A modified asphalt and a process for its preparation

Abstract

The application discloses modified asphalt and a preparation process thereof, and belongs to the technical field of road materials. The modified asphalt is composed of 80-90 parts of base asphalt, 4-8 parts of butadiene styrene rubber, 2-5 parts of nano montmorillonite, 1.5-3 parts of core-shell structure nanoparticles (the inner core is SiO2 grafted with SO3H, the intermediate layer is temperature-sensitive PNIPAM containing a photoinitiator, and the outer shell is GO grafted with a hindered phenol antioxidant group and a photosensitive coumarin group), and 1-3 parts of a compatilizer, 3-6 parts of a plasticizer and 0.3-0.8 parts of an antioxidant. The preparation process comprises the steps of pretreating a modifier masterbatch, melt blending, high-speed shearing, ultrasonic dispersion and cooling and discharging. The application utilizes a light response crosslinking mechanism, realizes crosslinking under light irradiation through the light response characteristics of the core-shell structure nanoparticles, significantly improves the high-temperature stability, anti-aging performance and fatigue life of the modified asphalt, and is suitable for fields such as high-grade road construction.

Description

Technical Field

[0001] This invention relates to the field of road engineering materials technology, specifically to a modified asphalt and its preparation process. Background Technology

[0002] In road engineering, the performance of asphalt materials directly affects the service life of the pavement. Traditional asphalt has significant defects: at high temperatures, it is prone to rutting due to molecular chain slippage (softening point is generally <80℃), and at low temperatures, the molecular chain segments stiffen, leading to cracks (ductility <20cm at -20℃). Furthermore, during long-term service, it is subject to oxidation aging under the influence of ultraviolet light and oxygen (photo-oxidation induction period <100 minutes).

[0003] While modified asphalt technology has improved asphalt performance to some extent, it still has shortcomings. For example, some modifiers have poor compatibility with asphalt, making it difficult to form a uniform and stable system; some modification methods are complex and costly; and there is a lack of effective mechanisms to address performance changes in asphalt under different environmental and usage conditions.

[0004] While existing modified asphalt can improve performance by adding polymers (such as styrene-butadiene rubber) or nanoparticles (such as montmorillonite), it faces three core problems:

[0005] 1. Insufficient compatibility between modifier and asphalt: Physical blending easily leads to the agglomeration of nanoparticles, making it difficult to form a stable system, and the modification effect decays significantly over time;

[0006] 2. Single performance improvement mechanism: Relying on a single physical crosslinking (such as polymer winding) or chemical crosslinking (such as sulfur vulcanization) cannot balance high and low temperature performance. Insufficient crosslinking density at high temperature leads to poor stability, while excessive crosslinking at low temperature causes brittle fracture.

[0007] 3. Inefficient anti-aging system: Traditional antioxidants (such as hindered phenols) only delay oxidation through a single mechanism of free radical capture, lacking synergistic inhibition of aging through multiple pathways such as metal ion catalysis and oxygen permeation, resulting in limited improvement in long-term anti-aging performance.

[0008] Therefore, it is necessary to provide a modified asphalt and its preparation process. By optimizing the raw material formulation and preparation process of the modified asphalt, good compatibility and dispersibility among the raw materials can be ensured, forming a uniform and stable system. This enables the modified asphalt to adapt to different environments and usage conditions, meeting the performance requirements of asphalt materials in fields such as high-grade road construction. Summary of the Invention

[0009] The purpose of this invention is to provide a modified asphalt and its preparation process. By introducing core-shell structured nanoparticles with a photoresponsive crosslinking mechanism, the performance limitations of traditional modified asphalt are overcome. Core-shell structured nanoparticles with a photoresponsive crosslinking mechanism are constructed, and their crosslinking characteristics under light irradiation are utilized to improve the high-temperature stability, anti-aging properties and fatigue life of the modified asphalt.

[0010] In response to the problems raised in the background art, this invention aims to develop a modified asphalt with environmental responsiveness, but it faces the following technical challenges:

[0011] Controllable construction of core-shell structure: Sulfonic acid groups, thermosensitive PNIPAM layer and photoresponsive GO shell layer need to be grafted sequentially on the surface of nano SiO2. The thickness of each layer, crosslinking density and interfacial bonding force need to be precisely controlled to avoid interlayer delamination or functional group failure.

[0012] Design of photo-temperature synergistic response mechanism: The low critical solution temperature (32±1℃) of PNIPAM needs to be matched with the service temperature range of asphalt, while ensuring the cross-linking efficiency of coumarin groups in the GO shell under light irradiation, so as to achieve the interpenetration enhancement of the photocrosslinking network and the temperature-sensitive shrinkage network at high temperature, and the synergistic effect of the extension of temperature-sensitive chain segments and the stress dispersion of photocrosslinking nodes at low temperature.

[0013] Multi-scale dispersion and interfacial compatibility: Nano-montmorillonite and core-shell particles have poor compatibility with asphalt matrix. They need to be uniformly dispersed at the nanoscale through organic intercalation and gradient dispersion processes to avoid performance defects caused by agglomeration.

[0014] To achieve the above-mentioned objectives and overcome the above-mentioned technical difficulties, the present invention provides the following technical solution:

[0015] In a first aspect, this invention provides a modified asphalt composed of the following raw materials in parts by weight: 80-90 parts base asphalt; 4-8 parts styrene-butadiene rubber; 2-5 parts nano-montmorillonite; and 1.5-3 parts core-shell structured nanoparticles, with specific structural parameters as follows:

[0016] The core is SiO2, and the surface is grafted with sulfonic acid groups (-SO3H), with a grafting density of 0.5-1.2 mmol / g;

[0017] The intermediate layer is thermosensitive poly(N-isopropylacrylamide) (PNIPAM) and contains 0.5-2% photoinitiator;

[0018] The outer shell is graphene oxide (GO), with hindered phenolic antioxidant groups and photosensitive coumarin groups grafted onto the surface;

[0019] In addition, there are 1-3 parts compatibilizer, 3-6 parts plasticizer, and 0.3-0.8 parts antioxidant.

[0020] The modified asphalt provided by this invention, through a specific weight ratio of raw materials, endows the modified asphalt with a variety of excellent properties. The base asphalt, as the fundamental material, provides adhesion. Styrene-butadiene rubber molecular chains intertwine with asphalt molecules, increasing the elasticity and toughness of the asphalt. Nano-montmorillonite, with its large specific surface area and layered structure, can adsorb components in the asphalt, improving its cohesiveness. In the core-shell structured nanoparticles, the SiO2 core provides a stable supporting structure, while sulfonic acid grafting increases surface activity; the thermosensitive PNIPAM interlayer undergoes a volume phase transition with temperature changes, and the presence of a photoinitiator makes the material responsive to light; the graphene oxide (GO) shell has good barrier and antioxidant properties, and the hindered phenolic antioxidant groups and photosensitive coumarin groups further enhance the asphalt's antioxidant properties and photoresponsive characteristics.

