KR20040072357A - Heat curable silicone rubber compositions having electrical insulation and high strength - Google Patents

Abstract

PURPOSE: Provided is a heat curable silicone rubber composition, which has excellent electric properties and mechanical properties suitable to be used as insulation materials under a high-voltage outdoor environment. CONSTITUTION: The silicone rubber composition comprises: 100 parts by weight of a dimethyl vinyl silicone polymer represented by the formula of R1aSiO(4-a)/2 (wherein R1 is a C1-C10 aliphatic saturated or unsaturated hydrocarbon, and a is an integer of 1.95-2.05); 5-100 parts by weight of silica; 100-200 parts by weight of aluminum hydroxide; 1-10 parts by weight of vinylsilane represented by the formula of R2SiX3 (wherein R2 is a C1-C10 aliphatic saturated or unsaturated hydrocarbon, and X is a hydrolyzable functional group and is selected from a halide, a C1-C6 alkoxy, iminooxy, acryloxy, alkenyloxy, aminoxy, amino and dialkylamino groups); 1-15 parts by weight of a silicone polymer represented by the formula of HO£(CH3)2SiO|xH as a plasticizer (wherein x is an integer of 10-20); 0.01-5 parts by weight of a compound represented by the formula of R3COOM as an internal release agent (wherein R3 is a C1-C17 aliphatic saturated hydrocarbon, and M is magnesium, calcium or zinc); and 0.4-3 parts by weight of an organic peroxide.

Description

Heat curable silicone rubber compositions having electrical insulation and high strength}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosetting silicone rubber composition having excellent electrical insulating properties and mechanical properties. The present invention relates to a thermosetting silicone rubber composition for improving insulation and excellent mechanical properties.

Ceramic materials, which are generally used as electrical insulators (insulators, bushings, etc.), have been mainly used as insulators because of their low cost, good chemical stability, and excellent heat resistance and insulation characteristics. However, it is difficult to manufacture an integral large insulator that has a low impact strength and satisfies mechanical strength, and has disadvantages in that the cost of producing, transporting, storing, and installing such large insulator is high. By enumerating the characteristics of the silicone rubber composition for high-pressure outdoor insulation to replace the ceramic material, the weight is only 20% of the ceramic material, so it is easy to produce, transport, store and install, and flashover due to leakage current due to excellent water repellency characteristics As the phenomenon is reduced, the insulation property is excellent in the ozone environment, the mechanical strength is excellent, and the tensile strength is twice as much as that of the ceramic material and the impact strength is 5 times, which is much more advantageous for transportation and installation.

Various methods are known in connection with the production of such high-pressure outdoor insulation silicone rubber composition, for example, a high-pressure outdoor insulation silicone rubber composition containing a platinum catalyst and a thermosetting resin (USP 3,511,698), a one-component outdoor insulation capable of room temperature curing Silicone rubber composition (USP 4,476,155), a method of improving electrical insulation properties by heating a silicone rubber composition containing aluminum hydroxide (100 ° C. or more, 30 minutes or more) (USP 3,965,065), in addition to methylalkyl in the silicone rubber composition Various methods have been proposed, such as a method (USP 5,519,080) which improves contact angle recovery characteristics over time by adding siloxane oil.

In the case of the high-pressure outdoor insulation silicone rubber composition, metal hydroxides such as aluminum hydroxide and magnesium hydroxide are mainly used as an insulating property improving agent, and when a large amount of such metal hydroxide is added, mechanical properties are markedly deteriorated, and dielectric constant and dielectric loss tangent are increased. There has been a problem that deterioration occurs.

Accordingly, the present inventors have found that in order to solve the above problems, surface treatment of aluminum hydroxide, which is an insulating property improving agent, with a hydrolyzable specific vinylsilane can improve the insulating properties while maintaining the mechanical properties of the silicone rubber composition. The invention has been completed.

Accordingly, an object of the present invention is to provide a thermosetting silicone rubber composition having excellent electrical insulation and mechanical properties.

