High-voltage submarine cable semiconductive shielding material and preparation method thereof

Abstract

The invention relates to the technical field of cable materials, and provides a high-voltage submarine cable semi-conductive shielding material and a preparation method thereof, the high-voltage submarine cable semi-conductive shielding material comprises 65-75 parts of matrix resin, 25-35 parts of conductive carbon black, 0.5-3 parts of an antioxidant-lubrication integrated auxiliary agent, 0.5-1.5 parts of a cross-linking agent and 0.2-0.5 part of an antioxidant, the antioxidant-lubricating integrated additive is obtained by grafting an antioxidant containing a carbon-carbon double bond to a fluorine-containing polymer lubricant, the grafting rate is 2%-10%, pre-crosslinking of a matrix molecular chain can be inhibited through the antioxidant-lubricating integrated additive, the free radical capture efficiency is improved through directional enrichment of the antioxidant, meanwhile, the situation that the high-temperature crosslinking efficiency is affected by the too high antioxidant dosage is avoided, and the service life of the lubricant is prolonged. In addition, the lubricating unit effectively reduces the friction coefficient between the melt and the surface of the equipment, reduces shear heat generation, is beneficial for balancing temperature distribution of the cavity, shortens the retention probability and time of the melt on the surface of the equipment, and remarkably improves the scorch resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of cable materials, and in particular to a semi-conductive shielding material for a high-voltage submarine cable and a preparation method thereof. Background Art

[0002] High-voltage submarine cables, essential electrical equipment for cross-sea power transmission projects, are the critical "lifeline" connecting power supplies across the ocean. They are widely used in projects such as offshore wind farm access, inter-island power grid interconnection between land and sea, and offshore drilling platforms. Compared to high-voltage land cables, high-voltage submarine cables are characterized by complex operating environments and high installation and maintenance costs. A single cable typically exceeds 20 km and requires an extremely long continuous extrusion process of at least 15 days. During this process, the shielding material melt is susceptible to factors such as long-term local temperature rise and the cumulative effect of retention, which can easily cause premature thermal decomposition of the crosslinker, triggering pre-crosslinking and gel formation, significantly increasing the risk of scorch. This not only changes the melt rheological properties and increases extrusion process instability, leading to internal unevenness and surface defects in the cable shielding layer, but can even force production interruptions due to gel clogging of the extrusion filter. Therefore, high-voltage submarine cable shielding materials must not only meet basic properties such as electrical, mechanical, and surface finish, but also possess excellent scorch resistance during extended continuous extrusion.

[0003] The scorch resistance of shielding materials refers to their ability to suppress gel formation during pre-crosslinking during melt extrusion and is a key indicator for evaluating their long-term continuous extrusion processability. High-voltage cable materials typically use peroxides such as dicumyl peroxide as crosslinkers, whose initial decomposition temperature is 120°C, well within the material's extrusion processing temperature range of 120-130°C. Antioxidants in the formulation not only provide antioxidant protection but also capture free radicals, providing a degree of scorch resistance. However, while conventional methods of simply increasing the antioxidant content or reducing the crosslinker dosage can reduce free radical concentration during extrusion and inhibit pre-crosslinking, this approach inevitably compromises the crosslink density during the subsequent high-temperature crosslinking process, resulting in insufficient mechanical properties and heat resistance. Therefore, the conflict between scorch resistance and crosslinking efficiency makes the development of scorch-resistant shielding materials challenging. Therefore, there is a need for a scorch-resistant high-voltage submarine cable shielding material and preparation method that does not compromise crosslinking efficiency. Summary of the Invention

[0004] The purpose of the present invention is to provide a semi-conductive shielding material for high-voltage submarine cables, which can inhibit the pre-crosslinking of the matrix molecular chain through an integrated antioxidant-lubricating additive, avoid the influence of excessive antioxidant dosage on the high-temperature crosslinking efficiency, and achieve a significant improvement in the scorch resistance.

