Aromatic diamine epoxy resin curing agent, anti-corrosion coating and preparation method and coating process of anti-corrosion coating

Abstract

The invention belongs to the technical field of high polymer material preparation and coatings, and particularly relates to an aromatic diamine epoxy resin curing agent, an anti-corrosion coating as well as a preparation method and a coating process of the anti-corrosion coating. The aromatic diamine provided by the invention is prepared by carrying out nucleophilic substitution reaction on aromatic diphenol, aromatic halide and p-hydroxyaniline. In an aromatic diamine structure, good stability of a molecular structure is guaranteed by a benzene ring and sulfuryl, and flexibility of diamine molecules is improved by rich ether bonds. Aromatic diamine can be used as a curing agent of epoxy resin, and the flexible molecular structure and lower amino content of aromatic diamine can change the structure of cured epoxy, properly reduce the crosslinking density and enhance the toughness and mechanical properties of the cured epoxy. The epoxy resin anticorrosive paint is also prepared from aromatic diamine, epoxy resin, a filler and a diluent, and has excellent corrosion resistance to a metal substrate.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer material preparation and coatings, and particularly relates to an aromatic diamine epoxy resin curing agent, an anti-corrosion coating, and a preparation method and a coating process thereof. Background Art

[0002] At present, the commonly used corrosion protection methods mainly include metal modification, corrosion inhibitor method, electrochemical protection method and coating method. Among them, the coating method is the most economical, simple and effective anti-corrosion method, and it is the most widely used and studied. Epoxy anti-corrosion coatings have the advantages of strong adhesion, high impact resistance, low shrinkage, good permeability, stable curing performance, good electrical insulation, excellent wear resistance and low price. Therefore, they are widely used in construction, transportation, petrochemical, machinery, electronics and aerospace and other fields, and they occupy the highest market share (35.01%) among commercial anti-corrosion coatings. However, epoxy cured products have strong internal stress, high cross-linking density and brittleness. Microcracks and voids are easily formed inside them, resulting in reduced permeability of anti-corrosive media. At the same time, insufficient impact resistance, heat resistance, acid and alkali resistance and weather resistance also greatly weaken the anti-corrosion ability of epoxy resin coatings.

[0003] Anti-corrosion coatings primarily consist of film-forming agents, fillers, solvents, and additives. The film-forming agent plays a crucial role in the performance of anti-corrosion coatings. The film-forming agent of epoxy coatings is a three-dimensional network polymer formed by the cross-linking reaction of epoxy resin and curing agent. Its performance can be improved by adjusting the epoxy resin or curing agent molecules. Compared to epoxy resins, curing agents are more diverse and numerous. Each new curing agent can lead to the development of a new range of epoxy resin materials, helping to solve practical problems and open up new applications. The development of curing agents will be a key direction in the future research and development of epoxy resin coatings.

[0004] Organic amine compounds are the most commonly used epoxy resin curing agents, primarily including aliphatic amine curing agents, alicyclic amine curing agents, and aromatic amine curing agents. Compared to aliphatic and alicyclic amine curing agents, aromatic amine curing epoxy resins can impart improved heat resistance and strength to epoxy resins. However, the molecular weight of commercial aromatic amine curing agents (such as 4,4-diaminodiphenyl sulfone) is too small, and the cured products with epoxy resins often exhibit brittleness, significantly affecting the corrosion resistance of the corresponding epoxy resin coatings. Yao Hongyan et al. (CN 117004024A, CN 117143495A) synthesized a series of aminopoly(aryl ether sulfone / ketone) polymers using 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane and aromatic diphenols through nucleophilic condensation and used them as epoxy resin curing agents. The novel aminopoly(aryl ether sulfone / ketone) curing agents disclosed in the patents can significantly improve the performance of epoxy cured products, and epoxy coatings prepared with them in combination with epoxy resins exhibit excellent corrosion resistance. However, the aminobisphenol monomer used in this aminopolyaryl ether sulfone / ketone is expensive, making it difficult to achieve large-scale commercial production and application. Summary of the Invention

[0005] Based on this, the present invention addresses the shortcomings of current commercial aromatic amine curing agents and addresses the challenges of commercial production and application. It provides a flexible aromatic amine epoxy curing agent with a long molecular chain, a preparation method thereof, and an epoxy resin anticorrosive coating using this curing agent as a primary component and its preparation method. The flexible molecular structure and low amino content of this aromatic amine can modify the structure of epoxy cured products and appropriately reduce crosslinking density, thereby enhancing the toughness and mechanical properties of the epoxy cured products, thereby improving the anticorrosive performance of the prepared anticorrosive coating.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] In a first aspect, the present invention provides an aromatic diamine epoxy resin curing agent comprising a structure represented by formula (I):

[0008]

[0009] Wherein A is one of the structures shown in A1 to A7;

[0010]

[0011] B is one of the structures shown in B1 to B4:

[0012]

[0013] In a second aspect, the present invention provides a method for preparing an aromatic diamine epoxy resin curing agent. In the presence of a salt-forming agent, an aromatic diphenol monomer, an aromatic dihalide monomer and a p-hydroxyaniline monomer undergo a nucleophilic substitution reaction in a polar aprotic solvent to obtain an aromatic diamine molecule.

