Modified asphalt mixture and preparation method thereof

Abstract

The invention provides a modified asphalt mixture and a preparation method thereof, and belongs to the technical field of modified asphalt. The preparation method comprises the following steps: (1) heating and mixing asphalt, rubber oil and an SBS thermoplastic elastomer to obtain a component A containing SBS modified asphalt; (2) the component B is added into the component A, heating and mixing are conducted, the component A activated through free radicals is obtained, and the component B comprises at least one of dibenzoyl peroxide and azodiisobutyronitrile; and (3) adding the polyurethane modifier serving as a component C into the component A activated by the free radicals, and stirring to obtain the polyurethane and SBS composite modified asphalt mixture. The isocyanate in the component C can chemically react with groups in the component A after free radical activation, a stable three-dimensional network structure is formed in the asphalt, and various properties of the asphalt are improved.

Description

Technical Field

[0001] The invention relates to the technical field of modified asphalt, and in particular to a modified asphalt mixture and a preparation method thereof. Background Art

[0002] Affected by factors such as overloaded vehicles, high vehicle traffic, and changes in ambient temperature with the changing seasons, traditional asphalt pavements have gradually exposed problems such as rutting, cracks and aging, reducing driving comfort and affecting traffic safety.

[0003] One approach in the related art is to add SBS (SBS) thermoplastic elastomer to the asphalt mixture, but the compatibility between asphalt and SBS is poor, making it difficult to evenly distribute the asphalt. The asphalt pavement formed by paving has insufficient high temperature performance and poor anti-aging performance. Summary of the invention

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

[0005] According to an embodiment of 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 a component A containing SBS modified asphalt; step (2) adding component B to component A, heating and mixing, to obtain a component A activated by free radicals, wherein component B comprises at least one of dibenzoyl peroxide and azobisisobutyronitrile; step (3) adding a polyurethane modifier as component C to the component A activated by free radicals and stirring the mixture, so that the isocyanate groups in the polyurethane interact with the active groups in the component A activated by free radicals, to obtain a composite modified asphalt mixture of polyurethane and SBS, wherein the active groups comprise hydroxyl groups, amine groups, and carboxylic acid groups.

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

[0007] According to an embodiment of the present invention, the first heating and mixing condition is: heating and stirring at 140-160°C for 20-40 minutes; the second heating and mixing condition is: heating from 140-160°C to 180-190°C, and heating and stirring at 180-190°C for 2-4 hours.

[0008] According to an embodiment of the present invention, the conditions for heating and mixing in step (2) are: cooling the temperature from 180-190° C. to 140-160° C., and heating and stirring at 140-160° C. for 5-15 minutes.

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

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

[0011] According to an embodiment of the present invention, the asphalt includes 20-30% saturates, 30-40% aromatics, 20-30% colloids, 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 an embodiment of another aspect of the present invention, there is provided a modified asphalt mixture, which is obtained by the above-mentioned preparation method of the modified asphalt mixture.

[0015] According to an embodiment of the present invention, by adding a free radical initiator of dibenzoyl peroxide and / or azobisisobutyronitrile to SBS modified asphalt, under the action of mixing and heating, the free radicals generated by the decomposition of the free radical initiator can react with a variety of groups with active hydrogen in the SBS modified asphalt, introduce more free radical sites, so that the active hydrogen groups are activated to generate more active groups, such as hydroxyl, amine, carboxylic acid, etc. When the polyurethane modifier is added to the SBS modified asphalt activated by free radicals, the isocyanate groups in the polyurethane can quickly undergo a cross-linking reaction with the activated hydroxyl, amine, and carboxylic acid groups, thereby increasing the interaction between asphalt molecules, forming a relatively stable three-dimensional network structure inside the asphalt molecules, effectively reducing the phenomenon that the SBS modified asphalt is easy to separate under high temperature conditions, improving the uniformity of the mixture of the two, and improving the storage stability and high temperature resistance of the modified asphalt mixture, while also improving the mechanical properties of the asphalt. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A flow chart showing a method for preparing a modified asphalt mixture according to an embodiment of the present invention;

[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 The infrared spectra of the modified asphalt of Comparative Example 2 of the present invention at different reaction times are shown; and

[0019] Figure 4 The infrared spectra of the modified asphalt at different reaction times in Example 4 of the present invention are shown. DETAILED DESCRIPTION

[0020] Below, 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 present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of concepts of the present invention.

[0021] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The term "comprising" used herein indicates the existence of features, steps, operations, but does not exclude the existence or addition of one or more other features.

