High-insulation flame-retardant sealant composition for intermediate joint of high-voltage cable as well as preparation method and application of sealant composition

Abstract

The invention relates to the technical field of sealants, in particular to a sealant composition for an intermediate joint of a high-insulation flame-retardant high-voltage cable as well as a preparation method and application of the sealant composition. The high-insulation flame-retardant sealant composition for the intermediate joint of the high-voltage cable is prepared from the following raw materials in parts by mass: 28 to 32 parts of modified castor oil, 14 to 16 parts of isophorone diisocyanate, 6 to 8 parts of chain extender, 0.5 to 0.6 part of catalyst, 1.2 to 1.5 parts of antioxidant, 8 to 10 parts of heat-conducting flame retardant, 6 to 8 parts of heat-conducting filler, 28 to 32 parts of calcium carbonate and 2 to 3 parts of silane coupling agent. The high-insulation flame-retardant sealant composition for the intermediate joint of the high-voltage cable, provided by the invention, has the advantages of excellent flame retardance, excellent insulativity, excellent thermal conductivity and better mechanical property, can meet special requirements in the fields of high-voltage cables and the like, and has important practical value and market potential.

Description

Technical Field

[0001] The present application relates to the technical field of sealants, and in particular to a high-insulation flame-retardant high-voltage cable intermediate joint sealant composition, and a preparation method and application thereof. Background Art

[0002] The middle joint of high-voltage cable is a key component in the cable line. The electronic plug-in components in the cable joint are connected together with the wire bundle after welding or crimping to achieve the requirements of anti-loosening, moisture-proof, vibration-proof and impact-resistant. In order to avoid the middle joint of high-voltage cable not being sealed in harsh environments such as high temperature, high humidity, and high salt spray, resulting in water vapor intrusion, insulation resistance reduction, corrosion of connectors, and cable joint disconnection, the high-voltage cable joint must ensure its air tightness, flame retardancy, thermal conductivity and insulation.

[0003] At present, the sealing method used for high-voltage cable intermediate joints is to fill the high-voltage cable joints with sealant. The connection quality between cable joints directly affects the reliability of the cable line, as well as the safety and operation stability of the entire power transmission and transformation line. The sealants currently used need to be improved in terms of flame retardancy, thermal conductivity and insulation.

[0004] Therefore, there is an urgent need to develop a high-insulation flame-retardant high-voltage cable intermediate joint sealant composition with good flame retardancy, thermal conductivity and good mechanical properties to meet market demand. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present application provides a high-insulation flame-retardant high-voltage cable intermediate joint sealant composition and a preparation method and application thereof. The high-insulation flame-retardant high-voltage cable intermediate joint sealant composition prepared in the present application has excellent flame retardancy, excellent insulation, thermal conductivity and good mechanical properties, and is widely used in the fields of sealing and protection of high-voltage cable intermediate joints, new energy charging pile interfaces or offshore wind power cables.

[0006] In the first aspect, the present application provides a high-insulation flame-retardant high-voltage cable intermediate joint sealant composition, which adopts the following technical solution: A high-insulation flame-retardant high-voltage cable intermediate joint sealant composition, wherein the raw materials for preparation include, by weight: 28-32 parts of modified castor oil, 14-16 parts of isophorone diisocyanate, 6-8 parts of chain extender, 0.5-0.6 parts of catalyst, 1.2-1.5 parts of antioxidant, 8-10 parts of thermal conductive flame retardant, 6-8 parts of thermal conductive filler, 28-32 parts of calcium carbonate and 2-3 parts of silane coupling agent.

