A magnetically responsive controlled-release microcapsule encapsulating asphalt regeneration agent and a preparation method thereof

Abstract

The invention discloses a magnetically responsive controlled-release microcapsule for encapsulating an asphalt regeneration agent and a preparation method thereof. The magnetically responsive controlled-release microcapsule uses a polymer resin wall material as a shell material, an asphalt regeneration agent as a core material, introduces nano-iron tetroxide particles as a composite nucleating agent, and is obtained by ultrasonic water bath mixing treatment; the preparation method is as follows: the regeneration agent, an emulsifier and water are mixed and then ultrasonically treated to obtain a regeneration agent emulsion; melamine, urea, formaldehyde solution and water are mixed and reacted to obtain a wall material prepolymer; the regeneration agent emulsion, the wall material prepolymer and the nano-iron tetroxide particles are mixed and reacted, and the obtained microcapsules are washed, filtered and dried. The magnetically responsive controlled-release microcapsule for encapsulating an asphalt regeneration agent of the invention has the characteristics of active response and controlled release. The ultra-high frequency alternating magnetic field can not only realize the controlled release of the microcapsule, but also soften the aged asphalt, promote the mutual infiltration and penetration repair of the regeneration agent and asphalt, and improve the pavement regeneration effect.

Description

Technical Field

[0001] The present invention relates to a controlled-release microcapsule and a preparation method thereof, and in particular to a magnetically responsive controlled-release microcapsule encapsulating an asphalt regeneration agent and a preparation method thereof, which belongs to the technical field of asphalt materials for road engineering and aims to improve the self-healing performance of asphalt materials. Background Art

[0002] Asphalt aging and fatigue cracking are the main diseases of asphalt pavements, and are the initiators of water seepage, looseness, potholes and even structural damage in asphalt pavements. In the scientific research on the pursuit of high-performance and long-life asphalt pavements, asphalt aging and fatigue cracking have always been the focus of research. At present, the commonly used technologies such as grouting, spraying regeneration agents, and pavement regeneration are passive repairs after the pavement is damaged. Can it be transformed from "closing the fold after the sheep have bolted" maintenance to "preparing for a rainy day" prevention, that is, when the asphalt pavement is born, it is given "microcapsule antibiotics" with the function of self-regeneration of aged asphalt and self-healing of fatigue cracks?

[0003] Microcapsules are tiny particles with polymer materials as capsule walls and releasable core materials. In 2010, García et al. developed the first generation of self-repairing asphalt microcapsules (millimeter-sized) using epoxy resin and cement as capsule walls and porous sand that absorbed regeneration agents. Subsequently, a large number of scholars began to use in-situ polymerization methods to develop the second generation of self-repairing asphalt microcapsules (micrometer-sized) using melamine formaldehyde resin or urea formaldehyde resin as wall materials and regeneration agents as core materials. At present, the repair mechanism of asphalt microcapsules is that after the asphalt material cracks, the cracks extend to the microcapsules, causing the capsule walls to rupture and release the core materials, thereby promoting the healing of the cracks. Obviously, this repair mechanism is still essentially passive release and single repair. At the same time, the crack extension path (coplanar with the microcapsules, offset), the decay of the properties of the asphalt matrix material and its mismatch with the mechanical properties of the capsule wall may cause uncertainty in the rupture of the microcapsules. In addition, the microcapsules in the parts without cracks do not play any repair role. More importantly, it is useless to repair the performance of asphalt mixtures that have not cracked.

[0004] Asphalt aging is often the cause of asphalt mixture performance decay and macroscopic diseases. If the microcapsules can be released in a timed, quantitative, active, and multiple controlled manner in response to asphalt aging, the self-repairing microcapsule technology will have greater development potential and application value. Therefore, the third-generation asphalt self-repairing microcapsules with active response, controlled release, and multiple repair capabilities have become the development direction and research focus. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a magnetically responsive controlled-release microcapsule encapsulating an asphalt regeneration agent and a preparation method thereof.

