Aqueous epoxy curing agent, its preparation method and application

Abstract

The application belongs to the technical field of epoxy curing agents, and specifically discloses a water-based epoxy curing agent, a preparation method and application thereof, the water-based epoxy curing agent is made of polyamine, dimer acid, polyethylene glycol, epoxy resin and water; the preparation steps are as follows: the polyamine, dimer acid and polyethylene glycol are mixed, stirred, heated and reacted, and then dehydrated by vacuum distillation; the temperature is lowered, the epoxy resin is added, stirred and heated and reacted; and then water is added to obtain the finished product. The water-based epoxy curing agent provided by the application contains a large number of amide and epoxy structures in the molecule, can balance the rigidity of the epoxy resin and the flexibility of the polyamide, maintains the flexibility of the curing agent and the fusion degree with the epoxy resin, has good hydrophilicity, and the paint film prepared by applying the water-based epoxy curing agent in the epoxy resin emulsion has excellent adhesion, water resistance and salt fog resistance.

Description

Technical Field

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

[0002] Epoxy resin is widely used in civil engineering, electronics, aerospace, automotive machinery, and other fields, and is an important part of national production. China is currently the world's largest producer of epoxy resin, accounting for 37.1% of global production. However, liquid epoxy resin is an amorphous viscous liquid that becomes plastic when heated, has no obvious melting point, and softens and gradually melts upon heating, becoming sticky.

[0003] Insoluble in water and not hardened on its own, epoxy has almost no practical use on its own. It only has application value when it reacts with a curing agent to form a three-dimensional network structure of infusible polymer. When a certain amount of curing agent is added, it gradually solidifies to form chemical substances with varying properties. Therefore, a curing agent must be added to form a formulated resin, and the curing reaction must be carried out under specific conditions to generate a three-dimensional network structure of polymer material. Only then will it exhibit various excellent properties and become a truly usable epoxy material.

[0004] Commonly used epoxy curing agents can be divided into oil-based and water-based epoxy curing agents. However, traditional oil-based epoxy curing agents contain a large amount of organic solvents, such as benzene-containing substances, which not only harm the global ecological environment but also endanger human health. The development of water-based epoxy curing agents has expanded the application range of epoxy curing agents. However, current water-based epoxy curing agent synthesis technologies mainly rely on two methods: grafting hydrophilic segments or neutralization to form salts. The neutralization to salt method introduces hydrophilic small molecule residues, leading to reduced water and salt spray resistance after film formation. The hydrophilic segment grafting method, for example, involves the high-temperature reaction of polyamide with hydrophilic polyethylene glycol. The resulting product has poor compatibility with epoxy molecules, resulting in reduced anti-corrosion performance after film formation. For example, products obtained by reacting polyetheramine with epoxy resin have good affinity with epoxy resin, but the film is too rigid, resulting in high stress along the film lines after formation, making it prone to blistering during destructive salt spray corrosion tests.

[0005] Therefore, developing a high-performance waterborne epoxy curing agent has become one of the important research directions in the field of epoxy curing agents. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide a waterborne epoxy curing agent, its preparation method, and its application. The waterborne epoxy curing agent provided by the present invention contains a large number of amide and epoxy structures within its molecule, which can balance the rigidity of epoxy resin and the flexibility of polyamide, maintaining the curing agent's flexibility and compatibility with epoxy resin. It not only has good hydrophilicity, but also produces a paint film with excellent adhesion, water resistance, and salt spray performance when applied to epoxy resin emulsions.

[0007] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows:

[0008] A first aspect of the present invention provides an aqueous epoxy curing agent comprising the following raw materials: polyamine, dimer acid, polyethylene glycol, epoxy resin and water, wherein the polyamine is selected from at least one of ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

[0009] Preferably, the above-mentioned waterborne epoxy curing agent comprises, according to the following parts by weight:

[0010]