[0021] Preferably, the nano-montmorillonite is pretreated with an organic intercalating agent, with an interlayer spacing of 4-6 nm; the core-shell structure nanoparticles have a core SiO2 diameter of 40-60 nm; the intermediate layer has a PNIPAM thickness of 8-12 nm, a crosslinking density of 1.2 × 10⁻³ - 2.0 × 10⁻³ mol / cm³, and a hydrogen bond density ≥ 0.8 mmol / g with the hindered phenolic groups of the GO shell; the outer shell has an oxidation degree of 40-60% for graphene oxide (GO), a sheet size of 5-10 μm, and an interlayer spacing of 1.2-1.5 nm; the photoinitiator is benzoin dimethyl ether; the compatibilizer is ethylene-vinyl acetate copolymer with a vinyl acetate content of 28-33%; and the antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0022] Organic intercalating agents pretreat nano-montmorillonite, expanding its interlayer spacing and facilitating the insertion of asphalt molecules into the interlayers, thus enhancing their interaction. In core-shell structured nanoparticles, the precise control of parameters such as SiO2 diameter, PNIPAM thickness, and crosslinking density ensures the stability and temperature sensitivity of the particles. The oxidation degree, lamellar size, and interlayer spacing of GO affect its bonding strength with other components and its improvement effect on asphalt performance. Benzoin dimethyl ether acts as a photoinitiator, triggering photochemical reactions under specific conditions. Ethylene-vinyl acetate copolymer acts as a compatibilizer; its vinyl acetate content affects its compatibility with asphalt and other additives. Pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] acts as an antioxidant, effectively capturing free radicals and delaying asphalt aging.

[0023] In a second aspect, the present invention provides a process for preparing modified asphalt, comprising the following steps:

[0024] (1) Pretreatment modifier masterbatch:

[0025] a) Preparation of graded functionalized SiO2 cores: Nano-SiO2 was dispersed in an ethanol-water mixed solvent (volume ratio 1:1), and 3-mercaptopropyltrimethoxysilane (MPTMS) was added. The reaction was carried out at 60-80℃ for 24 hours to obtain SiO2 cores with surface-grafted -SH groups. The pH value of the sulfonation reaction was adjusted by adding hydrochloric acid solution dropwise. The reaction was carried out for 6-8 hours to introduce -SO3H groups, thus obtaining SiO2 cores with surface-grafted -SO3H.

[0026] Grafting with sulfonic acid groups (-SO3H) (grafting density 0.5-1.2 mmol / g) imparts strong hydrophilicity and a positive charge (Zeta potential +30 to +50 mV) to the surface of SiO2 nanoparticles, solving the problem of nanoparticle dispersion in asphalt. The sulfonic acid groups can adsorb Fe through ion exchange. 3+ By using pro-oxidizing metal ions, free radical-initiated reactions are inhibited at the source, thus constructing the first layer of antioxidant barrier.

[0027] b) Construction of temperature-sensitive intermediate layer: PNIPAM was grafted onto the surface of SiO2 core grafted with -SO3H by atom transfer radical polymerization (ATRP) to obtain SiO2@PNIPAM core;

[0028] The ATRP technique is used to graft poly(N-isopropylacrylamide) (PNIPAM) to form a temperature-sensitive shell with a thickness of 8-12 nm. Its low critical solution temperature (LCST = 32 ± 1 °C) causes the material to contract at high temperatures (>32 °C) to form a physical cross-linked network, while at low temperatures (<32 °C) the chain segments extend, enhancing hydrogen bonding with the pitch (hydrogen bond density ≥ 0.8 mmol / g), achieving a dynamic balance between high and low temperature performance. Simultaneously, the benzoin dimethyl ether photoinitiator (0.5-2%) loaded in the intermediate layer generates free radicals under light irradiation, triggering the shell cross-linking reaction.

[0029] c) GO shell coating: The pretreated SiO2@PNIPAM core is mixed with GO dispersion and formed SiO2@PNIPAM@GO core-shell particles by electrostatic self-assembly. After centrifugation and washing, the particles are freeze-dried.

[0030] Graphene oxide (GO) sheets (oxidation degree 40-60%, sheet size 5-10 μm) are grafted with hindered phenolic antioxidant groups (to capture free radicals) and photosensitive coumarin groups (photoresponsive crosslinking sites). Under light irradiation (365 nm), the coumarin groups undergo [2+2] cycloaddition crosslinking, constructing a three-dimensional chemical crosslinking network between GO sheets. This network interpenetrates with the PNIPAM physical network, significantly improving high-temperature stability (softening point 110-120℃) and anti-aging properties (photooxidation induction period OIT ≥ 240 minutes).

[0031] (2) Melt blending: The base asphalt is heated and mixed with styrene-butadiene rubber, compatibilizer, plasticizer, antioxidant, SiO2@PNIPAM@GO core-shell particles and organic intercalated nano montmorillonite at low speed (30-50 rpm), and nitrogen gas is introduced for protection (flow rate 5-10 L / min) to obtain asphalt mixture;

[0032] (3) High-speed shearing: The asphalt mixture is sheared in two stages using a twin-screw extruder to obtain shear-dispersed asphalt;

[0033] (4) Ultrasonic dispersion: The shear-dispersed asphalt is treated at 170-180℃ for 10-15 minutes using a probe-type ultrasonic processor to obtain ultrasonically dispersed asphalt melt.

[0034] (5) Cooling and discharging: Cool the ultrasonically dispersed asphalt melt to room temperature at a cooling rate of 5-10℃ / min to obtain the modified asphalt product.

[0035] In the modified asphalt preparation process provided by this invention, during the pretreatment of the modifier masterbatch, core-shell structured nanoparticles with specific structures and properties are gradually constructed through steps such as gradient functionalization of SiO2 cores, construction of a temperature-sensitive intermediate layer, and GO shell coating. The melt blending process, under heating and low-speed stirring conditions, ensures initial homogeneous mixing of the raw materials, while nitrogen protection prevents oxidation. High-speed shearing utilizes the high shear force of a twin-screw extruder to further refine and disperse the components, improving the mixing effect. Ultrasonic dispersion uses ultrasound to make the particles more uniformly dispersed in the asphalt, eliminating agglomeration. Cooling discharge controls the cooling rate, ensuring the modified asphalt forms a stable structure during molding.

[0036] Preferably, in step (1) a), during the preparation of the gradient functionalized SiO2 core, the pH of the sulfonation reaction is adjusted to 2.0-3.5 by adding hydrochloric acid solution, and the mass ratio of SiO2 to MPTMS in the reaction system is 1:0.5-1.2. After grafting, the Zeta potential of the SiO2 core is +30 to +50 mV. Adjusting the pH of the sulfonation reaction to 2.0-3.5 is beneficial for the reaction between MPTMS and the hydroxyl groups on the surface of SiO2 to generate stable -SO3H groups. Controlling the mass ratio of SiO2 to MPTMS ensures a suitable grafting density. A Zeta potential of +30 to +50 mV indicates that the particle surface carries an appropriate amount of positive charge, which is beneficial for subsequent binding with negatively charged components through electrostatic interactions.

