Addition reaction-curable silicone rubber composition and method for producing aromatic hydrocarbon group-containing organopolysiloxane

Abstract

Provided is an addition reaction-curable silicone rubber composition comprising: (A) an aromatic hydrocarbon group-containing organopolysiloxane represented by formula (1) (R1s are each a monovalent hydrocarbon group excluding a monovalent aromatic hydrocarbon group, or an alkoxy group, where the content of the alkoxy group is less than 5 mol% in the total of the R1s. R2 is a monovalent aromatic hydrocarbon group, where the content of the monovalent aromatic hydrocarbon group is at least 40 mol% with respect to the total amount of all substituents bonded to a silicon atom. m and n are each a number of at least 1 and m+n is a number of less than 16.); (B) an organopolysiloxane having, per molecule, at least two alkenyl groups bonded to a silicon atom; (C) an organohydrogen polysiloxane having, per molecule, at least two hydrogen atoms bonded to a silicon atom; and (D) a platinum group metal catalyst.

Description

Addition reaction-curable silicone rubber composition and method for producing aromatic hydrocarbon group-containing organopolysiloxane 【0001】 The present invention relates to an addition reaction-curable silicone rubber composition and a method for producing an aromatic hydrocarbon group-containing organopolysiloxane used therefor. 【0002】 Conventionally, silicone rubber has been widely used in various fields such as building materials, electrical and electronic components, automotive parts, and OA equipment parts due to its excellent heat resistance, weather resistance, durability, and electrical properties. Among these, its spread as automotive parts has been remarkable, and it is used for oil seals, packings and rubber plugs in wire connector parts, O-rings, diaphragms, connectors, grommets for distributors, etc. In particular, in the fields of connectors and grommets for distributors, as a result of pursuing workability during assembly, sealing performance, waterproof performance, and insulation performance after mounting, an oil bleed silicone rubber in which oil bleeds on the surface of the molded product has been recognized as effective, and such oil bleed silicone rubber is widely used. 【0003】 Patent Documents 1 and 2 disclose an oil bleed silicone rubber composition containing an organopolysiloxane having a specific amount of phenyl groups, and Patent Document 2 mentions the viscosity of the organopolysiloxane. However, these Patent Documents 1 and 2 do not mention the content of hydroxyl groups and alkoxy groups remaining in the organopolysiloxane and deteriorating the heat resistance of the sheet. In addition, depending on the combination of the phenyl group content and the chain length in the organopolysiloxane, there is a problem that oil bleed property does not appear. 【0004】 Japanese Unexamined Patent Application Publication No. 6-93186, Japanese Unexamined Patent Application Publication No. 2010-215719 【0005】 The present invention has been made in view of the above circumstances, and an object thereof is to provide an addition reaction-curable silicone rubber composition that does not impair heat resistance and gives a molded product that exhibits bleed property regardless of the composition. Another object of the present invention is to provide a method for producing an aromatic hydrocarbon group-containing organopolysiloxane therefor. 【0006】As a result of diligent research to achieve the above objective, the present inventors have discovered that by adding a specific amount of an organopolysiloxane containing an aromatic hydrocarbon group having a specific structure to an addition reaction curing type silicone rubber composition, a silicone rubber composition can be obtained that provides molded articles with good oil bleeding properties and heat resistance, thus leading to the present invention. 【0007】 That is, the present invention relates to: 1. An addition-curing silicone rubber composition characterized by containing the following components (A) to (D): (A) an aromatic hydrocarbon group-containing organopolysiloxane represented by the following formula (1): 1 to 10 parts by mass, (In the formula, R 1 These are, independently of each other, monovalent hydrocarbon groups having 1 to 10 carbon atoms, excluding monovalent aromatic hydrocarbon groups, or alkoxy groups having 1 to 10 carbon atoms, and the content of the alkoxy groups is, total R 1 It is less than 5 mol% of the total. 2 (A) R in formula (1) of component (A) is a monovalent aromatic hydrocarbon group having 6 to 12 carbon atoms, and the content of the monovalent aromatic hydrocarbon group is 40 mol% or more relative to the total amount of substituents bonded to the silicon atom. m is a number of 1 or more, n is a number of 1 or more, and m + n is a number less than 16. (B) Organopolysiloxane having at least two alkenyl groups bonded to the silicon atom in one molecule: 100 parts by mass, (C) Organohydrogenpolysiloxane having at least two hydrogen atoms bonded to the silicon atom in one molecule: 0.2 to 20 parts by mass, and (D) Platinum group metal catalyst: catalytic amount 2. R in formula (1) of component (A) 2The addition reaction-curable silicone rubber composition according to 1, wherein the group is a phenyl group. 3. Further, the addition reaction-curable silicone rubber composition according to 1 or 2, containing 1 to 100 parts by mass of a reinforcing filler (E) with respect to 100 parts by mass of the component (B). 4. A cured product of the addition reaction-curable silicone rubber composition according to any one of 1 to 3. 5. A method for producing the aromatic hydrocarbon group-containing organopolysiloxane (A) contained in the addition reaction-curable silicone rubber composition according to any one of 1 to 3, which is represented by the following formula (1) by reacting a silane compound represented by the following formula (3) with a disiloxane compound represented by the following formula (4), comprising a step of reacting for 0.5 to 3 hours while removing the alcohol by-produced at 70 to 90 °C outside the reaction system after starting the reaction, and then aging for 6 hours or more. (In the formula, R 1 and R 2 are the same as above, and R 3 are each independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. p is an integer of 1 to 3, q is an integer of 0 to 3, r is an integer of 1 to 3, and p + q + r = 4.) (In the formula, R 1 , R 2 , m and n are the same as above.) 6. Provide the production method according to 5, wherein the aging temperature is 0 °C or higher and lower than 70 °C. 【0008】 The silicone rubber composition of the present invention gives a cured product excellent in oil bleeding property and heat resistance. 