A medium voltage flame retardant cable and its preparation method

Abstract

The invention discloses a medium-voltage flame-retardant cable and a preparation method thereof, relating to the field of cable technology. The medium-voltage flame-retardant cable includes a core, an insulating layer, a heat-insulating layer, a flame-retardant layer, and a protective layer, which are sequentially arranged from the inside to the outside. The flame-retardant layer comprises the following raw materials in parts by weight: 50-70 parts of ethylene-vinyl acetate copolymer, 1-10 parts of a bio-based flame retardant, 1-5 parts of a calcium-zinc stabilizer, 0.1-1 parts of an antioxidant, 5-10 parts of a plasticizer, and 1-10 parts of porous sepiolite. The bio-based flame retardant is composed of a POSS-based flame retardant and a vanillin-based flame retardant in a mass ratio of 2:1-4. The medium-voltage flame-retardant cable of the present invention has excellent flame retardant properties.

Description

Technical Field

[0001] The present invention relates to the technical field of cables, and in particular to a medium-voltage flame-retardant cable and a preparation method thereof. Background Art

[0002] With the ever-increasing demand for electricity in modern society, cables, as core components of power transmission, have been widely used in industries such as industry, construction, and transportation. Medium-voltage cables (6-35kV) are particularly popular in complex environments such as high-rise buildings, underground facilities, and offshore wind farms due to their efficient power transmission capabilities. However, cables are susceptible to factors such as high temperatures, short circuits, and overloads during operation, leading to fire accidents. Fires not only cause significant economic losses but can also threaten human life. Therefore, improving the flame retardancy of cables has become a critical issue that needs to be addressed in the power industry.

[0003] The flame-retardant properties of cables are directly related to the safety and reliability of power systems. Traditional cables easily burn in fires and release large amounts of toxic smoke, exacerbating the fire hazard. Flame-retardant cables effectively reduce fire risks by inhibiting the spread of flames and reducing smoke production, buying valuable time for evacuation and firefighting. The use of flame-retardant cables is particularly important in crowded places such as high-rise buildings and subway tunnels.

[0004] Currently, cable flame-retardant technology primarily relies on the addition of flame retardants. Common flame retardants include halogenated, halogen-free, and composite flame retardants. While halogenated flame retardants offer significant flame retardancy, they release toxic gases (such as hydrogen chloride and hydrogen bromide) during combustion, posing a threat to the environment and human health. Halogen-free flame retardants (such as aluminum hydroxide and magnesium hydroxide) are favored for their environmental friendliness, but their flame retardant efficiency is relatively low, and at high loadings, they can affect the mechanical and electrical properties of the cable.

[0005] In recent years, researchers have enhanced the performance of flame-retardant materials through modification techniques. For example, surface modification techniques (such as silane coupling agents) have been used to improve the compatibility of aluminum hydroxide with polymer materials, thereby enhancing its dispersibility and flame retardant effectiveness. Furthermore, significant progress has been made in the application of composite flame retardant technology. By combining aluminum hydroxide with other halogen-free flame retardants (such as phosphate esters and nitrogen-based compounds), it is possible to reduce the filler content while improving flame retardant efficiency.

[0006] The present invention aims to develop a medium-voltage flame-retardant cable with high-efficiency flame retardancy by improving the material of the cable flame-retardant layer. Summary of the Invention

[0007] Based on the technical problems existing in the background technology, the present invention proposes a medium voltage flame retardant cable and a preparation method thereof, wherein the medium voltage flame retardant cable has excellent flame retardant properties.

[0008] The present invention provides a medium voltage flame retardant cable, comprising a wire core, an insulating layer, a heat insulating layer, a flame retardant layer and a protective layer arranged in sequence from the inside to the outside;

[0009] The flame retardant layer comprises the following raw materials in parts by weight: 50-70 parts of ethylene-vinyl acetate copolymer, 1-10 parts of bio-based flame retardant, 1-5 parts of calcium zinc stabilizer, 0.1-1 parts of antioxidant, 5-10 parts of plasticizer, and 1-10 parts of porous sepiolite;

[0010] The bio-based flame retardant consists of a POSS-based flame retardant and a vanillin-based flame retardant in a mass ratio of 2:1-4.

