Preparation method of rubber asphalt material with self-recovery performance

Abstract

The present invention discloses a method for preparing a self-recovering rubber asphalt material. The specific preparation process comprises: thoroughly blending rubber powder, a microwave activator, a composite additive, a promoter, a microwave absorber, and a light oil component to produce a uniform rubber particle mixture S; and thoroughly fusing the rubber particle mixture S with matrix asphalt in a shearing apparatus to produce the rubber asphalt. After aging the rubber asphalt, it is placed in a microwave apparatus for microwave heating to produce the self-recovering rubber asphalt. This regenerated rubber asphalt not only forms a stable interconnected network structure, improving the rubber asphalt's crack resistance and enhancing the stability of its mechanical properties, but also significantly improves the rubber asphalt's adhesion and resistance to water damage.

Description

Technical Field

[0001] The invention belongs to the technical field of modified asphalt for road engineering, and in particular relates to a method for preparing a rubber asphalt material with self-recovering properties. Background Art

[0002] Asphalt is a polymer composite material. During pavement use, it is easily affected by external factors such as light, heat, oxygen, moisture, and traffic loads. These factors can cause a series of changes in the asphalt, such as volatilization, oxidation, decomposition, polymerization, and other physical and chemical reactions of the asphalt components. These reactions can cause changes in the internal structure and chemical composition of the asphalt, thereby reducing the asphalt's road performance, which is known as asphalt aging. When rubber asphalt ages, its low-temperature crack resistance and fatigue resistance are significantly reduced. Due to the high viscosity of rubber asphalt, its thermal regeneration process is relatively complex, and it is difficult to restore the performance of rubber asphalt simply through physical reactions such as heating and softening. Therefore, how to prepare rubber asphalt with self-recovering properties has become a key technology that needs to be urgently addressed.

[0003] Rubber particles have both physical and chemical effects on asphalt, significantly impacting its high-temperature and low-temperature properties, as well as its elastic recovery. The complex reaction mechanism between rubber particles and asphalt, coupled with ongoing physical and chemical reactions during the preparation of rubber asphalt, leads to moderate oxidative depolymerization of the rubber's spatial network macromolecules under high temperatures, transforming into numerous small network fragments and a small amount of chain-like structures. This imparts some plasticity and viscosity, but also results in a loss of some of the rubber's original elasticity. Existing research indicates that to address the aging resistance of rubber asphalt, domestic and international researchers have primarily optimized the properties of crumb rubber asphalt by adding various modifiers, resulting in improved aging resistance and road performance. For example, additives such as anti-aging agents, montmorillonite, layered silicates, and inorganic nanoparticles have been used as modifiers to significantly improve its resistance to thermal oxidative aging and UV oxidation. While these modifiers can extend the service life of rubber asphalt, they do not fundamentally address the technical challenges of self-recovery. Therefore, the development of a rubber asphalt material capable of self-recovery is crucial. Summary of the Invention

[0004] In order to improve the performance of aged rubber asphalt during use, the present invention provides a method for preparing a rubber asphalt material with self-recovering properties. This method can form a strong chemical connection between the rubber molecular structure and the asphalt in the aged rubber asphalt, and form a three-dimensional network reinforcement structure inside the rubber particle modified asphalt, thereby improving the mechanical properties of the aged rubber asphalt.

[0005] The present invention adopts the following technical solution to solve the above technical problems, namely, a method for preparing a rubber asphalt material with self-recovering performance, characterized by the following specific steps:

[0006] Step S1: placing 10 to 25 parts by weight of rubber powder, 1 to 4 parts by weight of a microwave activator, 0.2 to 3 parts by weight of a composite auxiliary agent, 0.08 to 2 parts by weight of an accelerator, 0.1 to 2 parts by weight of a microwave absorber, and 1 to 3 parts by weight of a light oil in a stirrer at a rotation speed of 200 r / min, maintaining a constant temperature of 60 to 80° C. and stirring for 1 hour, then continuing to vibrate the stirred mixture in an ultrasonic cleaner at a constant temperature of 60 to 80° C. for 1 hour, and then placing the stirred mixture in a vacuum apparatus and vacuuming for 5 to 30 minutes to obtain a uniform rubber particle mixture S, wherein the microwave activator is a compound of diphenyl disulfide, tetramethylthiuram disulfide, and bismaleimide, the composite auxiliary agent is a compound of maleic anhydride and potassium persulfate, the accelerator is octadecanoic acid, and the microwave absorber is a compound of nano-carbonyl iron powder and graphene;

