Anticorrosive paint for steel structure and preparation method thereof

Abstract

This invention discloses an anti-corrosion paint coating for steel structures and its preparation method, relating to the field of high-performance coating technology. The process includes the following steps: mixing epoxy resin, additives, pigments, fillers, anti-rust pigments, and solvents as component A; mixing curing agent, pigments, fillers, additives, and solvents as component B; and mixing component A and component B uniformly to obtain the anti-corrosion paint coating. The epoxy resin includes hyperbranched epoxy resin and epoxy phosphate resin. This invention utilizes hyperbranched epoxy resin to provide a high crosslinking density, dense film structure, and excellent hardness, heat resistance, and chemical resistance, blocking the penetration of corrosive media such as water, oxygen, and chloride ions. Epoxy phosphate resin has good compatibility with hyperbranched epoxy resin and, as a functional modifier, significantly improves the adhesion, flame retardancy, crosslinking density, and hydrophobicity of the paint film. The combination of hyperbranched epoxy resin and epoxy phosphate resin significantly improves the corrosion resistance of the paint film.

Description

Technical Field

[0001] This invention relates to the field of high-performance coatings technology, specifically an anti-corrosion paint coating for steel structures and its preparation method. Background Technology

[0002] With continuous social progress and the gradual development of science and technology, human production activities are undergoing rapid changes. In international trade, ships and containers play a vital role in transportation. Due to the complexity of the marine environment and biodiversity, the service life of metal structures is reduced, leading to structural failures. Applying anti-corrosion coatings to the surface of steel structures is one of the most common, economical, and effective methods for corrosion protection. However, ordinary organic anti-corrosion coatings experience decreased impermeability and poor durability after long-term use. Therefore, we propose an anti-corrosion paint coating for steel structures and its preparation method. Summary of the Invention

[0003] The purpose of this invention is to provide an anti-corrosion paint coating for steel structures and its preparation method, so as to solve the problems mentioned in the background art.

[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution: an anti-corrosion paint coating for steel structures, comprising the following components: epoxy resin, curing agent, pigments and fillers, anti-rust pigments, additives and solvents.

[0005] Furthermore, the epoxy resin is one or more of bisphenol A type epoxy resin, phenolic epoxy resin, epoxy phosphate resin, and branched epoxy resin.

[0006] Furthermore, the curing agent is one or a mixture of polyamide curing agents, polyamide amine curing agents, phenolic amine curing agents, and modified amine curing agents (epoxy amine adducts).

[0007] Furthermore, the pigments and fillers are one or more of barium sulfate, talc, calcium carbonate, kaolin, quartz powder, rutile titanium dioxide, iron oxide red, iron oxide yellow, and carbon black.

[0008] Furthermore, the anti-rust pigment is one or more of the following: mica iron oxide, glass flakes, aluminum powder, zinc phosphate, aluminum tripolyphosphate, and zinc powder.

[0009] Furthermore, the additives include, but are not limited to, one or more of the following: anti-settling agents, curing accelerators, dispersants, thixotropic agents, wetting agents, leveling agents, defoamers, drying agents, thickeners, adhesion promoters, diluents, and flash rust inhibitors.

[0010] A method for preparing an anti-corrosion paint coating for steel structures includes the following process steps:

[0011] Epoxy resin, additives, pigments, fillers, rust-preventive pigments, and solvents are mixed to form component A;

[0012] The curing agent, pigments, fillers, additives, and solvents are mixed to form component B;

[0013] Mix component A and component B evenly to obtain an anti-corrosion paint coating.

[0014] Furthermore, component A comprises the following components by weight: 100 parts epoxy resin, 40-65 parts pigments and fillers, 1.3-3.3 parts additives, and 10-15 parts solvent;

[0015] The pigments and fillers include the following components by weight: 20-30 parts mica iron oxide, 5-10 parts zinc phosphate, 10-15 parts barium sulfate, and 5-10 parts talc.

[0016] The additives include the following components by weight: 0.5 to 1.5 parts dispersant (BYK-163), 0.2 to 0.5 parts defoamer (BYK-066N), 0.1 to 0.3 parts leveling agent (BYK-331), and 0.5 to 1.0 parts thixotropic agent (fumed silica).

[0017] In the above technical solution, mica iron oxide is the key shielding pigment. Its lamellar structure is layered in the paint film to form a physical shielding layer, which can effectively block the penetration of water, oxygen, and ions. Zinc phosphate is a rust-preventive pigment that can react with metal surfaces and resins to form a passivation film, providing positive chemical rust prevention. Barium sulfate can improve the thickness, hardness, and wear resistance of the paint film. Talc is a functional filler with a lamellar structure, which helps to enhance the shielding effect and anti-settling properties of the paint film.

[0018] Furthermore, component B comprises the following components by weight: 70-80 parts curing agent, 5-10 parts pigments and fillers, 0.1-0.3 parts additives, and 10-20 parts solvent;

[0019] The curing agent selected is Cardell NX-2007; the pigment and filler is mica powder; and the additive is leveling agent (BYK-331).

[0020] Furthermore, the solvent is a mixture of propylene glycol methyl ether acetate and xylene, with a volume ratio of 7:3.

[0021] Furthermore, the mass ratio of component A to component B is (4-5):1;

[0022] After mixing components A and B evenly, allow them to mature for 15–30 minutes before use; cure for 48 hours or more or dry to form a paint film.

[0023] Furthermore, the epoxy resin comprises 60-70 parts of hyperbranched epoxy resin and 30-40 parts of epoxy phosphate resin.

[0024] Furthermore, the hyperbranched epoxy resin is prepared by the following process:

[0025] Step 1: Dissolve 2,2-bis[4-(4-aminophenoxy)phenyl]propane in N-methylpyrrolidone (NMP), cool to 0-5°C, and slowly add trimellitic anhydride under nitrogen atmosphere. After the addition is completed in 30 min, restore to room temperature and stir for 12-24 h. Add methanol / water mixture to precipitate, wash, and dry under vacuum at 40°C for 24 h to obtain amyl acid.

