Self-repairing modified graphene water-based coating composition as well as preparation method and application thereof

Abstract

The invention provides a self-repairing modified graphene water-based coating composition as well as a preparation method and application thereof. Graphene is modified through free radical polymerization of 4-styrylpyridine (BPP) on the surface of graphene, and then coulomb interaction between protonated positive charges of BPP polymer graphene and negative charges of phosphotungstic acid anions is realized, so that the self-repairing modified graphene water-based coating composition is obtained. According to the present invention, the combination effect needs to be optimized by regulating the pH value of the solution, the obtained coating material has characteristics of high corrosion resistance, high self-repairing ability and high mechanical property, and the coating can be used in the fields of self-building cleaning exterior walls, automobile finishing paints, sea-crossing bridges, offshore wind power towers, chemical pipelines, and mobile phone / computer shell antistatic coatings.

Description

Technical Field

[0001] The present invention relates to the technical field of waterborne coatings, and particularly relates to a graphene-containing waterborne coating composition with self-healing function, a preparation method thereof and an application thereof, which can be used in the fields of architectural coatings, interior decoration coatings, metal protection or outer coatings of electronic terminals. Background Art

[0002] Epoxy resin is a high-performance thermosetting plastic and is widely used in various industries due to its unique chemical structure and properties. Epoxy resin, a high molecular polymer containing more than two epoxy groups, has its molecular structural formula defined as (C 11 H 12 O 3 )n. Waterborne epoxy resin coatings have advantages such as good mechanical properties, chemical stability and strong adhesion, and have less volatile organic compounds (VOCs), so they are environmentally friendly coatings. Now they are widely used in the fields of electronics, industry, ocean engineering, construction engineering, etc. There are two types of waterborne epoxy coatings: the first type is that the curing agent and epoxy resin are mixed to form emulsion particles, and this kind of coating has high strength and adhesion; the second type is that the curing agent does not emulsify the resin, so there are unreacted epoxy resins (rich in amides) in the coating. When the coating is applied to the metal surface, the unpaired electrons on the amide group can enter the vacant orbit of the metal, so as to obtain good adhesion, corrosion resistance and longer service life. Traditional epoxy-based anti-corrosion coatings are typical solvent-based systems, containing a certain proportion of volatile compounds, which are extremely harmful to the environment and human health. It is imperative to develop environmentally friendly epoxy coatings to replace solvent-based epoxy coatings. In the past few years, several environmentally friendly coating technologies have been developed, including powder coatings, non-solvent coatings, and ultraviolet-cured epoxy coatings. The waterborne epoxy resin system contains hydrophilic groups or surfactants and cannot completely inhibit the penetration of water, oxygen and other corrosive ions. Therefore, traditional waterborne formulations cannot provide long-term protection for metal substrates in highly corrosive environments.

[0003] Graphene consists of a planar structure composed of sp2 carbon atoms and their derivatives. Graphene is a nanostructure with unique thermal, mechanical and electronic properties and a high specific surface area. Graphene materials have good optical, electrical, mechanical and other properties and have important research value in multiple fields such as materials science and new energy. This makes graphene nanocatalysts also become a promising carrier, and it is considered to be a revolutionary material in the future. Monolayer graphene is the basic structural unit of natural graphite, and multilayer graphene can be considered as a combination of monolayer graphene stacked in a certain order. GO is a common precursor for synthesizing graphene through chemical reduction or thermal annealing. The distance between adjacent carbon atoms is 0.1421nm, and the σ bond of each layer of carbon atoms is stronger than the σ bond in diamond. Graphene is a two-dimensional carbon atom structure with a hexagonal crystal structure and has sp2 Bond. The π bonds between carbon atoms are separated (similar to metallic bonding). Since the electrons in the conjugated large π bond move freely in the structural layer, the π bond plays an important role in the electrical conductivity of graphene.

