A low-smoke, halogen-free, flame-retardant, and environmentally friendly cable and its manufacturing process

Abstract

This invention discloses a low-smoke, halogen-free, flame-retardant, and environmentally friendly cable and its preparation process, relating to the field of polymer materials. The invention includes a conductor, a cross-linked polyethylene insulation layer, and a sheath layer; wherein the sheath layer is made of sheath masterbatch, which comprises the following raw materials in parts by weight: 267.5-277.5 parts of ethylene-vinyl acetate copolymer, 50-52 parts of low-density polyethylene, 30-31 parts of ethylene-octene copolymer, 2.5-2.7 parts of carbon black, 120-125 parts of a three-dimensional network hybrid flame retardant, 15-16 parts of aluminum hydroxide, 1.5-1.6 parts of silane coupling agent KH550, 10-11 parts of maleic anhydride-grafted ethylene-vinyl acetate copolymer, 3-3.2 parts of antioxidant, 3-3.2 parts of polyethylene wax, and 2-2.2 parts of calcium stearate. The introduction of the three-dimensional network hybrid flame retardant and other raw materials in this invention simultaneously improves mechanical strength, flame retardancy, smoke suppression, low-temperature resistance, and heat resistance.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a low-smoke, halogen-free, flame-retardant, and environmentally friendly cable and its preparation process. Background Technology

[0002] Halogen-free environmentally friendly cables, due to their low smoke emission and lack of toxic and corrosive gases during combustion, have become the preferred cable type for densely populated areas such as rail transit, high-rise buildings, and new energy power plants. Their sheath layer, as the outermost protective barrier, directly determines the cable's service life and operational safety.

[0003] However, in practical applications, the sheath layer of halogen-free environmentally friendly cables still has the following performance shortcomings: First, it is difficult to balance flame retardant efficiency and mechanical properties. Traditional inorganic flame retardants such as aluminum hydroxide and magnesium hydroxide have low flame retardant efficiency, requiring a large amount of filler to meet the flame retardant requirements. However, this will seriously damage the continuous phase structure of the polyolefin matrix, resulting in a significant decrease in the tensile strength and impact strength of the material, making it difficult to meet the crack resistance requirements in complex laying environments. Second, it has insufficient low-temperature resistance. The inorganic filler has poor interfacial compatibility with the non-polar resin matrix. In low-temperature environments, the toughness of the material decreases sharply, coupled with daytime... The internal stress caused by temperature differences between day and night can easily lead to sheath cracking, causing the insulation layer to become damp and fail. Thirdly, the insulation performance is unstable. The inorganic flame retardant surface is rich in hydroxyl groups, which easily absorb moisture from the air to form ionic conductive pathways, resulting in a significant decrease in volume resistivity. After long-term use, the flame retardant may also migrate and precipitate, further deteriorating electrical performance. Fourthly, the heat distortion resistance is limited. The polyolefin matrix itself has poor heat resistance. Although high-filler inorganic fillers can slightly increase the heat distortion temperature, the effect is limited. Under high-temperature environments, the sheath is prone to softening and deformation, losing its mechanical protection for the internal conductor. Therefore, the tensile strength, impact strength, flame retardancy, smoke suppression, low-temperature resistance, insulation, and heat resistance of the sheath layer of existing halogen-free environmentally friendly cables still need to be improved simultaneously. Summary of the Invention

[0004] The purpose of this invention is to provide a low-smoke, halogen-free, flame-retardant, and environmentally friendly cable and its manufacturing process, thereby solving the following technical problems: Existing halogen-free environmentally friendly cables still have problems with poor tensile strength, impact strength, flame retardancy, smoke suppression, low temperature resistance, insulation and heat resistance.

[0005] The objective of this invention can be achieved through the following technical solutions: A low-smoke, halogen-free, flame-retardant, and environmentally friendly cable includes a conductor, a cross-linked polyethylene insulation layer, and a sheath layer. The sheath layer is made of sheath masterbatch; the sheath masterbatch comprises the following raw materials in parts by weight: 267.5-277.5 parts of ethylene-vinyl acetate copolymer, 50-52 parts of low-density polyethylene, 30-31 parts of ethylene-octene copolymer, 2.5-2.7 parts of carbon black, 120-125 parts of three-dimensional network hybrid flame retardant, 15-16 parts of aluminum hydroxide, 1.5-1.6 parts of silane coupling agent KH550, 10-11 parts of maleic anhydride-grafted ethylene-vinyl acetate copolymer, 3-3.2 parts of antioxidant, 3-3.2 parts of polyethylene wax, and 2-2.2 parts of calcium stearate; The three-dimensional network hybrid flame retardant is prepared by electrostatic self-assembly of modified hydrotalcite nanosheets and composite modified core-shell fibers, followed by static aging. The modified hydrotalcite nanosheets are prepared by first mixing magnesium aluminum hydrotalcite with phytic acid aqueous solution, and then adding cerium nitrate solution dropwise to perform phytic acid-cerium chelation modification. The composite modified core-shell fiber is prepared by first shearing, ultrasonicating, and centrifuging sepiolite micron powder to form nano-sized sepiolite fibers, and then reacting them with calcium nitrate and diammonium hydrogen phosphate to grow a hydroxyapatite shell layer in situ on its surface to form a sepiolite core-shell composite fiber. After modification with silane coupling agent KH550, it is then prepared by carboxylation with succinic anhydride, activation with 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide, and grafting with L-carnosine.

[0006] Preferably, the modified hydrotalcite nanosheets are prepared as follows: A1: Add cerium nitrate hexahydrate to deionized water and stir for 20 minutes to obtain a cerium nitrate solution. A2: Add magnesium aluminum hydrotalcite to deionized water and ultrasonically disperse for 40-50 min. Then add phytic acid aqueous solution and stir for 30 min. Adjust the pH to 2.5-3.0 and then add cerium nitrate solution dropwise under a nitrogen atmosphere at 60℃. Maintain the pH at 2.5-3.0 during the dropwise addition. Then stir under a nitrogen atmosphere at 60℃ for 24 h. After cooling, centrifuge to separate, wash, dry, grind and sieve the precipitate to obtain modified hydrotalcite nanosheets.

[0007] Preferably, the mass ratio of deionized water to cerium nitrate hexahydrate in A1 is 500-510:43; The mass ratio of deionized water, magnesium aluminum hydrotalcite, phytic acid aqueous solution, and cerium nitrate solution in A2 is 1500-1600:50:120:543-553; The phytic acid aqueous solution described in A2 has a mass fraction of 50%.

