Rubber modified asphalt pavement maintenance waterproof coating and preparation method thereof

Abstract

The present application relates to the technical field of pavement maintenance waterproof coating, in particular to a rubber modified asphalt pavement maintenance waterproof coating and a preparation method thereof, which comprises the following components by mass fraction: petroleum asphalt 100 parts, waste rubber powder 15 to 25 parts, maleic anhydride grafted liquid polybutadiene 5 to 12 parts, tackifying resin 5 to 10 parts, softening agent 4 to 8 parts, vulcanizing agent 0.1 to 0.4 parts, filler 5 to 12 parts, and antioxidant 0.3 to 0.8 parts; the present application introduces low molecular weight amphiphilic reactive oligomer MAH-g-LPB, uses its spontaneous migration and in-situ reaction characteristics to build a chemical composition gradient adhesion interface layer between the coating and the aged asphalt pavement, improves the interface adhesion from van der Waals force to covalent bond level, improves the pull adhesion strength from 0.5 to 0.8 MPa of the prior art to more than 1.2 MPa, and improves the adhesion strength retention rate after 7 days of water immersion from 50 to 65% of the prior art to more than 80%.

Description

Technical Field

[0001] This invention relates to the field of road maintenance and waterproofing coating technology, specifically to a rubber-modified asphalt road maintenance and waterproofing coating and its preparation method. Background Technology

[0002] Rubber-modified asphalt pavement maintenance and waterproofing coating is a hot-melt pavement maintenance and waterproofing material made from petroleum asphalt as the base material and waste tire rubber powder as the rubber modifier, through high-temperature shear dispersion. It is widely used in the construction of waterproof sealing layers and bonding layers in the preventive maintenance of asphalt pavements. Utilizing the swelling and thickening effect of rubber powder in asphalt, this coating imparts properties such as crack resistance, noise reduction, and aging resistance. Simultaneously, it achieves the resource utilization of waste tires, representing an important development direction in the field of pavement maintenance.

[0003] CN118222108A discloses a stabilized rubber asphalt matrix, a composite modified asphalt, its preparation method, and its application. Using rubber-modified asphalt as the matrix, SBS modifier, natural asphalt, a accelerator, and a stabilizer are added. The storage stability of the rubber asphalt is improved through colloid mill shearing and long-term development. This solution addresses the segregation problem of rubber asphalt; however, the interfacial adhesion between the coating and the aged asphalt pavement still needs improvement. The adhesion between the coating and the pavement still relies solely on van der Waals forces, making it prone to interfacial peeling under dynamic water pressure.

[0004] CN111944424A discloses a sprayable quick-setting rubber asphalt waterproof coating and its preparation and application methods. The coating uses anionic emulsified asphalt modified with nano-mica powder and rubber latex as base materials, and adds coupling agents and additives to prepare the sprayable quick-setting waterproof coating. The coupling agent added in this scheme is a titanate or silane-based coupling agent, which mainly improves the adhesion and color matching between the coating and the railway subgrade. However, the amount of coupling agent added is low and it only plays a physical adsorption strengthening role. There is no chemical bond between the coating and the road surface, resulting in insufficient long-term water resistance and adhesion.

[0005] CN116676043A discloses a water-based asphalt waterproofing material and its preparation method and microwave curing method. The method involves a two-component mixture of rubber-modified asphalt emulsification and a specially formulated curing agent, followed by rapid curing via microwave heating. While this method improves film-forming efficiency through microwave curing, the asphalt particles and rubber particles in the water-based system only fuse through physical accumulation during film formation, resulting in weak interfacial bonding and insufficient film density. Furthermore, microwave curing equipment is difficult to widely implement in road maintenance and construction.

[0006] The aforementioned existing technologies have the following shortcomings: there is only physical entanglement between rubber and asphalt without chemical bonding, which leads to easy segregation of the coating at high temperatures and easy brittleness at low temperatures; there is no chemical anchoring mechanism between the coating and the aged asphalt pavement, resulting in low bond strength. Under repeated scouring by dynamic water pressure, the interface decays rapidly, and the bond strength retention rate after immersion is less than 60%; existing anti-stripping agents and coupling agents are non-migratory or only provide physical adsorption, and cannot spontaneously accumulate at the coating-pavement interface to form a chemical composition gradient transition layer. The sudden change in modulus at the interface leads to stress concentration and interlayer delamination. Summary of the Invention

[0007] The primary objective of this invention is to provide a rubber-modified asphalt pavement maintenance and waterproofing coating and its preparation method.

