Weather-resistant silane crosslinked polyethylene insulated power cable production process

Abstract

The invention discloses a weather-proof silane crosslinked polyethylene insulated power cable production process, which comprises the following steps: S1, preparing nano carbon black composite master batch to realize uniform dispersion of carbon black in a matrix; s2, solid-phase preparation of a silane grafted base material: preparing a silane grafted polyvinyl base material under a low-temperature condition by adopting an ultraviolet light-assisted solid-phase grafting technology; s3, performing catalytic mixing and low-temperature extrusion, and then coating the surface of a conductor with the base material through a low-temperature extrusion process to form an insulated wire core; s4, performing staged controllable humidity crosslinking, and completing hydrolysis and condensation reactions by accurately controlling humidity and temperature; and S5, performing post-curing treatment, and finally performing heat treatment and segmented cooling, and screening to obtain a finished cable. According to the process, through a nano carbon black dispersion technology, energy field auxiliary grafting and a precisely-controlled crosslinking process, the crosslinking uniformity and weather resistance of the cable are remarkably improved, so that the product has excellent mechanical strength, electrical insulation performance and environmental stress cracking resistance, meanwhile, the production energy consumption is reduced, and the green manufacturing requirement is met.

Description

Technical Field

[0001] This invention relates to the field of power cable manufacturing technology, specifically to a production process for a weather-resistant silane cross-linked polyethylene insulated power cable. Background Technology

[0002] Weather-resistant silane-crosslinked polyethylene (XLPE) insulated power cables are mainly used in harsh environments such as outdoor overhead lines, where they are exposed to air, rain, sunlight, and other climatic conditions for extended periods. This requires the insulation material to possess excellent weather resistance, tracking resistance, and long-term thermal stability. These cables utilize a silane crosslinking process to transform the linear structure of polyethylene molecules into a three-dimensional network structure, thereby achieving superior heat resistance and mechanical strength compared to ordinary polyethylene. This allows the conductor to operate at a maximum temperature of 90°C for extended periods and enables it to adapt to complex outdoor environments.

[0003] In the production of this cable, the existing core technologies mainly revolve around the silane crosslinking process, specifically including one-step and two-step methods. The one-step method completes grafting and extrusion in a single process, making it easier to ensure product quality, but it requires a precisely metered feeding system and a specially structured extruder. The two-step method first produces crosslinkable silane-grafted polyethylene, then mixes it with a masterbatch containing a catalyst before extrusion molding. Subsequently, warm water crosslinking is required to complete the final hydrolysis crosslinking reaction. This method has lower investment costs and is widely used. To improve the material's weather resistance, the industry commonly modifies it by adding carbon black to the polyethylene matrix; however, ensuring the uniform dispersion of carbon black in the polymer matrix remains a persistent technical challenge.

[0004] When carbon black is added in high amounts, it is difficult to achieve uniform dispersion in the polyethylene matrix, and it is easy to form agglomeration points. This not only affects the mechanical and electrical strength of the insulation material itself, but may also cause mechanical cracking or breakdown of the cable during operation. Traditional crosslinking processes, such as warm water bath or steam crosslinking, consume a lot of energy and may cause environmental pollution. On the other hand, rapid crosslinking or natural crosslinking technologies aimed at improving efficiency have problems such as slow crosslinking speed and unstable crosslinking degree in cold climates or dry air environments, which affect the quality and reliability of the final product. Summary of the Invention

[0005] The problem with existing technologies is that it is difficult to ensure that carbon black is uniformly dispersed in the polyethylene matrix in existing power cables, and to achieve a crosslinking process that is efficient, energy-saving and has a stable and controllable degree of crosslinking. In order to address the above technical problems, this invention provides a production process for weather-resistant silane crosslinked polyethylene insulated power cables.

[0006] The technical solution of this invention is: a manufacturing process for weather-resistant silane cross-linked polyethylene insulated power cables, comprising the following steps: S1. Preparation of nano-carbon black composite masterbatch Nano-carbon black with a particle size of 20-40 nm, styrene-ethylene-butene-styrene block copolymer (SEBS), and an amphiphilic comb-type polymer compatibilizer are placed in a mixer at a mass ratio of 1:3-5:0.05-0.1 and melt-blended at 100-120°C for 10-15 minutes to obtain a uniformly dispersed nano-composite additive of carbon black. Then, zinc stearate (0.5-1% by mass of the total composite additive) is added as a dispersant, and mixing continues for 5 minutes to obtain a uniform nano-carbon black composite material. The nano-carbon black composite material is melt-extruded through a twin-screw extruder, cooled, and pelletized to obtain nano-carbon black composite masterbatch. The amphiphilic comb-type polymer compatibilizer is a maleic anhydride-functionalized reactive compatibilizer, preferably POE-g-MAH (commercially available Dow Amplify TY series) or SEBS-g-MAH (commercially available Kraton FG1924GT). S2, Solid-phase preparation of silane-grafted matrix By weight, 50-70 parts of linear low-density polyethylene, 20-30 parts of low-density polyethylene, and 10-15 parts of nano-carbon black composite masterbatch (S1) are added to a high-speed mixer and premixed at 300-500 r / min for 3-5 minutes. Then, 1.5-2.5 parts of vinyltrimethoxysilane, 0.1-0.2 parts of dicumyl peroxide, and 0.05-0.1 parts of benzophenone are added, and a solid-phase grafting reaction is carried out at 90-110℃ for 5-8 minutes. During the reaction, the material surface is irradiated with a 365nm ultraviolet light source to obtain a silane-grafted polyethylene base material. The density of the linear low-density polyethylene is 0.918 - 0.935 g / cm³. 3 The density of the low-density polyethylene is 0.915 - 0.930 g / cm³. 3 ; S3, catalytic mixing and low-temperature extrusion By mass, 90-100 parts of the silane-grafted polyethylene base material described in S2 are mixed evenly with 0.5-1 parts of dibutyltin dilaurate catalyst, 0.1-0.3 parts of antioxidant 1010 and 0.2-0.5 parts of polyolefin elastomer, and then extruded onto the conductor surface through a single screw extruder at a temperature of 130-150°C, with the extrusion speed controlled at 20-30 meters / minute to form an insulated wire core; S4, Staged Controllable Humidity Crosslinking The insulated core described in S3 is first placed in a constant temperature and humidity environment of 60-70℃ and 80-90% for 2-3 hours to complete the initial hydrolysis; then it is transferred to dry hot air at 80-90℃ for condensation crosslinking for 2-3 hours. The crosslinking environment is maintained with forced air circulation of 0.5-1.0 m / s, so that the degree of crosslinking of the insulation layer reaches 85-95%, and the crosslinked cable is obtained. S5, Post-curing treatment The cross-linked cable described in S4 is heat-treated in a hot air circulation device at 70-80℃ for 1-2 hours, and then cooled to room temperature in sections. After the cable insulation layer diameter deviation is removed by a screening machine, the cable is wound up to obtain the weather-resistant silane cross-linked polyethylene insulated power cable.

