High-performance halogen-free flame-retardant flexible power cable

Abstract

The invention relates to the technical field of cables, and particularly discloses a high-performance halogen-free flame-retardant flexible power cable. The high-performance halogen-free flame-retardant flexible power cable comprises a core layer, an insulating layer, a flame-retardant layer, a shielding layer and a protective layer which are arranged in sequence, the flame-retardant layer is prepared from the following raw material components in parts by weight: 30 to 40 parts of ethylene-vinyl acetate copolymer, 10 to 20 parts of polyolefin elastomer, 8 to 10 parts of microencapsulated ammonium polyphosphate, 2.5 to 4.5 parts of pentaerythritol, 20 to 30 parts of inorganic flame retardant, 5 to 8 parts of expansible graphite, 2 to 3 parts of diatomite, 0.5 to 1.5 parts of nano kaolin, 2 to 3 parts of zinc borate, 0.1 to 0.5 part of antioxidant and 0.5 to 1.0 part of lubricant. The cable provided by the invention not only has good flame retardant property, but also has certain flexibility.

Description

Technical Field

[0001] This application relates to the technical field of cables, and in particular to a high-performance halogen-free flame-retardant flexible power cable. Background Technology

[0002] In the field of power transmission, power cables are a crucial infrastructure. With continuous technological advancements, the performance requirements for cables in power systems are constantly increasing. High-performance power cables ensure stable power transmission, reduce energy loss, and improve power utilization efficiency, and are widely used in various sectors including industrial, commercial, and residential power supply. Simultaneously, with growing awareness of safety and environmental protection, higher demands are being placed on the flame-retardant properties and environmental characteristics of cables.

[0003] To achieve the basic functions of power cables, the conventional approach is to use a conductor as the core component for current transmission, and then cover the conductor with an insulation layer to prevent current leakage. For flame-retardant performance, flame-retardant materials are typically added to the cable structure; common examples include halogenated flame retardants, which inhibit the combustion reaction through the hydrogen halide gas produced during combustion. To improve cable flexibility, materials with a certain degree of flexibility are selected for the outer sheath, or special cable structural designs are employed, such as multi-strand stranded conductor structures.

[0004] However, halogenated flame retardants produce large amounts of toxic and harmful hydrogen halide gases when burned, posing a threat to human health and causing serious environmental pollution. Furthermore, existing cables fail to achieve ideal combined performance in terms of flame retardancy and flexibility, thus failing to meet increasingly stringent safety and environmental protection requirements. Summary of the Invention

[0005] To improve the flame retardant performance of cables, this application provides a high-performance halogen-free flame-retardant flexible power cable.

[0006] Firstly, this application provides a high-performance halogen-free flame-retardant flexible power cable, which adopts the following technical solution: A high-performance halogen-free flame-retardant flexible power cable includes a core layer, an insulation layer, a flame-retardant layer, a shielding layer, and a protective layer arranged sequentially. The flame-retardant layer is made of the following components in parts by weight: 30-40 parts of ethylene-vinyl acetate copolymer, 10-20 parts of polyolefin elastomer, 8-10 parts of microencapsulated ammonium polyphosphate, 2.5-4.5 parts of pentaerythritol, 20-30 parts of inorganic flame retardant, 5-8 parts of expandable graphite, 2-3 parts of diatomaceous earth, 0.5-1.5 parts of nano-kaolin, 2-3 parts of zinc borate, 0.1-0.5 parts of antioxidant, and 0.5-1.0 parts of lubricant.

[0007] By adopting the above technical solutions, the ethylene-vinyl acetate copolymer itself has certain flame retardancy and good compatibility with inorganic flame retardants. The polyolefin elastomer can greatly improve the flexibility of the matrix and overcome the brittleness problem caused by high filling. Microencapsulated ammonium polyphosphate, pentaerythritol, inorganic flame retardants, and expandable graphite work synergistically to form a char layer for flame retardancy. Diatomaceous earth and nano-kaolin can further improve the quality of the char layer. Zinc borate can not only promote the formation of the char layer, but also significantly reduce the amount of smoke generated. As a result, the cable not only has good flame retardant properties, but also reduces the generation of smoke.

