Bio-based microcapsule as well as preparation method and application thereof

Abstract

The invention discloses a bio-based microcapsule as well as a preparation method and application thereof, and belongs to the technical field of concrete self-repairing materials. The prepared bio-based microcapsule is composed of a capsule core and a capsule wall, the capsule core is mineral oil, and the raw material of the capsule wall is an acrylate mixture; the bio-based microcapsule prepared on the basis of a microfluidic technology is uniform in property and stable in structure, and has good sphericity and monodispersity. The bio-based microcapsule is applied to preparation of self-repairing concrete, and the bio-based microcapsule can repair concrete cracks, improve the compressive strength of the concrete and enhance the bearing capacity and durability of the concrete; the soybean oil epoxidized acrylate is derived from soybean oil which is a renewable resource, has biodegradability and environmental friendliness, and is beneficial to reducing pollution and damage to the environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of concrete self-repairing materials, and in particular relates to a bio-based microcapsule and a preparation method and application thereof. Background Art

[0002] With the continuous advancement of my country's transportation infrastructure construction, the transportation industry has grown rapidly, and the mileage of high-grade highway construction has continued to increase. Cement concrete pavement has the characteristics of high strength, good durability, and is conducive to night driving, so cement concrete pavement has a good development prospect. Although the compressive strength of cement concrete is very high, it is a typical brittle material, and its tensile strength is only about one-tenth of its compressive strength. Under the combined effects of load, environmental factors, construction conditions, and maintenance level, cement concrete will have micro-cracks, resulting in reduced mechanical and durability properties. Moreover, with the development of micro-cracks, the cracks will eventually merge into a through crack. Rainwater and other substances enter the pavement system through the through cracks, which will then cause mud pumping, subsidence, misalignment, and broken boards. In addition, under the influence of today's heavy traffic and harsh climate environment, when cracks appear on cement concrete pavement, the disease will accelerate. Due to its high strength, cement concrete pavement is difficult to repair and requires special machinery and repair materials. The long maintenance cycle also causes a lot of interference to traffic and affects the road's traffic capacity. Although traditional post-maintenance can repair cracks visible to the naked eye, it can no longer meet the higher demand for cement concrete in today's society. Self-repairing concrete can repair micro-cracks inside cement concrete at an early stage, prevent serious diseases caused by further expansion of micro-cracks, and extend the service life of cement concrete structures. It is a development trend in the field of cement concrete materials.

[0003] At present, for the microencapsulation of cement-based self-healing materials, encapsulation technology generally uses methods such as in-situ polymerization and interfacial polymerization. When using the in-situ polymerization method to prepare microcapsules, the selection of initiators is more difficult, the polymerization reaction is not easy to intervene manually, and the post-processing of the reaction liquid is relatively complicated, which may involve tedious separation and purification steps; the interfacial polymerization method has a relatively low equipment utilization rate and is difficult to control the final product due to the fast reaction speed. These traditional preparation methods have the same shortcomings. The operation process is complicated and the operation is often accompanied by intense mechanical stirring, which makes it difficult to unify the size and structure of the generated microcapsules, and it is difficult to deeply explore the influence of microcapsule size and structure on the mechanical properties and self-healing properties of cement-based materials.

[0004] In the prior art, self-healing microcapsules with acrylate as the capsule wall are usually formed by the reaction of acrylic acid and alcohol under catalytic conditions, and the acrylic acid part usually comes from fossil fuel propylene. Although acrylate is a suitable shell material in terms of material properties, the preparation process continuously consumes fossil fuels, which further leads to the aggravation of the greenhouse effect. For large-scale production of microcapsules for pavement cracks in the civil engineering field, choosing bio-based materials as the wall material to prepare physically triggered self-healing microcapsules can not only reduce the use of fossil fuels, but also utilize waste from biodiesel production such as waste grease or microbial grease. Therefore, it is particularly important to find bio-based microcapsule materials. Summary of the Invention

[0005] In view of the above prior art, the present invention discloses a bio-based microcapsule, its preparation method and application, to solve the technical problems in the prior art such as the complex operation of the preparation method of self-healing microcapsule materials, the non-environmental protection of raw materials, the difficulty in unifying the size and structure of the prepared microcapsule materials, and the poor self-healing effect.