[0014] Furthermore, the aromatic diphenol monomer is one of the structures represented by R1 to R7.

[0015]

[0016] Furthermore, the aromatic dihalide is one of the structures represented by Y1 to Y4, wherein X is a halogen, preferably F or Cl:

[0017]

[0018] Furthermore, the preparation method of the aromatic diamine epoxy resin curing agent includes two schemes:

[0019] Option A:

[0020] Under an inert gas environment, an aromatic diphenol monomer, an aromatic dihalide monomer, a salt-forming agent, a polar aprotic solvent and a water-carrying agent are added to a reactor equipped with a mechanical stirring device, a thermometer, a water-carrying device and a condenser, the reaction system is heated to 120-150° C., refluxed and continuously stirred for 3-6 hours, the water-carrying agent is removed, the temperature is raised to 150-220° C., the reaction is carried out for 6-10 hours, the temperature is lowered to 50-110° C., a quantitative amount of p-hydroxyaniline and toluene are added to the system, the reaction system is reheated to 120-150° C., refluxed and continuously stirred for 3-6 hours, the water-carrying agent is removed, the temperature is raised to 150-220° C., the reaction is carried out for 6-10 hours, the temperature is lowered to 50-110° C., the material is discharged into ice water to obtain a product, the product is washed 3-8 times with distilled water and ethanol respectively, and the monomer powder is obtained after drying;

[0021] Option B:

[0022] Under an inert gas environment, an aromatic diphenol monomer, an aromatic dihalide monomer, p-hydroxyaniline, a salt-forming agent, and a polar aprotic solvent are added to a reactor equipped with a mechanical stirrer, a thermometer, a water collector, and a condenser. The reaction system is heated to 130-150°C, refluxed, and stirred for 3-6 hours. The water collector is removed, the temperature is raised to 150-220°C, the reaction is continued for 6-10 hours, the temperature is lowered to 50-110°C, and the product is discharged into ice water to obtain the product. The obtained product is washed with distilled water and ethanol 3-8 times respectively, and then dried to obtain a monomer powder.

[0023] Furthermore, the molar ratio of the aromatic diphenol monomer, the aromatic dihalide monomer, the p-hydroxyaniline and the salt-forming agent is (0.95-1.05):(1.90-2.20):(1.90-2.20):(1.00-2.20).

[0024] Furthermore, the salt-forming agent is one or more of potassium carbonate, sodium carbonate, lithium carbonate, cesium carbonate, potassium bicarbonate, and sodium bicarbonate;

[0025] Furthermore, the polar aprotic solvent includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, diphenyl sulfone and cyclopentane; and the water-carrying agent is one of toluene and cyclohexane.

[0026] Furthermore, in both solutions, the amount of polar aprotic solvent used is 1.5 to 9 times the total mass of all monomers, and the amount of water-carrying agent added is 20 to 60% of the solvent volume.

[0027] A third aspect of the present invention provides an aromatic diamine epoxy resin anti-corrosion coating, characterized in that it is prepared by using the above-mentioned aromatic diamine epoxy resin curing agent and epoxy resin.

[0028] The fourth aspect of the present invention provides a method for preparing an aromatic diamine epoxy resin anti-corrosion coating, comprising the following steps: weighing epoxy resin, aromatic diamine curing agent, diluent and filler, and using a sand mill to disperse and grind them at a speed of 2000-5000r / min for 0.5-6h to obtain the epoxy resin anti-corrosion coating.

[0029] Furthermore, the mass ratio of the epoxy resin, aromatic diamine curing agent, filler and diluent is (7-58): (1-40): (5-15): (30-70);

[0030] Furthermore, the epoxy resin is one or more of novolac epoxy resin (F-44, F-48, F-50, F-51), bisphenol A epoxy resin (E03, E06, E12, E20, E44, E51), bisphenol F epoxy resin, 4,4'-diaminodiphenylmethane epoxy resin (AG-80), and bisphenol S epoxy resin (DGEBS);

[0031] Furthermore, the filler is one or more of carbon black, iron black, iron red, mica iron oxide, manganese black, chromium oxide, titanium dioxide, lamellar pearl powder, organic bentonite, montmorillonite, and fumed silica;

[0032] Furthermore, the diluent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, toluene, acetone, butanone, cyclohexanone, and n-butanol.