[0007] Note: This process replaces traditional thermal crosslinking with synergistic initiation of ultraviolet light and low temperature, reducing energy consumption by approximately 40%. The use of staged crosslinking instead of a warm water bath reduces water consumption and wastewater discharge. The efficient dispersion of nano-carbon black also reduces the amount of filler required, and the process is free of harmful solvents, meeting green manufacturing requirements. The introduction of a screening machine further improves product consistency.

[0008] Furthermore, in step S1, the specific surface area of ​​the nano-carbon black is controlled at 80-100 m². 2 / g, and the melt index of the styrene-ethylene-butene-styrene block copolymer is 5-10g / 10min.

[0009] Note: By controlling the specific surface area of ​​nano-carbon black to 80-100m² 2 / g, ensuring high surface activity and resistance to agglomeration, while selecting SEBS with a melt index of 5-10 g / 10min, so that it can fully encapsulate carbon black while maintaining good flowability during melt blending. The synergistic effect of these two factors significantly improves the dispersion stability of nano-carbon black in the matrix, providing a uniform foundation for electrical conductivity and weather resistance for subsequent crosslinking.

[0010] Furthermore, in step S2, the solid-phase grafting reaction is carried out in a high-speed mixer with microwave-assisted heating, wherein the microwave power is 3-5kW and the frequency is 2450MHz; the working cycle is a cycle of microwave irradiation for 10-20 seconds followed by an interval of 5-10 seconds, and the reaction temperature is maintained at 90-110℃; nitrogen gas with a flow rate of 0.5-1.0 L / min is also circulated in the high-speed mixer.

[0011] Note: Microwave radiation promotes initiator decomposition through rapid molecular-level heating, while the 10-20 second intermittent mode avoids local overheating; nitrogen protection effectively isolates oxygen and prevents oxidative degradation of polyethylene chains, enabling the solid-phase grafting reaction to achieve a grafting rate of up to 95% at a low temperature of 90-110℃, and reducing by-products by more than 20%.

[0012] Further, in step S2, while adding the vinyltrimethoxysilane, 0.2-0.5 parts of vinyltriethoxysilane are added as a co-crosslinking agent, wherein the mass ratio of vinyltrimethoxysilane to vinyltriethoxysilane is 1.5-2.5:0.2-0.5.

[0013] Explanation: The addition of vinyltriethoxysilane utilizes its slower hydrolysis rate compared to methoxysilane to form a gradient cross-linking network: methoxysilane rapidly constructs the initial framework, while ethoxysilane subsequently fills and strengthens it, resulting in a more uniform cross-linking density distribution, improved tear resistance of the insulation layer, and avoidance of localized stress concentration.

[0014] Furthermore, in step S3, the antioxidant used is a composite antioxidant made by compounding antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1 to inhibit the pre-crosslinking reaction during processing; the die flow channel of the single screw extruder consists of two sections: the inlet section is a straight converging flow channel with a cone angle of 8-12°, and the outlet section is a cylindrical shaping flow channel with a length-to-diameter ratio of 15-20:1; the two flow channels are connected by a transition arc with a curvature radius of R3-R5 mm.

[0015] Note: Antioxidant 1010 and Antioxidant 168 work together to capture free radicals and decompose hydrogen peroxide, reducing the pre-crosslinking rate to below 3%; the 8-12° small cone angle of the die flow channel reduces shear heat generation, the 15-20:1 aspect ratio enhances melt homogenization, and the R3-R5mm rounded transition eliminates extrusion dead corners. The three work together to ensure that the surface roughness of the insulation layer is ≤0.1μm and free of gel particles.

[0016] Furthermore, during the condensation crosslinking process in step S4, carbon dioxide, accounting for 0.5-1% of the volume fraction of dry hot air, is introduced into a constant temperature and humidity environment to suppress the side reactions of the organotin catalyst.

[0017] Note: After introducing 0.5-1% carbon dioxide, it forms carbonic acid with water, which can neutralize the alkaline substances produced by cross-linking, prevent the dibutyltin dilaurate catalyst from being poisoned and deactivated, improve the stability of the condensation cross-linking reaction rate, and narrow the cross-linking degree fluctuation range from ±8% to ±3%.

[0018] Furthermore, in the initial hydrolysis stage of step S4, high-purity nitrogen gas is introduced into the constant temperature and humidity environment to control the oxygen content volume concentration in the environment within the range of 10-1000 ppm; wherein, the nitrogen gas flow rate is 0.5-1.5 L / min, and a slightly positive pressure environment is maintained throughout the hydrolysis stage, with the pressure value maintained at 10-50 Pa, in order to protect the activity of the dibutyltin dilaurate catalyst and prevent its oxidative deactivation.

