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  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
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  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/04—Polysiloxanes
  • C08G77/14—Polysiloxanes containing silicon bound to oxygen-containing groups
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  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
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  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
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  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L83/00—Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon only; Compositions of derivatives of such polymers
  • C08L83/04—Polysiloxanes
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  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L83/00—Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon only; Compositions of derivatives of such polymers
  • C08L83/04—Polysiloxanes
  • C08L83/06—Polysiloxanes containing silicon bound to oxygen-containing groups
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  • C08J2383/00—Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen, or carbon only; Derivatives of such polymers
  • C08J2383/04—Polysiloxanes
  • C08J2383/07—Polysiloxanes containing silicon bound to unsaturated aliphatic groups
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  • C08J2483/00—Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen, or carbon only; Derivatives of such polymers
  • C08J2483/04—Polysiloxanes
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  • C08J2483/00—Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen, or carbon only; Derivatives of such polymers
  • C08J2483/04—Polysiloxanes
  • C08J2483/06—Polysiloxanes containing silicon bound to oxygen-containing groups
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  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
  • C08K3/20—Oxides; Hydroxides
  • C08K3/22—Oxides; Hydroxides of metals
  • C08K2003/2227—Oxides; Hydroxides of metals of aluminium
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  • C08K3/00—Use of inorganic substances as compounding ingredients
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  • C08K2003/282—Binary compounds of nitrogen with aluminium
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  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/38—Boron-containing compounds
  • C08K2003/382—Boron-containing compounds and nitrogen
  • C08K2003/385—Binary compounds of nitrogen with boron
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  • C08K2201/00—Specific properties of additives
  • C08K2201/002—Physical properties
  • C08K2201/005—Additives being defined by their particle size in general
• • C—CHEMISTRY; METALLURGY
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  • C08K2201/014—Additives containing two or more different additives of the same subgroup in C08K
• • C—CHEMISTRY; METALLURGY
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  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2205/00—Polymer mixtures characterised by other features
  • C08L2205/03—Polymer mixtures characterised by other features containing three or more polymers in a blend
  • C08L2205/035—Polymer mixtures characterised by other features containing three or more polymers in a blend containing four or more polymers in a blend

Definitions

• the present invention relates to a thermally conductive millable silicone rubber composition and a thermally conductive sheet.
• Heat-generating components and integrated circuit elements used in various electronic devices may deteriorate in characteristics and shorten the lifespan of the elements due to heat generation.
• the arrangement of components within electronic devices is important for smooth heat dissipation.
• heat-generating components and the entire device are forcedly air-cooled using cooling fins, and heat generated in integrated circuit elements is released to the outside of the elements via heat dissipation sheets.
• a radiator such as a natural cooling type or forced cooling type radiating fin or heat pipe is installed near the element, and the heat generated by the element is transferred to the radiator via a heat radiating medium to radiate the heat. ing.
• a heat dissipation sheet with a thickness of approximately 0.2 to 10.0 mm is used in order to improve heat conduction between the element and the heat radiator.
• a heat dissipation sheet one in which a highly filled, highly hard silicone rubber layer is reinforced with a cloth-like reinforcing material such as glass cloth is well known (Patent Document 1).
• Patent Document 1 This type of heat dissipation sheet has a rubber layer with high hardness and is extremely useful because it not only conducts heat but also ensures insulation.
• a heat dissipation sheet In order to lower the contact thermal resistance, a heat dissipation sheet has also been proposed in which a low hardness thermally conductive silicone rubber layer is laminated on a high hardness thermally conductive silicone rubber sheet reinforced with the above-mentioned reinforcing material (Patent Document 2).
• Patent Document 2 a heat dissipation sheet
• the low hardness layer is compressively deformed by pressure, which may result in a decrease in insulation properties due to thinning or cracking or breaking of the low hardness layer.
• a high-hardness heat dissipation sheet has excellent heat dissipation properties and insulation reliability due to its strength, but has a problem in that efficient heat conduction cannot be obtained because of its high contact thermal resistance. Furthermore, in the case of composite sheets with low hardness and high hardness, the sheet becomes thin under high pressure, making it difficult to guarantee insulation. Furthermore, when attempting to apply a method of laminating a metal thin film such as metal foil to a silicone rubber sheet, there were problems such as an increase in contact thermal resistance, concerns about poor insulation, and an increase in manufacturing costs.
• the present invention was made to solve the above problems, and is a heat dissipation device that has excellent thermal conductivity, strength, and insulation properties, has appropriate hardness, has low contact thermal resistance, and has excellent long-term stability.
