Composition for crosslinked polyethylene and method of making and use thereof

Abstract

This application relates to the field of high-voltage insulation materials technology, and particularly to a cross-linked polyethylene composition, its preparation method, and its application. The cross-linked polyethylene composition comprises low-density polyethylene resin, a cross-linking agent, and 4,4'-thiobis(6-tert-butyl-3-methylphenol), wherein the chloride ion residue in the 4,4'-thiobis(6-tert-butyl-3-methylphenol) is ≤1100 ppm. This application limits the chloride ion content of 4,4'-thiobis(6-tert-butyl-3-methylphenol) added to the cross-linked polyethylene composition to within 1100 ppm, and has found that this significantly improves the aging resistance of cross-linked polyethylene, exhibiting good aging resistance at high temperatures, and meeting the requirements of Q / GDW 11883.2-2018 standard.

Description

Technical Field

[0001] This application relates to the field of high voltage insulation materials technology, and in particular to a cross-linked polyethylene composition, its preparation method, and its application. Background Technology

[0002] Low-density polyethylene (LDPE) and a crosslinking agent crosslink to form crosslinked polyethylene (XLPE). XLPE is commonly used as a cable material, but it is susceptible to thermal aging during long-term use, resulting in decreased mechanical properties, poor aging resistance, and compromised operational stability. Specifically, at high temperatures, the crosslinking structure and crystallinity of XLPE may be damaged, leading to molecular chain breakage and a weakened crosslinking structure. This deterioration results in reduced mechanical properties and can even cause cable breakdown and render the cable unusable. Summary of the Invention

[0003] Based on this, the first aspect of this application provides a composition for cross-linked polyethylene, the technical solution of which is as follows:

[0004] A composition for crosslinked polyethylene includes a low-density polyethylene resin, a crosslinking agent, and 4,4'-thiobis(6-tert-butyl-3-methylphenol), wherein the chloride ion residue in the 4,4'-thiobis(6-tert-butyl-3-methylphenol) is ≤1100 ppm.

[0005] Compared with traditional solutions, this application has the following advantages:

[0006] The inventors of this application discovered that when using 4,4'-thiobis(6-tert-butyl-3-methylphenol) as an antioxidant for cross-linked polyethylene, the residual chloride ion content in 4,4'-thiobis(6-tert-butyl-3-methylphenol) affects the aging resistance of cross-linked polyethylene. The reason for this is likely that the presence of chloride ions reacts with trace impurities or residual catalysts in the PE molecular chain, generating free radicals. These free radicals trigger oxidation reactions, leading to oxidative degradation of the molecular chain and affecting the improvement of aging resistance. Experimental verification showed that when the residual chloride ion content is >1100 ppm, it significantly restricts the improvement of aging resistance and fails to meet the standard requirements of Q / GDW 11883.2-2018 "Materials for AC Extruded Insulated Cables with Rated Voltage 110kV~220kV Part 1: Cross-linkable Polyethylene Insulation Materials". Based on the above findings, this application limits the chloride ion content of 4,4'-thiobis(6-tert-butyl-3-methylphenol) added to the cross-linked polyethylene composition to below 1100 ppm. This has been found to significantly improve the aging resistance of cross-linked polyethylene, exhibiting good aging resistance at high temperatures. After high-temperature aging, it meets the mechanical property requirements of the aforementioned standards. Furthermore, by limiting the residual chloride ion content, damage to production equipment caused by electrochemical corrosion of chloride ions during processing can be avoided, significantly extending the service life of the equipment and reducing the risk to cable safety. Simultaneously, the addition of 4,4'-thiobis(6-tert-butyl-3-methylphenol) can also inhibit premature decomposition of the cross-linking agent, which would lead to premature cross-linking and reduced stability of the cable material, enabling its application in high-voltage and ultra-high-voltage power cables.

[0007] Optionally, 4,4'-thiobis(6-tert-butyl-3-methylphenol) can be purchased commercially. For commercially available 4,4'-thiobis(6-tert-butyl-3-methylphenol), the sample is treated by alkaline fusion, and then the chloride ion residue is determined by ion chromatography. After determination, products with chloride ion content that meet the above requirements are screened as components of the cross-linked polyethylene composition of this application.

