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WO2025204325A1 - Composition de caoutchouc de silicone et objet durci obtenu à partir de celle-ci - Google Patents

Composition de caoutchouc de silicone et objet durci obtenu à partir de celle-ci

Info

Publication number
WO2025204325A1
WO2025204325A1 PCT/JP2025/005768 JP2025005768W WO2025204325A1 WO 2025204325 A1 WO2025204325 A1 WO 2025204325A1 JP 2025005768 W JP2025005768 W JP 2025005768W WO 2025204325 A1 WO2025204325 A1 WO 2025204325A1
Authority
WO
WIPO (PCT)
Prior art keywords
silicone rubber
rubber composition
mass
parts
component
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/JP2025/005768
Other languages
English (en)
Japanese (ja)
Inventor
義明 小池
晃洋 遠藤
篤 柳沼
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Shin Etsu Chemical Co Ltd
Original Assignee
Shin Etsu Chemical Co Ltd
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Filing date
Publication date
Application filed by Shin Etsu Chemical Co Ltd filed Critical Shin Etsu Chemical Co Ltd
Publication of WO2025204325A1 publication Critical patent/WO2025204325A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/34—Silicon-containing compounds
    • C08K3/36—Silica
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/38—Boron-containing compounds
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/04—Oxygen-containing compounds
    • C08K5/14—Peroxides
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/54—Silicon-containing compounds
    • C08K5/541—Silicon-containing compounds containing oxygen
    • C08K5/5415—Silicon-containing compounds containing oxygen containing at least one Si—O bond
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • 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
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • 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

Definitions

  • the present invention relates to a silicone rubber composition that provides a cured product with excellent dielectric breakdown strength, and to the cured product.
  • Patent Document 1 proposes blending boron nitride powder having an average particle size of 20 ⁇ m or less.
  • the present invention was made in consideration of the above circumstances, and aims to provide a silicone rubber composition that produces a cured silicone rubber product that exhibits high dielectric breakdown strength, and the cured product.
  • the present invention provides the following silicone rubber composition and cured product thereof.
  • A 100 parts by mass of an organopolysiloxane having a degree of polymerization of 100 or more and having two or more silicon-bonded alkenyl groups per molecule;
  • B reinforcing silica having a specific surface area of 50 m 2 /g or more as measured by the BET method: 30 to 70 parts by mass;
  • C flaky boron nitride having an average particle size of 3 to 50 ⁇ m and an aspect ratio of 5 or more: 5 to 50 parts by mass
  • Curing agent A silicone rubber composition containing an effective amount of component (A) to cure the silicone rubber composition.
  • the silicone rubber composition according to the present invention contains the following components (A) to (D) and provides a cured silicone rubber product with excellent dielectric breakdown strength.
  • A an organopolysiloxane having a degree of polymerization of 100 or more and having two or more silicon-bonded alkenyl groups per molecule;
  • B a reinforcing silica having a specific surface area of 50 m 2 /g or more as measured by the BET method;
  • C flat boron nitride having an average particle size of 3 to 50 ⁇ m and an aspect ratio of 5 or more; and
  • D a curing agent.
  • Component (A) in the silicone rubber composition of the present invention is an organopolysiloxane having two or more silicon-bonded alkenyl groups per molecule and a degree of polymerization of at least 100.
  • This alkenyl-group-containing organopolysiloxane is not particularly limited as long as it has the above degree of polymerization, but examples include those represented by the following average composition formula (1):
  • R represents the same or different unsubstituted or substituted monovalent hydrocarbon groups, which may be linear, branched, or cyclic, preferably having 1 to 12 carbon atoms, more preferably having 1 to 8 carbon atoms, and even more preferably having 1 to 6 carbon atoms.
  • R is preferably a methyl group, a vinyl group, a phenyl group, or a trifluoropropyl group.