• the object of the present invention is to provide a thermally conductive millable silicone rubber composition that provides a sheet.
• the thermally conductive millable silicone rubber composition of the present invention has excellent thermal conductivity, strength, and insulation properties, moderate hardness, low contact thermal resistance, and excellent long-term stability.
• a heat dissipation sheet can be provided.
• the proportion of particles with a particle size of 45 ⁇ m or more contained in the component (C) is 5% by mass or less.
• thermally conductive millable silicone rubber composition when a thermally conductive sheet is obtained by coating this composition, the thermally conductive filler protrudes from the coating surface and forms a part of the sheet surface. Smoothness is not compromised and thermal contact resistance is not increased.
• the above composition further contains 5 to 100 parts by mass of a polysiloxane modified with a trialkoxysilyl group at one end and represented by the following formula (1) as a wetter component (D).
• a polysiloxane modified with a trialkoxysilyl group at one end and represented by the following formula (1) as a wetter component (D).
• R 1 is an alkyl group having 1 to 6 carbon atoms
• n is an integer of 5 to 100.
• the component (C) is hydrophobized during composition preparation to improve wettability with the component (A), and the component (C) becomes the component (A).
• the component (C) becomes the component (A).
• the present invention also provides a thermally conductive sheet containing a cured product of the thermally conductive millable silicone rubber composition and a mesh reinforcing material.
• Such a thermally conductive sheet has excellent thermal conductivity, strength, and insulation, moderate hardness, low contact thermal resistance, and excellent long-term stability.
• the mesh reinforcing material is sealed.
• Such a thermally conductive sheet can improve the interface contact between the reinforcing material and the cured product of the thermally conductive millable silicone rubber composition, and can further reduce the contact thermal resistance.
• the thermally conductive millable silicone rubber composition of the present invention becomes a thermally conductive sheet suitable for heat dissipation in electronic devices and the like. Further, the thermally conductive sheet containing the cured product of the millable silicone rubber composition and the mesh reinforcing material has a low thermal resistance due to good contact without sacrificing the insulation guarantee. Furthermore, by controlling the particle size of the thermally conductive material, continuous coating molding can be performed, resulting in low-cost and simple manufacturing, and product properties that are stable over the long term. becomes.
• thermally conductive millable silicone characterized by containing the following components (A), (B), (C), (E), and (F).
• the inventors have discovered that the above problems can be solved with a rubber composition and a thermally conductive sheet using the composition, and have completed the present invention.
• the present invention provides an organopolysiloxane containing (A) the following components (A-1) to (A-3); (A-1) Raw rubbery organopolysiloxane having alkenyl groups only at both ends of the molecular chain (A-2) Raw rubbery organopolysiloxane having alkenyl groups at both ends and side chains of the molecular chain (A-3) 1 Linear organopolysiloxane having an alkenyl group, including an organopolysiloxane that is liquid at 25°C and having two or more alkenyl groups in the molecule: 100 parts by mass (B) (B-1) and (B-2) below organohydrogenpolysiloxane containing ingredients; (B-1) Organohydrogenpolysiloxane having hydrosilyl groups only in the side chains of the molecular chain and having 2 to 5 hydrosilyl groups in one molecule (B-2) Two or more hydrosilyl groups in one molecule Organohydrogen
• the thermally conductive millable silicone rubber composition of the present invention (hereinafter also referred to as "thermally conductive silicone rubber composition”) comprises (A) an organopolysiloxane having an alkenyl group, (B) an organohydrogenpolysiloxane, ( It contains C) a thermally conductive filler, (E) an addition reaction catalyst, and (F) an addition reaction control agent. Furthermore, additives such as (D) wetter can also be included as needed.
• the components contained in the composition of the present invention will be explained below.
• composition of the present invention is a main ingredient of the composition of the present invention.
• A Ingredients are listed below (A-1) to (A-3).
• A-1) Raw rubber-like organopolysiloxane having alkenyl groups only at both ends of the molecular chain
• A-2) Raw rubber-like organopolysiloxane having alkenyl groups at both ends and side chains of the molecular chain
• A-3) It is characterized by containing three types of organopolysiloxanes that are liquid at 25°C and have two or more alkenyl groups in one molecule.
• organopolysiloxanes having alkenyl groups are linear diorganopolysiloxanes in which the main chain portion is composed of repeating diorganosiloxane units.