[0008] In one specific implementation, the method for preparing the microencapsulated ammonium polyphosphate includes the following steps: Preparation of prepolymer liquid: Methanol solution and deionized water are stirred and mixed evenly. While stirring, the pH value of the mixture is adjusted to 8.5-9.0 with 10% NaOH solution. Melamine is added, and the temperature is slowly raised to 68-72℃. The mixture is stirred and reacted at this temperature for 45-60 min to obtain the prepolymer liquid. Water slurry preparation: Ammonium polyphosphate and sodium dodecylbenzene sulfonate are added to deionized water and sheared and stirred at 2000-3000 rpm for 30 minutes at 50-60℃ to form a water slurry; Mixing: Add the water slurry to the prepolymer liquid, stir at 300-500 rpm at 60-62℃, slowly add 10% hydrochloric acid dropwise to gradually lower the pH of the reaction system to 4.0-5.0, then keep the reaction at this temperature for 90-120 min, let it cool naturally to room temperature, adjust the pH to 7.0 with 10% NaOH solution, and the reaction is complete, yielding the reaction solution; Post-processing: The reaction solution was filtered, the filter cake was washed, dried to constant weight, and pulverized to obtain microencapsulated ammonium polyphosphate.

[0009] By adopting the above technical solution and using raw materials such as melamine to microencapsulate ammonium polyphosphate, not only is the dispersion performance of ammonium polyphosphate improved, but its stability is also enhanced.

[0010] In one specific implementation, in the prepolymer liquid preparation step, the weight ratio of methanol solution, deionized water, and melamine is 17:(60-80):(9-11); in the water slurry preparation step, the weight ratio of ammonium polyphosphate, sodium dodecylbenzenesulfonate, and deionized water is 100:(0.5-1):(100-120).

[0011] By adopting the above technical solution, the ratio of methanol solution, deionized water, and melamine, as well as the ratio of ammonium polyphosphate, sodium dodecylbenzenesulfonate, and deionized water, are further defined, thereby improving the effect of obtaining microencapsulated ammonium polyphosphate.

[0012] In one specific implementation, the inorganic flame retardant comprises a mixture of aluminum hydroxide and magnesium hydroxide.

[0013] By adopting the above technical solution, a composite flame retardant composed of aluminum hydroxide and magnesium hydroxide can be used to achieve heat absorption protection over a wide range from low temperature to high temperature, with synergistic effects. In addition, magnesium hydroxide also has a good smoke suppression effect.

[0014] In one specific implementation, the raw materials of the insulating layer include: cross-linked polyethylene, antioxidant, dicumyl peroxide, and color masterbatch.

[0015] In one specific implementation scheme, the raw materials of the shielding layer include: copper wire and aluminum-plastic composite tape.

[0016] In one specific implementation, the protective layer is made of thermoplastic polyurethane elastomer, chopped carbon fibers, and lubricant.

[0017] By adopting the above technical solution, the addition of short-cut carbon fiber can further improve the flame retardant performance of the cable, as well as improve the overall strength and stability of the cable.

[0018] Secondly, this application provides a method for preparing a high-performance halogen-free flame-retardant flexible power cable, which adopts the following technical solution: A method for preparing a high-performance halogen-free flame-retardant flexible power cable includes the following steps: Core layer preparation: Multiple strands of copper wire are stranded together using a stranding machine to form the core layer; Insulation layer preparation: Cross-linked polyethylene, antioxidant, dicumyl peroxide and color masterbatch are stirred and mixed evenly to obtain insulation material, which is then extruded onto the core layer to obtain insulation layer; Pretreatment: First, the inorganic flame retardant, diatomaceous earth, and nano-kaolin were modified with γ-aminopropyltriethoxysilane to obtain the pretreated filler. Flame retardant layer preparation: The pretreated filler is mixed with ethylene-vinyl acetate copolymer, polyolefin elastomer, microencapsulated ammonium polyphosphate, pentaerythritol, expandable graphite, zinc borate, antioxidant and lubricant and granulated to obtain flame retardant masterbatch; the flame retardant masterbatch is added to an extruder and extruded onto the insulation layer to obtain the flame retardant layer; Shielding layer preparation: Copper wire is first braided on the flame retardant layer with a braiding density of ≥85% and a braiding angle of 45°. Then, aluminum-plastic composite tape is used to overlap and wrap the layer with an overlap rate of ≥15% to obtain the shielding layer. Protective layer preparation: The thermoplastic polyurethane elastomer and chopped carbon fibers are dried first, then lubricant is added, stirred and mixed evenly, and extruded onto the shielding layer to form a protective layer, thus obtaining a high-performance halogen-free flame-retardant flexible power cable.