[0006] To achieve the above object, the technical solution adopted by the present invention is: to provide a bio-based microcapsule, which is composed of a core and a wall. The core is mineral oil; the raw material of the wall is an acrylate mixture. The acrylate mixture is prepared by the following method: adding epoxidized soybean oil acrylate (AESO) to an isobornyl acrylate (IBOA) solution to obtain an epoxidized soybean oil acrylate - isobornyl acrylate mixed solution, and then adding a photoinitiator to the epoxidized soybean oil acrylate - isobornyl acrylate mixed solution to obtain it.

[0007] Based on the above technical solution, the present invention can also be improved as follows.

[0008] Further, the solvent of the isobornyl acrylate solution is ethyl acetate, diethyl ether or ethanol, and the concentration of the isobornyl acrylate solution is 75wt%; the photoinitiator is a 5wt% methylpropiophenone solution, and the solvent of the methylpropiophenone solution is ethyl acetate, diethyl ether or ethanol.

[0009] Further, by weight, the epoxidized soybean oil acrylate - isobornyl acrylate - acrylate mixture includes 1 part of epoxidized soybean oil acrylate, 3 parts of isobornyl acrylate solution and 1 part of photoinitiator.

[0010] The present invention also discloses the preparation method of the above bio-based microcapsule, which includes the following steps: S1: Nest the conical outlet of the middle-phase capillary glass tube inside the outer-phase capillary glass tube with a nesting depth of 100 μm; then nest the conical outlet of the inner-phase capillary glass tube inside the middle-phase capillary glass tube with a nesting depth of 100 μm, and set up a feeding assistant system at the inlets of the inner-phase capillary glass tube, the middle-phase capillary glass tube and the outer-phase capillary glass tube respectively to complete the construction of the microfluidic device; S2: Inject mineral oil into the inner-phase capillary glass tube at a flow rate of 15 - 35 μL / min, while inject the acrylate mixture into the middle-phase capillary glass tube at a flow rate of 45 - 55 μL / min, and at the same time inject a polyvinyl alcohol solution with a concentration of 5 - 15 wt% into the outer-phase capillary glass tube at a flow rate of 350 - 550 μL / min, and collect the emulsion droplets formed at the bottom end of the outer-phase capillary glass tube with an aqueous solution of polyvinyl alcohol; S3: After the emulsion droplets are polymerized, washed and dried, they are obtained; the polymerization conditions are to irradiate the emulsion droplets with ultraviolet light, the power of the ultraviolet lamp is 400 W, and the irradiation time is 5 - 6 min; the drying temperature is 100 - 150 °C, and the drying time is 8 - 12 h.

[0011] Based on the above technical solutions, the present invention can also be improved as follows.

[0012] Further, in step S1, the diameter of the conical outlet of the inner-phase capillary glass tube is 100 - 200 μm; the diameter of the conical outlet of the middle-phase capillary glass tube is 200 - 300 μm; the outer diameter of the outer-phase capillary glass tube is 500 μm, and the inner diameter is 400 μm.

[0013] Further, in step S2, the solvent of the polyvinyl alcohol solution is methanol.

[0014] Further, in step S2, the concentration of the aqueous polyvinyl alcohol solution is 5 wt%.

[0015] Further, in step S3, the washing method is to wash with deionized water 5 - 7 times.

[0016] The present invention also discloses the application of this bio-based microcapsule in the preparation of self-healing concrete.

[0017] The beneficial effects of the present invention are: 1. The bio-based microcapsules prepared in the present invention have uniform properties and stable structures, and also have good sphericity and monodispersity. At the same time, the particle size of the microcapsules is less than 100 μm at the microscale. Their incorporation can promote the dispersion between cement particles, and the compressive strength and flexural strength of the concrete decrease less, and they can be applied to engineering fields such as the paving of bridge road surfaces and the construction of semi-rigid bases for highway road surfaces.

