Polyurethane modified asphalt material containing a structure of dynamic covalent bond and preparation method thereof

Abstract

The application provides a polyurethane modified asphalt material containing a dynamic covalent bond structure, which comprises 70-90 parts of base asphalt, 8-29 parts of isocyanate prepolymer, 0.5-5.0 parts of a dynamic crosslinking agent, 0.3-1.5 parts of a common crosslinking agent and 0.01-0.1 parts of a catalyst; the dynamic crosslinking agent is a double / multi-active end group compound containing a dynamic bond or a multi-functional compound which can react with an isocyanate group to form a dynamic bond group. The application further provides a preparation method of the polyurethane modified asphalt material containing the dynamic covalent bond structure. In conclusion, the polyurethane modified asphalt material containing the dynamic covalent bond structure has excellent low-temperature performance, fatigue resistance, active healing ability and good regeneration performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of road engineering materials, in particular to a polyurethane modified asphalt material containing a dynamic covalent bond structure and a preparation method thereof. BACKGROUND

[0002] With the gradual entry of China's road construction into a new era of maintenance and construction, how to improve the maintenance level and enhance the road traffic capacity is a problem facing us. Cracking is one of the main damage forms of asphalt pavement, which will seriously reduce the traffic capacity of the road with the passage of time. Therefore, it is of great significance to study how to inhibit the initiation of micro-cracks in asphalt pavement and reduce the crack propagation rate for improving road maintenance efficiency and prolonging the service life of the road. The self-repairing property of asphalt material itself can endow the asphalt pavement with certain damage recovery ability. Under the condition of no external load and sufficient intermittent time, the self-healing ability of asphalt can make the cracks gradually heal. However, the self-repairing ability of asphalt material under service conditions is very weak, which is not enough to resist the generation and propagation of cracks.

[0003] Current researches focus on the use of heat induction technology and microcapsule technology to promote the self-repairing process of asphalt. The heat induction technology is based on the temperature dependence of the flow rate of asphalt. By means of electromagnetic induction or microwave heating, the temperature of asphalt is raised to accelerate the flow of asphalt to the micro-cracks, thereby realizing the rapid healing of the cracks in the pavement. The microcapsule technology is to add microcapsules containing regenerants into asphalt. The capsules are broken under the stress at the crack tip to flow out the regenerants, thereby realizing the repair of the micro-cracks in the asphalt pavement. These self-repairing technologies are all externally assisted self-repairing technologies, which need electromagnetic / microwave generating devices and externally added electromagnetic induction materials or microcapsules. They have poor timeliness and will adversely affect the performance of asphalt itself. These problems limit their popularization and application in actual asphalt pavement.

[0004] In addition, the patent with publication number CN112852109A discloses a preparation method of a high-temperature self-repairing hot-mixed epoxy asphalt material. The basic principle of this technology is ester exchange reaction. The dynamic bond in the epoxy glass polymer material can only undergo ester exchange reaction at high temperature (above 180℃) to realize the toughening and self-healing performance improvement of the material. The patent with publication number CN113801490B discloses a preparation and recycling method of recyclable epoxy asphalt, which is based on the reversible principle of dynamic covalent bond to prepare a recyclable epoxy asphalt based on temperature regulation mechanism. In this technical solution, the dynamic bond is a thermally reversible dynamic bond (DA reaction), and the conditions for the forward and reverse reactions of the epoxy resin phase are temperature changes, which need to be heated to 120℃ to achieve the recyclable purpose. SUMMARY

[0005] Therefore, the polyurethane modified asphalt material containing a dynamic covalent bond structure and a preparation method thereof are provided, which introduces the dynamic covalent bond into the molecular structure of the polyurethane modified asphalt, constructs a dynamic reversible polyurethane crosslinking structure in the asphalt, improves the physical-rheological performance of the asphalt, and endows the asphalt with excellent self-repairing capability and good renewable performance, so that the polyurethane modified asphalt can be efficiently and actively healed and recycled.

