JPH08325459A - Silicone rubber composition for high-voltage electrical insulator - Google Patents

Abstract

PURPOSE: To obtain a silicone rubber compsn. for a high-voltage, electrical insulator which can provide a silicone rubber excellent in high-voltage, electrical characteristics, such as tracking resistance, erosion resistance, and arc resistance even upon being exposed to severe weather or contamination after heat curing, as well as in weather resistance and water repellency, and is suitable as a high-voltage electrical insulator, such as a high-tension insulator. CONSTITUTION: (1) An org. peroxide-curable or addition-curable silicone rubber compsn in an amount of 100 pts.wt., (2) 1 to 100 pts.wt. fine powder of silica, (3) 30 to 300 pts.wt. aluminum hydroxide, and (4) 0.1 to 50 pts.wt. antimony trioxide are mixed with one another to prepare a silicone rubber compsn. for a high-voltage electrical insulator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicone rubber composition for a high-voltage electrical insulator, which gives a silicone rubber which becomes an excellent high-voltage electrical insulator when cured by heating.

[0002]

2. Description of the Related Art High voltage electrical insulators used in insulators used in power transmission lines and the like are generally made of porcelain or glass. However, in an environment susceptible to pollution such as coastal areas and industrial areas, particles, salts, fog, etc. may pass through the surface of the high-voltage electrical insulator, resulting in leakage current or flashover. There was a problem that dry band discharge or the like occurs.

Therefore, various solutions have been proposed in order to improve the drawbacks of these porcelain or glass insulators. For example, in US Pat. No. 3,511,698,
A weather-resistant high-voltage electrical insulator composed of a member made of a curable resin and a platinum catalyst-containing organopolysiloxane elastomer has been proposed. Also, US Pat.
Japanese Patent Application Laid-Open No. 59-198604, which corresponds to Japanese Patent Publication No. 5-58604, discloses a method of applying a one-component room-temperature-curable organopolysiloxane composition to the outer surface of a glass product or a porcelain electric insulator to obtain moisture, Techniques have been proposed for maintaining the high-performance electrical performance of the electrical insulator even in the presence of outdoor stress such as air pollution and ultraviolet rays.

Further, JP-A-53-35982 corresponding to US Pat. No. 3965065 and JP-A-4-20965 corresponding to US Pat. No. 5,369,161.
Japanese Patent Publication No. 5 discloses a silicone rubber composition in which electrical insulation is improved by heating a mixture of an organopolysiloxane that becomes a silicone rubber by heat curing and an aluminum hydrate at a temperature higher than 100 ° C. for 30 minutes or more. It is proposed that the product be obtained.

However, in the above-mentioned conventional techniques, the high-voltage electrical insulation performance of the used silicone rubber materials is not yet sufficiently satisfactory, and therefore the conventional silicone rubber composition has improved electrical insulation performance. In order to do so, a large amount of aluminum hydroxide must be used, but this has the disadvantage that the mechanical strength of the rubber is weakened.

The present invention has been made in view of the above circumstances.
Silicone for high-voltage electrical insulators that provides silicone rubber with excellent high-voltage electrical insulation properties such as weather resistance, tracking resistance, arc resistance, and erogen resistance even under conditions that are exposed to severe air pollution or climate after heat curing An object is to provide a rubber composition.

[0007]

Means and Actions for Solving the Problems As a result of intensive studies to achieve the above object, the present inventor has found that an organic peroxide-curable or addition-curable silicone rubber composition and silica fine powder are contained. By blending a specific amount of aluminum hydroxide and antimony trioxide in the silicone rubber composition, the tracking resistance of the silicone rubber is further enhanced by the synergistic effect of the aluminum hydroxide and antimony trioxide. The characteristics such as erosion resistance and arc resistance are significantly improved, and it is possible to reduce the filling amount of aluminum hydroxide to obtain practical tracking resistance as a high-pressure insulator, and the weight of the silicone rubber insulator is lightweight. Can also contribute to the improvement of mechanical properties, therefore,
It was found that a silicone rubber composition for a high-voltage electrical insulator can be obtained which gives a silicone rubber excellent in high-voltage electrical insulation properties such as weather resistance, tracking resistance, arc resistance, erogen resistance, etc., and forms the present invention. Came to.