[0018] 2. When the bio-based microcapsules of the present invention are used to prepare self-repairing concrete, the raw materials of the capsule wall of the prepared bio-based microcapsules include soybean oil epoxidized acrylate, isoborneol acrylate and photoinitiator. After the photoinitiator receives the ultraviolet quantum emitted by the strong ultraviolet light, it initiates a polymerization reaction, and the mixed liquid solidifies into a solid state, which can effectively wrap the capsule core of the bio-based microcapsule, so that the cracks can be repaired after the subsequent capsule core is released. The soybean oil epoxidized acrylate has lubricity and permeability, and the isoborneol acrylate can improve the strength and toughness of the polymer. The synergistic effect of epoxidized soybean oil acrylate and isoborneol acrylate can significantly improve the toughness of the microcapsules. The bio-based microcapsule has good properties, which can help the microcapsules improve their rupture performance and ensure the integrity of the microcapsules when mixed with cement. At the same time, the microcapsule shell can meet a sufficiently low tensile strength to promote rupture in the cement matrix when it coincides with the extended crack. When the concrete crack extends to the location of the bio-based microcapsule, its capsule wall will rupture and release the capsule core components to play a repair effect. The capsule wall has good flexibility and elasticity, which can buffer the impact of crack expansion, extend the service life of the microcapsule and improve its repair effect. In addition, soybean oil epoxidized acrylate is derived from renewable resource soybean oil, is biodegradable and environmentally friendly, and helps reduce pollution and damage to the environment.

[0019] 3. The core of the bio-based microcapsules prepared in the present invention is mineral oil. Mineral oil has good lubricity and permeability, and can quickly penetrate into the tiny gaps in the cracks of the road surface, which helps to repair the cracks and further enhance the bearing capacity of the road surface. At the same time, mineral oil can be stored for a long time in the service environment of cement-based materials. When polymerization occurs, the volume shrinkage rate is low, the viscosity is low and it is easy to flow. It adapts to the alkaline environment inside the cement-based material and has strong durability. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the microfluidic device structure; Figure 2 is a microscopic image of the bio-based microcapsules prepared in Example 1; Among them, 1. inner phase capillary glass tube; 2. middle phase capillary glass tube; 3. outer phase capillary glass tube; 4. microfluidic chip; 5. syringe; 6. injection pump; 7. dispensing needle; 8. PE tube; 9. light source; 10. microscope lens; 11. high-speed camera; 12. computer; 13. collection bottle. DETAILED DESCRIPTION

[0021] The microfluidic device used in the present invention has a structure as follows: Figure 1As shown in the figure, it includes a microfluidic chip 4, a feeding system, a photographic system and a collection bottle 13. Among them, the microfluidic chip 4 includes a substrate and capillary glass tubes arranged on the substrate. The capillary glass tubes include an inner-phase capillary glass tube 1, a middle-phase capillary glass tube 2 and an outer-phase capillary glass tube 3. The inner-phase capillary glass tube 1 is nested in the middle-phase capillary glass tube 2, and the middle-phase capillary glass tube 2 is nested in the outer-phase capillary glass tube 3. After the three capillary glass tubes are centered, they are located on a straight line. At the entrances of the inner-phase capillary glass tube 1, the middle-phase capillary glass tube 2 and the outer-phase capillary glass tube 3, a feeding system is provided. The feeding system includes an injection pump 6 and a syringe 5. The outlet of the syringe 5 is connected to a PE tube 8 through a dispensing needle 7, and the end of the PE tube 8 is fixed to the entrance of the capillary glass tube through a dispensing needle 7. The photographic system includes a computer 12 and a high-speed camera 11 equipped with a microscope lens 10. The high-speed camera 11 is remotely controlled and set through the high-speed camera control software installed in the computer 12. When preparing droplets, the real-time situation of droplet generation is observed by using the microscope lens 10 of the high-speed camera 11 and corresponding adjustments are made. By adjusting the shooting parameters such as the frames per second, exposure time and light source brightness of the high-speed camera 11, the droplets are photographed after they are generated stably.

[0022] The following describes the specific implementation manners of the present invention in detail in conjunction with embodiments.

