Crosslinked polyethylene reinforced high-strength insulated overhead cable

Abstract

The invention discloses a crosslinked polyethylene reinforced high-strength insulating aerial cable, and belongs to the technical field of crosslinked polyethylene cable materials.The crosslinked polyethylene reinforced high-strength insulating aerial cable is prepared by the steps that hydroxyl is introduced to nano boron nitride powder, then amino is grafted through KH-550, nano alpha-Al2O3 powder is modified through gamma-glycidyl ether oxypropyl trimethoxy silane, and the cross-linked polyethylene reinforced high-strength insulating aerial cable is obtained; the preparation method comprises the following steps: preparing low-density polyethylene, compounding the low-density polyethylene with aminated nano boron nitride powder to form nano composite powder, improving the interface bonding force between the low-density polyethylene and the nano composite powder, carrying out melt blending on the low-density polyethylene and the nano composite powder to improve the dispersity of the nano composite powder in the low-density polyethylene, and carrying out nucleophilic acyl substitution reaction to obtain a fluorine-containing modified monomer. The nano boron nitride powder and the nano alpha-Al2O3 powder are subjected to a cross-linking reaction under the initiation action of an initiator and then coat the exterior of the thermal insulation layer, and the nano boron nitride powder and the nano alpha-Al2O3 powder are bridged through siloxane bonds to form a three-dimensional heat-conducting network, so that the heat resistance of the outer insulating layer is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of cross-linked polyethylene cable materials, in particular to a cross-linked polyethylene reinforced high-strength insulated overhead cable. Background Art

[0002] As power systems evolve toward higher voltages, larger capacities, and longer-distance transmission, traditional overhead insulated cables (such as PVC or ordinary polyethylene insulated cables) are increasingly exposed to problems such as poor heat resistance, insufficient mechanical strength, and limited environmental adaptability. Under high-temperature or high-current load conditions, traditional thermoplastic insulation materials are prone to thermal deformation and insulation aging, leading to a decrease in dielectric properties and even partial discharge or breakdown. Furthermore, overhead cables are constantly exposed to ultraviolet light, rainwater erosion, and complex meteorological conditions, and their tensile strength and resistance to environmental stress cracking directly impact the safety and reliability of grid operations. The emergence of cross-linked polyethylene (XLPE) technology offers a breakthrough solution to these problems. Through chemical or radiation cross-linking, a three-dimensional network structure is formed between polyethylene molecular chains, significantly improving the material's heat resistance (from 75°C to 90°C-130°C), mechanical strength, and creep resistance.

[0003] Chinese invention patent application CN114300188B discloses a cross-linked polyethylene (XLPE) insulated, corrosion-resistant power cable. The insulation layer is made of XLPE, which comprises the following raw materials: low-density polyethylene (LDPE), a cross-linking agent, a water tree growth inhibitor, and an antioxidant. The antioxidant's molecule contains a hindered phenol structure, a siloxane structure, and double bonds. The double bonds participate in the cross-linking of the polyethylene, fixing the hindered phenol structure and improving the stability of the polyethylene's aging resistance. This, in turn, enhances the insulation and mechanical properties of the XLPE material. The siloxane structure allows the antioxidant to be evenly distributed throughout the polyethylene base material.

[0004] Under the harsh working conditions of chemical parks, the outer insulation layer of the cable is exposed to acid, alkali and organic solvent media for a long time. In addition, the thermal activation effect of local high temperature around the reactor can accelerate the penetration of chemical media into the interior through the micro cracks of the outer insulation layer. When overhead cables are in this environment for a long time, the outer insulation layer is prone to lose its insulation protection function. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-strength insulated overhead cable reinforced with cross-linked polyethylene, which is obtained by melt-blending nanocomposite powder with low-density polyethylene, and then cross-linking with a fluorine-containing modified monomer to obtain a modified cross-linked polyethylene copolymer, which is then prepared into an outer insulation layer, thereby achieving the effect of high-temperature corrosion resistance.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A cross-linked polyethylene reinforced high-strength insulated overhead cable comprises, from the inside to the outside, a conductor, a filler layer, an inner insulating layer, a shielding layer, a thermal insulation layer, and an outer insulating layer, wherein the outer insulating layer is prepared by the following steps:

[0008] Step 1: Introduce hydroxyl groups on the nano-boron nitride powder to obtain hydroxylated nano-boron nitride powder, then modify it with KH-550 to obtain amino-dipeptide nano-boron nitride powder, modify the nano-α-Al2O3 powder with γ-glycidyloxypropyltrimethoxysilane to obtain modified nano-α-Al2O3 powder, and then compound it with amino-dipeptide nano-boron nitride powder to obtain nano-composite powder.

[0009] Step 2: melt-blending the low-density polyethylene and the nanocomposite powder to obtain modified polyethylene.

[0010] Step 3: Grafting hexafluorobisphenol A and acryloyl chloride through a nucleophilic acyl substitution reaction to obtain a fluorine-containing modified monomer, and chemically cross-linking the modified polyethylene and the fluorine-containing modified monomer to obtain a modified cross-linked polyethylene copolymer.

[0011] Step 4: Use an extruder to wrap the modified cross-linked polyethylene copolymer on the outside of the thermal insulation layer to obtain an outer insulation layer.