[0033] In a fifth aspect, the present invention provides a coating process for an aromatic diamine / epoxy resin anti-corrosion coating, which comprises the following steps: adjusting the viscosity of the coating by adding a diluent (coating 4 cups takes 50 to 70 seconds), spraying the coating with appropriate viscosity onto a sandblasted metal substrate using an air spray gun and an air compressor, drying the surface at 80 to 100°C for 0.2 to 1h, heating to 150 to 180°C and curing for 2 to 6h, and finally obtaining an anti-corrosion coating.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The flexible molecular structure and low amino content of aromatic amines can change the structure of epoxy cured products and appropriately reduce the cross-linking density, thereby enhancing the toughness and mechanical properties of epoxy cured products, thereby making the prepared anti-corrosion coatings have better anti-corrosion performance;

[0036] 2. Compared with commercial 4,4-diaminodiphenyl sulfone, the aromatic diamine provided by the present invention has a larger molecular size and a flexible molecular structure, which can increase the distance between crosslinking points in epoxy cured products and reduce the rigidity of epoxy cured products, thereby enhancing the toughness and mechanical properties of epoxy cured products;

[0037] 3. The aromatic diamine monomers provided herein may contain hexafluoroisopropyl and cyano groups, thereby enhancing the properties of epoxy coatings. For example, the introduction of hexafluoroisopropyl groups can improve the coating's hydrophobicity and enhance its permeability to corrosive media; the introduction of cyano groups can enhance the interaction between the coating and the metal substrate, improving the coating's adhesion. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0039] Figure 1 is an infrared spectrum of the aromatic diamine and 4,4'-diaminodiphenyl sulfone prepared in Example 1;

[0040] Figure 2 is the TGA curve of the aromatic diamine / epoxy resin anticorrosive coating prepared in Example 1;

[0041] Figure 3 is the electrochemical impedance spectroscopy Bode diagram of the aromatic diamine / epoxy resin anti-corrosion coating prepared in Example 1;

[0042] Figure 4 This is a cross-sectional electron microscope image of the aromatic diamine / epoxy resin anti-corrosion coating prepared in Example 1. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present invention are described clearly and completely below. The embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention. For the sake of clarity, the following embodiments are described in detail below.

[0044] Example 1

[0045] This embodiment provides a method for preparing an aromatic diamine curing agent, and the preparation and coating of an aromatic diamine / epoxy resin anti-corrosion coating.

[0046] (1) Preparation of aromatic diamines:

[0047] Under a nitrogen atmosphere, 1.0460g of hydroquinone, 5.4559g of 4,4'-dichlorodiphenyl sulfone, and 1.3821g of anhydrous potassium carbonate were added to a three-necked flask equipped with a mechanical stirrer, a thermometer, a water collector, and a condenser. 77mL of N-methylpyrrolidone (NMP) was used as the reaction solvent, and 15mL of toluene was added as a water collector. The system temperature was raised to 130°C to remove water for 4 hours, the toluene was evaporated, and the temperature was raised to 180°C for 6 hours. The reaction system was then cooled to 100°C, 2.0735g of p-hydroxyaniline and 15mL of toluene were added, the temperature was raised to 130°C to remove water for 4 hours, the toluene was evaporated, the temperature was raised to 180°C for 6 hours, and finally the temperature was lowered to 100°C and the product was discharged into ice water. The crude product was washed five times with distilled water and ethanol, and then dried under vacuum to obtain an aromatic diamine with the following structure. The infrared spectrum of the aromatic diamine is shown in the following figure. Figure 1 shown.

[0048]

[0049] The main process of the above reaction is as follows:

[0050]

[0051] (2) Preparation and application of aromatic diamine / epoxy resin anticorrosive coatings

[0052] Weigh 12.4g of bisphenol A epoxy resin E51, 10g of aromatic diamine, 3.1g of carbon black, and 11g of a diluent (N-methylpyrrolidone, N,N-dimethylacetamide, toluene, and butanone in a weight ratio of 8:4:4:1). Grind the mixture at 5000 r / min for 5 hours. Then, add the dispersion to a dispersing tank and grind it at 2000 r / min for 2 hours to produce an epoxy resin anti-corrosion coating.

[0053] The viscosity of the coating was adjusted by adding a thinner (apply 4 cups for 70 seconds), and then the coating with appropriate viscosity was sprayed onto the sandblasted metal substrate using an air spray gun and an air compressor. After the surface was dried at 80°C for 20 minutes, the temperature was raised to 150°C and cured for 2 hours to obtain the coating. The TGA curve of the anti-corrosion coating is shown in Figure 2. Figure 2 The impedance changes of the coated sample after being immersed in 3.5wt% NaCl solution for different days are shown in Figure 3 The cross-sectional morphology of the coating is shown in Figure 4 shown.

