Recyclable polyolefin high-voltage direct-current cable insulating material and preparation method thereof

Abstract

The invention discloses a recyclable polyolefin high-voltage direct-current cable insulating material and a preparation method thereof, and belongs to the technical field of cable insulating materials. The recyclable polyolefin high-voltage direct-current cable insulating material provided by the invention is prepared from the following raw material components in parts by mass: 100 parts of thermoplastic polyolefin and 0.01 to 2 parts of norbornene lauric acid zinc. Melting the thermoplastic polyolefin, adding the norbornene lauric acid zinc, and mixing to obtain the composite material. The recyclable polyolefin high-voltage direct-current cable insulating material is formed by adding the norbornene dodecanamide zinc in a specific proportion into thermoplastic polyolefin, the norbornene dodecanamide zinc serves as zinc-containing self-dispersing organic carboxylate, the defect that traditional nano-zinc oxide is difficult to disperse uniformly due to high surface energy is overcome, and the recyclable polyolefin high-voltage direct-current cable insulating material is obtained. Meanwhile, space charge accumulation in the material under the action of a direct-current electric field can be effectively inhibited after addition.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cable insulation materials, in particular to a recyclable polyolefin high-voltage direct-current cable insulation material and a preparation method thereof. BACKGROUND

[0002] With the breakthrough of polymer material technology, the performance and environmental impact of polyolefin insulated cables are increasingly concerned. Although traditional XLPE (cross-linked polyethylene) has excellent insulation performance due to its chemical cross-linking structure, it is extremely difficult to degrade in the natural environment - it takes hundreds of years to partially decompose in landfill, and burning will release harmful halogen-containing gases, causing long-term harm to the ecological environment. At the same time, the development of high-voltage direct-current transmission technology puts forward higher requirements for the performance and environmental friendliness of cable insulation materials, and the development of green alternative materials is imminent.

[0003] Recyclable polyolefin (un-crosslinked polyolefin) insulated direct-current cables, although simple and sturdy in structure, are suitable for large-scale application in submarine or land direct-current transmission lines, but still have significant defects: the insulation material will accumulate a large amount of space charges formed by electrode injection and ionization of various additives or impurities in the material under the action of direct-current electric field, resulting in distortion of the local electric field; especially when the polarity of the direct-current cable is reversed, the local electric field strength may be 5-11 times higher than the average field strength, which further causes the insulation material to significantly deteriorate in terms of electrical conductivity, breakdown performance, aging performance, etc., seriously affecting the long-term reliability of the direct-current cable and shortening its service life.

[0004] To improve this problem, existing technologies attempt to introduce a small amount of nanoparticles into the polyolefin insulation material to increase the trap density, uniform space charge distribution, and improve the direct-current dielectric performance, but the nanoparticles are prone to agglomeration due to high surface energy, making it difficult to disperse in polyolefin. The change in size of the agglomerated nanoparticles will directly affect the material performance, which makes it difficult for nano-composite dielectric to achieve large-scale industrial application. SUMMARY

[0005] Therefore, the present application provides a recyclable polyolefin high-voltage direct-current cable insulation material and a preparation method thereof. The present application adds zinc bisnorbornene dodecanamide to the polyolefin high-voltage direct-current cable insulation material, the compatibility between the additive and the matrix resin is good and the additive is uniformly dispersed, without the need for cross-linking treatment of the polyolefin, so the material is recyclable, and the obtained polyolefin high-voltage direct-current cable insulation material has excellent ability to suppress space charge accumulation.

[0006] In a first aspect, the present application provides a recyclable polyolefin high-voltage direct-current cable insulation material, the raw materials of which include the following components by mass: 100 parts of thermoplastic polyolefin and 0.01-2 parts of zinc bisnorbornene dodecanamide.

[0007] Optionally, the raw material comprises the following components by mass: 100 parts of thermoplastic polyolefin and 0.05-1 parts of zinc norbornene dodecanamide.

[0008] Optionally, the thermoplastic polyolefin is selected from one or more of polyethylene, polypropylene and ethylene-propylene copolymer.

[0009] In a second aspect, the application provides a preparation method of the recyclable polyolefin high-voltage direct-current cable insulation material, comprising the following steps: After the thermoplastic polyolefin is melted, the zinc norbornene dodecanamide is added, and the recyclable polyolefin high-voltage direct-current cable insulation material is obtained after mixing.

