Polyethylene insulating material for overhead conductor and its preparation method

Abstract

The application provides a polyethylene insulating material for overhead conductor wire and a preparation method thereof, and belongs to the technical field of high polymer compositions. The preparation method comprises the following steps: S1, preparing functionalized molecular sieve-ZnO; S2, preparing modified SiO2; S3, melt blending linear low-density polyethylene, glycidyl methacrylate grafted polyethylene, ethylene-acrylic acid copolymer, functionalized molecular sieve-ZnO, modified SiO2 and 4,4'-thiobis(6-tert-butyl-3-methylphenol), extruding, cooling, granulating, drying, and obtaining the polyethylene insulating material for overhead conductor wire. The application can improve the electrical insulation performance, and has certain heat aging resistance and weather resistance.

Description

Technical Field

[0001] This invention relates to the field of polymer composition technology, specifically to a polyethylene insulation material for overhead conductors and its preparation method. Background Technology

[0002] Overhead insulated conductors are commonly used in urban and rural power distribution networks due to their advantages such as simple line structure, convenient installation, small footprint, and reduced risk of short circuits and electric shock. Polyethylene, with its good electrical insulation properties, chemical corrosion resistance, flexibility, and processing performance, is one of the commonly used polymer materials for overhead conductor insulation. However, overhead conductors are exposed to the outdoor environment for extended periods and are susceptible to various harsh environmental factors, such as ultraviolet radiation and prolonged high temperatures, which can lead to aging and a decline in insulation performance, thus affecting the long-term operational safety of the overhead conductors.

[0003] Patent application CN104992754A discloses a graphene-containing cross-linked polyethylene insulation material and cable for overhead insulated cables. The cross-linked polyethylene insulation material is composed of the following parts by weight: 80-90 parts low-density polyethylene, 10-20 parts linear low-density polyethylene, 0.05-3.5 parts thermal conductive agent, 1-5 parts auxiliary thermal conductive agent, 0.5-3 parts silane coupling agent, 0.11-0.21 parts antioxidant, 0.03-0.15 parts plasticizer, and 0.03-0.15 parts initiator. Specifically, this application uses graphene or graphene oxide as the thermal conductive agent, and adds an auxiliary thermal conductive agent to improve the UV resistance and weather resistance of the overhead insulation material. However, the initiator dicumyl peroxide used in cross-linked polyethylene insulation materials produces certain small molecule byproducts during thermal decomposition and initiation of polyethylene cross-linking. If these byproducts are not fully removed, they will adversely affect the electrical insulation properties of the insulation material. In addition, graphene or graphene oxide has high surface energy and is prone to agglomeration and local enrichment in the polyethylene matrix. In particular, graphene has a certain degree of conductivity, and its local enrichment may increase the risk of carrier migration and local electric field distortion, thereby adversely affecting the electrical insulation performance of the insulation material.

[0004] Therefore, there is a need to provide a polyethylene insulation material for overhead conductors and its preparation method to solve the above-mentioned technical problems. Summary of the Invention

[0005] In view of this, the present invention provides a polyethylene insulation material for overhead conductors and its preparation method, which can improve electrical insulation performance while having certain heat aging resistance and weather resistance.

[0006] To achieve the above objectives, the present invention provides a method for preparing polyethylene insulation material for overhead conductors, comprising the following steps:

[0007] S1. Aminated molecular sieve-ZnO, 3,5-diaminobenzoic acid, pyridine and triphenyl phosphite were added to N-methylpyrrolidone and ultrasonically dispersed. The mixture was heated and reacted under inert gas protection, cooled, centrifuged to collect the precipitate, washed, dried, ground and sieved to obtain functionalized molecular sieve-ZnO. S2. Vacuum-dried nano-SiO2, cooled and added to anhydrous toluene, ultrasonically dispersed, then hexamethyldisilazane was added, heated and reacted under inert gas protection, cooled, centrifuged to collect the precipitate, washed, dried, ground and sieved to obtain modified SiO2. S3. Linear low-density polyethylene, glycidyl methacrylate-grafted polyethylene, ethylene-acrylic acid copolymer, functionalized molecular sieve-ZnO, modified SiO2 and 4,4′-thiobis(6-tert-butyl-3-methylphenol) are melt-blended, extruded, cooled, pelletized and dried to obtain polyethylene insulation material for overhead conductors. The aminated molecular sieve-ZnO was obtained by ultrasonically dispersing molecular sieve-ZnO in anhydrous ethanol, adding silane modification solution, stirring the reaction under nitrogen protection, collecting the precipitate by centrifugation, washing, and vacuum drying.

[0008] This invention uses linear low-density polyethylene as the main substrate and introduces glycidyl methacrylate-grafted polyethylene and ethylene-acrylic acid copolymer as reactive polyethylene components. During melt blending and subsequent molding, the epoxy groups in the glycidyl methacrylate-grafted polyethylene can undergo ring-opening reactions with the carboxyl groups in the ethylene-acrylic acid copolymer, which facilitates the formation of a polymer network structure within the polyethylene matrix. This restricts molecular chain slippage and thermal motion, improving the material's stability under thermal conditions. 4,4′-Thiobis(6-tert-butyl-3-methylphenol), as a hindered phenolic antioxidant, can capture free radicals generated during thermo-oxidative aging, delaying the degradation of polyethylene molecular chains and giving the resulting polyethylene insulation material good heat aging resistance.

