A salt spray resistant and anti-aging curing coating and its preparation method

Abstract

This invention relates to a salt spray resistant and anti-aging curing coating and its preparation method, belonging to the field of coating technology. The coating includes modified epoxy resin, ternary nanocomposite filler, composite light stabilizer, hydrophobic eutectic solvent, polysiloxane-modified aromatic amine curing agent, and bio-based polyurethane curing agent. The modified epoxy resin is prepared by reacting bisphenol F epoxy resin, KH-560 silane coupling agent, and tetrabutylammonium bromide, followed by the addition of bi-terminated epoxy silicone oil, 3,3'-dithiodipropionic acid, and p-toluenesulfonic acid, and then by adding pentaerythritol phosphate and antioxidant 1010. The polysiloxane-modified aromatic amine curing agent is prepared by reacting m-phenylenediamine as a matrix, KH-560 silane coupling agent, diphenylsilanediol, and dibutyltin dilaurate. The bio-based polyurethane curing agent is prepared by reacting castor oil-modified polyol, isophorone diisocyanate, dibutyltin dilaurate, dimethylolpropionic acid, and trimethylolpropane.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, specifically relating to a salt spray resistant and anti-aging curing coating and its preparation method. Background Technology

[0002] Curing coatings are functional coatings that rely on components such as resin, curing agent, and additives to rapidly cross-link and form a film through methods such as heating and ultraviolet light irradiation. With advantages such as fast film formation speed, excellent mechanical properties, and strong adhesion, they have become core surface protection materials in fields such as metal protection, engineering machinery, marine equipment, building steel structures, and automotive parts, and occupy an important position in the industrial coating market.

[0003] Currently, mainstream curing coatings are mainly divided into two categories: thermosetting and UV-curing. Thermosetting coatings use epoxy resin, polyurethane resin, and polyester resin as base materials, combined with amine and isocyanate curing agents, and form a three-dimensional network film through high-temperature baking. They possess good chemical resistance and mechanical strength and are widely used in heavy-duty anti-corrosion fields. UV-curing coatings use reactive diluents and oligomers as the core, and cure rapidly under UV light excitation. They are characterized by low VOC emissions and energy saving and environmental protection, and are mostly used for surface coating of light industrial products. With the development of global industry, the requirements for the protective performance of coatings in scenarios such as marine engineering, coastal infrastructure, and large outdoor equipment are constantly increasing. Although traditional curing coatings can meet the needs of normal environmental use, their protective shortcomings are becoming increasingly apparent in harsh environments such as high salt spray, strong ultraviolet radiation, and alternating humidity and heat.

[0004] Ordinary epoxy-based curing coatings have microscopic pores in their cross-linked network, allowing chloride ions and water molecules to easily penetrate the coating and reach the substrate interface, causing substrate corrosion and problems such as blistering, peeling, and corrosion at scratches. The neutral salt spray test duration is usually difficult to exceed 1000 hours. Polyurethane and polyester coatings have slightly improved salt spray resistance, but when exposed to salt spray environment for a long time, the ester bonds are easily hydrolyzed and broken, and the protective performance of the coating rapidly declines.

[0005] Bisphenol A type epoxy resin contains a large number of benzene rings, which are prone to photo-oxidation under ultraviolet radiation, leading to yellowing, chalking, and cracking of the coating, resulting in loss of protective effect; ordinary polyurethane coatings have limited weather resistance and are prone to aging and cracking after long-term outdoor exposure, with poor gloss and color retention, making them unsuitable for long-term outdoor use scenarios.

[0006] Most existing coatings focus on chemical corrosion resistance or weather resistance on one side only. Although fluorocarbon coatings have excellent weather resistance, they are expensive and have poor adhesion to the substrate, and their salt spray resistance does not meet the heavy-duty anti-corrosion standards. Some modified coatings improve a single property by adding additives, but this leads to a decrease in coating flexibility and curing efficiency, resulting in an imbalance in overall performance.

[0007] Coastal areas are characterized by multiple corrosive conditions, including high humidity, salt spray, and ultraviolet radiation. The diurnal temperature range and alternating wet and dry cycles can cause internal stress in coatings, leading to microcracks and accelerating the penetration of corrosive media. Existing coatings are ill-suited to this complex and harsh environment, resulting in a significantly shortened service life. Therefore, it is necessary to develop coatings that are resistant to humidity, heat, salt spray, and ultraviolet aging to improve protection in such challenging environments. Summary of the Invention

[0008] To improve the resistance to damp heat, salt spray, and UV aging of cured coatings, while balancing mechanical properties, this invention provides a salt spray-resistant and anti-aging cured coating and its preparation method. Through resin modification, functional filler modification, and curing system optimization, a dense and weather-resistant cross-linked coating film is constructed, simultaneously improving the coating's chloride ion barrier properties, UV resistance, and damp heat stability, meeting the long-term protection needs of marine engineering, infrastructure construction, and other fields. The specific technical solution is as follows:

[0009] A salt spray resistant and anti-aging curing coating is provided, wherein the coating is composed of a base material and a curing agent mixed at a mass ratio of 100:(75-80); the base material comprises the following raw materials in parts by mass: 60-65 parts modified epoxy resin, 4-6 parts ternary nanocomposite filler, 1.5-2.5 parts composite light stabilizer, 0.5-1.2 parts hydrophobic fumed silica, 0.5-1.0 parts KH-560 silane coupling agent, 0.2-0.4 parts BYK-052 defoamer, 0.2-0.5 parts BYK-333 leveling agent, 4-7 parts propylene glycol methyl ether acetate, 2-4 parts ethylene glycol butyl ether acetate, and 3-5 parts hydrophobic eutectic solvent; the curing agent comprises the following raw materials in parts by mass: 70-80 parts polysiloxane modified aromatic amine curing agent and 20-30 parts bio-based polyurethane curing agent.

[0010] In the above coating, the modified epoxy resin is prepared by using bisphenol F epoxy resin as a base and xylene as a solvent. First, KH-560 silane coupling agent and tetrabutylammonium bromide are added to react, then double-terminated epoxy silicone oil, 3,3'-dithiodipropionic acid and p-toluenesulfonic acid are added to react, then pentaerythritol phosphate and antioxidant 1010 are added to react, and xylene is removed.

[0011] In the preparation of the above modified epoxy resin, the mass ratio of bisphenol F epoxy resin, KH-560 silane coupling agent, tetrabutylammonium bromide, bi-terminated epoxy silicone oil, 3,3'-dithiodipropionic acid, p-toluenesulfonic acid, pentaerythritol phosphate, and antioxidant 1010 is (100-110):(18-22):(0.3-0.5):(8-10):(5-7):(0.2-0.3):(12-15):(0.1-0.2).

[0012] Further, the preparation method of the modified epoxy resin includes: by mass, preparing a premixed solution by mixing 100-110 parts of bisphenol F epoxy resin and 30-35 parts of xylene at 85-90°C; adding 18-22 parts of KH-560 silane coupling agent and 0.3-0.5 parts of tetrabutylammonium bromide, and refluxing and stirring at 105-110°C for 3.5-4 hours; cooling to 90-95°C, adding 8-10 parts of bi-terminated epoxy silicone oil, 5-7 parts of 3,3'-dithiodipropionic acid and 0.2-0.3 parts of p-toluenesulfonic acid, and stirring for 3-3.5 hours; cooling to 85-90°C, adding 12-15 parts of pentaerythritol phosphate dropwise, adding 0.1-0.2 parts of antioxidant 1010, and stirring for 4-4.5 hours; removing xylene by vacuum distillation to obtain the modified epoxy resin.

[0013] In the above coating, the ternary nanocomposite filler is nano-silica, nano-titanium dioxide and nano-zinc oxide with a mass ratio of (4-5):(3-5):(2-4) modified by KH-560 silane coupling agent surface modification.

