Phenyl silicone rubber composition and cured object thereof

Abstract

This phenyl silicone rubber composition is characterized by comprising (A) a green-rubber-state organopolysiloxane represented by general formula (1), (B) powdery silica having a BET specific surface area of 100 m2 / g or larger as reinforcing silica, (C) a mixture (i) of a platinum-based catalyst with a siloxane having two or more Si-H groups in the molecule or a peroxide (ii) as a harder, and (D) a dispersant. The phenyl silicone rubber composition gives cured phenyl silicone rubber objects which not only have satisfactory low-temperature characteristics, high hardness that makes the objects withstand high pressures but also have high extensibility that makes the objects withstand repetitions of a high-pressure environment and an ordinary-pressure environment.

Description

Phenylsilicone rubber composition and cured product thereof 【0001】 The present invention relates to a silicone rubber composition, and more specifically, to a silicone rubber composition having a specific siloxane composition. 【0002】 Silicone rubber compositions are used in various fields due to their ease of handling, moldability, and excellent properties such as heat resistance, cold resistance, weather resistance, and electrical insulation after molding. In particular, phenyl silicone rubber compositions, which mainly consist of phenyl silicone raw rubber containing a repeating structure of methylsiloxane units having phenyl groups, have excellent rubber properties even at low temperatures and are widely used in applications such as gaskets, coatings, and seals for transportation equipment parts and electrical and electronic components. Non-patent document 1 describes that the properties at low temperatures are particularly excellent when the amount of phenyl in the silicone rubber is within a certain range. 【0003】 In recent years, petroleum alternatives such as natural gas, ammonia, and hydrogen have attracted attention as clean fuels, and in the semiconductor industry, refrigerant gases are increasingly being used to cool equipment. In such applications, high reliability is required for sealing materials, and the properties required of silicone rubber have become highly sophisticated. For example, it is required that the rubber does not break down even under large pressure and temperature fluctuations and maintains its physical properties. In particular, during the process of depressurizing and compressing gases, the temperature of the rubber used in surrounding components can become extremely low, and it is required that the rubber properties are maintained even under such conditions. 【0004】 Conventionally, materials with excellent rubber properties at low temperatures have been investigated, for example, by introducing methylphenylsiloxane copolymers or methylfluoroalkylsiloxane units (Patent Documents 1 and 2). Polybutadiene and / or polystyrene-butadiene rubbers having a low glass transition temperature have also been investigated (Patent Document 3). 【0005】 International Publication No. 2007 / 145313, International Publication No. 2008 / 001625, Japanese Patent Publication No. 2018-172538 【0006】 "Silicone Handbook" by Kunio Ito, published by Nikkan Kogyo Shimbun, 1990. 【0007】 In recent years, when handling petroleum alternative fuels such as natural gas, ammonia, and hydrogen, which have attracted attention as clean fuels, as well as refrigerant gases, materials used as sealants require high reliability at low temperatures. Specifically, rubber must possess high levels of hardness, elongation, and excellent low-temperature properties. As a conventional technology, silicone rubber is cited as an elastic material with excellent low-temperature properties, but when polydimethylsiloxane is used as the silicone, sufficient low-temperature properties and elongation at break cannot be obtained. When phenylsiloxane is used as the silicone, it has excellent low-temperature properties, but to improve reliability in repeated use in high-pressure and atmospheric pressure environments, a silicone rubber with higher elongation is required. In the case of fluorosilicone rubber, low-temperature properties are good, but there is a potential problem of blister breakage occurring when the pressure changes rapidly. 【0008】 The present invention has been made in view of the above circumstances, and aims to provide a phenyl silicone rubber composition, particularly a millable type phenyl silicone rubber composition, that gives a cured phenyl silicone rubber product having good low-temperature properties, high hardness capable of withstanding high pressure, and high elongation capable of withstanding repeated exposure to high-pressure and normal-pressure environments. 