Modified asphalt mixture and method of making

Abstract

The application provides a modified asphalt mixture and a preparation method, and belongs to the technical field of modified asphalt. The preparation method comprises the following steps: (1) mixing asphalt, rubber oil and SBS thermoplastic elastomer to obtain an A component containing SBS modified asphalt; (2) adding a B component to the A component and mixing to obtain the A component activated by free radicals, wherein the B component comprises at least one of dibenzoyl peroxide and azobisisobutyronitrile; and (3) adding a polyurethane modifier as a C component to the A component activated by free radicals and stirring to obtain a polyurethane and SBS composite modified asphalt mixture. The isocyanate in the C component can chemically react with the groups in the A component activated by free radicals to form a stable three-dimensional network structure in the asphalt, thereby improving the performance of the asphalt.

Description

Technical Field

[0001] This invention relates to the field of modified asphalt technology, and more particularly to a modified asphalt mixture and its preparation method. Background Technology

[0002] Due to factors such as overloaded vehicles, high traffic volume, and seasonal temperature changes, traditional asphalt pavements are gradually showing problems such as ruts, cracks, and aging, which reduce driving comfort and affect traffic safety.

[0003] One approach in related technologies is to add SBS thermoplastic elastomer to asphalt mixtures. However, the poor compatibility between asphalt and SBS makes it difficult for the asphalt to be evenly distributed, resulting in insufficient high-temperature performance and poor anti-aging properties of the asphalt pavement. Summary of the Invention

[0004] In view of the above, in order to at least partially solve at least one of the aforementioned technical problems, the present invention provides a modified asphalt mixture and a preparation method thereof.

[0005] According to one aspect of the present invention, a method for preparing a modified asphalt mixture is provided, comprising: step (1) heating and mixing asphalt, rubber oil, and styrene-butadiene-styrene (SBS) thermoplastic elastomer to obtain component A containing SBS modified asphalt; step (2) adding component B to component A and heating and mixing to obtain component A activated by free radicals, wherein component B includes at least one of benzoyl peroxide and azobisisobutyronitrile; step (3) adding a polyurethane modifier as component C to component A activated by free radicals and stirring to allow the isocyanate groups in the polyurethane to interact with the active groups in component A activated by free radicals to obtain a polyurethane and SBS composite modified asphalt mixture, wherein the active groups include hydroxyl, amino, and carboxylic acid groups.

[0006] According to an embodiment of the present invention, step (1) may include: heating and mixing asphalt and rubber oil to obtain a first mixture; adding SBS thermoplastic elastomer to the first mixture for a second heating and mixing to obtain component A.

[0007] According to an embodiment of the present invention, the first heating and mixing conditions are: heating and stirring at 140~160°C for 20~40 min; the second heating and mixing conditions are: raising the temperature from 140~160°C to 180~190°C, and heating and stirring at 180~190°C for 2~4 h.

[0008] According to an embodiment of the present invention, the heating and mixing conditions in step (2) are as follows: the temperature is lowered from 180~190℃ to 140~160℃, and the mixture is heated and stirred at 140~160℃ for 5~15 minutes.

[0009] According to an embodiment of the present invention, the stirring temperature in step (3) is 130~160℃ and the time is 1~3h.

[0010] According to an embodiment of the present invention, by weight, component A contains 93-96 parts asphalt, 1-2 parts rubber oil, and 2-4 parts SBS thermoplastic elastomer; component B contains 0.05-0.3 parts; and component C contains 0.5-2 parts.

[0011] According to an embodiment of the present invention, the asphalt comprises 20-30% saturated components, 30-40% aromatic components, 20-30% resins, and 5-10% asphaltenes.

[0012] According to an embodiment of the present invention, the asphalt is petroleum asphalt.

[0013] According to an embodiment of the present invention, the asphalt is No. 70 petroleum asphalt.

[0014] According to another aspect of the present invention, a modified asphalt mixture is provided, which is obtained by the above-described method for preparing modified asphalt mixture.

