High-flame-retardant insulated cable material and preparation method thereof

Abstract

The invention provides a high-flame-retardancy insulated cable material and a preparation method thereof.The preparation method comprises the steps that a precursor solution and a multi-metal micellar dispersion liquid are prepared respectively, a precursor comprises modified polyether nitrile, a siloxane prepolymer and a cross-linking agent, and the multi-metal micellar dispersion liquid is prepared from modified polyether nitrile, a siloxane prepolymer and a cross-linking agent; the multi-metal micellar dispersion liquid comprises a weak base solution and a mixed solution of at least two metal salt solutions; carrying out pyrolytic reaction on the carbon source to obtain a three-dimensional carbonized framework with pores inside; soaking the three-dimensional carbonized skeleton in the precursor solution and the multi-metal micellar dispersion liquid respectively, and performing staged ultraviolet curing at the temperature of 80-150 DEG C to obtain the high-flame-retardant insulated cable material. The obtained cable material can better resist mechanical stress, thermal shock and environmental aging, so that the mechanical strength and weather resistance are effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of cable materials, and in particular relates to a highly flame-retardant insulating cable material and a preparation method thereof. Background Art

[0002] In the production of traditional cable materials, polymers such as polyvinyl chloride (PVC) or polyethylene (PE) are often used as the main insulation or sheath layer, and the flame retardancy mainly depends on the added flame retardant. PVC contains a large amount of chlorine, which will release gases such as HCl when burned, which can inhibit free radical chain reactions in the flame zone. Therefore, traditional PVC cables are relatively flame retardant. When combined with the addition of bromine or chlorine flame retardants, the flame retardant effect will be more obvious. Bromine-containing compounds produce a large amount of toxic and corrosive smoke (HBr, HCl) when burned, and also release hazardous substances such as dioxins, which pose a great threat to the environment and human health.

[0003] Halogen-free flame retardant materials are used in related technologies to solve the problem of smoke toxicity. For example, phosphorus-containing flame retardants (such as ammonium polyphosphate) can promote carbonization of the material surface and generate a sticky "carbon layer" to isolate heat and oxygen. The combustion of red phosphorus will generate metaphosphoric acid and phosphoric acid, which can also help to generate a protective carbon layer. While achieving the flame retardant effect, no toxic gas is released. However, halogen-free flame retardant materials have the following disadvantages. On the one hand, halogen-free flame retardants generally require a higher filling amount to dilute the proportion of combustible polymers and release inert gases in the combustion zone, but it will lead to poor structural strength. A large amount of powder is unevenly dispersed in the material and is prone to form micropores or impurity interfaces, which weakens the performance of electrical insulation, arc resistance and other high-frequency / high-voltage environments. It is also easy to lose fillers, resulting in a shortened life; on the other hand, halogen-free flame retardant materials usually meet the general industrial and building fire protection needs, but in extreme working conditions (such as offshore oil platforms, polar or desert environments, ultra-high voltage power grids, and high-temperature smelting occasions), a single halogen-free system is not weather-resistant and is easily invalidated due to long-term thermal aging, salt spray corrosion, etc. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a highly flame-retardant insulating cable material and a preparation method thereof, aiming to solve the problems of poor mechanical strength and weather resistance.

[0005] To solve the above technical problems, the present invention is implemented as follows: the present invention provides a method for preparing a highly flame-retardant insulating cable material, the steps comprising: S1. Preparing a precursor solution and a multi-metal microcluster dispersion respectively, wherein the precursor comprises a modified polyether nitrile, a siloxane prepolymer and a crosslinking agent, and the multi-metal microcluster dispersion comprises a mixture of a weak base solution and at least two metal salt solutions; S2, pyrolyzing the carbon source to obtain a three-dimensional carbonized skeleton with pores inside; S3, immersing the three-dimensional carbonized skeleton in the precursor solution and the multi-metal microcluster dispersion respectively, and then performing UV curing in stages at 80-150° C. to obtain a highly flame-retardant insulating cable material.

[0006] In some embodiments of the present invention, in step S1, the modified polyether nitrile includes at least one of polyether nitrile acrylate copolymer, epoxy-modified polyether nitrile, and modified polyether nitrile acrylate, the siloxane prepolymer includes at least one of tetraethoxysilane, methyltriethoxysilane, and chloromethyltriethoxysilane, the cross-linking agent includes at least one of dicumyl peroxide, dibenzoyl peroxide, and cyclohexane peroxide, the weak alkaline solution includes at least one of ammonia water, sodium hydroxide, and ammonium hydroxide, and the mixed solution includes at least two of sodium silicate solution, aluminum chloride solution, magnesium sulfate solution, and ferric nitrate solution.