[0011] In this invention, the main material for preparing the coating film—a pure epoxy resin curing material with a high crosslinking density—has a rigid crosslinking network skeleton, which makes it difficult for molecular chains to slide relative to each other. This easily leads to the accumulation of internal stress in the coating during the drying process, causing the coating to crack. Consequently, it suffers from drawbacks such as brittleness, poor fatigue resistance, heat resistance, and impact toughness. Therefore, the waterborne epoxy curing agent of this invention needs to have suitable rigidity and flexibility. Moreover, since epoxy resin is highly hydrophobic, the waterborne epoxy curing agent needs to have good compatibility with epoxy resin. Therefore, this invention generates polyamide through the condensation reaction of dimer acid, polyamine, and polyethylene glycol. Then, the polyamide reacts with the ring-opening epoxy resin. The resulting polymer contains a large number of amide and epoxy chemical structures, which can balance the rigidity of epoxy resin and the flexibility of polyamide, maintaining the flexibility of the waterborne epoxy curing agent and its compatibility with epoxy resin. Furthermore, the polyether bonds in the polyethylene glycol in the waterborne epoxy curing agent give it good hydrophilicity and film-forming properties, thereby improving its durability after curing with epoxy resin. The water-based epoxy curing agent of the present invention is applied to epoxy resin to prepare a coating film with excellent adhesion, water resistance and salt spray performance.

[0012] Preferably, the mass ratio of the polyamine, dimer acid, polyethylene glycol and epoxy resin is (8-4):(4-2):(2-0.5):1, and more preferably 8:4:2:1.

[0013] In this invention, through numerous inventive experiments, the inventors discovered that by setting the mass ratio of the polyamine, dimer acid, polyethylene glycol, and epoxy resin to (8-4):(4-2):(2-0.5):1, more preferably 8:4:2:1, the resulting waterborne epoxy curing agent contains a suitable proportion of amide and epoxy covalent bonds, which can effectively balance the rigidity of epoxy resin and the flexibility of polyamide. This waterborne epoxy curing agent, when applied to epoxy resin emulsions, exhibits superior adhesion, water resistance, and salt spray performance.

[0014] Furthermore, the epoxy resin is a liquid epoxy resin, preferably E51 and / or E44.

[0015] In this invention, E51 and / or E44 of the liquid epoxy resin were selected to facilitate batch addition during subsequent preparation.

[0016] In the aforementioned waterborne epoxy curing agent, the number average molecular weight of the polyethylene glycol is 1000-2000. If the number average molecular weight of the polyethylene glycol is too high, the viscosity of the entire system will be too high, requiring the addition of a large amount of water for dilution during the preparation process and subsequent use. If the number average molecular weight of the polyethylene glycol is too low, it will affect the compatibility between the curing agent and the epoxy resin, thereby reducing the performance of the coating after preparation, including water resistance and salt spray performance.

[0017] A second aspect of the present invention provides a method for preparing the above-mentioned waterborne epoxy curing agent, comprising the following steps:

[0018] S1. Mix polyamine, dimer acid and polyethylene glycol, stir and heat to 100-120℃ at 40-110 RPM, stir and react at a constant temperature for 5-6 hours to obtain the first intermediate product.

[0019] S2. Heat the first intermediate product to 150-250℃, stir at 40-110 RPM, react at a constant temperature for 4-8 hours, and then dehydrate by vacuum distillation for 1-5 hours to obtain the second intermediate product.

[0020] S3. Cool the second intermediate product to 100-120℃, add epoxy resin to the second intermediate product in two or more batches while stirring at 100-300 RPM, and then react at a constant temperature for 1-5 hours while stirring at 40-110 RPM to obtain the third intermediate product.

[0021] S4. Cool the third intermediate product to 50-80℃ and add water while stirring at a speed of 40-110 RPM to obtain a water-based epoxy curing agent.

[0022] In the preparation process of the waterborne epoxy curing agent of the present invention, in step S1, dimer acid reacts with polyamine and polyethylene glycol to obtain the first intermediate product mixed amine. In step S2, after the mixed amine is heated and reacted, it needs to be dehydrated by vacuum distillation for 1-5 hours to promote the reversible reaction to proceed in the direction of producing polyamide, and obtain the second intermediate product polyamide.

[0023] In step S3, the polyamide and epoxy resin react to produce a polymer containing a large number of covalent bonds of both amide and epoxy. This balances the rigidity of the epoxy resin and the flexibility of the polyamide, maintaining the flexibility and compatibility of the waterborne epoxy curing agent with the epoxy resin. It not only possesses good hydrophilicity but also, when applied to epoxy resins, imparts excellent adhesion, water resistance, and salt spray performance. It is important to note that in step S3, the epoxy resin must be added to the second intermediate product in two or more separate additions under high-speed stirring. Adding it all at once or stirring at a slow speed may lead to gelation, which would be detrimental to obtaining the waterborne epoxy curing agent of this invention.

[0024] Furthermore, the prepared waterborne epoxy curing agent has a solid content of 39-40.5% and a viscosity of 40,000-60,000 cp.

