A composite recycling method for endowing aged sbs modified asphalt with super-pristine performance

Abstract

The present application relates to the technical field of aging SBS modified asphalt regeneration, and specifically provides a composite regeneration method for giving super-pristine performance to aging SBS modified asphalt. The specific steps include: first, adding epoxy soybean oil, preliminarily adjusting the component ratio and releasing the hydroxyl active point on the SBS chain; then, adding isocyanate, reacting with the active point to repair the SBS chain; secondly, adding epoxy soybean oil, optimizing the component ratio to balance the stiffness and low-temperature performance of the regenerated asphalt; finally, curing the sample in an oven to obtain a composite regenerated aging SBS modified asphalt with stable structure. Compared with the existing regeneration method, the present application not only makes the performance of the regenerated asphalt surpass that of the original SBS modified asphalt, significantly improves the high-temperature anti-rutting, low-temperature anti-cracking, permanent deformation resistance, stress sensitivity and fatigue resistance, but also greatly improves the utilization rate of the aging SBS modified asphalt.

Description

Technical Field

[0001] This invention relates to the field of aged SBS modified asphalt recycling technology, and specifically proposes a composite recycling method that imparts super-original properties to aged SBS modified asphalt. Background Technology

[0002] Styrene-butadiene-styrene (SBS) modified asphalt is widely used in high-grade pavement due to its excellent high and low temperature performance. However, during long-term service, the coupled effect of thermo-oxidative aging leads to the loss of lightweight components in the asphalt, disrupting the original four-component balance system. Simultaneously, thermo-oxidative aging causes the continuous SBS molecular chains to break, resulting in a significant degradation of the modified asphalt's performance and severely impacting its service life. This phenomenon directly leads to frequent maintenance of SBS modified asphalt pavements, generating large amounts of recycled asphalt mixtures (RAP). Failure to effectively utilize RAP not only wastes resources but also pollutes the environment due to its disposal.

[0003] Existing technologies for the composite recycling of aged SBS-modified asphalt employ a two-stage addition of rejuvenating agents, aiming to achieve dual repair objectives: firstly, the performance restoration of the aged asphalt components, and secondly, the structural repair of the degraded SBS chains. However, this method has significant limitations in practical applications. From a macroscopic performance perspective, the recycled SBS-modified asphalt fails to reach the standard levels of newly produced SBS-modified asphalt in terms of mechanical properties and rheological characteristics. Furthermore, microscopic structural characterization analysis 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, existing composite recycling methods still face technical bottlenecks in achieving comprehensive recycling of aged SBS modified asphalt, and there is an urgent need to develop more effective recycling strategies to improve the overall performance of recycled materials. Summary of the Invention

[0005] This invention provides a composite recycling technology that utilizes a composite recyclering agent composed of epoxidized soybean oil (ESO) and isocyanate (TDI) to treat aged SBS modified asphalt, thereby enhancing its performance to surpass that of virgin SBS modified asphalt. This method effectively solves the problem of insufficient recycling performance of aged asphalt in the aforementioned background technologies, achieving efficient and economical recycling of asphalt materials.

[0006] This invention provides a composite recycling method for imparting super-native properties to aged SBS-modified asphalt, the specific steps of which are as follows:

[0007] S1. At 160-170℃, heat the aged SBS modified asphalt to a fluid state. Under stirring conditions, add epoxidized soybean oil and continue stirring until uniform. Initially adjust the ratio of its four components (asphaltite, resin, aromatics, and saturated components). On the one hand, this will initially restore the performance of the aged SBS modified asphalt, and on the other hand, it will create more reaction activation points for the subsequent reaction.

[0008] S2. At 160-170℃, add a certain amount of toluene diisocyanate to the mixture obtained in step S1 and continue stirring until homogeneous to repair the degraded SBS chains.

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

[0010] S4. Place the mixture obtained in step S3 in an oven at 160-170℃ for curing to complete the composite regeneration of the super-original properties of aged SBS modified asphalt.

