High-strength rain-erosion-resistant coating and preparation method thereof

Abstract

The present application relates to the technical field of functional coating, in particular to a high-strength rain-erosion-resistant coating and a preparation method thereof, the coating is composed of two components of polyaspartic ester resin (A) and high-elasticity aliphatic polyurea curing agent (B), the component A is prepared by addition reaction of dicyclohexylmethane diamine, 1,3-bis(aminomethyl)cyclohexane, chain-extending diamine and maleic acid diethyl ester; the component B is stepwisely synthesized by dicyclohexylmethane diisocyanate and isophorone diisocyanate, polycarbonate diol and hexamethylene diisocyanate trimer; by adding functional fillers, leveling agents, ultraviolet absorbers and environmentally friendly solvents into the stirring reaction kettle, and then stirring and keeping warm, the high-strength rain-erosion-resistant coating is obtained, the coating film of the high-strength rain-erosion-resistant coating has excellent mechanical strength, is more resistant to rain erosion, is convenient to construct, is significantly superior to the best-selling protective film, and can be widely used in the outer surface protection of high-end equipment such as aviation, wind power and high-speed rail.

Description

Technical Field

[0001] This invention relates to the field of functional coatings technology, and in particular to a high-strength rain-resistant coating and its preparation method. Background Technology

[0002] High-end equipment such as aircraft, wind turbine blades, and high-speed trains are often exposed to complex and harsh environments during their service life. In particular, they are subjected to continuous high-speed impacts from raindrops during high-speed operation. This high-frequency and high-intensity impact can easily cause damage such as pitting and cracking on the equipment surface, which not only damages the appearance integrity but also gradually weakens the structural strength and shortens the overall service life of the equipment. Traditional polyurethane or epoxy protective coatings, due to their own molecular structure limitations, generally have insufficient tensile strength or too low elongation. They are unable to withstand long-term impact loads under extreme working conditions and often fail in a short period of time due to cracking and peeling, failing to provide durable and reliable protection for the equipment. Although there are protective products on the market that are considered to have superior performance, these products have obvious limitations in practical applications. Their construction process has extremely high requirements for environmental conditions and operational precision. Moreover, during long-term use, they are prone to problems such as bulging and peeling from the edges due to factors such as temperature fluctuations, vibration, and external stress, which greatly increases the maintenance costs and safety hazards of the equipment.

[0003] Therefore, developing a high-strength rain-resistant coating with superior mechanical properties and longer weather resistance and rain erosion resistance, along with its preparation method, to replace traditional coatings and existing protective products, has become a key need for breakthroughs in the field of high-end equipment protection. Meanwhile, polyaspartic acid ester resin, due to the steric hindrance effect brought about by its unique molecular structure, can significantly extend the gel time of coatings, providing ample operational window for application. Furthermore, after reacting with aliphatic polyurea curing agents, it can form a high-crosslink density network structure, possessing excellent mechanical properties and weather resistance. However, existing polyaspartic acid ester resin systems are limited by formulation design and preparation processes, and their overall strength is insufficient to meet the performance requirements of next-generation high-end equipment for rain erosion protection. Based on this, by optimizing the polyaspartic acid ester resin synthesis process, screening high-performance curing agents and functional fillers, and developing a high-strength rain-resistant protective coating using polyaspartic acid ester resin as the base material and highly elastic aliphatic polyurea as the curing agent, it is of great significance for promoting the development of high-end equipment protection technology. Summary of the Invention

[0004] This application provides a high-strength rain-resistant coating and its preparation method, thereby solving the problems of poor mechanical strength, poor rain erosion resistance, and high construction difficulty of high-strength rain-resistant coatings.

[0005] The first aspect of this application provides a high-strength rain-resistant coating, which is composed of polyaspartic acid ester resin, a high-elasticity aliphatic polyurea curing agent, and additives.

[0006] Furthermore, the polyaspartic acid ester resin is prepared by a Michael addition reaction of dicyclohexylmethanediamine, 1,3-bis(aminomethyl)cyclohexane, polyether diamine and diethyl maleate.

[0007] Furthermore, the highly elastic aliphatic polyurea curing agent is prepared by reacting dicyclohexylmethane diisocyanate, isophorone diisocyanate and polycarbonate diol to generate isocyanate-terminated prepolymer, and then mixing and reacting it with hexamethylene diisocyanate trimer.

[0008] Furthermore, in the preparation of the polyaspartic acid ester resin, the molar ratio of dicyclohexylmethanediamine to 1,3-bis(aminomethyl)cyclohexane is 1:0.2-1.0, the amount of polyether diamine is 5-15% of the molar amount of dicyclohexylmethanediamine, the molar ratio of amino groups to diethyl maleate is 1:1.05-1.20, and the reaction is carried out under nitrogen protection at 40-70℃ for 3-5 hours until the amine value of the system is ≤5mgKOH / g.

[0009] Furthermore, in the preparation of the high-elasticity aliphatic polyurea curing agent, dicyclohexylmethane diisocyanate, isophorone diisocyanate, and polycarbonate diol are reacted at a ratio of isocyanate group to hydroxyl group of 2.0-3.0:1 for 2 hours to obtain an isocyanate-terminated prepolymer. Then, hexamethylene diisocyanate trimer with an isocyanate group mass fraction of 16-20% is added to make the final isocyanate group mass fraction of the reaction system reach 3.5-4.0%, and the mixture is cooled and discharged after being kept at 80℃ for 1 hour.

[0010] Furthermore, the polyether diamine is one or more of polyether diamine D-230, polyether diamine D-400, and polyether diamine T-403.

[0011] Furthermore, the polycarbonate diol is any one of polycyclohexanediethanol carbonate diol, polybutanediol carbonate diol, and polybutylene adipate carbonate diol.

[0012] It is understood that the embodiments of this application utilize polycarbonate diols with molecular weights of 500-2000 to construct a synergistic structure of flexible segments and rigid crosslinks within a highly elastic aliphatic polyurea curing agent system. This endows the coating with suitable mechanical properties, application compatibility, and environmental stability. The polycarbonate diols with molecular weights in the 500-2000 range have suitable chain lengths, allowing for efficient reaction with isocyanate groups during the curing process. This forms isocyanate-terminated prepolymers containing flexible segments, and through the synergistic extension and deformation of these flexible segments, the coating receives sufficient elongation at break, mitigating stress concentration under external forces. To prevent brittle fracture of the coating, the carbonate groups in its molecular chain have high bond energy and excellent chemical stability, which can significantly improve the hydrolysis and aging resistance of the curing agent and the final coating, reduce the performance degradation caused by chain segment degradation during long-term outdoor use, and ensure the durability of the coating's rain erosion resistance. At the same time, the appropriate molecular weight allows the polycarbonate diol to have both good solubility and viscosity characteristics, and mix evenly with the hexamethylene diisocyanate trimer in the curing agent system. It will not affect the flowability of the application due to excessive viscosity, and can also form a dense and uniform three-dimensional network during the crosslinking process, providing stable structural support for the coating.

[0013] The second aspect of this application provides a method for preparing a high-strength rain-resistant coating, comprising the following steps: mixing polyaspartic acid ester resin and a high-elasticity aliphatic polyurea curing agent in a stirred reactor at a molar ratio of amino to isocyanate groups of 1.0-1.1:1; pre-stirring at 200-300 r / min for 5-10 min under nitrogen protection at 25-30°C; then adding 1.5-5 wt% functional filler, 0.3-0.5 wt% leveling agent, 0.5-1 wt% UV absorber, and 5-10 wt% environmentally friendly solvent, adjusting the stirring speed to 300-500 r / min; maintaining the temperature at 25-30°C and continuing stirring for 20-30 min; and obtaining a system viscosity of 1500-2500 mPa·s with no visible particles, thus obtaining the high-strength rain-resistant coating.