[0019] Note: By controlling the oxygen content at 10-1000ppm and maintaining a slight positive pressure of 10-50Pa, the oxidation and damage of the tin catalyst by oxygen can be prevented, and the intrusion of external air can be prevented from causing humidity fluctuations, thereby improving the consistency of the crosslinking front during the hydrolysis stage.

[0020] Furthermore, in step S2, the irradiance of the ultraviolet light source is 80-120 mW / cm². 2Furthermore, an intermittent irradiation mode is adopted, with an interval of 1-2 minutes after irradiation for 2-4 minutes; the irradiation direction of the ultraviolet light source is at an angle of 45-60° to the stirring shaft of the high-speed mixer to ensure that the dynamically tumbling material can obtain uniform light.

[0021] Note: 80-120mW / cm 2 The combination of irradiation intensity and 2-4 minute intermittent mode maximizes the initiation efficiency of benzophenone and avoids overheating of the material surface; the 45-60° irradiation angle and stirring work together to ensure that each powder particle receives UV excitation, which greatly reduces the deviation of the grafting reaction space uniformity.

[0022] Furthermore, in the segmented cooling process of step S5, the cross-linked cable is first cooled to 40-50°C at a rate of 8-10°C / minute and held at that temperature for 20-40 minutes; then the cooling rate is reduced to 1-3°C / minute, and the cross-linked cable is cooled to room temperature.

[0023] Explanation: Rapid cooling to 40-50℃ at 8-10℃ / minute can quickly overcome the sensitive zone of polyethylene crystallization. Then, holding at the temperature for 20-40 minutes allows the molecular chain stress to fully relax. Finally, slow cooling at 1-3℃ / minute avoids secondary crystallization internal stress, stabilizing the crystallinity of the insulation layer at 40-45%, and significantly extending the time to withstand environmental stress cracking.

[0024] The beneficial effects of this invention are: This invention employs a synergistic formulation of nano-carbon black, styrene-ethylene-butene-styrene block copolymer, and an amphiphilic comb-type polymer compatibilizer. Through intensive mixing and twin-screw extrusion processes, molecular-level uniform dispersion of nano-carbon black in the matrix is ​​achieved. This not only effectively suppresses the risk of electrical breakdown caused by carbon black agglomeration but also enhances the environmental stress cracking resistance of the insulation layer by utilizing the elastic properties of the styrene-ethylene-butene-styrene block copolymer. In step S2, ultraviolet light-assisted solid-state grafting technology at 365 nm wavelength is used to stimulate the decomposition of dicumyl peroxide at 90-110℃, promoting the efficient grafting of vinyltrimethoxysilane onto the polyethylene molecular chains, increasing the grafting rate to over 95%, and avoiding high-temperature thermal degradation, providing uniform active sites for crosslinking network construction. The low-temperature extrusion in step S3, combined with the addition of polyolefin elastomers, suppresses the pre-crosslinking reaction, ensuring the surface smoothness and thickness consistency of the insulation layer. The S4 stage crosslinking process, through precise control of high-humidity hydrolysis and dry-heat condensation, utilizes gradient moisture penetration and forced air circulation at 0.5-1.0 m / s to achieve a stable crosslinking degree of 85-95%, forming a dense three-dimensional network that significantly improves power frequency breakdown strength and heat resistance. The S5 post-curing treatment eliminates internal stress through segmented cooling, enabling the product to maintain crack resistance and long service life even in extreme environments ranging from -50℃ to 90℃. The entire process chain is interconnected, achieving a synergistic leap in the weather resistance, mechanical strength, and electrical insulation performance of power cables. Detailed Implementation

[0025] To further illustrate the methods and effects of this invention, the technical solution of this invention will be clearly and completely described below in conjunction with experiments.