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

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

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

[0014] Furthermore, in the above method,

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

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

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

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

[0019] In this invention, by adding epoxidized soybean oil and isocyanate in stages, the proportions of the four components of aged SBS modified asphalt are effectively adjusted, the degraded SBS chains are repaired, and its low-temperature crack resistance is restored.

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

[0021] (1) Compared with the traditional two-step addition process, the present invention uses a three-step addition method to solve the problem of uneven performance after the regeneration of aged SBS modified asphalt. By first adding epoxidized soybean oil to adjust the component ratio of aged SBS modified asphalt, the low-temperature performance is improved and the SBS repair sites are activated. Then, isocyanate is introduced to repair the degraded SBS chains and restore the high-temperature performance. Finally, epoxidized soybean oil is added again to adjust the stiffness and optimize the composition, so as to achieve a synergistic improvement in the high and low temperature performance of the regenerated aged SBS modified asphalt.

[0022] (2) The composite recycling technology of this invention breaks through the limitations of traditional methods, not only fully restoring the performance indicators of aged SBS modified asphalt, but also making its macroscopic properties surpass those of new SBS modified asphalt. This significant improvement reflects the innovative advantages and practical value of this invention in the field of asphalt recycling.

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

[0024] (4) Compared with the prior art, the present invention systematically studies a wider range of mixing time and temperature combinations, which has a significant effect on improving the composite recycling performance of aged SBS modified asphalt, enriches the selection of recycling process parameters, provides diversified working condition schemes for practical engineering applications, and significantly improves the applicability and practical value of recycling technology. Attached Figure Description

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

[0026] Figure 2 The physical property diagram for determining the first epoxidized soybean oil content in the first step of Example 1 of the specific implementation method;

[0027] Figure 3 The diagram shows the physical properties determined by the isocyanate content in the second step of Example 1 of the specific implementation method;

[0028] Figure 4 The physical property diagram is shown in the third step of the specific implementation example 1, which is used to determine the amount of epoxidized soybean oil added for the second time.

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

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

[0031] Figure 7 The stress sensitivity coefficients of different experimental groups of asphalt at 64℃ with variations of 0.1 kPa and 3.2 kPa are given in the specific implementation method.

[0032] Figure 8 The phase angles of different experimental groups of asphalt under 76℃ conditions are shown in the specific implementation method.

[0033] Figure 9 The specific implementation details the regeneration effects of different experimental groups of asphalt SBS linear structures, including: (a) Comparative Example 1; (b) Comparative Example 2; (c) Example 1; (d) Example 2; (e) Example 3; (f) Example 4; (g) Example 5; and (h) Example 6. Detailed Implementation

[0034] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. These embodiments are only some examples of the present invention, not all examples. Other embodiments obtained by those skilled in the art without creative effort are all within the protection scope of the present invention.

[0035] It should be noted that:

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

[0037] The first step is to place commercial new SBS modified bitumen (SMB, containing 4% SBS) in a rotating film oven at 163°C for 5 hours to simulate its thermal aging behavior during construction.

[0038] The second step involves placing the SBS modified asphalt that underwent short-term aging in the first step into a pressure aging container and aging it for 20 hours at 100°C and 2.1 MPa to simulate its thermo-oxidative aging process from the end of construction to the decommissioning stage, thereby obtaining the final aged SBS modified asphalt sample.

[0039] II. The commercially available SBS modified asphalt used was purchased from Shanxi Transportation Holding Group Co., Ltd.; the aged SBS modified asphalt produced had a ductility of 6 mm at 5℃, a penetration of 35.6 d mm (1 d mm = 0.1 mm) at 25℃, a softening point of 76.1℃, and a viscosity of 3450 mPa·s at 135℃.

[0040] III. The epoxidized soybean oil used in this 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 mg KOH / g.

[0041] IV. The toluene diisocyanate (TDI-80) used in this invention was purchased from Wanhua Chemical Group Co., Ltd., and is composed of two isomers, 2,4-toluene diisocyanate [A] and 2,6-toluene diisocyanate [B], in a ratio of 80:20.

