Weather resistant aerial insulated cable and method of making same

Abstract

The application relates to the technical field of high polymer material preparation, and particularly discloses a weather-resistant overhead insulated cable and a preparation method thereof, which comprises a conductor and an insulation layer, and the insulation layer comprises A master batch and B master batch; the A master batch comprises the following components: 100 parts of composite polyethylene resin, 2-5 parts of vinyl trimethoxysilane, 3-8 parts of acrylate modified cardanol, 0.4-1 part of 2,2,6,6-tetramethyl-4-piperidyl methacrylate, 0.8-1.5 parts of triallyl isocyanurate, 0.4-0.8 parts of dicumyl peroxide, and 0.3-0.5 parts of antioxidant; and the B master batch comprises the following components: 100 parts of composite polyethylene resin, 25-45 parts of silanized inorganic filler, 8-15 parts of compatilizer, 0.5-2 parts of dibutyltin dilaurate, 0.3-0.5 parts of antioxidant, and 0.2-0.5 parts of lubricant. The weather-resistant overhead insulated cable prepared by the application can realize comprehensive balance of weather resistance and mechanics.

Description

Technical Field

[0001] This application relates to the technical field of polymer material preparation, and more specifically, it relates to a weather-resistant overhead insulated cable and its preparation method. Background Technology

[0002] Overhead insulated cables refer to overhead conductors equipped with weather-resistant insulation layers (some include shielding or reinforcing cores). Due to their long-term exposure to the complex outdoor environment, they are susceptible to photo-oxidative aging caused by ultraviolet radiation, temperature differences, and humidity, leading to insulation layer cracking and decreased dielectric strength, seriously threatening power grid safety. To improve the weather resistance defects of traditional insulation materials, the industry commonly uses cross-linking technology to construct a three-dimensional network molecular structure, supplemented with light stabilizers, antioxidants, and other additives to enhance the weather resistance of the insulation layer. While cross-linking can improve aging resistance, improper process control can result in residual cross-linking byproducts that can actually reduce the insulation layer's resistance to heat and oxygen aging.

[0003] Patent application CN122011548A discloses a high-toughness XLPE overhead insulated cable, comprising a cable core and an insulation layer. The insulation layer is made of an insulating material comprising the following raw materials in parts by weight: 50-60 parts of low-density polyethylene, 15-25 parts of linear low-density polyethylene, 15-25 parts of high-density polyethylene, 8-12 parts of modified nano-inorganic filler, 6-14 parts of double-ended vinyl silicone oil, 8-12 parts of initiator, 0.5-1 part of light stabilizer, 0.1-1 part of antioxidant, and 0.2-1 part of lubricant. The modified nano-inorganic filler is prepared by modifying nano-inorganic filler with a silane coupling agent. The initiator is benzoyl peroxide.

[0004] In this scheme, although the introduction of modified nano-inorganic fillers and dual-terminated vinyl silicone oil improves the toughness of the material to some extent, the high dosage of 8-12 parts of benzoyl peroxide initiator in the formulation can lead to excessive cross-linking of the polyethylene matrix or severe chain scission side reactions, disrupting the regularity of the polymer chains and easily inducing the initiation and propagation of microcracks under outdoor ultraviolet radiation and thermal cycling. In addition, the high proportion of dual-terminated vinyl silicone oil may participate in free radical side reactions in the free radical environment initiated by benzoyl peroxide, generating unstable cross-linked structures that may undergo oxidative degradation under long-term ultraviolet radiation, affecting the dielectric stability of the insulating layer. Summary of the Invention

[0005] To improve the weather resistance of cables, this application provides a weather-resistant overhead insulated cable and its preparation method.

[0006] A weather-resistant overhead insulated cable includes a conductor and an insulation layer covering the conductor. The insulation layer is obtained by mixing masterbatch A and masterbatch B, extruding the mixture onto the surface of the conductor, and then curing it through moisture crosslinking. The raw materials for masterbatch A, by weight, include: 100 parts of composite polyethylene resin, 2-5 parts of vinyltrimethoxysilane, 3-8 parts of acrylate-modified cashew nut shell powder, 0.4-1 parts of 2,2,6,6-tetramethyl-4-piperidinyl methacrylate, 0.8-1.5 parts of triallyl isocyanurate, 0.4-0.8 parts of dicumyl peroxide, and 0.3-0.5 parts of antioxidant. The raw materials for masterbatch B include: 100 parts of composite polyethylene resin, 25-45 parts of silanized inorganic filler, 8-15 parts of compatibilizer, 0.5-2 parts of dibutyltin dilaurate, 0.3-0.5 parts of antioxidant, and 0.2-0.5 parts of lubricant.

[0007] Preferably, the mass ratio of the A masterbatch to the B masterbatch is (75~80):(20~25).

