Aminated PET and desulfurized rubber powder composite modified asphalt and preparation method thereof

Abstract

The invention relates to the technical field of road paving materials, and discloses aminated PET (polyethylene terephthalate) and desulfurized rubber powder composite modified asphalt and a preparation method thereof, the aminated PET and desulfurized rubber powder composite modified asphalt is prepared from matrix asphalt, desulfurized rubber powder, tall oil fatty acid, epoxidized soybean oil, zinc isoocatanoate, aminated PET and styrene-maleic anhydride copolymer, coating the desulfurized rubber powder with tall oil fatty acid, and carrying out esterification ring-opening reaction on the tall oil fatty acid and the epoxidized soybean oil to generate an anti-migration structure; the terminal amino of the aminated PET and the epoxidized soybean oil are subjected to addition to form a bridging prepolymerization micro-area; and the styrene-maleic anhydride copolymer is subjected to dehydration ring-closure reaction, so that the pre-polymerized micro-area is grafted into the matrix asphalt in situ. According to the invention, a homogeneous three-dimensional interpenetrating network is constructed in an asphalt system through a chemical reaction, so that the interfacial compatibility of a modifier and matrix asphalt is improved, the unidirectional migration of light components and the segregation of polymers are inhibited, and the long-term storage stability and rutting deformation resistance of the composite modified asphalt are improved.

Description

Technical Field

[0001] This invention relates to the field of road paving materials technology, specifically to a composite modified asphalt made of amination PET and desulfurized rubber powder and its preparation method. Background Technology

[0002] Applying waste polyester and waste rubber powder to modify base asphalt is a technical means to realize the resource utilization of solid waste and improve the road performance of road engineering materials. However, waste PET, as a polar polymer, has certain thermodynamic differences with the non-polar base asphalt; waste rubber powder itself has a three-dimensional cross-linked network structure, resulting in poor interfacial compatibility when the two are directly physically blended with base asphalt. During hot storage and high-temperature construction, the modifier particles exhibit agglomeration and cohesive forces, leading to phase separation and polymer segregation in the composite system, thus disrupting the macroscopic homogeneity of the modified asphalt.

[0003] In rubber-modified asphalt systems, light components such as saturated and aromatic components in the base asphalt easily penetrate into the rubber powder. This unidirectional migration leads to excessive swelling of the rubber powder, disrupting the original component balance of the base asphalt colloidal system. As the light components migrate, the continuous phase of the modified asphalt hardens, resulting in decreased long-term storage stability of the composite modified asphalt.

[0004] Furthermore, existing modification processes typically involve directly adding various modifiers and additives to the entire base asphalt for mixing and reaction. During this process, the low concentration of reactants in the asphalt medium reduces the collision probability of the cross-linking reaction, making it impossible to construct an effective three-dimensional network structure within the asphalt. Simultaneously, if the water vapor generated during the high-temperature grafting reaction cannot be promptly removed, it hinders the forward shift of chemical equilibrium, leading to incomplete grafting and dehydration reactions. These limitations restrict the dispersion of the polymer in the asphalt phase, resulting in deficiencies in the composite modified asphalt's resistance to rutting deformation and structural solidification. Summary of the Invention

[0005] The technical problem solved by this invention is the poor compatibility of waste polyester and waste rubber powder in asphalt, their tendency to undergo phase separation, and their insufficient stability during high-temperature storage. In existing technologies, physical blending makes it difficult to establish stable chemical bonds between the modifiers and the base asphalt, leading to the easy migration of light components and polymer aggregation and segregation in the composite modified asphalt during long-term use and thermal storage.

[0006] To address the above problems, the present invention provides the following technical solution: In a first aspect, the present invention provides a composite modified asphalt made of amination PET and desulfurized rubber powder, using the following technical solution: A modified asphalt composed of aminated PET and desulfurized rubber powder is made from raw materials comprising the following parts by weight: 70-82 parts of base asphalt; 15-24 parts of desulfurized rubber powder; Tall oil fatty acids 0.435–1.5 parts; 0.435–1.2 parts of epoxidized soybean oil; Zinc isooctanoate 0.00174–0.0072 parts; Amine-treated PET: 3-6 parts; 0.29–0.9 parts of styrene-maleic anhydride copolymer; In the composite modified asphalt, the tall oil fatty acid coats the desulfurized rubber powder and undergoes an esterification ring-opening reaction with the epoxidized soybean oil to generate an anti-migration structure; the terminal amino groups of the amination PET undergo an addition reaction with the epoxy groups of the epoxidized soybean oil to form bridging prepolymer microdomains; the styrene-maleic anhydride copolymer undergoes a dehydration ring-closure reaction to form imide bonds, and the bridging prepolymer microdomains are grafted in situ into the matrix asphalt to form a homogeneous three-dimensional interpenetrating network.

[0007] By employing the above technical solution, a multi-layered chemically bonded network structure is constructed within the matrix asphalt system through a specific combination of tall oil fatty acids, epoxidized soybean oil, zinc isooctanoate, amination PET, and styrene-maleic anhydride copolymer. This results in improved compatibility and inhibition of phase separation. The specific reaction process and mechanism are as follows: Construction of Surface Coating and Anti-Migration Structure: The nonpolar aliphatic chains of tall oil fatty acids have a physical affinity for the hydrocarbon structures on the surface of desulfurized rubber powder, forming a coating layer on the powder surface. Under the catalysis of zinc isooctanoate, the carboxyl groups in the tall oil fatty acid molecules undergo an esterification ring-opening reaction with the epoxy groups in epoxidized soybean oil. This reaction bonds epoxidized soybean oil to the surface of desulfurized rubber powder, forming an anti-migration structure. This structure reduces the penetration rate of light components such as saturated and aromatic components in the base asphalt into the interior of the rubber powder, inhibits excessive swelling of the rubber powder, and maintains the stability of the colloidal structure of the base asphalt.

[0008] Formation of bridging prepolymer microdomains: The end groups of amination PET have reactive primary or secondary amine groups. These amine groups undergo an epoxy-amine nucleophilic addition reaction with the remaining unreacted epoxy groups in the epoxidized soybean oil molecule. Epoxidized soybean oil acts as a linking node in the crosslinking reaction, connecting the rigid polyester molecular chains with the elastic desulfurized rubber powder through chemical bonds. This forms bridging prepolymer microdomains with both rigid and flexible segments in the asphalt matrix, improving the interfacial compatibility between PET and the rubber powder.

[0009] In-situ grafting and curing of a three-dimensional interpenetrating network: The styrene-maleic anhydride copolymer, acting as a reactive compatibilizer, first undergoes an acylation reaction with the free amino groups of the amination residue in the prepolymerized microdomains via a dehydration and ring-closure reaction at high temperature to form imide bonds. Simultaneously, the styrene segments in the styrene-maleic anhydride copolymer exhibit thermodynamic compatibility with aromatic phenols and resin macromolecules in the matrix asphalt. Through the entanglement and polarity of the polymer chains, the aforementioned bridging prepolymerized microdomains are in-situ grafted into the continuous phase of the matrix asphalt. This reaction sequence achieves chemical bonding between the dispersed and continuous phases, forming a homogeneous three-dimensional interpenetrating network, reducing the agglomeration and cohesion between modifier particles, and improving the resistance to rutting deformation and long-term storage stability of the composite modified asphalt.

