Water-based epoxy paint for containers and method for preparing the same

Abstract

The application relates to the technical field of epoxy resin paint, and discloses a water-based epoxy paint suitable for containers and a preparation method thereof; a component A of the water-based epoxy paint comprises 100 parts by weight of a water-based epoxy resin and 0.5-0.8 parts by weight of a flash rust inhibitor; a component B comprises 6-8 parts by weight of a polyamide curing agent, 5-12 parts by weight of an organic silicon sulfonate polyurethane toughening agent and 0.2-1 part by weight of graphene oxide; the organic silicon polyurethane toughening agent can play the role of a dispersant, improves the dispersibility of graphene in the water-based epoxy paint, the main chain of the organic silicon polyurethane toughening agent contains imino groups, can react with the epoxy resin, bonds flexible organic polysiloxane molecular chains into the epoxy resin molecular chains, plays a good toughening role, and thus the flexibility, impact resistance and corrosion resistance of the paint film are improved.

Description

Technical Field

[0001] This invention relates to the field of epoxy resin paint technology, specifically to a water-based epoxy paint suitable for containers and its preparation method. Background Technology

[0002] Epoxy resin paints and coatings possess excellent insulation properties and high mechanical strength, and are widely used in containers, ships, automobiles, instruments, equipment, and sporting goods. Improving the toughness and corrosion resistance of epoxy resins is a research hotspot. Polyurethane has good toughness, elasticity, and mechanical properties, and is widely used in epoxy resin paints and coatings. Polysiloxanes have high toughness, strong water resistance, and good corrosion resistance, and can play a certain role in toughening epoxy resins. Patent CN116284655B discloses a method for preparing graphene-organosilicon synergistically reinforced polyurethane graft-modified epoxy resin. Graphene isocyanate modified and linked to a linear polyurethane polymer using a low-molecular-weight polyhydroxysilane as a bridging agent to obtain a graphene-organosilicon synergistically reinforced polyurethane prepolymer. After graft copolymerization with epoxy resin, the toughness and heat resistance of the epoxy resin are improved. However, this patent requires isocyanate modification of graphene, making the preparation method relatively complex, and it does not improve the corrosion resistance of the epoxy resin. Summary of the Invention

[0003] (I) Technical problem to be solved: The present invention provides a water-based epoxy paint with good anti-corrosion performance and high toughness suitable for containers.

[0004] (II) Technical Solution: A water-based epoxy paint suitable for containers, consisting of component A and component B. Component A includes 100 parts by weight of water-based epoxy resin, 0.5-0.8 parts by weight of anti-flash rust agent, 0.4-0.7 parts by weight of defoamer, and 0.3-0.6 parts by weight of leveling agent; component B consists of 6-8 parts by weight of polyamide curing agent, 5-12 parts by weight of organosilicon sulfonate polyurethane toughening agent, and 0.2-1 parts by weight of graphene oxide.

[0005] The preparation method of organosilicon sulfonate polyurethane toughening agent is as follows:

[0006] (1) Add epoxypropoxypropyl-terminated polydimethylsiloxane and 2-aminoethanesulfonic acid in a molar ratio of 1:(2-2.2) to tetrahydrofuran, stir the reaction at 40-50℃ for 8-12 h, concentrate under reduced pressure, and dry to obtain hydroxyimine sulfonic acid polysiloxane. The reaction formula is:

[0007]

[0008] (2) Add hydroxysulfonic acid polysiloxane and di-tert-butyl dicarbonate in a molar ratio of 1:(2.2-2.4) to the solvent in an ice-water bath. Stir the reaction at 20-25℃ for 6-8 hours, concentrate under reduced pressure, wash with sodium bicarbonate solution, and dry to obtain hydroxy-Boc aminosulfonic acid polysiloxane. The reaction formula is:

[0009]

[0010] (3) Add dried polyethylene glycol, hydroxy-Boc aminosulfonic acid polysiloxane, and dibutyltin dilaurate to methyl ethyl ketone solvent, heat to 70-80℃ in a nitrogen atmosphere, add diisocyanate monomer, react for 3-5h, then add 1,4-butanediol, react for 1-1.5h, concentrate under reduced pressure, add the product to dichloromethane, stir, add trifluoroacetic acid, stir at 20-30℃ for 4-6h, concentrate under reduced pressure, wash with sodium bicarbonate solution and sodium hydroxide solution in sequence, and dry to obtain organosilicon sulfonate polyurethane toughening agent.

