Antioxidant high-strength crosslinked polyethylene cable and preparation method thereof

Abstract

The invention belongs to the technical field of crosslinked polyethylene cables, and particularly relates to an antioxidant high-strength crosslinked polyethylene cable and a preparation method thereof. The structure of the antioxidant high-strength crosslinked polyethylene cable sequentially comprises a conductor, a shielding layer, an insulating layer, a water-blocking tape and a protective layer from inside to outside, the conductor is made of copper or aluminum alloy, the shielding layer is made of one of aluminum foil, copper foil, a braided copper net or conductive plastic, and the insulating layer is made of modified crosslinked polyethylene; and the protective layer is made of high-density polyethylene. The anti-oxidation high-strength crosslinked polyethylene cable prepared by the invention has excellent anti-oxidation performance, and the anti-oxidation performance and mechanical performance of the crosslinked polyethylene are improved by modifying the insulating layer material crosslinked polyethylene, so that the overall performance of the cable is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of cross-linked polyethylene cables, and in particular relates to an oxidation-resistant high-strength cross-linked polyethylene cable and a preparation method thereof. Background Art

[0002] High-voltage direct current (HVDC) transmission boasts low losses and low costs, making it widely used for long-distance power transmission. HVDC transmission utilizes high-voltage cables, whose structure primarily consists of a conductor, insulation layer, shielding layer, and protective layer. Currently, cross-linked polyethylene (XLPE) is one of the primary materials used for high-voltage cable insulation. XLPE utilizes a cross-linking agent to cross-link polyethylene molecules. This treatment significantly improves the heat resistance of the polyethylene molecules, raising their long-term operating temperature to over 90°C. Due to the cross-linked network structure between the molecular chains, its mechanical properties are enhanced, particularly in terms of hardness, wear resistance, and dimensional stability. However, during use, the thermal effects of the current inevitably cause oxidation of the high-voltage cable, leading to a degradation of the cable's insulation and mechanical properties over time.

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

[0004] The method of improving the antioxidant properties of cross-linked polyethylene mainly includes adding antioxidants, but antioxidants have poor compatibility with the matrix and are easy to migrate or precipitate during use, resulting in a decrease in the antioxidant and mechanical properties of cross-linked polyethylene.

[0005] In response to the above problems, the present invention proposes an oxidation-resistant high-strength cross-linked polyethylene cable and a preparation method thereof, aiming to improve the oxidation resistance of cross-linked polyethylene while increasing the strength of the material and extending its service life. Summary of the Invention

[0006] In order to solve the problems existing in the prior art, the present invention provides an antioxidant high-strength cross-linked polyethylene cable and a preparation method thereof, in which a cross-linked structure is formed between a hindered phenol structure with antioxidant effect and the cross-linked polyethylene, thereby avoiding easy migration or precipitation during use and improving the mechanical properties of the cross-linked polyethylene.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions: One of the purposes of the present invention is to provide an oxidation-resistant high-strength cross-linked polyethylene cable, the structure of which is, from inside to outside, a conductor, a shielding layer, an insulating layer, a water-blocking tape and a protective layer.

[0008] Preferably, the conductor material is copper or aluminum alloy.

[0009] Preferably, the shielding layer material is one of aluminum foil, copper foil, braided copper mesh or conductive plastic.

[0010] Preferably, the insulating layer is modified cross-linked polyethylene.

[0011] Preferably, the protective layer is high-density polyethylene.

[0012] Preferably, the preparation method of the modified cross-linked polyethylene comprises the following steps: S1. Preparation of intermediates Add 2,6-di-tert-butyl-p-cresol and catalyst sodium ethoxide into a reactor, heat to 110-120°C and keep warm for 60-80 minutes, then add allylamine dropwise and continue to keep warm for 4-5 hours. After the reaction is completed, cool to 50-60°C, add toluene to dilute, wash the organic layer with water 2-3 times, let it stand for stratification, and then distill under reduced pressure to recover toluene, and fractionate to obtain the intermediate.

