Reactive microcapsule for cold-mixed asphalt material as well as preparation method and application of reactive microcapsule

Abstract

The invention discloses a reactive microcapsule for a cold-mixed asphalt material as well as a preparation method and application of the reactive microcapsule, and relates to the technical field of road engineering materials. The reactive microcapsule comprises an outer shell and an inner capsule body, the outer shell is made of a water-soluble material, the inner capsule body is formed by taking modified polylactic acid as a capsule wall and taking a cold-mixed asphalt curing agent as a core material, and the modified polylactic acid is prepared by mixing polylactic acid, a plasticizer and a nucleating agent according to a specific proportion and then melting and granulating. According to the scheme, the reaction type microcapsule with a double-layer protection structure can be prepared, and when the reaction type microcapsule is mixed with the cold-mixed asphalt material, the reaction type microcapsule can be quickly broken and release the curing agent only by spraying and fixed-frequency vibration rolling of a paver in a construction site, so that the reaction degree of the cold-mixed asphalt material can be controlled, and the service life of the cold-mixed asphalt material is prolonged. And the bottleneck problems of low construction adaptability and high construction efficiency requirement caused by short operable time of the cold-mixed asphalt can be solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of road engineering materials, in particular to a reactive microcapsule for cold-mixed asphalt mixture and a preparation method and application thereof. BACKGROUND

[0002] In the field of road engineering materials, cold-mixed asphalt mixture as a key material is gradually attracting widespread attention. Since 2000, cold-mixed asphalt mixture as a product with high technology content has been widely used in national roads, provincial roads and municipal roads. Compared with traditional hot-mixed asphalt mixture, cold-mixed asphalt mixture does not need to be heated during construction, avoiding complex heating processes, and can be used at any time for repair of road pit and crack diseases, effectively improving road maintenance efficiency. Since it can be repaired at room temperature or low temperature, it greatly facilitates road maintenance work.

[0003] Due to the high viscosity and poor flowability of asphalt, it is difficult to harden quickly at room temperature or low temperature. Therefore, compared with traditional hot-mixed asphalt mixture, cold-mixed asphalt mixture needs to add a curing agent or a catalyst to forcibly trigger the hardening reaction of asphalt, so that the cold-mixed asphalt mixture can be hardened at room temperature or low temperature. As for the method of adding the curing agent and the catalyst, the conventional method is to directly mix the curing agent and the catalyst with the asphalt mixture before paving on site. Since this method is relatively simple and does not require complex equipment and technology, it has been widely promoted and applied.

[0004] However, it is found in many on-site constructions that the curing agent or the catalyst commonly used in cold-mixed asphalt mixture is directly added and mixed on site, and the material starts to react immediately after mixing. This results in a very short effective construction time window (i.e. operable retention time). The short reaction window period seriously restricts the adaptability of cold-mixed asphalt mixture to complex construction conditions and puts forward very high requirements on construction efficiency. For example, in the case of long-distance road construction, the material needs to delay the reaction rate to avoid premature hardening before completing paving and rolling. However, for this requirement, cold-mixed asphalt mixture that has been in the reaction process after on-site mixing is difficult to meet. Therefore, in order to solve the bottleneck problem of low adaptability and high construction efficiency requirement of cold-mixed asphalt mixture, it is of great significance to improve the controllability of the reaction degree of cold-mixed asphalt mixture from the raw materials or processing technology. SUMMARY

[0005] In order to improve the controllability of the reaction degree of cold-mixed asphalt mixture and solve the bottleneck problem of low adaptability and high construction efficiency requirement of cold-mixed asphalt mixture, the present application provides a reactive microcapsule for cold-mixed asphalt mixture and a preparation method and application thereof.

[0006] In a first aspect, the present application provides a reactive microcapsule using the following technical solution: A reactive microcapsule comprises an outer shell and an inner capsule, the outer shell is coated on the surface of the inner capsule by a water-soluble material and is formed by spray drying, and the inner capsule is formed by modified polylactic acid as a capsule wall, cold-mixed asphalt curing agent as a core material, and then solidified by emulsion. The water-soluble material is at least one of polyvinyl alcohol, gelatin or hydroxyalkyl methyl cellulose; and the modified polylactic acid is prepared by mixing polylactic acid, a plasticizer and a nucleating agent, and then melt granulating.

