A high-flame-retardant green and environment-friendly low-voltage AC cable for smart grid and a preparation method thereof

Abstract

The application relates to the field of cable manufacturing, and particularly discloses a high-flame-retardant green and environment-friendly low-voltage AC cable for smart grids and a preparation method thereof. The high-flame-retardant green and environment-friendly low-voltage AC cable for smart grids comprises at least three conductor cores, each of which comprises at least one conductor core and a fire-resistant wrapping and a flame-retardant polyethylene coating layer wrapped around the conductor core in sequence; the conductor core 1 is wrapped with a fire-resistant wrapping layer, a corona layer, a TPU foamed elastic buffer layer, an EVA adhesive layer, a flame-retardant polyethylene coating layer, a corona layer and a fluorosilicone rubber / TPE composite layer in sequence; the fluorosilicone rubber / TPE composite layer (5) comprises the following raw materials in parts by weight: 5-6 parts of fluorosilicone rubber, 4-5 parts of polyurethane, 0.1-1 part of a compatibilizer, 1-2 parts of a nano flame retardant and 0.1-0.5 parts of a silane coupling agent. The cable has the advantages of high bending resistance and low-temperature cracking resistance and excellent flame-retardant performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of cable manufacturing, more particularly, it relates to a high-flame-retardant green and environment-friendly low-voltage AC cable for smart grid and a preparation method thereof. BACKGROUND

[0002] Cables are one of the commonly used facilities for power and signal transmission. In the power grid, cables are the main equipment for power transmission, and different specifications of cables are required for the transmission of different power. Fireproof cables are generally composed of a conductor, an insulation layer, a separation layer, and an outer sheath. The conductor is formed by winding multiple strands of metal material to ensure good electrical conductivity. The insulation layer is a critical part of the fireproof cable and is made of high-temperature and non-combustible fire-resistant materials such as mica, ceramic, and magnesium oxide. These materials have high heat resistance and electrical properties, allowing the cable to maintain its integrity in high-temperature environments and preventing current leakage and short circuits. The separation layer is mainly used to enhance the fire resistance of the cable and is typically made of inorganic mineral materials that can effectively prevent the spread of flames, further protecting the internal structure of the cable from damage. The outer sheath is the outermost layer of the fireproof cable and is usually made of low-smoke and non-toxic plastic materials such as polyvinyl chloride or halogen-free low-smoke flame-retardant polyolefin materials. These materials can improve the corrosion resistance and electrical properties of the cable and reduce the production of toxic gases and smoke during a fire.

[0003] However, the polyvinyl chloride or cross-linked polyethylene used as the outer sheath in current flame-retardant cables freezes the molecular chain segments at low temperatures (such as -40°C), causing the sheath to become hard and lacking in bending performance, and producing brittleness, which can lead to cracking or even breaking. Additionally, filling a large amount of inorganic flame-retardant materials in the insulation layer improves the flame-retardant effect but significantly reduces the material toughness, resulting in insufficient bending performance of the cable at low temperatures. In view of the above-mentioned related technologies, the inventors have found that there is an urgent need to provide a cable that simultaneously has good flame-retardant properties and low-temperature flexibility. SUMMARY

[0004] To simultaneously improve the flame-retardant properties and low-temperature flexibility of the cable, the present application provides a high-flame-retardant green and environment-friendly low-voltage AC cable for smart grid and a preparation method thereof.

[0005] In a first aspect, the present application provides a high-flame-retardant green and environment-friendly low-voltage AC cable for smart grid, which adopts the following technical solution:

[0006] A high-flame-retardant green and environment-friendly low-voltage AC cable for smart grid includes at least three conductor cores, each conductor core including at least one conductor core and a fire-resistant wrapping and a flame-retardant polyethylene coating layer wrapped around the conductor core in sequence.

[0007] The conductor core 1 is wrapped with a fire-resistant wrapping layer, a corona layer, a TPU foamed elastic buffer layer, an EVA adhesive layer, a flame-retardant polyethylene coating layer, a corona layer, and a fluorosilicone rubber / TPU composite layer in sequence.

[0008] The fluorosilicone rubber / TPE composite layer (5) comprises the following raw materials by weight: 5-6 parts of fluorosilicone rubber, 4-5 parts of polyurethane, 0.1-1 parts of a compatibilizer, 1-2 parts of a nano flame retardant, and 0.1-0.5 parts of a silane coupling agent.

[0009] By adopting the above technical scheme, the fire-resistant wrapping layer and the flame-retardant polyethylene coating layer are sequentially located at the outer periphery of the conductor core, the fire-resistant wrapping layer can effectively isolate the conductor core from the external environment, prevent current leakage and short circuit phenomenon, thereby improving the electrical safety of the cable, the flame-retardant polyethylene layer is a material with flame-retardant properties, which can slow down the spread of fire and reduce the damage of fire to the cable. At the same time, it can also reduce the release of toxic smoke and harmful gases, providing favorable conditions for personnel evacuation and fire extinguishing work. The combination of the fluoromicat tape and the flame-retardant polyethylene layer further enhances the electrical insulation performance of the cable. The flame-retardant polyethylene layer not only has flame-retardant properties, but also has certain electrical insulation performance, and the two work together to provide more reliable electrical protection for the cable.

