High-toughness polyethylene insulated power cable and preparation method thereof

Abstract

The invention relates to the technical field of power cables, in particular to a high-toughness polyethylene insulated power cable and a preparation method thereof. The invention relates to a preparation method of a high-toughness polyethylene insulated power cable. The preparation method comprises the following steps: preparation of a toughening flame-retardant modifier, preparation of a montmorillonite compound, preparation of a toughening modified montmorillonite compound and preparation of the polyethylene insulated power cable. Through specific material mixing and grafting modification, the performance of the cable insulation layer is remarkably improved. The deep trapped charge trapping capability is enhanced, space charge accumulation and electric field distortion are avoided, the DC voltage level and the operation safety are improved, and the dielectric loss and the aging speed are reduced; the dispersibility of montmorillonite is also optimized, a physical reinforcing network is formed, and the mechanical property and the electric breakdown resistance are improved; meanwhile, toughening and flame retardance are coordinated, the problem of embrittlement caused by a traditional flame retardant is solved, and the service life of the insulating layer is comprehensively prolonged.

Description

Technical Field

[0001] This invention relates to the field of power cable technology, specifically to a high-toughness polyethylene insulated power cable and its preparation method. Background Technology

[0002] In the field of power transmission, polyethylene is widely used in the preparation of power cable insulation layers due to its excellent insulation properties, processing performance, and cost advantages. Among them, low-density polyethylene is a commonly used base material, but its inherent defects are gradually becoming apparent in high-voltage direct current transmission scenarios, making it difficult to meet the requirements of high voltage levels, long service life, and high safety.

[0003] Traditional low-density polyethylene (LDPE) insulation materials have weak deep-trap charge trapping capabilities. Under the influence of a DC electric field, charge carriers are easily injected and migrate and accumulate over long distances near electrodes or material defects, forming large-scale space charge accumulation. This leads to uneven electric field distribution within the insulation material, causing local electric field distortion, significantly increasing the probability of insulation breakdown, and limiting the improvement of cable DC voltage levels. Simultaneously, under high voltage or high temperature environments, LDPE has a high volume conductivity, resulting not only in a large dielectric loss factor and increased material self-heating, but also accelerating the insulation aging process and shortening cable service life. The mechanical strength of a simple LDPE insulation layer is limited, and it is easily damaged or cracked by mechanical stress during cable production, laying, and long-term operation, affecting insulation integrity. Traditional inorganic fillers (such as montmorillonite) introduced to improve mechanical properties often suffer from poor dispersion and easy aggregation due to small interlayer spacing and insufficient surface active sites, making it difficult to form an effective physical reinforcing network. This prevents them from fully utilizing their layered barrier and reinforcing effects and fails to help improve dielectric performance defects.

[0004] Furthermore, cable insulation layers need to possess certain flame-retardant properties to address fire risks. However, the addition of traditional flame retardants (such as phosphorus-based and halogen-based flame retardants) often significantly reduces the toughness of polyethylene materials, leading to increased brittleness and decreased impact resistance, making them prone to breakage under stress. Simultaneously, inorganic fillers such as montmorillonite have poor compatibility with the polyethylene matrix, further exacerbating the deterioration of material toughness, making it difficult to achieve the synergistic effect of "flame retardancy without compromising toughness, and toughening without reducing flame retardancy." In addition, the oxidative and electrical aging processes of traditional insulation materials are relatively rapid, affecting their long service life.

[0005] In summary, existing polyethylene cable insulation materials have many shortcomings in terms of space charge suppression, mechanical properties, flame retardancy and toughening synergy, and aging resistance. There is an urgent need to develop a high-toughness polyethylene insulated power cable and its preparation method that combines high toughness, excellent dielectric properties, high flame retardancy rating, and long service life to meet the development needs of the high-voltage power transmission field. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a high-toughness polyethylene insulated power cable and its preparation method.

[0007] This invention provides a high-toughness polyethylene insulated power cable, which includes a conductor, a shielding layer, and an insulation layer from the inside out. Specifically, a copper strip braided shielding layer is wrapped around the conductor to form a shielding layer. Then, modified crosslinkable polyethylene masterbatch is melt-extruded to wrap around the surface of the shielding layer to form an insulation layer, thus obtaining a polyethylene insulated power cable. The modified crosslinkable polyethylene masterbatch includes 100-120 parts by weight of low-density polyethylene, 0.3-0.5 parts by weight of 3-[(4-anilinophenyl)amino]-2-hydroxypropyl methacrylate, 10-12 parts by weight of toughened modified montmorillonite composite, 1.1-1.3 parts by weight of dicumyl peroxide and 0.3-0.5 parts by weight of N,N-diallyl aniline; The toughened modified montmorillonite composite comprises 2-5 parts by weight of montmorillonite composite and 1-2 parts by weight of toughening and flame retardant modifier; The montmorillonite composite was prepared by grafting montmorillonite with titanium dioxide; The toughening and flame-retardant modifier was prepared by reacting capsaicin with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide.