[0008] A further objective of this invention is to provide a rubber-modified asphalt pavement maintenance and waterproofing coating, comprising the following components by weight: 100 parts petroleum asphalt, 15 to 25 parts waste rubber powder, 5 to 12 parts maleic anhydride-grafted liquid polybutadiene, 5 to 10 parts tackifying resin, 4 to 8 parts softener, 0.1 to 0.4 parts vulcanizing agent, 5 to 12 parts filler, and 0.3 to 0.8 parts antioxidant; wherein the maleic anhydride-grafted liquid polybutadiene is a liquid polybutadiene graft with a number average molecular weight of 2000 to 6000 and a maleic anhydride grafting rate of 8 to 15% by weight, wherein the maleic anhydride grafting rate is the percentage of grafted maleic anhydride by weight of the liquid polybutadiene, and during the coating application process, it spontaneously migrates to the interface between the coating and the aged asphalt pavement and reacts in situ at the interface to form a chemically gradient adhesive interface layer.

[0009] Preferably, the maleic anhydride-grafted liquid polybutadiene has a number average molecular weight of 2,500 to 5,000, a maleic anhydride grafting rate of 8 to 15% by mass, and a vinyl content of 60 to 90% by mass.

[0010] Preferably, the waste rubber powder is 40 to 80 mesh waste tire rubber powder with a crosslinking density of 2.5 to 4.5 x 10⁻⁴ mol per cubic centimeter.

[0011] Preferably, the thickness of the chemical composition gradient adhesion interface layer is 50 to 200 μm, the concentration of maleic anhydride grafted liquid polybutadiene in the interface layer increases from the coating body to the substrate interface, the pull-out bond strength between the coating and the aged asphalt pavement is not less than 1.2 MPa, and the bond strength retention rate after immersion in water for 7 days is not less than 80%.

[0012] A method for preparing the rubber-modified asphalt pavement maintenance and waterproofing coating includes the following steps: Step 1, Preparation of maleic anhydride-grafted liquid polybutadiene: The liquid polybutadiene is heated to 180 to 200°C, and maleic anhydride and dicumyl peroxide initiator are added under nitrogen protection. The reaction is carried out for 2 to 4 hours to obtain maleic anhydride-grafted liquid polybutadiene with a maleic anhydride grafting rate of 8 to 15%. Step 2, preparing rubber-modified asphalt: Heat petroleum asphalt to 160 to 170°C until it melts, add waste rubber powder, stir at 500 to 800 r / min for 40 to 60 min to make the rubber powder swell, then raise the temperature to 175 to 185°C, and shear at 2000 to 3000 r / min for 30 to 45 min to make the rubber powder evenly dispersed; Step 3, preparing the coating: Add the maleic anhydride grafted liquid polybutadiene obtained in Step 1 to the rubber-modified asphalt obtained in Step 2, and shear it at 1500 to 2500 r / min for 20 to 30 minutes to make it evenly dispersed. Then add the softener and tackifying resin and stir for 15 to 20 minutes. Cool down to 155 to 165℃, add the vulcanizing agent and stir for 15 to 20 minutes. Finally, add the filler and antioxidant and stir for 10 to 15 minutes. After degassing, the rubber-modified asphalt pavement maintenance and waterproof coating is obtained. Step 4, coating and curing: Heat the coating to 160 to 180°C and apply it to the surface of aged asphalt pavement at a rate of 1.0 to 2.0 kg per square meter. Keep it at 140 to 160°C for 10 to 30 minutes to allow maleic anhydride-grafted liquid polybutadiene to migrate to the interface and react in situ. Then cool it to room temperature to form a chemically gradient adhesion interface layer.

[0013] Preferably, the liquid polybutadiene in step one has a number average molecular weight of 2,500 to 5,000, a vinyl content of 60 to 90%, an amount of maleic anhydride added of 8 to 18% of the mass of the liquid polybutadiene, and an amount of dicumyl peroxide added of 0.3 to 0.8% of the mass of the liquid polybutadiene.

[0014] Preferably, in step three, the maleic anhydride-grafted liquid polybutadiene is added after the rubber powder is dispersed and before the vulcanizing agent is added, and is sheared and dispersed at a speed of 1500 to 2500 r / min for 20 to 30 min to establish a spatial distribution in the rubber asphalt matrix.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention introduces a low molecular weight amphiphilic reactive oligomer MAH-g-LPB, utilizing its spontaneous migration and in-situ reaction characteristics to construct a chemically gradient adhesion interface layer between the coating and the aged asphalt pavement. This elevates the interfacial adhesion from van der Waals forces to covalent bonds, increasing the pull-out bond strength from 0.5 to 0.8 MPa in the prior art to over 1.2 MPa. After immersion in water for 7 days, the bond strength retention rate increases from 50 to 65% in the prior art to over 80%, fundamentally solving the problem of interfacial debonding between the coating and the aged pavement.

