Self-repairing anti-corrosion composite epoxy resin coating as well as preparation method and application thereof

Abstract

The invention discloses a self-repairing anti-corrosion composite epoxy resin coating as well as a preparation method and application thereof, and the composite epoxy resin coating is prepared from the following raw materials: lignin grafted graphene oxide and double-bond terminated epoxy resin, the lignin grafted graphene oxide is prepared from double-bond lignin and graphene oxide. A composite coating prepared from the composite epoxy resin coating not only has better corrosion resistance, but also has excellent self-repairing performance, and is beneficial to prolonging the service life of metal.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and particularly to a self-healing anti-corrosion composite epoxy resin coating, its preparation method and application. Background Art

[0002] At present, although modified nano-fillers represented by graphene, carbon nanotubes, etc. can improve the anti-corrosion performance of resin coatings through physical shielding and corrosion inhibition effects, their poor dispersibility and interfacial compatibility in the resin matrix are still technical bottlenecks. They are prone to form micro-defects due to the aggregation effect and weaken the interfacial bonding strength, resulting in discontinuous anti-corrosion networks. For the research and development of self-healing anti-corrosion composite epoxy resin coatings, existing technologies mostly use petroleum-based modifiers (such as silane coupling agents, polymer coating agents) to improve the filler dispersibility. However, the interfacial matching of such hydrophobic modifiers with polar resins is insufficient, and phase separation is easily caused during the curing process, making it difficult to construct a stable self-healing microcapsule delivery system. In contrast, biomass-derived materials (such as lignin, chitosan) are rich in active groups such as hydroxyl groups and amino groups, which can endow nano-fillers with excellent dispersibility and interfacial reaction activity through green chemical modification. At the same time, their multi-level structures can synergistically enhance the self-healing ability and corrosion medium barrier performance of the coating, providing new ideas for the development of environmentally friendly high-performance anti-corrosion coatings and meeting the demand for the utilization of renewable resources. Therefore, using renewable and resource-rich biomass materials to modify nano-fillers is a feasible strategy to solve the above problems. Summary of the Invention

[0003] The present invention aims to at least solve one of the above technical problems existing in the prior art. For this reason, the purpose of the present invention is to provide a self-healing anti-corrosion composite epoxy resin coating, its preparation method and application.

[0004] In order to achieve the above purpose, the technical solutions adopted by the present invention are as follows:

[0005] In the first aspect of the present invention, a composite epoxy resin coating is provided, which is prepared from raw materials including: graphene oxide grafted with lignin and epoxy resin capped with double bonds; the graphene oxide grafted with lignin is prepared from double-bonded lignin and graphene oxide.

[0006] In the present invention, during the process of forming graphene oxide grafted with lignin from double-bonded lignin and graphene oxide, the double-bonded lignin acts as an intercalating agent, increasing the distance between graphene oxides, improving its dispersibility and interfacial interaction; the graphene oxide grafted with lignin and the epoxy resin capped with double bonds carry out free radical polymerization to form a coating, endowing the coating with self-healing anti-corrosion performance.

[0007] In some embodiments of the present invention, in the graphene oxide grafted with lignin, the lignin is grafted onto the graphene oxide through a six-membered cycloalkenyl group.

[0008] In some embodiments of the present invention, in the composite epoxy resin coating, the proportion of graphene oxide grafted with lignin is 0.01 wt% to 10 wt%, such as 0.1 wt% to 8.0 wt%, 0.5 wt% to 7.0 wt%, 1 wt% to 5.0 wt%, etc.

[0009] In some embodiments of the present invention, the mass ratio of the double-bonded lignin to graphene oxide is (0.1 to 10):(0.1 to 50), such as (1 to 10):(1 to 50), 1:3 to 10, 1:4 to 8, 1:4 to 6, etc.

[0010] In some embodiments of the present invention, the double-bonded lignin provides double bonds by a double-bond monomer, and the double-bond monomer includes at least one of allyl bromide, allyl iodide, 6-bromo-1-hexene, allyl ether, and 10-undecenol.