[0008] This invention also provides a method for preparing a high-toughness polyethylene insulated power cable, comprising the following steps: S1: Preparation of toughening and flame-retardant modifier; Capsaicin and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were added to toluene, mixed under nitrogen, and then reacted with azobisisobutyronitrile toluene solution to prepare a toughening and flame retardant modifier. S2: Preparation of montmorillonite composite; Montmorillonite and ammonia were added to anhydrous ethanol, ultrasonically dispersed, and then a mixed solution of tetrabutyl titanate and ethanol was added dropwise under a nitrogen atmosphere. The reaction was carried out at room temperature to prepare the montmorillonite complex. S3: Preparation of toughened modified montmorillonite composite; Anhydrous ethanol was used to disperse montmorillonite composite and toughening flame retardant modifier separately to prepare toughening flame retardant modifier dispersion and montmorillonite composite dispersion. Under nitrogen atmosphere protection, toughening flame retardant modifier dispersion was added to montmorillonite composite dispersion and refluxed to obtain toughened modified montmorillonite composite. S4: Preparation of polyethylene insulated power cables; First, low-density polyethylene, 3-[(4-anilinophenyl)amino]-2-hydroxypropyl methacrylate, toughened modified montmorillonite composite, dicumyl peroxide and N,N-diallyl aniline are mixed and extruded to prepare modified crosslinkable polyethylene masterbatch. Then, a shielding layer and an insulating layer are sequentially coated on the outside of the conductor. The insulating layer is modified crosslinkable polyethylene.

[0009] As a preferred aspect, S1: the preparation of the toughening and flame-retardant modifier specifically includes the following steps: S1.1: Add 5-8 parts by weight of capsaicin and 3-5 parts by weight of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to 40-50 parts by weight of toluene, and then stir and mix for 20-30 minutes at 70-80℃ and 200-300 rpm under a nitrogen atmosphere to obtain a mixed solution. S1.2: Add 1-2 parts by weight of azobisisobutyronitrile to 20-30 parts by weight of toluene, and stir at 100-200 rpm to dissolve it, so as to obtain an azobisisobutyronitrile toluene solution; S1.3: Add azobisisobutyronitrile toluene solution to the mixed solution, and then react under nitrogen atmosphere at 55-60℃ for 24-48h. After the reaction is completed, perform vacuum distillation to obtain the toughening and flame retardant modifier.

[0010] As a preferred aspect, the preparation of S2: the montmorillonite complex specifically includes the following steps: S2.1: Add 2-3 parts by weight of montmorillonite and 10-12 parts by weight of ammonia water to 100-120 parts by weight of anhydrous ethanol, then ultrasonically disperse for 20-30 minutes to obtain a suspension. Under dry conditions, add 10-12 parts by weight of tetrabutyl titanate to 20-25 parts by weight of anhydrous ethanol, stir and mix to obtain a tetrabutyl titanate solution. S2.2: Under a nitrogen atmosphere, tetrabutyl titanate solution was added dropwise to the suspension using a constant pressure dropping funnel. After the addition was complete, the mixture was stirred at room temperature for 24-26 hours. After the reaction was complete, the mixture was centrifuged, and the precipitate was washed 3-5 times with anhydrous ethanol. After washing, the precipitate was dried in a drying oven at 60-80℃ for 6-8 hours to obtain the montmorillonite complex.

[0011] As a preferred aspect, the dripping time in step S2.2 is 60-70 min.

[0012] As a preferred aspect, S3: the preparation of the toughened modified montmorillonite composite specifically includes the following steps: S3.1: Add 2-5 parts by weight of montmorillonite composite to 50-60 parts by weight of anhydrous ethanol, stir and mix at 200-300 rpm for 20-30 min to obtain montmorillonite composite dispersion; add 1-2 parts by weight of toughening and flame retardant modifier to 20-30 parts by weight of anhydrous ethanol, stir and mix at 200-300 rpm for 20-30 min to obtain toughening and flame retardant modifier dispersion; S3.2: Under nitrogen atmosphere protection, the toughening and flame retardant modifier dispersion was added to the montmorillonite composite dispersion, and then refluxed. After the reaction was completed, the mixture was centrifuged, washed with deionized water, and dried to obtain the toughened modified montmorillonite composite.

[0013] As a preferred aspect, in step S3.2, the stirring speed is 100-120 rpm, the reflux reaction temperature is 75-80℃, and the reaction time is 12-14 h.

[0014] As a preferred aspect, S4: the preparation of polyethylene insulated power cables specifically includes the following steps: S4.1: Add 100-120 parts by weight of low-density polyethylene to a torque rheometer at 110-120℃ and 50-60r / min and mix until completely melted. Then add 0.3-0.5 parts by weight of 3-[(4-anilinophenyl)amino]-2-hydroxypropyl methacrylate and mix for 5-8 min. Then add 10-12 parts by weight of toughened modified montmorillonite composite and mix for 20-30 min. Finally, add 1.1-1.3 parts by weight of dicumyl peroxide and 0.3-0.5 parts by weight of N,N-diallyl aniline and mix for 1-2 min to obtain the blend. S4.2: The blend is added to a single screw extruder for extrusion granulation, and then cooled and pelletized to prepare modified crosslinkable polyethylene masterbatch; S4.3: After the copper strip braided shielding layer is wrapped around the conductor to form a shielding layer, the modified crosslinkable polyethylene masterbatch is melt-extruded at 150-160℃ to wrap it on the surface of the shielding layer to form an insulation layer. Then, a crosslinking grafting reaction is carried out in a saturated steam crosslinking pipe to obtain a polyethylene insulated power cable.

