Highly corrosion-resistant waterborne silane-nano zirconium oxide composite sealer and preparation method thereof

Abstract

The present application relates to high corrosion-resistant water-based silane-nano zirconium oxide composite sealant and its preparation method, including the following components by weight fraction: silane coupling agent 10-25 parts; nano zirconium oxide 1-5 parts; citric acid 0.5-2 parts; the present application builds the double-wall microcapsule structure of inner wall coating corrosion inhibitor and outer wall loading zirconium oxychloride, solves the problem that the existing sealant is corroded rapidly spread after the coating is damaged, when the coating produces microcracks, the double-wall microcapsule responds and breaks, the corrosion inhibitor and zirconium ion cooperate to generate a mixed passivation film in situ on the metal surface, which significantly improves the corrosion resistance and service life of the coating; the silanol groups generated by the hydrolysis of silane prepolymer can be chemically bonded with the hydroxyl groups on the metal surface to form stable Si-O-metal covalent bonds, and the introduction of crosslinking agent further constructs a three-dimensional crosslinked network, which greatly enhances the bonding strength of the sealing layer and the substrate.

Description

Technical Field

[0001] This invention relates to the field of metal surface technology, and in particular to a highly corrosion-resistant waterborne silane-nanozirconia composite sealant and its preparation method. Background Technology

[0002] Metallic materials are widely used in industrial production, construction, automobiles, aerospace, and other fields. However, most metals are prone to corrosion in complex environments such as humidity, acids, alkalis, and salt spray, leading to a decline in material performance, a shortened service life, and even safety hazards and economic losses. To inhibit metal corrosion, surface sealing treatment is one of the most common, economical, and effective technical means. Its core is to form a dense and stable protective film on the metal surface, isolating the corrosive medium from contact with the metal substrate, thereby achieving the purpose of corrosion prevention.

[0003] Currently, commonly used metal sealants in industry mainly include chromates, phosphates, and organic coatings. Among them, chromate sealants have excellent anti-corrosion effects, but hexavalent chromium is highly toxic and carcinogenic, seriously polluting the environment and endangering human health, and its use has been restricted or banned in many countries. Although phosphate sealants have improved environmental friendliness, the protective film they form is not dense enough and has limited corrosion resistance, making it difficult to meet the needs of use in complex and harsh environments. Traditional organic coating sealants have good film-forming properties, but their adhesion to the metal substrate is poor, and they are prone to problems such as peeling and cracking, resulting in poor long-term anti-corrosion effects. Therefore, a highly corrosion-resistant waterborne silane-nanozirconia composite sealant and its preparation method are proposed to solve this problem. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides the following technical solution: On the one hand, a highly corrosion-resistant waterborne silane-nanozirconia composite sealant is provided. The following components are included by weight: 10-25 parts of silane coupling agent; 1-5 parts of nano-zirconia; Citric acid 0.5-2 parts; Double-walled microcapsules, 1-4 parts; Crosslinking accelerator 0.5-3 parts; 2-8 parts of water-based film-forming aid.

[0005] As an improvement to the above technical solution, the silane coupling agent is selected from one or more of γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and vinyltrimethoxysilane.

[0006] As an improvement to the above technical solution, the particle size of the nano-zirconia is 10-80 nm.

[0007] As an improvement to the above technical solution, the crosslinking accelerator is tetraethyl orthosilicate or tetrabutyl titanate, and the aqueous film-forming aid is propylene glycol methyl ether or dipropylene glycol butyl ether.

[0008] As an improvement to the above technical solution, the double-walled microcapsule comprises the following components by weight: 1-5 parts corrosion inhibitor; 10-30 parts urea-formaldehyde resin prepolymer; 2-10 parts zirconium oxychloride; and 50-150 parts deionized water.

[0009] As an improvement to the above technical solution, the corrosion inhibitor is benzotriazole or cerium nitrate.

[0010] As an improvement to the above technical solution, the preparation method of the double-walled microcapsules includes the following steps: Preparation of S1 inner wall microcapsules: Dissolve 1-5 parts of corrosion inhibitor in 50-150 parts of deionized water, add urea-formaldehyde resin prepolymer, and react by in-situ polymerization at 50-60℃ and stirring rate of 300-500 rpm for 2-4 h to obtain microcapsules with corrosion inhibitor coated on the inner wall. Filter, wash and dry for later use. S2 outer wall loading: The microcapsules were dispersed in a 5-10 wt.% aqueous solution prepared from 2-10 parts of zirconium oxychloride, the pH was adjusted to 3-4 with hydrochloric acid, and the mixture was stirred at room temperature for 2-4 h to allow zirconium oxychloride to be adsorbed onto the surface of the microcapsules. The mixture was then filtered and dried under vacuum at 40-50℃ to obtain double-walled microcapsules with zirconium oxychloride loaded on the outer wall.

