An underwater construction and underwater curing anti-corrosion coating

Abstract

The present invention discloses an underwater construction and underwater curing anti-corrosion coating. The coating comprises component A and component B. Component A contains, by weight, 65-85 parts of epoxy resin, 20-45 parts of MS polymer, 10-30 parts of diluent, and 10-25 parts of additives; component B contains 90-105 parts of modified phenalkamine underwater curing agent, 1-3 parts of curing accelerator, and 1-5 parts of organotin catalyst. The MS polymer and epoxy / modified phenalkamine can independently crosslink to form a toughened fully interpenetrating network. The anti-corrosion coating contains no organic solvents, does not segregate, turn white, or sag when exposed to water, has good tolerance for poorly treated surfaces, can be directly constructed and cured underwater, is simple and efficient to apply, and can form a film thickness of up to millimeters in one application. It is suitable for the long-term protection of large-scale marine engineering facilities.

Description

Technical Field

[0001] The present invention relates to the field of coating materials, and in particular to an underwater construction and underwater curing anti-corrosion coating. Background Art

[0002] Fixed offshore facilities are generally large and heavy, located far from the shore, and maintenance is usually carried out on-site. Due to the constraints of the scene and weather, the offshore operation window is short, the cost is high, and the difficulty is great. It is often carried out by diving / diving (especially in tidal ranges and underwater areas), so there are many requirements for materials and processes (such as being as simple, efficient, and one-time as possible). Ordinary anti-corrosion coatings require deep rust removal of the substrate in advance (grinding to Sa2.5 level) and phased coating (to prevent sagging under high film thickness). They are only suitable for dry atmospheres and cannot adapt to offshore working conditions. It is advisable to use specific underwater curing products, which should have at least the following advantages: 1. No inert diluents to avoid water pollution and affect film formation; 2. Good hydrophobicity and chemical stability, no separation, diffusion, whitening, swelling or dissolution in water; 3. Appropriate density and viscosity, no floating or flowing in water; 4. Convenient and smooth thick coating, good thixotropy, and anti-sagging on vertical surfaces; 5. Thorough curing, high adhesion, and reliable bonding even on low-treated surfaces; 6. Effective shielding of Cl - 7. The paint layer has a tough texture and can withstand the impact of wind, waves, sand and gravel, and floating objects.

[0003] Based on this, researchers have made significant breakthroughs through tireless efforts over the years, but this has also exposed numerous problems. Patent application number CN109280464A provides a dedicated underwater waterproof and anti-corrosion coating, its production method, and construction process. It is primarily used for building waterproofing and leak-proofing (its anti-corrosion capabilities are unknown). However, the application process is cumbersome (requiring three coats of paint), and the underwater tensile bond strength is low (1.4-2.2 MPa). Patent announcement number CN116836615B provides a polyaspartic acid ester polyurea coating for underwater curing and its preparation method. However, even after two coats of brush application, a film thickness of only 200 μm is achieved. Furthermore, the coating cannot be applied directly underwater, requiring 20-40 minutes of application time before immersion.

[0004] Patent applications with publication numbers CN102212303A and CN102140297A each disclose an underwater solvent-free epoxy thick paste heavy anti-corrosion coating, in which the contained benzyl alcohol presents a risk of dissolution and contamination in water. Similarly, Ling Qin et al. (China Coatings, 2021, 36(8):11-14) prepared a high-solids underwater curing heavy anti-corrosion coating, in which the ethanol / isopropanol used to dilute the curing agent is also highly water-soluble. In addition, patent application CN108587399A discloses a polysilicon ceramic underwater construction anti-corrosion coating and its preparation method. After triethylenetetramine turns white in water (amine white), it is likely to cause incomplete reaction.

[0005] Another characteristic of underwater curing, compared to dry curing, is that the paint film is more brittle. To improve its toughness, liquid rubbers (polyethers, polysulfides, nitrile-butadiene rubbers), core-shell macromolecules, hyperbranched polymers, nanoparticles, thermoplastic resins, liquid crystals, and the like can be added. For example, patent applications CN108192471A, CN102719174A, CN108250910A, and CN102533058A all utilize polysulfide rubber for toughening, but this method suffers from a foul odor and the "sea-island" structures dispersed within the cross-linked network can easily induce severe interfacial phase separation.