[0011] Preferably, the preparation method of the POSS-based flame retardant is as follows:

[0012] S11: Under an inert atmosphere, black phosphorus nanosheets and 4-azidobenzoic acid are dispersed in dimethylformamide and heated for reaction, followed by centrifugation, washing, and drying to obtain an intermediate product;

[0013] S12: dispersing the intermediate product in tetrahydrofuran, adding aminopropyl isobutyl silsesquioxane and dicyclohexylcarbodiimide to react, and washing and drying the product to obtain a POSS-based flame retardant.

[0014] Preferably, the reaction temperature in S11 is 120-160°C and the reaction time is 24-48 hours; the reaction temperature in S12 is 55-75°C and the reaction time is 24-48 hours; the mass ratio of black phosphorus nanosheets and 4-azidobenzoic acid is 1:3-5; the mass ratio of the intermediate product, aminopropyl isobutyl silsesquioxane and dicyclohexylcarbodiimide is 1:3-5:0.5-1.5.

[0015] Preferably, the preparation method of the vanillin-based flame retardant is as follows:

[0016] S21: Under an inert atmosphere, vanillin is dissolved in tetrahydrofuran, and then anhydrous potassium carbonate and hexachlorocyclotriphosphazene are added in sequence to react. After the reaction, the mixture is filtered, washed, and dried to obtain an intermediate product;

[0017] S22: dissolving the intermediate product in dimethyl sulfoxide, adjusting the pH to 9-10, adding melamine and prepolymerizing at 80-90°C for 2-4 hours, adjusting the pH to 3-4, and then heating to react. After the reaction, cooling, filtering, washing and drying are performed to obtain a vanillin-based flame retardant.

[0018] Preferably, the reaction temperature in S21 is 65-75° C. and the reaction time is 24-36 h; the mass ratio of vanillin, anhydrous potassium carbonate and hexachlorocyclotriphosphazene is 1:0.4-0.6:0.2-0.4; the reaction temperature in S22 is 130-150° C. and the reaction time is 2-4 h; and the mass ratio of the intermediate product to melamine is 1:0.4-0.6.

[0019] Preferably, the antioxidant is one or more of antioxidant 1010, antioxidant 168, antioxidant 1076, antioxidant DLTP, antioxidant BHT, antioxidant MD-124, antioxidant 3114 and antioxidant 1098; the plasticizer is one or more of dioctyl phthalate, dioctyl terephthalate, dioctyl adipate, epoxy soybean oil, trioctyl trimellitate and trioctyl trimellitate.

[0020] Preferably, the insulating layer is one of cross-linked polyethylene, ethylene propylene rubber, polyvinyl chloride, silicone rubber and polyimide.

[0021] Preferably, the thermal insulation layer is one or more of ceramic silicone rubber, mica tape, zinc borate modified polymer, glass fiber braided layer and mineral wool.

[0022] Preferably, the protective layer is one of polyvinyl chloride, low-smoke halogen-free polyolefin, thermoplastic polyurethane, chloroprene rubber and polyamide.

[0023] The present invention proposes a method for preparing a medium-voltage flame-retardant cable. The medium-voltage flame-retardant cable is as described above, and is characterized by the following steps: an insulating layer, a heat-insulating layer, a flame-retardant layer and a protective layer are sequentially coated on the outside of the wire core from the inside to the outside to obtain a medium-voltage flame-retardant cable.

[0024] Beneficial technical effects of the present invention:

[0025] The medium-voltage flame-retardant cable of the present invention includes a wire core, an insulation layer, a heat-insulating layer, a flame-retardant layer and a protective layer arranged in sequence from the inside to the outside, wherein the heat-insulating layer can cooperate with the flame-retardant layer to form a "carbon-ceramic" double barrier, blocking the diffusion of heat and oxygen, and further improving the flame-retardant effect; the bio-based flame retardant added to the flame-retardant layer is composed of a POSS-based flame retardant and a vanillin-based flame retardant, which can improve the flame-retardant performance while also improving the mechanical strength; in addition, the POSS-based flame retardant and the vanillin-based flame retardant have a synergistic promoting effect in improving the flame-retardant performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic structural diagram of the medium voltage flame retardant cable proposed by the present invention;

[0027] Figure 2 The H-NMR spectrum of the POSS-based flame retardant of Example 1 proposed by the present invention;

[0028] Figure 3 The infrared spectrum of the POSS-based flame retardant of Example 1 proposed by the present invention;

[0029] Figure 4 Thermogravimetric analysis diagram of the POSS-based flame retardant of Example 1 proposed by the present invention;

[0030] Figure 5 This is the H NMR spectrum of the vanillin-based flame retardant of Example 1 proposed in the present invention;

[0031] Figure 6 This is an infrared spectrum of the vanillin-based flame retardant of Example 1 proposed by the present invention;

[0032] Figure 7 This is a thermogravimetric analysis diagram of the vanillin-based flame retardant of Example 1 proposed in the present invention.

