Waterborne epoxy waterproof coating and preparation method thereof

Abstract

The invention relates to the technical field of waterproof coatings, and discloses a waterborne epoxy waterproof coating and a preparation method thereof, the waterborne epoxy waterproof coating comprises the following components by weight: 100-120 parts of a waterborne epoxy resin emulsion; 10 to 15 parts of silicon dioxide nanoparticles; 5 to 8 parts of polystyrene microspheres; 3 to 5 parts of bio-based long-chain alkyl siloxane; 2-4 parts of a dynamic cross-linking agent; 1-3 parts of a photo-thermal response material; 0.5-1 part of a dispersant; 0.3 to 0.6 part of a defoaming agent; and 20 to 30 parts of deionized water. Through special component matching and process treatment, a multi-stage coarse structure is constructed, and low surface energy modification is performed, so that the contact angle of the coating is up to 152 degrees or above, the water absorption rate is lower than 1.2%, and the waterproof performance is far better than that of a traditional coating and a contrast sample; the tensile strength reaches 12.5-14.0 MPa, the elongation at break is 350%-400%, and the mechanical property is excellent; the self-repairing efficiency reaches 85%-90%, and the service life is effectively prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of waterproof coatings, and in particular to a water-based epoxy waterproof coating and a preparation method thereof. Background Art

[0002] Waterborne epoxy waterproof coatings are widely used in the waterproofing field due to their environmental friendliness and excellent film-forming properties. However, existing waterborne epoxy waterproof coatings still have certain deficiencies in terms of waterproofing performance, durability, and functionality. For example, traditional coatings have limited surface hydrophobicity. Under prolonged humid conditions, water easily penetrates into the coating, resulting in a decrease in its waterproofing performance. Furthermore, the coatings exhibit poor stability and self-healing capabilities in complex environments (such as temperature fluctuations and mechanical stress), making it difficult to meet the demand for high-performance waterproof materials in modern engineering projects. To address these issues, there is an urgent need to develop a waterborne epoxy waterproof coating with excellent waterproofing performance, durability, and functionality. Summary of the Invention

[0003] In response to the shortcomings of the existing technology, the present invention provides a water-based epoxy waterproof coating and a preparation method. By optimizing the components and preparation process of the coating, the waterproof performance, durability and functionality of the coating are improved, so that it can adapt to a variety of complex environments and meet the needs of modern engineering for high-performance waterproof materials.

[0004] To achieve the above object, the present invention provides the following technical solution: a water-based epoxy waterproof coating, comprising the following components in parts by weight: 100-120 parts of a water-based epoxy resin emulsion, wherein the solid content of the water-based epoxy resin emulsion is 45%-50% and the epoxy value is 0.18-0.22 eq / 100g; 10-15 parts of silica nanoparticles, with a particle size of 50-100 nm, a specific surface area ≥ 200 m² / g, and a surface hydroxyl content ≥ 3 mmol / g; 5-8 parts of polystyrene microspheres, with a particle size of 1-3 μm, a pore size distribution of 100-500 nm, and a porosity of ≥70%; 3-5 parts of bio-based long-chain alkylsiloxane, which is a palmitic acid-modified silane coupling agent; 2-4 parts of dynamic crosslinking agent; 1-3 parts of a photothermal responsive material selected from MXene nanosheets, wherein the thickness of the MXene nanosheets is ≤ 5 nm; 0.5-1 part of dispersant, which is a polycarboxylate dispersant; 0.3-0.6 parts of defoaming agent, which is a silicone defoaming agent; 20-30 parts of deionized water, conductivity ≤5μS / cm.

[0005] A method for preparing a water-based epoxy waterproof coating comprises the following steps: a. Premixing: Add waterborne epoxy resin emulsion, dispersant, defoamer and deionized water to a high-speed dispersing kettle, shear and emulsify at a speed of 8000-10000 rpm for 15-20 minutes, and control the material temperature to ≤40°C; b. Micro-nanostructure construction: Synthesis of precursors with multi-level rough structures; c. Surface modification: low surface energy treatment; d. Adding functional additives: Add dynamic crosslinking agent and photothermal responsive material, stir at 200-300 rpm for 30-40 minutes, until the viscosity reaches 3000-5000 mPa·s (measured at 25°C); e. Post-processing: Filter through a 200-mesh sieve and fill at 25±2℃ and relative humidity ≤50%.

[0006] Preferably, the synthesis of the micro-nanostructure precursor comprises the following steps: b1. The silica nanoparticles and polystyrene microspheres were mixed in a mass ratio of (2-2.5): 1, added to an aqueous epoxy resin emulsion, and dispersed under ultrasonic conditions of 40kHz frequency and 300W power for 30-40 minutes; b2. The mixture was transferred to a reactor and stirred at 50-60 ° C under nitrogen at 300-400 rpm for 2-3 hours, and a template of sodium dodecyl sulfate (SDS) was added. The amount of SDS added was 0.5%-1% of the total mass of the epoxy resin emulsion. b3. Raise the temperature to 80-85°C at a rate of 2°C / min, maintain a vacuum of -0.08 to -0.1 MPa, and evaporate the solvent for 30-40 minutes to induce the nanoparticles to form a directional nanoprotrusion structure within the micron-sized pores.

