JP2007180044A - Method of improving high-voltage electrical insulating characteristic of polymer insulator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an insulator excellent in high-voltage electrical characteristics such as water absorbing resistance, electrical resistance, weatherproofness, water repellency, antifouling property, withstand voltage property, tracking resistance, arc resistance, and erosion resistance even under the conditions that the insulator is exposed to severe air pollution, salt injury, or weather. <P>SOLUTION: In this method, the high-voltage electrical insulating characteristics of the polymer insulator are improved by coating the outer periphery of a thermoplastic resin core with a silicone rubber composition and hardening the silicone rubber composition to form the core into a glass or glass tube shape. As the silicone rubber composition, a silicone rubber composition for high-voltage electrical insulator containing (α) organic peroxide hardening type or addition hardening type organopolysiloxane composition, (β) silica fine powder, and (γ) aluminum hydroxide having 0.01 wt.% or less soluble Na ion content, 30 wt.% water slurry of 6.5≤pH≤8.0, and electrical conductivity of 50 μs/cm or less. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polymer insulator high voltage electricity obtained by coating and curing a silicone rubber composition for a high voltage electrical insulator on the outer periphery of a plastic core to provide a heat curable silicone rubber having a low water absorption and excellent electrical characteristics. The present invention relates to a method for improving insulation characteristics.

  High-voltage electrical insulators used for insulators used for transmission / distribution lines, etc., and insulators used for substations, etc. are generally made of porcelain or glass. However, they have the disadvantage of being heavy and fragile. Furthermore, in environments subject to contamination, such as coastal areas and industrial zones, the surface of the insulator is exposed to fine particles, salts, dust, etc., causing a leakage current or dry-discharge that leads to flashover. There is a problem that it is easy to occur.

  Various solutions have been proposed in the past to improve the disadvantages of these porcelain or glass insulators. For example, US Pat. No. 3,511,698 (Patent Document 1) proposes a weather-resistant high-voltage electrical insulator composed of a member made of a curable resin and a platinum catalyst-containing organopolysiloxane elastomer. Japanese Patent Application Laid-Open No. 59-198604 (Patent Document 2) discloses that a one-part room temperature-curable organopolysiloxane composition is applied to the outer surface of an electrical insulator made of glass or porcelain, thereby providing moisture. A technique for maintaining the high performance of the electrical insulator even in the presence of outdoor stress such as air pollution and ultraviolet rays has been proposed.

  Further, Japanese Patent Publication No. 53-35982 (Patent Document 3), U.S. Pat. No. 3,965,065 (Patent Document 4) and Japanese Patent Laid-Open No. 4-209655 (Patent Document 5) describe organos which become silicone rubber by heat curing. It has been proposed that a silicone composition with improved electrical insulation can be obtained by heating a mixture of polysiloxane and aluminum hydrate at a temperature higher than 100 ° C. for 30 minutes or more, and JP-A-7-57574. Japanese Patent Publication (Patent Document 6) proposes that by incorporating a methylalkylpolysiloxane oil into silicone rubber, contact angle recovery characteristics over time can be obtained, which is effective in preventing flashover.

  However, in the above-mentioned conventional technologies, the high voltage electrical characteristics of the silicone rubber materials used are insufficient, and a large amount of aluminum hydroxide must be used to improve the electrical insulation performance. Therefore, there is a disadvantage that the mechanical strength of the rubber is weakened. Furthermore, it becomes easy to get dirty in the long-time exposure test, which may lead to destruction.

US Pat. No. 3,511,698 JP 59-198604 A Japanese Patent Publication No.53-35982 US Pat. No. 3,965,065 JP-A-4-209655 JP 7-57574 A

  The present invention has been made in view of the above circumstances, and high voltage such as weather resistance, voltage resistance, tracking resistance, arc resistance and erosion resistance under conditions exposed to severe air pollution or climate after heat curing. A silicone rubber composition for high voltage electrical insulators that gives silicone rubber with excellent electrical insulation properties is coated and cured on the outer periphery of a core made of thermoplastic resin such as glass fiber reinforced plastic to form insulators, insulators, etc. It is an object of the present invention to provide a method for improving the high voltage electrical insulation properties of a molded high voltage electrical insulator (so-called polymer insulator).