[0008] In this scheme, during the preparation of masterbatch A, dicumyl peroxide initiates the grafting of various functional monomers onto the polyethylene backbone, accompanied by the formation of a small number of C-C bonds. Acrylate-modified cashew phenol, with its long alkyl side chains and benzene ring structure, imparts flexibility, hydrophobicity, and thermal stability to the matrix. 2,2,6,6-Tetramethyl-4-piperidinyl methacrylate inhibits photodegradation by capturing free radicals. The inorganic filler in masterbatch B provides UV shielding, synergistically constructing a multi-protection system with antioxidants to enhance resistance to yellowing, chalking, and long-term weathering. Finally, under catalysis, the grafted silane groups hydrolyze and condense to form a dense Si-O-Si inorganic crosslinked network, which, through physical entanglement with the matrix and C-C crosslinking points, constitutes a composite structure, increasing the crosslinking density and restricting molecular chain movement, thereby reducing the oxygen permeation rate and achieving high performance in the insulation layer.

[0009] Preferably, the method for preparing the acrylate-modified cashew phenol includes the following steps: Under an inert atmosphere, cashew nut shellac and glycidyl methacrylate were added to a reactor, along with toluene, a catalyst, and a polymerization inhibitor. The mixture was then heated to 100-110°C and reacted for 5-6 hours. After cooling, washing, drying, and vacuum distillation, acrylate-modified cashew nut shellac was obtained.

[0010] In this scheme, under catalysis, the phenolic hydroxyl group in the cashew phenol molecule undergoes nucleophilic attack on the epoxy group in glycidyl methacrylate, resulting in ring opening of the epoxy ring. After ring opening, the oxygen atom of cashew phenol is connected to the side chain of glycidyl methacrylate, and a secondary hydroxyl group is generated on the side chain, thereby grafting the methacrylate group containing carbon-carbon double bonds onto the cashew phenol skeleton.

[0011] Preferably, the molar ratio of cashew phenol, glycidyl methacrylate, catalyst and polymerization inhibitor is 1:(1.05~1.1):(0.01~0.015):(0.001~0.0015).

[0012] Preferably, the catalyst is triphenylphosphine.

[0013] Preferably, the polymerization inhibitor is p-hydroxyanisole.

[0014] Preferably, the silane used in the silanized inorganic filler is octyltriethoxysilane.

[0015] Preferably, the method for preparing the silanized inorganic filler includes the following steps: Nano-silica and nano-zinc oxide were mixed and dispersed in an ethanol aqueous solution. Octyltriethoxysilane was added, and the pH was adjusted to 4.0-5.0. The mixture was reacted at 60-80℃ for 4-6 hours. After solid-liquid separation, washing and drying, silanized inorganic filler was obtained.

[0016] Preferably, the amount of octyltriethoxysilane used is 3% to 5% of the total mass of nano-silica and nano-zinc oxide.

[0017] In this scheme, the octyl long chain can effectively impart hydrophobicity to the inorganic filler and improve its dispersibility in the polyethylene matrix. At the same time, the ethoxy groups on the filler surface can hydrolyze and condense during the moisture curing stage, participating in the formation of a Si-O-Si network, which enhances the density and water-tree resistance of the insulation layer.

[0018] Preferably, the mass ratio of the silanized nano-silica to the silanized nano-zinc oxide is (1~3):1.

[0019] Preferably, the compatibilizer is maleic anhydride-grafted polyethylene with a grafting rate of 0.5% to 2%.

[0020] Preferably, the antioxidant includes antioxidant 1010 and antioxidant 168.

[0021] Preferably, the lubricant is polyethylene wax and / or ethylene bis-stearamide.

[0022] Preferably, the composite polyethylene resin comprises 50-60 parts of linear low-density polyethylene, 20-25 parts of low-density polyethylene, and 20-25 parts of metallocene polyolefin elastomer.

[0023] In this solution, linear low-density polyethylene provides basic mechanical strength and resistance to environmental stress cracking, low-density polyethylene improves silane grafting efficiency, and metallocene polyolefin elastomer imparts low-temperature toughness. The three work together to achieve a comprehensive improvement in the mechanical properties, temperature resistance, and resistance to environmental stress cracking of the insulating material.

[0024] Preferably, the A masterbatch further includes 0.3 to 0.6 parts by weight of 2-phenoxyethyl acrylate.

[0025] In this scheme, 2-phenoxyethyl acrylate contains acrylate double bonds that can be polymerized by free radicals. During the preparation of masterbatch A, it participates in free radical co-grafting and is chemically bonded to the polyethylene molecular chain. The phenoxy aromatic ring structure of the molecular side chain can endow the insulating material with a certain ultraviolet absorption capacity and improve the photothermal stability of the polymer chain.

[0026] Preferably, the B masterbatch further includes 0.1 to 0.3 parts by weight of titanium diisopropoxybisacetylacetonate.

[0027] In this scheme, diisopropoxy diacetylacetone titanium inhibits the premature hydrolysis and self-condensation of alkoxy components during the storage of B masterbatch and the A / B blending extrusion stage by regulating the water activity and hydrolysis kinetics of the system; in the subsequent high temperature and high humidity environment of moisture curing, it promotes the hydrolysis and condensation reaction to occur in the curing process, which is beneficial to improving the uniformity and integrity of the crosslinking network.