[0014] It is understood that in this embodiment, the amino groups in the polyaspartic ester resin and the isocyanate groups in the high-elasticity aliphatic polyurea curing agent undergo a nucleophilic addition reaction at 25-30°C, gradually crosslinking. Excess amino groups ensure sufficient reaction of the isocyanate groups, avoiding residual active groups from affecting the stability of the coating. Nitrogen protection isolates air and moisture, preventing the isocyanate groups from reacting with water to generate bubbles and the amino groups from being oxidized, ensuring a stable crosslinking process. Low-speed pre-stirring in the early stage allows the resin and curing agent to come into uniform contact to initiate crosslinking. After adding functional fillers, leveling agents, and other additives, the speed is increased, and the filler agglomeration is broken by shear force, allowing the additives to be uniformly dispersed in the system. The leveling agent can reduce surface tension and improve the smoothness of the coating, while the UV absorber absorbs ultraviolet rays through its molecular structure to improve weather resistance. The constant temperature control at 25-30°C balances reaction and dispersion efficiency, avoiding uneven dispersion caused by low temperature and preventing premature gelation of the system caused by high temperature accelerating crosslinking. The final result is a uniform viscous liquid, ensuring that all components are evenly dispersed and the degree of crosslinking is moderate.

[0015] Furthermore, the environmentally friendly solvent is either propylene glycol methyl ether acetate or dimethyl diacid.

[0016] It is understood that the embodiments of this application select propylene glycol methyl ether acetate and dimethyl diacid as environmentally friendly solvents. Propylene glycol methyl ether acetate and dimethyl diacid balance low environmental hazards with process compatibility and performance support for the coating system. This satisfies environmental requirements while ensuring coating preparation and coating performance. Both propylene glycol methyl ether acetate and dimethyl diacid are low-volatile organic compounds with low vapor pressure and mild volatilization. The emission of harmful gases during production and construction is far lower than that of traditional solvents. They have low irritation to the human body, and their molecular structure is easily degraded by microorganisms, leaving no long-term environmental residue, thus meeting green coating standards. Propylene glycol methyl ether acetate and dimethyl diacid are suitable for polyaspartic acid ester resins and high-molecular-weight polyaspartic acid ester resins. Both the elastic aliphatic polyurea curing agent and the functional filler have excellent solubility and compatibility, which can effectively reduce the viscosity of the coating system, prevent component agglomeration, and ensure uniform dispersion of each substance during mixing. This provides suitable fluidity for spraying and reduces defects such as pinholes and orange peel in the coating film. At the same time, the evaporation rate of propylene glycol methyl ether acetate and dimethyl diacid ester is highly matched with the coating curing process. This can avoid premature curing of the coating surface due to excessively rapid solvent evaporation and loose structure caused by internal solvent retention, or excessively slow evaporation affecting curing efficiency. This ensures that the final coating film forms a dense and uniform cross-linked structure, indirectly improving the tensile strength of the coating, reducing internal weak points and raindrop penetration channels, and helping the coating achieve the dual requirements of high strength and rain erosion resistance.

[0017] Furthermore, the leveling agent is either BYK-333 or EFKA-3777.

[0018] Furthermore, the ultraviolet absorber is Tinuvin 1130.

[0019] It is understood that the embodiments of this application, by adding the ultraviolet absorber Tinuvin 1130 during the preparation of high-strength rain-resistant coatings, utilize the selective absorption and energy conversion capabilities of the benzotriazole structure in its molecular structure to block the damage of ultraviolet rays to the coating, while ensuring the performance stability of the coating and the final film. Tinuvin 1130 can efficiently absorb ultraviolet rays from sunlight, especially the UV-B and UV-A bands with wavelengths of 290-400nm, converting the absorbed ultraviolet light energy into low-energy heat energy or harmless fluorescent radiation release, avoiding direct action of ultraviolet rays on the molecular chains of polyaspartic acid ester resin and the cross-linking structure of the curing agent in the coating, and preventing organic molecules from reacting. Photooxidative degradation, chain breakage, or cross-linking bond destruction delays aging phenomena such as yellowing, chalking, and loss of gloss in the coating, extending its outdoor service life. Meanwhile, the UV absorber Tinuvin 1130 exhibits excellent compatibility with the coating system, preventing delamination, sedimentation, pinholes, and bubbles from forming in the coating film. It remains stably dispersed within the coating, continuously exerting its effect. Furthermore, by protecting the integrity of the coating's organic structure, it indirectly maintains the coating's original mechanical properties and rain erosion resistance, preventing UV degradation that leads to a porous coating structure and protecting it from damage or penetration by raindrops. This ensures the coating maintains high strength and excellent rain erosion resistance over a long period, meeting the demands of complex outdoor environments.

[0020] Furthermore, the functional filler is a mixed filler composed of amino-modified nano-silica and carboxylated nitrile rubber nanoparticles at a mass ratio of 1:0.3-1.0.

[0021] It is understood that, in this embodiment of the application, amino-modified nano-silica and carboxylated nitrile rubber nanoparticles are added. The amino groups on the surface of the amino-modified nano-silica undergo chemical cross-linking with the isocyanate groups in the system to form rigid reinforcing points. Its nanoscale effect refines the coating structure and improves the surface hardness and tensile strength. The carboxyl groups of the carboxylated nitrile rubber nanoparticles react with the amino groups in the resin to introduce flexible segments. The elastic deformation of the rubber phase is used to disperse stress and improve the toughness and elongation at break of the coating. The amino-modified nano-silica and carboxylated nitrile rubber nanoparticles are compounded at a mass ratio of 1:0.3-1.0. The nano-silica constructs a three-dimensional reinforcing network to resist external forces, and the nitrile rubber particles relieve stress concentration and avoid brittle fracture. At the same time, the size effect of the two nanoparticles can reduce agglomeration. Through the dual effects of physical filling and chemical bonding, the microstructure of the coating is optimized, the density is improved to enhance the rain erosion resistance, and the pitting corrosion under raindrop impact is delayed. Moreover, it has good compatibility with the matrix and does not affect the dispersion stability of the system.

[0022] The beneficial effects of this invention are as follows:

[0023] 1. This invention utilizes dicyclohexylmethane diamine in the synthesis of polyaspartic acid ester resin. The rigid cyclohexane structure provides molecular chain rigidity, while 1,3-bis(aminomethyl)cyclohexane increases crosslinking points. A mixed amine system consisting of polyether diamines D-230 / D-400 and flexible segments adjust toughness is then formed with diethyl maleate via a Michael addition reaction to create a resin backbone containing multiple secondary amine groups. This design gives the resin both rigid groups and flexible spacers, providing high initial molecular chain strength for the coating film. The curing agent, a high-elasticity aliphatic polyurea, is formed by reacting dicyclohexylmethane diisocyanate, isophorone diisocyanate, and polycarbonate diol to form an isocyanate-terminated prepolymer. Hexamethylene diisocyanate trimer is added as a high-functionality crosslinking agent, which reacts with the secondary amine groups of polyaspartic acid ester during curing to form urea bonds. Urea bonds themselves have extremely high bond energy and intermolecular hydrogen bonding ability. In addition, the three-dimensional cross-linking network introduced by hexamethylene diisocyanate trimer significantly improves the cross-linking density and intermolecular forces of the coating film, thereby greatly enhancing the tensile strength and modulus of the coating film. Furthermore, the amino-modified nano-silica in the functional filler forms chemical bonds with the resin-curing agent system through the amino groups on the surface. Its nanoscale rigid particles play a role in physical reinforcement and crack pinning in the matrix, effectively dispersing stress and hindering crack propagation. Meanwhile, the carboxylated nitrile rubber nanoparticles act as an elastomer toughening phase. Through their core-shell structure, they deform under tensile stress, induce crazes, and absorb energy. They work synergistically with rigid nano-SiO2 to achieve a rigid-toughness balance, improving tensile strength while avoiding increased material brittleness, thus achieving a significant improvement in the tensile strength of the coating film.

