Room temperature curing silicone rubber composition

Abstract

To provide a room temperature curable silicone rubber composition which significantly reduces yellowing and bubble entrapment and gives a cured product having high transparency and high strength.SOLUTION: There is provided a composition which comprises (A) a linear organopolysiloxane containing vinyl groups at both ends of the molecular chain, (B) a branched organopolysiloxane containing vinyl groups which is solid at 23°C, (C) a branched organopolysiloxane containing vinyl groups which is liquid at 23°C, (D) a linear organohydrogen polysiloxane and (E) a hydrosilylation reaction catalyst, wherein the number of SiH in (D) relative to the total number of vinyl groups in (A) to (C) is 0.7 to 3.0 times and the content of metal atoms derived from (E) is 20 mass ppm or less based on the total of (A) to (D).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an addition-curable silicone rubber composition that cures at room temperature to give a cured product that is highly transparent and has high strength. [Background technology]

[0002] Highly transparent silicone rubber materials are used in a wide range of applications, including optical device materials, 3D printer materials, and nanoimprint materials. In addition, because silicone materials have excellent durability, ornamental moldings have been proposed in which dried flowers, three-dimensional models, etc. are enclosed in silicone gel or silicone rubber (Patent Documents 1 and 2). The silicone rubber used for such potting is liquid before hardening, and when mixed with a hardener, it hardens easily at room temperature or under heat, becoming a highly transparent rubber material.

[0003] However, silicone rubber materials have problems such as bubbles that are generated when mixing with a curing agent or during potting, which remain after curing, peeling that can occur at the interface between the silicone rubber and the container or enclosed items due to shrinkage after curing, and yellowing of the material due to coloring caused by metal catalysts after an extended period of time. To address these issues, a room-temperature curing silicone rubber composition has been proposed that reduces yellowing and bubble entrapment and gives a cured product with little change in hardness (Patent Document 3). However, the cured product is brittle and prone to cracking when removed from the mold. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 8-92002 [Patent Document 2] JP 2000-336269 A [Patent Document 3] Patent Publication No. 2021-1257 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in view of the above circumstances, and has as its object to provide a room temperature curable silicone rubber composition which significantly reduces yellowing and bubble entrapment and gives a cured product which is highly transparent and has high strength. [Means for solving the problem]

[0006] As a result of extensive research into achieving the above object, the inventors have discovered that the specific addition-curable silicone rubber composition described below reduces the occurrence of bubble entrapment during mixing and provides a silicone rubber that is highly transparent and has high strength, thereby completing the present invention.

