Flame-retardant silicone rubber cable sheath material and preparation method thereof

Abstract

The invention relates to the technical field of cable materials, in particular to a flame-retardant silicone rubber cable sheath material and a preparation method thereof. The flame-retardant silicone rubber cable sheath material is prepared from the following raw materials in parts by mass: 50 to 55 parts of methyl vinyl silicone rubber, 5 to 7 parts of polydimethylsiloxane, 10 to 12 parts of a composite flame retardant, 18 to 23 parts of heat-conducting filler, 5 to 7 parts of modified glass fiber, 1 to 2 parts of a coupling agent, 1 to 1.2 parts of a vulcanizing agent, 2.5 to 3.5 parts of zinc oxide and 1 to 2 parts of stearate, the composite flame retardant is prepared by mixing modified ammonium polyphosphate and a nitrogen-boron-silicon flame retardant according to the mass part ratio of 2: 3. The flame-retardant silicone rubber cable sheath material prepared by the invention has good temperature resistance, good thermal conductivity, good flame retardance and excellent mechanical properties, and can meet the requirements of high-performance cables.

Description

Technical Field

[0001] The present application relates to the technical field of cable materials, and in particular to a flame retardant silicone rubber cable sheath material and a preparation method thereof. Background Art

[0002] Compared with traditional fuel vehicles, electric vehicles have added many high-voltage accessories, such as power batteries, high-voltage distribution boxes, drive motors, motor controllers, etc., which also puts forward new requirements for automotive cables. Cables are often arranged in the front cabin engine and chassis area, with the characteristics of high temperature, many bends, large wire diameter, and high heat generation. Therefore, the cable material must have good flexibility, flame retardancy, thermal conductivity, thermal stability, high and low temperature resistance, excellent bending resistance and tear resistance. At present, automotive power cable materials include cross-linked polyolefins, thermoplastic elastomers and silicone rubber.

[0003] CN109423052A discloses a silane cross-linked elastomeric cable material for high-voltage lines of new energy vehicles and a preparation method thereof. The silane cross-linked elastomeric cable material is composed of the following components in parts by weight: 15-35 parts of silicone rubber, 10-35 parts of ethylene-methyl acrylate, 10-25 parts of polyphosphazene, 10-30 parts of catalyst masterbatch, 10-20 parts of polyolefin, 2-10 parts of polyetheretherketone, 10-40 parts of phosphorus nitrogen flame retardant, 2-10 parts of silicon-based flame retardant synergist, 0.1-1 parts of vinyltrimethoxysilane, 1-10 parts of diisopropylbenzene peroxide, and 0.1-2 parts of antioxidant; wherein the catalyst masterbatch is composed of the following components in parts by weight: linear low-density polyethylene, di-n-butyltin dilaurate, triethylamine, siloxane, silicon dioxide, and antioxidant. The silane cross-linked elastomer cable material provided by this technical solution has a temperature resistance level of 150°C, and the mechanical property retention rate is above 80% after aging at 180°C for 7 days. Although the above materials have obtained cable materials with excellent performance, in order to meet the needs of high-voltage cables for electric vehicles, the temperature resistance, flame retardancy and thermal conductivity of cable materials still need to be improved.

[0004] Therefore, there is an urgent need to develop a flame-retardant silicone rubber cable sheath material with good temperature resistance, good thermal conductivity and good flame retardancy to meet market demand. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present application provides a flame retardant silicone rubber cable sheath material and a preparation method thereof. The flame retardant silicone rubber cable sheath material prepared in the present application has good temperature resistance, good thermal conductivity, good flame retardancy and excellent mechanical properties.

[0006] In the first aspect, the present application provides a flame retardant silicone rubber cable sheath material, which adopts the following technical solution: A flame retardant silicone rubber cable sheath material, comprising, by weight, 50-55 parts of methyl vinyl silicone rubber, 5-7 parts of polydimethylsiloxane, 10-12 parts of a composite flame retardant, 18-23 parts of a thermal conductive filler, 5-7 parts of a modified glass fiber, 1-2 parts of a coupling agent, 1-1.2 parts of a vulcanizing agent, 2.5-3.5 parts of zinc oxide, and 1-2 parts of a stearate, wherein the composite flame retardant is prepared by mixing modified ammonium polyphosphate and nitrogen borosilicate flame retardant in a weight ratio of 2:3.

