Extrusion molding process and method for cable insulating layer

Abstract

The invention relates to the technical field of cable production, in particular to an extrusion molding process and method for a cable insulating layer, and the technical scheme comprises the following steps: step 1, preparing a nano modified polyolefin-based composite material which is prepared by mixing base material resin, nano aluminum hydroxide, a flame retardant and a coupling agent in proportion and then processing by a twin-screw extruder; 2, a non-contact electromagnetic induction heating system with the working frequency being 20-40 kHz and the energy efficiency being 92% or above is adopted; step 3, synchronously extruding a conductor shielding layer, an insulating layer and an insulating shielding layer through a combined type multi-layer co-extrusion die of a gradual change type compression ratio runner of which the compression ratio gradually changes from the feeding area to the forming area; and step 4, utilizing an intelligent closed-loop cooling system which is provided with an infrared temperature measuring device and is based on a PID algorithm to control the flow and temperature of the deionized water. The method has the advantages that the performance of the insulating material is improved, the production energy consumption is reduced, and the cooling process is optimized.

Description

Technical Field

[0001] The present invention relates to the technical field of cable production, and specifically to a process and method for extruding and forming a cable insulating layer. Background Art

[0002] Currently, the extrusion molding process of cable insulating layers mainly uses traditional insulating materials such as polyethylene and polyvinyl chloride. The molten insulating material is coated on the surface of the conductor through an extruder and then cooled and shaped to form the insulating layer.

[0003] At present, there are bottlenecks in many aspects in the extrusion molding technology of cable insulating layers: in terms of material properties, traditional insulating materials have poor insulation and are prone to aging. Problems such as impurities, particles, and heavy metals exacerbate the performance degradation, and the insulation performance further decreases after being affected by moisture; in terms of energy consumption, the low efficiency of the extruder and heating system leads to energy waste. The energy expenditure in the industry accounts for a relatively high proportion of the cost budget, resulting in a relatively common situation of high energy consumption in traditional equipment; in the cooling link, traditional water cooling causes the insulating layer to be uneven, and thermal stress causes the insulation performance to decline.

[0004] Therefore, a process and method for extruding and forming a cable insulating layer are proposed to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a process and method for extruding and forming a cable insulating layer, which have the advantages of improving the performance of insulating materials, reducing production energy consumption, and optimizing the cooling process. It can effectively solve the problems of poor insulation and easy aging of traditional insulating materials, high energy consumption of extrusion equipment, unevenness of the insulating layer during the cooling process, and the influence of thermal stress on the insulation performance.

[0006] To achieve the above purpose, the present invention provides the following technical solution: A process for extruding and forming a cable insulating layer, comprising the following steps: Step 1: Prepare a nano-modified polyolefin-based composite material, which is processed by a twin-screw extruder after being mixed in proportion with a base resin, nano-aluminum hydroxide, a flame retardant, and a coupling agent. Step 2: Adopt a non-contact electromagnetic induction heating system with a working frequency of 20 - 40 kHz and an energy efficiency of more than 92%, and cooperate with an intelligent temperature control module to achieve heating with an accuracy of ±0.5°C. Step 3: Synchronously extrude a conductor shielding layer, an insulating layer, and an insulating shielding layer through a combined multi-layer co-extrusion die with a gradually changing compression ratio flow channel whose compression ratio gradually changes from the feeding area to the forming area. The channel length ratio of each layer is 1:1.5:1, and the accuracy of the independent temperature control area reaches ±1.5°C. Step 4: Use an intelligent closed-loop cooling system equipped with an infrared temperature measurement device and controlling the flow rate and temperature of deionized water based on the PID algorithm, with a response speed ≤ 1 s.

[0007] Preferably, the base resin of the nano-modified polyolefin-based composite material comprises linear low-density polyethylene, random copolymer polypropylene, and ethylene-vinyl acetate copolymer, and their mass ratios are 40%-60%, 20%-30%, and 10%-20% respectively; The vinyl acetate content of the ethylene-vinyl acetate copolymer is 18%-28%; the addition amount of nano-aluminum hydroxide is 8%-15% of the total mass of the base material, the addition amount of the flame retardant decabromodiphenylethane is 15%-25%, and the addition amount of the coupling agent γ-aminopropyltriethoxysilane is 3%-5% of the mass of the nano-material; 5%-8% of the hindered amine light stabilizer GW-944 is added to the ethylene-vinyl acetate copolymer. The nano-aluminum hydroxide is surface-treated with the silane coupling agent KH550, the coating temperature is 70°C, the time is 3 hours, and after treatment, the contact angle ≥ 120° and the water absorption rate ≤ 0.1%.

[0008] When adopting the above technical solution: The proportion of linear low-density polyethylene is 40%-60% as the continuous phase, providing flexibility and thermal stability. Linear low-density polyethylene has a good molecular chain structure, its molecular chain is relatively regular, and it can form a continuous network structure in the composite material, thereby endowing the material with flexibility and maintaining good thermal stability within a certain temperature range, preventing the material from deteriorating in performance due to temperature changes during processing and use.

[0009] The proportion of random copolymer polypropylene is 20%-30% as the dispersed phase, enhancing the crystallization performance. In the molecular chain of random copolymer polypropylene, different monomer units are randomly distributed. This structure enables it to exist as a dispersed phase in the composite material, promoting the crystallization process of the material, increasing the crystallinity of the material, and thereby enhancing the strength, hardness and other properties of the material.

[0010] The proportion of ethylene-vinyl acetate copolymer is 10%-20% as the interfacial compatibilizer, and its vinyl acetate content is strictly controlled in the range of 18%-28%. Through the adjustment of the compatibility of molecular chain segments, the three resins form a microscopic sea-island structure, where the continuous phase is linear low-density polyethylene, the dispersed phase is random copolymer polypropylene, and the ethylene-vinyl acetate copolymer is distributed at the interface of the two phases. The vinyl acetate groups in the ethylene-vinyl acetate copolymer can interact with linear low-density polyethylene and random copolymer polypropylene to varying degrees, thereby improving the interfacial bonding between the two phases, forming a stable microscopic sea-island structure, and improving the comprehensive performance of the material.

[0011] The addition amount of nano-aluminum hydroxide is 8%-15% of the total mass of the base material, and it forms a double flame-retardant system with 15%-25% of decabromodiphenylethane. Through the synergistic effect of gas-phase flame retardancy and condensed-phase flame retardancy, the peak value of the heat release rate tested by the cone calorimeter is reduced by 42% compared with the single flame-retardant system. Nano-aluminum hydroxide will undergo a dehydration reaction at high temperatures, absorbing a large amount of heat. At the same time, the generated aluminum oxide can form a heat-insulating layer on the material surface, preventing the transfer of heat and oxygen; decabromodiphenylethane will decompose to produce flame-retardant gases such as hydrogen bromide when heated, diluting the oxygen concentration in the combustion area and inhibiting the progress of the combustion reaction. The synergistic effect of the two greatly improves the flame-retardant performance of the material.

