Preparation method of high-durability high-modulus modified asphalt

Abstract

The invention discloses a preparation method of high-durability high-modulus modified asphalt. The preparation method comprises the following steps: (1) pre-emulsification: mixing a monomer system with an emulsification system; (2) seed polymerization and core-shell structure construction; and (3) chemical functionalization modification: adding 3-5 parts of epichlorohydrin and 0.1-0.2 part of tetramethylethylenediamine into the product, reacting for 4 hours at 70 + / -1 DEG C under the protection of nitrogen, and controlling the gel content to be less than or equal to 8%. Carboxyl introduced by methacrylic acid and polar groups in asphalt form chemical bonding, epoxy group crosslinking enhances the interface bonding force between latex and asphalt, and the water sensitivity is remarkably reduced; the performance of the latex can be adjusted according to the requirements of different climate zones through particle size grading and reaction parameter regulation and control, and the adaptability is wider.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of modified asphalt, in particular to a preparation method of high-durability high-modulus modified asphalt. BACKGROUND

[0002] With the increasing traffic volume and traffic load, rutting disease becomes the main object of asphalt pavement maintenance. In this regard, high modulus asphalt mixture has better rutting resistance due to its high dynamic modulus, so that practitioners consider using such asphalt when dealing with road rutting problems.

[0003] High modulus asphalt modification technology, as a core means to improve the rutting resistance of asphalt pavement, significantly improves the dynamic modulus of asphalt mixture by introducing high modulus modifier (such as hard asphalt, polymer, mineral filler or composite modifier), thereby showing excellent anti-deformation ability under high temperature and heavy load conditions.

[0004] However, the existing high modulus modified asphalt system faces significant durability bottlenecks in practical application: first, the addition of high modulus modifier improves the stiffness of the material, but often leads to imbalance of asphalt cement viscoelasticity, resulting in decreased low temperature crack resistance and deteriorated fatigue performance, and micro-cracks are easily generated and the structure is accelerated under the action of vehicle load and temperature cycle; second, the high dynamic modulus of high modulus asphalt mixture increases the compatibility of the modifier and the asphalt interface, and if the modifier and the asphalt matrix are not uniformly dispersed or there is weak interface bonding, the water sensitivity and aging process of the mixture will be aggravated; third, the existing process relies on high temperature mixing to improve the melting and dispersion effect of high modulus components, but high temperature environment may cause volatilization of light components of asphalt and thermal degradation of modifier, further weakening the durability of the material.

[0005] Therefore, how to maintain a high value of the dynamic modulus of high modulus modified asphalt while optimizing the compatibility of the modifier, the interface enhancement and the process control, and how to synergistically improve the fatigue resistance, aging resistance and water damage resistance have become a key challenge to break through the bottleneck of high modulus asphalt technology and prolong the service life of the pavement. SUMMARY

[0006] In view of the defects of the prior art, the purpose of the present application is to provide a preparation method of high-durability high-modulus modified asphalt to solve the problems raised in the background art.

[0007] The technical problem solved by the present application adopts the following technical solution: The present application provides a preparation method of high-durability high-modulus modified asphalt, comprising the following steps: (1) Pre-emulsification: mixing monomer system and emulsification system; (2) Seed polymerization and core-shell structure construction; (3) Chemical functional modification: add 3-5 parts of epichlorohydrin and 0.1-0.2 parts of tetramethyl ethylenediamine to the above product, and react at 70±1°C for 4h under nitrogen protection, and control the gel content to be ≤8%; (4) Post-treatment and particle size classification: vacuum dewatering to moisture content ≤0.2%, add 0.7-0.9 parts of polyvinylpyrrolidone for homogenization treatment, and obtain 80nm main peak component and 200nm secondary peak component by centrifugal classification, and mix them in a volume ratio of 6-7:3-4 to obtain the target SBS latex; (5) Pretreatment of Trinidad Lake asphalt; (6) Add SBS latex to step (5), and the SBS latex accounts for 3-5% of the total mass of the asphalt, and homogenize and stir at 150-160°C for 1h; develop the product in an oven at 140-150°C for 45min to obtain high-durability high-modulus modified asphalt.