[0006] The technical scheme of the present application is implemented as follows:

[0007] In a first aspect, the present application provides a polyurethane modified asphalt material containing a dynamic covalent bond structure, and the raw material components thereof include 70-90 parts of base asphalt, 8-29 parts of isocyanate prepolymer, 0.5-5.0 parts of dynamic crosslinking agent, 0.3-1.5 parts of ordinary crosslinking agent, and 0.01-0.1 parts of catalyst.

[0008] On the basis of the above technical scheme, preferably, the dynamic crosslinking agent is a double / multi-active end group compound containing a dynamic bond, or a multi-functional compound capable of generating a dynamic bond group by reacting with an isocyanate group. The active end group can be a hydroxyl group, a carboxyl group or an amine group. Since the triggering mechanism and applicable conditions of different dynamic covalent bonds are different, in order to be applicable to the temperature conditions (-15℃-60℃) in road service, the dynamic crosslinking agent is selected, and at least one of butanedione oxime, diaminodiphenyl disulfide, dithiodipropionic acid, selenocystamine, cystine and 2,2'-(1,4-phenylene)-bis[4-mercapto-1,3,2-dioxaborolane] is preferably selected. The dynamic crosslinking agent is used for crosslinking reaction with the isocyanate prepolymer, and the dynamic covalent bond is introduced through the dynamic crosslinking agent.

[0009] By introducing the dynamic covalent bond, a dynamic reversible crosslinking network structure is constructed in the asphalt, which has excellent structure rearrangement and conformation adjustment capability, and the dynamic reversible crosslinking network structure is controllable, so that the fatigue resistance of the polyurethane modified asphalt can be greatly improved. By introducing the dynamic covalent bond into the crosslinking structure of the polyurethane modified asphalt, due to the reversible cleavage-exchange reaction characteristics of the dynamic covalent bond, when the material has a damage microcrack, the material can be self-repaired through the reversible chemical interaction between the interface molecules, and long-term and repeated self-repairing can be realized. Since the reversible cleavage-exchange reaction rate of the dynamic covalent bond has temperature dependence, high temperature can accelerate the reversible reaction rate, so that the dynamic reversible crosslinking polyurethane modified asphalt has the characteristics of active viscosity reduction at high temperature, which is expected to reduce the construction temperature of the polyurethane modified asphalt mixture.

[0010] On the basis of the above technical scheme, preferably, the common crosslinking agent includes one or more of polyols, polyamines, and polyacids. Since a single type of functional group is not good for adjusting the crosslinking density, in order to realize the regulation of the performance of the polyurethane modified asphalt by adjusting the crosslinking density, the common crosslinking agent selected by the application includes difunctional, trifunctional, and tetrafunctional compounds, wherein preferably the common crosslinking agent includes multiple types of trimethylolpropane, pentaerythritol, di-o-chloro-diphenylamine methane, hexamethylene diamine, diethanolamine, or triethanolamine.

[0011] On the basis of the above technical scheme, preferably, the base asphalt is road petroleum asphalt, and more preferably one of 90# asphalt and 70# asphalt.

[0012] On the basis of the above technical scheme, preferably, the catalyst is one of N,N-dimethylbenzylamine, triethylenediamine, or dibutyltin dilaurate, which is used to accelerate the reaction process.

[0013] On the basis of the above technical scheme, preferably, the preparation method of the isocyanate prepolymer is as follows: first, the hydroxyl-terminated oligomer subjected to vacuum dehydration is heated to 70-80℃, then a diisocyanate compound is added, and the isocyanate prepolymer is obtained after stirring and reacting for 1.5-2 hours under a nitrogen atmosphere.

[0014] Further preferably, the hydroxyl-terminated oligomer used to prepare the isocyanate prepolymer is one or more of hydroxyl-terminated butadiene, hydroxyl-terminated butadiene-acrylonitrile, and polyether polyol, with an average molecular weight of 1000-4000 g / mol, and more preferably hydroxyl-terminated butadiene-acrylonitrile and hydroxyl-terminated butadiene, in order to improve the low-temperature performance of the polyurethane modified asphalt. Further preferably, the polyurethane modified asphalt material also includes sulfur, and the addition amount of sulfur in the polyurethane modified asphalt material is 0.01-0.1 parts.