[0010] Then the at least three conductor cores are wrapped with the fire-resistant wrapping layer, and the surface of the fire-resistant wrapping layer is treated by corona to introduce polar groups, improve the surface energy, increase the wettability, and improve the interfacial adhesion. Moreover, when the TPU foamed elastic buffer layer is extruded, the -OH and -COOH on the surface of the mica tape can chemically react with the isocyanate groups (-NCO) or amino groups (-NH2) in the TPU to form chemical bonds, and the micro-porous structure of the TPU foamed layer can be embedded into the micro-rough structure on the surface of the mica tape to increase the mechanical interlocking force.

[0011] Then, through three-layer co-extrusion technology, a TPU foamed elastic buffer layer, an EVA layer and a flame-retardant polyethylene coating layer are sequentially coated outside the conductor core. The TPU can maintain flexibility and high resilience at -40℃ or even lower temperature, avoiding brittle fracture. Moreover, after foaming, the rigidity of the material can be further reduced, the buffering capacity can be increased, and bending stress can be dispersed. The closed-cell structure of the TPU foamed elastic buffer layer can absorb mechanical impact, reduce internal stress concentration when the cable is bent, and reduce density, thereby reducing the weight of the cable and maintaining lightweight while maintaining sufficient mechanical strength. Moreover, the foamed structure can effectively absorb vibration and bending stress, thereby prolonging the service life of the cable in low-temperature mobile scenarios. The EVA adhesive layer can increase the adhesion between the TPU foamed elastic buffer layer and the flame-retardant polyethylene coating layer, improve the interfacial bonding strength, and reduce the interfacial processing procedure. The corona layer can improve the interlayer adhesion between the fluorosilicone rubber / TPU composite layer and the flame-retardant polyethylene coating layer.

[0012] The fluorosilicone rubber and TPE (thermoplastic elastomer) are used as main raw materials of the composite layer, the fluorosilicone rubber can keep soft within-60 to 200 DEG C, and has good flame retardant performance, and after adding polyurethane, the low-temperature impact resistance can be further improved, the brittle fracture can be avoided, the mechanical strength of the fluorosilicone rubber is low, the wear resistance and tear resistance are improved, and the polyurethane does not need to be vulcanized, compared with pure fluorosilicone rubber, the preparation of the composite layer is more environmentally friendly, the alkoxyl group of the silane coupling agent is hydrolyzed and condensed with the Si-OH bond of the fluorosilicone rubber, and the amino group or the epoxy group reacts with the -NH- or -OH of the polyurethane, to form a chemical bridge, improve the interface bonding, reduce the phase separation, improve the compatibility between the fluorosilicone rubber and the TPU, improve the interface bonding, and the nano flame retardant makes up for the defect that the polyurethane is easy to burn.

[0013] Optionally, the nano flame retardant is a carboxyl carbon nanotube / aramid fiber composite foam material, and the mass ratio of the carboxyl carbon nanotube to the aramid fiber is 1:0.3-0.5.

[0014] By using the above technical scheme, the carboxyl carbon nanotube and the aramid fiber are combined to prepare a foam material, the aramid fiber belongs to a flame-retardant fiber, forms a dense carbon layer at high temperature, inhibits combustion, and the high strength and toughness of the aramid fiber can prevent crack propagation at low temperature and improve the elongation at break, in addition, the amount of the aramid fiber is controlled to avoid limiting the movement of the polyurethane segment and affecting the toughness, the carboxylated carbon nanotube forms a network structure in the foam to hinder the diffusion of heat and combustible gas, and the carboxyl group promotes the dehydration of the aramid fiber into carbon at high temperature to improve the quality of the carbon layer, the network structure formed by the carboxyl group can absorb stress and inhibit low-temperature brittle fracture, in addition, the carboxyl group can form a hydrogen bond with the -NH- in the polyurethane to improve the interface bonding and reduce phase separation. Therefore, the foam material formed by the carboxyl carbon nanotube and the aramid fiber not only has high flame retardant capacity, but also can absorb deformation energy to prevent interface expansion caused by stress concentration at low temperature, and the light weight of the foam material can avoid increasing the rigidity of the cable. The amount of the carboxylated carbon nanotube and the aramid fiber is appropriate, the aramid fiber does not limit the movement of the polyurethane molecular chain, which is not conducive to improving the flexibility, and the carbon nanotube is not aggregated to become a stress concentration point, which affects the low-temperature performance.

[0015] Optionally, the carboxyl carbon nanotube / aramid fiber composite foam material is prepared by mixing a carboxyl carbon nanotube and aramid fiber dispersion liquid, freezing and shaping, soaking in a calcium chloride solution with a concentration of 0.1-0.5M, washing, and drying at normal pressure.