【0009】 To solve the above problems, the present invention provides (A) a natural rubber-like organopolysiloxane represented by the following general formula (1), (In formula (1), R １ These are, independently of each other, an alkenyl group having 1 to 10 carbon atoms, an alkyl group, or an aryl group having 6 to 10 carbon atoms, and R ２ These are, independently of each other, alkenyl groups having 1 to 10 carbon atoms, and R ３R is an alkyl group having 1 to 10 carbon atoms, independently of each other, R' is a phenyl group, n is a number from 50 to 1,000, m is a number from 1,000 to 50,000, and the number ratio (%) of the number of phenyl groups bonded to silicon atoms to the total number of organic substituents bonded to silicon atoms is 2% or more. In the general formula (1), each siloxane unit enclosed in parentheses may be bonded randomly or form a block structure.) (B) As the reinforcing silica, a powdered silica having a BET specific surface area of 100 m ２ / g or more, (C) As the curing agent, (i) a blend of a platinum-based catalyst and a siloxane having two or more Si-H groups in the molecule, or (ii) a peroxide, and (D) It is characterized by containing a dispersant, and provides a phenyl silicone rubber composition. 【0010】 The phenyl silicone rubber composition of the present invention can provide a phenyl silicone rubber cured product having good low-temperature characteristics, high hardness that can withstand high pressure, and high stretchability that can withstand repeated high-pressure and normal-pressure environments. 【0011】 In this case, R of the component (A) １ is preferably an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 10 carbon atoms, independently of each other. 【0012】 With such a component (A), the properties of the phenyl silicone rubber composition become better. 【0013】 Also, it is preferable that the component (D) contains one or more silicon compounds having both ends blocked with silanol groups represented by the following formula (2). (In formula (2), R ４ are each independently an unsubstituted or substituted alkyl group or alkenyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 10 carbon atoms, p is an integer from 1 to 100, and at least 1 mol% of the organic substituents bonded to silicon atoms in the entire silicon compound represented by formula (2) is a phenyl group.) 【0014】 The phenyl silicone rubber composition containing such a component (D) also has better properties. 【0015】 Furthermore, it is also preferable that component (C) is an organic peroxide. 【0016】 Using such a (C) component allows for the effective curing of the phenyl silicone rubber composition. 【0017】 The phenyl silicone rubber composition can be used as a vulcanization molding material for sealing materials of high-pressure gas filled containers. 【0018】 The phenyl silicone rubber composition of the present invention possesses excellent low-temperature properties, high hardness, and high extensibility, making it useful as a vulcanization molding material for sealing materials of high-pressure gas-filled containers where these properties are required. 【0019】 Furthermore, the present invention provides a gas leak prevention member for a high-pressure gas-filled container, characterized by being made of a cured product of the above-mentioned phenyl silicone rubber composition. 【0020】 Such gas leak prevention components not only possess excellent low-temperature properties and high hardness to withstand high pressure, but also have high elongation to withstand repeated exposure to high-pressure and normal-pressure environments, making them effective in preventing accidents such as high-pressure gas leaks and resulting fires. 【0021】 As described above, the phenyl silicone rubber composition of the present invention has good low-temperature properties, high hardness, and high elongation properties, and is effective in preventing accidents such as leaks of high-pressure gas and fires that may result. 【0022】 As a result of diligent research to achieve the above objective, the inventors of the present invention have found that using a silicone rubber compound prepared with a phenyl group-containing raw rubber-like organopolysiloxane having a specific structure is optimal for achieving good low-temperature properties, high hardness that can withstand high pressure, and high elongation that can withstand repeated exposure to high-pressure and normal-pressure environments, thus leading to the present invention. 【0023】 That is, the present invention relates to (A) a natural rubber-like organopolysiloxane represented by the following general formula (1), (B) As reinforcing silica, BET specific surface area 100 m ２Powder silica of 0 / g or more, (C) as a curing agent, (i) a blend of a platinum-based catalyst and a siloxane having two or more Si-H groups in the molecule, or (ii) a peroxide, and (D) a dispersant, and a phenyl silicone rubber composition characterized by containing the same. 【0024】 Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto. 【0025】 Component (A) Component (A) is a raw rubber-like organopolysiloxane represented by the following general formula (1). (In formula (1), R １ are each independently an alkenyl group, an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 10 carbon atoms, and R ２ are each independently an alkenyl group having 1 to 10 carbon atoms, R ３ are each independently an alkyl group having 1 to 10 carbon atoms, R' is a phenyl group, n is a number from 50 to 1,000, m is a number from 1,000 to 50,000, and the number ratio (%) of the phenyl groups bonded to silicon atoms to the total number of organic substituents bonded to silicon atoms is 2% or more. In the general formula (1), each siloxane unit enclosed in parentheses may be randomly bonded or form a block structure.) 