Multi-element synergistic smoke suppression flame retardant for asphalt as well as preparation method and application of multi-element synergistic smoke suppression flame retardant

Abstract

The invention discloses an asphalt multi-element synergistic smoke suppression flame retardant as well as a preparation method and application thereof, and belongs to the technical field of road engineering. The invention solves the problem of how to further optimize the defects of the existing asphalt smoke suppression flame retardant. According to the preparation method, graphene oxide is adopted as a raw material, a hydrothermal method reduction process and a surface modification grafting process are adopted, the uniform and stable asphalt multi-element synergistic smoke suppression flame retardant is finally prepared, and the asphalt multi-element synergistic smoke suppression flame retardant asphalt can be prepared from the asphalt multi-element synergistic smoke suppression flame retardant. Through a series of chemical and physical reactions at high temperature, the asphalt multi-element synergistic smoke suppression flame retardant greatly reduces the generation of smoke in the asphalt paving process and obviously reduces the combustion speed of asphalt in a fire disaster.

Description

Technical Field

[0001] The present invention belongs to the technical field of road engineering, and in particular relates to an asphalt multi-element synergistic smoke suppression and flame retardant, and a preparation method and application thereof. Background Art

[0002] Asphalt pavement is widely used in tunnel construction due to its excellent anti-skid properties, low noise levels, high driving comfort, and easy maintenance. However, the unique characteristics of tunnel environments make the fire risk significantly higher than on ordinary roads. The enclosed nature of tunnels and limited ventilation mean that in the event of a fire, high-temperature smoke will spread rapidly, easily causing casualties and serious damage to tunnel facilities. Asphalt is highly flammable in fires, and the combustion process rapidly releases large amounts of heat and produces toxic and hazardous smoke. During combustion, asphalt decomposes into a series of harmful substances, including volatile organic compounds, polycyclic aromatic hydrocarbons, sulfur oxides, and nitrogen oxides. These harmful gases can cause acute damage to the respiratory system, skin, and eyes of drivers and passengers. In the high temperatures of tunnel fires, toxic smoke further reduces oxygen levels within the tunnel, greatly complicating escape and rescue efforts. During tunnel construction, the toxic smoke released during asphalt laying can severely damage the respiratory system of construction workers. Long-term inhalation can lead to chronic bronchitis, asthma, lung disease, and even lung cancer. Inhalation of high concentrations of toxic gases can also cause acute poisoning, manifesting as dizziness, shortness of breath, chest tightness, and coughing. In summary, asphalt fumes have a significant negative impact on driving safety and the health of construction workers, and effective measures are urgently needed to address them in order to ensure safe tunnel operations and the health of personnel.

[0003] At present, smoke suppression flame retardants mainly include halogen smoke suppression flame retardants, phosphorus smoke suppression flame retardants, metal oxide smoke suppression flame retardants, etc. Halogen smoke suppression flame retardants are mainly composed of bromide smoke suppression flame retardants and chloride smoke suppression flame retardants, among which brominated diphenyl ether and hexabromocyclododecane are typical representatives. The flame retardant mechanism of halogen smoke suppression flame retardants is that the halogen atom free radicals (such as Cl · 、B r· ) and the highly active free radicals (such as H · OH ·)Reactions occur to generate molecules with lower reactivity. Through this process, the heat release rate during combustion is effectively reduced, and the gas-phase combustion chain reaction is inhibited. In addition, halogen-based smoke suppressants and flame retardants decompose or combine with toxic gases in the smoke through chemical reactions or physical adsorption, reducing the smoke concentration and mitigating the harm of flue gas in enclosed environments such as tunnels. For example, halogen atoms (chlorine or bromine) can undergo chemical reactions with toxic gases in the smoke during combustion, such as carbon monoxide (CO), nitrogen oxides (NOx), and volatile organic compounds (VOCs), to form relatively stable molecules. Through this reaction, halogen-based flame retardants can not only effectively reduce the harmful components in the smoke but also reduce its harm to the respiratory system. Although halogen-based smoke suppressants and flame retardants exhibit excellent flame retardant performance, under combustion conditions, they will generate other harmful by-products, such as organic chlorides and bromides, posing potential threats to the ecological environment and human health. Phosphorus-based smoke suppressants and flame retardants are regarded as environmentally friendly alternative products to halogen-based ones. Their smoke suppression and flame retardant effects can be manifested in the gas phase and the condensed phase. During combustion, phosphorus-based smoke suppressants and flame retardants decompose to produce free radicals such as PO · and PO2 · etc. These free radicals can combine with highly reactive free radicals such as H · and OH · in the combustion chain reaction, thus effectively inhibiting the progress of the combustion reaction. In addition, when phosphorus-based smoke suppressants and flame retardants are heated, substances such as phosphoric acid and metaphosphoric acid are generated. These substances can form a carbon layer with heat insulation and oxygen isolation effects on the material surface. This carbon layer can not only reduce the heat feedback to the interior of the material but also prevent the release of combustible gases, not only enhancing the flame retardant effect but also reducing the release of smoke. Among phosphorus-based smoke suppressants and flame retardants, inorganic phosphates (such as ammonium polyphosphate) have become a widely used smoke suppression and flame retardant additive due to their low cost and non-toxicity. However, phosphorus-based smoke suppressants and flame retardants are not perfect. Phosphorus-based smoke suppressants and flame retardants show negative effects on organisms and humans, and some phosphorus-based smoke suppressants and flame retardants show potential carcinogenic toxicity. Phosphorus-based smoke suppressants and flame retardants can enter the human body through inhalation, oral ingestion of phosphorus-based smoke suppressants and flame retardants in dust, and skin absorption. Metal hydroxides, such as aluminum hydroxide and magnesium hydroxide, belong to inorganic mineral-based smoke suppressants and flame retardants. Their flame retardant mechanism is mainly through endothermic decomposition to release water vapor, thereby cooling the combustion area, diluting combustible gases, and then slowing down the pyrolysis process. In addition, metal hydroxides also have smoke suppression performance and can adsorb harmful components in asphalt smoke. They are one of the environmentally friendly smoke suppressants and flame retardants that have received much attention and extensive research at present. However, for metal hydroxides represented by aluminum hydroxide (ATH) and magnesium hydroxide (MH), their pyrolysis temperature is greater than 180°C. Under such temperature conditions, the actual effects of ATH and MH on diluting and condensing asphalt smoke during heating, preparation, and construction still need to be further studied and verified.