[0007] By adopting the above technical scheme, the flame-retardant silicone rubber cable sheath material of the present application achieves excellent comprehensive performance by carefully selecting and proportioning various raw materials. Methyl vinyl silicone rubber: As a base polymer, it provides basic mechanical strength and elasticity. Its temperature resistance and weather resistance provide good environmental adaptability for the cable sheath. Polydimethylsiloxane: Increases the flexibility and processing performance of silicone rubber, while improving the thermal stability of the material. Composite flame retardant: Prepared by mixing modified ammonium polyphosphate and nitrogen boron silicon flame retardant in a mass fraction of 2:3. Modified ammonium polyphosphate introduces silicon-oxygen structure and boron element, which enhances the compatibility and flame retardant properties with silicone rubber; the boron atoms in the nitrogen boron silicon flame retardant promote the formation of a dense carbon layer, and the triazine ring structure releases non-flammable gas to dilute the flammable gas. The synergistic effect of the two significantly improves the flame retardant effect. Thermal conductive filler: After special treatment, the compatibility and dispersibility with silicone rubber are improved, forming a percolation network structure, effectively improving thermal conductivity, accelerating heat conduction, helping to dissipate heat and improve temperature resistance. Modified glass fiber: Surface modification with organic nitrogen-phosphorus flame retardant improves compatibility with silicone rubber and reduces agglomeration problems. During combustion, it generates non-combustible gas and promotes dehydration to form an expanded carbon layer, which enhances the flame retardant effect. At the same time, the evenly dispersed glass fiber improves the tensile strength and durability of silicone rubber. Coupling agent: used to improve the interfacial bonding between inorganic fillers and organic polymers and improve the overall performance of the material. Vulcanizing agent: promotes the cross-linking reaction of silicone rubber, forms a three-dimensional network structure, and improves the physical properties and heat resistance of the material. Zinc oxide and stearate: act as acid absorbers and lubricants, respectively, to help adjust the vulcanization speed and improve processing performance. In summary, this application, through reasonable formula design, has produced a good synergistic effect between the components, which not only improves the flame retardant properties of the flame retardant silicone rubber cable sheath material, but also enhances its mechanical properties, thermal conductivity and temperature resistance, meeting the requirements of high-performance cable sheaths.

[0008] Preferably, the preparation method of the modified ammonium polyphosphate is as follows: according to the mass fractions, under nitrogen protection, ammonium polyphosphate, polymethylphenylsiloxane and trimethyl borate are added to a reactor and placed in a heating jacket for heating and stirring, the heating temperature is set to 190-200°C, the heating rate is 10°C / minute, the stirring rate is 400rpm, and water is distilled off at the same time; after reacting for 50-60min, the product is placed in anhydrous ethanol and completely dissolved, and then deionized water is poured into it to precipitate the product, the precipitated product is filtered and vacuum dried at 80°C for 24h, and then ground and sieved to obtain the modified ammonium polyphosphate.

[0009] By adopting the above technical scheme, the modified ammonium polyphosphate prepared by the reaction of modified ammonium polyphosphate with polymethylphenylsiloxane and trimethyl borate introduces silicon-oxygen structure and boron element, which improves its compatibility with silicone rubber and helps to improve the overall performance of flame-retardant silicone rubber cable sheath material. The silicon-oxygen structure present in the modified ammonium polyphosphate can form a stable protective layer at high temperature, effectively blocking oxygen; and the introduction of boron element can promote the formation of a carbon layer, further enhancing the flame retardant effect. In addition, the modified ammonium polyphosphate itself has a flame retardant effect, and can be compounded with nitrogen boron silicon flame retardant in a specific proportion, synergistically, to form an overall flame retardant system, thereby improving the flame retardant grade and safety performance of the material. In summary, the modified ammonium polyphosphate plays a role in improving compatibility and enhancing flame retardant properties in this application, and further improves the comprehensive performance of the flame retardant silicone rubber cable sheath material through the synergistic effect with nitrogen boron silicon flame retardant.

[0010] Preferably, the mass ratio of the ammonium polyphosphate, polymethylphenylsiloxane, trimethyl borate, anhydrous ethanol and deionized water is 10:7:3:60:300.

[0011] Preferably, the preparation method of the nitrogen boron silicon flame retardant comprises the following steps: S41, add 0.2 mol melamine and 0.5 mol 3-formylphenylboric acid into a four-necked flask containing 1.5 L toluene, stir and mix evenly under nitrogen, then slowly heat to 110°C, condense and reflux to react for 7 hours, after the reaction is completed, cool to room temperature, pour into a beaker containing 1 L benzene, let stand for 20 minutes, filter, wash the filter cake with boiling water three times, and vacuum dry at 70°C to obtain a boron nitrogen flame retardant; S42. Add 0.3 mol of boron nitrogen flame retardant into a reactor containing 1LN, N-dimethylformamide, stir and mix evenly, then add 0.4 mol of hydroxymethyltriethoxysilane, and heat the reaction system to 130°C and reflux for 20 hours. After the reaction is completed, remove the solvent by rotary evaporation, and vacuum dry at 80°C for 24 hours to obtain nitrogen boron silicon flame retardant.

[0012] By adopting the above technical solution, the boron atoms in the prepared nitrogen-boron-silicon flame retardant can promote the formation of a dense carbon layer on the surface of the substrate during the combustion process, and the presence of the triazine ring structure causes the substrate to release non-flammable gases such as nitrogen and ammonia, diluting the flammable gas in the substrate, thereby improving the flame retardant properties of the substrate. The nitrogen-boron-silicon flame retardant not only has a flame retardant effect itself, but can also be compounded with modified ammonium polyphosphate in a specific ratio to form a synergistic effect to form an overall flame retardant system, thereby improving the flame retardant grade and safety performance of the material.

