Silicone rubber for shielding high-voltage wire sheath for automobile as well as preparation method and application of silicone rubber

Abstract

The invention relates to silicone rubber for a shielding high-voltage wire sheath for an automobile as well as a preparation method and application of the silicone rubber. The silicone rubber comprises the following raw materials in parts by weight: 100 parts of methyl vinyl silicone rubber; 16-20 parts of methyl phenyl vinyl silicone rubber; 5 to 10 parts of double-end vinyl polydimethylsiloxane; 0.5-2 parts of a vulcanizing agent; 8 to 12 parts of first double amino-terminated polydimethylsiloxane; 3 to 6 parts of a reaction product of pentaerythritol tetraglycidyl ether and second double amino-terminated polydimethylsiloxane; 2-4 parts of phosphorus-containing epoxy resin; 20 to 28 parts of modified mica powder; and 4-10 parts of modified nano silicon dioxide. The silicone rubber can keep good liquid resistance under the conditions of long-term high and low temperature change and vibration, and has good flame retardance, insulativity and mechanical properties.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of automobile wire sheath, in particular to a silicone rubber for shielding high-voltage wire sheath of automobile and a preparation method and application thereof. BACKGROUND

[0002] The shielding high-voltage wire for automobile is a core wire assembly responsible for high-voltage power transmission in the high-voltage electrical system of automobile, and its core feature is to add an electromagnetic shielding structure on the basis of traditional high-voltage wire, which can not only stably transmit high-voltage power, but also solve the problem of electromagnetic interference in the process of high-voltage power transmission. It is a key component of new energy vehicles and part of the high-voltage system of traditional fuel vehicles.

[0003] The installation environment of the shielding high-voltage wire for automobile can be the engine compartment or chassis, and various liquids may be present in the vehicle throughout its life cycle, such as engine oil, gasoline, diesel, cooling fluid that may leak from the engine cooling system, windshield washer that may splash from the pipeline, glass cleaning fluid used during vehicle cleaning, and salt water splashed from the road surface. At the same time, the shielding high-voltage wire for automobile also needs to withstand persistent vibration, including periodic high-frequency vibration generated during engine operation and jolt vibration caused by uneven road surface. In addition, the shielding high-voltage wire for automobile also needs to withstand high and low temperature changes. In high-latitude cold regions, the high-voltage wire will be completely in a low-temperature environment after the vehicle is parked, and the temperature in the engine compartment, chassis, battery compartment, etc. during vehicle driving may rise above 100℃.

[0004] The sheath of the shielding high-voltage wire for automobile is generally located at the outermost layer of the high-voltage wire and is used to directly contact with the outside world, usually having the functions of mechanical protection, auxiliary insulation and flame retardation. The material of the sheath is generally cross-linked polyethylene, polyurethane or silicone rubber, among which silicone rubber has good high-temperature resistance, low-temperature resistance, insulation performance and anti-aging performance. However, the existing silicone rubber has weak intermolecular force and large gap between molecular chains due to the main Si-O bond in the molecular chain, and its liquid resistance needs to be improved. Especially under the conditions of long-term high and low temperature changes and vibration, the silicone rubber sheath needs to maintain long-term liquid resistance to prevent safety hazards such as high-voltage leakage and electromagnetic interference out of control. The liquid resistance stability of the existing silicone rubber under the conditions of long-term high and low temperature changes and vibration needs to be improved. SUMMARY

[0005] In view of the deficiencies of the prior art, the first object of the present application is to provide a silicone rubber for shielding high-voltage wire sheath of automobile, which can maintain good liquid resistance under the conditions of long-term high and low temperature changes and vibration, and has good flame retardance, insulation and mechanical properties.

[0006] The second object of the present application is to provide a preparation method of the silicone rubber.

[0007] A third object of the present application is to provide the use of the silicone rubber in a high-voltage wire sheath for automobiles.

[0008] To achieve the first object of the present application, the present application provides a silicone rubber for a high-voltage wire sheath for automobiles, which comprises the following raw materials by weight: methyl vinyl silicone rubber 100 parts; methyl phenyl vinyl silicone rubber 16-20 parts; double-end vinyl polydimethylsiloxane 5-10 parts; vulcanizing agent 0.5-2 parts; first double-end amino polydimethylsiloxane 8-12 parts; reaction product of pentaerythritol tetraglycidyl ether and second double-end amino polydimethylsiloxane 3-6 parts; phosphorus-containing epoxy resin 2-4 parts; modified mica powder 20-28 parts; modified nano-silicon dioxide 4-10 parts; wherein the modified mica powder is prepared by modifying mica powder with a vinyl siloxane coupling agent and an epoxy siloxane coupling agent, and then reacting with a third double-end amino polydimethylsiloxane; and the modified nano-silicon dioxide is prepared by modifying nano-silicon dioxide with an epoxy siloxane coupling agent.