Therefore, the present invention provides (1) 100 parts by weight of an organic peroxide-curable or addition-curable silicone rubber composition (parts by weight, the same applies hereinafter) (2) 1 to 100 parts of fine silica powder (3) aluminum Hydroxide 30 to 300 parts (4) Antimony trioxide 0.1 to 50 parts The present invention provides a silicone rubber composition for high voltage electrical insulators.

The present invention will be described in more detail below. The first component of the silicone rubber composition for high-voltage electrical insulators of the present invention is an organic peroxide-curable or addition-curable silicone rubber composition. .

The organic peroxide-curable silicone rubber composition includes (a) the following average composition formula (1) R ¹ _a SiO 2 _{(4-a) / 2} (1) (where R ¹ is a substituent Or, it is an unsubstituted monovalent hydrocarbon group, but 0.01 to 20 mol% of R ¹ is an alkenyl group, and a is a positive number of 1.9 to 2.4). A silicone rubber composition having an organopolysiloxane (b) having at least two alkenyl groups on average as the main component (b) organic peroxide is preferably used.

In the alkenyl group-containing organopolysiloxane of the above formula (1), R ¹ preferably has 1 carbon atom.
To 12, more preferably a substituted or unsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms, specifically, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group. Group, hexyl group, cyclohexyl group, alkyl group such as octyl group, vinyl group, allyl group, alkenyl group such as propenyl group, isopropenyl group, butenyl group, aryl group such as phenyl group, tolyl group, xylyl group, benzyl group And the like, and haloalkyl groups such as chloromethyl group, chloromethyl group, 2-bromoethyl group, 3,3,3-trifluoropropyl group, 3-chloropropyl group and cyanoethyl group, and cyano group-substituted hydrocarbon groups. Each substituent may be different or the same, but it is preferable that 0.01 to 20 mol%, more preferably 0.1 to 10 mol% of R ¹ is an alkenyl group, It is also necessary that the molecule has at least two alkenyl groups on average. Again, R ¹
Although any of the above may be used, it is preferable to introduce a vinyl group as the alkenyl group and a methyl group or a phenyl group as the other substituent. Further, a is a positive number in the range of 1.9 to 2.4, preferably 1.95 to 2.2.

The organopolysiloxane of the above formula (1) has a linear molecular structure, or R ¹ Si.
_{Monoorganosiloxane} unit represented by O _3/2 or SiO
Including _4/2 units may be branched, but usually the main chain consists of repeating diorganosiloxane units basically R ¹ ₂ SiO _2/2, the molecular chain terminals R ¹ ₃ SiO _1/2
Is generally a linear diorganopolysiloxane blocked with triorganosiloxy units. The alkenyl group in the molecule may be bonded to either the terminal of the molecular chain or the silicon atom in the middle of the molecular chain, or may be bonded to both of them, but the curability, the physical properties of the cured product, etc. From this point, it is preferable that the alkenyl group is bonded to at least a silicon atom at the end of the molecular chain.

The alkenyl group-containing organopolysiloxane has a viscosity of 100 to 1,000,000 at 25 ° C.
cps, especially 500 to 500,000 cps is desirable.

The above alkenyl group-containing organopolysiloxane can be produced by a known method. Specifically, the equilibrium reaction of the organocyclopolysiloxane and the hexaorganodisiloxane is carried out in the presence of an alkali or acid catalyst. Can be obtained by

The organic peroxide is used as a catalyst for promoting the crosslinking reaction of the above alkenyl group-containing organopolysiloxane, and specific examples thereof include the compounds shown below.

[0016]

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The amount of the organic peroxide added is a catalytic amount and can be appropriately selected depending on the curing speed. Usually, it is 0.100 with respect to 100 parts of the alkenyl group-containing organopolysiloxane of the above formula (1). 1 to 10 parts, preferably 0.2 to
The range is 3 parts.

In addition to the above-mentioned main components, the organic peroxide-curable silicone rubber composition contains, as optional components, metal oxides such as titanium oxide, iron oxide, cerium oxide, vanadium oxide, chromium oxide, magnesium oxide and cobalt oxide. Compounds, metal hydroxides other than aluminum such as alkaline earth metals such as magnesium hydroxide, etc. can be added, but silica fine powder, aluminum hydroxide, and antimony trioxide are not contained.