[0010] Preferably, the amination PET is prepared by the following steps: waste polyester fragments and monoethanolamine are mixed at a mass ratio of 1:1.5 to 1:2.5 to form an initial mixture; the initial mixture is heated to 135°C to 145°C and stirred continuously at a speed of 180 to 220 rpm for 2 to 4 hours to generate a crude product system through ammonolysis and chain scission; the crude product system is cooled, washed with water 3 to 5 times, dried, and mechanically ground to a powder with a particle size of less than 60 mesh to obtain the amination PET.

[0011] By employing the above technical solution, waste polyester undergoes ammonolysis under heating and stirring conditions, resulting in the breakage and degradation of polyester macromolecular chains into oligomers with amine end groups. The washing step removes water-soluble impurities and small-molecule byproducts from the system, while grinding controls the particle size to less than 60 mesh, increasing the specific surface area of ​​the material. This preparation process achieves the chemical degradation and recycling of polyester materials while providing active amine reaction sites for subsequent addition reactions with the epoxy system.

[0012] Preferably, the desulfurized rubber powder is prepared by the following steps: feeding ordinary rubber powder into a twin-screw extruder to form a heated powder substrate; introducing micro-oxygen gas with a volume concentration of 2% to 5% into the heated powder substrate at a high temperature of 180℃ to 220℃, and generating extruded desulfurized material under the action of mechanical shearing and micro-oxygen; cooling and collecting the extruded desulfurized material to obtain the desulfurized rubber powder with a Mooney viscosity of 30 to 40.

[0013] By adopting the above technical solution, under the dual effects of strong mechanical shear force and high-temperature micro-oxygen environment of a twin-screw extruder, the cross-linked sulfur bonds inside ordinary rubber powder are selectively broken, achieving continuous dynamic desulfurization. A Mooney viscosity reduction to the 30-40 range indicates sufficient deentanglement of the rubber powder network structure and enhanced flowability. Simultaneously, the micro-oxygen effect introduces oxygen-containing functional groups onto the rubber powder surface, improving the surface activity of the desulfurized rubber powder and its physicochemical bonding ability with tall oil fatty acids.

[0014] Preferably, it is made from the following raw materials in parts by weight: 76 parts base bitumen; 20 parts desulfurized rubber powder; 0.96 parts tall oil fatty acid; 0.84 parts epoxidized soybean oil; 0.0042 parts zinc isooctanoate; 4 parts amination PET; and 0.6 parts styrene-maleic anhydride copolymer.

[0015] By adopting the above technical solution, the proportions of each raw material exhibit a good synergistic effect. The ratio of tall oil fatty acids to epoxidized soybean oil ensures the esterification coating structure on the surface of the desulfurized rubber powder and reserves some active epoxy groups for subsequent coupling. The ratio of amination PET to styrene-maleic anhydride copolymer ensures that the crosslinking density of the grafting reaction is within a reasonable range, avoiding local gelation of the system due to excessive crosslinking, thereby ensuring the high-temperature fluidity and pumpable construction performance of the modified asphalt.

[0016] Secondly, the present invention provides a method for preparing composite modified asphalt of amination-treated PET and desulfurized rubber powder, using the following technical solution: A method for preparing a composite modified asphalt of amination-modified PET and desulfurized rubber powder includes the following steps: A portion of the base asphalt is pumped into a premixing kettle, heated, and then desulfurized rubber powder and tall oil fatty acids are added sequentially and stirred to form a suspension slurry. Epoxidized soybean oil and zinc isooctanoate are added to the suspension slurry, the temperature is adjusted and stirred to initiate an esterification ring-opening reaction, generating an anti-migration intermediate. Amination-modified PET is added to the anti-migration intermediate, and the mixture is kept at a constant temperature and stirred to initiate an epoxy-amine addition reaction, thus obtaining a coupling prepolymer masterbatch. The remaining base asphalt is pumped into the main reactor, and after heating, the coupling prepolymer masterbatch is continuously pumped in. The vacuum system is turned on to keep the main reactor under negative pressure. Styrene-maleic anhydride copolymer is added, and water vapor is removed under stirring and grafting reaction is carried out to obtain primary grafted modified asphalt. The temperature of the primary grafted modified asphalt is controlled to perform high-shear homogenization treatment to obtain homogenized modified asphalt; the homogenized modified asphalt is slowed down and kept at a constant temperature for stirring to develop, thereby obtaining the composite modified asphalt.

[0017] By adopting the above technical solution, this invention uses a masterbatch method and a stepwise reaction process to promote the orderly conduct of multiple chemical reactions. The specific process and mechanism are as follows: Part of the asphalt is used as a liquid medium: a portion of the matrix asphalt is extracted for the preliminary reaction, which can maintain the low viscosity of the system with a low total amount of material, which is beneficial to the dispersion of desulfurized rubber powder and the coating of tall oil fatty acids.

[0018] Preparation of high-concentration prepolymer: Esterification ring-opening reaction and epoxy-amine addition reaction are sequentially initiated in a portion of the base asphalt. Due to the high concentration of reactants, the probability of intermolecular collisions is increased, promoting the reaction of epoxidized soybean oil with amination PET and desulfurized rubber powder to form a coupling prepolymer masterbatch with high crosslinking density. This reduces the risk of incomplete reaction due to excessively low concentration of reactants in the total asphalt.

[0019] Vacuum dehydration and grafting reaction: The coupling prepolymer masterbatch is introduced into the remaining matrix pitch in the main reactor, and a styrene-maleic anhydride copolymer is added. The styrene-maleic anhydride copolymer undergoes acylation and dehydration ring-closure reactions with the free amine groups in the prepolymer. Maintaining a negative pressure state by activating the vacuum system removes the water vapor generated during the reaction. This removal of moisture shifts the chemical equilibrium towards dehydration and ring closure, increasing the imide bond formation rate and grafting efficiency.

[0020] High shear and curing: After grafting, the system undergoes high shear treatment, which disperses the localized polymer network into the continuous asphalt phase, resulting in a refined distribution. Subsequent slow-deceleration and heat preservation curing causes swelling and interfacial diffusion between the asphalt components and the polymer network, releasing residual stress within the system, stabilizing the three-dimensional interpenetrating network structure, and improving the macroscopic uniformity of the finished product.

[0021] Preferably, in the step of forming the suspension slurry: The base asphalt is heated to 145℃~155℃, and after adding the desulfurized rubber powder and tall oil fatty acid, it is stirred at a speed of 200~400rpm for 10~20 minutes.

[0022] By adopting the above technical solution, the base asphalt is made fluid within this temperature and speed range, reducing the probability of tall oil fatty acid thermal decomposition or volatilization. At the same time, low-speed stirring suspends the desulfurized rubber powder in the asphalt, completing the initial physical coating process.

[0023] Preferably, in the step of generating the anti-migration intermediate: Adjust the temperature of the material in the premixing vessel to 155℃~165℃ and stir at a speed of 400~600rpm for 10~20 minutes.

[0024] By adopting the above technical solution, increasing the temperature provides the activation energy required for the esterification ring-opening reaction; increasing the stirring speed improves the mass transfer rate of the reaction system, enabling the fatty acids on the surface of epoxidized soybean oil and gum powder to chemically bond under the catalysis of zinc isooctanoate.

[0025] Preferably, in the step of preparing the coupling prepolymer masterbatch: Stir at 155℃~165℃ and 400~600rpm for 20~30 minutes.

[0026] By employing the above technical solution, maintaining these reaction conditions enables the terminal amino groups of the amination PET to undergo a nucleophilic addition reaction with the remaining epoxy groups. The set reaction time ensures the formation of bridging prepolymer microregions while avoiding aging of the asphalt component caused by excessively long holding time.

