Anti-aging chemical crosslinked polyethylene cable insulation material and preparation process thereof

Abstract

The invention relates to the technical field of cable insulation materials, in particular to an anti-aging chemical crosslinked polyethylene cable insulation material and a preparation process thereof. The insulating material is prepared from the following components in parts by mass: 50 to 60 parts of low-density polyethylene, 20 to 25 parts of polyolefin elastomer, 10 to 15 parts of maleic anhydride grafted SEBS (Styrene-Ethylene-Butylene-Styrene), 1.5 to 2.5 parts of dicumyl peroxide, 15 to 20 parts of composite flame-retardant filler and 3 to 5 parts of anti-aging composition, the preparation process comprises the following three steps: firstly, preparing the core-shell structure flame-retardant master batch of zinc borate coated talcum powder through ball milling and melt blending; secondly, mixing the anti-aging component with a polyolefin elastomer to prepare an anti-aging master batch; and finally, mixing the matrix resin with the two master batches and the cross-linking agent, carrying out reactive extrusion in a four-section temperature zone (150-195 DEG C), and carrying out water-cooling cutting and drying to obtain a finished product. The insulating material has the characteristics of no toxicity, long-term high temperature resistance, aging resistance and excellent flame retardance, and is suitable for low-voltage to medium-voltage power cables.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cable insulation materials, in particular to an anti-aging chemical cross-linked polyethylene cable insulation material and a preparation process thereof. BACKGROUND

[0002] In the field of power cable insulation materials, chemical cross-linked polyethylene (XLPE) has become the core insulation material for medium and low voltage cables due to its excellent insulation performance and processing convenience. However, the existing technology faces severe anti-aging performance bottlenecks in actual application, mainly in four key aspects:

[0003] Firstly, there is a contradiction between environmental protection and efficiency in the cross-linking system. Although traditional silane cross-linking technology can improve heat resistance, it relies on toxic organotin catalysts, which not only violates international environmental regulations, but also has long-term migration risks. While the scheme of replacing inorganic sulfides reduces toxicity, it leads to a significant decrease in cross-linking degree due to insufficient catalytic activity, causing material mechanical strength degradation and heat deformation hazards.

[0004] Secondly, the anti-aging protection mechanism is single. The mainstream technology relies on a single path of antioxidants (such as thio-phenol compounds), lacking a coordinated protection design for multiple aging factors such as heat, light, and metal ions. This leads to an imbalance in the consumption of anti-aging agents during cable operation - research has confirmed that the insulation layer exhibits a typical "sandwich effect" along the radial direction: under the action of electric field gradient and environmental penetration, the consumption rate of anti-aging agents in the outer and inner layers is much higher than that in the middle layer, and after ten years of operation, the oxidation degree of the inner and outer layers can be several times that of the middle layer, significantly expanding the electrical strength decay amplitude, ultimately leading to non-uniform aging failure.

[0005] Thirdly, flame retardation and anti-aging performance are mutually restrictive. High filler content flame retardant systems can meet fireproof standards, but severely damage material processing fluidity and hinder cross-linking reaction efficiency; at the same time, large size flame retardant fillers can form physical barriers, interfering with the diffusion and distribution of anti-aging agents in the matrix, accelerating the performance collapse of local aging areas.

[0006] The above systematic defects collectively lead to a chain failure of XLPE insulation material under long-term high temperature operating conditions: cross-linking network defects accelerate molecular chain rupture, anti-aging agents are consumed prematurely, inducing oxidative cracking, and finally the electrical performance drops sharply, with a service life far below the 30-year industry standard. Therefore, it is urgent to develop new anti-aging chemical cross-linked polyethylene insulation materials with comprehensive performance through formulation and process innovation, to meet the stringent requirements of smart grids, new energy and other fields for medium and low voltage power cables in terms of high reliability, long service life and anti-aging. SUMMARY

[0007] Based on the problems in the background art, an anti-aging chemical crosslinking polyethylene cable insulation material, by mass fraction, the insulation material comprises the following components, 50-60 parts of low density polyethylene, 20-25 parts of polyolefin elastomer, 10-15 parts of maleic anhydride grafted SEBS, 1.5-2.5 parts of dicumyl peroxide, 15-20 parts of composite flame-retardant filler and 3-5 parts of anti-aging combination.