[0015] Further preferably, the addition amount of the diisocyanate compound is 5%-15% of the mass of the polyol.

[0016] Further preferably, the diisocyanate compound is one of isophorone diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, or diphenylmethane diisocyanate.

[0017] In a second aspect, the application also provides a preparation method of the polyurethane modified asphalt material with a dynamic covalent bond structure according to the first aspect of the application, which includes the following steps:

[0018] S1 first heat the base asphalt to 120-140℃, and then add the dynamic crosslinking agent, the common crosslinking agent, and the catalyst according to the proportions, and stir at a speed of 400-500 rpm for 5-10 minutes;

[0019] S2Then isocyanate prepolymer and sulfur are added, and stirring is carried out at 140-150 DEG C for 25-30 min.

[0020] S3Finally, heat preservation is carried out at 100-110 DEG C for 1.5-2.5 h to obtain polyurethane modified asphalt.

[0021] The polyurethane modified asphalt material containing a dynamic covalent bond structure according to the present application has the following beneficial effects relative to the prior art:

[0022] 1.The dynamic reversible crosslinking network structure is constructed in the asphalt by introducing the dynamic covalent bond, which has excellent structure rearrangement and conformation adjustment capability, and the dynamic reversible crosslinking network structure is controllable, so that the low temperature performance and fatigue resistance of the polyurethane modified asphalt can be greatly improved.

[0023] The dynamic covalent bond is introduced into the crosslinking structure of the polyurethane modified asphalt, and due to the reversible cleavage-exchange reaction characteristics of the dynamic covalent bond, when the material appears a damaged microcrack, the material can be self-repaired at room temperature through the reversible chemical interaction between the interface molecules, and long-term and repeated self-repair can be realized, thereby excellent self-repairing capability is endowed to the polyurethane modified asphalt.

[0024] Since the reversible cleavage-exchange reaction rate of the dynamic covalent bond has temperature dependence, high temperature can accelerate the reversible reaction rate, so the dynamic reversible crosslinking polyurethane modified asphalt has the characteristics of active viscosity reduction at high temperature, and is expected to reduce the construction temperature of the polyurethane modified asphalt mixture.

[0025] The thermosetting polyurethane modified asphalt is difficult to melt at high temperature, so it is difficult to obtain effective reclaimed asphalt; and the present application introduces a large number of dynamic covalent bonds into the thermosetting polyurethane crosslinking network through a dynamic crosslinking agent, and utilizes the reversible breaking and reconstruction characteristics of the dynamic bond, so as to greatly improve the recyclable characteristics of the thermosetting polyurethane modified asphalt.

[0026] 2. The terminal hydroxyl oligomer, preferably terminal hydroxyl butadiene-acrylonitrile and terminal hydroxyl butadiene, can further improve the low temperature and fatigue resistance of the polyurethane modified asphalt material, but the carbon-carbon double bond in the hydroxyl butadiene-acrylonitrile and terminal hydroxyl butadiene is easy to be oxidized and broken during service, which makes the performance of the polyurethane modified asphalt material unstable. In order to improve the stability, the sulfur is added in the present application, the double bond is eliminated by the reaction between sulfur and carbon-carbon double bond, and the crosslinking density is improved to improve the high temperature performance of the polyurethane asphalt; at the same time, a certain amount of disulfide bond / multisulfide bond can be introduced in the reaction process, which belongs to dynamic covalent bond, and can also improve the low temperature toughness, fatigue resistance and self-healing ability of the polyurethane modified asphalt.

