Crosslinked polyethylene insulating material for middle and high voltage cables and preparation method thereof

Abstract

The invention discloses a cross-linked polyethylene insulating material for middle and high voltage cables and a preparation method of the cross-linked polyethylene insulating material. Comprising the following raw material components in parts by weight: 100 parts of a polyethylene base material, 1.0-2.5 parts of a peroxide cross-linking agent, 0.05-0.5 part of an anti-scorching agent, 0.1-5.0 parts of a water tree resistant additive, 0.1-1.0 part of a main antioxidant, 0.1-1.0 part of an auxiliary antioxidant, 0-2.0 parts of a processing aid and 0-0.5 part of a metal deactivator. The cross-linked polyethylene insulating material for the middle-high voltage cable is suitable for manufacturing a power cable insulating layer with the rated voltage of 10 kV or above. And the method is particularly suitable for application scenes with high requirements on processing stability, long-term reliability and energy efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of medium and low voltage power cables, and in particular relates to a cross-linked polyethylene insulation material for medium and high voltage cables and a preparation method thereof. Background Art

[0002] Cross-linked polyethylene (XLPE) insulation material used in medium and high voltage cables (usually referring to voltage levels of 10kV and above) is a core component of power cables. Its performance directly affects the electrical strength, thermomechanical properties and long-term reliability of the cables.

[0003] Cross-linked polyethylene (XLPE) production requires the use of peroxides for crosslinking. This crosslinking requires high-temperature vulcanization during the extrusion process. During extrusion, especially at the die head and die, improper temperature control or prolonged material residence time can prematurely decompose the peroxide crosslinks (pre-crosslinking), leading to gel particles and even blockage (scorching). This can severely impact production continuity and product quality stability, increasing scrap rates. Common methods for combating scorching include lowering the extrusion temperature or adding anti-scorch agents (such as certain phenols or phosphites). However, excessive cooling can affect plasticization and surface quality. Traditional anti-scorch agents can interfere with crosslinking efficiency, reduce the degree of crosslinking, or negatively impact dielectric loss and water tree resistance.

[0004] In humid environments, especially under the influence of electric fields, water-tree-like microchannels (water trees) are prone to forming within or on the surface of XLPE insulation. Long-term development can lead to insulation degradation, ultimately causing electrical treeing and breakdown, a key factor limiting the long-term reliability and lifespan of cables. Key methods for combating water treeing include: a) using ultra-clean base materials to reduce impurity nucleation sites; b) adding voltage stabilizers (such as styrene derivatives); and c) adding water tree inhibitors (such as specific surfactants and polyols). However, these additives may increase dielectric loss or have poor compatibility with the system, impacting processing and long-term stability.

[0005] The dielectric loss factor (tan δ) is a key indicator of electrical energy loss in insulating materials. Excessively high dielectric loss can increase cable operating temperatures, reduce transmission efficiency, accelerate aging, and even affect the cable's current carrying capacity. Traditional XLPE has low dielectric loss in its pure state, but this can increase with the introduction of anti-water tree additives, processing aids, or the presence of impurities / byproducts. Low dielectric loss relies on high-purity base materials, optimized peroxide types (selecting those with low-polarity decomposition residues), and strict control of processing and post-treatment processes (such as degassing). However, high-purity base materials are expensive and difficult to incorporate with both scorch and water tree modifiers.

[0006] Currently, there is a lack of an XLPE insulation formulation system that can synergistically address the three key issues of scorch resistance, water tree resistance, and low dielectric loss. Existing technologies often prioritize one property over another, sacrificing other properties while improving them. Therefore, developing an XLPE insulation system with superior comprehensive performance is urgently needed and has significant application value. Summary of the Invention

[0007] The object of the present invention is to provide a cross-linked polyethylene insulation material for medium and high voltage cables and a preparation method thereof.