[0004] In recent years, graphene has received extensive attention in the field of flame retardancy due to its excellent physical and chemical properties. Graphene and its oxides have a high aspect ratio, a large specific surface area, and a unique two-dimensional structure. These characteristics enable it to construct an effective physical barrier on the material surface, thereby significantly inhibiting the conduction and diffusion of heat and gas. In addition, graphene has high thermal stability and good anti-chemical corrosion performance, which lays a broad prospect for its application in the flame retardancy of polymers and composites. However, the original graphene sheets have the problem of low catalytic carbonization efficiency, which to a certain extent restricts the improvement effect of the flame retardancy of composites. Therefore, how to improve the flame retardancy efficiency of graphene, reduce the agglomeration of sheets, and enhance its compatibility with the matrix material through surface functionalization modification has become a common concern of researchers. Summary of the Invention

[0005] In view of the above problems in the existing asphalt smoke suppression and flame retardant, the present invention provides an asphalt multi-element synergistic smoke suppression and flame retardant, its preparation method and application, aiming to modify asphalt with a new type of graphene material, so that asphalt has smoke suppression and flame retardant properties. One is to reduce the generation of smoke during the paving process of asphalt pavement, and the other is to reduce the combustion speed of asphalt pavement in case of fire. In addition, to enable the smoke suppression and flame retardant to be effectively applied to asphalt, it is necessary to ensure its good stability and hydrophobic lipophilicity. In addition, to enable its industrial production, it is also necessary to ensure that the production process is environmentally friendly, does not emit harmful substances, and is economical and affordable.

[0006] The technical solution adopted by the present invention is as follows:

[0007] An asphalt multi-element synergistic smoke suppression and flame retardant is a grafting product obtained by grafting a heteroatom source onto the surface of reduced graphene oxide, and the heteroatom source includes one or more of urea, polyphosphoric acid, and phosphoric acid.

[0008] After adopting this technical solution, graphene oxide has the characteristics of high aspect ratio, large specific surface area and unique two-dimensional sheet structure, enabling it to form a continuous physical barrier on the material surface, preventing heat and oxygen from transferring into the material interior, while inhibiting the escape of combustible gases from the material interior and slowing down the combustion rate. In addition, its excellent thermal stability can maintain the stability of structure and performance at high temperatures, and its excellent thermal conductivity can quickly conduct heat away from the combustion area, reducing the temperature of the material surface and making it difficult for the material to reach the combustion point. Meanwhile, graphene promotes the formation of a carbon layer during the combustion process, effectively preventing heat and oxygen from transferring into the material interior and reducing the release of smoke and harmful gases. The surface of graphene oxide is rich in oxygen functional groups, which can adsorb and neutralize toxic gases generated during combustion, such as carbon monoxide (CO) and nitrogen oxides (NOx), thereby further inhibiting the generation of smoke. Through these mechanisms, graphene oxide can not only improve the flame retardancy of materials, but also effectively reduce the toxicity and release of smoke during the fire and construction processes. Therefore, graphene is used as the main component of the asphalt smoke suppressant and flame retardant. The heteroatom source grafts to form a nitrogen and phosphorus organic molecular layer on the reduced graphene oxide. The nitrogen and phosphorus organic molecular layer decomposes during combustion to produce incombustible gases such as ammonia and carbon dioxide, diluting the oxygen concentration around the asphalt, reducing the generation of toxic gases (such as nitrogen oxides), further reducing the release of toxic smoke and inhibiting the combustion rate. In addition, the free radicals generated by decomposition at high temperatures can capture the free radicals generated during combustion and convert them into stable compounds, achieving the purpose of smoke suppression and flame retardancy. Additionally, it improves the dispersibility and interfacial compatibility in the reduced graphene oxide polymer matrix, and combines the catalytic carbonization of the flame retardant and the nano-effects and barrier effects of graphene to enhance the smoke suppression and flame retardancy efficiency of the reduced graphene oxide.

[0009] Preferably, the graphene oxide for preparing the reduced graphene oxide is monolayer graphene oxide with an oxidation degree of 30%-40%. Further, it can be preferably monolayer graphene oxide with an oxidation degree of 35%.

[0010] After adopting this technical solution, through a reduction reaction, aromatic functional groups, edge functional groups and defective functional groups are removed from the graphene oxide to generate monolayer or few-layer reduced graphene oxide.

