JPH08222057A - Insulator - Google Patents

Abstract

PURPOSE: To provide a composite insulator in which water repellency recovering characteristic is improved, and the continuity of the water repellency recovering characteristic is also enhanced. CONSTITUTION: This insulator is a composite insulator in which a sheathing is connected in a prescribed form by a silicon rubber obtained by heating and hardening a component A. To the component A, a component B is mixed in a ratio of 1-100 parts by weight to 100 parts by weight of the component A. The component A is a diorganopolysiloxane component having at least two silicone atom-bonded alkenyl groups in one molecule, and the component B is a methylakyl polysiloxane oil having a viscosity at 25 deg.C of 1-1,000cSt and having a molecule chain both terminals of which are sealed by silanol groups.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulator used for supporting a power transmission line or the like and particularly excellent in water repellency recovery characteristics. Here, the “insulator” referred to in the present application includes an insulator tube.

[Prior art]

A so-called composite insulator is constructed by covering and forming a cap portion and a sheath portion made of silicone rubber or the like on the outer periphery of a core material made of FRP or the like. This composite insulator is
It is known that due to the excellent water repellency of silicone rubber, it exerts a great effect in preventing corona noise, flashing in a dirty area, and the like.

[Problems to be Solved by the Invention]

Generally, a molded article made of a high molecular compound exhibits water repellency at the initial stage, but when it is used outdoors, it will be repelled in a relatively short time by the irradiation of sunlight (ultraviolet rays). It had the drawback of being lost. On the other hand, it is known that fluororesins, silicone rubbers, and silicone resins represented by Teflon are strong against ultraviolet rays.

However, when a fluorine-based resin or even a silicone-based resin is used as a coating material for a high-voltage insulator, its surface is exposed to partial discharge or the like, or contaminants are attached to the surface, so There is a problem that the water repellency is lost. Under such circumstances, the silicone rubber loses its water repellency temporarily due to the surface being exposed to partial discharge, etc., or the surface being contaminated with contaminants, but then the water repellency is restored (for example, after 24 hours). It has been reported by some researchers, and this is a fact confirmed by the present inventors.

Although the mechanism for recovering the water repellency has not been clarified yet, according to some researchers, the low molecular weight silicone component contained in the silicone rubber is gradually surfaced with time. It is explained that it is due to seeping into. The inventors of the present invention have confirmed this through various experiments and support this theory.

This type of low molecular weight silicone component is not positively added to the silicone rubber, but is present in a very small amount as a by-product in the production process of the diorganopolysiloxane which is the main raw material of the silicone rubber. It was a thing. For this reason, as the number of years of use increases, this low-molecular-weight silicone component is exhausted, the time until the water repellency is restored becomes longer, and the effect of preventing corona noise and flashing in dirty areas becomes smaller. There was a problem.

In order to solve such problems of the prior art, Japanese Patent Application No. 5-203415 discloses that (A) contains a diorganopolysiloxane having at least two silicon-bonded alkenyl groups in one molecule. In an insulator using a silicone rubber obtained by heating and curing a composition, the composition has a viscosity of 1 to 1,00 at 25 ° C. as a component (B).
It is 0 centistokes, and 1 to 100 parts by weight of a methylalkylpolysiloxane oil whose both molecular chain ends are blocked with trialkylsiloxy groups is added to 100 parts by weight of the above-mentioned component (A). The low-molecular-weight silicone component is continuously transferred to the surface to improve the water-repellent recovery property, prevent corona noise, and prevent flashing in soiled areas. The present inventor
When we examined the technology of No. 15, we found the following problems.

That is, since both ends of the molecular chain of the component (B) methylalkylpolysiloxane oil are blocked with trialkylsiloxy groups, the binding force with the crosslinked component (A) is poor, and the inside of the component (A) is poor. You can move relatively freely. On the other hand, the component (B) sufficiently contributes to the water repellency recovery in the initial stage, but is consumed in a short time, and the sustainability of the water repellency recovery cannot be obtained. Also, if it is attempted to supplement this with the addition amount, the required physical properties of the silicone rubber composition will not be obtained.

