JPH0841347A - 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 a specified liquid organopolysiloxane, a specified organohydrogenpolysiloxane, a fine silica powder, an aluminum hydroxide an a platinum catalyst. CONSTITUTION:This composition comprises 100 pts.wt. organopolysiloxane (A) having at least two unsaturated aliphatic hydrocarbon groups in the molecule, 1-100 pts.wt. fine silica powder (B), 50-300 pts.wt. aluminum hydroxide (C), 1-20 pts.wt. liquid organopolysiloxane (D) terminated with (CH3)3SiO1/2 units at both ends, in which the organic groups bonded to the Si atoms are monovalent hydrocarbon groups except an unsaturated aliphatic hydrocarbon group and which has a viscosity of 30-100000cps at 25 deg.C, an organohydrogenpolysiloxane (E) having at least three Si-bonded hydrogen atoms in the molecule, in an amount to give 0.5-20mol of the above hydrogen atoms per mol of the unsaturated hydrocarbon groups of component A and a catalytically effective amount of a platinum catalyst (F).

Description

Detailed Description of the Invention

[0001]

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

[0002]

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

Therefore, various solutions have been proposed in order to improve the drawbacks of these porcelain or glass insulators. For example, in US Pat. No. 3,511,698,
A weather-resistant high-voltage electrical insulator composed of a member made of a curable resin and a platinum catalyst-containing organopolysiloxane elastomer has been proposed. In addition, JP-A-59-19860
No. 4, in the presence of outdoor stress such as humidity, air pollution, and ultraviolet rays by applying a one-part room temperature curable organopolysiloxane composition to the outer surface of a glass product or a porcelain electrical insulator. A technique for maintaining the high-performance electrical performance of the electrical insulator is proposed below.

Further, in Japanese Patent Publication No. 53-35982 and Japanese Patent Application 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. Thirty
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 the silicone rubber material is not satisfactory in curing for a long time. 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. Although oxides are often used, organic peroxide cross-linking has a high reaction temperature, making it difficult to control the curing temperature as compared with the addition curing method, and it also decomposes in the cured product after the reaction. There is a disadvantage that the residue remains and the properties of the cured product are adversely affected.

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

[0007]

Means for Solving the Problems The present inventors have conducted extensive studies to achieve the above object, and as a result, have found that organopolysiloxanes having two or more aliphatic unsaturated hydrocarbon groups in one molecule are mainly used. An addition-curable silicone rubber composition containing silica fine powder as a component, which is cured by an organohydrogenpolysiloxane and a platinum-based catalyst, has an aluminum hydroxide and (CH ₃ ) _{3 at} both ends.
Viscosity at 25 ° C. is from 30 to 100,000 cp, in which the organic group bonded to the silicon atom which is blocked by SiO _1/2 unit is a monovalent hydrocarbon group excluding the aliphatic unsaturated hydrocarbon group.
By blending a predetermined amount of s (centipoise) liquid organopolysiloxane, a silicone rubber having excellent weather resistance, tracking resistance, arc resistance, erosion resistance, and high voltage electrical insulation performance is provided. Rubber has been found to be useful as a high-voltage electrical insulator such as an insulator, and has completed the present invention.

That is, the present invention provides (A) 100 parts by weight of organopolysiloxane having 2 or more aliphatic unsaturated hydrocarbon groups in one molecule, (B) 1 to 100 parts by weight of fine silica powder, (C) ) Aluminum hydroxide 50 to 300 parts by weight, (D) Both ends are blocked with (CH ₃ ) ₃ SiO _1/2 units, and the organic group bonded to the silicon atom is 1 except aliphatic unsaturated hydrocarbon group. 1 to 20 parts by weight of liquid organopolysiloxane having a viscosity of 30 to 100,000 cps at 25 ° C., which is a valent hydrocarbon group, (E) Organohydro having 3 or more hydrogen atoms bonded to silicon atoms in one molecule. Genpolysiloxane: An amount of 0.5 to 20 moles of hydrogen atoms bonded to the silicon atom is supplied to 1 mole of the unsaturated hydrocarbon group of the component (A), and (F) contains a catalytic amount of a platinum-based catalyst. To provide high voltage electrical insulating-body silicone rubber composition characterized Rukoto.