[0011] Preferably, the urea is industrial-grade urea with a purity of 99%, the degree of polymerization of the polyphosphoric acid is 15-20, and the concentration of the phosphoric acid is 20%-25%. Further, the degree of polymerization of the polyphosphoric acid is 15, and the concentration of the phosphoric acid is 20%.

[0012] After adopting this technical solution, industrial-grade urea with a purity of 99% is selected, and one or more of the degree of polymerization of the polyphosphoric acid being 15-20 and the concentration of the phosphoric acid being 20%-25% are used as the nitrogen source and phosphorus source for the reduced graphene oxide, and a nitrogen and phosphorus organic molecular layer is grafted through a surface modification technique.

[0013] Preferably, when the heteroatom source is urea, the preparation raw materials include graphene oxide, a reducing agent and urea, with 85 - 95 parts of graphene oxide, 900 - 910 parts of urea, and the mass ratio of graphene oxide to the reducing agent being 1:4 - 7.

[0014] Preferably, when the heteroatom sources are phosphoric acid and polyphosphoric acid, the preparation raw materials include graphene oxide, a reducing agent, phosphoric acid and polyphosphoric acid, with 70 - 80 parts of graphene oxide, 765 - 775 parts of phosphoric acid, 150 - 160 parts of polyphosphoric acid, and the mass ratio of graphene oxide to the reducing agent being 1:4 - 7.

[0015] Preferably, when the heteroatom sources are urea, phosphoric acid and polyphosphoric acid, the preparation raw materials include graphene oxide, a reducing agent, urea, phosphoric acid and polyphosphoric acid, with 75 - 85 parts of graphene oxide, 410 - 420 parts of urea, 410 - 420 parts of phosphoric acid, 75 - 85 parts of polyphosphoric acid, and the mass ratio of graphene oxide to the reducing agent being 1:4 - 7.

[0016] The flame - retardant paths (gas phase / condensed phase / synergistic) of different elements are different, and the elements playing a dominant role are different. Therefore, the best ratio needs to be matched to optimize the performance; reduce the usage of expensive raw materials (such as polyphosphoric acid), reduce costs while maintaining high - efficiency flame retardancy; achieve a double improvement in technical feasibility and economy. Setting the ratio between each component in this way can ensure that each component in the multi - element smoke - suppressing flame retardant plays a synergistic role and improves the flame - retardant effect. If the content of graphene is too small, an effective barrier layer may not be formed; if the content of urea or polyphosphoric acid is insufficient, the non - flammable gas released will not be enough to dilute the concentration of combustible gas. Secondly, a suitable mixing ratio helps to uniformly disperse the reduced graphene oxide in the flame retardant, enabling it to fully exert its excellent performance; helps to improve the compatibility between the flame retardant and asphalt, avoiding problems such as stratification and precipitation, and ensuring the stability and long - term effectiveness of the smoke - suppressing flame retardant in asphalt. At the same time, it improves production efficiency, controls costs, meets environmental protection requirements, and reduces the emission of harmful substances.

[0017] Preferably, the reducing agent is ascorbic acid. Further, it can be preferably L - ascorbic acid.

[0018] After adopting this technical solution, using ascorbic acid, a naturally occurring organic compound, as the reducing agent will not produce toxic and harmful by - products, reducing environmental pollution and potential threats to the health of operators. Moreover, the reaction system is simple and the reaction conditions are relatively mild. This reducing agent can effectively remove oxygen - containing groups while reducing the risk of introducing heteroatoms. The molecular structure of L - ascorbic acid makes it have stronger reducibility and better antioxidant properties than other models (such as D - ascorbic acid) under the action of air, light and heat.

[0019] A preparation method of an asphalt multi-element synergistic smoke suppression and flame retardant, comprising the following steps:

[0020] S1: Prepare a mixed solution of graphene oxide and a reducing agent, and obtain reduced graphene oxide solid through a reduction reaction;

[0021] S2: Mix the reduced graphene oxide solid with a heteroatom source for graft modification to obtain a grafted product, namely an asphalt multi-element synergistic smoke suppression and flame retardant.

[0022] Further, in S1, mix graphene oxide and a reducing agent, add an appropriate amount of water, fully dissolve and stir evenly to obtain an original solution for redox reaction. Place the original solution in an oven at a specified temperature for a sufficient time, filter, wash and dry to obtain reduced graphene oxide solid.

[0023] Further, in S2, add the obtained reduced graphene oxide, according to the mixing ratio, to a quantitative heteroatom source (one or more of urea, polyphosphoric acid and phosphoric acid) and water, mix evenly, and place in an oven at a specified temperature for a sufficient time. After cooling, filter and dry to finally obtain a multi-element smoke suppression and flame retardant solid.

[0024] After adopting this technical solution, the smoke suppression and flame retardant can undergo a series of chemical reactions during the combustion of asphalt, generating a stable carbon layer that covers the surface of the asphalt. It can not only prevent heat and oxygen from entering the interior of the material, slow down the combustion speed, but also reduce the generation of smoke precursors produced by incomplete combustion and reduce the generation of smoke. At the same time, the thermal stability, thermal oxidation resistance, strength, toughness and bonding performance of the asphalt are all improved.