[0019] By adopting the above technical solution, firstly, multiple strands of copper wire are stranded together using a stranding machine to obtain the core layer, and then an insulation layer is laminated on top. Next, γ-aminopropyltriethoxysilane is used to modify inorganic flame retardants, diatomaceous earth, and nano-kaolin to obtain pretreated fillers. Then, these fillers are mixed with ethylene-vinyl acetate copolymer, polyolefin elastomer, microencapsulated ammonium polyphosphate, pentaerythritol, expandable graphite, zinc borate, antioxidants, and lubricants, granulated, and extruded onto the insulation layer to obtain a flame retardant layer. Finally, a shielding layer and a protective layer are laminated on top in sequence to obtain a high-performance halogen-free flame-retardant flexible power cable.

[0020] In summary, this application includes at least one of the following beneficial technical effects: In this application, the ethylene-vinyl acetate copolymer itself has certain flame retardancy and good compatibility with inorganic flame retardants. The polyolefin elastomer can greatly improve the flexibility of the matrix and overcome the brittleness problem caused by high filling. Microencapsulated ammonium polyphosphate, pentaerythritol, inorganic flame retardants, and expandable graphite work synergistically to form a char layer for flame retardancy. Diatomaceous earth and nano-kaolin can further improve the quality of the char layer. Zinc borate can not only promote the formation of the char layer, but also significantly reduce the amount of smoke generated, so that the obtained cable not only has good flame retardant performance, but also reduces the generation of smoke. The composite flame retardant composed of aluminum hydroxide and magnesium hydroxide used in this application can achieve heat absorption protection over a wide range from low temperature to high temperature, with synergistic effect. In addition, magnesium hydroxide also has a good smoke suppression effect. The method in this application first uses multiple strands of copper wire to be stranded together by a stranding machine to obtain a core layer, and then an insulation layer is laminated on it. Next, γ-aminopropyltriethoxysilane is used to modify inorganic flame retardants, diatomaceous earth, and nano-kaolin to obtain a pretreated filler. Then, it is mixed with ethylene-vinyl acetate copolymer, polyolefin elastomer, microencapsulated ammonium polyphosphate, pentaerythritol, expandable graphite, zinc borate, antioxidant, and lubricant, granulated, and extruded onto the insulation layer to obtain a flame retardant layer. Finally, a shielding layer and a protective layer are laminated on in sequence to obtain a high-performance halogen-free flame-retardant flexible power cable. Detailed Implementation

[0021] The present application will be further described in detail below with reference to the embodiments.

[0022] All raw materials used in the examples are commercially available. The polyolefin elastomer was provided by Shanghai Jufu New Material Technology Co., Ltd., model POE 7457; the expandable graphite was provided by Shanghai Yunguan Electromechanical Equipment Co., Ltd., model E196403-100g; the antioxidant was antioxidant 1010; the cross-linked polyethylene was provided by Beijing Lingbao Technology Co., Ltd.; the thermoplastic polyurethane elastomer CAS number was 1211-14-9; and the color masterbatch was PE2762 black masterbatch. Preparation Example

[0023] Preparation Example 1 Preparation Example 1 provides a method for preparing microencapsulated ammonium polyphosphate, comprising the following steps: Preparation of prepolymer liquid: Methanol solution and deionized water were stirred and mixed evenly. While stirring, the pH value of the mixture was adjusted to 8.5 with a 10% NaOH solution. Melamine was added, and the temperature was slowly raised to 68°C. The mixture was stirred and reacted at this temperature for 60 min to obtain the prepolymer liquid. The weight ratio of methanol solution, deionized water and melamine was 17:60:9. Water slurry preparation: Ammonium polyphosphate and sodium dodecylbenzene sulfonate were added to deionized water and sheared and stirred at 3000 rpm for 30 min at 50℃ to form a water slurry; wherein the weight ratio of ammonium polyphosphate, sodium dodecylbenzene sulfonate and deionized water was 100:0.5:100. Mixing: Add the water slurry to the prepolymer liquid, stir at 500 rpm at 60℃, slowly add 10% hydrochloric acid dropwise to gradually lower the pH of the reaction system to 4.0, then keep the reaction at this temperature for 120 min, let it cool naturally to room temperature, adjust the pH to 7.0 with 10% NaOH solution, and the reaction is complete to obtain the reaction solution; the weight ratio of water slurry to prepolymer liquid is 1:1. Post-processing: The reaction solution was filtered, and the filter cake was washed until the washing liquid was neutral and free of chloride ions. It was dried at 85°C to constant weight, pulverized and passed through a 200-mesh sieve to obtain microencapsulated ammonium polyphosphate.