[0027] Preferably, the specific implementation method for obtaining the primary grafted modified asphalt is as follows: The main reactor is heated to 175℃~185℃, and a negative pressure of -0.05MPa~-0.1MPa is maintained inside the main reactor. The reactor is stirred at a speed of 1800~2200rpm for 25~40 minutes.

[0028] By employing the above technical solution, the combined effects of high temperature (175℃~185℃) and negative pressure promote the dehydration and closed-loop reaction, eliminating moisture. A rotation speed of 1800~2200 rpm facilitates the dispersion and mixing of the high-viscosity coupling prepolymer masterbatch in the remaining matrix asphalt.

[0029] Preferably, in the step of obtaining the homogenized modified asphalt, the temperature is controlled at 170℃~180℃, and the homogenization treatment is carried out at a shear rate of 3000~3500rpm for 50~70 minutes; in the step of preparing the composite modified asphalt, the stirring speed is reduced to 1500~2500rpm, and the mixture is kept at 165℃~175℃ and stirred for 45~75 minutes.

[0030] By employing the above technical solution, a shear rate of 3000–3500 rpm provides mechanical shear force, enabling the polymer phase to disperse in the asphalt. After homogenization, the temperature and rotation speed are reduced for further development, avoiding thermo-oxidative aging of the asphalt under continuous high temperature and high shear, and mechanical degradation of the polymer chains, thus ensuring the stability of the physicochemical properties of the composite modified asphalt.

[0031] This invention provides a composite modified asphalt made from amination-treated PET and desulfurized rubber powder, and its preparation method. It has the following beneficial effects: 1. This invention constructs a three-dimensional interpenetrating network in the continuous phase of the matrix asphalt through esterification ring-opening, addition, and dehydration ring-closing reactions between tall oil fatty acids, epoxidized soybean oil, amination PET, and styrene-maleic anhydride copolymer. This chemical bonding method changes the original physical blending state, improves the interfacial compatibility between polyester, rubber powder, and matrix asphalt, reduces the agglomeration and cohesive force of modifier particles, and solves the problems of phase separation and polymer segregation in composite modified asphalt during thermal storage.

[0032] 2. This invention utilizes tall oil fatty acids to coat the surface of desulfurized rubber powder, and reacts it with epoxidized soybean oil under the catalysis of zinc isooctanoate to generate an anti-migration structure. This structure hinders the penetration of light components such as saturated and aromatic components in the base asphalt into the interior of the desulfurized rubber powder, limits the excessive swelling of the rubber powder, maintains the component balance of the base asphalt colloidal system, and further improves the long-term storage stability of modified asphalt.

[0033] 3. The preparation method of the present invention adopts a stepwise reaction process of prepolymer masterbatch, which forms a high-concentration reaction environment in part of the matrix asphalt, improves the crosslinking degree of the coupling prepolymer, and promotes the grafting reaction to proceed in the forward direction by combining the negative pressure dehydration conditions in the main reactor, as well as the subsequent high shear homogenization and deceleration development process, so that the polymer network can be dispersed and structurally solidified in the asphalt phase, thereby improving the resistance to rutting deformation and macroscopic uniformity of the composite modified asphalt. Attached Figure Description

[0034] Figure 1 This is a three-dimensional response surface plot showing the effect of variations in the dosage of desulfurized rubber powder and amination PET on the penetration of composite modified asphalt according to the present invention. Figure 2 This is a three-dimensional response surface plot showing the effect of variations in the dosage of desulfurized rubber powder and amination PET on the softening point of the composite modified asphalt. Figure 3 This is a three-dimensional response surface plot showing the effect of variations in the content of desulfurized rubber powder and amination PET on the ductility of the composite modified asphalt according to the present invention. Figure 4 This is a three-dimensional response surface plot showing the effect of changes in the dosage of desulfurized rubber powder and amination PET on the viscosity of composite modified asphalt according to the present invention. Figure 5 This is a bar chart illustrating the influence of the type of base asphalt on the performance of the composite modified asphalt. Figure 6 This is a bar chart showing the effect of the type of adhesive powder used in this invention on the performance of the composite modified asphalt. Figure 7 This is a bar chart comparing the performance of a single modified asphalt according to the present invention; Figure 8 This is a bar chart comparing the performance of the composite modified asphalt of the present invention; Figure 9 This is a bar chart illustrating the effect of the order of adding the modifiers of this invention on the performance of the composite modified asphalt. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the embodiments and comparative examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0036] Preparation Examples 1-6: Preparation Example 1: This preparation example provides an amination of PET, including the following steps: Waste polyester fragments and monoethanolamine were added to a sealed reactor equipped with a heating jacket and a tail gas condensation and recovery device at a mass ratio of 1:1.5 to form an initial mixture; The initial mixture was heated to 135°C and stirred continuously at 180 rpm for 2 hours to produce the crude product system through ammonolysis and chain scission. The crude product system was cooled to room temperature and washed three times with distilled water to dissolve and remove unreacted excess amine reagent and water-soluble small molecule byproducts, yielding a purified wet product. The purified wet product was dried in a vacuum drying oven and mechanically ground into powder with a particle size of less than 60 mesh to obtain amination PET.

[0037] Preparation Example 2: This preparation example provides an amination of PET, including the following steps: Waste polyester fragments and monoethanolamine were added to a sealed reactor equipped with a heating jacket and a tail gas condensation and recovery device at a mass ratio of 1:2.0 to form an initial mixture; The initial mixture was heated to 140°C and stirred continuously at 200 rpm for 3 hours to produce the crude product system through ammonolysis and chain scission. The crude product system was cooled to room temperature and washed four times with distilled water to dissolve and remove unreacted excess amine reagent and water-soluble small molecule byproducts, yielding a purified wet product. The purified wet product was dried in a vacuum drying oven and mechanically ground into powder with a particle size of less than 60 mesh to obtain amination PET.

[0038] Preparation Example 3: This preparation example provides an amination of PET, including the following steps: Waste polyester fragments and monoethanolamine were added to a sealed reactor equipped with a heating jacket and a tail gas condensation and recovery device at a mass ratio of 1:2.5 to form an initial mixture; The initial mixture was heated to 145°C and stirred continuously at 220 rpm for 4 hours to produce the crude product system through ammonolysis and chain scission. The crude product system was cooled to room temperature and washed five times with distilled water to dissolve and remove unreacted excess amine reagent and water-soluble small molecule byproducts, yielding a purified wet product. The purified wet product was dried in a vacuum drying oven and mechanically ground into powder with a particle size of less than 60 mesh to obtain amination PET.

[0039] Preparation Example 4: This preparation example provides a desulfurized rubber powder, including the following steps: 40-mesh ordinary rubber powder is fed into a twin-screw extruder with a temperature control system to form a heated powder substrate; The heated powder substrate is introduced with a volume concentration of 2% micro-oxygen gas at a high temperature of 180℃. Under the combined action of strong mechanical shear and micro-oxygen, the cross-linking bonds are selectively broken and the surface is oxidized to generate extruded desulfurized products. The extruded desulfurized material was cooled and collected to obtain desulfurized rubber powder with a Mooney viscosity of 40.

[0040] Preparation Example 5: This preparation example provides a desulfurized rubber powder, including the following steps: 40-mesh ordinary rubber powder is fed into a twin-screw extruder with a temperature control system to form a heated powder substrate; The heated powder substrate is introduced with a micro-oxygen gas of 3.5% by volume at a high temperature of 200℃. Under the combined action of strong mechanical shear and micro-oxygen, the cross-linking bonds are selectively broken and the surface is oxidized to generate extruded desulfurized products. The extruded desulfurized material was cooled and collected to obtain desulfurized rubber powder with a Mooney viscosity of 35.