[0016] 2. MAH-g-LPB acts as a compatibilizer at the rubber powder-asphalt interface, reducing interfacial tension and decreasing the tendency of rubber powder particles to separate during high-temperature storage. This reduces the difference in the segregation softening point to 1.0 to 2.0℃, significantly improving storage stability. This effect is a secondary effect of the amphiphilic molecular structure of MAH-g-LPB, which is an unexpected technical effect for those skilled in the art.

[0017] 3. The gradient adhesion interface layer eliminates the sharp interface and modulus abrupt change between the traditional coating and the road surface, so that the modulus transitions smoothly from the aged road surface to the coating body, the interface stress concentration factor is reduced, the interlayer shear strength reaches more than 0.8MPa, and the service life of the coating is significantly extended.

[0018] 4. The residual double bonds on the polybutadiene backbone of MAH-g-LPB form chemical crosslinks with the rubber powder under the action of the vulcanizing agent, so that the gradient interface layer and the coating body are connected by covalent bonds, forming a complete chemical bond chain from the road surface to the coating body, and there is no weak interface.

[0019] 5. This invention uses waste tire rubber powder as a rubber modifier, realizing the high-value resource utilization of waste tires, significantly improving the utilization rate of rubber powder in coatings, and achieving both environmental and economic benefits. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] The mechanism of this invention is as follows: During long-term service, the lightweight components in aging asphalt pavements volatilize and oxidize, generating numerous polar oxygen-containing functional groups such as carboxyl, sulfoxide, and ketone groups on the surface, giving the aged pavement a polar characteristic. Rubber-modified asphalt waterproof coatings, primarily composed of non-polar hydrocarbons, are intrinsically incompatible with the polar surface of aged pavements. This results in adhesion at the interface relying solely on van der Waals forces, with an adhesion energy of only 5 to 10 kJ / mol, far lower than the 200 to 400 kJ / mol required for covalent bonds. Under the repeated scouring of vehicle water pressure, water molecules preferentially occupy the polar sites at the interface, displacing the original physically adsorbed layer, leading to rapid debonding at the interface.

[0022] This invention proposes a spontaneous migration and self-organized gradient adhesion interface mechanism: maleic anhydride-grafted liquid polybutadiene (MAH-g-LPB) is introduced into a rubber-modified asphalt waterproof coating. This substance is an amphiphilic reactive oligomer with a number-average molecular weight of 2000 to 6000, and its molecular chain consists of a nonpolar polybutadiene backbone and polar maleic anhydride graft groups. The nonpolar backbone is compatible with the rubber asphalt matrix, and the polar MAH groups have a strong affinity for the polar oxygen-containing functional groups on the surface of aged asphalt. This amphiphilic characteristic endows MAH-g-LPB with a thermodynamic driving force for spontaneous migration to the coating-pavement interface in the rubber asphalt melt.

[0023] The gradient adhesion interface formation process of MAH-g-LPB consists of four stages: The first stage is the dispersion stage. During the coating preparation process, MAH-g-LPB is uniformly dispersed in the rubber asphalt matrix under high temperature shear. The MAH groups have weak coordination with a small amount of nitrogen-containing basic compounds in the asphalt, and some MAH groups form hydrogen bonds with asphaltene, which anchors the MAH-g-LPB molecules in the matrix, but most of the MAH groups remain reactive.

[0024] The second stage is the migration stage. After the coating is applied to the aged asphalt pavement, MAH-g-LPB spontaneously migrates to the coating-pavement interface driven by polar affinity. MAH-g-LPB has a number-average molecular weight of 2,000 to 6,000, and at the coating application temperature of 160 to 180°C, it has sufficient molecular chain mobility to achieve migration. In contrast, high molecular weight grafted products such as MAH-g-SEBS have a number-average molecular weight exceeding 50,000, and their molecular chains are entangled and fixed by the three-dimensional network of rubber asphalt, making interfacial migration impossible.

[0025] The third stage is the chemical anchoring stage. The MAH groups of MAH-g-LPB that migrate to the interface undergo esterification with the carboxyl groups on the aged asphalt pavement surface to form ester bonds, amidation with the amine groups to form amide or imide bonds, and ring-opening esterification with the hydroxyl groups to form half-ester bonds. These covalent bonds chemically anchor the coating to the pavement, increasing the interfacial adhesion energy from 5 to 10 kJ / mol for van der Waals forces to 200 to 400 kJ / mol for covalent bonds.

[0026] The fourth stage is the gradient structure formation stage. The concentration of MAH-g-LPB is highest at the interface and gradually decreases towards the coating bulk, forming an adhesive interface layer with a gradient distribution of chemical composition. In the interface layer, the residual double bonds on the polybutadiene backbone of MAH-g-LPB chemically cross-link with the rubber powder under the action of a vulcanizing agent, connecting the gradient interface layer and the coating bulk through covalent bonds, eliminating the sharp interface between the traditional coating and the road surface. The modulus of the gradient interface layer smoothly transitions from the high modulus of the aged road surface to the low modulus of the coating, eliminating abrupt modulus changes and stress concentration at the interface, fundamentally preventing interlayer delamination.

