A waterborne epoxy primer-surfacematerial and its preparation method and application

Abstract

This invention belongs to the field of coating technology, and specifically relates to a waterborne epoxy topcoat coating, its preparation method, and its application. The coating of this invention comprises component A and component B; component A includes a waterborne epoxy emulsion, a film-forming aid, and a salt spray resistant aid; component B includes an amine curing agent and additives; the amine curing agent is obtained by end-capping with a capping agent using polyamine, bisphenol A epoxy resin, and polyethylene glycol diglycidyl ether as the main chain segments; the epoxy value of the bisphenol A epoxy resin is greater than or equal to 0.48 eq / 100g. This invention uses polyamine, bisphenol A epoxy resin, and polyethylene glycol diglycidyl ether as the main chain segments, and end-capping with a capping agent to obtain the amine curing agent. The introduction of specific types of epoxy resin not only improves the compatibility between the amine curing agent and the waterborne epoxy emulsion and enhances gloss, but also increases the permeability of the film-forming material and enhances adhesion to multiple substrates. Simultaneously, combined with other components, the coating exhibits excellent protective properties.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, and specifically relates to a water-based epoxy topcoat coating, its preparation method, and its application. Background Technology

[0002] As one of the most commonly used modes of transportation, automobiles operate in complex and varied environments, often resulting in significant corrosion. Protecting the engine, the power source of the vehicle, to reduce or even prevent corrosion is crucial for the safe operation of the car.

[0003] Engine protection involves a wide variety of substrates, including cast iron, aluminum alloys, nylon composite fiberglass materials, various smooth machined surfaces, plastics, electrophoretic substrates, and powder substrates. This characteristic presents a significant challenge for engine protective coatings, as effective protection against these diverse substrates requires excellent adhesion between the protective coating and each substrate. For a long time, oil-based coatings have dominated the market due to their performance and price advantages. However, oil-based coatings emit large amounts of volatile organic compounds (VOCs) during use, causing serious environmental damage. Therefore, engine coatings have gradually shifted from oil-based to water-based coatings. However, current water-based coatings still suffer from poor adhesion to multiple substrates and poor corrosion resistance, failing to adequately meet the protection requirements of engines.

[0004] Therefore, it is of great significance to provide a coating that has good adhesion to multiple substrates and good anti-corrosion performance. Summary of the Invention

[0005] The present invention aims to solve one or more technical problems existing in the prior art, and at least provide a beneficial solution. Specifically, the present invention provides a water-based epoxy primer-topcoat coating that has good adhesion to multiple substrates and good anti-corrosion properties, thus achieving a good protective effect.

[0006] The inventive concept of this invention: The coating of this invention comprises component A and component B; component A includes an aqueous epoxy emulsion, a film-forming aid, and a salt spray resistant aid; component B includes an amine curing agent and additives; the amine curing agent is obtained by end-capping with a capping agent, using polyamine, bisphenol A epoxy resin, and polyethylene glycol diglycidyl ether as the main chain segments; the epoxy value of the bisphenol A epoxy resin is greater than or equal to 0.48 eq / 100g. This invention utilizes the reaction of epoxy groups with primary amine hydrogen, using polyamine, bisphenol A epoxy resin, and polyethylene glycol diglycidyl ether as the main chain segments, and end-capping with a capping agent to obtain the amine curing agent. The introduction of specific types of epoxy resins can not only improve the compatibility between the amine curing agent and the aqueous epoxy emulsion and enhance gloss, but also increase the permeability of the film-forming material and enhance adhesion to multiple substrates. Combined with other components, the coating exhibits excellent anti-corrosion properties, providing good protection for engines.

[0007] Therefore, a first aspect of the present invention provides a waterborne epoxy topcoat combined with a coating.

[0008] Specifically, the waterborne epoxy topcoat coating comprises component A and component B;

[0009] Component A includes an aqueous epoxy emulsion, a film-forming aid, and a salt spray resistant aid;

[0010] Component B includes amine curing agents and additives;

[0011] The amine curing agent is obtained by using a capping agent to end-cap the main chain segments of polyamine, bisphenol A epoxy resin, and polyethylene glycol diglycidyl ether.

[0012] The epoxy value of the bisphenol A type epoxy resin is greater than or equal to 0.48 eq / 100g.

