A temperature-controlled microcapsule flame retardant for tunnel asphalt pavement and its preparation method

Abstract

A temperature-controlled microcapsule flame retardant for tunnel asphalt pavement and its preparation method. The flame retardant consists of a core, a partitioned wall (chlorinated paraffin), and a temperature-controlled protective wall (ethyl cellulose); the core includes an initial core (zinc borate, aluminum hydroxide, and montmorillonite) and an external core (aluminum-based polyvinyl alcohol chitosan composite aerogel); the initial core is wrapped in the partitioned wall, and the external core is wrapped between the partitioned wall and the temperature-controlled protective wall. After heating and melting the chlorinated paraffin, the initial microcapsules are prepared by a fluidized bed process; the external core is ground and then mixed with the initial microcapsules, and then mixed with molten ethyl cellulose, quickly condensed to a solid state, and pulverized to obtain the temperature-controlled microcapsule flame retardant. The flame retardant obtained by this method can control the release of flame retardant substances according to temperature changes, and can also maintain the effectiveness of the core components during the daily use of the tunnel and the paving process of the asphalt pavement, effectively preventing and controlling the combustion of the tunnel asphalt pavement.

Description

Technical Field

[0001] The present invention belongs to the technical field of fire prevention and extinguishing for tunnel asphalt pavements, and particularly relates to a temperature-controlled microcapsule flame retardant for tunnel asphalt pavements and a preparation method thereof. Background Art

[0002] Tunnel spaces are relatively enclosed and narrow, with poor lighting, visibility, and ventilation. They are prone to traffic accidents and have a high evacuation difficulty. Many serious tunnel fire accidents have occurred in many countries around the world. At present, asphalt is often used in the construction of tunnel pavements. Compared with cement concrete pavements, asphalt pavements have the advantages of comfortable driving, low noise, smooth surface, and less road surface water accumulation. However, in the event of a tunnel fire, it may cause the asphalt pavement to burn, raising the tunnel temperature to 1000°C, generating a large amount of smoke and toxic gases, and being prone to flow after melting in a high-temperature environment. The combustion of asphalt is characterized by fierce momentum, rapid expansion, wide range, and difficulty in extinguishing. In a closed tunnel environment, it is difficult for smoke, toxic gases, and heat to disperse, leading to difficulties for people to escape and resulting in casualties.

[0003] Currently, domestic and foreign scholars mainly solve the problem of preventing and controlling the combustion of tunnel asphalt pavements by improving the flame retardant performance of asphalt pavements. Common methods include adding organic or inorganic flame retardants. Traditional organic flame retardants have poor smoke suppression effects, and inorganic flame retardants have poor compatibility with asphalt, which will also have a certain impact on the physical properties of asphalt. Moreover, hot mix asphalt concrete pavements are often used in the paving process of asphalt pavements, and the construction temperature is about 170°C, which may cause premature loss of the flame retardant. In summary, in view of the flame retardant problem of tunnel asphalt pavements, it is of great significance to develop a flame retardant with good effects, green safety. Summary of the Invention

[0004] The purpose of the present invention is to provide a temperature-controlled microcapsule flame retardant for tunnel asphalt pavements and a preparation method thereof. The preparation process of this method is simple, green, and safe. The prepared temperature-controlled microcapsule flame retardant can control the release of flame retardant substances according to temperature changes, maintain the effectiveness of the core components during the daily use of tunnels and the paving process of asphalt pavements, extend the service life of the flame retardant, and effectively prevent and control the combustion of tunnel asphalt pavements.

[0005] To achieve the above purpose, the present invention provides a temperature-controlled microcapsule flame retardant for tunnel asphalt pavements, which is composed of a core, a partitioned capsule wall, and a temperature-controlled protective capsule wall; the core includes an initial core and an external core; the initial core is wrapped in the partitioned capsule wall, and the external core is wrapped between the partitioned capsule wall and the temperature-controlled protective capsule wall; the initial core is zinc borate, aluminum hydroxide, and montmorillonite; the external core is an aluminum-based polyvinyl alcohol chitosan composite aerogel; the raw material of the partitioned capsule wall is chlorinated paraffin; the raw material of the temperature-controlled protective capsule wall is ethyl cellulose.