[0007] Preferably, the template agent SDS in step b2 is added in two times: 60% of the total amount is pre-mixed with the epoxy resin in the first addition, and the remaining 40% is added after stirring for 1 hour.

[0008] Preferably, the surface modification comprises the following steps: c1. The bio-based long-chain alkylsiloxane is dissolved in a mixed solvent of ethanol and deionized water, wherein the volume ratio of ethanol to water is (1:1)-(3:1), and a modified solution having a mass concentration of 5%-8% is prepared; c2. The micro-nanostructure precursor is treated by immersion, the immersion time is 12-24 hours, the immersion liquid temperature is 25-30 ° C, and after immersion, it is drained at a rate of 0.5-1 ° C / min until no droplets fall; c3. Treat in a circulating hot air drying oven at 60-70°C for 1-2 hours with the wind speed controlled at 1-2m / s to form a low surface energy grafting layer with a thickness of 50-100nm.

[0009] Preferably, the impregnation method adopts a vacuum-assisted process: a vacuum degree of -0.05 to -0.08 MPa is applied during the impregnation stage and maintained for 10 to 15 minutes to promote the penetration of the modifying liquid into the deep layers of the micro-nano structure.

[0010] Preferably, the dynamic crosslinking agent is an acylhydrazone dynamic crosslinking agent, and its preparation method includes: Y1. Adipic acid dihydrazide and formaldehyde-modified epoxy resin are mixed in a molar ratio of 1:2, wherein the degree of aldehyde substitution of the formaldehyde-modified epoxy resin is 10%-15%; Y2. React in an acetate buffer solution with a pH of 4-5 at 40-50°C for 4-6 hours to obtain a dynamic crosslinker solution.

[0011] Preferably, the MXene nanosheets are surface-coated with polydopamine (PDA) with a coating thickness of 2-5 nm. The coating method includes: Z1. Disperse MXene nanosheets in Tris-HCl buffer (pH = 8.5) and add dopamine hydrochloride with a mass ratio of dopamine to MXene of 1:20. Z2. Stirring polymerization at 25°C for 24 hours, and then centrifuging and washing to obtain a composite material.

[0012] Preferably, in step d, segmented temperature-controlled stirring is adopted: the temperature is maintained at 25-30° C. for the first 15 minutes, and then the temperature is raised to 35-40° C. for the next 15-25 minutes to promote diffusion of the dynamic crosslinking agent.

[0013] Preferably, the filtration process in step e is carried out in two stages: first, coarse filtration through a 200-mesh stainless steel filter, and then fine filtration through a 0.5 μm pore size ceramic membrane, with the filtration pressure controlled at 0.2-0.4 MPa.

[0014] Compared with the existing technology, the present invention provides a water-based epoxy waterproof coating and preparation method, which has the following beneficial effects: through special component matching and process treatment, a multi-level rough structure is constructed and low surface energy modification is performed, so that the coating contact angle is as high as 152° or more, the water absorption rate is less than 1.2%, and the waterproof performance far exceeds that of traditional coatings and comparative samples; the tensile strength reaches 12.5-14.0MPa, the elongation at break is 350%-400%, and the mechanical properties are excellent; the self-repair efficiency reaches 85%-90%, effectively extending the service life; Unique functionality: The introduction of MXene nanosheets imparts photothermal responsiveness to the coating, enhancing its mechanical and waterproof properties. This also allows for applications in special scenarios such as snow melting and de-icing, broadening the product's application areas. Collaborative innovation: Each component and the preparation process work closely together to enhance synergy. The lack of any key element will lead to a significant decline in performance. DETAILED DESCRIPTION

[0015] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0016] Contact angle test Reference Standard: Tested in accordance with GB / T30693-2014, "Measurement of the Contact Angle of Plastic Film with Water." This standard specifies the method for measuring the contact angle of plastic film with water. This test is used to evaluate the hydrophobicity of waterborne epoxy waterproof coatings. A larger contact angle indicates a more hydrophobic coating surface and stronger waterproofing properties.

[0017] Test steps: Use a contact angle meter to test. Apply the prepared coating evenly onto a clean, flat glass substrate. Dry and cure according to standard construction procedures to form a coating of uniform thickness. Under ambient temperature (23±2)°C and relative humidity (50±5)%, apply tiny droplets of deionized water to the coating surface. The optical system of the contact angle meter captures the contact image between the droplet and the coating surface. Use relevant software to analyze the image and measure and record the water contact angle. Measure at least five different locations on each sample, and take the average value as the contact angle for that sample.

[0018] Tensile strength and elongation at break tests Reference Standard: Refer to GB / T528-2009, "Vulcanized or Thermoplastic Rubber - Determination of Tensile Stress-Strain Properties." This standard is applicable to determining the stress-strain properties of vulcanized or thermoplastic rubber during tension and is used to evaluate the mechanical properties of cured waterborne epoxy waterproof coatings.

[0019] Test steps: First, prepare the coating into a standard dumbbell-shaped specimen according to the prescribed construction method. The specimen size and preparation process strictly follow the standard requirements. After the specimen is prepared, it is cured under standard environmental conditions for the specified time. Use an electronic universal material testing machine for testing. Install the specimen on the fixture of the testing machine and stretch the specimen at a constant tensile rate of (500±50) mm / min until the specimen breaks. During the stretching process, the testing machine automatically records the tensile force and displacement data. Through the data processing software, the tensile strength is calculated based on the tensile force and the original cross-sectional area of ​​the specimen, and the elongation at break is calculated based on the displacement change and the original gauge length of the specimen. Prepare 5 valid specimens for each sample, and take the average value as the tensile strength and elongation at break of the sample.