[0026] Step 2: Take the amic acid obtained in the previous step, dissolve it in N-methylpyrrolidone, add 1,3,5-tris(2-hydroxyethyl)cyanuric acid and catalyst, add dehydrating agent under nitrogen atmosphere, heat to 80-100℃, stir and react for 8-12 hours; cool to room temperature, filter, add water to precipitate, filter again, wash with saturated sodium bicarbonate solution and deionized water, and vacuum dry at 60℃ for 48 hours to obtain hydroxyl-terminated polyimide;

[0027] Step 3: Take the hydroxyl-terminated polyimide obtained in the previous step, dissolve it in anhydrous dichloromethane (DCM), add an acid absorbent, and slowly add undecenoyl chloride under nitrogen atmosphere at 0-5℃. After the addition is completed in 30 minutes, restore the reaction to room temperature for 6-12 hours. Wash with 1M dilute hydrochloric acid, wash with saturated sodium bicarbonate solution until neutral, wash with water, dry the separated organic phase with anhydrous magnesium sulfate or sodium sulfate, filter, rotary evaporate, add the concentrated solution to cold methanol to precipitate, filter, wash with cold methanol, and vacuum dry at 40℃ for 24 hours to obtain alkenyl-terminated polyimide.

[0028] Step 4: Dissolve the terminal alkenyl polyimide obtained in the previous step in anhydrous dichloromethane. Under nitrogen atmosphere protection at 0-5°C, add the catalyst, restore to room temperature, and stir in the dark for 24-48 hours. Quench with saturated sodium sulfite solution, filter, wash with water, dry the separated organic phase with anhydrous magnesium sulfate, filter, rotary evaporate, add to cold methanol to precipitate, filter, wash with methanol, and vacuum dry at 40-50°C for 48 hours to obtain hyperbranched epoxy resin.

[0029] Furthermore, in step 1, the molar ratio of 2,2-bis[4-(4-aminophenoxy)phenyl]propane to trimellitic anhydride is 1:(2.2~3.0).

[0030] The added solvent NMP resulted in a solid content of 15–20% wt in the reaction system.

[0031] In the methanol / water mixture, the volume ratio of methanol to deionized water is 1:1.

[0032] In this process step, trimellitic anhydride is used in excess to ensure that the amino groups at both ends of the diamine react completely, thereby generating an amide acid chain with a carboxyl group at the end.

[0033] Furthermore, in step 2, the molar ratio of the carboxyl group to 1,3,5-tris(2-hydroxyethyl)cyanuric acid in the amic acid is (2.2-2.5):1;

[0034] The catalyst is concentrated sulfuric acid or p-toluenesulfonic acid, and the amount used is 5 to 10% wt of the total mass of amyl acid and 1,3,5-tris(2-hydroxyethyl)cyanuric acid;

[0035] The added solvent NMP resulted in a solid content of 10–15% wt in the reaction system.

[0036] The dehydrating agent is N,N'-dicyclohexylcarbodiimide (DCC), and the amount used is 1.2 to 1.3 equiv of the amount of carboxyl group in the amyl acid.

[0037] Using 1,3,5-tris(2-hydroxyethyl)cyanuric acid (THEC) as the branching unit, the amide acid chains are linked through esterification; and through stoichiometric design, the product is terminally hydroxyl. DCC is used as a dehydrating agent to promote esterification and imidization.

[0038] Furthermore, in step 3, the molar ratio of hydroxyl groups to undecenoic chloride in the terminal hydroxyl polyimide is 1:(1.5-2.0) to ensure complete reaction;

[0039] The acid absorbent is triethylamine (TEA) or pyridine, used to neutralize the HCl produced in the reaction, and the amount used is 2.0 to 2.5 equiv of the amount of hydroxyl substances in the terminal hydroxyl polyimide;

[0040] The added solvent DCM resulted in a solid content of 10-15% in the reaction system.

[0041] In hydroxyl-terminated polyimides, the hydroxyl groups are esterified with undecenoyl chloride. The long aliphatic chain of undecenoyl chloride provides long and flexible spacer arms, which helps improve the flexibility of the resin and its compatibility with the curing agent.

[0042] Furthermore, in step 4, the catalyst is m-chloroperoxybenzoic acid;

[0043] The molar ratio of alkenyl group to m-chloroperoxybenzoic acid in terminal alkenyl polyimide is 1:(1.1~1.3).

[0044] The added solvent DCM resulted in a solid content of 8–10% wt in the reaction system.

[0045] The alkenyl groups in terminal alkenyl polyimide undergo epoxidation under the action of a catalyst to generate terminal epoxy groups, thereby obtaining hyperbranched epoxy resin.

[0046] In the above technical solutions, compared with linear epoxy resins, hyperbranched epoxy resins have lower viscosity, higher reactivity, and more functional groups, making them easier to process and promoting the formation of a coating film with high crosslinking density. The polyimide backbone endows the resin with excellent high-temperature resistance, mechanical strength, and chemical stability. The rigid aromatic ring structure is chemically stable, providing a higher glass transition temperature, resulting in better thermal stability of the coating film and making it less prone to softening; it also better resists the erosion of acids, alkalis, and other chemicals, increasing the difficulty of the diffusion path of corrosive media in the coating film and enhancing its barrier effect. The long-chain flexible spacer arms introduced by undecenoyl chloride effectively improve the brittleness caused by the rigid polyimide backbone, improving the flexibility and impact resistance of the coating film, while also enhancing its compatibility with other resins. Due to its high functionality and polarity, hyperbranched epoxy resin, as the main component of coatings, provides a high crosslinking density, a dense film structure, and excellent hardness, heat resistance, and chemical resistance. It can effectively block the penetration of corrosive media such as water, oxygen, and chloride ions, and significantly improve the corrosion resistance of the coating film.