[0009] In some embodiments of the present application, the raw materials are as follows by weight: methyl vinyl silicone rubber 100 parts; methyl phenyl vinyl silicone rubber 18-20 parts; double-end vinyl polydimethylsiloxane 7-10 parts; vulcanizing agent 1-2 parts; first double-end amino polydimethylsiloxane 10-12 parts; reaction product of pentaerythritol tetraglycidyl ether and second double-end amino polydimethylsiloxane 3-5 parts; phosphorus-containing epoxy resin 3-4 parts; modified mica powder 20-23 parts; modified nano-silicon dioxide 4-8 parts.

[0010] In some embodiments of the present application, in the reaction product of pentaerythritol tetraglycidyl ether and second double-end amino polydimethylsiloxane, the molar ratio of pentaerythritol tetraglycidyl ether to second double-end amino polydimethylsiloxane is (2-3):1.

[0011] In some embodiments of the present application, the weight average molecular weight of the double-end vinyl polydimethylsiloxane is 20000-22000.

[0012] In some embodiments of the present application, the weight average molecular weight of the first double-end amino polydimethylsiloxane is 2500-3500; the weight average molecular weight of the second double-end amino polydimethylsiloxane is 800-1500; and the weight average molecular weight of the third double-end amino polydimethylsiloxane is 800-1500.

[0013] In some embodiments of the present application, the phosphorus content in the phosphorus-containing epoxy resin is 3-5 wt%.

[0014] In some embodiments of the present application, the mass ratio of the mica powder, the vinyl siloxane coupling agent and the epoxy siloxane coupling agent in the modified mica powder is 100:(0.5-1):(0.5-1), and the molar ratio of the epoxy siloxane coupling agent and the third bis-amino polydimethylsiloxane is 1:1.

[0015] In some embodiments of the present application, the particle size of the mica powder is 600-1200 mesh.

[0016] In some embodiments of the present application, the mass ratio of the nano-silica and the epoxy siloxane coupling agent in the modified nano-silica is 100:(0.5-1).

[0017] In some embodiments of the present application, the particle size of the nano-silica is 20-50 nm.

[0018] To achieve the second object of the present application, the present application further provides a preparation method of the silicone rubber for the shielding high-voltage wire sheath of the automobile according to any one of the above-mentioned schemes, which comprises the following steps: mixing the methyl vinyl silicone rubber and the methyl phenyl vinyl silicone rubber in an internal mixer, sequentially adding the bis-vinyl polydimethylsiloxane, the first bis-amino polydimethylsiloxane, the modified mica powder and the modified nano-silica, and rolling until completely dispersed, then adding the reaction product of the pentaerythritol tetraglycidyl ether and the second bis-amino polydimethylsiloxane and the phosphorus-containing epoxy resin, rolling for 2-3 minutes, finally adding a vulcanizing machine, rolling for 1-2 minutes, and obtaining the silicone rubber.

[0019] In some embodiments of the present application, the temperature of the internal mixer is controlled at 50-65℃.

[0020] In some embodiments of the present application, the preparation method of the reaction product of the pentaerythritol tetraglycidyl ether and the second bis-amino polydimethylsiloxane comprises heating the pentaerythritol tetraglycidyl ether and the second bis-amino polydimethylsiloxane in toluene to react, and obtaining the reaction product after removing the solvent.

[0021] In some embodiments of the present application, the preparation method of the modified mica powder comprises ultrasonic dispersion of the mica powder in an ethanol or ethyl acetate solution in which the vinyl siloxane coupling agent and the epoxy siloxane coupling agent are dissolved, stirring and dispersing, then removing the solvent, and then dispersing the obtained product in a toluene solution containing the third bis-amino polydimethylsiloxane, heating to react, filtering, washing and drying to obtain the modified mica powder.

[0022] In some embodiments of the present application, the preparation method of the modified nano-silica comprises ultrasonic dispersion of the nano-silica in an ethanol or ethyl acetate solution in which the epoxy siloxane coupling agent is dissolved, stirring and dispersing, then removing the solvent and drying to obtain the modified nano-silica.

[0023] To achieve the third objective of this invention, this invention provides a shielded high-voltage wire for automobiles, comprising a conductor, an insulation layer, a shielding layer, and a sheath arranged sequentially from the inside out, wherein the sheath is silicone rubber as described in any of the above embodiments for shielded high-voltage wire sheaths for automobiles.

[0024] Compared with the prior art, the present invention can achieve the following beneficial effects: This invention provides a silicone rubber for shielding high-voltage lines used in automobiles. This silicone rubber utilizes two crosslinking systems: vinyl silicone rubber crosslinking and epoxy resin crosslinking with amino-terminated polysiloxanes. This improves the crosslinking density and compactness of the silicone rubber. Furthermore, modified mica powder enhances the liquid shielding properties of the silicone rubber, and modified nano-silica improves its mechanical properties. The synergistic effect of these components allows the silicone rubber to maintain good resistance to various liquids even after long-term exposure to high and low temperatures and vibrations, while also retaining good flame retardancy, insulation, and mechanical properties. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of an embodiment of the shielded high-voltage wire for automobiles of the present invention. In the figure, 1-sheath, 2-wrapping layer, 3-conductor, 4-insulation layer, and 5-braided layer.