It is an object of the present invention to improve the water repellency recovery property of an insulator and to enhance the durability (life) of this recovery property.

[0010]

Means for Solving the Problems and Actions / Effects In order to achieve the above object, the present invention relates to an insulator in which an outer cover is formed in a predetermined shape with a silicone rubber obtained by heat-curing the component (A). Ingredient (B) in the above (A) ingredient 10
It is characterized in that 1 to 100 parts by weight is mixed with 0 part by weight. Component (A): Diorganopolysiloxane having at least two silicon atom-bonded alkenyl groups in one molecule Component (B): Viscosity of 1 to 1,000 centistokes at 25 ° C and silanol groups at both ends of the molecular chain Blocked methyl alkyl polysiloxane oil

The methylalkylpolysiloxane oil in which both ends of the molecular chain of the component (B) are capped with silanol groups is
It is a component that is a characteristic of this invention. The difference from Japanese Patent Application No. 5-203415, which is a methylalkylpolysiloxane oil (B) in which both ends of the molecular chain are capped with trialkylsiloxane groups, is that both ends of the molecular chain are capped with silanol groups. Since this silanol group is relatively reactive with the component (A), it has the same molecular weight as the above (B) and Japanese Patent Application No. 5-2034.
When comparing with the component (B) of No. 15, the moving speed to the surface is smaller in the latter. Due to this characteristic, in the latter case, the low-molecular-weight silicone oil is consumed in a relatively short period of time, whereas the component (B) of the present invention stably moves to the surface for a long period of time. The number of hydroxyl groups of silanol groups at both ends of the molecule can be from 1 to 3. That is, -Si
Rn (OH) _3-n (R: alkyl group, n = 0, 1, 2). Examples of the alkyl group of R include a methyl group and an ethyl group.

Component (B) also acts to improve the dispersibility of silica fine powder of component (C) and aluminum hydroxide of component (D) when they are used. At this time, the dispersibility of the components (C) and (D) can be improved by using a silane coupling material in order to improve the bonding property between the filler and the rubber. Therefore, the amount of the component (B) added can be adjusted by increasing or decreasing the amount of the silane coupling agent used.

According to the insulator of the present invention, by adding the component (B), effects such as prevention of corona noise in the insulator and prevention of flash in a dirty area can be maintained. As a result, it is possible to extend the period until the insulator is repainted or replaced with a new insulator, and it is possible to reduce costs.

It is preferable that the composition (C) fine silica powder and the component (D) aluminum hydroxide are blended with the composition comprising the above components (A) and (B).

In the insulator of the present invention, the component (B)
The alkyl group therein is preferably a methyl group. The reason is that when an ethyl group or a phenyl group is introduced as an alkyl group, steric hindrance becomes large, the movement in the rubber becomes slow, and the water-repellent recovery time is delayed. The terminal silanol group also makes it difficult to move, but since the number in one molecule is small, it has an appropriate migration speed and does not significantly delay the water-repellent recovery time.

Next, the present invention will be described in more detail. First, the components (A)-(E) used in the present invention will be described. Further, the diorganopolysiloxane of the component (A) used in the silicone rubber constituting the insulator of the present invention is
It is necessary that the polysiloxane has at least two silicon-bonded alkenyl groups in one molecule.

Examples of such alkenyl group include vinyl group, allyl group, propenyl group and the like. Examples of the organic group other than the alkenyl group include alkyl groups such as methyl group, ethyl group and propyl group; aryl groups exemplified by phenyl group and tolyl group; 3,3,3-trifluoropropyl group,
The substituted alkyl group etc. which are illustrated by a 3-chloropropyl group are mentioned. Of the above-mentioned organic groups, the methyl group has hydrophobicity and can migrate to the insulator surface effectively, which is preferable.

The structure of the component (A) may be linear or linear including branched. Ingredient (A)
The molecular weight of is not particularly limited, and those within the range referred to as organopolysiloxane raw rubber in the technical field can be used. Usually, the viscosity at 25 ° C. is 10 ⁷ centistokes or more, and the average molecular weight is 5 × 10 5. ⁴ or more, preferably 40 × 10 ⁴ or more are used. The silica fine powder as the component (C) is a reinforcing filler for improving the strength of the silicone rubber.

