A silane cross-linked insulating material for 35kV cables and a preparation method thereof

Abstract

The present application relates to the technical field of power cable insulation materials, and specifically discloses a 35kV cable silane cross-linked insulating material and a preparation method. A 35kV cable silane cross-linked insulating material, on the basis of polyethylene, adds ethylene propylene rubber, polyethylene octene co-elastic body, compatibilizer, improves cross-linking performance, by adding PEMAGMA, (E)-octane-4-enedioic acid, by double bond polymerization, epoxy and carboxyl polymerization, further improves the degree of cross-linking, achieves insulation performance and heat resistance, mechanical properties and electrical properties of the joint promotion, by adding fumed silica, in addition to improving dispersibility, the coupling effect of silane coupling agent can also play a role in connecting organic insulating matrix and inorganic nanoparticles, improve insulation performance. The cable silane cross-linked insulating material prepared in this application has high degree of cross-linking, insulation performance, heat resistance, mechanical properties and electrical properties, and meets the use requirements of 35kV voltage level.

Description

Technical Field

[0001] The present application relates to the technical field of power cable insulation materials, and more specifically, to a silane cross-linked insulation material for 35kV cables and a preparation method thereof. Background Art

[0002] With the continuous development of the electric power industry, the performance requirements for cable insulation materials are getting higher and higher. Traditional insulation materials may have problems such as insufficient electrical performance and poor heat resistance under high voltage environments. Silane cross-linked insulation materials have excellent electrical properties, heat resistance and mechanical properties, and have been widely used in the field of power cables. Compared with peroxide cross-linking and radiation cross-linking, silane cross-linking production equipment is simple, equipment operation is simple, occupies less space, and has low comprehensive cost. It dominates the low-voltage power cable industry. Existing silane cross-linked polyethylene insulation materials are widely used as the main materials for the insulation layer of power cables of 10kV and below. However, when used for 35kV voltage levels, there are problems such as insufficient cross-linking degree and unstable insulation performance. Summary of the invention

[0003] In order to further improve the insulation and stability of silane cross-linked insulating materials, the present application provides a silane cross-linked insulating material for 35kV cables and a preparation method thereof.

[0004] In the first aspect, the present application provides a silane cross-linked insulation material for 35kV cables, which adopts the following technical solution:

[0005] A silane cross-linked insulating material for 35kV cables, comprising material A and material B, wherein the weight ratio of material A to material B is (80-90):(10-20); material A is composed of the following raw materials in parts by weight: 40 parts of polyethylene, 10-20 parts of ethylene-propylene rubber, 35-38 parts of polyethylene-octene co-elastomer, 0.3-0.5 parts of (E)-oct-4-enedioic acid, 2-5 parts of a compatibilizer, 1.5-2.0 parts of a silane coupling agent, and 0.1-0.2 parts of an initiator; material B is composed of the following raw materials in parts by weight: 70-80 parts of polyethylene , poly(ethylene-co-methyl acrylate-co-glycidyl methacrylate) (hereinafter abbreviated as PEMAGMA) 32-56 parts, polyethylene octene co-elastomer 20-25 parts, antioxidant 5-10 parts, anti-copper agent 0.5-1 part, rheological agent 1-2 parts, auxiliary dispersant 2-5 parts, catalyst 0.3-0.5 parts, zinc acetate 0.027-0.42 parts; the silane coupling agent is vinyl trimethoxy silane; the auxiliary dispersant is fumed silica powder with a particle size of less than 200 microns.

[0006] By adopting the above technical scheme, with polyethylene, ethylene propylene rubber, polyethylene octene co-elastomer and PEMAGMA as the main raw materials, the production and processing efficiency can be effectively improved through process control, and high-speed extrusion and high cross-linking can be achieved. The prepared cable silane cross-linked insulation material has a high degree of cross-linking, which can effectively improve the insulation performance and heat resistance, and has excellent mechanical and electrical properties, meeting the use requirements of 35kV voltage level.

[0007] Preferably, the polyethylene is a linear low-density polyethylene with a melt index ranging from 4 to 8 g / 10 min.