[0008] Preferably, the method for preparing the composite modified core-shell fiber is as follows: B1: Add sodium hexametaphosphate to deionized water and stir for 10 min. Then add sepiolite micron powder and shear at 10000 r / min for 20 min. Then ultrasonically disperse under ice-water bath cooling for 30 min. Then centrifuge at 3000 r / min for 5 min. Then take the upper stable suspension and concentrate it at 90℃ to a solid content of 25%-30%. Finally, vacuum dry at 60℃ for 12 h to obtain nano-sized sepiolite fibers. B2: Add calcium nitrate tetrahydrate to deionized water and stir for 20-30 minutes to obtain a calcium nitrate solution; B3: Add diammonium hydrogen phosphate to deionized water and stir for 20-30 minutes. Then adjust the pH to 10.3-10.7 to obtain a diammonium hydrogen phosphate solution. B4: Nano-sized sepiolite fibers were added to deionized water and ultrasonically dispersed for 15 min. Then, calcium nitrate solution was added dropwise and stirred for 30 min. Then, diammonium hydrogen phosphate solution was added dropwise, and the pH of the system was maintained between 10.0 and 10.5 during the dropwise addition. Then, the mixture was stirred at 80℃ for 6 h. After centrifugation, the precipitate was washed and dried to obtain sepiolite core-shell composite fibers. B5: Add sepiolite core-shell composite fibers to a mixture of anhydrous ethanol and deionized water and ultrasonically disperse for 20-30 min. Then add silane coupling agent KH550 and adjust the pH to 4.0 with glacial acetic acid. Stir at 60℃ for 5 h, then centrifuge, wash and dry the precipitate to obtain aminated core-shell fibers. B6: Aminated core-shell fibers were added to anhydrous ethanol and ultrasonically dispersed for 20-30 min. Then, succinic anhydride was added and stirred for 12 h. The precipitate was then centrifuged, washed, dried, and redispersed in 2-(N-morpholino)ethanesulfonic acid buffer and ultrasonicated for 15 min. 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide were added and stirred for 30 min. L-carnosine was then added and stirred in the dark for 20 h. Finally, the precipitate was centrifuged, washed, and freeze-dried to obtain the composite modified core-shell fibers.

[0009] Preferably, the mass ratio of deionized water, sodium hexametaphosphate, and sepiolite micron powder in B1 is 800:0.4:70-80; The mass ratio of deionized water to calcium nitrate tetrahydrate described in B2 is 200-220:50-55.

[0010] Preferably, the mass ratio of deionized water to diammonium hydrogen phosphate in B3 is 200:16.5-18.5; The mass ratio of deionized water, nano-sized sepiolite fiber, calcium nitrate solution, and diammonium hydrogen phosphate solution in B4 is 1000:50-60:250-275:216.5-218.5.

[0011] Preferably, the ratio of anhydrous ethanol, deionized water, sepiolite core-shell composite fiber, and silane coupling agent KH550 in B5 is 800mL:200mL:69-75g:2-3g; The ratio of anhydrous ethanol, aminated core-shell cellulose, succinic anhydride, 2-(N-morpholino)ethanesulfonic acid buffer, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide, and L-carnosine described in B6 is 1000mL: 70-75g: 10g: 1500mL: 7.5g: 5g: 8-12g; The 2-(N-morpholino)ethanesulfonic acid buffer solution described in B6 has a pH of 5.5 and a concentration of 0.1 mol / L; The 2-(N-morpholino)ethanesulfonic acid buffer solution described in B6 is prepared from 2-(N-morpholino)ethanesulfonic acid and deionized water.

[0012] Preferably, the preparation method of the three-dimensional network hybrid flame retardant is as follows: C1: Modified hydrotalcite nanosheets were added to deionized water and ultrasonically dispersed for 1 hour to obtain a modified nanosheet suspension. C2: Add the composite modified core-shell fiber to deionized water and ultrasonically disperse it for 45 min. Then add it dropwise to the modified nanosheet suspension, heat it to 60℃ and stir for 6-8 h, then let it stand and age at 20-34℃ for 12 h, then filter and separate it, vacuum dry it at 80℃ for 24 h, grind it and pass it through a 300-mesh standard sieve to obtain the three-dimensional network hybrid flame retardant.

[0013] Preferably, the mass ratio of deionized water to modified hydrotalcite nanosheets in C1 is 1000-1100:48-50; The mass ratio of deionized water, composite modified core-shell fiber, and modified nanosheet suspension in C2 is 1200:72-75:1048-1150.

[0014] A manufacturing process for a low-smoke, halogen-free, flame-retardant, and environmentally friendly cable includes the following steps: S1: Ethylene-vinyl acetate copolymer, low-density polyethylene, ethylene-octene copolymer, and carbon black are mixed and mixed at 80°C for 3 min. Then, a three-dimensional network hybrid flame retardant, aluminum hydroxide, and silane coupling agent KH550 are added and mixed at 80°C for 5 min. Then, maleic anhydride-grafted ethylene-vinyl acetate copolymer, antioxidant, polyethylene wax, and calcium stearate are added and mixed at 80°C for 2 min. Subsequently, melt blending is performed. The extrudate is water-cooled, air-dried, pelletized, and dried to obtain sheath masterbatch. S2: Oxygen-free copper wire with a diameter of 2.5mm is drawn, annealed, and stranded to form a conductor. Then, cross-linked polyethylene is extruded onto the surface of the conductor and cross-linked in 90℃ warm water for 6 hours to form a cross-linked polyethylene insulation layer with a thickness of 0.8mm. Subsequently, sheath masterbatch is extruded onto the outer surface of the insulation layer and water-cooled to form a sheath layer with a thickness of 1.2mm, resulting in a low-smoke halogen-free flame-retardant environmentally friendly cable.

[0015] The beneficial effects of this invention are: This invention provides a low-smoke halogen-free flame-retardant environmentally friendly cable and its manufacturing process. This invention simultaneously improves the tensile strength, impact strength, flame retardancy, smoke suppression, low-temperature resistance, insulation, and heat resistance of the halogen-free environmentally friendly cable through the following methods.