[0008] Preferably, the composite flame-retardant filler comprises talcum powder and zinc borate, the mass percentage of talcum powder in the composite flame-retardant filler is 80-90%, and the mass percentage of zinc borate in the composite flame-retardant filler is 10-20%. Zinc borate releases crystallization water endothermically upon heating, talcum powder enhances carbonization, and the composite flame-retardant filler cooperatively improves the flame retardancy, and the coating structure avoids filler agglomeration.

[0009] Preferably, the anti-aging combination comprises 1-2 parts of antioxidant 1010, 1-2 parts of ultraviolet absorber UV531 and 1 part of copper inhibitor MD1024 by mass fraction. The triple protection mechanism inhibits thermal, light and metal ion aging.

[0010] Preferably, a preparation process of an anti-aging chemical crosslinking polyethylene cable insulation material, the steps are as follows,

[0011] Step 1: Preparation of composite flame-retardant filler masterbatch

[0012] (1.1) Put talcum powder and zinc borate into a ball mill according to a certain mass percentage for grinding, and use anhydrous ethanol as a dispersion medium to form a core-shell structure composite filler of zinc borate coated talcum powder;

[0013] (1.2) Vacuum dry the composite filler obtained in step (1.1) at a temperature of 60-80℃ for 12 hours;

[0014] (1.3) Premix the dried composite filler in step (1.2) with 10 parts of low density polyethylene for 5 minutes, melt blend through a twin-screw extruder at a temperature of 160-180℃, and water ring pelletize to obtain a flame-retardant masterbatch with a particle size of 3mm;

[0015] Step 2: Preparation of anti-aging masterbatch

[0016] (2.1) Mix 1-2 parts of antioxidant 1010, 1-2 parts of ultraviolet absorber UV531 and 1 part of copper inhibitor MD1024 with 5 parts of polyolefin elastomer at 800rpm for 10 minutes to obtain a premix;

[0017] (2.2) Extrude the premix through a twin-screw extruder at a temperature of 150-170℃, air-cool and pelletize to obtain an anti-aging masterbatch;

[0018] Step 3: Insulation material reaction extrusion molding

[0019] (3.1) Mix the remaining low density polyethylene 40-50 parts, polyolefin elastomer 15-20 parts and maleic anhydride grafted SEBS 10-15 parts at a rotation speed of 1000 rpm for 15 minutes to form a base resin;

[0020] (3.2) Add dicumyl peroxide 1.5-2.5 parts, the flame-retardant master batch of step (1.3) 15-20 parts and the anti-aging master batch of step (2.2) 3-5 parts to the base resin, and mix for 10 minutes to obtain a mixture;

[0021] (3.3) Reactively extrude the mixture through a twin-screw extruder, and control the reaction process according to the following four temperature zones: feeding section 150℃ (to prevent premature decomposition of DCP), compression section 170℃ (to initiate preliminary crosslinking), homogenization section 185℃ (to complete the main crosslinking reaction), and die head section 195℃ (to ensure melt flowability);

[0022] (3.4) Solidify the extruded strip in step (3.3) by water cooling, cut it into 2-4 mm particles, and dry them at a temperature of 80℃ for 4 hours to obtain a cable insulation material.

[0023] Preferably, in step (1.1), the ball milling parameters are: rotation speed 200-300 rpm, ball milling time 2-3 hours, and the particle size of the talc is 1-5 μm.

[0024] Preferably, in step (1.1), the mass percentage of talc to zinc borate is 85:15.

[0025] Preferably, in step (2.1), the mass ratio of antioxidant 1010, ultraviolet absorber UV531 and copper inhibitor MD1024 is 1.5:1.5:1.

[0026] Preferably, in step (3.3), the temperature of the homogenization section is controlled at 185±2℃, and the residence time of the homogenization section is ≥40 seconds.

[0027] Preferably, in step (3.4), the particle size of the cut particles is 3±0.5 mm.

[0028] Preferably, the polyethylene cable insulation material is prepared by the preparation process of the anti-aging chemically crosslinked polyethylene cable insulation material.

[0029] Compared with the prior art, the beneficial effects of the present application are: 1) dicumyl peroxide (DCP) is used as a crosslinking agent to completely replace toxic organic tin catalyst; four-stage temperature control is used to ensure that the crosslinking degree is >85%, effectively solving the problem of mechanical strength degradation caused by insufficient crosslinking of inorganic sulfide system, and the tensile strength retention rate is increased by more than 25%.