[0005] Another object of the present invention is to provide a method for preparing a semi-conductive shielding material for a high-voltage submarine cable, preparing an antioxidant-lubricating integrated additive through a free radical grafting reaction, and regulating the diffusion behavior of antioxidant-lubricating molecules under the external processing field to make them directionally enriched and distributed in the scorch risk area of ​​the material melt and quickly form a dynamic super-lubricating molecular layer, forming a synergistic scorch resistance mechanism of "rapid migration-dynamic external lubrication-precise capture of free radicals".

[0006] The technical solution adopted in the present invention is: On the one hand, the present invention provides a semi-conductive shielding material for a high-voltage submarine cable. The raw materials include, by mass, 65-75 parts of a base resin, 25-35 parts of conductive carbon black, 0.5-3 parts of an integrated antioxidant-lubricating additive, 0.5-1.5 parts of a cross-linking agent, and 0.2-0.5 parts of an antioxidant. The integrated antioxidant-lubricating additive is obtained by grafting an antioxidant containing a carbon-carbon double bond onto a fluoropolymer lubricant, and the grafting rate is 2%-10%.

[0007] Furthermore, the raw materials of the integrated antioxidant-lubricating additive include a fluoropolymer lubricant, an oxidant containing a carbon-carbon double bond, and an initiator. The raw materials of the integrated antioxidant-lubricating additive include a fluoropolymer lubricant, an oxidant containing a carbon-carbon double bond, and an initiator. The mass ratio of the fluoropolymer lubricant to the oxidant containing a carbon-carbon double bond is 100:2-10; the mass ratio of the fluoropolymer lubricant to the initiator is 100:0.4-0.8.

[0008] Furthermore, the fluorine-containing polymer lubricant includes one or more of a 26-type vinylidene fluoride / hexafluoropropylene binary copolymer and a 246-type vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene terpolymer.

[0009] Furthermore, the antioxidant containing a carbon-carbon double bond includes one or more of 2-(2-hydroxy-3-tert-butyl-5-methylbenzyl)-4-methyl-6-tert-butylphenyl acrylate, N-(4-anilinophenyl)maleimide, and 3-[(4-anilinophenyl)amino]-2-hydroxypropyl methacrylate.

[0010] Furthermore, the initiator is dicumyl peroxide.

[0011] Further, the base resin includes one or more of ethylene-butyl acrylate copolymer and ethylene-ethyl acrylate copolymer.

[0012] Furthermore, the conductive carbon black has an oil absorption value of 120 ml / 100 g to 200 ml / 100 g, and an ash content of less than 0.2%.

[0013] Furthermore, the antioxidant includes one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate and 4,4'-thiobis(6-tert-butyl-3-methylphenol); and the crosslinking agent includes one or more of dicumyl peroxide and di-tert-butylperoxyisopropylbenzene.

[0014] On the other hand, the present invention provides a method for preparing a semi-conductive shielding material for a high-voltage submarine cable, comprising the following steps: S1. uniformly mixing a matrix resin, conductive carbon black, an antioxidant-lubricating integrated additive and an antioxidant to obtain a mixture, S2. melt-mixing the mixture at a mixing temperature of 120°C-160°C and a rotation speed of 100rpm-150rpm, and shearing and granulating to obtain pellets, S3. preheating the pellets at 50-80°C for 2-4h, adding a cross-linking agent, and mixing by liquid phase impregnation adsorption to obtain a semi-conductive shielding material.

[0015] Furthermore, the preparation method of the antioxidant-lubricating integrated auxiliary agent in S1 includes the following steps: I. melt-mixing a fluoropolymer lubricant and an antioxidant containing a carbon-carbon double bond to obtain a mixture A, II. mixing the mixture A and an initiator, reacting at 150°C-200°C for 20min-40min to obtain a reaction product, III. extracting and purifying the reaction product with ethanol at 70°C-90°C for 10h-15h to remove unreacted antioxidant, initiator and initiator decomposition by-products, and drying at 50°C-70°C for 10h-15h to completely evaporate the ethanol to obtain the antioxidant-lubricating integrated auxiliary agent.

[0016] Furthermore, the initiator decomposition byproducts in step III include acetophenone and cumyl alcohol.

