Antistatic composite rubber sheet and method for manufacturing the same

Abstract

This invention relates to an antistatic composite rubber sheet, comprising, by weight, the following components: 100 parts of a ternary blended rubber matrix, 12-28 parts of a core-shell hybrid filler, 3-6 parts of zinc oxide, 2-5 parts of sulfur, 0.8-2.5 parts of accelerator, 1.5-3.5 parts of calcium stearate, 2-6 parts of plasticizer, and 0.2-0.8 parts of anti-scorching agent. The core-shell hybrid filler is a core-shell structure with a hybrid framework of in-situ grown carbon nanotubes from carbon fibers, and the surface grafted with hindered phenol-hindered amine-benzotriazole ternary anti-aging groups. The core-shell hybrid filler uses carbon fibers as the core to grow carbon nanotubes in situ, forming a one-dimensional to three-dimensional hybrid framework of carbon fibers and carbon nanotubes. The carbon nanotubes grow vertically on the surface of the carbon fibers, forming a "sea urchin-like" structure, upgrading the contact mode between the fillers from the traditional point contact of one-dimensional carbon fibers to line and surface contact. This allows for the construction of a three-dimensional conductive network throughout the entire rubber matrix with extremely low filler content.

Description

Technical Field

[0001] This invention relates to the field of rubber sheet technology, specifically to an antistatic composite rubber sheet and its preparation method. Background Technology

[0002] Rubber sheets, as a core industrial material, are widely used in electronics, petrochemicals, mining, metallurgy, aerospace, and other fields, playing a crucial role in electrostatic protection, shock absorption and sealing, and wear and corrosion resistance. Traditional rubber materials are insulating materials with a volume resistivity reaching 10⁻⁶. 14 -10 16 Ω・cm, during use, easily leads to charge accumulation, triggering electrostatic discharge. This can cause minor issues like electronic equipment malfunction and data loss, or even serious accidents like fires and explosions in flammable and explosive environments, resulting in personal injury and property damage. Furthermore, over long-term use, rubber sheets are subjected to multiple factors such as heat, oxygen, ultraviolet light, ozone, and mechanical stress, causing aging and degradation, resulting in a significant decrease in mechanical and antistatic properties and a drastically shortened lifespan.

[0003] In existing technologies, antistatic properties are typically imparted to rubber by adding conductive fillers (such as carbon black, carbon fibers, carbon nanotubes, and metal fillers) to the rubber matrix, while anti-aging agents are added to improve aging resistance. Among these, invention patent CN118325207B discloses an antistatic composite rubber sheet and its preparation method, which simultaneously improves the antistatic properties, mechanical properties, and resistance to thermo-oxidative aging of the rubber sheet by adding multifunctional carbon fibers with surface-grafted hindered amine and hindered phenolic groups to natural rubber. However, this technical solution still has the following drawbacks: 1. Using one-dimensional carbon fiber as a single conductive filler, only point-contact conductive networks can be formed between the fillers. A high filling amount is required to achieve the ideal antistatic effect. Moreover, a high filling amount will deteriorate the processing fluidity and resilience of the rubber. Under long-term dynamic use and high and low temperature cycling conditions, the carbon fiber is prone to slippage and overlap failure, the conductive network breaks, the antistatic performance decays rapidly, and the long-term performance is poor; 2. The thermo-oxidative aging protection is achieved only through hindered phenol and hindered amine groups, which cannot resist ultraviolet light aging and ozone aging. Under outdoor, high-altitude, and high ozone concentration conditions, the rubber matrix is ​​prone to chain breakage and cross-linking hardening, resulting in a rapid decline in performance; 3. Using a single natural rubber as the matrix, the oil resistance, solvent resistance, and low-temperature resistance are poor, which cannot meet the requirements for use in oilfield chemical and low-temperature and high-altitude scenarios; 4. The use of an open mill intermittent mixing process results in poor uniformity of the conductive filler dispersion in the rubber matrix, large performance fluctuations between batches, and failure to meet the consistency requirements of large-scale industrial production. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] This invention provides an antistatic composite rubber sheet and its preparation method, which solves the problems mentioned in the background art.

[0006] (II) Technical Solution

[0007] To achieve the above objectives, the present invention provides the following technical solution: an antistatic composite rubber sheet, comprising, by weight, the following components: 100 parts of a ternary blended rubber matrix, 12-28 parts of a core-shell hybrid filler, 3-6 parts of zinc oxide, 2-5 parts of sulfur, 0.8-2.5 parts of accelerator, 1.5-3.5 parts of calcium stearate, 2-6 parts of plasticizer, and 0.2-0.8 parts of scorching inhibitor; the ternary blended rubber matrix is ​​obtained by compounding natural rubber, butadiene rubber, and nitrile rubber in a mass ratio of 60-75:15-25:5-20; the core-shell hybrid filler is a core-shell structure filler with a hybrid framework of in-situ grown carbon nanotubes as the core and a surface grafted with hindered phenol-hindered amine-benzotriazole ternary anti-aging groups.