[0022] In the case of using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.). In the case of using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, or C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0023] Styrene-butadiene-styrene (SBS) thermoplastic elastomer is widely used in the field of modified asphalt due to its excellent elasticity and durability. However, traditional SBS thermoplastic elastomer is only physically mixed with asphalt, which has poor compatibility and is prone to segregation at high temperatures, resulting in uneven asphalt performance. In addition, the high-temperature performance of single SBS modified asphalt is insufficient and the anti-aging performance is poor.

[0024] In the process of realizing the concept of the present invention, it was found that the isocyanate groups in the polyurethane can react chemically with the internal groups of the asphalt to form a stable spatial network structure. And by combining polyurethane with SBS, it helps to further improve the high temperature performance and storage stability of the modified asphalt, improve the segregation phenomenon, and effectively reduce the rutting problem at high temperature. However, due to the small number and different types of active groups of colloid and asphaltene in asphalt, the reaction speed of asphalt and polyurethane is slow and the modification effect is seriously dependent on the quality of the asphalt itself, which limits the wide application of polyurethane modified asphalt technology.

[0025] In order to solve the above problems, a free radical initiator is first added to the SBS modified asphalt to activate some groups in the SBS modified asphalt and generate active groups. The activated SBS modified asphalt is mixed with a polyurethane modifier, so that the isocyanate groups in the polyurethane can undergo a three-dimensional cross-linking reaction with more active groups such as hydroxyl groups, amine groups, and carboxylic acid groups, forming a more stable spatial network structure and improving the various properties of the asphalt.

[0026] Specifically, according to an embodiment of one aspect of the present invention, a method for preparing a modified asphalt mixture is provided. Figure 1 A flow chart showing a method for preparing a modified asphalt mixture according to an embodiment of the present invention is shown. 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 the embodiment of the present invention, the addition of rubber oil helps to improve the low temperature performance of asphalt, and the addition of SBS thermoplastic elastomer helps to improve the low temperature toughness and high temperature stability of asphalt. Heating and mixing helps to fully mix the three raw materials.

[0029] In step (2), component B is added to component A, and the mixture is heated and mixed to obtain component A activated by free radicals, wherein component B includes at least one of dibenzoyl peroxide and azobisisobutyronitrile.

[0030] According to an embodiment of the present invention, component B includes at least one of dibenzoyl peroxide and azobisisobutyronitrile, which are free radical initiators. Under heating conditions, the free radical initiators will decompose and generate free radicals. The generated free radicals will interact with the macromolecular chains in component A, especially generate molecules with active hydrogen (such as hydroxyl, amine, carboxylic acid), thereby introducing more free radical sites, so that component A is activated.

[0031] It should be noted that there are some hydroxyl, amino, carboxylic acid and other groups in asphalt, but the number is small and the activity is poor. The present invention introduces a free radical initiator to generate free radicals, which then interact with benzene rings or carbon to generate carbon free radicals. The obtained carbon free radicals then react with water, oxygen, etc. to generate active groups such as carboxyl and hydroxyl, 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 that 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 that has been activated by free radicals, thereby obtaining a polyurethane and SBS composite modified asphalt mixture, wherein the active groups include hydroxyl, amine, and carboxylic acid groups.

[0033] According to an embodiment of the present invention, component C includes a polyurethane modifier. The polyurethane has an isocyanate group (-N=C=O). The isocyanate group can chemically react with more hydroxyl groups, amine groups, carboxylic acid groups and other groups in the activated asphalt to generate carbamate 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 above reaction process, R represents other groups connected to the isocyanate in the polyurethane, R 1 Represents other groups connected to hydroxyl, amine, carboxylic acid, etc. Since the isocyanate group further reacts chemically with the above groups in the activated asphalt, the interaction between the asphalt molecules is enhanced, and a more stable three-dimensional network structure is formed inside the asphalt, so that the modified asphalt mixture forms an integrated structure, which helps to improve the storage stability, high temperature performance and mechanical properties of the modified asphalt mixture.

[0038] According to an embodiment of the present invention, by introducing free radical initiators such as dibenzoyl peroxide and / or azobisisobutyronitrile as component B, the free radicals generated by their thermal decomposition can more efficiently activate components such as saturated components, colloids and asphalt 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, effectively reducing the phenomenon that SBS modified asphalt is easy to segregate under high temperature conditions, and improving the uniformity of polyurethane and SBS composite modified asphalt mixture under high temperature conditions, thereby improving the actual application effect of polyurethane and SBS composite modified asphalt mixture.