[0008] Preferably, the monomer system contains styrene 45-55 parts, butadiene 35-45 parts, and methacrylic acid 1.5-2.5 parts by mass; The emulsifying system contains sodium dodecyl sulfate 1-1.5 parts, nonylphenol polyoxyethylene ether 0.4-0.8 parts, and cetyltrimethylammonium bromide 0.3-0.7 parts by mass; add deionized water with a total water content of 60%, and form a pre-emulsion with a particle size of 80-120nm by high-pressure homogenization.

[0009] Preferably, the high-pressure homogenization conditions are 20MPa pressure for 3 cycles, and the stirring rates in step (2) are 300rpm (seed stage) and 600rpm (dropping stage), respectively.

[0010] Preferably, in step (2), inject the remaining 40% deionized water into the reaction kettle, heat to 60°C, then add 10% pre-emulsion and initiator system, the initiator system contains 0.1% ammonium persulfate and 0.05% sodium bisulfite (relative to the total mass of the pre-emulsion), and the reaction generates seed particles with a particle size of 50-70nm; then drop the remaining pre-emulsion at a rate of 1.8mL / min, simultaneously heat to 80°C, and add the initiator in 5 portions, and form a rigid core (styrene accounts for 60%) -elastic shell (butadiene accounts for 55%) structure after reaction.

[0011] Preferably, in step (4), the centrifugal conditions for particle size classification are: the main peak component is collected by centrifugation at 3000rpm for 20min, and the secondary peak component is collected by centrifugation at 8000rpm for 30min.

[0012] Preferably, the specific steps for the pretreatment of Lake Trinidad asphalt are as follows: first, the Lake Trinidad asphalt is pre-ground to 500-800 mesh, and mixed with No. 70 base asphalt at a mass ratio of 30-40:60-70, and preheated and premixed at 150-160℃ for 1.5h; the mixture is sheared at 170-185℃ at 4000-5000r / min for 60-70min, and after cooling to 160-165℃, it is sheared again at 2000-3000r / min for 30-40min.

[0013] Preferably, in step (3), when the SBS latex solid content is 50%, the homogenization stirring time is 55-65 min.

[0014] Preparation process of special SBS latex: By optimizing monomer ratios, constructing core-shell structures, introducing functionalization modifications, and controlling particle size distribution, SBS latex with both rigidity and elasticity was prepared. The specific steps are as follows: Pre-emulsification stage: Styrene (rigid segment), butadiene (flexible segment), and methacrylic acid (carboxyl functionalized monomer) are mixed in proportion and homogenized with composite emulsifiers (sodium dodecyl sulfate, OP-10, and hexadecyltrimethylammonium bromide) in deionized water to form a stable pre-emulsion; Core-shell structure construction: A rigid core enriched with styrene is first formed through seed polymerization, and then an elastic shell enriched with butadiene is formed by adding monomers dropwise, balancing strength and ductility; Functionalization modification: In-situ crosslinking with epichlorohydrin is used to introduce epoxy groups to improve anti-aging properties, while controlling the gel content to avoid embrittlement; Particle size classification: The latex with a bimodal distribution of 80nm (filling micropores) and 200nm (bridging cracks) is obtained by centrifugation. After being mixed in proportion, it enhances the density and stress dissipation capacity of asphalt.