[0007] By adopting the above technical solutions, the modified castor oil is used as the matrix material. By introducing amide groups and epoxy groups, the modified castor oil improves the mechanical properties, fluidity and chemical bonding force with the surface of the cable joint. At the same time, the modified castor oil also has good polarity and adhesion, which helps to enhance the adhesion between the sealant composition and the cable joint. In addition, the modified castor oil can provide low-polarity groups to reduce leakage current, thereby improving insulation. Isophorone diisocyanate is used as a crosslinking agent. Isophorone diisocyanate can react with the active groups in the modified castor oil to form stable chemical bonds, thereby enhancing the mechanical properties and heat resistance of the material. The chain extender is used to improve the processing performance of the material and increase the strength of the material. By reacting with isophorone diisocyanate, the chain extender can increase the length of the molecular chain, thereby improving the toughness of the material. The catalyst is used to accelerate the chemical reaction process to ensure that the reaction of the material is faster and more uniform. The antioxidant can prevent the material from degrading due to oxidation during long-term use and extend the service life of the material. The thermal conductive flame retardant generates magnesium hydroxide on the surface of graphene oxide and introduces P, N, and S elements. The thermal conductive flame retardant not only improves the thermal conductivity of the material but also significantly improves the flame retardant performance of the material through multiple mechanisms. Thermal conductive filler: The combined use of modified boron nitride nanosheets and graphene oxide forms an ordered layered arrangement in the plane through hydrogen bond interaction, providing a good heat transfer path, thereby significantly improving the thermal conductivity of the material. At the same time, the dispersibility and compatibility of the material modified by nanocellulose in the sealant composition system are improved. Calcium carbonate: Calcium carbonate is used as a filler, which can increase the rigidity and hardness of the material while reducing costs. Silane coupling agent: The silane coupling agent is used to improve the interfacial compatibility between the filler and the matrix material and improve the overall performance of the material. In summary, these components, through their respective functions and their synergistic effects, jointly improve the flame retardancy, insulation, thermal conductivity and mechanical properties of the high-insulation flame-retardant high-voltage cable joint sealant composition. This sealant composition can meet the sealing and protection requirements of high-voltage cable joints, new energy charging pile interfaces or offshore wind power cables.

[0008] Preferably, the preparation method of the modified castor oil includes the following steps: S21. According to the mass parts, add 9-10 parts of lysine to 100 parts of castor oil, and heat at 146-150 °C for 5-6 hours to obtain amidated castor oil; S22. According to the mass parts, add 5 parts of formic acid to 20 parts of amidated castor oil, stir for 20 minutes, add 0.13 parts of sulfuric acid with a mass concentration of 98%, continue to stir for 5 minutes, add 4.5 parts of hydrogen peroxide aqueous solution with a mass concentration of 20%, heat to 65 °C and react for 8 hours, cool to room temperature, wash the oil layer with a 5% sodium carbonate aqueous solution and deionized water in sequence until neutral, and after drying, obtain the modified castor oil.

[0009] By adopting the above technical solution, the modified castor oil can increase the mechanical properties and fluidity of the material and is beneficial to processing and molding by introducing amide groups into the castor oil. Then, epoxy groups are further introduced into the castor oil, which can react chemically with functional groups such as hydroxyl groups on the surface of the cable joint, thereby enhancing the chemical bonding force between the sealant composition and the cable joint. Moreover, the introduction of epoxy groups enables the sealant composition to still maintain a good adhesion effect under high-temperature conditions. Castor oil also has certain polarity and adhesiveness, which can form good interfacial compatibility between the sealant composition and the cable joint, thereby enhancing the adhesiveness between them. The modified castor oil can improve the mechanical properties of the sealant composition. At the same time, the modified castor oil provides low-polarity groups to reduce leakage current and improve the insulation of the sealant composition.

[0010] Preferably, the preparation method of the thermally conductive flame retardant includes the following steps: S31. According to the mass parts, disperse 5 parts of graphene oxide and 100 parts of deionized water by ultrasonic for 30 - 40 minutes, then add 9.6 parts of magnesium chloride hexahydrate and 0.8 part of sodium chloride, heat up to 40 - 45 °C, stir and react for 50 - 60 minutes, slowly drop 150 parts of sodium hydroxide aqueous solution with a mass concentration of 21% and continue stirring for 6 - 8 hours. After vacuum filtration, wash with absolute ethanol 3 times, and vacuum dry at 80 °C for 24 hours to obtain a composite flame retardant; S32. According to the mass parts, place 10 parts of the composite flame retardant in 70 parts of absolute ethanol, then add 5 parts of vinyltris(2 - methoxyethoxy)silane, heat up to 40 - 45 °C, stir and react for 8 - 10 hours, centrifuge to obtain the solid, wash with absolute ethanol 3 times, and vacuum dry at 80 °C for 24 hours to obtain a silane - modified composite flame retardant; S33. According to the mass parts, place the silane - modified composite flame retardant in absolute ethanol and ultrasonically mix for 25 - 30 minutes, then add diethyl allyl phosphate and a mixed monomer and stir - mix for 50 - 60 minutes. Under a nitrogen atmosphere, add photoinitiator 184, and irradiate with 365 nm ultraviolet light at 45 °C and stir for 4 - 5 h. Centrifuge to obtain the solid, wash with absolute ethanol 3 times, and vacuum dry at 80 °C for 24 hours to obtain the thermally conductive flame retardant.

