Bio-based flame-retardant antistatic cover rubber and preparation method thereof

Abstract

The invention discloses a bio-based flame-retardant antistatic cover rubber and a preparation method thereof, and belongs to the technical field of conveyor belts, a blend of a bio-based polyamide elastomer and a bio-based thermoplastic polyester elastomer is used as a matrix, and a halogen-free intumescent flame retardant, an antistatic agent and a nano aluminum hydroxide multi-component functional aid are added to prepare the bio-based flame-retardant antistatic cover rubber. The prepared covering rubber is excellent in mechanical property, the flame retardant property and the antistatic property of the covering rubber completely meet the strict requirements for the covering layer of the conveying belt, and the covering rubber has the advantages of being environmentally friendly, easy and convenient to process, capable of being recycled and the like and is suitable for replacing a traditional PVC rubber covering layer; the antistatic agent is formed by compounding the MXene conductive hollow microspheres and the conductive carbon black, the hollow structures of the MXene conductive hollow microspheres have certain elastic deformation capacity, interface stress between a matrix and filler can be buffered in the processing process, and material embrittlement caused by rigid filler is avoided.

Description

Technical Field

[0001] This invention belongs to the field of conveyor belt technology, specifically a bio-based flame-retardant and antistatic covering adhesive and its preparation method. Background Technology

[0002] Flame-retardant conveyor belts for coal mines are the "lifeline" of underground coal transportation, and their safety is of paramount importance. The national coal industry standard MT / 914 sets forth clear requirements for the mechanical properties, flame-retardant properties, and antistatic properties of the cover layer of such conveyor belts. Currently, the cover layer materials for flame-retardant conveyor belts on the market are mainly divided into two categories: one is thermoplastic plastics represented by polyvinyl chloride (PVC), and the other is vulcanized rubber represented by chloroprene rubber (CR).

[0003] While PVC cover rubber offers good flame retardancy and low cost, its plasticizers are prone to migration, leading to deterioration in performance and poor low-temperature toughness. Furthermore, it produces large amounts of toxic fumes and hydrogen chloride gas when burned, posing threats to the environment and user safety. Chloroprene rubber cover rubber boasts excellent overall performance, but its production requires high-temperature vulcanization, resulting in high energy consumption and low efficiency. Moreover, its raw materials are derived from non-renewable petroleum resources, which does not align with sustainable development requirements.

[0004] In recent years, thermoplastic elastomers (TPEs) have attracted attention due to their combination of the elasticity of rubber and the thermoplastic processability of plastics. However, ordinary TPEs struggle to simultaneously meet the extremely demanding flame-retardant and antistatic requirements of underground coal mines. Existing technologies also employ flame-retardant modifications using polyolefin-based TPEs, but their mechanical strength and abrasion resistance often fail to meet the high standards of mining conveyor belts. Furthermore, most TPE formulations still heavily rely on petroleum-based raw materials and halogenated flame retardants, posing environmental risks.

[0005] Therefore, developing a new type of cover adhesive material that is based on renewable resources, fully complies with the MT / 914 standard, is environmentally friendly, and is easy to process has become an urgent technical problem to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to provide a bio-based flame-retardant and antistatic cover adhesive and its preparation method. Through the synergistic effect of multi-component functional additives, the product fully meets and exceeds the MT / 914 standard in terms of tensile strength, elongation at break, abrasion loss, flame retardancy and antistatic properties.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] A bio-based flame-retardant and antistatic covering adhesive comprises the following components by weight:

[0009] 100-110 parts bio-based polyamide elastomer, 15-35 parts bio-based thermoplastic polyester elastomer, 40-60 parts halogen-free intumescent flame retardant, 13-20 parts antistatic agent, 10-20 parts nano aluminum hydroxide, 1-3 parts lubricant and 0.5-1.5 parts 2,6-di-tert-butyl-4-methylphenol.

[0010] A method for preparing a bio-based flame-retardant and antistatic covering adhesive includes the following steps:

[0011] Step 1: Prepare an MXene nanosheet suspension by etching titanium aluminum carbide with hydrochloric acid; use the abundant functional groups and numerous defects on the surface of the MXene nanosheets in the MXene nanosheet suspension as landing sites for Ni metal nanoparticles to obtain an MXene-Ni suspension.