[0015] Preparation process of high-durability, high-modulus modified asphalt: Natural asphalt (Trinidad Lake asphalt) is used to provide the basic modulus, and the above-mentioned SBS latex is combined to improve toughness. The steps are as follows: Natural asphalt and base asphalt are pretreated and then fused by high-speed shearing to form a rigid matrix. By adding special SBS latex for secondary shearing, a "rigid skeleton-elastic network" composite structure is constructed through chemical bonding (reaction of carboxyl groups with active groups of asphalt) and physical filling of the latex and asphalt; low-temperature development eliminates air bubbles and ensures the uniformity and stability of the modified system.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes the composite effect of core-shell structured SBS latex and natural asphalt to modify the asphalt to achieve a dynamic modulus ≥14000MPa (meeting high modulus requirements), while maintaining a low-temperature flexural failure strain ≥3100με and a fatigue life ≥1.5 million cycles (more than 50% higher than traditional high modulus asphalt). Interfacial compatibility is optimized: the carboxyl groups introduced by methacrylic acid form chemical bonds with the polar groups in the asphalt, and the epoxy cross-linking enhances the interfacial bonding between the latex and asphalt, significantly reducing water sensitivity. The process is highly controllable: through particle size classification and reaction parameter adjustment, the latex properties can be adjusted according to the needs of different climate zones, resulting in wider adaptability. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to specific examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] In this embodiment, an SBS latex preparation process is described, comprising, by weight, 94-97 parts monomer system, 1.7-3 parts emulsification system, and 0.2-0.4 parts other additives.

[0019] Monomer system: Styrene (St, industrial grade, purity ≥99.5%) rigid segments are used to improve crack resistance; butadiene (Bd, polymer grade, purity ≥99.8%) flexible segments are used to impart elasticity and fatigue resistance; methacrylic acid (MAA, chemically pure, containing polymerization inhibitor) carboxyl functionalized monomers are used to enhance chemical bonding with asphalt.

[0020] Emulsification system: Sodium dodecyl sulfate (SDS, anionic, purity ≥95%) is used as the main emulsifier, and nonylphenol polyoxyethylene ether stabilized micelles (OP-10, nonionic, HLB=13.3) is used for synergistic emulsification to reduce interfacial tension; hexadecyltrimethylammonium bromide (CTAB, cationic, purity ≥98%) is used as a co-emulsifier to enhance the adhesion between latex and aggregate.

[0021] Other additives include, but are not limited to, ammonium persulfate (APS, initiator, purity ≥98%) oxidant, used for low-temperature initiation of polymerization; sodium bisulfite (SHS, reducing agent, purity ≥95%), which forms a redox system with APS to control the reaction rate; and dodecyl mercaptan (DDM, chain transfer agent, purity ≥90%) to regulate molecular weight (target Mn = 80,000-120,000), used to balance strength and ductility.

[0022] The specific preparation includes the following steps: A. Pre-emulsification stage of monomer system, seed generation and core-shell structure construction, and precise control of solid content.

[0023] B. Chemical functionalization modification, mainly in-situ crosslinking of epoxy groups for synergistic optimization of anti-aging and anti-fatigue.

[0024] C. Post-treatment and particle size classification include: dehydration and stabilization, and particle size classification (optimization of bimodal distribution). In a specific embodiment, a method for preparing SBS latex includes the following steps: St, Bd, and MAA monomers were mixed evenly in a mass ratio of 45-55:35-45:1.5-2.5, and then 60% of the total water volume was added with deionized water.

[0025] Add SDS, OP-10, and CTAB in a mass ratio of 1-1.5:0.4-0.8:0.3-0.7, and dissolve them in a high-pressure homogenizer at 45°C and 1000 rpm for 20 minutes.

[0026] The mixture was then homogenized by cycling it three times under a pressure of 20 MPa to form a pre-emulsion with a particle size of 80-120 nm.

[0027] The remaining 40% of deionized water was injected into the reactor and the temperature was raised to 60°C.

[0028] Add 10% pre-emulsion, APS (0.1%) and SHS (0.05%) to the reactor, stir at 300 rpm, and react for 80 min to generate seed particles with a particle size of 50-70 nm.

[0029] The remaining preemulsion was added dropwise at a rate of 1.8 mL / min, while the temperature was simultaneously raised to 80 °C. During the dropwise addition, APS (0.1%) and SHS (0.03%) were added in 5 separate additions, while maintaining a stirring rate of 600 rpm. After the dropwise addition was completed, the mixture was kept at this temperature for 2 hours to form a rigid core (St60%) - elastic shell (Bd55%) structure.

[0030] The amount of solids can be precisely controlled, but post-processing requirements must be considered.

[0031] The complete emulsion polymerization process is followed by targeted chemical functionalization modification.

