JP2002294074A - Method for producing silicone rubber composition for high-voltage electrical insulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently producing a silicone rubber composition for high-voltage electrical insulators having excellent processability. SOLUTION: This method for producing the silicone rubber composition for the high-voltage electrical insulators comprises kneading (A) 100 pts.wt. of an organopolysiloxane represented by the following average compositional formula (1) Rn SiO(4-n)/2 (1) (Rs are each an unsubstituted or a substituted monovalent hydrocarbon groups of the same or different kind; and n is a positive number of 1.98-2.02) with (B) 1-100 pts.wt. of a silica fine powder, (C) 50-300 pts.wt. of aluminum hydroxide having 0.1-10.0 μm average particle diameter and (D) 0.03-5 pts.wt. of a metal salt of a >=10C fatty acid in a composition composed of the components (A), (B), (C), (D) and (E) 0.01-10 pts.wt. of an organic peroxide at 80-200 deg.C temperature for >=30 min, then cooling the resultant compound to <=80 deg.C and subsequently compounding the component (E).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently producing a silicone rubber composition for a high-voltage electrical insulator having excellent processability.

[0002]

Technical background of the invention and its problems High-voltage electrical insulators used for insulators used in power transmission lines are generally made of porcelain or glass. In an environment that is susceptible to such a problem, there is a problem in that fine particles, salts, fog, and the like pass through the surface of the high-voltage electrical insulator, thereby generating a leakage current and generating a dry over which leads to flashover.

Therefore, in order to improve the disadvantages of the insulators made of porcelain and glass, various kinds of polyorganosiloxane-based high-voltage electrical insulators have been proposed.

[0004] These polyorganosiloxane-based electrical insulator materials generally contain an aluminum hydroxide for improving tracking resistance and arc resistance, but are wetted by the hygroscopic property of the aluminum hydroxide itself. There is a problem that the electrical characteristics in the state are reduced and the corona resistance is reduced. Therefore, a method of blending an aluminum hydroxide surface-treated with a silazane or the like (Japanese Unexamined Patent Application Publication No.
59820), a method of blending an aluminum hydroxide surface-treated with a silane having an alkenyl group (Japanese Patent Laid-Open No. 9-208828), and a method of blending an aluminum hydroxide surface-treated with various organosilanes (see Japanese Unexamined Patent Publication (Kokai) No. 9-316337), a method of blending two or more types of aluminum hydroxides having different average particle sizes and surface-treated with a silicon-containing compound (Japanese Patent Application Laid-Open No. 2000-2000).
38511) has been proposed.

Although these methods can solve the problem of deterioration of electrical characteristics due to moisture absorption of aluminum hydroxide, aluminum hydroxide surface-treated with a silicon-containing compound in advance is relatively expensive. There was a problem in terms of cost. On the other hand, according to another surface treatment method described in the above-mentioned publication, a method of mixing and kneading together a silicon-containing compound with aluminum hydroxide at the time of compounding the material, the problem of cost is reduced, but in this case, the product stability is reduced Heating is required at the time of kneading for kneading, but there is a problem that simply heating causes sticking to a processing device and makes processing impossible. In particular, this problem is remarkable when aluminum hydroxide is highly filled.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method of producing a silicone rubber composition for a high-voltage electrical insulator excellent in processability at a low cost.

[0007]

The present inventors have conducted intensive studies in order to achieve the above object. As a result, it has been found that it is extremely effective to incorporate a fatty acid metal salt into a composition and to employ a production process under a specific temperature condition. And completed the present invention.

That is, the present invention provides: (A) the following average composition formula (1) R _n SiO _{(4-n) / 2} (1) (where R is the same or different, unsubstituted or substituted monovalent) A hydrocarbon group, and n is a positive number of 1.98 to 2.02.) 100 parts by weight of an organopolysiloxane (B) 1 to 100 parts by weight of silica fine powder (C) an average particle diameter of 0 0.1 to 10.0 μm aluminum hydroxide 50 to 300 parts by weight (D) a fatty acid metal salt having 10 or more carbon atoms 0.03 to 5 parts by weight (E) an organic peroxide 0.01 to 10 parts by weight (A), (B), (C), (D) of the composition
A method for producing a silicone rubber composition for a high-voltage electrical insulator, comprising kneading the components at a temperature of 80 to 200 ° C. for 30 minutes or more, cooling the mixture to 80 ° C. or less, and then compounding the component (E). A) The following average composition formula (1): R _n SiO _{(4-n) / 2} (1) (where R is the same or different unsubstituted or substituted monovalent hydrocarbon group, and n is 1. 100 parts by weight of an organopolysiloxane represented by the following formula: (B) 1 to 100 parts by weight of silica fine powder (C) Aluminum hydroxide having an average particle diameter of 0.1 to 10.0 μm 50-300 parts by weight (D) Fatty acid metal salt having 10 or more carbon atoms 0.03-5 parts by weight (E) Organic peroxide 0.01-10 parts by weight (F) Organosilane 0.1-5 parts by weight (A), (B), (C),
A silicone rubber composition for a high-voltage electrical insulator, comprising kneading the components (D) and (F) at a temperature of 80 to 200 ° C. for 30 minutes or more, cooling the mixture to 80 ° C. or less, and then mixing the component (E). It is a method of manufacturing a product.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The organopolysiloxane (A), which is the first essential component of the silicone rubber composition for a high-voltage electrical insulator of the present invention, is represented by the following average composition formula (1).