[0037] Preferably, in step (1)b), during the construction of the thermosensitive interlayer, the ATRP polymerization reaction employs a CuBr / bipyridine (bpy) catalytic system, with a CuBr to PNIPAM monomer molar ratio of 1:100-200, a polymerization temperature of 50-70℃, a polymerization time of 12-18 hours, and a PNIPAM lower critical solution temperature (LCST) of 32±1℃ and a phase transition enthalpy of 80-120 J / g. The CuBr / bipyridine catalytic system, at a specific molar ratio, can effectively initiate the polymerization reaction of PNIPAM monomers. By controlling the polymerization temperature and time, the molecular weight and structure of PNIPAM can be adjusted, thereby achieving a lower critical solution temperature of 32±1℃ and a phase transition enthalpy of 80-120 J / g. This allows the thermosensitive interlayer to undergo corresponding volume changes at different temperatures, achieving temperature control of the modified asphalt properties.

[0038] Preferably, in step (1)c), the concentration of the GO dispersion in the GO shell coating is 0.5-1.0 mg / mL, and the mass ratio of SiO2@PNIPAM core to GO during blending is 1:0.3-0.8. When the concentration of the GO dispersion is 0.5-1.0 mg / mL, it has a suitable dispersion state and surface charge density in the solution. Blending the SiO2@PNIPAM core and GO at a mass ratio of 1:0.3-0.8 allows for sufficient contact between the two and the formation of a tight core-shell structure through electrostatic self-assembly. The GO shell can effectively encapsulate the internal SiO2@PNIPAM core, exerting its barrier and antioxidant properties.

[0039] Preferably, in step (2), during the melt blending stage, the heating temperature of the base asphalt is 160-170℃, and the styrene-butadiene rubber is pre-crushed to a particle size <5mm before melt blending. Heating the base asphalt to 160-170℃ reduces its viscosity, increases its fluidity, and facilitates mixing with other components. Pre-crushing the styrene-butadiene rubber to a particle size <5mm increases its contact area with the asphalt, which is beneficial for the uniform dispersion of the styrene-butadiene rubber in the asphalt, improves the interaction between the two, and thus better improves the performance of the asphalt.

[0040] Preferably, in step (3), when performing two-stage shearing on the asphalt mixture, the settings of the twin-screw extruder are as follows:

[0041] The temperature in the primary shearing zone is 180-190℃, the speed is 8000rpm, and the treatment time is 15-20 minutes.

[0042] The secondary shear zone is at a temperature of 170-180℃ and a speed of 6000 rpm for 10-15 minutes. The primary shear zone, at a higher temperature (180-190℃) and speed (8000 rpm), is treated for 15-20 minutes to break up large particles in the asphalt mixture and initially disperse the components evenly. The secondary shear zone, at a slightly lower temperature (170-180℃) and speed (6000 rpm), further treats the initially dispersed components for 10-15 minutes, performing fine shearing and mixing to achieve a more uniform distribution of the components at the microscale, thereby improving the performance stability and consistency of the modified asphalt.

[0043] Preferably, in step (4), the ultrasonic dispersion employs a probe-type ultrasonic processor with a probe diameter of 15-20 mm and an amplitude of 50-70%. A probe-type ultrasonic processor with a probe diameter of 15-20 mm and an amplitude of 50-70% can generate suitable ultrasonic energy. At a temperature of 170-180℃, the high-frequency vibration of the ultrasound can help core-shell structured nanoparticles overcome agglomeration forces in asphalt, achieving more uniform dispersion, thereby fully utilizing the improving effect of nanoparticles on asphalt performance and enhancing the overall performance of modified asphalt.

[0044] Preferably, the GO shell of the core-shell structured nanoparticles is grafted with photosensitive coumarin groups via an amidation reaction. The reaction temperature is 80-100℃, the reaction time is 12-18 hours, and the grafting rate is ≥95%. After grafting, the fluorescence emission peak of GO red-shifts to 430-450nm. A reflux condenser is used to control solvent evaporation during the reaction, and unreacted materials are removed by multiple centrifugal washings after the reaction. At a reaction temperature of 80-100℃, photosensitive coumarin groups are grafted onto the GO shell via an amidation reaction. The reaction time of 12-18 hours ensures a complete reaction, and the grafting rate of ≥95% ensures a sufficient number of photosensitive coumarin groups are grafted onto GO. The red-shift of the fluorescence emission peak of GO to 430-450nm after grafting indicates successful grafting of photosensitive coumarin groups and corresponding changes in the structure and properties of GO. The use of a reflux condenser to control solvent evaporation maintains the stability of the reaction system. Multiple centrifugal washing processes remove unreacted raw materials, ensuring the purity of the product and thus giving the modified asphalt excellent photoresponse and antioxidant properties.

[0045] This invention focuses on the photoresponsive crosslinking mechanism to carry out intelligent synergistic design of modified asphalt, significantly improving the overall performance of asphalt. When irradiated with 365nm ultraviolet light, the benzoin dimethyl ether in the PNIPAM intermediate layer undergoes photolysis. The generated free radicals transfer energy to the coumarin groups in the GO shell through the π-π conjugation effect, stimulating them to undergo a [2+2] cycloaddition crosslinking reaction, constructing a three-dimensional crosslinking network between the GO layers.

[0046] Regarding the synergistic enhancement of interpenetrating networks, at high temperatures, PNIPAM segments contract to form a physical cross-linked network, which interpenetrates with the simultaneously occurring photocrosslinked chemical network, significantly increasing the composite modulus. At low temperatures, the photocrosslinked network acts as physical crosslinking points, inhibiting the movement of asphalt molecular chain segments and maintaining good ductility. AFM and SAXS characterization confirmed that photocrosslinking increases the interlamellar spacing of GO, forming a dense interlayer structure, inhibiting asphalt molecular chain slippage, and reducing the carbonyl index after photo-oxidation. Compared to traditional physical blending modification, this invention, through the spatiotemporal synergy of photoresponsive chemical crosslinking and temperature-sensitive physical networks, not only achieves a balance between high-temperature stability and low-temperature toughness but also constructs a multi-layered antioxidant system, significantly improving the service life of asphalt.

[0047] Specifically, in high-temperature environments (>32℃), PNIPAM shrinks to form physical cross-links, while photocross-linking reactions are enhanced. The dual network inhibits the slippage of asphalt molecular chains, resulting in a dynamic stability of over 8000 cycles / mm (compared to <5000 cycles / mm for traditional modified asphalt).

[0048] Specifically, in low-temperature scenarios (<32℃), PNIPAM segments extend and enhance the flexibility of asphalt through hydrogen bonds (25-30cm ductility at -20℃), while the photocrosslinked network acts as a rigid node, inhibiting crack propagation (≥28000με failure strain at -10℃).

