An environmentally friendly, moisture-resistant epoxy coating for substrates, its preparation method, and its application.

Abstract

This invention provides an environmentally friendly, moisture-resistant epoxy coating for substrates, its preparation method, and its application. The epoxy coating is obtained by mixing and curing a mixture of component A and component B. Component A includes a resin matrix, a solvent, and additives, including dispersants, defoamers, thixotropic agents, and fluorosilane coupling agents. Component B includes a curing agent. The resin matrix includes bisphenol F type epoxy resin, and the curing agent includes a ketimine curing agent. This invention utilizes the synergistic effect of bisphenol F type epoxy resin, fluorosilane coupling agent, and ketimine curing agent to actively displace interfacial water films and achieve controllable crosslinking upon contact with moisture, fundamentally solving the problem of moisture interference. This imparts excellent wet adhesion and permeability to the coating, effectively avoiding defects such as whitening of the paint film and incomplete crosslinking.

Description

Technical Field

[0001] This invention relates to the field of coating engineering technology, and more specifically, to an environmentally friendly, moisture-resistant epoxy coating for substrates, its preparation method, and its application. Background Technology

[0002] Epoxy resin coatings are widely used in heavy-duty corrosion protection of steel structures, concrete, and other substrates due to their excellent adhesion, chemical corrosion resistance, and mechanical properties. However, traditional epoxy coatings are extremely sensitive to moisture. When applied to damp substrates, amine curing agents compete with water molecules, resulting in insufficient cross-linking of the coating and whitening defects on the surface. Simultaneously, moisture easily forms a weak bonding layer at the interface between the coating and the substrate, significantly reducing coating adhesion and, in severe cases, causing the entire coating to peel off. In engineering scenarios such as steel structure corrosion protection in tidal zones, repair of water conservancy and hydropower facilities, and maintenance of outdoor pipelines, the substrate is often difficult to dry completely. Direct application can easily lead to coating failure; using methods such as drainage, baking, or sun drying to dry the substrate will increase construction costs and delay the project schedule.

[0003] Patent application number 201911073662.0 discloses a coating that can be applied to damp or even wet substrates. This system uses aldehydes and glycidyl ethers as reactive diluents, combining them to reduce the contact angle and facilitate water molecule migration and removal. Simultaneously, hydration-reactive fillers consume residual moisture on the substrate, and the exothermic hydration process promotes the reaction between epoxy and the curing agent, improving wet curing performance. However, this formulation uses a large amount of aldehydes and ketones, which generally have irritating odors, and some components are toxic, increasing the emission of volatile harmful substances and failing to meet the requirements for green and environmentally friendly coatings. Patent application number 202010197876.5 discloses a moisture-curing epoxy coating and its preparation method. This method uses bisphenol A and bisphenol F epoxy resins as the matrix, combined with a self-made modified ketimine curing agent. It utilizes the property of ketimine decomposing in water to produce active amines to achieve wet curing, effectively improving the coating whitening problem and exhibiting good wet adhesion. However, this method relies on complex chemical modification of the curing agent to achieve the wet curing effect. Not only is the preparation process complicated and the production difficult, but the large number of new functional groups introduced during the modification process will also weaken the overall chemical corrosion resistance of the cured paint film.

[0004] Therefore, there is an urgent need for a green, low-volatile epoxy coating that does not require complex chemical modification. This coating must have excellent substrate penetration and moisture repulsion properties, and can be rapidly cured on damp or even saturated hydrated substrates to ensure strong adhesion and long-term protection of the coating. Summary of the Invention

[0005] In view of this, the present invention aims to propose an environmentally friendly, moisture-resistant epoxy coating for substrates, its preparation method, and its application, in order to solve the problems of traditional epoxy coatings being difficult to apply to damp substrates and easily resulting in coating whitening and peeling; at the same time, it solves the defects of existing moisture-curing epoxy coatings, which rely on complex chemical modification, have cumbersome production processes, and have additives that easily release harmful volatile substances, resulting in poor overall anti-corrosion performance of the paint film.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0007] This invention provides an environmentally friendly, moisture-resistant epoxy coating for substrates. The epoxy coating is obtained by mixing and curing a mixture of component A and component B. Component A includes a resin matrix, a solvent, and additives, including dispersants, defoamers, thixotropic agents, and fluorosilane coupling agents. Component B includes a curing agent. The resin matrix includes bisphenol F type epoxy resin, and the curing agent includes a ketimine curing agent.

