Halogen-free flame-retardant tunnel waterproof board

Abstract

The invention discloses a halogen-free flame-retardant tunnel waterproof board, which is prepared from the following component raw materials in parts by mass: 100 to 120 parts of high-density polyethylene, 10 to 15 parts of ethylene-vinyl acetate copolymer, 4 to 5 parts of maleic anhydride grafted polyethylene, 15 to 20 parts of modified antistatic flame retardant, 20 to 25 parts of linear low-density polyethylene and 30 to 35 parts of metallocene polyethylene. The prepared halogen-free flame-retardant tunnel waterproof board uses the halogen-free flame retardant expansible graphite, is small in environmental pollution and good in flame retardant property, synergistically improves the flame retardant property by compounding the metal organic framework with a porous structure on the surface of the expansible graphite, and improves the flame retardant property by combining the composite expansible graphite and the carbon nanotubes on the acidified carbon fibers. And the carbon fibers are staggered to form a path, so that the conductivity is improved, and the antistatic performance of the halogen-free flame-retardant tunnel waterproof plate is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer compound compositions, and particularly relates to a halogen-free flame-retardant tunnel waterproof board. Background Art

[0002] Inside the tunnel, it is hot, humid and relatively enclosed in space. Combustibles such as fuels, water supply and drainage materials, and plates are relatively concentrated. Especially in the areas rich in gas, the fire risk coefficient is high. The waterproof boards used in tunnels are mostly polyethylene (PE) waterproof boards, ethylene-vinyl acetate copolymer modified polyethylene (EVA) waterproof boards, and ethylene-vinyl acetate and asphalt copolymer modified polyethylene (ECB) waterproof boards. Polymer compounds are flammable, and the waterproof boards for tunnels need to be flame-retardant modified to meet the application requirements of corresponding fields.

[0003] Halogen-based flame retardants are inexpensive and have good flame-retardant effects. However, the decomposition and combustion of halogen-based flame retardants will generate a large amount of soot and toxic and corrosive gases, causing "secondary disasters", seriously polluting the atmospheric environment and damaging the ozone layer. However, halogen-free flame retardants will reduce the mechanical properties of the waterproof board.

[0004] The Chinese patent application with the publication number CN112210158A discloses an EVA antistatic and flame-retardant waterproof board for tunnels, which is prepared by mixing linear low-density polyethylene, metallocene polyethylene, ethylene-vinyl acetate copolymer, a flame retardant and an antistatic agent to obtain a flame-retardant waterproof board with excellent performance and having flame-retardant and antistatic effects. However, the halogen-based flame retardant used in this scheme is inexpensive, and toxic hydrogen halide gas will be released during combustion, causing harm to the human body and the environment.

[0005] The Chinese patent application with the publication number CN110317389A discloses a composite flame-retardant tunnel waterproof board. By adding a magnesium hydroxide / aluminum hydroxide-graphene oxide composite flame retardant to high-density polyethylene, the two-dimensional sheet structures of magnesium hydroxide / aluminum hydroxide and graphene oxide can be stacked layer by layer to form a dense physical isolation layer, improving the flame-retardant performance. Although the use of inorganic flame retardants in this scheme avoids the harm of halogen-based flame retardants to the environment, the antistatic performance in this scheme is poor and it cannot be applied to the tunnel environment with a high frequency of static electricity generation.

[0006] During tunnel construction, due to friction and dry air, during tunnel excavation, blasting, etc., friction between rocks and tools will generate static electricity, which is easy to cause static electricity accumulation. There is a need for a halogen-free flame-retardant tunnel waterproof board with antistatic and flame-retardant properties to avoid environmental pollution and at the same time be applicable to the field of tunnel construction. Summary of the Invention

[0007] The object of the present invention is to solve the problem of how to improve the antistatic performance of a flame-retardant tunnel waterproof board, and have good mechanical properties and flame-retardant properties, and provide a halogen-free flame-retardant tunnel waterproof board.