【0026】 R １ are each independently an alkenyl group, an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 10 carbon atoms, such as an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a cycloalkyl group such as a cyclohexyl group, an alkenyl group such as a vinyl group, an allyl group, a butenyl group, a hexenyl group, an aryl group such as a phenyl group, or a part or all of the hydrogen atoms bonded to the carbon atoms of these groups are substituted with a halogen atom, a cyano group, etc., such as a chloromethyl group, a trifluoropropyl group, a cyanoethyl group, etc., preferably a methyl group, a vinyl group, a phenyl group, particularly preferably a methyl group, a phenyl group. 【0027】 R ２These are, independently of each other, alkenyl groups having 1 to 10 carbon atoms, and examples include vinyl groups, allyl groups, etc., with vinyl groups being particularly preferred. 【0028】 R ３ R' is a phenyl group. R' is an alkyl group having 1 to 10 carbon atoms, such as a methyl group, ethyl group, propyl group, or butyl group, and is preferably a methyl group. 【0029】 (A) One example of a preferred embodiment of component R １ is a methyl group, R ２ is a vinyl group, R ３ One example is when the group is a methyl group; in other words, it is preferable that component (A) is a polysiloxane containing one alkenyl group at each end of the molecular chain and a diphenyl group and a dimethyl group in the side chain. 【0030】 In formula (1), n ​​is a number between 50 and 1,000, preferably between 100 and 700, and more preferably between 200 and 500, from the viewpoint of physical properties at low temperatures. 【0031】 In formula (1), m is a number between 1,000 and 50,000, preferably between 2,000 and 20,000, and more preferably between 3,000 and 15,000, from the viewpoint of workability with two rolls. 【0032】 In formula (1), the average degree of polymerization, n+m, is preferably 2,000 or more, more preferably 3,000 or more, and even more preferably 4,000 or more and 8,000 or less. From the viewpoint of roll processability, 2,000 or more is preferred. The upper limit of the average degree of polymerization is not particularly limited, but as long as it can be roll-processed, it can be 8,000 or less. 【0033】 In this invention, the average degree of polymerization and n and m may be the weight-average molecular weight obtained by converting a polystyrene with a known molecular weight as a standard substance using gel permeation chromatography (GPC) analysis measured under the conditions shown below, and the value obtained from NMR analysis. 【0034】[GPC Measurement Conditions] Developing solvent: Tetrahydrofuran (THF) Flow rate: 0.6 mL / min Detector: Differential refractive index detector (RI) Column: TSK Guardcolumn SuperH-H TSKgel SuperH4000 (6.0 mm I.D. × 15 cm × 1) TSKgel SuperH3000 (6.0 mm I.D. × 15 cm × 1) TSKgel SuperH2000 (6.0 mm I.D. × 15 cm × 1) (All manufactured by Tosoh Corporation) Column temperature: 40°C Sample injection volume: 50 μL (2.0 mass% THF solution) 【0035】 [NMR measurement conditions] 【0036】 Using a 300MHz-NMR measuring instrument manufactured by JEOL Ltd., with deuterated chloroform as the solvent, １ H-NMR and ２９ It is calculated from the integrated value of the detection spectrum in Si-NMR. 【0037】 In component (A), from the viewpoint of rubber properties at low temperatures, the ratio (%) of phenyl groups bonded to silicon atoms to the total number of organic substituents bonded to silicon atoms is preferably 2% or more, more preferably 2-30%, and particularly preferably 3-20%. 【0038】 In component (A), from the viewpoint of curability and rubber properties, at least one alkenyl group is contained at each end of the molecular chain, and it is preferable that the alkenyl group is contained in an amount of 0.01 to 1 mol%, and particularly preferably 0.02 to 0.5 mol%, relative to the silicon atoms (moles) in the organopolysiloxane molecule. 【0039】 In the general formula (1) above, each siloxane unit enclosed in parentheses ([R'SiO ２／２ ] Units and [R ３ SiO ２／２ The units may be randomly connected or form a block structure. 【0040】[Component (B)] The reinforcing silica (silica-based filler) of component (B) is a reinforcing filler required to obtain a silicone rubber compound with excellent mechanical strength. The reinforcing silica has a BET specific surface area of ​​100 m². ２ Although it is powdered silica of a certain density ( / g or more), typically, considering the required physical strength and heat resistance, a specific surface area of ​​100 to 380 m² is obtained by the BET method (nitrogen adsorption method). ２ / g, preferably 100 to 300m ２ / g, particularly preferably 100 to 250m ２ Select a silica within the range of / g. Both fumes (dry silica) and precipitated silica (wet silica) can be used as reinforcing silica. Furthermore, if necessary, the surfaces of these silica can be pre-treated with organopolysiloxane, organopolysilazane, chlorosilane, alkoxysilane, etc. As reinforcing silica, commercially available products are available, for example, Aerosil 200 (BET specific surface area of ​​200 m²) manufactured by Nippon Aerosil Co., Ltd. ２ (Fumed silica at 1 / g) and Aerosil R972 (BET specific surface area of ​​110 m²) ２ Surface treatments such as fumed silica ( / g) may also be used. 