Semi-conductive shielding material, preparation method and application thereof, and AC cable

Abstract

The invention provides a semi-conductive shielding material, a preparation method and application thereof and a high-voltage alternating-current cable, and belongs to the technical field of ultra-high-voltage cable semi-conductive shielding materials. The semiconductive shielding material is prepared from the following raw materials in parts by mass: 30 to 35 parts of conductive filler, 57.5 to 71 parts of silane coupling agent modified matrix resin, 1 to 2 parts of cross-linking agent, 1 to 2 parts of lubricant and 0.5 to 2 parts of phenolic acid antioxidant, wherein the silane coupling agent modified matrix resin is prepared from the following raw materials in parts by mass: 54 to 65 parts of matrix resin, 0.5 to 1 part of initiating auxiliary agent and 3 to 5 parts of silane coupling agent. The conductive filler, the silane coupling agent modified matrix resin, the cross-linking agent, the lubricant and the phenolic acid antioxidant are adopted as the raw materials of the semiconductive shielding material, so that the thermal aging resistance, the electrical property and the mechanical property of the semiconductive shielding material can be remarkably improved.

Description

Technical Field

[0001] This application relates to the field of cable semiconductive shielding materials, and in particular to a semiconductive shielding material, its preparation method and application, and AC cables. Background Technology

[0002] Ultra-high voltage (UHV) power transmission is a key technology for long-distance inter-regional power transmission. UHV cables, as the "blood vessels" of inter-regional power transmission, have material properties crucial for the long-term safe and stable operation of my country's inter-regional power grid. The semi-conductive shielding layer, a critical component connecting the conductor core and insulation layer in UHV cables, not only plays a vital role in homogenizing the electric field and eliminating air gaps, but also significantly affects charge injection into the insulation layer. The semi-conductive shielding material constituting the shielding layer is mainly prepared by melt blending conductive carbon black, matrix resin, and processing aids. Due to its low surface polarity and large specific surface area, conductive carbon black easily agglomerates in the matrix resin, forming interface protrusions in the semi-conductive shielding layer. The higher the voltage level, the more easily these interface protrusions form a strong local field at the shield-insulation interface of the cable, exacerbating the charge injection problem in the insulation layer and even causing partial discharge leading to insulation failure.

[0003] Furthermore, due to the electrothermal effect of the copper core conductor, the semiconductive shielding layer is subjected to prolonged heat-oxygen interaction during cable service, making it highly susceptible to thermal aging. This affects the electrical and mechanical properties of the material, impacting cable stability and shortening its service life. In the production of semiconductive shielding materials, highly efficient antioxidants such as 300 are often introduced to synthesize hindered phenolic antioxidants to improve heat aging resistance. However, these phenolic antioxidants have small molecular weights and are prone to migration and precipitation from the interior of the semiconductive shielding material during cable production and use, deteriorating its heat aging resistance. Moreover, these artificially synthesized antioxidants are biotoxic, and traditional preparation processes rely on toxic solvents, which is unsuitable for current eco-friendly production principles. Therefore, reducing the agglomeration of conductive fillers, antioxidant migration and precipitation, and antioxidant toxicity in semiconductive shielding materials to improve their heat aging resistance, electrical properties, mechanical properties, and environmental friendliness has become a pressing technical challenge for ultra-high voltage cable semiconductive shielding materials. Summary of the Invention

[0004] Based on this, the main objective of this application is to provide a semiconductive shielding material, its preparation method and application, and AC cables, so as to improve the heat aging resistance, electrical properties and mechanical properties of the semiconductive shielding material.

[0005] The first aspect of this application provides a semiconductive shielding material comprising the following raw materials in parts by weight:

[0006] The composition includes 30-35 parts conductive filler, 57.5-71 parts silane coupling agent modified matrix resin, 1-2 parts crosslinking agent, 1-2 parts lubricant, and 0.5-2 parts phenolic acid antioxidant.

[0007] The silane coupling agent modified matrix resin comprises the following raw materials in parts by weight:

[0008] The matrix resin consists of 54-65 parts, the initiator consists of 0.5-1 parts, and the silane coupling agent consists of 3-5 parts.

