Viscosity-reducing rubber powder modified asphalt based on reversible dynamic covalent bonds and preparation method thereof

Abstract

The application belongs to the technical field of road materials, and particularly relates to a viscosity-reducing rubber powder modified asphalt based on reversible dynamic covalent bonds and a preparation method thereof. Raw materials of the rubber powder modified asphalt include: 100 parts of base asphalt, 21-29 parts of mixed devulcanized rubber powder, 1-5 parts of viscosity reducer and 0.5-2 parts of surface functionalized nanomaterials, wherein the surface functionalized nanomaterials include multi-walled carbon nanotubes containing at least one functional group of carboxyl, hydroxyl or amino on the surface. A temperature-responsive interfacial chemical buffer system is constructed through reversible dynamic covalent bonds formed between the functionalized multi-walled carbon nanotubes and the viscosity reducer styrene-maleic anhydride copolymer, and the contradiction that viscosity reduction and interfacial stability cannot be achieved simultaneously in the prior art is solved. The modified asphalt simultaneously considers excellent viscosity reduction effect, storage stability and large-temperature-difference resistance durability, and provides an effective solution for road surface materials in large-temperature-difference areas.

Description

Technical Field

[0001] This invention relates to the field of road materials technology, and in particular to a viscosity-reducing modified asphalt based on reversible dynamic covalent bonds and its preparation method. Background Technology

[0002] With the continuous prosperity and development of the global economy and the rapid increase in car ownership, a large amount of waste tires have accumulated and become difficult to dispose of, resulting in insufficient utilization of rubber resources and seriously affecting environmental safety and ecological balance. Grinding waste tires into rubber powder and preparing rubber-modified asphalt for paving asphalt roads can not only implement the sustainable development strategy but also reduce economic costs, resulting in good economic benefits.

[0003] Rubber-modified asphalt has great potential for application in road construction and maintenance due to its excellent performance. However, existing rubber-modified asphalt has problems such as high viscosity, difficulty in production and construction, low compatibility with asphalt, and poor storage stability of finished asphalt.

[0004] Therefore, there is an urgent need for a viscosity-reducing, performance-stable rubber-modified asphalt and its preparation method. Summary of the Invention

[0005] In view of this, this invention proposes a viscosity-reducing modified asphalt based on reversible dynamic covalent bonds and its preparation method. This invention mainly uses a high-content desulfurized rubber powder and a viscosity reducer to reduce viscosity and lower the asphalt mixing temperature. However, it was found that the viscosity reducer exacerbates the interfacial stress problem between the rubber powder and asphalt under large temperature differences. Therefore, multi-walled carbon nanotubes (MWCNTs) with specific functional groups on their surface are introduced. These surface functional groups form reversible dynamic covalent bonds with the active groups of the viscosity reducer, creating a temperature-responsive interfacial buffer system: at high construction temperatures, the dynamic covalent bonds break, ensuring the viscosity-reducing effect and workability; at pavement service temperatures, the dynamic covalent bonds are rebuilt, restoring and enhancing the interfacial bonding force, effectively buffering the interfacial stress caused by thermal expansion differences. Ultimately, this achieves improved viscosity reduction and stability performance of the rubber powder-modified asphalt.

[0006] The coefficients of thermal expansion of rubber powder and asphalt naturally differ. Viscosity reducers primarily work by breaking down the polymer chains in rubber-modified asphalt or reducing intermolecular entanglement, thereby decreasing intermolecular forces and internal resistance. However, reduced entanglement also means a decrease in the relaxation capacity of interfacial stress. In regions with large temperature differences, this interfacial stress is further amplified, impairing interfacial stability and fatigue resistance, leading to cracks and fissures in the pavement and shortening its service life. Therefore, resolving the contradiction between viscosity reduction and interfacial stability is crucial to ensuring the performance of rubber-modified asphalt.

[0007] The technical solution of this invention is implemented as follows: In a first aspect, the present invention provides a viscosity-reducing rubber powder modified asphalt, wherein the raw materials of the rubber powder modified asphalt, by mass parts, include: 100 parts of base asphalt, 21 to 29 parts of mixed desulfurized rubber powder, 1 to 5 parts of viscosity reducer and 0.5 to 2 parts of surface functionalized nanomaterials.

