High-voltage submarine cable semi-conductive shielding material and preparation method thereof

Abstract

The application relates to the technical field of cable materials, and discloses a high-voltage submarine cable semiconductive shielding material and a preparation method thereof, which comprises 65-75 parts of a base resin, 25-35 parts of conductive carbon black, 0.5-3 parts of an antioxidant-lubricant integrated additive, 0.5-1.5 parts of a crosslinking agent and 0.2-0.5 parts of an antioxidant. The antioxidant-lubricant integrated additive is obtained by grafting an antioxidant containing a carbon-carbon double bond to a fluoropolymer lubricant, and the grafting rate is 2%-10%. The antioxidant-lubricant integrated additive can inhibit the pre-crosslinking of the base molecular chain, the directional enrichment of the antioxidant improves the free radical capture efficiency, meanwhile, the high-temperature crosslinking efficiency is not affected by the excessive antioxidant amount, in addition, the lubricating unit effectively reduces the friction coefficient of the melt and the surface of the equipment, reduces the shear heat generation, helps to balance the cavity temperature distribution, simultaneously shortens the residence probability and time of the melt on the surface of the equipment, and significantly improves the scorch resistance.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of cable materials, in particular to a high-voltage submarine cable semi-conductive shielding material and a preparation method. BACKGROUND

[0002] As indispensable power equipment for cross-sea power transmission projects, high-voltage submarine cables are the key 'lifeline' for connecting power supply on both sides of the sea, and are widely used in offshore wind farm access, island power grid interconnection and offshore drilling platform projects. Compared with high-voltage land cables, high-voltage submarine cables are usually more than 20 km long due to the complex operating environment, high laying and operation and maintenance costs, and need to be continuously extruded for more than 15 days. During this process, the shielding material melt is easily affected by factors such as long-term local temperature rise and stagnation accumulation, which can cause the crosslinking agent to decompose prematurely, leading to the formation of gel and increasing the risk of scorching. This not only changes the rheological properties of the melt, increases the instability of the extrusion process, causes unevenness in the cable shielding layer and surface defects, and even causes the production to be interrupted due to gel blocking the extrusion filter. Therefore, high-voltage submarine cable shielding materials not only need to meet basic performance requirements such as electrical, mechanical and surface smoothness, but also need to have excellent scorching resistance during long-time continuous extrusion.

[0003] The scorching resistance of the shielding material refers to the ability to inhibit the formation of gel during the melting and extrusion process, and is an important indicator for evaluating its long-time continuous extrusion process. High-voltage cable materials usually use peroxide such as dicumyl peroxide as a crosslinking agent, and its initial decomposition temperature is 120 DEG C, which is exactly in the material extrusion processing temperature range of 120-130 DEG C. In addition to the anti-oxidation function, antioxidants in the formula system can also capture free radicals and have certain scorching resistance. However, the conventional method of simply increasing the amount of antioxidants or reducing the amount of crosslinking agent can reduce the concentration of free radicals during the extrusion process and inhibit the pre-crosslinking behavior, but this method inevitably sacrifices the crosslinking density during the subsequent high-temperature crosslinking process, resulting in insufficient mechanical properties and heat resistance of the material. Therefore, the contradiction between scorching resistance and crosslinking efficiency makes it difficult to develop a scorching-resistant shielding material. Therefore, it is necessary to provide a scorching-resistant high-voltage submarine cable shielding material and a preparation method without reducing the crosslinking efficiency. SUMMARY

[0004] The purpose of the present application is to provide a high-voltage submarine cable semi-conductive shielding material, which can inhibit the pre-crosslinking of the base molecular chain through the use of an antioxidant-lubricating integrated additive, avoid the influence of excessive antioxidant dosage on the high-temperature crosslinking efficiency, and significantly improve the scorching resistance.