[0012] Step 2: Modified thermally expandable microspheres are obtained by nucleophilic addition of the amino group of hydroxylamine to the cyano group on the surface of the thermally expandable microspheres; MXene conductive hollow microspheres are obtained by electrostatic interaction between the MXene-Ni suspension and the modified thermally expandable microspheres; MXene conductive hollow microspheres and conductive carbon black are stirred and mixed at a mass ratio of 1-1.5:1 to obtain an antistatic agent.

[0013] Step 3: Mix bio-based polyamide elastomer, bio-based thermoplastic polyester elastomer, halogen-free intumescent flame retardant, antistatic agent, nano aluminum hydroxide, lubricant and 2,6-di-tert-butyl-4-methylphenol to obtain a premix, melt-blend and extrude, cool and cure to obtain bio-based flame retardant and antistatic cover adhesive.

[0014] Furthermore, the specific preparation steps of the MXene nanosheet suspension are as follows:

[0015] Lithium fluoride and a 35-40% hydrochloric acid solution were added to a reaction vessel and stirred at 20-25℃ and 500-600 rpm for 20-30 min. Then, titanium aluminum carbide was added and stirring was continued for 48-50 h. The mixture was centrifuged at 5000-6000 rpm for 3-4 min, filtered, and the precipitate was washed with deionized water and ethanol until the last wash solution was neutral. The precipitate was then dispersed in deionized water and sonicated at 500-600 W for 10-12 min under argon protection. The mixture was then centrifuged at 5000-6000 rpm for 1-2 min, and the supernatant was retained to obtain an MXene nanosheet suspension.

[0016] Furthermore, the ratio of lithium fluoride, hydrochloric acid solution, and titanium aluminum carbide is 30-40g: 500-600mL: 12-14g.

[0017] Furthermore, the specific preparation steps of the MXene-Ni suspension are as follows:

[0018] Nickel nitrate powder and polyvinylpyrrolidone (PVP) with a mass fraction of 1-2% were stirred and mixed to prepare a nickel nitrate solution with a concentration of 0.1-0.12 mol / L. Then, the nickel nitrate solution and MXene nanosheet suspension were added to a reaction vessel at a mass ratio of 1:7 and stirred at 40-45℃ and 150-160 r / min for 6-7 h. After filtration, the precipitate was washed 2-4 times with deionized water and then dispersed in deionized water to obtain an MXene-Ni suspension with a solid content of 5-7 g / L.

[0019] Furthermore, the specific preparation steps of the modified thermally expandable microspheres are as follows:

[0020] A 1 mol / L hydroxylamine solution and thermally expanded microspheres were added to a reaction vessel at a mass ratio of 5-6 L: 10-20 g. The mixture was stirred at 70-75 °C and 500-600 r / min for 10-12 min. The mixture was then filtered, and the precipitate was washed 2-4 times with deionized water and dried under vacuum at 60-70 °C for 1-2 h to obtain the modified thermally expanded microspheres.

[0021] Furthermore, the specific preparation steps of the antistatic agent are as follows:

[0022] MXene-Ni suspension and modified thermally expanded microspheres were stirred and mixed at a mass ratio of 1:8 for 1-2 hours, then freeze-dried at -20℃ for 72-74 hours. The product was transferred to a muffle furnace and calcined at 420-440℃ for 2-3 hours under a nitrogen atmosphere to obtain MXene conductive hollow microspheres. MXene conductive hollow microspheres and conductive carbon black were stirred and mixed at a mass ratio of 1-1.5:1 to obtain an antistatic agent.

[0023] Furthermore, the specific preparation steps of the premix are as follows:

[0024] Bio-based polyamide elastomer and bio-based thermoplastic polyester elastomer are dried at 80-100℃ for 4-6 hours to reduce the moisture content to below 0.05-0.07%. Then, they are transferred to a high-speed mixer and, under conditions of 20-25℃ and 400-500 r / min, antistatic agent, lubricant and 2,6-di-tert-butyl-4-methylphenol are added sequentially and stirred for 3-5 minutes. Then, halogen-free intumescent flame retardant and nano aluminum hydroxide are added and the mixture is stirred for another 5-10 minutes to obtain a premix.