[0006] Patent publication number CN112760006B provides a solvent-free, heavy-duty anti-corrosion coating composition capable of wet coating, as well as its preparation and application. The coating exhibits high hardness, excellent toughness, and resistance to cracking and cathodic disbonding. A thorough analysis reveals certain deficiencies in this approach: 1. Of the inactive diluents, phenylethanol, cashew nut shell liquid polyol, and cardanol glycidyl ether are inherently inert solvents, potentially migrating and causing a decrease in the coating's water and media resistance. Furthermore, phenylethanol is soluble in water, and cardanol glycidyl ether can also participate in the reaction, making it not truly "solvent-free" or "inactive." 2. The complex amine curing agent may whiten upon contact with water. 3. The functional filler has limited hydrophobicity due to lack of special treatment. 4. The examples were applied only with wet coating, not directly underwater, making it impossible to assess the exact film thickness, anti-dispersion, anti-sagging properties, and consolidation performance in the first instance underwater.

[0007] In summary, existing technologies have more or less limitations and may not be fully compatible with the special needs of in-situ maintenance of marine engineering facilities. The development of professional underwater anti-corrosion coatings has practical significance. Summary of the Invention

[0008] The present invention aims to provide an underwater construction and underwater curing anti-corrosion coating with high viscosity and strong thixotropy, low requirements for substrate pre-treatment, and a millimeter-level film thickness can be obtained with a simple coating, which can greatly shorten the operation time.

[0009] To achieve the above purpose, the technical solution of the present invention is as follows:

[0010] Disclosed is an underwater construction and underwater curing anti-corrosion coating, comprising a component A and a component B. Component A contains an epoxy resin and a diluent, and component B contains a modified phenolic amine underwater curing agent. Component A further contains an MS polymer and an additive, wherein, by weight, the epoxy resin, the MS polymer, the diluent, and the additive are 65-85 parts, 20-45 parts, 10-30 parts, and 10-25 parts, respectively. Component B further contains a curing accelerator and an organotin catalyst, wherein, by weight, the modified phenolic amine underwater curing agent, the curing accelerator, and the organotin catalyst are 90-105 parts, 1-3 parts, and 1-5 parts, respectively. Component A and component B are mixed in a mass ratio of (6-8):1.

[0011] MS polymers are a class of siloxane-terminated, pre-crosslinked macromolecules commonly used for bonding in prefabricated buildings, the automotive industry, power batteries, and other fields. This invention utilizes these polymers as functional components in anti-corrosion coatings. Working synergistically with epoxy resins, diluents, and modified phenalkamines, they not only repel and absorb moisture from the substrate interface, maintaining a relatively dry state to facilitate underwater coating and curing, but also form a fully interpenetrating network with the epoxy system, effectively improving the coating's toughness.

[0012] Preferably, the component A contains 70-80 parts of epoxy resin, 20-40 parts of MS polymer, 10-20 parts of diluent, and 10-20 parts of auxiliary agent; the component B contains 95-100 parts of modified phenalkamine underwater curing agent, 1-3 parts of curing accelerator, and 1-3 parts of organic tin catalyst.

[0013] In a preferred embodiment of the present invention, the epoxy resin is selected from at least one of liquid or semi-solid bisphenol A and bisphenol F epoxies, with an epoxy equivalent of 170 to 230 g / eq and a hydrolyzable chlorine content of less than 300 ppm. For cost considerations, one or a combination of cost-effective bisphenol A types E-51, E-54, and E-44 is preferred.

[0014] In a preferred embodiment of the present invention, the MS polymer is a siloxane-terminated, pre-crosslinked macromolecule. One end of the MS polymer contains a trialkoxysilane selected from at least one of trimethoxysilane, triethoxysilane, and tripropoxysilane; the other end contains a long-chain polymer selected from at least one of polyether, polyester, polyurethane, and their derivatives. The siloxane units in the MS polymer absorb moisture from the surrounding environment under the influence of a catalyst at room temperature, condensing to form a three-dimensional network. The long-chain polymer "tail" imparts elasticity to the polymer.