[0028] This application also provides a method for preparing a weather-resistant overhead insulated cable, comprising the following steps: S1: After mixing the composite polyethylene resin, vinyltrimethoxysilane, acrylate-modified cashew phenol, 2,2,6,6-tetramethyl-4-piperidinyl methacrylate, triallyl isocyanurate, dicumyl peroxide, antioxidant, and optionally added 2-phenoxyethyl acrylate, the mixture is fed into a twin-screw extruder, extruded, granulated, and dried to obtain masterbatch A. S2: Under the condition of relative humidity ≤45%, the composite polyethylene resin, silanized inorganic filler, compatibilizer, dibutyltin dilaurate, antioxidant, lubricant and optional diisopropoxydiacetylacetonate titanium are mixed and fed into a twin-screw extruder, extruded, granulated and dried to obtain B masterbatch. S3: After mixing masterbatch A and masterbatch B in the specified ratio, the mixture is extruded onto the outer surface of the conductor to form an insulation layer. After moisture curing, a weather-resistant overhead insulated cable is obtained.

[0029] In this method, masterbatch A and masterbatch B are physically mixed in a predetermined ratio and then extruded onto the outer surface of the conductor to form an insulation layer. Subsequently, moisture curing is performed. During this process, the silane groups grafted onto the polyethylene chain undergo hydrolysis and condensation under the catalysis of moisture and dibutyltin dilaurate, forming a Si-O-Si three-dimensional network. Simultaneously, the C-C bond nodes formed in masterbatch A interpenetrate with the Si-O-Si network, constituting an interpenetrating polymer network or a composite cross-linked structure. Ultimately, a weather-resistant overhead insulated cable with excellent insulation properties, mechanical properties, and long-term resistance to UV and heat-oxidative aging is obtained.

[0030] Preferably, in step S1, the temperature settings for each zone of the twin-screw extruder are: zone 1 100~110℃, zone 2 145~160℃, zone 3 165~175℃, zone 4 170~175℃, and die head 165~170℃.

[0031] Preferably, in step S2, the temperature settings for each zone of the twin-screw extruder are: zone 1 110~120℃, zone 2 130~140℃, zone 3 140~150℃, zone 4 140~150℃, and die head 135~145℃.

[0032] Preferably, in step S3, the moisture curing is performed by moisture crosslinking curing in a warm water bath at 90~95℃ for 6~12 hours.

[0033] Preferably, in step S3, the extrusion temperature is 165~170℃.

[0034] In summary, this application has the following beneficial effects: This application is based on a multi-component synergistic modification mechanism using a dual masterbatch system. First, masterbatch A is prepared by simultaneously grafting silane crosslinking groups, acrylate-modified cashew nut shells, photostable groups, and triallyl isocyanurate modification units onto the polyethylene molecular chain. This utilizes the synergistic effect between multiple monomers to improve the material's resistance to environmental stress cracking, UV aging, and mechanical strength. Second, masterbatch B, containing silanized inorganic fillers and a catalytic system, is prepared to enhance the material's structural stability and curing efficiency. Finally, masterbatches A and B are mixed in a specific ratio and extruded onto the conductor surface, followed by moisture curing to form a high-performance insulating layer. Attached Figure Description

[0035] Figure 1 The infrared spectra of cashew phenol, glycidyl methacrylate, and acrylate-modified cashew phenol used in Example 1 of this application are shown in the comparison diagram. Among them, 1 is cashew phenol, 2 is glycidyl methacrylate, and 3 is acrylate-modified cashew phenol. Figure 2 The image shows the infrared spectrum comparison of the blank composite polyethylene matrix, masterbatch A, and weather-resistant overhead insulated cable insulation layer in Example 1 of this application; wherein, 1 is the blank polyethylene matrix, 2 is masterbatch A, and 3 is the weather-resistant overhead insulated cable insulation layer. Detailed Implementation

[0036] The present application will be further described in detail below with reference to the embodiments.

[0037] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application are all commercially available.

[0038] Nano-silica, with an average particle size of 20 nm and a specific surface area of ​​200 m². 2 / g; Nano zinc oxide, average particle size 30nm, specific surface area 30m² 2 / g; Preparation Example 1 The preparation method of acrylate-modified cashew nut shell powder in this example includes the following steps: Under a nitrogen atmosphere, 1 mol of cashew nut shellac and 1.05 mol of glycidyl methacrylate were added to a reactor, along with 300 mL of toluene, 0.01 mol of triphenylphosphine, and 0.001 mol of p-hydroxyanisole. The mixture was heated to 100 °C and reacted for 6 h. After cooling to room temperature, the mixture was washed once with 5% sodium bicarbonate by mass. The organic phase was collected, dried with anhydrous magnesium sulfate, filtered, and then distilled under reduced pressure to obtain acrylate-modified cashew nut shellac.

