Waterborne epoxy curing agent based on enamine bonds as well as preparation method and application of waterborne epoxy curing agent

Abstract

The invention provides a waterborne epoxy curing agent based on enamine bonds as well as a preparation method and application of the waterborne epoxy curing agent, and belongs to the technical field of coatings. The waterborne epoxy curing agent based on the enamine bond is prepared from the following raw materials in parts by weight: 12 to 14 parts of a polyepoxy compound, 7 to 12 parts of a polyamine compound, 37 to 42 parts of a polyether-based polyacetoacetate compound, 9 to 14 parts of a diacetoacetate compound, 5 to 7 parts of a monoacetoacetate compound and 20 to 50 parts of a solvent. According to the waterborne epoxy curing agent constructed through enamine bonds, the free amine content of the obtained waterborne epoxy curing agent can be effectively reduced, and the activation period of the waterborne epoxy curing agent during use is prolonged.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and in particular to an enamine bond-based waterborne epoxy curing agent, its preparation method, and its application. Background Technology

[0002] Waterborne epoxy systems have seen rapid development due to their environmental advantages. However, the nucleophilic addition reaction between epoxy and amines inherently has a high activation energy and slow reaction kinetics at room temperature. In an aqueous environment, water molecules dilute the reactant concentration and bind to amine groups, significantly weakening their nucleophilicity and further drastically reducing the reaction rate. This inherently slow reaction, coupled with the negative effects of water, results in waterborne epoxy systems generally suffering from long curing times, low construction efficiency, and slow early performance improvement, thus limiting their wider application.

[0003] Compounds containing acetoacetate groups (hereinafter referred to as β-dicarbonyl compounds) can react rapidly with amine groups at relatively low temperatures to form enamine bonds, and the activation energy of the reaction is lower than that of the reaction between epoxy and the corresponding amine. For example, Chinese invention patent application number CN202210894041.4 discloses isosorbide diacetate, which replaces part of the isosorbide diglycidyl ether in the reaction with polyamines to prepare a reprocessable epoxy resin. Using β-dicarbonyl compounds to react with amines instead of epoxy to react with amines can prepare amine-based epoxy curing agent solutions at lower temperatures. Chinese invention patent application number CN202111588674.4 describes a method for preparing a solvent-based bisphenol A type epoxy curing agent solution containing dynamic enamine bonds and a biodegradable epoxy resin, as well as its preparation, reshaping, and degradation methods. However, the aforementioned patents use a large amount of solvent in the preparation process, requiring subsequent distillation, extraction and other steps, which makes the process complex and environmentally unfriendly; some steps require temperatures of 100-150°C, the curing agent has a short pot life, and its salt spray resistance is poor during application.

[0004] Therefore, it is of great significance to provide a water-based epoxy curing agent with simplified process, mild conditions, long pot life and good salt spray resistance. Summary of the Invention

[0005] The purpose of this invention is to provide an enamine bond-based waterborne epoxy curing agent, its preparation method, and its application, in order to solve the technical problem that the preparation method requires a large amount of solvent and cannot simultaneously meet the requirements for pot life and salt spray resistance.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a waterborne epoxy curing agent based on enamine bonds, prepared from raw materials comprising the following parts by weight:

[0008]

[0009] Furthermore, the polyepoxide compound includes aliphatic epoxy resins and / or aromatic epoxy resins.

[0010] The polyamine compound includes one or more of aliphatic polyamines, alicyclic polyamines, and aromatic polyamines;

[0011] The polyether-based polyacetylacetate compound includes polyethylene glycol diacetylacetate and / or polypropylene glycol diacetylacetate;

[0012] The solvent is one or more of water, alcohol ether solvents, and alcohol solvents.

[0013] Furthermore, the polyether-based polyacetylacetate compound contains 2 to 3 hydroxyl groups in the structure of the polyether-based diol, and the number of ethoxy or propoxy groups is 10 to 20.

[0014] The molar ratio of the sum of the acetoacetic acid groups in the diacetoacetate compounds and the epoxy groups in the polyepoxide compounds to the amino groups in the polyamine compounds is 1:1 to 1.05.