[0009] In some embodiments, the silane coupling agent comprises γ-methacryloyloxypropyltrimethoxysilane.

[0010] In some embodiments, the matrix resin includes ethylene-acrylate copolymers.

[0011] In some embodiments, the ethylene-acrylate copolymer includes one or both of ethylene-butyl acrylate copolymer and ethylene-ethyl acrylate copolymer.

[0012] In some embodiments, the initiating agent includes one or more of azo initiating agents and peroxide initiating agents.

[0013] In some embodiments, the azo initiator includes azobisisobutyronitrile (AIBN).

[0014] In some embodiments, the peroxide-based initiator includes benzoyl peroxide.

[0015] In some embodiments, the phenolic acid antioxidant includes rosmarinic acid.

[0016] In some embodiments, the conductive filler includes one or both of acetylene black and carbon black.

[0017] In some embodiments, the crosslinking agent includes a peroxide-based crosslinking agent.

[0018] In some embodiments, the peroxide crosslinking agent includes bis-tert-butylperoxyisopropylbenzene.

[0019] In some embodiments, the lubricant includes one or both of stearic acid and polyethylene wax.

[0020] A second aspect of this application provides a method for preparing the semiconductive shielding material described in the first aspect, comprising the following steps:

[0021] The initiator, matrix resin, and silane coupling agent are first melt-blended to prepare a silane coupling agent modified matrix resin.

[0022] The conductive filler, phenolic antioxidant and lubricant are mixed and then melt-blended with the matrix resin modified by the silane coupling agent, and then extruded and granulated to prepare granules.

[0023] The granules are mixed with a crosslinking agent to prepare the semiconductive shielding material.

[0024] In some embodiments, the conditions for the first melt blending include: a temperature of 110-120°C, a time of 2-3 hours, and a rotation speed of 60-100 rpm;

[0025] And / or, the conditions for the second melt blending include: a temperature of 150-160°C, a time of 10-20 min, and a rotation speed of 80-150 rpm.

[0026] The third aspect of this application provides the application of the semiconductive shielding material described in the first aspect or the semiconductive shielding material prepared by the preparation method described in the second aspect in AC cables.

[0027] In a fourth aspect of this application, an AC cable is provided, the raw materials of which include the semi-conductive shielding material described in the first aspect or the semi-conductive shielding material prepared by the preparation method described in the second aspect.

[0028] Compared with traditional technologies, this application has at least the following beneficial effects:

[0029] This application utilizes conductive fillers, silane coupling agent-modified matrix resin, crosslinking agents, lubricants, and phenolic acid antioxidants as raw materials for semiconductive shielding materials, which significantly improves the heat aging resistance, electrical properties, and mechanical properties of the materials. Specifically, by using matrix resin, initiator, and silane coupling agent as raw materials for the silane coupling agent-modified matrix resin, the matrix resin is modified. The silane coupling agent-modified matrix resin and the conductive filler exhibit good interfacial compatibility, enabling good dispersion of the conductive filler. Simultaneously, the phenolic acid antioxidants form a multiple hydrogen bond network with the silane coupling agent-modified matrix resin through phenolic hydroxyl groups, inhibiting the migration of antioxidants within the matrix resin and improving the heat aging resistance of the semiconductive shielding material. Attached Figure Description

[0030] To better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments or examples, or the best mode of conduct of these applications as currently understood. In the drawings:

[0031] Figure 1The diagram shows the oxidation-induced results of the semiconductive shielding materials prepared in Examples 1-6 and Comparative Examples 1-7, where S1-S6 represent the semiconductive shielding materials prepared in Examples 1-6, and D1-D7 represent the semiconductive shielding materials prepared in Comparative Examples 1-7. Detailed Implementation

[0032] The present application will be further described in detail below with reference to the embodiments and examples. These embodiments and examples are only for illustrating the present application and are not intended to limit the scope of the present application. The purpose of providing these embodiments and examples is to make the disclosure of the present application more thorough and comprehensive. It should also be understood that the present application can be implemented in many different forms and is not limited to the embodiments and examples described herein. Those skilled in the art can make various modifications or alterations without departing from the spirit of the present application, and the equivalent forms obtained also fall within the protection scope of the present application. In addition, numerous specific details are set forth in the following description to provide a fuller understanding of the present application. It should be understood that the present application can be implemented without one or more of these details.