[0025] Furthermore, the mass ratio of bio-based polyamide elastomer, bio-based thermoplastic polyester elastomer, antistatic agent, lubricant, 2,6-di-tert-butyl-4-methylphenol, halogen-free intumescent flame retardant, and nano-aluminum hydroxide is 100-110:15-35:13-20:1-3:0.5-1.5:40-60:10-20.

[0026] Furthermore, the specific preparation steps of the bio-based flame-retardant and antistatic covering adhesive are as follows:

[0027] The premixed material is melt-blended and extruded using a twin-screw extruder. The extruder temperature is set at a gradient of 180-220℃ from the feed port to the die head, and the screw speed is 250-400 r / min. After melting, shearing, and mixing, the material is fully plasticized to obtain molten strips. The molten strips are then cooled and solidified in a cooling water bath at a temperature of 20-40℃, and then dried at 90-110℃ for 2-4 hours to obtain a bio-based flame-retardant and antistatic cover adhesive.

[0028] The beneficial effects of this invention are:

[0029] 1. The bio-based flame-retardant and antistatic cover adhesive prepared by this invention, through the synergistic effect of multi-component functional additives, enables the product to fully meet and exceed the MT / 914 standard in terms of tensile strength, elongation at break, abrasion loss, flame retardancy and antistatic properties.

[0030] 2. The bio-based flame-retardant and antistatic covering adhesive prepared by this invention uses a bio-based polymer as its core substrate, which reduces fossil energy consumption and carbon emissions; and it adopts a halogen-free flame-retardant system, which avoids the environmental risks of halogenated flame retardants.

[0031] 3. The bio-based flame-retardant and antistatic covering adhesive prepared in this invention uses bio-based polyamide elastomer as the matrix material, providing excellent tensile strength, abrasion resistance, and flexibility; bio-based thermoplastic polyester elastomer, as a compatibilizing and toughening phase, can form a good sea-island structure when blended with bio-based polyamide elastomer, significantly improving the material's impact resistance and flexural fatigue performance; halogen-free intumescent flame retardant can work synergistically during combustion to generate an expanded, dense, and robust char layer, effectively isolating heat and oxygen, achieving highly efficient flame retardancy with low smoke production and low toxicity; antistatic agent constructs electronic conductive pathways, providing durable antistatic properties; nano-alumina, as a flame-retardant and smoke-suppressing filler, can reduce the surface temperature of the material through its decomposition endothermic effect, and the released water vapor can dilute combustible gases while effectively suppressing smoke generation.

[0032] 4. The antistatic agent of the present invention is formulated by compounding MXene conductive hollow microspheres and conductive carbon black. After coating MXene nanosheets with nickel metal nanoparticles, an MXene-Ni suspension is obtained. Then, the expanded thermally expanded microspheres are coated with MXene-Ni to obtain MXene conductive hollow microspheres. The hollow structure has a certain elastic deformation capability, which can buffer the interfacial stress between the matrix and the filler during processing and avoid material embrittlement caused by rigid fillers. The hollow structure can absorb energy through slight deformation. Combined with the toughening effect of bio-based thermoplastic polyester elastomer, it further improves the flexural fatigue performance and impact resistance of the cover adhesive. The hollow structure is conducive to the construction of a continuous conductive network.

[0033] 5. The MXene conductive hollow microspheres of the present invention have a negative lattice energy, meaning that the structure is highly stable at room temperature and pressure, but it is easily oxidized when in contact with oxygen or water. The coating of elemental nickel can inhibit the oxidation of MXene, maintain the long-term stability of conductivity, and MXene has strong interfacial catalytic activity, which can play a role in catalyzing carbonization during combustion. Detailed Implementation

[0034] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0035] Example 1: A method for preparing a bio-based flame-retardant and antistatic covering adhesive, comprising the following steps:

[0036] S1: Add 30g of lithium fluoride and 500mL of 35% hydrochloric acid solution to the reactor, stir at 20℃ and 500r / min for 20min, then add 12g of titanium aluminum carbide, continue stirring for 48h, centrifuge at 5000r / min for 3min, filter, wash the precipitate with deionized water and ethanol until the last wash solution is neutral, then disperse the precipitate in deionized water, sonicate at 500W for 10min under argon protection, centrifuge at 5000r / min for 1min, retain the supernatant to obtain MXene nanosheet suspension.