[0027] MAH-g-LPB acts as an interfacial compatibilizer during coating storage. Its amphiphilic molecules spontaneously accumulate at the rubber powder-asphalt interface, reducing the interfacial tension between the rubber powder and asphalt, and reducing the tendency of rubber powder particles to float or sink during high-temperature storage. This reduces the difference in the segregation softening point of the coating to 1.0 to 2.0℃, significantly improving storage stability.

[0028] This effect is not an intrinsic function of MAH-g-LPB as an adhesion promoter, but rather a secondary effect produced by its amphiphilic molecular structure at the rubber powder-asphalt interface.

[0029] Example 1:

[0030] Raw material formula: Raw material formula: 70 Road Petroleum Asphalt, 25℃ Penetration 68 (0.1mm), sourced from China Petroleum Karamay Petrochemical Company, 100 parts by weight; Waste Tire Rubber Powder, 60 mesh, Crosslinking Density 3.2 x 10⁻⁴ mol / cm³, sourced from Nanjing Environmental Resources Recycling Technology Company, 24 parts by weight; Maleic Anhydride Grafted Liquid Polybutadiene, MAH Grafting Rate 10%, Number Average Molecular Weight 3500, Vinyl Content 80%, 8 parts by weight; C5 Petroleum Resin, Softening Point 98℃, sourced from China Petroleum & Chemical Corporation Maoming Petrochemical Company, 7 parts by weight; Aromatic Oil, WKD Type, sourced from China Petroleum & Chemical Corporation Jinan Branch, 6 parts by weight; Sulfur Powder, Purity 99.5%, sourced from China Petroleum & Chemical Corporation Nanjing Chemical Industry Co., Ltd., 0.2 parts by weight; Talc Powder, 325 mesh, sourced from Liaoning Haicheng Talc Mine, 8 parts by weight; Antioxidant 1010, sourced from BASF China Company, 0.5 parts by weight.

[0031] Preparation process of maleic anhydride-grafted liquid polybutadiene: Liquid polybutadiene (POP), with a number average molecular weight of 3500 and a vinyl content of 80%, sourced from Synthomer's Lithene ULTRA N4-5000, was added in a 100-part mass ratio to a four-necked flask equipped with a stirrer, thermometer, and nitrogen delivery tube. The mixture was heated to 190°C, and under nitrogen protection, 16 parts by mass of maleic anhydride and 0.5 parts by mass of dicumyl peroxide were added. The mixture was stirred at 200 rpm for 3 hours. After the reaction was completed, volatiles were removed under a vacuum of 0.09 MPa for 5 minutes. The mixture was then cooled to room temperature to obtain MAH-g-LPB with a MAH grafting rate of 10%. The FTIR spectrum showed characteristic peaks of the C-O stretching vibration of anhydride at 1780 and 1860 cm⁻¹, confirming successful grafting.

[0032] Preparation process: Step 1: Prepare maleic anhydride-grafted liquid polybutadiene according to the above method; Step 2: Add No. 70 road petroleum asphalt to a reaction vessel equipped with stirring and heating functions, heat to 165°C until it melts, add waste tire rubber powder, stir at 600 r / min for 50 min to make the rubber powder swell, then raise the temperature to 180°C, and shear at 2500 r / min for 35 min to make the rubber powder evenly dispersed in the asphalt. Step 3: Add MAH-g-LPB to the rubber-modified asphalt obtained in Step 2, and shear it at 2000 r / min for 25 min to disperse it evenly. Then add aromatic oil and C5 petroleum resin, and stir at 600 r / min for 18 min. Cool down to 160℃, add sulfur powder, and stir at 600 r / min for 18 min. Finally, add talc powder and antioxidant 1010, and stir at 600 r / min for 12 min. Degas under a vacuum of 0.085 MPa for 12 min to obtain the rubber-modified asphalt pavement maintenance and waterproof coating. Step 4: Heat the coating obtained in Step 3 to 170°C and apply it to the surface of the accelerated-aged asphalt pavement test panel at a rate of 1.5 kg per square meter. The aged test panel is treated in a 165°C oven for 72 hours to simulate the service aging state of the pavement. It is then kept at 150°C for 10 minutes to allow MAH-g-LPB to migrate to the interface and react in situ. Finally, it is allowed to cool naturally to room temperature.