[0025] An application of an asphalt multi-element synergistic smoke suppression and flame retardant for preparing a multi-element synergistic smoke suppression and flame retardant asphalt.

[0026] Preferably, the specific steps for preparing the multi-element synergistic smoke suppression and flame retardant asphalt include:

[0027] SA: Melt the asphalt;

[0028] SB: Add the asphalt multi-element synergistic smoke suppression and flame retardant to the melted asphalt;

[0029] SC: Make the asphalt and the asphalt multi-element synergistic smoke suppression and flame retardant mix evenly through shearing to obtain a multi-element synergistic smoke suppression and flame retardant asphalt.

[0030] Further, in SA, place the asphalt in a container and heat it in an oven at a preset temperature until the asphalt is completely melted. Keep observing during this period to ensure uniform heating.

[0031] Further, in SB, take out the melted asphalt, place it on a preheated electric hot plate, start a low-speed stirring device, and slowly and evenly add the accurately weighed smoke suppression and flame retardant to ensure uniform mixing.

[0032] Furthermore, after adding the smoke suppressant and flame retardant, the low-speed stirring is stopped, and a high-speed shearing machine is used for shearing. The rotation speed is adjusted to the set value, and the shearing temperature is controlled to ensure that the asphalt and the smoke suppressant and flame retardant are fully mixed to prepare high-quality smoke suppressant and flame retardant asphalt.

[0033] After adopting this technical solution, the asphalt is loaded into a metal container and placed in an oven with a set temperature, which can precisely control the heating environment. This ensures that the basic state of the asphalt is stable when it is subsequently mixed with the smoke suppressant and flame retardant, laying a good foundation for the uniform mixing of the two, avoiding local overheating or insufficient melting of the asphalt due to temperature fluctuations, and effectively maintaining the stability of the asphalt material. The low-speed stirring process promotes the initial mixing of the two, laying a solid foundation for further uniform dispersion by subsequent high-speed shearing. The smoke suppressant and flame retardant is slowly and evenly added to the continuously stirred asphalt, ensuring the stability of the addition process and allowing the smoke suppressant and flame retardant to be gradually and completely immersed in the asphalt. The magnetic shearing device of the high-speed shearing process continuously shears the asphalt at a specified speed and temperature, which can greatly improve the mixing efficiency of the smoke suppressant and flame retardant with the asphalt. The smoke suppressant and flame retardant can be fully and evenly dispersed in the asphalt, thereby significantly improving the smoke suppression effect, flame retardant properties, and stability of the smoke suppressant and flame retardant asphalt. Secondly, the high-speed shearing process refines the particle size of the smoke suppressant and flame retardant in the asphalt and makes it evenly distributed in the microstructure of the asphalt, making the performance of the smoke suppressant and flame retardant asphalt more stable during storage and use, and less likely to experience component separation or precipitation, effectively ensuring product quality and service life.

[0034] Preferably, the asphalt is base asphalt, and the dosage of the asphalt multi-element synergistic smoke suppression and flame retardant is 5-9%. It should be noted that the dosage described in the present invention is the proportion of the substance in the obtained mixed product.

[0035] Furthermore, the asphalt is matrix asphalt, and the dosage of the asphalt multi-element synergistic smoke suppression and flame retardant is 7%.

[0036] With this technical solution, both the matrix asphalt components (such as asphaltenes and colloids) and the flame retardant possess polar functional groups, enabling efficient bonding through charge interactions. Furthermore, the matrix asphalt possesses a moderate viscosity, facilitating uniform dispersion of the flame retardant. Without the interference of modifiers, the flame retardant's inherent properties are more precisely reflected, resulting in a more pronounced smoke suppression and flame retardant effect. When the asphalt multi-element synergistic smoke suppression flame retardant is incorporated at a 7% dosage, it forms a sufficient barrier layer during asphalt combustion, ensuring the release of sufficient flame-retardant gases. Furthermore, the smoke suppression and flame retardant does not significantly affect the asphalt's basic physical properties, such as penetration, softening point, and ductility.

[0037] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are as follows: The components (such as asphaltenes and resins) are polar-matched with the flame retardant, and can form a stable carbon layer through chemical bonding; at the same time, the matrix asphalt has a moderate viscosity, which is conducive to the uniform dispersion of the flame retardant, and there is no interference from modifiers. The thermal decomposition of the flame retardant (such as gas release and catalytic carbonization) can efficiently cooperate with the thermal degradation process of asphalt, thereby more accurately reflecting the essence of the flame retardant mechanism.

[0038] 1. When the asphalt smoke and flame retardant is burned, a series of chemical reactions will occur, reducing the generation of smoke during the paving process of asphalt pavement and reducing the burning speed of asphalt pavement in a fire. Thus, the life and property safety of each person are guaranteed when a fire occurs on the road surface.

[0039] 2. When synthesizing the smoke and flame retardant asphalt with the asphalt smoke and flame retardant, a three-stage synthesis process of precise temperature control, low-speed stirring, and high-speed shearing is adopted, so that the smoke and flame retardant is fully and evenly dispersed in the asphalt, significantly improving the smoke suppression, flame retardant performance and stability of the smoke and flame retardant asphalt, refining the particles and evenly distributing them in the microstructure, and ensuring the product quality and service life.

