Quick-drying high-performance waterborne epoxy curing agent and preparation method thereof

Abstract

The invention discloses a quick-drying high-performance waterborne epoxy curing agent in the technical field of coatings, the curing agent is prepared from a compound, and the compound is prepared by introducing a polyether chain segment and a bisphenol A chain segment to primary amine positions of R groups at two ends in ketimine modified amine; the ketimine modified amine is synthesized by carrying out Micheal addition on diacetone acrylamide carbon-carbon double bonds and carrying out condensation dehydration on the diacetone acrylamide carbon-carbon double bonds and primary amine; the ketimine modified amine waterborne epoxy curing agent is good in water solubility, high in crosslinking reaction degree with waterborne epoxy emulsion and short in surface drying time, and meanwhile, an obtained coating has excellent mechanical performance and weather resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and in particular to a waterborne epoxy curing agent and a preparation method thereof. Background Art

[0002] With the improvement of green environmental protection concept, the development of zero VOC or low VOC waterborne epoxy curing agent has great advantages. Nowadays, non-ionic waterborne epoxy curing agent has become the mainstream research direction of waterborne epoxy curing agent. However, although the commercially available waterborne epoxy curing agent has excellent mechanical properties and weather resistance, it has disadvantages such as slow drying speed, which causes the coating to lose gloss during the curing process, resulting in low gloss on the coating surface and limited application range. Therefore, it is particularly important to prepare a fast-drying and high-hardness waterborne curing agent. Diacetone acrylamide has a high gloss content in its structure. N -Substituted amides and ketones can be copolymerized with other monomers and can be used as a new type of vinyl functional monomer and are widely used in the coating industry. The C=C double bond in the diacetone acrylamide structure undergoes Michael addition reaction with the primary amine in the polyamine. N The ketone carbonyl group in the -substituted amide can undergo dehydration condensation with polyamines to obtain the same imine structure.

[0003] Patent CN112321801A discloses a method for preparing a cationic self-emulsifying waterborne epoxy resin fast-drying curing agent, and the curing agent also has the characteristics of high cross-linking density, fast surface drying, and high hardness when reacting with epoxy resin, but the addition of organic acid salt during the synthesis of the ionic curing agent has an adverse effect on the metal anti-corrosion performance of the paint film. Patent CN117987060A discloses a one-component structural adhesive and a preparation method thereof, which mainly uses methyl ethyl ketone or methyl isobutyl ketone to react with polyamines to prepare ketimine, and uses ketimine as a one-component structural adhesive film-forming material, without acting on the waterborne epoxy curing agent. This patent uses Micheal addition, diacetone acrylamide carbon-carbon double bonds react with primary amines and condense and dehydrate to prepare carbonyl-containing ketimine modified amines, and ketimine and epoxy resin undergo chain extension reaction to obtain a waterborne epoxy curing agent, and the curing agent has a high degree of cross-linking reaction with waterborne epoxy emulsion, fast surface drying time, high gloss, and excellent mechanical properties and weather resistance. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a fast-drying, high-performance water-based epoxy curing agent and a preparation method thereof. The water-based epoxy curing agent has good water solubility, a high degree of cross-linking reaction with a water-based epoxy emulsion, a short surface drying time and high gloss, and the obtained coating has excellent mechanical properties and weather resistance.

[0005] The object of the present invention is achieved in that: Compared with the prior art, the present invention has the following beneficial effects: the preparation method is relatively simple and easy to operate, and the present invention is prepared based on the introduction of bisphenol A and polyether segments into the primary amine of the R group of the ketimine-modified amine. The water-based epoxy curing agent prepared by the ketimine-modified amine has good water solubility, high activity, long application period, good compatibility with water-based epoxy emulsion, and the coating prepared by compounding with the water-based epoxy topcoat has fast drying speed, high gloss, good hardness, and excellent weather resistance (water and salt spray resistance). BRIEF DESCRIPTION OF THE DRAWINGS

[0006] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0007] Figure 1 This is the H NMR spectrum of the ketimine-modified amine in Example 1.

[0008] Figure 2 This is the infrared spectrum of the ketimine-modified amine in Example 1.