[0054] Table 1 Coating performance data of Example 1

[0055]

[0056]

[0057] Example 2

[0058] This embodiment provides a method for preparing an aromatic diamine curing agent, and the preparation and coating of an aromatic diamine / epoxy resin anti-corrosion coating.

[0059] (1) Preparation of aromatic diamines:

[0060] Under a nitrogen atmosphere, a three-necked flask equipped with a mechanical stirrer, thermometer, water trap, and condenser was charged with 1.8621 g of 4,4'-dihydroxybiphenyl, 5.8866 g of 4,4'-dichlorodiphenyl sulfone, and 2.2114 g of anhydrous potassium carbonate. 50 mL of N-methylpyrrolidone (NMP) was used as the reaction solvent, and 20 mL of toluene was added as a water trap. The system was heated to 150°C to trap water for 4 hours, toluene was evaporated, and the temperature was raised to 200°C for 8 hours. The reaction system was then cooled to 80°C, and 2.2372 g of p-hydroxyaniline and 20 mL of toluene were added. The temperature was then raised to 150°C to trap water for 4 hours, toluene was evaporated, and the temperature was raised to 180°C for 6 hours. Finally, the temperature was cooled to 100°C and discharged into ice water to yield the product. The crude product was washed eight times with distilled water and eight times with ethanol, then dried under vacuum to yield the aromatic diamine with the following structure.

[0061]

[0062] The main process of the above reaction is as follows:

[0063]

[0064] (2) Preparation and application of aromatic diamine / epoxy resin anticorrosive coatings

[0065] Weigh 13g of bisphenol A epoxy resin E44, 10g of aromatic diamine, 2.3g of titanium dioxide, and 25g of a diluent (N-methylpyrrolidone, N,N-dimethylacetamide, toluene, and butanone in a weight ratio of 8:4:4:1). Grind the mixture at 5000 r / min for 5 hours. Then, add the dispersion to a dispersing tank and grind it at 2000 r / min for 2 hours to produce an epoxy resin anti-corrosion coating.

[0066] The viscosity of the coating was adjusted by adding a thinner (apply 4 cups for 50 seconds), and then the coating with appropriate viscosity was sprayed onto the sandblasted metal substrate using an air spray gun and an air compressor. After the surface was dried at 90°C for 25 minutes, the temperature was raised to 160°C and cured for 3 hours to obtain the coating.

[0067] Table 2 Coating performance data of Example 2

[0068]

[0069] Example 3

[0070] This embodiment provides a method for preparing an aromatic diamine curing agent, and the preparation and coating of an aromatic diamine / epoxy resin anti-corrosion coating.

[0071] (1) Preparation of aromatic diamines:

[0072] Under a nitrogen atmosphere, a three-necked flask equipped with a mechanical stirrer, thermometer, water collector, and condenser was charged with 2.6278g of 4,4'-dihydroxydiphenyl sulfone, 6.3173g of 4,4'-dichlorodiphenyl sulfone, 2.4009g of p-hydroxyaniline, and 3.0360g of anhydrous potassium carbonate. 35mL of N-methylpyrrolidone (NMP) was used as the reaction solvent, and 20mL of toluene was added as a water collector. The system temperature was raised to 130°C to remove the water for 4 hours. The toluene was then evaporated, and the reaction temperature was raised to 180°C for 6 hours. The reaction was then cooled to 100°C and discharged into ice water to obtain the product. The crude product was washed five times with distilled water and five times with ethanol. After vacuum drying, the aromatic diamine with the structure shown below was obtained.

[0073]

[0074] The main process of the above reaction is as follows:

[0075]

[0076] (2) Preparation and application of aromatic diamine / epoxy resin anticorrosive coatings

[0077] Weigh 26.8g of bisphenol A epoxy resin E20, 10g of aromatic diamine, 4.7g of graphite, and 97g of a diluent (N-methylpyrrolidone, N,N-dimethylacetamide, toluene, and butanone in a weight ratio of 8:4:4:1). Grind the mixture at 5000 r / min for 5 hours. Then, add the dispersion to a dispersing tank and grind it at 2000 r / min for 2 hours to produce an epoxy resin anti-corrosion coating.

[0078] The viscosity of the coating was adjusted by adding a thinner (apply 4 cups for 60 seconds), and then the coating with appropriate viscosity was sprayed onto the sandblasted metal substrate using an air spray gun and an air compressor. After the surface was dried at 100°C for 30 minutes, the temperature was raised to 170°C and cured for 3 hours to obtain the coating.

