A quick-drying high-performance water-based epoxy curing agent and a preparation method thereof

Abstract

The application discloses a kind of fast-drying high-performance waterborne epoxy curing agent in the field of coating technology, the curing agent preparation includes compound, compound is in the primary amine position of two ends R group in ketimine modified amine Polyether segment and bisphenol A segment are introduced;The synthesis of ketimine modified amine is made into compound by Micheal addition diacetone acrylamide carbon-carbon double bond and primary amine reaction condensation dehydration;Ketimine modified amine waterborne epoxy curing agent good water solubility, with waterborne epoxy emulsion crosslinking reaction degree is high, short surface dry time, while obtaining coating has excellent mechanical properties and weather resistance, obtain coating has excellent mechanical properties and weather resistance.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and in particular to a water-based epoxy curing agent and its preparation method. Background Technology

[0002] With the increasing emphasis on green and environmentally friendly concepts, the development of zero-VOC or low-VOC waterborne epoxy curing agents has significant advantages. Currently, nonionic waterborne epoxy curing agents have become the mainstream research direction. However, while commercially available waterborne epoxy curing agents possess excellent mechanical properties and weather resistance, they suffer from disadvantages such as slow drying speeds, leading to a loss of gloss during the curing process and resulting in low surface gloss, thus limiting their application range. Therefore, the preparation of fast-drying, high-hardness waterborne curing agents is particularly important. Diacetone acrylamide, due to its structure... N Substituted amides and methyl ketones can copolymerize with other monomers, serving as novel vinyl functional monomers and are widely used in the coatings industry. The C=C double bond in the diacetone acrylamide structure undergoes a Michael addition reaction with the primary amine in polyamines, while... N The methyl ketone carbonyl group in a substituted amide can undergo dehydration condensation with a polyamine to yield a homoimine structure.

[0003] Patent CN112321801A discloses a method for preparing a cationic self-emulsifying waterborne epoxy resin fast-drying curing agent. This curing agent, when reacting with epoxy resin, exhibits high crosslinking density, fast surface drying, and high hardness. However, the addition of organic acids during the synthesis of the ionic curing agent forms salts, which adversely affects the metal corrosion resistance of the paint film. Patent CN117987060A discloses a single-component structural adhesive and its preparation method, primarily using methyl ethyl ketone or methyl isobutyl ketone to react with polyamines to prepare ketimine. The ketimine is used as the single-component structural adhesive film-forming material and does not interact with the waterborne epoxy curing agent. This patent utilizes Michael addition, reacting the carbon-carbon double bond of diacetone acrylamide with a primary amine followed by condensation and dehydration to prepare a carbonyl-containing ketimine-modified amine. The ketimine undergoes a chain extension reaction with epoxy resin to obtain a waterborne epoxy curing agent. This curing agent exhibits a high degree of crosslinking reaction with the waterborne epoxy emulsion, fast surface drying time, high gloss, and excellent mechanical properties and weather resistance. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a fast-drying, high-performance waterborne epoxy curing agent and its preparation method. The waterborne epoxy curing agent has good water solubility, a high degree of crosslinking reaction with waterborne epoxy emulsion, short surface drying time, and high gloss, resulting in a coating with excellent mechanical properties and weather resistance.

[0005] The objective of this invention is achieved as follows:

[0006] Compared with the prior art, the beneficial effects of the present invention are as follows: the preparation method is relatively simple and easy to operate. The present invention is based on the introduction of bisphenol A and polyether segments onto the primary amine of the R group of ketimine-modified amine. The waterborne epoxy curing agent prepared by ketimine-modified amine has good water solubility, high activity, long pot life, good compatibility with waterborne epoxy emulsion, and the coating prepared by compounding with waterborne epoxy topcoat has fast drying speed, high gloss, good hardness, and excellent weather resistance (water and salt spray resistance). Attached Figure Description

[0007] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0008] Figure 1 The 1H NMR spectrum of the ketimine-modified amine in Example 1 is shown.

[0009] Figure 2 The infrared spectrum of the ketimine-modified amine in Example 1 is shown.