[0005] Another object of the present application is to provide a preparation method of a high-voltage submarine cable semi-conductive shielding material, an anti-oxidation-lubrication integrated additive is prepared through a free radical grafting reaction, and the anti-oxidation-lubrication molecular diffusion behavior under a processing external field is regulated to make the anti-oxidation-lubrication molecules be distributed in a risk area of material melt scorching and form a dynamic super-lubricating molecular layer quickly, and a synergistic scorching resistance mechanism of "fast migration-dynamic external lubrication-precise capture of free radicals" is formed.

[0006] The technical scheme adopted by the present application is:

[0007] In one aspect, the present application provides a high-voltage submarine cable semi-conductive shielding material, raw materials include 65-75 parts by mass of a base resin, 25-35 parts by mass of conductive carbon black, 0.5-3 parts by mass of an anti-oxidation-lubrication integrated additive, 0.5-1.5 parts by mass of a crosslinking agent, and 0.2-0.5 parts by mass of an antioxidant, the anti-oxidation-lubrication integrated additive is obtained by grafting an antioxidant containing a carbon-carbon double bond to a fluoropolymer lubricant, and the grafting rate is 2%-10%.

[0008] Further, the raw materials of the anti-oxidation-lubrication integrated additive include the fluoropolymer lubricant, the antioxidant containing a carbon-carbon double bond, and the initiator, the raw materials of the anti-oxidation-lubrication integrated additive include the fluoropolymer lubricant, the antioxidant containing a carbon-carbon double bond, and the initiator, the fluoropolymer lubricant and the antioxidant containing a carbon-carbon double bond are in a mass ratio of 100:2-10; the fluoropolymer lubricant and the initiator are in a mass ratio of 100:0.4-0.8.

[0009] Further, the fluoropolymer lubricant includes one or more of a 26 type vinylidene fluoride / hexafluoropropylene binary copolymer and a 246 type vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene ternary copolymer.

[0010] Further, 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-butyl phenyl acrylate, N-(4-anilino phenyl) maleimide, and 3-[(4-anilino phenyl) amino]-2-hydroxy propyl methacrylate.

[0011] Further, the initiator is dicumyl peroxide.

[0012] Further, the base resin includes one or more of an ethylene-butyl acrylate copolymer and an ethylene-ethyl acrylate copolymer.

[0013] Further, the conductive carbon black has a carbon black oil absorption value of 120 ml / 100g-200 ml / 100g and an ash content of <0.2%.

[0014] Further, the antioxidant includes one or more of tetrakis[β-(3,5-di-tert-butyl-4- hydroxyphenyl)propionate]pentaerythritol ester and 4,4'-thiobis(6-tert-butyl-3-methylphenol); and the crosslinking agent includes one or more of dicumyl peroxide and di-tert-butyl peroxide isopropyl benzene.

[0015] In another aspect, the application provides a method for preparing a semi-conductive shielding material for high-voltage submarine cables, comprising the following steps: S1. mixing a base resin, conductive carbon black, an antioxidant-lubricant integrated additive, and an antioxidant to obtain a mixture; S2. melt-kneading the mixture at a temperature of 120-160°C and a rotation speed of 100-150 rpm to obtain granules by shearing and granulation; and S3. preheating the granules at 50-80°C for 2-4 hours, adding a crosslinking agent, and mixing by liquid-phase immersion adsorption to obtain the semi-conductive shielding material.

[0016] Further, the method for preparing the antioxidant-lubricant integrated additive in S1 comprises the following steps: I. melt-mixing a fluorine-containing polymer lubricant and an antioxidant containing a carbon-carbon double bond to obtain a mixture A; II. mixing the mixture A and an initiator, and reacting at 150-200°C for 20-40 minutes to obtain a reaction product; III. extracting and purifying the reaction product at 70-90°C for 10-15 hours using ethanol to remove unreacted antioxidant, initiator, and initiator decomposition by-products, and drying at 50-70°C for 10-15 hours to completely volatilize the ethanol to obtain the antioxidant-lubricant integrated additive.