[0008] Based on the above technical solutions, preferably, the surface-functionalized nanomaterial includes multi-walled carbon nanotubes with at least one functional group (carboxyl, hydroxyl, or amino) on the surface; the viscosity reducer includes styrene-maleic anhydride copolymer (SMA).

[0009] The maleic anhydride group (-CO-O-CO-) in SMA is the core active site. This five-membered cyclic anhydride has high reactivity and can undergo ring-opening reactions at high temperatures. The styrene unit provides π-π affinity with the aromatic components in asphalt, enhancing the dispersion and compatibility of SMA in asphalt. The C=C unsaturated double bond in the maleic anhydride unit provides a potential anchor point for subsequent cross-linking reactions. Under high temperature (≥180℃) and strong shear force, the maleic anhydride group of SMA can insert into the hydrogen bond network between asphaltene molecules. Through the strong interaction between the anhydride ring and the polar groups (-OH, -NH-) of asphaltene, it breaks the original intermolecular association, thereby reducing molecular entanglement and lowering the viscosity of the system. Furthermore, the maleic anhydride group of SMA undergoes an esterification ring-opening reaction with the -OH on the surface of MWCNTs to generate β-hydroxy ester bonds. The β-hydroxy ester bonds are in a dynamic equilibrium of breakage and reconstruction. At high temperatures, the bonding network dissociates, the temperature decreases, and the thermodynamic equilibrium shifts towards the bonding direction. Dynamic ester bond re-establishment covalently anchors MWCNTs to the SMA-asphalt network, forming a chemically cross-linked buffer layer at the interface between rubber powder and asphalt. A strong hydrogen bond network is formed between the -COOH group on the MWCNTs surface and the anhydride group of SMA. The -OH portion of the -COOH group can also undergo ring-opening esterification with the anhydride, generating a cross-linked structure containing ester bonds. The buffering effect is achieved through a dynamic hydrogen bond-ester bond synergistic network. The -NH2 group on the MWCNTs surface reacts with the anhydride group of SMA, first generating an amide acid intermediate, which then closes at high temperature to form a stable imide bond. Its reversibility is weaker than that of the ester bond, resulting in a lower reconstruction efficiency at low temperatures compared to the ester bond system.

[0010] Based on the above technical solutions, a further preferred embodiment is that the surface functionalized nanomaterial includes multi-walled carbon nanotubes with hydroxyl groups on the surface; the raw materials of the rubber powder modified asphalt include: 100 parts of base asphalt, 21 parts of mixed desulfurized rubber powder, 1 part of viscosity reducer SMA and 1 part of multi-walled carbon nanotube material with hydroxyl groups on the surface.

[0011] Based on the above technical solutions, preferably, the preparation method of the surface-functionalized nanomaterial includes: S1, the step of mixing multi-walled carbon nanotubes (MWCNTs) with mixed acids to react and obtain carboxylated multi-walled carbon nanotubes; Alternatively, step S2 involves reacting the carboxylated multi-walled carbon nanotubes from step S1 with thionyl chloride and N,N-dimethylformamide to obtain an acyl chloride intermediate; then reacting the acyl chloride intermediate with an alcohol to obtain hydroxylated multi-walled carbon nanotubes. Alternatively, in step S3, the carboxylated multi-walled carbon nanotubes from step S1 are mixed with 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide to activate the carboxyl groups; then 1,6-hexanediamine is added to react and obtain aminated multi-walled carbon nanotubes.

[0012] Based on the above technical solutions, preferably, in step S1, the mixed acid includes sulfuric acid and nitric acid; and in step S2, the alcohol includes ethylene glycol.