[0008] The present invention improves the antistatic performance and flame-retardant performance of the halogen-free flame-retardant tunnel waterproof board by compounding the antistatic agent carbon nanotubes and the halogen-free flame retardant expandable graphite with carbon fibers, synergistically improves the flame-retardant performance by compounding a porous metal-organic framework on the surface of the expandable graphite, and improves the mechanical properties of the halogen-free flame-retardant tunnel waterproof board by carbon fibers.

[0009] The object of the present invention can be achieved by the following technical solutions:

[0010] A halogen-free flame-retardant tunnel waterproof board, by mass, comprises the following component raw materials:

[0011] 100 - 120 parts of high-density polyethylene, 10 - 15 parts of ethylene-vinyl acetate copolymer, 4 - 5 parts of maleic anhydride grafted polyethylene, 15 - 20 parts of modified antistatic flame retardant, 20 - 25 parts of linear low-density polyethylene, and 30 - 35 parts of metallocene polyethylene.

[0012] Further, the modified antistatic flame retardant is prepared by the following steps:

[0013] Step 1: Add 3-aminopropyltriethoxysilane to a 2 - 3 wt% carbon fiber dispersion in a reaction kettle, stir at 40 - 50 °C for 10 - 12 h, centrifuge to collect the precipitate, redisperse the precipitate in N,N-dimethylformamide, add carbon nanotubes and composite expandable graphite, heat to 40 - 50 °C, ultrasonically treat for 2 - 3 h, centrifuge to collect the bottom precipitate, and vacuum dry to obtain the antistatic flame retardant.

[0014] Step 2: Add polydimethylsiloxane and a curing agent to chloroform in a reaction kettle, add the antistatic flame retardant and ultrasonically treat for 30 - 40 min, filter to obtain the precipitate, wash the precipitate with ethanol, and air-dry the precipitate to obtain the modified antistatic flame retardant.

[0015] Further, the dosage ratio of the carbon fiber dispersion, 3-aminopropyltriethoxysilane, N,N-dimethylformamide, carbon nanotubes, and composite expandable graphite in Step 1 is 1 - 1.25 L : 8 - 10 g : 1 - 1.25 L : 2 - 3 g : 4 - 6 g.

[0016] The carbon fiber dispersion is prepared by ultrasonically dispersing acidified carbon fibers in N,N-dimethylformamide.

[0017] Further, the acidified carbon fibers are prepared by the following steps:

[0018] Soak the dried carbon fiber in an aqueous solution of 5 wt% phosphoric acid in a reaction kettle for 30 - 40 min, with ultrasonic treatment during this period. After filtration, wash the precipitate with deionized water and dry it to obtain acidified carbon fiber.

[0019] Furthermore, the carbon fiber is short carbon fiber with a diameter of 7 - 8 μm and a length of 0.5 - 1 mm.

[0020] Furthermore, the carbon nanotubes have a diameter of 5 - 15 nm and a length of 10 - 30 μm.

[0021] Furthermore, the composite expandable graphite is prepared by the following steps:

[0022] Dissolve copper nitrate and 2 - aminoterephthalic acid in N, N - dimethylformamide and absolute ethanol in a reaction kettle, add expandable graphite, disperse it ultrasonically, then heat it to 100 - 110 °C and react for 20 - 24 h. After cooling, centrifuge to collect the precipitate, wash the precipitate, and dry it under vacuum to obtain the composite expandable graphite.

[0023] Furthermore, the dosage ratio of copper nitrate, 2 - aminoterephthalic acid, N, N - dimethylformamide, absolute ethanol and expandable graphite is 6 - 10 g : 4 - 6 g : 300 - 400 mL : 120 - 150 mL : 8 - 10 g.

[0024] Furthermore, the expandable graphite has a diameter of 6 - 7 μm.

[0025] Furthermore, in step two, the dosage ratio of polydimethylsiloxane, curing agent, chloroform and antistatic flame retardant is 6 - 8 g : 0.6 - 0.8 g : 150 - 200 mL : 15 - 20 g.

