Antioxidant high strength crosslinked polyethylene cable and method of making same

Abstract

The application belongs to the technical field of crosslinked polyethylene cables, in particular to an antioxidant high-strength crosslinked polyethylene cable and a preparation method thereof. The structure of the antioxidant high-strength crosslinked polyethylene cable from inside to outside is successively a conductor, a shielding layer, an insulation layer, a water-blocking tape and a protective layer. The conductor material is copper or aluminum alloy. The shielding layer material is one of aluminum foil, copper foil, braided copper mesh or conductive plastic. The insulation layer is modified crosslinked polyethylene. The protective layer is high-density polyethylene. The antioxidant high-strength crosslinked polyethylene cable prepared by the application has excellent antioxidant performance. By modifying the crosslinked polyethylene of the insulation layer material, the antioxidant performance and mechanical performance of the crosslinked polyethylene are improved, and the overall performance of the cable is improved.

Description

Technical Field

[0001] This invention belongs to the field of cross-linked polyethylene cable technology, specifically relating to antioxidant high-strength cross-linked polyethylene cables and their preparation methods. Background Technology

[0002] High-voltage direct current (HVDC) transmission has advantages such as low loss and low cost, and is widely used in long-distance power transmission. HVDC transmission uses high-voltage cables, whose structure mainly includes a conductor, insulation layer, shielding layer, and protective layer. Currently, cross-linked polyethylene (XLPE) is one of the main materials for the insulation layer of high-voltage cables. XLPE is produced by cross-linking polyethylene molecules together using a cross-linking agent. After cross-linking treatment, the heat resistance of polyethylene molecules is significantly improved, increasing the long-term operating temperature to over 90℃. Due to the cross-linked network structure between the molecular chains, its mechanical properties are improved, especially in terms of hardness, abrasion resistance, and dimensional stability. However, during the use of high-voltage cables, the thermal effect of the current inevitably causes oxidation, leading to a decrease in the insulation and mechanical properties of the cable over long-term operation.

[0003] Currently, the main research directions for improving the properties of cross-linked polyethylene are to improve its insulation properties, mechanical properties, and antioxidant properties.

[0004] The main methods to improve the antioxidant properties of cross-linked polyethylene include adding antioxidants. However, antioxidants have poor compatibility with the matrix and are prone to migration or precipitation during use, resulting in a decrease in both the antioxidant and mechanical properties of cross-linked polyethylene.

[0005] To address the aforementioned problems, this invention proposes an antioxidant high-strength cross-linked polyethylene cable and its preparation method, aiming to improve the antioxidant properties of cross-linked polyethylene while increasing the strength of the material and extending its service life. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides an antioxidant high-strength cross-linked polyethylene cable and its preparation method. The method involves forming a cross-linked structure between the hindered phenolic structure with antioxidant properties and the cross-linked polyethylene, which avoids easy migration or precipitation during use and improves the mechanical properties of the cross-linked polyethylene.

[0007] To solve the above technical problems, the present invention adopts the following technical solution:

[0008] One of the objectives of this invention is to provide an antioxidant high-strength cross-linked polyethylene cable, wherein the structure of the antioxidant high-strength cross-linked polyethylene cable, from the inside out, consists of a conductor, a shielding layer, an insulation layer, a water-blocking strip, and a protective layer.

[0009] Preferably, the conductor material is copper or aluminum alloy.

[0010] Preferably, the shielding layer material is one of aluminum foil, copper foil, woven copper mesh, or conductive plastic.

[0011] Preferably, the insulating layer is modified cross-linked polyethylene.

[0012] Preferably, the protective layer is high-density polyethylene.

[0013] Preferably, the method for preparing the modified cross-linked polyethylene includes the following steps:

[0014] S1, Preparation of intermediates

[0015] 2,6-Di-tert-butyl-p-cresol and sodium ethoxide catalyst were added to a reaction vessel, heated to 110-120°C and kept at that temperature for 60-80 min. Allylamine was then added dropwise and the reaction was kept at that temperature for another 4-5 h. After the reaction was completed, the mixture was cooled to 50-60°C and diluted with toluene. The organic layer was washed with water 2-3 times, allowed to stand for separation, and then the toluene was recovered by vacuum distillation. The intermediate was obtained by fractional distillation.

