WO2024157680A1 - 導電性シリコーンゴム組成物及びその硬化物 - Google Patents

導電性シリコーンゴム組成物及びその硬化物 Download PDF

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WO2024157680A1
WO2024157680A1 PCT/JP2023/045849 JP2023045849W WO2024157680A1 WO 2024157680 A1 WO2024157680 A1 WO 2024157680A1 JP 2023045849 W JP2023045849 W JP 2023045849W WO 2024157680 A1 WO2024157680 A1 WO 2024157680A1
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silicone rubber
groups
component
group
rubber composition
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French (fr)
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佐太央 平林
和弘 土田
恒雄 木村
知哉 南川
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Shin Etsu Chemical Co Ltd
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Shin Etsu Chemical Co Ltd
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Priority to EP23918634.9A priority Critical patent/EP4656685A1/en
Priority to CN202380092191.6A priority patent/CN120584160A/zh
Priority to JP2024572898A priority patent/JPWO2024157680A1/ja
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    • 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
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
    • C08G59/02—Polycondensates containing more than one epoxy group per molecule
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
    • C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
    • C08G59/20—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the epoxy compounds used
    • C08G59/32—Epoxy compounds containing three or more epoxy groups
    • C08G59/3254—Epoxy compounds containing three or more epoxy groups containing atoms other than carbon, hydrogen, oxygen or nitrogen
    • C08G59/3281—Epoxy compounds containing three or more epoxy groups containing atoms other than carbon, hydrogen, oxygen or nitrogen containing silicon
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • 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
    • C08G77/12—Polysiloxanes containing silicon bound to hydrogen
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • 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
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • 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
    • C08G77/20—Polysiloxanes containing silicon bound to unsaturated aliphatic groups
    • 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
    • C08K2201/00—Specific properties of additives
    • C08K2201/001—Conductive additives

Definitions

  • the present invention relates to a conductive silicone rubber composition, and more specifically, to a conductive silicone rubber composition and its cured product that, by adding a reactive epoxy group-containing silanol oligomer, can provide a cured product that has excellent rubber compound processability and improved impact resilience and compression set.
  • the conductive silicone rubber composition is a silicone polymer to which carbon black or the like has been added in order to impart electrical conductivity to the silicone rubber after curing.
  • carbon black generally deteriorates the rebound resilience and compression set of the silicone rubber due to the action of the carbon black as a filler.
  • Patent Document 1 proposes a method of adding a high molecular weight polyester acid amide amine salt or the like as a method for dispersing carbon black in a silicone polymer. Furthermore, Patent Document 2 proposes a method of improving the dispersibility of carbon black by adding a (meth)acrylate/silicone copolymer or the like to a carbon black-containing paint.
  • Patent Document 3 proposes a method of compounding and adding a silanol group-containing silicone oil or a silane coupling agent having a hydrolyzable silyl group to a silicone rubber composition as a silica dispersant. According to this method, it is reported that it is possible to control the reactivity of the silanol groups on the surface of the added silica, thereby improving creep hardening properties, storage stability, and compression set of the cured product.
  • Patent Document 4 also proposes a method of adding a polyether-modified silicone oil having hydroxyl and epoxy groups to a conductive silicone rubber composition. It is reported that the added polyether component can control and accelerate the charge amount and charge decay rate.
  • silicone rubber compositions in which a silane coupling agent or silanol group-containing silicone oil is added as a dispersant for the silica or carbon black to a conductive silicone rubber composition to which reinforcing silica or carbon black has been added, and a polyether-modified silicone oil is used for charge decay control.
  • a silane coupling agent or silanol group-containing silicone oil is added as a dispersant for the silica or carbon black to a conductive silicone rubber composition to which reinforcing silica or carbon black has been added
  • a polyether-modified silicone oil is used for charge decay control.
  • proactively proposing techniques that can improve the impact resilience or compression set of the cured product of an electrically conductive silicone rubber composition.
  • rubber compounds that contain conductive carbon in silicone polymers may have their silicone polymers broken if they are subjected to strong kneading (shearing) or stored for long periods of time (six months or more). When this occurs, the rubber compound becomes sticky and its processability decreases, but there have been no examples of any proactive proposals for technologies that can improve this.
  • the present invention has been made in consideration of the above circumstances, and aims to provide a conductive silicone rubber composition that has good processability and gives a cured product with improved rebound resilience and compression set, and a cured product thereof.
  • the present invention provides 1.