[0017] Further, the initiator decomposition by-products in step III include acetophenone and cumyl alcohol.

[0018] Compared with the prior art, the embodiments of the application have at least the following advantages or beneficial effects:

[0019] 1. The antioxidant-lubricant integrated additive significantly prolongs the scorch time of the semi-conductive shielding material.

[0020] 2. The problem of reducing the crosslinking density of the material in the subsequent high-temperature crosslinking process by simply increasing the amount of antioxidant or reducing the amount of crosslinking agent is avoided, and the balance between scorch resistance and crosslinking efficiency is achieved.

[0021] 3. In the processing process, the fluorine-containing additive quickly migrates to the surface of the cylinder and screw due to its low molecular weight and low surface energy, forms a stable and uniform lubricating protective film, effectively reduces the friction coefficient between the melt and the metal surface, reduces shear heat generation, helps to balance the temperature distribution in the cavity, and at the same time shortens the probability and time of melt retention on the surface of the equipment, avoiding the intensification of pre-crosslinking due to local overheating and long retention.

[0022] 4. Ensure that the antioxidant can be released accurately at the key high temperature point, quickly capture the free radicals generated during the processing process, inhibit the high temperature induced pre-crosslinking reaction, form an efficient scorch protection mechanism, and avoid the introduction of excessive antioxidants affecting the vulcanization crosslinking efficiency. Form a synergistic scorch resistance mechanism of "fast migration-dynamic external lubrication-precise capture of free radicals".

[0023] 5. The semi-conductive shielding material has more stable melt rheological properties during extrusion, the number of surface defects is greatly reduced, and the processing stability and surface smoothness are improved.

[0024] 6. The application is simple to operate, does not involve toxic reagents, and does not need to modify the existing industrial production process of semi-conductive shielding materials, and has good large-scale application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0026] Figure 1 The reaction process for preparing the antioxidant-lubricating integrated additive of the present application;

[0027] Figure 2 The preparation flowchart of the semi-conductive shielding material in the embodiments of the present application;

[0028] Figure 3 The Fourier infrared spectrum of the material before and after the grafting reaction in the embodiments of the present application;

[0029] Figure 4 The oxidation induction time diagram of the material before and after the grafting reaction in the embodiments of the present application;

[0030] Figure 5 The contact angle diagram of the material before and after the grafting reaction in the embodiments of the present application.

[0031] Note: FPI in the figure is a fluorine-containing polymer lubricant; 246-FPI is a 246 type of vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene terpolymer; AO3052 is 2-(2-hydroxy-3-tert-butyl-5-methylbenzyl)-4-methyl-6-tert-butyl phenyl acrylate; AO3052@246-FPI is the antioxidant-lubricating integrated additive obtained by grafting reaction; DCP is dicumyl peroxide. DETAILED DESCRIPTION

[0032] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. If specific conditions are not indicated in the embodiments, conventional conditions or manufacturer recommended conditions are adopted. If the manufacturers of the reagents or instruments are not indicated, they are all conventional products that can be purchased in the market.

[0033] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to specific embodiments.

[0034] Please refer to Figures 1-2 , Figure 1 The reaction process for preparing the anti-oxidation and lubrication integrated auxiliary agent of the present application, Figure 2 The preparation flowchart of the semi-conductive shielding material, based on the basic theoretical route of the present application, a preparation method of the semi-conductive shielding material of the high-voltage submarine cable is proposed, which comprises the following steps:

[0035] S1. 65-75 parts by mass of the base resin, 25-35 parts by mass of the conductive carbon black, 0.5-3 parts by mass of the anti-oxidation and lubrication integrated auxiliary agent and 0.2-0.5 parts by mass of the antioxidant are uniformly mixed to obtain a mixture, the base resin comprises one or more of ethylene-butyl acrylate copolymer and ethylene-ethyl acrylate copolymer, the carbon black oil absorption value of the conductive carbon black is 120 ml / 100g-200 ml / 100g, the ash content is <0.2%, the antioxidant comprises one or more of tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid]pentaerythritol ester and 4,4'-thiobis(6-tert-butyl-3-methylphenol), and the preparation method of the anti-oxidation and lubrication integrated auxiliary agent comprises the following steps:

