An electrically insulating rubber sheet and a method for producing the same

Abstract

The application relates to the technical field of high polymer materials, and discloses an electrically insulating rubber plate and a preparation method thereof. The electrically insulating rubber plate comprises the following components in parts by mass: 100 parts of methyl vinyl phenyl silicone rubber, 20-25 parts of silane modified talcum powder, 2-5 parts of lubricant, 1-3 parts of activator, 0.5-1 part of antioxidant, 8-10 parts of voltage stabilizer, 1-2 parts of vulcanizing agent, and 0.5-1.5 parts of accelerator; and the talcum powder in the silane modified talcum powder comprises one or both of silica coated talcum powder and tannic acid coated talcum powder. Through the technical scheme, the dispersibility of the talcum powder in the matrix and the compatibility of the talcum powder with the matrix are improved, and the problems of poor flame retardance and low mechanical strength of the electrically insulating rubber plate are solved.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to an electrically insulating rubber sheet and its preparation method. Background Technology

[0002] Electrically insulating rubber sheets, as auxiliary protective equipment for electrical devices, are widely used in large, medium, and small power distribution rooms across various industries. Their quality and performance directly affect personal safety. With the continuous development of science and technology, users are constantly raising their performance requirements for these products, especially in terms of flame retardancy and mechanical strength.

[0003] The insulation properties of electrically insulating rubber sheets depend on the type of rubber and the electrical properties of the fillers. Ethylene propylene rubber, butyl rubber, and silicone rubber all possess good insulation properties and are commonly used in the manufacture of insulating products. Among them, silicone rubber exhibits the best high-temperature characteristics, insulation resistance, and dielectric properties, making it a frequent choice for manufacturing electrically insulating rubber sheets. As for fillers, talc is often used as a filler in electrically insulating rubber sheets because it can increase the material's resistance. However, the poor dispersibility and compatibility of talc in the matrix limit the flame retardancy and mechanical strength of the electrically insulating rubber sheets. Summary of the Invention

[0004] This invention proposes an electrically insulating rubber sheet and its preparation method, which solves the problems in related technologies where the talc powder has poor dispersibility and poor compatibility with the matrix, resulting in poor flame retardancy and low mechanical strength of the electrically insulating rubber sheet.

[0005] The technical solution of the present invention is as follows:

[0006] An electrically insulating rubber sheet comprises the following components in parts by weight: 100 parts methyl vinyl phenyl silicone rubber, 20-25 parts silane-modified talc, 2-5 parts lubricant, 1-3 parts activator, 0.5-1 part antioxidant, 8-10 parts voltage stabilizer, 1-2 parts vulcanizing agent, and 0.5-1.5 parts accelerator. The talc in the silane-modified talc includes one or both of silica-coated talc and tannic acid-coated talc.

[0007] Compared to other types of silicone rubber, methyl vinyl phenyl silicone rubber introduces a small amount of bulky phenyl groups into its side chains, disrupting the regularity of the macromolecular chain and hindering the crystallization of ordinary silicone rubber molecules at low temperatures. This results in excellent low-temperature resistance while retaining the advantages of methyl vinyl silicone rubber. Therefore, this invention uses methyl vinyl phenyl silicone rubber as the matrix material for electrically insulating rubber sheets.

[0008] In this invention, the addition of a lubricant reduces friction between the polymer and the processing equipment, as well as internal friction between polymer molecular chains, increases polymer flowability, and ensures the smoothness of the electrically insulating rubber sheet. The lubricant can be any one or more conventional lubricants in the art, such as natural paraffin wax, microcrystalline wax, polyethylene wax, etc., preferably microcrystalline wax.

[0009] In this invention, the addition of an activator is used to accelerate and fully utilize the activating and promoting effect of the accelerator, thereby reducing the amount of accelerator used and shortening the vulcanization time. The activator can be any one or more conventional activators in the art, such as zinc oxide, magnesium oxide, stearic acid, etc., preferably stearic acid.

[0010] In this invention, the addition of an antioxidant is used to prevent the oxidation of methyl vinyl phenyl silicone rubber. The antioxidant can be any one or more conventional antioxidants in the art, such as phenolic antioxidants, amine antioxidants, etc., preferably antioxidant 1010.

[0011] In this invention, the addition of a voltage stabilizer is used to absorb high-energy electrons in the polymer, reduce electron injection under a strong electric field, and prevent dendrite breakdown. The voltage stabilizer can be any one or more conventional voltage stabilizers in the art, such as aminoquinoline, N,N'-diphenyl-p-phenylenediamine, dibenzoyl-p-benzoquinone dioxime, etc., preferably N,N'-diphenyl-p-phenylenediamine.