[0033] 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. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0034] To address the issues of conductive filler agglomeration, antioxidant migration and precipitation, and the toxicity of existing synthetic antioxidants in semiconductive shielding materials, this application utilizes conductive fillers, silane coupling agent-modified matrix resin, crosslinking agents, lubricants, and phenolic acid antioxidants as raw materials for semiconductive shielding materials. This significantly improves the heat aging resistance, electrical properties, and mechanical properties of the semiconductive shielding materials. Specifically, by using matrix resin, initiator, and silane coupling agent as raw materials for silane coupling agent-modified matrix resin, the matrix resin is modified. The silane coupling agent-modified matrix resin and conductive fillers exhibit good interfacial compatibility, enabling good dispersion of the conductive fillers. Simultaneously, the phenolic acid antioxidants, through their phenolic hydroxyl groups, form a multiple hydrogen bond network with the silane coupling agent-modified matrix resin, inhibiting antioxidant migration within the matrix resin and improving the heat aging resistance of the semiconductive shielding material.

[0035] The first aspect of this application provides a semiconductive shielding material comprising the following raw materials in parts by weight:

[0036] The composition includes 30-35 parts conductive filler, 57.5-71 parts silane coupling agent modified matrix resin, 1-2 parts crosslinking agent, 1-2 parts lubricant, and 0.5-2 parts phenolic acid antioxidant.

[0037] The silane coupling agent modified matrix resin comprises the following raw materials in parts by weight:

[0038] The matrix resin consists of 54-65 parts, the initiator consists of 0.5-1 parts, and the silane coupling agent consists of 3-5 parts.

[0039] This application utilizes phenolic acid antioxidants, whose phenolic hydroxyl groups form a multiple hydrogen bond network with the silane coupling agent-modified matrix resin, inhibiting the migration of antioxidants within the matrix resin and improving the heat aging resistance of the semiconductive shielding material. Simultaneously, by using the matrix resin, initiator, and silane coupling agent as raw materials for the silane coupling agent-modified matrix resin, the matrix resin is modified. The silane coupling agent-modified matrix resin exhibits good interfacial compatibility with the conductive filler, enabling excellent dispersion of the conductive filler.

[0040] In some embodiments, the silane coupling agent comprises γ-methacryloyloxypropyltrimethoxysilane.

[0041] In some embodiments, the matrix resin includes ethylene-acrylate copolymers.

[0042] The carbon-carbon double bonds in the silane coupling agent γ-methacryloxypropyltrimethoxysilane undergo a grafting reaction with ethylene-acrylate copolymers, thereby modifying the matrix resin.

[0043] In some embodiments, the ethylene-acrylate copolymer includes one or both of ethylene-butyl acrylate copolymer and ethylene-ethyl acrylate copolymer.

[0044] In some embodiments, the initiating agent includes one or more of azo initiating agents and peroxide initiating agents.

[0045] In some embodiments, the azo initiator includes azobisisobutyronitrile (AIBN).

[0046] In some embodiments, the peroxide-based initiator includes benzoyl peroxide.

[0047] This application employs an initiating agent to initiate a free radical grafting reaction between the silane coupling agent and the matrix resin.

[0048] In some embodiments, the phenolic acid antioxidant includes rosmarinic acid. Rosmarinic acid is derived from natural plants, is inexpensive, and its production process does not involve toxic solvents, aligning with current green production principles.

[0049] In some embodiments, the conductive filler includes one or both of acetylene black and carbon black.

[0050] In some embodiments, the crosslinking agent includes a peroxide-based crosslinking agent.

[0051] In some embodiments, the peroxide crosslinking agent includes bis-tert-butylperoxyisopropylbenzene.

[0052] In some embodiments, the lubricant includes one or both of stearic acid and polyethylene wax.

[0053] In some embodiments, the conductive filler in the semiconductive shielding material is 30-35 parts by mass, which can be 30, 31, 32, 33, 34 or 35 parts.

