Composite regeneration method for endowing aged SBS (Styrene Butadiene Styrene) modified asphalt with super-native performance

Abstract

The invention relates to the technical field of regeneration of aged SBS (Styrene Butadiene Styrene) modified asphalt, and particularly provides a composite regeneration method for endowing aged SBS modified asphalt with super-native performance. The preparation method comprises the following specific steps: firstly, adding epoxidized soybean oil, preliminarily adjusting the component proportion and releasing hydroxyl activation points on an SBS chain; then adding isocyanate to react with the activation point to repair an SBS chain; the epoxidized soybean oil is added for the second time, and the component proportion is optimized to balance the rigidity and low-temperature performance of the recycled asphalt; and finally, maintaining the sample in a drying oven to obtain the composite regenerated aged SBS modified asphalt with a stable structure. Compared with an existing regeneration method, the performance of the regenerated asphalt comprehensively exceeds that of original SBS modified asphalt, the high-temperature rut resistance, low-temperature crack resistance, permanent deformation resistance, stress sensitivity and fatigue resistance are remarkably improved, and the utilization rate of the aged SBS modified asphalt is greatly increased.

Description

Technical Field

[0001] The invention relates to the technical field of aged SBS modified asphalt regeneration, and specifically proposes a composite regeneration method for imparting super-original properties to aged SBS modified asphalt. Background Art

[0002] Styrene-butadiene-styrene (SBS) modified asphalt is widely used in high-grade road paving due to its excellent high and low temperature performance. However, during long-term service, the coupling effect of thermal oxidative aging causes the loss of lightweight components of the asphalt, destroying the original four-component equilibrium system. At the same time, thermal oxidative aging causes the continuous SBS molecular chain to break, resulting in a significant decline in the performance of the modified asphalt, seriously affecting its service life. This phenomenon directly leads to the frequent maintenance of SBS modified asphalt pavement and the production of large amounts of recycled asphalt mixture (RAP). If RAP is not effectively utilized, it will not only waste resources, but its stacking and processing will also pollute the environment.

[0003] Existing composite regeneration methods for aged SBS-modified asphalt employ a two-step regeneration agent addition process, aiming to achieve dual remediation objectives: first, restoring the properties of aged asphalt components, and second, structurally repairing degraded SBS chains. However, this approach has significant limitations in practical application. Macroscopically, the mechanical and rheological properties of regenerated SBS-modified asphalt fail to meet the standards of freshly produced SBS-modified asphalt. Microstructural characterization also reveals significant differences between the recycled material and the original material in key parameters such as molecular chain structure and phase distribution.

[0004] In summary, the existing composite regeneration methods still have technical bottlenecks in achieving the comprehensive regeneration of aged SBS modified asphalt, and it is urgent to develop more effective regeneration strategies to improve the comprehensive performance of recycled materials. Summary of the Invention

[0005] This invention provides a composite regeneration technology that uses a composite regeneration agent composed of epoxidized soybean oil (ESO) and isocyanate (TDI) to treat aged SBS-modified asphalt, resulting in performance exceeding that of new SBS-modified asphalt. This method effectively addresses the aforementioned issue of insufficient regeneration performance of aged asphalt in the prior art, achieving efficient and economical asphalt recycling.

[0006] The present invention provides a composite regeneration method for imparting super-original properties to aged SBS modified asphalt, and the specific steps are as follows:

[0007] S1. Heat the aged SBS modified asphalt at 160-170°C until it is fluid. Add epoxidized soybean oil while stirring and continue stirring until it is uniform. Initially adjust the ratio of the four components (asphalt, resin, aromatics, and saturates) to restore the performance of the aged SBS modified asphalt and create more activation points for the subsequent reaction.

[0008] S2. Add a certain amount of toluene diisocyanate to the mixture obtained in step S1 at 160-170° C. and continue stirring until uniform to repair the degraded SBS chains;

[0009] S3. Add a certain amount of epoxidized soybean oil to the mixture obtained in step S2 at 160-170° C. and stir until uniform, so as to reduce the increase in the stiffness of the mixture caused by the degradation of SBS by isocyanate repair, optimize the proportion of the recycled asphalt components, and improve the low-temperature crack resistance of the aged SBS modified asphalt;

[0010] S4. The mixture obtained in step S3 is placed in an oven at 160-170° C. for curing to complete the composite regeneration of the super-original performance of the aged SBS modified asphalt.

[0011] Furthermore, the amount of epoxidized soybean oil in S1 is 4%-8% of the mass of the aged SBS modified asphalt, preferably 6%;

[0012] Furthermore, the amount of toluene diisocyanate in S2 is 0.25%-1.5% of the mass of the aged SBS modified asphalt, preferably 1%;

[0013] Furthermore, the amount of epoxidized soybean oil in S3 is 1%-7% of the mass of the aged SBS modified asphalt, preferably 4%;

[0014] Furthermore, in the above method,

[0015] The stirring speed in S1-S3 is 1000 rpm.