[0014] Furthermore, the preparation method of the ternary nanocomposite filler includes: dissolving 7-8 parts of polyethylene glycol in 90-100 parts of anhydrous ethanol by mass, adding 4-5 parts of nano-silica, 3-5 parts of nano-titanium dioxide and 2-4 parts of nano-zinc oxide, dispersing, grinding, adding 2-3 parts of KH-560 silane coupling agent, grinding, drying, and pulverizing to a particle size D90 < 3 μm to obtain the ternary nanocomposite filler.

[0015] In the above coating, the hydrophobic eutectic solvent is prepared by menthol, n-decanoic acid, α-lipoic acid and sodium benzoate in a mass ratio of (15-17):(33-36):(10-13):(1.3-1.5).

[0016] In the above coating, the polysiloxane-modified aromatic amine curing agent is prepared by using m-phenylenediamine as a matrix, anhydrous ethanol as a solvent, adding KH-560 silane coupling agent, diphenylsilanediol, and dibutyltin dilaurate, and then adjusting the solid content to 75-80 wt%.

[0017] In the preparation of the above-mentioned polysiloxane-modified aromatic amine curing agent, the mass ratio of m-phenylenediamine, KH-560 silane coupling agent, diphenylsilanediol, and dibutyltin dilaurate is (50-55):(22-25):(10-13):(0.2-0.4).

[0018] Furthermore, the preparation method of the polysiloxane-modified aromatic amine curing agent includes: stirring 50-55 parts of m-phenylenediamine and 35-40 parts of anhydrous ethanol by mass, adding 22-25 parts of KH-560 silane coupling agent at 75-80°C and stirring for 2.5-3 hours; adding 10-13 parts of diphenylsilanediol and 0.2-0.4 parts of dibutyltin dilaurate, stirring for 3-3.5 hours at 85-90°C; removing ethanol by vacuum distillation, adjusting the solid content to 75-80 wt%, filtering, and obtaining the polysiloxane-modified aromatic amine curing agent.

[0019] In the above-mentioned coating, the preparation of the bio-based polyurethane curing agent is based on castor oil modified polyol and isophorone diisocyanate as raw materials, prepolymerized under the catalysis of dibutyltin dilaurate, and then chain extended with dimethylolpropionic acid and trimethylolpropane in N-methylpyrrolidone to remove N-methylpyrrolidone.

[0020] In the preparation of the above-mentioned bio-based polyurethane curing agent, the mass of castor oil modified polyol, isophorone diisocyanate, dibutyltin dilaurate, dimethylolpropionic acid, and trimethylolpropane is (50-55):(40-45):(0.1-0.2):(7-8):(2-3).

[0021] Furthermore, the preparation method of the bio-based polyurethane curing agent includes: mixing 50-55 parts by mass of castor oil-modified polyol with 40-45 parts by mass of isophorone diisocyanate; adding 0.1-0.2 parts by mass of dibutyltin dilaurate at 85-90°C and stirring for 2.5-3 hours; adding a mixture of 7-8 parts by mass of dimethylolpropionic acid, 2-3 parts by mass of trimethylolpropane and 25-30 parts by mass of N-methylpyrrolidone at 60-65°C and stirring for 2.5-3 hours; removing N-methylpyrrolidone by vacuum distillation to obtain the bio-based polyurethane curing agent.

[0022] In the above coating, the composite light stabilizer is prepared by compounding hindered amine light stabilizer and benzotriazole ultraviolet absorber in a mass ratio of (1-1.5):1.

[0023] The preparation method of the above-mentioned salt spray resistant and anti-aging curing coating includes the following steps: S1: According to the base material formula, the modified epoxy resin, propylene glycol methyl ether acetate and ethylene glycol butyl ether acetate are stirred and mixed evenly; ternary nanocomposite filler, composite light stabilizer and hydrophobic fumed silica are added and dispersed, and ground to a fineness of less than 25μm; KH-560 silane coupling agent, BYK-052 defoamer, BYK-333 leveling agent and hydrophobic eutectic solvent are added, stirred evenly, filtered, and the base material is obtained; S2: When using, stir evenly according to the mass ratio of base material to curing agent, adjust to the viscosity of Forte 4 cup 30-35s with propylene glycol methyl ether acetate, and obtain the coating after standing to defoam.

[0024] The present invention provides a salt spray resistant and anti-aging curing coating and its preparation method, which have the following beneficial effects: I. The salt spray resistant and anti-aging curing coating provided by this invention, through epoxy resin modification, ternary nanofiller interface modification, compound curing agent for strong toughness synergy, hydrophobic low eutectic solvent design and three-stage temperature-controlled curing molding, constructs a coating film with dense molecular structure, strong interface bonding and excellent hydrophobic chlorine barrier properties. It solves the problems of traditional curing coatings being prone to penetration and corrosion, yellowing and powdering, and brittle cracking and peeling in high salt spray, strong ultraviolet and humid heat alternating environments, and improves the comprehensive protection capability and service life of the coating in harsh scenarios such as marine engineering, coastal infrastructure, and large outdoor equipment.

[0025] II. The modified epoxy resin is based on bisphenol F epoxy resin, modified with siloxanes, bi-terminated epoxy silicone oil, 3,3'-dithiodipropionic acid, pentaerythritol phosphate, etc., and treated with antioxidant 1010 for heat stabilization. The siloxane groups enhance the interfacial bonding and hydrophobicity between the coating and the substrate / filler; the flexible silicone oil segments effectively reduce the coating modulus, improving flexibility and impact resistance; reversible disulfide bond dynamic breaking and recombination inhibits the initiation and propagation of microcracks; phosphorus groups further enhance the coating's heat resistance, acid and alkali resistance, and reduce water absorption. Segmented temperature-controlled reaction and reduced-pressure solvent removal ensure sufficient resin grafting, uniform structure, no solvent residue, and higher film stability.

[0026] III. In the ternary nanocomposite filler, nano-silica, rutile nano-titanium dioxide, and nano-zinc oxide are dispersed in polyethylene glycol and surface-modified with KH-560 silane coupling agent to achieve uniform dispersion of nanoparticles and chemical bonding with the resin. Nano-silica effectively fills the micropores of the coating, improving the film density; rutile titanium dioxide and nano-zinc oxide synergistically achieve ultraviolet absorption and scattering, reducing the rate of photo-oxidative degradation; the coupling agent coating eliminates the surface polarity of the nanoparticles, improves compatibility with the resin, and avoids the formation of interfacial gaps and corrosion channels. After fine grinding and low-temperature drying, the filler forms a continuous physical barrier layer within the coating, reducing the diffusion rate of the medium.

[0027] IV. The polysiloxane-modified aromatic amine curing agent is based on m-phenylenediamine, grafted with KH-560 silane coupling agent and modified with diphenylsilanediol, to obtain a highly active curing component under mild catalysis. After curing, it provides a rigid skeleton for the coating, improving hardness, heat resistance, and interfacial adhesion; the siloxane structure significantly enhances the coating's hydrophobicity, hydrolysis resistance, and weather resistance; temperature-controlled synthesis and solid content adjustment ensure good compatibility with the base material, and the crosslinking reaction is stable and controllable, guaranteeing uniform crosslinking and a dense structure in the coating.

[0028] V. Bio-based polyurethane curing agents are prepared from castor oil-modified polyols and isophorone diisocyanates through prepolymerization, branching chain extension, and desolventizing. They impart excellent flexibility, low-temperature flexibility, and wet adhesion to the coating; the alicyclic isocyanate structure exhibits superior resistance to yellowing, aging, and hydrolysis compared to conventional aromatic systems; the chain extension reaction increases molecular weight and crosslinking point density, enhancing the coating's cohesion and resistance to media. When combined with polysiloxane-modified aromatic amines, a synergistic balance between rigidity and flexibility is achieved, avoiding excessive brittleness or insufficient crosslinking issues associated with single curing agents, and reducing internal stress accumulation.