[0008] A cross-linked polyethylene insulation material for medium and high voltage cables comprises the following raw material components in parts by weight: 100 parts of a polyethylene base material, 1.0-2.5 parts of a peroxide cross-linking agent, 0.05-0.5 parts of an anti-scorch agent, 0.1-5.0 parts of an anti-water tree additive, 0.1-1.0 parts of a primary antioxidant, 0.1-1.0 parts of a secondary antioxidant, 0.1-2.0 parts of a processing aid, and 0-0.5 parts of a metal passivator.

[0009] The polyethylene base material is a mixture of one or more of low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, and high-density polyethylene.

[0010] The peroxide crosslinking agent is a mixture of one or more of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, di-tert-butyl peroxide isopropylbenzene, and dicumyl peroxide.

[0011] The anti-scorch agent is a mixture of one or more of hindered phenol 1076, hindered phenol 1010, phosphite 168, dilauryl thiodipropionate, pentaerythritol tetrakis (β-dodecylthiopropionate), N,N'-m-phenylene bismaleimide, and polydimethylsiloxane with a molecular weight of 1000-10000.

[0012] The anti-water tree additive is a mixture of one or more of poly (α-methylstyrene) with a molecular weight of 1500-5000, sorbitan monooleate, and alkylphenol polyoxyethylene ether with a specific molecular structure; the alkylphenol polyoxyethylene ether with a specific molecular structure is selected from the group consisting of (C2H4O)nC 15 H 24 O nonylphenol polyoxyethylene ether, molecular formula (C2H4O)nC 14 H 24 O's octylphenol polyoxyethylene ether, molecular formula (C2H4O)nC 18 H 24 O dodecyl polyoxyethylene ether, molecular formula (C2H4O)nC 24 H 42 One or more of dinonylphenol polyoxyethylene ethers of O, wherein n=4-20.

[0013] The main antioxidant is one or more of antioxidant 1010, antioxidant 264, antioxidant 1076, antioxidant 3114, and antioxidant 1024; the auxiliary antioxidant is one or more of antioxidant 168, antioxidant PEP-36, and antioxidant DSTP.

[0014] The processing aid is one or more of polyethylene wax, allyl phenyl sulfide, 2,4-diphenyl-4-methyl-1-pentene, and PPA1026.

[0015] The metal passivator is one or more of benzoyl hydrazide, salicylic hydrazide, oxalyl dihydrazide, benzotriazole, methylbenzotriazole, triphenyl phosphite, and diphenyl phosphite.

[0016] The preparation method of the cross-linked polyethylene insulation material for medium and high voltage cables is carried out according to the following steps: (1) mixing: adding the polyethylene base material, the anti-scorch agent, the anti-water tree additive, the main antioxidant, the auxiliary antioxidant, the processing aid, and the metal passivator to an internal mixer or an open mixer, and mixing them uniformly at 70-110°C to obtain a masterbatch; after cooling, mixing the masterbatch and the peroxide cross-linking agent uniformly through a low-speed cold mixing device; or, adding the polyethylene base material, the anti-scorch agent, the anti-water tree additive, the main antioxidant, the auxiliary antioxidant, the processing aid, and the metal passivator from the main feed port to the twin-screw extruder, and adding the peroxide cross-linking agent to the twin-screw extruder through the side feed port, and mixing them uniformly at 70-110°C. Directly extrude and granulate at 70-110°C; alternatively, add polyethylene base material, anti-scorch agent, anti-water tree additive, peroxide crosslinking agent, primary antioxidant, auxiliary antioxidant, processing aid, and metal passivator into a double-cone rotary vacuum dryer and shake evenly at 70-110°C; (2) Cable extrusion and crosslinking: The mixed material in step (1) is extruded onto the conductor through a cable extruder, and the extruded wire core enters a high-temperature vulcanization pipe, and the peroxide is decomposed at 160-350°C to complete the crosslinking reaction; (3) Post-treatment: The cable core after high-temperature vulcanization and crosslinking in step (2) is heat-baked at 70-90°C for 1-7 days.

[0017] The low-speed cold mixing equipment is a drum mixer; the high-temperature vulcanization pipeline is CCV, MDCV, VCV or FZCV.