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Detailed Implementation

[0027] Embodiments of the present invention provide a silicone rubber for use as a sheathing material for shielded high-voltage lines in automobiles. This silicone rubber can be used as a sheathing material for shielded high-voltage lines in automobiles, providing protection for the shielded high-voltage lines. Figure 1 As shown, a shielded high-voltage wire for automobiles may include, for example, a conductor 3, an insulation layer 4, a shielding layer, and a sheath 1 arranged sequentially from the inside out. The conductor 3 may be formed by twisting multiple conductive wires together. The insulation layer 4 may be made of insulating plastic or rubber. The shielding layer, covering the outside of the insulation layer, may include a braided layer 5 and a wrapping tape layer 2 to improve shielding efficiency. The sheath 1 may be made of silicone rubber as described in this embodiment, ensuring that the sheath 1 maintains good resistance to various liquids commonly encountered in automotive applications after enduring long-term high and low temperature changes and vibrations, while also maintaining good flame retardancy, insulation, and mechanical properties, thus providing better protection for the shielded high-voltage wire for automobiles. In some examples, the insulation layer 4 may also be made of silicone rubber as described in this embodiment, meaning both the insulation layer 4 and the sheath 1 are made of silicone rubber as described in this embodiment. Of course, the silicone rubber of this invention can also be applied to other fields.

[0028] Specifically, the silicone rubber of the present embodiment includes the following raw materials by weight: methyl vinyl silicone rubber 100 parts; methyl phenyl vinyl silicone rubber 16-20 parts; double-end vinyl polydimethylsiloxane 5-10 parts; vulcanizing agent 0.5-2 parts; first double-end amino polydimethylsiloxane 8-12 parts; reaction product of pentaerythritol tetraglycidyl ether and second double-end amino polydimethylsiloxane 3-6 parts; phosphorus-containing epoxy resin 2-4 parts; modified mica powder 20-28 parts; modified nano-silicon dioxide 4-10 parts.

[0029] The methyl vinyl silicone rubber, as the main rubber, has good high and low temperature resistance, aging resistance and insulation performance, and a large number of vinyl groups as active sites for vulcanization reaction, which can improve the crosslinking density and compactness of the system.

[0030] The methyl phenyl vinyl silicone rubber, as one of the main components of the rubber, introduces a phenyl group, which can improve the temperature resistance and flame resistance of the silicone rubber. The amount of methyl phenyl vinyl silicone rubber can be 16-20 parts, for example, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, etc., relative to the amount of methyl vinyl silicone rubber, which is 100 parts by weight.

[0031] The double-end vinyl polydimethylsiloxane can act as an active plasticizer in the base rubber composed of methyl vinyl silicone rubber and methyl phenyl vinyl silicone rubber. The two end vinyl groups can participate in the vulcanization reaction, which can adjust the crosslinking density, make the vulcanized silicone rubber softer, improve the fatigue resistance, and enable the silicone rubber to better maintain the liquid resistance and mechanical properties in high and low temperature changes and vibration environments. At the same time, the double-end vinyl polydimethylsiloxane can also reduce the viscosity of the rubber compound, improve the flowability during mixing and injection molding, and avoid the migration problem of traditional plasticizers. The amount of double-end vinyl polydimethylsiloxane can be 5-10 parts, for example, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, etc., relative to the amount of methyl vinyl silicone rubber, which is 100 parts by weight.

[0032] The vulcanizing agent is used to initiate the crosslinking of the vinyl groups in the rubber molecules. The vulcanizing agent can be a peroxide, which generates free radicals through decomposition, causing the molecular chains of linear silicone rubber to crosslink through covalent bonds, forming a three-dimensional network structure and giving the material sufficient mechanical strength. The peroxide can also promote the crosslinking of epoxy groups. The amount of vulcanizing agent can be 0.5-2 parts, for example, 0.5 parts, 1 part, 1.5 parts, 2 parts, etc., relative to the amount of methyl vinyl silicone rubber, which is 100 parts by weight.

[0033] The first double-end amino polydimethylsiloxane is a polydimethylsiloxane with amino groups at both ends, which can react with the epoxy groups to form a crosslinking system of amino and epoxy groups, improving the mechanical strength of the silicone rubber, and the amino polar groups can enhance the oil resistance of the material. The first double-end amino polydimethylsiloxane has polydimethylsiloxane segments, which can improve the flexibility of the material, reduce stress concentration, and improve the performance of the material in high and low temperature and vibration. The amount of the first double-end amino polydimethylsiloxane can be 8-12 parts, for example, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, etc., relative to 100 parts by weight of the amount of methyl vinyl silicone rubber.