[0006] Preferably, the mass ratio between the external capsule core and the initial capsule core is 1:4.

[0007] Preferably, the chlorinated paraffin is one or more of chlorinated paraffin 42, chlorinated paraffin 52, and chlorinated paraffin 70.

[0008] The present invention also provides a preparation method of the above temperature-controlled microcapsule flame retardant for tunnel asphalt pavement, comprising the following steps:

[0009] S1. Preparation of initial microcapsules

[0010] S1-1. Weigh zinc borate, aluminum hydroxide, and montmorillonite according to a certain mass ratio, and seal and place them separately as three initial capsule cores;

[0011] S1-2. Under an inert gas atmosphere, heat the chlorinated paraffin to 95°C, which is the softening point temperature, and keep it at a constant temperature. During the heating process, continuously stir. After it melts into a waxy liquid, keep it at 95°C for constant temperature storage;

[0012] S1-3. Use the fluidized bed process method to evenly distribute the three initial capsule cores in the fluidized bed, evenly spray the waxy chlorinated paraffin obtained in step S1-2 on the surface of the initial capsule cores, and repeat the drying and spraying processes multiple times until the partitioned capsule wall is evenly covered to obtain the corresponding three initial microcapsules, and then uniformly mix them to obtain the initial microcapsules;

[0013] S2. Grind the external capsule core under an inert gas atmosphere, sieve out the external capsule core powder with a mesh size below 100, and then evenly stir and mix it with the initial microcapsules obtained in step S1 according to a certain mass ratio to obtain a mixture of the initial microcapsules and the external capsule core;

[0014] S3. Under an inert gas atmosphere, heat ethyl cellulose to 185°C, which is the softening point temperature, and keep it at a constant temperature. During the heating process, continuously stir until ethyl cellulose melts into a liquid state and then keep it at 185°C for constant temperature storage;

[0015] S4. Use the melting dispersion condensation method to gradually add the liquid ethyl cellulose obtained in step S3 to the mixture of the initial microcapsules and the external capsule core obtained in step S2 in portions. Stir after each addition until the mixture of the initial microcapsules and the external capsule core is fully wrapped by ethyl cellulose and then continue to add. After that, quickly cool down until ethyl cellulose quickly condenses to a solid state;

[0016] S5. Thoroughly crush the solid obtained in step S4, sieve out the finished product with a mesh size of 20-40, and thus obtain the temperature-controlled microcapsule flame retardant for tunnel asphalt pavement.

[0017] Preferably, in step S1-1, the mass ratio between zinc borate, aluminum hydroxide, and montmorillonite is 1:(3-5):1.

[0018] Preferably, in step S1-3, the spraying temperature set in the fluidized bed process is higher than 95°C.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] (1) By using the microcapsule technology, the present invention realizes the controllability of the release rate and release temperature of the core components by utilizing the characteristics of the capsule wall. The core material is released only when the external environmental temperature is higher than the softening temperature of the temperature-controlled protective capsule wall, and it plays a role in isolating the environmental air. Its own hydrophobicity can also ensure that the microcapsules of the present invention can maintain their effectiveness even in a humid environment, and can also reduce the influence of the flame retardant on the performance of asphalt for road use; the external core itself has flame retardancy and smoke suppression properties, and can also isolate temperature to prevent the premature release of the internal core material by the partitioned capsule wall; the partitioned capsule wall is used to separate the core components during daily use to prevent the failure of the core material caused by premature mixing.