[0037] S2: Nickel nitrate powder and 1% polyvinylpyrrolidone were stirred and mixed to prepare a nickel nitrate solution with a concentration of 0.1 mol / L; then the nickel nitrate solution and MXene nanosheet suspension were added to the reactor at a mass ratio of 1:7, and stirred at 40℃ and 150 r / min for 6 h. After filtration, the precipitate was washed twice with deionized water and dispersed in deionized water to obtain an MXene-Ni suspension with a solid content of 5 g / L.

[0038] S3: Add 5L of 1mol / L hydroxylamine solution and 10g of thermally expanded microspheres to the reaction vessel, stir for 10min at 70℃ and 500r / min, filter, wash the precipitate twice with deionized water, and dry under vacuum at 60℃ for 1h to obtain modified thermally expanded microspheres.

[0039] S4: Mix MXene-Ni suspension and modified thermally expanded microspheres at a mass ratio of 1:8 for 1 hour, then freeze-dry at -20℃ for 72 hours. Transfer the product to a muffle furnace and calcine at 420℃ for 2 hours under a nitrogen atmosphere to obtain MXene conductive hollow microspheres. Mix MXene conductive hollow microspheres and conductive carbon black at a mass ratio of 1:1 to obtain an antistatic agent.

[0040] S5: Dry 100g of bio-based polyamide elastomer and 15g of bio-based thermoplastic polyester elastomer at 80℃ for 4h to reduce the moisture content to below 0.05%. Then transfer them to a high-speed mixer and add 13g of antistatic agent, 1g of lubricant and 0.5g of 2,6-di-tert-butyl-4-methylphenol sequentially at 20℃ and 400r / min. Stir and mix for 3min. Then add 40g of ammonium polyphosphate and melamine cyanurate in a mass ratio of 1.5:1 as a halogen-free intumescent flame retardant and 10g of nano aluminum hydroxide. Continue mixing for 5min to obtain the premix.

[0041] S6: The premixed material is melt-blended and extruded through a twin-screw extruder. The extruder temperature is set from the feed port to the die head as a gradient temperature of 185℃ in zone 1, 200℃ in zone 2, 210℃ in zone 3, 205℃ in zone 4, and 205℃ at the die head. The screw speed is 250 r / min. After melting, shearing, and mixing, the material is fully plasticized to obtain melt strips. The melt strips are then cooled and solidified in a cooling water tank at 20℃ and dried at 90℃ for 2 hours to obtain a bio-based flame-retardant and antistatic cover adhesive.

[0042] Example 2: A method for preparing a bio-based flame-retardant and antistatic covering adhesive, comprising the following steps:

[0043] S1: Add 35g of lithium fluoride and 550mL of 37.5% hydrochloric acid solution to the reactor, stir at 22.5℃ and 550r / min for 25min, then add 13g of titanium aluminum carbide, continue stirring for 49h, centrifuge at 5500r / min for 3.5min, filter, wash the precipitate with deionized water and ethanol until the last wash solution is neutral, then disperse the precipitate in deionized water, sonicate at 550W for 11min under argon protection, centrifuge at 5500r / min for 1.5min, retain the supernatant to obtain MXene nanosheet suspension.

[0044] S2: Nickel nitrate powder and 1.5% polyvinylpyrrolidone were stirred and mixed to prepare a nickel nitrate solution with a concentration of 0.11 mol / L; then the nickel nitrate solution and MXene nanosheet suspension were added to the reactor at a mass ratio of 1:7, and stirred at 42.5℃ and 155 r / min for 6.5 h. After filtration, the precipitate was washed three times with deionized water and dispersed in deionized water to obtain an MXene-Ni suspension with a solid content of 6 g / L.

[0045] S3: Add 5.5 L of 1 mol / L hydroxylamine solution and 15 g of thermally expanded microspheres to the reaction vessel, stir for 11 min at 72.5 °C and 550 r / min, filter, wash the precipitate three times with deionized water, and dry under vacuum at 65 °C for 1.5 h to obtain modified thermally expanded microspheres.

[0046] S4: The MXene-Ni suspension and modified thermally expanded microspheres were stirred and mixed at a mass ratio of 1:8 for 1.5 h, and then freeze-dried at -20℃ for 73 h. The product was transferred to a muffle furnace and calcined at 430℃ for 2.5 h under a nitrogen atmosphere to obtain MXene conductive hollow microspheres. The MXene conductive hollow microspheres and conductive carbon black were stirred and mixed at a mass ratio of 1.25:1 to obtain an antistatic agent.