[0049] Meanwhile, the hindered phenolic antioxidant groups in the GO shell and the photocrosslinking network synergistically inhibit asphalt oxidation, while the -SO3H groups in the inner SiO2 core capture metal ions, jointly constructing a dual antioxidant barrier and significantly extending the asphalt oxidation induction period.

[0050] Specifically, in terms of chemical antioxidant properties, the hindered phenolic groups in the GO shell directly capture oxidative free radicals, while the sulfonic acid groups in the SiO2 core adsorb metal ions, thus blocking the free radical initiation source.

[0051] Specifically, in terms of physical barriers, the interlayer spacing (1.2-1.5 nm) and high specific surface area of ​​GO sheets form a barrier, delaying the penetration of oxygen and moisture, and ensuring that the carbonyl index increase (after photo-oxidation) is ≤0.05 / 1000 cm⁻¹. -1 It reduces costs by more than 80% compared to traditional asphalt.

[0052] Compared with the prior art, the beneficial effects of the present invention are:

[0053] 1. This invention utilizes a photo-responsive crosslinking mechanism. At high temperatures, the PNIPAM intermediate layer shrinks to form a physical crosslinking network, while the photosensitive coumarin groups in the GO shell crosslink under light to form a chemical network. This dual network synergistically inhibits the slippage of asphalt molecular chains. In the examples, the dynamic stability reaches over 8000 cycles / mm, far exceeding that of traditional modified asphalt (<5000 cycles / mm), and the softening point is increased to 110-120℃, effectively enhancing the asphalt's resistance to rutting deformation at high temperatures. At low temperatures, the PNIPAM chain segments extend and form hydrogen bonds with asphalt molecules, increasing the asphalt's flexibility; the ductility at -20℃ can reach 25-30cm. The photo-crosslinking network acts as a rigid node, inhibiting crack propagation; the destructive strain at -10℃ is ≥28000με, reducing the risk of road surface cracking at low temperatures.

[0054] 2. This invention constructs a dual antioxidant barrier, where the -SO3H groups of the core SiO2 adsorb Fe. 3+ Metal ions inhibit free radical-induced reactions at the source; the hindered phenolic antioxidant groups in the GO shell directly capture oxidative free radicals, while the interlayer spacing and high specific surface area of ​​the GO sheets form a physical barrier, delaying oxygen and moisture penetration. The photo-oxidation induction period (OIT) is increased to over 240 minutes, and the carbonyl index increase (after photo-oxidation) is ≤0.05 / 1000cm. -1 It reduces costs by more than 80% compared to traditional asphalt, significantly extending the service life of asphalt.

[0055] 4. This invention utilizes a photoresponsive crosslinking mechanism to form a stable interpenetrating network structure within the asphalt. Under certain stress levels, this effectively disperses stress concentration and delays the accumulation of fatigue damage. In the embodiments, the fatigue life reached over 5000 cycles at a stress ratio of 0.5, while traditional modified asphalt and some comparative examples showed lower fatigue life. This indicates that the modified asphalt of this invention significantly extends fatigue life and can reduce the frequency of road maintenance. Attached Figure Description

[0056] Figure 1 The softening points of modified asphalt in different embodiments and comparative examples of the present invention are shown in comparison.

[0057] Figure 2 The ductility of modified asphalt in different embodiments and comparative examples of the present invention is compared at -20°C.

[0058] Figure 3 The photo-oxidation induction period (OIT) of different embodiments of the present invention and comparative modified asphalt is shown;

[0059] Figure 4 The composite modulus of modified asphalt in different embodiments and comparative examples of the present invention at 120°C is compared.

[0060] Figure 5The invention presents a comparison of the carbonyl index increments after photo-oxidation of modified asphalt in different embodiments and comparative examples.

[0061] Figure 6 The comparison of the dynamic stability of modified asphalt in different embodiments and comparative examples of the present invention is shown.

[0062] Figure 7 The comparison of failure strain of modified asphalt at -10℃ in different embodiments and comparative examples of the present invention is shown.

[0063] Figure 8 The comparison of fatigue cycles under different embodiments of the present invention and comparative examples of modified asphalt with a stress ratio of 0.5 is shown. Detailed Implementation

[0064] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. 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.

[0065] This invention provides a modified asphalt, composed of the following raw materials in parts by weight:

[0066] 80-90 parts of base bitumen; 4-8 parts of styrene-butadiene rubber; 2-5 parts of nano-montmorillonite;

[0067] 1.5-3 parts of core-shell structured nanoparticles, with specific structural parameters as follows:

[0068] The core is SiO2, and the surface is grafted with sulfonic acid groups (-SO3H), with a grafting density of 0.5-1.2 mmol / g;

[0069] The intermediate layer is thermosensitive poly(N-isopropylacrylamide) (PNIPAM) and contains 0.5-2% photoinitiator;

[0070] The outer shell is graphene oxide (GO), with hindered phenolic antioxidant groups and photosensitive coumarin groups grafted onto the surface;

[0071] In addition, there are 1-3 parts compatibilizer, 3-6 parts plasticizer, and 0.3-0.8 parts antioxidant.

[0072] More specifically, the nano-montmorillonite is pretreated with an organic intercalating agent, with an interlayer spacing of 4-6 nm; the core-shell structured nanoparticles have a SiO2 core diameter of 40-60 nm; and the intermediate layer contains PNIPAM with a thickness of 8-12 nm and a crosslinking density of 1.2 × 10⁻⁶. -3 -2.0×10 -3The mol / cm³ hydrogen bond density formed with hindered phenolic groups in the GO shell is ≥0.8 mmol / g; the oxidation degree of graphene oxide (GO) in the shell is 40-60%, the sheet size is 5-10 μm, and the interlayer spacing is 1.2-1.5 nm; the photoinitiator is benzoin dimethyl ether; the compatibilizer is ethylene-vinyl acetate copolymer with a vinyl acetate content of 28-33%; the antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0073] This invention also provides a process for preparing modified asphalt, characterized by comprising the following steps:

[0074] (1) Pretreatment modifier masterbatch:

[0075] a) Preparation of graded functionalized SiO2 cores: Nano-SiO2 was dispersed in an ethanol-water mixed solvent (volume ratio 1:1), and 3-mercaptopropyltrimethoxysilane (MPTMS) was added. The reaction was carried out at 60-80℃ for 24 hours to obtain SiO2 cores with surface-grafted -SH groups. The pH value of the sulfonation reaction was adjusted by adding hydrochloric acid solution dropwise. The reaction was carried out for 6-8 hours to introduce -SO3H groups, thus obtaining SiO2 cores with surface-grafted -SO3H.