[0009] In functionalized molecular sieve-ZnO, the molecular sieve possesses a porous structure and a large specific surface area, enabling the formation of abundant inorganic-organic interfaces within the polyethylene matrix. This facilitates the formation of charge traps and restricts carrier migration, thereby improving the material's electrical insulation stability. The ZnO loaded on the molecular sieve surface can absorb and scatter some ultraviolet radiation, reducing the damage of ultraviolet light to the polyethylene molecular chains and improving the material's weather resistance. Simultaneously, 3,5-diaminobenzoic acid undergoes a condensation reaction to form an organic functional layer containing aromatic amide structures on the surface of the molecular sieve-ZnO, which helps regulate the surface properties of the composite particles and improve their dispersion stability. The aromatic structures in the organic functional layer containing aromatic amide structures have high thermal stability, which helps maintain the stability of the functionalized molecular sieve-ZnO during thermal aging. The residual amino groups on its surface can undergo a ring-opening reaction with the epoxy groups in glycidyl methacrylate-grafted polyethylene, allowing the molecular sieve-ZnO to form an interfacial connection with the polyethylene matrix through the polyethylene segments of the glycidyl methacrylate-grafted polyethylene. This reduces interfacial defects between the filler and the polymer, thus improving the mechanical properties, electrical insulation properties, and weather resistance of the insulating material.

[0010] In addition, hexamethyldisilazane was used to hydrophobically modify nano-SiO2, introducing hydrophobic silane groups on its surface to reduce the surface polarity and water adsorption capacity of nano-SiO2, thereby reducing the accumulation of water at the interface between the polymer and inorganic filler. At the same time, the modified SiO2 helps to improve the density and stability of the interface between the polymer and inorganic filler, reduce the tendency of the composite system to absorb moisture at the interface, reduce the insulation performance degradation caused by moisture intrusion, and thus improve the insulation stability of the material in humid and hot environments.

[0011] Optionally, the aminated molecular sieve-ZnO is obtained by adding molecular sieve-ZnO to anhydrous ethanol, ultrasonically dispersing it at 300W for 30-40 min, adding silane modification solution, and stirring the mixture at 60-65℃ and 500r / min for 6-8 h under nitrogen protection. The precipitate is collected by centrifugation, washed 3-5 times with anhydrous ethanol, and vacuum dried at 60-70℃ for 10-12 h.

[0012] Optionally, the amination molecular sieve-ZnO comprises the following raw materials in parts by weight: 5-7 parts molecular sieve-ZnO, 120-130 parts anhydrous ethanol, and 46-56 parts silane modification solution.

[0013] Optionally, the silane-modified solution is obtained by mixing γ-aminopropyltriethoxysilane, anhydrous ethanol, and deionized water, and ultrasonically treating for 20-30 minutes; the molecular sieve-ZnO is obtained by adding ZnCl2 to deionized water, mixing and stirring for 10-15 minutes, then adding 13X molecular sieve and mixing and stirring at 500 r / min at 80-90℃ for 50-60 minutes, then adding sodium hydroxide solution dropwise, and continuing to stir for 60-80 minutes after the addition is complete. After cooling to room temperature, the precipitate is collected by centrifugation, washed 3-5 times with deionized water and anhydrous ethanol, vacuum dried at 60-70℃ for 22-24 hours, and then heat-treated at 280-300℃ for 2-3 hours.

[0014] 13X molecular sieve was used as the ZnO carrier. 13X molecular sieve has a large specific surface area and strong ion exchange capacity. It can promote the distribution of zinc-containing components on the surface and near the pores of the molecular sieve through ion exchange and surface adsorption. Subsequently, it is deposited under alkaline conditions and then heat-treated to form ZnO particles.

[0015] Optionally, the silane-modified liquid comprises the following raw materials in parts by weight: 6-8 parts γ-aminopropyltriethoxysilane, 35-40 parts anhydrous ethanol and 5-8 parts deionized water; the molecular sieve-ZnO comprises the following raw materials in parts by weight: 0.8-1 parts ZnCl2, 20 parts deionized water, 8-10 parts 13X molecular sieve and 18-20 parts sodium hydroxide solution; the concentration of the sodium hydroxide is 5 wt%.

[0016] Optionally, in step S1, the aminated molecular sieve-ZnO, 3,5-diaminobenzoic acid, pyridine, and triphenyl phosphite are added to N-methylpyrrolidone and ultrasonically dispersed at 300W for 20-30 min. The mixture is then stirred and reacted at 70-80℃ and 500 r / min under nitrogen protection for 3-5 h. After cooling to room temperature, the precipitate is collected by centrifugation and washed 3-5 times with N,N-dimethylformamide and methanol, and then vacuum dried at 60℃ for 12 h. Finally, the precipitate is ground and passed through a 200-mesh sieve to obtain the functionalized molecular sieve-ZnO.

[0017] The present invention can remove larger agglomerated particles formed after grinding by passing the particles through a 200-mesh sieve, improve the particle size distribution of functionalized molecular sieve-ZnO, which is beneficial to its uniform dispersion in polyethylene matrix and reduces local agglomeration and the resulting interface defects.

[0018] Optionally, in step S2, nano-SiO2 is vacuum dried at 100-110℃ for 6-8 hours, cooled to room temperature, added to anhydrous toluene, and ultrasonically dispersed at 300W for 20-30 minutes. Then, hexamethyldisilazane is added, and the mixture is stirred at 100-110℃ and 400-500 r / min for 4-6 hours under nitrogen protection and reflux conditions. After cooling to room temperature, the precipitate is collected by centrifugation, washed 3-5 times with anhydrous ethanol, vacuum dried at 60-70℃ for 12-18 hours, ground, and passed through a 200-mesh sieve to obtain modified SiO2.