[0008] Preferably, the core-shell hybrid filler is prepared by the following steps:

[0009] Step 1: Place the carbon fiber in a muffle furnace and calcine it at 380-420℃ for 10-20 minutes to remove the sizing agent. After cooling with the furnace, add concentrated nitric acid and stir the reaction at 40-45℃ for 2-4 hours. Centrifuge and wash until neutral, and dry to obtain acidified carbon fiber.

[0010] Step 2: Disperse the acidified carbon fiber in anhydrous ethanol by ultrasonication, add ferric nitrate and nickel nitrate catalyst precursors, stir evenly and dry, place in a chemical vapor deposition furnace, purge with argon gas and heat to 650-750℃, purge with acetylene gas and keep the reaction at the temperature for 15-30 min, and cool with the furnace to obtain the carbon fiber-carbon nanotube hybrid framework.

[0011] Step 3: Add the hybrid framework and silane coupling agent to an 80-85% (v / v) ethanol solution, sonicate at 50-60 kHz for 30-60 min, stir at 80-85 ℃ for 3-5 h, centrifuge, wash and dry to obtain the aminated hybrid framework.

[0012] Step 4: Dissolve cyanuric chloride and anhydrous toluene by stirring. Stir and react at 25-30℃ for 15-20 min. Add 2,2,6,6-tetramethylpiperidineamine dropwise. After the addition is complete, add 30-35% sodium hydroxide solution. Heat to 75-80℃ and react for 10-15 h. Post-treatment yields intermediate 1 containing hindered amine groups.

[0013] Step B5: Methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate was dissolved in anhydrous ethanol by stirring. Under nitrogen protection, 30-35% sodium hydroxide solution was added dropwise. The mixture was heated to 65-70℃ and reacted for 4-6 hours. The pH was then acidified to 3-4. After post-treatment, intermediate 2 containing hindered phenolic groups was obtained. Intermediate 2 was mixed with chloroform, and thionyl chloride was added dropwise. The mixture was heated to 50-55℃ and reacted for 5-7 hours. The mixture was then rotary evaporated to obtain acyl chloride hindered phenol intermediate 3.

[0014] Step 6: Mix 2-(2'-hydroxy-5'-carboxyphenyl)benzotriazole and chloroform, add thionyl chloride dropwise under nitrogen protection, heat to 50-55℃ and react for 4-6 hours, then rotary evaporate to obtain benzotriazole acyl chloride intermediate 4;

[0015] Step 7: Mix intermediate 1, intermediate 3, intermediate 4, aminated hybrid framework, 30-35% sodium hydroxide solution, and xylene. Stir and pre-react at 25-30℃ for 15-20 min under nitrogen protection. Then, heat to 110-125℃ and react for 8-12 h. After centrifugation, washing, and drying, the core-shell hybrid filler is obtained.

[0016] In a further preferred embodiment, the mass ratio of acidified carbon fiber, ferric nitrate, and nickel nitrate in step 2 is 10:0.8-1.5:0.2-0.5, the argon flow rate is 200-300 sccm, and the acetylene flow rate is 50-80 sccm.

[0017] In a further preferred embodiment, the ratio of the hybrid framework, silane coupling agent, and ethanol solution used in step 3 is 3g:1.0-3.0g:50-60mL.

[0018] In a further preferred embodiment, the mass ratio of intermediate 1, intermediate 3, intermediate 4, and aminated hybrid skeleton in step 7 is 0.5-1.2:0.6-1.8:0.4-1.0:3.

[0019] The present invention also provides the following technical solution: a method for preparing an antistatic composite rubber sheet, comprising the following steps: ingredient preparation: weighing each component according to the weight parts for later use;

[0020] Plasticizing: The ternary blended rubber matrix is ​​placed in a two-mill and plasticized in a thin pass at 45-50℃ for 8-12 times to obtain plasticized rubber.

[0021] Ultrasonic pre-dispersion: The core-shell hybrid filler and plasticizer are added to anhydrous ethanol and ultrasonically dispersed at 40-60 kHz for 20-40 min to obtain the filler pre-dispersion solution;

[0022] Internal mixing premix: Add the plasticized rubber to the internal mixer and mix at 60-70℃ for 3-5 minutes. Add the filler predispersant, zinc oxide, and calcium stearate, and mix for 8-12 minutes. Discharge the rubber to obtain the premixed rubber.