  • R 1 is a monovalent hydrocarbon group having 1 to 10 carbon atoms
  • R 2 are each independently a monovalent hydrocarbon group having 1 to 10 carbon atoms which may be substituted with a glycidyloxy group
  • R 3 is a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms
  • x and y are numbers which satisfy x ⁇ 1.0
  • the conductive silicone rubber composition according to 1 or 2, wherein in the above formula (1), b, c, and d are numbers that satisfy b 0, 0 ⁇ c ⁇ 0.5, and 0 ⁇ d ⁇ 0.2. 4.
  • a cured product of the conductive silicone rubber composition according to any one of 1 to 3 is provided.
  • the conductive silicone rubber composition of the present invention containing the 3-glycidyloxypropylsilanol oligomer has good processability and can give a cured conductive silicone rubber with improved impact resilience and compression set.
  • FIG. 1 is a 1 H-NMR spectrum of the 3-glycidyloxypropylsilanol oligomer obtained in Synthesis Example 1.
  • the conductive silicone rubber composition of the present invention contains the following components (A) to (D).
  • component (A) is an organopolysiloxane having two or more alkenyl groups bonded to silicon atoms in each molecule.
  • the alkenyl group preferably has 2 to 8 carbon atoms, and more preferably has 2 to 6 carbon atoms.
  • Specific examples thereof include vinyl, allyl, butenyl, pentenyl, hexenyl, and cyclohexenyl groups. Of these, the vinyl group is preferred.
  • Substituents other than alkenyl groups bonded to silicon atoms are not particularly limited, and examples thereof include monovalent hydrocarbon groups having 1 to 12 carbon atoms, preferably 1 to 8 carbon atoms.
  • the monovalent hydrocarbon group may be linear, branched, or cyclic, and specific examples thereof include alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, and octyl groups; cycloalkyl groups such as cyclopentyl and cyclohexyl groups; aryl groups such as phenyl and tolyl groups; and aralkyl groups such as benzyl and 2-phenylethyl groups.
  • fluoroalkyl groups such as fluoromethyl groups in which some or all of the hydrogen atoms of these monovalent hydrocarbon groups have been substituted with halogen atoms such as chlorine atoms, fluorine atoms, bromine atoms, etc.
  • halogen atoms such as chlorine atoms, fluorine atoms, bromine atoms, etc.
  • halogen-substituted monovalent hydrocarbon groups such as bromoethyl, chloromethyl, 3-chloropropyl, and 3,3,3-trifluoropropyl groups
  • a methyl group and a phenyl group are preferred, and a methyl group is more preferred.
  • the component (A) has two or more alkenyl groups in one molecule, preferably 2 to 50, and more preferably 2 to 20 alkenyl groups. Of these, those having a vinyl group are particularly preferred. In this case, it is preferred that 0.01 to 20 mol %, and particularly 0.02 to 10 mol %, of all siloxane units in the organopolysiloxane are siloxane units having an alkenyl group.
  • the alkenyl group may be bonded to a silicon atom at the molecular chain terminal, or to a silicon atom in the middle of the molecular chain (non-terminal of the molecular chain), or both, but it is preferred that the alkenyl group is bonded to a silicon atom at at least the molecular chain terminal.
  • 80 mol % or more, preferably 90 mol % or more, more preferably 95 mol % or more, of all the siloxane units in the organopolysiloxane, and even more preferably all the siloxane units except for the siloxane units having an alkenyl group are dialkylsiloxy groups, and more preferably dimethylsiloxy groups.
  • the molecular structure of the organopolysiloxane, component (A), is preferably linear or partially branched.
  • the repeating structure of the diorganosiloxane units constituting the main chain of the organopolysiloxane is preferably one consisting of repeating dimethylsiloxane units alone, or one in which diorganosiloxane units such as diphenylsiloxane units, methylphenylsiloxane units, methylvinylsiloxane units, or methyl-3,3,3-trifluoropropylsiloxane units have been introduced as part of this.
  • both molecular chain terminals are preferably capped with a group selected from, for example, a trimethylsiloxy group, a dimethylphenylsiloxy group, a vinyldimethylsiloxy group, a divinylmethylsiloxy group, a trivinylsiloxy group, a methylphenylvinylsiloxy group, and the like, and are particularly preferably capped with a vinyldimethylsiloxy group.