[0026] A preparation method of a halogen - free flame - retardant tunnel waterproof board includes the following steps:

[0027] Add high - density polyethylene, ethylene - vinyl acetate copolymer, maleic anhydride - grafted polyethylene, modified antistatic flame retardant, linear low - density polyethylene and metallocene polyethylene into a mixer for uniform mixing. During the mixing process, conduct drying. Add the mixed and dried raw materials into an extruder for heating and plasticizing, and extrude and calender the raw materials in the extruder to obtain the halogen - free flame - retardant tunnel waterproof board.

[0028] The beneficial effects of the present invention:

[0029] (1) The halogen-free flame-retardant tunnel waterproof board prepared by the present invention uses the halogen-free flame retardant expandable graphite, which has little environmental pollution and good flame retardant performance. By compounding a metal-organic framework with a porous structure on the surface of expandable graphite, the flame retardant performance is synergistically improved. By combining the composite expandable graphite with carbon nanotubes on acidified carbon fiber, and using the interlacing of carbon fibers to form a path, the electrical conductivity is improved, thereby enhancing the antistatic performance of the halogen-free flame-retardant tunnel waterproof board.

[0030] (2) The preparation method of the present invention acidifies carbon fiber, and uses the basic group on 3-aminopropyltriethoxysilane to react with the acidic group on acidified carbon fiber to firmly graft 3-aminopropyltriethoxysilane on the surface of acidified carbon fiber. By using the cross-linking reaction between the ligand of Cu-MOF on the surface of the composite expandable graphite and 3-aminopropyltriethoxysilane, the composite strength of the composite expandable graphite and acidified carbon fiber is improved. By compounding carbon nanotubes on the surface of acidified carbon fiber, with acidified carbon fiber as the conductive path and carbon nanotubes as the conductive agent, the electrical conductivity of acidified carbon fiber is improved, thereby enhancing the antistatic performance. The composite expandable graphite has good flame retardant performance and certain electrical conductivity, improving the antistatic performance while enhancing the flame retardant performance. The micro-nano composite structure formed by carbon nanotubes, composite expandable graphite and acidified carbon fiber also helps to improve the hydrophobic performance and enhance the hydrophobic modification of the antistatic flame retardant to the material. Detailed implementation mode

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the scope of protection of the present invention.

[0032] Example 1: A halogen-free flame-retardant tunnel waterproof board is prepared by the following steps:

[0033] S1. In a reaction kettle, carbon fiber is first soaked in acetone at 50 °C for 30 minutes, filtered and washed with deionized water. Then, it is dried at 80 °C for 1 hour. Then, the dried carbon fiber is soaked in a 5wt% phosphoric acid aqueous solution for 30 minutes, during which ultrasonic treatment is carried out. After filtration again, the precipitate is washed with deionized water and finally dried at 70 °C for 2 hours to obtain acidified carbon fiber.

[0034] S2. In another reaction kettle, dissolve 6 g of copper nitrate and 4 g of 2-aminoterephthalic acid in 300 mL of N,N-dimethylformamide and 120 mL of absolute ethanol. After adding 8 g of expandable graphite, perform ultrasonic dispersion and heat to 100 °C for reaction for 20 hours. After cooling, centrifuge to collect the precipitate and wash it with N,N-dimethylformamide, ethanol and deionized water. Finally, dry it under vacuum at 60 °C for 10 hours to obtain composite expandable graphite.

[0035] S3. In the reaction kettle, ultrasonically disperse acidified carbon fiber in N,N-dimethylformamide to prepare a 2 wt% carbon fiber dispersion. Add 8 g of 3-aminopropyltriethoxysilane to 1 L of the carbon fiber dispersion and stir at 40 °C for 10 hours. After centrifuging to collect the precipitate, disperse it again in 1 L of N,N-dimethylformamide, add 2 g of carbon nanotubes and 4 g of composite expandable graphite. Heat to 40 °C and perform ultrasonic treatment for 2 hours. Centrifuge to collect the bottom precipitate and dry it under vacuum at 60 °C for 10 hours to obtain the antistatic and flame retardant agent.