[0013] Preferably, the ratio of epoxy equivalent in component A to active hydrogen equivalent in component B is (1.1-1.5):1.

[0014] More preferably, the ratio of the epoxy equivalent in component A to the active hydrogen equivalent in component B is (1.2-1.4):1.

[0015] Preferably, the epoxy value of the bisphenol A type epoxy resin is 0.48-0.58 eq / 100g; more preferably, the epoxy value of the bisphenol A type epoxy resin is 0.48-0.54 eq / 100g.

[0016] Preferably, the bisphenol A type epoxy resin is epoxy resin E-51.

[0017] Preferably, the aqueous epoxy emulsion includes at least one of a solid epoxy emulsion, a liquid epoxy emulsion, and an acrylic-modified epoxy emulsion; when the aqueous epoxy emulsion includes a solid epoxy emulsion and an acrylic-modified epoxy emulsion, the amount of the solid epoxy emulsion is greater than the amount of the acrylic-modified epoxy emulsion.

[0018] Preferably, the film-forming aid comprises an ether ester solvent; more preferably, the film-forming aid comprises dipropylene glycol butyl ether (DPNB).

[0019] Preferably, the salt spray resistant additive comprises a compound of phosphate and organic matter.

[0020] Preferably, the polyamine includes triethylenetetramine (TETA).

[0021] Preferably, the capping agent comprises n-butyl glycidyl ether (BGE).

[0022] Preferably, component A further includes at least one of a thickener and water.

[0023] Preferably, the thickener comprises a polyurethane thickener.

[0024] Preferably, component B further includes water; the additives include at least one of defoamer, wetting agent, leveling agent, anti-flash rust additive, and cosolvent.

[0025] More preferably, the additives include defoamers, wetting agents, leveling agents, anti-flash rust additives, and solubilizers.

[0026] Preferably, the defoamer includes an organosilicone defoamer.

[0027] Preferably, the wetting agent includes an organosilicon wetting agent; more preferably, the wetting agent is Tego4100, which is a polyether-modified organosilicon with a twin-star structure, which can significantly reduce the surface tension of the coating, prevent pinholes, help improve the adhesion of the coating, and also improve the surface smoothness and gloss of the coating.

[0028] Preferably, the leveling agent comprises an organosilicon leveling agent.

[0029] Preferably, the anti-flash rust additive comprises at least one of nitrite, molybdate, multi-organometallic chelate, and multifunctional phosphate polymer.

[0030] Preferably, the co-solvent comprises ethylene glycol butyl ether (BCS).

[0031] Preferably, the coating comprises component A and component B; component A comprises an aqueous epoxy emulsion, a film-forming aid, a salt spray resistant aid, a thickener, and water; component B comprises an amine curing agent, a defoamer, a wetting agent, a leveling agent, an anti-flash rust aid, a co-solvent, and water; and by weight, component A comprises 65-85 parts of aqueous epoxy emulsion, 3.5-5.5 parts of film-forming aid, 0.9-2.2 parts of salt spray resistant aid, 0.9-2.2 parts of thickener, and 14-28 parts of water; component B comprises 35-55 parts of amine curing agent, 0.5-1.1 parts of defoamer, 0.5-1.1 parts of wetting agent, 0.5-1.1 parts of leveling agent, 2.5-4.5 parts of anti-flash rust aid, 9-16 parts of co-solvent, and 25-45 parts of water.

[0032] More preferably, the coating comprises component A and component B; component A comprises an aqueous epoxy emulsion, a film-forming aid, a salt spray resistant aid, a thickener, and water; component B comprises an amine curing agent, a defoamer, a wetting agent, a leveling agent, an anti-flash rust aid, a co-solvent, and water; and by weight, component A comprises 70-80 parts of aqueous epoxy emulsion, 4-5 parts of film-forming aid, 1-2 parts of salt spray resistant aid, 1-2 parts of thickener, and 15-25 parts of water; component B comprises 40-50 parts of amine curing agent, 0.5-1 part of defoamer, 0.5-1 part of wetting agent, 0.5-1 part of leveling agent, 3-4 parts of anti-flash rust aid, 10-15 parts of co-solvent, and 30-40 parts of water.