[0012] Furthermore, hydroxylated nano boron nitride powder is prepared by the following steps:

[0013] Add nano boron nitride powder and 3 mol / L sodium hydroxide solution into a reactor, perform ultrasonic dispersion, reflux at 80-90° C. for 24-26 hours, cool to room temperature, filter, wash, and dry to obtain hydroxylated nano boron nitride powder.

[0014] Furthermore, the usage ratio of nano boron nitride powder and sodium hydroxide solution is 1.5-2 g: 150-160 mL.

[0015] Furthermore, the amination-modified nano-boron nitride powder is prepared by the following steps:

[0016] KH-550 and a 50 vol% ethanol aqueous solution are added to a reactor, the pH value is adjusted to 4-5 with acetic acid, and the reaction is carried out at 60-65°C and 300-500 r / min for 30-40 minutes. Then, hydroxylated nano-boron nitride powder and an 80 vol% ethanol aqueous solution are added to the reactor, ultrasonically dispersed, reacted for 6 hours, filtered, washed, and dried to obtain amino-treated nano-boron nitride powder.

[0017] Furthermore, the usage ratio of KH-550, 50 vol% ethanol aqueous solution, hydroxylated nano-boron nitride powder and 80 vol% ethanol aqueous solution is 2-4 mL: 20-30 mL: 1-2 g: 200-300 mL.

[0018] Furthermore, the nanocomposite powder is prepared by the following steps:

[0019] γ-glycidyloxypropyltrimethoxysilane and a 50 vol% ethanol aqueous solution are added to a reactor, the pH value is adjusted to 4-5 with acetic acid, and the reaction is carried out at 60-65°C and 500-800 r / min for 30-40 minutes. Nano α-Al2O3 powder with a particle size of 30-50 nm and a 80 vol% ethanol aqueous solution are added to the reactor, ultrasonically dispersed, reacted for 6-8 hours, filtered, washed, and dried to obtain modified nano α-Al2O3 powder; amino nano boron nitride powder and modified nano α-Al2O3 powder are added to the reactor, dispersed with deionized water to a solid content of 5%, adjusted to a pH of 8 with ammonia water, reacted for 24-26 hours, filtered, washed, dried, and ground to obtain nano composite powder.

[0020] Furthermore, the usage ratio of γ-glycidyloxypropyltrimethoxysilane, 50 vol% ethanol aqueous solution, nano α-Al2O3 powder and 80 vol% ethanol aqueous solution is 3-5 mL: 20-30 mL: 4-5 g: 200-300 mL; the usage ratio of modified nano α-Al2O3 powder and amino-treated nano boron nitride powder is 4-5 g: 1-2 g.

[0021] Furthermore, the modified polyethylene is prepared by the following steps:

[0022] Low-density polyethylene, KH-550 and nano-composite powder are uniformly mixed and melt-blended using a twin-screw extruder at a temperature of 110-115° C. and a rotation speed of 100-200 r / min to obtain modified polyethylene.

[0023] Furthermore, the usage ratio of low-density polyethylene, KH-550 and nano-composite powder is 40-50 g: 0.5-1 mL: 1.5-2 g.

[0024] Furthermore, the usage ratio of hexafluorobisphenol A, triethylamine, dichloromethane and acryloyl chloride is 3-4 g: 2.4-3 mL: 70-80 mL: 2.3-3 mL.

[0025] Furthermore, the fluorine-containing modified monomer is prepared by the following steps:

[0026] Hexafluorobisphenol A, triethylamine and dichloromethane are added to a reactor, stirred for 30-40 minutes under nitrogen protection, 0-4°C and 300-500r / min, and then acryloyl chloride is dropped into the reactor, reacted for 3-4 hours, filtered, extracted, dried, and rotary evaporated to obtain a fluorine-containing modified monomer.

[0027] Furthermore, the usage ratio of hexafluorobisphenol A, triethylamine, dichloromethane and acryloyl chloride is 3-4 g: 2.4-3 mL: 70-80 mL: 2.3-3 mL.

[0028] Furthermore, the modified cross-linked polyethylene copolymer is prepared by the following steps:

[0029] Antioxidant 1010, dicumyl peroxide, modified polyethylene and fluorine-containing modified monomer are added to a rheometer, mixed at 110-115°C and 50-100 r / min for 7-10 minutes, and vulcanized and cross-linked on a flat vulcanizer at a temperature of 173-178°C and a pressure of 15-17 MPa for 30-45 minutes. The mixture is short-circuited at 80-90°C for 48-50 hours to obtain a modified cross-linked polyethylene copolymer.

[0030] Furthermore, the usage ratio of antioxidant 1010, dicumyl peroxide, modified polyethylene and fluorine-containing modified monomer is 0.12-0.2 g: 0.52-1.0 g: 42-50 g: 2-4 g.

[0031] Beneficial effects of the present invention:

[0032] 1. The outer insulation layer of the cross-linked polyethylene reinforced high-strength insulated overhead cable in the present invention is prepared by first introducing hydroxyl groups into nano-boron nitride powder, then grafting amino groups onto it through KH-550, modifying nano-α-Al2O3 powder by γ-glycidyloxypropyltrimethoxysilane, and then compounding it with amino-treated nano-boron nitride powder to form a nano-composite powder to enhance the interfacial bonding strength between the two, and then melt-blending low-density polyethylene and the nano-composite powder to enhance the dispersibility of the nano-composite powder in the low-density polyethylene.