[0042] Example 1

[0043] This embodiment presents a composite recycling method for imparting super-native properties to aged SBS-modified asphalt, the specific process steps of which are as follows:

[0044] S1. At 160℃, the aged SBS modified asphalt is heated to a fluid state. Under stirring conditions of 1000rpm, a certain amount of epoxidized soybean oil is added for the first time, and stirring is continued for 5 minutes.

[0045] S2. Under stirring conditions of 160℃ and 1000rpm, a certain amount of toluene diisocyanate is added to the mixture obtained in step S1, and stirring is continued for 5 minutes.

[0046] S3. Under the stirring conditions of 160℃ and 1000rpm, add a certain amount of epoxidized soybean oil to the mixture obtained in step S2 and stir for 5 minutes.

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

[0048] The dosage of epoxidized soybean oil and toluene diisocyanate in S1-S3 above shall be determined according to the following steps:

[0049] In step S1, epoxidized soybean oil (ESO) was added to the aged SBS modified asphalt in a gradient of 4%-8% (1% intervals) by mass, and stirred at 160°C for 5 minutes. Its low-temperature performance was evaluated by testing ductility at 5°C (ASTM D113) and penetration at 25°C (ASTM D5). The experimental results are shown below. Figure 2 The results show that the ductility and penetration of the samples increase with increasing ESO content, which is attributed to ESO replenishing the lost lightweight components and effectively dispersing the degraded SBS molecules. When the ESO content reaches 6%, the low-temperature performance of the aged asphalt is closest to that of new SBS-modified asphalt (SMB). However, further research found that excessive ESO leads to a gradual decrease in high-temperature performance, and the high-temperature performance at 6% content is lower than that of SMB, indicating that further optimization of the modification scheme is needed.

[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. Following the S1 procedure, an aged SBS asphalt mixture regenerated from epoxidized soybean oil was obtained. Isocyanate was then added to this mixture in a gradient of 0.5-1.5% (0.25% intervals) of the mass of the aged SBS modified asphalt, and the process was repeated in step S2. This aimed to improve high-temperature performance while maintaining acceptable low-temperature performance. Experimental results are shown below. Figure 3 The results show that the ductility and penetration of the mixture decrease in two stages with increasing isocyanate content: performance declines slowly when the content is below 1%, and deteriorates sharply above 1%, indicating that 1% is a critical inflection point. Softening point and viscosity increase with increasing isocyanate content, attributed to the increased stiffness caused by isocyanate repair of degraded SBS. However, when the isocyanate content exceeds 1%, the viscosity rises sharply to over 10,000 mPa·s, severely impacting practical application performance. This finding reveals the limitations of traditional composite regeneration methods and underscores the necessity of optimizing the regeneration process.

[0051] The third step, building upon the second step, involved fixing the amount of toluene diisocyanate in S2 at 1% of the mass of the aged SBS modified asphalt. A second addition of epoxidized soybean oil was then conducted, specifically in S3, to explore the appropriate dosage. The percentage of epoxidized soybean oil in S3, representing 3% to 5% of the mass of the aged SBS modified asphalt, was set in increments of 1%, aiming to further optimize and improve the performance of the aged SBS modified asphalt, ultimately surpassing the performance benchmark of new SBS modified asphalt (SMB). The performance evaluation of the mixture at this stage is as follows: Figure 4As shown, with the increase of the second epoxidized soybean oil content, the softening point (ASTM D36) and viscosity at 135℃ (ASTM D4402) of the asphalt both showed a decreasing trend, while the ductility at 5℃ (ASTM D113) and penetration at 25℃ (ASTM D5) also improved. Notably, when the second ESO content reached 4%, several key indicators of the recycled asphalt, including ductility, penetration, softening point, and viscosity, not only closely approximated the corresponding performance indicators of the new SBS modified asphalt, but even showed a tendency to surpass the new SBS modified asphalt in some aspects, such as ductility, penetration, softening point, and viscosity. This result strongly indicates that, through the above three consecutive optimization steps, aged SBS modified asphalt has successfully surpassed the comprehensive performance of new SBS modified asphalt. This significant performance improvement can be attributed to the synergistic effect of the secondary ESO addition. First, the introduction of secondary ESO promoted further swelling of the previously only dot-like dispersed SBS polymer, thereby increasing the opportunity for isocyanate to undergo a linear repair reaction with the degraded SBS chains. Secondly, the addition of the second ESO effectively suppressed potential side effects such as further degradation of the SBS chain products formed during the second repair process, which promoted the formation of more linear SBS structures. For example... Figure 9 As shown, the number of linear SBS structures in the final recycled asphalt exceeds the number of linear SBS structures in the new SBS modified asphalt, providing a structural basis for the macroscopic performance improvement from a microscopic level.

