Microwave activated lignin-based double-shell microcapsule modified asphalt with anti-aging and self-regeneration functions and preparation method of microwave activated lignin-based double-shell microcapsule modified asphalt

Abstract

The invention discloses microwave activated lignin-based double-shell microcapsule modified asphalt with anti-aging and self-regeneration functions and a preparation method of the microwave activated lignin-based double-shell microcapsule modified asphalt, and belongs to the technical field of road engineering materials. The double-shell microcapsule comprises a second-layer shell, a first-layer shell and a core material, the second shell layer is a cross-linked polymer shell layer formed by copolymerization of styrene, butyl acrylate and N-isopropylacrylamide; the first shell layer is a microwave activated lignin-based polyurethane composite shell layer; and the core material is an asphalt regenerant. When the microcapsule is doped into matrix asphalt, the anti-aging performance and the self-regeneration performance of an asphalt material can be remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of road engineering materials technology, and particularly relates to a microwave-activated lignin-based double-shell microcapsule modified asphalt with both anti-aging and self-regeneration functions and its preparation method. Background Technology

[0002] Asphalt, as the most widely used binder in road engineering, occupies a core position in pavement construction due to its excellent bonding properties and construction adaptability. However, during long-term service, asphalt is susceptible to the combined effects of multiple environmental factors such as ultraviolet radiation, heat-oxidative erosion, and moisture, leading to the gradual deterioration of its internal chemical structure. This manifests as hardening and embrittlement, cracking and damage, and decreased bond strength, directly weakening pavement durability and shortening its service life. Currently, mainstream anti-aging solutions mainly include adding antioxidants, ultraviolet absorbers, or using modified asphalt systems. However, these methods generally suffer from drawbacks such as short anti-aging time, easy volatilization and loss of functional components, and insufficient environmental friendliness, making it difficult to achieve long-term protection for asphalt pavements.

[0003] Furthermore, microcracks that develop in asphalt pavements during their service life, if not repaired in a timely manner, will continue to expand and cause structural damage, seriously affecting road safety. In recent years, self-healing asphalt materials have become a research hotspot in the field, among which the technology of microencapsulating regenerators has attracted widespread attention because it can achieve directional release and in-situ repair at the crack site. However, existing microencapsulation systems mostly use petrochemical-based polymers as shell materials, which have poor thermal stability and are prone to problems such as premature leakage of regenerators and shell aging failure; moreover, traditional microencapsulation designs focus more on self-healing functions and pay insufficient attention to the synergistic improvement of anti-aging performance, failing to take into account the long-term stability of the asphalt system.

[0004] Lignin, an abundant natural polymer compound, is rich in active groups such as phenolic hydroxyl and methoxy groups, possessing excellent antioxidant, UV shielding, and free radical scavenging properties, making it a highly promising green anti-aging modifier. However, the poor compatibility of lignin with polymer matrices severely restricts its large-scale application in polymer composite systems. If the reactivity of lignin can be enhanced through specific activation techniques and it can be embedded into microcapsule shell structures via interfacial polymerization, it is expected to achieve a synergistic effect of anti-aging and regenerative repair functions.

[0005] Therefore, it is urgent to develop a new type of modified asphalt material that combines anti-aging and self-regeneration functions. This material needs to slow down the aging process of asphalt by utilizing the antioxidant properties of lignin, and at the same time achieve in-situ self-repair of cracks through the thermal response-oriented release of regenerators in microcapsules, ultimately significantly improving the durability and service life of asphalt pavement materials. Summary of the Invention

[0006] To address the problems of poor anti-aging effect and insufficient self-regeneration capacity of existing asphalt materials, this invention proposes a microwave-activated lignin-based double-shell microcapsule modified asphalt with both anti-aging and self-regeneration functions, as well as its preparation method, in order to extend the long-term service performance and service life of asphalt pavement materials.

[0007] To achieve the above objectives, the present invention provides the following technical solution: One of the objectives of this invention is to provide a microwave-activated lignin-based double-shell microcapsule, comprising: a second shell, a first shell, and a core material (wherein the second shell completely covers the first shell and the core material). The second shell is a cross-linked polymer shell formed by copolymerization of styrene, butyl acrylate and N-isopropylacrylamide; The first shell is a microwave-activated lignin-based polyurethane composite shell; The core material is an asphalt recycling agent.

