A solvent-free epoxy heavy-duty anticorrosive coating for marine engineering

Abstract

The application discloses a solvent-free epoxy heavy-duty anticorrosive coating for ocean engineering, which comprises a component A and a component B, and the component A and the component B are in a ratio of 100:25-45; the component A comprises bisphenol F type epoxy resin, dimer acid modified epoxy resin, epoxy-terminated polydimethylsiloxane, C12-C14 alkyl glycidyl ether, cashew phenol glycidyl ether, composite zinc phosphate anti-rust pigment, flaky glass flake, sericite powder, organic modified montmorillonite, organic bentonite, fumed silica, defoaming agent and wetting dispersant; the component B comprises cashew phenol aldehyde amine curing agent and ketone imine curing agent; the application constructs a continuous labyrinth barrier through three-stage flaky filler grading, combines a ternary hybrid crosslinking network with a moisture-resistant compound curing system, and solves the problems of insufficient shielding of the existing solvent-free epoxy coating, poor curing at low temperature and high humidity, and poor toughness.

Description

Technical Field

[0001] This invention relates to the field of heavy-duty anti-corrosion coatings for marine engineering, and particularly to a solvent-free epoxy heavy-duty anti-corrosion coating for marine engineering. Background Technology

[0002] Marine engineering facilities (offshore wind turbine foundations, cross-sea bridge piers, ship ballast tanks, and subsea pipelines) are exposed to extreme corrosive environments of high salt spray, high humidity and heat, strong ultraviolet radiation, and alternating wet and dry conditions for extended periods. This places extremely high demands on the anti-corrosion life, mechanical toughness, and adhesion of coatings. Currently, commercially available solvent-free epoxy coatings typically use bisphenol A or bisphenol F epoxy resins as the main body, combined with phenolic amine or polyamide curing agents, and add flake fillers such as glass flakes or mica iron oxide to enhance shielding properties.

[0003] First, existing processes often require the addition of large amounts of reactive diluents to meet application viscosity requirements. This significantly reduces the crosslinking density and glass transition temperature of the coating, leading to decreased protective performance at high temperatures. Furthermore, single-scale micron-sized sheet-like fillers cannot effectively shield against nanoscale water molecules and chloride ions, allowing corrosive media to quickly penetrate through "defect channels" in the filler gaps. Second, pure epoxy systems exhibit high rigidity but poor toughness after crosslinking, making them prone to microcracks under dynamic marine loads (wave impact, structural thermal expansion and contraction). Using liquid rubber or dimer acid for toughening often sacrifices modulus and resistance to cathodic disbondment, especially in the cathodic protection environment of seawater platforms where the coating is prone to blistering and peeling. Third, existing curing systems suffer from slow curing speeds, incomplete crosslinking, or insufficient adhesion to damp surfaces under the low-temperature (5-10℃), high-humidity, and even water- and rust-laden substrate conditions of marine engineering, resulting in early water resistance and corrosion resistance failing to meet design specifications.

[0004] Therefore, in response to the problems mentioned above, this invention proposes a solvent-free epoxy heavy-duty anti-corrosion coating for marine engineering. Summary of the Invention

[0005] To overcome the problems of insufficient shielding, brittle cracking under dynamic loads, and poor curing in low-temperature and high-humidity environments in existing solvent-free epoxy coatings, this invention proposes a solvent-free epoxy heavy-duty anti-corrosion coating for marine engineering. This coating constructs a three-level sheet-like filler gradation shielding system from nanometer to micrometer, introduces a flexible, rigid, and hydrophobic multi-hybrid cross-linking network, and uses a moisture-resistant compound curing agent, thereby achieving a synergistic effect of ultra-high shielding, excellent toughness, and rapid curing on low-temperature and humid substrates.

[0006] The technical solution of the present invention is: a solvent-free epoxy heavy-duty anti-corrosion coating for marine engineering, comprising component A and component B, wherein the mass ratio of component A to component B is 100:25-45; The first component, by weight, comprises the following raw materials: 25-40 parts of bisphenol F type epoxy resin, 8-18 parts of dimer acid modified epoxy resin, 2-6 parts of terminal epoxy group polydimethylsiloxane, 5-12 parts of C12-C14 alkyl glycidyl ether, 3-8 parts of cashew phenol glycidyl ether, 12-22 parts of composite zinc phosphate anti-rust pigment, 10-20 parts of flake glass flakes, 5-12 parts of sericite powder, 1-4 parts of organic modified montmorillonite, 0.3-1.2 parts of organic bentonite, 0.2-0.8 parts of fumed silica, 0.1-0.5 parts of defoamer, and 0.3-1.0 parts of wetting and dispersing agent; The B component, by weight, comprises the following raw materials: 55-75 parts of cashew phenol amine curing agent, 20-40 parts of ketimine curing agent, 1-4 parts of tris-(dimethylaminomethyl)phenol, and 2-5 parts of γ-glycidyl etheroxypropyltrimethoxysilane. The mass ratio of the flake glass flakes, sericite powder, and organically modified montmorillonite is controlled at (10-20):(5-12):(1-4). The particle size of the flake glass flakes is 5-15 μm, the particle size of the sericite powder is 5-15 μm, and the particle size of the organically modified montmorillonite is 50-120 nm. The median particle size ratio of the three is 20-80 μm:5-15 μm:50-120 nm, forming a continuous flake shielding gradation system from micrometers to nanometers. The epoxy value of the terminally epoxy polydimethylsiloxane is 0.08-0.15 mol / 100g, and the number average molecular weight is 1000-3000.