[0026] Example 1: A manufacturing process for a weather-resistant silane cross-linked polyethylene insulated power cable, comprising the following steps: S1. Preparation of nano-carbon black composite masterbatch Nano-carbon black with a particle size of 30-35 nm, styrene-ethylene-butene-styrene block copolymer (SEBS), and an amphiphilic comb-type polymer compatibilizer were placed in a mixer at a mass ratio of 1:4:0.08 and melt-blended at 110°C for 12 minutes to obtain a uniformly dispersed nano-composite additive of carbon black. Then, zinc stearate (0.8% by mass of the total additive) was added as a dispersant, and mixing continued for 5 minutes to obtain a uniform nano-carbon black composite material. This nano-carbon black composite material was melt-extruded using a twin-screw extruder, cooled, and pelletized to obtain nano-carbon black composite masterbatch. The specific surface area of ​​the nano-carbon black was controlled to be 90 m². 2 / g, and the melt index of the styrene-ethylene-butene-styrene block copolymer is 8g / 10min; the amphiphilic comb polymer compatibilizer is a maleic anhydride-functionalized reactive compatibilizer, preferably SEBS-g-MAH, using the commercially available Kraton FG1924GT product. S2, Solid-phase preparation of silane-grafted matrix By weight, 60 parts of linear low-density polyethylene, 25 parts of low-density polyethylene, and 12.5 parts of nano-carbon black composite masterbatch from step S1 were added to a high-speed mixer and premixed at 400 r / min for 4 minutes. Then, 2 parts of vinyltrimethoxysilane, 0.15 parts of dicumyl peroxide, and 0.08 parts of benzophenone were added, and a solid-phase grafting reaction was carried out at 100°C for 7.5 minutes. During the reaction, the material surface was irradiated with a 365 nm ultraviolet light source to obtain a silane-grafted polyethylene base material. The solid-phase grafting reaction was carried out in a high-speed mixer with microwave-assisted heating, wherein the microwave power was 4 kW and the frequency was 2450 MHz; the working cycle was a 15-second microwave irradiation followed by a 7-second interval, and the reaction temperature was maintained at 100°C. Nitrogen gas with a flow rate of 0.8 L / min was also circulated in the high-speed mixer. In step S2, the irradiance of the ultraviolet light source was 100 mW / cm². 2 The ultraviolet light source is used in an intermittent irradiation mode, with a 1.5-minute interval after 3 minutes of irradiation; the irradiation direction of the ultraviolet light source is at a 50° angle to the stirring shaft of the high-speed mixer; the linear low-density polyethylene is DFDA-7042N product produced by Lanzhou Petrochemical; the low-density polyethylene is 2426H produced by Lanzhou Petrochemical. S3, catalytic mixing and low-temperature extrusion By weight, 95 parts of the silane-grafted polyethylene base material described in S2 are mixed evenly with 0.75 parts of dibutyltin dilaurate catalyst, 0.2 parts of antioxidant 1010, and 0.4 parts of polyolefin elastomer. The mixture is then extruded through a single-screw extruder at 140°C to coat the conductor surface, with the extrusion speed controlled at 25 m / min, forming an insulated wire core. The antioxidant used is a composite antioxidant formed by compounding antioxidant 1010 and antioxidant 168 in a 1:1 weight ratio. The die flow channel of the single-screw extruder consists of two sections: an inlet section is a straight converging flow channel with a cone angle of 10°, and an outlet section is a cylindrical shaping flow channel with a length-to-diameter ratio of 18:1. The two flow channels are connected by a transition arc with a radius of curvature of R4 mm. S4, Staged Controllable Humidity Crosslinking The insulated core described in S3 is first placed in a constant temperature and humidity environment of 65°C and 85% for 2.5 hours to complete the initial hydrolysis; then it is transferred to dry hot air at 85°C for condensation crosslinking for 2.5 hours. The crosslinking environment is maintained with forced air circulation of 0.8 m / s, so that the degree of crosslinking of the insulation layer reaches 90%, and the crosslinked cable is obtained. S5, Post-curing treatment The cross-linked cable described in S4 is heat-treated in a hot air circulation device at 75°C for 1.5 hours, and then cooled to room temperature in sections. The section cooling method is as follows: first, the cross-linked cable is cooled to 45°C at a rate of 9°C / min and held at that temperature for 30 minutes; then, the cooling rate is reduced to 2°C / min, and the cross-linked cable is cooled to room temperature. After the cable insulation diameter deviation is removed by a screening machine, the cable is wound up to obtain the weather-resistant silane cross-linked polyethylene insulated power cable. The benzophenone and polyolefin elastomer are commercially available products.

[0027] Example 2: This example is basically the same as Example 1, except that 0.2 parts of vinyltrimethoxysilane are added as a co-crosslinking agent at the same time as vinyltrimethoxysilane, wherein the mass ratio of vinyltrimethoxysilane to vinyltriethoxysilane is 1.5:0.2.

[0028] Example 3: This example is basically the same as Example 1, except that 0.2-0.5 parts of vinyltrimethoxysilane are added as a co-crosslinking agent at the same time as vinyltrimethoxysilane, wherein the mass ratio of vinyltrimethoxysilane to vinyltriethoxysilane is 1:0.2.

[0029] Example 4: This example is basically the same as Example 1, except that 0.2-0.5 parts of vinyltrimethoxysilane are added as a co-crosslinking agent at the same time as vinyltrimethoxysilane, wherein the mass ratio of vinyltrimethoxysilane to vinyltriethoxysilane is 2.5:0.5.

[0030] Example 5: This example is basically the same as Example 1, except that in the condensation crosslinking process of step S4, carbon dioxide with a volume fraction of 0.5% of dry hot air is introduced into a constant temperature and humidity environment to suppress the side reaction of the organotin catalyst.

[0031] Example 6: This example is basically the same as Example 1, except that in the condensation crosslinking process of step S4, carbon dioxide with a volume fraction of 0.8% of dry hot air is introduced into a constant temperature and humidity environment to suppress the side reaction of the organotin catalyst.

[0032] Example 7: This example is basically the same as Example 1, except that in the condensation crosslinking process of step S4, carbon dioxide with a volume fraction of 0.1% of dry hot air is introduced into a constant temperature and humidity environment to suppress the side reaction of the organotin catalyst.

[0033] Example 8: This example is basically the same as Example 1, except that in the preliminary hydrolysis stage of step S4, high-purity nitrogen gas is introduced into the constant temperature and humidity environment to control the oxygen content volume concentration in the environment within the range of 10 ppm; wherein, the nitrogen gas flow rate is 0.5 L / min, and a slightly positive pressure environment is maintained throughout the hydrolysis stage, with the pressure value maintained at 10 Pa.

[0034] Example 9: This example is basically the same as Example 1, except that in the preliminary hydrolysis stage of step S4, high-purity nitrogen gas is introduced into the constant temperature and humidity environment to control the oxygen content volume concentration in the environment within the range of 500 ppm; wherein, the nitrogen gas flow rate is 1 L / min, and a slightly positive pressure environment is maintained throughout the hydrolysis stage, with the pressure value maintained at 30 Pa.

[0035] Example 10: This example is basically the same as Example 1, except that in the preliminary hydrolysis stage of step S4, high-purity nitrogen gas is introduced into the constant temperature and humidity environment to control the oxygen content volume concentration in the environment within the range of 1000 ppm; wherein, the nitrogen gas flow rate is 1.5 L / min, and a slightly positive pressure environment is maintained throughout the hydrolysis stage, with the pressure value maintained at 50 Pa.

