Bi-component aliphatic polyamine epoxy graphene acid-resistant coating

Abstract

The invention belongs to the technical field of epoxy resin coatings, and particularly relates to a bi-component aliphatic polyamine epoxy graphene acid-resistant coating which comprises epoxy resin in a component A and a curing agent in a component B. The curing agent is perfluoroalkyl secondary amine. Alicyclic diamine and perfluoroalkyl ethylene are subjected to a Michael addition reaction under the action of a catalyst cupric trifluoroacetate, the cupric trifluoroacetate catalyst effectively prevents the perfluoroalkyl ethylene and a generated target product secondary amine from being further subjected to an excessive addition reaction, and the reaction efficiency is improved; after the curing agent is subjected to cross-linking reaction with the epoxy resins in the scheme, a large number of ether bonds existing in a traditional phenolic epoxy amine curing system can be eliminated, so that nucleophilic reagent attack sites are reduced, meanwhile, the curing agent perfluoroalkyl secondary amine is converted into a tertiary amine structure, coordination activation of H to nitrogen atoms is reduced, and a coating is more stable.

Description

Technical Field

[0001] This invention belongs to the field of epoxy resin coating technology, and specifically relates to a two-component aliphatic polyamine epoxy graphene acid-resistant coating. Background Technology

[0002] Epoxy resin is a compound containing two (or more) active epoxy groups in its molecular structure. When a curing agent is added to epoxy resin, a three-dimensional network structure is formed through ring-opening reactions of the epoxy groups. Amine curing agents promote the smooth curing of epoxy resin into a film at room temperature. Amine curing agents are used in large quantities and come in many varieties. Based on their molecular structure, they can be classified into aromatic amine curing agents, polyamide curing agents, and aliphatic amine curing agents. Aromatic amine curing agents have large steric hindrance, resulting in slow curing rates and poor toughness. In contrast, aliphatic and polyamide curing agents have good molecular flexibility, small steric hindrance, fast curing speeds, and good toughness.

[0003] As one of the reactants in the curing of epoxy resins, the curing agent eventually becomes part of the cured product and is distributed within the epoxy coating film. Therefore, the molecular structure of the curing agent often has a significant impact on the performance of the epoxy coating film. Many coating preparation and modification routes focus on the reactive modification of the curing agent. For example, the primary amine structure in amine curing agents has two active hydrogen atoms. One of these active hydrogen atoms can be used to react and modify the primary amine, simultaneously converting the primary amine structure into a secondary amine. Thus, while retaining the reactivity with epoxy groups, the molecular structure of the curing agent is modified. However, this reaction process is difficult to control and often leads to overreaction, causing both active hydrogen atoms on the primary amine structure to be reacted away, resulting in the formation of a tertiary amine structure that is no longer reactive with epoxy resin. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides a two-component aliphatic polyamine epoxy graphene acid-resistant coating, comprising component A and component B in a weight ratio of 1:3 to 4, wherein component A contains epoxy resin and component B contains curing agent;

[0005] The curing agent includes a perfluoroalkyl secondary amine, which is obtained by a Michael addition reaction of an alicyclic diamine and a perfluoroalkyl ethylene in the presence of a copper trifluoroacetate catalyst.

[0006] Alicyclic diamines include one or more of the following: 1,4-cyclohexanediamine, 1,2-cyclohexanediamine, 4,4'-diaminodicyclohexylmethane, and 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane;

[0007] Perfluoroalkyl ethylene includes one or a combination of perfluorobutylethylene, perfluorohexylethylene, and perfluorooctylethylene;

[0008] As a preferred embodiment, the molar ratio of alicyclic diamine to perfluoroalkyl ethylene is 1 to 1.1:2, the amount of copper trifluoroacetate catalyst is 1% to 5% of the total weight of alicyclic diamine and perfluoroalkyl ethylene, the catalytic reaction temperature is 25℃ to 40℃, and the reaction time is 2h to 4h.