[0007] The above technical solution can form a reactive microcapsule with an outer shell-inner capsule double-layer protection structure, which has strong stability and storage, can ensure that the reactive microcapsule does not break during mixing, and can be fully broken by 30-40Hz frequency vibration in a water-containing environment. When the reactive microcapsule is mixed with cold-mixed asphalt material, only water spraying and paving machine fixed frequency mechanical vibration are needed at the construction site to make the reactive microcapsule fully broken and release the internal curing agent component, at which time the cold-mixed asphalt material starts to cure, realizing the control of the reaction degree of the cold-mixed asphalt material in the construction process, and being beneficial to solve the bottleneck problem of low construction adaptability and high construction efficiency requirement of the cold-mixed asphalt material.

[0008] Optionally, in the preparation of the modified polylactic acid, the mass ratio of the polylactic acid, the plasticizer and the nucleating agent is (92-95):(2-7):(1-3). The plasticizer is at least one of polyethylene glycol, citrate or castor oil, and the nucleating agent is at least one of coupled talc or organic metal salt nucleating agent.

[0009] By using the above technical solution, the modified polylactic acid can achieve the target crystallinity under the modification of a specific ratio of plasticizer and nucleating agent, which not only makes the capsule wall have high comprehensive strength and not easy to break in the mixing stage or static load, but also makes the capsule wall formed by the modified polylactic acid have a resonance frequency of 30-40Hz. Since the conventional compaction vibration frequency of the asphalt paving machine is 25-40Hz, in the field construction, the asphalt paving machine is vibrated at a frequency of 30-40Hz, the capsule wall of the reactive microcapsule can crack and quickly expand and break due to resonance, and the reactive microcapsule can quickly release the cold-mixed asphalt curing agent by spraying water during construction, realizing controllable reaction in the construction process, and being beneficial to meet the construction requirements in different situations.

[0010] Optionally, the plasticizer is a mixture of polyethylene glycol and acetyl tri-n-butyl citrate, and the nucleating agent is coupled talc. The mass ratio of the polyethylene glycol and the acetyl citric acid tri-n-butyl ester is 1:(1-2), and the mass ratio of the polylactic acid, the plasticizer, and the nucleating agent is (94-95):(2-3):3.

[0011] By adopting the technical scheme, the polyethylene glycol and the acetyl citric acid tri-n-butyl ester can produce a certain synergistic effect, the capsule wall can maintain a high breakage rate under the vibration of 30-40 Hz frequency, and the breakage rate of the capsule wall under the vibration of 20 Hz frequency is further reduced, which is beneficial to improving the stability and storage of the reactive microcapsule and preventing the cold-mixed asphalt curing agent from being released before the paving and watering stage, and the reaction of the cold-mixed asphalt material can be controlled. In addition, the cost of the coupling-treated talcum powder is much lower than that of the organic metal salt nucleating agent, so the coupling-treated talcum powder is used as the nucleating agent, which is beneficial to controlling the raw material cost and reducing the overall preparation cost of the reactive microcapsule.

[0012] Optionally, the water-soluble material is polyvinyl alcohol, and the alcoholysis degree of the polyvinyl alcohol is 87%-89% and the polymerization degree is 500-1700.

[0013] By adopting the technical scheme, the polyvinyl alcohol with the alcoholysis degree of 87%-89% and the polymerization degree of 500-1700 is used as the shell, so that the shell can be quickly dissolved in the paving and watering stage of the cold-mixed asphalt material, the capsule wall is resonantly destroyed, and the cold-mixed asphalt curing agent is fully released. In addition, the cost of the polyvinyl alcohol is lower than that of gelatin and hydroxyalkyl methyl cellulose, so the polyvinyl alcohol is used as the shell, which is also beneficial to controlling the raw material cost and reducing the overall preparation cost of the reactive microcapsule.

[0014] In the second aspect, the application provides a preparation method of a reactive microcapsule, which adopts the following technical scheme: A preparation method of a reactive microcapsule, comprising the following steps.

[0015] S1, add the emulsifier I to the deionized water according to 0.5-1 wt%, fully stir and dissolve to obtain a bottom liquid; add the modified polylactic acid to dichloromethane according to 8-10 wt%, fully stir and dissolve, then add the cold-mixed asphalt curing agent, and fully shake by ultrasonic wave to obtain an oil phase solution; S2, add the oil phase solution prepared in step S1 to the bottom liquid dropwise, keep stirring during the dropwise adding process and control the temperature to be not higher than 25℃, heat to 30-35℃ after the dropwise adding is completed and continuously stir for 30-60 min, homogenize 3-4 times under high pressure, then evaporate the dichloromethane, collect the solid precipitate by centrifugal filtration, wash with anhydrous ethanol, and vacuum dry to obtain an inner capsule. S3, add water-soluble material to deionized water at 5-10wt%, heat to fully dissolve the water-soluble material, cool to 55-65℃, add the inner capsule and emulsifier II, fully shake for 30min with ultrasonic, then spray dry to obtain a reactive microcapsule.