The present invention is 100 parts by weight of dimethyl vinyl silicone polymer represented by the following formula (1), 5 to 100 parts by weight of silica, 100 to 200 parts by weight of aluminum hydroxide, 1 to 10 parts by weight of vinyl silane represented by the following formula (2), a plasticizer It is characterized by a thermosetting silicone rubber composition containing 1 to 15 parts by weight of the silicone polymer represented by the above, 0.01 to 5 parts by weight of the compound represented by the following formula (4) and 0.4 to 3 parts by weight of the organic peroxide as an internal mold release agent.

R ¹ _a SiO _{(4-a) / 2}

In said Formula (1), R <^1> is a C1-C10 aliphatic saturated hydrocarbon or unsaturated hydrocarbon, and a is an integer of 1.95-2.05.

R ² SiX ₃

In Formula 2, R ² is an aliphatic saturated hydrocarbon or unsaturated hydrocarbon having 1 to 10 carbon atoms, X is a hydrolyzable functional group, a halide group, an alkoxy group having 1 to 6 carbon atoms, an imoxy group, and an acryloxy group. , Alkenyloxy, aminooxy, amino group or dialkylamino group.

HO [(CH ₃ ) ₂ SiO] _x H

In Chemical Formula 3, x is an integer of 10 to 20

R ³ COOM

In Formula 4, R ³ is an aliphatic saturated hydrocarbon having 1 to 17 carbon atoms, and M is magnesium, calcium, or zinc.

Referring to the present invention in more detail as follows.

As the first component constituting the composition of the present invention, 100 parts by weight of the dimethylvinylsilicon polymer represented by the formula (1) is used. The molecular structure of the dimethylvinylsilicon polymer may be linear or branched, and the degree of polymerization is preferably from 100 to 20,000 in terms of mechanical properties and processability. In addition, the dimethylvinylsilicon polymer contains 0.006 to 0.250 mol% of vinyl groups.

Particularly preferably, a mixture of the following ① and ② is used.

(1) The sock end is a linear polymer composed of a trimethylsilyl group or a dimethylvinylsilyl group, and 10,000,000 to 30,000,000 Cp at 25 ° C and a vinylmethylsiloxy group is 0.006 to 0.250 mol%.

②: linear polymer composed of trimethylsilyl group or dimethylvinylsilyl group in the sock end, the viscosity is 35,000,000-120,000,000 Cp at 25 ° C and the vinylmethylsiloxy group is 0.006-0.250 mol%.

As a second component constituting the composition of the present invention, 1-10 parts by weight of the vinylsilane represented by Formula 2 is added to 100 parts by weight of the dimethylvinylsilicon polymer, and the surface of the aluminum hydroxide is used for mechanical properties and insulation. Improve properties. In particular, the composition of the present invention is condensation reaction between the hydroxyl group present in the aluminum hydroxide and the hydrolyzable group of the vinylsilane by using the vinyl silane to place the vinyl group on the surface of the aluminum hydroxide, surface-treated with such a vinyl group Aluminum hydroxide improves mechanical properties and insulation properties by improving compatibility with silicone polymers and participating in radical reactions to form silicone rubber phases.

The silica used as the third component in the composition of the present invention serves as a reinforcing filler, and it is preferable to use a synthetic silica having an amorphous, specific surface area (BET method) of 50 to 600 m ² / g, and plasticity during storage. Silica surface-treated with silane (Silane) and silazane may be used to reduce the extent of the rise. In addition, the silica is preferably contained 5 to 100 parts by weight based on 100 parts by weight of the dimethylvinylsilicon polymer, and if the content is less than 5 parts by weight, there is a problem of weak mechanical properties, if the content exceeds 100 parts by weight There is a difficult problem.

Aluminum hydroxide used as the fourth component in the composition of the present invention is used to improve the insulating properties of the silicone rubber, in particular to improve arc resistance and tracking resistance, and the general formula is Al ₂ O ₃ · 3H ₂ O Or Al (OH) ₃ . Preferably, aluminum hydroxide has a particle diameter of 0.5 to 15 µm and a specific surface area (BET) of 0.5 to 10 m ² / g, and such aluminum hydroxide is 100 to 200 parts by weight based on 100 parts by weight of the dimethylsilicone polymer. If the content is less than 100 parts by weight, the tracking resistance is weak. If the content is more than 200 parts by weight, the mechanical properties are weak and the dielectric properties (dielectric constant and dielectric loss tangent) are high.