[0036] Example 11: This example is basically the same as Example 1, except that in step S2, the irradiance of the ultraviolet light source is 80 mW / cm².2 Furthermore, an intermittent irradiation mode is adopted, with an interval of 1 minute after irradiation for 2 minutes; the irradiation direction of the ultraviolet light source is at a 45° angle to the stirring shaft of the high-speed mixer.

[0037] Example 12: This example is basically the same as Example 1, except that in step S2, the irradiance of the ultraviolet light source is 120 mW / cm². 2 Furthermore, an intermittent irradiation mode is adopted, with an interval of 2 minutes after irradiation for 4 minutes; the irradiation direction of the ultraviolet light source is at a 60° angle to the stirring shaft of the high-speed mixer.

[0038] Example 13: This example is basically the same as Example 1, except that in step S1, the specific surface area of ​​the nano-carbon black is controlled at 80m². 2 / g, and the melt index of the styrene-ethylene-butene-styrene block copolymer is 5g / 10min.

[0039] Example 14: This example is basically the same as Example 1, except that in step S1, the specific surface area of ​​the nano-carbon black is controlled at 100 m². 2 / g, and the melt index of the styrene-ethylene-butene-styrene block copolymer is 10g / 10min.

[0040] Example 15: This example is basically the same as Example 1, except that in step S2, the solid-phase grafting reaction is carried out in a high-speed mixer with microwave-assisted heating function, wherein the microwave power is 3kW and the frequency is 2450MHz; the working cycle is a cycle of 10 seconds of microwave irradiation followed by a 5-second interval, and the reaction temperature is maintained at 90℃; nitrogen gas with a flow rate of 0.5 L / min is also passed through the high-speed mixer.

[0041] Example 16: This example is basically the same as Example 1, except that in step S2, the solid-phase grafting reaction is carried out in a high-speed mixer with microwave-assisted heating function, wherein the microwave power is 5kW and the frequency is 2450MHz; the working cycle is a cycle of 20 seconds of microwave irradiation followed by a 10-second interval, and the reaction temperature is maintained at 110℃; nitrogen gas with a flow rate of 1.0 L / min is also passed through the high-speed mixer.

[0042] Example 17: This example is basically the same as Example 1, except that it includes the following steps: S1. Preparation of nano-carbon black composite masterbatch Nano-carbon black with a particle size of 20-30 nm, styrene-ethylene-butene-styrene block copolymer (SEBS), and an amphiphilic comb-type polymer compatibilizer were placed in a mixer at a mass ratio of 1:3:0.05 and melt-blended at 100°C for 10 minutes to obtain a uniformly dispersed nano-composite additive of carbon black. Then, zinc stearate (0.5% by mass of the total additive) was added as a dispersant, and mixing continued for 5 minutes to obtain a uniform nano-carbon black composite material. This nano-carbon black composite material was melt-extruded using a twin-screw extruder, cooled, and pelletized to obtain nano-carbon black composite masterbatch. The specific surface area of ​​the nano-carbon black was controlled to be 80 m². 2 / g, and the melt index of the styrene-ethylene-butene-styrene block copolymer is 5g / 10min; S2, Solid-phase preparation of silane-grafted matrix By weight, 50 parts of linear low-density polyethylene, 20 parts of low-density polyethylene, and 10 parts of nano-carbon black composite masterbatch from step S1 were added to a high-speed mixer and premixed at 300 r / min for 3 minutes. Then, 1.5 parts of vinyltrimethoxysilane, 0.1 parts of dicumyl peroxide, and 0.05 parts of benzophenone were added, and a solid-phase grafting reaction was carried out at 90°C for 5 minutes. During the reaction, the material surface was irradiated with a 365 nm ultraviolet light source to obtain a silane-grafted polyethylene base material. The solid-phase grafting reaction was carried out in a high-speed mixer with microwave-assisted heating, wherein the microwave power was 3 kW and the frequency was 2450 MHz; the working cycle was a 10-second microwave irradiation followed by a 5-second interval, and the reaction temperature was maintained at 90°C. Nitrogen gas with a flow rate of 0.5 L / min was also circulated in the high-speed mixer. In step S2, the irradiance of the ultraviolet light source was 80 mW / cm². 2 Furthermore, an intermittent irradiation mode is adopted, with an interval of 1 minute after irradiation for 2 minutes; the irradiation direction of the ultraviolet light source is at a 45° angle to the stirring shaft of the high-speed mixer; S3, catalytic mixing and low-temperature extrusion By weight, 90 parts of the silane-grafted polyethylene base material described in S2 are mixed evenly with 0.5 parts of dibutyltin dilaurate catalyst, 0.1 parts of antioxidant 1010, and 0.2 parts of polyolefin elastomer. The mixture is then extruded through a single-screw extruder at 130°C to coat the conductor surface, with the extrusion speed controlled at 20 m / min, forming an insulated wire core. The antioxidant used is a composite antioxidant formed by compounding antioxidant 1010 and antioxidant 168 in a 1:1 weight ratio. The die flow channel of the single-screw extruder consists of two sections: an inlet section is a straight converging flow channel with a cone angle of 8°, and an outlet section is a cylindrical shaping flow channel with a length-to-diameter ratio of 15:1. The two flow channels are connected by a transition arc with a radius of curvature of R3 mm. S4, Staged Controllable Humidity Crosslinking The insulated core described in S3 is first placed in a constant temperature and humidity environment of 60°C and 80% for 2 hours to complete the initial hydrolysis; then it is transferred to dry hot air at 80°C for condensation crosslinking for 2 hours. The crosslinking environment is maintained with forced air circulation of 0.5 m / s, so that the degree of crosslinking of the insulation layer reaches 85%, and the crosslinked cable is obtained. S5, Post-curing treatment The cross-linked cable described in S4 is heat-treated in a hot air circulation device at 70°C for 1 hour, and then cooled to room temperature in sections. The section cooling method is as follows: first, the cross-linked cable is cooled to 40°C at a rate of 8°C / min and held at that temperature for 20 minutes; then the cooling rate is reduced to 1°C / min, and the cross-linked cable is cooled to room temperature. After the cable insulation layer diameter deviation is removed by a screening machine, the cable is wound up to obtain the weather-resistant silane cross-linked polyethylene insulated power cable.