[0054] In some embodiments, the silane coupling agent modified matrix resin of the semiconductive shielding material is 57.5-71 parts by mass, and can be 57.5 parts, 59 parts, 60 parts, 62.5 parts, 65 parts, 68.5 parts or 71 parts.

[0055] In some embodiments, the matrix resin modified with silane coupling agent in the semiconductive shielding material has a mass fraction of 57.5-71 parts, which can be 57.7 parts, 58 parts, 58.7 parts, 59 parts, 60 parts, 61 parts, 62 parts, 63 parts, 63.5 parts, 64 parts, 65 parts, 66 parts, 67 parts, 68 parts, 69 parts, 70 parts, or 71 parts.

[0056] In some embodiments, the initiator in the silane coupling agent modified matrix resin of the semiconductive shielding material is 0.5-1 part by mass, which can be 0.5, 0.6, 0.7, 0.8, 0.9 or 1 part.

[0057] In some embodiments, the silane coupling agent in the matrix resin modified with the silane coupling agent of the semiconductive shielding material is 3-5 parts by mass, which can be 3 parts, 3.5 parts, 4 parts, 4.5 parts or 5 parts.

[0058] In some embodiments, the phenolic acid antioxidant in the semiconductive shielding material is 0.5-2 parts by mass, which can be 0.5 parts, 1 part, 1.5 parts or 2 parts.

[0059] A second aspect of this application provides a method for preparing the semiconductive shielding material described in the first aspect, comprising the following steps:

[0060] The initiator, matrix resin, and silane coupling agent are first melt-blended to prepare a silane coupling agent modified matrix resin.

[0061] The conductive filler, phenolic antioxidant and lubricant are mixed and then melt-blended with the matrix resin modified by the silane coupling agent, and then extruded and granulated to prepare granules.

[0062] The granules are mixed with a crosslinking agent to prepare the semiconductive shielding material.

[0063] In some embodiments, the silane coupling agent is γ-methacryloyloxypropyltrimethoxysilane (KH570). This application utilizes an initiator to initiate a melt grafting reaction, grafting a silane coupling agent containing polar groups such as carbonyl groups onto the macromolecular chain of the matrix resin. This increases the polarity of the matrix resin macromolecular chain, enhances the interfacial compatibility between the matrix resin and the conductive filler, improves the dispersion of the conductive filler in the matrix resin, and promotes the construction of the conductive network. Simultaneously, the added phenolic antioxidant rosmarinic acid, through its phenolic hydroxyl groups, can form a multiple hydrogen bond network with the carbonyl groups in the silane coupling agent and the ester groups on the matrix resin, inhibiting the migration of the antioxidant in the matrix resin and improving the heat aging resistance of the semiconductive shielding material.

[0064] In some embodiments, the conditions for the first melt blending include: a temperature of 110-120°C, a time of 2-3 hours, and a rotation speed of 60-100 rpm;

[0065] And / or, the conditions for the second melt blending include: a temperature of 150-160°C, a time of 10-20 min, and a rotation speed of 80-150 rpm.

[0066] The third aspect of this application provides the application of the semiconductive shielding material described in the first aspect or the semiconductive shielding material prepared by the preparation method described in the second aspect in AC cables.

[0067] In a fourth aspect of this application, an AC cable is provided, the raw materials of which include the semi-conductive shielding material described in the first aspect or the semi-conductive shielding material prepared by the preparation method described in the second aspect.

[0068] The embodiments of this application will be described in detail below with reference to examples. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of this application. For experimental methods in the following embodiments where specific conditions are not specified, please refer to the guidelines given in this application, or follow experimental manuals or conventional conditions in the art, or follow the conditions recommended by the manufacturer, or refer to experimental methods known in the art.

[0069] Example 1

[0070] A semiconductive shielding material, the raw material of which is composed of the following components in parts by mass:

[0071] 34 parts conductive carbon black, 63.5 parts silane coupling agent modified matrix resin, 1 part crosslinking agent, 1 part lubricant, and 0.5 parts phenolic acid antioxidant;

[0072] The raw material for the silane coupling agent modified matrix resin consists of the following components in parts by weight:

[0073] The matrix resin consists of 59 parts, the initiator consists of 0.5 parts, and the silane coupling agent consists of 4 parts.

