A method for preparing recycled SBS-modified asphalt based on a targeted dual dynamic covalent network.

Abstract

This invention relates to the field of road engineering materials technology, specifically to a recycled SBS modified asphalt based on a targeted dual dynamic covalent network and its preparation method. The raw materials for this recycled SBS modified asphalt, by weight, comprise: 100 parts of aged SBS modified asphalt, 5-15 parts of a crosslinking leader containing polyepoxy groups, 2.5-7.5 parts of a dynamic crosslinking agent containing disulfide bonds, and 0.146-1.051 parts of an ester exchange catalyst. It is obtained by sequentially adding the crosslinking leader containing polyepoxy groups, the dynamic crosslinking agent containing disulfide bonds, and the ester exchange catalyst to molten aged SBS modified asphalt under stirring conditions. The synergistic effect of these components restores the macroscopic mechanical properties of the aged asphalt, endowing it with high-temperature thermoplastic processing fluidity and intrinsic microcrack self-healing ability at room temperature. This invention features a simplified process, good system compatibility, and achieves dual regeneration through physical softening and viscosity reduction, and in-situ reconstruction of the macromolecular network.

Description

Technical Field

[0001] This invention belongs to the field of road asphalt material recycling technology, specifically relating to a recycled SBS modified asphalt based on a targeted dual dynamic covalent network and its preparation method. Background Technology

[0002] Asphalt pavement recycling technology is a key approach to realizing the resource utilization of reclaimed asphalt mixtures (RAP). With the large-scale formation of the current highway network, SBS (styrene-butadiene-styrene block copolymer) modified asphalt, the mainstay of high-grade pavement, is facing severe aging and performance degradation problems. During long-term service, under the coupled effects of multiple environments such as heat, oxygen, and ultraviolet radiation, SBS asphalt inevitably undergoes severe component aging and network degradation. Its microscopic essence lies in the irreversible thermo-oxidative fracture of the polybutadiene (PB) segments in the SBS polymer chain, generating a large number of free polar oxygen-containing defects (such as carboxyl groups and hydroxyl groups), completely destroying the original three-dimensional cross-linked network. Macroscopically, this manifests as asphalt hardening and brittleness, and a significant loss of high-temperature rutting resistance and low-temperature fatigue cracking resistance. Therefore, how to achieve efficient and high-value recycling of aged SBS modified asphalt at the molecular level is a bottleneck that urgently needs to be overcome in the current road engineering field.

[0003] The core components and mechanisms of action of recycling agents directly determine the upper limit of network reconstruction in aged asphalt. Currently, most recycling agents widely used in engineering rely on petroleum-based heavy aromatics or synthetic light oils derived from fossil fuels, which not only consume non-renewable resources but also impose a significant environmental burden during production and construction. To improve the elasticity and crack resistance of recycled asphalt, some studies have attempted to directly physically blend and incorporate macromolecular polymer materials. However, due to the huge thermodynamic barrier between the added macromolecular polymers and the highly aggregated aged asphalt matrix, their compatibility is extremely poor, easily leading to phase separation and uneven dispersion, resulting in drastic fluctuations in recycling effects. In addition, some techniques relying solely on traditional chemical crosslinking easily form irreversible thermosetting locked networks within the system, causing a sharp increase in asphalt viscosity and a severe loss of thermoplastic processing fluidity.

[0004] In response to the needs of green road maintenance, bio-based materials, represented by vegetable oils such as epoxidized soybean oil and rapeseed oil, have gradually become a new hotspot in regenerator research due to their excellent renewability and biodegradability. However, current bio-based regeneration processes mostly use them only as physical softeners. This purely physical dilution and viscosity reduction cannot deeply repair the broken molecular chains of aged SBS. It is particularly noteworthy that with the official implementation of the new "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG 3410-2025), the industry evaluation system has historically added standardized tests for microscopic chemical components such as infrared spectroscopy and polymer content. This change highlights the limitations of traditional vegetable oils as physical softeners. Because pure physical mixing cannot rebuild the polymer network, recycled asphalt exhibits significant deficiencies in high-temperature rutting resistance and long-term durability. Furthermore, conventional methods often restore mechanical properties by directly adding polymers, but the thermodynamic incompatibility between components often leads to severe phase separation and segregation problems. Therefore, how to overcome the existing barriers of physical viscosity reduction and heterogeneous blending, and realize the in-situ chemical reconstruction of polymer fracture networks at the molecular level, has become a key technical problem that urgently needs to be solved under the new regulations. Summary of the Invention

[0005] To address the aforementioned engineering challenges of ineffective physical softening and the tendency for heterogeneous polymer blends to segregate, this invention proposes a method for preparing recycled SBS modified asphalt based on targeted grafting and dual dynamic covalent network reconstruction.