[0030] 2) Innovative adoption of ternary anti-aging combination, in which antioxidant 1010 inhibits thermal-oxidative aging chain reaction, UV531 absorbs ultraviolet radiation energy, and MD1024 passivates copper ion catalytic activity; the three are realized molecular dispersion through the process of masterbatching (extrusion at 150-170℃), so that the radial aging difference of the insulation layer is reduced by 60%, the electrical strength decay rate is <5%, and the "sandwich effect" bottleneck is broken through.

[0031] 3) Design of core-shell structure composite flame-retardant filler (talc powder core / zinc borate shell), which improves the flame-retardant efficiency by 40%; talc powder as a nanoscale reinforcing phase avoids the diffusion barrier caused by large-size filler to anti-aging agents.

[0032] 4) Stepwise masterbatching process optimizes the dispersibility of flame-retardant filler through ball milling and extrusion at 160-180℃, realizes uniform distribution of anti-aging components; combined with reaction extrusion integration technology (synchronous feeding of base resin and double masterbatch, four-stage temperature zone 150→195℃), realizes one-step completion of crosslinking-blending, avoids the risk of delamination of multi-layer composite interface, product qualification rate >98% and production capacity is increased by 30%.

[0033] 5) The prepared insulation material has long-term temperature resistance, excellent flame retardancy and low temperature adaptability, and is suitable for 30-year long-life design of low-voltage cables in new energy power generation, smart grid and other fields. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application. In the present application, the parts involved are all parts by weight unless otherwise specified.

[0035] Embodiment 1

[0036] An anti-aging chemical crosslinking polyethylene cable insulation material, by mass parts, comprises the following components: 55 parts of low-density polyethylene, 22 parts of polyolefin elastomer, 12 parts of maleic anhydride grafted SEBS, 2 parts of dicumyl peroxide, 17 parts of composite flame-retardant filler and 4 parts of anti-aging combination.

[0037] The above components are prepared to obtain a polyethylene cable insulation material according to the following steps,

[0038] Step 1: Preparation of composite flame-retardant filler masterbatch

[0039] (1.1) Talc powder and zinc borate were added to a ball mill at a mass percentage of 85%:15% for grinding. The ball milling parameters were: rotation speed 250 rpm, ball milling time 2.5 hours, and anhydrous ethanol was used as the dispersion medium to form a core-shell structured composite filler of zinc borate coated with talc powder.

[0040] (1.2) The composite filler obtained in step (1.1) is vacuum dried at 70°C for 12 hours;

[0041] (1.3) The composite filler dried in step (1.2) is premixed with 10 parts of low-density polyethylene for 5 minutes, melt-blended at 170°C using a twin-screw extruder, and then water ring pelletized to obtain flame retardant masterbatch with a particle size of 3 mm.

[0042] Step 2: Preparation of anti-aging masterbatch

[0043] (2.1) 1.5 parts of antioxidant 1010, 1.5 parts of ultraviolet absorber UV53, 1 part of copper inhibitor MD1024, and 5 parts of polyolefin elastomer were mixed at 800 rpm for 10 minutes to obtain a premix.

[0044] (2.2) The premixed material was extruded through a twin-screw extruder at 160°C and air-cooled and pelletized to obtain anti-aging masterbatch;

[0045] Step 3: Reactive extrusion molding of insulating material

[0046] (3.1) Mix the remaining 45 parts of low-density polyethylene, 17 parts of polyolefin elastomer and 12 parts of maleic anhydride-grafted SEBS at 1000 rpm for 15 minutes to form a matrix resin.

[0047] (3.2) Add 2 parts of dicumyl peroxide, 17 parts of the flame retardant masterbatch from step (1.3) and the anti-aging masterbatch prepared in step (2.2) to the matrix resin, and mix for 10 minutes to obtain a mixture;

[0048] (3.3) The mixture is extruded through a twin-screw extruder, and the reaction process is controlled in the following four temperature zones: feeding zone 150℃, compression zone 170℃, homogenization zone 185℃, die head zone 195℃, and residence time in the homogenization zone ≥40 seconds.

[0049] (3.4) The extruded strip from step (3.3) is water-cooled and cured, cut into 3mm particles, and dried at 80°C for 4 hours to obtain cable insulation material.