[0074] The matrix resin is ethylene-butyl acrylate copolymer (EBA), manufactured by Repsol, model E1770, with a melt index of 8.7 g / min at 190°C and 2.16 kg, and a tensile strength >12 MPa.

[0075] The DBP absorption value of conductive carbon black is 148 ml / 100g;

[0076] The crosslinking agent is bis-tert-butylperoxide isopropylbenzene;

[0077] The lubricant is zinc stearate;

[0078] The initiator is benzoyl peroxide;

[0079] The phenolic acid antioxidant is rosmarinic acid;

[0080] The silane coupling agent is KH570.

[0081] The preparation method of the semiconductive shielding material is as follows:

[0082] Weigh each component according to the formula, add EBA into a mixer, melt at 110℃ for 10 min at a speed of 60 rpm, then add initiator, melt and mix at a speed of 80 rpm for 5 min, then add silane coupling agent, mix at a speed of 100 rpm for 2 h to prepare silane coupling agent modified matrix resin.

[0083] Conductive carbon black, phenolic antioxidants, and lubricants were mixed and stirred in a high-speed mixer at room temperature (23°C) at a speed of 100 rpm for 40 minutes. After mixing and stirring, the mixture was dried at 80°C for 6 hours to obtain a dried mixture.

[0084] The silane coupling agent modified matrix resin was melted in an internal mixer at 80 rpm and 160°C for 5 minutes until the resin was completely melted. Then, the dried mixture was added for melt blending. The melt blending conditions were: all three zones were set at 160°C, the speed was 120 rpm, and the time was 15 minutes. The mixture was then extruded, sheared, and granulated to prepare granules.

[0085] The prepared granules were placed in an oven and heated to 60°C for 30 minutes. Then, they were mixed and stirred with a crosslinking agent at 60 rpm and room temperature for 10 minutes. The mixture was then placed in an oven and kept warm for 8 hours to allow the crosslinking agent to be fully absorbed, thus preparing the semiconductive shielding material.

[0086] Example 2

[0087] The raw material composition of the semiconductive shielding material in Example 2 is basically the same as that in Example 1, except that "59 parts of matrix resin and 0.5 parts of initiator" are replaced with "58.7 parts of matrix resin and 0.8 parts of initiator".

[0088] The semiconductive shielding material was prepared according to the method in Example 1.

[0089] Example 3

[0090] The raw material composition of the semiconductive shielding material in Example 3 is basically the same as that in Example 1, except that: "63.5 parts of silane coupling agent modified matrix resin, 59 parts of matrix resin, 0.5 parts of initiator, and 0.5 parts of phenolic acid antioxidant" is replaced with "62.5 parts of silane coupling agent modified matrix resin, 57.7 parts of matrix resin, 0.8 parts of initiator, and 1.5 parts of phenolic acid antioxidant".

[0091] The semiconductive shielding material was prepared according to the method in Example 1.

[0092] Example 4

[0093] The preparation method and raw materials of the semiconductive shielding material in Example 4 are basically the same as those in Example 1, except that "zinc stearate is used as lubricant" is replaced with "polyethylene wax is used as lubricant".

[0094] The semiconductive shielding material was prepared according to the method in Example 1.

[0095] Example 5

[0096] The preparation method and raw materials of the semiconductive shielding material in Example 5 are basically the same as those in Example 1, except that the raw materials for the semiconductive shielding material are composed of the following components in parts by mass:

[0097] 35 parts conductive carbon black, 60 parts silane coupling agent modified matrix resin, 1 part crosslinking agent, 2 parts lubricant, and 2 parts phenolic acid antioxidant.

[0098] The raw material for the silane coupling agent modified matrix resin consists of the following components in parts by weight:

[0099] 54 parts of matrix resin, 1 part of initiator, and 5 parts of silane coupling agent.

[0100] The semiconductive shielding material was prepared according to the method in Example 1.