[0019] This invention employs hexamethyldisilazane to hydrophobically modify nano-SiO2. Hexamethyldisilazane reacts with the silanol groups on the surface of nano-SiO2, introducing a hydrophobic structure onto the particle surface. This reduces surface hydrophilic sites and improves its dispersibility and interfacial compatibility within the polyethylene matrix. After the modified SiO2 is added to the polyethylene insulation system, it forms a dispersed inorganic barrier phase, prolonging the diffusion path of moisture into the material's interior. It also helps improve the density of the polymer-inorganic filler interface, reduces the hygroscopic tendency of the composite system, and decreases moisture accumulation at the polymer-inorganic filler interface, thereby improving the insulation stability of the material under humid and hot environments.

[0020] Optionally, the functionalized molecular sieve-ZnO comprises the following parts by weight of raw materials: 5-7 parts of aminated molecular sieve-ZnO, 0.5-0.7 parts of 3,5-diaminobenzoic acid, 5-8 parts of pyridine, 5-8 parts of triphenyl phosphite, and 180-200 parts of N-methylpyrrolidone; the modified SiO2 comprises the following parts by weight of raw materials: 0.8-1 parts of nano-SiO2, 80-100 parts of anhydrous toluene, and 0.15-0.25 parts of hexamethyldisilazane.

[0021] Optionally, in step S3, linear low-density polyethylene, glycidyl methacrylate-grafted polyethylene, ethylene-acrylic acid copolymer, functionalized molecular sieve-ZnO, modified SiO2, and 4,4′-thiobis(6-tert-butyl-3-methylphenol) are added to a high-speed mixer and premixed at 600 r / min for 15-20 min. Then, the mixture is added to a twin-screw extruder and melt-blended at 120-150°C. After extrusion, cooling, pelletizing, and vacuum drying at 60-70°C for 5-6 h, polyethylene insulation material for overhead conductors is obtained.

[0022] In the process of preparing polyethylene insulation material for overhead conductors, the present invention first premixes the raw materials, which helps to initially and uniformly disperse the polyethylene components, functionalized molecular sieve-ZnO, modified SiO2 and antioxidants, reduces local agglomeration of functional fillers and segregation of additives, and improves the dispersion efficiency and compositional uniformity of subsequent twin-screw melt blending, thereby helping to obtain insulation materials with more stable structure and performance.

[0023] The present invention also provides a polyethylene insulation material for overhead conductors, which is prepared by the above preparation method and comprises the following raw materials in parts by weight: 45-50 parts linear low-density polyethylene, 32-35 parts glycidyl methacrylate-grafted polyethylene, 18-20 parts ethylene-acrylic acid copolymer, 2-3 parts functionalized molecular sieve-ZnO, 0.8-1 parts modified SiO2 and 0.8-1 parts 4,4′-thiobis(6-tert-butyl-3-methylphenol).

[0024] This invention prepares a polyethylene insulation material for overhead conductors using the above-mentioned component ratio. It utilizes the reactive network structure formed by glycidyl methacrylate grafted polyethylene and ethylene-acrylic acid copolymer, combined with the synergistic reinforcing effect of functionalized molecular sieve-ZnO and modified SiO2, so that the material has good mechanical properties, electrical insulation properties, heat aging resistance and weather resistance.

[0025] The above-described technical solution of the present invention has at least the following beneficial effects: 1. This invention uses linear low-density polyethylene as the matrix and introduces glycidyl methacrylate-grafted polyethylene and ethylene-acrylic acid copolymer to form a reactive network structure. During melt blending and subsequent molding, epoxy groups and carboxyl groups undergo ring-opening reactions, improving the stability of the polymer network and restricting molecular chain movement, thereby improving the stability of the material under thermal conditions. Simultaneously, 4,4′-thiobis(6-tert-butyl-3-methylphenol), as a hindered phenolic antioxidant, can capture free radicals generated by thermo-oxidative aging, delaying the degradation of polyethylene molecular chains and improving the material's heat aging resistance.

[0026] 2. In functionalized molecular sieve-ZnO, the porous structure and large specific surface area of ​​the molecular sieve provide abundant interfaces, which are conducive to the formation of charge traps and restrict carrier migration, thereby improving the electrical insulation stability of the material. The ZnO loaded on its surface can absorb and scatter ultraviolet radiation, reducing the damage of ultraviolet light to the polyethylene molecular chains and improving the weather resistance of the material. At the same time, 3,5-diaminobenzoic acid forms an organic functional layer containing an aromatic amide structure on the surface of molecular sieve-ZnO through a condensation reaction. This functional layer is beneficial to regulating the surface properties of the composite particles and improving their dispersion stability. Its residual amino groups can react with the epoxy groups in glycidyl methacrylate-grafted polyethylene to enhance the interfacial bonding between the filler and the polyethylene matrix, reduce interfacial defects, and thus improve the mechanical properties, electrical insulation properties, and weather resistance of the insulation material.

[0027] 3. This invention uses hexamethyldisilazane to hydrophobically modify nano-SiO2, reducing its surface polarity and water adsorption capacity, thereby reducing the accumulation of water at the interface between the polymer and the filler; at the same time, it improves the dispersibility and interfacial stability of the filler, reduces the insulation performance degradation caused by water intrusion under humid and hot conditions, and improves the long-term humid and hot insulation stability of the material. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. The described embodiments are some embodiments of the present invention, and all other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0029] In the following examples, the 13X molecular sieve has a particle size of 1~5μm and a specific surface area of ​​600~800m². 2 / g; SiO2 particle size is 20~30nm; linear low-density polyethylene type is 2102TN00, density is 0.919~0.923g / cm³ 3 The melt flow rate is 2.5 g / 10 min; the ethylene-acrylic acid copolymer is model EAA5980, with an acrylic acid unit content of 8 wt%; the glycidyl methacrylate-grafted polyethylene has a grafting rate of 0.5%~0.6% and a density of 0.92 g / cm³. 3 .

