A method for preparing vulcanized natural latex modified asphalt.

Abstract

This invention belongs to the technical field of asphalt modification materials, specifically relating to a vulcanized natural rubber latex modified asphalt and its preparation method. It is made from the following raw materials in parts by weight: 100 parts base asphalt, 15-20 parts natural rubber latex, 0.18-0.28 parts sulfur (vulcanizing agent), 0.15-0.36 parts silica, 0.075-0.14 parts 2,6-di-tert-butyl-4-methylphenol (antioxidant), 0.09-0.16 parts zinc ethylphenyl dithiocarbamate, 0.045-0.08 parts 2-mercaptobenzothiazole, 0.075-0.14 parts zinc oxide, and 0.015-0.06 parts naphthalenesulfonate formaldehyde condensate. This invention first vulcanizes the natural rubber latex, significantly improving its elasticity, toughness, and anti-aging properties. Then, it is used for asphalt modification, ultimately producing vulcanized natural rubber latex modified asphalt with excellent low-temperature toughness and high-temperature deformation resistance.

Description

Technical Field

[0001] This invention belongs to the field of asphalt modification materials technology, specifically relating to a vulcanized natural latex modified asphalt and its preparation method. Background Technology

[0002] Natural rubber is a green, renewable, and sustainable material, and its remarkable elastic properties make it a promising candidate for application in road engineering. Adding natural rubber latex as a modifier to asphalt can not only improve the road performance of asphalt pavements and extend their service life, but also contribute to the construction of an efficient and green transportation system with advantages such as low carbon emissions, energy conservation, and environmental friendliness.

[0003] However, in practical applications, natural rubber latex still faces a series of technical bottlenecks as an asphalt modifier. Despite its outstanding elastic properties, when blending with asphalt for modification, the asphalt usually needs to be heated to above 170°C to ensure good compatibility and dispersion. This high-temperature environment easily leads to the breakage, oxidative degradation, or structuring of rubber molecular chains in natural rubber latex, significantly reducing its elasticity and mechanical properties, thereby affecting the modification effect of the asphalt. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a vulcanized natural latex-modified asphalt and its preparation method. This invention utilizes a vulcanization reaction to form a dense and stable three-dimensional cross-linked network structure in natural latex, thereby inhibiting the degradation of natural latex at high temperatures and effectively improving the high-temperature performance of asphalt. This solves the problems of insufficient thermal stability and limited modification effect that are common in ordinary natural latex-modified asphalt.

[0005] This invention is specifically achieved through the following technical solutions: The first objective of this invention is to provide a vulcanized natural latex modified asphalt, made from the following raw materials in parts by weight: The composition includes 100 parts base asphalt, 15-20 parts natural latex, 0.18-0.28 parts sulfur vulcanizing agent, 0.15-0.36 parts silica, 0.075-0.14 parts antioxidant 2,6-di-tert-butyl-4-methylphenol (BHT), 0.09-0.16 parts accelerator zinc ethylphenyl dithiocarbamate (PX), 0.045-0.08 parts accelerator 2-mercaptobenzothiazole (MBT), 0.075-0.14 parts crosslinking activator zinc oxide, and 0.015-0.06 parts dispersant naphthalene sulfonate formaldehyde condensate (NNO).

[0006] The above components are formulated in appropriate proportions, such as the appropriate ratios of modifiers, natural latex, vulcanizing agents, crosslinking activators, accelerators, dispersants, and other additives, to construct a stable crosslinked network structure, thereby enabling the product to have excellent high-temperature performance during use.