[0076] b) Construction of temperature-sensitive intermediate layer: PNIPAM was grafted onto the surface of SiO2 core grafted with -SO3H by atom transfer radical polymerization (ATRP) to obtain SiO2@PNIPAM core;

[0077] c) GO shell coating: The pretreated SiO2@PNIPAM core is mixed with GO dispersion and formed SiO2@PNIPAM@GO core-shell particles by electrostatic self-assembly. After centrifugation and washing, the particles are freeze-dried.

[0078] (2) Melt blending: The base asphalt is heated and mixed with styrene-butadiene rubber, compatibilizer, plasticizer, antioxidant, SiO2@PNIPAM@GO core-shell particles and organic intercalated nano montmorillonite at low speed (30-50 rpm), and nitrogen gas is introduced for protection (flow rate 5-10 L / min) to obtain asphalt mixture;

[0079] (3) High-speed shearing: The asphalt mixture is sheared in two stages using a twin-screw extruder to obtain shear-dispersed asphalt;

[0080] (4) Ultrasonic dispersion: The shear-dispersed asphalt is treated at 170-180℃ for 10-15 minutes using a probe-type ultrasonic processor to obtain ultrasonically dispersed asphalt melt.

[0081] (5) Cooling and discharging: Cool the ultrasonically dispersed asphalt melt to room temperature at a cooling rate of 5-10℃ / min to obtain the modified asphalt product.

[0082] More specifically, in step (1) a), during the preparation of gradient functionalized SiO2 cores, the pH of the sulfonation reaction is adjusted to 2.0-3.5 by adding hydrochloric acid solution, and the mass ratio of SiO2 to MPTMS in the reaction system is 1:0.5-1.2. The zeta potential of the grafted SiO2 core is +30 to +50 mV.

[0083] More specifically, in step (1) b), in the construction of the temperature-sensitive intermediate layer, the ATRP polymerization reaction adopts a CuBr / bipyridine (bpy) catalytic system, the molar ratio of CuBr to PNIPAM monomer is 1:100-200, the polymerization temperature is 50-70℃, the time is 12-18 hours, the low critical solution temperature (LCST) of PNIPAM is 32±1℃, and the phase transition enthalpy is 80-120J / g.

[0084] More specifically, in step (1) c), the concentration of the GO dispersion in the GO shell coating is 0.5-1.0 mg / mL, and the mass ratio of SiO2@PNIPAM core to GO during blending is 1:0.3-0.8.

[0085] More specifically, in step (2), during the melt blending stage, the heating temperature of the base asphalt is 160-170℃, and the styrene-butadiene rubber is pre-crushed to a particle size of <5mm before melt blending.

[0086] More specifically, in step (3), when performing two-stage shearing on the asphalt mixture, the set parameters of the twin-screw extruder are as follows:

[0087] The temperature in the primary shearing zone is 180-190℃, the speed is 8000rpm, and the treatment time is 15-20 minutes.

[0088] The secondary shearing zone temperature is 170-180℃, the speed is 6000rpm, and the treatment time is 10-15 minutes.

[0089] More specifically, in step (4), the ultrasonic dispersion uses a probe-type ultrasonic processor with a probe diameter of 15-20 mm and an amplitude of 50-70%.

[0090] More specifically, the GO shell of the core-shell structured nanoparticles is grafted with photosensitive coumarin groups through an amidation reaction at a temperature of 80-100℃ for 12-18 hours, with a grafting rate of ≥95%. After grafting, the fluorescence emission peak of GO is red-shifted to 430-450nm. Furthermore, a reflux condenser is used to control the solvent evaporation of the reaction system during the reaction process, and unreacted raw materials are removed by multiple centrifugal washings after the reaction is completed.

[0091] The synergistic mechanism of the multi-shell structure:

[0092] High temperature response: When the temperature is >32℃, the PNIPAM intermediate layer shrinks to form a cross-linked network, which, together with the hindered phenolic groups of the GO shell, increases the softening point to 110-120℃;

[0093] Low-temperature toughening: When the temperature is <32℃, the PNIPAM chain segments extend and form hydrogen bonds with the asphalt molecules, and the ductility reaches 25-30cm at -20℃.

[0094] Antioxidant enhancement: The -SO3H group of the core SiO2 adsorbs metal ions such as Fe³⁺ through ion exchange, inhibiting free radical-initiated reactions. At the same time, the hindered phenolic antioxidant groups on the GO surface capture free radicals, forming a dual antioxidant barrier.

[0095] Photoresponsive crosslinking: When irradiated with ultraviolet light (365nm), the photoinitiator in the PNIPAM intermediate layer triggers the photosensitive coumarin groups in the GO shell to undergo a crosslinking reaction, forming a photocrosslinking structure that interpenetrates with the temperature-sensitive network. This inhibits the slippage of pitch molecular chains at high temperatures and increases the photooxidation induction period (OIT) to 240 minutes.

[0096] Example

[0097] Example 1: Preparation of the complete formula and standard process

[0098] Raw material formulation: Following the proportions in the original formulation, use 85 parts matrix asphalt, 6 parts styrene-butadiene rubber, 3 parts nano-montmorillonite, 2 parts core-shell structured nanoparticles, 2 parts compatibilizer, 4 parts plasticizer, and 0.5 parts antioxidant. The parameters of each layer of the core-shell structured nanoparticles, such as the grafting density of the SiO2 core, the photoinitiator content of the PNIPAM intermediate layer, and the grafting groups of the GO shell, are all within the proportions specified in the original formulation.

[0099] Preparation process: From the preparation of gradient functionalized SiO2 cores of pretreated modifier masterbatch, construction of temperature-sensitive intermediate layer, GO shell coating, to melt blending, high-speed shearing, ultrasonic dispersion, and finally cooling and discharge, the parameters of each step, such as reaction temperature, time, and rotation speed, are all carried out in accordance with the original standard process in the invention.

[0100] Example 2: Optimizing the photoresponse crosslinking effect

[0101] Raw material formulation: While keeping the proportions of other raw materials unchanged, the grafting density of photosensitive coumarin groups in the GO shell of the core-shell structured nanoparticles was increased to 0.6 mmol / gGO, and the content of benzoin dimethyl ether in the PNIPAM intermediate layer was increased to 2%.

[0102] Preparation process: The overall preparation process is consistent with that in Example 1, but in the reaction process of grafting photosensitive coumarin groups onto the GO shell, the reaction temperature is controlled at 100°C and the reaction time is extended to 18 hours to ensure that the grafting rate reaches more than 95%.

[0103] Example 3: Enhancing Antioxidant Properties

[0104] Raw material formulation: The basic formulation remains unchanged, but the dual antioxidant barrier is enhanced by increasing the grafting density of hindered phenolic antioxidant groups in the GO shell to 1.5 mmol / g GO and increasing the grafting density of sulfonic acid groups in the SiO2 core to 1.2 mmol / g.

[0105] Preparation process: In the preparation of gradient functionalized SiO2 cores and GO shell coating, the density of sulfonic acid groups and hindered phenolic antioxidant groups was increased by optimizing the reaction conditions. The remaining preparation steps are the same as in Example 1.

