A halogen-free flame-retardant semi-conductive shielded cable material

Abstract

The present invention provides a halogen-free flame-retardant semi-conductive shielded cable material, belonging to the technical field of cable material preparation. The cable material raw materials include 40 to 55 parts of low-density polyethylene, 75 to 92 parts of ethylene-vinyl acetate copolymer, 75 to 85 parts of mesoporous SiO₂ loaded with a conductive agent and a flame retardant, 2 to 4 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2 to 6 parts of zinc stearate, and 5 to 8 parts of epoxidized soybean oil; the mesoporous SiO₂ loaded with a conductive agent and a flame retardant is made from the following raw materials: single-walled carbon nanotubes, graphene nanosheets, conductive carbon black, sodium dodecylbenzenesulfonate, melamine phosphate, zinc borate, and modified mesoporous SiO₂; the modified mesoporous SiO₂ is prepared by using γ-aminoethylaminopropyltrimethoxysilane and alkyl glycoside as modifiers. The present invention has good flame retardancy, high strength, and good electrical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of cable material preparation, in particular to a halogen-free flame-retardant semi-conductive shielded cable material. Background Art

[0002] Common base materials for the semi-conductive shielding layer of flame-retardant cables include polyethylene (PE), cross-linked polyethylene (XLPE), ethylene propylene rubber (EPR), etc. Among them, polyethylene has good electrical insulation properties and processing properties and is suitable for medium and high voltage cables.

[0003] Existing flame-retardant cable semi-conductive shielding materials generally add bromine-based or chlorine-based halogen-containing flame retardants to the base material. Although these materials have a good flame retardant effect, they release toxic and corrosive gases such as HBr under high temperature conditions, which can be harmful to the environment and human health. Some technicians are currently trying to use halogen-free flame retardants such as aluminum hydroxide and magnesium hydroxide to replace halogen-containing flame retardants. However, these flame retardants need to be added in large quantities to meet the flame retardant requirements, resulting in a high volume resistivity of the cable material, which is difficult to meet the low volume resistivity requirements of the semi-conductive shielding layer of medium and high voltage cables. In addition, to achieve good conductivity of the semi-conductive shielding layer, 36-50wt% of carbon black is usually required when producing shielded cable materials according to traditional processes. However, a high proportion of carbon black will result in poor processing performance of the cable material, a rough surface, and easy to cause partial discharge.

[0004] From the above, it can be seen that the current semi-conductive shielding layer of flame-retardant cables still has problems such as poor environmental protection, insufficient mechanical properties, and high surface roughness. Summary of the Invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a halogen-free flame-retardant semi-conductive shielded cable material and achieves the following invention objectives: to prepare a halogen-free, flame-retardant, low-surface-roughness, and good-mechanical-property semi-conductive shielded cable material.

[0006] To achieve the above objectives, the technical solutions adopted are as follows:

[0007] A halogen-free flame-retardant semi-conductive shielded cable material, the raw materials of which include a base material and auxiliary materials; the base material includes low-density polyethylene and ethylene-vinyl acetate copolymer; the auxiliary materials include mesoporous SiO2 loaded with a conductive agent and a flame retardant, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], zinc stearate, and epoxy soybean oil.

[0008] The weight ratio of the above raw materials is: 40-55 parts of low-density polyethylene, 75-92 parts of ethylene-vinyl acetate copolymer, 75-85 parts of mesoporous SiO2 loaded with conductive agent and flame retardant, 2-4 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2-6 parts of zinc stearate, and 5-8 parts of epoxidized soybean oil;

[0009] The mesoporous SiO2 loaded with a conductive agent and a flame retardant is made of the following raw materials: single-walled carbon nanotubes, graphene nanosheets, conductive carbon black, sodium dodecylbenzenesulfonate, melamine phosphate, zinc borate, and modified mesoporous SiO2;

[0010] The modified mesoporous SiO2 uses γ-aminoethylaminopropyltrimethoxysilane and alkyl glycoside as modifiers.

[0011] A method for preparing a halogen-free flame-retardant semi-conductive shielded cable material, comprising the steps of preparing modified mesoporous SiO2, loading a conductive agent and a flame retardant, and melt-blending to prepare the cable material;

[0012] The raw materials for preparing the modified mesoporous SiO2 include, in parts by weight: 45-50 parts of ethyl orthosilicate, 2-5 parts of γ-aminoethylaminopropyltrimethoxysilane, 5-7 parts of glacial acetic acid, 150-160 parts of ethanol, 50-60 parts of deionized water, and 3-5 parts of alkyl glycoside.