[0006] The magnetically responsive controlled-release microcapsules for encapsulating asphalt regeneration agent provided by the present invention use polymer resin wall materials as shell materials, asphalt regeneration agent as core materials, introduce nano-ferroferric oxide particles as composite nucleating agents, and adopt ultrasonic water bath mixing treatment to obtain the magnetically responsive controlled-release microcapsules.

[0007] Furthermore, the mass ratio of the nano-ferroferric oxide particles, the asphalt regeneration agent core material and the polymer resin wall material is (6-10):7.5:(10-15).

[0008] Furthermore, the polymer resin wall material comprises melamine, urea and formaldehyde, and the mass ratio of melamine to urea is (4-8):(2-6).

[0009] Furthermore, the mass ratio of melamine, urea and formaldehyde is 7:3:8.

[0010] Furthermore, the particle size of the nano-iron tetroxide particles is 20-100 nm.

[0011] Furthermore, the microcapsule encapsulation rate is above 99%, and after controlled release using an ultra-high frequency alternating magnetic field for 15-25 seconds, the macroscopic temperature reaches 165° C. to 180° C., and the regeneration agent release rate reaches above 90%.

[0012] The method for preparing the magnetically responsive controlled-release microcapsules encapsulating asphalt regeneration agent provided by the present invention comprises the following steps:

[0013] S1) mixing the regeneration agent, emulsifier and deionized water in proportion, keeping the mixture in a water bath at 65° C. for 15-30 min, and ultrasonically treating the mixture to form a uniform core material emulsion;

[0014] S2) mixing melamine, urea and formaldehyde solution in proportion, adding deionized water to the resulting mixture in a mass ratio of 1:(4-8), adjusting the pH to 8-9, and stirring in a 70° C. water bath for 30 minutes to form a uniform wall material prepolymer;

[0015] S3) The core material emulsion obtained in step S1, the wall material prepolymer obtained in step S2 and the nano-iron tetroxide particles are mixed in proportion, continuously stirred in a 65°C water bath, the pH is slowly adjusted to 2.5-3.5, reacted for 5.5-6h, washed with deionized water, filtered and dried to obtain the magnetically responsive controlled-release microcapsules encapsulating the asphalt regeneration agent.

[0016] Furthermore, in step S1, the regeneration agent, emulsifier and deionized water are mixed in a mass ratio of 7.5:(1.5-3):150.

[0017] Furthermore, in step S1, the emulsifier is sodium dodecylbenzene sulfonate.

[0018] Furthermore, the ultrasonic treatment time in step S1 is 20-30 min.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: the magnetically responsive controlled-release microcapsules of the present invention are composed of a nano-ferroferric oxide particle core, an asphalt regeneration agent core material and a polymer resin wall material, and are of a "honeycomb structure" hybrid type; the microcapsules obtained by the method provided by the present invention have the characteristics of active response and controlled release, which changes the previous single passive release defect; the encapsulated regeneration agent can achieve the effects of self-regeneration of aged asphalt and self-repair of fatigue diseases; the ultra-high frequency alternating magnetic field can not only control the release of the microcapsules, but also benefit from the magnetocaloric effect of the nano-ferroferric oxide in the microcapsules, and can also heat the microcapsules and the surrounding asphalt, while releasing the regeneration agent while softening the aged asphalt, promoting the mutual infiltration and penetration repair of the regeneration agent and asphalt, and greatly improving the regeneration efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The microscopic morphology of the microcapsules prepared in the embodiment of the present invention;

[0021] Figure 2 This is a thermal imaging image of the microcapsule prepared in an embodiment of the present invention after 20 seconds of controlled release. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0023] The magnetically responsive controlled-release microcapsules for encapsulating asphalt regeneration agent provided by the present invention use polymer resin wall materials as shell materials, asphalt regeneration agent as core materials, introduce nano-iron tetroxide particles as composite nucleating agents, and use ultrasonic water bath mixing treatment to obtain magnetically responsive controlled-release microcapsules. Figure 1 As shown, the nano-iron tetroxide particles are concentrated in the core of the microcapsule, and the small particles of the regeneration agent are mostly wrapped around it, forming a unique "honeycomb" structure.

