JP3360264B2 - Silicone rubber composition for high voltage electrical insulator - Google Patents

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 for glass used in power transmission lines and the like are generally made of porcelain or glass. However, in environments that are susceptible to contamination, such as coastal areas and industrial areas, the passage of fine particles, salts, fog, etc., on the surface of the high-voltage electrical insulator may cause leakage current or flashover. There is a problem that a dry discharge or the like occurs.

[0003] Various solutions have been proposed to improve the disadvantages of these porcelain or glass insulators. For example, U.S. Pat.
A weather-resistant high-voltage electrical insulator comprising a member made of a curable resin and a platinum catalyst-containing organopolysiloxane elastomer has been proposed. Also, JP-A-59-19860
No. 4 discloses that a one-part room-temperature-curable organopolysiloxane composition is applied to the outer surface of a glass or porcelain electrical insulator to prevent the presence of stress in the field such as moisture, air pollution and ultraviolet rays. A technique for maintaining the high-performance electrical performance of the electrical insulator has been proposed below.

Further, JP-A-53-35982, US Pat. No. 3,965,065 and JP-A-4-2096
No. 55 discloses a silicone rubber composition having improved electrical insulation by heating a mixture of an organopolysiloxane and an aluminum hydrate which becomes a silicone rubber by heat curing at a temperature higher than 100 ° C. for 30 minutes or more. It is proposed to give things.

[0005] However, in the above-mentioned prior arts, the high-voltage electrical insulation performance of any of the silicone rubber materials used has not been sufficiently satisfactory.

Further, in order to improve the voltage electric insulation performance, it is necessary to use a large amount of aluminum hydroxide, and to maintain fluidity, use aluminum hydroxide having a large particle size and a small specific surface area. I have to do it,
There is a limit in filling such aluminum hydroxide at a high level, and it has not been possible to fill at a high density.

[0007] The present invention has been made in view of the above circumstances,
It has good fluidity and excellent workability, and has high-voltage electrical insulation properties such as weather resistance, tracking resistance, arc resistance, and erosion resistance even under conditions of severe air pollution or weather exposure after heat curing. An object of the present invention is to provide a silicone rubber composition for a high-voltage electrical insulator that gives an excellent silicone rubber.

[0008]

Means for Solving the Problems and Embodiments of the Invention The present inventors have made intensive studies to achieve the above object, and as a result, have found that an organic peroxide-curable or addition-reaction-curable silicone rubber composition, silica (A) 10 to 95% by weight of an aluminum hydroxide having an average particle size of 7 to 50 μm and (b) an average particle size of 7 μm with respect to the silicone rubber composition containing the fine powder.
When an aluminum hydroxide filler consisting of 90 to 5% by weight of aluminum hydroxide having a particle size of less than 50 m is mixed, (a)
By using the aluminum hydroxide of (b) and the aluminum hydroxide of (b) in combination, high-density and high-filling can be performed, and the fluidity is not impaired. The characteristics such as erosion resistance and arc resistance are greatly improved, and therefore, the fluidity is good, and high voltage electrical insulation characteristics such as weather resistance, tracking resistance, arc resistance, erosion resistance, etc. The present inventors have found that a silicone rubber composition for a high-voltage electrical insulator that gives an excellent silicone rubber can be obtained, and have accomplished the present invention.

Accordingly, the present invention provides: (1) 100 parts of an organic peroxide-curable or addition-reaction-curable silicone rubber composition (parts by weight, hereinafter the same) (2) 1 to 100 parts of fine silica powder (3) 100 to 900 parts by weight of an aluminum hydroxide filler composed of 10 to 95% by weight of aluminum hydroxide having an average particle diameter of 7 to 50 μm and 90 to 5% by weight of aluminum hydroxide having an average particle diameter of less than 7 μm. Provided is a silicone rubber composition for a high-voltage electrical insulator, characterized by the following.

Hereinafter, the present invention will be described in more detail. The first component of the silicone rubber composition for a high-voltage electrical insulator of the present invention is an organic peroxide-curable or addition-reaction-curable silicone rubber composition. is there.