[0008] The microcapsule provided by this invention has a first shell composed of microwave-activated lignin-grafted polyurethane. Microwave radiation technology is used to target and degrade lignin, partially breaking easily cleavable bonds (such as β-O-4 and COC bonds), increasing the exposure of phenolic hydroxyl and methoxy functional groups, and improving its oxidation activity and grafting ability. It can preferentially react with oxygen sources and free radicals in the asphalt system, quenching reactive oxygen species and thus delaying the oxidative aging process of asphalt. The second shell is a cross-linked polymer shell that encapsulates the core component, asphalt rejuvenator, and the first shell. Under high-temperature environments or mechanical loads, it can achieve slow release of the rejuvenator, repairing the deteriorated properties of asphalt materials and endowing asphalt with self-regeneration capabilities. The two shells work synergistically, significantly improving the long-term service durability and anti-aging ability of asphalt materials. Furthermore, through the regulation of the rejuvenator release behavior by the outer temperature-sensitive shell and the antioxidant effect of the inner microwave-activated lignin functional groups, the microcapsule possesses both anti-aging and self-regeneration functions.

[0009] The second objective of this invention is to provide a method for preparing microwave-activated lignin-based bishell microcapsules, comprising the following steps: (1) Disperse lignin in a solvent (polar solution), add a catalyst under an inert atmosphere, and conduct a radiation reaction using microwave radiation technology. After microwave treatment, cool the reaction system to room temperature, separate the solid and liquid phases by centrifugation or vacuum filtration, collect the solid part, and wash it with deionized water and ethanol alternately 3-5 times to remove catalyst residue, low molecular weight by-products and solvent impurities in the system until the pH of the washing solution is close to neutral. Place the washed solid in a vacuum drying oven and dry it at 40-60℃ for 12-24 hours until the moisture content is less than 3wt% to obtain pure microwave-activated lignin. The molecular weight of the microwave-activated lignin is 3200-5800 g / mol (e.g., 3200 g / mol, 4300 g / mol or 5800 g / mol), and the molecular weight distribution is controlled in the range of 1.3-1.7 (e.g., 1.3, 1.5 or 1.7) to ensure that the activated lignin molecules are uniform and the reaction is controllable. (2) Mix isophorone diisocyanate with anhydrous acetone, add catalyst, preheat to 70°C, then add a mixture of 1,4-butanediol, polypropylene glycol 2000 and anhydrous acetone to react, so that the isocyanate groups react with the polyol. After the reaction is complete, remove acetone by rotary evaporation and dry to obtain a polyurethane prepolymer with isocyanate active groups at the end. This prepolymer is used to construct the first shell structure for coating the core of the regenerator. (3) The polyurethane prepolymer is mixed with styrene, N-isopropylacrylamide, butyl acrylate, regenerator, crosslinking agent and initiator to obtain a homogeneous and stable oil phase mixture; (4) The oil phase mixture is added to deionized water containing sodium dodecylbenzenesulfonate and then ultrasonically emulsified to form a stable water-in-oil emulsion; (5) Heat the water-in-oil emulsion to 50°C and add dropwise an aqueous solution containing microwave-activated lignin, ethylene glycol and catalyst prepared in step (1), so that ethylene glycol in the aqueous phase reacts with the isocyanate at the end of the prepolymer in the oil phase to form a polyurethane chain. At the same time, the hydroxyl groups of microwave-activated lignin are grafted onto the polyurethane chain at the interface to form the first shell with polyurethane as the main body and lignin as the functional component. The lignin introduced in the first shell serves as a functional component. When the microcapsules are used together with the asphalt material, their phenolic hydroxyl and methoxy structures can quench oxygen free radicals, thereby inhibiting the oxidative aging reaction of asphalt. (6) After the first shell is formed, the temperature is raised to 75°C to initiate a free radical copolymerization reaction of styrene, butyl acrylate and temperature-sensitive monomer (N-isopropylacrylamide) in the oil phase. The crosslinking agent divinylbenzene in the oil phase participates in crosslinking to form the second shell of crosslinked polymer. The second shell has temperature response characteristics, which can adjust the shell structure state according to temperature changes during asphalt mixing and service. (7) Freeze-drying to obtain solid microwave-activated lignin-based bishell microcapsules.

