Waterproof and antirust synergistic interaction method of high-elasticity reflective thermal insulation coating

Abstract

The invention relates to the technical field of coatings, and discloses a waterproof and antirust synergistic interaction method of a high-elasticity reflective thermal insulation coating. According to the method, core resin is prepared through emulsion polymerization, and monomers of the core resin comprise a silane monomer and N-vinyl imidazole; and blending the resin emulsion with a functional filler containing a photothermal conversion agent and a metal salt solution. According to the invention, a dual-network synergistic structure is constructed in the coating; a Si-O-Si covalent network ensures high adhesion to a base material and basic waterproofness; the metal imidazole dynamic coordination network endows the coating with high elasticity and self-repairing ability. The photothermal conversion agent absorbs light energy and converts the light energy into heat energy, dynamic network recombination can be accelerated, and rapid repair of scratches is achieved. When the coating is damaged, the dynamic network can responsively release corrosion inhibition ions, and a chemical passivation layer is formed on the surface of the metal base material to inhibit corrosion. The coating prepared by the invention has the functions of high elasticity, strong adhesive force, low water absorption rate, light-induced self-repairing and damage response type anti-corrosion.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coatings, in particular to a waterproof and rust-proof synergistic method of high-elasticity reflective thermal insulation coating. BACKGROUND

[0002] Reflective thermal insulation coatings are widely used on the surfaces of metal substrates such as building roofs and storage tanks. Their main function is to regulate the surface temperature of the substrate by reflecting solar radiation and reducing heat conduction. Since the metal substrate will expand and contract due to sunlight and environmental temperature changes, the coating on its surface is required to have high elasticity to adapt to the size changes of the substrate and prevent the coating from cracking or falling off due to stress concentration.

[0003] To achieve high elasticity, existing coatings usually use a low cross-linking density polymer system. However, this low cross-linking density network structure also leads to a large free volume between polymer segments, increasing the permeability of the coating to corrosive media such as water molecules, oxygen and chloride ions, thereby reducing its waterproof and corrosion-resistant performance as a physical barrier. Therefore, in the prior art, there is an inherent technical contradiction between the high elasticity of the coating and its barrier protection performance.

[0004] In addition, the protective function of these coatings completely depends on the integrity of their physical barrier. When the coating is scratched or has micro-cracks due to external forces during use, the metal substrate will be directly exposed to the corrosive environment at the damage site. Corrosion will start from this exposed point and spread along the interface between the coating and the substrate to both sides, causing corrosion under the coating, and eventually leading to large-scale failure of the coating.

[0005] To solve the problem of mechanical damage, some technical solutions introduce self-repairing function. Based on microcapsule release of repair agent, the number of repair times is limited by the number of microcapsules, and usually only single repair can be achieved, and the pre-embedded microcapsules reduce the mechanical properties of the coating. The intrinsic self-repairing system based on dynamic chemical bonds usually has a low reaction kinetics rate of dynamic bond exchange or recombination at ambient temperature, resulting in a repair process that takes several hours or even days, or requires external application of high temperature and other conditions that are not easy to implement, which cannot meet the demand for rapid response to damage.

[0006] Therefore, there is a lack of a synergistic protective coating in the prior art that can simultaneously satisfy high elasticity, high barrier property, and can achieve rapid physical repair and active chemical passivation to inhibit corrosion when mechanical damage occurs. SUMMARY

[0007] In view of the deficiencies of the prior art, the present application provides a waterproof and rust-proof synergistic method of high-elasticity reflective thermal insulation coating, which solves the technical problems of the difficulty of efficient synergy of waterproof and rust-proof functions in traditional reflective thermal insulation coatings and the lack of active repair and responsive protection capability after mechanical damage of the coating.

[0008] To achieve the above object, the present application is implemented by the following technical solutions: A waterproof and anti-rust synergistic method of high-elasticity reflective thermal insulation coating, which forms a coating with excellent barrier performance, self-repairing ability and active corrosion inhibition function by constructing specific internal crosslinking network and functional units. The method comprises the following steps: S1: Synthesis of core functional resin emulsion A semi-continuous seed emulsion polymerization method is adopted. In a reaction kettle with stirring and temperature control device, specific monomers are polymerized at a stirring speed of 200-300 rpm and a reaction temperature of 75-85℃. The monomers include butyl acrylate, methyl methacrylate, organosiloxane-modified acrylate, N-vinylimidazole and methacryloyloxypropyl trimethoxysilane. After the polymerization reaction is completed, the pH value of the reaction system is adjusted to 7.5-8.5 using ammonia water, and finally the core functional resin emulsion is obtained.

[0009] In a specific embodiment, the monomer components for synthesizing the core functional resin emulsion can include, by mass fraction: Butyl acrylate: 180-220 parts; Methyl methacrylate: 100-140 parts; Organosiloxane-modified acrylate: 25-35 parts; N-vinylimidazole: 8-15 parts; Methacryloyloxypropyl trimethoxysilane: 5-10 parts.