[0016] 2,6-Di-tert-butyl-p-cresol has a hindered phenolic structure, and allylamine is highly reactive. Under the action of a catalyst, the hydrogens at C3 and C5 on the benzene ring of 2,6-di-tert-butyl-p-cresol become more reactive and undergo an addition reaction with allylamine, modifying the benzene ring with an amine group to obtain an intermediate containing a diamine and a hindered phenolic structure.

[0017] Preferably, the molar ratio of 2,6-di-tert-butyl-p-cresol to allylamine is 1:1.9 to 2.2.

[0018] Preferably, the amount of sodium ethoxide added is 2 to 5% of the mass of 2,6-di-tert-butyl-p-cresol.

[0019] Preferably, the dropping rate of the allylamine is 20-30 ml / min.

[0020] S2, Preparation of Composite Antioxidants

[0021] Maleic anhydride, DMF, and toluene were added to a reaction vessel and stirred for 10–20 min. A toluene solution of the intermediate was added dropwise under ice bath conditions. After the addition was complete, the reaction was carried out at 45–55 °C for 2–3 h under nitrogen protection. After the reaction was completed, the mixture was cooled to room temperature to generate bismaleimide acid containing a hindered phenolic structure. Then, p-toluenesulfonic acid was added to the system, and the mixture was heated to boiling using azeotropic distillation. Water was separated until no more water flowed out. The temperature was raised to 125–135 °C to distill off the toluene. Deionized water was added to precipitate the product. The product was washed sequentially with acetone and deionized water, and then dried under vacuum to obtain bismaleimide containing a hindered phenolic structure, i.e., a composite antioxidant.

[0022] Preferably, the mass ratio of maleic anhydride to intermediate is 1:1.2 to 1.5.

[0023] Preferably, the mass ratio of maleic anhydride, DMF and toluene is 1:20-30:20-30.

[0024] Preferably, the temperature of the ice bath is 0–10°C.

[0025] Preferably, the toluene solution of the intermediate is dropped at a rate of 20–40 ml / min.

[0026] Preferably, the mass fraction of the intermediate in the toluene solution is 5-10%.

[0027] Preferably, the amount of p-toluenesulfonic acid added is 5-6% of the amount of maleic anhydride added.

[0028] Preferably, the vacuum drying temperature is 80-90°C and the time is 8-12 hours.

[0029] The intermediate contains a diamine structure and a hindered phenolic structure. The diamine in the intermediate reacts with maleic anhydride to form maleimide acid, which further undergoes a cyclization reaction under the action of p-toluenesulfonic acid to obtain a maleimide ring. Therefore, the final product is a bismaleimide containing a hindered phenolic structure, i.e., a composite antioxidant. The bismaleimide structure in the composite antioxidant contains two carbon-carbon double bonds, which can play a cross-linking role, avoiding the influence of simple grafting or blending on the degree of cross-linking of cross-linked polyethylene, and further affecting its mechanical properties. Furthermore, the carbonyl group in the bismaleimide structure can improve the electrical properties of cross-linked polyethylene, enhancing its insulation performance. The hindered phenolic structure in the composite antioxidant can capture oxygen-containing free radicals and carbon free radicals generated during polymer aging, improving the material's antioxidant properties.

[0030] S3. Preparation of modified cross-linked polyethylene

[0031] Low-density polyethylene and composite antioxidants are mixed at 195-205℃ for 4-7 minutes, and then DCP (diisopropylbenzene peroxide) is added at 100-110℃ and mixed for another 2-4 minutes. The mixing speed is 50-80 rpm to obtain the mixture.

[0032] The mixture is extruded through a twin-screw extruder, granulated, and dried to obtain modified cross-linked polyethylene.

[0033] Preferably, the low-density polyethylene is 100-110 parts by weight, the composite antioxidant is 0.15-0.3 parts, and the DCP is 0.8-1.2 parts.

[0034] During the mixing process, because the composite antioxidant has a high melting point, a two-stage mixing process is adopted. The low-density polyethylene and the composite antioxidant are first mixed at high temperature, and then the temperature is lowered and DCP is added to continue mixing.