[0012] The dosage of the coupling agent γ-aminopropyltriethoxysilane is 3%-5% of the mass of the nano-material. Through the reaction of the silanol groups generated by the hydrolysis of silane with the hydroxyl groups on the surface of nano-aluminum hydroxide, Si-O-Al covalent bonds are formed, enhancing the interfacial bonding force between the nano-particles and the base resin. γ-aminopropyltriethoxysilane will undergo a hydrolysis reaction in an aqueous environment to generate silanol groups, and these silanol groups can undergo a condensation reaction with the hydroxyl groups on the surface of nano-aluminum hydroxide to form strong Si-O-Al covalent bonds, thus better binding nano-aluminum hydroxide and the base resin together and improving the mechanical properties and stability of the material.

[0013] Preferably, the non-contact electromagnetic induction heating system has an adaptive energy efficiency adjustment function. It can collect the phase difference data of the coil current in real time through a third-order frequency tracking algorithm and dynamically adjust the working frequency. The working frequency range is 20-40 kHz, the accuracy of the temperature control module is ±0.5 °C, and the overall energy efficiency of the system is ≥92%.

[0014] When adopting the above technical solution: The system collects the phase difference data of the coil current and voltage in real time. When the impedance fluctuates due to the change in the load, such as the molten state of the material, the working frequency is dynamically adjusted within the range of 20-40 kHz, so that the power factor is always maintained above 0.98, avoiding reactive power loss. Through the accurate measurement and analysis of the phase difference between the coil current and voltage, the third-order frequency tracking algorithm can quickly and accurately sense the change of the load and timely adjust the working frequency, making the system always in an efficient working state and reducing energy waste.

[0015] The inner ring is a fiber Bragg grating sensor with an accuracy of ±0.1 °C, which is used to monitor the surface temperature of the heating body in real time. The outer ring obtains the melting temperature of the material through an infrared thermometer with a response time of ≤50 ms. After the data of the two are fused, a regulation signal is output through a fuzzy algorithm to achieve "millisecond-level response with an accuracy of ±0.5 °C", shortening the temperature stabilization time by more than 60% compared with traditional PID control. The double-closed-loop fuzzy control combines the high precision of the fiber Bragg grating sensor and the fast response characteristics of the infrared thermometer. By processing the collected temperature data through a fuzzy algorithm, it can adjust the output power of the heating system more accurately and quickly, so that the temperature is stabilized near the set value.

[0016] Preferably, the combined multi-layer co-extrusion die adopts a gradually variable compression ratio runner design. The runner is a three-zone and five-section structure. The compression ratio gradually transitions from 1.2:1 in the feeding zone to 3.5:1 in the forming zone. The runner convergence angle is 120°. The channel length ratio of each layer is 1:1.5:1. The independent temperature control zone is equipped with a high-precision sensor, and the temperature control error is ≤1.5 °C.

[0017] When the above technical solutions are adopted: The compression ratio in the feeding zone is 1.2:1, and the transition zones are 2.0:1 and 2.8:1 in sequence, and the forming zone is 3.5:1. The runner convergence angle is optimized to 120° through dynamic rheological simulation, reducing the pressure gradient of the melt in the runner by 28% and avoiding melt fracture caused by sudden changes in shear rate. This three-zone and five-section gradually variable compression ratio runner design can gradually compress the melt in the runner, making the changes in pressure and shear rate smoother, reducing the risk of melt fracture. At the same time, the optimized runner convergence angle further improves the flow performance of the melt.

[0018] Each temperature control zone is equipped with a nanoscale platinum resistance sensor with a resolution of 0.01 °C. The layout of the heating rods is optimized through finite element analysis to ensure that the uniformity deviation of the temperature field on the die surface is ≤±0.8 °C, and the temperature difference at the interface of each layer of material is controlled within 1 °C to avoid interlayer peeling caused by uneven temperature. The fractal tree-like runner layout can make the cooling medium or heating medium more evenly distributed in the die. The nanoscale platinum resistance sensor can accurately measure the temperature, and the layout of the heating rods is optimized in combination with finite element analysis, ensuring the temperature uniformity of the die and improving the quality of multi-layer co-extrusion.

[0019] Preferably, the intelligent closed-loop cooling system adopts a closed-loop circulating deionized water structure, with a double-channel counter-flow channel set. The deionized water medium flows reversely in the upper and lower layers. The eddy current generators are evenly distributed with a spacing of 50 mm to enhance the turbulence intensity. An infrared temperature measurement device and a PID control algorithm are equipped. The PID control algorithm incorporates a feedforward-feedback composite compensation. The medium flow rate and temperature are dynamically adjusted, with a response speed ≤ 1 s. The PID control algorithm calculates the theoretical cooling demand in real time through the feedforward link, and the feedback link collects the surface temperature of the insulation layer to achieve the dynamic adjustment of the medium flow rate and temperature.

[0020] When the above technical solutions are adopted: The deionized water medium flows reversely in the upper and lower layers. The water flow speed in the lower layer is 0.8 - 1.2 m / s, and the water flow speed in the upper layer is 1.5 - 2.0 m / s. Combining with the eddy current generators evenly distributed with a spacing of 50 mm, the turbulence intensity is increased by 40%, and the heat exchange efficiency is increased by 35% compared with the single-channel structure. The design of the double-channel counter-flow channel enables the deionized water to form convection in the channel, increasing the contact area and time between the water and the material. The eddy current generators further enhance the turbulence degree of the water, improving the heat exchange efficiency.

[0021] The feedforward link calculates the theoretical cooling demand in real time according to the extrusion speed and die temperature. The feedback link collects the surface temperature of the insulation layer through an infrared temperature measurement device with an accuracy of ±1°C, and dynamically adjusts the deionized water flow rate and temperature, saving more than 30% of water compared with the traditional open-loop control. The PID control algorithm with feedforward-feedback composite compensation combines the predictability of feedforward control and the accuracy of feedback control, and can adjust the operation of the cooling system in a timely manner according to various parameter changes during the extrusion process, achieving accurate flow rate and temperature control while saving water resources.

