Flame-retardant polyethylene sheathed cable and production equipment thereof

Abstract

The invention provides a flame-retardant polyethylene sheathed cable and production equipment thereof, and relates to the technical field of cable production, the cable comprises a conductor cable core, a flame-retardant polyethylene sheath containing a flame retardant is wrapped outside the conductor cable core, the flame retardant contains 60 parts of magnesium hydroxide on the basis of 100 parts of polyethylene matrix, a phase change heat conduction cavity is formed in the sheath and contains 20wt% of borax aqueous solution, and the phase change heat conduction cavity is communicated with the flame-retardant polyethylene sheath. The production equipment comprises an extrusion die head, an extrusion die core in the extrusion die head is formed by splicing six groups of split die cores, injection cavity channels are arranged among the die cores, one end of the extrusion die core is inserted into a heat conduction cavity forming die, and the other end of the extrusion die core is inserted into a heat conduction cavity forming die. According to the cable, the high temperature resistance and flame retardance are improved through the phase change heat management system, efficient production is achieved through equipment, and it is guaranteed that solution filling and structure forming are synchronous.

Description

Technical Field

[0001] The present invention relates to the technical field of cable production, and particularly relates to a flame-retardant polyethylene sheath cable and its production equipment. Background Art

[0002] With the acceleration of the urbanization process and the improvement of industrial automation, the application of cables in fields such as high-rise buildings, rail transit, and new energy is becoming increasingly intensive, posing stringent requirements on the flame-retardant performance and thermal management ability of cables.

[0003] Traditional flame-retardant cables mainly rely on adding chemical flame retardants such as magnesium hydroxide and intumescent flame retardants to inhibit combustion through mechanisms such as endothermic decomposition and carbon formation barrier. However, there are the following technical bottlenecks: the endothermic efficiency of chemical flame retardants gradually decays with the increase in temperature at high temperatures, and it is unable to effectively cope with the continuous temperature rise caused by cable overload or external fire sources, and is prone to the problem of "flame retardancy without heat dissipation", resulting in heat accumulation and triggering a chain fire. At the same time, traditional cables improve thermal conductivity through the modification of sheath materials, but metal fillers are prone to oxidation, have poor compatibility with polyethylene, and can only conduct heat in the solid state, unable to achieve latent heat absorption during phase change, and the heat dissipation effect is limited in local overheating scenarios. Summary of the Invention

[0004] The purpose of the present invention is to provide a flame-retardant polyethylene sheath cable and its production equipment to solve the problem of limited heat dissipation effect of traditional flame-retardant cables in local overheating scenarios mentioned in the above background.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is a flame-retardant polyethylene sheathed cable and its production equipment, including: a conductor core, the outside of the conductor core is wrapped with a flame-retardant polyethylene sheath, a phase-change heat-conducting cavity is formed inside the flame-retardant polyethylene sheath, and a phase-change heat-conducting solution is injected into the phase-change heat-conducting cavity. By utilizing the heat absorption-exotherm characteristics during the phase change process of the desorption of borax crystal water and the condensation reflux in the phase-change heat-conducting solution, efficient dissipation and circulation of heat during cable operation are realized, and the high-temperature resistance performance of the flame-retardant sheath is improved; the production equipment for preparing a flame-retardant polyethylene sheathed cable includes an extrusion die head, an extrusion die core is arranged inside the extrusion die head, the extrusion die core is inserted into the extrusion die head from one end, and the extrusion die core is composed of six split die cores spliced and combined. The modular design of the split die cores facilitates equipment disassembly and maintenance, and adapts to the rapid replacement of cable core channels of different specifications. Two copper hoops are arranged outside the six split die cores for fixation. The fixed copper hoops apply radial pressure to the split die cores through interference fit to ensure the tightness of the die core splicing gap, and at the same time realize the seal between the extrusion die core and the extrusion die head to prevent molten polyethylene from infiltrating into the injection channel. An injection channel for the borax solution to pass through is arranged between every two groups of split die cores. The injection channel is the transmission channel for the borax solution, and its distribution corresponds one-to-one with the injection ports of the heat-conducting cavity forming die to ensure uniform injection of the solution into each phase-change heat-conducting cavity. A cable core channel for the conductor core to pass through is arranged in the center of the extrusion die core. The cable core channel plays a positioning role for the conductor core to ensure that the cable core is centered inside the sheath and avoid uneven heat dissipation caused by eccentricity; six groups of heat-conducting cavity forming dies are inserted into one end of the extrusion die core. The heat-conducting cavity forming die is the forming die for the phase-change heat-conducting cavity, and its outer shape matches the phase-change cavity structure of the inner wall of the sheath. An injection port is arranged inside the heat-conducting cavity forming die, and the injection port is communicated with the injection channel, which is the final outlet for injecting the borax solution into the phase-change heat-conducting cavity.