[0011] By adopting the above technical solution, magnesium hydroxide is uniformly generated on the surface of graphene oxide, reducing its own agglomeration phenomenon and increasing its dispersibility in the sealant composition system. Then, through organic modification, the thermally conductive flame retardant is uniformly distributed in the sealant composition, enhancing the interfacial interaction. While improving the mechanical properties and thermal conductivity, P, N, and S elements are introduced, and through multiple mechanisms such as carbonization effect, barrier effect, and smoke suppression effect, the flame - retardant performance of the sealant composition is significantly improved.

[0012] Preferably, in step S33, the mixed monomers are composed of thioglycerol and aminothiophenol in a mass ratio of 1:2.

[0013] Preferably, in step S33, the mass ratio of the silane-modified composite flame retardant, absolute ethanol, diethyl allyl phosphate, mixed monomers, and photoinitiator 184 is 10:(25 - 30):(2.5 - 2.8):(1.5 - 1.7):(0.6 - 0.8).

[0014] Preferably, the preparation method of the heat-conducting filler comprises the following steps: S61. According to the mass parts, disperse 10 parts of boron nitride nanosheets in 10 parts of an ethanol aqueous solution with a concentration of 75% to obtain a boron nitride suspension after ultrasonic dispersion. Add 10 parts of tannic acid and 0.8 part of vinyltriethoxysilane to the boron nitride suspension, mix and stir to react. After the reaction, filter, wash, and dry to obtain modified boron nitride nanosheets for standby; S62. According to the mass parts, disperse 10 parts of the modified boron nitride nanosheets and 5 parts of graphene oxide in 100 parts of a nanocellulose solution with a mass concentration of 0.8% and ultrasonically disperse for 50 minutes to obtain a mixture. Vacuum freeze-dry the mixture at 60 °C for 24 h to obtain the heat-conducting filler.

[0015] By adopting the above technical solution, the modified boron nitride nanosheets and graphene oxide in the heat-conducting filler will produce a synergistic effect. On the one hand, the thermal conductivity of the sealant composition will be significantly enhanced after the modification of boron nitride nanosheets and graphene oxide. This is because there is a strong hydrogen bond interaction between the modified boron nitride nanosheets and graphene oxide. Under the action of hydrogen bonds, the two-dimensional boron nitride nanosheets and one-dimensional graphene oxide can be tightly stacked together after mixing and are highly oriented in the plane direction to form a "brick-mortar" layered structure. This highly oriented ordered in-plane arrangement will provide a good path for the transfer of heat energy between adjacent boron nitride nanosheets and can significantly improve the thermal conductivity of the sealant composition. On the other hand, after the modified boron nitride nanosheets and graphene oxide are modified by nanocellulose, their dispersibility and compatibility in the sealant composition system can be improved, thereby significantly enhancing the thermal conductivity and mechanical properties of the sealant composition.

[0016] Preferably, the silane coupling agent is composed of vinyltris(2-methoxyethoxy)silane and N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane in a mass ratio of 2:3.

[0017] By adopting the above technical solutions, the silane coupling agent can improve the interfacial compatibility of the sealant composition, enhance the adhesion between materials, and at the same time improve the mechanical properties, flame retardancy and thermal conductivity of the materials. The synergistic effect between vinyltris(2-methoxyethoxy)silane and N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane may include the following aspects: The silicon alkyl groups in the silane coupling agent can form chemical bonds with other components in the sealant composition through hydrolysis and condensation reactions, thereby improving the stability and adhesion of the materials. The polar groups such as amino groups and hydroxyl groups in the silane coupling agent can form non-covalent interactions with other components in the sealant composition through physical adsorption, thereby improving the compatibility and dispersibility of the materials. The silane coupling agent can improve the interfacial compatibility between the sealant composition and the cable joint, thereby enhancing the adhesion and mechanical properties between them. The silicon alkyl groups in the silane coupling agent can form chemical bonds with the modified boron nitride nanosheets and graphene oxide in the thermal conductive filler, thereby improving the thermal conductivity of the sealant composition. In summary, the silane coupling agent plays a key role in the preparation of the high-insulation and flame-retardant high-voltage cable joint sealant composition, not only improving the adhesion and mechanical properties of the materials, but also improving the thermal conductivity and interfacial compatibility of the materials.