• the alkenyl group possessed by these three organopolysiloxanes is preferably an alkenyl group having 2 to 8 carbon atoms, such as a vinyl group, an allyl group, a propenyl group, an isopropenyl group, a butenyl group, a hexenyl group, and a cyclohexenyl group. etc.
• a vinyl group and an allyl group are preferred, and a vinyl group is particularly preferred.
• functional groups other than the alkenyl group bonded to the silicon atom of these three organopolysiloxanes include an alkyl group having 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms, an aryl group having 6 to 10 carbon atoms, and A monovalent hydrocarbon group selected from aralkyl groups having 7 to 10 carbon atoms is preferred.
• alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, heptyl group, octyl group, cyclopentyl group, cyclohexyl group
• Examples include cycloalkyl groups such as cycloheptyl, aryl groups such as phenyl, tolyl, xylyl, and naphthyl, and aralkyl groups such as benzyl, phenylethyl, and phenylpropyl.
• the functional groups other than the alkenyl group bonded to the silicon atom are not limited to all being the same.
• organopolysiloxanes having alkenyl groups include dimethylsiloxane/methylvinylsiloxane copolymers with trimethylsiloxy groups endblocked at both molecular chain ends, methylvinylpolysiloxane endblocked with trimethylsiloxy groups at both molecular chain ends, and methylvinylpolysiloxane endblocked with trimethylsiloxy groups at both molecular chain ends.
• Trimethylsiloxy group-blocked dimethylsiloxane/methylvinylsiloxane/methylphenylsiloxane copolymer dimethylpolysiloxane blocked with dimethylvinylsiloxy groups at both molecular chain ends, methylvinylpolysiloxane blocked with dimethylvinylsiloxy groups at both molecular chain ends, dimethyl at both molecular chain ends Dimethylsiloxane/methylvinylsiloxane copolymer blocked with vinylsiloxy groups, dimethylsiloxane/methylvinylsiloxane/methylphenylsiloxane copolymer blocked with dimethylvinylsiloxy groups at both ends of the molecular chain, dimethylpolysiloxane blocked with divinylmethylsiloxy groups at both ends of the molecular chain, Dimethylsiloxane/methylvinylsiloxane copolymer with divinylmethylsiloxy groups blocked at both ends of the
• the component (A-1) is a raw rubber-like organopolysiloxane having alkenyl groups only at both ends of the molecular chain.
• raw rubber-like means either a liquid with a very high viscosity of 200,000 mPa ⁇ s or more at room temperature (25°C), or a non-liquid (paste or solid) without self-flowing properties. means.
• the viscosity in the present invention refers to a value measured using a rotational viscometer according to the method described in JIS Z8803:2011.
• the polymerization degree of component (A-1) is preferably 2,000 to 20,000, more preferably 3,000 to 15,000.
• the degree of polymerization in the present invention generally refers to a value calculated from the weight average degree of polymerization in terms of polystyrene measured by gel permeation chromatography (GPC) analysis using toluene as a developing solvent.
• GPC gel permeation chromatography
• the raw rubbery organopolysiloxane having alkenyl groups at both ends and side chains of the molecular chain (A-2) component is a raw rubbery organopolysiloxane having alkenyl groups at both ends and side chains of the molecular chain.
• the degree of polymerization of component (A-2) is preferably from 2,000 to 20,000, more preferably from 3,000 to 15,000.
• the number of side chain alkenyl groups in one molecule is preferably 1 to 200, more preferably 2 to 100.
• liquid means having self-flowing properties at 25°C.
• the degree of polymerization of component (A-3) is preferably 100 to 2,000, more preferably 500 to 1,500.
• the number of alkenyl groups in one molecule is characterized by being 2 or more, preferably 2 to 10, more preferably 2 to 5.
• the alkenyl group may be present at the end of the molecular chain or at the side chain, but it is preferable to have the alkenyl group only at the end of the molecular chain.
• the structure of component (A-3) is a linear structure in which the main chain portion is composed of repeating diorganosiloxane units.
• Component (A-3) is characterized by being liquid at 25°C.
• the viscosity thereof is preferably 500 to 200,000 mPa ⁇ s, more preferably 10,000 to 150,000 mPa ⁇ s.
• the ratio of the amounts of (A-1) to (A-3) is, when the total amount of component (A) is 100% by mass, component (A-1) is 20 to 45% by mass, and component (A-2) is 20 to 45% by mass. It is preferable that the amount of the component is 20 to 45% by weight, and the amount of component (A-3) is 10 to 40% by weight.
