Preparation method of directionally arranged coating

Abstract

The invention discloses a preparation method of a directionally arranged coating, which comprises the following steps: mixing epoxy resin with a first volatile solvent to obtain a resin solution, and adding a flaky functional filler into the resin solution for dispersion treatment to obtain a dispersed suspension; a second volatile solvent and an amine curing agent are added into the dispersed suspension liquid and stirred, the coating composition is obtained, and the melting point of the first volatile solvent is lower than that of the second volatile solvent; the coating composition is applied to the surface of a base material to form a wet coating, the wet coating is dried at a first temperature and a second temperature respectively to obtain a directionally arranged coating, and the first temperature is lower than the second temperature. Efficient orientation is achieved through solvent volatilization characteristic difference and temperature grading control, complex external field auxiliary equipment is not needed, and the technical problems that in the prior art, the orientation arrangement degree of the flaky functional filler is insufficient, and performance improvement is limited are solved.

Description

Technical Field

[0001] This application relates to the field of coating preparation technology, and in particular to a method for preparing a directionally arranged coating. Background Technology

[0002] Flake-shaped functional fillers, such as mica powder, glass flakes, or talc powder, are widely used in the coating industry due to their high aspect ratio. When these fillers are oriented parallel to the substrate surface in a coating, they can improve the barrier properties, corrosion resistance, and mechanical strength of the coating, forming a multi-layered barrier similar to fish scales, effectively extending the penetration path of corrosive media into the substrate. This type of coating is widely used in heavy-duty corrosion protection, thermal conductivity, or electromagnetic shielding. In existing technologies, functional coatings are prepared by adding flake-shaped functional fillers to coatings and using conventional coating and drying processes to achieve certain performance improvements.

[0003] In existing technologies for preparing coatings containing lamellar functional fillers, only solvents with similar volatility characteristics are used in the coating composition, and drying is performed at room temperature or a single temperature. Under this process, the solvent evaporates relatively uniformly from the wet coating, and the viscosity change within the coating lacks a significant gradient. During the drying process, the lamellar functional fillers are mainly affected by gravity, Brownian motion, and interaction forces, tending to maintain random orientation or only form limited local ordered structures. However, it is difficult to achieve a highly parallel directional arrangement of the lamellar functional fillers to the substrate surface in the coating, resulting in the filler's layered barrier effect not being fully realized.

[0004] Due to insufficient orientation of sheet-like functional fillers in existing technologies, the resulting coatings exhibit significant limitations in barrier properties, corrosion resistance, and mechanical properties. This restricts the full realization of the potential of sheet-like functional fillers, forcing the industry to increase filler dosage or coating thickness when pursuing higher coating performance. This leads to secondary problems such as increased costs, increased construction difficulty, and decreased coating flexibility. Therefore, there is an urgent need for a preparation method that can effectively improve the orientation of sheet-like functional fillers to solve the above problems. Summary of the Invention

[0005] The purpose of this application is to provide a method for preparing an oriented coating, thereby solving the technical problem of insufficient coating performance caused by the random orientation of fillers in the prior art.

[0006] To achieve this objective, the present application adopts the following technical solution: A method for preparing an oriented coating, comprising: An epoxy resin is mixed with a first volatile solvent to obtain a resin solution. A sheet-like functional filler is added to the resin solution for dispersion treatment to obtain a dispersion suspension. A second volatile solvent and an amine curing agent are added to the dispersion suspension and stirred to obtain a coating composition, wherein the melting point of the first volatile solvent is lower than that of the second volatile solvent; The coating composition is applied to the surface of a substrate to form a wet coating. The wet coating is then dried at a first temperature and a second temperature to obtain an oriented coating, wherein the first temperature is lower than the second temperature.

[0007] Furthermore, the first volatile solvent is at least one of acetone, ethyl acetate, and butanone, and the melting point of the first volatile solvent is 56~80℃.

[0008] Furthermore, the second volatile solvent is at least one of xylene, toluene, and solvent oil, and the melting point of the second volatile solvent is 100~200℃.

[0009] Furthermore, the sheet-like functional filler is at least one of mica powder, glass flakes, and talc powder.

[0010] Further, the step of mixing the epoxy resin with the first volatile solvent to obtain a resin solution includes: Using epoxy resin as a film-forming substance, a first volatile solvent is added to the epoxy resin, wherein the weight ratio of the epoxy resin to the first volatile solvent is 1:1.5 to 2. The epoxy resin with the first volatile solvent added was stirred at room temperature to obtain the resin solution.

[0011] Further, the step of adding sheet-like functional fillers to the resin solution for dispersion treatment to obtain a dispersion suspension includes: The sheet-like functional filler is gradually added to the resin solution for mixing to form a filler mixture, wherein the weight ratio of the sheet-like functional filler to the epoxy resin is 0.1 to 0.3:1. The filler mixture is subjected to high-speed stirring at a stirring speed of 500~1000 rpm to obtain the dispersed suspension.