[0004] Heteropolyacids (HPAs) are a class of widely studied discrete anionic metal oxide clusters. Commercial heteropolyacids with the Keggin structure have many advantages, such as strong acidity higher than inorganic acids, no corrosiveness, no irritation, and excellent redox properties. They are applicable to fields such as electrochemistry, photochemistry, energy storage, environmental protection, and catalysis. However, due to their low surface area (1 - 5 m 2 / g) and the characteristics of being difficult to separate and recycle after mixing with solvents, the application scope of these active heteropolyacids is limited. The dispersion of polyoxometalates on certain carriers enhances the activity of the active sites and the actual activity of polyoxometalates, and polyoxometalates are no longer soluble in water after being mixed with the carrier, thus solving the problem of difficult recovery of polyoxometalates. This has prompted researchers to anchor POM on carrier materials through various methods such as sol - gel technology, electrostatic interaction, ion exchange, covalent grafting, and impregnation. The most reported method currently is the most traditional impregnation technique to disperse polyoxometalates on the surface of the carrier. However, inappropriate impregnation may cause the carrier to lose the POM deposited on the surface, so this method also has certain limitations. The most common carriers for loading heteropolyacids currently are mesoporous silica, MOFs, polymer polymers, metal oxides, and modified substances, magnetic nanomaterials, and carbon - based materials.

[0005] CN117902859A discloses a recycled concrete with self - healing performance, belonging to the technical field of recycled concrete. It is achieved by modifying recycled aggregates with heteropolyacids and phosphomolybdic acid. Protons in phosphomolybdic acid can combine with oxygen atoms in heteropolyacids to form coordination bonds at room temperature. This bonding is a reversible bonding reaction. Therefore, when heteropolyacids and phosphomolybdic acid modify recycled aggregates simultaneously, the recycled aggregates are endowed with the characteristics of this reversible bonding and thus have self - healing performance. When the recycled concrete cracks, the modified aggregates can achieve self - healing through reversible bonding. Heteropolyacid anions play the role of cross - linkers, increasing the charge number of polyacid anions, making the cross - link points more concentrated, increasing the force conduction when the material is stressed, and enhancing the tensile resistance of the recycled concrete. Summary of the Invention

[0006] The present invention provides a self-healing modified graphene aqueous coating composition, a preparation method thereof and an application thereof. 4-Styrylpyridine (BPP) is used to carry out free radical polymerization on the surface of graphene to modify the graphene. Then, through the Coulomb interaction between the protonated positive charge of the BPP polymer graphene and the negative charge of the phosphotungstic acid anion, the binding effect needs to be optimized by regulating the solution pH environment. The obtained coating material has high corrosion resistance, self-healing ability and mechanical properties. The coating can be used in the fields of self-cleaning exterior walls of buildings, automotive topcoats, cross-sea bridges, offshore wind power towers, chemical pipelines, and antistatic coatings for mobile phone / computer casings.

[0007] The specific content is as follows: A self-healing modified graphene aqueous coating composition, comprising component A and component B, and the mass ratio of component A to component B is 1-2:1.

[0008] Component A comprises the following components in parts by weight: 40-60 parts of waterborne epoxy resin; 2-4 parts of film-forming aid; 10-15 parts of heteropolyacid-modified graphene filler; 0.5-2 parts of dispersant; 0.2-1 part of defoamer; 1-2 parts of wetting agent; 0.5-2 parts of thickener; 0.2-0.5 part of leveling agent; pH regulator; 10-15 parts of water; Component B: 10-20 parts of diethylenetriamine.

[0009] The heteropolyacid-modified graphene filler is obtained through the following steps: (1) Place graphene powder in a mixed solution of concentrated nitric acid and concentrated sulfuric acid, heat it in a water bath at 90-95 °C for 2-4 h, cool it naturally, filter and wash it until neutral to obtain neutral graphene powder. After ultrasonic dispersion for 20-30 min, place it in a refrigerator for 10-12 h, and perform freeze-drying treatment to obtain flaky graphene. Then, physically mix the graphene with potassium persulfate to obtain a mixture of flaky graphene and potassium persulfate; (2) Mix 4-styrylpyridine with deionized water, exhaust it with nitrogen for 10-20 min, add the mixture of flaky graphene and potassium persulfate prepared in step (1), continuously stir, and carry out free radical polymerization reaction at 60-65 °C for 40-48 h. After natural cooling, filter to obtain a black precipitate. Wash the black precipitate successively with hydrochloric acid, ethanol and deionized water, and then perform freeze-drying to obtain a modified graphene material; (3) Take an appropriate amount of phosphotungstic heteropolyacid H3 PW 12 O 40 . nH 2 Disperse the phosphotungstic acid modified graphene material prepared in step (2) and O by ultrasonic in deionized hydrochloric acid water with a pH value of 4.8 - 5.2, at a temperature of 30 - 35 °C, and for a dispersion time of 1 - 2 h, then filter, wash, and dry to obtain the phosphotungstic acid modified graphene filler.