[0010] The double-shell structure prepared by this invention achieves the slow release of the regenerator in the asphalt system through the dense coating of the regenerator by the second shell and the temperature response regulation, avoiding the rapid migration and volatilization of the regenerator in the early stages of construction and service. At the same time, the microwave lignin functional components that enter the asphalt system with the microcapsules work synergistically with the slow-release regenerator, significantly improving the anti-aging performance and self-regenerating performance of the asphalt material through multiple mechanisms such as physical barrier, oxygen free radical quenching and component regeneration.

[0011] Further, in step (1), the lignin is natural or modified biomass lignin, including but not limited to one or more of softwood lignin, hardwood lignin, sulfate lignin and alkaline lignin; The lignin has a particle size of 60-120 mesh (about 125-250 μm), preferably 70-100 mesh, to facilitate uniform microwave action and subsequent dispersion; The solvent is anhydrous ethanol and / or water; The catalyst is sodium hydroxide; The conditions for the radiation reaction are: microwave frequency of 2.45 GHz, microwave power of 200-1000 W, and processing time of 2-10 min.

[0012] During microwave treatment, the degree of lignin activation can be controlled by adjusting microwave power, time, solvent, and catalyst type to achieve different levels of functional group exposure, molecular weight regulation, and free radical content adjustment, thereby adapting to different anti-aging requirements of modified asphalt.

[0013] Further, in step (2), the mass ratio of isophorone diisocyanate, catalyst, 1,4-butanediol and polypropylene glycol 2000 is 5:0.05:0.45:2; The catalyst is dibutyltin dilaurate; The ultrasound power was 300W and the duration was 15 minutes.

[0014] Further, in step (3), the mass ratio of the polyurethane prepolymer, styrene, N-isopropylacrylamide, butyl acrylate and regenerator is 2:2.5:1:0.5:2.5; The regenerant is bio-oil; The crosslinking agent is divinylbenzene; The initiator is azobisisobutyronitrile.

[0015] Further, in step (4), the sodium dodecylbenzenesulfonate has a mass fraction of 5 wt% and the amount of deionized water is 150 mL, in order to ensure uniform dispersion of oil droplets in the aqueous phase and control the microcapsule particle size.

[0016] Further, in step (5), the mass ratio of the microwave-activated lignin, ethylene glycol, and catalyst is 0.1:0.6:0.06; the catalyst is dibutyltin dilaurate. The interfacial polymerization reaction takes 12 hours.

[0017] Furthermore, in step (6), the free radical copolymerization reaction time is 8 hours.

[0018] The third objective of this invention is to provide an application of microwave-activated lignin-based bishell microcapsules in the field of asphalt.

[0019] The fourth objective of this invention is to provide a microwave-activated lignin-based double-shell microcapsule modified bitumen with both anti-aging and self-regenerating functions. The raw materials include: base bitumen and the microwave-activated lignin-based double-shell microcapsules; the amount of the microwave-activated lignin-based double-shell microcapsules incorporated is 1-5 wt%.

[0020] The modified asphalt core component provided by this invention comprises matrix asphalt and microwave-activated lignin-based double-shell microcapsules, wherein the matrix asphalt serves as the main substrate constituting the material body, and the microwave-activated lignin-based double-shell microcapsules serve as the functional component, endowing the asphalt with dual core effects of anti-aging and self-regeneration.

[0021] Furthermore, the base asphalt is 70# asphalt or 90# asphalt.

[0022] The fifth objective of this invention is to provide a method for preparing microwave-activated lignin-based double-shell microcapsule modified asphalt with both anti-aging and self-regenerating functions, comprising the following steps: adding dried microwave-activated lignin-based double-shell microcapsules (moisture content not exceeding 1%) to base asphalt, and performing high-shear stirring at 130-150℃ for 30-60 minutes, with the stirring speed controlled at 100-3000 rpm, so that the microcapsules are uniformly dispersed in the asphalt and maintain structural integrity, and cooling the uniformly stirred mixture to 30-40℃ to obtain microwave-activated lignin-based double-shell microcapsule modified asphalt with both anti-aging and self-regenerating functions.