[0017] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects: 1. Through the action of the antioxidant-lubricating integrated additive, the scorch time of the semi-conductive shielding material is significantly prolonged.

[0018] 2. It avoids the problem of sacrificing the cross-linking density of the material in the subsequent high-temperature cross-linking process by simply increasing the antioxidant or reducing the amount of cross-linking agent, and achieves a balance between scorch resistance and cross-linking efficiency.

[0019] 3. During the processing, fluorinated additives rely on their low molecular weight and low surface energy to quickly migrate to the barrel and screw surfaces, forming a stable and uniform lubricating protective film, effectively reducing the friction coefficient between the melt and the metal surface, reducing shear heat generation, and helping to balance the temperature distribution in the cavity. At the same time, it shortens the probability and time of melt retention on the equipment surface, avoiding the aggravation of pre-crosslinking due to local overheating and long-term retention.

[0020] 4. Ensure that antioxidants are precisely released at key high-temperature points, quickly capturing free radicals generated during processing and inhibiting high-temperature-induced pre-crosslinking reactions. This creates a highly effective scorch protection mechanism and prevents the introduction of excessive antioxidants that could affect vulcanization and crosslinking efficiency. This creates a synergistic scorch resistance mechanism of "rapid migration, dynamic external lubrication, and precise free radical capture."

[0021] 5. Make the melt rheological properties of semi-conductive shielding materials more stable during the extrusion process, greatly reduce the number of surface defects, and improve processing stability and surface smoothness.

[0022] 6. The present invention is easy to operate, does not involve toxic reagents, does not require changes to the existing industrial production process of semi-conductive shielding materials, and has good prospects for large-scale application. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 This is the reaction process for preparing the antioxidant-lubricating integrated additive of the present application; Figure 2 Schematic diagram of the preparation process of the semi-conductive shielding material in the embodiment of the present application; Figure 3 This is a Fourier infrared spectrum of the material before and after the grafting reaction in the embodiment of the present application; Figure 4 Schematic diagram of the oxidation induction time of the material before and after the grafting reaction in the embodiment of the present application; Figure 5 Schematic diagram of the contact angle of the material before and after the grafting reaction in the examples of this application.

[0025] Note: In the figure, FPI is a fluoropolymer lubricant; 246-FPI is a 246-type vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene terpolymer; AO3052 is 2-(2-hydroxy-3-tert-butyl-5-methylbenzyl)-4-methyl-6-tert-butylphenyl acrylate; AO3052@246-FPI is an antioxidant-lubricant integrated additive obtained by grafting reaction; DCP is diisopropylbenzene peroxide. DETAILED DESCRIPTION

[0026] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0027] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to specific embodiments.

[0028] Please refer to Figure 1-2 , Figure 1 The reaction process for preparing the antioxidant-lubricating integrated additive of this application is as follows: Figure 2 The figure is a schematic diagram of the preparation process of a semi-conductive shielding material. Based on the basic theoretical concept of the present invention, a method for preparing a semi-conductive shielding material for a high-voltage submarine cable is proposed, which includes the following steps: S1. By weight, 65-75 parts of a base resin, 25-35 parts of conductive carbon black, 0.5-3 parts of an antioxidant-lubricating integrated additive, and 0.2-0.5 parts of an antioxidant are uniformly mixed to obtain a mixture, wherein the base resin comprises one or more of ethylene-butyl acrylate copolymer and ethylene-ethyl acrylate copolymer, the conductive carbon black has an oil absorption value of 120 ml / 100 g to 200 ml / 100 g and an ash content of less than 0.2%, and the antioxidant comprises one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate and 4,4'-thiobis(6-tert-butyl-3-methylphenol). The preparation method of the antioxidant-lubricating integrated additive comprises the following steps: I. melt-mixing and grafting a fluoropolymer lubricant and an antioxidant containing a carbon-carbon double bond at a grafting rate of 2%-10% to obtain a mixture A, wherein the fluoropolymer lubricant and the antioxidant containing a carbon-carbon double bond are in a mass ratio of 100:2-10, the fluoropolymer lubricant comprises one or more of a 26-type vinylidene fluoride / hexafluoropropylene binary copolymer and a 246-type vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene terpolymer, and the antioxidant containing a carbon-carbon double bond comprises one or more of 2-(2-hydroxy-3-tert-butyl-5-methylbenzyl)-4-methyl-6-tert-butylphenyl acrylate, N-(4-anilinophenyl)maleimide, and 3-[(4-anilinophenyl)amino]-2-hydroxypropyl methacrylate; II. The mixture A and the initiator are mixed and reacted at 150 ℃ -200 ℃ for 20min-40min to obtain a reaction product. The initiator is dicumyl peroxide, and the amount of the initiator added is in a mass ratio of fluoropolymer lubricant: initiator is 100: 0.4-0.8; III. The reaction product is extracted and purified using ethanol at 70°C-90°C for 10h-15h to remove unreacted antioxidant, initiator and initiator decomposition byproducts, and dried at 50°C-70°C for 10h-15h to volatilize the ethanol to obtain an antioxidant-lubricating integrated additive.