[0027] 3. After eliminating the double bond by adding sulfur and improving the crosslinking density, the crosslinking density needs to be further adjusted by adding a common crosslinking agent. Since the selection of a single type of functional group has poor effect on the adjustment of crosslinking density, the common crosslinking agent selected in the present application covers difunctional, trifunctional and tetrafunctional compounds, which is beneficial to the adjustment of the crosslinking density of polyurethane, so as to better realize the regulation and control of the performance of the polyurethane modified asphalt. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0029] Figure 1 It is a schematic diagram of the self-healing principle of the dynamic crosslinking polyurethane modified asphalt damage crack.

[0030] Figure 2 It is a schematic diagram of the loading mode of the dynamic shear rheometer for testing the self-healing performance of the sample. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application will be described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0032] Example 1:

[0033] Preparation of isocyanate prepolymer: 76g of hydroxyl-terminated butadiene was added to a three-necked glass flask and heated to 110℃. The mixture was then dehydrated under reduced pressure for 3h, cooled to 75℃, and 12.6g of isophorone diisocyanate and 0.05g of dibutyltin dilaurate catalyst were added. The mixture was reacted under a nitrogen atmosphere with a stirring rate of 500rpm for 1.5h to obtain the binary isocyanate prepolymer.

[0034] Then, the 70# base asphalt was heated to 130℃, and 70g was poured into an iron mixing tank. Then, 0.3g of ordinary crosslinking agent (including 0.15g of trimethylolpropane, 0.05g of pentaerythritol, and 0.10g of hexamethylenediamine), 0.5g of dynamic crosslinking agent dimethylglyoxime, and 0.01g of catalyst dibutyltin dilaurate were added. The mixture was stirred at 500rpm for 5 minutes to disperse it evenly. Then, 8g of binary isocyanate prepolymer (of which the terminal hydroxyl oligomer is terminal hydroxyl butadiene) and 0.01g of sulfur were added. The temperature was raised to 150℃ and stirring was continued for 28 minutes. The mixture was then transferred to a heat-insulating oven and kept at 105℃ for 2 hours to obtain polyurethane modified asphalt.

[0035] Example 2:

[0036] The preparation of the isocyanate prepolymer is the same as in Example 1.

[0037] 70# base asphalt was heated to 130℃, and 80g was poured into an iron mixing tank. Then, 0.9g of ordinary crosslinking agent (including 0.3g of trimethylolpropane, 0.45g of pentaerythritol, and 0.15g of hexamethylenediamine), 3.5g of dynamic crosslinking agent dithiodipropionic acid, and 0.05g of catalyst dibutyltin dilaurate were added. The mixture was stirred at 500rpm for 5 minutes to disperse it evenly. Then, 15g of binary isocyanate prepolymer (of which the terminal hydroxyl oligomer is terminal hydroxyl butadiene) and 0.03g of sulfur were added. The temperature was raised to 150℃ and stirring was continued for 28 minutes. The mixture was then transferred to a heat-insulating oven and kept at 105℃ for 2 hours to obtain polyurethane modified asphalt.

[0038] Example 3:

[0039] The preparation of the isocyanate prepolymer is the same as in Example 1.

[0040] Take 70# base pitch and heat to 130°C, pour 90g into an iron stirring tank, then add common crosslinking agent 1.5g (including trimethylolpropane 0.45g, pentaerythritol 0.35g, hexanediamine 0.7g), dynamic crosslinking agent cystine 5g, catalyst dibutyltin dilaurate 0.1g, stir for 5 minutes at 500rpm to disperse uniformly, then add diisocyanate prepolymer 29g (in which, the terminal hydroxyl oligomer is terminal hydroxyl butadiene) and sulfur 0.03g, continue to stir at 150°C for 28 minutes; then transfer it to a holding oven, and hold at 105°C for 2 hours to obtain polyurethane modified pitch.

[0041] Example 4 (terminal hydroxyl oligomer is polyether triol):

[0042] Preparation of isocyanate prepolymer: take 76g polyether triol and add to a three-necked glass flask, heat to 110°C, vacuum dehydration for 3 hours under reduced pressure, then cool to 75°C, then add isophorone diisocyanate 12.6g and catalyst dibutyltin dilaurate 0.05g, stir at 500rpm under nitrogen atmosphere for 1.5 hours to obtain diisocyanate prepolymer.