• organohydrogenpolysiloxane which is the component (B) reacts with the component (A) and acts as a crosslinking agent.
• Component (B) has a hydrosilyl group only in the side chain of the molecular chain of component (B-1) and (B-2) below, and has 2 to 5 hydrosilyl groups in one molecule.
• organohydrogenpolysiloxane having (B-2) Using an organohydrogenpolysiloxane containing two types of organohydrogenpolysiloxanes having two or more hydrosilyl groups in one molecule, two of which are at the ends of the molecular chain. It is characterized by
• the functional groups other than the hydrosilyl group in the organohydrogenpolysiloxane (B) component include an alkyl group having 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aryl group having 7 to 10 carbon atoms.
• a monovalent hydrocarbon group selected from 10 aralkyl groups is preferred.
• alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, cyclohexyl group, octyl group, nonyl group, decyl group, Among them, aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group, aralkyl groups such as benzyl group, phenylethyl group, phenylpropyl group, etc.
• the functional groups other than the hydrogen atom (hydrosilyl group) bonded to the silicon atom are not limited to all being the same.
• the organohydrogenpolysiloxane (B-1) component has hydrosilyl groups only in the side chains of the molecular chain and has 2 to 5 hydrosilyl groups in one molecule. It is an organohydrogenpolysiloxane having only a hydrosilyl group in one molecule and 2 to 5, preferably 2 to 4 hydrosilyl groups in one molecule.
• having a hydrosilyl group in the side chain of a molecular chain means having a Si-H bond in the D unit or T unit constituting the main chain of polysiloxane, or having a Si-H bond on the side chain of polysiloxane. This means that it has an H bond.
• component (B-1) may be either linear or branched, but is preferably linear.
• the degree of polymerization of component (B-1) is preferably from 4 to 350, more preferably from 10 to 200.
• the organohydrogenpolysiloxane (B-2) component has two or more hydrosilyl groups in one molecule, two of which are at the ends of the molecular chain. It is an organohydrogenpolysiloxane having 2 or more hydrosilyl groups, preferably 2 to 50, more preferably 2 to 20 hydrosilyl groups, two of which are at the ends of the molecular chain.
• the hydrosilyl group may be present at the end of the main chain (the longest polysiloxane chain) or at the end of the side chain.
• the terminus of the molecular chain of polysiloxane means both the terminus of the polysiloxane main chain and the terminus of the polysiloxane side chain. It means one end.
• component (B-2) may be either linear or branched, but is preferably linear.
• the degree of polymerization of component (B-2) is preferably from 4 to 200, more preferably from 10 to 100.
• the content of organohydrogenpolysiloxane as component (B) is such that the total amount of hydrosilyl groups in component (B) is 0.5 to 4 per mole of alkenyl groups in component (A).
• the amount is .0 mol, preferably 0.6 to 3.0. If the content of this component is less than 0.5 mol, the resulting thermally conductive silicone rubber may be too tacky and may cause blocking when rolled. Furthermore, since the rate of change in thickness increases during compression, there is a concern that insulation properties may deteriorate. On the other hand, if the content of this component is more than 4.0 moles but less than 6.0 moles, the pot life of the resulting thermally conductive silicone rubber composition will be shortened and it will harden before the curing process.
• the ratio of the amounts of (B-1) and (B-2) is, when the total amount of component (B) is 100% by mass, component (B-1) is 30 to 95% by mass, and (B-2) is 30 to 95% by mass.
• the component is 5 to 70% by weight.
• the rubber-like organopolysiloxane in component (A) can be easily handled, and the The crosslinking structure (chain length extension, crosslinking density) of siloxane can be precisely controlled.
• Component (C) is a thermally conductive filler that imparts thermal conductivity to the thermally conductive silicone rubber composition.
• Suitable examples of the thermally conductive filler include inorganic powders such as aluminum oxide, zinc oxide, silicon oxide, silicon carbide, aluminum nitride, and boron nitride.
• Component (C) can be used alone or in combination of two or more.
• the blending amount of component (C) needs to be 150 to 2,400 parts by mass, and preferably in the range of 200 to 2,300 parts by mass, per 100 parts by mass of component (A). If the amount is less than 150 parts by mass, the thermal conductivity is likely to be insufficient, while if it is more than 2,400 parts by mass, it becomes difficult to uniformly blend component (C) into the composition and the molding becomes difficult. Processability may deteriorate.