[0079] Table 3 Coating performance data of Example 3

[0080]

[0081] Example 4

[0082] This embodiment provides a method for preparing an aromatic diamine curing agent, and the preparation and coating of an aromatic diamine / epoxy resin anti-corrosion coating.

[0083] (1) Preparation of aromatic diamines:

[0084] Under a nitrogen atmosphere, a three-necked flask equipped with a mechanical stirrer, thermometer, water collector, and condenser was charged with 3.1942 g of 4,4'-(hexafluoroisopropylidene)diphenol, 5.4559 g of 4,4'-dichlorodiphenyl sulfone, 2.0735 g of p-hydroxyaniline, and 1.3821 g of anhydrous potassium carbonate. 16 mL of N-methylpyrrolidone (NMP) was used as the reaction solvent, and 5 mL of toluene was added as a water collector. The system temperature was raised to 130°C to remove the water for 4 hours. The toluene was then evaporated, and the reaction temperature was raised to 180°C for 6 hours. The reaction was then cooled to 100°C and discharged into ice water to yield the product. The crude product was washed five times with distilled water and five times with ethanol. After vacuum drying, the aromatic diamine with the following structure was obtained.

[0085]

[0086] The main process of the above reaction is as follows:

[0087]

[0088] (2) Preparation and application of aromatic diamine / epoxy resin anticorrosive coatings

[0089] Weigh 16.3g of bisphenol A epoxy resin E03, 1g of aromatic diamine, 1.8g of lamellar pearl powder, and 45g of a diluent (N-methylpyrrolidone, N,N-dimethylacetamide, toluene, and butanone in a weight ratio of 8:4:4:1). Grind the mixture at 5000 r / min for 5 hours. Then, add the dispersion to a dispersing tank and grind it at 2000 r / min for 2 hours to produce an epoxy resin anti-corrosion coating.

[0090] The viscosity of the coating was adjusted by adding a thinner (apply 4 cups for 70 seconds), and then the coating with appropriate viscosity was sprayed onto the sandblasted metal substrate using an air spray gun and an air compressor. After the surface was dried at 100°C for 30 minutes, the temperature was raised to 180°C and cured for 5 hours to obtain the coating.

[0091] Table 4 Coating performance data of Example 4

[0092]

[0093]

[0094] Example 5

[0095] This embodiment provides a method for preparing an aromatic diamine curing agent, and the preparation and coating of an aromatic diamine / epoxy resin anti-corrosion coating.

[0096] (1) Preparation of aromatic diamines:

[0097] Under a nitrogen atmosphere, a three-necked flask equipped with a mechanical stirrer, thermometer, water trap, and condenser was charged with 1.1011 g of hydroquinone, 2.8516 g of 2,6'-difluorobenzonitrile, and 2.2114 g of anhydrous potassium carbonate. 56 mL of N-methylpyrrolidone (NMP) was used as the reaction solvent, and 12 mL of toluene was added as a water trap. The system was heated to 130°C to trap water for 4 hours, toluene was evaporated, and the reaction temperature was raised to 180°C for 6 hours. The reaction system was then cooled to 110°C, and 2.2372 g of p-hydroxyaniline and 12 mL of toluene were added. The temperature was then raised to 120°C to trap water for 4 hours, toluene was evaporated, and the reaction temperature was raised to 200°C for 6 hours. Finally, the temperature was lowered to 90°C and discharged into ice water to yield the product. The crude product was washed eight times with distilled water and eight times with ethanol, then dried under vacuum to yield the aromatic diamine shown in the following formula.

[0098]

[0099] The main process of the above reaction is as follows:

[0100]

[0101] (2) Preparation and application of aromatic diamine / epoxy resin anticorrosive coatings

[0102] Weigh 30.4g of bisphenol A epoxy resin E03, 1g of aromatic diamine, 7.6g of titanium dioxide, and 91g of a diluent (N-methylpyrrolidone, N,N-dimethylacetamide, toluene, and butanone in a weight ratio of 8:4:4:1). Grind the mixture at 5000 r / min for 5 hours. Then, add the dispersion to a dispersing tank and grind it at 2000 r / min for 2 hours to produce an epoxy resin anti-corrosion coating.

[0103] The viscosity of the coating was adjusted by adding a thinner (apply 4 cups for 70 seconds), and then the coating with appropriate viscosity was sprayed onto the sandblasted metal substrate using an air spray gun and an air compressor. After the surface was dried at 100°C for 30 minutes, the temperature was raised to 180°C and cured for 5 hours to obtain the coating.