[0016] (1) The modified hydrotalcite nanosheets of this invention are two-dimensional layered nanomaterials obtained by surface modification of magnesium aluminum hydrotalcite by phytic acid chelating cerium ions. After phytic acid-cerium modification, the surface of the hydrotalcite nanosheets becomes organic, significantly improving its compatibility with the ethylene-vinyl acetate copolymer matrix and reducing stress concentration points caused by agglomeration; its two-dimensional layered structure can dissipate energy through mechanisms such as crack deflection, thereby improving tensile strength. The uniformly dispersed nanosheets can hinder the initial propagation of microcracks and increase the tortuosity of the crack propagation path, thereby absorbing some impact energy. The interlayer crystal water of the modified nanosheets decomposes upon heating, absorbing a large amount of heat and diluting the concentration of combustible gases; the magnesium aluminum oxides produced by decomposition can form an inorganic barrier layer; at the same time, phytic acid forms acidic substances upon heating, catalyzing the dehydration of the matrix into char, and the introduction of cerium ions further enhances the char formation efficiency and the thermal oxidation stability of the char layer, improving the flame retardant effect. The high specific surface area oxides produced by the decomposition of hydrotalcite layers can physically adsorb soot particles; phytic acid and cerium ions jointly promote the formation of a denser and more complete carbon layer, inhibiting the release of combustible gases and soot; the catalytic oxidation of cerium also helps reduce the organic volatiles produced by incomplete combustion. Surface modification enhances interfacial bonding, facilitating stress transfer and distribution at low temperatures and limiting the slippage and breakage of matrix molecular chains under stress. Hydrotalcite itself is a good inorganic insulator, but its surface hydroxyl groups readily absorb moisture from the air, forming ionic conductive pathways; phytic acid-cerium modification can cover most of the surface hydroxyl groups, significantly reducing water absorption, thus resulting in a higher volume resistivity than unmodified hydrotalcite. Rigid two-dimensional nanosheets can restrict the thermal motion of polymer molecular chains, improving the matrix's resistance to heat deformation.

[0017] (2) The composite modified core-shell fiber of this invention is a one-dimensional nanomaterial obtained by amination of nano-sized sepiolite fiber as core and hydroxyapatite as shell with silane coupling agent and grafting L-carnosine. The one-dimensional sepiolite fiber has a high aspect ratio. The active functional groups on the L-carnosine molecule can chemically bond or strongly physically interact with the matrix resin, especially the maleic anhydride-grafted ethylene-vinyl acetate copolymer, to build a high-strength interface layer, realize the efficient transfer of stress from the matrix to the fiber, and thus give full play to the reinforcing potential of the fiber. The composite modified core-shell fiber can transfer load across the two sides of the crack through fiber bridging, preventing the crack from further propagating; and consume a lot of energy through fiber pull-out and fiber breakage processes; at the same time, the strong interface binding formed by L-carnosine modification can effectively avoid premature interface debonding, ensuring that these three mechanisms occur fully before fracture, thereby dissipating impact energy to the maximum extent. In the initial stage of combustion, the fibers themselves do not melt, forming a three-dimensional network rudimentary structure, providing a supporting template for subsequent char formation and preventing the char layer from collapsing under gravity and airflow. Simultaneously, the calcium phosphate / phosphate produced by the decomposition of hydroxyapatite, and the nitrogen element in L-carnosine, form a phosphorus-nitrogen-cerium multi-element synergistic effect with the phosphorus and cerium elements in the hydrotalcite system, jointly promoting the formation of a more stable, more expansive, and more effective shielding char layer. The fibrous char skeleton can physically adsorb carbon black particles in the flue gas, while the dense, expanded char layer can prevent the release of flue gas to the outside. The continuous fiber skeleton can effectively resist the embrittlement and shrinkage of the matrix at low temperatures, and the strong interfacial bonding can prevent the fibers from debonding from the matrix at low temperatures, avoiding the generation and propagation of interfacial cracks. The chemical modification or reaction of L-carnosine consumes a large amount of hydrophilic silanol groups on the surface of sepiolite fibers, significantly reducing their hygroscopicity, thereby inhibiting the ionic conductivity pathways formed due to the presence of moisture. Hydroxyapatite itself has a certain ionic conductivity, but because it is encapsulated inside the fiber and its content is low, its negative impact on the overall insulation performance is limited. The skeletal structure formed by one-dimensional fibers can effectively support the shape of the material at high temperatures and restrict the slippage of molecular chains.

[0018] (3) The three-dimensional network hybrid flame retardant of the present invention is a continuous three-dimensional structure formed by uniformly loading modified hydrotalcite nanosheets onto the surface of composite modified core-shell fibers through electrostatic self-assembly. The three-dimensional network structure is not a simple addition of fibers and nanosheets, but forms a micro-nano hierarchical reinforcement system of "micron-scale fiber skeleton - nano-scale sheet attachment". This structure can hinder the initiation and propagation of cracks at different scales. The fibers bridge macroscopic cracks, and the nanosheets passivate the tips of microcracks. Compared with physical mixing, it provides a more uniform stress field and a more tortuous crack propagation path, avoiding the problem of stress concentration at the fiber ends in a single fiber system, thereby achieving synergistic reinforcement and toughening. During combustion, the three-dimensional network can quickly transform into a protective carbon layer with a "brick-mud" structure on the matrix surface. After pyrolysis, the composite modified core-shell fibers form a "steel" skeleton, maintaining the structural integrity of the carbon layer and preventing it from cracking and collapsing during combustion. The modified hydrotalcite nanosheets fill, fuse and form a dense barrier layer between the skeletons, effectively isolating the transmission of heat, oxygen and combustible gases. This perfect synergy in physical structure, combined with the chemical synergy of hydrotalcite decomposition and endothermic reaction, phytic acid, and multi-element catalytic char formation, results in flame retardant and smoke suppression efficiencies far exceeding those of individual components or simple physical mixtures, making it a highly efficient integrated flame retardant solution. The continuous and complete three-dimensional network can form a global stress transfer network at low temperatures, effectively dispersing local stress concentrations, inhibiting matrix embrittlement and microcrack propagation, and exhibiting superior low-temperature mechanical stability compared to physical mixture systems. The three-dimensional network structure reduces direct contact between flame retardant particles, avoiding the formation of continuous conductive pathways; simultaneously, strong interfacial bonding eliminates voids between the matrix and the flame retardant, reducing moisture intrusion, thus resulting in superior insulation performance compared to physical mixture systems. The skeletal support of the three-dimensional interpenetrating network is far stronger than that of single fibers or nanosheets, effectively restricting the thermal motion and slippage of polymer molecular chains at higher temperatures, maintaining the dimensional stability of the material.

[0019] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. The embodiments described below are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] Unless otherwise specified, the following information pertains to some of the raw materials used in the following embodiments and comparative examples of this invention: Ethylene-vinyl acetate copolymer (melt index 4 g / 10 min), brand: DuPont TMElvax® 260; Low-density polyethylene (melt index 2 g / 10 min), grade: SABIC HP2023J (Saudi Arabia); Ethylene-octene copolymer (melt index 1.0 g / 10 min), grade: Dow ENGAGE TM 8157 POE; Maleic anhydride-grafted ethylene-vinyl acetate copolymer, brand name: Arkema OREVAC® 18211.