  As a result of intensive studies to achieve the above object, the present inventor has found that an organic peroxide curable or addition curable organopolysiloxane composition has a silica fine powder and a water-soluble Na ion content of 0.01. By adding aluminum hydroxide having a water slurry of not more than wt% and 30 wt% water slurry of 6.5 ≦ pH ≦ 8.0 and electric conductivity of not more than 50 μs / cm, low water absorption, especially after water immersion It has been found that a silicone rubber composition can be obtained that provides a silicone rubber that is excellent in electrical characteristics and has high voltage electrical insulation characteristics such as weather resistance, voltage resistance, tracking resistance, erosion resistance, and arc resistance. Moreover, in this case, the above effect can be exhibited more significantly by adding aluminum hydroxide hydrophobized with a surface treatment agent that imparts hydrophobicity to the surface of such high-purity aluminum hydroxide. I found out. That is, aluminum hydroxide originally contains an ionic component that comes from the manufacturing process, particularly water-soluble Na ions, and it has been found that this Na ion has an adverse effect on the electrical characteristics, and this ionic component is The object of the present invention is effectively achieved by using aluminum hydroxide that has been removed and has the above properties, in particular, aluminum hydroxide that has been subjected to a hydrophobic treatment as described above.

Accordingly, the present invention is a method for improving the high voltage electrical insulation properties of a polymer insulator formed by coating a silicone rubber composition on the outer periphery of a thermoplastic resin core and curing it into a shape of an insulator or insulator. As a silicone rubber composition,
(B) Organic peroxide curable or addition curable organopolysiloxane composition
100 parts by weight,
(B) 1 to 100 parts by weight of silica fine powder,
(C) Aluminum hydroxide having a water-soluble Na ion content of 0.01% by weight or less, a 30% by weight water slurry of 6.5 ≦ pH ≦ 8.0, and an electric conductivity of 50 μs / cm or less.
There is provided a method for improving the high voltage electrical insulation properties of a polymer insulator, characterized by using a silicone rubber composition for a high voltage electrical insulator comprising 30 to 500 parts by weight. In this case, it is preferable that the (C) component aluminum hydroxide is washed and purified with a polar solvent or precipitated from a high-purity sodium aluminate solution. However, it is preferable that the surface treatment agent imparting hydrophobicity to the surface is subjected to a hydrophobic treatment. In this case, the surface treatment agent is preferably a silane coupling agent or a partial hydrolyzate thereof, and the method for improving high voltage electrical insulation characteristics is a method for preventing a decrease in dielectric breakdown voltage. Is preferred.

  According to the present invention, even under conditions exposed to severe air pollution, salt damage or climate, water absorption resistance, electrical resistance characteristics, weather resistance, water repellency, antifouling properties, voltage resistance, tracking resistance, arc resistance, etc. Gives insulators with excellent high voltage electrical properties such as heat resistance and erosion resistance.

  Hereinafter, the present invention will be described in more detail. 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 organopolysiloxane composition.

As an organic peroxide curable organopolysiloxane composition,
(I) The following average composition formula (1)
R ¹ _a SiO _{(4-a) / 2} (1)
(But R ¹ 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 .)
An organopolysiloxane composition mainly composed of an organopolysiloxane (II) organic peroxide having at least two alkenyl groups on average in one molecule is preferably used.