[0024] 2. This invention, in the preparation of polyaspartic ester resin, introduces polyether diamine, utilizing the flexibility of the polyether segments to endow the resin molecular chain with deformability. The flexible segments provide space for molecular movement through rotation and extension, avoiding premature breakage caused by excessive rigidity. Simultaneously, the molar ratio of amine to diethyl maleate is controlled at 1:1.05-1.20 to ensure sufficient addition reaction, forming a regular main chain containing an appropriate amount of flexible segments. In the preparation of the high-elasticity aliphatic polyurea curing agent, a polycarbonate diol with a molecular weight of 500-2000 is selected. Its long-chain carbonate structure introduces flexible segments, and the prepolymer generated by the reaction with isocyanate retains elastic characteristics, synergistically enhancing network elasticity when crosslinked with the resin. The hexamethylene diisocyanate trimer regulates... The isocyanate group content is 3.5-4.0% to avoid excessive crosslinking that restricts deformation. The functional filler is a compound of amino-modified nano-silica and carboxylated nitrile rubber nanoparticles. The carboxylated nitrile rubber reacts with the resin amino group to form an elastic phase at the nanoscale. Under external force, it absorbs energy through deformation, relieves stress concentration, and avoids brittle fracture. The nano-silica balances rigidity and elasticity at this ratio. During coating preparation, the molar ratio of amino to isocyanate group is 1.0-1.1:1 to ensure appropriate crosslinking, which maintains structural stability and leaves space for chain segment movement. Staged stirring at 25-30℃ ensures uniform composition, avoids filler agglomeration to form rigid regions, and ensures uniform action of the elastic phase, thereby significantly improving the elongation at break of the coating film.

[0025] 3. In this invention, during the construction of the matrix resin and curing agent system, polyaspartic acid ester resin forms regular molecular chains through the Michael addition reaction principle. The high-elasticity aliphatic polyurea curing agent uses polycarbonate diol as raw material and combines hexamethylene diisocyanate trimer to regulate the isocyanate group content. The two react at a molar ratio of amino to isocyanate groups of 1.0-1.1:1 to form a high-density cross-linked network. This network structure reduces the internal porosity of the coating and reduces the channels for water penetration during raindrop impact. At the same time, the toughness of the cross-linked network can buffer the impact energy of raindrops and avoid surface damage caused by local stress concentration. Amino-modified nano-silica and carboxylated nitrile rubber nanoparticles are mixed at a ratio of 1:0.3-1.0. The nano-silica fills the microscopic gaps in the coating with the nanoscale effect, further improving the density. Its rigidity enhances the surface hardness of the coating and resists the physical abrasion caused by raindrop impact. The carboxylated nitrile rubber nanoparticles absorb impact energy through elastic deformation, preventing the coating from generating new pitting corrosion sources due to brittle fracture. The two work together to form a rigid and dense-elastic buffer protective structure. The ultraviolet absorber added to the coating can absorb ultraviolet rays, slowing down the aging and degradation of the coating in outdoor environments, and preventing the coating structure from becoming loose and the impact resistance from decreasing due to aging. The constant temperature control, staged stirring and nitrogen protection in the preparation process ensure that each component is evenly dispersed, avoiding the formation of local weak areas due to filler agglomeration or uneven reaction, which accelerates pitting corrosion. In addition, the environmentally friendly solvent evaporates evenly during the coating film formation process, avoiding the formation of pores by residual solvent. The leveling agent optimizes the surface smoothness of the coating, reduces surface protrusions or depressions, and reduces local stress concentration points when raindrops impact. Thus, it achieves a triple protection against raindrop impact: physical blocking, energy buffering and long-term anti-aging, thereby significantly extending the time of rain erosion and pitting.

[0026] 4. This invention, by introducing dicyclohexylmethanediamine, 1,3-bis(aminomethyl)cyclohexane, and polyetherdiamine during the preparation of polyaspartic ester resin, utilizes the steric hindrance effect of the amine compound molecular structure to significantly prolong the gel time of the coating, slowing down the reaction rate between the amino and isocyanate groups. This prevents the coating from losing fluidity due to rapid gelation during on-site construction, allowing sufficient time for large-area application and coating thickness adjustment, thus meeting the needs of longer construction periods. It solves the problems of short application windows and easy clumping in traditional coatings. Furthermore, the reaction conditions are designed to fit actual on-site conditions; no high-temperature environment is required during coating preparation and application. Resin synthesis requires only 40-70℃, curing agent preparation requires 70-90℃, and the coating mixing stage is controlled within the 25-30℃ room temperature range. This eliminates the need for complex on-site heating equipment, reducing energy consumption and operational risks. Moreover, during preparation… The process employs a staged mixing technique. First, low-speed pre-mixing initially mixes the resin and curing agent. Then, high-speed mixing disperses the functional fillers and additives, preventing uneven coating caused by filler agglomeration. Simultaneously, the addition of environmentally friendly solvents such as propylene glycol methyl ether acetate or dimethyl diacid reduces the system viscosity and improves the coating's fluidity, facilitating application through various commonly used on-site methods such as brushing and spraying. The solvent evaporation rate is also moderate, preventing defects such as pinholes and orange peel caused by rapid evaporation. Meanwhile, the leveling agent reduces the surface tension of the coating, minimizing pinholes caused by uneven substrate wetting during application and ensuring a smooth coating surface. Furthermore, the final coating is a homogeneous viscous liquid, facilitating storage and transportation. The reactivity of each component is controllable, and premature curing is less likely after on-site mixing. The dosage can be flexibly adjusted according to the construction progress, reducing material waste and significantly enhancing its suitability for on-site construction.

[0027] 5. This invention utilizes propylene glycol methyl ether acetate and dimethyl diacid as environmentally friendly solvents, with strict control over their addition amounts. Propylene glycol methyl ether acetate, as a low-volatility organic compound solvent, exhibits low volatility, with only a small amount evaporating into the air during application and film formation, significantly reducing volatile organic compound solvent pollution to the atmospheric environment. Dimethyl diacid is an environmentally friendly ester solvent, not only with low volatility but also possessing good biodegradability, allowing it to be decomposed by microorganisms in the natural environment after disposal, avoiding long-term residue pollution of soil or water bodies. The combination of these two solvents not only meets the process requirements of coatings for flowability and solubility but also fundamentally replaces traditional high-volatile organic compound solvents and recalcitrant solvents, reducing the risk of inhalation by construction workers and the environmental burden. Furthermore, the polyaspartic acid ester resin is prepared using dicyclohexylmethanediamine and 1,3-bis(amino)dimethylamine... Methylcyclohexane and polyether diamine are both low-toxicity amine compounds. Their irritation to human skin and respiratory tract during production and use is far lower than that of traditional highly toxic amines. The synthesis of polyaspartic acid ester resin and curing agent is carried out in a closed stirred reactor, and nitrogen protection is used in the resin synthesis stage. This not only avoids the oxidation of raw materials with air, which produces harmful byproducts, but also prevents the leakage of volatile raw materials. The entire coating preparation stage is controlled within the ambient temperature range of 25-30℃, which eliminates the need for high-temperature heating and the consumption of large amounts of energy. It also reduces the possibility of raw material decomposition at high temperatures, which produces toxic substances. At the same time, the staged stirring process ensures that all components are fully mixed, avoiding waste of raw materials due to uneven mixing and reducing the amount of waste coating. Thus, the harm to the environment and human body is reduced throughout the entire life cycle from production and construction to disposal, significantly improving environmental performance and meeting the development requirements of green coatings. Attached Figure Description

[0028] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0029] Figure 1 This is a process diagram of the synthesis of polyaspartic acid ester resin for a method of preparing a high-strength rain-resistant coating according to an embodiment of this application;

[0030] Figure 2 This is a process diagram illustrating the synthesis of a high-elasticity aliphatic polyurea curing agent in a method for preparing a high-strength rain-resistant coating according to an embodiment of this application.