[0011] Preferably, the solvent in (2) is dichloromethane, tetrahydrofuran or acetonitrile.

[0012] Preferably, in (3), the molar ratio of polyethylene glycol, hydroxy-Boc aminosulfonic acid polysiloxane, and diisocyanate monomer is (0.6-0.8):(0.2-0.4):(2.4-2.6):(1.2-1.3). The diisocyanate monomer is hexamethylene diisocyanate, toluene diisocyanate, or isophorone diisocyanate.

[0013] Preferably, the volume ratio of dichloromethane to trifluoroacetic acid in (3) is 1:(0.4-0.6).

[0014] A preferred method for preparing waterborne epoxy paint suitable for containers is as follows: Anti-flash rust agent, defoamer, and leveling agent are added to waterborne epoxy resin and stirred until homogeneous to obtain component A; graphene oxide is added to water and ultrasonically dispersed, followed by the addition of organosilicon sulfonate polyurethane toughening agent, and stirred for 1-2 hours; then a polyamide curing agent is added and stirred until dispersed to obtain component B; component B is added to component A and stirred until homogeneous to obtain waterborne epoxy paint suitable for containers.

[0015] The technical effect of this invention is as follows: the terminal epoxy groups of epoxy-propylene-propyl-terminated polydimethylsiloxane are reacted with 2-aminoethanesulfonic acid, and then the imino group is protected with di-tert-butyl dicarbonate to obtain hydroxy-Boc aminosulfonic acid polysiloxane, which contains hydroxyl groups at both ends. It is then polymerized with polyethylene glycol and diisocyanate monomers, and the Boc protecting group is removed by trifluoroacetic acid / dichloromethane and neutralized with sodium hydroxide to obtain an organosilicone sulfonate polyurethane toughening agent containing imino and sulfonate groups.

[0016] This invention incorporates graphene oxide and an organosilicon sulfonate polyurethane toughening agent into a waterborne epoxy resin. The polyurethane toughening agent contains hydrophilic sulfonate groups, which improves the hydrophilicity and water solubility of the polyurethane, resulting in excellent dispersibility in the waterborne epoxy resin emulsion and preventing sedimentation. Furthermore, the sulfonate groups of the polyurethane toughening agent interact with the graphene oxide surface through hydrogen bonding and other mechanisms, acting as a dispersant to improve the dispersibility of graphene in the waterborne epoxy paint, reduce the aggregation and sedimentation of graphene oxide, and thus give the waterborne epoxy paint excellent storage stability.

[0017] The organosilicon polyurethane toughening agent of this invention acts as a dispersant, improving the dispersibility of graphene in waterborne epoxy paint, reducing the agglomeration of graphene oxide, and thus enhancing the mechanical properties of the waterborne epoxy paint. Furthermore, the main chain of the organosilicon polyurethane toughening agent contains imino groups, which act as a curing agent, reacting with the epoxy resin to bond the flexible organopolysiloxane molecular chains to the epoxy resin molecular chains, resulting in excellent toughening and improved flexibility and impact resistance of the paint film. Moreover, the formation of a stable polysiloxane chemical crosslinking network between the polyurethane toughening agent and the epoxy resin inhibits the penetration of corrosive media such as acids, alkalis, and salts into the paint film matrix. Simultaneously, the uniformly dispersed graphene acts as a barrier against corrosive media, thereby improving the corrosion resistance of the paint film. Detailed Implementation