[0010] Optionally, in the mixing step, the mixing temperature is 120-220℃, and the mixing time is 8-30 min.

[0011] Optionally, after the thermoplastic polyolefin is melted, it is subjected to preliminary mixing, the preliminary mixing time is 3-8 min, and then the zinc norbornene dodecanamide is added.

[0012] Optionally, the zinc norbornene dodecanamide is obtained by reacting zinc norbornene dodecanamide with a strong base and then with a zinc salt.

[0013] Further, the strong base is selected from one or more of NaOH, KOH, LiOH, sodium methoxide or sodium ethoxide, and the zinc salt is selected from one or more of zinc chloride, zinc sulfate, zinc nitrate, zinc acetate or zinc carbonate.

[0014] Further, the zinc norbornene dodecanamide is obtained by reacting zinc norbornene dodecanamide with a strong base and then with a zinc salt.

[0015] Further, the reaction temperature of the reaction of the zinc norbornene dodecanamide with the strong base is 10-40℃, the reaction time is 1-5 h, and the solvent is toluene or xylene.

[0016] Compared with the prior art, the application has the following beneficial effects: (1) By adding zinc norbornene dodecanamide in a specific proportion to the thermoplastic polyolefin, the recyclable polyolefin high-voltage direct-current cable insulation material is formed, and the zinc norbornene dodecanamide as a zinc-containing self-dispersing organic carboxylate avoids the defect that traditional nano zinc oxide is difficult to uniformly disperse due to high surface energy, and can effectively inhibit the accumulation of space charges in the material under the action of a direct-current electric field.

[0017] (2) The thermoplastic polyolefin is used as the base material, and the preparation process does not require crosslinking treatment, and the insulation life can be directly recycled after expiration, which meets the development needs of green environmental protection.

[0018] (3) The zinc norbornene dodecanamide acid is fully combined with the polyolefin molecular chain through the process of melting and mixing, the uniformity of the internal structure of the material is ensured, the preparation method is simple and efficient, and the method is suitable for industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0019] The drawings accompanying the specification of this application form a part thereof, serve to further provide a further understanding of the application, and together with the description of the exemplary embodiments of the application, explain the application, and do not limit the application in any way. Obviously, other drawings can be obtained by those skilled in the art without creative effort based on these drawings.

[0020] Figure 1 is the infrared spectrum of zinc norbornene dodecanamide acid prepared in the preparation example of the application; Figure 2 is a scanning electron microscope picture of the recyclable polypropylene high-voltage direct-current cable insulation material added with zinc norbornene dodecanamide acid prepared in embodiment 1 of the application; Figure 3 is a scanning electron microscope picture of the recyclable polypropylene high-voltage direct-current cable insulation material added with zinc norbornene dodecanamide acid prepared in embodiment 1 of the application; Figure 4 is a scanning electron microscope picture of the recyclable polypropylene high-voltage direct-current cable insulation material added with nano zinc oxide prepared in comparative example 1 of the application; Figure 5 is a scanning electron microscope picture of the recyclable polypropylene high-voltage direct-current cable insulation material without additives prepared in comparative example 2 of the application; Figure 6 is a space charge distribution diagram of the recyclable polypropylene high-voltage direct-current cable insulation material added with zinc norbornene dodecanamide acid prepared in embodiment 1 of the application after applying a direct-current electric field for pressurization; Figure 7 is a space charge distribution diagram of the recyclable polypropylene high-voltage direct-current cable insulation material added with zinc norbornene dodecanamide acid prepared in embodiment 2 of the application after applying a direct-current electric field for pressurization; Figure 8 is a space charge distribution diagram of the recyclable polypropylene high-voltage direct-current cable insulation material added with nano zinc oxide prepared in comparative example 1 of the application after applying a direct-current electric field for pressurization; Figure 9 is a space charge distribution diagram of the recyclable polypropylene high-voltage direct-current cable insulation material without additives prepared in comparative example 2 of the application after applying a direct-current electric field for pressurization; Figure 10is the space charge distribution diagram of the recoverable polypropylene high-voltage direct-current cable insulation material after pressure short-circuiting, which is prepared by adding zinc norbornene dodecanamide acid in the embodiment 1 of the present application; Figure 11 is the space charge distribution diagram of the recoverable polypropylene high-voltage direct-current cable insulation material after pressure short-circuiting, which is prepared by adding zinc norbornene dodecanamide acid in the embodiment 2 of the present application; Figure 12 is the space charge distribution diagram of the recoverable polypropylene high-voltage direct-current cable insulation material after pressure short-circuiting, which is prepared by adding nano zinc oxide in the comparative example 1 of the present application; Figure 13 is the space charge distribution diagram of the recoverable polypropylene high-voltage direct-current cable insulation material after pressure short-circuiting, which is prepared by adding no additive in the comparative example 2 of the present application. DETAILED DESCRIPTION

[0021] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0022] The present application provides a recoverable polyolefin high-voltage direct-current cable insulation material, the raw material of which comprises the following components by mass fraction: 100 parts of thermoplastic polyolefin and 0.01-2 parts of zinc norbornene dodecanamide acid.