[0010] In another specific embodiment, the specific process parameters of the semi-continuous seed emulsion polymerization method in step S1 are: First, 5-10% of the total amount of pre-emulsion containing the monomers is added to the reaction kettle for seed preparation and reacted for 20-30 minutes; then, the remaining pre-emulsion containing the monomers is continuously added to the reaction kettle within 2.5-3.5 hours; after the addition is completed, continue to incubate at the same temperature for 1.5-2.5 hours to ensure complete conversion of the monomers, thereby obtaining the core functional resin emulsion.

[0011] S2: Preparation of high-elasticity reflective thermal insulation coating This step includes the following specific operations: First, mix water, dispersant, defoaming agent and functional fillers. The functional fillers include rutile titanium dioxide, hollow glass microbeads, and antimony-doped tin oxide nanometer powder as a light-heat conversion agent. Disperse and grind the mixture at a high speed of 1500-2500 rpm until a uniform and stable functional filler colorant is formed. In a specific embodiment, the particle size of the antimony-doped tin oxide nanometer powder is 30-60 nm to ensure its uniform dispersion in the coating system and its light-heat conversion efficiency.

[0012] Then, under the condition of low to medium speed stirring at 200-400 rpm, the core functional resin emulsion prepared in step S1 and film-forming aids are added to the prepared functional filler colorant slurry in sequence and mixed.

[0013] Finally, a multifunctional metal salt aqueous solution and a thickening agent are added to the above mixture. The multifunctional metal salt aqueous solution contains a metal salt selected from zinc acetate or cerium nitrate, and the pH value thereof has been adjusted to 6.5-7.5 by an acid or a base before use. In a preferred embodiment, the metal salt is zinc acetate. After all the components are uniformly mixed, the high-elasticity reflective thermal insulation coating is obtained.

[0014] In a specific embodiment, the specific time parameters for preparing the high-elasticity reflective thermal insulation coating in step S2 are as follows: The duration of the high-speed dispersion and grinding step is 40-60 minutes; after the core functional resin emulsion and the film-forming aids are added to the functional filler colorant slurry, stirring is performed for 15-20 minutes; the step of adding the multifunctional metal salt aqueous solution is completed by slowly dropping it in 10-15 minutes, and after the dropping is completed, stirring is continued for 20-30 minutes to ensure uniform crosslinking.

[0015] In a specific embodiment, the composition of the finally prepared high-elasticity reflective thermal insulation coating can include, by mass percentage: The core functional resin emulsion: 40.0%-60.0%; the rutile titanium dioxide: 15.0%-25.0%; the hollow glass microbeads: 5.0%-10.0%; the antimony-doped tin oxide nano-powder: 0.5%-2.0%; the solid content of the metal salt in the multifunctional metal salt aqueous solution accounts for 0.15%-1.0% of the total mass of the high-elasticity reflective thermal insulation coating.

[0016] S3: forming a water-proof and rust-proof synergistic coating The high-elasticity reflective thermal insulation coating prepared in step S2 is applied to the surface of a substrate by spraying, brushing or rolling, etc. During the curing and film-forming process of the coating, two key structural formation processes occur in the system: Firstly, the imidazole groups carried by the N-vinylimidazole in the core functional resin emulsion undergo coordination reaction with the metal ions in the multifunctional metal salt aqueous solution. This reaction takes the metal ions as the crosslinking center and the imidazole groups as the ligand, forming a large number of metal imidazole dynamic coordination bonds that can be dynamically broken and recombined. These dynamic coordination bonds crosslink the linear polymer chains, forming a three-dimensional network structure that permeates the entire coating system. This network structure not only constitutes the water-proof matrix of the coating, but also the corrosion inhibitor, i.e. the components of the crosslinking bonds (metal ions and imidazole groups), thereby realizing the structural integration of water-proof and rust-proof functions.

[0017] Secondly, during the curing process, the methacryloxypropyltrimethoxysilane in the core functional resin emulsion is hydrolyzed to form silicon hydroxyl groups, and further condenses to form a stable Si-O-Si covalent crosslinking network. The covalent network and the three-dimensional network structure composed of the above-mentioned metal imidazole dynamic coordination bond penetrate each other and synergize, thereby enhancing the overall structural stability of the coating and the adhesion to the substrate.

[0018] The finally formed waterproof and rust-proof synergistic coating contains a photo-thermal synergistic unit composed of antimony-doped tin oxide nano-powder and metal imidazole dynamic coordination bond. The structural feature of the unit is that the antimony-doped tin oxide nano-powder is uniformly dispersed in the three-dimensional network structure as an independent particle. The physical function is to convert the absorbed near-infrared light (such as sunlight) into heat energy, and directly transfer the heat energy to the adjacent metal imidazole dynamic coordination bond. The photo-thermal synergistic unit endows the coating with the ability of active repair and responsive protection when damaged. When the coating is damaged, the unit uses the heat energy to promote the release of metal ions from the broken metal imidazole dynamic coordination bond and the formation of a dense passivation layer on the substrate surface with imidazole molecules.

[0019] The application provides a waterproof and rust-proof synergistic method for high-elasticity reflective thermal insulation coating. 1. The application unifies the waterproof matrix and the corrosion inhibitor component at the molecular level by constructing a three-dimensional network structure with metal imidazole dynamic coordination bond as the crosslinking point. The network structure of the coating not only acts as a physical barrier to prevent the intrusion of water and corrosive media, but also has corrosion inhibition function because the metal ions and imidazole groups that constitute the network skeleton are corrosion inhibitors themselves.