  • organopolysiloxane of component (A) above include dimethylpolysiloxane capped at both molecular chain terminals with dimethylvinylsiloxy groups, dimethylpolysiloxane capped at both molecular chain terminals with methylphenylvinylsiloxy groups, dimethylsiloxane-methylphenylsiloxane copolymers capped at both molecular chain terminals with dimethylvinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers capped at both molecular chain terminals with dimethylvinylsiloxy groups, and dimethylsiloxane-methylvinylsiloxane copolymers capped at both molecular chain terminals with trimethylsiloxy groups.
  • organopolysiloxanes can be obtained, for example, by (co)hydrolytic condensation of one or more organohalogenosilanes, or by ring-opening polymerization of cyclic polysiloxanes (siloxane trimers, tetramers, etc.) using an alkaline or acidic catalyst.
  • the average degree of polymerization of the above organopolysiloxane is preferably 100 to 100,000, more preferably 1,000 to 50,000, further preferably 2,500 to 30,000, and particularly preferably 3,000 to 20,000.
  • a preferred property of this organopolysiloxane is that it has no self-flowing property at room temperature (25° C.), that is, it is in the form of raw rubber (non-liquid state). If the average degree of polymerization is too low, it may become difficult to disperse the carbon black.
  • the average degree of polymerization of component (A) is determined as a weight-average degree of polymerization calculated from the weight-average molecular weight determined by gel permeation chromatography (GPC) analysis measured under the conditions shown below, using polystyrene of known molecular weight as a standard substance.
  • GPC gel permeation chromatography
  • TSKgel SuperH2000 (6.0mm I.D. x 15cm x 1) (All manufactured by Tosoh Corporation) Column temperature: 40°C Sample injection volume: 50 ⁇ L (THF solution with a concentration of 2.0% by mass) Standard: Monodisperse polystyrene
  • Component (A) may be used alone or in the form of a mixture of two or more types differing in molecular weight (degree of polymerization) or molecular structure.
  • the conductive carbon black of component (B) is an additive that imparts electrical conductivity to the silicone rubber composition.
  • the conductive carbon black is not particularly limited, and any carbon black commonly used in conductive rubber compositions can be used. Specific examples thereof include acetylene black, conductive furnace black (CF), super conductive furnace black (SCF), extra conductive furnace black (XCF), conductive channel black (CC), furnace black or channel black that has been heat-treated at a high temperature of about 1,500° C., carbon fiber, carbon nanotube, fullerene, and the like.
  • examples of acetylene black include Denka Acetylene Black (manufactured by Denki Kagaku Co.), Shawnigan Acetylene Black (manufactured by Shawnigan Chemical Co.), etc.;
  • examples of conductive furnace black include Continex CF (manufactured by Continental Carbon Corp.) and Vulcan C (manufactured by Cabot Corp.);
  • examples of super conductive furnace black include Continex SCF (manufactured by Continental Carbon Corp.) and Vulcan SC (manufactured by Cabot Corp.);
  • examples of extra conductive furnace black include Asahi HS-500 (manufactured by Asahi Carbon Co., Ltd.) and Vulcan XC-72 (manufactured by Cabot Corp.);
  • examples of conductive channel black include Kourax L (manufactured by Degussa Co., Ltd.).
  • furnace blacks such as Ketjen Black EC and Ketjen Black EC-600JD (manufactured by Ketjen Black International Co., Ltd.).
  • acetylene black and furnace black are particularly preferably used in the present invention, with acetylene black being particularly preferred.
  • These conductive carbon blacks may be used alone or in combination of two or more.
  • the amount of the (B) component added is 0.5 to 40 parts by mass, preferably 2 to 30 parts by mass, and more preferably 8 to 20 parts by mass, per 100 parts by mass of the (A) component described above. If the amount added is less than 0.5 parts by mass, the desired conductivity cannot be obtained in the resulting silicone rubber, and if it exceeds 40 parts by mass, it becomes difficult to add it to the (A) component, and the resulting silicone rubber will have a significantly reduced strength and elongation at break, resulting in a significant decrease in rubber strength.
  • component (C) 3-glycidyloxypropylsilanol oligomer represented by the following formula (1) is used as component (C).
  • Component (C) is an essential component that acts as an additive for improving the impact resilience of the silicone rubber and improving the compression set by interacting or reacting with the carboxyl groups and phenolic hydroxyl groups on the surface of the carbon black in component (B) and surface-modifying the carbon black in component (B), thereby suppressing surface interactions such as excessive van der Waals forces with component (A) and hydrogen bonds with the carbon-bonding hydroxyl groups.
  • R 1 is a monovalent hydrocarbon group having 1 to 10 carbon atoms, preferably a monovalent hydrocarbon group having 1 to 6 carbon atoms.