  • component (A) in the above average composition formula (1), preferred are organopolysiloxanes in which the main chain is composed of dimethylsiloxane units, or dimethylpolysiloxanes in which diphenylsiloxane units having phenyl groups, vinyl groups, 3,3,3-trifluoropropyl groups, etc., methylvinylsiloxane units, methyl-3,3,3-trifluoropropylsiloxane units, etc., have been introduced into part of the main chain.
  • the organopolysiloxane of component (A) has two or more alkenyl groups (preferably vinyl groups) bonded to silicon atoms per molecule.
  • alkenyl groups preferably vinyl groups
  • R in the average composition formula (1) above preferably 0.01 to 10 mol %, and more preferably 0.02 to 5 mol %, are alkenyl groups.
  • the alkenyl group may be bonded to a silicon atom at a molecular chain terminal, to a silicon atom in a side chain, or both. However, it is preferable that at least one is bonded to a silicon atom at a molecular chain terminal, and it is even more preferable that at least one is bonded to silicon atoms at both molecular chain terminals.
  • the organopolysiloxane of component (A) is preferably one in which both molecular chain terminals are blocked with dimethylvinylsilyl groups, methyldivinylsilyl groups, trivinylsilyl groups, or the like.
  • a is a positive number of 1.95 to 2.05, preferably 1.98 to 2.02, and more preferably 1.99 to 2.01.
  • the shape of the organopolysiloxane of component (A) generally, both molecular chain terminals are capped with triorganosiloxy groups, and the main chain is linear, consisting of repeating diorganosiloxane units; however, it may be branched as long as it does not impair rubber elasticity.
  • the degree of polymerization of the organopolysiloxane of component (A) is 100 or more, preferably 3,000 to 100,000, and more preferably 4,000 to 20,000. If the degree of polymerization is less than 100, sufficient rubber strength will not be obtained.
  • degree of polymerization refers to the average degree of polymerization, which is determined from the weight-average molecular weight measured by gel permeation chromatography (GPC) under the following conditions using polystyrene as a standard substance (the same applies hereinafter).
  • GPC gel permeation chromatography
  • component (A) include dimethylpolysiloxanes terminally blocked with dimethylvinylsiloxy groups, dimethylpolysiloxanes terminally blocked with methyldivinylsiloxy groups, dimethylpolysiloxanes terminally blocked with trivinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers terminally blocked with trimethylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers terminally blocked with dimethylvinylsiloxy groups, and dimethylsiloxane-methylvinylsiloxane copolymers in which one molecular end is blocked with dimethylvinylsiloxy groups and the other molecular end is blocked with trimethylsiloxy groups.
  • dimethylpolysiloxanes terminally blocked with dimethylvinylsiloxy groups
  • dimethylsiloxane-methylvinylsiloxane copolymers terminally blocked with trimethylsiloxy groups
  • dimethylsiloxane-methylvinylsiloxane copolymers terminally blocked with dimethylvinylsiloxy groups.
  • the organopolysiloxane of component (A) may be used alone or in combination with two or more types with different molecular structures or degrees of polymerization.
  • Component (B) in the silicone rubber composition of the present invention is a reinforcing silica having a specific surface area of at least 50 m 2 /g as measured by the BET method.
  • the reinforcing silica of component (B) is a powdered reinforcing filler, and although there are no particular limitations on the type, examples include fumed silica (dry silica or fumed silica), calcined silica, and precipitated silica (wet silica), and of these, fumed silica is preferred from the standpoint of dielectric breakdown strength.
  • the specific surface area of the reinforcing silica of component (B), as measured by the BET method, is at least 50 m /g, and preferably at least 100 m /g. There is no particular upper limit, but it is preferably at most 400 m /g, and more preferably at most 300 m /g. If the specific surface area measured by the BET method is less than 50 m /g, the mechanical strength of the resulting silicone rubber cured product will be insufficient.
  • the reinforcing silica may be either surface-untreated or surface-treated, and is not particularly limited; however, if necessary, using untreated silica whose surface has been hydrophobized is preferred in terms of dispersibility in component (A) and reinforcing properties.