[0020] 2. The application introduces a photo-thermal synergistic unit composed of antimony-doped tin oxide nano-powder and metal imidazole dynamic coordination bond into the coating, which endows the coating with the function of light-irradiation accelerated self-repair. Under sunlight, the antimony-doped tin oxide nano-powder converts the absorbed near-infrared light into heat energy, which can increase the fracture and recombination rate of the adjacent metal imidazole dynamic coordination bond, thereby healing the micro-cracks in the coating and restoring the integrity of the physical barrier.

[0021] 3. The application endows the coating with damage-responsive passivation protection ability. When the coating is physically damaged, the metal imidazole dynamic coordination bond in the damaged area breaks and releases corrosion-inhibiting metal ions and imidazole molecules. At the same time, the local heat energy generated by the photo-thermal synergistic unit can promote the migration of these corrosion inhibitors on the exposed substrate surface and form a dense chemical passivation layer, thereby inhibiting the initial corrosion of the substrate. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work belong to the protection scope of the present application.

[0023] Experimental materials: The main raw materials and reagents used in the following examples and comparative examples are as follows, and the reagents not specifically described are commercially available analytical pure or higher grade products.

[0024] Butyl acrylate, CAS number: 141-32-2; Methyl methacrylate, CAS number: 80-62-6; 3-[tris (trimethylsiloxy) silyl] methyl propyl methacrylate, CAS number: 17096-07-0; N-vinylimidazole, CAS number: 1072-63-5; Methacryloyloxypropyl trimethoxysilane, CAS number: 2530-85-0; Rutile titanium dioxide, CAS number: 13463-67-7; Barium sulfate, CAS number: 7727-43-7; Zinc acetate dihydrate, CAS number: 5970-45-6; Cerium nitrate hexahydrate, CAS number: 10294-41-4; Ammonium persulfate, CAS number: 7727-54-0; Sodium dodecyl sulfate, CAS number: 151-21-3; 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, CAS number: 25265-77-4; Hydroxyethyl cellulose, CAS number: 9004-62-0; Ammonia, CAS number: 1336-21-6; Acetone, CAS number: 67-64-1.

[0025] Examples 1-3: Example 1: The present embodiment provides a preparation method of a high-elasticity reflective thermal insulation coating.

[0026] (1) Preparation of core functional resin emulsion A a. Preparation of the pre-emulsion: 200 parts of butyl acrylate, 120 parts of methyl methacrylate, 30 parts of 3-[tris(trimethylsiloxy)silyl]propyl methacrylate, 12 parts of N-vinylimidazole, 8 parts of methacryloyloxypropyltrimethoxysilane, 15 parts of sodium dodecyl sulfate and 150 parts of deionized water were mixed and emulsified for 30 minutes under stirring at 300 rpm to obtain a uniform monomer pre-emulsion.

[0027] b. Polymerization: Into a four-necked flask equipped with a mechanical stirrer, reflux condenser and thermometer, 200 parts of deionized water and 2 parts of sodium dodecyl sulfate were added, stirred at a rotation speed of 250 rpm under nitrogen protection, and heated to 80°C. 10% of the total amount of the pre-emulsion was added as a seed crystal, and 0.5 parts of ammonium persulfate initiator was added, and the reaction was carried out at this temperature for 25 minutes. Then, the remaining 90% of the pre-emulsion and 30 parts of deionized water in which 1.5 parts of ammonium persulfate was dissolved were continuously and uniformly added dropwise into the reaction flask within 3 hours. After the dropwise addition was completed, the reaction was continued at 80°C for 2 hours.

[0028] c. Post-treatment: The reaction product was cooled to room temperature, and the pH value was adjusted to 8.0 with 10% aqueous ammonia solution. After filtration, the core functional resin A with a solid content of 45% was obtained.

[0029] (2) Preparation of a high-elasticity reflective thermal insulation coating a. Preparation of the functional filler color paste: 13.0 parts of deionized water, 0.5 parts of polycarboxylate dispersant, 0.2 parts of defoaming silicone mixture, 20.0 parts of rutile titanium dioxide, 8.0 parts of hollow glass microbeads and 1.0 parts of antimony-doped tin oxide nano-powder with an average particle size of 45 nm were added into a dispersing tank, and dispersed and ground at a rotation speed of 2000 rpm for 50 minutes to obtain the functional filler color paste.

[0030] b. Coating preparation: The rotation speed of the dispersing tank was reduced to 300 rpm, and 50.0 parts of the core functional resin emulsion A and 2.0 parts of 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate were added into the above functional filler color paste, and stirred for 20 minutes. Then, 5.0 parts of zinc acetate aqueous solution (solid content 10%) with a pH value of 7.0 prepared from zinc acetate dihydrate was slowly added dropwise within 10 minutes. After the dropwise addition was completed, 0.3 parts of hydroxyethyl cellulose was added, and stirring was continued for 25 minutes to obtain the coating sample of Example 1.

[0031] Example 2: The preparation method of this example is basically the same as that of Example 1, and the main difference is that the amounts of N-vinylimidazole and antimony-doped tin oxide nano-powder are adjusted.