[0013] Preferably, the method for preparing the modified glass fiber comprises the following steps: S51, according to the mass fraction, add 50 parts of glass fiber to 300 parts of toluene, mix well, heat to 60°C, add 30 parts of diallyl chlorophosphate and 10 parts of pyridine, react for 3 hours, after the reaction is completed, centrifuge and separate the solid product, wash, and dry to obtain a modified glass fiber intermediate; S52. Disperse 50 parts of the modified glass fiber intermediate into 300 parts of tetrahydrofuran according to the mass fractions, stir evenly, then add 80 parts of 1-(3-aminopropyl)imidazole, stir and react at 32°C for 9 hours, filter after the reaction, wash, and vacuum dry to obtain the modified glass fiber.

[0014] By adopting the above technical scheme, the modified glass fiber is obtained by a specific preparation method, and its compatibility with silicone rubber can be improved by modifying the organic nitrogen-phosphorus flame retardant on the surface of the glass fiber. This modified glass fiber can be better dispersed in silicone rubber, effectively improving the agglomeration problem of the glass fiber, thereby improving the overall performance of the cable sheath material. The nitrogen-phosphorus flame retardant on the surface of the modified glass fiber can generate non-combustible gases (such as nitrogen, ammonia, etc.) and phosphoric acid derivatives that promote the rapid dehydration of silicone rubber when the silicone rubber burns, forming an expanded carbon layer. This expanded carbon layer can effectively block oxygen and heat, produce a highly efficient flame retardant effect, and prevent further combustion. The modified glass fiber is evenly dispersed in the silicone rubber, which can not only disperse and transfer stress, but also improve the tensile strength of the silicone rubber. This makes the cable sheath less likely to be damaged when pulled by external forces, thereby improving the durability and service life of the cable sheath.

[0015] Preferably, the method for preparing the thermally conductive filler comprises the following steps: S61. According to the mass fraction, 60 parts of boron nitride are placed in 160 parts of 1 mol / L NaOH solution, pretreated at 90° C. for 5 hours, the surface oil is washed off, filtered, and the deoiled boron nitride is placed in an ozonation treatment device for ozonation treatment for 4 hours, and the solid-liquid separation is performed to obtain ozonated modified boron nitride; S62. Add 60 parts of ozonated modified boron nitride into a reactor containing 130 parts of 3-(isomethacryloyloxy)propyltrimethoxysilane and 200 parts of toluene according to their mass fractions, place in an oil bath at 90°C with stirring, and reflux the cold gel for 5 hours. Rinse the boron nitride treated with 3-(isomethacryloyloxy)propyltrimethoxysilane with ethanol three times, then wash it with distilled water once, filter it with suction, and dry it to obtain a thermally conductive filler.

[0016] By adopting the above technical scheme, the thermal conductive filler prepared in the present application plays a vital role in the flame retardant silicone rubber cable sheath material. First, the surface of the boron nitride particles treated with ozonation and 3-(isobutylene oxy)propyl trimethoxysilane is oxidized and reacts with the organosilicon compound, thereby improving the hydrophobicity of boron nitride and its compatibility with silicone rubber. This significantly improves the dispersibility and uniformity of the thermal conductive filler in silicone rubber. Secondly, the thermal conductive filler forms a "percolation network" structure in the cable sheath material, which effectively improves the thermal conductivity of the cable sheath material. This structure strengthens the conduction of heat, so that the heat generated by the cable during use can be quickly dissipated, thereby reducing the temperature of the cable and improving the service life and safety of the cable. In addition, the thermal conductive filler also has excellent temperature resistance. In a high temperature environment, the thermal conductive filler can maintain stable performance and will not reduce its thermal conductivity due to the increase in temperature. This enables the flame retardant silicone rubber cable sheath material to still maintain good thermal conductivity in a high temperature environment, ensuring the safe operation of the cable. In summary, the thermal conductive filler prepared in this application plays a role in improving thermal conductivity, enhancing temperature resistance and improving the overall performance of the material in the flame-retardant silicone rubber cable sheath material. Through the synergistic effect with other components, an efficient and safe flame retardant system is formed, which provides a strong guarantee for the safe operation of the cable.

[0017] Preferably, the coupling agent is composed of methyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane and γ-(2,3-epoxypropyloxy)propyltrimethoxysilane in a mass ratio of 6:5:4.