[0007] That is, the present invention provides 1. (A) an organopolysiloxane represented by the following average formula (1): [Vi (3-a) R 1 a SiO 1 / 2 ]2[R 1 2SiO 2 / 2 ] m (1) (In the formula, R 1 each independently represents an unsubstituted or substituted monovalent hydrocarbon group not containing an alkenyl group, Vi represents a vinyl group, m represents a number from 13 to 400, and a represents a number from 0 to 2. (B) an organopolysiloxane having a constitutional unit ratio represented by the following formula (2) and being solid at 23°C; [R 1 3SiO 1 / 2 ] p [Vi (3-b) R 1 b SiO 1 / 2 ] q [SiO 4 / 2 ] r (2) (In the formula, R 1 and Vi have the same meaning as above, p, q, and r respectively represent numbers satisfying p>0, q>0, r>0, and p+q+r=1, and b represents a number from 0 to 2.) (C) an organopolysiloxane which has a constitutional unit ratio represented by the following formula (3) and is liquid at 23°C; [Vi (3-c) R 1 c SiO 1 / 2 ] s [R 1 S iO 3 / 2 ] t (3) (In the formula, R 1 and Vi have the same meaning as above, s and t respectively represent numbers that satisfy s>0, t>0, and s+t=1, and c represents a number from 0 to 2.) (D) an organohydrogenpolysiloxane represented by the following average formula (4): [R 2 R 1 2SiO 1 / 2 ]2[HR 1 SiO 2 / 2 ] u [R 1 2SiO 2 / 2 ] v (4) (In the formula, R 1 has the same meaning as above, R 2 represents a hydrogen atom or a methyl group, and u and v represent numbers that satisfy u≧2, v≧2, and 10≦u+v≦100, respectively. and (E) Hydrosilylation reaction catalyst Contains a room-temperature-curable silicone rubber composition in which the number of SiH groups in component (D) is 0.7 to 3.0 times the total number of vinyl groups in components (A), (B), and (C), and the content of metal atoms derived from a hydrosilylation reaction catalyst in component (E) is 20 ppm by mass or less based on the total amount of components (A) to (D); 2. R in the above formula (1) 1 1. A room-temperature curable silicone rubber composition according to claim 1, wherein 1 to 10 mol % of the above is a phenyl group. 3. R ​​in the above formula (4) 2is a hydrogen atom, and u and v are numbers that satisfy u≧2, v≧2, 10≦u+v≦50, and 0.05≦u / (u+v)≦0.5, respectively. 4. A room-temperature curable silicone rubber composition according to any one of 1 to 3, wherein the number of SiH groups in component (D) is 1.0 to 2.5 times the total number of vinyl groups in components (A), (B), and (C). 5. Any one of the room-temperature curable silicone rubber compositions according to 1 to 4, having a viscosity at 23°C of 1,000 mPa s or less. 6. A silicone rubber obtained by curing the room temperature curable silicone rubber composition according to any one of 1 to 5. 7. Silicone rubber according to claim 6, wherein the difference between the Durometer A hardness of the cured product cured at 23°C for 24 hours and the Durometer A hardness of the cured product cured at 23°C for 72 hours is 1 or less. 8. Silicone rubber of 6 or 7, whose transmittance for light with a wavelength of 400 nm at a thickness of 2 mm is 90% or more. to provide. Effect of the Invention

[0008] The room-temperature curable silicone rubber composition of the present invention provides silicone rubber that has excellent bubble releasing properties, is highly transparent, has high strength and exhibits little change in hardness, and is therefore suitable for sealing specimens such as herbariums, three-dimensional models, decorative items, etc. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The present invention will be specifically described below. The room temperature curable silicone rubber composition of the present invention contains the following components (A) to (E). (A) Linear organopolysiloxane containing vinyl groups at both ends of the molecular chain (B) A vinyl group-containing branched organopolysiloxane that is solid at 23°C. (C) a vinyl group-containing branched organopolysiloxane that is liquid at 23°C (D) Linear organohydrogenpolysiloxane (E) Hydrosilylation reaction catalyst

[0010] [1] Component (A) Component (A) is a linear organopolysiloxane having vinyl groups at both molecular chain terminals and represented by the following average formula (1). [Vi (3-a) R 1 a SiO 1 / 2 ]2[R 1 2SiO 2 / 2 ] m (1)

[0011] In the average formula (1), R 1 each independently represents an unsubstituted or substituted monovalent hydrocarbon group not containing an alkenyl group, and Vi represents a vinyl group (the same applies hereinafter). R 1 There is no particular limitation on the alkyl group as long as it does not have an alkenyl group, and it may be linear, branched, or cyclic, but it is preferably a monovalent hydrocarbon group having 1 to 20 carbon atoms, more preferably a monovalent hydrocarbon group having 1 to 10 carbon atoms, and even more preferably a monovalent hydrocarbon group having 1 to 5 carbon atoms. Specific examples thereof include linear or branched alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, and n-hexyl groups; cyclic alkyl groups such as cyclohexyl groups; aryl groups such as phenyl and tolyl groups; and aralkyl groups such as benzyl and phenylethyl groups. In addition, some or all of the hydrogen atoms of these monovalent hydrocarbon groups may be substituted with halogen atoms such as F, Cl, Br, etc., cyano groups, etc., and specific examples of such groups include halogen-substituted hydrocarbon groups such as 3,3,3-trifluoropropyl group, etc.; and cyano-substituted hydrocarbon groups such as 2-cyanoethyl group, etc. Among these, methyl and phenyl groups are preferred, and R 1 Of these, 1 to 10 mol % is more preferably a phenyl group.