[0011] On the other hand, a method for preparing a highly corrosion-resistant waterborne silane-nanozirconia composite sealant is provided, comprising the following steps: Preparation of S1 modified nano-zirconia dispersion: Add 0.5-2 parts of citric acid to 15-30 parts of deionized water, adjust the pH to 3-5, add 1-5 parts of nano-zirconia, and ultrasonically disperse for 30-60 min to obtain modified nano-zirconia dispersion. Preparation of S2 silane hydrolysate: Add 10-25 parts of silane coupling agent to 25-50 parts of deionized water, adjust the pH to 4.0-5.0, and hydrolyze at 35-45℃ for 1-2 h to obtain silane hydrolysate; Addition of S3 crosslinking accelerator: Cool the silane hydrolysate to 25-30℃, add 0.5-3 parts of crosslinking accelerator while stirring, and continue stirring for 15-30 min to obtain silane prepolymer containing crosslinking agent; Preparation of S4 composite sealant base liquid: Modified nano-zirconia dispersion was slowly added to silane prepolymer, pH was adjusted to 4.5-5.5, and the reaction was continued at 30-40℃ for 6-12 h to obtain composite sealant base liquid; Addition of S5 film-forming aid: Cool the composite blocking agent base liquid to room temperature, add 2-8 parts of water-based film-forming aid, and stir evenly; Addition of S6 double-walled microcapsules: Add 1-4 parts of double-walled microcapsules, stir evenly, and filter through a 200-400 mesh filter to obtain silane-nanozirconia composite sealing agent.

[0012] The beneficial effects of this invention are: By constructing a double-walled microcapsule structure with an inner wall coated with corrosion inhibitor and an outer wall loaded with zirconium oxychloride, the problem of rapid corrosion spread after coating damage was solved by existing sealants. When microcracks are generated in the coating, the double-walled microcapsules rupture in response, and the corrosion inhibitor and zirconium ions synergistically generate a mixed passivation film in situ on the metal surface, which significantly improves the corrosion resistance and service life of the coating. The silanol groups generated after the hydrolysis of silane prepolymer can chemically bond with the hydroxyl groups on the metal surface to form stable Si-O-metal covalent bonds. At the same time, the introduction of crosslinking agent further constructs a three-dimensional crosslinking network, which greatly enhances the bonding strength between the sealing layer and the substrate. Meanwhile, the citric acid-modified nano-zirconia is uniformly dispersed in the silane prepolymer, effectively filling the micropore defects inside the coating and forming an interpenetrating structure with the silane network, which significantly improves the density and cohesive strength of the sealing layer. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0014] Unless otherwise specified, the main components involved in the following embodiments of this application are all purchased from commercially available products.