[0013] The modified mesoporous SiO2 is prepared by mixing and stirring ethyl orthosilicate, ethanol, glacial acetic acid and deionized water, and hydrolyzing to generate a uniform and transparent SiO2 sol; adding γ-aminoethylaminopropyltrimethoxysilane to the SiO2 sol, and ultrasonically treating the sol at a frequency of 26 kHz at 70-90°C for 2-4 hours; then adding alkyl glycoside, continuing the ultrasonic treatment for 1-2 hours, and then centrifuging to retain the solid phase; and calcining the solid phase to obtain the modified mesoporous SiO2.

[0014] The calcination is carried out at 500-600° C. for 3-6 hours.

[0015] The loaded conductive agent and flame retardant, in parts by weight, include the following raw materials: 2-4 parts of single-walled carbon nanotubes, 2-5 parts of graphene nanosheets, 4-6 parts of conductive carbon black, 0.02-0.05 parts of sodium dodecylbenzenesulfonate, 60-70 parts of modified mesoporous SiO2, 10-15 parts of melamine phosphate, and 5-9 parts of zinc borate.

[0016] The method comprises the following steps: placing single-walled carbon nanotubes, graphene nanosheets, conductive carbon black, and sodium dodecylbenzenesulfonate into N,N-dimethylformamide, and ultrasonically treating the mixture at a frequency of 32kHz for 2 to 3 hours; then adding modified mesoporous SiO2, melamine phosphate, and zinc borate, and stirring the mixture to obtain a mixed solution; ultrasonically dispersing the mixture at 32kHz for 1 to 2 hours, filtering the mixture after the ultrasonic dispersion, and retaining a solid; and vacuum drying the solid to obtain mesoporous SiO2 loaded with a conductive agent and a flame retardant.

[0017] The cable material is prepared by melt blending, and the raw materials include, in parts by weight, 40-55 parts of low-density polyethylene, 75-92 parts of ethylene-vinyl acetate copolymer, 75-85 parts of mesoporous SiO2 loaded with a conductive agent and a flame retardant, 2-4 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2-6 parts of zinc stearate, and 5-8 parts of epoxidized soybean oil.

[0018] The cable material is prepared by melt blending: low-density polyethylene, ethylene-vinyl acetate copolymer, mesoporous SiO2 loaded with a conductive agent and a flame retardant, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], zinc stearate, and epoxy soybean oil are mixed, and the mixed materials are added to a twin-screw extruder for melt extrusion to obtain a halogen-free flame-retardant semi-conductive shielded cable material.

[0019] The low-density polyethylene (LDPE) has a density of 0.910-0.925 g / cm³;

[0020] The ethylene-vinyl acetate copolymer (EVA) has a density of 0.91-0.94 g / cm³ and a vinyl acetate content of 30-40 wt%. Beneficial effects

[0021] The present invention provides a halogen-free flame-retardant semi-conductive shielded cable material. Through the innovation of flame-retardant fillers and conductive fillers, the obtained cable material has good flame retardancy and is halogen-free, high strength, low volume resistivity and surface roughness, and good electrical properties. DETAILED DESCRIPTION

[0022] To make the purpose, technical solutions and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0023] Example 1 A halogen-free flame-retardant semi-conductive shielded cable material

[0024] A method for preparing a halogen-free flame-retardant semi-conductive shielded cable material:

[0025] Step 1: Preparation of modified mesoporous SiO2

[0026] The raw materials include, by weight, 45 parts of tetraethyl orthosilicate (TEOS), 2 parts of γ-aminoethylaminopropyltrimethoxysilane (KH-792), 5 parts of glacial acetic acid, 155 parts of ethanol, 52 parts of deionized water, and 3 parts of alkyl polyglycoside (APG).

[0027] TEOS, ethanol, glacial acetic acid and deionized water were mixed and stirred, and hydrolyzed to generate a uniform and transparent SiO2 sol. KH-792 was added to the SiO2 sol, and ultrasonic reaction was carried out at 75°C and 26kHz for 2.5 hours. After the ultrasonic reaction, APG was added and ultrasonic treatment was continued for 1 hour. The material after ultrasonic treatment was centrifuged to retain the solid phase. The solid phase was calcined at 500°C for 6 hours to obtain modified mesoporous SiO2.