[0011] In some embodiments of the present invention, the double-bonded lignin is prepared from a double-bond monomer and lignin.

[0012] In some embodiments of the present invention, the graphene oxide further includes graphene oxide containing a pyridyl group. In the present invention, the pyridyl group on the graphene oxide containing a pyridyl group can form a chelate with metal ions. When the coating is applied to the metal corrosion interface, the pyridyl group can form a chelate with iron ions to cover the metal corrosion area, isolating the contact between the corrosion medium and the metal, and improving the corrosion resistance of the coating.

[0013] In some embodiments of the present invention, the graphene oxide containing a pyridyl group is prepared from a pyridyl monomer and graphene oxide.

[0014] In some embodiments of the present invention, the pyridyl monomer includes at least one of 4'-(4-chlorophenyl)-2,2':6',2"-terpyridine, 4'-bromo-2,2':6',2”-terpyridine, 4'-(4-fluorophenyl)-2,2':6',2”-terpyridine, 4'-(4-bromophenyl)-2,2':6',2”-terpyridine, 6,6”-dibromo-2,2':6',2”-terpyridine, and 4'-(4-aminophenyl)-2,2':6',2-terpyridine.

[0015] In some embodiments of the present invention, the double-bond terminated epoxy resin is prepared from an epoxy resin, an amino monomer, and an acrylic monomer.

[0016] In some embodiments of the present invention, the mass ratio of the epoxy resin, amino monomer, and acrylic monomer is (1 to 150):(0.1 to 50):(1 to 100), such as (10 to 100):(0.5 to 10):(6 to 30), (30 to 80):(1 to 5):(10 to 25), etc.

[0017] In some embodiments of the present invention, the epoxy resin is capped with an epoxy group.

[0018] In some embodiments of the present invention, the epoxy resin includes at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, polyphenol glycidyl ether epoxy resin, glycidyl ether epoxy resin, and heterocyclic epoxy resin.

[0019] In some embodiments of the present invention, the amino monomer includes at least one of 3-butoxypropylamine, ethylenediamine, aniline, acrylamide, 2-aminopurine, and glucosamine.

[0020] In some embodiments of the present invention, the acrylic monomer includes at least one of acrylic acid, methacrylic acid, 2-fluoroacrylic acid, and 2-propylacrylic acid.

[0021] The second aspect of the present invention provides a method for preparing the composite epoxy resin coating described above, comprising the following steps:

[0022] Graft lignin-modified graphene oxide, double-bond-capped epoxy resin, and styrene are subjected to a polymerization reaction to obtain the composite epoxy resin coating described above.

[0023] In the present invention, styrene solvent is used in the free radical polymerization reaction, effectively avoiding the volatilization of the solvent and having environmental friendliness.

[0024] In some embodiments of the present invention, the mass ratio of styrene to double-bond-capped epoxy resin is 1:19 to 7:3.

[0025] In some embodiments of the present invention, the polymerization reaction is carried out under the action of an auxiliary agent; the mass ratio of the auxiliary agent to the double-bond-capped epoxy resin is 1:(1 to 10).

[0026] In some embodiments of the present invention, the auxiliary agent includes at least two of cobalt naphthenate, 2-butyl peroxide ketone, 2,2,6,6-tetramethyl-1-piperidinyloxy, azobisisobutyronitrile, benzoyl peroxide, and diisopropylbenzene peroxide.

[0027] In some embodiments of the present invention, the preparation method of the composite epoxy resin coating comprises the following steps: dissolving the double bond-terminated epoxy resin in styrene, adding graphene oxide grafted with lignin, and ultrasonically dispersing for 10 - 40 min; then adding an auxiliary agent and ultrasonically dispersing for 1 - 120 min, and carrying out a polymerization reaction to obtain the composite epoxy resin coating; preferably, the ultrasonic frequency of the ultrasonic dispersion is 50 - 500 Hz.

