High-stability microcapsule and emulsification process thereof

Abstract

This application relates to the field of self-healing coating materials, mainly to a highly stable microcapsule and its emulsification process. The highly stable microcapsule comprises: 1-5 parts nano-titanium dioxide, 0.1-1 parts oleic acid, 0.5-2 parts polyhydroxystearic acid, 45-55 parts hexadecane, 30-40 parts water, 1-5 parts active material, 0.01-1 parts silane coupling agent, alcohol solvent, 1-5 parts Span, and 0.5-2 parts polyethylene glycol. The emulsification process includes: modifying nano-titanium dioxide with polyethylene glycol and silane coupling agent to obtain PEG-modified TiO2; mixing hexadecane, PEG-modified TiO2, polyhydroxystearic acid, and Span to obtain oil phase A; mixing oil phase A and oleic acid to obtain oil phase B; mixing water and active material to obtain an aqueous phase; adding the aqueous phase to oil phase B and emulsifying to obtain emulsion A; and freeze-drying emulsion A to obtain the highly stable microcapsule. This application can improve the self-healing effect of microcapsules in coatings.

Description

Technical Field

[0001] This application relates to the field of self-healing coating materials technology, and mainly to a highly stable microcapsule and its emulsification process. Background Technology

[0002] In the coatings industry, microcapsules are often used as self-healing carriers, encapsulating repair agents (such as resins and curing agents) and dispersing them in the coating matrix. When cracks appear on the coating surface, the microcapsules rupture to release the core material, thus repairing the cracks. The emulsification process is one of the core steps in microcapsule preparation, directly determining the stability of the emulsion and the morphology of the microcapsules.

[0003] However, traditional microcapsules often use a single surfactant for emulsification, which easily leads to droplet coalescence and particle agglomeration, resulting in poor emulsion stability and affecting the encapsulation efficiency of the microcapsules. At the same time, the interfacial bonding between microcapsules and the coating matrix is ​​weak, making them prone to delamination during application. The migration of traditional surfactants can also reduce the mechanical properties and weather resistance of the coating. These shortcomings limit the large-scale application of microcapsules in high-end coating applications.

[0004] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this application is to provide a highly stable microcapsule and its emulsification process, which aims to improve the self-healing effect of microcapsules in coatings.

[0006] The technical solution of this application is as follows:

[0007] A highly stable microcapsule, comprising the following raw materials in parts by weight:

[0008] 1-5 parts nano titanium dioxide, 0.1-1 parts oleic acid, 0.5-2 parts polyhydroxystearic acid, 45-55 parts hexadecane, 30-40 parts water, 1-5 parts active substance, 0.01-1 parts silane coupling agent, alcohol solvent, 1-5 parts Span, 0.5-2 parts polyethylene glycol.

[0009] Furthermore, the active material includes waterborne polyurethane resin.

[0010] Furthermore, silane coupling agents include KH-550;

[0011] The strategist includes the strategist-80.

[0012] This application also provides an emulsification process for highly stable microcapsules, comprising the following steps:

[0013] PEG-modified TiO2 was obtained by modifying nano-titanium dioxide with polyethylene glycol and silane coupling agent.

[0014] Hexadecane, PEG-modified TiO2, polyhydroxystearic acid, and Span were ultrasonically mixed to obtain oil phase A;

[0015] Oil phase A and oleic acid react to yield oil phase B;

[0016] Water and active substances are mixed to obtain an aqueous phase;

[0017] The aqueous phase is added to the oil phase B for emulsification. The emulsification temperature is 20-30℃, the emulsification speed is 5500-6500 rpm, and the emulsification time is 20-45 minutes to obtain emulsion A.

[0018] Emulsion A was freeze-dried to obtain highly stable microcapsules.

[0019] Furthermore, the preparation of PEG-modified TiO2 includes the following steps:

[0020] Nano-titanium dioxide is mixed with an alcohol solvent to obtain a suspension;

[0021] The suspension and polyethylene glycol are dispersed and mixed, and then a silane coupling agent is added and stirred to react.