[0016] Optionally, in step S1, the mass ratio of the modified polylactic acid and the cold-mixed asphalt curing agent is 1:(1.5-2); In step S2, the volume ratio of the bottom liquid to the oil phase solution is controlled to be 2:1.

[0017] By adopting the above technical solution, when the mass ratio of the modified polylactic acid and the cold-mixed asphalt curing agent is 1:(1.5-2), a relatively thin and uniform capsule wall can be formed on the surface of the modified polylactic acid and the cold-mixed asphalt curing agent, which is conducive to ensuring that the capsule wall can be fully broken under the vibration of 30-40Hz frequency. Secondly, the bottom liquid system is twice the oil phase solution, the bottom liquid can provide sufficient continuous phase and reduce the collision probability of oil phase droplets, cooperate with emulsifier I, can fully maintain the stability of the oil-in-water emulsion, and also conducive to promoting the orderly evaporation of dichloromethane.

[0018] Optionally, in step S3, the mass ratio of the water-soluble material, the inner capsule and emulsifier II is (0.3-0.5):1:(0.02-0.03).

[0019] By adopting the above technical solution, a uniform outer shell can be formed on the surface of the inner capsule, which is conducive to balancing the protection structure strength and core material release efficiency of the reactive microcapsule, and can achieve sufficient protection and sufficient dissolution and breakage under specific conditions.

[0020] Optionally, the emulsifier I is polyvinylpyrrolidone, and the emulsifier II is at least one of sodium alkyl benzene sulfonate or alkyl phenol polyoxyethylene ether.

[0021] In a third aspect, the cold-mixed asphalt material provided by the present application adopts the following technical solution: A cold-mixed asphalt material is prepared by mixing component A and component B at a mass ratio of (84-90):(10-16). Component A includes the following raw materials by weight: 43-65 parts of rubber modified asphalt, 12.5-20 parts of bisphenol A epoxy resin, 10-20 parts of bio-based diluent, and 2.5-5 parts of compatibilizer; The component B is a reactive microcapsule prepared by the above preparation method, wherein the cold-mixed asphalt curing agent in the reactive microcapsule is one of 2-phenylimidazole or triethylene tetramine.

[0022] Optionally, the mixing speed of the cold-mixed asphalt mixture is controlled to be 50-200 rpm, and the mixing time is 10-20 min. After paving or filling the road surface, a proper amount of water is atomized and sprayed, and the paving machine is vibrated at a vibration frequency of 30-40 Hz for compaction, and the paving is completed after curing.

[0023] By controlling the mixing speed, the present application can prevent the reaction-type microcapsules from breaking and releasing the internal cold-mixed asphalt curing agent during the mixing process of the cold-mixed asphalt mixture, and the spraying and vibration processes during paving are beneficial to controlling the reaction degree of the cold-mixed asphalt mixture, thereby effectively solving the bottleneck problem of low construction adaptability and high construction efficiency requirement of the cold-mixed asphalt mixture.

[0024] In summary, the technical solution of the present application has at least one of the following beneficial effects: 1. The reaction-type microcapsule with a double-layer protection structure is provided, which can be fully broken and release the internal curing agent component by only spraying water and vibrating the paving machine at a fixed frequency during construction on site, thereby controlling the reaction degree of the cold-mixed asphalt mixture during the construction process, and solving the bottleneck problem of low construction adaptability and high construction efficiency requirement of the cold-mixed asphalt mixture.

[0025] 2. The polylactic acid is modified by using a specific ratio of plasticizer and nucleating agent, which can achieve the target crystallinity of the modified polylactic acid, and the capsule wall is not easy to break during the mixing stage or under static load, and its resonance frequency also falls within 30-40 Hz. Since the conventional compaction vibration frequency of the asphalt paving machine is 25-40 Hz, the capsule wall formed by the modified polylactic acid can be cracked and quickly expanded by vibration at a frequency of 30-40 Hz using the asphalt paving machine during on-site construction.