[0047] S5: Dry 105g of bio-based polyamide elastomer and 25g of bio-based thermoplastic polyester elastomer at 90℃ for 5h to reduce the moisture content to below 0.06%. Then transfer them to a high-speed mixer and add 16.5g of antistatic agent, 2g of lubricant and 1g of 2,6-di-tert-butyl-4-methylphenol sequentially at 22.5℃ and 450r / min. Stir and mix for 4min. Then add 50g of ammonium polyphosphate and melamine cyanurate in a mass ratio of 1.75:1 as a halogen-free intumescent flame retardant and 15g of nano aluminum hydroxide. Continue mixing for 7.5min to obtain the premix.

[0048] S6: The premixed material is melt-blended and extruded through a twin-screw extruder. The extruder temperature is set from the feed port to the die head as a gradient temperature of 187.5℃ in zone 1, 202.5℃ in zone 2, 212.5℃ in zone 3, 207.5℃ in zone 4, and 212.5℃ at the die head. The screw speed is 325 r / min. After melting, shearing, and mixing, the material is fully plasticized to obtain melt strips. The melt strips are then cooled and solidified in a cooling water tank at 30℃ and dried at 100℃ for 3 hours to obtain a bio-based flame-retardant and antistatic cover adhesive.

[0049] Example 3: A method for preparing a bio-based flame-retardant and antistatic covering adhesive, comprising the following steps:

[0050] S1: Add 40g of lithium fluoride and 600mL of 40% hydrochloric acid solution to the reactor, stir at 25℃ and 600r / min for 30min, then add 14g of titanium aluminum carbide, continue stirring for 50h, centrifuge at 6000r / min for 4min, filter, wash the precipitate with deionized water and ethanol until the last wash solution is neutral, then disperse the precipitate in deionized water, sonicate at 600W for 12min under argon protection, centrifuge at 6000r / min for 2min, retain the supernatant to obtain MXene nanosheet suspension.

[0051] S2: Nickel nitrate powder and 2% polyvinylpyrrolidone were stirred and mixed to prepare a nickel nitrate solution with a concentration of 0.12 mol / L; then the nickel nitrate solution and MXene nanosheet suspension were added to the reactor at a mass ratio of 1:7, and stirred at 45℃ and 160 r / min for 7 h. After filtration, the precipitate was washed 4 times with deionized water and dispersed in deionized water to obtain an MXene-Ni suspension with a solid content of 7 g / L.

[0052] S3: Add 6 L of 1 mol / L hydroxylamine solution and 20 g of thermally expanded microspheres to the reaction vessel, stir for 12 min at 75 °C and 600 r / min, filter, wash the precipitate 4 times with deionized water, and dry under vacuum at 70 °C for 2 h to obtain modified thermally expanded microspheres.

[0053] S4: Mix MXene-Ni suspension and modified thermally expanded microspheres at a mass ratio of 1:8 for 2 hours, then freeze-dry at -20℃ for 74 hours. Transfer the product to a muffle furnace and calcine at 440℃ for 3 hours under a nitrogen atmosphere to obtain MXene conductive hollow microspheres. Mix MXene conductive hollow microspheres and conductive carbon black at a mass ratio of 1.5:1 to obtain an antistatic agent.

[0054] S5: Dry 110g of bio-based polyamide elastomer and 35g of bio-based thermoplastic polyester elastomer at 100℃ for 6h to reduce the moisture content to below 0.07%. Then transfer them to a high-speed mixer and add 20g of antistatic agent, 3g of lubricant and 1.5g of 2,6-di-tert-butyl-4-methylphenol sequentially at 25℃ and 500r / min. Stir and mix for 5min. Then add 60g of ammonium polyphosphate and melamine cyanurate in a mass ratio of 2:1 as a halogen-free intumescent flame retardant and 20g of nano aluminum hydroxide. Continue mixing for 10min to obtain the premix.