[0033] A fluorine-containing modified monomer is obtained by a nucleophilic acyl substitution reaction, and then a cross-linking reaction is generated with modified polyethylene under the initiation of an initiator, and then coated on the outside of the thermal insulation layer. Nano boron nitride powder and nano α-Al2O3 powder are bridged by siloxane bonds to form a three-dimensional thermal conductive network, which improves the heat resistance of the outer insulation layer. In addition, the strong electronegativity and high bond energy of fluorine atoms resist electrophilic or nucleophilic attacks of acids and alkalis. At the same time, fluorine atoms can also form a super-hydrophobic surface, and acid and alkali solutions are difficult to adhere to the surface. The boron-nitrogen bond of boron nitride is stable and can resist the attack of hydrogen ions in the acid, reflecting acid resistance. Nano α-Al2O3 powder has a compact crystal structure that can play an alkali-resistant effect, and a passivation layer will also be generated in strong alkali. The synergistic effect of the three can show the effect of acid and alkali corrosion resistance in a high temperature environment, maintain the insulating effect of the outer insulation layer, and improve the service life of the cross-linked polyethylene reinforced high-strength insulated overhead cable.

[0034] 2. The nanocomposite powder of the present invention first uses a strong base to form hydroxyl groups on the surface of the nano-boron nitride powder, and then uses the hydroxyl groups to react with the silanol groups on KH-550 to form Si-O-B bonds. At the same time, the silanol groups generated by the hydrolysis of γ-glycidyloxypropyltrimethoxysilane react with the hydroxyl groups of the nano-α-Al2O3 powder to form Si-O-Al bonds. Then, the epoxy groups on the γ-glycidyloxypropyltrimethoxysilane react with the amino groups on the KH-550 to form a cross-linked network. The crystal structure of the nano-α-Al2O3 powder can provide rigid support, and the nano-boron nitride powder can absorb stress through intermolecular slip. The two complement each other, which can not only improve the strength of the outer insulating layer without reducing toughness, but also improve the tensile strength of the outer insulating layer. At the same time, the cross-linked network can reduce interface defects, inhibit space charge accumulation, and reduce the risk of interface breakdown. The benzene ring of the fluorine-containing modified monomer has the ability to suppress conductive current at high temperatures, while the nano-boron nitride powder and nano-α-Al2O3 powder are acid and alkali resistant and still have excellent insulation properties under acid and alkali conditions.

[0035] 3. In the present invention, the hydroxyl group of hexafluorobisphenol A and the acyl chloride bond of acryloyl chloride react to form an ester bond, thereby introducing a fluorine group into the fluorine-containing modified monomer, and then the nano-composite powder and low-density polyethylene are melt-blended, and then cross-linking occurs under the initiation of the initiator diisopropylbenzene peroxide to form a modified cross-linked polyethylene copolymer. The carbon-carbon double bonds in the fluorine-containing modified monomer are opened to form carbon-carbon cross-linked bonds with the modified polyethylene chain. The network structure of the nano-composite powder further improves the cross-linking density of the two. In addition, the modified cross-linked polyethylene copolymer decomposes at high temperature to release highly reactive fluorine free radicals, which capture hydrogen free radicals in the combustion chain reaction to generate hydrogen fluoride. It can also form a dense fluorine-rich carbon layer to isolate heat, while boron nitride can form a dense boric acid glass layer covering the surface of the material at high temperature. Nano-α-Al2O3 powder can fill the pores of the material to form a dense structure layer to isolate oxygen, thereby synergistically improving the flame retardant properties of the outer insulating layer. DETAILED DESCRIPTION

[0036] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0037] Example 1: This example provides a cross-linked polyethylene reinforced high-strength insulated overhead cable, which is prepared by the following steps:

[0038] S1: 1.75 g of nano-boron nitride powder and 155 mL of 3 mol / L sodium hydroxide solution were added to a reactor, ultrasonically dispersed for 50 min, refluxed at 85°C for 25 h, cooled to room temperature, filtered, and the precipitate was washed with deionized water until neutral, and freeze-dried to obtain hydroxylated nano-boron nitride powder.

[0039] S2: 3 mL of KH-550 and 25 mL of a 50 vol% ethanol aqueous solution were added to a reactor, the pH value was adjusted to 4 with acetic acid, and the reaction was carried out at 62°C and 400 r / min for 35 min. 1.5 g of hydroxylated nano-boron nitride powder and 250 mL of an 80 vol% ethanol aqueous solution were added to the reactor, ultrasonically dispersed for 1.5 h, and reacted at 62°C and 650 r / min for 7 h. KH-550 was hydrolyzed to produce silanol groups, which formed Si-OB bonds with the hydroxyl groups on the hydroxylated nano-boron nitride powder, introducing amino groups into the hydroxylated nano-boron nitride powder. The precipitate was centrifuged and washed four times with deionized water and ethanol, and vacuum dried at 65°C for 25 h to obtain amino-treated nano-boron nitride powder.