[0015] As a preferred aspect, the extrusion temperature of the single-screw extruder in S4.2 is 120-130℃.

[0016] As a preferred aspect, in S4.3, the crosslinking temperature in the saturated steam crosslinking pipeline is 170-180℃, and the crosslinking time is 30-50min.

[0017] The present invention has the following advantages: 1. This invention uses low-density polyethylene and 3-[(4-anilinophenyl)amino]-2-hydroxypropyl methacrylate for compounding, and adds N,N-diallyl aniline. With the aid of crosslinking by N,N-diallyl aniline, 3-[(4-anilinophenyl)amino]-2-hydroxypropyl methacrylate can be efficiently grafted onto the low-density polyethylene molecular chain, significantly enhancing the deep-trap charge-trapping capability of the insulating layer. The deep traps can effectively trap and "lock" injected charge carriers, preventing them from migrating long distances and accumulating near electrodes or defects under the influence of an electric field. Because the charge is dispersed and fixed in the deep traps... Within the trap, large-scale accumulation of space charge cannot occur, thus ensuring a uniform distribution of the electric field within the insulation material, avoiding local electric field distortion, reducing the probability of insulation breakdown, and significantly improving the DC voltage level and operational safety of the cable. Furthermore, the charges bound by the deep trap are difficult to participate in conduction, thus maintaining a very low volume conductivity even under high voltage / high temperature. Low conductivity directly means a low dielectric loss factor, which reduces the heat generation of the insulation material itself and significantly slows down the aging process. At the same time, the stable graft cross-linking structure can delay the oxidative aging and electrical aging processes of the insulation material, thereby extending the service life of the insulation layer.

[0018] 2. This invention grafts titanium oxide groups onto the surface of montmorillonite sheets, increasing the interlayer spacing. This not only retains the layered barrier and physical reinforcement properties of montmorillonite itself, but also provides more active sites for subsequent composite reactions with toughening and flame-retardant modifiers. Introducing this into the insulating layer, the nanoscale dispersed montmorillonite sheets form a physical reinforcement network in the polyethylene matrix, significantly enhancing the mechanical properties of the insulating layer. This effectively reduces mechanical damage and cracking risks, extends the physical service life of the insulating layer, and the layered structure of the montmorillonite composite forms a "maze effect." On the one hand, it blocks the migration path of free charges and assists the deep-trap charge trapping effect of 3-[(4-anilinophenyl)amino]-2-hydroxypropyl methacrylate, further reducing space charge accumulation and local electric field distortion. On the other hand, the uniformly dispersed montmorillonite fills the microscopic voids and defects in the polyethylene matrix, reducing the probability of partial discharge caused by dielectric inhomogeneity and significantly improving the dielectric breakdown strength and long-term dielectric stability of the insulating layer.

[0019] 3. This invention employs a toughening and flame-retardant modifier to modify the montmorillonite composite. The organic segments of the toughening and flame-retardant modifier bond with the titanium oxide groups on the surface of the montmorillonite composite, achieving graft modification. The organic segments of the toughening and flame-retardant modifier further modify the surface of the montmorillonite sheets, expanding the interlamellar spacing. Simultaneously, its hydrophobic segments can entangle with the molecular chains of polymer matrices such as polyethylene, improving the nano-agglomeration problem of montmorillonite and enabling the composite to achieve uniform nanoscale dispersion in the organic matrix. By modifying the montmorillonite composite with a toughening and flame-retardant modifier, a synergistic effect of "flame retardancy without compromising toughness and toughening without reducing flame retardancy" can be achieved, solving the problem of polymerization after the addition of traditional flame retardants. To address the challenge of reduced toughness, DOPO's phosphorus-based flame retardancy and capsaicin's smoke-suppressing flame retardancy form a chemical synergy, inhibiting the pyrolysis and combustion chain reaction of polyethylene. Montmorillonite's layered structure creates a physical barrier, a "maze effect," slowing the transfer of heat and combustible gases while reducing molten dripping. The combination of these two factors significantly improves the flame retardancy of the insulation layer. Furthermore, the nanosheets of montmorillonite form a physical reinforcing network within the polyethylene matrix. Combined with the entanglement and grafting of the organic segments of the toughening and flame-retardant modifier with the polyethylene molecular chains, this effectively improves the inherent brittleness of low-density polyethylene. The deformation, silvering, and shear banding of the flexible chains of the toughening and flame-retardant modifier absorb a large amount of impact energy, significantly enhancing the toughness of the insulation layer. Attached Figure Description

[0020] Figure 1 This is a process flow diagram of the preparation method of the high-toughness polyethylene insulated power cable used in the embodiments of the present invention.