[0015] According to embodiments of the present invention, by adding benzoyl peroxide and / or azobisisobutyronitrile (AIB) free radical initiators to SBS modified asphalt, under mixed heating, the free radicals generated by the decomposition of the free radical initiators can react with various groups with active hydrogen in the SBS modified asphalt, introducing more free radical sites. This activates the active hydrogen groups to generate more active groups, such as hydroxyl, amino, and carboxylic acid groups. When a polyurethane modifier is added to the free radical-activated SBS modified asphalt, the isocyanate groups in the polyurethane can rapidly undergo cross-linking reactions with the activated hydroxyl, amino, and carboxylic acid groups, increasing the interaction forces between asphalt molecules and forming a relatively stable three-dimensional network structure within the asphalt molecules. This effectively reduces the tendency of SBS modified asphalt to segregate under high-temperature conditions, improves the uniformity of the mixture, enhances the storage stability and high-temperature resistance of the modified asphalt mixture, and simultaneously improves the mechanical properties of the asphalt. Attached Figure Description

[0016] Figure 1 A flowchart illustrating a method for preparing modified asphalt mixture according to an embodiment of the present invention is shown;

[0017] Figure 2 The infrared spectra of the modified asphalt and petroleum asphalt raw materials prepared in Comparative Example 2 of the present invention are shown.

[0018] Figure 3 Infrared spectra of modified asphalt with different reaction times in Comparative Example 2 of the present invention are shown; and

[0019] Figure 4 The infrared spectra of modified asphalt with different reaction times in Example 4 of the present invention are shown. Detailed Implementation

[0020] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0021] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "comprising" as used herein indicates the presence of features, steps, or operations, but does not exclude the presence or addition of one or more other features.

[0022] When using expressions such as "at least one of A, B, and C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, and C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.). When using expressions such as "at least one of A, B, or C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, or C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.).

[0023] Styrene-butadiene-styrene (SBS) thermoplastic elastomers are widely used in modified asphalt due to their excellent elasticity and durability. However, traditional SBS thermoplastic elastomers and asphalts are only physically mixed, resulting in poor compatibility and a tendency to segregate at high temperatures. This leads to uneven asphalt performance, and SBS-modified asphalts have insufficient high-temperature performance and poor anti-aging properties.

[0024] In realizing the concept of this invention, it was discovered that the isocyanate groups in polyurethane can chemically react with the internal groups of asphalt to form a stable spatial network structure. Furthermore, combining polyurethane with SBS helps to further improve the high-temperature performance and storage stability of modified asphalt, reduce segregation, and effectively reduce rutting problems at high temperatures. However, due to the limited number and variety of active groups in the resins and asphaltenes of asphalt, the reaction rate between asphalt and polyurethane is slow, and the modification effect is heavily dependent on the quality of the asphalt itself, thus limiting the widespread application of polyurethane-modified asphalt technology.

[0025] To address the aforementioned issues, a free radical initiator is first added to the SBS-modified asphalt to activate some of the functional groups, generating active groups. The activated SBS-modified asphalt is then mixed with a polyurethane modifier, allowing the isocyanate groups in the polyurethane to undergo three-dimensional cross-linking reactions with more active groups such as hydroxyl, amine, and carboxylic acid groups, forming a more stable spatial network structure and improving the various properties of the asphalt.

[0026] Specifically, according to one embodiment of the present invention, a method for preparing modified asphalt mixture is provided. Figure 1 A flowchart illustrating the preparation method of modified asphalt mixture according to an embodiment of the present invention is shown, as follows: Figure 1 As shown, it includes steps (1) to (3).

[0027] In step (1), asphalt, rubber oil, and styrene-butadiene-styrene (SBS) thermoplastic elastomer are heated and mixed to obtain component A containing SBS modified asphalt.

[0028] According to embodiments of the present invention, the addition of rubber oil helps improve the low-temperature performance of asphalt, while the addition of SBS thermoplastic elastomer helps enhance the low-temperature toughness and high-temperature stability of asphalt. Heating and mixing helps to ensure thorough mixing of the three raw materials.