[0010] in, 1 ¹H NMR was measured in a 400 UltraShield instrument, with the sample dissolved in deuterated dimethyl sulfoxide (DMSO), and scanned at 25 °C. Infrared spectroscopy was performed in a Nicolet iS20 spectrometer, with eight scans of the sample at a resolution of 4 cm⁻¹, and a wavelength range of 500–4000 cm⁻¹. Figure 1 middle 1 The δ = 5-7 ppm peak in the ¹H NMR spectrum can be used to determine whether a substance has undergone a reaction. As shown in the graph, the disappearance of the signal peak at δ = 5-7 ppm, i.e., the disappearance of the C=C double bond peak, indicates the synthesis of a C=C bond compound. The ketone carbonyl infrared fluctuation peak of diacetone acrylamide is located at 1630-1680 cm⁻¹. -1 ketimine infrared fluctuation peak: 1650-1690 cm⁻¹ -1 The active hydrogen infrared fluctuation peaks of primary amines and amides are at 3200 cm⁻¹. -1 The results, as confirmed by NMR and IR, indicate that ketimine can be prepared under the conditions of Case 1. Detailed Implementation

[0011] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0012] A method for preparing a fast-drying, high-performance waterborne epoxy curing agent includes the following two steps:

[0013] Step 1: Preparation of ketimine-modified intermediates.

[0014] In one implementation method, the ketimine-modified intermediate is prepared by adding diacetone acrylamide and a polyamine to a 500 mL three-necked flask, mixing and stirring until homogeneous, and then reacting in an oil bath at 100-140 °C for 3-5 h. The polyamine is one or more of m-phenylenediamine, 1,2-cyclohexanediamine, ethylenediamine, diethylenetriamine, isophoronediamine, polyetheramine T403, and polyetheramine D230, preferably at least one of m-phenylenediamine, ethylenediamine, diethylenetriamine, and polyetheramine T403.

[0015] Step 2: Introduce bisphenol A and polyether segments into the structure of the ketimine-modified amine intermediate. This invention mainly involves reacting the ketimine-modified amine intermediate with aqueous and oily epoxy resins, followed by dilution with deionized water to obtain an epoxy-polyamine adduct with a solid content of 50-60%. The molar ratio of ketimine-modified amine: aqueous epoxy resin: oily epoxy resin is 0.2-0.3:0.05-0.09:0.10-0.18. The epoxy resins include aqueous and oily epoxy resins. The aqueous epoxy resins include one or more of polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and polybutylene glycol diglycidyl ether. The oily epoxy resins include one or more of E44 epoxy resin, E51 epoxy resin, and E20 epoxy resin.

[0016] The features and performance of this application will be further described in detail below with reference to the embodiments.

[0017] Example 1

[0018] The present invention will be further described in conjunction with specific embodiments, and the following specific embodiments are the preferred embodiments of the present invention.

[0019] A method for preparing a fast-drying, high-hardness waterborne epoxy curing agent, comprising the following steps:

[0020] Step 1: Preparation of ketimine-modified amine intermediates. The ketimine-modified intermediates were prepared by adding diacetone acrylamide (0.1 mol), diethylenetriamine (0.2 mol), and m-phenylenediamine (0.1 mol) to a 500 mL three-necked flask, respectively, and stirring until homogeneous. The mixture was then reacted in an oil bath at 100-140 ℃ with stirring at 300 r / s for 2-5 h to obtain a ketimine-modified amine solution.

[0021] The ketimine-modified amine solution is a pale yellow liquid with a solid content of 95% and a viscosity of 1500 mPa·s. It exhibits good stability and remains stable after 30 days of heat storage at 50 ℃.

[0022] The reaction formula for the ketimine-modified amine solution is as follows:

[0023]

[0024] Step 2: Introduce bisphenol A and polyether segments into the ketimine-modified amine intermediate structure to prepare a waterborne epoxy curing agent. By molar weight, add 0.2 mol of the ketimine-modified amine solution to a 250 mL three-necked flask. Separately weigh 0.05 mol of ethylene glycol diglycidyl ether and 0.10 mol of E-44 epoxy resin into a disposable cup, stir and disperse evenly, pour into a constant pressure funnel, and add dropwise to the three-necked flask at a rate of 1 d / s. During the dropwise addition, maintain the water bath temperature at 50℃ to allow the epoxy and amine to slowly complete chain extension. After the dropwise addition is complete, raise the temperature to 65℃ and maintain the reaction for 2 h. After the reaction is complete, dilute with deionized water to a solid content of 50% to obtain the waterborne epoxy curing agent.

[0025] Example 2

[0026] Using the ketimine-modified amine intermediate prepared in Case 1 as the main reactant, bisphenol A and polyether segments were introduced into the structure to prepare a waterborne epoxy curing agent. 0.2 mol of the ketimine-modified amine solution was added to a 250 mL three-necked flask by molar weight. Separately, 0.05 mol of propylene glycol diglycidyl ether and 0.18 mol of E-51 epoxy resin were weighed into a disposable cup, stirred and dispersed evenly, and poured into a constant pressure funnel. The mixture was then added dropwise to the three-necked flask at a rate of 1 d / s. During the addition, the temperature of the water bath was maintained at 50℃ to allow the epoxy and amine to slowly complete chain extension. After the addition was complete, the temperature was raised to 65℃ and the reaction was maintained for 2 hours. After the reaction was complete, the mixture was diluted with deionized water to a solid content of 50%, yielding the waterborne epoxy curing agent.