[0052] In the experimental process of the specific embodiments of the present invention, 100 parallel experiments were set up for each experimental group, and the average value of the experimental data of each group was taken.

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

[0054] Example 2

[0055] The composite recycled aged SBS modified asphalt provided in this embodiment of the invention is prepared using the same method and composition as in Example 1, except that the continuous stirring time in step S2 is modified to 10 minutes.

[0056] Example 3

[0057] The composite recycled aged SBS modified asphalt provided in this embodiment of the invention is prepared using the same method and composition as in Example 1, except that the continuous stirring time in step S2 is modified to 15 minutes.

[0058] Example 4

[0059] The composite recycled aged SBS modified asphalt provided in this embodiment of the invention is prepared using the same method and composition as in Example 1. The difference is that the stirring temperature of all steps S1 to S4 is uniformly set to 170°C in this embodiment.

[0060] Example 5

[0061] The composite recycled aged SBS modified asphalt provided in this embodiment of the invention is prepared in the same way and with the same components as in Example 1. The difference is that 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 recycled aged SBS modified asphalt provided in this embodiment of the invention is prepared in the same way and with the same components as in Example 1. The difference is that 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 commercially available SBS-modified asphalt;

[0066] The new SBS modified bitumen has a ductility of 308 mm at 5℃, a penetration of 56.2 d mm at 25℃, a softening point of 63.7℃, and a viscosity of 2610 mPa·s at 135℃, where 1 d mm = 0.1 mm.

[0067] Comparative Example 2

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

[0069] Among them, the ductility of aged SBS modified asphalt at 5℃ is 6mm, the 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-step preparation method for traditional composite recycled aged SBS modified bitumen, and the specific process steps are as follows:

[0072] S1. At 160℃, heat the aged SBS modified asphalt to a fluid state. Under stirring at 1000 rpm, add 10% of the mass of the aged SBS modified asphalt with epoxidized soybean oil for the first time, and continue stirring for 5 minutes.

[0073] S2. At 160°C, add toluene diisocyanate at a mass fraction of 1% of the aged SBS modified asphalt to the mixture obtained in step S1, and continue stirring for 5 minutes.

[0074] S3. The mixture obtained in S2 is placed in an oven at 160℃ for curing for 40 minutes to obtain the final traditional composite recycled SBS modified asphalt sample.

[0075] Performance testing

[0076] Referring to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering JTGE20-2011", the physical properties (ASTM D5, ASTM D36, ASTM D113 and ASTM D4402), high-temperature rheological properties (AASHTO T315), low-temperature rheological properties (ASTM D6648), stress sensitivity properties (ASTM D7405-20), viscoelastic properties (AASHTO T315), fatigue life (AASHTO T101-14), and SBS linear structure regeneration effect of the new SBS modified asphalt in Examples 1-6 and Comparative Example 1 and the aged SBS modified asphalt in Comparative Example 2 were tested. The average value of the properties of each sample was taken as the basis for the results analysis. The results are as follows. Figure 5-9 As shown in Tables 1 and 2.