[0029] VI. The hydrophobic eutectic solvent is a compound of menthol, n-decanoic acid, α-lipoic acid, and sodium benzoate. When added in appropriate amounts, it exhibits excellent compatibility with the resin. During curing, it is uniformly distributed on the coating surface and within the micropores, filling microscopic defects and forming a dynamic hydrophobic layer. This reduces the surface energy and water absorption rate of the coating, significantly inhibiting the adsorption, spreading, and penetration of water molecules and chloride ions, further enhancing its resistance to salt spray and damp heat.

[0030] VII. Hindered amine light stabilizers are combined with benzotriazole UV absorbers to form a dual protection mechanism of UV absorption and free radical capture, effectively inhibiting coating photo-oxidation, yellowing, and chalking. Hydrophobic fumed silica improves the thixotropy and workability of the coating, while also providing reinforcement and hydrophobic effects; specialized defoamers and leveling agents eliminate bubbles and improve surface condition, avoiding defects such as pinholes, craters, and orange peel; the mixed slow-drying solvents evaporate smoothly, ensuring complete resin dissolution and a uniform and dense film.

[0031] 8. In the preparation method, the three-stage temperature-controlled curing process involves low-temperature pre-baking to slowly remove the solvent and avoid defects caused by sudden boiling of the solvent; medium-temperature curing allows the epoxy groups and curing agent to fully cross-link and form a complete network; high-temperature curing further releases internal stress and improves the cross-linking structure, ultimately resulting in a complete protective coating with strong bonding and high density.

[0032] In summary, the components of this coating exhibit highly efficient synergy: the modified epoxy resin provides a molecular basis for low permeability, hydrolysis resistance, and stress self-healing; the ternary nanofiller constructs a continuous physical barrier layer and enhances UV protection; the compounded curing agent achieves a balance between high strength and high toughness; the hydrophobic eutectic solvent enhances interfacial hydrophobicity and micropore sealing; the composite light stabilizer provides long-term inhibition of photoaging; and the matching additives and preparation process ensure defect-free film formation. This synergistic effect endows the coating with excellent salt spray resistance, damp heat resistance, UV aging resistance, mechanical strength, and resistance to various media, resulting in a well-balanced and comprehensive performance without any weaknesses, meeting the long-term protection requirements of highly corrosive environments. Detailed Implementation

[0033] Some embodiments are given below, but the present invention is not limited to these embodiments.

[0034] Example 1 A salt spray resistant and anti-aging curing coating is provided, comprising a base material and a curing agent mixed at a mass ratio of 100:78. The base material comprises the following raw materials in parts by mass: 63 parts modified epoxy resin, 5 parts ternary nanocomposite filler, 2 parts composite light stabilizer, 0.8 parts hydrophobic fumed silica, 0.7 parts KH-560 silane coupling agent, 0.3 parts BYK-052 defoamer, 0.35 parts BYK-333 leveling agent, 5.5 parts propylene glycol methyl ether acetate, 3 parts ethylene glycol butyl ether acetate, and 4 parts hydrophobic eutectic solvent. The curing agent comprises the following raw materials in parts by mass: 75 parts polysiloxane-modified aromatic amine curing agent and 25 parts bio-based polyurethane curing agent. The composite light stabilizer is composed of hindered amine light stabilizer (Tinuvin 292) and benzotriazole ultraviolet absorber (Tinuvin 1130) in a mass ratio of 1.2:1.

[0035] The preparation method of the modified epoxy resin includes: under nitrogen positive pressure protection and reflux condensation, 105 parts by mass of bisphenol F epoxy resin (epoxy value 0.52 eq / 100g) and 32 parts by mass of xylene are added to a reaction vessel and stirred at 85-90℃ and 250r / min to obtain a premix; 20 parts of KH-560 silane coupling agent and 0.4 parts of tetrabutylammonium bromide are added, and the mixture is heated to 105-110℃ and stirred under reflux for 3.5h; the mixture is then cooled to 90-95℃, and 9 parts of double-terminated epoxy silicone oil, 6.5 parts of 3,3'-dithiodipropionic acid, and 0. 25 parts of p-toluenesulfonic acid were stirred at 250 r / min for 3.5 h (until the acid value dropped to below 10% of the initial value); then the temperature was lowered to 85-90℃, 13 parts of pentaerythritol phosphate were added dropwise, and 0.15 parts of antioxidant 1010 were added, and the mixture was stirred at 250 r / min for 4 h; finally, xylene was removed by vacuum distillation at 90-95℃, and the product was discharged after cooling to obtain modified epoxy resin (epoxy value 0.41 eq / 100g).

[0036] The preparation method of the ternary nanocomposite filler includes: dissolving 7.5 parts by mass of polyethylene glycol (PEG-4000) in 95 parts by mass of anhydrous ethanol, stirring and dissolving under closed conditions at a temperature range of 50-55℃, then sequentially adding 4.5 parts by mass of nano-silica, 4 parts by mass of nano-titanium dioxide and 3 parts by mass of nano-zinc oxide, and dispersing at high speed of 2800 r / min for 40 min to obtain a nano slurry; transferring the slurry to a ball mill, using zirconia balls with a particle size range of 0.3-0.5 mm as the grinding medium, grinding at a ball-to-material ratio of 7:1 for 3.5 h (stopping for 12 min to cool every 40 min of grinding); adding 2.5 parts by mass of KH-560 silane coupling agent and continuing grinding for 1 h, vacuum drying at a temperature range of 65-70℃ to constant weight, and then pulverizing by airflow to a particle size D90 of 2.1 μm to obtain the ternary nanocomposite filler.

[0037] The preparation method of the hydrophobic eutectic solvent includes: stirring menthol, n-decanoic acid and α-lipoic acid in a temperature range of 75-80℃ to prepare a transparent liquid according to the mass ratio of menthol: n-decanoic acid: α-lipoic acid: sodium benzoate = 16:35:12:1.4, adding sodium benzoate and stirring for another 35 minutes to obtain the hydrophobic eutectic solvent.

[0038] The preparation method of polysiloxane-modified aromatic amine curing agent includes: under nitrogen positive pressure protection and reflux condensation, 53 parts by mass of m-phenylenediamine and 38 parts by mass of anhydrous ethanol are added to a reaction vessel, stirred and dissolved at 320 r / min, and then heated to 78℃; 23 parts of KH-560 silane coupling agent are added, and the reaction is stirred at 320 r / min in the temperature range of 75-80℃ for 2.5 h; 12 parts of diphenylsilanediol and 0.3 parts of dibutyltin dilaurate are added, and the reaction is continued in the temperature range of 85-90℃ for 3.5 h; finally, some ethanol is removed by vacuum distillation in the temperature range of 45-50℃, the solid content is adjusted to 78 wt%, and the product is filtered through a 150-mesh sieve to obtain the polysiloxane-modified aromatic amine curing agent.

[0039] The preparation method of the bio-based polyurethane curing agent includes: under nitrogen positive pressure protection, adding 53 parts by mass of castor oil modified polyol (hydroxyl value 265 mg KOH / g) and 43 parts by mass of isophorone diisocyanate to a reaction vessel, heating to 87°C, adding 0.15 parts by mass of dibutyltin dilaurate, and stirring at 85-90°C and 320 r / min for 2.5 h until the NCO content drops to 13%; cooling to 62°C, adding a mixture of 7.5 parts by mass of dimethylolpropionic acid, 2.5 parts by mass of trimethylolpropane and 28 parts by mass of N-methylpyrrolidone, and stirring at 60-65°C and 320 r / min for 2.5 h until the NCO content drops to 5.6%; after the reaction, removing N-methylpyrrolidone by vacuum distillation at 90-100°C to obtain a bio-based polyurethane curing agent with a solid content of 98 wt%.