[0018] By adopting the above technical scheme, the main function of the coupling agent is to improve the compatibility between inorganic fillers and organic polymers, improve the dispersion and uniformity of fillers in silicone rubber, and thus enhance the overall performance of the material. Methyltrimethoxysilane: This coupling agent can improve the compatibility of inorganic fillers such as boron nitride with silicone rubber, and form a stable chemical bond with silicone rubber through its silicon oxygen bond, thereby improving the mechanical properties and temperature resistance of the material. γ-mercaptopropyltrimethoxysilane: This coupling agent contains mercapto (-SH), which can react with the double bonds in silicone rubber to form a cross-linked structure, enhancing the strength and wear resistance of the material. At the same time, it can also promote the dispersion of inorganic fillers such as boron nitride in silicone rubber and improve the thermal conductivity of the material. γ-(2,3-epoxypropyloxy)propyltrimethoxysilane: This coupling agent contains epoxy groups, which can react with hydroxyl groups or other active groups in silicone rubber to form a stable chemical bond. This helps to improve the chemical resistance and weather resistance of the material, and also improves the compatibility of inorganic fillers with silicone rubber. The synergy between these three coupling agents lies in their complementary characteristics, working together between the inorganic filler and the silicone rubber to form a more stable and uniform interface layer. Such an interface layer can not only improve the mechanical properties of the material, but also enhance the material's temperature resistance, chemical resistance and mechanical properties. In addition, good compatibility and dispersibility also help improve the overall flame retardant and safety performance of the material.

[0019] Preferably, the vulcanizing agent is 2,5-dimethyl-2,5-di-tert-butyl peroxide hexane.

[0020] Preferably, the stearate is at least one of zinc stearate, magnesium stearate and calcium stearate.

[0021] In a second aspect, the present application provides a method for preparing a flame retardant silicone rubber cable sheath material, using the following technical solution: As a general technical concept, the present application also provides a method for preparing the above-mentioned flame retardant silicone rubber cable sheath material, comprising the following steps: S101, mixing methyl vinyl silicone rubber, composite flame retardant, thermal conductive filler, modified glass fiber and coupling agent according to their weight parts, adding them into a kneader for heating and kneading, wherein the kneading temperature is 105-115° C. and the kneading time is 4-5 hours, to obtain a mixture A; S102, mixing polydimethylsiloxane, zinc oxide and stearate according to their weight parts to obtain a mixture B; S103, adding mixture B and a vulcanizing agent to mixture A according to parts by mass, and kneading to obtain mixture C; S104, placing the mixture C in a flat vulcanizer for vulcanization, the vulcanization process is: temperature 170-190° C., vulcanization time 10-15 min, to obtain a flame retardant silicone rubber cable sheath material.

[0022] In summary, the present application includes at least one of the following beneficial technical effects: 1. Good temperature resistance: Through the synergistic effect of modified ammonium polyphosphate and nitrogen boron silicon flame retardant, as well as the addition of thermal conductive filler, the cable sheath material can maintain stable performance at high temperatures and is not easy to deform or damage.

[0023] 2. Good thermal conductivity: After special treatment, the thermal conductive filler has improved compatibility with silicone rubber and can form a percolation network structure in the cable sheath material, effectively improving thermal conductivity and enhancing heat conduction.

[0024] 3. Good flame retardancy: The compound use of modified ammonium polyphosphate and nitrogen boron silicon flame retardant forms an overall flame retardant system, which improves the flame retardant grade and safety performance of the material. At the same time, the nitrogen phosphorus flame retardant on the surface of the modified glass fiber can generate non-combustible gas and phosphoric acid derivatives that promote the rapid dehydration of silicone rubber during combustion, forming an expanded carbon layer, effectively blocking oxygen and heat, and producing a highly efficient flame retardant effect.

[0025] 4. Excellent mechanical properties: The modified glass fiber is evenly dispersed in the silicone rubber, which can not only disperse and transfer stress, but also improve the tensile strength of the silicone rubber. This makes the cable sheath less likely to be damaged when pulled by external forces, and improves the durability and service life of the cable sheath. DETAILED DESCRIPTION

[0026] The embodiments of the present application will be described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0027] In the following examples and preparation examples, 1 part means 100 g.

[0028] Preparation Example 1 Preparation of modified ammonium polyphosphate The preparation method of modified ammonium polyphosphate is as follows: according to the mass fractions, under nitrogen protection, 10 parts of ammonium polyphosphate, 7 parts of polymethylphenylsiloxane and 3 parts of trimethyl borate are added into a reactor and placed in a heating jacket for heating and stirring, the heating temperature is set to 195°C, the heating rate is 10°C / minute, the stirring rate is 400rpm, and water is distilled off at the same time; after reacting for 55 minutes, the product is placed in 60 parts of anhydrous ethanol and completely dissolved, and then 300 parts of deionized water are poured into it to precipitate the product, the precipitated product is filtered and vacuum dried at 80°C for 24 hours, and then ground and sieved to obtain modified ammonium polyphosphate.