[0018] To facilitate understanding of the present invention, preferred embodiments are provided below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0019] The waterborne epoxy resin of this invention has a solid content of 50%; Shandong Chengtian Chemical Co., Ltd.; graphene oxide, model HL-GO, Shanghai Hanlang New Material Technology Co., Ltd.; defoamer, DF 5800C, Nanjing Chuhai New Material Technology Co., Ltd.; leveling agent WL-104E, Nanjing Chuhai New Material Technology Co., Ltd.; flash rust inhibitor, Defros-T750, Shenzhen Longdi Chemical Co., Ltd.; epoxypropoxypropyl-terminated polydimethylsiloxane, Wuhan Lanabai Pharmaceutical Chemical Co., Ltd.; dihydroxyl-terminated polydimethylsiloxane, Wuhan Lanabai Pharmaceutical Chemical Co., Ltd.

[0020] Example 1:

[0021] (1) Add 20 mmol of epoxypropoxypropyl-terminated polydimethylsiloxane and 40 mmol of 2-aminoethanesulfonic acid to 200 mL of tetrahydrofuran, stir and react at 45 °C for 12 h, concentrate under reduced pressure and dry to obtain hydroxyiminosulfonic acid polysiloxane.

[0022] (2) Add 30 mmol of hydroxysulfonic acid polysiloxane and 70 mmol of ditert-butyl dicarbonate to 300 mL of acetonitrile solvent in an ice-water bath. Stir the reaction at 20 °C for 8 h, concentrate under reduced pressure, wash with sodium bicarbonate solution, and dry to obtain hydroxy-Boc aminosulfonic acid polysiloxane.

[0023] (3) 80 mmol of dry polyethylene glycol 1000, 20 mmol of hydroxy-Boc aminosulfonic acid polysiloxane, and 0.12 g of dibutyltin dilaurate were added to 300 mL of butanone solvent. The mixture was heated to 75 °C under a nitrogen atmosphere, and 240 mmol of toluene diisocyanate was added. The mixture was reacted for 5 h, and then 120 mmol of 1,4-butanediol was added. The mixture was reacted for 1 h, and the mixture was concentrated under reduced pressure. The product was added to 2 L of dichloromethane, stirred, and then 1 L of trifluoroacetic acid was added. The mixture was stirred at 25 °C for 6 h, concentrated under reduced pressure, washed successively with sodium bicarbonate solution and sodium hydroxide solution, and dried to obtain organosilicon sulfonate polyurethane toughening agent.

[0024] (4) Add 8g of anti-flash rust agent, 5g of defoamer and 6g of leveling agent to 1000g of waterborne epoxy resin, stir and mix well to obtain component A; add 2g of graphene oxide to 100mL of water, disperse by ultrasonication and then add 50g of organosilicon sulfonate polyurethane toughening agent, stir for 1h, then add 80g of polyamide 650 curing agent, stir and disperse to obtain component B; add component B to component A, stir and mix well to obtain waterborne epoxy paint suitable for containers.

[0025] Example 2:

[0026] (1) Add 20 mmol of epoxypropoxypropyl-terminated polydimethylsiloxane and 44 mmol of 2-aminoethanesulfonic acid to 250 mL of tetrahydrofuran, stir and react at 40 °C for 12 h, concentrate under reduced pressure and dry to obtain hydroxyiminosulfonic acid polysiloxane.

[0027] (2) Add 30 mmol of hydroxysulfonic acid polysiloxane and 72 mmol of ditert-butyl dicarbonate to 400 mL of dichloromethane solvent in an ice-water bath. Stir the reaction at 25 °C for 6 h, concentrate under reduced pressure, wash with sodium bicarbonate solution, and dry to obtain hydroxy-Boc aminosulfonic acid polysiloxane.