[0006] Further, a flame retardant is added to the flame-retardant polyethylene sheath. Based on 100 parts of the polyethylene matrix, 60 parts of magnesium hydroxide, 12.5 parts of ammonium polyphosphate, 5 parts of melamine, 7.5 parts of pentaerythritol, and 5 parts of nano-montmorillonite are added.

[0007] Further, the phase-change heat-conducting solution is an aqueous solution of borax with a concentration of 20wt%, 1wt% sodium carboxymethyl cellulose is added as a thickening agent, and 5wt% glycerol is added as an anti-evaporation agent.

[0008] Further, a dense thin-wall forming groove is arranged on the outer side of one end of the heat-conducting cavity forming die, and a heat-conducting thin wall is arranged inside the phase-change heat-conducting cavity. The thin-wall forming groove extrudes the molten polyethylene during the extrusion process, and a heat-conducting thin wall is synchronously formed on the inner wall of the phase-change heat-conducting cavity without subsequent processing, which improves the production efficiency and ensures the uniformity of the thin-wall structure.

[0009] Furthermore, an extrusion cavity is provided between the extrusion die core and the extrusion die head. The extrusion cavity serves as a temporary storage and pressurization channel for the molten polyethylene, ensuring that the polyethylene uniformly coats the conductor core under high pressure. A polyethylene injection port is provided on one side of the extrusion cavity. The polyethylene injection port is connected to a twin-screw extruder for introducing the raw material of flame-retardant polyethylene in a molten state. An extrusion port is provided at one end of the extrusion die head. The extrusion port is the sheath forming outlet. The molten polyethylene is compounded with the conductor core here and forms a sheath structure with a phase-change heat conduction cavity under the constraint of the heat conduction cavity forming die.

[0010] Furthermore, a metering injection valve is provided at one end of the extrusion die head. The metering injection valve is used to precisely control the injection amount of the borax solution, ensuring synchronization with the sheath extrusion speed and avoiding the influence of excessive or insufficient solution on the cable performance. A honeycomb piston cylinder and a circular partition are provided inside the metering injection valve. A solution introduction cavity is provided between the honeycomb piston cylinder and the circular partition. The solution introduction cavity temporarily stores the borax solution input from the solution inlet, providing buffering for the liquid suction process of the driving piston. A solution inlet is provided on one side of the solution introduction cavity. The solution inlet is connected to a borax solution storage tank for continuously replenishing the solution. A pressurized injection cavity is provided on the right side of the honeycomb piston cylinder. The pressurized injection cavity performs secondary pressurization on the borax solution, ensuring that the solution penetrates and fills the phase-change heat conduction cavity before the polyethylene sheath is completely cured. A dispersion injection port is provided on the right side of the pressurized injection cavity. The dispersion injection port is communicated with the injection channel, evenly distributing the pressurized solution to each injection channel. A core passing tube penetrates through the metering injection valve. The core passing tube is a guiding channel for the conductor core, and its inner diameter matches the core channel, ensuring that the core passes through the equipment in a straight line and avoiding deviation.