[0015] This application employs a double-walled microcapsule structure with an inner wall coated with a corrosion inhibitor and an outer wall loaded with zirconium oxychloride. When the coating is intact, the microcapsules are uniformly dispersed within the sealing layer. The rigid urea-formaldehyde resin wall material provides a certain physical barrier. When the coating develops microcracks due to mechanical damage or environmental stress, corrosive media (water, chloride ions, oxygen) penetrate along the defects and come into contact with the microcapsules. Under acidic or ionic stimulation, the urea-formaldehyde resin wall material ruptures, releasing the benzotriazole corrosion inhibitor coated on the inner wall. This inhibitor molecules form coordination bonds with the exposed metal surface through nitrogen atoms, rapidly adsorbing and forming a dense chemical adsorption film or precipitate film, effectively blocking anodic dissolution and cathodic reduction reactions, thereby significantly reducing the corrosion current density and shifting the corrosion potential positively. Simultaneously, the zirconium oxychloride loaded on the outer wall hydrolyzes in the corrosive microenvironment, releasing zirconium ions (ZrO₂). 2+ or Zr 4+These zirconium ions, together with corrosion inhibitor molecules, form a mixed passivation film (such as Zr-O-Fe or zirconium-corrosion inhibitor complex) on the metal surface, further improving the density and stability of the protective film; The composite sealing agent base solution is formed by reacting citric acid-modified nano-zirconia dispersion with a silane prepolymer containing a crosslinking agent to form a bilayer network structure. The silane coupling agent is hydrolyzed to generate silanol groups, which form hydrogen bonds with hydroxyl groups on the metal surface, subsequently condensing to form Si-O-metal covalent bonds, thus significantly improving the adhesion between the sealing layer and the substrate. The introduction of crosslinking agents (tetrabutyl orthosilicate, tetrabutyl titanate) further constructs a three-dimensional Si-O-Si or Si-O-Ti network, increasing the crosslinking density and reducing microporous defects within the coating. After citric acid modification, the nano-zirconia has active groups such as carboxyl or hydroxyl groups introduced onto its surface, enabling it to chemically bond or hydrogen bond with the silanol or epoxy groups in the silane prepolymer, effectively preventing nanoparticle aggregation. The uniformly dispersed nano-zirconia particles fill... The micropores of the silane network form a dense organic-inorganic hybrid structure, which significantly extends the diffusion path of corrosive media and improves the barrier performance of the sealing layer. In addition, the modified nano-zirconia and silane prepolymer react for a long time at an appropriate temperature to form an interpenetrating network or core-shell structure, which significantly improves the cohesive strength of the sealing layer. This is also the reason why all examples can withstand high impact resistance tests. When the coating is intact, the silane-nano-zirconia bilayer network provides a physical barrier with high adhesion and high density through chemical bonding and nanofilling, effectively isolating the intrusion of external corrosive media. When the coating is damaged, the double-walled microcapsules responsively release corrosion inhibitors and zirconium ions. The two work together to generate a mixed passivation film in situ on the exposed metal surface, realizing the active protection of the coating.

[0016] Example 1

[0017] Preparation method of double-walled microcapsules: Dissolve 3 kg of benzotriazole in 100 kg of deionized water, add 20 kg of urea-formaldehyde resin prepolymer, and react in situ at 55 °C and 400 rpm for 3 h to obtain microcapsules with corrosion inhibitors on the inner wall. Filter, wash and dry for later use. The microcapsules were dispersed in a 7.5 wt.% aqueous solution prepared from 6 kg of zirconium oxychloride, the pH was adjusted to 3.5 with hydrochloric acid, and the mixture was stirred at room temperature for 3 h to allow zirconium oxychloride to be adsorbed onto the surface of the microcapsules. The mixture was then filtered and dried under vacuum at 45 °C to obtain double-walled microcapsules with zirconium oxychloride loaded on the outer wall, which were then set aside for later use. The preparation method of the composite sealant is as follows: 1.25 kg of citric acid was added to 22.5 kg of deionized water, the pH was adjusted to 4.0, 3 kg of 45 nm nano-zirconia was added, and the mixture was ultrasonically dispersed for 45 min to obtain a modified nano-zirconia dispersion; 17.5 kg of γ-glycidoxypropyltrimethoxysilane was added to 37.5 kg of deionized water, the pH was adjusted to 4.5, and the mixture was hydrolyzed at 40 °C for 1.5 h to obtain a silane hydrolysate; The silane hydrolysate was cooled to about 27°C, and 1.75 kg of tetraethyl orthosilicate was added while stirring. Stirring was continued for 22 min to obtain a silane prepolymer containing a crosslinking agent. The modified nano-zirconia dispersion was slowly added to the silane prepolymer, the pH was adjusted to 5.0, and the reaction was continued at 35℃ for 9 hours to obtain the composite blocking agent base liquid. Cool the composite sealant base liquid to room temperature, add 5 kg of propylene glycol methyl ether, and stir evenly; add 2.5 kg of the prepared double-walled microcapsules, stir evenly, and filter through a 300-mesh filter to obtain the high corrosion-resistant waterborne silane-nanozirconia composite sealant of this embodiment. Example 2