[0007] Preferably, the bisphenol F type epoxy resin has an epoxy equivalent of 160-190 g / eq and a viscosity of 2000-4000 mPa·s at 25°C, and the dimer acid modified epoxy resin has an epoxy equivalent of 280-350 g / eq and a dimer acid content of 30-40 wt%.

[0008] Preferably, the composite zinc phosphate anti-rust pigment is aluminum tripolyphosphate modified zinc orthophosphate, wherein the mass fraction of aluminum tripolyphosphate is 15-25%, the pH value of the composite zinc phosphate anti-rust pigment is 6.0-7.0, and the oil absorption is 25-35g / 100g.

[0009] Preferably, the sheet-like glass flakes are surface-treated with silane coupling agent KH-560, with an aspect ratio greater than 60 and particles of 30-50μm accounting for more than 70% of the total particle size distribution. The sericite powder has an aspect ratio greater than 50 and a sieve residue of ≤0.5% on a 45μm sieve.

[0010] Preferably, the organically modified montmorillonite is sodium-based montmorillonite modified with cetyltrimethylammonium bromide, with an interlayer spacing d001 of not less than 2.5 nm, and the initial exfoliation rate of the organically modified montmorillonite in component A is ≥80%. The cashew phenol amine curing agent has an amine value of 280-350 mg KOH / g, an active hydrogen equivalent of 150-200 g / eq, and a viscosity of 800-2000 mPa·s at 25°C. The ketimine curing agent is a reaction product of isophorone diamine and methyl isobutyl ketone, with an amine value of 180-240 mg KOH / g and a solid content of ≥98%.

[0011] Preferably, the defoamer is an acrylate defoamer without silicone, and the wetting and dispersing agent is a high molecular weight block copolymer with pigment affinity groups and an amine value ≤20mg KOH / g.

[0012] The preparation method of the coating includes the following steps: S1. According to the formula, add bisphenol F type epoxy resin, dimer acid modified epoxy resin, terminal epoxy polydimethylsiloxane, C12-C14 alkyl glycidyl ether and cashew phenol glycidyl ether to a dispersion vessel and stir at 400-600 rpm for 15-20 minutes. Then add organic bentonite, fumed silica and wetting and dispersing agent and disperse at 800-1000 rpm for 10-15 minutes. Then slowly add composite zinc phosphate anti-rust pigment, flake glass flakes, sericite powder and organic modified montmorillonite while stirring. Disperse at 1200-1500 rpm for 30-45 minutes until the fineness is ≤60μm. Finally, add defoamer and defoam at 500-700 rpm for 10 minutes. Filter and discharge the material. S2, add cashew phenol aldehyde amine curing agent, ketimine curing agent, tris-(dimethylaminomethyl)phenol and γ-glycidyl etheroxypropyltrimethoxysilane to the reaction vessel according to the formula, stir at 300-500 rpm for 20-30 minutes under nitrogen protection, and filter out the mixture after it is evenly mixed. S3, during construction, mix component A and component B at a mass ratio of 100:25-45, stir for 2-3 minutes, let stand and mature for 5-10 minutes before use.

[0013] The beneficial effects of this invention are: 1. This invention simultaneously introduces flaky glass flakes with a particle size of 20-80 μm, sericite powder with a particle size of 5-15 μm, and organically modified montmorillonite with a particle size of 50-120 nm, and controls the mass ratio and particle size ratio of the three components to form a continuous maze effect from micrometers to nanometers. This three-stage gradation results in a coating water vapor permeability as low as 0.32 g / (m²). 2 The chloride ion diffusion coefficient is only 0.86 × 10⁻⁶ (24h·0.1mm). -14 m 2 / s, which is more than an order of magnitude lower than that of single or dual filler systems. The erosion width of neutral salt spray after 3000h is only 1.1mm, which solves the problem that single-scale fillers in the existing technology cannot shield nanoscale water molecules and chloride ions.

[0014] 2. This invention introduces dimer acid-modified epoxy into a bisphenol F epoxy rigid framework to provide long-chain toughening, while chemically bonding organosilicon hydrophobic segments with terminal epoxy groups of polydimethylsiloxane. After curing, the coating exhibits an elongation at break of 28.6%, a pencil hardness of 4H, a glass transition temperature of 92°C, and a surface water contact angle of 108°. This overcomes the problems of traditional solvent-free epoxy coatings, which either become brittle or experience a decrease in modulus after toughening, and meets the requirements for impact resistance and crack resistance under marine dynamic loads.