[0015] Furthermore, the polyether-based polyacetylacetate compound is obtained by reacting polyethylene glycol and / or polypropylene glycol with an acetylacetic agent;

[0016] The molar ratio of the acetoacetic acid group of the acetoacetic acid oxidizing agent to the hydroxyl group of polyethylene glycol and / or polypropylene glycol is ≥1.05:1.

[0017] Furthermore, the diacetylacetate compound is obtained by reacting an aliphatic and / or alicyclic diol with an acetoacetic acidifying agent;

[0018] The aliphatic and / or alicyclic diols include one or more of neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, 1,10-decanediol, 2-butyl-2-ethyl-1,3-propanediol, hydrogenated bisphenol A, 1,4-cyclohexanediol, isosorbide, 1,4-cyclohexanediol, and 3,3-dihydroxy-dicyclohexylmethane;

[0019] The molar ratio of the acetoacetic acid group to the hydroxyl group of the aliphatic and / or alicyclic diol in the acetoacetic acidification reagent is ≥1.05:1.

[0020] Furthermore, the monoacetoacetate compound is obtained by reacting a monofunctional alcohol with an acetoacetic acidifying agent;

[0021] The monofunctional alcohols include one or more of benzyl alcohol, butanol, C12-14 alcohols, octanol, nonanol, and o-methylbenzyl alcohol;

[0022] The molar ratio of the acetoacetic acid group to the hydroxyl group of the monofunctional alcohol in the acetoacetic acid oxidizing agent is ≥1.05:1.

[0023] Furthermore, the acetoacetic acidification agent is independently one or more of diketene, ethyl acetoacetate, propyl acetoacetate, tert-butyl acetoacetate, pentyl acetoacetate, and heptyl acetoacetate.

[0024] This invention provides a method for preparing an enamine-based waterborne epoxy curing agent, comprising the following steps:

[0025] 1) Mix polyepoxide, polyether-based polyacetate compound and diacetate compound to obtain resin component;

[0026] 2) The polyamine compound and solvent are mixed to obtain the polyamine component;

[0027] 3) The resin component is added to the polyamine component for an addition reaction to obtain an intermediate;

[0028] 4) The monoacetyl acetate compound and the intermediate were mixed and then subjected to a capping reaction to obtain the capped product;

[0029] 5) Mix water and end-capping products to obtain a waterborne epoxy curing agent with a solid content of 60-80%.

[0030] Furthermore, in step 3), the temperature of the addition reaction is 40–60°C, and the time of the addition reaction is 2–4 hours.

[0031] In step 4), the temperature of the end-capping reaction is 70–100°C, and the time of the end-capping reaction is 1–3 hours.

[0032] In step 5), the mixing time is 0.5 to 1 hour.

[0033] This invention also provides the application of an enamine bond-based waterborne epoxy curing agent in epoxy coatings.

[0034] The beneficial effects of this invention are:

[0035] 1) The waterborne epoxy curing agent constructed by the present invention via enamine bonds can be prepared at a temperature as low as 40°C during the reaction process, which is much lower than the temperature (≥60°C) required for the preparation of waterborne epoxy curing agents by commonly used epoxy-amine reactions.

[0036] 2) The waterborne epoxy curing agent constructed by the present invention has a fast reaction rate and low temperature between β-dicarbonyl compounds and amines, and the small molecule amine raw materials have a low degree of vaporization, thereby effectively reducing the free amine content of the obtained waterborne epoxy curing agent and extending its activation period during use.

[0037] 3) The waterborne epoxy curing agent constructed by the present invention via enamine bonds can be used to prepare various structures of epoxy addition amine waterborne epoxy curing agents through the combination design of β-dicarbonyl compounds. The water generated during the reaction does not require treatment, making the process simple and environmentally friendly.

[0038] 4) The waterborne epoxy curing agent constructed via enamine bonds and the nonionic waterborne epoxy curing agent prepared according to the aforementioned method are suitable for preparing epoxy coatings. The resulting epoxy coatings exhibit a long open period and excellent application performance. Detailed Implementation

[0039] This invention provides a waterborne epoxy curing agent based on enamine bonds, prepared from raw materials comprising the following parts by weight:

[0040]

[0041] In this invention, the content of the polyepoxide compound is preferably 13 parts by weight.

[0042] In this invention, the polyepoxy compound includes aliphatic epoxy resin and / or aromatic epoxy resin, preferably aliphatic epoxy resin.