[0029] In step (2), component B is added to component A and heated and mixed to obtain component A after free radical activation. Component B includes at least one of benzoyl peroxide and azobisisobutyronitrile.

[0030] According to an embodiment of the present invention, component B includes at least one of benzoyl peroxide and azobisisobutyronitrile (AIB). Benzoyl peroxide and AIB are free radical initiators. Under heating conditions, the free radical initiators decompose and generate free radicals. The generated free radicals interact with the macromolecular chains in component A, especially generating molecules with active hydrogen (such as hydroxyl, amino, and carboxylic acid groups), thereby introducing more free radical sites and activating component A.

[0031] It should be noted that asphalt itself contains some hydroxyl, amino, and carboxylic acid groups, but in small quantities and with poor activity. This invention introduces a free radical initiator to generate free radicals, which then interact with benzene rings or carbon to form carbon free radicals. These carbon free radicals then react with water, oxygen, etc., to generate active groups such as carboxyl and hydroxyl groups, thereby increasing the number of active groups in component A.

[0032] In operation S103, a polyurethane modifier is added as component C to component A, which has been activated by free radicals, and stirred to allow the isocyanate groups in the polyurethane to interact with the active groups in component A, which has been activated by free radicals, to obtain a polyurethane and SBS composite modified asphalt mixture. The active groups include hydroxyl, amino, and carboxylic acid groups.

[0033] According to an embodiment of the present invention, component C includes a polyurethane modifier, the polyurethane having isocyanate groups (-N=C=O), the isocyanate groups being able to chemically react with the numerous hydroxyl, amine, and carboxylic acid groups in the activated asphalt to generate urethane and urea.

[0034] R-NCO+R 1 -OH→R-NH-CO-OR 1

[0035] R-NCO+R 1 -NH2→R-NHCONH-R 1

[0036]

[0037] As shown in the reaction process above, R represents other groups attached to the isocyanate in the polyurethane. 1 These represent other groups that are respectively attached to hydroxyl, amino, carboxylic acid, etc. Because the isocyanate groups further react chemically with the aforementioned groups in the activated asphalt, the interaction forces between asphalt molecules are increased, forming a more stable three-dimensional network structure within the asphalt. This results in a unified structure for the modified asphalt mixture, which helps improve its storage stability, high-temperature performance, and mechanical properties.

[0038] According to embodiments of the present invention, by introducing free radical initiators such as benzoyl peroxide and / or azobisisobutyronitrile in component B, the free radicals generated by their thermal decomposition can efficiently activate saturated components, resins, and asphaltenes in SBS and asphalt, thereby significantly shortening the reaction time of isocyanate and asphalt and improving the modification effect of polyurethane modifier on SBS modified asphalt. This effectively reduces the phenomenon of easy segregation of SBS modified asphalt under high temperature conditions, improves the uniformity of polyurethane and SBS composite modified asphalt mixtures under high temperature conditions, and thus improves the practical application effect of polyurethane and SBS composite modified asphalt mixtures.

[0039] Understandably, traditional SBS-modified asphalt is produced by physically mixing SBS and asphalt, resulting in poor compatibility between the two. In contrast, the polyurethane and SBS composite modified asphalt mixture of this invention achieves chemical modification of the asphalt through a chemical cross-linking reaction between the polyurethane modifier and the SBS-modified asphalt. This is accomplished by the interaction of isocyanate with the active hydrogen-containing functional groups in the SBS-modified asphalt, forming a cross-linking reaction that enhances the mechanical strength, elasticity, and chemical corrosion resistance of the modified asphalt mixture. It also broadens the compatibility temperature range of the modified asphalt mixture and improves its anti-aging ability and adhesion.

[0040] For example, taking component B as benzoyl peroxide, by adding benzoyl peroxide to component A and heating it, the benzoyl peroxide decomposes thermally, generating two benzoyl free radicals. When these benzoyl free radicals come into contact with the various components of the asphalt, addition or substitution reactions may occur, modifying the asphalt molecules through chain initiation, chain propagation, and chain termination, resulting in more active groups, such as hydroxyl, amino, or carboxylic acid groups. The generated active groups are more numerous than those in asphalt molecules that have not undergone free radical activation, providing more active sites. This facilitates interaction with subsequently added isocyanate groups, forming a three-dimensional cross-linked network structure, thereby enhancing the bonding strength between asphalt and SBS and improving the modification effect.