[0106] Comparative Example

[0107] Comparative Example 1: Core-shell-less nanoparticles

[0108] Raw material formulation: Remove core-shell structured nanoparticles, increase the amount of base asphalt to 93 parts, and keep the proportion of other additives unchanged.

[0109] Preparation process: The preparation process in the invention is followed, but the pretreatment modifier masterbatch step is omitted due to the lack of core-shell structured nanoparticles.

[0110] Comparative Example 2: No GO shell

[0111] Raw material formulation: Nanoparticles containing only a SiO2 core and a PNIPAM intermediate layer were prepared, while the GO shell was removed. Accordingly, the amount of matrix bitumen was adjusted to 90 parts, styrene-butadiene rubber to 4 parts, nano-montmorillonite to 2 parts, and nanoparticles without the GO shell to 1.5 parts, while the proportions of other additives remained unchanged.

[0112] Preparation process: Only the steps of preparing gradient functionalized SiO2 cores and constructing temperature-sensitive intermediate layers are performed, omitting the GO shell coating step. Subsequent preparation steps are the same as the invention process.

[0113] Comparative Example 3: No photoinitiator

[0114] Raw material formulation: Remove the benzoin dimethyl ether photoinitiator from the PNIPAM intermediate layer, while keeping the types and proportions of other raw materials unchanged.

[0115] Preparation process: No photoinitiator is added during the construction of the temperature-sensitive intermediate layer, and the remaining preparation steps are consistent with the invention process.

[0116] Comparative Example 4: Changing the type of photoinitiator

[0117] Raw material formulation: Replace benzoin dimethyl ether with benzophenone, and keep the amount in the range of 0.5%-2% of the PNIPAM intermediate layer, while keeping the proportion of other raw materials unchanged.

[0118] Preparation process: During the construction of the temperature-sensitive intermediate layer, benzophenone photoinitiator is added, and the remaining preparation steps are the same as the invention process.

[0119] Comparative Example 5: Non-thermosensitive intermediate layer

[0120] Raw material formulation: Nanoparticles containing only SiO2 cores and GO shells were prepared, and the PNIPAM interlayer was removed. The amount of matrix bitumen was adjusted to 91 parts, styrene-butadiene rubber to 5 parts, nano-montmorillonite to 3 parts, and nanoparticles without the PNIPAM interlayer to 2 parts, while the proportions of other additives remained unchanged.

[0121] Preparation process: Only the steps of preparing gradient functionalized SiO2 core and GO shell coating are performed, omitting the construction of temperature-sensitive intermediate layer. Subsequent preparation steps are the same as the invention process.

[0122] Comparative Example 6: Changing the preparation process parameters

[0123] Raw material formulation: The standard raw material formulation in the invention is adopted.

[0124] Preparation process: In the high-speed shearing stage, the temperature of the first-stage shearing zone is reduced to 160℃, the speed is reduced to 6000rpm, and the processing time is shortened to 10 minutes; the temperature of the second-stage shearing zone is reduced to 150℃, the speed is reduced to 4000rpm, and the processing time is shortened to 8 minutes. Other preparation steps are the same as the invention process.

[0125] Comparative Example 7: No organic intercalation treatment performed

[0126] Raw material formulation: Nano-montmorillonite without organic intercalation agent pretreatment is used, and the proportions of other raw materials remain unchanged.

[0127] Preparation process: The organic intercalation step of nano-montmorillonite is omitted, and the remaining preparation steps are the same as those of the invention.

[0128] Comparative Example 8: Changing the proportion of raw materials

[0129] Raw material formulation: The proportions of raw materials were significantly changed, using 90 parts of base asphalt, 4 parts of styrene-butadiene rubber, 2 parts of nano-montmorillonite, 1.5 parts of core-shell structured nanoparticles, 1 part of compatibilizer, 3 parts of plasticizer, and 0.3 parts of antioxidant.

[0130] Preparation process: The standard preparation process described in the invention is adopted.

[0131] Comparative Example 9: No antioxidants

[0132] Raw material formulation: Remove antioxidants and increase the amount of base asphalt to 90.8 parts, while keeping the proportions of other additives unchanged.

[0133] Preparation process: The preparation process in the invention is used, but without adding antioxidants.

[0134] Comparative Example 10: Traditional Physical Blending Method

[0135] Raw material formulation: The standard raw material formulation in the invention is adopted.

[0136] Preparation process: All raw materials are directly physically blended, without performing the pretreatment of the modifier masterbatch, high-speed shearing, and ultrasonic dispersion steps described in the invention; only simple stirring and mixing are performed. Experimental data for the modified asphalt prepared in the above examples and comparative examples are shown in Table 1:

[0137] Table 1

[0138]

[0139] This experiment tested three examples and ten comparative examples of modified asphalt, analyzing multiple key performance indicators such as softening point, ductility at -20℃, photo-oxidation induction period (OIT), composite modulus (120℃), and carbonyl index increment. The results comprehensively evaluated the performance advantages of modified asphalt based on the photoresponsive crosslinking mechanism and the influence of various factors. A detailed summary of the experimental data follows:

[0140] 1. Performance of the Example

[0141] Example 1: As a standard example, the softening point reached 115℃, the ductility at -20℃ was 27cm, the photo-oxidation induction period (OIT) was as long as 240 minutes, the composite modulus at 120℃ was 2.8GPa, and the carbonyl index increase after photo-oxidation was only 0.05 / 1000cm. -1 This embodiment demonstrates that the modified asphalt based on the photoresponsive crosslinking mechanism of the present invention possesses good high-temperature stability, low-temperature toughness, and excellent antioxidant properties.

[0142] Example 2: By optimizing the photoresponsive crosslinking effect, i.e., increasing the grafting density of photosensitive coumarin groups in the GO shell and the content of benzoin dimethyl ether in the PNIPAM intermediate layer, the softening point was increased to 120℃, the elongation at -20℃ was 28cm, the OIT was extended to 280 minutes, the composite modulus at 120℃ reached 3.0GPa, and the carbonyl index increment was further reduced to 0.04 / 1000cm. -1 This indicates that enhancing the photoresponsive crosslinking effect can effectively improve the overall performance of asphalt, especially its high-temperature stability and antioxidant properties.

[0143] Example 3: After enhancing antioxidant properties, the softening point is 113℃, the ductility at -20℃ is 26cm, the OIT (Oxygen Intake) is significantly improved to 300 minutes, the composite modulus at 120℃ is 2.7GPa, and the carbonyl index increment is as low as 0.03 / 1000cm. -1 This indicates that increasing the grafting density of hindered phenolic antioxidant groups in the GO shell and sulfonic acid groups in the SiO2 core can significantly enhance the oxidation resistance of asphalt.

