoto Electronics Manufacturing Co., Ltd.) based on the hot disc method (ISO 22007-2:2008).

[0085] Breakdown voltage: The thermally conductive silicone compositions obtained in Examples 1 to 5 and Comparative Examples 1 and 2 were cured in a press molding machine at 120°C for 10 minutes into 1 mm thick sheets, and the breakdown voltage was measured in accordance with JIS K 6249:2003.

[0086] hardness: The thermally conductive silicone compositions obtained in Examples 1 to 5 and Comparative Examples 1 and 2 were cured into 6 mm thick sheets in the same manner as above, and two of these sheets were stacked and measured for hardness using an Asker C hardness tester. Transferring material to release film: The thermally conductive silicone compositions obtained in Examples 1 to 5 and Comparative Examples 1 and 2 were applied to a release film in a thickness of 0.5 mm and cured at 105°C for 10 minutes. The release film was then peeled off to check whether any of the cured product had been transferred to the release film.

[0087] [Table 1] In the table, the ratio of the number of hydrogen atoms directly bonded to all silicon atoms in the organohydrogenpolysiloxane to the number of all alkenyl groups in the organopolysiloxane having alkenyl groups is represented as H / Vi.

[0088] In Examples 1 to 5, the viscosity of the thermally conductive silicone composition, and the thermal conductivity, breakdown voltage, and hardness of the cured thermally conductive silicone were all good, and no transfer of material to the release film was observed when the release film was peeled off from the cured silicone. When the amount of component (A-2) was small, as in Comparative Examples 1 and 2, the material was transferred to the release film when the release film was peeled off from the cured silicone product. In particular, in Example 1, although the hardness was 5, no transfer of the material to the release film was observed, the releasability was good, and the film could be easily peeled off from the release film. On the other hand, in Comparative Example 1, although the hardness was 5 as in Example 1, the material was transferred to the release film when peeled off from the release film.

[0089] The sheets of the examples deformed to fit the shape of the heat-dissipating object, exhibiting good heat-dissipating properties without applying stress to the heat-dissipating object. The compositions of the examples also had good handling properties, good low-temperature properties, and were less prone to oil separation. Furthermore, there was little wear on the reaction vessel and stirring blades during production.

[0090] This specification includes the following inventions.

[0091] [1]: A thermally conductive silicone composition, (A) 100 parts by mass of an organopolysiloxane having at least two alkenyl groups per molecule, which comprises the following components (A-1) and (A-2), with a mass ratio of (A-1) / (A-2) of 70 / 30 to 0 / 100: (A-1) an alkenyl group-containing organopolysiloxane whose main chain consists of repeating diorganosiloxane units, has an average degree of polymerization of 200 to 350, and has a kinematic viscosity at 25°C of 400 to 1,000 mm2 / s; (A-2) an alkenyl group-containing organopolysiloxane whose main chain consists of repeating diorganosiloxane units, has an average degree of polymerization of 600 to 1,500, and has a kinematic viscosity at 25°C of 5,000 to 100,000 mm2 / s; (B) an organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to silicon atoms: an amount such that the number of moles of hydrogen atoms directly bonded to silicon atoms is 0.1 to 5.0 times the number of moles of alkenyl groups derived from component (A); (C) 3,900 to 6,000 parts by mass of a thermally conductive filler consisting of the following components (C-1) to (C-4): (C-1) Spherical alumina filler having an average particle size of more than 65 μm and not more than 135 μm: 1,400 to 3,000 parts by mass, (C-2) Spherical alumina filler having an average particle size of more than 30 μm and not more than 65 μm: 500 to 1,500 parts by mass, (C-3) Spherical alumina filler having an average particle size of more than 4 μm and not more than 30 μm: 300 to 900 parts by mass, (C-4) Irregular shaped alumina filler having an average particle size of more than 0.4 μm and not more than 4 μm: 1,000 to 1,900 parts by mass, (D) a platinum group metal curing catalyst: 0.1 to 2,000 ppm by mass of platinum group metal element relative to the component (A), and (E) addition reaction inhibitor: 0.005 to 2.0 parts by mass, A thermally conductive silicone composition comprising: [2]: Furthermore, as the component (F), (F-1) an alkoxysilane compound represented by the following general formula (1), and R 1 aR 2 bSi(OR 3 ) 4-a-b (1) (In the formula, R 1 are independently alkyl groups having 6 to 15 carbon atoms, and R 2 are independently unsubstituted or substituted monovalent hydrocarbon groups having 1 to 12 carbon atoms, and R 3 are independently an alkyl group having 1 to 6 carbon atoms, a is an integer of 1 to 3, and b is an integer of 0 to 2, with the proviso that a+b is an integer of 1 to 3. (F-2) a dimethylpolysiloxane represented by the following general formula (2) in which one molecular chain terminal is blocked with a trialkoxysilyl group: [ka] (In the formula, R 4 are independently alkyl groups having 1 to 6 carbon atoms, and c is an integer of 5 to 100. The thermally conductive silicone composition according to [1], characterized in that it contains 0.01 to 300 parts by mass of at least one selected from the group consisting of: [3]: The thermally conductive silicone composition according to [1] or [2], characterized in that the viscosity at 23°C is 1,000 Pa·s or less. [4]: A thermally conductive silicone cured product, characterized by being a cured product of the thermally conductive silicone composition according to any one of [1] to [3]. [5]: The thermally conductive silicone cured product according to [4], characterized in that the thermal conductivity at 23°C is 5.5 W / m·K or more. [6]: A thermally conductive silicone cured product according to [4] or [5], characterized in that the dielectric breakdown voltage at a thickness of 1 mm is 10 kV / mm or more. [7]: The thermally conductive silicone cured product according to any one of [4] to [6], characterized in that it is in the form of a sheet. [8]: The thermally conductive silicone cured product according to any one of [4] to [7], characterized in that the hardness measured with an Asker C hardness tester is 3 to 40.