Next, as an addition-curable silicone rubber composition, (a) an alkenyl group-containing organopolysiloxane of the above formula (1) (c) the following average composition formula (2) R ² _b H _c SiO _{(4) -bc) / 2} (2) (wherein, R ² is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms, and b is 0.7 to 2.1, preferably 1-2, c is 0.002-1, preferably 0.
01 to 0.5, and b + c is a positive number satisfying 0.8 to 3, preferably 1.5 to 2.6. ),
A silicone rubber composition mainly composed of an organohydrogenpolysiloxane (d) addition reaction catalyst which is liquid at room temperature and has at least two hydrogen atoms bonded to silicon atoms is preferably used.

As the alkenyl group-containing organopolysiloxane of the above formula (1), the same one as the above organic peroxide-curable silicone rubber is used.

In the organohydrogenpolysiloxane of the above formula (2), R ² is the same as R ¹ but preferably has no aliphatic unsaturated bond. b is 0.7-2.1, preferably 1-2, c is 0.002-1, preferably 0.01-0.5, and b + c is 0.8-3, preferably 1.5-. It is a positive number that satisfies 2.6, and more preferably 1.8 to 2.2.

This organohydrogenpolysiloxane acts as a cross-linking agent for the component (a) in the presence of an addition reaction catalyst, and at least two in the molecule,
It preferably has 3 or more hydrogen atoms bonded to silicon atoms (that is, SiH groups). This SiH group may be located at the end of the molecular chain or in the middle of the molecular chain, or at both positions. It may be one that does.

Examples of such an organohydrogenpolysiloxane include trimethylsiloxy group-blocked methylhydrogenpolysiloxane at both terminals, dimethylsiloxy group-blocked dimethylsiloxane / methylhydrogenpolysiloxane copolymer at both terminals, and dimethylhydrogensiloxy at both terminals. End-capped dimethyl siloxane, both ends dimethyl hydrogen polysiloxy end-capped dimethyl siloxane, both ends dimethyl hydrogen polysiloxy end-capped dimethyl siloxane / methyl hydrogen polysiloxane copolymer, both ends trimethyl siloxy end-capped methyl hydrogen polysiloxane Diphenyl siloxane / dimethyl siloxane copolymer, (CH ₃ ) ₂ HSiO
Copolymer consisting of _1/2 unit and SiO _4/2 unit, (C
H ₃ ) ₂ H SiO _1/2 unit, SiO _4/2 unit and (C ₆ H ₅ ) S
Examples thereof include a copolymer composed of iO _3/2 units.

The organohydrogenpolysiloxane of the above formula (2) may have a linear, cyclic or branched molecular structure, but it must be liquid at room temperature and its viscosity is 25. Usually 1 to 10000c at ℃
ps, preferably 3 to 5000 cps, especially 5 to 100
It is desirable that the organohydrogenpolysiloxane has a number of silicon atoms in the molecule of usually 3 to 400, preferably 4 to 200.

The above organohydrogenpolysiloxane can be manufactured by a known method.

The amount of the above-mentioned organohydrogenpolysiloxane is usually 0.1 to 100 parts, preferably 0.3 to 50 parts, and particularly preferably 0.3 to 50 parts, relative to 100 parts of the first component (component (a)) organopolysiloxane. It is in the range of 0.5 to 30 parts.

Further, in this organohydrogenpolysiloxane, the hydrogen atom (SiH group) bonded to the silicon atom in the molecule is in a molar ratio of 0.8 to 0.8 with respect to the alkenyl group in the organopolysiloxane of the component (a). It may also be blended in an amount of 10, preferably 1 to 5 mol / mol.

As the addition reaction catalyst, platinum black, second chloride
Platinum, a reaction product of chloroplatinic acid and a monohydric alcohol, a complex of chloroplatinic acid and an olefin, a platinum-based catalyst such as platinum bisacetoacetate, a palladium-based catalyst, a rhodium-based catalyst and the like. The addition amount of this addition reaction catalyst is a catalytic amount, and is usually 0.1 to 500 ppm as platinum, palladium or rhodium metal relative to the first component, especially 1
~ 100 ppm.