[0101] Example 6

[0102] The preparation method and raw materials of the semiconductive shielding material in Example 6 are basically the same as those in Example 1, except that: "63.5 parts of silane coupling agent modified matrix resin, 59 parts of matrix resin, and 4 parts of silane coupling agent" are replaced with "68.5 parts of silane coupling agent modified matrix resin, 65 parts of matrix resin, and 3 parts of silane coupling agent"; and "34 parts of conductive carbon black" are replaced with "30 parts of conductive carbon black".

[0103] The semiconductive shielding material was prepared according to the method in Example 1.

[0104] Comparative Example 1

[0105] The raw material composition of the semiconductive shielding material in Comparative Example 1 and Example 1 is basically the same, except that: the "initiator" is replaced with an equal mass of "matrix resin"; and the phenolic antioxidant "rosmarinic acid" is replaced with "antioxidant 300 (4,4'-thiobis(6-tert-butyl-3-methylphenol))".

[0106] The semiconductive shielding material was prepared according to the method in Example 1.

[0107] Comparative Example 2

[0108] The raw material composition of the semiconductive shielding material in Comparative Example 2 is basically the same as that in Example 1, except that the "initiator" is replaced with an equal mass fraction of "matrix resin".

[0109] The semiconductive shielding material was prepared according to the method in Example 1.

[0110] Comparative Example 3

[0111] The raw material composition of the semiconductive shielding material in Comparative Example 3 is basically the same as that in Example 1, except that the phenolic antioxidant "rosmarinic acid" is replaced with "antioxidant 300 (4,4'-thiobis(6-tert-butyl-3-methylphenol))".

[0112] The semiconductive shielding material was prepared according to the method in Example 1.

[0113] Comparative Example 4

[0114] The raw material composition of the semiconductive shielding material in Comparative Example 4 is basically the same as that in Example 1, except that "0.5 parts of initiator" is replaced with "0.2 parts of initiator".

[0115] The semiconductive shielding material was prepared according to the method in Example 1.

[0116] Comparative Example 5

[0117] The raw material composition of the semiconductive shielding material in Comparative Example 5 is basically the same as that in Example 1, except that "4 parts of silane coupling agent" is replaced with "2 parts of silane coupling agent".

[0118] The semiconductive shielding material was prepared according to the method in Example 1.

[0119] Comparative Example 6

[0120] The raw material composition of the semiconductive shielding material in Comparative Example 6 is basically the same as that in Example 1, except that "0.5 parts of initiator" is replaced with "1.5 parts of initiator".

[0121] The semiconductive shielding material was prepared according to the method in Example 1.

[0122] Comparative Example 7

[0123] The raw material composition of the semiconductive shielding material in Comparative Example 7 is basically the same as that in Example 1, except that "4 parts of silane coupling agent" is replaced with "8 parts of silane coupling agent".

[0124] The semiconductive shielding material was prepared according to the method in Example 1.

[0125] Experimental Example 1

[0126] (1) The semiconductive shielding materials prepared in Examples 1-6 and Comparative Examples 1-7 were melted in a 120°C flat vulcanizing machine, pressurized to 10 MPa, and hot-pressed at 120°C. They were then transferred to a 180°C flat vulcanizing machine for crosslinking for 20 min to obtain grafted and ungrafted semiconductive shielding material samples. Rectangular samples with dimensions of 5 cm × 12 cm × 1 mm and dumbbell-shaped samples with dimensions of 4 mm × 75 mm × 1 mm were prepared by cutting, and used to measure the electrical and mechanical properties of the materials, respectively. The semiconductive shielding material samples were prepared into strip-shaped semiconductive shielding layers using a single-screw extruder, and their surface finish was tested. The volume resistivity at 23°C, volume resistivity at 90°C, tensile strength, elongation at break, and the number of protrusions > 50 μm are shown in Table 1.

[0127] Electrical performance, mechanical performance, and surface finish testing methods: Tests shall be conducted in accordance with the requirements of GB / T 22078.2-2008.

[0128] Table 1. Electrical properties, mechanical properties, and surface finish properties of the semiconductive shielding materials prepared in Examples 1-6 and Comparative Examples 1-7.