[0025] In this invention, because the waterborne epoxy curing agent prepared by the above method contains a large amount of both amide and epoxy chemical structures, the epoxy curing agent of this invention is a high-molecular-weight copolymer with a large molecular weight. After dilution with water, the viscosity of the product is affected by the size of its molecular weight and the interaction of its various functional groups, thus indirectly determining the solid content. The amount of solid content affects the performance and cost of the waterborne epoxy curing agent; too little solid content results in poor performance, while too much solid content leads to excessively high costs. The waterborne epoxy curing agent of this invention has a solid content of 39-40.5%, simultaneously achieving the advantages of good performance and low cost.

[0026] A third aspect of the present invention provides the application of the above-mentioned waterborne epoxy curing agent, wherein a coating film is prepared by using the above-mentioned waterborne epoxy curing agent, and the steps are as follows:

[0027] Preparation of T1 and A components: Mix 25-40 parts of epoxy resin emulsion, 5-15 parts of titanium dioxide, 5-15 parts of barium sulfate, 3-5 parts of talc, 5-12 parts of mica powder, 1-2 parts of dispersant, 0.1-1 part of defoamer, 0.1-1 part of leveling agent, 0.1-2 parts of thickener, and 10-20 parts of water evenly.

[0028] Preparation of T2 and B components: Mix 8-12 parts of epoxy curing agent, 0.5-2 parts of anti-flash rust agent, 0.5-2 parts of propylene glycol methyl ether, and 1-10 parts of water evenly;

[0029] T3. Coating film preparation: Mix component A and component B at a mass ratio of (8-4):1, preferably 5:1, stir evenly at a speed of 450-550 RPM, and then apply to prepare the coating film.

[0030] In the process of preparing the coating film with the above-mentioned waterborne epoxy curing agent, the components A and B are mixed at a mass ratio of (8-4):1, preferably 5:1. If the ratio is too high, the drying speed will be slowed down; if the ratio is too low, the water and salt spray resistance will decrease.

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

[0032] (1) The waterborne epoxy curing agent provided by the present invention contains a large number of amide and epoxy chemical structures in its molecule, which can balance the rigidity of epoxy resin and the flexibility of polyamide, maintain the flexibility of the curing agent and the degree of integration with epoxy resin. It not only has good hydrophilicity, but also the paint film made by applying it to epoxy resin has excellent adhesion, water resistance and salt spray performance.

[0033] (2) The preparation method of the waterborne epoxy curing agent provided by the present invention is simple and easy to industrialize. Detailed Implementation

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the technical solutions of the present invention will be described in detail below with specific embodiments.

[0035] Preparation of waterborne epoxy curing agent

[0036] Preparation Example 1

[0037] The specific composition of each raw material in the water-based epoxy curing agent is shown in Table 1 below, and its preparation method includes the following steps:

[0038] S1. Triethylenetetramine, dimer acid, and polyethylene glycol are mixed and stirred at 50 RPM until the temperature is raised to 120°C. The mixture is then kept at this temperature for 5 hours to obtain the first intermediate product.

[0039] S2. The first intermediate product is heated to 250°C and reacted at a constant temperature for 6 hours with stirring at 70 RPM. Then, it is dehydrated by vacuum distillation for 1 hour to obtain the second intermediate product.

[0040] S3. Cool the second intermediate product to 100°C, add epoxy resin to the second intermediate product in two equal batches while stirring at 200 RPM, and then react at a constant temperature for 2 hours while stirring at 60 RPM to obtain the third intermediate product.

[0041] S4. Cool the third intermediate product to 80°C, add water while stirring at 60 RPM, and obtain a water-based epoxy curing agent.

[0042] Preparation Example 2

[0043] The specific composition of each raw material in the water-based epoxy curing agent is shown in Table 1 below, and its preparation method includes the following steps:

[0044] S1. Diethylenetriamine, dimer acid, and polyethylene glycol are mixed and heated to 100°C at a speed of 40 RPM. The mixture is then kept at a constant temperature for 5 hours to obtain the first intermediate product.

[0045] S2. The first intermediate product is heated to 150°C and reacted at a constant temperature for 4 hours with stirring at 40 RPM. Then, it is dehydrated by vacuum distillation for 1 hour to obtain the second intermediate product.

[0046] S3. Cool the second intermediate product to 110°C, add epoxy resin to the second intermediate product in three equal batches while stirring at 100 RPM, and then react at a constant temperature for 2 hours while stirring at 10 RPM to obtain the third intermediate product.