[0007] In some embodiments of the present invention, calculated by weight ratio, the modified polyether nitrile: the siloxane prepolymer: the cross-linking agent = 5-6: 2-3: 1, and the weak base solution: the mixed solution = 1: 1-2.

[0008] In some embodiments of the present invention, step S1 comprises: S1.1, adding the modified polyether nitrile powder to a solvent, stirring and dissolving to obtain a polymer solution, then adding a siloxane prepolymer and a crosslinking agent to the polymer solution, controlling the solution temperature within the range of 25-30°C and continuing stirring for 80-120 minutes to obtain a precursor solution; S1.2. Dissolve various metal salts in deionized water according to the component ratio, stir the solution until the metal salt is completely dissolved to obtain a mixed solution, slowly add an alkaline solution to the mixed solution, adjust the pH to 8-9, precipitate for 30 minutes, filter and wash in sequence to obtain a micellar precipitate; S1.3. The microcluster precipitate is dried at 100-200°C, and then calcined at 500-700°C in air or argon atmosphere. After cooling, a solvent and a surfactant are added to obtain a multi-metallic microcluster dispersion.

[0009] In some embodiments of the present invention, step S2 includes: S2.1, grinding the carbon source, and then adding a pore generating agent to dissolve it to obtain a carbon source solution; S2.2, in an inert atmosphere, heat the carbon source solution at a heating rate of 5-10°C / min until it reaches 700-900°C, and keep the temperature for 120-240 min; S2.3. After the insulation is completed, stop heating, increase the gas flow rate of the inert atmosphere to cool, and place it in a coupling agent after lowering it to room temperature. After soaking for 20 to 30 minutes, wash and dry it to obtain a three-dimensional carbonized skeleton.

[0010] In some embodiments of the present invention, in step S2, the carbon source includes at least one of glucose, polystyrene, and lignin, the pore generating agent includes at least one of sodium hydroxide, sodium carbonate, and calcium chloride, and the coupling agent includes at least one of a silane coupling agent, a titanate coupling agent, and a zirconate coupling agent.

[0011] In some embodiments of the present invention, step S3 includes: S3.1, the three-dimensional carbonized skeleton is first immersed in part of the precursor solution for the first time, the immersion time is 60 to 120 minutes, and the excess solution is removed by low-pressure filtration. After repeating the immersion and filtration steps 2 to 3 times, it is placed at 60 to 80 ° C for pre-drying to obtain a three-dimensional carbonized skeleton coated with a polymer; S3.2, transferring the three-dimensional carbonized skeleton coated with the polymer to the multi-metal microcluster dispersion, performing a second immersion by vibration or ultrasound, filtering to remove excess liquid again, and drying at a temperature of 100 to 120° C. to obtain a three-dimensional carbonized skeleton coated with metal microcluster; S3.3. Add the remaining precursor solution and flame retardant to the three-dimensional carbonized skeleton coated with metal microclusters, stir, heat to 80-150°C and irradiate with ultraviolet light with a wavelength of 250-400 nm, keep warm at 80-100°C for 10-20 min, keep warm at 100-120°C for 10-20 min, keep warm at 120-150°C for 10-20 min, and obtain a highly flame retardant insulating cable material after cooling.

[0012] The present invention provides a highly flame-retardant insulating cable material, which is prepared by the above-mentioned method for preparing a highly flame-retardant insulating cable material. The highly flame-retardant insulating cable material comprises a three-dimensional carbonized skeleton, modified polyether nitrile, a siloxane prepolymer and at least two metal salts, wherein: The three-dimensional carbonized skeleton is used to provide mechanical support and enhance flame retardant properties; The modified polyether nitrile is used to provide electrical insulation; The siloxane prepolymer is used to improve the flame retardant properties and weather resistance of the highly flame retardant insulating cable material; The metal salt releases inert gas by decomposition, thereby enhancing the flame retardancy and electrical insulation of the highly flame retardant insulating cable material.