[0022] Example 1: The manufacturing process of a low-smoke halogen-free flame-retardant environmentally friendly cable is as follows: S1: Add 43g of cerium nitrate hexahydrate to 500mL of deionized water and stir for 20min to obtain a cerium nitrate solution. S2: Add 50g of magnesium aluminum hydrotalcite (particle size 50-100nm) to 1500mL of deionized water and ultrasonically disperse it for 40min under ice bath conditions. Then add 120g of 50% phytic acid aqueous solution and stir for 30min. Adjust the pH to 2.5 with 1mol / L nitric acid. Then add 543g of cerium nitrate solution dropwise at 200r / min under nitrogen atmosphere at 60℃. During the dropwise addition, continuously maintain the pH at 2.5 with 1mol / L nitric acid. Then stir for 24h under nitrogen atmosphere at 60℃. After cooling to room temperature, centrifuge and wash the precipitate with deionized water until the pH of the filtrate is neutral. Wash twice with anhydrous ethanol. Finally, vacuum dry at 70℃ for 24h and grind through a 200-mesh sieve to obtain modified hydrotalcite nanosheets. S3: Add 0.4g sodium hexametaphosphate to 800mL of deionized water and stir for 10min. Then add 70g sepiolite micron powder and shear at 10000r / min for 20min. Then ultrasonically disperse under ice-water bath cooling for 30min. Then centrifuge at 3000r / min for 5min. Then take the upper stable suspension and concentrate it at 90℃ to the solid content of 25%. Finally, vacuum dry at 60℃ for 12h to obtain nano-sized sepiolite fibers. S4: Add 50g of calcium nitrate tetrahydrate to 200mL of deionized water and stir for 20min to obtain a calcium nitrate solution; S5: Add 16.5g of diammonium hydrogen phosphate to 200mL of deionized water and stir for 20min. Then adjust the pH to 10.3 with 25% ammonia water to obtain a diammonium hydrogen phosphate solution. S6: Add 50g of nano-sized sepiolite fibers to 1000mL of deionized water and ultrasonically disperse for 15min. Then, add 250g of calcium nitrate solution and stir for 30min. Next, add 216.5g of diammonium hydrogen phosphate solution, maintaining the pH of the system between 10.0 and 10.5 during the addition process. Then, stir at 80℃ for 6h, centrifuge and wash the precipitate with deionized water until the pH of the filtrate is neutral. Finally, vacuum dry at 60℃ for 12h to obtain sepiolite core-shell composite fibers. S7: Add 69g of sepiolite core-shell composite fiber to a mixture of 800mL anhydrous ethanol and 200mL deionized water and ultrasonically disperse for 20min. Then add 2g of silane coupling agent KH550 and adjust the pH to 4.0 with glacial acetic acid. Stir at 60℃ for 5h, then centrifuge and wash the precipitate three times with anhydrous ethanol. Finally, vacuum dry at 60℃ for 12h to obtain aminated core-shell fiber. S8: 70g of aminated core-shell fibers were added to 1000mL of anhydrous ethanol and ultrasonically dispersed for 20min. Then, 10g of succinic anhydride was added and stirred for 12h. The mixture was then centrifuged and the precipitate was washed three times with anhydrous ethanol. After vacuum drying, the precipitate was redispersed in 1500mL of 2-(N-morpholino)ethanesulfonic acid buffer at pH 5.5 and a concentration of 0.1mol / L and ultrasonicated for 15min. Then, 7.5g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 5g of N-hydroxysuccinimide were added and stirred for 30min. Subsequently, 8g of L-carnosine was added and stirred in the dark for 20h. Finally, the mixture was centrifuged and washed with deionized water until the supernatant showed no UV absorption at 280nm (to remove unreacted L-carnosine). After freeze-drying for 48h, the composite modified core-shell fibers were obtained. S9: Add 48g of modified hydrotalcite nanosheets to 1000mL of deionized water and ultrasonically disperse for 1h to obtain a modified nanosheet suspension. S10: 72g of composite modified core-shell fiber was added to 1200mL of deionized water and ultrasonically dispersed for 45min. Then it was added dropwise to 1048g of modified nanosheet suspension stirred at 800r / min. The temperature was then raised to 60℃ and stirred for 6h. After that, it was allowed to stand and age at 20℃ for 12h. Then it was filtered and separated and vacuum dried at 80℃ for 24h. After grinding, it was passed through a 300-mesh standard sieve to obtain a three-dimensional network hybrid flame retardant. S11: Mix 267.5g of ethylene-vinyl acetate copolymer, 50g of low-density polyethylene, 30g of ethylene-octene copolymer, and 2.5g of carbon black at 80℃ for 3 minutes. Then add 120g of three-dimensional network hybrid flame retardant, 15g of aluminum hydroxide (particle size 1-3μm), and 1.5g of silane coupling agent KH550 and mix at 80℃ for 5 minutes. Finally, add 10g of maleic anhydride-grafted ethylene-vinyl acetate copolymer and 1.5g of antioxidant 101. 0, 1.5g antioxidant 168, 3g polyethylene wax, and 2g calcium stearate were mixed at 80℃ for 2 minutes. Then, the mixture was added to a twin-screw extruder (length-to-diameter ratio 44:1) for melt blending at a feed port temperature of 135℃, a conveying section temperature of 150℃, a compression section temperature of 160℃, a metering section temperature of 165℃, a die head temperature of 155℃, a screw speed of 300r / min, and a feeding speed of 20kg / h. The extrudate was water-cooled, air-dried, pelletized, and dried at 90℃ for 6 hours to obtain sheath masterbatch. S12: Oxygen-free copper wire with a diameter of 2.5mm is drawn, annealed, and stranded (stretching pitch ratio of 12:1) to form a cross-sectional area of ​​4mm². 2 The conductor is then extruded with cross-linked polyethylene using a φ65 extruder. The cross-linked polyethylene is then cross-linked in a 90℃ warm water cross-linking tank for 6 hours to form a cross-linked polyethylene insulation layer with a thickness of 0.8mm. Subsequently, a sheath masterbatch is extruded onto the outer surface of the insulation layer using a φ90 single screw extruder. After water cooling, a sheath layer with a thickness of 1.2mm is formed, resulting in a low-smoke halogen-free flame-retardant environmentally friendly cable.