[0032] (1) Preparation of the core functional resin emulsion B Except that the amount of N-vinylimidazole is adjusted from 12 parts to 8 parts, all the other raw materials, proportions and preparation steps are exactly the same as in Example 1, part (1). Finally, core functional resin emulsion B is obtained.

[0033] (2) Preparation of high-elasticity reflective thermal insulation coating Except that the amount of antimony-doped tin oxide nano-powder is adjusted from 1.0 part to 0.5 part, and the amount of deionized water is increased to 13.5 parts accordingly, all the other raw materials, proportions and preparation steps are exactly the same as in Example 1, part (2), wherein the resin emulsion used is core functional resin emulsion B. Finally, the coating sample of Example 2 is obtained.

[0034] Example 3: The preparation method of this example is basically the same as that of Example 1, with the main difference being that the metal salt is replaced from zinc acetate to cerium nitrate.

[0035] (1) Preparation of core functional resin emulsion This example directly uses the core functional resin emulsion A prepared in Example 1.

[0036] (2) Preparation of high-elasticity reflective thermal insulation coating Except that the zinc acetate aqueous solution is replaced by 5.0 parts of cerium nitrate aqueous solution (solid content 10%) with pH value of 7.0 prepared from cerium nitrate hexahydrate, all the other raw materials, proportions and preparation steps are exactly the same as in Example 1, part (2). Finally, the coating sample of Example 3 is obtained.

[0037] Comparative Examples 1-3: Comparative Example 1: Compared with Example 1, the difference lies in that, in the preparation of core functional resin emulsion, N-vinylimidazole is not added, and its mass is replaced by an equal amount of butyl acrylate; and in the preparation of coating, zinc acetate aqueous solution is not added, and its mass is replaced by an equal amount of deionized water. The rest of the raw materials and preparation steps are the same.

[0038] Comparative Example 2: Compared with Example 1, the difference lies in that, in the preparation of high-elasticity reflective thermal insulation coating, antimony-doped tin oxide nano-powder is not added, and its mass is replaced by an equal amount of barium sulfate. The rest of the raw materials and preparation steps are the same.

[0039] Comparative Example 3: Compared with Example 1, the difference lies in that, in the preparation of core functional resin emulsion, methyl methacryloyloxypropyl trimethoxysilane is not added, and its mass is replaced by an equal amount of butyl acrylate. The rest of the raw materials and preparation steps are the same.

[0040] Test Examples 1-4: Test Example 1: Coating basic physical property test The coating samples prepared in Examples 1-3 and Comparative Examples 1-3 were respectively coated on pretreated Q235 steel plates for adhesion and flexibility tests.

[0041] (1) Sample preparation Q235 steel plates with a size of 150 mm x 70 mm x 2 mm were selected as substrates. The surface of the substrate was sanded using 400 grit sandpaper, and then ultrasonically cleaned with acetone to remove oil stains, and dried for use. Each coating sample was uniformly coated on the treated substrate surface using a wet film applicator, and the dry film thickness was controlled to be 100 ± 10 μm. All coating samples were cured for 7 days in an environment with a temperature of 25°C and a relative humidity of 50%, and after complete drying, subsequent tests were performed.

[0042] (2) Adhesion test The test was performed in accordance with the GB / T9286 1998 standard. A multi-blade cutting tool was used to draw 11 parallel cuts on the surface of the cured coating, with a spacing of 1 mm, and then another 11 parallel cuts were drawn at a 90-degree angle perpendicular to the original direction, forming a grid area with 100 small squares. The debris in the grid area was cleaned with a soft brush, and then the standard adhesive tape was pasted on the grid area and compacted, and the tape was smoothly torn off at an angle of about 60 degrees. The peeling of the coating in the grid area was observed, and the results were recorded according to the 05 level in the standard.

[0043] (3) Flexibility test The test was performed in accordance with the GB / T1731 1993 standard. The coated and cured sample plate was placed on an axle rod with different diameters, with the coating surface facing up. Within 23 seconds, the sample plate was bent 180 degrees around the axle rod. The sample plate was removed, and the coating surface in the bending area was observed for cracking or peeling. The smallest axle rod diameter (unit: mm) at which the coating did not crack or peel was recorded as the evaluation result of flexibility.

[0044] (4) Test results The coating basic physical property test results of Examples 1-3 and Comparative Examples 1-3 are summarized in Table 1.

[0045] Table 1. Coating basic physical property test results Based on the summary analysis of Test Example 1: From the test data of Table 1, it can be seen that the coatings prepared in Examples 1-3 all exhibit 0 or 1 level of adhesion, while the minimum bending bar diameter in the flexibility test is less than or equal to 3 mm. This is because during the curing process, the methacryloxypropyltrimethoxysilane in the system hydrolyzes and condenses to form a Si-O-Si covalent crosslinking network, which provides firm adhesion by forming chemical bonds at the interface between the coating and the metal substrate. At the same time, the dynamic coordination bond of metal imidazole formed by N-vinylimidazole and metal ions in the system constitutes a three-dimensional network structure, which can reversibly break and recombine when subjected to external force, thereby effectively dissipating stress and imparting excellent flexibility to the coating.