In addition to the above-mentioned main components, the addition-curable silicone rubber composition may contain, as optional components, metal oxides such as titanium oxide, iron oxide, cerium oxide, vanadium oxide, chromium oxide, magnesium oxide and cobalt oxide.
Metal hydroxides other than aluminum such as alkaline earth metals such as magnesium hydroxide, addition reaction control agents such as acetylene compounds such as ethynylcyclohexanol and the like can be added within a range not hindering the effect of the present invention, It does not contain fine silica powder, aluminum hydroxide or antimony trioxide.

Next, as the second component of silica fine powder,
The type is not particularly limited, and those used in conventional silicone rubber compositions can be used. Such fine silica powder, for example, specific surface area by BET method of 50 m ² / g or more, particularly precipitated silica of 50 to 400 m ² / g, fumed silica, and fired silica, average particle diameter of 50μm or less, particularly 0 Pulverized quartz of 1 to 20 μm, diatomaceous earth, etc. are preferably used.

Although these silica fine powders may be used as they are, they may be surface-treated with an organic silicon compound such as hexamethyldisilazane, trimethylchlorosilane and polymethylsiloxane and used as hydrophobic silica fine powders.

The amount of the fine silica powder to be blended is in the range of 1 to 100 parts, preferably 2 to 50 parts, relative to 100 parts of the first component. If it exceeds the amount, it becomes difficult to highly fill the third component aluminum hydroxide.

In the present invention, aluminum hydroxide is used as the third component, and by blending this component, the electrical insulation performance such as arc resistance and tracking resistance of the silicone rubber can be improved, It is essential in the composition of the present invention.

Here, as the aluminum hydroxide,
A compound represented by the following formula (3) Al ₂ O ₃ .3H ₂ O (3) and having an average particle diameter of 10 μm or less, usually 0.
Those having a BET specific surface area of 1 to 10 μm, particularly 0.5 to 9 μm and a BET specific surface area of 0.5 to 10 m ² / g are preferably used.

The aluminum hydroxide may be surface-treated, for example, using a silane-based or titanate-based coupling agent, dimethylpolysiloxane oil, dimethylhydrogenpolysiloxane oil, or the like. preferable.

Specific examples of silane coupling agents include hexamethyldisilazane, divinyltetramethyldisilazane, diphenyltetramethyldisilazane, vinyltriethoxysilane, vinyltrimethoxysilane, trimethylethoxysilane, vinyltris (methoxyethoxy). Silane, trimethylchlorosilane, trimethylaminosilane, glycidoxypropyltrimethoxysilane,
Examples include glycidoxypropylmethyldiethoxysilane, (epoxycyclohexyl) ethyltrimethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropyltriethoxysilane, dimethyldimethoxysilane, divinyldimethoxysilane and chloropropyltrimethoxysilane. .

As titanate coupling agents, tetraisopropyl titanate, tetra-n-butyl titanate, butyl titanate dimer, tetrastearyl titanate, triethanolamine titanate,
Titanium acetyl acetate, titanium ethyl acetoacetate, titanium lactate, octylene glycol titanate, isopropyl tristearoyl titanate, isopropyl tris (dodecylbenzenesulfonyl) titanate, isopropyl tris (dioctyl pyrophosphate) titanate, bis (dioctyl pyrophosphate) oxyacetate titanate, Examples thereof include bis (dioctylpyrophosphate) ethylene titanate.

Further, the dimethylpolysiloxane oil has a cyclic or linear viscosity at 25 ° C. of 0.65.
A material of -100 centistokes is preferably used.

The methylhydrogenpolysiloxane may have a linear, branched, cyclic, or network molecular structure, but the linear one represented by the following general formula (4) is preferably used. To be done.

[0040]

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In the above formula, r is an integer of 0 to 50, preferably 0 to 25, and s is 1 to 50, preferably 2 to
It is an integer of 25. If r exceeds 50, the viscosity may be high and it may be difficult to process, and if s exceeds 50, the viscosity may be high and the surface may be difficult to wet.

In the present invention, of the above-mentioned surface treatment agents, organosilazanes, particularly hexaorganodisilazanes such as hexamethyldisilazane are more preferably used.

The surface treatment agent is preferably used in an amount of 1 to 50 parts, particularly 5 to 30 parts, relative to 100 parts of aluminum hydroxide, and if the amount is less than 1 part, the effect as a treatment agent is not obtained. In some cases, if the amount exceeds 50 parts, the process may be wasteful and the cost may be disadvantageous.