[0034] The reaction product of pentaerythritol tetraglycidyl ether and the second double-end amino polydimethylsiloxane is a compound or oligomer obtained by reacting the epoxy groups of pentaerythritol tetraglycidyl ether with the amino groups of the second double-end amino polydimethylsiloxane. The number of moles of the epoxy groups of pentaerythritol tetraglycidyl ether can be greater than the number of moles of the amino groups of the second double-end amino polydimethylsiloxane, so that the reaction product is a product with epoxy group end-capping, and the epoxy groups of the product are crosslinked with the amino groups at both ends of the first double-end amino polydimethylsiloxane. The reaction product of pentaerythritol tetraglycidyl ether and the second double-end amino polydimethylsiloxane has both the molecular structure of pentaerythritol, which can improve the carbon-forming ability of the material and thus improve the flame retardancy of the material, and the structure of polydimethylsiloxane, which improves its compatibility and dispersibility in the silicone rubber matrix, and at the same time improves the flexibility of the material. The amount of the reaction product of pentaerythritol tetraglycidyl ether and the second double-end amino polydimethylsiloxane can be 3-6 parts, for example, 3 parts, 4 parts, 5 parts, 6 parts, etc., relative to 100 parts by weight of the amount of methyl vinyl silicone rubber.

[0035] The phosphorus-containing epoxy resin refers to an epoxy resin containing phosphorus elements, which can impart flame retardancy to the material. The phosphorus elements in the phosphorus-containing epoxy resin can form a synergistic flame-retardant effect with silicon elements, phenyl groups, pentaerythritol groups, etc. in the system, promote carbonization to form a stable carbon layer at high temperature, and improve the flame retardant grade of the material. At the same time, the large number of epoxy groups in the epoxy resin can react with the amino groups of the first double-end amino polydimethylsiloxane to form a crosslinking structure, improving the liquid resistance and mechanical properties of the system. The amount of the phosphorus-containing epoxy resin can be 2-4 parts, for example, 2 parts, 3 parts, 4 parts, etc., relative to 100 parts by weight of the amount of methyl vinyl silicone rubber.

[0036] The modified mica powder is prepared by modifying mica powder with vinyl siloxane coupling agent and epoxy siloxane coupling agent, and then reacting with the third double-terminated amino polydimethylsiloxane. The mica powder has a flaky structure and can form a "physical barrier" in rubber to improve mechanical strength, dimensional stability, insulation and liquid resistance, while also delaying heat and gas transmission, enhancing aging resistance and flame retardation effect. The alkoxyl groups in the molecules of the vinyl siloxane coupling agent and the epoxy siloxane coupling agent can hydrolyze and bind to the surface of the mica powder, forming stable chemical bonds with the hydroxyl groups on the surface of the mica powder. The vinyl group at the other end of the vinyl siloxane coupling agent can participate in vulcanization, connecting the mica powder to the silicone rubber crosslinking system. The epoxy group at the other end of the epoxy siloxane coupling agent can react with the amino groups at both ends of the second double-terminated amino polydimethylsiloxane to form an amino-terminated end, which is combined into the epoxy and amino curing system, making the system more uniform in dispersion, while the polydimethylsiloxane segments in the second double-terminated amino polydimethylsiloxane can improve its compatibility with the silicone rubber system. The amount of modified mica powder can be 20-28 parts, for example, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, 25 parts, 26 parts, 27 parts, 28 parts, etc., relative to the amount of 100 parts by weight of methyl vinyl silicone rubber.

[0037] The modified nano-silica is prepared by modifying nano-silica with epoxy siloxane coupling agent. Nano-silica can play a reinforcing role to improve the mechanical strength of the material. The alkoxyl groups in the molecules of the epoxy siloxane coupling agent can hydrolyze and bind to the surface of the nano-silica, forming stable chemical bonds with the surface hydroxyl groups of the nano-silica, and the epoxy group at the other end can react with the amino groups in the system to disperse the nano-silica into the system, avoiding the migration of nano-silica. The amount of modified nano-silica can be 4-10 parts, for example, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, etc., relative to the amount of 100 parts by weight of methyl vinyl silicone rubber.

[0038] As can be seen from the above, the present embodiment combines various types of silicone rubber raw rubber and various types of linear polysiloxane with end groups, and combines flame-retardant epoxy resin systems and fillers such as modified mica powder and modified nano-silica. The above raw materials cooperate with each other to obtain a silicone rubber that can maintain good liquid resistance, mechanical properties, flame retardation and insulation properties under high and low temperature changes and vibration conditions, which can be used to manufacture a sheath for shielding high-voltage lines in automobiles.

[0039] In some examples, the silicone rubber of the present embodiment is mainly composed of the following raw materials by weight: methyl vinyl silicone rubber 100 parts; methyl phenyl vinyl silicone rubber 16-20 parts; double-end vinyl polydimethylsiloxane 5-10 parts; vulcanizing agent 0.5-2 parts; first double-end amino polydimethylsiloxane 8-12 parts; reaction product of pentaerythritol tetraglycidyl ether and second double-end amino polydimethylsiloxane 3-6 parts; phosphorus-containing epoxy resin 2-4 parts; modified mica powder 20-28 parts; modified nano-silicon dioxide 4-10 parts. In addition to the above-mentioned raw materials, the silicone rubber can also contain a small amount of functional additives, such as colorants, pigments, etc., which can be used to impart specific colors to the cable for specific purposes.