【0009】 Hereinafter, the present invention will be described in more detail. [Addition reaction-curable silicone rubber composition] The addition reaction-curable silicone rubber composition of the present invention contains the following components (A) to (D). (A) Aromatic hydrocarbon group-containing organopolysiloxane represented by the following formula (1) (B) Alkenyl group-containing organopolysiloxane (C) Organohydrogenpolysiloxane (D) Platinum group metal catalyst 【0010】[(A) Aromatic hydrocarbon group-containing organopolysiloxane] Component (A) is an aromatic hydrocarbon group-containing organopolysiloxane represented by the following general formula (1). In the composition of the present invention, component (A) functions as a bleed oil for the molded article. Component (A) has a specific structure in which the content of monovalent aromatic hydrocarbon groups and the number of repeating units (siloxane chain length) are within the range described later, thereby imparting good heat resistance and oil bleed properties to the molded article obtained by curing the composition. 【0011】 【0012】 In the above formula (1), R 1 These are, independently of each other, a monovalent hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 3 carbon atoms, or an alkoxy group having 1 to 10 carbon atoms, preferably 1 to 3 carbon atoms, with unsubstituted monovalent hydrocarbon groups or alkoxy groups being more preferred. 1 The monovalent hydrocarbon group can be anything other than a monovalent aromatic hydrocarbon group, and may be linear, branched, or cyclic. Specific examples include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl groups. Among these, methyl, ethyl, and propyl groups are preferred, methyl and ethyl groups are more preferred, and methyl groups are even more preferred. 1 The alkoxy group can be either linear or branched in its hydrocarbon chain. Specific examples include methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, tert-butoxy, and pentoxy groups. Among these, methoxy, ethoxy, and propoxy groups are preferred, methoxy and ethoxy groups are more preferred, and methoxy groups are even more preferred. 1 The alkoxy group is total R 1 The alkoxy group content is less than 5 mol%, preferably 4 mol% or less, more preferably 3 mol% or less, and even more preferably 0 mol%. By limiting the alkoxy group content to less than 5 mol%, good heat resistance can be obtained. 【0013】 R 2These are, independently of each other, monovalent aromatic hydrocarbon groups having 6 to 12 carbon atoms, preferably 6 to 10, more preferably 6 to 8 carbon atoms. 2 Specific examples of monovalent aromatic hydrocarbon groups include aryl groups such as phenyl and tolyl groups; and aralkyl groups such as benzyl and 2-phenylethyl groups, with phenyl groups being preferred among them. 【0014】 The aromatic hydrocarbon group-containing organopolysiloxane used in this invention is R 2 The monovalent aromatic hydrocarbon group is bonded to the silicon atom, all substituents (i.e., R 1 and R 2 It is characterized by having 40 mol% or more of the total of ( ). Preferably, it is 45 mol% or more. If the proportion of monovalent aromatic hydrocarbon groups is less than the above lower limit, the bleeding properties will decrease. Furthermore, there is no particular upper limit to the proportion of monovalent aromatic hydrocarbon groups, but if the content is high, the silicone oil may crystallize and the bleeding properties may decrease, so it is preferably 70% or less, and more preferably 60% or less. 【0015】 Note R 1 and R 2 It is preferable that the material does not contain functional groups involved in the crosslinking reaction, such as aliphatic unsaturated groups represented by alkenyl groups. 【0016】 In the above formula (1), m is a number of 1 or more, n is a number of 1 or more, and m+n is a number less than 16. Preferably, m is a number of 1.5 or more, and n is a number of 2 or more. m+n is preferably a number of 3 or more and less than 16, and more preferably a number of 5 to 13. When m+n is 16 or more, even if there are 40 mol% or more of monovalent aromatic hydrocarbon groups, the oil separation rate slows down and bleeding becomes less likely to occur. In addition to the number of m+n, in the present invention, the R at both ends 1 The value obtained by adding the 2 for the 3Si group is called the chain length. 【0017】 In the present invention, the content of monovalent aromatic hydrocarbon groups, the content of alkoxy groups, and the number of m and n in component (A) are: 29 The values ​​are those measured by Si-NMR under the following conditions. 29Si-NMR measurement conditions] Measuring device: ECX500 II (manufactured by JEOL RESONANCE) 29 Si nucleus measurement frequency: 99.325 MHz; Number of integrations: 5,000; Sample concentration: 20% by mass (solvent: chloroform-d); Temperature: 25°C 【0018】 (A) Aromatic hydrocarbon group-containing organopolysiloxane is more preferably represented by the following general formula (2). 【0019】 (In formula (2), R 1 As stated above, Ph is a phenyl group, and the phenyl group content is the total substituents bonded to the silicon atom (i.e., total R 1 The sum of (and Ph) is 40 mol% or more, and m, n, and m+n are as described above. 【0020】 The amount of component (A) is 1 to 10 parts by mass per 100 parts by mass of component (B), which will be described later, preferably 3 to 8 parts by mass, and more preferably 5 to 8 parts by mass. If the amount is less than 1 part by mass, oil bleeding will not occur sufficiently, and if it exceeds 10 parts by mass, the physical properties of the resulting cured product will deteriorate and cause mold contamination during molding. Component (A) can be used alone or in combination of two or more types. 【0021】 The aromatic hydrocarbon group-containing organopolysiloxane represented by formula (1) above can be produced, for example, by the following method. That is, an organosiloxane having hydroxyl groups and / or alkoxy groups at its terminals can be subjected to a condensation reaction (equilibrium reaction) under acidic conditions, and both ends of the resulting silicone compound can be sealed with trimethylchlorosilane, hexamethyldisiloxane, etc. Before the equilibrium reaction is completely completed, for example, the reaction can be carried out using a Dean-Stark apparatus, stirring at 70-90°C for 0.5-3 hours to remove the by-product alcohol from the reaction system, and then aging can be performed to obtain an aromatic hydrocarbon group-containing organopolysiloxane that does not contain or has reduced alkoxy groups. 【0022】Specifically, for example, a silane compound represented by formula (3) and a disiloxane compound represented by formula (4) are subjected to an equilibration reaction in the presence of an acidic catalyst and water. 【0023】 【0024】 In the above formula, R 1 and R 2 This is the same as above, R 3 R is independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, preferably 1 to 3 carbon atoms. 3 The alkyl group can have a straight or branched hydrocarbon group, and a specific example is R 1 Examples of alkyl groups include those similar to those exemplified, and preferred groups are also similar. Among them, R 3 Hydrogen atoms and methyl groups are particularly preferred. 【0025】 p is an integer between 1 and 3, preferably 1 or 2. q is an integer between 0 and 3, preferably 0 or 1. r is an integer between 1 and 3, preferably 1 or 2. Note that p + q + r = 4. 