The organic peroxide-curable silicone rubber composition includes: (a) the following average composition formula (1): R ¹ _a SiO _{(4-a) / 2} (1) (where R ¹ is a substituted Or an unsubstituted monovalent hydrocarbon group, wherein 0.01 to 20 mol% of R ¹ is an alkenyl group; a is a positive number of 1.9 to 2.4) A silicone rubber composition containing an organopolysiloxane having at least two or more alkenyl groups on average (ii) an organic peroxide as a main component 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 8 carbon atoms, specifically, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl Alkyl group such as group, hexyl group, cyclohexyl group and octyl group, alkenyl group such as vinyl group, allyl group, propenyl group, isopropenyl group and butenyl group, aryl group such as phenyl group, tolyl group and xylyl group, and benzyl group Aralkyl groups such as phenylethyl group, chloromethyl group, bromoethyl group, 3,3,3
Halogen-substituted groups such as -trifluoropropyl group, 3-chloropropyl group and cyanoethyl group; and cyano-substituted hydrocarbon groups. In addition, although each substituent may be different or the same, 0.01 to 20 in R ¹
It is preferable that the alkenyl group accounts for mol%, more preferably 0.1 to 10 mol%, and it is necessary that the molecule has at least two alkenyl groups on average.
In addition, R ¹ may be any of the above, but it is preferable to introduce a vinyl group as an alkenyl group and a methyl group or a phenyl group as another substituent. A is 1.9 to 2.
4, preferably a positive number in the range of 1.95 to 2.2.

The organopolysiloxane of the above formula (1) may have a linear molecular structure or R ¹ S
iO may be _3/2 or SiO _4/2 branched containing units, but usually the main chain consists of repeating diorganosiloxane units basically R ¹ ₂ SiO _2/2, molecular it is common chain terminal is R ¹ ₃ are blocked with triorganosiloxy units of SiO _1/2 the linear diorganopolysiloxane. The alkenyl group in the molecule may be bonded to either the terminal of the molecular chain or a silicon atom in the middle of the molecular chain, or may be bonded to both of them. In view of the above, it is preferable that the compound has at least an alkenyl group bonded to silicon atoms at both ends of the molecular chain.

The alkenyl group-containing organopolysiloxane has a viscosity of 100 to 1,000,000 at 25.degree.
cps, particularly 500 to 500,000 cps.

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

The organic peroxide is used as a catalyst for accelerating the crosslinking reaction of the alkenyl group-containing organopolysiloxane, and specific examples include the following compounds.

[0017]

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The amount of the organic peroxide to be added is a catalytic amount and can be appropriately selected according to the curing speed. Usually, the amount is 0.1 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 three parts.

In the above-mentioned organic peroxide-curable silicone rubber composition, metal oxides such as alkaline earth metals such as calcium oxide and magnesium oxide; magnesium hydroxide; Metal hydroxides other than aluminum, such as alkaline earth metals such as calcium, can be added, but fine silica powder and aluminum hydroxide are not blended.

Next, the addition reaction-curable silicone rubber composition includes (a) an alkenyl group-containing organopolysiloxane of the above formula (1) (c) an average composition formula (2) below: 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. In addition, b is 0.7 to 2.1, preferably b is 0.7 to 2.1.) Is 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. The silicone rubber composition mainly containing an organohydrogenpolysiloxane (d) addition reaction catalyst which is liquid at room temperature and has at least two, preferably three or more hydrogen atoms bonded to silicon atoms, which is represented by the formula (1): Is done.

As the alkenyl group-containing organopolysiloxane of the above formula (1), the same ones as described for the organic peroxide-curable silicone rubber composition are used.

In the organohydrogenpolysiloxane of the formula (2), R ² is the same as R ¹ but preferably does not have an aliphatic unsaturated bond. b is 0.7 to 2.1, preferably 1 to 2, c is 0.002 to 1, preferably 0.01 to 0.5, and b + c is 0.8 to 3, preferably 1.5 to 1.5. It is a positive number that satisfies 2.6.

The organohydrogenpolysiloxane functions as a crosslinking agent for the main component of the component (a) in the presence of an addition reaction catalyst, and has at least two, preferably at least three, silicon atoms per molecule. Having a hydrogen atom (ie, a SiH group) bonded to an atom,
The SiH group may be located at the terminal of the molecular chain or at the middle of the molecular chain, or may be located at both.