[0055] S6: The premixed material is melt-blended and extruded through a twin-screw extruder. The extruder temperature is set in a gradient from the feed port to the die head: 190℃ in zone 1, 205℃ in zone 2, 215℃ in zone 3, 210℃ in zone 4, and 220℃ at the die head. The screw speed is 400 r / min. After melting, shearing, and mixing, the material is fully plasticized to obtain melt strips. The melt strips are then cooled and solidified in a cooling water tank at 40℃ and dried at 110℃ for 4 hours to obtain a bio-based flame-retardant and antistatic cover adhesive.

[0056] Comparative Example 1: The bio-based flame-retardant and antistatic cover adhesive was replaced with the PVC flame-retardant conveyor belt cover adhesive, its preparation method and its application disclosed in Chinese Patent Publication No. CN115433418A, as described in paragraph 42 of the specification.

[0057] Comparative Example 2: Based on Example 3, the antistatic agent in step S5 was replaced with the conductive carbon black in step S4, while the other steps remained unchanged, to prepare a bio-based flame-retardant and antistatic covering adhesive.

[0058] Comparative Example 3: Based on Example 3, the MXene conductive hollow microspheres in step S4 were replaced with MXene-Ni suspension, while the other steps remained unchanged, to prepare a bio-based flame-retardant and antistatic covering adhesive.

[0059] In the examples and comparative examples:

[0060] The bio-based polyamide elastomer is PA1012 or PA11 nylon elastomer with a bio-based content of more than 40%. PA1012 was purchased from Dongguan Yanmei New Material Technology Co., Ltd., grade: PA1012; PA11 nylon elastomer was purchased from Suzhou Buffett Engineering Plastics Co., Ltd., grade: 70R53. In Example 1, the bio-based polyamide elastomer was PA1012, in Example 2 it was PA11 nylon elastomer, and in Example 3 it was a mixture of PA1012 and PA11 nylon elastomer in a mass ratio of 1:1.

[0061] The lubricant is zinc stearate or vinyl bis-stearamide. Vinyl bis-stearamide was purchased from Sigma-Aldrich, CAS No.: 110-30-5, molecular weight: 593.02. In Example 1, the lubricant was zinc stearate, in Example 2 it was vinyl bis-stearamide, and in Example 3 it was a mixture of zinc stearate and vinyl bis-stearamide in a mass ratio of 1:1.

[0062] Polyvinylpyrrolidone was purchased from Sigma-Aldrich, CAS No.: 9003-39-8.

[0063] The thermal expansion microspheres were purchased from Ranju (Shanghai) High-Tech Materials Co., Ltd.

[0064] After pelleting the bio-based flame-retardant and antistatic coating rubber prepared in Examples 1-3 and Comparative Examples 1-3, masterbatch was obtained. The masterbatch was pressed into standard test strips using a flat vulcanizing machine, and performance tests were conducted according to the MT / T914 standard. The results are shown in Table 1.

[0065] Table 1 Performance Test Table of Bio-based Flame Retardant and Antistatic Cover Adhesive

[0066] project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 MT / T914 requirements Tensile strength (MPa) 16.8 17.2 17.5 14.5 14.9 15.5 ≥10 Elongation at break (%) 425 438 445 360 371 383 ≥350 <![CDATA[Wear amount (mm 3 )]]> 95 92 90 185 150 120 ≤200 Surface resistivity (Ω) <![CDATA[1.6×10 7 ]]> <![CDATA[1.5×10 7 ]]> <![CDATA[1.4×10 7 ]]> <![CDATA[2.9×10 8 ]]> <![CDATA[1.8×10 8 ]]> <![CDATA[2.5×10 7 ]]> <![CDATA[≤3×10 8 ]]> Average value of flaming / flameless combustion in alcohol torch burning test (s) 1.15 1.08 1.02 2.68 1.80 1.60 ≤3 Bio-based carbon content (%) 45 47 48 0 46 46 -

[0067] As can be seen from Table 1, the bio-based flame-retardant and antistatic covering adhesives prepared in Examples 1-3 are significantly better than the comparative examples in terms of tensile strength, elongation at break, abrasion loss, flame retardancy and antistatic properties, and fully meet and exceed the MT / 914 standard.