【0026】 Specific examples of the silane compounds represented by formula (3) above include dimethoxydiphenylsilane, diethoxydiphenylsilane, dipropoxydiphenylsilane, dimethoxymethylphenylsilane, dimethoxyethylphenylsilane, dimethoxypropylphenylsilane, diethoxymethylphenylsilane, diethoxyethylphenylsilane, diethoxypropylphenylsilane, dipropoxymethylphenylsilane, dipropoxyethylphenylsilane, dipropoxypropylsilane, dioldiphenylsilane, diolmethylphenylsilane, diolethylphenylsilane, and diolpropylphenylsilane. These can be used individually or in combination of two or more. Among these, dimethoxydiphenylsilane, dimethoxymethylphenylsilane, and dioldiphenylsilane are preferred. 【0027】Specific examples of the disiloxane compound represented by formula (4) above include hexamethyldisiloxane, hexaethyldisiloxane, and di-tert-butyltetramethyldisiloxane, which can be used individually or in combination of two or more. Among these, hexamethyldisiloxane is preferred. 【0028】 The blending ratio of the raw material compounds is not particularly limited, but it is preferable that the ratio of the disiloxane compound represented by formula (4) is 0.01 to 0.5 moles, and more preferably 0.05 to 0.3 moles, per mole of the silane compound represented by formula (3) above. 【0029】 Examples of acidic catalysts include sulfuric acid and trifluoromethanesulfonic acid. The amount added is usually 1,000 to 100,000 ppm relative to the total mass of the raw material compounds, and 10,000 to 100,000 ppm is preferred. 【0030】 The equilibration reaction can be carried out, for example, at 0 to 90°C for 6.5 to 24 hours. The above reaction can be carried out without using a solvent, and if necessary, a solvent such as toluene or xylene may be used, as long as it does not inhibit the reaction. 【0031】 In this invention, after starting the equilibration reaction, the reaction is carried out for 0.5 to 3 hours, preferably 0.5 to 2.5 hours, at a temperature of 70 to 90°C, preferably 70 to 85°C, while removing the by-product alcohol from the reaction system. If the reaction is carried out at a temperature or time below the above, the removal of the alkoxy group is insufficient, and if the reaction is carried out at a temperature higher than the above or for a longer time than the above, the aromatic hydrocarbon group is eliminated, and the T unit (SiO 3 / 2 R units (R is R 1 or R 2 This indicates that the problem arises where )) occurs. 【0032】Next, the reaction system is stirred and aged for at least 6 hours, preferably at least 8 hours, at a temperature of 0°C to less than 70°C, preferably 0 to 50°C, more preferably 0 to 30°C. If the aging time is less than 6 hours, alkoxy groups will remain at the ends. There is no particular upper limit to the aging time, but it can be 21 hours or less. After the reaction is complete, the catalyst is neutralized, and the mixture is purified by distillation or other means under air or reduced pressure to obtain the desired organopolysiloxane. 【0033】 [(B) Alkenyl group-containing organopolysiloxane] Component (B) is an organopolysiloxane having at least two alkenyl groups bonded to silicon atoms in one molecule. This organopolysiloxane is the main component (base polymer) of this composition. Any known alkenyl group-containing organopolysiloxane that has been conventionally used in addition-curing type silicone rubber compositions is acceptable. 【0034】 (B) The organopolysiloxane may have at least two alkenyl groups bonded to silicon atoms in one molecule. Preferably, the organopolysiloxane contains 1.0 × 10 -6 moles / g ~ 3.0 × 10 -3 moles / g, especially 1.0 × 10⁻⁶ -5 moles / g ~ 2.0 × 10 -3 The composition contains an amount of alkenyl groups equivalent to moles / g. If the amount of alkenyl groups is less than the lower limit, the resulting composition may have too low a rubber hardness and become gel-like. Conversely, if the amount of alkenyl groups is more than the upper limit, the crosslinking density of the composition may become too high, resulting in extremely high hardness and loss of elasticity in the resulting rubber. The alkenyl groups in the organopolysiloxane may be bonded to silicon atoms at the ends of the molecular chain, to silicon atoms in the middle of the molecular chain (non-terminants), or to both, but it is preferable that they are bonded to silicon atoms at the ends of the molecular chain (one end or both ends), and it is preferable that they are bonded to silicon atoms at both ends of the molecular chain. 【0035】(B) The average degree of polymerization of the organopolysiloxane is preferably 100 to 50,000, more preferably 150 to 20,000, and even more preferably 150 to 2,000. If the average degree of polymerization is below the lower limit, the cured product may not be given sufficient rubber properties. If the average degree of polymerization is higher than the upper limit, the viscosity of the resulting composition may become high, making molding difficult. Note that the average degree of polymerization in this invention refers to: 29 This was measured using Si-NMR under the same conditions as described for component (A). 【0036】 (B) Organopolysiloxanes are represented, for example, by the following average composition formula (5). 4 a SiO (4-a) / 2 (5) In formula (5), R 4 These are, independently of each other, unsubstituted or substituted monovalent hydrocarbon groups having 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms, and at least two R 4 is an alkenyl group. a is a positive number between 1.5 and 2.8, preferably between 1.8 and 2.5, and more preferably between 1.95 and 2.05. 【0037】 In the above formula (5), R 4The unsubstituted or substituted monovalent hydrocarbon group shown can be linear, branched, or cyclic, and examples include alkyl groups having 1 to 10 carbon atoms, preferably 1 to 8; aryl groups having 6 to 10 carbon atoms, preferably 6 to 8; aralkyl groups having 7 to 10 carbon atoms; and alkenyl groups having 2 to 10 carbon atoms. Specific examples include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl groups; aryl groups such as phenyl, tolyl, xylyl, and naphthyl groups; aralkyl groups such as benzyl, phenylethyl, and phenylpropyl groups; alkenyl groups such as vinyl, allyl, propenyl, isopropenyl, butenyl, hexenyl, cyclohexenyl, and octenyl groups; and groups in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms such as fluorine, bromine, or chlorine, or cyano groups, such as chloromethyl, chloropropyl, bromoethyl, trifluorofluoropropyl, and cyanoethyl groups. Among these, alkyl groups having 1 to 3 carbon atoms are preferred, and methyl groups are more preferred. 4 It is preferable that 90 mol% or more of the group consists of methyl groups. 【0038】 In the above formula (5), R 4 At least two of these are alkenyl groups. The alkenyl groups preferably have 2 to 8 carbon atoms, more preferably 2 to 6 carbon atoms, and even more preferably vinyl groups. 【0039】 (B) The structure of organopolysiloxane is such that both ends of the molecular chain are triorganosiloxy groups (R 4 3SiO 1 / 2 The chain is sealed with diorganosiloxane units (R 4 2SiO 2 / 2 Preferably, it is a linear diorganopolysiloxane consisting of repeating units of ). Partially monoorganosilsesquioxane units (R 4 SiO 3 / 2 ) may be a branched chain structure or annular structure (R 4 (As stated above.) 