[0026] 3. The polylactic acid is modified by using a mixture of polyethylene glycol and acetyl citric acid tri-n-butyl ester as a plasticizer, which can produce a certain synergistic effect, so that the capsule wall has a high breakage rate under vibration at a frequency of 30-40 Hz, and further reduces the breakage rate under vibration at a frequency of 20 Hz, which is beneficial to improving the stability and storage of the reaction-type microcapsule. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a schematic view of the cross-sectional structure of a reaction-type microcapsule in Embodiment 1 of the present application.

[0028] Explanation of Reference Signs: 1. outer shell; 2. inner capsule; 21. capsule wall; 22. core material. DETAILED DESCRIPTION

[0029] The present application will be further described in detail below with reference to the accompanying drawings, embodiments, comparative examples and application examples.

[0030] The polylactic acid was specifically purchased from L-polylactic acid from Qifei Pharmaceutical Chemical Co., Ltd.

[0031] The organometallic salt nucleating agent was specifically purchased from Beijia Fine Chemicals, with the brand name P-26.

[0032] The degree of polymerization of type 05-88 polyvinyl alcohol is 500, and the degree of hydrolysis is 87%-89%; the degree of polymerization of type 17-88 polyvinyl alcohol is 1700, and the degree of hydrolysis is 87%-89%. Preparation Example

[0033]

Preparation Example 1

[0034]

Preparation Example 2-1

[0035] In this preparation example, the plasticizer is polyethylene glycol with an average molecular weight of 400; the nucleating agent is a coupling-treated talc powder prepared in [Preparation Example 1].

[0036]

Preparation Example 2-2

[0037] In this preparation example, castor oil was selected as the plasticizer; organometallic salt nucleating agent was selected, specifically brand P-26.

[0038]

Preparation Examples 2-3

[0039] In this preparation example, polyethylene glycol with an average molecular weight of 600 was selected as the plasticizer.

[0040]

Preparation Examples 2-4

[0041] In this preparation example, polyethylene glycol with an average molecular weight of 1000 was selected as the plasticizer.

[0042]

Preparation Examples 2-5

[0043] In this preparation example, castor oil was specifically selected as the plasticizer.

[0044]

Preparation Examples 2-6

[0045] In this preparation example, the plasticizer specifically selected is tributyl acetylcitrate.

[0046]

Preparation Examples 2-7

[0047] In this preparation example, the plasticizer is specifically a mixture of 1 kg polyethylene glycol and 2 kg tributyl acetyl citrate, wherein the polyethylene glycol is polyethylene glycol with an average molecular weight of 400.

[0048]

Preparation Examples 2-8

[0049] In this preparation example, the modified polylactic acid was prepared by mixing 95 kg of polylactic acid, 2 kg of plasticizer and 3 kg of nucleating agent, followed by melt granulation and grinding. The plasticizer was a mixture of 1 kg of polyethylene glycol and 1 kg of tributyl acetyl citrate, and the polyethylene glycol was specifically polyethylene glycol with an average molecular weight of 600. Example

[0050]

Example 1

[0051] A method for preparing reactive microcapsules includes the following steps: S1. Add 1 kg of polyvinylpyrrolidone to deionized water at 1 wt%, stir thoroughly to dissolve, and obtain the base liquid; add 5 kg of modified polylactic acid to dichloromethane at 10 wt%, stir thoroughly to dissolve, then add 10 kg of cold-mix asphalt curing agent, and shake thoroughly using ultrasound to obtain the oil phase solution. S2. Take the base liquid and oil phase solution obtained in step S1 at a volume ratio of 2:1. Add the oil phase solution dropwise to the base liquid. During the dropwise addition, keep stirring and control the temperature not to exceed 25°C. After the dropwise addition is completed, heat to 35°C and stir continuously for 30 minutes. Homogenize 3-4 times under high pressure. Then evaporate dichloromethane. Collect the solid precipitate by centrifugation and filtration. Wash with anhydrous ethanol and vacuum dry to obtain an inner capsule 2. S3. Add 5 kg of polyvinyl alcohol to deionized water at 10 wt%, heat to 85°C to fully dissolve the water-soluble material, cool to 65°C, add 10 kg of inner capsule 2 and 0.3 kg of sodium dodecylbenzene sulfonate, shake thoroughly with ultrasound for 30 min, and then spray dry to obtain a reactive microcapsule.

[0052]

Example 2

[0053] In this embodiment, the outer shell 1 is formed by coating the surface of the inner capsule 2 with a mixture of gelatin and hydroxypropyl methylcellulose and then spray-drying it; the inner capsule 2 is formed by using a capsule wall 21 made of modified polylactic acid and a cold-mix asphalt curing agent as the core material 22, and then curing it with an emulsion. In this embodiment, the modified polylactic acid is specifically prepared according to [Preparation Example 2-2], and the cold-mix asphalt curing agent is specifically triethylenetetramine.