  • silica that has been surface-hydrophobized directly with a silica surface treatment agent in powder form may be used, or the silica surface treatment agent may be added when mixing the silica fine powder with component (A), and the mixture may be heated and mixed to hydrophobize the surface.
  • the surface treatment method is not particularly limited, and can be selected appropriately from conventionally known methods.
  • one method involves placing untreated silica fine powder and a silica surface treatment agent in a mechanical mixer or fluidized bed sealed at atmospheric pressure, and mixing them at room temperature or by heat treatment, if necessary in the presence of an inert gas.
  • a catalyst may be used to promote the surface treatment. After mixing, drying can produce a reinforcing silica fine powder with a hydrophobic surface.
  • silica surface treatment agents include known treatment agents such as chlorosilanes such as trimethylchlorosilane, dimethyldichlorosilane, and methyltrichlorosilane; and silazanes such as hexamethyldisilazane and 1,3-divinyl-1,1,3,3-tetramethyldisilazane.
  • the amount of silica surface treatment agent used is not particularly limited, but is preferably 5 to 75 parts by mass, more preferably 5 to 60 parts by mass, per 100 parts by mass of surface-untreated fine silica powder.
  • surface-untreated fumed silica includes Aerosil 130, Aerosil 200, and Aerosil 300 manufactured by Nippon Aerosil Co., Ltd., and Reolosil QS-10, Reolosil QS-102, and Reolosil QS-30 manufactured by Tokuyama Corporation.
  • Surface-hydrophobically treated fumed silica includes Aerosil R-812, Aerosil R-974, and Aerosil R976S manufactured by Nippon Aerosil Co., Ltd., and Reolosil DM-20 and DM-30 manufactured by Tokuyama Corporation. These may be used alone or in combination of two or more types.
  • the amount of reinforcing silica (component (B)) added is 30 to 70 parts by mass, preferably 30 to 60 parts by mass, per 100 parts by mass of organopolysiloxane (component (A)). If the amount of component (B) added is less than 30 parts by mass, the amount added is too small, and the strength and processability of the resulting silicone rubber will be reduced. If it exceeds 70 parts by mass, the processability of the silicone rubber composition will be poor and the mechanical strength of the cured silicone rubber will be reduced.
  • Component (C) in the silicone rubber composition of the present invention is flat boron nitride.
  • the flat boron nitride of component (C) functions as a barrier layer against electrical breakdown in the cured silicone rubber.
  • the crystal structure of the flat boron nitride of component (C) is not particularly limited, but from the perspective of forming a barrier layer, hexagonal boron nitride is preferred.
  • Component (C) is also particulate and its shape is flat, but this also includes scale-like, plate-like, and flake-like shapes.
  • hexagonal boron nitride is oriented in its planar direction within the silicone rubber composition, strengthening its function as a barrier layer against electrical breakdown after curing.
  • the aspect ratio of the flat boron nitride of component (C) is 5 or more, preferably 7 or more. If the aspect ratio is less than 5, the orientation of the boron nitride in the plane direction is suppressed, making it impossible to obtain sufficient dielectric breakdown strength. There is no particular upper limit, but it is preferably 40 or less, more preferably 35 or less, and even more preferably 30 or less.
  • the aspect ratio is the value obtained by dividing the longest diameter of a particle by the particle thickness, i.e., longest diameter/thickness. When a particle is spherical, the aspect ratio is 1, and as the degree of flattening increases, the aspect ratio increases. In the present invention, the aspect ratio can be obtained by measuring the longest diameter and thickness of a particle using a scanning electron microscope and calculating longest diameter/thickness.
  • the average particle size of the flat boron nitride in component (C) is 3 to 50 ⁇ m, preferably 5 to 50 ⁇ m, and more preferably 8 to 50 ⁇ m. If the particle size is less than 3 ⁇ m, the voids between the boron nitride particles oriented in the silicone rubber composition will become large, reducing their function as a barrier layer against electrical breakdown after curing, preventing sufficient dielectric breakdown strength from being achieved. If the particle size is greater than 50 ⁇ m, processability will be significantly reduced.