[0012] In the average formula (1), a is a number from 0 to 2. m is a number from 13 to 400, preferably a number from 30 to 350, and more preferably a number from 100 to 300. If m is smaller than 13, the compound will volatilize during curing, and if it is larger than 400, the composition will not defoam well when mixed, and workability will be impaired.

[0013] The viscosity of component (A) at 23°C is preferably 10 to 2,000 mPa s, and more preferably 20 to 1,500 mPa s, from the viewpoints that bubbles generated during mixing of the composition can be easily removed and that the composition is in a liquid state and hardens to become a rubber-like elastomer. Note that the viscosity in the present invention is a value measured using a rotational viscometer.

[0014] Examples of such component (A) include organopolysiloxanes represented by the following average formula: The component (A) may be used alone or in combination of two or more different types.

[0015] [ka] (In the formula, the siloxane units in the parentheses may be arranged in any order.)

[0016] [2](B) Component Component (B) has the structural unit ratio represented by formula (2) below and is a vinyl group-containing branched organopolysiloxane that is solid at 23°C. It is a component that provides a reinforcing effect to the composition by crosslinking accompanying hydrosilylation. [R 1 3SiO 1 / 2 ] p [Vi (3-b) R 1 b SiO 1 / 2 ] q [SiO 4 / 2 ] r (2)

[0017] In formula (2), R 1 has the same meaning as above, and specific examples thereof include the same unsubstituted or substituted monovalent hydrocarbon groups other than alkenyl groups as exemplified in the above average formula (1), and among these, a methyl group is preferred. p, q, and r are numbers that respectively satisfy p>0, q>0, r>0, and p+q+r=1. From the viewpoint of the mechanical properties of the resulting cured product, the ratio of M units to Q units in the organopolysiloxane of component (B), (p+q) / r, is preferably 0.3 to 2.0, and more preferably 0.4 to 1.0. b is a number from 0 to 2.

[0018] The molecular weight of component (B) is not particularly limited, but from the viewpoints of compatibility with other components and the mechanical properties of the resulting cured product, it is preferably 1,000 to 50,000, and more preferably 2,000 to 10,000. The molecular weight is the weight average molecular weight calculated as standard polystyrene by gel permeation chromatography (GPC).

[0019] Specific examples of the component (B) include organopolysiloxanes represented by the following formula: (Me3SiO 1 / 2 ) 0.4 (ViMe2SiO 1 / 2 ) 0.05 (SiO 4 / 2 ) 0.55 (Me3SiO 1 / 2 ) 0.1 (Vi3SiO 1 / 2 ) 0.2 (SiO 4 / 2 ) 0.7 (Me3SiO 1 / 2 ) 0.35 (ViMe2SiO 1 / 2 ) 0.2 (Vi3SiO 1 / 2 ) 0.1 (SiO 4 / 2 ) 0.35

[0020] The blending amount of the (B) component is preferably 2 to 20 parts by mass, more preferably 3 to 7 parts by mass, per 100 parts by mass of the (A) component, from the viewpoints of the viscosity of the composition and the mechanical properties of the resulting cured product. The (B) component may be dissolved in the (A) component before use. Further, the component (B) may be used alone or in combination of two or more thereof.

[0021] [3] Component (C) The component (C) is a vinyl group-containing branched organopolysiloxane that has a constitutional unit ratio represented by the following formula (3) and is liquid at 23°C. It consists of a monosiloxy unit and a trisiloxy unit having a vinyl group bonded to a silicon atom, and is a component that promotes crosslinking by hydrosilylation. [Vi (3-c) R 1 c SiO 1 / 2 ) s [R 1 S iO 3 / 2 ) t (3)

[0022] In formula (3), R 1 represents the same meaning as above. Specifically, examples thereof include the same as the unsubstituted or substituted monovalent hydrocarbon groups other than the alkenyl group exemplified in the above average formula (1), and among them, a methyl group is preferable. s and t are numbers that satisfy s > 0, t > 0, and s + t = 1, respectively, and c is a number from 0 to 2. From the viewpoint of imparting fluidity to this component and suppressing volatility, 0.4 < s < 0.7 is preferable, and 0.45 < s < 0.6 is more preferable.