[0018] The beneficial effects of this invention are as follows: The cross-linked polyethylene insulation material for medium- and high-voltage cables is suitable for manufacturing the insulation layer of power cables with rated voltages above 10 kV. It is particularly well-suited for applications requiring high processing stability (scorch resistance), long-term reliability (water tree resistance), and energy efficiency (low dielectric loss), such as urban power grid reconstruction and construction, industrial and mining power distribution, rail transit power supply, offshore wind power generation and humid environment power transmission and distribution, and data center power supply systems. Under standard testing conditions, the material exhibits significantly prolonged scorch time and a wide processing safety window. DETAILED DESCRIPTION

[0019] To facilitate understanding of the present invention, the present invention will be described more fully below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive. Example 1

[0020] A cross-linked polyethylene insulation material for medium and high voltage cables comprises the following raw material components in parts by weight: 100 parts of low-density polyethylene (0.915 g / cm³), 1.5 parts of a peroxide cross-linking agent, 0.25 parts of an anti-scorch agent, 0.35 parts of an anti-water tree additive, 0.6 parts of an antioxidant 1010, 0.4 parts of an antioxidant 168, 0.8 parts of polyethylene wax, and 0.2 parts of benzoyl hydrazide; the peroxide cross-linking agent is a mixture of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane and di-tert-butylperoxyisopropylbenzene in a mass ratio of 2:1; the anti-scorch agent is a mixture of pentaerythritol tetrakis(β-dodecylthiopropionate) and N,N'-m-phenylene bismaleimide in a mass ratio of 1:1; the anti-water tree additive is a mixture of poly(α-methylstyrene) with a molecular weight of 3000 and a molecular formula of (C2H4O)10C 24 H 42 A mixture of dinonylphenol polyoxyethylene ether and dinonylphenol polyoxyethylene ether in a mass ratio of 1:2.

[0021] The preparation method of the cross-linked polyethylene insulation material for medium and high voltage cables is carried out according to the following steps: (1) mixing: adding low-density polyethylene, anti-scorch agent, anti-water tree additive, antioxidant 1010, antioxidant 168, polyethylene wax, and benzoyl hydrazide into an internal mixer or an open mixer, and mixing them evenly at 90°C to obtain a masterbatch; after cooling, the masterbatch and the peroxide cross-linking agent are mixed evenly by a drum mixer; (2) cable extrusion and cross-linking: the material mixed in step (1) is extruded onto the conductor through a cable extruder, and the extruded wire core enters a high-temperature vulcanization pipe (CCV) at 280°C to decompose the peroxide and complete the cross-linking reaction; (3) post-treatment: the cable core after high-temperature vulcanization and cross-linking in step (2) is heat-baked at 80°C for 3 days. Example 2

[0022] A cross-linked polyethylene insulation material for medium- and high-voltage cables comprises the following raw material components in parts by weight: 100 parts of linear low-density polyethylene (0.922 g / cm³), 1.2 parts of dicumyl peroxide, 0.2 parts of an anti-scorch agent, 0.2 parts of sorbitan monooleate, 0.3 parts of an antioxidant 1076, 0.3 parts of an antioxidant PEP-36, 0.2 parts of allyl phenyl sulfide, and 0.1 parts of oxalyl dihydrazide; the anti-scorch agent is a mixture of hindered phenol 1076 and polydimethylsiloxane with a molecular weight of 5000 in a mass ratio of 1:1.

[0023] The preparation method of the cross-linked polyethylene insulation material for medium and high voltage cables is carried out according to the following steps: (1) mixing: linear low-density polyethylene, anti-scorch agent, sorbitan monooleate, antioxidant 1076, antioxidant PEP-36, allyl phenyl sulfide, and oxalyl dihydrazide are added to a twin-screw extruder from a main feed port, and diisopropylbenzene peroxide is added to the twin-screw extruder through a side feed port, and directly extruded and granulated at 95°C; (2) cable extrusion and cross-linking: the material mixed in step (1) is extruded onto a conductor through a cable extruder, and the extruded core enters a high-temperature vulcanization pipe (MDCV) at 250°C to decompose the peroxide and complete the cross-linking reaction; (3) post-treatment: the cable core after high-temperature vulcanization and cross-linking in step (2) is heat-baked at 70°C for 6 days. Example 3