[0023] Compared with the prior art, the present invention has the following advantages and technical effects: This invention achieves anti-aging and self-regeneration functions in asphalt materials through microcapsules with an inner and outer double-shell structure. The first shell of the microcapsule is formed by a microwave-activated lignin-based polyurethane composite shell, in which the hydroxyl and methoxy groups on the lignin surface preferentially react with free radicals and reactive oxygen species in the asphalt system, quenching the oxygen source and thus delaying the oxidative aging of the asphalt. The second shell of the microcapsule is a cross-linked polymer shell formed by copolymerization of styrene, butyl acrylate, and the temperature-sensitive monomer N-isopropylacrylamide, effectively encapsulating the core regenerator. By regulating the shell structure through temperature response characteristics, the regenerator is released in a targeted and slow-release manner during the service life of the asphalt, thereby promoting the self-regeneration of the asphalt material.

[0024] In summary, the microcapsules possess both anti-aging and self-regenerating capabilities, which can significantly slow down the performance degradation of asphalt materials during long-term service and extend the service life of asphalt pavement materials. Detailed Implementation

[0025] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0026] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0027] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0028] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0029] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0030] 1. Preparation of raw materials and instruments 1.1 Experimental Materials Lignin: Natural or modified biomass lignin, including but not limited to one or more of softwood lignin, hardwood lignin, sulfate lignin, and alkaline lignin, pulverized to 60-120 mesh (approximately 125-250 μm), preferably 70-100 mesh (e.g., 80 mesh), with a moisture content ≤3wt%; Reagents: Isophorone diisocyanate, anhydrous acetone, 1,4-butanediol, polypropylene glycol 2000, styrene, N-isopropylacrylamide, butyl acrylate, bio-oil (regenerator), divinylbenzene (crosslinking agent), azobisisobutyronitrile (initiator), sodium dodecylbenzenesulfonate (surfactant), ethylene glycol, sodium hydroxide (catalyst), dibutyltin dilaurate (catalyst), deionized water, anhydrous ethanol; Base asphalt: 70# or 90# base asphalt.

[0031] 1.2 Experimental Apparatus Microwave reactors, ultrasonic emulsification equipment, vacuum drying ovens, high-speed centrifuges, vacuum filtration devices, oil baths, rotary evaporators, high-shear stirrers, electronic balances, pH meters, and freeze dryers.

[0032] 2. Preparation of microwave-activated lignin (1) Weigh an appropriate amount of pulverized lignin, disperse it in a polar solvent (anhydrous ethanol, water or ethanol / water mixture), and stir until homogeneous; (2) Add 3 wt% sodium hydroxide catalyst of lignin and transfer it to a microwave reactor under nitrogen or inert gas protection; (3) Set the microwave reactor parameters: frequency 2.45 GHz, power 200-1000 W (e.g. 500 W), radiation reaction 2-10 min (e.g. 2 min, 5 min or 8 min) to achieve partial breakage of lignin's easily cleavable bonds (β-O-4 bond and COC bond) while preserving the integrity of the aromatic ring structure; (4) After the reaction is complete, cool the system to room temperature, separate the solid and liquid phases by centrifugation or vacuum filtration, and collect the solid fraction; (5) Wash the solid with deionized water and ethanol alternately 3-5 times until the pH of the washing solution is close to neutral to remove catalyst residue, low molecular weight by-products and solvent impurities. (6) Place the washed solid in a vacuum drying oven and dry it at 40-60℃ (e.g., 50℃) for 12-24 hours (e.g., 18 hours) until the moisture content is less than 3wt%. Then seal and store for later use.

[0033] 3. Preparation of microwave-activated lignin-based bishell microcapsules 3.1 Preparation of polyurethane prepolymer (1) Weigh isophorone diisocyanate, dibutyltin dilaurate, 1,4-butanediol and polypropylene glycol 2000 in a mass ratio of 5:0.05:0.45:2. (2) Mix isophorone diisocyanate with 30 mL of anhydrous acetone, add dibutyltin dilaurate, and preheat in an oil bath at 70 °C; (3) Mix 1,4-butanediol and polypropylene glycol 2000 with an appropriate amount of anhydrous acetone, and after ultrasonic treatment at 300W for 15 minutes, mix well and add to the above preheated system for reaction. (4) After the reaction is complete, acetone is removed by rotary evaporation and dried to obtain a polyurethane prepolymer with isocyanate active groups at the end, for later use.