[0030] Example 1 0.9 g ZnCl2 was added to 20 g deionized water and stirred for 12 min. Then 9 g 13X molecular sieve was added and stirred at 500 r / min at 85 °C for 55 min. Then 19 g 5 wt% sodium hydroxide solution was added dropwise. After the addition was completed, stirring was continued for 70 min. After cooling to room temperature, the precipitate was collected by centrifugation and washed four times with deionized water and anhydrous ethanol. The precipitate was dried under vacuum at 65 °C for 23 h and then heat-treated at 290 °C for 2.5 h to obtain molecular sieve-ZnO.

[0031] 7g of γ-aminopropyltriethoxysilane, 38g of anhydrous ethanol, and 6.5g of deionized water were mixed and sonicated for 25min to obtain a silane-modified solution. 6g of molecular sieve-ZnO was added to 125g of anhydrous ethanol and sonicated at 300W for 35min. Then, 51.5g of the silane-modified solution was added, and the mixture was stirred at 63℃ and 500r / min for 7h under nitrogen protection. The precipitate was collected by centrifugation, washed four times with anhydrous ethanol, and dried under vacuum at 65℃ for 11h to obtain aminated molecular sieve-ZnO.

[0032] 6g of aminated molecular sieve-ZnO, 0.6g of 3,5-diaminobenzoic acid, 6.5g of pyridine, and 6.5g of triphenyl phosphite were added to 190g of N-methylpyrrolidone and ultrasonically dispersed at 300W for 25min. The mixture was then stirred at 75℃ and 500r / min under nitrogen protection for 4h. After cooling to room temperature, the precipitate was collected by centrifugation and washed four times successively with N,N-dimethylformamide and methanol. The precipitate was then vacuum dried at 60℃ for 12h, ground, and passed through a 200-mesh sieve to obtain functionalized molecular sieve-ZnO.

[0033] 0.9 g of nano-SiO2 was vacuum dried at 105 °C for 7 h, cooled to room temperature, and then added to 90 g of anhydrous toluene. The mixture was ultrasonically dispersed at 300 W for 25 min, followed by the addition of 0.2 g of hexamethyldisilazane. Under nitrogen protection and reflux, the mixture was stirred at 105 °C and 450 r / min for 5 h. After cooling to room temperature, the precipitate was collected by centrifugation, washed four times with anhydrous ethanol, vacuum dried at 65 °C for 15 h, ground, and passed through a 200-mesh sieve to obtain modified SiO2.

[0034] 48g of linear low-density polyethylene, 34g of glycidyl methacrylate-grafted polyethylene, 19g of ethylene-acrylic acid copolymer, 2.5g of functionalized molecular sieve-ZnO, 0.9g of modified SiO2 and 0.9g of 4,4′-thiobis(6-tert-butyl-3-methylphenol) were added to a high-speed mixer and premixed at 600r / min for 18min. Then, the mixture was fed into a twin-screw extruder and melt-blended at 130℃. After extrusion, cooling and pelletizing, the mixture was vacuum dried at 65℃ for 5.5h to obtain polyethylene insulation material for overhead conductors.

[0035] Example 2 Add 0.8g ZnCl2 to 20g deionized water and mix for 10min. Then add 8g 13X molecular sieve and mix and stir at 500r / min at 80℃ for 50min. Then add 18g 5wt% sodium hydroxide solution dropwise. After the addition is complete, continue stirring for 60min. After cooling to room temperature, centrifuge to collect the precipitate. Wash it three times with deionized water and anhydrous ethanol. Dry it under vacuum at 60℃ for 22h. Then heat treat it at 280℃ for 2h to obtain molecular sieve-ZnO.

[0036] 6g of γ-aminopropyltriethoxysilane, 35g of anhydrous ethanol, and 5g of deionized water were mixed and sonicated for 20min to obtain a silane-modified solution. 5g of molecular sieve-ZnO was added to 120g of anhydrous ethanol and sonicated at 300W for 30min. 46g of the silane-modified solution was added, and the mixture was stirred at 60℃ and 500r / min for 6h under nitrogen protection. The precipitate was collected by centrifugation, washed three times with anhydrous ethanol, and vacuum dried at 60℃ for 10h to obtain aminated molecular sieve-ZnO.

[0037] 5g of aminated molecular sieve-ZnO, 0.5g of 3,5-diaminobenzoic acid, 5g of pyridine, and 5g of triphenyl phosphite were added to 180g of N-methylpyrrolidone and ultrasonically dispersed at 300W for 20min. The mixture was then stirred at 70℃ and 500r / min under nitrogen protection for 3h. After cooling to room temperature, the precipitate was collected by centrifugation and washed three times with N,N-dimethylformamide and methanol, respectively. The precipitate was then vacuum dried at 60℃ for 12h, ground, and passed through a 200-mesh sieve to obtain functionalized molecular sieve-ZnO.

[0038] 0.8 g of nano-SiO2 was vacuum dried at 100 °C for 6 h, cooled to room temperature, and then added to 80 g of anhydrous toluene. The mixture was ultrasonically dispersed at 300 W for 20 min, followed by the addition of 0.15 g of hexamethyldisilazane. Under nitrogen protection and reflux, the mixture was stirred at 100 °C and 400 r / min for 4 h. After cooling to room temperature, the precipitate was collected by centrifugation, washed three times with anhydrous ethanol, vacuum dried at 60 °C for 12 h, ground, and passed through a 200-mesh sieve to obtain modified SiO2.