[0021] (2) In the core material of the present invention, the initial core material zinc borate is non-toxic, odorless, and inexpensive, and has multiple functions such as flame retardancy, smoke suppression, char formation, inhibition of afterglow combustion, and prevention of dripping. It can act simultaneously in the gas phase and the solidification phase. It melts at high temperature and covers the surface of the asphalt to form a glassy coating layer to isolate air and heat. The crystal water generated by thermal decomposition can effectively reduce the temperature and dilute oxygen; aluminum hydroxide is an inexpensive inorganic flame retardant. When heated, it releases bound water and absorbs a large amount of heat. The water turns into water vapor at high temperature, diluting the combustible gas and smoke, and further oxidizing reaction occurs with the carbon particles to reduce the smoke emission. Adding aluminum hydroxide can also improve the high-temperature permanent deformation resistance of the asphalt mixture and reduce the rutting marks on the road surface; montmorillonite will release a large amount of water vapor and organic gases when encountering high temperature, absorb the surrounding heat to form a heat insulation layer. The nano-layered structure of montmorillonite has a certain barrier effect, which will promote combustion and carbon formation, and form a dense heat insulation layer on the surface of the asphalt to further improve the heat insulation performance. The external core aluminum-based polyvinyl alcohol chitosan composite aerogel is green and environmentally friendly, and has good thermal stability, fire safety, heat insulation, and smoke suppression properties. It will form a dense carbon layer at high temperature to inhibit the release of heat and smoke during the combustion process and isolate oxygen.

[0022] (3) By combining the temperature-controlled microcapsule technology with the flame retardant, the present invention effectively improves the flame retardancy and smoke suppression of asphalt, and solves the problem of premature loss of the flame retardant during the paving process of tunnel asphalt pavement. The highest temperature during the construction of asphalt pavement is about 170°C, which may cause the flame retardant to play a role in advance. The temperature-controlled protective capsule wall and the external core of the present invention can jointly protect the internal core to ensure that the structure of the internal initial microcapsule is not damaged.

[0023] (4) The materials of the present invention are green, environmentally friendly, safe and pollution-free. The preparation process is simple, the usage method is simple, the service life is long, the flame retardant and smoke suppression effects are good, and the application range is wide. It can be used in the paving and repair of asphalt pavements and other situations.

[0024] (5) The temperature-controlled microcapsule flame retardant prepared by the present invention can improve the flame retardant and smoke suppression performance of asphalt pavements in tunnels, reduce problems such as casualties caused by the combustion of asphalt pavements due to tunnel fires and great difficulties in later repair, and gain time for rescue. Description of the Drawings

[0025] Figure 1 is the flow chart of the preparation process of the present invention. Detailed Embodiments

[0026] The present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0027] Embodiment 1

[0028] A temperature-controlled microcapsule flame retardant for tunnel asphalt pavements is composed of a core, a partitioned wall and a temperature-controlled protective wall; the core includes an initial core (zinc borate, aluminum hydroxide, montmorillonite) and an external core (aluminum-based polyvinyl alcohol chitosan composite aerogel), the initial core is wrapped in the partitioned wall, and the external core is wrapped between the partitioned wall and the temperature-controlled protective wall; the raw material of the partitioned wall is chlorinated paraffin, and the raw material of the temperature-controlled protective wall is ethyl cellulose; the mass ratio between zinc borate, aluminum hydroxide, montmorillonite and aluminum-based polyvinyl alcohol chitosan composite aerogel is 3:10:3:4.

[0029] As Figure 1 shown, a preparation method of the above-mentioned temperature-controlled microcapsule flame retardant for tunnel asphalt pavements includes the following steps:

[0030] S1. Preparation of initial microcapsules

[0031] S1-1. Weigh zinc borate, aluminum hydroxide, and montmorillonite according to a mass ratio of 3:10:3, and seal and place them separately as three initial cores;

[0032] S1-2. Under an inert gas atmosphere, use a programmable temperature-controlled oven to heat chlorinated paraffin-70 at a heating rate of 10 °C / min. Heat it to 95 °C, which is the softening point temperature, and keep it at a constant temperature. Stir continuously during the heating process until it melts into a waxy liquid with certain fluidity, and store it at 95 °C at a constant temperature;

[0033] S1-3. Using the fluidized bed process, evenly distribute the three initial core materials in the fluidized bed, evenly spray the waxy chlorinated paraffin obtained in step S1-2 on the surface of the initial core materials. After repeated drying and spraying for multiple times until the partitioned capsule wall is evenly covered, the corresponding three initial microcapsules are obtained, and then they are evenly mixed to obtain the initial microcapsules for standby.