[0023] The kinematic viscosity of the component (C) is not particularly limited, but from the viewpoint of compatibility with other components and the mechanical properties of the resulting cured product, it is preferably 1 to 500 mm 2 / s, and more preferably 10 to 100 mm 2 / s. The kinematic viscosity is the value at 23°C measured by a Cannon-Fenske viscometer.

[0024] Specific examples of the component (C) include organopolysiloxanes having a constitutional unit ratio represented by the following formula. (ViMe2SiO 1 / 2 ) 0.5 (R 1 S iO3 / 2 ) 0.5 (ViMe2SiO 1 / 2 ) 0.55 (R 1 S iO 3 / 2 ) 0.45 (ViMe2SiO 1 / 2 ) 0.6 (R 1 S iO 3 / 2 ) 0.4

[0025] The blend amount of the (C) component is preferably 2 to 20 parts by mass, and more preferably 3 to 10 parts by mass, per 100 parts by mass of the (A) component, from the standpoint of the viscosity of the composition and the mechanical properties of the resulting cured product. The component (C) may use either a single type alone, or a combination of two or more types.

[0026] [4](D) component Component (D) is a linear organohydrogenpolysiloxane having hydrogen atoms bonded to silicon atoms (i.e., SiH groups) and is represented by the following average formula (4). It acts as a crosslinking agent through a hydrosilylation reaction between the vinyl groups in components (A) to (C) and the SiH groups in this component. [R 2 R 1 2SiO 1 / 2 ]2[HR 1 SiO 2 / 2 ] u [R 1 2SiO 2 / 2 ] v (4)

[0027] In the average equation (4), R 1 has the same meaning as above, and specific examples thereof include the same unsubstituted or substituted monovalent hydrocarbon groups other than alkenyl groups as exemplified in the above average formula (1), and among these, a methyl group is preferred. R 2 is a hydrogen atom or a methyl group, and of these, a hydrogen atom is preferred.

[0028] u and v are numbers that satisfy u≧2, v≧2, and 10≦u+v≦100, respectively. The value of u is preferably u≧5, and more preferably u≧10, and the value of v is preferably v≦70, and more preferably v≦50. In addition, a number satisfying 0.05≦u / (u+v)≦0.5 is preferable. If u+v is less than 10, the composition will volatilize during curing, whereas if it exceeds 100, the viscosity of the composition will increase, making it difficult to remove bubbles and also reducing workability.

[0029] Specific examples of the organohydrogenpolysiloxane of component (D) include a dimethylsiloxane-methylhydrogensiloxane copolymer capped at both molecular chain terminals with trimethylsiloxy groups, represented by the average formula below, and a methylhydrogenpolysiloxane capped at both molecular chain terminals with trimethylsiloxy groups. The component (D) may use either a single type alone, or a combination of two or more types.

[0030] [ka] (In the formula, the siloxane units may be arranged in any order.)

[0031] The amount of component (D) is such that the number of SiH groups in component (D) is 0.7 to 3.0 times, and preferably 1.0 to 2.5 times, the total number of vinyl groups in components (A), (B), and (C). If the number of SiH groups is less than 0.7 times, crosslinking will be insufficient, while if it exceeds 3.0 times, foaming will occur due to the generation of hydrogen gas during curing, and voids will occur inside the cured product, reducing transparency and rubber strength.

[0032] [5](E) component Component (E) is a hydrosilylation catalyst for promoting the hydrosilylation reaction between the vinyl groups in components (A) to (C) and the SiH groups in component (D). The hydrosilylation catalyst of component (E) is preferably a platinum group metal catalyst, and specific examples thereof include platinum-based catalysts such as platinum black, platinic chloride, chloroplatinic acid, reaction products of chloroplatinic acid and monohydric alcohols, complexes of chloroplatinic acid and olefins, platinum bisacetoacetate, etc., palladium-based catalysts such as tetrakis(triphenylphosphine)palladium and dichlorobis(triphenylphosphine)palladium, and rhodium-based catalysts such as chlorotris(triphenylphosphine)rhodium and tetrakis(triphenylphosphine)rhodium.