【0040】 (B) Specific examples of organopolysiloxanes include, for example, diorganopolysiloxanes with diorganoalkenylsiloxy group blockage at both ends of the molecular chain, diorganopolysiloxanes with organodialkenylsiloxy group blockage at both ends of the molecular chain, diorganopolysiloxanes with triorganosiloxy group blockage at both ends of the molecular chain, diorganosiloxane / organoalkenylsiloxane copolymers with diorganoalkenylsiloxy group blockage at both ends of the molecular chain, and diorganosiloxane / organoalkenylsiloxane copolymers in which one end of the molecular chain is diorganoalkenylsiloxy group blocked and the other end is triorganosiloxy group blocked. Preferably, these are diorganopolysiloxanes with diorganoalkenylsiloxy groups sealed at both ends of the molecular chain, diorganosiloxane / organoalkenylsiloxane copolymers with triorganosiloxy groups sealed at both ends of the molecular chain, and diorganosiloxane / organoalkenylsiloxane copolymers with diorganoalkenylsiloxy groups sealed at both ends of the molecular chain. In each of the above siloxanes, the "organo group" refers to R in formula (5). 4 Of these, the monovalent hydrocarbon groups are unsubstituted or substituted, excluding aliphatic unsaturated groups such as alkenyl groups. Component (B) may be used alone or in combination of two or more. 【0041】 [(C) Organohydrogenpolysiloxane] Component (C) is an organohydrogenpolysiloxane having at least two, preferably three or more, hydrogen atoms (SiH groups) bonded to silicon atoms in one molecule. Component (C) acts as a curing agent (crosslinking agent) for curing the composition, and the SiH groups in component (C) crosslink with the alkenyl groups in component (B) through a hydrosilylation addition reaction to cure. 【0042】 Component (C) may be a conventionally known organohydrogenpolysiloxane included in an addition-curing type organopolysiloxane composition. Preferably, it has at least two silicon-bonded hydrogen atoms (SiH groups) per molecule, preferably three or more, more preferably 3 to 100, and even more preferably 4 to 50. 【0043】 The SiH group content is preferably 0.0005 mol / g to 0.020 mol / g, particularly 0.001 mol / g to 0.017 mol / g, in the organohydrogenpolysiloxane. If the amount of SiH groups is less than 0.0005 mol / g, the crosslinking may be insufficient. If it is more than 0.020 mol / g, the volatility will increase, and some of the organohydrogenpolysiloxane may volatilize outside the composition during compounding, manufacturing, or product storage. 【0044】 The number of silicon atoms in one molecule of component (C) (average degree of polymerization) is preferably 2 to 300, and more preferably 3 to 150. Component (C) is preferably a liquid at room temperature (25°C) with approximately 4 to 100 silicon atoms. The hydrogen atoms bonded to the silicon atoms may be located at the ends of the molecular chain, in the middle of the molecular chain (non-terminants), or in both locations. Furthermore, the molecular structure of the organohydrogenpolysiloxane may be linear, cyclic, branched, or a three-dimensional network. 【0045】 (C) Organohydrogenpolysiloxanes are represented, for example, by the following average composition formula (6). R 5 b H c SiO (4-b-c) / 2 (6) In formula (6), R 5 These are, independently of each other, unsubstituted or substituted monovalent hydrocarbon groups having 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms. b is a positive number between 0.7 and 2.1, c is a positive number between 0.001 and 1.0, and b + c is a positive number satisfying 0.8 to 3.0. 【0046】 In the above formula (6), R 5 Specific examples of the monovalent hydrocarbon group shown are the above-mentioned R 4 Examples of groups similar to those exemplified above include those without aliphatic unsaturated bonds, alkyl groups having 1 to 3 carbon atoms are more preferred, and methyl groups are even more preferred. 【0047】In the above formula (6), b is a positive number between 0.7 and 2.1, preferably between 0.8 and 2.0; c is a positive number between 0.001 and 1.0, preferably between 0.01 and 1.0; and b + c is a positive number between 0.8 and 3.0, preferably between 1.0 and 2.5. 【0048】 (C) Specific examples of organohydrogenpolysiloxanes include, for example, 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, tris(hydrogendimethylsiloxy)methylsilane, tris(hydrogendimethylsiloxy)phenylsilane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane / dimethylsiloxane cyclic copolymer, methylhydrogenpolysiloxane with trimethylsiloxy groups sealed at both ends, dimethylsiloxane / methylhydrogensiloxane copolymer with trimethylsiloxy groups sealed at both ends, dimethylpolysiloxane with dimethylhydrogensiloxy groups sealed at both ends Tylsiloxane / methylhydrogensiloxane copolymer, methylhydrogensiloxane / diphenylsiloxane copolymer with trimethylsiloxy groups sealed at both ends, methylhydrogensiloxane / diphenylsiloxane / dimethylsiloxane copolymer with trimethylsiloxy groups sealed at both ends, methylhydrogensiloxane / methylphenylsiloxane / dimethylsiloxane copolymer with trimethylsiloxy groups sealed at both ends, methylhydrogensiloxane / dimethylsiloxane / diphenylsiloxane copolymer with dimethylhydrogensiloxy groups sealed at both ends, methylhydrogensiloxane / dimethylsiloxane / methylphenylsiloxane copolymer with dimethylhydrogensiloxy groups sealed at both ends, (CH3)2HSiO 1 / 2 Units and (CH3)3SiO 1 / 2 Units and SiO 4 / 2 A copolymer consisting of units, (CH3)2HSiO 1 / 2 Units and SiO 4 / 2 A copolymer consisting of units, (CH3)2HSiO 1 / 2 Units and SiO 4 / 2 Units and (C6H5)SiO 3 / 2Examples include copolymers consisting of units, and in these exemplary compounds, some or all of the methyl groups are substituted with other alkyl groups, phenyl groups, etc. 【0049】 Furthermore, (C) organohydrogenpolysiloxane may be a polyvalent aromatic ring-containing organohydrogenpolysiloxane in which a portion of the siloxane skeleton (-Si-O-Si-) constituting the molecule (usually a portion of the position of the oxygen atom that forms the siloxane bond) contains a hydrocarbon skeleton containing an aromatic ring, usually divalent to tetravalent (for example, a phenylene skeleton, a bisphenylene skeleton, a bis(phenylene) ether skeleton, a bis(phenylene) methane skeleton, a 2,2-bis(phenylene) propane skeleton, a 2,2-bis(phenylene) hexafluoropropane skeleton, etc.). 【0050】 The amount of component (C) is 0.2 to 20 parts by mass, preferably 0.3 to 10 parts by mass, per 100 parts by mass of the total of component (B). Furthermore, it is preferable that the molar ratio (SiH groups / alkenyl groups) of hydrogen atoms (SiH groups) bonded to silicon atoms in component (C) to the total amount of alkenyl groups bonded to silicon atoms in components (B) and (C) (particularly in component (B)) is 0.8 to 10, particularly 1.0 to 5. If this ratio is less than 0.8, the curing (crosslinking density) may be insufficient, and the resulting rubber may become sticky. If it is greater than 10, foaming may be observed in the silicone rubber molded product, and it may become difficult to release it from the mold. 【0051】 [(D) Platinum group metal catalyst] Component (D) is a platinum group metal catalyst. The platinum group metal catalyst can be any catalyst that is conventionally known as an addition reaction catalyst. Examples of platinum group metal catalysts include platinum (including platinum black), platinum-dicidium chloride, chloroplatinic acid, reaction products of chloroplatinic acid and monohydric alcohols, complexes of chloroplatinic acid and olefins, and platinum bisacetate. 