[0040] 3. The asphalt smoke and flame retardant belongs to a composite smoke and flame retardant, which has good uniformity and can be more evenly dispersed in the asphalt, making the smoke and flame retardant effect more stable and reliable, and filling more tightly in the microstructure of the asphalt, forming a more stable interaction with the asphalt molecules, and improving the overall performance of the asphalt.

[0041] 4. The asphalt smoke and flame retardant is hydrophobic and lipophilic, ensuring that the material can continuously exist inside the asphalt during long-term service, and is evenly distributed, stably exerting the flame retardant and smoke suppression performance.

[0042] 5. The asphalt smoke and flame retardant combines multiple elements into one through chemical bonding, avoiding agglomeration to form local high-concentration areas, making its performance more consistent during storage and use, and at the same time reducing the mutual interference between elements, which helps to maintain the chemical stability of the flame retardant.

[0043] 6. The preparation method of the asphalt smoke and flame retardant is simple and easy to implement, and the process is environmentally friendly and harmless, without releasing harmful substances, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a schematic diagram of the surface modification principle of graphene oxide in the present invention;

[0045] Figure 2 is a schematic diagram of the reduction principle of graphene oxide of the present invention;

[0046] Figure 3 is a preparation flow chart of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0047] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the following will clearly and completely describe the technical solutions in the embodiments of this application in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part rather than all of the embodiments of this application.

[0048] It should be noted that the raw materials used in the following embodiments and comparative examples are respectively sourced from:

[0049] Graphene oxide: Nanjing Xianfeng Nano XFGO-1;

[0050] Ascorbic acid: Shijiazhuang Pharmaceutical Group VC-FCC;

[0051] Urea: Sinochem Group SINOCHEM U;

[0052] Phosphoric acid: Yuntianhua Group YTH-PA85;

[0053] Polyphosphoric acid: Sichuan Chenghong Phospho-Chemical Industry CHP-PPA115.

[0054] The parts in the following embodiments and comparative examples are all parts by weight.

[0055] Example 1

[0056] An asphalt multi-element synergistic smoke suppression and flame retardant, the preparation raw materials include graphene oxide, ascorbic acid, and heteroatom source, wherein the heteroatom source is urea, as Figure 1 shown, and its preparation method is as follows:

[0057] S1: As Figure 2 shown, add 90 parts of graphene oxide, 500 parts of ascorbic acid, and 99400 parts of water to a beaker, stir and disperse at room temperature for 2 hours, so that the graphene oxide powder and ascorbic acid are fully dissolved in the solvent, put it into a reaction kettle, and place the reaction kettle in an 80°C oven and heat continuously for 6 hours to fully reduce the graphene oxide. After the solution is completely cooled, filter the solution and wash it with water until the pH≥6 to remove the remaining ascorbic acid. Finally, dry the obtained solid at 80°C for 12 hours;

[0058] S2: Add 90 parts of reduced graphene oxide, 905 parts of urea, and 99000 parts of water to a beaker, disperse ultrasonically at room temperature for 2 hours, so that the reduced graphene oxide and urea are fully dissolved in the solvent. Put it into a reaction kettle and place it in an 180°C oven and heat continuously for 10 hours. After the solution is completely cooled, filter the solution and wash it with water until the pH value is in the range of 6-8 to remove the remaining heteroatom source. Finally, dry the obtained solid at 80°C for 12 hours to obtain the nitrogen-doped graphene smoke suppression and flame retardant.

[0059] Preparation of multi-element synergistic smoke suppression and flame retardant asphalt, including the following steps:

[0060] SA: Load the AH-70# asphalt produced by Liaohe Oilfield into a metal container, place it in an oven set at a temperature of 160°C, and leave it for about 30 minutes until the asphalt is completely in a flowing state. During this period, closely observe to ensure uniform heating and complete melting.

[0061] SB: After the asphalt melts, take it out and place it on an electric hot plate preheated to 150°C. Turn on the low-speed stirring equipment (rotation speed 100 revolutions per minute). During the stirring process, slowly and evenly add 35 grams of smoke suppression and flame retardant agent (dosage 7%) within 5 - 10 minutes, ensure it is completely submerged, and continue stirring for 15 minutes to achieve preliminary uniform mixing.

[0062] SC: After preliminary mixing, stop the low-speed stirring. Smoothly place the magnetic shearing device of the high-speed shearer into the container, gradually adjust the rotation speed to 5000 revolutions per minute, control the shearing temperature at 160°C, and continue shearing for 30 minutes. During this period, closely monitor the equipment and the state of the asphalt to ensure sufficient and efficient mixing, and prepare high-performance smoke suppression and flame retardant asphalt.

[0063] For the smoke suppression and flame retardant asphalt finally obtained in this example, the limiting oxygen index of the smoke suppression and flame retardant asphalt was measured at 140°C and 160°C respectively using a limiting oxygen index tester. At the same time, the particulate matter release amount was measured by the filter membrane method (using the filter membrane to intercept the smoke particles generated by heating the asphalt, then weighing the mass of the filter membrane before and after interception and calculating the difference to calculate the mass of the particulate matter, so as to measure the release amount of smoke particles during the heating process of the asphalt), and finally compared with the blank control group of asphalt without adding the smoke suppression and flame retardant agent. The experimental results of the limiting oxygen index at 140°C and 160°C are shown in Table 1, and the experimental results of the particulate matter release amount are shown in Table 2:

[0064] Table 1

[0065]

[0066] As can be seen from Table 1, after adding the multi-element synergistic smoke suppression and flame retardant agent, the limiting oxygen index at 140°C and 160°C increased significantly.