In the alkenyl group-containing organopolysiloxane of the above formula (1), R ¹ is preferably a substituted or unsubstituted monovalent hydrocarbon group having 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms. Alkyl group such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, hexyl group, cyclohexyl group, octyl group, vinyl group, allyl group, propenyl group, isopropenyl group, butenyl Alkenyl groups such as phenyl groups, aryl groups such as phenyl groups, tolyl groups and xylyl groups, aralkyl groups such as benzyl groups and phenylethyl groups, chloromethyl groups, bromoethyl groups, 3,3,3-trifluoropropyl groups, 3- Examples thereof include halogen substitution such as chloropropyl group and cyanoethyl group, and cyano group-substituted hydrocarbon group. Each substituent may be different or the same, but 0.01 to 20 mol%, more preferably 0.1 to 10 mol% in R ¹ is preferably an alkenyl group, Further, it is necessary that the molecule has at least two alkenyl groups on average. R ¹ may be any of the above, but it is preferable to introduce a vinyl group as the alkenyl group and a methyl group or a phenyl group as the other substituent. 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) may have a linear molecular structure or a branched structure containing R ¹ SiO _3/2 units or SiO _4/2 units. The main chain portion is basically composed of repeating R ¹ ₂ SiO _2/2 diorganosiloxane units, and both ends of the molecular chain are blocked with R ¹ ₃ SiO _1/2 triorganosiloxy units. Generally, it is a diorganopolysiloxane. In addition, the alkenyl group in the molecule may be bonded to either the end of the molecular chain or the silicon atom in the middle of the molecular chain, or may be bonded to both. In view of the above, it is preferable to have an alkenyl group bonded to silicon atoms at both ends of the molecular chain.

  The alkenyl group-containing organopolysiloxane preferably has an average degree of polymerization of 50 to 100,000, particularly 100 to 20,000, and has a viscosity at 25 ° C. of 100 cps or more, usually 100 to 10,000,000 cps, particularly 500 to 1,000,000 cps, more preferably 800 to 500,000 cps. It is preferable that

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

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

  The addition amount of the organic peroxide is a catalyst amount and can be appropriately selected according to the curing rate. Usually, it is 100 parts by weight of the alkenyl group-containing organopolysiloxane of the above formula (1) (the same applies hereinafter). The range is 0.1 to 10 parts, preferably 0.2 to 3 parts.

  Note that silica fine powder and other inorganic fillers are basically not blended with the organic peroxide curable organopolysiloxane composition.

Next, as an addition-curable organopolysiloxane composition,
(I) Alkenyl group-containing organopolysiloxane of the above formula (1) (III) The following average composition formula (2)
R ² _b H _c SiO _{(4-bc) / 2} (2)
(In the formula, R ² is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms. B is 0.7 to 2.1, preferably 1 to 2, and 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.
An organopolysiloxane composition mainly containing an organohydrogenpolysiloxane (IV) addition reaction catalyst which is liquid at room temperature and has at least 2, preferably 3 or more hydrogen atoms bonded to silicon atoms represented by Is done.

  As the alkenyl group-containing organopolysiloxane of the above formula (1), the same alkenyl group-containing organopolysiloxane as that described in the organic peroxide curable organopolysiloxane composition is used.

In the organohydrogenpolysiloxane of the above 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 It is a positive number satisfying 2.6.

  This organohydrogenpolysiloxane acts as a cross-linking agent for the main component of the component (I) in the presence of an addition reaction catalyst, and has an average of at least 2, preferably 3 or more silicon atoms in one molecule. It has a bonded hydrogen atom (that is, SiH group), and this SiH group may be located either at the end of the molecular chain, in the middle of the molecular chain, or at both.

Examples of such organohydrogenpolysiloxane include methylhydrogen cyclic polysiloxane, trimethylsiloxy group-capped methylhydrogen polysiloxane at both ends, trimethylsiloxy group-capped dimethylsiloxane / methylhydrogenpolysiloxane copolymer, both ends Dimethylhydrogensiloxy group-blocked dimethylsiloxane, both ends dimethylhydrogenpolysiloxy group-blocked dimethylsiloxane, both ends dimethylhydrogenpolysiloxy group-blocked dimethylsiloxane / methylhydrogenpolysiloxane copolymer, both ends trimethylsiloxy group-blocked methylhydro polysiloxane-diphenylsiloxane-dimethylsiloxane copolymer, co consisting of (CH _{3) 2} HSiO _1/2 units and SiO _4/2 unit weight Body, and the like (CH _{3) 2} HSiO _1/2 units and the SiO _4/2 units (C ₆ H ₅₎ consisting of SiO _3/2 units, and copolymers thereof.