[0016] Furthermore, the stirring time in S1 and S3 is 5 minutes; and / or

[0017] The stirring time in S2 is 5-15 min, preferably 5 min.

[0018] Furthermore, the curing time in S4 is 20-60 minutes.

[0019] In the present invention, epoxy soybean oil and isocyanate are added step by step to effectively adjust the proportions of the four major components of aged SBS modified asphalt, repair the degraded SBS chains, and restore its low-temperature crack resistance.

[0020] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0021] (1) Compared with the traditional two-step addition process, the present invention adopts a three-step addition method to solve the problem of uneven performance after regeneration of aged SBS modified asphalt. By first adding epoxy soybean oil to adjust the proportion of aged SBS modified asphalt components, improving low-temperature performance and activating SBS repair sites, then introducing isocyanate to repair degraded SBS chains and restore high-temperature performance. Finally, epoxy soybean oil is added again to reconcile stiffness and optimize components, achieving a synergistic improvement in high and low-temperature performance after regeneration of aged SBS modified asphalt.

[0022] (2) The composite regeneration technology of the present invention overcomes the limitations of traditional methods, not only completely restoring the performance indicators of aged SBS-modified asphalt but also enabling its macroscopic performance to surpass that of new SBS-modified asphalt. This significant improvement demonstrates the innovative advantages and practical value of the present invention in the field of asphalt regeneration.

[0023] (3) Compared with traditional composite regeneration technology, the present invention can effectively repair the degradation chain structure in aged SBS at the microscopic level, generating uniform and more numerous linear SBS structures. Its restoration effect is better than that of new SBS modified asphalt, significantly improving the structural integrity and performance stability of the recycled material.

[0024] (4) Compared with the existing technology, the present invention systematically studies a wider range of stirring time and temperature combinations, which has a significant effect on improving the composite regeneration performance of aged SBS modified asphalt, enriches the selection of regeneration process parameters, provides a variety of working conditions for actual engineering applications, and significantly improves the applicability and practical value of the regeneration technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a flow chart of the composite regeneration method of the present invention;

[0026] Figure 2 This is a physical property diagram of the first epoxidized soybean oil dosage determined in the first step of Example 1;

[0027] Figure 3 This is a physical property diagram determined by the isocyanate dosage in the second step of Example 1;

[0028] Figure 4 This is a physical property diagram determined by the second epoxidized soybean oil dosage in the third step of Example 1;

[0029] Figure 5 The high temperature rheological properties of asphalt in different experimental groups in the specific implementation method;

[0030] Figure 6The low temperature (-24°C) rheological properties of asphalt in different experimental groups in the specific implementation method;

[0031] Figure 7 is the stress sensitivity coefficient of asphalt in different experimental groups at 64°C when the pressure changes by 0.1 kPa and 3.2 kPa in the specific implementation manner;

[0032] Figure 8 is the phase angle of asphalt in different experimental groups at 76°C in a specific embodiment;

[0033] Figure 9 It is the regeneration effect of the asphalt SBS linear structure in different experimental groups in a specific embodiment, wherein: (a) Comparative Example 1; (b) Comparative Example 2; (c) Example 1; (d) Example 2; (e) Example 3; (f) Example 4; (g) Example 5; (h) Example 6. DETAILED DESCRIPTION

[0034] The technical solutions of the present invention are described clearly and completely below in conjunction with the embodiments. The embodiments described are only some embodiments of the present invention, not all. Other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0035] It should be noted that:

[0036] 1. The aged SBS modified asphalt in Examples of the present invention and Comparative Example 2 was prepared by the following method:

[0037] In the first step, commercial new SBS-modified asphalt (SMB, containing 4% SBS) was placed in a rotary thin film oven at a temperature of 163°C for 5 hours to simulate its thermal aging behavior during construction.

[0038] In the second step, the SBS modified asphalt that had undergone short-term aging in the first step was placed in a pressure aging container and aged for 20 hours at 100°C and 2.1 MPa to simulate its thermal oxidative aging process from the end of construction to the decommissioning stage, and obtain the final aged SBS modified asphalt sample.

[0039] 2. The commercial SBS modified asphalt used was purchased from Shanxi Communications Holding Group Co., Ltd.; the aged SBS modified asphalt prepared had an ductility of 6 mm at 5°C, a needle penetration of 35.6 dmm (1 dmm = 0.1 mm) at 25°C, a softening point of 76.1°C, and a viscosity of 3450 mPa·s at 135°C.