[0015] In a preferred embodiment of the present invention, the MS polymer is a trimethoxysilyl-terminated polyether with a viscosity of 5-80 Pa·s, preferably 10-15 Pa·s. To accelerate moisture cure while balancing crosslinked elasticity and hardness, a medium-viscosity (10-15 Pa·s) trimethoxysilyl-terminated polyether is preferred in this embodiment. Compared to ethanol and propanol, methanol offers less steric hindrance and is easier to remove. Polyethers are more flexible than polyesters and are colorless and odorless (polyurethanes may have a pungent odor due to residual isocyanate). However, if the viscosity is too low, the tail segments will be too short, impairing elasticity, while if the viscosity is too high, the hardness will be insufficient.

[0016] The diluent is used to reduce the viscosity of the epoxy resin and increase the amount of pigments and fillers added. It is selected from one or more of glycidyl ethers, glycidyl esters, and glycidyl amines. Replacing inert solvents with reactive diluents allows for the formulation of high-solids, solvent-free products, preventing water contamination from solvent precipitation during underwater construction. Considering the diluent's viscosity, hydrophobicity (ether > ester > amine), and molecular flexibility, it is preferred that low-viscosity, highly hydrophobic cardanol monoglycidyl ether and difunctional polypropylene glycol diglycidyl ether, which can participate in network chain extension and flexibility, be miscible in a ratio of (1-2 parts by weight): (1-2 parts by weight).

[0017] The auxiliary agent is a combination of a coupling agent, a defoaming agent, a wetting and dispersing agent, a leveling agent, and a thixotropic agent. In a preferred embodiment, the auxiliary agent comprises, by weight, 3 to 6 parts of a silane coupling agent, 1 to 2 parts of a defoaming agent, 1 to 3 parts of a wetting and dispersing agent, 1 to 3 parts of a leveling agent, and 4 to 9 parts of a thixotropic agent. The silane coupling agent is selected from one or more combinations of KH560, KH563, KH530, and KH531; the defoaming agent is selected from one or more combinations of BYK-A530, BYK-A535, BYK-066N, BYK-A141, BYK-300, BYK-301, and BYK-335; the wetting and dispersing agent is selected from one or more combinations of BYK-9076, BYK-110, BYK-W965, and DS-9104; the leveling agent is selected from one or more combinations of BYK-354, BYK-306, BYK-310, BYK-320, and BYK-333; and the thixotropic agent is selected from one or more combinations of modified polyethylene wax, polyamide wax, fumed silica, organic bentonite, and cellulose ether.

[0018] In one preferred embodiment, Component A also contains 210-250 parts of pigments and fillers. These pigments and fillers, by weight, include 10-20 parts of fiber, 30-50 parts of coated titanium dioxide, 140-160 parts of glass flakes, and 10-30 parts of hydrotalcite-modified hollow microspheres. To ensure slurry fineness and film density, the particle size of the glass flakes and hydrotalcite-modified hollow microspheres is preferably 300-500 mesh, and the coated titanium dioxide is preferably 800-1000 mesh. Combining different particle sizes allows for the densest packing and minimizes porosity.

[0019] In one preferred embodiment, the fibers are either or both glass fiber and basalt fiber, hydrophobically modified. The modification method comprises the following steps: after screening, the fibers are soaked in a 1-5 wt% KH560 ethanol solution for 24-48 hours to fully seal the Si-OH bonds on the surface. After hydrophobic modification, the fibers are dried for later use. This modification improves the fiber's wettability with epoxy and diluents, as well as its compatibility in paint films (the epoxy groups at the ends of KH560 are cross-linkable, ensuring a seamless transition between the fiber interface and the resin system). The fibers are preferably 20-60 μm in length.

[0020] Titanium dioxide has outstanding whiteness, hiding power, and colorability. Modification with zirconium, aluminum, silicon, and other materials can achieve high hardness and UV aging resistance. The coated titanium dioxide is zirconium-coated. The preparation method includes slowly dripping a 100-120 g / L Zr(SO4)2 solution into a TiO2 dispersion under continuous stirring at 55-60°C, adjusting the pH to 9-10, aging for 1-2 hours, then washing, filtering, drying, grinding, and sieving. Wet zirconium coating forms a highly wear-resistant ZrO2 coating on the titanium dioxide surface.