[0033] In the figure: 1-wire core, 2-insulation layer, 3-thermal insulation layer, 4-flame retardant layer, 5-protective layer. DETAILED DESCRIPTION

[0034] The present invention will be further explained below with reference to specific embodiments.

[0035] Unless otherwise specified, all raw materials of the present invention are commercially available.

[0036] Example 1

[0037] An insulating layer, a heat-insulating layer, a flame-retardant layer and a protective layer are sequentially coated on the outside of the wire core from the inside to the outside to produce a medium-voltage flame-retardant cable.

[0038] The flame retardant layer comprises the following raw materials in parts by weight: 60 parts of ethylene-vinyl acetate copolymer, 5 parts of bio-based flame retardant, 3 parts of calcium zinc stabilizer, 0.5 parts of antioxidant, 8 parts of plasticizer, and 5 parts of porous sepiolite;

[0039] The bio-based flame retardant consists of a POSS-based flame retardant and a vanillin-based flame retardant in a mass ratio of 1:1.

[0040] The preparation method of POSS-based flame retardant is as follows:

[0041] S11: Under an inert atmosphere, black phosphorus nanosheets and 4-azidobenzoic acid are dispersed in dimethylformamide and heated for reaction, followed by centrifugation, washing, and drying to obtain an intermediate product;

[0042] S12: dispersing the intermediate product in tetrahydrofuran, adding aminopropyl isobutyl silsesquioxane and dicyclohexylcarbodiimide to react, and washing and drying the product to obtain a POSS-based flame retardant.

[0043] The reaction temperature in S11 is 140°C and the reaction time is 36 hours; the reaction temperature in S12 is 65°C and the reaction time is 36 hours; the mass ratio of black phosphorus nanosheets and 4-azidobenzoic acid is 1:4; the mass ratio of the intermediate product, aminopropylisobutylsilsesquioxane and dicyclohexylcarbodiimide is 1:4:1.

[0044] Figure 2This is the H NMR spectrum of a POSS-based flame retardant: benzene ring hydrogens: 7.5-8.5 ppm (4H, from the benzene ring of 4-azidobenzoic acid); isobutyl hydrogens: 0.8-1.0 (d, -CH3), 1.5-1.7 (m, -CH2-CH(CH3)2); aminopropyl hydrogens: 1.2-1.4 (m, -CH2-CH2-NH-), 2.6-2.8 (t, -CH2-NH-); and amide hydrogens: 6.5-7.0 (broad peak, 1H, -NH-CO-). Based on the H NMR spectrum, this application successfully synthesized a POSS-based flame retardant.

[0045] Figure 3 This is the infrared spectrum of POSS-based flame retardant, 1050-1100cm -1 The peak is attributed to the stretching vibration of Si-O-Si, 2850-2970 cm -1 The isobutyl group signal is shown at 1650–1680 cm -1 and 1550-1580cm -1 The peaks at the bottom are the C=O stretching peak and the NH bending peak of the amide group, respectively, indicating that the black phosphorus nanosheet intermediate product undergoes a bonding reaction with aminopropyl isobutyl silsesquioxane during the preparation of the POSS-based flame retardant, indicating that the POSS-based flame retardant is successfully synthesized.

[0046] Figure 4 This is the thermogravimetric analysis diagram of the POSS-based flame retardant. It can be seen from the figure that the residual carbon content of the POSS-based flame retardant is still higher than 35% at 800°C, indicating that the POSS-based flame retardant has excellent high-temperature thermal stability.

[0047] The preparation method of the vanillin-based flame retardant is as follows:

[0048] S21: Under an inert atmosphere, vanillin is dissolved in tetrahydrofuran, and then anhydrous potassium carbonate and hexachlorocyclotriphosphazene are added in sequence to react. After the reaction, the mixture is filtered, washed, and dried to obtain an intermediate product;

[0049] S22: The intermediate product is dissolved in dimethyl sulfoxide, the pH is adjusted to 10, melamine is added and prepolymerized at 85°C for 3 hours, the pH is adjusted to 4, and the temperature is raised to react. After the reaction, the product is cooled, filtered, washed and dried to obtain a vanillin-based flame retardant.