  The organohydrogenpolysiloxane of the above formula (2) may be linear or cyclic or branched, but it must be liquid at room temperature, and its viscosity is The temperature is preferably 0.1 to 10000 cps at 25 ° C., particularly 0.5 to 5000 cps, and the average number of SiH groups in the molecule is usually 2.01 to 300, preferably about 2.5 to 100 Anything is acceptable.

  The organohydrogenpolysiloxane can be produced by a known method.

  The amount of the above-mentioned organohydrogenpolysiloxane is usually 0.1 to 300 parts, preferably 0.3 to 200 parts, particularly 0.5 to 100 parts with respect to 100 parts of the organopolysiloxane of the component (A). It is.

  The organohydrogenpolysiloxane has a hydrogen atom (SiH group) bonded to a silicon atom in the molecule in a molar ratio of 0.5 to 5 mol / mole with respect to the alkenyl group in the organopolysiloxane of the component (I). It can also mix | blend so that it may become a mol, Preferably 0.8-3 mol / mol.

  The addition reaction catalyst includes platinum black, platinous chloride, a reaction product of chloroplatinic acid and a monohydric alcohol, a complex of chloroplatinic acid and olefins, platinum bisacetoacetate, a palladium catalyst, a rhodium catalyst. Etc. 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 with respect to the component (I).

  In the addition-curable organopolysiloxane composition, silica fine powder and other inorganic fillers are basically not blended, but addition reaction control of acetylene alcohol compounds such as ethynylcyclohexanol as optional components in addition to the main components described above. An agent or the like can be added as long as the effects of the present invention are not impaired.

Next, the type of silica fine powder of component (b) is not particularly limited, and those used in conventional silicone rubber compositions can be used. Such silica fine 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 size of 50μm or less, particularly 0 .1-20 μm pulverized quartz, diatomaceous earth, etc. are preferably used. Silica fine powder is necessary as a reinforcing material for rubber.

  These silica fine powders may be used as they are, but they are surface-treated with an organic silazane such as hexamethyldisilazane, a silane coupling agent such as trimethylchlorosilane, or an organosilicon compound such as polymethylsiloxane, and hydrophobic silica. You may use as a fine powder and you may hydrophobize at the time of a mixing | blending. The organic silazanes, silane coupling agents, and organosilicon compounds used as the surface treatment agent are the same as those exemplified as the surface treatment agent used for the hydrophobizing treatment of aluminum hydroxide as the component (c) described later. It can also be adopted.

  Component (B) is preferably blended in an amount of 1 to 100 parts per 100 parts of component (A). If it is less than 1 part, the mechanical strength is weakened. Filling with aluminum becomes difficult and workability deteriorates. Preferably 2-50 parts is good.

Next, (C) component aluminum hydroxide is represented by Al ₂ O ₃ .3H ₂ O or Al (OH) ₃ , which improves electrical properties and heat resistance. In untreated aluminum hydroxide that is usually used, water-soluble ionic components, particularly water-soluble Na ions, remain in the production process, which adversely affects water absorption characteristics and electrical characteristics. It is indispensable to remove these ionic components having an adverse effect in order to prevent moisture from entering during long-term use, and to maintain the electrical characteristics without deteriorating even if invaded. This untreated aluminum hydroxide is washed with deionized water, low molecular alcohols such as methanol, ethanol, butanol, low molecular ethers, or a polar solvent capable of removing water-soluble Na ions and other unnecessary ion components, By purifying and using, the above object can be achieved. Alternatively, instead of purifying and using the untreated aluminum hydroxide, high-purity aluminum hydroxide precipitated from a high-purity sodium aluminate solution can be used.

  The purified or high-purity aluminum hydroxide has a water-soluble Na ion content of 0.01% by weight or less, that is, 0 to 0.01% by weight, usually 1 ppb to 0.01% by weight, preferably 0.1 wt% to 0.005 wt%, and 30 wt% water slurry is 6.5 ≦ pH ≦ 8.0, preferably 7.0 ≦ pH ≦ 8.0 and electric conductivity is 50 μs / cm or less, It is characterized by 0-50 μs / cm, preferably 0.01-10 μs / cm.