[0031] Figure 3 This is a characteristic diagram showing the effect of functional fillers on tensile strength in a method for preparing a high-strength rain-resistant coating according to an embodiment of this application.

[0032] Figure 4 This diagram illustrates the effect of functional fillers on section elongation in a method for preparing a high-strength rain-resistant coating according to an embodiment of this application. Detailed Implementation

[0033] The technical solution of the present invention is illustrated below through specific examples. It should be understood that the one or more method steps mentioned in the present invention do not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps; it should also be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or defining the scope of the present invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the present invention.

[0034] To better understand the above technical solutions, exemplary embodiments of the present invention are described in more detail below. While exemplary embodiments of the present invention are shown, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the invention to those skilled in the art.

[0035] The dicyclohexylmethane diamine used in this application's embodiments is from Guangzhou Yuanda New Materials Co., Ltd.; the 1,3-bis(aminomethyl)cyclohexane used is from Guangdong Wengjiang Chemical Reagent Co., Ltd.; the polyether diamine D-230 used is from Shanghai Aladdin Biochemical Technology Co., Ltd.; the polyether diamine D-400 used is from Shanghai Aladdin Biochemical Technology Co., Ltd.; the polyether diamine T-403 used is from Shanghai Aladdin Biochemical Technology Co., Ltd.; the diethyl maleate used is from Nanjing Chengyi Chemical Co., Ltd.; the dicyclohexylmethane diisocyanate used is from Nantong Zhonghe Chemical New Materials Co., Ltd.; the isophorone diisocyanate used is from Wuhan Kanos Technology Co., Ltd.; and the polycarbonate diol used is from... The following components were used: Shanghai McLean Biochemical Technology Co., Ltd.; hexamethylene diisocyanate trimer from Shanghai Mairui Biochemical Technology Co., Ltd.; propylene glycol methyl ether acetate from Shandong Mantanghong New Materials Co., Ltd.; dimethyl diacid from Bengbu Zhongshi Chemical Technology Co., Ltd.; BYK-333 from Guangzhou Qianguang Trading Co., Ltd.; EFKA-3777 from Liyang Ruipu New Materials Co., Ltd.; Tinuvin 1130 from Guangdong Shengke Biochemical Technology Co., Ltd.; amino-modified nano-silica from Shanghai Jiute Nanomaterials Technology Co., Ltd.; and carboxylated nitrile butadiene rubber nanoparticles from Dongguan Nabaichuan Plastics Co., Ltd.

[0036] The following describes a high-strength rain-resistant coating and its preparation method according to an embodiment of this application. Addressing the problems of poor mechanical strength and poor rain erosion resistance in high-strength rain-resistant coatings mentioned in the background art, this application provides a high-strength rain-resistant coating and its preparation method: During the synthesis stage of polyaspartic acid ester resin, a mixed amine system composed of dicyclohexylmethane diamine, 1,3-bis(aminomethyl)cyclohexane, and polyether diamine is used to undergo an addition reaction with diethyl maleate, forming a resin skeleton containing secondary amine groups. This gives the resin both rigidity and flexibility, providing high initial molecular chain strength while preventing premature material breakage through flexible segments. Simultaneously, the specific ratio of the mixed amines extends the coating gel time through steric hindrance, providing ample operating window for on-site construction. In the preparation stage of the high-elasticity aliphatic polyurea curing agent, hexamethylene diisocyanate trimer is added as a high-functionality crosslinking agent. During curing, it reacts with the secondary amine groups in the resin to form high-bond-energy urea bonds and a three-dimensional crosslinking network, improving... This process increases the crosslinking density of the coating and enhances its tensile strength. Simultaneously, it avoids limiting molecular chain deformation due to excessive crosslinking, ensuring coating toughness. Amino-modified nano-silica chemically bonds with the system through surface amino groups, filling microscopic gaps in the coating at the nanoscale and improving surface hardness. This not only resists physical wear caused by raindrop impact but also acts as a crack pinning agent. Carboxylated nitrile rubber nanoparticles, acting as an elastomer toughening phase, absorb energy through deformation, alleviating stress concentration and preventing brittle fracture of the coating. Furthermore, the UV absorber added to the coating delays outdoor aging, while environmentally friendly solvents reduce system viscosity to optimize workability and reduce volatile organic compound pollution. Leveling agents improve the surface smoothness of the coating. The entire preparation process is carried out at room temperature with a closed reactor, and staged stirring ensures uniform dispersion of all components, facilitating coating storage and transportation while guaranteeing stable product performance. This solves the problems of poor mechanical strength, poor rain erosion resistance, and high application difficulty inherent in high-strength rain-resistant coatings.

[0037] The following describes in detail an embodiment of this application of a high-strength rain-resistant coating and its preparation method.

[0038] Specifically, the preparation method of this high-strength rain-resistant coating includes the following steps: Polyaspartic acid ester resin and high-elasticity aliphatic polyurea curing agent are mixed in a stirred reactor at a molar ratio of amino to isocyanate groups of 1.0-1.1:1. The mixture is pre-stirred at 200-300 r / min for 5-10 min under nitrogen protection at 25-30°C. Then, 1.5-5 wt% of functional filler, 0.3-0.5 wt% of leveling agent, 0.5-1 wt% of UV absorber, and 5-10 wt% of environmentally friendly solvent are added according to the total mass of the coating. The stirring speed is adjusted to 300-500 r / min, and the mixture is stirred for another 20-30 min at 25-30°C until the system viscosity reaches 1500-2500 mPa·s and no visible particles are observed, thus obtaining the high-strength rain-resistant coating.

[0039] Furthermore, the environmentally friendly solvent is either propylene glycol methyl ether acetate or dimethyl diacid, the leveling agent is either BYK-333 or EFKA-3777, the ultraviolet absorber is Tinuvin 1130, and the functional filler is a mixed filler composed of amino-modified nano-silica and carboxylated nitrile rubber nanoparticles at a mass ratio of 1:0.3-1.0.

[0040] It is understood that in this embodiment, the amino groups in the polyaspartic ester resin and the isocyanate groups in the high-elasticity aliphatic polyurea curing agent undergo a nucleophilic addition reaction at 25-30°C, gradually crosslinking. Excess amino groups ensure sufficient reaction of the isocyanate groups, avoiding residual active groups from affecting the stability of the coating. Nitrogen protection isolates air and moisture, preventing the isocyanate groups from reacting with water to generate bubbles and the amino groups from being oxidized, ensuring a stable crosslinking process. Low-speed pre-stirring in the early stage allows the resin and curing agent to come into uniform contact to initiate crosslinking. After adding functional fillers, leveling agents, and other additives, the speed is increased, and the filler agglomeration is broken by shear force, allowing the additives to be uniformly dispersed in the system. The leveling agent can reduce surface tension and improve the smoothness of the coating, while the UV absorber absorbs ultraviolet rays through its molecular structure to improve weather resistance. The constant temperature control at 25-30°C balances reaction and dispersion efficiency, avoiding uneven dispersion caused by low temperature and preventing premature gelation of the system caused by high temperature accelerating crosslinking. The final result is a uniform viscous liquid, ensuring that all components are evenly dispersed and the degree of crosslinking is moderate.

[0041] Specifically, in a stirred reactor, polyaspartic acid ester resin and high-elasticity aliphatic polyurea curing agent are added at a molar ratio of amino to isocyanate groups of 1.0-1.1:1. The reaction environment temperature is then controlled at 25-30℃, and nitrogen gas is introduced for protection. The two raw materials are pre-stirred at a speed of 200-300 r / min for 5-10 minutes to ensure initial homogeneity. After pre-stirring, a mixed filler consisting of amino-modified nano-silica and carboxylated nitrile rubber nanoparticles at a mass ratio of 1:0.3-1.0 is added sequentially to the reactor. Add 1.5-5 wt% of the total coating mass, along with 0.3-0.5 wt% of leveling agent, 0.5-1 wt% of UV absorber, and 5-10 wt% of environmentally friendly solvent composed of propylene glycol methyl ether acetate and dimethyl diacid in a mass ratio of 1-3:1. Then adjust the stirring speed to 300-500 r / min and maintain a temperature of 25-30℃ for 20-30 min, continuously observing the system status until a uniform viscous liquid is formed in the reactor. This completes the preparation of the high-strength rain-resistant coating.