[0040] The preparation method of the above-mentioned salt spray resistant and anti-aging curing coating includes: S1: According to the base material formula, add modified epoxy resin, propylene glycol methyl ether acetate and ethylene glycol butyl ether acetate to the dispersion tank and stir at 280 r / min for 6 min to mix evenly; add ternary nanocomposite filler, composite light stabilizer and hydrophobic fumed silica under stirring at 28℃, and disperse at 1100 r / min for 35 min; transfer the dispersed slurry to a sand mill and grind it to a fineness of less than 25 μm using zirconia beads with a particle size range of 0.8-1.0 mm as the grinding medium; transfer the ground slurry to a paint mixing tank, add KH-560 silane coupling agent, BYK-052 defoamer, BYK-333 leveling agent and hydrophobic eutectic solvent, stir at 380 r / min for 18 min until uniform, and filter through a 150 mesh sieve to obtain the base material; S2: When using, weigh the two components according to the mass ratio of base material to curing agent of 100:78, stir at 280r / min for 12min until uniform, adjust to the viscosity of Forte 4 cup 32s (25℃) with propylene glycol methyl ether acetate, let stand for 18min to defoam before construction.

[0041] Example 2 A salt spray resistant and anti-aging curing coating is provided, comprising a base material and a curing agent mixed at a mass ratio of 100:75. The base material includes the following raw materials in parts by mass: 60 parts modified epoxy resin, 4 parts ternary nanocomposite filler, 1.5 parts composite light stabilizer, 0.5 parts hydrophobic fumed silica, 0.5 parts KH-560 silane coupling agent, 0.2 parts BYK-052 defoamer, 0.2 parts BYK-333 leveling agent, 4 parts propylene glycol methyl ether acetate, 2 parts ethylene glycol butyl ether acetate, and 3 parts hydrophobic eutectic solvent. The curing agent includes the following raw materials in parts by mass: 70 parts polysiloxane-modified aromatic amine curing agent and 20 parts bio-based polyurethane curing agent. The composite light stabilizer is composed of hindered amine light stabilizer (Tinuvin 292) and benzotriazole ultraviolet absorber (Tinuvin 1130) in a mass ratio of 1:1.

[0042] The preparation method of the modified epoxy resin includes: under nitrogen positive pressure protection and reflux conditions, 110 parts by mass of bisphenol F epoxy resin (epoxy value 0.51 eq / 100g) and 35 parts by mass of xylene are added to a reaction vessel and stirred at 85-90℃ and 300 r / min to obtain a premix; 22 parts by mass of KH-560 silane coupling agent and 0.5 parts by mass of tetrabutylammonium bromide are added, and the mixture is heated to 105-110℃ and stirred for 4 hours; the temperature is lowered to 90-95℃, and 10 parts by mass of double-terminated epoxy silicone oil, 7 parts by mass of 3,3'-dithiodipropionic acid, and 0.3 parts by mass of xylene are added. Add p-toluenesulfonic acid and continue stirring at 300 r / min for 3.5 h (until the acid value drops to below 10% of the initial value); then cool to 85-90℃, add 15 parts pentaerythritol phosphate and 0.2 parts antioxidant 1010, and stir at 300 r / min for 4.5 h; finally, remove xylene by vacuum distillation at 90-95℃, cool and discharge to obtain modified epoxy resin (epoxy value 0.38 eq / 100g).

[0043] The preparation method of the ternary nanocomposite filler includes: dissolving 7 parts by mass of polyethylene glycol (PEG-4000) in 100 parts by mass of anhydrous ethanol, stirring and dissolving under closed conditions at a temperature of 50-55℃, then adding 4 parts by mass of nano-silica, 5 parts by mass of nano-titanium dioxide and 2 parts by mass of nano-zinc oxide, and dispersing at a high speed of 3000 r / min for 30 min to obtain a nano slurry; transferring the slurry to a ball mill, using zirconia balls with a particle size range of 0.3-0.5 mm as the grinding medium, grinding at a ball-to-material ratio of 6:1 for 4 h (stopping the mill for 15 min to cool every 30 min of grinding); adding 2 parts by mass of KH-560 silane coupling agent and continuing grinding for 1.5 h, vacuum drying at a temperature of 65-70℃ to constant weight, and then pulverizing by airflow to a particle size D90 of 2.6 μm to obtain the ternary nanocomposite filler.

[0044] The preparation method of the hydrophobic eutectic solvent includes: stirring menthol, n-decanoic acid and α-lipoic acid in a temperature range of 75-80℃ to prepare a transparent liquid according to the mass ratio of menthol: n-decanoic acid: α-lipoic acid: sodium benzoate = 17:33:13:1.3, adding sodium benzoate and stirring for another 40 min to obtain the hydrophobic eutectic solvent.

[0045] The preparation method of polysiloxane-modified aromatic amine curing agent includes: under nitrogen positive pressure protection and reflux conditions, 50 parts by mass of m-phenylenediamine and 40 parts by mass of anhydrous ethanol are added to a reaction vessel, stirred and dissolved at 300 r / min, and then heated to 80℃. 22 parts of KH-560 silane coupling agent are added, and the mixture is stirred and reacted at 75-80℃ and 350 r / min for 2.5 h. 13 parts of diphenylsilanediol and 0.2 parts of dibutyltin dilaurate are added, and the mixture is heated to 85-90℃ and stirred and reacted for another 3.5 h. Finally, some ethanol is removed by vacuum distillation at 45-50℃, the solid content is adjusted to 75 wt%, and the mixture is filtered through a 200-mesh sieve to obtain the polysiloxane-modified aromatic amine curing agent.

[0046] The preparation method of the bio-based polyurethane curing agent includes: under nitrogen positive pressure protection, adding 50 parts by weight of castor oil modified polyol (hydroxyl value 265 mg KOH / g) and 40 parts by weight of isophorone diisocyanate to a reaction vessel, heating to 85°C, adding 0.1 parts by weight of dibutyltin dilaurate, and stirring at 85-90°C and 300 r / min for 2.5 h until the NCO content drops to 15%; cooling to 60°C, adding a mixture of 7 parts by weight of dimethylolpropionic acid, 2 parts by weight of trimethylolpropane and 25 parts by weight of N-methylpyrrolidone, and stirring at 60-65°C and 300 r / min for 3 h until the NCO content drops to 5%; after the reaction, removing N-methylpyrrolidone by vacuum distillation at 90-100°C to obtain a bio-based polyurethane curing agent with a solid content of 98.5 wt%.

[0047] The preparation method of the above-mentioned salt spray resistant and anti-aging curing coating includes: S1: According to the base material formula, add modified epoxy resin, propylene glycol methyl ether acetate and ethylene glycol butyl ether acetate to the dispersion tank and stir at 250 r / min for 8 min to mix evenly; add ternary nanocomposite filler, composite light stabilizer and hydrophobic fumed silica under stirring at 25℃, and disperse at 1200 r / min for 30 min; transfer the dispersed slurry to a sand mill and grind it to a fineness of less than 25 μm using zirconia beads with a particle size range of 0.8-1.0 mm as the grinding medium; transfer the ground slurry to a paint mixing tank, add KH-560 silane coupling agent, BYK-052 defoamer, BYK-333 leveling agent and hydrophobic eutectic solvent, stir at 400 r / min for 15 min until uniform, and filter through a 200 mesh sieve to obtain the base material; S2: When using, weigh the two components according to the mass ratio of base material to curing agent of 100:75, stir at 250r / min for 15min until uniform, adjust to the viscosity of Forte 4 cup 30s (25℃) with propylene glycol methyl ether acetate, let stand for 20min to defoam before construction.