[0033] Example 2:

[0034] Raw material formula: 70# road petroleum asphalt, penetration 68 (0.1 mm) at 25℃, source same as Example 1, 100 parts by weight; waste tire rubber powder, 60 mesh, crosslinking density 3.2 x 10⁻⁴ mol / cm³, source same as Example 1, 20 parts by weight; MAH-g-LPB, MAH grafting rate 10%, number average molecular weight 3500, vinyl content 80%, preparation method same as Example 1, 5 parts by weight; C5 petroleum resin, softening point 98℃, source same as Example 1, 6 parts by weight; aromatic oil, source same as Example 1, 5 parts by weight; sulfur powder, source same as Example 1, 0.15 parts by weight; talc powder, 325 mesh, source same as Example 1, 6 parts by weight; antioxidant 1010, source same as Example 1, 0.4 parts by weight.

[0035] The preparation process is the same as in Example 1, except that the amount of MAH-g-LPB added is 5 parts by mass.

[0036] Example 3:

[0037] Raw material formula: 70# road petroleum asphalt, penetration 68 (0.1 mm) at 25℃, source same as Example 1, 100 parts by weight; waste tire rubber powder, 60 mesh, crosslinking density 3.2 x 10⁻⁴ mol / cm³, source same as Example 1, 25 parts by weight; MAH-g-LPB, MAH grafting rate 10%, number average molecular weight 3500, vinyl content 80%, preparation method same as Example 1, 12 parts by weight; C5 petroleum resin, softening point 98℃, source same as Example 1, 8 parts by weight; aromatic oil, source same as Example 1, 7 parts by weight; sulfur powder, source same as Example 1, 0.3 parts by weight; talc powder, 325 mesh, source same as Example 1, 10 parts by weight; antioxidant 1010, source same as Example 1, 0.6 parts by weight.

[0038] The preparation process is the same as in Example 1, except that the amount of MAH-g-LPB added is 12 parts by mass.

[0039] Comparative Example 1: The raw material formula is the same as in Example 1, but MAH-g-LPB is not added, and 8 parts by mass of MAH-g-LPB are replaced with an equal amount of No. 70 road petroleum asphalt.

[0040] The preparation process is the same as in Example 1, except that the MAH-g-LPB addition step is omitted.

[0041] Comparative Example 2: The raw material formulation is the same as in Example 1, but MAH-g-LPB is replaced with an equal amount of MAH-g-SEBS. MAH-g-SEBS is a maleic anhydride-grafted styrene-ethylene / butene-styrene block copolymer with a MAH grafting rate of 1.0% and a number average molecular weight of 70,000. It is sourced from KETEN Polymers Co., Ltd. under the G1642M standard.

[0042] The preparation process is the same as in Example 1, where MAH-g-SEBS is dispersed in rubber-modified asphalt by shearing at 2000 r / min for 25 min.

[0043] MAH-g-SEBS is a high molecular weight graft product with a number average molecular weight exceeding 50,000, and it cannot undergo interfacial migration in the three-dimensional network of rubber asphalt.

[0044] Comparative Example 3: The raw material formulation is the same as in Example 1, but MAH-g-LPB is replaced with an equal amount of ungrafted liquid polybutadiene. The number-average molecular weight of LPB is 3500, the vinyl content is 80%, and it is sourced from Synthomer Lithene ULTRA N4-5000.

[0045] The preparation process is the same as in Example 1. Ungrafted LPB does not contain MAH groups, does not have the ability to react with polar functional groups on the surface of aged asphalt, and has no driving force to migrate to the polar interface.

[0046] Comparative Example 4: The raw material formula is the same as in Example 1, but instead of adding MAH-g-LPB, amine anti-stripping agent UA-14 is added, sourced from Chongqing CCCC High-Tech Co., Ltd. The amount added is 0.6% of the asphalt mass, i.e., 0.6 parts by mass. The difference of 7.4 parts by mass between MAH-g-LPB and amine anti-stripping agent is made up with No. 70 road petroleum asphalt.

[0047] The preparation process is the same as in Example 1, except that the amine anti-stripping agent is added at the same time as the softener and the tackifying resin.

[0048] Comparative Example 5: The raw material formula is the same as in Example 1, but instead of adding MAH-g-LPB, silane coupling agent KH-550 is added, sourced from Nanjing Shuguang Silane Chemical Co., Ltd. The amount added is 0.8% of the asphalt mass, i.e., 0.8 parts by mass. The difference of 7.2 parts by mass between MAH-g-LPB and silane coupling agent is made up with No. 70 road petroleum asphalt.

[0049] The preparation process is the same as in Example 1, except that the silane coupling agent is added at the same time as the softener and the tackifying resin.

[0050] Comparative Example 6: The raw material formulation is the same as in Example 1, but MAH-g-LPB is replaced with an equal amount of physical blend of MAH and LPB, wherein LPB is 7.27 parts by mass and MAH is 0.73 parts by mass, so that the mass ratio of MAH to LPB is consistent with the grafting ratio of MAH-g-LPB in Example 1.

[0051] The preparation process is the same as in Example 1, with LPB and MAH added to the rubber-modified asphalt and sheared at 2000 r / min for 25 min.