[0021] The fiber hydrophobic modification method and the zirconium-coated titanium dioxide preparation method are both preferred treatment methods, and other hydrophobic modification methods and zirconium-coated titanium dioxide preparation methods can also be used.

[0022] Ultra-thin flat glass flakes can form a "maze" effect by stacking, slowing down the flow of H2O, O2, Cl - 、SO4 2- Its high hardness also helps it withstand the impact and abrasion of wind, waves, and floating objects. Furthermore, its physical and chemical properties are stable, including insulation, resistance to water, acid, alkali, salt, and cathodic disbonding, and it can block micro-conductive pathways and inhibit the formation of chemical galvanic cells. In practice, most offshore steel structures below the waterline are equipped with impressed current devices to assist in corrosion protection. Traditional zinc- or graphene-containing (rich) coatings are susceptible to flaking due to the conductivity of zinc or graphene, making them inadequate for this application. Glass flakes, however, effectively prevent this.

[0023] Hollow microspheres are lightweight, have low oil absorption, and are easily rolled by lateral external forces. This significantly improves smoothness during construction and reduces the amount of paint used per unit coating area. They can also fill the tiny gaps formed by the misaligned stacking of glass flakes, improving density. After being modified with hydrotalcite, they can effectively absorb, capture, and fix Cl in seawater with their unique intercalation structure. - , weakening the penetration of corrosive ions and thus enhancing the protective ability.

[0024] In one preferred embodiment, the modified phenalkamine underwater curing agent has a viscosity of 600-1200 mPa·s. It contains no residual monomers such as phenol, formaldehyde, and ethylenediamine, does not whiten or spread in water, has a viscosity between 600-1200 mPa·s, is insensitive to moisture and temperature, and reacts rapidly at 5°C or underwater. Combinations of different modified phenalkamines are preferred to balance molecular toughness, hydrophobicity, and curing activity.

[0025] The organotin catalyst is selected from at least one of trialkylamine, tin butyrate, stannous isooctanoate, dibutyltin diacetate, dibutyltin dioctoate, dibutyltin dilaurate, and bis(acetylacetonato)dibutyltin. Given the long molecular chain length and high steric hindrance of MS polymers, the highly efficient chelated catalyst bis(acetylacetonato)dibutyltin is preferred.

[0026] There are no special requirements for the preparation of the component A and the component B, and conventional anti-corrosion coating production equipment is used according to normal procedures.

[0027] Taking into account the factors such as the difficulty in pre-treatment of the substrate and the inconvenience of multiple coatings during on-site maintenance of marine engineering facilities, the present invention only requires simple removal of rust on the metal substrate in advance, and the A component and the B component are mixed uniformly according to the ratio. Simple tools such as scrapers, brushes, rollers, etc. are used to directly apply the coating with water or underwater by scraping, brushing or roller coating. The coating film thickness can reach 800 to 1200 μm at a time, avoiding intermittent repeated operations.

[0028] The formation mechanism and characteristics of the fully interpenetrating network of the present invention are further explained below:

[0029] Epoxy resins are widely known for their promising applications in the coatings and adhesives industries. However, due to their numerous rigid benzene rings, their cross-linked networks are brittle, necessitating toughening in specific applications. Traditional methods often involve incorporating rubber, hyperbranched polymers, and nanoparticles. These "exotic" substances disrupt the continuity and consistency of the epoxy system, easily leading to varying degrees of interfacial separation between the "sea" and "island" layers, and weakening the toughening effect. Unlike the "physical doping" approach, the introduction of semi- and fully interpenetrating networks (IPNs) promotes the interpenetration and fusion of the two distinct three-dimensional structures, maximizing their strengths and minimizing their weaknesses.