[0008] Optionally, the preparation method of 4,4'-thiobis(6-tert-butyl-3-methylphenol) includes the following steps:

[0009] alkylation of m-cresol with isobutylene yields 3-methyl-6-tert-butylphenol;

[0010] The 3-methyl-6-tert-butylphenol was subjected to a thiolation reaction with sulfur dichloride to obtain 4,4'-thiobis(6-tert-butyl-3-methylphenol).

[0011] After the thiolation reaction, the reaction system undergoes post-treatment steps such as filtration, drying and recrystallization to obtain the product 4,4'-thiobis(6-tert-butyl-3-methylphenol).

[0012] The residual chloride ion content in the product 4,4'-thiobis(6-tert-butyl-3-methylphenol) can be controlled by controlling the reaction conditions and post-treatment conditions of the above preparation method. By using the above method for determining the residual chloride ion content, a product with the chloride ion content that meets the above requirements can be obtained as a component of the cross-linked polyethylene composition of this application.

[0013] The lower the residual chloride ion content, the less limiting its effect on improving the aging resistance of cross-linked polyethylene, and the better the aging resistance. Optionally, the residual chloride ion in 4,4'-thiobis(6-tert-butyl-3-methylphenol) is ≤1100 ppm, further optionally, it is ≤900 ppm, and even more optionally, it is ≤700 ppm. Generally speaking, considering the difficulty in preparing 4,4'-thiobis(6-tert-butyl-3-methylphenol), the residual chloride ion is difficult to reduce indefinitely.

[0014] Optionally, the 4,4'-thiobis(6-tert-butyl-3-methylphenol) accounts for 0.1% to 1% of the mass of the low-density polyethylene resin. For example, it accounts for 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1% of the mass of the low-density polyethylene resin.

[0015] Optionally, the density of the low-density polyethylene resin is 0.91 g / cm³. 3 ~0.93g / cm 3 0.92g / cm³ is an optional value. 3 ~0.925g / cm 3 .

[0016] Optionally, the low-density polyethylene resin has a melt index of 1 g / 10 min to 4 g / 10 min at 190°C and 2.16 kg pressure. It can be optionally 2 g / 10 min to 3 g / 10 min.

[0017] In some examples, the low-density polyethylene matrix resin is selected from one or more of Yangba Petrochemical 2220H, Shenhua Yulin 2220H, Shanghai Petrochemical J182A, Shanghai Petrochemical J182B, and Yanshan Petrochemical LD9202W. Preferably, it is Yangba Petrochemical 2220H or Shanghai Petrochemical J182B.

[0018] Optionally, the crosslinking agent includes one or more of dicumyl peroxide (DCP), benzoyl peroxide (BPO), di-tert-butyl peroxide (DTBP), and 2,5-dimethyl-2,5-di(tert-butylperoxide)hexane. Dicumyl peroxide is preferred.

[0019] Optionally, the crosslinking agent accounts for 0.1% to 5% of the mass of the low-density polyethylene resin. For example, it accounts for 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, and 5% of the mass of the low-density polyethylene resin.

[0020] Optionally, the composition for cross-linked polyethylene also includes a thioester antioxidant. 4,4'-Thiobis(6-tert-butyl-3-methylphenol) can exhibit a good synergistic antioxidant and anti-aging effect with thioester antioxidants, further improving the aging resistance of cross-linked polyethylene. However, the inventors of this application have discovered that residual chloride ions in 4,4'-thiobis(6-tert-butyl-3-methylphenol) can react with thioester antioxidants to generate polar products such as chlorinated hydrocarbons and thiocarboxylic acid esters, which may inhibit the anti-aging performance of thioester antioxidants, thus limiting the improvement of the aging resistance of cross-linked polyethylene. Experimental verification has shown that controlling the residual chloride ions to ≤1100 ppm can mitigate the above-mentioned limitations to some extent.

[0021] Optionally, the thioester antioxidant includes one or more of dioctadecyl thiodipropionate (DSTDP) and didodecyl thiodipropionate (DLTDP).

[0022] Optionally, the thioester antioxidant accounts for 0% to 1% of the mass of the low-density polyethylene resin. For example, it accounts for 0.01%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1% of the mass of the low-density polyethylene resin.