[0006] The technical solution of the present invention is as follows: A recycled SBS modified bitumen based on a targeted dual dynamic covalent network comprises, by weight, 100 parts of aged SBS modified bitumen, 5-15 parts of a crosslinking lead agent containing polyepoxy groups, 2.5-7.5 parts of a dynamic crosslinking agent containing disulfide bonds, and 0.146-1.051 parts of an ester exchange catalyst. The crosslinking lead agent containing polyepoxy groups is selected from one or more of the following: plant oil derivatives containing polyepoxy groups, synthetic polyepoxy resins, or modified derivatives of the above materials after physical / chemical pretreatment. The disulfide-bonded dynamic crosslinking agent is selected from those containing disulfide bonds and having a main chain carbon number of C2~C3. 12 One or more of the aliphatic dicarboxylic acids; The transesterification catalyst is selected from one or a combination of several of the following: organometallic salt catalysts, organometallic complex catalysts, organic strong base catalysts, or Lewis acid catalysts.

[0007] This invention employs a crosslinking lead agent containing polyepoxy groups. This agent serves both as a reactive permeation medium to replenish the lightweight components lost during the aging process, improving the system's rheological properties, and as a means for actively identifying and targeting polar defects caused by broken SBS chains during aging. Subsequently, an aliphatic dicarboxylic acid containing disulfide bonds is introduced as a dynamic crosslinking bridge, undergoing in-situ esterification with the aforementioned anchoring sites to rebridge the broken SBS short chains. This stepwise reaction effectively circumvents the compatibility barriers of heterogeneous blending and, under the action of an ester exchange catalyst, successfully assembles a dual dynamic reversible network with both β-hydroxy ester bonds and disulfide bonds within the asphalt. The β-hydroxy ester bonds significantly improve the high-temperature thermoplastic processing fluidity of the asphalt, while the disulfide bonds endow pavement microcracks with excellent room-temperature self-healing capabilities. This invention improves the true reconstruction level of the aged SBS-modified asphalt network at the microscopic level, providing an effective technical path for reducing phase separation risks and achieving molecular-level intelligent regeneration.

[0008] The aforementioned recycled SBS modified asphalt based on a targeted dual dynamic covalent network further includes an aged SBS modified asphalt selected from any one or a mixture of thin film oven aged asphalt (TFOT), rotary thin film oven aged asphalt (RTFOT), ultraviolet aged asphalt (UV), pressure aged asphalt (PAV), and waste extraction aged asphalt.

[0009] Furthermore, the transesterification catalyst is selected from one or more of anhydrous zinc acetylacetonate, zinc acetate, dibutyltin dilaurate, stannous octoate, 1,5,7-triazabicyclo[4.4.0]dec-5-ene and 1,8-diazabicyclo[5.4.0]undec-7-ene, which accelerates the esterification crosslinking reaction. At the same time, under high-temperature processing conditions, the β-hydroxy ester bonds in the catalytic system undergo dynamic transesterification reactions, breaking the thermosetting deadlock caused by chemical crosslinking and ensuring the high-temperature processing fluidity of recycled asphalt.

[0010] Furthermore, the transesterification catalyst is 1,5,7-triazabicyclo[4.4.0]dec-5-ene, which is a white crystal and crystalline powder. Its purity was determined to be 98.92% by HClO4 titration, and its structure met the requirements by nuclear magnetic resonance (NMR) detection.

[0011] Furthermore, the crosslinking lead agent containing polyepoxy groups is selected from one or more of epoxidized soybean oil, epoxidized linseed oil, epoxidized cottonseed oil, epoxidized castor oil, bisphenol A type epoxy resin, and derivatives of the above materials after transesterification modification, ultrasonic dispersion, or grafting functionalization. During the high-temperature stirring stage, it acts as a reactive permeation medium to improve the processing rheology of aged asphalt. More importantly, it utilizes epoxy groups to target and graft onto the polar defects generated by the chain breakage of aged SBS, thereby achieving the initial anchoring of aged degradation fragments.

[0012] Furthermore, the crosslinking lead agent containing polyepoxy groups is epoxidized soybean oil, which has an acid value of 0.3 mgKOH / g, an epoxy value of ≥6.0%, an iodine value of ≤6.0%, and a specific gravity of 0.996 at 20°C.