[0020] Water absorption test Reference Standard: Testing was conducted in accordance with GB / T1733-1993, "Determination of Water Resistance of Paint Films." This standard specifies methods for determining the water resistance of paint films. By measuring changes in the performance of a paint film after immersion in water for a specified period of time, the water resistance of the paint film is evaluated. This test is used to measure the waterproofing properties of waterborne epoxy waterproof coatings.

[0021] Test Procedure: Apply the coating to a cement mortar board measuring 100 mm x 100 mm x 3 mm to form a uniform coating. After curing according to the specified process, dry the specimen in an oven at (60 ± 2)°C to constant weight, and record the initial mass m0. Then, completely immerse the specimen in deionized water at (23 ± 2)°C for the specified time (usually 24 hours, 48 ​​hours, 72 hours, etc., depending on the test situation). Remove the specimen and gently blot the surface moisture with filter paper. Immediately weigh the mass m1 at this point. The water absorption formula is: Water absorption (%) = [(m1 - m0) / m0] × 100%. Three specimens are tested for each sample, and the average value is used as the water absorption rate for that sample.

[0022] Self-repair efficiency test (simulated scratch repair) Reference Standard: There is no fully corresponding national standard at present. This test is designed with reference to the general methods of self-healing performance research of related materials and the experience of similar tests in the industry.

[0023] Test steps: Use a stylus of appropriate hardness to create a 10mm scratch on the prepared coating surface at a specific pressure and speed. Place the scratched specimen in a specific environment (e.g., 25°C, 50% relative humidity) for a period of time to allow the dynamic crosslinker in the coating to function and self-repair. After the repair period, observe the micromorphological changes in the scratched area using a laser confocal microscope or scanning electron microscope. Image analysis software is used to measure the change in scratch width or depth before and after repair, and the self-repair efficiency is calculated. Self-repair efficiency (%) = [(initial scratch width or depth - repaired scratch width or depth) / initial scratch width or depth] × 100%. Each sample is scratched three times, and the average value is taken as the self-repair efficiency of that sample.

[0024] Equipment Name: Contact Angle Meter Related Model: SL200B Contact Angle Meter. This instrument utilizes optical imaging principles and is equipped with a high-resolution camera and precision optical lenses, clearly capturing images of tiny droplets contacting a coating surface. Equipped with automatic analysis software, it quickly and accurately measures contact angles with an accuracy of ±0.1°. It is suitable for measuring the hydrophobicity of various surface materials and complies with the measurement equipment requirements of the GB / T30693-2014 standard.

[0025] Tensile strength and elongation at break tests: Equipment name: Electronic universal material testing machine; Related Model: WDW-100E Electronic Universal Materials Testing Machine. This machine has a maximum test force of 100kN and a test force measurement range of 0.4%-100% FS, with a relative error within ±1%. Equipped with high-precision load cells and displacement sensors, it accurately measures tensile force and displacement. It features multiple test speed control modes and meets the tensile rate requirement of (500±50) mm / min specified in the GB / T528-2009 standard. It is suitable for measuring the tensile stress-strain properties of materials such as rubber and plastics.

[0026] Water absorption test Equipment name: Electric constant temperature blast drying oven, electronic balance; Related models: Electric constant temperature blast drying oven: DHG-9140A, the temperature control range is room temperature + 5℃-250℃, the temperature fluctuation is ±1℃, which can ensure that the specimen is dried to constant weight at (60±2)℃.

[0027] Electronic balance: FA2004B, with a maximum weighing capacity of 200 g and a graduation value of 0.1 mg, can accurately weigh the mass of the specimen before and after drying and after immersion, meeting the requirements for mass measurement accuracy for water absorption calculation.

[0028] Self-repair efficiency test (simulated scratch repair): Equipment name: Laser confocal microscope, hardness stylus; Related models: The Leica TCS SP8 laser confocal microscope offers high-resolution imaging capabilities, enabling microscopic observation of scratched areas at the micron and even nanometer levels. Laser scanning and confocal imaging techniques enable clear 3D images of scratches before and after repair, facilitating precise width and depth measurements using image analysis software.

[0029] Hardness stylus: A tungsten carbide stylus with a hardness of HRC60 and a tip curvature radius of approximately 50μm is used. When a certain pressure is applied, a stable and repeatable scratch can be formed on the coating surface, meeting the requirements of the simulated scratch repair test.

[0030] MXene nanosheets are a new type of two-dimensional inorganic carbide or nitride material, whose chemical formula is usually expressed as M n+1 X n T x , where M is a transition metal (such as Ti, V, Mo, etc.), X is carbon (C) or nitrogen (N), and Tx represents a surface functional group (such as -OH, -F, -O, etc.).

[0031] Structurally, MXene nanosheets possess a unique layered structure, typically measuring less than a few nanometers thick and with lateral dimensions up to micrometers. This two-dimensional structure gives them a large surface area, enabling them to fully exploit surface effects and providing a foundation for improved material performance.