[0129]

[0130] Table 1 shows that the semiconductive shielding materials prepared by grafting with initiating agents in Examples 1-6 have significantly better electrical, mechanical, and surface finish properties than the semiconductive shielding materials prepared by direct blending without initiating agents in Comparative Examples 1-2. This is because the initiating agent used in this application grafts KH570 containing carbonyl polar groups onto the macromolecular chain of the matrix resin, which can increase the molecular chain polarity of the matrix resin, improve the interfacial compatibility between the matrix resin and conductive carbon black, and thus improve the dispersion of conductive carbon black in the matrix resin, promoting a more developed conductive network and stress-dissipating network inside the semiconductive shielding material. In contrast, Comparative Examples 1-2 improved the interface by mechanically blending the silane coupling agent KH570 with the matrix resin, resulting in weak physical adsorption and easy desorption at high temperatures.

[0131] Comparing Examples 1-2 and Comparative Example 4, it can be seen that when the content of initiating agent in the semiconductive shielding material is low, the number of free radicals generated is small, the grafting reaction is incomplete, the polar groups have limited improvement on the interfacial compatibility between the matrix resin and the conductive carbon black, and the electrical properties, mechanical properties and surface finish properties are all low.

[0132] Comparing the results of Example 1 and Example 4, it can be seen that the type of lubricant has no significant effect on the mechanical and electrical properties of the semiconductive shielding material, but has a certain impact on the surface finish. This is because the molecular weight of polyethylene wax is much lower than that of the matrix resin, and it will migrate to the interface between the melt and the screw in the molten state to play an external lubricating role.

[0133] The results of Examples 5-6 show that although the presence of silane coupling agents improves interfacial compatibility, excessively high conductive carbon black content still has a certain impact on the elongation at break of the semiconductive shielding material; when the conductive carbon black content is low, the conductive network is imperfect, and thus the bulk resistivity of the semiconductive shielding material increases.

[0134] Compared to Comparative Example 3, which used antioxidant 300, Example 1, which used a phenolic acid antioxidant, showed a 20% increase in elongation at break, a 16.5 Ω·cm decrease in resistivity at 90°C, and a 20% decrease in the number of protrusions >50 μm. The results indicate that the type of antioxidant significantly affects the dispersion of conductive carbon black in the semiconductive shielding material. This is attributed to the fact that antioxidant 300 has a bisphenol structure, while the phenolic acid antioxidant rosmarinic acid has multiple phenolic hydroxyl groups, and these polar groups improve the dispersion of conductive carbon black in the matrix resin.

[0135] Comparing Example 1 and Comparative Examples 4-7, the results show that the amount of initiator and silane coupling agent added affects the grafting modification effect of the matrix resin. Insufficient initiator addition fails to generate enough free radicals to graft the coupling agent onto the matrix resin molecular chains, resulting in the conductive carbon black still easily agglomerating in the matrix resin. Excessive initiator addition easily causes pre-crosslinking of the matrix resin, increasing melt viscosity, which is detrimental not only to the dispersion of conductive fillers but also to the processing and extrusion of the material. Insufficient silane coupling agent addition has limited improvement on the interfacial compatibility between the filler and the matrix resin, resulting in poor dispersion of the conductive carbon black. Excessive silane coupling agent addition leads to excessive free coupling agent bridging between conductive carbon black molecules, which in turn exacerbates the agglomeration of the conductive carbon black, thereby deteriorating the electrical properties and surface finish of the semiconductive shielding material.

[0136] (2) The semiconductive shielding materials prepared in Examples 1-6 were named S1-S6, and the semiconductive shielding materials prepared in Comparative Examples 1-7 were named D1-D7. Oxidation induction tests were performed on samples S1-S6 and D1-D7 respectively. The oxidation induction test method was conducted according to the standard requirements specified in GB-T 19466.6-2009. The results are as follows: Figure 1 As shown, S1-S6 represent the semiconductive shielding materials prepared in Examples 1-6, and D1-D7 represent the semiconductive shielding materials prepared in Comparative Examples 1-7.

[0137] Figure 1 The results show that, compared with comparative examples 1-7, the semiconductive shielding materials of examples 1-6 of this application have a longer oxidation induction time (21.4-46.2 min) and higher heat aging resistance.