[0022] Preferably, after the base resin is mixed with nano-aluminum hydroxide, a flame retardant, and a coupling agent, it is stirred by a high-speed mixer at a speed of 1000 r / min for 10 minutes, and granulated by a twin-screw extruder at a temperature of 200°C ± 2°C. A vacuum chamber is set in the feeding section during granulation to reduce the moisture content of the material to less than 0.02%. The granulation water temperature is controlled at 20°C ± 1°C, and compressed air pulse cutting is used. The particle size distribution coefficient is controlled between 0.8 - 1.2, and the granular material is dried at 70°C ± 2°C for 6 hours.

[0023] When the above technical solutions are adopted: The high-speed mixer rotates at 1000 r / min and stirs for 10 minutes to ensure that the nano-aluminum hydroxide reaches a monodisperse state in the base resin. In the high-speed mixer, through appropriate rotation speed and stirring time, the nano-aluminum hydroxide can be fully dispersed in the base resin, avoiding the agglomeration of nano-particles and ensuring the uniformity of the material properties.

[0024] A vacuum chamber is set in the feeding section of the twin-screw extruder to reduce the moisture content of the material to below 0.02%, avoiding extrusion bubbles caused by moisture. The granulation water temperature is controlled at 20°C ± 1°C by a phase change energy storage device. Compressed air pulsed pelletizing is used, and the particle size distribution coefficient is controlled between 0.8 - 1.2 to ensure consistent particle fluidity. The setting of the vacuum chamber can effectively remove the moisture in the material, preventing moisture from forming bubbles during extrusion and affecting product quality; the phase change energy storage device can precisely control the granulation water temperature, and the compressed air pulsed pelletizing method can make the particle size more uniform, ensuring the fluidity of the particles and subsequent processing performance.

[0025] A method for extruding and forming a cable insulation layer, using the cable insulation layer extrusion and forming process described in any one of the above, the method includes the following steps: The particle size of the nanomaterial is classified to D50 ≤ 50nm before modification; The base resin is vacuum dried, and the drying parameters are 70°C for linear low-density polyethylene, 60°C for random copolymer polypropylene, and 80°C for ethylene-vinyl acetate copolymer, the vacuum degree ≤ -0.09MPa, and the time is 4 hours; The intelligent closed-loop cooling system is configured with an automatic chip removal device and the filtration accuracy is 50μm; When the insulation surface temperature threshold of 250°C is exceeded, the current automatically increases to 150%; The temperature difference control of the cooling medium ≤ 2°C; The finished product passes the UL94V-0 flame retardancy test, IEC60502 electrical performance test, and 150°C × 168h thermal aging test, and the tensile strength retention rate ≥ 85%.

[0026] Preferably, the screw rotation speed of the extruder is 80 - 120r / min, the die temperature is zone-controlled as 170°C ± 2°C for the conductor shielding layer, 190°C ± 2°C for the insulation layer, and 170°C ± 2°C for the insulation shielding layer. The traction speed adopts electronic gear synchronization technology, and the linear speed is monitored in real time through an encoder and matched with the extrusion speed to ensure the cable outer diameter tolerance of ±0.05mm.

[0027] When adopting the above technical solutions: The screw rotation speed of the extruder is set to 80 - 120r / min, and this speed range is optimized and determined by a melt index tester to ensure that the base resin and nano-fillers are fully melted and mixed under the shearing action of the screw, while avoiding thermal degradation of the material caused by too high a rotation speed. The screw adopts an equidistant and unequal-depth structure, and the length of the compression section accounts for 35% of the total length of the screw, controlling the residence time of the material in the screw within 45 - 60 seconds to ensure uniform dispersion of nano-aluminum hydroxide in the base material.

[0028] Conductor shielding layer temperature: 170°C ± 2°C. By simulating the interface bonding process between the conductor and the shielding layer through a thermal-fluid coupling simulation software such as Moldflow, this temperature range ensures that the shielding layer material forms intermolecular entanglement with the conductor surface in a molten state. Verified by peel strength tests, the bonding strength stably reaches over 25 N / mm, avoiding interface peeling between the conductor and the insulation layer.

[0029] Insulation layer temperature: 190°C ± 2°C. This temperature is the optimal melting processing temperature for the nano-modified polyolefin-based composite material. Tests using a torque rheometer show that the melt index of the material is controlled within 0.3 - 0.5 g / 10 min at this temperature, ensuring both good fluidity of the melt to fill the mold runner and avoiding uneven insulation layer thickness caused by too high a melt index.

[0030] Insulation shielding layer temperature: 170°C ± 2°C. 5% of antioxidant type 1010 is added to the shielding layer material formulation. The decomposition rate of the antioxidant is lower than 0.1% / h at this temperature. Combined with the shielding layer thickness, it can effectively inhibit thermal oxidative degradation caused by the contact between the insulation layer surface and air during high-temperature extrusion. Tested by a differential scanning calorimeter, the oxidation induction time of the material is extended to over 60 minutes at 170°C.

[0031] The electronic gear synchronous technology is adopted. The wire speed of the cable is collected in real time through a high-precision encoder with 2000 pulses per revolution. The encoder signal is dynamically matched with the rotational speed of the extruder screw through real-time monitoring by a torque sensor via the PLC control system. When the outer diameter deviation feedback by the cable outer diameter detection device, i.e., a laser diameter gauge, exceeds ±0.03 mm, the system automatically adjusts the rotational speed of the traction motor to form a closed-loop control, ultimately achieving stable control of the cable outer diameter tolerance within ±0.03 mm, with a 40% improvement in accuracy compared to traditional mechanical synchronous methods.

[0032] Preferably, when the insulation surface temperature exceeds 220°C, the primary flow increase is initiated to 120%, and when it exceeds 250°C, the flow is automatically increased to 150% and the standby circuit is activated, with the temperature difference between the medium inlet and outlet ≤ 2°C.

[0033] When the above technical solutions are adopted: Primary flow increase mode: When the infrared thermometer with a wavelength of 8 - 14 μm and a response time of 50 ms detects that the insulation layer surface temperature first exceeds 220°C, the system sends a signal to the electromagnetic flowmeter through a proportional-integral-derivative controller to increase the deionized water flow rate from the rated value, such as 10 L / min, to 120%, i.e., 12 L / min. This temperature threshold is determined based on material thermal stability tests. 220°C is the critical temperature at which nano-modified polyolefin begins to show slight thermal decomposition. Increasing the cooling medium flow rate in advance can effectively prevent local overheating problems.

[0034] Secondary flow - increasing mode: When the temperature continuously rises to 250 °C, in addition to increasing the flow rate to 150% (i.e., 15 L / min), the system will automatically start a standby cooling circuit parallel to the main circuit. This standby circuit is equipped with an independent water pump and a heat exchanger. The inner diameter of the pipeline of the standby circuit is 20% smaller than that of the main circuit, which can increase the fluid flow velocity to 2.5 m / s to ensure rapid replenishment of cooling capacity when the flow rate of the main circuit is insufficient. Measured by the thermocouple array with a spacing of 10 mm, the surface temperature drop rate of the insulation layer in this mode can reach more than 5 °C / s, which can effectively control abnormal temperature rise.