  • the flat boron nitride of component (C) may have a single average particle size, or multiple types with different average particle sizes may be mixed together.
  • the average particle size is the cumulative 50% particle size (D50) on a volume basis measured using a Microtrac Bell MT3000II particle size distribution analyzer.
  • organic peroxide curing agents include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-methylbenzoyl peroxide, o-methylbenzoyl peroxide, 2,4-dicumyl peroxide, 2,5-dimethyl-bis(2,5-t-butylperoxy)hexane, di-t-butyl peroxide, t-butyl perbenzoate, 1,6-hexanediol-bis-t-butylperoxycarbonate, etc. These may be used alone or in combination of two or more.
  • an organohydrogenpolysiloxane and a platinum group metal catalyst are used.
  • the organohydrogenpolysiloxane may be linear, branched, or cyclic, as long as it contains two or more, preferably three or more, more preferably 3 to 200, and even more preferably about 4 to 100 hydrogen atoms bonded to silicon atoms (SiH groups) per molecule, but preferably has a degree of polymerization of 300 or less.
  • organohydrogenpolysiloxanes include dimethylpolysiloxanes blocked at both ends with dimethylhydrogensiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymers blocked at both ends with trimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymers blocked at both ends with dimethylhydrogensiloxy groups, and copolymers of dimethylhydrogensiloxane units (H(CH 3 ) 2 SiO 0.5 units) and SiO
  • Examples of such compounds include low-viscosity fluids consisting of 2 units, 1,3,5,7-tetrahydrogen-1,3,5,7-tetramethylcyclotetrasiloxane, 1-propyl-3,5,7-trihydrogen-1,3,5,7-tetramethylcyclotetrasiloxane, 1,5-dihydrogen-3,7-dihexyl-1,3,5,7-tetramethylcyclotetrasiloxane,
  • platinum group metal catalysts include platinum group metals (platinum, palladium, rhodium, etc.) and their compounds, and specific examples include elemental platinum, platinum compounds, platinum complexes, chloroplatinic acid, alcohol compounds of chloroplatinic acid, aldehyde compounds, ether compounds, and complexes with various olefins.
  • the amount of platinum group metal catalyst added is preferably 1 to 2,000 ppm (by mass) of platinum group metal atoms relative to the organopolysiloxane of component (A). If the amount added is less than the above lower limit, the addition reaction may not be sufficiently promoted, resulting in insufficient curing. On the other hand, if the amount added exceeds the above upper limit, the effect on reactivity may be reduced, which may be uneconomical.
  • the silicone rubber composition of the present invention preferably contains, as an optional component, (E) an organosilane or organosiloxane compound represented by the following general formula (2):
  • Component (E) acts as a dispersant (wetter) to improve the dispersibility of the reinforcing silica of component (B) in component (A), and by incorporating component (E), the workability, extrusion properties, etc. of the silicone rubber composition of the present invention are improved.
  • R 1 is a hydrogen atom or the same or different unsubstituted or substituted alkyl groups
  • R 2 is the same or different unsubstituted or substituted monovalent hydrocarbon groups
  • m is a positive number from 1 to 50.
  • the alkyl group for R1 preferably has 1 to 4 carbon atoms, and specific examples thereof include a methyl group, an ethyl group, a propyl group, a butyl group, etc. Further examples include groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms such as chlorine, fluorine, or bromine, or with a cyano group (for example, a trifluoropropyl group, a cyanoethyl group, etc.). Among these, R 1 is preferably a hydrogen atom, a methyl group, or an ethyl group.
  • the amount of organosilane/organosiloxane of component (E) added is preferably 0.1 to 50 parts by mass, more preferably 0.5 to 30 parts by mass, and even more preferably 0.5 to 20 parts by mass, per 100 parts by mass of organopolysiloxane of component (A).