[0034] 3.2 Preparation of oil phase mixture Weigh out polyurethane prepolymer, styrene, N-isopropylacrylamide, butyl acrylate, and bio-oil in a mass ratio of 2:2.5:1:0.5:2.5. Add appropriate amounts of crosslinking agent divinylbenzene and initiator azobisisobutyronitrile and stir to form a homogeneous and stable oil phase mixture.

[0035] 3.3 Preparation of oil-water emulsion The oil phase mixture was slowly added to 150 mL of deionized water containing 5 wt% sodium dodecylbenzenesulfonate, and then subjected to ultrasonic emulsification to form a stable water-in-oil emulsion.

[0036] 3.4 First Shell (Microwave-Activated Lignin-Based Polyurethane Composite Shell) Polymerization (1) Weigh microwave-activated lignin, ethylene glycol, and dibutyltin dilaurate in a mass ratio of 0.1:0.6:0.06, dissolve them in 10 mL of deionized water, and prepare an aqueous solution. (2) Heat the oil-water emulsion to 50°C, add the above aqueous solution dropwise, and keep the reaction at the temperature for 12 hours; the volume ratio of the aqueous solution to the oil-in-water solution is 1:5.

[0037] In the aqueous phase, ethylene glycol and the terminal isocyanate of the oil phase prepolymer undergo interfacial polymerization to form polyurethane chains. Microwave-activated lignin is grafted onto the polyurethane chains via hydroxyl groups, forming the first composite shell with polyurethane as the main component and lignin as the functional component.

[0038] 3.5 Polymerization of the Second Shell (Cross-linked Polymer Shell) The system was heated to 75°C to initiate a free radical copolymerization reaction of styrene, butyl acrylate, and N-isopropylacrylamide in the oil phase. The crosslinking agent divinylbenzene participated in the crosslinking. The reaction was kept at the temperature for 8 hours to form a second shell of crosslinked polymer with temperature-responsive characteristics.

[0039] 3.6 Microcapsule Collection and Drying After the reaction was completed, water and residual solvent were separated and removed to obtain wet solid microcapsules; these were then dried using a freeze dryer to obtain solid microwave-activated lignin-based bishell microcapsules, which were then sealed and stored (moisture content controlled to be less than 1%).

[0040] 4. Preparation of microwave-activated lignin-based bishell microcapsule-modified pitch (1) Weigh out dried microwave-activated lignin-based double-shell microcapsules (moisture content ≤1%) at a ratio of 1-5 wt% (e.g., 1 wt%, 3 wt% or 5 wt%) of the matrix bitumen mass. (2) Heat the base asphalt (70# or 90#) to 130-150℃ (e.g., 135℃) and add the weighed microcapsules; (3) Start the high-shear mixer and control the mixing speed to 100-3000 rpm (e.g., 2000 rpm), and continue mixing for 30-60 min (e.g., 30 min) to ensure that the microcapsules are uniformly dispersed in the asphalt and have an intact structure; (4) After stirring, the mixture is cooled to 30-40℃ to obtain microwave-activated lignin-based double-shell microcapsule modified asphalt with anti-aging and self-regeneration functions.

[0041] 5. Application The microwave-activated lignin-based double-shell microcapsule modified asphalt can be used in the field of road engineering as a pavement binder. With its synergistic function of anti-aging and self-regeneration, it can improve the durability and service life of asphalt pavement.

[0042] Unless otherwise specified, "room temperature" in this invention refers to 25±2℃.

[0043] All raw materials used in this invention were purchased from the market.

[0044] The technical solution of the present invention will be further illustrated by the following embodiments.