[0040] In some examples, the raw materials are as follows by weight: methyl vinyl silicone rubber 100 parts; methyl phenyl vinyl silicone rubber 18-20 parts; double-end vinyl polydimethylsiloxane 7-10 parts; vulcanizing agent 1-2 parts; first double-end amino polydimethylsiloxane 10-12 parts; reaction product of pentaerythritol tetraglycidyl ether and second double-end amino polydimethylsiloxane 3-5 parts; phosphorus-containing epoxy resin 3-4 parts; modified mica powder 20-23 parts; modified nano-silicon dioxide 4-8 parts. When the amounts of the components are within the above ranges, the obtained silicone rubber has better mechanical properties, flame retardant properties, insulation properties, and liquid resistance.

[0041] In some examples, in the reaction product of pentaerythritol tetraglycidyl ether and second double-end amino polydimethylsiloxane, the molar ratio of pentaerythritol tetraglycidyl ether to second double-end amino polydimethylsiloxane is (2-3):1, for example, it can be 2:1, 2.5:1, 3:1, etc. Using the above ratio of pentaerythritol tetraglycidyl ether to second double-end amino polydimethylsiloxane, the number of epoxy groups in the reaction product is appropriate, which facilitates the reaction of the reaction product of pentaerythritol tetraglycidyl ether and second double-end amino polydimethylsiloxane with the amino groups at both ends of the first double-end amino polydimethylsiloxane for crosslinking.

[0042] In some examples, the weight average molecular weight of the double-end vinyl polydimethylsiloxane is 20000-22000. Using double-end vinyl polydimethylsiloxane with this weight average molecular weight can better adjust the flexibility of the silicone rubber and improve the high and low temperature resistance and vibration resistance.

[0043] In some examples, the first amino-terminated polydimethylsiloxane has a weight average molecular weight of 2500-3500; the second amino-terminated polydimethylsiloxane has a weight average molecular weight of 800-1500; and the third amino-terminated polydimethylsiloxane has a weight average molecular weight of 800-1500. The first amino-terminated polydimethylsiloxane has a larger molecular weight, which increases the molecular chain length of the polydimethylsiloxane, and is conducive to the reaction between the amino groups of the first amino-terminated polydimethylsiloxane and the epoxy group-containing substances dispersed in the system. The second and third amino-terminated polydimethylsiloxanes have smaller molecular weights, which improve the mobility of the second and third amino-terminated polydimethylsiloxanes, and are conducive to the preparation of the reaction product of the pentaerythritol tetraglycidyl ether and the second amino-terminated polydimethylsiloxane and the modified mica powder.

[0044] In some examples, the phosphorus content in the phosphorus-containing epoxy resin is 3-5 wt%, for example, it can be 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, etc. When the phosphorus content of the phosphorus-containing epoxy resin is in the above range, the flame retardancy can be improved, while the mechanical properties and insulation of the material are not affected.

[0045] In some examples, in the modified mica powder, the mass ratio of the mica powder, the vinyl siloxane coupling agent, and the epoxy siloxane coupling agent is 100:(0.5-1):(0.5-1), which is conducive to the dispersion of the mica powder. The molar ratio of the epoxy siloxane coupling agent to the third amino-terminated polydimethylsiloxane is 1:1, so that the epoxy groups in the modified mica powder are basically replaced by amino groups, reducing the agglomeration of the modified mica powder.

[0046] In some examples, the particle size of the mica powder is 600-1200 mesh, which is conducive to the dispersion, modification, and reinforcement of the system.

[0047] In some examples, in the modified nano-silica, the mass ratio of the nano-silica and the epoxy siloxane coupling agent is 100:(0.5-1), which is conducive to the dispersion of the nano-silica.

[0048] In some examples, the particle size of the nano-silica is 20-50 nm, and the nano-silica with the above particle size has a good reinforcing effect on the material.

[0049] In some examples, the method for preparing the silicone rubber for shielding high-voltage wire sheaths for automobiles includes the following steps: mixing methyl vinyl silicone rubber and methyl phenyl vinyl silicone rubber in an internal mixer, sequentially adding double-end vinyl polydimethylsiloxane, first double-end amino polydimethylsiloxane, modified mica powder, and modified nano-silicon dioxide, and kneading until completely dispersed, then adding the reaction product of pentaerythritol tetraglycidyl ether and second double-end amino polydimethylsiloxane and phosphorus-containing epoxy resin, and kneading for 2-3 minutes, finally adding a vulcanizing machine and kneading for 1-2 minutes to obtain the silicone rubber. The above steps can uniformly disperse the components and avoid premature curing of the system.

[0050] In some examples, the temperature of the internal mixer is controlled at 50-65℃ to avoid premature curing of the components.