[0035] The temperature difference between the inlet and outlet of the cooling medium deionized water is controlled by a plate heat exchanger designed based on the reverse Carnot cycle principle. The heat exchanger uses 316L stainless - steel corrugated plates with a plate spacing of 0.5 mm. It adopts a structural design with counter - flow of hot and cold fluids to ensure that when the inlet temperature of deionized water is 25 °C, the outlet temperature does not exceed 26.5 °C, strictly controlling the temperature difference between the inlet and outlet within 1.5 °C, thereby ensuring the uniformity of the insulation layer cooling process.

[0036] PID parameter self - tuning function: The system uses a fuzzy expert system to continuously monitor the cooling load. The monitored parameters include 12 key variables such as extrusion speed, die temperature, and ambient temperature. The proportional coefficient range of the PID controller is automatically adjusted every 5 seconds to be 0.8 - 1.2, the integral time is 10 - 20 seconds, and the derivative time is 2 - 5 seconds, so that the energy efficiency ratio of the cooling system is stabilized above 6.8. Compared with fixed - parameter control, this strategy can save 22% of energy. Through energy balance calculation, the cooling energy consumption per unit product is reduced to 0.3 kWh / kg, significantly lower than the industry average level of 0.45 kWh / kg.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention significantly improves the comprehensive performance of the insulation layer through a nano - modified polyolefin - based composite material system. By using linear low - density polyethylene, random copolymer polypropylene, ethylene - vinyl acetate copolymer, combined with nano - aluminum hydroxide, flame retardants, and coupling agents, a ternary synergistic compatibilized micro - island structure is achieved, increasing the impact strength by more than 35% and reducing the decline in insulation performance after moisture absorption by more than 60%. The double - flame - retardant system of nano - aluminum hydroxide + decabromodiphenylethane reduces the peak heat release rate by 42%. The surface treatment with silane coupling agent KH550 improves the dispersion of nano - particles and the interfacial bonding strength by 60%. After long - term thermal aging, the tensile strength retention rate ≥ 85%.

[0038] In terms of environmental adaptability, by introducing hindered amine light stabilizers and hydrophobically modified nanoparticles, the material can withstand 500 cycles of high and low temperature cycling from -40°C to 85°C, with the insulation resistance change rate ≤ 5%; after 1000 hours of damp heat alternating at 85°C / 85%RH, the volume resistivity retention rate ≥ 90%, and there are no obvious cracks on the surface; after 240 hours of salt spray corrosion, the tensile strength retention rate ≥ 80%, meeting the requirements of harsh environments such as ocean engineering and high-voltage power transmission and distribution.

[0039] The heating system uses non-contact electromagnetic induction heating at 20 - 40 kHz, combined with an intelligent temperature control module. The system energy efficiency ≥ 92%, saving 18% energy compared to traditional resistance heating. The third-order frequency tracking algorithm maintains the power factor ≥ 0.98, and the double closed-loop fuzzy control combines infrared temperature measurement and fiber optic sensors to achieve a millisecond-level response of ±0.5°C, reducing heat conduction losses.

[0040] The multi-layer co-extrusion die adopts a gradually changing compression ratio flow channel with three zones and five sections, 1.2:1 - 3.5:1. Combined with dynamic rheological simulation optimization, the melt pressure gradient is reduced by 28%. The independent temperature control zone is equipped with a nano-platinum resistance sensor with an accuracy ≤ 1.5°C, an interface temperature difference of ±0.8°C. The die temperature is divided into zones to control the conductor shielding layer at 170°C ± 2°C, the insulation layer at 190°C ± 2°C, and the insulation shielding layer at 170°C ± 2°C. The traction speed matches the extrusion speed, and the wire and cable outer diameter tolerance is ±0.05 mm.

[0041] The intelligent closed-loop cooling system integrates infrared temperature measurement and PID algorithm. The double-channel counter-flow structure + eddy current generator increases the turbulence intensity by 40%. The medium flow rate adjustment accuracy is 0.5 L / min, saving 30% water, and the temperature difference control ≤ 2°C. The double-threshold control strategy is 220°C / 120% flow rate, 250°C / 150% flow rate + standby circuit combined with the PID adaptive algorithm, and the cooling system energy efficiency ratio ≥ 6.8. Description of the Drawings

[0042] Figure 1 It is the process flow chart of the cable insulation layer extrusion forming process of the present invention; Figure 2 It is the threshold logic schematic diagram of the intelligent closed-loop cooling system of the present invention; Figure 3 It is the control logic schematic diagram of the intelligent closed-loop cooling system of the present invention; Figure 4 It is the schematic diagram of the material performance test and verification process of the present invention. Detailed Embodiments

[0043] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0044] Embodiment 1: Preparation of nano-modified polyolefin-based composite material: As Figures 1 to 4 shown, the materials selected for preparing the nano-modified polyolefin-based composite material in this embodiment are as follows: The base resin consists of linear low-density polyethylene, random copolymer polypropylene, and ethylene-vinyl acetate copolymer, and the mass ratios of the three are 40%-60%, 20%-30%, and 10%-20% respectively; among them, the vinyl acetate content of the ethylene-vinyl acetate copolymer is controlled at 18%-28% to achieve the synergistic compatibilization effect of the ternary components as an interfacial compatibilizer. The nano material uses nano aluminum hydroxide surface-treated with silane coupling agent KH550, and its addition amount is 8%-15% of the total mass of the base material; the coating treatment process of this nano material is to treat at 70°C for 3 hours, and the contact angle after treatment is ≥120°, which can increase the interfacial bonding strength by 60%. The flame retardant selects decabromodiphenylethane, and the addition amount is 15%-25% of the total mass of the base material; the coupling agent uses γ-aminopropyltriethoxysilane, and the addition amount is 3%-5% of the mass of the nano material.

[0045] In addition, the preferred pretreatment steps are as follows: Nano-particle treatment: First, screen the particle size of nano aluminum hydroxide to ensure that the average particle size does not exceed 50 nanometers, and then perform surface coating treatment with silane coupling agent KH550 (treatment temperature 70°C, time 3 hours) to form a hydrophobic layer on the particle surface. The contact angle after treatment is ≥120°, and the water absorption rate is ≤0.1%, significantly improving the compatibility with the base resin; Drying of the base resin: Vacuum dry the three base resins respectively: linear low-density polyethylene at 70°C, random copolymer polypropylene at 60°C, and ethylene-vinyl acetate copolymer at 80°C, with a vacuum degree ≤ -0.09 MPa and a drying time of 4 hours to remove moisture to avoid extrusion bubbles.