[0032] In terms of properties, MXene nanosheets exhibit many excellent characteristics. First, they have excellent electrical conductivity and high electron mobility, which give them unique advantages in the field of photothermal conversion. Under illumination, MXene nanosheets can efficiently absorb light energy and convert it into heat, thereby achieving photothermal response. Second, MXene nanosheets have excellent mechanical properties. Their layered structure gives the material high strength and toughness, which can effectively enhance the mechanical properties of coatings and improve the coating's tensile and tear resistance. In addition, the rich functional groups on the surface of MXene nanosheets make them hydrophilic and chemically active, facilitating surface modification and enabling better integration with other components in the coating, enhancing the stability of the coating system.

[0033] Selective etching is a common method for preparing MXene nanosheets. For example, using hydrofluoric acid (HF) or a fluorine-containing etchant to selectively remove the A layer (e.g., the Al layer) from the MAX phase (M is a transition metal, A is a main group element, and X is carbon or nitrogen) yields Ti3C2Tx (MXene). Subsequently, ultrasonic exfoliation or other methods can be used to further exfoliate the multilayer MXene into single-layer or few-layer nanosheets.

[0034] In the waterborne epoxy waterproof coating of this invention, the MXene nanosheets are surface-coated with polydopamine (PDA). This polydopamine coating not only improves the dispersion of the MXene nanosheets in the coating system, preventing their aggregation and ensuring their full functionality, but also generates heat when exposed to light. This not only improves the coating's application performance and curing speed in low-temperature environments but also thermally repairs microcracks within the coating. This reinforcing effect synergizes with other reinforcing components in the coating to significantly enhance its overall waterproofing and mechanical properties.

[0035] Waterborne epoxy resin emulsion is a stable emulsion system formed by dispersing epoxy resin in water using an emulsification technique, based on epoxy resin. Its solid content is 45%-50%, and its epoxide value is 0.18-0.22eq / 100g. Structurally, the epoxy resin molecule contains a large amount of epoxy groups, which have very high reactivity and can undergo a cross-linking reaction with a curing agent to form a high molecular weight polymer with a three-dimensional network structure, thereby imparting good film-forming properties and mechanical strength to the coating. In the coating of the present invention, the waterborne epoxy resin emulsion, as a film-forming substance, is the basis for the coating to form a continuous, dense waterproof coating. Its stable emulsion state ensures the uniformity and workability of the coating during construction. Simultaneously, suitable solid content and epoxide value ensure that the cross-linking reaction is fully carried out, playing a key role in the final performance of the coating.

[0036] Silica nanoparticles have a particle size of 50-100 nm, a specific surface area ≥200 m² / g, and a surface hydroxyl content ≥3 mmol / g. Structurally, they are composed of covalently linked silicon-oxygen tetrahedra (SiO₄) forming a three-dimensional network. Their nanoscale size gives them an extremely large specific surface area and surface energy. This unique structure imparts a series of exceptional properties: First, the high specific surface area enables them to interact fully with other coating components, enhancing the stability of the coating system. Second, the abundant surface hydroxyl groups impart excellent hydrophilicity and chemical activity, facilitating surface modification and enabling better bonding with waterborne epoxy resin emulsions. Third, the small size of the nanoparticles enables them to fill micropores in the coating, improving its compactness and water-repellency. In this invention, the silica nanoparticles synergistically work with polystyrene microspheres to create a hierarchical roughness structure, which is one of the key components in achieving the coating's superhydrophobic properties.

[0037] Polystyrene microspheres have a particle size of 1-3 μm, a pore size distribution of 100-500 nm, and a porosity of ≥70%. Their chemical structure is a linear polymer formed by the polymerization reaction of styrene monomers. The molecular chain contains a benzene ring structure, which imparts a certain degree of rigidity and stability. The micron-scale size of the microspheres and the rich internal pore structure are their main characteristics: their micron-scale size enables them to serve as a skeleton for constructing the rough structure of the coating, forming a multi-level rough surface together with silica nanoparticles; their high porosity and specific pore size distribution facilitate the filling and arrangement of nanoparticles within their pores. During the preparation process, the nanoparticles are induced to form a directional nano-protrusion structure within the micron-scale pores, further enhancing the hydrophobic properties of the coating. Furthermore, the presence of polystyrene microspheres can also adjust the rheological properties of the coating and improve its application performance.

[0038] Bio-based long-chain alkylsiloxane is a palmitic acid modified silane coupling agent with the molecular formula C 18 H 37 Si(OCH3)3. Its molecular structure contains long chain alkyl (C 18 H 37 -) and siloxane (-Si(OCH3)3). The long-chain alkyl group imparts low surface energy, reducing the surface tension of the coating and making it hydrophobic. The siloxane portion can hydrolyze under certain conditions to form silanol groups (-SiOH). These silanol groups can undergo condensation reactions with other components in the coating (such as hydroxyl groups on the surface of silica nanoparticles) to form chemical bonds, thereby firmly grafting the long-chain alkyl group to the coating surface and achieving low-surface-energy modification. In the present invention, bio-based long-chain alkylsiloxane is surface-modified to form a low-surface-energy grafted layer with a thickness of 50-100nm on the coating surface. This layer, in synergistically with the multi-level roughness structure, achieves a super-hydrophobic effect on the coating surface, significantly improving the coating's waterproof properties.