[0039] It is understandable that the conventional SBS modified asphalt is made by physically mixing SBS with asphalt, so that the compatibility between the two is poor. However, the polyurethane and SBS composite modified asphalt mixture in the present invention realizes the chemical modification of asphalt by SBS and polyurethane modifiers through chemical crosslinking reaction between polyurethane modifier and SBS modified asphalt, and forms a crosslinking reaction through the interaction between isocyanate and the functional groups containing active hydrogen in SBS modified asphalt, thereby enhancing the mechanical strength, elasticity and chemical corrosion resistance of the modified asphalt mixture, broadening the adaptability temperature of the modified asphalt mixture, and improving the anti-aging ability and adhesion of the modified asphalt mixture.

[0040] For example, taking component B as dibenzoyl peroxide, dibenzoyl peroxide is added to component A and heated, so that dibenzoyl peroxide is thermally decomposed to generate two benzoyl free radicals. When the benzoyl free radicals come into contact with the various components of asphalt, addition reactions or substitution reactions may occur, and the asphalt molecules are modified by chain initiation, chain growth, and chain termination to generate more active groups, such as hydroxyl, amine or carboxylic acid groups. The generated active groups are more than the active groups of asphalt molecules that have not been activated by free radicals, and can provide more active sites, which are helpful to interact with the isocyanate groups added later to form a three-dimensional cross-linked network structure, thereby enhancing the bonding strength of 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 first 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 mixing to obtain component A.

[0044] According to the embodiment of the present invention, by adding rubber oil to asphalt, the viscosity of asphalt is reduced and the processability of asphalt is improved. The first heating and mixing helps to promote the full mixing of the two to obtain a uniform first mixture. Then, adding SBS thermoplastic elastomer helps to improve the high temperature stability of asphalt.

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

[0046] According to an embodiment of the present invention, the first heating and mixing condition is: at 140~160℃, for example, it can be 140℃, 150℃ or 160℃, preferably 160℃, heating and stirring for 20~40min, for example, it can be 20min, 30min or 40min, preferably 30min. Raising to the above temperature range first helps to fully melt and evenly disperse the asphalt and rubber oil to ensure the fluidity of the raw materials. The second heating and mixing condition is: heating from 140~160℃ to 180~190℃, for example, it can be 180℃, 185℃ or 190℃, preferably 185℃, heating and stirring at 180~190℃ for 2~4h, for example, it can be 2h, 3h or 4h, preferably 3h. Raising the temperature to 180~190℃ is to better dissolve the SBS thermoplastic elastomer, and to promote the SBS thermoplastic elastomer to be evenly dispersed in the asphalt, enhance the elasticity and recovery ability of the asphalt, and improve 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: cooling the temperature from 180-190°C to 140-160°C, for example, 140°C, 150°C or 160°C, preferably 150°C, and heating and stirring at 140-160°C 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 relatively stable uniform structure.

[0048] According to an embodiment of the present invention, the stirring temperature in step (3) is 130-160°C, for example, 130°C, 140°C, 150°C or 160°C, 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 ranges helps to promote the isocyanate group to fully interact with the hydroxyl group, amine group and carboxylic acid group, and 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, and improving the storage stability, high temperature performance and mechanical properties of the modified asphalt mixture through the above modification means.

[0049] Furthermore, since the SBS modified asphalt is activated by free radicals, more active groups such as hydroxyl, amine, and carboxylic acid groups are formed, so that the isocyanate and the above active groups undergo a relatively rapid cross-linking reaction. When isocyanate-modified asphalt is used directly in the traditional way, the reaction time is 3 to 6 hours, but in the present invention, after free radical activation, the reaction time between isocyanate and SBS modified asphalt is shortened to 1 to 2 hours, thereby improving the production efficiency of polyurethane and SBS composite modified asphalt mixture, and thus improving the actual application efficiency.

[0050] According to an embodiment of the present invention, the addition of SBS thermoplastic elastomer in component A improves the elasticity and recovery ability of asphalt, reduces rutting, and improves the high temperature performance of modified asphalt mixture. The addition of rubber oil reduces the viscosity of asphalt, making it easy to construct and maintaining good fluidity. Component B includes a free radical initiator, which helps to cross-link the SBS thermoplastic elastomer, asphalt and polyurethane modifier, improve the mechanical strength and thermal stability of the modified asphalt mixture, and improve the anti-aging performance. The isocyanate group in the polyurethane can interact with the SBS modified asphalt to form a stable spatial network structure, enhance the stability of the modified asphalt mixture, effectively reduce the phenomenon of SBS modified asphalt (by physical mixing of asphalt and SBS) in the related art that is easy to separate under high temperature conditions, and improve the uniformity of the modified asphalt mixture under high temperature conditions.