[0028] Step 2: Loading conductive agent and flame retardant

[0029] In parts by weight, the raw materials include: 2 parts of single-walled carbon nanotubes (SWCNTs), 4 parts of graphene nanosheets (GNSs), 6 parts of conductive carbon black, 0.04 parts of sodium dodecylbenzenesulfonate (SDBS), 68 parts of modified mesoporous SiO2, 15 parts of melamine phosphate (MPP), and 9 parts of zinc borate (ZB).

[0030] SWCNTs, GNSs, conductive carbon black, and SDBS were put into N,N-dimethylformamide (DMF) and ultrasonically treated at 32kHz for 3h. Modified mesoporous SiO2, MPP, and ZB were then added and stirred for 30min to obtain a mixed solution. The mixed solution was ultrasonically dispersed at 32kHz for 2h. After the ultrasonic dispersion, the mixed solution was filtered to retain the solid, which was then vacuum dried at 80°C for 7h to obtain mesoporous SiO2 loaded with a conductive agent and a flame retardant.

[0031] DMF is a solvent and does not participate in the reaction. The amount used is based on its ability to dissolve the solute.

[0032] Step 3: Melt blending to prepare cable material

[0033] In parts by weight, the raw materials include: 48 parts of low-density polyethylene (LDPE), 90 parts of ethylene-vinyl acetate copolymer (EVA), 83 parts of mesoporous SiO2 loaded with conductive agent and flame retardant, 2 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2 parts of zinc stearate, and 7 parts of epoxidized soybean oil.

[0034] LDPE, EVA, mesoporous SiO2 loaded with a conductive agent and flame retardant, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], zinc stearate, and epoxidized soybean oil were mixed in a high-speed mixer for 15 minutes. The mixed materials were then fed into a twin-screw extruder for melt extrusion to produce a halogen-free, flame-retardant, semi-conductive shielded cable material. The twin-screw extruder temperature was controlled at 150°C in the feed zone, 165°C in the melt zone, 180°C in the mixing zone, and 175°C in the die zone.

[0035] Example 2 A halogen-free flame-retardant semi-conductive shielded cable material

[0036] A method for preparing a halogen-free flame-retardant semi-conductive shielded cable material:

[0037] Step 1: Preparation of modified mesoporous SiO2

[0038] The raw materials include, by weight, 50 parts of tetraethyl orthosilicate (TEOS), 4 parts of γ-aminoethylaminopropyltrimethoxysilane (KH-792), 6 parts of glacial acetic acid, 160 parts of ethanol, 60 parts of deionized water, and 5 parts of alkyl polyglycoside (APG).

[0039] TEOS, ethanol, glacial acetic acid and deionized water were mixed and stirred, and hydrolyzed to generate a uniform and transparent SiO2 sol. KH-792 was added to the SiO2 sol, and ultrasonic reaction was carried out at 70°C and 26kHz for 4 hours. After the ultrasonic reaction, APG was added and ultrasonic treatment was continued for 1 hour. The material after ultrasonic treatment was centrifuged to retain the solid phase. The solid phase was calcined at 550°C for 4 hours to obtain modified mesoporous SiO2.

[0040] Step 2: Loading conductive agent and flame retardant

[0041] In parts by weight, the raw materials include: 4 parts of single-walled carbon nanotubes (SWCNTs), 5 parts of graphene nanosheets (GNSs), 5 parts of conductive carbon black, 0.05 parts of sodium dodecylbenzenesulfonate (SDBS), 70 parts of modified mesoporous SiO2, 12 parts of melamine phosphate (MPP), and 6 parts of zinc borate (ZB).

[0042] SWCNTs, GNSs, conductive carbon black, and SDBS were put into DMF and ultrasonically treated at 32kHz for 2h. Modified mesoporous SiO2, MPP, and ZB were then added and stirred for 30min to obtain a mixed solution. The mixed solution was ultrasonically dispersed at 32kHz for 1h. After the ultrasonic dispersion, the mixed solution was filtered to retain the solid, and the solid was vacuum dried at 80℃ for 8h to obtain mesoporous SiO2 loaded with a conductive agent and a flame retardant.

[0043] DMF is a solvent and does not participate in the reaction. The amount used is based on its ability to dissolve the solute.

[0044] Step 3: Melt blending to prepare cable material

[0045] In parts by weight, the raw materials include: 40 parts of low-density polyethylene (LDPE), 92 parts of ethylene-vinyl acetate copolymer (EVA), 85 parts of mesoporous SiO2 loaded with a conductive agent and a flame retardant, 3 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 4 parts of zinc stearate, and 5 parts of epoxidized soybean oil.