[0021] Figure 2 The structural reaction formula of the toughening and flame-retardant modifier in the embodiments of the present invention is shown. Detailed Implementation

[0022] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this invention.

[0023] Example 1: A method for preparing a high-toughness polyethylene insulated power cable, referring to... Figures 1-2 ,include: S1: Preparation of toughening and flame-retardant modifiers S1.1: Add 5 parts by weight of capsaicin and 3 parts by weight of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to 40 parts by weight of toluene, and then stir and mix for 20 min at 70°C and 200 rpm under a nitrogen atmosphere to obtain a mixed solution. S1.2: Add 1 part by weight of azobisisobutyronitrile to 20 parts by weight of toluene and stir at 100 rpm to dissolve it, so as to obtain an azobisisobutyronitrile toluene solution. S1.3: Azobisisobutyronitrile toluene solution was added to the mixed solution, and then the reaction was carried out under nitrogen atmosphere at 55°C for 24 hours. After the reaction was completed, vacuum distillation was performed to obtain the toughening and flame retardant modifier. S2: Preparation of montmorillonite composite S2.1: Add 2 parts by weight of montmorillonite and 10 parts by weight of ammonia water to 100 parts by weight of anhydrous ethanol, then ultrasonically disperse for 20 min to obtain a suspension. Under dry conditions, add 10 parts by weight of tetrabutyl titanate to 20 parts by weight of anhydrous ethanol, stir and mix to obtain a tetrabutyl titanate solution. S2.2: Under a nitrogen atmosphere, tetrabutyl titanate solution was added dropwise to the suspension using a constant pressure dropping funnel over a period of 60 min. After the addition was complete, the mixture was stirred at room temperature for 24 h. After the reaction was complete, the mixture was centrifuged and then washed three times with anhydrous ethanol. After washing, the mixture was dried in a 60 °C drying oven for 6 h to obtain the montmorillonite complex. S3: Preparation of toughened modified montmorillonite composite S3.1: Add 2 parts by weight of montmorillonite composite to 50 parts by weight of anhydrous ethanol, stir and mix at 200 rpm for 20 min to obtain montmorillonite composite dispersion, add 1 part by weight of toughening flame retardant modifier to 20 parts by weight of anhydrous ethanol, stir and mix at 200 rpm for 20 min to obtain toughening flame retardant modifier dispersion. S3.2: Under nitrogen atmosphere protection, the toughening flame retardant modifier dispersion was added to the montmorillonite composite dispersion, then the temperature was raised to 75℃, and the mixture was refluxed for 12h with stirring at 100rpm. After the reaction was completed, the mixture was centrifuged, washed with deionized water, and dried to obtain the toughened modified montmorillonite composite. S4: Preparation of polyethylene insulated power cables S4.1: Add 100 parts by weight of low-density polyethylene to a torque rheometer at 110℃ and 50 r / min and mix until completely melted. Then add 0.3 parts by weight of 3-[(4-anilinophenyl)amino]-2-hydroxypropyl methacrylate and mix for 5 min. Then add 10 parts by weight of toughened modified montmorillonite composite and mix for 20 min. Finally, add 1.1 parts by weight of dicumyl peroxide and 0.3 parts by weight of N,N-diallyl aniline and mix for 1-2 min to obtain the blend. S4.2: The blend is added to a single screw extruder and extruded and granulated at 120°C. After cooling and pelletizing, modified crosslinkable polyethylene masterbatch is obtained. S4.3: After the copper strip braided shielding layer is wrapped around the conductor to form a shielding layer, the modified crosslinkable polyethylene masterbatch is melt-extruded at 150°C to wrap the shielding layer surface to form an insulation layer. Then, the crosslinking grafting reaction is carried out in a saturated steam crosslinking pipe at 170°C for 30 minutes to obtain a polyethylene insulated power cable.