The present invention will be described in more detail below. The organopolysiloxane of component (A) which constitutes the silicone rubber composition for high-voltage electrical insulators of the present invention contains at least two silicon atoms in one molecule. Those having an aliphatic unsaturated hydrocarbon group to be bonded and represented by the following general formula (1) can be used. R ¹ _a R ² _b SiO _{(4-ab) / 2} (1)

In the formula, R ¹ is an aliphatic unsaturated hydrocarbon group, and such a group has 2 to 8 carbon atoms, preferably 2 to 4 carbon atoms.
Examples thereof include vinyl group, allyl group and propenyl group. R ² is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 12 carbon atoms, particularly 1 to 10 carbon atoms, which does not have an aliphatic unsaturated bond, and is a methyl group, an ethyl group, a propyl group,
An alkyl group exemplified by a butyl group and the like, a cycloalkyl group such as a cyclohexyl group, an aryl group exemplified by a phenyl group and a tolyl group, an aralkyl group exemplified by a benzyl group, a phenylethyl group and the like, 3, 3, 3 -Substituted alkyl groups such as a trifluoropropyl group and a 3-chloropropyl group are exemplified.

Further, a is 0 <a ≦ 1, preferably 0.0.
005 ≦ a ≦ 0.5, more preferably 0.001 ≦ a ≦
0.2, b is 0.8 <b <3, preferably 1 ≦ b <2.
5, more preferably 1.5 ≦ b <2.2, and a + b is 0.
8 <a + b <3, preferably 1.5 ≦ a + b ≦ 2.5,
More preferably, it is a positive number that satisfies 1.8 ≦ a + b ≦ 2.2.

Here, as the molecular structure of the component (A),
It may be linear, branched, cyclic, or mesh-like. The molecular weight of the component (A) is not particularly limited, and it can be used from a liquid having a low viscosity to a raw rubber having a high viscosity, but at 25 ° C. to cure into a rubber-like elastic body. Has a viscosity of 100 cps or more, usually 100 to
1,000,000 cps, especially 1,000-100,
000 cps is desirable.

Specific examples of such an organopolysiloxane having a chain structure include the following.

[0014]

Embedded image

However, in the above formula, m and p are positive integers and n is 0.
As described above, q is an integer of 2 or more, and m + n and p + q are numbers which make these vinyl group-containing organopolysiloxanes fall within the above viscosity range. The above-mentioned organopolysiloxane may be used alone or as a mixture of two or more kinds, and may have a partially branched structure.

The fine silica powder used as the component (B) may be one used in conventional silicone rubber compositions,
The type is not particularly limited. Such a silica fine powder has, for example, a BET specific surface area of 50 m ² /
Precipitated silica, fumed silica, calcined silica and pulverized quartz having an average particle size of 50 μm or less, particularly 0.1 to 20 μm, diatomaceous earth, and the like are preferably used, if they are g or more, especially 50 to 400 m ² / g. These fine powders may be used as they are, but organosilazanes such as hexamethyldisilazane,
It is also preferable to use hydrophobic silica which is surface-treated with an organosilicon compound such as organochlorosilane such as trimethylchlorosilane and organopolysiloxane such as polymethylsiloxane. When the amount of this component (B) is less than 1 part by weight with respect to 100 parts by weight of the component (A), the mechanical strength becomes weak, and when it exceeds 100 parts by weight, the aluminum hydroxide of the component (C) is used. It becomes difficult to highly fill. Therefore, the blending amount of the component (B) is 100
The amount is 1 to 100 parts by weight, preferably 2 to 50 parts by weight, based on parts by weight.