[0045] Example 1 A method for preparing microwave-activated lignin-based double-shell microcapsule modified bitumen with both anti-aging and self-regenerating functions includes the following steps: S1. Preparation of microwave-activated lignin Weigh 10g of dried lignin (enzymatically hydrolyzed lignin, pulverized to 80 mesh, with a moisture content ≤3wt%), disperse it in 100mL of ethanol / water mixed solution (volume ratio 1:1), and stir until homogeneous; add 3wt% sodium hydroxide catalyst (by weight of lignin), and transfer to a microwave reactor under nitrogen protection; set the microwave reactor parameters as follows: frequency 2.45GHz, power 500W, radiation reaction for 5min; after the reaction, cool the system to room temperature, separate the solid and liquid phases by centrifugation, and collect the solid fraction; wash the solid four times alternately with deionized water and ethanol until the pH of the washing solution is close to neutral; place the washed solid in a vacuum drying oven and dry at 50℃ for 18h to obtain microwave-activated lignin; The microwave-activated lignin was tested and found to have a molecular weight of 3200 g / mol, a molecular weight distribution of 1.5, and a DPPH free radical scavenging rate of 78%.

[0046] S2. Preparation of microwave-activated lignin-based bishell microcapsules (I) Preparation of polyurethane prepolymer 5.0 g of isophorone diisocyanate was mixed with 30 mL of anhydrous acetone, and 0.05 g of dibutyltin dilaurate was added. The mixture was preheated in an oil bath at 70 °C. 0.45 g of 1,4-butanediol, 2.0 g of polypropylene glycol 2000 and 10 mL of anhydrous acetone were ultrasonically treated at 300 W for 15 min and then mixed. The mixture was then added to the oil bath system and reacted for 180 min. After the reaction was completed, the acetone was removed by rotary evaporation and the mixture was dried to obtain a polyurethane prepolymer with terminal isocyanate active groups. (ii) Preparation of oil phase mixture 2g of polyurethane prepolymer, 2.5g of styrene, 1g of N-isopropylacrylamide, 0.5g of butyl acrylate, 2.5g of bio-oil, 0.1g of crosslinking agent (divinylbenzene) and 0.05g of initiator (azobisisobutyronitrile) were added and stirred to form a homogeneous and stable oil phase mixture. (III) Preparation of oil-water emulsion The oil phase mixture was slowly added to 150 mL of deionized water containing 5 wt% sodium dodecylbenzenesulfonate, and then subjected to ultrasonic emulsification to form a stable water-in-oil emulsion. (iv) Polymerization of the first shell (microwave-activated lignin-based polyurethane composite shell) Weigh 0.1g of microwave-activated lignin, 0.6g of ethylene glycol, and 0.06g of dibutyltin dilaurate, dissolve them in 10mL of deionized water, and prepare an aqueous solution. Heat 100 mL of the water-in-oil emulsion from step (III) to 50 °C, add 20 mL of the above aqueous solution dropwise, and keep the reaction at this temperature for 12 h to form the first shell layer. (v) Polymerization of the second shell (cross-linked polymer shell) The system was further heated to 75°C and kept at that temperature for 8 hours to form a second cross-linked polymer shell with temperature-responsive properties. (vi) Microcapsule collection and drying After the reaction was completed, water and residual solvent were separated and removed to obtain wet solid microcapsules; these were then dried using a freeze dryer to obtain solid microwave-activated lignin-based bishell microcapsules, which were then sealed and stored (moisture content controlled below 1%). S3. Preparation of microwave-activated lignin-based bishell microcapsule modified asphalt Heat 70# base asphalt to 135℃, add 1wt% of microwave-activated lignin-based double-shell microcapsules by weight of the base asphalt, start a high-shear stirrer, control the stirring speed at 2000rpm, and continue stirring for 30min. After stirring, cool the mixture to 35℃ to obtain microwave-activated lignin-based double-shell microcapsule modified asphalt with both anti-aging and self-regeneration functions.

[0047] Example 2 Same as Example 1, except that in step S3, microwave-activated lignin-based bishell microcapsules of 3 wt% of the matrix bitumen are added.

[0048] Example 3 Same as Example 1, except that in step S3, microwave-activated lignin-based double-shell microcapsules of 5 wt% of the matrix bitumen are added.

[0049] Example 4 Same as Example 1, except that in step S1, the microwave reaction time is 2 minutes.

[0050] Tests showed that microwave-activated lignin had a molecular weight of 4300 g / mol, a molecular weight distribution of 1.3, and a DPPH free radical scavenging rate of 54%.