[0030] MS polymer is green and environmentally friendly, has no irritating odor, and the siloxane end groups are highly active when stimulated by catalysts, and can be moisture-cured and dealcoholized to form -Si-O-Si- macromolecules ( Figure 1 -a), its tail long chain is highly elastic. At the same time, epoxy + modified phenolic amine can also be ring-opened to form a network. The MS polymer cross-linked network and the epoxy / phenolic amine cross-linked network are independently constructed without interfering with each other, but are interconnected ( Figure 1 -b). The elastic MS polymer cross-linked network can contact and fully integrate into the rigid epoxy / phenalkamine cross-linked network at the molecular level, and its toughening mechanism and function are significantly superior to macroscopic "physical doping".

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. Leveraging the hydrophobic properties of each raw material, the substrate interface is displaced and moisture is removed, leaving it relatively dry. The MS polymer and silane coupling agent can also absorb moisture and dealcoholize, further dissolving residual moisture to facilitate underwater coating and consolidation. Both the MS polymer and epoxy / modified phenalkamine can independently crosslink to form a fully interpenetrating network, enhancing the toughness of the epoxy system while eliminating potential interfacial incompatibility risks.

[0033] Second, the "bridge" effect of the fiber can effectively conduct and dissipate internal stress, improve the overall strength of the paint film, and prevent peeling and cracking. Hollow microspheres are very easy to roll, which can improve the smoothness of construction, reduce the amount of paint used per unit coating area, increase density, and are more Cl after being modified with hydrotalcite. - Glass flakes not only help prevent corrosion at the waterline and below, but their high hardness, similar to that of zirconium-coated titanium dioxide, also protects against impacts from wind, waves, sand, and floating objects.

[0034] Third, after careful formulation, underwater construction and underwater curing anti-corrosion coatings contain no organic solvents. They sink to the bottom in water, do not segregate, spread, whiten, or flow, and are highly tolerant of poorly treated surfaces. Application is simple and quick, requiring a single coat (common anti-corrosion products have minimal sagging and require at least two to three recoats), significantly reducing offshore workload. It's worth noting that "underwater curing" doesn't necessarily mean it can only cure underwater; the coating can also form successfully in dry environments or on damp surfaces (in fact, eliminating water molecule interference improves the overall performance of the coating). This coating not only accommodates the tidal range and underwater operations of offshore facilities, but also the splash zone and atmospheric zone, meeting the protection needs of all stages of the process, both before and after the installation. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The cross-linking mechanism of MS polymers ( Figure 1 -a) and fully interpenetrating network configuration ( Figure 1 -b).

[0036] Figure 2This is a diagram showing the anti-dispersion and anti-flow effects of the underwater construction and underwater curing anti-corrosion coating prepared in Example 2 in water.

[0037] Figure 3 These are photos showing the smoothness of underwater construction and underwater curing of the anti-corrosion coating prepared in Example 1.

[0038] Figure 4 This is the microscopic morphology (SEM) of the paint film in Example 1. DETAILED DESCRIPTION

[0039] The present invention is described in detail below with reference to the embodiments and the accompanying drawings. The embodiments and features of the embodiments of the present invention may be combined with each other without conflict.

[0040] Sample and specimen preparation and performance testing were based on the following guidelines: General Preparation Methods for Paint Films (GB / T 1727-2021), Determination of Impact Resistance of Paint Films (GB / T 1732-2020), Determination of Flexibility of Paint and Putty Films (GB / T 1731-2020), Paints and Varnishes - Determination of Neutral Salt Spray Resistance (GB / T 1771-2007), Paints and Varnishes - Pull-Off Adhesion Test (GB / T 5210-2006), Paints and Varnishes - Determination of Film Hardness by the Pencil Method (GB / T 6739-2006), Paints and Varnishes - Determination of Abrasion Resistance (GB / T 1768-2006), and Paints and Varnishes - Determination of Cathodic Disbonding Resistance of Coatings Exposed to Seawater (GB / T 7790-2008). Raw materials were purchased commercially. Steel substrates were briefly sanded and then coated underwater in a single pass, followed by underwater curing. The criterion for judging the resistance to acid, alkali, salt and salt spray is to observe whether the paint film is bubbling, cracking, falling off or rusting after a period of testing.