[0012] Further, the step of adding a second volatile solvent and an amine curing agent to the dispersed suspension and stirring to obtain the coating composition includes: A second volatile solvent is added to the dispersed suspension and mixed to obtain a solvent mixture, wherein the weight ratio of the second volatile solvent to the first volatile solvent is 0.3 to 0.5:1; An amine curing agent is added to the solvent mixture and stirred to obtain the coating composition, wherein the weight ratio of the amine curing agent to the epoxy resin is 0.2 to 0.5:1.

[0013] Further, the step of applying the coating composition to the substrate surface to form a wet coating includes: Add a defoamer to the coating composition and stir evenly at a stirring speed of 300-600 rpm to obtain a coating mixture; The coating mixture is applied to the surface of the pretreated substrate to form a first wet film layer. The first wet film layer is left to stand for 5 to 15 minutes at a temperature of 20 to 40°C. The coating mixture is then applied to the surface of the first wet film layer to form a second wet film layer, resulting in a layered wet film. Under the conditions of room temperature of 20~30℃ and relative humidity of 40~60%, the layered wet film is left to stand for 5~15 minutes to obtain the wet coating.

[0014] Further, the step of drying the wet coating at a first temperature includes: The wet coating is pre-dried for 5-10 minutes at a temperature of 60-70°C and a relative humidity of 40-60% to obtain a dry coating. The drying coating is gradually heated to the first temperature and dried for 20-30 minutes to obtain the first dried layer. The first temperature is higher than the boiling point of the first volatile solvent and lower than the boiling point of the second volatile solvent. The first temperature is 70-90°C.

[0015] Further, the step of drying the wet coating at a second temperature includes: The first drying layer is heated to 90-100°C at a rate of 3-6°C / min for pre-drying treatment for 5-10 minutes to obtain a pre-cured coating. The pre-cured coating is heated to a second temperature at a rate of 2-4°C / min and dried for 20-30 minutes to obtain the oriented coating. The second temperature is higher than the boiling point of the second volatile solvent and lower than the initial reaction temperature of the amine curing agent. The second temperature is 100-120°C.

[0016] Compared with the prior art, this application has the following beneficial effects: The method for preparing the oriented coating of this application involves adding a first volatile solvent and a second volatile solvent with significantly different boiling points to the coating composition, and employing a graded temperature drying process. First, drying at a lower first temperature causes the rapidly volatile solvent to evaporate preferentially, resulting in a rapid increase in the viscosity of the coating surface and forming a significant viscosity gradient. Then, drying at a higher second temperature causes the slowly volatile solvent to evaporate slowly while simultaneously completing the curing reaction. This effectively induces the sheet-like functional fillers to achieve a highly parallel oriented arrangement to the substrate surface within the coating. This method is simple, achieving efficient orientation through differences in solvent evaporation characteristics and graded temperature control. It does not require the introduction of magnetic fields, electric fields, or other complex external auxiliary equipment, making it highly feasible for industrial scale-up and economical. It is suitable for high-performance functional coatings such as heavy-duty anti-corrosion, heat conduction and dissipation, and electromagnetic shielding, solving the technical problems of insufficient oriented arrangement and limited performance improvement of sheet-like functional fillers in existing technologies. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] The structures, proportions, sizes, etc., shown in the accompanying drawings are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the implementation conditions of this application. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size should still fall within the scope of the technical content disclosed in this application, provided that they do not affect the effects and purposes that this application can produce.

[0019] Figure 1 This is a schematic diagram illustrating the overall steps of a method for preparing a directional coating. Detailed Implementation

[0020] To make the inventive objectives, features, and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] In the description of this application, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be a component centrally located at the same time.

[0022] Unless otherwise specified, the preparation methods and materials used in the following examples are conventional methods; unless otherwise specified, the parts of the materials used in the following examples are calculated by mass, and all materials used are new materials purchased from the market.

[0023] The technical solution of this application will be further described below with reference to the accompanying drawings and specific embodiments.