[0043] In this invention, the content of the polyamine compound is preferably 8 to 11 parts by weight, and more preferably 9 to 10 parts by weight.

[0044] In this invention, the polyamine compound includes one or more of aliphatic polyamines, alicyclic polyamines, and aromatic polyamines, preferably aliphatic polyamines and / or aromatic polyamines, and more preferably aliphatic polyamines.

[0045] In this invention, the content of the polyether-based polyacetylacetate compound is preferably 38 to 41 parts by weight, and more preferably 39 to 40 parts by weight.

[0046] In this invention, the polyether-based polyacetate compound includes polyethylene glycol diacetate and / or polypropylene glycol diacetate, preferably polyethylene glycol diacetate.

[0047] In this invention, the polyether-based polyacetylacetate compound contains 2 to 3 hydroxyl groups in the structure of the polyether-based diol, preferably 2; the number of ethoxy or propoxy groups is 10 to 20, preferably 12 to 18, and more preferably 14 to 16.

[0048] In this invention, the polyether-based polyacetylacetate compound is obtained by reacting polyethylene glycol and / or polypropylene glycol with an acetylacetic agent;

[0049] The molar ratio of the acetoacetic acid group of the acetoacetic acid oxidizing agent to the hydroxyl group of polyethylene glycol and / or polypropylene glycol is ≥1.05:1, preferably ≥1.08:1, and more preferably ≥1.1:1.

[0050] In this invention, polyethylene glycol and / or polypropylene glycol, along with an acetoacetic acid ester reagent, are dissolved in an organic solvent and reacted at 100–140°C for 6–10 h. The residual acetoacetic acid ester reagent is then removed under reduced pressure to obtain a polyether-based polyacetoacetate compound.

[0051] In this invention, the content of the diacetyl acetate compound is preferably 10 to 13 parts by weight, and more preferably 11 to 12 parts by weight.

[0052] In this invention, the molar ratio of the sum of the acetoacetic acid group and the epoxy group of the polyepoxide in the diacetoacetate compound and the monoacetoacetate compound to the amino group in the polyamine compound is 1:1 to 1.05, preferably 1:1.01 to 1.04, and more preferably 1:1.02 to 1.03.

[0053] In this invention, the diacetylacetate compound is obtained by reacting an aliphatic and / or alicyclic diol with an acetylation reagent;

[0054] The aliphatic and / or alicyclic diols include one or more of neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, 1,10-decanediol, 2-butyl-2-ethyl-1,3-propanediol, hydrogenated bisphenol A, 1,4-cyclohexanediol, isosorbide, 1,4-cyclohexanediol, and 3,3-dihydroxy-dicyclohexylmethane, preferably neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, 2- One or more of butyl-2-ethyl-1,3-propanediol, hydrogenated bisphenol A, 1,4-cyclohexanediol, isosorbide, 1,4-cyclohexanediol and 3,3-dihydroxy-dicyclohexylmethane, more preferably one or more of neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, 2-butyl-2-ethyl-1,3-propanediol, hydrogenated bisphenol A and 3,3-dihydroxy-dicyclohexylmethane;

[0055] The molar ratio of the acetoacetic acid group and the hydroxyl group of the aliphatic and / or alicyclic diol in the acetoacetic acid oxidizing agent is ≥1.05:1, preferably ≥1.08:1, and more preferably ≥1.1:1.

[0056] In this invention, aliphatic and / or alicyclic diols and acetoacetic acidification reagents are dissolved in an organic solvent and reacted at 100–140°C for 6–10 h. The residual aliphatic or alicyclic diols and acetoacetic acidification reagents are then removed under reduced pressure to obtain diacetoacetate compounds.

[0057] In this invention, the content of the monoacetylacetate compound is preferably 6 parts by weight.

[0058] In this invention, the monoacetoacetate compound is obtained by reacting a monofunctional alcohol with an acetoacetic acidifying agent;

[0059] The monofunctional alcohol includes one or more of benzyl alcohol, butanol, C12-14 alcohol, octanol, nonanol and o-methylbenzyl alcohol, preferably one or more of benzyl alcohol, C12-14 alcohol, octanol, nonanol and o-methylbenzyl alcohol, and more preferably one or more of benzyl alcohol, octanol, nonanol and o-methylbenzyl alcohol.