[0067] Table 2

[0068]

[0069] As can be seen from Table 2, after adding the multi-element synergistic smoke suppression and flame retardant agent, the particulate matter release amount at 140°C and 160°C decreased significantly.

[0070] Example 2

[0071] S1: As Figure 2As shown, 77 parts of graphene oxide, 500 parts of ascorbic acid, and 99,400 parts of water were added to a beaker and stirred and dispersed at room temperature for 2 hours to fully dissolve the graphene oxide powder and ascorbic acid in the solvent. Then it was put into a reaction kettle, and the reaction kettle was placed in an oven at 80 °C and continuously heated for 6 hours to fully reduce the graphene oxide. After the solution was completely cooled, the solution was filtered and washed with water until the pH ≥ 6 to remove the remaining ascorbic acid. Finally, the obtained solid was dried at 80 °C for 12 hours;

[0072] S2: As Figure 3 shown, 77 parts of reduced graphene oxide, 770 parts of phosphoric acid, 155 parts of polyphosphoric acid, and 99,000 parts of water were added to a beaker and stirred and dispersed at room temperature for 2 hours to fully dissolve the reduced graphene oxide, phosphoric acid, and polyphosphoric acid in the solvent. It was put into a reaction kettle and placed in an oven at 180 °C and continuously heated for 10 hours. After the solution was completely cooled, the solution was filtered and washed with water until the pH value was in the range of 6 - 8 to remove the remaining heteroatom source. Finally, the obtained solid was dried at 80 °C for 12 hours to obtain the phosphorus-doped graphene smoke suppression and flame retardant.

[0073] Preparation of smoke suppression and flame retardant asphalt:

[0074] SA: Load the SV-70# asphalt produced by Shengli Oilfield into a metal container and place it in an oven set at a temperature of 160 °C for about 30 minutes until the asphalt is completely in a flowing state. During this period, it is necessary to closely observe to ensure uniform heating and full melting.

[0075] SB: After the asphalt is melted, take it out and place it on a hot plate preheated to 150 °C, and turn on the low-speed stirring equipment (rotation speed 100 revolutions per minute). During stirring, slowly and evenly add 35 grams of smoke suppression and flame retardant (dosage 7%) within 5 - 10 minutes to ensure it is completely submerged and continue stirring for 15 minutes to achieve preliminary uniform mixing.

[0076] SC: After preliminary mixing, stop the low-speed stirring, smoothly place the magnetic shearing device of the high-speed shearer into the container, gradually adjust the rotation speed to 5000 revolutions per minute, control the shearing temperature at 160 °C, and continuously shear for 30 minutes. During this period, closely monitor the equipment and the state of the asphalt to ensure sufficient and efficient mixing to prepare high-performance smoke suppression and flame retardant asphalt.

[0077] For the smoke suppression and flame retardant asphalt finally obtained in this example, the limiting oxygen index of the smoke suppression and flame retardant asphalt was measured at 140 °C and 160 °C respectively using a limiting oxygen index tester, and the particulate matter release amount was measured by the filter membrane method. Finally, it was compared with the blank control group of asphalt without adding the smoke suppression and flame retardant. The experimental results of the limiting oxygen index at 140 °C and 160 °C are shown in Table 3, and the experimental results of the particulate matter release amount are shown in Table 4.

[0078] Table 3

[0079]

[0080] As can be seen from Table 3, the limiting oxygen index at 140 °C and 160 °C increases significantly after adding the multi-element synergistic smoke suppression and flame retardant, but the increase is smaller compared to using urea as the heteroatom source. The reason for this trend is that the decomposition temperature of the phosphorus-based smoke suppression and flame retardant is relatively high (its efficient decomposition temperature is usually > 200 °C), and it has not been completely decomposed at 140 - 160 °C, resulting in a lag in the flame retardant effect. While the urea-based flame retardant can decompose to generate gas and form a flame retardant carbon layer at 100 °C, and the flame retardant effect at this temperature is better than that of the phosphorus-based smoke suppression and flame retardant.

[0081]

[0082] As can be seen from Table 4, the particulate matter release at 140 °C and 160 °C decreases significantly after adding the multi-element synergistic smoke suppression and flame retardant, and the decrease at 140 °C is close to that of using urea as the heteroatom source, while the decrease at 160 °C is smaller. The main reason for this trend is that the particulate matter suppression effect of the phosphorus-based flame retardant is close to that of the urea-based flame retardant at 140 °C, mainly relying on the initial carbon layer coverage; but at 160 °C, the generated phosphoric acid may react with metal ions in the asphalt (such as Ca 2+ 、Fe 3+ ) to form phosphate precipitates (such as Ca3(PO4)2), weakening the continuity of the carbon layer. Such side reactions intensify at high temperatures (160 °C), leading to a decrease in the barrier efficiency against asphalt fume. While urea maintains a high inhibition efficiency at high temperatures through the synergistic effect of gas-phase dilution and nitrogen-doped carbon layer.