[0024] refer to Figure 1 This application provides a method for preparing an oriented coating, comprising: S1: Epoxy resin is mixed with a first volatile solvent to obtain a resin solution, and sheet-like functional filler is added to the resin solution for dispersion treatment to obtain a dispersion suspension; In step S1, the epoxy resin, a thermosetting polymer film-forming material, is prepared by reacting bisphenol A with epichlorohydrin. Its molecular chain contains multiple epoxy groups, which can undergo ring-opening addition reactions after the subsequent addition of an amine curing agent to form a cross-linked network structure. The first volatile solvent mixed with the epoxy resin is an organic solvent with a relatively low boiling point and fast evaporation rate, such as acetone, ethyl acetate, or butanone. Its key characteristic is that its melting point is lower than that of the subsequently introduced second volatile solvent. This difference in melting point reflects a significant difference in volatility, as a lower melting point corresponds to a lower boiling point, resulting in a faster evaporation rate at the same temperature. The purpose of mixing the epoxy resin with the first volatile solvent is to fully dissolve the solid or high-viscosity epoxy resin, forming a transparent, homogeneous, and low-viscosity resin solution. The mixing process can be achieved by mechanical stirring for 30 to 60 minutes to ensure complete dissolution of the epoxy resin and eliminate any remaining air bubbles. The weight ratio of the first volatile solvent to the epoxy resin is typically 1.5:1 to 2:1, meaning 1.5 to 2 parts of the first volatile solvent per part of epoxy resin. This maintains a low viscosity in the resin solution, facilitating the subsequent addition and dispersion of fillers. Simultaneously, the solvent's rapid evaporation rate at room temperature helps to quickly increase the surface viscosity of the coating during the initial drying stage after coating, creating a gradient environment conducive to the orientation of the sheet-like fillers. Sheet-like functional fillers are then added to the resin solution and dispersed. Sheet-like functional fillers refer to two-dimensional sheet-like structural materials with a high aspect ratio, such as mica powder, glass flakes, or talc powder, with an average particle size of 5 to 50 micrometers and a thickness of 0.5 to 5 micrometers. This flattened morphology allows the filler to form a multilayered barrier structure in the coating, significantly improving the coating's barrier properties, corrosion resistance, and mechanical strength. The weight ratio of the sheet-like functional filler to the epoxy resin is 0.1:1 to 0.3:1, meaning 0.1 to 0.3 parts filler per part of epoxy resin. This ensures the effective function of the filler and avoids excessive content that could lead to dispersion difficulties or increased coating brittleness. The addition of the sheet-like functional filler is carried out under continuous stirring at a speed of 500 to 1000 rpm for 1 to 2 hours. This allows the filler particles to be fully wetted, deagglomerated, and uniformly suspended in the low-viscosity resin solution, forming a stable dispersion suspension. Due to the low viscosity of the resin solution, the first volatile solvent still dominates, and the sheet-like functional filler is mainly randomly distributed, without immediate and significant sedimentation or agglomeration. This dispersion treatment utilizes a low-viscosity environment to achieve efficient dispersion, avoiding the filler agglomeration phenomenon common in high-viscosity systems.

[0025] S2: Add a second volatile solvent and an amine curing agent to the dispersed suspension and stir to obtain a coating composition, wherein the melting point of the first volatile solvent is lower than that of the second volatile solvent; In step S2, a second volatile solvent is added to the dispersion suspension. The melting point of the second volatile solvent is higher than that of the first volatile solvent. The amount of the second volatile solvent is controlled to be between 0.3:1 and 0.5:1 by weight ratio with the first volatile solvent. This ratio adjusts the volatility characteristics of the overall solvent system, reduces the initial evaporation rate of the coating, and the introduction of the second volatile solvent forms a mixed solvent system in which the first volatile solvent has a relatively high proportion but evaporates faster, and the second volatile solvent has a relatively low proportion but evaporates slower. During or after the addition of the second volatile solvent, an amine curing agent is added to the dispersion suspension. The amine curing agent is a compound that can undergo a ring-opening addition reaction with the epoxy groups in the epoxy resin. It can be a polyamine or a modified amine, such as aliphatic amines, aromatic amines, or polyamides. The amount is controlled between 0.2:1 and 0.5:1 by weight of the epoxy resin. The reactivity of the amine curing agent is relatively mild at room temperature and is mainly accelerated in the subsequent drying stage at a higher temperature. Therefore, it does not affect the initial coating and volatile-induced orientation process, forming a three-dimensional cross-linked network structure, which further enhances the durability and barrier properties of the coating. After adding the second volatile solvent and amine curing agent, stir for 30 to 60 minutes at a medium speed to ensure that all components are fully mixed and a uniform coating composition is formed. At this point, the solvent system in the coating composition has changed from a single first volatile solvent to a mixed system. The boiling points of the first and second volatile solvents are significantly different. The former typically boils below 80°C, while the latter boils above 100°C. This difference enhances the formation of the volatile gradient, and the stirring process helps to eliminate potential bubbles, improve the stability of the coating, and maintain the suspension of the sheet-like functional filler to prevent sedimentation.

[0026] S3: The coating composition is applied to the surface of a substrate to form a wet coating, and the wet coating is dried at a first temperature and a second temperature to obtain an oriented coating, wherein the first temperature is lower than the second temperature.