[0039] Preparation Example 2 The preparation method of acrylate-modified cashew nut shell powder in this example includes the following steps: Under a nitrogen atmosphere, 1 mol of cashew nut shellac and 1.1 mol of glycidyl methacrylate were added to a reactor, along with 300 mL of toluene, 0.015 mol of triphenylphosphine, and 0.0015 mol of p-hydroxyanisole. The mixture was heated to 110 °C and reacted for 5 h. After cooling to room temperature, the mixture was washed once with 5% sodium bicarbonate. The organic phase was collected, dried with anhydrous magnesium sulfate, filtered, and then distilled under reduced pressure to obtain acrylate-modified cashew nut shellac.

[0040] Example 1 The method for preparing the weather-resistant overhead insulated cable in this embodiment includes the following steps: S0: 210g of nano-silica and 70g of nano-zinc oxide were mixed and dispersed in 1L of ethanol aqueous solution (the volume ratio of anhydrous ethanol to deionized water was 9:1). After ultrasonic dispersion at 200W and 20kHz for 30min, 8.4g of octyltriethoxysilane was added. The pH was adjusted to 5.0 with 8% glacial acetic acid. The mixture was stirred and reacted at 60℃ for 5h. After the reaction was completed, the mixture was centrifuged, washed three times with anhydrous ethanol, and vacuum dried at 45℃ for 6h to obtain silanized inorganic filler. S1: 500g of linear low-density polyethylene, 250g of low-density polyethylene, 250g of metallocene ethylene-octene copolymer, 20g of vinyltrimethoxysilane, 30g of acrylate-modified cashew phenol from Preparation Example 1, 4g of 2,2,6,6-tetramethyl-4-piperidinyl methacrylate, 8g of triallyl isocyanurate, 4g of dicumyl peroxide, 2g of antioxidant 1010, and 1g of antioxidant 168 were premixed in a high-speed mixer for 3 minutes, and then fed into a twin-screw extruder. The temperatures of each zone were set as follows: Zone 1 100℃, Zone 2 145℃, Zone 3 165℃, Zone 4 170℃, and Die head 165℃. A vacuum devolatilization section was set with a vacuum degree of -0.08MPa and a melt residence time of about 2 minutes. After extrusion, the mixture was water-cooled and pelletized, and then vacuum-dried at 45℃ for 6 hours to obtain Masterbatch A. S2: Under conditions of relative humidity ≤45%, 500g of linear low-density polyethylene, 250g of low-density polyethylene, 250g of metallocene ethylene-octene copolymer, 250g of silanized inorganic filler, 80g of maleic anhydride grafted polyethylene, 5g of dibutyltin dilaurate, 2g of antioxidant 1010, 1g of antioxidant 168, and 2g of ethylene bis-stearamide were put into a high-speed mixer for premixing for 3 minutes, and then fed into a twin-screw extruder. The temperature settings for each zone were: zone 1 110℃, zone 2 130℃, zone 3 140℃, zone 4 140℃, and die head 135℃. After extrusion, the pellets were water-cooled and pelletized, vacuum-dried at 45℃ for 6 hours, and then sealed and stored in a moisture-proof container to obtain masterbatch B. S3: After thoroughly mixing masterbatch A and masterbatch B at a mass ratio of 75:25, the mixture is extruded onto the outer surface of the conductor to form an insulation layer. The extrusion temperature is 170℃. The extruded cable is then placed in a 90℃ warm water bath for moisture cross-linking and curing for 10 hours to obtain a weather-resistant overhead insulated cable.

[0041] Example 2 The method for preparing the weather-resistant overhead insulated cable in this embodiment includes the following steps: S0: 250g of nano-silica and 250g of nano-zinc oxide were mixed and dispersed in 1.5L of ethanol aqueous solution (the volume ratio of anhydrous ethanol to deionized water was 9:1). After ultrasonic dispersion at 200W and 20kHz for 30min, 25g of octyltriethoxysilane was added. The pH was adjusted to 4.0 with 8% glacial acetic acid. The mixture was stirred and reacted at 80℃ for 6h. After the reaction was completed, the mixture was centrifuged, washed three times with anhydrous ethanol, and vacuum dried at 45℃ for 6h to obtain silanized inorganic filler. S1: 500g of linear low-density polyethylene, 250g of low-density polyethylene, 250g of metallocene ethylene-octene copolymer, 50g of vinyltrimethoxysilane, 80g of acrylate-modified cashew phenol from Preparation Example 1, 10g of 2,2,6,6-tetramethyl-4-piperidinyl methacrylate, 15g of triallyl isocyanurate, 8g of dicumyl peroxide, 3.4g of antioxidant 1010, and 1.7g of antioxidant 168 were premixed in a high-speed mixer for 3 minutes, and then fed into a twin-screw extruder. The temperatures of each zone were set as follows: Zone 1 110℃, Zone 2 160℃, Zone 3 175℃, Zone 4 175℃, and Die head 170℃. A vacuum devolatilization section was set with a vacuum degree of -0.08MPa and a melt residence time of about 2 minutes. After extrusion, the mixture was water-cooled and pelletized, and then vacuum-dried at 45℃ for 6 hours to obtain Masterbatch A. S2: Under conditions of relative humidity ≤45%, 500g of linear low-density polyethylene, 250g of low-density polyethylene, 250g of metallocene ethylene-octene copolymer, 450g of silanized inorganic filler, 150g of maleic anhydride grafted polyethylene, 20g of dibutyltin dilaurate, 3.4g of antioxidant 1010, 1.7g of antioxidant 168, and 5g of ethylene bis-stearamide were added to a high-speed mixer for premixing for 3 minutes, and then fed into a twin-screw extruder. The temperature settings for each zone were: zone 1 120℃, zone 2 140℃, zone 3 150℃, zone 4 150℃, and die head 145℃. After extrusion, the mixture was water-cooled and pelletized, vacuum dried at 45℃ for 6 hours, and then sealed and stored in a moisture-proof container to obtain masterbatch B. S3: After thoroughly mixing masterbatch A and masterbatch B at a mass ratio of 75:25, the mixture is extruded onto the outer surface of the conductor to form an insulation layer. The extrusion temperature is 170℃. The extruded cable is then placed in a 95℃ warm water bath for moisture cross-linking and curing for 6 hours to obtain a weather-resistant overhead insulated cable.