[0046] LDPE, EVA, mesoporous SiO2 loaded with a conductive agent and flame retardant, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], zinc stearate, and epoxidized soybean oil were mixed in a high-speed mixer for 15 minutes. The mixed materials were then fed into a twin-screw extruder for melt extrusion to produce a halogen-free, flame-retardant, semi-conductive shielded cable material. The twin-screw extruder temperature was controlled at 150°C in the feed zone, 165°C in the melt zone, 180°C in the mixing zone, and 175°C in the die zone.

[0047] Example 3 A halogen-free flame-retardant semi-conductive shielded cable material

[0048] A method for preparing a halogen-free flame-retardant semi-conductive shielded cable material:

[0049] Step 1: Preparation of modified mesoporous SiO2

[0050] The raw materials include, by weight, 50 parts of tetraethyl orthosilicate (TEOS), 5 parts of γ-aminoethylaminopropyltrimethoxysilane (KH-792), 7 parts of glacial acetic acid, 160 parts of ethanol, 56 parts of deionized water, and 4 parts of alkyl polyglycoside (APG).

[0051] TEOS, ethanol, glacial acetic acid and deionized water were mixed and stirred, and hydrolyzed to generate a uniform and transparent SiO2 sol. KH-792 was added to the SiO2 sol, and ultrasonic reaction was carried out at 85°C and 26kHz for 3 hours. After the ultrasonic reaction, APG was added and ultrasonic treatment was continued for 1.5 hours. The material after ultrasonic treatment was centrifuged to retain the solid phase. The solid phase was calcined at 600°C for 3 hours to obtain modified mesoporous SiO2.

[0052] Step 2: Loading conductive agent and flame retardant

[0053] In parts by weight, the raw materials include: 3 parts of single-walled carbon nanotubes (SWCNTs), 3 parts of graphene nanosheets (GNSs), 4 parts of conductive carbon black, 0.02 parts of sodium dodecylbenzenesulfonate (SDBS), 60 parts of modified mesoporous SiO2, 11 parts of melamine phosphate (MPP), and 5 parts of zinc borate (ZB).

[0054] SWCNTs, GNSs, conductive carbon black, and SDBS were put into DMF and ultrasonically treated at 32kHz for 2h. Modified mesoporous SiO2, MPP, and ZB were then added and stirred for 30min to obtain a mixed solution. The mixed solution was ultrasonically dispersed at 32kHz for 1h. After the ultrasonic dispersion, the mixed solution was filtered to retain the solid, and the solid was vacuum dried at 80℃ for 8h to obtain mesoporous SiO2 loaded with a conductive agent and a flame retardant.

[0055] DMF is a solvent and does not participate in the reaction. The amount used is based on its ability to dissolve the solute.

[0056] Step 3: Melt blending to prepare cable material

[0057] In parts by weight, the raw materials include: 55 parts of low-density polyethylene (LDPE), 75 parts of ethylene-vinyl acetate copolymer (EVA), 78 parts of mesoporous SiO2 loaded with conductive agent and flame retardant, 2 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 6 parts of zinc stearate, and 8 parts of epoxidized soybean oil.

[0058] LDPE, EVA, mesoporous SiO2 loaded with a conductive agent and flame retardant, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], zinc stearate, and epoxidized soybean oil were mixed in a high-speed mixer for 15 minutes. The mixed materials were then fed into a twin-screw extruder for melt extrusion to produce a halogen-free, flame-retardant, semi-conductive shielded cable material. The twin-screw extruder temperature was controlled at 150°C in the feed zone, 165°C in the melt zone, 180°C in the mixing zone, and 175°C in the die zone.

[0059] Example 4 A halogen-free flame-retardant semi-conductive shielded cable material

[0060] A method for preparing a halogen-free flame-retardant semi-conductive shielded cable material:

[0061] Step 1: Preparation of modified mesoporous SiO2

[0062] The raw materials include, by weight, 48 parts of tetraethyl orthosilicate (TEOS), 4 parts of γ-aminoethylaminopropyltrimethoxysilane (KH-792), 6 parts of glacial acetic acid, 150 parts of ethanol, 50 parts of deionized water, and 3 parts of alkyl polyglycoside (APG).