Examples of such an organohydrogenpolysiloxane include methylhydrogenpolysiloxane having trimethylsiloxy groups at both ends, a dimethylsiloxane / methylhydrogenpolysiloxane copolymer having trimethylsiloxy groups at both ends, and dimethylhydrogensiloxy at both ends. Group-blocked dimethylsiloxane, dimethylhydrogenpolysiloxy group-blocked dimethylsiloxane at both ends, dimethylhydrogenpolysiloxy-group-blocked dimethylsiloxane-methylhydrogenpolysiloxane copolymer at both ends, methylhydrogenpolysiloxane-blocked at both ends trimethylsiloxy group Diphenylsiloxane / dimethylsiloxane copolymer, (CH ₃ ) ₂ HSiO
_A copolymer composed of _1/2 unit and SiO _4/2 unit, (C
H ₃ ) ₂ HSiO _1/2 unit, SiO _4/2 unit and (C ₆ H ₅ ) S
Copolymers composed of iO _3/2 units can be used.

The organohydrogenpolysiloxane of the above formula (2) may have a linear or branched molecular structure, but it needs to be liquid at room temperature and has a viscosity of 0.1-500 cps at 25 ° C.
In particular, it is desirably 0.5 to 300 cps, and the number of silicon atoms in the molecule is usually 3 to 300, preferably about 4 to 100.

The above-mentioned organohydrogenpolysiloxane can be produced by a known method.

The amount of the organohydrogenpolysiloxane is usually 0.1 to 100 parts, preferably 0.3 part, per 100 parts of the first component organopolysiloxane.
To 50 parts, especially 0.5 to 30 parts.

In this organohydrogenpolysiloxane, a hydrogen atom (SiH group) bonded to a silicon atom in the molecule has a molar ratio of 0.5 to 0.5 with respect to an alkenyl group in the organopolysiloxane (a). 5 mol / mol, preferably 0.8 to 3 mol / mol can be added.

Examples of the addition reaction catalyst include platinum black, platinic chloride, a reaction product of chloroplatinic acid and a monohydric alcohol,
Examples include complexes of chloroplatinic acid and olefins, platinum bisacetoacetate, palladium-based catalysts, rhodium-based catalysts, and the like. The addition amount of the addition reaction catalyst is a catalytic amount, and is usually 0.1 to 500 ppm, particularly 1 to 100 ppm as platinum, palladium or rhodium metal based on the first component.

In addition to the above main components, the above addition reaction-curable silicone rubber composition may optionally contain, as optional components, metal oxides such as alkaline earth metals such as calcium oxide and magnesium oxide, magnesium hydroxide, calcium hydroxide and the like. Metal hydroxides other than aluminum, such as alkaline earth metals, addition reaction control agents, such as acetylene alcohol compounds such as ethynylcyclohexanol, can be added in a range that does not hinder the effects of the present invention. And aluminum hydroxide are not blended.

Next, as the silica fine powder of the second component,
The type is not particularly limited, and those used in conventional silicone rubber compositions can be used. As such silica fine powder, for example, specific surface area by BET method of 50 m ² / g or more, usually 50~1000m ² /
g, especially 100 to 500 m ² / g of precipitated silica, fumed silica, calcined silica, ground quartz having an average particle diameter of 50 μm or less, particularly 0.1 to 20 μm, and diatomaceous earth are preferably used.

These silica fine powders may be used as they are, or may be used as hydrophobic silica fine powder after surface treatment with an organosilicon compound such as hexamethyldisilazane, trimethylchlorosilane or polymethylsiloxane.

The amount of the fine silica powder to be compounded is as follows:
1 part to 100 parts, preferably 2 to 50 parts with respect to 00 parts, and if less than 1 part, the mechanical strength becomes weak,
If it exceeds 100 parts, it becomes difficult to highly fill the third component of aluminum hydroxide.

In the present invention, the third component comprises (a) an aluminum hydroxide having an average particle diameter of 7 to 50 μm and (b) an aluminum hydroxide having an average particle diameter of less than 7 μm, preferably 0.1 μm or more. Use aluminum hydroxide filler. Fluidity can be obtained by blending the aluminum hydroxide of the above-mentioned component (a), and it can be filled most densely by blending of the aluminum hydroxide of the above-mentioned component (b). By using the above-mentioned (a) and (b) aluminum hydroxides having different average particle diameters in combination, it becomes possible to pack at a high density,
In addition to being able to obtain excellent fluidity, it is also possible to improve the electrical insulation performance such as arc resistance and tracking resistance of the silicone rubber, which is essential in the composition of the present invention.