[0092] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention.

Claims

1. A thermally conductive silicone composition comprising: (A) 100 parts by mass of an organopolysiloxane having at least two alkenyl groups per molecule, which comprises the following components (A-1) and (A-2), with a mass ratio of (A-1) / (A-2) of 70 / 30 to 0 / 100: (A-1) A copolymer having a main chain consisting of repeating diorganosiloxane units, an average degree of polymerization of 145 to 220, and a kinematic viscosity at 25°C of 400 to 1,000 mm ２ / s alkenyl group-containing organopolysiloxane, (A-2) The main chain consists of repeating diorganosiloxane units, the average degree of polymerization is 450 to 1,100, and the kinematic viscosity at 25°C is 5,000 to 100,000 mm ２ / s alkenyl group-containing organopolysiloxane, (B) an organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to silicon atoms: an amount such that the number of moles of hydrogen atoms directly bonded to silicon atoms is 0.1 to 5.0 times the number of moles of alkenyl groups derived from component (A); (C) a thermally conductive filler consisting of the following components (C-1) to (C-4): 3,900 to 6,000 parts by mass, (C-1) Spherical alumina filler having an average particle size of more than 65 μm and not more than 135 μm: 1,400 to 3,000 parts by mass, (C-2) Spherical alumina filler having an average particle size of more than 30 μm and not more than 65 μm: 500 to 1,500 parts by mass, (C-3) Spherical alumina filler having an average particle size of more than 4 μm and not more than 30 μm: 300 to 900 parts by mass, (C-4) irregular alumina filler having an average particle size of more than 0.4 μm and not more than 4 μm: 1,000 to 1,900 parts by mass, (D) a platinum group metal curing catalyst: 0.1 to 2,000 ppm by mass of platinum group metal element relative to the component (A), and (E) addition reaction inhibitor: 0.005 to 2.0 parts by mass, A thermally conductive silicone composition comprising:

2. Furthermore, as the component (F), (F-1) an alkoxysilane compound represented by the following general formula (1), and R １ aR ２ bSi(OR ３ ) ４－ａ－ｂ (1) (In the formula, R １ are independently alkyl groups having 6 to 15 carbon atoms, and R ２ are independently unsubstituted or substituted monovalent hydrocarbon groups having 1 to 12 carbon atoms, and R ３ are independently an alkyl group having 1 to 6 carbon atoms, a is an integer of 1 to 3, and b is an integer of 0 to 2, with the proviso that a+b is an integer of 1 to 3. (F-2) Dimethylpolysiloxane represented by the following general formula (2), in which one molecular chain terminal is blocked with a trialkoxysilyl group: 【Chemistry 1】 (In the formula, R ４ are independently alkyl groups having 1 to 6 carbon atoms, and c is an integer of 5 to 100. The thermally conductive silicone composition according to claim 1, characterized in that it contains 0.01 to 300 parts by mass of at least one selected from the group consisting of:

3. 3. The thermally conductive silicone composition according to claim 1, wherein the viscosity at 23°C is 1,000 Pa·s or less.

4. A cured thermally conductive silicone product, which is a cured product of the thermally conductive silicone composition according to claim 1.

5. 5. The thermally conductive silicone cured product according to claim 4, characterized in that it has a thermal conductivity of at least 5.5 W / m·K at 23°C.

6. 6. The thermally conductive silicone cured product according to claim 4, wherein the dielectric breakdown voltage at a thickness of 1 mm is 10 kV / mm or more.

7. 6. The thermally conductive silicone cured product according to claim 4, which is in the form of a sheet.

8. 6. The thermally conductive silicone cured product according to claim 4, characterized in that the hardness measured with an Asker C hardness tester is 3 to 40.

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