[0008] This invention adds a fluorosilane coupling agent to component A. This component has good tolerance to moisture on the substrate surface. Compared with the traditional method of using ketimine alone as a curing agent, it can reduce the amount of ketimine used and effectively reduce the release of harmful small molecule amine gases. In addition, bisphenol F type epoxy resin connects bisphenol F diglycidyl ether units with methylene bridges. The molecular chain is regular, the steric hindrance is small, and the overall viscosity is low. During construction, it can easily penetrate into the micropores and gaps of the substrate, effectively dissipating the water film and forming a stable mechanical anchor. At the same time, its epoxy group density is high and the number of hydrophobic side groups is small. After curing, it can form a dense cross-linked network, which greatly improves the wetting ability and adhesion reliability of the paint film to steel, concrete and other substrates in humid environments. The ketimine curing agent is a latent curing agent. Its internal amine groups exist in the form of imine bonds. It undergoes reversible hydrolysis when it comes into contact with water and releases free amines. It has the characteristics of low initial viscosity, long pot life and activation by moisture, which can realize the cross-linking and film formation of epoxy resin in humid environments.

[0009] In this invention, the viscosity of the bisphenol F type epoxy resin is preferably 2000~5000 cP, the epoxy equivalent is preferably 160~220 g / mol, and the density is preferably 1.1~1.25 g / mL; the fluorosilane coupling agent is preferably one or more of perfluorodecyltriethoxysilane, tridecafluorooctyltriethoxysilane, and (3,3,3-trifluoropropyl)methyldimethoxysilane.

[0010] In this invention, a specific viscosity range ensures that the coating does not sag while rapidly penetrating and displacing the interfacial water film; an appropriate epoxy equivalent ensures the formation of a dense, high-strength cross-linked network after reacting with the curing agent; and fluorosilane coupling agents, with their extremely low surface energy, can oriented at the interface to construct a strong hydrophobic isolation layer and achieve chemical anchoring.

[0011] In this invention, the ketimine curing agent is a latent curing agent, which is prepared by blocking polyamines with ketone substances.

[0012] Furthermore, the curing agent also includes a cashew nut shell oil-modified amine curing agent, and the mass ratio of the cashew nut shell oil-modified amine curing agent to the ketimine curing agent is 4~5:4~5.

[0013] Cashew nutshell oil-modified amine curing agent is made from natural cashew phenol, which is combined with aliphatic amines, phenolic hydroxyl groups, and C15 unsaturated long side chains via the Mannich reaction. The benzene ring in the molecule can improve the structural rigidity, while the C15 long straight-chain aliphatic hydrocarbon with 0-3 double bonds gives the material excellent hydrophobicity, flexibility, and the ability to displace water films on damp substrates. At the same time, the phenolic hydroxyl groups can catalyze the ring-opening of epoxy, ensuring rapid curing of the coating at low temperatures and on damp substrates. This invention combines the two curing agents to form a good synergistic effect: the cashew nutshell oil-modified amine, relying on its hydrophobic long side chains and catalytic effect, quickly displaces the interfacial water film, achieves surface drying of the coating, and establishes initial adhesion, improving the problem of slow initial curing and sticky surface of pure ketimine systems; the ketimine curing agent, also known as a ketimine latent curing agent, relies on its latent properties to extend the coating's working time, and subsequently continuously releases active amines to promote deep cross-linking of the entire coating film. The compound system creates a "rapid moisture removal and anchoring + deep and long-lasting cross-linking" effect. The resulting paint film has excellent wet adhesion, flexibility, impact resistance and dense cross-linking structure. It is suitable for high humidity conditions such as tidal zones and underwater structures that are difficult to dry completely, and can form a long-lasting protective coating.

[0014] Furthermore, the resin matrix also includes an alicyclic epoxy resin, and the mass ratio of the bisphenol F type epoxy resin to the alicyclic epoxy resin is 6~35:1.

[0015] In this invention, the alicyclic epoxy resin is preferably composed of a six-membered saturated alicyclic structure directly connected to an epoxy group, and its molecular skeleton does not contain an aromatic ring.

[0016] This invention selects a six-membered ring alicyclic epoxy resin as an auxiliary film-forming agent. This resin has no aromatic rings in its molecular skeleton, and the epoxy groups are directly attached to the saturated alicyclic rings, exhibiting high electron cloud density and strong reactivity. In humid environments, it can rapidly crosslink with the amine groups generated by the hydrolysis of ketimine, completing curing before moisture interference occurs. This effectively accelerates the surface drying of the paint film and synergistically regulates the overall reaction time of the ketimine curing agent, quickly imparting initial strength and water resistance to the paint film. Furthermore, the saturated alicyclic rings do not contain chromophores, giving the coating excellent resistance to UV yellowing and chemical stability.