[0060] The molar ratio of the acetoacetic acid group to the hydroxyl group of the monofunctional alcohol in the acetoacetic acid oxidizing agent is ≥1.05:1, preferably ≥1.08:1, and more preferably ≥1.1:1.

[0061] In this invention, the acetoacetic acidification agent is independently one or more of diketene, ethyl acetoacetate, propyl acetoacetate, tert-butyl acetoacetate, pentyl acetoacetate, and heptyl acetoacetate, preferably one or more of diketene, ethyl acetoacetate, tert-butyl acetoacetate, pentyl acetoacetate, and heptyl acetoacetate, and more preferably one or more of ethyl acetoacetate, tert-butyl acetoacetate, pentyl acetoacetate, and heptyl acetoacetate.

[0062] In this invention, a monofunctional alcohol and an acetoacetic acid ester reagent are dissolved in an organic solvent and reacted at 100–140°C for 6–10 h. The residual monofunctional alcohol and acetoacetic acid ester reagent are then removed under reduced pressure to obtain a monoacetoacetate ester compound.

[0063] In this invention, the solvent content is preferably 25 to 45 parts by weight, and more preferably 30 to 40 parts by weight.

[0064] In this invention, the solvent is one or more of water, alcohol ether solvents and alcohol solvents, preferably one or more of water, propylene glycol methyl ether, isopropanol, benzyl alcohol, propylene glycol butyl ether and dipropylene glycol butyl ether, and more preferably one or more of water, propylene glycol methyl ether, benzyl alcohol, propylene glycol butyl ether and dipropylene glycol butyl ether.

[0065] This invention provides a method for preparing an enamine-based waterborne epoxy curing agent, comprising the following steps:

[0066] 1) Mix polyepoxide, polyether-based polyacetate compound and diacetate compound to obtain resin component;

[0067] 2) The polyamine compound and solvent are mixed to obtain the polyamine component;

[0068] 3) The resin component is added to the polyamine component for an addition reaction to obtain an intermediate;

[0069] 4) The monoacetyl acetate compound and the intermediate were mixed and then subjected to a capping reaction to obtain the capped product;

[0070] 5) Mix water and end-capping products to obtain a waterborne epoxy curing agent with a solid content of 60-80%.

[0071] In this invention, in step 3), the temperature of the addition reaction is 40-60°C, preferably 45-55°C, and more preferably 50°C; the time of the addition reaction is 2-4 hours, preferably 2.5-3.5 hours, and more preferably 3 hours.

[0072] In this invention, the primary amine molecule in the polyamine compound contains two active hydrogens. Theoretically, one primary amine molecule can react with two molecules of acetoacetyl compound to generate a disubstituted byproduct. At lower temperatures, the reaction rate is easier to control. When the first acetoacetyl group combines with the amine, the resulting enamine product has significantly weakened nucleophilicity due to steric hindrance and reduced electron cloud density (the lone pair electrons of the nitrogen atom participate in conjugation), making it difficult for it to attack the second molecule of acetoacetate. Low temperature conditions favor monosubstituted reactions as the dominant product under kinetic control, reducing the generation of disubstituted byproducts.

[0073] In this invention, in step 4), the temperature of the end-capping reaction is 70-100°C, preferably 75-95°C, and more preferably 80-90°C; the time of the end-capping reaction is 1-3 hours, preferably 1.5-2.5 hours, and more preferably 2 hours.

[0074] In this invention, in step 5), the mixing time is 0.5 to 1 hour, preferably 0.6 to 0.9 hours, and more preferably 0.7 to 0.8 hours.

[0075] This invention also provides the application of an enamine bond-based waterborne epoxy curing agent in epoxy coatings.

[0076] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0077] Example 1

[0078] 100g of polyethylene glycol PEG-1000 (Mn=1000) and 33.22g of tert-butyl acetoacetate (t-BAA) were dissolved in 40mL of xylene. The mixture was then reacted at 120℃ under a nitrogen atmosphere. The reaction was completed after 7h. The tert-butanol was removed by simultaneous distillation, and the polyether-based polyacetoacetate compound S1 was obtained by vacuum distillation.