[0052] This comparative example is used to verify that MAH must be chemically grafted onto the LPB main chain to achieve migration-anchoring functionality.

[0053] Comparative Example 7: The raw material formula is the same as in Example 1.

[0054] The preparation process is the same as in Example 1, but the timing of MAH-g-LPB addition and dispersion time are changed: after all other components have been added and degassed, MAH-g-LPB is added to the coating and stirred at 600 r / min for 3 min before packaging.

[0055] This comparative example is used to verify that MAH-g-LPB needs to be sufficiently dispersed in the rubber asphalt matrix to establish an effective spatial distribution.

[0056] Performance testing methods: (1) Softening point: determined according to the ring and ball method of T0606 in JTG E20-2011; (2) Ductility at 5℃: Measured according to T0605 in JTG E20-2011, with a tensile speed of 5 cm per min; (3) Rotational viscosity at 60℃: determined according to the Brookfield rotational viscometer method (T0625) in JTG E20-2011, with a rotational speed of 20 r / min; (4) Storage stability: According to the T0661 segregation test of polymer modified bitumen in JTG E20-2011, the sample was placed vertically at 163℃ for 48h and the difference in softening point between the upper and lower sections was measured. (5) Elastic recovery: measured according to T0662 in JTG E20-2011, 25℃; (6) Pull-out bond strength: determined according to Appendix A of JC / T 975-2005. The substrate was an aged asphalt mixture test board treated in an oven at 165℃ for 72 hours. The coating thickness was 1.5 mm, the test temperature was 25℃, the pull-out rate was 10 mm per min, and the average value of 5 samples in each group was taken. (7) Pull-out bond strength after immersion in water: After immersing the coated test plate in water at 25°C for 7 days, the pull-out bond strength is determined according to the above method; (8) Interfacial shear strength: determined according to Appendix B of JC / T 975-2005, with the substrate being an aged asphalt mixture test plate, the coating thickness being 1.5 mm, the test temperature being 25 ℃, and the shear rate being 10 mm per min; (9) Bond strength after thermo-oxidative aging: After aging the coated test plate according to the test conditions of T0610 rotating film oven in JTG E20-2011, the pull-out bond strength is determined by the above method. (10) Gradient interface layer characterization: The FTIR surface scanning method was used to scan along the coating-substrate interface with a step size of 10 μm. The ratio of the intensity of the anhydride C equals O peak at 1780 cm to the CH2 peak at 1460 cm was used as the relative concentration index of MAH-g-LPB, and the concentration-distance distribution curve was plotted.

[0057] Table 1. Basic physical performance test results:

[0058] Test methods: Softening point was determined according to T0606 in JTG E20-2011, ductility at 5℃ was determined according to T0605, rotational viscosity at 60℃ was determined according to T0625, segregation softening point difference was determined according to T0661, and elastic recovery was determined according to T0662.

[0059] Results analysis: Examples 1 to 3 had softening points of 73.5 to 76.8°C, ductility at 5°C of 36.5 to 42.3 cm, a difference in softening point due to segregation of 1.2 to 1.7°C, and an elastic recovery of 75.3% to 82.1%. Comparative Example 1, without the addition of MAH-g-LPB, had a difference in softening point due to segregation of 3.8°C and an elastic recovery of 68.2%, indicating that the storage stability and elastic recovery were poor without MAH-g-LPB.

[0060] Comparative Example 2 used MAH-g-SEBS instead of MAH-g-LPB, and the difference in the separation softening point was 2.4℃, which was an improvement over Comparative Example 1. This indicates that the high molecular weight MAH graft can provide a certain compatibility effect, but it is far less than the 1.2℃ of Example 1.

[0061] Comparative Example 3 used ungrafted LPB, with a segregation softening point difference of 4.3℃ and an elastic recovery of 66.8%. Not only did it fail to improve compatibility, it was slightly worse than Comparative Example 1, indicating that ungrafted LPB does not contain polar MAH groups and cannot play the role of compatibility agent at the rubber powder-asphalt interface.

[0062] Comparative Example 6 uses a physical blend of MAH and LPB, with a separation softening point difference of 4.0℃, which is close to that of Comparative Example 1, indicating that ungrafted MAH and LPB cannot achieve compatibility.

[0063] The segregation softening point difference in Examples 1 to 3 was reduced by 55% to 68% compared to Comparative Example 1 and by 42% to 50% compared to Comparative Example 2. This is an unexpected technical effect of MAH-g-LPB playing a compatibility role at the rubber powder-asphalt interface, because the purpose of adding MAH-g-LPB is to enhance interfacial adhesion rather than improve storage stability.