• the proportion of particles with a particle size of 45 ⁇ m or more contained therein is preferably 5% by mass or less, and more preferably 2% by mass or less. . If the proportion of particles with a particle size of 45 ⁇ m or more is 5% by mass or less, when a thermally conductive sheet is obtained by coating the thermally conductive millable silicone rubber composition, the thermally conductive filler (filler) will not be present in the coating film. There is no risk of protruding from the surface and impairing the smoothness of the sheet surface, and there is no risk of increasing contact thermal resistance.
• fillers having multiple particle size distributions may be used as long as the proportion of particles with a particle size of 45 ⁇ m or more is 5% by mass or less.
• a filler with convex portions at particle sizes of 1 ⁇ m and 10 ⁇ m on the particle size distribution curve may be used, or a filler with an average particle size of 5 ⁇ m and a filler with an average particle size of 20 ⁇ m may be used together. .
• the average particle size is preferably 0.1 to 30 ⁇ m, more preferably 0.1 to 10 ⁇ m. If the average particle size is 30 ⁇ m or less, when a thermally conductive sheet is obtained by coating with a thermally conductive silicone rubber composition, there is no risk that the thermally conductive filler will protrude from the coating surface and impair the smoothness of the sheet surface. There is no risk of an increase in contact thermal resistance. A thermally conductive filler with an average particle size of 0.1 ⁇ m or more is easily available.
• the above average particle size can usually be determined as the cumulative volume average diameter D 50 (or median diameter) etc. in particle size distribution measurement by laser light diffraction, but specifically, particles manufactured by Microtrac Bell Co., Ltd. This is the volume-based cumulative 50% particle diameter (D 50 ) value measured by a diameter distribution measuring device MT3000II.
• the proportion of particles having a specific particle size (for example, particle size 45 ⁇ m) or more can be determined from the above particle size distribution measurement.
• the thermally conductive silicone rubber composition of the present invention preferably contains a wetter component (D).
• Component (D) is obtained by subjecting component (C) to hydrophobization treatment during composition preparation to improve wettability with component (A) and uniformly distributing component (C) into the matrix consisting of component (A). The purpose is to disperse.
• the component (D) is particularly preferably a polysiloxane modified with a trialkoxysilyl group at one end represented by the following formula (1).
• R 1 is an alkyl group having 1 to 6 carbon atoms, preferably an alkyl group having 1 to 3 carbon atoms. Further, n is an integer of 5 to 100, preferably 10 to 50.
• the amount of component (D) to be blended is 5 to 100 parts by mass, particularly preferably 10 to 60 parts by mass, per 100 parts by mass of component (A). If the proportion of this component is within the above range, there is no risk of inducing oil separation.
• the addition reaction catalyst of component (E) promotes the addition reaction between the silicon-bonded alkenyl group in component (A) and the hydrosilyl group in component (B).
• the addition reaction catalyst is a platinum group metal or a platinum group metal compound.
• platinum group metals such as platinum, palladium, and rhodium; chloroplatinic acid; alcohol-modified chloroplatinic acid; coordination compounds of chloroplatinic acid and olefins, vinyl siloxanes, or acetylene compounds; tetrakis(triphenylphosphine) palladium;
• platinum group metal compounds such as chlorotris(triphenylphosphine)rhodium.
• the content of component (E) is 0.01 to 1,000 ppm, preferably 0.1 to 500 ppm, in terms of platinum group metal atomic mass relative to component (A). This is the amount. If the content of this component is too low, the resulting thermally conductive silicone rubber composition may not be sufficiently cured; on the other hand, even if a large amount is used, the curing speed of the resulting silicone rubber composition will not improve. , it may be economically disadvantageous.
• the addition reaction control agent is not particularly limited as long as it is a compound that has a curing reaction inhibiting effect on the addition reaction catalyst of component (E), and conventionally known ones can be used. Specific examples thereof include phosphorus-containing compounds such as triphenylphosphine; compounds containing nitrogen atoms such as tributylamine, tetramethylethylenediamine, and benzotriazole; compounds containing sulfur atoms; 1-ethynyl-1-cyclohexanol, 3 - Acetylenic compounds such as butyn-1-ol, 2-methyl-3-butyn-2-ol, 3-methyl-1-tridecyn-3-ol; 1,3-divinyl-1,1,3,3- Examples include vinyl group-containing siloxanes such as tetramethyldisiloxane and 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane; hydroperoxy compounds; maleic
• the amount of the addition reaction control agent is not particularly limited, but it should be blended in an amount that is 50 to 150 times as much as 1 mole of platinum group metal atoms contained in the addition reaction catalyst of component (E). Can be done.