[0023] Embodiment 1 A method for preparing a bio-based microcapsule, the method comprising the following steps: ① Prepare an acrylate mixture By weight, 1 part of AESO is added to 3 parts of an IBOA solution with a concentration of 75 wt% (the solvent is ethanol). After mixing evenly, an AESO-IBOA mixed solution is obtained. Then, 1 part of a methylpropiophenone solution with a concentration of 0.5 wt% (the solvent is ethanol) is added to the AESO-IBOA mixed solution to obtain the mixture.

[0024] ② Prepare the bio-based microcapsule S1: Select 2 original capillary round glass tubes that have not been drawn. Grind the end of one of them with 2500-mesh sandpaper to a conical shape. The diameter of the conical outlet is 150 μm and the tip of the conical outlet is flat and without notches. This capillary round glass tube serves as the inner-phase capillary glass tube 1. Grind the end of the other one with 2000-mesh sandpaper to a conical shape. The diameter of the conical outlet is 250 μm and the tip of the conical outlet is flat and without notches. This capillary round glass tube serves as the middle-phase capillary glass tube 2. Then select an original capillary round with an outer diameter of 500 μm and an inner diameter of 400 μm that has not been drawn as the outer-phase capillary glass tube 3. Nest the conical outlet of the middle-phase capillary glass tube 2 inside the outer-phase capillary glass tube 3 under a microscope, with a nesting depth of 100 μm. Then nest the conical outlet of the inner-phase capillary glass tube 1 inside the middle-phase capillary glass tube 2, with a nesting depth of 100 μm, and align the 3 capillary glass tubes so that they are on the same straight line; S2: Use a syringe 5 to suck in 20 mL of mineral oil, 20 mL of acrylate mixture, and 20 mL of a 10 wt% polyvinyl alcohol solution (the solvent is methanol) respectively. Then fix the syringe 5 on an injection pump 6 respectively. Inject the mineral oil into the inner-phase capillary glass tube 1 at a flow rate of 20 μL / min through the injection pump 6. At the same time, inject the acrylate mixture into the middle-phase capillary glass tube 2 at a flow rate of 50 μL / min through the injection pump 6. At the same time, inject the polyvinyl alcohol solution into the outer-phase capillary glass tube 3 at a flow rate of 400 μL / min through the injection pump 6. The acrylate mixture serves as the middle phase to surround the mineral oil, and the polyvinyl alcohol solution serves as the outer phase to surround the middle phase. An emulsion droplet is formed at the bottom of the outer-phase capillary glass tube 3, and the emulsion droplet is collected with a 5 wt% aqueous solution of polyvinyl alcohol; S3: 30 s after the emulsion droplet is formed, irradiate the emulsion droplet in the aqueous solution with an ultraviolet lamp with a power of 400 W. The emulsion droplet undergoes a polymerization reaction under ultraviolet light irradiation. After reacting for 5 min, stable microcapsules are formed. Then wash the microcapsules with deionized water repeatedly 6 times, and then put the microcapsules into a vacuum drying oven and dry them at 120 °C for 10 h to obtain them.

[0025] Example 2 A method for preparing bio-based microcapsules, which comprises the following steps: ① Prepare acrylate mixture By weight, add 1 part of AESO to 3 parts of a 75 wt% IBOA solution (the solvent is ethanol), mix evenly to obtain an AESO-IBOA mixed solution, and then add 1 part of a 0.5 wt% methylpropiophenone solution (the solvent is ethanol) to the AESO-IBOA mixed solution to obtain it.