[0041] According to an embodiment of the present invention, step (1) includes sub-steps (101) to (102).

[0042] In sub-step (101), asphalt and rubber oil are heated and mixed to obtain a first mixture.

[0043] In sub-step (102), SBS thermoplastic elastomer is added to the first mixture for a second heating and mixing to obtain component A.

[0044] According to embodiments of the present invention, adding rubber oil to asphalt helps to reduce the viscosity of the asphalt and improve its processability. First heating and mixing helps to ensure thorough mixing of the two materials to obtain a homogeneous first mixture. Further addition of SBS thermoplastic elastomer helps to improve the high-temperature stability of the asphalt.

[0045] It can be understood that sub-steps (101) to (102) prepared SBS modified bitumen (i.e., a physical mixture of bitumen and SBS thermoplastic elastomer).

[0046] According to an embodiment of the present invention, the first heating and mixing conditions are: heating and stirring at 140~160°C, for example, 140°C, 150°C, or 160°C, preferably 160°C, for 20~40 minutes, for example, 20 minutes, 30 minutes, or 40 minutes, preferably 30 minutes. Raising the temperature to the above-mentioned range helps to fully melt and uniformly disperse the asphalt and rubber oil, ensuring the fluidity of the raw materials. The second heating and mixing conditions are: raising the temperature from 140~160°C to 180~190°C, for example, 180°C, 185°C, or 190°C, preferably 185°C, and heating and stirring at 180~190°C for 2~4 hours, for example, 2 hours, 3 hours, or 4 hours, preferably 3 hours. Raising the temperature to 180~190°C is to better dissolve the SBS thermoplastic elastomer and promote the uniform dispersion of the SBS thermoplastic elastomer in the asphalt, improving the elasticity and recovery ability of the asphalt and improving the long-term stability of the modified asphalt mixture.

[0047] According to an embodiment of the present invention, the heating and mixing conditions in step (2) are as follows: the temperature is lowered from 180~190℃ to 140~160℃, for example, 140℃, 150℃ or 160℃, preferably 150℃, and heated and stirred at 140~160℃ for 5~15 minutes, for example, 5 minutes, 10 minutes or 15 minutes, preferably 10 minutes. After the SBS thermoplastic elastomer is fully dissolved, lowering the temperature helps to reduce the fluidity of the SBS composite modified asphalt and form a more stable and uniform structure.

[0048] According to an embodiment of the present invention, the stirring temperature in step (3) is 130~160℃, for example, 130℃, 140℃, 150℃ or 160℃, and the stirring time is 1~3h, for example, 1h, 2h or 3h, preferably 1.5h. Adjusting the stirring temperature and time to the above range helps to promote sufficient interaction between the isocyanate groups and the hydroxyl, amino, and carboxylic acid groups, which helps to form a stable three-dimensional network structure inside the polyurethane and SBS composite modified asphalt mixture, thereby integrating the SBS thermoplastic elastomer and asphalt. The above modification method improves the storage stability, high-temperature performance and mechanical properties of the modified asphalt mixture.

[0049] Furthermore, because SBS-modified asphalt is activated by free radicals, it forms more active groups such as hydroxyl, amino, and carboxylic acid groups, enabling isocyanate to undergo a relatively rapid cross-linking reaction with these active groups. Traditionally, when isocyanate-modified asphalt is used directly, the reaction time is 3-6 hours. However, in this invention, based on free radical activation, the reaction time between isocyanate and SBS-modified asphalt is shortened to 1-2 hours, improving the production efficiency of polyurethane and SBS composite modified asphalt mixtures, thereby enhancing practical application efficiency.