[0040] 3. The epoxidized soybean oil used in the present invention is a transparent liquid purchased from Shanghai MacLean Biochemical Technology Co., Ltd., with a specific gravity of 0.996 and an acid value of 0.5 mgKOH / g.

[0041] 4. Toluene diisocyanate (TDI-80) used in the present invention was purchased from Wanhua Chemical Group Co., Ltd. and was prepared by mixing two isomers of 2,4-toluene diisocyanate [A] and 2,6-toluene diisocyanate [B] in a ratio of 80:20.

[0042] Example 1

[0043] This embodiment provides a composite regeneration method for imparting super-virgin properties to aged SBS modified asphalt, and the specific process steps are as follows:

[0044] S1. Heat the aged SBS modified asphalt at 160°C until it becomes fluid. Add a certain amount of epoxidized soybean oil for the first time while stirring at 1000 rpm and continue stirring for 5 minutes.

[0045] S2. Add a certain amount of toluene diisocyanate to the mixture obtained in step S1 at 160° C. and 1000 rpm, and continue stirring for 5 minutes;

[0046] S3. Add a certain amount of epoxidized soybean oil to the mixture obtained in step S2 at 160° C. and 1000 rpm, and stir for 5 minutes;

[0047] S4. Place the mixture obtained in step S3 in an oven at 160° C. for curing for 40 minutes to obtain a final composite regenerated aged SBS modified asphalt sample.

[0048] Determine the dosage of epoxy soybean oil and toluene diisocyanate in S1-S3 as follows:

[0049] In the first step, S1, epoxidized soybean oil (ESO) was added to the aged SBS modified asphalt in a gradient of 4% to 8% (1% interval) of the mass percentage of the aged SBS modified asphalt and stirred at 160°C for 5 minutes. The low temperature performance was evaluated by testing the ductility at 5°C (ASTM D113) and the needle penetration at 25°C (ASTM D5). The experimental results are shown in Figure 2 , showing that as the ESO content increases, the ductility and penetration of the sample show an upward trend, which is attributed to the fact that ESO replenishes the lost lightweight components and effectively disperses the degraded SBS molecules. When the ESO content reaches 6%, the low-temperature performance of the aged asphalt is closest to that of the new SBS modified asphalt (SMB). However, further research found that excessive ESO will lead to a gradual decline in high-temperature performance, and the high-temperature performance at a 6% content is lower than the SMB standard, indicating that the modification scheme needs to be further optimized.

[0050] In the second step, the amount of epoxidized soybean oil in S1 was fixed at 6% of the mass of the aged SBS modified asphalt. After the operation of S1, the aged SBS asphalt mixture regenerated with epoxidized soybean oil was obtained. Isocyanate was added to the above mixture in a gradient of 0.5-1.5% (in intervals of 0.25%) of the mass percentage of the aged SBS modified asphalt, and the operation S2 was performed to improve the high temperature performance while maintaining acceptable low temperature performance. The experimental results are shown in Figure 3 , showing that as the isocyanate content increases, the ductility and needle penetration of the mixture show a two-stage downward trend: when the content is less than 1%, the performance slowly decreases; when it exceeds 1%, it deteriorates sharply, indicating that 1% is a critical turning point. The softening point and viscosity increase with increasing isocyanate content, which is attributed to the increase in stiffness caused by the degradation of SBS by isocyanate repair. However, when the isocyanate content exceeds 1%, the viscosity rises sharply to over 10,000 mPa.s, seriously affecting the performance in practical applications. This finding reveals the limitations of traditional composite regeneration methods and emphasizes the need to optimize the regeneration process.

[0051] In the third step, based on the second step, the amount of toluene diisocyanate in S2 was fixed at 1% of the mass of the aged SBS modified asphalt, and the mixture was added with epoxy soybean oil for the second time, that is, the amount of epoxy soybean oil in S3 was explored. The percentage of epoxy soybean oil in S3 to the mass of the aged SBS modified asphalt was set at 3% to 5%, with a gradient increase of 1%, aiming to further optimize and improve the performance of the aged SBS modified asphalt, in order to surpass the performance benchmark of the new SBS modified asphalt (SMB). The performance of the mixture at this stage was evaluated as follows: Figure 4As shown in the figure, increasing the amount of second epoxidized soybean oil added decreases the asphalt's softening point (ASTM D36) and 135°C viscosity (ASTM D4402). Meanwhile, the ductility at 5°C (ASTM D113) and 25°C penetration (ASTM D5) also improve. Notably, when the second ESO addition reaches 4%, the regenerated asphalt's key performance indicators, such as ductility, penetration, softening point, and viscosity, not only closely match those of fresh SBS-modified asphalt but even surpass them in some areas, such as ductility, penetration, softening point, and viscosity. This result strongly suggests that, after the three consecutive optimization steps described above, the aged SBS-modified asphalt has successfully surpassed the comprehensive performance of fresh SBS-modified asphalt. This significant performance improvement can be attributed to the synergistic effect of the secondary ESO addition. First, the introduction of the secondary ESO promotes further swelling of the previously dispersed SBS polymers, thereby increasing the opportunities for linear repair reactions between isocyanates and degraded SBS chains. Secondly, the addition of the second ESO effectively inhibits the possible further degradation of the SBS chain products formed during the second repair process, which promotes the generation of more linear SBS structures. Figure 9 As shown in the figure, the number of linear SBS structures in the final recycled asphalt has surpassed the number of linear SBS structures in the new SBS modified asphalt, providing a structural basis for surpassing the macroscopic performance from the microscopic level.