【0052】The amount of component (D) should be a catalytic amount. The catalytic amount is the effective amount necessary to carry out the addition reaction between component (B) and component (C) described above. Typically, as a platinum group metal element (by mass), 0.5 to 1,000 ppm and more preferably 1 to 500 ppm is used relative to the total mass of components (A) to (D). 【0053】 [(E) Reinforcing Filler] The silicone rubber composition of the present invention preferably further contains (E) a reinforcing filler in addition to the above components (A) to (D). Component (E) may be any conventionally known reinforcing filler, but reinforcing silica fine powder is preferred. The type of silica used for the reinforcing silica fine powder is not particularly limited; any silica commonly used as a reinforcing agent for rubber is acceptable, and those contained in conventional silicone rubber compositions can be used. Component (E) has a specific surface area of ​​50 m² as determined by the BET method. 2 A reinforcing silica fine powder with a specific surface area of ​​50 to 400 m² or more is preferred. 2 / g, more preferably 100 to 350m 2 The amount is / g. For example, precipitated silica (wet silica), fumed silica (dry silica), calcined silica, etc., are preferably used. From the viewpoint of improving rubber strength, fumed silica is particularly preferred. 【0054】 The reinforcing silica fine powder may be silica fine powder whose surface has been hydrophobized with a surface treatment agent. Examples of surface treatment agents include organosilicon compounds (usually hydrolyzable) such as chlorosilane, alkoxysilane, and organosilazane. The silica fine powder may be pre-treated in powder form with a surface treatment agent to directly hydrophobize its surface, or it may be treated by adding a surface treatment agent during the mixing of component (B) and the reinforcing silica fine powder, for example. 【0055】Surface treatment can be carried out according to conventionally known methods. For example, the untreated silica fine powder and the treatment agent are placed in a sealed mechanical kneading apparatus or fluidized bed at atmospheric pressure and mixed at room temperature or under heat treatment (heating) in the presence of an inert gas as needed. The treatment may be accelerated by using a catalyst (such as a hydrolysis accelerator). After kneading, the treated silica fine powder can be produced by drying. The amount of treatment agent used should be equal to or greater than the amount calculated from the coating area of ​​the treatment agent. 【0056】 Examples of surface treatment agents include silazanes such as hexamethyldisilazane; silane coupling agents such as methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, dimethyldimethoxysilane, diethyldimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, trimethylmethoxysilane, triethylmethoxysilane, vinyltris(methoxyethoxy)silane, trimethylchlorosilane, dimethyldichlorosilane, divinyldimethoxysilane, and chloropropyltrimethoxysilane; polymethylsiloxanes such as hexamethyldisiloxane, and organosilicon compounds such as organohydrogenpolysiloxane. Among these, polymethylsiloxanes such as hexamethyldisiloxane, silane coupling agents, or silazanes are particularly preferred, with hexamethyldisiloxane being preferred. 【0057】 When component (E) is included, the amount included is 1 to 100 parts by mass, preferably 5 to 60 parts by mass, and more preferably 10 to 60 parts by mass, per 100 parts by mass of component (B). Including it within the above range provides a sufficient reinforcing effect, and the silicone rubber composition has good viscosity, resulting in good workability and processability, which is preferable. 【0058】[Other Additives] The addition-curing silicone rubber composition of the present invention may contain other components as needed. Other components include fillers other than the above (E) component such as quartz powder, diatomaceous earth, and calcium carbonate; conductive agents such as carbon black, conductive zinc oxide, and metal powder; hydrosilylation reaction control agents such as nitrogen-containing compounds, acetylene compounds, phosphorus compounds, nitrile compounds, carboxylates, tin compounds, mercury compounds, and sulfur compounds; heat-resistant agents such as iron oxide and cerium oxide; adhesion promoters (especially organosilicon compounds such as functional alkoxysilanes that contain at least one functional group selected from alkenyl groups, epoxy groups, amino groups, (meth)acryloxy groups, mercapto groups, etc. in the molecule, and do not contain SiH groups in the molecule); and thixotropic agents. The amounts of these components can be appropriately selected from conventionally known ranges and adjusted as appropriate without impairing the effects of the present invention. 【0059】 The method for producing the addition-curing silicone rubber composition of the present invention is not particularly limited, but for example, components (B) to (D) may be mixed with other components as needed, and then component (A) may be added and mixed further. Alternatively, when incorporating component (E), a base compound may be prepared by mixing a portion of component (B), component (E), and a surface treatment agent for component (E) as needed, then the remaining components (B), (C), (D), and other components as needed may be added and mixed, and finally component (A) may be added and mixed further. As a mixing device, for example, a kneader, roll mill, Banbury mixer, etc. can be used. 【0060】 The molding and curing methods for the addition-curing type silicone rubber composition of the present invention are not particularly limited, and conventional methods can be employed. However, as a molding method, it is possible to select the most suitable means for the purpose from, for example, injection molding, transfer molding, injection molding, and compression molding. As for the curing conditions, a heat treatment (primary vulcanization) condition of 3 seconds to 160 minutes at 40 to 230°C can be employed. Furthermore, if necessary, a secondary vulcanization (post-cure) of 10 minutes to 24 hours at 40 to 230°C may be performed as needed. 【0061】The present invention will be described in more detail below with reference to synthesis examples, comparative synthesis examples, preparation examples, examples, and comparative examples, but the present invention is not limited to the following examples. In the following examples, parts refer to parts by mass. Also, room temperature refers to 25°C. Me represents a methyl group, Ph represents a phenyl group, and MeO represents a methoxy group. The measurement conditions are as follows. <Measurement conditions for average degree of polymerization> The average degree of polymerization is, 29 The measurements were taken using Si-NMR under the following conditions. 