[0050] According to embodiments of the present invention, the addition of SBS thermoplastic elastomer in component A improves the elasticity and resilience of asphalt, reduces rutting, and improves the high-temperature performance of modified asphalt mixtures. The addition of rubber oil reduces the viscosity of the asphalt, making it easier to apply and maintaining good fluidity. Component B includes a free radical initiator, which helps to crosslink the SBS thermoplastic elastomer, asphalt, and polyurethane modifier, improving the mechanical strength and thermal stability of the modified asphalt mixture and enhancing its anti-aging properties. The isocyanate groups in the polyurethane can interact with the SBS modified asphalt to form a stable spatial network structure, enhancing the stability of the modified asphalt mixture and effectively reducing the tendency of SBS modified asphalt (through physical mixing of asphalt and SBS) to segregate under high-temperature conditions, thus improving the uniformity of the modified asphalt mixture under high-temperature conditions.

[0051] According to embodiments of the present invention, by weight, component A comprises 93-96 parts asphalt, 1-2 parts rubber oil, and 2-4 parts SBS thermoplastic elastomer. Asphalt, as the main component, provides the basic structure and bonding strength of the asphalt mixture. Component B comprises 0.05-0.3 parts; component C comprises 0.5-2 parts. During the relevant experiments of the present invention, it was found that adjusting the above components within the aforementioned ranges helps to obtain modified asphalt mixtures with better mechanical properties, wider temperature adaptability, and longer service life.

[0052] According to embodiments of the present invention, the asphalt comprises 20-30% saturated components, 30-40% aromatic components, 20-30% resins, and 5-10% asphaltenes. It is understood that the saturated components may include, for example, saturated alkanes, cycloalkanes, etc., which provide the asphalt with fluidity and help reduce the viscosity of the asphalt at high temperatures, thus facilitating paving. The aromatic components may include, for example, polycyclic aromatic hydrocarbons, whose π-electron clouds can interact with SBS elastomers, improving the asphalt modification effect. The addition of aromatic components increases the hardness, durability, and resistance to deformation at high temperatures of the asphalt. The resins may include, for example, compounds containing oxygen, nitrogen, or sulfur heteroatoms, such as resins, which help connect the aromatic components and asphaltenes, improving the stability and elasticity of the asphalt. The asphaltenes may include, for example, polar macromolecules, which help form a filling effect, increasing the viscosity and strength of the asphalt and enhancing its anti-aging ability.

[0053] Preferably, the asphalt is petroleum asphalt, which has high adhesion and good elasticity and recovery ability, helps to reduce rutting, can adapt to temperature changes, and has high stability and anti-aging properties.

[0054] More preferably, the asphalt is No. 70 petroleum asphalt. During the relevant experiments of this invention, it was found that when using No. 70 petroleum asphalt, the modified asphalt mixture prepared by polyurethane and SBS composite modification has better mechanical properties and improved stability.

[0055] In one embodiment, the method for preparing the modified asphalt mixture includes:

[0056] Weigh out petroleum asphalt and rubber oil, heat and stir them in a temperature range of 140~160℃ until they are mixed evenly to obtain a mixture.

[0057] Add SBS to the mixture, heat and stir to obtain component A;

[0058] Lower the temperature to 140~160℃, add component B and stir for 10 minutes to mix it evenly, and obtain component A after free radical activation.

[0059] Add polyurethane modifier and stir for 1.5 hours to obtain modified asphalt mixture.

[0060] According to another aspect of the present invention, a modified asphalt mixture is provided, which is obtained by the above-described method for preparing modified asphalt mixture from component A (containing asphalt, rubber oil, styrene-butadiene-styrene (SBS) thermoplastic elastomer), component B (at least one of benzoyl peroxide and azobisisobutyronitrile), and component C (polyurethane modifier).

[0061] The present invention will be further illustrated below through embodiments and related test experiments and results. In the following detailed description, numerous specific details are set forth for ease of explanation to provide a comprehensive understanding of the embodiments of the present invention. However, it will be apparent that one or more embodiments may be practiced without these specific details. Moreover, the details in the following embodiments can be arbitrarily combined to form other feasible embodiments without conflict.

[0062] It should be noted that the specific embodiments described below are merely illustrative examples, and the scope of protection of this invention is not limited thereto. The chemicals and raw materials used in the following embodiments are all commercially available or prepared using recognized processing methods.