[0018] Preferably, the chain extender is ethylene glycol; the catalyst is dibutyltin dilaurate; the antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0019] In a second aspect, the present application provides a method for preparing a high-insulation and flame-retardant high-voltage cable joint sealant composition, adopting the following technical solutions: As a general technical concept, the present application also provides a method for preparing the above high-insulation and flame-retardant high-voltage cable joint sealant composition, including the following steps: S91. According to the mass parts, put the modified castor oil, isophorone diisocyanate and chain extender into a reactor, stir for 15-20 minutes to obtain a reactant to be reacted; S92. According to the mass parts, keep the reactant to be reacted at 100-110°C, add a catalyst to the reactant to be reacted, react for 40-45 minutes, then reduce the holding temperature to 60-70°C, and sequentially add an antioxidant, a thermal conductive flame retardant, a thermal conductive filler, calcium carbonate and a silane coupling agent, stir and mix for 30-40 minutes, then cool down, evacuate, stand for defoaming, discharge and package to obtain a high-insulation and flame-retardant high-voltage cable joint sealant composition.

[0020] In a third aspect, the present application provides an application of a high-insulation and flame-retardant high-voltage cable joint sealant composition, adopting the following technical solutions: As a general technical concept, the present application also provides the above-mentioned high-insulation and flame-retardant high-voltage cable joint sealant composition for the sealing and protection of high-voltage cable joints, new energy charging pile interfaces, or offshore wind power cables.

[0021] In summary, the present application includes at least one of the following beneficial technical effects: 1. Excellent flame-retardant performance: By introducing a thermally conductive flame retardant and a composite material of modified boron nitride nanosheets and graphene oxide, and through multiple mechanisms such as carbonization effect, barrier effect, and smoke suppression effect, the flame-retardant performance of the sealant composition is significantly improved.

[0022] 2. Excellent insulation performance: The modified castor oil provides low-polarity groups, reducing leakage current, thereby enhancing the insulation performance of the sealant composition.

[0023] 3. Excellent thermal conductivity: Through the synergistic effect of modified boron nitride nanosheets and graphene oxide, and their modification treatment with nanocellulose, the thermal conductivity of the sealant composition is significantly enhanced.

[0024] 4. Good mechanical properties: The introduction of modified castor oil and thermally conductive fillers, and their chemical bonding force with the surface of the cable joint, enhance the mechanical properties of the sealant composition.

[0025] 5. Enhanced interfacial compatibility: The modified castor oil and thermally conductive fillers form good interfacial compatibility between the sealant composition and the cable joint, enhancing their adhesion.

[0026] 6. Wide application scenarios: Due to the above advantages, this high-insulation and flame-retardant high-voltage cable joint sealant composition is widely used in the sealing and protection of high-voltage cable joints, new energy charging pile interfaces, offshore wind power cables and other fields. Specific Embodiments

[0027] The following will describe the implementation embodiments of the present application in detail. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present application and should not be regarded as limiting the scope of the present application. For those not specified in the embodiments, they are carried out under conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0028] In the following examples and preparation examples, 1 part means 100 g.

[0029] Preparation Example 1 Preparation of Modified Castor Oil The preparation method of modified castor oil includes the following steps: S21. Add 9.5 parts of lysine to 100 parts of castor oil by mass fraction, and heat at 148 °C for 5.6 hours to obtain amidated castor oil; S22. Add 5 parts of formic acid to 20 parts of amidated castor oil by mass fraction, stir for 20 minutes, add 0.13 parts of sulfuric acid with a mass concentration of 98%, continue to stir for 5 minutes, add 4.5 parts of hydrogen peroxide aqueous solution with a mass concentration of 20%, heat to 65 °C and react for 8 hours, cool to room temperature, wash the oil layer with sodium carbonate aqueous solution with a mass concentration of 5% and deionized water in sequence until neutral, and after drying, obtain modified castor oil.