[0017] This invention combines bisphenol F epoxy resin with alicyclic epoxy resin to achieve a synergistic effect: bisphenol F epoxy resin, with its low viscosity and high permeability, ensures the coating fully wets the damp substrate; the alicyclic epoxy resin, with its high reactivity, enhances the early strength, surface hardness, and weather resistance of the paint film. Combining the latent curing characteristics of ketimines with the interfacial drainage effect of fluorosilanes, this compound system balances the curing efficiency, adhesion strength, and long-term performance of the coating in humid and underwater environments, solving the problems of insufficient penetration and curing, and inadequate adhesion and durability, inherent in single epoxy resin systems for wet surface application.

[0018] Furthermore, the epoxy coating is obtained by mixing component A and component B in a mass ratio of 5-6:1 and then curing. Component A contains the following parts by weight: 30-35 parts of bisphenol F type epoxy resin, 1-5 parts of alicyclic epoxy resin, 0.2-0.8 parts of dispersant, 0.1-0.5 parts of defoamer, 0.2-0.8 parts of thixotropic agent, 0.1-0.5 parts of fluorosilane coupling agent, and 5-10 parts of solvent A. Component B contains the following parts by weight: 40-50 parts of cashew nut shell oil modified amine curing agent, 40-50 parts of ketimine curing agent, and 5-10 parts of solvent B.

[0019] In this invention, the epoxy coating is obtained by mixing component A and component B in a mass ratio of 5-6:1 and then curing. Component A consists of the following raw materials in parts by weight: 30-35 parts of bisphenol F type epoxy resin, 1-5 parts of alicyclic epoxy resin, 0.2-0.8 parts of dispersant, 0.1-0.5 parts of defoamer, 0.2-0.8 parts of thixotropic agent, 0.3-0.5 parts of fluorosilane coupling agent, and 7-9 parts of solvent A. Component B consists of the following raw materials in parts by weight: 40-50 parts of cashew nut shell oil modified amine curing agent, 40-50 parts of ketimine curing agent, and 5-10 parts of solvent B.

[0020] Furthermore, by mass, component A also contains 50 to 55 parts of pigments and fillers.

[0021] In this invention, the ratio of resin matrix: pigments and fillers: thixotropic agent by mass parts is preferably 40:50:0.8 or 35:55:0.2.

[0022] It should be noted that in this invention, the amount of thixotropic agent added is matched with the total content of resin matrix, pigments and fillers. When the proportion of resin matrix is ​​too low, the rheological support of the system is weakened, and the amount of thixotropic agent needs to be increased to build a stable thixotropic network, effectively improve the coating's anti-sagging ability, and avoid sagging and flow defects. If the amount of thixotropic agent is insufficient, the viscosity of the system is insufficient, the anti-sagging performance is greatly reduced, and it cannot meet the requirements of on-site construction.

[0023] Furthermore, the pigments and fillers include one or more of iron oxide red, aluminum tripolyphosphate, talc, feldspar powder, and mica powder.

[0024] This invention utilizes aluminum tripolyphosphate to release active ions to form a passivation film, providing active chemical corrosion and rust prevention. It employs layered mica powder and other sheet-like structures to create a "maze effect," significantly extending the penetration path of corrosive media and enhancing physical shielding. Talc powder is added to improve the hardness, wear resistance, and dimensional stability of the coating, while iron oxide red is added as an anti-corrosion filler, providing basic hiding power. Furthermore, the addition of a large amount of pigments and fillers effectively reduces the volume shrinkage rate during resin curing and significantly reduces the amount of expensive resin used, thereby lowering overall production costs.

[0025] In this invention, the particle size of the pigments and fillers is preferably 325-800 mesh.

[0026] In this invention, the pigments and fillers are preferably a mixture of iron oxide red, talc powder, mica powder, feldspar powder, and aluminum tripolyphosphate; the mass ratio of iron oxide red, talc powder, mica powder, feldspar powder, and aluminum tripolyphosphate is preferably 20~25:9~10:10~12:5~10:5~10; wherein, the particle size of the iron oxide red is preferably 325 mesh, the particle size of the talc powder is preferably 325 mesh, the particle size of the mica powder is preferably 800 mesh, the particle size of the feldspar powder is preferably 800 mesh, and the particle size of the aluminum tripolyphosphate is preferably 325 mesh.