[0013] Based on the above technical solution, in a further preferred embodiment, in step S1, 1g of multi-walled carbon nanotubes are mixed with 100ml of mixed acid, ultrasonically dispersed, stirred and refluxed in an oil bath at 80℃ for 4-6 hours, cooled to room temperature, diluted with deionized water, filtered, and the filter cake is washed with deionized water until the pH of the filtrate is neutral. The filter cake is then dried in a vacuum at 80℃ for 12 hours to obtain carboxylated multi-walled carbon nanotubes (MWCNTs-COOH). The mixed acid comprises concentrated sulfuric acid (approximately 98% by mass) and concentrated nitric acid (approximately 65-68% by mass) in a volume ratio of 3:1. In step S2, 1g of the carboxylated multi-walled carbon nanotubes from step S1 were mixed with 50ml of thionyl chloride and 2ml of N,N-dimethylformamide and magnetically stirred under reflux in an oil bath at 70℃ for 24 hours. The mixture was then distilled to obtain an acyl chloride intermediate. The acyl chloride intermediate was added to 50mL of ethylene glycol that had been dried using molecular sieves and ultrasonically dispersed for 15 minutes. The mixture was then magnetically stirred in an oil bath at 120℃ for 48 hours. After cooling, the mixture was filtered and washed three times each with anhydrous ethanol and deionized water. Finally, it was vacuum dried at 80℃ for 12 hours to obtain hydroxylated multi-walled carbon nanotubes (MWCNTs-OH). In step S3, 1g of carboxylated multi-walled carbon nanotubes from step S1 were added to 50 mL of anhydrous ethanol and ultrasonically dispersed for 20 minutes. Then, 2g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl) and 1.2g of N-hydroxysuccinimide (NHS) were added and stirred at room temperature for 30 minutes to activate the carboxyl groups. Then, 5g of 1,6-hexanediamine was added and stirred in an oil bath at 60℃ for 24 hours. After cooling, the mixture was filtered and washed three times each with anhydrous ethanol and deionized water. The mixture was then vacuum dried at 80℃ for 12 hours to obtain aminated multi-walled carbon nanotubes (MWCNTs-NH2).

[0014] Based on the above technical solutions, preferably, the diameter of the multi-walled carbon nanotube is 10~30nm and the length is 1~10μm.

[0015] Multi-walled carbon nanotubes of suitable length can form an effective network structure while maintaining dispersibility. If the multi-walled carbon nanotubes are too short, they can only be embedded in the shallow surface of the powder and cannot form an effective anchor. This can easily lead to the shedding of the interface buffer layer and make them not durable. On the other hand, if the multi-walled carbon nanotubes are too long, they are prone to entanglement and clumping, making them difficult to disperse and easily forming agglomerates, which can lead to stress concentration.

[0016] Based on the above technical solutions, preferably, the mixed desulfurized rubber powder includes 40 mesh, 60 mesh and 80 mesh desulfurized rubber powder.

[0017] Based on the above technical solutions, preferably, the mass ratio of the 40-mesh, 60-mesh, and 80-mesh desulfurized rubber powder is 1:(0.75~1.3):(0.25~0.5).

[0018] Based on the above technical solution, a further preferred embodiment is that the mass ratio of the 40-mesh, 60-mesh, and 80-mesh desulfurized rubber powder is 1:1:0.33.

[0019] Secondly, a method for preparing viscosity-reducing rubber powder modified asphalt as described above is provided, comprising the following steps: S11, surface-functionalized nanomaterials are mixed with 80-mesh desulfurized rubber powder, heated and stirred to obtain nano-functionalized rubber powder particles; S12: Heat the base asphalt to a molten state, add nano-functionalized rubber powder particles, 40 mesh and 60 mesh desulfurized rubber powder while stirring, stir and swell; S13, after swelling, is subjected to high-speed shearing to obtain mixed rubber powder modified asphalt; S14, after shearing and cooling, then adding viscosity reducer, stirring evenly, and then undergoing high-temperature development, yields viscosity-reducing rubber powder modified asphalt.

[0020] Based on the above technical solutions, preferably, in step S11, the heating and stirring temperature is 160~170℃ and the time is 30~60min; in step S12, the swelling temperature is 165~175℃ and the time is 60~90min.

[0021] Based on the above technical solutions, in a further preferred embodiment, in step S11, the heating and stirring temperature is 165℃ and the time is 45min; in step S12, the swelling temperature is 170℃ and the time is 75min.