• component (F) when an acetylene compound such as 3-methyl-1-tridecyn-3-ol is used as component (F), it is preferable to blend it in an amount within the above range.
• the thermally conductive silicone rubber composition of the present invention may further contain other components as required.
• optional components such as a heat resistance improver such as iron oxide; a viscosity modifier such as silica; a coloring agent; and a mold release agent may be blended.
• the thermally conductive silicone rubber composition can be cured under known conditions. Curing conditions are not particularly limited, but are, for example, 80 to 150° C. for about 30 seconds to 1 hour.
• the hardness of the cured product of the thermally conductive silicone rubber composition is 40 to 70, more preferably 50 to 60 in durometer A hardness measured by the method described in JIS K 6253:2012. If the hardness is 40 or more, the cured product is less likely to deform (or become thinner) under pressure, and the insulation properties can be easily maintained. If the hardness is 70 or less, the contact thermal resistance is sufficiently low and sufficient heat dissipation characteristics can be exhibited.
• the thermally conductive sheet of the present invention contains a cured product of the thermally conductive millable silicone rubber composition and a mesh reinforcing material.
• a thermally conductive sheet contains a cured product obtained by curing the thermally conductive millable silicone rubber composition of the present invention and a mesh reinforcing material, so it has excellent thermal conductivity, strength, and insulation properties. It has moderate hardness, low contact thermal resistance, and excellent long-term stability.
• the mesh reinforcing material used to reinforce the thermally conductive sheet is not particularly limited, but examples include inorganic fiber cloth such as glass cloth and ceramic cloth, organic fiber cloth such as nylon and polyester, or composite materials thereof. .
• inorganic fiber cloth such as glass cloth and ceramic cloth
• organic fiber cloth such as nylon and polyester, or composite materials thereof.
• seal the reinforcing material it is preferable to seal the reinforcing material. The sealing fills the openings of the mesh reinforcing material to increase the adhesive strength with the cured product of the thermally conductive silicone rubber composition, and also fixes the mesh of the reinforcing material, making the shape more stable.
• the filler material is not particularly limited, and for example, an addition reaction curing type or a peroxide curing type material can be used. Among them, thermally conductive silicone rubber materials are most suitable. As the thermally conductive silicone rubber material, the thermally conductive millable silicone rubber composition described above may be used, regardless of the curable type, or other materials may be used. When the thermally conductive millable silicone rubber composition that provides the cured product constituting the thermally conductive sheet is the same as the filler material, it has superior thermal conductivity, strength, and insulation properties, has appropriate hardness, and It is particularly preferable because it has low contact thermal resistance and improves productivity.
• the thickness of the present reinforcing material is, for example, 20 to 100 ⁇ m, more preferably 30 to 80 ⁇ m. If the thickness of the reinforcing material is 20 ⁇ m or more, the strength of the thermally conductive sheet will be sufficient. On the other hand, if the thickness is 100 ⁇ m or less, thermal conductivity will be sufficient.
• the contact thermal resistance of the thermally conductive sheet of the present invention to the adherend is preferably 40 mm 2 K/W or less, more preferably 5 to 35 mm 2 K/W, when measured at 50°C/700 kPa according to ASTM D5470. It is W. If the contact thermal resistance is 40 mm 2 ⁇ K/W or less, the adhesion between the adherend and the thermally conductive sheet will be sufficient, and the heat conduction efficiency will be good. Note that the contact thermal resistance of the thermally conductive sheet to the adherend can be determined by the method described in Examples described later.
• the rate of change in thickness after 20 minutes of compressing the thermally conductive sheet by applying a pressure of 700 kPa is the initial thickness of the thermally conductive sheet. It is preferably 20% or less, and more preferably 10% or less. When the rate of change in thickness is 20% or less, the rate of change in thickness becomes small under high-voltage mounting, making it easier to maintain insulation properties.
• the method for producing the thermally conductive sheet of the present invention is not particularly limited, but a pressing method, a coating method, etc. can be applied, and a coating method is generally effective.
• a thermally conductive sheet by the coating method for example, the following steps (1) to (3) are performed.
• Coating composition preparation process In addition to the components (A) to (F) and the solvent, additives are added and mixed as necessary. This is a step of preparing a coating composition by treating the obtained mixture as necessary and stirring and mixing.