[0007] Step S2: placing 15 to 25 parts by weight of the rubber particle mixture S and 75 to 85 parts by weight of the base asphalt in a shearing apparatus, and rapidly shearing them at 175 to 185° C. for 10 to 30 minutes to fully fuse the rubber asphalt to obtain rubber asphalt S1;

[0008] Step S3: The aged or fatigue-reduced rubber asphalt S1 is placed in a microwave apparatus for heating treatment to restore the performance of the rubber asphalt S1. The heating temperature T1 of the microwave apparatus is adjusted to 120-150°C and the heating time t1 is adjusted to 1-10 minutes to fully soften, plasticize and desulfurize the rubber particles. The heating temperature T2 of the microwave apparatus is then adjusted to 155-170°C and the heating time t2 is adjusted to 1-10 minutes to finally obtain a rubber asphalt with self-recovering performance.

[0009] It is further defined that the microwave frequency of the microwave instrument is 2450 MHz ± 50 Hz, and the microwave power is 500 to 2000 W.

[0010] It is further defined that the microwave activator mainly refers to the microwave activator that reacts with the sulfur cross-linking bonds in the rubber particles when the microwave environment reaches a certain temperature condition, thereby achieving the controllable desulfurization of the rubber asphalt; when the microwave environment reaches a certain high temperature condition, the microwave activator can further promote the vulcanization between the rubber particles, thereby achieving the staged controllable implementation of the desulfurization and vulcanization of the rubber asphalt. The microwave activator is a composite component, preferably composed of 0.1 to 0.8 parts by weight of diphenyl disulfide, 0.5 to 2 parts by weight of tetramethylthiuram disulfide and 0.2 to 2 parts by weight of bismaleimide. Under the action of microwaves, when the temperature reaches 120-150°C, diphenyl disulfide and tetramethylthiuram disulfide will react with the sulfur cross-linking bonds in the cross-linked rubber through a free radical mechanism. After the cross-linking bonds are broken by microwave action and mechanical shearing, they are grafted onto the rubber main chain, promoting the rapid desulfurization and depolymerization of the rubber asphalt, thereby achieving the release of light oil inside the rubber particles, which can partially replenish the oil lost in the aged rubber asphalt; after the process is completed, the microwave energy is increased to make the temperature reach 155-170°C. Under this high temperature condition, the vulcanization activity of bismaleimide can be effectively stimulated, thereby reducing the apparent activation energy of the vulcanization reaction, increasing the reaction rate constant, and increasing the network structure parameters of the vulcanized rubber, which is beneficial to improving the mechanical properties of the rubber asphalt. Its mechanism of action lies in the fact that as the reaction time of rubber asphalt increases, the number of macromolecular free radicals generated by the breakage of rubber molecular chains increases. However, the amount of desulfurization radicals generated by diphenyl disulfide and tetramethylthiuram disulfide is insufficient to terminate the binding of all rubber molecular free radicals. At this time, when the vulcanization temperature is high enough, bismaleimide can react with the rubber without the need for a free radical source, thereby promoting the coupling of rubber macromolecular free radicals and generating a chain extension reaction. The bifunctional bismaleimide not only increases the crosslinking speed and crosslink density during the vulcanization process, but also inhibits polymer disproportionation and chain scission, thereby improving the overall performance of rubber asphalt.

[0011] The composite additive is further defined as a mixture of a polar solubilizer and an initiator. This composite additive can promote a grafting reaction on the surface of rubber particles, improving the compatibility of the rubber particles. It can also enhance the polarity of the rubber particles, thereby improving the efficiency of microwave treatment. Preferably, it is a compound of maleic anhydride and potassium persulfate, wherein the mass fraction of potassium persulfate is 0.01% to 0.5%. First, the maleic anhydride monomer initiates grafting on the surface of the rubber particles and simultaneously polymerizes with the monomer swollen within the rubber particles, changing the properties of the rubber particles and improving the compatibility of the two-phase interface. Second, the evenly distributed polar maleic anhydride can improve the uniformity of microwave energy transfer under the action of microwaves, thereby improving the heat transfer effect during the rubber asphalt preparation process.