[0027] In step S3, the coating composition is uniformly applied to the surface of the substrate. The substrate refers to a solid support that requires a protective or functional layer. Depending on the application, it can be a metal sheet (such as steel or aluminum), a plastic substrate, a concrete surface, glass, ceramics, or other engineering materials. The substrate surface must be pre-cleaned, degreased, sanded, or primed to ensure good adhesion and uniform spreading of the coating composition. Various conventional processes can be used for coating, such as brushing, rolling, spraying, or scraping; the specific choice depends on the shape, size, and production scale of the substrate. After coating, the thickness of the wet coating is controlled between 100 and 500 micrometers. After the wet coating is formed, the sheet-like functional fillers (such as high aspect ratio fillers like mica powder, glass flakes, or talc powder) are still randomly distributed within it. At this point, the coating system simultaneously contains a first volatile solvent (i.e., a solvent with a low boiling point and fast evaporation, such as acetone, ethyl acetate, or methyl ethyl ketone) and a second volatile solvent (i.e., a solvent with a high boiling point and slow evaporation, such as xylene, toluene, or solvent oil), as well as epoxy resin and amine curing agents, resulting in good overall fluidity. The wet coating is then dried at a first temperature, which can be set between 70 and 90°C, for 10 to 30 minutes. This first temperature is higher than the boiling point of the first volatile solvent (which has a boiling point between 50 and 80°C) but lower than the boiling point of the second volatile solvent (which typically has a boiling point above 100°C). Therefore, under these conditions, the first volatile solvent will preferentially and rapidly evaporate from the coating surface, causing a rapid decrease in the solvent content on the coating surface, a sharp increase in resin concentration, and a rapid increase in surface viscosity. The coating interior still retains a significant amount of the second volatile solvent, resulting in a relatively low viscosity. This viscosity gradient from the surface inward (higher at the surface, lower in the interior) generates strong surface tension and coating shrinkage force, driving the sheet-like functional filler to rotate and move, gradually aligning it parallel to the substrate surface. Under the influence of the viscosity gradient, the sheet-like filler is flattened and stacked parallel like a sheet, avoiding performance loss caused by random orientation. At this stage, the orientation of the filler can be increased from an initial near-random state to about 20% to 40%, forming a preliminary ordered structure. At this point, the coating is in a semi-dry state, with a certain degree of surface hardness, but still containing a significant amount of solvent and unreacted components. After drying at the first temperature, the semi-dry coating is transferred to a second temperature for further drying, set between 100 and 120°C, for a drying time of generally 1 to 2 hours. This temperature is higher than the boiling point of the second volatile solvent, but still much lower than the thermal decomposition temperature of the epoxy resin or the over-reaction temperature of the amine curing agent. Therefore, the remaining second volatile solvent can continue to evaporate from the interior of the coating in a relatively slow and uniform manner. At the same time, the amine curing agent and epoxy resin begin to cross-link, gradually curing the coating into a hard network structure.During this process, the slow evaporation of the second volatile solvent results in a relatively gradual change in solvent concentration within the coating, preventing drastic disturbances and thus avoiding damage to the initially formed oriented structure. The curing reaction locks the parallel alignment of the lamellar fillers within the resin matrix, permanently fixing the orientation. In the oriented coating obtained after deep drying, the parallel orientation of the lamellar functional fillers typically reaches over 80%, even approaching complete parallel orientation. This highly oriented microstructure significantly improves the layered barrier properties of the coating, effectively extending the penetration path of corrosive media (such as water, oxygen, and chloride ions), thereby greatly enhancing the coating's anti-corrosion, weather resistance, or shielding functions.

[0028] In summary, this embodiment achieves precise control over the orientation of the sheet-like filler by first rapidly evaporating a low-boiling-point solvent to create a surface viscosity gradient that induces initial orientation, and then slowly evaporating a high-boiling-point solvent at a higher temperature and simultaneously curing it. This process eliminates the need for magnetic fields, electric fields, shear fields, or other complex external force auxiliary equipment. This staged temperature drying method is simple, requires minimal equipment, and is easily scaled up industrially, offering significant technical advantages and practical value. The resulting oriented coating exhibits excellent performance and low preparation cost, making it suitable for applications requiring high-performance anti-corrosion coatings, such as shipbuilding, bridges, storage tanks, and pipelines, as well as other functional coating applications requiring oriented alignment of functional fillers.