[0048] Example 3 A salt spray resistant and anti-aging curing coating is provided, comprising a base material and a curing agent mixed at a mass ratio of 100:80. The base material comprises the following raw materials in parts by mass: 65 parts modified epoxy resin, 6 parts ternary nanocomposite filler, 2.5 parts composite light stabilizer, 1.2 parts hydrophobic fumed silica, 1.0 part KH-560 silane coupling agent, 0.4 parts BYK-052 defoamer, 0.5 parts BYK-333 leveling agent, 7 parts propylene glycol methyl ether acetate, 4 parts ethylene glycol butyl ether acetate, and 5 parts hydrophobic eutectic solvent. The curing agent comprises the following raw materials in parts by mass: 80 parts polysiloxane-modified aromatic amine curing agent and 30 parts bio-based polyurethane curing agent. The composite light stabilizer is composed of hindered amine light stabilizer (Tinuvin 292) and benzotriazole ultraviolet absorber (Tinuvin 1130) in a mass ratio of 1.5:1.

[0049] The preparation method of the modified epoxy resin includes: under nitrogen positive pressure protection and reflux condensation conditions, 100 parts by mass of bisphenol F epoxy resin (epoxy value 0.54) are added. Add 100g of xylene (eq / 100g) to a reactor and stir at 200 rpm to dissolve and obtain a premix. Add 18 parts of KH-560 silane coupling agent and 0.3 parts of tetrabutylammonium bromide, heat to 105-110℃ and reflux for 3.5 h. Cool to 90-95℃, add 8 parts of bi-terminated epoxy silicone oil, 5 parts of 3,3'-dithiodipropionic acid and 0.2 parts of p-toluenesulfonic acid, and continue stirring at 200 rpm for 3 h (acid value drops to below 10% of the initial value). Cool to 85-90℃ again, add 12 parts of pentaerythritol phosphate and 0.1 parts of antioxidant 1010, and stir at 200 rpm for 4 h. Finally, remove xylene by vacuum distillation at 90-95℃, cool and discharge to obtain modified epoxy resin (epoxy value 0.42). (eq / 100g).

[0050] The preparation method of the ternary nanocomposite filler includes: dissolving 8 parts by mass of polyethylene glycol (PEG-4000) in 90 parts by mass of anhydrous ethanol, stirring and dissolving under closed conditions at a temperature range of 50-55℃, then sequentially adding 5 parts by mass of nano-silica, 3 parts by mass of nano-titanium dioxide and 4 parts by mass of nano-zinc oxide, and dispersing at high speed of 2500 r / min for 50 min to obtain a nano slurry; transferring the slurry to a ball mill, using zirconia balls with a particle size range of 0.3-0.5 mm as the grinding medium and a ball-to-material ratio of 8:1, grinding for 3 h, stopping for 10 min every 50 min of grinding to cool; adding 3 parts by mass of KH-560 silane coupling agent and continuing grinding for 1 h, vacuum drying at a temperature range of 65-70℃ to constant weight, and then pulverizing by airflow to a particle size D90 of 1.8 μm to obtain the ternary nanocomposite filler.

[0051] The preparation method of the hydrophobic eutectic solvent includes: menthol, n-decanoic acid, and α-lipoic acid are ultrasonically prepared into a transparent liquid in the temperature range of 75-80℃ according to the mass ratio of menthol: n-decanoic acid: α-lipoic acid: sodium benzoate = 15:36:10:1.5, sodium benzoate is added, and ultrasonication is continued for 30 min to obtain the hydrophobic eutectic solvent.

[0052] The preparation method of polysiloxane-modified aromatic amine curing agent includes: under nitrogen positive pressure protection and reflux condensation, 55 parts by mass of m-phenylenediamine and 35 parts by mass of anhydrous ethanol are added to a reaction vessel, stirred and dissolved at 350 r / min, and then heated to 75℃; 25 parts of KH-560 silane coupling agent are added, and the mixture is stirred and reacted at 75-80℃ and 300 r / min for 3 h; 10 parts of diphenylsilanediol and 0.4 parts of dibutyltin dilaurate are added, and the mixture is heated to 85-90℃ and stirred and reacted for another 3 h; finally, some ethanol is removed by vacuum distillation at 45-50℃, the solid content is adjusted to 80 wt%, and the mixture is filtered through a 150-mesh sieve to obtain the polysiloxane-modified aromatic amine curing agent.

[0053] The preparation method of the bio-based polyurethane curing agent includes: under nitrogen positive pressure protection, 55 parts by mass of castor oil modified polyol (hydroxyl value 265 mg KOH / g) and 45 parts by mass of isophorone diisocyanate are added to a reaction vessel, heated to 90°C, and 0.2 parts by mass of dibutyltin dilaurate are added. The mixture is stirred at 85-90°C and 350 r / min for 3 h until the NCO content drops to 10%. The temperature is lowered to 65°C, and a mixture of 8 parts by mass of dimethylolpropionic acid, 3 parts by mass of trimethylolpropane and 30 parts by mass of N-methylpyrrolidone is added. The mixture is stirred at 60-65°C and 350 r / min for 2.5 h until the NCO content drops to 6%. After the reaction, N-methylpyrrolidone is removed by vacuum distillation at 90-100°C to obtain a bio-based polyurethane curing agent with a solid content of 99 wt%.

[0054] The preparation method of the above-mentioned salt spray resistant and anti-aging curing coating includes: S1: According to the base material formula, add modified epoxy resin, propylene glycol methyl ether acetate and ethylene glycol butyl ether acetate to the dispersion tank and stir at 300 r / min for 5 min to mix evenly; add ternary nanocomposite filler, composite light stabilizer and hydrophobic fumed silica under stirring at 30℃, and disperse at 1000 r / min for 40 min; transfer the dispersed slurry to a sand mill and grind it to a fineness of less than 25 μm using zirconia beads with a particle size range of 0.8-1.0 mm as the grinding medium; transfer the ground slurry to a paint mixing tank, add KH-560 silane coupling agent, BYK-052 defoamer, BYK-333 leveling agent and hydrophobic eutectic solvent, stir at 350 r / min for 20 min until uniform, and filter through a 150 mesh sieve to obtain the base material; S2: When using, weigh the two components according to the mass ratio of base material to curing agent of 100:80, stir at 300r / min for 10min until uniform, adjust to the viscosity of Fort-4 cup 35s (25℃) with propylene glycol methyl ether acetate, let stand for 15min to defoam before construction.

[0055] Recommended curing methods for the coatings in the above embodiments: pre-baking at 60-80℃ for 20-30 minutes, curing at 120-130℃ for 30-45 minutes, and maturing at 90-100℃ for 20-30 minutes.

[0056] The raw material specifications and sources involved in the above embodiments are as follows: The hindered amine light stabilizer is BASF Tinuvin 292. The benzotriazole UV absorber is BASF Tinuvin 1130. The hydrophobic fumed silica is Evonik AEROSIL R 974, with a specific surface area of ​​170±20 m². 2 / g. KH-560 silane coupling agent is from Dongguan Shanyi Plastics Co., Ltd. Propylene glycol methyl ether acetate is from Wuhan Jixin Yibang Biotechnology Co., Ltd., purity 99.5%. Ethylene glycol butyl ether acetate is from Shandong Xinheng Chemical Co., Ltd., purity 99.5%. Bisphenol F epoxy resin is bisphenol F diglycidyl ether, from Hubei Wande Chemical Co., Ltd., liquid, purity 99%. Xylene is from Jinan Jinhong Chemical Co., Ltd. Bisphenol F epoxy-terminated silicone oil is from Shandong Baiqian Chemical Co., Ltd., number average molecular weight 100,000. Pentaerythritol phosphate is from Hubei Fangde New Materials Co., Ltd. Antioxidant 1010 is from Wuhan Lingjia Yi Chemical Co., Ltd. Polyethylene glycol PEG-4000 is from Linyi Guoli Chemical Co., Ltd. Nano-silica (particle size range 5-40nm) is from Hangzhou Jiupeng New Materials Co., Ltd., specific surface area 200±25m². 2 / g. The nano-titanium dioxide is rutile nano-titanium dioxide with an average particle size of 20nm, sourced from Guangzhou Yanrui Chemical Co., Ltd. The nano-zinc oxide has an average particle size of 30nm and is sourced from Hangzhou Jiupeng New Materials Co., Ltd. The dibutyltin dilaurate is sourced from Jinan Century Tongda Chemical Co., Ltd., with a purity of 99.5%. The castor oil-modified polyol (hydroxyl value 265mgKOH / g) is selected from Vantrus castor oil-modified polyol D265, distributed by Guangzhou Haoyi New Materials Technology Co., Ltd. The purity of other unlisted raw materials is above 98%.