[0046] The comparison results of Comparative Example 1 and Example 1 show that in the absence of N-vinylimidazole and metal salt, the flexibility test result of the coating increases from 2 mm to 8 mm. The reason is that the network structure of metal imidazole dynamic coordination bond cannot be formed in the coating system of Comparative Example 1, and there is a lack of dynamic crosslinking points between polymer chains that can dissipate stress, so the coating is more prone to brittle fracture under bending stress. This result shows that the introduction of metal imidazole dynamic coordination bond is a decisive factor for the coating to obtain high flexibility.

[0047] The comparison results of Comparative Example 3 and Example 1 show that in the absence of methacryloxypropyltrimethoxysilane, the adhesion level of the coating decreases from 0 level to 4 level. The reason is that the Si-O-Si covalent crosslinking network cannot be formed in the coating system of Comparative Example 3, and the coating and the metal substrate can only be combined by physical interactions such as van der Waals force, and the interfacial bonding force is greatly weakened. This result shows that the covalent network structure formed by the hydrolysis and condensation of methacryloxypropyltrimethoxysilane is the structural basis for achieving high adhesion between the coating and the substrate.

[0048] Test Example 2: Waterproofness Test The waterproofness of the coatings prepared in Examples 1-3 and Comparative Examples 1-3 was evaluated by measuring the water absorption of the cured coating film.

[0049] (1) Sample Preparation Each coating sample was applied to a polytetrafluoroethylene plate, with a dry film thickness of 150 ± 10 μm. All coating samples were cured at a temperature of 25°C and a relative humidity of 50% for 7 days. After complete curing, the coating film was completely peeled off from the polytetrafluoroethylene plate and cut into a sample piece with a size of 50 mm x 50 mm. The cut sample piece was dried to constant weight in a vacuum drying oven at 50°C.

[0050] (2) Water Absorption Test The test was performed according to GB / T 17331 1993 standard. The sample pieces dried to constant weight were weighed, and the initial dry weight (m0) was recorded. Subsequently, all sample pieces were completely immersed in a beaker containing deionized water, and soaked for 24 hours at a temperature of 23±2℃. After 24 hours, the sample pieces were taken out of the water, the water on the surface of the sample pieces was quickly absorbed with filter paper, and immediately weighed, and the wet weight (m1) was recorded. Three parallel samples were tested for each group of samples, and the average value was taken. The water absorption rate (W) was calculated by the following formula: W (%) = [(m1-m0) / m0]x100%; (3) Test results The water absorption rate test results of the coatings of Examples 1-3 and Comparative Examples 1-3 were summarized in Table 2.

[0051] Table 2. Test results of the water resistance (water absorption rate) of each coating Based on the summary analysis of Test Example 2: From the test data in Table 2, it can be seen that the coatings prepared in Examples 1, 2 and 3 all showed a water absorption rate of less than 1.5%. This result is attributed to the synergistic structure of the double network formed inside the coating. During the curing and film-forming process, the Si-O-Si covalent network formed by the hydrolysis and condensation of methacryloyloxypropyl trimethoxysilane and the metal imidazole dynamic network formed by the coordination of N-vinylimidazole and metal ions penetrate each other, and together form a dense polymer matrix. This structure effectively reduces the free volume between polymer chains and increases the tortuosity of the water molecule penetration path, thereby significantly inhibiting the intrusion of water molecules.

[0052] The water absorption rate of Comparative Example 1 (4.55%) was much higher than that of Example 1 (1.12%). The reason is that N-vinylimidazole and metal salt were not introduced into the system of Comparative Example 1, and therefore the metal imidazole dynamic coordination network could not be formed. There was only physical entanglement of polymer chains in the system, and the structure was relatively loose, with low crosslinking density, resulting in a large number of water molecules entering the polymer interior. This comparative result shows that the construction of the metal imidazole dynamic coordination network plays a decisive role in improving the denseness of the coating and reducing its water absorption rate.

[0053] The water absorption rate of Comparative Example 3 (3.86%) was also significantly higher than that of Example 1. The reason is that methacryloyloxypropyl trimethoxysilane was not introduced into the system of Comparative Example 3, and therefore the Si-O-Sil covalent crosslinking network could not be formed. Without the filling and reinforcing effect of the hydrophobic inorganic network formed by the hydrolysis and condensation of this siloxane on the polymer matrix, the overall denseness of the coating decreased, and therefore the water blocking ability was weakened. The results of Comparative Example 1 and Comparative Example 3 together show that the synergistic effect of the double network is the structural basis for achieving low water absorption rate of the coating.

[0054] Test Example 3: Light Accelerated Self-Repairing Performance Quantitative Test The barrier performance recovery of the coatings of Examples 1-3 and Comparative Examples 1-2 after mechanical damage under light condition was quantitatively evaluated by electrochemical impedance spectroscopy method.

[0055] (1) Sample Preparation and Test System Each coating sample was coated on a pretreated Q235 steel plate, with a dry film thickness of 100 ± 10 μm, and cured for 7 days under standard conditions. The test was carried out on an electrochemical workstation with a three-electrode system, with the coated sample plate as the working electrode (exposed area 1 cm²), a platinum plate as the counter electrode, and a saturated calomel electrode (SCE) as the reference electrode. The test electrolyte was a 3.5% sodium chloride aqueous solution.