[0036] S4. In the reaction kettle, add 6 g of polydimethylsiloxane and 0.6 g of curing agent to 150 mL of chloroform. Add 15 g of the antistatic and flame retardant agent and perform ultrasonic treatment for 30 minutes. After filtering to obtain the precipitate, wash the precipitate with ethanol and air-dry it to obtain the modified antistatic and flame retardant agent.

[0037] S5. Add 100 g of high-density polyethylene, 10 g of ethylene-vinyl acetate copolymer, 4 g of maleic anhydride-grafted polyethylene, 15 g of the modified antistatic and flame retardant agent, 20 g of linear low-density polyethylene and 30 g of metallocene polyethylene to a mixer for uniform mixing. During the mixing process, perform drying, and then add the mixed and dried raw materials to an extruder for heating and plasticization. Finally, extrude and calender the raw materials in the extruder to obtain a halogen-free flame retardant tunnel waterproof board.

[0038] Example 2: A halogen-free flame retardant tunnel waterproof board is prepared by the following steps:

[0039] S1. In the reaction kettle, soak carbon fiber in acetone at 55 °C for 35 minutes, filter and wash it with deionized water. Then, dry it at 85 °C for 1.5 hours. Then, soak the dried carbon fiber in a 5 wt% phosphoric acid aqueous solution for 35 minutes, with ultrasonic treatment during this period. Filter again and wash the precipitate with deionized water, and finally dry it at 75 °C for 2.5 hours to obtain acidified carbon fiber.

[0040] S2. In another reaction kettle, dissolve 8 g of copper nitrate and 5 g of 2-aminoterephthalic acid in 350 mL of N,N-dimethylformamide and 135 mL of absolute ethanol. After adding 9 g of expandable graphite, perform ultrasonic dispersion and heat to 105 °C for reaction for 22 hours. After cooling, centrifuge to collect the precipitate and wash it with N,N-dimethylformamide, ethanol, and deionized water. Finally, dry it under vacuum at 65 °C for 11 hours to obtain composite expandable graphite.

[0041] S3. In the reaction kettle, ultrasonically disperse acidified carbon fiber in N,N-dimethylformamide to prepare a 2.5 wt% carbon fiber dispersion. Add 9 g of 3-aminopropyltriethoxysilane to 1.125 L of the carbon fiber dispersion and stir at 45 °C for 11 hours. After centrifuging to collect the precipitate, disperse it again in 1.125 L of N,N-dimethylformamide, add 2.5 g of carbon nanotubes and 5 g of composite expandable graphite. Heat up to 45 °C and perform ultrasonic treatment for 2.5 hours. Centrifuge to collect the bottom precipitate and dry it under vacuum at 65 °C for 11 hours to obtain the antistatic flame retardant.

[0042] S4. In the reaction kettle, add 7 g of polydimethylsiloxane and 0.7 g of curing agent to 175 mL of chloroform. Add 17.5 g of the antistatic flame retardant and perform ultrasonic treatment for 35 minutes. After filtering to obtain the precipitate, wash the precipitate with ethanol and air-dry it to obtain the modified antistatic flame retardant.

[0043] S5. Add 110 g of high-density polyethylene, 12.5 g of ethylene-vinyl acetate copolymer, 4.5 g of maleic anhydride-grafted polyethylene, 17.5 g of the modified antistatic flame retardant, 22.5 g of linear low-density polyethylene, and 32.5 g of metallocene polyethylene to a mixer for uniform mixing. During the mixing process, perform drying, and then add the mixed and dried raw materials to an extruder for heating and plasticization. Finally, extrude and calender the raw materials in the extruder to obtain a halogen-free flame retardant tunnel waterproof board.

[0044] Example 3: A halogen-free flame retardant tunnel waterproof board is prepared by the following steps:

[0045] S1. Immerse carbon fiber in acetone at 60 °C in the reaction kettle for 40 min, filter and wash the carbon fiber with deionized water, dry it at 90 °C for 2 h, soak the dried carbon fiber in a 5 wt% phosphoric acid aqueous solution for 40 min, perform ultrasonic treatment during this period, filter and wash the precipitate with deionized water, and dry it at 80 °C for 3 h to obtain acidified carbon fiber.