[0039] 45g of linear low-density polyethylene, 32g of glycidyl methacrylate-grafted polyethylene, 18g of ethylene-acrylic acid copolymer, 2g of functionalized molecular sieve-ZnO, 0.8g of modified SiO2 and 0.8g of 4,4′-thiobis(6-tert-butyl-3-methylphenol) were added to a high-speed mixer and premixed at 600r / min for 15min. Then, the mixture was fed into a twin-screw extruder and melt-blended at 120℃. After extrusion, cooling and pelletizing, the mixture was vacuum dried at 60℃ for 5h to obtain polyethylene insulation material for overhead conductors.

[0040] Example 3 Add 1g ZnCl2 to 20g deionized water and mix for 15min. Then add 10g 13X molecular sieve and mix and stir at 500r / min at 90℃ for 60min. Then add 20g 5wt% sodium hydroxide solution dropwise. After the addition is complete, continue stirring for 80min. After cooling to room temperature, centrifuge to collect the precipitate. Wash it 5 times with deionized water and anhydrous ethanol. Dry it under vacuum at 70℃ for 24h. Then heat treat it at 300℃ for 3h to obtain molecular sieve-ZnO.

[0041] 8g of γ-aminopropyltriethoxysilane, 40g of anhydrous ethanol and 8g of deionized water were mixed and ultrasonically treated for 30min to obtain a silane-modified solution. 7g of molecular sieve-ZnO was added to 130g of anhydrous ethanol and ultrasonically dispersed at 300W for 40min. 56g of the silane-modified solution was added, and the mixture was stirred and reacted at 65℃ and 500r / min for 8h under nitrogen protection. The precipitate was collected by centrifugation, washed 5 times with anhydrous ethanol, and vacuum dried at 70℃ for 12h to obtain aminated molecular sieve-ZnO.

[0042] 7g of aminated molecular sieve-ZnO, 0.7g of 3,5-diaminobenzoic acid, 8g of pyridine, and 8g of triphenyl phosphite were added to 200g of N-methylpyrrolidone and ultrasonically dispersed at 300W for 30min. The mixture was then stirred at 80℃ and 500r / min under nitrogen protection for 5h. After cooling to room temperature, the precipitate was collected by centrifugation and washed five times successively with N,N-dimethylformamide and methanol. The precipitate was then vacuum dried at 60℃ for 12h, ground, and passed through a 200-mesh sieve to obtain functionalized molecular sieve-ZnO.

[0043] 1 g of nano-SiO2 was vacuum dried at 110 °C for 8 h, cooled to room temperature, and added to 100 g of anhydrous toluene. The mixture was ultrasonically dispersed at 300 W for 30 min, followed by the addition of 0.25 g of hexamethyldisilazane. Under nitrogen protection and reflux, the mixture was stirred at 110 °C and 500 r / min for 6 h. After cooling to room temperature, the precipitate was collected by centrifugation, washed five times with anhydrous ethanol, vacuum dried at 70 °C for 18 h, ground, and passed through a 200-mesh sieve to obtain modified SiO2.

[0044] 50g of linear low-density polyethylene, 35g of glycidyl methacrylate-grafted polyethylene, 20g of ethylene-acrylic acid copolymer, 3g of functionalized molecular sieve-ZnO, 1g of modified SiO2 and 1g of 4,4′-thiobis(6-tert-butyl-3-methylphenol) were added to a high-speed mixer and premixed at 600r / min for 20min. Then, the mixture was added to a twin-screw extruder and melt-blended at 150℃. After extrusion, cooling and pelletizing, the mixture was vacuum dried at 70℃ for 6h to obtain polyethylene insulation material for overhead conductors.

[0045] Example 4 0.85 g ZnCl2 was added to 20 g deionized water and stirred for 11 min. Then 8.5 g 13X molecular sieve was added and stirred at 500 r / min at 83 °C for 53 min. Then 18.5 g 5 wt% sodium hydroxide solution was added dropwise. After the addition was completed, stirring was continued for 65 min. After cooling to room temperature, the precipitate was collected by centrifugation and washed three times with deionized water and anhydrous ethanol. The precipitate was vacuum dried at 63 °C for 22.5 h and then heat-treated at 285 °C for 2.2 h to obtain molecular sieve-ZnO.

[0046] 6.5 g of γ-aminopropyltriethoxysilane, 36 g of anhydrous ethanol, and 6 g of deionized water were mixed and sonicated for 23 min to obtain a silane-modified solution. 5.5 g of molecular sieve-ZnO was added to 123 g of anhydrous ethanol and sonicated at 300 W for 33 min. Then, 48.5 g of the silane-modified solution was added, and the mixture was stirred at 62 °C and 500 r / min for 6.5 h under nitrogen protection. The precipitate was collected by centrifugation, washed three times with anhydrous ethanol, and vacuum dried at 63 °C for 10.5 h to obtain aminated molecular sieve-ZnO.

[0047] 5.5 g of aminated molecular sieve-ZnO, 0.55 g of 3,5-diaminobenzoic acid, 6 g of pyridine, and 6 g of triphenyl phosphite were added to 185 g of N-methylpyrrolidone and ultrasonically dispersed at 300 W for 23 min. The mixture was then stirred at 73 °C and 500 r / min under nitrogen protection for 3.5 h. After cooling to room temperature, the precipitate was collected by centrifugation and washed three times with N,N-dimethylformamide and methanol, respectively. The precipitate was then vacuum dried at 60 °C for 12 h, ground, and passed through a 200-mesh sieve to obtain functionalized molecular sieve-ZnO.