The plasticizer used as the fifth component in the composition of the present invention is preferably used 1 to 15 parts by weight of the silicone polymer represented by the formula (3) with respect to 100 parts by weight of the dimethylvinylsilicon polymer, if the amount is 1 part by weight If it is less than the compounding problem is difficult, if it exceeds 15 parts by weight, there is a problem that the roll operation is difficult due to stickiness.

The internal mold release agent used as the sixth component in the composition of the present invention may use a compound represented by the formula (4) consisting of a salt of an organic fatty acid and a metal, and contains 0.01 to 5 parts by weight based on 100 parts by weight of a dimethylvinylsilicone polymer. If the content is less than 0.01 parts by weight and the releasability is poor, it is difficult to remove from the mold and the kneader. If the content exceeds 5 parts by weight, ink printing is difficult on the surface of the molded rubber sheet and the mold is easily contaminated. . Since the melting point of the internal mold release agent varies depending on the metal component, the temperature range of the release effect may be adjusted.

The organic peroxide used as the seventh component in the composition of the present invention serves as a radical reaction initiator and preferably contains 0.4 to 3 parts by weight based on 100 parts by weight of the dimethylvinylsilicon polymer, and if the content is less than 0.4 part by weight. The uncured problem occurs and the rubber after hardening becomes too soft or becomes a cheese state and cannot be used for the intended purpose. If it exceeds 3 parts by weight, the mechanical properties decrease and the amount of hardening agent removed after hardening takes more time. . The organic peroxide may be an organic peroxide capable of generating radicals by pyrolysis at 120 to 200 ° C., such as benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-t-butylhexane peroxide (2,5-Dimethyl-2,5-t-butylhexane Peroxide) may be used.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the Examples.

Examples 1-3 and Comparative Examples 1-3

Next, the thermosetting silicone compound was prepared by the following method using the composition and the content shown in Table 1, and then a molded article (sheet) was manufactured using the same.

First of all, the sock end is a linear polymer composed of trimethylsiloxy group, and the dimethyl vinyl silicone polymer having 20,000,000 Cp at 25 ° C. and the vinyl methylsiloxy group at 0.1 mol% and the sock end are linear polymer composed of vinyldimethylsiloxy group. 100 parts by weight of dimethylvinylsilicon polymer having a vinyl content of 0.11 mol% by mixing 50:50 of dimethylvinylsilicon polymer having 90,000,000 Cp and 0.2 mol% of vinylmethylsiloxy group at 25 ° C. and dry fumed silica (Aerosil) R104, Degussa), aluminum hydroxide (Highlite H42-M, Showa Denko), vinyltriethoxysilane (VTEO, Degussa), plasticizer having a hydroxyl group on the side chain (HEO-7, Kumkang Korea Chemical) Internal release agents (Songstab, Songwon) were evenly dispersed in Kneader (Hermann Linden, LK III 2).

In order to enhance the dispersion effect of silica, the mixture was heated at 160 ° C. for 4 hours and then cooled to room temperature. 0.5 parts by weight of 2,5-dimethyl-2,5-t-butylhexane peroxide (45%) was added to the thermosetting silicone compound thus prepared, which was then uniformly dispersed in a roll for 5 minutes to prepare a preform. Molding was performed at 170 ° C. for 10 minutes using a pressure press to prepare sheets 6 mm, 2 mm and 1 mm thick.

The prepared sheet was subjected to secondary curing for thermal decomposition of excess organic peroxides and stabilization of silicone rubber in a 200 ° C. hot air circulating oven for 4 hours, and then cooled at room temperature for 12 hours or more. It measured according to the specification. The physical properties of plasticity were measured in accordance with JIS K6249 standard. The 1mm thick silicon rubber sheet insulation breakdown strength was measured according to ASTM D149, and the insulation properties (surface resistance and volume resistance) were measured according to ASTM D257. , Dielectric properties (dielectric constant, dielectric loss tangent) were measured according to ASTM D150, and the tracking resistance test of 6mm thick silicone rubber sheet was measured according to IEC60587. Table 1 summarizes the mechanical and electrical properties.