[0051] In some examples, the method for preparing the reaction product of pentaerythritol tetraglycidyl ether and second double-end amino polydimethylsiloxane includes heating pentaerythritol tetraglycidyl ether and second double-end amino polydimethylsiloxane in toluene to react, and removing the solvent by rotary evaporation to obtain the reaction product.

[0052] In some examples, the method for preparing the modified mica powder includes ultrasonic dispersion of mica powder in an ethanol or ethyl acetate solution in which vinyl siloxane coupling agent and epoxy siloxane coupling agent are dissolved, removal of the solvent after stirring and dispersion to obtain first-step modified mica powder, then dispersion of the obtained first-step modified mica powder in a toluene solution containing third double-end amino polydimethylsiloxane and heating to react, filtration, washing, and drying to obtain mica powder modified by coupling agent and having end-amino polydimethylsiloxane.

[0053] In some examples, the method for preparing the modified nano-silicon dioxide includes ultrasonic dispersion of nano-silicon dioxide in an ethanol or ethyl acetate solution in which epoxy siloxane coupling agent is dissolved, removal of the solvent after stirring and dispersion, and drying to obtain the modified nano-silicon dioxide.

[0054] The technical solutions of the present application will be further described in detail through specific examples. In the following examples and comparative examples, the substances with the same name have the same substance type and source of raw materials.

[0055] The raw materials used in the following examples and comparative examples are as follows: Methyl vinyl silicone rubber, model MY 110, purchased from Anhui Mingyi Silicone; Methyl phenyl vinyl silicone rubber, model MY 3120, purchased from Anhui Mingyi Silicone; Double-end vinyl polydimethylsiloxane, Mw 20000-22000, purchased from Hubei Xinyu Hong; Vulcanizing agent, double-dipentasulfide vulcanizing agent, purchased from Aite Chemical; First amino-terminated polydimethylsiloxane, Mw about 3000, purchased from Guangdong Fangxin; Phosphorus-containing epoxy resin, phosphorus content 3.9~4.1wt%, purchased from Jiangsu Xinsu; Second amino-terminated polydimethylsiloxane and third amino-terminated polydimethylsiloxane are the same raw material, Mw about 1000, purchased from Guangdong Fangxin; Pentaerythritol tetraglycidyl ether, purchased from Jinan Yunuo; Mica powder, 800 mesh white mica powder, purchased from Lingshou Chuanshi; Vinyl silane coupling agent, vinyl trimethoxysilane A171, purchased from Shandong Yuanjin; Epoxy silane coupling agent, γ-(2,3-epoxypropoxy) propyl trimethoxysilane KH560, purchased from Qufu Yisun; Nano-silica, HN-SP30S, particle size 30±5nm, purchased from Hangzhou Hengge.

[0056] In the following examples and comparative examples, unless otherwise specified, the preparation steps of the silicone rubber are as follows: (1) The pentaerythritol tetraglycidyl ether and the second amino-terminated polydimethylsiloxane were heated in toluene to react, and the solvent was removed by rotary evaporation to obtain the reaction product.

[0057] (2) The mica powder was ultrasonically dispersed in an ethanol or ethyl acetate solution containing the vinyl silane coupling agent and the epoxy silane coupling agent, and after stirring and dispersion, the solvent was removed to obtain the first step modified mica powder. Then the obtained first step modified mica powder was dispersed in a toluene solution containing the third amino-terminated polydimethylsiloxane and heated to react, and then filtered, washed and dried to obtain the mica powder modified by the coupling agent and containing the amino-terminated polydimethylsiloxane.

[0058] (3) The nano-silica was ultrasonically dispersed in an ethanol or ethyl acetate solution containing the epoxy silane coupling agent, and after stirring and dispersion, the solvent was removed and dried to obtain the modified nano-silica.

[0059] (4) The methyl vinyl silicone rubber and the methyl phenyl vinyl silicone rubber were placed in an internal mixer and mixed for 5 min, with the temperature of the internal mixer controlled at 60°C. The amino-terminated polydimethylsiloxane, the first amino-terminated polydimethylsiloxane, the modified mica powder and the modified nano-silica were added in turn, and turned over for about 8 min until completely dispersed. Then the reaction product of the pentaerythritol tetraglycidyl ether and the second amino-terminated polydimethylsiloxane and the phosphorus-containing epoxy resin were added, and turned over for 3 min. Finally, the vulcanizing agent was added, and turned over for 1 min to obtain the silicone rubber.

[0060] In the above, in Example 6, the second and third amino-terminated polydimethylsiloxane are both replaced by the first amino-terminated polydimethylsiloxane having a Mw of about 3000, i.e. in step (1) of Example 6, the pentaerythritol tetraglycidyl ether and the first amino-terminated polydimethylsiloxane having a Mw of about 3000 are heated to react in toluene, and after removing the solvent by rotary evaporation and the like, the reaction product is obtained; and in step (2), the obtained first modified mica powder is dispersed in a toluene solution containing the first amino-terminated polydimethylsiloxane having a Mw of about 3000, and heated to react.