[0013] 2,6-di-tert-butyl-p-cresol has a hindered phenol structure, and allylamine is highly active. Under the action of a catalyst, the hydrogen atoms C3 and C5 on the benzene ring of 2,6-di-tert-butyl-p-cresol become more active, and undergo an addition reaction with allylamine, modifying the amino group on the benzene ring to obtain an intermediate containing a diamine and a hindered phenol structure.

[0014] Preferably, the molar ratio of 2,6-di-tert-butyl-p-cresol to allylamine is 1:1.9-2.2.

[0015] Preferably, the amount of sodium ethoxide added is 2-5% of the mass of 2,6-di-tert-butyl-p-cresol.

[0016] Preferably, the dropping rate of the allylamine is 20-30 ml / min.

[0017] S2. Preparation of composite antioxidant Maleic anhydride, DMF and toluene are added to a reactor and stirred for 10 to 20 minutes. The toluene solution of the intermediate is added dropwise under ice bath conditions. After the addition is completed, the reaction is carried out at 45 to 55° C. under nitrogen protection for 2 to 3 hours. After the reaction is completed, the reaction is cooled to room temperature to generate a bismaleimide acid containing a hindered phenol structure. Then, p-toluenesulfonic acid is added to the system, and the system is heated to boiling by azeotropic distillation and water is separated by a water separator until no water flows out. The temperature is raised to 125 to 135° C. to evaporate the toluene, and deionized water is added to precipitate the product. The product is washed with acetone and deionized water in sequence and then vacuum dried to obtain a bismaleimide containing a hindered phenol structure, i.e., a composite antioxidant.

[0018] Preferably, the mass ratio of maleic anhydride to the intermediate is 1:1.2-1.5.

[0019] Preferably, the mass ratio of maleic anhydride, DMF and toluene is 1:20-30:20-30.

[0020] Preferably, the temperature of the ice bath condition is 0-10°C.

[0021] Preferably, the toluene solution of the intermediate is added at a rate of 20 to 40 ml / min.

[0022] Preferably, the mass fraction of the intermediate in the toluene solution of the intermediate is 5 to 10%.

[0023] Preferably, the amount of p-toluenesulfonic acid added is 5-6% of the amount of maleic anhydride added.

[0024] Preferably, the vacuum drying temperature is 80-90° C. and the time is 8-12 hours.

[0025] The intermediate contains a diamine structure and a hindered phenol structure. The diamine structure in the intermediate reacts with maleic anhydride to form maleimide acid. This cyclization reaction continues under the action of p-toluenesulfonic acid to form a maleimide ring. The final product is a bismaleimide containing a hindered phenol structure, which is a composite antioxidant. The bismaleimide structure in the composite antioxidant contains two carbon-carbon double bonds, which act as a crosslinking agent, preventing the effect of simple grafting or blending on the crosslinking degree of cross-linked polyethylene, which further affects its mechanical properties. Furthermore, the carbonyl group in the bismaleimide structure can improve the electrical properties of cross-linked polyethylene and enhance its insulation properties. The hindered phenol structure in the composite antioxidant can capture oxygen-containing free radicals and carbon free radicals generated during polymer aging, thereby improving the material's antioxidant properties.

[0026] S3. Preparation of modified cross-linked polyethylene The low-density polyethylene and the composite antioxidant are mixed at 195-205°C for 4-7 minutes, and then DCP (dicumyl peroxide) is added at 100-110°C and mixed for 2-4 minutes at a mixing speed of 50-80 rpm to obtain a mixture; The mixed material is extruded through a twin-screw extruder, granulated and dried to obtain modified cross-linked polyethylene.

[0027] Preferably, in parts by weight, the low-density polyethylene is 100 to 110 parts, the composite antioxidant is 0.15 to 0.3 parts, and the DCP is 0.8 to 1.2 parts.