[0008] By adopting the above technical solution, the linear low-density polyethylene has good insulation properties and fewer short chain branches, which is beneficial to improving its extrusion process performance.

[0009] Preferably, the EPDM rubber is semi-crystalline EPDM rubber, wherein the mass percentage of ethylene is 60-75%.

[0010] By adopting the above technical scheme, EPDM rubber is a copolymer of ethylene, propylene and a small amount of non-conjugated dienes, the main chain of which is composed of chemically stable saturated hydrocarbons, and only the side chains contain unsaturated double bonds. Adding them can improve its ozone resistance, heat resistance, weather resistance and other aging resistance.

[0011] Preferably, the polyethylene-octene co-elastomer is a transparent grade polyolefin elastomer with a melt index ranging from 4 to 10 g / 10 min.

[0012] By adopting the above technical solution, the internal crystallization condition is effectively improved, the crystal to amorphous state is reasonably transitioned, and the water tree phenomenon is effectively improved.

[0013] Preferably, the compatibilizer is ethylene butyl acrylate, and the melt index range is 10-15 g / 10 min; the melt index of the poly(ethylene-co-methyl acrylate-co-glycidyl methacrylate) is 6-8 g / 10 min, wherein the content of glycidyl methacrylate is 8-10 wt%.

[0014] By adopting the above technical scheme, the compatibility between raw materials such as polyethylene, ethylene propylene rubber, polyethylene octene co-elastomer, etc. can be improved, the uniformity of the blending system can be improved, the phase separation can be reduced, the cross-linking reaction speed can be increased, and its comprehensive performance can be improved.

[0015] Preferably, the initiator is one of dicumyl peroxide, tert-butyl benzoyl peroxide, di-tert-butyl dicumyl peroxide, or a mixture of the above.

[0016] By adopting the above technical solution, silane grafting is initiated by adding an initiator.

[0017] Preferably, the antioxidant is one or a mixture of antioxidant 1010, antioxidant 1035, tris(2,4-di-tert-butylphenyl)phosphite, and didodecyl thiodipropionate.

[0018] By adopting the above technical solution and adding antioxidants, the self-oxidation reaction rate of the cross-linked polyethylene insulation layer can be slowed down, and the aging and degradation of the silane cross-linked insulation material can be slowed down, thereby effectively improving its service life.

[0019] Preferably, the anti-copper agent is 1,2-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine; the rheological agent is an organic fluorine polymer; and the catalyst is dibutyltin dilaurate.

[0020] By adopting the above technical scheme, using 1,2-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine as an anti-copper agent can effectively inhibit the catalytic aging ability of the dibutyltin dilaurate catalyst; using an organic fluorine polymer as a rheological agent can effectively improve the extrusion fluidity in the preparation process, and the product molding is more stable; using dibutyltin dilaurate as a catalyst can significantly shorten the cross-linking time and have higher production efficiency.

[0021] In a second aspect, the present application provides a method for preparing the above-mentioned silane cross-linked insulation material for 35kV cables.

[0022] A method for preparing a 35 kV cable silane cross-linked insulating material comprises the following steps:

[0023] S1, prepare material A: pre-mix the initiator and the silane coupling agent to obtain a silane mixed liquid; weigh polyethylene, ethylene-propylene rubber, polyethylene-octene co-elastomer, (E)-oct-4-enedioic acid, and compatibilizer in proportion and add them into a high-speed mixer, then slowly add the silane mixed liquid, stir evenly, and then add it into a twin-screw extruder (the temperature setting of each zone of the screw extruder is gradually increased from 110-130°C to 190-210°C, and the aspect ratio is (40-42):1), blend and connect. S2, preparation of material B: polyethylene, poly (ethylene-co-methyl acrylate-co-glycidyl methacrylate), polyethylene octene co-elastomer, antioxidant, anti-copper agent, rheological agent, auxiliary dispersant, catalyst, zinc acetate are mixed in proportion, added into a twin screw (the temperature setting of each zone of the screw extruder is gradually increased from 110-130°C to 150-170°C, the aspect ratio is (40-42): 1), extrusion, granulation, and drying;

[0024] S3, when used, mix material A and material B, mix them evenly in a blending device, feed them into a screw extruder (the temperature setting of each zone of the screw extruder is gradually increased from 110-130℃ to 170-190℃, and the aspect ratio is (40-42):1) for extrusion molding, and steam cross-link at 90-100℃ for 8-10h.