[0061] In Comparative Example 1, the first amino-terminated polydimethylsiloxane, the reaction product of the pentaerythritol tetraglycidyl ether and the second amino-terminated polydimethylsiloxane, and the phosphorus-containing epoxy resin are not used, the preparation steps omit step (1), and the adding steps of the corresponding components in step (4) are omitted; and the epoxy silane coupling agent in step (2) is replaced by a vinyl silane coupling agent, which is not further reacted with the third amino-terminated polydimethylsiloxane; and the epoxy silane coupling agent in step (3) is replaced by a vinyl silane coupling agent.

[0062] In Comparative Example 2, the reaction product of the pentaerythritol tetraglycidyl ether and the second amino-terminated polydimethylsiloxane is not used, the preparation steps omit step (1), and the adding steps of the corresponding components in step (4) are omitted.

[0063] In Comparative Example 3, the second amino-terminated polydimethylsiloxane is not used, and the adding steps of the corresponding components in step (4) are omitted.

[0064] In Comparative Example 4, the reaction product of the pentaerythritol tetraglycidyl ether and the second amino-terminated polydimethylsiloxane is not used, but the pentaerythritol tetraglycidyl ether is directly added, the preparation steps omit step (1), and the reaction product of the pentaerythritol tetraglycidyl ether and the second amino-terminated polydimethylsiloxane in step (4) is replaced by the pentaerythritol tetraglycidyl ether.

[0065] In Comparative Example 5, the third amino-terminated polydimethylsiloxane is not used to modify the modified mica powder, and in step (2), the mica powder is ultrasonically dispersed in an ethanol or ethyl acetate solution in which the vinyl silane coupling agent and the epoxy silane coupling agent are dissolved, the solvent is removed after stirring and dispersing to obtain the modified mica powder. The modified mica powder is directly used in step (4).

[0066] The amounts (parts by weight) of the raw materials used in each of the examples and comparative examples are shown in Table 1 below.

[0067] Table 1 The silicon rubber obtained from the examples and comparative examples was used to prepare a high-voltage wire sheath for a car. 1128 bare copper filaments were twisted to form a conductor, and the outer diameter of the conductor was 8.11 mm. An insulating layer was extruded outside the conductor, and the average thickness of the insulating layer was 1.11 mm. A shielding layer formed by tinned copper braiding was arranged outside the insulating layer. An aluminum-plastic composite tape layer was arranged outside the shielding layer. The silicon rubber of the example was extruded outside the aluminum-plastic composite tape layer, and the sheath was formed after baking and vulcanization, the average thickness of the sheath was 1.69 mm, and the outer diameter of the sheath was 14.10 mm.

[0068] The obtained high-voltage wire for a car was subjected to accelerated aging under high-low temperature change and vibration conditions: the obtained wire was arranged in a temperature control device, and the high-low temperature change was as follows: -65℃ for 1 h, increased to 205℃ at a rate of 9℃ / min, 250℃ for 3 h, and then decreased to -65℃ at a rate of 9℃ / min, which was one cycle, and the cycle was continuously repeated for 300 times; vibration was applied to the wire outside the temperature control device, and the frequency was 100 Hz.

[0069] After the aging of the high-voltage wire for a car, the wire was soaked in engine oil, gasoline, diesel, coolant, windshield washer, and road salt water for 24 h, then washed with clean water, naturally dried, and then the following tests were performed.

[0070] Mechanical strength test: the tensile test was performed according to GB / T2951.11-2008; Flame retardant performance test: the flame retardant grade test was performed according to UL94; Insulation performance test: the volume resistivity was tested according to ISO6722-1:2011; Winding test: the high-voltage wire for a car was wound, and whether the sheath cracked was observed; Pressure resistance test: the AC voltage resistance test was performed according to ISO6722-1:2011, and the voltage of 1kV was applied to both sides of the sheath for 30 min, and then the voltage was increased to 5kV for 5 min.

[0071] The test results are shown in Table 2 below.

[0072] Table 2 As shown in the above table, the high-voltage wire sheath for a car prepared from the silicon rubber of the example has good mechanical properties, flame retardant properties, insulation properties, and liquid resistance after high-low temperature change and vibration.

[0073] Finally, it should be noted that the above-described embodiments are merely preferred embodiments of the present application, and are not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. Silicone rubber for use as shielded high-voltage wire sheaths in automobiles, characterized in that... Including the following parts by weight of raw materials: 100 parts of methyl vinyl silicone rubber; 16-20 parts of methyl phenyl vinyl silicone rubber; 5-10 parts of double-terminated vinyl polydimethylsiloxane; Vulcanizing agent 0.5~2 parts; 8-12 parts of the first double-terminated amino polydimethylsiloxane; 3-6 parts of the reaction product of pentaerythritol tetraglycidyl ether and second diamino-terminated polydimethylsiloxane; 2-4 parts of phosphorus-containing epoxy resin; 20-28 parts of modified mica powder; 4-10 parts of modified nano-silica; The modified mica powder is prepared by modifying mica powder with vinyl siloxane coupling agent and epoxy siloxane coupling agent and then reacting it with third double-terminated amino polydimethyl siloxane. The modified nano-silica is prepared by modifying nano-silica with an epoxy-based siloxane coupling agent.