[0036] I. The fluoropolymer lubricant and the carbon-carbon double bond-containing antioxidant are melt-mixed and grafted, and the grafting rate is 2%-10%, to obtain a mixture A, the mass ratio of the fluoropolymer lubricant and the carbon-carbon double bond-containing antioxidant is 100:2-10, the fluoropolymer lubricant comprises one or more of 26 type vinylidene fluoride / hexafluoropropylene binary copolymer and 246 type vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene ternary copolymer, and the carbon-carbon double bond-containing antioxidant comprises one or more of 2-(2-hydroxy-3-tert-butyl-5-methylbenzyl)-4-methyl-6-tert-butylphenyl acrylate, N-(4-anilino phenyl) maleimide and 3-[(4-anilino phenyl)amino]-2-hydroxypropyl methacrylate;

[0037] II. mixing mixture A and initiator, reacting at 150-200℃ for 20-40 min to obtain a reaction product, the initiator being dicumyl peroxide, the amount of initiator added being 100:0.4-0.8 in mass ratio of fluorine-containing polymer lubricant: initiator;

[0038] III. extracting and purifying the reaction product with ethanol at 70-90℃ for 10-15 h to remove unreacted antioxidant, initiator and initiator decomposition by-products, and drying at 50-70℃ for 10-15 h to volatilize ethanol to obtain an antioxidant-lubrication integrated additive.

[0039] S2. melt mixing the mixture, the mixing temperature being 120-160℃, the rotation speed being 100-150 rpm, and shearing and granulating to obtain granules;

[0040] S3. preheating the granules at 50-80℃ for 2-4 h, adding 0.5-1.5 parts of a crosslinking agent, and mixing by liquid phase immersion adsorption to obtain a semiconductive shielding material, the crosslinking agent including one or more of dicumyl peroxide and di-tert-butyl peroxide isopropyl benzene.

[0041] The features and performances of the present application are further described in detail below in combination with examples.

[0042] Example 1

[0043] The present example provides a semiconductive shielding material for high-voltage submarine cables.

[0044] Specifically, the semiconductive shielding material of the present example is applied in the field of high-voltage submarine cables, and the raw materials thereof include, in mass parts, 65 parts of a base resin, 35 parts of conductive carbon black, 1 part of an antioxidant-lubrication integrated additive, 0.5 parts of an antioxidant, and 1 part of a crosslinking agent, wherein the base resin is an ethylene-butyl acrylate copolymer resin with a butyl acrylate content of 18 wt%, a melt index of 7.0 g / min at 190℃ and 2.16 kg, and an elongation at break of 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 crosslinking agent is dicumyl peroxide.

[0045] The anti-oxidation and lubrication integrated additive raw material includes 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-butyl phenyl acrylate and 0.5 parts of diisopropylbenzene peroxide by mass fraction, the grafting rate is 5%, wherein the melting point of the 26 type vinylidene fluoride / hexafluoropropylene binary copolymer is 60℃, the melting point of the 2-(2-hydroxy-3-tert-butyl-5-methylbenzyl)-4-methyl-6-tert-butyl phenyl acrylate is 130℃, and the melting point of the diisopropylbenzene peroxide is 40℃.