【0041】 The amount of reinforcing silica added is 5 to 100 parts by mass, preferably 10 to 60 parts by mass, and particularly preferably 45 to 60 parts by mass, per 100 parts by mass of component (A), from the viewpoint of achieving both sufficient reinforcing effect and processability. 【0042】[Component (C)] Component (C) is a curing agent. By compounding it with components (A) and (B) and mixing them uniformly, a phenyl silicone rubber composition can be prepared. By curing this composition by a conventional method, a cured phenyl silicone rubber product can be obtained. In the present invention, as the curing agent (C), (i) a formulation of a platinum-based catalyst and a siloxane having two or more Si-H groups (also called "SiH groups") in its molecule, or (ii) a peroxide is used. The formulation in (i) is a curing agent that utilizes the addition reaction between an alkenyl group in another component and a siloxane (organohydrogen (poly)siloxane) having Si-H groups, and the peroxide in (ii) is a curing agent that utilizes the radical reaction produced by the decomposition of the peroxide. The curing agent (including the curing catalyst described later) should be selected according to the desired curing reaction. 【0043】 In this case, conventionally known curing catalysts, preferably organic peroxides, can be used for curing. Specifically, examples of organic peroxides include diacyl peroxides such as benzoyl peroxide, orthomethylbenzoyl peroxide, and paramethylbenzoyl peroxide; dialkyl peroxides such as di-tert-butyl peroxide and dicumyl peroxide; peroxyesters such as tert-butyl perbenzoate; peroxyketals such as 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane; and polyvalent dialkyl peroxides such as 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane and 2,5-dimethyl-2,5-di(tert-butylperoxy)-3-hexine, with 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane being preferred. These may be used individually or in combination of two or more types. 【0044】 The amount of these organic peroxide-based curing agents can be a catalytic amount, but it is preferable to use 0.1 to 2 parts by mass, particularly 0.2 to 1.5 parts by mass, per 100 parts by mass of component (A). 【0045】Furthermore, as an example of a preferred curing agent, an addition reaction curing agent can be used, which is a compound of a platinum-based catalyst (curing catalyst) and a siloxane (organohydrogenpolysiloxane) having at least two or more Si-H groups in its molecule. 【0046】 Examples of platinum-based catalysts include elemental platinum, platinum compounds, platinum complexes, chloroplatinic acid, alcohol compounds of chloroplatinic acid, aldehyde compounds, ether compounds, and complexes with various olefins. Among these, complexes of chloroplatinic acid and olefins are preferred. Complexes of chloroplatinic acid and olefins are commercially available as Karsted catalysts. 【0047】 In this case, it is preferable to use a platinum-based catalyst in an amount of approximately 1 to 2,000 ppm by mass of platinum-based metal relative to component (A). The organohydrogenpolysiloxane used in combination at this time, which has two or more hydrogen atoms (Si-H groups) directly bonded to silicon atoms, may have any polymer structure, whether linear, branched, or cyclic, and multiple types of organohydrogenpolysiloxanes may be used in combination. The hydrogen atoms (Si-H groups) directly bonded to silicon atoms may be located in either the side chains or terminals of the polymer molecule, or may be located in both the side chains and terminals of the polymer molecule. For example, the average composition formula (3) R ５ ｄ H ｅ SiO （４－ｄ－ｅ）／２　 (3) (wherein, R ５ is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms. Also, d is a positive number satisfying 0.7 to 2.1, e is a positive number satisfying 0.001 to 1.0, and d + e is a positive number satisfying 0.8 to 3.0.) It is preferably used that has at least 2, preferably 3 to 100, and more preferably 3 to 50 silicon-bonded hydrogen atoms in one molecule. 【0048】 Here, R ５Examples of monovalent hydrocarbon groups include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, and hexyl groups, aryl groups such as phenyl and tolyl groups, aralkyl groups such as benzyl groups, and trifluoropropyl groups, which have 1 to 10 carbon atoms, particularly 1 to 6 carbon atoms, with methyl, ethyl, and phenyl groups being especially preferred. 【0049】 The molecular structure of organohydrogenpolysiloxane is not particularly limited and may be linear, cyclic, branched, or three-dimensional network (resin-like) structure. The number of silicon atoms in one molecule (i.e., degree of polymerization) is usually 3 to 70, preferably 5 to 50. 