Here, the aluminum hydroxide can be represented by the following formula (3): Al ₂ O ₃ .3H ₂ O (3)

Further, the aluminum hydroxide of the component (a) has an average particle diameter of 7 to 50 μm, preferably 9 to 30 μm.
If the average particle diameter is less than 7 μm, the particles cannot be packed most densely. If the average particle diameter exceeds 50 μm, the above-mentioned rubber properties cannot be obtained.

The aluminum hydroxide of the component (b) has an average particle diameter of less than 7 μm, preferably 0.1 μm or more and less than 7 μm, more preferably 0.5 to 5 μm, and an average particle diameter of 0.1 μm If it is less than it will be difficult to mix,
In some cases, the desired fluidity may not be obtained, and if it is 7 μm or more, it will not be possible to pack the particles most closely.

The components (a) and (b) both have a particle diameter of 75.
the content of particles having a particle size of 2 μm or less of the entire filler
In particular, it is preferably 0 to 1% by weight, and the BET specific surface area is 10 m ² / g or less and the oil absorption is 60 ml / 100.
g or less are preferably used.

The component (a) and the component (b) may be used in a proportion of 10 to 95% by weight, preferably 30 to 95% by weight of the component (a).
The content of the component (b) must be less than 10% by weight, and the content of the component (b) must be less than 10% by weight. Exceeds 90% by weight, fluidity cannot be obtained satisfactorily. If the amount of component (a) is more than 95% by weight, the amount of component (b) is less than 5% by weight. .

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

Specific examples of the silane coupling agent include organosilazanes such as hexamethyldisilazane, divinyltetramethyldisilazane and diphenyltetramethyldisilazane, vinyltriethoxysilane, vinyltrimethoxysilane, trimethylethoxysilane, and the like. Alkoxysilanes such as dimethyldimethoxysilane, divinyldimethoxysilane and vinyltris (methoxyethoxy) silane; chlorosilanes such as trimethylchlorosilane;
Aminosilanes such as trimethylaminosilane, glycidoxypropyltrimethoxysilane, glycidoxypropylmethyldiethoxysilane, (epoxycyclohexyl) ethyltrimethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropyltriethoxysilane and chloropropyltrimethoxysilane Examples thereof include alkoxysilanes having a functional group such as an epoxy functional group such as methoxysilane and a (meth) acryl functional group.

Examples of titanate coupling agents include 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 dodecylbenzenesulfonyl titanate, isopropyl tris (dioctyl pyrophosphate) titanate, bis (dioctyl pyrophosphate) oxyacetate titanate, bis (dioctyl) (Pyrophosphate) ethylene titanate and the like.

As the dimethylpolysiloxane oil, those having a cyclic or chain viscosity of 0.65 to 100 cps are preferably used.

The methyl hydrogen polysiloxane oil has a molecular structure of linear, branched, cyclic,
Although any of a network shape may be used, a linear one represented by the following general formula (4) in which both terminals of the molecular chain are blocked with a trimethylsilyl group is preferably used.

[0045]

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In the above formula, r is 0 to 50, preferably 0 to 25, and s is a number of 1 to 50, preferably 2 to 25. When r exceeds 50, the viscosity may be so high that the treatment may be difficult, and when s exceeds 50, the viscosity may be too high and the surface may be difficult to wet.

In the present invention, among the above surface treating agents, silazanes, particularly hexamethyldisilazane, are more preferably used.

The surface treating agent is preferably used in an amount of 1 to 50 parts, especially 5 to 30 parts, based on 100 parts of aluminum hydroxide. If the amount is less than 1 part, there is no effect as a treating agent. In some cases, when the number exceeds 50 parts, the process becomes useless 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 surface treatment may be carried out directly on the aluminum hydroxide or kneaded with other components. In particular, it is preferable to perform direct treatment in advance. Specifically, aluminum hydroxide and a treating agent are put in a mechanical kneading device sealed at normal pressure or in a fluidized bed, and mixed at room temperature or heat treatment in the presence of an inert gas, if necessary, and kneaded. It can be adjusted by post-drying. In some cases, a catalyst may be used in accordance with each treating agent to promote the treatment.