[0007] It should be noted that zinc oxide, acting as a crosslinking activator, promotes the vulcanization reaction and improves crosslinking efficiency. The accelerators zinc ethylphenyl dithiocarbamate (PX) and 2-mercaptobenzothiazole (MBT) work together to accelerate the vulcanization rate and sulfur utilization efficiency, further converting sulfur into more active vulcanization intermediates. Under suitable vulcanization conditions, a stable crosslinked network structure is obtained. When the naphthalene sulfonate formaldehyde condensate (NNO) is subjected to graded wet grinding, the uniform dispersion of solid compounding agents such as sulfur, silica, and zinc oxide is ensured. Natural latex is a green, environmentally friendly, and renewable natural resource; its application in the asphalt field can reduce the consumption of petroleum resources. Furthermore, natural latex is a high-molecular-weight polymer with abundant unsaturated double bonds in its molecular structure. These double bonds readily undergo vulcanization crosslinking reactions to form a stable three-dimensional network structure.

[0008] The natural latex is a low-ammonia natural latex preserved with ammonia water, with a solid content of 60%~65%. When natural latex is mixed with asphalt, it forms a flexible interface layer, which helps to improve the elasticity and high-temperature performance of asphalt.

[0009] A suitable amount of sulfur is preferred as a vulcanizing agent to promote the formation of vulcanization crosslinks between natural latex molecular chains, thereby increasing the crosslink density of the natural latex after vulcanization. Zinc oxide is preferred as a crosslinking activator, which can promote the vulcanization reaction and improve the crosslinking efficiency.

[0010] The second objective of this invention is to provide a method for preparing vulcanized natural latex modified asphalt, comprising the following steps: A vulcanizing mixture was prepared by wet grinding of dispersant naphthalene sulfonate formaldehyde condensate (NNO), vulcanizing agent sulfur, silica, antioxidant 2,6-di-tert-butyl-4-methylphenol, accelerator zinc ethylphenyl dithiocarbamate (PX), accelerator 2-mercaptobenzothiazole (MBT) and crosslinking activator zinc oxide using water as the grinding medium. Natural latex and vulcanizing mixture are mixed and vulcanized to obtain vulcanized natural latex. Vulcanized natural latex was added as a modifier to the heated base asphalt, and water was removed under stirring conditions to obtain pre-vulcanized natural latex modified asphalt.

[0011] Preferably, the specific preparation process of the vulcanized mixture includes the following steps: A horizontal sand mill was used to mix and grind water, dispersant naphthalene sulfonate formaldehyde condensate (NNO), and sulfurizing agent sulfur with silicon dioxide. Then add the antioxidant 2,6-di-tert-butyl-4-methylphenol (BHT) and grind it. Then, zinc ethylphenyl dithiocarbamate (PX) and 2-mercaptobenzothiazole (MBT) are added as accelerators and mixed and ground. Finally, zinc oxide, a cross-linking activator, is added and ground to generate a vulcanized mixture.

[0012] Preferably, during the grinding stage of the horizontal sand mill, an appropriate grinding time is used to achieve better grinding results, thereby improving the high-temperature performance of vulcanized latex and its modified asphalt. During the grinding process, the grinding speed is 700 rpm, and the total grinding time is 75 minutes.

[0013] More preferably, the order of adding materials is designed based on the dispersion characteristics and grinding effect of different materials. During grinding, the order of adding raw materials and the grinding time are as follows: In the water and dispersant system, only sulfur and silica are added at the beginning stage. After 20 minutes, the antioxidant 2,6-di-tert-butyl-4-methylphenol (BHT) is added. After 55 minutes (this means that the timing starts from the beginning stage, 55 minutes later), the accelerator 2-mercaptobenzothiazole (MBT) and the accelerator zinc ethylphenyl dithiocarbamate (PX) are added. After 65 minutes (this means that the timing starts from the beginning stage, 65 minutes later), the crosslinking activator zinc oxide is added. The total grinding time for the above raw materials is 75 minutes.

[0014] Preferably, the solid particle size in the vulcanization mixture is between 1 μm and 10 μm.

[0015] Preferably, when preparing vulcanized natural rubber latex, the natural rubber latex is first heated to 50°C~70°C in a water bath, and then a vulcanizing mixture is added and the vulcanization reaction is carried out for 150~160 minutes.