[0083] Example 3

[0084] Prepare nitrogen-doped phosphorus graphene smoke suppression and flame retardant:

[0085] S1: As Figure 2 shown, add 85 parts of graphene oxide, 500 parts of ascorbic acid, and 99400 parts of water to a beaker, stir and disperse at room temperature for 2 hours to fully dissolve the graphene oxide powder and ascorbic acid into the solvent, put it into a reaction kettle, and place the reaction kettle in an 80 °C oven and heat continuously for 6 hours to fully reduce the graphene oxide. After the solution is completely cooled, filter the solution by suction and wash it with water until the pH ≥ 6 to remove the remaining ascorbic acid, and finally dry the obtained solid at 80 °C for 12 hours;

[0086] S2: Add 85 parts of reduced graphene oxide, 415 parts of urea, 415 parts of phosphoric acid, 80 parts of polyphosphoric acid, and 99000 parts of water into a beaker, stir and disperse at room temperature for 2 hours to fully dissolve the reduced graphene oxide and urea in the solvent. Put it into a reaction kettle and place it in an oven at 180 °C for continuous heating for 10 hours. After the solution is completely cooled, filter the solution and wash it with water until the pH value is in the range of 6 - 8 to remove the remaining heteroatom sources. Finally, dry the obtained solid at 80 °C for 12 hours to obtain the nitrogen-doped phosphorus graphene smoke suppression and flame retardant.

[0087] Preparation of smoke suppression and flame retardant asphalt:

[0088] SA: Load the CQ-70# asphalt produced by Changqing Oilfield into a metal container, place it in an oven set at a temperature of 160 °C, and let it stand for about 30 minutes until the asphalt is completely in a flowing state. During this period, closely observe to ensure uniform heating and full melting.

[0089] SB: After the asphalt melts, take it out and place it on a hot plate preheated to 150 °C, turn on the low-speed stirring equipment (rotation speed 100 revolutions per minute). During the stirring process, slowly and evenly add 35 grams of smoke suppression and flame retardant (dosage 7%) within 5 - 10 minutes, ensure it is completely immersed, and continue stirring for 15 minutes to achieve preliminary uniform mixing.

[0090] SC: After preliminary mixing, stop the low-speed stirring, smoothly place the magnetic shearing device of the high-speed shearing machine into the container, gradually adjust the rotation speed to 5000 revolutions per minute, control the shearing temperature at 160 °C, and continue shearing for 30 minutes. During this period, closely monitor the equipment and the state of the asphalt to ensure sufficient and efficient mixing to prepare high-performance smoke suppression and flame retardant asphalt.

[0091] For the smoke suppression and flame retardant asphalt finally obtained in this example, use a limiting oxygen index tester to measure the limiting oxygen index of the smoke suppression and flame retardant asphalt at 140 °C and 160 °C respectively. At the same time, measure the particulate matter release amount by the filter membrane method, and finally compare it with the blank control group of asphalt without adding the smoke suppression and flame retardant. The experimental results of the limiting oxygen index at 140 °C and 160 °C are shown in Table 5, and the experimental results of the particulate matter release amount are shown in Table 6.

[0092] Table 5

[0093]

[0094] As can be seen from Table 5, the limiting oxygen index at 140 °C and 160 °C increased significantly after adding the multi-element synergistic smoke suppression and flame retardant, and the increase was greater compared to using only urea as the heteroatom source. The reason for this trend is due to its multi-mechanism synergistic effect and optimized temperature adaptability. NH3 and CO2 generated by the decomposition of the urea-based flame retardant inhibit the flame propagation in the initial stage of combustion through gas-phase dilution, while the phosphorus-based flame retardant catalyzes the formation of a dense expanded carbon layer in the asphalt, blocking the diffusion of heat and oxygen. The two complement each other in time and space to cover the entire combustion chain. Nitrogen doping (C-N bond) improves the oxidation resistance of the carbon layer, and the porous structure generated by phosphorus catalysis enhances the physical barrier. The synergistic effect makes the increase in LOI superimposed. At the same time, nitrogen and phosphorus free radicals synergistically quench the H· / HO· free radicals in the combustion chain reaction, inhibiting the combustion reaction chain.

[0095] Table 6

[0096]

[0097] As can be seen from Table 6, the particulate matter release at 140 °C and 160 °C decreased significantly after adding the multi-element synergistic smoke suppression and flame retardant, but the decrease was greater compared to using urea as the heteroatom source. The main reason for this trend is that it achieves efficient smoke suppression through a multi-dimensional synergistic mechanism in the gas phase and the condensed phase. Inert gases such as NH3 and CO2 generated by the decomposition of the urea-based flame retardant (gas-phase effect) dilute oxygen and inhibit the combustion chain reaction, reducing the formation of soot precursors such as polycyclic aromatic hydrocarbons (PAHs); at the same time, the phosphorus-based flame retardant catalyzes the formation of a dense expanded carbon layer in the asphalt, physically blocking the escape of unburned carbon particles and using the surface charge enhancement effect of the nitrogen-doped carbon layer (C-N-C structure) to efficiently adsorb soot. At 140 °C, the early inhibition in the gas phase and the preliminary barrier in the condensed phase are synergistic; at 160 °C, the dense carbon layer catalyzed by phosphorus further intercepts particles, while the urea-based flame retardant continuously inhibits the cracking of the carbon layer. However, a single urea group lacks the support of the carbon layer and has a low smoke suppression efficiency. In addition, the nitrogen-phosphorus synergistic system inhibits the condensation of soot precursors through free radical quenching (·NH2 and PO 3- capturing H· / HO·) and oxidizes the surface of the soot through phosphoric acid catalysis, converting it into gas products, ultimately reducing the particulate matter concentration in a wide temperature range.