2. The silicone rubber for shielded high-voltage line sheaths in automobiles according to claim 1, characterized in that... The weight parts of the raw materials are: 100 parts of methyl vinyl silicone rubber; 18-20 parts of methyl phenyl vinyl silicone rubber; 7-10 parts of double-terminated vinyl polydimethylsiloxane; 1-2 parts of vulcanizing agent; 10-12 parts of the first double-terminated amino polydimethylsiloxane; 3-5 parts of the reaction product of pentaerythritol tetraglycidyl ether and second diamino-terminated polydimethylsiloxane; 3-4 parts of phosphorus-containing epoxy resin; 20-23 parts of modified mica powder; 4-8 parts of modified nano-silica.

3. The silicone rubber for shielded high-voltage line sheaths in automobiles according to claim 1 or 2, characterized in that... In the reaction product of pentaerythritol tetraglycidyl ether and second diamino-terminated polydimethylsiloxane, the molar ratio of pentaerythritol tetraglycidyl ether to second diamino-terminated polydimethylsiloxane is (2~3):

1.

4. The silicone rubber for shielded high-voltage line sheaths in automobiles according to claim 1 or 2, characterized in that... The weight-average molecular weight of the dual-terminated vinyl polydimethylsiloxane is 20,000 to 22,000. The first diamino-terminated polydimethylsiloxane has a weight-average molecular weight of 2500-3500; the second diamino-terminated polydimethylsiloxane has a weight-average molecular weight of 800-1500; and the third diamino-terminated polydimethylsiloxane has a weight-average molecular weight of 800-1500. The phosphorus content in the phosphorus-containing epoxy resin is 3-5 wt%.

5. The silicone rubber for shielded high-voltage line sheaths in automobiles according to claim 1 or 2, characterized in that... In the modified mica powder, the mass ratio of mica powder, vinyl siloxane coupling agent and epoxy siloxane coupling agent is 100:(0.5~1):(0.5~1), and the molar ratio of epoxy siloxane coupling agent and third diamino-terminated polydimethylsiloxane is 1:

1. The mica powder has a particle size of 600-1200 mesh.

6. The silicone rubber for shielded high-voltage line sheaths in automobiles according to claim 1 or 2, characterized in that... In the modified nano-silica, the mass ratio of nano-silica to epoxy siloxane coupling agent is 100:(0.5~1); The particle size of the nano-silica is 20~50nm.

7. The method for preparing silicone rubber for shielded high-voltage line sheaths in automobiles according to any one of claims 1 to 6, characterized in that... Includes the following steps: Methyl vinyl silicone rubber and methyl phenyl vinyl silicone rubber are mixed in a mixer. Then, double-terminated vinyl polydimethylsiloxane, first double-terminated amino polydimethylsiloxane, modified mica powder and modified nano silica are added in sequence. The mixture is stirred until completely dispersed. Then, the reaction product of pentaerythritol tetraglycidyl ether and second double-terminated amino polydimethylsiloxane and phosphorus-containing epoxy resin are added and stirred for 2-3 minutes. Finally, the mixture is added to a vulcanizing machine and stirred for 1-2 minutes to obtain silicone rubber.

8. The method for preparing silicone rubber for shielded high-voltage line sheaths in automobiles according to claim 7, characterized in that... The temperature of the internal mixer is controlled at 50~65℃.

9. The method for preparing silicone rubber for shielded high-voltage line sheaths in automobiles according to claim 7 or 8, characterized in that... The method for preparing the reaction product of pentaerythritol tetraglycidyl ether and second diamino-terminated polydimethylsiloxane includes heating pentaerythritol tetraglycidyl ether and second diamino-terminated polydimethylsiloxane in toluene to react, and removing the solvent to obtain the reaction product. The method for preparing the modified mica powder includes ultrasonically dispersing mica powder in an ethanol or ethyl acetate solution containing vinyl siloxane coupling agent and epoxy siloxane coupling agent, stirring and dispersing, removing the solvent, then dispersing the resulting product in a toluene solution containing third diamino-terminated polydimethylsiloxane, heating and reacting, filtering, washing and drying to obtain the modified mica powder. The method for preparing the modified nano silica includes ultrasonically dispersing nano silica in an ethanol or ethyl acetate solution containing an epoxy siloxane coupling agent, stirring and dispersing, removing the solvent, and drying to obtain modified nano silica.

10. A shielded high-voltage wire for automobiles, characterized in that... It includes a conductor, an insulating layer, a shielding layer, and a sheath arranged sequentially from the inside out, wherein the sheath is the silicone rubber for shielded high-voltage lines for automobiles as described in any one of claims 1 to 6, or the silicone rubber obtained by the preparation method described in any one of claims 7 to 9.

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