[0016] Preferably, the base asphalt is heated to 170°C, and the vulcanized natural rubber latex is added dropwise to the hot asphalt at a rate of 2 mL / min to 10 mL / min. After the addition is completed, the mixture is placed in an oil bath at 180°C and stirred continuously to allow the water in the system to fully vaporize and be discharged until no bubbles are generated, thus obtaining pre-vulcanized natural rubber latex modified asphalt.

[0017] Preferably, the natural latex is a low-ammonia natural latex preserved with ammonia water, with a solid content of 60% to 65%.

[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a modified asphalt using vulcanized natural rubber latex. The vulcanized natural rubber latex is used as a modifier to modify the asphalt. This invention induces a vulcanization reaction in the natural rubber latex, forming a dense and stable three-dimensional cross-linked network structure, thereby inhibiting the degradation of natural rubber at high temperatures and effectively improving the high-temperature performance of the asphalt. Furthermore, the elastic properties of the natural rubber are enhanced after vulcanization, strengthening the interfacial bonding between the asphalt and natural rubber, which helps improve the service performance of road materials under harsh environments such as high temperature, heavy rainfall, and oxidation. Specifically, vulcanized natural rubber latex is vulcanized using the following components: 15-20 parts natural rubber latex, 0.18-0.28 parts sulfur (vulcanizing agent), 0.15-0.36 parts silica, 0.075-0.14 parts 2,6-di-tert-butyl-4-methylphenol (BHT) antioxidant, 0.09-0.16 parts zinc ethylphenyl dithiocarbamate (PX) accelerator, 0.045-0.08 parts 2-mercaptobenzothiazole (MBT) accelerator, 0.075-0.14 parts zinc oxide (crosslinking activator), and 0.015-0.06 parts naphthalenesulfonate formaldehyde condensate (NNO) dispersant. Zinc oxide, as a crosslinking activator, promotes the vulcanization reaction and improves crosslinking efficiency. The accelerators zinc ethylphenyl dithiocarbamate (PX) and 2-mercaptobenzothiazole (MBT) work together to promote the vulcanization rate and sulfur utilization efficiency, further converting sulfur into more active vulcanization intermediates. Under suitable vulcanization conditions, a stable cross-linked network structure is obtained. When the naphthalene sulfonate formaldehyde condensate (NNO) is subjected to graded wet grinding, the uniform dispersion of solid compounding agents such as sulfur, silica, and zinc oxide is ensured. Natural latex is a green, environmentally friendly, and renewable natural resource; its application in the asphalt industry can reduce the consumption of petroleum resources. Furthermore, natural latex is a high-molecular-weight polymer with abundant unsaturated double bonds in its molecular structure. These double bonds readily undergo vulcanization cross-linking reactions to form a stable three-dimensional network structure.

[0019] The raw materials used in this invention are widely available, the preparation process is simple, the conditions are mild, and it is easy to implement, which is conducive to promoting the application of natural latex in asphalt. This invention is suitable for widespread application. Attached Figure Description

[0020] Figure 1 The diagram shows the rutting factor curves for Examples 1-2 and Comparative Examples 1-3.

[0021] Figure 2 The graph shows the creep stiffness (S) data of Examples 1-2 and Comparative Examples 1-3.

[0022] Figure 3 The graph shows the creep rate (m) data for Examples 1-2 and Comparative Examples 1-3. Detailed Implementation

[0023] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below with reference to specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the present invention. Unless otherwise specified, the experimental methods and detection methods described in the following embodiments are conventional methods; unless otherwise specified, the reagents and materials described are commercially available.