【0050】 Specifically, organohydrogenpolysiloxanes include: methylhydrogenpolysiloxane with trimethylsiloxy group-sealed at both ends, dimethylsiloxane / methylhydrogensiloxane copolymer with trimethylsiloxy group-sealed at both ends, dimethylsiloxane / methylhydrogensiloxane copolymer with dimethylhydrogensiloxy group-sealed at both ends, methylhydrogensiloxane / diphenylsiloxane copolymer with trimethylsiloxy group-sealed at both ends, methylhydrogensiloxane / diphenylsiloxane / dimethylsiloxane copolymer with trimethylsiloxy group-sealed at both ends, (CH ３ ) ２ HSiO １／２ Units and SiO ４／２ A copolymer consisting of units, (CH ３ ) ２ HSiO １／２ Units and SiO ４／２ Units and C ６ H ５ SiO ３／２ Examples include copolymers consisting of units, and preferably methylhydrogenpolysiloxanes with trimethylsiloxy groups sealed at both ends. 【0051】The amount of organohydrogenpolysiloxane used is preferably such that it supplies 0.5 to 5 SiH groups, particularly 0.8 to 4, of the organohydrogenpolysiloxane for each alkenyl group in component (A). 【0052】 [Component (D)] Component (D) is a dispersant and is added to facilitate uniform mixing when mixing components (A) to (C) using commonly used mixers such as double-roll mixers, kneaders, and Banbury mixers. Preferably, it is a silicon compound represented by the following formula (2) in which both ends are sealed with hydroxyl groups (silanol groups). Component (D) functions as a surface treatment agent for uniformly dispersing (B) reinforcing silica in a matrix consisting of (A) raw rubber-like organosiloxane during composition preparation. (In formula (2), R ４ Each of these is independently an unsubstituted or substituted alkyl or alkenyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 10 carbon atoms, where p is an integer from 1 to 100, and at least 1 mol% of the organic substituents bonded to the silicon atoms in the entire silicon compound represented by formula (2) are phenyl groups. 【0053】 In formula (2), R ４ Each of these is independently an unsubstituted or substituted alkyl or alkenyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 10 carbon atoms, preferably a methyl group, ethyl group, propyl group, butoxy group, pentyl group, vinyl group, allyl group, phenyl group, tolyl group, or naphthyl group, and particularly preferably a methyl group, vinyl group, or phenyl group. 【0054】 In the entire organosilicon compound represented by formula (2), the organic substituents (R) bonded to the silicon atom ４At least 1 mol% of ) is a phenyl group, preferably 1 mol% to 30 mol% is a phenyl group, and particularly preferably 3 mol% to 20 mol% is a phenyl group. Furthermore, as component (D), two or more organosilicon compounds represented by formula (2) can be used in combination. In this case, at least 1 mol% of the organic substituents bonded to the silicon atoms in the two or more silicon compounds as a whole are phenyl groups, preferably 1 mol% to 30 mol% are phenyl groups, and particularly preferably 3 mol% to 20 mol% are phenyl groups. 【0055】 p is an integer between 1 and 100, preferably between 1 and 30, and particularly preferably between 1 and 10. 【0056】 The amount of component (D) is 3 to 100 parts by mass, preferably 5 to 50 parts by mass, per 100 parts by mass of component (A), in order to ensure the wettability of components (A) and (B) while also ensuring the compatibility of component (C). By blending within this range, components (B) and (C) can be uniformly dispersed in the matrix consisting of component (A). 【0057】 (D) Examples of components that can be used as component (D) include dimethylpolysiloxane containing silanol groups at both ends, methylphenylpolysiloxane containing silanol groups at both ends, diphenylsilanediol, and diphenylpolysiloxane containing silanol groups at both ends, and these may be used individually or in combination of two or more in order to satisfy the requirements of formula (2). For example, as component (D), dimethylpolysiloxane containing silanol groups at both ends (R ４ (where p=4) is a methyl group, and diphenylsilanediol (R ４ When a phenyl group (p=1) is used in combination in a ratio of 3 parts by mass, the phenyl group in the organic substituent bonded to the silicon atom in the entirety of component (D) becomes 10 mol%, which is preferable in terms of the dispersibility of component (B). 【0058】[Other Components] The phenyl silicone rubber composition of the present invention may optionally contain an alkoxysilane represented by the following general formula (4) as component (E) (auxiliary dispersant) to further improve the dispersibility of component (B). Note that component (E) is a different component from component (D) above. (In formula (4), R ６ R is an alkyl group having 6 to 15 carbon atoms independently. ７ R is an alkyl group having 1 to 5 carbon atoms independently. ８ (where r is an alkyl group having 1 to 6 carbon atoms, r is a number from 1 to 3, and t is a number from 0 to 2, but r+t is a number from 1 to 3) 【0059】 The alkoxysilane to be added is preferably vinyltrimethoxysilane, vinyltrimethoxysilane, methyltrimethoxysilane, or dimethyldimethoxysilane, with vinyltrimethoxysilane being particularly preferred. Such a silane coupling agent as an auxiliary dispersant can effectively improve the dispersibility of component (B). 