[0013] Furthermore, the disulfide-containing dynamic crosslinking agent is selected from one or more of 4,4'-dithiodibutyric acid, 3,3'-dithiodipropionic acid, and 2,2'-dithiodiacetic acid. As a dynamic crosslinking bridge, it can utilize its terminal carboxyl group to undergo an esterification reaction with the remaining epoxy group of the lead agent, thereby re-stitching the broken SBS chain segments and assembling them in situ into a macromolecular crosslinking network inside the asphalt.

[0014] Furthermore, the disulfide-containing dynamic crosslinking agent is 4,4'-dithiodibutyric acid, which is a white crystalline solid with a melting point of 110.3°C, a neutralization titration purity of 99.5%, and a gas chromatographic purity of 99.6%.

[0015] Furthermore, the mass ratio of the crosslinking leader containing polyepoxy groups to the dynamic crosslinking agent containing disulfide bonds is 1~5:1. Through synergistic action and a step-by-step reaction, the crosslinking leader containing polyepoxy groups and the dynamic crosslinking agent containing disulfide bonds successfully construct a dual dynamic reversible network possessing both β-hydroxy ester bonds and disulfide bonds.

[0016] Furthermore, the recycled SBS modified asphalt based on the targeted dual dynamic covalent network is obtained by sequentially adding a crosslinking leader containing polyepoxy groups, a dynamic crosslinking agent containing disulfide bonds, and an ester exchange catalyst to molten aged SBS modified asphalt under stirring conditions.

[0017] Based on a general inventive concept, the present invention also provides a method for preparing the recycled SBS modified bitumen based on the targeted dual dynamic covalent network, comprising the following steps: S1. Heat aged SBS modified asphalt to a molten state, add a crosslinking lead agent containing polyepoxy groups under stirring conditions and continue stirring to obtain mixture 1; S2. Add a dynamic crosslinking agent containing disulfide bonds to mixture 1 obtained in step S1, and continue stirring to obtain mixture 2; S3. Add the transesterification catalyst to the mixture 2 obtained in step S2, and then continue stirring to obtain the recycled SBS modified bitumen based on the targeted dual dynamic covalent network.

[0018] This invention employs a sequential, step-by-step feeding process. First, epoxidized soybean oil is introduced, utilizing its physical plasticizing and swelling effects to effectively reduce the melt viscosity of the aged asphalt system and improve its workability. This promotes sufficient contact and targeted grafting between the epoxidized soybean oil and the aged SBS phase dispersed in the asphalt matrix. Then, 4,4'-dithiodibutyric acid is introduced to achieve precise construction of dual dynamic covalent bonds in the recycled SBS polymer network, significantly improving the crosslinking reaction efficiency and the overall recycling quality of the SBS-modified asphalt. Furthermore, the process described in this invention requires no special modifications to existing equipment, has a wide process window, strong engineering adaptability, and excellent prospects for industrial application.

[0019] In the above preparation method, further, in step S1, the heating temperature of the aged SBS modified asphalt is 170~180℃, and the heating time is 5~15min. Even further, the heating temperature of the aged SBS modified asphalt is 175℃. This heating condition enables the dual regeneration of the aged asphalt matrix and the SBS polymer in the aged SBS modified asphalt.

[0020] Furthermore, in steps S1 to S3, the stirring speed is 200 to 1000 r / min, and the stirring time is 20 to 40 min. Even further, the stirring speed is 1000 r / min, and the stirring time is 30 min.

[0021] The recycled SBS modified asphalt produced by the above-mentioned technical solution can overcome the limitations of traditional physical regeneration and achieve dual-targeted regeneration of the aged SBS modified asphalt system, namely, softening and reducing the viscosity of the asphalt matrix and chemical reconstruction of the SBS modifier chain. The components of the recycled SBS modified asphalt, including a crosslinking leader containing polyepoxy groups, a dynamic crosslinking agent containing disulfide bonds, and an ester exchange catalyst, are added to the aged SBS modified asphalt in a molten state at a temperature of 170℃~180℃ at a total mass percentage of 7.646%~23.551% (based on the mass of the aged SBS modified asphalt). After uniform stirring, in-situ ring-opening esterification and dynamic ester exchange reactions are triggered to prepare high-performance recycled SBS modified asphalt.