[0079] 24.38 g of hydrogenated bisphenol A and 33.22 g of t-BAA were dissolved in 30 mL of xylene, and then the reaction was carried out at 120 °C under nitrogen atmosphere. After 7 h, the reaction was completed, and diacetyl acetate compound K1 was obtained by vacuum distillation.

[0080] 7.41 g of n-butanol and 17.4 g of t-BAA were dissolved in 10 mL of xylene, and then the reaction was carried out at 120 °C under nitrogen atmosphere. The reaction was completed after 7 h, and the butyl monoacetate end-capping agent F1 was obtained by vacuum distillation.

[0081] A polyamine component was obtained by mixing 36.05g of diethylenetriamine, 5g of water, and 15g of propylene glycol methyl ether. 37.8g of E51, 116.82g of S1, and 41.20g of K1 were mixed and added dropwise to the polyamine component. An addition reaction was then carried out at 50°C for 3 hours, yielding an intermediate. 15.82g of F1 was added dropwise to the intermediate while stirring, completing the addition over 0.5 hours. The mixture was then heated to 80°C for a capping reaction over 3 hours, yielding a capped product. Finally, 41.92g of deionized water was added to the capped product and mixed thoroughly for 0.5 hours to obtain an aqueous epoxy curing agent C1 with a solid content of 80% and an active hydrogen equivalent of 294.9g / eq.

[0082] Example 2

[0083] 60g of polyethylene glycol PEG-600 (Mn=600) and 33.22g of tert-butyl acetoacetate (t-BAA) were dissolved in 40mL of xylene. The reaction was carried out at 120℃ under nitrogen atmosphere. After 7h, the reaction was completed. The tert-butanol was removed by simultaneous distillation. The polyether-based polyacetoacetate compound S2 was obtained by vacuum distillation.

[0084] 11.62 g of 1,4-cyclohexanediol and 33.22 g of t-BAA were dissolved in 30 mL of xylene, and then the reaction was carried out at 120 °C under nitrogen atmosphere. After 7 h, the reaction was completed, and the diacetyl acetate compound K2 was obtained by vacuum distillation.

[0085] A polyamine component was obtained by mixing 18.02 g of diethylenetriamine, 18.02 g of m-phenylenediamine, 5 g of water, and 15 g of propylene glycol methyl ether. 37.8 g of E51, 76.82 g of S2, and 28.44 g of K2 were mixed and added dropwise to the polyamine component. An addition reaction was then carried out at 50 °C for 3 hours, yielding an intermediate. 15.82 g of F1 was added dropwise to the intermediate while stirring, completing the addition over 0.5 hours. The mixture was then heated to 80 °C for a capping reaction over 3 hours, yielding a capped product. Finally, 63.54 g of deionized water was added to the capped product and mixed thoroughly for 0.5 hours to obtain an aqueous epoxy curing agent C2 with a solid content of 70% and an active hydrogen equivalent of 395.1 g / eq.

[0086] Example 3

[0087] 100g of polyethylene glycol PEG-1000 (Mn=1000) and 31.95g of ethyl acetoacetate (EAA) were dissolved in 40mL of xylene. The reaction was carried out at 120℃ under nitrogen atmosphere. After 7h, the reaction was completed. Tert-butanol was removed by simultaneous distillation, and polyether-based polyacetoacetate compound S3 was obtained by vacuum distillation.

[0088] 11.62 g of 1,6-hexanediol and 31.95 g of EAA were dissolved in 30 mL of dimethyl sulfoxide, and then the reaction was carried out at 120 °C under nitrogen atmosphere. After 7 h, the reaction was completed and diacetyl acetate compound K3 was obtained by vacuum distillation.

[0089] 7.41 g of n-butanol and 16.7 g of EAA were dissolved in 10 mL of dimethyl sulfoxide, and then the reaction was carried out at 120 °C under nitrogen atmosphere. The reaction was completed after 7 h, and the butyl monoacetate end-capping agent F2 was obtained by vacuum distillation.