[0042] Example 3 The method for preparing the weather-resistant overhead insulated cable in this embodiment includes the following steps: S0: 200g of nano-silica and 100g of nano-zinc oxide were mixed and dispersed in 1.2L of ethanol aqueous solution (the volume ratio of anhydrous ethanol to deionized water was 9:1). After ultrasonic dispersion at 200W and 20kHz for 30min, 15g of octyltriethoxysilane was added. The pH was adjusted to 4.0 with 8% glacial acetic acid. The mixture was stirred and reacted at 70℃ for 4h. After the reaction was completed, the mixture was centrifuged, washed three times with anhydrous ethanol, and vacuum dried at 45℃ for 6h to obtain silanized inorganic filler. S1: 500g of linear low-density polyethylene, 250g of low-density polyethylene, 250g of metallocene ethylene-octene copolymer, 40g of vinyltrimethoxysilane, 60g of acrylate-modified cashew phenol from Preparation Example 1, 8g of 2,2,6,6-tetramethyl-4-piperidinyl methacrylate, 12g of triallyl isocyanurate, 6g of dicumyl peroxide, 3g of antioxidant 1010, and 1.5g of antioxidant 168 were added to a high-speed mixer for premixing for 3 minutes, and then fed into a twin-screw extruder. The temperatures of each zone were set as follows: Zone 1 100℃, Zone 2 145℃, Zone 3 165℃, Zone 4 170℃, and Die head 165℃. A vacuum devolatilization section was set with a vacuum degree of -0.09MPa and a melt residence time of about 2 minutes. After extrusion, the mixture was water-cooled and pelletized, and then vacuum-dried at 45℃ for 6 hours to obtain Masterbatch A. S2: Under conditions of relative humidity ≤45%, 500g of linear low-density polyethylene, 250g of low-density polyethylene, 250g of metallocene ethylene-octene copolymer, 300g of silanized inorganic filler, 120g of maleic anhydride grafted polyethylene, 15g of dibutyltin dilaurate, 3g of antioxidant 1010, 1.5g of antioxidant 168, and 4g of ethylene bis-stearamide were added to a high-speed mixer for premixing for 3 minutes, and then fed into a twin-screw extruder. The temperature settings for each zone were: zone 1 110℃, zone 2 130℃, zone 3 140℃, zone 4 140℃, and die head 135℃. After extrusion, the mixture was water-cooled and pelletized, vacuum dried at 45℃ for 6 hours, and then sealed and stored in a moisture-proof container to obtain masterbatch B. S3: After thoroughly mixing masterbatch A and masterbatch B at a mass ratio of 75:25, the mixture is extruded onto the outer surface of the conductor to form an insulation layer. The extrusion temperature is 165℃. The extruded cable is then placed in a 90℃ warm water bath for moisture cross-linking and curing for 12 hours to obtain a weather-resistant overhead insulated cable.