[0024] Example 2: A method for preparing a high-toughness polyethylene insulated power cable, see [link to example]. Figures 1-2 ,include: S1: Preparation of toughening and flame-retardant modifiers S1.1: Add 8 parts by weight of capsaicin and 5 parts by weight of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to 50 parts by weight of toluene, and then stir and mix for 30 min at 80°C and 300 rpm under a nitrogen atmosphere to obtain a mixed solution. S1.2: Add 2 parts by weight of azobisisobutyronitrile to 30 parts by weight of toluene and stir at 200 rpm to dissolve it, so as to obtain an azobisisobutyronitrile toluene solution; S1.3: Azobisisobutyronitrile toluene solution was added to the mixed solution, and then the reaction was carried out under nitrogen atmosphere at 60°C for 48 hours. After the reaction was completed, the mixture was distilled under reduced pressure to obtain the toughening and flame retardant modifier. S2: Preparation of montmorillonite composite S2.1: Add 3 parts by weight of montmorillonite and 12 parts by weight of ammonia water to 120 parts by weight of anhydrous ethanol, then ultrasonically disperse for 30 min to obtain a suspension. Under dry conditions, add 12 parts by weight of tetrabutyl titanate to 25 parts by weight of anhydrous ethanol, stir and mix to obtain a tetrabutyl titanate solution. S2.2: Under a nitrogen atmosphere, tetrabutyl titanate solution was added dropwise to the suspension using a constant pressure dropping funnel over a period of 70 min. After the addition was complete, the mixture was stirred at room temperature for 26 h. After the reaction was complete, the mixture was centrifuged and then washed five times with anhydrous ethanol. After washing, the mixture was dried in an 80 °C drying oven for 8 h to obtain the montmorillonite complex. S3: Preparation of toughened modified montmorillonite composite S3.1: Add 5 parts by weight of montmorillonite composite to 60 parts by weight of anhydrous ethanol, stir and mix at 300 rpm for 30 min to obtain montmorillonite composite dispersion; add 2 parts by weight of toughening flame retardant modifier to 30 parts by weight of anhydrous ethanol, stir and mix at 300 rpm for 30 min to obtain toughening flame retardant modifier dispersion. S3.2: Under nitrogen atmosphere protection, the toughening flame retardant modifier dispersion was added to the montmorillonite composite dispersion, then the temperature was raised to 80℃, and the mixture was refluxed for 14h with stirring at 120rpm. After the reaction was completed, the mixture was centrifuged, washed with deionized water, and dried to obtain the toughened modified montmorillonite composite. S4: Preparation of polyethylene insulated power cables S4.1: 120 parts by weight of low-density polyethylene were added to a torque rheometer at 120℃ and 60 r / min and mixed until completely melted. Then, 0.5 parts by weight of 3-[(4-anilinophenyl)amino]-2-hydroxypropyl methacrylate were added and mixed for 8 min. Then, 12 parts by weight of toughened modified montmorillonite composite were added and mixed for 30 min. Finally, 1.3 parts by weight of dicumyl peroxide and 0.5 parts by weight of N,N-diallyl aniline were added and mixed for 2 min to obtain the blend. S4.2: The blend is added to a single screw extruder and extruded and granulated at 130°C. After cooling and pelletizing, modified crosslinkable polyethylene masterbatch is obtained. S4.3: After the copper strip braided shielding layer is wrapped around the conductor to form a shielding layer, the modified crosslinkable polyethylene masterbatch is melt-extruded at 160°C to wrap the shielding layer surface to form an insulation layer. Then, the crosslinking grafting reaction is carried out in a saturated steam crosslinking pipe at 180°C for 50 minutes to obtain a polyethylene insulated power cable.

[0025] Example 3: A method for preparing a high-toughness polyethylene insulated power cable, see [link to example]. Figures 1-2 ,include: S1: Preparation of toughening and flame-retardant modifiers S1.1: 6.5 parts by weight of capsaicin and 4 parts by weight of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were added to 45 parts by weight of toluene, and then stirred and mixed for 25 minutes at 75°C and 250 rpm under a nitrogen atmosphere to obtain a mixed solution. S1.2: Add 1.5 parts by weight of azobisisobutyronitrile to 25 parts by weight of toluene and stir at 150 rpm to dissolve it, so as to obtain an azobisisobutyronitrile toluene solution. S1.3: Azobisisobutyronitrile toluene solution was added to the mixed solution, and then the reaction was carried out under nitrogen atmosphere at 56.5℃ for 36 h. After the reaction was completed, vacuum distillation was performed to obtain the toughening and flame retardant modifier. S2: Preparation of montmorillonite composite S2.1: Add 2.5 parts by weight of montmorillonite and 11 parts by weight of ammonia water to 110 parts by weight of anhydrous ethanol, then ultrasonically disperse for 25 min to obtain a suspension. Under dry conditions, add 11 parts by weight of tetrabutyl titanate to 22.5 parts by weight of anhydrous ethanol, stir and mix to obtain a tetrabutyl titanate solution. S2.2: Under a nitrogen atmosphere, tetrabutyl titanate solution was added dropwise to the suspension using a constant pressure dropping funnel over a period of 65 min. After the addition was complete, the mixture was stirred at room temperature for 25 h. After the reaction was complete, the mixture was centrifuged and then the precipitate was washed 3-5 times with anhydrous ethanol. After washing, the precipitate was dried in a 70 °C drying oven for 7 h to obtain the montmorillonite complex. S3: Preparation of toughened modified montmorillonite composite S3.1: Add 3.5 parts by weight of montmorillonite composite to 55 parts by weight of anhydrous ethanol, stir and mix at 250 rpm for 25 min to obtain montmorillonite composite dispersion, add 1.5 parts by weight of toughening and flame retardant modifier to 25 parts by weight of anhydrous ethanol, stir and mix at 250 rpm for 25 min to obtain toughening and flame retardant modifier dispersion. S3.2: Under nitrogen atmosphere protection, the toughening flame retardant modifier dispersion was added to the montmorillonite composite dispersion, then the temperature was raised to 76.5℃, and the mixture was refluxed at 110 rpm for 13 h. After the reaction was completed, the mixture was centrifuged, washed with deionized water, and dried to obtain the toughened modified montmorillonite composite. S4: Preparation of polyethylene insulated power cables S4.1: Add 110 parts by weight of low-density polyethylene to a torque rheometer at 115℃ and 55r / min and mix until completely melted. Then add 0.4 parts by weight of 3-[(4-anilinophenyl)amino]-2-hydroxypropyl methacrylate and mix for 6.5 min. Then add 11 parts by weight of toughened modified montmorillonite composite and mix for 25 min. Finally, add 1.2 parts by weight of dicumyl peroxide and 0.4 parts by weight of N,N-diallyl aniline and mix for 1-2 min to obtain the blend. S4.2: The blend is added to a single screw extruder and extruded and granulated at 125°C. After cooling and pelletizing, the modified crosslinkable polyethylene masterbatch is obtained. S4.3: After the copper strip braided shielding layer is wrapped around the conductor to form a shielding layer, the modified crosslinkable polyethylene masterbatch is melt-extruded at 155°C to wrap the shielding layer surface to form an insulation layer. Then, the crosslinking grafting reaction is carried out in a saturated steam crosslinking pipe at 175°C for 40 minutes to obtain a polyethylene insulated power cable.