[0042] The following describes a high-strength rain-resistant coating and its preparation method according to an embodiment of this application. Addressing the problems of poor mechanical strength and poor rain erosion resistance in high-strength rain-resistant coatings mentioned in the background art, this application provides a high-strength rain-resistant coating and its preparation method: During the synthesis stage of polyaspartic acid ester resin, a mixed amine system composed of dicyclohexylmethane diamine, 1,3-bis(aminomethyl)cyclohexane, and polyether diamine is used to undergo an addition reaction with diethyl maleate, forming a resin skeleton containing secondary amine groups. This gives the resin both rigidity and flexibility, providing high initial molecular chain strength while preventing premature material breakage through flexible segments. Simultaneously, the specific ratio of the mixed amines extends the coating gel time through steric hindrance, providing ample operating window for on-site construction. In the preparation stage of the high-elasticity aliphatic polyurea curing agent, hexamethylene diisocyanate trimer is added as a high-functionality crosslinking agent. During curing, it reacts with the secondary amine groups in the resin to form high-bond-energy urea bonds and a three-dimensional crosslinking network, improving... This process increases the crosslinking density of the coating and enhances its tensile strength. Simultaneously, it avoids limiting molecular chain deformation due to excessive crosslinking, ensuring coating toughness. Amino-modified nano-silica chemically bonds with the system through surface amino groups, filling microscopic gaps in the coating at the nanoscale and improving surface hardness. This not only resists physical wear caused by raindrop impact but also acts as a crack pinning agent. Carboxylated nitrile rubber nanoparticles, acting as an elastomer toughening phase, absorb energy through deformation, alleviating stress concentration and preventing brittle fracture of the coating. Furthermore, the UV absorber added to the coating delays outdoor aging, while environmentally friendly solvents reduce system viscosity to optimize workability and reduce volatile organic compound pollution. Leveling agents improve the surface smoothness of the coating. The entire preparation process is carried out at room temperature with a closed reactor, and staged stirring ensures uniform dispersion of all components, facilitating coating storage and transportation while guaranteeing stable product performance. This solves the problems of poor mechanical strength, poor rain erosion resistance, and high application difficulty inherent in high-strength rain-resistant coatings.

[0043] The following specific embodiments will illustrate a high-strength rain-erosion resistant coating and its preparation method, including:

[0044] Example 1

[0045] This application proposes a high-strength rain-resistant coating, which is composed of polyaspartic acid ester resin, a high-elasticity aliphatic polyurea curing agent, and additives.

[0046] Polyaspartic acid ester resin is prepared by a Michael addition reaction of dicyclohexylmethanediamine, 1,3-bis(aminomethyl)cyclohexane, polyether diamine, and diethyl maleate. Figure 1 As shown;

[0047] The high-elasticity aliphatic polyurea curing agent is prepared by reacting dicyclohexylmethane diisocyanate, isophorone diisocyanate, and polycarbonate diol to generate isocyanate-terminated prepolymers, which are then mixed and reacted with hexamethylene diisocyanate trimers. Figure 2 As shown.

[0048] Furthermore, in the preparation of polyaspartic acid ester resin, 210g of dicyclohexylmethane diamine, 42g of 1,3-bis(aminomethyl)cyclohexane, and 28g of polyether diamine D-400 were added to a 2L stirred reactor at 400rpm. After heating to 60℃, 396g of diethyl maleate was added dropwise over 2 hours. The reaction was maintained at this temperature for 3 hours. When the amine value of the system reached 3.2mgKOH / g, the product was cooled and discharged to obtain a pale yellow transparent product with a viscosity of 1800mPa·s at 25℃.

[0049] Furthermore, in the preparation of the high-elasticity aliphatic polyurea curing agent, 400g of polycarbonate diol and 334g of dicyclohexylmethane diisocyanate were added to a 1L stirred reactor at 400rpm. After reacting at 80℃ for 2h, 266g of hexamethylene diisocyanate trimer was added, and the reaction was continued at 80℃ for 1h. When the mass fraction of isocyanate groups in the system reached 18.5%, the mixture was cooled and discharged to obtain a product with a viscosity of 2400mPa·s at 25℃.

[0050] Furthermore, the polyether diamine is polyether diamine D-400.

[0051] Furthermore, the polycarbonate diol is polycyclohexanediethanol carbonate diol.

[0052] This application also proposes a high-strength rain-resistant coating and its preparation method, comprising the following steps: taking 1100g of polyaspartic acid ester resin, 1105g of high-elasticity aliphatic polyurea curing agent, 38g of functional filler, 7.5g of leveling agent BYK-333, 12.0g of ultraviolet absorber Tinuvin 1130, and 120g of propylene glycol methyl ether acetate, mixing and stirring for 10min, the viscosity at 25℃ is 2100mPa・s, spraying on an aluminum alloy plate that has been sandblasted to Sa2.5 grade, the dry film thickness is 120μm, and curing at 23℃ for 7 days.

[0053] Furthermore, the environmentally friendly solvent is propylene glycol methyl ether acetate.

[0054] Furthermore, the leveling agent is BYK-333.

[0055] Furthermore, the UV absorber is Tinuvin 1130.

[0056] Furthermore, the functional filler is a mixed filler composed of amino-modified nano-silica and carboxylated nitrile rubber nanoparticles at a mass ratio of 1:0.3-1.0.

[0057] Example 2

[0058] The preparation method of the high-strength rain-resistant coating in this embodiment is the same as that in Example 1, except for the following parameters:

[0059] The molar ratio of dicyclohexylmethanediamine to 1,3-bis(aminomethyl)cyclohexane was changed to 1:0.5.

[0060] Example 3

[0061] The preparation method of the high-strength rain-resistant coating in this embodiment is the same as that in Example 1, except for the following parameters:

[0062] The preparation process and dosage of polyaspartic acid ester resin and high-elasticity aliphatic polyurea curing agent remain unchanged. The functional filler is adjusted to a mixed filler composed of amino-modified nano-silica and carboxylated butadiene-acrylonitrile rubber nanoparticles at a mass ratio of 1:1.0, with a total addition amount of 42g.

[0063] Example 4

[0064] The preparation method of the high-strength rain-resistant coating in this embodiment is the same as that in Example 1, except for the following parameters:

[0065] When preparing polyaspartic acid ester resin, replace 28g of polyether diamine D-400 with an equimolar amount of polyether diamine D-23014g.

[0066] Example 5

[0067] The preparation method of the high-strength rain-resistant coating in this embodiment is the same as that in Example 1, except for the following parameters:

[0068] The environmentally friendly solvent was replaced by a mixed solvent consisting of 120g of pure propylene glycol methyl ether acetate and dimethyl diacid in a mass ratio of 3:1, with a total addition of 120g, including 90g of propylene glycol methyl ether acetate and 30g of dimethyl diacid.

[0069] Comparative Example 1

[0070] The preparation method of the high-strength rain-resistant coating in this comparative example is the same as that in Example 1, except for the following parameters:

[0071] No functional filler composed of amino-modified nano-silica and carboxylated nitrile rubber nanoparticles was added during the preparation of the coating. Only 1100g of polyaspartic acid ester resin, 1105g of high-elasticity aliphatic polyurea curing agent, 7.5g of leveling agent BYK-333, 12.0g of ultraviolet absorber Tinuvin 1130, and 120g of propylene glycol methyl ether acetate were mixed.

