JPH0841348A - Silicone rubber composition for high-voltage electrical insulator - Google Patents

Abstract

PURPOSE:To obtain a silicone rubber composition excellent in high-voltage electrical insulation properties by mixing a specified organopolysiloxane with an inorganic filler, aluminum hydroxide and an organic peroxide. CONSTITUTION:This composition comprises 100 pts.wt. organopolysiloxane mixture comprising at least one organopolysiloxane represented by the formula: RaSiO(4-a)/2 (wherein R is a monovalent hydrocarbon group; and a is 1.85-2.10) and terminated with trivinylsilyl groups (a), divinylmethylsilyl groups (b) or vinyldimethylsilyl groups (c) at both ends, having a content of an organopolysiloxane terminated with groups (a) or (b) at both ends of at least 70wt.% and having a viscosity of 400-100000cps at 25 deg.C, 1-100 pts.wt. inorganic filler, 50-300 pts.wt. aluminum hydroxide, 0-20 pts.wt. organopolysiloxane represented by the formula: R<1>bSiO(4-b)/2 (wherein R<1> is a monovalent hydrocarbon except an unsaturated aliphatic hydrocarbon group; and b is 1.85-2.2) and 0.1-10 pts.wt. organic peroxide.

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 electric insulator, which gives a silicone rubber which becomes an excellent high-voltage electric insulator by heat curing.

[0002]

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

Therefore, various solutions have been proposed in order to improve the drawbacks of these porcelain or glass insulators. For example, U.S. Pat. No. 3,511,698 proposes a weather-resistant high-voltage electrical insulator composed of a member made of a curable resin and a platinum catalyst-containing organopolysiloxane elastomer. In addition, JP-A-59-198604.
In the publication, by applying a one-part room temperature curable organopolysiloxane composition to the outer surface of an electrical insulator made of glass or porcelain, the presence of outdoor stress such as humidity, air pollution, and ultraviolet rays. In the above, a technique for maintaining the high-performance electric performance of the electric insulator has been proposed.

Further, in Japanese Patent Publication No. 53-35982 and Japanese Patent Laid-Open No. 4-209655, a mixture of an organopolysiloxane which becomes a silicone rubber by heat curing and an aluminum hydrate is heated at a temperature higher than 100.degree.
It has been proposed that a silicone rubber composition with improved electrical insulation can be obtained by heating for more than a minute.

However, in the above-mentioned conventional techniques, the high-voltage electrical insulation performance of the used silicone rubber materials is not yet sufficiently satisfactory, and there is a complaint that it takes a long time to cure the silicone rubber material. It was In addition, in the conventional technology, when a platinum catalyst is used to cure a silicone rubber material, the electrical insulating property of the silicone rubber is deteriorated. To prevent this deterioration, an organic peroxide is used instead of the addition curing method using a platinum catalyst. Often, oxides are used. However, since the organic peroxide cross-linking is mainly composed of a high-viscosity raw rubber-like organopolysiloxane, it is kneaded by a roll kneading machine or the like, and is dispensed into a shape that can be supplied to the molding machine (preforming step). However, this process requires more manpower than the injection molding work, and is also a bottleneck for labor saving.

The present invention has been made in view of the above circumstances.
Silicone rubber that can be injection-molded and has excellent high voltage electrical insulation properties such as weather resistance, tracking resistance, arc resistance and erogen resistance under conditions that are exposed to severe air pollution, salt damage or climate after heat curing. It is an object of the present invention to provide a silicone rubber composition for a high voltage electrical insulator that gives

[0007]

Means for Solving the Problems and Actions The inventors of the present invention have conducted extensive studies to achieve the above object, and as a result, contain an organopolysiloxane as a main component and an inorganic filler,
In the silicone rubber composition cured by an organic peroxide, the following average compositional formula (1) _Ra SiO _{(4-a) / 2} (1) (where R is a substituted or unsubstituted It is a monovalent hydrocarbon group, a is 1.85 to 2.10), and one end of the molecular chain is blocked with a trivinylsilyl group, a divinylmethylsilyl group or a vinyldimethylsilyl group. Or 2
Organopolysiloxanes of at least one kind, and organopolysiloxanes whose both molecular chain ends are blocked with trivinylsilyl groups or divinylmethylsilyl groups account for 70% by weight or more of the whole, and have a viscosity of 400 to 1000 at 25 ° C.
Using the organopolysiloxane 00Cps (centipoise), and with formulating a predetermined amount of aluminum hydroxide, the average compositional formula necessary ^{_{(2) R 1 b SiO (}} 4-b) / 2 (2) ( where, In the formula, R ¹ is a substituted or unsubstituted monovalent hydrocarbon group excluding an aliphatic unsaturated hydrocarbon group, and b is 1.85 to
It is 2.2. ), And both ends of the molecular chain are (CH ₃ ) ₃
Viscosity at 25 ° C blocked by SiO _1/2 units is 30
By adding ~ 100,000 cps of organopolysiloxane, injection molding can be performed without troublesome operations, workability is excellent, and cost is also advantageous.
Provides silicone rubber with excellent weather resistance, tracking resistance, arc resistance, erogen resistance under conditions of severe air pollution, salt damage, and climate, and high voltage electrical insulation performance. This silicone rubber is an insulator. It has been found that the present invention is useful as a high-voltage electrical insulator such as that of the present invention, and has completed the present invention.