[0012] In this invention, the addition of a vulcanizing agent causes the linear molecules of the raw rubber to cross-link and form a three-dimensional network structure, giving the raw rubber a certain strength and toughness. The vulcanizing agent can be any one or more conventional vulcanizing agents in the art, such as sulfur, organic peroxides, etc., preferably the organic peroxide TBPB.

[0013] In this invention, the addition of an accelerator is used to shorten the vulcanization time and lower the vulcanization temperature. The accelerator can be any one or more conventional accelerators in the art, such as accelerator D, accelerator DM, accelerator TMTD, etc., preferably accelerator D and accelerator DM in a mass ratio of 3:1.

[0014] As a further technical solution, the raw materials for the silica-coated talc powder include talc powder and tetraethyl orthosilicate in a mass-to-volume ratio of 1g:0.5~1mL.

[0015] As a further technical solution, the method for preparing silica-coated talc includes the following steps:

[0016] A1. Disperse talc powder ultrasonically in a mixed solution of water and ethanol to obtain a suspension;

[0017] A2. After adjusting the pH of the suspension to alkaline, add tetraethyl orthosilicate while stirring, wash, filter, and dry to obtain silica-coated talc powder.

[0018] As a further technical solution, the raw materials for the tannic acid-coated talc powder include talc powder and tannic acid in a mass ratio of 1:0.4~0.6.

[0019] As a further technical solution, the preparation method of the tannic acid-coated talc powder includes the following steps:

[0020] B1. Disperse talc powder in water to obtain a mixture;

[0021] B2. After adjusting the pH of the mixture to alkaline, add tannic acid and mix. Wash the product with water until neutral, and dry to obtain tannic acid-coated talc powder.

[0022] As a further technical solution, the silane in the silane-modified talc powder includes one or two of vinylsilane and phenylsilane; the raw materials of the silane-modified talc powder include talc powder and silane in a mass ratio of 100:3~5.

[0023] As a further technical solution, the preparation method of the silane-modified talc powder includes the following steps:

[0024] C1. After mixing water and anhydrous ethanol, a mixture is obtained;

[0025] C2. Add silane coupling agent and talc to the mixture in sequence for modification, separate the products, wash and dry to obtain silane-modified talc.

[0026] As a further technical solution, the silane-modified talc powder includes phenylsilane-modified pretreated talc powder, wherein the pretreated talc powder in the phenylsilane-modified pretreated talc powder is silica-coated talc powder; the silane-modified talc powder also includes vinylsilane-modified pretreated talc powder, wherein the pretreated talc powder in the vinylsilane-modified pretreated talc powder is tannic acid-coated talc powder.

[0027] In this invention, the mechanical strength of the electrically insulating rubber sheet is further improved by using silica-coated talc and tannic acid-coated talc in combination. At the same time, the silica-coated talc is modified with phenylsilane, and the tannic acid-coated talc is modified with vinylsilane.

[0028] As a further technical solution, the mass ratio of the phenylsilane-modified pretreated talc powder to the vinylsilane-modified pretreated talc powder is 2~4:1.

[0029] The present invention also proposes a method for preparing an electrically insulating rubber sheet, which includes the following steps: mixing the components other than the vulcanizing agent, adding the vulcanizing agent and continuing to mix and vulcanize to obtain the electrically insulating rubber sheet.

[0030] The working principle and beneficial effects of this invention are as follows:

[0031] The silane-modified talc powder of this invention uses one or both of the following: talc powder coated with silica or talc powder coated with tannic acid. This improves the flame retardancy and mechanical strength of the electrical insulating rubber sheet. The reason is that after talc powder is coated with silica or tannic acid, its surface has a large number of active hydroxyl groups. When further modified with silane, the modification effect of the silane is improved, thereby increasing the dispersibility and compatibility of the talc powder in the matrix, achieving the effect of improving the flame retardancy and mechanical strength of the electrical insulating rubber sheet. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0033] In the following embodiments and comparative examples:

[0034] Methyl vinyl phenyl silicone rubber: vinyl content 0.23% and phenyl content 25%, purchased from Ningbo Daoruo Organosilicon Co., Ltd.

[0035] Talc powder: 1250 mesh.