[0027] Example 3

[0028] Using the ketimine-modified amine intermediate prepared in Case 1 as the main reactant, bisphenol A and polyether segments were introduced structurally to prepare a waterborne epoxy curing agent. 0.2 mol of the ketimine-modified amine solution was added to a 250 mL three-necked flask. Separately, 0.07 mol of propylene glycol diglycidyl ether and 0.14 mol of E-44 epoxy resin were weighed into a disposable cup, stirred and dispersed evenly, and poured into a constant pressure funnel. The mixture was then added dropwise to the three-necked flask at a rate of 1 d / s. During the addition, the temperature of the water bath was maintained at 50 °C to allow the epoxy and amine to slowly complete chain extension. After the addition was complete, the temperature was raised to 65 °C and maintained for 2 h. After the reaction was complete, the mixture was diluted with deionized water to a solid content of 50%, yielding the waterborne epoxy curing agent.

[0029] Example 4

[0030] Using the ketimine-modified amine intermediate prepared in Case 1 as the main reactant, bisphenol A and polyether segments were introduced into the structure to prepare a waterborne epoxy curing agent. 0.3 mol of the ketimine-modified amine solution was added to a 250 mL three-necked flask by molarity. 0.06 mol of E-20 was weighed and dissolved in a solvent under heating conditions to dissolve the E-20 epoxy resin. Separately, 0.12 mol of ethylene glycol diglycidyl ether was weighed into a disposable cup, stirred and dispersed evenly, and poured into a constant pressure funnel. The solution was then added dropwise to the three-necked flask at a rate of 1 d / s. During the addition, the temperature of the water bath was maintained at 50 °C to allow the epoxy and amine to slowly complete chain extension. After the addition was complete, the temperature was raised to 90 °C and maintained for 2 h. After the reaction was complete, the solution was diluted with deionized water to a solid content of 60%, yielding the waterborne epoxy curing agent.

[0031] Example 5

[0032] Using the ketimine-modified amine intermediate prepared in Case 1 as the main reactant, bisphenol A and polyether segments were introduced into the structure to prepare a waterborne epoxy curing agent. 0.3 mol of the ketimine-modified amine solution was added to a 250 mL three-necked flask by molarity. 0.06 mol of E-20 was weighed and dissolved in a solvent under heating conditions to remove E-20 epoxy resin. Separately, 0.05 mol of ethylene glycol diglycidyl ether and 0.06 mol of propylene glycol diglycidyl ether were weighed into a disposable cup, stirred and dispersed evenly, and poured into a constant pressure funnel. The mixture was then added dropwise to the three-necked flask at a rate of 1 d / s. During the addition, the temperature of the water bath was maintained at 50 °C to allow the epoxy and amine to slowly complete chain extension. After the addition was complete, the temperature was raised to 90 °C and the reaction was maintained for 2 h. After the reaction was complete, the mixture was diluted with deionized water to a solid content of 60%, yielding the waterborne epoxy curing agent.

[0033] Example 6

[0034] Using the ketimine-modified amine intermediate prepared in Case 1 as the main reactant, bisphenol A and polyether segments were introduced into the structure to prepare a waterborne epoxy curing agent. By molar weight, 0.08 mol of ethylene glycol diglycidyl ether, 0.09 mol of E51, and 0.06 mol of E44 epoxy resin were weighed into a disposable cup and stirred until evenly dispersed. The mixture was then poured into a constant pressure funnel and added dropwise to the three-necked flask at a rate of 1 d / s. During the addition, the temperature of the water bath was maintained at 50 °C to allow the epoxy and amine to slowly complete chain extension. After the addition was complete, the temperature was raised to 70 °C and maintained for 2 h. After the reaction was complete, the mixture was diluted with deionized water to a solid content of 50%, yielding the waterborne epoxy curing agent.

[0035] Experimental methods:

[0036] The waterborne epoxy curing agent obtained in this embodiment is a room-temperature curing two-component epoxy curing agent. Therefore, it needs to undergo a cross-linking curing reaction with component A, the waterborne epoxy emulsion. The waterborne epoxy emulsion can be purchased or made in-house, and its epoxy equivalent is 1060 g / mol. A two-component waterborne epoxy coating is obtained by mixing active hydrogen and epoxy groups at a molar ratio of 1:1.25. The two-component waterborne epoxy varnish is then sprayed, the coating film is dried, and its performance is tested.

[0037] The test was conducted according to the following standard method:

[0038] Surface drying time: The surface drying time of various paint films was tested using the finger touch method in accordance with the requirements of the national standard GB / T1728-1979.