Example Comparative example One 2 3 One 2 3 Ingredient Polymethylvinylsiloxane 100 100 100 100 100 100 Dry fumed silica 45 45 45 45 45 45 Aluminum hydroxide 100 150 200 100 150 200 Vinyltriethoxysilane 3 6 9 0 0 0 Plasticizer 5 5 5 5 5 5 Internal release agent 0.1 0.1 0.1 0.1 0.1 0.1 Hardener 0.5 0.5 0.5 0.5 0.5 0.5 Mechanical property Williams 223 252 278 247 275 293 Hardness (shore A) 67 72 76 66 70 73 Tear strength (kgf / cm) 21 17 14 18 15 13 Tensile strength (kgf / cm ² ) 72 65 57 51 48 44 % Elongation 260 200 160 270 210 180 Player Ratio (%) 3.8 3.6 3.7 3.7 3.6 3.7 importance 1.48 1.52 1.55 1.47 1.52 1.55 Electrical characteristics Dielectric breakdown (kv / mm) 31.7 30.3 29.3 30.6 29.5 28.6 Surface resistance (10 ¹⁶ Ω) 3.5 0.30 0.08 3.2 0.28 0.07 Volume resistance (10 ¹⁶ Ωcm) 6.7 0.71 0.04 5.9 0.65 0.02 Dielectric constant (50 Hz) 2.8 4.0 4.8 3.1 4.3 5.2 Dielectric tangent (50 Hz) 0.004 0.0189 0.0322 0.006 0.0213 0.0375 Tracking resistance (4.5kv) > 290 seconds > 360 seconds > 360 seconds > 270 seconds > 360 seconds > 360 seconds

As shown in Table 1, in the case of the embodiment according to the present invention was confirmed that the mechanical properties and electrical properties are excellent, but in Comparative Examples 1 to 3 outside the scope of the present invention mechanical properties such as tearing and tensile strength And poor electrical properties.

As described above, the silicone rubber composition according to the present invention has excellent mechanical and electrical properties and can be usefully used as a material for high pressure outdoor insulation, that is, an insulator (insulator, bushing, etc.).

Claims (3)

Next, 100 parts by weight of a dimethylvinylsilicon polymer represented by Formula 1, 5 to 100 parts by weight of silica, 100 to 200 parts by weight of aluminum hydroxide, 1 to 10 parts by weight of vinylsilane represented by the following Formula 2, and a plasticizer represented by Formula 3 1 to 15 parts by weight of the silicone polymer, 0.01 to 5 parts by weight of the compound represented by the following formula (4) as an internal mold release agent and 0.4 to 3 parts by weight of the organic peroxide are contained. [Formula 1] R ¹ _a SiO _{(4-a) / 2} In Formula 1, R ¹ is an aliphatic saturated hydrocarbon or unsaturated hydrocarbon having 1 to 10 carbon atoms, and a is an integer of 1.95 to 2.05; [Formula 2] R ² SiX ₃ In Formula 2, R ² is an aliphatic saturated hydrocarbon or unsaturated hydrocarbon having 1 to 10 carbon atoms, X is a hydrolyzable functional group, a halide group, an alkoxy group having 1 to 6 carbon atoms, an imoxy group, and an acryloxy group. , Alkenyloxy, aminooxy, amino group or dialkylamino group; [Formula 3] HO [(CH ₃ ) ₂ SiO] _x H In Chemical Formula 3, x is an integer of 10 to 20; [Formula 4] R ³ COOM In Formula 4, R ³ is an aliphatic saturated hydrocarbon having 1 to 17 carbon atoms, and M is magnesium, calcium, or zinc. The thermosetting silicone rubber composition according to claim 1, wherein the silica is amorphous and has a specific surface area (BET) of 50 to 600 m ² / g. The thermosetting silicone rubber composition according to claim 1, wherein the aluminum hydroxide has a particle diameter of 0.5 to 15 µm and a specific surface area (BET) of 0.5 to 10 m ² / g.