[0034] S2. Grind the external core aluminum-based polyvinyl alcohol chitosan composite aerogel in an inert gas atmosphere using a ball mill, and screen out the external core powder with a mesh size below 100. Then, uniformly stir and mix it with the initial microcapsules obtained in step S1 at a mass ratio of 1:4 to obtain a mixture of the initial microcapsules and the external core for standby.

[0035] S3. In an inert gas atmosphere, use a programmable temperature chamber to heat ethyl cellulose at a heating rate of 10 °C / min. Heat it to 185 °C, which is the softening point temperature, and keep it at a constant temperature. Continuously stir during the heating process until the wall material melts into a liquid state and then keep it at 185 °C for constant temperature storage.

[0036] S4. Using the melting dispersion condensation method, gradually add the mixture of the initial microcapsules and the external core obtained in step S2 to the liquid ethyl cellulose obtained in step S3 in portions. Stir after each addition until the mixture of the initial microcapsules and the external core is fully wrapped by ethyl cellulose and then continue to add. After that, rapidly cool down until ethyl cellulose rapidly condenses into a solid state for standby.

[0037] S5. Thoroughly crush the solid obtained in step S4, and screen out the finished product with a mesh size of 20 - 40 to obtain the temperature-controlled microcapsule flame retardant for tunnel asphalt pavement.

[0038] Preheat the SBS modified asphalt to a molten state and ensure that the temperature is constantly 180 °C. Manually stir and add the temperature-controlled microcapsule flame retardant prepared in this example, which is 10%, 20%, 30%, and 40% of the mass of the SBS modified asphalt respectively. After the addition is completed, use a stirrer to rotate at a high speed for 35 min, then rotate at a low speed for 5 min to discharge air bubbles. Keep the temperature constant at 180 °C during the stirring process. After the stirring is completed, seal it and wait for it to solidify into a solid state, then cut it into long strips for the limiting oxygen index test and observe the smoke condition.

[0039] Example 2

[0040] A temperature-controlled microcapsule flame retardant for tunnel asphalt pavement, which is composed of a core, a partitioned capsule wall and a temperature-controlled protective capsule wall; the core includes an initial core (zinc borate, aluminum hydroxide, montmorillonite) and an external core (aluminum-based polyvinyl alcohol chitosan composite aerogel), the initial core is wrapped in the partitioned capsule wall, and the external core is wrapped between the partitioned capsule wall and the temperature-controlled protective capsule wall; the partitioned capsule wall is chlorinated paraffin, and the temperature-controlled protective capsule wall is ethyl cellulose; the mass ratio of zinc borate, aluminum hydroxide, montmorillonite, and aluminum-based polyvinyl alcohol chitosan composite aerogel is 2:8:2:3.

[0041] As Figure 1 shown, a preparation method of the above-mentioned temperature-controlled microcapsule flame retardant for tunnel asphalt pavement includes the following steps:

[0042] S1. Preparation of initial microcapsules

[0043] S1-1. Weigh zinc borate, aluminum hydroxide, and montmorillonite according to a mass ratio of 1:4:1, and place them separately and sealed as three initial cores;

[0044] S1-2. Under an inert gas atmosphere, use a programmed temperature chamber to heat chlorinated paraffin-70 at a heating rate of 10 °C / min, heat to 95 °C, which is the softening point temperature, and keep it at a constant temperature. During the heating process, continuously stir until it melts into a waxy liquid with a certain fluidity, and keep it at 95 °C for storage;