[0023] Twin-screw continuous mixing: Premixed rubber, sulfur, accelerator, and anti-scorching agent are added to a twin-screw extruder. The extrusion temperature is 50-70℃ and the screw speed is 150-250rpm. The mixture is continuously mixed and extruded to obtain a mixed rubber compound.

[0024] Compression vulcanization: The mixed rubber compound is placed in the mold of a flat vulcanizing machine, the vulcanization temperature is 140-155℃, the vulcanization pressure is 10-15MPa, and the vulcanization time is 20-40min to obtain an antistatic composite rubber sheet.

[0025] Preferably, the twin-screw extruder has a length-to-diameter ratio of 40:1, and the twin-screw extruder adopts segmented temperature control, with the feeding section at 50-55℃, the plasticizing section at 55-65℃, the homogenizing section at 60-70℃, and the die head section at 55-60℃.

[0026] In a further preferred embodiment, after the initial vulcanization is completed during the molding vulcanization process, the mixture is vulcanized at room temperature for 24 hours.

[0027] (III) Beneficial Effects

[0028] Compared with the prior art, the present invention provides an antistatic composite rubber sheet and its preparation method, which has the following beneficial effects:

[0029] 1. In this invention, the core-shell hybrid filler uses carbon fiber as the core to grow carbon nanotubes in situ, forming a one-dimensional to three-dimensional hybrid framework of carbon fiber and carbon nanotubes. The carbon nanotubes grow vertically on the surface of the carbon fiber, forming a "sea urchin-like" structure. This upgrades the contact mode between the fillers from the traditional point contact of one-dimensional carbon fibers to line and surface contact, enabling the construction of a three-dimensional conductive network that runs through the entire rubber matrix with extremely low filler content. Simultaneously, the in-situ grown carbon nanotubes are covalently bonded to the carbon fiber, eliminating the risk of detachment. Under long-term dynamic use and high / low temperature cycling conditions, the conductive network structure remains stable, solving the problem of insufficient long-term performance of traditional antistatic rubbers.

[0030] 2. In this invention, a ternary synergistic anti-aging group consisting of hindered phenol, hindered amine, and benzotriazole is grafted onto the surface of a hybrid filler. The hindered phenol acts as a chain-terminating antioxidant, capturing peroxide free radicals; the hindered amine acts as a free radical scavenger, also decomposing hydrogen peroxide and enabling the cyclic regeneration of anti-aging functions; and the benzotriazole acts as a UV absorber, absorbing 280-400nm UV light to prevent the rubber molecular chains from breaking due to UV excitation. The synergistic effect of these three components provides comprehensive aging protection against heat, oxygen, UV, and ozone. Combined with the physical barrier effect of carbon nanotubes (blocking oxygen, water vapor, and UV light penetration), the anti-aging performance is further enhanced.

[0031] 3. In this invention, a ternary blend matrix of natural rubber, butadiene rubber, and nitrile rubber is used. Natural rubber provides excellent mechanical strength and elasticity; butadiene rubber enhances the low-temperature resistance and resilience of the rubber sheet; and nitrile rubber improves the oil and solvent resistance of the rubber sheet. The synergistic blend of these three materials balances the mechanical properties, resilience, low-temperature resistance, and oil and solvent resistance of the rubber sheet, solving the problem of narrow applicability of traditional single-natural rubber matrices. It can simultaneously meet the application requirements of various scenarios such as indoor electronic workshops, outdoor power transmission and transformation, oilfield chemical plants, and high-altitude cold regions. Attached Figure Description

[0032] Figure 1 This is a flowchart illustrating the preparation process of the core-shell hybrid filler according to the implementation plan.

[0033] Figure 2 This is a flowchart illustrating the preparation process of the antistatic composite rubber sheet according to the implementation plan. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Example 1

[0036] Please see Figure 1 and Figure 2 The antistatic composite rubber sheet provided in this embodiment has the following components by weight: 100 parts of ternary blended rubber matrix (NR:BR:NBR=70:20:10), 18 parts of core-shell hybrid filler, 5 parts of zinc oxide, 3.5 parts of sulfur, 1.5 parts of accelerator M, 2.5 parts of calcium stearate, 4 parts of plasticizer DOA, and 0.5 parts of anti-scorching agent CTP.

[0037] The preparation steps of the core-shell hybrid filler are as follows:

[0038] Step 1: Carbon fiber pretreatment: Place 3g of T30012K carbon fiber in a muffle furnace and calcine at 400℃ for 15min to remove the sizing agent. After cooling in the furnace, add 45mL of 68% concentrated nitric acid and stir at 42℃ for 3h. Centrifuge and wash with distilled water until neutral. Vacuum dry at 75℃ for 6h to obtain acidified carbon fiber.