[0011] Furthermore, six groups of driving pistons are provided inside the honeycomb piston cylinder. The six groups of driving pistons reciprocate synchronously, realizing the quantitative suction and pushing of the solution through the volume change. The multi-piston design can reduce the volume flow fluctuation of a single piston and improve the metering accuracy. One end of the driving piston is fixedly connected to a piston rod. The piston rod penetrates through the circular partition. An inclined disk rotates inside the metering injection valve. The inclined disk is a driving mechanism for the piston movement, and its inclination angle determines the piston stroke, thereby controlling the single injection volume. A sliding groove is provided on the inclined disk. One end of the piston rod is fixedly connected to a sliding ball head. The sliding ball head is slidably connected to the sliding groove. The cooperation between the sliding ball head and the sliding groove converts the rotational movement of the inclined disk into the linear reciprocating movement of the piston rod, with a compact structure and high transmission efficiency.

[0012] Furthermore, the piston rod is slidably connected to the circular partition through a sealing sleeve. The sealing sleeve ensures the sealing performance during the movement of the piston rod and prevents the solution from leaking.

[0013] Furthermore, a first one-way valve is provided inside the driving piston. The first one-way valve controls the one-way inflow of the solution into the driving piston, opening during liquid suction and closing during liquid discharge. A second one-way valve is provided at the right opening of the honeycomb piston cylinder. The second one-way valve controls the one-way outflow of the solution from the honeycomb piston cylinder, opening during liquid discharge and closing during liquid suction, and cooperates with the first one-way valve to achieve the directional transportation of the solution.

[0014] Furthermore, a first gear is fixedly connected to one side of the inclined disk. The first gear meshes with a second gear, and the second gear meshes with a third gear. The three-stage gear transmission system reduces the speed and increases the torque of the driving motor, ensuring the smooth rotation of the inclined disk. At the same time, the movement frequency of the piston is precisely controlled through the gear tooth ratio to match the extrusion speed of the sheath. A driving motor is provided inside the metering injection valve. The driving motor provides power for the entire metering injection system. The injection rate can be adjusted through frequency conversion control to adapt to different production conditions. The output shaft of the driving motor is fixedly connected to the third gear.

[0015] Compared with the prior art, the beneficial effects of the present invention include: 1. A flame-retardant polyethylene sheath cable and its production equipment proposed by the present invention, through a multi-stage phase change heat management mechanism, utilize the three-stage phase change process of borax decahydrate dehydrating initially at 32.4°C, completely dehydrating at 60°C, and vaporizing water at 100°C to achieve gradient heat absorption from the initial stage of local overheating of the cable to the extreme high-temperature scenario. The total latent heat of phase change reaches 2350 kJ / kg, which is greatly improved compared with traditional paraffin-based phase change materials, filling the low-temperature response blank area of 30 - 100°C. 2. A flame-retardant polyethylene sheath cable and its production equipment proposed by the present invention, through the collaborative design of structure and material, utilize the sheet-shaped heat-conducting thin wall formed by integral molding of the mold to provide a three-dimensional attachment surface for borax crystallization, cooperate with the hexagonal array layout of the phase change heat-conducting cavity and the capillary reflux network to increase the condensate reflux speed, and form a "heat absorption - condensation - reflux" closed cycle without external power. 3. A flame-retardant polyethylene sheath cable and its production equipment proposed by the present invention, through a triple collaborative flame-retardant barrier, combine the glassy protective layer generated by borax dehydration with magnesium hydroxide and intumescent flame retardant inside the sheath to reduce the flame spread speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The disclosure of the present invention will be described with reference to the accompanying drawings. It should be understood that the drawings are only for illustrative purposes and are not intended to limit the protection scope of the present invention. In the drawings, the same reference numerals are used to refer to the same components. Among them: Figure 1 Schematically shows a cross-sectional structural view of a flame-retardant polyethylene sheath cable proposed according to an embodiment of the present invention; Figure 2 Schematically shows an external structural view of a production equipment of a flame-retardant polyethylene sheath cable proposed according to an embodiment of the present invention; Figure 3Schematically shows a cross-sectional structural schematic diagram of a production device for a flame-retardant polyethylene sheath cable according to an embodiment of the present invention; Figure 4 Schematically shows a structural schematic diagram of an extrusion die head of a production device for a flame-retardant polyethylene sheath cable according to an embodiment of the present invention; Figure 5 Schematically shows a structural schematic diagram of an extrusion die core of a production device for a flame-retardant polyethylene sheath cable according to an embodiment of the present invention; Figure 6 Schematically shows a side view structural schematic diagram of an extrusion die core of a production device for a flame-retardant polyethylene sheath cable according to an embodiment of the present invention; Figure 7 Schematically shows a structural schematic diagram of a heat conduction cavity forming die of a production device for a flame-retardant polyethylene sheath cable according to an embodiment of the present invention; Figure 8 Schematically shows a structural schematic diagram of a quantitative injection valve of a production device for a flame-retardant polyethylene sheath cable according to an embodiment of the present invention.