[0013] Compared with the prior art, the highly flame-retardant insulating cable material and the preparation method thereof in the present invention have the following beneficial effects: By pyrolyzing the carbon source, a three-dimensional carbonized skeleton with pores inside is obtained. The skeleton has structural stability at high temperatures and excellent mechanical support. Compared with traditional cables that only rely on organic polymers as insulation layers, the new material forms a multiphase structure of carbonized skeleton + polymer network + multi-metal oxide inside, making the cable material less likely to crack or deform when heated, stressed or bent. The precursor solution contains modified polyether nitrile with unsaturated groups and siloxane prepolymers that can be cross-linked with organic groups. The two form a high-strength, high-thermal-stability organic-inorganic hybrid network under the action of cross-linking agents and ultraviolet curing. This cross-linked network combines the toughness of organic polymers and the heat resistance and aging resistance of inorganic silicon-oxygen skeletons, which improves the overall strength and life of the material. Multi-metal microclusters (oxide particles formed by at least two metal salts) are evenly dispersed on the surface and pores of the skeleton, which not only contribute to the flame retardant function, but also play a filling role at the polymer / carbon skeleton interface, which can improve the deformation resistance and mechanical stability of the material in high temperature and high humidity environments. In summary, the synergy of three-dimensional carbonized skeleton + highly cross-linked polymer + metal microclusters makes the cable material have the structural advantages of multi-phase composite, which can better resist mechanical stress, thermal shock and environmental aging, thereby effectively improving mechanical strength and weather resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic flow chart of a method for preparing a highly flame-retardant insulating cable material in one embodiment of the present invention. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0016] Please refer to Figure 1 The present invention provides a method for preparing a highly flame-retardant insulating cable material, the steps comprising: S1. Prepare a precursor solution and a multi-metal microcluster dispersion respectively, wherein the precursor comprises modified polyether nitrile, siloxane prepolymer and a crosslinking agent, and the multi-metal microcluster dispersion comprises a mixture of a weak base solution and at least two metal salt solutions.

[0017] In step S1, the modified polyether nitrile includes at least one of a polyether nitrile acrylate copolymer, an epoxy-modified polyether nitrile, and a modified polyether nitrile acrylate, the siloxane prepolymer includes at least one of tetraethoxysilane, methyltriethoxysilane, and chloromethyltriethoxysilane, the cross-linking agent includes at least one of dicumyl peroxide, dibenzoyl peroxide, and cyclohexane peroxide, the weak alkaline solution includes at least one of ammonia water, sodium hydroxide, and ammonium hydroxide, and the mixed solution includes at least two of a sodium silicate solution, an aluminum chloride solution, a magnesium sulfate solution, and a ferric nitrate solution.

[0018] Calculated by weight ratio, modified polyether nitrile powder: siloxane prepolymer: cross-linking agent = 5~6:2~3:1, weak alkaline solution: mixed solution = 1:1~2.

[0019] Step S1 includes: S1.1. Add the modified polyether nitrile powder into a solvent, stir and dissolve to obtain a polymer solution, then add the siloxane prepolymer and the crosslinking agent into the polymer solution, control the solution temperature within the range of 25-30°C and continue stirring for 80-120 minutes to obtain a precursor solution.

[0020] The unsaturated double bonds in the modified polyether nitrile make it have the potential for crosslinking reactions. Unsaturated double bonds (C=C) can undergo addition polymerization or crosslinking reactions under certain conditions (such as free radical or ion initiation, or in combination with photoinitiators under ultraviolet light irradiation). When unsaturated double bonds are introduced into the molecular chain of the modified polyether nitrile, these double bonds become reaction centers that can participate in chemical reactions.

[0021] During the modification process, by reacting with acrylic acid or acrylate, a C=C group (acrylate group) will be grafted onto the polyether nitrile chain or epoxy acrylate will be introduced, so that the polyether nitrile has both epoxy groups and double bonds that can participate in free radical polymerization. The modified polyether nitrile not only retains the excellent mechanical properties, thermal stability and chemical resistance of the original polyether nitrile, but also has the additional cross-linking property. Under the subsequent thermal curing, UV curing or free radical initiation, the double bonds react to connect countless polyether nitrile chain segments to each other to obtain a three-dimensional cross-linked network.

[0022] After synergizing with siloxane prepolymer, an organic-inorganic hybrid network can be formed, further improving the thermal stability, hydrophobicity and aging resistance of the material. The crosslinking agent can generate free radicals in the subsequent curing process, triggering the crosslinking of active groups on the modified polyether nitrile or siloxane prepolymer, and improving the mechanical strength, thermal stability and flame retardancy of the material. Under the conditions of 25-30°C and stirring for 80-120 minutes, the solvent can be prevented from volatilizing too quickly or side reactions can be caused, so that the polyether nitrile and siloxane components are fully mixed and stably dissolved, thereby obtaining a uniform precursor solution. By adjusting the ratio of modified polyether nitrile to siloxane prepolymer and crosslinking agent, the insulation performance or flame retardant efficiency can be customized according to the needs of cables with different voltage levels or temperature resistance levels.

[0023] S1.2. Dissolve various metal salts in deionized water according to the component ratio, stir the solution until the metal salt is completely dissolved to obtain a mixed solution, slowly add an alkaline solution to the mixed solution, adjust the pH to 8-9, precipitate for 30 minutes, filter and wash in sequence to obtain a micellar precipitate.