[0022] Based on the above technical solutions, preferably, in step S13, the temperature of the high-speed shearing is 180~190℃; in step S14, the temperature of the cooling is 150~160℃, and the temperature of the high-temperature development is 165~175℃ for 1~2 hours.

[0023] Based on the above technical solution, in a further preferred embodiment, in step S13, the temperature of the high-speed shearing is 185℃; in step S14, the temperature of the cooling is 155℃, and the temperature of the high-temperature development is 170℃ for 1.5 hours.

[0024] The viscosity-reducing modified asphalt based on reversible dynamic covalent bonds and its preparation method of the present invention have the following advantages over the prior art: 1. This invention recognizes that the use of viscosity reducers weakens the entanglement between asphalt molecules and reduces the relaxation ability of interfacial stress, which in turn exacerbates the risk of debonding at the rubber powder-asphalt interface under large temperature difference conditions. Therefore, by introducing surface-functionalized multi-walled carbon nanotubes (MWCNTs) to synergistically construct a reversible dynamic covalent bond network with the viscosity reducer styrene-maleic anhydride copolymer (SMA), the viscosity reduction effect and interfacial stability are fundamentally unified.

[0025] 2. This invention constructs a temperature-responsive interfacial chemical buffer system through reversible dynamic covalent bonds formed between the surface functional groups (such as -OH, -COOH, -NH2) of MWCNTs and the maleic anhydride groups of SMA: at high construction temperatures (≥160℃), the dynamic covalent bonds break, and SMA freely exerts its viscosity-reducing effect, ensuring workability during construction; at pavement service temperatures (-30~70℃), the dynamic covalent bonds are rebuilt, and MWCNTs are covalently anchored to the SMA-asphalt network, forming a chemically cross-linked buffer layer at the interface between the rubber powder and asphalt; this is fundamentally different from the physical filling route of existing technologies.

[0026] 3. The modified asphalt of this invention achieves three synergistic optimizations: viscosity reduction, storage stability, and durability against large temperature differences. In the preferred embodiment, the rotational viscosity at 135℃ can be reduced to 2.38 Pa·s, the segregation softening point difference can be as low as 1.5℃, and after large temperature difference cycling, the ductility decay rate at 5℃ can be as low as 9.2%, while the ordinary MWCNTs scheme is as high as 34.5% and the scheme without SMA is as high as 49.8%. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a flow chart of the preparation process of the rubber powder modified asphalt of the present invention. Detailed Implementation

[0029] 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 a part of the embodiments of the present invention, and not all of the 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.

[0030] The desulfurized rubber powder used in this invention was purchased from Shandong Luke Composite Materials Co., Ltd., with different particle sizes corresponding to different product models; multi-walled carbon nanotubes were purchased from Suzhou CarbonFeng Graphene Technology Co., Ltd.; SMA was purchased from Unilon Industrial Co., Ltd., model SMA-900; unless otherwise specified, all materials used in this invention are conventional commercially available products. The base asphalt is Panjin 90# base asphalt, and its technical specifications are shown in Table 1.

[0031] Table 1 Performance Indicators of 90# Base Asphalt

[0032] Example 1 Preparation of a viscosity-reducing rubber powder modified asphalt.

[0033] 1. Preparation of MWCNTs-OH: 1g of multi-walled carbon nanotubes were mixed with 67ml of concentrated sulfuric acid and 33ml of concentrated nitric acid, ultrasonically dispersed, and stirred under reflux in an oil bath at 80℃ for 5h. After cooling to room temperature, the mixture was diluted with deionized water, filtered, and the filter cake was washed with deionized water until the pH of the filtrate was neutral. The filter cake was dried under vacuum at 80℃ for 12h to obtain MWCNTs-COOH. 1g of MWCNTs-COOH was then mixed with 50ml of thionyl chloride and 2ml of N,N-dimethylformamide, and magnetically stirred under reflux in an oil bath at 70℃ for 24h. After distillation, an acyl chloride intermediate was obtained. The acyl chloride intermediate was added to 50mL of ethylene glycol dried by molecular sieves, ultrasonically dispersed for 15 minutes, and magnetically stirred in an oil bath at 120℃ for 48h. After cooling, the mixture was filtered, washed three times each with anhydrous ethanol and deionized water, and dried under vacuum at 80℃ for 12h to obtain MWCNTs-OH.