R _n SiO _{(4-n) / 2} (1) wherein R is the same or different unsubstituted or substituted monovalent hydrocarbon group, and n is 1.98 to 2.02. Is a number.

[0011] Of all R groups in the molecule, 0.001 to 5 mol%, particularly 0.01 to 0.05 mol%, is preferably an alkenyl group, and the remaining R is a methyl group or a phenyl group. Preferably, in this case, 95 of all R groups
It is preferred that at least mol%, especially at least 99.95 mol%, be methyl groups.

Although the molecular structure of the organopolysiloxane of the above formula (1) is not particularly limited, the molecular chain ends thereof are particularly preferably trimethylsilyl, dimethylvinylsilyl, divinylmethylsilyl, trivinylsilyl and the like. Those blocked with an organosilyl group or the like are preferred. Further, it is preferable that the main chain is a linear diorganopolysiloxane whose molecular main chain is basically formed by repeating diorganosiloxane units, but a branched siloxane unit such as a monoorganosiloxane unit or a SiO ₂ unit is contained in the molecule. It may contain a small amount, or may be one or a mixture of two or more kinds having different molecular structures.

The above-mentioned organopolysiloxane has an average degree of polymerization (or the number of silicon atoms in the molecule) of 100 to 100,
000, particularly preferably 4,000 to 20,000.

Next, the silica fine powder of the component (B) constituting the silicone rubber composition is essential for obtaining a silicone rubber having excellent mechanical strength. The specific surface area (BET method) is 50 m ² / g
Above, usually 50 to 500 m ² / g, especially 100 to 300
It is preferably m ² / g. The specific surface area is 50 m ² / g
If less than the above, the mechanical strength of the cured product may decrease.

As such reinforcing silica, for example, fumed silica, precipitated silica and their surfaces are treated with organochlorosilane, organoalkoxysilane, organosilazane, diorganocyclopolysiloxane, 1,3-
Hydrophobic silica treated with disiloxane diol and the like;

The amount of the fine silica powder is preferably 1 to 100 parts, more preferably 20 to 50 parts, and preferably 1 part, per 100 parts (parts by weight, hereinafter the same) of the organopolysiloxane (A). If it is less than 100 parts, the reinforcing effect may not be obtained due to too small an amount, and if it exceeds 100 parts, the processability is poor and the mechanical strength of the obtained silicone rubber may be reduced.

In the present invention, aluminum hydroxide is blended as the component (C). This aluminum hydroxide is basically represented by the following composition formula.

Al ₂ O ₃ .3H ₂ O or Al (OH) _{3 In the} present invention, by using an aluminum hydroxide having an average particle diameter of 0.1 to 10.0 μm as the component (C), A silicone rubber having improved corona resistance and improved arc resistance and tracking resistance of the silicone rubber can be provided.

The average particle diameter can be obtained as a weight average value (median diameter) or the like by a particle size distribution analyzer using an analysis means such as a laser light diffraction method.

According to the method of the present invention, even if an aluminum hydroxide which is not particularly subjected to a surface treatment is used, a decrease in electric properties in an atmosphere in contact with water can be obtained by a usual kneading method. It is significantly smaller than that obtained.

Of course, in the present invention, it is possible to use a surface-treated aluminum hydroxide. However, as described above, a material previously surface-treated with a silicon-containing compound is relatively expensive. It is preferable to take a method of surface treating the aluminum hydroxide by mixing and kneading the organosilane of the component (F) described later together with the aluminum hydroxide during the compounding.

The amount of component (C) is 50 to 300 parts per 100 parts of organopolysiloxane of component (A).
Particularly, the range of 100 to 200 parts is preferable. Compounding amount is 50
If the amount is less than 300 parts, the cured composition may not be able to obtain the required arc resistance and tracking resistance, and if it exceeds 300 parts, it may be difficult to add the composition to the composition and the workability may be deteriorated.