[0043] Then take 70# base pitch and heat to 130°C, pour 70g into an iron stirring tank, then add common crosslinking agent 0.3g (including trimethylolpropane 0.15g, pentaerythritol 0.05g, hexanediamine 0.10g), dynamic crosslinking agent butanedione oxime 0.5g, catalyst dibutyltin dilaurate 0.01g, stir for 5 minutes at 500rpm to disperse uniformly, then add diisocyanate prepolymer 8g (in which, the terminal hydroxyl oligomer is polyether triol) and sulfur 0.01g, continue to stir at 150°C for 28 minutes; then transfer it to a holding oven, and hold at 105°C for 2 hours to obtain polyurethane modified pitch.

[0044] Example 5 (without sulfur):

[0045] Preparation of isocyanate prepolymer as in Example 1.

[0046] Take 70# base pitch and heat to 130°C, pour 80g into an iron stirring tank, then add common crosslinking agent 0.9g (including trimethylolpropane 0.3g, pentaerythritol 0.45g, hexanediamine 0.15g), dynamic crosslinking agent dithiodipropionic acid 3.5g, catalyst dibutyltin dilaurate 0.05g, stir for 5 minutes at 500rpm to disperse uniformly, then add diisocyanate prepolymer 15g (in which, the terminal hydroxyl oligomer is terminal hydroxyl butadiene), continue to stir at 150°C for 28 minutes; then transfer it to a holding oven, and hold at 105°C for 2 hours to obtain polyurethane modified pitch.

[0047] Example 6 (ordinary crosslinking agent is a single type of functional group):

[0048] The preparation of the isocyanate prepolymer is the same as in Example 1.

[0049] 70# base bitumen was heated to 130°C, 90g was poured into an iron stirring tank, then ordinary crosslinking agent trimethylolpropane 1.5g, dynamic crosslinking agent cystine 5g, catalyst dibutyltin dilaurate 0.1g were added, stirring at 500rpm for 5 minutes to disperse uniformly, then binary isocyanate prepolymer 29g (in which the terminal hydroxyl oligomer is terminal hydroxyl butadiene) and sulfur 0.03g were added, and the temperature was raised to 150°C and stirring was continued for 28 minutes; then it was transferred to a holding oven and held at 105°C for 2 hours to obtain polyurethane modified bitumen.

[0050] Example 7 (without dynamic crosslinking agent):

[0051] The preparation of the isocyanate prepolymer is the same as in Example 1.

[0052] Then 70# base bitumen was heated to 130°C, 70g was poured into an iron stirring tank, then ordinary crosslinking agent 0.3g (including trimethylolpropane 0.15g, pentaerythritol 0.05g, hexanediamine 0.10g), catalyst dibutyltin dilaurate 0.01g were added, stirring at 500rpm for 5 minutes to disperse uniformly, then binary isocyanate prepolymer 8g (in which the terminal hydroxyl oligomer is terminal hydroxyl butadiene) and sulfur 0.01g were added, and the temperature was raised to 150°C and stirring was continued for 28 minutes; then it was transferred to a holding oven and held at 105°C for 2 hours to obtain polyurethane modified bitumen.

[0053] Example 8 (dynamic crosslinking agent is bismaleimide and furfurylamine):

[0054] The preparation of the isocyanate prepolymer is the same as in Example 1.

[0055] Then 70# base bitumen was heated to 130°C, 70g was poured into an iron stirring tank, then ordinary crosslinking agent 0.3g (including trimethylolpropane 0.15g, pentaerythritol 0.05g, hexanediamine 0.10g), dynamic crosslinking agent 0.5g (including bismaleimide 0.3g and furfurylamine 0.2g), catalyst dibutyltin dilaurate 0.01g were added, stirring at 500rpm for 5 minutes to disperse uniformly, then binary isocyanate prepolymer 8g (in which the terminal hydroxyl oligomer is terminal hydroxyl butadiene) and sulfur 0.01g were added, and the temperature was raised to 150°C and stirring was continued for 28 minutes; then it was transferred to a holding oven and held at 105°C for 2 hours to obtain polyurethane modified bitumen.