[0040] S3: 4 mL of γ-glycidyloxypropyltrimethoxysilane and 25 mL of a 50 vol% ethanol aqueous solution were added to a reactor, the pH value was adjusted to 4 with acetic acid, and the reaction was carried out at 62°C and 400 r / min for 35 min. 4.5 g of nano-α-Al2O3 powder with a particle size of 30-50 nm (model HN-L100260, purchased from Hangzhou Hengna New Materials Co., Ltd.) and 250 mL of an 80 vol% ethanol aqueous solution were added to the reactor, ultrasonically dispersed for 1.5 h, and reacted at 62°C and 350 r / min for 7 h. After hydrolysis of γ-glycidyloxypropyltrimethoxysilane, silanol groups were generated, which reacted with hydroxyl groups on the nano-α-Al2O3 powder to form Si-O-Al bonds. The precipitate was centrifuged and washed four times with deionized water and ethanol, and vacuum dried at 65°C for 25 h to obtain modified nano-α-Al2O3 powder.

[0041] Then, 1.5 g of amination-modified nano-boron nitride powder and 4.5 g of modified nano-α-Al2O3 powder were added to the reactor, dispersed with deionized water to a solid content of 5%, adjusted to a pH of 8 with ammonia water, and reacted at 62°C and 650 r / min for 25 h. The epoxy groups on γ-glycidyloxypropyltrimethoxysilane reacted with the amino groups on the amination-modified nano-boron nitride powder to form a cross-linked network. The mixture was centrifuged and filtered. The precipitate was washed four times with deionized water and ethanol, dried in vacuo at 65°C for 25 h, ground, and passed through a 200-mesh sieve to obtain a nano-composite powder.

[0042] S4: 45 g of low-density polyethylene, 0.75 mL of KH-550 and 1.75 g of nanocomposite powder were mixed uniformly, and melt-blended using a twin-screw extruder with the temperature set at 112° C. and the rotation speed set at 150 r / min to obtain modified polyethylene.

[0043] S5: 3.5 g of hexafluorobisphenol A, 2.7 mL of triethylamine and 75 mL of dichloromethane were added to a reactor, and stirred for 35 min under nitrogen protection, 2°C and 400 r / min. Then 2.6 mL of acryloyl chloride was dropwise added to the reactor and reacted for 3.5 h. The phenolic hydroxyl group of hexafluorobisphenol A and the acyl chloride bond of acryloyl chloride underwent nucleophilic acyl substitution to form an ester bond. The precipitate was removed by centrifugation, and the filtrate was extracted three times with 1 mol / L hydrochloric acid solution, 1 mol / L sodium hydroxide solution and deionized water. The filtrate was dried over anhydrous magnesium sulfate and rotary evaporated to obtain a fluorine-containing modified monomer.

[0044] S6: 0.16g of antioxidant 1010, 0.76g of diisopropylbenzene peroxide as an initiator, 46g of modified polyethylene and 3g of fluorine-containing modified monomer were added to the rheometer, mixed at 112°C and 75r / min for 8min, and then vulcanized and cross-linked on a flat vulcanizer. The cross-linking reaction was carried out at 175°C and 16MPa for 37min. Diisopropylbenzene peroxide decomposed to produce alkyl free radicals, which captured hydrogen atoms from the chain of the prepolymer composite. The carbon-carbon double bonds on the fluorine-containing modified monomer opened and formed carbon-carbon cross-linked bonds with the modified polyethylene chain. The sample was cooled to room temperature and short-circuited in a vacuum drying oven at 82°C for 49h to eliminate the internal stress of the sample to obtain a modified cross-linked polyethylene copolymer.

[0045] S7: The metal wires are concentrically twisted to obtain a cable core, and the conductor composed of the cable core is sent to an extruder. The extruder sequentially extrudes fillers and an inner insulating layer on the outside of the conductor, and then a cable braiding machine uses copper wire to weave a shielding layer on the outside of the inner insulating layer. The extruder is then used to extrude a thermal insulation layer on the outside of the shielding layer, and the extruder is then used to cover the modified cross-linked polyethylene copolymer on the outside of the thermal insulation layer to form an outer insulating layer, thereby obtaining a cross-linked polyethylene reinforced high-strength insulated overhead cable.

[0046] Example 2: This example provides a cross-linked polyethylene reinforced high-strength insulated overhead cable, which is prepared by the following steps:

[0047] S1: 1.5 g of nano-boron nitride powder and 150 mL of 3 mol / L sodium hydroxide solution were added to a reactor, ultrasonically dispersed for 40 min, refluxed at 80°C for 24 h, cooled to room temperature, filtered, and the precipitate was washed with deionized water until neutral, and freeze-dried to obtain hydroxylated nano-boron nitride powder.

[0048] S2: 2 mL of KH-550 and 20 mL of a 50 vol% ethanol aqueous solution were added to a reactor, the pH value was adjusted to 4 with acetic acid, and the reaction was carried out at 60°C and 300 r / min for 30 min. 1 g of hydroxylated nano-boron nitride powder and 200 mL of an 80 vol% ethanol aqueous solution were added to the reactor, ultrasonically dispersed for 1 h, and reacted at 60°C and 500 r / min for 6 h. KH-550 was hydrolyzed to produce silanol groups, which formed Si-OB bonds with the hydroxyl groups on the hydroxylated nano-boron nitride powder, introducing amino groups into the hydroxylated nano-boron nitride powder. The precipitate was centrifuged and washed three times with deionized water and ethanol, and vacuum dried at 60°C for 24 h to obtain amino-treated nano-boron nitride powder.