[0022] After the reaction was completed, the product was centrifuged, washed, and dried to obtain PEG-modified TiO2.

[0023] Furthermore, the preparation of oil phase A includes the following steps:

[0024] Under stirring, PEG-modified TiO2 is added and mixed with hexadecane, followed by the addition of polyhydroxystearic acid and Span. The mixture is then ultrasonically dispersed for 20-45 minutes at a power of 150-250W and a frequency of 18-23kHz to obtain oil phase A.

[0025] Furthermore, the oil phase A and oleic acid are mixed by adding oleic acid dropwise to oil phase A at a rate of 0.5-1.5 drops / second and stirring continuously for 15-45 minutes.

[0026] Furthermore, after emulsion A is ultrasonically emulsified for 10-20 minutes at a power of 150-250W and a frequency of 18-23kHz, emulsion B is obtained, and then emulsion B is freeze-dried.

[0027] Furthermore, the amount of polyethylene glycol added is 15-25% of the mass of nano-titanium dioxide;

[0028] The amount of silane coupling agent added is 1-5% of the mass of nano-titanium dioxide.

[0029] This application also provides the application of highly stable microcapsules in coatings.

[0030] Compared with the prior art, this application has the following beneficial effects:

[0031] 1. The nano-TiO2 in this application is modified with PEG and oleic acid, and combined with the steric hindrance effect of PHS and the chemical bonding effect of silane coupling agent, it not only prevents particle agglomeration and droplet coalescence, but also enhances the compactness of the wall material structure. The ultrasonic-high shear synergistic emulsification process further refines the droplet size and avoids secondary agglomeration.

[0032] Compared with traditional technologies, the microcapsules of this application have high encapsulation efficiency and excellent wall material mechanical strength, and can be stored for a long time without leakage of core material. This effectively solves the problems of unstable microcapsule emulsion and loose wall material in existing microcapsule systems, and significantly improves the stability of microcapsules.

[0033] 2. This application can effectively improve the interfacial bonding force between microcapsules and the coating matrix. Simultaneously, the modified nano-TiO2 and PHS synergistically optimize the oleophilic / hydrophilic compatibility of the microcapsules, enabling them to be uniformly dispersed in the coating without agglomeration. Furthermore, nano-TiO2 replaces traditional surfactants, eliminating migration risk and not affecting the mechanical properties and weather resistance of the coating, thus solving the technical pain points of poor dispersibility and weak bonding with the matrix in existing microcapsules. Detailed Implementation

[0034] To facilitate understanding of this application, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of this application.

[0035] This application provides a highly stable microcapsule, comprising the following raw materials in parts by weight:

[0036] 1-5 parts nano titanium dioxide, 0.1-1 parts oleic acid, 0.5-2 parts polyhydroxystearic acid, 45-55 parts hexadecane, 30-40 parts water, 1-5 parts active substance, 0.01-1 parts silane coupling agent, alcohol solvent, 1-5 parts Span, 0.5-2 parts polyethylene glycol.

[0037] Polyhydroxystearic acid (PHS), commercially available, CAS No.: 27924-99-8.

[0038] The active ingredient is a water-based polyurethane resin, which is commercially available.

[0039] The preferred silane coupling agent is KH-550.

[0040] Anhydrous ethanol is preferred as the alcohol solvent.

[0041] The preferred value for the span is span-80.

[0042] Furthermore, the amount of polyethylene glycol (PEG) added is preferably 15-25% of the mass of nano-titanium dioxide (TiO2).

[0043] Furthermore, the amount of KH-550 silane coupling agent added is 1-5% of the mass of nano-titanium dioxide (TiO2).

[0044] This application also provides an emulsification process for highly stable microcapsules, comprising the following steps:

[0045] Step 1: Preparation of PEG-modified TiO2, including the following steps:

[0046] Nano-titanium dioxide (TiO2) is dispersed in anhydrous ethanol to form a suspension with a concentration of 5-10%.