[0050] Compared with traditional insulation products, the insulation material prepared in Example 1 adopts a non-toxic DCP crosslinking system combined with a four-stage precise temperature control process, achieving a crosslinking degree of 88.5% (traditional ≤75%), completely solving the problems of organotin toxicity and insufficient crosslinking; the innovative ternary anti-aging synergistic system (1010 / UV531 / MD1024 = 1.5:1.5:1) achieves molecular-level dispersion through masterbatch, and the electrical strength decay rate after aging at 125℃ for 3000h is only 4.2% (traditional >12%), providing highly reliable insulation protection for smart grid and new energy cables.

[0051] Example 2

[0052] An anti-aging chemically cross-linked polyethylene cable insulation material, by weight, comprises the following components: 50 parts of low-density polyethylene, 20 parts of polyolefin elastomer, 10 parts of maleic anhydride-grafted SEBS, 1.5 parts of dicumyl peroxide, 15 parts of composite flame-retardant filler, and 3 parts of anti-aging compound.

[0053] The above components are prepared according to the following steps to obtain polyethylene cable insulation material.

[0054] Step 1: Preparation of composite flame retardant filler masterbatch

[0055] (1.1) Talc powder and zinc borate were added to a ball mill at a mass percentage of 80%:20% for grinding. The ball milling parameters were: 200 rpm and 2 hours. Anhydrous ethanol was used as the dispersion medium to form a core-shell structured composite filler with zinc borate coating talc powder.

[0056] (1.2) The composite filler obtained in step (1.1) is vacuum dried at 60°C for 12 hours;

[0057] (1.3) The composite filler dried in step (1.2) was premixed with 10 parts of low-density polyethylene for 5 minutes, melt-blended at 16°C using a twin-screw extruder, and then water ring pelletized to obtain flame retardant masterbatch with a particle size of 3 mm.

[0058] Step 2: Preparation of anti-aging masterbatch

[0059] (2.1) Mix 10101 parts of antioxidant, 11 parts of UV5311 parts of ultraviolet absorber and 1 part of copper inhibitor MD10241 parts of polyolefin elastomer with 5 parts of polyolefin elastomer at 800 rpm for 10 minutes to obtain a premix.

[0060] (2.2) The premixed material was extruded through a twin-screw extruder at 150°C and air-cooled and pelletized to obtain anti-aging masterbatch;

[0061] Step 3: Reactive extrusion molding of insulating material

[0062] (3.1) Mix the remaining 40 parts of low-density polyethylene, 15 parts of polyolefin elastomer and 10 parts of maleic anhydride-grafted SEBS at 1000 rpm for 15 minutes to form a matrix resin.

[0063] (3.2) Add 1.5 parts of dicumyl peroxide, 15 parts of the flame retardant masterbatch from step (1.3) and the anti-aging masterbatch prepared in step (2.2) to the matrix resin, and mix for 10 minutes to obtain a mixture;

[0064] (3.3) The mixture is extruded through a twin-screw extruder, and the reaction process is controlled in the following four temperature zones: feeding zone 150℃, compression zone 170℃, homogenization zone 183℃, die head zone 195℃, and residence time in the homogenization zone ≥40 seconds.

[0065] (3.4) The extruded strip from step (3.3) is water-cooled and cured, cut into 2mm particles, and dried at 80°C for 4 hours to obtain cable insulation material.

[0066] Example 3

[0067] An anti-aging chemically cross-linked polyethylene cable insulation material, by weight, comprises the following components: 60 parts of low-density polyethylene, 25 parts of polyolefin elastomer, 15 parts of maleic anhydride-grafted SEBS, 2.5 parts of dicumyl peroxide, 20 parts of composite flame-retardant filler, and 5 parts of anti-aging compound.

[0068] The above components are prepared according to the following steps to obtain polyethylene cable insulation material.

[0069] Step 1: Preparation of composite flame retardant filler masterbatch

[0070] (1.1) Talc powder and zinc borate were added to a ball mill at a mass percentage of 90%:10% for grinding. The ball milling parameters were: 300 rpm and 3 hours. Anhydrous ethanol was used as the dispersion medium to form a core-shell structured composite filler with zinc borate coating talc powder.

[0071] (1.2) The composite filler obtained in step (1.1) is vacuum dried at 80°C for 12 hours;

[0072] (1.3) The composite filler dried in step (1.2) is premixed with 10 parts of low-density polyethylene for 5 minutes, melt-blended at 180°C using a twin-screw extruder, and then water ring pelletized to obtain flame retardant masterbatch with a particle size of 3 mm.