[0027] First, this invention ensures a perfect synergy between chemical corrosion protection, physical shielding, and mechanical support through a specific ratio of five powders. Second, the use of 325-mesh and 800-mesh particle size distribution allows the fine powder to fully fill the gaps in the coarse powder, significantly improving the density of the paint film and blocking the penetration path of corrosive media. In addition, this scientific particle size distribution and ratio design not only ensures that the coating has excellent flowability and anti-sagging properties during application, but also maximizes the volume effect of mineral fillers, thereby effectively reducing the amount of expensive resin used and significantly reducing production costs.

[0028] Furthermore, solvent A and solvent B are independently selected from one or more mixtures of xylene, n-butanol, and cyclohexanone.

[0029] In this invention, solvent A is preferably a mixture of xylene and n-butanol, and the mass ratio of xylene to n-butanol is preferably 1:1 to 2:1; solvent B is preferably xylene.

[0030] Furthermore, the thixotropic agent includes one or more of bentonite-type thickeners, polyamide waxes, and fumed silica; the dispersant is a polymeric compound with pigment affinity groups; and the defoamer is an organosilicon defoamer.

[0031] In this invention, the bisphenol F type epoxy resin is preferably YDF-170; the alicyclic epoxy resin is preferably 2021P; the dispersant is preferably one or more of Eucalyptus 710S, Eucalyptus 550S, and BYK-110 (solid content ≥40%); the defoamer is preferably one or more of Eucalyptus 272S, Eucalyptus 235S, and Eucalyptus 245S; the thixotropic agent is preferably one or more of organobentonite 140#, polyamide wax ULTRA, polyamide wax LV, and fumed silica; the cashew nut shell oil modified amine curing agent is preferably one or more of NX8402, NX9001, and KDX-2015A; and the ketimine curing agent is preferably one or more of FT-610, FT-335, and HS-865.

[0032] The present invention also provides a method for preparing the epoxy coating described in the above technical solution, comprising the following steps:

[0033] Step S1: Mix the bisphenol F type epoxy resin, alicyclic epoxy resin, dispersant, defoamer, fluorosilane coupling agent and solvent A evenly to obtain a first mixture. Add pigments, fillers and thixotropic agents to the first mixture in sequence, mix evenly and then obtain component A.

[0034] Step S2: Mix the cashew nut shell oil modified amine curing agent, ketimine curing agent, and solvent B evenly to obtain component B;

[0035] Step S3: Mix component A and component B evenly at a mass ratio of 5~6:1, and apply the mixture to the surface of the substrate to obtain the epoxy coating; under normal temperature conditions, the surface drying time of the epoxy coating is 2~3 hours, and the actual drying time is 7~8 hours.

[0036] In step S1, preferably, bisphenol F type epoxy resin, alicyclic epoxy resin, dispersant, defoamer, fluorosilane coupling agent and solvent A are first dispersed at 1000~1500 rpm for 10~20 min to obtain a first mixture; then pigments and fillers are added to the first mixture and dispersed at 2000~3000 rpm for 30~50 min; then the speed is adjusted to 1000~1500 rpm, thixotropic agent is added and dispersion is continued for 10~20 min to obtain component A.

[0037] In step S2, cashew nut shell oil modified amine curing agent, ketimine curing agent, and solvent B are preferably dispersed at a speed of 1000~1500 rpm for 10~20 min to obtain component B.

[0038] This invention also provides the application of the epoxy coating described in the above technical solution. The epoxy coating is applied to scenarios such as corrosion protection of steel structures in tidal zones, repair of water conservancy and hydropower facilities, and pipeline maintenance, and is applied to the surface of a substrate with a moisture content of 5wt% to 10wt%.

[0039] Compared with existing technologies, the environmentally friendly moisture-resistant epoxy coating for substrates, its preparation method, and its application described in this invention have the following advantages:

[0040] (1) This invention introduces a ketimine curing agent into component B, utilizing its slow hydrolysis upon contact with water to avoid direct competitive reaction between the amine group and water, thus endowing the system with a longer pot life and controllable curing kinetics. Simultaneously, a fluorosilane coupling agent is added to component A, utilizing its extremely low surface energy to quickly displace the adsorbed water film on the substrate surface and form a hydrophobic layer at the interface to prevent water backflow. The synergistic effect of these two agents not only solves the problems of easy whitening and delamination when coating on damp surfaces, but also significantly improves wet adhesion and long-term corrosion protection reliability.