[0024] The magnetically responsive controlled-release microcapsules provided by the present invention have a mass ratio of the nano-ferroferric oxide particles, the asphalt regeneration agent core material and the polymer resin wall material of (6-10):7.5:(10-15), preferably 8:7.5:12.5. Exceeding the preferred range may cause problems such as microcapsule agglomeration or large morphological differences; the particle size of the nano-ferroferric oxide particles is 20-10050nm, preferably 50nm.

[0025] The magnetically responsive controlled-release microcapsules provided by the present invention, the polymer resin wall material comprises melamine, urea and formaldehyde, the mass ratio of melamine, urea and formaldehyde is (4-8):(2-6):8, preferably 7:3:8, exceeding the preferred range may cause failure to form capsules or serious agglomeration of microcapsules. According to the above mass ratio, the mechanical strength of the microcapsules can be taken into account while the regeneration agent core material can be quickly released at a suitable temperature; the frequency of the electromagnetic induction heating equipment used needs to be at least 100kHz, otherwise the stimulation intensity cannot meet the controlled release requirements, and the stimulation time should be controlled within 15-25s to meet the rapid release of the regeneration agent while avoiding local hot spot aging problems. Figure 2 As shown in the figure, after the microcapsules are heated for 20 seconds, the macroscopic temperature is 165℃~180℃, which is suitable for softening aged asphalt and promoting the compatibility of the regeneration agent with asphalt. At the same time, due to the small size of the microcapsules and fast heat dissipation, they will not cause further aging of the asphalt. In addition, the macroscopic temperature of the microcapsules is lower than the internal core temperature, and the core ferroferric oxide can bring enough heat due to the magnetocaloric effect to destroy the above-mentioned "honeycomb" structure microcapsule wall material, thereby quickly releasing the regeneration agent.

[0026] The present invention also provides a method for preparing a magnetically responsive controlled-release microcapsule encapsulating an asphalt regeneration agent, comprising the following steps:

[0027] S1) mixing a regeneration agent, an emulsifier and deionized water in proportion, keeping the mixture in a water bath at 65°C for 15-15min-30min, and ultrasonically treating the mixture for 20-30min to form a uniform core material emulsion; the regeneration agent, the emulsifier and the deionized water are mixed in a mass ratio of 7.5:(1.5-3)2:150, preferably 7.5:2:150. Exceeding the preferred range may result in insufficient emulsification of the regeneration agent and affect the capsule forming effect; the emulsifier may be sodium dodecylbenzene sulfonate;

[0028] S2) mixing melamine, urea and formaldehyde solution in proportion, adding deionized water to the resulting mixture in a mass ratio of 1:(4-8), adjusting the pH to 8-9, and stirring in a 70° C. water bath for 30 minutes to form a uniform wall material prepolymer;

[0029] S3) The core material emulsion obtained in step S1, the wall material prepolymer obtained in step S2 and the nano-iron tetroxide particles are mixed in proportion, continuously stirred in a 65°C water bath, the pH is slowly adjusted to 2.5-3.5, reacted for 5.5-6h, washed with deionized water, filtered and dried to obtain the magnetically responsive controlled-release microcapsules encapsulating the asphalt regeneration agent.

[0030] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, etc. used in the following examples are all commercially available unless otherwise specified.

[0031] The following experimental examples evaluate the controlled release performance of the obtained microcapsule regeneration agent according to the following method:

[0032] Take 0.3g of microcapsules and put them into a glass culture dish. Place the culture dish above the heating coil of the electromagnetic induction equipment, and control the release for 20s. After cooling, add n-hexane to wash. Add n-hexane to the washing solution to make it 25ml. Use a pipette to take 0.25ml and continue to add n-hexane to make it 10ml to obtain the release test solution. Use an ultraviolet spectrophotometer to test its absorbance at 228.2nm, calculate the content of the regeneration agent in the release solution through the standard curve, and use this to determine the release rate of the regeneration agent in the microcapsules:

[0033]

[0034] Example

[0035] S1) 7.5 g of regeneration agent, 2.0 g of sodium dodecylbenzene sulfonate and 150.0 g of deionized water were mixed, kept in a 65° C. water bath for 15 min, and then placed in an ultrasonic disperser for emulsification for 20 min to form a uniform core material emulsion;