[0104] Table 5 Coating performance data of Example 5

[0105]

[0106] Example 6

[0107] This embodiment provides a method for preparing an aromatic diamine curing agent, and the preparation and coating of an aromatic diamine / epoxy resin anti-corrosion coating.

[0108] (1) Preparation of aromatic diamines:

[0109] Under a nitrogen atmosphere, a three-necked flask equipped with a mechanical stirrer, thermometer, water trap, and condenser was charged with 1.9552 g of 4,4'-dihydroxybiphenyl, 3.0602 g of 2,6'-difluorobenzonitrile, and 3.0406 g of anhydrous potassium carbonate. 37 mL of N-methylpyrrolidone (NMP) was used as the reaction solvent, and 15 mL of toluene was added as a water trap. The system was heated to 130°C to trap water for 4 hours, toluene was evaporated, and the reaction temperature was raised to 180°C for 6 hours. The reaction system was then cooled to 100°C, and 2.4009 g of p-hydroxyaniline and 15 mL of toluene were added. The temperature was then raised to 130°C to trap water for 4 hours, toluene was evaporated, and the reaction temperature was raised to 150°C for 8 hours. Finally, the temperature was lowered to 70°C and the product was discharged into ice water. The crude product was washed six times with distilled water and six times with ethanol, then dried under vacuum to yield the aromatic diamine shown in the following formula.

[0110]

[0111] The main process of the above reaction is as follows:

[0112]

[0113] (2) Preparation and application of aromatic diamine / epoxy resin anticorrosive coatings

[0114] Weigh 40g of bisphenol A epoxy resin E20, 10g of aromatic diamine, 7.1g of mica iron oxide, and 133g of a diluent (N-methylpyrrolidone, N,N-dimethylacetamide, toluene, and butanone in a weight ratio of 8:4:4:1). Grind the mixture at 5000 r / min for 5 hours. Then, add the dispersion to a dispersing tank and grind it at 2000 r / min for 2 hours to produce an epoxy resin anti-corrosion coating.

[0115] The viscosity of the coating was adjusted by adding a thinner (apply 4 cups for 60 seconds), and then the coating with appropriate viscosity was sprayed onto the sandblasted metal substrate using an air spray gun and an air compressor. After the surface was dried at 100°C for 30 minutes, the temperature was raised to 180°C and cured for 4 hours to obtain the coating.

[0116] Table 6 Coating performance data of Example 6

[0117]

[0118] Example 7

[0119] This embodiment provides a method for preparing an aromatic diamine curing agent, and the preparation and coating of an aromatic diamine / epoxy resin anti-corrosion coating.

[0120] (1) Preparation of aromatic diamines:

[0121] Under a nitrogen atmosphere, a three-necked flask equipped with a mechanical stirrer, thermometer, water collector, and condenser was charged with 2.3776g of 4,4'-dihydroxydiphenyl sulfone, 2.6429g of 2,6'-difluorobenzonitrile, 2.0735g of p-hydroxyaniline, and 1.3821g of anhydrous potassium carbonate. 22mL of N-methylpyrrolidone (NMP) was used as the reaction solvent, and 12mL of toluene was added as a water carrier. The system temperature was raised to 150°C to carry out the water reaction for 4 hours. The toluene was then evaporated, and the reaction temperature was raised to 180°C for 6 hours. The reaction was then cooled to 50°C and discharged into ice water to yield the product. The crude product was washed six times with distilled water and six times with ethanol, then dried under vacuum to yield the aromatic diamine shown in the following formula.

[0122]

[0123] The main process of the above reaction is as follows:

[0124]

[0125] (2) Preparation and application of aromatic diamine / epoxy resin anticorrosive coatings

[0126] Weigh 16.4g of bisphenol A epoxy resin E44, 10g of aromatic diamine, 2.9g of graphite, and 29g of a diluent (N-methylpyrrolidone, N,N-dimethylacetamide, toluene, and butanone in a weight ratio of 8:4:4:1). Grind the mixture at 5000 r / min for 5 hours. Then, add the dispersion to a dispersing tank and grind it at 2000 r / min for 2 hours to produce an epoxy resin anti-corrosion coating.

[0127] The viscosity of the coating was adjusted by adding a thinner (apply 4 cups for 50 seconds), and then the coating with appropriate viscosity was sprayed onto the sandblasted metal substrate using an air spray gun and an air compressor. After the surface was dried at 90°C for 25 minutes, the temperature was raised to 160°C and cured for 3 hours to obtain the coating.

[0128] Table 7 Coating performance data of Example 7

[0129]

[0130]

[0131] Example 8

[0132] This embodiment provides a method for preparing an aromatic diamine curing agent, and the preparation and coating of an aromatic diamine / epoxy resin anti-corrosion coating.