[0028] (3) 70 mmol of dry polyethylene glycol 1000, 30 mmol of hydroxy-Boc aminosulfonic acid polysiloxane, and 0.1 g of dibutyltin dilaurate were added to 400 mL of butanone solvent. The mixture was heated to 80 °C under a nitrogen atmosphere, and 260 mmol of isophorone diisocyanate was added. The mixture was reacted for 3 h, and then 130 mmol of 1,4-butanediol was added. The mixture was reacted for 1.5 h, concentrated under reduced pressure, and the product was added to 2 L of dichloromethane. After stirring, 0.8 L of trifluoroacetic acid was added, and the mixture was stirred at 30 °C for 4 h. The mixture was concentrated under reduced pressure, washed successively with sodium bicarbonate solution and sodium hydroxide solution, and dried to obtain organosilicon sulfonate polyurethane toughening agent.

[0029] (4) Add 6g of anti-flash rust agent, 7g of defoamer and 3g of leveling agent to 1000g of waterborne epoxy resin, stir and mix well to obtain component A; add 5g of graphene oxide to 150mL of water, disperse by ultrasonication and then add 70g of organosilicon sulfonate polyurethane toughening agent, stir for 2h, then add 74g of polyamide 650 curing agent, stir and disperse to obtain component B; add component B to component A, stir and mix well to obtain waterborne epoxy paint suitable for containers.

[0030] Example 3:

[0031] (1) Add 20 mmol of epoxypropoxypropyl-terminated polydimethylsiloxane and 40 mmol of 2-aminoethanesulfonic acid to 200 mL of tetrahydrofuran, stir and react at 50 °C for 8 h, concentrate under reduced pressure and dry to obtain hydroxyimine sulfonic acid polysiloxane.

[0032] (2) Add 30 mmol of hydroxysulfonic acid polysiloxane and 66 mmol of ditert-butyl dicarbonate to 300 mL of tetrahydrofuran solvent in an ice-water bath. Stir the reaction at 20 °C for 8 h, concentrate under reduced pressure, wash with sodium bicarbonate solution, and dry to obtain hydroxy-Boc aminosulfonic acid polysiloxane.

[0033] (3) 60 mmol of dry polyethylene glycol 1000, 40 mmol of hydroxy-Boc aminosulfonic acid polysiloxane, and 0.15 g of dibutyltin dilaurate were added to 400 mL of butanone solvent. The mixture was heated to 70 °C under a nitrogen atmosphere, and 260 mmol of hexamethylene diisocyanate was added. The mixture was reacted for 5 h, and then 130 mmol of 1,4-butanediol was added. The mixture was reacted for 1 h, and the mixture was concentrated under reduced pressure. The product was added to 2 L of dichloromethane, stirred, and then 1.2 L of trifluoroacetic acid was added. The mixture was stirred at 20 °C for 6 h, and then concentrated under reduced pressure. The product was washed with sodium bicarbonate solution and sodium hydroxide solution in sequence, and then dried to obtain organosilicon sulfonate polyurethane toughening agent.

[0034] (4) Add 5g of anti-flash rust agent, 7g of defoamer and 4g of leveling agent to 1000g of waterborne epoxy resin, stir and mix well to obtain component A; add 7g of graphene oxide to 200mL of water, disperse by ultrasonication and then add 100g of organosilicon sulfonate polyurethane toughening agent, stir for 2h, then add 67g of polyamide 650 curing agent, stir and disperse to obtain component B; add component B to component A, stir and mix well to obtain waterborne epoxy paint suitable for containers.

[0035] Example 4:

[0036] (1) Add 5g of anti-flash rust agent, 4g of defoamer, and 6g of leveling agent to 1000g of waterborne epoxy resin, stir and mix well to obtain component A; add 10g of graphene oxide to 200mL of water, disperse by ultrasonication, add 120g of organosilicon sulfonate polyurethane toughening agent (prepared by the same method as in Example 1), stir for 2h, then add 60g of polyamide 650 curing agent, stir and disperse to obtain component B; add component B to component A, stir and mix well to obtain waterborne epoxy paint suitable for containers.