[0047] Furthermore, the epoxy phosphate resin is prepared by the following process:

[0048] The terminal alkenyl polyimide obtained in the previous process is mixed with a solvent, heated to 80-85°C, and stirred until dissolved to obtain a terminal alkenyl polyimide solution; the acrylate monomers are mixed to obtain a monomer mixture; the initiator is dissolved in the solvent to obtain an initiator solution;

[0049] Take a terminal alkenyl polyimide solution, heat it to 85-90℃, and under nitrogen atmosphere protection, stir and slowly add the monomer mixture and initiator solution, adding them at a uniform rate for 2-3 hours; after the addition is complete, keep the reaction at 85-90℃ for 3-4 hours; heat to 90-95℃ and continue the reaction for 1-2 hours; vacuum distill at 50-60℃ to obtain epoxy phosphate resin.

[0050] Furthermore, the acrylate monomers include the following components: methyl phosphate acrylate (CAS No.: 52628-03-2), isobornyl methacrylate (CAS No.: 7534-94-3), glycidyl methacrylate and styrene;

[0051] The initiator is azobisisobutyronitrile.

[0052] Furthermore, the raw materials for the epoxy phosphate resin include the following components by weight: 40-60 parts of terminal alkenyl polyimide, 30-50 parts of methyl phosphate acrylate, 5-15 parts of glycidyl methacrylate, 5-15 parts of styrene, 15-30 parts of isobornyl methacrylate, and 0.5-1.5 parts of azobisisobutyronitrile.

[0053] Furthermore, the solvent is a mixture of propylene glycol monomethyl ether acetate and xylene in a volume ratio of 7:3;

[0054] The solid content of the terminal alkenyl polyimide solution is 15-20%wt; the solid content of the initiator solution is 5-10%wt.

[0055] In the above technical solution, the initiator decomposes to generate free radicals, which initiate the copolymerization of terminal alkenyl polyimide chains and mixed monomers to generate epoxy phosphate resin. Methyl phosphate acrylate introduces phosphate groups, enabling it to form strong phosphorus-oxygen-metal covalent bonds with the metal surface, significantly improving wet adhesion and enhancing the flame retardant and corrosion resistance of the prepared paint film. Glycidyl methacrylate introduces epoxy groups, which can participate in crosslinking during curing, increasing the crosslinking density and compactness of the paint film, thus preventing phase separation and performance degradation. Styrene increases the rigidity / hydrophobic structure of the system, enhancing rigidity, strength, and hydrophobicity. Isobornyl methacrylate has a large hydrophobic carbon cage structure, effectively reducing the water absorption rate of the paint film, improving its hydrophobicity, and providing good flexibility and leveling properties. The prepared epoxy phosphate resin also has a polyimide backbone, providing a basis for heat resistance and physical strength, and exhibits good compatibility with hyperbranched epoxy resins. Hyperbranched epoxy resins, as functional modifiers for coatings, can significantly improve the adhesion, flame retardancy, crosslinking density, and hydrophobicity of paint films, and enhance their corrosion resistance.

[0056] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0057] This invention describes an anti-corrosion paint coating for steel structures. Hyperbranched epoxy resin provides a high cross-linking density, a dense film structure, and excellent hardness, heat resistance, and chemical resistance, preventing the penetration of corrosive media such as water, oxygen, and chloride ions. Epoxy phosphate resin has good compatibility with hyperbranched epoxy resin and, as a functional modifier, significantly improves the adhesion of the paint film and provides flame retardancy. The combination of hyperbranched epoxy resin and epoxy phosphate resin significantly enhances the corrosion resistance of the paint film. Detailed Implementation

[0058] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0059] The following specific implementation methods are all laboratory-scale tests, which can be scaled up proportionally; the number of “parts” mentioned refers to parts by mass (unless otherwise specified).

[0060] Mica iron oxide: industrial grade, 400 mesh; Zinc phosphate: industrial grade, 400 mesh; Barium sulfate: industrial grade, 400 mesh; Talc: industrial grade, 1250 mesh;

[0061] The solvent is a mixture of propylene glycol monomethyl ether acetate and xylene in a volume ratio of 7:3; curing agent: Cardell NX-2007 curing agent; dispersant: BYK-163; defoamer: BYK-066N; leveling agent: BYK-331; thixotropic agent: fumed silica; dehydrating agent: N,N'-dicyclohexylcarbodiimide (DCC); epoxy resin E51: industrial grade.

[0062] Example 1: A method for preparing an anti-corrosion paint coating for steel structures, comprising the following process steps:

[0063] Step 1. Preparation of hyperbranched epoxy resin:

[0064] 2,2-bis[4-(4-aminophenoxy)phenyl]propane was dissolved in N-methylpyrrolidone and cooled to 5°C. Trimeric tricarboxylic anhydride was slowly added under a nitrogen atmosphere. After the addition was completed in 30 min, the mixture was allowed to return to room temperature and stirred for 12 h. A methanol / water mixture (V / V = 1:1) was added to precipitate the mixture. The precipitate was washed and dried under vacuum at 40°C for 24 h to obtain ammonic acid. The molar ratio of 2,2-bis[4-(4-aminophenoxy)phenyl]propane to trimellitic anhydride was 1:2.2. The solid content of the reaction system was 15% wt.

[0065] The amic acid obtained in the previous step was dissolved in N-methylpyrrolidone, and 1,3,5-tris(2-hydroxyethyl)cyanuric acid and 5%wt of p-toluenesulfonic acid catalyst were added. Under a nitrogen atmosphere, a dehydrating agent was added, the temperature was raised to 80℃, and the reaction was stirred for 12 h. After cooling to room temperature, the mixture was filtered, water was added to precipitate, and the mixture was filtered again. The precipitate was washed with saturated sodium bicarbonate solution and deionized water, and then dried under vacuum at 60℃ for 48 h to obtain hydroxyl-terminated polyimide. The molar ratio of carboxyl groups to 1,3,5-tris(2-hydroxyethyl)cyanuric acid in the amic acid was 2.2:1. The solid content of the reaction system was 10%wt. The amount of dehydrating agent used was 1.2 eq of the amount of carboxyl groups in the amic acid.