  • the monovalent hydrocarbon group of R 1 may be linear, branched, or cyclic, and specific examples thereof include alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, and decyl groups; cycloalkyl groups such as cyclopentyl and cyclohexyl groups; alkenyl groups such as vinyl and allyl groups; and aryl groups such as phenyl and naphthyl groups.
  • methyl, ethyl, propyl, and phenyl groups are preferred, methyl and ethyl groups are more preferred, and methyl is even more preferred.
  • Each R 2 is independently a monovalent hydrocarbon group having 1 to 10 carbon atoms which may be substituted with a glycidyloxy group, and is preferably a monovalent hydrocarbon group having 1 to 6 carbon atoms.
  • the monovalent hydrocarbon group of R 2 may be linear, branched, or cyclic, and specific examples thereof include the same as those exemplified for R 1 above, and glycidyloxy-substituted alkyl groups such as glycidyloxypropyl and glycidyloxyoctyl groups.
  • methyl, ethyl, propyl, glycidyloxypropyl, and phenyl groups are preferred, methyl, ethyl, and glycidyloxypropyl groups are more preferred, and methyl and glycidyloxypropyl groups are even more preferred.
  • R3 is a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms, and more preferably a monovalent saturated or unsaturated aliphatic hydrocarbon group having 1 to 4 carbon atoms.
  • the monovalent aliphatic hydrocarbon group of R3 may be linear, branched, or cyclic, and specific examples thereof include alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, and decyl groups; cycloalkyl groups such as cyclopentyl and cyclohexyl groups; and alkenyl groups such as vinyl and allyl groups.
  • methyl, ethyl, propyl, and butyl groups are preferred, with methyl and ethyl groups being more preferred, and methyl being even more preferred.
  • the number b is preferably a number that satisfies 0 ⁇ b ⁇ 0.5, and 0 is more preferable.
  • c is a number that satisfies 0 ⁇ c ⁇ 0.5.
  • the number d is preferably a number that satisfies 0 ⁇ d ⁇ 0.2, and 0 is more preferable.
  • x and y are the numbers of hydroxyl groups or alkoxy groups bonded to 1 mole of silicon atoms in the siloxane units a to d, and are numbers that satisfy x ⁇ 1.0 and y ⁇ 0.5. It is preferable that x is a number that satisfies 1 ⁇ x ⁇ 2.
  • the value of y is preferably a number that satisfies y ⁇ 0.4, and more preferably a number that satisfies y ⁇ 0.3.
  • the component (C) is preferably represented by the following formula (1a):
  • the component (C) may be used alone or in combination of two or more types.
  • the weight average molecular weight of the oligomer of component (C) is preferably 500 to 10,000, and more preferably 500 to 1,000, from the viewpoint of the handling viscosity of the composition of the present invention.
  • the weight average molecular weight of component (C) in the present invention is a value determined by gel permeation chromatography (GPC) measured under the conditions shown below, converted using polystyrene of known molecular weight as a standard substance.
  • the kinematic viscosity of component (C) is preferably from 10 to 1,000 mm 2 /s, and more preferably from 100 to 800 mm 2 /s.
  • the kinematic viscosity is a value at 25° C. measured using a Cannon-Fenske viscometer according to the method described in JIS Z8803:2011.
  • the method for producing component (C) used in the present invention is not particularly limited, but it can be produced, for example, by using a 3-glycidyloxypropyl group-containing silane compound such as 3-glycidyloxypropyltrimethoxysilane or 3-glycidyloxypropyltriethoxysilane represented by the following formula (i) or a mixture thereof as the essential silane monomer raw material, and, if necessary, (co)hydrolyzing under acidic conditions a silane monomer containing one or more of a silane compound represented by the following formula (ii), a silane compound represented by the following formula (iii), and a silane compound represented by the following formula (iv).
  • 3-glycidyloxypropyl group-containing silane compound represented by the above formula (i) include 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, 3-glycidyloxypropyltripropoxysilane, 3-glycidyloxypropyltributoxysilane, and the like.
  • silane compound represented by the above formula (ii) examples include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, butyltrimethoxysilane, butyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, and decyltriethoxys
  • silane compound represented by the above formula (iii) include dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, methylethyldimethoxysilane, methylethyldiethoxysilane, methylpropyldimethoxysilane, methylpropyldiethoxysilane, 3-glycidyloxypropylmethyldimethoxysilane, 3-glycidyloxypropylmethyldiethoxysilane, cyclopentylmethyldimethoxysilane, cyclohexylmethyldimethoxysilane, methylphenyldimethoxysilane, methylphenyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, methyloctyldimethoxysilane, and the like.