[0025] In summary, this application has the following beneficial effects:

[0026] 1. This application uses polyethylene, ethylene-propylene rubber, polyethylene-octene co-elastomer, and poly(ethylene-co-methyl acrylate-co-glycidyl methacrylate) as main raw materials, and through reasonable compatibility and process control, effectively improves production and processing efficiency, achieves high-speed extrusion and high cross-linking. The prepared cable silane cross-linked insulation material has a high degree of cross-linking, can effectively improve insulation performance and heat resistance, and has excellent mechanical and electrical properties, meeting the use requirements of 35kV voltage level.

[0027] 2. In this application, on the basis of traditional polyethylene as raw material, ethylene-propylene rubber, polyethylene-octene co-elastomer and compatibilizer are added to improve the crosslinking performance. By adding poly (ethylene-co-methyl acrylate-co-glycidyl methacrylate), (E)-oct-4-enedioic acid, double bond polymerization, epoxy group and carboxyl group polymerization, the crosslinking degree is further improved to achieve the improvement of insulation performance and heat resistance, mechanical performance and electrical performance. By adding fumed silica, in addition to improving the dispersibility, the coupling effect of the silane coupling agent can also play a role in connecting the organic insulating matrix and the inorganic nanoparticles, thereby improving the insulation performance.

[0028] 3. The cable silane cross-linked insulation material prepared by the preparation method of the present application has excellent comprehensive performance and meets the use requirements of 35kV voltage level. DETAILED DESCRIPTION

[0029] The present application is further described in detail below with reference to the embodiments.

[0030] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present application are all commercially available. Example Example 1

[0031] A silane cross-linked insulation material for 35 kV cables, comprising material A and material B, wherein the weight ratio of material A to material B is 90:10;

[0032] Material A is composed of the following raw materials by weight:

[0033] Polyethylene 40 parts

[0034] 10 parts of EPDM

[0035] 38 parts of polyethylene octene copolymer

[0036] (E)-Oct-4-enedioic acid 0.3 parts

[0037] 2 parts of compatibilizer

[0038] Silane coupling agent 2.0 parts

[0039] Initiator 0.2 parts

[0040] Material B is composed of the following raw materials by weight:

[0041] Polyethylene 75 parts

[0042] PEMAGMA 54 parts

[0043] 25 parts of polyethylene octene copolymer

[0044] 10 parts antioxidant

[0045] 1 part of anti-copper agent

[0046] 2 parts rheological agent

[0047] 5 parts auxiliary dispersant

[0048] 0.5 parts of catalyst

[0049] 0.027 parts of zinc acetate;

[0050] The silane coupling agent is vinyl trimethoxy silane; the auxiliary dispersant is fumed silica powder with a particle size of 180 microns.

[0051] The polyethylene is a linear low-density polyethylene with a melt index range of 4 g / 10 min;

[0052] The EPDM rubber is a semi-crystalline EPDM rubber, wherein the mass percentage of ethylene is 70%;

[0053] The polyethylene octene co-elastomer is a transparent grade polyolefin elastomer with a melt index range of 7g / 10min;

[0054] The compatibilizer is ethylene butyl acrylate, and the melt index range is 10g / 10min;

[0055] The PEMAGMA has a melt index of 6 g / 10 min, wherein the content of glycidyl methacrylate is 8 wt %;

[0056] The initiator is dicumyl peroxide;

[0057] The antioxidant is antioxidant 1010;

[0058] The anti-copper agent is 1,2-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine;

[0059] The rheological agent is an organic fluorine polymer;

[0060] The catalyst is dibutyltin dilaurate.