[0047] Add polyethylene glycol (PEG) to the suspension and ultrasonically disperse for 20-45 minutes.

[0048] Then, while stirring, slowly add the silane coupling agent dropwise, controlling the dropping rate to ensure uniform dispersion of the silane coupling agent. Continue stirring at room temperature for 2-4 hours to allow the silane coupling agent to fully react with the surface of nano-titanium dioxide (TiO2).

[0049] After the reaction was completed, the modified nano-titanium dioxide (TiO2) was separated by centrifugation. The nano-titanium dioxide (TiO2) was washed several times with anhydrous ethanol to remove unreacted silane coupling agent and polyethylene glycol (PEG). The washed nano-titanium dioxide (TiO2) was dried to constant weight in a vacuum drying oven to obtain PEG-modified TiO2.

[0050] Drying temperature: 35-45℃, drying time: 12-24 hours.

[0051] Step 2: Prepare oil phase A, including the following steps:

[0052] Add hexadecane to a beaker, and while stirring, slowly add PEG-modified TiO2, followed by polyhydroxystearic acid (PHS) and Span80. Turn on the ultrasonic disperser, set the power to 150-250W and the frequency to 18-23kHz, and ultrasonically disperse for 20-45 minutes to obtain a uniformly dispersed oil phase A.

[0053] Step 3: Oleic acid modification, including the following steps:

[0054] In the above oil phase A, oleic acid is slowly added dropwise, with the dropping rate controlled at 0.5-1.5 drops / second, and the mixture is stirred continuously for 15-45 minutes to allow the oleic acid to be fully adsorbed on the surface of the PEG-modified TiO2, thus obtaining oil phase B.

[0055] Step 4: Prepare the aqueous phase, including the following steps:

[0056] Add deionized water to another beaker, and while stirring, add the active substance (waterborne polyurethane resin). Stir for 20-45 minutes to ensure that the active substance is completely dissolved or uniformly dispersed in the water to obtain the aqueous phase.

[0057] Step 5: Emulsification:

[0058] The aqueous phase was slowly added to the oil phase B, and emulsification was performed using a high-shear dispersing emulsifier. The emulsification temperature was controlled at 20-30℃, the emulsification speed was set to 5500-6500 rpm, and the emulsification time was 20-45 minutes. Emulsion A was obtained.

[0059] Step 6: Ultrasonic-assisted emulsification:

[0060] Emulsion A was transferred to an ultrasonic reactor, and the ultrasonic waves were turned on at a power of 150-250W and a frequency of 18-23kHz. Ultrasonic emulsification was performed for 10-20 minutes to further refine the emulsion particle size, resulting in emulsion B.

[0061] Step 7: Drying:

[0062] Emulsion B was dried by freeze drying, with the pre-freezing temperature set to -45~-35℃, the drying temperature set to -30~-20℃, and the drying time set to 36-60 hours, to obtain highly stable microcapsules.

[0063] This application focuses on the Pickering emulsification properties of nano-TiO2 particles. Through multi-component modification and precise adaptation of process parameters, it achieves stable formation of water-in-oil emulsions, laying a solid foundation for microcapsule preparation. Specifically, the particles are first modified with polyethylene glycol (PEG). The hydrophilicity of PEG enhances its dispersibility in the aqueous phase, reducing particle agglomeration at the source. Subsequent oleic acid modification further optimizes its hydrophobic properties, enhancing its compatibility in the oil phase and creating key conditions for particle adsorption at the oil-water interface. Polyhydroxystearic acid (PHS), as a steric hindrance stabilizer, forms a specific interaction with the modified nano-TiO2. The hydroxyl groups in its molecular structure form hydrogen bonds or coordination bonds with the hydroxyl groups on the surface of PEG-modified TiO2, allowing PHS molecules to be firmly adsorbed onto the particle surface. The long-chain alkyl groups of PHS are well soluble in the hexadecane oil phase, forming a steric hindrance layer around the particles after adsorption, effectively preventing the PEG-modified TiO2 particles from approaching each other and agglomerating. The addition of γ-aminopropyltriethoxysilane (KH-550) provides supplementary modification. After hydrolysis of its ethoxysilane, it forms silanol groups, which undergo a condensation reaction with the hydroxyl groups on the surface of PEG-modified TiO2. Through Si-O-Si chemical bonds, KH-550 molecules are firmly connected to the particle surface, which not only enhances the structural stability of the particles themselves, but also helps to improve compatibility with coating systems.