[0073] Step 2: Preparation of anti-aging masterbatch

[0074] (2.1) 10102 parts of antioxidant, 12 parts of UV absorber UV5312 parts and 1 part of copper inhibitor MD10241 parts were mixed with 5 parts of polyolefin elastomer at 800 rpm for 10 minutes to obtain a premix.

[0075] (2.2) The premixed material was extruded through a twin-screw extruder at 170°C and air-cooled and pelletized to obtain anti-aging masterbatch;

[0076] Step 3: Reactive extrusion molding of insulating material

[0077] (3.1) Mix the remaining 50 parts of low-density polyethylene, 20 parts of polyolefin elastomer and 15 parts of maleic anhydride-grafted SEBS at 1000 rpm for 15 minutes to form a matrix resin.

[0078] (3.2) Add 2.5 parts of dicumyl peroxide, 20 parts of the flame retardant masterbatch from step (1.3) and the anti-aging masterbatch prepared in step (2.2) to the matrix resin, and mix for 10 minutes to obtain a mixture;

[0079] (3.3) The mixture is extruded through a twin-screw extruder, and the reaction process is controlled in the following four temperature zones: feeding zone 150℃, compression zone 170℃, homogenization zone 187℃, die head zone 195℃, and residence time in the homogenization zone ≥40 seconds.

[0080] (3.4) The extruded strip from step (3.3) is water-cooled and cured, cut into 4mm particles, and dried at 80°C for 4 hours to obtain cable insulation material.

[0081] Example 4

[0082] An anti-aging chemical cross-linked polyethylene cable insulation material, by weight, comprises the following components: 52 parts of low-density polyethylene, 22 parts of polyolefin elastomer, 12 parts of maleic anhydride-grafted SEBS, 1.8 parts of dicumyl peroxide, 17 parts of composite flame-retardant filler, and 4 parts of anti-aging compound.

[0083] The above components are prepared according to the following steps to obtain polyethylene cable insulation material.

[0084] Step 1: Preparation of composite flame retardant filler masterbatch

[0085] (1.1) Talc powder and zinc borate were added to a ball mill at a mass percentage of 83%:17% for grinding. The ball milling parameters were: rotation speed 220 rpm, ball milling time 2.5 hours, and anhydrous ethanol was used as the dispersion medium to form a core-shell structured composite filler of zinc borate coated with talc powder.

[0086] (1.2) The composite filler obtained in step (1.1) is vacuum dried at 65°C for 12 hours;

[0087] (1.3) The composite filler dried in step (1.2) is premixed with 10 parts of low-density polyethylene for 5 minutes, melt-blended at 165°C using a twin-screw extruder, and then water ring pelletized to obtain flame retardant masterbatch with a particle size of 3 mm.

[0088] Step 2: Preparation of anti-aging masterbatch

[0089] (2.1) 10102 parts of antioxidant, 11 parts of UV absorber UV5311 parts and 1 part of copper inhibitor MD10241 parts were mixed with 5 parts of polyolefin elastomer at 800 rpm for 10 minutes to obtain a premix.

[0090] (2.2) The premixed material was extruded through a twin-screw extruder at 155°C and air-cooled and pelletized to obtain anti-aging masterbatch;

[0091] Step 3: Reactive extrusion molding of insulating material

[0092] (3.1) Mix the remaining 42 parts of low-density polyethylene, 17 parts of polyolefin elastomer and 12 parts of maleic anhydride-grafted SEBS at 1000 rpm for 15 minutes to form a matrix resin.

[0093] (3.2) Add 1.8 parts of dicumyl peroxide, 17 parts of the flame retardant masterbatch from step (1.3) and the anti-aging masterbatch prepared in step (2.2) to the matrix resin, and mix for 10 minutes to obtain a mixture;

[0094] (3.3) The mixture is extruded through a twin-screw extruder, and the reaction process is controlled in the following four temperature zones: feeding zone 150℃, compression zone 170℃, homogenization zone 185℃, die head zone 195℃, and residence time in the homogenization zone ≥40 seconds.

[0095] (3.4) The extruded strip from step (3.3) is water-cooled and cured, cut into 2.5mm particles, and dried at 80°C for 4 hours to obtain cable insulation material.

[0096] Example 5

[0097] An anti-aging chemical cross-linked polyethylene cable insulation material, by weight, comprises the following components: 57 parts of low-density polyethylene, 24 parts of polyolefin elastomer, 14 parts of maleic anhydride-grafted SEBS, 2.3 parts of dicumyl peroxide, 19 parts of composite flame-retardant filler, and 4 parts of anti-aging compound.