[0052] During the experiment of the specific embodiment of the present invention, 100 parallel experiments were set up in each experimental group, and the experimental data of each group were averaged.

[0053] In Example 1, it was finally confirmed that the amount of epoxidized soybean oil in S1 was 6% of the mass of the aged SBS modified asphalt; the amount of toluene diisocyanate in S2 was 1% of the mass of the aged SBS modified asphalt; and the amount of epoxidized soybean oil in S3 was 4% of the mass of the aged SBS modified asphalt. The addition of each component in the following examples was based on this dosage relationship.

[0054] Example 2

[0055] The composite regenerated aged SBS modified asphalt provided in this embodiment of the present invention has the same preparation method and components as in Example 1, except that the continuous stirring time in step S2 is modified to 10 minutes in this embodiment.

[0056] Example 3

[0057] The composite regenerated aged SBS modified asphalt provided in this embodiment of the present invention has the same preparation method and components as in Example 1, except that the continuous stirring time in step S2 is modified to 15 minutes in this embodiment.

[0058] Example 4

[0059] The composite regenerated aged SBS modified asphalt provided in this embodiment of the present invention has the same preparation method and components as in Example 1, except that the stirring temperature in all steps S1 to S4 is uniformly set to 170°C in this embodiment.

[0060] Example 5

[0061] The composite regenerated aged SBS modified asphalt provided in this embodiment of the present invention has the same preparation method and components as in Example 1, except that in this embodiment, the stirring temperature of steps S1 to S4 is uniformly set to 170°C, and the continuous stirring time of step S2 is set to 10 minutes.

[0062] Example 6

[0063] The composite regenerated aged SBS modified asphalt provided in this embodiment of the present invention has the same preparation method and components as Example 1, except that in this embodiment, the stirring temperature of steps S1 to S4 is uniformly set to 170°C, and the continuous stirring time of step S2 is set to 15 minutes.

[0064] Comparative Example 1

[0065] This comparative example provides commercial SBS modified asphalt;

[0066] Among them, the new SBS modified asphalt has an ductility of 308mm at 5℃, a needle penetration of 56.2dmm at 25℃, a softening point of 63.7℃, and a viscosity of 2610mPa.s at 135℃, where 1dmm=0.1mm.

[0067] Comparative Example 2

[0068] This comparative example provides aged SBS modified asphalt;

[0069] Among them, the ductility of aged SBS modified asphalt at 5℃ is 6mm, the needle penetration at 25℃ is 35.6dmm, the softening point is 76.1℃, and the viscosity at 135℃ is 3450mPa.s, where 1dmm=0.1mm.

[0070] Comparative Example 3

[0071] This comparative example provides a two-addition preparation method for traditional composite regenerated aged SBS modified asphalt, and the specific process steps are as follows:

[0072] S1. Heat the aged SBS modified asphalt at 160°C until it is fluid. Add epoxidized soybean oil (10% by weight of the aged SBS modified asphalt) for the first time under stirring at 1000 rpm and continue stirring for 5 minutes.

[0073] S2. Add 1% by mass of toluene diisocyanate based on the aged SBS modified asphalt to the mixture obtained in step S1 at 160° C. and continue stirring for 5 minutes;

[0074] S3. The mixture obtained in S2 is placed in an oven at 160° C. for curing for 40 minutes to obtain a final conventional composite regenerated aged SBS modified asphalt sample.