[0063] TEOS, ethanol, glacial acetic acid and deionized water were mixed and stirred, and hydrolyzed to generate a uniform and transparent SiO2 sol. KH-792 was added to the SiO2 sol, and ultrasonic reaction was carried out at 90°C and 26kHz for 2 hours. After the ultrasonic reaction, APG was added and ultrasonic treatment was continued for 2 hours. The material after ultrasonic treatment was centrifuged to retain the solid phase. The solid phase was calcined at 530°C for 5 hours to obtain modified mesoporous SiO2.

[0064] Step 2: Loading conductive agent and flame retardant

[0065] In parts by weight, the raw materials include: 2 parts of single-walled carbon nanotubes (SWCNTs), 2 parts of graphene nanosheets (GNSs), 5 parts of conductive carbon black, 0.03 parts of sodium dodecylbenzenesulfonate (SDBS), 65 parts of modified mesoporous SiO2, 10 parts of melamine phosphate (MPP), and 7 parts of zinc borate (ZB).

[0066] SWCNTs, GNSs, conductive carbon black, and SDBS were put into DMF and ultrasonically treated at 32kHz for 3h. Modified mesoporous SiO2, MPP, and ZB were then added and stirred for 30min to obtain a mixed solution. The mixed solution was ultrasonically dispersed at 32kHz for 1h. After the ultrasonic dispersion, the mixed solution was filtered to retain the solid, and the solid was vacuum dried at 80℃ for 6h to obtain mesoporous SiO2 loaded with a conductive agent and a flame retardant.

[0067] DMF is a solvent and does not participate in the reaction. The amount used is based on its ability to dissolve the solute.

[0068] Step 3: Melt blending to prepare cable material

[0069] In parts by weight, the raw materials include: 50 parts of low-density polyethylene (LDPE), 80 parts of ethylene-vinyl acetate copolymer (EVA), 75 parts of mesoporous SiO2 loaded with conductive agent and flame retardant, 4 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 5 parts of zinc stearate, and 6 parts of epoxidized soybean oil.

[0070] LDPE, EVA, mesoporous SiO2 loaded with a conductive agent and flame retardant, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], zinc stearate, and epoxidized soybean oil were mixed in a high-speed mixer for 15 minutes. The mixed materials were then fed into a twin-screw extruder for melt extrusion to produce a halogen-free, flame-retardant, semi-conductive shielded cable material. The twin-screw extruder temperature was controlled at 150°C in the feed zone, 165°C in the melt zone, 180°C in the mixing zone, and 175°C in the die zone.

[0071] Performance Testing

[0072] The cable materials prepared in Examples 1 to 4 were subjected to performance tests. The test items, test standards adopted, and test results are shown in the following table.

[0073] Table 1 Performance test results of cable materials prepared in Examples 1 to 4

[0074] Test items Test standards Example 1 Example 2 Example 3 Example 4 Volume resistivity (Ω・cm) GB / T31838.2-2019 8.5×10² 7.2×10² 6.8×10² 8.2×10² Interface protrusion (mm) GB / T18890.1-2015 0.03 0.03 0.03 0.04 Oxygen index (%) GB / T2406.2-2009 34 35 34 33 Flame retardant properties GB / T18380.33-2022 A-level A-level A-level A-level Tensile strength (MPa) GB / T2951.11-2008 15.6 16.2 17.8 17.1 Elongation at break (%) GB / T2951.11-2008 403 417 420 415

[0075] The data in Table 1 demonstrates that the cable materials prepared in Examples 1-4 exhibit low volume resistivities ranging from 6.8×10² to 8.5×10²Ω·cm. Their interfacial protrusions are ≤0.04mm, resulting in a smooth surface that effectively prevents electric field distortion and partial discharge. These characteristics demonstrate their excellent electric field shielding capabilities. The cable materials prepared in Examples 1-4 exhibit an oxygen index greater than 33%, a tensile strength exceeding 15 MPa, and an elongation at break greater than 400%, demonstrating their excellent flame retardancy and mechanical properties.

[0076] The single-walled carbon nanotubes used in Examples 1-4 of the present invention have a diameter of 1-2 nm and an aspect ratio of >10. 4 ; The graphene nanosheets used have a thickness of 3~5nm and a diameter of 5~10μm; the conductive carbon black used has a particle size of 30~40nm; low-density polyethylene (LDPE) has a density of 0.910~0.925g / cm³; ethylene-vinyl acetate copolymer (EVA) has a density of 0.91~0.94g / cm³ and a vinyl acetate content of 30~40wt%.