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

[0078]

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

[0080] Table 1 shows that, compared to Comparative Example 1, Comparative Example 2 exhibits decreased ductility and penetration, but increased softening point and viscosity. This is attributed to the increased hardness caused by the volatilization of lightweight components and the degradation of SBS chains during the aging process of the SBS modified asphalt. While the traditional composite recycling method (Comparative Example 3) improved the performance of the aged SBS modified asphalt, its low-temperature performance indicators still did not reach the level of the new SBS modified asphalt (Comparative Example 1), and the increased viscosity affected its workability. This limitation stems from the fact that the traditional technology did not consider the stiffness problem generated when reactive regenerators repair degraded SBS, and the one-time addition of biological regenerators increased the dispersibility of degraded SBS chains, reducing the repair effect. In contrast, the novel method proposed in this 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 degraded SBS, providing sufficient activation points for the reactive regenerator, avoiding the isocyanate self-polymerization side reaction, and promoting the swelling of point-like SBS to form a linear structure. Second, the addition of the second epoxidized soybean oil inhibits the hydrolysis of unstable ester intermediates generated from the repaired SBS chains, 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 proportion of asphalt components, ultimately achieving a comprehensive improvement in performance. Given that traditional composite recycling methods cannot achieve the performance level of new SBS-modified asphalt, subsequent evaluations will directly use the performance indicators of new SBS-modified asphalt as a reference standard.

[0081] Figure 5 The results show that the rutting factor curves of the composite recycled aged SBS modified asphalt in Examples 1-6 are superior to those of Comparative Example 1 (new SBS modified asphalt) and Comparative Example 2 (aged SBS modified asphalt). This performance improvement stems from the innovative strategy of adding epoxidized soybean oil in stages: it inhibits the hydrolytic side reaction during the repair and degradation of SBS chains by reactive regenerators, while promoting the swelling of point-like SBS structures, synergistically generating more linear structures with the reactive regenerators, thus improving the asphalt stiffness and high-temperature resistance. The stirring time exhibits a non-linear response to the regeneration effect: the comparison of Examples 1-3 shows that 10 minutes is the critical point. Less than 10 minutes shows a synergistic repair effect; at the critical point, cross-linking reactions dominate, leading to a reduction in linear structures; more than 10 minutes activates an entropy-driven molecular self-optimization process, increasing the number of regenerated structures. Examples 4-6 show a similar trend. Temperature effect studies (Examples 4-6 compared to 1-3) reveal that increased temperature reduces high-temperature performance. When the temperature rises from 160℃ to 170℃, isocyanate transforms from a traditional crosslinking agent into a dynamic bonding medium. The synergistic effect of molecular diffusion mass transfer and crosslinking reaction kinetics enables targeted repair of SBS molecular chain breakage sites. Notably, all recycled samples exhibited superior rutting resistance compared to virgin SBS-modified asphalt.

[0082] Figure 6 The results show that the creep stiffness to creep rate ratio (S / m) of Comparative Example 2 (aged SBS modified asphalt) at -24℃ is higher than that of Comparative Example 1 (new SBS modified asphalt), confirming that thermo-oxidative aging increases asphalt brittleness. The S / m values ​​of Examples 1-6 are not only lower than Comparative Example 2, but also significantly lower than Comparative Example 1, indicating that the epoxidized soybean oil and isocyanate composite regeneration system successfully achieved component regeneration and SBS chain repair, enabling the low-temperature crack resistance of the regenerated asphalt to surpass that of the new SBS modified asphalt. This performance improvement is attributed to the innovative strategy of adding epoxidized soybean oil in stages: effectively suppressing the hydrolytic side reaction during the reactive regenerator repair process, while promoting the swelling of the dotted SBS structure, synergistically generating more linear structures with the reactive regenerator, significantly improving the asphalt ductility. The stirring time exhibits a non-linear response characteristic to the regeneration effect. Comparing Examples 1-3 reveals the importance of 10 minutes as a critical critical point: stirring times shorter than 10 minutes exhibit a synergistic repair effect; at the critical point, crosslinking reactions may dominate, leading to a reduction in linear structures; while stirring times exceeding 10 minutes activate an entropy-driven molecular self-optimization process, thereby increasing the number of regenerated structures. Examples 4-6 also show a similar trend. Further temperature effect studies (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 isocyanate changes from a traditional crosslinking agent to a dynamic bonding medium. During this process, the synergistic effect of molecular diffusion mass transfer rate and crosslinking reaction kinetics enables more targeted repair of SBS molecular chain breakage sites. Notably, all samples regenerated using the method of this invention exhibit significantly better resistance to low-temperature cracking than new SBS-modified asphalt.