[0026] ② Prepare bio-based microcapsules S1: Select 2 original capillary round glass tubes that have not been drawn. Grind the end of one of them with 2500 - mesh sandpaper to a cone shape. The diameter of the conical outlet is 100 μm and the tip of the conical outlet is flat and without notch. This capillary round glass tube serves as the inner - phase capillary glass tube 1. Grind the end of the other one with 2000 - mesh sandpaper to a cone shape. The diameter of the conical outlet is 200 μm and the tip of the conical outlet is flat and without notch. This capillary round glass tube serves as the middle - phase capillary glass tube 2. Then select an original capillary round glass tube with an outer diameter of 500 μm and an inner diameter of 400 μm that has not been drawn as the outer - phase capillary glass tube 3. Nest the conical outlet of the middle - phase capillary glass tube 2 inside the outer - phase capillary glass tube 3 under a microscope, with a nesting depth of 100 μm. Then nest the conical outlet of the inner - phase capillary glass tube 1 inside the middle - phase capillary glass tube 2, with a nesting depth of 100 μm, and align the 3 capillary glass tubes so that they are on the same straight line. S2: Use a syringe 5 to suck in 20 mL of mineral oil, 20 mL of acrylate mixture, and 20 mL of a 5 wt% polyvinyl alcohol solution (solvent is methanol) respectively. Then fix the syringe 5 on an injection pump 6 respectively. Inject the mineral oil into the inner - phase capillary glass tube 1 at a flow rate of 15 μL / min through the injection pump 6. At the same time, inject the acrylate mixture into the middle - phase capillary glass tube 2 at a flow rate of 45 μL / min through the injection pump 6. At the same time, inject the polyvinyl alcohol solution into the outer - phase capillary glass tube 3 at a flow rate of 350 μL / min through the injection pump 6. The acrylate mixture serves as the middle - phase surrounding the mineral oil, and the polyvinyl alcohol solution serves as the outer - phase surrounding the middle - phase. An emulsion droplet is formed at the bottom of the outer - phase capillary glass tube 3, and the emulsion droplet is collected with a 5 wt% aqueous solution of polyvinyl alcohol. S3: After 30 s of forming the emulsion droplet, irradiate the emulsion droplet in the aqueous solution with an ultraviolet lamp with a power of 400 W. The emulsion droplet undergoes a polymerization reaction under ultraviolet light irradiation. After 6 min of reaction, stable microcapsules are formed. Then wash the microcapsules repeatedly with deionized water 5 times, and then put the microcapsules into a vacuum drying oven and dry them at 100 °C for 12 h to obtain the product.

[0027] Example 3 A preparation method of bio - based microcapsules, which comprises the following steps: ① Prepare acrylate mixture By weight, add 1 part of AESO to 3 parts of a 75 wt% IBOA solution (solvent is ethyl acetate), mix evenly to obtain an AESO - IBOA mixed solution, and then add 1 part of a 0.5 wt% methylpropiophenone solution (solvent is ethyl acetate) to the AESO - IBOA mixed solution to obtain the product.

[0028] ② Prepare bio - based microcapsules S1: Select 2 original capillary round glass tubes that have not been drawn. Grind the end of one of them with 2500 - mesh sandpaper to a conical shape. The diameter of the conical outlet is 200 μm and the tip of the conical outlet is flat and without notch. This capillary round glass tube serves as the inner - phase capillary glass tube 1. Grind the end of the other one with 2000 - mesh sandpaper to a conical shape. The diameter of the conical outlet is 300 μm and the tip of the conical outlet is flat and without notch. This capillary round glass tube serves as the middle - phase capillary glass tube 2. Then select an original capillary round glass tube with an outer diameter of 500 μm and an inner diameter of 400 μm that has not been drawn as the outer - phase capillary glass tube 3. Nest the conical outlet of the middle - phase capillary glass tube 2 inside the outer - phase capillary glass tube 3 under a microscope, with a nesting depth of 100 μm. Then nest the conical outlet of the inner - phase capillary glass tube 1 inside the middle - phase capillary glass tube 2, with a nesting depth of 100 μm, and align the 3 capillary glass tubes so that they are on the same straight line. S2: Use a syringe 5 to suck in 20 mL of mineral oil, 20 mL of acrylate mixture, and 20 mL of a polyvinyl alcohol solution with a concentration of 15 wt% (the solvent is methanol) respectively. Then fix the syringe 5 on an injection pump 6 respectively. Inject the mineral oil into the inner - phase capillary glass tube 1 at a flow rate of 35 μL / min through the injection pump 6. At the same time, inject the acrylate mixture into the middle - phase capillary glass tube 2 at a flow rate of 55 μL / min through the injection pump 6. At the same time, inject the polyvinyl alcohol solution into the outer - phase capillary glass tube 3 at a flow rate of 550 μL / min through the injection pump 6. The acrylate mixture serves as the middle - phase surrounding the mineral oil, and the polyvinyl alcohol solution serves as the outer - phase surrounding the middle - phase. Emulsion droplets are formed at the bottom of the outer - phase capillary glass tube 3, and the emulsion droplets are collected with an aqueous solution of polyvinyl alcohol with a concentration of 5 wt%. S3: 30 s after the formation of the emulsion droplets, irradiate the emulsion droplets in the aqueous solution with an ultraviolet lamp with a power of 400 W. The emulsion droplets undergo a polymerization reaction under ultraviolet light irradiation. After 5 min of reaction, stable microcapsules are formed. Then wash the microcapsules with deionized water 7 times repeatedly, and then put the microcapsules into a vacuum drying oven and dry them at 150 °C for 12 h to obtain the product.