[0075] Performance Testing

[0076] With reference to the "Test Procedure for Asphalt and Asphalt Mixtures for Highway Engineering JTGE20-2011" and other standards, the new SBS modified asphalt in Examples 1-6, Comparative Example 1, and the aged SBS modified asphalt in Comparative Example 2 were tested for physical properties (ASTM D5, ASTMD36, ASTM D113, and ASTM D4402), high-temperature rheological properties (AASHTO T315), low-temperature rheological properties (ASTMD6648), stress sensitivity (ASTM D7405-20), viscoelastic properties (AASHTO T315), fatigue life (AASHTO TP101-14), and SBS linear structure regeneration effect. The average value of the performance of each sample was taken as the basis for the analysis of the results. The results are as follows: Figure 5-9 , as shown in Table 1 and Table 2.

[0077] Table 1. Comparison of the physical properties of asphalt in different experimental groups

[0078]

[0079] Note: Example 2 has the worst physical properties among all the examples.

[0080] The data in Table 1 show that compared with Comparative Example 1, Comparative Example 2 has a decrease in ductility and needle penetration, and an increase in softening point and viscosity. This is attributed to the increase in hardness caused by the volatilization of light components and degradation of SBS chains during the aging process of SBS modified asphalt. Although the traditional composite regeneration method (Comparative Example 3) improves the performance of aged SBS modified asphalt, its low-temperature performance index still does not reach the level of new SBS modified asphalt (Comparative Example 1), and the increase in viscosity affects the construction performance. This limitation stems from the fact that traditional technology does not take into account the stiffness problem caused by the reactive regeneration agent when repairing degraded SBS, and the one-time addition of the biological regeneration agent increases the dispersibility of the degraded SBS chain, reducing the repair effect. In contrast, the new method proposed in the present invention (Example 2) surpasses the new SBS modified asphalt in both low-temperature and high-temperature performance. Its advantages are as follows: First, the appropriate addition of the first epoxidized soybean oil achieves moderate dispersion of the degraded SBS, providing sufficient reaction activation points for the reactive regeneration agent, avoiding the side reaction of isocyanate self-polymerization, and promoting the swelling of the point-like SBS to form a linear structure; second, the second addition of epoxidized soybean oil inhibits the hydrolysis of the repaired SBS chain to form unstable ester intermediates, consumes amine intermediates, neutralizes the acidic environment, and inhibits the oxidation reaction pathway. This optimization strategy not only promotes the formation of more linear SBS structures, but also improves the ratio of asphalt components, ultimately achieving an overall improvement in performance. Given that traditional composite regeneration methods cannot reach the performance level of the new SBS modified asphalt, subsequent evaluations will directly use the performance indicators of the new SBS modified asphalt as the reference standard.

[0081] Figure 5 It shows that the rutting factor curves of the composite regenerated aged SBS modified asphalt of Examples 1-6 are better than those of Comparative Example 1 (new SBS modified asphalt) and Comparative Example 2 (aged SBS modified asphalt). This performance improvement is due to the innovative strategy of adding epoxidized soybean oil in batches: it inhibits the hydrolysis side reaction when the reactive regenerator repairs the degraded SBS chain, while promoting the swelling of the point-like SBS structure, and synergistically interacts with the reactive regenerator to generate more linear structures, thereby improving the stiffness and high temperature resistance of the asphalt. The stirring time exhibits a nonlinear response characteristic to the regeneration effect: the comparison of Examples 1-3 shows that 10 minutes is the critical point. When it is shorter than 10 minutes, it exhibits a synergistic repair effect; at the critical point, the cross-linking reaction dominates, resulting in a reduction in linear structures; when it exceeds 10 minutes, the entropy-driven molecular self-optimization process is activated, increasing the number of regenerated structures. Examples 4-6 show a similar trend. The temperature effect study (Examples 4-6 vs. 1-3) reveals that increased temperature reduces high temperature performance. When the temperature rises from 160°C to 170°C, isocyanate transforms from a traditional crosslinking agent into a dynamic bonding medium. The synergistic effect of molecular diffusion and mass transfer and crosslinking reaction kinetics enables targeted repair of SBS molecular chain breakage sites. Notably, the anti-rutting performance of all recycled samples is superior to that of new SBS-modified asphalt.