[0144] 2. Comparison of proportional performance and analysis of influencing factors

[0145] - Core-shell-free nanoparticles (Comparative Example 1): All properties decreased significantly, with a softening point of only 80℃, a ductility of 15cm at -20℃, an OIT (open-interval time) shortened to 60 minutes, a composite modulus of 1.0 GPa at 120℃, and a carbonyl index increase as high as 0.3 / 1000cm⁻¹. This highlights the crucial role of core-shell nanoparticles in improving asphalt performance.

[0146] - Without the GO shell (Comparative Example 2): Performance is significantly worse, softening point 90℃, ductility 18cm at -20℃, OIT time 80 minutes, composite modulus 1.2GPa at 120℃, carbonyl index increment 0.2 / 1000cm -1 This demonstrates that the GO shell layer is indispensable for improving the performance of asphalt, especially in terms of oxidation resistance and enhancing the composite modulus.

[0147] - No photoinitiator (Comparative Example 3): Softening point 95℃, ductility 20cm at -20℃, OIT 100min, composite modulus 1.5GPa at 120℃, carbonyl index increment 0.15 / 1000cm -1 This indicates that photoinitiators are crucial for triggering the photoresponsive crosslinking mechanism and improving asphalt performance.

[0148] - Changing the type of photoinitiator (Comparative Example 4): Performance decreased; softening point 100℃, ductility 22cm at -20℃, OIT 150 minutes, composite modulus 1.8GPa at 120℃, carbonyl index increase 0.1 / 1000cm -1 This indicates that benzoin dimethyl ether, as a photoinitiator, has a good effect on achieving photoresponsive crosslinking, while other photoinitiators are difficult to achieve the same performance improvement.

[0149] - Non-thermosensitive intermediate layer (Comparative Example 5): softening point 98℃, ductility 21cm at -20℃, OIT 120 minutes, composite modulus 1.6GPa at 120℃, carbonyl index increment 0.12 / 1000cm -1 This demonstrates the importance of the temperature-sensitive intermediate layer in balancing the high and low temperature properties of asphalt and participating in the construction of photoresponsive crosslinking networks.

[0150] - Changing the preparation process parameters (Comparative Example 6): Performance deteriorated, softening point 105℃, ductility 24cm at -20℃, OIT 200 minutes, composite modulus 2.2GPa at 120℃, carbonyl index increase 0.08 / 1000cm -1 This demonstrates that strict control of the preparation process parameters is crucial for obtaining high-performance modified asphalt.

[0151] - No organic intercalation treatment (Comparative Example 7): Softening point 100℃, ductility 23cm at -20℃, OIT 180 minutes, composite modulus 2.0GPa at 120℃, carbonyl index increment 0.1 / 1000cm -1 This indicates that the organic intercalation treatment of nano-montmorillonite helps to improve the overall performance of asphalt.

[0152] - Changing the raw material ratio (Comparative Example 8): Performance decreased, softening point 92℃, ductility 19cm at -20℃, OIT 130 minutes, composite modulus 1.4GPa at 120℃, carbonyl index increase 0.18 / 1000cm -1 This illustrates that a proper ratio of raw materials is crucial for ensuring the performance of asphalt.

[0153] - No antioxidant (Comparative Example 9): Softening point 110℃, ductility 25cm at -20℃, OIT 160 minutes, composite modulus 2.5GPa at 120℃, carbonyl index increment 0.2 / 1000cm -1 This indicates that antioxidants play an important role in prolonging the photo-oxidation induction period of asphalt and reducing the increase in carbonyl index.

[0154] - Traditional physical blending method (Comparative Example 10): Poor performance, softening point 95℃, ductility 20cm at -20℃, OIT 100 minutes, composite modulus 1.5GPa at 120℃, carbonyl index increment 0.25 / 1000cm -1 This demonstrates the significant advantages of the photoresponsive crosslinking mechanism-based preparation method of this invention in improving asphalt performance compared to traditional physical blending methods.

[0155] In summary, the modified asphalt based on the photoresponsive crosslinking mechanism of this invention achieves synergistic improvements in high-temperature stability, low-temperature toughness, and antioxidant properties through reasonable raw material formulation, core-shell nanoparticles with specific structures, and precise preparation process. Compared with traditional methods and comparative methods after changing key factors, it has significant performance advantages.

[0156] To highlight the advantages of the invention, this invention comprehensively demonstrates the performance advantages of the modified asphalt under the photoresponsive crosslinking mechanism from three key aspects: high temperature, low temperature, and fatigue durability, through the comparison of the following three types of test data. This powerfully proves that the modified asphalt of this invention can effectively solve the performance defects of traditional asphalt in complex environments and long-term use in practical applications.

[0157] Rutting test data: Rutting tests are an important method for evaluating the high-temperature stability of asphalt pavements. The dynamic stability (cycles / mm) data of modified asphalt is an important indicator of the high-temperature stability of asphalt pavements. The higher the dynamic stability, the stronger the asphalt's ability to resist rutting deformation at high temperatures.

[0158] Low-temperature bending test data: The low-temperature bending test is used to measure the low-temperature crack resistance of asphalt. The failure strain (με) data at a specific low temperature (such as -10℃) is an important indicator for measuring the low-temperature crack resistance of asphalt. The larger the failure strain, the better the flexibility of the asphalt at low temperature, and the less likely it is to crack.

[0159] Fatigue test data: Fatigue tests can reflect the fatigue life of asphalt, and the number of fatigue cycles under a certain stress level is an important indicator of the fatigue life of asphalt. The performance test data of the modified asphalt prepared in each embodiment and comparative example are shown in Table 2:

[0160] Table 2

[0161]

[0162] These experiments aim to verify, from multiple dimensions, the significant performance improvement of the modified asphalt of this invention compared to traditional modified asphalt and other comparative examples under the photoresponsive crosslinking mechanism, as detailed below:

[0163] 1. Verify high-temperature stability: Rutting tests obtain dynamic stability data, which directly reflects the ability of modified asphalt to resist rutting deformation under high-temperature conditions. They also verify the constraint effect of the photoresponsive cross-linking structure on the asphalt molecular chains at high temperatures, preventing excessive slippage and thus improving the rutting resistance of the pavement.

[0164] 2. Verification of Low-Temperature Crack Resistance: The failure strain data determined by the low-temperature bending test demonstrates the flexibility and crack resistance of the modified asphalt under low-temperature conditions. Comparative examples and comparative data prove that components such as the temperature-sensitive intermediate layer in the core-shell structure improve the performance of asphalt at low temperatures, reducing the occurrence of low-temperature cracks in the pavement.

[0165] 3. Verifying Fatigue Life: Fatigue test data on the number of fatigue cycles are used to measure the durability of modified asphalt under a certain stress level. By comparing the number of fatigue cycles of different embodiments and comparative examples, the advantages of the photoresponsive crosslinking mechanism in improving the internal structural stability of asphalt, dispersing stress concentration, and delaying the accumulation of fatigue damage are highlighted, thereby extending the service life of the pavement.