[0051] Example 5 Same as Example 1, except that in step S1, the microwave reaction time is 8 minutes.

[0052] Tests showed that microwave-activated lignin had a molecular weight of 5800 g / mol, a molecular weight distribution of 1.7, and a DPPH free radical scavenging rate of 62%.

[0053] Comparative Example 1 Similar to Example 1, except that step S1 is not performed, that is, the lignin is not microwave activated, and the enzymatically hydrolyzed lignin directly participates in the reaction of step S2.

[0054] Comparative Example 2 Same as Example 2, except that no microwave-activated lignin shell is prepared. The specific steps in step S2 (a) are as follows: 2.5g styrene, 1g N-isopropylacrylamide, 0.5g butyl acrylate, 2.5g bio-oil, 0.1g crosslinking agent (divinylbenzene) and 0.05g initiator (azobisisobutyronitrile) are added and stirred to form an oil phase mixture.

[0055] Comparative Example 3 Same as Example 3, except that microcapsules were not prepared; instead, lignin was directly added to asphalt after microwave activation treatment. The specific steps are as follows: S1. Preparation of microwave-activated lignin: Same as in Example 1; S2. Preparation of microwave-activated lignin-modified pitch Heat 70# base asphalt to 135℃, add 1wt% microwave-activated lignin by weight of the base asphalt, start a high-shear mixer, control the stirring speed at 2000rpm, and continue stirring for 30min. After stirring, cool the mixture to 35℃ to obtain microwave-activated lignin-modified asphalt.

[0056] Performance testing: The modified asphalts prepared in each embodiment and comparative example were subjected to short-term and long-term aging tests according to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTGE20-2011). The complex modulus (64℃, 10rad / s) of the modified asphalt before and after aging was tested, and its anti-aging index (AI) was calculated according to Equation 1. The results are shown in Table 1. The smaller the anti-aging index, the stronger its comprehensive anti-aging ability.

[0057] (1); In the formula, | G | A The complex modulus of asphalt after aging, | G | V This represents the complex modulus of asphalt before aging.

[0058] Table 1. Anti-aging properties of Examples 1-5 and Comparative Examples 1-3 Based on the data in Table 1, comparing Example 1, Example 2, and Example 3, it can be clearly found that the addition of microwave-activated lignin bishell microcapsules can significantly improve the overall anti-aging performance of the asphalt matrix, and the overall anti-aging ability of the asphalt shows a significant increasing trend with the increase of the dosage.

[0059] Comparing Examples 1, 4, and 5, it can be seen that microwave treatment time has a significant impact on the molecular weight and oxidative activity of lignin. When the microwave treatment time is too short (2 min), lignin degradation is insufficient, and the exposure of active groups is limited, affecting its grafting reaction with polyurethane segments. Simultaneously, it reduces the quenching ability of oxygen sources, leading to a decrease in the overall anti-aging performance of the modified asphalt. When the microwave treatment time is too long (8 min), lignin is prone to intermolecular condensation and local gelation under strong microwave action, resulting in a wider molecular weight distribution. Some active groups are consumed or shielded, thereby reducing its grafting efficiency with polyurethane chains. At the same time, the number of effective active sites that can participate in oxygen free radical quenching is reduced, weakening the effect of microcapsules on improving the anti-aging performance of asphalt materials.

[0060] Comparing Example 1 with Comparative Example 1, it can be found that microwave-activated lignin bishell microcapsules can significantly improve the overall anti-aging properties of asphalt compared to unactivated lignin microcapsules.

[0061] Comparing Example 2 with Comparative Example 2, it can be found that microwave-activated lignin-based bishell microcapsules not only exert the anti-aging effect of microwave lignin, but also realize the self-regeneration function of microcapsules. Compared with microcapsules that only add a single self-regeneration function, the comprehensive anti-aging ability of asphalt will be further enhanced.

[0062] Comparing Example 3 with Comparative Example 3, it can be observed that microwave-activated lignin bishell microcapsules can simultaneously exert the dual functions of lignin anti-aging and microcapsule self-regeneration. Compared with the single anti-aging function of only adding microwave-activated lignin, the comprehensive anti-aging performance of asphalt will be further improved.