[0023] Optionally, the composition for cross-linked polyethylene also includes an anti-scorching agent.

[0024] Optionally, the anti-scorching agent comprises one or more of phthalic anhydride, N-dinitrodiphenylamine, N-cyclohexylthiophthalimide, 2,4-diphenyl-4-methyl-1-pentene, and 1,4-hydroquinone. Preferably, the anti-scorching agent comprises 2,4-diphenyl-4-methyl-1-pentene. Optionally, the residual α-methylstyrene in the 2,4-diphenyl-4-methyl-1-pentene is ≤10 wt%.

[0025] Optionally, the anti-scorching agent accounts for 0.2% to 1% of the mass of the low-density polyethylene resin. For example, it accounts for 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1% of the mass of the low-density polyethylene resin.

[0026] Optionally, the composition for cross-linked polyethylene also includes a water tree inhibitor.

[0027] Optionally, the water tree inhibitor includes one or more of polyethylene glycol (PEG), ethylene-vinyl acetate copolymer (EVA), styrene-ethylene-butene-styrene block copolymer (SEBS), and sorbitol. Preferably, the water tree inhibitor includes one or more of polyethylene glycol and ethylene-vinyl acetate copolymer.

[0028] Optionally, the water tree inhibitor accounts for 0% to 1% of the mass of the low-density polyethylene resin. For example, it accounts for 0.01%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1% of the mass of the low-density polyethylene resin.

[0029] After crosslinking, the above-mentioned crosslinked polyethylene composition can achieve a sample holding time (time without breakage at high temperature) of more than 60 min, or even more than 65 min, or even more than 70 min, or even more than 75 min, exhibiting excellent anti-aging properties.

[0030] The second aspect of this application provides a method for preparing a composition for cross-linked polyethylene, the technical solution of which is as follows:

[0031] A method for preparing a composition for cross-linked polyethylene includes the following steps:

[0032] The low-density polyethylene resin and the 4,4'-thiobis(6-tert-butyl-3-methylphenol) were mixed and then melt-extruded to obtain granules.

[0033] The crosslinking agent is melt-atomized and then mixed with the granular material to obtain a composition for crosslinked polyethylene.

[0034] The aforementioned low-density polyethylene resin and 4,4'-thiobis(6-tert-butyl-3-methylphenol) are mixed after drying. Mixing can be carried out in a high-speed mixer until the components are evenly distributed. The mixing speed can be 100 rpm to 200 rpm, and the mixing time can be 10 min to 30 min. Optionally, the melt extrusion parameters for the granules include: an extrusion temperature of 160℃ to 200℃ and a main machine speed of 80 rpm to 140 rpm. The extrudate is then pelletized and dried to obtain granules. Optionally, the drying temperature is 40℃ to 80℃, and the drying time is 2 h to 6 h.

[0035] When the composition for cross-linked polyethylene includes a thioester antioxidant, the thioester antioxidant may be added during the mixing of low-density polyethylene resin and 4,4'-thiobis(6-tert-butyl-3-methylphenol).

[0036] When the composition for cross-linked polyethylene includes an anti-scorching agent, the anti-scorching agent may be added during the mixing of low-density polyethylene resin and 4,4'-thiobis(6-tert-butyl-3-methylphenol).

[0037] When the composition for cross-linked polyethylene includes a water tree inhibitor, the water tree inhibitor may be added during the mixing of low-density polyethylene resin and 4,4'-thiobis(6-tert-butyl-3-methylphenol).

[0038] After the crosslinking agent is melted and atomized, it is mixed with the granular material. The molten and atomized crosslinking agent can be sprayed into the granular material, then allowed to stand for absorption, ensuring thorough mixing. Optionally, the ambient temperature during spraying and standing is 70-90℃, and the standing absorption time is 8-12 hours.

[0039] The above method is simple and rapid, and the cross-linked polyethylene composition prepared has good aging resistance.

[0040] A third aspect of this application provides a cross-linked polyethylene, the raw materials of which include the above-mentioned cross-linked polyethylene composition.

[0041] Cross-linked polyethylene can be prepared from the composition using conventional extrusion vulcanization methods, and this application does not impose any limitations.