[0024] A cross-linked polyethylene insulation material for medium and high voltage cables comprises the following raw material components in parts by weight: 100 parts of high-density polyethylene (0.955 g / cm³), 1.8 parts of a peroxide cross-linking agent, 0.45 parts of an anti-scorch agent, 0.45 parts of an anti-water tree additive, 0.8 parts of an antioxidant 1024, 0.6 parts of an antioxidant DSTP, 1.2 parts of 2,4-diphenyl-4-methyl-1-pentene, and 0.4 parts of triphenyl phosphite; the peroxide cross-linking agent is a mixture of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane and di-tert-butylperoxyisopropylbenzene in a mass ratio of 1:1; the anti-scorch agent is a mixture of hindered phenol 1010 and dilauryl thiodipropionate in a mass ratio of 2:1; the anti-water tree additive is sorbitan monooleate and 1,2-diisopropyl benzoate of the molecular formula (C2H4O)8C 18 H 24 A mixture of 2,4-dimethyl-1,2-dioxane and 2,4-dioxane in a mass ratio of 2:1.

[0025] The preparation method of the cross-linked polyethylene insulation material for medium and high voltage cables is carried out according to the following steps: (1) mixing: adding high-density polyethylene, anti-scorch agent, anti-water tree additive, peroxide cross-linking agent antioxidant 1024, antioxidant DSTP, 2,4-diphenyl-4-methyl-1-pentene, and triphenyl phosphite into a double-cone rotary vacuum dryer and shaking at 100°C; (2) cable extrusion and cross-linking: the material mixed in step (1) is extruded onto the conductor through a cable extruder, and the extruded core enters a high-temperature vulcanization pipe (VCV) at 300°C to decompose the peroxide and complete the cross-linking reaction; (3) post-treatment: the cable core after high-temperature vulcanization and cross-linking in step (2) is heat-baked at 90°C for 2d.

[0026] Comparative Example 1: A cross-linked polyethylene insulation material for medium and high voltage cables, comprising the following raw material components in parts by weight: 100 parts of low-density polyethylene (0.915 g / cm³), 1.5 parts of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 0.25 parts of an anti-scorch agent, 0.35 parts of an anti-water tree additive, 0.6 parts of an antioxidant 1010, 0.4 parts of an antioxidant 168, 0.8 parts of polyethylene wax, and 0.2 parts of benzoyl hydrazide; the anti-scorch agent is a mixture of pentaerythritol tetra(β-dodecylthiopropionate) and N,N'-m-phenylene bismaleimide in a mass ratio of 1:1; the anti-water tree additive is poly(α-methylstyrene) with a molecular weight of 3000 and a molecular formula of (C2H4O)10C 24 H 42 A mixture of dinonylphenol polyoxyethylene ether and dinonylphenol polyoxyethylene ether in a mass ratio of 1:2.

[0027] The preparation method of the cross-linked polyethylene insulation material for medium and high voltage cables is carried out according to the following steps: (1) mixing: adding low-density polyethylene, anti-scorch agent, anti-water tree additive, antioxidant 1010, antioxidant 168, polyethylene wax, and benzoyl hydrazide into an internal mixer or an open mixer, and mixing them uniformly at 90°C to obtain a masterbatch; after cooling, the masterbatch is mixed uniformly with 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane through a drum mixer; (2) cable extrusion and cross-linking: the mixed material in step (1) is extruded onto the conductor through a cable extruder, and the extruded core enters a high-temperature vulcanization pipe (CCV) at 280°C to decompose the peroxide and complete the cross-linking reaction; (3) post-treatment: the cable core after high-temperature vulcanization and cross-linking in step (2) is heat-baked at 80°C for 3 days.