[0064] At the process level, ultrasonic dispersion and high-shear emulsification work together. The cavitation effect of ultrasound helps to break the initial agglomerates of nano-TiO2 and promotes the uniform adsorption of PHS and KH-550 molecules on the particle surface. Combined with high-shear emulsification, the aqueous phase is dispersed into tiny droplets. Subsequent secondary ultrasonic-assisted emulsification further refines the emulsion particle size. The nano-TiO2 particles are orderly stacked at the oil-water interface to form a physical protective layer, preventing the dispersion droplets from coalescing.

[0065] Compared to traditional surfactants, nano-TiO2 particles are less prone to migration, avoiding interference with the performance of subsequent systems. Ultimately, through a multi-dimensional synergistic effect of "PEG modification + oleic acid modification + PHS steric hindrance + KH-550 chemical bonding + ultrasonic-high shear synergistic emulsification", the stability of water-in-oil emulsions is significantly improved.

[0066] The structural stability of the highly stable microcapsules benefits from the synergistic cooperation of multiple parties, jointly constructing a composite system that combines storage stability and responsiveness. Specifically, modified nano-TiO2 is orderly stacked at the oil-water interface to form a physically reinforced interfacial film, while PHS molecules fill the interparticle gaps, significantly improving the density of the wall material. The synergy of these two elements ensures that the wall material possesses suitable mechanical strength to withstand external impacts during preparation and storage, while also enabling precise rupture when the matrix is ​​damaged. This ensures efficient encapsulation of the core material while preventing premature leakage. KH-550 is firmly connected to the modified nano-TiO2 through Si-O-Si chemical bonds, further strengthening the bonding force between the nano-TiO2 and other components of the wall material, effectively preventing a loose wall structure and thus endowing the microcapsules with high stability.

[0067] Regarding the application of highly stable microcapsules in coatings:

[0068] In terms of dispersibility, the synergistic effect between PEG- and oleic acid-modified nano-TiO2 and PHS gives the microcapsules good compatibility, allowing them to be uniformly dispersed in the coating matrix, avoiding agglomeration and forming a self-healing response network.

[0069] In terms of stability, KH-550 plays a key bridging role. The amino groups in its molecules, anchored on the microcapsule wall material, can chemically react with coating resins (such as the epoxy groups of epoxy resins and the carboxyl groups of acrylic resins), strengthening the interfacial bonding between the microcapsules and the coating matrix through chemical bonding. This effectively prevents the microcapsules from peeling off from the matrix during use and ensures the overall mechanical properties of the coating.

[0070] In terms of functional synergy, it forms a dual effect of "self-healing + protective enhancement": when cracks occur on the coating surface, the microcapsules rupture to release the water-based polyurethane core material, which quickly forms a film at the crack and fills the gaps, thereby restoring the mechanical properties of the coating; the modified nano-TiO2 dispersed in the coating not only improves the wear resistance and weather resistance of the coating through its own characteristics, but its synergistic effect with PHS can also form a protective enhancement layer at the repair site, delaying the further expansion of cracks.

[0071] In addition, the non-migration property of nano-TiO2 avoids the negative impact that traditional surfactants may have on coating performance. The chemical bonding of KH-550 further enhances the structural stability of the coating system. The photocatalytic performance of nano-TiO2 can also decompose pollutants and aging substances on the coating surface, complementing the micro-defect repair function of the core material and synergistically extending the service life of the coating. Ultimately, it achieves multiple superpositions of self-repair, aging resistance and enhanced protection functions.