[0045] S1-3. Using the fluidized bed process method, evenly distribute the three initial cores in the fluidized bed, evenly spray the waxy chlorinated paraffin obtained in step S1-2 on the surface of the initial cores, and repeat the drying and spraying processes many times until the partitioned capsule wall is evenly covered to obtain the corresponding three initial microcapsules, and then mix them evenly to obtain the initial microcapsules for standby;

[0046] S2. Grind the external core aluminum-based polyvinyl alcohol chitosan composite aerogel in a ball mill under an inert gas atmosphere, screen out the external core powder below 100 mesh, and then uniformly stir and mix it with the initial microcapsules obtained in step S1 according to a mass ratio of 1:4 to obtain a mixture of the initial microcapsules and the external core for standby;

[0047] S3. Under an inert gas atmosphere, use a programmed temperature chamber to heat ethyl cellulose at a heating rate of 10 °C / min, heat to 185 °C, which is the softening point temperature, and keep it at a constant temperature. During the heating process, continuously stir until the wall material melts into a liquid state and then keep it at 185 °C for storage;

[0048] S4. Using the melting dispersion condensation method, gradually and quantitatively add the mixture of the initial microcapsules and the external core obtained in step S2 to the liquid ethyl cellulose obtained in step S3. Stir after each addition until the mixture of the initial microcapsules and the external core is fully wrapped by ethyl cellulose, and then continue to add. After that, rapidly cool down until the ethyl cellulose rapidly condenses into a solid state and set aside;

[0049] S5. Thoroughly crush the solid obtained in step S4, and screen out the finished product with a mesh size of 20 - 40 meshes, thus obtaining the temperature-controlled microcapsule flame retardant for tunnel asphalt pavement.

[0050] Preheat the SBS modified asphalt to the molten state and ensure that the temperature is kept constant at 180 °C. Manually stir and add the temperature-controlled microcapsule flame retardant prepared in this embodiment, which is 10%, 20%, 30%, and 40% of the mass of the SBS modified asphalt respectively. After the addition is completed, use a stirrer to rotate at a high speed for 35 min, then rotate at a low speed for 5 min to discharge the bubbles. Keep the temperature constant at 180 °C during the stirring process. After the stirring is completed, seal and store it until it solidifies into a solid state, then cut it into strips for the limiting oxygen index test and observe the smoke condition.

[0051] Comparative Example 1

[0052] Prepare a mixed flame retardant with a mass ratio of aluminum hydroxide to montmorillonite of 10:3.

[0053] Preheat the SBS modified asphalt to the molten state and ensure that the temperature is kept constant at 180 °C. Manually stir and add the mixed flame retardant, which is 10%, 20%, 30%, and 40% of the mass of the SBS modified asphalt respectively. After the addition is completed, use a stirrer to rotate at a high speed for 35 min, then rotate at a low speed for 5 min to discharge the bubbles. Keep the temperature constant at 180 °C during the stirring process. After the stirring is completed, seal and store it until it solidifies into a solid state, then cut it into strips for the limiting oxygen index test and observe the smoke condition.

[0054] Comparative Example 2

[0055] Conduct the limiting oxygen index test on the SBS modified asphalt without adding any flame retardant and observe the smoke condition.

[0056] The limiting oxygen index (LOI) is the volume fraction concentration of oxygen at which a polymer can just maintain its combustion in a mixed gas of oxygen and nitrogen. The calculation formula for the limiting oxygen index is as follows:

[0057]

[0058] In the formula: LOI is the limiting oxygen index, %; [O2] is the oxygen gas volume flow rate at the critical oxygen concentration; [N2] is the nitrogen gas volume flow rate at the critical oxygen concentration.

[0059] In SBS modified asphalt of the same quality, the temperature-controlled microcapsule flame retardants in Example 1 and Example 2 with different dosages and the mixed flame retardant in Comparative Example 1 were added, and the experimental results of the limiting oxygen index test of Comparative Example 2 without adding any flame retardant are shown in Table 1 below.

[0060] Table 1 Limiting oxygen index of examples and comparative examples

[0061]

[0062] Note: The limiting oxygen index of Comparative Example 2 is 21.6%.