[0041] (2) This invention optimizes film-forming properties by combining bisphenol F type epoxy resin with alicyclic epoxy resin and by combining cashew nut shell oil modified amine curing agent with ketimine. Bisphenol F type resin provides low viscosity and high permeability, ensuring that the coating can penetrate into the micropores of the substrate; alicyclic resin achieves rapid surface drying and early strength due to its high reactivity. Cashew nut shell oil modified amine, with its hydrophobic structure and catalytic effect of long side chains, rapidly displaces the water film and achieves initial anchoring, compensating for the slow initial curing of ketimine; ketimine ensures subsequent deep and long-lasting crosslinking.

[0042] (3) The coating prepared by this invention exhibits excellent comprehensive performance on damp substrates. In terms of mechanical properties, the wet adhesion is as high as 7.86~8.25MPa, the surface drying time is only 2~3 hours, and the film flexibility reaches level 1, passing the 50cm impact test. In terms of corrosion resistance, the salt spray resistance can reach 3000 hours, and the performance is stable in acid, alkali and salt water immersion environments, without bubbling or peeling. This performance breakthrough allows the coating to be directly applied to marine facilities and underwater structures that cannot be completely dried, eliminating the need for cofferdam drainage. Combined with the use of renewable cashew nut shell oil raw materials, it significantly reduces construction costs and environmental impact while ensuring high performance. Detailed Implementation

[0043] The present invention will be further described below with reference to specific embodiments. First, it should be noted that the data in the following experimental examples were obtained by the inventors through numerous experiments. Due to space limitations, only a portion of these data is shown in the specification, and those skilled in the art can understand and implement the present invention based on this data. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various modifications or alterations to the invention, and these modifications or alterations also fall within the scope of protection of this application.

[0044] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0045] The present invention will now be described in detail with reference to embodiments.

[0046] This embodiment provides an environmentally friendly, moisture-resistant epoxy coating for substrates. The epoxy coating is obtained by mixing and curing a mixture of component A and component B. Component A includes a resin matrix, a solvent, and additives, including dispersants, defoamers, thixotropic agents, and fluorosilane coupling agents. Component B includes a curing agent. The resin matrix includes bisphenol F type epoxy resin, and the curing agent includes a ketimine curing agent.

[0047] This embodiment innovatively introduces a fluorosilane compound with an asymmetric structure as a coupling agent, with the general molecular formula CF3(CF2). m (CH2) n -SiX3, where X is a hydrolyzable group. Its molecular structure is "asymmetric": the hydrolyzable silane group at one end of the molecule can form stable chemical bonds with resins, pigments, and fillers, while the low surface energy fluorocarbon chain at the other end can strongly repel moisture from the substrate surface during coating, achieving physical active drainage. Compared with traditional silane coupling agents such as aminosilanes and vinylsilanes, fluorosilanes have more outstanding bonding ability and hydrophobic effect. This physical "active drainage" and the chemical "wet-reactive crosslinking" of ketimine curing agents form a perfect dual protection mechanism, fundamentally ensuring the long-term strong adhesion of coatings on extremely humid surfaces. At the same time, compared with the traditional solution that uses only ketimine as a single curing agent, fluorosilanes have good tolerance to moisture on the substrate surface, which can reduce the amount of ketimine curing agent used, thereby reducing the emission of toxic and harmful gases from small molecule amines.

[0048] In this embodiment, the curing agent further includes a cashew nut shell oil-modified amine curing agent, and the mass ratio of the cashew nut shell oil-modified amine curing agent to the ketimine curing agent is 4~5:4~5.

[0049] This embodiment introduces an alicyclic epoxy resin without aromatic rings. Its saturated alicyclic skeleton is directly linked to epoxy groups, resulting in a concentrated electron cloud density and extremely high reactivity. In humid environments, this high reactivity allows it to rapidly crosslink with the free amines released from the hydrolysis of ketimine, establishing initial strength and locking in water resistance before water molecules interfere. Furthermore, the lack of chromophores in the saturated alicyclic structure further endows the coating with excellent resistance to UV yellowing and chemical media stability. Additionally, a bisphenol F type epoxy resin is selected, whose molecular structure uses methylene bridges to connect bisphenol F diglycidyl ether units, resulting in a regular molecular chain with low steric hindrance. This low viscosity allows it to deeply penetrate into the micropores and cracks of the substrate during application to damp surfaces, effectively displacing the interfacial water film and forming a strong mechanical anchor. Simultaneously, due to its high epoxy group density and few hydrophobic side groups, the crosslinked network after curing is more dense, significantly enhancing the wettability and adhesion of the coating to polar substrates such as steel and concrete under wet conditions.