[0016] By adopting the technical scheme, the carboxyl carbon nanotubes and aramid fibers are uniformly mixed, then are rapidly frozen and shaped by liquid nitrogen, are soaked, and are freeze-dried, so that a more uniform microporous structure is formed, the foam material is endowed with a lower density, so that lightweight is realized, the rigidity of the cable is increased, the deformation is buffered, the low-temperature flexibility is improved, ion cross-linking is performed after soaking in a calcium chloride solution, the calcium ions fully penetrate and coordinate with the carboxyl groups of the carboxylated carbon nanotubes and the polar groups, such as hydroxyl groups and amino groups, of the aramid fibers to form ion cross-linking points, and the formation of the cross-linking network can prevent the collapse of the pores in the freeze-drying process, improve the compression resilience of the foam material, and improve the buffering effect, and when burning, the calcium ions generate calcium carbonate and are further decomposed into calcium oxide to cover the carbon layer, isolate oxygen, release carbon dioxide, dilute combustible gas, and the calcium ions can also promote the aramid fibers and the carbon nanotubes to form a more stable graphitized carbon layer at high temperatures, so that the flame-retardant effect of the composite foam material is increased.

[0017] Optionally, the surface of the aramid fiber is adhered with hydroxyapatite super-long nanowires through polydopamine, and the mass ratio of the aramid fiber to the hydroxyapatite super-long nanowires is 7-8:2-3.

[0018] By adopting the technical scheme, the hydroxyapatite super-long nanowires are loaded on the surface of the aramid fiber through the polydopamine, the roughness of the surface of the composite foam material is improved, the mechanical interlocking effect of the composite foam material with the polyurethane and the fluorosilicone rubber is improved, the polar hydroxyl groups and phosphate groups in the hydroxyapatite super-long nanowires can form hydrogen bonds or chemical bonds with the polymer matrix to reduce interface defects and improve the mechanical strength, the hydroxyapatite super-long nanowires are decomposed into calcium oxide and diphosphorus pentoxide at high temperatures to absorb heat and release water vapor, the phosphate promotes the aramid fibers to form a dense carbon layer through dehydration to inhibit combustion, the network structure formed by the hydroxyapatite super-long nanowires can also hinder the diffusion of heat and combustible gas to improve the flame retardancy, and in addition, the compression strength and resilience of the composite foam material are improved, and the fracture is delayed.

[0019] Optionally, the compatibilizer includes perfluoropolyether diol and maleic anhydride grafted TPU at a mass ratio of 1:0.2-0.3.

[0020] By adopting the technical scheme, the perfluoropolyether diol is a fluorine-containing polymer, which has similar low surface energy, hydrophobicity and chemical inertness with the fluorosilicon segment (such as -Si-O-Si- and -CF3) of the fluorosilicon rubber, can reduce the interfacial tension, promote the mixing of the two at the molecular level, the hydroxyl group can chemically react with the isocyanate group (-NCO) or the terminal hydroxyl group in the TPU to form a chemical bond, and the interfacial bonding force between the TPU and the fluorosilicon rubber is enhanced; and the perfluoropolyether segment decomposes to generate fluorinated free radicals (such as CF3·) when burning, which can capture H· and OH· free radicals in the combustion chain reaction to inhibit flame propagation, and the perfluoropolyether diol can promote the formation of a dense carbon layer between the TPU and the fluorosilicon rubber when burning to isolate oxygen and heat transfer; the maleic anhydride grafted TPU is modified TPU with anhydride groups formed by grafting maleic anhydride onto the molecular chain of TPU through chemical reaction, and the anhydride groups (-CO-O-CO-) contained therein can undergo ring-opening reaction with the silicon hydroxyl group (-Si-OH) or the terminal amino group (-NH2) in the fluorosilicon rubber to form a chemical bond, thereby enhancing the interfacial bonding force.

[0021] Optionally, the flame-retardant polyethylene coating layer (13) comprises the following raw materials by weight: 10-15 parts of linear low-density polyethylene polyethylene, 4-9 parts of flame retardant, 0.3-1 part of lubricant, and 0.6-1 part of antioxidant.

[0022] By adopting the technical scheme, linear low-density polyethylene is used as the main raw material, and the molecular structure contains a linear main chain and short branches, so that the linear low-density polyethylene has higher tensile strength, puncture resistance and impact resistance than traditional low-density polyethylene, can effectively protect the cable from mechanical damage, and remains soft at low temperature, which is suitable for cold environments or application scenarios requiring frequent bending.

[0023] Optionally, the TPU foamed elastic buffer layer (3) comprises the following raw materials by weight: 8-10 parts of TPU, 0.1-0.5 parts of azobisformamide, 0.05-0.1 parts of zinc stearate, and 0.1-0.3 parts of silane coupling agent KH550.

[0024] By adopting the technical scheme, azobisformamide is used as a foaming agent, and zinc stearate is used as a foam stabilizer, so that the TPU is foamed during extrusion, a buffer layer with uniform and stable pores is obtained, the bending resistance and buffering effect of the cable are increased, and the cable remains lightweight.

[0025] Optionally, the EVA bonding layer (4) comprises EVA resin and maleic anhydride grafted PE in a mass ratio of 1:0.05-0.1.

[0026] By adopting the technical scheme, the maleic anhydride grafted PE can improve the interface bonding of the EVA resin and the TPU, fluorosilicon rubber and the like during extrusion, increase the interface strength between the TPU foamed elastic buffer layer and the fluorosilicon rubber / TPU composite layer, and make the layer structure formed by co-extrusion not easy to be delaminated.

[0027] Optionally, the thickness ratio of the TPU foamed elastic buffer layer (3), the EVA bonding layer (4) and the flame-retardant polyethylene cladding layer (13) is 3:1:5.

[0028] By adopting the technical scheme, the co-extrusion layer structure with the above thickness ratio can ensure the balance between the mechanical strength and the buffering performance of the cable.