[0017] Reference numerals in the figure: 1, conductor core; 2, flame-retardant polyethylene sheath; 3, phase change heat conduction cavity; 4, heat conduction thin wall; 5, extrusion die head; 501, extrusion cavity; 502, polyethylene injection port; 503, extrusion outlet; 6, extrusion die core; 601, split die core; 602, copper hoop; 603, injection cavity channel; 604, core channel; 7, heat conduction cavity forming die; 701, injection port; 702, thin wall forming groove; 8, quantitative injection valve; 9, honeycomb piston cylinder; 901, driving piston; 902, piston rod; 903, inclined disk; 904, sliding groove; 905, sliding ball head; 906, first one-way valve; 907, second one-way valve; 10, circular partition; 11, solution introduction cavity; 12, solution introduction port; 13, pressurized injection cavity; 14, dispersion injection port; 15, first gear; 16, second gear; 17, third gear; 18, driving motor; 19, core passing tube. Specific embodiments

[0018] It is easily understood that according to the technical solution of the present invention, without changing the essence of the present invention, those of ordinary skill in the art can propose various interchangeable structural ways and implementation ways. Therefore, the following specific embodiments and the accompanying drawings are only exemplary descriptions of the technical solution of the present invention, and should not be regarded as all of the present invention or as a limitation or restriction on the technical solution of the present invention.

[0019] According to the embodiments of the present invention in combination with Figure 1Shown. A flame-retardant polyethylene sheathed cable includes a conductor core 1, and a flame-retardant polyethylene sheath 2 is wrapped around the conductor core 1. A flame retardant is added into the flame-retardant polyethylene sheath 2. Based on 100 parts of polyethylene matrix, 60 parts of magnesium hydroxide, 12.5 parts of ammonium polyphosphate, 5 parts of melamine, 7.5 parts of pentaerythritol and 5 parts of nano-montmorillonite are added.

[0020] A phase change heat conduction cavity 3 is formed in the flame-retardant polyethylene sheath 2 and is used to accommodate a phase change heat conduction solution. By utilizing the heat absorption-exotherm characteristics during the phase change process of desorption of borax crystal water and condensation reflux of the phase change heat conduction solution, efficient dissipation and circulation of heat during cable operation are achieved, and the high-temperature resistance performance of the flame-retardant sheath is improved. The phase change heat conduction solution is an aqueous solution of borax with a concentration of 20wt%, 1wt% of sodium carboxymethyl cellulose is added as a thickening agent, and 5wt% of glycerol is also added as an anti-evaporation agent.