[0039] Step 2, In-situ growth of carbon nanotubes: 10g of acidified carbon fiber was placed in 200mL of anhydrous ethanol and ultrasonically dispersed at 55kHz for 30min. 1.0g of ferric nitrate and 0.3g of nickel nitrate were added, and the mixture was stirred for 2h and then dried. The mixture was placed in a CVD furnace, protected with argon gas (250sccm), heated to 700℃, and acetylene gas (60sccm) was introduced to maintain the temperature for 20min. The mixture was then cooled with the furnace to obtain a carbon fiber-carbon nanotube hybrid framework.

[0040] Step 3, Hybrid framework coupling modification: Add 3g of hybrid framework and 1.5g of silane coupling agent KH-792 to 55mL of 85% ethanol solution, sonicate at 55kHz for 40min, stir at 82℃ for 4h, centrifuge and wash, and vacuum dry at 85℃ for 6h to obtain aminated hybrid framework.

[0041] Step 4, Synthesis of hindered amine intermediate: 10 mmol of cyanuric chloride and 52 mL of anhydrous toluene were added to a three-necked flask and stirred at 28 °C and 350 r / min for 18 min. 24 mmol of 2,2,6,6-tetramethylpiperidineamine was added dropwise. After the addition was complete, 22 mL of 32% sodium hydroxide solution was added. The temperature was raised to 78 °C and the reaction was carried out for 12 h. After cooling, deionized water was poured in, and the mixture was extracted four times with ethyl acetate. After drying with anhydrous sodium sulfate, the mixture was rotary evaporated to obtain intermediate 1.

[0042] Step 5, Synthesis of hindered phenol intermediate: 10 mmol of methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate and 32 mL of anhydrous ethanol were added to a three-necked flask. The mixture was stirred at 28 °C for 18 min under nitrogen protection. 18 mL of 32% sodium hydroxide solution was added dropwise, and the mixture was heated to 68 °C and reacted for 4.5 h. After cooling, the mixture was acidified to pH 3.5 with 21% hydrochloric acid, filtered, and dried under vacuum at 62 °C for 1.2 h to obtain intermediate 2. 10 mmol of intermediate 2 and 32 mL of chloroform were added to a three-necked flask. 6 mL of thionyl chloride was added dropwise under nitrogen protection, and the mixture was heated to 52 °C and reacted for 5.5 h. The mixture was then rotary evaporated to obtain intermediate 3.

[0043] Step 6, Synthesis of benzotriazole intermediate: 10 mmol of 2-(2'-hydroxy-5'-carboxyphenyl)benzotriazole and 30 mL of chloroform were added to a three-necked flask. Under nitrogen protection, 5 mL of thionyl chloride was added dropwise, and the mixture was heated to 52 °C and reacted for 5 h. The mixture was then rotary evaporated to obtain intermediate 4.

[0044] Step 7, Ternary group grafting modification: 1.0 g intermediate 1, 1.2 g intermediate 3, 0.7 g intermediate 4, 3 g aminated hybrid backbone, 32 mL 32% sodium hydroxide solution, and 52 mL xylene were added to a three-necked flask. The mixture was stirred and pre-reacted at 28 °C for 18 min under nitrogen protection, then heated to 115 °C and reacted for 10 h. After cooling, the mixture was centrifuged and washed three times with ethyl acetate and distilled water, respectively. The mixture was then vacuum dried at 65 °C for 8 h to obtain the core-shell hybrid filler.

[0045] The preparation steps of the composite rubber sheet are as follows:

[0046] Ingredients: Weigh each component according to the specified weight and set aside.

[0047] Plasticizing: Plasticizing: The ternary blended rubber matrix is ​​placed in a two-mill and plasticized in a thin pass at 48°C 10 times to obtain plasticized rubber;

[0048] Ultrasonic pre-dispersion: The core-shell bifunctional hybrid filler and plasticizer DOA were added to anhydrous ethanol and ultrasonically dispersed at 55 kHz for 30 min to obtain the filler pre-dispersion solution.

[0049] Internal mixing premix: Add the plasticized rubber to the internal mixer and mix at 65°C for 4 minutes. Add the filler predispersant, zinc oxide, and calcium stearate, and mix for 10 minutes. Discharge the rubber to obtain the premixed rubber.