[0041] Preparation Example 6: This preparation example provides a desulfurized rubber powder, including the following steps: 40-mesh ordinary rubber powder is fed into a twin-screw extruder with a temperature control system to form a heated powder substrate; The heated powder substrate is introduced with a volume concentration of 5% micro-oxygen gas at a high temperature of 220℃. Under the combined action of strong mechanical shear and micro-oxygen, the cross-linking bonds are selectively broken and the surface is oxidized to generate extruded desulfurized products. The extruded desulfurized material was cooled and collected to obtain desulfurized rubber powder with a Mooney viscosity of 30.

[0042] Examples 1-3: Example 1: This embodiment provides a composite modified asphalt made from amination PET and desulfurized rubber powder and its preparation method, including the following steps: S1. Take 15 kg of Xinhai No. 90 base asphalt as the liquid phase reaction medium and pump it into a premixing kettle with a heating jacket. Heat it to 145°C, and add 15 kg of desulfurized rubber powder obtained in Preparation Example 4 and 0.435 kg of tall oil fatty acid in sequence. Stir at 200 rpm for 10 minutes to form a suspension slurry. S2. Add 0.435 kg of epoxidized soybean oil and 0.00174 kg of zinc isooctanoate to the suspension slurry, adjust the temperature to 155℃, and stir at 400 rpm for 10 minutes to initiate the esterification ring-opening reaction and generate an anti-migration intermediate. S3. Add 3 kg of the amination PET obtained in Example 1 to the anti-migration intermediate, and stir at 155°C and 400 rpm for 20 minutes to initiate the epoxy-amine addition reaction and obtain the coupling prepolymer masterbatch. S4. Pump the remaining 67kg of Xinhai No. 90 base asphalt into the main reactor equipped with a high shear device, heat it to 175℃, and continuously pump the coupling prepolymer masterbatch into the main reactor through a gear pump. Turn on the vacuum pump to maintain a negative pressure of -0.05MPa in the main reactor, slowly add 0.29kg of styrene-maleic anhydride copolymer, stir at 1800rpm for 25 minutes to remove water vapor and carry out the grafting reaction to obtain primary grafted modified asphalt. S5. Control the temperature of the primary grafted modified asphalt at 170℃, start the high shear emulsifier, and homogenize it for 50 minutes at a shear rate of 3000 rpm to obtain homogenized modified asphalt. S6. Reduce the stirring speed of the homogenized modified asphalt to 1500 rpm, and keep it at 165℃ for 45 minutes to obtain the composite modified asphalt of amination PET and desulfurized rubber powder.

[0043] Example 2: This embodiment provides a composite modified asphalt made from amination PET and desulfurized rubber powder and its preparation method, including the following steps: S1. 13.3 kg of Xinhai No. 90 base asphalt was pumped into a premixing kettle with a heating jacket as a liquid phase reaction medium and heated to 150°C. 20 kg of desulfurized rubber powder obtained in Preparation Example 5 and 0.96 kg of tall oil fatty acid were added in sequence and stirred at 300 rpm for 15 minutes to form a suspension slurry. S2. Add 0.84 kg of epoxidized soybean oil and 0.0042 kg of zinc isooctanoate to the suspension slurry, adjust the temperature to 160℃, and stir at 500 rpm for 15 minutes to initiate the esterification ring-opening reaction and generate an anti-migration intermediate. S3. Add 4 kg of the amination PET obtained in Preparation Example 2 to the anti-migration intermediate, and stir at 160°C and 500 rpm for 25 minutes to initiate the epoxy-amine addition reaction and obtain the coupling prepolymer masterbatch. S4. Pump the remaining 62.7 kg of Xinhai No. 90 base asphalt into the main reactor equipped with a high shear device, heat it to 180°C, and continuously pump the coupling prepolymer masterbatch into the main reactor through a gear pump. Turn on the vacuum pump to maintain a negative pressure of -0.08 MPa in the main reactor, slowly add 0.6 kg of styrene-maleic anhydride copolymer, stir at 2000 rpm for 30 minutes to remove water vapor and carry out the grafting reaction to obtain the primary grafted modified asphalt. S5. Control the temperature of the primary grafted modified asphalt at 176℃, start the high shear emulsifier, and homogenize it for 57 minutes at a shear rate of 3300rpm to obtain homogenized modified asphalt. S6. Reduce the stirring speed of the homogenized modified asphalt to 2000 rpm, and keep it at 170℃ for 60 minutes to obtain the composite modified asphalt of amination PET and desulfurized rubber powder.

[0044] Example 3: This embodiment provides a composite modified asphalt made from amination PET and desulfurized rubber powder and its preparation method, including the following steps: S1. 14 kg of Xinhai No. 90 base asphalt was pumped into a premixing kettle with a heating jacket as a liquid phase reaction medium and heated to 155°C. 24 kg of desulfurized rubber powder obtained in Preparation Example 6 and 1.5 kg of tall oil fatty acid were added in sequence and stirred at 400 rpm for 20 minutes to form a suspension slurry. S2. Add 1.2 kg of epoxidized soybean oil and 0.0072 kg of zinc isooctanoate to the suspension slurry, adjust the temperature to 165℃, and stir at 600 rpm for 20 minutes to initiate the esterification ring-opening reaction and generate an anti-migration intermediate. S3. Add 6 kg of the amination PET obtained in Example 3 to the anti-migration intermediate, and stir at 165°C and 600 rpm for 30 minutes to initiate the epoxy-amine addition reaction and obtain the coupling prepolymer masterbatch. S4. Pump the remaining 56kg of Xinhai No. 90 base asphalt into the main reactor equipped with a high shear device, heat it to 185℃, and continuously pump the coupling prepolymer masterbatch into the main reactor through a gear pump. Turn on the vacuum pump to maintain a negative pressure of -0.1MPa in the main reactor. Slowly add 0.9kg of styrene-maleic anhydride copolymer, stir at 2200rpm for 40 minutes to remove water vapor and carry out the grafting reaction to obtain primary grafted modified asphalt. S5. Control the temperature of the primary grafted modified asphalt at 180℃, start the high shear emulsifier, and homogenize it for 70 minutes at a shear rate of 3500rpm to obtain homogenized modified asphalt. S6. Reduce the stirring speed of the homogenized modified asphalt to 2500 rpm, and keep it at 175℃ for 75 minutes to obtain the composite modified asphalt of amination PET and desulfurized rubber powder.

[0045] Comparative Examples 1-5: Comparative Example 1: Compared with Example 2, the difference is that tall oil fatty acids, epoxidized soybean oil, zinc isooctanoate and styrene-maleic anhydride copolymer were not added, and the prepolymerization process in steps S1 to S3 was omitted. All the matrix asphalt was directly heated to 180°C and then desulfurized rubber powder and amination PET were added at one time for subsequent stirring, shearing homogenization and development. All other aspects are the same.

[0046] Comparative Example 2: Compared with Example 2, the difference is that epoxidized soybean oil and zinc isooctanoate were not added, step S2 was omitted, and the suspension slurry obtained in step S1 was directly mixed with amination PET in step S3. All other aspects are the same.

[0047] Comparative Example 3: Compared with Example 2, the difference is that the styrene-maleic anhydride copolymer was not added, and the operation of adding the styrene-maleic anhydride copolymer was not performed in step S4; all other steps are the same.