[0021] A heat conduction thin wall 4 is arranged in the phase change heat conduction cavity 3. The heat conduction thin wall 4 is formed by extrusion in a thin wall forming groove 702. Its densely distributed sheet structure can significantly increase the heat dissipation surface area of the inner wall of the phase change heat conduction cavity 3, strengthen the heat exchange efficiency between the borax solution and the sheath, and provide an attachment carrier for the crystallization of borax decahydrate. The borax solution in the phase change heat conduction cavity 3 crystallizes to form borax decahydrate at low temperature, that is , and an endothermic dehydration reaction occurs at high temperature: ; The heat of cable operation or external fire source is absorbed through the latent heat of phase change, the temperature rise of the sheath is inhibited, and combustion is delayed; the precipitated water vapor is circulated and condensed in the phase change heat conduction cavity 3 and then refluxed to form a continuous heat management system.

[0022] According to the embodiments of the present invention, in combination with Figures 2 - 8 Shown. A production device for a flame-retardant polyethylene sheathed cable includes an extrusion die head 5. An extrusion die core 6 is arranged in the extrusion die head 5. The extrusion die core 6 is inserted into the extrusion die head 5 from one end, and an extrusion cavity 501 is arranged between the extrusion die core 6 and the extrusion die head 5. The extrusion cavity 501 is a temporary storage and pressurization channel for molten polyethylene to ensure that the polyethylene uniformly wraps the conductor core 1 under high pressure. A polyethylene injection port 502 is opened on one side of the extrusion cavity 501. The polyethylene injection port 502 is connected to a twin-screw extruder for introducing the raw material of flame-retardant polyethylene in a molten state. An extrusion port 503 is opened at one end of the extrusion die head 5. The extrusion port 503 is a sheath forming outlet. The molten polyethylene is compounded with the conductor core 1 here and forms a sheath structure with a phase change heat conduction cavity 3 under the constraint of a heat conduction cavity forming die 7.

[0023] The extrusion die core 6 is assembled by splicing six component die cores 601. The modular design of the component die cores 601 facilitates the disassembly, assembly and maintenance of the equipment, and is suitable for the rapid replacement of cable core channels 604 of different specifications. Two copper hoops 602 are arranged on the outer side of the six component die cores 601 for fixation. The copper hoops 602 apply radial pressure to the component die cores 601 through interference fit to ensure the tightness of the die core splicing gap, and at the same time realize the seal between the extrusion die core 6 and the extrusion die head 5 to prevent the molten polyethylene from infiltrating into the injection cavity 603. An injection cavity 603 for the passage of borax solution is provided between every two groups of component die cores 601. The injection cavity 603 is the transmission channel of the borax solution, and its distribution corresponds one by one to the injection ports 701 of the heat conduction cavity forming die 7 to ensure that the solution is evenly injected into each phase change heat conduction cavity 3. A cable core channel 604 for the passage of the conductor cable core 1 is provided in the center of the extrusion die core 6. The cable core channel 604 positions the conductor cable core 1 to ensure that the cable core is centered in the sheath and avoid uneven heat dissipation caused by eccentricity.

[0024] Six groups of heat conduction cavity forming dies 7 are inserted at one end of the extrusion die core 6. The heat conduction cavity forming die 7 is the forming die of the phase change heat conduction cavity 3, and its outer shape matches the phase change cavity structure of the inner wall of the sheath. An injection port 701 is provided in the heat conduction cavity forming die 7. The injection port 701 is communicated with the injection cavity 603 and is the final outlet for injecting the borax solution into the phase change heat conduction cavity 3. A dense thin-wall forming groove 702 is provided on the outer side at one end of the heat conduction cavity forming die 7. The thin-wall forming groove 702 extrudes the molten polyethylene during the extrusion process, and synchronously forms a heat conduction thin wall 4 on the inner wall of the phase change heat conduction cavity 3, eliminating the need for subsequent processing, improving production efficiency and ensuring the uniformity of the thin-wall structure.