[0098] The above embodiments show that the asphalt smoke suppression and flame retardant prepared by the present invention has the function of greatly slowing down the combustion of asphalt and the release of smoke, and is an efficient smoke suppression and flame retardant asphalt additive. This asphalt smoke suppression and flame retardant greatly reduces the oxygen consumption and particulate matter release during asphalt combustion by forming a carbon layer and non-combustible gases, thus greatly protecting the health of the people when an asphalt pavement catches fire. In addition, this asphalt smoke suppression and flame retardant is economical and environmentally friendly, promoting China's progress towards a resource-saving and environment-friendly sustainable development path.

[0099] Since the added heteroatom sources are different and there are also differences in the material dosage ratios, in order to demonstrate the importance of the ratios, the present invention has also made relevant examples and comparative examples, as shown in Table 7 below:

[0100] Table 7

[0101]

[0102]

[0103] As can be seen from Table 7, when using different heteroatom sources, the ratios between the components also need to be adjusted accordingly in order to achieve better cooperation among the components and play a better role.

[0104] In addition, the present invention has also studied the effects of the self-parameters of graphene oxide, urea, polyphosphoric acid, and phosphoric acid on the results, as shown in Table 8 below:

[0105] Table 8

[0106]

[0107] As can be seen from Table 8, the selection of raw materials also affects the flame retardant effect. The best results are obtained when the graphene oxide is monolayer graphene oxide with an oxidation degree of 30%-40%, the urea is industrial-grade urea with a purity of 99%, the polymerization degree of the polyphosphoric acid is 15, and the concentration of the phosphoric acid is 20%.

[0108] The above-described embodiments only represent the specific implementation manners of the present application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the protection scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the technical solution of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application.

Claims

1. An asphalt multi-element synergistic smoke suppression and flame retardant, characterized in that: The grafted product obtained by grafting a heteroatom source onto the surface of reduced graphene oxide, wherein the heteroatom source includes one or more of urea, polyphosphoric acid, and phosphoric acid.

2. The asphalt multi-element synergistic smoke suppression and flame retardant according to claim 1, characterized in that: The graphene oxide for preparing the reduced graphene oxide is monolayer graphene oxide with an oxidation degree of 30%-40%.

3. The asphalt multi-element synergistic smoke suppression and flame retardant according to claim 1, characterized in that: The urea is industrial-grade urea with a purity of 99%, the polyphosphoric acid has a polymerization degree of 15-20, and the phosphoric acid concentration is 20%-25%.

4. An asphalt multi-element synergistic smoke suppression and flame retardant according to any one of claims 1-3, characterized in that: When the heteroatom source is urea, the preparation raw materials include graphene oxide, a reducing agent, and urea, and there are 85-95 parts of graphene oxide, 900-910 parts of urea, and the mass ratio of graphene oxide to the reducing agent is 1:4 to 7.

5. A multi-element synergistic smoke suppression and flame retardant for asphalt according to any one of claims 1-3, characterized in that: When the heteroatom source is phosphoric acid and polyphosphoric acid, the preparation raw materials include graphene oxide, a reducing agent, phosphoric acid, and polyphosphoric acid, and there are 70-80 parts of graphene oxide, 765-775 parts of phosphoric acid, 150-160 parts of polyphosphoric acid, and the mass ratio of graphene oxide to the reducing agent is 1:4 to 7.

6. An asphalt multi-element synergistic smoke and flame retardant according to any one of claims 1-3, characterized in that: When the heteroatom source is urea, phosphoric acid, and polyphosphoric acid, the preparation raw materials include graphene oxide, a reducing agent, urea, phosphoric acid, and polyphosphoric acid, and there are 75-85 parts of graphene oxide, 410-420 parts of urea, 410-420 parts of phosphoric acid, 75-85 parts of polyphosphoric acid, and the mass ratio of graphene oxide to the reducing agent is 1:4 to 7.

7. A method for preparing the asphalt multi-element synergistic smoke suppression and flame retardant according to any one of claims 1-6, characterized in that: It includes the following steps: S1: Prepare a mixed solution of graphene oxide and a reducing agent, and obtain reduced graphene oxide solid through a reduction reaction; S2: Mix the reduced graphene oxide solid with the heteroatom source for grafting modification to obtain a grafted product, namely a multi-element synergistic smoke suppression and flame retardant for asphalt.

8. Use of the multi-element synergistic smoke suppression and flame retardant for asphalt according to any one of claims 1-6, characterized in that: It is used for preparing multi-element synergistic smoke suppression and flame retardant asphalt.

9. Use of an asphalt multi-element synergistic smoke suppression and flame retardant according to claim 8, characterized in that: The specific steps for preparing multi-element synergistic smoke suppression and flame retardant asphalt include: SA: Melt the asphalt; SB: Add the multi-element synergistic smoke suppression and flame retardant for asphalt to the melted asphalt; SC: Mix the asphalt and the multi-element synergistic smoke suppression and flame retardant for asphalt evenly by shearing to obtain multi-element synergistic smoke suppression and flame retardant asphalt.

10. The application of an asphalt multi-element synergistic smoke suppression and flame retardant according to claim 9, characterized in that: The asphalt is matrix asphalt, and the dosage of the multi-element synergistic smoke suppression and flame retardant for asphalt is 5%-9%.

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