[0061] A silane cross-linked insulation material for 35kV cables is prepared by the following steps:

[0062] S1, preparing material A: premixing the initiator and the silane coupling agent to obtain a silane mixed liquid; weighing polyethylene, ethylene-propylene rubber, polyethylene-octene co-elastomer, (E)-oct-4-enedioic acid, and a compatibilizer in proportion and adding them into a high-speed mixer, then slowly adding the silane mixed liquid, stirring evenly, and then adding the mixture into a twin-screw extruder (the temperature setting of each zone of the screw extruder is gradually increased from 110° C. to 190° C., and the aspect ratio is 40:1), blending, grafting, extrusion granulation, drying, and vacuum packaging;

[0063] S2, preparation of material B: polyethylene, PEMAGMA, polyethylene octene co-elastomer, antioxidant, anti-copper agent, rheological agent, auxiliary dispersant, catalyst, and zinc acetate are mixed in proportion, added into a twin-screw extruder (the temperature of each zone of the screw extruder is set to gradually increase from 110°C to 150°C, the aspect ratio is 40:1, extrusion, granulation, and drying;

[0064] S3, when in use, mix material A and material B, mix them evenly in a blending device, feed them into a screw extruder for extrusion molding, and steam cross-link them at 90°C for 10 hours. Example 2

[0065] A silane cross-linked insulation material for 35 kV cables, comprising material A and material B, wherein the weight ratio of material A to material B is 80:20;

[0066] Material A is composed of the following raw materials in parts by weight:

[0067] Polyethylene 40 parts

[0068] 20 parts of EPDM

[0069] 35 parts of polyethylene octene copolymer

[0070] (E)-Oct-4-enedioic acid 0.4 parts

[0071] 3 parts of compatibilizer

[0072] 1.5 parts of silane coupling agent

[0073] Initiator 0.1 part

[0074] Material B is composed of the following raw materials by weight:

[0075] Polyethylene 80 parts

[0076] PEMAGMA 32 parts

[0077] 20 parts of polyethylene octene copolymer

[0078] 5 parts antioxidant

[0079] 0.5 parts of anti-copper agent

[0080] Rheological agent 1 part

[0081] 2 parts auxiliary dispersant

[0082] 0.3 parts of catalyst

[0083] 0.032 parts of zinc acetate;

[0084] The silane coupling agent is vinyl trimethoxy silane; the auxiliary dispersant is fumed silica powder with a particle size of 150 microns;

[0085] The polyethylene is a linear low-density polyethylene with a melt index range of 6 g / 10 min;

[0086] The EPDM rubber is a semi-crystalline EPDM rubber, wherein the mass percentage of ethylene is 60%;

[0087] The polyethylene octene co-elastomer is a transparent grade polyolefin elastomer with a melt index range of 4g / 10min;

[0088] The compatibilizer is ethylene butyl acrylate, and the melt index range is 12g / 10min;

[0089] The melt index of the PEMAGMA is 7 g / 10 min, wherein the content of glycidyl methacrylate is 9 wt %;

[0090] The initiator is tert-butyl benzoyl peroxide;

[0091] The antioxidant 1035;

[0092] The anti-copper agent is 1,2-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine;

[0093] The rheological agent is an organic fluorine polymer;

[0094] The catalyst is dibutyltin dilaurate.

[0095] A silane cross-linked insulation material for 35kV cables is prepared by the following steps:

[0096] S1, preparing material A: premixing the initiator and the silane coupling agent to obtain a silane mixed liquid; weighing polyethylene, ethylene-propylene rubber, polyethylene-octene co-elastomer, (E)-oct-4-enedioic acid, and a compatibilizer in proportion and adding them into a high-speed mixer, then slowly adding the silane mixed liquid, stirring evenly, and then adding the mixture into a twin-screw extruder (the temperature setting of each zone of the screw extruder is gradually increased from 120°C to 200°C, and the aspect ratio is 41:1), blending, grafting, extrusion granulation, drying, and vacuum packaging;