29 Si-NMR measurement conditions] Measuring device: ECX500 II (manufactured by JEOL RESONANCE) 29 Si nucleus measurement frequency: 99.325 MHz Number of cumulative measurements: 5,000 Sample concentration: 20% by mass (solvent: chloroform-d) Temperature: 25°C <Viscosity> Viscosity is the value measured at 25°C using a rotational viscometer. <m and n> m and n are the same as those shown in formula (1). <Chain length> Chain length is the number of m and n plus 2, which is the number of terminal trimethylsilyl groups. <Ph content> The Ph content described below is the ratio (%) of moles of Ph groups to the total number of moles of substituents (i.e., Me groups, Ph groups, and MeO groups) bonded to the silicon atoms of the phenyl group-containing organopolysiloxane. <MeO group content> The MeO group content (concentration of terminal methoxy groups) is the ratio (%) of moles of MeO groups to the total number of moles of Me groups and MeO groups bonded to the silicon atoms of the phenyl group-containing organopolysiloxane. <Methods for measuring pH content, MeO group content, m, and n> 29 The average degree of polymerization was measured using Si-NMR under the same conditions as the measurement. 【0062】[1] Production of Phenyl Group-Containing Organopolysiloxane (Silicone Oil) [Synthesis Example 1] Synthesis of Silicone Oil (A1) 21.38 g (0.087 mol) of dimethoxydiphenylsilane, 57.42 g (0.315 mol) of dimethoxymethylphenylsilane, and 9.20 g (0.057 mol) of hexamethyldisiloxane were charged into a flask equipped with a dropping funnel, a condenser, a thermometer, and a stirring device, and stirred at room temperature for 30 minutes. After that, the flask was immersed in a cooling bath and, after confirming that the internal temperature was below 5°C, 3.40 g of sulfuric acid and 7.97 g of water were added dropwise. The dropping funnel was switched to a Dean-Stark apparatus, and 10 mL of methanol was removed from the system by stirring at 75°C for 2 hours. The flask was then returned to room temperature and stirred overnight (16 hours). 1.46 g of water was added and the mixture was stirred at room temperature for 1 hour. After the reaction was complete, waste acid was separated and the mixture was washed with a 5% by mass sodium sulfate aqueous solution. Then, a vacuum strip was formed at 150°C for 5 hours to obtain 57.6 g of oil (referred to as silicone oil (A1)). 29 Analysis using Si-NMR confirmed that the structure is an oil with a chain length of 11.0 (m=1.9, n=7.1), a pH content of 45 mol%, and 0 mol% terminal methoxy groups. 【0063】 [Synthesis Example 2] Synthesis of Silicone Oil (A2) Using the same apparatus as in Synthesis Example 1, 16.22 g (0.075 mol) of dioldiphenylsilane, 41.02 g (0.225 mol) of dimethoxymethylphenylsilane, and 4.71 g (0.029 mol) of hexamethyldisiloxane were charged as raw materials and stirred at room temperature for 30 minutes. Then, the flask was immersed in a cooling bath and, after confirming that the internal temperature was below 5°C, 2.58 g of sulfuric acid and 2.70 g of water were added dropwise. The dropping funnel was switched to a Dean-Stark apparatus and 10 mL of methanol was removed from the system by stirring at 75°C for 2 hours. The flask was returned to room temperature and stirred overnight (16 hours). 1.10 g of water was added and stirred at room temperature for 1 hour. After the reaction was complete, waste acid was separated and washed with a 5% by mass aqueous solution of sodium sulfate, and then a vacuum strip was performed at 150°C for 5 hours to obtain 39.9 g of oil (referred to as silicone oil (A2)). 29Analysis using Si-NMR confirmed that the oil structure has a chain length of 14.8 (m=3.1, n=9.7), a pH content of 50 mol%, and 0 mol% terminal methoxy groups. 【0064】 [Comparative Synthesis Example 1] Synthesis of Silicone Oil (A1 ratio) Using the same apparatus as in Synthesis Example 1, 7.57 g (0.035 mol) of dioldiphenylsilane, 60.61 g (0.332 mol) of dimethoxymethylphenylsilane, and 9.20 g (0.057 mol) of hexamethyldisiloxane were charged as raw materials and stirred at room temperature for 30 minutes. After that, the flask was immersed in a cooling bath and it was confirmed that the internal temperature was below 5°C, and then 3.10 g of sulfuric acid and 2.68 g of water were added dropwise. The dropping funnel was switched to a Dean-Stark apparatus, and 12 mL of methanol was removed from the system by stirring at 75°C for 2 hours, and the flask was returned to room temperature and stirred overnight (16 hours). 1.33 g of water was added and the mixture was stirred at room temperature for 1 hour. After the reaction was complete, waste acid was separated and the mixture was washed with a 5% by mass sodium sulfate aqueous solution. Then, a vacuum strip was performed at 150°C for 5 hours to obtain 47.2 g of oil (referred to as silicone oil (A1 ratio)). 29 Analysis using Si-NMR confirmed that the structure is an oil with a chain length of 10.6 (m=0.4, n=8.2), a pH content of 39 mol%, and 0 mol% terminal methoxy groups. 【0065】 [Comparative Synthesis Example 2] Synthesis of Silicone Oil (A2 ratio) Using the same apparatus as in Synthesis Example 1, 63.80 g (0.350 mol) of dimethoxymethylphenylsilane and 9.20 g (0.057 mol) of hexamethyldisiloxane were charged as raw materials and stirred at room temperature for 30 minutes. Then, the flask was immersed in a cooling bath and, after confirming that the internal temperature was below 5°C, 2.84 g of sulfuric acid and 6.93 g of water were added dropwise. The dropping funnel was switched to a Dean-Stark apparatus and 10 mL of methanol was removed from the system by stirring at 75°C for 2 hours. The flask was returned to room temperature and stirred overnight (16 hours). 1.22 g of water was added and stirred at room temperature for 1 hour. After the reaction was complete, waste acid was separated and washed with a 5% by mass aqueous solution of sodium sulfate, and then a vacuum strip was performed at 150°C for 5 hours to obtain 52.2 g of oil (referred to as silicone oil (A2 ratio)). 29Analysis using Si-NMR confirmed that the oil structure has a chain length of 18.8 (m=0, n=16.8), a pH content of 42 mol%, and 0 mol% terminal methoxy groups. 【0066】 [Comparative Synthesis Example 3] Synthesis of Silicone Oil (A3 ratio) Using the same apparatus as in Synthesis Example 1, 21.38 g (0.087 mol) of dimethoxydiphenylsilane, 57.42 g (0.315 mol) of dimethoxymethylphenylsilane, and 9.20 g (0.057 mol) of hexamethyldisiloxane were charged as raw materials and stirred at room temperature for 30 minutes. After that, the flask was immersed in a cooling bath and it was confirmed that the internal temperature was below 5°C, and then 3.40 g of sulfuric acid and 7.97 g of water were added dropwise. The dropping funnel was switched to a Dean-Stark apparatus, and 10 mL of methanol was removed from the system by stirring at 75°C for 1 hour, and the flask was returned to room temperature and stirred overnight (16 hours). 1.46 g of water was added and the mixture was stirred at room temperature for 1 hour. After the reaction was complete, waste acid was separated and the mixture was washed with a 5% by mass sodium sulfate aqueous solution. Then, a vacuum strip was performed at 150°C for 5 hours to obtain 52.2 g of oil (referred to as silicone oil (A3 ratio)). 29 Analysis using Si-NMR confirmed that the oil structure has a chain length of 11.3 (m=1.9, n=7.4), a pH content of 46 mol%, and 10 mol% terminal methoxy groups. 