[0066] The hydroxyl-terminated polyimide obtained in the previous step was dissolved in anhydrous dichloromethane. Triethylamine, an acid absorbent, was added, and undecenoyl chloride was slowly added at 5°C under a nitrogen atmosphere. After 30 minutes of addition, the mixture was allowed to return to room temperature and react for 6 hours. The mixture was washed with 1M dilute hydrochloric acid and then with saturated sodium bicarbonate solution until neutral. After washing with water, the separated organic phase was dried with anhydrous magnesium sulfate or sodium sulfate, filtered, and rotary evaporated. The concentrated solution was added to cold methanol to precipitate the precipitate. The precipitate was filtered, washed with cold methanol, and dried under vacuum at 40°C for 24 hours to obtain alkenyl-terminated polyimide. The molar ratio of hydroxyl groups to undecenoyl chloride in the hydroxyl-terminated polyimide was 1:1.5. The amount of acid absorbent used was 2.0 eq of the molar amount of hydroxyl groups in the hydroxyl-terminated polyimide. The solid content of the reaction system was 10%.

[0067] The terminal alkenyl polyimide obtained in the previous step was dissolved in anhydrous dichloromethane. Under a nitrogen atmosphere at 5°C, the catalyst m-chloroperoxybenzoic acid was added, and the mixture was allowed to return to room temperature and stirred in the dark for 24 hours. The reaction was quenched with saturated sodium sulfite solution, filtered, washed with water, and the separated organic phase was dried with anhydrous magnesium sulfate, filtered, rotary evaporated, and precipitated in cold methanol. The precipitate was then filtered, washed with methanol, and dried under vacuum at 40°C for 48 hours to obtain a hyperbranched epoxy resin. The molar ratio of alkenyl groups to m-chloroperoxybenzoic acid in the terminal alkenyl polyimide was 1:1.1; the solid content of the reaction system was 8% wt.

[0068] Step 2. Preparation of epoxy phosphate resin:

[0069] The terminal alkenyl polyimide obtained in the previous process is mixed with a solvent, heated to 80°C, and stirred until dissolved to obtain a 20%wt terminal alkenyl polyimide solution; methyl phosphate acrylate, isobornyl methacrylate, glycidyl methacrylate, and styrene are mixed to obtain a monomer mixture; azobisisobutyronitrile is dissolved in a solvent to obtain a 10%wt initiator solution.

[0070] Take a terminal alkenyl polyimide solution, heat it to 85℃, and under nitrogen atmosphere protection, slowly add the monomer mixture and initiator solution while stirring, and add them at a uniform rate for 2 hours; after the addition is complete, keep the reaction at 85℃ for 3 hours; heat to 90℃ and continue the reaction for 2 hours; vacuum distill at 50℃ to obtain epoxy phosphate resin; the raw materials of epoxy phosphate resin include the following mass components: 60 parts terminal alkenyl polyimide, 30 parts methyl phosphate acrylate, 5 parts glycidyl methacrylate, 5 parts styrene, 15 parts isobornyl methacrylate, and 0.5 parts azobisisobutyronitrile;

[0071] Step 3. Preparation of anti-corrosion paint coating:

[0072] Component A is a mixture of 100 parts epoxy resin, 53 parts pigments and fillers, 2.3 parts additives, and 12 parts solvent. The pigments and fillers include the following components by weight: 25 parts mica iron oxide, 8 parts zinc phosphate, 12 parts barium sulfate, and 8 parts talc. The additives include the following components by weight: 1 part dispersant, 0.3 parts defoamer, 0.2 parts leveling agent, and 0.8 parts thixotropic agent. The epoxy resin includes 70 parts hyperbranched epoxy resin and 30 parts epoxy phosphate resin.

[0073] Mix 80 parts of curing agent, 8 parts of pigment and filler mica powder, 0.2 parts of additive leveling agent, and 15 parts of solvent to form component B; mix component A and component B at a mass ratio of 5:1 and allow to mature for 15 minutes to obtain anti-corrosion paint coating.

[0074] Example 2: A method for preparing an anti-corrosion paint coating for steel structures, comprising the following process steps:

[0075] Step 1. Preparation of hyperbranched epoxy resin:

[0076] 2,2-bis[4-(4-aminophenoxy)phenyl]propane was dissolved in N-methylpyrrolidone and cooled to 2°C. Trimeric tricarboxylic anhydride was slowly added under a nitrogen atmosphere. After the addition was completed in 30 min, the mixture was allowed to return to room temperature and stirred for 18 h. A methanol / water mixture (V / V = 1:1) was added to precipitate the mixture. The precipitate was washed and dried under vacuum at 40°C for 24 h to obtain ammonic acid. The molar ratio of 2,2-bis[4-(4-aminophenoxy)phenyl]propane to trimellitic anhydride was 1:2.6. The solid content of the reaction system was 18% wt.

[0077] The amic acid obtained in the previous step was dissolved in N-methylpyrrolidone, and 1,3,5-tris(2-hydroxyethyl)cyanuric acid and 8%wt of p-toluenesulfonic acid catalyst were added. Under a nitrogen atmosphere, a dehydrating agent was added, the temperature was raised to 90℃, and the reaction was stirred for 10 h. After cooling to room temperature, the mixture was filtered, water was added to precipitate, and the mixture was filtered again. The precipitate was washed with saturated sodium bicarbonate solution and deionized water, and then dried under vacuum at 60℃ for 48 h to obtain hydroxyl-terminated polyimide. The molar ratio of carboxyl groups to 1,3,5-tris(2-hydroxyethyl)cyanuric acid in the amic acid was 2.3. The solid content of the reaction system was 12%wt. The amount of dehydrating agent used was 1.25 times the molar amount of carboxyl groups in the amic acid.