[0047] S4. Cool the third intermediate product to 50°C, add water while stirring at 40 RPM, and obtain a water-based epoxy curing agent.

[0048] Preparation Example 3

[0049] The specific composition of each raw material in the water-based epoxy curing agent is shown in Table 1 below, and its preparation method includes the following steps:

[0050] S1. Tetraethylenepentamine, dimer acid, and polyethylene glycol are mixed and stirred at 110 RPM until heated to 110°C. The mixture is then kept at this temperature for 6 hours to obtain the first intermediate product.

[0051] S2. The first intermediate product is heated to 200℃ and reacted at a constant temperature for 8 hours. Then, under stirring at 110 RPM, it is dehydrated by vacuum distillation for 1 hour to obtain the second intermediate product.

[0052] S3. Cool the second intermediate product to 110°C, add epoxy resin to the second intermediate product in five batches while stirring at 300 RPM, and then react at a constant temperature for 2 hours while stirring at 110 RPM to obtain the third intermediate product.

[0053] S4. Cool the third intermediate product to 70°C, add water while stirring at 110 RPM, and obtain a water-based epoxy curing agent.

[0054] Preparation Examples 4-5

[0055] The specific composition of each raw material in the water-based epoxy curing agent is shown in Table 1 below, and its preparation method is the same as in Example 1:

[0056] Comparative Examples 1-3

[0057] The specific composition of each raw material in the water-based epoxy curing agent is shown in Table 1 below, and its preparation method is the same as in Example 1:

[0058] Comparative Example 4

[0059] The specific composition of each raw material is shown in Table 1 below, and the preparation method includes the following steps:

[0060] S1. Mix triethylenetetramine and polyethylene glycol, stir at 50 RPM and heat to 120°C, then keep the temperature constant for 5 hours to obtain the first intermediate product.

[0061] S2. The first intermediate product is heated to 250°C and reacted at a constant temperature for 6 hours with stirring at 70 RPM. Then, it is dehydrated by vacuum distillation for 1 hour to obtain the second intermediate product.

[0062] S3. Cool the second intermediate product to 80°C, add water while stirring at 60 RPM, and obtain the product.

[0063] Comparative Example 5

[0064] The specific composition of each raw material is shown in Table 1 below, and the preparation method includes the following steps:

[0065] S1. Triethylenetetramine and polyethylene glycol are mixed, stirred and heated to 120°C, and stirred at 50 RPM for 5 hours to obtain the first intermediate product.

[0066] S2. The first intermediate product is heated to 250°C and reacted at a constant temperature for 6 hours. Under stirring at 70 RPM, it is dehydrated by vacuum distillation for 1 hour to obtain the second intermediate product.

[0067] S3. Cool the second intermediate product to 100°C, add epoxy resin to the second intermediate product in two equal batches while stirring at 200 RPM, and then react at a constant temperature for 2 hours while stirring at 60 RPM to obtain the third intermediate product.

[0068] S4. Cool the third intermediate product to 80°C, add water while stirring at 60 RPM, and obtain a water-based epoxy curing agent.

[0069] Comparative Example 6

[0070] The specific composition of each raw material is shown in Table 1 below, and the preparation method includes the following steps:

[0071] S1. Mix triethylenetetramine and dimer acid, stir and heat to 120°C, and stir at 50 RPM for 5 hours to obtain the first intermediate product.

[0072] S2. The first intermediate product is heated to 250°C and reacted at a constant temperature for 6 hours. Then, under stirring at 70 RPM, it is dehydrated by vacuum distillation for 1 hour to obtain the second intermediate product.

[0073] S3. Cool the second intermediate product to 100°C, add epoxy resin to the second intermediate product in two equal batches while stirring at 200 RPM, and then react at a constant temperature for 2 hours while stirring at 60 RPM to obtain the third intermediate product.

[0074] S4. Cool the third intermediate product to 80°C, add water while stirring at 60 RPM, and obtain a water-based epoxy curing agent.

[0075] Table 1. Composition of raw materials in Preparation Examples 1-5 and Comparative Examples 1-6

[0076]

[0077]

[0078] The physicochemical properties of the waterborne epoxy curing agents prepared in Examples 1-5 and Comparative Examples 1-6 were tested, and the results are shown in Table 2.

[0079] Solid content: The solid content is tested according to ASTM D1259. Take a 5-gram sample, put it in an oven, bake it at 150°C for 1 hour, and calculate the solid content by measuring the weight of the remaining components.