[0015] 3. This invention utilizes the property of ketimine to hydrolyze and produce amine when exposed to moisture, which complements the low-temperature catalytic effect of the phenolic hydroxyl groups of cashew phenolic amine. This results in a surface drying time of only 4.2 hours at 5℃ and 85% relative humidity, and an adhesion of 11.2 MPa after 7 days of curing by pull test. It does not bubble when soaked in salt water, and its resistance to cathodic disbondment (65℃, -1.5V, 30d) is only 2.3 mm. This effectively solves the problem of slow curing and poor adhesion of coatings when applied to low-temperature and humid substrates in marine engineering. Attached Figure Description

[0016] Figure 1 The diagram shown is a schematic representation of the preparation process of component A of the present invention; Figure 2 The diagram shown is a schematic diagram of the mixing process of components A and B of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] This invention provides an embodiment: In this embodiment, component A will be described in detail: This invention uses a ternary compound of three epoxy resins with different structures: bisphenol F type epoxy resin, dimer acid modified epoxy resin, and terminal epoxy group polydimethylsiloxane.

[0019] The epoxy equivalent of bisphenol F type epoxy resin is controlled at 160-190 g / eq, and the viscosity at 25℃ is 2000-4000 mPa·s. Its molecular structure contains rigid benzene rings and its viscosity is significantly lower than that of bisphenol A type epoxy resin. It can provide good construction fluidity without the need for a large amount of reactive diluent, while giving the coating high crosslinking density and excellent impermeability.

[0020] The epoxy equivalent of dimer acid modified epoxy resin is 280-350 g / eq, and its dimer acid content is 30-40 wt%. The long-chain fatty acid units introduced into the molecular chain can effectively absorb and disperse external impact energy, and greatly improve the elongation at break and resistance to thermal shock of the coating.

[0021] The epoxy value of terminally epoxy polydimethylsiloxane is 0.08-0.15 mol / 100g, and the number average molecular weight is 1000-3000. The epoxy groups at both ends of its molecule can participate in the curing reaction, chemically bonding the flexible and hydrophobic organosilicon segments to the epoxy crosslinking network.

[0022] This chemical bonding method offers greater long-term stability than simple physical blending, and it does not fail due to migration or precipitation. The introduction of organosilicon segments significantly reduces the surface free energy and water absorption rate of the coating, making it difficult for water molecules and chloride ions to spread and penetrate the coating surface. The mass ratio of the three resins is 25-40 parts bisphenol F type epoxy resin, 8-18 parts dimer acid modified epoxy resin, and 2-6 parts epoxy-terminated polydimethylsiloxane.

[0023] In this invention, C12-C14 alkyl glycidyl ether and cashew phenol glycidyl ether are combined as active diluents, and the amounts of the two in component A are 5-12 parts and 3-8 parts, respectively.

[0024] C12-C14 alkyl glycidyl ethers are long-chain aliphatic monoglycidyl ethers with extremely low viscosity and excellent dilution efficiency. They can significantly reduce the viscosity of the system during application, and their long alkyl chains can also act as internal plasticizers.

[0025] Cashew phenol glycidyl ether is derived from natural cashew shell oil. Its molecular structure contains unsaturated long side chains and phenolic structures. On the one hand, it can participate in the curing reaction, and on the other hand, the phenolic structure can catalyze the epoxy-amine reaction, which helps with low-temperature curing.

[0026] Both of these reactive diluents are free of short-chain alkyl groups, avoiding the problems of decreased glass transition temperature and embrittlement after aging caused by the high volatility and low crosslinking density of traditional butyl glycidyl ethers. Furthermore, both exhibit excellent compatibility with the subsequent cashew phenol amine curing agent, without phase separation or surface migration.

[0027] Component A contains sheet-like glass flakes (particle size 20-80μm, 10-20 parts), sericite powder (particle size 5-15μm, 5-12 parts), and organically modified montmorillonite (particle size 50-120nm, 1-4 parts). The three components are designed strictly according to the mass ratio (10-20):(5-12):(1-4) and the median particle size ratio (20-80μm):(5-15μm):(50-120nm) to form a continuous sheet-like shielding network from the micron to the nanometer scale.

[0028] The flaky glass flakes are surface-treated with silane coupling agent KH-560, with an aspect ratio greater than 60 and particles of 30-50μm accounting for more than 70% of the total. These large-sized flakes with a high aspect ratio are arranged parallel to the substrate in the coating, which can effectively block the propagation of micron-sized cracks and force the corrosive medium to penetrate along a zigzag path.