[0090] A polyamine component was obtained by mixing 23.8 g of m-phenylenediamine, 29.75 g of isophorone diamine, 5 g of water, and 15 g of propylene glycol methyl ether. A mixture of 37.8 g of E51, 62.74 g of S1, 60 g of S3, and 33.03 g of K3 was added dropwise to the polyamine component, followed by an addition reaction at 50°C for 3 hours. After the reaction, an intermediate was obtained. 18.02 g of F2 was added dropwise to the intermediate while stirring, completing the addition over 0.5 hours. The mixture was then heated to 80°C for a capping reaction over 3 hours, yielding a capped product. Finally, 156.76 g of deionized water was added to the capped product and mixed thoroughly for 0.5 hours to obtain an aqueous epoxy curing agent C3 with a solid content of 60% and an active hydrogen equivalent of 631.3 g / eq.

[0091] Example 4

[0092] 40g of polyethylene glycol PEG400 (Mn=400) and 31.95g of ethyl acetoacetate (EAA) were dissolved in 40mL of xylene. The reaction was carried out at 120℃ under nitrogen atmosphere. After 7h, the reaction was completed. Tert-butanol was removed by simultaneous distillation. The polyether-based polyacetoacetate compound S4 was obtained by vacuum distillation.

[0093] 11.82 g of 1,6-hexanediol and 31.95 g of EAA were dissolved in 30 mL of xylene, and then the reaction was carried out at 120 °C under nitrogen atmosphere. After 7 h, the reaction was completed and diacetyl acetate compound K4 was obtained by vacuum distillation.

[0094] 10.81 g benzyl alcohol and 16.73 g EAA were dissolved in 10 mL xylene, and then the reaction was carried out at 120 °C under nitrogen atmosphere. The reaction was completed after 7 h, and butyl monoacetate end-capping agent F3 was obtained by vacuum distillation.

[0095] A polyamine component was obtained by mixing 10.5g ethylenediamine, 29.75g isophorone diamine, 5g water, and 15g propylene glycol methyl ether. 37.8g E51, 61.21g S4, and 33.03g K4 were mixed and added dropwise to the polyamine component. An addition reaction was then carried out at 50°C for 3 hours, yielding an intermediate. 21.42g F3 was added dropwise to the intermediate while stirring, completing the addition over 0.5 hours. The mixture was then heated to 80°C for a capping reaction over 3 hours, yielding a capped product. Finally, 28.43g deionized water was added to the capped product and mixed thoroughly for 0.5 hours to obtain an aqueous epoxy curing agent C4 with a solid content of 80% and an active hydrogen equivalent of 345.9g / eq.

[0096] Comparative Example 1

[0097] A polyamine component was obtained by mixing 51.5g of diethylenetriamine, 5g of water, and 15g of propylene glycol methyl ether. 37.8g of E51 and 40g of PEG-400 (Mn=400) were mixed and added dropwise to the polyamine component. An addition reaction was then carried out at 60℃ for 3 hours, yielding an intermediate. 13g of butyl glycidyl ether was added dropwise to the intermediate while stirring, completing the addition over 0.5 hours. The mixture was then heated to 80℃ for a capping reaction over 3 hours, yielding a capped product. Finally, 15.58g of deionized water was added to the capped product and mixed thoroughly for 0.5 hours to obtain an aqueous epoxy curing agent C5 with a solid content of 80% and an active hydrogen equivalent of 237.2g / eq.

[0098] Comparative Example 2

[0099] A polyamine component was obtained by mixing 12.88g of diethylenetriamine, 17g of m-phenylenediamine, 5g of water, and 15g of propylene glycol methyl ether. A mixture of 37.8g of E51 and 60g of PEG-600 (Mn=600) was added dropwise to the polyamine component, followed by an addition reaction at 60℃ for 3 hours. After the reaction, an intermediate was obtained. 13g of butyl glycidyl ether was added dropwise to the intermediate while stirring, completing the addition over 0.5 hours. The mixture was then heated to 80℃ for a capping reaction over 3 hours, yielding a capped product. Finally, 40.29g of deionized water was added to the capped product and mixed thoroughly for 0.5 hours to obtain a waterborne epoxy curing agent C6 with a solid content of 70% and an active hydrogen equivalent of 321.55g / eq.