[0036] Example 1

[0037] (1) Disperse 10g of talc powder in 2L of a mixed solution of deionized water and ethanol with a volume ratio of 1:1. After sonication for 2h, adjust the pH value to 9 with 25% ammonia water. Add 5mL of tetraethyl orthosilicate while stirring. Tetraethyl orthosilicate hydrolyzes under alkaline conditions to generate silica, which coats the surface of talc powder. Wash the product with ethanol and deionized water, filter, and dry to obtain silica-coated talc powder.

[0038] (2) Mix 20g of water and 180g of anhydrous ethanol, stir for 15min and continue ultrasonic mixing for 1h, add 0.3g of phenyltriethoxysilane and stir for 10min, then add 10g of silica-coated talc powder, heat to 65℃ and continue stirring for 5h, centrifuge to separate the product, wash the product with ethanol and deionized water, and dry to obtain silane-modified talc powder;

[0039] (3) Mix 100 parts of methyl vinyl phenyl silicone rubber, 20 parts of silane-modified talc, 2 parts of microcrystalline wax, 1 part of stearic acid, 0.5 parts of antioxidant 1010, 8 parts of N,N'-diphenyl-p-phenylenediamine, 1.125 parts of accelerator D and 0.375 parts of accelerator DM, then knead the mixture, add 1 part of tert-butyl peroxide and knead again, and then vulcanize at 150°C to obtain an electrically insulating rubber sheet.

[0040] Example 2

[0041] (1) Disperse 10g of talc powder in 2L of a mixed solution of deionized water and ethanol with a volume ratio of 1:1. After sonication for 2h, adjust the pH value to 9 with 25% ammonia water. Add 10mL of tetraethyl orthosilicate while stirring. Tetraethyl orthosilicate hydrolyzes under alkaline conditions to generate silica, which coats the surface of talc powder. Wash the product with ethanol and deionized water, filter, and dry to obtain silica-coated talc powder.

[0042] (2) Mix 20g of water and 180g of anhydrous ethanol, stir for 10min and continue ultrasonic mixing for 1h, add 0.5g of vinyltriethoxysilane and stir for 15min, then add 10g of silica-coated talc powder, heat to 60℃ and continue stirring for 5h, centrifuge to separate the product, wash the product with ethanol and deionized water, and dry to obtain silane-modified talc powder;

[0043] (3) Mix 100 parts of methyl vinyl phenyl silicone rubber, 25 parts of silane-modified talc, 5 parts of microcrystalline wax, 3 parts of stearic acid, 1 part of antioxidant 1010, 10 parts of N,N'-diphenyl-p-phenylenediamine, 0.375 parts of accelerator D and 0.125 parts of accelerator DM, then knead the mixture, add 2 parts of tert-butyl peroxide and knead again, and vulcanize at 150°C to obtain an electrically insulating rubber sheet.

[0044] Example 3

[0045] (1) Disperse 10g of talc powder in 1.5L of deionized water, stir for 10min and sonicate for 2.5h, add sodium bicarbonate to adjust the pH value to 8.5, add 5g of tannic acid and stir for 10h, wash the product with deionized water until neutral, and dry to obtain tannic acid coated talc powder.

[0046] (2) Mix 20g water and 180g anhydrous ethanol, stir for 15min and continue ultrasonic mixing for 1h, add 0.3g phenyltriethoxysilane and stir for 10min, then add 10g tannic acid-coated talc powder, heat to 65℃ and continue stirring for 5h, centrifuge to separate the product, wash the product with ethanol and deionized water, and dry to obtain silane-modified talc powder;

[0047] (3) Mix 100 parts of methyl vinyl phenyl silicone rubber, 20 parts of silane-modified talc, 2 parts of microcrystalline wax, 1 part of stearic acid, 0.5 parts of antioxidant 1010, 8 parts of N,N'-diphenyl-p-phenylenediamine, 1.125 parts of accelerator D and 0.375 parts of accelerator DM, then knead the mixture, add 1 part of tert-butyl peroxide and knead again, and then vulcanize at 150°C to obtain an electrically insulating rubber sheet.

[0048] Example 4

[0049] The only difference from Example 1 is:

[0050] Replace phenyltriethoxysilane with an equal amount of vinyltriethoxysilane.

[0051] Example 5

[0052] The only difference from Example 3 is that:

[0053] Replace phenyltriethoxysilane with an equal amount of vinyltriethoxysilane.