Next, the aluminum hydroxide as the component (C) is used for improving the arc resistance and tracking resistance of the silicone rubber, and is essential in the present composition. The aluminum hydroxide is represented by the following formula (2) Al ₂ O ₃ .3H ₂ O (2), and the average particle diameter of the aluminum hydroxide is 10 μm or less, preferably 0.1 to 10 μm.
m, and more preferably 0.5 to 9 μm.

This aluminum hydroxide may be used as it is, or may be surface-treated with a silane or titanate coupling agent, dimethylpolysiloxane oil, stearic acid or the like. If the content of the component (C) is less than 50 parts by weight with respect to 100 parts by weight of the component (A), the composition after curing will not have the necessary arc resistance and tracking resistance, and will be 300
When it exceeds the weight part, it becomes difficult to fill the composition and the workability is deteriorated. Therefore, the blending amount of the component (C) is 50 to 300 parts by weight, preferably 150 to 250 parts by weight, relative to 100 parts by weight of the component (A).

The liquid organopolysiloxane of component (D) is used to improve the weather resistance and tracking resistance of the composition and is an essential component of the present invention. As described above, in this liquid organopolysiloxane, the organic group bonded to the silicon atom is a monovalent hydrocarbon group excluding the aliphatic unsaturated hydrocarbon group, and both terminals are (C
H ₃ ) ₃ SiO _1/2 units are blocked, and basically have a linear diorganopolysiloxane structure, but even if they partially contain a branched structure Often,
The viscosity at 25 ° C. is 30 to 100,000 cps, preferably 100 to 100,000 cps, and particularly preferably 1,
000 to 50,000 cps. As the liquid organopolysiloxane, those represented by the following general formula (3) are preferably used.

[0020]

Embedded image

In the formula, R ³ and R ⁴ each represent a monovalent hydrocarbon group except an aliphatic unsaturated hydrocarbon group, and R ³ and R ⁴ may be the same or different. Examples of the monovalent hydrocarbon group excluding the aliphatic unsaturated hydrocarbon group include an alkyl group having 1 to 8 carbon atoms such as a methyl group, an ethyl group, a propyl group, a butyl group and a cyclohexyl group, a phenyl group and a tolyl group. Examples thereof include an aryl group having 6 to 12 carbon atoms, and an alkyl group represented by a methyl group is particularly preferable in the present invention. In addition, r is a number which makes this organopolysiloxane the above viscosity.

The blending amount of this component (D) is the same as component (A) 1
If the amount of this component is less than 1 part by weight with respect to 00 parts by weight, the composition after curing will not obtain the required weather resistance and tracking resistance, and if it exceeds 20 parts by weight, the surface of the cured rubber elastic body will be It gets wet with the organosiloxane and the workability of the composition deteriorates. Therefore, the blending amount of the component (D) is
The amount is 1 to 20 parts by weight, preferably 3 to 10 parts by weight, relative to 100 parts by weight of the component (A).

Organohydrogen poly (E)
Siloxane is a crosslinking agent for the silicone rubber composition of the present invention.
And in the presence of the platinum catalyst of component (F), component (E)
Of the silicon atom-bonded hydrogen atom (that is, SiH group) of (A)
Addition reaction of silicon atom-bonded aliphatic unsaturated hydrocarbon groups
As a result, it is crosslinked and cured. this
Organohydrogenpolysiloxane as component (E)
Is the following general formula (4) R^Five _dH_eSiO_{(4-de) / 2} (4) (where, d is 0.5 <d <2.5, preferably 0.
8 <d ≦ 2, e is 0 <e ≦ 1, preferably 0.001 <
e ≦ 0.5, d + e is 0.8 <d + e ≦ 3, preferably
It is a positive number that satisfies 1.5 ≦ d + e ≦ 2.5. )
And at least 3 silicon atoms in one molecule
It is necessary to have a hydrogen atom bonded to. Silicon
Organic groups other than atom-bonded hydrogen atoms R^Five As a methyl
Group, an ethyl group, an alkyl group exemplified by a propyl group,
Cycloalkyl group of cyclohexyl group, phenyl group,
Aryl group, benzyl group, phenyl group, etc.
Aralkyl groups such as ruethyl group, 3,3,3-trifluoro
Substitution exemplified by propyl group, 3-chloropropyl group, etc.
The above R such as an alkyl group²Except for aliphatic unsaturated groups similar to
1 to 12 carbon atoms, especially 1 to 10 carbon atoms, not substituted or substituted.
An alternative monovalent hydrocarbon group may be mentioned. Here, of the (E) component
As an organohydrogenpolysiloxane molecular structure
May be linear, branched, cyclic, or mesh-like
good. (E) Component organohydrogen polysiloxy
Sun has a viscosity of 1 to 10,000 cps at 25 ° C,
It is preferably in the range of 3 to 5,000 cps.
The following are exemplified.