[0029] In a second aspect, the application provides a preparation method of a high-flame-retardant green and environment-friendly low-voltage AC cable for smart grids, which adopts the following technical scheme:

[0030] A preparation method of a high-flame-retardant green and environment-friendly low-voltage AC cable for smart grids, comprising the following steps:

[0031] S1, at least one conductor core (11) is drawn, annealed and stranded, and then fluorine mica tape is wrapped around the surface of the conductor core to form a fire-resistant wrapping layer (12); 10-15 parts of linear low-density polyethylene, 4-9 parts of a flame retardant, 0.3-1 part of a lubricant and 0.6-1 part of an antioxidant are uniformly mixed to form a cladding layer raw material; the cladding layer raw material is extruded on the outer surface of the fire-resistant wrapping layer (12) to form a flame-retardant polyethylene cladding layer (13), thereby obtaining a conductor core (1);

[0032] S2, at least one conductor core (1) is stranded, and fluorine mica tape is wrapped around the surface of the conductor core to form a fire-resistant wrapping layer (12); the fire-resistant wrapping layer (12) is subjected to corona treatment to form a corona layer (2) on the surface thereof;

[0033] S3, 10-15 parts of linear low-density polyethylene, 4-9 parts of a flame retardant, 0.3-1 part of a lubricant and 0.6-1 part of an antioxidant are uniformly mixed to obtain a cladding layer raw material; EVA resin and maleic anhydride grafted PE are mixed to obtain an EVA layer raw material; 10-15 parts of TPU, 0.05-0.1 parts of zinc stearate and 0.1-0.3 parts of silane coupling agent KH550 are mixed to obtain a buffer layer material; 0.1-0.5 parts of azodicarbonamide is prepared for standby; the buffer layer material, the EVA layer material and the cladding layer raw material are respectively fed into the inner layer, the middle layer and the outer layer of a three-layer co-extrusion equipment; the azodicarbonamide is mixed with the buffer layer material through side feeding; the product obtained in step S2 is subjected to three-layer co-extrusion to form a TPU foamed elastic buffer layer (3), an EVA bonding layer (4) and a flame-retardant polyethylene cladding layer (13) on the corona layer (2) in sequence;

[0034] S4, the surface of the material obtained in step S3 is subjected to corona treatment to obtain a corona layer (2), then 5-6 parts of fluorosilicone rubber, 4-5 parts of polyurethane, 0.1-1 parts of a compatibilizer, 1-2 parts of a nano flame retardant, and 0.1-0.5 parts of a silane coupling agent are uniformly mixed and then extruded on the surface of the material obtained in S3 subjected to corona treatment to obtain a fluorosilicone rubber / TPU composite layer (5), thereby obtaining the cable.

[0035] By adopting the technical scheme, the cable prepared by the above method has good flame retardation effect, high mechanical strength, strong low-temperature bending resistance, and good low-temperature embrittlement resistance.

[0036] In summary, the present application has the following beneficial effects:

[0037] 1. The TPU foamed elastic buffer layer, the EVA adhesive layer, the flame-retardant polyethylene cladding layer, and the fluorosilicone rubber / TPU composite layer used in the present application make the cable not only have strong flame retardation effect, but also have good buffering effect and flexibility, and are less likely to crack at low temperature, and have a small low-temperature bending radius, which is suitable for cold environments or application scenarios that require frequent bending.

[0038] 2. The carboxylated carbon nanotubes and aramid fibers are preferably used to prepare the foamed material in the present application, and the foamed material is used as a nano flame retardant and added to the fluorosilicone rubber / TPU composite layer, which not only improves the flame retardation effect of the cable, but also makes the composite layer have strong buffering effect, good bending resistance, and strong low-temperature embrittlement resistance. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 Fig. 1 is a structural schematic diagram of the high-flame-retardant green and environmentally friendly low-voltage AC cable for smart grids according to the present application.

[0040] Figure 1 Fig. 1 is a structural schematic diagram of the high-flame-retardant green and environmentally friendly low-voltage AC cable for smart grids according to the present application. DETAILED DESCRIPTION

[0041] The following examples further illustrate the present application.

[0042] Preparation Examples 1-4 of carboxylated carbon nanotube / aramid fiber composite foamed material

[0043] Preparation Example 1: aramid short fiber was dispersed in water to form a dispersion liquid of aramid fiber with a concentration of 1 g / l, carboxyl carbon nanotubes were added, stirred at room temperature for 30 min, pre-frozen in liquid nitrogen for 4 h, then soaked in a calcium chloride aqueous solution with a concentration of 0.5 M for 12 h, and then dried in a blast drying oven at 60°C for 6 h to obtain a composite foam material, the aramid short fiber was selected from Shanghai Ruian Trade Twaron, the yarn count was 1.7 dtex, and the fiber length was 50 mm, the carboxyl carbon nanotube was selected from Nanjing Muke Nano, the number was MK2048, and the article number was 102048, and the mass ratio of the carboxyl carbon nanotube to the aramid fiber was 1:0.5.