[0042] A fourth aspect of this application provides a cable material comprising a conductor and an insulating material covering the conductor, the insulating material comprising cross-linked polyethylene as described above.

[0043] The above-mentioned cable materials have good aging resistance and can be used in AC extruded insulated cables with voltage ratings of 100kV~220kV. Detailed Implementation

[0044] The present application will be further described in detail below with reference to specific embodiments. The present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0046] the term

[0047] Unless otherwise stated or in case of contradiction, the terms or phrases used herein shall have the following meanings:

[0048] In this application, the terms "multiple", "various", "multiple times", "multi-dimensional", etc., unless otherwise specified, refer to a quantity greater than or equal to 2. For example, "one or more" means one or more or more.

[0049] In this application, the terms "optionally," "optionally," and "optional" refer to options that are optional, meaning they can be selected from either "with" or "without." If multiple "optional" options appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" option is independent.

[0050] In this application, the terms "first aspect," "second aspect," "third aspect," and "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," and "fourth," etc., serve only a non-exhaustive enumeration purpose and should be understood not to constitute a closed limitation on quantity.

[0051] In this application, numerical intervals (i.e. numerical ranges) are involved. Unless otherwise specified, the selected numerical distributions within the above-mentioned numerical intervals are considered continuous, and include the two numerical endpoints (i.e., the minimum value and the maximum value) of the numerical range, as well as every value between the two numerical endpoints.

[0052] Unless otherwise specified, the temperature parameters in this application are permitted to be either constant-temperature treatment or variations within a certain temperature range. It should be understood that the constant-temperature treatment allows temperature fluctuations within the precision range of the instrument control, such as ±5℃, ±4℃, ±3℃, ±2℃, or ±1℃.

[0053] In this application, %(w / w) and wt% both represent weight percentage, %(v / v) refers to volume percentage, and %(w / v) refers to mass-volume percentage.

[0054] The following description is further illustrated with specific embodiments and comparative examples. Unless otherwise specified, the raw materials involved in the following specific embodiments and comparative examples are all commercially available. Unless otherwise specified, the instruments used are all commercially available. Unless otherwise specified, the processes involved are conventionally selected by those skilled in the art.

[0055] Among them, low-density polyethylene (LDPE), Shanghai Petrochemical J182B, has a melt index of 2.02 g / 10 min (190℃, 2.16 kg) and a density of 0.922 g / cm³. 3 ;

[0056] Crosslinking agent: dicumyl peroxide (DCP), Nouryon, purity 99.0%;

[0057] Antioxidant A-1: ​​4,4'-thiobis(6-tert-butyl-3-methylphenol), model RIANOX 300, source: Tianjin Lialong, purity 99.0%, its chlorine content was tested to be 1230ppm;

[0058] Antioxidant A-2: 4,4'-thiobis(6-tert-butyl-3-methylphenol), model antioxidant 300, source: Jiangsu Xinluda, purity 99.0%, its chlorine content was tested to be 1020ppm;

[0059] Antioxidant A-3: 4,4'-thiobis(6-tert-butyl-3-methylphenol), model TBM-6, source: Saint-Lecter, purity 99.0%, chlorine content tested at 800 ppm;

[0060] Antioxidant A-4: 4,4'-thiobis(6-tert-butyl-3-methylphenol), model antioxidant 300, source: Zibo Vanke, purity 99.0%, its chlorine content was tested to be 500ppm;

[0061] Antioxidant B: Antioxidant DLTDP, source: Tianjin Lianlong Company, purity 99.0%;

[0062] Anti-scorching agent: 2,4-diphenyl-4-methyl-1-pentene, source: TCI Corporation, purity 99.0%;

[0063] Water tree inhibitor: Polyethylene glycol 20000, source: Clariant GmbH, Germany, purity 99.5%;

[0064] Example 1

[0065] This embodiment provides a crosslinking polyethylene composition and its preparation method, including the following steps:

[0066] Step 1: Prepare the components of the crosslinking polyethylene composition according to the mass ratios shown in Table 1.