As the fatty acid portion of the fatty acid metal salt of the component (D), not only normal ones but also isomers and substituents having an isomer can be used. If the fatty acid portion has less than 10 carbon atoms, the lipophilicity is low. Therefore, it is hardly compatible with silicone polymer, and organopolysiloxane (A) and (C)
Since the affinity for the component aluminum hydroxide cannot be sufficiently increased, no improvement in workability is observed. The fatty acid metal salt used as the component (D) preferably has 30 or less carbon atoms from the viewpoint of ease of synthesis and the like. Examples of the metal portion of the fatty acid metal salt of the component (D) include magnesium, calcium, aluminum, lithium, barium, strontium, zinc, cadmium, and lead, but are not particularly limited. In particular, a fatty acid metal salt having a fatty acid portion having 12 to 20 carbon atoms and a metal portion of magnesium, calcium, zinc, aluminum or the like is suitable as the component (D) in the present invention.

Specific examples of the above-mentioned fatty acid metal salt having 10 or more carbon atoms (metal soap) include magnesium stearate, aluminum stearate, calcium stearate, lithium stearate, zinc stearate, strontium stearate, lead stearate, and the like. Barium stearate, cadmium stearate, calcium chlorostearate, barium chlorostearate, cadmium chlorostearate, zinc laurate, barium laurate, cadmium laurate, magnesium laurate, zinc myristate, aluminum myristate, barium ricinoleate, Examples include zinc ricinoleate, cadmium ricinoleate, and lead, cadmium,
Barium fatty acid salts are toxic and should be avoided if possible.

The component (D) in the present invention includes, for example, Al (OH) (C ₁₇ H ₃₅ COO) ₂ and Al
A basic salt such as (OH) ₂ (C ₁₇ H ₃₅ COO) can be used, and two or more kinds of metal soaps may be mixed and used. Specific examples of the fatty acid metal salt suitable as the component (D) include zinc stearate, magnesium stearate, calcium stearate, magnesium laurate, zinc myristate, and aluminum myristate.

If the amount of component (D) is too small, the polyorganosiloxane of component (A) and (C)
It is not possible to increase the affinity with the aluminum hydrate of the component, and if the blending amount is too large, the compression set, heat resistance, mechanical strength, etc. of the obtained rubber-like elastic body are reduced. ) In the range of 0.03 to 5 parts with respect to 100 parts of the component. It is preferable that the component (D) is particularly blended in the range of 0.05 to 3 parts.

As the organic peroxide of the component (E), conventionally known organic peroxides can be used. For example, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-methylbenzoyl peroxide, o-methyl Benzoyl peroxide, 2,4-dicumyl peroxide, 2,5-dimethyl-bis (2,5-t-butylperoxy) hexane, di-t-butyl peroxide, t-butyl perbenzoate, 1,1 -Screw (t-
(Butylperoxy) 3,3,5-trimethylcyclohexane, 1,6-bis (t-butylperoxycarboxy) hexane and the like.

The amount of the organic peroxide is from 0.01 to 10 parts per 100 parts of the organopolysiloxane (A).
Parts, or 0.01 in the silicone rubber composition.
The content is preferably set to 3% by weight.

As described above, in the present invention, it is preferable to mix organosilane as the component (F). Examples of such organosilane include methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, ethyltomethoxysilane, n-propyltrimethoxysilane, vinyltrimethoxysilane,
Allyltrimethoxysilane, butynyltrimethoxysilane, hexenyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diphenyldimethoxysilane, tetraethoxysilane and their partially hydrolyzed products Can be The component (F) is used in an amount of 0.1 to 5 parts based on 100 parts of the organopolysiloxane of the component (A).

The method of the present invention comprises the steps of (A), (B),
(C) and (D) components, and (F) used as required
After kneading the components at a temperature of 80 to 200 ° C. for 30 minutes or more, the components are once cooled to 80 ° C. or less, and then the component (E) is blended.

When the heating temperature is 80 ° C. or lower, the dispersion of the component (D) becomes insufficient, and the effect cannot be obtained. Also, 200
If the temperature exceeds ℃, the polymer may be thermally degraded, which is economically disadvantageous.

The composition kneaded under such conditions is excellent in roll workability at the time of molding and has improved electric resistance under an atmosphere in contact with water.

The silicone rubber composition according to the present invention includes:
In addition to the above-mentioned essential components, a filler such as crushed quartz, diatomaceous earth, or calcium carbonate as an extender may be added as an optional component as needed, as long as the effects of the present invention are not impaired.