[0046] The preparation process includes the following steps:

[0047] S1. 100 parts of 26 type vinylidene fluoride / hexafluoropropylene binary copolymer and 5 parts of 2-(2-hydroxy-3-tert-butyl-5-methylbenzyl)-4-methyl-6-tert-butyl phenyl acrylate are fully melt mixed at 135℃ to form a mixture;

[0048] S2. The mixture is cooled to 70℃, 0.5 parts of diisopropylbenzene peroxide is added as an initiator and fully mixed uniformly, the temperature is raised to 160℃, and the reaction is carried out for 30 min to obtain a reaction product;

[0049] S3. The reaction product is extracted with sufficient ethanol at 80℃ for 12 h to remove unreacted antioxidants, initiators and initiator decomposition by-products acetophenone and cumyl alcohol to obtain a purified product;

[0050] S4. The purified product is dried at 60℃ for 12 h to volatilize the residual ethanol to obtain a pure anti-oxidation and lubrication integrated additive;

[0051] S5. 65 parts of ethylene-butyl acrylate copolymer resin, 35 parts of conductive carbon black, 1 part of anti-oxidation and lubrication integrated additive, and 0.5 parts of 4,4'-thiobis(6-tert-butyl-3-methylphenol) are premixed to obtain a mixture A;

[0052] S6. The mixture A is melt mixed by a double screw at a mixing temperature of 120~160℃ and a rotating speed of 100~150 rmp to obtain a melt extruded material;

[0053] S7. The melt extruded material is sheared and granulated and dried to obtain a granular material;

[0054] S8. The granular material is preheated at 60℃ for 3 h, diisopropylbenzene peroxide is added, and the granular material and diisopropylbenzene peroxide are mixed by liquid phase immersion adsorption for 6 h to form a semi-conductive shielding material.

[0055] Example 2

[0056] This embodiment 2 provides a kind of high-voltage submarine cable semi-conductive shield material, and the semi-conductive shield material preparation process of this embodiment 2 is basically same with embodiment 1, different is that the antioxidant-lubricating integrated auxiliary agent is 2 parts, to verify the influence of the addition amount of antioxidant-lubricating integrated auxiliary agent on the performance of semi-conductive shield material.

[0057] Example 3

[0058] This embodiment 3 provides a kind of high-voltage submarine cable semi-conductive shield material, and the semi-conductive shield material preparation process of this embodiment 3 is basically same with embodiment 1, different is that the antioxidant-lubricating integrated auxiliary agent is 3 parts, to verify the influence of the addition amount of antioxidant-lubricating integrated auxiliary agent on the performance of semi-conductive shield material.

[0059] Example 4

[0060] This embodiment 4 provides a kind of high-voltage submarine cable semi-conductive shield material, and the semi-conductive shield material preparation process of this embodiment 4 is basically same with embodiment 1, different is that the grafting rate of antioxidant-lubricating integrated auxiliary agent is 2%, i.e. 100 parts of 26 type vinylidene fluoride / hexafluoropropylene binary copolymer, 2 parts of 2-(2-hydroxy-3-tert-butyl-5-methyl benzyl)-4-methyl-6-tert-butyl phenyl acrylate, to verify the influence of the grafting rate of antioxidant-lubricating integrated auxiliary agent on the performance of semi-conductive shield material.

[0061] Example 5

[0062] This embodiment 5 provides a kind of high-voltage submarine cable semi-conductive shield material, and the semi-conductive shield material preparation process of this embodiment 5 is basically same with embodiment 1, different is that the grafting rate of antioxidant-lubricating integrated auxiliary agent is 10%, i.e. 100 parts of 26 type vinylidene fluoride / hexafluoropropylene binary copolymer, 10 parts of 2-(2-hydroxy-3-tert-butyl-5-methyl benzyl)-4-methyl-6-tert-butyl phenyl acrylate, to verify the influence of the grafting rate of antioxidant-lubricating integrated auxiliary agent on the performance of semi-conductive shield material.

[0063] Comparative Example 1

[0064] This comparative example 1 provides a kind of high-voltage submarine cable semi-conductive shield material, and the semi-conductive shield material preparation process of this comparative example 1 is basically same with embodiment 1, different is that antioxidant-lubricating integrated auxiliary agent is not added, to verify the effect of adding antioxidant-lubricating integrated auxiliary agent on improving the anti-burning performance of semi-conductive shield material compared with not adding antioxidant-lubricating integrated auxiliary agent.