[0046] During the material mixing process, the above-mentioned base resin, nano aluminum hydroxide, flame retardant, and coupling agent are put into a high-speed mixer and stirred at a speed of 1000 r / min for 10 minutes to ensure the uniform dispersion of each component. The granulation process uses a twin-screw extruder and is carried out at a temperature of 200°C ± 2°C; during granulation, vacuum-induced mixing technology is applied, and a vacuum chamber is set at the feeding section to reduce the moisture content of the material to less than 0.02%; the granulation water temperature is controlled at 20°C ± 1°C by a phase change energy storage device, and pulsed cutting with compressed air is used to control the particle size distribution coefficient between 0.8 and 1.2. After granulation, the composite material is dried at a temperature of 70°C ± 2°C for 6 hours to ensure the stability of the subsequent extrusion molding process.

[0047] In terms of equipment configuration, the screw speed of the extruder is controlled at 80 - 120 r / min to provide an appropriate shear rate for the melting and plasticization of the material.

[0048] Verification process and comparative examples: Comparative example 1: Nano aluminum hydroxide without surface treatment is used, and silane coupling agent KH550 is not used. The remaining formulation and process parameters are the same as those in Example 1. Specific verification methods: Interface bonding strength test: According to GB / T2792 - 2014, bonding specimens of the composite material and the metal substrate are prepared, and the peel strength of Example 1 and Comparative Example 1 is tested. The interface bonding strength of Example 1 is increased by more than 60%, while there is no significant increase in Comparative Example 1.

[0049] Mechanical property test: According to GB / T1043.1 - 2008, a pendulum impact tester is used to test the impact strength. The impact strength of Example 1 is increased by more than 35% compared with the traditional material without adding nano aluminum hydroxide and the ternary synergistic compatibilization system.

[0050] Flame retardancy test: The peak value of the heat release rate is tested using a cone calorimeter ISO5660 - 1. The peak value of the heat release rate of Example 1 is reduced by 42% compared with Comparative Example 1. The double flame retardant system formed by the flame retardant decabromodiphenylethane and nano aluminum hydroxide has a significant effect.

[0051] Insulation property test: The specimen is placed in an environment with a humidity of 90% and a temperature of 25°C for 48 h, and the volume resistivity is tested according to GB / T1410 - 2006. The decline amplitude of the insulation property of Example 1 after being exposed to moisture is reduced by more than 60% compared with similar materials.

[0052] Aging resistance test: A thermal aging test at 150°C × 168 h is carried out to test the tensile strength retention rate. For Example 1, it is ≥85%, while for Comparative Example 1, it is only 70%.

[0053] Extreme environment adaptability test: High and low temperature cycle: Conducted according to GB / T2423.34, -40°C to 85°C cycle for 500 times. The insulation resistance change rate of Example 1 is 3.2%, and that of the traditional material (Comparative Example 1) is 18%. Humid heat alternation: In an environment of 85°C / 85%RH for 1000h. SEM observation shows that there are no cracks on the surface of Example 1, while dense microcracks appear on the traditional material. Salt spray corrosion: Tested according to GB / T10125. The volume resistivity retention rate of Example 1 is 92%, and that of the traditional material is 65%.

[0054] This composite material forms a microscopic island structure through the ternary synergistic compatibilization principle. After the above verification process, it is confirmed that its various performance indicators are superior to those of the comparative example and traditional materials.

[0055] Example 2: Configuration of non-contact electromagnetic induction heating system: As Figures 1 to 4 shown, the working frequency of the non-contact electromagnetic induction heating system in this example is 20 - 40kHz, mainly composed of an intelligent temperature control module and a double closed-loop fuzzy control unit, which can achieve precise control and efficient regulation of the heating process.

[0056] The temperature control accuracy of the system reaches ±0.5°C, which can meet the temperature control requirements of high-precision heating processes; equipped with an adaptive energy efficiency adjustment function, which uses a third-order frequency tracking algorithm to collect coil current phase difference data in real time and dynamically adjusts the working frequency to make the power factor ≥0.98, ensuring that the system is always in a high-efficiency operating state; The third-order frequency tracking algorithm realizes dynamic frequency adjustment through three stages: Real-time monitoring stage: Continuously collect the current and voltage signals of the coil using sensors, calculate the phase difference between the two, and trigger the frequency adjustment mechanism when the phase difference exceeds the preset angle; Frequency scanning stage: Automatically scan at intervals of 5kHz within the frequency range of 20 - 40kHz, and screen the optimal working frequency that keeps the power factor above 0.98 to ensure efficient energy utilization; Fine tuning stage: Update the phase difference data every 20 milliseconds, and make small adjustments to the frequency (accuracy up to 0.1kHz) through an intelligent controller to keep the system always in a high-efficiency resonance state and avoid reactive power loss.

[0057] When the molten state of the material changes (such as a 10% fluctuation in melt viscosity), the third-order frequency tracking algorithm can quickly adjust the frequency to keep the power factor stable, and the stability is 3 times higher than that of traditional fixed-frequency control, effectively avoiding energy waste.

[0058] Actual tests show that the frequency adjustment response time does not exceed 30 milliseconds, and the power factor is stably maintained in the high value range of 0.985 - 0.995.

[0059] After actual measurement, the overall energy efficiency of the system is ≥92%, saving 18% of energy compared with the traditional resistance heating method, and significantly reducing the energy consumption cost.

[0060] Compared with the traditional resistance heating system, the heating system of the present invention has no resistance wire loss, the maintenance period is extended to 5 years, the average annual maintenance cost is reduced from 150,000 yuan to 30,000 yuan, and the equipment reliability is increased by 60%.

[0061] The temperature control module adopts a double-closed-loop fuzzy control algorithm, combines infrared temperature measurement and fiber Bragg grating sensors, realizes a millisecond-level response to temperature changes, and effectively improves the dynamic control performance of the system; the working frequency can be dynamically adjusted within the range of 20 - 40 kHz according to the load change, ensuring that it can maintain an efficient heating state under different working conditions and avoiding energy waste.

[0062] Verification process and comparative example: Comparative example 2: Adopt a traditional resistance heating system with the same power but without intelligent temperature control and energy efficiency adjustment functions. Specific verification method: Temperature control accuracy test: During the heating process, the temperature data is recorded in real time through a high-precision temperature sensor with an accuracy of ±0.1°C. The temperature control accuracy of Example 2 is ±0.5°C, and that of Comparative example 2 is ±2°C.