[0051] According to the embodiment of the present invention, in terms of weight, the asphalt in component A is 93-96 parts, the rubber oil is 1-2 parts, and the SBS thermoplastic elastomer is 2-4 parts. Asphalt, as the main component, provides the basic structure and bonding force of the asphalt mixture. Component B is 0.05-0.3 parts; component C is 0.5-2 parts. In the process of conducting relevant experiments of the present invention, it was found that adjusting the above components within the above ranges can help obtain a modified asphalt mixture with better mechanical properties, wider temperature adaptability, and longer service life.

[0052] According to an embodiment of the present invention, asphalt includes 20-30% saturated fractions, 30-40% aromatic fractions, 20-30% colloids, and 5-10% asphaltenes. It is understood that saturated fractions may include, for example, saturated alkanes, cycloalkanes, etc., and saturated fractions provide the fluidity of asphalt, which helps to reduce the viscosity of asphalt at high temperatures, thereby facilitating paving. Aromatic fractions may include, for example, polycyclic aromatic hydrocarbons, etc., in which the π electron cloud can interact with the SBS elastomer to improve the asphalt modification effect, and the hardness, durability and deformation resistance of asphalt at high temperatures are improved by the addition of aromatic fractions. Colloids may include, for example, compounds containing oxygen, nitrogen or sulfur, etc., which help to connect aromatic fractions and asphaltene, and enhance the stability and elasticity of asphalt. Asphaltene may include, for example, polar macromolecules, which help to form a filling effect, improve the viscosity and strength of asphalt, and enhance the anti-aging ability of asphalt.

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

[0054] Further preferably, the asphalt is No. 70 petroleum asphalt. In the process of conducting relevant experiments of the present invention, it is found that when No. 70 petroleum asphalt is used, the modified asphalt mixture prepared by composite modification of polyurethane and SBS has better mechanical properties and improved stability.

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

[0056] Weigh petroleum asphalt and rubber oil, heat and stir at a temperature range of 140-160°C to mix them 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°C, add component B and stir for 10 minutes to mix evenly to obtain component A activated by free radicals.

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

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

[0061] The present invention is further described below by embodiments and related test experiments and results thereof. In the detailed description below, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present invention. However, it is obvious that one or more embodiments may also be implemented without these specific details. And, in the absence of conflict, the details in the following embodiments may be combined into other feasible embodiments at will.

[0062] It should be noted that the following specific examples are only for illustration, and the protection scope of the present invention is not limited thereto. The chemicals and raw materials used in the following examples are all commercially available or homemade by recognized processing methods.

[0063] It should be noted that the asphalt used in the embodiments and comparative examples is No. 70 asphalt, in which the four components range as follows: saturated fraction 20-30%, aromatic fraction 30-40%, colloid 20-30%, asphaltene 5-10%). The model of the SBS thermoplastic elastomer used is linear YH-502, and the manufacturer is a certain petrochemical company. The model of the polyurethane modifier used is B2 last, and the manufacturer is a certain joint-stock company. The manufacturer of the rubber oil used is a certain Shandong Chemical Company.

[0064] Embodiment 1:

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

[0066] 3 parts of SBS were added, the temperature was raised to 185°C and stirred for 3 hours to obtain a physical mixture of SBS and asphalt. The temperature was then lowered to 150°C, 0.1 parts of dibenzoyl peroxide (BPO initiator) were added and stirred for 10 minutes to make it uniformly mixed, 0.5 parts of polyurethane modifier were added and stirred for 1.5 hours, and the asphalt mixture 1 prepared in Example 1 was tested for discharge, and the test results are shown in Table 1 below.

[0067] Comparative Example 1:

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

[0069] 3 parts of SBS were added, and the temperature was raised to 185° C. and stirred 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 a discharge test, and the test results are shown in Table 1 below.