[0024] Preparation Example 2 Preparation Example 2 provides a method for preparing microencapsulated ammonium polyphosphate, comprising the following steps: Preparation of prepolymer liquid: Methanol solution and deionized water were stirred and mixed evenly. While stirring, the pH value of the mixture was adjusted to 8.5 with a 10% NaOH solution. Melamine was added, and the temperature was slowly raised to 70°C. The mixture was stirred and reacted at this temperature for 50 min to obtain the prepolymer liquid. The weight ratio of methanol solution, deionized water and melamine was 17:70:10. Water slurry preparation: Ammonium polyphosphate and sodium dodecylbenzene sulfonate were added to deionized water and sheared and stirred at 2500 rpm for 30 min at 55℃ to form a water slurry; wherein the weight ratio of ammonium polyphosphate, sodium dodecylbenzene sulfonate and deionized water was 100:0.7:110. Mixing: Add the water slurry to the prepolymer liquid, stir at 400 rpm at 61°C, slowly add 10% hydrochloric acid dropwise to gradually lower the pH of the reaction system to 4.5, then keep the reaction at this temperature for 100 min, allow it to cool naturally to room temperature, adjust the pH to 7.0 with 10% NaOH solution, and the reaction is complete to obtain the reaction solution; the weight ratio of water slurry to prepolymer liquid is 1:1. Post-processing: The reaction solution was filtered, and the filter cake was washed until the washing liquid was neutral and free of chloride ions. It was dried at 85°C to constant weight, pulverized and passed through a 200-mesh sieve to obtain microencapsulated ammonium polyphosphate.

[0025] Preparation Example 3 Preparation Example 3 provides a method for preparing microencapsulated ammonium polyphosphate, comprising the following steps: Preparation of prepolymer liquid: Methanol solution and deionized water were stirred and mixed evenly. While stirring, the pH value of the mixture was adjusted to 9.0 with a 10% NaOH solution. Melamine was added, and the temperature was slowly raised to 72°C. The mixture was stirred and reacted at this temperature for 45 min to obtain the prepolymer liquid. The weight ratio of methanol solution, deionized water and melamine was 17:80:11. Water slurry preparation: Ammonium polyphosphate and sodium dodecylbenzene sulfonate were added to deionized water and sheared and stirred at 2000 rpm for 30 min at 60℃ to form a water slurry; wherein the weight ratio of ammonium polyphosphate, sodium dodecylbenzene sulfonate and deionized water was 100:1:120. Mixing: Add the water slurry to the prepolymer liquid, stir at 300 rpm at 62℃, slowly add 10% hydrochloric acid dropwise to gradually lower the pH of the reaction system to 5.0, then keep the reaction at this temperature for 90 min, allow it to cool naturally to room temperature, adjust the pH to 7.0 with 10% NaOH solution, and the reaction is complete to obtain the reaction solution; the weight ratio of water slurry to prepolymer liquid is 1:1. Post-processing: The reaction solution was filtered, and the filter cake was washed until the washing liquid was neutral and free of chloride ions. It was dried at 85°C to constant weight, pulverized and passed through a 200-mesh sieve to obtain microencapsulated ammonium polyphosphate. Example

[0026] Example 1 Example 1 provides a high-performance halogen-free flame-retardant flexible power cable.

[0027] A high-performance halogen-free flame-retardant flexible power cable includes a core layer, an insulation layer, a flame-retardant layer, a shielding layer, and a protective layer arranged sequentially.

[0028] Example 1 also provides a method for preparing a high-performance halogen-free flame-retardant flexible power cable.