• Sealing process This is a step of applying the coating composition obtained from the above step to the reinforcing material as needed and heating it as needed to obtain a sealed reinforcing material.
• Coating process This is a step of applying a thermally conductive silicone rubber composition to the sealed reinforcing material, and then heating and laminating (coating) a cured product of the composition.
• component (A), an organopolysiloxane having an alkenyl group, component (C), a thermally conductive filler, and component (D), a wetter are mixed in a mixer such as a kneader, Banbury mixer, planetary mixer, Shinagawa mixer, etc.
• a mixer such as a kneader, Banbury mixer, planetary mixer, Shinagawa mixer, etc.
• the mixture is kneaded while being heated to a temperature of about 100° C. or higher, if necessary.
• reinforcing silica such as fumed silica and precipitated silica
• flame retardants such as platinum, titanium oxide, benzotriazole, etc.
• the homogeneous mixture obtained in the kneading step is cooled to room temperature and then filtered through a strainer or the like.
• colorants such as organic pigments and inorganic pigments, heat resistance improvers such as iron oxide and cerium oxide, internally added mold release agents, catalysts, etc. are added to the mixture as desired. May be added or mixed.
• a curing agent, an acetylene compound-based addition reaction control agent such as 1-ethynyl-1-cyclohexanol (component (F)), a catalyst (component (E)), etc. are added to the composition obtained in this second kneading step.
• a solvent such as toluene is further added and mixed using a stirrer such as a planetary mixer or a kneader.
• a crosslinking agent component (B) is added and further mixed to obtain a coating composition.
• the coating composition obtained in the above step is applied to the reinforcing material to seal it.
• a coating device such as a knife coater or kiss coater equipped with a drying oven, heating oven, and winding device, the solvent etc. are dried and evaporated.
• the reinforcing material is sealed by heating to 80 to 200°C, preferably about 100 to 150°C, and in the case of peroxide curing type, heating to 100 to 200°C, preferably about 110 to 180°C. get.
• a coating composition that becomes a cured product of a thermally conductive silicone rubber composition is applied to one or both sides of the sealed reinforcing material obtained in the above step.
• a coating device such as a knife coater or kiss coater equipped with a drying furnace, heating furnace, and winding device, the solvent etc. are dried and evaporated.
• Lamination is carried out by heating to 80 to 200°C, preferably 100 to 150°C.
• the present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to the Examples below.
• the average degree of polymerization, viscosity, particle size, and average particle size were measured by the methods described above.
• One molecule of organopolysiloxane raw rubber (A-2) consists of 7,998 dimethylsiloxane units and 2 dimethylvinylsiloxane units and has an average degree of polymerization of 8,000
• Dimethylsiloxane is contained in one molecule of organopolysiloxane raw rubber (A-3), which consists of 7960 dimethylsiloxane units, 38 methylvinylsiloxane units, and 2 dimethylvinylsiloxane units, and has an average degree of polymerization of 8,000.
• the organopolysiloxane is composed of 1,128 units and 2 dimethylvinylsiloxane units, has an average degree of polymerization of 1,130, is liquid at 25°C, and has a viscosity of 105,000 mPa ⁇ s.
• Component (B): Hydrogenpolysiloxane The following (B-1) and (B-2) were mixed at a ratio of 3:1.
• Component (C): Thermal conductive filler] (C-1) Amorphous aluminum oxide having an average particle size of 1 ⁇ m and containing 0.8% by mass of particles with a particle size of 45 ⁇ m or more (C-2) An average particle size of 1 ⁇ m and containing 0.8% by mass of particles with a particle size of 45 ⁇ m or more Spherical aluminum oxide (C-3) with a particle amount of 0.6% by mass; average particle size of 10 ⁇ m; spherical aluminum oxide (C-4) with an average particle size of 1.2% by mass of particles with a particle size of 45 ⁇ m or more; Boron nitride (C-5) whose particle size is 5 ⁇ m and the amount of particles with a particle size of 45 ⁇ m or more is 0.9% by mass.
• the average particle size is 1 ⁇ m and the amount of particles with a particle size of 45 ⁇ m or more is 1.1 Spherical aluminum oxide having an average particle size of aluminum nitride (C-6) of 10 ⁇ m and the amount
• Mesh reinforcement material Glass cloth (thickness: 55 ⁇ m) equivalent to IPC spec 1080.
• Example 1 to 5 and Comparative Examples 1 to 5 Thermal conductive sheets of Examples 1 to 5 and Comparative Examples 1 to 5 were manufactured as follows.