[0023] Example 2: The manufacturing process of a low-smoke halogen-free flame-retardant environmentally friendly cable is as follows: S1: Add 43g of cerium nitrate hexahydrate to 505mL of deionized water and stir for 20min to obtain a cerium nitrate solution. S2: Add 50g of magnesium aluminum hydrotalcite (particle size 50-100nm) to 1550mL of deionized water and ultrasonically disperse for 45min under ice bath conditions. Then add 120g of 50% phytic acid aqueous solution and stir for 30min. Adjust the pH to 2.8 with 1mol / L nitric acid. Then add 548g of cerium nitrate solution dropwise at 200r / min under nitrogen atmosphere at 60℃. During the dropwise addition, continuously maintain the pH at 2.8 with 1mol / L nitric acid. Then stir for 24h under nitrogen atmosphere at 60℃. After cooling to room temperature, centrifuge and wash the precipitate with deionized water until the pH of the filtrate is neutral. Wash twice with anhydrous ethanol. Finally, vacuum dry at 70℃ for 24h and grind through a 200-mesh sieve to obtain modified hydrotalcite nanosheets. S3: Add 0.4g sodium hexametaphosphate to 800mL of deionized water and stir for 10min. Then add 75g sepiolite micron powder and shear at 10000r / min for 20min. Then ultrasonically disperse under ice-water bath cooling for 30min. Then centrifuge at 3000r / min for 5min. Then take the upper stable suspension and concentrate it at 90℃ to the solid content of 28%. Finally, vacuum dry at 60℃ for 12h to obtain nano-sized sepiolite fibers. S4: Add 53g of calcium nitrate tetrahydrate to 210mL of deionized water and stir for 25min to obtain calcium nitrate solution; S5: Add 17.5g of diammonium hydrogen phosphate to 200mL of deionized water and stir for 25min. Then adjust the pH to 10.5 with 25% ammonia water to obtain a diammonium hydrogen phosphate solution. S6: Add 55g of nano-sized sepiolite fibers to 1000mL of deionized water and ultrasonically disperse for 15min. Then, add 263g of calcium nitrate solution and stir for 30min. Next, add 217.5g of diammonium hydrogen phosphate solution, maintaining the pH of the system between 10.0 and 10.5 during the addition process. Then, stir at 80℃ for 6h, centrifuge and wash the precipitate with deionized water until the pH of the filtrate is neutral. Finally, vacuum dry at 60℃ for 14h to obtain sepiolite core-shell composite fibers. S7: Add 72g of sepiolite core-shell composite fiber to a mixture of 800mL anhydrous ethanol and 200mL deionized water and ultrasonically disperse for 25min. Then add 2.5g of silane coupling agent KH550 and adjust the pH to 4.0 with glacial acetic acid. Stir at 60℃ for 5h, then centrifuge and wash the precipitate 3-5 times with anhydrous ethanol. Finally, vacuum dry at 60℃ for 14h to obtain aminated core-shell fiber. S8: 72g of aminated core-shell fibers were added to 1000mL of anhydrous ethanol and ultrasonically dispersed for 25min. Then, 10g of succinic anhydride was added and stirred for 12h. The mixture was then centrifuged and the precipitate was washed four times with anhydrous ethanol. After vacuum drying, the precipitate was redispersed in 1500mL of 2-(N-morpholino)ethanesulfonic acid buffer at pH 5.5 and a concentration of 0.1mol / L and ultrasonicated for 15min. Then, 7.5g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 5g of N-hydroxysuccinimide were added and stirred for 30min. Subsequently, 10g of L-carnosine was added and stirred in the dark for 20h. Finally, the mixture was centrifuged and washed with deionized water until the supernatant showed no UV absorption at 280nm (to remove unreacted L-carnosine). After freeze-drying for 48h, the composite modified core-shell fibers were obtained. S9: Add 49g of modified hydrotalcite nanosheets to 1050mL of deionized water and ultrasonically disperse for 1h to obtain a modified nanosheet suspension. S10: 73.5g of composite modified core-shell fiber was added to 1200mL of deionized water and ultrasonically dispersed for 45min. Then it was added dropwise to 1099g of modified nanosheet suspension stirred at 800r / min. The temperature was then raised to 60℃ and stirred for 7h. After that, it was allowed to stand and age at 27℃ for 12h. Then it was filtered and separated and vacuum dried at 80℃ for 24h. After grinding, it was passed through a 300-mesh standard sieve to obtain a three-dimensional network hybrid flame retardant. S11: Mix 272.5g of ethylene-vinyl acetate copolymer, 51g of low-density polyethylene, 30.5g of ethylene-octene copolymer, and 2.6g of carbon black at 80℃ for 3 minutes. Then add 122.5g of three-dimensional network hybrid flame retardant, 15.5g of aluminum hydroxide (particle size 1-3μm), and 1.55g of silane coupling agent KH550 and mix at 80℃ for 5 minutes. Finally, add 10.5g of maleic anhydride-grafted ethylene-vinyl acetate copolymer and 1.55g of antioxidant. 1010, 1.55g antioxidant 168, 3.1g polyethylene wax, and 2.1g calcium stearate were mixed at 80℃ for 2 minutes, and then added to a twin-screw extruder (length-to-diameter ratio 44:1) for melt blending at a feed port temperature of 135℃, a conveying section temperature of 150℃, a compression section temperature of 160℃, a metering section temperature of 165℃, a die head temperature of 160℃, a screw speed of 300r / min, and a feeding speed of 20kg / h. The extrudate was water-cooled, air-dried, pelletized, and dried at 90℃ for 6 hours to obtain sheath masterbatch. S12: Oxygen-free copper wire with a diameter of 2.5mm is drawn, annealed, and stranded (stretching pitch ratio of 12:1) to form a cross-sectional area of ​​4mm². 2 The conductor is then extruded with cross-linked polyethylene using a φ65 extruder. The cross-linked polyethylene is then cross-linked in a 90℃ warm water cross-linking tank for 6 hours to form a cross-linked polyethylene insulation layer with a thickness of 0.8mm. Subsequently, a sheath masterbatch is extruded onto the outer surface of the insulation layer using a φ90 single screw extruder. After water cooling, a sheath layer with a thickness of 1.2mm is formed, resulting in a low-smoke halogen-free flame-retardant environmentally friendly cable.