[0083] Figure 7The stress sensitivity of asphalt at 64°C was assessed using the stress sensitivity coefficient. The results showed that the stress sensitivity coefficient of aged SBS-modified asphalt (Comparative Example 2) was lower than that of virgin SBS-modified asphalt (Comparative Example 1). This indicates that thermo-oxidative aging leads to the volatilization of lightweight components in the asphalt, thereby increasing its hardness and reducing its sensitivity to external stress, but at the cost of increased brittleness. Notably, the stress sensitivity coefficients of the composite recycled aged SBS-modified asphalt developed in this invention (Examples 1-6) were all negative, and their absolute values ​​were significantly lower than those of virgin SBS-modified asphalt (Comparative Example 1). This finding indicates that recycled asphalt exhibits less deformation under high stress and possesses superior stress sensitivity characteristics. This performance improvement is mainly attributed to the phased addition strategy of epoxidized soybean oil (ESO). This strategy effectively suppresses adverse effects such as byproduct hydrolysis that may occur during the repair and degradation of SBS chains by reactive regenerators. Furthermore, ESO promotes the swelling of the previously dotted SBS structure, thereby providing more active sites for subsequent reactions with reactive regenerators and promoting the formation of more linear SBS structures. The increase in linear structure not only enhances the density of SBS in the asphalt matrix, but more importantly, it strengthens the asphalt's resistance to stress deformation, thus significantly reducing its stress sensitivity. Furthermore, the mixing time exhibits a non-linear response to the recycling effect. Comparing Examples 1-3, the relevant indices of stress sensitivity show non-monotonic changes. At shorter mixing times (e.g., 5 minutes), localized short-range crosslinking networks may be incomplete; however, at 10 minutes, the optimal crosslinking state may be reached, with the lowest ester content and the best continuity of the rigid network, thus imparting optimal stress sensitivity to the asphalt. However, when the mixing time is extended to 15 minutes, the self-polymerization side reaction of isocyanates may lead to the breakage of crosslinking points, causing physical entanglement rather than chemical crosslinking to dominate viscous flow. Examples 4-6 also show a similar trend. Further temperature effect studies (by comparing Examples 4-6 with 1-3) reveal that increasing the recycling 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 coupling reaction of isocyanates, it also enhances their self-condensation tendency, potentially forming oligomers; simultaneously, ESO diffusion causes SBS chains to untangle, possibly resulting in a "pseudo-reinforced" interface with locally increased rigidity but reduced overall ductility. This study elucidates the temperature-induced reaction path shift phenomenon during chemical regeneration—when the temperature exceeds a certain threshold, the role of isocyanates may shift from network builder to viscosity enhancer. Essentially, this shift is a result of topological order decoupling and viscoelastic equilibrium collapse driven by entropy increase. Despite these complex microscopic mechanisms, all samples regenerated using this method showed significantly better stress sensitivity than newly SBS-modified asphalt.