[0028] During the mixing process, due to the high melting point of the composite antioxidant, secondary mixing is adopted. The low-density polyethylene and the composite antioxidant are first mixed at high temperature, and then the temperature is lowered to add DCP and continue mixing.

[0029] During the cross-linking process, DCP decomposes to produce free radicals. The bismaleimide structure in the composite antioxidant contains two double bonds. The double bonds open and form a cross-linked structure with the polymer free radicals. Cross-linked bonds are also formed between the two polymer free radicals. The composite antioxidant and cross-linked polyethylene form a cross-linked structure in the form of chemical bonds. The combination is more stable and not easy to migrate and lose in the subsequent process. The antioxidant performance is more lasting and the service life is extended.

[0030] The second object of the present invention is to provide a method for preparing an antioxidant high-strength cross-linked polyethylene cable. The preparation method is: a shielding layer material is coated on a conductor material to form a shielding layer, and then cross-linked polyethylene is coated on the shielding layer to form an insulating layer. After a water-blocking tape is coated on the insulating layer, high-density polyethylene is coated on the water-blocking tape to form a protective layer, thereby obtaining an antioxidant high-strength cross-linked polyethylene cable.

[0031] Due to the adoption of the above technical solution, the technical effects achieved by the present invention are: 1. The antioxidant high-strength cross-linked polyethylene cable prepared by the present invention has excellent antioxidant properties. By modifying the cross-linked polyethylene of the insulation layer material, the antioxidant properties and mechanical properties of the cross-linked polyethylene are improved, thereby improving the overall performance of the cable.

[0032] 2. The present invention prepares a composite antioxidant containing a hindered phenol structure and carbon-carbon double bonds. The two carbon-carbon double bonds allow the addition of the composite antioxidant to act as a crosslinking agent, preventing the effects of simple grafting or blending on the crosslinking degree of the crosslinked polyethylene, which further affects its mechanical properties. The bond between the composite antioxidant and the crosslinked polyethylene is more stable, making it less likely to migrate and lose during subsequent processing, thus preventing any impact on the antioxidant and mechanical properties of the crosslinked polyethylene. DETAILED DESCRIPTION

[0033] The present invention will be further described below with reference to specific embodiments.

[0034] Example 1: Anti-oxidation high-strength cross-linked polyethylene cable and its preparation method The invention discloses an oxidation-resistant high-strength cross-linked polyethylene cable. The structure of the oxidation-resistant high-strength cross-linked polyethylene cable comprises, from the inside to the outside, a conductor, a shielding layer, an insulating layer, a water-blocking tape and a protective layer.

[0035] The conductor material is copper.

[0036] The shielding layer material is a braided copper mesh.

[0037] The insulating layer is made of modified cross-linked polyethylene.

[0038] The protective layer is high-density polyethylene.

[0039] The preparation method of the modified cross-linked polyethylene comprises the following steps: S1. Preparation of intermediates 2,6-di-tert-Butyl-p-cresol and catalyst sodium ethoxide were added into the reactor, and the temperature was raised to 115°C and kept for reaction for 70 minutes. Allylamine was then added dropwise and kept for reaction for 4 hours. After the reaction was completed, the reaction was cooled to 55°C and toluene was added for dilution. The organic layer was washed with water for 3 times, and the toluene was recovered by vacuum distillation after standing and stratification, and the intermediate was obtained by fractionation.

[0040] The molar ratio of the 2,6-di-tert-butyl-p-cresol to the allylamine is 1:2.1.

[0041] The added amount of the sodium ethoxide is 3.5% of the mass of 2,6-di-tert-butyl-p-cresol.

[0042] The allylamine was added at a rate of 25 ml / min.