[0082] Figure 6 It shows that the creep stiffness to creep rate ratio (S / m) of Comparative Example 2 (aged SBS modified asphalt) at -24°C is higher than that of Comparative Example 1 (new SBS modified asphalt), confirming that thermal oxidative aging increases the brittleness of asphalt. The S / m values ​​of Examples 1-6 are not only lower than those of Comparative Example 2, but also significantly lower than those of Comparative Example 1, indicating that the composite regeneration system of epoxidized soybean oil and isocyanate successfully achieved component regeneration and SBS chain repair, making the low-temperature crack resistance of the regenerated asphalt surpass that of the new SBS modified asphalt. This performance improvement is attributed to the innovative strategy of adding epoxidized soybean oil in batches: it effectively inhibits the hydrolysis side reaction during the repair process of the reactive regeneration agent, while promoting the swelling of the point-like SBS structure, synergizing with the reactive regeneration agent to generate more linear structures, and significantly improving the ductility of the asphalt. The stirring time shows a nonlinear response characteristic to the regeneration effect. By comparing Examples 1-3, the importance of 10 minutes as a critical point is revealed: a stirring time shorter than 10 minutes shows a synergistic repair effect; at the critical point, the cross-linking reaction may dominate, resulting in a reduction in linear structures; and when the stirring time exceeds 10 minutes, an entropy-driven molecular self-optimization process is activated, thereby increasing the number of regenerated structures. Examples 4-6 also show a similar trend. Further temperature effect studies (by comparing Examples 4-6 with 1-3) reveal that increasing the regeneration temperature can further improve low-temperature performance. When the temperature rises from 160°C to 170°C, the function of the isocyanate changes from a traditional cross-linking agent to a dynamic bonding medium. In this process, the synergistic effect of molecular diffusion and mass transfer rate and cross-linking reaction kinetics achieves a more targeted repair of the SBS molecular chain breakage sites. It is worth noting that all samples regenerated using the method of the present invention have significantly better resistance to low-temperature cracking than new SBS modified asphalt.

[0083] Figure 7Shown: The stress sensitivity of asphalt at 64°C is evaluated by the stress sensitivity coefficient. The results show that the stress sensitivity coefficient of the aged SBS modified asphalt (Comparative Example 2) is lower than that of the new SBS modified asphalt (Comparative Example 1), which indicates that thermal oxidative aging causes the volatilization of light components in the asphalt, thereby increasing its hardness and reducing its sensitivity to external stress, but at the cost of increased brittleness. It is worth noting that the stress sensitivity coefficients of the composite regenerated aged SBS modified asphalt (Examples 1-6) developed by the present invention are all negative, and their absolute values ​​are significantly lower than those of the new SBS modified asphalt (Comparative Example 1). This finding shows that the regenerated asphalt exhibits smaller deformation under high stress and has better stress sensitivity properties. This performance improvement is mainly attributed to the strategy of adding epoxidized soybean oil (ESO) in batches. On the one hand, this strategy effectively suppresses the adverse effects such as hydrolysis of byproducts that may be produced by the reactive regeneration agent in the process of repairing degraded SBS chains; on the other hand, ESO promotes the swelling of the SBS structure that was originally distributed in a point-like manner, thereby providing more active sites for subsequent reactions with the reactive regeneration agent, prompting the formation of more linear SBS structures. The increase in linear structure not only increases the density of SBS in the asphalt matrix, but more importantly, enhances the ability of asphalt to resist stress deformation, thereby significantly reducing its stress sensitivity. In addition, the stirring time shows a nonlinear response characteristic to the regeneration effect. By comparing Examples 1-3, the relevant indicators of stress sensitivity show non-monotonic changes. At a shorter stirring time (for example, 5 minutes), the local short-range cross-linking network may be incomplete; while at 10 minutes, the optimal cross-linking state may be reached, at which time the ester content is the lowest and the continuity of the rigid network is the best, thus giving the asphalt the best stress sensitivity. However, when the stirring time is extended to 15 minutes, the self-polymerization side reaction of the isocyanate may cause the cross-linking point to break, so that physical entanglement rather than chemical cross-linking dominates the viscous flow. Examples 4-6 also show a similar trend. Further temperature effect studies (by comparing Examples 4-6 with 1-3) revealed that increasing the regeneration temperature (from 160°C to 170°C) has a complex effect on stress sensitivity. This effect can be explained by a dual antagonistic effect: while increasing temperature promotes the isocyanate coupling reaction, it also enhances its self-condensation tendency, which may form oligomers; at the same time, the diffusion of ESO promotes the disentanglement of the SBS chains, which may eventually form a "pseudo-reinforced" interface with increased local rigidity but reduced overall ductility. This study elucidates the phenomenon of temperature-induced reaction path deviation during chemical regeneration - when the temperature exceeds a certain threshold, the role of isocyanate may change from a network builder to a viscosity enhancer. In essence, this transition is the result of the decoupling of topological order and the collapse of viscoelastic equilibrium driven by entropy increase. Despite these complex microscopic mechanisms, the stress sensitivity of all samples regenerated by this method is significantly better than that of new SBS modified asphalt.