[0054] Example 6

[0055] (1) Disperse 10g of talc powder in 2L of a mixed solution of deionized water and ethanol with a volume ratio of 1:1. After sonication for 2h, adjust the pH value to 9 with 25% ammonia water. Add 5mL of tetraethyl orthosilicate while stirring. Tetraethyl orthosilicate hydrolyzes under alkaline conditions to generate silica, which coats the surface of talc powder. Wash the product with ethanol and deionized water, filter, and dry to obtain silica-coated talc powder.

[0056] (2) Mix 20g of water and 180g of anhydrous ethanol, stir for 15min and continue ultrasonic mixing for 1h, add 0.3g of phenyltriethoxysilane and stir for 10min, then add 10g of silica-coated talc powder, heat to 65℃ and continue stirring for 5h, centrifuge to separate the product, wash the product with ethanol and deionized water, and dry to obtain phenylsilane-modified talc powder;

[0057] (3) Mix 20g of water and 180g of anhydrous ethanol, stir for 15min and continue ultrasonic mixing for 1h, add 0.3g of vinyltriethoxysilane and stir for 10min, then add 10g of silica-coated talc powder, heat to 65℃ and continue stirring for 5h, centrifuge to separate the product, wash the product with ethanol and deionized water, and dry to obtain vinylsilane-modified talc powder;

[0058] (4) Mix 100 parts of methyl vinyl phenyl silicone rubber, 20 parts of silane-modified talc (composed of phenyl silane-modified talc and vinyl silane-modified talc in a mass ratio of 3:1), 2 parts of microcrystalline wax, 1 part of stearic acid, 0.5 parts of antioxidant 1010, 8 parts of N,N'-diphenyl-p-phenylenediamine, 1.125 parts of accelerator D and 0.375 parts of accelerator DM, and then knead the mixture. After kneading, add 1 part of tert-butyl peroxide and knead the mixture. Finally, vulcanize the mixture at 150°C to obtain an electrically insulating rubber sheet.

[0059] Example 7

[0060] (1) Disperse 10g of talc powder in 1.5L of deionized water, stir for 10min and sonicate for 2.5h, add sodium bicarbonate to adjust the pH value to 8.5, add 5g of tannic acid and stir for 10h, wash the product with deionized water until neutral, and dry to obtain tannic acid coated talc powder.

[0061] (2) Mix 20g of water and 180g of anhydrous ethanol, stir for 15min and continue ultrasonic mixing for 1h, add 0.3g of phenyltriethoxysilane and stir for 10min, then add 10g of tannic acid-coated talc powder, heat to 65℃ and continue stirring for 5h, centrifuge to separate the product, wash the product with ethanol and deionized water, and dry to obtain phenylsilane-modified talc powder;

[0062] (3) Mix 20g of water and 180g of anhydrous ethanol, stir for 15min and continue ultrasonic mixing for 1h, add 0.3g of vinyltriethoxysilane and stir for 10min, then add 10g of tannic acid-coated talc powder, heat to 65℃ and continue stirring for 5h, centrifuge to separate the product, wash the product with ethanol and deionized water, and dry to obtain vinylsilane-modified talc powder;

[0063] (4) Mix 100 parts of methyl vinyl phenyl silicone rubber, 20 parts of silane-modified talc (composed of phenyl silane-modified talc and vinyl silane-modified talc in a mass ratio of 3:1), 2 parts of microcrystalline wax, 1 part of stearic acid, 0.5 parts of antioxidant 1010, 8 parts of N,N'-diphenyl-p-phenylenediamine, 1.125 parts of accelerator D and 0.375 parts of accelerator DM, and then knead the mixture. After kneading, add 1 part of tert-butyl peroxide and knead the mixture. Finally, vulcanize the mixture at 150°C to obtain an electrically insulating rubber sheet.

[0064] Example 8

[0065] (1) Disperse 10g of talc powder in 1.5L of deionized water, stir for 10min and sonicate for 2.5h, add sodium bicarbonate to adjust the pH value to 8.5, add 5g of tannic acid and stir for 10h, wash the product with deionized water until neutral, and dry to obtain tannic acid coated talc powder.