[0029] A method for preparing a high-performance halogen-free flame-retardant flexible power cable includes the following steps: Core layer preparation: Multiple copper wires are stranded together by a stranding machine to form a core layer, wherein the diameter of a single copper wire is 0.20 mm and the stranding pitch is 16 times the diameter of the core layer; Insulation layer preparation: 100 kg of cross-linked polyethylene, 0.3 kg of antioxidant, 2 kg of dicumyl peroxide, and 2 kg of color masterbatch were mixed evenly to obtain an insulating material, which was then extruded onto the core layer and then fed into a steam cross-linking pipeline. The material was treated for 5 minutes at a pressure of 1.2 MPa and a temperature of 200℃ to obtain an insulation layer with a thickness of 1.2 mm. The temperatures of each section of the extruder were 120℃, 150℃, and 170℃, and the die head temperature was 155℃. Pretreatment: 20 kg of inorganic flame retardant, 2 kg of diatomaceous earth, and 0.5 kg of nano-kaolin were stirred to obtain a mixture. During the stirring process, 1.7 kg of spraying liquid was slowly sprayed into the mixture. After the spraying liquid was completely sprayed, stirring was continued for 0.5 h, and then dried at 90℃ for 0.5 h to obtain the pretreated filler. The spraying liquid was a mixture of γ-aminopropyltriethoxysilane, ethanol, and water, with a weight ratio of 5:18:2. The inorganic flame retardant was a mixture of aluminum hydroxide and magnesium hydroxide, with a weight ratio of 2:1. Flame retardant layer preparation: The pretreated filler was mixed and granulated at 170°C with 30 kg of ethylene-vinyl acetate copolymer, 10 kg of polyolefin elastomer, 8 kg of microencapsulated ammonium polyphosphate from Preparation Example 1, 2.5 kg of pentaerythritol, 5 kg of expandable graphite, 2 kg of zinc borate, 0.1 kg of antioxidant, and 0.5 kg of lubricant to obtain flame retardant masterbatch; the flame retardant masterbatch was added to an extruder and extruded onto the insulating layer to obtain a flame retardant layer with a thickness of 1 mm; the lubricant was zinc stearate; the temperatures of each section of the extruder were 135°C, 150°C, and 160°C, and the die head temperature was 155°C; Shielding layer preparation: Copper wire with a diameter of 0.1 mm is first braided on the flame retardant layer with a braiding density of 85% and a braiding angle of 45°. Then, aluminum-plastic composite tape with a thickness of 0.06 mm is used to overlap and wrap the layer with an overlap rate of 15% to obtain the shielding layer. Protective layer preparation: 100 kg of thermoplastic polyurethane elastomer and 6 kg of 4 mm chopped carbon fibers are dried at 80°C for 2 hours. Then, 0.5 kg of lubricant is added, and the mixture is stirred and mixed evenly. The mixture is then extruded onto the shielding layer to form a 1 mm thick protective layer, resulting in a high-performance halogen-free flame-retardant flexible power cable. The lubricant is zinc stearate. The temperatures of each section of the extruder are 160°C, 175°C, and 185°C, and the die head temperature is 180°C.

[0030] Example 2 The difference between Example 2 and Example 1 is the pretreatment: 25 kg of inorganic flame retardant, 2.5 kg of diatomaceous earth, and 1 kg of nano-kaolin are stirred to obtain a mixture. During the stirring process, 2.1 kg of spraying liquid is slowly sprayed into the mixture. After the spraying liquid is completely sprayed, stirring continues for 0.5 h, and then drying is carried out at 90°C for 0.5 h to obtain the pretreated filler. The spraying liquid is a mixture of γ-aminopropyltriethoxysilane, ethanol, and water, and the weight ratio of γ-aminopropyltriethoxysilane, ethanol, and water is 5:18:2. The inorganic flame retardant is a mixture of aluminum hydroxide and magnesium hydroxide, and the weight ratio of aluminum hydroxide to magnesium hydroxide is 2:1. Flame retardant layer preparation: The pretreated filler was mixed and granulated at 170°C with 35 kg of ethylene-vinyl acetate copolymer, 150 kg of polyolefin elastomer, 9 kg of microencapsulated ammonium polyphosphate from Preparation Example 1, 3.5 kg of pentaerythritol, 6.5 kg of expandable graphite, 2.5 kg of zinc borate, 0.3 kg of antioxidant, and 0.75 kg of lubricant to obtain flame retardant masterbatch; the flame retardant masterbatch was added to an extruder and extruded onto the insulating layer to obtain a flame retardant layer with a thickness of 1 mm; the lubricant was zinc stearate; the temperatures of each section of the extruder were 135°C, 150°C, and 160°C, and the die head temperature was 155°C; the remaining steps were the same as in Example 1.