[0044] Preparation Example 2: aramid short fiber was dispersed in water to form a dispersion liquid of aramid fiber with a concentration of 1 g / l, carboxyl carbon nanotubes were added, stirred at room temperature for 30 min, pre-frozen in liquid nitrogen for 4 h, then soaked in a calcium chloride aqueous solution with a concentration of 0.1 M for 24 h, and then dried in a blast drying oven at 60°C for 6 h to obtain a composite foam material, the aramid short fiber was selected from Shanghai Ruian Trade Twaron, the yarn count was 1.7 dtex, and the fiber length was 50 mm, the carboxyl carbon nanotube was selected from Nanjing Muke Nano, the number was MK2048, and the article number was 102048, and the mass ratio of the carboxyl carbon nanotube to the aramid fiber was 1:0.3.

[0045] Preparation Example 3: The difference from Preparation Example 1 is that no calcium chloride solution is soaked, and freeze drying is used instead of atmospheric drying, and the specific method is as follows: aramid short fiber is soaked in a sodium hydroxide solution with a concentration of 15 wt%, the water bath ratio is 1:250, 80°C heat treatment for 4 h, suction filtration, washing to neutral, dispersing in water to form a dispersion liquid of aramid fiber with a concentration of 1 g / l, adding carboxyl carbon nanotubes, stirring at room temperature for 30 min, pre-freezing in liquid nitrogen for 4 h, and freeze drying at-60°C for 48 h to obtain a composite foam material, the aramid short fiber is selected from Shanghai Ruian Trade Twaron, the yarn count is 1.7 dtex, and the fiber length is 50 mm, the carboxyl carbon nanotube is selected from Nanjing Muke Nano, the number is MK2048, and the article number is 102048, and the mass ratio of the carboxyl carbon nanotube to the aramid fiber is 1:0.5.

[0046] Preparation Example 4: (1) aramid fibers were dispersed in water to obtain a dispersion liquid with a concentration of 1 g / l, 100 ml of the dispersion liquid was taken, 1.5 ml of dopamine solution with a concentration of 2 mg / ml and 200 ml of Tris buffer (pH = 8.5) were added, and stirring was carried out under water bath at 65℃ for 12 h, and then filtration, washing until pH = 7, adding deionized water, and stirring to form a functionalized aramid fiber dispersion liquid with a concentration of 1 mg / ml; hydroxyapatite super-long nanowires were dispersed in deionized water, and a nanowire dispersion liquid with a concentration of 4 mg / ml was obtained after ultrasonic dispersion for 40 min, and the mass ratio of aramid fibers to hydroxyapatite super-long nanowires was 8:2; 100 ml of the functionalized aramid fiber dispersion liquid and 10.7 ml of the nanowire dispersion liquid were mixed, and after stirring for 3 h, filtration, pre-freezing in liquid nitrogen for 20 min, freeze-drying at-60℃ and 10 Pa for 48 h;

[0047] (2) aramid short fibers obtained in step (1) were dispersed in water to form an aramid fiber dispersion liquid with a concentration of 1 g / l, carboxyl carbon nanotubes were added, and stirring was carried out at room temperature for 30 min, liquid nitrogen pre-freezing was carried out for 4 h, and then soaking in a 0.5 M calcium chloride aqueous solution was carried out, soaking was carried out for 12 h, and then drying was carried out in a 60℃ air drying oven for 6 h to obtain a composite foam material, aramid short fibers were selected from Shanghai Ruianjia Trade Twaron, the yarn count was 1.7 dtex, the fiber length was 50 mm, carboxyl carbon nanotubes were selected from Nanjing Muke Nano, the number was MK2048, and the article number was 102048, and the mass ratio of carboxyl carbon nanotubes to aramid fibers was 1:0.5.

[0048] Embodiment

[0049] Embodiment 1: A high-flame-retardant green and environment-friendly low-voltage AC cable for smart grid, comprising at least three conductor cores 1, the conductor core 1 comprising at least one conductor core 11, the conductor core 11 being wrapped with a fire-resistant wrapping layer 12 and a flame-retardant polyethylene coating layer 13 in sequence, the conductor core 1 being wrapped with the fire-resistant wrapping layer 12, a corona layer 2, a TPU foamed elastic buffer layer 3, an EVA adhesive layer 4, the flame-retardant polyethylene coating layer 13, the corona layer 2 and a fluorosilicone rubber / TPU composite layer 5 in sequence; the thickness ratio of the TPU foamed buffer layer 3, the EVA adhesive layer 4 and the flame-retardant polyethylene coating layer is 3:1:5.

[0050] The raw material amount of the fluorosilicone rubber / TPU rubber layer, the TPU foamed elastic buffer layer, the EVA adhesive layer, and the flame-retardant polyethylene cladding layer is shown in Table 1, wherein the fluorosilicone rubber in the fluorosilicone rubber / TPU rubber layer is selected from Dow Corning, and the model number is LS-2940U, the polyurethane is selected from BASF in Germany, and the model number is S85A10, the compatibilizer includes perfluoropolyether diol and maleic anhydride grafted TPU with a mass ratio of 1:0.3, the maleic anhydride grafted TPU is selected from Dongguan Yutai Plastic, and the model number is ssd023, the nano flame retardant is nano magnesium hydroxide, and the silane coupling agent is KH550.