[0065] Comparative Example 2

[0066] The comparative example 2 provides a high-voltage submarine cable semi-conductive shielding material. The semi-conductive shielding material of the comparative example 2 has substantially the same preparation process as that of the example 1, except that the antioxidant-lubricant integrated additive is not added, and the antioxidant-lubricant integrated additive is replaced by a 26 type vinylidene fluoride / hexafluoropropylene binary copolymer, so as to verify the effect of the antioxidant-lubricant integrated additive on improving the anti-burning performance of the semi-conductive shielding material after the fluorine-containing lubricant is grafted with the antioxidant, compared with the fluorine-containing lubricant without grafting the antioxidant.

[0067] Comparative example 3

[0068] The comparative example 3 provides a high-voltage submarine cable semi-conductive shielding material. The semi-conductive shielding material of the comparative example 3 has substantially the same preparation process as that of the example 1, except that the antioxidant-lubricant integrated additive is not added, and the antioxidant-lubricant integrated additive is replaced by 2 parts of polyethylene wax, which is a conventional external lubricant, so as to verify the effect of the antioxidant-lubricant integrated additive on improving the anti-burning performance of the semi-conductive shielding material, compared with the conventional external lubricant.

[0069] Comparative example 4

[0070] The comparative example 4 provides a high-voltage submarine cable semi-conductive shielding material. The semi-conductive shielding material of the comparative example 3 has substantially the same preparation process as that of the example 1, except that the antioxidant-lubricant integrated additive is not added, and the antioxidant-lubricant integrated additive is replaced by 2 parts of zinc stearate, which is a conventional external lubricant, so as to verify the effect of the antioxidant-lubricant integrated additive on improving the anti-burning performance of the semi-conductive shielding material, compared with the conventional external lubricant.

[0071] Comparative example 5

[0072] The comparative example 5 provides a high-voltage submarine cable semi-conductive shielding material. The semi-conductive shielding material of the comparative example 5 has substantially the same preparation process as that of the example 1, except that the antioxidant-lubricant integrated additive is not added, and the antioxidant-lubricant integrated additive is replaced by a blend of 1.9 parts of a 26 type vinylidene fluoride / hexafluoropropylene binary copolymer and 0.1 parts of an antioxidant, so as to verify the advantages of the grafting method compared with the blending method and the selective distribution of the antioxidant.

[0073] Comparative example 6

[0074] The comparative example 6 provides a high-voltage submarine cable semi-conductive shielding material. The semi-conductive shielding material of the comparative example 6 has substantially the same preparation process as that of the example 1, except that the antioxidant-lubricant integrated additive is added, and the antioxidant-lubricant integrated additive is replaced by an additional 0.5 parts of an antioxidant, so as to verify the effect of the single increase of the amount of the antioxidant.

[0075] Test example

[0076] 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.

[0077] The scorch resistance was evaluated using an internal mixer, and the time required to reach the equilibrium torque was defined as the scorch time.

[0078] The gel content test method is: soak in xylene at 130°C for 24 hours and calculate the remaining solid mass percentage.

[0079] 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:

[0080] Table 1 Performance test of semi-conductive shielding materials

[0081] Test item Scorch time (s) Equilibrium torque (N-m) Processing temperature rise (°C) Number of surface defects (pieces / 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

[0082] 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.

[0083] In the comparison between the embodiments, Example 2 has greater improvement compared to Example 1, indicating that higher dosage of antioxidant-lubricant integrated additive can play a stronger functional effect, but Example 3 has smaller improvement compared to Example 2, which may be due to the fact that the additive usage is close to saturation, and considering that too high dosage of additive may have certain negative impact on the electrical and mechanical properties of the shielding material, therefore, taking into account comprehensively, using 2 parts of antioxidant-lubricant integrated additive is the optimal solution.