[0054] A method for preparing reactive microcapsules includes the following steps: S1. Add 1 kg of polyvinylpyrrolidone to deionized water at 0.5 wt%, stir thoroughly to dissolve, and obtain the base liquid; add 5 kg of modified polylactic acid to dichloromethane at 8 wt%, stir thoroughly to dissolve, add 7.5 kg of cold-mix asphalt curing agent, and shake thoroughly with ultrasound to obtain the oil phase solution. S2. Take the base liquid and oil phase solution obtained in step S1 at a volume ratio of 2:1. Add the oil phase solution dropwise to the base liquid. During the dropwise addition, keep stirring and control the temperature not to exceed 25°C. After the dropwise addition is completed, heat to 30°C and stir continuously for 60 minutes. Homogenize 3-4 times under high pressure. Then evaporate dichloromethane. Collect the solid precipitate by centrifugation and filtration. Wash with anhydrous ethanol and vacuum dry to obtain an inner capsule 2. S3. Add a mixture of 2.4 kg gelatin and 0.6 kg hydroxypropyl methylcellulose at 5 wt% to deionized water, heat to 70°C to fully dissolve the water-soluble material, cool to 55°C, add 10 kg inner capsule 2 and 0.2 kg sodium dodecylbenzene sulfonate, shake thoroughly with ultrasound for 30 min, and then spray dry to obtain a reactive microcapsule.

[0055]

Example 3

[0056] In this embodiment, the modified polylactic acid was prepared according to [Preparation Examples 2-3].

[0057]

Example 4

[0058] In this embodiment, the modified polylactic acid was prepared according to [Preparation Examples 2-4].

[0059]

Example 5

[0060] In this embodiment, the modified polylactic acid was prepared according to [Preparation Examples 2-5].

[0061]

Example 6

[0062] In this embodiment, the modified polylactic acid was prepared according to [Preparation Examples 2-6].

[0063]

Example 7

[0064] In this embodiment, the modified polylactic acid was prepared according to [Preparation Examples 2-7].

[0065]

Example 8

[0066] In this embodiment, the modified polylactic acid was prepared according to [Preparation Examples 2-8].

[0067]

Example 9

[0068] In this embodiment, the polyvinyl alcohol specifically selected is type 05-88 polyvinyl alcohol. Comparative Example

[0069] Comparative Example 1 A reactive microcapsule differs from [Example 1] in that the composition of the inner capsule 2 is different, specifically the modified polylactic acid used in step S1 of the preparation method.

[0070] In this comparative example, polylactic acid was used to replace the modified polylactic acid in step S1 in an equal amount.

[0071] Comparative Example 2 A reactive microcapsule, differing from [Example 1] in that the outer shell 1, made directly from a water-soluble material, coats the core material 22. Specifically, it is prepared using the following method: 5 kg of polyvinyl alcohol was added to deionized water at 10 wt%, heated to 85 °C to fully dissolve the water-soluble material, cooled to 65 °C, and 10 kg of 2-phenylimidazole and 0.3 kg of sodium dodecylbenzenesulfonate were added. The mixture was then shaken thoroughly with ultrasound for 30 min and spray-dried to obtain a reactive microcapsule. Application examples

[0072]

Application Example 1

[0073] In this application example, component A includes 43 kg of rubber-modified asphalt, 20 kg of bisphenol A epoxy resin, 20 kg of bio-based diluent, and 5 kg of compatibilizer; component B is a reactive microcapsule prepared in [Example 1].

[0074] Specifically, the bisphenol A epoxy resin used is E51 type bisphenol A epoxy resin, the bio-based diluent is epoxidized soybean oil, and the compatibilizer is methyl epoxy stearate.

[0075] A method for using cold-mix asphalt is to follow the conventional mixing and paving process for cold-mix asphalt. During mixing, the mixing speed is 200 rpm and the mixing time is 10 minutes. After paving or filling the road surface, 2% water by weight of the cold-mix asphalt should be sprayed onto it, and then vibratory compaction should be performed using a paver at a vibration frequency of 30-40 Hz. After curing, the paving is complete. Performance test data

[0076] Preparation of test microcapsules: Test microcapsules were prepared according to the formulations and preparation methods of each embodiment and comparative example. During microcapsule preparation, the inner capsule was pre-stained with 1% Congo red at low temperature for 24 hours. Excess Congo red on the surface of the inner capsule was then washed off with cold water to obtain the stained inner capsule, which served as a reference structure for subsequent performance testing. The remaining steps were the same as in the corresponding embodiments and comparative examples. If the microcapsule only had a single-layer shell structure, the test microcapsule was directly stained at low temperature.