The viscosity of a methylalkylpolysiloxane oil (B) having both ends of its molecular chain blocked with silanol groups is 25 ° C.
In the range of 1 to 1,000 centistokes. If the viscosity is high, the moving speed of the surface will be slow and the water repellency recovery property will be applied. If the viscosity is low, the moving speed will be too fast and the low molecular weight silicone component will be consumed quickly. Therefore, the viscosity of this methylalkyl polysiloxane oil is preferably 10 to
It is in the range of 100 centistokes. Examples of such a methylalkylpolysiloxane oil include dimethylpolysiloxane and diethylpolysiloxane. In the present invention, dimethylpolysiloxane is preferable.

The blending amount of this component (B) is 10 parts of the component (A).
The content is in the range of 1 to 100 parts by weight with respect to 0 parts by weight. If the amount is too small, the water repellency recovery property is deteriorated, and if it is too large, the mechanical properties of the silicone rubber are deteriorated. Considering the effect of the component (B) which is such a low molecular weight silicone component and the balance of the physical properties of the silicone rubber composition, the range of 5 to 80 parts by weight is preferable.

Examples of such silica fine powder include fumed silica, precipitated silica and silica aerogel. Among these, ultrafine particle fumed silica having a particle diameter of 50 μm or less and a specific surface area of 100 m ² / g or more is preferable. Further, surface-treated silica, for example, hydrophobic silica surface-treated with organosilane, hexaorganodisilazane, diorganocyclopolysiloxane or the like may be used.

If the amount of this component (C) is too small, the mechanical strength of the insulator becomes weak, and if it is too large, it becomes difficult to fill the aluminum hydroxide of the component (D) in a high content. Therefore, the content of the component (C) is 1
It is preferably in the range of 10 to 100 parts by weight, more preferably in the range of 20 to 80 parts by weight, relative to 00 parts by weight.

The component (D) aluminum hydroxide serves to improve the arc resistance of the silicone rubber. This aluminum hydroxide has the chemical formula Al ₂ O ₃ .3H ₂ O or A
It is a compound represented by 1 (OH) ₃ and has an average particle size of 5μ.
It is preferably less than m, more preferably less than 1 μm. If the blending amount of this component (D) is too small, the arc resistance necessary for maintaining the life is lost, and if it is too large, the workability becomes poor. Therefore, the content of the component (D) is preferably 15 to 300 parts by weight, more preferably 50 to 200 parts by weight, based on 100 parts by weight of the component (A).

In order to cure the composition comprising the diorganopolysiloxane component (A) having at least two silicon-bonded alkenyl groups in the molecule and the component (B), an organic peroxide is usually used. Examples of the organic peroxide include benzoyl peroxide, bis-2,4-dichlorobenzoyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5- (tbutylperoxy) hexane, and parachlorobenzoylperoxide. oxide,
Examples thereof include di-t-butyl peroxide, t-butyl peroxybenzoate, orthochlorobenzoyl peroxide and the like.

The silicone rubber constituting the insulator of the present invention is a silicone rubber composition which is cured at room temperature or by heating. In addition to these components, the addition of an additive known to be added to a conventional silicone rubber composition to the silicone rubber composition may be incorporated unless the object of the present invention is impaired.

Examples of such additives include non-reinforcing fillers, pigments, heat resistance agents, flame retardants, internal mold release agents, plasticizers and the like. Specific examples of the non-reinforcing filler include diatomaceous earth, quartz powder, calcium carbonate, mica, aluminum oxide, magnesium oxide and titanium oxide. Examples of the pigment include carbon black and red iron oxide, and examples of the heat-resistant agent include rare earth oxide, rare earth hydroxide, cerium silanolate, and cerium fatty acid salt.

The silicone rubber composition used in the present invention comprises the above-mentioned components (A) and (B), or those obtained by blending the components (C) and (D) and various additives as required. It can be easily produced by a known kneading means such as a two-roll or kneader mixer.