[0100] Comparative Example 3

[0101] A polyamine component was obtained by mixing 12.88g of diethylenetriamine, 17g of m-phenylenediamine, 5g of water, and 15g of propylene glycol methyl ether. A mixture of 37.8g of E51 and 100g of PEG-1000 (Mn=1000) was added dropwise to the polyamine component, followed by an addition reaction at 60℃ for 3 hours. After the reaction, an intermediate was obtained. 13g of butyl glycidyl ether was added dropwise to the intermediate while stirring, completing the addition over 0.5 hours. The mixture was then heated to 80℃ for a capping reaction over 3 hours, yielding a capped product. Finally, 103.12g of deionized water was added to the capped product and mixed thoroughly for 0.5 hours to obtain a waterborne epoxy curing agent C7 with a solid content of 60% and an active hydrogen equivalent of 492.5g / eq.

[0102] The waterborne epoxy curing agents prepared in Examples 1-4 and Comparative Examples 1-3 were used in combination with AQUAER-3011 emulsion (Jiangsu Fuqisen New Material Co., Ltd.), with a molar ratio of epoxy groups to amine hydrogen of 1.25:1. The mixture was sprayed onto tinplate and cold-rolled steel plate. After the wet coating was leveled at room temperature for 15 minutes, it was baked at 80°C for 2 hours and then placed for 24 hours before performance testing.

[0103] The adhesion was determined using the cross-cut test, and the test standard was GB / T 9286-1998.

[0104] Viscosity was measured using a Forecast cup (4 cup), and the test standard was GB / T 1723-1993.

[0105] The standard for testing the pencil hardness of paint film is GB / T 6739-1996;

[0106] The standard for testing the flexibility of paint film is GB / T 1731-1993;

[0107] The standard for water resistance at 40℃ is GB / T 5209-1985;

[0108] The impact test standard is GB / T 1732-2020, where the table shows a 50cm normal impact.

[0109] Test for resistance to neutral salt spray, GB / T 1771-2007.

[0110] Component A was prepared by combining 40 parts epoxy emulsion, 58 parts water-based colorant, 0.5 parts solvent, 0.2 parts wetting and leveling agent, 0.2 parts defoamer, 0.3 parts substrate wetting agent, 0.3 parts flash rust inhibitor, and 0.5 parts thickener. Component B was prepared by mixing the water-based epoxy curing agent prepared in Examples 1-4 and Comparative Examples 1-3 with propylene glycol methyl ether at a mass ratio of 7:3. The basic performance test results are shown in Table 1. Adhesion, viscosity, and gloss were tested within the 4-hour pot life, and their changes were observed.

[0111] The results of the applicability period test are shown in Table 2.

[0112] Table 1. Basic properties of the waterborne epoxy curing agents prepared in Examples 1-4 and Comparative Examples 1-3

[0113]

[0114]

[0115] Table 2 shows the test results of the applicable period of Examples 1-4 and Comparative Examples 1-3.

[0116]

[0117]

[0118] The examples involve two types of waterborne epoxy curing agents. Examples 1-4 are waterborne epoxy curing agents constructed with enamine bonds, while Comparative Examples 1-3 are waterborne epoxy curing agents constructed with epoxy-amine bonds. Regarding reaction temperature, the reaction temperature of the acetoacetyl-amine in Examples 1-4 is lower than that of the epoxy-amine in Comparative Examples 1-3. Simultaneously, regarding measured solid content, the measured solid content of Examples 1-4 is higher than that of Comparative Examples 1-3. As can be seen from Table 1, the basic mechanical properties of the waterborne epoxy curing agents prepared by this invention in Examples 1-4 are not significantly different from those in Comparative Examples 1-3, but their salt spray resistance is superior.

[0119] As shown in Table 2, the waterborne epoxy curing agents prepared in this invention, including Examples 1-4 and Comparative Examples 1-3, showed no significant viscosity increase within the 4-hour pot life, and all exhibited an adhesion grade of 0. In summary, the waterborne epoxy curing agent constructed using enamine bonds prepared in this invention has certain advantages.

[0120] As can be seen from the above embodiments, the present invention provides an enamine-based waterborne epoxy curing agent, its preparation method, and its application. The enamine-based waterborne epoxy curing agent of the present invention is prepared from raw materials comprising the following parts by weight: 12-14 parts of a polyepoxy compound, 7-12 parts of a polyamine compound, 37-42 parts of a polyether-based polyacetate compound, 9-14 parts of a diacetate compound, 5-7 parts of a monoacetate compound, and 20-50 parts of a solvent. The waterborne epoxy curing agent constructed through enamine bonds in this invention can effectively reduce the free amine content of the obtained waterborne epoxy curing agent and extend its activation period during use.