[0024] In the preparation of vulcanized natural latex modified asphalt, firstly, deionized water and the dispersant naphthalene sulfonate formaldehyde condensate (NNO) are thoroughly mixed with a glass rod and then poured into a horizontal sand mill. This step effectively improves the homogeneity of the mixture before the subsequent addition of solid compounding agents such as sulfur, silica, and zinc oxide. Subsequently, the sulfur and silica vulcanizing agents are mixed and ground in a horizontal sand mill to fully utilize shear force and ensure thorough and uniform grinding. After grinding, the antioxidant 2,6-di-tert-butyl-4-methylphenol (BHT) is introduced to effectively improve the antioxidant stability of the vulcanization system. Next, the accelerators zinc ethylphenyl dithiocarbamate (PX) and accelerator 2-mercaptobenzothiazole (MBT) synergistically promote the vulcanization rate and sulfur utilization efficiency, activating the sulfur under the promoting effect and forming a uniformly dispersed active vulcanization system under appropriate formulation conditions. Zinc oxide, as a crosslinking activator, promotes the vulcanization reaction and improves crosslinking efficiency. Crosslinking activators and accelerators work synergistically to form an active vulcanization system, improving vulcanization efficiency. Subsequently, the vulcanized natural rubber exhibits a high crosslinking density, further consolidating its three-dimensional network structure and thus enhancing the deformation recovery ability of the vulcanized latex. Finally, asphalt and vulcanized natural rubber latex are mixed at high temperatures to generate a pre-vulcanized natural rubber latex-modified asphalt resistant to high-temperature degradation.

[0025] The present invention will be further described in detail below with reference to the embodiments, which are merely representative examples of the present invention.

[0026] The accelerator, zinc ethylphenyl dithiocarbamate (PX), has a molecular weight of 458.02. The antioxidant, 2,6-di-tert-butyl-4-methylphenol (BHT), has a molecular weight of 220.35. The accelerator, 2-mercaptobenzothiazole (MBT), has a molecular weight of 167.25. The crosslinking activator, zinc oxide, has a molecular weight of 81.39. The dispersant, naphthalenesulfonate formaldehyde condensate (NNO), has a molecular weight of 472.44.

[0027] Before modifying the asphalt, this invention first separately verified the performance of vulcanized natural latex, as follows.

[0028] Preparation Example 1 The vulcanization treatment method for natural rubber latex includes the following steps: The dosage of each compounding agent in the vulcanized latex is calculated based on the ratio of the latex to 100 parts by weight of asphalt. The natural latex used is a low-ammonia natural latex with a solid content of 60%.

[0029] S1: Various rubber additives are graded and wet-mixed using a horizontal sand mill. First, deionized water and 0.015 parts of dispersant naphthalene sulfonate formaldehyde condensate (NNO) are thoroughly mixed with a glass rod and then poured into the horizontal sand mill. Deionized water is used as the wet grinding medium, controlling its proportion to 45% of the total mass of the grinding mixture, and is not included in the final formulation.

[0030] S2: Subsequently, add 0.18 parts of sulfur as a vulcanizing agent and 0.15 parts of silicon dioxide and mix and grind.

[0031] S3: After grinding for 20 minutes, add 0.075 parts of antioxidant 2,6-di-tert-butyl-4-methylphenol (BHT) and continue grinding; after grinding for 55 minutes, add 0.09 parts of accelerator zinc ethylphenyl dithiocarbamate (PX) and 0.045 parts of accelerator 2-mercaptobenzothiazole (MBT) to the horizontal sand mill and continue grinding.

[0032] S4: After grinding for 65 minutes, add 0.075 parts of crosslinking activator (zinc oxide) and continue grinding until finished, generating a vulcanized mixture. The grinding speed is 700 rpm, and the total grinding time is 75 minutes.

[0033] S5: 15 parts of natural rubber latex are vulcanized by water bath heating. The water bath heating temperature is set to 60℃. Heating starts from room temperature. After reaching the temperature, the vulcanization mixture is added and the vulcanization reaction is carried out for 150 minutes.

[0034] S6: During the vulcanization process, the natural rubber latex is slowly stirred to ensure that it is heated and mixed evenly, ultimately obtaining vulcanized natural rubber latex.