[0133] (1) Preparation of aromatic diamines:

[0134] Under a nitrogen atmosphere, a three-necked flask equipped with a mechanical stirrer, thermometer, water trap, and condenser was charged with 3.3623 g of 4,4'-(hexafluoroisopropylidene)diphenol, 2.8516 g of 2,6'-difluorobenzonitrile, 2.2372 g of p-hydroxyaniline, and 2.2114 g of anhydrous potassium carbonate. 13 mL of N-methylpyrrolidone (NMP) was used as the reaction solvent, and 6 mL of toluene was added as a water trap. The system temperature was raised to 130°C to trap water for 4 hours, to remove the toluene, and the reaction temperature was raised to 150°C for 8 hours. The reaction temperature was then lowered to 60°C and discharged into ice water to yield the product. The crude product was washed five times with distilled water and five times with ethanol, then dried under vacuum to yield the aromatic diamine shown in the following formula.

[0135]

[0136] The main process of the above reaction is as follows:

[0137]

[0138] (2) Preparation and application of aromatic diamine / epoxy resin anticorrosive coatings

[0139] Weigh 12.5g of bisphenol A epoxy resin E51, 10g of aromatic diamine, 1.4g of carbon black, and 10.2g of a diluent (N-methylpyrrolidone, N,N-dimethylacetamide, toluene, and butanone in a weight ratio of 8:4:4:1). Grind the mixture at 5000 r / min for 5 hours. Then, add the dispersion to a dispersing tank and grind it at 2000 r / min for 2 hours to produce an epoxy resin anti-corrosion coating.

[0140] The viscosity of the coating was adjusted by adding a thinner (apply 4 cups for 70 seconds), and then the coating with appropriate viscosity was sprayed onto the sandblasted metal substrate using an air spray gun and an air compressor. After the surface was dried at 80°C for 20 minutes, the temperature was raised to 150°C and cured for 2 hours to obtain the coating.

[0141] Table 8 Coating performance data of Example 8

[0142]

[0143] Comparative Example 1

[0144] This comparative example differs from Example 2 in that 4,4-diaminodiphenyl sulfone was used instead of the aromatic diamine in Example 2. The coating prepared in this comparative example was tested for basic performance and corrosion resistance. The coating was prepared using 44g of bisphenol A epoxy resin E44, 10g of 4,4-diaminodiphenyl sulfone, 7.8g of titanium dioxide, and 62g of diluent.

[0145] Table 9 Coating performance data of Comparative Example 1

[0146]

[0147] Comparative Example 2

[0148] This comparative example differs from Example 2 in that a commercial modified aliphatic amine epoxy curing agent R-2210 is used instead of the aromatic diamine in Example 2. The following ingredients are used: 28g of bisphenol A epoxy resin E44, 10g of modified aliphatic amine epoxy curing agent R-2210, 5g of titanium dioxide, and 43g of diluent. Basic performance and corrosion resistance tests were performed on the coating prepared in this comparative example.

[0149] Table 10 Coating performance data of comparative example 2

[0150]

[0151] Depend on Figure 1 The infrared spectrum in FIG clearly shows the characteristic absorption peak of the amino group, indicating that the aromatic diamine described in Example 1 was successfully synthesized.

[0152] Depend on Figure 2The thermal weight loss curve of the medium aromatic diamine / epoxy resin anti-corrosion coating can show that the epoxy resin is cured and the cured coating has excellent thermal stability.

[0153] Depend on Figure 3 The electrochemical impedance spectroscopy Bode diagram of the aromatic diamine / epoxy resin anti-corrosion coating shows that the impedance value of the coating is still significantly higher than 10 in the low frequency region after being immersed in 3.5wt% NaCl solution for 30 days. 9 Ω·cm 2 , indicating that the coating still has good anti-corrosion performance on the metal substrate.

[0154] Depend on Figure 4 From the cross-sectional electron microscope photograph of the aromatic diamine / epoxy resin anti-corrosion coating, it can be seen that the prepared coating has a relatively smooth and dense micromorphology and structure, which can have a good barrier effect on corrosive media, thereby achieving effective protection for the metal substrate.

[0155] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0156] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. An aromatic diamine epoxy resin curing agent, It is characterized in that Including the structure shown in formula (I): Wherein A is one of the structures shown in A1 to A7; B is one of the structures shown in B1 to B4:

2. A method for preparing an aromatic diamine epoxy resin curing agent, It is characterized in that Under the action of a salt-forming agent, aromatic diphenol monomers, aromatic dihalide monomers and p-hydroxyaniline monomers undergo a nucleophilic substitution reaction in a polar aprotic solvent to obtain aromatic diamine molecules.