[0056] Example 9 (without sulfur, ordinary crosslinking agent is a single type of functional group)

[0057] The isocyanate prepolymer was prepared as in Example 1.

[0058] The 70# base asphalt was heated to 130°C, 80g was poured into an iron stirring tank, then the ordinary crosslinking agent pentaerythritol 0.9g, the dynamic crosslinking agent dithiodipropionic acid 3.5g, the catalyst dibutyltin dilaurate 0.05g were added, and stirred at a speed of 500 rpm for 5 minutes to disperse uniformly, then the diisocyanate prepolymer 15g (in which the terminal hydroxyl oligomer was terminal hydroxyl butadiene) was added, and the temperature was raised to 150°C and continued to stir for 28 min; then it was transferred to a holding oven, and kept at 105°C for 2h to obtain the polyurethane modified asphalt.

[0059] Example 10 (the terminal hydroxyl oligomer was polyether triol, and the ordinary crosslinking agent was a single type of functional group)

[0060] Preparation of isocyanate prepolymer: 76g of polyether triol was added to a three-necked glass flask, heated to 110°C, and vacuum dehydrated at reduced pressure for 3h, then the temperature was lowered to 75°C, then isophorone diisocyanate 12.6g and catalyst dibutyltin dilaurate 0.05g were added, and stirred at a speed of 500 rpm for 1.5h under nitrogen atmosphere to obtain the diisocyanate prepolymer.

[0061] Then the 70# base asphalt was heated to 130°C, 70g was poured into an iron stirring tank, then the ordinary crosslinking agent hexanediamine 0.3g, the dynamic crosslinking agent butanedione oxime 0.5g, the catalyst dibutyltin dilaurate 0.01g were added, and stirred at a speed of 500 rpm for 5 minutes to disperse uniformly, then the diisocyanate prepolymer 8g (in which the terminal hydroxyl oligomer was polyether triol) and sulfur 0.01g were added, and the temperature was raised to 150°C and continued to stir for 28 min; then it was transferred to a holding oven, and kept at 105°C for 2h to obtain the polyurethane modified asphalt.

[0062] Example 11 (the terminal hydroxyl oligomer was polyether triol, and no sulfur was added)

[0063] Preparation of isocyanate prepolymer: 76g of polyether triol was added to a three-necked glass flask, heated to 110°C, and vacuum dehydrated at reduced pressure for 3h, then the temperature was lowered to 75°C, then isophorone diisocyanate 12.6g and catalyst dibutyltin dilaurate 0.05g were added, and stirred at a speed of 500 rpm for 1.5h under nitrogen atmosphere to obtain the diisocyanate prepolymer.

[0064] Then 70# base bitumen is heated to 130°C, 70g is poured into an iron stirring tank, then 0.3g of common crosslinking agent (including 0.15g of trimethylolpropane, 0.05g of pentaerythritol, and 0.10g of hexanediamine), 0.5g of dynamic crosslinking agent butanedione oxime, and 0.01g of catalyst dibutyltin dilaurate are added, and stirred at a speed of 500 rpm for 5 minutes to disperse uniformly, then 8g of diisocyanate prepolymer (in which the terminal hydroxyl oligomer is polyether triol) is added, and the temperature is raised to 150°C to continue stirring for 28 minutes; then it is transferred to a heat preservation oven, and heat preserved at 105°C for 2 hours to obtain polyurethane modified bitumen.

[0065] Example 12 (terminal hydroxyl oligomer is polyether triol, without dynamic covalent bond)

[0066] Preparation of isocyanate prepolymer: 76g of polyether triol is added to a three-necked glass flask, heated to 110°C, and vacuum dehydrated under reduced pressure for 3 hours, then the temperature is lowered to 75°C, then 12.6g of isophorone diisocyanate and 0.05g of catalyst dibutyltin dilaurate are added, and stirred at a speed of 500 rpm for 1.5 hours under nitrogen atmosphere to obtain diisocyanate prepolymer.