[0012] Furthermore, the accelerator primarily promotes the formation of sulfur-sulfur bonds and carbon-sulfur bonds in the rubber asphalt, thereby increasing the vulcanization efficiency of the rubber asphalt, and is preferably octadecanoic acid. The accelerator also improves the acid value of the rubber asphalt, thereby enhancing the adhesion of the asphalt.

[0013] Further specified, the microwave absorber primarily improves the efficiency of microwave heat conversion in the rubber asphalt, thereby fully utilizing the microwave activator's effects. It is preferably composed of a compound of 0.1-0.5 parts by weight of nano-carbonyl iron powder and 0.1-0.5 parts by weight of graphene. First, the microwave absorber is fully adsorbed onto the surface of the rubber particles through the treatment in step S1. Simultaneously, a portion of the microwave absorber also penetrates into the rubber particles along with the light oil, allowing it to fully bond with the rubber particles. When microwaves pass through the microwave absorber, molecular vibrations occur within the absorber, converting the lost microwave energy into heat. This generates relatively high temperatures in the rubber particles, achieving targeted heating, increasing microwave efficiency, and promoting the desulfurization and vulcanization effects of the microwave activator, thereby improving the performance of the rubber asphalt.

[0014] Further defined, the density of the light oil is generally 0.7 to 0.9 g / cm 3 The viscosity is between 1 and 10 cSt, and it has good fluidity and easy volatility. It is preferably one or more of naphtha, paraffin oil or aromatic oil.

[0015] Further specified, the rubber asphalt performance restoration process is achieved by subjecting aged or fatigue-degraded rubber asphalt to microwave heating in a microwave oven. When the rubber asphalt's fatigue cracking resistance is significantly reduced, the heating time t1 is preferably low, t2 is preferably high, and the heating temperature T1 is preferably low, while T2 is preferably high. When the fatigue cracking resistance of the rubber asphalt is less reduced, the heating time t1 is preferably high, t2 is preferably low, while the heating temperature T1 is preferably high, while T2 is preferably low. Controlling the heating time t1 and heating temperature T2 is a key technical point in implementing the present invention and an important parameter for optimizing the performance of the rubber asphalt. This is because the length of the heating time t1 controls the amount of rubber-breaking free radicals, thereby affecting further crosslinking between rubber molecules; while the heating temperature T2 is a key parameter influencing the activity of bismaleimide.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0017] 1. The present invention adopts a continuous activation regeneration preparation process, organically combines microwave desulfurization with microwave vulcanization, and realizes the integrated implementation of the desulfurization and vulcanization process of aged rubber asphalt. It can significantly reduce the frequent setting of process flow and addition of additives in the thermal regeneration process of rubber asphalt, and simplify the complex thermal regeneration preparation process.

[0018] To restore the properties of aged rubber asphalt, this invention innovatively proposes a microwave activator based on the microwave effect to control the phased desulfurization and vulcanization of the rubber particles in the rubber asphalt, achieving secondary crosslinking of the rubber particles. First, a pre-coated rubber particle mixture (S) is prepared, whereby additives such as light oil, microwave activator, and microwave absorber are fully infiltrated into the rubber particles, preparing them for later use in the rubber asphalt regeneration process. When the performance of rubber asphalt deteriorates, it is subjected to microwave regeneration treatment. Under the action of microwaves, when the temperature first reaches 120-150°C, diphenyl disulfide and tetramethylthiuram disulfide will react with the sulfur cross-linking bonds in the cross-linked rubber through a free radical mechanism. After the microwave action breaks the cross-linking bonds, they are grafted onto the rubber main chain, promoting the rapid desulfurization and depolymerization of the rubber asphalt, thereby achieving the release of light oil inside the rubber particles, which can replenish the light oil lost in the aged rubber asphalt, improve the ductility of the rubber asphalt, and reduce its viscosity. After the process is completed, the microwave energy is immediately increased to bring the temperature to 155-170°C. Under this high temperature condition, the vulcanization activity of bismaleimide can be effectively stimulated, thereby reducing the apparent activation energy of the vulcanization reaction, increasing the reaction rate constant, and increasing the network structure parameters of the vulcanized rubber, which is beneficial to improving the mechanical properties of the rubber asphalt. In addition, since some vulcanized rubber is non-polar rubber, microwave desulfurization only has a good thermal effect on vulcanized polar rubber, which limits the selection of rubber types in rubber asphalt. The microwave desulfurization of rubber asphalt based on the present invention can significantly reduce the dependence on rubber type. First, the present invention adds a nano-absorbing material. The nano-absorbing material is adsorbed and combined with rubber particles and microwave activators. When microwaves pass through the absorbing material, molecular vibration occurs within the material, and the lost microwave energy is converted into heat energy, causing the rubber particles to locally generate a relatively high temperature, so as to achieve the effect of targeted fixed-point heating, improve the efficiency of microwave action, and promote the desulfurization and vulcanization effects of microwave activators. In addition, asphalt is complex and contains a large amount of polar and non-polar substances. Through the full mutual solubility of rubber and polar components in asphalt, and under the grafting effect of polar maleic anhydride, the microwave desulfurization effect of different types of rubber can be significantly improved, thereby improving the applicability of the process of the present invention. Secondly, maleic anhydride can also significantly modify the compatibility of rubber particles with asphalt, helping to improve the high-temperature stability of rubber asphalt. At the same time, the maleic anhydride, potassium persulfate, and octadecanoic acid selected in the present invention can further improve the acid value of the rubber asphalt, optimize the adhesion between the rubber asphalt and the alkaline aggregate, and improve the water damage resistance of the rubber asphalt.