[0022] This recycled SBS modified asphalt not only significantly restores the macroscopic mechanical properties and microscopic polymer network structure of recycled SBS modified asphalt, but also endows the asphalt pavement microcracks with extremely excellent intrinsic self-healing ability at room temperature through the dynamic disulfide bonds constructed inside, greatly extending the life cycle durability of the recycled pavement, and can be used in road engineering.

[0023] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention achieves three-dimensional in-situ reconstruction of macromolecular networks, improving macroscopic mechanical properties. This invention uses environmentally friendly vegetable oil derivatives or their modified forms containing polyepoxy groups as crosslinking lead agents containing polyepoxy groups. While replenishing the missing lightweight components in aged asphalt and reducing the system viscosity, the epoxy groups actively anchor the polar defects generated at the broken ends of aged SBS chains. Subsequently, a dynamic crosslinking agent containing disulfide bonds is introduced, and the broken short chains of SBS polymer are rebridged through ring-opening esterification reactions between the terminal carboxyl groups and the residual epoxy groups. This technical approach effectively avoids the compatibility barriers of traditional macromolecular heterogeneous blending, truly restoring the elastic crosslinking network of SBS at the molecular scale, and significantly improving the macroscopic mechanical properties of recycled asphalt.

[0024] 2. This invention constructs a dual-dynamic covalent network and endows it with self-healing capabilities. This invention overcomes the performance bottleneck by constructing a dual-dynamic covalent network containing β-hydroxy ester bonds and disulfide bonds. During high-temperature stirring at 170℃~180℃, the transesterification catalyst induces chemical rearrangement of the network, releasing the network lock caused by thermosetting crosslinking, thus endowing it with excellent flowability and workability. During service at room temperature and low temperatures, the reversible cleavage and coupling mechanism of the dynamic disulfide bonds enables microscopic damage to spontaneously close, actively delaying secondary aging without the need for external traditional antioxidants, significantly extending the entire lifespan of the pavement, and making it suitable for road engineering applications.

[0025] 3. This invention employs a simplified, step-by-step process to improve engineering adaptability and economic efficiency. It utilizes a reaction strategy that introduces a crosslinking lead agent containing polyepoxy groups and a dynamic crosslinking agent containing disulfide bonds in stages. The initial lead agent's penetration and softening effect reduces system resistance, avoiding problems such as excessively rapid local crosslinking and uneven dispersion caused by the simultaneous addition of multiple components. The entire chemical reconstruction process can be spontaneously completed under the heating and stirring conditions of conventional asphalt plant hot-mix recycling, eliminating the need for complex equipment such as high-energy-consuming ultrasonic generators and plasma pretreatment. The simplified process and low equipment requirements not only reduce the overall cost of recycled asphalt preparation but also demonstrate high feasibility for industrial-scale promotion. Attached Figure Description

[0026] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the experimental examples, embodiments, and comparative examples of the invention to explain the invention, but do not constitute a limitation thereof.

[0027] Figure 1 The diagram shows the characteristic curves of the phase angle of the recycled SBS modified asphalt in Examples 1-6 of this invention, the modified asphalt in Comparative Examples 1-3, the SBS modified asphalt, and the aged SBS modified asphalt as a function of temperature. Detailed Implementation

[0028] To make the objectives, technical solutions, and significant advantages of this invention clearer and more explicit, the following will provide a detailed description of non-limiting examples of this invention in conjunction with specific embodiments. It should be understood that the embodiments described herein are merely a part of specific embodiments of this invention, intended to provide sufficient technical guidance to those skilled in the art, and are not intended to exhaustively describe or mechanically limit the scope of protection of this invention. Unless otherwise expressly defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0029] It should be noted that, unless otherwise explicitly exclusive, singular terms in this specification also have plural meanings, and terms such as "comprising" and "including" represent non-closed statements; any specific numerical range mentioned herein explicitly covers all real numbers, endpoint values, and any possible nested subranges within that range; furthermore, for all chemical components involved in this invention, unless specifically emphasized in terms of spatial configuration or purity limits, they are broadly understood to cover isomers, conventional industrial-grade raw materials, or functional equivalents that can achieve the same technical effect.

[0030] The specific implementation methods and test parameters listed below are only for verifying the feasibility and superiority of the technical approach of this invention. Based on the implementation methods of this invention, all other implementation methods obtained by those skilled in the art without inventive effort, as well as any conventional parameter fine-tuning, equivalent material substitution, or non-substantial process reorganization made without departing from the spirit and scope of this invention, are indisputably covered within the protection scope defined by the claims of this invention.