[0078] The hydroxyl-terminated polyimide obtained in the previous step was dissolved in anhydrous dichloromethane. Triethylamine, an acid absorbent, was added, and undecenoyl chloride was slowly added at 2°C under a nitrogen atmosphere. After the addition was complete in 30 minutes, the mixture was allowed to return to room temperature and react for 9 hours. The mixture was washed with 1M dilute hydrochloric acid and then with saturated sodium bicarbonate solution until neutral. After washing with water, the separated organic phase was dried with anhydrous magnesium sulfate or sodium sulfate, filtered, and rotary evaporated. The concentrated solution was added to cold methanol to precipitate the precipitate. The precipitate was filtered, washed with cold methanol, and dried under vacuum at 40°C for 24 hours to obtain alkenyl-terminated polyimide. The molar ratio of hydroxyl groups to undecenoyl chloride in the hydroxyl-terminated polyimide was 1:1.8. The amount of acid absorbent used was 2.2 times the molar amount of hydroxyl groups in the hydroxyl-terminated polyimide. The solid content of the reaction system was 12%.

[0079] The terminal alkenyl polyimide obtained in the previous step was dissolved in anhydrous dichloromethane. Under a nitrogen atmosphere at 2°C, the catalyst m-chloroperoxybenzoic acid was added, and the mixture was allowed to return to room temperature and stirred in the dark for 36 hours. The reaction was quenched with saturated sodium sulfite solution, filtered, washed with water, and the separated organic phase was dried with anhydrous magnesium sulfate, filtered, rotary evaporated, and precipitated in cold methanol. The precipitate was then filtered, washed with methanol, and dried under vacuum at 45°C for 48 hours to obtain a hyperbranched epoxy resin. The molar ratio of alkenyl groups to m-chloroperoxybenzoic acid in the terminal alkenyl polyimide was 1:1.2. The solid content of the reaction system was 9% wt.

[0080] Step 2. Preparation of epoxy phosphate resin:

[0081] The terminal alkenyl polyimide obtained in the previous process is mixed with a solvent, heated to 82°C, and stirred until dissolved to obtain an 18% wt terminal alkenyl polyimide solution; methyl phosphate acrylate, isobornyl methacrylate, glycidyl methacrylate, and styrene are mixed to obtain a monomer mixture; azobisisobutyronitrile is dissolved in a solvent to obtain an 8% wt initiator solution.

[0082] A terminal alkenyl polyimide solution was heated to 88°C. Under a nitrogen atmosphere, the monomer mixture and initiator solution were slowly added while stirring, and the addition was completed at a uniform rate over 2.5 hours. After the addition was complete, the mixture was kept at 88°C for 3.5 hours. The temperature was then raised to 92°C, and the reaction was continued for 1.5 hours. The mixture was then vacuum distilled at 55°C to obtain an epoxy phosphate resin. The raw materials for the epoxy phosphate resin included the following components by mass: 50 parts terminal alkenyl polyimide, 40 parts methyl phosphate acrylate, 10 parts glycidyl methacrylate, 10 parts styrene, 22 parts isobornyl methacrylate, and 1.0 part azobisisobutyronitrile.

[0083] Step 3. Preparation of anti-corrosion paint coating:

[0084] Component A is a mixture of 100 parts epoxy resin, 53 parts pigments and fillers, 2.3 parts additives, and 12 parts solvent. The pigments and fillers include the following components by weight: 25 parts mica iron oxide, 8 parts zinc phosphate, 12 parts barium sulfate, and 8 parts talc. The additives include the following components by weight: 1 part dispersant, 0.3 parts defoamer, 0.2 parts leveling agent, and 0.8 parts thixotropic agent. The epoxy resin includes 65 parts hyperbranched epoxy resin and 35 parts epoxy phosphate resin.

[0085] Mix 75 parts curing agent, 8 parts pigment and filler mica powder, 0.2 parts auxiliary agent leveling agent, and 15 parts solvent to form component B; mix component A and component B at a mass ratio of 4.5:1 and allow to mature for 20 minutes to obtain anti-corrosion paint coating.

[0086] Example 3: A method for preparing an anti-corrosion paint coating for steel structures, comprising the following process steps:

[0087] Step 1. Preparation of hyperbranched epoxy resin:

[0088] 2,2-bis[4-(4-aminophenoxy)phenyl]propane was dissolved in N-methylpyrrolidone and cooled to 0°C. Trimeric tricarboxylic anhydride was slowly added under a nitrogen atmosphere. After the addition was completed in 30 min, the mixture was allowed to return to room temperature and stirred for 24 h. A methanol / water mixture (V / V = 1:1) was added to precipitate the mixture. The precipitate was washed and dried under vacuum at 40°C for 24 h to obtain ammonic acid. The molar ratio of 2,2-bis[4-(4-aminophenoxy)phenyl]propane to trimellitic anhydride was 1:3.0. The solid content of the reaction system was 20% wt.

[0089] The amic acid obtained in the previous step was dissolved in N-methylpyrrolidone, and 1,3,5-tris(2-hydroxyethyl)cyanuric acid and 10%wt of p-toluenesulfonic acid catalyst were added. Under a nitrogen atmosphere, a dehydrating agent was added, the temperature was raised to 100℃, and the reaction was stirred for 8 hours. After cooling to room temperature, the mixture was filtered, water was added to precipitate, and the mixture was filtered again. The precipitate was washed with saturated sodium bicarbonate solution and deionized water, and then dried under vacuum at 60℃ for 48 hours to obtain hydroxyl-terminated polyimide. The molar ratio of carboxyl groups to 1,3,5-tris(2-hydroxyethyl)cyanuric acid in the amic acid was 2.5:1. The solid content of the reaction system was 15%wt. The amount of dehydrating agent used was 1.3 eq of the amount of carboxyl groups in the amic acid.