[0039] The dynamic crosslinker is an acylhydrazone dynamic crosslinker, prepared by a specific reaction between adipic acid dihydrazide and an aldehyde-modified epoxy resin. Chemically, its molecule contains an acylhydrazone bond (-C=N-NH-), a chemical bond with unique dynamic reversibility. Under certain conditions (such as temperature and pH changes), the acylhydrazone bond can break and reform, thereby achieving dynamic adjustment of the crosslinked network. In the coating of the present invention, when the coating is subjected to external forces and produces microcracks or damage, the broken acylhydrazone bonds can react under appropriate conditions to form a crosslinked structure, enabling the coating to achieve self-repair capabilities, effectively improving the durability and stability of the coating and extending the service life of the coating.

[0040] Polycarboxylate dispersants are a class of high-molecular-weight polymers containing hydrophilic groups such as carboxyl (-COOH) and hydrophobic groups such as long-chain alkyl groups. In coating systems, their mechanism of action is based on steric hindrance and electrostatic repulsion: the hydrophilic carboxyl groups can ionize in water, imparting a negative charge to the dispersant molecules, thereby forming a double layer on the particle surface and generating electrostatic repulsion, preventing particle aggregation. The hydrophobic long-chain alkyl groups adsorb on the surfaces of solid particles (such as silica nanoparticles), forming a steric hindrance layer that further hinders particle aggregation. In the present invention, polycarboxylate dispersants can effectively disperse the solid particles in the coating, ensuring uniform distribution of the various components in the coating system, improving the coating's stability and workability, and avoiding coating defects caused by particle agglomeration.

[0041] Silicone defoamers are primarily composed of polydimethylsiloxane and its derivatives. In their molecular structure, the polydimethylsiloxane segments possess low surface tension and excellent hydrophobicity, allowing them to quickly spread across the foam surface, reducing the surface tension and causing it to burst. Furthermore, the specialized functional groups (such as polyether segments) in the defoamer provide compatibility with other components of the coating system, ensuring stable dispersion and no impact on the coating's film-forming properties. During the preparation of the coating of this invention, the silicone defoamer effectively eliminates bubbles introduced during high-speed dispersion and stirring, preventing them from remaining in the coating and forming pores, thereby ensuring the coating's density and water-resistance.

[0042] Deionized water is high-purity water obtained by removing various anions and cations from water through methods such as ion exchange and reverse osmosis. Its conductivity is ≤5 μS / cm. In the water-based epoxy waterproof coating of this invention, deionized water serves as a solvent, diluting the coating and adjusting its viscosity, resulting in excellent workability and ease of application, such as brushing and spraying. Furthermore, high-purity deionized water avoids the adverse effects of impurities (such as calcium and magnesium ions) found in ordinary water on coating performance, ensuring the stability of the coating system and the proper reaction between its components.

[0043] Example 1 A preparation method of a water-based epoxy waterproof coating comprises the following steps: weighing, by weight, 100 parts of a water-based epoxy resin emulsion (solid content 45%, epoxy value 0.18 eq / 100 g), 10 parts of silicon dioxide nanoparticles (particle size 50 nm, specific surface area 200 m² / g, surface hydroxyl content 3 mmol / g), 5 parts of polystyrene microspheres (particle size 1 μm, pore size distribution 100 nm, porosity 70%), 3 parts of bio-based long-chain alkyl siloxane, 2 parts of a dynamic crosslinking agent, 1 part of MXene nanosheets coated with polydopamine, 0.5 parts of a polycarboxylate dispersant, 0.3 parts of a silicone defoaming agent, and 20 parts of deionized water.

[0044] The preparation method is as follows: a. Premixing: Add waterborne epoxy resin emulsion, dispersant, defoamer and deionized water to a high-speed dispersing kettle, shear and emulsify at 8000 rpm for 15 minutes, and control the material temperature to ≤40°C; b. Micro-nanostructure construction: b1. The silica nanoparticles and polystyrene microspheres were mixed in a mass ratio of 2: 1, added to an aqueous epoxy resin emulsion, and dispersed under ultrasonic conditions of 40kHz frequency and 300W power for 30 minutes; b2. The mixture was transferred to a reactor and stirred at 300 rpm for 2 hours at 50 ° C under nitrogen protection. The template sodium dodecyl sulfate (SDS, added in an amount of 0.5% of the total mass of the epoxy resin emulsion) was first added, and 60% of the total amount was premixed with the epoxy resin. After stirring for 1 hour, the remaining 40% of SDS was added. b3. The temperature was raised to 80°C at a rate of 2°C / min, the vacuum was maintained at -0.08MPa, and the solvent was evaporated for 30 minutes to induce the nanoparticles to form a directional nanoprotrusion structure within the micron-sized pores; c. Surface modification: c1. The bio-based long-chain alkylsiloxane was dissolved in a mixed solvent of ethanol and deionized water in a volume ratio of 1:1 to prepare a modified solution with a mass concentration of 5%; c2. The micro-nanostructure precursor was treated by vacuum-assisted impregnation (-0.05 MPa vacuum was applied during the impregnation stage for 10 minutes). The immersion time was 12 hours, the immersion liquid temperature was 25°C, and after immersion, the solution was drained at a rate of 0.5°C / min until no droplets fell. c3 in a circulating hot air drying oven at 60 ℃ for 1 hour, the wind speed was controlled at 1m / s, forming a low surface energy grafted layer with a thickness of 50nm; d. Addition of functional additives: Add dynamic crosslinker and photothermal responsive material, maintain 25°C for the first 15 minutes, then raise the temperature to 35°C for the next 15 minutes, and stir at 200 rpm for 30 minutes until the viscosity reaches 3000 mPa·s (measured at 25°C). e. Post-processing: First coarse filter through a 200-mesh stainless steel filter, then fine filter through a 0.5μm pore size ceramic membrane (filtration pressure is controlled at 0.2MPa), and fill at 25±2℃ and relative humidity ≤50%.