[0029] Preparation Example 2 Preparation of Nitrogen-Boron-Silicon Flame Retardant The preparation method of nitrogen boron silicon flame retardant comprises the following steps: S41, add 0.2 mol melamine and 0.5 mol 3-formylphenylboric acid into a four-necked flask containing 1.5 L toluene, stir and mix evenly under nitrogen, then slowly heat to 110°C, condense and reflux to react for 7 hours, after the reaction is completed, cool to room temperature, pour into a beaker containing 1 L benzene, let stand for 20 minutes, filter, wash the filter cake with boiling water three times, and vacuum dry at 70°C to obtain a boron nitrogen flame retardant; S42. Add 0.3 mol of boron nitrogen flame retardant into a reactor containing 1LN, N-dimethylformamide, stir and mix evenly, then add 0.4 mol of hydroxymethyltriethoxysilane, and heat the reaction system to 130°C and reflux for 20 hours. After the reaction is completed, remove the solvent by rotary evaporation, and vacuum dry at 80°C for 24 hours to obtain nitrogen boron silicon flame retardant.

[0030] Preparation Example 3 Preparation of modified glass fiber The preparation method of modified glass fiber comprises the following steps: S51, according to the mass fraction, add 50 parts of glass fiber to 300 parts of toluene, mix well, heat to 60°C, add 30 parts of diallyl chlorophosphate and 10 parts of pyridine, react for 3 hours, after the reaction is completed, centrifuge and separate the solid product, wash, and dry to obtain a modified glass fiber intermediate; S52. Disperse 50 parts of the modified glass fiber intermediate into 300 parts of tetrahydrofuran according to the mass fractions, stir evenly, then add 80 parts of 1-(3-aminopropyl)imidazole, stir and react at 32°C for 9 hours, filter after the reaction, wash, and vacuum dry to obtain the modified glass fiber.

[0031] Preparation Example 4 Preparation of thermally conductive filler The preparation method of the thermal conductive filler comprises the following steps: S61. According to the mass fraction, 60 parts of boron nitride are placed in 160 parts of 1 mol / L NaOH solution, pretreated at 90° C. for 5 hours, the surface oil is washed off, filtered, and the deoiled boron nitride is placed in an ozonation treatment device for ozonation treatment for 4 hours, and the solid-liquid separation is performed to obtain ozonated modified boron nitride; S62. Add 60 parts of ozonated modified boron nitride into a reactor containing 130 parts of 3-(isomethacryloyloxy)propyltrimethoxysilane and 200 parts of toluene according to their mass fractions, place in an oil bath at 90°C with stirring, and reflux the cold gel for 5 hours. Rinse the boron nitride treated with 3-(isomethacryloyloxy)propyltrimethoxysilane with ethanol three times, then wash it with distilled water once, filter it with suction, and dry it to obtain a thermally conductive filler.

[0032] Example 1 A flame retardant silicone rubber cable sheath material, comprising, by weight, 50 parts of methyl vinyl silicone rubber, 5 parts of polydimethylsiloxane, 10 parts of a composite flame retardant, 18 parts of a thermally conductive filler, 5 parts of modified glass fiber, 1 part of a coupling agent, 1 part of a vulcanizing agent, 2.5 parts of zinc oxide, and 1 part of a stearate, wherein the composite flame retardant is prepared by mixing modified ammonium polyphosphate and nitrogen borosilicate flame retardant in a weight ratio of 2:3, the coupling agent is composed of methyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, and γ-(2,3-epoxypropyloxy)propyltrimethoxysilane in a weight ratio of 6:5:4, the vulcanizing agent is 2,5-dimethyl-2,5-di-tert-butylperoxyhexane, and the stearate is zinc stearate.

[0033] The method for preparing the flame retardant silicone rubber cable sheath material comprises the following steps: S101. Mix methyl vinyl silicone rubber, composite flame retardant, thermal conductive filler, modified glass fiber and coupling agent according to their weight percentages, add them into a kneader, heat and knead them, the kneading temperature is 105° C., and the kneading time is 5 hours to obtain a mixture A. S102. Mix polydimethylsiloxane, zinc oxide and stearate according to their weight percentages and stir them to obtain a mixture B. S103, adding mixture B and a vulcanizing agent to mixture A according to parts by mass, and kneading to obtain mixture C; S104, placing the mixture C in a flat vulcanizer for vulcanization, the vulcanization process is: temperature 170° C., vulcanization time 15 min, to obtain a flame retardant silicone rubber cable sheath material.

[0034] Example 2 A flame retardant silicone rubber cable sheath material, comprising, by weight, 55 parts of methyl vinyl silicone rubber, 7 parts of polydimethylsiloxane, 12 parts of a composite flame retardant, 23 parts of a thermally conductive filler, 7 parts of modified glass fiber, 2 parts of a coupling agent, 1.2 parts of a vulcanizing agent, 3.5 parts of zinc oxide, and 2 parts of a stearate, wherein the composite flame retardant is prepared by mixing modified ammonium polyphosphate and nitrogen borosilicate flame retardant in a weight ratio of 2:3, the coupling agent is composed of methyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, and γ-(2,3-epoxypropyloxy)propyltrimethoxysilane in a weight ratio of 6:5:4, the vulcanizing agent is 2,5-dimethyl-2,5-di-tert-butylperoxyhexane, and the stearate is magnesium stearate.