[0029] In another embodiment, referring to Table 1, comparative examples were selected for performance testing. The performance test table is based on the same formulation (epoxy resin, flake functional filler such as glass flakes at a ratio of 0.2:1, amine curing agent at a ratio of 0.3:1) and coating thickness (300 μm). The oriented coating prepared in this embodiment was compared with two comparative examples. All samples were coated on the surface of steel plate substrates that had been derusted and cleaned. After curing, the performance was evaluated. The orientation of the flake filler was determined by observing the cross-section of the filler and counting the proportion of filler parallel to the substrate surface using a scanning electron microscope. The water vapor transmission rate was tested according to the standard at a relative humidity of 90% and a temperature of 38°C. The salt spray test was conducted according to the standard in a neutral salt spray environment with 5% NaCl solution. The tensile adhesion was determined according to the standard using the pull-off method. The impact strength was determined according to the standard using a drop hammer impact tester. The difference between Comparative Example 1 and this embodiment is that only the first volatile solvent (such as acetone) is used as a single solvent, without introducing a second volatile solvent, and the drying process is only natural drying at room temperature. This results in uniform solvent evaporation and no obvious viscosity gradient. The sheet-like functional filler mainly maintains random orientation and only forms limited local order under the influence of gravity, failing to generate a parallel arrangement driven by surface tension. Consequently, the barrier performance is poor, water vapor and corrosive media can easily penetrate, and the adhesion and mechanical strength are low. The difference between Comparative Example 2 and this embodiment is that a mixed solvent with similar volatility characteristics (such as a mixture of acetone and butanone with small boiling point differences) is used, and drying is carried out at a single medium temperature (80°C). Although there is a certain volatile gradient, it is insufficient to form a strong difference in viscosity between the surface and the interior. The sheet-like filler has moderate orientation, and the barrier effect is partially exerted, but it is still far lower than the staged temperature drying process of this embodiment. This embodiment first dries at 7°C. The process involves rapidly evaporating a low-boiling-point first volatile solvent at 0-90℃ to form a high viscosity gradient on the surface, inducing the initial parallel orientation of the sheet-like filler. Then, at 100-120℃, a high-boiling-point second volatile solvent is slowly evaporated and simultaneously cured to lock the structure, achieving a highly oriented filler arrangement (orientation exceeding 80%). This significantly extends the penetration path of corrosive media, reduces permeability, and increases salt spray corrosion resistance to over 5000 hours (24 hours of acetic acid salt spray testing is equivalent to 3 years of corrosion under natural conditions). Simultaneously, the cross-linked network enhances coating adhesion and impact toughness, resulting in excellent overall performance. This demonstrates the crucial role of evaporation gradient and staged drying in controlling filler orientation, avoiding the limitations of existing processes, such as insufficient performance due to random filler distribution and increased costs due to the need to increase filler quantity or thickness. This embodiment features a simple process, is easily industrialized, and is suitable for heavy-duty corrosion protection, offering significant advantages.

[0030] Table 1 In another embodiment, step S3 can divide the coating composition into two parts. One part contains silane coupling agent-modified nano-silica particles with surface grafted epoxy groups as an auxiliary orientation agent. The main chain of the nano-silica particles is a polysiloxane structure, and the side chains contain multiple epoxy groups, which can undergo partial ring-opening reactions with epoxy resin molecular chains to form a chemically bonded interfacial network. At the same time, the spherical shape of the nanoparticles generates a mild volume shrinkage force and surface tension difference during subsequent volatilization, which helps drive the sheet-like functional filler to rotate and initially orient parallel to the substrate. The coating composition without modified nano-silica is first coated as the bottom wet coating layer, with a thickness controlled between 80 and 250 micrometers, so that the sheet-like functional filler in the bottom layer remains relatively aligned. The mixture is distributed in a certain state, and then a coating composition with surface-modified nano-silica is applied as the upper wet coating layer with a thickness controlled between 100 and 400 micrometers. The bonding reaction between the nanoparticles and epoxy resin in the upper layer is slowly initiated after coating, forming a cross-linked structure extending from the upper layer to the lower layer. The polysiloxane segments of the main chain of the structure give the upper layer higher flexibility and tension gradient, further enhancing the viscosity difference induced by volatilization. At the same time, the uniform dispersion of nanoparticles avoids agglomeration, allowing the upper filler to begin preliminary parallel orientation in the initial stage. The lower filler is gradually oriented following the upper layer due to the shrinkage force and gradient traction, thus forming a more uniform sheet-like filler stacked prestructure. This avoids uneven orientation or local disturbance in a single coating, resulting in a gradient multilayer wet coating with chemical gradient transition. The gradient multilayer wet coating is subjected to a first temperature drying treatment at 70 to 90°C for 10 to 30 minutes. This temperature is higher than the boiling point of the first volatile solvent but lower than the boiling point of the second volatile solvent. The first volatile solvent preferentially and rapidly evaporates from the surface of the upper wet coating, resulting in a rapid increase in the upper resin concentration and a sharp increase in surface viscosity. At the same time, the surface-modified nano-silica particles generate a synergistic shrinkage effect during evaporation. The grafted epoxy groups react initially with the amine curing agent to form a flexible cross-linked bridge extending from the upper layer to the lower layer. The main chain polysiloxane segment of this bridge structure provides elastic buffering to avoid microcracks caused by severe shrinkage. The branched epoxy groups penetrate deep into the lower wet coating and become entangled with the epoxy resin molecular chain and partially open the ring, strengthening the interlayer interface bonding force. The high viscosity region of the upper layer drives the sheet-like functional filler to rotate rapidly parallel to the substrate surface, forming a highly ordered preliminary oriented structure.The initially oriented semi-dry multilayer coating is subjected to a second temperature-deep drying and curing treatment at 100 to 120°C for 1 to 2 hours. This temperature is higher than the boiling point of the second volatile solvent, promoting the uniform and slow evaporation of the remaining solvent. At the same time, the ring-opening addition reaction between the amine curing agent and the epoxy resin is fully accelerated. The polysiloxane backbone of the surface-modified nano-silica particles in the upper layer flexibly extends to the cross-linking points of the bottom layer at high temperature, forming an elastic reinforcing network that runs through multiple layers. The reinforcing network further anchors the position of the sheet-like functional filler from the residual reaction of the branched epoxy groups in the upper layer, permanently locking the parallel oriented structure of the upper and lower layers. The overall orientation degree reaches more than 80%. The bridging effect of the multilayer gradient combined with the nanoparticles extends the tortuous diffusion path of the corrosive medium. At the same time, the flexible embedding of the polysiloxane segments improves the mechanical strength and impact resistance of the coating, resulting in a highly oriented pre-cured multilayer coating with a highly ordered microstructure. A highly oriented pre-cured multilayer coating is subjected to surface hydrophobic functionalization treatment. A diluted solution of fluorinated alkyl silane is applied as a post-treatment layer at room temperature. One end of the fluorinated alkyl silane molecule contains a siloxane group, which can react with the residual epoxy group or the hydroxyl group on the surface of nano-silica to form a chemical bond. The other end contains a long-chain fluorinated alkyl segment, which migrates and accumulates outward to form a low surface energy hydrophobic surface. The thickness of this surface layer is controlled between 10 and 30 micrometers. It achieves seamless integration with the upper resin matrix through chemical bonding and polysiloxane backbone extension, avoiding the risk of peeling. At the same time, the low polarity of the fluorinated alkyl segment further enhances the barrier effect of the coating against water, oxygen and chloride ions. Together with the highly parallel stacking of the internal sheet filler, the nano-bridging network and the gradient cross-linking structure, a multiple barrier mechanism is formed, which greatly improves the long-term corrosion resistance, weather resistance and self-cleaning performance of the coating, without affecting the adhesion between the bottom layer and the substrate and the overall flexibility. This results in an oriented coating with enhanced surface hydrophobicity and optimized performance.