[0063] According to the limiting oxygen index test results, the limiting oxygen index of the asphalt after adding the temperature-controlled microcapsule flame retardant with a mass ratio of not less than 10% is higher than that of the original asphalt and Comparative Example 1, indicating that the temperature-controlled microcapsule flame retardant has a good effect on improving the flame retardancy of asphalt. In 2010, the "Oxygen Index Method for Determining the Combustion Performance of Asphalt" (NB / SH / T 0815-2012) promulgated in China stated that the limiting oxygen index of flame-retardant asphalt for tunnels should be greater than 23%. It can be concluded from the experimental results that the prepared temperature-controlled microcapsule flame retardants (Example 1 and Example 2) are both greater than 23% under the dosage ratios set in the experiment, meeting the specified requirements, and can be used in tunnel asphalt. Moreover, their values are higher than those of Comparative Example 1, and when the mass ratio is not less than 20%, the limiting oxygen index is greater than 30%, meeting the expected effect. With the increase of the doping mass ratio, the flame inhibition effect of the temperature-controlled microcapsule flame retardant is better, and the flame retardant characteristics of the asphalt are further improved. Regarding the smoke suppression effect, the asphalt without any flame retardant in Comparative Example 2 produced relatively more black smoke in the experiment. The smoke produced by the asphalt added with the temperature-controlled microcapsule flame retardant prepared by the present invention changed from a small amount of black smoke to a small amount of smoke with the increase of the doping mass ratio, and the smoke concentration decreased. The smoke produced by Example 2 was less than that of Example 1 under the same mass ratio, and the examples were all less than those of the comparative examples, indicating that the temperature-controlled microcapsule flame retardant of the present invention has a good smoke suppression effect.

[0064] In summary, a temperature-controlled microcapsule flame retardant for tunnel asphalt pavement prepared by the present invention has good flame inhibition and smoke suppression effects, can effectively improve the flame retardant characteristics of asphalt, and at the same time uses the microcapsule technology to solve the problem of premature loss of traditional flame retardants in tunnel paving and daily use scenarios, and also reduces the impact of flame retardants on the road performance of asphalt pavement. In addition, the preparation process of the present invention is simple, the use method is simple, the service life is long, and it is green, environmentally friendly and safe, with broad application prospects.

Claims

1. A temperature-controlled microcapsule flame retardant for tunnel asphalt pavement, characterized in that: The invention is composed of a capsule core, a partitioning capsule wall and a temperature-controlling protective capsule wall; the capsule core includes an initial capsule core and an external capsule core; the initial capsule core is wrapped in the partitioning capsule wall, and the external capsule core is wrapped between the partitioning capsule wall and the temperature-controlling protective capsule wall; the initial capsule core is zinc borate, aluminum hydroxide and montmorillonite; the external capsule core is aluminum-based polyvinyl alcohol chitosan composite aerogel; the raw material of the partitioning capsule wall is chlorinated paraffin; the raw material of the temperature-controlling protective capsule wall is ethyl cellulose; The method for preparing the temperature-controlled microcapsule flame retardant for tunnel asphalt pavement comprises the following steps: S1. Preparation of initial microcapsules S1-1. Weigh zinc borate, aluminum hydroxide, and montmorillonite in a certain mass ratio, and seal them separately as three initial capsule cores; S1-2. In an inert gas atmosphere, heat the chlorinated paraffin to 95°C, i.e., the softening point, and keep the temperature constant. Stir continuously during the heating process, and store it at 95°C after it melts into a waxy liquid; S1-3, using a fluidized bed process to evenly distribute the three initial capsule cores in a fluidized bed, spray the waxy chlorinated paraffin obtained in step S1-2 evenly on the surface of the initial capsule cores, and dry and spray repeatedly until the partitioned capsule wall is evenly covered to obtain the corresponding three initial microcapsules, and then evenly mix them to obtain initial microcapsules; S2, grinding the outer capsule core under an inert gas atmosphere, sieving the outer capsule core powder below 100 mesh, and then uniformly stirring and mixing the powder with the initial microcapsules obtained in step S1 at a certain mass ratio to obtain a mixture of the initial microcapsules and the outer capsule core; S3. In an inert gas atmosphere, the ethyl cellulose is heated to 185° C., i.e., the softening point, and kept at a constant temperature. The ethyl cellulose is stirred continuously during the heating process until the ethyl cellulose melts into a liquid state and then stored at a constant temperature of 185° C.; S4, using a melt dispersion condensation method, gradually adding the liquid ethyl cellulose obtained in step S3 to the mixture of the initial microcapsules and the external capsule core obtained in step S2, stirring after each addition, and continuing to add until the mixture of the initial microcapsules and the external capsule core is fully wrapped by the ethyl cellulose, and then rapidly cooling until the ethyl cellulose is rapidly condensed into a solid state; S5. Fully crush the solid obtained in step S4 and sieve out the finished product with a mesh size of 20-40 to obtain the temperature-controlled microcapsule flame retardant for tunnel asphalt pavement.