[0036] S2) 4.86 g of melamine, 2.08 g of urea, 15.02 g of 37% formaldehyde solution and 28.04 g of deionized water were mixed, 5% sodium hydroxide solution was added to adjust the pH to 9, and the mixture was stirred in a 70° C. water bath for 30 min to form a uniform wall material prepolymer;

[0037] S3) The obtained core material emulsion, wall material prepolymer and 8.0g of nano-iron tetroxide particles are mixed, and stirred continuously in a 65°C water bath. 10% citric acid solution is slowly added to adjust the pH to 3. This process lasts for 5.75h. The mixture is washed with deionized water, filtered and dried to obtain the magnetically responsive controlled-release microcapsules encapsulating the asphalt regeneration agent.

[0038] In step S3) of this embodiment, all reactions are carried out in a 500 ml beaker. After the reaction is completed, the microcapsules are precipitated, and the upper part is a clear liquid without excess regeneration agent emulsion. Therefore, the encapsulation rate of the obtained microcapsules is almost 100%, and the total amount of regeneration agent in the microcapsules is close to the amount of regeneration agent input.

[0039] The release rate of the regeneration agent from the microcapsules prepared in this example was 91.2% after 20s of controlled release.

[0040] The embodiments of the present invention are described in detail above; however, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

Claims

1. A magnetically responsive controlled-release microcapsule encapsulating an asphalt regeneration agent, characterized in that: The magnetic responsive controlled-release microcapsules were obtained by using polymer resin wall material as shell material, asphalt regeneration agent as core material, introducing nano-iron tetroxide particles as composite nucleating agent, and using ultrasonic water bath mixing treatment. The mass ratio of the nano-ferroferric oxide particles, the asphalt regeneration agent core material and the polymer resin wall material is (6-10): 7.5:(10-15)； The polymer resin wall material comprises melamine, urea and formaldehyde, and the mass ratio of melamine to urea is (4-8):(2-6); The particle size of the nano-iron tetroxide particles is 20-100nm.

2. The magnetically responsive controlled-release microcapsule according to claim 1, characterized in that: The mass ratio of the melamine, urea and formaldehyde is 7:3:

8.

3. The magnetically responsive controlled-release microcapsule according to claim 1, characterized in that: The encapsulation rate of the microcapsule is more than 99%. After using an ultra-high frequency alternating magnetic field to control the release for 15-25 seconds, the macroscopic temperature reaches 165° C. to 180° C., and the release rate of the regeneration agent reaches more than 90%.

4. A method for preparing the magnetically responsive controlled-release microcapsules encapsulating asphalt regeneration agent as claimed in claim 1, characterized in that: The steps include: S1) Mix the regeneration agent, emulsifier and deionized water in proportion, keep in a water bath at 65°C for 15-30 minutes, and perform ultrasonic treatment to form a uniform core material emulsion; S2) melamine, urea and formaldehyde solution are mixed in proportion, deionized water is added to the resulting mixture in a mass ratio of 1:(4-8), the pH is adjusted to 8-9, and the mixture is stirred in a 70°C water bath for 30 minutes to form a uniform wall material prepolymer; S3) The core material emulsion obtained in step S1, the wall material prepolymer obtained in step S2 and the nano-iron tetroxide particles are mixed in proportion, continuously stirred in a 65° C. water bath, the pH value is slowly adjusted to 2.5-3.5, the mixture is reacted for 5.5-6 hours, and the mixture is washed with deionized water, filtered and dried to obtain the magnetically responsive controlled-release microcapsules encapsulating the asphalt regeneration agent.

5. The preparation method according to claim 4, characterized in that: In step S1, the regeneration agent, emulsifier and deionized water are mixed in a mass ratio of 7.5:(1.5-3):

150.

6. The preparation method according to claim 4, characterized in that: The emulsifier in step S1 is sodium dodecylbenzene sulfonate.

7. The preparation method according to claim 4, characterized in that: The ultrasonic treatment time in step S1 is 20-30 min.

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