[0030] Preparation Example 2 Preparation of Thermal Conductive Flame Retardant A method for preparing a thermal conductive flame retardant, comprising the following steps: S31. Ultrasonically disperse 5 parts of graphene oxide and 100 parts of deionized water by mass fraction for 35 minutes, add 9.6 parts of magnesium chloride hexahydrate and 0.8 parts of sodium chloride, raise the temperature to 43 °C, stir and react for 55 minutes, then slowly drop 150 parts of sodium hydroxide aqueous solution with a mass concentration of 21%, continue to stir for 7 hours, after vacuum filtration, wash with absolute ethanol 3 times, and vacuum dry at 80 °C for 24 hours to obtain a composite flame retardant; S32. Place 10 parts of the composite flame retardant in 70 parts of absolute ethanol by mass fraction, add 5 parts of vinyltris(2-methoxyethoxy)silane, raise the temperature to 44 °C, stir and react for 9 hours, centrifuge to obtain the solid, wash with absolute ethanol 3 times, and vacuum dry at 80 °C for 24 hours to obtain a silane-modified composite flame retardant; S33. Ultrasonically mix 10 parts of the silane-modified composite flame retardant in 28 parts of absolute ethanol by mass fraction for 28 minutes, add 2.7 parts of diethyl allyl phosphate and 1.6 parts of a mixed monomer, stir and mix for 55 minutes, under a nitrogen atmosphere, add 0.7 parts of photoinitiator 184, and irradiate with 365 nm ultraviolet light at 45 °C and stir for 4.5 h, centrifuge to obtain the solid, wash with absolute ethanol 3 times, and vacuum dry at 80 °C for 24 hours to obtain a thermal conductive flame retardant, and the mixed monomer is composed of thioglycerol and aminothiophenol in a mass fraction ratio of 1:2.

[0031] Preparation Example 3 Preparation of Thermal Conductive Filler A method for preparing a thermal conductive filler, comprising the following steps: S61. According to the mass parts, disperse 10 parts of boron nitride nanosheets in 10 parts of ethanol aqueous solution with a concentration of 75% to obtain a boron nitride suspension after ultrasonic dispersion. Add 10 parts of tannic acid and 0.8 part of vinyltriethoxysilane to the boron nitride suspension, mix and stir to react. After the reaction, filter, wash and dry to obtain modified boron nitride nanosheets for standby; S62. According to the mass parts, disperse 10 parts of modified boron nitride nanosheets and 5 parts of graphene oxide in 100 parts of nanocellulose solution with a mass concentration of 0.8% and ultrasonically disperse for 50 minutes to obtain a mixture. Vacuum freeze-dry the mixture at 60 °C for 24 h to obtain a thermal conductive filler.

[0032] Example 1 A high-insulation and flame-retardant high-voltage cable joint sealant composition. By mass parts, the preparation raw materials include: 28 parts of modified castor oil, 14 parts of isophorone diisocyanate, 6 parts of ethylene glycol, 0.5 part of dibutyltin dilaurate, 1.2 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 8 parts of thermal conductive flame retardant, 6 parts of thermal conductive filler, 28 parts of calcium carbonate, 2 parts of silane coupling agent. The silane coupling agent is composed of vinyltris(2-methoxyethoxy)silane and N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane in a mass parts ratio of 2:3; The preparation method of the above high-insulation and flame-retardant high-voltage cable joint sealant composition includes the following steps: S91. According to the mass parts, put the modified castor oil, isophorone diisocyanate and ethylene glycol into a reactor, stir for 15 minutes to obtain a reactant to be reacted; S92. According to the mass parts, keep the reactant to be reacted at 100 °C, add dibutyltin dilaurate to the reactant to be reacted, react for 40 minutes, then lower the heat preservation temperature to 60 °C, and sequentially add pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], thermal conductive flame retardant, thermal conductive filler, calcium carbonate and silane coupling agent, stir and mix for 30 minutes, then cool down, evacuate, stand for defoaming, discharge and package to obtain a high-insulation and flame-retardant high-voltage cable joint sealant composition.

[0033] Example 2 A high-insulation and flame-retardant high-voltage cable intermediate joint sealant composition. By mass fraction, the preparation raw materials include: 32 parts of modified castor oil, 16 parts of isophorone diisocyanate, 8 parts of ethylene glycol, 0.6 part of dibutyltin dilaurate, 1.5 parts of pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 10 parts of a thermal conductive flame retardant, 8 parts of a thermal conductive filler, 32 parts of calcium carbonate, and 3 parts of a silane coupling agent. The silane coupling agent is composed of vinyltris(2-methoxyethoxy)silane and N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane in a mass fraction ratio of 2:3; The preparation method of the above high-insulation and flame-retardant high-voltage cable intermediate joint sealant composition includes the following steps: S91. According to the mass fraction, put the modified castor oil, isophorone diisocyanate, and ethylene glycol into a reactor, stir for 20 minutes to obtain a reactant to be reacted; S92. According to the mass fraction, keep the reactant to be reacted at 110 °C, add dibutyltin dilaurate to the reactant to be reacted, react for 45 minutes, then lower the heat preservation temperature to 70 °C, and successively add pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], the thermal conductive flame retardant, the thermal conductive filler, calcium carbonate, and the silane coupling agent, stir and mix for 40 minutes, then cool down, evacuate, stand for defoaming, discharge, and package to obtain the high-insulation and flame-retardant high-voltage cable intermediate joint sealant composition.