[0063] Energy efficiency test: Use a power analyzer such as WT3000 to measure the input power and the effective output power, and calculate the energy efficiency ratio. The energy efficiency of Example 2 is ≥92%, and that of Comparative example 2 is only 75%.

[0064] Energy-saving effect verification: Under the same heating task, such as heating 10 kg of materials from 25°C to 200°C, record the energy consumption data. Example 2 saves more than 18% of energy compared with Comparative example 2.

[0065] Dynamic response test: Manually set a temperature step change, such as suddenly rising from 180°C to 220°C, and record the time for the system to reach the stable temperature. The response time of Example 2 is ≤5 s, and Comparative example 2 requires more than 20 s.

[0066] In terms of system energy efficiency optimization, the heating system forms a synergistic effect with the intelligent closed-loop cooling system of Example 4, and the combined action reduces the comprehensive energy consumption of the overall process by more than 25% compared with the traditional method, achieving the goal of energy conservation and emission reduction.

[0067] Example 3: Design of a combined multi-layer coextrusion die: Such as Figures 1 to 4As shown in the figure, the mold adopts a gradually variable compression ratio runner design, which is a three-zone and five-section structure. The channel length ratio of each layer is 1:1.5:1. The compression ratio gradually transitions from 1.2:1 in the feeding area to 3.5:1 in the forming area. This design is conducive to the smooth flow and uniform compaction of the material, improving the quality of the extruded product.

[0068] The runner is specifically divided into three functional zones: Feeding area: The compression ratio is 1.2:1, and the length is 50 mm, initially compacting the material; Transition area: Divided into two sections, the compression ratio is successively increased to 2.0:1 and 2.8:1, and the total length is 80 mm, gradually increasing the melt pressure; Forming area: The compression ratio is 3.5:1, and the length is 70 mm, ensuring uniform densification of the material.

[0069] The convergence angle of the runner is designed to be 120°. Through computer simulation optimization, the pressure gradient of the melt in the runner is reduced by 28%, avoiding melt fracture caused by sudden changes in shear rate.

[0070] The mold is equipped with an independent temperature control zone. High-precision nanoscale platinum resistance sensors are installed in each area. Heating rods are evenly distributed using a fractal tree-shaped runner layout. Verified by finite element analysis, the deviation of the surface temperature uniformity of the mold is ≤±0.8°C, and the temperature difference at the interface of each layer of material is controlled within 1°C.

[0071] Through dynamic rheological simulation, the convergence angle of the runner is optimized and adjusted to 120°, reducing the melt pressure gradient by 28%, effectively reducing flow resistance and energy loss. The mold is equipped with an independent temperature control zone, adopts a fractal tree-shaped runner layout, and installs nanoscale platinum resistance sensors to achieve precise temperature control of each area, with a temperature control error ≤1.5°C. Verified by finite element analysis, the temperature field uniformity of the mold is good, and the interface temperature difference is controlled within ±0.8°C, providing a stable temperature environment for multi-layer coextrusion molding. During the extrusion process, the conductor shield layer, insulation layer, and insulation shield layer are coextruded synchronously, and the temperatures of each layer are controlled at 170°C±2°C, 190°C±2°C, and 170°C±2°C respectively. Through thermal-fluid coupling simulation, the temperature zoning control of the mold is optimized to ensure that the bonding strength between the conductor shield layer and the conductor is ≥25 N / mm, the melt index of the insulation layer is controlled at 0.3 - 0.5 g / 10 min, and at the same time, the insulation shield layer can effectively prevent thermal oxidative degradation.

[0072] In terms of equipment and precision control, the traction system adopts electronic gear synchronization technology, and the linear velocity is monitored in real time through an encoder, controlling the outer diameter tolerance of the cable within ±0.05 mm. Further quality control measures enable the outer diameter tolerance of the finished product to reach within ±0.03 mm, and the deviation of the thickness uniformity of each layer is ≤0.02 mm, significantly improving the forming precision of the product.

[0073] Verification process and comparative examples: Comparative Example 3: A traditional single-layer runner die was used, with a fixed compression ratio of 2.0:1 and no independent temperature control zone. The specific verification methods are as follows: Melt pressure test: Pressure sensors were installed in the feeding area and the forming area of the die. The melt pressure gradient in Example 3 decreased by 28% compared to Comparative Example 3, and the flow resistance decreased significantly.

[0074] Temperature field uniformity test: The surface temperature distribution of the die was scanned by an infrared thermal imager. The interface temperature difference in Example 3 was ±0.8°C, while that in Comparative Example 3 reached ±3°C.

[0075] Bonding strength test: According to GB / T1452-2005, the peel strength between the conductor shielding layer and the conductor was tested. In Example 1, it was ≥25 N / mm, while in Comparative Example 3, it was only 15 N / mm.

[0076] Dimensional accuracy test: A laser diameter gauge with an accuracy of ±0.01 mm was used to measure the outer diameter of the cable and the thickness of each layer. In Example 3, the outer diameter tolerance was ±0.03 mm, and the thickness uniformity deviation of each layer was ≤0.02 mm. In Comparative Example 3, the outer diameter tolerance was ±0.1 mm, and the thickness deviation was ≤0.05 mm.

[0077] Through the above verification, the gradient runner design and the independent temperature control zone significantly improved the die performance and met the requirements of high-precision extrusion molding.

[0078] Example 4: Integration of an intelligent closed-loop cooling system: As Figures 1 to 4 shown, this cooling system adopts a closed-loop circulating deionized water structure, equipped with an infrared temperature measurement device and a PID control algorithm, which can realize the dynamic adjustment of the flow rate and temperature of the cooling medium. The response speed is ≤1 s, and it can quickly adapt to the temperature changes in the process.

[0079] The feedforward-feedback composite compensation strategy enables the flow rate adjustment accuracy of the cooling medium to reach 0.5 L / min, which is 50% higher than that of a single feedback control. Under typical production conditions, that is, an extrusion speed of 50 m / min and a die temperature of 190°C, the flow rate of deionized water can be adjusted dynamically according to the temperature in real time, and the error is controlled within 5%, ensuring uniform and stable cooling effect.

[0080] The runner structure is designed in a double-channel counterflow form, and the deionized water flows reversely in the upper and lower layers. Combining with a vortex generator, the turbulence intensity is increased by 40%, enhancing the heat exchange efficiency; the energy consumption efficiency is optimized through a PID adaptive algorithm, and the temperature difference between the inlet and outlet of the medium is controlled ≤2°C. The energy efficiency ratio of the cooling system is ≥6.8, achieving a high energy utilization efficiency; the feedforward-feedback composite compensation technology is incorporated into the PID control algorithm, enabling the flow rate adjustment accuracy of the medium to reach 0.5 L / min, saving 30% of water compared to traditional open-loop control, and having the advantages of energy conservation and environmental protection.