[0035] S7: After the vulcanized latex is cast into the mold to form a film, it is aged at 80°C for 210 minutes. After the time is reached, the film is quickly removed and left to stand for 24 hours. Then the mechanical properties of the 2mm thick dry film are tested.

[0036] Comparative Example A The difference between this comparative example and Preparation Example 1 is that the pre-vulcanization treatment in steps S1-S6 is not performed, and the unvulcanized natural latex is directly subjected to the conditions of step S7 (aging at 80°C for 210 minutes) of Preparation Example 1 to prepare a film.

[0037] Comparative Example B Compared with Preparation Example 1, the grinding time has changed. The grinding time in the first part of step S3 has been reduced from 20 minutes to 15 minutes, and the grinding time in the second part has been adjusted to 45 minutes. The grinding time in step S4 has been adjusted from 65 minutes to 50 minutes, and the total grinding time is 60 minutes. The other steps have not changed.

[0038] The tensile strength, elongation at break, and stress at 100% elongation of the samples prepared by the experimental methods of Preparation Example 1, Comparative Example A, and Comparative Example B were analyzed, and the results are shown in Table 1.

[0039] Table 1 Tensile test data of vulcanized natural rubber latex The test results in Table 1 show that Preparation Example 1 exhibits better mechanical properties. Compared to Comparative Example A, the tensile strength increased by 52%, the elongation at break increased by 24%, and the stress at 100% elongation decreased by 20%. This is likely because the natural latex after vulcanization has uniformly dispersed rubber particles, thus constructing a dense and stable three-dimensional cross-linked network structure, which improves the mechanical properties of the latex film. However, Comparative Example B shows improvement compared to Comparative Example A, but it is still lower than Preparation Example 1. The possible reason is insufficient grinding, which prevents solid particles such as sulfur and silica from being uniformly dispersed in the natural latex, thereby affecting the cross-linking reaction.

[0040] Based on the above conclusions, vulcanized natural rubber latex was used to modify asphalt, and relevant performance tests were conducted.

[0041] Example 1 A method for preparing vulcanized natural latex modified asphalt includes the following steps: Vulcanized natural latex modified asphalt, using low-ammonia natural latex with a solid content of 60%. The following raw materials are listed in parts by weight.

[0042] S1: Various rubber additives are graded and wet-mixed using a horizontal sand mill. First, deionized water and 0.015 parts of dispersant naphthalene sulfonate formaldehyde condensate (NNO) are thoroughly mixed with a glass rod and then poured into the horizontal sand mill. Deionized water is used as the wet grinding medium, controlling its proportion to 45% of the total mass of the grinding mixture, and is not included in the final formulation.

[0043] S2: Subsequently, add 0.18 parts of sulfur as a vulcanizing agent and 0.15 parts of silicon dioxide and mix and grind.

[0044] S3: After grinding for 20 minutes, add 0.075 parts of antioxidant 2,6-di-tert-butyl-4-methylphenol (BHT) and continue grinding; after grinding for 55 minutes, add 0.09 parts of accelerator zinc ethylphenyl dithiocarbamate (PX) and 0.045 parts of accelerator 2-mercaptobenzothiazole (MBT) to the horizontal sand mill and continue grinding.

[0045] S4: After grinding for 65 minutes, add 0.075 parts of crosslinking activator (zinc oxide) and continue grinding until finished, generating a vulcanized mixture. The grinding speed is 700 rpm, and the total grinding time is 75 minutes.

[0046] S5: 15 parts of natural rubber latex were vulcanized by water bath heating. The water bath heating temperature was set to 60℃, starting from room temperature. After reaching the temperature, the vulcanization mixture was added, and the vulcanization reaction was carried out for 150 minutes. During the vulcanization process, the natural rubber latex was slowly stirred to ensure that it was heated and mixed evenly, and finally vulcanized natural rubber latex was obtained.