[0010] In step (1), the dosage of graphene is 150 - 200 mg, the dosage of potassium persulfate is 15 - 20 mg, the dosage of 4 - vinylpyridine is 2 - 2.5 mg, and the dosage of deionized water is 50 - 60 mL.

[0011] In step (3), the dosage of phosphotungstic acid is 100 - 120 mg, the dosage of the modified graphene material is 150 - 200 mg, and the dosage of deionized water is 40 - 50 mL.

[0012] The film - forming aid is selected from diethylene glycol methyl ether or dipropylene glycol methyl ether; the dispersant is selected from Efka EFKA - 5065 or Efka EFKA - 4540 dispersant.

[0013] The defoamer is selected from BYK BKY052 or BYK BKY054 defoamer; the wetting agent is selected from SN - WET990 or SN - WET996 wetting agent.

[0014] The thickener is selected from SN - 612 or SN - 636 thickener; the leveling agent is selected from Rohm and Haas RM - 2020; the pH regulator is selected from ammonia water or triethylamine.

[0015] In the present invention, first, a commercial graphene is treated by heating with a mixed solution of concentrated nitric acid and concentrated sulfuric acid. During the heating process, the steam needs to be refluxed to avoid the loss of the mixed acid and the solution. The mixed - acid treatment can introduce oxygen - containing functional groups (such as carboxyl groups, hydroxyl groups) on the surface of graphene, and anchor the BPP monomer or initiator (potassium thiosulfate) on the surface through chemical bonds.

[0016] Under the catalytic action of potassium thiosulfate in the present invention, 4 - vinylpyridine undergoes a radical polymerization reaction on the surface of graphene. The radical polymerization process may be as follows: First, the initiator decomposes: Potassium thiosulfate decomposes under heating conditions to generate sulfate radicals (SO 3 ⁻•); Then chain initiation: The sulfate radical attacks the double bond of the 4-styrylpyridine BPP monomer (Py-CH=CH-Ph), and the radical transfers to the α-carbon of BPP, forming a monomer radical; Then chain growth: The monomer radical reacts with more BPP molecules, opening the double bond in turn to form a polymer chain. In each growth step, the radical transfers from the end of the polymer chain to the α-carbon of the new monomer, forming a long chain; Finally, chain termination: Two radical chains terminate by coupling to generate the final polymer.

[0017] In the above process, the graphene surface provides a high specific surface area, promotes the adsorption of monomers and radicals, enhances the reaction efficiency, and may stabilize the intermediate through π-π stacking interactions.

[0018] In addition, the reasons for the radical polymerization of 4-styrylpyridine (BPP) of the present invention on the graphene surface are analyzed as follows: (1) In the present invention, graphene is pre-mixed with an initiator, that is, potassium thiosulfate is fixed on the graphene surface by physical adsorption or chemical bonding, and the radicals (SO 3 ⁻•) generated by decomposition only exist near the surface and only activate the adsorbed 4-styrylpyridine monomers, and the unadsorbed part in the solution cannot participate in the reaction; (2) There is a strong π-π stacking interaction between the benzene ring and pyridine ring in the BPP molecule and the sp² hybrid carbon structure of graphene, which enriches the monomers on the graphene surface, increases the local concentration, and thus accelerates the reaction rate; (3) The active sites at the edges or defects of graphene may promote the decomposition of potassium thiosulfate to generate radicals or directly participate in the chain initiation step; (4) The high conductivity of graphene may participate in the process of radical generation or transfer. For example, it stabilizes the radical intermediate through electron transfer and reduces the reaction activation energy; The above possible reasons all provide a controllable approach for the graphene-polymer composite functional material.

[0019] After the radical polymerization of 4-styrylpyridine (BPP) on the graphene surface, its mutual attraction and directional attraction with phosphotungstic acid (heteropolyacid) may proceed as follows: (1) The BPP monomer forms a poly(4-styrylpyridine) chain on the graphene surface through radical polymerization. Graphene as a substrate may promote the adsorption and polymerization of monomers through π-π interactions. Under acidic conditions with pH = 4.8 - 5.2, the pyridine groups (nitrogen atoms with lone pairs of electrons) in the polymer are protonated to form positively charged pyridinium ions (-NH⁺), making the entire polymer chain surface positively charged.