[0067] Step 2: Add LDPE, antioxidant A, antioxidant B, anti-scorch agent, and water tree inhibitor (addition amount of 0 indicates that this raw material has not been added) to a high-speed mixer. Mix at 150 rpm for 20 minutes, then feed the mixture into a twin-screw extruder for melt extrusion at a temperature of 160℃~200℃ and a main extruder speed of 110 rpm. The extrudate is then pelletized and dried at 60℃ for 2 hours to obtain granules.

[0068] Step 3: Melt and atomize the crosslinking agent, spray it onto the granules at 80°C for 30 minutes, and let it stand at 80°C for 10 hours to absorb, thereby obtaining crosslinked polyethylene composition granules.

[0069] Other embodiments and comparative examples

[0070] Other embodiments and comparative examples provide a crosslinking polyethylene composition and its preparation method, wherein the components of the crosslinking polyethylene composition are shown in Tables 1 and 2, and the preparation method of the crosslinking polyethylene composition is shown in Example 1.

[0071] Test Project

[0072] Project 1: Thermal Extension Test

[0073] The cross-linked polyethylene compositions obtained in the various examples and comparative examples were used to prepare test strips. Referring to GB / T2951.21-2008 "General Test Methods for Insulation and Sheath Materials of Cables and Optical Cables - Part 12: General Test Methods - Thermal Aging Test Methods" and GB / T 1040.2-2022 "Plastics - Determination of Tensile Properties - Part 2: Test Conditions for Molded and Extruded Plastics", the test strips were first directly molded and vulcanized at 175℃ and 15 MPa for 15 min to prepare type 5A specimens. Then, a thermal elongation test was performed on the specimens. The test temperature was set to 200±3℃, the specimen thickness was 1.0±0.1 mm, and a load of 0.2 MPa was applied below the specimen. The time from the start of the test to the complete fracture of the specimen was recorded. The time from the start of the test to the complete fracture of the specimen was the specimen holding time. Five test strips were used in each group. The minimum and maximum values ​​of the specimen holding times for the five test strips were recorded in Tables 1 and 2. The average value of the specimen holding times for the five test strips was calculated, and the results are shown in Tables 1 and 2.

[0074] Project 2: Air-heat aging test of insulation sheet after cabling

[0075] The following three layers were co-extruded using a Telest extruder CCV crosslinking line (cross-sectional area 630 mm²). 2 The material is then heated to 380°C under a nitrogen atmosphere to vulcanize it and prepare it into a cable.

[0076] First layer: An inner semiconductive layer (conductor shielding layer) is formed using a semiconductive composition comprising ethylene-vinyl acetate copolymer, organic peroxide crosslinking agent, carbon black and antioxidant.

[0077] Second layer: An insulating layer is formed using cross-linked polyethylene composition granules obtained from the various examples and comparative examples.

[0078] Third layer: An outer semiconducting layer (insulating shielding layer) is formed using the same semiconducting composition as the first layer.

[0079] The sheeting test after cabling was conducted in accordance with the standards GB / T 2951.12-2008 "General Test Methods for Insulation and Sheath Materials of Cables and Optical Cables - Part 12: General Test Methods - Thermal Aging Test Method" and Q / GDW 11883.2-2018 "Materials for Extruded Insulated Cables with Rated Voltage of 110kV~220kV AC - Part 1: Crosslinkable Polyethylene Insulation Materials". The air thermal aging oven should meet the requirements of GB / T 2951.12-2008. The tensile strength and elongation at break tests after thermal aging were conducted according to regulations. The aged samples were conditioned in an environment with a temperature of 23±3℃ and a relative humidity of 50±5% for no less than 17 hours. The changes in tensile strength and elongation at break before and after aging were recorded in Tables 1 and 2.

[0080] Table 1

[0081]

[0082] Table 2

[0083]