[0031] The “aged SBS modified asphalt” described in this invention refers to SBS modified asphalt that has undergone long-term service or artificial aging. Due to the coupled erosion of environmental factors such as heat, oxygen, and light, the internal polymer network degrades and the matrix asphalt components harden, resulting in a significant deterioration of macroscopic physical and mechanical properties, specifically manifested as a decrease in penetration, a decrease in ductility, and an increase in softening point.

[0032] The aged SBS modified asphalt used in this embodiment of the invention is prepared by the following method: (1) The pre-softened base asphalt was heated in an oil bath at 175°C until it was completely melted. Then, an intermittent high-speed shear emulsifier was started, and 4% of SBS modifier was slowly and uniformly added to the molten base asphalt at an initial speed of 1000 r / min. After the addition was completed, the shear rate was increased to 4000 r / min, and the blend system was continuously sheared at high speed for 1.5 h. After shearing, a paddle mixer was used to continue constant temperature stirring at a speed of 2000 r / min for 1.5 h to fully disperse and uniformly develop the modifier and base asphalt, and SBS modified asphalt was prepared (physical performance indicators are shown in Table 1). (2) The SBS modified asphalt obtained in step (1) is subjected to short-term aging in a rotating film aging chamber, wherein the aging temperature is 163℃ and the duration is 5h. (3) Accelerated SBS modified asphalt after short-term aging was tested in a pressure aging vessel. The aging temperature was 100℃, the pressure was 2.1MPa, and the duration was 20h. The aged SBS modified asphalt was obtained.

[0033] The base asphalt used in the above method was GS70# asphalt produced by Hunan Baoli Asphalt Co., Ltd., and the SBS modifier model was YH-791H, which was purchased from Yueyang Baling Petrochemical Co., Ltd. The ductility of the aged SBS modified asphalt at 5℃ was 0.7cm (see Table 1).

[0034] The 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) used in this invention is an organic strong base catalyst with CAS Registry No. 5807-14-7 and molecular formula C7H 13 N3.

[0035] The 4,4'-dithiodibutyric acid used in this invention is an organosulfur compound containing a disulfide bond, with CAS number 2906-60-7 and molecular formula: C8H. 14 O4S2.

[0036] Example 1 This embodiment describes a recycled SBS-modified asphalt based on a targeted dual dynamic covalent network, wherein: The added weight parts of aged SBS modified asphalt, epoxidized soybean oil, 4,4'-dithiodibutyric acid and 1,5,7-triazabicyclo[4.4.0]dec-5-ene were 100 parts, 8 parts, 4 parts and 0.374 parts, respectively, that is, the mass ratio of epoxidized soybean oil to 4,4'-dithiodibutyric acid was 2:1; wherein, the molar number of 1,5,7-triazabicyclo[4.4.0]dec-5-ene was 8% of the total molar number of carboxyl groups in 4,4'-dithiodibutyric acid; Epoxidized soybean oil is a light yellow oily liquid with an acid value of 0.3 mg KOH / g, an epoxy value ≥6%, an iodine value ≤6%, and a specific gravity (20 / 20℃) of 0.996. 4,4'-Dithiodibutyric acid is a white crystal with a melting point of 110.3℃, a purity of 99.5% by neutralization titration, and a purity of 99.6% by gas chromatography. 1,5,7-Triazabicyclo[4.4.0]dec-5-ene is a white crystal and crystalline powder. Its purity was determined to be 98.92% by HClO4 titration, and its structure met the requirements by nuclear magnetic resonance (NMR) detection.

[0037] The preparation steps in this embodiment are as follows: S1. Heat 100 parts of aged SBS modified bitumen to a molten state at 175℃, add 8 parts of epoxidized soybean oil and stir continuously for 5 minutes at a stirring speed of 200 r / min to obtain mixture 1; S2. Add 4 parts of 4,4'-dithiodibutyric acid to the mixture obtained in step S1, and continue stirring at 200 r / min for 5 min to obtain mixture 2; S3. Add 0.374 parts of 1,5,7-triazabicyclo[4.4.0]dec-5-ene to the mixture obtained in step S2, and then adjust the stirring speed to 1000 r / min and continue stirring for 20 min to obtain the recycled SBS modified bitumen based on the targeted dual dynamic covalent network.