2. The temperature-controlled microcapsule flame retardant for tunnel asphalt pavement according to claim 1, characterized in that: The mass ratio between the external capsule core and the initial capsule core is 1:

4.

3. A temperature-controlled microcapsule flame retardant for tunnel asphalt pavement according to claim 1 or 2, characterized in that: The chlorinated paraffin is one or more of chlorinated paraffin 42, chlorinated paraffin 52, and chlorinated paraffin 70.

4. A method for preparing a temperature-controlled microcapsule flame retardant for tunnel asphalt pavement according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1. Preparation of initial microcapsules S1-1. Weigh zinc borate, aluminum hydroxide, and montmorillonite in a certain mass ratio, and seal them separately as three initial capsule cores; S1-2. In an inert gas atmosphere, heat the chlorinated paraffin to 95°C, i.e., the softening point, and keep the temperature constant. Stir continuously during the heating process, and store it at 95°C after it melts into a waxy liquid; S1-3, using a fluidized bed process to evenly distribute the three initial capsule cores in a fluidized bed, spray the waxy chlorinated paraffin obtained in step S1-2 evenly on the surface of the initial capsule cores, and dry and spray repeatedly until the partitioned capsule wall is evenly covered to obtain the corresponding three initial microcapsules, and then evenly mix them to obtain initial microcapsules; S2, grinding the outer capsule core under an inert gas atmosphere, sieving the outer capsule core powder below 100 mesh, and then uniformly stirring and mixing the powder with the initial microcapsules obtained in step S1 at a certain mass ratio to obtain a mixture of the initial microcapsules and the outer capsule core; S3. In an inert gas atmosphere, the ethyl cellulose is heated to 185° C., i.e., the softening point, and kept at a constant temperature. The ethyl cellulose is stirred continuously during the heating process until the ethyl cellulose melts into a liquid state and then stored at a constant temperature of 185° C.; S4, using a melt dispersion condensation method, gradually adding the liquid ethyl cellulose obtained in step S3 to the mixture of the initial microcapsules and the external capsule core obtained in step S2, stirring after each addition, and continuing to add until the mixture of the initial microcapsules and the external capsule core is fully wrapped by the ethyl cellulose, and then rapidly cooling until the ethyl cellulose is rapidly condensed into a solid state; S5. Fully crush the solid obtained in step S4 and sieve out the finished product with a mesh size of 20-40 to obtain the temperature-controlled microcapsule flame retardant for tunnel asphalt pavement.

5. The method for preparing a temperature-controlled microcapsule flame retardant for tunnel asphalt pavement according to claim 4, characterized in that: In step S1-1, the mass ratio of the zinc borate, aluminum hydroxide and montmorillonite is 1:(3-5):

1.

6. The method for preparing a temperature-controlled microcapsule flame retardant for tunnel asphalt pavement according to claim 4 or 5, characterized in that: In step S1-3, the spraying temperature set in the fluidized bed process is higher than 95°C.

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