[0050] In this embodiment, the resin matrix further includes an alicyclic epoxy resin, and the mass ratio of the bisphenol F type epoxy resin to the alicyclic epoxy resin is 6~35:1.

[0051] The cashew nutshell oil-modified amine curing agent used in this embodiment is derived from natural cashew phenol, and a C15 unsaturated long straight-chain aliphatic hydrocarbon containing 0-3 double bonds is introduced through the Mannich reaction. This unique long side chain not only endows the system with excellent hydrophobicity and flexibility, but also actively penetrates and displaces moisture from the surface of damp substrates. Simultaneously, the phenolic hydroxyl groups in the molecular structure can act as a self-catalyst for epoxy ring-opening, ensuring that the coating maintains rapid curing ability even under low temperature or wet surface conditions. Furthermore, the ketimine curing agent is a latent curing system, where its polyamine is blocked by ketones (such as methyl isobutyl ketone) to form imine bonds. This structure gives the system extremely low initial viscosity and an ultra-long pot life, and it remains inert in a dry state; once exposed to a humid environment, the imine bonds undergo reversible hydrolysis, releasing free amines in situ, achieving a "moisture-activated" chemical curing mechanism.

[0052] It should be noted that the raw materials used in the following embodiments are limited as follows: In component A, the bisphenol F type epoxy resin is YDF-170, the alicyclic epoxy resin is 2021P, the dispersant is U-Cure 550S, the defoamer is U-Cure 245S, the thixotropic agent is polyamide wax, specifically the ULTRA model product, the fluorosilane coupling agent is perfluorodecyltriethoxysilane, and solvent A is a homogeneous liquid mixture of xylene and n-butanol in a mass ratio of 1.2:1; the pigments and fillers, iron oxide red, talc, and aluminum tripolyphosphate all have a particle size of 325 mesh, and mica powder and feldspar powder all have a particle size of 800 mesh; In component B, the cashew nut shell oil modified amine curing agent is NX8402, the ketimide curing agent is FT-610, and solvent B is a xylene solution. All of the above raw materials are commercially available.

[0053] It should be noted that in practical applications, this embodiment does not specifically limit the stirring speed and stirring time when mixing components A and B; the standard for judgment is that the two components are mixed evenly.

[0054] Example 1

[0055] A method for preparing an environmentally friendly, moisture-resistant epoxy coating for substrates includes the following steps:

[0056] Step S1: First, bisphenol F type epoxy resin, alicyclic epoxy resin, dispersant, defoamer, fluorosilane coupling agent and solvent A are dispersed at 1200 rpm for 15 min to obtain the first mixture; then pigments and fillers are added to the first mixture and dispersed at 2500 rpm for 40 min; then the speed is adjusted to 1200 rpm, thixotropic agent is added and dispersion is continued for 15 min to obtain component A;

[0057] Step S2: Disperse the cashew nut shell oil modified amine curing agent, ketimine curing agent, and solvent B at 1300 rpm for 15 min to obtain component B.

[0058] Step S3: Mix component A and component B at a mass ratio of 5.5:1 until homogeneous, and apply the mixture to the surface of the substrate to obtain the epoxy coating.

[0059] Based on a total mass fraction of 100 parts for each of components A and B, the specific formulation is shown in Table 1 below. The pigments and fillers are obtained by mixing the following raw materials in the indicated mass fractions: 20 parts of iron oxide red, 9 parts of talc powder, 10 parts of feldspar powder, 8 parts of mica powder, and 8 parts of aluminum tripolyphosphate.

[0060] Example 2

[0061] An environmentally friendly, moisture-resistant epoxy coating for substrates is prepared by mixing and curing component A and component B at a mass ratio of 5.7:1. The raw materials and preparation process are the same as in Example 1, except for the selection and proportion of raw materials: based on a total mass of 100 parts for each of component A and component B, the specific formula is shown in Table 1 below. The pigments and fillers are obtained by mixing the following raw materials in the indicated mass proportions: 25 parts of iron oxide red, 9 parts of talc powder, 8 parts of mica powder, and 8 parts of aluminum tripolyphosphate.