[0068] In Comparative Example 1, the traditional PVC cover adhesive uses polyvinyl chloride as the base material and has a bio-based carbon content of 0, which contradicts the environmentally friendly design concept of the flame-retardant and antistatic cover adhesive of this invention. Moreover, chlorine-containing pollutants are easily generated during the PVC production process, and they are difficult to degrade after disposal, posing a long-term environmental risk. The flexibility and wear resistance of PVC base material are far inferior to those of bio-based polyamide elastomers. Long-term use in coal mine conveyor belts will cause the cover adhesive to wear and crack rapidly due to frequent friction and bending, shortening the service life of the conveyor belt.

[0069] In Comparative Example 2, the lack of MXene conductive hollow microspheres creates a three-dimensional conductive network. Relying solely on conductive carbon black makes it difficult to construct a continuous and stable electronic conduction pathway. The conductive network contains numerous gaps, making its antistatic properties highly susceptible to environmental influences. Furthermore, the loss of the elastic deformation buffering function of the MXene conductive hollow microspheres means that the conductive carbon black, as a rigid filler, cannot alleviate the interfacial stress between the matrix and the filler. This leads to stress concentration and microcracks in the material under stress. The absence of MXene's catalytic carbonization effect, where the hollow microsphere structure forms a physical barrier during combustion to slow heat transfer, is a function that conductive carbon black alone cannot provide.

[0070] In Comparative Example 3, the hollow structure can undergo elastic deformation under stress, buffering the interfacial stress between the matrix and the filler and preventing material embrittlement caused by rigid fillers. In contrast, MXene-Ni is a solid sheet structure with no elastic deformation capability, resulting in stress concentration at the interface and a significant decrease in material toughness. It cannot adapt to the dynamic working conditions of frequent bending and impact of conveyor belts. The hollow structure can reduce the frictional resistance between the filler and the matrix and improve wear resistance. On the other hand, the solid sheet structure of MXene-Ni has high hardness and is prone to forming stress concentration points in the matrix. It is easy to fall off during wear, which aggravates the loss of the cover adhesive. At the same time, the continuity of the conductive network is insufficient.

[0071] Although embodiments of the invention have been shown and described, it will be understood by those skilled 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 invention.

Claims

1. A bio-based flame-retardant and antistatic covering adhesive, characterized in that, The following components are included by mass: 100-110 parts bio-based polyamide elastomer, 15-35 parts bio-based thermoplastic polyester elastomer, 40-60 parts halogen-free intumescent flame retardant, 13-20 parts antistatic agent, 10-20 parts nano aluminum hydroxide, 1-3 parts lubricant and 0.5-1.5 parts 2,6-di-tert-butyl-4-methylphenol.

2. A method for preparing a bio-based flame-retardant and antistatic covering adhesive as described in claim 1, characterized in that, Includes the following steps: Step 1: Prepare an MXene nanosheet suspension by etching titanium aluminum carbide with hydrochloric acid; use the abundant functional groups and numerous defects on the surface of the MXene nanosheets in the MXene nanosheet suspension as landing sites for Ni metal nanoparticles to obtain an MXene-Ni suspension; Step 2: Modified thermally expandable microspheres are obtained by nucleophilic addition of the amino group of hydroxylamine to the cyano group on the surface of the thermally expandable microspheres; MXene conductive hollow microspheres are obtained by electrostatic interaction between the MXene-Ni suspension and the modified thermally expandable microspheres; MXene conductive hollow microspheres and conductive carbon black are stirred and mixed at a mass ratio of 1-1.5:1 to obtain an antistatic agent. Step 3: Mix bio-based polyamide elastomer, bio-based thermoplastic polyester elastomer, halogen-free intumescent flame retardant, antistatic agent, nano aluminum hydroxide, lubricant and 2,6-di-tert-butyl-4-methylphenol to obtain a premix, melt-blend and extrude, cool and cure to obtain bio-based flame retardant and antistatic cover adhesive.

3. The preparation method of a bio-based flame-retardant and antistatic covering adhesive according to claim 2, characterized in that, The specific preparation steps of the MXene nanosheet suspension are as follows: Lithium fluoride and a 35-40% hydrochloric acid solution were added to a reaction vessel and stirred at 20-25℃ and 500-600 rpm for 20-30 min. Then, titanium aluminum carbide was added and stirring was continued for 48-50 h. The mixture was centrifuged at 5000-6000 rpm for 3-4 min, filtered, and the precipitate was washed with deionized water and ethanol until the last wash solution was neutral. The precipitate was then dispersed in deionized water and sonicated at 500-600 W for 10-12 min under argon protection. The mixture was then centrifuged at 5000-6000 rpm for 1-2 min, and the supernatant was retained to obtain an MXene nanosheet suspension.