[0009] As a preferred embodiment, an alicyclic diamine and a perfluoroalkyl ethylene are dispersed in an organic solvent to carry out a Michael addition reaction, wherein the total weight ratio of the alicyclic diamine and the perfluoroalkyl ethylene to the organic solvent is 1:5 to 20.

[0010] As a preferred option, hexafluoroisopropanol is added as a reaction promoter to the reaction system of alicyclic diamine and perfluoroalkyl ethylene, wherein the amount of hexafluoroisopropanol is 1% to 10% of the total weight of alicyclic diamine and perfluoroalkyl ethylene;

[0011] Preferably, the epoxy resin includes one or a combination of several of SH-470, SWE-90, SW-70, and SW-80, wherein the molecular structure of each epoxy resin is as follows:

[0012] SH-470:

[0013]

[0014] SWE-90:

[0015]

[0016] SW-70, SW-80:

[0017] ;

[0018] As a preferred embodiment, component A further includes 2 to 6 parts by weight of fluorinated segment grafted graphene, 1 to 5 parts by weight of dispersant, 3 to 6 parts by weight of defoamer, 5 to 20 parts by weight of inorganic filler, and 15 to 45 parts by weight of cosolvent.

[0019] As a preferred method, the preparation of fluorinated segment grafted graphene is as follows: graphene oxide is fully dispersed in a uniform mixture of N,N-dimethylformamide and water at a volume ratio of 90:10 at a ratio of 0.5 to 2:100 g / mL. Then, tridecafluorooctyltrimethoxysilane at a volume ratio of 5 to 10:100 is added to the mixture. The mixture is heated to 90°C to 100°C under magnetic stirring and then refluxed for 8 to 12 hours. After centrifugation and filtration, the filter cake is thoroughly washed with toluene and then vacuum dried at 100°C.

[0020] As a preferred option, the inorganic filler includes one or a combination of several of the following: nano-titanium dioxide, nano-zirconia, silicon fiber, silicon carbide, and nano-silica.

[0021] As a preferred option, the co-solvent includes one or a combination of several of methyl nonafluorobutyl ether, propylene glycol methyl ether acetate, and benzyl alcohol.

[0022] As a preferred option, benzyl alcohol accounts for 1 to 2% of the mass of the coating (the sum of component A and component B).

[0023] The beneficial effects of this application are as follows: Firstly, in the process of preparing secondary amine curing agents from alicyclic diamines and perfluoroalkyl ethylene via Michael addition reaction, the use of copper trifluoroacetate catalyst effectively prevents further excessive addition reaction between perfluoroalkyl ethylene and the generated target product secondary amine, so that the proportion of single addition product can reach more than 95%; at the same time, by adding hexafluoroisopropanol (HFIP) to the reaction system to promote the polarization of perfluoroalkyl ethylene, the reaction is accelerated and the reaction efficiency is improved.

[0024] By adding a small amount of benzyl alcohol, the curing agent and epoxy resin can maintain a longer working period at room temperature after mixing, making the coating application easier.

[0025] Furthermore, in the coating components, the cross-linking reaction between the perfluoroalkyl secondary amine curing agent and the epoxy resins specified in this scheme can completely eliminate the ether bonds (COC) that are easily broken by H⁺ protonation in the traditional phenolic epoxy amine curing system, thereby reducing the nucleophilic attack sites. After the cross-linking reaction, the perfluoroalkyl secondary amine curing agent is transformed into a tertiary amine structure (increased steric hindrance), which also helps to reduce the coordination activation of nitrogen atoms by H⁺, resulting in a more balanced and stable coating performance.

[0026] Because hydroxyl groups (>5 OH / molecule) are formed at the molecular junctions after the cross-linking reaction, they have strong hydrogen bonding with the substrate and strong adhesion.