[0031] Example 3 The difference between Example 3 and Example 1 is the pretreatment: 30 kg of inorganic flame retardant, 3 kg of diatomaceous earth, and 1.5 kg of nano-kaolin are stirred to obtain a mixture. During the stirring process, 2.6 kg of spraying liquid is slowly sprayed into the mixture. After the spraying liquid is completely sprayed, stirring is continued for 0.5 h, and then dried at 90°C for 0.5 h to obtain the pretreated filler. The spraying liquid is a mixture of γ-aminopropyltriethoxysilane, ethanol, and water, and the weight ratio of γ-aminopropyltriethoxysilane, ethanol, and water is 5:18:2. The inorganic flame retardant is a mixture of aluminum hydroxide and magnesium hydroxide, and the weight ratio of aluminum hydroxide to magnesium hydroxide is 2:1. Flame retardant layer preparation: The pretreated filler was mixed and granulated at 170°C with 40 kg of ethylene-vinyl acetate copolymer, 20 kg of polyolefin elastomer, 10 kg of microencapsulated ammonium polyphosphate from Preparation Example 1, 4.5 kg of pentaerythritol, 8 kg of expandable graphite, 3 kg of zinc borate, 0.5 kg of antioxidant, and 1.0 kg of lubricant to obtain flame retardant masterbatch; the flame retardant masterbatch was added to an extruder and extruded onto the insulating layer to obtain a flame retardant layer with a thickness of 1 mm; the lubricant was zinc stearate; the temperatures of each section of the extruder were 135°C, 150°C, and 160°C, and the die head temperature was 155°C; the remaining steps were the same as in Example 1.

[0032] Example 4 The difference between Example 4 and Example 2 lies in the preparation of the flame-retardant layer: the pretreated filler was mixed and granulated at 170°C with 35 kg of ethylene-vinyl acetate copolymer, 150 kg of polyolefin elastomer, 9 kg of microencapsulated ammonium polyphosphate from Example 2, 3.5 kg of pentaerythritol, 6.5 kg of expandable graphite, 2.5 kg of zinc borate, 0.3 kg of antioxidant, and 0.75 kg of lubricant to obtain a flame-retardant masterbatch; the flame-retardant masterbatch was added to an extruder and extruded onto the insulating layer to obtain a flame-retardant layer with a thickness of 1 mm; the lubricant was zinc stearate; the temperatures of each section of the extruder were 135°C, 150°C, and 160°C, and the die head temperature was 155°C; the remaining steps were the same as in Example 2.

[0033] Example 5 The difference between Example 5 and Example 2 lies in the preparation of the flame-retardant layer: the pretreated filler was mixed and granulated at 170°C with 35 kg of ethylene-vinyl acetate copolymer, 150 kg of polyolefin elastomer, 9 kg of microencapsulated ammonium polyphosphate from Example 3, 3.5 kg of pentaerythritol, 6.5 kg of expandable graphite, 2.5 kg of zinc borate, 0.3 kg of antioxidant, and 0.75 kg of lubricant to obtain a flame-retardant masterbatch; the flame-retardant masterbatch was added to an extruder and extruded onto the insulating layer to obtain a flame-retardant layer with a thickness of 1 mm; the lubricant was zinc stearate; the temperatures of each section of the extruder were 135°C, 150°C, and 160°C, and the die head temperature was 155°C; the remaining steps were the same as in Example 2.

[0034] Example 6 The difference between Example 6 and Example 4 is the pretreatment: 25 kg of inorganic flame retardant, 2.5 kg of diatomaceous earth, and 1 kg of nano-kaolin are stirred to obtain a mixture. During the stirring process, 2.1 kg of spraying liquid is slowly sprayed into the mixture. After the spraying liquid is finished, stirring is continued for 0.5 h, and then dried at 90°C for 0.5 h to obtain the pretreated filler. The spraying liquid is a mixture of γ-aminopropyltriethoxysilane, ethanol, and water, and the weight ratio of γ-aminopropyltriethoxysilane, ethanol, and water is 5:18:2. The inorganic flame retardant is aluminum hydroxide. The remaining steps are the same as in Example 4.