[0024] Example 3: The manufacturing process of a low-smoke halogen-free flame-retardant environmentally friendly cable is as follows: S1: Add 43g of cerium nitrate hexahydrate to 510mL of deionized water and stir for 20min to obtain a cerium nitrate solution. S2: Add 50g of magnesium aluminum hydrotalcite (particle size 50-100nm) to 1600mL of deionized water and ultrasonically disperse it for 50min under ice bath conditions. Then add 120g of 50% phytic acid aqueous solution and stir for 30min. Adjust the pH to 3.0 with 1mol / L nitric acid. Then add 553g of cerium nitrate solution dropwise at 200r / min under nitrogen atmosphere at 60℃. During the dropwise addition, continuously maintain the pH at 3.0 with 1mol / L nitric acid. Then stir at 60℃ under nitrogen atmosphere for 24h. After cooling to room temperature, centrifuge and wash the precipitate with deionized water until the pH of the filtrate is neutral. Then wash twice with anhydrous ethanol. Finally, vacuum dry at 70℃ for 24h and grind through a 200-mesh sieve to obtain modified hydrotalcite nanosheets. S3: Add 0.4g sodium hexametaphosphate to 800mL of deionized water and stir for 10min. Then add 80g sepiolite micron powder and shear at 10000r / min for 20min. Then ultrasonically disperse under ice-water bath cooling for 30min. Then centrifuge at 3000r / min for 5min. Then take the upper stable suspension and concentrate it at 90℃ to the solid content of 30%. Finally, vacuum dry at 60℃ for 12h to obtain nano-sized sepiolite fibers. S4: Add 55g of calcium nitrate tetrahydrate to 220mL of deionized water and stir for 30min to obtain a calcium nitrate solution; S5: Add 18.5g of diammonium hydrogen phosphate to 200mL of deionized water and stir for 30min. Then adjust the pH to 10.7 with 25% ammonia water to obtain a diammonium hydrogen phosphate solution. S6: Add 60g of nano-sized sepiolite fibers to 1000mL of deionized water and ultrasonically disperse for 15min. Then, add 275g of calcium nitrate solution and stir for 30min. Next, add 218.5g of diammonium hydrogen phosphate solution, maintaining the pH of the system between 10.0 and 10.5 during the addition process. Then, stir at 80℃ for 6h, centrifuge and wash the precipitate with deionized water until the pH of the filtrate is neutral. Finally, vacuum dry at 60℃ for 16h to obtain sepiolite core-shell composite fibers. S7: Add 75g of sepiolite core-shell composite fiber to a mixture of 800mL anhydrous ethanol and 200mL deionized water and ultrasonically disperse for 30min. Then add 3g of silane coupling agent KH550 and adjust the pH to 4.0 with glacial acetic acid. Stir at 60℃ for 5h, then centrifuge and wash the precipitate 5 times with anhydrous ethanol. Finally, vacuum dry at 60℃ for 14h to obtain aminated core-shell fiber. S8: 75g of aminated core-shell fibers were added to 1000mL of anhydrous ethanol and ultrasonically dispersed for 30min. Then, 10g of succinic anhydride was added and stirred for 12h. The mixture was then centrifuged and the precipitate was washed 5 times with anhydrous ethanol. After vacuum drying, the precipitate was redispersed in 1500mL of 2-(N-morpholino)ethanesulfonic acid buffer at pH 5.5 and a concentration of 0.1mol / L and ultrasonicated for 15min. Then, 7.5g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 5g of N-hydroxysuccinimide were added and stirred for 30min. Subsequently, 12g of L-carnosine was added and stirred in the dark for 20h. Finally, the mixture was centrifuged and washed with deionized water until the supernatant showed no UV absorption at 280nm (to remove unreacted L-carnosine). After freeze-drying for 48h, the composite modified core-shell fibers were obtained. S9: Add 50g of modified hydrotalcite nanosheets to 1100mL of deionized water and ultrasonically disperse for 1h to obtain a modified nanosheet suspension. S10: Add 75g of composite modified core-shell fiber to 1200mL of deionized water and ultrasonically disperse for 45min. Then add it dropwise to 1150g of modified nanosheet suspension stirred at 800r / min. Then heat to 60℃ and stir for 8h. Then let it stand and age at 34℃ for 12h. Then filter and separate, and vacuum dry at 80℃ for 24h. After grinding, pass through a 300-mesh standard sieve to obtain a three-dimensional network hybrid flame retardant. S11: Mix 277.5g of ethylene-vinyl acetate copolymer, 52g of low-density polyethylene, 31g of ethylene-octene copolymer, and 2.7g of carbon black at 80℃ for 3 minutes. Then add 125g of three-dimensional network hybrid flame retardant, 16g of aluminum hydroxide (particle size 1-3μm), and 1.6g of silane coupling agent KH550 and mix at 80℃ for 5 minutes. Finally, add 11g of maleic anhydride-grafted ethylene-vinyl acetate copolymer and 1.6g of antioxidant 1010. 1.6g of antioxidant 168, 3.2g of polyethylene wax, and 2.2g of calcium stearate were mixed at 80℃ for 2 minutes. Then, the mixture was added to a twin-screw extruder (length-to-diameter ratio 44:1) for melt blending at a feed port temperature of 135℃, a conveying section temperature of 150℃, a compression section temperature of 160℃, a metering section temperature of 165℃, a die head temperature of 165℃, a screw speed of 300r / min, and a feeding speed of 20kg / h. The extrudate was water-cooled, air-dried, pelletized, and dried at 90℃ for 6 hours to obtain sheath masterbatch. S12: Oxygen-free copper wire with a diameter of 2.5mm is drawn, annealed, and stranded (stretching pitch ratio of 12:1) to form a cross-sectional area of ​​4mm². 2The conductor is then extruded with cross-linked polyethylene using a φ65 extruder. The cross-linked polyethylene is then cross-linked in a 90℃ warm water cross-linking tank for 6 hours to form a cross-linked polyethylene insulation layer with a thickness of 0.8mm. Subsequently, a sheath masterbatch is extruded onto the outer surface of the insulation layer using a φ90 single screw extruder. After water cooling, a sheath layer with a thickness of 1.2mm is formed, resulting in a low-smoke halogen-free flame-retardant environmentally friendly cable.

[0025] Comparative Example 1: Compared with Example 1, this comparative example only omits the addition of "cerium nitrate solution" in the preparation process of S2. All other steps and parameters are the same, and will not be repeated here. The final result is a low-smoke halogen-free flame-retardant environmentally friendly cable.

[0026] Comparative Example 2: Compared with Example 1, this comparative example only replaces the "120g three-dimensional network hybrid flame retardant" added during the preparation of S11 with "48g modified hydrotalcite nanosheets and 72g composite modified core-shell fiber". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, a low-smoke halogen-free flame-retardant environmentally friendly cable is obtained.

[0027] Comparative Example 3: Compared with Example 1, this comparative example only replaces the "120g three-dimensional network hybrid flame retardant" added during the preparation of S11 with "48g magnesium aluminum hydrotalcite (particle size 50-100nm) and 72g composite modified core-shell fiber". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, a low-smoke halogen-free flame-retardant environmentally friendly cable is obtained.

[0028] Comparative Example 4: Compared with Example 1, this comparative example only replaces the "120g three-dimensional network hybrid flame retardant" added during the preparation of S11 with "48g modified hydrotalcite nanosheets and 72g sepiolite core-shell composite fiber". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, a low-smoke halogen-free flame-retardant environmentally friendly cable is obtained.