[0009] in, 1 H NMR was measured in a nuclear magnetic resonance instrument (400 UItraShield), the sample was dissolved in deuterated dimethyl sulfoxide (DMSO) and scanned at 25 °C. IR was measured in an infrared spectrometer (Nicolet iS20), the sample was scanned 8 times, the resolution was 4 cm-1, and the wavelength test range was 500-4000 cm-1. Figure 1 middle 1 The δ = 5-7 ppm of the H NMR spectrum can be used to determine whether the substance has reacted. From the figure, it can be seen that the signal peak at δ = 5-7 ppm disappears, that is, the C=C double bond peak disappears, and the CN bond compound is synthesized. The infrared fluctuation peak of the keto carbonyl group of diacetone acrylamide: 1630-1680 cm -1 , ketimine infrared fluctuation peak: 1650-1690 cm -1 The active hydrogen infrared peaks of primary amines and amides are at 3200 cm -1 It can be determined by NMR and IR that the conditions in Case 1 can prepare ketimine. DETAILED DESCRIPTION

[0010] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0011] A method for preparing a fast-drying, high-performance water-based epoxy curing agent comprises the following two steps: Step 1: Preparation of ketimine modified intermediate.

[0012] As an embodiment, the ketimine modified intermediate is prepared mainly by the amount of substance, and diacetone acrylamide and polyamine are added to a 500 mL three-necked flask, mixed and stirred evenly, and kept warm in an oil bath pot at 100-140 ° C for 3-5 hours. The polyamine is one or more of m-phenylenediamine, 1,2-cyclohexanediamine, ethylenediamine, diethylenetriamine, isophoronediamine, polyetheramine T403, and polyetheramine D230, wherein at least one of m-phenylenediamine, ethylenediamine, diethylenetriamine, and polyetheramine T403 is preferred.

[0013] Step 2: Introduce bisphenol A and polyether segments into the structure of the ketimine modified amine intermediate. The present invention mainly comprises a ketimine modified amine intermediate reacting with a water-based and oily epoxy resin, and then diluting with deionized water as a solvent to obtain an epoxy-polyamine adduct with a solid content of 50-60%. In terms of molar weight, the ketimine modified amine: water-based epoxy resin: oily epoxy resin = 0.2-0.3: 0.05-0.09: 0.10-0.18. Among them, the epoxy resin, water-based and oily epoxy resin, the water-based epoxy resin includes one or more of polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and polybutylene glycol diglycidyl ether. The oily epoxy resin includes one or more of E44 epoxy resin, E51 epoxy resin, and E20 epoxy resin.

[0014] The features and performance of the present application are further described in detail below in conjunction with the embodiments.

[0015] Example 1 The present invention is further described in conjunction with specific embodiments. The following specific embodiments are all the best implementation modes of the present invention.

[0016] A method for preparing a fast-drying, high-hardness water-based epoxy curing agent, comprising the following steps: Step 1: Prepare ketimine modified amine intermediates. The ketimine modified intermediates are prepared mainly based on the amount of substance. Diacetone acrylamide (0.1 mol), diethylenetriamine (0.2 mol), and meta-phenylenediamine (0.1 mol) are added to a 500 mL three-necked flask and mixed and stirred evenly. The mixture is kept warm in an oil bath at 100-140 °C and stirred at a speed of 300 r / s for 2-5 h to obtain a ketimine modified amine solution.

[0017] The ketimine-modified amine solution is a light yellow liquid with a solid content of 95%, a viscosity of 1500 mpa·s, good stability, and stable performance after thermal storage at 50 ℃ for 30 days.

[0018] The reaction formula of the ketimine modified amine solution is:

[0019] Step 2: Introduce bisphenol A and polyether segments into the structure of the ketimine modified amine intermediate to prepare a water-based epoxy curing agent. According to the amount of substance, add 0.2 mol of ketimine modified amine solution into a 250 mL three-necked flask, 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 drop into the three-necked flask at a speed of 1 d / s. During the dropwise addition, keep the temperature of the water bath at 50°C to allow the epoxy and amine to slowly complete the chain extension. After the dropwise addition is completed, heat to 65°C and keep warm for 2 h. After the reaction is completed, deionize water and dilute to 50% solid content to obtain a water-based epoxy curing agent.

[0020] Example 2 The ketimine modified amine intermediate prepared in Case 1 was used as the main reaction body, and bisphenol A and polyether segments were introduced into the structure to prepare a water-based epoxy curing agent. According to the amount of substance, 0.2 mol of ketimine modified amine solution was added to a 250 mL three-necked flask, and 0.05 mol of propylene glycol diglycidyl ether and 0.18 mol of E-51 epoxy resin were weighed in a disposable cup, stirred and dispersed evenly, poured into a constant pressure funnel, and added dropwise to the three-necked flask at a speed of 1 d / s. During the dropping process, the temperature of the water bath was maintained at 50°C to allow the epoxy and amine to slowly complete the chain extension. After the dropping was completed, the temperature was raised to 65°C for insulation reaction for 2 hours. After the reaction was completed, deionized water was added and the solid content was diluted to 50% to obtain a water-based epoxy curing agent.