[0018] The preparation method of the double-walled microcapsules is as follows: 1 kg of cerium nitrate is dissolved in 50 kg of deionized water, and 10 kg of urea-formaldehyde resin prepolymer is added. The mixture is reacted by in-situ polymerization at 50 °C and a stirring rate of 300 rpm for 2 h to obtain microcapsules with corrosion inhibitors coated on the inner wall. The microcapsules are then filtered, washed, and dried for later use. The microcapsules are dispersed in a 5 wt.% aqueous solution prepared from 2 kg of zirconium oxychloride, and the pH is adjusted to 3.0 with hydrochloric acid. The mixture is stirred at room temperature for 2 h to allow zirconium oxychloride to be adsorbed onto the surface of the microcapsules. The mixture is then filtered and vacuum dried at 40 °C to obtain double-walled microcapsules with zirconium oxychloride loaded on the outer wall for later use. The preparation method of the composite blocking agent is as follows: 0.5 kg of citric acid is added to 15 kg of deionized water, the pH is adjusted to 3.0, 1 kg of nano-zirconia with a particle size of 10 nm is added, and ultrasonic dispersion is carried out for 30 min to obtain modified nano-zirconia dispersion; 10 kg of γ-aminopropyltriethoxysilane is added to 25 kg of deionized water, the pH is adjusted to 4.0, and hydrolysis is carried out at 35 °C for 1 h to obtain silane hydrolysate; the silane hydrolysate is cooled to 25 °C, and 0.5 kg of tetrabutyl titanate is added under stirring, and stirring is continued for 15 min to obtain silane prepolymer containing crosslinking agent; The modified nano-zirconia dispersion was slowly added to the silane prepolymer, the pH was adjusted to 4.5, and the reaction was continued at 30°C for 6 hours to obtain the composite blocking agent base liquid. Cool the composite sealant base liquid to room temperature, add 2 kg of dipropylene glycol butyl ether, and stir evenly; add 1 kg of the above-prepared double-walled microcapsules, stir evenly, and filter through a 200-mesh filter to obtain the high corrosion-resistant waterborne silane-nanozirconia composite sealant of this embodiment. Example 3