[0031] In one embodiment, the step of mixing the epoxy resin with a first volatile solvent to obtain a resin solution includes: Using epoxy resin as a film-forming substance, a first volatile solvent is added to the epoxy resin, wherein the weight ratio of the epoxy resin to the first volatile solvent is 1:1.5 to 2. The epoxy resin with the first volatile solvent added was stirred at room temperature to obtain the resin solution.

[0032] In this embodiment, epoxy resin is used as the film-forming substance, and a first volatile solvent is added to it, wherein the weight ratio of epoxy resin to the first volatile solvent is 1:1.5 to 2. The resin solution is obtained by stirring at room temperature. The first volatile solvent, as described in claim 2, is at least one of acetone, ethyl acetate, and butanone, with a boiling point between 56 and 80°C. It has a fast evaporation rate and can quickly dissolve the epoxy resin to form a low-viscosity, transparent, and uniform solution. By utilizing the characteristics of the fast-evaporating solvent, the epoxy resin is completely dissolved without the generation of bubbles, while providing good fluidity. The control of the weight ratio ensures that the solution viscosity is moderate, avoiding excessive viscosity that affects dispersion or excessive thinness that causes filler sedimentation. Furthermore, the room temperature stirring conditions are simple and easy to control.

[0033] In one embodiment, the step of adding sheet-like functional fillers to the resin solution for dispersion treatment to obtain a dispersion suspension includes: The sheet-like functional filler is gradually added to the resin solution for mixing to form a filler mixture, wherein the weight ratio of the sheet-like functional filler to the epoxy resin is 0.1 to 0.3:1. The filler mixture is subjected to high-speed stirring at a stirring speed of 500~1000 rpm to obtain the dispersed suspension.

[0034] In this embodiment, the sheet-like functional filler is gradually added to the resin solution for mixing to form a filler mixture. The weight ratio of the sheet-like functional filler to the epoxy resin is 0.1 to 0.3:1. Then, high-speed stirring is carried out at a stirring speed of 500 to 1000 rpm to obtain a dispersion suspension. The weight ratio ensures that the filler dosage is appropriate, which can significantly improve the functionality of the coating without affecting the fluidity of the coating. High-speed stirring uses shear force to achieve uniform dispersion of the filler and avoid agglomeration. At this time, the viscosity of the coating is still low, and the sheet-like filler is randomly distributed. Moreover, the gradual addition method prevents excessively high local concentrations caused by one-time addition. The aforementioned low-viscosity resin solution serves as a carrier to achieve efficient dispersion of the sheet-like functional filler.

[0035] In one embodiment, the step of adding a second volatile solvent and an amine curing agent to the dispersed suspension and stirring to obtain a coating composition includes: A second volatile solvent is added to the dispersed suspension and mixed to obtain a solvent mixture, wherein the weight ratio of the second volatile solvent to the first volatile solvent is 0.3 to 0.5:1; An amine curing agent is added to the solvent mixture and stirred to obtain the coating composition, wherein the weight ratio of the amine curing agent to the epoxy resin is 0.2 to 0.5:1.