[0043] S2. Preparation of composite antioxidant Maleic anhydride, DMF and toluene are added to a reactor and stirred for 15 minutes. The toluene solution of the intermediate is added dropwise under ice bath conditions. After the addition is completed, the mixture is reacted at 50°C under nitrogen protection for 2.5 hours. After the reaction is completed, the mixture is cooled to room temperature to generate a bismaleimide acid containing a hindered phenol structure. p-Toluenesulfonic acid is then added to the system, and the mixture is heated to boiling by azeotropic distillation and water is separated by a water separator until no more water flows out. The temperature is raised to 130°C to evaporate the toluene, and deionized water is added to precipitate the product. The product is washed with acetone and deionized water in sequence and then dried in vacuo to obtain a bismaleimide containing a hindered phenol structure, i.e., a composite antioxidant.

[0044] The mass ratio of the maleic anhydride to the intermediate is 1:1.4.

[0045] The mass ratio of the maleic anhydride, DMF and toluene is 1:25:25.

[0046] The temperature of the ice bath condition was 5°C.

[0047] The toluene solution of the intermediate was added at a rate of 30 ml / min.

[0048] The mass fraction of the intermediate in the toluene solution of the intermediate is 7%.

[0049] The amount of p-toluenesulfonic acid added is 5.5% of the amount of maleic anhydride added.

[0050] The vacuum drying temperature is 85° C. and the time is 10 h.

[0051] S3. Preparation of modified cross-linked polyethylene Low-density polyethylene and composite antioxidant were mixed at 200°C for 5 minutes, and then DCP was added at 105°C and mixed for 3 minutes at a mixing speed of 70 rpm to obtain a mixture; The mixed material is extruded through a twin-screw extruder, granulated and dried to obtain modified cross-linked polyethylene.

[0052] In terms of parts by weight, the low-density polyethylene is 105 parts, the composite antioxidant is 0.3 parts, and the DCP is 1 part.

[0053] A method for preparing an oxidation-resistant high-strength cross-linked polyethylene cable, the preparation method comprising: coating a shielding layer material on a conductor material to form a shielding layer, then coating the shielding layer with cross-linked polyethylene to form an insulating layer, coating the insulating 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.

[0054] Example 2: Anti-oxidation high-strength cross-linked polyethylene cable and its preparation method The invention discloses an oxidation-resistant high-strength cross-linked polyethylene cable. The structure of the oxidation-resistant high-strength cross-linked polyethylene cable comprises, from the inside to the outside, a conductor, a shielding layer, an insulating layer, a water-blocking tape and a protective layer.

[0055] The conductor material is copper.

[0056] The shielding layer material is a braided copper mesh.

[0057] The insulating layer is made of modified cross-linked polyethylene.

[0058] The protective layer is high-density polyethylene.

[0059] The preparation method of the modified cross-linked polyethylene comprises the following steps: S1. Preparation of intermediates 2,6-di-tert-Butyl-p-cresol and catalyst sodium ethoxide were added into the reactor, and the temperature was raised to 110°C and kept for reaction for 60 minutes. Allylamine was then added dropwise and kept for reaction for 4.5 hours. After the reaction was completed, the reaction was cooled to 50°C and toluene was added for dilution. The organic layer was washed twice with water, and the toluene was recovered by vacuum distillation after standing and stratification, and the intermediate was obtained by fractionation.

[0060] The molar ratio of the 2,6-di-tert-butyl-p-cresol to the allylamine is 1:1.9.

[0061] The added amount of the sodium ethoxide is 2% of the mass of 2,6-di-tert-butyl-p-cresol.

[0062] The allylamine was added at a rate of 20 ml / min.

[0063] S2. Preparation of composite antioxidant Maleic anhydride, DMF and toluene are added to a reactor and stirred for 10 minutes. The toluene solution of the intermediate is added dropwise under ice bath conditions. After the addition is completed, the mixture is reacted at 45°C under nitrogen protection for 2 hours. After the reaction is completed, the mixture is cooled to room temperature to generate a bismaleimide acid containing a hindered phenol structure. Then, p-toluenesulfonic acid is added to the system, and the mixture is heated to boiling by azeotropic distillation and water is separated by a water separator until no more water flows out. The temperature is raised to 125°C to evaporate the toluene, and deionized water is added to precipitate the product. The product is washed with acetone and deionized water in sequence and then dried in vacuo to obtain a bismaleimide containing a hindered phenol structure, i.e., a composite antioxidant.