[0020] (2) Phosphotungstic acid (H 3 PW 12 O 40 ) dissociates in the solution into [PW 12 O 40³⁻ anions and H⁺. This anion has a high negative charge density (3 negative charges) and exists stably in solution.

[0021] (3) The positively charged poly(4-vinylpyridine) chain and the negatively charged [PW 12 O 40 ³⁻ are attracted to each other by the Coulomb force of positive and negative charges, forming a stable complex.

[0022] That is, the core of the composite of PW and the graphene-polymer composite functional material lies in: the Coulomb interaction between the protonated positive charge of the BPP polymer and the negative charge of the phosphotungstic acid anion. The binding effect needs to be optimized by regulating the solution pH environment. If the above lacks 4-vinylpyridine (BPP) modified graphene, then the heteropolyacid and graphene are mainly adsorbed by van der Waals forces, and no directional adsorption effect can be achieved, which is just a simple physical mixture.

[0023] Using the above-prepared graphene composite material as an inorganic additive component in the coating, coating it on the surface of the metal substrate has a self-healing function. See the appendix Figure 1 , and it has excellent scratch resistance and self-healing performance for small scratches. The reason analysis is as follows: The core mechanism for the heteropolyacid-modified graphene nanomaterial to achieve coating self-healing is completed through the redox activity and corrosion inhibitor ion release ability of the heteropolyacid (HPA), combined with the physical barrier and conductive synergistic effect of graphene. Specifically: When a scratch appears on the coating surface, the exposed metal substrate contacts water and oxygen in the environment, triggering local electrochemical corrosion (anodic metal dissolution, cathodic oxygen reduction). The heteropolyacid phosphomolybdic acid in the scratched area is exposed to the humid environment due to the coating damage and gradually dissolves and releases corrosion inhibitor ions (such as MoO 4 ²⁻, PO 4 ³⁻). The released heteropolyacid anions migrate to the surface of the metal substrate through diffusion. Then, the MoO 4 ²⁻ released by the heteropolyacid reacts with the metal substrate (such as Fe) to form a dense iron molybdate (FeMoO 4 ) passivation film, which covers the metal surface and blocks the anodic process of the corrosion reaction (Fe→Fe 2+ + 2e - ). In addition, the heteropolyacid itself has multi-electron redox ability and can participate in the cathodic reaction. The heteropolyacid acts as an electron acceptor to inhibit the oxygen reduction reaction (such as: O 2 + 2H 2 O + 4e⁻→4OH⁻), thereby slowing down the corrosion rate. And the synergy of graphene for self-healing: The high conductivity of graphene promotes the uniform distribution of charges in the coating, avoids local current concentration, and assists the directional migration of heteropolyacid ions to the damaged area; the graphene sheets rearrange at the scratch edge to form a secondary barrier, delaying the further penetration of the corrosive medium.

[0024] Beneficial technical effects: The heteropolyacid-modified graphene nanomaterial of the present invention, as a coating additive, can endow the coating with a variety of unique functions through the synergistic effect of heteropolyacid and graphene: (1) Corrosion resistance: The two-dimensional sheet structure of graphene forms a dense barrier in the coating to block the penetration of water, oxygen, and corrosive ions (such as Cl⁻); the heteropolyacid passivates the metal surface through redox reactions and inhibits electrochemical corrosion; (2) Self-healing ability: The heteropolyacid releases corrosion inhibitor ions (such as molybdate and tungstate) to repair small defects in the coating; (3) Self-cleaning property: The heteropolyacid (such as phosphomolybdic acid) generates reactive oxygen species (ROS) under light to decompose organic pollutants (such as VOCs). By regulating the roughness of graphene and heteropolyacid modification, a self-cleaning coating with a contact angle > 150° can be achieved; (4) Uniform dispersion: Graphene and heteropolyacid are adsorbed directionally and can be uniformly dispersed in the coating, significantly improving the stability and anisotropic uniformity of the physical and chemical properties of the coating. The above beneficial technical effects enable the coating of the present invention to be used in fields such as self-cleaning exterior walls of buildings, automotive topcoats, cross-sea bridges, offshore wind towers, chemical pipelines, antistatic coatings for mobile phone / computer casings, and electromagnetic shielding coatings. Description of the Drawings