[0070] Comparative Example 2:

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

[0072] Add 3 parts of SBS, raise the temperature to 185°C and stir for 3 hours to obtain a mixture of SBS and asphalt. Lower the temperature to 150°C, add 2 parts of polyurethane modifier, and take samples every hour after adding the polyurethane modifier to measure infrared until 2270cm -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 the present invention are shown. Figure 2 As shown in the figure, the modified asphalt is specifically the infrared spectrum of polyurethane modified asphalt after being reacted at 150℃ for 1h. Compared with the base asphalt, the polyurethane modified asphalt has higher infrared spectra at 2270, 1715, 1650, 1512, and 1240cm -1 A new absorption peak appeared at 2270cm -1 The absorption peak at the position is the absorption peak of the unreacted isocyanate-NCO, 1715 cm -1 The absorption peak at position belongs to the stretching vibration of C=O of amide I, 1650cm -1 The absorption peak at 1512cm is the characteristic peak of urea derivatives. -1 The absorption peak at 1240 cm is attributed to the coupling effect of NH bending vibration and CN stretching vibration of amide II band. -1 The absorption peak at the position is attributed to the coupling effect of the CN stretching vibration and the NH bending vibration of the amide III band. From the above infrared image, it can be seen that the isocyanate functional group in the modifier can react chemically with the hydroxyl group, amine group and other groups in the asphalt molecule to form carbamate and urea.

[0074] After adding the polyurethane modifier, samples were taken every 30 minutes to measure infrared and observe the 2270cm -1 The changes of infrared characteristic peaks at. Figure 3 The infrared spectra of the modified asphalt of Comparative Example 2 of the present invention at different reaction times are shown. Figure 3 As shown, the reaction was carried out for 6 h at 2270 cm -1 The infrared characteristic peak of isocyanate still exists at , and the consumption of isocyanate is slow from 5h to 6h, indicating that there are insufficient active groups in the asphalt that can react with isocyanate.

[0075] Embodiment 2:

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

[0077] 3 parts of SBS were added, the temperature was raised to 185°C and stirred for 3 hours to obtain a physical mixture of SBS and asphalt. The temperature was then lowered to 150°C, 0.1 parts of BPO initiator were added and stirred for 10 minutes to make it uniformly mixed, 1 part of polyurethane modifier was added and stirred for 1.5 hours, and the asphalt mixture 2 prepared in Example 2 was tested for discharge, and the test results are shown in Table 1 below.

[0078] Embodiment 3:

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

[0080] 3 parts of SBS were added, the temperature was raised to 185°C and stirred for 3 hours to obtain a physical mixture of SBS and asphalt. The temperature was lowered to 150°C, 0.1 parts of BPO initiator were added and stirred for 10 minutes to make it uniformly mixed, 1.5 parts of polyurethane modifier were added and stirred for 1.5 hours, and the asphalt mixture 3 prepared in Example 3 was tested for discharge, and the test results are shown in Table 1 below.

[0081] Embodiment 4:

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

[0083] 3 parts of SBS were added, the temperature was raised to 185°C and stirred for 3 hours to obtain a physical mixture of SBS and asphalt. The temperature was then lowered to 150°C, 0.1 parts of BPO initiator were added and stirred for 10 minutes to make it uniformly mixed, 2 parts of polyurethane modifier were added and stirred for 1.5 hours, and the asphalt mixture 4 prepared in Example 4 was tested for discharge, and the test results are shown in Table 1 below.

[0084] Figure 4 The infrared spectra of the modified asphalt of Example 4 of the present invention at different reaction times are shown. Figure 4 It can be seen that after adding BPO initiator, the 2270 cm-1 peak is almost invisible after 1.5 h of reaction. -1 The infrared absorption peak of isocyanate at shows that the BPO initiator can activate each component in the SBS composite modified asphalt, thereby significantly shortening the reaction time of isocyanate and asphalt, and accelerating the reaction speed of isocyanate and asphalt.

[0085] Table 1 shows the test results of Examples 1 to 3 and Comparative Example 1. As shown in Table 1, the penetration values ​​of Examples 1 to 3 are all less than that of Comparative Example 1, indicating that the modified asphalt prepared therefrom has a higher hardness and has good high temperature resistance and high load resistance. The softening points of Examples 1 to 3 are all higher than those of Comparative Example 1, indicating that the asphalt has better stability at high temperatures, is not easy to deform, and can effectively reduce rutting. The viscosities of Examples 1 to 3 are all higher than those of Comparative Example 1, which helps to ensure good construction operability and uniform distribution of the asphalt. The softening point difference values ​​of Examples 1 to 3 are all lower than those of Comparative Example 1, indicating that the modified asphalt prepared therefrom has good homogeneity, that is, the components are mixed more evenly and are not easy to segregate under high temperature conditions.