[0063] It should be noted that the asphalt used in the examples and comparative examples is No. 70 asphalt, with the following four components: saturated components 20-30%, aromatic components 30-40%, resins 20-30%, and asphaltenes 5-10%. The SBS thermoplastic elastomer used is linear YH-502, manufactured by a certain petrochemical company. The polyurethane modifier used is B2 last, manufactured by a certain joint-stock company. The rubber oil used is manufactured by a certain chemical company in Shandong.

[0064] Example 1:

[0065] Weigh out 94.9 parts asphalt and 1.5 parts rubber oil, heat and stir at 160℃ for 30 minutes to ensure the raw materials are fully mixed.

[0066] Add 3 parts SBS, raise the temperature to 185℃ and stir for 3 hours to obtain a physical mixture of SBS and asphalt. Then lower the temperature to 150℃, add 0.1 parts benzoyl peroxide (BPO initiator) and stir for 10 minutes to mix it evenly. Add 0.5 parts polyurethane modifier and stir for 1.5 hours. Perform a discharge test on the asphalt mixture 1 prepared in Example 1. The test results are shown in Table 1 below.

[0067] Comparative Example 1:

[0068] Weigh out 95.5 parts asphalt and 1.5 parts rubber oil, heat and stir at 160℃ for 30 minutes to ensure the raw materials are fully mixed.

[0069] Add 3 parts of SBS, raise the temperature to 185℃ and stir for 3 hours to obtain a physical mixture 1' of SBS and asphalt. The physical mixture 1' prepared in Comparative Example 1 was subjected to discharge test, and the test results are shown in Table 1 below.

[0070] Comparative Example 2:

[0071] Weigh out 93.5 parts asphalt and 1.5 parts rubber oil, heat and stir at 160℃ for 30 minutes to ensure the materials are fully mixed.

[0072] Add 3 parts SBS, raise the temperature to 185℃ and stir for 3 hours to obtain a mixture of SBS and asphalt. Lower the temperature to 150℃, add 2 parts polyurethane modifier, and take infrared samples every hour after adding the polyurethane modifier until the sample reaches 2270 cm⁻¹. -1 The reaction endpoint is determined when the infrared characteristic peak of isocyanate changes very little within 1 hour.

[0073] Figure 2 The infrared spectra of the modified asphalt and petroleum asphalt raw materials prepared in Comparative Example 2 of this invention are shown. Figure 2 The image shows the infrared spectrum of polyurethane-modified asphalt after reaction at 150℃ for 1 hour. Compared to base asphalt, polyurethane-modified asphalt exhibits higher infrared spectra at 2270, 1715, 1650, 1512, and 1240 cm⁻¹. -1 A new absorption peak appeared at 2270 cm⁻¹. -1 The absorption peak at position 1715 cm⁻¹ is the absorption peak of unreacted isocyanate-NCO. -1 The absorption peak at position 1650 cm⁻¹ belongs to the stretching vibration of the C=O band of amide I. -1 The absorption peak at 1512 cm⁻¹ is a characteristic peak of urea derivatives. -1 The absorption peak at 1240 cm⁻¹ is attributed to the coupling effect of the NH bending vibration and CN stretching vibration of the amide II band. -1 The absorption peak at the specified position is attributed to the coupling effect of the CN stretching vibration and NH bending vibration of the amide III band. As shown in the infrared spectrum above, the isocyanate functional groups in the modifier can react chemically with hydroxyl and amino groups in the asphalt molecules to form carbamates and ureas.

[0074] After adding the polyurethane modifier, samples were taken every 30 minutes to measure infrared radiation, and the results were observed at 2270 cm⁻¹. -1 The changes in the infrared characteristic peaks at that location. Figure 3 Infrared spectra of the modified asphalt with different reaction times in Comparative Example 2 of the present invention are shown. Figure 3 As shown, the reaction proceeded for 6 hours at 2270 cm⁻¹. -1 The infrared characteristic peaks of isocyanate were still present, and the consumption of isocyanate was slow from 5 to 6 hours, indicating that there were not enough active groups in the asphalt that could react with isocyanate.