[0046] After the carbon fiber is treated by immersion in acetone, the sizing agent and impurities on the surface can be removed, which helps the grafting of phosphoric acid groups onto the carbon fiber surface. Ultrasonic treatment is used to disperse the carbon fiber, increasing the contact area between the carbon fiber and phosphoric acid and improving the grafting efficiency of phosphoric acid groups.

[0047] S2. Dissolve 10 g of copper nitrate and 6 g of 2-aminoterephthalic acid in 400 mL of N,N-dimethylformamide and 150 mL of absolute ethanol in a reaction kettle. Add 10 g of expandable graphite, ultrasonically disperse it, then heat to 110 °C and react for 24 h. After cooling, centrifuge to collect the precipitate, and wash the precipitate with N,N-dimethylformamide, ethanol and deionized water. Dry it in vacuum at 70 °C for 12 h to obtain composite expandable graphite.

[0048] By in-situ generating Cu-MOF on the surface of expandable graphite, Cu-MOF is compounded on the surface of expandable graphite. Utilizing the high porosity of Cu-MOF, the carbonization of expandable graphite is promoted, and the flame retardant effect of expandable graphite is enhanced.

[0049] S3. Ultrasonically disperse acidified carbon fiber in N,N-dimethylformamide in a reaction kettle to prepare a 3 wt% carbon fiber dispersion. Add 10 g of 3-aminopropyltriethoxysilane to 1.25 L of the carbon fiber dispersion, stir at 50 °C for 12 h, centrifuge to collect the precipitate. Redisperse the precipitate in 1.25 L of N,N-dimethylformamide, add 3 g of carbon nanotubes and 6 g of composite expandable graphite, heat to 50 °C, ultrasonically treat for 3 h, centrifuge to collect the bottom precipitate, and dry it in vacuum at 70 °C for 12 h to obtain the antistatic flame retardant.

[0050] Through the reaction of the basic group on 3-aminopropyltriethoxysilane with the acidic group on acidified carbon fiber, the Si-O-R of 3-aminopropyltriethoxysilane is hydrolyzed into Si-O-H, and Si-O-H dehydrates and condenses on the surface of acidified carbon fiber, so that 3-aminopropyltriethoxysilane is firmly grafted on the surface of acidified carbon fiber. After filtration, it is redispersed in N,N-dimethylformamide. Using 3-aminopropyltriethoxysilane to compound carbon nanotubes and composite expandable graphite on the acidified carbon fiber matrix, the ligand of Cu-MOF on the surface of composite expandable graphite cross-links with 3-aminopropyltriethoxysilane, enhancing the composite strength of composite expandable graphite and acidified carbon fiber. By compounding carbon nanotubes on the surface of acidified carbon fiber, with acidified carbon fiber as the conductive path and carbon nanotubes as the conductive agent, the conductive performance of acidified carbon fiber is enhanced, thereby enhancing the antistatic performance. The composite expandable graphite has good flame retardant performance and certain conductivity, enhancing the flame retardant performance while enhancing the antistatic performance. The micro-nano composite structure formed by carbon nanotubes, composite expandable graphite and acidified carbon fiber also helps to enhance the hydrophobic performance and improve the hydrophobic modification effect of the antistatic flame retardant on materials.

[0051] S4. Add 8 g of polydimethylsiloxane and 0.8 g of curing agent to 200 mL of chloroform in a reaction kettle, add 20 g of antistatic flame retardant and ultrasonically treat for 40 min, filter to obtain the precipitate, wash the precipitate with ethanol, and air-dry the precipitate to obtain the modified antistatic flame retardant.

[0052] S5. Add 120 g of high-density polyethylene, 15 g of ethylene-vinyl acetate copolymer, 5 g of maleic anhydride grafted polyethylene, 20 g of modified antistatic flame retardant, 25 g of linear low-density polyethylene and 35 g of metallocene polyethylene into a mixer for uniform mixing. During the mixing process, dry the materials. Then add the mixed and dried raw materials into an extruder for heating and plasticizing. Extrude and calender the raw materials in the extruder to obtain a halogen-free flame retardant tunnel waterproof board.