[0023] The present application uses thermoplastic polyolefin as the base material and zinc norbornene dodecanamide acid as the functional additive, and realizes the double optimization of the high-voltage direct-current cable insulation material in inhibiting space charge accumulation and recyclability through the composite of the two.

[0024] The thermoplastic polyolefin as the base material has a non-polar carbon-carbon main chain as the main chain of the molecular chain, has good intrinsic electrical insulation and thermoplastic processing performance, and is the basic choice of high-voltage cable insulation. However, pure polyolefin is easy to cause charge injection and migration under high-voltage direct-current electric field due to too high electric field, which causes space charge accumulation, causes electric field distortion and reduces insulation reliability. The introduction of zinc norbornene dodecanamide acid in the present application is the key to solve this problem, and its molecular structure contains three parts of characteristics: the rigid cyclic skeleton of norbornene provides structural stability; the dodecyl chain is connected through an amide bond, has good compatibility with the non-polar molecular chain of polyolefin (self-disperses through van der Waals force or physical entanglement), avoids the defect that traditional nanoparticles are easy to agglomerate due to too high surface energy; the zinc carboxylate group as a polar functional unit, the Zn 2+The trap energy level distribution inside the material can be adjusted as a trap center regulating material. During the material preparation process, the zinc bis (norbornene dodecanoyl amide) acid is decomposed by heat: first, the amide bond is partially broken, and the dodecyl chain is separated in the form of an amine derivative, leaving a zinc carboxylate fragment containing a norbornene ring; then, the norbornene ring undergoes an aromatic rearrangement due to the instability of the double bond, converting into an aromatic-like structure (such as a benzene ring derivative), forming a zinc aryl carboxylate. The zinc aryl carboxylate has good compatibility with the polyolefin resin, can improve the effective concentration and reduce agglomeration, and can effectively capture charge carriers, limiting their migration, thereby inhibiting the accumulation of space charges.

[0025] In the present application, excessive addition of zinc bis (norbornene dodecanoyl amide) acid may cause agglomeration, which may cause new defects or interfacial polarization problems; too low an addition amount makes it difficult to effectively inhibit the accumulation of space charges. The addition amount of zinc bis (norbornene dodecanoyl amide) acid is more preferably 0.05 to 1 parts, and further preferably 0.3 to 1 parts, for example, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 part, etc.

[0026] In the present application, the above-mentioned thermoplastic polyolefin is selected from one or more of polyethylene, polypropylene, and ethylene-propylene copolymer. The above-mentioned thermoplastic polyolefin is a non-polar or weakly polar carbon chain polymer, which has intrinsic electrical insulation and thermoplastic processability. Its non-polar or weakly polar characteristics have good compatibility (similar solubility) with the dodecyl chain (long-chain alkyl) of zinc bis (norbornene dodecanoyl amide), which can promote the uniform dispersion of the additive in the matrix and avoid insulation defects caused by phase separation.

[0027] The present application also provides a preparation method of the above-mentioned recyclable polyolefin high-voltage direct-current cable insulation material, which comprises the following steps: After the thermoplastic polyolefin is melted, zinc bis (norbornene dodecanoyl amide) acid is added, and after mixing, the recyclable polyolefin high-voltage direct-current cable insulation material is obtained.

[0028] In the present application, the thermoplastic polyolefin needs to be melted first to form a viscous flow state melt, at which time the molecular chain segment movement ability is enhanced, providing a flow environment for the dispersion of the additive. Then, zinc bis (norbornene dodecanoyl amide) acid is added and mixed, and the mechanical shear force is used to break and disperse the solid additive into the melt. This process avoids uneven dispersion (such as agglomeration) caused by the non-melting of the matrix during solid-state mixing, and at the same time, the molecular chains in the molten state and the dodecyl chains (non-polar) of the additive interact through van der Waals forces, further promoting the stable dispersion of the additive and ensuring the uniformity of the overall performance of the material. The present application does not make special restrictions on the melting temperature, which is selected according to the type of thermoplastic polyolefin selected.