[0066] (2) Mix 20g of water and 180g of anhydrous ethanol, stir for 15min and continue ultrasonic mixing for 1h, add 0.3g of vinyltriethoxysilane and stir for 10min, then add 10g of tannic acid-coated talc powder, heat to 65℃ and continue stirring for 5h, centrifuge to separate the product, wash the product with ethanol and deionized water, and dry to obtain vinylsilane-modified talc powder;

[0067] (3) Disperse 10g of talc powder in 2L of a mixed solution of deionized water and ethanol with a volume ratio of 1:1. After sonication for 2h, adjust the pH value to 9 with 25% ammonia water. Add 5mL of tetraethyl orthosilicate while stirring. Tetraethyl orthosilicate hydrolyzes under alkaline conditions to generate silica, which coats the surface of talc powder. Wash the product with ethanol and deionized water, filter, and dry to obtain silica-coated talc powder.

[0068] (4) Mix 20g of water and 180g of anhydrous ethanol, stir for 15min and continue ultrasonic mixing for 1h, add 0.3g of phenyltriethoxysilane and stir for 10min, then add 10g of silica-coated talc powder, heat to 65℃ and continue stirring for 5h, centrifuge to separate the product, wash the product with ethanol and deionized water, and dry to obtain phenylsilane-modified talc powder;

[0069] (5) Mix 100 parts of methyl vinyl phenyl silicone rubber, 20 parts of silane-modified talc (composed of phenyl silane-modified talc and vinyl silane-modified talc in a mass ratio of 3:1), 2 parts of microcrystalline wax, 1 part of stearic acid, 0.5 parts of antioxidant 1010, 8 parts of N,N'-diphenyl-p-phenylenediamine, 1.125 parts of accelerator D and 0.375 parts of accelerator DM, and then knead the mixture. After kneading, add 1 part of tert-butyl peroxide and knead the mixture. Finally, vulcanize the mixture at 150°C to obtain an electrically insulating rubber sheet.

[0070] Example 9

[0071] (1) Disperse 10g of talc powder in 1.5L of deionized water, stir for 10min and sonicate for 2.5h, add sodium bicarbonate to adjust the pH value to 8.5, add 5g of tannic acid and stir for 10h, wash the product with deionized water until neutral, and dry to obtain tannic acid coated talc powder.

[0072] (2) Mix 20g of water and 180g of anhydrous ethanol, stir for 15min and continue ultrasonic mixing for 1h, add 0.3g of phenyltriethoxysilane and stir for 10min, then add 10g of tannic acid-coated talc powder, heat to 65℃ and continue stirring for 5h, centrifuge to separate the product, wash the product with ethanol and deionized water, and dry to obtain phenylsilane-modified talc powder;

[0073] (3) Disperse 10g of talc powder in 2L of a mixed solution of deionized water and ethanol with a volume ratio of 1:1. After sonication for 2h, adjust the pH value to 9 with 25% ammonia water. Add 5mL of tetraethyl orthosilicate while stirring. Tetraethyl orthosilicate hydrolyzes under alkaline conditions to generate silica, which coats the surface of talc powder. Wash the product with ethanol and deionized water, filter, and dry to obtain silica-coated talc powder.

[0074] (4) Mix 20g of water and 180g of anhydrous ethanol, stir for 15min and continue ultrasonic mixing for 1h, add 0.3g of vinyltriethoxysilane and stir for 10min, then add 10g of silica-coated talc powder, heat to 65℃ and continue stirring for 5h, centrifuge to separate the product, wash the product with ethanol and deionized water, and dry to obtain vinylsilane-modified talc powder;

[0075] (5) Mix 100 parts of methyl vinyl phenyl silicone rubber, 20 parts of silane-modified talc (composed of phenyl silane-modified talc and vinyl silane-modified talc in a mass ratio of 3:1), 2 parts of microcrystalline wax, 1 part of stearic acid, 0.5 parts of antioxidant 1010, 8 parts of N,N'-diphenyl-p-phenylenediamine, 1.125 parts of accelerator D and 0.375 parts of accelerator DM, and then knead the mixture. After kneading, add 1 part of tert-butyl peroxide and knead the mixture. Finally, vulcanize the mixture at 150°C to obtain an electrically insulating rubber sheet.

[0076] Comparative Example 1

[0077] (1) Mix 20g water and 180g anhydrous ethanol, stir for 15min and continue ultrasonic mixing for 1h, add 0.3g phenyltriethoxysilane and stir for 10min, then add 10g talc powder, heat to 65℃ and continue stirring for 5h, centrifuge to separate the product, wash the product with ethanol and deionized water, and dry to obtain silane modified talc powder.