[0049] S3: 3 mL of γ-glycidyloxypropyltrimethoxysilane and 20 mL of a 50 vol% ethanol aqueous solution were added to a reactor, the pH value was adjusted to 4 with acetic acid, and the mixture was reacted at 60°C and 300 r / min for 30 min. 4 g of nano-α-Al2O3 powder (model HN-L100260, purchased from Hangzhou Hengna New Materials Co., Ltd.) with a particle size of 30-50 nm and 200 mL of an 80 vol% ethanol aqueous solution were added to the reactor, ultrasonically dispersed for 1 h, and reacted at 60°C and 500 r / min for 6 h. γ-glycidyloxypropyltrimethoxysilane was hydrolyzed to produce silanol groups, which reacted with the hydroxyl groups on the nano-α-Al2O3 powder to form Si-O-Al bonds. The mixture was centrifuged and filtered. The precipitate was washed three times with deionized water and ethanol, and dried in vacuo at 60°C for 24 h to obtain modified nano-α-Al2O3 powder.

[0050] Then add 1g of amination-treated nano-boron nitride powder and 4g of modified nano-α-Al2O3 powder into the reactor, disperse them with deionized water to a solid content of 5%, adjust the pH value to 8 with ammonia water, react at 60°C and 500r / min for 24h, and the epoxy groups on γ-glycidyloxypropyltrimethoxysilane react with the amino groups on the amination-treated nano-boron nitride powder to form a cross-linked network. Centrifugal filtration is performed, and the precipitate is washed three times with deionized water and ethanol, vacuum dried at 60°C for 24h, ground, and passed through a 200-mesh sieve to obtain a nano-composite powder.

[0051] S4: 40 g of low-density polyethylene, 0.5 mL of KH-550 and 1.5 g of nanocomposite powder were mixed uniformly, and melt-blended using a twin-screw extruder with the temperature set at 110° C. and the rotation speed set at 100 r / min to obtain modified polyethylene.

[0052] S5: 3 g of hexafluorobisphenol A, 2.4 mL of triethylamine and 70 mL of dichloromethane were added to a reactor, and stirred for 30 min under nitrogen protection, 0°C and 300 r / min. Then 2.3 mL of acryloyl chloride was dropwise added to the reactor and reacted for 3 h. The phenolic hydroxyl group of hexafluorobisphenol A and the acyl chloride bond of acryloyl chloride underwent nucleophilic acyl substitution to form an ester bond. The precipitate was removed by centrifugation, and the filtrate was extracted three times with 1 mol / L hydrochloric acid solution, 1 mol / L sodium hydroxide solution and deionized water. The filtrate was dried over anhydrous magnesium sulfate and rotary evaporated to obtain a fluorine-containing modified monomer.

[0053] S6: 0.12g of antioxidant 1010, 0.52g of diisopropylbenzene peroxide as an initiator, 42g of modified polyethylene and 2g of fluorine-containing modified monomer were added to the rheometer, mixed at 110°C and 50r / min for 7min, and then vulcanized and cross-linked on a flat vulcanizer. The cross-linking reaction was carried out at 173°C and 15MPa for 30min. Diisopropylbenzene peroxide decomposed to produce alkyl free radicals, which captured hydrogen atoms from the chain of the prepolymer composite. The carbon-carbon double bonds on the fluorine-containing modified monomer opened and formed carbon-carbon cross-linked bonds with the modified polyethylene chain. The sample was cooled to room temperature and short-circuited in a vacuum drying oven at 80°C for 48h to eliminate the internal stress of the sample to obtain a modified cross-linked polyethylene copolymer.

[0054] S7: The metal wires are concentrically twisted to obtain a cable core, and the conductor composed of the cable core is sent to an extruder. The extruder sequentially extrudes fillers and an inner insulating layer on the outside of the conductor, and then a cable braiding machine uses copper wire to weave a shielding layer on the outside of the inner insulating layer. The extruder is then used to extrude a thermal insulation layer on the outside of the shielding layer, and the extruder is then used to cover the modified cross-linked polyethylene copolymer on the outside of the thermal insulation layer to form an outer insulating layer, thereby obtaining a cross-linked polyethylene reinforced high-strength insulated overhead cable.

[0055] Example 3: This example provides a cross-linked polyethylene reinforced high-strength insulated overhead cable, which is prepared by the following steps:

[0056] S1: 2 g of nano-boron nitride powder and 160 mL of 3 mol / L sodium hydroxide solution were added to a reactor, ultrasonically dispersed for 60 min, refluxed at 90°C for 26 h, cooled to room temperature, filtered, and the precipitate was washed with deionized water until neutral, and freeze-dried to obtain hydroxylated nano-boron nitride powder.

[0057] S2: 4 mL of KH-550 and 30 mL of a 50 vol% ethanol aqueous solution were added to a reactor, the pH value was adjusted to 5 with acetic acid, and the reaction was carried out at 65°C and 500 r / min for 40 min. 2 g of hydroxylated nano-boron nitride powder and 300 mL of an 80 vol% ethanol aqueous solution were added to the reactor, ultrasonically dispersed for 2 h, and reacted at 65°C and 800 r / min for 8 h. KH-550 was hydrolyzed to produce silanol groups, which formed Si-OB bonds with the hydroxyl groups on the hydroxylated nano-boron nitride powder, introducing amino groups into the hydroxylated nano-boron nitride powder. The precipitate was centrifuged and washed with deionized water and ethanol 5 times, and vacuum dried at 70°C for 26 h to obtain amino-containing nano-boron nitride powder.