[0026] Comparative Example 1 differs from Example 1 in that it removes 3-[(4-anilinophenyl)amino]-2-hydroxypropyl methacrylate and N,N-diallyl aniline from step S4.1, while keeping the other steps unchanged in preparing a polyethylene insulated power cable. This is referred to as Comparative Example 1.

[0027] Comparative Example 2 differs from Example 1 in that N,N-diallylaniline in step S4.1 is removed, while the remaining steps remain unchanged in preparing a polyethylene insulated power cable. This is referred to as Comparative Example 2.

[0028] Comparative Example 3 differs from Example 1 in that the toughening modified montmorillonite composite in steps S1-S3 and S4.1 is removed, while the remaining steps remain unchanged to prepare a polyethylene insulated power cable, and is referred to as Comparative Example 3.

[0029] Comparative Example 4 differs from Example 1 in that the toughening modified montmorillonite complex, 3-[(4-anilinophenyl)amino]-2-hydroxypropyl methacrylate and N,N-diallyl aniline in steps S1-S3 and S4.1 are removed, while the remaining steps remain unchanged to prepare a polyethylene insulated power cable, which is referred to as Comparative Example 4.

[0030] Comparative Example 5 differs from Example 1 in that steps S1 and S3 are removed, and the toughening modified montmorillonite composite in step S4.1 is replaced with an equal amount of montmorillonite composite. The remaining steps are unchanged to prepare a polyethylene insulated power cable, and this is referred to as Comparative Example 5.

[0031] Comparative Example 6 differs from Example 1 in that step S2 is removed, and the montmorillonite compound in step S3.1 is replaced with an equal amount of montmorillonite, while the remaining steps remain unchanged to prepare a polyethylene insulated power cable. This is referred to as Comparative Example 6.

[0032] The volume conductivity and dielectric breakdown strength of the polyethylene insulated power cables prepared in Examples 1-3 and Comparative Examples 1-4 were measured three times and the average value was taken. The results are shown in Table 1.

[0033] Volumetric conductivity: Measured using a high-resistivity meter at 90℃ and a DC electric field of 100kV / mm.

[0034] Electrical breakdown strength: Measured in an oil bath using the step-up method (voltage rate 2kV / s) according to IEC60243 standard.

[0035] Table 1. Results of volumetric conductivity and electrical breakdown strength measurements in Examples 1-3 and Comparative Examples 1-4 Volumetric conductivity (S / m) Electrical breakdown strength (kV / mm) Example 1 1.02 x 10 -15 ]]> 247 Example 2 1.18 x 10 -15 ]]> 252 Example 3 1.10 x 10 -15 ]] 250 Comparative Example 1 5.12 x 10 -14 ]] 179 Comparative Example 2 2.05 x 10 -14 ]] 198 Comparative Example 3 3.20 x 10 -14 ]]> 184 Comparative Example 4 7.93 x 10 -14 ]] 151 As can be seen from the data in Table 1, the polyethylene insulated power cable prepared by this invention exhibits extremely low conductivity. This indicates that the insulation layer prepared by this invention can effectively suppress carrier migration, reduce dielectric loss, and lower the probability of insulation breakdown under high temperature and high pressure, significantly improving the DC voltage level and operational safety of the cable. Data from Comparative Example 1 shows that the lack of 3-[(4-anilinophenyl)amino]-2-hydroxypropyl methacrylate significantly increases the volumetric conductivity. This is because the absence of deep-trap charge-trapping structures leads to the easy accumulation of space charge, resulting in a significant increase in conductivity and breakdown risk. Data from Comparative Example 2 shows that the addition of N,N-diallylaniline can enhance the deep-trap charge-trapping capability of the insulation layer, thereby reducing volumetric conductivity and breakdown risk. Data from Comparative Examples 1 and 3-4 show that the added toughening modified montmorillonite composite can assist the deep-trap charge-trapping effect of 3-[(4-anilinophenyl)amino]-2-hydroxypropyl methacrylate, further reducing space charge accumulation, lowering volumetric conductivity, and reducing breakdown risk. The impact strength of the polyethylene insulated power cables prepared in Examples 1-3 and Comparative Examples 3 and 5-6 was measured three times, and the average value was taken. The results are shown in Table 2.