[0072] In addition, when microcracks develop in the coating, the nano-TiO2 interfacial film ruptures at the stress concentration point of the crack tip, releasing the encapsulated repair agent, which then penetrates to the crack tip via capillary action. Furthermore, the nano-TiO2 continues to provide UV shielding even after the microcapsules rupture. Upon microcapsule rupture, the nano-TiO2 may disperse around the crack or to other areas of the coating, forming a "localized high-concentration shielding zone." This zone absorbs / scatters UV radiation, reducing secondary aging damage and creating a synergistic "repair-shield" effect. Its amphiphilic interface ensures compatibility with the coating base, maintaining uniform dispersion and preventing agglomeration failure.

[0073] The present application will be further described below through specific embodiments.

[0074] Example 1

[0075] A highly stable microcapsule comprises the following raw materials:

[0076] 4kg nano titanium dioxide, 0.4kg oleic acid, 0.6kg polyhydroxystearic acid, 50kg hexadecane, 35kg water, 3kg active material, 0.08kg silane coupling agent, anhydrous ethanol, 2kg Span, 0.8kg polyethylene glycol.

[0077] Polyhydroxystearic acid (PHS), commercially available, CAS No.: 27924-99-8.

[0078] The active ingredient is a water-based polyurethane resin, which is commercially available.

[0079] The silane coupling agent is KH-550.

[0080] The strategist's value is strategist -80.

[0081] This application also provides an emulsification process for highly stable microcapsules, comprising the following steps:

[0082] Step 1: Preparation of PEG-modified TiO2, including the following steps:

[0083] Nano-titanium dioxide (TiO2) was dispersed in anhydrous ethanol to form a suspension with a concentration of 8%.

[0084] Add polyethylene glycol (PEG) to the suspension and ultrasonically disperse for 30 minutes.

[0085] Then, while stirring, the silane coupling agent was slowly added dropwise, controlling the dropping rate to ensure uniform dispersion of the silane coupling agent. Stirring was continued at room temperature for 3 hours to allow the silane coupling agent to fully react with the surface of nano-titanium dioxide (TiO2).

[0086] After the reaction was completed, the modified nano-titanium dioxide (TiO2) was separated by centrifugation. The modified nano-titanium dioxide (TiO2) was washed three times with anhydrous ethanol to remove unreacted silane coupling agent and polyethylene glycol (PEG). The washed product was dried to constant weight in a vacuum drying oven to obtain PEG-modified TiO2.

[0087] Drying temperature: 40℃, drying time: 18 hours.

[0088] Step 2: Prepare oil phase A, including the following steps:

[0089] Add hexadecane to a beaker, and while stirring, slowly add PEG-modified TiO2, followed by polyhydroxystearic acid (PHS) and Span80. Turn on the ultrasonic disperser, set the power to 200W and the frequency to 20kHz, and ultrasonically disperse for 30 minutes to obtain a uniformly dispersed oil phase A.

[0090] Step 3: Oleic acid modification, including the following steps:

[0091] In the above oil phase, oleic acid is slowly added dropwise at a rate of 1 drop / second, and the mixture is stirred continuously for 30 minutes to allow the oleic acid to be fully adsorbed onto the PEG-modified TiO2 surface, thus obtaining oil phase B.

[0092] Step 4: Prepare the aqueous phase, including the following steps:

[0093] Add deionized water to another beaker, and while stirring, add the active substance (waterborne polyurethane resin). Stir for 30 minutes to ensure that the active substance is completely dissolved or uniformly dispersed in the water to obtain the aqueous phase.

[0094] Step 5: Emulsification:

[0095] The aqueous phase was slowly added to the oil phase B, and emulsification was performed using a high-shear dispersing emulsifier. The emulsification temperature was controlled at 25℃, the emulsification speed was set to 6000 rpm, and the emulsification time was 30 minutes. Emulsion A was obtained.