[0062] Example 3

[0063] An environmentally friendly, moisture-resistant epoxy coating for substrates is prepared by mixing and curing component A and component B at a mass ratio of 5.1:1. The raw materials and preparation process are the same as in Example 1, except for the selection and proportion of raw materials: based on a total mass of 100 parts for each of component A and component B, the specific formula is shown in Table 1 below. The pigments and fillers are obtained by mixing the following raw materials in the indicated mass proportions: 20 parts of iron oxide red, 9 parts of talc powder, 10 parts of feldspar powder, 8 parts of mica powder, and 8 parts of aluminum tripolyphosphate.

[0064] Comparative Example 1

[0065] An epoxy coating, whose raw materials and preparation process are the same as those in Example 1, the only difference between the two is that, as shown in Table 1 below, no fluorosilane coupling agent was added in Comparative Example 1.

[0066] Comparative Example 2

[0067] An epoxy coating, whose raw materials and preparation process are the same as in Example 1, the only difference between the two is that, as shown in Table 1 below, the content of ketimine curing agent in Comparative Example 2 is lower than that in Example 1, and the content of cashew nut shell oil modified amine curing agent is higher than that in Example 1.

[0068] Comparative Example 3

[0069] An epoxy coating, whose raw materials and preparation process are the same as in Example 1, the only difference between the two is that, as shown in Table 1 below, the content of cashew nut shell oil modified amine curing agent in Comparative Example 3 is lower than that in Example 1, and the content of ketimine curing agent is higher than that in Example 1.

[0070] Comparative Example 4

[0071] An epoxy coating, whose raw materials and preparation process are the same as in Example 2, the only difference being that: as shown in Table 1 below, alicyclic epoxy resin was not used in Comparative Example 4.

[0072] Comparative Example 5

[0073] An epoxy coating, whose raw materials and preparation process are the same as in Example 2, the only difference between the two is that, as shown in Table 1 below, the content of bisphenol F epoxy resin in Comparative Example 5 is much lower than that in Example 2, and the content of alicyclic epoxy resin is much higher than that in Example 2.

[0074] Comparative Example 6

[0075] An epoxy coating, whose raw materials and preparation process are the same as in Example 2, the only difference between the two is that, as shown in Table 1 below, the content of thixotropic agent in Comparative Example 6 is much lower than that in Example 2.

[0076] Comparative Example 7

[0077] An epoxy coating, whose raw materials and preparation process are the same as in Example 2, the only difference between the two is that, as shown in Table 1 below, the pigments and fillers in Comparative Example 7 are obtained by mixing the following parts by mass of raw materials: 25 parts of iron oxide red, 10 parts of talc powder, 12 parts of feldspar powder, 8 parts of mica powder, and no aluminum tripolyphosphate is added.

[0078] Comparative Example 8

[0079] An epoxy coating, whose raw materials and preparation process are the same as in Example 2, the only difference between the two is that, as shown in Table 1 below, the pigments and fillers in Comparative Example 8 are obtained by mixing the following parts by mass of raw materials: 25 parts of iron oxide red, 10 parts of talc powder, 12 parts of feldspar powder, 8 parts of aluminum tripolyphosphate, and no mica powder is added.

[0080] Table 1. Formulations (parts by mass) of components A and B in Examples 1-3 and Comparative Examples 1-8

[0081]

[0082]

[0083] Test case

[0084] The coatings obtained in Examples 1-3 and Comparative Examples 1-8 were subjected to performance tests according to the standards in Table 2 below, and the test results are shown in Table 3 below.

[0085] Table 2. Main performance indicators and test methods of Examples 1-3 and Comparative Examples 1-8

[0086]

[0087] Table 3 Performance test results of the coatings prepared in Examples 1-3 and Comparative Examples 1-8

[0088]

[0089]

[0090]

[0091]

[0092]

[0093] As shown in Table 2, the epoxy coating prepared by this invention possesses excellent mechanical properties such as flexibility, impact strength, and adhesion, while also exhibiting excellent salt spray resistance. Compared to Example 1, Comparative Example 1, which did not add a fluorosilane coupling agent, showed worse adhesion to damp substrates; Comparative Example 2, with reduced ketimine curing agent dosage, showed decreased adhesion to wet surfaces and secondary adhesion after acid immersion; Comparative Example 3, with reduced cashew nutshell oil-modified amine curing agent dosage, showed prolonged drying time and reduced secondary adhesion after alkali immersion. Compared to Example 2, Comparative Example 4, which did not use alicyclic epoxy resin, showed slower surface drying and decreased mechanical properties; Comparative Example 5, with significantly reduced bisphenol F epoxy resin dosage, showed overall deterioration in adhesion, anti-sagging properties, salt spray resistance, and chemical corrosion resistance; Comparative Example 6, with low thixotropic agent content, showed insufficient anti-sagging properties and poor workability. Comparative Example 7, which lacked aluminum tripolyphosphate in its pigments and fillers, showed decreased salt spray resistance and secondary adhesion after immersion; Comparative Example 8, which did not contain mica powder, showed significantly reduced secondary adhesion after immersion in chemical media.