[0036] Impact strength: Cantilever beam impact test was conducted according to ISO 180 standard (specimen size 80×10×4mm).

[0037] Table 2. Impact strength test results of Examples 1-3 and Comparative Examples 3, 5-6 <![CDATA[Impact strength (kJ / m 2 )]]> Example 1 28.4 Example 2 29.3 Example 3 28.8 Comparative Example 3 10.3 Comparative Example 5 12.2 Comparative Example 6 20.3 As can be seen from the data in Table 2, the polyethylene insulated power cable prepared by this invention has high toughness. As can be seen from the data in Comparative Examples 3 and 5, the toughened modified montmorillonite composite treated with a toughening and flame-retardant modifier can effectively improve the toughness of the power cable. As can be seen from the data in Comparative Example 6, the toughness of the montmorillonite composite without grafting titanium oxide groups on the surface of the montmorillonite sheets is significantly reduced. This is because grafting titanium oxide groups on the surface of the montmorillonite sheets provides more active sites for the subsequent composite reaction with the toughening and flame-retardant modifier. By modifying the surface of montmorillonite through its organic segments, a "rigid sheet + flexible interface" structure is formed, which significantly increases the toughness of the power cable.

[0038] The flame retardancy of the polyethylene insulated power cables prepared in Examples 1-3 and Comparative Examples 3 and 5 was tested three times, and the average value was taken. The test results are shown in Table 3.

[0039] Limiting Oxygen Index (LOI): Measured according to ISO 4589-2 standard.

[0040] UL-94 rating: Vertical burning test performed according to UL-94 standard.

[0041] Table 3. Flame retardancy test results of Examples 1-3 and Comparative Examples 3 and 5 Limiting oxygen index (%) UL-94 rating Example 1 33.5 V-0 Example 2 34.2 V-0 Example 3 33.9 V-0 Comparative Example 3 18.2 No grade Comparative Example 5 22.2 V-2 As can be seen from the data in Table 3, the power cable prepared by the present invention has good flame retardant properties. The data from comparative examples 3 and 5 show that the present invention can significantly improve the flame retardancy by using a toughening flame retardant modifier to modify the montmorillonite composite, thereby significantly improving the flame retardant rating of the insulation layer.

[0042] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims. Parts not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A high-toughness polyethylene insulated power cable, characterized in that, It consists of a conductor, a shielding layer, and an insulation layer from the inside out. Specifically, after the copper strip braided shielding layer is wrapped around the conductor to form a shielding layer, the modified crosslinkable polyethylene masterbatch is melt-extruded to wrap around the surface of the shielding layer to form an insulation layer, thus obtaining a polyethylene insulated power cable. The modified crosslinkable polyethylene masterbatch includes 100-120 parts by weight of low-density polyethylene, 0.3-0.5 parts by weight of 3-[(4-anilinophenyl)amino]-2-hydroxypropyl methacrylate, 10-12 parts by weight of toughened modified montmorillonite composite, 1.1-1.3 parts by weight of dicumyl peroxide and 0.3-0.5 parts by weight of N,N-diallyl aniline; The toughened modified montmorillonite composite comprises 2-5 parts by weight of montmorillonite composite and 1-2 parts by weight of toughening and flame retardant modifier; The montmorillonite composite was prepared by grafting montmorillonite with titanium dioxide; The toughening and flame-retardant modifier was prepared by reacting capsaicin with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide.

2. A method for preparing a high-toughness polyethylene insulated power cable according to claim 1, characterized in that, Includes the following steps: S1: Preparation of toughening and flame-retardant modifier; Capsaicin and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide were added to toluene, mixed under nitrogen, and then reacted with azobisisobutyronitrile toluene solution to prepare a toughening and flame retardant modifier. S2: Preparation of montmorillonite composite; Montmorillonite and ammonia were added to anhydrous ethanol, ultrasonically dispersed, and then a mixed solution of tetrabutyl titanate and ethanol was added dropwise under a nitrogen atmosphere. The reaction was carried out at room temperature to prepare the montmorillonite complex. S3: Preparation of toughened modified montmorillonite composite; Anhydrous ethanol was used to disperse montmorillonite composite and toughening flame retardant modifier separately to prepare toughening flame retardant modifier dispersion and montmorillonite composite dispersion. Under nitrogen atmosphere protection, toughening flame retardant modifier dispersion was added to montmorillonite composite dispersion and refluxed to obtain toughened modified montmorillonite composite. S4: Preparation of polyethylene insulated power cables; First, low-density polyethylene, 3-[(4-anilinophenyl)amino]-2-hydroxypropyl methacrylate, toughened modified montmorillonite composite, dicumyl peroxide and N,N-diallyl aniline are mixed and extruded to prepare modified crosslinkable polyethylene masterbatch. Then, a shielding layer and an insulating layer are sequentially coated on the outside of the conductor. The insulating layer is modified crosslinkable polyethylene.