[0036] In this embodiment, a second volatile solvent is added to the dispersed suspension and mixed to obtain a solvent mixture, wherein the weight ratio of the second volatile solvent to the first volatile solvent is 0.3 to 0.5:1. Then, an amine curing agent is added to the solvent mixture and stirred to obtain a coating composition, wherein the weight ratio of the amine curing agent to the epoxy resin is 0.2 to 0.5:1. The second volatile solvent is at least one of xylene, toluene, and solvent oil, which has a high boiling point, usually between 100 and 200°C, and a slow evaporation rate. In this embodiment, a solvent system with significantly different evaporation rates is added to form a clear evaporation gradient. The weight ratio is controlled to ensure that the amount of the second volatile solvent is moderate, reducing the overall evaporation rate while providing gradient control for drying. The addition of the amine curing agent ensures the final curing reaction without interfering with the initial evaporation process, and the stirring treatment makes the composition uniform. The coating composition has a moderate viscosity, which is easy to apply.

[0037] In one embodiment, the step of applying the coating composition to the surface of a substrate to form a wet coating includes: Add a defoamer to the coating composition and stir evenly at a stirring speed of 300-600 rpm to obtain a coating mixture; The coating mixture is applied to the surface of the pretreated substrate to form a first wet film layer. The first wet film layer is left to stand for 5 to 15 minutes at a temperature of 20 to 40°C. The coating mixture is then applied to the surface of the first wet film layer to form a second wet film layer, resulting in a layered wet film. Under the conditions of room temperature of 20~30℃ and relative humidity of 40~60%, the layered wet film is left to stand for 5~15 minutes to obtain the wet coating.

[0038] In this embodiment, a defoamer is added to the coating composition, and the mixture is stirred uniformly at a stirring speed of 300-600 rpm to obtain a coating mixture. The coating mixture is then applied to the surface of a pretreated substrate to form a first wet film layer. After the first wet film layer is left to stand at 20-40°C for 5-15 minutes, a second layer is applied to form a second wet film layer, resulting in a layered wet film. Finally, the mixture is left to stand at room temperature of 20-30°C and relative humidity of 40-60% for 5-15 minutes to obtain a wet coating layer. This layered coating and standing process ensures uniform coating coverage, avoids bubbles and sagging, and multi-layer application helps to form a thicker wet film. The standing conditions control humidity and temperature, promoting the initial trace evaporation of solvent. Using the aforementioned coating composition as the coating material, a uniform wet coating layer is formed. At this time, the flake filler is still randomly distributed, while the rapidly evaporating solvent begins to evaporate preferentially, resulting in an increase in surface viscosity, which provides an initial gradient for subsequent drying-induced orientation. Furthermore, the addition of the defoamer eliminates stirring bubbles, ensuring a smooth coating.

[0039] In one embodiment, the step of drying the wet coating at a first temperature includes: The wet coating is pre-dried for 5-10 minutes at a temperature of 60-70°C and a relative humidity of 40-60% to obtain a dry coating. The drying coating is gradually heated to the first temperature and dried for 20-30 minutes to obtain the first dried layer. The first temperature is higher than the boiling point of the first volatile solvent and lower than the boiling point of the second volatile solvent. The first temperature is 70-90°C.

[0040] The step of drying the wet coating at a second temperature includes: The first drying layer is heated to 90-100°C at a rate of 3-6°C / min for pre-drying treatment for 5-10 minutes to obtain a pre-cured coating. The pre-cured coating is heated to a second temperature at a rate of 2-4°C / min and dried for 20-30 minutes to obtain the oriented coating. The second temperature is higher than the boiling point of the second volatile solvent and lower than the initial reaction temperature of the amine curing agent. The second temperature is 100-120°C.

[0041] In this embodiment, the wet coating is dried at a first temperature, including pre-drying for 5-10 minutes at 60-70°C and 40-60% relative humidity to obtain a dried coating. Then, the temperature is gradually increased to a first temperature of 70-90°C and dried for 20-30 minutes to obtain a first dried layer. The first temperature is higher than the boiling point of the first volatile solvent but lower than the boiling point of the second volatile solvent, which causes the rapidly volatile solvent to evaporate preferentially in large quantities. The viscosity of the coating surface increases rapidly, forming a viscosity gradient. Under this gradient, the sheet-like functional filler is affected by surface tension and shrinkage force and begins to initially orient in a direction parallel to the substrate surface. Moreover, pre-drying and gradual heating avoid defects caused by sudden evaporation. Selective evaporation is achieved through temperature control, forming a gradient that is conducive to parallel orientation and improving the orientation degree by more than 20-40%. A pre-cured coating is obtained by heating to 90-100℃ at a rate of 3-6℃ / min and pre-drying for 5-10 minutes. Then, the temperature is increased to a second temperature of 100-120℃ at a rate of 2-4℃ / min and dried for 20-30 minutes to obtain an oriented coating. The second temperature is higher than the boiling point of the second volatile solvent but lower than the initial reaction point of the amine curing agent, so that the remaining slowly volatile solvent evaporates uniformly, while the curing agent begins to react and cure, strengthening the pre-oriented sheet filler and further forming a highly parallel arrangement. The final orientation degree reaches more than 80%, which improves the barrier properties, mechanical strength and corrosion resistance of the coating. Moreover, the gradual heating rate control prevents disturbance to the already oriented structure. The staged drying utilizes the volatile gradient and temperature gradient to achieve the orientation of the sheet filler without external force induction.