[0047] S6: Heat 100 parts of base asphalt to 170°C. Then, add vulcanized natural rubber latex to the asphalt at a rate of 2 mL / min. After the addition is complete, place the mixture in an oil bath at 180°C and stir continuously to allow the water in the system to fully vaporize and be discharged until no bubbles are generated, thus obtaining pre-vulcanized natural rubber latex modified asphalt.

[0048] Example 2 A method for preparing vulcanized natural latex modified asphalt includes the following steps: Vulcanized natural latex modified asphalt, the natural latex used is low-ammonia natural latex with a solid content of 60%, the following raw materials are in parts by weight.

[0049] S1: Various rubber additives are graded and wet-mixed using a horizontal sand mill. First, deionized water and 0.06 parts of dispersant naphthalene sulfonate formaldehyde condensate (NNO) are thoroughly mixed with a glass rod and then poured into the horizontal sand mill. Deionized water is used as the wet grinding medium, controlling its proportion to 45% of the total mass of the grinding mixture, and is not included in the final formulation.

[0050] S2: Subsequently, add 0.28 parts of sulfur as a vulcanizing agent and 0.36 parts of silicon dioxide and mix and grind.

[0051] S3: After grinding for 20 minutes, add 0.14 parts of antioxidant 2,6-di-tert-butyl-4-methylphenol (BHT) and continue grinding; after grinding for 55 minutes, add 0.16 parts of accelerator zinc ethylphenyl dithiocarbamate (PX) and 0.08 parts of accelerator 2-mercaptobenzothiazole (MBT) to the horizontal sand mill and continue grinding.

[0052] S4: After grinding for 65 minutes, add 0.14 parts of crosslinking activator (zinc oxide) and continue grinding until finished, generating a vulcanized mixture. The grinding speed is 700 rpm, and the total grinding time is 75 minutes.

[0053] S5: 20 parts of natural rubber latex were vulcanized by water bath heating at 60°C, starting from room temperature. After reaching the temperature, the vulcanization mixture was added, and the vulcanization reaction was carried out for 150 minutes. During the vulcanization process, the natural rubber latex was slowly stirred to ensure uniform heating and mixing, ultimately obtaining vulcanized natural rubber latex.

[0054] S6: Heat 100 parts of base asphalt to 170°C. Then, add vulcanized natural rubber latex to the asphalt at a rate of 2 mL / min. After the addition is complete, place the mixture in an oil bath at 180°C and stir continuously to allow the water in the system to fully vaporize and be discharged until no bubbles are generated, thus obtaining vulcanized natural rubber latex modified asphalt.

[0055] Comparative Example 1 This comparative example provides unmodified No. 70 base bitumen.

[0056] Comparative Example 2 The difference between this comparative example and Example 1 is that the vulcanization treatment in steps S1-S5 is not performed. Under the same conditions in step S6, 15 parts of unvulcanized natural latex are directly mixed into 100 parts of asphalt.

[0057] Comparative Example 3 The difference between this comparative example and Example 2 is that the vulcanization treatment in steps S1-S5 is not performed, and under the same conditions in step S6, 20 parts of SBR latex are directly mixed into 100 parts of asphalt.

[0058] The following performance evaluations are conducted on the asphalt samples prepared in each of the above groups.

[0059] (1) Conventional performance test of asphalt The asphalt prepared according to the experimental schemes of Examples 1 and 2 and Comparative Examples 1 to 3 was subjected to conventional tests on the three major indicators.