[0029] Comparative Example 5: Compared with Example 1, this comparative example only replaces the "three-dimensional network hybrid flame retardant" added during the preparation of S11 with "48g modified hydrotalcite nanosheets and 72g sepiolite micron powder". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, a low-smoke halogen-free flame-retardant environmentally friendly cable is obtained.

[0030] Comparative Example 6: Compared with Example 1, this comparative example only replaces the "three-dimensional network hybrid flame retardant" added during the preparation of S11 with "sepiolite micron powder". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, a low-smoke halogen-free flame-retardant environmentally friendly cable is obtained.

[0031] Comparative Example 7: Compared with Example 1, this comparative example only replaces the "three-dimensional network hybrid flame retardant" added during the preparation of S11 with "magnesium aluminum hydrotalcite (particle size 50-100nm)". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, a low-smoke halogen-free flame-retardant environmentally friendly cable is obtained.

[0032] Comparative Example 8: Compared with Example 1, this comparative example only omits the addition of "three-dimensional network hybrid flame retardant" in the preparation process of S11. All other steps and parameters are the same, and will not be repeated here. The final result is a low-smoke halogen-free flame-retardant environmentally friendly cable.

[0033] Performance testing: Determination of tensile strength: Referring to GB / T 2951.11-2008 standard, the tensile strength (MPa) of the low-smoke halogen-free flame-retardant environmentally friendly cable sheath materials prepared in Examples 1-3 and Comparative Examples 1-8 of this invention was determined using the dumbbell tensile test method at 25°C and a tensile rate of 250 mm / min. The test results are shown in Table 1.

[0034] Impact strength determination: Referring to GB / T 1043.1-2008 standard, the impact strength (kJ·m) of the low-smoke halogen-free flame-retardant environmentally friendly cable sheath materials prepared in Examples 1-3 and Comparative Examples 1-8 of this invention was determined using the simply supported beam impact method at 25°C and a pendulum energy of 5J. -2 The test results are shown in Table 1.

[0035] Flame retardancy testing: Referring to GB / T 2406.2-2009 standard, at 25℃, the lowest oxygen volume fraction (%) when the flame spread beyond the 50mm mark line below the top of the specimen after the low-smoke halogen-free flame-retardant environmentally friendly cable sheath material prepared in Examples 1-3 and Comparative Examples 1-8 of this invention was determined by vertical combustion method in an oxygen-nitrogen mixed gas flow. The test results are shown in Table 1.

[0036] Determination of smoke suppression properties: Referring to GB / T 8323.2-2008 standard, the optical density method was used to determine the low-smoke halogen-free flame-retardant environmentally friendly cable sheath materials prepared in Examples 1-3 and Comparative Examples 1-8 of this invention. After preparing 25mm × 25mm specimens, they were tested in a 1m³ test chamber. 3 The maximum smoke density when the radiant heat source power is 25kW is shown in Table 1.

[0037] Low temperature resistance test: Referring to GB / T 2951.14-2008 standard, the tensile strength (MPa) of the low-smoke halogen-free flame-retardant environmentally friendly cable sheath materials prepared in Examples 1-3 and Comparative Examples 1-8 of this invention was determined using the dumbbell tensile test method at -40℃ for 16 hours, at a tensile rate of 250 mm / min. The test results are shown in Table 2.

[0038] Measurement of volume resistivity: Referring to GB / T 1410-2006, the volume resistivity (Ω·cm) of the low-smoke halogen-free flame-retardant environmentally friendly cable sheath materials prepared in Examples 1-3 and Comparative Examples 1-8 of this invention was measured, and the test results are shown in Table 2.

[0039] Determination of heat resistance: Referring to GB / T 1634.1-2004 standard, the three-point bending method was used to determine the temperature (°C) of the low-smoke halogen-free flame-retardant environmentally friendly cable sheath material prepared in Examples 1-3 and Comparative Examples 1-8 of this invention. After preparing 80mm×10mm×4mm specimens, the temperature (°C) was measured at a load of 0.45MPa, a heating rate of 2°C / min, and a specimen deformation of 0.21mm. The test results are shown in Table 2.

[0040] Table 1: Performance test results of Examples 1-3 and Comparative Examples 1-8

[0041] Table 2: Performance test results of Examples 1-3 and Comparative Examples 1-8

[0042] Data Analysis: As can be seen from Tables 1 and 2, the low-smoke halogen-free flame-retardant environmentally friendly cable prepared according to the embodiments of the present invention has excellent tensile strength, impact strength, flame retardancy, smoke suppression, low temperature resistance, insulation and heat resistance.

[0043] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A low-smoke, halogen-free, flame-retardant, and environmentally friendly cable, characterized in that, Includes conductor, cross-linked polyethylene insulation layer, and sheath layer; The sheath layer is made of sheath masterbatch; the sheath masterbatch comprises the following raw materials in parts by weight: 267.5-277.5 parts of ethylene-vinyl acetate copolymer, 50-52 parts of low-density polyethylene, 30-31 parts of ethylene-octene copolymer, 2.5-2.7 parts of carbon black, 120-125 parts of three-dimensional network hybrid flame retardant, 15-16 parts of aluminum hydroxide, 1.5-1.6 parts of silane coupling agent KH550, 10-11 parts of maleic anhydride-grafted ethylene-vinyl acetate copolymer, 3-3.2 parts of antioxidant, 3-3.2 parts of polyethylene wax, and 2-2.2 parts of calcium stearate; The three-dimensional network hybrid flame retardant is prepared by electrostatic self-assembly of modified hydrotalcite nanosheets and composite modified core-shell fibers, followed by static aging. The modified hydrotalcite nanosheets are prepared by first mixing magnesium aluminum hydrotalcite with phytic acid aqueous solution, and then adding cerium nitrate solution dropwise to perform phytic acid-cerium chelation modification. The composite modified core-shell fiber is prepared by first shearing, ultrasonicating, and centrifuging sepiolite micron powder to form nano-sized sepiolite fibers, and then reacting them with calcium nitrate and diammonium hydrogen phosphate to grow a hydroxyapatite shell layer in situ on its surface to form a sepiolite core-shell composite fiber. After modification with silane coupling agent KH550, it is then prepared by carboxylation with succinic anhydride, activation with 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide, and grafting with L-carnosine.

2. The low-smoke halogen-free flame-retardant environmentally friendly cable according to claim 1, characterized in that, The modified hydrotalcite nanosheets are prepared as follows: A1: Add cerium nitrate hexahydrate to deionized water and stir for 20 minutes to obtain a cerium nitrate solution. A2: Add magnesium aluminum hydrotalcite to deionized water and ultrasonically disperse for 40-50 min. Then add phytic acid aqueous solution and stir for 30 min. Adjust the pH to 2.5-3.0 and then add cerium nitrate solution dropwise under a nitrogen atmosphere at 60℃. Maintain the pH at 2.5-3.0 during the dropwise addition. Then stir under a nitrogen atmosphere at 60℃ for 24 h. After cooling, centrifuge to separate, wash, dry, grind and sieve the precipitate to obtain modified hydrotalcite nanosheets.