[0034] Example 3 A high-insulation and flame-retardant high-voltage cable intermediate joint sealant composition. By mass fraction, the preparation raw materials include: 30 parts of modified castor oil, 15 parts of isophorone diisocyanate, 7 parts of ethylene glycol, 0.53 part of dibutyltin dilaurate, 1.4 parts of pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 9 parts of a thermal conductive flame retardant, 7 parts of a thermal conductive filler, 30 parts of calcium carbonate, and 2.5 parts of a silane coupling agent. The silane coupling agent is composed of vinyltris(2-methoxyethoxy)silane and N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane in a mass fraction ratio of 2:3; The preparation method of the above high-insulation and flame-retardant high-voltage cable intermediate joint sealant composition includes the following steps: S91. According to the mass fraction, put the modified castor oil, isophorone diisocyanate, and ethylene glycol into a reactor, stir for 18 minutes to obtain a reactant to be reacted; S92. By mass fraction, keep the reactants to be reacted at 105 °C, add dibutyltin dilaurate to the reactants to be reacted. After reacting for 43 minutes, then lower the heat preservation temperature to 65 °C, and successively add pentaerythritol tetrakis [β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], thermal conductive flame retardant, thermal conductive filler, calcium carbonate and silane coupling agent, stir and mix for 35 minutes, then cool down, evacuate the air, stand for defoaming, discharge, and package to obtain a high-insulation flame-retardant high-voltage cable intermediate joint sealant composition.

[0035] Comparative Example 1 Same as Example 3, except that: unmodified castor oil with equal mass fraction is used instead of modified castor oil.

[0036] Comparative Example 2 Same as Example 3, except that: magnesium hydroxide with equal mass fraction is used instead of the thermal conductive flame retardant.

[0037] Comparative Example 3 Same as Example 3, except that: a mixture with equal mass fraction (prepared by mixing boron nitride nanosheets and graphene oxide in a mass ratio of 2:1) is used instead of the thermal conductive filler.

[0038] Comparative Example 4 Same as Example 3, except that: the silane coupling agent is vinyltris(2-methoxyethoxy)silane.

[0039] Comparative Example 5 Same as Example 3, except that: the silane coupling agent is N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane.

[0040] Performance detection test Respectively take samples of the high-insulation flame-retardant high-voltage cable intermediate joint sealant compositions prepared in Examples 1 - 3 and Comparative Examples 1 - 5, pour them into a polytetrafluoroethylene mold, and after standing at room temperature for 12 h, place them in an environment of 50 °C for 48 h to obtain sheet materials with a thickness of about 0.2 mm. Cut them into tensile test specimens with a length of 40 mm and a width of 5 mm, and conduct the following tests. The test results are shown in Table 1; Limiting oxygen index: Test according to ASTM D2863; Tensile strength and elongation at break are tested according to standard number GB / T528 - 2009, and the tensile rate is 50 mm / min; Volume resistivity: Test according to EC 60093; Thermal conductivity: Test according to ASTM D5470.

[0041] Table 1 Performance test Analyzing the data in Table 1, it can be seen that: 1) The high-insulation flame-retardant high-voltage cable joint sealing adhesive composition prepared in Examples 1-3 has excellent flame retardancy, excellent insulation, thermal conductivity, and good mechanical properties, and is suitable for applications in fields such as high-voltage cable joints, new energy charging pile interfaces, or the sealing and protection of offshore wind power cables.

[0042] 2) The performance comparative analysis of the high-insulation flame-retardant high-voltage cable joint sealing adhesive composition prepared by combining Example 3 and Comparative Example 1 shows that the modified castor oil prepared in this application can increase the mechanical properties and fluidity of the material by introducing amide groups into castor oil, which is beneficial to processing and molding. Continuing to introduce epoxy groups onto the castor oil enables it to chemically react with functional groups such as hydroxyl groups on the surface of the cable joint, thereby enhancing the chemical bonding force between the sealing adhesive composition and the cable joint. Moreover, the introduction of epoxy groups enables the sealing adhesive composition to still maintain a good bonding effect under high-temperature conditions. Castor oil also has certain polarity and adhesiveness, which can form good interfacial compatibility between the sealing adhesive composition and the cable joint, thereby enhancing the adhesiveness between them. The modified castor oil can improve the mechanical properties of the sealing adhesive composition, and at the same time, the modified castor oil provides low-polarity groups to reduce leakage current and improve the insulation of the sealing adhesive composition.