[0064] The mass ratio of the maleic anhydride to the intermediate is 1:1.2.

[0065] The mass ratio of the maleic anhydride, DMF and toluene is 1:20:30.

[0066] The temperature of the ice bath condition was 0°C.

[0067] The toluene solution of the intermediate was added at a rate of 20 ml / min.

[0068] The mass fraction of the intermediate in the toluene solution of the intermediate is 5%.

[0069] The amount of p-toluenesulfonic acid added is 5% of the amount of maleic anhydride added.

[0070] The vacuum drying temperature is 90° C. and the time is 8 h.

[0071] S3. Preparation of modified cross-linked polyethylene Low-density polyethylene and composite antioxidant were mixed at 195°C for 4 minutes, and then DCP was added at 100°C and mixed for 4 minutes at a mixing speed of 80 rpm to obtain a mixture; The mixed material is extruded through a twin-screw extruder, granulated and dried to obtain modified cross-linked polyethylene.

[0072] In terms of weight, the low-density polyethylene is 100 parts, the composite antioxidant is 0.15 parts, and the DCP is 0.8 parts.

[0073] A method for preparing an oxidation-resistant high-strength cross-linked polyethylene cable, the preparation method comprising: coating a shielding layer material on a conductor material to form a shielding layer, then coating the shielding layer with cross-linked polyethylene to form an insulating layer, coating the insulating 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.

[0074] Example 3: Anti-oxidation high-strength cross-linked polyethylene cable and its preparation method The invention discloses an oxidation-resistant high-strength cross-linked polyethylene cable. The structure of the oxidation-resistant high-strength cross-linked polyethylene cable comprises, from the inside to the outside, a conductor, a shielding layer, an insulating layer, a water-blocking tape and a protective layer.

[0075] The conductor material is copper.

[0076] The shielding layer material is a braided copper mesh.

[0077] The insulating layer is made of modified cross-linked polyethylene.

[0078] The protective layer is high-density polyethylene.

[0079] The preparation method of the modified cross-linked polyethylene comprises the following steps: S1. Preparation of intermediates 2,6-di-tert-Butyl-p-cresol and catalyst sodium ethoxide were added into the reactor, and the temperature was raised to 120°C and kept for reaction for 80 minutes. Allylamine was then added dropwise and kept for reaction for 5 hours. After the reaction was completed, the reaction was cooled to 60°C and toluene was added for dilution. The organic layer was washed with water for 3 times, and the toluene was recovered by vacuum distillation after standing and stratification, and the intermediate was obtained by fractionation.

[0080] The molar ratio of the 2,6-di-tert-butyl-p-cresol to the allylamine is 1:2.2.

[0081] The added amount of the sodium ethoxide is 5% of the mass of 2,6-di-tert-butyl-p-cresol.

[0082] The allylamine was added at a rate of 30 ml / min.

[0083] S2. Preparation of composite antioxidant Maleic anhydride, DMF and toluene are added to a reactor and stirred for 20 minutes. The toluene solution of the intermediate is added dropwise under ice bath conditions. After the addition is completed, the reaction is carried out at 55°C under nitrogen protection for 3 hours. After the reaction is completed, the reaction is cooled to room temperature to generate a bismaleimide acid containing a hindered phenol structure. Then, p-toluenesulfonic acid is added to the system, and the system is heated to boiling by azeotropic distillation and water is separated by a water separator until no more water flows out. The temperature is raised to 135°C to evaporate the toluene, and deionized water is added to precipitate the product. The product is washed with acetone and deionized water in sequence and then vacuum dried to obtain a bismaleimide containing a hindered phenol structure, i.e., a composite antioxidant.

[0084] The mass ratio of the maleic anhydride to the intermediate is 1:1.5.

[0085] The mass ratio of the maleic anhydride, DMF and toluene is 1:30:20.