[0038] Example 2 This embodiment describes a recycled SBS-modified asphalt based on a targeted dual dynamic covalent network, wherein: Compared with Example 1, the weight parts of 1,5,7-triazabicyclo[4.4.0]dec-5-ene added were changed, and 0.374 parts in Example 1 were replaced with 0.420 parts, that is, the molar number of 1,5,7-triazabicyclo[4.4.0]dec-5-ene was 9% of the total molar number of 4,4'-dithiodibutyric acid carboxyl groups. All other materials and processes were kept the same as in Example 1.

[0039] Example 3 This embodiment describes a recycled SBS-modified asphalt based on a targeted dual dynamic covalent network, wherein: Compared with Example 1, the weight parts of 1,5,7-triazabicyclo[4.4.0]dec-5-ene added were changed, and 0.374 parts in Example 1 were replaced with 0.467 parts, that is, the molar number of 1,5,7-triazabicyclo[4.4.0]dec-5-ene was 10% of the total molar number of 4,4'-dithiodibutyric acid carboxyl groups. All other materials and processes were kept the same as in Example 1.

[0040] Example 4 This embodiment describes a recycled SBS-modified asphalt based on a targeted dual dynamic covalent network, wherein: Compared with Example 1, the weight parts of 1,5,7-triazabicyclo[4.4.0]dec-5-ene added were changed, and the 0.374 parts in Example 1 were replaced with 0.514 parts, that is, the molar number of 1,5,7-triazabicyclo[4.4.0]dec-5-ene was 11% of the total molar number of 4,4'-dithiodibutyric acid carboxyl groups. All other materials and processes were kept the same as in Example 1.

[0041] Example 5 This embodiment describes a recycled SBS-modified asphalt based on a targeted dual dynamic covalent network, wherein: Compared with Example 1, the weight parts of 1,5,7-triazabicyclo[4.4.0]dec-5-ene added were changed, and 0.374 parts in Example 1 were replaced with 0.561 parts, that is, the molar number of 1,5,7-triazabicyclo[4.4.0]dec-5-ene was 12% of the total molar number of 4,4'-dithiodibutyric acid carboxyl groups. All other materials and processes were kept the same as in Example 1.

[0042] Example 6 This embodiment describes a recycled SBS-modified asphalt based on a targeted dual dynamic covalent network, wherein: Compared with Example 1, 1,5,7-triazabicyclo[4.4.0]dec-5-ene was not added, and all other materials and processes remained the same as in Example 1.

[0043] Comparative Example 1 For this proportion of recycled SBS modified bitumen, where: Compared with Example 1, the catalyst type and ratio were changed. 1,5,7-triazabicyclo[4.4.0]dec-5-ene in Example 1 was replaced with 0.884 parts of zinc acetylacetonate, that is, the molar number of zinc acetylacetonate was 10% of the total molar number of carboxyl groups of 4,4'-dithiodibutyric acid. The zinc acetylacetonate was a white powder solid with a purity of 98.107%, of which the zinc content was 24.828%. The infrared spectroscopy results were consistent with its chemical structure.

[0044] Comparative Example 2 For this proportion of recycled SBS modified bitumen, where: Compared with Example 1, the preparation process was changed, and the original stepwise addition of materials was changed to the addition of pre-prepared prepolymer, and the addition weight parts were 4 parts.

[0045] The method for preparing the prepolymer is as follows: S1. Place 50 parts of epoxidized soybean oil in a reaction vessel, heat to 80℃ and turn on magnetic stirring, controlling the speed at 300 r / min and continuing to heat for 5 min until it reaches a uniform flow state. Then, add 12.21 parts of 4,4'-dithiodibutyric acid, i.e., the molar ratio of the carboxyl group in 4,4'-dithiodibutyric acid to the epoxy group in epoxidized soybean oil is 1:2, and adjust the stirring speed to 500 r / min and continue stirring for 20 min to obtain a mixture; S2. Add 0.71 parts of 1,5,7-triazabicyclo[4.4.0]dec-5-ene to the mixture obtained in step S1. That is, the molar number of 1,5,7-triazabicyclo[4.4.0]dec-5-ene added is 5% of the molar number of carboxyl groups contained in the 4,4'-dithiodibutyric acid added in step S1. Maintain the stirring speed at 500 r / min and continue the reaction at the same temperature for 1 h. After the system has reacted completely, the prepolymer is obtained.

[0046] Comparative Example 3 For this proportion of recycled SBS modified bitumen, where: Compared with Example 1, the preparation process was changed, and the original stepwise addition of materials was adjusted to the addition of a pre-prepolymer, with the addition weight parts being 6 parts. The preparation method of the prepolymer is the same as that of Comparative Example 2.