[0096] Step 6: Ultrasonic-assisted emulsification:

[0097] Emulsion A was transferred to an ultrasonic reactor, and the ultrasonic waves were turned on at a power of 200W and a frequency of 20kHz. Ultrasonic emulsification was performed for 15 minutes to further refine the emulsion particle size, resulting in emulsion B.

[0098] Step 7: Drying:

[0099] Emulsion B was dried by freeze-drying, with the pre-freezing temperature set at -40℃, the drying temperature set at -25℃, and the drying time set at 48 hours, to obtain highly stable microcapsules.

[0100] Performance testing:

[0101] 1. Encapsulation efficiency: The encapsulation efficiency of the high-stability microcapsules was determined using ultraviolet-visible spectrophotometry. A certain amount of high-stability microcapsules were dissolved in ethanol and sonicated for 30 minutes to break them down and completely release the active substances. The content of the active substances was then calculated, and the encapsulation efficiency of the high-stability microcapsules was calculated according to the following formula.

[0102] Encapsulation efficiency = (Actual content of active substance in microcapsules / Theoretical content of active substance in microcapsules) × 100%

[0103] Test results: Encapsulation rate: 82%.

[0104] 2. Storage stability of microcapsules: The highly stable microcapsules were stored at 45℃ and 90% humidity for 14 days. After being removed, the encapsulation efficiency was measured again.

[0105] Test results: Encapsulation rate: 80%.

[0106] 3. Dispersion stability: High-stability microcapsules were added to the water-based acrylic coating base (solid content 40%), and the amount of high-stability microcapsules added was 5 wt% of the coating base.

[0107] High-stability microcapsules were dispersed into the coating base using a high-speed disperser at a speed of 2000 rpm for 15 minutes.

[0108] The dispersed coating was left to stand for 60 days, and the layering of the coating was observed.

[0109] The stratification status is divided into: no stratification, slight stratification, obvious stratification, and severe stratification.

[0110] Test results: No stratification.

[0111] 4. Self-healing effect: Highly stable microcapsules are added to water-based acrylic coatings and mixed with film-forming agents and other additives to prepare the coating. After the coating is applied and dried, a coating layer is obtained.

[0112] Scratches are created on the coating surface, with a depth of 0.1 mm and a width of 0.3 mm.

[0113] The scratched coating was placed in an environment of 25°C and UV intensity level 3 for 48 hours. The degree of repair of the scratches was then observed using an optical microscope, and the width of the scratches was measured.

[0114] Self-repair rate (%) = (Initial scratch width - Repaired scratch width) / Initial scratch width × 100%

[0115] Test result: 85%.

[0116] Based on the above test results, the high-stability microcapsules prepared in this application exhibit high encapsulation efficiency and good weather resistance, maintaining a high encapsulation efficiency even after high-temperature and high-humidity storage. When applied to coatings, the high-stability microcapsules show no stratification, excellent dispersibility, and good self-healing properties, demonstrating excellent performance in all aspects.

[0117] Comparative Example 1

[0118] Microcapsules with commercially available waterborne polyurethane resin as the core material were used as Comparative Example 1 for performance testing.

[0119] Test results:

[0120] 1. Dispersion stability: slight stratification.

[0121] 2. Self-repair effect: 68%.

[0122] Comparative Example 2

[0123] Replace nano titanium dioxide with commercially available nano silicon dioxide; the rest remains the same and will not be described in detail here.

[0124] Test results:

[0125] 1. Encapsulation rate: 72%.

[0126] 2. Storage stability of microcapsules: 65%.

[0127] 3. Dispersion stability: slight stratification.

[0128] 4. Self-repair effect: 73%.