[0028] Comparative Example 2: A cross-linked polyethylene insulation material for medium and high voltage cables, comprising the following raw material components in parts by weight: 100 parts of low-density polyethylene (0.915 g / cm³), 1.5 parts of di-tert-butyl peroxide isopropyl benzene, 0.25 parts of an anti-scorch agent, 0.35 parts of an anti-water tree additive, 0.6 parts of antioxidant 1010, 0.4 parts of antioxidant 168, 0.8 parts of polyethylene wax, and 0.2 parts of benzoyl hydrazide; the anti-scorch agent is a mixture of pentaerythritol tetra(β-dodecylthiopropionate) and N,N'-m-phenylene bismaleimide in a mass ratio of 1:1; the anti-water tree additive is poly(α-methylstyrene) with a molecular weight of 3000 and a molecular formula of (C2H4O)10C 24 H 42 A mixture of dinonylphenol polyoxyethylene ether and dinonylphenol polyoxyethylene ether in a mass ratio of 1:2.

[0029] The preparation method of the cross-linked polyethylene insulation material for medium and high voltage cables is carried out according to the following steps: (1) mixing: adding low-density polyethylene, anti-scorch agent, anti-water tree additive, antioxidant 1010, antioxidant 168, polyethylene wax, and benzoyl hydrazide into an internal mixer or an open mixer, and mixing them uniformly at 90°C to obtain a masterbatch; after cooling, the masterbatch and di-tert-butyl peroxide isopropyl benzene are mixed uniformly through a drum mixer; (2) cable extrusion and cross-linking: the material mixed in step (1) is extruded onto the conductor through a cable extruder, and the extruded core enters a high-temperature vulcanization pipe (CCV) at 280°C to decompose the peroxide and complete the cross-linking reaction; (3) post-treatment: the cable core after high-temperature vulcanization and cross-linking in step (2) is heat-baked at 80°C for 3d.

[0030] Comparative Example 3: A cross-linked polyethylene insulation material for medium and high voltage cables, comprising the following raw material components in parts by weight: 100 parts of low-density polyethylene (0.915 g / cm³), 1.5 parts of a peroxide cross-linking agent, 0.25 parts of pentaerythritol tetrakis (β-dodecylthiopropionate), 0.35 parts of an anti-water tree additive, 0.6 parts of an antioxidant 1010, 0.4 parts of an antioxidant 168, 0.8 parts of polyethylene wax, and 0.2 parts of benzoyl hydrazide; the peroxide cross-linking agent is a mixture of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane and di-tert-butylperoxyisopropylbenzene in a mass ratio of 2:1; the anti-water tree additive is poly(α-methylstyrene) with a molecular weight of 3000 and a molecular formula of (C2H4O)10C 24 H 42 A mixture of dinonylphenol polyoxyethylene ether and dinonylphenol polyoxyethylene ether in a mass ratio of 1:2.

[0031] The preparation method of the cross-linked polyethylene insulation material for medium and high voltage cables is carried out according to the following steps: (1) mixing: low-density polyethylene, pentaerythritol tetra (β-dodecylthiopropionate), anti-water tree additive, antioxidant 1010, antioxidant 168, polyethylene wax, and benzoyl hydrazide are added to an internal mixer or an open mixer and mixed evenly at 90°C to obtain a masterbatch; after cooling, the masterbatch and the peroxide cross-linking agent are mixed evenly by a drum mixer; (2) cable extrusion and cross-linking: the material mixed in step (1) is extruded onto the conductor through a cable extruder, and the extruded wire core enters a high-temperature vulcanization pipe (CCV) at 280°C to decompose the peroxide to complete the cross-linking reaction; (3) post-treatment: the cable core after high-temperature vulcanization and cross-linking in step (2) is heat-baked at 80°C for 3d.