[0048] Comparative Example 4: Compared with Example 2, the difference lies in the change of the feeding sequence and environment of the preparation process. The liquid phase carrier and kinetic step-by-step control in steps S1 to S3 are cancelled. Instead, the desulfurized rubber powder, tall oil fatty acid, epoxidized soybean oil, zinc isooctanoate, amination PET and styrene-maleic anhydride copolymer are all added to the matrix asphalt at 180°C at one time for mixing and homogenization. In addition, the vacuum pump is not turned on to remove negative pressure during the reaction process. All other aspects are the same.

[0049] Comparative Example 5: Compared with Example 2, the difference lies in the pretreatment state of the raw materials. The desulfurized rubber powder in step S1 is replaced with ordinary rubber powder that has not undergone desulfurization and activation treatment, and the amination PET in step S3 is replaced with waste polyester fragments that have not undergone ammonolysis treatment. All other aspects are the same.

[0050] Test Example 1: Following the process steps of Example 2, composite modified asphalt samples were prepared according to different mass percentages of desulfurized rubber powder and amination PET as specified in the experimental design. A standard penetration tester was used; the samples were placed in a 25°C constant-temperature water bath for insulation, and the depth of penetration within 5 seconds was measured by releasing the standard needle, recording the penetration data. A ring and ball softening point tester was used; the samples were poured into standard copper rings and heated in a heating bath at a specified heating rate, and the temperature at which a steel ball placed on the sample touched the bottom plate after falling a specific distance was measured, recording the softening point data. A standard ductility tester was used; the samples were prepared into figure-eight shaped standard specimens, and tensile tests were conducted in a constant-temperature water bath at a constant tensile speed, measuring the tensile length at fracture and recording the ductility data. A Brookfield rotational viscometer was used; the test temperature was set to 135°C, and a suitable rotor was selected for constant rotation to measure the dynamic viscosity of the sample at this temperature, recording the viscosity data.

[0051] Table 1. Influencing factors and levels of composite modified asphalt

[0052] Table 2. Experimental Design and Results

[0053] Table 3. Surface Correspondence Regression Model

[0054] Figure 1 - Figure 4 This figure presents a three-dimensional response surface to various performance indicators of asphalt caused by changes in the content of desulfurized rubber powder and amination-modified PET. The English terms and their meanings in the figure are as follows: Penetration, Softening point, Ductility, Viscosity, PET-MEA, and DRP. The three-dimensional surface reflects the trend of the indicators with changes in variables, the contour lines on the bottom surface reflect the projection distribution of the surface onto a two-dimensional plane, and the dots on the surface represent data points obtained from actual tests.

[0055] Figure 1 In the middle, the penetration response surface is in a downward sloping state. As the mass fraction of desulfurized rubber powder and amination PET increases, the surface transitions from high to low, and the bottom contour lines are distributed as parallel straight lines. Figure 2 In the middle, the softening point response surface exhibits an upward-curving nonlinear characteristic. When the desulfurized rubber powder content is close to 25% and the aminated PET content is in the range of 4% to 5%, the surface reaches its highest point, and the bottom contour lines are densely distributed in the corresponding area. Figure 3In the middle, the ductility response surface has a parabolic structure with a raised area in the center. The highest point is located in the middle of the desulfurized rubber powder content of 15% to 20% and the amination PET content of 3% to 4%. The ductility response surface decreases from the center to the surrounding boundary. The bottom contour lines are distributed in a closed elliptical arc shape. Figure 4 In the middle, the viscosity response surface shows an upward trend. In the region with high content of desulfurized rubber powder, the slope of the surface increases, and the bottom contour lines show an outward radiating arc-shaped distribution.

[0056] Table 4. Optimal Formulation of Dynamic PET / Rubber Composite Asphalt Raw Material (Verification of Predicted and Tested Values)

[0057] Note: "—" indicates that there is no corresponding test item or that the deviation does not need to be calculated.

[0058] According to Tables 1 to 4 and Figures 1 to 4 Test data shows that increasing the amount of desulfurized rubber powder and amination PET reduces the penetration and increases the softening point of the system. The terminal amine groups of amination PET nucleophilically attack the epoxy groups of epoxidized soybean oil, forming a covalent bridge with the desulfurized rubber powder coated with tall oil fatty acids. The rigid polyester component and the elastic rubber powder component form prepolymer microregions, enhancing the structural stiffness and shear deformation resistance of the asphalt matrix under high temperature conditions.

[0059] Figure 3 The ductility exhibits a parabolic trend. Within the intermediate dosage range, the epoxidized soybean oil molecular backbone connects the desulfurized rubber powder and amination PET, preserving the deformability of the rubber powder's elastic micro-crosslinked network. The carboxyl groups of tall oil fatty acids undergo nucleophilic substitution reactions with epoxy groups to generate sterically hindered structures, restricting the migration and exudation of small molecules and maintaining the integrity of the asphaltenes. When the modifier is added in excess, the grafting density of macromolecules increases, limiting the system's flexibility and decreasing the ductility value.

[0060] Figure 4 The viscosity increased as shown in Table 4. The styrene-maleic anhydride copolymer forms imide bonds through a ring-opening and dehydration ring-closing reaction of the maleic anhydride ring, grafting the prepolymer. Compatibility reduces phase separation, and free small molecules are consumed. The three-dimensional network increases hydrodynamic resistance, leading to an increase in viscosity. The deviation data in Table 4 indicate that the rheological properties of the system remain within the operable range, and no mass transfer limitation or solidification has occurred. The experimental data verify the tandem crosslinking reaction process of the multifunctional substances.

[0061] Test Example 2: The composite modified asphalt samples prepared in Examples 1 to 3 were obtained and, while still hot, injected into aluminum tubes with an outer diameter of 32 mm, one end sealed, to a depth of approximately 140 mm. The tube openings were then folded and sealed. The aluminum tubes containing the samples were placed vertically on a metal tube rack and placed in a 163°C constant temperature oven for 48 hours. After the oven drying period, the aluminum tubes were removed, kept vertical, and immersed in a 0°C ice-water mixture for 30 minutes to allow the asphalt samples inside to solidify. The cooled aluminum tubes were removed, the surface moisture was wiped dry, and the aluminum tubes, along with the solidified asphalt inside, were divided transversely into three equal sections: upper, middle, and lower. The outer aluminum layer was peeled off, and asphalt samples from the upper and lower sections were collected separately. The softening points of the upper and lower samples were determined using the ring and ball method, and the difference between the softening points of the upper and lower samples was calculated.

[0062] Table 5. High-Temperature Storage Stability Test Data of Composite Modified Asphalt from Examples

[0063] According to the data in Table 5, after standing at 163℃ for 48 hours, the difference in softening point between the upper and lower sections in Examples 1 to 3 was relatively small, while the difference in softening point in Example 2 was 1.1℃. Conventional physically blended polyester or rubber-modified asphalt, under high-temperature storage conditions, undergoes phase separation due to differences in material density and thermodynamic incompatibility. This manifests as polyester particles sinking and rubber powder particles floating, leading to an increase in the difference in softening point between the upper and lower sections. The softening point difference data in the tests indicate the formation of an anti-segregation crosslinking network within the asphalt system.