[0024]

[Chemical 3]

However, in the above formula, s, t and u are positive integers, v
Is an integer of 3 or more, and s + t and u + v are numbers in which the organohydrogenpolysiloxane is in the above viscosity range.

The amount of the organohydrogenpolysiloxane as the component (E) in the composition is such that the number of moles of the silicon atom-bonded unsaturated hydrocarbon group as the component (A) and the silicon atom-bonded hydrogen atom as the component. The amount is such that the ratio with the number of moles of (ie SiH group) is 1: 0.5 to 1:20, preferably 1: 1 to 1: 3. this is,
If the number of moles of silicon atom-bonded hydrogen atoms of this component is less than 0.5 relative to the number of moles of silicon atom-bonded unsaturated hydrocarbon group of component (A), the silicone rubber composition cannot be sufficiently cured. If it exceeds 20, the silicone rubber composition may foam.

The platinum catalyst as the component (F) is a catalyst for curing the silicone rubber composition. As the platinum-based catalyst of the component (F), chloroplatinic acid, an alcohol solution of chloroplatinic acid, a complex compound of chloroplatinic acid and olefins, platinum black, a catalyst on which platinum is supported, and the like are conventionally used hydrosilation reactions. Known catalysts are used. The amount of the component (F) added is a catalytic amount,
Usually, it is 0.1 to 1,000 parts by weight, preferably 1 to 500 parts by weight, as platinum metal, based on the total amount of 1 million parts by weight of the entire composition. This is because if it is less than 0.1 part by weight, the curing does not proceed sufficiently, and if it exceeds 1,000 parts by weight, it is uneconomical.

If desired, the silicone rubber composition of the present invention may be added with various additives, for example, metal oxides such as titanium oxide, iron oxide, cerium oxide, vanadium oxide and chromium oxide. However, pigments, heat-resistant agents, flame retardants, plasticizers and the like may be added as long as the intended characteristics are not impaired.

The silicone rubber composition of the present invention can be obtained by simply mixing the above-mentioned components (A) to (F) and optional components uniformly at room temperature, but if necessary,
The components (A) to (D) and optional components are heat-treated in a planetary mixer or kneader at 100 to 200 ° C. for 2 to 4 hours, and then the components (E) and (F) are mixed and cured and molded. Is also good. The molding method can be freely selected according to the viscosity of the mixture, and may be injection molding, compression molding, injection molding, transfer molding, or the like.

The curing is usually carried out at 80 to 200 ° C. for 3 minutes to
It can be performed by heating for 3 hours.

[0031]

According to the silicone rubber composition for a high-voltage electrical insulator of the present invention, the electrical insulating property of the silicone rubber composition, which has been considered to be deteriorated by the inclusion of a platinum catalyst, can be improved. Even if it contains a platinum-based catalyst, it has weather resistance, water repellency under severe pollution and climatic conditions,
It is possible to provide a silicone rubber having excellent high-voltage electrical characteristics such as tracking resistance.