[0051] The TPU in the TPU foamed elastic buffer layer is selected from Dongguan Zhangmutou Jinyunlai Plastic, and the model number is Bayer 2915 in Germany, the EVA resin in the EVA adhesive layer is selected from Japan Mitsui, and the model number is 40W, the maleic anhydride grafted PE is selected from Suzhou Dijie Plastic, and the model number is MD226D4100, the linear low-density polyethylene in the flame-retardant polyethylene cladding layer is selected from South Korea Hanchwa, and the article number is 3224, the flame retardant is magnesium hydroxide, the lubricant is polyethylene wax, and the antioxidant is antioxidant 1010.

[0052] The preparation method of the high-flame-retardant green and environment-friendly low-voltage AC cable for smart grids, comprising the following steps:

[0053] S1, at least one conductor core 11 is drawn, annealed, stranded, and then wrapped with fluoromicat tape on the surface to form a fire-resistant wrapping layer 12, the linear low-density polyethylene polyethylene, the flame retardant, the lubricant, and the antioxidant are mixed uniformly according to the raw material amount of the flame-retardant polyethylene cladding layer in Table 1 to form a cladding layer raw material, the cladding layer raw material is extruded and coated on the outer surface of the fire-resistant wrapping layer 12 at 150 DEG C to form a flame-retardant polyethylene cladding layer 13, and a conductor core 1 is prepared.

[0054] S2, at least one conductor core 1 is stranded, and fluoromicat tape is wrapped on the surface to form a fire-resistant wrapping layer 12, the fire-resistant wrapping layer 12 is subjected to corona treatment to form a corona layer 2 on the surface, the power density is 0.3 W / cm 2 , the treatment time is 10 s under air atmosphere, the electrode spacing is 1 mm, and the frequency is 10 kHz.

[0055] S3, according to the raw material amount of the flame-retardant polyethylene coating layer in Table 1, the linear low-density polyethylene polyethylene, the flame retardant, the lubricant, the antioxidant were mixed uniformly to prepare the coating layer raw material, according to the amount of EVA adhesive layer in Table 1, the EVA resin and maleic anhydride grafted PE were mixed to prepare the EVA layer raw material, according to the raw material amount of the TPU foamed elastic buffer layer in Table 1, the TPU, the zinc stearate and the silane coupling agent KH550 were mixed to prepare the buffer layer material, and the azodicarbonamide was taken for standby, the buffer layer material, the EVA layer material and the coating layer raw material were respectively put into the inner layer, the middle layer and the outer layer feeding port of the three-layer co-extrusion equipment, and the azodicarbonamide was mixed with the buffer layer material through the side feeding, and the three-layer co-extrusion was carried out on the obtained material of step S2, and the TPU foamed elastic buffer layer 3, the EVA adhesive layer 4 and the flame-retardant polyethylene coating layer 13 were formed on the corona layer 2 in sequence, the drawing speed was 10 m / min during the three-layer co-extrusion, the TPU foamed elastic buffer layer adopted the metering screw, the compression ratio was 2:1, the EVA adhesive layer adopted the general screw, the compression ratio was 2:1, and the flame-retardant polyethylene coating layer adopted the gradual change screw, the compression ratio was 3:1, the extrusion temperature of the buffer layer raw material was 80 DEG C in the feeding section, 150 DEG C in the compression section, 170 DEG C in the metering section, 180 DEG C in the front section of the die head and 160 DEG C at the die head outlet, the extrusion pressure was 8 MPa, and the screw rotation speed was 15 rpm; the extrusion temperature of the EVA layer raw material was 100 DEG C in the feeding section, 120 DEG C in the compression section, 130 DEG C in the metering section, 140 DEG C in the front section of the die head and 130 DEG C at the die head outlet, the extrusion pressure was 12 MPa, and the screw rotation speed was 30 rpm; the extrusion temperature of the flame-retardant polyethylene coating layer was 120 DEG C in the feeding section, 140 DEG C in the compression section, 150 DEG C in the metering section, 160 DEG C in the front section of the die head and 150 DEG C at the die head outlet, the extrusion pressure was 15 MPa, and the screw rotation speed was 25 rpm.

[0056] S4, the surface of the obtained material of step S3 was subjected to corona treatment, the power density was 0.5 W / cm 2 during the corona treatment, the treatment time was 20 s in the air atmosphere, the electrode distance was 3 mm, and the frequency was 30 kHz, and a corona layer 2 was obtained.

[0057] Table 1

[0058]

[0059] Example 2-3: A high-flame-retardant green and environment-friendly low-voltage AC cable for smart grid, which is different from example 1 in that the raw material amount of the fluorosilicone rubber / TPU composite layer, the flame-retardant polyethylene coating layer, the EVA adhesive layer and the TPU foamed elastic buffer layer is shown in Table 1.

[0060] Example 4: A high flame-retardant green environmental protection low-voltage AC cable for smart grid, which is different from Example 1 in that the nano flame retardant in the fluorosilicone rubber / TPU composite layer is carboxyl carbon nanotube / aramid fiber composite foam material, and is made by Preparation Example 1.

[0061] Example 5: A high flame-retardant green environmental protection low-voltage AC cable for smart grid, which is different from Example 1 in that the nano flame retardant in the fluorosilicone rubber / TPU composite layer is carboxyl carbon nanotube / aramid fiber composite foam material, and is made by Preparation Example 2.