[0019] 3. In order to improve the crack resistance of aged rubber asphalt, the present invention further adopts a preparation method of microwave-vulcanized rubber asphalt. Under the action of microwave activator and accelerator, the composite additive can, on the one hand, enhance the network structure connection between rubber molecules, and on the other hand, promote the chemical bonding between rubber molecules and asphalt molecules, forming a more solid macromolecular network three-dimensional interpenetrating structure, thereby improving the interfacial cross-linking ability of aged rubber asphalt, and thus improving the crack resistance and high-temperature stability of aged rubber asphalt.

[0020] In summary, this patent realizes the process of simultaneous desulfurization and vulcanization of aged rubber asphalt in stages by organically combining microwave desulfurization and microwave vulcanization, forming a preparation method for efficient and stable performance recovery of rubber asphalt, improving the application efficiency of aged rubber asphalt, and restoring the performance of aged rubber asphalt by more than 80%, with significant economic and social benefits. DETAILED DESCRIPTION

[0021] The technical solutions in the specific implementation process of the present invention will be clearly and completely explained below.

[0022] The test used Karamay 90# asphalt as the base asphalt, and the experimental ratio of the rubber particle mixture S is shown in Table 1. Based on previous research and experimental experience, the pre-treated rubber particle mixture S was first prepared, and then the base asphalt was heated to about 180°C, and then the pre-treated rubber particle mixture S was added, and the temperature was maintained at about 180°C and the speed was 4500 r·min. -1 The rubber asphalt with self-recovering performance was prepared by high-speed shearing for 30 minutes.

[0023] According to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011), the prepared rubber asphalt samples were subjected to short-term aging in a thin-film heating oven, followed by long-term aging using a pressure aging test. Subsequently, they were subjected to multi-stress creep loading using a DSR rheometer to induce fatigue failure in the rubber asphalt. The fatigue specimens were then placed in a microwave apparatus for microwave heating. The microwave apparatus's heating temperature (T1) was initially adjusted to 130°C and the heating time (t1) was 2 minutes. The microwave apparatus's heating temperature (T2) was then adjusted to 165°C and the heating time (t2) was 4 minutes. This yielded a self-healing rubber asphalt, which was then tested for performance. The test results are shown in Table 2.

[0024] Table 1 Experimental mix design

[0025]

[0026] Table 2 Test results of specimens

[0027]

[0028] As shown in Table 2, analysis of fatigue factor, low-temperature stiffness modulus, and other indicators reveals that Example 3 of the self-recovering rubber asphalt prepared by the present invention exhibits a 43% improvement in fatigue resistance and a 56% improvement in low-temperature crack resistance compared to Comparative Example 1. Furthermore, the performance changes compared to unaged rubber asphalt are less than 16%, indicating that the performance recovery rate of the rubber asphalt can reach 84%. Table 2 also shows that the low-temperature performance of the rubber asphalt gradually improves with increasing bismaleimide content. Compared to Comparative Example 1, Example 3 exhibits superior low-temperature crack resistance, demonstrating a significant degree of crosslinking during vulcanization of the rubber particles. This also further enhances the adhesion of the rubber asphalt. This demonstrates that the present invention, by organically combining microwave desulfurization with microwave vulcanization, leverages the synergistic effects of these composite processes, significantly improving the crosslinking capacity of aged rubber asphalt and promoting the formation of a rubber-asphalt composite interpenetrating network structure, thereby improving its mechanical properties.