[0050] Twin-screw continuous mixing: Premixed rubber, sulfur, accelerator M, and anti-scorching agent CTP are added to a twin-screw extruder (length-to-diameter ratio 40:1). The temperature is controlled in stages: feeding section 52℃, plasticizing section 60℃, homogenizing section 65℃, die head section 58℃, screw speed 200rpm, and continuous mixing and extrusion are carried out to obtain a mixed rubber compound.

[0051] Compression vulcanization: The mixed rubber compound is placed in the mold of a flat vulcanizing machine. The vulcanization temperature is 150℃, the vulcanization pressure is 12MPa, and the vulcanization time is 30min. After vulcanization, it is vulcanized at room temperature for 24h to obtain a long-lasting antistatic composite rubber sheet.

[0052] The combined process of ultrasonic pre-dispersion, internal mixing, and twin-screw continuous mixing can break up filler agglomerates through ultrasound and achieve uniform dispersion through the strong shear of twin screws.

[0053] Example 2

[0054] This embodiment provides an antistatic composite rubber sheet, which, by weight, comprises the following components: 100 parts of ternary blended rubber matrix (NR:BR:NBR=65:20:15), 24 parts of core-shell bifunctional hybrid filler, 6 parts of zinc oxide, 4.5 parts of sulfur, 2.0 parts of accelerator M, 3.0 parts of calcium stearate, 5 parts of plasticizer DOA, and 0.6 parts of anti-scorching agent CTP.

[0055] The preparation methods for the core-shell hybrid filler and the antistatic composite rubber sheet are basically the same as in Example 1, with the only difference being:

[0056] In step 7 of the preparation of the core-shell hybrid filler, the mass ratio of intermediate 1, intermediate 3, intermediate 4, and aminated hybrid framework is 1.2:1.5:0.9:3.

[0057] In the molding and vulcanization process of the antistatic composite rubber sheet preparation method, the vulcanization temperature is 155℃ and the vulcanization time is 35min.

[0058] Example 3

[0059] This embodiment provides an antistatic composite rubber sheet, which, by weight, comprises the following components: 100 parts of ternary blended rubber matrix (NR:BR:NBR=75:15:10), 12 parts of core-shell bifunctional hybrid filler, 4 parts of zinc oxide, 2.5 parts of sulfur, 1.0 part of accelerator M, 2.0 parts of calcium stearate, 3 parts of plasticizer DOA, and 0.3 parts of anti-scorching agent CTP.

[0060] The preparation methods for the core-shell hybrid filler and the antistatic composite rubber sheet are basically the same as in Example 1, with the only difference being:

[0061] In step 7 of the preparation of the core-shell hybrid filler, the mass ratio of intermediate 1, intermediate 3, intermediate 4, and aminated hybrid framework is 0.6:0.8:0.5:3.

[0062] In the molding and vulcanization process of the antistatic composite rubber sheet preparation method, the vulcanization temperature is 145℃ and the vulcanization time is 25min.

[0063] Comparative Example 1

[0064] This comparative example is Example 3 of the existing patent CN118325207B. For specific formulations and preparation methods, please refer to the existing patent documents.

[0065] Comparative Example 2

[0066] The only difference between this comparative example and Example 1 is that the core-shell hybrid filler is replaced with an equal mass of the multifunctional carbon fiber in the existing patent CN118325207B, while the other components and preparation methods are completely consistent.

[0067] Comparative Example 3

[0068] The only difference between this comparative example and Example 1 is that the core-shell hybrid filler is only grafted with hindered phenol and hindered amine groups, and not with benzotriazole groups. The other components are completely consistent with the preparation method.

[0069] Comparative Example 4

[0070] The only difference between this comparative example and Example 1 is that the rubber matrix uses a single natural rubber, while the other components and preparation methods are completely consistent.

[0071] The samples from Examples 1-3 and Comparative Examples 1-4 were subjected to performance tests according to the following standards:

[0072] Volume resistivity: Tested according to GB / T1410-2006 "Test methods for volume resistivity and surface resistivity of solid insulating materials";

[0073] Tensile strength: Tested in accordance with GB / T528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber";

[0074] Hot air aging performance: According to GB / T3512-2014 "Accelerated aging and heat resistance test of vulcanized rubber or thermoplastic rubber in hot air", the tensile strength was tested after aging in hot air at 200℃ for 72 hours, and the retention rate was calculated.

[0075] UV aging performance: According to GB / T16422.3-2014 "Laboratory Light Source Exposure Test Methods for Plastics - Part 3: Fluorescent Ultraviolet Lamps", using UVB-313 lamp tubes, irradiance 0.71W / (m²・nm), tensile strength was tested after aging for 500h, and retention rate was calculated.