[0035] Example 7 The difference between Example 7 and Example 4 is the pretreatment: 25 kg of inorganic flame retardant, 2.5 kg of diatomaceous earth, and 1 kg of nano-kaolin are stirred to obtain a mixture. During the stirring process, 2.1 kg of spraying liquid is slowly sprayed into the mixture. After the spraying liquid is finished, stirring is continued for 0.5 h, and then dried at 90°C for 0.5 h to obtain the pretreated filler. The spraying liquid is a mixture of γ-aminopropyltriethoxysilane, ethanol, and water, and the weight ratio of γ-aminopropyltriethoxysilane, ethanol, and water is 5:18:2. The inorganic flame retardant is magnesium hydroxide. The remaining steps are the same as in Example 4. Comparative Example

[0036] Comparative Example 1 The difference between Comparative Example 1 and Example 1 lies in the preparation of the flame-retardant layer: the pretreated filler was mixed and granulated with 40.5 kg of ethylene-vinyl acetate copolymer, 10 kg of polyolefin elastomer, 5 kg of expandable graphite, 2 kg of zinc borate, 0.1 kg of antioxidant, and 0.5 kg of lubricant at 170°C to obtain flame-retardant masterbatch; the flame-retardant masterbatch was added to an extruder and extruded onto the insulating layer to obtain a flame-retardant layer with a thickness of 1 mm; the lubricant was zinc stearate; the temperatures of each section of the extruder were 135°C, 150°C, and 160°C, and the die head temperature was 155°C; the remaining steps were the same as in Example 1.

[0037] Comparative Example 2 The difference between Comparative Example 2 and Example 1 lies in the preparation of the flame retardant layer: the pretreated filler was mixed and granulated at 170°C with 35 kg of ethylene-vinyl acetate copolymer, 10 kg of polyolefin elastomer, 8 kg of microencapsulated ammonium polyphosphate from Example 1, 2.5 kg of pentaerythritol, 2 kg of zinc borate, 0.1 kg of antioxidant, and 0.5 kg of lubricant to obtain flame retardant masterbatch; the flame retardant masterbatch was added to an extruder and extruded onto the insulating layer to obtain a flame retardant layer with a thickness of 1 mm; the lubricant was zinc stearate; the temperatures of each section of the extruder were 135°C, 150°C, and 160°C, and the die head temperature was 155°C; the remaining steps were the same as in Example 1.

[0038] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is the pretreatment: 22.5 kg of inorganic flame retardant was stirred, and during the stirring process, 1.7 kg of spraying liquid was slowly sprayed into the inorganic flame retardant. After the spraying liquid was finished, stirring was continued for 0.5 h, and then dried at 90 °C for 0.5 h to obtain the pretreated filler. The spraying liquid was a mixture of γ-aminopropyltriethoxysilane, ethanol, and water, and the weight ratio of γ-aminopropyltriethoxysilane, ethanol, and water was 5:18:2. The inorganic flame retardant was a mixture of aluminum hydroxide and magnesium hydroxide, and the weight ratio of aluminum hydroxide to magnesium hydroxide was 2:1. The remaining steps were the same as in Example 1. Performance testing

[0039] Flame retardant performance: The cables in each embodiment and comparative example were tested according to GB / T 18380.35 to obtain the carbonization height. The lower the carbonization height, the better the flame retardant performance of the cable.

[0040] Table 1. Performance test results of the cable

[0041] Combining Example 1 and Comparative Examples 1-3, the cable in Example 1 exhibits the best flame-retardant performance. This demonstrates that during the preparation of the flame-retardant layer, the addition of microencapsulated ammonium polyphosphate, pentaerythritol, inorganic flame retardant, expandable graphite, diatomaceous earth, and nano-kaolin creates a synergistic effect, forming a char layer for flame retardancy. Diatomaceous earth and nano-kaolin further enhance the quality of the char layer, thereby improving the flame-retardant performance of the cable.

[0042] Based on Examples 1-3, it can be seen that when preparing the flame-retardant layer, following the proportions of the raw materials in Examples 1-3 results in cables with better flame-retardant properties.

[0043] Combining Examples 2, 4, and 5, the cable in Example 4 exhibits the best flame-retardant properties. This indicates that the preparation conditions in Example 2 are optimal for preparing microencapsulated ammonium polyphosphate, resulting in the best performance of the microencapsulated ammonium polyphosphate.

[0044] Combining Examples 4, 6, and 7, the cable in Example 4 exhibits the best flame-retardant properties. It is evident that when preparing the flame-retardant layer, the preferred inorganic flame retardant is a mixture of aluminum hydroxide and magnesium hydroxide, which results in better flame-retardant performance of the cable.