Accordingly, the present invention provides (1) one kind represented by the above average composition formula (1), wherein both ends of the molecular chain are blocked with a trivinylsilyl group, a divinylmethylsilyl group or a vinyldimethylsilyl group, or An organopolysiloxane that is two or more kinds of organopolysiloxanes having both ends of the molecular chain blocked with a trivinylsilyl group or a divinylmethylsilyl group accounts for 70% by weight or more of the whole and has a viscosity of 400 at 25 ° C. To 100,000 cps organopolysiloxane 100 parts by weight (2) inorganic filler 1 to 100 parts by weight (3) aluminum hydroxide 50 to 300 parts by weight (4) both ends of the molecular chain represented by the average composition formula (2) An organopolysiloxane having a viscosity of 30 to 100,000 cps at 25 ° C., which is blocked with a (CH ₃ ) ₃ SiO _{1/2 unit.} Part by weight (5) Organic peroxide 0.1 to 10 parts by weight are blended to provide a silicone rubber composition for a high-voltage electrical insulator.

The present invention will be described in more detail below. The first component of the silicone rubber composition for high-voltage electrical insulators of the present invention is represented by the following average composition formula (1) _Ra SiO _{(4-a) / 2.} (1) (wherein R is a substituted or unsubstituted monovalent hydrocarbon group, and a is 1.85 to 2.10), and both ends of the molecular chain are a trivinylsilyl group, 1 or 2 blocked with a divinylmethylsilyl group or a vinyldimethylsilyl group
Organopolysiloxanes of one or more kinds and having both ends of the molecular chain blocked with trivinylsilyl groups or divinylmethylsilyl groups account for 70% by weight or more of the whole and have a viscosity of 400 to 1000 at 25 ° C.
It is an organopolysiloxane that is liquid at room temperature of 00 cps.

Here, R in the above formula (1) is preferably a substituted or unsubstituted monovalent hydrocarbon group having 1 to 12 carbon atoms, particularly 1 to 10 carbon atoms, such as a methyl group or an ethyl group. , Propyl, isopropyl, butyl, hexyl, cyclohexyl, octyl, and other alkyl groups, vinyl, allyl, propenyl, butenyl, hexenyl, and other alkenyl groups, phenyl, tolyl, and other aryl groups Group, benzyl group, aralkyl group such as phenylethyl group and chloromethyl group in which hydrogen atom of these hydrocarbon groups is partially substituted with halogen atom, cyano group, trifluoropropyl group, cyanoethyl group, etc. . In particular, at least 50 mol%, more preferably 60 to 99.7 mol%, of all R groups are methyl groups, and
It is suitable that 10 to 10 mol%, more preferably 0.3 to 3 mol% is a vinyl group. In addition, a is 1.85 to
It is 2.10.

The organopolysiloxane of the first component is an organopolysiloxane whose molecular chain ends are blocked with trivinylsilyl groups or divinylmethylsilyl groups in an amount of 70% by weight or more, preferably 80 to 100% by weight. %, It is difficult to achieve a practical short-time curing in injection molding if the content is less than 70% by weight.
The mechanical properties of the cured product are also impaired.

The organopolysiloxane of the above formula (1) has a viscosity at 25 ° C. of 400 to 100,000 cp.
s, preferably 1000 to 50,000 cps, and when mixing two or more kinds of the organopolysiloxane of the formula (1), it is necessary that the viscosity of the mixture is within the above range. Although this organopolysiloxane is substantially a linear structure diorganopolysiloxane, it may contain a trifunctional siloxane unit (that is, a monoorganosiloxane unit).