[0064] Table 2. Results of interfacial adhesion performance tests:

[0065] Test methods: Pull-out bond strength was determined according to Appendix A of JC / T 975-2005. The substrate was an aged asphalt mixture test plate treated at 165℃ for 72 hours. The immersion test conditions were immersion in water at 25℃ for 7 days. The interfacial shear strength was determined according to Appendix B of JC / T 975-2005. The bond strength after aging was determined after aging according to the test conditions of JTG E20-2011 T0610 rotating thin film oven.

[0066] Results analysis: The dry pull-out bond strength of Examples 1 to 3 was 1.23 to 1.68 MPa, the bond strength after immersion in water for 7 days was 1.00 to 1.45 MPa, the water retention rate was 81.3% to 86.3%, and the interfacial shear strength was 0.78 to 1.15 MPa.

[0067] Comparative Example 1, without the addition of MAH-g-LPB, showed a dry pull-out bond strength of 0.58 MPa and a strength of 0.31 MPa after immersion in water for 7 days, with a retention rate of 53.4%. This indicates that without a chemical anchoring mechanism, the interface relies solely on van der Waals forces for adhesion, and water molecules easily replace the physical adsorption layer at the interface, leading to rapid bond decay.

[0068] Comparative Example 2 uses MAH-g-SEBS, with a dry pull-out bond strength of 0.85 MPa, which is slightly higher than that of Comparative Example 1 but not significantly. The water retention rate is 69.4%, indicating that although MAH-g-SEBS contains MAH groups, its number average molecular weight exceeds 50,000 and it is entangled and fixed by the three-dimensional network of rubber asphalt. It cannot migrate to the interface to form a gradient adhesion layer and only provides limited chemical compatibility by being uniformly dispersed in the matrix.

[0069] Comparative Example 3 uses ungrafted LPB, and its dry pull-out bond strength is 0.53 MPa, which is close to that of Comparative Example 1. This indicates that the ungrafted LPB does not contain MAH groups, has no driving force to migrate to the polar interface, and has no chemical ability to react with the surface of the aged road surface.

[0070] Comparative Examples 4 and 5 used amine-based anti-stripping agents and silane coupling agents, respectively. The dry pull-out bond strengths were 0.75 and 0.78 MPa, and the water retention rates were 61.3% and 62.8%, respectively. Although there was an improvement, they were still far lower than those of the examples, indicating that traditional anti-stripping methods only provide physical adsorption reinforcement and cannot form covalent chemical anchoring at the interface.

[0071] Comparative Example 6 uses a physical blend of MAH and LPB. The dry pull-out bond strength is 0.56 MPa, which is close to that of Comparative Example 1. The water retention rate is 57.1%, indicating that the ungrafted MAH reacts rapidly with asphalt in the asphalt and is consumed, while LPB is uniformly dispersed and has no migration force. The two can independently perform their known functions and cannot work together to achieve migration-anchoring.

[0072] Comparative Example 7 had the same formulation as Example 1, but MAH-g-LPB was added at the end of the coating preparation and dispersed for only 3 minutes. The dry pull-out bond strength was 0.95 MPa and the water retention rate was 69.5%, which was significantly lower than that of Example 1. This indicates that MAH-g-LPB needs to be fully dispersed in the rubber asphalt matrix to establish an effective spatial distribution in order to achieve interface migration during construction. Short-term dispersion is insufficient to establish the spatial distribution gradient required for migration.

[0073] Example 1 shows that the dry pull-out bond strength is 162% higher than that of Comparative Example 1, 79% higher than that of Comparative Example 2, 103% higher than that of Comparative Example 4, 95% higher than that of Comparative Example 5, 171% higher than that of Comparative Example 6, and 60% higher than that of Comparative Example 7. The above data fully demonstrate that the spontaneous migration and in-situ chemical anchoring of MAH-g-LPB are the key to the formation of gradient adhesion interface.

[0074] Table 3. FTIR surface scan results of MAH-g-LPB concentration distribution:

[0075] Test method: FTIR surface scanning method was used, scanning along the coating-substrate interface in a step size of 10 μm. The ratio of the intensity of the anhydride C equals O peak at 1780 cm to the CH2 peak at 1460 cm was used as the relative concentration index of MAH-g-LPB.

[0076] Results analysis: In Example 1, the C-O / CH2 ratio at the interface was 0.82, gradually decreasing to 0.08 towards the coating bulk, showing obvious gradient distribution characteristics, confirming that MAH-g-LPB spontaneously migrates and accumulates towards the interface during construction.

[0077] In Comparative Example 2, the C / O / CH2 ratio was 0.10 to 0.11 at all positions, showing no gradient distribution, confirming that MAH-g-SEBS, due to its high molecular weight, could not migrate and was uniformly dispersed in the coating. In Comparative Example 3, the C / O / CH2 ratio was 0.07 to 0.08 at all positions, consistent with the background value of the coating, confirming that the ungrafted LPB did not contain MAH groups and showed no interfacial enrichment.