[0045] Example 2 A method for preparing a water-based epoxy waterproof coating comprises the following steps: weighing, by weight, 105 parts of a water-based epoxy resin emulsion (solid content 46%, epoxy value 0.19 eq / 100 g), 11.5 parts of silicon dioxide nanoparticles (particle size 60 nm, specific surface area 210 m² / g, surface hydroxyl content 3.1 mmol / g), 6 parts of polystyrene microspheres (particle size 1.5 μm, pore size distribution 200 nm, porosity 72%), 3.5 parts of a bio-based long-chain alkylsiloxane, 2.5 parts of a dynamic crosslinking agent, 1.5 parts of MXene nanosheets coated with polydopamine, 0.6 parts of a polycarboxylate dispersant, 0.35 parts of an organosilicon defoaming agent, and 22 parts of deionized water; and the remaining steps are the same as those in Example 1.

[0046] Example 3 A method for preparing a water-based epoxy waterproof coating comprises the following steps: weighing, by weight, 110 parts of a water-based epoxy resin emulsion (solid content 47%, epoxy value 0.20 eq / 100 g), 12.5 parts of silicon dioxide nanoparticles (particle size 75 nm, specific surface area 220 m² / g, surface hydroxyl content 3.2 mmol / g), 6.5 parts of polystyrene microspheres (particle size 2 μm, pore size distribution 300 nm, porosity 75%), 4 parts of a bio-based long-chain alkylsiloxane, 3 parts of a dynamic crosslinking agent, 2 parts of MXene nanosheets coated with polydopamine, 0.75 parts of a polycarboxylate dispersant, 0.45 parts of a silicone defoaming agent, and 25 parts of deionized water. The remaining steps are the same as those in Example 1.

[0047] Example 4 A method for preparing a water-based epoxy waterproof coating comprises the following steps: weighing, by weight, 115 parts of a water-based epoxy resin emulsion (solid content 48%, epoxy value 0.21 eq / 100 g), 13.5 parts of silicon dioxide nanoparticles (particle size 85 nm, specific surface area 230 m² / g, surface hydroxyl content 3.3 mmol / g), 7 parts of polystyrene microspheres (particle size 2.5 μm, pore size distribution 400 nm, porosity 78%), 4.5 parts of a bio-based long-chain alkylsiloxane, 3.5 parts of a dynamic crosslinking agent, 2.5 parts of MXene nanosheets coated with polydopamine, 0.85 parts of a polycarboxylate dispersant, 0.5 parts of a silicone defoaming agent, and 27 parts of deionized water. The remaining steps are the same as those in Example 1.

[0048] Example 5 A method for preparing a water-based epoxy waterproof coating comprises the following steps: weighing, by weight, 120 parts of a water-based epoxy resin emulsion (solid content 50%, epoxy value 0.22 eq / 100 g), 15 parts of silicon dioxide nanoparticles (particle size 100 nm, specific surface area 250 m² / g, surface hydroxyl content 3.5 mmol / g), 8 parts of polystyrene microspheres (particle size 3 μm, pore size distribution 500 nm, porosity 80%), 5 parts of bio-based long-chain alkylsiloxane, 4 parts of a dynamic crosslinking agent, 3 parts of MXene nanosheets coated with polydopamine, 1 part of a polycarboxylate dispersant, 0.6 parts of an organosilicon defoaming agent, and 30 parts of deionized water. The remaining steps are the same as those in Example 1.

[0049] Comparative Example 1: Compared with Example 3, no silicon dioxide nanoparticles were added, and other components and preparation methods were the same.

[0050] Comparative Example 2: Compared with Example 3, no dynamic crosslinking agent was added, and other components and preparation methods were the same.

[0051] Comparative Example 3: Compared with Example 3, no surface modification treatment was performed, and other components and preparation methods were the same.

[0052] Comparative Example 4: Compared with Example 3, no MXene nanosheets were added, and other components and preparation methods were the same.

[0053] Comparative Example 5: Commercially available water-based epoxy waterproof coating was purchased and obtained using a traditional formula and preparation process.

[0054] Comparative Example 6: Compared with Example 3, the micro-nanostructure precursor synthesis step was not performed (ie, step b was omitted), and the components were directly mixed in a conventional manner, with other conditions being the same.

[0055] Comparative Example 7: Compared with Example 3, the low surface energy modification step was not performed (ie, step c was omitted), and other preparation methods and components were the same.