[0097] S2, preparation of material B: polyethylene, PEMAGMA, polyethylene octene co-elastomer, antioxidant, anti-copper agent, rheological agent, auxiliary dispersant, catalyst, and zinc acetate are mixed in proportion, added into a twin-screw extruder (the temperature setting of each zone of the screw extruder is gradually increased from 120°C to 160°C, and the aspect ratio is 41:1), extruded, granulated, and dried;

[0098] S3, when in use, mix material A and material B, mix them evenly in a blending device, feed them into a screw extruder for extrusion molding, and steam cross-link them at 95°C for 9h. Example 3

[0099] A silane cross-linked insulation material for 35 kV cables, comprising material A and material B, wherein the weight ratio of material A to material B is 85:15;

[0100] Material A is composed of the following raw materials in parts by weight:

[0101] Polyethylene 40 parts

[0102] 15 parts of EPDM

[0103] 36 parts of polyethylene octene copolymer

[0104] (E)-Oct-4-enedioic acid 0.5 parts

[0105] Compatibilizer 5 parts

[0106] Silane coupling agent 1.8 parts

[0107] Initiator 0.15 parts

[0108] Material B is composed of the following raw materials by weight:

[0109] Polyethylene 80 parts

[0110] PEMAGMA 56 parts

[0111] 23 parts of polyethylene octene copolymer

[0112] 8 parts antioxidant

[0113] 0.8 parts of anti-copper agent

[0114] Rheological agent 1.5 parts

[0115] 3 parts auxiliary dispersant

[0116] 0.4 parts of catalyst

[0117] 0.42 parts of zinc acetate;

[0118] The silane coupling agent is vinyl trimethoxy silane; the auxiliary dispersant is fumed silica powder with a particle size of 100 microns;

[0119] The polyethylene is a linear low-density polyethylene with a melt index range of 8 g / 10 min;

[0120] The EPDM rubber is a semi-crystalline EPDM rubber, wherein the mass percentage of ethylene is 75%;

[0121] The polyethylene octene co-elastomer is a transparent grade polyolefin elastomer with a melt index range of 10g / 10min;

[0122] The compatibilizer is ethylene butyl acrylate, and the melt index range is 15g / 10min;

[0123] The PEMAGMA has a melt index of 8 g / 10 min, wherein the content of glycidyl methacrylate is 10 wt %;

[0124] The initiator is diisopropylbenzene di-tert-butyl peroxide;

[0125] The antioxidant is tris(2,4-di-tert-butylphenyl)phosphite;

[0126] The anti-copper agent is 1,2-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine;

[0127] The rheological agent is an organic fluorine polymer;

[0128] The catalyst is dibutyltin dilaurate.

[0129] A silane cross-linked insulation material for 35kV cables is prepared by the following steps:

[0130] S1, preparing material A: premixing the initiator and the silane coupling agent to obtain a silane mixed liquid; weighing polyethylene, ethylene-propylene rubber, polyethylene-octene co-elastomer, (E)-oct-4-enedioic acid, and a compatibilizer in proportion and adding them into a high-speed mixer, then slowly adding the silane mixed liquid, stirring evenly, and then adding the mixture into a twin-screw extruder (the temperature setting of each zone of the screw extruder is gradually increased from 130° C. to 210° C., and the aspect ratio is 42:1), blending, grafting, extrusion granulation, drying, and vacuum packaging;

[0131] S2, preparation of material B: polyethylene, PEMAGMA, polyethylene octene co-elastomer, antioxidant, anti-copper agent, rheological agent, auxiliary dispersant, catalyst, and zinc acetate are mixed in proportion, added into a twin screw (the temperature setting of each zone of the screw extruder is gradually increased from 130°C to 170°C, and the aspect ratio is 42:1), extruded, granulated, and dried;

[0132] S3, when in use, mix material A and material B, mix them evenly in a blending device, feed them into a screw extruder for extrusion molding, and steam cross-link them at 100°C for 8 hours. Comparative Example

[0133] Comparative Example 1

[0134] The same as Example 2, except that (E)-oct-4-enedioic acid is not added to material A, and PEMAGMA and zinc acetate are not added to material B.