  • An amount of 0.1 part by mass or more ensures sufficient workability and extrusion properties for the silicone rubber composition of the present invention, while an amount of 50 parts by mass or less prevents the resulting silicone rubber composition from becoming tacky, thereby eliminating the risk of reduced processability or reduced physical properties of the resulting rubber.
  • the silicone rubber composition of the present invention may contain optional components, as needed, within the range that does not impair the effects of the present invention.
  • optional components include platinum compounds other than the platinum group metal catalysts described above, iron oxides, flame retardants such as halogen compounds, heat resistance improvers such as cerium oxide, antioxidants, ultraviolet absorbers, colorants, and mold release agents, and are known additives for silicone rubber compositions.
  • the method for producing the silicone rubber composition of the present invention is not particularly limited, but it can be obtained by kneading the predetermined amounts of the above-mentioned components using a known kneading machine such as a two-roll mill, kneader, Banbury mixer, etc. If necessary, heat treatment (kneading under heat) may also be performed. Specifically, a preferred method is to knead components (A) and (B) together (when component (E) is added, components (A), (B), and (E) are kneaded together), optionally heat-treat, and then add component (D) at room temperature.
  • a known kneading machine such as a two-roll mill, kneader, Banbury mixer, etc.
  • heat treatment kneading under heat
  • a preferred method is to knead components (A) and (B) together (when component (E) is added, components (A), (B),
  • component (C) may be added before or after heat-treatment, but is preferably added after heat-treatment. Also, component (D) is preferably added after component (C) has been added.
  • the heat treatment temperature and time are not particularly limited, but are preferably 100 to 250° C., more preferably 140 to 180° C., and are preferably about 30 minutes to 5 hours.
  • the mixture obtained by mixing components (A) and (B) (or components (A), (B), and (E) when component (E) is added) is referred to as a silicone rubber compound.
  • the plasticity of this silicone rubber compound is preferably 200 or more, and more preferably 220 or more. If the plasticity is less than 200, when boron nitride (C) is added, the orientation of the boron nitride in the silicone rubber composition is insufficient, and the desired dielectric breakdown strength may not be obtained after curing.
  • the plasticity value mentioned above refers to the Williams plasticity value obtained by mixing components (A) and (B) (or components (A), (B), and (E) when component (E) is added) and measuring the resulting silicone rubber compound in accordance with JIS-K6249:2003.
  • the molding method can be appropriately selected depending on the required application (molded product).
  • Specific molding methods include compression molding, injection molding, transfer molding, atmospheric hot air vulcanization, and steam vulcanization.
  • the curing conditions are not particularly limited and may be appropriately selected depending on the curing method and molded product.
  • primary vulcanization is preferably carried out at 80 to 600°C, more preferably 100 to 450°C, and preferably for several seconds to several days, more preferably for about 5 seconds to 1 hour. Secondary vulcanization may also be carried out as necessary. Secondary vulcanization may be carried out, for example, at 180 to 250°C for about 1 to 10 hours.
  • the silicone rubber composition of the present invention can provide a cured silicone rubber product with excellent dielectric breakdown properties. That is, the cured product of the silicone rubber composition of the present invention preferably has a dielectric breakdown strength of 30 kV/mm or more, more preferably 35 kV/mm, where the dielectric breakdown strength value is measured in accordance with JIS K 6249:2003.
  • [Average particle size] The volume-based cumulative 50% particle diameter (D50) was measured using a particle size distribution measuring device MT3000II manufactured by Microtrac Bell. [Kinematic viscosity] Measurement was carried out at 25°C using an Ostwald viscometer. [Plasticity] The silicone rubber compound obtained by kneading components (A), (B), and (E) was kneaded 15 times using a triple roll mill, and 10 minutes later, the Williams plasticity was measured using the method described in JIS-K6249:2003.