[0076] Ozone aging performance: According to GB / T7762-2014 "Static tensile test for ozone cracking of vulcanized rubber or thermoplastic rubber", the ozone concentration is 50pphm, the temperature is 40℃, the elongation rate is 20%, and the tensile strength is tested after aging for 72 hours. The retention rate is calculated.

[0077] Oil resistance: According to GB / T1690-2010 "Test method for resistance of vulcanized rubber or thermoplastic rubber to liquid", the mass change rate is tested by immersing the rubber in ASTM No.1 oil at 23°C for 72 hours.

[0078] Low temperature resistance: The brittle temperature was tested according to GB / T15256-2014 "Determination of low temperature brittleness of vulcanized rubber (multiple sample method)".

[0079] The test results are shown in the table below:

[0080]

[0081] The test results show that:

[0082] The antistatic properties of Examples 1-3 of this invention are superior to those of Comparative Example 1. Example 2, with a fill amount of 24 parts, has a volume resistivity as low as 8.6 × 10¹ Ω・cm, reaching the conductivity standard, which is superior to 2.6 × 10³ Ω・cm of Comparative Example 1, proving that the design of the three-dimensional conductive network improves the antistatic properties.

[0083] The performance retention rate of the embodiments of the present invention after thermo-oxidative, ultraviolet and ozone aging is all above 98%, which is better than that of comparative examples 1, 2 and 3, proving that the ternary synergistic anti-aging system achieves aging protection in all scenarios and solves the problem of the single dimension of anti-aging in existing patents.

[0084] The oil resistance and low-temperature resistance of the embodiments of the present invention are superior to those of Comparative Example 1 and Comparative Example 4 with a single rubber matrix, proving that the ternary blended rubber matrix expands the applicability of working conditions.

[0085] The tensile strength of the embodiments of the present invention is higher than that of Comparative Example 1, which proves that the core-shell structure filler and the rubber matrix have a good interfacial bond and achieve simultaneous improvement of mechanical properties.

[0086] In this embodiment, during the in-situ growth of carbon nanotubes (CVD covalent bonding) to form a one-dimensional-three-dimensional hybrid framework, the carbon fibers are first calcined at high temperature to remove the surface slurry, and then etched with concentrated nitric acid. This introduces polar active sites on the carbon fiber surface, providing covalent bonding sites for the in-situ growth of carbon nanotubes. Activated carbon fibers loaded with an iron / nickel catalyst are placed in a CVD furnace, and acetylene gas is introduced. At a high temperature of 650-750℃, carbon atoms generated from acetylene decomposition directly nucleate and grow at the active sites on the carbon fiber surface. The carbon nanotubes are tightly bonded to the carbon fibers through C-C covalent bonds, rather than through physical adsorption or coating. The carbon fiber acts as a one-dimensional rigid backbone, with carbon nanotubes growing vertically outward on its surface to form a three-dimensional branching structure, ultimately forming a "trunk + branches" "sea urchin-like" hybrid framework. The contact method of the conductive filler is upgraded from the traditional point contact of one-dimensional carbon fibers to line-to-surface contact and surface-to-surface contact. Covalent bonds are far stronger than physical forces, allowing carbon nanotubes and carbon fibers to become an integrated whole. This can withstand the strong shear forces of open-mill / twin-screw compounding of rubber, preventing the skeleton from breaking and the carbon nanotubes from detaching. The three-dimensional dendrites increase the contact probability with the filler, forming a continuous three-dimensional conductive pathway even with a low filler content. Under dynamic conditions such as stretching, compression, and high / low temperature cycling, the conductive network remains intact, thus solving the problem of slippage and conductivity failure associated with traditional one-dimensional carbon fibers' "point contact." The covalently integrated skeleton has no physical bonding interface, preventing breakage and carbon nanotube detachment under strong shear during compounding, ensuring stable conductivity and avoiding interruptions in the conductive pathway due to filler breakage. The one-dimensional / three-dimensional hybrid skeleton can efficiently transfer stress, combining the high strength of carbon fibers with the high modulus of carbon nanotubes, significantly improving the tensile strength, tear strength, and abrasion resistance of the rubber sheet.