【0067】 [Synthesis Example 3] Synthesis of Silicone Oil (A3) Using the same apparatus as in Synthesis Example 1, 21.38 g (0.087 mol) of dimethoxydiphenylsilane, 57.42 g (0.315 mol) of dimethoxymethylphenylsilane, and 9.20 g (0.057 mol) of hexamethyldisiloxane were charged as raw materials and stirred at room temperature for 30 minutes. Then, the flask was immersed in a cooling bath and, after confirming that the internal temperature was below 5°C, 3.40 g of sulfuric acid and 7.97 g of water were added dropwise. The dropping funnel was switched to a Dean-Stark apparatus and 10 mL of methanol was removed from the system by stirring at 75°C for 2 hours. The flask was then returned to room temperature and stirred for 6 hours. 1.46 g of water was added and stirred at room temperature for 1 hour. After the reaction was complete, waste acid was separated and washed with a 5% by mass aqueous sodium sulfate solution, and then a vacuum strip was performed at 150°C for 5 hours to obtain 53.0 g of oil (referred to as silicone oil (A3)). 29Analysis using Si-NMR confirmed that the oil structure has a chain length of 11.1 (m=1.8, n=7.3), a pH content of 41 mol%, and 0.5 mol% terminal methoxy groups. 【0068】 [Synthesis Example 4] Synthesis of Silicone Oil (A4) Using the same apparatus as in Synthesis Example 1, 21.38 g (0.087 mol) of dimethoxydiphenylsilane, 57.42 g (0.315 mol) of dimethoxymethylphenylsilane, and 9.20 g (0.057 mol) of hexamethyldisiloxane were charged as raw materials and stirred at room temperature for 30 minutes. Then, the flask was immersed in a cooling bath and, after confirming that the internal temperature was below 5°C, 3.40 g of sulfuric acid and 7.97 g of water were added dropwise. The dropping funnel was switched to a Dean-Stark apparatus and 10 mL of methanol was removed from the system by stirring at 80°C for 1 hour. The flask was returned to room temperature and stirred overnight (16 hours). 1.46 g of water was added and stirred at room temperature for 1 hour. After the reaction was complete, waste acid was separated and washed with a 5% by mass aqueous sodium sulfate solution, and then a reduced-pressure strip was performed at 150°C for 5 hours to obtain 51.5 g of oil (referred to as silicone oil (A4)). 29 Analysis using Si-NMR confirmed that the oil structure has a chain length of 10.9 (m=1.8, n=7.1), a pH content of 49 mol%, and 3 mol% terminal methoxy groups. 【0069】 [2] Preparation of base compound [Preparation example 1] 60 parts of dimethylpolysiloxane (B1) with vinyldimethylsiloxy groups sealed at both ends of the molecular chain, having a viscosity of approximately 30,000 mPa·s and an average degree of polymerization of 750, and a specific surface area of ​​approximately 240 m² by the BET method. 2 40 parts of finely powdered silica (E) (product name: Aerosil R976S, manufactured by Nippon Aerosil Co., Ltd.) at a concentration of / g, 2 parts of hexamethyldisiloxane as a surface treatment agent, and 1.5 parts of 28% by mass aqueous ammonia were mixed in a kneader for 1 hour. Then, the temperature in the kneader was raised to 150°C and mixing continued for 3 hours. Next, the temperature was lowered to 100°C, and then 30 parts of dimethylpolysiloxane (B1) were added and mixed until homogeneous. The resulting mixture is referred to as base compound (X). 【0070】[Preparation Example 2] 60 parts of dimethylpolysiloxane (B1) with vinyldimethylsiloxy groups sealed at both ends of the molecular chain, having a viscosity of approximately 30,000 mPa·s and an average degree of polymerization of 750, and a specific surface area of ​​approximately 300 m² by the BET method. 2 40 parts of finely powdered silica (E) (product name: Aerosil 300, manufactured by Nippon Aerosil Co., Ltd.) at a concentration of / g, 8 parts of hexamethyldisiloxane as a surface treatment agent, and 2 parts of water were mixed in a kneader for 1 hour. Then, the temperature in the kneader was raised to 150°C and mixing continued for 3 hours. Next, the temperature was lowered to 100°C, and then 30 parts of dimethylpolysiloxane (B1) were added and mixed until homogeneous. The resulting mixture is referred to as the base compound (Y). 【0071】 [3] Production of Silicone Rubber Composition [Example 1] To 130 parts of the base compound (X) obtained above, 11 parts of dimethylpolysiloxane (B1), 2 parts of dimethylpolysiloxane (B2) with vinyldimethylsiloxy groups sealed at both ends of the molecular chain having a viscosity of approximately 700 mPa·s and an average degree of polymerization of 185, and 2.0 parts of methylhydrogenpolysiloxane (C1) (an average degree of polymerization of 46, with an SiH group content of 0.0055 mol / g, trimethylsiloxy group sealed at both ends of the molecular chain and methylhydrogensiloxane copolymer) were added as a crosslinking agent. The ratio of the total number of moles of SiH groups to the total number of moles of vinyl groups was 1.8. Furthermore, 0.095 parts of ethinylcyclohexanol were added as a reaction control agent, and the mixture was stirred at room temperature for 15 minutes. Next, 0.1 parts of a toluene solution (D1) of a complex of platinum and 1,3-divinyl-1,1,3,3-tetramethyldisiloxane (1% by mass in terms of platinum atoms) were added, and the mixture was stirred at room temperature for 15 minutes to obtain a mixture (referred to as silicone rubber mixture A). 100 parts of the silicone rubber mixture A obtained above were mixed with 4.2 parts of the silicone oil (A1) obtained in Synthesis Example 1 to obtain a homogeneous silicone rubber composition (referred to as silicone rubber composition 1). 【0072】[Example 2] To 130 parts of the base compound (Y) obtained above, 11 parts of dimethylpolysiloxane (B1), 2 parts of dimethylpolysiloxane (B2) with vinyldimethylsiloxy groups sealed at both ends of the molecular chain having a viscosity of approximately 700 mPa·s and an average degree of polymerization of 185, and 2.0 parts of methylhydrogenpolysiloxane (C1) (an average degree of polymerization of 46, with an SiH group content of 0.0055 mol / g, trimethylsiloxy group sealed at both ends of the molecular chain and methylhydrogensiloxane copolymer) were added as a crosslinking agent. The ratio of the total number of moles of SiH groups to the total number of moles of vinyl groups was 1.8. Furthermore, 0.095 parts of ethinylcyclohexanol were added as a reaction control agent, and the mixture was stirred at room temperature for 15 minutes. Next, 0.1 parts of a toluene solution (D1) of a complex of platinum and 1,3-divinyl-1,1,3,3-tetramethyldisiloxane (1% by mass in terms of platinum atoms) were added, and the mixture was stirred at room temperature for 15 minutes to obtain a mixture (referred to as silicone rubber mixture B). 100 parts of the silicone rubber mixture B obtained above were mixed with 4.2 parts of the silicone oil (A1) obtained in Synthesis Example 1 to obtain a homogeneous silicone rubber composition (referred to as silicone rubber composition 2). 【0073】 [Example 3] 100 parts of the silicone rubber mixture A prepared in Example 1 were mixed with 4.2 parts of the silicone oil (A2) obtained in Synthesis Example 2 to obtain a uniform silicone rubber composition (referred to as silicone rubber composition 3). 