[0035] During the crosslinking process, DCP decomposes to generate free radicals. The bismaleimide structure in the composite antioxidant contains two double bonds. The double bonds open and form a crosslinking structure with the polymer free radicals. Crosslinking bonds are also formed between the two polymer free radicals. The composite antioxidant and crosslinked polyethylene form a crosslinking structure in the form of chemical bonds, which is more stable and less prone to migration and loss in subsequent processes. The antioxidant performance is more durable and the service life is extended.

[0036] The second objective of this invention is to provide a method for preparing an antioxidant high-strength cross-linked polyethylene cable. The method comprises: coating a shielding material onto a conductor material to form a shielding layer; then coating the shielding layer with cross-linked polyethylene to form an insulation layer; coating the insulation layer with a water-blocking tape; and finally coating the water-blocking tape with high-density polyethylene to form a protective layer, thereby obtaining an antioxidant high-strength cross-linked polyethylene cable.

[0037] By adopting the above technical solution, the technical effect achieved by this invention is as follows:

[0038] 1. The antioxidant high-strength cross-linked polyethylene cable prepared by this invention has excellent antioxidant properties. By modifying the cross-linked polyethylene insulation material, the antioxidant and mechanical properties of the cross-linked polyethylene are improved, thereby improving the overall performance of the cable.

[0039] 2. This invention prepares a composite antioxidant containing hindered phenolic structures and carbon-carbon double bonds. The two carbon-carbon double bonds enable the addition of the composite antioxidant to achieve cross-linking, avoiding the impact of simple grafting or blending on the degree of cross-linking of cross-linked polyethylene, which would further affect its mechanical properties. The bond between the composite antioxidant and cross-linked polyethylene is more stable and less prone to migration and loss in subsequent processes, thus avoiding any impact on the antioxidant and mechanical properties of cross-linked polyethylene. Detailed Implementation

[0040] The present invention will be further illustrated below with reference to specific embodiments.

[0041] Example 1: Antioxidant High-Strength Cross-linked Polyethylene Cable and its Preparation Method

[0042] An antioxidant high-strength cross-linked polyethylene cable, wherein the structure of the antioxidant high-strength cross-linked polyethylene cable, from the inside out, consists of a conductor, a shielding layer, an insulation layer, a water-blocking strip, and a protective layer.

[0043] The conductor material is copper.

[0044] The shielding layer material is woven copper mesh.

[0045] The insulating layer is modified cross-linked polyethylene.

[0046] The protective layer is made of high-density polyethylene.

[0047] The preparation method of the modified cross-linked polyethylene includes the following steps:

[0048] S1, Preparation of intermediates

[0049] 2,6-Di-tert-butyl-p-cresol and sodium ethoxide catalyst were added to a reaction vessel, heated to 115°C and kept at that temperature for 70 min. Allylamine was then added dropwise and the reaction was kept at that temperature for another 4 h. After the reaction was completed, the mixture was cooled to 55°C and diluted with toluene. The organic layer was washed three times with water, allowed to stand and separate into layers, and then the toluene was recovered by vacuum distillation. The intermediate was obtained by fractional distillation.

[0050] The molar ratio of 2,6-di-tert-butyl-p-cresol to allylamine is 1:2.1.

[0051] The amount of sodium ethoxide added is 3.5% of the mass of 2,6-di-tert-butyl-p-cresol.

[0052] The dropping rate of the allylamine was 25 ml / min.

[0053] S2, Preparation of Composite Antioxidants

[0054] Maleic anhydride, DMF, and toluene were added to a reaction vessel and stirred for 15 minutes. The toluene solution of the intermediate was added dropwise under ice bath conditions. After the addition was complete, the reaction was carried out at 50°C for 2.5 hours under nitrogen protection. After the reaction was completed, the mixture was cooled to room temperature to generate bismaleimide acid containing a hindered phenolic structure. Then, p-toluenesulfonic acid was added to the system, and the mixture was heated to boiling using an azeotropic distillation method. Water was separated using a water separator until no more water flowed out. The temperature was raised to 130°C to distill off the toluene. Deionized water was added to precipitate the product. The product was washed successively with acetone and deionized water and then dried under vacuum to obtain bismaleimide containing a hindered phenolic structure, i.e., a composite antioxidant.