  When the water-soluble Na ion content exceeds 0.01% by weight, the water absorption rate of the composition is increased, and the electrical characteristics are deteriorated due to moisture that has intruded after long-term use. Even if the pH of the 30 wt% water slurry is less than 6.5, even if it exceeds 8.0, the electrical characteristics are similarly lowered, and the same is true even if the electrical conductivity exceeds 50 μs / cm. The lower limit of Na ion content and electrical conductivity is ideally 0 (zero), but in consideration of the complexity of the purification process, the purification limit, etc. The lower limit value can be adopted.

  In addition, as a purification method of the untreated aluminum hydroxide, a polar solvent is diluted with 200 parts or more with respect to 100 parts of untreated aluminum hydroxide, and stirred at a temperature from room temperature to the boiling point of each polar solvent for 3 hours or more. A method of washing and repeating until the above conditions are satisfied is suitable. Usually, this operation may be repeated about three times. Then, it is dried and used at a temperature of 150 ° C. or lower.

  The polar solvent is particularly preferably deionized water, but it is particularly preferred to use another polar solvent in combination, and in this case, unnecessary organic substances can be removed.

  Commercially available products such as H320, H320I, HS320, and HS330 (trade names manufactured by Showa Denko KK) can be used as the high-purity aluminum hydroxide precipitated from the high-purity sodium aluminate solution.

  If the aluminum hydroxide has a large number of fine particles of 0.3 μm or less, the specific surface area becomes large, which may easily absorb moisture and absorb water, and may adversely affect electrical characteristics. The average particle diameter is not particularly limited, but is preferably 1 to 100 μm, more preferably 1.5 to 50 μm, and particularly 2 to 20 μm. This average particle diameter is obtained as a weight average value using a particle size distribution meter by laser light diffraction, for example. In this case, particles obtained by precipitation are preferable because fine particles are difficult to form.

  The purified or high-purity aluminum hydroxide may be used as it is, but is preferably subjected to a hydrophobic treatment. Examples of surface treatment agents that impart hydrophobicity to aluminum hydroxide include silane coupling agents or partial hydrolysates thereof, organic silazanes, titanate coupling agents, organopolysiloxane oils, or organohydrogenpolysiloxane oils. It is done.

  Among the surface treatment agents used, silane coupling agents include methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, dimethyldimethoxysilane, diethyldimethoxysilane, vinyltrichlorosilane, vinyltrimethoxysilane. Ethoxysilane, vinyltrimethoxysilane, trimethylmethoxysilane, triethylmethoxysilane, vinyltris (methoxyethoxy) silane, trimethylchlorosilane, trimethylaminosilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltrie Examples of organosilane compounds having 1 or more, preferably 2 to 3 hydrolyzable groups or atoms, such as organoalkoxysilanes such as toxisilane, dimethyldimethoxysilane, divinyldimethoxysilane and γ-chloropropyltrimethoxysilane, and organochlorosilane However, there is no particular limitation as long as it is a silane type, and a partial hydrolyzate of the above silane can also be used.

  Examples of the organic silazanes used include hexaorganodisilazanes such as hexamethyldisilazane, divinyltetramethyldisilazane, diphenyltetramethyldisilazane, and trisilazanes such as octamethyltrisilazane.

  Titanate coupling agents used include tetra-i-propyl titanate, tetra-n-butyl titanate, butyl titanate dimer, tetrastearyl titanate, triethanolamine titanate, titanium acetylacetonate, titanium ethyl acetoacetate, titanium lactate and octylene glycol Examples thereof include titanate, isopropyl tristearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, isopropyl tris (dioctyl pyrophosphate) titanate, bis (dioctyl pyrophosphate) oxyacetate titanate, and bis (dioctyl pyrophosphate) ethylene titanate.

  The organopolysiloxane oil used may be any of cyclic, chain, branched, and network, and those having a viscosity of 0.65 to 100,000 centistokes (25 ° C.) are preferably used.

  The organohydrogenpolysiloxane oil used may have a cyclic, chain, branched, or network molecular structure, but only a methyl group or a methyl group and phenyl as a monovalent hydrocarbon group bonded to a silicon atom. An inert organopolysiloxane having a group is preferable, and those represented by the following average composition formula (3) are desirably used.