[0060] Table 2 Results of routine experiments The softening point reflects the high-temperature stability of asphalt. The 5℃ ductility is a key technical indicator characterizing the low-temperature ductility of asphalt. The base asphalt (Comparative Example 1) sample exhibited brittle fracture at the 5℃ ductility, therefore no valid value could be obtained. As shown in Table 2, compared to Comparative Example 2, the softening point of Example 1 increased from 72.3℃ to 84.1℃, and the 5℃ ductility increased from 10.8 cm to 16.7 cm. This indicates that, under the same natural latex content, the pre-vulcanized natural latex-modified asphalt significantly improved in both low-temperature crack resistance and high-temperature stability. Compared to Example 1, the softening point of Example 2 increased from 84.1℃ to 91.0℃, and the 5℃ ductility increased from 16.7 cm to 23.9 cm. This indicates that increasing the latex content can further enhance its modification effect. The softening point and 5℃ ductility of Example 2 are significantly better than those of Comparative Example 3, further demonstrating the excellent performance of the pre-vulcanized natural latex-modified asphalt in both high and low temperature conditions. However, due to the different types of latex, this comparison is mainly used to reflect the performance differences of asphalt under different types of latex. The core effect is mainly based on the comparison of the same type of latex in Comparative Example 2 and Examples 1-2.

[0061] (2) Rutting factor In dynamic rheometer (DSR) testing of asphalt, the rutting factor is typically used to characterize the asphalt's ability to resist permanent deformation under high-temperature conditions. Under the same temperature conditions, a higher rutting factor value indicates greater stability of the asphalt at high temperatures. Figure 1 As shown.

[0062] Depend on Figure 1 The experimental results show that the rutting factor value decreases with increasing temperature, and the rate of decrease gradually levels off when the temperature reaches a certain point. At the same temperature, the rutting factor values ​​of Examples 1-2 are significantly higher than those of Comparative Examples 1-3, indicating that the high-temperature rutting resistance of Examples 1-2 is superior to that of Comparative Examples 1-3. Compared to Comparative Example 2, the rutting factor value of Example 1 is significantly higher, indicating that the vulcanized natural latex helps improve the asphalt's resistance to permanent deformation.

[0063] (3) Low-temperature bending creep stiffness test The low-temperature crack resistance of asphalt was evaluated using a bending beam rheometer (BBR). A smaller creep stiffness (S) and a larger creep rate (m) indicate better stress relaxation performance of the asphalt under low-temperature conditions. Figure 2 and Figure 3 As shown.

[0064] Depend on Figure 2 and Figure 3The results show that as the temperature decreases, the creep stiffness (S) of Examples 1 and 2, and Comparative Examples 1-3, tends to increase, while the creep rate (m) tends to decrease. This may be because lower temperatures significantly affect the thermal motion within asphalt molecules, causing the asphalt to change from a highly elastic state to a glassy state, thus altering its low-temperature crack resistance. Under the same natural latex content, the creep stiffness (S) of Example 1 is lower than that of Comparative Example 2, and the creep rate (m) is higher. This indicates that, under the same content, pre-vulcanized natural latex modified asphalt exhibits better low-temperature crack resistance than unvulcanized natural latex modified asphalt. Under the same latex content, Example 2 shows a lower creep stiffness (S) and a higher creep rate (m) compared to Comparative Example 3. This suggests that pre-vulcanized natural latex modified asphalt has a greater advantage in low-temperature stress relaxation ability; however, due to the different latex types, this comparison mainly reflects the performance differences of asphalt under different latex types. Compared with Comparative Example 1 (base asphalt), Examples 1-2 generally exhibited lower creep stiffness (S) and higher creep rate (m), further verifying that pre-vulcanized natural latex helps improve the low-temperature crack resistance of asphalt.

[0065] (4) Linear amplitude scanning test The fatigue performance of asphalt in Examples 1 and 2 and Comparative Examples 1 to 3 was evaluated using linear amplitude scanning tests, as shown in Table 3.

[0066] Table 3 Fatigue life of asphalt under different strain levels As can be seen from the test results in Table 3, the effect of strain level on asphalt fatigue behavior varies. With the increase of strain level, the difference between Examples 1 and 2 and Comparative Examples 1 to 3 gradually narrows, and the larger the strain, the smaller the difference. Under different strain levels, the asphalt fatigue life of Example 2 is higher than that of Example 1 and Comparative Examples 1 to 3, indicating that pre-vulcanized natural latex is beneficial to improving the fatigue resistance of asphalt.