【0060】 The amount of component (E), when added, is 0.1 to 20 parts by mass, preferably 0.3 to 10 parts by mass, per 100 parts by mass of component (B), from the viewpoint of supplementarily improving the dispersibility of component (B). By blending within this range, component (B) can be uniformly dispersed in the matrix of the composition. 【0061】 Furthermore, the phenyl silicone rubber composition of the present invention may also contain additives such as unreinforced silica including crushed quartz and diatomaceous earth, carbon black including acetylene black, furnace black, and channel black, fillers including calcium carbonate, flame retardant enhancers, acid acceptors, and thermal conductivity enhancers, as well as additional dispersants (different from components (D) and (E) above) such as alkoxysilanes, diphenylsilanediols, carbon functional silanes, and low molecular weight siloxanes with sealed silanol groups at both ends, to disperse these additives. The amounts of these listed components can be examined and optimized for a specific purpose. 【0062】Furthermore, in addition to the above components, the phenyl silicone rubber composition of the present invention may optionally contain known additives in silicone rubber compositions, such as cerium compounds, heat-resistant agents like iron oxide, antioxidants, colorants, and mold release agents, as needed. The amounts of these listed components can be examined and optimized for a specific purpose. 【0063】 [Method for producing and molding the phenylsilicone rubber composition of the present invention] The phenylsilicone rubber composition for obtaining the phenylsilicone rubber molded product (rubber cured product) of the present invention can be obtained by uniformly mixing the above-mentioned components using a rubber mixing machine such as a two-roll mixer, Banbury mixer, or Dow mixer (kneader). 【0064】 There are no particular restrictions on the molding method (curing method) of the phenyl silicone rubber composition. It can be molded into a desired shape according to general rubber molding methods such as compression molding, transfer molding, injection molding, extrusion molding, and calendering, and can be used to make rubber molded products such as O-rings, diaphragms, packings, and gaskets. In this case, curing can be done at 120 to 400°C, particularly 120 to 200°C for 1 to 30 minutes, especially 5 to 20 minutes. If necessary, secondary vulcanization may be performed at 180 to 250°C, particularly 190 to 220°C for 1 to 10 hours, especially 2 to 8 hours. 【0065】 [Uses of Phenyl Silicone Rubber Composition] The phenyl silicone rubber composition of the present invention can be used as a vulcanization molding material for sealing materials of high-pressure gas filled containers. The phenyl silicone rubber composition of the present invention possesses good low-temperature properties, high hardness, and high extensibility, making it useful as a sealing material for equipment that handles high-pressure gas, such as high-pressure gas filled containers, where these properties are required. 【0066】 Furthermore, the present invention provides a gas leak prevention member for a high-pressure gas filled container, which is made of a cured product of the above-mentioned phenyl silicone rubber composition. Such a gas leak prevention member not only has good low-temperature properties and high hardness that can withstand high pressure, but also possesses high elongation that can withstand repeated exposure to high-pressure and normal-pressure environments, making it effective in preventing accidents such as high-pressure gas leaks and resulting fires. 【0067】 The molded articles obtained from the phenyl silicone rubber of the present invention possess rubber properties at low temperatures, high hardness, and excellent extensibility. Therefore, they can be used as packing and sealing components to prevent leaks in gas-filled containers, and their high reliability makes them effective in preventing accidents such as gas leaks and resulting fires. Gas-filled containers to which molded articles obtained from the phenyl silicone rubber of the present invention are applied as components can be operated at any pressure, whether high or low, or fluctuating between high and low pressure. The operating temperature range can be arbitrary, and it is possible to apply the rubber molded articles obtained from the phenyl silicone rubber composition of the present invention as components to gas-filled containers operated at extremely low temperatures (preferably below -40°C, more preferably below -60°C). The gases to be filled are envisioned to be clean fuels such as liquefied natural gas, ammonia, helium, and hydrogen, as well as refrigerant gases, but are not limited to these. The state of the substance to be filled may be liquid, gas, or supercritical. Gas-filled containers using molded products obtained from the phenyl silicone rubber of the present invention can be envisioned as being fixed to the ground, built into any type of transportation equipment, used in automobiles traveling on land, buried underground, floating on water, submerged in water, or floating in outer space, but the manner in which these containers can be socially implemented is not limited in any way. 