[0086] The relevant properties of modified asphalt are tested, among which the needle penetration test method is expressed by the depth of the standard needle vertically penetrating the asphalt sample under certain load, time and temperature conditions, and the unit is 1 / 10mm. Among them, the total mass of the standard needle, needle connecting rod and additional weight is (100±0.05)g, the temperature is (25±0.1)℃, and the time is 5s. The same sample is measured three times, and the distance between each test point and the edge of the sample dish is not less than 10mm. Softening point test method. Place the modified asphalt in a shoulder or conical brass ring, flatten the surface, place a standard steel ball, and heat it at a rate of 5℃ / min in water or glycerin as the heating medium until the modified asphalt softens and sags to 25mm. The temperature is the softening point.

[0087] Ductility test method: Pour the modified asphalt into an 8-shaped mold, flatten the surface, place it in a 5°C water bath for at least 2 hours, stretch it with a ductility meter at a stretching speed of 5 cm / min, and record the length of the modified asphalt from the beginning of stretching to the time it breaks, in cm. Viscosity test method: Pour the modified asphalt into a viscosity tube, select a suitable rotor, start the test at a temperature of 135°C, and record the viscosity value. Segregation test method: Pour the modified asphalt into a segregation tube, place it vertically in an oven at 163°C for 48 hours, measure the softening points of the upper and lower parts of the segregation tube, and the difference in softening points is the segregation. The relevant data are shown in Table 1 below.

[0088] Table 1 Test results of modified asphalt of Examples 1 to 3 and Comparative Example 1

[0089]

[0090] The present invention accelerates the reaction speed of isocyanate and asphalt, shortens the reaction time, improves production efficiency and modification effect, and reduces production costs by adding dibenzoyl peroxide and / or azobisisobutyronitrile. In the related art, the traditional SBS modified asphalt has serious segregation phenomenon at high temperature. By adding polyurethane to form a stable three-dimensional network structure inside the asphalt, the stability of the asphalt is enhanced, the segregation phenomenon of the original SBS modified asphalt at high temperature is effectively reduced, and the uniformity of the material under high temperature conditions is improved. Furthermore, by adding a polyurethane modifier, the present invention can significantly improve the high temperature performance of the modified asphalt mixture, so that the modified asphalt maintains a low penetration at high temperature, which can effectively reduce the rutting phenomenon and extend the service life of the road surface.

[0091] In summary, this SBS modified asphalt mixture based on polyurethane modifier and free radical initiator (such as dibenzoyl peroxide or azobisisobutyronitrile) and preparation method not only improves the performance of asphalt pavement, but also improves production efficiency, and has relatively significant economic and social benefits.

[0092] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is 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 in the scope of protection of the present invention.

Claims

1. A method for preparing a modified asphalt mixture, 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, heating and mixing, to obtain component A activated by free radicals, wherein component B comprises at least one of dibenzoyl peroxide and azobisisobutyronitrile; Step (3) adds a polyurethane modifier as component C to the component A that has been activated by free radicals and stirs them so that the isocyanate groups in the polyurethane interact with the active groups in the component A that has been activated by free radicals to obtain a polyurethane and SBS composite modified asphalt mixture, wherein the active groups include: hydroxyl, amine, and carboxylic acid.

2. The preparation method according to claim 1, wherein Step (1) includes: The asphalt and the rubber oil are first heated and mixed to obtain a first mixture; The SBS thermoplastic elastomer is added into the first mixture for a second heating and mixing to obtain the A component.

3. The preparation method according to claim 2, wherein 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: heating from 140-160° C. to 180-190° C., and heating and stirring at 180-190° C. for 2-4 hours.

4. The preparation method according to claim 1, wherein The conditions for heating and mixing in step (2) are: Lower the temperature from 180~190℃ to 140~160℃, and heat with stirring at 140~160℃ for 5~15min.

5. The preparation method according to claim 1, wherein The stirring temperature in step (3) is 130-160° C. and the stirring time is 1-3 h.

6. The preparation method according to claim 1, wherein In terms of weight, the asphalt in component A is 93-96 parts, the rubber oil is 1-2 parts, and the SBS thermoplastic elastomer is 2-4 parts; Component B is 0.05~0.3 parts; Component C is 0.5~2 parts.

7. The preparation method according to claim 1, wherein The asphalt includes 20-30% saturated fraction, 30-40% aromatic fraction, 20-30% colloid, and 5-10% asphaltenes.

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

9. The preparation method according to claim 1 or 8, wherein: The asphalt is No. 70 petroleum asphalt.

10. A modified asphalt mixture obtained by the preparation method according to any one of claims 1 to 9.

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