3. A method for preparing an aromatic diamine epoxy resin curing agent according to claim 2, It is characterized in that The aromatic diphenol monomer is one of the structures shown in R1 to R7; The aromatic dihalide is one of the structures shown in Y1 to Y4, wherein X is a halogen, preferably F or Cl:

4. A method for preparing an aromatic diamine epoxy resin curing agent according to claim 2, It is characterized in that The preparation method includes two schemes: Option A: Under an inert gas environment, an aromatic diphenol monomer, an aromatic dihalide monomer, a salt-forming agent, a polar aprotic solvent and a water-carrying agent are added to a reactor equipped with a mechanical stirring device, a thermometer, a water-carrying agent and a condenser, the reaction system is heated to 120-150° C., refluxed and continuously stirred for 3-6 hours, the water-carrying agent is removed, the temperature is raised to 150-220° C., the reaction is carried out for 6-10 hours, the temperature is lowered to 50-110° C., a quantitative amount of p-hydroxyaniline and toluene are added to the system, the reaction system is reheated to 120-150° C., refluxed and continuously stirred for 3-6 hours, the water-carrying agent is removed, the temperature is raised to 150-220° C., the reaction is carried out for 6-10 hours, the temperature is lowered to 50-110° C., the product is discharged in ice water to obtain the product, the product is washed 3-8 times with distilled water and ethanol respectively, and the monomer powder is obtained after drying; Option B: In an inert gas environment, an aromatic diphenol monomer, an aromatic dihalide monomer, p-hydroxyaniline, a salt-forming agent and a polar aprotic solvent are added to a reactor equipped with a mechanical stirring device, a thermometer, a water-carrying agent and a condenser, the reaction system is heated to 130-150° C., refluxed and continued to stir for 3-6 hours, the water-carrying agent is removed, the temperature is raised to 150-220° C., the reaction is carried out for 6-10 hours, the temperature is lowered to 50-110° C., the material is discharged into ice water to obtain a product, the obtained product is washed with distilled water and ethanol for 3-8 times respectively, and the monomer powder is obtained after drying.

5. A method for preparing an aromatic diamine epoxy resin curing agent according to claim 2, It is characterized in that The molar ratio of the aromatic diphenol monomer, the aromatic dihalide monomer, the p-hydroxyaniline and the salt-forming agent is (0.95-1.05): (1.90-2.20): (1.90-2.20): (1.00-2.20).

6. A method for preparing an aromatic diamine epoxy resin curing agent according to claim 4, It is characterized in that In the two schemes, the salt-forming agent is one or more of potassium carbonate, sodium carbonate, lithium carbonate, cesium carbonate, potassium bicarbonate, and sodium bicarbonate; The polar aprotic solvent includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, diphenyl sulfone and sulfolane; The water-carrying agent is one of toluene and cyclohexane; The usage amount of the polar aprotic solvent is 1.5 to 9 times of the total mass of all monomers, and the addition amount of the water-carrying agent is 20 to 60% of the volume of the solvent.

7. An aromatic diamine epoxy resin anti-corrosion coating, It is characterized in that The curing agent is prepared by using the aromatic diamine curing agent described in claim 1 and epoxy resin.

8. A method for preparing an aromatic diamine epoxy resin anticorrosion coating, It is characterized in that The method comprises the following steps: weighing epoxy resin, aromatic diamine curing agent, diluent and filler, and dispersing and grinding them for 0.5 to 6 hours at a rotating speed of 2000 to 5000 r / min using a sand mill to obtain epoxy resin anti-corrosion coating.

9. The method for preparing an aromatic diamine epoxy resin anticorrosion coating according to claim 8, It is characterized in that The mass ratio of the epoxy resin, aromatic diamine curing agent, filler and diluent is (7-58): (1-40): (5-15): (30-70); The epoxy resin is one or more of phenolic epoxy resin, bisphenol A epoxy resin, bisphenol F epoxy resin, 4,4'-diaminodiphenylmethane epoxy resin, and bisphenol S epoxy resin; The filler is one or more of carbon black, iron black, iron red, mica iron oxide, manganese black, chromium trioxide, titanium dioxide, lamellar pearl powder, organic bentonite, montmorillonite, and fumed silica; The diluent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, toluene, acetone, butanone, cyclohexanone and n-butanol.

10. A coating method for an aromatic diamine epoxy resin anticorrosion coating, It is characterized in that The method comprises the following steps: adjusting the viscosity of the coating by adding a diluent, spraying the coating onto a metal substrate treated with sandblasting by using an air spray gun and an air compressor, drying at 80-100° C. for 0.2-1 h, heating to 150-180° C. for curing for 2-6 h, and finally obtaining an anti-corrosion coating.

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