[0098] The above components are prepared according to the following steps to obtain polyethylene cable insulation material.

[0099] Step 1: Preparation of composite flame retardant filler masterbatch

[0100] (1.1) Talc powder and zinc borate were added to a ball mill at a mass percentage of 87%:13% for grinding. The ball milling parameters were: rotation speed 280 rpm, ball milling time 2.5 hours, and anhydrous ethanol was used as the dispersion medium to form a core-shell structured composite filler of zinc borate coated with talc powder.

[0101] (1.2) The composite filler obtained in step (1.1) is vacuum dried at 75°C for 12 hours;

[0102] (1.3) The composite filler dried in step (1.2) is premixed with 10 parts of low-density polyethylene for 5 minutes, melt-blended at 175°C using a twin-screw extruder, and then water ring pelletized to obtain flame retardant masterbatch with a particle size of 3 mm.

[0103] Step 2: Preparation of anti-aging masterbatch

[0104] (2.1) Mix 10101 parts of antioxidant, 12 parts of UV5312 parts of UV absorber and 1 part of copper inhibitor MD10241 parts of polyolefin elastomer with 5 parts of polyolefin elastomer at 800 rpm for 10 minutes to obtain a premix.

[0105] (2.2) The premixed material was extruded through a twin-screw extruder at 165°C and air-cooled and pelletized to obtain anti-aging masterbatch;

[0106] Step 3: Reactive extrusion molding of insulating material

[0107] (3.1) Mix the remaining 47 parts of low-density polyethylene, 19 parts of polyolefin elastomer and 14 parts of maleic anhydride-grafted SEBS at 1000 rpm for 15 minutes to form a matrix resin.

[0108] (3.2) Add 2.3 parts of dicumyl peroxide, 19 parts of the flame retardant masterbatch from step (1.3) and the anti-aging masterbatch prepared in step (2.2) to the matrix resin, and mix for 10 minutes to obtain a mixture;

[0109] (3.3) The mixture is extruded through a twin-screw extruder, and the reaction process is controlled in the following four temperature zones: feeding zone 150℃, compression zone 170℃, homogenization zone 185℃, die head zone 195℃, and residence time in the homogenization zone ≥40 seconds.

[0110] (3.4) The extruded strip from step (3.3) is water-cooled and cured, cut into 3.5mm particles, and dried at 80°C for 4 hours to obtain cable insulation material.

[0111] Comparative Example 1

[0112] In Example 1, 2 parts of dicumyl peroxide were replaced with 0.8 parts of dibutyltin dilaurate, and all flame-retardant fillers were replaced with aluminum hydroxide (40% water content). The remaining steps and process parameters were the same as in Example 1. The results showed that due to the catalytic toxicity of organotin leading to excessive migration, and the high filler content of aluminum hydroxide easily inducing agglomeration, the measured crosslinking degree was only 71.2%, and the electrical strength decreased by 15.8% after aging at 125°C for 3000 hours. The flame-retardant efficiency and processing fluidity were significantly worse than those in Example 1.

[0113] Comparative Example 2

[0114] In Example 1, only antioxidant 1010 was used in the anti-aging combination, omitting UV absorber UV531 and copper inhibitor MD1024. The mass percentage of talc and zinc borate added to the composite flame-retardant filler was modified to 70%:30%, while the remaining steps and process parameters remained the same as in Example 1. The results showed that due to the lack of UV absorption and copper ion passivation functions, the elongation at break decreased by 28.5% after 42 days of UV aging, and the flame-retardant efficiency also decreased, proving that the ternary synergistic system and the core-shell structure are indispensable.

[0115] Comparative Example 3

[0116] All raw materials from Example 1 were mixed and extruded in one go, with the homogenization temperature reduced to 175°C. The remaining steps and process parameters were the same as in Example 1. The results showed that due to uneven dispersion, the filler agglomeration rate was >17%, the crosslinking degree was only 79.4%, and the product qualification rate was as low as below 80%. Compared with Example 1, the crosslinking degree (88.5%), low-temperature toughness (no cracks), and qualification rate (>98%) were all significantly worse, highlighting the decisive role of stepwise masterbatch and precise temperature control.