[0028] In some embodiments of the present invention, the preparation method of the graphene oxide grafted with lignin comprises the following steps: ultrasonically dispersing graphene oxide, double bond-functionalized lignin, and an inhibitor in a solvent, and carrying out a heating reaction to obtain the graphene oxide grafted with lignin. In the present invention, a Diels - Alder reaction occurs between the double bonds on the double bond-functionalized lignin and the conjugated double bonds on the graphene oxide, so that lignin is grafted onto the graphene oxide.

[0029] In some embodiments of the present invention, the ultrasonic frequency of the ultrasonic dispersion is 50 - 500 Hz; the time of the ultrasonic dispersion is 10 - 60 min.

[0030] In some embodiments of the present invention, the heating reaction is carried out in a high-pressure reactor; the reaction temperature of the heating reaction is 80 - 200 °C; the reaction time of the heating reaction is 2 - 36 h.

[0031] In some embodiments of the present invention, the mass ratio of the graphene oxide to the solvent is (0.1 - 50):(10 - 120); the solvent comprises at least one of N-methylpyrrolidone, dimethylformamide, dimethylacetamide, tetrahydrofuran, chloroform, dimethyl sulfoxide, and toluene.

[0032] In some embodiments of the present invention, the preparation method of the graphene oxide grafted with lignin further comprises purifying the reaction product; the specific operation of the purification treatment includes centrifuging, washing, and drying the reaction product; the washing is carried out with a second solvent; the second solvent comprises at least one of water, absolute ethanol, hexane, toluene, tetrahydrofuran, and methanol.

[0033] In some embodiments of the present invention, the preparation method of the double bond-terminated epoxy resin comprises the following steps: carrying out a ring-opening reaction on the epoxy resin and an amino monomer, adding an inhibitor and a phase transfer catalyst, and then adding an acrylic monomer for a capping reaction to obtain the double bond-terminated epoxy resin.

[0034] In some embodiments of the present invention, the ring-opening reaction is carried out at 60 - 150 °C and 80 - 200 °C for 1 - 18 h.

[0035] In some embodiments of the present invention, the reaction system is cooled to 10 - 80 °C and then an inhibitor and a phase transfer catalyst are added.

[0036] In some embodiments of the present invention, the reaction system is heated to 80 - 180 °C and then an acrylic monomer is added.

[0037] In some embodiments of the present invention, the reaction temperature of the end-capping reaction is 90 - 200 °C; the induction time of the end-capping reaction is 1 - 24 h.

[0038] In the third aspect of the present invention, a coating is provided, which is obtained by curing the composite epoxy resin coating as described above.

[0039] In some embodiments of the present invention, the curing temperature is 80 - 200 °C; the curing time is 1 - 10 h; such as 1 - 5 h, etc.

[0040] In the fourth aspect of the present invention, an application of the composite epoxy resin coating or the coating as described above in the anti-corrosion of metal products is provided.

[0041] In some embodiments of the present invention, the metal products include any one of offshore engineering equipment, ships, petrochemical transportation pipelines, and building materials.

[0042] The beneficial effects of the present invention are as follows:

[0043] (1) The lignin used in the present invention is derived from plantations or pulp and paper making, thus achieving the purpose of turning waste into treasure. In addition, the grafting of lignin onto the nano-fillers acts as an intercalating agent, improving the dispersion and interfacial interaction of the nano-fillers in the resin. Lignin can form chelates with metal ions, helping to improve the anti-corrosion performance of the coating. Most importantly, the use of lignin reduces the consumption of petroleum-based products, promoting the development of the anti-corrosion coating field towards the direction of green and sustainable development.

[0044] (2) The epoxy resin, amine monomer, and acrylic monomer used in the present invention are inexpensive and have a simple preparation method. Moreover, the synthesized epoxy resin end-capped with double bonds has good anti-corrosion performance, which is convenient for industrial production.

[0045] (3) The composite coating prepared in the present invention not only has good anti-corrosion performance but also has excellent self-healing performance, which is beneficial to extending the service life of metals.