[0043] Example 18: This example is basically the same as Example 1, except that it includes the following steps: S1. Preparation of nano-carbon black composite masterbatch Nano-carbon black with a particle size of 30-40 nm, styrene-ethylene-butene-styrene block copolymer (SEBS), and an amphiphilic comb-type polymer compatibilizer were placed in a mixer at a mass ratio of 1:5:0.1 and melt-blended at 120°C for 15 minutes to obtain a uniformly dispersed nano-composite additive of carbon black. Then, zinc stearate (1% by mass of the total additive) was added as a dispersant, and mixing continued for 5 minutes to obtain a uniform nano-carbon black composite material. This nano-carbon black composite material was melt-extruded using a twin-screw extruder, cooled, and pelletized to obtain nano-carbon black composite masterbatch. The specific surface area of ​​the nano-carbon black was controlled to be 100 m². 2 / g, and the melt index of the styrene-ethylene-butene-styrene block copolymer is 10g / 10min; S2, Solid-phase preparation of silane-grafted matrix By weight, 70 parts of linear low-density polyethylene, 30 parts of low-density polyethylene, and 15 parts of nano-carbon black composite masterbatch from step S1 were added to a high-speed mixer and premixed at 500 r / min for 5 minutes. Then, 2.5 parts of vinyltrimethoxysilane, 0.2 parts of dicumyl peroxide, and 0.1 parts of benzophenone were added, and a solid-phase grafting reaction was carried out at 110°C for 8 minutes. During the reaction, the material surface was irradiated with a 365 nm ultraviolet light source to obtain a silane-grafted polyethylene base material. The solid-phase grafting reaction was carried out in a high-speed mixer with microwave-assisted heating, wherein the microwave power was 5 kW and the frequency was 2450 MHz; the working cycle was a 20-second microwave irradiation followed by a 10-second interval, and the reaction temperature was maintained at 110°C. Nitrogen gas with a flow rate of 1.0 L / min was also circulated in the high-speed mixer. In step S2, the irradiance of the ultraviolet light source was 120 mW / cm². 2 Furthermore, an intermittent irradiation mode is adopted, with an irradiation time of 4 minutes followed by a 2-minute interval; the irradiation direction of the ultraviolet light source is at a 60° angle to the stirring shaft of the high-speed mixer; S3, catalytic mixing and low-temperature extrusion By weight, 100 parts of the silane-grafted polyethylene base material described in S2 are mixed evenly with 1 part of dibutyltin dilaurate catalyst, 0.3 parts of antioxidant 1010, and 0.5 parts of polyolefin elastomer. The mixture is then extruded through a single-screw extruder at 150°C to coat the conductor surface, with the extrusion speed controlled at 30 m / min, forming an insulated wire core. The antioxidant used is a composite antioxidant formed by compounding antioxidant 1010 and antioxidant 168 in a 1:1 weight ratio. The die channel of the single-screw extruder consists of two sections: an inlet section is a straight converging channel with a cone angle of 12°, and an outlet section is a cylindrical shaping channel with a length-to-diameter ratio of 20:1. The two channels are connected by a transition arc with a radius of curvature of R5 mm. S4, Staged Controllable Humidity Crosslinking The insulated wire core described in S3 is first placed in a constant temperature and humidity environment of 70°C and 90% for 3 hours to complete the initial hydrolysis; then it is transferred to dry hot air at 90°C for condensation crosslinking for 3 hours. The crosslinking environment is maintained with forced air circulation of 1.0 m / s, so that the degree of crosslinking of the insulation layer reaches 95%, and the crosslinked cable is obtained. S5, Post-curing treatment The cross-linked cable described in S4 is heat-treated in a hot air circulation device at 80°C for 2 hours, and then cooled to room temperature in sections. The section cooling method is as follows: first, the cross-linked cable is cooled to 50°C at a rate of 10°C / min and held at that temperature for 40 minutes; then the cooling rate is reduced to 3°C / min, and the cross-linked cable is cooled to room temperature. After the cable insulation layer diameter deviation is removed by a screening machine, the cable is wound up to obtain the weather-resistant silane cross-linked polyethylene insulated power cable.

[0044] Comparative Example 1: Referring to Example 1, steps S1-S3 and S5 are exactly the same as in Example 1; however, unlike the staged controlled humidity crosslinking in Example 1, this comparative example uses traditional warm water bath crosslinking: the insulated wire core obtained in S3 is directly immersed in a constant temperature water bath at 90°C for 5 hours to complete the crosslinking.

[0045] Comparative Example 2: Referring to Example 1, the amphiphilic comb-type polymer compatibilizer was omitted in step S1, and the mass ratio of nano-carbon black to SEBS was changed to 1:2. Other conditions were the same as in Example 1.

[0046] Comparative Example 3: Referring to Example 1, the difference between step S5 and the segmented cooling in Example 1 is that this comparative example uses a conventional cooling method: the cross-linked cable is cooled from 75°C to room temperature of 25°C at a rate of 15°C / minute, without any heat preservation treatment.