[0055] The mass ratio of maleic anhydride to intermediate is 1:1.4.

[0056] The mass ratio of maleic anhydride, DMF and toluene is 1:25:25.

[0057] The temperature of the ice bath is 5°C.

[0058] The toluene solution of the intermediate was dropped at a rate of 30 ml / min.

[0059] The mass fraction of the intermediate in the toluene solution is 7%.

[0060] The amount of p-toluenesulfonic acid added is 5.5% of the amount of maleic anhydride added.

[0061] The vacuum drying temperature is 85℃ and the time is 10 hours.

[0062] S3. Preparation of modified cross-linked polyethylene

[0063] Low-density polyethylene and composite antioxidants were mixed at 200°C for 5 minutes, and then DCP was added at 105°C and mixed for another 3 minutes. The mixing speed was 70 rpm to obtain the mixture.

[0064] The mixture is extruded through a twin-screw extruder, granulated, and dried to obtain modified cross-linked polyethylene.

[0065] The low-density polyethylene comprises 105 parts by weight, the composite antioxidant comprises 0.3 parts by weight, and the DCP comprises 1 part by weight.

[0066] A method for preparing an oxidation-resistant high-strength cross-linked polyethylene cable, the method comprising: coating a shielding layer material onto a conductor material to form a shielding layer, then coating the shielding layer with cross-linked polyethylene to form an insulation layer, coating the insulation layer with a water-blocking tape, and then coating the water-blocking tape with high-density polyethylene to form a protective layer, thereby obtaining an oxidation-resistant high-strength cross-linked polyethylene cable.

[0067] Example 2: Antioxidant high-strength cross-linked polyethylene cable and its preparation method

[0068] An antioxidant high-strength cross-linked polyethylene cable, wherein the structure of the antioxidant high-strength cross-linked polyethylene cable, from the inside out, consists of a conductor, a shielding layer, an insulation layer, a water-blocking strip, and a protective layer.

[0069] The conductor material is copper.

[0070] The shielding layer material is woven copper mesh.

[0071] The insulating layer is modified cross-linked polyethylene.

[0072] The protective layer is made of high-density polyethylene.

[0073] The preparation method of the modified cross-linked polyethylene includes the following steps:

[0074] S1, Preparation of intermediates

[0075] 2,6-Di-tert-butyl-p-cresol and sodium ethoxide catalyst were added to a reaction vessel, heated to 110°C and kept at that temperature for 60 min. Allylamine was then added dropwise and the reaction was kept at that temperature for another 4.5 h. After the reaction was completed, the mixture was cooled to 50°C and diluted with toluene. The organic layer was washed twice with water, allowed to stand and separate into layers, and then the toluene was recovered by vacuum distillation. The intermediate was obtained by fractional distillation.

[0076] The molar ratio of 2,6-di-tert-butyl-p-cresol to allylamine is 1:1.9.

[0077] The amount of sodium ethoxide added is 2% of the mass of 2,6-di-tert-butyl-p-cresol.

[0078] The dropping rate of the allylamine was 20 ml / min.

[0079] S2, Preparation of Composite Antioxidants

[0080] Maleic anhydride, DMF, and toluene were added to a reaction vessel and stirred for 10 minutes. The toluene solution of the intermediate was added dropwise under ice bath conditions. After the addition was complete, the reaction was carried out at 45°C for 2 hours under nitrogen protection. After the reaction was completed, the mixture was cooled to room temperature to generate bismaleimide acid containing a hindered phenolic structure. Then, p-toluenesulfonic acid was added to the system, and the mixture was heated to boiling using an azeotropic distillation method. Water was separated using a water separator until no more water flowed out. The temperature was raised to 125°C to distill off the toluene. Deionized water was added to precipitate the product. The product was washed successively with acetone and deionized water and then dried under vacuum to obtain bismaleimide containing a hindered phenolic structure, i.e., a composite antioxidant.