[0072] Comparative Example 2

[0073] The preparation method of the high-strength rain-resistant coating in this comparative example is the same as that in Example 1, except for the following parameters:

[0074] The high-elasticity aliphatic polyurea curing agent prepared from dicyclohexylmethane diisocyanate-polycarbonate diol-hexamethylene diisocyanate trimer was replaced with commercially available common aliphatic polyurethane curing agent isophorone diisocyanate trimer, with an isocyanate group mass fraction of 20% and a dosage of 1105g.

[0075] Comparative Example 3

[0076] The preparation method of the high-strength rain-resistant coating in this comparative example is the same as that in Example 1, except for the following parameters:

[0077] In the preparation of polyaspartic acid ester resin, the molar ratio of amino groups to diethyl maleate was adjusted from 1:1.1 to 1:0.9, that is, the amount of diethyl maleate was reduced to 320g.

[0078] Performance testing

[0079] 1. Tensile property test

[0080] Testing equipment: electronic universal testing machine, high-precision coating thickness gauge, dumbbell-shaped coating sample cutter, surface cleaning cloth.

[0081] Test Step 1: After curing at 23℃ for 7 days, samples of each batch of high-strength rain-resistant coating film were sprayed onto Sa2.5 grade aluminum alloy plates. Samples were cut from three different areas: the center, edge, and near the substrate corner, ensuring complete separation of the sample from the substrate and no damage to the coating. These samples were cut into Type I dumbbell-shaped coating film samples conforming to GB / T1040.3-2006 standards. For thin film / coating testing, five samples were prepared from each area. The sample surface was wiped clean with a surface cleaning cloth to remove impurities. The samples were checked for bubbles, cracks, coating peeling, and stains. The coating thickness was measured at three points—the center and both ends—using a high-precision coating thickness gauge, and the average value was recorded to an accuracy of 0.001 mm. The standard width of the sample was also recorded; the width of the Type I sample was 10 mm.

[0082] Test Step Two: Set the clamping distance of the electronic universal testing machine to 50mm, adapt to the type I dumbbell-shaped coating sample specification, adjust the tensile speed to 200mm / min, preheat the machine for 30 minutes, and after the force and displacement parameters of the equipment stabilize, use standard weights to calibrate the force sensor, and use the displacement calibration block to calibrate the displacement sensor with an accuracy of ±0.01mm to ensure that the force and displacement errors are both ≤±1%.

[0083] Test Step 3: Use tweezers to pick up the dumbbell-shaped coating sample and fix its two ends in the upper and lower clamps of the testing machine. Avoid direct contact between your fingers and the test area of ​​the sample when clamping. Adjust the position of the sample so that the axis of the sample is completely aligned with the center line of the clamps and the coating is free of wrinkles and skewing. Ensure that the sample is subjected to uniform force during the tensile process and avoid test data deviation due to clamping offset.

[0084] Test Step 4: Start the electronic universal testing machine and begin the tensile test. The equipment automatically records the force and displacement data in real time until the coated sample breaks. Record the maximum tensile force and corresponding elongation at the time of breakage. If the sample breaks at the clamping point, or if there is coating delamination at the breakage point, or if there is abnormal breakage due to substrate residue, the data is invalid. Select a new sample from the spare samples in the same area and retest to ensure that there are no less than 4 sets of valid data for each area.

[0085] Test Step 5: After the effective sample tests in each region are completed, calculate the tensile strength and elongation at break: Tensile strength = maximum tensile force / original cross-sectional area of ​​the coating sample (cross-sectional area = average sample thickness × standard width), unit MPa; Elongation at break = (elongation at break / initial clamping distance) × 100%. Take the average value of each region as the tensile performance result of that region. Finally, take the average tensile strength and average elongation at break of the three regions as the overall tensile performance index of this batch of high-strength rain-resistant coating film.

[0086] Test Step Six: After the test, use tweezers to clean any remaining coating fragments inside the holder, wipe the contact surface of the holder with a surface cleaning cloth, check the flatness of the holder, turn off the power to the equipment, compile the force-displacement curve, maximum tensile force, thickness value and calculation process data for each sample, clearly mark the test date, coating batch, corresponding example / comparative example number and substrate type, form a complete tensile performance test report, and archive it.

[0087] 2. Rain erosion resistance test

[0088] Testing equipment: rain test chamber, coating thickness gauge, stereo microscope, timer, sample holder, surface cleaning cloth.

[0089] Test Step 1: After curing at 23℃ for 7 days, samples of each batch of high-strength rain-resistant coating film were sprayed onto Sa2.5 grade aluminum alloy plates. Samples were taken from three different areas: the center, the edge, and near the corner. Three samples were prepared for each area. The surface of the samples was wiped clean with a surface cleaning cloth to remove dust and stains. The samples were checked for initial scratches, bubbles, and coating peeling. The dry film thickness of each sample was verified with a coating thickness gauge to ensure that the deviation was ≤ ±5μm. The sample number and corresponding area were recorded.

[0090] Test Step Two: Adjust the rain test chamber. Set the parameters according to GB / T2423.38-2021 standard: raindrop spray pressure 0.3MPa, raindrop flow rate 10L / min, angle between sample and spray nozzle 45°, and test environment temperature 23±2℃. Fix the sample in the test chamber with the fixing bracket, ensuring that the coating surface is facing the direction of raindrop spray without obstruction. Turn on the test chamber and preheat for 10 minutes. After the raindrop pressure and flow rate stabilize, record the initial time with a timer.

[0091] Test Step 3: Start the rain test, maintain the set parameters and spray continuously. Pause the test every 2 hours, take out the sample, gently absorb the surface moisture with an absorbent cloth, and let it stand at room temperature for 30 minutes. Observe the surface condition of the coating through a stereomicroscope, focusing on checking for defects such as pitting, blistering, coating peeling or substrate exposure. Record the observation results and the corresponding test duration. If no defects are found, fix the sample again and continue the rain test.

[0092] Test Step 4: Repeat Step 3 until a pitting defect with a diameter ≥ 0.5 mm appears on the surface of any sample. Record the cumulative test time at this point, which is the rain erosion pitting time of the sample. If no defect appears after the sample has been exposed to rain for 30 hours, the test can be terminated and the rain erosion pitting time is determined to be ≥ 30 hours. If the sample is loosely fixed during the test, resulting in uneven stress or abnormal raindrop parameters, the data of the sample is invalidated and a spare sample from the same area is selected for retesting.

[0093] Test Step 5: After the three valid samples in each area have been tested, calculate the average rain erosion pitting time for that area. If the data of a single sample deviates from the average value of the area by more than 10%, the test process needs to be reviewed. After confirming that there are no abnormalities, the data is retained. Finally, the average rain erosion pitting time of the three areas is used as the overall rain erosion resistance performance index of this batch of high-strength rain erosion resistant coatings.

[0094] Test Step Six: After the test, turn off the power to the rain test chamber, clean the residual water stains and impurities inside the test chamber, check whether the spray nozzles are blocked, organize the defect observation records, rain erosion pitting time and test parameters for each sample, clearly mark the test date, coating batch, corresponding example / comparative example number and sample substrate information, form a complete rain erosion resistance test report, and archive it.

[0095] 3. Gel time test

[0096] Test equipment: constant temperature and humidity chamber, electronic balance, glass beaker, glass rod, stopwatch, scraper, thermometer, anhydrous ethanol.

[0097] Test Step 1: Take samples from each batch of high-strength rain-resistant coating that is uniformly mixed according to the preparation process ratio, select three different batches of coating, prepare 3 samples for each batch, accurately weigh each component with an electronic balance to ensure that the ratio error is ≤±0.1%, check that the container is free of oil and moisture residue, measure the ambient temperature with a thermometer to ensure it is 25±2℃, and record the sample number and corresponding batch.