[0033] The amount of component (E) is 20 ppm or less, preferably 15 ppm or less, calculated as the mass of platinum group metal atoms in this component relative to the total of components (A) to (D). The lower limit is preferably 1 ppm or more, more preferably 3 ppm or more. Within this range, the reaction rate of the addition reaction is appropriate, and coloration of the cured product due to metal atoms derived from the catalyst can be suppressed.

[0034] [6] (F) component If necessary, a reaction regulator (F) may be added to the room-temperature-curable silicone rubber composition of the present invention for the purpose of controlling the reactivity of the hydrosilylation reaction catalyst so as to prevent thickening or gelation during preparation of the composition or before heat curing.

[0035] Specific examples of the reaction inhibitor include 3-methyl-1-butyn-3-ol, 3-methyl-1-pentyn-3-ol, 3,5-dimethyl-1-hexyn-3-ol, 1-ethynylcyclohexanol, ethynylmethyldecylcarbinol, 3-methyl-3-trimethylsiloxy-1-butyne, 3-methyl-3-trimethylsiloxy-1-pentyne, 3,5-dimethyl-3-trimethylsiloxy-1-hexyne, 1-ethynyl- Examples of such siloxanes include 1-trimethylsiloxycyclohexane, bis(2,2-dimethyl-3-butynoxy)dimethylsilane, 1,3,5-trimethyl-1,3,5-trivinylcyclotetrasiloxane, 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, and 1,1,3,3-tetramethyl-1,3-divinyldisiloxane. These may be used alone or in combination of two or more. Of these, 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane is preferred.

[0036] When component (F) is used, the amount added is preferably 0.001 to 2 parts by mass, and more preferably 0.006 to 1.5 parts by mass, per 100 parts by mass of components (A) to (D) combined. Within this range, the reaction control effect is sufficiently exhibited.

[0037] [7] Other ingredients In addition to the above components (A) to (F), the room temperature curable silicone rubber composition of the present invention may contain other components, such as those exemplified below, as long as the object of the present invention is not impaired. Other components include fillers such as fumed silica, crystalline silica (quartz powder), precipitated silica, and silica whose surfaces have been treated to make them hydrophobic; conductive agents such as iron oxide, carbon black, conductive zinc oxide, and metal powder; heat resistance agents such as titanium oxide and cerium oxide; internal release agents such as dimethyl silicone oil; adhesion imparting agents; thixotropy imparting agents; and colorants.

[0038] The room temperature curable silicone rubber composition of the present invention can be prepared by mixing the above-mentioned components (A) to (E), the optional component (F), and other components by a known method using a kneader, planetary mixer, or the like. The room temperature curable silicone rubber composition of the present invention may be a two-part composition in which a first part consisting of components (A), (E), and other components as required, and a second part consisting of components (A) to (D), (F), and other components as required, are separately prepared, and the first part and the second part are mixed before use. There may be a component that is used in common in both the first part and the second part. By forming the composition into such a two-part type, storage stability can be further ensured.

[0039] The room temperature curable silicone rubber composition of the present invention can be cured by using known curing methods and conditions. For example, the composition can be cured by leaving the composition at rest at 10 to 40° C. for 24 hours or more.