[0024] Different metal salts (such as aluminum salts, magnesium salts, iron salts, sodium silicate, etc.) form precipitation of multi-metal hydroxides / oxides under alkaline conditions. These metal oxides can release inert gases (such as water vapor, CO2) or form a dense oxide layer when burning, which inhibits the spread of flames in many ways and significantly enhances flame retardancy.

[0025] The multi-metal precipitates are not single crystals, but exist in the form of microclusters (aggregates), which provide more surface area and binding sites for subsequent bonding with the three-dimensional carbonized skeleton or polymer matrix.

[0026] Adjust the solution pH to 8-9, and slowly add weak alkaline solution to make multiple metal salts precipitate and co-precipitate simultaneously, avoiding the problem of single component crystallization or uneven precipitation, and making the metal oxides more evenly distributed in the micelles. After filtering and washing to remove impurities and excess salt in the solution, purer metal oxide micelles with controllable particle size can be obtained, preparing for subsequent drying and calcination.

[0027] S1.3. The microcluster precipitate is dried at 100-200°C, and then calcined at 500-700°C in air or argon atmosphere. After cooling, a solvent and a surfactant are added to obtain a multi-metallic microcluster dispersion.

[0028] Drying at 100-200°C can remove free water, crystal water or residual solvent in the precipitate. High-temperature calcination at 500-700°C can completely decompose the metal hydroxide or salt into a more stable metal oxide structure, thereby improving the heat resistance and chemical stability of the material.

[0029] Different metal salts will be transformed into corresponding oxides (such as aluminum oxide, magnesium oxide, iron oxide, silicon oxide, etc.) during the calcination process to form a multi-phase complementary metal oxide system. When flame retardant, it has multiple functions such as releasing inert gas, forming a ceramic shell or barrier layer. A moderate calcination temperature (500~700℃) can not only ensure full conversion, but also avoid excessive grain growth and retain a high specific surface area. Adding a surfactant after cooling can reduce the tendency of micelles to agglomerate, making them more evenly dispersed when they are subsequently compounded with a polymer system. The multi-metallic micelle dispersion obtained can be directly applied to the subsequent impregnation process (combined with a three-dimensional carbonized skeleton or a polymer precursor), forming a uniform distribution in the material and providing effective flame retardant assistance.

[0030] S2. Pyrolyzing the carbon source to obtain a three-dimensional carbonized skeleton with pores inside.

[0031] Step S2 includes: S2.1. Grind the carbon source, then add a pore-forming agent to dissolve it to obtain a carbon source solution.

[0032] Grind the carbon source into fine powder to increase its specific surface area, making subsequent dissolution or dispersion more uniform. The powder form can be evenly heated in the subsequent pyrolysis reaction, reducing local overheating or incomplete decomposition, and facilitating the formation of a more uniform porous structure. The pore generator will decompose and release gas or react chemically / physically with the carbon source at high temperature during the subsequent pyrolysis process, leaving pores in the solid skeleton. Dissolving or dispersing the carbon source and the pore generator together can ensure that the two are evenly mixed at the microscopic level, providing better prerequisites for subsequent pore formation. The solution state or highly dispersed state can ensure that the chemical reaction, gas release, and skeleton formation during pyrolysis are more uniform, which is conducive to the formation of a stable skeleton and pore structure at the micrometer or nanometer scale.

[0033] S2.2. Heat the carbon source solution under an inert atmosphere at a heating rate of 5-10°C / min until it reaches 700-900°C and keep warm for 120-240 min.

[0034] An inert gas environment is selected to prevent oxidation of the carbon source at high temperatures. This ensures efficient pyrolysis and carbonization in the range of 700-900°C, rather than combustion or over-oxidation.

[0035] A slow heating rate can make the decomposition of the pore generator and the release of gas more stable, which is conducive to the formation and maintenance of pores. If the temperature rises too quickly, it will cause a large amount of gas to burst out instantly, causing the pores to collapse or be unevenly distributed. Sufficient holding time ensures that the carbon source is completely transformed into a stable carbonization product and the pore generator is completely reacted or decomposed, so as to form stable and connected pores in the final skeleton.

[0036] During the high-temperature pyrolysis process, the carbon source decomposes and releases small molecules (such as carbon dioxide, water vapor, carbon monoxide, etc.), and the added pore generator (such as sodium carbonate, sodium hydroxide, etc.) will also decompose and produce gases or react with the carbon source to produce volatile products after being heated. When these gases escape from the carbon skeleton, they will leave randomly distributed or semi-ordered pores and voids in the solid skeleton, eventually forming a three-dimensional carbonized skeleton with a porous structure.

[0037] S2.3. After the insulation is completed, stop heating, increase the gas flow rate for cooling, and place it in a coupling agent after lowering it to room temperature. After soaking for 20 to 30 minutes, wash and dry it to obtain a three-dimensional carbonized skeleton.