[0086] The temperature of the ice bath condition was 10°C.

[0087] The toluene solution of the intermediate was added at a rate of 40 ml / min.

[0088] The mass fraction of the intermediate in the toluene solution of the intermediate is 10%.

[0089] The amount of p-toluenesulfonic acid added is 6% of the amount of maleic anhydride added.

[0090] The vacuum drying temperature is 80° C. and the time is 12 h.

[0091] S3. Preparation of modified cross-linked polyethylene Low-density polyethylene and composite antioxidant were mixed at 205°C for 7 minutes, and then DCP was added at 110°C and mixed for 2 minutes at a mixing speed of 50 rpm to obtain a mixture; The mixed material is extruded through a twin-screw extruder, granulated and dried to obtain modified cross-linked polyethylene.

[0092] In terms of weight, the low-density polyethylene is 110 parts, the composite antioxidant is 0.2 parts, and the DCP is 1.2 parts.

[0093] A method for preparing an oxidation-resistant high-strength cross-linked polyethylene cable, the preparation method comprising: coating a shielding layer material on a conductor material to form a shielding layer, then coating the shielding layer with cross-linked polyethylene to form an insulating layer, coating the insulating 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.

[0094] Comparative Example 1 Representative Example 1 was selected as Comparative Example 1, with the composite antioxidant removed and an equal proportion of conventional antioxidant 2,6-di-tert-butyl-p-cresol directly added, while the rest was the same as in Example 1.

[0095] Comparative Example 2 Representative Example 1 was selected as Comparative Example 2, with the composite antioxidant removed and the intermediate directly added in equal proportion, while the rest was consistent with Example 1.

[0096] The cross-linked polyethylene prepared in Examples 1-3 and Comparative Examples 1-2 was subjected to performance tests, and the specific results are shown in Table 1.

[0097] Table 1 The cross-linked polyethylene prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to aging tests, and their performance was tested and compared with that of the unaged polyethylene, as shown in Table 2.

[0098] Table 2 Note: The detection method is as follows: Tensile strength: measured in accordance with GB / T 1040.1-2018, with a tensile rate of 250 mm / min; Elongation at break: measured in accordance with GB / T 1040.1-2018, with a tensile rate of 250 mm / min; Volume resistivity: measured in accordance with GB / T 1048.1-2006; Dielectric constant: measured in accordance with GB / T 1048.1-2006; Elongation under load: measured in accordance with GB / T 2951.21-2008; Cooling permanent deformation rate: measured in accordance with GB / T 2951.21-2008; Aging test: measured in accordance with GB / T 2951.12-2008, temperature 135°C, time 168h.

[0099] It can be seen from Table 1 and Table 2 that the cross-linked polyethylene prepared in Examples 1-3 not only has excellent mechanical properties and insulation properties, but also has reduced mechanical properties and dielectric constants after aging, indicating that the cross-linked polyethylene prepared in the present invention has stronger antioxidant stability. Therefore, the overall performance of the cables prepared using Examples 1-3 is also better.

[0100] In Comparative Example 1, the composite antioxidant was removed and an equal proportion of conventional antioxidant 2,6-di-tert-butyl-p-cresol was directly added. The performance declined, 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 unstable in the matrix and easily migrates, so the performance after aging is not as good as that of the embodiment.

[0101] In Comparative Example 2, the composite antioxidant was removed and an intermediate in equal proportion was directly 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, less cross-linking structure is formed, and the overall effect is worse than that of the embodiment.

[0102] Unless otherwise specified, the ratios and percentages described in the present invention are all by mass; all raw materials are commercially available.

[0103] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. Anti-oxidation high-strength cross-linked polyethylene cable, characterized by: The structure of the anti-oxidation high-strength cross-linked polyethylene cable is, from the inside to the outside, a conductor, a shielding layer, an insulating 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 insulating layer is modified cross-linked polyethylene; The protective layer is high-density polyethylene.