[0056] (2) Repair Efficiency Test Steps a. Initial state test: immerse the intact coated sample plate in the electrolyte solution, and after the open circuit potential stabilizes, test its initial alternating current impedance spectrum, and record the impedance modulus at a frequency of 0.01 Hz, denoted as .

[0057] b. Making damage: remove the sample plate from the solution, and use a scalpel to draw a 10 mm long and substrate deep scratch in the center of the coating.

[0058] c. Damage state test: immediately immerse the sample plate with the scratch back into the electrolyte solution, and test its alternating current impedance spectrum after damage, and record the impedance modulus at a frequency of 0.01 Hz, denoted as .

[0059] d. Light repair: place the scratched sample plate under a simulated sunlight source (light intensity: 100 mW / cm²) for 2 hours.

[0060] e. Post-repair state test: after the light exposure is completed, immerse the sample plate again in the electrolyte solution, and test its repaired alternating current impedance spectrum, and record the impedance modulus at a frequency of 0.01 Hz, denoted as .

[0061] f. Calculate repair efficiency: the repair efficiency (η) is calculated by the following formula: ; Wherein: Z0 is the impedance modulus at 0.01 Hz under the initial state of the coating; Z1 is the impedance modulus at 0.01 Hz after damage of the coating; Z2 is the impedance modulus at 0.01 Hz after light repair of the coating.​

[0062] (3) Test results The coating repair efficiency test results of Examples 1-3 and Comparative Examples 1-2 are summarized in Table 3.

[0063] Table 3. Test results of each coating light repair efficiency Based on the summary analysis of Test Example 3: From the test data in Table 3, it can be seen that the coatings of Examples 1, 2 and 3 all obtained a repair efficiency of more than 85% after light irradiation. This result is due to the role of the photo-thermal synergistic unit inside the coating. Under light conditions, the antimony-doped tin oxide nano-powder dispersed in the network absorbs light energy and converts it into heat energy, which is transferred to the surrounding polymer chain segments, increasing their movement ability and significantly accelerating the recombination rate of the broken metal imidazole dynamic coordination bond at the scratch interface. This rapid bond exchange process allows the polymer chain to cross the scratch area again, restoring the physical integrity of the coating and thus its barrier performance to the electrolyte (characterized by low-frequency impedance modulus) to near the initial level.

[0064] The repair efficiency of Comparative Example 1 is only 4.6%, which is much lower than that of Example 1 (92.7%). The reason is that the coating system of Comparative Example 1 does not contain N-vinylimidazole and metal salt, and thus lacks the metal imidazole dynamic coordination bond as the repair basis. When the coating is scratched, the irreversible rupture of the internal covalent bond cannot be repaired under light conditions, so its barrier performance is basically not restored. This comparison result directly shows that the existence of the metal imidazole dynamic coordination bond is a structural prerequisite for the coating to realize self-repair function.

[0065] The repair efficiency of Comparative Example 2 (34.2%) is significantly lower than that of Example 1, but higher than that of Comparative Example 1. The reason is that although the system of Comparative Example 2 contains the metal imidazole dynamic coordination bond, it lacks the antimony-doped tin oxide nano-powder as a photo-thermal converter. Without additional heat energy input, the exchange rate of the dynamic coordination bond is relatively slow at room temperature, and only limited and incomplete repair can be achieved. This comparison result shows that the introduction of antimony-doped tin oxide nano-powder, which converts light energy into heat energy to promote bond exchange, is a key technical element to achieve rapid and efficient repair.

[0066] Test Example 4: Damage-responsive passivation performance test The neutral salt spray corrosion test method was used to evaluate the corrosion resistance of the coatings of Examples 1-3 and Comparative Examples 1-3 after artificial scratching, to characterize their damage-responsive passivation ability.

[0067] (1) Sample preparation and test conditions Each paint sample was applied to a pretreated Q235 steel panel with a controlled dry film thickness of 100 ± 10 μιη and cured for 7 days under standard conditions. An "X" shaped scribe was made in the center of each panel using a scribe knife, with the scribe depth penetrating through the coating to the metal substrate. The scribed panels were placed in a neutral salt spray test chamber and exposed for 240 hours according to GB / T 17712007 standard.

[0068] (2) Corrosion Evaluation After 240 hours of exposure, the panels were removed from the salt spray chamber and rinsed with flowing deionized water to remove salt residue and then dried with a soft cloth. The corrosion propagation width on both sides of the scribe was measured using a magnifying glass with a scale according to GB / T 17712007 standard. The corrosion propagation width was measured at three different locations for each scribe, and the average value was taken as the final result.

[0069] (3) Test Results The results of the salt spray corrosion test for the coatings of Examples 1-3 and Comparative Examples 1-3 are summarized in Table 4.

[0070] Table 4. Results of the corrosion propagation width test at the scribe of each coating Based on the summary analysis of Test Example 4: As shown by the test data in Table 4, the corrosion propagation width at the scribe of the coatings of Examples 1, 2 and 3 were all less than 1.0 mm after 240 hours of neutral salt spray exposure. This result indicates that when the coating is scratched and the metal substrate is exposed, the dynamic coordination bond of the metal imidazole in the scribe area is broken, and the metal ions and imidazole molecules with corrosion inhibition function are released to the damage interface in response. These released substances migrate on the exposed metal substrate surface and form a dense chemical passivation layer, which acts as a new physical barrier to effectively prevent the corrosion medium from directly contacting the substrate, thereby inhibiting the further propagation of corrosion.