[0038] After the insulation is finished, the flow rate of nitrogen or argon can be quickly increased to take away the residual heat and precipitated gas in the furnace, avoid secondary oxidation or local deformation of the pore structure during the cooling process, prevent chemical reactions from continuing in the high-temperature section, and allow the pores of the carbonized skeleton to be fixed. The coupling agent can physically / chemically combine with the surface of the carbonized skeleton, introduce specific functional groups (such as silane, titanate groups, etc.) on the surface of the skeleton, and enhance the subsequent binding force with polymers or inorganic nanoparticles. In the subsequent composite or coating (such as combining with the precursor solution and multi-metal micro-cluster dispersion), it can improve the interface adhesion and dispersion stability, and optimize the overall mechanical and flame retardant properties of the material.

[0039] The residual unbound coupling agent and impurities on the surface are removed so that the functional groups on the surface of the final skeleton are evenly distributed and the pore structure is not blocked by residues, forming a porous and surface-modified three-dimensional carbonized skeleton, providing an efficient substrate for subsequent cable insulation material processes (impregnation, coating, etc.).

[0040] In step S2.2, in order to control the porosity of the three-dimensional carbonized skeleton, the porosity of the three-dimensional carbonized skeleton can be regulated by controlling the target temperature T and the holding time t. The control equation is: in, is the effective porosity of the three-dimensional carbonized skeleton (%), is the theoretical solid density when the three-dimensional carbonized skeleton is completely dense and pore-free. The quality of the three-dimensional carbonized skeleton obtained after pyrolysis and various reactions. is the initial mass of the carbon source before pyrolysis, is the pyrolysis weight loss function, which indicates the mass loss caused by the decomposition / volatilization of the carbon source under specified process conditions. is the decomposition weight loss function of the pore generator, which indicates the mass loss caused by the decomposition / removal of the pore generator under the above process conditions. is the final volume of the three-dimensional carbonized skeleton, is the initial volume of the carbon source before pyrolysis, is the volume expansion factor (dimensionless), which indicates the expansion ratio caused by the release of gas when the carbon source and pore-forming agent are heated. is the skeleton shrinkage, which indicates the volume reduction of the carbonized skeleton due to sintering or structural collapse at high temperature. is the target temperature, For the insulation time, For the atmosphere flow, is the mass fraction of the ith component, is the density of the ith component.

[0041] This formula uses the difference between "final mass after pyrolysis" and "volume" relative to "dense state" to define the porosity of the three-dimensional carbonized skeleton. Each loss function and volume change function quantifies key processes such as carbon source decomposition, pore formation, and skeleton sintering, and is bound to process parameters. Mass loss, volume expansion, and contraction are described in the form of sub-functions, so that the model can be flexibly modified according to actual experiments or kinetic fitting. The porosity can be quickly estimated under different temperature curves and atmosphere flow rates, which is convenient for iterative optimization and industrial scale-up. Using the same porosity index to measure the degree of porous structure is closely connected with the subsequent application of the material.

[0042] for Thermal decomposition weight loss function, Pore ​​forming agent decomposition weight loss function, Volume expansion factor, The four calculation equations for skeleton shrinkage, in some embodiments, in, The maximum weight loss of the carbon source under extreme conditions is measured by thermogravimetric analysis (TGA) under conditions of long-term heat preservation at a temperature higher than the material's complete decomposition temperature (e.g. 800-1000°C). For example, it can be 70-85%. The starting temperature at which the carbon source begins to decompose significantly is analyzed by TGA curve to find the inflection point temperature at which the main weight loss begins. If the carbon source is biomass such as lignin and cellulose, the starting pyrolysis temperature is 200-300°C. It is the reference time of the pyrolysis reaction in the time dimension, indicating the minimum time required before the decomposition of the carbon source begins, and can range from 0 to 30 min. and is an empirical constant related to the temperature decomposition rate and time decomposition rate. , , Under the premise of using multiple sets of TGA data (different temperature / time conditions) for fitting, least squares method or exponential regression to estimate, for example, it can be 10 -3 ~10 0 , the unit can be min -1 or °C -1 .

[0043] It is the total mass loss caused by the maximum decomposition / volatilization of the pore-forming agent under extreme process conditions, and is determined by measuring the remaining solid mass after sufficient decomposition at high temperature. For example, it can be 1% to 20%. and This is the temperature range where the pore forming agent mainly decomposes, as can be seen from the TGA curve: Sodium carbonate is about 600-850°C, and sodium hydroxide is about 300-600°C. In order to control the sensitivity constant of the decomposition rate of the pore generating agent to time, a constant is obtained by fitting multiple sets of temperature-time experimental data, for example, 10 -3 ~10 0 , the unit can be min -1 or °C -1 . The minimum time for the start of decomposition, which can range from 0 to 30 min.