[0029] S2. The mixture was melt-kneaded at a mixing temperature of 120°C-160°C and a speed of 100rpm-150rpm, and sheared and granulated to obtain pellets; S3. Preheat the pellets at 50-80°C for 2-4h, add 0.5-1.5 parts of a cross-linking agent, and mix by liquid phase impregnation adsorption to obtain a semiconductive shielding material, wherein the cross-linking agent includes one or more of diisopropylbenzene peroxide and di-tert-butyl peroxyisopropylbenzene.

[0030] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0031] Example 1 This embodiment provides a semi-conductive shielding material for a high-voltage submarine cable.

[0032] Specifically, the semi-conductive shielding material of this embodiment is used in the field of high-voltage submarine cables. Its raw materials include 65 parts of base resin, 35 parts of conductive carbon black, 1 part of antioxidant-lubricating integrated additive, 0.5 part of antioxidant and 1 part of cross-linking agent in parts by mass, wherein the base resin is ethylene-butyl acrylate copolymer resin, the butyl acrylate content is 18wt%, the melt index at 190°C and 2.16 kg is 7.0 g / min, and the elongation at break is 900%. The conductive carbon black is a high-purity conductive carbon black with a carbon black oil absorption value (DBP absorption value) of 172 ml / 100g and an ash content of 0.1%. The antioxidant is 4,4'-thiobis(6-tert-butyl-3-methylphenol), and the cross-linking agent is diisopropylbenzene peroxide.

[0033] The raw materials of the integrated antioxidant-lubricating additive include, by mass, 100 parts of 26-type vinylidene fluoride / hexafluoropropylene binary copolymer, 5 parts of 2-(2-hydroxy-3-tert-butyl-5-methylbenzyl)-4-methyl-6-tert-butylphenyl acrylate and 0.5 parts of diisopropylbenzene peroxide, with a grafting rate of 5%. Among them, the melting point of the 26-type vinylidene fluoride / hexafluoropropylene binary copolymer is 60°C, the melting point of 2-(2-hydroxy-3-tert-butyl-5-methylbenzyl)-4-methyl-6-tert-butylphenyl acrylate is 130°C, and the melting point of diisopropylbenzene peroxide is 40°C.