[0084] Figure 8Display: Changes in the phase angle of asphalt at 76°C. The results show that the phase angle of the SBS modified asphalt after thermal oxidative aging (Comparative Example 2) is higher than that of the new SBS modified asphalt (Comparative Example 1), which indicates that aging causes the proportion of viscous components in the asphalt to increase and the elastic properties to decrease. After the aged SBS modified asphalt was regenerated using the new regeneration method developed by the present invention (Examples 1-6), its phase angle was effectively restored, and the restored values ​​were lower than those of the new SBS modified asphalt in Comparative Example 1. This result clearly shows that the regeneration method shows excellent performance in restoring the elastic proportion of asphalt, which is better than the new SBS modified asphalt. This significant elastic recovery ability is mainly attributed to the ability of this method to generate more linear SBS structures, thereby enhancing the ability of the aged SBS modified asphalt to resist deformation. The study of the dependence on stirring time, by comparing Examples 1-3, revealed that at a constant temperature, the phase angle showed a non-monotonic change trend of "medium-small-large" with stirring time. Specifically, a reaction time of 10 minutes corresponds to the lowest phase angle, indicating that under these conditions, the rigid cross-linking reaction of the isocyanate is most complete and the arrangement of the SBS segments is most orderly, thereby maximizing the elasticity of the asphalt. A similar trend is also confirmed in Examples 4-6. Notably, by comparing Examples 4-6 with 1-3, it is found that increasing the reaction temperature to 170°C leads to a significant increase in the phase angle. This phenomenon can be attributed to the synergistic effect of two main factors: the intensification of the isocyanate self-condensation reaction and the phase separation induced by epoxidized soybean oil (ESO), which together destroy the continuity of the polymer network in the asphalt matrix. These findings not only clarify the mechanism of the dynamic competition between the elastic phase and the viscous phase during chemical regeneration, but more importantly, reveal the dual characteristics of the reaction path under thermal activation conditions, providing a key process parameter window for the precise regeneration of aged polymer-modified asphalt. In summary, the phase angles of all samples regenerated using this method are significantly lower than those of new SBS-modified asphalt, which directly indicates that they have superior high-temperature deformation resistance.

[0085] Table 2 shows that the fatigue life of SBS modified asphalt (Comparative Example 2) caused by thermal oxidative aging is reduced by an order of magnitude relative to the new SBS modified asphalt (Comparative Example 1), which highlights the serious damage that aging causes to the durability of the material. In sharp contrast, the fatigue life of the aged SBS modified asphalt samples (Examples 1-6) prepared by the novel composite regeneration method of the present invention is significantly longer than that of the new SBS modified asphalt (Comparative Example 1), which strongly demonstrates that the innovative regeneration technology has shown outstanding superiority in improving the fatigue performance of asphalt. This performance surpasses not only the recovery of fatigue performance, but also the realization of the material's "defect-guided adaptive topology" effect through multi-scale structural reconstruction. This effect originates from the preferential reaction of the active sites on the broken SBS chains with isocyanates, thereby forming a dynamic cross-linked network; at the same time, epoxidized soybean oil (ESO) constructs a hierarchical structure with gradient viscoelastic dissipation capabilities. The regeneration system exhibits a unique three-level energy buffering mechanism, which synergistically inhibits the initiation and propagation of cracks: first, energy is dissipated by bond rotation and conformational changes at the molecular scale; second, microcracks are blunted at the interface scale; and finally, sacrificial bonds at the macroscale break, which delays the further propagation of cracks. The study of stirring time (by comparing Examples 1-3) revealed its non-monotonic "medium-low-high" influence on fatigue life. At a stirring time of 5 minutes, the crosslinking density and physical entanglement reach a dynamic equilibrium; while at 10 minutes, due to the formation of a relatively rigid network, a "rigid-brittle transition critical point" may appear, resulting in a temporary decrease in fatigue performance. However, when the stirring time exceeds 15 minutes, the crosslinking network may degenerate, accompanied by the reconstruction of the viscous flow path, thereby further improving the fatigue life. A similar trend was also verified in Examples 4-6. In addition, by comparing Examples 4-6 with 1-3, it was found that increasing the reaction temperature to 170°C can significantly increase the fatigue life. This temperature effect (increasing from 160°C to 170°C) is believed to be achieved by promoting the formation of short-chain ester bonds and enhancing the molecular diffusion effect. Under these conditions, isocyanate is transformed from a traditional rigid cross-linker into a nanoscale "elastic hinge", constructing a multi-scale dissipative interface with dynamic self-healing capabilities in the SBS network. Based on the above analysis, all samples regenerated using this method have significantly better fatigue life than new SBS modified asphalt, which fully demonstrates the great potential of this invention in achieving high-performance regeneration of aged asphalt.