  • Example 1 A silicone rubber compound was obtained by kneading in a kneader 100 parts by mass of methylvinylpolysiloxane raw rubber (A) consisting of 99.85 mol% dimethylsiloxane units and 0.15 mol% methylvinylsiloxane units, with both molecular chain terminals blocked with dimethylvinylsiloxane units and an average degree of polymerization of approximately 7,000, 35 parts by mass of fumed silica (Aerosil 200 (manufactured by Nippon Aerosil Co., Ltd.)) (B) with a specific surface area of 200 m2 /g measured by the BET method, and 5 parts by mass of dimethylpolysiloxane (E) having silanol groups at both terminals, an average degree of polymerization of 13, and a kinematic viscosity at 25°C of 15 mm2 /s.
  • A methylvinylpolysiloxane raw
  • the resulting silicone rubber compound was heat-treated at 180°C for 3 hours, and after cooling, 30 parts by mass of flat boron nitride (C-1) with an aspect ratio of 7 and an average particle size of 3 ⁇ m was added and kneaded to obtain a millable silicone rubber composition. 0.8 parts by mass of the organic peroxide p-methylbenzoyl peroxide (D-1) was added to this and mixed uniformly using a twin roll mill to obtain a silicone rubber composition.
  • C-1 flat boron nitride
  • D-1 organic peroxide p-methylbenzoyl peroxide
  • the resulting silicone rubber composition was press-cured for 10 minutes at 120°C and 686 Pa to produce a 1 mm thick sheet for testing dielectric breakdown strength. This test sheet was then post-cured in an oven at 150°C for 1 hour.
  • the dielectric breakdown strength of the resulting cured product was measured using Transformer Oil A manufactured by Showa Shell Sekiyu K.K. at a voltage rise rate of 2 kV/sec according to the method described in JIS K 6249:2003, and the results are shown in Table 1.
  • Example 2 In Example 1, the dielectric breakdown strength was measured using the same millable silicone rubber composition, except that the amount of fumed silica (B) with a specific surface area of 200 m2 /g measured by the BET method was changed to 47 parts by mass and the amount of dimethylpolysiloxane (E) having silanol groups at both ends as a dispersant was changed to 10 parts by mass.
  • B fumed silica
  • E dimethylpolysiloxane
  • Example 3 the dielectric breakdown strength was measured using the same millable silicone rubber composition, except that the component (C-1) was changed to 30 parts by mass of flat boron nitride (C-2) having an aspect ratio of 10 and an average particle size of 10 ⁇ m.
  • Example 4 the dielectric breakdown strength was measured using the same millable silicone rubber composition, except that component (C-1) was changed to 30 parts by mass of flat boron nitride (C-3) having an aspect ratio of 25 and an average particle size of 45 ⁇ m.
  • Example 5 the dielectric breakdown strength was measured using the same millable silicone rubber composition, except that component (C-1) was changed to 30 parts by mass of flat boron nitride (C-4) having an aspect ratio of 28 and an average particle size of 50 ⁇ m.
  • Example 6 In Example 4, the same millable type silicone rubber composition was used to measure the dielectric breakdown strength, except that the amount of flat boron nitride (C-3) having an aspect ratio of 25 and an average particle size of 45 ⁇ m was changed to 5 parts by mass.
  • Example 2 In Example 1, the amount of fumed silica (B) having a specific surface area of 200 m2 /g by the BET method was changed to 25 parts by mass, and the amount of dimethylpolysiloxane (E) having silanol groups at both ends as a dispersant was changed to 4 parts by mass, and the dielectric breakdown strength was measured using the same millable type silicone rubber composition except that no flat boron nitride (C) was added.
  • B fumed silica
  • E dimethylpolysiloxane
  • Comparative Example 3 In Comparative Example 2, the dielectric breakdown strength was measured using the same millable silicone rubber composition except that 30 parts by mass of flat boron nitride (C-1) having an aspect ratio of 7 and an average particle size of 3 ⁇ m was added.