[0039] Hardness: Tested according to national standard GB / T6739-2006 "Determination of hardness of paint film by pencil method for paints and varnishes";

[0040] Adhesion: In accordance with the requirements of the national standard GB / T9286-1998, the adhesion of different paint films was rated by manually drawing a grid.

[0041] Water resistance: Tested according to the requirements of national standard GB / T1733-99;

[0042] Resistance to neutral salt spray: Tested in accordance with the requirements of national standard GB / T1771-2007.

[0043] Testing environment conditions: temperature 25 ℃±2 ℃; humidity (50±5%)RH.

[0044] The composition of different two-component waterborne epoxy primers and the corresponding performance test results of the coating films are shown in Table 1.

[0045] Table 1. Composition and film performance test results of two-component waterborne epoxy topcoat

[0046]

[0047] 3132 is a product of Jiangsu Fuqisen New Materials Co., Ltd.

[0048] In summary, ketimine-modified amine solutions exhibit fast drying speed, high gloss, high hardness, and good weather resistance. The incorporation of bisphenol A type epoxy resin and polyether segments into the ketimine-modified amine structure significantly improves its curing rate with waterborne epoxy emulsions, thereby enhancing the mechanical properties, water resistance, and salt spray resistance of the corresponding coating film.

[0049] The above description of the embodiments is only for the purpose of helping to understand the method and 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 method for preparing a fast-drying, high-performance waterborne epoxy curing agent, characterized in that, A waterborne epoxy curing agent is prepared by reacting a ketimine-modified amine with waterborne and oilborne epoxy resins, and controlling the solid content by adding a solvent. The ketimine-modified amine is a carbonyl-containing ketimine compound obtained by reacting diacetone acrylamide with a polyamine under heating conditions. The waterborne epoxy resin is an epoxy resin containing polyether segments, and the oilborne epoxy resin is an epoxy resin containing bisphenol A segments.

2. The preparation method of the fast-drying, high-performance waterborne epoxy curing agent according to claim 1, characterized in that, The waterborne epoxy resin includes one or more of polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and polybutylene glycol diglycidyl ether; the oilborne epoxy resin includes one or more of E44 epoxy resin, E51 epoxy resin, and E20 epoxy resin.

3. The preparation method of the fast-drying, high-performance waterborne epoxy curing agent according to claim 1, characterized in that, The ketimine-modified amine solution has a solid content of 92-98%, and the molar ratio of the ketimine-modified amine solution to the aqueous epoxy resin and the oil-based epoxy resin is 0.2-0.3:0.05-0.09:0.10-0.

18.

4. The preparation method of the fast-drying, high-performance waterborne epoxy curing agent according to claim 1, characterized in that, The water-based epoxy resin and the oil-based epoxy resin are stirred evenly and then added dropwise at a uniform rate to the ketimine-modified amine solution. The addition temperature is controlled at 50-65 ℃. After the addition is completed, the temperature is raised to 65-90 ℃ and the reaction is maintained at this temperature for 2-4 h. The stirring speed is 200-400 r / min.

5. The preparation method of the fast-drying, high-performance waterborne epoxy curing agent according to claim 1, characterized in that, The solvent is deionized water, and the solid content of the curing agent is controlled at 50-60%.

6. The preparation method of the fast-drying, high-performance waterborne epoxy curing agent according to claim 1, characterized in that, The polyamine solution is at least one of m-phenylenediamine, 1,2-cyclohexanediamine, ethylenediamine, diethylenetriamine, isophoronediamine, polyetheramine T403, and polyetheramine D230.

7. The preparation method of the fast-drying, high-performance waterborne epoxy curing agent according to claim 1, characterized in that, The synthesis of the ketimine-modified amine solution mainly involves the reaction of diacetone acrylamide and polyamine in a molar ratio. Specifically, 0.01-0.05 mol of diacetone acrylamide and 0.03-0.15 mol of polyamine are weighed and reacted in a one-pot manner at a reaction temperature of 100-140 ℃ for 3-5 h under stirring to obtain the ketimine-modified amine solution.

8. The preparation method of the fast-drying, high-performance waterborne epoxy curing agent according to claim 1, characterized in that, Since epoxy resins with amines as curing agents are mainly two-component epoxy resins that cure at room temperature, component A is an aqueous epoxy emulsion and component B is the aqueous epoxy curing agent prepared in this application. Components A and B are mixed with an active hydrogen to epoxy group molar ratio of 1:0.8-1.25 to obtain a two-component aqueous epoxy coating. The two-component aqueous epoxy coating is then sprayed and baked to form a coating film, and its performance is tested.

9. A fast-drying, high-performance waterborne epoxy curing agent prepared by the method described in claim 1.

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