[0034] The preparation process includes the following steps: S1. 100 parts of a 26-type vinylidene fluoride / hexafluoropropylene binary copolymer and 5 parts of 2-(2-hydroxy-3-tert-butyl-5-methylbenzyl)-4-methyl-6-tert-butylphenyl acrylate were melt-mixed at 135° C. to form a mixture; S2. The mixture was cooled to 70 ° C, 0.5 parts of diisopropylbenzene peroxide was added as an initiator, and mixed thoroughly, the temperature was raised to 160 ° C, and the reaction was carried out for 30 minutes to obtain a reaction product; S3. The reaction product was extracted with sufficient ethanol at 80 ° C for 12 h to remove unreacted antioxidant, initiator and initiator decomposition byproducts acetophenone and cumyl alcohol to obtain a purified product; S4. The purified product was dried at 60 ° C for 12 h to evaporate the residual ethanol to obtain a pure antioxidant - lubricating integrated additive; S5 65 parts of ethylene - butyl acrylate copolymer resin, 35 parts of conductive carbon black, 1 part of antioxidant - lubricating integrated additive, 0.5 parts of 4,4 '- thiobis (6-tert-butyl-3-methylphenol) premixed to obtain a mixture A; S6. The mixture A was melt-mixed by a twin-screw extruder at a mixing temperature of 120 to 160°C and a speed of 100 to 150 rpm to obtain a melt-extruded material; S7. The melt-extruded material is sheared and granulated and dried to obtain pellets; S8. Preheat the pellets at 60° C. for 3 h, add diisopropylbenzene peroxide, and mix the pellets and diisopropylbenzene peroxide for 6 h by liquid phase impregnation adsorption to form a semi-conductive shielding material.

[0035] Example 2 This embodiment 2 provides a high-voltage submarine cable semi-conductive shielding material. The preparation process of the semi-conductive shielding material of this embodiment 2 is basically the same as that of Example 1, except that the amount of the antioxidant-lubricating integrated additive is 2 parts, so as to verify the effect of the addition amount of the antioxidant-lubricating integrated additive on the performance of the semi-conductive shielding material.

[0036] Example 3 This embodiment 3 provides a high-voltage submarine cable semi-conductive shielding material. The preparation process of the semi-conductive shielding material in this embodiment 3 is basically the same as that in Example 1, except that the amount of the antioxidant-lubricating integrated additive is 3 parts, so as to verify the effect of the addition amount of the antioxidant-lubricating integrated additive on the performance of the semi-conductive shielding material.

[0037] Example 4 This embodiment 4 provides a high-voltage submarine cable semi-conductive shielding material. The preparation process of the semi-conductive shielding material in this embodiment 4 is basically the same as that in Example 1, except that the grafting rate of the antioxidant-lubricating integrated additive is 2%, that is, 100 parts of 26-type vinylidene fluoride / hexafluoropropylene binary copolymer and 2 parts of 2-(2-hydroxy-3-tert-butyl-5-methylbenzyl)-4-methyl-6-tert-butylphenyl acrylate, so as to verify the influence of the grafting rate of the antioxidant-lubricating integrated additive on the performance of the semi-conductive shielding material.

[0038] Example 5 This embodiment 5 provides a high-voltage submarine cable semi-conductive shielding material. The preparation process of the semi-conductive shielding material in this embodiment 5 is basically the same as that in Example 1, except that the grafting rate of the antioxidant-lubricating integrated additive is 10%, that is, 100 parts of 26-type vinylidene fluoride / hexafluoropropylene binary copolymer and 10 parts of 2-(2-hydroxy-3-tert-butyl-5-methylbenzyl)-4-methyl-6-tert-butylphenyl acrylate, so as to verify the influence of the grafting rate of the antioxidant-lubricating integrated additive on the performance of the semi-conductive shielding material.

[0039] Comparative Example 1 This comparative example 1 provides a high-voltage submarine cable semi-conductive shielding material. The preparation process of the semi-conductive shielding material of this comparative example 1 is basically the same as that of Example 1, except that no antioxidant-lubricating integrated additive is added to verify the effect of adding the antioxidant-lubricating integrated additive on improving the scorch resistance of the semi-conductive shielding material compared to not adding the antioxidant-lubricating integrated additive.

[0040] Comparative Example 2 This comparative example 2 provides a high-voltage submarine cable semi-conductive shielding material. The preparation process of the semi-conductive shielding material of this comparative example 2 is basically the same as that of Example 1, except that no antioxidant-lubricating integrated auxiliary agent is added, and the antioxidant-lubricating integrated auxiliary agent is changed to a 26-type vinylidene fluoride / hexafluoropropylene binary copolymer to verify the effect of the antioxidant-lubricating integrated auxiliary agent after the fluorine-containing lubricant is grafted with an antioxidant on improving the scorch resistance of the semi-conductive shielding material compared with the fluorine-containing lubricant without the grafted antioxidant.