[0037] Comparative Example 1:

[0038] (1) Add 8g of anti-flash rust agent, 5g of defoamer and 6g of leveling agent to 1000g of waterborne epoxy resin, stir and mix well to obtain component A; add 2g of graphene oxide to 100mL of water, disperse by ultrasonication and then add 80g of polyamide 650 curing agent, stir and disperse to obtain component B; add component B to component A, stir and mix well to obtain waterborne epoxy paint suitable for containers.

[0039] Comparative Example 2:

[0040] (1) 80 mmol of dry polyethylene glycol 1000, 20 mmol of dihydroxy-terminated polydimethylsiloxane, and 0.12 g of dibutyltin dilaurate were added to 300 mL of butanone solvent. The mixture was heated to 75 °C under a nitrogen atmosphere, and 240 mmol of toluene diisocyanate was added. The mixture was reacted for 5 h, and then 120 mmol of 1,4-butanediol was added. The mixture was reacted for 1 h, concentrated under reduced pressure, and dried to obtain organosilicon polyurethane.

[0041] (2) Add 8g of anti-flash rust agent, 5g of defoamer and 6g of leveling agent to 1000g of waterborne epoxy resin, stir and mix well to obtain component A; add 2g of graphene oxide to 100mL of water, disperse by ultrasonication and then add 50g of organosilicon polyurethane, stir for 1h, then add 80g of polyamide 650 curing agent, stir and disperse to obtain component B; add component B to component A, stir and mix well to obtain waterborne epoxy paint suitable for containers.

[0042] Comparative Example 3:

[0043] (1) 80 mmol of dry polyethylene glycol 1000, 20 mmol of hydroxy-Boc aminosulfonic acid polysiloxane, and 0.12 g of dibutyltin dilaurate were added to 300 mL of butanone solvent. The mixture was heated to 75 °C under a nitrogen atmosphere, and 240 mmol of toluene diisocyanate was added. The mixture was reacted for 5 h, and then 120 mmol of 1,4-butanediol was added. The mixture was reacted for 1 h, concentrated under reduced pressure, washed with sodium hydroxide solution, and dried to obtain organosilicon sulfonate polyurethane.

[0044] (2) Add 8g of anti-flash rust agent, 5g of defoamer and 6g of leveling agent to 1000g of waterborne epoxy resin, stir and mix well to obtain component A; add 2g of graphene oxide to 100mL of water, disperse by ultrasonication and then add 50g of organosilicon sulfonate polyurethane, stir for 1h, then add 80g of polyamide 650 curing agent, stir and disperse to obtain component B; add component B to component A, stir and mix well to obtain waterborne epoxy paint suitable for containers.

[0045] The storage stability of waterborne epoxy paint was tested according to GB / T 6753.3-1986. The storage temperature was 25℃, and the time was 7-21 days. No polyamide 650 curing agent was added to the waterborne epoxy paint during the test.

[0046] Water-based epoxy paint is sprayed onto the substrate surface and cured at 120°C for 4 hours to form a paint film coating.

[0047] Impact resistance shall be tested according to GB / T 1732-2020. Salt spray resistance shall be tested according to GB / T 1771-2007. Cross-cut adhesion test and adhesion grade test shall be performed according to GB / T 9286-2021. Flexibility shall be tested according to GB / T 1731-2020.