[0035] The method for preparing the flame retardant silicone rubber cable sheath material comprises the following steps: S101, mixing methyl vinyl silicone rubber, composite flame retardant, thermal conductive filler, modified glass fiber and coupling agent according to their weight proportions, adding the mixture to a kneader for heating and kneading, wherein the kneading temperature is 115° C. and the kneading time is 4 hours, to obtain a mixture A; S102, mixing polydimethylsiloxane, zinc oxide and stearate according to their weight parts to obtain a mixture B; S103, adding mixture B and a vulcanizing agent to mixture A according to parts by mass, and kneading to obtain mixture C; S104, placing the mixture C in a flat vulcanizer for vulcanization, the vulcanization process is: temperature 190° C., vulcanization time 10 min, to obtain a flame retardant silicone rubber cable sheath material.

[0036] Example 3 A flame retardant silicone rubber cable sheath material, comprising, by weight, 53 parts of methyl vinyl silicone rubber, 6 parts of polydimethylsiloxane, 11 parts of a composite flame retardant, 20 parts of a thermally conductive filler, 6 parts of modified glass fiber, 1.5 parts of a coupling agent, 1.1 parts of a vulcanizing agent, 3 parts of zinc oxide, and 1.5 parts of a stearate, wherein the composite flame retardant is prepared by mixing modified ammonium polyphosphate and nitrogen borosilicate flame retardant in a weight ratio of 2:3, the coupling agent is composed of methyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, and γ-(2,3-epoxypropyloxy)propyltrimethoxysilane in a weight ratio of 6:5:4, the vulcanizing agent is 2,5-dimethyl-2,5-di-tert-butylperoxyhexane, and the stearate is calcium stearate.

[0037] The method for preparing the flame retardant silicone rubber cable sheath material comprises the following steps: S101. Mix methyl vinyl silicone rubber, composite flame retardant, thermal conductive filler, modified glass fiber and coupling agent according to their weight percentages, add them into a kneader for heating and kneading, the kneading temperature is 110° C., and the kneading time is 4.5 hours to obtain a mixture A; S102. Mix polydimethylsiloxane, zinc oxide and stearate according to their weight percentages and stir to obtain a mixture B; S103, adding mixture B and a vulcanizing agent to mixture A according to parts by mass, and kneading to obtain mixture C; S104, placing the mixture C in a flat vulcanizer for vulcanization, the vulcanization process is: temperature 180° C., vulcanization time 12 min, to obtain a flame retardant silicone rubber cable sheath material.

[0038] Comparative Example 1 The same as Example 3, except that: the composite flame retardant is modified ammonium polyphosphate.

[0039] Comparative Example 2 The same as Example 3, except that: the composite flame retardant is a nitrogen boron silicon flame retardant.

[0040] Comparative Example 3 The same as Example 3, except that an equal amount of glass fiber is used instead of the modified glass fiber.

[0041] Comparative Example 4 The same as Example 3, except that an equal amount of boron nitride is used to replace the thermal conductive filler.

[0042] Comparative Example 5 The same as Example 3, except that: the coupling agent is methyltrimethoxysilane.

[0043] Comparative Example 6 The same as Example 3, except that: the coupling agent is γ-mercaptopropyltrimethoxysilane.

[0044] Comparative Example 7 The same as Example 3, except that: the coupling agent is γ-(2,3-epoxypropoxy)propyltrimethoxysilane.

[0045] Performance testing The flame retardant silicone rubber cable sheath materials prepared in Examples 1 to 3 and Comparative Examples 1 to 7 were sampled and processed into test strips for testing. The test results are shown in Table 1. The Shore A hardness tester is used to test the Shore A hardness according to the method of GB / T531.1-2008. The tensile strength and elongation at break were tested according to standard GB / T528-2009, with a tensile rate of 50 mm / min; Oxygen index: The oxygen index of the material is tested according to GB / T 10707-2008; Thermal conductivity: Tested in accordance with ASTM D5470; Tear strength: tested according to GB / T5292008; Volume resistivity: Tested in accordance with GB / T1692-2008; Breakdown strength: Tested in accordance with GB / T1695-2005; Table 1 Performance test Analyzing the data in Table 1, we can see that: 1) The flame-retardant silicone rubber cable sheath material prepared in Examples 1 to 3 has good thermal conductivity, good flame retardancy and excellent mechanical properties, and can meet the needs of high-performance cables.

[0046] 2) A comparative analysis of the performance of the flame-retardant silicone rubber cable sheath material obtained in combination with Example 3 and Comparative Examples 1-2 shows that the flame retardant and comprehensive performance of the flame-retardant silicone rubber cable sheath material can be improved by using a composite flame retardant prepared by mixing modified ammonium polyphosphate and nitrogen borosilicate flame retardant in a mass ratio of 2:3 and utilizing the synergistic effect therebetween.