[0029] In the step of mixing, the mixing temperature is 120-220°C, more preferably 160-210°C, and the specific mixing temperature is determined according to the selected thermoplastic polyolefin, which needs to ensure the complete melting of the thermoplastic polyolefin and avoid the degradation of the thermoplastic polyolefin. The mixing time is 8-30 min, more preferably 10-20 min, which ensures the uniform distribution of the additive in the matrix.

[0030] In the present application, the thermoplastic polyolefin is melted and then subjected to preliminary mixing for 3-8 min, and then zinc norbornene dodecanamide acid is added. This step is to eliminate the “unmelted area” in the melt by using shear force to avoid local enrichment of the additive, and to homogenize the melt temperature to form a stable melt flow environment and pre-vent the air in the melt.

[0031] In the present application, the above-mentioned zinc norbornene dodecanamide acid is obtained by reacting zinc norbornene dodecanamide acid with a strong base and then with a zinc salt.

[0032] The reaction with the strong base is a neutralization reaction, and the present application does not make special limitations on the specific conditions of this process, and those skilled in the art can obtain the corresponding product according to the conditions of the neutralization reaction. Optionally, the temperature for the reaction with the strong base is 30-80°C, the reaction time is 0.5-5 h, and the solvent is water.

[0033] The above-mentioned strong base is selected from one or more of NaOH, KOH, LiOH, sodium methoxide or sodium ethoxide. In one or more embodiments of the present application, the above-mentioned strong base is selected from NaOH. This process increases the water solubility of the intermediate, which is more conducive to the subsequent reaction. The present application does not make special limitations on the amount of solvent added in this step, which can be determined according to the amount of solvent required for the conventional neutralization reaction in the art.

[0034] The reaction with the zinc salt is a double decomposition reaction, which directly obtains the target product through ion exchange. The present application does not make special limitations on the specific conditions of this process, and those skilled in the art can obtain the corresponding product according to the conditions of the double decomposition reaction.

[0035] Optionally, the conditions for the reaction with the zinc salt are: temperature 50-80°C, reaction time 0.5-5 h, and solvent water. In the present application, the above-mentioned zinc salt is selected from one or more of zinc chloride, zinc sulfate, zinc nitrate, zinc acetate or zinc carbonate; which can be flexibly selected according to specific needs. In one or more embodiments of the present application, the above-mentioned zinc salt is selected from zinc chloride.

[0036] In the present application, the above norbornene dodecanamide acid is obtained by reacting norbornene dicylic anhydride with dodecylamine, and the two undergo amidation reaction. The reaction route relies on the high reactivity of the anhydride, and the product structure is clear, and an anhydride bond is attacked by an amino group, avoiding the generation of polysubstituted by-products. Further, the reaction temperature of the reaction of the above norbornene dicylic anhydride and dodecylamine is 20-40℃, the reaction time is 1-5h, more preferably 1-3h; the solvent is toluene or xylene, and the solvent needs to ensure water as much as possible.

[0037] The technical solutions of the present application will be further described below in combination with specific examples. The reagents used in the following examples of the present application are not specially limited, and commercially available goods known to those skilled in the art can be used. The room temperature mentioned in the following examples refers to 25±3℃.

[0038] Preparation Example The present preparation example provides the synthesis of norbornene dodecanamide acid zinc.

[0039] (1) Synthesis of norbornene dodecanamide acid A 500mL four-necked flask equipped with a dropping funnel and a sealed stirrer was added with 100mmol (16.42g) norbornene dicylic anhydride, 200mL toluene, and stirred to dissolve. 102mmol dodecylamine (18.90g) was added dropwise from the dropping funnel, and a wind gun was used to uniformly heat the dropping funnel during the experiment to keep the dodecylamine liquid. After the dropwise addition was completed, the reaction was carried out at room temperature for 2 hours. Filtration was performed, the filter cake was washed twice with toluene, and then washed once with saturated water, and dried in a vacuum oven at 80℃ for 12 hours to obtain a white solid. The reaction formula is as follows: .