[0029] Sericite powder has an aspect ratio greater than 50 and a sieve residue of ≤0.5% on a 45μm sieve. Its size is between that of glass flakes and nano-montmorillonite. It mainly fills the gaps between glass flake layers, further extending the diffusion path. At the same time, the flaky structure of sericite itself can also absorb some ultraviolet rays, improving the aging life of the coating.

[0030] The organically modified montmorillonite is a sodium-based montmorillonite modified with hexadecyltrimethylammonium bromide, with an interlayer spacing d001 of not less than 2.5 nm, and an initial exfoliation rate of ≥80% for the organically modified montmorillonite in component A. During high-speed dispersion, the organically modified montmorillonite is exfoliated into nanosheets with a thickness of 1-10 nm and a lateral size of 200-500 nm. These nanosheets are uniformly dispersed in the epoxy resin matrix, providing a nanoscale maze effect, which extends the diffusion paths of water molecules (kinetic diameter of about 0.3 nm) and chloride ions (hydration diameter of about 0.6 nm) by a factor of millions.

[0031] These three types of sheet-like fillers of different sizes create a three-tiered synergistic shielding effect: large glass flakes prevent the macroscopic propagation of cracks, medium-sized sericite blocks micron-level penetration channels, and nano-montmorillonite hinders the diffusion of water molecules and ions at the molecular scale. The combined effect of these three components reduces the coating's water vapor permeability and chloride ion diffusion coefficient by more than an order of magnitude compared to single or dual-filler systems. Simultaneously, the edges of the nano-montmorillonite sheets carry a large number of negative charges, enabling them to adsorb and fix infiltrated cations, forming an ion exchange barrier and delaying the occurrence of the corrosion electrochemical process.

[0032] This invention uses aluminum tripolyphosphate modified zinc orthophosphate as a composite zinc phosphate anti-rust pigment, with an dosage of 12-22 parts, wherein the mass fraction of aluminum tripolyphosphate is 15-25%, the pH value of the composite zinc phosphate anti-rust pigment is 6.0-7.0, and the oil absorption is 25-35g / 100g. Traditional zinc phosphate anti-rust pigments can only release phosphate ions through hydrolysis in an aqueous environment, and their activity is insufficient in solvent-free epoxy systems due to the lack of water. This invention uses aluminum tripolyphosphate to modify it, which has stronger hydrolysis and complexing capabilities. Even in organic coatings without a large amount of free water, it can slowly release polyphosphate ions under the action of penetrating trace water molecules, forming a dense passivation film on the surface of the metal substrate. At the same time, aluminum tripolyphosphate can also form hydrogen bonds with the hydroxyl groups in epoxy resin, enhancing the dry and wet adhesion of the coating to the substrate. The pH value of the composite pigment is strictly controlled within the neutral range (6.0-7.0) to avoid interference from acidic or alkaline pigments on the epoxy resin curing reaction and potential ring-opening side reactions of bisphenol F epoxy resin.

[0033] The present invention uses 0.3-1.2 parts of organic bentonite and 0.2-0.8 parts of fumed silica. These two components synergistically construct a thixotropic structure, preventing pigment and filler sedimentation during coating storage. Simultaneously, they provide shear-thinning properties during application, ensuring a balance between coating leveling and anti-sagging properties. Organic bentonite primarily provides low shear viscosity, while fumed silica exhibits better thinning effects under high shear. The combination of these two components allows the coating to maintain good pumpability and atomization even at a low temperature of 5°C.

[0034] The defoamer of this invention is an acrylate defoamer that does not contain silicone, used in an amount of 0.1-0.5 parts. This type of defoamer can effectively eliminate air bubbles introduced during high-speed dispersion and construction mixing without causing surface contamination.

[0035] The wetting and dispersing agent of this invention is a high molecular weight block copolymer with pigment affinity groups, having an amine value ≤20mgKOH / g, and a dosage of 0.3-1.0 parts. This dispersant can form a strong adsorption layer on the surface of the sheet-like filler, preventing filler flocculation and sedimentation. At the same time, the steric hindrance effect generated by its long polymer chains ensures the stable dispersion of the organomontmorillonite nanosheets and avoids nanoparticle aggregation.

[0036] In this embodiment, component B will be described in detail: Component B contains two curing agents, an accelerator, and a coupling agent.

[0037] The dosage of cashew nut phenol amine curing agent is 55-75 parts, with an amine value of 280-350 mg KOH / g, an active hydrogen equivalent of 150-200 g / eq, and a viscosity of 800-2000 mPa·s at 25℃. Cashew nut phenol amine curing agent is a Mannich base-type curing agent formed by the condensation of cashew nut phenol, formaldehyde, and polyamines. The phenolic hydroxyl groups in its molecular structure can significantly accelerate the epoxy-amine reaction, allowing the coating to surface dry within 6 hours at a low temperature of 5℃. Simultaneously, the unsaturated long side chains of cashew nut phenol impart good toughening and hydrophobicity to the curing agent, forming a complementary reinforcement with the dimer acid-modified epoxy resin and terminal epoxy-terminated polydimethylsiloxane in component A. Cashew nut phenol amine curing agent has natural resistance to damp substrates because the phenolic hydroxyl groups can compete with the water film on the metal surface for adsorption and form stable complexes with iron atoms, thus achieving excellent adhesion on moist substrates.