[0138] With the same amount of antioxidant added, compared to Comparative Example 3 which used Antioxidant 300, Example 1 which used the phenolic acid antioxidant rosmarinic acid showed a 38% increase in oxidation induction time. This indicates that utilizing the polyphenolic hydroxyl groups of the rosmarinic acid antioxidant to form a hydrogen bond network with the polar groups of the silane coupling agent graft chain to inhibit antioxidant migration is an effective technical means to improve the heat aging resistance of semiconductive shielding materials.

[0139] Compared with Comparative Example 2, Example 1 uses an initiator to graft the silane coupling agent onto the macromolecular chain of the matrix resin, which increases the oxidation induction period by 1.1 times and significantly improves the heat aging resistance of the semiconductive shielding material.

[0140] Compared with Example 1, the use of excessive or insufficient initiating agents and silane coupling agents in Comparative Examples 4-7 is detrimental to the construction of hydrogen bond networks between phenolic antioxidants and coupling agents in the semiconductive shielding material, reduces the migration inhibition effect of antioxidants, and is not conducive to improving the heat aging resistance of the semiconductive shielding material.

[0141] 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.

[0142] 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 patent application. 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 semiconductive shielding material, characterized in that, The raw materials include the following parts by weight: The composition includes 30-35 parts conductive filler, 57.5-71 parts silane coupling agent modified matrix resin, 1-2 parts crosslinking agent, 1-2 parts lubricant, and 0.5-2 parts phenolic acid antioxidant. The silane coupling agent modified matrix resin comprises the following raw materials in parts by weight: The matrix resin consists of 54-65 parts, the initiator consists of 0.5-1 parts, and the silane coupling agent consists of 3-5 parts.

2. The semiconductive shielding material according to claim 1, characterized in that, The silane coupling agent includes γ-methacryloxypropyltrimethoxysilane.

3. The semiconductive shielding material according to claim 1, characterized in that, The matrix resin includes ethylene-acrylate copolymers.

4. The semiconductive shielding material according to claim 3, characterized in that, The ethylene-acrylate copolymers include one or both of ethylene-butyl acrylate copolymers and ethylene-ethyl acrylate copolymers.

5. The semiconductive shielding material according to any one of claims 1-4, characterized in that, The initiating agent includes one or more of azo initiating agents and peroxide initiating agents; Optionally, the azo initiator includes azobisisobutyronitrile; Optionally, the peroxide-based initiator includes benzoyl peroxide.

6. The semiconductive shielding material according to any one of claims 1-4, characterized in that, It meets one or more of the following characteristics: (1) The phenolic acid antioxidants include rosmarinic acid; (2) The conductive filler includes one or both of acetylene black and carbon black; (3) The crosslinking agent includes peroxide-based crosslinking agents; Optionally, the peroxide-based crosslinking agent includes bis-tert-butylperoxyisopropylbenzene; (4) The lubricant includes one or both of stearic acid and polyethylene wax.

7. The method for preparing the semiconductive shielding material according to any one of claims 1-6, characterized in that, Includes the following steps: The initiator, matrix resin, and silane coupling agent are first melt-blended to prepare a silane coupling agent modified matrix resin. The conductive filler, phenolic antioxidant and lubricant are mixed and then melt-blended with the matrix resin modified by the silane coupling agent, and then extruded and granulated to prepare granules. The granules are mixed with a crosslinking agent to prepare the semiconductive shielding material.

8. The preparation method according to claim 7, characterized in that... The conditions for the first melt blending include: a temperature of 110-120℃, a time of 2-3 hours, and a rotation speed of 60-100 rpm; And / or, the conditions for the second melt blending include: a temperature of 150-160°C, a time of 10-20 min, and a rotation speed of 80-150 rpm.

9. The application of the semiconductive shielding material as described in any one of claims 1-6 or the semiconductive shielding material prepared by the preparation method described in claim 7 or 8 in AC cables.

10. An AC cable, characterized in that, The raw materials include the semiconductive shielding material as described in any one of claims 1-6 or the semiconductive shielding material prepared by the preparation method described in claim 7 or 8.

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