[0025] Appendix Figure 1 Scratch repair effect of the coating on the iron sheet surface of the present invention. Detailed Description of the Invention Example 1

[0026] A self-healing modified graphene waterborne coating composition, comprising component A and component B, and the mass ratio of component A to component B is 1:1. Component A includes the following components in parts by weight: 40 parts of waterborne epoxy resin; 2 parts of a film-forming aid such as diethylene glycol methyl ether or dipropylene glycol methyl ether; 10 parts of heteropolyacid-modified graphene filler; 0.5 part of a dispersant such as Efka EFKA-5065 or Efka EFKA-4540; 0.2 part of an antifoaming agent such as BYK BKY052 or BYK BKY054; 1 part of a wetting agent such as SN-WET990 or SN-WET996; 0.5 part of a thickener such as SN-612 or SN-636; 0.2 part of a leveling agent such as Rohm and Haas RM-2020; A pH regulator such as ammonia water or triethylamine; 10 parts of water.

[0027] Component B: 10 parts of diethylenetriamine.

[0028] The heteropolyacid-modified graphene filler is prepared through the following steps.

[0029] (1) Place graphene powder in a mixed solution of concentrated nitric acid and concentrated sulfuric acid, heat it in a water bath at 90 °C for 2 h, naturally cool it, filter and wash it until neutral to obtain neutral graphene powder. After ultrasonic dispersion for 20 min, place it in a refrigerator for 10 h, and perform freeze-drying treatment to obtain flaky graphene. Then, physically mix 150 mg of graphene with 15 mg of potassium persulfate to obtain a mixture of flaky graphene and potassium persulfate.

[0030] (2) Mix 2 mg of 4-styrylpyridine with 50 mL of deionized water, exhaust it with nitrogen for 10 min, add the mixture of flaky graphene and potassium persulfate prepared in step (1), continuously stir, and carry out a free radical polymerization reaction at 60 °C for 40 h. After natural cooling, filter to obtain a black precipitate, wash the black precipitate successively with hydrochloric acid, ethanol, and deionized water, and then perform freeze-drying to obtain a modified graphene material.

[0031] (3) Take an appropriate amount of phosphotungstic heteropolyacid H 3 PW 12 O 40 . nH 2 O and the modified graphene material prepared in step (2) are ultrasonically dispersed in hydrochloric acid deionized water with a pH value of 4.8 at a temperature of 30 °C for 1 h, and then filtered, washed, and dried to obtain a heteropolyacid-modified graphene filler.

[0032] In step (3), the dosage of phosphotungstic heteropolyacid is 100 mg, the dosage of the modified graphene material is 150 mg, and the dosage of deionized water is 40 mL. Example 2

[0033] A self-healing modified graphene waterborne coating composition includes component A and component B, and the mass ratio of component A to component B is 1.5:1. Component A includes the following components in parts by weight: 50 parts of waterborne epoxy resin; 3 parts of a film-forming aid such as diethylene glycol methyl ether or dipropylene glycol methyl ether; 12.5 parts of a heteropolyacid-modified graphene filler; 1.25 parts of a dispersant such as Efka EFKA-5065 or Efka EFKA-4540; 0.6 part of an antifoaming agent such as BYK BKY052 or BYK BKY054; 1.5 parts of a wetting agent such as SN-WET990 or SN-WET996; 1.25 parts of a thickener such as SN-612 or SN-636; Rohm and Haas RM-2020 leveling agent; 0.35 parts; Ammonia water or triethylamine pH regulator; Water 12.5 parts.

[0034] Component B: Diethylenetriamine 15 parts.

[0035] The heteropolyacid-modified graphene filler is prepared through the following steps.

[0036] (1) Place graphene powder in a mixed solution of concentrated nitric acid and concentrated sulfuric acid, heat it in a water bath at 92.5 °C for 3 h, after natural cooling, filter and wash it until neutral to obtain neutral graphene powder. After ultrasonic dispersion for 25 min, place it in the refrigerator for 11 h, and perform freeze-drying treatment to obtain flaky graphene. Then, physically mix 175 mg of graphene with 17.5 mg of potassium persulfate to obtain a mixture of flaky graphene and potassium persulfate.