[0053] The antistatic flame retardant is wrapped and modified with polydimethylsiloxane and the curing agent of polydimethylsiloxane. After physical mixing, the modified antistatic flame retardant is uniformly mixed in the polyethylene matrix. During the heating and plasticizing process, the polydimethylsiloxane and the curing agent of polydimethylsiloxane undergo a curing reaction, curing the modified antistatic flame retardant in the mixing matrix, reducing the agglomeration of the modified antistatic agent, increasing the bonding strength between the modified antistatic flame retardant and the polyethylene matrix, and improving the mechanical properties of the obtained halogen-free flame retardant tunnel waterproof board.

[0054] Comparative Example 1: The difference from Example 1 is that in S3, carbon fiber is used to replace acidified carbon fiber to obtain a halogen-free flame retardant tunnel waterproof board.

[0055] Comparative Example 2: The difference from Example 1 is that in S3, expandable graphite is used to replace composite expandable graphite to obtain a halogen-free flame retardant tunnel waterproof board.

[0056] Comparative Example 3: The difference from Example 1 is that in S5, the antistatic flame retardant is used to replace the modified antistatic flame retardant to obtain a halogen-free flame retardant tunnel waterproof board.

[0057] Some material parameters in the examples and comparative examples are as follows:

[0058] The carbon fiber is short carbon fiber, with a diameter of 7 - 8 μm and a length of 0.5 - 1 mm.

[0059] Carbon nanotubes, with a diameter of 5 - 15 nm and a length of 10 - 30 μm.

[0060] The expandable graphite has a diameter of 6 - 7 μm.

[0061] The model of polydimethylsiloxane is Sylgard 184A, and the model of the curing agent is Sylgard184B.

[0062] Conduct performance tests on the halogen-free flame retardant tunnel waterproof boards prepared in Examples 1 - 3 and Comparative Examples 1 - 3. Test the tensile strength, elongation at break and water impermeability according to the standard GB / T18173.1 - 2012; measure the surface resistance of the halogen-free flame retardant tunnel waterproof board; conduct UL-94 vertical burning test and LOI test to test the flame retardant performance.

[0063] The results obtained are shown in Table 1 as follows:

[0064] Table 1: Performance Test Results Table of Halogen-Free Flame-Retardant Tunnel Waterproof Plate

[0065]

[0066] As can be seen from Table 1, the halogen-free flame-retardant tunnel waterproof plate prepared by the present invention has good mechanical strength and water impermeability, and the surface resistance reaches 10 7 Ω, has good antistatic performance, high flame-retardant grade, and can meet the requirements of tunnel scenarios.

[0067] In Comparative Example 1, since the surface of the carbon fiber was not acidified, the grafting strength between 3-aminopropyltriethoxysilane and the carbon fiber surface was low, and the grafting rate was low, resulting in a low degree of compounding of the carbon fiber with expandable graphite and carbon nanotubes. The performance of the halogen-free flame-retardant tunnel waterproof plate prepared was worse than that of Examples 1 - 3.

[0068] In Comparative Example 2, since a metal-organic framework with a porous structure was not mixed with expandable graphite, the grafting effect between the metal-organic framework and 3-aminopropyltriethoxysilane was lacking, reducing the compounding strength of expandable graphite with acidified carbon fiber, thereby leading to a decrease in the dispersibility of expandable graphite and a significant decrease in flame-retardant performance due to the lack of the synergistic flame-retardant effect of the metal-organic framework.

[0069] In Comparative Example 3, since polydimethylsiloxane was not used to modify the antistatic flame retardant, the curing effect of polydimethylsiloxane was lacking, and the improvement of the mechanical properties of the halogen-free flame-retardant tunnel waterproof plate was less than that of Examples 1 - 3.