[0084] Figure 8The results show the change in phase angle of asphalt at 76℃. The phase angle of the thermo-oxidative aged SBS modified asphalt (Comparative Example 2) is higher than that of the new SBS modified asphalt (Comparative Example 1), indicating that aging leads to an increase in the proportion of viscous components and a decrease in elastic properties. After regenerating the aged SBS modified asphalt using the novel recycling method developed in this invention (Examples 1-6), its phase angle was effectively restored, and the restored values ​​were all lower than those of the new SBS modified asphalt in Comparative Example 1. This result clearly demonstrates that the recycling method exhibits superior performance in restoring the elasticity of asphalt, outperforming new SBS modified asphalt. This significant elastic recovery ability is mainly attributed to the method's ability to generate more linear SBS structures, thereby enhancing the resistance of aged SBS modified asphalt to deformation. The study on the dependence of stirring time, through comparison of Examples 1-3, reveals that at a constant temperature, the phase angle exhibits a non-monotonic 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 crosslinking reaction of isocyanate is most complete, and the arrangement of SBS segments is most ordered, thereby maximizing the elasticity of the asphalt. A similar trend was also verified in Examples 4-6. Notably, comparing Examples 4-6 with Examples 1-3, it was 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 isocyanate self-condensation reaction and the phase separation induced by epoxidized soybean oil (ESO), both of which jointly disrupt the continuity of the polymer network in the asphalt matrix. These findings not only elucidate the mechanism of dynamic competition between the elastic and viscous phases during chemical regeneration, but more importantly, reveal the dual nature of the reaction pathway under thermally activated conditions, providing a crucial process parameter window for the precise regeneration of aged polymer-modified asphalt. In summary, all samples regenerated using this method exhibited significantly lower phase angles than virgin SBS-modified asphalt, directly indicating superior high-temperature deformation resistance.

[0085] Table 2 shows that thermo-oxidative aging caused the fatigue life of SBS-modified asphalt (Comparative Example 2) to decrease by an order of magnitude compared to virgin SBS-modified asphalt (Comparative Example 1), highlighting the severe damage aging causes to material durability. In stark contrast, the aged SBS-modified asphalt samples (Examples 1-6) prepared using the novel composite regeneration method of this invention exhibited significantly longer fatigue lives than virgin SBS-modified asphalt (Comparative Example 1), strongly demonstrating the superior performance of this innovative regeneration technology in improving asphalt fatigue performance. This performance improvement lies not only in the recovery of fatigue performance but also in the realization of a "defect-guided adaptive topology" effect through multi-scale structural reconstruction. This effect originates from the preferential reaction between active sites on broken SBS chains and isocyanates, forming a dynamic cross-linked network; simultaneously, epoxidized soybean oil (ESO) constructs a hierarchical structure with gradient viscoelastic dissipation capabilities. This regeneration system exhibits a unique three-tiered energy buffering mechanism, synergistically suppressing crack initiation and propagation: firstly, energy is dissipated through bond rotation and conformational changes at the molecular scale; secondly, microcrack passivation occurs at the interface scale; and finally, sacrificial bond breaking at the macroscopic scale delays further crack propagation. Studies on stirring time (through comparison of Examples 1-3) revealed its non-monotonic "medium-low-high" effect on fatigue life. At 5 minutes of stirring time, crosslinking density and physical entanglement reach dynamic equilibrium; while at 10 minutes, due to the formation of a relatively rigid network, a "rigid-brittle transition critical point" may occur, leading to a temporary decrease in fatigue performance. However, when the stirring time exceeds 15 minutes, the crosslinking network may degrade, accompanied by the reconstruction of viscous flow paths, thereby improving fatigue life again. Similar trends were also verified in Examples 4-6. Furthermore, comparing Examples 4-6 with 1-3, it was found that increasing the reaction temperature to 170°C significantly increases fatigue life. This temperature effect (from 160℃ to 170℃) is believed to be achieved by promoting the formation of short-chain ester bonds and enhancing molecular diffusion. Under these conditions, isocyanate transforms from a traditional rigid crosslinking agent into a nanoscale "elastic hinge," constructing a multi-scale dissipative interface with dynamic self-healing capabilities within the SBS network. Based on the above analysis, all samples regenerated using this method exhibit significantly better fatigue life than virgin SBS-modified asphalt, fully demonstrating the enormous potential of this invention for achieving high-performance regeneration of aged asphalt.

[0086] Table 2 lists the fatigue life (Nf / cycle) of asphalt in different experimental groups under 0.1% controlled strain.