【0068】 The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited thereto. 【0069】 <Hardness and Elongation at Cut> The hardness (durometer A) and elongation at cut of the cured silicone rubber compositions prepared in the following examples and comparative examples were measured according to JIS K6249:2003. Hardness (durometer A) was evaluated as "○" if it was 75 or higher and "×" if it was less than 75. Elongation at cut was evaluated as "○" if it was 400% or higher and "×" if it was less than 400%. 【0070】<Low Temperature Characteristics> The cured silicone rubber compositions prepared in the following examples and comparative examples were measured at TR-50 in accordance with JIS K6261:2006. TR-50 is the temperature at which the shrinkage rate becomes 50% when a test piece is stretched to 50%, frozen, and then heated to restore its elastic modulus. The lower the temperature measured at TR-50, the better the rubber elasticity is restored at low temperatures, indicating superior low-temperature characteristics. For sealing components that provide sealing properties through rubber elasticity, a lower temperature is desirable. Such material properties indicate favorable sealing behavior from the viewpoint of rubber elasticity. A TR-50 of -60°C or lower was evaluated as "○", and a TR-50 above -60°C was evaluated as "×". The results are shown in Table 1. 【0071】 (A) Natural rubber-like organopolysiloxane (A-1) Represented by the following general formula (1), where n = 250, m = 4,700, R １ is a methyl group, R ２ is a vinyl group, R ３ A natural rubber-like organopolysiloxane in which R' is a methyl group and R' is a phenyl group. 【0072】 (A-2) It is expressed by the following general formula (1'), where n = 250, m = 4,700, R １ is a methyl group, R ２ A natural rubber-like organopolysiloxane in which R' is a vinyl group and R' is a phenyl group. 【0073】 (A-3) It is expressed by the following general formula (1''), where p = 6,000, q = 8, R １ is a methyl group, R ２ Dimethylsiloxane, a natural rubber-like organopolysiloxane, has a vinyl group. 【0074】 (B) Reinforced silica (B-1) Specific surface area of ​​200 m² measured by the BET method ２ 1 / g of fumed silica (product name: Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) (B-2) Specific surface area of ​​110 m² measured by BET method ２ fumed silica surface-treated with dimethyldichlorosilane at a concentration of / g (product name: Aerosil R972, manufactured by Nippon Aerosil Co., Ltd.) 【0075】 (C) Peroxide (C-1) 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane 【0076】 (D) Dispersant (D-1) Dimethylpolysiloxane containing silanol groups at both ends (average degree of polymerization: 4, viscosity (25°C): 15 mPa·s) (D-2) Diphenylsilanediol 【0077】 (E) Auxiliary dispersant (E-1) Vinyltrimethoxysilane 【0078】 [Example 1] 100 parts by mass of (A-1), 55 parts by mass of (B-1), 1.5 parts by mass of (E-1), 10 parts by mass of (D-1), and 3 parts by mass of (D-2) were added and heated under mixing conditions in a kneader at 170°C for 2 hours to prepare a base compound. 0.8 parts by mass of (C-1) was added to the base compound and uniformly mixed with a double roll to obtain a silicone rubber composition (mirrorable type silicone rubber composition). The silicone rubber composition was press-cured at 165°C and 6.9 MPa for 10 minutes to prepare a 2 mm thick test sheet. The test sheet was then post-cured in an oven at 200°C for 4 hours. The hardness (durometer A), elongation at break, and low-temperature properties of the obtained cured product were evaluated as described above. The results are shown in Table 1. 【0079】 [Examples 2, 3, Comparative Examples 1-3] Silicone rubber compositions were prepared using the formulations described in Table 1 in the same manner as in Example 1. The hardness (durometer A), elongation at break, and low-temperature properties of the resulting cured products were evaluated in the same manner as in Example 1. The results are shown in Table 1. 【0080】 【0081】From the results in Table 1, it was found that the silicone compositions of the present invention (Examples 1, 2, and 3) using a natural rubber-like organopolysiloxane having a specific structure as component (A) have good low-temperature properties, high hardness that can withstand high pressure, and high elongation that can withstand repeated high-pressure and normal-pressure environments. On the other hand, Comparative Example 1, which used a silicone natural rubber having vinyl groups in the side chain instead of component (A) as defined in the present invention, did not achieve sufficient elongation. When a silicone natural rubber without phenyl groups was used instead of component (A) as defined in the present invention, the elongation and low-temperature properties deteriorated (Comparative Example 2). In the composition of Comparative Example 1, when the amount of reinforcing silica was reduced to achieve high elongation, the hardness was insufficient (Comparative Example 3). Thus, the phenyl silicone rubber composition of the present invention can have all of the following: excellent hardness, high elongation, and low-temperature properties. 