[0029] The above embodiments describe the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for illustrating the principles of the present invention. Without departing from the scope of the principles of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a self-recovering rubber asphalt material, characterized in that The specific steps are: Step S1: placing 10-25 parts by weight of rubber powder, 1-4 parts by weight of a microwave activator, 0.2-3 parts by weight of a composite auxiliary agent, 0.08-2 parts by weight of an accelerator, 0.1-2 parts by weight of a microwave absorber, and 1-3 parts by weight of a light oil in a stirrer, maintaining a constant temperature of 60-80° C. and stirring, then continuing to oscillate the stirred mixture in an ultrasonic cleaner at a constant temperature of 60-80° C., and then placing the stirred mixture in a vacuum apparatus and vacuuming to obtain a uniform rubber particle mixture S, wherein the microwave activator is a compound of diphenyl disulfide, tetramethylthiuram disulfide, and bismaleimide, the composite auxiliary agent is a compound of maleic anhydride and potassium persulfate, the accelerator is octadecanoic acid, and the microwave absorber is a compound of nano-carbonyl iron powder and graphene; Step S2: placing 15 to 25 parts by weight of the rubber particle mixture S and 75 to 85 parts by weight of the base asphalt in a shearing apparatus, and rapidly shearing them at 175 to 185° C. for 10 to 30 minutes to fully fuse the rubber asphalt to obtain rubber asphalt S1; Step S3: The aged or fatigue-reduced rubber asphalt S1 is placed in a microwave apparatus for heating treatment to achieve performance recovery of the rubber asphalt S1. The heating temperature T1 of the microwave apparatus is adjusted to 120-150°C, and the heating time t1 is adjusted to 1-10 minutes, so that the rubber particles are fully softened, plasticized, and desulfurized. The heating temperature T2 of the microwave apparatus is then adjusted to 155-170°C, and the heating time t2 is adjusted to 1-10 minutes, and finally, the rubber asphalt with self-recovery performance is obtained. The microwave frequency of the microwave apparatus is 2450 MHz ± 50 Hz, and the microwave power is 500-2000 W.

2. The method for preparing the self-recovering rubber asphalt material according to claim 1, characterized in that: The microwave activator refers to a microwave activator that reacts with the sulfur cross-linking bonds in the rubber particles when the microwave environment reaches 120-150°C, thereby achieving controllable desulfurization of the rubber asphalt; when the microwave environment reaches 155-170°C, the microwave activator can further promote the vulcanization between the rubber particles, thereby achieving controllable staged implementation of the desulfurization and vulcanization of the rubber asphalt. The microwave activator is compounded with 0.1-0.8 parts by weight of diphenyl disulfide, 0.5-2 parts by weight of tetramethylthiuram disulfide, and 0.2-2 parts by weight of bismaleimide.

3. The method for preparing the self-recovering rubber asphalt material according to claim 1, characterized in that: The composite auxiliary agent is a mixture of a polar solubilizer and an initiator. The composite auxiliary agent promotes a grafting reaction on the surface of the rubber particles, improves the compatibility of the rubber particles, enhances the polarity of the rubber particles, and facilitates improving the efficiency of microwave treatment. The mass fraction of potassium persulfate in the composite auxiliary agent is 0.01% to 0.5%.

4. The method for preparing the self-recovering rubber asphalt material according to claim 1, characterized in that: The microwave absorber is used to improve the efficiency of microwave heat conversion in rubber asphalt so as to give full play to the role of microwave activator. The microwave absorber is compounded by 0.1-0.5 parts by weight of nano carbonyl iron powder and 0.1-0.5 parts by weight of graphene.

5. The method for preparing the self-recovering rubber asphalt material according to claim 1, characterized in that: The density of the light oil is 0.7-0.9 g / cm 3 The viscosity is between 1 and 10 cSt, and it has good fluidity and easy volatility. The light oil is divided into one or more of naphtha, paraffin oil or aromatic oil.

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