  • Example 2 the dielectric breakdown strength was measured using the same millable silicone rubber composition, except that component (C-1) was changed to 30 parts by mass of flat boron nitride (C-5) with an aspect ratio of 3 and an average particle size of 3 ⁇ m.
  • Example 5 the dielectric breakdown strength was measured using the same millable silicone rubber composition, except that component (C-1) was changed to 30 parts by mass of flat boron nitride (C-6) with an aspect ratio of 4 and an average particle size of 20 ⁇ m.
  • Comparative Example 4 when the aspect ratio of the added boron nitride is as low as 3, it is not possible to obtain a cured product having a dielectric breakdown characteristic exceeding 30 kV/mm, even when the same amount of boron nitride is added as in Examples 1 to 5. Furthermore, as shown in Comparative Example 3, even when the aspect ratio of the added boron nitride is 7, if the amount of silica is small and the plasticity is low at 140, a cured product having a dielectric breakdown characteristic exceeding 30 kV/mm cannot be obtained.
  • Examples 1 and 2 when the components specified in the present invention are contained and the plasticity is 200 or more, high dielectric breakdown characteristics exceeding 30 kV/mm can be achieved after curing. Furthermore, as shown in Examples 4 and 5, even if the particle size of the boron nitride is large, by adding boron nitride with a high aspect ratio, it is possible to obtain a cured product with good dielectric breakdown characteristics.

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Abstract

L'invention concerne une composition de caoutchouc de silicone comprenant : 100 parties en masse de (A) un organopolysiloxane ayant un degré de polymérisation de 100 ou plus et ayant deux groupes alcényle ou plus liés à un atome de silicium dans la molécule ; 25 à 70 parties en masse de (B) de la silice de renforcement ayant une surface spécifique, telle que mesurée par une méthode BET, de 50 m2/g ou plus ; 5 à 50 parties en masse de (C) du nitrure de bore plat ayant un diamètre moyen de particule de 3 à 50 µm et un rapport d'aspect de 5 ou plus ; et (D) un agent de durcissement en une quantité efficace pour durcir le composant (A).
PCT/JP2025/005768 2024-03-26 2025-02-20 Composition de caoutchouc de silicone et objet durci obtenu à partir de celle-ci Pending WO2025204325A1 (fr)

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JP2024049430A JP2025149010A (ja) 2024-03-26 2024-03-26 シリコーンゴム組成物及びその硬化物
JP2024-049430 2024-03-26

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01221454A (ja) * 1988-02-29 1989-09-04 Shin Etsu Chem Co Ltd 押出成形用シリコーンゴム組成物
JPH0741675A (ja) * 1993-07-28 1995-02-10 Shin Etsu Chem Co Ltd シリコーンゴム製品及びその製造方法
JPH09199880A (ja) * 1996-01-16 1997-07-31 Denki Kagaku Kogyo Kk 放熱シート
JP2012251101A (ja) * 2011-06-06 2012-12-20 Nitto Denko Corp シリコーン樹脂組成物および熱伝導シート
WO2021187609A1 (fr) * 2020-03-19 2021-09-23 デンカ株式会社 Feuille de dissipation de chaleur et méthode de fabrication d'une feuille de dissipation de chaleur

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01221454A (ja) * 1988-02-29 1989-09-04 Shin Etsu Chem Co Ltd 押出成形用シリコーンゴム組成物
JPH0741675A (ja) * 1993-07-28 1995-02-10 Shin Etsu Chem Co Ltd シリコーンゴム製品及びその製造方法
JPH09199880A (ja) * 1996-01-16 1997-07-31 Denki Kagaku Kogyo Kk 放熱シート
JP2012251101A (ja) * 2011-06-06 2012-12-20 Nitto Denko Corp シリコーン樹脂組成物および熱伝導シート
WO2021187609A1 (fr) * 2020-03-19 2021-09-23 デンカ株式会社 Feuille de dissipation de chaleur et méthode de fabrication d'une feuille de dissipation de chaleur

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