The composition of the present invention may further comprise a flame retardant, a fire resistance improver, a sensitizer, a colorant, a heat resistance improver, if necessary.
Various additives such as a reducing agent, a reaction inhibitor, a release agent, a filler dispersant, and the like can be added. In addition, it is preferable that the amount of various alkoxysilanes, carbon functional silanes, low molecular weight siloxanes containing silanol groups, and the like used as the filler dispersant be kept to a minimum amount so as not to impair the effects of the present invention.

[0035]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. Example 1 To 100 parts of a rubbery organopolysiloxane having 99.975 mol% of dimethylsiloxane units and 0.025 mol% of methylvinylsiloxy units and having an average degree of polymerization of about 6,000, a dimethyl terminal silanol group was used as a dispersant. Fumed silica (R976 manufactured by Nippon Aerosil Co., Ltd.) 30 having a specific surface area of 200 m ² / g treated with 5 parts of polysiloxane (average polymerization degree 6) and dimethyldichlorosilane treatment 30
Parts until uniform, and the average particle size is 8 μm
150 parts of aluminum hydroxide (manufactured by Showa Denko KK, Hygilite H32), magnesium stearate 0.2
And kneaded at 150 ° C. for 1 hour to prepare a compound.

Then, after cooling to 50 ° C., 1.5 parts of dicumyl peroxide was added to the compound, and the mixture was uniformly dispersed with two rolls, followed by press curing at 170 ° C. for 10 minutes. 2 mm and 1 mm silicone rubber sheets were obtained. Example 2 A silicone rubber sheet was obtained in the same manner as in Example 1, except that 0.5 parts of vinyltriethoxysilane was added together with aluminum hydroxide and kneaded to prepare a compound. Comparative Example 1 A compound was prepared in the same manner as in Example 1 except that the kneading temperature was changed to 30 ° C. to obtain a silicone rubber sheet. Comparative Example 2 A compound was prepared in the same manner as in Example 1 except that magnesium stearate was not blended in the compound and the kneading temperature was 30 ° C. to obtain a silicone rubber sheet. Comparative Example 3 A compound was prepared in the same manner as in Example 1 except that the compound was not mixed with magnesium stearate and the kneading temperature was set to 150 ° C. to obtain a silicone rubber sheet.

The silicone rubber sheets obtained in the above Examples and Comparative Examples were evaluated by the following methods. Table 1 shows the results. Workability: The roll width (mm) that can be rolled with an 8-inch roll was measured. Dielectric breakdown voltage: JIS for 1 mm thick sheet
The dielectric breakdown voltage was measured according to K6911, and then the sheet was immersed in deionized water at room temperature (25 ° C.) for 100 hours, and the dielectric breakdown voltage was measured similarly.

[0038]

[Table 1]

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C08K 5/14 C08K 5/14 5/5415 5/5415 F term (reference) 4F070 AA60 AC15 AC23 AC42 AC52 AC56 AE01 FA01 FA03 FA07 FB06 4J002 CP031 DE147 DJ016 EG038 EG048 EK039 EK049 EK059 EK069 EX039 GQ01

Claims (2)

[Claims] (A) The following average composition formula (1): R _n SiO _{(4-n) / 2} (1) (wherein R is the same or different unsubstituted or substituted monovalent hydrocarbon group) 100 parts by weight of organopolysiloxane (B) 1 to 100 parts by weight of silica fine powder (C) having an average particle diameter of 0.1 to 10 0.0 μm aluminum hydroxide 50 to 300 parts by weight (D) 0.03 to 5 parts by weight of fatty acid metal salt having 10 or more carbon atoms (E) 0.01 to 10 parts by weight of organic peroxide (A), (B), (C), (D)
A method for producing a silicone rubber composition for a high-voltage electrical insulator, comprising kneading the components at a temperature of 80 to 200 ° C. for 30 minutes or more, cooling the mixture to 80 ° C. or less, and then blending the component (E). (A) The following average composition formula (1): R _n SiO _{(4-n) / 2} (1) (wherein R is the same or different unsubstituted or substituted monovalent hydrocarbon group) 100 parts by weight of organopolysiloxane (B) 1 to 100 parts by weight of silica fine powder (C) having an average particle diameter of 0.1 to 10 0.0 μm aluminum hydroxide 50 to 300 parts by weight (D) Fatty acid metal salt having 10 or more carbon atoms 0.03 to 5 parts by weight (E) Organic peroxide 0.01 to 10 parts by weight (F) Organosilane 0 (A), (B), (C),
A silicone rubber composition for a high-voltage electrical insulator, comprising kneading the components (D) and (F) at a temperature of 80 to 200 ° C. for 30 minutes or more, cooling the mixture to 80 ° C. or less, and then mixing the component (E). Method of manufacturing a product.