[0045] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A high performance halogen-free flame-retardant flexible power cable, characterized in that: The flame-retardant layer comprises the following components in parts by weight: ethylene-vinyl acetate copolymer 30-40 parts, polyolefin elastomer 10-20 parts, microencapsulated ammonium polyphosphate 8-10 parts, pentaerythritol 2.5-4.5 parts, inorganic flame retardant 20-30 parts, expandable graphite 5-8 parts, diatomite 2-3 parts, nano kaolin 0.5-1.5 parts, zinc borate 2-3 parts, antioxidant 0.1-0.5 parts, and lubricant 0.5-1.0 parts.

2. A high performance halogen free flame retardant flexible power cable according to claim 1, characterized in that: The preparation method of the microencapsulated ammonium polyphosphate comprises the following steps: Preparation of prepolymer solution: uniformly stir and mix methanol solution and deionized water, adjust the pH value of the mixed solution to 8.5-9.0 with 10% NaOH solution under stirring, add melamine, slowly heat to 68-72℃, and stir at this temperature for 45-60 min to obtain the prepolymer solution; Preparation of water slurry: add ammonium polyphosphate and sodium dodecyl benzene sulfonate into deionized water, shear stir at 2000-3000 rpm for 30 min at 50-60℃ to form the water slurry; Mixing: add the water slurry into the prepolymer solution, stir at 300-500 rpm at 60-62℃, slowly add 10% hydrochloric acid, gradually reduce the pH value of the reaction system to 4.0-5.0, then incubate for 90-120 min, naturally cool to room temperature, adjust the pH value to 7.0 with 10% NaOH solution, and the reaction is completed to obtain the reaction solution; Post-treatment: filter the reaction solution, wash the filter cake, dry to constant weight, crush, and obtain the microencapsulated ammonium polyphosphate.

3. A high performance halogen-free flame-retardant flexible power cable according to claim 2, characterized in that: In the preparation step of the prepolymer solution, the weight ratio of methanol solution, deionized water and melamine is 17: (60-80): (9-11); in the preparation step of the water slurry, the weight ratio of ammonium polyphosphate, sodium dodecyl benzene sulfonate and deionized water is 100: (0.5-1): (100-120).

4. A high performance halogen free flame retardant flexible power cable according to claim 1, characterized in that: The inorganic flame retardant comprises a mixture of aluminum hydroxide and magnesium hydroxide.

5. A high performance halogen free flame retardant flexible power cable according to claim 1, characterized in that: The raw material of the insulation layer comprises crosslinked polyethylene, antioxidant, dicumyl peroxide and color master batch.

6. A high performance halogen free flame retardant flexible power cable according to claim 1, characterized in that: The raw material of the shielding layer comprises copper wire and aluminum-plastic composite tape.

7. A high performance halogen free flame retardant flexible power cable as claimed in claim 1, wherein: The raw material of the protective layer comprises thermoplastic polyurethane elastomer, chopped carbon fiber and lubricant.

8. A process for the preparation of a high performance halogen-free flame-retardant flexible power cable according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: Preparation of core layer: twist a plurality of copper wires through a stranding machine to form the core layer; Preparation of insulation layer: uniformly stir and mix crosslinked polyethylene, antioxidant, dicumyl peroxide and color master batch to obtain insulation material, and then extrude the insulation material onto the core layer to obtain the insulation layer; Pre-treatment: modify the inorganic flame retardant, diatomite and nano kaolin with γ-aminopropyl triethoxysilane to obtain pre-treatment filler; The flame-retardant layer is prepared by mixing and granulating the pretreated filler, ethylene-vinyl acetate copolymer, polyolefin elastomer, microencapsulated ammonium polyphosphate, pentaerythritol, expandable graphite, zinc borate, antioxidant and lubricant to obtain a flame-retardant master batch; the flame-retardant master batch is added into an extruder and extruded onto the insulating layer to obtain the flame-retardant layer; The shielding layer is prepared by first weaving copper wires on the flame-retardant layer at a weaving density of ≥ 85% and a weaving angle of 45°, and then overlapping and wrapping the shielding layer with an aluminum-plastic composite tape at an overlapping rate of ≥ 15% to obtain the shielding layer; The protective layer is prepared by drying the thermoplastic polyurethane elastomer and chopped carbon fibers, adding a lubricant, stirring and uniformly mixing, and extruding onto the shielding layer to form the protective layer, thereby obtaining the high-performance halogen-free flame-retardant flexible power cable.

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