[0075] Example 2:

[0076] Weigh out 94.4 parts asphalt and 1.5 parts rubber oil, heat and stir at 160℃ for 30 minutes to ensure the raw materials are fully mixed.

[0077] Add 3 parts SBS, raise the temperature to 185℃ and stir for 3 hours to obtain a physical mixture of SBS and asphalt. Then lower the temperature to 150℃, add 0.1 parts BPO initiator and stir for 10 minutes to make it uniformly mixed. Add 1 part polyurethane modifier and stir for 1.5 hours. Perform a discharge test on the asphalt mixture 2 prepared in Example 2. The test results are shown in Table 1 below.

[0078] Example 3:

[0079] Weigh out 93.9 parts asphalt and 1.5 parts rubber oil, heat and stir at 160℃ for 30 minutes to ensure the raw materials are fully mixed.

[0080] Add 3 parts SBS, raise the temperature to 185℃ and stir for 3 hours to obtain a physical mixture of SBS and asphalt. Lower the temperature to 150℃, add 0.1 parts BPO initiator and stir for 10 minutes to mix it evenly. Add 1.5 parts polyurethane modifier and stir for 1.5 hours. Perform a discharge test on the asphalt mixture 3 prepared in Example 3. The test results are shown in Table 1 below.

[0081] Example 4:

[0082] Weigh out 93.4 parts asphalt and 1.5 parts rubber oil, heat and stir at 160℃ for 30 minutes to ensure the raw materials are fully mixed.

[0083] Add 3 parts SBS, raise the temperature to 185℃ and stir for 3 hours to obtain a physical mixture of SBS and asphalt. Then lower the temperature to 150℃, add 0.1 parts BPO initiator and stir for 10 minutes to make it uniformly mixed. Add 2 parts polyurethane modifier and stir for 1.5 hours. Perform a discharge test on the asphalt mixture 4 prepared in Example 4. The test results are shown in Table 1 below.

[0084] Figure 4 Infrared spectra of modified asphalt with different reaction times in Example 4 of the present invention are shown. Figure 4 It can be seen that after adding the BPO initiator, the 2270 cm⁻¹ is barely visible after 1.5 hours of reaction. -1 The infrared absorption peak of isocyanate at the specified location indicates that the BPO initiator can activate the various components in the SBS composite modified asphalt, thereby significantly shortening the reaction time between isocyanate and asphalt and accelerating the reaction rate between isocyanate and asphalt.

[0085] Table 1 shows the test results of Examples 1-3 and Comparative Example 1. As shown in Table 1, the penetration values ​​of Examples 1-3 are all lower than those of Comparative Example 1, indicating that the modified asphalt prepared in Examples 1-3 has higher hardness and better resistance to high temperatures and high loads. The softening points of Examples 1-3 are all higher than those of Comparative Example 1, indicating that the asphalt has better stability at high temperatures, is less prone to deformation, and can effectively reduce rutting. The viscosity of Examples 1-3 is all higher than that of Comparative Example 1, which helps to ensure good workability and uniform distribution of the asphalt. The difference in softening points of Examples 1-3 is lower than that of Comparative Example 1, indicating that the modified asphalt prepared in Examples 1-3 has better homogeneity, that is, the components are mixed more evenly and are less prone to segregation under high temperature conditions.

[0086] The relevant properties of modified asphalt were tested. The penetration test was performed by measuring the depth to which a standard needle vertically penetrated the asphalt sample under specific load, time, and temperature conditions, expressed in 1 / 10 mm. The total mass of the standard needle, needle rod, and additional weights was (100 ± 0.05) g, the temperature was (25 ± 0.1) ℃, and the time was 5 s. The same sample was tested three times, with each test point at least 10 mm from the edge of the sample dish. The softening point test method involved placing the modified asphalt in a shoulder or conical brass ring, leveling the surface, placing a standard steel ball, and heating it in water or glycerin at a rate of 5 ℃ / min until the modified asphalt softened and drooped to 25 mm; this temperature was the softening point.