[0019] The preparation method of double-walled microcapsules is as follows: 5 kg of benzotriazole was dissolved in 150 kg of deionized water, and 30 kg of urea-formaldehyde resin prepolymer was added. The mixture was reacted by in-situ polymerization at 60 °C and a stirring rate of 500 rpm for 4 h to obtain microcapsules with corrosion inhibitors coated on the inner wall. The microcapsules were filtered, washed, and dried for later use. The above microcapsules were dispersed in a 10 wt.% aqueous solution prepared from 10 kg of zirconium oxychloride. The pH was adjusted to 4.0 with hydrochloric acid, and the mixture was stirred at room temperature for 4 h to allow zirconium oxychloride to be adsorbed onto the surface of the microcapsules. The mixture was filtered, and vacuum dried at 50 °C to obtain double-walled microcapsules with zirconium oxychloride loaded on the outer wall for later use. The preparation method of the composite sealant is as follows: 2 kg of citric acid is added to 30 kg of deionized water, the pH is adjusted to 5.0, 5 kg of nano-zirconia with a particle size of 80 nm is added, and ultrasonic dispersion is carried out for 60 min to obtain modified nano-zirconia dispersion. 25 kg of mixed silane coupling agent (vinyltrimethoxysilane and γ-aminopropyltriethoxysilane mixed in a 1:1 ratio) was added to 50 kg of deionized water, the pH was adjusted to 5.0, and hydrolyzed at 45 °C for 2 h to obtain silane hydrolysate; The silane hydrolysate was cooled to 30°C, and 3 kg of mixed crosslinking accelerator (a 2:1 mixture of tetrabutyl orthosilicate and tetrabutyl titanate) was added under stirring. Stirring was continued for 30 min to obtain a silane prepolymer containing the crosslinking agent. The modified nano-zirconia dispersion was slowly added to the silane prepolymer, the pH was adjusted to 5.5, and the reaction was continued at 40℃ for 12 hours to obtain the composite blocking agent base liquid. Cool the composite sealing agent base liquid to room temperature, add 8 kg of mixed aqueous film-forming aid (propylene glycol methyl ether and dipropylene glycol butyl ether mixed in a 3:1 ratio), and stir evenly. Addition of double-walled microcapsules: Add 4 kg of the prepared double-walled microcapsules, stir evenly, and filter through a 400-mesh filter to obtain the high corrosion-resistant waterborne silane-nanozirconia composite sealant of this embodiment. Comparative Example 1 The difference from Example 1 is that double-walled microcapsules are not added, while other conditions are the same as in Example 1; Comparative Example 2 The difference from Example 1 is that the nano-zirconia was not modified with citric acid, while the other conditions were the same as in Example 1; Comparative Example 3 The difference from Example 1 is that the microcapsules are ordinary single-walled microcapsules (coated only with benzotriazole, without an outer layer of zirconium chloride). Preparation of single-walled microcapsules: 3 kg of benzotriazole was dissolved in 100 kg of deionized water, 20 kg of urea-formaldehyde resin prepolymer was added, the reaction was carried out at 55 °C for 3 h, filtered and dried, and other conditions were the same as in Example 1. Performance testing Sealing layer adhesion test: According to GB / T9286-2021 standard, an adhesion test was conducted on the sealing layer using an adhesion cross-cut test board. Eleven intersecting scratches with a 1mm spacing were made on the paint film surface, forming 100 squares. Transparent tape was then adhered to the scratched surface and quickly peeled off at a 45°-60° angle. The extent of paint film peeling off the squares was observed. According to the standard, the best result is grade 0, with completely smooth cut edges and no paint film peeling off the squares. The worst result is grade 5, with paint film peeling exceeding 65%. Corrosion resistance test: Following GB / T40299-2021 "Corrosion of Metals and Alloys - Electrochemical Measurement Methods for Corrosion Testing - Applicable Conventions", a three-electrode system was used. A self-prepared water-based zinc-plated sealing layer was used as the working electrode, a 1cm diameter Pt electrode as the counter electrode, and a saturated calomel electrode as the reference electrode. The auxiliary platinum electrode was aligned parallel to the working electrode to ensure a uniform current distribution around the electrode. The reference electrode was always immersed in the bulk solution to reduce the voltage. The corrosion current and corrosion voltage were tested. Impact resistance test: The impact resistance of the coating is tested using a paint film impact tester according to GB / T1732-1993 standard. The coating is placed face up on a base, and the impact hammer is raised to a certain height and dropped freely. The coating surface is observed for any damage or other defects. For reverse impact, the coating is placed face down, and the remaining steps are the same as for forward impact. Multiple tests are performed, and the average value is taken. It is required that the impact point not fall within 10cm of the coating edge, and the distance between each impact point should not be less than 10cm to prevent experimental errors. Self-healing test: A scratch was made on the sealing layer with a sharp knife, and then the sample was placed in a salt spray chamber. The sealing layer was divided into three groups: the original sample, the sample marked with the surface scratch (damaged sample), and the sample marked after self-healing (repaired sample). Electrochemical impedance spectroscopy was performed using an electrochemical workstation to analyze the self-healing performance. A three-electrode system was used, with a tinplate plate coated with the sealing layer as the working electrode, a saturated calomel electrode as the reference electrode, and a graphite rod as the counter electrode. The electrolyte solution was a solution containing 3.5% NaCl. The frequency range of the test was 10⁻² Hz to 10⁵ Hz. The highly corrosion-resistant waterborne silane-nanozirconia composite sealant prepared in Example 13 and Comparative Example 13 was applied to the surface of a metal plate and its performance was tested. The results are shown in Table 1. Table 1 As shown in Table 1, Examples 1-3 containing double-walled microcapsules have a much lower corrosion current density than Comparative Example 1 which does not contain microcapsules, and a significantly higher corrosion potential than Comparative Example 1. This indicates that the benzotriazole corrosion inhibitor encapsulated in the double-walled microcapsules can be effectively released when the coating is damaged, forming a protective adsorption film on the metal surface, inhibiting the corrosion reaction, and exhibiting excellent active protection capabilities. In contrast, Comparative Example 1, lacking microcapsules, cannot provide immediate passivation protection after damage and has the worst corrosion resistance. Comparing Example 1 with Comparative Example 3 (ordinary single-walled microcapsules), it can be seen that the corrosion current density of Example 1 is lower than that of Comparative Example 3, the corrosion potential is higher than that of Comparative Example 3, and the adhesion and impact resistance (50 / 50) of Example 1 are both better. This indicates that the zirconium oxychloride loaded on the outer wall can not only form a stronger interfacial bond with the silane sealing layer, improving adhesion and density, but also have a synergistic effect with the corrosion inhibitor on the inner wall, further improving the anti-corrosion effect. Example 1 showed an adhesion grade of 0 and an impact resistance of 50 / 50 cm, both of which were better than Comparative Example 2. This indicates that citric acid modification can improve the dispersion uniformity of nano-zirconia in the sealant, reduce agglomeration, and thus obtain a denser sealant layer with higher mechanical strength. These data indicate that the synergistic design of double-walled microcapsules and silane-nanozirconia composite sealants can produce a water-based sealing layer with excellent adhesion, high impact resistance and outstanding corrosion resistance, and the self-healing function can significantly extend the protective life of the coating.