[0033] Preferably, the mass ratio of component A to component B is 2.5-5.5:1; more preferably, the mass ratio of component A to component B is 3-5:1.

[0034] A second aspect of the present invention provides a method for preparing the waterborne epoxy primer-topcoat combined coating described in the first aspect of the present invention.

[0035] Specifically, the preparation method of the waterborne epoxy primer-topcoat integrated coating includes the following steps:

[0036] (1) Mix the raw material components of component A to obtain component A;

[0037] (2) Mix the raw material components of component B to obtain component B;

[0038] The coating is prepared by mixing component A and component B.

[0039] Preferably, step (1) specifically involves mixing the aqueous epoxy emulsion, film-forming aid, salt spray resistant aid, and water, performing a first dispersion, then adding a thickener, performing a second dispersion, adjusting the viscosity, and obtaining component A.

[0040] Preferably, the rotation speed of the first dispersion is 700-1100 rpm, and the dispersion time is 9-17 min; more preferably, the rotation speed of the first dispersion is 750-1000 rpm, and the dispersion time is 10-15 min.

[0041] Preferably, the rotation speed of the second dispersion is 450-800 rpm, and the dispersion time is 9-17 min; more preferably, the rotation speed of the second dispersion is 500-750 rpm, and the dispersion time is 10-15 min.

[0042] Preferably, the viscosity is adjusted to 60-90 kDa; more preferably, the viscosity is adjusted to 70-80 kDa.

[0043] Preferably, in step (2), the mixing is carried out by stirring and dispersing.

[0044] Preferably, the stirring and dispersing speed is 700-1100 rpm, and the stirring and dispersing time is 9-17 min; more preferably, the stirring and dispersing speed is 750-1000 rpm, and the stirring and dispersing time is 10-15 min.

[0045] Preferably, the preparation method of the amine curing agent includes the following steps:

[0046] A polyamine, bisphenol A epoxy resin, and polyethylene glycol diglycidyl ether are mixed and subjected to a first reaction. Then, a capping agent is added and a second reaction is carried out to obtain the amine curing agent.

[0047] Preferably, the temperature of the first reaction is 55-75℃ and the reaction time is 3-5 hours; more preferably, the temperature of the first reaction is 60-70℃ and the reaction time is 3.5-4.5 hours; even more preferably, the temperature of the first reaction is 65℃ and the reaction time is 4 hours.

[0048] Preferably, the temperature of the second reaction is 55-75℃ and the time of the second reaction is 1.5-3.5h; more preferably, the temperature of the second reaction is 60-70℃ and the time of the second reaction is 2-3h; even more preferably, the temperature of the second reaction is 65℃ and the time of the second reaction is 2.5h.

[0049] Specifically, the amine curing agent described in this invention is crucial for improving the adhesion between coatings and various substrates. This invention utilizes the reaction of epoxy groups with primary amine hydrogen, using polyamines, bisphenol A type epoxy resin, and polyethylene glycol diglycidyl ether (PEGDGE) as the main chain segments, and end-capping with a capping agent to obtain the amine curing agent. Introducing a specific bisphenol A type epoxy resin into the curing agent not only improves the compatibility between the amine curing agent and the epoxy emulsion and enhances gloss, but also increases the permeability of the film-forming material and strengthens adhesion to the substrate.

[0050] A third aspect of the present invention provides an engine.

[0051] Specifically, the engine includes a coating formed by the water-based epoxy primer-topcoat integrated coating described in the first aspect of the present invention.

[0052] Compared with the prior art, the beneficial effects of the technical solution provided by the present invention are as follows:

[0053] (1) This invention utilizes the reaction of epoxy groups with primary amine hydrogen to prepare an amine curing agent by using polyamines, bisphenol A type epoxy resin, and polyethylene glycol diglycidyl ether as the main chain segments and end-capping with a capping agent. The introduction of specific types of epoxy resins can not only improve the compatibility between amine curing agents and waterborne epoxy emulsions and enhance gloss, but also increase the permeability of the film-forming material and enhance adhesion to multiple substrates. At the same time, combined with the synergistic effect of other components, the coating can simultaneously possess good anti-corrosion properties, achieving good protection for engines.