[0062] Example 6: A high flame-retardant green environmental protection low-voltage AC cable for smart grid, which is different from Example 4 in that the nano flame retardant in the fluorosilicone rubber / TPU composite layer is carboxyl carbon nanotube / aramid fiber composite foam material, and is made by Preparation Example 3.

[0063] Example 7: A high flame-retardant green environmental protection low-voltage AC cable for smart grid, which is different from Example 4 in that the nano flame retardant in the fluorosilicone rubber / TPU composite layer is carboxyl carbon nanotube / aramid fiber composite foam material, and is made by Preparation Example 4.

[0064] Comparative Example

[0065] Comparative Example 1: A high flame-retardant green environmental protection low-voltage AC cable for smart grid, which is different from Example 1 in that no TPU foamed elastic buffer layer (3) and EVA adhesive layer (4) are provided, the raw material of the flame-retardant polyethylene cladding layer (13) is directly extruded on the surface of the corona layer (2) of the fire-resistant wrapping layer (12) after melting, and the extrusion thickness of the flame-retardant polyethylene cladding layer (13) is the same as the total thickness of the TPU foamed buffer layer (3) and the EVA adhesive layer (4).

[0066] Comparative Example 2: A high flame-retardant green environmental protection low-voltage AC cable for smart grid, which is different from Example 1 in that the flame-retardant polyethylene cladding layer (13) with the same thickness is used instead of the fluorosilicone rubber / TPU composite layer (5).

[0067] Performance detection test

[0068] The cable is prepared according to the method in the examples and comparative examples, and the performance is detected according to the following method, and the detection results are recorded in Table 2.

[0069] 1. Tensile strength and elongation at break: detected according to GB / T528-1998 "Determination of tensile stress-strain properties of vulcanized or thermoplastic rubber", and the tensile rate is 50 m / min.

[0070] 2. Low temperature impact strength: according to GB / T1843-2008 "Determination of Izod Impact Strength of Plastics", the low temperature impact strength of the sample was tested by using a simple beam impact testing machine, and the test temperature was -50±2℃.

[0071] 3. Limiting oxygen index: according to GB / T2406.2-2009 "Determination of the Burning Behavior of Electrical Cables - Part 2: Test Methods - Measurement of the Minimum Oxygen Concentration for Sustained Combustion of the Material", the limiting oxygen index was tested.

[0072] 4. Bending radius: according to JB / T10696.3-2008 "Test Methods for Electrical Cables - Mechanical and Physical Properties - Part 3: Bending Test", the bending radius was tested.

[0073] Table 2 Performance test results of the high flame-retardant green environment-friendly low-voltage AC cable

[0074]

[0075] As can be seen from the layer structure of the cable, the selection of raw materials in Examples 1-3 and the data in Table 2, the cable prepared in Examples 1-3 has good mechanical properties such as large tensile strength and elongation at break, tensile resistance, and large impact strength at low temperature, good low-temperature flexibility, good flame retardancy, good bending resistance, good low-temperature flexibility, and not easy to harden at low temperature.

[0076] In Examples 4 and 5, the carboxyl carbon nanotube / aramid fiber composite foam material prepared in Preparation Examples 1 and 2 was used as a nano flame retardant in the fluorosilicone rubber / TPU composite layer, and the data in Table 2 shows that the cable prepared in Examples 4 and 5 has increased limiting oxygen index, improved flame retardant ability, slightly increased low temperature impact strength, increased tensile strength and elongation at break, and increased bending radius.

[0077] In Example 6, the carboxyl carbon nanotube / aramid fiber composite foam material prepared in Preparation Example 3 was used as a nano flame retardant, and compared with Example 4 using Preparation Example 1, the cable prepared in Example 6 has decreased low temperature impact strength, decreased limiting oxygen index, decreased flame retardant effect, and weakened low temperature impact resistance.

[0078] In Example 7, the carboxyl carbon nanotube / aramid fiber composite foam material prepared in Preparation Example 4 was used as a nano flame retardant, and compared with Example 4, the cable has increased limiting oxygen index, increased mechanical strength, increased low temperature impact strength, and improved low temperature brittleness resistance.

[0079] Comparative Example 1, compared with Example 1, does not have a TPU foamed elastic buffer layer and an EVA adhesive layer, and uses a flame-retardant polyethylene coating layer instead, and it can be seen that the bending radius at both room temperature and low temperature is significantly increased, the low temperature impact strength is decreased, and the low temperature bending resistance is weakened.

[0080] Compared with Example 1, the overmolding layer of flame-retardant polyethylene is used instead of the fluorosilicone rubber / TPU composite layer in Comparative Example 2, and it can be seen that the bending resistance, tensile resistance and low-temperature resistance of the cable prepared thereby are all decreased.