[0021] Example 3 The ketimine modified amine intermediate prepared in Case 1 was used as the main reaction body, and bisphenol A and polyether segments were introduced into the structure to prepare a water-based epoxy curing agent. According to the amount of substance, 0.2 mol of ketimine modified amine solution was added to a 250 mL three-necked flask, and 0.07 mol of propylene glycol diglycidyl ether and 0.14 mol of E-44 epoxy resin were weighed in a disposable cup, stirred and dispersed evenly, poured into a constant pressure funnel, and added dropwise to the three-necked flask at a speed of 1 d / s. During the dropping process, the temperature of the water bath was maintained at 50 °C to allow the epoxy and amine to slowly complete the chain extension. After the dropping was completed, the temperature was raised to 65 °C for insulation reaction for 2 h. After the reaction was completed, deionized water was added and the solid content was diluted to 50% to obtain a water-based epoxy curing agent.

[0022] Example 4 The ketimine modified amine intermediate prepared in Case 1 was used as the main reaction body, and bisphenol A and polyether segments were introduced into the structure to prepare a water-based epoxy curing agent. According to the amount of substance, 0.3 mol of ketimine modified amine solution was added to a 250 mL three-necked flask, 0.06 mol of E-20 was weighed, and the E-20 epoxy resin was dissolved with a solvent under heating conditions. In addition, 0.12 mol of ethylene glycol diglycidyl ether was weighed in a disposable cup, stirred and dispersed evenly, poured into a constant pressure funnel, and added dropwise to the three-necked flask at a speed of 1 d / s. During the dropping process, the temperature of the water bath was maintained at 50 °C to allow the epoxy and amine to slowly complete the chain extension. After the dropping was completed, the temperature was raised to 90 °C and kept warm for 2 h. After the reaction was completed, deionized water was added and the solid content was diluted to 60% to obtain a water-based epoxy curing agent.

[0023] Example 5 The ketimine modified amine intermediate prepared in Case 1 was used as the main reaction body, and bisphenol A and polyether segments were introduced into the structure to prepare a water-based epoxy curing agent. According to the amount of substance, 0.3 mol of ketimine modified amine solution was added to a 250 mL three-necked flask, 0.06 mol of E-20 was weighed, and the E-20 epoxy resin was dissolved with a solvent under heating conditions. In addition, 0.05 mol of ethylene glycol diglycidyl ether and 0.06 mol of propylene glycol diglycidyl ether were weighed in a disposable cup, stirred and dispersed evenly, poured into a constant pressure funnel, and added dropwise to the three-necked flask at a speed of 1d / s. During the dropping process, the temperature of the water bath was maintained at 50°C to allow the epoxy and amine to slowly complete the chain extension. After the dropping was completed, the temperature was raised to 90°C and kept warm for 2 h. After the reaction was completed, deionized water was added and the solid content was diluted to 60% to obtain a water-based epoxy curing agent.

[0024] Example 6 The ketimine modified amine intermediate prepared in Case 1 was used as the main reaction body, and bisphenol A and polyether segments were introduced into the structure to prepare a water-based epoxy curing agent. According to the amount of substance, 0.3 mol of ketimine modified amine solution was placed in a three-necked flask, 0.08 mol of ethylene glycol diglycidyl ether and 0.09 mol of E51 and 0.06 mol of E44 epoxy resin were weighed in a disposable cup, stirred and dispersed evenly, poured into a constant pressure funnel, and dripped into the three-necked flask at a speed of 1 d / s. During the dripping process, the temperature of the water bath was maintained at 50 °C to allow the epoxy and amine to slowly complete the chain extension. After the dripping was completed, the temperature was raised to 70 °C for insulation reaction for 2 h. After the reaction was completed, deionized water was added and the solid content was diluted to 50% to obtain a water-based epoxy curing agent.

[0025] Experimental methods: The waterborne epoxy curing agent obtained in the embodiment of the present application is a two-component epoxy curing agent that cures at room temperature, so it needs to undergo a cross-linking curing reaction with the A-component waterborne epoxy emulsion, which can be purchased or homemade, and has an epoxy equivalent of 1060 g / mol. The two-component waterborne epoxy coating is obtained by mixing the active hydrogen and epoxy groups at a molar ratio of 1:1.25, and then the two-component waterborne epoxy varnish is sprayed, the coating is dried, and the performance is tested.