The amount of the aluminum hydroxide filler as the third component is 100 to 900 parts per 100 parts of the first component.
Parts, preferably in the range of 150 to 800 parts, 100
If the amount is less than 900 parts, the intended electrical properties cannot be exceeded. If the amount exceeds 900 parts, the composition has a high viscosity, making it difficult to fill the composition, resulting in poor processability.

The silicone rubber composition of the present invention may further contain, if necessary, various additives other than the above-mentioned components, such as metal oxides such as cobalt oxide, titanium oxide, iron oxide and antimony oxide, and carbon dioxide. Etc. can be added, and pigments, as long as the desired properties are not impaired.
You may add a heat-resistant agent, a flame retardant, a plasticizer, etc. In addition, the addition amount of these optional components can be a usual amount as long as the effect of the present invention is not hindered.

The silicone rubber composition of the present invention can be obtained by simply mixing the above-mentioned first to fifth components and optional components uniformly at room temperature. (B), (c), (d) the essential components other than the components, and optional components with a planetary mixer or kneader
Heat treatment may be performed at a temperature in the range of 00 to 200 ° C. for 2 to 4 hours, and then the components (b), (c), and (d) may be mixed and cured. The molding method can be freely selected depending on the viscosity of the mixture, and any method such as injection molding, compression molding, injection molding, extrusion molding, and transfer molding may be employed. The curing condition is usually 80 to 200 ° C. for 3 minutes to 3 minutes.
Can be heated for hours.

[0053]

The silicone rubber composition for a high-voltage electrical insulator according to the present invention can be filled with aluminum hydroxide in the closest density, has excellent filling properties and fluidity, and has good workability. Even under conditions exposed to severe weather and pollution, not only is it excellent in high-voltage electrical properties such as tracking resistance, erosion resistance, and arc resistance, but it also provides a silicone rubber with excellent weather resistance and water repellency. Silicone rubber is useful as a high-voltage electrical insulator such as high-pressure glass.

[0054]

EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. In addition, all the parts in each example are parts by weight, and all% are% by weight.

[Examples 1 to 3] A dimethylpolysiloxane (organopolysiloxane (a) having a viscosity of 5000 cps at 25.degree. )) 9
4 parts, wet silica (Nipsil LP, manufactured by Nippon Silica Industry Co., Ltd., BET specific surface area 180
m ² / g) 5 parts, as a third component, aluminum hydroxide shown in Table 1 was mixed as shown in Table 2, stirred at 150 ° C. for 2 hours with a planetary mixer, and then cooled to room temperature. Further, methyl hydrogen polysiloxane represented by the following formula (5) as the component (c), a 1% 2-chlorohexanol solution of chloroplatinic acid as the component (d), and the component (e) in the remaining first component. (Ethynylcyclohexanol) was added as a reaction control agent in the amounts shown in Table 2 and uniformly mixed to obtain a silicone rubber composition. This silicone rubber composition was cured by heating at 120 ° C. for 10 minutes to obtain a silicone rubber sheet of 128 mm × 44 mm × 6 mm (thickness).

[0056]

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Example 4 As shown in Table 2, as a component (a) in the first component, both ends of the molecular chain were blocked with trivinylsiloxy groups, and the viscosity at 25 ° C. was 30,000 cp.
s) dimethylpolysiloxane (organopolysiloxane (b)) was used, and the components were heated and mixed in the same manner as in Example 1 except that the components (c), (d), and (e) were not added. ) Dicumyl peroxide was added as a component and mixed at room temperature until uniform to obtain a silicone rubber composition. After this silicone rubber composition was cured by heating at 165 ° C. for 10 minutes, it was secondarily cured at 200 ° C. for 4 hours to obtain a 128 mm × 44 mm × 6 mm (thickness) silicone rubber sheet.

Comparative Examples 1 to 3 Using the components shown in Table 2, silicone rubber sheets were obtained in the same manner as in Example 1.