[0043] Example 4 The method for preparing the weather-resistant overhead insulated cable in this embodiment includes the following steps: S0: 200g of nano-silica and 100g of nano-zinc oxide were mixed and dispersed in 1.2L of ethanol aqueous solution (the volume ratio of anhydrous ethanol to deionized water was 9:1). After ultrasonic dispersion at 200W and 20kHz for 30min, 15g of octyltriethoxysilane was added. The pH was adjusted to 4.0 with 8% glacial acetic acid. The mixture was stirred and reacted at 70℃ for 4h. After the reaction was completed, the mixture was centrifuged, washed three times with anhydrous ethanol, and vacuum dried at 45℃ for 6h to obtain silanized inorganic filler. S1: 600g of linear low-density polyethylene, 200g of low-density polyethylene, 200g of metallocene ethylene-octene copolymer, 40g of vinyltrimethoxysilane, 60g of acrylate-modified cashew phenol from Preparation Example 2, 8g of 2,2,6,6-tetramethyl-4-piperidinyl methacrylate, 12g of triallyl isocyanurate, 6g of dicumyl peroxide, 3g of antioxidant 1010, and 1.5g of antioxidant 168 were premixed in a high-speed mixer for 3 minutes, and then fed into a twin-screw extruder. The temperatures of each zone were set as follows: Zone 1 100℃, Zone 2 145℃, Zone 3 165℃, Zone 4 170℃, and Die head 165℃. A vacuum devolatilization section was set with a vacuum degree of -0.09MPa and a melt residence time of about 2 minutes. After extrusion, the mixture was water-cooled and pelletized, and then vacuum-dried at 45℃ for 6 hours to obtain Masterbatch A. S2: Under conditions of relative humidity ≤45%, 600g of linear low-density polyethylene, 200g of low-density polyethylene, 200g of metallocene ethylene-octene copolymer, 300g of silanized inorganic filler, 120g of maleic anhydride grafted polyethylene, 15g of dibutyltin dilaurate, 3g of antioxidant 1010, 1.5g of antioxidant 168, and 4g of ethylene bis-stearamide were added to a high-speed mixer for premixing for 3 minutes, and then fed into a twin-screw extruder. The temperature settings for each zone were: zone 1 110℃, zone 2 130℃, zone 3 140℃, zone 4 140℃, and die head 135℃. After extrusion, the pellets were water-cooled and pelletized, vacuum-dried at 45℃ for 6 hours, and then sealed and stored in a moisture-proof container to obtain masterbatch B. S3: After thoroughly mixing masterbatch A and masterbatch B at a mass ratio of 80:20, the mixture is extruded onto the outer surface of the conductor to form an insulation layer. The extrusion temperature is 165℃. The extruded cable is then placed in a 90℃ warm water bath for moisture cross-linking and curing for 12 hours to obtain a weather-resistant overhead insulated cable.

[0044] Example 5 The difference between this embodiment and embodiment 4 is that: S1: 600g of linear low-density polyethylene, 200g of low-density polyethylene, 200g of metallocene ethylene-octene copolymer, 40g of vinyltrimethoxysilane, 60g of acrylate-modified cashew phenol from Preparation Example 2, 8g of 2,2,6,6-tetramethyl-4-piperidinyl methacrylate, 12g of triallyl isocyanurate, 6g of dicumyl peroxide, 3g of antioxidant 1010, 1.5g of antioxidant 168, and 3g of 2-phenoxyethyl acrylate were premixed in a high-speed mixer for 3 minutes, and then fed into a twin-screw extruder. The temperatures of each zone were set as follows: Zone 1 100℃, Zone 2 145℃, Zone 3 165℃, Zone 4 170℃, and Die head 165℃. A vacuum devolatilization section was set with a vacuum degree of -0.09MPa and a melt residence time of approximately 2 minutes. After extrusion, the mixture was water-cooled and pelletized, and then vacuum-dried at 45℃ for 6 hours to obtain Masterbatch A. The rest is the same as in Example 4.

[0045] Example 6 The difference between this embodiment and embodiment 5 is as follows: The amount of 2-phenoxyethyl acrylate used is 6g; The rest is the same as in Example 5.

[0046] Example 7 The difference between this embodiment and embodiment 4 is that: S2: Under conditions of relative humidity ≤45%, 600g of linear low-density polyethylene, 200g of low-density polyethylene, 200g of metallocene ethylene-octene copolymer, 300g of silanized inorganic filler, 120g of maleic anhydride grafted polyethylene, 15g of dibutyltin dilaurate, 3g of antioxidant 1010, 1.5g of antioxidant 168, 4g of ethylene bis-stearamide, and 1g of diisopropoxydiacetylacetonate titanium were premixed in a high-speed mixer for 3 minutes, and then fed into a twin-screw extruder. The temperature settings for each zone were: zone 1 110℃, zone 2 130℃, zone 3 140℃, zone 4 140℃, and die head 135℃. After extrusion, the pellets were water-cooled and granulated, vacuum-dried at 45℃ for 6 hours, and then sealed and stored in a moisture-proof container to obtain masterbatch B. The rest is the same as in Example 4.

[0047] Example 8 The difference between this embodiment and embodiment 6 is that: The dosage of diisopropoxydiacetylacetone titanium is 3g; The rest is the same as in Example 6.

[0048] Comparative Example 1 The difference between this comparative example and Example 1 is as follows: In Masterbatch A, an equal mass of light stabilizer 944 is used to replace 2,2,6,6-tetramethyl-4-piperidinyl methacrylate. Everything else is the same as in Example 1.