[0070] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A halogen-free flame-retardant tunnel waterproof board, characterized in that: By weight, it contains the following raw materials: 100-120 parts of high density polyethylene, 10-15 parts of ethylene-vinyl acetate copolymer, 4-5 parts of maleic anhydride grafted polyethylene, 15-20 parts of modified antistatic flame retardant, 20-25 parts of linear low density polyethylene and 30-35 parts of metallocene polyethylene; The modified antistatic flame retardant is prepared by the following steps: Step 1, adding 3-aminopropyltriethoxysilane to a 2-3wt% carbon fiber dispersion in a reaction kettle, stirring at 40-50°C for 10-12h, collecting the precipitate by centrifugation, dispersing the precipitate again in N,N-dimethylformamide, adding carbon nanotubes and composite expandable graphite, heating to 40-50°C, ultrasonically treating for 2-3h, collecting the bottom precipitate by centrifugation, and vacuum drying to obtain an antistatic flame retardant; Step 2: Add polydimethylsiloxane and curing agent into chloroform in a reaction kettle, add antistatic flame retardant and ultrasonically treat for 30-40 minutes, filter to obtain a precipitate, wash the precipitate with ethanol, and air-dry the precipitate to obtain a modified antistatic flame retardant.

2. The halogen-free flame-retardant tunnel waterproof board according to claim 1, characterized in that: The amount ratio of the carbon fiber dispersion, 3-aminopropyltriethoxysilane, N,N-dimethylformamide, carbon nanotubes and composite expandable graphite in step 1 is 1-1.25L: 8-10g: 1-1.25L: 2-3g: 4-6g; The carbon fiber dispersion is prepared by ultrasonically dispersing acidified carbon fibers in N,N-dimethylformamide.

3. The halogen-free flame-retardant tunnel waterproof board according to claim 2, characterized in that: The acidified carbon fiber is prepared by the following steps: The dried carbon fiber is soaked in a 5wt% phosphoric acid aqueous solution in a reaction kettle for 30-40 minutes, during which ultrasonic treatment is performed. After filtering, the precipitate is washed with deionized water and dried to obtain the acidified carbon fiber.

4. The halogen-free flame-retardant tunnel waterproof board according to claim 3, characterized in that: The carbon fiber is short carbon fiber with a diameter of 7-8 μm and a length of 0.5-1 mm.

5. The halogen-free flame-retardant tunnel waterproof board according to claim 2, characterized in that: The carbon nanotube has a diameter of 5-15 nm and a length of 10-30 μm.

6. The halogen-free flame-retardant tunnel waterproof board according to claim 2, characterized in that: The composite expandable graphite is prepared by the following steps: In a reaction kettle, copper nitrate and 2-aminoterephthalic acid are dissolved in N, N-dimethylformamide and anhydrous ethanol, expandable graphite is added, and the mixture is heated to 100-110° C. for reaction for 20-24 hours after ultrasonic dispersion. After cooling, the precipitate is collected by centrifugation, washed, and vacuum dried to obtain composite expandable graphite.

7. The halogen-free flame-retardant tunnel waterproof board according to claim 6, characterized in that: The usage ratio of the copper nitrate, 2-aminoterephthalic acid, N,N-dimethylformamide, anhydrous ethanol and expandable graphite is 6-10g: 4-6g: 300-400mL: 120-150mL: 8-10g.

8. The halogen-free flame-retardant tunnel waterproof board according to claim 7, characterized in that: The diameter of the expandable graphite is 6-7 μm.

9. The halogen-free flame-retardant tunnel waterproof board according to claim 1, characterized in that: The usage ratio of polydimethylsiloxane, curing agent, chloroform and antistatic flame retardant in step 2 is 6-8g: 0.6-0.8g: 150-200mL: 15-20g.

10. The halogen-free flame-retardant tunnel waterproof board according to claim 1, characterized in that: The preparation method of the halogen-free flame-retardant tunnel waterproof board comprises the following steps: High-density polyethylene, ethylene-vinyl acetate copolymer, maleic anhydride grafted polyethylene, modified antistatic flame retardant, linear low-density polyethylene and metallocene polyethylene are added into a mixer for uniform mixing, and dried during the mixing process. The mixed and dried raw materials are added into an extruder for heating and plasticization, and the raw materials in the extruder are extruded and calendered to obtain a halogen-free flame-retardant tunnel waterproofing board.

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