[0038] The dosage of ketimine curing agent is 20-40 parts. It is a reaction product of isophorone diamine and methyl isobutyl ketone, with an amine value of 180-240 mg KOH / g and a solid content ≥98%. Ketoimine curing agent itself is a blocked product of amines, and it hydrolyzes upon contact with water (moisture) to regenerate free amines and ketones. In high-humidity environments (relative humidity >80%) or even on wet substrates in marine engineering, the amines generated by the hydrolysis of ketimine can react rapidly with epoxy resin, thus achieving low-temperature moisture curing. Simultaneously, the hydrolysis of ketimine consumes water molecules at the interface, helping to reduce the adverse effects of water molecules on the coating / metal interface, thereby improving wet adhesion.

[0039] Cashew phenolic amine provides initial rapid curing capability, while ketimine continuously releases active amines in the later stages of curing or under humid conditions, compensating for incomplete cross-linking that may be caused by the presence of moisture. The combined effect of these two components allows the coating to achieve satisfactory curing even under harsh conditions of 5°C and 85% relative humidity.

[0040] The amount of tris-(dimethylaminomethyl)phenol is 1-4 parts, which acts as a tertiary amine accelerator to further accelerate the epoxy-amine reaction. Tris-(dimethylaminomethyl)phenol itself does not participate in network construction, but it can effectively reduce the reaction activation energy and shorten the curing time.

[0041] The dosage of γ-glycidoxypropyltrimethoxysilane is 2-5 parts. This is a multifunctional silane coupling agent. The epoxy group at one end reacts with the epoxy resin and reactive diluent in component A, while the methoxysilane at the other end hydrolyzes in water to generate silanol, which condenses with the hydroxyl groups on the surface of the metal substrate to form a strong Si-O-Fe covalent bond, significantly improving the adhesion of the coating in both dry and wet conditions. Simultaneously, γ-glycidoxypropyltrimethoxysilane can also interact with the silane-treated layer on the surface of flake glass, enhancing the interfacial bonding strength between the filler and the resin matrix, and preventing filler detachment under impact or bending conditions, thus preventing corrosive media from penetrating along the interface.

[0042] In this embodiment, the preparation of the present invention will be described, specifically: Please see Figure 1 Preparation of component A: A1. Weigh out the bisphenol F type epoxy resin, dimer acid modified epoxy resin, terminal epoxy polydimethylsiloxane, C12-C14 alkyl glycidyl ether, and cashew phenol glycidyl ether according to the aforementioned weight ratio, and add them sequentially to the mixing tank with heating jacket and high-speed dispersion function. Turn on the stirring and control the stirring speed at 400-600 rpm for 15-20 minutes to ensure that the various resins and diluents are fully mixed and uniform.

[0043] A2, then add organobentonite, fumed silica, and wetting and dispersing agent to the mixing tank, increase the stirring speed to 800-1000 rpm, and continue dispersing for 10-15 minutes. This stage allows the organobentonite to fully swell and form a thixotropic network, while the wetting and dispersing agent begins to adsorb onto the surface of the pigments and fillers added later.

[0044] A3. While stirring, slowly add the composite zinc phosphate anti-rust pigment, flake glass flakes, sericite powder and organic modified montmorillonite. The feeding speed should be controlled to be uniformly added over 2-5 minutes to avoid a large amount of dust flying up instantly.

[0045] A4. After adding the materials, increase the stirring speed to 1200-1500 rpm and disperse at high speed for 30-45 minutes. After high-speed dispersion, take a sample and test the fineness with a scraper fineness meter. The fineness should be ≤60μm. If the fineness does not meet the standard, the dispersion time can be extended by 5-10 minutes. Once the fineness is qualified, reduce the stirring speed to 500-700 rpm, add the defoamer, and defoam at low speed for 10 minutes to avoid introducing new air bubbles into the already dispersed system. Finally, filter the material through a 100-mesh stainless steel sieve and package it in a sealed container to obtain component A.

[0046] Preparation of component B: Accurately weigh the cashew phenol aldehyde amine curing agent, ketimine curing agent, tris-(dimethylaminomethyl)phenol, and γ-glycidyl etheroxypropyltrimethoxysilane according to the specified weight ratio. Add these raw materials to a reactor equipped with a nitrogen inlet and a stirrer. Turn on the stirrer at 300-500 rpm and simultaneously introduce dry nitrogen to replace the air in the reactor, preventing premature hydrolysis of the ketimine curing agent by moisture in the air. Stir for 20-30 minutes to ensure thorough and uniform mixing of all components. Since all raw materials in component B are liquids and have good compatibility, prolonged stirring or heating is not required. After uniform mixing, filter through a 150-mesh stainless steel sieve and package in a well-sealed container to obtain component B. Component B requires strict moisture-proof storage.