[0032] Comparative Example 4: A cross-linked polyethylene insulation material for medium and high voltage cables, comprising the following raw material components in parts by weight: 100 parts of low-density polyethylene (0.915 g / cm³), 1.5 parts of a peroxide cross-linking agent, 0.25 parts of N,N'-m-phenylene bismaleimide, 0.35 parts of an anti-water tree additive, 0.6 parts of an antioxidant 1010, 0.4 parts of an antioxidant 168, 0.8 parts of polyethylene wax, and 0.2 parts of benzoyl hydrazide; the peroxide cross-linking agent is a mixture of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane and di-tert-butylperoxyisopropylbenzene in a mass ratio of 2:1; the anti-water tree additive is poly(α-methylstyrene) with a molecular weight of 3000 and a molecular formula of (C2H4O)10C 24 H 42 A mixture of dinonylphenol polyoxyethylene ether and dinonylphenol polyoxyethylene ether in a mass ratio of 1:2.

[0033] The preparation method of the cross-linked polyethylene insulation material for medium and high voltage cables is carried out according to the following steps: (1) mixing: adding low-density polyethylene, N,N'-m-phenylene bismaleimide, anti-water tree additive, antioxidant 1010, antioxidant 168, polyethylene wax, and benzoyl hydrazide to an internal mixer or an open mixer, and mixing them uniformly at 90°C to obtain a masterbatch; after cooling, the masterbatch and the peroxide cross-linking agent are mixed uniformly by a drum mixer; (2) cable extrusion and cross-linking: the material mixed in step (1) is extruded onto the conductor through a cable extruder, and the extruded wire core enters a high-temperature vulcanization pipe (CCV) at 280°C to decompose the peroxide to complete the cross-linking reaction; (3) post-treatment: the cable core after high-temperature vulcanization and cross-linking in step (2) is heat-baked at 80°C for 3d.

[0034] Comparative Example 5: A cross-linked polyethylene insulation material for medium and high voltage cables, comprising the following raw material components in parts by weight: 100 parts of low-density polyethylene (0.915 g / cm³), 1.5 parts of a peroxide cross-linking agent, 0.25 parts of an anti-scorching agent, 0.35 parts of poly(α-methylstyrene) with a molecular weight of 3000, 0.6 parts of an antioxidant 1010, 0.4 parts of an antioxidant 168, 0.8 parts of polyethylene wax, and 0.2 parts of benzoyl hydrazide; the peroxide cross-linking agent is a mixture of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane and di-tert-butylperoxide isopropylbenzene in a mass ratio of 2:1; the anti-scorching agent is a mixture of pentaerythritol tetrakis(β-dodecylthiopropionate) and N,N'-m-phenylene bismaleimide in a mass ratio of 1:1.

[0035] The preparation method of the cross-linked polyethylene insulation material for medium and high voltage cables is carried out according to the following steps: (1) mixing: adding low-density polyethylene, anti-scorch agent, poly (α-methylstyrene) with a molecular weight of 3000, antioxidant 1010, antioxidant 168, polyethylene wax, and benzoyl hydrazide to an internal mixer or an open mixer, and mixing them uniformly at 90°C to obtain a masterbatch; after cooling, the masterbatch and the peroxide cross-linking agent are mixed uniformly by a drum mixer; (2) cable extrusion and cross-linking: the material mixed in step (1) is extruded onto the conductor through a cable extruder, and the extruded wire core enters a high-temperature vulcanization pipe (CCV) at 280°C to decompose the peroxide and complete the cross-linking reaction; (3) post-treatment: the cable core after high-temperature vulcanization and cross-linking in step (2) is heat-baked at 80°C for 3 days.

[0036] Comparative Example 6: A cross-linked polyethylene insulation material for medium and high voltage cables, comprising the following raw material components in parts by weight: 100 parts of low-density polyethylene (0.915 g / cm³), 1.5 parts of a peroxide cross-linking agent, 0.25 parts of an anti-scorching agent, and 10 parts of a molecular formula (C2H4O). 24 H 42 The invention relates to a novel polyoxyethylene dinonylphenol ether (DO) containing 0.35 parts of dinonylphenol polyoxyethylene ether, 0.6 parts of antioxidant 1010, 0.4 parts of antioxidant 168, 0.8 parts of polyethylene wax, and 0.2 parts of benzoyl hydrazide; the peroxide crosslinking agent is a mixture of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane and di-tert-butylperoxide isopropyl benzene in a mass ratio of 2:1; the anti-scorching agent is a mixture of pentaerythritol tetrakis(β-dodecylthiopropionate) and N,N'-m-phenylene bismaleimide in a mass ratio of 1:1.