2. The oxidation-resistant high-strength cross-linked polyethylene cable according to claim 1, characterized in that: The preparation method of the modified cross-linked polyethylene includes the preparation of intermediates, the preparation of composite antioxidants and the preparation of modified cross-linked polyethylene.

3. The oxidation-resistant high-strength cross-linked polyethylene cable according to claim 2, characterized in that: The intermediate is prepared by adding 2,6-di-tert-butyl-p-cresol and a catalyst, sodium ethoxide, into a reaction kettle, heating the temperature to 110-120° C. and then keeping the temperature for reaction for 60-80 minutes, then dropwise adding allylamine and continuing to keep the temperature for reaction for 4-5 hours, cooling the reaction to 50-60° C. after the reaction is completed, adding toluene for dilution, washing the organic layer with water for 2-3 times, allowing the reaction to stand for stratification, and then performing reduced pressure distillation to recover the toluene, and fractionating to obtain the intermediate.

4. The oxidation-resistant high-strength cross-linked polyethylene cable according to claim 3, characterized in that: The molar ratio of 2,6-di-tert-butyl-p-cresol to allylamine is 1:1.9-2.2; The amount of sodium ethoxide added is 2-5% of the mass of 2,6-di-tert-butyl-p-cresol; The dropping rate of the allylamine is 20-30 ml / min.

5. The oxidation-resistant high-strength cross-linked polyethylene cable according to claim 2, characterized in that: The composite antioxidant is prepared by adding maleic anhydride, DMF and toluene into a reaction kettle, stirring for 10 to 20 minutes, adding a toluene solution of an intermediate dropwise under ice bath conditions, reacting at 45 to 55° C. for 2 to 3 hours under nitrogen protection after the addition is completed, cooling to room temperature after the reaction is completed to generate a bismaleimide acid containing a hindered phenol structure; then adding p-toluenesulfonic acid into the system, heating to boiling by an azeotropic distillation method, separating water with a water separator until no water flows out, heating to 125 to 135° C. to evaporate the toluene, adding deionized water to precipitate the product, washing the product with acetone and deionized water in sequence, and then vacuum drying to obtain a bismaleimide containing a hindered phenol structure, namely the composite antioxidant.

6. The oxidation-resistant high-strength cross-linked polyethylene cable according to claim 5, characterized in that: The mass ratio of maleic anhydride to 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°C.

7. The oxidation-resistant high-strength cross-linked polyethylene cable according to claim 5, characterized in that: The toluene solution of the intermediate is added at a rate of 20 to 40 ml / min; The mass fraction of the intermediate in the toluene solution of the intermediate is 5 to 10%; The amount of p-toluenesulfonic acid added is 5-6% of the amount of maleic anhydride added; The vacuum drying temperature is 80-90° C. and the time is 8-12 hours.

8. The oxidation-resistant high-strength cross-linked polyethylene cable according to claim 2, characterized in that: The modified cross-linked polyethylene is prepared by mixing low-density polyethylene and a composite antioxidant at 195-205° C. for 4-7 minutes, then adding DCP at 100-110° C. and continuing to mix for 2-4 minutes at a mixing speed of 50-80 rpm to obtain a mixture; The mixed material is extruded through a twin-screw extruder, granulated and dried to obtain modified cross-linked polyethylene.

9. The oxidation-resistant high-strength cross-linked polyethylene cable according to claim 8, characterized in that: In terms of weight, the low-density polyethylene is 100 to 110 parts, the composite antioxidant is 0.15 to 0.3 parts, and the DCP is 0.8 to 1.2 parts.

10. The method for preparing an oxidation-resistant high-strength cross-linked polyethylene cable according to any one of claims 1 to 9, 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 cross-linked polyethylene on the shielding layer to form an insulating layer, coating a water-blocking tape on the insulating layer, and then coating high-density polyethylene on the water-blocking tape to form a protective layer, thereby obtaining an oxidation-resistant high-strength cross-linked polyethylene cable.

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