[0027] Meanwhile, the intramolecular plasticizing effect of perfluoroalkyl groups makes the coating flexible and changes the defect of traditional phenolic epoxy amine cured coatings being brittle.

[0028] Nano-zirconia and graphene significantly enhance the chemical stability and physical properties of the coating through multi-scale synergistic effects: multilayer graphene sheets form a 3D framework, pre-grafted perfluorooctyl groups can inhibit the aggregation between multilayer graphene, nano-zirconia fills the pores of the framework, and nanoparticles offset curing shrinkage and reduce internal stress; the Zr-OH groups on the surface of nano-zirconia undergo reversible protonation in an acidic environment, which greatly extends the service life of the coating; during epoxy curing, nano-zirconia preferentially migrates to the coating-substrate interface to form a continuous barrier layer with a thickness of about 50 nm, and its Mohs hardness (8.5) can effectively inhibit substrate corrosion caused by acid penetration; graphene has super-barrier properties, which makes the coating have a tortuous path effect, and the conductive network of graphene can shift the corrosion potential positively and inhibit electrochemical corrosion.

[0029] The coating has surpassed the performance of traditional phenolic epoxy coatings in extreme acid resistance applications, and is irreplaceable in extreme scenarios such as the protection of the inner walls of concentrated acid storage tanks (98% sulfuric acid / 40% hydrofluoric acid). It also has broad application prospects in fields such as the protection of electroplating production line equipment, corrosion prevention of lithium battery electrolytic cells, photovoltaic acid texturing equipment, and special protection for marine engineering. Detailed Implementation

[0030] Example 1

[0031] Add 60 parts by weight of perfluorohexylethylene, 21 parts by weight of 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, 3 parts by weight of copper trifluoroacetate, and 5 parts by weight of hexafluoroisopropanol to 600 parts by weight of chloroform. After heating to 37°C under magnetic stirring, react for 4 hours. Then, evaporate the solvent at 70°C to a constant weight (81.7 parts by weight) to obtain the reaction product, perfluoroalkyl secondary amine.

[0032] The reaction products obtained above were analyzed by normal-phase liquid chromatography (Agilent 1260, stationary phase: cyano-bonded silica gel; mobile phase: a mixture of n-hexane and chloroform (volume ratio 1:1); injection concentration 0.6 μg / mL; injection volume 30 μL; injection temperature 40℃; flow rate 0.8 mL / min; pressure 130 bar): the content of perfluoroalkyl secondary amines was 95.2% (mass percentage, the same below), the content of perfluoroalkyl tertiary amines was 0.7%, and the remainder were mainly small amounts of by-products and catalyst substances remaining in the products.

[0033] Example 2

[0034] Add 50 parts by weight of perfluorobutylethylene, 12 parts by weight of 1,4-cyclohexanediamine, 2 parts by weight of copper trifluoroacetate, and 4 parts by weight of hexafluoroisopropanol to 500 parts by weight of chloroform. After heating to 32°C under magnetic stirring, react for 4 hours. Then, evaporate the solvent at 90°C to a constant weight (59.6 parts by weight), which is the reaction product perfluoroalkyl secondary amine.

[0035] The reaction products obtained above were analyzed by normal-phase liquid chromatography (Agilent 1260, stationary phase: cyano-bonded silica gel; mobile phase: a mixture of n-hexane and chloroform (volume ratio 1:1); injection concentration 0.6 μg / mL; injection volume 30 μL; injection temperature 37℃; flow rate 0.65 mL / min; pressure 100 bar): the content of perfluoroalkyl secondary amines was 94.4%, the content of perfluoroalkyl tertiary amines was 1.1%, and the remainder were mainly small amounts of by-products and catalyst substances remaining in the products.