[0077] Obviously, there are many specific implementation methods that can be changed under the concept of the present invention. Here, it should be stated that any changes made under the inventive concept of the present invention will fall within the scope of protection of the present invention.

Claims

1. A halogen-free flame-retardant semi-conductive shielded cable material, characterized by: In parts by weight, the raw materials include 40-55 parts of low-density polyethylene, 75-92 parts of ethylene-vinyl acetate copolymer, 75-85 parts of mesoporous SiO2 loaded with a conductive agent and a flame retardant, 2-4 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2-6 parts of zinc stearate, and 5-8 parts of epoxidized soybean oil; The mesoporous SiO2 loaded with a conductive agent and a flame retardant 2， The invention is prepared from the following raw materials: single-walled carbon nanotubes, graphene nanosheets, conductive carbon black, sodium dodecylbenzene sulfonate, melamine phosphate, zinc borate, and modified mesoporous SiO2; the raw material ratios, in parts by weight, are: 2-4 parts of single-walled carbon nanotubes, 2-5 parts of graphene nanosheets, 4-6 parts of conductive carbon black, 0.02-0.05 parts of sodium dodecylbenzene sulfonate, 60-70 parts of modified mesoporous SiO2, 10-15 parts of melamine phosphate, and 5-9 parts of zinc borate; The modified mesoporous SiO2 uses γ-aminoethylaminopropyltrimethoxysilane and alkyl glycoside as modifiers.

2. The method for preparing a halogen-free flame-retardant semi-conductive shielded cable material according to claim 1, characterized in that: The method comprises the steps of preparing modified mesoporous SiO2, loading a conductive agent and a flame retardant, and preparing a cable material by melt blending.

3. The method for preparing a halogen-free flame-retardant semi-conductive shielded cable material according to claim 2, characterized in that: The modified mesoporous SiO2 is prepared as follows: ethyl orthosilicate, ethanol, glacial acetic acid and deionized water are mixed and stirred, and hydrolyzed to generate a uniform and transparent SiO2 sol; γ-aminoethylaminopropyltrimethoxysilane is added to the SiO2 sol, and ultrasonic treatment is performed; alkyl glycoside is then added, and the mixture is ultrasonically treated and centrifuged to retain a solid phase; and the solid phase is calcined to obtain the modified mesoporous SiO2.

4. The method for preparing a halogen-free flame-retardant semi-conductive shielded cable material according to claim 2, characterized in that: The raw materials for preparing modified mesoporous SiO2 are as follows: 45-50 parts of ethyl orthosilicate, 2-5 parts of γ-aminoethylaminopropyltrimethoxysilane, 5-7 parts of glacial acetic acid, 150-160 parts of ethanol, 50-60 parts of deionized water, and 3-5 parts of alkyl glycoside in a weight ratio.

5. The method for preparing a halogen-free flame-retardant semi-conductive shielded cable material according to claim 3, characterized in that: The calcination is carried out at 500-600° C. for 3-6 hours.

6. The method for preparing a halogen-free flame-retardant semi-conductive shielded cable material according to claim 2, characterized in that: The method comprises the following steps: placing single-walled carbon nanotubes, graphene nanosheets, conductive carbon black, and sodium dodecylbenzenesulfonate into N,N-dimethylformamide for ultrasonic treatment; adding modified mesoporous SiO2, melamine phosphate, and zinc borate for stirring to obtain a mixed solution; ultrasonically dispersing the mixed solution, filtering the mixed solution after the ultrasonic dispersion is completed, and retaining the solid; and vacuum drying the solid to obtain mesoporous SiO2 loaded with the conductive agent and flame retardant.

7. The method for preparing a halogen-free flame-retardant semi-conductive shielded cable material according to claim 2, characterized in that: The cable material is prepared by melt blending: low-density polyethylene, ethylene-vinyl acetate copolymer, mesoporous SiO2 loaded with a conductive agent and a flame retardant, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], zinc stearate, and epoxy soybean oil are mixed and then added into a twin-screw extruder for melt extrusion.

8. The method for preparing a halogen-free flame-retardant semi-conductive shielded cable material according to claim 7, characterized in that: The low-density polyethylene has a density of 0.910-0.925 g / cm³.

9. The method for preparing a halogen-free flame-retardant semi-conductive shielded cable material according to claim 7, characterized in that: The ethylene-vinyl acetate copolymer has a density of 0.91-0.94 g / cm³ and a vinyl acetate content of 30-40 wt%.