【0074】 [Example 4] 100 parts of the silicone rubber mixture A prepared in Example 1 were mixed with 4.2 parts of the silicone oil (A3) obtained in Synthesis Example 3 to obtain a uniform silicone rubber composition (referred to as silicone rubber composition 4). 【0075】 [Example 5] 100 parts of the silicone rubber mixture A prepared in Example 1 were mixed with 4.2 parts of the silicone oil (A4) obtained in Synthesis Example 4 to obtain a uniform silicone rubber composition (referred to as silicone rubber composition 5). 【0076】[Comparative Example 1] 100 parts of the silicone rubber mixture A prepared in Example 1 were mixed with 4.2 parts of silicone oil (product name: KF-53, manufactured by Shin-Etsu Chemical Co., Ltd.) having a chain length of 21 and a pH content of 21%, to obtain a uniform silicone rubber composition (referred to as silicone rubber composition 6). 【0077】 [Comparative Example 2] 100 parts of the silicone rubber mixture A prepared in Example 1 were mixed with 4.2 parts of the silicone oil (A1 ratio) obtained in Comparative Synthesis Example 1 to obtain a uniform silicone rubber composition (referred to as silicone rubber composition 7). 【0078】 [Comparative Example 3] 100 parts of the silicone rubber mixture A prepared in Example 1 were mixed with 4.2 parts of the silicone oil (A2 ratio) obtained in Comparative Synthesis Example 2 to obtain a uniform silicone rubber composition (referred to as silicone rubber composition 8). 【0079】 [Comparative Example 4] 100 parts of the silicone rubber mixture A prepared in Example 1 were mixed with 4.2 parts of the silicone oil (A3 ratio) obtained in Comparative Synthesis Example 3 to obtain a uniform silicone rubber composition (referred to as silicone rubber composition 9). 【0080】 The silicone rubber compositions 1 to 9 obtained in the above examples and comparative examples were subjected to oil bleed evaluation tests and heat resistance tests. The results are shown in Tables 1, 2, and 3. 【0081】 <Evaluation of Oil Bleeding Properties of Silicone Rubber Compositions> Each silicone rubber composition was press-cured at 150°C for 10 minutes to a thickness of 2 mm and allowed to cure. The cured material was then cut into 15 mm x 35 mm sheet pieces, and the resulting samples were left at room temperature (25°C) for one day. Afterward, the presence or absence of oil seeping onto the sample surface was checked, and the oil bleeding properties were evaluated. The evaluation criteria are as follows: ○: Oil bleeding present ×: No oil bleeding 【0082】<Heat Resistance Evaluation of Silicone Rubber Compositions> Each silicone rubber composition was press-cured to a thickness of 2 mm at 150°C for 10 minutes to cure. The cured material was then cut into six 15 mm x 35 mm sheets. Three of these sheets were left at room temperature (25°C) for one day, and the remaining three sheets were placed in a drying oven at 225°C for 70 hours. After that, three sheets of each composition were stacked together, and the hardness was measured using an ASKER P2 hardness tester (manufactured by Polymer Instruments Co., Ltd.), and the difference in hardness with and without heating was compared. 【0083】 【0084】 【0085】 【0086】 As shown in Table 1, the silicone rubber composition of the present invention demonstrated oil bleeding properties when either silicone mixture A or B was used (Examples 1 and 2). Conventionally, KF-53, which was used for oil bleeding, did not exhibit oil bleeding properties when silicone mixture A, which contains silica with a high degree of surface treatment, was used (Comparative Example 1). It is thought that the silicone oil (A1) used in Examples 1 and 2 had a shorter chain length and a higher pH content compared to KF-53, which increased the oil separation rate and made it easier to bleed. 【0087】 As shown in Table 2, even if the m+n of component (A) was less than 16, oil bleeding could not be confirmed if the pH content was below 40 mol% (Comparative Example 2). Furthermore, even if the pH content of component (A) was 40 mol% or more, oil bleeding could not be confirmed if the m+n was 16 or more (Comparative Example 3). 【0088】 As shown in Table 3, when component (A) containing less than 5 mol% of methoxy groups was used, there was almost no change in hardness after the heat resistance test (Examples 1, 4, and 5). In contrast, when silicone oil with 10 mol% of methoxy groups remaining (compared to A3) was used, the hardness changed significantly after the heat resistance test, even though the m+n and Ph content were almost the same as that of silicone oil (A1) (Comparative Example 4). This is thought to be because the methoxy groups detach during heat resistance, causing the oil to expand and thus increasing its hardness. 【0089】 In summary, the cured products obtained from the silicone rubber compositions of Examples 1 to 5 exhibited excellent oil bleed resistance and heat resistance.

Claims

1. An addition-curing silicone rubber composition characterized by containing the following components (A) to (D). (A) An aromatic hydrocarbon group-containing organopolysiloxane represented by the following formula (1): 1 to 10 parts by mass, (In the formula, R 1 These are, independently of each other, monovalent hydrocarbon groups having 1 to 10 carbon atoms, excluding monovalent aromatic hydrocarbon groups, or alkoxy groups having 1 to 10 carbon atoms, and the content of the alkoxy groups is, total R 1 It is less than 5 mol% of the total. 2 (B) an organopolysiloxane having at least two alkenyl groups bonded to silicon atoms: 100 parts by mass, (C) an organohydrogenpolysiloxane having at least two hydrogen atoms bonded to silicon atoms: 0.2 to 20 parts by mass, and (D) a platinum group metal catalyst: catalytic amount 2. R in formula (1) of component (A) 2 The addition reaction curing type silicone rubber composition according to claim 1, wherein the group is a phenyl group.

3. The addition reaction curing type silicone rubber composition according to claim 1, further comprising (E) a reinforcing filler in 1 to 100 parts by mass of component (B) per 100 parts by mass.

4. A cured product of an addition-curing type silicone rubber composition according to any one of claims 1 to 3.

5. A method for producing an (A) aromatic hydrocarbon group-containing organopolysiloxane contained in the addition reaction-curable silicone rubber composition according to any one of claims 1 to 3, which is represented by the following formula (1) by reacting a silane compound represented by the following formula (3) with a disiloxane compound represented by the following formula (4). After starting the reaction, the reaction is carried out for 0.5 to 3 hours while removing the alcohol by-produced at 70 to 90 °C outside the reaction system, and then aged for 6 hours or more. The method for producing the (A) aromatic hydrocarbon group-containing organopolysiloxane having this step. (In the formula, R 1 and R 2 are the same as described above, and R 3 is, independently of each other, a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. p is an integer of 1 to 3, q is an integer of 0 to 3, r is an integer of 1 to 3, and p + q + r = 4.) (In the formula, R 1 , R 2 , m and n are the same as described above.) 6. The manufacturing method according to claim 5, wherein the maturation temperature is 0°C or higher and less than 70°C.

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