[0036] Comparative Example 1

[0037] Replace “copper trifluoroacetate” with “lithium bis(trimethylsilylamine)”, and keep all other components and operations the same as in Example 1:

[0038] Add 60 parts by weight of perfluorohexylethylene, 21 parts by weight of 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, 3 parts by weight of bistrimethylsilylaminolithium, and 5 parts by weight of hexafluoroisopropanol to 600 parts by weight of chloroform. After heating to 37°C under magnetic stirring, react for 4 hours and then evaporate the solvent at 70°C to constant weight (82.3 parts by weight).

[0039] The reaction products obtained above were analyzed by normal-phase liquid chromatography (Agilent 1260, stationary phase: cyano-bonded silica gel; mobile phase: a mixture of n-hexane and chloroform (volume ratio 1:1); injection concentration 0.6 μg / mL; injection volume 30 μL; injection temperature 40℃; flow rate 0.8 mL / min; pressure 130 bar): the content of perfluoroalkyl secondary amine was 65.4%, the content of perfluoroalkyl tertiary amine was 22.1%, and the remainder was mainly excess reactant 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, a small amount of by-products, and catalyst residues in the products.

[0040] Based on the results of Comparative Example 1, after changing the catalyst, a significant over-addition occurred during the reaction, resulting in the presence of a significant perfluoroalkyl tertiary amine in the product. Furthermore, since the initial molar ratio between the reactants perfluorohexylethylene and 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane was close to 1:1, after the over-addition occurred, naturally, after the reaction proceeded to completion, some of the reactants 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane remained due to the lack of perfluorohexylethylene to react and combine with it.

[0041] Comparative Example 2

[0042] Omit "hexafluoroisopropanol", and the remaining components and operations are the same as in Example 1:

[0043] Add 60 parts by weight of perfluorohexylethylene, 21 parts by weight of 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, and 3 parts by weight of copper trifluoroacetate to 600 parts by weight of chloroform. After heating to 37°C under magnetic stirring, react for 4 hours and then evaporate the solvent at 70°C to constant weight (81.4 parts by weight).

[0044] The reaction products obtained above were analyzed by normal-phase liquid chromatography (Agilent 1260, stationary phase: cyano-bonded silica gel; mobile phase: a mixture of n-hexane and chloroform (volume ratio 1:1); injection concentration 0.6 μg / mL; injection volume 30 μL; injection temperature 40℃; flow rate 0.8 mL / min; pressure 130 bar): the content of perfluoroalkyl secondary amine was 85.7%, the content of perfluoroalkyl tertiary amine was 0.3%, and the remainder was mainly unreacted raw materials perfluorohexylethylene and 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, as well as a small amount of by-products and catalyst substances remaining in the products.

[0045] The results of Comparative Example 2 show that without the intervention of hexafluoroisopropanol, the raw materials did not react sufficiently after undergoing the same preparation process. This also indicates that hexafluoroisopropanol has a promoting effect on this addition reaction.

[0046] Example 3

[0047] Two-component aliphatic polyamine epoxy graphene acid-resistant coating:

[0048] Component A:

[0049] SWE-90 (Hunan Servi New Material Technology Co., Ltd.) 100 parts by weight

[0050] 2 parts by weight of fluorine segment grafted graphene

[0051] Dispersant BYK-2152 4 parts by weight

[0052] Defoamer FS-1265 3 parts by weight

[0053] 2 parts by weight of nano titanium dioxide

[0054] 3 parts by weight of nano-zirconia

[0055] 1 part by weight of silicon carbide

[0056] 20 parts by weight of methyl nonafluorobutyl ether

[0057] 14 parts by weight of propylene glycol methyl ether acetate

[0058] 6.5 parts by weight of benzyl alcohol

[0059] Component B:

[0060] 470 parts by weight of the perfluoroalkyl secondary amine prepared in Example 1 above.

[0061] Comparative Example 3

[0062] Replace “SWE-90” in Example 3 with “SW-0500” (Hunan Servi New Material Technology Co., Ltd., molecular structure as follows)”, an epoxy resin with a different molecular structure. All other components and operations are the same as in Example 3.