[0049] Comparative Example 2 The comparative method for preparing weather-resistant overhead insulated cables includes the following steps: S0: 210g of nano-silica and 70g of nano-zinc oxide were mixed and dispersed in 1L of ethanol aqueous solution (the volume ratio of anhydrous ethanol to deionized water was 9:1). After ultrasonic dispersion at 200W and 20kHz for 30min, 8.4g of octyltriethoxysilane was added. The pH was adjusted to 5.0 with 8% glacial acetic acid. The mixture was stirred and reacted at 60℃ for 5h. After the reaction was completed, the mixture was centrifuged, washed three times with anhydrous ethanol, and vacuum dried at 45℃ for 6h to obtain silanized inorganic filler. S1: 500g of linear low-density polyethylene, 250g of low-density polyethylene, 250g of metallocene ethylene-octene copolymer, 20g of vinyltrimethoxysilane, 30g of acrylate-modified cashew phenol from Preparation Example 1, 4g of 2,2,6,6-tetramethyl-4-piperidinyl methacrylate, 8g of triallyl isocyanurate, 4g of dicumyl peroxide, 56g of silanized inorganic filler, 18g of maleic anhydride-grafted polyethylene, 0.67g of dibutyltin dilaurate, 4g of antioxidant 1010, and antioxidant 168. 2g of ethylene bis-stearamide and 2g of ethylene bis-stearamide were added to a high-speed mixer and premixed for 3 minutes. Then, the mixture was fed into a twin-screw extruder with the following temperature settings for each zone: Zone 1 100℃, Zone 2 145℃, Zone 3 165℃, Zone 4 170℃, and Die head 165℃. A vacuum devouring section was set with a vacuum degree of -0.08MPa and a melt residence time of about 2 minutes. The melt was extruded and directly extruded onto the outer surface of the conductor to form an insulation layer. The extruded cable was then placed in a 90℃ warm water bath for moisture cross-linking and curing for 10 hours to obtain a weather-resistant overhead insulated cable.

[0050] Comparative Example 3 The difference between this comparative example and Example 1 is as follows: Masterbatch A does not contain acrylate-modified cashew phenol or triallyl isocyanurate; Everything else is the same as in Example 1.

[0051] Performance testing The weather-resistant overhead insulated cables prepared in Examples 1-8 and Comparative Examples 1-3 were subjected to the following performance tests, and the test results are shown in Table 1 and Table 2. 1. Mechanical property testing: Test the tensile strength and elongation at break of the specimen; 2. Electrical performance testing: Test the volume resistivity and dielectric strength of the sample; 3. Aging resistance test (1) Test conditions for ultraviolet aging: an ultraviolet aging test chamber was used, with an irradiation intensity of 0.7 W / m. 2 The lamp was placed 50cm away from the lamp tube, and the cycle consisted of 60℃ illumination for 8 hours and 50℃ condensation for 4 hours, with no spraying. The total cycle time was 720 hours. After the cycle, the retention rates of tensile strength and elongation at break were measured. (2) Test conditions for thermo-oxidative aging: 100℃, aging for 168h; after the end of the test, the retention rates of tensile strength and elongation at break were determined. 4. Thermal elongation performance test: The test conditions are 200℃, 0.2MPa, 15min, elongation under load and permanent deformation rate after cooling.

[0052] Table 1. Test data on the mechanical properties and aging resistance of weather-resistant overhead insulated cables prepared in Examples 1-8 and Comparative Examples 1-3.

[0053] Table 2. Test data on electrical properties and thermal elongation properties of weather-resistant overhead insulated cables obtained in Examples 1-8 and Comparative Examples 1-3.

[0054] The specific analysis based on the detection data in Tables 1 and 2 is as follows: Comparing Example 1 with Comparative Examples 1-3, it can be seen that: Comparative Example 1 uses an equal mass of light stabilizer 944 to replace 2,2,6,6-tetramethyl-4-piperidinyl methacrylate, and the initial properties of the two are similar. However, the tensile strength and elongation at break retention rates of Comparative Example 1 after UV aging are significantly lower than those of Example 1. Comparative Example 2 uses a one-step blending extrusion process, and its initial mechanical properties, aging resistance, and thermal elongation properties are all inferior to those of Example 1. In Comparative Example 3, the A masterbatch does not contain acrylate-modified cashew nut shell phenol and triallyl isocyanurate, and its elongation at break is slightly higher than that of Example 1, but the tensile strength is somewhat reduced. The elongation at break retention rate after UV aging is significantly lower, and the permanent deformation rate of thermal elongation is also somewhat increased.

[0055] Examples 1-4 show that under the dual masterbatch process of A and B masterbatches, the dosage of each functional component and the ratio of polyethylene resin have good adjustability. Within the range of formula adjustment, the materials can achieve a comprehensive balance between weather resistance and mechanical and electrical properties.

[0056] As can be seen from Examples 4-8, Examples 5 and 6, based on Example 4, gradually added 2-phenoxyethyl acrylate, which improved the retention rate of tensile strength and aging performance, slightly reduced the elongation at break, and optimized the thermal elongation performance.

[0057] Example 7 introduced diisopropoxydiacetylacetonate titanium into masterbatch B. The tensile strength was basically maintained, the elongation at break fluctuated slightly, the bulk mechanical properties did not deteriorate, and the thermal elongation properties were not further improved. This indicates that simply increasing the curing catalytic rate cannot continuously optimize the overall performance of the crosslinking network.

[0058] Example 8 combines a higher amount of 2-phenoxyethyl acrylate and diisopropoxy diacetylacetone titanium, which optimizes aging resistance and thermal elongation, further improves tensile strength, moderately reduces elongation at break, and maintains overall mechanical properties at a high level.