[0135] Comparative Example 2

[0136] The same as Example 2, except that the addition amount of (E)-oct-4-enedioic acid in material A is adjusted to 0.6 parts, the addition amount of PEMAGMA in material B is adjusted to 48 parts, and the addition amount of zinc acetate is adjusted to 0.048 parts.

[0137] Comparative Example 3

[0138] The same as Example 2, except that the preparation method of material A is as follows: polyethylene, ethylene-propylene rubber, polyethylene-octene co-elastomer, (E)-oct-4-enedioic acid, a compatibilizer, an initiator, and a silane coupling agent are weighed in proportion and added to a high-speed mixer, and then the silane mixed liquid is slowly added and stirred evenly, and then added to a twin-screw extruder (the temperature setting of each zone of the screw extruder is gradually increased from 130° C. to 210° C., and the aspect ratio is 42:1), blending, grafting, extrusion granulation, drying, and vacuum packaging.

[0139] Comparative Example 4

[0140] The same as Example 2, except that no auxiliary dispersant fumed silica powder is added to Material A.

[0141] Performance testing

[0142] The above embodiments and comparative examples were tested and judged according to the method and performance requirements of industry standard JB / T 10437 and GB / T 12706.1. The test data are shown in Table 1:

[0143] Table 1. Performance test results

[0144] performance unit standard Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Tensile Strength MPa ≥13.5 25.2 23.4 24.1 12.5 16.2 21.7 22.3 Elongation at break % ≥350.2 680.3 650.6 670.4 380.1 460.3 570.4 610.3 Thermal aging test Maximum change rate of tensile strength Maximum change rate of elongation at break %% ≤20≤20 8.512.2 13.19.4 10.311.7 23.419.1 20.617.4 18.315.3 15.512.1 Hot stretching test Maximum elongation Permanent deformation after cooling %% ≤80≥5 55.22.5 78.34.8 63.23.2 101.715.1 92.311.6 87.48.3 80.26.8 Failure number of low temperature impact embrittlement test ℃ ≤15 / 30 0.27 0.33 0.31 0.62 0.54 0.57 0.55 Volume resistivity Ω·m <![CDATA[≥1.0×10 14 ]]> <![CDATA[5.4×10 14 ]]> <![CDATA[4.2×10 14 ]]> <![CDATA[4.8×10 14 ]]> <![CDATA[3.6×10 13 ]]> <![CDATA[5.2×10 13 ]]> <![CDATA[9.4×10 13 ]]> <![CDATA[4.3×10 13 ]]> Relative dielectric constant — ≤2.35 1.78 1.65 1.72 3.16 2.98 2.54 2.73 Dielectric strength MV / m ≥25 31.2 30.4 31.8 27.3 28.2 29.8 26.5 Dielectric loss factor — <![CDATA[≤5.0×10 -4 ]]> <![CDATA[1.4×10 -4 ]]> <![CDATA[3.5×10 -4 ]]> <![CDATA[2.2×10 -4 ]]> <![CDATA[1.2×10 -4 ]]> <![CDATA[2.4×10 -4 ]]> <![CDATA[1.8×10 -4 ]]> <![CDATA[8.2×10 -3 ]]>

[0145] It can be seen from Table 1 that, compared with Comparative Examples 1 to 4, the cable silane cross-linked insulation materials prepared in Examples 1 to 3 of the present application have excellent properties and meet the requirements of 35kV cable silane cross-linked insulation materials.

[0146] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, a person skilled in the art may make non-creative modifications to the present embodiment as needed, and such modifications shall be protected by the patent law as long as they are within the scope of protection claimed in the present application.