[0064] The terminal carboxyl groups in tall oil fatty acids undergo esterification and ring-opening reactions with the epoxy groups on the epoxidized soybean oil molecular chain, generating sterically hindered β-hydroxy ester structures. Small-molecule tall oil fatty acids are tethered to the epoxidized soybean oil molecular backbone through esterification and ring-opening, preventing the release and exudation of surfactants under high-temperature conditions. The maleic anhydride rings on the styrene-maleic anhydride copolymer molecular chain undergo ring-opening and intramolecular dehydration and ring-closure reactions under the influence of residual amine groups on the periphery of the prepolymer, generating imide bonds and achieving in-situ grafting of macromolecules. The styrene side groups of the styrene-maleic anhydride copolymer are inserted into the asphaltenes and aromatic component networks through intermolecular forces and π-π stacking. The chemical bonding process eliminates the phase separation interface between rigid polyester, elastic rubber powder, and nonpolar asphalt, allowing various components to combine into a homogeneous three-dimensional interpenetrating network. The components lose the kinetics of free migration in the high-temperature liquid asphalt matrix, and the softening point data of the upper and lower sections of the sample tend to be consistent. The test results verify the technical effectiveness of the esterification ring-opening locking mechanism and the in-situ interface grafting mechanism.

[0065] Test Example 3: A glass reactor with volume markings was selected as the test container and connected to a vacuum system with a pressure regulating valve and a temperature-controlled heating jacket. The coupling prepolymer masterbatch and remaining matrix asphalt obtained in step S3 of Examples 1 to 3 were extracted and added to the glass reactor according to the corresponding proportions. The reactor was heated to the main reactor temperature set in each example, and the initial volume marking of the asphalt liquid level was recorded. The corresponding stirring speed was set, and the pressure inside the reactor was evacuated to the negative pressure state set in Examples 1 to 3 through the pressure regulating valve. A normal pressure control group was set up, with the temperature and proportions the same as in Example 2, but the vacuum system was not turned on, and normal pressure was maintained. A set mass of styrene-maleic anhydride copolymer was added, and timing was started while stirring was continued. During the 30-minute reaction period after the addition of the styrene-maleic anhydride copolymer, the highest liquid level marking of the asphalt foaming and expanding in the reactor was recorded. Based on the difference between the highest liquid level marking and the initial volume marking, the maximum volume expansion rate under each process condition was calculated.

[0066] Table 6. Test data on volumetric expansion rate of asphalt under different pressure process conditions

[0067] Note: "-" indicates that the pressure inside the vessel is in a negative pressure (vacuum) state.

[0068] According to the data in Table 6, after adding styrene-maleic anhydride copolymer to the asphalt in the normal pressure control group, a large number of bubbles were generated, with a maximum volume expansion rate of 85.6%. In Examples 1 to 3, under a set negative pressure condition, the maximum volume expansion rate ranged from 1.5% to 4.5%, and the asphalt surface remained stable. The test results indicate that a negative pressure process environment can control the volume expansion during the preparation of composite modified asphalt.

[0069] The styrene-maleic anhydride copolymer molecular chain contains a five-membered ring of maleic anhydride. Upon contact with residual amine groups on the surface of the prepolymer within the asphalt matrix, a ring-opening reaction occurs, generating amyl acid. At 175℃ to 185℃, the amyl acid undergoes an intramolecular dehydration ring-closure reaction to form imide bonds. The water byproduct of the dehydration reaction vaporizes into water vapor at high temperatures. Under normal pressure, this vaporized water vapor is trapped within the high-viscosity asphalt matrix and does not easily dissipate, causing the asphalt to expand and foam, increasing the risk of overflow. Maintaining a negative pressure state by activating a vacuum pump allows the generated water vapor to be extracted from the reactor, preventing gas from stagnating and expanding within the asphalt. From a chemical thermodynamic perspective, the negative pressure system continuously removes the reaction product water, reducing the water pressure in the system and promoting a positive shift in the chemical equilibrium of the dehydration ring-closure reaction, thereby increasing the grafting rate between the styrene-maleic anhydride copolymer and the prepolymer. Tests verified the effectiveness of the negative pressure dehydration process in eliminating the risk of overflow and promoting in-situ grafting reactions.

[0070] Test Example 4: Modified asphalt samples prepared in Example 2 and Comparative Examples 1, 2, 3, and 5 were extracted and heated to a fluid state. The fluid samples were injected into aluminum tubes with an outer diameter of 32 mm, controlling the injection height, and the tube openings were folded and sealed. The aluminum tubes filled with samples were placed vertically on a support and placed in a 163°C constant temperature oven for 48 hours. After standing, the aluminum tubes were removed, kept vertical, and placed in an ice-water bath to cool and solidify the samples inside. The solidified aluminum tubes were transversely cut into three equal sections: upper, middle, and lower. The upper and lower sections were taken, the outer aluminum skin was peeled off, and the internal asphalt samples were collected separately. The softening point and penetration at 25°C of the upper and lower samples were measured respectively, and the difference in softening point and penetration between the upper and lower samples were calculated.

[0071] Table 7. Comparison of Anti-migration and Anti-segregation Performance Test Data between Examples and Comparative Examples

[0072] According to the data in Table 7, the difference in softening point and penetration in Example 2 was relatively small, while the comparative example system showed segregation and component migration. The test results of Example 2 and Comparative Example 2 indicate that Comparative Example 2, lacking epoxidized soybean oil and zinc isooctanoate, lacked the esterification ring-opening reaction medium. Tall oil fatty acids migrated upwards under static conditions at 163°C, leading to the enrichment of light components and oil in the upper sample. This resulted in a decrease in the softening point and an increase in penetration in the upper sample, with a softening point difference of 16.7°C. In Example 2, epoxidized soybean oil tethered tall oil fatty acids to the molecular backbone through esterification ring-opening, blocking the migration pathways of small molecules and maintaining the consistency of physical properties across the upper and lower sections of the system.

[0073] The test results of Example 2 and Comparative Example 3 show that Comparative Example 3 lacks styrene-maleic anhydride copolymer. Desulfurized rubber powder, epoxidized soybean oil, and amination PET form prepolymer microregions, but fail to form covalent bonds with the asphalt matrix. The prepolymer network and the asphalt matrix have density differences, leading to phase separation during high-temperature storage and resulting in data discrepancies between the upper and lower segments. Example 2 utilizes the dehydration and ring-closing reaction between the maleic anhydride ring of the styrene-maleic anhydride copolymer and the residual amine groups of the prepolymer to generate imide bonds. In-situ grafting is achieved by utilizing the π-π stacking of styrene side groups with asphaltene, eliminating the phase separation interface.

[0074] The test results of Example 2, Comparative Examples 1 and 5 show that Comparative Example 1 uses a one-time mixing process without additives, while Comparative Example 5 uses unactivated ordinary rubber powder and unammonized polyester fragments. The systems of Comparative Examples 1 and 5 lack active groups and do not undergo amine-epoxy specific addition coupling reactions. The polyester and rubber powder components exist in the asphalt in a physically suspended state. Under high-temperature conditions, the polyester macromolecules sink due to gravity, while the rubber powder and lighter components float, causing the softening point of the lower part to rise above 80°C, the penetration to decrease, and the softening point difference to be greater than 24°C. The test data indicate that, lacking covalent network chemical bridging, the physically blended system cannot overcome the thermodynamic incompatibility between materials. The crosslinking reaction mechanism and stepwise preparation process are technically necessary to solve the problems of asphalt phase separation and migration prevention.