[0057] In the above embodiments: The modified epoxy resin is a complex polymer system containing epoxy-modified products of different molecular weights and grafting degrees, a small amount of incompletely reacted raw materials, byproducts, and molecules with different end-group structures. It is a polymer mixture and cannot be represented by a single chemical formula. The polysiloxane-modified aromatic amine curing agent is a multi-component amine curing agent mixture containing aromatic amine derivatives with different degrees of substitution and different amounts of siloxane grafting, solvent residues, and oligomerization byproducts. It is a mixture and cannot be represented by a single chemical formula. The bio-based polyurethane curing agent is a polyurethane prepolymer system with varying degrees of branching and the number of NCO end groups, containing a small amount of unreacted monomers and oligomers. It is a polymer mixture and cannot be represented by a single chemical formula.

[0058] Comparative Example 1 The difference from Example 1 is that the coating is made by mixing the base material and the curing agent at a mass ratio of 100:40.

[0059] Comparative Example 2 The difference from Example 1 is that the curing agent includes 50 parts of polysiloxane-modified aromatic amine curing agent and 50 parts of bio-based polyurethane curing agent.

[0060] Comparative Example 3 The difference from Example 1 is that the curing agent used is polysiloxane-modified aromatic amine curing agent.

[0061] Comparative Example 4 The difference from Example 1 is that the curing agent used is entirely a bio-based polyurethane curing agent.

[0062] Comparative Example 5 The difference from Example 1 is that the modified epoxy resin is directly replaced by bisphenol F epoxy resin.

[0063] Comparative Example 6 The difference from Example 1 is that in the preparation of the modified epoxy resin, the step of "cooling down to the temperature range of 90-95°C, adding 9 parts of double-terminated epoxy silicone oil, 6.5 parts of 3,3'-dithiodipropionic acid and 0.25 parts of p-toluenesulfonic acid, and continuing to stir the reaction at 250 r / min for 3.5 h" is omitted.

[0064] Comparative Example 7 The difference from Example 1 is that the ternary nanocomposite filler is directly replaced by a mixture of nano-silica, nano-titanium dioxide and nano-zinc oxide in a mass ratio of 4.5:4:3.

[0065] Comparative Example 8 The difference from Example 1 is that in the preparation of the bio-based polyurethane curing agent, the step of "cooling down to 62°C, adding a mixture of 7.5 parts of dimethylolpropionic acid, 2.5 parts of trimethylolpropane and 28 parts of N-methylpyrrolidone, stirring and reacting at 60-65°C and 320 r / min for 2.5 h until the NCO content drops to 5.6%; after the reaction is completed, removing N-methylpyrrolidone by vacuum distillation at 90-100°C" is omitted.

[0066] Comparative Example 9 The difference from Example 1 is that no hydrophobic eutectic solvent is added.

[0067] The following coating film curing temperature parameters are uniformly set as follows: pre-baking at 80℃ for 20 minutes, curing at 120℃ for 30 minutes, and aging at 100℃ for 30 minutes.

[0068] I. Adhesion test by pull-off method: Sample specifications: Q235 steel plate, 150mm×70mm×1.0mm, conforming to GB / T 9271-2008; 3 parallel samples per group, 3 measurements taken at each sample and average value taken; dry film thickness 80±5μm; sample curing for 7 days.

[0069] Test method: According to GB / T 5210-2006 "Paints and Varnishes - Pull-off Adhesion Test". A 20mm diameter test column was used, with a loading speed of 10mm / min.

[0070] II. Cross-cut adhesion test: Sample specifications: Q235 steel plate, 120mm×50mm×1.0mm, conforming to GB / T 9271-2008; 3 parallel samples per group; dry film thickness 80±5μm; sample curing for 7 days.

[0071] Test method: According to GB / T 9286-2021 "Paints and Varnishes - Cross-cut Test". A cross-cut tester with a 2mm tooth spacing is used.

[0072] III. Pencil Hardness Testing: Sample specifications: Q235 steel plate, 120mm×50mm×1.0mm, conforming to GB / T 9271-2008; 3 parallel samples per group; dry film thickness 80±5μm; sample curing for 7 days.

[0073] Test method: According to GB / T 6739-2022 "Determination of Hardness of Paints and Varnishes by Pencil Method". Load: 750g, angle: 45°.

[0074] IV. Coating film flexibility test: Sample specifications: tinplate, 120mm×50mm×0.28mm, conforming to GB / T 9271-2008; 3 parallel samples per group; dry film thickness 80±5μm.

[0075] Test method: According to GB / T 1731-2020 "Test method for flexibility of paint film and putty film", record the minimum diameter without cracks.

[0076] V. Impact resistance test: Sample specifications: tinplate, 120mm×50mm×0.28mm, conforming to GB / T 9271-2008; 3 parallel samples per group; dry film thickness 80±5μm.

[0077] Test method: According to GB / T 1732-2020 "Test Method for Impact Resistance of Coating Film". The weight of the hammer is 1kg, and the diameter of the steel ball in the impactor is 8mm, increasing in increments of 5cm. The minimum impact height without cracks is recorded.

[0078] VI. Neutral Salt Spray Performance Testing: Sample specifications: Q235 steel plate, 150mm×70mm×1.0mm, conforming to GB / T 9271-2008; 3 parallel samples per group; dry film thickness 80±5μm; the sample is pretreated by sandblasting Sa2.5 grade, with a surface roughness of 50-60μm, and cured for 7 days under standard environment; the back and edges of the sample are sealed and protected with edge sealing wax, and a cross scratch is made in the middle of the coating, with a depth reaching the substrate, a length of 50mm, and an included angle of 60°.

[0079] Test method: According to GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test". A salt spray test chamber was used, with the sample placed at an angle of 20±5° to the vertical. Test parameters: NaCl solution concentration 50 g / L, collected spray solution pH 6.5~7.2 (35℃), test temperature 35℃, continuous spraying, and sedimentation rate 1.5 mL / (80 cm²). 2 •h). The test cycle is 2000h. The comprehensive rating of blistering, chalking, cracking, peeling and corrosion is carried out according to GB / T 1766-2008 "Rating Method for Aging of Paint and Varnish Coatings"; the width of corrosion spread on one side at the cross-section is measured.

[0080] VII. Moisture and Heat Resistance Test: Sample specifications: Q235 steel plate, 150mm×70mm×1.0mm, conforming to GB / T 9271-2008; 3 parallel samples per group; dry film thickness 80±5μm; after curing the sample for 7 days, the back and edges are sealed for protection, and the initial colorimetric value is tested.

[0081] Test method: According to GB / T 1740-2007 "Determination of Damp Heat Resistance of Paint Films". A damp heat test chamber was used, with samples placed vertically at intervals ≥20mm. Test parameters: temperature 47±2℃, relative humidity 95±2%RH. Continuous test for 1500h. A comprehensive rating of discoloration, blistering, wrinkling, cracking, peeling, and corrosion was conducted according to GB / T1766-2008 "Rating Method for Aging of Paint and Varnish Coatings".

[0082] VIII. Xenon Arc Lamp Artificial Climate Aging Performance Testing: Sample specifications: Q235 steel plate, 150mm×70mm×1.0mm, conforming to GB / T 9271-2008; 3 parallel samples per group; dry film thickness 80±5μm; initial colorimetric value tested after 7 days of curing.