[0090] The hydroxyl-terminated polyimide obtained in the previous step was dissolved in anhydrous dichloromethane. Triethylamine, an acid absorbent, was added, and undecenoyl chloride was slowly added at 0°C under a nitrogen atmosphere. After the addition was complete in 30 minutes, the mixture was allowed to return to room temperature and react for 12 hours. The mixture was washed with 1M dilute hydrochloric acid and then with saturated sodium bicarbonate solution until neutral. After washing with water, the separated organic phase was dried with anhydrous magnesium sulfate or sodium sulfate, filtered, and rotary evaporated. The concentrated solution was added to cold methanol to precipitate the precipitate. The precipitate was filtered, washed with cold methanol, and dried under vacuum at 40°C for 24 hours to obtain alkenyl-terminated polyimide. The molar ratio of hydroxyl groups to undecenoyl chloride in the hydroxyl-terminated polyimide was 1:2.0. The amount of acid absorbent used was 2.5 eq of the molar amount of hydroxyl groups in the hydroxyl-terminated polyimide. The solid content of the reaction system was 15%.

[0091] The terminal alkenyl polyimide obtained in the previous step was dissolved in anhydrous dichloromethane. Under a nitrogen atmosphere at 0°C, the catalyst m-chloroperoxybenzoic acid was added, and the mixture was allowed to return to room temperature and stirred in the dark for 48 hours. The reaction was quenched with saturated sodium sulfite solution, filtered, washed with water, and the separated organic phase was dried with anhydrous magnesium sulfate, filtered, rotary evaporated, and precipitated in cold methanol. The precipitate was then filtered, washed with methanol, and dried under vacuum at 50°C for 48 hours to obtain a hyperbranched epoxy resin. The molar ratio of alkenyl groups to m-chloroperoxybenzoic acid in the terminal alkenyl polyimide was 1:1.3; the solid content of the reaction system was 10% wt.

[0092] Step 2. Preparation of epoxy phosphate resin:

[0093] The terminal alkenyl polyimide obtained in the previous process is mixed with a solvent, heated to 85°C, and stirred until dissolved to obtain a 15%wt terminal alkenyl polyimide solution; methyl phosphate acrylate, isobornyl methacrylate, glycidyl methacrylate, and styrene are mixed to obtain a monomer mixture; azobisisobutyronitrile is dissolved in a solvent to obtain a 5%wt initiator solution.

[0094] Take a terminal alkenyl polyimide solution, heat it to 90℃, and under nitrogen atmosphere protection, slowly add the monomer mixture and initiator solution while stirring, and add them at a uniform rate for 3 hours; after the addition is complete, keep the reaction at 90℃ for 4 hours; heat to 95℃ and continue the reaction for 1 hour; vacuum distill at 60℃ to obtain epoxy phosphate resin; the raw materials of epoxy phosphate resin include the following mass components: 40 parts terminal alkenyl polyimide, 50 parts methyl phosphate acrylate, 15 parts glycidyl methacrylate, 15 parts styrene, 30 parts isobornyl methacrylate, and 1.5 parts azobisisobutyronitrile;

[0095] Step 3. Preparation of anti-corrosion paint coating:

[0096] Component A is a mixture of 100 parts epoxy resin, 53 parts pigments and fillers, 2.3 parts additives, and 12 parts solvent. The pigments and fillers include the following components by weight: 25 parts mica iron oxide, 8 parts zinc phosphate, 12 parts barium sulfate, and 8 parts talc. The additives include the following components by weight: 1 part dispersant, 0.3 parts defoamer, 0.2 parts leveling agent, and 0.8 parts thixotropic agent. The epoxy resin includes 60 parts hyperbranched epoxy resin and 40 parts epoxy phosphate resin.

[0097] Mix 70 parts of curing agent, 8 parts of pigment and filler mica powder, 0.2 parts of additive leveling agent, and 15 parts of solvent to form component B; mix component A and component B at a mass ratio of 4:1 and allow to mature for 30 minutes to obtain anti-corrosion paint coating.

[0098] Comparative Example 1: A method for preparing an anti-corrosion paint coating for steel structures, wherein step 1. The preparation of hyperbranched epoxy resin is the same as in Example 1; step 2. The preparation of the anti-corrosion paint coating is the same as in Example 1, wherein the epoxy resin comprises 70 parts of hyperbranched epoxy resin and 30 parts of epoxy resin E51, thereby obtaining the anti-corrosion paint coating.

[0099] Comparative Example 2: A method for preparing an anti-corrosion paint coating for steel structures, wherein step 1, the preparation of epoxy phosphate resin is the same as in Example 1; step 2, the preparation of the anti-corrosion paint coating is the same as in Example 1; the epoxy resin includes 70 parts of epoxy resin E51 and 30 parts of epoxy phosphate resin, thereby obtaining the anti-corrosion paint coating.

[0100] Comparative Example 3: A method for preparing an anti-corrosion paint coating for steel structures, comprising the following process steps: Step 1. Preparation of epoxy phosphate resin:

[0101] Take 100 parts of epoxy resin E51, 10 parts of palmitoleic acid, 0.3 parts of catalyst triphenylphosphine and 0.03 parts of polymerization inhibitor p-methoxyphenol, mix them in propylene glycol methyl ether acetate (the solid content of the system is 75%), heat to 95°C under nitrogen atmosphere, stir and mix evenly; heat to 115°C and react for 4 hours; cool to obtain alkenyl epoxy resin;

[0102] The alkenyl epoxy resin obtained in the previous step is mixed with a solvent, heated to 80°C, and stirred until dissolved to obtain a 20%wt end-alkenyl polyimide solution; methyl phosphate acrylate, isobornyl methacrylate, glycidyl methacrylate, and styrene are mixed to obtain a monomer mixture; azobisisobutyronitrile is dissolved in a solvent to obtain a 10%wt initiator solution.