[0044] In order to control the scale factor of the shrinkage amplitude of the three-dimensional carbonized skeleton, the three-dimensional carbonized skeleton is sintered within a certain temperature range, and the volume shrinkage is measured and fitted, for example, it can be 0.1 to 5 cm³ / g. It is the characteristic temperature at which the three-dimensional carbonized skeleton shrinks at high temperature, obtained through the data of sintering / carbonization experiments. is a temperature index, which may be, for example, 300 to 1000°C. >1, indicating that a higher temperature will significantly increase shrinkage; if <1, the temperature sensitivity is low. Through experiments or numerical fitting, the dependence of volume shrinkage on temperature is measured at multiple points and a curve regression is performed to obtain, for example, 0.5 to 5. is the time-dependent "shrinkage rate constant", reflecting the cumulative effect of the holding time on the skeleton shrinkage. It is obtained by measuring the volume change over time at a fixed temperature for a long time and then regressing and fitting. For example, it can be 10-3 ~10 0 , the unit can be min -1 or °C -1 . refer to > It takes effect only after the sintering rearrangement is set. Otherwise, it takes 0. It is used to set the threshold time for the earliest sintering rearrangement to occur. It can be 10 to 60 minutes.

[0045] It is the scaling coefficient of the volume expansion of the three-dimensional carbonized skeleton, which determines the overall expansion amplitude. The volume increment of the material when heated is measured experimentally (discharge method, geometric method, etc.), and the maximum increment is obtained by fitting near the peak temperature, for example, it can be 0.1 to 1. and Reflects the temperature deviation from a certain optimal expansion temperature ( ), the expansion decay rate. If the value is larger, the expansion will decrease rapidly when leaving the peak temperature. The volume is measured at multiple temperature points, and curve fitting is performed to determine the decay constant. For example, it can be 10 -3 ~10 -1 , the unit can be ℃ -1 . It is the center temperature of the expansion peak (or optimum decomposition temperature). There are one or two main peaks. In the experiment, we observe the temperature range in which the volume expansion of the material is most significant. The peak position of the curve is used to determine the value range, which can be 300-700℃.

[0046] By mapping the mass and volume changes of materials in pyrolysis, pore formation, sintering shrinkage, volume expansion and other stages to corresponding functions, the chemical / physical changes in each stage can be numerically modeled. This allows the preparation operator to more systematically analyze how much mass the material will lose, how much it will expand, and how much it will shrink at different temperatures, heating rates, holding times and gas flows, thereby making quantitative predictions on the structure and porosity of the final three-dimensional carbonized skeleton.

[0047] Traditional preparation of porous carbon materials often relies on experience or a large number of experiments to explore the appropriate heating system and formula. Using these model equations, numerical simulations or rough estimates can be made before the experiment to screen the most promising process routes, greatly reducing the number and time of trial and error. Especially when scaling up industrially, it can reduce the waste of raw materials and energy consumption, and improve process efficiency and repeatability.

[0048] S3. The three-dimensional carbonized skeleton is immersed in the precursor solution and the multi-metal microcluster dispersion respectively, and then UV-cured in stages at 80 to 150° C. to obtain a highly flame-retardant insulating cable material.

[0049] Step S3 includes: S3.1. Place the three-dimensional carbonized skeleton in part of the precursor solution for the first immersion. The immersion time is 60 to 120 minutes. Remove the excess solution by low-pressure filtration. Repeat the immersion and filtration steps 2 to 3 times, and then pre-dry at 60 to 80°C to obtain a three-dimensional carbonized skeleton coated with a polymer.

[0050] Multiple impregnations and low-pressure filtration allow the precursor solution to fully penetrate into the pores of the three-dimensional carbonized skeleton, thereby evenly forming a modified polymer coating layer inside the carbonized skeleton and on the surface of the pore wall. Since the modified polyether nitrile and siloxane prepolymers have excellent electrical insulation and high temperature resistance, this step significantly improves the overall electrical insulation performance of the skeleton. During the pre-drying process at 60~80℃, the solvent evaporates, allowing the polymer to form initial adhesion and condensation in the pores and on the surface of the skeleton, laying a good foundation for subsequent UV curing or further coating, while avoiding excessive volatilization or uneven distribution of the polymer at high temperature, ensuring a more stable material structure.

[0051] Although the carbonized skeleton itself has good heat resistance and porous structure, it is prone to brittleness. By coating a certain amount of polymer, a composite interface can be formed at the microscopic pore wall to improve the overall mechanical toughness and meet the bending or stretching requirements during cable laying.