[0067] Then 70# base bitumen is heated to 130°C, 70g is poured into an iron stirring tank, then 0.3g of common crosslinking agent (including 0.15g of trimethylolpropane, 0.05g of pentaerythritol, and 0.10g of hexanediamine), 0.01g of catalyst dibutyltin dilaurate are added, and stirred at a speed of 500 rpm for 5 minutes to disperse uniformly, then 8g of diisocyanate prepolymer (in which the terminal hydroxyl oligomer is polyether triol) and 0.01g of sulfur are added, and the temperature is raised to 150°C to continue stirring for 28 minutes; then it is transferred to a heat preservation oven, and heat preserved at 105°C for 2 hours to obtain polyurethane modified bitumen.

[0068] Example 13 (without dynamic crosslinking agent, without sulfur)

[0069] Preparation of isocyanate prepolymer is the same as in Example 1.

[0070] Then 70# base bitumen is heated to 130°C, 70g is poured into an iron stirring tank, then 0.3g of common crosslinking agent (including 0.15g of trimethylolpropane, 0.05g of pentaerythritol, and 0.10g of hexanediamine), 0.01g of catalyst dibutyltin dilaurate are added, and stirred at a speed of 500 rpm for 5 minutes to disperse uniformly, then 8g of diisocyanate prepolymer (in which the terminal hydroxyl oligomer is polyether triol) and 0.01g of sulfur are added, and the temperature is raised to 150°C to continue stirring for 28 minutes; then it is transferred to a heat preservation oven, and heat preserved at 105°C for 2 hours to obtain polyurethane modified bitumen.

[0071] Example 14 (without dynamic crosslinking agent, end-hydroxyl oligomer is polyether triol)

[0072] Preparation of isocyanate prepolymer: 76 g of polyether triol was taken into a three-necked glass flask and heated to 110°C, vacuum dehydration for 3 h under reduced pressure, then cooled to 75°C, then 12.6 g of isophorone diisocyanate and 0.05 g of catalyst dibutyltin dilaurate were added, and the reaction was carried out under nitrogen atmosphere at a stirring rate of 500 rpm for 1.5 h, and then a diisocyanate prepolymer was obtained.

[0073] Then 70# base asphalt was heated to 130°C, 70 g was poured into an iron stirring tank, then 0.3 g of common crosslinking agent (including 0.15 g of trimethylolpropane, 0.05 g of pentaerythritol, and 0.10 g of hexanediamine) and 0.01 g of catalyst dibutyltin dilaurate were added, and stirring was carried out at a rate of 500 rpm for 5 min to disperse uniformly, then 8 g of diisocyanate prepolymer (in which the end-hydroxyl oligomer is polyether triol) was added, and the temperature was raised to 150°C and stirring was continued for 28 min; then it was transferred to a holding oven and kept at 105°C for 2 h to obtain polyurethane modified asphalt.

[0074] In order to verify the related performance of the polyurethane modified asphalt material containing the structure of dynamic covalent bond, the low temperature ductility of the sample was tested at room temperature (20-30°C) by a dynamic rheometer, and the low temperature toughness of the sample could be analyzed; the amplitude and frequency scanning of the sample were carried out by a dynamic shear rheometer, and then the fatigue life of the sample under different strains could be obtained through data analysis, as shown in Table 1.

[0075] Table 1: Low temperature ductility and fatigue resistance of the sample

[0076]

[0077] As can be seen from the above table data, the introduction of dynamic covalent bond into the polyurethane crosslinking network through the dynamic crosslinking agent helps to improve the low temperature performance and fatigue resistance of the polyurethane modified asphalt, and the dynamic crosslinking agent in the present application has a better effect on improving the low temperature performance and fatigue resistance of the polyurethane modified asphalt than the dynamic crosslinking agents in the prior art, i.e. bismaleimide and furfurylamine.