[0040] (2) Synthesis of norbornene dodecanamide acid sodium 13.11g of norbornene dodecanamide acid (37.5mmol) and 1.51g of NaOH (37.5mmol) were added to a 250mL three-necked flask equipped with a sealed stirrer, about 120mL of deionized water was added as a solvent, and after stirring and mixing, the reaction was carried out at 70℃ for 1h, and then the heating was stopped.

[0041] The reaction formula is as follows: .

[0042] (3) Synthesis of norbornene dodecanamide acid zinc Sodium norbornenedodecanamide acid 13.90 g (37.4 mmol) and ZnCl2 2.55 g (18.7 mmol) were added into a 250 mL three-necked flask equipped with a sealed stirrer, about 100 mL of deionized water was added as solvent, the mixture was stirred, the reaction was carried out at 70 degrees Celsius for 1 h, the heating was stopped, the filter cake was washed with ionized water for 3 times, and dried in a vacuum oven at 50 degrees Celsius for 24 hours to obtain zinc norbornenedodecanamide acid. The reaction formula is shown as follows: .

[0043] The structure of the synthesized zinc norbornenedodecanamide acid was characterized by infrared spectrum, and the results are shown in Figure 1 , wherein 3350.2292 cm -1 is the stretching vibration of N-H, 1607.8593 cm -1 is the stretching vibration of C=O, 1365.3546 cm -1 is the bending vibration of N-H, 1468.0454 cm -1 and 1340.7666 cm -1 are the symmetric and antisymmetric stretching vibrations of -COO - ion, proving that zinc norbornenedodecanamide acid is generated.

[0044] Example 1 The embodiment provides a preparation method of a recyclable polypropylene high-voltage direct-current cable insulation material added with zinc norbornenedodecanamide acid.

[0045] 40 g of polypropylene was added into a banbury mixer, melted at 200 degrees Celsius, and the rotation speed was 50 r / min, after the polypropylene was melted, the polypropylene was primarily mixed for 5 min, then 0.16 g of zinc norbornenedodecanamide acid was added, and the mixing was carried out at the same temperature and rotation speed for 10 min, in the process of melt blending, the zinc norbornenedodecanamide acid was thermally decomposed into aryl zinc oxide nanoparticles, and the aryl zinc oxide nanoparticles were uniformly dispersed in the polypropylene molecular chain, thereby obtaining the recyclable polypropylene high-voltage direct-current cable insulation material added with zinc norbornenedodecanamide acid.

[0046] The recyclable polypropylene high-voltage direct-current cable insulation material added with zinc norbornenedodecanamide acid in the embodiment was subjected to liquid nitrogen brittle fracture, and a scanning electron microscope image of the fracture surface was observed, as shown in Figure 2 . It can be seen from the figure that the aryl zinc oxide nanoparticles are uniformly dispersed in the polypropylene, and the compatibility between the aryl zinc oxide nanoparticles and the polypropylene is good.

[0047] Example 2 Compared with example 1, the difference of the embodiment is that the addition amount of zinc norbornenedodecanamide acid is 0.32 g.

[0048] The cross-section scanning electron microscope image of the recyclable polypropylene high-voltage direct current cable insulating material added with zinc norbornenedodecanoate in the embodiment is shown in Figure 3 As can be seen from the figure, the nano aryl zinc oxide particles are uniformly dispersed in the polypropylene, and the compatibility between the nano aryl zinc oxide particles and the polypropylene is good.

[0049] Comparative Example 1 The present comparative example provides a recyclable polypropylene high-voltage direct current cable insulating material added with nano zinc oxide.

[0050] 40 g of polypropylene was added to an internal mixer and melted at 200°C at a speed of 50 r / min. After melting, it was preliminarily mixed for 5 min, and 0.16 g of nano zinc oxide was added. The mixture was mixed at the same temperature and speed for 10 min. During the melting and blending process, the nano zinc oxide was dispersed in the polypropylene molecular chain, and a recyclable polypropylene high-voltage direct current cable insulating material added with nano zinc oxide was obtained.

[0051] The recyclable polypropylene high-voltage direct current cable insulating material added with nano zinc oxide prepared in the present comparative example was subjected to liquid nitrogen brittle fracture, and the cross-section scanning electron microscope image thereof was observed, as shown in Figure 4 As can be seen from the figure, the nano zinc oxide particles are aggregated in the polypropylene and are not uniformly dispersed, and there is an obvious interface between them, indicating poor compatibility.

[0052] Comparative Example 2 The present comparative example provides a method for preparing a recyclable polypropylene high-voltage direct current cable insulating material without additives.