[0087] In this embodiment, during the chemical grafting of the hindered phenol-hindered amine-benzotriazole ternary anti-aging group, the one-dimensional-three-dimensional hybrid framework is modified with silane coupling agent KH-792, introducing amino active groups on the framework surface to provide reaction sites for the covalent grafting of the anti-aging group. The hindered amine intermediate (containing reactive Cl atoms), acyl-chlorinated hindered phenol, and acyl-chlorinated benzotriazole undergo nucleophilic substitution and acylation reactions with the amino groups on the framework surface, firmly fixing them to the hybrid framework surface by covalent bonds, rather than through physical adsorption or blending. The grafted ternary anti-aging group is an organic polymer segment, with polarity matching with the natural rubber, butadiene rubber, and nitrile rubber matrix, eliminating the interfacial energy difference between the inorganic filler and the organic rubber, and achieving nanoscale uniform dispersion of the filler in the rubber. The covalently grafted group does not migrate, volatilize, or precipitate, and can withstand high-temperature vulcanization of rubber at 140-155℃. It will not detach from the filler surface under long-term dynamic deformation, thus extending the anti-aging effectiveness. The organic grafted layer acts as an "interfacial bridge," eliminating interfacial defects between inorganic fillers and organic rubber, preventing interfacial debonding and stress concentration, and simultaneously improving the mechanical properties and fatigue resistance of the rubber. The anti-aging groups are fixed on the filler surface and will not migrate to the rubber surface like small molecule anti-aging agents, thus avoiding contamination of electronic components and affecting appearance and performance.

[0088] In this embodiment, in the covalently bonded core-shell structure of carbon nanotubes grown in situ from carbon fibers, the core layer, through a one-dimensional to three-dimensional covalent hybrid framework of carbon fibers and carbon nanotubes grown in situ by CVD, is responsible for electrical conductivity, mechanical reinforcement, and structural support; the shell layer, through a covalently grafted hindered phenol-hindered amine-benzotriazole ternary organic layer, is responsible for anti-aging, interfacial compatibility, and functional protection; the core-shell covalent bonding means that the amino groups on the surface of the core layer are bonded to the anti-aging intermediates of the shell layer through a chemical reaction, and the entire core-shell structure is a fully covalent system without physical coating interfaces. The covalent bond energy (300-500 kJ / mol) is much higher than that of intermolecular forces and hydrogen bonds. The core layer and shell layer, and the carbon nanotubes and carbon fibers are all integrally covalently bonded. Throughout the entire life cycle of rubber processing and long-term use, the core-shell structure will not peel off, break, or fail. The core layer focuses on enhancing conductivity, while the shell layer focuses on anti-aging compatibility. The two layers do not interfere with each other and work synergistically to achieve long-lasting antistatic properties, all-scenario anti-aging, high mechanical properties, and excellent interfacial compatibility—a multi-functional integration that traditional single-filler, physical core-shell structures cannot achieve. Furthermore, unlike physical core-shell structures used for rigid materials, this covalent core-shell structure is specifically designed for rubber elastomers, solving the problems of easy breakage, shell detachment, and functional failure in traditional core-shell structures within rubber. In addition, the covalent core-shell filler has good dispersibility, with no agglomeration or sedimentation. Combined with a twin-screw continuous mixing process, it exhibits minimal batch-to-batch performance fluctuations, making it suitable for large-scale industrial production.

[0089] In the description of this invention, it should be noted that the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance, unless otherwise expressly specified and limited. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0090] 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 alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An antistatic composite rubber sheet and its preparation method, characterized in that, By weight, it includes the following components: 100 parts of ternary blended rubber matrix, 12-28 parts of core-shell hybrid filler, 3-6 parts of zinc oxide, 2-5 parts of sulfur, 0.8-2.5 parts of accelerator, 1.5-3.5 parts of calcium stearate, 2-6 parts of plasticizer, and 0.2-0.8 parts of scorch inhibitor; The ternary blended rubber matrix is ​​obtained by compounding natural rubber, butadiene rubber and nitrile rubber in a mass ratio of 60-75:15-25:5-20. The core-shell hybrid filler is a core with a hybrid framework of carbon nanotubes grown in situ from carbon fibers, and a surface grafted with hindered phenol-hindered amine-benzotriazole ternary anti-aging groups.