[0050] The reaction temperature in S21 is 70° C. and the reaction time is 30 h; the mass ratio of vanillin, anhydrous potassium carbonate and hexachlorocyclotriphosphazene is 1:0.5:0.3; the reaction temperature in S22 is 140° C. and the reaction time is 3 h; the mass ratio of the intermediate product to melamine is 1:0.5.

[0051] Figure 5This is the H NMR spectrum of a vanillin-based flame retardant: benzene ring hydrogen: 6.7-7.5 ppm (3H, H on the vanillin benzene ring); methoxy group (-OCH3): 3.8 ppm (3H); aldehyde group (-CHO): 9.8 ppm (1H); amino group (-NH-): 5.0-6.0 ppm (broad peak, 2H); triazine ring hydrogen: 7.5-8.0 ppm (1H). Based on the H NMR spectrum, this application successfully synthesized a vanillin-based flame retardant.

[0052] Figure 6 This is the infrared spectrum of the vanillin-based flame retardant, where 1550 cm -1 and 811cm -1 The characteristic absorption peak of the triazine ring is 863 cm -1 and 1194cm -1 It is the characteristic absorption peak of PN and P=N bond, 1320cm -1 It is the characteristic absorption peak of CN bond. The infrared spectrum also shows that the present application has successfully synthesized the vanillin-based flame retardant.

[0053] Figure 7 This is the thermogravimetric analysis diagram of the vanillin-based flame retardant. It can be seen from the figure that the residual carbon content of the vanillin-based flame retardant at 800°C is about 20%, indicating that the vanillin-based flame retardant has good high-temperature thermal stability.

[0054] The antioxidant is composed of antioxidant 1010 and antioxidant 168 in a mass ratio of 5:1; the plasticizer is dioctyl terephthalate; the insulating layer is cross-linked polyethylene; the thermal insulation layer is ceramic silicone rubber; and the protective layer is low-smoke halogen-free polyolefin.

[0055] Example 2

[0056] An insulating layer, a heat-insulating layer, a flame-retardant layer and a protective layer are sequentially coated on the outside of the wire core from the inside to the outside to produce a medium-voltage flame-retardant cable.

[0057] The flame retardant layer comprises the following raw materials in parts by weight: 50 parts of ethylene-vinyl acetate copolymer, 1 part of bio-based flame retardant, 1 part of calcium zinc stabilizer, 0.1 part of antioxidant, 5 parts of plasticizer, and 1 part of porous sepiolite;

[0058] The bio-based flame retardant consists of a POSS-based flame retardant and a vanillin-based flame retardant in a mass ratio of 2:1.

[0059] The preparation method of POSS-based flame retardant is as follows:

[0060] S11: Under an inert atmosphere, black phosphorus nanosheets and 4-azidobenzoic acid are dispersed in dimethylformamide and heated for reaction, followed by centrifugation, washing, and drying to obtain an intermediate product;

[0061] S12: dispersing the intermediate product in tetrahydrofuran, adding aminopropyl isobutyl silsesquioxane and dicyclohexylcarbodiimide to react, and washing and drying the product to obtain a POSS-based flame retardant.

[0062] The reaction temperature in S11 is 120°C and the reaction time is 48 hours; the reaction temperature in S12 is 55°C and the reaction time is 48 hours; the mass ratio of black phosphorus nanosheets and 4-azidobenzoic acid is 1:3; the mass ratio of the intermediate product, aminopropylisobutylsilsesquioxane and dicyclohexylcarbodiimide is 1:3:0.5.

[0063] The preparation method of the vanillin-based flame retardant is as follows:

[0064] S21: Under an inert atmosphere, vanillin is dissolved in tetrahydrofuran, and then anhydrous potassium carbonate and hexachlorocyclotriphosphazene are added in sequence to react. After the reaction, the mixture is filtered, washed, and dried to obtain an intermediate product;

[0065] S22: The intermediate product is dissolved in dimethyl sulfoxide, the pH is adjusted to 9, melamine is added and prepolymerized at 80°C for 2 hours, the pH is adjusted to 3, and the temperature is raised to react. After the reaction, the product is cooled, filtered, washed and dried to obtain a vanillin-based flame retardant.