3. The low-smoke halogen-free flame-retardant environmentally friendly cable according to claim 2, characterized in that, The mass ratio of deionized water to cerium nitrate hexahydrate in A1 is 500-510:43; The mass ratio of deionized water, magnesium aluminum hydrotalcite, phytic acid aqueous solution, and cerium nitrate solution in A2 is 1500-1600:50:120:543-553; The phytic acid aqueous solution described in A2 has a mass fraction of 50%.

4. The low-smoke halogen-free flame-retardant environmentally friendly cable according to claim 1, characterized in that, The preparation method of the composite modified core-shell fiber is as follows: B1: Add sodium hexametaphosphate to deionized water and stir for 10 min. Then add sepiolite micron powder and shear at 10000 r / min for 20 min. Then ultrasonically disperse under ice water bath cooling for 30 min. Then centrifuge at 3000 r / min for 5 min. Then take the upper suspension and concentrate it at 90℃ to a solid content of 25%-30%. Finally dry to obtain nano-sized sepiolite fibers. B2: Add calcium nitrate tetrahydrate to deionized water and stir for 20-30 minutes to obtain a calcium nitrate solution; B3: Add diammonium hydrogen phosphate to deionized water and stir for 20-30 minutes. Then adjust the pH to 10.3-10.7 to obtain a diammonium hydrogen phosphate solution. B4: Nano-sized sepiolite fibers were added to deionized water and ultrasonically dispersed for 15 min. Then, calcium nitrate solution was added dropwise and stirred for 30 min. Then, diammonium hydrogen phosphate solution was added dropwise, and the pH of the system was maintained between 10.0 and 10.5 during the dropwise addition. Then, the mixture was stirred at 80℃ for 6 h. After centrifugation, the precipitate was washed and dried to obtain sepiolite core-shell composite fibers. B5: Add sepiolite core-shell composite fibers to a mixture of anhydrous ethanol and deionized water and ultrasonically disperse for 20-30 min. Then add silane coupling agent KH550 and adjust the pH to 4.0 with glacial acetic acid. Stir at 60℃ for 5 h, then centrifuge, wash and dry the precipitate to obtain aminated core-shell fibers. B6: Aminated core-shell fibers were added to anhydrous ethanol and ultrasonically dispersed for 20-30 min. Then, succinic anhydride was added and stirred for 12 h. The precipitate was then centrifuged, washed, dried, and redispersed in 2-(N-morpholino)ethanesulfonic acid buffer and ultrasonicated for 15 min. 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide were added and stirred for 30 min. L-carnosine was then added and stirred in the dark for 20 h. Finally, the precipitate was centrifuged, washed, and freeze-dried to obtain the composite modified core-shell fibers.

5. The low-smoke halogen-free flame-retardant environmentally friendly cable according to claim 4, characterized in that, The mass ratio of deionized water, sodium hexametaphosphate, and sepiolite micron powder in B1 is 800:0.4:70-80; The mass ratio of deionized water to calcium nitrate tetrahydrate described in B2 is 200-220:50-55.

6. The low-smoke halogen-free flame-retardant environmentally friendly cable according to claim 4, characterized in that, The mass ratio of deionized water to diammonium hydrogen phosphate in B3 is 200:16.5-18.5; The mass ratio of deionized water, nano-sized sepiolite fiber, calcium nitrate solution, and diammonium hydrogen phosphate solution in B4 is 1000:50-60:250-275:216.5-218.

5.

7. The low-smoke halogen-free flame-retardant environmentally friendly cable according to claim 4, characterized in that, The ratio of anhydrous ethanol, deionized water, sepiolite core-shell composite fiber, and silane coupling agent KH550 described in B5 is 800mL:200mL:69-75g:2-3g; The ratio of anhydrous ethanol, aminated core-shell cellulose, succinic anhydride, 2-(N-morpholino)ethanesulfonic acid buffer, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide, and L-carnosine described in B6 is 1000mL: 70-75g: 10g: 1500mL: 7.5g: 5g: 8-12g; The 2-(N-morpholino)ethanesulfonic acid buffer solution described in B6 has a pH of 5.5 and a concentration of 0.1 mol / L.

8. The low-smoke halogen-free flame-retardant environmentally friendly cable according to claim 1, characterized in that, The preparation method of the three-dimensional network hybrid flame retardant is as follows: C1: Modified hydrotalcite nanosheets were added to deionized water and ultrasonically dispersed for 1 hour to obtain a modified nanosheet suspension. C2: Add composite modified core-shell fibers to deionized water and ultrasonically disperse for 45 min. Then add them dropwise to the modified nanosheet suspension, heat to 60℃ and stir for 6-8 h, then let stand and age at 20-34℃ for 12 h, then filter, dry, grind and sieve to obtain a three-dimensional network hybrid flame retardant.

9. The low-smoke halogen-free flame-retardant environmentally friendly cable according to claim 8, characterized in that, The mass ratio of deionized water to modified hydrotalcite nanosheets in C1 is 1000-1100:48-50; The mass ratio of deionized water, composite modified core-shell fiber, and modified nanosheet suspension in C2 is 1200:72-75:1048-1150.

10. A manufacturing process for a low-smoke halogen-free flame-retardant environmentally friendly cable according to any one of claims 1-9, characterized in that, Includes the following steps: S1: Ethylene-vinyl acetate copolymer, low-density polyethylene, ethylene-octene copolymer, and carbon black are mixed and mixed at 80°C for 3 min. Then, a three-dimensional network hybrid flame retardant, aluminum hydroxide, and silane coupling agent KH550 are added and mixed at 80°C for 5 min. Then, maleic anhydride-grafted ethylene-vinyl acetate copolymer, antioxidant, polyethylene wax, and calcium stearate are added and mixed at 80°C for 2 min. Subsequently, melt blending is performed. The extrudate is water-cooled, air-dried, pelletized, and dried to obtain sheath masterbatch. S2: Oxygen-free copper wire is drawn, annealed, and stranded to form a conductor. Then, cross-linked polyethylene is extruded onto the surface of the conductor and cross-linked in 90°C water for 6 hours to form a cross-linked polyethylene insulation layer. Subsequently, sheath masterbatch is extruded onto the outer surface of the insulation layer and water-cooled to form a sheath layer, resulting in a low-smoke halogen-free flame-retardant environmentally friendly cable.

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