  • silane compound represented by the above formula (iv) examples include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane.
  • hydrolysis condensation products of these may also be used. These may be used alone or in combination of two or more.
  • the amount of these silane monomers used is preferably adjusted according to the molar ratio of each siloxane unit constituting the desired organopolysiloxane (the values of a to d in formula (1)).
  • the amount of water used in the hydrolysis and condensation reaction is preferably 0.8 to 1.1 times by mole per mole of Si(OR 3 ) group (R 3 is the same as above) such as an alkoxysilyl group of the silane monomer used as a raw material.
  • the acid component used to adjust the acidic conditions during the hydrolysis reaction is not particularly limited as long as it is a commercially available Br ⁇ nsted acid, but from the viewpoint of ease of availability, formic acid, acetic acid, citric acid, hydrochloric acid, and nitric acid are preferred.
  • the amount of acid used is preferably 0.0001 to 0.01 moles per mole of silane monomer from the viewpoint of suppressing an increase in the molecular weight of the organopolysiloxane obtained by an excessive dehydration condensation reaction between silanols and a decrease in water solubility due to a decrease in the amount of silanol groups.
  • an organic solvent may be used as necessary within a range that does not inhibit the reaction.
  • the organic solvent used is preferably one that is compatible with water, which is the reaction raw material, and is preferably an alcohol, an ester, a ketone, an ether, or the like.
  • the organic solvent preferably has a low boiling point, and is preferably a solvent having a boiling point of 150° C. or less under atmospheric pressure.
  • specific examples of alcohols include methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentyl alcohol, neopentyl alcohol, hexyl alcohol, and cyclohexyl alcohol.
  • esters include ethyl acetate and butyl acetate.
  • ketones include acetone, methyl ethyl ketone, and cyclohexanone.
  • ethers include tetrahydrofuran, tetrahydropyran, and dioxane.
  • reaction conditions it is preferable to mix the silane monomer with water and stir, for example, at 55 to 70°C for 1 to 5 hours to allow the hydrolysis reaction of the silane monomer to proceed, and then distill off the water/alcohol mixture under reduced pressure at a temperature range of 30 to 80°C.
  • the 3-glycidyloxypropylsilanol oligomer used in the present invention preferably contains 1% by mass or less of water and free alcohol.
  • This composition allows the material to be free of volatile organic compounds (VOCs), which is advantageous in reducing the VOCs in the entire conductive silicone composition to which it is added.
  • VOCs volatile organic compounds
  • free of VOCs means that the content of free alcohol in the oligomer or the composition of the present invention is preferably 1% by mass or less.
  • alcohol refers in particular to methanol or ethanol.
  • the amount of component (C) added is 0.01 to 10 parts by mass, and preferably 0.2 to 2.0 parts by mass, per 100 parts by mass of component (A). If the amount of component (C) added is less than 0.01 parts by mass, it will not contribute to the desired improvement in rebound resilience or reduction in compression set, and if it exceeds 10 parts by mass, the resulting compound will be sticky, resulting in poor processability and reduced mechanical properties such as tensile strength of the silicone rubber produced by curing this compound.
  • the component (D) is a curing agent.
  • the curing agent is not particularly limited as long as it can cure the component (A), but generally, any known rubber curing agent can be used, such as the following components (D1) and (D2).
  • D1 An addition reaction (hydrosilylation reaction) type curing agent, that is, a curing agent for a hydrosilylation reaction, which is a combination of an organohydrogenpolysiloxane (crosslinking agent) and a hydrosilylation catalyst.
  • D2 An organic peroxide.
  • organohydrogenpolysiloxane used as the crosslinking agent of the above-mentioned (D1) addition reaction type curing agent is preferably one having two or more hydrosilyl groups in one molecule.
  • organohydrogenpolysiloxanes represented by the following formula (2) are preferred.
  • R 4s are each independently a hydrogen atom, or a group selected from an alkyl group having 1 to 8, preferably 1 to 6, carbon atoms, a cycloalkyl group having 6 to 10, preferably 6 to 8, carbon atoms, an aryl group having 6 to 10, preferably 6 to 8, carbon atoms, and an aralkyl group having 7 to 10, preferably 7 to 9, carbon atoms.
  • 2 or more, preferably 2 to 200, more preferably 2 to 130 R 4s are hydrogen atoms.