As a molding method for obtaining an insulator from a silicone rubber composition, a known molding method such as a compression molding method, an injection molding method or a transfer molding method is adopted. Then, according to these molding methods, the silicone rubber composition is heated at 100 to 250 ° C. for several seconds to several tens of minutes to cure the composition, thereby producing an insulator such as an insulator as a molded product. Even if the surface of this insulator is exposed to partial discharge, or if a contaminant is attached to the surface, the water repellency is promptly recovered, and the water repellency is maintained for a long time.

The insulator of the present invention includes a composite insulator, an electrical insulating bushing, an insulator tube, a cable head, a covering material for electric wires, and the like.

[0030]

EXAMPLES Next, the present invention will be specifically described with reference to Examples and Comparative Examples. In the examples and comparative examples, “part” means “part by weight” and the viscosity is a value at 25 ° C. Further, in the examples, the evaluation of the water repellency recovery property was performed as follows.

Evaluation of water repellency recovery characteristics In order to confirm the water repellency recovery characteristics in a short time, an accelerated deterioration test by a smoke method was conducted. The test conditions of the accelerated deterioration test by this salt water spray are shown below, and the sample arrangement diagram in the haze chamber in this test is shown in FIGS. In these figures, a test piece 1 is configured by connecting two round bars having a diameter of 25 mm and a length of 250 mm, and is suspended in a plurality of rows in a test device 2 made of stainless steel via insulators 3. An electric wire 4 for applying a voltage to the test piece 1 is connected to a lower portion of the test piece 1 via a bushing 5. The spray nozzle 6 is mounted in the test apparatus 2 and sprays salt water. The flameproof curtain 7 is provided on the front surface of the test apparatus 2. Then, a voltage of 30 kV was applied to the test piece 1 via the electric wire 4. In the test, salt water spray was cycled for 8 hours and pause 1 and the voltage was continuously applied. Potential gradient 60V / mm brine conductivity 500 ± 50μ / cm (Test Voltage AC30kV / 2 lines) fog chamber volume 5.8 m ³ spray amount 0.5 ± 0.21 m ³ / hr inclination vertical test cycle wetting / 8 hours of sample drying / 16 hours Temperature / 20 ° C. ± 5 ° C. In order to measure the water-repellent recovery characteristic (recovery time), first the evaluation sample is made water-repellent, the contact angle is measured every hour, and the change over time is taken. As a method of eliminating the water repellency, here, a method of bringing the surface of the sample close to a place where partial discharge is performed externally and holding it for a certain period of time is adopted. By doing so, the water repellency of the silicone rubber drops to 0 at the contact angle. The angle was measured by dropping a water drop of pure water on the surface of the vulcanized product of the silicone composition (water drop particle size: 5 mm) and measuring the contact angle of the water drop.

Example 1 Dimethylsiloxane unit 9
A diorganopolysiloxane raw rubber consisting of 9.8 mol% and a methylvinylsiloxane unit of 0.2 mol% (polymerization degree: 5
000) 100 parts, (component (A)), vinyltriethoxysilane 20 parts (silane coupling agent), viscosity 50
Centistokes 5.0-part silanol group-capped dimethylsiloxane oligomer (component (B)) and 25 parts of fumed silica having a specific surface area of 200 m ² / g were charged into a kneader mixer and kneaded under heating until uniform. To prepare a silicone rubber base compound.

This silicone rubber base compound 1
To 100 parts of aluminum hydroxide, 100 parts of aluminum hydroxide, 0.08 part of calcium stearate and 0.5 part of vinyltriethoxysilane (silane coupling agent) were added and blended using a double roll. A silicone rubber composition was prepared by kneading 0.4 parts of 2,5-dimethyl-2,5-di (t-butylperoxy) hexane with 100 parts of this rubber composition using a two-roll mill. This composition was heated at 170 ° C. for 10
It was compression-molded for a minute to produce a round bar-shaped insulator made of silicone rubber (Sample 1).

Example 2 In Example 1, the viscosity was 5
A round rod-shaped insulator was obtained in the same manner as in Example 1 except that 10 parts of dimethylpolysiloxane oil having 0 centistokes and having silanol groups at both ends blocked with silanol was used (Sample 2).