[0083] Test method: According to GB / T 1865-2009 "Artificial weathering and artificial radiation exposure of paints and varnishes - filtered xenon arc radiation". A xenon arc lamp aging test chamber was used, with the following test parameters: irradiance at 340nm 0.51W / (m²). 2 The test conditions were as follows: (nm), black standard temperature 65℃, relative humidity 50%RH, cycle period 102min light exposure (no spray) + 18min light exposure + spray, continuous test period 2000h. Discoloration, blistering, chalking, cracking, peeling, and corrosion were comprehensively rated according to GB / T 1766-2008 "Rating Method for Aging of Paint and Varnish Coatings".

[0084] IX. Fluorescence UV Aging Performance Testing: Sample specifications: Q235 steel plate, 150mm×70mm×1.0mm, conforming to GB / T 9271-2008; 3 parallel samples per group; dry film thickness 80±5μm; initial colorimetric value tested after 7 days of curing.

[0085] Test method: According to GB / T 16422.3-2022 "Laboratory Light Source Exposure Test Methods for Plastics - Part 3: Fluorescent Ultraviolet Lamps". A UVA-340 fluorescent ultraviolet lamp was used. Test parameters: irradiance 0.55 W / (m²). 2 The test was conducted at 60℃ for 8 hours and then at 50℃ for 4 hours, for a total of 300 hours. The overall rating for discoloration, chalking, and cracking was performed according to GB / T 1766-2008, "Rating Method for Aging of Paint and Varnish Coatings".

[0086] 10. Water resistance test: Sample specifications: Q235 steel plate, 150mm×70mm×1.0mm, conforming to GB / T 9271-2008; 3 parallel samples per group; dry film thickness 80±5μm; sample curing for 7 days.

[0087] Test method: According to GB / T 1733-1993 "Determination of Water Resistance of Paint Films" (Method A). Test parameters: Water temperature 23℃, immersion time 720h. The test surface of the sample is immersed in distilled water with the test surface facing upwards. After 720h, observe the condition of the paint film. No obvious loss of gloss, no softening, and no bubbling are considered passing.

[0088] XI. Chemical resistance testing: Sample specifications: Q235 steel plate, 150mm×70mm×1.0mm, conforming to GB / T 9271-2008; 3 parallel samples per group; dry film thickness 80±5μm; sample curing for 7 days.

[0089] Test method: According to GB / T 9274-1988 "Determination of resistance to liquid media for paints and varnishes" (Method A). The test media are 5wt% NaCl solution, 5wt% H2SO4 solution, 5wt% NaOH solution, No. 10 machine oil, and No. 93 gasoline. The temperature is 23±2℃, and the immersion time is 168h. The paint film condition is observed. No obvious loss of gloss, no softening, and no bubbling are considered passing.

[0090] Table 1. Test Results (Average Value / Same Grade / Same Phenomenon) Table 1 (continued) Test Results The coatings in Examples 1 to 3 exhibit excellent salt spray resistance, aging resistance, and mechanical properties. The modified epoxy resin, based on bisphenol F epoxy resin, undergoes multi-component modification to form a molecular network with low free volume and high cross-linking density. This enhances hydrophobicity and hydrolysis resistance while alleviating internal stress, reducing the diffusion coefficient of corrosive media at the molecular level. The ternary nanocomposite filler consists of silica, rutile titanium dioxide, and zinc oxide dispersed in polyethylene glycol and coated with KH-560 silane coupling agent. This achieves nanoscale uniform dispersion and chemical bonding with the resin, filling the micropores of the coating while forming a continuous physical barrier layer. The polysiloxane-modified aromatic amine curing agent provides high interfacial adhesion, high heat resistance, and a hydrophobic rigid framework, while the bio-based polyurethane curing agent introduces flexible segments and wet stability. This precise blend compensates for the performance limitations of a single curing agent, achieving a synergistic effect of high strength and high toughness in the cross-linked network, reducing internal stress accumulation. The menthol-decanoic acid-α-lipoic acid-based hydrophobic eutectic solvent exhibits excellent compatibility with the resin. During curing, it is uniformly distributed at the coating interface and in the micropores, filling defects while forming a dynamic hydrophobic layer. This reduces the coating's water absorption and media spreadability, and inhibits the penetration of water and chloride ions. The three-stage temperature-controlled process of pre-baking, curing, and ripening allows the solvent to slowly escape and the cross-linking reaction to proceed gradually, fully releasing the internal stress of the coating, avoiding molding defects such as pinholes and microcracks, and forming a smooth, dense, and complete protective coating, thus enhancing long-term protective performance.

[0091] In Comparative Example 1, the curing agent was severely insufficient, with the amount used far below the stoichiometric ratio. This resulted in insufficient cross-linking of the epoxy groups, leading to extremely low cross-linking density, a loose structure, and a significant increase in porosity. The loose structure caused a comprehensive decline in mechanical properties, while also allowing for easy penetration of corrosive media such as water and chloride ions, thus deteriorating the protective function.

[0092] In Comparative Example 2, the ratio of polysiloxane amine to polyurethane was unbalanced, and the proportion of bio-based polyurethane curing agent was too high. Excessive flexible chains led to a decrease in the crosslinking density of the coating, insufficient rigidity, and reduced hardness and salt spray resistance. The proportion of polysiloxane-modified aromatic amine was insufficient, so its advantages of hydrophobic barrier, high weather resistance, and strong adhesion could not be reflected.

[0093] In Comparative Example 3, only polysiloxane-modified aromatic amine curing agent was used, lacking the flexible chain segment of bio-based polyurethane. The cross-linking network of the coating was too rigid, and the internal stress accumulated significantly, resulting in a decrease in flexibility and impact resistance. The lack of synergistic curing function of bio-based polyurethane curing agent also led to a deterioration in the properties of the paint film, affecting its durability and stability.

[0094] In Comparative Example 4, only bio-based polyurethane curing agent was used. Excessive bio-based polyurethane curing agent is prone to uncontrollable hydrolysis and chain scission in humid, hot, salt spray and alkaline environments, leading to rapid destruction of the coating structure. At the same time, the use of only bio-based polyurethane curing agent resulted in low crosslinking density, poor coating compactness, poor durability, and only good retention of flexibility.

[0095] In Comparative Example 5, unmodified bisphenol F epoxy resin was used, without modification of siloxane, disulfide bond, or phosphorus groups. The epoxy molecular network is highly polar and hydrophilic, resulting in a high diffusion coefficient in corrosive media. At the same time, the benzene ring is prone to photo-oxidation, which cannot relieve internal stress, and the coating has relatively poor durability in terms of corrosion resistance and aging resistance.

[0096] In Comparative Example 6, the epoxy modification omitted silicone oil and dithiodipropionic acid, resulting in the absence of flexible segments of the double-ended epoxy silicone oil. This increased the brittleness of the coating and reduced its flexibility and impact resistance. Furthermore, the absence of reversible disulfide bonds constructed by 3,3'-dithiodipropionic acid made it impossible to alleviate the internal stress generated by humid heat cycling, making the coating prone to damage under humid heat, aging, and impact conditions.

[0097] In Comparative Example 7, the ternary nanofiller was not modified, and the nanoparticles were not coated with KH-560 silane coupling agent, resulting in agglomeration problems, weak interfacial bonding with the resin, and interfacial defects in the coating, making it impossible to construct a continuous physical barrier layer.

[0098] In Comparative Example 8, the unbranched chain extension modification of bio-based polyurethane omitted the chain extension reaction of dimethylolpropionic acid and trimethylolpropane. Polyurethane is a linear molecule with a low molecular weight. After crosslinking with epoxy resin, it forms a relaxed network structure with poor interfacial bonding and uneven crosslinking density, resulting in relatively poor performance.