  • the alkyl group of R 4 may be either linear or branched, and specific examples thereof include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, and hexyl groups.
  • Specific examples of the cycloalkyl group include cyclopentyl and cyclohexyl groups.
  • Specific examples of the aryl group include phenyl and tolyl groups.
  • Specific examples of the aralkyl group include benzyl and 2-phenylpropyl groups.
  • fluoroalkyl groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms such as fluorine atoms may also be used.
  • e is an integer satisfying 2 ⁇ e ⁇ 30, and preferably 2 ⁇ e ⁇ 20.
  • f is an integer satisfying 0 ⁇ f ⁇ 300, preferably 3 ⁇ f ⁇ 200.
  • g is an integer satisfying 0 ⁇ g ⁇ 10, preferably 0 ⁇ g ⁇ 5.
  • h is an integer satisfying 0 ⁇ h ⁇ 30, preferably 0 ⁇ h ⁇ 20.
  • the molecular structure of the organohydrogenpolysiloxane may be linear, cyclic, branched, or three-dimensional network.
  • the number of silicon atoms (or degree of polymerization) in one molecule is preferably 2 to 300, more preferably 4 to 200, and it is preferably liquid at 25°C.
  • the hydrosilyl group may be at the end of the molecular chain, in the side chain (in the middle of the molecular chain), or both.
  • the method for measuring the degree of polymerization is as explained for component (A).
  • organohydrogenpolysiloxanes include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane-dimethylsiloxane cyclic copolymer, tris(dimethylhydrogensiloxy)methylsilane, tris(dimethylhydrogensiloxy)phenylsilane, methylhydrogenpolysiloxane capped at both ends with trimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymer capped at both ends with trimethylsiloxy groups, and dimethylsiloxane-methylhydrogensiloxane copolymer capped at both ends with dimethylsiloxy groups.
  • k is an integer from 2 to 10
  • s and t are each an integer from 0 to 10.
  • the organohydrogenpolysiloxane preferably has a kinetic viscosity at 25° C. of 0.5 to 10,000 mm 2 /s, more preferably 1 to 300 mm 2 /s, and even more preferably 1 to 100 mm 2 /s.
  • the kinetic viscosity is a value measured using a Cannon-Fenske viscometer according to the method described in JIS Z8803:2011.
  • this organohydrogenpolysiloxane in an amount such that the molar ratio (hydrosilyl groups/alkenyl groups) of hydrogen atoms bonded to silicon atoms in the organohydrogenpolysiloxane to the alkenyl groups bonded to silicon atoms in component (A) is preferably 0.5 to 10, more preferably 0.8 to 6, and even more preferably 1 to 5. If it is less than 0.5, crosslinking will be insufficient and sufficient mechanical strength may not be obtained after curing, while if it exceeds 10, the physical properties after curing will decrease, and in particular the heat resistance and compression set resistance may be significantly deteriorated.
  • the hydrosilylation catalyst used in the above (D1) addition reaction type curing agent is a catalyst that promotes the addition reaction of the alkenyl groups in the above component (A) with the hydrosilyl groups in the above organohydrogenpolysiloxane serving as a crosslinking agent.
  • hydrosilylation catalysts include platinum group metal catalysts. Platinum group metal catalysts include platinum group metals and their compounds. For these catalysts, those that have been conventionally known as catalysts for addition reaction curing silicone rubber compositions can be used.
  • platinum catalysts such as fine particle platinum metal adsorbed on carriers such as silica, alumina or silica gel, platinic chloride, chloroplatinic acid, reaction product of chloroplatinic acid and monohydric alcohol, complex of chloroplatinic acid and olefins, complex of chloroplatinic acid and vinyl group-containing (poly)siloxane, complex of chloroplatinic acid and phosphorous acid ester, palladium catalyst, rhodium catalyst, ruthenium catalyst, etc. These may be used alone or in combination of two or more. Among them, platinum or platinum compounds are preferred.
  • the amount of hydrosilylation catalyst added may be a catalytic amount capable of promoting the addition reaction, and is usually preferably 1 ppm to 1 mass %, and more preferably 10 to 500 ppm, calculated as the mass of platinum group metal relative to the mass of component (A) above. If the amount added is less than 1 ppm, the addition reaction may not be promoted sufficiently, resulting in insufficient curing, whereas if the amount added exceeds 1 mass %, the effect on reactivity is small, even if more than this amount is added, and this may be uneconomical.
  • an addition crosslinking regulator may be used to adjust the curing speed.