[0056] The model of comparative example 5 is specifically the traditional water-based epoxy waterproof coating WX-100, and the specific composition ratio is calculated by weight: 100 parts of ordinary water-based epoxy resin emulsion, solid content of about 40%, epoxy value of 0.15-0.17eq / 100g; 20 parts of calcium carbonate filler, particle size about 5-10 μm; 0.5 parts of dispersant, which is a conventional polyacrylate dispersant; 0.3 parts of defoamer, which is a common mineral oil defoamer; 3 parts of film-forming aid, using propylene glycol butyl ether; 30 parts of deionized water, conductivity ≤ 5μS / cm; 0.2 parts of thickener, which is hydroxyethyl cellulose; 0.1 parts of preservative, sodium benzoate is selected.

[0057] The products of the examples and comparative examples were subjected to performance tests, including contact angle, tensile strength, elongation at break, water absorption, and self-repair efficiency (simulated scratch repair). The test results are shown in Tables 1 and 2: Table 1 Contact angle (°) Tensile strength (MPa) Elongation at break (%) Example 1 152 12.5 350 Example 2 153 12.8 360 Example 3 155 13.2 380 Example 4 156 13.6 390 Example 5 158 14 400 Comparative Example 1 120 10 300 Comparative Example 2 150 12 320 Comparative Example 3 135 11.5 330 Comparative Example 4 154 13 370 Comparative Example 5 110 9.5 280 Comparative Example 6 130 11 320 Comparative Example 7 138 12 340 Table 2 Water absorption rate (%) Self-repair efficiency (%) Example 1 1.2 85 Example 2 1.1 86 Example 3 1 88 Example 4 0.9 89 Example 5 0.8 90 Comparative Example 1 3.5 - Comparative Example 2 1.8 50 Comparative Example 3 2.5 - Comparative Example 4 1.3 85 Comparative Example 5 4 - Comparative Example 6 2.8 - Comparative Example 7 2 88 As can be seen from the test data, the contact angles of the coatings prepared in Examples 1 to 5 all reached more than 152°, which are much higher than those in Comparative Example 1, Comparative Example 3, Comparative Example 6 and Comparative Example 7. This is due to the multi-level rough structure constructed by silica nanoparticles and polystyrene microspheres, combined with the low surface energy modification treatment of bio-based long-chain alkylsiloxanes, to form a super-hydrophobic surface similar to the lotus leaf effect, effectively preventing water penetration. Comparative Example 1 did not add silica nanoparticles, Comparative Example 6 did not perform micro-nanostructure precursor synthesis, and Comparative Example 7 did not perform low surface energy modification, all of which led to a significant decrease in contact angle and an increase in water absorption, fully demonstrating the key role of the special components and processes of this application in improving waterproof performance. In addition, the water absorption of the embodiments is generally lower than 1.2%, while the water absorption of the samples in the comparative examples that did not optimize the waterproof structure is as high as 2.5%-4.0%, further reflecting the excellent waterproof performance of the coating of this application.

[0058] In tensile strength and elongation at break tests, Examples 1 to 5 achieved tensile strengths of 12.5-14.0 MPa and elongations at break of 350%-400%, significantly outperforming samples using conventional processes and formulations, such as Comparative Example 5. This is due to the waterborne epoxy resin emulsion providing a good film-forming foundation, the silica nanoparticles and MXene nanosheets providing reinforcement, and the crosslinked network formed by the dynamic crosslinker making the coating structure more stable, effectively dispersing stress when subjected to external forces and improving overall mechanical properties.

[0059] The self-healing efficiency of Examples 1 to 5 reached 85%-90%, while that of Comparative Example 2, which lacked a dynamic crosslinker, was only 50%. The dynamic crosslinker (acylhydrazone dynamic crosslinker) enables self-healing through a reversible crosslinking reaction when the coating is damaged, effectively extending the coating's service life and improving its durability and stability.

[0060] The introduction of MXene nanosheets imparts photothermal responsiveness to the coating. While this performance wasn't directly demonstrated in the tests, the overall performance improvements in mechanical and waterproofing properties of the example samples are also attributed to the enhanced and synergistic effects of the MXene nanosheets. Furthermore, the material's photothermal conversion properties under illumination can be used in specialized applications such as snow melting and de-icing, expanding the coating's application range.

[0061] The test results of the comparative examples show that the lack of any key component or process step will lead to a decline in coating performance. For example, the lack of surface modification in Comparative Example 3 and the lack of micro-nanostructure precursor synthesis in Comparative Example 6 both severely affected the waterproofing and mechanical properties of the coating. This fully demonstrates that the selection of components and the design of the preparation process in this application work in a coordinated and synergistic manner, jointly improving the overall performance of the coating and giving the product outstanding substantive characteristics and significant advancements.

[0062] The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications based on the present invention to solve substantially the same technical problems and achieve substantially the same technical effects are all included in the scope of protection of the present invention.

Claims

1. A method for preparing a water-based epoxy waterproof coating, characterized in that: By weight, it is composed of the following components: 100-120 parts of a water-based epoxy resin emulsion, wherein the solid content of the water-based epoxy resin emulsion is 45%-50% and the epoxy value is 0.18-0.22 eq / 100g; 10-15 parts of silica nanoparticles, with a particle size of 50-100 nm, a specific surface area ≥ 200 m² / g, and a surface hydroxyl content ≥ 3 mmol / g; 5-8 parts of polystyrene microspheres, with a particle size of 1-3 μm, a pore size distribution of 100-500 nm, and a porosity of ≥70%; 3-5 parts of bio-based long-chain alkylsiloxane, which is a palmitic acid-modified silane coupling agent; 2-4 parts of dynamic crosslinking agent; 1-3 parts of a photothermal responsive material selected from MXene nanosheets, wherein the thickness of the MXene nanosheets is ≤ 5 nm; 0.5-1 part of dispersant, which is a polycarboxylate dispersant; 0.3-0.6 parts of defoaming agent, which is a silicone defoaming agent; 20-30 parts of deionized water, conductivity ≤5μS / cm.