[0047] 3) The performance comparison analysis of the flame-retardant silicone rubber cable sheath material obtained in combination with Example 3 and Comparative Example 3 shows that the modified glass fiber of the present application is obtained by a specific preparation method, and its compatibility with silicone rubber can be improved by modifying the organic nitrogen-phosphorus flame retardant on the surface of the glass fiber. This modified glass fiber can be better dispersed in silicone rubber, effectively improving the agglomeration problem of the glass fiber, thereby improving the overall performance of the cable sheath material. The nitrogen-phosphorus flame retardant on the surface of the modified glass fiber can generate non-combustible gases (such as nitrogen, ammonia, etc.) and phosphoric acid derivatives that promote rapid dehydration of silicone rubber when the silicone rubber burns, forming an expanded carbon layer. This expanded carbon layer can effectively block oxygen and heat, produce an efficient flame retardant effect, and prevent further combustion. The modified glass fiber is evenly dispersed in the silicone rubber, which can not only disperse and transfer stress, but also improve the tensile strength of the silicone rubber. This makes the cable sheath less likely to be damaged when pulled by external forces, and improves the durability and service life of the cable sheath.

[0048] 4) The performance comparison analysis of the flame retardant silicone rubber cable sheath material prepared in combination with Example 3 and Comparative Example 4 shows that the thermal conductive filler prepared in the present application, first, the surface of the boron nitride particles after ozonation and 3-(isobutylene acyloxy)propyltrimethoxysilane treatment is oxidized and reacts with the organosilicon compound, thereby improving the hydrophobicity and compatibility of boron nitride with silicone rubber. This significantly improves the dispersibility and uniformity of the thermal conductive filler in silicone rubber. Secondly, the thermal conductive filler forms a "percolation network" structure in the cable sheath material, which effectively improves the thermal conductivity of the cable sheath material. This structure strengthens the conduction of heat, so that the heat generated by the cable during use can be quickly dissipated, thereby reducing the temperature of the cable and improving the service life and safety of the cable. In addition, the thermal conductive filler also has excellent temperature resistance. In a high temperature environment, the thermal conductive filler can maintain stable performance and will not reduce its thermal conductivity due to the increase in temperature. This allows the flame retardant silicone rubber cable sheath material to still maintain good thermal conductivity in a high temperature environment, ensuring the safe operation of the cable. In summary, the thermal conductive filler prepared in this application plays a role in improving thermal conductivity, enhancing temperature resistance and improving the overall performance of the material in the flame-retardant silicone rubber cable sheath material. Through the synergistic effect with other components, an efficient and safe flame retardant system is formed, which provides a strong guarantee for the safe operation of the cable.

[0049] 5) The performance comparison analysis of the flame-retardant silicone rubber cable sheath material obtained in combination with Example 3 and Comparative Examples 5-7 shows that the coupling agent is composed of methyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane and γ-(2,3-epoxypropoxy)propyltrimethoxysilane in a mass ratio of 6:5:4. The synergistic effect between these three coupling agents is that their respective characteristics can complement each other and work together between the inorganic filler and the silicone rubber to form a more stable and uniform interface layer. Such an interface layer can not only improve the mechanical properties of the material, but also enhance the temperature resistance, chemical resistance and mechanical properties of the material. In addition, good compatibility and dispersibility also help to improve the overall flame retardant and safety performance of the material.

[0050] The above embodiments are only used to explain the technical solutions of the present application rather than to limit them. Although the above embodiments provide a specific description of the present application, relevant technical personnel should understand that the specific implementation methods of the present application can still be modified or replaced by equivalents, and any modifications and equivalent replacements that do not depart from the spirit and scope of the present application should be included in the protection scope of the present application.

Claims

1. A flame retardant silicone rubber cable sheath material, It is characterized in that The raw materials include, by weight: 50-55 parts of methyl vinyl silicone rubber, 5-7 parts of polydimethylsiloxane, 10-12 parts of composite flame retardant, 18-23 parts of thermal conductive filler, 5-7 parts of modified glass fiber, 1-2 parts of coupling agent, 1-1.2 parts of vulcanizing agent, 2.5-3.5 parts of zinc oxide, and 1-2 parts of stearate. The composite flame retardant is prepared by mixing modified ammonium polyphosphate and nitrogen borosilicate flame retardant in a weight ratio of 2:

3.

2. According to claim 1, a flame retardant silicone rubber cable sheath material, It is characterized in that The preparation method of the modified ammonium polyphosphate is as follows: according to the mass fractions, under the protection of nitrogen, ammonium polyphosphate, polymethylphenylsiloxane and trimethyl borate are added into a reactor and placed in a heating jacket for heating and stirring, the heating temperature is set to 190-200°C, the heating rate is 10°C / minute, the stirring rate is 400rpm, and water is removed by distillation; after reacting for 50-60min, the product is placed in anhydrous ethanol to be completely dissolved, and then deionized water is poured into it to precipitate the product, the precipitated product is filtered and vacuum dried at 80°C for 24h, and then ground and sieved to obtain the modified ammonium polyphosphate.