[0077] 1. Mixing Stability Test: Based on the formulation in [Application Example 1], corresponding cold-mix asphalt mixtures were prepared using the microcapsules from each example and comparative example. During mixing, the mixture was stirred at 600 rpm for 20 minutes. After mixing, the mixture was divided into two equal portions. One portion was left unmixed to verify the effect of humidity on the outer shell during the mixing stage. The other portion was mixed with 1.5% water (by weight of the cold-mix asphalt mixture) to verify the effect of the inner capsule wall on the mixing stage. Both portions were then poured directly into molds and allowed to stand for 24 hours. The viscosity changes of each cold-mix asphalt mixture were observed. A viscosity change of no more than 5% was recorded as "no significant change"; a change between 5% and 20% was recorded as "slight increase in viscosity"; a change exceeding 20% ​​was recorded as "significant increase in viscosity"; and if the mixture was completely cured or the viscosity was difficult to measure, it was recorded as "cured". If the viscosity increases significantly or solidifies, it indicates that the microcapsules being tested were partially broken due to the humidity in the system or the shear force of the paddle during normal mixing. If the viscosity does not change significantly, it indicates that the microcapsules being tested did not break during normal mixing.

[0078] 2. Fixed-frequency vibration breakage rate test: The microcapsules to be tested in each embodiment and comparative example were quantitatively dispersed in water. A high-frequency micro-vibration platform was used to vibrate the microcapsules to be tested at a vibration frequency of 20Hz, 30Hz and 40Hz for 30 minutes with an amplitude of 0.5mm to simulate the vibration frequency of the paver on site. Random samples were taken and observed under a microscope and the breakage rate (%) of the microcapsules was calculated.

[0079] 3. Dissolution rate of the outer shell: Appropriate amounts of the microcapsules to be tested from each embodiment and comparative example were placed on a glass slide, water was added and the capsules were fully submerged, and the dissolution of the outer shell at room temperature was observed using a microscope. The time at which the outer shell began to dissolve was recorded every 10 minutes. If the outer shell was made of the same material, the test was not repeated.

[0080] Table 1. Performance Tests of Reactive Microcapsules

[0081] Based on Examples 1 and Comparative Examples 1-2, and referring to the data in Table 1, it can be seen that this application uses modified polylactic acid as the capsule wall 21 of the inner capsule 2 to coat the cold-mix asphalt curing agent. Combined with the outer shell 1 made of water-soluble material, this forms a reactive microcapsule with a double-layer protective structure. This not only has strong stability and storage properties, ensuring that the reactive microcapsule does not rupture during mixing, but also achieves full rupture through vibration at a frequency of 30-40Hz in a water-containing environment. Furthermore, when the reactive microcapsule is mixed with the cold-mix asphalt, spraying water and fixed-frequency mechanical vibration of the paver at the construction site are required to fully rupture the reactive microcapsule and release the internal curing agent components. Only then does the cold-mix asphalt begin its curing reaction, which is beneficial for controlling the degree of reaction of the cold-mix asphalt during the construction process.

[0082] The mixing stability test results show that, compared to using polylactic acid (PLA) as the capsule wall 21 of the inner capsule 2, using modified PLA as the capsule wall 21 effectively prevents the reactive microcapsules from rupturing during the mixing process due to humidity and shear force from the paddles. This helps prevent the cold-mix asphalt from reacting at the beginning of the mixing process, leading to a short subsequent construction time window. This is likely because unmodified PLA molecules have high rigidity and poor toughness, making them prone to brittle fracture under compression or shear force during mixing with cold-mix asphalt. However, PLA modified with plasticizers and nucleating agents has a moderately increased crystallinity, which not only improves the overall strength of the capsule wall 21 but also balances its flexibility and rigidity, making it less prone to rupture under compression or shear force during mixing.