[0041] Comparative Example 3 This comparative example 3 provides a high-voltage submarine cable semi-conductive shielding material. The preparation process of the semi-conductive shielding material of this comparative example 3 is basically the same as that of Example 1, except that no antioxidant-lubricating integrated auxiliary agent is added, and the antioxidant-lubricating integrated auxiliary agent is replaced with 2 parts of polyethylene wax, wherein polyethylene wax is a conventional external lubricant, in order to verify the effect of the patented antioxidant-lubricating integrated auxiliary agent on improving the scorch resistance of the semi-conductive shielding material compared with conventional external lubricants.

[0042] Comparative Example 4 This comparative example 4 provides a high-voltage submarine cable semi-conductive shielding material. The preparation process of the semi-conductive shielding material of this comparative example 3 is basically the same as that of Example 1, except that no antioxidant-lubricating integrated auxiliary agent is added, and the antioxidant-lubricating integrated auxiliary agent is changed to 2 parts of zinc stearate, wherein zinc stearate is a conventional external lubricant, in order to verify the effect of the patented antioxidant-lubricating integrated auxiliary agent on improving the scorch resistance of the semi-conductive shielding material compared with conventional external lubricants.

[0043] Comparative Example 5 This comparative example 5 provides a semi-conductive shielding material for a high-voltage submarine cable. The preparation process of the semi-conductive shielding material of this comparative example 5 is basically the same as that of Example 1, except that no antioxidant-lubricating integrated auxiliary agent is added, and the antioxidant-lubricating integrated auxiliary agent is changed to a blend of 1.9 parts of 26-type vinylidene fluoride / hexafluoropropylene binary copolymer and 0.1 parts of antioxidant to verify the advantages of the grafting method over the blending method and the selective distribution of the antioxidant.

[0044] Comparative Example 6 This comparative example 6 provides a high-voltage submarine cable semi-conductive shielding material. The preparation process of the semi-conductive shielding material of this comparative example 6 is basically the same as that of Example 1, except that an antioxidant-lubricating integrated auxiliary agent is added, and the antioxidant-lubricating integrated auxiliary agent is changed to an additional 0.5 parts of antioxidant to verify the effect of simply increasing the amount of antioxidant.

[0045] Test Case This test example is used to perform performance tests on the semi-conductive shielding materials obtained in Examples 1-5 and Comparative Examples 1-6. The semi-conductive shielding materials obtained in Examples 1-5 and Comparative Examples 1-6 are heat-treated at 180°C and 15 MPa for 15 minutes to fully cross-link them and form sheets. The scorch resistance, surface smoothness, and gel content of the sheets are tested.

[0046] The scorch resistance was evaluated using an internal mixer, and the time required to reach the equilibrium torque was defined as the scorch time.

[0047] The gel content test method is: soak in xylene at 130°C for 24 hours and calculate the remaining solid mass percentage.