[0078] (2) Mix 100 parts of methyl vinyl phenyl silicone rubber, 20 parts of silane-modified talc, 2 parts of microcrystalline wax, 1 part of stearic acid, 0.5 parts of antioxidant 1010, 8 parts of N,N'-diphenyl-p-phenylenediamine, 1.125 parts of accelerator D and 0.375 parts of accelerator DM, then knead the mixture, add 1 part of tert-butyl peroxide and knead again, and vulcanize at 150°C to obtain an electrically insulating rubber sheet.

[0079] Performance testing:

[0080] Flame retardancy, electrical properties and tensile strength were tested according to the method in HG / T 2949-2023 "Electrically Insulating Rubber Sheet". Type 1 dumbbell-shaped specimens with a thickness of 3 mm and a tensile rate of 50 mm / min were used. The test results are recorded in Tables 1 and 2.

[0081] Table 1. Test results of flame retardancy and tensile strength of electrically insulating rubber sheets

[0082]

[0083] As shown in Table 1, the electrical insulating rubber sheet provided by this invention achieves a vertical flammability rating of FV-0 and a tensile strength of over 5.7 MPa, exhibiting good flame retardancy and mechanical strength, meeting the requirements of HG / T 2949-2023 "Electrically Insulating Rubber Sheets". Furthermore, the electrical insulating rubber sheets obtained in Examples 1-9 show better vertical flammability ratings and tensile strengths than Comparative Example 1, indicating that using one or both of silica-coated talc and tannic acid-coated talc in the silane-modified talc improves the flame retardancy and mechanical strength of the electrical insulating rubber sheet.

[0084] Table 2. Electrical performance test results of electrically insulating rubber sheets (AC, continuous voltage boosting method)

[0085]

[0086] As can be seen from Table 2, the electrically insulating rubber sheet provided by the present invention has good electrical properties and meets the requirements of HG / T 2949-2023 "Electrically Insulating Rubber Sheet".

[0087] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An electrically insulating rubber sheet, characterized in that, The product comprises the following components in parts by weight: 100 parts methyl vinyl phenyl silicone rubber, 20-25 parts silane-modified talc, 2-5 parts lubricant, 1-3 parts activator, 0.5-1 part antioxidant, 8-10 parts voltage stabilizer, 1-2 parts vulcanizing agent, and 0.5-1.5 parts accelerator. The talc in the silane-modified talc includes one or both of silica-coated talc and tannic acid-coated talc. The raw material for the silica-coated talc includes talc and tetraethyl orthosilicate in a mass-to-volume ratio of 1 g:0.5-1 mL. The method for preparing silica-coated talc includes the following steps: A1. Disperse talc powder ultrasonically in a mixed solution of water and ethanol to obtain a suspension; A2. After adjusting the pH of the suspension to alkaline, add tetraethyl orthosilicate while stirring, wash, filter, and dry to obtain silica-coated talc powder. The raw materials for the tannic acid-coated talc powder include talc powder and tannic acid in a mass ratio of 1:0.4~0.6; The method for preparing tannic acid-coated talc includes the following steps: B1. Disperse talc powder in water to obtain a mixture; B2. After adjusting the pH of the mixture to alkaline, add tannic acid and mix. Wash the product with water until neutral and dry to obtain tannic acid-coated talc powder. The silane in the silane-modified talc powder includes one or both of vinylsilane and phenylsilane; the raw materials of the silane-modified talc powder include talc powder and silane in a mass ratio of 100:3~5. The preparation method of the silane-modified talc powder includes the following steps: C1. After mixing water and anhydrous ethanol, a mixture is obtained; C2. Silane and talc are added sequentially to the mixture for modification. The products are separated, washed, and dried to obtain silane-modified talc.

2. The electrically insulating rubber sheet according to claim 1, characterized in that, The silane-modified talc powder includes phenylsilane-modified pretreated talc powder, wherein the pretreated talc powder in the phenylsilane-modified pretreated talc powder is silica-coated talc powder; the silane-modified talc powder also includes vinylsilane-modified pretreated talc powder, wherein the pretreated talc powder in the vinylsilane-modified pretreated talc powder is tannic acid-coated talc powder.

3. The electrically insulating rubber sheet according to claim 2, characterized in that, The mass ratio of the phenylsilane-modified pretreated talc to the vinylsilane-modified pretreated talc is 2~4:

1.

4. A method for preparing an electrically insulating rubber sheet, used to prepare the electrically insulating rubber sheet according to any one of claims 1 to 3, characterized in that, Includes the following steps: After mixing the remaining components except for the vulcanizing agent, the vulcanizing agent is added and the mixing and vulcanization are continued to obtain an electrically insulating rubber sheet.

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