[0052] S3.2. Transfer the three-dimensional carbonized skeleton coated with the polymer to the multi-metal microcluster dispersion, perform a second immersion by vibration or ultrasound, remove the excess liquid by suction again, and dry it at a temperature of 100-120°C to obtain a three-dimensional carbonized skeleton coated with metal microclusters.

[0053] Through vibration or ultrasound, micelles (oxide particles obtained by calcining multiple metal salts) can be fully dispersed and evenly attached to the polymer coating and skeleton surface / pores. When exposed to high temperatures, multi-metal oxides usually release inert gases or form an oxidative isolation layer, which can effectively inhibit the spread of flames and provide multiple flame retardant mechanisms for materials.

[0054] There are certain surface interactions between the micelles and the existing polymer layer (such as hydrogen bonds, van der Waals forces or coupling agent effects), which can form a denser protective layer in a high temperature or flame environment to block heat and oxygen transfer. Drying at 100-120°C can further remove the solvent in the dispersion and stabilize the triple interface of "skeleton-polymer-metal micelles". Multi-metal micelles not only increase the material's combustion resistance, but also enhance the rigidity and mechanical stability of the skeleton to a certain extent, which is conducive to maintaining the integrity of the material in a high temperature fire environment.

[0055] S3.3. Add the remaining precursor solution and flame retardant to the three-dimensional carbonized skeleton coated with metal microclusters, stir, heat to 80-150°C and irradiate with ultraviolet light with a wavelength of 250-400 nm, keep warm at 80-100°C for 10-20 min, keep warm at 100-120°C for 10-20 min, keep warm at 120-150°C for 10-20 min, and obtain a highly flame retardant insulating cable material after cooling.

[0056] On the basis of the skeleton that has been coated with micelles, the remaining precursor solution and special flame retardant additives (such as flame retardant components containing phosphorus and nitrogen) are added to fill the remaining space in the pores of the material and form a multi-layer flame retardant structure on the surface. This can achieve a stacked flame retardant mechanism: metal oxides release inert gases + high thermal stability of the polymer matrix + flame retardant additives (to capture free radicals, reduce smoke toxicity, etc.). With the help of unsaturated functional groups (acrylates, epoxy groups, etc.) and crosslinkers in modified polyether nitrile, a three-dimensional crosslinked network can be quickly formed under UV irradiation, significantly improving the mechanical strength, high temperature resistance and electrical insulation properties of the material. Staged heating with UV can avoid local foaming or uneven curing caused by excessive temperature, and ensure that the crosslinker and photoinitiator react fully. While UV curing, the skeleton maintains a certain pore structure, which is conducive to heat dissipation and diffusion of flame retardant gases, but forms a dense crosslinked film on the pore wall and surface layer to improve electrical insulation and flame retardancy. Three-stage heat preservation can fully cure areas with different curing rates, reduce internal stress, and ensure uniform overall quality of the material. The modified polyether nitrile and siloxane prepolymers form a stable three-dimensional network after UV curing, which combines with the skeleton to enable the material to have good dielectric properties even in high voltage, high frequency, and hot and humid environments.

[0057] The present invention provides a highly flame-retardant insulating cable material, which is prepared by a method for preparing the highly flame-retardant insulating cable material. The highly flame-retardant insulating cable material comprises a three-dimensional carbonized skeleton, modified polyether nitrile, a siloxane prepolymer and at least two metal salts, wherein: The three-dimensional carbonized skeleton is used to provide mechanical support and enhance flame retardant properties; Modified polyether nitrile is used to provide electrical insulation; Siloxane prepolymers are used to improve the flame retardancy and weather resistance of highly flame retardant insulation cable materials; The metal salt releases inert gas by decomposition, thereby enhancing the flame retardancy and electrical insulation of the highly flame retardant insulating cable material.

[0058] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a highly flame-retardant insulating cable material, characterized in that the steps include: S1. Preparing a precursor solution and a multi-metal microcluster dispersion respectively, wherein the precursor comprises a modified polyether nitrile, a siloxane prepolymer and a crosslinking agent, and the multi-metal microcluster dispersion comprises a mixture of a weak base solution and at least two metal salt solutions; S2, pyrolyzing the carbon source to obtain a three-dimensional carbonized skeleton with pores inside; S3, immersing the three-dimensional carbonized skeleton in the precursor solution and the multi-metal microcluster dispersion respectively, and then performing UV curing in stages at 80-150° C. to obtain a highly flame-retardant insulating cable material.