[0063] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A microwave-activated lignin-based bishell microcapsule, characterized in that, It includes: a second shell, a first shell, and a core material; The second shell is a cross-linked polymer shell formed by copolymerization of styrene, butyl acrylate and N-isopropylacrylamide; The first shell is a microwave-activated lignin-based polyurethane composite shell; The core material is an asphalt recycling agent.

2. A method for preparing microwave-activated lignin-based bishell microcapsules as described in claim 1, characterized in that, Includes the following steps: (1) Disperse lignin in a solvent, add the first catalyst under an inert atmosphere, and carry out the radiation reaction using microwave radiation technology to obtain solid microwave activated lignin; (2) Mix isophorone diisocyanate with anhydrous acetone, add a second catalyst, preheat, and then add a mixture of 1,4-butanediol, polypropylene glycol 2000 and anhydrous acetone to react and obtain a polyurethane prepolymer with isocyanate active groups at the end. (3) The polyurethane prepolymer is mixed with styrene, N-isopropylacrylamide, butyl acrylate, asphalt recycling agent, crosslinking agent and initiator to obtain an oil phase mixture; (4) The oil phase mixture is added to deionized water containing sodium dodecylbenzenesulfonate and then ultrasonically emulsified to form a stable water-in-oil emulsion; (5) Heat the water-in-oil emulsion to 50°C and add dropwise an aqueous solution containing microwave-activated lignin, ethylene glycol and a third catalyst prepared in step (1) to form the first shell. (6) Continue heating to 75°C to continue the reaction and form a second shell; (7) Freeze-drying to obtain the microwave-activated lignin-based bishell microcapsules.

3. The method for preparing microwave-activated lignin-based bishell microcapsules according to claim 2, characterized in that, In step (1), the lignin is selected from one or more of softwood lignin, hardwood lignin, sulfate lignin, and alkaline lignin; The lignin has a particle size of 60-120 mesh; The solvent is anhydrous ethanol and / or water; The first catalyst is sodium hydroxide; The conditions for the radiation reaction are: microwave frequency of 2.45 GHz, microwave power of 200-1000 W, and processing time of 2-10 min.

4. The method for preparing microwave-activated lignin-based bishell microcapsules according to claim 2, characterized in that, In step (2), the mass ratio of isophorone diisocyanate, catalyst, 1,4-butanediol and polypropylene glycol 2000 is 5:0.05:0.45:2; The second catalyst is dibutyltin dilaurate.

5. The method for preparing microwave-activated lignin-based bishell microcapsules according to claim 2, characterized in that, In step (3), the mass ratio of the polyurethane prepolymer, styrene, N-isopropylacrylamide, butyl acrylate and regenerator is 2:2.5:1:0.5:2.5; The regenerant is bio-oil; The crosslinking agent is divinylbenzene; The initiator is azobisisobutyronitrile.

6. The method for preparing microwave-activated lignin-based bishell microcapsules according to claim 2, characterized in that, In step (4), the deionized water containing sodium dodecylbenzenesulfonate has a mass fraction of 5 wt% for sodium dodecylbenzenesulfonate. In step (5), the mass ratio of microwave-activated lignin, ethylene glycol and catalyst is 0.1:0.6:0.06; the third catalyst is dibutyltin dilaurate.

7. The application of the microwave-activated lignin-based bishell microcapsule as described in claim 1 in the field of asphalt.

8. A microwave-activated lignin-based double-shell microcapsule modified bitumen with both anti-aging and self-regenerating functions, characterized in that, Raw materials include: The matrix pitch and the microwave-activated lignin-based bishell microcapsules of claim 1; The amount of microwave-activated lignin-based bishell microcapsules incorporated is 1-5 wt%.

9. The microwave-activated lignin-based double-shell microcapsule modified bitumen with both anti-aging and self-regenerating functions according to claim 8, characterized in that, The base asphalt is 70# asphalt or 90# asphalt.

10. A method for preparing microwave-activated lignin-based double-shell microcapsule modified bitumen with both anti-aging and self-regenerating functions as described in claim 8 or 9, characterized in that, Includes the following steps: Microwave-activated lignin-based bishell microcapsules were added to the matrix bitumen and sheared and stirred at 130-150℃ for 30-60 minutes, with the stirring speed controlled at 100-3000 rpm.

Images