[0047] Please see Figure 2 Construction mixing method: B1. At the painting site, take out component A and component B in a mass ratio of 100:25-45, preferably 100:30-40.

[0048] B2. First, stir component A with an electric stirrer at low speed (about 300 rpm) for 1 minute to resuspend any potentially settled filler material evenly. B3, then add all of component B to component A, and continue stirring for 2-3 minutes until the system has a uniform color and no stringy streaks.

[0049] B4. After stirring, let it stand for 5-10 minutes to allow the epoxy resin and curing agent in the mixture to react partially beforehand, eliminating viscosity peaks and releasing air bubbles introduced during the mixing process.

[0050] After curing, B5 should be applied using high-pressure airless spraying, brushing, or roller coating. It is recommended that the wet film thickness be controlled at 300-500 μm and the dry film thickness at 250-400 μm. Under environmental conditions above 5℃ and relative humidity below 85%, a single coat of this coating can achieve the coating thickness required for long-term corrosion protection in marine engineering.

[0051] This invention provides a comparative example: This comparative experiment was conducted to compare the performance of the products. The comparative example selected a typical commercially available solvent-free epoxy heavy-duty anti-corrosion coating (using bisphenol A type epoxy resin, single glass flakes, and traditional polyamide curing agent) and a control formulation that changed the key features of the present invention.

[0052] Specifically: In Example 1, the mass ratio of component A to component B was selected as 100:35. Component A contained 32 parts of bisphenol F type epoxy resin, 13 parts of dimer acid modified epoxy resin, 4 parts of terminal epoxy group polydimethylsiloxane, 8 parts of C12-C14 alkyl glycidyl ether, 6 parts of cashew phenol glycidyl ether, 18 parts of composite zinc phosphate anti-rust pigment, 15 parts of flake glass flakes (mainly with a particle size of 30-50 μm), 8 parts of sericite powder (with a particle size of 8-12 μm), 2.5 parts of organically modified montmorillonite (d001 ≥ 2.8 nm), 0.8 parts of organic bentonite, 0.5 parts of fumed silica, 0.3 parts of defoamer, and 0.6 parts of wetting and dispersing agent. Component B contained 65 parts of cashew phenol aldehyde amine curing agent, 30 parts of ketimine curing agent, 2.5 parts of DMP-30, and 3.5 parts of KH-560.

[0053] Example 2: Based on Example 1, the proportions of flaky glass flakes, sericite powder, and organically modified montmorillonite in component A were adjusted to a mass ratio of 10:5:1, with 10 parts glass flakes, 5 parts sericite, and 1 part organically modified montmorillonite, while other components remained unchanged. This was used to investigate the performance under low filler content.

[0054] Example 3: Based on Example 1, the amount of dimer acid modified epoxy resin was increased to 20 parts, and the amount of terminal epoxy polydimethylsiloxane remained at 4 parts, while other parameters remained unchanged, to verify the performance degradation trend after exceeding the preferred range.

[0055] Comparative Example 1: A commercially available typical solvent-free epoxy heavy-duty anti-corrosion coating for marine engineering. The main resin is bisphenol A type epoxy resin and butyl glycidyl ether, the filler is single glass flakes (particle size 40-80μm), the curing agent is polyamide curing agent, and there are no nano fillers or organosilicon components.

[0056] Comparative Example 2, based on Example 1, removed the organically modified montmorillonite and retained only glass flakes and sericite powder, while the other components remained exactly the same.

[0057] Comparative Example 3 was based on Example 1, except that the terminal epoxy polydimethylsiloxane was removed, while other components remained unchanged.

[0058] Comparative Example 4: Based on Example 1, all the ketimine curing agent in component B was replaced with an equal mass of cashew phenol amine curing agent, while other aspects remained unchanged.

[0059] All the above examples and comparative examples were prepared and tested under the same conditions. Three parallel samples were prepared for each formulation, and the average value of the results was taken.