[0053] 40 g of polypropylene was added to an internal mixer and melted at 200°C at a speed of 50 r / min. After melting, it was mixed for 15 min, and a recyclable polypropylene high-voltage direct current cable insulating material without additives was obtained.

[0054] The polypropylene high-voltage direct current cable insulating material of the present comparative example was subjected to liquid nitrogen brittle fracture, and the cross-section scanning electron microscope image thereof was observed, as shown in Figure 5 As can be seen from the figure, the surface is relatively smooth.

[0055] Test Example The recyclable polypropylene high-voltage direct current cable insulating materials of Examples 1-2 and Comparative Examples 1-2 were prepared into film samples with a thickness of 300 μm, and space charge density distribution tests were performed. A -40 kV / mm direct current electric field was applied, and the space charge density distribution of the sample was measured at intervals of 5 s within 60 min of pressurization. The experimental results of Examples 1, 2, Comparative Example 1 and Comparative Example 2 are shown in Figure 6 , Figure 7 , Figure 8 , Figure 9As shown; then, the space charge density distribution of the sample space is measured at intervals of 3s within 30min of short circuit, as shown in Figure 10 , Figure 11 , Figure 12 and Figure 13 .

[0056] It can be known from the analysis that, after the de-pressurized short circuit, at 6s, the space charge density at the electrode of the material of Example 1 is about 5C·m -3 ; the space charge density at the electrode of the material of Example 2 is about 8C·m -3 ; the space charge density at the electrode of the material of Comparative Example 1 is about 12C·m -3 ; and the space charge density at the electrode of the material of Comparative Example 2 is about 20C·m -3 , and it can be seen that the space charge short-circuit dissipation of the materials of Example 1 and Example 2 is faster, and the space charge density at the electrode at 300s is about 2C·m -3 ; while the space charge densities of the material of Comparative Example 1 and the pure polypropylene material of Comparative Example 2 at 300s are not much different from the initial space charge density, which indicates that the space charge accumulation phenomenon of the materials is more serious, while the materials of Example 1 and Example 2 of the present application can significantly improve the space charge accumulation phenomenon of the polypropylene material. In addition, the material does not need to be cross-linked in the preparation process, and is a recyclable thermoplastic material.

[0057] The above merely provides preferred embodiments of the present application but is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A recyclable polyolefin high-voltage DC cable insulation material, characterized in that, Its raw materials include the following components in parts by weight: 100 parts thermoplastic polyolefin and 0.01~2 parts norbornene dodecanoate zinc.

2. The recyclable polyolefin high-voltage DC cable insulation material as described in claim 1, characterized in that, Its raw materials include the following components in parts by weight: 100 parts thermoplastic polyolefin and 0.05~1 parts norbornene dodecanoate zinc.

3. The recyclable polyolefin high-voltage DC cable insulation material as described in claim 1, characterized in that, The thermoplastic polyolefin is selected from one or more of polyethylene, polypropylene, and ethylene-propylene copolymer.

4. The method for preparing recyclable polyolefin high-voltage DC cable insulation material according to any one of claims 1 to 3, characterized in that, Includes the following steps: After melting thermoplastic polyolefin, zinc norbornene dodecanoate is added and mixed to obtain recyclable polyolefin high-voltage DC cable insulation material.

5. The preparation method according to claim 4, characterized in that, In the mixing step, the mixing temperature is 120~220℃ and the mixing time is 8~30min.

6. The preparation method according to claim 4, characterized in that, After the thermoplastic polyolefin is melted, it is initially kneaded for 3-8 minutes, and then zinc norbornene dodecanoate is added.

7. The preparation method according to claim 4, characterized in that, The zinc norbornene dodecanoate is obtained by reacting norbornene dodecanoate with a strong base first, and then with a zinc salt.

8. The preparation method according to claim 7, characterized in that, The strong base is selected from one or more of NaOH, KOH, LiOH, sodium methoxide, or sodium ethoxide, and the zinc salt is selected from one or more of zinc chloride, zinc sulfate, zinc nitrate, zinc acetate, or zinc carbonate.

9. The preparation method according to claim 7, characterized in that, The norbornene dodecanoic acid is obtained by reacting norbornene anhydride with dodecylamine.

10. The preparation method according to claim 9, characterized in that, The reaction temperature of norborneol olefinic anhydride with dodecylamine is 10~40℃, the reaction time is 1~5h, and the solvent is toluene or xylene.

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