Next, the silicone rubber sheets obtained in the above Examples and Comparative Examples were subjected to various tests by the following methods. Table 2 shows the results of the filler filling property, tracking time and erosion loss weight, and Table 3 shows the results of the spiral flow of Example 1 and Comparative Example 2. Filler filling property : ○ Visually, a viscous block-like compound at the time of compounding and retaining fluidity × Visually, a viscous block-like compound at the time of compounding, without fluidity Tracking test method : ASTM D-2303-64
The test was performed according to the T standard. That is, a contaminated liquid (0.1% NH ₄ Cl and 0.1.
0.6% aqueous solution of a 02% nonionic surfactant)
The droplets were dropped from the upper electrode at a rate of "in" to measure the time required for a track to be generated and conducting, and the weight of erosion loss (% by weight) caused by the time. Erosion loss weight : While a part of the rubber sheet performs the above test,
Degraded and eroded by heat and arc. This erosion amount was calculated by the following equation. (Weight lost by erosion / weight of entire sheet before test)
× 100 spiral flow : Measured at 120 ° C. and 100 kgf / cm ² using a mold conforming to the EMMI standard.

From the results shown in Tables 2 and 3, the silicone rubber composition of the present invention was excellent in fillability, tracking resistance and erosion resistance, and could be filled at the highest density. . The third component containing less aluminum hydroxide (Comparative Example 1) has a large erosion amount, and the one containing aluminum hydroxide having a single average particle size (Comparative Examples 2 and 3) has poor tracking resistance. In particular, it was confirmed that Comparative Example 3 was inferior in fillability and fluidity. Further, from the spiral flow values shown in Table 3, the silicone rubber composition of the present invention (Example 1) is superior in fluidity as compared with a composition containing aluminum hydroxide particles having a single average particle diameter (Comparative Example 2). This was also confirmed.

[0061]

[Table 1]

[0062]

[Table 2]

[0063]

[Table 3]

Claims (7)

(57) [Claims] (1) 100 parts by weight of an organic peroxide-curable or addition-reaction-curable silicone rubber composition (2) 1 to 100 parts by weight of silica fine powder (3) (a) Average particle diameter 7 to 50 μm 100 to 900 parts by weight of an aluminum hydroxide filler consisting of 10 to 95% by weight of aluminum hydroxide and (b) 90 to 5% by weight of aluminum hydroxide having an average particle diameter of less than 7 μm. A silicone rubber composition for a high-voltage electrical insulator, comprising: 2. The silicone rubber composition for a high-voltage electrical insulator according to claim 1, wherein a tracking time of the cured product of the silicone rubber composition for a high-voltage electrical insulator according to ASTM D-2303-64T standard exceeds 25 hours. (3) The component (b) has an average particle size of 0.5 to 0.5.
3. The silicone rubber composition for a high-voltage electrical insulator according to claim 1, which is 5 μm of aluminum hydroxide. 4. The composition according to claim 3, wherein the proportion of the component (a) is 30.
The silicone rubber composition for a high-voltage electrical insulator according to any one of claims 1 to 3, wherein the proportion of the component (b) is 70 to 10% by weight. 5. An organic peroxide-curable silicone rubber composition comprising: (a) the following average composition formula (1): R ¹ _a SiO _{(4-a) / 2} (1) ¹ is a substituted or unsubstituted monovalent hydrocarbon group, and 0.01 to 20 mol% of R ¹ is an alkenyl group; a is a positive number of 1.9 to 2.4.) 5. An organic polysiloxane having an average of at least two alkenyl groups in one molecule to be obtained, wherein the main component is 100 parts by weight of (b) an organic peroxide catalyst amount.
Item 7. The silicone rubber composition for a high-voltage electrical insulator according to the above item. 6. An addition reaction-curable silicone rubber composition comprising: (a) the following average composition formula (1): R ¹ _a SiO _{(4-a) / 2} (1) wherein R ¹ is Although it is a substituted or unsubstituted monovalent hydrocarbon group, 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 an organopolysiloxane having an average of at least 2 alkenyl groups in the molecule (c) 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, b is 0.7 to 2.1, c is 0.002 to 1, and b + c is 0. 0.1 to 100 parts by weight of an organohydrogenpolysiloxane that is liquid at room temperature and which is a positive number that satisfies 0.8 to 3. The catalyst according to any one of claims 1 to 4, wherein the main component is a catalyst amount.
Item 7. The silicone rubber composition for a high-voltage electrical insulator according to the above item. 7. The silicone rubber composition for a high-voltage electrical insulator according to claim 1, wherein a surface treatment is applied to the aluminum hydroxide filler.