[0087]

[0088] Figure 9The results of observing the linear structure of SBS in different asphalt samples using a 40X fluorescence microscope aim to elucidate the aging process and its regeneration effect. Microstructural comparison analysis reveals that aged SBS-modified asphalt (Comparative Example 2) exhibits significant structural deterioration compared to virgin SBS-modified asphalt (Comparative Example 1), characterized by the degradation of the SBS linear structure into fragmented small pieces and a darkening of the asphalt phase color. In stark contrast, the composite regenerated aged SBS-modified asphalt samples (Examples 1-6) prepared using the novel method of this invention demonstrate a significant structural recovery effect. Microscopic morphological observation shows that the regenerated asphalt samples not only successfully restored the SBS linear structure, but the number of linear structures even surpassed that of virgin SBS-modified asphalt (Comparative Example 1). This superior regeneration effect is mainly attributed to the dual mechanism of the fractional addition of epoxidized soybean oil (ESO): on the one hand, ESO inhibits the hydrolytic side reactions of esters that may be generated during the repair and degradation of SBS by isocyanates; on the other hand, ESO promotes the swelling of the point-like distributed SBS after degradation, increasing its volume and significantly increasing the reaction probability between these swollen SBS and isocyanates, thereby promoting the formation of more linear SBS structures. These results confirm that the regeneration method of this invention can not only effectively repair the linear structure of aged SBS-modified asphalt, but also successfully replenish the volatile light components lost during aging, restoring the bright color of the aged asphalt. In summary, this method not only achieves effective regeneration of aged SBS-modified asphalt, but also optimizes its microstructure phase to a degree surpassing that of new SBS-modified asphalt, providing an innovative solution for aged asphalt regeneration technology. Furthermore, process parameters also show a significant impact on microstructure regeneration. Comparing Examples 1-3, the number of regenerated linear structures showed a trend of medium-low-high as time increased, indicating that stirring time has a non-monotonic effect on SBS network formation: a medium-density ester bond network is formed at 5 minutes; a critical point is reached at 10 minutes, where dense crosslinking may lead to rigid folding of chain segments; and at 15 minutes, the synergistic effect of isocyanate self-condensation and ESO infiltration reconstructs a high-density linear entangled structure. Similar trends were also verified in Examples 4-6. Furthermore, 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 thermally induced reaction-diffusion synergistic effect: on the one hand, isocyanate self-condensation forms short-chain oligopolyesters as "flexible hinges"; on the other hand, the increase in the ESO diffusion coefficient promotes the physical rearrangement of broken chains, and the combined effect of both significantly increases the number of linear SBS structures. In summary, all samples regenerated using this method showed a significantly higher number of linear SBS structures compared to virgin SBS-modified asphalt. This provides a solid microstructural basis for the aforementioned macroscopic properties (such as rutting resistance, low-temperature crack resistance, and fatigue life) that surpass those of virgin SBS-modified asphalt.

[0089] The core of this invention lies in the combined application of specific component ratios and process parameters. Those skilled in the art can, based on the technical teachings of this invention, appropriately adjust or optimize the specific implementation parameters, process steps, or material composition without departing from the basic principles of this invention; such adjustments or optimizations also fall within the technical protection scope of this invention.

Claims

1. A composite recycling method for imparting super-native properties to aged SBS-modified asphalt, the specific steps of which are as follows: S1. Heat the aged SBS modified asphalt to a fluid state at 160-170℃, add epoxidized soybean oil under stirring conditions, and continue stirring until uniform. S2. At 160-170℃, add toluene diisocyanate to the mixture obtained in step S1 and continue stirring until homogeneous; S3. At 160-170℃, add epoxidized soybean oil to the mixture obtained in step S2 and stir until homogeneous; S4. Place the mixture obtained in step S3 in an oven at 160-170℃ for curing to complete the composite regeneration of the super-original properties of aged SBS modified asphalt. The amount of epoxidized soybean oil in S1 is 4%-8% of the mass of aged SBS modified asphalt; The amount of toluene diisocyanate in S2 is 0.25%-1.5% of the mass of aged SBS modified asphalt; The amount of epoxidized soybean oil in S3 is 1%-7% of the mass of aged SBS modified asphalt.

2. The method according to claim 1, characterized in that, The stirring rate 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.

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

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