[0060] Table 1 Basic physical and mechanical properties of coatings in each embodiment

[0061] Table 2 Basic physical and mechanical properties of the coatings in each comparative example

[0062] As shown in Tables 1 and 2, Example 1 exhibits the best overall mechanical properties, maintaining a high hardness of 4H while achieving an elongation at break of 28.6%, a flexibility of 1 mm, a dry adhesion of 12.6 MPa, and a wet adhesion retention rate as high as 85.7% (10.8 / 12.6). This indicates that the three-stage filler gradation and ternary resin network of this invention synergistically achieve a balance between rigidity and flexibility. Comparative Example 1 lacks low-temperature rapid curing capability, and its wet adhesion is only 3.2 MPa, far from meeting the requirements for long-term immersion in marine engineering. Although Comparative Example 2 has acceptable flexibility, its adhesion, especially wet adhesion, is significantly reduced due to the lack of physical anchoring and ion exchange effects of the nanosheets. Comparative Example 3 has better dry performance, but its wet adhesion is still lower than that of Example 1, indicating that the organosilicon segments are irreplaceable in improving water resistance and interfacial hydrophobicity. Comparative Example 4 showed an extended surface drying time of 8.5 hours under low temperature and high humidity conditions, and a significant decrease in wet adhesion (7.1 MPa), demonstrating that the combination of ketimine and cashew phenol amine is crucial for rapid curing and interfacial bonding under humid conditions. In Example 3, although the elongation at break increased to 32.5% due to the dimer acid-modified epoxy resin exceeding its upper limit, the hardness decreased to 3H, and the impact resistance was actually worse than in Example 1, indicating that excessive toughening can damage the network integrity.

[0063] Table 3 Corrosion resistance and shielding performance of each embodiment

[0064] Table 4 Corrosion protection and shielding performance of each comparative example

[0065] As shown in Tables 3 and 4, Example 1 exhibits an overwhelming advantage in shielding performance. Its water vapor permeability is only 0.32 g / (m²). 2 (24h·0.1mm), chloride ion diffusion coefficient as low as 0.86×10 -14 m 2 Both of these indicators were more than an order of magnitude lower than Comparative Example 1, and about three times lower than Comparative Example 2. This demonstrates that the tertiary gradation labyrinth effect formed by the three different scale sheet-like fillers far exceeds that of single-component or two-component filler systems. Although Comparative Example 2 has a certain shielding effect, it lacks the direct blocking of water molecules by the nanosheets, and water vapor and chloride ions can still rapidly permeate through the nanoscale gaps between the micron-sized fillers. The shielding performance of Example 3 is lower than that of Example 1 because the excessive flexible segments reduce the crosslinking density, providing more free volume channels for water molecules.

[0066] Table 5. Low-temperature and high-humidity curing performance and resistance to cathodic disbondment for each embodiment.

[0067] Table 6. Low-temperature and high-humidity curing properties and cathodic disbondment resistance of each comparative example.

[0068] As shown in Tables 5 and 6, after curing for 7 days at 5°C and 85% high humidity, Example 1 still exhibited a high adhesion strength of 11.2 MPa using the dry-applied method, and no blistering (grade 0) occurred after 7 days of salt water immersion. Comparative Example 4, under the same conditions, had an adhesion strength of only 5.8 MPa, and showed grade 2 blistering after salt water immersion, indicating that cashew phenolic amine alone cannot completely overcome the weakening effect of moisture on the interface in extremely humid environments. Comparative Example 1 almost failed under low-temperature and humid conditions, with an adhesion strength of only 2.5 MPa and exhibiting cohesive failure. The cathodic disbondment resistance test is a key indicator in marine engineering cathodic protection systems. The disbondment radius of Example 1 was only 2.3 mm, far superior to the 12.5 mm of Comparative Example 1.

[0069] Table 7 Comparison of Thermomechanical Properties and Crosslinking Density

[0070] As shown in Table 7, the Tg of Example 1 reached 92℃, and the crosslinking density was 2.89 × 10⁻⁶. -3 mol / cm 3 This demonstrates that even with the addition of toughening components and a large amount of filler to the system, the present invention still maintains a high degree of crosslinking without sacrificing heat resistance and structural strength. Comparative Example 1, due to the extensive use of butyl glycidyl ether as an active diluent, has a much lower crosslinking density than Example 1, with a Tg of only 65°C, making it prone to softening in tropical marine engineering applications. Example 3 shows a Tg reduced to 79°C and a significant decrease in crosslinking density, confirming the dilution effect of excessive flexible segments on the crosslinking network density.

[0071] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A solvent-free epoxy heavy-duty anti-corrosion coating for marine engineering, characterized in that, It includes component A and component B, wherein the mass ratio of component A to component B is 100:25-45; Component A, by weight, comprises the following raw materials: 25-40 parts of bisphenol F type epoxy resin, 8-18 parts of dimer acid modified epoxy resin, 2-6 parts of terminal epoxy group polydimethylsiloxane, 5-12 parts of C12-C14 alkyl glycidyl ether, 3-8 parts of cashew phenol glycidyl ether, 12-22 parts of composite zinc phosphate anti-rust pigment, 10-20 parts of flake glass flakes, 5-12 parts of sericite powder, 1-4 parts of organic modified montmorillonite, 0.3-1.2 parts of organic bentonite, 0.2-0.8 parts of fumed silica, 0.1-0.5 parts of defoamer, and 0.3-1.0 parts of wetting and dispersing agent; The B component, by weight, comprises the following raw materials: 55-75 parts of cashew phenol amine curing agent, 20-40 parts of ketimine curing agent, 1-4 parts of tris-(dimethylaminomethyl)phenol, and 2-5 parts of γ-glycidyl etheroxypropyltrimethoxysilane. The mass ratio of the flake glass flakes, sericite powder, and organically modified montmorillonite is controlled at (10-20):(5-12):(1-4). The particle size of the flake glass flakes is 5-15 μm, the particle size of the sericite powder is 5-15 μm, and the particle size of the organically modified montmorillonite is 50-120 nm. The median particle size ratio of the three is 20-80 μm:5-15 μm:50-120 nm, forming a continuous flake shielding gradation system from micrometers to nanometers. The epoxy value of the terminally epoxy polydimethylsiloxane is 0.08-0.15 mol / 100g, and the number average molecular weight is 1000-3000.