2. The antistatic composite rubber sheet according to claim 1, characterized in that: The core-shell hybrid filler was prepared by the following steps: Step 1: Place the carbon fiber in a muffle furnace and calcine it at 380-420℃ for 10-20 minutes to remove the sizing agent. After cooling with the furnace, add concentrated nitric acid and stir the reaction at 40-45℃ for 2-4 hours. Centrifuge and wash until neutral, and dry to obtain acidified carbon fiber. Step 2: Disperse the acidified carbon fiber in anhydrous ethanol by ultrasonication, add ferric nitrate and nickel nitrate catalyst precursors, stir evenly and dry, place in a chemical vapor deposition furnace, purge with argon gas and heat to 650-750℃, purge with acetylene gas and keep the reaction at the temperature for 15-30 min, and cool with the furnace to obtain the carbon fiber-carbon nanotube hybrid framework. Step 3: Add the hybrid framework and silane coupling agent to an 80-85% (v / v) ethanol solution, sonicate at 50-60 kHz for 30-60 min, stir at 80-85 ℃ for 3-5 h, centrifuge, wash and dry to obtain the aminated hybrid framework. Step 4: Dissolve cyanuric chloride and anhydrous toluene by stirring. Stir and react at 25-30℃ for 15-20 min. Add 2,2,6,6-tetramethylpiperidineamine dropwise. After the addition is complete, add 30-35% sodium hydroxide solution. Heat to 75-80℃ and react for 10-15 h. Post-treatment yields intermediate 1 containing hindered amine groups. Step B5: Methyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate was dissolved in anhydrous ethanol by stirring. Under nitrogen protection, 30-35% sodium hydroxide solution was added dropwise. The mixture was heated to 65-70℃ and reacted for 4-6 hours. The pH was then acidified to 3-4. After post-treatment, intermediate 2 containing hindered phenolic groups was obtained. Intermediate 2 was mixed with chloroform, and thionyl chloride was added dropwise. The mixture was heated to 50-55℃ and reacted for 5-7 hours. The mixture was then rotary evaporated to obtain acyl chloride hindered phenol intermediate 3. Step 6: Mix 2-(2'-hydroxy-5'-carboxyphenyl)benzotriazole and chloroform, add thionyl chloride dropwise under nitrogen protection, heat to 50-55℃ and react for 4-6 hours, then rotary evaporate to obtain benzotriazole acyl chloride intermediate 4; Step 7: Mix intermediate 1, intermediate 3, intermediate 4, aminated hybrid framework, 30-35% sodium hydroxide solution, and xylene. Stir and pre-react at 25-30℃ for 15-20 min under nitrogen protection. Then, heat to 110-125℃ and react for 8-12 h. After centrifugation, washing, and drying, the core-shell hybrid filler is obtained.

3. The antistatic composite rubber sheet according to claim 2, characterized in that: In step 2, the mass ratio of acidified carbon fiber, ferric nitrate, and nickel nitrate is 10:0.8-1.5:0.2-0.5, the argon flow rate is 200-300 sccm, and the acetylene flow rate is 50-80 sccm.

4. The antistatic composite rubber sheet according to claim 2, characterized in that: The ratio of the hybrid framework, silane coupling agent, and ethanol solution used in step 3 is 3g:1.0-3.0g:50-60mL.

5. The antistatic composite rubber sheet according to claim 2, characterized in that: In step 7, the mass ratio of intermediate 1, intermediate 3, intermediate 4, and aminated hybrid skeleton is 0.5-1.2:0.6-1.8:0.4-1.0:

3.

6. A method for preparing an antistatic composite rubber sheet according to any one of claims 1-5, characterized in that, Includes the following steps: Ingredients: Weigh each component according to the specified weight and set aside. Plasticizing: The ternary blended rubber matrix is ​​placed in a two-mill and plasticized in a thin pass at 45-50℃ for 8-12 times to obtain plasticized rubber. Ultrasonic pre-dispersion: The core-shell hybrid filler and plasticizer are added to anhydrous ethanol and ultrasonically dispersed at 40-60 kHz for 20-40 min to obtain the filler pre-dispersion solution; Internal mixing premix: Add the plasticized rubber to the internal mixer and mix at 60-70℃ for 3-5 minutes. Add the filler predispersant, zinc oxide, and calcium stearate, and mix for 8-12 minutes. Discharge the rubber to obtain the premixed rubber. Twin-screw continuous mixing: Premixed rubber, sulfur, accelerator, and anti-scorching agent are added to a twin-screw extruder. The extrusion temperature is 50-70℃ and the screw speed is 150-250rpm. The mixture is continuously mixed and extruded to obtain a mixed rubber compound. Compression vulcanization: The mixed rubber compound is placed in the mold of a flat vulcanizing machine, the vulcanization temperature is 140-155℃, the vulcanization pressure is 10-15MPa, and the vulcanization time is 20-40min to obtain an antistatic composite rubber sheet.

7. The method for preparing an antistatic composite rubber sheet according to claim 6, characterized in that: The twin-screw extruder has a length-to-diameter ratio of 40:

1. The twin-screw extruder adopts segmented temperature control, with the feeding section at 50-55℃, the plasticizing section at 55-65℃, the homogenizing section at 60-70℃, and the die head section at 55-60℃.

8. The method for preparing an antistatic composite rubber sheet according to claim 6, characterized in that: During the molding vulcanization process, after vulcanization is completed, the mixture is vulcanized at room temperature for 24 hours.

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