[0066] The reaction temperature in S21 is 65°C and the reaction time is 36 hours; the mass ratio of vanillin, anhydrous potassium carbonate and hexachlorocyclotriphosphazene is 1:0.4:0.2; the reaction temperature in S22 is 130°C and the reaction time is 4 hours; the mass ratio of the intermediate product to melamine is 1:0.4.

[0067] The antioxidant is antioxidant 1010; the plasticizer is epoxy soybean oil; the insulating layer is ethylene propylene rubber; the thermal insulation layer is mica tape; and the protective layer is thermoplastic polyurethane.

[0068] Example 3

[0069] An insulating layer, a heat-insulating layer, a flame-retardant layer and a protective layer are sequentially coated on the outside of the wire core from the inside to the outside to produce a medium-voltage flame-retardant cable.

[0070] The flame retardant layer comprises the following raw materials in parts by weight: 70 parts of ethylene-vinyl acetate copolymer, 10 parts of bio-based flame retardant, 5 parts of calcium zinc stabilizer, 1 part of antioxidant, 10 parts of plasticizer, and 10 parts of porous sepiolite;

[0071] The bio-based flame retardant consists of a POSS-based flame retardant and a vanillin-based flame retardant in a mass ratio of 1:2.

[0072] The preparation method of POSS-based flame retardant is as follows:

[0073] S11: Under an inert atmosphere, black phosphorus nanosheets and 4-azidobenzoic acid are dispersed in dimethylformamide and heated for reaction, followed by centrifugation, washing, and drying to obtain an intermediate product;

[0074] S12: dispersing the intermediate product in tetrahydrofuran, adding aminopropyl isobutyl silsesquioxane and dicyclohexylcarbodiimide to react, and washing and drying the product to obtain a POSS-based flame retardant.

[0075] The reaction temperature in S11 is 160°C and the reaction time is 24 hours; the reaction temperature in S12 is 75°C and the reaction time is 2 hours; the mass ratio of black phosphorus nanosheets and 4-azidobenzoic acid is 1:5; the mass ratio of the intermediate product, aminopropylisobutylsilsesquioxane and dicyclohexylcarbodiimide is 1:5:1.5.

[0076] The preparation method of the vanillin-based flame retardant is as follows:

[0077] S21: Under an inert atmosphere, vanillin is dissolved in tetrahydrofuran, and then anhydrous potassium carbonate and hexachlorocyclotriphosphazene are added in sequence to react. After the reaction, the mixture is filtered, washed, and dried to obtain an intermediate product;

[0078] S22: The intermediate product is dissolved in dimethyl sulfoxide, the pH is adjusted to 9, melamine is added and prepolymerized at 90°C for 2 hours, the pH is adjusted to 3, and the temperature is raised to react. After the reaction, the product is cooled, filtered, washed and dried to obtain a vanillin-based flame retardant.

[0079] The reaction temperature in S21 is 75°C and the reaction time is 24 hours; the mass ratio of vanillin, anhydrous potassium carbonate and hexachlorocyclotriphosphazene is 1:0.6:0.4; the reaction temperature in S22 is 150°C and the reaction time is 2 hours; the mass ratio of the intermediate product to melamine is 1:0.6.

[0080] The antioxidant is DLTP; the plasticizer is trioctyl trimellitate; the insulating layer is silicone rubber; the heat insulating layer is zinc borate modified polymer; and the protective layer is polyvinyl chloride.

[0081] Comparative Example 1

[0082] An insulating layer, a heat-insulating layer, a flame-retardant layer and a protective layer are sequentially coated on the outside of the wire core from the inside to the outside to produce a medium-voltage flame-retardant cable.

[0083] The flame retardant layer comprises the following raw materials in parts by weight: 60 parts of ethylene-vinyl acetate copolymer, 5 parts of bio-based flame retardant, 3 parts of calcium zinc stabilizer, 0.5 parts of antioxidant, 8 parts of plasticizer, and 5 parts of porous sepiolite;

[0084] The bio-based flame retardant is a POSS-based flame retardant. The preparation method of the POSS-based flame retardant is as follows:

[0085] S11: Under an inert atmosphere, black phosphorus nanosheets and 4-azidobenzoic acid are dispersed in dimethylformamide and heated for reaction, followed by centrifugation, washing, and drying to obtain an intermediate product;

[0086] S12: dispersing the intermediate product in tetrahydrofuran, adding aminopropyl isobutyl silsesquioxane and dicyclohexylcarbodiimide to react, and washing and drying the product to obtain a POSS-based flame retardant.