[0086] Table 2. Fatigue life (Nf / time) of asphalt in different experimental groups under 0.1% controlled strain

[0087]

[0088] Figure 9Display: The results of observations of the SBS linear structure of different asphalt samples using a 40X fluorescence microscope are intended to illustrate the aging process and its regeneration effect. Through comparative analysis of the microstructure, it can be seen that the aged SBS modified asphalt (Comparative Example 2) exhibits obvious structural degradation characteristics compared to the new SBS modified asphalt (Comparative Example 1), which is manifested as the degradation of the SBS linear structure into small broken fragments, and the asphalt phase color becomes darker. In sharp contrast to this, the composite regenerated aged SBS modified asphalt samples (Examples 1-6) prepared by the novel method of the present invention exhibited a significant structural recovery effect. Microscopic morphology observations show that the regenerated asphalt sample not only successfully restored the SBS linear structure, but the number of its linear structures even surpassed that of the new SBS modified asphalt (Comparative Example 1). This excellent regeneration effect is mainly attributed to the dual action mechanism of the gradual addition of epoxidized soybean oil (ESO): on the one hand, ESO inhibits the hydrolysis side reaction of ester substances that may be generated by isocyanates in the process of repairing degraded SBS; on the other hand, ESO promotes the swelling of the SBS that is distributed in a point-like manner after degradation, thereby increasing its volume, thereby significantly increasing the reaction probability between these swollen SBS and isocyanate, and further promoting the generation of more linear SBS structures. This series of results confirms that the regeneration method of the present invention can not only effectively repair the linear structure of aged SBS modified asphalt, but also successfully replenish the light components volatilized during the aging process, so that the dull color of the aged asphalt is restored to brightness. In summary, this method not only achieves the effective regeneration of aged SBS modified asphalt, but also makes the optimization degree of its microstructure phase surpass that of new SBS modified asphalt, providing an innovative solution for aged asphalt regeneration technology. In addition, process parameters also show an important influence on microstructure regeneration. By comparing Examples 1-3, as time increases, the number of regenerated linear structures shows a trend of medium-small-large, which indicates that the stirring time has a non-monotonic effect on the formation of the SBS network: a medium-density ester bond network is formed at 5 minutes; the critical point is reached at 10 minutes, at which time dense cross-linking may lead to rigid folding of the chain segments; and at 15 minutes, the self-condensation of isocyanate and the penetration of ESO synergistically reconstruct a high-density linear entanglement structure. A similar trend was also verified in Examples 4-6. Further, by comparing Examples 4-6 with 1-3, it was found that increasing the reaction temperature to 170°C significantly enhanced the repair efficiency. This enhancement mechanism can be attributed to the reaction-diffusion synergistic effect induced by heat: on the one hand, the self-condensation of isocyanate forms short-chain oligoesters as "flexible hinges"; on the other hand, the increase in the diffusion coefficient of ESO promotes the physical rearrangement of the broken chains. The two work together to significantly increase the number of linear SBS structures. Based on the above analysis, the number of regenerated SBS linear structures in all samples regenerated using this method is significantly better than that of new SBS modified asphalt, which provides a solid microstructural foundation for the aforementioned macroscopic properties (such as rutting resistance, low-temperature crack resistance and fatigue life) to surpass new SBS modified asphalt.

[0089] The core of the present invention lies in the combined application of specific component ratios and process parameters. Based on the technical teachings of this invention, those skilled in the art may, without violating the underlying principles of the invention, appropriately adjust or optimize the specific implementation parameters, process steps, or material components. Such adjustments or optimizations fall within the scope of the present invention.

Claims

1. A composite regeneration method for imparting super-virgin properties to aged SBS modified asphalt, comprising the following steps: S1. Heat the aged SBS modified asphalt at 160-170°C until it becomes fluid. Add epoxidized soybean oil while stirring and continue stirring until it is uniform. S2. Add toluene diisocyanate to the mixture obtained in step S1 at 160-170° C. and continue stirring until uniform; S3. Add epoxidized soybean oil to the mixture obtained in step S2 at 160-170° C. and stir until uniform; S4. The mixture obtained in step S3 is placed in an oven at 160-170° C. for curing to complete the composite regeneration of the super-original performance of the aged SBS modified asphalt.

2. The method according to claim 1, characterized in that The amount of epoxidized soybean oil in S1 is 4%-8% of the mass of the aged SBS modified asphalt.

3. The method according to claim 1, characterized in that The amount of toluene diisocyanate in S2 is 0.25%-1.5% of the mass of the aged SBS modified asphalt.

4. The method according to claim 1, wherein The amount of epoxidized soybean oil in S3 is 1%-7% of the mass of the aged SBS modified asphalt.

5. The method according to claim 1, characterized in that The stirring speed in S1-S3 is 1000 rpm; and / or The stirring time in S1 and S3 is 5 min; and / or The stirring time in S2 is 5-15 min.

6. The method according to claim 1, characterized in that The curing time in S4 is 20-60 minutes.

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