The surface treatment of the aluminum hydroxide can be carried out by a generally known technique. For example, the aluminum hydroxide may be directly treated in advance or may be treated while being kneaded with other components. In particular, it is preferable to directly process in advance. Specifically, aluminum hydroxide and a treating agent are put in a mechanical kneading apparatus closed at atmospheric pressure or in a fluidized bed, and if necessary, the mixture is kneaded at room temperature or heat treatment in the presence of an inert gas, and kneaded. It can be adjusted by post-drying. Depending on the case, a catalyst may be used in accordance with each treating agent to accelerate the treatment.

The content of the third component, aluminum hydroxide, is in the range of 30 to 300 parts, preferably 50 to 250 parts, relative to 100 parts of the first component. If the amount exceeds 300 parts, it will be difficult to fill the composition and the workability will deteriorate.

In the present invention, antimony trioxide is used as the fourth component, and the antimony resistance of the silicone rubber is tracked by the synergistic effect with the aluminum hydroxide of the third component by blending the antimony trioxide in a specific amount. sex,
The erosion resistance and arc resistance can be further improved.

Here, antimony trioxide is represented by the following formula (5) Sb ₂ O ₃ (5).

The compounding amount of the fourth component, antimony trioxide, is
It is in the range of 0.1 to 50 parts, preferably 0.3 to 17 parts, relative to 100 parts of the first component, and if it is less than 0.1 part, the expected improvement in tracking resistance cannot be obtained, and 50 parts is obtained. If it exceeds, the obtained rubber strength becomes insufficient, aluminum hydroxide cannot be highly filled, and the tracking property cannot be further improved.

To the silicone rubber composition of the present invention, if desired, various additives such as metal oxides not containing the above metal elements and carbon carbonates can be added according to the purpose. Further, a pigment, a heat-resistant agent, a flame retardant, a plasticizer, an antioxidant, etc. may be added as long as the desired characteristics are not impaired. In addition, the addition amount of these optional components can be a normal amount within a range that does not impair the effects of the present invention.

The silicone rubber composition of the present invention can be obtained only by uniformly mixing the above-mentioned first to fifth components and optional components at room temperature, but if necessary, the above-mentioned (in the first component) B) or (c), essential components other than (d) component, optional components with a planetary mixer or kneader 1
You may heat-process in the range of 00-200 degreeC for 2 to 4 hours, and after that, mix the (b) or (c) and (d) component, and carry out hardening molding. The molding method can be freely selected depending on the viscosity of the mixture, and any of injection molding, compression molding, injection molding, extrusion molding, transfer molding, and the like may be adopted. The curing condition is usually 80 to 200 ° C. for 3 minutes or more.
It can be heated for 3 hours.

[0051]

EFFECTS OF THE INVENTION The silicone rubber composition for a high voltage electrical insulator of the present invention has high voltage electrical characteristics such as tracking resistance, erosion resistance and arc resistance even under conditions exposed to severe weather and pollution. It gives a silicone rubber which is not only excellent, but also excellent in weather resistance and water repellency, and this silicone rubber is useful as a high-voltage electrical insulator such as a high-voltage insulator.

[0052]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. All parts in each example are parts by weight.

[Examples 1 to 3] As shown in Table 1, the component (a) in the first component had a viscosity at 25 ° C of which both ends were blocked with dimethylvinylsiloxy groups and a viscosity of 5000 cp.
Dimethylpolysiloxane (organopolysiloxane a), silica fine powder of the second component, wet silica (Nipsil LP, manufactured by Nippon Silica Industry Co., Ltd., BET specific surface area 180)
m ² / g) part, average particle diameter of 8 μm as the third component, BET
Aluminum hydroxide having a specific surface area of 2 cm ² / g and antimony trioxide as a fourth component were mixed in the amounts shown in Table 1, and the mixture was stirred and mixed at 150 ° C. for 2 hours in a planetary mixer, and then cooled to room temperature. Furthermore, dimethylhydrogenpolysiloxane represented by the following formula (6) as the component (c) in the remaining first component, a 1% 2-ethylhexanol solution of chloroplatinic acid as the component (d), and the component (e) As a reaction control agent, ethynylcyclohexanol was added in an amount shown in Table 1 and uniformly mixed to obtain a silicone rubber composition. This silicone rubber composition is
128 mm x 44 m after heat curing at ℃ for 10 minutes
A silicone rubber sheet of m × 6 mm (thickness) was obtained.