[0058] S3: 5 mL of γ-glycidyloxypropyltrimethoxysilane and 30 mL of a 50 vol% ethanol aqueous solution were added to a reactor, the pH value was adjusted to 5 with acetic acid, and the mixture was reacted at 65°C and 500 r / min for 40 min. 5 g of nano-α-Al2O3 powder (model HN-L100260, purchased from Hangzhou Hengna New Materials Co., Ltd.) with a particle size of 30-50 nm and 300 mL of an 80 vol% ethanol aqueous solution were added to the reactor, ultrasonically dispersed for 2 h, and reacted at 65°C and 800 r / min for 8 h. γ-glycidyloxypropyltrimethoxysilane was hydrolyzed to produce silanol groups, which reacted with the hydroxyl groups on the nano-α-Al2O3 powder to form Si-O-Al bonds. The mixture was centrifuged and filtered, and the precipitate was washed 5 times with deionized water and ethanol, and vacuum dried at 70°C for 26 h to obtain modified nano-α-Al2O3 powder.

[0059] Then, 2 g of amination-modified nano-boron nitride powder and 5 g of modified nano-α-Al2O3 powder were added to the reactor, dispersed with deionized water to a solid content of 5%, adjusted to a pH of 8 with ammonia water, and reacted at 65°C and 800 r / min for 26 h. The epoxy groups on γ-glycidyloxypropyltrimethoxysilane reacted with the amino groups on the amination-modified nano-boron nitride powder to form a cross-linked network. The mixture was centrifuged and filtered. The precipitate was washed 5 times with deionized water and ethanol, vacuum dried at 70°C for 26 h, ground, and passed through a 200-mesh sieve to obtain a nano-composite powder.

[0060] S4: 50 g of low-density polyethylene, 1 mL of KH-550 and 2 g of nanocomposite powder were mixed uniformly, and melt-blended using a twin-screw extruder with the temperature set at 115° C. and the rotation speed set at 200 r / min to obtain modified polyethylene.

[0061] S5: 4 g of hexafluorobisphenol A, 3 mL of triethylamine and 80 mL of dichloromethane were added to a reactor, and stirred for 40 min under nitrogen protection, 4°C and 500 r / min. Then 3 mL of acryloyl chloride was dropwise added to the reactor and reacted for 4 h. The phenolic hydroxyl group of hexafluorobisphenol A and the acyl chloride bond of acryloyl chloride underwent nucleophilic acyl substitution to form an ester bond. The precipitate was removed by centrifugation, and the filtrate was extracted three times with 1 mol / L hydrochloric acid solution, 1 mol / L sodium hydroxide solution and deionized water. The filtrate was dried over anhydrous magnesium sulfate and rotary evaporated to obtain a fluorine-containing modified monomer.

[0062] S6: 0.2g of antioxidant 1010, 1.0g of diisopropylbenzene peroxide as an initiator, 50g of modified polyethylene and 4g of fluorine-containing modified monomer were added to the rheometer, mixed at 115°C and 100r / min for 10min, and then vulcanized and cross-linked on a flat vulcanizer. The cross-linking reaction was carried out at 178°C and 17MPa for 45min. Diisopropylbenzene peroxide decomposed to produce alkyl free radicals, which captured hydrogen atoms from the chain of the prepolymer composite. The carbon-carbon double bonds on the fluorine-containing modified monomer opened and formed carbon-carbon cross-linked bonds with the modified polyethylene chain. The sample was cooled to room temperature and short-circuited in a vacuum drying oven at 85°C for 50h to eliminate the internal stress of the sample to obtain a modified cross-linked polyethylene copolymer.

[0063] S7: The metal wires are concentrically twisted to obtain a cable core, and the conductor composed of the cable core is sent to an extruder. The extruder sequentially extrudes fillers and an inner insulating layer on the outside of the conductor, and then a cable braiding machine uses copper wire to weave a shielding layer on the outside of the inner insulating layer. The extruder is then used to extrude a thermal insulation layer on the outside of the shielding layer, and the extruder is then used to cover the modified cross-linked polyethylene copolymer on the outside of the thermal insulation layer to form an outer insulating layer, thereby obtaining a cross-linked polyethylene reinforced high-strength insulated overhead cable.

[0064] Comparative Example 1: Based on Example 1, nano-α-Al2O3 powder (purchased from Hangzhou Hengna New Materials Co., Ltd.) was used instead of nano-composite powder in step S4, and subsequent steps remained unchanged to prepare a cross-linked polyethylene reinforced high-strength insulated overhead cable.

[0065] Comparative Example 2: Based on Example 1, the hydroxylated nano-boron nitride powder prepared in step S1 is used instead of the nano-composite powder in step S4, and the subsequent steps remain unchanged to prepare a cross-linked polyethylene reinforced high-strength insulated overhead cable.

[0066] Comparative Example 3: Based on Example 1, the fluorine-containing modified monomer is removed in step S6, and the subsequent steps remain unchanged to prepare a cross-linked polyethylene reinforced high-strength insulated overhead cable.

[0067] The cross-linked polyethylene reinforced high-strength insulated overhead cables in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests:

[0068] Flame retardant properties: The limiting oxygen index test was carried out using a limiting oxygen index instrument (JF-3 model, Nanjing Jiangning District Analytical Instrument Factory) in accordance with GB / T 2406.2-2009. The sample size was 100 mm × 6.5 mm × 3 mm. Five samples were tested in each group, and the average value was taken. LOI stands for limiting oxygen index.