[0041] The fiber hydrophobic modification method is as follows: glass fibers with a length of 20 to 60 μm are selected through screening, ultrasonically dispersed in a 5 wt% KH560 ethanol solution at room temperature, taken out after 24 hours, and dried for later use.

[0042] The preparation method of zirconium-coated titanium dioxide is as follows: 120 g / L Zr(SO4)2 solution is slowly dripped into TiO2 dispersion under continuous stirring at 60°C, the pH is adjusted to 10, and after aging for 2 hours, it is washed, filtered, dried, ground, and sieved for use.

[0043] Underwater construction and underwater curing anti-corrosion coating preparation process:

[0044] (1) By mass, add 70-80 parts of epoxy resin, 20-40 parts of MS polymer, 10-20 parts of diluent, 3-6 parts of coupling agent, 1-2 parts of defoaming agent, 1-3 parts of wetting dispersant, and 1-3 parts of leveling agent into a double-layer jacketed tank and stir at 1000 rpm for 20 minutes to make it into a uniform slurry; then add 4-9 parts of thixotropic agent, 10-20 parts of the above-mentioned modified fiber, 30-50 parts of the above-mentioned zirconium-coated titanium dioxide, and 140-160 parts of glass flakes in small amounts in stages and disperse at 1500 rpm for 2 hours, and finally add 10-30 parts of hydrotalcite-modified hollow microspheres and disperse at 800 rpm for 30 minutes (during which the mixture is cooled by water to control the heating temperature of the mixture to be no higher than 40°C). After passing the fineness test, the paste-like component A is obtained.

[0045] All liquid components are added in the same batch at the same time, and can be quickly mixed at a low stirring rate to obtain a thin slurry. Powdered raw materials such as thixotropic agents and modified fibers will cause the viscosity of the system to increase sharply, so they need to be added in small amounts and multiple times in stages, and the rotation speed should be increased. At the same time, water cooling should be used to prevent the dispersion disk from seizing the shaft or the core temperature from being too high. Hollow microspheres have thin walls and are fragile, so they need to be mixed under low shear force.

[0046] (2) 95-100 parts of modified phenolic amine underwater curing agent, 1-3 parts of curing accelerator, and 1-3 parts of organic tin catalyst were stirred at 1200 rpm for 30 minutes until uniform, to obtain low viscosity component B.

[0047] (3) In actual use, component A and component B are mixed thoroughly in a mass ratio of (6-8):1 at 600 rpm for 3 minutes. After simply removing the rust layer on the surface of the substrate, it can be directly applied with water or underwater by scraping, brushing, or roller coating manually or mechanically.

[0048] The comprehensive properties of the paint films of each embodiment and comparative example are shown in Table 1. The ingredients of each embodiment and comparative example are shown in Table 2.

[0049] In Table 2, modified phenalkamine underwater curing agent (from Cardolite Chemical (Zhuhai) Co., Ltd., NX-5653), modified phenalkamine underwater curing agent (from Shanghai Duer Chemical Co., Ltd., D0965), phenalkamine curing agent (from Cardolite Chemical (Zhuhai) Co., Ltd., NX-6032).

[0050] It is not difficult to find from the attached drawings that the density and viscosity of the mixed slurry of Examples 1 and 2, which are strictly selected for each raw material, are moderate, they do not suspend or disperse when in contact with water, the water quality is clear and pure, there is no dissolved matter, the thixotropy is good, and the pile height of 12 mm does not collapse basically ( Figure 2 ); Underwater scraping is smooth, which can form an ideal surface that is flat, smooth, uniform in thickness, impact-resistant and wear-resistant ( Figure 3Under a scanning electron microscope (SEM), the paint layer can be observed to have clear outlines of spherical hollow microspheres, filamentous reinforcing fibers, and reflective glass flakes. No interfacial phase separation or "sea-island" conformation is observed, indicating that the MS polymer and epoxy system have been perfectly integrated into a fully interpenetrating network ( Figure 1 -a, Figure 1 -b, Figure 4 ).