[0047] To investigate the performance of the power cables in the above embodiments and control examples, the main materials were determined according to the experimental formula, and samples were obtained for testing. The degree of crosslinking (%) was determined using the solvent extraction method according to GB / T 18474-2001; the power frequency breakdown strength (kV / mm) was tested under power frequency voltage according to GB / T 1408.1-2016; and the tensile strength (MPa) was measured using a universal testing machine according to GB / T2951.11-2008. The tensile strength retention rate after heat aging was tested according to GB / T 2951.12-2008. The environmental stress cracking time was tested according to GB / T 2951.10-2008 using the needle indentation method; tensile strength test values ​​were rounded to one decimal place, and environmental stress cracking time was rounded to an integer. All performance data were taken as the average of three sets of parallel valid samples to ensure the accuracy and comparability of the results. The results are shown in Table 1 below. Specific investigations are as follows: Table 1 Performance test results of power cable samples from Examples 1-18 and Comparative Examples 1-3

[0048] 1. Investigating the effect of the ratio of silane-grafted monomers on the performance of power cable samples. A comparison of Examples 2, 3, and 4 reveals that the silane blending ratio significantly impacts the crosslinking effect. Example 4, with a blending ratio of 2.5:0.5, exhibits the best overall performance, demonstrating the highest degree of crosslinking and mechanical strength. This is attributed to the appropriate proportion of ethoxysilane, which slows down the crosslinking rate, resulting in a more complete network. Example 2, with a ratio of 1.5:0.2, performs second best, while Example 3, using a ratio of 1:0.2, shows the weakest performance. This indicates that an excessively high proportion of methoxysilane may lead to excessively rapid initial crosslinking, affecting network uniformity. Therefore, controlling the difference in hydrolysis rate is crucial for achieving gradient crosslinking, and appropriately increasing the proportion of slow-hydrolyzing components helps improve material performance.

[0049] 2. Investigating the impact of cross-linking environment gas composition regulation on the performance of power cable samples. A comparison of Examples 5, 6, and 7 reveals significant differences in the effectiveness of carbon dioxide concentration in catalyst protection within the crosslinking environment. Example 6, with the introduction of 0.8% carbon dioxide, exhibits the best performance, effectively neutralizing by-reaction products and maintaining high catalyst activity. Example 5, using a 0.5% concentration, shows the second best effect, while Example 7, with only 0.1% carbon dioxide, demonstrates the weakest effect and limited effectiveness. The data indicate that maintaining an appropriate carbon dioxide concentration is crucial for inhibiting catalyst poisoning; too low a concentration results in insufficient protection, while too high a concentration may affect the hydrolysis reaction equilibrium. 0.8% is considered a relatively ideal parameter.

[0050] 3. Investigate the influence of ultraviolet irradiation process parameters on the performance of power cable samples. A comparison of Examples 11 and 12 shows that the UV light process parameters have a significant impact on the uniformity of grafting. Example 12 used 120 mW / cm². 2 The optimal irradiance, combined with a 4-minute irradiation followed by a 2-minute interval, yielded the best results. High-intensity intermittent lighting ensured a thorough and uniform reaction. Example 11, using lower irradiance and a shorter irradiation time, showed slightly less success. This demonstrates that sufficient light supply and a reasonable interval are both essential for achieving a deep and uniform grafting reaction, and optimizing the lighting strategy can significantly improve material consistency.

[0051] 4. Investigate the impact of different process route optimization levels on the performance of power cable samples. A comparison of Examples 17 and 18 with Comparative Examples 1, 2, and 3 reveals that the degree of optimization of the process route has a decisive impact on the final performance. Example 18 demonstrates superior overall performance; Example 17, using the lower limit of parameters, still maintains good performance. Comparative Example 3 exhibits the worst crack resistance due to internal stress generated by rapid cooling; Comparative Example 1's traditional water bath process results in the lowest degree of crosslinking due to residual moisture; and Comparative Example 2 suffers from the weakest electrical strength and mechanical properties due to insufficient carbon black dispersion. This clearly demonstrates that the optimized overall process significantly improves defects in each stage, and any simplification or deviation from any stage will lead to significant performance degradation.

[0052] 5. Investigate the impact of whole-process process optimization on the weather resistance of power cable samples. A comparison of Examples 18, 1, and Control Example 1 reveals that the synergistic optimization of process parameters has a decisive impact on the weather resistance of cable insulation materials. Example 18, employing high-specific-surface-area carbon black, strong energy field assistance, and precise segmented cooling, achieved a 93.5% tensile strength retention rate after thermal aging and a long environmental stress cracking resistance time of 1254 hours, demonstrating optimal weather resistance. This is attributed to the synergistic effect of efficient dispersion of nano-carbon black, uniformity of silane grafting, and densification of the crosslinking network. Example 1, serving as the baseline, exhibited stable and good weather resistance, with a tensile strength retention rate of 87.6% and a cracking resistance time of 1105 hours. In contrast, Control Example 1, due to the use of traditional warm water bath crosslinking, suffered from residual moisture and uneven crosslinking, resulting in significantly deteriorated weather resistance, with a tensile strength retention rate of only 77.5% and a cracking resistance time of only 602 hours. The comparison clearly demonstrates that precise control throughout the entire process, from masterbatch preparation and solid-phase grafting to staged crosslinking and post-curing, is the core mechanism for constructing a stable three-dimensional network and improving the long-term weather resistance of materials.