[0054] (2) In this invention, when the aqueous epoxy emulsion includes a solid epoxy emulsion and an acrylic-modified epoxy emulsion, the amount of solid epoxy emulsion used is greater than that of acrylic-modified epoxy emulsion, which can improve the appearance gloss, hardness, and damp heat resistance of the coating. In addition, the use of specific salt spray resistant additives in this invention can improve the salt spray resistance of the coating.

[0055] (3) The preparation process of this invention is simple and easy to apply in large-scale production. Detailed Implementation

[0056] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0057] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0058] The raw material information for Examples 1-4 and Comparative Examples 1-4 of the present invention is shown in Table 1.

[0059] Table 1: Raw material information for Examples 1-4 and Comparative Examples 1-4 of the present invention

[0060]

[0061] In Table 1, "-" indicates "not tested".

[0062] Example 1

[0063] A water-based epoxy topcoat coating, the composition and dosage of which are shown in Table 2.

[0064] Table 2: Composition and dosage of waterborne epoxy primer and topcoat combined coating in Example 1

[0065]

[0066]

[0067] A method for preparing a waterborne epoxy primer-topcoat integrated coating includes the following steps:

[0068] (1) Mix the waterborne epoxy emulsion, film-forming aid, salt spray resistant aid and deionized water, disperse at 750 rpm for 12 min, then add thickener, disperse at 500 rpm for 12 min, adjust the viscosity to 75 kDa, mix evenly to obtain component A.

[0069] (2) Mix all the raw material components of component B evenly and disperse them at a speed of 750 rpm for 12 min to obtain component B; mix component A and component B obtained in step (1) evenly to obtain a water-based epoxy topcoat coating.

[0070] The preparation method of the amine curing agent in component B includes the following steps:

[0071] Add TETA to a four-necked flask, heat to 65°C, and then add a mixture of E-51 and PEGDGE dropwise while stirring. The molar ratio of TETA to epoxy resin E-51 is 2.2:1. The addition is completed within 2 hours, and the reaction continues for another 2 hours to obtain an epoxy polyamine adduct. Excess polyamine is removed by vacuum distillation. Add the end-capping agent BGE dropwise to the adduct. After the addition is complete, react at 65°C for 2 hours. Add distilled water to the product, stir for 1 hour, and then stop stirring to obtain an amine curing agent.

[0072] Example 2

[0073] A water-based epoxy topcoat coating, the composition and dosage of which are shown in Table 3.

[0074] Table 3: Composition and dosage of waterborne epoxy primer and topcoat combined coating in Example 2

[0075]

[0076]

[0077] A method for preparing a waterborne epoxy primer-topcoat integrated coating includes the following steps:

[0078] (1) Mix the waterborne epoxy emulsion, film-forming aid, salt spray resistant aid and deionized water, disperse at 900 rpm for 10 min, then add thickener, disperse at 600 rpm for 10 min, adjust the viscosity to 75 kDa, mix evenly to obtain component A.

[0079] (2) Mix all the raw material components of component B evenly and disperse them at a speed of 900 rpm for 10 min to obtain component B; mix component A and component B obtained in step (1) evenly to obtain a water-based epoxy topcoat coating.

[0080] In component B, the amine curing agent is prepared using the same method as in Example 1.

[0081] Example 3

[0082] A water-based epoxy topcoat coating, the composition and dosage of which are shown in Table 4.

[0083] Table 4: Composition and dosage of the waterborne epoxy primer-topcoat combined coating in Example 3

[0084]

[0085]

[0086] A method for preparing a waterborne epoxy primer-topcoat integrated coating includes the following steps:

[0087] (1) Mix the waterborne epoxy emulsion, film-forming aid, salt spray resistant aid and deionized water, disperse at 1000 rpm for 10 min, then add thickener, disperse at 750 rpm for 10 min, adjust the viscosity to 80 kDa, mix evenly to obtain component A.

[0088] (2) Mix all the raw material components of component B evenly and disperse them for 10 minutes at a speed of 1000 rpm to obtain component B; mix component A and component B obtained in step (1) evenly to obtain a water-based epoxy topcoat coating.

[0089] In component B, the amine curing agent is prepared using the same method as in Example 1.

[0090] Example 4

[0091] A water-based epoxy topcoat coating, the composition and dosage of which are shown in Table 5.