[0078] The self-healing performance test was carried out at room temperature (20-30°C), and the sample was subjected to constant temperature and constant strain continuous loading by a dynamic shear rheometer until the complex shear modulus decreased to 80% (G b1 ), 60% (G b2 ), 40% (G b3 ) of the initial value, then the loading was stopped for 900 seconds, and then the loading was resumed, and the specific test loading mode was as follows: Figure 2The self-repairing performance of the sample is evaluated by the recovery degree of complex modulus before and after the gap (evaluated by self-healing index), two self-healing index indicators are selected for evaluation and analysis in the experiment, specifically as formula (1) and (2), and the test results are shown in Table 2.

[0079]

[0080]

[0081] G b1 , G b2 , G b3 are 80%, 60%, and 40% of G b2 , respectively.

[0082] Table 2: Self-healing index of the sample under different damage degrees

[0083]

[0084]

[0085] As can be seen from the above table data, by introducing dynamic covalent bonds into the polyurethane crosslinked network through the dynamic crosslinking agent, the self-healing index of the polyurethane modified asphalt under different damage degrees is improved, and the improvement effect is more significant under the condition of more serious damage (the complex modulus is attenuated to 40% of the initial value). For example, the improvement amount of example 1 compared with example 7 is 34.4% ((57.8%-43%) / 43%=34.4%). This shows that the introduction of dynamic bonds in polyurethane modified asphalt significantly improves its self-repairing ability, and the self-repairing ability after multiple damage is improved more obviously.

[0086] In addition, compared with the dynamic crosslinking agent in the prior art: bismaleimide and furfurylamine, the dynamic crosslinking agent in the present application has better effect in improving the self-healing index of polyurethane modified asphalt.

[0087] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A polyurethane modified bitumen material containing a structure of dynamic covalent bonds, characterized in that, The raw material components include 70-90 parts of base pitch, 8-29 parts of isocyanate prepolymer, 0.5-5.0 parts of dynamic crosslinking agent, 0.3-1.5 parts of common crosslinking agent, 0.01-0.1 parts of catalyst, and 0.01-0.1 parts of sulfur, by weight; The dynamic crosslinking agent is a double / multi-active end group compound containing a dynamic bond, or a multi-functional compound that reacts with an isocyanate group to form a dynamic bond group; The dynamic crosslinking agent includes at least one of butanedione oxime, diamino diphenyl disulfide, dithiodipropionic acid, selenocystamine, cystine, and 2,2'-(1,4-phenylene)-bis[4-mercapto-1,3,2-dioxaborinane]; The common crosslinking agent includes one or more of a polyol, a polyamine, and a polyacid; The common crosslinking agent includes di-functional, tri-functional, and tetra-functional compounds; The preparation method of the isocyanate prepolymer is: first, heat the vacuum-dried hydroxyl-terminated oligomer to 70-80℃, then add a diisocyanate compound, and obtain the isocyanate prepolymer after stirring and reacting for 1.5-2h under a nitrogen atmosphere; The hydroxyl-terminated oligomer is a hydroxyl-terminated butadiene-acrylonitrile or a hydroxyl-terminated butadiene.

2. The polyurethane modified bitumen material containing a dynamic covalent structure of claim 1, wherein: The active end group is a hydroxyl group, a carboxyl group, or an amine group.

3. A method for preparing a polyurethane modified bitumen material containing a structure of dynamic covalent bonds according to claim 1 or 2, characterized in that: The method includes the following steps: S1, first heat the base pitch to 120-140℃, and add the dynamic crosslinking agent, the common crosslinking agent, and the catalyst according to the proportions, and stir at a speed of 400-500 rpm for 5-10 minutes; S2, then add the isocyanate prepolymer and sulfur, and stir at 140-150℃ for 25-30 minutes; S3, finally, heat at 100-110℃ for 1.5-2.5h to obtain the polyurethane modified pitch.

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