[0032] Epichlorohydrin (ECH) was used for in-situ crosslinking of epoxy groups, and tetramethylethylenediamine (TEMED) was used as a catalyst to accelerate the crosslinking process. By weight, when the latex solid content was 100 parts, the composition was 4 parts epichlorohydrin and 0.2 parts tetramethylethylenediamine.

[0033] Specific operating procedure: Under nitrogen protection, the above SBS emulsion, epichlorohydrin and tetramethylethylenediamine are added to the reactor in sequence, and the reaction is continued for 4 hours at 70±1℃.

[0034] It is worth noting that after the reaction process is halfway complete, the gel content should be measured every 10 minutes using the swelling method, and the target value should be ≤8% to avoid embrittlement.

[0035] For complete and targeted chemical functionalization modification, final processing and particle size classification are then carried out.

[0036] The product was dehydrated under vacuum at 50°C and -0.09 MPa. The Karl Fischer method was used to determine the endpoint, and the moisture content was controlled to be ≤0.2%.

[0037] When the above product is recorded as 100 parts by mass, 0.8 parts of polyvinylpyrrolidone are added. The two are placed in a high-pressure homogenizer and homogenized at 500 rpm and 70°C for 45 minutes to finally obtain the target emulsion.

[0038] The target emulsion was fractionated by particle size, and the specific methods and performance contributions are shown in the table below.

[0039] Following the above processing method, two types of latex with different particle sizes were obtained. The main peak and secondary peak were then homogenized and mixed at a volume ratio of 6-7:3-4. The final SBS latex was then obtained.

[0040] The second aspect of the present invention provides a process for preparing high-durability, high-modulus modified asphalt, characterized in that, by weight, the asphalt portion comprises: 60-70 parts of base asphalt and 30-40 parts of natural asphalt. The SBS latex prepared in the above process accounts for 3-5% of the total asphalt mass.

[0041] The base asphalt is No. 70 asphalt, and the natural asphalt is selected from one or more of Trinidad Lake asphalt, Gilsonite from Utah, USA, and Swiss rock asphalt. However, Trinidad Lake asphalt is preferred.

[0042] The specific process for high-durability, high-modulus modified asphalt is as follows: The selected Trinidad Lake asphalt was pre-ground to 500-800 mesh using a ball mill, and then pre-mixed with No. 70 base asphalt in an oven at 150-160℃ for 1.5 hours. A high-speed shearing machine is used to shear for 60-70 minutes at an ambient temperature of 170-185℃ and a rotation speed of 4000-5000r / min. The shearing temperature and shearing time are dynamically adjusted according to the amount of natural asphalt added. Cool to 160-165℃ and shear at 2000-3000 r / min for 30-40 min to eliminate bubbles and stabilize the mixture; Add the SBS latex in the proportions described above to the sheared product, and homogenize and stir at 150-160°C for 1 hour. The stirring time is dynamically adjusted according to the solid content in the SBS latex. Preferably, when the solid content in the SBS latex is 50%, the stirring time is 55-65 minutes.

[0043] The above-mentioned shearing and mixing treatment of high-durability, high-modulus modified asphalt was completed. Then, the product was placed in an oven and developed at 140-150℃ for 45 minutes, thus completing the preparation of the high-durability, high-modulus modified asphalt described in this invention.

[0044] The main purpose of this invention is to prepare a high-durability, high-modulus modified asphalt. However, to determine whether it can solve the common rutting problem on roads and overcome the disadvantages of high-modulus asphalt mixtures in terms of crack resistance and fatigue resistance, it is ultimately necessary to test the mixture for dynamic stability (T0719), dynamic modulus test (EN12697-26), low-temperature bending failure strain (T0715), and fatigue life (EN12697-24).

[0045] For the selection of aggregates for the mixture, basalt is preferred, and the gradation adopts AC-16C, as shown in the table below: The oil-aggregate ratio is dynamically adjusted from 5.6% to 5.8%. The mixture is formed using rotary compaction, and the specimens are cut according to specifications based on the required test pieces.