[0087] The reaction temperature in S11 is 140°C and the reaction time is 36 hours; the reaction temperature in S12 is 65°C and the reaction time is 36 hours; the mass ratio of black phosphorus nanosheets and 4-azidobenzoic acid is 1:4; the mass ratio of the intermediate product, aminopropylisobutylsilsesquioxane and dicyclohexylcarbodiimide is 1:4:1.

[0088] The antioxidant is composed of antioxidant 1010 and antioxidant 168 in a mass ratio of 5:1; the plasticizer is dioctyl terephthalate; the insulating layer is cross-linked polyethylene; the thermal insulation layer is ceramic silicone rubber; and the protective layer is low-smoke halogen-free polyolefin.

[0089] Comparative Example 2

[0090] An insulating layer, a heat-insulating layer, a flame-retardant layer and a protective layer are sequentially coated on the outside of the wire core from the inside to the outside to produce a medium-voltage flame-retardant cable.

[0091] The flame retardant layer comprises the following raw materials in parts by weight: 60 parts of ethylene-vinyl acetate copolymer, 5 parts of bio-based flame retardant, 3 parts of calcium zinc stabilizer, 0.5 parts of antioxidant, 8 parts of plasticizer, and 5 parts of porous sepiolite;

[0092] The bio-based flame retardant is a vanillin-based flame retardant. The preparation method of the vanillin-based flame retardant is as follows:

[0093] S21: Under an inert atmosphere, vanillin is dissolved in tetrahydrofuran, and then anhydrous potassium carbonate and hexachlorocyclotriphosphazene are added in sequence to react. After the reaction, the mixture is filtered, washed, and dried to obtain an intermediate product;

[0094] S22: The intermediate product is dissolved in dimethyl sulfoxide, the pH is adjusted to 10, melamine is added and prepolymerized at 85°C for 3 hours, the pH is adjusted to 4, and the temperature is raised to react. After the reaction, the product is cooled, filtered, washed and dried to obtain a vanillin-based flame retardant.

[0095] The reaction temperature in S21 is 70° C. and the reaction time is 30 h; the mass ratio of vanillin, anhydrous potassium carbonate and hexachlorocyclotriphosphazene is 1:0.5:0.3; the reaction temperature in S22 is 140° C. and the reaction time is 3 h; the mass ratio of the intermediate product to melamine is 1:0.5.

[0096] The antioxidant is composed of antioxidant 1010 and antioxidant 168 in a mass ratio of 5:1; the plasticizer is dioctyl terephthalate; the insulating layer is cross-linked polyethylene; the thermal insulation layer is ceramic silicone rubber; and the protective layer is low-smoke halogen-free polyolefin.

[0097] The components of the flame retardant layer of Example 1 and Comparative Examples 1-2 were mixed, extruded and pelletized to obtain flame retardant layer A, flame retardant layer B and flame retardant layer C respectively through the flame retardant layer masterbatch. The flame retardant properties of each flame retardant layer were measured with reference to GB / T2406.2-2009. The test results are shown in Table 1.

[0098] Table 1 Flame retardant layer performance test results

[0099] Group Oxygen index (%) Flame retardant layer A 44.6 Flame retardant layer B 32.5 Flame retardant layer C 30.7

[0100] It can be seen from the test results in Table 1 that the oxygen index of the flame retardant layer of the present invention is as high as 44.6%, indicating that the flame retardant layer has excellent flame retardant effect. At the same time, the cable of the present invention also includes a thermal insulation layer, which can be ceramic silicone rubber, which can cooperate with the flame retardant layer to form a "carbon-ceramic" double barrier, blocking the diffusion of heat and oxygen, and further improving the flame retardant effect; in addition, according to the oxygen index results of flame retardant layer A, flame retardant layer B and flame retardant layer C, it can be seen that the POSS-based flame retardant and vanillin-based flame retardant in the flame retardant layer have a synergistic promoting effect in improving the flame retardant performance.

[0101] Although the embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present application. The scope of the present application is defined by the appended claims and their equivalents, and all should be included in the scope of protection of the present application.