[0025] A quantitative injection valve 8 is provided at one end of the extrusion die head 5. The quantitative injection valve 8 is used to accurately control the injection amount of the borax solution to ensure synchronization with the extrusion speed of the sheath and avoid the influence of excessive or insufficient solution on the cable performance. A honeycomb piston cylinder 9 and a circular partition 10 are provided in the quantitative injection valve 8. A solution introduction cavity 11 is provided between the honeycomb piston cylinder 9 and the circular partition 10. The solution introduction cavity 11 temporarily stores the borax solution input from the solution inlet 12 and provides buffering for the liquid suction process of the driving piston 901. A solution inlet 12 is provided on one side of the solution introduction cavity 11. The solution inlet 12 is connected to the borax solution storage tank for continuous solution replenishment. A pressurized injection cavity 13 is provided on the right side of the honeycomb piston cylinder 9. The pressurized injection cavity 13 performs secondary pressurization on the borax solution to ensure that the solution penetrates and fills the phase change heat conduction cavity 3 before the polyethylene sheath is completely cured. A dispersion injection port 14 is provided on the right side of the pressurized injection cavity 13. The dispersion injection port 14 is communicated with the injection cavity 603 to evenly distribute the pressurized solution to each injection cavity 603.

[0026] There are six groups of driving pistons 901 arranged inside the honeycomb piston cylinder 9. The six groups of driving pistons 901 reciprocate synchronously, and the quantitative suction and pushing of the solution are realized through the volume change. The multi-piston design can reduce the volume flow rate fluctuation of a single piston and improve the metering accuracy. One end of the driving piston 901 is fixedly connected to a piston rod 902. The piston rod 902 penetrates through the circular partition 10, and the piston rod 902 is slidably connected to the circular partition 10 through a sealing sliding sleeve. The sealing sliding sleeve ensures the sealing performance when the piston rod 902 moves and prevents the solution from leaking. There is an inclined disk 903 rotating inside the metering injection valve 8. The inclined disk 903 is the driving mechanism for the piston movement, and its inclination angle determines the piston stroke, thereby controlling the single injection volume. A sliding groove 904 is formed on the inclined disk 903. One end of the piston rod 902 is fixedly connected to a sliding ball head 905. The sliding ball head 905 is slidably connected to the sliding groove 904. The cooperation between the sliding ball head 905 and the sliding groove 904 converts the rotational motion of the inclined disk 903 into the linear reciprocating motion of the piston rod 902, with a compact structure and high transmission efficiency. A first one-way valve 906 is arranged inside the driving piston 901. The first one-way valve 906 controls the one-way inflow of the solution into the driving piston 901, opening during liquid suction and closing during liquid discharge. A second one-way valve 907 is arranged at the right opening of the honeycomb piston cylinder 9. The second one-way valve 907 controls the one-way outflow of the solution from the honeycomb piston cylinder 9, opening during liquid discharge and closing during liquid suction, and cooperating with the first one-way valve 906 to achieve the directional transportation of the solution.

[0027] One side of the inclined disk 903 is fixedly connected to a first gear 15. The first gear 15 meshes with a second gear 16, and the second gear 16 meshes with a third gear 17. The three-stage gear transmission system reduces the speed and increases the torque of the driving motor 18, ensuring the smooth rotation of the inclined disk 903. At the same time, the piston movement frequency is precisely controlled through the gear tooth ratio to match the sheath extrusion speed. A driving motor 18 is arranged inside the metering injection valve 8. The driving motor 18 provides power for the entire metering injection system. The injection rate can be adjusted through frequency conversion control to adapt to different production working conditions. The output shaft of the driving motor 18 is fixedly connected to the third gear 17.