[0048] 0.85 g of nano-SiO2 was vacuum dried at 103 °C for 6.5 h, cooled to room temperature, and added to 85 g of anhydrous toluene. The mixture was ultrasonically dispersed at 300 W for 23 min, followed by the addition of 0.18 g of hexamethyldisilazane. Under nitrogen protection and reflux, the mixture was stirred at 103 °C and 430 r / min for 4.5 h. After cooling to room temperature, the precipitate was collected by centrifugation, washed three times with anhydrous ethanol, vacuum dried at 63 °C for 14 h, ground, and passed through a 200-mesh sieve to obtain modified SiO2.

[0049] 46g of linear low-density polyethylene, 33g of glycidyl methacrylate-grafted polyethylene, 18.5g of ethylene-acrylic acid copolymer, 2.2g of functionalized molecular sieve-ZnO, 0.85g of modified SiO2 and 0.85g of 4,4′-thiobis(6-tert-butyl-3-methylphenol) were added to a high-speed mixer and premixed at 600r / min for 16min. Then, the mixture was fed into a twin-screw extruder and melt-blended at 125℃. After extrusion, cooling and pelletizing, the mixture was vacuum dried at 63℃ for 5.2h to obtain polyethylene insulation material for overhead conductors.

[0050] Example 5 0.95 g ZnCl2 was added to 20 g deionized water and stirred for 14 min. Then 9.5 g 13X molecular sieve was added and stirred at 500 r / min at 88 °C for 58 min. Then 19.5 g 5 wt% sodium hydroxide solution was added dropwise. After the addition was completed, stirring was continued for 75 min. After cooling to room temperature, the precipitate was collected by centrifugation and washed 5 times with deionized water and anhydrous ethanol. The precipitate was vacuum dried at 68 °C for 23.5 h and then heat-treated at 295 °C for 2.8 h to obtain molecular sieve-ZnO.

[0051] 7.5 g of γ-aminopropyltriethoxysilane, 39 g of anhydrous ethanol, and 7 g of deionized water were mixed and ultrasonically treated for 28 min to obtain a silane-modified solution. 6.5 g of molecular sieve-ZnO was added to 128 g of anhydrous ethanol and ultrasonically dispersed at 300 W for 38 min. 53.5 g of the silane-modified solution was added, and the mixture was stirred and reacted at 64 °C and 500 r / min for 7.5 h under nitrogen protection. The precipitate was collected by centrifugation, washed 5 times with anhydrous ethanol, and vacuum dried at 68 °C for 11.5 h to obtain aminated molecular sieve-ZnO.

[0052] 6.5 g of aminated molecular sieve-ZnO, 0.65 g of 3,5-diaminobenzoic acid, 7 g of pyridine, and 7 g of triphenyl phosphite were added to 195 g of N-methylpyrrolidone and ultrasonically dispersed at 300 W for 28 min. The mixture was then stirred at 78 °C and 500 r / min under nitrogen protection for 4.5 h. After cooling to room temperature, the precipitate was collected by centrifugation and washed five times successively with N,N-dimethylformamide and methanol. The precipitate was then vacuum dried at 60 °C for 12 h, ground, and passed through a 200-mesh sieve to obtain functionalized molecular sieve-ZnO.

[0053] 0.95 g of nano-SiO2 was vacuum dried at 108 °C for 7.5 h, cooled to room temperature, and then added to 95 g of anhydrous toluene. The mixture was ultrasonically dispersed at 300 W for 28 min, followed by the addition of 0.23 g of hexamethyldisilazane. Under nitrogen protection and reflux, the mixture was stirred at 108 °C and 480 r / min for 5.5 h. After cooling to room temperature, the precipitate was collected by centrifugation, washed five times with anhydrous ethanol, vacuum dried at 68 °C for 16 h, ground, and passed through a 200-mesh sieve to obtain modified SiO2.

[0054] 49g of linear low-density polyethylene, 34.5g of glycidyl methacrylate-grafted polyethylene, 19.5g of ethylene-acrylic acid copolymer, 2.8g of functionalized molecular sieve-ZnO, 0.95g of modified SiO2 and 0.95g of 4,4′-thiobis(6-tert-butyl-3-methylphenol) were added to a high-speed mixer and premixed at 600r / min for 19min. Then, the mixture was fed into a twin-screw extruder and melt-blended at 140℃. After extrusion, cooling and pelletizing, the mixture was vacuum dried at 68℃ for 5.8h to obtain polyethylene insulation material for overhead conductors.

[0055] The present invention also includes comparative examples and related experiments.

[0056] Comparative Example 1 Compared with Example 1, the only difference is that no functionalized molecular sieve-ZnO was added. All other preparation steps and components are completely the same, and the final product is polyethylene insulation material for overhead conductors.

[0057] Comparative Example 2 Compared with Example 1, the only difference is that nano-SiO2 is used instead of modified SiO2, while the other preparation steps and components are completely the same, and the final product is polyethylene insulation material for overhead conductors.

[0058] Comparative Example 3 Compared with Example 1, the only difference is that glycidyl methacrylate-grafted polyethylene is replaced with an equal mass of linear low-density polyethylene, while the other preparation steps and components are completely the same, and the polyethylene insulation material for overhead conductors is finally obtained.

[0059] Comparative Example 4 Compared with Example 1, the only difference is that aminated molecular sieve-ZnO is used instead of functionalized molecular sieve-ZnO. The other preparation steps and components are completely the same, and the final product is polyethylene insulation material for overhead conductors.