[0042] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application 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. Such 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 this application.

Claims

1. A method for preparing an oriented coating, characterized in that, include: An epoxy resin is mixed with a first volatile solvent to obtain a resin solution. A sheet-like functional filler is added to the resin solution for dispersion treatment to obtain a dispersion suspension. A second volatile solvent and an amine curing agent are added to the dispersion suspension and stirred to obtain a coating composition, wherein the melting point of the first volatile solvent is lower than that of the second volatile solvent; The coating composition is applied to the surface of a substrate to form a wet coating. The wet coating is then dried at a first temperature and a second temperature to obtain an oriented coating, wherein the first temperature is lower than the second temperature.

2. The method for preparing the oriented coating according to claim 1, characterized in that, The first volatile solvent is at least one of acetone, ethyl acetate, and butanone, and the melting point of the first volatile solvent is 56~80℃.

3. The method for preparing the oriented coating according to claim 1, characterized in that, The second volatile solvent is at least one of xylene, toluene, and solvent oil, and the melting point of the second volatile solvent is 100~200℃.

4. The method for preparing the oriented coating according to claim 1, characterized in that, The sheet-like functional filler is at least one of mica powder, glass flakes, and talc powder.

5. The method for preparing the oriented coating according to claim 1, characterized in that, The step of mixing epoxy resin with a first volatile solvent to obtain a resin solution includes: Using epoxy resin as a film-forming substance, a first volatile solvent is added to the epoxy resin, wherein the weight ratio of the epoxy resin to the first volatile solvent is 1:1.5 to 2. The epoxy resin with the first volatile solvent added was stirred at room temperature to obtain the resin solution.

6. The method for preparing the oriented coating according to claim 1, characterized in that, The step of adding sheet-like functional fillers to the resin solution for dispersion treatment to obtain a dispersion suspension includes: The sheet-like functional filler is gradually added to the resin solution for mixing to form a filler mixture, wherein the weight ratio of the sheet-like functional filler to the epoxy resin is 0.1 to 0.3:

1. The filler mixture is subjected to high-speed stirring at a stirring speed of 500~1000 rpm to obtain the dispersed suspension.

7. The method for preparing the oriented coating according to claim 1, characterized in that, The step of adding a second volatile solvent and an amine curing agent to the dispersion suspension and stirring to obtain a coating composition includes: A second volatile solvent is added to the dispersed suspension and mixed to obtain a solvent mixture, wherein the weight ratio of the second volatile solvent to the first volatile solvent is 0.3 to 0.5:1; An amine curing agent is added to the solvent mixture and stirred to obtain the coating composition, wherein the weight ratio of the amine curing agent to the epoxy resin is 0.2 to 0.5:

1.

8. The method for preparing the oriented coating according to claim 1, characterized in that, The step of applying the coating composition to the surface of a substrate to form a wet coating includes: Add a defoamer to the coating composition and stir evenly at a stirring speed of 300-600 rpm to obtain a coating mixture; The coating mixture is applied to the surface of the pretreated substrate to form a first wet film layer. The first wet film layer is left to stand for 5 to 15 minutes at a temperature of 20 to 40°C. The coating mixture is then applied to the surface of the first wet film layer to form a second wet film layer, resulting in a layered wet film. Under conditions of room temperature of 20~30℃ and relative humidity of 40~60%, the layered wet film is left to stand for 5~15 minutes to obtain the wet coating.

9. The method for preparing the oriented coating according to claim 1, characterized in that, The step of drying the wet coating at a first temperature includes: The wet coating is pre-dried for 5-10 minutes at a temperature of 60-70°C and a relative humidity of 40-60% to obtain a dry coating. The drying coating is gradually heated to the first temperature and dried for 20-30 minutes to obtain the first dried layer. The first temperature is higher than the boiling point of the first volatile solvent and lower than the boiling point of the second volatile solvent. The first temperature is 70-90°C.

10. The method for preparing the oriented coating according to claim 9, characterized in that, The step of drying the wet coating at a second temperature includes: The first drying layer is heated to 90-100°C at a rate of 3-6°C / min for pre-drying treatment for 5-10 minutes to obtain a pre-cured coating. The pre-cured coating is heated to a second temperature at a rate of 2-4°C / min and dried for 20-30 minutes to obtain the oriented coating. The second temperature is higher than the boiling point of the second volatile solvent and lower than the initial reaction temperature of the amine curing agent. The second temperature is 100-120°C.

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