[0081] The mass ratio of maleic anhydride to intermediate is 1:1.2.

[0082] The mass ratio of maleic anhydride, DMF and toluene is 1:20:30.

[0083] The temperature of the ice bath is 0°C.

[0084] The toluene solution of the intermediate was dropped at a rate of 20 ml / min.

[0085] The mass fraction of the intermediate in the toluene solution is 5%.

[0086] The amount of p-toluenesulfonic acid added is 5% of the amount of maleic anhydride added.

[0087] The vacuum drying temperature is 90℃ and the time is 8 hours.

[0088] S3. Preparation of modified cross-linked polyethylene

[0089] Low-density polyethylene and composite antioxidants were mixed at 195°C for 4 minutes, and then DCP was added at 100°C and mixed for another 4 minutes. The mixing speed was 80 rpm to obtain the mixture.

[0090] The mixture is extruded through a twin-screw extruder, granulated, and dried to obtain modified cross-linked polyethylene.

[0091] The low-density polyethylene comprises 100 parts by weight, the composite antioxidant comprises 0.15 parts by weight, and the DCP comprises 0.8 parts by weight.

[0092] A method for preparing an oxidation-resistant high-strength cross-linked polyethylene cable, the method comprising: coating a shielding layer material onto a conductor material to form a shielding layer, then coating the shielding layer with cross-linked polyethylene to form an insulation layer, coating the insulation layer with a water-blocking tape, and then coating the water-blocking tape with high-density polyethylene to form a protective layer, thereby obtaining an oxidation-resistant high-strength cross-linked polyethylene cable.

[0093] Example 3: Antioxidant high-strength cross-linked polyethylene cable and its preparation method

[0094] An antioxidant high-strength cross-linked polyethylene cable, wherein the structure of the antioxidant high-strength cross-linked polyethylene cable, from the inside out, consists of a conductor, a shielding layer, an insulation layer, a water-blocking strip, and a protective layer.

[0095] The conductor material is copper.

[0096] The shielding layer material is woven copper mesh.

[0097] The insulating layer is modified cross-linked polyethylene.

[0098] The protective layer is made of high-density polyethylene.

[0099] The preparation method of the modified cross-linked polyethylene includes the following steps:

[0100] S1, Preparation of intermediates

[0101] 2,6-Di-tert-butyl-p-cresol and sodium ethoxide catalyst were added to a reaction vessel, heated to 120°C and kept at that temperature for 80 min. Allylamine was then added dropwise and the reaction was kept at that temperature for another 5 h. After the reaction was completed, the mixture was cooled to 60°C and diluted with toluene. The organic layer was washed three times with water, allowed to stand and separate into layers, and then the toluene was recovered by vacuum distillation. The intermediate was obtained by fractional distillation.

[0102] The molar ratio of 2,6-di-tert-butyl-p-cresol and allylamine is 1:2.2.

[0103] The amount of sodium ethoxide added is 5% of the mass of 2,6-di-tert-butyl-p-cresol.

[0104] The dropping rate of the allylamine was 30 ml / min.

[0105] S2, Preparation of Composite Antioxidants

[0106] Maleic anhydride, DMF, and toluene were added to a reaction vessel and stirred for 20 minutes. The toluene solution of the intermediate was added dropwise under ice bath conditions. After the addition was complete, the reaction was carried out at 55°C for 3 hours under nitrogen protection. After the reaction was completed, the mixture was cooled to room temperature to generate bismaleimide acid containing a hindered phenolic structure. Then, p-toluenesulfonic acid was added to the system, and the mixture was heated to boiling using an azeotropic distillation method. Water was separated using a water separator until no more water flowed out. The temperature was raised to 135°C to distill off the toluene. Deionized water was added to precipitate the product. The product was washed successively with acetone and deionized water and then dried under vacuum to obtain bismaleimide containing a hindered phenolic structure, i.e., a composite antioxidant.

[0107] The mass ratio of maleic anhydride to intermediate is 1:1.5.

[0108] The mass ratio of maleic anhydride, DMF and toluene is 1:30:20.

[0109] The temperature of the ice bath is 10°C.