[0081] The feedforward link pre-calculates the theoretical cooling demand according to the real-time changes in the extrusion speed and die temperature: the faster the extrusion speed or the higher the die temperature, the greater the required cooling medium flow rate, and the two are quantitatively correlated through empirical parameters.

[0082] The feedback link, on the other hand, uses a high-precision infrared temperature measurement device to collect the surface temperature of the insulating layer in real time. After comparing it with the preset temperature thresholds (220°C and 250°C), the PID control algorithm is used to dynamically adjust the flow rate and temperature of deionized water: Proportional regulation: directly adjust the flow rate according to the magnitude of the current temperature deviation; Integral regulation: accumulate the historical temperature deviation to eliminate the long-term existing small temperature difference; Derivative regulation: predict the temperature change trend and adjust the cooling intensity in advance.

[0083] The combination of the three realizes the dynamic coupling control of flow rate and temperature, enabling the adjustment accuracy to reach 0.5 L / min and the response speed ≤ 1 second.

[0084] The automatic chip removal device and backwashing filter equipped in the cooling system increase the service life of the water pump from 2 years to 4 years, reduce the annual maintenance cost by 60%, and significantly reduce the downtime for maintenance.

[0085] Adopt a dual-threshold control logic: when the insulating surface temperature exceeds 220°C, activate the primary flow rate increase mode and increase the flow rate to 120%; if the temperature exceeds 250°C, activate the secondary flow rate increase mode, increase the flow rate to 150% and switch to the standby cooling circuit to ensure effective temperature control under abnormal temperature rise conditions. Design the heat exchange process based on the reverse Carnot cycle principle, and by optimizing the heat exchanger structure, make the temperature difference between the inlet and outlet ≤ 1.5°C, further improving the stability and efficiency of the cooling system.

[0086] Verification process and comparative examples: Comparative example 4: Adopt a traditional open-loop cooling system without PID control and flow rate adjustment functions. Specific verification method: Response speed test: Manually set a sudden change in the insulating surface temperature, such as rising from 200°C to 230°C, and record the time when the system starts the flow rate increase mode. The response speed of Example 4 ≤ 1 s, and Comparative example 4 has no active adjustment function and relies on manual intervention.

[0087] Heat exchange efficiency test: Calculate the heat exchange efficiency by measuring the heat absorbed by the cooling medium per unit time. The heat exchange efficiency of Example 4 is 40% higher than that of Comparative example 4.

[0088] Energy consumption and water saving test: Continuously operate for 24 hours, record the consumption of deionized water and the power consumption. The water saving rate of Example 4 is 30%, the energy efficiency ratio ≥ 6.8, and the energy efficiency ratio of Comparative example 4 is only 4.5.

[0089] Abnormal temperature rise control test: Simulate a sudden temperature rise exceeding 250°C caused by equipment failure. In Example 4, the secondary current increase mode is started and the standby circuit is switched. The temperature drops back to the safe range within 30s. Comparative Example 4 does not have this function, which is likely to cause thermal oxidative degradation of the insulation layer.

[0090] In terms of system energy efficiency coordination, this cooling system cooperates with the electromagnetic induction heating system of Example 2. By precisely controlling the heating and cooling processes, the overall process energy-saving goal is jointly achieved. The water-saving rate and energy efficiency ratio indicators play a key supporting role in the technical effect of reducing the comprehensive energy consumption by more than 25%.

[0091] Example 5: Pilot and production test verification: As Figures 1 to 4 shown, in order to verify the stability and economic benefits of the process in large-scale production, pilot and production tests are carried out.

[0092] The pilot test uses a material preparation scale of 5 tons per batch, supporting an industrial-grade extrusion production line with a production capacity of 500 kg / h. The key equipment includes a twin-screw extruder with a screw diameter of 90 mm, a 1000L high-speed mixer, and an intelligent closed-loop cooling system equipped with online conductivity monitoring. The process parameters are optimized as follows: The vacuum drying time is extended to 4.5 hours, and the vacuum degree is -0.095 MPa to ensure that the moisture content of the material drops to 0.015%; the granulation water temperature is controlled at 20°C ± 1°C, and the particle size distribution coefficient is stable at 0.9 ± 0.1, which is an optimized value within the range of 0.8 - 1.2. The test results show that the particle moisture content is 0.018%, the melt index is 0.42 g / 10min, and the stability deviation compared with the laboratory data is ≤ 5%; the unit energy consumption slightly increases to 0.85 kWh / kg, mainly due to equipment heat dissipation; the response speed of the intelligent system is ≤ 1.2 s, and the outer diameter tolerance of the cable is controlled within ±0.04 mm, verifying the feasibility of 10-fold scale-up.

[0093] The production test is carried out on a ten-thousand-ton industrial production line. The core system upgrades include: expanding the electromagnetic induction heating power module to 500 kW, and shortening the response time of the third-order frequency tracking algorithm to 20 ms; the cooling system adopts a four-channel matrix structure, increasing the turbulence intensity by 50%, and adding a 25μm precision automatic backwashing filter; the PLC integrated MES system realizes cloud monitoring of process parameters, with a collection frequency of 100 Hz. The economic test shows that the unit power consumption is reduced by 25% compared with the traditional process, to 90 kWh / km; the scrap rate drops from 3% to 0.8%; the comprehensive cost decreases by 15.3%, to 720 yuan / km.

[0094] Cost item The process of the present invention Traditional process Comparison result Unit power consumption (kWh / km) 90 120 Reduce by 25% Scrap rate 0.80% 3% Decrease by 66.7% Annual average maintenance cost (10,000 yuan) 20 50 Reduce by 60% Comprehensive production cost (yuan / km) 720 850 Decrease by 15.3% Verified by an industrial-grade production line, the initial investment in the intelligent system is 37% higher than that of traditional equipment. However, through energy consumption savings, reduced scrap rates, and lower maintenance costs, the cumulative cost savings exceed 49 million yuan within a 10-year cycle, and the return on investment is significantly better than the industry average.

[0095] In the 168-hour continuous operation stability test, the temperature control error of the mold is ≤±1.2°C. The standby circuit of the cooling system starts within 2s in case of equipment failure. The medium temperature difference control is ≤2.5°C and it recovers quickly. Through Fourier transform infrared spectroscopy detection, the peak increase of the C-O-C bond in the aged material is only 12%, significantly lower than 35% of the traditional material. Thermogravimetric analysis shows that the weight loss rate at 150°C for 1000h is 1.8%, verifying the synergistic anti-aging effect of nano-aluminum hydroxide and hindered amine light stabilizer. The tensile strength retention rate after thermal aging is 86.2%, and the flame retardant grade stably passes UL94V-0.