The second component, the inorganic filler, is mainly used for increasing the mechanical strength of the composition of the present invention. Examples of such an inorganic filler include BET.
Specific surface area by the method of 50 m ² / g or more, especially 50-40
Examples include silica-based reinforcing fillers such as 0 m ² / g precipitated silica, fumed silica, and calcined silica. Further, a filler such as quartz powder, diatomaceous earth, calcium carbonate or the like can be used although the reinforcing property is not so strong. These inorganic fillers may be used as they are, or may be surface-treated with an organic silicon compound such as hexamethyldisilazane or polymethylsiloxane to make the surface hydrophobic to be used.

The amount of the inorganic filler to be compounded is 1 to 100 parts, preferably 2 to 50 parts, relative to 100 parts (parts by weight, hereinafter the same) of the first component, organopolysiloxane. If it is not, the reinforcing effect is weak, and if it exceeds 100 parts, it becomes difficult to highly fill the aluminum hydroxide of the third component.

The third component, aluminum hydroxide, is used to improve the arc resistance and tracking resistance of the silicone rubber composition and is essential in the composition of the present invention.

In this case, the aluminum hydroxide is represented by the following formula (3) Al ₂ O ₃ .3H ₂ O (3) and has an average particle diameter of 30 μm or less, preferably 0.1.
1 to 30 μm, more preferably 0.5 to 15 μm, and B
Those having an ET specific surface area of 0.1 to ²⁰ m ² / g are preferably used.

The aluminum hydroxide may be used as it is, but may be surface-treated with a silane or titanate coupling agent, dimethylpolysiloxane oil, stearic acid or the like.

The amount of the third component, aluminum hydroxide, to be blended is in the range of 50 to 300 parts, preferably 150 to 250 parts, relative to 100 parts of the first component. If the amount exceeds 300 parts, it will be difficult to fill the composition and the workability will deteriorate.

Furthermore, the organopolysiloxane of the fourth component, which is optionally compounded, has the following average compositional formula (2) R ¹ _b SiO _{(4-b) / 2} (2) (wherein R ¹ is A substituted or unsubstituted monovalent hydrocarbon group excluding an aliphatic unsaturated hydrocarbon group, and b is 1.85 to
It is 2.2. ), And both ends of the molecular chain are (CH ₃ ) ₃
Viscosity at 25 ° C blocked by SiO _1/2 units is 30
It is a liquid at room temperature of up to 100,000 cps, for example, a linear diorganopolysiloxane. By blending this, the silicone rubber composition has weather resistance, water repellency,
The tracking resistance can be further improved.

Here, R ¹ in the above formula (2) is a substituted or unsubstituted monovalent hydrocarbon group excluding an aliphatic unsaturated group,
Examples of R in the above-mentioned average composition formula (1) are the same as those having 1 to 12 carbon atoms, particularly 1 to 10 carbon atoms, other than the alkenyl group, such as a methyl group, an ethyl group,
Propyl group, isopropyl group, butyl group, hexyl group,
Examples thereof include an alkyl group having 1 to 8 carbon atoms such as a cyclohexyl group and an octyl group, and an aryl group having 6 to 12 carbon atoms such as a phenyl group and a tolyl group. Particularly, an alkyl group represented by a methyl group is preferable. b is 1.85 to 2.2, preferably 1.9 to 2.1.

The organopolysiloxane of the above formula (2) has a viscosity at 25 ° C. of 30 to 100,000 cps,
It is preferably 100 to 100,000 cps, more preferably 1,000 to 50,000 cps.

The content of the fourth component, organopolysiloxane, is in the range of 0 to 20 parts, preferably 3 to 15 parts, relative to 100 parts of the first component, and when the content exceeds 20 parts, the cured rubber is obtained. The strength of the elastic body is reduced, and the oil bleeds on the surface to impair workability.

The fifth component, an organic peroxide, is used as a curing catalyst for the composition of the present invention. As the organic peroxide, an organic peroxide generally used for curing silicone rubber can be used, and specific examples thereof include the following compounds, but the organic peroxide is not limited thereto.

[0024]

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The blending amount of the above organic peroxide can be appropriately selected according to the desired curing rate, but in order to obtain a practical curing rate, it is 0.1 per 100 parts of the first component.
The range is -10 parts, preferably 0.2-2 parts.

In the composition of the present invention, in addition to the above-mentioned components, various additives such as titanium oxide, iron oxide, cerium oxide, vanadium oxide, chromium oxide, and other metal oxides, pigments, heat-resistant agents, difficult additives, etc. A flammability-imparting agent and the like can be added within a range that does not impair the characteristics of the composition of the present invention.

The silicone rubber composition of the present invention can be obtained by uniformly mixing the above-mentioned components at room temperature, but if necessary, the components other than the organic peroxide are first mixed with a planetary mixer, a kneader, etc. After the heat treatment in the range of 200 ° C. for 2 to 4 hours, the organic peroxide may be added and mixed.