[0046] Example 1: The preparation of high-durability SBS latex was completed according to the above. It is worth noting that for this example, the solid content of SBS latex was selected as 50%, and the volume ratio of the main peak to the secondary peak was selected as 0.65. The composite modification of No. 70 asphalt with high-durability SBS latex and Lake Trinidad asphalt was completed as described above. It is worth noting that in this example, every 100 parts of the mixture of No. 70 asphalt and lake asphalt contains 60 parts of No. 70 asphalt and 40 parts of lake asphalt, and the SBS latex accounts for 4% of the total mass of asphalt. The prepared modified asphalt is used as a binder to complete the mixing of aggregates, thereby forming a high-durability, high-modulus modified asphalt mixture.

[0047] Example 2: The high-durability SBS latex was prepared according to the above method. It is worth noting that for this example, the solid content of the SBS latex was selected as 60%, and the volume ratio of the main peak to the secondary peak was selected as 0.65. The composite modification of No. 70 asphalt with high-durability SBS latex and Trinidad Lake bitumen was completed as described above. It is worth noting that in this example, every 100 parts of the mixture of No. 70 asphalt and lake bitumen contains 65 parts of No. 70 asphalt and 35 parts of lake bitumen, and the SBS latex accounts for 4% of the total mass of the asphalt. The prepared modified asphalt is used as a binder to complete the mixing of aggregates, thereby forming a high-durability, high-modulus modified asphalt mixture.

[0048] Example 3: The preparation of high-durability SBS latex was completed according to the above. It is worth noting that for this example, the solid content of SBS latex was selected as 50%, and the volume ratio of the main peak to the secondary peak was selected as 0.7. The composite modification of No. 70 asphalt with high-durability SBS latex and Trinidad Lake bitumen was completed as described above. It is worth noting that in this example, every 100 parts of the mixture of No. 70 asphalt and lake bitumen contains 55 parts of No. 70 asphalt and 45 parts of lake bitumen, and the SBS latex accounts for 4% of the total mass of the asphalt. The prepared modified asphalt is used as a binder to complete the mixing of aggregates, thereby forming a high-durability, high-modulus modified asphalt mixture.

[0049] Example 4: The preparation of high-durability SBS latex was completed according to the above. It is worth noting that for this example, the solid content of SBS latex was selected as 50%, and the volume ratio of the main peak to the secondary peak was selected as 0.65. The composite modification of No. 70 asphalt with high-durability SBS latex and Trinidad Lake bitumen was completed as described above. It is worth noting that in this example, every 100 parts of the mixture of No. 70 asphalt and lake bitumen contains 60 parts of No. 70 asphalt and 40 parts of lake bitumen, and the SBS latex accounts for 5% of the total mass of the asphalt. The prepared modified asphalt is used as a binder to complete the mixing of aggregates, thereby forming a high-durability, high-modulus modified asphalt mixture.

[0050] Comparative Example 1: SBS latex was removed, and only the homogeneous fusion of natural asphalt and No. 70 asphalt was completed.

[0051] It is worth noting that for this ratio, every 100 parts of the mixture of No. 70 bitumen and lake bitumen contains 60 parts of No. 70 bitumen and 40 parts of lake bitumen.

[0052] The prepared modified asphalt is used as a binder to complete the mixing of aggregates, thereby forming a high-durability, high-modulus modified asphalt mixture.

[0053] The four types of tests described above were performed on Examples 1-4 and Comparative Example 1. The specific test results are shown in the table below: Analysis of the data in the table above reveals that the addition of SBS latex effectively compensates for the inherent disadvantages of high-modulus modified asphalt in low-temperature crack resistance and fatigue life.

[0054] In addition, within a certain range, appropriately increasing the solid content and particle size distribution of SBS latex can more significantly improve the low-temperature and fatigue performance of this type of mixture.

[0055] When the solid content and particle size distribution of SBS latex are determined, increasing the proportion of SBS latex to asphalt mixture can also improve the low-temperature and fatigue performance of this type of mixture. This also proves that the composite modification of No. 70 asphalt by SBS latex and natural asphalt is successful and can effectively solve the shortcomings of current high modulus asphalt mixtures.