[0166] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A modified bitumen, characterized in that, Consists of the following raw materials by weight: Matrix asphalt 80-90 parts, styrene-butadiene rubber 4-8 parts, nano-montmorillonite 2-5 parts, core-shell structure nanoparticles 1.5-3 parts, compatibilizer 1-3 parts, plasticizer 3-6 parts and antioxidant 0.3-0.8 parts; The core-shell structure of the nanoparticles comprises: The inner core is SiO2, and sulfonic acid groups are grafted on the surface thereof, with a grafting density of 0.5-1.2 mmol / g; The intermediate layer is temperature-sensitive poly-N-isopropyl acrylamide and contains 0.5-2% photoinitiator; The outer shell is graphene oxide, and the surface is grafted with hindered phenolic antioxidant groups and photosensitive coumarin groups.

2. The modified bitumen of claim 1, wherein, The nano-montmorillonite is pretreated with an organic intercalating agent, and the interlayer spacing is 4-6 nm; The diameter of SiO2 in the inner core of the core-shell structure nanoparticles ranges from 40 to 60 nm; The thickness of PNIPAM in the intermediate layer is 8-12 nm, and the crosslinking density is 1.2 x 10 -3 mol / cm³-2.0 x 10 -3 mol / cm³, and the hydrogen bonding density with the hindered phenol groups of the shell layer is ≥0.8 mmol / g; The degree of oxidation of graphene oxide in the outer shell is 40-60%, the sheet size is 5-10 μm, and the interlayer spacing is 1.2-1.5 nm; The photoinitiator is anisole dimethyl ether; The compatibilizer is ethylene-vinyl acetate copolymer, and the vinyl acetate content is 28-33%; The antioxidant is antioxidant 1010.

3. A process for the preparation of the modified bitumen according to claim 2, characterized in that, Comprises the following steps: (1) Gradient functionalized SiO2 core preparation, temperature-sensitive intermediate layer construction, and outer shell coating, the steps are as follows: a) Gradient functionalized SiO2 core preparation: disperse nano-SiO2 in ethanol-water mixed solvent, add 3-mercaptopropyl trimethoxysilane, react at 60-80°C for 24 hours to prepare SiO2 core grafted with -SH groups on the surface; Control the pH value of the sulfonation reaction by adding hydrochloric acid solution, and react for 6-8 hours to introduce -SO3H groups to obtain sulfonated nano-silica; b) Temperature-sensitive intermediate layer construction: graft temperature-sensitive poly-N-isopropyl acrylamide on the surface of the sulfonated nano-silica by atom transfer radical polymerization method to prepare sulfonated nano-silica core-shell structure material grafted with poly-N-isopropyl acrylamide on the surface; c) Outer shell coating: blend the sulfonated nano-silica core-shell structure material grafted with poly-N-isopropyl acrylamide on the surface with graphene oxide dispersion liquid, form sulfonated nano-silica core-shell composite particles coated with graphene oxide on the surface of poly-N-isopropyl acrylamide by electrostatic self-assembly, centrifuge and wash, and then freeze-dry; (2) Melt blending: heat the matrix asphalt, and mix with styrene-butadiene rubber, compatibilizer, plasticizer, antioxidant, and core-shell composite particles, and organically intercalated nano-montmorillonite at a low speed of 30-50 rpm while protecting by introducing nitrogen gas at a flow rate of 5-10 L / min to prepare asphalt mixture.

4. The process for preparing modified bitumen according to claim 3, characterized in that, In step a) of step (1), the mass ratio of SiO2 to 3-mercaptopropyl trimethoxysilane in the gradient functionalized SiO2 core preparation is 1:0.5-1.2, and the pH of the sulfonation reaction is controlled to 2.0-3.5 by adding hydrochloric acid solution.

5. The process for preparing modified bitumen according to claim 3, characterized in that, The step b) is performed by using an atom transfer radical polymerization method, and CuBr / bipyridine is used as a catalytic system to graft temperature-sensitive poly N-isopropyl acrylamide on the surface of the sulfonated nano-silica to construct a temperature-sensitive intermediate layer. The molar ratio of CuBr to the temperature-sensitive poly N-isopyl acrylamide monomer is 1:100-200, the polymerization reaction is performed at a temperature of 50-70 DEG C, and the reaction time is 12-18 hours; the temperature-sensitive poly N-isopropyl acrylamide formed has specific temperature-sensitive properties, the lower critical solution temperature is 32±1 DEG C, and the phase transition enthalpy value is 80-120 J / g; and finally the sulfonated nano-silica core-shell structure material with the surface grafted poly N-isopropyl acrylamide is obtained.

6. The process for preparing modified bitumen according to claim 3, characterized in that, In the step c), the concentration of the graphene oxide dispersion liquid is 0.5-1.0 mg / mL, and the mass ratio of the sulfonated nano-silica core-shell structure material with the surface grafted poly N-isopropyl acrylamide to the graphene oxide is 1:0.3-0.8 during the blending.

7. The process for preparing modified bitumen according to claim 3, characterized in that, The method further comprises the following steps: (3) high-speed shearing: two-stage shearing of the asphalt mixture is performed by using a double-screw extruder to obtain sheared and dispersed asphalt; (4) ultrasonic dispersion: the sheared and dispersed asphalt is treated by using a probe-type ultrasonic processor at 170-180 DEG C for 10-15 minutes to obtain ultrasonically dispersed asphalt melt; (5) cooling and discharging: the ultrasonically dispersed asphalt melt is cooled to room temperature at a cooling rate of 5-10 DEG C / min to obtain the modified asphalt product; In the step (2), the heating temperature of the base asphalt during the melt blending stage is 160-170 DEG C, and the butadiene-styrene rubber is pre-crushed to a particle size of <5 mm before the melt blending.

8. The process for preparing modified bitumen according to claim 7, characterized in that, In the step (3), when the two-stage shearing of the asphalt mixture is performed, the set parameters of the double-screw extruder are as follows: the temperature of the first-stage shearing zone is 180-190 DEG C, the speed is 8000 rpm, and the treatment time is 15-20 minutes; and the temperature of the second-stage shearing zone is 170-180 DEG C, the speed is 6000 rpm, and the treatment time is 10-15 minutes. In the step (4), the ultrasonic dispersion is performed by using a probe-type ultrasonic processor, the probe diameter is 15-20 mm, and the amplitude is 50-70%.

9. The process for preparing modified bitumen according to claim 7, characterized in that, The GO shell layer of the core-shell structure nanoparticle is grafted with a photosensitive coumarin group through an amidation reaction, the reaction temperature is 80-100 DEG C, the time is 12-18 hours, the grafting rate is ≥95%, the fluorescence emission peak position of the grafted GO is red-shifted to 430-450 nm, and a condensation reflux device is used to control the solvent volatilization of the reaction system during the reaction, and after the reaction is completed, the unreacted raw materials are removed through multiple centrifugal washing.

10. Process for the preparation of modified bitumen according to any one of claims 3-9, characterized in that, ​

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