[0071] The comparison results of Comparative Example 1 and Example 1 show that the corrosion propagation width at the scribe reaches 5.8 mm, which is significantly greater than the 0.6 mm of Example 1. The reason is that the coating system of Comparative Example 1 does not contain N-vinylimidazole or metal salt, so the polymer network does not have the ability to release active corrosion inhibitors. When the substrate is exposed, no responsive passivation layer can be formed, resulting in rapid and uncontrolled corrosion of the substrate in the salt spray environment. This result confirms that the structural unit composed of metal ions and imidazole groups in the coating is the basis for achieving the damage-responsive passivation function.

[0072] The corrosion propagation width of Comparative Example 3 was 3.2 mm, which was also significantly worse than Example 1. The reason was that, although there were metal imidazole dynamic coordination bonds capable of releasing corrosion inhibitors in the system of Comparative Example 3, the overall adhesion of the coating to the substrate was insufficient due to the lack of Si-O-Si covalent network formed by methacryloxypropyl trimethoxysilane. This led to the coating at the edge of the scratch being prone to peeling under the erosion of the corrosion medium, resulting in more serious corrosion under the coating. This result showed that the dual network structure of the present application, i.e. the firm adhesion provided by the Si-O-Si covalent network and the responsive passivation function provided by the metal imidazole dynamic network, both of which synergistically work, are necessary conditions for obtaining comprehensive corrosion resistance.

[0073] Fifth part: test results and analysis To systematically evaluate the effect of the technical scheme of the present application, the test results of the various properties of Examples 1-3 and Comparative Examples 1-3 are summarized in Table 5.

[0074] Table 5. Summary of comprehensive performance test results of each example and comparative example Note: Comparative Example 3 had a low adhesion of the coating to the substrate, and large-area peeling occurred during the scratch and immersion process, so the data for the repair efficiency test was not available and is marked as “-”.

[0075] The comparison of the test results of Comparative Example 1 and Example 1 showed that after removing N-vinylimidazole and metal salt from the coating system, the flexibility, water resistance, self-repairing ability and corrosion resistance after damage of the coating were all significantly reduced. This was because the absence of metal imidazole dynamic coordination bonds formed by the reaction of the two components prevented the formation of a dynamic network capable of dissipating stress within the coating, and also prevented the formation of a dense crosslinked structure to block water. At the same time, when the coating was damaged, there were neither reversible chemical bonds to heal the physical barrier nor substances with corrosion inhibition function to release to the damaged area to form a passivation layer. Therefore, the construction of the metal imidazole dynamic coordination network was the technical basis for the realization of the multiple core functions of the present application.

[0076] The comparison of the test results of Comparative Example 2 and Example 1 showed that in the absence of antimony-doped tin oxide nano-powder, the light-induced repair efficiency of the coating decreased from 92.7% to 34.2%. The reason was that, although there were repairable metal imidazole dynamic coordination bonds in the coating of Comparative Example 2, in the absence of a light-heat conversion agent, the exchange and recombination of dynamic bonds relied solely on the ambient temperature, and the kinetics was slow. The introduction of antimony-doped tin oxide nano-powder significantly improved the movement ability of the polymer chain segments and the exchange rate of the dynamic bonds by converting light energy into local heat energy, thereby achieving rapid and efficient repair. This comparison confirmed the role of the light-heat synergistic unit in the present application.

[0077] Comparative Example 3 and Example 1 test results show that after removing the methacryloxypropyltrimethoxysilane, the adhesion rating of the coating decreases from 0 to 4, the water absorption increases from 1.12% to 3.86%, and the corrosion propagation at the scratch is more severe. This is because the absence of the Si-O-Si covalent network formed by the hydrolysis and condensation of this component, the coating cannot form a strong chemical bond with the metal substrate, and at the same time the compactness and hydrophobicity of the coating matrix are also reduced. The loss of adhesion leads to the coating more easily peeling at the edge of the scratch under the erosion of the corrosion medium, thereby weakening the protective effect of the damage-responsive passive layer. The results show that the dual network structure of the Si-O-Si covalent network and the metal imidazole dynamic coordination network is necessary for achieving the comprehensive protective performance of the coating.