[0020] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A highly corrosion-resistant water-based silane-nanozirconia composite sealant, characterized in that, The following components are included by weight: 10-25 parts of silane coupling agent; 1-5 parts of nano-zirconia; Citric acid 0.5-2 parts; Double-walled microcapsules, 1-4 parts; Crosslinking accelerator 0.5-3 parts; 2-8 parts of water-based film-forming aid.

2. The highly corrosion-resistant waterborne silane-nanozirconia composite sealant according to claim 1, characterized in that: The silane coupling agent is selected from one or more of γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and vinyltrimethoxysilane.

3. The highly corrosion-resistant waterborne silane-nanozirconia composite sealant according to claim 1, characterized in that: The nano-zirconia has a particle size of 10-80 nm.

4. The highly corrosion-resistant waterborne silane-nanozirconia composite sealant according to claim 1, characterized in that: The crosslinking accelerator is tetraethyl orthosilicate or tetrabutyl titanate, and the aqueous film-forming aid is propylene glycol methyl ether or dipropylene glycol butyl ether.

5. The highly corrosion-resistant waterborne silane-nanozirconia composite sealant according to claim 1, characterized in that: The double-walled microcapsules comprise the following components by weight: 1-5 parts corrosion inhibitor; 10-30 parts urea-formaldehyde resin prepolymer; 2-10 parts zirconium oxychloride; and 50-150 parts deionized water.

6. The highly corrosion-resistant waterborne silane-nanozirconia composite sealant according to claim 5, characterized in that: The corrosion inhibitor is benzotriazole or cerium nitrate.

7. The highly corrosion-resistant waterborne silane-nanozirconia composite sealant according to claim 6, characterized in that: The preparation method of the double-walled microcapsules includes the following steps: Preparation of S1 inner wall microcapsules: Dissolve 1-5 parts of corrosion inhibitor in 50-150 parts of deionized water, add urea-formaldehyde resin prepolymer, and react by in-situ polymerization at 50-60℃ and stirring rate of 300-500 rpm for 2-4 h to obtain microcapsules with corrosion inhibitor coated on the inner wall. Filter, wash and dry for later use. S2 outer wall loading: The microcapsules were dispersed in a 5-10 wt.% aqueous solution prepared from 2-10 parts of zirconium oxychloride, the pH was adjusted to 3-4 with hydrochloric acid, and the mixture was stirred at room temperature for 2-4 h to allow zirconium oxychloride to be adsorbed onto the surface of the microcapsules. The mixture was then filtered and dried under vacuum at 40-50℃ to obtain double-walled microcapsules with zirconium oxychloride loaded on the outer wall.

8. A method for preparing a highly corrosion-resistant waterborne silane-nanozirconia composite sealant as described in any one of claims 1 to 7, characterized in that: Includes the following steps: Preparation of S1 modified nano-zirconia dispersion: Add 0.5-2 parts of citric acid to 15-30 parts of deionized water, adjust the pH to 3-5, add 1-5 parts of nano-zirconia, and ultrasonically disperse for 30-60 min to obtain modified nano-zirconia dispersion. Preparation of S2 silane hydrolysate: Add 10-25 parts of silane coupling agent to 25-50 parts of deionized water, adjust the pH to 4.0-5.0, and hydrolyze at 35-45℃ for 1-2 h to obtain silane hydrolysate; Addition of S3 crosslinking accelerator: Cool the silane hydrolysate to 25-30℃, add 0.5-3 parts of crosslinking accelerator while stirring, and continue stirring for 15-30 min to obtain silane prepolymer containing crosslinking agent; Preparation of S4 composite sealant base liquid: Modified nano-zirconia dispersion was slowly added to silane prepolymer, pH was adjusted to 4.5-5.5, and the reaction was continued at 30-40℃ for 6-12 h to obtain composite sealant base liquid; Addition of S5 film-forming aid: Cool the composite blocking agent base liquid to room temperature, add 2-8 parts of water-based film-forming aid, and stir evenly; Addition of S6 double-walled microcapsules: Add 1-4 parts of double-walled microcapsules, stir evenly, and filter through a 200-400 mesh filter to obtain silane-nanozirconia composite sealing agent.

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