[0032]

EXAMPLES Hereinafter, the present invention will be specifically described by showing Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Examples 1 to 3 (A) Dimethylpolysiloxane having viscosities of 5,000 cps at 25 ° C., both ends blocked with dimethylvinylsiloxy groups, and (B) silica fine powder (Nipsil LP, Nippon Silica) Manufactured by Kogyo Co., BET specific surface area 180 m ² / g),
(C) An aluminum hydroxide having an average particle diameter of 8 μm and a BET specific surface area of 2 m ² / g, (D) Both ends thereof are each blocked with a trimethylsiloxy group, and a viscosity at 25 ° C. is 30,000.
cps dimethylpolysiloxane, (E) the following formula (5)
Methyl hydrogen siloxane represented by the formula (1), (F) 1% 2-ethylhexanol solution of chloroplatinic acid, and (G) ethynylcyclohexanol in the amounts shown in Table 1 were used. First, components (A) to (D) were used. Is stirred and mixed with a planetary mixer at room temperature (25 ° C.), and then the remaining components (E), (F) and (G) are added and uniformly mixed at room temperature to obtain a silicone rubber composition. It was This composition was heated and cured at 120 ° C. for 10 minutes, and then secondarily cured at 200 ° C. for 4 hours to obtain 128 mm × 44 mm × 6 mm, respectively.
A (thickness) silicone rubber sheet was obtained.

[0034]

[Chemical 4]

[Example 4] The same components as in Examples 1 to 3 were used, and the components (A) to (D) were stirred at 150 ° C for 2 hours.
Silicone rubber sheets were obtained in the same manner as in Examples 1 to 3 except for mixing.

[Comparative Examples 1 and 2] Silicone rubber sheets were obtained in the same manner as in Example 4, except that the components shown in Table 1 were used.

[Comparative Example 3] (A) similar to Examples 1 to 3
~ (C) component, (A) ~ (C) component at 150 ℃
After stirring and mixing for 2 hours at room temperature and cooling to room temperature, heating and curing were performed in the same manner as in Examples 1 to 3 except that 0.6 g of dicumyl peroxide was added and mixed as an organic peroxide for vulcanization. A silicone rubber sheet was obtained.

Next, a tracking test was performed on the silicone rubber sheets obtained in the above Examples and Comparative Examples by the following method. The results are shown in Table 1. Tracking test method It was performed according to the standard of ASTM D-2303-64T. That is, a contaminated liquid (0.1% NH ₄ Cl and 0.02% nonionic surfactant aqueous solution) was dropped from the upper electrode at a load voltage of 4 kV and an electrode distance of 50 mm at a rate of 0.6 ml / min. Then, the time required for the track to be generated and to be conducted, and the resulting weight loss of erosion were measured.

[0039]

[Table 1]

From the results shown in Table 1, the silicone rubber composition of the present invention gives a silicone rubber excellent in tracking property and is not inferior in high voltage electrical insulation property to the organic peroxide curing type. Is recognized.

Claims (1)

[Claims] 1. (A) 100 parts by weight of organopolysiloxane having two or more aliphatic unsaturated hydrocarbon groups in one molecule, (B) 1 to 100 parts by weight of fine silica powder, (C) aluminum hydroxide 50 to 300 parts by weight, (D) both ends are blocked with (CH ₃ ) ₃ SiO _1/2 units, and the organic group bonded to the silicon atom is a monovalent hydrocarbon except an aliphatic unsaturated hydrocarbon group. 1 to 20 parts by weight of a liquid organopolysiloxane having a viscosity of 30 to 100,000 cps at 25 ° C., (E) an organohydrogenpolysiloxane having 3 or more hydrogen atoms bonded to silicon atoms in one molecule: An amount of 0.5 to 20 moles of hydrogen atoms bonded to the silicon atom is supplied to 1 mole of the unsaturated hydrocarbon group of the component (A), and (F) a catalytic amount of a platinum-based catalyst is contained. When High-voltage electrical insulating-body silicone rubber composition that.