[0048] Simulate the cable extrusion process, through the single screw extrusion test, set the temperature to 120℃, the speed to 15 rpm, obtain the strip material, and record the processing temperature rise. Use an optical microscope to observe the surface finish of the strip material, select 1m 2 In the test area, the number of defects with a height exceeding 50µm was counted, which appeared as convexities or concavities. The test results are shown in Table 1: Table 1 Performance test of semi-conductive shielding materials Test items Scorch time (s) Balance torque (N•m) Processing temperature rise (℃) <![CDATA[Number of surface defects (pcs / m 2 )]]> Gel content (%) Example 1 491 20.6 15.2 3 88.4 Example 2 651 17.5 12.4 0 87.3 Example 3 668 17.1 11.7 0 87.9 Example 4 524 20.2 13.7 4 89.1 Example 5 352 22.5 17.8 13 81.3 Comparative Example 1 327 24.6 21.5 18 89.5 Comparative Example 2 398 22.4 16.3 9 87.4 Comparative Example 3 342 23.7 18.4 14 86.9 Comparative Example 4 351 23.5 18.1 13 87.2 Comparative Example 5 466 21.2 15.8 7 78.5 Comparative Example 6 573 18.5 15.8 5 46.1 As can be seen in Table 1, the overall performance of the semiconductive shielding materials prepared in Examples 1-5 is excellent. Compared with Comparative Examples 1-6, Examples 1-5 show significant improvements in scorch time, processing temperature rise, and surface finish, fully demonstrating the significant role of the integrated antioxidant-lubricant in improving the scorch resistance of semiconductive shielding materials. Example 2 exhibits even better scorch resistance than Comparative Example 2, indicating that the fluorinated lubricant grafted with an antioxidant has a stronger effect in improving the scorch resistance of the material than the fluorinated lubricant without the grafted antioxidant. This result is attributed to the enrichment effect of the grafted antioxidant in the high-risk area, which captures free radicals in time and significantly inhibits the occurrence of the pre-crosslinking reaction. At the same time, the gel content of Examples 1-5 and Comparative Examples 1-4 is comparable, verifying that the present invention improves the scorch resistance while ensuring the final crosslinking efficiency of the material. Comparative Example 5 affects the crosslinking effect due to its blending method, resulting in a decrease in gel content. Comparative Example 6 adds an antioxidant to improve the scorch resistance, but seriously affects the crosslinking effect, resulting in a significant decrease in gel content, and cannot meet the technical requirements of this application.

[0049] In the comparison between the examples, Example 2 has a greater improvement compared with Example 1, indicating that a higher dosage of the antioxidant-lubricating integrated additive can exert a stronger functional effect, but the improvement of Example 3 is smaller than that of Example 2. This may be because the use of the additive has been close to saturation, and considering that too high an additive dosage will have a certain negative impact on the electrical, mechanical and other properties of the shielding material, therefore, taking all factors into consideration, using 2 parts of the antioxidant-lubricating integrated additive is the optimal solution.

[0050] In terms of grafting rate, Example 2 is better than Examples 4 and 5, indicating that a grafting rate of 5% is preferred. A grafting rate that is too low limits the function of the antioxidant, while a grafting rate that is too high inhibits the rapid migration of the lubricant, making it difficult to enrich the antioxidant and affecting the lubrication performance.

[0051] Furthermore, Comparative Examples 2-4 outperform Comparative Example 1, demonstrating that lubricants contribute to a certain degree of scorch resistance in semiconductive shielding materials. On the one hand, lubricants reduce the processing temperature, thereby inhibiting the extent of the pre-crosslinking reaction; on the other hand, lubricants reduce the adhesion and retention of the material melt on the equipment surface, reducing the duration of the pre-crosslinking reaction. Comparative Example 2 outperforms Comparative Examples 3 and 4, demonstrating that fluoropolymer lubricants offer superior lubrication compared to conventional lubricants such as polyethylene wax and zinc stearate, primarily due to their ultra-low surface energy properties.

[0052] Example 2 significantly outperformed Comparative Example 5, demonstrating that the integrated antioxidant-lubricant additive offers superior performance compared to simple blending. This additive achieves targeted enrichment of the antioxidant, significantly improving free radical capture efficiency and thus effectively reducing the risk of scorch. Comparative Example 6 also exhibited superior scorch resistance to Comparative Example 1, demonstrating that while adding an antioxidant alone can improve scorch resistance, it inevitably sacrifices ultimate crosslinking efficiency.

[0053] Please refer to Figure 3-5 , Figure 3 The free radical grafting reaction successfully grafted the antioxidant onto the fluoropolymer lubricant. The Fourier infrared results showed that compared with the fluoropolymer lubricant (246-FPI) molecule, the purified antioxidant-lubricant integrated additive (AO3052@246-FPI) molecule showed the characteristic peaks of the phenolic hydroxyl group (–OH) and ester carbonyl group (C=O) of the antioxidant (AO3052) molecule. This change clearly shows that the antioxidant has been successfully grafted onto the lubricant molecular chain. In addition, Figure 4 The oxidation induction time was significantly increased from 0.8 min for the fluoropolymer lubricant (246-FPI) to 29.4 min for the grafted product, further verifying the antioxidant properties of the antioxidant-lubricant integrated additive and also indirectly confirming the effectiveness of the grafting reaction. Figure 5 In the experiment, the contact angle of the fluoropolymer lubricant (246-FPI), an integrated antioxidant-lubricant, decreased slightly from 114.8° to 106.7°, and the surface properties did not change significantly, which verified that the grafting reaction had little effect on the original lubricating function of the fluoropolymer lubricant, and the integrated antioxidant-lubricant functional additive still had a strong lubricating function.