[0078] The above FTIR surface scan results directly confirm the spontaneous migration and gradient distribution effect of MAH-g-LPB, and that neither high molecular weight MAH grafted products nor ungrafted LPB can achieve this effect.

[0079] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A rubber-modified asphalt pavement maintenance and waterproofing coating, characterized in that, The coating comprises the following components by weight: 100 parts petroleum asphalt, 15 to 25 parts waste rubber powder, 5 to 12 parts maleic anhydride-grafted liquid polybutadiene, 5 to 10 parts tackifying resin, 4 to 8 parts softener, 0.1 to 0.4 parts vulcanizing agent, 5 to 12 parts filler, and 0.3 to 0.8 parts antioxidant. The maleic anhydride-grafted liquid polybutadiene is a liquid polybutadiene graft with a number average molecular weight of 2000 to 6000 and a maleic anhydride grafting rate of 8 to 15% by weight. The maleic anhydride grafting rate is the percentage of grafted maleic anhydride by weight of liquid polybutadiene. During the coating application process, it spontaneously migrates to the interface between the coating and the aged asphalt pavement and reacts in situ at the interface to form a chemically gradient adhesive interface layer.

2. The rubber-modified asphalt pavement maintenance and waterproofing coating as described in claim 1, characterized in that, The maleic anhydride-grafted liquid polybutadiene has a number average molecular weight of 2,500 to 5,000, a maleic anhydride grafting rate of 8 to 15% by mass, and a vinyl content of 60 to 90% by mass.

3. The rubber-modified asphalt pavement maintenance and waterproofing coating as described in claim 1, characterized in that, The waste rubber powder is 40 to 80 mesh waste tire rubber powder with a crosslinking density of 2.5 to 4.5 x 10^-4 mol per cubic centimeter.

4. The rubber-modified asphalt pavement maintenance and waterproofing coating as described in claim 1, characterized in that, The thickness of the chemical composition gradient adhesion interface layer is 50 to 200 μm. The concentration of maleic anhydride-grafted liquid polybutadiene in the interface layer increases from the coating body to the substrate interface. The pull-out bond strength between the coating and the aged asphalt pavement is not less than 1.2 MPa, and the bond strength retention rate is not less than 80% after immersion in water for 7 days.

5. A method for preparing a rubber-modified asphalt pavement maintenance and waterproof coating as described in any one of claims 1 to 4, characterized in that, Includes the following steps: Step 1, Preparation of maleic anhydride-grafted liquid polybutadiene: The liquid polybutadiene is heated to 180 to 200°C, and maleic anhydride and dicumyl peroxide initiator are added under nitrogen protection. The reaction is carried out for 2 to 4 hours to obtain maleic anhydride-grafted liquid polybutadiene with a maleic anhydride grafting rate of 8 to 15%. Step 2, preparing rubber-modified asphalt: Heat petroleum asphalt to 160 to 170°C until it melts, add waste rubber powder, stir at 500 to 800 r / min for 40 to 60 min to make the rubber powder swell, then raise the temperature to 175 to 185°C, and shear at 2000 to 3000 r / min for 30 to 45 min to make the rubber powder evenly dispersed; Step 3, preparing the coating: Add the maleic anhydride grafted liquid polybutadiene obtained in Step 1 to the rubber-modified asphalt obtained in Step 2, and shear it at 1500 to 2500 r / min for 20 to 30 minutes to make it evenly dispersed. Then add the softener and tackifying resin and stir for 15 to 20 minutes. Cool down to 155 to 165℃, add the vulcanizing agent and stir for 15 to 20 minutes. Finally, add the filler and antioxidant and stir for 10 to 15 minutes. After degassing, the rubber-modified asphalt pavement maintenance and waterproof coating is obtained. Step 4, coating and curing: Heat the coating to 160 to 180°C and apply it to the surface of aged asphalt pavement at a rate of 1.0 to 2.0 kg per square meter. Keep it at 140 to 160°C for 10 to 30 minutes to allow maleic anhydride-grafted liquid polybutadiene to migrate to the interface and react in situ. Then cool it to room temperature to form a chemically gradient adhesion interface layer.

6. The preparation method according to claim 5, characterized in that, The liquid polybutadiene mentioned in step one has a number average molecular weight of 2,500 to 5,000, a vinyl content of 60 to 90%, an amount of maleic anhydride added of 8 to 18% of the mass of the liquid polybutadiene, and an amount of dicumyl peroxide added of 0.3 to 0.8% of the mass of the liquid polybutadiene.

7. The preparation method according to claim 5, characterized in that, In step three, the maleic anhydride-grafted liquid polybutadiene is added after the rubber powder is dispersed and before the vulcanizing agent is added. It is sheared and dispersed at a speed of 1500 to 2500 r / min for 20 to 30 minutes to establish a spatial distribution in the rubber asphalt matrix.

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