[0051] Table 1 summarizes the comprehensive performance of each example and comparative example. Example 1 has a film thickness and underwater adhesion much higher than that of the Chinese patent application with publication number CN109280464A (7.45MPa vs. 2.2MPa). It is tough (hardness > 6H, impact strength > 60cm / kg, wear loss only 52mg), can withstand the impact of wind and waves, gravel, and floating objects, and is resistant to long-term erosion by high-concentration acids / alkalis / salts. Thanks to the Cl - Capture and galvanic cell blocking ability of glass flakes, its resistance to Cl - Excellent penetration and cathodic stripping effects.

[0052] By slightly adjusting the content of MS polymer and hydrotalcite-modified hollow microspheres, the paint film indicators of Example 2 had no substantial difference from those of Example 1.

[0053] Comparative Example 1, which instead used liquid nitrile butadiene rubber (CTBN) with a similar viscosity (13.5 Pa·s) for physical toughening, exhibited lower impact strength than the MS polymer (<40 cm / kg). Furthermore, while CTBN's hydrophobicity displaced most of the water on the substrate surface, it was unable to absorb moisture, and the small amount of residual water formed a barrier between the substrate and the paint film, reducing adhesion by nearly 30% (5.24 MPa). Consequently, media resistance was inferior to that of Example 1. Experiments revealed that further increasing the CTBN dosage induced interfacial incompatibility.

[0054] In Comparative Example 2, equal parts by weight of conventional phenalkamine with similar viscosity and active hydrogen equivalent (η = 1200 mPa·s, AHEW = 133) were selected as the curing agent. Although both NX-6032 and NX-5653 are cardanol derivatives, the former readily turns white (deteriorates) in water and is difficult to fully cure, resulting in a soft and sticky film surface and low network crosslinking. Furthermore, the lack of glass fiber reinforcement significantly diminishes adhesion, flexibility, hardness, and corrosion resistance. Blisters of varying sizes appeared after immersion for equivalent periods of time: 10% NaOH / 1680 hours, 10% H₂SO₄ / 1200 hours, and 5% NaCl / 2880 hours. This demonstrates the significant impact of curing agent type on underwater curing.

[0055] After reducing the amount of TS-720, the thixotropy of comparative example 3 is insufficient, the sagging limit is low (0.4-0.6mm), and it is easy to flow when applied too thickly. In addition, the modified hollow microspheres are eliminated, and there is a sense of blockage when scraping. The paint film is not dense (there are pores between the fillers), the surface flatness is poor, and the acid, alkali and salt resistance (especially NaCl resistance, neutral salt spray resistance, Cl resistance) is poor. - The performance of the invention is difficult to be on the same level as that of Example 1.

[0056] It is worth noting that all embodiments and comparative examples can be cured normally in a dry environment, and the adhesion is generally higher than that under water.

[0057] In order to investigate the synergistic gain effect between other components, the present invention also tried the following possible solutions:

[0058] 1. Change the hydrophilicity of the raw materials. For example, if relatively hydrophilic glycidylamine or hydrophilic gas silica M5 is selected, the water non-diffusion of the mixed slurry will decrease, the water will become translucent and misty (which means that a certain material is dissolved or infiltrated and suspended in water), and the anti-sagging ability will be almost lost.

[0059] 2. If you choose titanium dioxide for construction, or use two-dimensional sheets such as mica instead of glass flakes, the coating will be soft, with a pencil hardness of about 1 to 2H and limited wear resistance.

[0060] 3. Using high-viscosity MS polymer (η = 100 Pa.s) presents the following drawbacks: 1. Component A has an excessively high viscosity, making it difficult to mix evenly. This requires reducing the proportion of MS polymer or increasing the amount of diluent, which delays crosslinking of the MS polymer (the long-chain molecules provide significant steric hindrance, slowing the dehydration and polycondensation of the siloxane ends). Furthermore, the ratio of the MS polymer crosslinking network to the epoxy / phenalkamine crosslinking network (the fully interpenetrating network formed by crosslinking the MS polymer, epoxy resin, and phenalkamine) in the fully interpenetrating network is unbalanced, compromising the toughening effect. 2. The paint film is soft but not hard, increasing abrasion. Using a low-viscosity MS polymer (η < 5 Pa.s) instead results in insufficient toughness and reduced impact strength due to the shortened polyether segments.