[0094] This invention utilizes a composite curing system formed by compounding bisphenol F epoxy resin with alicyclic epoxy resin, combined with cashew nutshell oil-modified amine and ketimine curing agent. Through the synergistic effect of water-activated curing by ketimine and the drainage membrane created by fluorosilane, the prepared coating can be directly applied to damp substrates, effectively avoiding problems such as coating whitening and peeling. The product uses renewable raw materials and low volatile components, making it environmentally friendly, while also possessing advantages such as strong adhesion, corrosion resistance, durability, and convenient application.

[0095] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. An environmentally friendly, moisture-resistant epoxy coating for substrates, characterized in that, The epoxy coating is obtained by mixing and curing component A and component B; component A includes a resin matrix, solvent and additives, the additives include dispersants, defoamers, thixotropic agents and fluorosilane coupling agents; component B includes a curing agent; the resin matrix includes bisphenol F type epoxy resin, and the curing agent includes ketimine curing agent.

2. The epoxy coating according to claim 1, characterized in that, The curing agent also includes a cashew nut shell oil-modified amine curing agent, and the mass ratio of the cashew nut shell oil-modified amine curing agent to the ketimine curing agent is 4~5:4~5.

3. The epoxy coating according to claim 1, characterized in that, The resin matrix further includes alicyclic epoxy resin, and the mass ratio of the bisphenol F type epoxy resin to the alicyclic epoxy resin is 6~35:

1.

4. The epoxy coating according to any one of claims 1 to 3, characterized in that, The epoxy coating is obtained by mixing component A and component B in a mass ratio of 5-6:1 and then curing. Component A contains the following parts by weight: 30-35 parts of bisphenol F type epoxy resin, 1-5 parts of alicyclic epoxy resin, 0.2-0.8 parts of dispersant, 0.1-0.5 parts of defoamer, 0.2-0.8 parts of thixotropic agent, 0.1-0.5 parts of fluorosilane coupling agent, and 5-10 parts of solvent A. Component B contains the following parts by weight: 40-50 parts of cashew nut shell oil modified amine curing agent, 40-50 parts of ketimine curing agent, and 5-10 parts of solvent B.

5. The epoxy coating according to claim 4, characterized in that, By weight, component A further comprises 50 to 55 parts of pigments and fillers.

6. The epoxy coating according to claim 5, characterized in that, The pigments and fillers include one or more of iron oxide red, aluminum tripolyphosphate, talc, feldspar powder, and mica powder.

7. The epoxy coating according to claim 4, characterized in that, Solvent A and solvent B are independently selected from one or more mixtures of xylene, n-butanol, and cyclohexanone.

8. The epoxy coating according to claim 4, characterized in that, The thixotropic agent includes one or more of bentonite-type thickeners, polyamide waxes, and fumed silica; the dispersant is a polymeric compound with pigment affinity groups; and the defoamer is an organosilicon defoamer.

9. The method for preparing the epoxy coating according to any one of claims 1 to 8, characterized in that, Includes the following steps: Step S1: Mix the bisphenol F type epoxy resin, alicyclic epoxy resin, dispersant, defoamer, fluorosilane coupling agent and solvent A evenly to obtain a first mixture. Add pigments, fillers and thixotropic agents to the first mixture in sequence, mix evenly and then obtain component A. Step S2: Mix the cashew nut shell oil modified amine curing agent, ketimine curing agent, and solvent B evenly to obtain component B; Step S3: Mix component A and component B evenly at a mass ratio of 5~6:1, and apply the mixture to the surface of the substrate to obtain the epoxy coating; under normal temperature conditions, the surface drying time of the epoxy coating is 2~3 hours, and the actual drying time is 7~8 hours.

10. The application of the epoxy coating according to any one of claims 1 to 8, characterized in that, The epoxy coating is applied to steel structure corrosion protection in tidal zones, repair of water conservancy and hydropower facilities, and pipeline maintenance. It is applied to the surface of a substrate with a water content of 5wt% to 10wt%.

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