[0048] Table 1: Test Results

[0049]

[0050] As shown in Table 1, the waterborne epoxy paints in Examples 1-4 incorporated graphene oxide and organosilicon sulfonate polyurethane toughening agents. The polyurethane toughening agent contains hydrophilic sulfonate groups, which improves the hydrophilicity and water solubility of the polyurethane, resulting in excellent dispersibility in the waterborne epoxy resin emulsion and preventing sedimentation. Furthermore, the sulfonate groups of the polyurethane toughening agent interact with the graphene oxide surface through hydrogen bonding and other interactions, acting as a dispersant to improve the dispersibility of graphene in the waterborne epoxy paint, reduce the aggregation and sedimentation of graphene oxide, and thus give the waterborne epoxy paint excellent storage stability.

[0051] In Comparative Example 1, no organosilicon sulfonate polyurethane toughening agent was added. During long-term storage, the graphene oxide tended to agglomerate and settle, resulting in poor storage stability of the waterborne epoxy paint.

[0052] Comparative Example 2 used dihydroxy-terminated polydimethylsiloxane as a raw material. The resulting organosilicon polyurethane did not contain hydrophilic sulfonate groups. The polyurethane had poor hydrophilicity and water solubility, resulting in poor dispersibility in waterborne epoxy resin emulsions and easy sedimentation. Furthermore, since the polyurethane did not contain sulfonate groups, it could not form hydrogen bonds or other interactions with the surface of graphene oxide, and therefore could not act as a dispersant. It did not improve the dispersibility of graphene in waterborne epoxy paint, nor could it reduce the phenomenon of graphene oxide agglomeration and sedimentation, resulting in poor storage stability of waterborne epoxy paint.

[0053] The organosilicon sulfonate polyurethane of Comparative Example 3 contains hydrophilic sulfonate groups, which have good dispersibility in waterborne epoxy resin emulsions and can act as a dispersant to improve the dispersibility of graphene in waterborne epoxy paint, reduce the agglomeration and sedimentation of graphene oxide, and make the waterborne epoxy paint have good storage stability.

[0054] Table 2: Test Results

[0055]

[0056] As shown in Table 2, the waterborne epoxy paints in Examples 1-4 exhibit good adhesion, high flexibility and impact resistance, and a salt spray resistance of 384-504 hours, demonstrating excellent toughness, mechanical properties, and corrosion resistance. This is because the organosilicon polyurethane toughening agent acts as a dispersant, improving the dispersion of graphene in the waterborne epoxy paint, reducing the agglomeration of graphene oxide, and thus enhancing the mechanical properties of the waterborne epoxy paint. Furthermore, the main chain of the organosilicon polyurethane toughening agent contains imino groups, which act as a curing agent, reacting with the epoxy resin to bond the flexible organopolysiloxane molecular chains to the epoxy resin molecular chains, resulting in excellent toughening and improved film flexibility and impact resistance. The formation of a stable polysiloxane chemical crosslinking network between the polyurethane toughening agent and the epoxy resin inhibits the entry of corrosive media such as acids, alkalis, and salts into the paint film matrix. Simultaneously, the uniformly dispersed graphene acts as a barrier against corrosive media, thereby improving the corrosion resistance of the paint film.

[0057] Comparative Example 1 did not contain any silicone polyurethane toughening agent, so it did not play a toughening or graphene dispersing role, resulting in poor toughness, mechanical properties, and corrosion resistance of the paint film.

[0058] The silicone polyurethane in Comparative Example 2 lacks sulfonate groups and imino groups, thus failing to disperse graphene and unable to undergo a curing reaction with epoxy resin. This results in poor compatibility between the silicone polyurethane and epoxy resin, leading to inadequate toughening effect. Consequently, the coating film exhibits poor toughness, mechanical properties, and corrosion resistance.

[0059] The organosilicon sulfonate polyurethane in Comparative Example 3 does not contain imino groups and therefore cannot undergo a curing reaction with epoxy resin. The organosilicon polyurethane has poor compatibility with epoxy resin, resulting in poor toughening effect. This leads to poor toughness, mechanical properties, and corrosion resistance of the coating film.