[0098] Test Step 2: Adjust the constant temperature and humidity chamber and set the parameters: temperature 25±1℃, relative humidity 55±5%RH. Place the glass beaker and glass rod into the chamber and preheat for 20 minutes. Add the polyaspartic acid ester resin, high elastic aliphatic polyurea curing agent and other components to the beaker according to the ratio. Stir initially with a spatula for 1 minute, and then stir with a glass rod at a speed of 100-120r / min for 5 minutes. After mixing evenly, immediately record the initial time with a stopwatch.

[0099] Test Step 3: After starting the timer, put the beaker back into the constant temperature and humidity chamber. Observe every 2 minutes for the first 10 minutes, and every 1 minute after 10 minutes. When observing, insert the glass rod vertically into the coating 15mm, hold for 5 seconds, and then lift it up at a speed of 5cm / s to check the state of the coating brought out. Record the observation results and the corresponding time. If the gel state has not been reached, continue the test.

[0100] Test Step 4: Continue to repeat Step 3 until the glass rod can only bring out a ≤2mm thin filament that is easy to break when it is lifted, and there is no obvious paint residue. Record the cumulative time at this time, which is the gel time of the sample. If the ambient temperature and humidity exceed the set range or the paint agglomerates during the test, the data of the sample is invalid and a new sample is selected from the spare samples in the same batch for retesting.

[0101] Test Step 5: After the three valid samples of each batch are tested, calculate the average gel time of the batch. If the data of a single sample deviates from the average of the batch by more than 5%, the test process needs to be reviewed. After confirming that there are no abnormalities, the data is retained. Finally, the average gel time of the three batches is used as the overall gel time index of the high-strength rain-resistant coating.

[0102] Test Step Six: After the test, turn off the power to the constant temperature and humidity chamber, clean the residual coating on the beaker and glass rod with anhydrous ethanol, organize the observation records of the state of each sample, gel time and test parameters, clearly mark the test date, coating batch, corresponding example / comparative example number and environmental condition information, form a complete gel time test report, and archive it.

[0103] The following are the performance test results of Examples 1-5 and Comparative Examples 1-3, as shown in Table 1:

[0104] Table 1: Performance test results of examples and comparative examples

[0105]

[0106] As shown in Table 1, the baseline group of Example 1 serves as the formulation and performance benchmark. The synergistic effect of each component ensures stable performance. In the polyaspartic acid ester resin, dicyclohexylmethane diamine provides rigid molecular chains, 1,3-bis(aminomethyl)cyclohexane increases crosslinking points, and polyether diamine D-400 introduces flexible segments. The three react fully with diethyl maleate to form a resin skeleton with a balance between rigidity and flexibility. The highly elastic aliphatic polyurea curing agent enhances the crosslinking density and elasticity through the three-dimensional crosslinking network of the flexible segments of polycarbonate diol and hexamethylene diisocyanate trimer. In the functional filler, amino-modified nano-silica fills the micropores and enhances rigidity, while carboxylated nitrile rubber nanoparticles alleviate stress concentration and improve toughness. Environmentally friendly solvents and additives ensure uniform dispersion and dense film formation, ultimately resulting in stable tensile strength, elongation at break, and rain erosion pitting time, with the gel time matching the requirements of the construction operation window.

[0107] As shown in Table 1, in Example 2, the molar ratio of dicyclohexylmethanediamine to 1,3-bis(aminomethyl)cyclohexane was adjusted to 1:0.5, increasing the proportion of 1,3-bis(aminomethyl)cyclohexane. Although this raw material contains a rigid cyclohexane ring, the aminomethyl group is more dispersed in space, and the molecular chain rotational freedom is slightly higher, resulting in a slight decrease in the overall rigidity of the resin, which in turn slightly reduces the tensile strength. At the same time, the flexibility of the molecular chain is enhanced, making it easier to undergo synergistic deformation under stress, and the elongation at break is increased accordingly. The slight decrease in the rigidity of the resin slightly weakens the structural support of the coating against raindrop impact, and slightly reduces the rain erosion pitting time. In addition, the molecular steric hindrance of 1,3-bis(aminomethyl)cyclohexane is slightly higher than that of dicyclohexylmethanediamine, which slows down the crosslinking reaction rate between amino and isocyanate groups, resulting in a longer gel time.

[0108] As shown in Table 1, in Example 3, the functional filler was adjusted to be a mixture of amino-modified nano-silica and carboxylated nitrile rubber nanoparticles at a mass ratio of 1:1.0, with an increase in the total amount added. The proportion of amino-modified nano-silica was relatively increased, resulting in more significant rigidity. Through chemical bonding and physical filling, the coating structure strength was further enhanced, stress concentration points were reduced, and tensile strength was improved. The proportion of carboxylated nitrile rubber nanoparticles did not decrease, but the relative proportion decreased, and its elastic toughening effect was slightly weakened, resulting in a slight decrease in elongation at break. More rigid filler filled the micro-gaps in the coating, improving surface hardness and density, and enhancing the ability to resist raindrop impact and wear. At the same time, the elastomer could still buffer some impact energy, and the rain erosion pitting time was increased accordingly. The functional filler did not directly participate in the crosslinking reaction, but only affected the system through physical dispersion, without significantly interfering with the crosslinking reaction rate, and the gel time remained basically unchanged.

[0109] As shown in Table 1, in Example 4, polyether diamine D-400 was replaced with an equimolar amount of D-230. D-230 has a smaller molecular weight and shorter flexible segments. The short flexible segments enhance the mobility of the resin molecular chains, improve the contact efficiency between amino and isocyanate groups, accelerate the crosslinking reaction rate, and shorten the gel time. At the same time, while maintaining the basic deformation capability, the short flexible segments reduce the stress concentration caused by long chain entanglement, making the coating easier to stretch and deform under stress, and increasing the elongation at break. The overall rigidity of the resin molecular chains slightly decreases due to the change in the proportion of short flexible segments, the structural support is weakened, and the tensile strength is slightly reduced. The slight decrease in coating rigidity slightly weakens the resistance to raindrop impact and slightly reduces the time to rain erosion and pitting.

[0110] As shown in Table 1, in Example 5, the environmentally friendly solvent was replaced with a mixed solvent of propylene glycol methyl ether acetate and dimethyl diacid. Dimethyl diacid evaporates more slowly than pure propylene glycol methyl ether acetate, and the mixed solvent evaporates more gently, avoiding premature surface curing and internal pores caused by rapid solvent evaporation during film formation. This results in a denser and more uniform cross-linked structure of the coating, reducing raindrop penetration channels and increasing the time for rain erosion and pitting. The solvent only plays a role in dispersing and adjusting viscosity, without changing the cross-linking nature of the resin and curing agent. It has no significant effect on tensile strength and elongation at break, which remain essentially unchanged. At the same time, the slow-evaporating solvent slightly dilutes the concentration of the reaction system, reducing the reaction rate between amino and isocyanate groups, thus prolonging the gel time.

[0111] As shown in Table 1, Comparative Example 1, without the addition of functional fillers, directly disrupted the rigid-toughness balance of the coating. The lack of amino-modified nano-silica prevented the filling of micropores in the coating, resulting in a significant decrease in surface hardness and structural support. Furthermore, the absence of pinning resistance during crack propagation led to a significant reduction in tensile strength. Figure 3 As shown, the elastic buffer of the non-carboxylated nitrile rubber nanoparticles cannot alleviate stress concentration under stress, making it prone to brittle fracture and significantly reducing the elongation at break. Figure 4 As shown, unfilled micro-gaps become weak points for raindrop impact, making it easier for raindrops to penetrate and erode the coating. This significantly reduces the time of rain erosion and pitting. In addition, the amino groups on the surface of the amino-modified nano-silica in the functional filler form weak bonds with the system, slightly hindering cross-linking. After removal, this obstacle disappears, the cross-linking reaction rate accelerates, and the gelation time is shortened.