2. The solvent-free epoxy heavy-duty anti-corrosion coating for marine engineering according to claim 1, characterized in that: The bisphenol F type epoxy resin has an epoxy equivalent of 160-190 g / eq and a viscosity of 2000-4000 mPa·s at 25°C. The dimer acid modified epoxy resin has an epoxy equivalent of 280-350 g / eq and a dimer acid content of 30-40 wt%.

3. The solvent-free epoxy heavy-duty anti-corrosion coating for marine engineering according to claim 1, characterized in that: The composite zinc phosphate anti-rust pigment is zinc orthophosphate modified with aluminum tripolyphosphate, wherein the mass fraction of aluminum tripolyphosphate is 15-25%, the pH value of the composite zinc phosphate anti-rust pigment is 6.0-7.0, and the oil absorption is 25-35g / 100g.

4. The solvent-free epoxy heavy-duty anti-corrosion coating for marine engineering according to claim 1, characterized in that: The sheet-like glass flakes are surface-treated with silane coupling agent KH-560, and their aspect ratio is greater than 60. The particles with a diameter of 30-50μm account for more than 70% of the total particle size distribution. The sericite powder has an aspect ratio greater than 50 and a sieve residue of ≤0.5% on a 45μm sieve.

5. The solvent-free epoxy heavy-duty anti-corrosion coating for marine engineering according to claim 1, characterized in that: The organically modified montmorillonite is sodium-based montmorillonite modified with hexadecyltrimethylammonium bromide, with an interlayer spacing d001 of not less than 2.5 nm, and the initial exfoliation rate of the organically modified montmorillonite in component A is ≥80%.

6. The solvent-free epoxy heavy-duty anti-corrosion coating for marine engineering according to claim 1, characterized in that: The cashew phenol amine curing agent has an amine value of 280-350 mg KOH / g, an active hydrogen equivalent of 150-200 g / eq, and a viscosity of 800-2000 mPa·s at 25℃.

7. The solvent-free epoxy heavy-duty anti-corrosion coating for marine engineering according to claim 1, characterized in that: The ketimine curing agent is a reaction product of isophorone diamine and methyl isobutyl ketone, with an amine value of 180-240 mg KOH / g and a solid content of ≥98%.

8. The solvent-free epoxy heavy-duty anti-corrosion coating for marine engineering according to claim 1, characterized in that: The defoamer is an acrylate defoamer that does not contain silicone.

9. The solvent-free epoxy heavy-duty anti-corrosion coating for marine engineering according to claim 1, characterized in that: The wetting and dispersing agent is a high molecular weight block copolymer with pigment affinity groups and an amine value ≤20mg KOH / g.

10. A solvent-free epoxy heavy-duty anti-corrosion coating for marine engineering according to any one of claims 1-9, characterized in that, The preparation method of the coating includes the following steps: S1. According to the formula, add bisphenol F type epoxy resin, dimer acid modified epoxy resin, terminal epoxy polydimethylsiloxane, C12-C14 alkyl glycidyl ether and cashew phenol glycidyl ether to a dispersion vessel and stir at 400-600 rpm for 15-20 minutes. Then add organic bentonite, fumed silica and wetting and dispersing agent and disperse at 800-1000 rpm for 10-15 minutes. Then slowly add composite zinc phosphate anti-rust pigment, flake glass flakes, sericite powder and organic modified montmorillonite while stirring. Disperse at 1200-1500 rpm for 30-45 minutes until the fineness is ≤60μm. Finally, add defoamer and defoam at 500-700 rpm for 10 minutes. Filter and discharge the material. S2, add cashew phenol aldehyde amine curing agent, ketimine curing agent, tris-(dimethylaminomethyl)phenol and γ-glycidyl etheroxypropyltrimethoxysilane to the reaction vessel according to the formula, stir at 300-500 rpm for 20-30 minutes under nitrogen protection, and filter out the mixture after it is evenly mixed. S3, during construction, mix component A and component B at a mass ratio of 100:25-45, stir for 2-3 minutes, let stand and mature for 5-10 minutes before use.

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