[0096] The above tests prove that the core performance indicators of the process of the present invention fluctuate ≤5% in large-scale production, the energy consumption and cost are significantly optimized, and the intelligent redundant design ensures the reliability of the production line, providing sufficient support for industrial application.

[0097] The foregoing shows and describes the basic principles, main features and advantages of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, in any regard, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

[0098] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A wire and cable insulation layer extrusion molding process, characterized in that, It includes the following steps: Step 1: Prepare a nano-modified polyolefin-based composite material, which is processed by a twin-screw extruder after being mixed in proportion with a base resin, nano-aluminum hydroxide, a flame retardant, and a coupling agent; Step 2: Adopt a non-contact electromagnetic induction heating system with a working frequency of 20 - 40 kHz and an energy efficiency of over 92%, and cooperate with an intelligent temperature control module to achieve heating with an accuracy of ±0.5°C; Step 3: Synchronously extrude a conductor shield layer, an insulating layer, and an insulation shield layer through a combined multi-layer co-extrusion die with a gradually changing compression ratio flow channel whose compression ratio gradually changes from the feeding area to the forming area. The channel length ratio of each layer is 1:1.5:1, and the accuracy of the independent temperature control area reaches ±1.5°C; Step 4: Utilize an intelligent closed-loop cooling system equipped with an infrared temperature measurement device and controlling the flow rate and temperature of deionized water based on the PID algorithm, with a response speed ≤1 s.

2. The extrusion molding process of a cable insulation layer according to claim 1, characterized in that, The base resin of the nano-modified polyolefin-based composite material includes linear low-density polyethylene, random copolymerized polypropylene, and ethylene-vinyl acetate copolymer, and their mass ratios are 40% - 60%, 20% - 30%, and 10% - 20% respectively; The vinyl acetate content of the ethylene-vinyl acetate copolymer is 18% - 28%; the addition amount of the nano-aluminum hydroxide is 8% - 15% of the total mass of the base material, the addition amount of the flame retardant decabromodiphenylethane is 15% - 25%, and the addition amount of the coupling agent γ-aminopropyltriethoxysilane is 3% - 5% of the mass of the nano-material; 5% - 8% of a hindered amine light stabilizer GW-944 is added to the ethylene-vinyl acetate copolymer. The nano-aluminum hydroxide is surface-treated with a silane coupling agent KH550, the coating temperature is 70°C, the time is 3 hours, the contact angle after treatment is ≥120°, and the water absorption rate is ≤0.1%.

3. A wire and cable insulation layer extrusion molding process according to claim 1, characterized in that The non-contact electromagnetic induction heating system has an adaptive energy efficiency adjustment function, collects coil current phase difference data in real time through a third-order frequency tracking algorithm and dynamically adjusts the working frequency. The working frequency range is 20 - 40 kHz, the accuracy of the temperature control module is ±0.5°C, and the overall energy efficiency of the system is ≥92%.

4. A wire and cable insulation layer extrusion molding process according to claim 1, characterized in that, The combined multi-layer co-extrusion die adopts a gradually changing compression ratio flow channel design. The flow channel is a three-zone and five-section structure, and the compression ratio gradually transitions from 1.2:1 in the feeding area to 3.5:1 in the forming area. The flow channel convergence angle is 120°, the channel length ratio of each layer is 1:1.5:1, and the independent temperature control area is equipped with a high-precision sensor, and the temperature control error is ≤1.5°C.

5. A wire and cable insulation layer extrusion molding process according to claim 1, characterized in that, The intelligent closed-loop cooling system adopts a closed-loop circulating deionized water structure, sets a double-flow channel countercurrent channel, the deionized water medium flows reversely in the upper and lower layers, the eddy current generators are evenly distributed at an interval of 50 mm to enhance the turbulence intensity, and is equipped with an infrared temperature measurement device and a PID control algorithm. The PID control algorithm incorporates a feedforward-feedback composite compensation, dynamically adjusts the medium flow rate and temperature, the response speed is ≤1 s, the PID control algorithm calculates the theoretical cooling demand in real time through the feedforward link, and the feedback link collects the surface temperature of the insulating layer to achieve the dynamic adjustment of the medium flow rate and temperature.

6. A wire and cable insulation layer extrusion molding process according to claim 1, characterized in that, After mixing the base resin with nano aluminum hydroxide, flame retardant, and coupling agent, it is stirred by a high-speed mixer at a speed of 1000 r / min for 10 minutes, granulated by a twin-screw extruder at a temperature of 200°C ± 2°C. When granulating, a vacuum chamber is set in the feeding section to reduce the moisture content of the material to less than 0.02%. The granulation water temperature is controlled at 20°C ± 1°C, and compressed air pulse cutting is used. The particle size distribution coefficient is controlled between 0.8 - 1.2, and the granulated material is dried at 70°C ± 2°C for 6 hours.

7. A method for extrusion molding of a cable insulation layer, which adopts the cable insulation layer extrusion molding process described in any one of claims 1-6, characterized in that, This method includes the following steps: Before modification, the particle size of the nanomaterial is classified to D50 ≤ 50 nm; The base resin is vacuum dried. The drying parameters are 70°C for linear low-density polyethylene, 60°C for random copolymer polypropylene, and 80°C for ethylene-vinyl acetate copolymer. The vacuum degree ≤ -0.09 MPa, and the time is 4 hours; The intelligent closed-loop cooling system is equipped with an automatic chip removal device and the filtration accuracy is 50 μm; When the insulation surface temperature threshold of 250°C is exceeded, the current automatically increases to 150%; The temperature difference control of the cooling medium ≤ 2°C; The finished product passes the UL94V-0 flame retardancy test, IEC60502 electrical performance test, and 150°C × 168 h thermal aging test, and the tensile strength retention rate ≥ 85%.

8. A method for extruding and forming a cable insulating layer according to claim 7, characterized in that, The screw speed of the extruder is 80 - 120 r / min. The die temperature is zone-controlled as 170°C ± 2°C for the conductor shielding layer, 190°C ± 2°C for the insulation layer, and 170°C ± 2°C for the insulation shielding layer. The traction speed adopts electronic gear synchronization technology, and the linear speed is monitored in real time through an encoder and matched with the extrusion speed to ensure that the cable outer diameter tolerance is ±0.05 mm.

9. A method for extruding and forming a cable insulating layer according to claim 7, characterized in that, When the insulation surface temperature exceeds 220°C, the primary current increase is started to 120%. When it exceeds 250°C, the current automatically increases to 150% and the standby circuit is started. The temperature difference between the medium inlet and outlet ≤ 2°C.

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