[0054] The embodiments described above are some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

Claims

1. A semi-conductive shielding material for a high-voltage submarine cable, characterized in that: The raw materials include, by mass, 65-75 parts of base resin, 25-35 parts of conductive carbon black, 0.5-3 parts of antioxidant-lubricant integrated additive, 0.5-1.5 parts of crosslinking agent and 0.2-0.5 parts of antioxidant; The antioxidant-lubricating integrated auxiliary agent is obtained by grafting an antioxidant containing a carbon-carbon double bond onto a fluorine-containing polymer lubricant, with a grafting rate of 2%-10%.

2. The semiconductive shielding material according to claim 1, characterized in that: The raw materials of the integrated antioxidant-lubricating additive include a fluoropolymer lubricant, an oxidant containing a carbon-carbon double bond, and an initiator. The mass ratio of the fluoropolymer lubricant to the oxidant containing a carbon-carbon double bond is 100:2-10; the mass ratio of the fluoropolymer lubricant to the initiator is 100:0.4-0.

8.

3. The semiconductive shielding material according to claim 2, characterized in that: The fluorine-containing polymer lubricant includes one or more of a 26-type vinylidene fluoride / hexafluoropropylene binary copolymer and a 246-type vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene terpolymer.

4. The semiconductive shielding material according to claim 2, characterized in that: The antioxidant containing a carbon-carbon double bond includes one or more of 2-(2-hydroxy-3-tert-butyl-5-methylbenzyl)-4-methyl-6-tert-butylphenyl acrylate, N-(4-anilinophenyl)maleimide, and 3-[(4-anilinophenyl)amino]-2-hydroxypropyl methacrylate.

5. The semiconductive shielding material according to claim 2, characterized in that: The initiator is dicumyl peroxide.

6. The semiconductive shielding material according to claim 1, characterized in that: The base resin includes one or more of ethylene-butyl acrylate copolymer and ethylene-ethyl acrylate copolymer.

7. The semiconductive shielding material according to claim 1, characterized in that: The conductive carbon black has an oil absorption value of 120 ml / 100g to 200 ml / 100g and an ash content of less than 0.2%.

8. The semiconductive shielding material according to claim 1, characterized in that: The antioxidant includes one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate and 4,4'-thiobis(6-tert-butyl-3-methylphenol); the crosslinking agent includes one or more of dicumyl peroxide and di-tert-butylperoxyisopropylbenzene.

9. A method for preparing a semiconductive shielding material according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1. The base resin, conductive carbon black, antioxidant - lubricating integrated additive and antioxidant are mixed to obtain a mixture; S2. The mixture was melt-kneaded at a mixing temperature of 120°C-160°C and a speed of 100rpm-150rpm, and sheared and granulated to obtain pellets; S3. Preheat the pellets at 50°C-80°C for 2h-4h, add a crosslinking agent, and mix them by liquid phase impregnation adsorption to obtain a semiconductive shielding material.

10. The preparation method according to claim 9, characterized in that The preparation method of the antioxidant-lubricating integrated additive in S1 comprises the following steps: I. melt-mixing the fluoropolymer lubricant and the antioxidant containing a carbon-carbon double bond to obtain a mixture A; II. The mixture A and the initiator are mixed and reacted at 150 ℃-200 ℃ for 20min-40min to obtain a reaction product; III. The reaction product is extracted and purified by ethanol at 70°C-90°C for 10h-15h to remove unreacted antioxidant, initiator and initiator decomposition byproducts, and dried at 50°C-70°C for 10h-15h to completely evaporate the ethanol to obtain an antioxidant-lubricating integrated additive.

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