Claims

1. A waterproof and rust-proof synergistic enhancement method for a highly elastic reflective thermal insulation coating, characterized in that: include: S1. Synthetic core functional resin emulsion: A semi-continuous seed emulsion polymerization method is used to polymerize monomers including butyl acrylate, methyl methacrylate, organosiloxane-modified acrylate, N-vinyl imidazole, and methacryloxypropyltrimethoxysilane under stirring at 200-300 rpm and a reaction temperature of 75° C.-85° C. After the reaction, the pH value is adjusted to 7.5-8.5 with aqueous ammonia to obtain the core functional resin emulsion. S2. The steps for preparing the highly elastic reflective thermal insulation coating include: First, water, a dispersant, and a defoamer are mixed with rutile titanium dioxide, hollow glass microspheres, and antimony-doped tin oxide nanopowder as functional fillers, and ground at a speed of 1500-2500 rpm to prepare a functional filler color paste; Then, under stirring conditions of 200-400 rpm, the core functional resin emulsion and the film-forming aid are sequentially added to the functional filler paste and mixed; Finally, adding a multifunctional metal salt aqueous solution and a thickener, wherein the multifunctional metal salt aqueous solution comprises a metal salt selected from zinc acetate or cerium nitrate and is adjusted to a pH of 6.5-7.5, and finally mixing to obtain the highly elastic reflective thermal insulation coating; S3, forming a waterproof and anti-rust synergistic coating: The highly elastic reflective thermal insulation coating is applied to the surface of a substrate. During the curing and film-forming process, the imidazole groups of the N-vinyl imidazole in the core functional resin emulsion react with the metal ions in the multifunctional metal salt aqueous solution to form a three-dimensional network structure with the metal imidazole dynamic coordination bonds as cross-linking points, thereby constituting a waterproof matrix.

2. The waterproof and rust-proof synergistic enhancement method of a highly elastic reflective thermal insulation coating according to claim 1, characterized in that: In step S1, the monomer components for synthesizing the core functional resin emulsion include, by mass: Butyl acrylate: 180-220 parts; Methyl methacrylate: 100-140 parts; Organosiloxane modified acrylate: 25-35 parts; N-vinylimidazole: 8-15 parts; Methacryloxypropyltrimethoxysilane: 5 to 10 parts.

3. The waterproof and rust-proof synergistic enhancement method of a highly elastic reflective thermal insulation coating according to claim 1, characterized in that: In the step S2, the composition for preparing the highly elastic reflective thermal insulation coating comprises, by mass percentage: The core functional resin emulsion: 40.0% to 60.0%; The rutile titanium dioxide: 15.0% to 25.0%; The hollow glass microspheres: 5.0% to 10.0%; The antimony-doped tin oxide nanopowder: 0.5% to 2.0%; The solid content of the metal salt in the multifunctional metal salt aqueous solution accounts for 0.15% to 1.0% of the total mass of the high-elasticity reflective thermal insulation coating.

4. The waterproof and rust-proof synergistic enhancement method of a highly elastic reflective thermal insulation coating according to claim 1, characterized in that: The specific process of the semi-continuous seed emulsion polymerization method in step S1 is: First, 5% to 10% of the total amount of the pre-emulsion containing the monomer is used to prepare seed crystals and reacted for 20 to 30 minutes; Next, adding the remaining pre-emulsion containing the monomer dropwise within 2.5 to 3.5 hours; Finally, after the dropwise addition is completed, the reaction is continued for 1.5 to 2.5 hours to complete the polymerization, thereby obtaining the core functional resin emulsion.

5. The waterproof and rust-proof synergistic enhancement method of a highly elastic reflective thermal insulation coating according to claim 1, characterized in that: In the step S2, the particle size of the antimony-doped tin oxide nanopowder is 30-60 nm, and the antimony-doped tin oxide nanopowder is uniformly dispersed in the coating system as a light-to-heat conversion agent.

6. The waterproof and rust-proof synergistic enhancement method of a highly elastic reflective thermal insulation coating according to claim 1, characterized in that: In the step S3, the waterproof and rust-proof synergistic coating comprises a photothermal synergistic unit composed of the antimony-doped tin oxide nanopowder and the metal imidazole dynamic coordination bond, wherein the unit is characterized by: The antimony-doped tin oxide nanopowder is dispersed in the three-dimensional network structure and is used to convert the absorbed near-infrared light into thermal energy, and transfer the thermal energy to the adjacent metal imidazole dynamic coordination bonds.

7. The waterproof and rust-proof synergistic enhancement method of a highly elastic reflective thermal insulation coating according to claim 1, characterized in that: The specific time parameters for preparing the highly elastic reflective thermal insulation coating in step S2 are: The duration of the grinding step is 40 to 60 minutes; Adding the core functional resin emulsion and the film-forming aid to the functional filler paste and stirring for 15 to 20 minutes; The step of adding the multifunctional metal salt aqueous solution is completed by slowly adding the solution dropwise within 10 to 15 minutes, and stirring is continued for 20 to 30 minutes after the addition is completed.

8. The waterproof and rust-proof synergistic enhancement method of a highly elastic reflective thermal insulation coating according to claim 1, characterized in that: During the film-forming curing process of step S3, the methacryloxypropyltrimethoxysilane is also hydrolyzed and condensed to form a Si-O-Si covalent cross-linked network. The covalent cross-linked network works together with the three-dimensional network structure to enhance the adhesion and structural stability of the coating.

9. The waterproof and rust-proof synergistic enhancement method of a highly elastic reflective thermal insulation coating according to claim 1, characterized in that: In the step S2, the metal salt in the multifunctional metal salt aqueous solution is zinc acetate.

10. The waterproof and rust-proof synergistic enhancement method of a highly elastic reflective thermal insulation coating according to claim 6, characterized in that: The light-heat synergy unit is further used to utilize the heat energy to promote the metal ions released from the broken metal imidazole dynamic coordination bonds and the imidazole molecules to form a passivation layer on the surface of the substrate when the coating is damaged.

Images