[0067] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, it is intended to include any modifications and variations that fall within the scope of the claims and their equivalents.

Claims

1. A type of modified asphalt using vulcanized natural latex, characterized in that, Made from the following parts by weight of raw materials: The composition includes 100 parts base asphalt, 15-20 parts natural latex, 0.18-0.28 parts sulfur vulcanizing agent, 0.15-0.36 parts silica, 0.075-0.14 parts antioxidant 2,6-di-tert-butyl-4-methylphenol, 0.09-0.16 parts accelerator zinc ethylphenyl dithiocarbamate, 0.045-0.08 parts accelerator 2-mercaptobenzothiazole, 0.075-0.14 parts crosslinking activator zinc oxide, and 0.015-0.06 parts dispersant naphthalenesulfonate formaldehyde condensate.

2. A method for preparing vulcanized natural latex modified asphalt according to claim 1, characterized in that, Includes the following steps: A vulcanized mixture was prepared by wet grinding of dispersant naphthalene sulfonate formaldehyde condensate, vulcanizing agent sulfur, silica, antioxidant 2,6-di-tert-butyl-4-methylphenol, accelerator zinc ethylphenyl dithiocarbamate, accelerator 2-mercaptobenzothiazole and crosslinking activator zinc oxide using water as the grinding medium. Natural latex and vulcanizing mixture are mixed and vulcanized to obtain vulcanized natural latex. Vulcanized natural rubber latex was added as a modifier to the heated base asphalt, and water was removed under stirring conditions to obtain vulcanized natural rubber latex modified asphalt.

3. The preparation method according to claim 2, characterized in that, The specific preparation process of the vulcanized mixture includes the following steps: A horizontal sand mill was used to mix and grind water, dispersant naphthalene sulfonate formaldehyde condensate, and sulfur and silica as a sulfiding agent. Then add the antioxidant 2,6-di-tert-butyl-4-methylphenol and grind it. Then, zinc ethylphenyl dithiocarbamate and 2-mercaptobenzothiazole are added as accelerators and mixed and ground. Finally, zinc oxide, a cross-linking activator, is added and ground to generate a vulcanized mixture.

4. The preparation method according to claim 2, characterized in that, During the grinding process, the grinding speed is 700 rpm and the total grinding time is 75 minutes.

5. The preparation method according to claim 4, characterized in that, During grinding, the order of adding raw materials and the grinding time are as follows: In the water and dispersant system, only sulfur and silica are added at the beginning. After 20 minutes, antioxidant 2,6-di-tert-butyl-4-methylphenol is added. After 55 minutes, accelerator 2-mercaptobenzothiazole and accelerator zinc ethylphenyl dithiocarbamate are added. After 65 minutes, crosslinking activator zinc oxide is added. The total grinding time is 75 minutes.

6. The preparation method according to claim 2, characterized in that, In the vulcanized mixture, the solid particle size is 1μm~10μm.

7. The preparation method according to claim 2, characterized in that, When preparing vulcanized natural rubber latex, the natural rubber latex is first heated in a water bath to 50℃~70℃, and then a vulcanizing mixture is added and the vulcanization reaction is carried out for 150~160 minutes.

8. The preparation method according to claim 2, characterized in that, The base asphalt is heated to 170℃, and vulcanized natural rubber latex is added dropwise to the hot asphalt at a rate of 2mL / min to 10mL / min. After the addition is complete, the mixture is placed in an oil bath at 180℃ and stirred continuously to allow the water in the system to fully vaporize and be discharged until no more bubbles are generated, thus obtaining vulcanized natural rubber latex modified asphalt.

9. The preparation method according to claim 2, characterized in that, The natural latex is a low-ammonia natural latex preserved with ammonia water, with a solid content of 60%~65%.

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