[0083] Furthermore, as can be seen from Comparative Example 2, the outer shell 1 formed by the water-soluble material is also affected by the humidity of the system or the shear force of the blades during the mixing process, causing partial cracking and damage. However, after achieving a double-layer structure protection with the inner capsule 2's capsule wall 21, the overall cracking situation can be significantly reduced. This may be because the water-soluble material will partially swell or dissolve after contact with water, and will be affected by the humidity of the system to some extent during the mixing process, resulting in a decrease in strength. Therefore, when only a single layer of water-soluble material is used to cover the core material 22, cracking is likely to occur during the mixing process. However, by cooperating with the inner capsule 2's capsule wall 21, the outer shell 1 can benefit from the support of the capsule wall 21, and despite partial swelling, the overall shell layer of the microcapsule is not easily damaged. Moreover, as shown by the data from Comparative Example 1, some of the outer shell 1 can still cover the core material 22 even if the inner capsule 2's capsule wall 21 cracks, reducing the leakage of the core material 22.

[0084] Based on Examples 1 and 3-4, and referring to the data in Table 1, it can be seen that when polyethylene glycol is used as the plasticizer for the capsule wall 21 of the inner capsule 2 and coupled-treated talc is used as the nucleating agent, the breakage rate of the capsule wall 21 is low at a vibration frequency of 20 Hz, but high at a vibration frequency of 30-40 Hz. This may be because the crystallinity of the modified polylactic acid is increased by modifying it with a specific ratio of plasticizer and nucleating agent, thus causing its resonance frequency to fall within the 30-40 Hz range. When vibrating at a frequency of 30-40 Hz, the capsule wall 21 develops cracks due to resonance, which propagate rapidly, leading to rapid rupture.

[0085] Secondly, as the molecular weight of polyethylene glycol (PEG) increases, the rupture rate of the capsule wall 21 of the inner capsule 2 gradually increases under vibration at a frequency of 20-40 Hz, especially at 20 Hz, where the rupture rate is significantly higher. Furthermore, damage to the capsule wall 21 also occurred during the mixing stage. This may be because, under the same degree of crystallinity, as the molecular weight of PEG increases, the plasticizing and toughening effect of PEG on polylactic acid (PLA) decreases. This increases the overall brittleness of the capsule wall 21 due to the increased crystallinity, making it more prone to stress concentration points and brittle fracture under the same vibration frequency. Although using high molecular weight PEG for plasticizing is beneficial for the subsequent rupture of the capsule wall 21 under vibration at 30-40 Hz, it also exhibits a high rupture rate at 20 Hz and may even rupture during mixing. Therefore, to improve the storage performance of reactive microcapsules, PEG with a molecular weight of 400-600 is selected for plasticizing, resulting in a better overall effect on the capsule wall 21.

[0086] Combining Examples 1 and 5-8 with the data in Table 1, it can be seen that using bio-based castor oil or citrate esters can achieve the same plasticizing effect as polyethylene glycol, balancing the toughness and strength of the capsule wall 21, and enabling the capsule wall 21 to rupture mostly under vibration at a frequency of 30-40Hz. The capsule wall 21 plasticized and modified with castor oil showed a higher breakage rate under vibration at a frequency of 20Hz, while the capsule wall 21 plasticized and modified with citrate esters showed a lower breakage rate under vibration at a frequency of 20Hz, while maintaining a higher breakage rate under vibration at a frequency of 30-40Hz.

[0087] Furthermore, using a mixture of polyethylene glycol and citrate as a plasticizer not only resulted in a lower breakage rate of the capsule wall 21 under 20Hz vibration, but also further improved the breakage rate under 30-40Hz vibration, demonstrating a certain synergistic effect. This may be because the highly efficient plasticizing effect of citrate can form a homogeneous amorphous structure in polylactic acid, resulting in excessively high overall toughness, making it difficult for the capsule wall 21 to be fully broken under 20-40Hz vibration. Using an appropriate amount of polyethylene glycol in combination can not only appropriately suppress the plasticizing effect of citrate, but also stabilize the resonant frequency of the capsule wall 21 mainly in the 30-40Hz range, which is beneficial for achieving full rupture of the capsule wall 21 under 30-40Hz vibration.

[0088] Based on Examples 7 and 9 and the data in Table 1, it can be seen that by using polyvinyl alcohol with a lower degree of polymerization as the outer shell 1 of the reactive microcapsules, the dissolution rate of the outer shell 1 can be effectively increased. Furthermore, through the coordination of water spraying and the fixed-frequency vibration of the paver in the construction process, the rupture rate of the reactive microcapsules during the water spraying stage of cold-mix asphalt paving can be further increased, which is beneficial to improving construction efficiency.