[0084] Q / GDW 11883.2-2018 specifies that the change rate of tensile strength and elongation at break of cross-linked polyethylene after aging should be less than 20%. As can be seen above, the change rates of tensile strength and elongation at break of cross-linked polyethylene after aging in each embodiment meet the standard of Q / GDW 11883.1-2018, and can be applied to high-voltage cross-linked polyethylene cable insulation materials with voltage ratings of 100kV~220kV. Furthermore, the sample holding time is longer than that of the corresponding comparative examples (Comparative Example 1 and Examples 1-3 form one group, Comparative Example 2 and Example 4 form one group, and Comparative Example 3 and Example 5 form one group), and the average holding time is greater than 55 minutes. Under high-temperature load, the longer the sample holding time, the slower the frequency of molecular chain breakage due to oxidative degradation, and the stronger the resistance to oxidative aging. In Examples 6 and 7, the addition of anti-scorching agents significantly improved the holding time of the samples and reduced the thermal aging change rate of the shavings after cabling. This indicates that after using an antioxidant with chloride ion residue ≤1100ppm, the addition of anti-scorching agents can further improve the holding time of the samples under high temperature load and the thermal aging performance of the shavings after cabling, demonstrating excellent anti-aging properties.

[0085] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0086] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A composition for cross-linked polyethylene, characterized in that, It includes low-density polyethylene resin, crosslinking agent and 4,4'-thiobis(6-tert-butyl-3-methylphenol), wherein the chloride ion residue in the 4,4'-thiobis(6-tert-butyl-3-methylphenol) is ≤1100ppm.

2. The composition for cross-linked polyethylene according to claim 1, characterized in that, The mass of the 4,4'-thiobis(6-tert-butyl-3-methylphenol) accounts for 0.1% to 1% of the mass of the low-density polyethylene resin.

3. The composition for cross-linked polyethylene according to claim 1, characterized in that, It also includes thioester antioxidants; Optionally, the thioester antioxidant includes one or more of dioctadecyl thiodipropionate and didodecyl thiodipropionate; Optionally, the thioester antioxidant accounts for 0% to 1% of the mass of the low-density polyethylene resin.

4. The composition for cross-linked polyethylene according to claim 1, characterized in that, It also includes anti-scorching agents; Optionally, the anti-scorching agent comprises one or more of phthalic anhydride, N-dinitrodiphenylamine, N-cyclohexylthiophthalimide, 2,4-diphenyl-4-methyl-1-pentene, and 1,4-hydroquinone; optionally, the anti-scorching agent comprises 2,4-diphenyl-4-methyl-1-pentene; optionally, the residual α-methylstyrene in the 2,4-diphenyl-4-methyl-1-pentene is ≤10 wt%. Optionally, the anti-scorching agent accounts for 0.2% to 1% of the mass of the low-density polyethylene resin.

5. The composition for cross-linked polyethylene according to any one of claims 1 to 4, characterized in that, The low-density polyethylene resin satisfies at least one of the following conditions: (1) The density of the low-density polyethylene resin is 0.91 g / cm³. 3 ~0.93g / cm 3 The option is 0.92 g / cm³. 3 ~0.925g / cm 3 ; (2) The melt index of the low-density polyethylene resin at 190°C and 2.16 kg pressure is 1 g / 10 min to 4 g / 10 min.

6. The composition for cross-linked polyethylene according to any one of claims 1 to 4, characterized in that, The crosslinking agent satisfies at least one of the following conditions: (1) The crosslinking agent includes one or more of dicumyl peroxide, benzoyl peroxide, di-tert-butyl peroxide and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane; (2) The crosslinking agent accounts for 0.1% to 5% of the mass of the low-density polyethylene resin.

7. The composition for cross-linked polyethylene according to any one of claims 1 to 4, characterized in that, It also includes water tree inhibitors; Optionally, the water tree inhibitor includes one or more of polyethylene glycol, ethylene-vinyl acetate copolymer, styrene-ethylene-butene-styrene block copolymer, and sorbitol; Optionally, the water tree inhibitor accounts for 0% to 1% of the mass of the low-density polyethylene resin.

8. A method for preparing a cross-linked polyethylene composition according to any one of claims 1 to 7, characterized in that, Includes the following steps: The low-density polyethylene resin and the 4,4'-thiobis(6-tert-butyl-3-methylphenol) were mixed and then melt-extruded to obtain granules. The crosslinking agent is melt-atomized and then mixed with the granular material to obtain a composition for crosslinked polyethylene.

9. A cross-linked polyethylene, characterized in that, Its raw materials include the cross-linked polyethylene composition according to any one of claims 1 to 7.

10. A cable material, characterized in that, It includes a conductor and an insulating material covering the conductor, the insulating material including the cross-linked polyethylene of claim 9.

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