[0037] (2) Mix 2.25 mg of 4-vinylpyridine with 55 mL of deionized water, exhaust it with nitrogen for 15 min, then add the mixture of flaky graphene and potassium persulfate prepared in step (1). After continuous stirring, carry out a free radical polymerization reaction at 62.5 °C for 44 h. After natural cooling, filter to obtain a black precipitate. Wash the black precipitate successively with hydrochloric acid, ethanol and deionized water, and then perform freeze-drying to obtain a modified graphene material.

[0038] (3) Take an appropriate amount of phosphotungstic heteropolyacid H 3 PW 12 O 40 . nH 2 O and the modified graphene material prepared in step (2) are ultrasonically dispersed in hydrochloric acid deionized water with a pH value of 5.0, at a temperature of 32.5 °C, and the dispersion time is 1.5 h. After filtration, washing and drying, a heteropolyacid-modified graphene filler is obtained.

[0039] In step (3), the dosage of phosphotungstic heteropolyacid is 110 mg, the dosage of the modified graphene material is 175 mg, and the dosage of deionized water is 45 mL. Example 3

[0040] A self-healing modified graphene waterborne coating composition, comprising component A and component B, and the mass ratio of component A to component B is 2:1. Component A includes the following components in parts by weight: Waterborne epoxy resin 60 parts; Diethylene glycol methyl ether or dipropylene glycol methyl ether film-forming aid 4 parts; Heteropolyacid-modified graphene filler 15 parts; 2 parts of Efka EFKA-5065 or Efka EFKA-4540 dispersant; 1 part of BYK BKY052 or BYK BKY054 antifoaming agent; 2 parts of SN-WET990 or SN-WET996 wetting agent; 2 parts of SN-612 or SN-636 thickener; 0.5 part of Rohm and Haas RM-2020 leveling agent; Ammonia water or triethylamine pH regulator; 15 parts of water.

[0041] Component B: 20 parts of diethylenetriamine.

[0042] The heteropolyacid-modified graphene filler is prepared through the following steps.

[0043] (1) Place graphene powder in a mixed solution of concentrated nitric acid and concentrated sulfuric acid, heat it in a water bath at 95 °C for 4 h, cool it naturally, filter and wash it until neutral to obtain neutral graphene powder. After ultrasonic dispersion for 30 min, place it in a refrigerator for 12 h, and perform freeze-drying treatment to obtain flaky graphene. Then, physically mix 200 mg of graphene with 20 mg of potassium persulfate to obtain a mixture of flaky graphene and potassium persulfate.

[0044] (2) Mix 2.5 mg of 4-vinylpyridine with 60 mL of deionized water, exhaust it with nitrogen for 20 min, add the mixture of flaky graphene and potassium persulfate prepared in step (1), continuously stir, and carry out a free radical polymerization reaction at 65 °C for 48 h. After natural cooling, filter to obtain a black precipitate. Wash the black precipitate successively with hydrochloric acid, ethanol, and deionized water, and then perform freeze-drying to obtain a modified graphene material.

[0045] (3) Take an appropriate amount of phosphotungstic heteropolyacid H 3 PW 12 O 40 . nH 2 O and the modified graphene material prepared in step (2) are ultrasonically dispersed in hydrochloric acid deionized water with a pH value of 5.2 at a temperature of 35 °C for 2 h, and then filtered, washed, and dried to obtain a heteropolyacid-modified graphene filler.

[0046] In step (3), the dosage of phosphotungstic heteropolyacid is 120 mg, the dosage of the modified graphene material is 200 mg, and the dosage of deionized water is 50 mL.

[0047] Comparative Example 1 A self-healing modified graphene waterborne coating composition, including Component A and Component B, and the mass ratio of Component A to Component B is 1.5:1. The A component comprises the following components in parts by weight: 50 parts of waterborne epoxy resin; 3 parts of a film-forming aid such as diethylene glycol methyl ether or dipropylene glycol methyl ether; 12.5 parts of a heteropolyacid-graphene filler; 1.25 parts of a dispersant such as Efka EFKA-5065 or Efka EFKA-4540; 0.6 part of an antifoaming agent such as BYK BKY052 or BYK BKY054; 1.5 parts of a wetting agent such as SN-WET990 or SN-WET996; 1.25 parts of a thickener such as SN-612 or SN-636; 0.35 part of a leveling agent such as Rohm and Haas RM-2020; A pH regulator such as ammonia water or triethylamine; 12.5 parts of water.