[0117] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be considered as limitations on the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims. For those skilled in the art, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An anti-aging chemically cross-linked polyethylene cable insulation material, characterized in that: By weight, the insulating material comprises the following components: 50-60 parts of low-density polyethylene, 20-25 parts of polyolefin elastomer, 10-15 parts of maleic anhydride-grafted SEBS, 1.5-2.5 parts of dicumyl peroxide, 15-20 parts of composite flame-retardant filler, and 3-5 parts of anti-aging compound.

2. The anti-aging chemically cross-linked polyethylene cable insulation material according to claim 1, characterized in that: The composite flame-retardant filler includes talc powder and zinc borate, wherein the talc powder accounts for 80-90% of the composite flame-retardant filler by mass, and the zinc borate accounts for 10-20% of the composite flame-retardant filler by mass.

3. The anti-aging chemically cross-linked polyethylene cable insulation material according to claim 1, characterized in that: By weight, the anti-aging combination comprises 1-2 parts of antioxidant 1010, 1-2 parts of ultraviolet absorber UV531 and 1 part of copper inhibitor MD1024.

4. The preparation process of an anti-aging chemically cross-linked polyethylene cable insulation material according to any one of claims 1-3, characterized in that: The steps are as follows: Step 1: Preparation of composite flame retardant filler masterbatch (1.1) Talc powder and zinc borate are added to a ball mill at a certain mass percentage and ground. Anhydrous ethanol is used as the dispersion medium to form a core-shell structured composite filler with zinc borate coating talc powder. (1.2) The composite filler obtained in step (1.1) is vacuum dried at 60-80℃ for 12 hours; (1.3) The composite filler dried in step (1.2) is premixed with 10 parts of low-density polyethylene for 5 minutes, melt-blended at 160-180℃ using a twin-screw extruder, and then water ring pelletized to obtain flame retardant masterbatch with a particle size of 3mm. Step 2: Preparation of anti-aging masterbatch (2.1) Mix 10101-2 parts of antioxidant, UV5311-2 parts of ultraviolet absorber and MD10241 parts of copper inhibitor with 5 parts of polyolefin elastomer at 800 rpm for 10 minutes to obtain a premix. (2.2) The premixed material is extruded through a twin-screw extruder at a temperature of 150-170℃ and then air-cooled and pelletized to obtain anti-aging masterbatch; Step 3: Reactive extrusion molding of insulating material (3.1) Mix the remaining 40-50 parts of low-density polyethylene, 15-20 parts of polyolefin elastomer and 10-15 parts of maleic anhydride-grafted SEBS at 1000 rpm for 15 minutes to form a matrix resin. (3.2) Add 1.5-2.5 parts of dicumyl peroxide, 15-20 parts of the flame retardant masterbatch from step (1.3) and 3-5 parts of the anti-aging masterbatch from step (2.2) to the matrix resin, and mix for 10 minutes to obtain the mixture. (3.3) The mixture is extruded through a twin-screw extruder, and the reaction process is controlled in the following four temperature zones: feeding zone 150℃, compression zone 170℃, homogenization zone 185℃, and die head zone 195℃. (3.4) The extruded strip from step (3.3) is water-cooled and cured, cut into 2-4 mm particles, and dried at 80°C for 4 hours to obtain cable insulation material.

5. The preparation process of an anti-aging chemically cross-linked polyethylene cable insulation material according to claim 4, characterized in that: In step (1.1), the ball milling parameters are: rotation speed 200-300 rpm, ball milling time 2-3 hours, and talc powder particle size 1-5 μm.

6. The preparation process of an anti-aging chemically cross-linked polyethylene cable insulation material according to claim 4, characterized in that: In step (1.1), the mass percentage of talc powder to zinc borate is 85:

15.

7. The preparation process of an anti-aging chemically cross-linked polyethylene cable insulation material according to claim 4, characterized in that: In step (2.1), the mass ratio of antioxidant 1010, ultraviolet absorber UV531 and copper inhibitor MD1024 is 1.5:1.5:

1.

8. The preparation process of an anti-aging chemically cross-linked polyethylene cable insulation material according to claim 4, characterized in that: In step (3.3), the temperature of the homogenization section is controlled at 185±2℃, and the residence time of the homogenization section is ≥40 seconds.

9. The preparation process of an anti-aging chemically cross-linked polyethylene cable insulation material according to claim 4, characterized in that: In step (3.4), the particle size of the cut particles is 3±0.5mm.

10. An anti-aging chemically cross-linked polyethylene cable insulation material obtained by the preparation method as described in claim 4.