[0061] In a nutshell, through strict selection and modification of each component, the underwater construction and curing of the anti-corrosion coating are achieved. It has good performance, low requirements for substrate treatment, and high film thickness in one time. It can greatly simplify the on-site coating process of marine engineering. It is applicable to but not limited to the early anti-corrosion and later repair and maintenance of all sections above and below water, such as offshore wind power / photovoltaic, exploration / oil and gas platforms, deep blue ranches, and cross-sea bridges.

[0062] The above embodiments should be understood as being merely intended to more clearly illustrate the present invention, and not to limit the scope of the present invention. Any modifications and alterations to these embodiments inspired by the present invention, including any equivalent modifications, are intended to fall within the scope of protection defined by the appended claims.

Claims

1. An underwater construction and underwater curing anti-corrosion coating, comprising component A and component B, wherein component A contains epoxy resin and diluent, and component B contains modified phenolic amine underwater curing agent, characterized in that: The component A further contains MS polymer and auxiliary agent. In parts by mass, the epoxy resin, MS polymer, diluent, and auxiliary agent are 65-85 parts, 20-45 parts, 10-30 parts, and 10-25 parts, respectively. The component B further contains a curing accelerator and an organotin catalyst. In parts by mass, the modified phenolic amine underwater curing agent, curing accelerator, and organotin catalyst are 90-105 parts, 1-3 parts, and 1-5 parts, respectively. The component A and the component B are mixed in a mass ratio of (6-8):

1. The MS polymer is a siloxane-terminated pre-crosslinked macromolecule, one end of the MS polymer is a trialkoxysilane, and the trialkoxysilane is selected from at least one of trimethoxysilane, triethoxysilane, and tripropoxysilane; the other end of the MS polymer is a long-chain polymer, and the long-chain polymer is selected from at least one of polyether, polyester, polyurethane, and derivatives thereof; The auxiliary agent comprises, by weight, 3 to 6 parts of a silane coupling agent, 1 to 2 parts of a defoaming agent, 1 to 3 parts of a wetting and dispersing agent, 1 to 3 parts of a leveling agent, and 4 to 9 parts of a thixotropic agent; the thixotropic agent is hydrophobic fumed silica; The modified phenalkamine underwater curing agent is one or both of NX-5653 and D0965.

2. The underwater construction and underwater curing anti-corrosion coating according to claim 1, characterized in that: The MS polymer is trimethoxysilyl terminated polyether with a viscosity of 5 to 80 Pa·s.

3. The underwater construction and underwater curing anti-corrosion coating according to claim 1, characterized in that: The component A also includes 210 to 250 parts of pigments and fillers, which, by mass, include 10 to 20 parts of fibers, 30 to 50 parts of coated titanium dioxide, 140 to 160 parts of glass flakes, and 10 to 30 parts of hydrotalcite-modified hollow microspheres.

4. The underwater construction and underwater curing anti-corrosion coating according to claim 3, characterized in that: The fiber is one or both of glass fiber and basalt fiber, and is obtained by hydrophobic modification; the modification method comprises the following steps: the fiber is soaked in 1-5wt% KH560 ethanol solution for 24-48 hours to fully seal the surface Si-OH bonds.

5. The underwater construction and underwater curing anti-corrosion coating according to claim 3, characterized in that: The coated titanium dioxide is zirconium-coated titanium dioxide. The preparation method of the zirconium-coated titanium dioxide includes: slowly dripping 100-120 g / L Zr(SO4)2 solution into TiO2 dispersion under continuous stirring at 55-60°C, adjusting the pH to 9-10, aging for 1-2 hours, and then washing, filtering, drying, grinding, and screening.

6. The underwater construction and underwater curing anti-corrosion coating according to claim 1, characterized in that: The modified phenalkamine underwater curing agent has a viscosity of 600 to 1200 mPa·s.

7. The underwater construction and underwater curing anti-corrosion coating according to any one of claims 1 to 6, characterized in that: The component A and the component B are uniformly mixed according to a proportion, and the coating is directly carried out with water or underwater by scraping, brushing or roller coating, with a coating film thickness of 800 to 1200 μm.

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