3. The method for preparing a high-toughness polyethylene insulated power cable according to claim 2, characterized in that, S1: The preparation of the toughening and flame-retardant modifier includes the following steps: S1.1: Add 5-8 parts by weight of capsaicin and 3-5 parts by weight of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to 40-50 parts by weight of toluene, and then stir and mix for 20-30 minutes at 70-80℃ and 200-300 rpm under a nitrogen atmosphere to obtain a mixed solution. S1.2: Add 1-2 parts by weight of azobisisobutyronitrile to 20-30 parts by weight of toluene, and stir at 100-200 rpm to dissolve it, so as to obtain an azobisisobutyronitrile toluene solution; S1.3: Add azobisisobutyronitrile toluene solution to the mixed solution, and then react under nitrogen atmosphere at 55-60℃ for 24-48h. After the reaction is completed, perform vacuum distillation to obtain the toughening and flame retardant modifier.

4. The method for preparing a high-toughness polyethylene insulated power cable according to claim 2, characterized in that, S2: The preparation of the montmorillonite complex includes the following steps: S2.1: Add 2-3 parts by weight of montmorillonite and 10-12 parts by weight of ammonia water to 100-120 parts by weight of anhydrous ethanol, then ultrasonically disperse for 20-30 minutes to obtain a suspension. Under dry conditions, add 10-12 parts by weight of tetrabutyl titanate to 20-25 parts by weight of anhydrous ethanol, stir and mix to obtain a tetrabutyl titanate solution. S2.2: Under a nitrogen atmosphere, tetrabutyl titanate solution was added dropwise to the suspension using a constant pressure dropping funnel. After the addition was complete, the mixture was stirred at room temperature for 24-26 hours. After the reaction was complete, the mixture was centrifuged, and the precipitate was washed 3-5 times with anhydrous ethanol. After washing, the precipitate was dried in a drying oven at 60-80℃ for 6-8 hours to obtain the montmorillonite complex.

5. The method for preparing a high-toughness polyethylene insulated power cable according to claim 4, characterized in that, The dripping time in step S2.2 is 60-70 minutes.

6. The method for preparing a high-toughness polyethylene insulated power cable according to claim 2, characterized in that, S3: Preparation of toughened modified montmorillonite composite, specifically including the following steps: S3.1: Add 2-5 parts by weight of montmorillonite composite to 50-60 parts by weight of anhydrous ethanol, stir and mix at 200-300 rpm for 20-30 min to obtain montmorillonite composite dispersion; add 1-2 parts by weight of toughening and flame retardant modifier to 20-30 parts by weight of anhydrous ethanol, stir and mix at 200-300 rpm for 20-30 min to obtain toughening and flame retardant modifier dispersion; S3.2: Under nitrogen atmosphere protection, the toughening and flame retardant modifier dispersion was added to the montmorillonite composite dispersion, and then refluxed. After the reaction was completed, the mixture was centrifuged, washed with deionized water, and dried to obtain the toughened modified montmorillonite composite.

7. The method for preparing a high-toughness polyethylene insulated power cable according to claim 6, characterized in that, In step S3.2, the stirring speed is 100-120 rpm, the reflux reaction temperature is 75-80℃, and the reaction time is 12-14 h.

8. The method for preparing a high-toughness polyethylene insulated power cable according to claim 2, characterized in that, S4: the preparation of the polyethylene insulated power cable specifically includes the following steps: S4.1: Add 100-120 parts by weight of low-density polyethylene to a torque rheometer at 110-120℃ and 50-60r / min and mix until completely melted. Then add 0.3-0.5 parts by weight of 3-[(4-anilinophenyl)amino]-2-hydroxypropyl methacrylate and mix for 5-8 min. Then add 10-12 parts by weight of toughened modified montmorillonite composite and mix for 20-30 min. Finally, add 1.1-1.3 parts by weight of dicumyl peroxide and 0.3-0.5 parts by weight of N,N-diallyl aniline and mix for 1-2 min to obtain the blend. S4.2: The blend is added to a single screw extruder for extrusion granulation, and then cooled and pelletized to prepare modified crosslinkable polyethylene masterbatch; S4.3: After the copper strip braided shielding layer is wrapped around the conductor to form a shielding layer, the modified crosslinkable polyethylene masterbatch is melt-extruded at 150-160℃ to wrap it on the surface of the shielding layer to form an insulation layer. Then, a crosslinking grafting reaction is carried out in a saturated steam crosslinking pipe to obtain a polyethylene insulated power cable.

9. The method for preparing a high-toughness polyethylene insulated power cable according to claim 8, characterized in that, The extrusion temperature of the single-screw extruder in S4.2 is 120-130℃.

10. The method for preparing a high-toughness polyethylene insulated power cable according to claim 8, characterized in that, In S4.3, the cross-linking temperature in the saturated steam cross-linking pipeline is 170-180℃, and the cross-linking time is 30-50min.

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