• thermoly conductive silicone rubber composition (Preparation example 1) The components in the amounts (parts by mass) shown in Tables 1 and 2 were put into a Banbury mixer and kneaded for 20 minutes to form thermally conductive silicone rubber compositions (a) to (e) and (f) to (c). was prepared.
• thermally conductive sheet (Production Example 1) Sealing for Glass Cloth
• the thermally conductive silicone rubber composition obtained in the above (Preparation Example 1) was used as a sealing composition, and 20% by mass of toluene was added thereto.
• a coating material was prepared by kneading using a planetary mixer. The glass cloth was sealed by applying this coating material to one side of the glass cloth using a comma coater. Thereafter, it was dried at 80° C. for 10 minutes, and further cured at 170° C. for 15 minutes. The thickness of the sealed glass cloth was 80 ⁇ m.
• the thermal resistance of the thermally conductive sheet was measured according to ASTM D 5470 according to the following procedure. Thermal conductive sheets with thicknesses of 0.2 mm, 0.3 mm, and 0.45 mm were prepared and pressed at 50° C./700 kPa to measure the thermal resistance of the thermally conductive sheets of each thickness. Further, the contact thermal resistance was determined from the intercept of a graph in which the thickness (mm) of the thermally conductive sheet when pressurized (700 kPa or less) was plotted on the horizontal axis and the thermal resistance was plotted on the vertical axis.
• ⁇ Thickness change rate> The thickness of the thermally conductive sheet under pressure was measured in the same manner as the measurement of the thermal resistance. Furthermore, the rate of change in thickness was determined using the following formula.
• Example 2 After the glass cloth was sealed using the composition (a), the sealed glass cloth was coated with the composition (a) to obtain a thermally conductive sheet.
• Example 3 After the glass cloth was sealed using the composition (C), the sealed glass cloth was coated with the composition (C) to obtain a thermally conductive sheet.
• Example 4 After the glass cloth was sealed using the composition (d), the sealed glass cloth was coated with the composition (d) to obtain a thermally conductive sheet.
• Composition (ke) contained too much thermally conductive filler, making it impossible to obtain a uniform composition.
• the thermally conductive sheets of Examples 1 to 5 use the thermally conductive millable silicone rubber composition of the present invention, as shown in Table 1, the contact thermal resistance is small, the thermal conductivity is excellent, and the thermal conductivity is moderate. It has hardness.
• the thermally conductive sheet is composed of a highly flexible mesh-like reinforcing material, it has excellent strength, and since there is little change in thickness under pressure, there is little deterioration in insulation properties (i.e., insulation (excellent in sex).
• the thermally conductive millable silicone rubber composition of the present invention has excellent long-term stability since it contains an effective amount of (F) an addition reaction control agent.
• the present invention does not involve stacking metal thin films such as metal foils, there are no problems such as increased contact thermal resistance, concerns about poor insulation, or increased manufacturing costs. Furthermore, (C) by optimizing the particle size of the thermally conductive filler, continuous coating molding can be performed, resulting in low-cost and simple manufacturing, and long-term product properties. It becomes stable.
• the products of the present invention all have low contact thermal resistance, excellent flexibility, little deterioration in insulation properties under pressure, and can be manufactured with a low cost and simple manufacturing process. It can be seen that the comparative examples that do not meet the requirements of the present invention have problems such as high contact thermal resistance and insufficient material strength. That is, in Comparative Example 1, in which a thermally conductive sheet was obtained by sealing and coating a glass cloth using a peroxide-curable composition (F), the contact thermal resistance was too large, and (A-2 Comparative Example 2 in which glass cloth was sealed and coated using a composition (g) that did not contain the component (C), and glass cloth was sealed and coated using a composition (h) that contained too much of the component (C).
• Comparative Example 3 a thermally conductive sheet was obtained, but the contact thermal resistance and thickness could not be accurately measured, and the composition (k) in which the amount of thermally conductive filler was too large was
• Comparative Example 5 in which a uniform composition could not be obtained and the composition (C) containing a large excess of component (B) was used to seal and coat the glass cloth, it did not contribute to the crosslinking reaction. Since the component (B), which is not used, acts like a plasticizer, the obtained thermally conductive sheet showed a large change in thickness under pressure, resulting in concerns about deterioration in insulation properties.
• a thermally conductive sheet comprising a cured product of the thermally conductive millable silicone rubber composition according to any one of [1] to [3] and a mesh reinforcing material.

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