[0028] A core cable through-tube 19 penetrates through the metering injection valve 8. The core cable through-tube 19 is the guiding channel for the conductor core cable 1, and its inner diameter matches the core cable channel 604, ensuring that the core cable passes through the equipment in a straight line and avoiding deviation. The core cable through-tube 19 penetrates through the first gear 15, the inclined disk 903, the circular partition 10, and the honeycomb piston cylinder 9, and the core cable through-tube 19 is communicated with the core cable channel 604.

[0029] Working principle: When the flame-retardant polyethylene sheath 2 is extruded and formed, the metering injection valve 8 is also working. The driving motor 18 drives the swash plate 903 to rotate through gears. With the cooperation of the sliding groove 904 and the sliding ball head 905, the six groups of driving pistons 901 reciprocate in the honeycomb piston cylinder 9. By setting the inclination angle of the swash plate 903 to match the gear speed, the single liquid suction volume and injection frequency of each piston can be accurately controlled, ensuring that the injection volume of the borax solution is completely synchronized with the extrusion speed of the sheath and the volume of the phase change heat conduction cavity 3, avoiding solution waste or insufficient filling. When the driving piston 901 moves to the left, the first one-way valve 906 opens and the second one-way valve 907 closes, so that the borax solution in the solution introduction cavity 11 will enter the honeycomb piston cylinder 9; as the driving piston 901 starts to move to the right, the first one-way valve 906 closes and the second one-way valve 907 opens, so that the borax solution in the honeycomb piston cylinder 9 will be squeezed into the pressurized injection cavity 13. The cross-sectional area of the pressurized injection cavity 13 is smaller than that of the honeycomb piston cylinder 9, and the solution pressure is further increased through the cross-sectional area difference, ensuring that the solution can still quickly fill the phase change heat conduction cavity 3 when the viscosity of the polyethylene melt is relatively high, and then enters the extrusion die core 6 through the dispersion injection port 14, passes through the injection channel 603 and the injection port 701 in sequence, and then enters the just-formed phase change heat conduction cavity 3. At this time, the polyethylene sheath has not been completely cured, and after the solution is injected, it can be in full contact with the heat conduction thin wall 4 on the inner wall of the sheath, providing conditions for subsequent crystal attachment.

[0030] The completed cable is introduced into the cooling tank. The flame-retardant polyethylene sheath 2 is quickly cooled, and the borax solution will also generate borax decahydrate due to cooling and crystallization, and adhere to the heat conduction thin wall 4. The sheet structure of the heat conduction thin wall 4 increases the crystal attachment area, avoiding the deposition of the solution at the bottom of the cavity, and ensuring the uniform distribution of the phase change material. When encountering high temperature, borax decahydrate will gradually lose its crystal water, thereby absorbing heat, and the precipitated water will also evaporate and absorb heat to become water vapor. Each mole of borax decahydrate dehydrates and can absorb about 215 kJ of heat, effectively inhibiting the temperature of the sheath from rising to the ignition point, flowing along the phase change heat conduction cavity 3 to the low-temperature place, then condensing into liquid water, and flowing back to the high-temperature place along the gaps between the heat conduction thin walls 4 and the gaps between the borax crystals, forming a cycle. The through structure of the phase change heat conduction cavity 3 and the thin wall gaps provide a flow channel for water vapor, and the heat is continuously transferred through the convection cycle, constructing a passive thermal management system of "heat absorption - heat dissipation - reflux", significantly improving the flame retardancy and long-term operation reliability of the cable.

[0031] The technical scope of the present invention is not limited to the content described above. Those skilled in the art can make various deformations and modifications to the above embodiments without departing from the technical idea of the present invention, and these deformations and modifications should all fall within the protection scope of the present invention.