  In the formula, r is 0 to 50, and s is 1 to 50. When r exceeds 50, the viscosity becomes high and the treatment becomes difficult. Even if s exceeds 50, the viscosity is similarly high and the surface is hardly wetted, which is not preferable.

  As the treating agent, a silane coupling agent is preferable, and a silicon compound having a hydrolyzable group is particularly effective. By using these, the water absorption rate is further reduced, the electrical characteristics are improved, the adhesiveness with the core material for a long period or after water immersion is good, and the tracking resistance is also improved. As the silane coupling agent, methyltrimethoxysilane and ethyltrimethoxysilane are particularly preferable, and hexamethyldisilazane is also preferably used.

  When the blending amount of the treating agent is less than 0.3 parts with respect to 100 parts of aluminum hydroxide, there is no effect as a treating agent, and when it exceeds 50 parts, the process is wasted and the cost is disadvantageous. Therefore, the amount is 0.3 to 50 parts, preferably 0.3 to 30 parts, more preferably 0.3 to 20 parts, especially 0.5 to 10 parts.

  The treatment method may be either treatment directly on aluminum hydroxide or treatment while kneading with other components, but treatment can be carried out by a generally known technique, preferably one that has been directly treated beforehand. preferable. For example, aluminum hydroxide and a treatment agent are put in a mechanical kneading apparatus sealed at normal pressure or in a fluidized bed, and kneading is performed at room temperature or heat treatment in the presence of an inert gas as necessary. In some cases, a catalyst may be used to accelerate the treatment, but it can be prepared by drying after kneading.

As the aluminum hydroxide of component (c), the properties of aluminum hydroxide are not limited except that the water-soluble Na ion content, the pH of the 30 wt% water slurry, and the electrical conductivity specified in the above values are used. but are not limited to, average particle size 1 to 100 [mu] m, preferably 1.5～50Myuemu, particularly 2 to 20 [mu] m, a BET specific surface area 0.1 to 20 m ² / g, especially 0.2 to 10 m ² / Those having g are preferably used.

  Component (C) is blended in an amount of 30 to 500 parts per 100 parts of component (A). If it is less than 30 parts, high voltage electrical characteristics that require a cured composition, especially arc resistance and tracking resistance, are required. When the amount exceeds 500 parts, filling becomes difficult, workability deteriorates, and rubber physical properties also deteriorate. 50 to 300 parts are preferred.

  In addition to the above-described components, the silicone rubber composition of the present invention can contain free silicone oil such as linear dimethylpolysiloxane and hydroxyl group-containing dimethylpolysiloxane for the purpose of imparting water repellency. Depending on the type, various additives such as titanium oxide, iron oxide, cerium oxide, vanadium oxide, cobalt oxide, chromium oxide, manganese oxide and other metal oxides, carbon, etc. can be added, and the desired properties can be obtained. As long as they are not impaired, pigments, heat-resistant agents, flame retardants, plasticizers, reaction control agents, and the like may be added. In addition, the addition amount of these arbitrary components can be made into a normal amount in the range which does not inhibit the effect of this invention.

  The silicone rubber composition of the present invention can be obtained simply by uniformly mixing the above-mentioned components (a) to (c) and optional components at room temperature, but if necessary, (II), (III) , (IV) component is removed and heat treated in a planetary mixer or kneader at 100 to 200 ° C. for 2 to 4 hours, and then (II), (III) and (IV) components are mixed and cured. Good. 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, or transfer molding may be employed. The curing condition can be a condition of heating at 80 to 200 ° C. for 3 minutes to 3 hours.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example. In addition, all the parts in each example are parts by weight, and all the percentages are by weight.

Purification method of aluminum hydroxide Untreated aluminum hydroxide having an average particle diameter of 8 μm and a BET specific surface area of 2 m ² / g was washed with 200 parts of deionized water for 3 hours with boiling and stirring, and then filtered. The above process was repeated twice, and then dried and pulverized at 105 ° C. for 5 hours to obtain purified aluminum hydroxide.