[0034] 2. Preloading of nanomaterials: 1 g of MWCNTs-OH was ultrasonically dispersed in 20 ml of anhydrous ethanol and mixed evenly with 3 g of 80 mesh desulfurized rubber powder. The mixture was stirred at 165℃ and 700 r / min for 45 minutes to obtain nanofunctionalized rubber powder.

[0035] 3. Weigh 100g of base asphalt and heat it to a molten state at 155℃. While stirring at 700r / min, add the nano-functionalized rubber powder from step 2, 9g of 40-mesh desulfurized rubber powder, and 9g of 60-mesh desulfurized rubber powder in sequence, and stir for 15 minutes. Then, swell it at 170℃ for 75 minutes. On a heating platform at 185℃, shear it at a shear rate of 4000r / min for 1.5 hours until it is fully pyrolyzed. After shearing, cool it down to 155℃ and add 1g of SMA while stirring at 700r / min. Stir until it is completely dissolved and evenly dispersed, and then stop stirring. The stirring time is about 5 minutes. After developing at 170℃ for 1.5 hours, the viscosity-reducing rubber powder modified asphalt is obtained.

[0036] Example 2 Preparation of a viscosity-reducing rubber powder modified asphalt.

[0037] 1. Preparation of MWCNTs-OH: Same as in Example 1.

[0038] 2. Preloading of nanomaterials: 0.5g of MWCNTs-OH was ultrasonically dispersed in 20ml of anhydrous ethanol and mixed evenly with 3g of 80-mesh desulfurized rubber powder. The mixture was stirred at 160℃ and 700r / min for 60 minutes to obtain nanofunctionalized rubber powder.

[0039] 3. Weigh 100g of base asphalt and heat it to a molten state at 155℃. While stirring at 700r / min, add the nano-functionalized rubber powder from step 2, 9g of 40-mesh desulfurized rubber powder, and 9g of 60-mesh desulfurized rubber powder in sequence, and stir for 15 minutes. Then, swell it at 165℃ for 90 minutes. On a heating platform at 180℃, shear it at a shear rate of 4000r / min for 1.5 hours until it is fully pyrolyzed. After shearing, cool it down to 150℃ and add 1g of SMA while stirring at 700r / min. Stir until it is completely dissolved and evenly dispersed, and then stop stirring. The stirring time is about 5 minutes. After developing at 165℃ for 2 hours, the viscosity-reducing rubber powder modified asphalt is obtained.

[0040] Example 3 Preparation of a viscosity-reducing rubber powder modified asphalt.

[0041] 1. Preparation of MWCNTs-OH: Same as in Example 1.

[0042] 2. Preloading of nanomaterials: 2 g of MWCNTs-OH was ultrasonically dispersed in 20 ml of anhydrous ethanol and mixed evenly with 5 g of 80 mesh desulfurized rubber powder. The mixture was stirred at 170℃ and 700 r / min for 30 minutes to obtain nanofunctionalized rubber powder.

[0043] 3. Weigh 100g of base asphalt and heat it to a molten state at 155℃. While stirring at 700r / min, add the nano-functionalized rubber powder from step 2, 12g of 40-mesh desulfurized rubber powder, and 12g of 60-mesh desulfurized rubber powder in sequence, and stir for 15 minutes. Then, swell it at 175℃ for 60 minutes. On a heating platform at 190℃, shear it at a shear rate of 4000r / min for 1.5 hours until it is fully pyrolyzed. After shearing, cool it down to 160℃ and add 5g of SMA while stirring at 700r / min. Stir until it is completely dissolved and evenly dispersed, and then stop stirring. The stirring time is about 5 minutes. After developing at 175℃ for 1 hour, the viscosity-reducing rubber powder modified asphalt is obtained.

[0044] Example 4 Preparation of a viscosity-reducing rubber powder modified asphalt.