[0069] Insulation performance: A DC breakdown test was conducted on the sample using a DC breakdown system according to the international standard IEC60243. A cylindrical electrode was used with an upper electrode diameter of 25 mm and a lower electrode diameter of 75 mm. Both electrodes had 5 mm rounded corners. A circular thin film sample with a thickness of 50 μm and a diameter of 100 mm was used. In order to prevent the solid medium from introducing bubbles during the test, the sample and the electrodes were immersed in silicone oil during the experiment. During the experiment, the voltage was kept rising at a uniform ramp rate of 1 kV / s, and the DC breakdown performance of the sample was tested at 80°C. The voltage value at the time of breakdown was read, and the corresponding breakdown field strength was calculated according to the formula E=U / d, where U is the voltage at the time of sample breakdown, d is the sample thickness, and E is the breakdown field strength of the sample.

[0070] Corrosion resistance: The samples were immersed in 20wt% hydrochloric acid solution and 20wt% sodium hydroxide solution under the same conditions for 168h, and then taken out to observe the surface corrosion.

[0071] Mechanical properties: The tensile strength and elongation at break of the specimens were tested using a universal mechanical testing machine (WDW-10H, Jinan Zhongluchang Testing Machine Manufacturing Co., Ltd.) at a tensile speed of 5 mm / min. The test results are as follows:

[0072] Table 1

[0073]

[0074] As can be seen from Table 1, the LOI in Examples 1-3 is higher than that in Comparative Examples 1-3. In step S4 of Comparative Example 1, nano-α-Al2O3 powder (purchased from Hangzhou Hengna New Materials Co., Ltd.) is used instead of the nano-composite powder. In step S4 of Comparative Example 2, the hydroxylated nano-boron nitride powder prepared in step S1 is used instead of the nano-composite powder. In step S5 of Comparative Example 3, the fluorine-containing modified monomer is removed, which shows that the fluorine groups in the nano-boron nitride powder, nano-α-Al2O3 powder and the fluorine-containing modified monomer jointly improve the flame retardancy of the cross-linked polyethylene reinforced high-strength insulated overhead cable.

[0075] The DC characteristic breakdown field strength in Examples 1-3 is higher than that in Comparative Example 1 and Comparative Example 3. In step S4 of Comparative Example 1, nano-α-Al2O3 powder is used instead of nano-composite powder, and in step S5 of Comparative Example 3, the fluorine-containing modified monomer is removed, which shows that the nano-boron nitride powder and the fluorine-containing modified monomer jointly improve the insulation performance of the cross-linked polyethylene reinforced high-strength insulated overhead cable.

[0076] The acid and alkali corrosion resistance in Examples 1-3 is higher than that in Comparative Examples 1-3. In step S4 of Comparative Example 1, nano-α-Al2O3 powder is used instead of nano-composite powder, in step S4 of Comparative Example 2, hydroxylated nano-boron nitride powder prepared in step S1 is used instead of nano-composite powder, and in step S5 of Comparative Example 3, the fluorine-containing modified monomer is removed, which shows that nano-boron nitride powder, nano-α-Al2O3 powder and fluorine-containing modified monomer jointly improve the corrosion resistance of cross-linked polyethylene reinforced high-strength insulated overhead cable.

[0077] The tensile strength and elongation at break in Examples 1-3 are greater than those in Comparative Examples 1-3. In step S4 of Comparative Example 1, nano-α-Al2O3 powder is used instead of nano-composite powder. In step S4 of Comparative Example 2, hydroxylated nano-boron nitride powder prepared in step S1 is used instead of nano-composite powder. In step S5 of Comparative Example 3, the fluorine-containing modified monomer is removed. This indicates that nano-boron nitride powder, nano-α-Al2O3 powder and fluorine-containing modified monomer jointly improve the tensile strength of the cross-linked polyethylene reinforced high-strength insulated overhead cable.

[0078] It should be noted that, in this document, terms such as "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements that are inherent to such process, method, article or apparatus.

[0079] While the embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that various changes, modifications, substitutions, and alterations can be made to the embodiments without departing from the principles and spirit of the invention.

Claims

1. A cross-linked polyethylene reinforced high-strength insulated overhead cable, comprising, from the inside to the outside, a conductor, a filler layer, an inner insulating layer, a shielding layer, a thermal insulation layer and an outer insulating layer, characterized in that: The outer insulating layer is prepared by the following steps: Step 1: introducing hydroxyl groups into nano-boron nitride powder to obtain hydroxylated nano-boron nitride powder, which is then modified with KH-550 to obtain amino-dipeptide nano-boron nitride powder; modifying nano-α-Al2O3 powder with γ-glycidyloxypropyltrimethoxysilane to obtain modified nano-α-Al2O3 powder, which is then composited with amino-dipeptide nano-boron nitride powder to obtain nano-composite powder; Step 2: melt-blending the low-density polyethylene and the nanocomposite powder to obtain modified polyethylene; Step 3: grafting hexafluorobisphenol A and acryloyl chloride through a nucleophilic acyl substitution reaction to obtain a fluorine-containing modified monomer, and chemically cross-linking the modified polyethylene and the fluorine-containing modified monomer to obtain a modified cross-linked polyethylene copolymer; Step 4: Use an extruder to wrap the modified cross-linked polyethylene copolymer on the outside of the thermal insulation layer to obtain an outer insulation layer.