[0037] The preparation method of the cross-linked polyethylene insulation material for medium and high voltage cables is carried out according to the following steps: (1) mixing: low-density polyethylene, anti-scorch agent, molecular formula (C2H4O) 10C 24 H 42O-based dinonylphenol polyoxyethylene ether, antioxidant 1010, antioxidant 168, polyethylene wax, and benzoyl hydrazide are added to an internal mixer or an open mixer and mixed uniformly at 90°C to obtain a masterbatch; after cooling, the masterbatch and the peroxide crosslinking agent are mixed uniformly by a drum mixer; (2) cable extrusion and crosslinking: the mixed material in step (1) is extruded onto the conductor through a cable extruder, and the extruded core enters a high-temperature vulcanization pipe (CCV) at 280°C to decompose the peroxide and complete the crosslinking reaction; (3) post-treatment: the cable core after high-temperature vulcanization and crosslinking in step (2) is heat-baked at 80°C for 3 days.

[0038] Experimental Example: The dielectric loss of the cross-linked polyethylene insulation materials for medium- and high-voltage cables prepared in Examples 1-3 and Comparative Examples 1-2 was measured according to the measurement method specified in GB / T 12706. Specifically, the tanδ value was measured at an operating frequency of 50 Hz or an ultra-low frequency of 0.1 Hz. The experimental results were statistically analyzed using SPSS 24.0 software. The measurement data were expressed as `x ± (mean ± standard deviation). The Kolmogorov-Smirnov test was used to test the data for normality. For data that conformed to a normal distribution, the t-test was used to compare the mean differences between the two groups. P < 0.05 was considered statistically significant. The measurement results are shown in Table 1: Table 1 Experimental group <![CDATA[50Hz tanδ ×10 ⁻6 ]]> <![CDATA[0.1Hz tanδ ×10 ⁻6 ]]> Example 1 113.2±6.3 3273.2±27.3 Example 2 108.7±11.1 3199.3±31.5 Example 3 121.6±9.9 3312.9±21.4 Comparative Example 1 233.2±7.3* 6523.3±33.7* Comparative Example 2 211.6±11.4* 5829.9±42.9* Note: * represents P < 0.05 compared with the group in Example 1.

[0039] At 120°C, the viscosity of the rubber materials prepared in step (1) of Examples 1-3 and Comparative Examples 3-4 was measured over time using a Mooney viscometer. The time required for the viscosity to increase by 5 Mooney units was recorded as the scorch time (t5). The measurement results are shown in Table 2: Table 2 Experimental group <![CDATA[t 5 min]]> Example 1 25.2±1.3 Example 2 24.7±1.2 Example 3 23.9±1.9 Comparative Example 3 13.2±1.2* Comparative Example 4 16.4±0.9* Note: * represents P < 0.05 compared with the group in Example 1.

[0040] Accelerated water tree aging test: Supplementary detailed determination method and approximate values ​​of water tree initiation density and maximum water tree length.

[0041] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A cross-linked polyethylene insulation material for medium and high voltage cables, characterized in that: The invention comprises the following raw material components in parts by weight: 100 parts of polyethylene base material, 1.0-2.5 parts of peroxide cross-linking agent, 0.05-0.5 parts of anti-scorch agent, 0.1-5.0 parts of anti-water tree additive, 0.1-1.0 parts of main antioxidant, 0.1-1.0 parts of auxiliary antioxidant, 0-2.0 parts of processing aid and 0-0.5 parts of metal passivator.

2. The cross-linked polyethylene insulation material for medium and high voltage cables according to claim 1, characterized in that: The polyethylene base material is a mixture of one or more of low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, and high-density polyethylene.