[0045] 1. Preparation of MWCNTs-COOH: Mix 1g of multi-walled carbon nanotubes with 67ml of concentrated sulfuric acid and 33ml of concentrated nitric acid, disperse by ultrasonication, stir and reflux in an oil bath at 80℃ for 5h, cool to room temperature, dilute with deionized water, filter, wash the filter cake with deionized water until the pH of the filtrate is neutral, and dry the filter cake in vacuum at 80℃ for 12h to obtain MWCNTs-COOH.

[0046] 2. Preloading of nanomaterials: 1 g of MWCNTs-COOH was ultrasonically dispersed in 20 ml of anhydrous ethanol and mixed evenly with 3 g of 80 mesh desulfurized rubber powder. The mixture was stirred at 165℃ and 700 r / min for 45 minutes to obtain nanofunctionalized rubber powder.

[0047] 3. Weigh 100g of base asphalt and heat it to a molten state at 155℃. While stirring at 700r / min, add the nano-functionalized rubber powder from step 2, 9g of 40-mesh desulfurized rubber powder, and 9g of 60-mesh desulfurized rubber powder in sequence, and stir for 15 minutes. Then, swell it at 170℃ for 75 minutes. On a heating platform at 185℃, shear it at a shear rate of 4000r / min for 1.5 hours until it is fully pyrolyzed. After shearing, cool it down to 155℃ and add 1g of SMA while stirring at 700r / min. Stir until it is completely dissolved and evenly dispersed, and then stop stirring. The stirring time is about 5 minutes. After developing at 170℃ for 1.5 hours, the viscosity-reducing rubber powder modified asphalt is obtained.

[0048] Example 5 Preparation of a viscosity-reducing rubber powder modified asphalt.

[0049] 1. Preparation of MWCNTs-NH2: 1g of multi-walled carbon nanotubes were mixed with 67ml of concentrated sulfuric acid and 33ml of concentrated nitric acid, ultrasonically dispersed, and stirred under reflux in an oil bath at 80℃ for 5h. After cooling to room temperature, the mixture was diluted with deionized water, filtered, and the filter cake was washed with deionized water until the pH of the filtrate was neutral. The filter cake was dried in a vacuum at 80℃ for 12h to obtain MWCNTs-COOH. 1g of MWCNTs-COOH was added to 50mL of anhydrous ethanol and ultrasonically dispersed for 20 minutes. Then, 2g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl) and 1.2g of N-hydroxysuccinimide (NHS) were added and stirred at room temperature for 30 minutes to activate the carboxyl groups. Then, 5g of... 1,6-Hexanediamine was stirred in an oil bath at 60°C for 24 hours, cooled, filtered, washed three times each with anhydrous ethanol and deionized water, and dried under vacuum at 80°C for 12 hours to obtain aminated multi-walled carbon nanotubes (MWCNTs-NH2).

[0050] 2. Preloading of nanomaterials: 1 g of MWCNTs-NH2 was ultrasonically dispersed in 20 ml of anhydrous ethanol and mixed evenly with 3 g of 80 mesh desulfurized rubber powder. The mixture was stirred at 165℃ and 700 r / min for 45 minutes to obtain nanofunctionalized rubber powder.

[0051] 3. Weigh 100g of base asphalt and heat it to a molten state at 155℃. While stirring at 700r / min, add the nano-functionalized rubber powder from step 2, 9g of 40-mesh desulfurized rubber powder, and 9g of 60-mesh desulfurized rubber powder in sequence, and stir for 15 minutes. Then, swell it at 170℃ for 75 minutes. On a heating platform at 185℃, shear it at a shear rate of 4000r / min for 1.5 hours until it is fully pyrolyzed. After shearing, cool it down to 155℃ and add 1g of SMA while stirring at 700r / min. Stir until it is completely dissolved and evenly dispersed, and then stop stirring. The stirring time is about 5 minutes. After developing at 170℃ for 1.5 hours, the viscosity-reducing rubber powder modified asphalt is obtained.

[0052] Example 6 Preparation of a viscosity-reducing rubber powder modified asphalt.