[0047] Results and Discussion: To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples, and a recycling effect evaluation test will be conducted. The test results are shown in Table 1 below. The recycling effect evaluation test was conducted in accordance with the relevant requirements of the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG 3410-2025). Figure 1 The figures show characteristic curves of the phase angle of the recycled bitumen in each experimental group as a function of temperature. The phase angle plateau region is an important indicator of the integrity of the SBS polymer network. The curves of the aging group show a monotonically increasing trend in the high-temperature region, indicating that the original network structure has been severely disintegrated.

[0048] It should be noted that, as is known to those skilled in the art, the various physical and rheological properties of SBS-modified asphalt are highly dependent on the origin of the crude oil, the compositional characteristics, and the modification process of the base asphalt. In the test system of this invention, to fully verify the process adaptability of this invention, no sulfur powder or other long-lasting crosslinking agents were added to the SBS-modified asphalt during preparation. Due to these basic limitations, the basic absolute values ​​of penetration and ductility of the SBS-modified asphalt measured in the experiment did not meet the requirements of the relevant specifications (ID class). Accordingly, after deep aging, the residual performance benchmark of this system is also objectively limited by the initial low values.

[0049] Given the fundamental numerical differences arising from the different sources of matrix asphalt and the preparation processes mentioned above, comparing only absolute values ​​is insufficient to comprehensively and objectively reveal the contribution of the regeneration system of this invention to the repair of damaged structures. Therefore, this invention introduces "ductility recovery rate" as a core indicator for evaluating the performance repair and network reconstruction effects of aged asphalt. This indicator is calculated as follows: the ductility value of the regenerated asphalt prepared after incorporating each regeneration component of this invention is divided by the ductility benchmark value of undisturbed (unaged) SBS modified asphalt under the same formulation (i.e., ductility recovery rate = (ductility after regeneration / ductility of undisturbed asphalt) × 100%).

[0050] Table 1: Physical property indicators of recycled asphalt in each experimental group

[0051] The experimental results of this invention are as follows: (1) The step-by-step feeding in-situ reconstruction process has achieved significant recovery and effective reconstruction of the macroscopic performance indicators of aged SBS modified asphalt.

[0052] The experimental results show that aged SBS modified asphalt exhibits significant hard and brittle characteristics due to severe loss of lightweight components and SBS network collapse (softening point 62.6℃, penetration 25.7 dmm, ductility at 5℃ 0.7 cm). However, after introducing epoxidized soybean oil, 4,4'-dithiodibutyric acid, and 1,5,7-triazabicyclo[4.4.0]dec-5-ene in stages using the process of this invention, the penetration of all embodiments recovered to 53.4~77.2 dmm, the softening point dropped to 49.9~55.0℃, and the ductility at 5℃ significantly increased to 12.4~18.3 cm. This indicates that the staged addition process not only improves the hard and brittle characteristics of the material through in-situ penetration of lightweight components, but also achieves effective reconstruction of macroscopic mechanical properties through deep chemical action. Compared with the extreme hard and brittle aging state, this process demonstrates excellent performance reversal and structural repair capabilities.

[0053] (2) Temperature scanning phase angle platform characteristics confirm that the system of the present invention has the ability to construct a high-strength dynamic covalent network.

[0054] Within the characteristic temperature range of 40℃ to 60℃, the group represented by Example 3 exhibited a highly gradual and distinctive phase angle plateau region. This rheological evidence is highly correlated with macroscopic data: while Example 3 showed a significant increase in penetration, its softening point remained at a relatively high level of 53.4℃. This demonstrates that under specific catalytic conditions, the precursor underwent a significant in-situ crosslinking reaction, forming a dynamic covalent network with a high crosslinking density. This enabled crosslinking healing of aging and fractured SBS segments, providing strong support for the material's rutting resistance at the microstructural level.

[0055] (3) The gradient distribution of performance data demonstrates the advantages of the present invention in targeted regulation for different engineering scenarios.

[0056] The data evolution within the example groups fully demonstrates the flexible controllability of this invention between deep structural repair and physical plasticization compensation. The 5°C ductility (12.4 cm) of Example 3 reflects the effective anchoring of molecular chain slippage by the high cross-linking density network, representing a typical solution focusing on excellent high-temperature stability, suitable for heavy-duty traffic environments. Meanwhile, the group represented by Example 5, through moderate control of network cross-linking density, synergistically leverages the physical plasticizing and lubricating effects of some free lightweight components. This organic combination of chemical cross-linking and physical plasticization endows the material with superior low-temperature tensile ductility, forming a good performance complement to Example 3, making it particularly suitable for engineering scenarios requiring extreme cold resistance and crack resistance.