[0029] Comparative Example 1 A preparation method of microcapsules, the difference from the preparation method in Example 1 is that the components of the acrylate mixture in step ① are different, and the IBOA solution is omitted.

[0030] Comparative Example 2 A preparation method of microcapsules, the difference from the preparation method in Example 1 is that the components of the acrylate mixture in step ① are different, and AESO is omitted.

[0031] Comparative Example 3 A preparation method of microcapsules, which is different from the preparation method in Example 1 in that the component parts of the acrylate mixture in step ① are different. By weight, the amount of the IBOA solution (with ethanol as the solvent) in the acrylate mixture in this comparative example is 1 part, accounting for 75wt%.

[0032] Comparative Example 4 A preparation method of microcapsules, which is different from the preparation method in Example 1 in that the components of the acrylate mixture in step ① are different. 1 part of AESO and 3 parts of the IBOA solution with a concentration of 75wt% are replaced by 4 parts of polyurea.

[0033] Comparative Example 5 A preparation method of microcapsules, which is different from the preparation method in Example 1 in that the flow rate of the mineral oil in step S2 is adjusted to 45 μL / min, the flow rate of the acrylate mixture is adjusted to 70 μL / min, and the flow rate of the polyvinyl alcohol solution is adjusted to 650 μL / min.

[0034] Experimental Example ① Structure test The image of the bio-based microcapsules prepared in Example 1 under an optical microscope is as Figure 2 shown. It can be seen from the figure that the surface morphology of the microcapsules is smooth, and it has a core-shell structure, with good sphericity and high monodispersity.

[0035] ② Incorporate the microcapsules prepared in Examples 1 to 3 and Comparative Examples 1 to 5 into the production of concrete specimens to self-repair concrete cracks of the same degree, and detect the overall performance after crack repair. The repair steps are as follows: Apply a constant pressure of 70% of the maximum stress value to the specimen for 180 s and then unload. Place the damaged specimen for 2 d to allow the microcapsules to repair its cracks. The detected values after repair are shown in Table 1. It can be seen from the table that the strength repair rate and strength recovery rate of the microcapsules prepared in the examples for repairing concrete cracks are higher, and the compressive strength of the repaired concrete is also higher. In Comparative Example 1, the IBOA solution is omitted. IBOA can improve the strength and toughness of the microcapsules. In addition, AESO cannot play a synergistic role with IBOA, resulting in a further reduction in the toughness of this microcapsule compared with the example sample, and the integrity of the microcapsule also decreases during concrete mixing. Therefore, it shows poor performance when repairing concrete cracks; AESO has lubricity and permeability. In Comparative Example 2, AESO is omitted, which is not conducive to the microcapsule penetrating into the tiny voids of the crack and is not conducive to crack repair. IBOA cannot play a synergistic role with AESO, resulting in a decrease in the toughness and strength of the capsule wall and a weakened repair effect; in Comparative Example 3, the IBOA solution in the acrylate mixture is only 1 part. The reduction in the amount of IBOA leads to insufficient strength and toughness of the microcapsules, and it also shows poor performance when repairing concrete cracks; in Comparative Example 4, IBOA and AESO are replaced with polyurea, resulting in a significant decrease in the repair performance of the microcapsules; in Comparative Example 5, after adjusting the flow rate, the properties of the microcapsules are non-uniform, and it shows poor repair performance when repairing concrete cracks.