[0053] The preparation method of this embodiment is basically the same as that of Example 1, except that in step 2, the amount of MWCNTs-OH used is 0.5g.

[0054] Example 7 Preparation of a viscosity-reducing rubber powder modified asphalt.

[0055] The preparation method of this embodiment is basically the same as that of Example 1, except that in step 2, the amount of MWCNTs-OH used is 2g.

[0056] Comparative Example 1 The preparation method of this comparative example is basically the same as that of Example 1, except that in step 2, the amount of MWCNTs-OH used is 0.3g.

[0057] Comparative Example 2 The preparation method of this comparative example is basically the same as that of Example 1, except that in step 2, the amount of MWCNTs-OH used is 2.5g.

[0058] Comparative Example 3 The preparation method of this comparative example is basically the same as that of Example 1, except that in step 2, an equal amount of MWCNTs is used directly instead of MWCNTs-OH.

[0059] Comparative Example 4 The preparation method of this comparative example is basically the same as that of Example 1, except that in step 3, the viscosity reducer SMA was not added.

[0060] The asphalt samples prepared in Examples 1-7 and Comparative Examples 1-4 were tested under the same conditions using conventional methods for penetration (25℃, 100g, 5s, 0.1mm), softening point, ductility at 5℃, Brookfield rotational viscosity at 135℃, and difference in segregation softening point; as well as the ductility at 5℃ and its decay rate before and after large temperature difference cycling. The test methods are as follows: The initial ductility at 5℃ of each sample was tested by subjecting each sample to 30 cycles from -30℃ to 60℃. Each cycle consisted of: holding at -30℃ for 4 hours, raising the temperature to 60℃ for 1 hour, holding at 60℃ for 4 hours, and lowering the temperature to -30℃ for 1 hour. The ductility at 5℃ after the cycle was then tested. The ductility decay rate was calculated as (ductility before cycle - ductility after cycle) / ductility before cycle × 100%. The results are shown in Table 1.

[0061] Table 1

[0062] The penetration (45.6~47.1), softening point (65.8~68.2℃), ductility at 5℃ (24.5~25.1cm), and penetration index (PI) (0.773~0.854) of all embodiments met the technical requirements. The PI values ​​of the embodiments were all at a high level (>0.7), indicating that the chemical cross-linking network formed by functionalized MWCNTs and SMA effectively improved the temperature sensitivity of asphalt. The rotational viscosity at 135℃ of Examples 1~5 was in the range of 2.38~2.51 Pa·s, significantly lower than the 3.07 Pa·s of Comparative Example 4, and met the technical requirement of ≤3.0 Pa·s. This demonstrates that the SMA copolymer can effectively reduce viscosity in high-content rubber powder systems (21~29%), and the addition of functionalized MWCNTs did not negate this effect. Example 1 achieved excellent storage stability and resistance to large temperature difference cycling with a segregation softening point difference of 1.5℃ and a ductility decay rate of 9.2%. This directly proves that the interfacial chemical buffer system constructed by functionalized MWCNTs and SMA through reversible dynamic covalent bonds is an effective means to resolve the contradiction between viscosity reduction and interfacial stability. Furthermore, the ductility decay rate of Example 1 (9.2%) is lower than that of Examples 4 (13.1%) and 5 (17.3%), indicating that the β-hydroxy ester bond formed between MWCNTs-OH and SMA has the optimal dynamic reversibility efficiency.

[0063] When the amount of MWCNTs-OH in the 1st example was insufficient (<0.5g), the coverage of MWCNTs-OH on the surface of 80-mesh rubber powder was too low, and a continuous interfacial chemical buffer layer could not be formed. The dynamic ester bond density formed by SMA and carbon nanotubes was insufficient to effectively dissipate the interfacial stress generated by large temperature differences, and the protective effect was significantly reduced. When the amount of MWCNTs-OH in the 2nd example was too high, MWCNTs-OH was already supersaturated on the surface of rubber powder. Due to the high surface energy, the excess carbon nanotubes tended to agglomerate in the asphalt matrix. The agglomerates became stress concentration points, which induced interfacial defects and led to negative effects.