[0046] (4) The reaction conditions for preparing the lignin-grafted graphene oxide / pyridine-group-containing graphene oxide (GO / TGO), epoxy resin end-capped with double bonds, and composite coating in the present invention are relatively simple and convenient for operation.

[0047] (5) During the preparation of the composite coating of the present invention, styrene solvent participates in the free radical polymerization reaction, effectively avoiding the volatilization of the solvent, protecting the environment, reducing the harm to construction workers, and having the characteristics of environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is the reaction route diagram for preparing the double bond-terminated epoxy resin of the present invention.

[0049] Figure 2 It is the reaction route diagram for preparing the composite coating of the present invention.

[0050] Figure 3 It is the infrared structure of the double bond-terminated epoxy resin of the present invention.

[0051] Figure 4 It is the Bode diagram of the coating (ABE) prepared from the double bond-terminated epoxy resin of the present invention.

[0052] Figure 5 It is the Bode result of the lignin-grafted GO composite coating (LGO-ABE) of the present invention.

[0053] Figure 6 It is the Bode result of the lignin-grafted TGO composite coating (LTGO-ABE) of the present invention.

[0054] Figure 7 It is the morphology diagram of the scratched ABE coating of the present invention.

[0055] Figure 8 It is the morphology diagram of the scratched LGO-ABE composite coating of the present invention.

[0056] Figure 9 It is the morphology diagram of the scratched LTGO-ABE composite coating of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0057] The content of the present invention will be further described in detail through specific embodiments below. Unless otherwise specified, the raw materials, reagents or devices used in the examples and comparative examples can be obtained from conventional commercial channels or can be obtained by existing technical methods. Unless otherwise specified, the test or testing methods are all conventional methods in the art.

[0058] In the following examples or comparative examples, the preparation method of double-bonded lignin refers to Chang-An Xu et al. Mimosainspired intelligent anti-corrosive composite coating by incorporating lignin and pyridine derivatives grafted graphene oxide. Chemical Engineering Journal. 2024, 483, 149316 (DOI: 10.1016 / j.cej.2024.149316)

[0059] In the following examples or comparative examples, the preparation method of lignin-grafted GO / TGO is as follows: 0.1 g of GO / TGO, 0.02 g of double-bonded lignin, and 0.00048 g of inhibitor were added to 50 g of N-methylpyrrolidone solvent, ultrasonically dispersed for 30 min, and then the mixture was transferred to a high-pressure reactor and reacted at 100 °C for 6 h. The mixture was centrifuged and rinsed with absolute ethanol. Finally, the mixture was dried in an oven overnight to obtain lignin-grafted GO / TGO. The material obtained by reacting lignin with GO was labeled as LGO, and the material obtained by reacting lignin with TGO was labeled as LTGO.

[0060] Figure 1 The reaction route map of double-bonded epoxy resin is shown. In the following examples and comparative examples, the preparation method of double-bonded epoxy resin is as follows: 60 g of epoxy resin and 3.275 g of 3-butoxypropylamine were added to a flask and heated at 100 °C and 150 °C for 2 h. Then the system temperature was lowered to room temperature, 0.01574 g of inhibitor and 0.3935 g of benzyltriethylammonium chloride were added. After heating to 90 °C, 15.43 g of acrylic acid was slowly added to the flask and reacted under a nitrogen atmosphere at 110 °C for 3 h. Finally, after the system temperature was lowered to 70 °C, 33.73 g of styrene was added and stirred for 15 min to obtain a double-bonded epoxy resin solution.

[0061] Example 1

[0062] A composite epoxy resin coating was prepared in this example, Figure 2 The reaction route map of the coating is shown, and the specific process is as follows:

[0063] 3.0 g of the double-bond terminated epoxy resin solution and 0.003 g of LGO were added to a glass bottle for ultrasonic dispersion, and then 0.009 g of cobalt naphthenate and 0.03 g of 2-butyl peroxide were added for continuous ultrasonic dispersion. Then it was spread on 304 stainless steel with a coater, left at room temperature overnight, and cured at 100 °C, 120 °C, and 160 °C for 3 h, 4 h, and 2 h, respectively. The resulting coating was labeled as LGO-ABE.