[0059] from Figure 1 It can be seen that, compared with cashew phenol and glycidyl methacrylate, the characteristic absorption peak of epoxy in the product spectrum disappears, the hydroxyl absorption peak shifts, and the ester carbonyl absorption peak of acrylate is retained, indicating that cashew phenol reacts with glycidyl methacrylate to obtain acrylate-modified cashew phenol.

[0060] from Figure 2It can be seen that, compared with the blank composite polyethylene matrix, the characteristic absorption corresponding to the functional groups can be observed in Masterbatch A; compared with the uncrosslinked Masterbatch A, the characteristic absorption of Si-O-Si in the crosslinked insulating layer is enhanced, the characteristic absorption of silane methoxy is weakened, and the absorption of ester carbonyl is retained, indicating that silane hydrolysis condensation crosslinking has occurred and the grafted functional groups are retained in the insulating matrix.

Claims

1. A weather-resistant overhead insulated cable, comprising a conductor and an insulation layer covering the conductor, characterized in that, The insulating layer is obtained by mixing masterbatch A and masterbatch B, extruding the mixture onto the surface of the conductor, and then curing it through moisture crosslinking. The raw materials for preparing Masterbatch A, by weight, include: 100 parts of composite polyethylene resin, 2-5 parts of vinyltrimethoxysilane, 3-8 parts of acrylate-modified cashew nut shell powder, 0.4-1 parts of 2,2,6,6-tetramethyl-4-piperidinyl methacrylate, 0.8-1.5 parts of triallyl isocyanurate, 0.4-0.8 parts of dicumyl peroxide, and 0.3-0.5 parts of antioxidant; the raw materials for preparing Masterbatch B include: 100 parts of composite polyethylene resin, 25-45 parts of silanized inorganic filler, 8-15 parts of compatibilizer, 0.5-2 parts of dibutyltin dilaurate, 0.3-0.5 parts of antioxidant, and 0.2-0.5 parts of lubricant.

2. The weather-resistant overhead insulated cable according to claim 1, characterized in that, The mass ratio of Masterbatch A to Masterbatch B is (75~80):(20~25).

3. The weather-resistant overhead insulated cable according to claim 1, characterized in that, The preparation method of the acrylate-modified cashew phenol includes the following steps: Under an inert atmosphere, cashew nut shellac and glycidyl methacrylate were added to a reactor, along with toluene, a catalyst, and a polymerization inhibitor. The mixture was then heated to 100-110°C and reacted for 5-6 hours. After cooling, washing, drying, and vacuum distillation, acrylate-modified cashew nut shellac was obtained.

4. The weather-resistant overhead insulated cable according to claim 3, characterized in that, The molar ratio of cashew phenol, glycidyl methacrylate, catalyst and polymerization inhibitor is 1:(1.05~1.1):(0.01~0.015):(0.001~0.0015).

5. The weather-resistant overhead insulated cable according to claim 1, characterized in that, The silanized inorganic filler uses octyltriethoxysilane as the silane.

6. The weather-resistant overhead insulated cable according to claim 5, characterized in that, The preparation method of the silanized inorganic filler includes the following steps: Nano-silica and nano-zinc oxide were mixed and dispersed in an ethanol aqueous solution. Octyltriethoxysilane was added, and the pH was adjusted to 4.0-5.

0. The mixture was reacted at 60-80℃ for 4-6 hours. After solid-liquid separation, washing and drying, silanized inorganic filler was obtained.

7. The weather-resistant overhead insulated cable according to claim 1, characterized in that, The composite polyethylene resin comprises 50-60 parts of linear low-density polyethylene, 20-25 parts of low-density polyethylene, and 20-25 parts of metallocene polyolefin elastomer.

8. The weather-resistant overhead insulated cable according to claim 6, characterized in that, The masterbatch A also includes 0.3 to 0.6 parts by weight of 2-phenoxyethyl acrylate.

9. The weather-resistant overhead insulated cable according to claim 1, characterized in that, The B masterbatch also includes 0.1 to 0.3 parts by weight of diisopropoxydiacetylacetone titanium.

10. A method for preparing a weather-resistant overhead insulated cable as described in claim 1, characterized in that, The process includes the following steps: S1: The composite polyethylene resin, vinyltrimethoxysilane, acrylate-modified cashew nut shell powder, 2,2,6,6-tetramethyl-4-piperidinyl methacrylate, triallyl isocyanurate, dicumyl peroxide, antioxidant, and optionally added 2-phenoxyethyl acrylate are mixed and fed into a twin-screw extruder for extrusion, granulation, and drying to obtain masterbatch A; S2: Under the condition of relative humidity ≤45%, the composite polyethylene resin, silanized inorganic filler, compatibilizer, dibutyltin dilaurate, antioxidant, lubricant and optional diisopropoxydiacetylacetonate titanium are mixed and fed into a twin-screw extruder, extruded, granulated and dried to obtain B masterbatch. S3: After mixing masterbatch A and masterbatch B in the specified ratio, the mixture is extruded onto the outer surface of the conductor to form an insulation layer. After moisture curing, a weather-resistant overhead insulated cable is obtained.

Images