[0089] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this specific embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A reactive microcapsule, characterized in that: It includes an outer shell (1) and an inner bladder (2). The outer shell (1) is formed by coating the surface of the inner bladder (2) with a water-soluble material and then spray drying. The inner bladder (2) is formed by using modified polylactic acid as the bladder wall (21) and cold-mixed asphalt curing agent as the core material (22), and then curing it with emulsion. The water-soluble material is at least one of polyvinyl alcohol, gelatin or hydroxyalkyl methyl cellulose; the modified polylactic acid is obtained by melt granulation after mixing polylactic acid, plasticizer and nucleating agent, and the mass ratio of polylactic acid, plasticizer and nucleating agent is (92-95):(2-7):(1-3).

2. The reactive microcapsule according to claim 1, characterized in that: The plasticizer is at least one of polyethylene glycol, citrate, or castor oil, and the nucleating agent is at least one of coupling-treated talc or organometallic salt nucleating agents.

3. The reactive microcapsule according to claim 2, characterized in that: The plasticizer is specifically a mixture of polyethylene glycol and tributyl acetylglucosamine, and the nucleating agent is specifically coupling-treated talc. The polyethylene glycol has an average molecular weight of 400-600, the mass ratio of polyethylene glycol to tributyl acetyl citrate is 1:(1-2), and the mass ratio of polylactic acid, plasticizer and nucleating agent is (94-95):(2-3):

3.

4. The reactive microcapsule according to claim 1, characterized in that: The water-soluble material is specifically polyvinyl alcohol, and the degree of alcoholysis of the polyvinyl alcohol is 87%-89% and the degree of polymerization is 500-1700.

5. A method for preparing reactive microcapsules, used to prepare a reactive microcapsule as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Add emulsifier I to deionized water at 0.5-1 wt%, stir thoroughly to dissolve, and obtain the base solution; Modified polylactic acid was added to dichloromethane at 8-10 wt%, stirred and dissolved thoroughly, and then cold-mix asphalt curing agent was added. The mixture was then shaken thoroughly with ultrasound to obtain an oil phase solution. S2. Take the oil phase solution obtained in step S1 and add it dropwise to the bottom liquid. During the dropwise addition process, keep stirring and control the temperature not higher than 25°C. After the dropwise addition is completed, heat to 30-35°C and stir continuously for 30-60 minutes. Homogenize 3-4 times under high pressure. Then evaporate dichloromethane, collect the solid precipitate by centrifugation and filtration, wash with anhydrous ethanol and vacuum dry to obtain the inner capsule (2). S3. Add water-soluble material at 5-10 wt% to deionized water, heat to fully dissolve the water-soluble material, cool to 55-65℃, add inner capsule (2) and emulsifier II, shake thoroughly with ultrasound for 30 min, and then spray dry to obtain a reactive microcapsule.

6. The method for preparing reactive microcapsules according to claim 5, characterized in that: In step S1, the mass ratio of the modified polylactic acid to the cold-mix asphalt curing agent is 1:(1.5-2). In step S2, the volume ratio of the base liquid to the oil phase solution is controlled to be 2:

1.

7. The method for preparing reactive microcapsules according to claim 5, characterized in that: In step S3, the mass ratio of the water-soluble material, the inner capsule (2), and the emulsifier II is (0.3-0.5):1:(0.02-0.03).

8. The method for preparing reactive microcapsules according to claim 5, characterized in that: The emulsifier I is polyvinylpyrrolidone, and the emulsifier II is at least one of sodium alkylbenzene sulfonate or alkylphenol polyoxyethylene ether.

9. An application of a reactive microcapsule, characterized in that: Used to prepare cold-mix asphalt, wherein the cold-mix asphalt is made by mixing component A and component B in a mass ratio of (84-90):(10-16); Component A comprises the following raw materials in parts by weight: 43-65 parts rubber-modified asphalt, 12.5-20 parts bisphenol A epoxy resin, 10-20 parts bio-based diluent, and 2.5-5 parts compatibilizer; Component B is a reactive microcapsule prepared by the preparation method according to any one of claims 5-8, wherein the cold-mix asphalt curing agent in the reactive microcapsule is specifically one of 2-phenylimidazole or triethylenetetramine.

10. The application of a reactive microcapsule according to claim 9, characterized in that: During the mixing process, the mixing speed of the cold-mix asphalt material needs to be controlled at 50-200 rpm, and the mixing time should be 10-20 min. After paving or filling the road surface, water must be sprayed in atomized form and then vibrated and compacted by a paver at a vibration frequency of 30-40Hz. The paving is then completed after curing.

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