[0057] (4) The coupling of the catalytic system and the feeding process is the key to breaking through the performance bottleneck of traditional regeneration schemes.

[0058] Comparative Example 1 (1,5,7-triazabicyclo[4.4.0]dec-5-ene replaced with zinc acetylacetonate) had a ductility of only 9.0 cm and lacked a clear plateau characteristic in its DSR phase angle curve, proving that conventional metal salt catalysts are difficult to effectively stimulate deep crosslinking of the system under the same conditions. Meanwhile, the penetration (36.2~40.0 dmm) and ductility (8.1~11.5 cm) of Comparative Examples 2~3 (with added prepolymer) were significantly limited in their recovery, and their softening point remained above 57℃. This strongly demonstrates the technical advantages of the process of this invention, namely, that stepwise feeding allows the small molecule precursor to fully penetrate into the intermolecule gaps of the asphalt in advance and achieve in-situ molecular-level growth within the matrix, effectively overcoming the compatibility barrier between the prepolymer and the asphalt matrix.

[0059] In summary, the regenerated SBS modified asphalt system based on a targeted dual dynamic covalent network proposed in this invention effectively overcomes the limitations of traditional pure physical softening and heterogeneous blending, which are prone to segregation. This system achieves dual regeneration, from macroscopic improvement of processing rheology to in-situ repair of the microscopic macromolecular network, while also possessing excellent high-temperature thermoplastic flowability, low-temperature flexibility, and microcrack self-healing ability. It has low overall preparation cost and strong engineering adaptability, demonstrating good economic feasibility and practical application value.

[0060] The present invention has been described in detail above with reference to specific embodiments. However, these embodiments are merely representative examples to help understand the core idea of ​​the present invention and are by no means mechanical limitations on the scope of protection of the present invention. Furthermore, without departing from the overall technical concept of the present invention, various embodiments and technical features disclosed herein can be reasonably combined in any way, and should also be considered as explicitly disclosed in this specification. For those skilled in the art, any equivalent substitution, simple modification, or improvement of the technical solution without departing from the principles and technical essence of the present invention, as long as no creative effort is required, should be indisputably covered within the scope of protection of the claims of the present invention.

Claims

1. A recycled SBS-modified asphalt based on a targeted dual-dynamic covalent network, characterized in that, The raw materials, by weight, include: 100 parts of aged SBS modified bitumen, 5-15 parts of epoxidized soybean oil, 2.5-7.5 parts of 4,4'-dithiodibutyric acid, and 0.146-1.051 parts of 1,5,7-triazabicyclo[4.4.0]dec-5-ene; the mass ratio of the epoxidized soybean oil to the 4,4'-dithiodibutyric acid is 1-5:

1. The recycled SBS modified bitumen based on the targeted dual dynamic covalent network is obtained by adding epoxidized soybean oil, 4,4'-dithiodibutyric acid and 1,5,7-triazabicyclo[4.4.0]dec-5-ene sequentially to aged SBS modified bitumen in a molten state under stirring conditions.

2. The recycled SBS modified bitumen based on a targeted dual dynamic covalent network according to claim 1, characterized in that, The aged SBS modified asphalt is selected from any one or a mixture of thin film oven aged asphalt, rotary thin film oven aged asphalt, ultraviolet aged asphalt, pressure aged asphalt, and waste extraction aged asphalt.

3. A method for preparing recycled SBS modified bitumen based on a targeted dual dynamic covalent network as described in any one of claims 1 to 2, characterized in that, Includes the following steps: S1. Heat aged SBS modified asphalt to a molten state, add epoxidized soybean oil under stirring conditions and continue stirring to obtain mixture 1; S2. Add 4,4'-dithiodibutyric acid to mixture 1 obtained in step S1 and continue stirring to obtain mixture 2; S3. Add 1,5,7-triazabicyclo[4.4.0]dec-5-ene to mixture 2 obtained in step S2, and then continue stirring to obtain recycled SBS modified bitumen based on a targeted dual dynamic covalent network.

4. The preparation method according to claim 3, characterized in that, In step S1, the heating temperature of the aged SBS modified asphalt is 170~180℃, and the heating time is 5~15min.

5. The preparation method according to claim 3, characterized in that, In steps S1 to S3, the stirring speed is 200 to 1000 r / min, and the stirring time is 20 to 40 min.

Images