[0064] Example 2

[0065] In this example, a composite epoxy resin coating was prepared. The specific process was as follows:

[0066] 3.0 g of the double-bond terminated epoxy resin solution and 0.003 g of LTGO were added to a glass bottle for ultrasonic dispersion, and then 0.009 g of cobalt naphthenate and 0.03 g of 2-butyl peroxide were added for continuous ultrasonic dispersion. Then it was spread on 304 stainless steel with a coater, left at room temperature overnight, and cured at 100 °C, 120 °C, and 160 °C for 3 h, 4 h, and 2 h, respectively. The resulting coating was labeled as LTGO-ABE.

[0067] Comparative Example 1

[0068] In this comparative example, a composite epoxy resin coating was prepared. The specific process was as follows:

[0069] 3.0 g of the double-bond terminated epoxy resin solution was added to a glass bottle, and then 0.009 g of cobalt naphthenate and 0.03 g of 2-butyl peroxide were added for ultrasonic dispersion. Then it was spread on 304 stainless steel with a coater, left at room temperature overnight, and cured at 100 °C, 120 °C, and 160 °C for 3 h, 4 h, and 2 h, respectively. The resulting coating was labeled as ABE.

[0070] Test Example

[0071] The coatings prepared in the examples and comparative examples were characterized. The specific process was as follows:

[0072] Testing method:

[0073] (1) Chemical structure characterization

[0074] Testing method: The functional groups of the samples were characterized by Fourier transform infrared spectroscopy (FTIR, Nicolet iS10, Germany). The test wavelength range was 4000 - 500 cm -1 , and the number of scans was 32 times.

[0075] (2) Electrochemical testing

[0076] Test method: Use an electrochemical workstation (CHI-660E) to obtain the electrochemical test data of the coating. During the test, the corrosive medium is 3.5 wt% brine, the Ag / AgCl electrode is used as the reference electrode, and the platinum plate is used as the counter electrode.

[0077] (3) Self-healing performance test

[0078] Test method: Use a sharp scalpel to scratch a line on the surface of the coating, then immerse it in salt water for 3 days, and observe the morphology of the scratched area through a scanning electron microscope.

[0079] Test results:

[0080] The performance test results of the composite coatings prepared in Examples 1-2 and the coatings prepared in Comparative Example 1 are shown in Table 1.

[0081] Table 1

[0082] / Example 1 Example 2 Comparative Example 1 <![CDATA[Immersed in salt water for 120 days, the impedance modulus of the coating (Ωcm 2 )]]> <![CDATA[4.79×10 7 > <![CDATA[6.76×10 8 > <![CDATA[1.17×10 9 >

[0083] Figure 3 It is the infrared structure diagram of the double bond-terminated epoxy resin.

[0084] Figures 4 to 6 They respectively correspond to the Bode results of the coatings in Comparative Example 1, Example 1, and Example 2; Figures 7 to 9 They respectively correspond to the morphology diagrams of the coatings in Comparative Example 1, Example 1, and Example 2 after scratching and soaking.

[0085] From Figure 2 it can be found that both the intermediate B-E44 and the final product AB-E44 retain the main characteristic peaks of the raw material epoxy resin E44. For B-E44, the hydroxyl peak decreases from 3493 cm -1 to 3440 cm -1 , which is due to the reaction of amino groups with epoxy groups to generate more hydroxyl groups, resulting in enhanced intermolecular hydrogen bonding in B-E44. At the same time, the intensity of the epoxy group peak at 915 cm -1 of B-E44 decreases, and a C-N characteristic peak is detected at 1461 cm -1 . For AB-E44, the epoxy characteristic peak on it disappears, and as the number of hydroxyl groups further increases, the hydroxyl peak drops to 3430 cm -1 . It should be noted that the ester group and double bond of AB-E44 are located at 1725 cm -1 and 1634 cm -1 respectively, indicating that the double bond-terminated epoxy resin has been successfully prepared.