[0103] Take an alkenyl polyimide solution, heat it to 85℃, and under a nitrogen atmosphere, slowly add the monomer mixture and initiator solution while stirring. The addition is completed at a uniform rate over 2 hours. After the addition is complete, keep the reaction at 80℃ for 5 hours. Vacuum distillation is carried out at 50℃ to obtain epoxy phosphate resin. The raw materials for epoxy phosphate resin include the following components by mass: 60 parts alkenyl epoxy resin, 30 parts methyl phosphate acrylate, 5 parts glycidyl methacrylate, 5 parts styrene, 15 parts isobornyl methacrylate, and 0.5 parts azobisisobutyronitrile.

[0104] Step 2. The preparation of the anti-corrosion paint coating is the same as in Example 1; the epoxy resin includes 70 parts of epoxy resin E51 and 30 parts of epoxy phosphate resin to obtain the anti-corrosion paint coating.

[0105] Comparative Example 4: A method for preparing an anti-corrosion paint coating for steel structures, comprising the following process steps:

[0106] Mix 100 parts epoxy resin E51, 53 parts pigments and fillers, 2.3 parts additives, and 12 parts solvent to form component A; the pigments and fillers include the following components by weight: 25 parts mica iron oxide, 8 parts zinc phosphate, 12 parts barium sulfate, and 8 parts talc powder; the additives include the following components by weight: 1 part dispersant, 0.3 parts defoamer, 0.2 parts leveling agent, and 0.8 parts thixotropic agent; mix 80 parts curing agent, 8 parts mica powder pigments and fillers, 0.2 parts leveling agent, and 15 parts solvent to form component B; mix component A and component B at a mass ratio of 5:1 until homogeneous, and cure for 15 minutes to obtain the anti-corrosion paint coating.

[0107] Experiment: The anti-corrosion paints obtained in Examples 1-3 and Comparative Examples 1-4 were applied to the surface of Q235 steel plates with a coating thickness of 200 μm. The plates were then placed in a room temperature environment for 7 days to form a paint film, and samples were prepared. The performance of these samples was tested, and the results were recorded.

[0108] Referencing standard GB / T 9286-2021, the adhesion grade of the sample is evaluated by testing the paint film peeling. Referring to standard GB / T 6739-2022, the hardest pencil grade of the paint film sample that does not scratch it is tested. Referring to standard GB / T 1040.3-2006, the tensile strength and elongation at break of the sample are tested. Referring to standard GB / T 1732-2020, the maximum height from which the sample does not crack or peel off is tested by dropping a heavy hammer freely onto the paint film. Referring to standard GB / T 30693-2014, the static contact angle of the sample is tested. Referring to standard GB / T 2408-2021, the flame retardancy grade of the sample is evaluated using the vertical burning method (UL-94). The paint film sample is placed in a salt spray chamber at 35℃ with a 5% NaCl solution, and the time it takes for bubbles, rust, peeling, cracking, or severe discoloration to appear is recorded.

[0109]

[0110] Based on the data in the table above, the following conclusions can be clearly drawn:

[0111] The anti-corrosion paints obtained in Examples 1-3 were compared with those obtained in Comparative Examples 1-4. The test results show that...

[0112] Compared with the comparative examples, the anti-corrosion paints obtained in Examples 1-3 exhibit higher adhesion, hardness, strength, impact resistance, hydrophobicity, flame retardancy, and corrosion resistance time. This fully demonstrates that the present invention improves the anti-corrosion performance of the prepared paints while comprehensively enhancing their adhesion, hardness, impact resistance, and flame retardancy.

[0113] Compared to Example 1, in Comparative Example 1, the epoxy phosphate resin was replaced, and the epoxy resin was a hyperbranched epoxy resin and epoxy resin E51. In Comparative Example 2, the hyperbranched epoxy resin was replaced, and the epoxy resin was epoxy resin E51 and epoxy phosphate resin. In Comparative Example 3, the hyperbranched epoxy resin was replaced, and the preparation method of the epoxy phosphate resin was different. In Comparative Example 4, the epoxy resin was E51.

[0114] Regarding adhesion, the examples achieved high film adhesion through the high functionality and permeability of the hyperbranched epoxy resin and the strong chemical bonds formed between the epoxy phosphate resin and the metal substrate. Comparative Example 1 only contained hyperbranched epoxy resin, but lacked the strong chemical bonds of the phosphate ester, resulting in a lower adhesion level. Comparative Examples 2 and 3 contained phosphate esters, but the adhesion and crosslinking density of the main resin (E51) were not as good as the hyperbranched structure. Comparative Example 4 was a pure E51 system, with a relatively basic adhesion level.

[0115] Regarding pencil hardness, the examples improved the film hardness through a rigid polyimide (PI) framework. Comparative Examples 2-4 lacked a PI framework, resulting in a significant decrease in film hardness.

[0116] In terms of mechanical properties, the examples achieved high film strength through a rigid PI framework and hyperbranched high crosslinking density; and good toughness was achieved while maintaining high strength through undecenoyl chloride flexible spacers and epoxy phosphate resin. In Example 3, the highest content of epoxy phosphate resin disrupted the strong rigid continuous phase formed by the hyperbranched epoxy resin, resulting in a decrease in the macroscopic tensile strength of the film, and the higher crosslinking density increased the probability of brittle fracture and poor impact resistance. Example 2 demonstrated a balance between rigidity and toughness. Comparative Example 1 had excessively high rigidity and insufficient toughness, making it prone to brittle cracking. Comparative Examples 2 and 3 lacked hyperbranched epoxy resin and contained flexible acrylate long chains, resulting in the highest elongation but the lowest strength.

[0117] Regarding hydrophobicity, Examples 1-3 exhibit good hydrophobicity due to the synergistic effect of the long fatty chain of undecenoyl chloride and isobornyl methacrylate. In contrast, the comparative examples, lacking these hydrophobic structures or containing them in lower amounts, show decreased hydrophobicity data.