[0026] The test was performed according to the following standard method: Surface drying time: According to the requirements of the national standard GB / T1728-1979, the surface drying time of various paint films is tested by finger touch method; Hardness: Tested in accordance with the national standard GB / T6739-2006 "Determination of paint film hardness by pencil method for paints and varnishes"; Adhesion: According to the requirements of national standard GB / T9286-1998, the adhesion of different paint films is rated by manual gridding method; Water resistance: tested in accordance with the national standard GB / T1733-99; Neutral salt spray resistance: tested in accordance with the national standard GB / T1771-2007.

[0027] Testing environment conditions: temperature 25 ℃±2 ℃; humidity (50±5%) RH.

[0028] The compositions of different two-component waterborne epoxy primers and the performance test results of the corresponding paint films are shown in Table 1.

[0029] Table 1 Composition and film performance test results of two-component waterborne epoxy topcoat

[0030] 3132 is a product of Jiangsu Fuqisen New Materials Co., Ltd. In summary, the ketimine-modified amine solution itself has a fast drying speed, high gloss, high hardness and good weather resistance. After adding bisphenol A epoxy resin and polyether segments into the ketimine-modified amine structure, the curing rate with water-based epoxy emulsion is significantly improved, and the mechanical properties, water resistance and salt spray resistance of the corresponding paint film are improved.

[0031] The above embodiments are only used to help understand the method and core idea of ​​the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A fast-drying, high-performance water-based epoxy curing agent, characterized in that: The invention comprises a compound, wherein a polyether segment and a bisphenol A segment are introduced into the primary amine position of the R groups at both ends of the ketimine-modified amine; the structural formula of the ketimine-modified amine is: 。 2. A method for preparing the fast-drying, high-performance water-based epoxy curing agent according to claim 1, characterized in that: The water-based epoxy curing agent is prepared by reacting ketimine-modified amine with water-based epoxy resin and oil-based epoxy resin, and adding solvent to control the solid content; wherein the ketimine-modified amine is a carbonyl-containing ketimine compound obtained by reacting diacetone acrylamide with polyamine under heating conditions; the water-based epoxy resin is an epoxy resin containing a polyether segment; and the oil-based epoxy resin is an epoxy resin containing a bisphenol A segment.

3. The method for preparing the fast-drying, high-performance water-based epoxy curing agent according to claim 2, characterized in that: The water-based epoxy resin includes one or more of polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and polybutylene glycol diglycidyl ether; the oil-based epoxy resin includes one or more of E44 epoxy resin, E51 epoxy resin, and E20 epoxy resin.

4. The method for preparing the fast-drying, high-performance water-based epoxy curing agent according to claim 2, characterized in that: The solid content of the ketimine modified amine solution is 92-98%. The molar ratio of the ketimine modified amine solution, the water-based epoxy resin and the oily epoxy resin is 0.2-0.3: 0.05-0.09: 0.10-0.

18.

5. The method for preparing the fast-drying, high-performance water-based epoxy curing agent according to claim 2, characterized in that: The water-based epoxy resin and the oil-based epoxy resin are stirred evenly, and then uniformly dripped into the ketimine-modified amine solution. The dropping temperature is controlled at 50-65°C. After the dropping is completed, the temperature is raised to 65-90°C, and the reaction is kept warm for 2-4 hours. The stirring speed is 200-400r / min.

6. The method for preparing the fast-drying, high-performance water-based epoxy curing agent according to claim 2, characterized in that: The solvent is deionized water, and the solid content of the curing agent is controlled at 50-60%.

7. The method for preparing the fast-drying, high-performance water-based epoxy curing agent according to claim 2, characterized in that: The polyamine solution is at least one of meta-phenylenediamine, 1,2-cyclohexanediamine, ethylenediamine, diethylenetriamine, isophoronediamine, polyetheramine T403 and polyetheramine D230.

8. The method for preparing the fast-drying, high-performance water-based epoxy curing agent according to claim 2, characterized in that: The synthesis of the ketimine modified amine solution is mainly based on the molar ratio of diacetone acrylamide and polyamine; wherein, 0.01-0.05 mol of diacetone acrylamide and 0.03-0.15 mol of polyamine are weighed, a one-pot method is adopted, the reaction temperature is 100-140°C, and the ketimine modified amine solution is obtained by heat preservation reaction for 3-5 hours under stirring conditions.

9. The method for preparing the fast-drying, high-performance water-based epoxy curing agent according to claim 2, characterized in that: Since the epoxy resin with amine as a curing agent is mainly a two-component epoxy resin that cures at room temperature, component A is a water-based epoxy emulsion, component B is a water-based epoxy curing agent prepared in the present application, and components AB are mixed with a molar ratio of active hydrogen to epoxy group of 1:0.8-1.25 to obtain a two-component water-based epoxy coating, and then the two-component water-based epoxy coating is sprayed and baked to form a coating film, and its performance is tested.

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