2. The method for preparing a highly flame-retardant insulated cable material according to claim 1, characterized in that: In the step S1, the modified polyether nitrile includes at least one of a polyether nitrile acrylate copolymer, an epoxy-modified polyether nitrile, and a modified polyether nitrile acrylate; the siloxane prepolymer includes at least one of tetraethoxysilane, methyltriethoxysilane, and chloromethyltriethoxysilane; the cross-linking agent includes at least one of dicumyl peroxide, dibenzoyl peroxide, and cyclohexane peroxide; the weak alkaline solution includes at least one of ammonia water, sodium hydroxide, and ammonium hydroxide; and the mixed solution includes at least two of a sodium silicate solution, an aluminum chloride solution, a magnesium sulfate solution, and a ferric nitrate solution.

3. The method for preparing a highly flame-retardant insulated cable material according to claim 1 or 2, characterized in that: Calculated by weight ratio, the modified polyether nitrile: the siloxane prepolymer: the cross-linking agent = 5-6: 2-3: 1, and the weak base solution: the mixed solution = 1: 1-2.

4. The method for preparing a highly flame-retardant insulated cable material according to claim 1, characterized in that: The step S1 comprises: S1.1, adding the modified polyether nitrile powder to a solvent, stirring and dissolving to obtain a polymer solution, then adding a siloxane prepolymer and a crosslinking agent to the polymer solution, controlling the solution temperature within the range of 25-30°C and continuing stirring for 80-120 minutes to obtain a precursor solution; S1.

2. Dissolve various metal salts in deionized water according to the component ratio, stir the solution until the metal salt is completely dissolved to obtain a mixed solution, slowly add an alkaline solution to the mixed solution, adjust the pH to 8-9, precipitate for 30 minutes, filter and wash in sequence to obtain a micellar precipitate; S1.

3. The microcluster precipitate is dried at 100-200°C, and then calcined at 500-700°C in air or argon atmosphere. After cooling, a solvent and a surfactant are added to obtain a multi-metallic microcluster dispersion.

5. The method for preparing a highly flame-retardant insulated cable material according to claim 1, characterized in that: The step S2 comprises: S2.1, grinding the carbon source, and then adding a pore generating agent to dissolve it to obtain a carbon source solution; S2.2, in an inert atmosphere, heat the carbon source solution at a heating rate of 5-10°C / min until it reaches 700-900°C, and keep the temperature for 120-240 min; S2.

3. After the insulation is completed, stop heating, increase the gas flow rate of the inert atmosphere to cool, and place it in a coupling agent after lowering it to room temperature. After soaking for 20 to 30 minutes, wash and dry it to obtain a three-dimensional carbonized skeleton.

6. The method for preparing a highly flame-retardant insulating cable material according to claim 5, characterized in that: In step S2, the carbon source includes at least one of glucose, polystyrene, and lignin, the pore generating agent includes at least one of sodium hydroxide, sodium carbonate, and calcium chloride, and the coupling agent includes at least one of a silane coupling agent, a titanate coupling agent, and a zirconate coupling agent.

7. The method for preparing a highly flame-retardant insulated cable material according to claim 1, characterized in that: The step S3 comprises: S3.1, the three-dimensional carbonized skeleton is first immersed in part of the precursor solution for the first time, the immersion time is 60 to 120 minutes, and the excess solution is removed by low-pressure filtration. After repeating the immersion and filtration steps 2 to 3 times, it is placed at 60 to 80 ° C for pre-drying to obtain a three-dimensional carbonized skeleton coated with a polymer; S3.2, transferring the three-dimensional carbonized skeleton coated with the polymer to the multi-metal microcluster dispersion, performing a second immersion by vibration or ultrasound, filtering to remove excess liquid again, and drying at a temperature of 100 to 120° C. to obtain a three-dimensional carbonized skeleton coated with metal microcluster; S3.

3. Add the remaining precursor solution and flame retardant to the three-dimensional carbonized skeleton coated with metal microclusters, stir, heat to 80-150°C and irradiate with ultraviolet light with a wavelength of 250-400 nm, keep warm at 80-100°C for 10-20 min, keep warm at 100-120°C for 10-20 min, keep warm at 120-150°C for 10-20 min, and obtain a highly flame retardant insulating cable material after cooling.

8. A highly flame-retardant insulating cable material, characterized in that: The highly flame-retardant insulating cable material is prepared by the method for preparing the highly flame-retardant insulating cable material according to any one of claims 1 to 7, wherein the highly flame-retardant insulating cable material comprises a three-dimensional carbonized skeleton, modified polyether nitrile, a siloxane prepolymer and at least two metal salts, wherein: The three-dimensional carbonized skeleton is used to provide mechanical support and enhance flame retardant properties; The modified polyether nitrile is used to provide electrical insulation; The siloxane prepolymer is used to improve the flame retardant properties and weather resistance of the highly flame retardant insulating cable material; The metal salt releases inert gas by decomposition, thereby enhancing the flame retardancy and electrical insulation of the highly flame retardant insulating cable material.

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