  Pure water was added so that the purified aluminum hydroxide would be 30%, and the pH and electrical conductivity of the slurry were measured. The pH was 7.0 and the electrical conductivity was 0.43 μs / cm. Further, Na quantitative analysis (%: in aluminum hydroxide) was performed from the extracted water by the flame light method. The results are shown in Table 1 together with aluminum hydroxide precipitated from high-purity sodium aluminate (deposited aluminum hydroxide) and a comparison with untreated general standard aluminum hydroxide.

[Example 1]
As shown in Table 2, dimethylpolysiloxane having a viscosity of 10000 cps at 25 ° C. having both ends blocked with dimethylvinylsiloxy groups as component (a) in component (a) in component (a), and silica in component (b) Wet silica (Nippsil LP, manufactured by Nippon Silica Kogyo Co., Ltd., BET specific surface area of 180 m ² / g) as the fine powder, aluminum hydroxide as component (C) is blended with the above refined product, and then at 150 ° C. for 2 hours with a planetary mixer After stirring and mixing, after cooling to room temperature, methylhydrogenpolysiloxane represented by the following average formula (4) as component (III) in the remaining component (a), 1% of chloroplatinic acid as component (IV) A 2-ethylhexanol solution and ethynylcyclohexanol as a reaction control agent were added and mixed uniformly to obtain a silicone rubber composition. This composition was heat-cured at 120 ° C. for 10 minutes to obtain an 80 mm × 80 mm × 2 mm (thickness) silicone rubber sheet and a 1 mm (thickness) rubber sheet, respectively. After measuring the initial weight from a 2 mm sheet, the weight after being immersed in pure water at 25 ° C. for 100 hours was measured, and the weight change rate is shown in Table 2 as the water absorption rate. The initial volume resistance, dielectric constant, dielectric loss, and dielectric breakdown voltage were measured from a 1 mm sheet according to JIS K6911. Similarly, the volume resistance, dielectric constant, dielectric loss, insulation after immersion in pure water at 25 ° C. for 100 hours. The results of measuring the breakdown voltage are shown in Table 2.

[Example 2]
(I) In component (I), component (b) is the same as component (b) described in Example 1 and component (b) described in Example 1 and dimethylpolysiloxane having a viscosity of 30000 cps at both ends blocked with trivinylsiloxy groups. The components (c) and dicumyl peroxide described in Example 1 were added and mixed until uniform at room temperature to obtain a silicone rubber composition. The composition was heat-cured at 165 ° C. for 10 minutes, and then secondarily cured at 200 ° C. for 4 hours to obtain the same sheet as in Example 1. Table 2 shows the result of the same measurement.

[Comparative Examples 1 and 2]
A silicone rubber sheet was obtained in the same manner as in Example 1 except that the above-described untreated aluminum hydroxide was used as it was and the components shown in Table 2 were used. Table 2 shows the result of the same measurement.

  From the results shown in Table 2, the silicone rubber composition for high voltage electrical insulators of the present invention is excellent in low water absorption after immersion, electrical resistance and voltage resistance, and is subject to long-term wind and rain and other severe environments. It is recognized that water can be prevented from entering and electrical characteristics can be maintained.

Example 3
As shown in Table 3, dimethylpolysiloxane having a viscosity of 5000 cps at 25 ° C. having both ends blocked with dimethylvinylsiloxy groups as component (a) in component (a) and component (a) in component (a) and silica in component (b) Wet silica (Nippil LP, manufactured by Nippon Silica Kogyo Co., Ltd., BET specific surface area 180 m ² / g) as the fine powder, (C) component aluminum hydroxide is the above-mentioned purified aluminum hydroxide methyltrimethoxysilane (100 parts aluminum hydroxide) 1 part was mixed and heat treated at 100 ° C. for 1 hour), and the mixture was mixed with stirring at room temperature with a planetary mixer for 1 hour, and then (III) in the remaining component (a) ) Methyl hydrogen polysiloxane represented by the above average formula (4) as the component, and (IV) 1% 2-ethylhexachloroplatinic acid as the component. Lumpur solution, further ethynyl cyclohexanol was added as a reaction controlling agent, uniformly mixed, yielding a silicone rubber composition. This composition was heat-cured at 120 ° C. for 10 minutes to obtain an 80 mm × 80 mm × 2 mm (thickness) silicone rubber sheet and a 1 mm (thickness) rubber sheet, respectively. After measuring the initial weight from a 2 mm sheet, the weight after being immersed in pure water at 25 ° C. for 200 hours was measured, and the weight change rate is shown in Table 3 as the water absorption rate. The initial volume resistance, dielectric constant, dielectric loss and dielectric breakdown voltage were measured from a 1 mm sheet according to JIS K6911. Similarly, the volume resistance, dielectric constant, dielectric loss and insulation after immersion in pure water at 25 ° C. for 200 hours. The results of measuring the breakdown voltage are shown in Table 3.