[0099] Compared to Example 9, which lacks a hydrophobic eutectic solvent, the dynamic hydrophobic layer and micropore filling effect increase the surface energy and enhance hydrophilicity of the coating. The adsorption and permeation resistance of water and chloride ions are significantly reduced, and the water absorption rate increases. Although the coating itself still has some hydrophobicity due to siloxane modification, the medium permeation rate accelerates under long-term humid heat and salt spray environments.

Claims

1. A salt spray resistant and anti-aging curing coating, characterized in that, The coating is composed of a base material and a curing agent mixed at a mass ratio of 100:(75-80); the base material comprises the following raw materials in parts by mass: 60-65 parts modified epoxy resin, 4-6 parts ternary nanocomposite filler, 1.5-2.5 parts composite light stabilizer, 0.5-1.2 parts hydrophobic fumed silica, 0.5-1.0 parts KH-560 silane coupling agent, 0.2-0.4 parts BYK-052 defoamer, 0.2-0.5 parts BYK-333 leveling agent, 4-7 parts propylene glycol methyl ether acetate, 2-4 parts ethylene glycol butyl ether acetate, and 3-5 parts hydrophobic eutectic solvent; the curing agent comprises the following raw materials in parts by mass: 70-80 parts polysiloxane modified aromatic amine curing agent and 20-30 parts bio-based polyurethane curing agent.

2. The salt spray resistant and anti-aging curing coating according to claim 1, characterized in that, The modified epoxy resin is prepared using bisphenol F epoxy resin as a base and xylene as a solvent. First, KH-560 silane coupling agent and tetrabutylammonium bromide are added and reacted. Then, bi-terminated epoxy silicone oil, 3,3'-dithiodipropionic acid, and p-toluenesulfonic acid are added and reacted. Next, pentaerythritol phosphate and antioxidant 1010 are added and reacted to remove xylene. The ternary nanocomposite filler is nano-silica, nano-titanium dioxide, and nano-zinc oxide with a surface-modified KH-560 silane coupling agent in a mass ratio of (4-5):(3-5):(2-4). The hydrophobic eutectic solvent is composed of menthol, n-decanoic acid, α-lipoic acid, and sodium benzoate in a mass ratio of (15-17):(33-36):(10-13). (1.3-1.5) Preparation; The polysiloxane-modified aromatic amine curing agent is prepared by using m-phenylenediamine as a matrix, anhydrous ethanol as a solvent, adding KH-560 silane coupling agent, diphenylsilanediol, and dibutyltin dilaurate, and then adjusting the solid content to 75-80 wt%; The bio-based polyurethane curing agent is prepared by using castor oil-modified polyol and isophorone diisocyanate as raw materials, prepolymerizing under the catalysis of dibutyltin dilaurate, and then reacting with dimethylolpropionic acid and trimethylolpropane in N-methylpyrrolidone to remove N-methylpyrrolidone; The composite light stabilizer is prepared by compounding hindered amine light stabilizer and benzotriazole ultraviolet absorber in a mass ratio of (1-1.5):

1.

3. The salt spray resistant and anti-aging curing coating according to claim 2, characterized in that, In the preparation of the modified epoxy resin, the mass ratio of the bisphenol F epoxy resin, KH-560 silane coupling agent, tetrabutylammonium bromide, bi-terminated epoxy silicone oil, 3,3'-dithiodipropionic acid, p-toluenesulfonic acid, pentaerythritol phosphate, and antioxidant 1010 is (100-110):(18-22):(0.3-0.5):(8-10):(5-7):(0.2-0.3):(12-15):(0.1-0.2).

4. A salt spray resistant and anti-aging curing coating according to claim 2 or 3, characterized in that, The method for preparing the modified epoxy resin includes: preparing a premixed solution by mass of 100-110 parts of bisphenol F epoxy resin and 30-35 parts of xylene at 85-90°C; adding 18-22 parts of KH-560 silane coupling agent and 0.3-0.5 parts of tetrabutylammonium bromide, and refluxing and stirring at 105-110°C for 3.5-4 hours; cooling to 90-95°C, adding 8-10 parts of bi-terminated epoxy silicone oil, 5-7 parts of 3,3'-dithiodipropionic acid and 0.2-0.3 parts of p-toluenesulfonic acid, and stirring for 3-3.5 hours; cooling to 85-90°C, adding 12-15 parts of pentaerythritol phosphate dropwise, adding 0.1-0.2 parts of antioxidant 1010, and stirring for 4-4.5 hours; and removing xylene by vacuum distillation to obtain the modified epoxy resin.

5. The salt spray resistant and anti-aging curing coating according to claim 2, characterized in that, The preparation method of the ternary nanocomposite filler includes: dissolving 7-8 parts of polyethylene glycol in 90-100 parts of anhydrous ethanol by mass, adding 4-5 parts of nano-silica, 3-5 parts of nano-titanium dioxide and 2-4 parts of nano-zinc oxide, dispersing, grinding, adding 2-3 parts of KH-560 silane coupling agent, grinding, drying, and pulverizing to a particle size D90 < 3 μm to obtain the ternary nanocomposite filler.

6. The salt spray resistant and anti-aging curing coating according to claim 2, characterized in that, In the preparation of polysiloxane-modified aromatic amine curing agent, the mass ratio of m-phenylenediamine, KH-560 silane coupling agent, diphenylsilanediol, and dibutyltin dilaurate is (50-55):(22-25):(10-13):(0.2-0.4).

7. A salt spray resistant and anti-aging curing coating according to claim 2 or 6, characterized in that, The preparation method of the polysiloxane-modified aromatic amine curing agent includes: stirring 50-55 parts of m-phenylenediamine and 35-40 parts of anhydrous ethanol by mass, adding 22-25 parts of KH-560 silane coupling agent at 75-80°C and stirring for 2.5-3 hours; adding 10-13 parts of diphenylsilanediol and 0.2-0.4 parts of dibutyltin dilaurate, stirring for 3-3.5 hours at 85-90°C; removing ethanol by vacuum distillation, adjusting the solid content to 75-80 wt%, filtering, and obtaining the polysiloxane-modified aromatic amine curing agent.

8. The salt spray resistant and anti-aging curing coating according to claim 2, characterized in that, In the preparation of the bio-based polyurethane curing agent, the mass of the castor oil modified polyol, isophorone diisocyanate, dibutyltin dilaurate, dimethylolpropionic acid, and trimethylolpropane is (50-55):(40-45):(0.1-0.2):(7-8):(2-3).

9. A salt spray resistant and anti-aging curing coating according to claim 2 or 8, characterized in that, The preparation method of the bio-based polyurethane curing agent includes: mixing 50-55 parts by mass of castor oil-modified polyol with 40-45 parts by mass of isophorone diisocyanate; adding 0.1-0.2 parts by mass of dibutyltin dilaurate at 85-90°C and stirring for 2.5-3 hours; adding a mixture of 7-8 parts by mass of dimethylolpropionic acid, 2-3 parts by mass of trimethylolpropane and 25-30 parts by mass of N-methylpyrrolidone at 60-65°C and stirring for 2.5-3 hours; removing N-methylpyrrolidone by vacuum distillation to obtain the bio-based polyurethane curing agent.

10. The method for preparing a salt spray resistant and anti-aging curing coating according to claim 1, characterized in that, Includes the following steps: S1: According to the base material formula, the modified epoxy resin, propylene glycol methyl ether acetate and ethylene glycol butyl ether acetate are stirred and mixed evenly; ternary nanocomposite filler, composite light stabilizer and hydrophobic fumed silica are added and dispersed, and ground to a fineness of less than 25μm; KH-560 silane coupling agent, BYK-052 defoamer, BYK-333 leveling agent and hydrophobic eutectic solvent are added, stirred evenly, filtered, and the base material is obtained; S2: When using, stir evenly according to the mass ratio of base material to curing agent, adjust to the viscosity of Forte 4 cup 30-35s with propylene glycol methyl ether acetate, and obtain the coating after standing to defoam.

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