[0060] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A water-based epoxy paint suitable for containers, characterized in that, The waterborne epoxy paint comprises component A and component B. Component A comprises 100 parts by weight of waterborne epoxy resin, 0.5-0.8 parts by weight of anti-flash rust agent, 0.4-0.7 parts by weight of defoamer, and 0.3-0.6 parts by weight of leveling agent; component B comprises 6-8 parts by weight of polyamide curing agent, 5-12 parts by weight of organosilicon sulfonate polyurethane toughening agent, and 0.2-1 parts by weight of graphene oxide. The preparation method of the organosilicon sulfonate polyurethane toughening agent is as follows: (1) Add epoxypropoxypropyl-terminated polydimethylsiloxane and 2-aminoethanesulfonic acid to tetrahydrofuran, stir the reaction, concentrate under reduced pressure, and dry to obtain hydroxyimine sulfonic acid polysiloxane. (2) Add hydroxy sulfonate polysiloxane and di-tert-butyl dicarbonate to the solvent in an ice-water bath, stir and react, concentrate under reduced pressure, wash with sodium bicarbonate solution, and dry to obtain hydroxy-Boc aminosulfonate polysiloxane. (3) Add dried polyethylene glycol, hydroxy-Boc aminosulfonic acid polysiloxane, and dibutyltin dilaurate to methyl ethyl ketone solvent, heat to 70-80℃ in a nitrogen atmosphere, add diisocyanate monomer, react for 3-5h, then add 1,4-butanediol, react for 1-1.5h, concentrate under reduced pressure, add the product to dichloromethane, stir, add trifluoroacetic acid, stir at 20-30℃ for 4-6h, concentrate under reduced pressure, wash with sodium bicarbonate solution and sodium hydroxide solution in sequence, and dry to obtain organosilicon sulfonate polyurethane toughening agent.

2. The water-based epoxy paint suitable for containers according to claim 1, characterized in that, The molar ratio of the epoxypropoxypropyl-terminated polydimethylsiloxane and 2-aminoethanesulfonic acid in (1) is 1:(2-2.2).

3. The water-based epoxy paint suitable for containers according to claim 1, characterized in that, The reaction in (1) is carried out at 40-50℃ for 8-12 hours.

4. The water-based epoxy paint suitable for containers according to claim 1, characterized in that, The solvent in (2) is dichloromethane, tetrahydrofuran, or acetonitrile.

5. The water-based epoxy paint suitable for containers according to claim 1, characterized in that, The molar ratio of hydroxysulfonic acid polysiloxane and ditert-butyl dicarbonate in (2) is 1:(2.2-2.4).

6. The waterborne epoxy paint suitable for containers according to claim 1, characterized in that, The reaction in (2) is carried out at 20-25℃ for 6-8 hours.

7. The water-based epoxy paint suitable for containers according to claim 1, characterized in that, The molar ratio of polyethylene glycol, hydroxy-Boc aminosulfonic acid polysiloxane, and diisocyanate monomer in (3) is (0.6-0.8):(0.2-0.4):(2.4-2.6):(1.2-1.3).

8. The waterborne epoxy paint suitable for containers according to claim 7, characterized in that, The diisocyanate monomer is hexamethylene diisocyanate, toluene diisocyanate, or isophorone diisocyanate.

9. The waterborne epoxy paint suitable for containers according to claim 1, characterized in that, The volume ratio of dichloromethane to trifluoroacetic acid in (3) is 1:(0.4-0.6).

10. A method for preparing a waterborne epoxy paint suitable for containers as described in any one of claims 1-9, characterized in that, The preparation method is as follows: add anti-flash rust agent, defoamer, and leveling agent to waterborne epoxy resin, stir and mix well to obtain component A; add graphene oxide to water, disperse ultrasonically, add organosilicon sulfonate polyurethane toughening agent, stir for 1-2 hours, then add polyamide curing agent, stir and disperse to obtain component B; add component B to component A, stir and mix well to obtain waterborne epoxy paint suitable for containers.

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