2. A method for preparing the waterborne epoxy waterproof coating according to claim 1, characterized in that: The following steps are involved: a. Premixing: Add waterborne epoxy resin emulsion, dispersant, defoamer and deionized water to a high-speed dispersing kettle, shear and emulsify at a speed of 8000-10000 rpm for 15-20 minutes, and control the material temperature to ≤40°C; b. Micro-nanostructure construction: Synthesis of precursors with multi-level rough structures; c. Surface modification: low surface energy treatment; d. Adding functional additives: Add dynamic crosslinking agent and photothermal response material, stir at 200-300 rpm for 30-40 minutes, until the viscosity reaches 3000-5000 mPa·s; e. Post-processing: Filter through a 200-mesh sieve and fill at 25±2℃ and relative humidity ≤50%.

3. The preparation method of the water-based epoxy waterproof coating according to claim 2, characterized in that: The synthesis of the micro-nanostructure precursor comprises the following steps: b1. The silica nanoparticles and polystyrene microspheres were mixed in a mass ratio of (2-2.5): 1, added to an aqueous epoxy resin emulsion, and dispersed under ultrasonic conditions of 40kHz frequency and 300W power for 30-40 minutes; b2. The mixture was transferred to a reactor and stirred at 50-60 ° C under nitrogen at 300-400 rpm for 2-3 hours, and a template of sodium lauryl sulfate was added, wherein the amount of sodium lauryl sulfate added was 0.5% -1% of the total mass of the epoxy resin emulsion; b3. Raise the temperature to 80-85°C at a rate of 2°C / min, maintain a vacuum of -0.08 to -0.1 MPa, and evaporate the solvent for 30-40 minutes to induce the nanoparticles to form a directional nanoprotrusion structure within the micron-sized pores.

4. The preparation method of the waterborne epoxy waterproof coating according to claim 3, characterized in that: In step b2, the template sodium lauryl sulfate is added in two portions: 60% of the total amount is premixed with the epoxy resin in the first addition, and the remaining 40% is added after stirring for 1 hour.

5. The preparation method of the water-based epoxy waterproof coating according to claim 2, characterized in that: The surface modification comprises the following steps: c1. The bio-based long-chain alkylsiloxane is dissolved in a mixed solvent of ethanol and deionized water, wherein the volume ratio of ethanol to water is (1:1)-(3:1), and a modified solution having a mass concentration of 5%-8% is prepared; c2. The micro-nanostructure precursor is treated by immersion, the immersion time is 12-24 hours, the immersion liquid temperature is 25-30 ° C, and after immersion, it is drained at a rate of 0.5-1 ° C / min until no droplets fall; c3. Treat in a circulating hot air drying oven at 60-70°C for 1-2 hours with the wind speed controlled at 1-2m / s to form a low surface energy grafting layer with a thickness of 50-100nm.

6. The method for preparing the waterborne epoxy waterproof coating according to claim 5, characterized in that: The impregnation method adopts a vacuum-assisted process: a vacuum degree of -0.05 to -0.08 MPa is applied during the impregnation stage and maintained for 10 to 15 minutes to promote the penetration of the modification liquid into the deep layer of the micro-nano structure.

7. The method for preparing a waterborne epoxy waterproof coating according to claim 2, wherein: The dynamic crosslinking agent is an acylhydrazone dynamic crosslinking agent, and its preparation method includes: Y1. Adipic acid dihydrazide and formaldehyde-modified epoxy resin are mixed in a molar ratio of 1:2, wherein the degree of aldehyde substitution of the formaldehyde-modified epoxy resin is 10%-15%; Y2. React in an acetate buffer solution with a pH of 4-5 at 40-50°C for 4-6 hours to obtain a dynamic crosslinker solution.

8. The method for preparing a waterborne epoxy waterproof coating according to claim 2, wherein: The MXene nanosheets are surface-coated with polydopamine, and the coating layer has a thickness of 2-5 nm. The coating method includes: Z1. Disperse MXene nanosheets in Tris-HCl buffer at pH 8.5 and add dopamine hydrochloride with a mass ratio of dopamine to MXene of 1:

20. Z2. Stirring polymerization at 25°C for 24 hours, and then centrifuging and washing to obtain a composite material.

9. The method for preparing a waterborne epoxy waterproof coating according to claim 2, wherein: In step d, staged temperature control and stirring are adopted: the temperature is maintained at 25-30° C. for the first 15 minutes, and then the temperature is raised to 35-40° C. for the next 15-25 minutes to promote the diffusion of the dynamic crosslinking agent.

10. The method for preparing a waterborne epoxy waterproof coating according to claim 2, wherein: The filtration process in step e is carried out in two stages: first, coarse filtration through a 200-mesh stainless steel filter, and then fine filtration through a 0.5 μm pore size ceramic membrane, with the filtration pressure controlled at 0.2-0.4 MPa.