4. The preparation method of a bio-based flame-retardant and antistatic covering adhesive according to claim 3, characterized in that, The ratio of lithium fluoride, hydrochloric acid solution, and titanium aluminum carbide is 30-40g: 500-600mL: 12-14g.

5. The preparation method of a bio-based flame-retardant and antistatic covering adhesive according to claim 2, characterized in that, The specific preparation steps of the MXene-Ni suspension are as follows: Nickel nitrate powder and polyvinylpyrrolidone (PVP) with a mass fraction of 1-2% were stirred and mixed to prepare a nickel nitrate solution with a concentration of 0.1-0.12 mol / L. Then, the nickel nitrate solution and MXene nanosheet suspension were added to a reaction vessel at a mass ratio of 1:7 and stirred at 40-45℃ and 150-160 r / min for 6-7 h. After filtration, the precipitate was washed 2-4 times with deionized water and then dispersed in deionized water to obtain an MXene-Ni suspension with a solid content of 5-7 g / L.

6. The method for preparing a bio-based flame-retardant and antistatic covering adhesive according to claim 2, characterized in that, The specific preparation steps of the modified thermally expandable microspheres are as follows: A 1 mol / L hydroxylamine solution and thermally expanded microspheres were added to a reaction vessel at a mass ratio of 5-6 L: 10-20 g. The mixture was stirred at 70-75 °C and 500-600 r / min for 10-12 min. The mixture was then filtered, and the precipitate was washed 2-4 times with deionized water and dried under vacuum at 60-70 °C for 1-2 h to obtain the modified thermally expanded microspheres.

7. The preparation method of a bio-based flame-retardant and antistatic covering adhesive according to claim 2, characterized in that, The specific preparation steps for the antistatic agent are as follows: MXene-Ni suspension and modified thermally expanded microspheres were stirred and mixed at a mass ratio of 1:8 for 1-2 hours, then freeze-dried at -20℃ for 72-74 hours. The product was transferred to a muffle furnace and calcined at 420-440℃ for 2-3 hours under a nitrogen atmosphere to obtain MXene conductive hollow microspheres. MXene conductive hollow microspheres and conductive carbon black were stirred and mixed at a mass ratio of 1-1.5:1 to obtain an antistatic agent.

8. The method for preparing a bio-based flame-retardant and antistatic covering adhesive according to claim 2, characterized in that, The specific preparation steps for the premix are as follows: Bio-based polyamide elastomer and bio-based thermoplastic polyester elastomer are dried at 80-100℃ for 4-6 hours to reduce the moisture content to below 0.05-0.07%. Then, they are transferred to a high-speed mixer and, under conditions of 20-25℃ and 400-500 r / min, antistatic agent, lubricant and 2,6-di-tert-butyl-4-methylphenol are added sequentially and stirred for 3-5 minutes. Then, halogen-free intumescent flame retardant and nano aluminum hydroxide are added and the mixture is stirred for another 5-10 minutes to obtain a premix.

9. The preparation method of a bio-based flame-retardant and antistatic covering adhesive according to claim 8, characterized in that, The mass ratio of the bio-based polyamide elastomer, bio-based thermoplastic polyester elastomer, antistatic agent, lubricant, 2,6-di-tert-butyl-4-methylphenol, halogen-free intumescent flame retardant, and nano-aluminum hydroxide is 100-110:15-35:13-20:1-3:0.5-1.5:40-60:10-20.

10. The method for preparing a bio-based flame-retardant and antistatic covering adhesive according to claim 1, characterized in that, The specific preparation steps of the bio-based flame-retardant and antistatic cover adhesive are as follows: The premixed material is melt-blended and extruded using a twin-screw extruder. The extruder temperature is set at a gradient of 180-220℃ from the feed port to the die head, and the screw speed is 250-400 r / min. After melting, shearing, and mixing, the material is fully plasticized to obtain molten strips. The molten strips are then cooled and solidified in a cooling water bath at a temperature of 20-40℃, and then dried at 90-110℃ for 2-4 hours to obtain a bio-based flame-retardant and antistatic cover adhesive.