Claims

1. A flame-retardant polyethylene sheathed cable, characterized in that, Comprising: A conductor core, with a flame-retardant polyethylene sheath wrapped around the outside of the conductor core. A phase-change heat-conducting cavity is provided in the flame-retardant polyethylene sheath, and a phase-change heat-conducting solution is injected into the phase-change heat-conducting cavity; The phase-change heat-conducting solution is an aqueous solution of borax with a concentration of 20wt%, and 1wt% sodium carboxymethyl cellulose is added as a thickening agent, and 5wt% glycerol is also added as an anti-evaporation agent.

2. A flame-retardant polyethylene sheathed cable according to claim 1, characterized in that, A flame retardant is added to the flame-retardant polyethylene sheath. Based on 100 parts of the polyethylene matrix, 60 parts of magnesium hydroxide, 12.5 parts of ammonium polyphosphate, 5 parts of melamine, 7.5 parts of pentaerythritol, and 5 parts of nano-montmorillonite are added.

3. A production device for a flame-retardant polyethylene sheathed cable, which is used to prepare the flame-retardant polyethylene sheathed cable as described in claim 1, and is characterized in that, Including an extrusion die head, an extrusion die core is arranged in the extrusion die head. The extrusion die core is inserted into the extrusion die head from one end. The extrusion die core is composed of six split die cores spliced and combined. Two copper hoops are arranged on the outside of the six split die cores. An injection channel for the borax solution to pass through is provided between every two groups of the split die cores. A core channel for the conductor core to pass through is provided in the center of the extrusion die core; Six groups of heat-conducting cavity forming dies are inserted into one end of the extrusion die core. An injection port is provided in the heat-conducting cavity forming die, and the injection port is communicated with the injection channel.

4. The production equipment of a flame-retardant polyethylene sheathed cable according to claim 3, characterized in that, A dense thin-wall forming groove is provided on the outside of one end of the heat-conducting cavity forming die, and a heat-conducting thin wall is arranged in the phase-change heat-conducting cavity.

5. The production equipment of a flame-retardant polyethylene sheathed cable according to claim 3, characterized in that, An extrusion cavity is provided between the extrusion die core and the extrusion die head. A polyethylene injection port is provided on one side of the extrusion cavity, and an extrusion port is provided at one end of the extrusion die head.

6. The production equipment of a flame-retardant polyethylene sheathed cable according to claim 3, characterized in that, A quantitative injection valve is provided at one end of the extrusion die head. A honeycomb piston cylinder and a circular partition are arranged in the quantitative injection valve. A solution introduction cavity is provided between the honeycomb piston cylinder and the circular partition. A solution introduction port is provided on one side of the solution introduction cavity. A pressurized injection cavity is provided on the right side of the honeycomb piston cylinder. A dispersion injection port is provided on the right side of the pressurized injection cavity. The dispersion injection port is communicated with the injection channel. A core passing tube penetrates through the quantitative injection valve.

7. The production equipment of a flame-retardant polyethylene sheathed cable according to claim 6, characterized in that, Six groups of driving pistons are arranged in the honeycomb piston cylinder. One end of the driving piston is fixedly connected with a piston rod. The piston rod penetrates through the circular partition. An inclined disk rotates in the quantitative injection valve. A sliding groove is provided on the inclined disk. One end of the piston rod is fixedly connected with a sliding ball head, and the sliding ball head is slidably connected with the sliding groove.

8. The production equipment of a flame-retardant polyethylene sheathed cable according to claim 7, characterized in that, The piston rod is slidably connected with the circular partition through a sealing sliding sleeve.

9. The production equipment of a flame-retardant polyethylene sheathed cable according to claim 7, characterized in that, A first one-way valve is arranged in the driving piston, and a second one-way valve is arranged at the opening on the right side of the honeycomb piston cylinder.

10. The production equipment of a flame-retardant polyethylene sheathed cable according to claim 7, characterized in that, A first gear is fixedly connected to one side of the inclined disk. The first gear meshes with a second gear, and the second gear meshes with a third gear. A driving motor is arranged in the quantitative injection valve, and the output shaft of the driving motor is fixedly connected with the third gear.

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