2. The cross-linked polyethylene reinforced high-strength insulated overhead cable according to claim 1, characterized in that: The hydroxylated nano-boron nitride powder in step 1 is prepared by the following steps: Add nano boron nitride powder and 3 mol / L sodium hydroxide solution into a reactor, perform ultrasonic dispersion, reflux at 80-90°C for 24-26 hours, cool to room temperature, filter, wash, and dry to obtain hydroxylated nano boron nitride powder; The dosage ratio of the nano boron nitride powder and the sodium hydroxide solution is 1.5-2 g: 150-160 mL.

3. The cross-linked polyethylene reinforced high-strength insulated overhead cable according to claim 1, characterized in that: The amination-modified nano-boron nitride powder in step 1 is prepared by the following steps: KH-550 and a 50 vol% ethanol aqueous solution were added to a reactor, the pH value was adjusted to 4-5 with acetic acid, and the reaction was carried out at 60-65°C and 300-500 r / min for 30-40 minutes. Then, hydroxylated nano-boron nitride powder and an 80 vol% ethanol aqueous solution were added to the reactor, ultrasonically dispersed, reacted for 6 hours, filtered, washed, and dried to obtain amino-treated nano-boron nitride powder.

4. The cross-linked polyethylene reinforced high-strength insulated overhead cable according to claim 3, characterized in that: The usage ratio of the KH-550, 50 vol% ethanol aqueous solution, hydroxylated nano-boron nitride powder and 80 vol% ethanol aqueous solution is 2-4 mL: 20-30 mL: 1-2 g: 200-300 mL.

5. The cross-linked polyethylene reinforced high-strength insulated overhead cable according to claim 1, characterized in that: The modified nano-α-Al2O3 powder in step 1 is specifically prepared by the following steps: γ-glycidyloxypropyltrimethoxysilane and a 50 vol% ethanol aqueous solution are added to a reactor, the pH value is adjusted to 4-5 with acetic acid, and the reaction is carried out at 60-65° C. and 500-800 rpm for 30-40 minutes. Nano-α-Al2O3 powder with a particle size of 30-50 nm and a 80 vol% ethanol aqueous solution are added to the reactor, ultrasonically dispersed, reacted for 6-8 hours, filtered, washed, and dried to obtain modified nano-α-Al2O3 powder. The usage ratio of the γ-glycidyloxypropyltrimethoxysilane, 50 vol% ethanol aqueous solution, nano α-Al2O3 powder and 80 vol% ethanol aqueous solution is 3-5 mL: 20-30 mL: 4-5 g: 200-300 mL.

6. The cross-linked polyethylene reinforced high-strength insulated overhead cable according to claim 1, characterized in that: The nanocomposite powder in step 1 is prepared specifically by the following steps: Add amination nano boron nitride powder and modified nano α-Al2O3 powder into a reactor, disperse with deionized water to a solid content of 5%, adjust the pH value to 8 with ammonia water, react for 24-26 hours, filter, wash, dry, and grind to obtain nano composite powder; The usage ratio of the modified nano-α-Al2O3 powder and the amino-treated nano-boron nitride powder is 4-5g:1-2g.

7. The cross-linked polyethylene reinforced high-strength insulated overhead cable according to claim 1, characterized in that: The modified polyethylene in step 2 is prepared by the following steps: Low-density polyethylene, KH-550 and nano-composite powder are uniformly mixed and melt-blended using a twin-screw extruder at a temperature of 110-115° C. and a rotation speed of 100-200 r / min to obtain modified polyethylene.

8. The cross-linked polyethylene reinforced high-strength insulated overhead cable according to claim 7, characterized in that: The usage ratio of the low-density polyethylene, KH-550 and nano-composite powder is 40-50 g: 0.5-1 mL: 1.5-2 g.

9. The cross-linked polyethylene reinforced high-strength insulated overhead cable according to claim 1, characterized in that: The fluorine-containing modified monomer described in step 3 is prepared by the following steps: Hexafluorobisphenol A, triethylamine and dichloromethane were added to a reaction kettle, stirred for 30-40 minutes under nitrogen protection, 0-4°C and 300-500 r / min, and then acryloyl chloride was dropped into the reaction kettle, reacted for 3-4 hours, filtered, extracted, dried, and rotary evaporated to obtain a fluorine-containing modified monomer; The usage ratio of hexafluorobisphenol A, triethylamine, dichloromethane and acryloyl chloride is 3-4 g: 2.4-3 mL: 70-80 mL: 2.3-3 mL.

10. The cross-linked polyethylene reinforced high-strength insulated overhead cable according to claim 1, characterized in that: The modified cross-linked polyethylene copolymer described in step 3 is prepared by the following steps: Add antioxidant 1010, dicumyl peroxide, modified polyethylene and fluorine-containing modified monomer into a rheometer, mix at 110-115° C. and 50-100 r / min for 7-10 minutes, perform vulcanization cross-linking on a flat vulcanizer at a temperature of 173-178° C. and a pressure of 15-17 MPa for 30-45 minutes, and short-circuit treat at 80-90° C. for 48-50 hours to obtain a modified cross-linked polyethylene copolymer; The dosage ratio of the antioxidant 1010, dicumyl peroxide, modified polyethylene and fluorine-containing modified monomer is 0.12-0.2g: 0.52-1.0g: 42-50g: 2-4g.

Images