【0082】 This specification includes the following embodiments: [1]: (A) a natural rubber-like organopolysiloxane represented by the following general formula (1), (In formula (1), R １ These are, independently of each other, an alkenyl group having 1 to 10 carbon atoms, an alkyl group, or an aryl group having 6 to 10 carbon atoms, and R ２ These are, independently of each other, alkenyl groups having 1 to 10 carbon atoms, and R ３ (B) As reinforcing silica, R' is a phenyl group, n is a number from 50 to 1,000, m is a number from 1,000 to 50,000, the ratio (%) of phenyl groups bonded to silicon atoms to the total number of organic substituents bonded to silicon atoms is 2% or more, and each siloxane unit enclosed in parentheses in the general formula (1) may be bonded randomly or form a block structure. ２ A phenyl silicone rubber composition characterized by containing (C) powder silica of 1 / g or more, (i) a compound of a platinum-based catalyst and a siloxane having two or more Si-H groups in the molecule, or (ii) a peroxide, and (D) a dispersant as a curing agent. [2]: R of component (A) １The phenyl silicone rubber composition of [1], characterized in that each of the members is independently an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 10 carbon atoms. [3] The phenyl silicone rubber composition of [1] or [2], characterized in that the (D) component contains one or more silicon compounds represented by the following formula (2) in which both ends are sealed with silanol groups. (In formula (2), R ４ Each of these is independently an unsubstituted or substituted alkyl or alkenyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 10 carbon atoms, where p is an integer from 1 to 100, and at least 1 mol% of the organic substituents bonded to the silicon atom in the entire silicon compound represented by formula (2) is a phenyl group.) [4]: ​​A phenyl silicone rubber composition according to any one of [1] to [3], characterized in that the (C) component is an organic peroxide. [5]: A phenyl silicone rubber composition according to any one of [1] to [4], characterized in that the phenyl silicone rubber composition is used as a vulcanization molding material for a sealing material of a high-pressure gas filled container. [6]: A gas leak prevention member for a high-pressure gas filled container, characterized in that it consists of a cured product of any one of [1] to [5] phenyl silicone rubber compositions. 【0083】 It should be noted that the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention.

Claims

1. (A) A natural rubber-like organopolysiloxane represented by the following general formula (1), (In formula (1), R １ These are, independently of each other, an alkenyl group having 1 to 10 carbon atoms, an alkyl group, or an aryl group having 6 to 10 carbon atoms, and R ２ These are, independently of each other, alkenyl groups having 1 to 10 carbon atoms, and R ３ (B) As reinforcing silica, R' is a phenyl group, n is a number from 50 to 1,000, m is a number from 1,000 to 50,000, the ratio (%) of phenyl groups bonded to silicon atoms to the total number of organic substituents bonded to silicon atoms is 2% or more, and each siloxane unit enclosed in parentheses in the general formula (1) may be bonded randomly or form a block structure. ２ A phenyl silicone rubber composition characterized by containing (C) powder silica of 1g or more, (i) a compound of a platinum-based catalyst and a siloxane having two or more Si-H groups in the molecule, or (ii) a peroxide, and (D) a dispersant as a curing agent.

2. R of component (A) １ The phenyl silicone rubber composition according to claim 1, characterized in that each member is independently an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 10 carbon atoms.

3. The phenyl silicone rubber composition according to claim 1, characterized in that the (D) component contains one or more silicon compounds represented by the following formula (2) in which both ends are sealed with silanol groups. (In formula (2), R ４ Each of these is independently an unsubstituted or substituted alkyl or alkenyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 10 carbon atoms, where p is an integer from 1 to 100, and at least 1 mol% of the organic substituents bonded to the silicon atoms in the entire silicon compound represented by formula (2) are phenyl groups.

4. The phenyl silicone rubber composition according to claim 1, characterized in that the (C) component is an organic peroxide.

5. The phenyl silicone rubber composition according to claim 1, characterized in that it is used as a vulcanization molding material for sealing materials of high-pressure gas filled containers.

6. A gas leak prevention member for a high-pressure gas filled container, characterized in that it is made of a cured product of the phenyl silicone rubber composition described in claim 1.

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