[0054]

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Example 4 As shown in Table 1, as component (a) in the first component, dimethylpolysiloxane (organopolysiloxane) having a viscosity of 30,000 cps at 25 ° C. and having both ends blocked with trivinylsiloxy groups. b) 1
00 parts and the second, third, and fourth components of Examples 1 to 3 are heated and mixed in the same manner, and 0.6 part of dicumyl peroxide as an organic peroxide is added thereto to homogenize at room temperature. To obtain a silicone rubber composition. This silicone rubber composition was heat-cured at 165 ° C. for 10 minutes, and then secondarily cured at 200 ° C. for 4 hours to obtain 128 mm each.
A silicone rubber sheet of x44 mm x 6 mm (thickness) was obtained.

Comparative Examples 1 to 3 Silicone rubber sheets were obtained in the same manner as in Example 1 except that the components shown in Table 1 were used. Next, the silicone rubber sheets obtained in the above Examples and Comparative Examples were subjected to a tracking test by the following method. The results are shown in Table 1. Tracking test method : ASTM D-2303-64
It carried out according to the standard of T. That is, a contaminated liquid (0.1% NH ₄ Cl and 0.
Aqueous solution of 02% nonionic surfactant) 0.6 ml / m
Dropping was performed from the upper electrode at a speed of in, and the time until a track was generated and conduction was caused, and the erosion loss weight (wt%) caused thereby was measured. Erosion loss weight : While a part of the rubber sheet was tested above,
It is deteriorated by heat and arc and eroded. This erosion amount was calculated by the following formula. Erosion amount = (weight lost by erosion / weight of entire sheet before test) × 100

From the results shown in Table 1, the silicone rubber composition of the present invention is excellent in tracking resistance and erosion resistance, and in particular, the tracking resistance is significantly improved by the synergistic effect of aluminum hydroxide and antimony trioxide. It was confirmed. Further, the silicone rubber composition of the present invention, in order to obtain practical tracking resistance as a high-pressure insulator, it is possible to reduce the filling amount of conventional aluminum hydroxide, and to reduce the weight of the silicone rubber insulator, It was confirmed that it can contribute to the improvement of mechanical properties.

[0058]

[Table 1]

Claims (3)

[Claims] 1. An organic peroxide curable or addition curable silicone rubber composition 100 parts by weight (2) Silica fine powder 1 to 100 parts by weight (3) Aluminum hydroxide 30 to 300 parts by weight ( 4) 0.1-50 parts by weight of antimony trioxide, a silicone rubber composition for high-voltage electrical insulators. 2. An organic peroxide-curable silicone rubber composition comprising: (a) the following average composition formula (1) R ¹ _a SiO 2 _{(4-a) / 2} (1) (wherein R ¹ is It is a substituted or unsubstituted monovalent hydrocarbon group, but 0.01 to 20 mol% of R ¹ is an alkenyl group, and a is a positive number of 1.9 to 2.4. The silicone rubber composition for a high voltage electrical insulator according to claim 1, which comprises 100 parts by weight of an organopolysiloxane having at least two alkenyl groups in the molecule as a main component (b) an organic peroxide catalyst amount. . 3. The addition-curable silicone rubber composition has the following average composition formula (1) R ¹ _a SiO 2 _{(4-a) / 2} (1) (wherein R ¹ is substituted or non-substituted) It is a substituted monovalent hydrocarbon group, but 0.01 to 20 mol% of R ¹ is an alkenyl group. A is a positive number of 1.9 to 2.4. 100 parts by weight of organopolysiloxane having at least two alkenyl groups (C) The following average composition formula (2) R ² _b H _c SiO ² _{(4-bc) / 2} (2) (where R ² is It is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms, b is 1 to 2.1, c is 0.01 to 1, and b + c is 1.5 to 2.6. An organohydrogenpolysiloxane that is liquid at room temperature and has at least two hydrogen atoms bonded to silicon atoms, .1～100 parts by weight (d) as a main component an addition reaction catalyst catalytic amount claim 1 high-voltage electrical insulating-body silicone rubber composition.