[0063]

[0064] Component A:

[0065] SW-0500 93 parts by weight

[0066] 2 parts by weight of fluorine segment grafted graphene

[0067] Dispersant BYK-2152 4 parts by weight

[0068] Defoamer FS-1265 3 parts by weight

[0069] 2 parts by weight of nano titanium dioxide

[0070] 3 parts by weight of nano-zirconia

[0071] 1 part by weight of silicon carbide

[0072] 20 parts by weight of methyl nonafluorobutyl ether

[0073] 14 parts by weight of propylene glycol methyl ether acetate

[0074] 6.5 parts by weight of benzyl alcohol

[0075] Component B:

[0076] 470 parts by weight of the perfluoroalkyl secondary amine prepared in Example 1 above.

[0077] To compare the resistance of epoxy resin coatings with different molecular structures to strong irritant environments in Example 3 and Comparative Example 3: The coating obtained by thoroughly mixing component A and component B was applied to a copper substrate (1m×1m×2mm) with a thickness of about 100µm. After heat curing in an oven at 80℃ for 45min, it was left to stand at room temperature (25℃, the same below) for 24 hours until fully cooled to obtain a coating with a complete morphology. The copper substrate and the coating were then placed flat and immersed in an excess of room temperature test reagent (the depth of the test reagent in the immersion tank was about 5cm to ensure that it was always in excess). Every 24 hours, the copper substrate was taken out of the tank, rinsed with clean water, and the surface coating of the substrate was observed for cracking, powdering, peeling, or other damage. If such damage occurred, the experiment was stopped, and the duration of the last observation without damage was recorded. If no damage occurred, the copper substrate was immersed in the original test reagent again and observed continuously. The testing reagents for each coating included 98% concentrated sulfuric acid, 60% sulfuric acid aqueous solution, 37% hydrochloric acid aqueous solution, 40% hydrofluoric acid aqueous solution, and 10% sodium hydroxide aqueous solution. In addition, adhesion, hardness, and flexibility tests were performed on each coating. Three parallel samples were prepared for each experiment, and the average results were recorded. The results are shown in Table 1.

[0078] Table 1

[0079]

[0080] As shown in Table 1, the coating of Example 3 exhibits significantly greater stability against strong acids and alkalis after film formation compared to Comparative Example 3. This is because the epoxy resin in Comparative Example 3 contains ether bonds (COC), which are more susceptible to breakage by nucleophiles after cross-linking and film formation, leading to faster corrosion and damage of the coating in strong acid and alkali environments. In contrast, Example 3 does not contain such ether bonds and instead uses ester bonds, resulting in a more stable and durable acid resistance.

[0081] Comparative Example 4

[0082] In Example 3, "benzyl alcohol" was replaced with "a mixed cosolvent of methyl nonafluorobutyl ether and propylene glycol methyl ether acetate", and the remaining components and operations were the same as in Example 3.

[0083] Two-component aliphatic polyamine epoxy graphene acid-resistant coating:

[0084] Component A:

[0085] SWE-90 (Hunan Servi New Material Technology Co., Ltd.) 100 parts by weight

[0086] 2 parts by weight of fluorine segment grafted graphene

[0087] Dispersant BYK-2152 4 parts by weight

[0088] Defoamer FS-1265 3 parts by weight

[0089] 2 parts by weight of nano titanium dioxide

[0090] 3 parts by weight of nano-zirconia

[0091] 1 part by weight of silicon carbide

[0092] 23.8 parts by weight of methyl nonafluorobutyl ether

[0093] 16.7 parts by weight of propylene glycol methyl ether acetate

[0094] Component B:

[0095] 470 parts by weight of the perfluoroalkyl secondary amine prepared in Example 1 above.

[0096] Components A and B in Example 3 and Comparative Example 4 were thoroughly mixed (600 r / min, 5 min) and then allowed to stand at room temperature (25°C). Viscosity was measured every hour (GB / T7193-2008 (4.1), 25°C, 750 r / min) and recorded, as shown in Table 2.