[0060] Performance testing The polyethylene insulation materials for overhead conductors prepared in Examples 1-5 and Comparative Examples 1-4 were placed in molds and preheated at 110°C and 5 MPa for 8 minutes. The temperature was then increased to 185°C and the pressure increased to 15 MPa, held for 30 minutes, and then cooled to 50°C before depressurization and demolding to prepare samples. The tensile strength and elongation at break of the samples were determined according to GB / T2951.11-2008. Hot air aging tests were conducted according to GB / T2951.12-2008, and the retention rates of tensile strength and elongation at break were calculated. The volume resistivity was determined according to GB / T31838.2-2019. The breakdown strength was determined according to GB / T1408.1-2016. A xenon arc lamp aging test was conducted according to GB / T16422.2-2022 to evaluate the mechanical properties, heat aging resistance, electrical insulation properties, and weather resistance of the obtained polyethylene insulation materials.

[0061] The hot air aging test conditions were set at 135±2℃ for 168 hours; the xenon arc lamp aging test time was set at 1000 hours. After aging, the tensile strength and elongation at break of each sample were measured, and the corresponding performance retention rate was calculated. The specific test results are shown in Tables 1 and 2.

[0062] Table 1

[0063] As shown in Table 1, the polyethylene insulation materials for overhead conductors prepared in Examples 1-5 have a tensile strength of 21.8-22.4 MPa, an elongation at break of 512%-524%, and a volume resistivity of 1.57 × 10⁻⁶ MPa. 15 ~1.68×10 15 The breakdown strength is 34.5~35.6 kV / mm, exhibiting good basic mechanical properties and electrical insulation properties. Compared with Example 1, Comparative Example 1, without the addition of functionalized molecular sieve-ZnO, showed a significant decrease in volume resistivity and breakdown strength; Comparative Example 2, using nano-SiO2, also showed a reduction in electrical insulation properties; Comparative Example 3, after replacing glycidyl methacrylate-grafted polyethylene with an equal mass of linear low-density polyethylene, showed the most significant decrease in tensile strength and elongation at break; Comparative Example 4, after replacing functionalized molecular sieve-ZnO with aminated molecular sieve-ZnO, also showed lower tensile strength and elongation at break than Example 1.

[0064] Table 2

[0065] Table 2 shows that Examples 1-5 maintained high tensile strength and elongation at break retention rates after hot air aging and xenon arc lamp aging, indicating that the obtained polyethylene insulation materials have good heat aging resistance and weather resistance. Among them, Comparative Example 1, without the addition of functionalized molecular sieve-ZnO, showed the most significant decrease in performance retention rate after xenon arc lamp aging, and also a certain decrease in performance retention rate after heat aging; Comparative Example 3, without glycidyl methacrylate-grafted polyethylene, had the lowest performance retention rate after heat aging; Comparative Example 4, after replacing functionalized molecular sieve-ZnO with aminated molecular sieve-ZnO, also showed a certain decrease in performance retention rate after heat aging, indicating that functionalized molecular sieve-ZnO is beneficial for maintaining the material's performance after heat aging. In summary, this invention, through the optimization of raw materials and the addition of functional fillers, enables the obtained polyethylene insulation materials to possess good mechanical properties, electrical insulation properties, heat aging resistance, and weather resistance.

[0066] To evaluate the insulation stability of the obtained polyethylene insulation material under long-term humid and hot conditions, the samples prepared in Examples 1-5 and Comparative Examples 1-4 were placed in a constant temperature and humidity environment of 85±2℃ and 85±5% for 1000h. After being removed, they were adjusted to 23±2℃ and 50±5% relative humidity for 24h. Subsequently, the volume resistivity and breakdown strength of the samples after humid and hot treatment were measured, and the breakdown strength retention rate was calculated. The specific test results are shown in Table 3.

[0067] Table 3

[0068] As shown in Table 3, after 1000 hours of treatment in a humid and hot environment at 85±2℃ and 85±5% relative humidity, the polyethylene insulation materials for overhead conductors prepared in Examples 1-5 still maintained high volume resistivity and breakdown strength, with a breakdown strength retention rate of 94.5%~95.0%. In Comparative Example 2, after replacing modified SiO2 with nano-SiO2, the volume resistivity and breakdown strength retention rate after humid and hot treatment decreased significantly, indicating that modified SiO2 is beneficial to enhancing the insulation retention capacity of the material in a long-term humid and hot environment.

[0069] In summary, the polyethylene insulation material for overhead conductors prepared by this invention has good mechanical properties, electrical insulation properties, heat aging resistance, weather resistance, and insulation stability under long-term humid and hot environments. It can be used as an insulation material for overhead conductors in outdoor transmission lines.

[0070] The above are preferred embodiments of the present invention. Those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing polyethylene insulation material for overhead conductors, characterized in that, The steps include the following: S1. Aminated molecular sieve-ZnO, 3,5-diaminobenzoic acid, pyridine and triphenyl phosphite were added to N-methylpyrrolidone and ultrasonically dispersed. The mixture was heated and reacted under inert gas protection, cooled, centrifuged to collect the precipitate, washed, dried, ground and sieved to obtain functionalized molecular sieve-ZnO. S2. Vacuum-dried nano-SiO2, cooled and added to anhydrous toluene, ultrasonically dispersed, then hexamethyldisilazane was added, heated and reacted under inert gas protection, cooled, centrifuged to collect the precipitate, washed, dried, ground and sieved to obtain modified SiO2. S3. Linear low-density polyethylene, glycidyl methacrylate-grafted polyethylene, ethylene-acrylic acid copolymer, functionalized molecular sieve-ZnO, modified SiO2 and 4,4′-thiobis(6-tert-butyl-3-methylphenol) are melt-blended, extruded, cooled, pelletized and dried to obtain polyethylene insulation material for overhead conductors. The aminated molecular sieve-ZnO was obtained by ultrasonically dispersing molecular sieve-ZnO in anhydrous ethanol, adding silane modification solution, stirring the reaction under nitrogen protection, collecting the precipitate by centrifugation, washing, and vacuum drying.