Example 4
Same as (I) component (b) in component (a), dimethylpolysiloxane having a viscosity of 5000 cps at both ends sealed with trivinylsiloxy groups at both ends, and component (b) described in Example 3 The components (c) and dicumyl peroxide described in Example 3 were added and mixed until uniform at room temperature to obtain a silicone rubber composition. This composition was heat-cured at 165 ° C. for 10 minutes, and then second-cured at 200 ° C. for 4 hours to obtain the same sheet as in Example 3. Table 3 shows the result of the same measurement.

Example 5
The same components as in Example 3 were used except that the precipitated aluminum hydroxide treated with methyltrimethoxysilane (the treatment method was the same as in Example 3) was used as the component (c) described in Example 3. The mixture was mixed until uniform at room temperature to obtain a silicone rubber composition. This composition was heat-cured at 120 ° C. for 10 minutes to obtain the same sheet as in Example 3, and the results of the same measurement are shown in Table 3.

Example 6
The same components as in Example 3 were used, except that the precipitated aluminum hydroxide treated with ethyltrimethoxysilane (the treatment method was the same as in Example 3) was used as the component (c) described in Example 3. The mixture was mixed until uniform at room temperature to obtain a silicone rubber composition. This composition was heat-cured at 120 ° C. for 10 minutes to obtain the same sheet as in Example 3, and the results of the same measurement are shown in Table 3.

[Comparative Example 3]
The components shown in Table 2 were used except that the untreated general aluminum hydroxide treated with methyltrimethoxysilane (the treatment method was the same as in Example 3) described in Example 3 was used. Table 3 shows the results of using and using the same method as in Example 3 to obtain a silicone rubber sheet and performing the same measurement.

  From the results shown in Table 3, the silicone rubber composition for high voltage electrical insulators of the present invention is excellent in low water absorption, electrical resistance and voltage resistance after immersion, and after being immersed in pure water for 200 hours. However, it is recognized that water can be prevented from entering and electrical characteristics can be maintained.

Claims (5)

A method of improving the high-voltage electrical insulation properties of a polymer insulator formed by coating a silicone rubber composition on the outer periphery of a core made of a thermoplastic resin and curing it into a shape of an insulator or a insulator tube, as the silicone rubber composition,
(B) Organic peroxide curable or addition curable organopolysiloxane composition
100 parts by weight,
(B) 1 to 100 parts by weight of silica fine powder,
(C) Aluminum hydroxide having a water-soluble Na ion content of 0.01% by weight or less, a 30% by weight water slurry of 6.5 ≦ pH ≦ 8.0, and an electric conductivity of 50 μs / cm or less.
A method for improving the high-voltage electrical insulation characteristics of a polymer insulator, comprising using a silicone rubber composition for a high-voltage electrical insulator comprising 30 to 500 parts by weight.   The method according to claim 1, wherein the aluminum hydroxide as component (c) is washed and purified with a polar solvent or precipitated from a high-purity sodium aluminate solution.   The method according to claim 1 or 2, wherein the aluminum hydroxide as component (c) is subjected to a hydrophobic treatment with a surface treating agent that imparts hydrophobicity to the surface.   The method according to claim 1, 2 or 3, wherein the surface treatment agent is a silane coupling agent or a partial hydrolyzate thereof.   The method according to any one of claims 1 to 4, wherein the method for improving high-voltage electrical insulation characteristics is a method for preventing a decrease in dielectric breakdown voltage.