[0092] Table 5: Composition and dosage of waterborne epoxy primer and topcoat combined coating in Example 4

[0093]

[0094]

[0095] A method for preparing a waterborne epoxy primer-topcoat integrated coating includes the following steps:

[0096] (1) Mix the waterborne epoxy emulsion, film-forming aid, salt spray resistant aid and deionized water, disperse at 800 rpm for 15 min, then add thickener, disperse at 600 rpm for 15 min, adjust the viscosity to 80 kDa, mix evenly to obtain component A.

[0097] (2) Mix all the raw material components of component B evenly and disperse them at 800 rpm for 15 min to obtain component B; mix component A and component B obtained in step (1) evenly to obtain a water-based epoxy topcoat coating.

[0098] In component B, the amine curing agent is prepared using the same method as in Example 1.

[0099] Comparative Example 1

[0100] The only difference between Comparative Example 1 and Example 1 is that Comparative Example 1 uses 33 parts by mass of curing agent 38-1 (different curing agents result in different active hydrogen equivalents; this amount of addition ensures that the ratio of epoxy equivalent to active hydrogen equivalent in Comparative Example 1 remains consistent with that in Example 1) instead of the amine curing agent in Example 1, and the amount of deionized water used is 48.7 parts, otherwise the same as in Example 1.

[0101] Comparative Example 2

[0102] The only difference between Comparative Example 2 and Example 1 is that the amounts of epoxy emulsion 2060 and epoxy emulsion AEH20 used in Comparative Example 2 are 30 parts and 50 parts, respectively, and the amount of deionized water is 13 parts. Otherwise, they are the same as in Example 1.

[0103] Comparative Example 3

[0104] The only difference between Comparative Example 3 and Example 1 is that in the preparation of the amine curing agent, Comparative Example 3 uses an equal amount of epoxy resin E44 (epoxy value 0.41-0.47 eq / 100g) to replace E-51 in Example 1, while the rest is the same as in Example 1.

[0105] Comparative Example 4

[0106] The only difference between Comparative Example 4 and Example 1 is that Comparative Example 4 uses an equal amount of phosphate salt spray resistant additive 6110 to replace the salt spray resistant additive 142DA in Example 1, while the rest is the same as Example 1.

[0107] Performance testing

[0108] The coatings prepared in Examples 1-4 and Comparative Examples 1-4 were sprayed onto steel plates and other substrates (plastic, electrophoretic base, powder base, and smooth machined surface) using an air spraying method. The spray thickness was controlled at 40±5 μm, leveled for 10 min, and baked at 60°C for 1 h to obtain the coating. The coatings were then tested. For plastic, electrophoretic base, powder base, and smooth machined surface, only the coating adhesion was tested. Other tests were performed on the coating formed on the steel plate (adhesion was also tested on carbon steel substrates).

[0109] The test items and the standards referenced for the tests are shown in Table 6.

[0110] Table 6: Test Items and Standards Referenced for Testing

[0111] Test item Standard for testing reference Adhesion Cross-hatch method GB / T 9286-2021 Hardness GB / T 6739-2022 Gloss GB / T 9754-2007 Water resistance GB / T 1733-1993 (Method A) Resistance to motor oil GB / T 9274-1988 (Method A) Resistance to diesel oil GB / T 9274-1988 (Method A) Resistant to 5% H2SO4 GB / T 9274-1988 (Method A) Resistance to 5% NaOH GB / T 9274-1988 (Method A) Salt spray resistance GB / T 1771-2007 Resistance to artificial aging (Q-Sun) GB / T 1865-2009 Moisture and heat resistance GB / T 1740-2007

[0112] The performance test results of the coatings formed by the coatings of Examples 1-4 and Comparative Examples 1-4 are shown in Table 7.

[0113] Table 7: Performance test results of coatings formed by the coatings of Examples 1-4 and Comparative Examples 1-4

[0114]

[0115]

[0116] As shown in Table 7, the coating prepared by the present invention has good adhesion, corrosion resistance, weather resistance and hardness to a variety of substrates, and can play a good protective role for many substrates.

[0117] The curing agent in Comparative Example 1 was replaced with a commonly used curing agent on the market, which resulted in poor adhesion of the paint film to multiple substrates, making it difficult to meet product requirements.