[0084] In terms of grafting rate, Example 2 is better than Examples 4 and 5, indicating that 5% grafting rate is preferred, and too low grafting rate limits the function of antioxidants, and too high grafting rate inhibits the rapid migration of lubricants, making it difficult for antioxidants to enrich, and the lubrication performance is also affected.

[0085] In addition, Comparative Examples 2-4 are better than Comparative Example 1, indicating that lubricants also help to improve the scorch resistance of semi-conductive shielding materials to some extent. On the one hand, lubricants can reduce the processing temperature rise, thereby inhibiting the degree of pre-crosslinking reaction; on the other hand, lubricants can weaken the adhesion and retention effect of the material melt on the surface of the equipment, reducing the time for pre-crosslinking reaction to occur. Comparative Example 2 is better than Comparative Examples 3 and 4, verifying that fluoropolymer lubricants have better lubrication effect than conventional lubricants such as polyethylene wax and zinc stearate, which is mainly due to their ultra-low surface energy characteristics.

[0086] Example 2 is significantly better than Comparative Example 5, indicating that antioxidant-lubricant integrated additive has better effect compared to simple blending method. The additive realizes the directional enrichment of antioxidants, significantly improves the free radical capture efficiency, thereby effectively reducing the scorching risk. The scorch resistance of Comparative Example 6 is better than that of Comparative Example 1, verifying that increasing antioxidants alone can indeed improve the scorch resistance, but at the same time, the final crosslinking efficiency will inevitably be sacrificed.

[0087] Please refer to Figures 3-5 , Figure 3 It is confirmed that the free radical grafting reaction successfully grafts antioxidants onto the fluoropolymer lubricant, and the Fourier infrared results show that, compared with the molecules of the fluoropolymer lubricant (246-FPI), the phenolic hydroxyl group (-OH) and ester carbonyl group (C=O) characteristic peaks of the antioxidant (AO3052) molecules appear in the purified antioxidant-lubricant integrated additive (AO3052@246-FPI) molecules, which clearly indicates that the antioxidants have been successfully grafted onto the molecular chain of the lubricant. In addition, Figure 4 In Example 2, the oxidation induction time is significantly improved from 0.8 min of the fluoropolymer lubricant (246-FPI) to 29.4 min of the grafted product, further verifying the antioxidant performance of the antioxidant-lubricant integrated additive, and also indirectly confirming the effectiveness of the grafting reaction. In addition, Figure 5In the middle, the contact angle of the antioxidant-lubrication integrated functional additive containing fluoropolymer lubricant (246-FPI) slightly decreased from only 114.8° to 106.7°, and the surface properties did not change greatly, verifying that the grafting reaction has little effect on the original lubricating function of the fluoropolymer lubricant, and the antioxidant-lubrication integrated functional additive still has strong lubricating function.

[0088] The above-described embodiments are part of the embodiments of the present application, but not all the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the claimed application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

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 additive is obtained by grafting an antioxidant containing a carbon-carbon double bond onto a fluoropolymer lubricant, with a grafting rate of 2%-10%; 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; the antioxidant containing a carbon-carbon double bond is 2-(2-hydroxy-3-tert-butyl-5-methylbenzyl)-4-methyl-6-tert-butylphenyl acrylate; and the base resin includes one or more of an ethylene-butyl acrylate copolymer and an ethylene-ethyl acrylate copolymer.

2. The semiconductive shielding material according to claim 1, characterized in that: The raw materials of the integrated antioxidant-lubricating auxiliary agent 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 initiator is dicumyl peroxide.

4. 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%.

5. 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.

6. A method for preparing a semiconductive shielding material according to any one of claims 1 to 5, 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.

7. The preparation method according to claim 6, 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 antioxidants, initiators, and initiator decomposition byproducts containing carbon-carbon double bonds, 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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