Claims

1. A manufacturing process for weather-resistant silane cross-linked polyethylene insulated power cables, characterized in that, Includes the following steps: S1. Preparation of nano-carbon black composite masterbatch Nano-carbon black with a particle size of 20-40 nm is mixed with styrene-ethylene-butene-styrene block copolymer and amphiphilic comb polymer compatibilizer at a mass ratio of 1:3-5:0.05-0.1 in an internal mixer and melt-blended at 100-120°C for 10-15 minutes to obtain a uniformly dispersed nano-composite additive of carbon black. Then, zinc stearate at 0.5-1% of the total mass of the composite additive is added as a dispersant, and mixing is continued for 5 minutes to obtain a uniform nano-carbon black composite material. The nano-carbon black composite material is melt-extruded through a twin-screw extruder, cooled, and pelletized to obtain nano-carbon black composite masterbatch. S2, Solid-phase preparation of silane-grafted matrix By mass, 50-70 parts of linear low-density polyethylene, 20-30 parts of low-density polyethylene, and 10-15 parts of nano-carbon black composite masterbatch described in S1 are added to a high-speed mixer and premixed at 300-500 r / min for 3-5 minutes; then 1.5-2.5 parts of vinyltrimethoxysilane, 0.1-0.2 parts of dicumyl peroxide, and 0.05-0.1 parts of benzophenone are added, and a solid-phase grafting reaction is carried out at 90-110℃ for 5-8 minutes. During the reaction, the surface of the material is irradiated with an ultraviolet light source with a wavelength of 365nm to obtain silane-grafted polyethylene base material; S3, catalytic mixing and low-temperature extrusion By mass, 90-100 parts of the silane-grafted polyethylene base material described in S2 are mixed evenly with 0.5-1 parts of dibutyltin dilaurate catalyst, 0.1-0.3 parts of antioxidant 1010 and 0.2-0.5 parts of polyolefin elastomer, and then extruded onto the conductor surface through a single screw extruder at a temperature of 130-150°C, with the extrusion speed controlled at 20-30 meters / minute to form an insulated wire core; S4, Staged Controllable Humidity Crosslinking The insulated core described in S3 is first placed in a constant temperature and humidity environment of 60-70℃ and 80-90% for 2-3 hours to complete the initial hydrolysis; then it is transferred to dry hot air at 80-90℃ for condensation crosslinking for 2-3 hours. The crosslinking environment is maintained with forced air circulation of 0.5-1.0 m / s, so that the degree of crosslinking of the insulation layer reaches 85-95%, and the crosslinked cable is obtained. S5, Post-curing treatment The cross-linked cable described in S4 is heat-treated in a hot air circulation device at 70-80℃ for 1-2 hours, and then cooled to room temperature in sections. After the cable insulation layer diameter deviation is removed by a screening machine, the cable is wound up to obtain the weather-resistant silane cross-linked polyethylene insulated power cable.

2. The manufacturing process for a weather-resistant silane cross-linked polyethylene insulated power cable according to claim 1, characterized in that, In step S1, the specific surface area of ​​the nano-carbon black is controlled at 80-100 m². 2 / g, and the melt index of the styrene-ethylene-butene-styrene block copolymer is 5-10g / 10min.

3. The manufacturing process for a weather-resistant silane cross-linked polyethylene insulated power cable according to claim 1, characterized in that, In step S2, the solid-phase grafting reaction is carried out in a high-speed mixer with microwave-assisted heating, wherein the microwave power is 3-5kW and the frequency is 2450MHz; the working cycle is a cycle of microwave irradiation for 10-20 seconds followed by an interval of 5-10 seconds, and the reaction temperature is maintained at 90-110℃; nitrogen gas with a flow rate of 0.5-1.0 L / min is also circulated in the high-speed mixer.

4. The manufacturing process for a weather-resistant silane cross-linked polyethylene insulated power cable according to claim 1, characterized in that, In step S2, 0.2-0.5 parts of vinyltrimethoxysilane are added as a co-crosslinking agent along with the vinyltrimethoxysilane, wherein the mass ratio of vinyltrimethoxysilane to vinyltriethoxysilane is 1.5-2.5:0.2-0.

5.

5. The manufacturing process for a weather-resistant silane cross-linked polyethylene insulated power cable according to claim 1, characterized in that, In step S3, the antioxidant used is a composite antioxidant made by compounding antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1; the die flow channel of the single screw extruder consists of two sections: the inlet section is a straight converging flow channel with a cone angle of 8-12°, and the outlet section is a cylindrical shaping flow channel with a length-to-diameter ratio of 15-20:

1.

6. The manufacturing process for a weather-resistant silane cross-linked polyethylene insulated power cable according to claim 1, characterized in that, During the condensation crosslinking process in step S4, carbon dioxide, accounting for 0.5-1% of the volume fraction of dry hot air, is introduced into a constant temperature and humidity environment.

7. The manufacturing process for a weather-resistant silane cross-linked polyethylene insulated power cable according to claim 1, characterized in that, In the initial hydrolysis stage of step S4, high-purity nitrogen gas is introduced into the constant temperature and humidity environment to control the oxygen content volume concentration in the environment within the range of 10-1000 ppm; wherein, the nitrogen gas flow rate is 0.5-1.5 L / min, and a slightly positive pressure environment is maintained throughout the hydrolysis stage, with the pressure value maintained at 10-50 Pa.

8. The manufacturing process for a weather-resistant silane cross-linked polyethylene insulated power cable according to claim 1, characterized in that, In step S2, the irradiance of the ultraviolet light source is 80-120 mW / cm². 2 Furthermore, an intermittent irradiation mode is adopted, with an interval of 1-2 minutes after irradiation for 2-4 minutes; the irradiation direction of the ultraviolet light source is at an angle of 45-60° to the stirring shaft of the high-speed mixer.

9. The manufacturing process for a weather-resistant silane cross-linked polyethylene insulated power cable according to claim 1, characterized in that, In the segmented cooling process described in step S5, the cross-linked cable is first cooled to 40-50°C at a rate of 8-10°C / minute and held at that temperature for 20-40 minutes. The cooling rate was then reduced to 1-3°C / minute, and the cross-linked cable was cooled to room temperature.

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