[0118] Comparative Example 2 adjusted the amounts of solid epoxy emulsion and acrylic modified epoxy emulsion. It was found that when the amount of acrylic modified epoxy emulsion exceeded the amount of solid epoxy emulsion, the coating's gloss, hardness, and resistance to damp heat decreased, making it difficult to meet product requirements.

[0119] Comparative Example 3 uses epoxy resin E44 instead of epoxy resin E-51 in Example 1. As a result, the adhesion of the coating of Comparative Example 3 on substrates such as plastic, electrophoretic base, powder base and smooth machined surface is significantly worse than that of Example 1. That is, the adhesion to multiple substrates is significantly worse than that of Example 1. Comparative Example 3 cannot well meet the actual requirement that the engine protective coating needs to have good adhesion to multiple substrates.

[0120] Comparative Example 4 replaced the salt spray resistance additive 142DA in Example 1 with an equal amount of phosphate salt spray resistance additive 6110, resulting in Comparative Example 4 having significantly worse neutral salt spray resistance than Example 1. This demonstrates that using specific salt spray resistance additives plays an important role in improving the salt spray resistance of coatings.

[0121] In summary, this invention utilizes the reaction of epoxy groups with primary amine hydrogen to prepare an amine-based curing agent using polyamines, bisphenol A type epoxy resin, and polyethylene glycol diglycidyl ether as the main chain segments, and end-capping with a capping agent. The introduction of specific types of epoxy resins not only improves the compatibility between the amine curing agent and the waterborne epoxy emulsion and enhances gloss, but also increases the permeability of the film-forming material and strengthens adhesion to multiple substrates. Furthermore, combined with the synergistic effect of other components, the coating can simultaneously possess excellent anti-corrosion properties.

[0122] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A coating, characterized in that, The product comprises component A and component B; and by weight, component A comprises 65-85 parts of aqueous epoxy emulsion, 3.5-5.5 parts of film-forming aid, 0.9-2.2 parts of salt spray resistant aid, 0.9-2.2 parts of thickener, and 14-28 parts of water; component B comprises 35-55 parts of amine curing agent, 0.5-1.1 parts of defoamer, 0.5-1.1 parts of wetting agent, 0.5-1.1 parts of leveling agent, 2.5-4.5 parts of anti-flash rust aid, 9-16 parts of cosolvent, and 25-45 parts of water. The amine curing agent is obtained by using a capping agent to end-cap the main chain segments of polyamine, bisphenol A epoxy resin, and polyethylene glycol diglycidyl ether. The epoxy value of the bisphenol A type epoxy resin is greater than or equal to 0.48 eq / 100g; The aqueous epoxy emulsion includes a solid epoxy emulsion and an acrylic-modified epoxy emulsion, wherein the amount of the solid epoxy emulsion is greater than the amount of the acrylic-modified epoxy emulsion. The solid epoxy emulsion is solid epoxy emulsion 2060; the acrylic modified epoxy emulsion is either acrylic modified epoxy emulsion AEH20 or ME2000. The salt spray resistance additive is any one of salt spray resistance additives 550WF and 142DA; The ratio of the epoxy equivalent in component A to the active hydrogen equivalent in component B is (1.1-1.5):

1.

2. The coating according to claim 1, characterized in that, The polyamine includes triethylenetetramine; and / or the capping agent includes n-butyl glycidyl ether.

3. The method for preparing the coating according to any one of claims 1-2, characterized in that, Includes the following steps: (1) Mix the raw material components of component A to obtain component A; (2) Mix the raw material components of component B to obtain component B; mix component A and component B to obtain the coating.

4. The preparation method according to claim 3, characterized in that, The preparation method of the amine curing agent includes the following steps: A polyamine, bisphenol A epoxy resin, and polyethylene glycol diglycidyl ether are mixed and subjected to a first reaction. Then, a capping agent is added and a second reaction is carried out to obtain the amine curing agent.

5. The preparation method according to claim 4, characterized in that, The temperature of the first reaction is 55-75℃, and the time of the first reaction is 3-5h; and / or, the temperature of the second reaction is 55-75℃, and the time of the second reaction is 1.5-3.5h.

6. An engine, characterized in that, The coating formed by the coating as described in any one of claims 1-2.

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