[0110] The toluene solution of the intermediate was dropped at a rate of 40 ml / min.

[0111] The mass fraction of the intermediate in the toluene solution is 10%.

[0112] The amount of p-toluenesulfonic acid added is 6% of the amount of maleic anhydride added.

[0113] The vacuum drying temperature is 80℃ and the time is 12 hours.

[0114] S3. Preparation of modified cross-linked polyethylene

[0115] Low-density polyethylene and composite antioxidants were mixed at 205°C for 7 minutes, and then DCP was added at 110°C and mixed for another 2 minutes. The mixing speed was 50 rpm to obtain the mixture.

[0116] The mixture is extruded through a twin-screw extruder, granulated, and dried to obtain modified cross-linked polyethylene.

[0117] The low-density polyethylene comprises 110 parts by weight, the composite antioxidant comprises 0.2 parts by weight, and the DCP comprises 1.2 parts by weight.

[0118] A method for preparing an oxidation-resistant high-strength cross-linked polyethylene cable, the method comprising: coating a shielding layer material onto a conductor material to form a shielding layer, then coating the shielding layer with cross-linked polyethylene to form an insulation layer, coating the insulation layer with a water-blocking tape, and then coating the water-blocking tape with high-density polyethylene to form a protective layer, thereby obtaining an oxidation-resistant high-strength cross-linked polyethylene cable.

[0119] Comparative Example 1

[0120] Example 1, a representative example, was selected. The composite antioxidant was removed, and an equal proportion of the conventional antioxidant 2,6-di-tert-butyl-p-cresol was added directly. All other aspects were the same as in Example 1. This example was used as Comparative Example 1.

[0121] Comparative Example 2

[0122] Example 1, a representative example, was selected. The composite antioxidant was removed, and an intermediate in equal proportion was added directly. Everything else was the same as in Example 1. This was used as Comparative Example 2.

[0123] The cross-linked polyethylenes prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to performance tests, and the specific results are shown in Table 1.

[0124] Table 1

[0125]

[0126] The cross-linked polyethylene prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to aging tests, and their performance was compared with that of unaged polyethylene, as shown in Table 2.

[0127] Table 2

[0128]

[0129] Note: The detection method is as follows:

[0130] Tensile strength: Measured according to GB / T 1040.1-2018, the tensile rate is 250 mm / min;

[0131] Elongation at break: Measured according to GB / T 1040.1-2018, the tensile rate is 250 mm / min;

[0132] Volume resistivity: determined according to GB / T 1048.1-2006;

[0133] Dielectric constant: determined according to GB / T 1048.1-2006;

[0134] Elongation under load: determined according to GB / T 2951.21-2008;

[0135] Cooling permanent deformation rate: determined according to GB / T 2951.21-2008;

[0136] Aging test: measured according to GB / T 2951.12-2008, with a temperature of 135℃ and a time of 168h.

[0137] As can be seen from Tables 1 and 2, the cross-linked polyethylene prepared in Examples 1-3 not only has excellent mechanical and insulation properties, but also exhibits a decrease in mechanical properties and dielectric constant after aging. This indicates that the cross-linked polyethylene prepared in this invention has stronger antioxidant stability. Therefore, the overall performance of the cables prepared using Examples 1-3 is also better.

[0138] Comparative Example 1 removed the composite antioxidant and directly added an equal proportion of the conventional antioxidant 2,6-di-tert-butyl-p-cresol. The performance of both examples decreased, and the performance degradation rate after aging was high. This is because the antioxidant has relatively poor compatibility with the matrix in cross-linked polyethylene, resulting in slightly lower mechanical properties of the material. It is also unstable in the matrix and easily migrates, so the performance after aging is not as good as that of the example.

[0139] In Comparative Example 2, the composite antioxidant was removed, and an equal proportion of intermediate was added. The intermediate contained a diamine structure and a hindered phenol structure. The diamine structure can also participate in cross-linking, but its activity is not as good as that of the bismaleimide structure. Therefore, fewer cross-linked structures were formed, and the overall effect was worse than that of the example.

[0140] Unless otherwise specified, all proportions and percentages mentioned in this invention are mass proportions and mass percentages; all raw materials are commercially available.