[0129] Replacing nano-titanium dioxide with commercially available nano-silica resulted in particle agglomeration leading to uneven wall material, and poor interfacial compatibility resulting in poor encapsulation. This is because the modification in this application is achieved through a subtle and specific combination of raw materials; if the modification is inappropriate, the particle surface remains hydrophilic, easily agglomerating into large particles in the hydrophobic hexadecane oil phase, failing to disperse uniformly in the oil phase, and thus failing to effectively encapsulate the aqueous phase active material. Some active material is exposed outside the oil phase and will be washed or lost during subsequent drying and testing. During the preparation of highly stable microcapsules, if the hydrophilic-hydrophobic balance is disrupted (either becoming too hydrophilic or too hydrophobic), the interfacial tension with the aqueous phase (waterborne polyurethane) becomes too high, preventing the formation of a stable water-in-oil structure during emulsification. The aqueous phase droplets easily fuse and break, the active material is not encapsulated, and the encapsulation rate drops significantly.

[0130] It should be understood that the application of this application is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of this application.

Claims

1. An emulsification process for highly stable microcapsules, characterized in that, The following raw materials are included in the preparation according to parts by weight: 1-5 parts nano titanium dioxide, 0.1-1 parts oleic acid, 0.5-2 parts polyhydroxystearic acid, 45-55 parts hexadecane, 30-40 parts water, 1-5 parts active substance, 0.01-1 parts silane coupling agent, alcohol solvent, 1-5 parts Span, 0.5-2 parts polyethylene glycol; The emulsification process of the highly stable microcapsules includes the following steps: PEG-modified TiO2 was obtained by modifying nano-titanium dioxide with polyethylene glycol and silane coupling agent. Hexadecane, PEG-modified TiO2, polyhydroxystearic acid, and Span were ultrasonically mixed to obtain oil phase A; Oil phase A and oleic acid react to yield oil phase B; Water and active substances are mixed to obtain an aqueous phase; The aqueous phase is added to the oil phase B for emulsification. The emulsification temperature is 20-30℃, the emulsification speed is 5500-6500 rpm, and the emulsification time is 20-45 minutes to obtain emulsion A. Emulsion A was freeze-dried to obtain highly stable microcapsules; The preparation of PEG-modified TiO2 includes the following steps: Nano-titanium dioxide is mixed with an alcohol solvent to obtain a suspension; The suspension and polyethylene glycol are dispersed and mixed, and then a silane coupling agent is added and stirred to react. After the reaction was completed, the product was centrifuged, washed, and dried to obtain PEG-modified TiO2.

2. The emulsification process for the highly stable microcapsules according to claim 1, characterized in that, The active material includes waterborne polyurethane resin.

3. The emulsification process for the highly stable microcapsules according to claim 1, characterized in that, Silane coupling agents include KH-550; The strategist includes the strategist-80.

4. The emulsification process for the highly stable microcapsules according to claim 1, characterized in that, The preparation of oil phase A includes the following steps: Under stirring, PEG-modified TiO2 is added and mixed with hexadecane, followed by the addition of polyhydroxystearic acid and Span. The mixture is then ultrasonically dispersed for 20-45 minutes at a power of 150-250W and a frequency of 18-23kHz to obtain oil phase A.

5. The emulsification process for the highly stable microcapsules according to claim 1, characterized in that, The oil phase A and oleic acid are mixed by adding oleic acid dropwise to oil phase A at a rate of 0.5-1.5 drops / second and stirring continuously for 15-45 minutes.

6. The emulsification process for the highly stable microcapsules according to claim 1, characterized in that, Emulsion A is ultrasonically emulsified for 10-20 minutes at a power of 150-250W and a frequency of 18-23kHz to obtain emulsion B, which is then freeze-dried.

7. The emulsification process for the highly stable microcapsules according to claim 1, characterized in that, The amount of polyethylene glycol added is 15-25% of the mass of nano-titanium dioxide; The amount of silane coupling agent added is 1-5% of the mass of nano-titanium dioxide.

8. A highly stable microcapsule obtained by an emulsification process based on the highly stable microcapsules according to any one of claims 1-7.

9. An application of the highly stable microcapsules according to claim 8 in coatings.