Claims

1. A silane cross-linked insulation material for 35kV cables, characterized in that: The invention comprises material A and material B, wherein the weight ratio of material A to material B is (80-90): (10-20); material A is composed of the following raw materials in parts by weight: 40 parts of polyethylene, 10-20 parts of ethylene-propylene rubber, 35-38 parts of polyethylene-octene co-elastomer, 0.3-0.5 parts of (E)-oct-4-enedioic acid, 2-5 parts of compatibilizer, 1.5-2.0 parts of silane coupling agent, and 0.1-0.2 parts of initiator; material B is composed of the following raw materials in parts by weight: 70- 80 parts, poly(ethylene-co-methyl acrylate-co-glycidyl methacrylate) 32-56 parts, polyethylene octene co-elastomer 20-25 parts, antioxidant 5-10 parts, anti-copper agent 0.5-1 part, rheological agent 1-2 parts, auxiliary dispersant 2-5 parts, catalyst 0.3-0.5 parts, zinc acetate 0.027-0.42 parts; the silane coupling agent is vinyl trimethoxy silane; the auxiliary dispersant is fumed silica powder.

2. The silane cross-linked insulating material for 35kV cable according to claim 1, characterized in that: The polyethylene is a linear low-density polyethylene with a melt index range of 4-8 g / 10 min.

3. The silane cross-linked insulating material for 35kV cable according to claim 2, characterized in that: The EPDM rubber is semi-crystalline EPDM rubber, wherein the mass percentage of ethylene is 60-75%.

4. The silane cross-linked insulating material for 35kV cable according to claim 3, characterized in that: The polyethylene-octene co-elastomer is a transparent grade polyolefin elastomer with a melt index range of 4-10 g / 10 min.

5. The silane cross-linked insulating material for 35kV cable according to claim 4, characterized in that: The compatibilizer is ethylene butyl acrylate copolymer, and the melt index range is 10-15g / 10min; the melt index of the poly(ethylene-co-methyl acrylate-co-glycidyl methacrylate) is 6-8g / 10 min, wherein the content of glycidyl methacrylate is 8-10wt%.

6. The silane cross-linked insulating material for 35kV cable according to claim 5, characterized in that: The initiator is one of dicumyl peroxide, tert-butyl benzoyl peroxide, di-tert-butyl dicumyl peroxide or a mixture of the above.

7. The silane cross-linked insulating material for 35kV cable according to claim 6, characterized in that: The antioxidant is one of antioxidant 1010, antioxidant 1035, tris(2,4-di-tert-butylphenyl)phosphite, and didodecyl thiodipropionate or a mixture thereof.

8. The silane cross-linked insulating material for 35kV cable according to claim 7, characterized in that: The anti-copper agent is 1,2-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine; the rheological agent is an organic fluorine polymer; and the catalyst is dibutyltin dilaurate.

9. A method for preparing a silane cross-linked insulation material for 35 kV cables according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1, preparing material A: premixing the initiator and the silane coupling agent to obtain a silane mixed liquid; weighing polyethylene, ethylene-propylene rubber, polyethylene-octene co-elastomer, (E)-oct-4-enedioic acid, and a compatibilizer in proportion and adding them into a high-speed mixer, then slowly adding the silane mixed liquid, stirring evenly, and then adding the mixture into a twin-screw extruder, blending, grafting, extruding granulation, drying, and vacuum packaging; S2, preparing material B: polyethylene, poly(ethylene-co-methyl acrylate-co-glycidyl methacrylate), polyethylene-octene co-elastomer, antioxidant, anti-copper agent, rheological agent, auxiliary dispersant, catalyst, and zinc acetate are mixed in proportion, added into a twin-screw extruder, granulated, and dried; S3, when in use, mix material A and material B, mix them evenly in a blending device, feed them into a screw extruder for extrusion molding, and steam cross-link them at 90-100°C for 8-10h.

10. The method for preparing silane cross-linked insulation material for 35kV cables according to claim 9, characterized in that: In S1, the temperature setting of each zone of the screw extruder is gradually increased from 110-130°C to 190-210°C, and the length-to-diameter ratio is (40-42):1; in S2, the temperature setting of each zone of the screw extruder is gradually increased from 110-130°C to 150-170°C, and the length-to-diameter ratio is (40-42):1.