[0141] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. Antioxidant high-strength crosslinked polyethylene cable, characterized in that, The structure of the antioxidant high-strength crosslinked polyethylene cable from inside to outside is conductor, shielding layer, insulation layer, water-blocking tape and protective layer; The conductor material is copper or aluminum alloy; The shielding layer material is one of aluminum foil, copper foil, braided copper mesh or conductive plastic; The insulation layer is modified crosslinked polyethylene; The protective layer is high-density polyethylene; The preparation method of the modified crosslinked polyethylene includes intermediate preparation, composite antioxidant preparation and modified crosslinked polyethylene preparation; In the intermediate preparation, 2,6-di-tert-butyl-p-cresol and sodium ethoxide are added into a reaction kettle, heated to 110-120 DEG C and kept for 60-80 min, then allylamine is added dropwise and kept for 4-5 h, after the reaction, the mixture is cooled to 50-60 DEG C, diluted with toluene, washed with water for 2-3 times, separated and distilled under reduced pressure to recover toluene, and the intermediate is obtained by fractional distillation; In the composite antioxidant preparation, maleic anhydride, DMF and toluene are added into a reaction kettle and stirred for 10-20 min, the intermediate toluene solution is added dropwise under ice bath condition, after the dropwise addition, the reaction is carried out at 45-55 DEG C under nitrogen protection for 2-3 h, after the reaction, the mixture is cooled to room temperature, and the double-maleimide acid containing hindered phenol structure is obtained; then p-toluene sulfonic acid is added, the mixture is heated and distilled by azeotropic distillation, water is removed by a water removal device, the mixture is heated to 125-135 DEG C to distill toluene, deionized water is added to precipitate the product, the product is washed with acetone and deionized water in sequence, and vacuum dried to obtain the double-maleimide containing hindered phenol structure, i.e. the composite antioxidant; In the modified crosslinked polyethylene preparation, low-density polyethylene and the composite antioxidant are mixed at 195-205 DEG C for 4-7 min, then DCP is added at 100-110 DEG C and mixed for 2-4 min, the mixing speed is 50-80 rpm, and the mixed material is obtained; The mixed material is extruded by a double-screw extruder, granulated and dried to obtain the modified crosslinked polyethylene.

2. The antioxidant high-strength crosslinked polyethylene cable of claim 1, wherein, The molar ratio of 2,6-di-tert-butyl-p-cresol to allylamine is 1:1.9-2.2; The addition amount of sodium ethoxide is 2-5% of the mass of 2,6-di-tert-butyl-p-cresol; The dropwise addition speed of allylamine is 20-30 ml / min.

3. The antioxidant high-strength crosslinked polyethylene cable of claim 1, wherein, The mass ratio of maleic anhydride to the intermediate is 1:1.2-1.5; The mass ratio of maleic anhydride, DMF and toluene is 1:20-30:20-30; The temperature of the ice bath condition is 0-10 DEG C.

4. The antioxidant high-strength crosslinked polyethylene cable of claim 1, wherein, The dropwise addition speed of the intermediate toluene solution is 20-40 ml / min; The mass fraction of the intermediate in the intermediate toluene solution is 5-10%; The addition amount of p-toluene sulfonic acid is 5-6% of the addition amount of maleic anhydride; The temperature of the vacuum drying is 80-90 DEG C, and the time is 8-12 h.

5. The antioxidant high-strength crosslinked polyethylene cable of claim 1, wherein, According to weight parts, the low-density polyethylene is 100-110 parts, the composite antioxidant is 0.15-0.3 parts, and the DCP is 0.8-1.2 parts.

6. The process for the preparation of antioxidant high strength crosslinked polyethylene cables according to any one of claims 1-5, characterized in that, The preparation method comprises the following steps: coating a shielding layer material on a conductor material to form a shielding layer, coating a cross-linked polyethylene on the shielding layer to form an insulating layer, coating a water-blocking tape on the insulating layer, and then coating a high-density polyethylene on the water-blocking tape to form a protective layer, thereby obtaining the oxidation-resistant high-strength cross-linked polyethylene cable.

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