The silicone rubber composition of the present invention has the property of being injection-moldable, and is molded with a liquid silicone rubber injection molding machine or a transfer molding machine to give 120-1.
It can be easily cured by heating at 80 ° C. for a short time of about 20 to 200 seconds.

[0029]

INDUSTRIAL APPLICABILITY The silicone rubber composition for a high-voltage electrical insulator of the present invention can be injection-molded without troublesome operations, has excellent workability, and is advantageous in terms of cost.
Provides silicone rubber with excellent weather resistance, tracking resistance, arc resistance, and erogen resistance under conditions of severe air pollution, salt damage, and climate, and high-voltage electrical insulation performance. This silicone rubber is an insulator. Are useful as high-voltage electrical insulators such as.

[0030]

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

Examples 1 to 4 As shown in Table 1, organopolysiloxanes (1) to (3), wet silica, alumina hydrate and organopolysiloxane (4) were mixed at room temperature (2).
After stirring and mixing with a planetary mixer at 5 ° C.), dicumyl peroxide was added and mixed until uniform at room temperature to obtain a silicone rubber composition. This silicone rubber composition was subjected to 165 using a liquid silicone injection molding machine.
After curing by heating at ℃ for 150 seconds, secondary curing at 200 ℃ for 4 hours, each 128mm × 44mm ×
A sheet-like cured product of a 6 mm (thickness) silicone rubber composition was obtained.

[Example 5, Comparative Examples 1 and 2] As shown in Table 1, organopolysiloxanes (1) to (3), wet silica and alumina hydrate were mixed by stirring at 150 ° C for 2 hours. Was obtained in the same manner as in Example 1 to obtain a sheet-shaped cured product of the silicone rubber composition.

The obtained sheet-shaped cured product was subjected to a tracking test by the following method. The results are shown in Table 1. Tracking test: Contaminated liquid (aqueous solution of 0.1% NH ₄ Cl and 0.02% nonionic surfactant) at a loading voltage of 4 KV and an electrode distance of 50 mm in accordance with the standard of ASTM D-2303-64T. Was dropped from the upper electrode at a speed of 0.6 ml / min, and a track was generated, and the time until it became conductive and the resulting weight loss of erosion were measured.

From the results shown in Table 1, the silicone rubber composition (Example) of the present invention can be easily injection-molded,
It was confirmed that these sheet-shaped cured products have excellent tracking resistance and good rubber physical properties. On the other hand, although the sheet-like cured product of Comparative Example 1 has good tracking resistance, the cured product has an insufficient vulcanization degree under the above-mentioned injection molding condition range in consideration of productivity, and has a rubber physical property. It was scarce. Further, the sheet-shaped cured product of Comparative Example 2 was inferior in tracking resistance.

[0035]

[Table 1]

[0036]

[Chemical 2]* 4: Nipsyl LP (manufactured by Nippon Silica Industry Co., Ltd.) * 5: Average particle size 8 μm, BET specific surface area 2 m²/ g
Aluminum hydroxide * 6: Organopolysiloxane (4) A trimethylsiloxy group at both ends of the molecular chain with a viscosity of 30,000 cps
Dimethylpolysiloxane blocked with

Claims (1)

[Claims] (1) The following average composition formula (1) R _a SiO _{(4-a) / 2} (1) (wherein R is a substituted or unsubstituted monovalent hydrocarbon group, and a is 1.85 to 2.10), and one or more kinds of organopolysiloxanes whose both ends are blocked with a trivinylsilyl group, a divinylmethylsilyl group or a vinyldimethylsilyl group. Organopolysiloxane whose molecular chain both ends are blocked with trivinylsilyl group or divinylmethylsilyl group occupies 70% by weight or more of the total 100% by weight of organopolysiloxane having a viscosity at 25 ° C of 400 to 100,000 centipoise Parts (2) Inorganic filler 1 to 100 parts by weight (3) Aluminum hydroxide 50 to 300 parts by weight (4) The following average composition formula (2) R ¹ _b SiO _{(4-b) / 2} (2) (however, , wherein R ¹ A substituted or unsubstituted monovalent hydrocarbon group excluding aliphatic unsaturated hydrocarbon radical, b is indicated by a 1.85 to 2.2.), Both ends of the molecular chain (CH _{3) 3} Organopolysiloxane having a viscosity of 30 to 100,000 centipoise at 25 ° C. blocked with SiO _1/2 units 0 to 20 parts by weight (5) Organic peroxide 0.1 to 10 parts by weight A characteristic silicone rubber composition for high-voltage electrical insulators.