[0086] From Figure 4 , Figure 5 , Figure 6It can be found from Table 1 that when the coatings start to be immersed, they all have similar impedance values. After the coatings are immersed in salt water for 120 days, the impedance modulus of the coatings decreases, indicating that the anti-corrosion performance of the coatings depends on time, and the anti-corrosion performance of the coatings deteriorates with the extension of time. The modulus of the control group coating decreases to 4.79×10 7 Ω·cm 2 , and its anti-corrosion performance is the worst. When LGO and LTGO reinforcing fillers are introduced into the coatings, the anti-corrosion performance of the coatings is effectively improved. After the coatings LGO-ABE and LTGO-ABE are immersed in salt water for 120 days, the impedance modulus is 6.76×10 8 Ω·cm 2 and 1.17×10 9 Ω·cm 2 . Their values are all higher than that of the control group, 1 and 2 orders of magnitude higher than the control group. Among them, the coating LTGO-ABE has the best anti-corrosion performance.

[0087] From Figure 7 , Figure 8 and Figure 9 , it can be found that after the scratched coating ABE is immersed in salt water for 3 days, a large amount of loose corrosion products are found at the scratched part, indicating that the coating does not have self-healing performance. For the coatings LGO-ABE and LTGO-ABE, there are fewer corrosion products at the scratched parts. Among them, a relatively dense protective layer is formed at the scratched part of LTGO-ABE, which is the result of the product formed by the chelation of lignin and pyridine groups and metal ions covering the scratched part. By comparison, it is found that the coating LTGO-ABE has excellent self-healing anti-corrosion performance.

[0088] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A composite epoxy resin coating, characterized in that: Prepared from raw materials including: graphene oxide grafted with lignin and epoxy resin capped with double bonds; the graphene oxide grafted with lignin is prepared from double-bonded lignin and graphene oxide.

2. The composite epoxy resin coating according to claim 1, characterized in that: In the graphene oxide grafted with lignin, lignin is grafted onto the graphene oxide through a six-membered cycloalkenyl group.

3. The composite epoxy resin coating according to claim 1, wherein: In the composite epoxy resin coating, the proportion of graphene oxide grafted with lignin is 0.01 wt% to 10 wt%.

4. The composite epoxy resin coating according to claim 1, characterized in that: The mass ratio of the double-bonded lignin to the graphene oxide is (0.1 to 10):(0.1 to 50).

5. The composite epoxy resin coating according to claim 1, characterized in that: The graphene oxide further includes graphene oxide containing a pyridyl group.

6. The composite epoxy resin coating according to claim 1, wherein: The epoxy resin capped with double bonds is prepared from an epoxy resin, an amino monomer, and an acrylic monomer.

7. The composite epoxy resin coating according to claim 6, wherein: The composite epoxy resin coating satisfies at least one of the following conditions: (I) The mass ratio of the epoxy resin, the amino monomer, and the acrylic monomer is (1 to 150):(0.1 to 50):(1 to 100); (II) The epoxy resin includes being capped with an epoxy group; (III) The epoxy resin includes at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, polyphenol glycidyl ether epoxy resin, glycidyl ether epoxy resin, and heterocyclic epoxy resin; (IV) The amino monomer includes at least one of 3-butoxypropylamine, ethylenediamine, aniline, acrylamide, 2-aminopurine, and glucosamine; (V) The acrylic monomer includes at least one of acrylic acid, methacrylic acid, 2-fluoroacrylic acid, and 2-propylacrylic acid.

8. A method for preparing the composite epoxy resin coating according to any one of claims 1 to 7, characterized in that: Including the following steps: Carry out a polymerization reaction on the graphene oxide grafted with lignin, the epoxy resin capped with double bonds, and styrene to obtain the composite epoxy resin coating.

9. A coating, cured from the composite epoxy resin coating according to any one of claims 1 to 7.

10. Use of the composite epoxy resin coating according to any one of claims 1 to 7 or the coating according to claim 9 in the anti-corrosion of metal products.

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