Example 3 In Example 1, the viscosity was 5
A round bar was prepared under the same conditions as in Example 1 except that 90 parts by weight of 0 centistokes dimethylpolysiloxane oil capped with silanol groups at both ends was used (Sample 3).

Example 4 In Example 1, the viscosity was 5
A circular rod insulator was prepared under the same conditions except that 1 part of 0 centistokes dimethylpolysiloxane oil capped with silanol groups at both ends was prepared (Sample 4).

Example 5 Dimethylsiloxane Unit 9
A diorganopolysiloxane raw rubber consisting of 9.8 mol% and a methylvinylsiloxane unit of 0.2 mol% (polymerization degree: 5
000) 100 parts (component (A)), viscosity of 50 centistokes silanol group-capped dimethylsiloxane oil at both ends 9.0 parts (component (B)), specific surface area 200 m ² /
25 parts of fumed silica (g) was charged into a kneader mixer and kneaded under heating until it became uniform to prepare a silicone rubber base compound. To 100 parts of this silicone rubber base compound, 100 parts of aluminum hydroxide, 0.08 part of calcium stearate, and 2.7 parts of dimethylsiloxane oil blocked with silanol groups at both ends and having a viscosity of 50 centistokes (component B) were rolled into two rolls. Used and added. A silicone rubber composition was prepared by kneading 0.4 parts of 2,5-dimethyl-2,5-di (t-butylperoxy) hexane with 100 parts of this rubber composition using a two-roll mill. 170 ° C of this composition,
Compression molding was carried out for 10 minutes to prepare a round bar-shaped insulator made of silicone rubber (Sample 5).

(Comparative Example 1) In Example 1, the viscosity was 5
A round bar (Sample 6) was obtained in the same manner as in Example 1 except that 0 centistokes of a dimethylpolysiloxane oil capped with silanol groups at both ends of the molecular chain was not blended.

Comparative Example 2 In Example 1, the viscosity was 5
A round bar was obtained in the same manner as in Example 1 under the same conditions as in Example 1 except that 0.5 part by weight of dimethylpolysiloxane oil having 0 centistokes and having silanol groups at both ends of the molecular chain was used (Sample 7).

(Comparative Example 3) In Example 1, the viscosity was 5
An attempt was made to prepare a round bar in the same manner as in Example 1 except that 110 parts by weight of 0 centistokes dimethylpolysiloxane oil capped with silanol groups at both ends was used. In this case, an attempt was made to make a round rod-shaped insulator, but the silicone rubber composition was not cured and could not be molded.

With respect to the above Examples 1-4 and Comparative Examples 1-2, the water repellency recovery characteristics after 1-cycle, 200-cycle and 500-cycle tests were measured with time. The results are shown in Tables 1 to 4, respectively.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

[0045]

[Table 4]

From the above test results, the insulator prepared by mixing the silanol group-capped dimethylpolysiloxane oil having molecular chains at both ends with a predetermined viscosity within the range of the present invention can maintain good water repellency recovery property even over time. However, it can be seen that the water repellency recovery characteristics cannot be maintained well over time for insulators that do not contain the oil or that are out of the scope of the present invention even if the oil is added.

[Brief description of drawings]

FIG. 1 is a schematic front view showing an acceleration test device using salt spray.

FIG. 2 is a schematic plan view showing an acceleration test device using salt spray.

[Explanation of symbols]

 1 test piece 2 test equipment

Claims (3)

[Claims] 1. A composite insulator having an outer cover formed in a predetermined shape from a silicone rubber obtained by heating and curing the component (A),
An insulator, wherein the component (B) is blended in the component (A) in an amount of 1 to 100 parts by weight based on 100 parts by weight of the component (A). Component (A): Diorganopolysiloxane having at least 2 silicon-bonded alkenyl groups in one molecule Component (B): Viscosity at 25 ° C is 1 to 1,000 centistokes, and both ends of the molecular chain are silanol groups. Blocked methyl alkyl polysiloxane oil 2. An insulator, wherein component (C): fine silica powder and component (D): aluminum hydroxide are blended in said component (A). 3. The insulator according to claim 1, wherein the alkyl group in the component (D) is a methyl group.