[0040] It is preferable that the difference in Durometer A hardness between the cured product obtained by curing the room temperature curable silicone rubber composition of the present invention at 23°C for 24 hours and the cured product obtained by curing at 23°C for 72 hours is 1 or less. Furthermore, it is preferable that the cured product obtained by curing the room temperature curable silicone rubber composition of the present invention at 23° C. for 24 hours has a transmittance of 90% or more for light with a wavelength of 400 nm at a thickness of 2 mm. EXAMPLES

[0041] The present invention will be described more specifically below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0042] [Examples 1-1 to 1-4, Comparative Examples 1-1 to 1-4] A silicone rubber composition was prepared by mixing the following components in the compounding ratio (parts by mass) shown in Table 1. The average molecular weight is the weight average molecular weight converted into standard polystyrene by gel permeation chromatography (GPC), the viscosity is the value measured at 23°C using a Brookfield type rotational viscometer, and the kinetic viscosity is the value measured at 23°C using a Cannon-Fenske viscometer.

[0043] (A) Component: (A-1) Organopolysiloxane represented by the following average formula (viscosity: 1,000 mPa s, vinyl value: 0.013 mol / 100 g) [ka]

[0044] (A-2) Organopolysiloxane represented by the following average formula (viscosity: 1,500 mPa s, vinyl value: 0.02 mol / 100 g) [ka]

[0045] (A-3) Organopolysiloxane represented by the following average formula (viscosity: 1,000 mPa s, vinyl value: 0.013 mol / 100 g) [ka]

[0046] (A-4: Comparative component) Organopolysiloxane represented by the following average formula (viscosity: 5,000 mPa·s, vinyl value: 0.006 mol / 100 g) [ka]

[0047] (B) Ingredients: (B-1) An organopolysiloxane that has a structural unit ratio represented by the following formula and is solid at 23°C (average molecular weight: 4,000, vinyl value: 0.08 mol / 100 g): (Me3SiO1 / 2 ) 0.4 (ViMe2SiO 1 / 2 ) 0.05 (SiO 4 / 2 ) 0.55

[0048] (C) Ingredients: (C-1) Organopolysiloxane having a constitutional unit ratio represented by the following formula (kinematic viscosity 32 mm 2 / s, vinyl value: 0.52 mol / 100g) (ViMe2SiO 1 / 2 ) 0.5 (MeSiO 3 / 2 ) 0.5

[0049] (D) Ingredients: (D-1) Organohydrogenpolysiloxane represented by the following average formula (SiH group amount: 0.55 mol / 100 g) [ka] (In the formula, the arrangement of the siloxane units is random or block.)

[0050] (E) Ingredients: (E-1) Toluene solution of chloroplatinic acid-divinyltetramethyldisiloxane complex (platinum concentration 1% by mass)

[0051] [Table 1] H / Vi: Ratio of the number of SiH groups in component (D) to the total number of vinyl groups in components (A), (B), and (C)

[0052] [Examples 2-1 to 2-4, Comparative Examples 2-1 to 2-4] The silicone rubber compositions prepared in Examples 1-1 to 1-4 and Comparative Examples 1-1 to 1-4 were used to evaluate the following properties. The results are shown in Tables 2 and 3. [Bubble release] The composition immediately after mixing was poured into a glass bottle with an inner diameter of 40 mm and a height of 60 mm until the height reached 50 mm, and then cured at 23° C. for 10 hours. The cured product was visually observed and rated as ◯ if bubbles were removed and × if bubbles remained. [Light transmittance] The composition was poured into a mold to a thickness of 2 mm and cured at 23° C. for 24 hours. The light transmittance of the sheet at a wavelength of 400 nm was measured using a spectrophotometer U-3900 (manufactured by Hitachi High-Tech Science Corporation). [Tensile strength, elongation at break] The composition was poured into a mold to a thickness of 2 mm and cured at 23°C for 24 hours to prepare No. 2 dumbbell test pieces. The tensile strength (MPa) and elongation at break (%) were measured in accordance with JIS K 6249:2003. [Hardness] The composition was poured into a mold to a thickness of 2 mm, and the hardness (Durometer A) of the cured product cured at 23°C for 24 hours was measured in accordance with JIS K 6253-3: 2012. The hardness of the cured product cured at 23°C for 72 hours was also measured in the same manner.