[0097] Table 2

[0098]

[0099] As shown in Table 2, adding a small amount of benzyl alcohol to the coating can effectively delay the self-curing phenomenon of the coating under natural conditions, thereby extending the pot life of the coating after mixing and providing greater operational flexibility during coating application. The applicant believes that this is related to the high boiling point and plasticizing effect of benzyl alcohol itself. Benzyl alcohol is stably dispersed in the coating through methyl nonafluorobutyl ether and propylene glycol methyl ether acetate and does not volatilize. Through its plasticizing effect, it reduces the stable contact between the effective components of the coating, thereby reducing its reactivity.

Claims

1. A two-component aliphatic polyamine epoxy graphene acid resistant coating characterized by: The coating comprises component A and component B, wherein the component A comprises an epoxy resin, the component B comprises a curing agent, the curing agent comprises a perfluoroalkyl secondary amine, the perfluoroalkyl secondary amine is obtained by Michael addition reaction of alicyclic diamine and perfluoroalkyl ethylene under the action of a catalyst copper trifluoroacetate.

2. The two-component aliphatic polyamine epoxy graphene acid resistant paint according to claim 1, characterized by: The alicyclic diamine comprises one or a combination of 1,4-cyclohexanediamine, 1,2-cyclohexanediamine, 4,4'-diaminodicyclohexylmethane, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane.

3. The two-component aliphatic polyamine epoxy graphene acid resistant paint according to claim 1, characterized by: The perfluoroalkyl ethylene comprises one or a combination of perfluorobutyl ethylene, perfluorohexyl ethylene, perfluorooctyl ethylene.

4. The two-component aliphatic polyamine epoxy graphene acid resistant paint according to claim 1, characterized by: The molar ratio of the alicyclic diamine to the perfluoroalkyl ethylene is 1-1.1:2, the amount of the catalyst copper trifluoroacetate is 1%-5% of the total weight of the alicyclic diamine and the perfluoroalkyl ethylene, the reaction temperature of the Michael addition reaction is 25-40°C, and the reaction time is 2-4h.

5. The two-component aliphatic polyamine epoxy graphene acid resistant paint according to claim 1, characterized by: The alicyclic diamine and the perfluoroalkyl ethylene are dispersed in an organic solvent to carry out the Michael addition reaction, and the mass ratio of the total weight of the alicyclic diamine and the perfluoroalkyl ethylene to the organic solvent is 1:5-20.

6. The two-component aliphatic polyamine epoxy graphene acid resistant paint according to claim 1, characterized by: In the Michael addition reaction, hexafluoroisopropanol is added to the reaction system as a reaction promoter, and the amount of the hexafluoroisopropanol is 1%-10% of the total weight of the alicyclic diamine and the perfluoroalkyl ethylene.

7. The two-component aliphatic polyamine epoxy graphene acid resistant paint according to claim 1, characterized by: The epoxy resin is one or a combination of SH-470, SWE-90, SW-70, and SW-80.

8. The two-component aliphatic polyamine epoxy graphene acid resistant paint according to claim 7, characterized by: The component A comprises 100 parts by weight of the epoxy resin, 2-6 parts by weight of a fluorine segment grafted graphene, 1-5 parts by weight of a dispersing agent, 3-6 parts by weight of an antifoaming agent, 5-20 parts by weight of an inorganic filler, and 15-45 parts by weight of a cosolvent.

9. The two-component aliphatic polyamine epoxy graphene acid resistant coating as claimed in claim 8, wherein: The cosolvent comprises one or a combination of methyl nonafluorobutyl ether, propylene glycol methyl ether acetate, and benzyl alcohol.

10. The two-component aliphatic polyamine epoxy graphene acid resistant paint according to claim 9, characterized by: The mass fraction of the benzyl alcohol in the coating is 1-2%.

Images