3. The cross-linked polyethylene insulation material for medium and high voltage cables according to claim 1, characterized in that: The peroxide crosslinking agent is a mixture of one or more of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, di-tert-butyl peroxide isopropylbenzene, and dicumyl peroxide.

4. The cross-linked polyethylene insulation material for medium and high voltage cables according to claim 1, characterized in that: The anti-scorch agent is a mixture of one or more of hindered phenol 1076, hindered phenol 1010, phosphite 168, dilauryl thiodipropionate, and polydimethylsiloxane with a molecular weight of 1000-10000.

5. The cross-linked polyethylene insulation material for medium and high voltage cables according to claim 1, characterized in that: The anti-water tree additive is a mixture of one or more of poly (α-methylstyrene) with a molecular weight of 1500-5000, sorbitan monooleate, and alkylphenol polyoxyethylene ether with a specific molecular structure; the alkylphenol polyoxyethylene ether with a specific molecular structure is selected from the group consisting of (C2H4O)nC 15 H 24 O nonylphenol polyoxyethylene ether, molecular formula (C2H4O)nC 14 H 24 O's octylphenol polyoxyethylene ether, molecular formula (C2H4O)nC 18 H 24 O dodecyl polyoxyethylene ether, molecular formula (C2H4O)nC 24 H 42 One or more of dinonylphenol polyoxyethylene ethers of O, wherein n=4-20.

6. The cross-linked polyethylene insulation material for medium and high voltage cables according to claim 1, characterized in that: The main antioxidant is one or more of antioxidant 1010, antioxidant 264, antioxidant 1076, antioxidant 3114, and antioxidant 1024; the auxiliary antioxidant is one or more of antioxidant 168, antioxidant PEP-36, and antioxidant DSTP.

7. The cross-linked polyethylene insulation material for medium and high voltage cables according to claim 1, characterized in that: The processing aid is one or more of polyethylene wax, allyl phenyl sulfide, 2,4-diphenyl-4-methyl-1-pentene, and PPA1026.

8. The cross-linked polyethylene insulation material for medium and high voltage cables according to claim 1, characterized in that: The metal passivator is one or more of benzoyl hydrazide, salicylic hydrazide, oxalyl dihydrazide, benzotriazole, methylbenzotriazole, triphenyl phosphite, and diphenyl phosphite.

9. The method for preparing the cross-linked polyethylene insulation material for medium and high voltage cables according to claim 1, characterized in that: The process is as follows: (1) Mixing: Add polyethylene base material, anti-scorch agent, anti-water tree additive, primary antioxidant, auxiliary antioxidant, processing aid, and metal passivator to an internal mixer or an open mixer, mix them uniformly at 70-110°C to obtain a masterbatch; after cooling, mix the masterbatch and peroxide crosslinking agent uniformly through a low-speed cold mixing device; or, add polyethylene base material, anti-scorch agent, anti-water tree additive, primary antioxidant, auxiliary antioxidant, processing aid, and metal passivator to a twin-screw extruder from the main feed port, and add the peroxide crosslinking agent to the twin-screw extruder through the side feed port, and directly extruder at 70-110°C. Extrusion granulation; or, adding polyethylene base material, anti-scorch agent, anti-water tree additive, peroxide crosslinking agent, primary antioxidant, auxiliary antioxidant, processing aid, and metal passivator into a double-cone rotary vacuum dryer and shaking at 70-110°C; (2) cable extrusion and crosslinking: the mixed material in step (1) is extruded onto the conductor through a cable extruder, and the extruded wire core enters a high-temperature vulcanization pipe at 160-350°C to decompose the peroxide and complete the crosslinking reaction; (3) post-treatment: the cable core after high-temperature vulcanization and crosslinking in step (2) is heat-baked at 70-90°C for 1-7 days.

10. The method for preparing cross-linked polyethylene insulation material for medium and high voltage cables according to claim 9, characterized in that: The low-speed cold mixing equipment is a drum mixer; the high-temperature vulcanization pipeline is CCV, MDCV, VCV or FZCV.