[0064] Comparative Example 4 showed the worst performance in terms of segregation softening point difference (4.8℃) and ductility decay rate (49.8%), indicating that without any interface stabilization measures, the negative impact of viscosity reduction (decreased interface relaxation ability) will be fully exposed under large temperature differences, leading to severe storage instability and interface debonding.

[0065] Although Comparative Example 3 (ordinary MWCNTs) showed some improvement compared to Comparative Example 4, the segregation value (3.2℃) still exceeded the standard and the ductility decay rate still reached 34.5%, proving that simple physical blending cannot compensate for the weakening of the interface by viscosity reducers.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A viscosity-reducing modified asphalt powder, characterized in that, The raw materials of the rubber-modified asphalt, by weight, include: 100 parts base asphalt, 21-29 parts mixed desulfurized rubber powder, 1-5 parts viscosity reducer, and 0.5-2 parts surface functionalized nanomaterials.

2. The viscosity-reducing modified asphalt as described in claim 1, characterized in that: The surface-functionalized nanomaterials include multi-walled carbon nanotubes with at least one functional group (carboxyl, hydroxyl, or amino) on their surface; the viscosity reducer includes styrene-maleic anhydride copolymer.

3. The viscosity-reducing modified asphalt as described in claim 2, characterized in that, The preparation method of the surface-functionalized nanomaterials includes: S1, the step of mixing multi-walled carbon nanotubes with mixed acid and reacting to obtain carboxylated multi-walled carbon nanotubes; Alternatively, step S2 involves reacting the carboxylated multi-walled carbon nanotubes from step S1 with thionyl chloride and N,N-dimethylformamide to obtain an acyl chloride intermediate; then reacting the acyl chloride intermediate with an alcohol to obtain hydroxylated multi-walled carbon nanotubes. Alternatively, in step S3, the carboxylated multi-walled carbon nanotubes from step S1 are mixed with 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide to activate the carboxyl groups; then 1,6-hexanediamine is added to react and obtain aminated multi-walled carbon nanotubes.

4. The viscosity-reducing modified asphalt as described in claim 3, characterized in that: In step S1, the mixed acid includes sulfuric acid and nitric acid; in step S2, the alcohol includes ethylene glycol.

5. The viscosity-reducing modified asphalt as described in claim 2, characterized in that: The multi-walled carbon nanotubes have a diameter of 10~30nm and a length of 1~10μm.

6. The viscosity-reducing modified asphalt as described in claim 1, characterized in that: The mixed desulfurized rubber powder includes 40 mesh, 60 mesh and 80 mesh desulfurized rubber powder.

7. The viscosity-reducing modified asphalt as described in claim 6, characterized in that: The mass ratio of the 40-mesh, 60-mesh, and 80-mesh desulfurized rubber powder is 1:(0.75~1.3):(0.25~0.5).

8. A method for preparing viscosity-reducing modified asphalt as described in claim 1, characterized in that, Includes the following steps: S11, surface-functionalized nanomaterials are mixed with 80-mesh desulfurized rubber powder, heated and stirred to obtain nano-functionalized rubber powder particles; S12: Heat the base asphalt to a molten state, add nano-functionalized rubber powder particles, 40 mesh and 60 mesh desulfurized rubber powder while stirring, stir and swell; S13, after swelling, is subjected to high-speed shearing to obtain mixed rubber powder modified asphalt; S14, after shearing and cooling, then adding viscosity reducer, stirring evenly, and then undergoing high-temperature development, yields viscosity-reducing rubber powder modified asphalt.

9. The method for preparing viscosity-reducing modified asphalt as described in claim 8, characterized in that: In step S11, the heating and stirring temperature is 160~170℃ and the time is 30~60min; in step S12, the swelling temperature is 165~175℃ and the time is 60~90min.

10. The method for preparing viscosity-reducing modified asphalt according to claim 8, characterized in that: In step S13, the temperature of the high-speed shearing is 180~190℃; in step S14, the temperature of the cooling is 150~160℃, and the temperature of the high-temperature development is 165~175℃ for 1~2 hours.

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