Claims

1. A medium voltage flame retardant cable, characterized in that: It comprises a wire core (1), an insulating layer (2), a heat-insulating layer (3), a flame-retardant layer (4) and a protective layer (5) which are arranged in sequence from the inside to the outside; The flame retardant layer (4) comprises the following raw materials in parts by weight: 50-70 parts of ethylene-vinyl acetate copolymer, 1-10 parts of bio-based flame retardant, 1-5 parts of calcium zinc stabilizer, 0.1-1 parts of antioxidant, 5-10 parts of plasticizer, and 1-10 parts of porous sepiolite; The bio-based flame retardant is composed of a POSS-based flame retardant and a vanillin-based flame retardant in a mass ratio of 2:1-4; The preparation method of POSS-based flame retardant is as follows: S11: Under an inert atmosphere, black phosphorus nanosheets and 4-azidobenzoic acid are dispersed in dimethylformamide and heated for reaction, followed by centrifugation, washing, and drying to obtain an intermediate product; S12: dispersing the intermediate product in tetrahydrofuran, adding aminopropyl isobutyl silsesquioxane and dicyclohexylcarbodiimide to react, and washing and drying the product to obtain a POSS-based flame retardant; The preparation method of the vanillin-based flame retardant is as follows: S21: Under an inert atmosphere, vanillin is dissolved in tetrahydrofuran, and then anhydrous potassium carbonate and hexachlorocyclotriphosphazene are added in sequence to react. After the reaction, the mixture is filtered, washed, and dried to obtain an intermediate product; S22: dissolving the intermediate product in dimethyl sulfoxide, adjusting the pH to 9-10, adding melamine and prepolymerizing at 80-90°C for 2-4 hours, adjusting the pH to 3-4, and then heating to react. After the reaction, cooling, filtering, washing and drying are performed to obtain a vanillin-based flame retardant.

2. A medium voltage flame retardant cable according to claim 1, characterized in that: The reaction temperature in S11 is 120-160°C and the reaction time is 24-48 hours; the reaction temperature in S12 is 55-75°C and the reaction time is 24-48 hours; the mass ratio of black phosphorus nanosheets and 4-azidobenzoic acid is 1:3-5; the mass ratio of the intermediate product, aminopropyl isobutyl silsesquioxane and dicyclohexylcarbodiimide is 1:3-5:0.5-1.

5.

3. A medium voltage flame retardant cable according to claim 1, characterized in that: The reaction temperature in S21 is 65-75°C and the reaction time is 24-36 hours; the mass ratio of vanillin, anhydrous potassium carbonate and hexachlorocyclotriphosphazene is 1:0.4-0.6:0.2-0.4; the reaction temperature in S22 is 130-150°C and the reaction time is 2-4 hours; the mass ratio of the intermediate product to melamine is 1:0.4-0.

6.

4. A medium voltage flame retardant cable according to claim 1, characterized in that: The antioxidant is one or more of antioxidant 1010, antioxidant 168, antioxidant 1076, antioxidant DLTP, antioxidant BHT, antioxidant MD-124, antioxidant 3114 and antioxidant 1098; the plasticizer is one or more of dioctyl phthalate, dioctyl terephthalate, dioctyl adipate, epoxy soybean oil, trioctyl trimellitate and trioctyl trimellitate.

5. The medium voltage flame retardant cable according to claim 1, characterized in that: The insulating layer (2) is one of cross-linked polyethylene, ethylene propylene rubber, polyvinyl chloride, silicone rubber and polyimide.

6. The medium voltage flame retardant cable according to claim 1, characterized in that: The thermal insulation layer (3) is one or more of ceramic silicone rubber, mica tape, zinc borate modified polymer, glass fiber braided layer and mineral wool.

7. The medium voltage flame retardant cable according to claim 1, characterized in that: The protective layer (5) is one of polyvinyl chloride, low-smoke halogen-free polyolefin, thermoplastic polyurethane, chloroprene rubber and polyamide.

8. A method for preparing a medium voltage flame retardant cable, the medium voltage flame retardant cable being as described in any one of claims 1 to 7, characterized in that: The method comprises the following steps: an insulating layer (2), a heat-insulating layer (3), a flame-retardant layer (4) and a protective layer (5) are sequentially coated on the outer side of a wire core (1) from the inside to the outside to prepare a medium-voltage flame-retardant cable.

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