3. According to claim 2, a flame retardant silicone rubber cable sheath material, It is characterized in that The mass ratio of the ammonium polyphosphate, polymethylphenylsiloxane, trimethyl borate, anhydrous ethanol and deionized water is 10:7:3:60:

300.

4. According to claim 1, a flame retardant silicone rubber cable sheath material, It is characterized in that The preparation method of the nitrogen boron silicon flame retardant comprises the following steps: S41, 0.2mol melamine and 0.5mol 3-formylphenylboronic acid were added to a four-necked flask containing 1.5L toluene, stirred and mixed evenly under nitrogen, then slowly heated to 110°C, condensed and refluxed for 7h, after the reaction was completed, cooled to room temperature, poured into a beaker containing 1L benzene, allowed to stand for 20min, filtered, the filter cake was washed three times with boiling water, and vacuum dried at 70°C to obtain a boron nitrogen flame retardant; S42. Add 0.3 mol of boron nitrogen flame retardant into a reactor containing 1 L of N,N-dimethylformamide, stir and mix evenly, then add 0.4 mol of hydroxymethyltriethoxysilane, and heat the reaction system to 130°C and reflux for 20 hours. After the reaction is completed, remove the solvent by rotary evaporation, and vacuum dry at 80°C for 24 hours to obtain nitrogen boron silicon flame retardant.

5. According to claim 1, a flame retardant silicone rubber cable sheath material, It is characterized in that The preparation method of the modified glass fiber comprises the following steps: S51, according to the mass fraction, add 50 parts of glass fiber to 300 parts of toluene, mix well, heat to 60°C, add 30 parts of diallyl chlorophosphate and 10 parts of pyridine, react for 3 hours, after the reaction is completed, centrifuge and separate the solid product, wash, and dry to obtain a modified glass fiber intermediate; S52. Disperse 50 parts of the modified glass fiber intermediate into 300 parts of tetrahydrofuran according to the mass fractions, stir evenly, then add 80 parts of 1-(3-aminopropyl)imidazole, stir and react at 32°C for 9 hours, filter after the reaction, wash, and vacuum dry to obtain the modified glass fiber.

6. The flame retardant silicone rubber cable sheath material according to claim 1, It is characterized in that The preparation method of the thermal conductive filler comprises the following steps: S61. According to the mass fraction, 60 parts of boron nitride are placed in 160 parts of 1 mol / L NaOH solution, pretreated at 90° C. for 5 hours, the surface oil is washed off, filtered, and the deoiled boron nitride is placed in an ozonation treatment device for ozonation treatment for 4 hours, and the solid-liquid separation is performed to obtain ozonated modified boron nitride; S62. Add 60 parts of ozonated modified boron nitride into a reactor containing 130 parts of 3-(isomethacryloyloxy)propyltrimethoxysilane and 200 parts of toluene according to their mass proportions, place in an oil bath at 90°C with stirring, and reflux the cold gel for 5 hours. Rinse the boron nitride treated with 3-(isomethacryloyloxy)propyltrimethoxysilane with ethanol three times, then wash it once with distilled water, filter it, and dry it to obtain a thermally conductive filler.

7. The flame retardant silicone rubber cable sheath material according to claim 1, It is characterized in that The coupling agent is composed of methyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane and γ-(2,3-epoxypropyloxy)propyltrimethoxysilane in a mass ratio of 6:5:

4.

8. The flame retardant silicone rubber cable sheath material according to claim 1, It is characterized in that The vulcanizing agent is 2,5-dimethyl-2,5-di-tert-butyl peroxide hexane.

9. The flame retardant silicone rubber cable sheath material according to claim 1, It is characterized in that The stearate is at least one of zinc stearate, magnesium stearate and calcium stearate.

10. A method for preparing a flame retardant silicone rubber cable sheath material according to any one of claims 1 to 9, It is characterized in that The following steps are involved: S101, mixing methyl vinyl silicone rubber, composite flame retardant, thermal conductive filler, modified glass fiber and coupling agent according to their weight parts, adding them into a kneader for heating and kneading, wherein the kneading temperature is 105-115° C. and the kneading time is 4-5 hours, to obtain a mixture A; S102, mixing polydimethylsiloxane, zinc oxide and stearate according to their weight parts to obtain a mixture B; S103, adding mixture B and a vulcanizing agent to mixture A according to parts by mass, and kneading to obtain mixture C; S104, placing the mixture C in a flat vulcanizer for vulcanization, the vulcanization process is: temperature 170-190° C., vulcanization time 10-15 min, to obtain a flame retardant silicone rubber cable sheath material.

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