[0075] Test Example 5: The composite modified asphalt sample corresponding to the code PMDA in Example 2, and the asphalt samples of the control group with codes CRA, DRA, PMCA, PTCA, and PTDA, were heated to a fluid state. The PET-TETA used in codes PTCA and PTDA was prepared using the same method as in Example 2, except that the monoethanolamine was replaced by triethylenetetramine. The fluid samples were poured into standard molds to prepare specimens for penetration, softening point, ductility, and viscosity testing, and the physical properties were measured. High-temperature rheological properties were tested using a dynamic shear rheometer. The asphalt samples were placed in a parallel plate test fixture, and the test temperature range was set from 58°C to 82°C. The strain was controlled within the linear viscoelastic range, and the complex shear modulus and phase angle were measured to calculate the rutting factor. Low-temperature rheological properties were tested using a bending beam rheometer. Asphalt samples were injected into a rectangular mold to form small beam specimens, which were then placed in a low-temperature constant-temperature ethanol bath. The test temperatures were set to -12℃ and -18℃, and a constant load was applied for 60 seconds. The deflection deformation at the middle of the specimen was measured, and the creep stiffness modulus and creep rate were calculated.

[0076] Table 8. Raw material formulations for different asphalts

[0077] Note: "—" indicates that the component was not added. Code explanation: BA means base asphalt; PMDA is the composite modified asphalt corresponding to the formulation of Example 2; PMCA corresponds to the comparative system of undesulfurized ordinary rubber powder; CRA and DRA are single rubber powder modified control groups.

[0078] Table 9. Rheological property test data of composite modified asphalt and comparative sample.

[0079] Figure 5This plot illustrates the effect of base asphalt type on the properties of composite modified asphalt. The horizontal axis labels the base asphalt grades: CNPC 70#, CNPC 90#, CNOOC 70#, CNOOC 90#, Xinhai 70#, and Xinhai 90#. The left vertical axis represents penetration, softening point, and ductility values, while the right vertical axis represents viscosity values ​​(Pa·s). The legend includes penetration, softening point, ductility, and viscosity. The bar chart is grouped by base asphalt type, with bars for penetration, softening point, ductility, and viscosity distributed within each group. The height distribution trend of the bars in each group is similar.

[0080] Figure 6 This graph illustrates the effect of different types of rubber powder on the properties of composite modified asphalt. The horizontal axis represents the test items: penetration, softening point, ductility, and viscosity. The left vertical axis represents the values ​​of penetration, softening point, and ductility, while the right vertical axis represents the viscosity values. In the legend, CRP refers to ordinary rubber powder, while 45DRP, 35DRP, and 25DRP represent desulfurized rubber powders of different mesh sizes. The bar charts are grouped according to the test items. The data within the penetration group are similar; in the softening point and ductility groups, the DRP bars are taller than the CRP bars; in the viscosity group, the bars show a step-like decreasing distribution.

[0081] Figure 7 This chart compares the performance of single modified asphalts. The horizontal axis is labeled with penetration, softening point, ductility, and viscosity. In the legend, BA represents base asphalt, CRA represents ordinary rubber powder modified asphalt, DRA represents desulfurized rubber powder modified asphalt, PMA represents single PET-MEA modified asphalt, and PTA represents single PET-TETA modified asphalt. The bar chart is grouped according to the test items. In the penetration group, the BA bar is the highest; in the softening point group, the DRA and PMA bars are relatively high; and there are missing values ​​in the ductility group.

[0082] Figure 8 This chart compares the properties of composite modified asphalt. The horizontal axis represents penetration, softening point, ductility, and viscosity. The legend includes PMCA, PMDA, PTCA, and PTDA. The bar charts are grouped by test item. In the softening point and ductility group, the PMDA and PTDA bars are taller than the PMCA and PTCA bars.

[0083] According to Tables 8 and 9, Figure 5 , Figure 6 , Figure 7 , Figure 8 Data shows that the rheological and high- and low-temperature mechanical properties of the composite modified asphalt (PMDA) system change. Table 9 shows that the rutting factor of PMDA at 76℃ is 3.25 kPa, which is higher than that of base asphalt and single modified asphalt; the creep rate m value at -12℃ is 0.384, and the stiffness modulus is 125.7 MPa. Figure 8 The comparison shows that composite modified asphalt makes up for the performance shortcomings of single modified asphalt.

[0084] Changes in macroscopic performance indicators are related to the construction of a multidimensional covalent network within the system. Table 8 shows that PMDA uses amination-modified PET and desulfurized rubber powder. The oxygen-containing functional groups on the surface of the desulfurized rubber powder undergo esterification and ring-opening reactions with tall oil fatty acids and epoxidized soybean oil. The terminal amine groups of the amination-modified PET attack the remaining epoxy groups through addition reactions. The styrene-maleic anhydride copolymer forms imide bonds through a dehydration and ring-closure reaction, grafting the prepolymer onto the asphalt matrix. The chemical process combines the amination-modified PET with the desulfurized rubber powder. The polyester macromolecules increase the modulus of the asphalt system, improving the rutting factor and softening point; the rubber powder network is connected by the molecular backbone of epoxidized soybean oil, maintaining deformability and improving low-temperature ductility and creep rate.

[0085] Comparing PMCA and PMDA data, PMCA, using ordinary rubber powder, showed lower softening point, ductility, and rutting factor compared to PMDA. Ordinary rubber powder has fewer surface crosslinking sites and did not fully participate in the ring-opening coupling reaction. Desulfurized rubber powder provided crosslinking sites, enabling the system to form a three-dimensional interpenetrating network. Rheological data verified the influence of anti-migration esterification ring-opening, amine-epoxy coupling, and in-situ grafting mechanisms on the mechanical properties of asphalt.

[0086] Test Example 6: Equal amounts of base asphalt were weighed and placed in four reactors equipped with torque monitoring devices, and heated to a fluid state at the processing temperature. Following the procedure of Method 1, desulfurized rubber powder was added to the first reactor and stirred continuously for 30 minutes, followed by the addition of amination PET, and stirring continued. Following the procedure of Method 2, amination PET was added to the second reactor and stirred continuously for 30 minutes, followed by the addition of desulfurized rubber powder, and stirring continued. Following the procedure of Method 3, desulfurized rubber powder and amination PET were simultaneously added to the third reactor and stirring continued. Following the one-pot dry mixing procedure of Comparative Example 4, all solid powdered modifiers were added to the fourth reactor at once and dry-mixed. After the reaction was completed, modified asphalt samples were extracted from each reactor, and the penetration at 25°C, softening point, ductility, and rotational viscosity at 135°C were measured. The peak torque of the reactor agitators was summarized.

[0087] Table 10. Physical properties and state test data of composite modified asphalt under different preparation processes

[0088] Note: "—" indicates that the sample is brittle and no effective ductility data can be measured.

[0089] Figure 9This graph illustrates the effect of the order of modifier addition on the properties of composite modified asphalt. The horizontal axis represents the test items: penetration, softening point, ductility, and viscosity. The left vertical axis represents the values ​​of penetration, softening point, and ductility, and the right vertical axis represents the viscosity value (Pa·s). The legend includes Method 1, Method 2, and Method 3. The graph layout is grouped by test item, with bars representing the three addition methods arranged side-by-side within each group. Error bars are attached to the top of the bars. In the penetration test group, the bar for Method 1 is the tallest, and the bar for Method 2 is the shortest. In the softening point test group, the bar for Method 3 is the tallest. In the ductility test group, the bar for Method 3 is the tallest, and the bar for Method 2 is the shortest. In the viscosity test group, the bar for Method 2 is taller than that for Methods 1 and 3.

[0090] According to Table 10 and Figure 9 Data shows that the order of additive addition and the preparation process affect the physical properties of composite modified asphalt. In Comparative Example 4 in Table 10, a one-pot dry-mixing process was used, resulting in a lower softening point, increased viscosity and peak stirring torque, and the occurrence of torque alarms and overflow during the preparation process. Direct dry mixing of powdered materials in the high-temperature asphalt matrix caused powder agglomeration, hindering the mass transfer process at the phase interface. The solid-phase modifier was not effectively dispersed, the chemical grafting rate decreased, and the construction of the cross-linked network was limited.