[0121] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A waterborne epoxy curing agent based on enamine bonds, characterized in that, It is prepared from raw materials comprising the following parts by weight:

2. The waterborne epoxy curing agent based on enamine bonds according to claim 1, characterized in that, The polyepoxide compounds include aliphatic epoxy resins and / or aromatic epoxy resins; The polyamine compound includes one or more of aliphatic polyamines, alicyclic polyamines, and aromatic polyamines; The polyether-based polyacetylacetate compound includes polyethylene glycol diacetylacetate and / or polypropylene glycol diacetylacetate; The solvent is one or more of water, alcohol ether solvents, and alcohol solvents.

3. The waterborne epoxy curing agent based on enamine bonds according to claim 1 or 2, characterized in that, The polyether-based polyacetylacetate compound contains 2 to 3 hydroxyl groups in its polyether-based diol structure, and the number of ethoxy or propoxy groups is 10 to 20. The molar ratio of the sum of the acetoacetic acid groups in the diacetoacetate compounds and the epoxy groups in the polyepoxide compounds to the amino groups in the polyamine compounds is 1:1 to 1.

05.

4. The waterborne epoxy curing agent based on enamine bonds according to claim 3, characterized in that, Polyether-based polyacetylacetate compounds are obtained by reacting polyethylene glycol and / or polypropylene glycol with an acetylacetic agent; The molar ratio of the acetoacetic acid group of the acetoacetic acid oxidizing agent to the hydroxyl group of polyethylene glycol and / or polypropylene glycol is ≥1.05:

1.

5. The waterborne epoxy curing agent based on enamine bonds according to claim 4, characterized in that, The diacetyl acetate compound is obtained by reacting an aliphatic and / or alicyclic diol with an acetoacetic acidifying agent; The aliphatic and / or alicyclic diols include one or more of neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, 1,10-decanediol, 2-butyl-2-ethyl-1,3-propanediol, hydrogenated bisphenol A, 1,4-cyclohexanediol, isosorbide, 1,4-cyclohexanediol, and 3,3-dihydroxy-dicyclohexylmethane; The molar ratio of the acetoacetic acid group to the hydroxyl group of the aliphatic and / or alicyclic diol in the acetoacetic acidification reagent is ≥1.05:

1.

6. The waterborne epoxy curing agent based on enamine bonds according to claim 5, characterized in that, The monoacetoacetate compound is obtained by reacting a monofunctional alcohol with an acetoacetic acidifying agent; The monofunctional alcohols include one or more of benzyl alcohol, butanol, C12-14 alcohols, octanol, nonanol, and o-methylbenzyl alcohol; The molar ratio of the acetoacetic acid group to the hydroxyl group of the monofunctional alcohol in the acetoacetic acid oxidizing agent is ≥1.05:

1.

7. The waterborne epoxy curing agent based on enamine bonds according to claim 4, 5, or 6, characterized in that, The acetoacetic acidification reagent is independently one or more of diketene, ethyl acetoacetate, propyl acetoacetate, tert-butyl acetoacetate, pentyl acetoacetate, and heptyl acetoacetate.

8. A method for preparing an enamine-based aqueous epoxy curing agent according to any one of claims 1 to 7, characterized in that, Includes the following steps: 1) Mix polyepoxide, polyether-based polyacetate compound and diacetate compound to obtain resin component; 2) The polyamine compound and solvent are mixed to obtain the polyamine component; 3) The resin component is added to the polyamine component for an addition reaction to obtain an intermediate; 4) The monoacetyl acetate compound and the intermediate were mixed and then subjected to a capping reaction to obtain the capped product; 5) Mix water and end-capping products to obtain a waterborne epoxy curing agent with a solid content of 60-80%.

9. The method for preparing the waterborne epoxy curing agent based on enamine bonds according to claim 8, characterized in that, In step 3), the temperature of the addition reaction is 40–60°C, and the reaction time is 2–4 hours. In step 4), the temperature of the end-capping reaction is 70–100°C, and the time of the end-capping reaction is 1–3 hours. In step 5), the mixing time is 0.5 to 1 hour.

10. The application of an enamine bond-based waterborne epoxy curing agent according to any one of claims 1 to 7 in epoxy coatings.

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