[0056] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0057] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing high-durability, high-modulus modified asphalt, characterized in that, Includes the following steps: (1) Pre-emulsification: Mixing the monomer system with the emulsion system; (2) Seed aggregation and core-shell structure construction; (3) Chemical functionalization modification: Add 3-5 parts of epichlorohydrin and 0.1-0.2 parts of tetramethylethylenediamine to the above product, react at 70±1℃ for 4h under nitrogen protection, and control the gel content ≤8%; (4) Post-treatment and particle size classification: Vacuum dehydration to moisture content ≤0.2%, add 0.7-0.9 parts of polyvinylpyrrolidone for homogenization, obtain the 80nm main peak component and the 200nm secondary peak component by centrifugation and classification, mix them in a volume ratio of 6-7:3-4 to obtain the target SBS latex. (5) Pre-treat the asphalt from Lake Trinidad; (6) Add SBS latex to step (5), wherein the SBS latex accounts for 3-5% of the total mass of asphalt, and stir homogenously at 150-160℃ for 1 hour; then let the product mature in an oven at 140-150℃ for 45 minutes to obtain high-durability high-modulus modified asphalt.

2. The method for preparing high-durability, high-modulus modified asphalt according to claim 1, characterized in that, The monomer system contains, by weight, 45-55 parts styrene, 35-45 parts butadiene, and 1.5-2.5 parts methacrylic acid.

3. The method for preparing high-durability, high-modulus modified asphalt according to claim 2, characterized in that, The emulsion system comprises, by weight, 1-1.5 parts sodium dodecyl sulfate, 0.4-0.8 parts nonylphenol polyoxyethylene ether, and 0.3-0.7 parts hexadecyltrimethylammonium bromide; 60% of the total water volume is added with deionized water, and the mixture is subjected to high-pressure homogenization to form a pre-emulsion with a particle size of 80-120 nm.

4. The method for preparing high-durability, high-modulus modified asphalt according to claim 3, characterized in that, The high-pressure homogenization conditions are 3 cycles at 20MPa pressure, and the stirring rates in step (2) are 300rpm (seed stage) and 600rpm (dropping stage).

5. The method for preparing high-durability, high-modulus modified asphalt according to claim 1, characterized in that, In step (2), the remaining 40% deionized water is injected into the reactor, and after heating to 60°C, 10% pre-emulsion and initiation system are added. The initiation system contains 0.1% ammonium persulfate and 0.05% sodium bisulfite (relative to the total mass of the pre-emulsion). The reaction generates seed particles of 50-70 nm. Then, the remaining pre-emulsion is added dropwise at a rate of 1.8 mL / min, and the temperature is simultaneously raised to 80°C. The initiator is added in 5 portions. After the reaction, a rigid core (60% styrene) - elastic shell (55% butadiene) structure is formed.

6. The method for preparing high-durability, high-modulus modified asphalt according to claim 1, characterized in that, The centrifugation conditions for particle size fractionation in step (4) are as follows: the main peak component is centrifuged at 3000 rpm for 20 min and the supernatant is collected; the secondary peak component is centrifuged at 8000 rpm for 30 min and the lower precipitate is collected and reconstituted.

7. The method for preparing high-durability, high-modulus modified asphalt according to claim 1, characterized in that, The specific steps for the pretreatment of Lake Trinidad asphalt are as follows: First, the Lake Trinidad asphalt is pre-ground to 500-800 mesh and mixed with No. 70 base asphalt at a mass ratio of 30-40:60-70. The mixture is preheated and premixed at 150-160℃ for 1.5 hours. The mixture is then sheared at 170-185℃ at 4000-5000 r / min for 60-70 minutes. After cooling to 160-165℃, it is sheared again at 2000-3000 r / min for 30-40 minutes.

8. The method for preparing high-durability, high-modulus modified asphalt according to claim 1, characterized in that, In step (3), when the solid content of SBS latex is 50%, the homogenization stirring time is 55-65 min.

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