[0091] Figure 9 Data shows that the mixing mode of Method 2 results in increased viscosity and lower ductility compared to Method 1. When using the process of adding amination-modified PET first, the polar amination-modified PET molecules are difficult to disperse in the asphalt matrix, and local aggregation increases the viscous resistance of the system. In Table 10, the peak stirring torque of Method 2 is 26.5 N·m. The high viscosity hinders the subsequent absorption and swelling process of light components in the asphalt by the desulfurized rubber powder, and the system's flexibility decreases.

[0092] In Method 1, desulfurized rubber powder is first added. The desulfurized rubber powder particles preferentially absorb asphalt oil and expand. Subsequently, amination-modified PET is added, utilizing the dispersion space created by the desulfurized rubber powder to distribute within the asphalt matrix. The dispersed rubber powder contacts the amination-modified PET, providing interfacial conditions for the ring-opening coupling reaction. Figure 9 The physical performance indicators of Method 1 and Method 3 are similar, but as shown in Table 10, the peak stirring torque of Method 1 (14.2 N·m) is significantly lower than that of Method 3 (16.8 N·m). The test data verifies the technical effectiveness of the stepwise sequential feeding process combining liquid-phase carrier premixing with kinetics. The stepwise process of first adding desulfurized rubber powder to absorb oil swelling, and then adding amination PET, can effectively reduce the processing viscosity of the system, alleviate the mass transfer barrier caused by powder agglomeration, and ensure the in-situ grafting and cross-linking coupling reactions.

Claims

1. A composite modified asphalt made of amination-modified PET and desulfurized rubber powder, characterized in that, Made from the following ingredients in parts by weight: 70-82 parts of base asphalt; 15-24 parts of desulfurized rubber powder; Tall oil fatty acids 0.435–1.5 parts; 0.435–1.2 parts of epoxidized soybean oil; Zinc isooctanoate 0.00174–0.0072 parts; Amine-treated PET: 3-6 parts; 0.29–0.9 parts of styrene-maleic anhydride copolymer; In the composite modified asphalt, the tall oil fatty acid coats the desulfurized rubber powder and undergoes an esterification ring-opening reaction with the epoxidized soybean oil to generate an anti-migration structure; the terminal amino groups of the amination PET undergo an addition reaction with the epoxy groups of the epoxidized soybean oil to form bridging prepolymer microdomains; the styrene-maleic anhydride copolymer undergoes a dehydration ring-closure reaction to form imide bonds, and the bridging prepolymer microdomains are grafted in situ into the matrix asphalt to form a homogeneous three-dimensional interpenetrating network.

2. The modified asphalt composite of aminated PET and desulfurized rubber powder according to claim 1, characterized in that, The amination PET is prepared by the following steps: Waste polyester fragments and monoethanolamine are mixed at a mass ratio of 1:1.5 to 1:2.5 to form an initial mixture; The initial mixture is heated to 135℃~145℃ and stirred continuously at a speed of 180~220rpm for 2~4 hours to generate a crude product system through ammonolysis and chain scission. The crude product system was cooled, washed with water 3 to 5 times, dried and mechanically ground to a powder with a particle size of less than 60 mesh, to obtain the amination PET.

3. The modified asphalt composite of aminated PET and desulfurized rubber powder according to claim 1, characterized in that, The desulfurized rubber powder is prepared by the following steps: Ordinary rubber powder is fed into a twin-screw extruder to form a heated powder substrate; The heated powder substrate is introduced with a micro-oxygen gas of 2% to 5% by volume at a high temperature of 180℃ to 220℃, and extruded desulfurized product is generated under the action of mechanical shearing and micro-oxygen. The extruded desulfurized material is cooled and collected to obtain the desulfurized rubber powder with a Mooney viscosity of 30-40.

4. The modified asphalt composite of aminated PET and desulfurized rubber powder according to claim 1, characterized in that, Made from the following parts by weight of raw materials: 76 parts of base asphalt; 20 parts of desulfurized rubber powder; Tall oil fatty acids 0.96 parts; 0.84 parts of epoxidized soybean oil; 0.0042 parts of zinc isooctanoate; 4 parts of amination-modified PET; 0.6 parts of styrene-maleic anhydride copolymer.

5. A method for preparing a composite modified asphalt of amination-modified PET and desulfurized rubber powder, characterized in that, The method for preparing the composite modified asphalt of aminated PET and desulfurized rubber powder according to any one of claims 1-4 includes the following steps: A portion of the base asphalt is pumped into a premixing kettle, and after heating, desulfurized rubber powder and tall oil fatty acid are added in sequence and stirred to form a suspension slurry. Epoxidized soybean oil and zinc isooctanoate were added to the suspension slurry, and the temperature was adjusted and the mixture was stirred to initiate an esterification ring-opening reaction to generate an anti-migration intermediate. Amination PET was added to the anti-migration intermediate, and the epoxy-amine addition reaction was initiated by heating and stirring to obtain the coupling prepolymer masterbatch. The remaining base asphalt is pumped into the main reactor, and after heating, the coupling prepolymer masterbatch is continuously pumped in. The vacuum system is turned on to keep the main reactor under negative pressure. Styrene-maleic anhydride copolymer is added, and water vapor is removed under stirring and grafting reaction is carried out to obtain primary grafted modified asphalt. The temperature of the primary grafted modified asphalt is controlled, and a high-shear homogenization treatment is performed to obtain homogenized modified asphalt. The homogenized modified asphalt is slowed down and kept at a constant temperature while being stirred to develop, thereby obtaining the composite modified asphalt.

6. The method for preparing a composite modified asphalt of amination-modified PET and desulfurized rubber powder according to claim 5, characterized in that, In the step of forming the suspension slurry: The base asphalt is heated to 145℃~155℃, and after adding the desulfurized rubber powder and tall oil fatty acid, it is stirred at a speed of 200~400rpm for 10~20 minutes.

7. The method for preparing a composite modified asphalt of amination-modified PET and desulfurized rubber powder according to claim 5, characterized in that, In the step of generating the anti-migration intermediate: Adjust the temperature of the material in the premixing vessel to 155℃~165℃ and stir at a speed of 400~600rpm for 10~20 minutes.

8. The method for preparing a composite modified asphalt of amination-modified PET and desulfurized rubber powder according to claim 5, characterized in that, In the step of preparing the coupling prepolymer masterbatch: Stir at 155℃~165℃ and 400~600rpm for 20~30 minutes.

9. The method for preparing a composite modified asphalt of amination-modified PET and desulfurized rubber powder according to claim 5, characterized in that, The specific implementation method for obtaining the primary grafted modified asphalt is as follows: The main reactor is heated to 175℃~185℃, and a negative pressure of -0.05MPa~-0.1MPa is maintained inside the main reactor. The reactor is stirred at a speed of 1800~2200rpm for 25~40 minutes.

10. The method for preparing a composite modified asphalt of amination-modified PET and desulfurized rubber powder according to claim 5, characterized in that, In the step of obtaining the homogenized modified asphalt, the temperature is controlled at 170℃~180℃, and the homogenization treatment is carried out at a shear rate of 3000~3500rpm for 50~70 minutes. In the step of preparing the composite modified asphalt, the stirring speed is reduced to 1500-2500 rpm, and the mixture is kept at 165℃-175℃ and stirred for 45-75 minutes.

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