[0080] Viscosity: The viscosity was tested according to ASTM D2196 at 25°C using a Shanghai Jingtian RVDV-1 viscometer with a No. 5 rotor at 10 RPM.

[0081] Table 2. Results of physicochemical performance tests

[0082] Solid content Viscosity Preparation Example 1 39.8 50020 Preparation Example 2 40.5 43200 Preparation Example 3 40.3 58030 Preparation Example 4 40.1 55000 Preparation Example 5 39.6 56000 Comparative Example 1 38.8 42000 Comparative Example 2 39.2 43000 Comparative Example 3 40.2 48000 Comparative Example 4 41.0 18060 Comparative Example 5 41.6 23500 Comparative Example 6 40.8 28560

[0083] As shown in Table 2, the raw materials for preparing the curing agent—polyamine, dimer acid, polyethylene glycol, and epoxy resin—directly affect the viscosity of the curing agent. For example, comparing the data from Example 1 and Example 4, it can be seen that the curing agent with a significantly lower viscosity is formed when polyamine is lacking. This may be because the absence of polyamine prevents it from reacting with polyamine and polyethylene glycol, affecting the chain extension of the molecules and thus the final molecular weight, which in turn affects the viscosity of the water-based epoxy curing agent.

[0084] Application Example 1 and Application Comparative Examples 1-6

[0085] Using the waterborne epoxy curing agents prepared in Preparation Example 1 and Comparative Examples 1-6 as raw materials, and commercially available JT-WBE521 as epoxy emulsion, paint films were prepared respectively. The specific steps are as follows:

[0086] T1. Preparation of component A: 40 parts epoxy resin emulsion, 10 parts titanium dioxide, 15 parts barium sulfate, 5 parts talc, 10 parts mica powder, 1.2 parts dispersant, 0.5 parts defoamer, 0.3 parts leveling agent, 0.5 parts thickener, and 17.5 parts water. Mix the above raw materials evenly.

[0087] T2. Preparation of component B: 11 parts epoxy curing agent, 1 part anti-flash rust agent, 2 parts propylene glycol methyl ether, and 6 parts water. Mix the above raw materials evenly.

[0088] T3. Preparation of paint film: After preparing components A and B, mix components A and B evenly at a mass ratio of 5:1 and stir at 500 rpm for 5 minutes. Prepare the paint film on the cold-rolled plate by air spraying. The dry film thickness is controlled at 50 μm. After air drying for 7 days at 25℃ / 50%RH, take it out and test its water resistance and salt spray performance.

[0089] Application Comparative Example 7

[0090] Using a commercially available water-based epoxy curing agent with a solid content of 40% and a viscosity of 25000 cP as the raw material, and using commercially available JT-WBE521 as the epoxy emulsion, paint films were prepared. The specific steps are as follows:

[0091] T1. Preparation of component A: 40 parts epoxy resin emulsion, 10 parts titanium dioxide, 15 parts barium sulfate, 5 parts talc, 10 parts mica powder, 1.2 parts dispersant, 0.5 parts defoamer, 0.3 parts leveling agent, 0.5 parts thickener, and 17.5 parts water. Mix the above raw materials evenly.

[0092] T2. Preparation of component B: 11 parts epoxy curing agent, 1 part anti-flash rust agent, 2 parts propylene glycol methyl ether, and 6 parts water. Mix the above raw materials evenly.

[0093] T3. Preparation of the paint film: After preparing components A and B, mix components A and B evenly at a mass ratio of 5:1 and stir at 500 rpm for 5 minutes. Prepare the paint film on the cold-rolled plate by air spraying. The dry film thickness is controlled at 50 μm. After air drying for 7 days at 25°C / 50% RH, test the water resistance and salt spray performance.

[0094] The water resistance test was conducted according to the GB / T1771 standard, which includes water resistance at room temperature and water resistance at high temperature. The high temperature water resistance test was conducted in a water bath at a set temperature of 40℃, and the test results were recorded in Table 3.

[0095] The neutral salt spray test was conducted according to the GB / T1771 standard. After marking the salt spray plate with an X, the salt spray chamber was placed for the test, and the test results were recorded in Table 3.

[0096] The adhesion test was conducted according to ASTM D3359 standard. After the paint film was prepared, it was allowed to air dry for 7 days. The test results of the paint film thickness of 45-55 μm are shown in Table 3.

[0097] Impact resistance was tested according to GB / T1732 standard, with a positive impact value of kg·cm. The flexibility of the paint film was tested according to GB / T6742 standard, measuring bending performance, and the test results are recorded in Table 3.