[0053] [Table 2]

[0054] [Table 3]

[0055] As shown in Tables 2 and 3, the room temperature curable silicone rubber compositions prepared in Examples 1-1 to 1-4 are excellent in defoaming properties and post-curing physical properties, and give highly transparent cured products with little change in hardness. On the other hand, it is clear that in Comparative Example 2-1, in which a high-viscosity (m exceeding 400) vinyl-containing organopolysiloxane was used in place of component (A), the bubble releasing properties were poor. It can be seen that Comparative Example 2-2, which does not contain the component (C), is inferior in bubble releasing properties and mechanical properties, and Comparative Example 2-3, which does not contain the component (B), is inferior in light transmittance and mechanical properties. Moreover, it is clear that the cured product of Comparative Example 2-4, in which the H / Vi value exceeds the range of the present invention, is inferior in elongation at break and exhibits a large change in hardness.

Claims

1. (A) an organopolysiloxane represented by the following average formula (1): [Vi (3-a) R 1 a Yes 1 / 2 ] 2 [R 1 2 Yes 2 / 2 ] m (1) (In the formula, R 1 each independently represents an unsubstituted or substituted monovalent hydrocarbon group not containing an alkenyl group, Vi represents a vinyl group, m represents a number from 13 to 400, and a represents a number from 0 to 2. (B) an organopolysiloxane having a constitutional unit ratio represented by the following formula (2) and being solid at 23°C; [R 1 3 Yes 1 / 2 ] p [Live] (3-b) R 1 b Yes 1 / 2 ] q [YesO 4 / 2 ] r (2) (In the formula, R 1 and Vi have the same meaning as above, p, q, and r respectively represent numbers that satisfy p>0, q>0, r>0, and p+q+r=1, and b represents a number from 0 to 2.) (C) an organopolysiloxane which has a constitutional unit ratio represented by the following formula (3) and is liquid at 23°C; [Vi (3-c) R 1 c SiO 1 / 2 , s [R1 SiO 3 / 2 , t (3) (In the formula, R 1 and Vi have the same meaning as above, s and t are numbers that satisfy s>0, t>0, and s+t=1, and c is a number from 0 to 2. (D) an organohydrogenpolysiloxane represented by the following average formula (4): [R 2 R 1 2 SiO 1 / 2 ] 2 [HR 1 SiO 2 / 2 ] u [R 1 2 SiO 2 / 2 ] v (4) (In the formula, R 1 has the same meaning as above, R 2 represents a hydrogen atom or a methyl group, and u and v represent numbers that satisfy u≧2, v≧2, and 10≦u+v≦100. and (E) Hydrosilylation reaction catalyst Contains A room-temperature-curable silicone rubber composition, in which the number of SiH groups in component (D) is 0.7 to 3.0 times the total number of vinyl groups in components (A), (B), and (C), and the content of metal atoms derived from a hydrosilylation reaction catalyst in component (E) is 20 ppm by mass or less based on the total amount of components (A) to (D).

2. R in the formula (1) 1 2. The room temperature curable silicone rubber composition according to claim 1, wherein 1 to 10 mol % of said groups are phenyl groups.

3. R in the formula (4) 2 3. The room temperature curable silicone rubber composition according to claim 1, wherein: is a hydrogen atom; and u and v are numbers that satisfy u≧2, v≧2, 10≦u+v≦50, and 0.05≦u / (u+v)≦0.5, respectively.

4. 4. The room-temperature-curable silicone rubber composition according to claim 1, wherein the number of SiH groups in component (D) is 1.0 to 2.5 times the total number of vinyl groups in components (A), (B), and (C).

5. 5. The room temperature curable silicone rubber composition according to claim 1, which has a viscosity at 23° C. of 1,000 mPa·s or less.

6. A silicone rubber obtained by curing the room temperature curable silicone rubber composition according to any one of claims 1 to 5.

7. 7. The silicone rubber according to claim 6, wherein the difference in Durometer A hardness between a cured product cured at 23°C for 24 hours and a cured product cured at 23°C for 72 hours is 1 or less.

8. 8. The silicone rubber according to claim 6, which has a transmittance of at least 90% for light with a wavelength of 400 nm at a thickness of 2 mm.

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