2. The method for preparing polyethylene insulation material for overhead conductors according to claim 1, characterized in that, The aminated molecular sieve-ZnO was prepared by adding molecular sieve-ZnO to anhydrous ethanol, ultrasonically dispersing it at 300W for 30-40 min, adding silane modification solution, and stirring the mixture at 60-65℃ and 500r / min for 6-8 h under nitrogen protection. The precipitate was collected by centrifugation, washed 3-5 times with anhydrous ethanol, and vacuum dried at 60-70℃ for 10-12 h.

3. The method for preparing polyethylene insulation material for overhead conductors according to claim 2, characterized in that, The aminated molecular sieve-ZnO comprises the following raw materials in parts by weight: 5-7 parts molecular sieve-ZnO, 120-130 parts anhydrous ethanol, and 46-56 parts silane modification solution.

4. The method for preparing polyethylene insulation material for overhead conductors according to claim 2, characterized in that, The silane-modified solution is obtained by mixing γ-aminopropyltriethoxysilane, anhydrous ethanol, and deionized water, and ultrasonically treating for 20-30 minutes; the molecular sieve-ZnO is obtained by adding ZnCl2 to deionized water, mixing and stirring for 10-15 minutes, then adding 13X molecular sieve and mixing and stirring at 500 r / min at 80-90℃ for 50-60 minutes, then adding sodium hydroxide solution dropwise, and continuing to stir for 60-80 minutes after the addition is complete. After cooling to room temperature, the precipitate is collected by centrifugation, washed 3-5 times with deionized water and anhydrous ethanol, vacuum dried at 60-70℃ for 22-24 hours, and then heat-treated at 280-300℃ for 2-3 hours.

5. The method for preparing polyethylene insulation material for overhead conductors according to claim 4, characterized in that, The silane-modified solution comprises the following raw materials in parts by weight: 6-8 parts γ-aminopropyltriethoxysilane, 35-40 parts anhydrous ethanol and 5-8 parts deionized water; the molecular sieve-ZnO comprises the following raw materials in parts by weight: 0.8-1 parts ZnCl2, 20 parts deionized water, 8-10 parts 13X molecular sieve and 18-20 parts sodium hydroxide solution; the concentration of the sodium hydroxide is 5 wt%.

6. The method for preparing polyethylene insulation material for overhead conductors according to claim 1, characterized in that, In step S1, the aminated molecular sieve-ZnO, 3,5-diaminobenzoic acid, pyridine, and triphenyl phosphite are added to N-methylpyrrolidone and ultrasonically dispersed at 300W for 20-30 min. The mixture is then stirred and reacted at 70-80℃ and 500 r / min under nitrogen protection for 3-5 h. After cooling to room temperature, the precipitate is collected by centrifugation and washed 3-5 times with N,N-dimethylformamide and methanol, and then vacuum dried at 60℃ for 12 h. Finally, the mixture is ground and passed through a 200-mesh sieve to obtain the functionalized molecular sieve-ZnO.

7. The method for preparing polyethylene insulation material for overhead conductors according to claim 1, characterized in that, In step S2, nano-SiO2 is vacuum dried at 100-110℃ for 6-8 hours, cooled to room temperature, added to anhydrous toluene, and ultrasonically dispersed at 300W for 20-30 minutes. Then, hexamethyldisilazane is added, and the mixture is stirred at 100-110℃ and 400-500 r / min for 4-6 hours under nitrogen protection and reflux conditions. After cooling to room temperature, the precipitate is collected by centrifugation, washed 3-5 times with anhydrous ethanol, vacuum dried at 60-70℃ for 12-18 hours, ground, and passed through a 200-mesh sieve to obtain modified SiO2.

8. The method for preparing polyethylene insulation material for overhead conductors according to claim 1, characterized in that, The functionalized molecular sieve-ZnO comprises the following raw materials in parts by weight: 5-7 parts of aminated molecular sieve-ZnO, 0.5-0.7 parts of 3,5-diaminobenzoic acid, 5-8 parts of pyridine, 5-8 parts of triphenyl phosphite, and 180-200 parts of N-methylpyrrolidone; the modified SiO2 comprises the following raw materials in parts by weight: 0.8-1 parts of nano-SiO2, 80-100 parts of anhydrous toluene, and 0.15-0.25 parts of hexamethyldisilazane.

9. A method for preparing polyethylene insulation material for overhead conductors according to claim 1, characterized in that, In step S3, linear low-density polyethylene, glycidyl methacrylate-grafted polyethylene, ethylene-acrylic acid copolymer, functionalized molecular sieve-ZnO, modified SiO2, and 4,4′-thiobis(6-tert-butyl-3-methylphenol) are added to a high-speed mixer and premixed at 600 r / min for 15-20 min. Then, the mixture is added to a twin-screw extruder and melt-blended at 120-150°C. After extrusion, cooling, pelletizing, and vacuum drying at 60-70°C for 5-6 h, polyethylene insulation material for overhead conductors is obtained.

10. A polyethylene insulation material for overhead conductors, characterized in that, The material is prepared using the method for preparing polyethylene insulation for overhead conductors according to any one of claims 1 to 9, comprising the following parts by weight of raw materials: 45 to 50 parts of linear low-density polyethylene, 32 to 35 parts of glycidyl methacrylate-grafted polyethylene, 18 to 20 parts of ethylene-acrylic acid copolymer, 2 to 3 parts of functionalized molecular sieve-ZnO, 0.8 to 1 part of modified SiO2, and 0.8 to 1 part of 4,4′-thiobis(6-tert-butyl-3-methylphenol).

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