[0036] Table 1

[0037] Although the specific implementation manners of the present invention have been described in detail in conjunction with the embodiments, it should not be construed as a limitation on the protection scope of this patent. Within the scope described in the claims, various modifications and deformations that can be made by those skilled in the art without creative efforts still fall within the protection scope of this patent.

Claims

1. A bio-based microcapsule, characterized in that: The bio-based microcapsule consists of a capsule core and a capsule wall, wherein the capsule core is mineral oil; the raw material of the capsule wall is an acrylate mixture; the acrylate mixture is prepared by the following method: soybean oil epoxidized acrylate is added to an isobornyl acrylate solution to obtain a soybean oil epoxidized acrylate-isobornyl acrylate mixed solution, and then a photoinitiator is added to the soybean oil epoxidized acrylate-isobornyl acrylate mixed solution to obtain the obtained product.

2. The bio-based microcapsule according to claim 1, characterized in that: The solvent of the isobornyl acrylate solution is ethyl acetate, ether or ethanol, and the concentration of the isobornyl acrylate solution is 75wt%; the photoinitiator is a methyl acryloyl phenone solution with a concentration of 5wt%, and the solvent of the methyl acryloyl phenone solution is ethyl acetate, ether or ethanol.

3. The bio-based microcapsule according to claim 2, characterized in that: The acrylate mixture includes, by weight, 1 part of soybean oil epoxidized acrylate, 3 parts of isobornyl acrylate solution and 1 part of photoinitiator.

4. The method for preparing the bio-based microcapsules according to any one of claims 1 to 3, characterized in that: The steps include: S1: The conical outlet of the middle phase capillary glass tube (2) is nested in the outer phase capillary glass tube (3) with a nesting depth of 100 μm; then the conical outlet of the inner phase capillary glass tube (1) is nested in the middle phase capillary glass tube (2) with a nesting depth of 100 μm, and injection systems are respectively arranged at the inlets of the inner phase capillary glass tube (1), the middle phase capillary glass tube (2) and the outer phase capillary glass tube (3), thereby completing the construction of the microfluidic device; S2: inject mineral oil into the inner phase capillary glass tube (1) at a flow rate of 15-35 μL / min, inject the acrylate mixture into the middle phase capillary glass tube (2) at a flow rate of 45-55 μL / min, and inject a polyvinyl alcohol solution with a concentration of 5-15 wt% into the outer phase capillary glass tube (3) at a flow rate of 350-550 μL / min, and collect the emulsion droplets formed at the bottom of the outer phase capillary glass tube (3) with the polyvinyl alcohol aqueous solution; S3: The emulsion droplets are obtained after polymerization, washing and drying; the polymerization conditions are: irradiating the emulsion droplets with ultraviolet light, the power of the ultraviolet lamp is 400W, and the irradiation time is 5-6 minutes; the drying temperature is 100-150°C, and the drying time is 8-12 hours.

5. The method for preparing bio-based microcapsules according to claim 4, characterized in that: In step S1, the diameter of the tapered outlet of the inner phase capillary glass tube (1) is 100-200 μm; the diameter of the tapered outlet of the middle phase capillary glass tube (2) is 200-300 μm; the outer diameter of the outer phase capillary glass tube (3) is 500 μm, and the inner diameter is 400 μm.

6. The method for preparing bio-based microcapsules according to claim 4, characterized in that: The solvent of the polyvinyl alcohol solution in step S2 is methanol.

7. The method for preparing bio-based microcapsules according to claim 4, characterized in that: The concentration of the polyvinyl alcohol aqueous solution in step S2 is 5 wt %.

8. The method for preparing bio-based microcapsules according to claim 4, characterized in that: The washing method in step S3 is to wash with deionized water 5 to 7 times.

9. An application of a bio-based microcapsule, characterized in that: The bio-based microcapsules described in any one of claims 1 to 3 are used to prepare self-repairing concrete.

Images