[0043] 3) The performance comparative analysis of the high-insulation flame-retardant high-voltage cable joint sealing adhesive composition prepared by combining Example 3 and Comparative Example 2 shows that the thermal conductive flame retardant prepared in this application: by uniformly generating magnesium hydroxide on the surface of graphene oxide, reducing its own agglomeration phenomenon and increasing its dispersibility in the sealing adhesive composition system, and then through organic modification, making the thermal conductive flame retardant uniformly distributed in the sealing adhesive composition, enhancing the interfacial interaction, improving the mechanical properties and thermal conductivity, and introducing P, N, and S elements, significantly improving the flame retardant performance of the sealing adhesive composition through various mechanisms such as carbonization effect, barrier effect, and smoke suppression effect.

[0044] 4) Comparative analysis of the performance of the high-insulation and flame-retardant high-voltage cable joint sealant composition prepared by combining Example 3 and Comparative Example 3 shows that the modified boron nitride nanosheets and graphene oxide in the heat-conducting filler prepared in this application have a synergistic effect. On the one hand, the combination of modified boron nitride nanosheets and graphene oxide significantly enhances the thermal conductivity of the sealant composition. This is because there is a strong hydrogen bond interaction between the modified boron nitride nanosheets and graphene oxide. Under the action of hydrogen bonds, the two-dimensional boron nitride nanosheets and one-dimensional graphene oxide can be closely stacked together after mixing and are highly oriented in the plane direction, forming a "brick-mortar" layered structure. This highly oriented ordered in-plane arrangement provides a good path for the transfer of heat energy between adjacent boron nitride nanosheets, which can significantly improve the thermal conductivity of the sealant composition. On the other hand, after the modified boron nitride nanosheets and graphene oxide are modified by nanocellulose, their dispersibility and compatibility in the sealant composition system can be improved, thereby significantly enhancing the thermal conductivity and mechanical properties of the sealant composition.

[0045] 5) Comparative analysis of the performance of the high-insulation and flame-retardant high-voltage cable joint sealant composition prepared by combining Example 3 and Comparative Examples 4 - 5 shows that the silane coupling agent is composed of vinyltris(2-methoxyethoxy)silane and N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane in a mass ratio of 2:3. By virtue of their combined action, through enhancing the interfacial binding force and forming stable chemical bonds, the comprehensive performance of the high-insulation and flame-retardant high-voltage cable joint sealant composition can be improved.

[0046] The above embodiments are only used to explain the technical solutions of this application and not to limit them. Although the above embodiments have specifically described this application, those skilled in the art should understand that the specific implementation manners of this application can still be modified or equivalently replaced. Any modification and equivalent replacement that do not depart from the spirit and scope of this application should be covered by the protection scope of this application.

Claims

1. A high-insulation flame-retardant high-voltage cable intermediate joint sealant composition, characterized in that: The raw materials include, by weight: 28-32 parts of modified castor oil, 14-16 parts of isophorone diisocyanate, 6-8 parts of chain extender, 0.5-0.6 parts of catalyst, 1.2-1.5 parts of antioxidant, 8-10 parts of thermal conductive flame retardant, 6-8 parts of thermal conductive filler, 28-32 parts of calcium carbonate and 2-3 parts of silane coupling agent.

2. A high-insulation flame-retardant high-voltage cable intermediate joint sealant composition according to claim 1, characterized in that: The preparation method of the modified castor oil comprises the following steps: S21, adding 9-10 parts of lysine to 100 parts of castor oil by weight, and heating at 146-150° C. for 5-6 hours to obtain amidated castor oil; S22. Add 5 parts of formic acid to 20 parts of amidated castor oil in parts by mass, stir for 20 minutes, add 0.13 parts of 98% sulfuric acid, continue stirring for 5 minutes, add 4.5 parts of 20% aqueous hydrogen peroxide solution, heat to 65° C. and react for 8 hours, cool to room temperature, wash the oil layer with 5% aqueous sodium carbonate solution and deionized water in turn until it is neutral, and obtain modified castor oil after drying.