[0112] As shown in Table 1, in Comparative Example 2, the self-made high-elasticity aliphatic polyurea curing agent was replaced with commercially available ordinary aliphatic polyurethane curing agent isophorone diisocyanate trimer. The commercially available curing agent lacks the long-chain flexible segments of polycarbonate diol, and the cross-linking network is too rigid. When the chain segments are under stress, they are difficult to deform effectively, and the elongation at break is significantly reduced. At the same time, the cross-linking structure with excessive rigidity is prone to microcracks due to stress accumulation, and the structural integrity is easily destroyed, resulting in a significant reduction in tensile strength. Under long-term impact of raindrops, the microcracks in the coating with excessive rigidity are prone to rapid propagation, and the rain erosion resistance is greatly weakened, and the rain erosion pitting time is significantly reduced. In addition, the isocyanate group activity of the isophorone diisocyanate trimer in the commercially available curing agent is higher than that of the self-made curing agent, and the reaction rate with amino groups is greatly accelerated, and the gel time is significantly shortened.

[0113] As shown in Table 1, when preparing the polyaspartic acid ester resin in Comparative Example 3, the molar ratio of amino groups to diethyl maleate was adjusted to 1:0.9. The insufficient amount of diethyl maleate resulted in some amino groups not participating in the reaction, leaving excessive free amino groups in the resin. The reactivity of free amino groups with the isocyanate groups of the curing agent is higher than that of the secondary amino groups of polyaspartic acid ester, accelerating the crosslinking reaction rate and shortening the gel time. However, the free amino groups cannot form a regular resin backbone, resulting in an incomplete resin structure. The network density formed after crosslinking with the curing agent is reduced, and the structure is loose, which cannot effectively transfer stress, significantly reducing the tensile strength. The loose network structure weakens the chain segment bonding force, significantly reducing the elongation at break, and providing more channels for raindrop penetration. The coating's resistance to rain erosion is greatly weakened, and the rain pitting time is significantly reduced.

[0114] The following describes a high-strength rain-resistant coating and its preparation method according to an embodiment of this application. Addressing the problems of poor mechanical strength and poor rain erosion resistance in high-strength rain-resistant coatings mentioned in the background art, this application provides a high-strength rain-resistant coating and its preparation method: During the synthesis stage of polyaspartic acid ester resin, a mixed amine system composed of dicyclohexylmethane diamine, 1,3-bis(aminomethyl)cyclohexane, and polyether diamine is used to undergo an addition reaction with diethyl maleate, forming a resin skeleton containing secondary amine groups. This gives the resin both rigidity and flexibility, providing high initial molecular chain strength while preventing premature material breakage through flexible segments. Simultaneously, the specific ratio of the mixed amines extends the coating gel time through steric hindrance, providing ample operating window for on-site construction. In the preparation stage of the high-elasticity aliphatic polyurea curing agent, hexamethylene diisocyanate trimer is added as a high-functionality crosslinking agent. During curing, it reacts with the secondary amine groups in the resin to form high-bond-energy urea bonds and a three-dimensional crosslinking network, improving... This process increases the crosslinking density of the coating and enhances its tensile strength. Simultaneously, it avoids limiting molecular chain deformation due to excessive crosslinking, ensuring coating toughness. Amino-modified nano-silica chemically bonds with the system through surface amino groups, filling microscopic gaps in the coating at the nanoscale and improving surface hardness. This not only resists physical wear caused by raindrop impact but also acts as a crack pinning agent. Carboxylated nitrile rubber nanoparticles, acting as an elastomer toughening phase, absorb energy through deformation, alleviating stress concentration and preventing brittle fracture of the coating. Furthermore, the UV absorber added to the coating delays outdoor aging, while environmentally friendly solvents reduce system viscosity to optimize workability and reduce volatile organic compound pollution. Leveling agents improve the surface smoothness of the coating. The entire preparation process is carried out at room temperature with a closed reactor, and staged stirring ensures uniform dispersion of all components, facilitating coating storage and transportation while guaranteeing stable product performance. This solves the problems of poor mechanical strength, poor rain erosion resistance, and high application difficulty inherent in high-strength rain-resistant coatings.

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-strength rain-erosion resistant coating, characterized in that, The high-strength rain-resistant coating comprises: polyaspartic acid ester resin, high-elasticity aliphatic polyurea curing agent, and additives; The polyaspartic acid ester resin is prepared by a Michael addition reaction of dicyclohexylmethanediamine, 1,3-bis(aminomethyl)cyclohexane, polyether diamine, and diethyl maleate. In the preparation of the polyaspartic acid ester resin, the molar ratio of dicyclohexylmethanediamine to 1,3-bis(aminomethyl)cyclohexane is 1:0.2-1.0, the amount of polyether diamine is 5-15% of the molar amount of dicyclohexylmethanediamine, and the molar ratio of amino groups to diethyl maleate is 1:1.05-1.

20. The reaction is carried out under nitrogen protection at 40-70℃ for 3-5 hours until the amine value of the system is ≤5mgKOH / g. The high-elasticity aliphatic polyurea curing agent is prepared by reacting dicyclohexylmethane diisocyanate, isophorone diisocyanate and polycarbonate diol to generate an isocyanate-terminated prepolymer, which is then mixed and reacted with hexamethylene diisocyanate trimer. In the preparation of the high-elasticity aliphatic polyurea curing agent, dicyclohexylmethane diisocyanate, isophorone diisocyanate and polycarbonate diol are reacted at 200-400 rpm and 70-90℃ for 2 hours at a molar ratio of isocyanate group to hydroxyl group of 2.0-3.0:1 to obtain the isocyanate-terminated prepolymer. Then, hexamethylene diisocyanate trimer with a mass fraction of 16-20% of isocyanate group is added to make the final mass fraction of isocyanate group in the reaction system reach 3.5-4.0%. After holding at 80℃ for 1 hour, the mixture is cooled and discharged. The molecular weight of the polycarbonate diol is 500-2000. The high-strength rain-resistant coating also includes a functional filler consisting of a mixture of amino-modified nano-silica and carboxylated nitrile rubber nanoparticles in a mass ratio of 1:0.3-1.

0.

2. The high-strength rain-resistant coating according to claim 1, characterized in that, The polyether diamine is one or more of polyether diamine D-230 and polyether diamine D-400.

3. The high-strength rain-resistant coating according to claim 1, characterized in that, The polycarbonate diol is either polycyclohexanediethanol carbonate diol or polybutanediol carbonate diol.

4. The method for preparing a high-strength rain-erosion resistant coating according to claim 1, characterized in that, The preparation method of the high-strength rain-resistant coating includes the following steps: Polyaspartic acid ester resin and high-elasticity aliphatic polyurea curing agent are mixed in a stirred reactor at a molar ratio of amino to isocyanate groups of 1.0-1.1:

1. The mixture is pre-stirred at 200-300 r / min for 5-10 min under nitrogen protection at 25-30°C. Then, 1.5-5 wt% of functional filler, 0.3-0.5 wt% of leveling agent, 0.5-1 wt% of UV absorber, and 5-10 wt% of environmentally friendly solvent (based on the total mass of the coating) are added. The stirring speed is adjusted to 300-500 r / min, and the mixture is stirred for another 20-30 min at 25-30°C until the system viscosity reaches 1500-2500 mPa·s and no visible particles are observed. This yields the high-strength rain-resistant coating.

5. The method for preparing a high-strength rain-erosion resistant coating according to claim 4, characterized in that, The environmentally friendly solvent is either propylene glycol methyl ether acetate or dimethyl diacid.

6. The method for preparing a high-strength rain-erosion resistant coating according to claim 4, characterized in that, The leveling agent is either BYK-333 or EFKA-3777.

7. The method for preparing a high-strength rain-erosion resistant coating according to claim 4, characterized in that, The ultraviolet absorber is Tinuvin 1130.

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