[0081] The specific embodiments are only an explanation of the present application, and are not a limitation of the present application. Those skilled in the art can make modifications to the embodiments without creative contribution after reading the specification, and as long as the modifications are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A high flame-retardant, environmentally friendly, low-voltage AC cable for smart grids, characterized in that: It includes at least three conductor cells (1), each conductor cell (1) including at least one conductor core (11) and a fire-resistant wrapping layer (12) and a flame-retardant polyethylene wrapping layer (13) sequentially covering the outer periphery of the conductor core (11). The conductor core (1) is sequentially covered with a fire-resistant wrapping layer (12), a corona layer (2), a TPU foam elastic buffer layer (3), an EVA adhesive layer (4), a flame-retardant polyethylene coating layer (13), a corona layer (2), and a fluorosilicone rubber / TPU composite layer (5). The fluorosilicone rubber / TPE composite layer (5) comprises the following parts by weight of raw materials: 5-6 parts fluorosilicone rubber, 4-5 parts polyurethane, 0.1-1 parts compatibilizer, 1-2 parts nano flame retardant and 0.1-0.5 parts silane coupling agent; The nano flame retardant is a carboxylated carbon nanotube / aramid fiber composite foam material, with a mass ratio of carboxylated carbon nanotubes to aramid fibers of 1:0.3-0.

5. The surface of the aramid fibers is coated with hydroxyapatite ultralong nanowires via polydopamine, with a mass ratio of aramid fibers to hydroxyapatite ultralong nanowires of 7-8:2-3.

2. The high flame-retardant, green, and environmentally friendly low-voltage AC cable for smart grids according to claim 1, characterized in that: The carboxylated carbon nanotube / aramid fiber composite foam material is prepared by mixing carboxylated carbon nanotubes and aramid fiber dispersions, freeze-setting, soaking in a calcium chloride solution with a concentration of 0.1-0.5M, washing, and then drying under normal pressure.

3. The high flame-retardant, green, and environmentally friendly low-voltage AC cable for smart grids according to claim 1, characterized in that: The compatibilizer comprises perfluoropolyether diol and maleic anhydride-grafted TPU in a mass ratio of 1:0.2-0.

3.

4. The high flame-retardant, green, and environmentally friendly low-voltage AC cable for smart grids according to claim 1, characterized in that: The flame-retardant polyethylene coating layer (13) comprises the following parts by weight of raw materials: 10-15 parts of linear low-density polyethylene, 4-9 parts of flame retardant, 0.3-1 parts of lubricant, and 0.6-1 parts of antioxidant.

5. The high flame-retardant, green, and environmentally friendly low-voltage AC cable for smart grids according to claim 1, characterized in that: The TPU foamed elastic buffer layer (3) contains the following raw materials by weight: 8-10 parts TPU, 0.1-0.5 parts azodicarbonamide, 0.05-0.1 parts zinc stearate, and 0.1-0.3 parts silane coupling agent KH550.

6. The high flame-retardant, green, and environmentally friendly low-voltage AC cable for smart grids according to claim 1, characterized in that: The EVA adhesive layer (4) comprises EVA resin and maleic anhydride-grafted PE in a mass ratio of 1:0.05-0.

1.

7. The high flame-retardant, green, and environmentally friendly low-voltage AC cable for smart grids according to claim 1, characterized in that: The thickness ratio of the TPU foamed elastic buffer layer (3), the EVA adhesive layer (4), and the flame-retardant polyethylene coating layer (13) is 3:1:

5.

8. The method for preparing the high flame-retardant, green, and environmentally friendly low-voltage AC cable for smart grids according to any one of claims 1-7, characterized in that: Includes the following steps: S1. At least one conductor core (11) is drawn, annealed and stranded, and then wrapped with fluorophlogopite tape to form a fire-resistant wrapping layer (12). 10-15 parts of linear low-density polyethylene, 4-9 parts of flame retardant, 0.3-1 parts of lubricant and 0.6-1 parts of antioxidant are mixed evenly to form a coating material. The coating material is extruded onto the outer surface of the fire-resistant wrapping layer (12) to form a flame-retardant polyethylene coating layer (13) to obtain the conductor core (1). S2. At least one conductor core (1) is stranded together and wrapped with fluorophlogopite tape to form a fire-resistant wrapping layer (12). The fire-resistant wrapping layer (12) is subjected to corona treatment to form a corona layer (2) on its surface. S3. Mix 10-15 parts of linear low-density polyethylene, 4-9 parts of flame retardant, 0.3-1 parts of lubricant, and 0.6-1 parts of antioxidant evenly to obtain the coating layer material. Mix EVA resin and maleic anhydride-grafted PE to obtain the EVA layer material. Mix 10-15 parts of TPU, 0.05-0.1 parts of zinc stearate, and 0.1-0.3 parts of silane coupling agent KH550 to obtain the buffer layer material. Take 0.1-0.5 parts of azodicarbonamide for later use. Put the buffer layer material, EVA layer material, and coating layer material into the inner, middle, and outer feed ports of the three-layer co-extrusion equipment, respectively. Mix the azodicarbonamide with the buffer layer material through side feeding. Perform three-layer co-extrusion on the material obtained in step S2 to form a TPU foamed elastic buffer layer (3), an EVA adhesive layer (4), and a flame-retardant polyethylene coating layer (13) on the corona layer (2). S4. The surface of the material obtained in step S3 is subjected to corona treatment to obtain a corona layer (2). Then, 5-6 parts of fluorosilicone rubber, 4-5 parts of polyurethane, 0.1-1 parts of compatibilizer, 1-2 parts of nano flame retardant and 0.1-0.5 parts of silane coupling agent are mixed evenly and extruded onto the surface of the material obtained in step S3 after corona treatment to obtain a fluorosilicone rubber / TPU composite layer (5) and a cable is obtained.

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