[0118] Regarding flame retardant performance, Examples 1-3 utilize a highly efficient synergistic flame retardant system composed of triazine rings, phosphorus (phosphate ester), and polyimide, exhibiting both gas-phase and condensed-phase flame retardant mechanisms and demonstrating excellent flame retardant capabilities. Comparative Example 1 lacks phosphorus; Comparative Examples 2 and 3 have incomplete flame retardant systems and poor flame retardant performance; while Comparative Example 4 lacks any flame retardant design.

[0119] Regarding corrosion resistance, the paint films in Examples 1-3 exhibit strong adhesion, a dense cross-linked network, excellent hydrophobicity, and the combined effect of lamellar filler layers, achieving an ultimate anti-corrosion effect. In contrast, the comparative examples lack a PI skeleton, hyperbranched structure, and phosphate ester modification, resulting in weakened anti-corrosion performance.

[0120] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for preparing an anticorrosive paint coating for steel structures, characterized by: The process includes the following steps: Epoxy resin, additives, pigments, fillers, rust-preventive pigments, and solvents are mixed to form component A; The curing agent, pigments, fillers, additives, and solvents are mixed to form component B; Mix component A and component B evenly to obtain the anti-corrosion paint coating; The epoxy resin includes hyperbranched epoxy resin and epoxy phosphate resin; The hyperbranched epoxy resin is prepared by the following process: Step 1: Dissolve 2,2-bis[4-(4-aminophenoxy)phenyl]propane in N-methylpyrrolidone, cool to 0-5°C, and slowly add trimellitic anhydride under nitrogen atmosphere. After the addition is completed in 30 minutes, restore to room temperature and stir the reaction for 12-24 hours to obtain amide acid. Step 2: Take the amic acid obtained in the previous step, dissolve it in N-methylpyrrolidone, add 1,3,5-tris(2-hydroxyethyl)cyanuric acid and catalyst, add dehydrating agent under nitrogen atmosphere protection, heat to 80-100℃, stir and react for 8-12 hours to obtain hydroxyl-terminated polyimide. Step 3: Take the hydroxyl-terminated polyimide obtained in the previous step, dissolve it in anhydrous dichloromethane, add an acid absorbent, and slowly add undecenoyl chloride under nitrogen atmosphere at 0-5°C. After the addition is completed in 30 minutes, restore the room temperature and react for 6-12 hours to obtain alkenyl-terminated polyimide. Step 4: Dissolve the terminal alkenyl polyimide obtained in the previous step in anhydrous dichloromethane, add m-chloroperoxybenzoic acid at 0-5°C under nitrogen atmosphere, restore to room temperature, and stir in the dark for 24-48 hours to obtain hyperbranched epoxy resin.

2. A method of preparing a corrosion resistant paint coating for steel structures according to claim 1, characterized in that: The epoxy phosphate resin is prepared by the following process: Dissolve terminal alkenyl polyimide in a solvent, heat to 85-90℃, and under nitrogen atmosphere protection, stir and slowly add acrylate monomer and initiator, adding at a uniform rate for 2-3 hours; after addition, keep the reaction at 85-90℃ for 3-4 hours; heat to 90-95℃ and continue the reaction for 1-2 hours; vacuum distill at 50-60℃ to obtain epoxy phosphate resin. The acrylate monomer comprises the following components: methyl phosphate acrylate, isobornyl methacrylate, glycidyl methacrylate, and styrene.

3. The method for preparing an anti-corrosion paint coating for steel structures according to claim 1, characterized in that: In step 1, the molar ratio of 2,2-bis[4-(4-aminophenoxy)phenyl]propane to trimellitic anhydride is 1:(2.2~3.0). In step 2, the molar ratio of the carboxyl group to 1,3,5-tris(2-hydroxyethyl)cyanuric acid in the amic acid is (2.2-2.5):1; In step 3, the molar ratio of hydroxyl groups to undecenoic chloride in the hydroxyl-terminated polyimide is 1:(1.5~2.0). In step 4, the molar ratio of alkenyl group to m-chloroperoxybenzoic acid in the terminal alkenyl polyimide is 1:(1.1~1.3).

4. The method for preparing an anti-corrosion paint coating for steel structures according to claim 2, characterized in that: The raw materials of the epoxy phosphate resin include the following components by weight: 40-60 parts of terminal alkenyl polyimide, 30-50 parts of methyl phosphate acrylate, 5-15 parts of glycidyl methacrylate, 5-15 parts of styrene, 15-30 parts of isobornyl methacrylate, and 0.5-1.5 parts of initiator.

5. The method for preparing an anti-corrosion paint coating for steel structures according to claim 1, characterized in that: Component A comprises the following components by weight: 100 parts epoxy resin, 40-65 parts pigments and fillers, 1.3-3.3 parts additives, and 10-15 parts solvent; The epoxy resin comprises 60-70 parts of hyperbranched epoxy resin and 30-40 parts of epoxy phosphate resin. The anti-rust pigments are mica iron oxide and zinc phosphate; the pigments and fillers include the following components by weight: 20-30 parts mica iron oxide, 5-10 parts zinc phosphate, 10-15 parts barium sulfate and 5-10 parts talc.

6. The method for preparing an anti-corrosion paint coating for steel structures according to claim 5, characterized in that: Component B comprises the following components by weight: 70-80 parts curing agent, 5-10 parts pigments and fillers, 0.1-0.3 parts additives, and 10-20 parts solvent.

7. The method for preparing an anti-corrosion paint coating for steel structures according to claim 6, characterized in that: The solvent is a mixture of propylene glycol monomethyl ether acetate and xylene in a volume ratio of 7:

3. The mass ratio of component A to component B is (4-5):

1.

8. A corrosion-resistant paint coating for steel structures prepared by the preparation method according to any one of claims 1-7.

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