  • specific examples include ethynylcyclohexanol, tetramethyltetravinylcyclotetrasiloxane, etc.
  • examples of the (D2) organic peroxide include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-methylbenzoyl peroxide, o-methylbenzoyl peroxide, 2,4-dicumyl peroxide, 2,5-dimethyl-2,5-bis(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.
  • the amount of organic peroxide added is an effective curing amount, and is preferably 0.1 to 15 parts by mass, and more preferably 0.2 to 10 parts by mass, per 100 parts by mass of component (A). If the amount added is sufficient, the crosslinking reaction will proceed sufficiently and there will be no deterioration in physical properties such as a decrease in hardness, insufficient rubber strength, or increased compression set. Furthermore, if the amount added does not exceed the above amount, it is economically preferable, and there will be sufficiently little decomposition product of the curing agent, so there will be no deterioration in physical properties such as increased compression set, or increased discoloration of the obtained sheet.
  • the conductive silicone rubber composition of the present invention may contain reinforcing silica having a specific surface area (BET adsorption method) of 100 to 450 m2 /g, provided that the effects of the present invention are not impaired.
  • specific examples of the reinforcing silica include fumed silica and precipitated silica (wet silica), as well as those whose surfaces have been hydrophobized with chlorosilane, hexamethyldisilazane, or the like. Of these, hydrophobized fumed silica is preferred.
  • the conductive silicone rubber composition of the present invention can further contain additives such as flame retardants such as iron oxides and halogen compounds, antistatic agents, softeners, antioxidants, ultraviolet absorbers, colorants, etc.
  • the method for producing the silicone rubber composition according to the present invention is not particularly limited, but for example, the silicone rubber composition can be obtained by uniformly mixing the above-mentioned components using a rubber kneader such as a two-roll mill, a Banbury mixer, or a dough mixer (kneader), and subjecting the mixture to heat treatment as necessary.
  • a rubber kneader such as a two-roll mill, a Banbury mixer, or a dough mixer (kneader
  • the components (A) to (C) and other components such as fine powder silica-based filler as reinforcing silica as necessary are mixed to prepare a base compound, to which the curing agent (D) is added and mixed to obtain the composition of the present invention.
  • the organopolysiloxane (A), the silanol oligomer (C), and other components such as fine powder silica-based filler as reinforcing silica as necessary may be mixed in advance to prepare a base compound, and the carbon black powder (B) may be mixed into the base compound in the same manner using a rubber kneader to prepare the composition, or the curing agent (D) may be added and mixed.
  • the conductive silicone rubber composition thus obtained can be molded according to the required application by various molding methods that are usually used to mold silicone compositions, such as molded under pressure, extrusion, injection molding, etc.
  • the molding conditions are not particularly limited, but a temperature of 100 to 400°C for 5 seconds to 1 hour is preferable.
  • a silicone rubber cured product is obtained by secondary vulcanization at 150 to 250°C for 1 to 30 hours.
  • the thus obtained cured product (silicone rubber) of the present invention preferably has a compression set of 30% or less, more preferably 25% or less, and even more preferably 20% or less, as measured according to the method specified in JIS K6249:2003.
  • the rebound resilience measured according to the method specified in JIS K6255:2013 is preferably 50% or more, more preferably 55% or more, and even more preferably 60% or more.
  • the cured product of the present invention preferably satisfies both the above-mentioned compression set and rebound resilience.
  • the conductive silicone rubber composition of the present invention provides a conductive silicone rubber (cured product) that has excellent compression set and rebound resilience.
  • the conductive silicone rubber composition of the present invention is also expected to find wide application in applications where conductive silicone rubber is used, such as electrical equipment, office machine rolls, automobiles, construction, medical care, and food fields.
  • TSKgel SuperH2000 (6.0mmI.D. ⁇ 15 cm x 1) (All manufactured by Tosoh Corporation) Column temperature: 40°C Sample injection volume: 50 ⁇ L (2.0% THF solution) Standard: Method for measuring weight average molecular weight of component (A) in monodisperse polystyrene-rubber compound Measurement was performed using the same device and conditions as above.
  • Measurement method for weight average molecular weight of component (C) Apparatus: HLC-8320GPC manufactured by Tosoh Corporation Developing solvent: tetrahydrofuran (THF) Flow rate: 0.6 mL/min Detector: Differential refractive index detector (RI) Column: TSK Guard column Super H-H TSKgel SuperHM-N (6.0mm I.D. x 15c m x 1) TSKgel SuperH2500 (6.0mm I.D.