[0098] The test results of Application Example 1 and Application Comparative Examples 1-7 are shown in Table 3 below.

[0099] Table 3 Performance Test Results

[0100]

[0101] According to the data in Table 1, when the water-based curing agent prepared by the present invention is applied to the preparation of paint film, it can effectively improve the performance of the paint film, such as high temperature water resistance and salt spray resistance. The raw materials for preparing the curing agent by the present invention and their proportional relationship have a direct impact on the performance of the prepared paint film.

[0102] Comparing the data from Application Example 1 and Comparative Examples 1-3, it can be seen that when the proportion of the curing agent raw materials is no longer within the range of this application, the performance of the coating film also decreases significantly, such as a 1.4-2.8-fold decrease in high-temperature water resistance and a 1.4-3.3-fold decrease in salt spray resistance.

[0103] Comparing the data from Application Example 1 and Comparative Examples 4-6, it can be seen that the performance of the coating film is significantly reduced when one of the raw materials is missing, such as high-temperature water resistance and salt spray resistance.

[0104] Comparing the data from Application Example 1 and Comparative Example 7, it can be seen that the paint film prepared by the water-based epoxy curing agent of the present invention has better water resistance and salt spray resistance than the paint film prepared by commercially available curing agents.

[0105] The embodiments provided by the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention, and the descriptions of the embodiments above are only for the purpose of helping to understand the core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A water-based epoxy curing agent, characterized in that, It includes the following raw materials: polyamine, dimer acid, polyethylene glycol, epoxy resin and water, wherein the polyamine is selected from at least one of ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine; The water-based epoxy curing agent comprises, by weight, the following components: 30-40 parts of polyamine; 10-30 parts of dimer acid; 5-20 parts of polyethylene glycol; 5-10 parts epoxy resin; 100-120 parts water; The epoxy resin is a liquid epoxy resin, and the epoxy resin is E51 and / or E44; The preparation method of water-based epoxy curing agent is as follows: S1. Mix the polyamine, dimer acid, and polyethylene glycol, stir and heat to 100-120°C at a speed of 40-110 RPM, and then react at a constant temperature for 5-6 hours to obtain the first intermediate product. S2. Heat the first intermediate product to 150-250℃, stir at 40-110 RPM, react at a constant temperature for 4-8 hours, and then dehydrate by vacuum distillation for 1-5 hours to obtain the second intermediate product. S3. Cool the second intermediate product to 100-120℃, add epoxy resin to the second intermediate product in two or more batches while stirring at 100-300 RPM, and then react at a constant temperature for 1-5 hours while stirring at 40-110 RPM to obtain the third intermediate product. S4. Cool the third intermediate product to 50-80℃ and add water while stirring at a speed of 40-110 RPM to obtain a water-based epoxy curing agent.

2. The water-based epoxy curing agent according to claim 1, characterized in that, The mass ratio of the polyamine, dimer acid, polyethylene glycol and epoxy resin is (8-4):(4-2):(2-0.5):

1.

3. The waterborne epoxy curing agent according to claim 1, characterized in that, The number average molecular weight of the polyethylene glycol is 1000-2000.

4. The water-based epoxy curing agent according to claim 1, characterized in that, The water-based epoxy curing agent has a solid content of 39-40.5% and a viscosity of 40,000-60,000 cp.

5. An application of a water-based epoxy curing agent, characterized in that, The preparation of a coating film using the water-based epoxy curing agent as described in any one of claims 1-4 includes the following steps: Preparation of T1 and A components: Mix 25-40 parts of epoxy resin emulsion, 5-15 parts of titanium dioxide, 5-15 parts of barium sulfate, 3-5 parts of talc powder, 5-12 parts of mica powder, 1-2 parts of dispersant, 0.1-1 part of defoamer, 0.1-1 part of leveling agent, 0.1-2 parts of thickener, and 10-20 parts of water evenly; Preparation of T2 and B components: Mix 8-12 parts of water-based epoxy curing agent, 0.5-2 parts of anti-flash rust agent, 0.5-2 parts of propylene glycol methyl ether, and 1-10 parts of water evenly; T3. Coating film preparation: Mix component A and component B at a mass ratio of (8–4):1 at a speed of 450-550 RPM until homogeneous, and then apply the mixture to prepare the coating film.

6. The application of the waterborne epoxy curing agent according to claim 5, characterized in that, The components A and B are in a mass ratio of 5:1.

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