[0087] Ductility test method: Pour the modified asphalt into an 8-shaped mold, smooth the surface, and place it in a water bath at 5℃ for at least 2 hours. Stretch the asphalt using a ductility tester at a tensile speed of 5 cm / min, and record the length of the modified asphalt from the start of stretching to the point of breakage, in cm. Viscosity test method: Pour the modified asphalt into a viscosity tube, select a suitable rotor, and start the test at 135℃, recording the viscosity value. Segregation test method: Pour the modified asphalt into a segregation tube, place it vertically in an oven at 163℃ for 48 hours, and measure the softening point of the upper and lower parts of the segregation tube. The difference in softening points is the segregation value. Relevant data are shown in Table 1 below.

[0088] Table 1. Test results of modified asphalt in Examples 1-3 and Comparative Example 1

[0089]

[0090] This invention accelerates the reaction rate between isocyanate and asphalt by adding benzoyl peroxide and / or azobisisobutyronitrile, shortening the reaction time, improving production efficiency and modification effect, and reducing production costs. In related technologies, traditional SBS-modified asphalt suffers from severe segregation at high temperatures. By adding polyurethane to form a stable three-dimensional network structure within the asphalt, the stability of the asphalt is enhanced, effectively reducing the segregation phenomenon of the original SBS-modified asphalt at high temperatures and improving the uniformity of the material under high-temperature conditions. Furthermore, by adding a polyurethane modifier, this invention significantly improves the high-temperature performance of modified asphalt mixtures, enabling the modified asphalt to maintain a low penetration at high temperatures, effectively reducing rutting and extending the service life of the pavement.

[0091] In summary, this SBS-modified asphalt mixture and its preparation method based on polyurethane modifiers and free radical initiators (such as benzoyl peroxide or azobisisobutyronitrile) not only improves the performance of asphalt pavements but also increases production efficiency, resulting in significant economic and social benefits.

[0092] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a modified asphalt mixture, comprising: Step (1) The asphalt and rubber oil are heated and mixed for the first time to obtain a first mixture. Styrene-butadiene-styrene (SBS) thermoplastic elastomer is added to the first mixture for a second heating and mixing to obtain component A containing SBS modified asphalt. The conditions for the first heating and mixing are heating and stirring at 140~160℃ for 20~40 min, and the conditions for the second heating and mixing are heating from 140~160℃ to 180~190℃ and heating and stirring at 180~190℃ for 2~4 h. Step (2) Add component B to component A and heat and mix to obtain component A after free radical activation. The free radicals generated by the decomposition of component B react with the active hydrogen groups in SBS modified asphalt, so that the active hydrogen is activated to generate active groups. Component B includes at least one of benzoyl peroxide and azobisisobutyronitrile. The heating and mixing conditions are to cool the temperature from 180~190℃ to 140~160℃ and heat and stir at 140~160℃ for 5~15 minutes. Step (3) The polyurethane modifier is added as component C to the free radical activated component A and stirred so that the isocyanate groups in the polyurethane interact with the active groups in the free radical activated component A to obtain a polyurethane and SBS composite modified asphalt mixture. The active groups include hydroxyl and carboxylic acid groups.

2. The preparation method according to claim 1, wherein, The stirring temperature in step (3) is 130~160℃ and the stirring time is 1~3h.

3. The preparation method according to claim 1, wherein, By weight, component A contains 93-96 parts asphalt, 1-2 parts rubber oil, and 2-4 parts SBS thermoplastic elastomer; Component B is 0.05~0.3 parts; Component C is divided into 0.5 to 2 parts.

4. The preparation method according to claim 1, wherein, The asphalt comprises 20-30% saturated components, 30-40% aromatic components, 20-30% resins, and 5-10% asphaltenes.

5. The preparation method according to claim 1, wherein, The asphalt is petroleum asphalt.

6. The preparation method according to claim 1 or 5, wherein, The asphalt is No. 70 petroleum asphalt.

7. A modified asphalt mixture obtained by the preparation method according to any one of claims 1-6.

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