  • Comparative Synthesis Example 2 Synthesis of Component (Comparative to C-2) A linear polymer having silanol ends not containing 3-glycidyloxypropyl groups was obtained in the same manner as in Synthesis Example 1, except that 120 g (1.0 mol) of dimethyldimethoxysilane was used instead of 3-glycidyloxypropyltrimethoxysilane, and the amount of 0.2% hydrochloric acid was 90 g (5.0 mol as water). The resulting polymer had a kinetic viscosity of 13 mm 2 /s at 25° C. and a weight average molecular weight of 270. Analysis by 1 H-NMR and GPC measurements revealed that the polymer had a structure represented by the following formula (7).
  • (D2) Organic peroxide curing agent: 2,5-dimethyl-2,5-di-(t-butylperoxy)hexane was used. The amounts added were (A), (B), and (C). Silicone rubber compound 10 containing component (A) and reinforcing silica, excluding component (D). 0 parts was added 0.5 parts. Other additives: Reinforcing silica surface-treated with dimethyldichlorosilane, BET specific surface area 110 m2 /g, carbon content 0.9% The fumed silica (trade name: R-972, manufactured by Nippon Aerosil Co., Ltd.) was used.
  • Example 1 100 parts of organopolysiloxane raw rubber (A), 30 parts of carbon black (B), and 1.0 part of 3-glycidyloxypropylsilanol oligomer (C-1) were charged into a pressure kneader and kneaded for 5 minutes to obtain a silicone rubber compound. 100 parts of this silicone rubber compound was mixed uniformly with 0.5 parts of (D2) curing agent using a two-roll mill, and then molded in a mold at 120° C. for 10 minutes or at 165° C. for 10 minutes, followed by post-curing at 200° C. for 4 hours to prepare a 2 mm thick test sheet and a 12.5 mm thick, 29.5 mm diameter disk-shaped rubber molded product. The obtained rubber sheets and rubber molded products were used to evaluate the rubber properties shown in Table 1. The results are also shown in Table 1.
  • Examples 2 to 5, Comparative Examples 1 to 6 As shown in Table 1, silicone rubber compositions were prepared by compounding the components of Examples 2 to 5 and Comparative Examples 1 to 6, and rubber sheets and rubber molded products were produced in the same manner as in Example 1, and various rubber properties were evaluated. The results are also shown in Table 1.
  • Comparative Example 5 a linear silanol polymer not containing a 3-glycidyloxypropyl group was used as component (C), and similarly, the impact resilience was worse than that of Comparative Example 2.
  • Comparative Example 6 is a composition containing 3-glycidyloxypropyltrimethoxysilane (KBM-403), which is the starting material for the 3-glycidyloxypropylsilanol oligomer of component (C-1).
  • KBM-403 3-glycidyloxypropyltrimethoxysilane
  • the rebound resilience is significantly worse than that of Comparative Example 2, which contains no additive.
  • the compression set is improved compared to Comparative Example 2, but does not reach the values of Examples 2, 4, and 5, and it is clear that this does not result in improvements in compression set and rebound resilience.
  • the plasticity of each of the millable type silicone rubber compounds of Reference Examples 1 to 4, which contain the 3-glycidyloxypropylsilanol oligomer of component (C), is sufficient or higher than that of Comparative Reference Examples 1 to 5, which do not contain component (C), and the decrease in plasticity after six months of storage at 50°C/80% RH is kept very small, demonstrating good rubber processability.
  • the degree of decrease in polymerization of component (A) of the rubber compound containing component (C) is less after six months of storage at 50°C/80% RH compared to immediately after the carbon is added, and it can be considered that the factor that suppresses the decrease in plasticity of the silicone rubber compound is the improvement effect of preventing polymer cleavage of component (A).

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JPH07133433A (ja) 1993-11-08 1995-05-23 Shin Etsu Chem Co Ltd シリコーンゴム組成物
JP2000039755A (ja) 1998-07-24 2000-02-08 Hokushin Ind Inc 導電部材
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JP2021021058A (ja) * 2019-07-30 2021-02-18 デュポン・東レ・スペシャルティ・マテリアル株式会社 ホットメルト性硬化性シリコーン組成物、封止剤、フィルム、光半導体素子

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JPH07133433A (ja) 1993-11-08 1995-05-23 Shin Etsu Chem Co Ltd シリコーンゴム組成物
JP2000039755A (ja) 1998-07-24 2000-02-08 Hokushin Ind Inc 導電部材
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