3. A high-insulation flame-retardant high-voltage cable intermediate joint sealant composition according to claim 1, characterized in that: The preparation method of the thermal conductive flame retardant comprises the following steps: S31. After ultrasonically dispersing 5 parts of graphene oxide and 100 parts of deionized water for 30-40 minutes, 9.6 parts of magnesium chloride hexahydrate and 0.8 parts of sodium chloride were added, the temperature was raised to 40-45°C, and the mixture was stirred for 50-60 minutes. Then, 150 parts of a 21% sodium hydroxide aqueous solution were slowly added dropwise and the mixture was stirred for 6-8 hours. After vacuum filtration, the mixture was washed with anhydrous ethanol for 3 times, and vacuum dried at 80°C for 24 hours to obtain a composite flame retardant. S32. According to the mass ratio, 10 parts of the composite flame retardant are placed in 70 parts of anhydrous ethanol, and then 5 parts of vinyl tris (2-methoxyethoxy) silane are added, the temperature is raised to 40-45 ° C, and the reaction is stirred for 8-10 hours, and the solid is centrifuged, washed with anhydrous ethanol for 3 times, and vacuum dried at 80 ° C for 24 hours to obtain a silane-modified composite flame retardant; S33. According to the mass fractions, the silane-modified composite flame retardant is placed in anhydrous ethanol and ultrasonically mixed for 25-30 minutes, then allyl diethyl phosphate and the mixed monomer are added and stirred for 50-60 minutes. In a nitrogen atmosphere, photoinitiator 184 is added, and the mixture is irradiated with 365nm ultraviolet light and stirred at 45°C for 4-5h. The solid is centrifuged, washed with anhydrous ethanol for 3 times, and vacuum dried at 80°C for 24 hours to obtain a thermal conductive flame retardant.

4. A high-insulation flame-retardant high-voltage cable intermediate joint sealant composition according to claim 3, characterized in that: In step S33, the mixed monomer consists of thioglycerol and aminothiophenol in a mass ratio of 1:

2.

5. A high-insulation flame-retardant high-voltage cable intermediate joint sealant composition according to claim 3, characterized in that: In step S33, the mass ratio of the silane-modified composite flame retardant, anhydrous ethanol, allyl diethyl phosphate, mixed monomer and photoinitiator 184 is 10: (25-30): (2.5-2.8): (1.5-1.7): (0.6-0.8).

6. According to the high-insulation flame-retardant high-voltage cable intermediate joint sealant composition of claim 1, the preparation method of the thermal conductive filler comprises the following steps: S61. Dispersing 10 parts of boron nitride nanosheets in 10 parts of 75% ethanol aqueous solution by weight, obtaining a boron nitride suspension after ultrasonic dispersion, adding 10 parts of tannic acid and 0.8 parts of vinyltriethoxysilane to the boron nitride suspension, mixing and stirring to react, and after the reaction is completed, filtering, washing and drying to obtain modified boron nitride nanosheets for standby use; S62. Disperse 10 parts of modified boron nitride nanosheets and 5 parts of graphene oxide in 100 parts of nanocellulose solution with a mass concentration of 0.8% and ultrasonically disperse for 50 minutes to obtain a mixture, and freeze-dry the mixture at 60° C. in a vacuum oven for 24 hours to obtain a thermally conductive filler.

7. A high-insulation flame-retardant high-voltage cable intermediate joint sealant composition according to claim 1, characterized in that: The silane coupling agent is composed of vinyl tris(2-methoxyethoxy)silane and N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane in a mass ratio of 2:

3.

8. The high-insulation flame-retardant high-voltage cable intermediate joint sealant composition according to claim 1, characterized in that: The chain extender is ethylene glycol; the catalyst is dibutyltin dilaurate; and the antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

9. A method for preparing a high-insulation flame-retardant high-voltage cable intermediate joint sealant composition as claimed in any one of claims 1 to 8, characterized in that: The following steps are involved: S91, placing modified castor oil, isophorone diisocyanate and a chain extender into a reactor according to their weight proportions, and stirring for 15-20 minutes to obtain a reactant; S92. Insulate the reactants at 100-110°C according to their mass fractions, add a catalyst to the reactants, react for 40-45 minutes, then reduce the insulation temperature to 60-70°C, add antioxidant, thermal conductive flame retardant, thermal conductive filler, calcium carbonate and silane coupling agent in sequence, stir and mix for 30-40 minutes, cool and evacuate, let stand to degas, discharge and package to obtain a high-insulation flame-retardant high-voltage cable intermediate joint sealant composition.

10. An application of the high-insulation flame-retardant high-voltage cable intermediate joint sealant composition according to any one of claims 1 to 8, characterized in that: Used for sealing protection of high-voltage cable intermediate joints, new energy charging pile interfaces or offshore wind power cables.

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