[0048] The B component: 15 parts of diethylenetriamine.

[0049] The heteropolyacid-graphene filler is obtained through the following steps.

[0050] (1) Place graphene powder in a mixed solution of concentrated nitric acid and concentrated sulfuric acid, heat it in a water bath at 92.5 °C for 3 h, naturally cool it, filter and wash it until neutral to obtain neutral graphene powder. After ultrasonic dispersion for 25 min, place it in a refrigerator for 11 h and perform freeze-drying treatment to obtain flaky graphene.

[0051] (2) Take an appropriate amount of phosphotungstic heteropolyacid H 3 PW 12 O 40 . nH 2 O and the graphene material prepared in step (1) and ultrasonically disperse them in hydrochloric acid deionized water with a pH value of 5.0 at a temperature of 32.5 °C for 1.5 h. Filter, wash, and dry to obtain the heteropolyacid-graphene filler.

[0052] In step (3), the dosage of phosphotungstic heteropolyacid is 110 mg, the dosage of the modified graphene material is 175 mg, and the dosage of deionized water is 45 mL.

[0053] Blank example, an aqueous coating composition, comprising the following components in parts by weight.

[0054] 50 parts of waterborne epoxy resin; 3 parts of a film-forming aid such as diethylene glycol methyl ether or dipropylene glycol methyl ether; 12.5 parts of a heteropolyacid-graphene filler; 1.25 parts of Efka EFKA-5065 or Efka EFKA-4540 dispersant; 0.6 parts of BYK BKY052 or BYK BKY054 antifoaming agent; 1.5 parts of SN-WET990 or SN-WET996 wetting agent; 1.25 parts of SN-612 or SN-636 thickener; 0.35 parts of Rohm and Haas RM-2020 leveling agent; Ammonia water or triethylamine pH regulator; 12.5 parts of water.

[0055]

[0056] Using stainless steel as the coating substrate and adding heteropolyacid-modified graphene filler, the corrosion resistance of the coating is improved compared with the blank example. Among them, the corrosion current density of Example 2 is the best, which is 6.2*10 -9 A / cm 2 ; In Comparative Example 1, the poor dispersibility of heteropolyacid-modified graphene leads to uneven coating, poor stability and reduced density, which in turn affects the corrosion resistance of the coating. Moreover, the corresponding wear resistance (mass loss), tensile strength and impact resistance all decrease to a certain extent. Heteropolyacid-modified graphene in the coating can not only be used as a reinforcement to enhance the internal bonding force and overall strength of epoxy resin, but also be dispersed in the coating to play a toughening role, prevent destructive cracking, and thus improve the bonding strength and erosion wear performance of the epoxy resin coating.

[0057] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor limit the invention to the specific embodiments described. Obviously, many modifications and changes can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principle and practical application of the present invention, so that those skilled in the art can understand and utilize the present invention well. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A self-repairing modified graphene water-based coating composition, characterized in that: It includes component A and component B, and the mass ratio of component A to component B is 1-2:

1. Component A includes the following components in parts by weight: 40-60 parts of waterborne epoxy resin; 2-4 parts of film-forming aid; 10-15 parts of heteropolyacid modified graphene filler; Dispersant 0.5-2 parts; Defoaming agent 0.2-1 part; 1-2 parts of wetting agent; Thickener 0.5-2 parts; Leveling agent: 0.2-0.5 parts; pH adjusters; 10-15 parts water; Component B: 10-20 parts of diethylenetriamine.

2. A self-repairing modified graphene water-based coating composition as claimed in claim 1, characterized in that The heteropolyacid-modified graphene filler is prepared by the following steps: (1) placing graphene powder in a mixture of concentrated nitric acid and concentrated sulfuric acid, heating in a water bath to 90-95° C. for 2-4 hours, naturally cooling, filtering and washing until neutral to obtain neutral graphene powder, ultrasonically dispersing for 20-30 minutes, placing in a refrigerator for 10-12 hours, freeze-drying to obtain flaky graphene, and then physically mixing the graphene with potassium persulfate to obtain a mixture of flaky graphene and potassium persulfate; (2) Mix 4-phenylvinylpyridine with deionized water, exhaust with nitrogen for 10-20 minutes, add the flaky graphene and potassium persulfate mixture prepared in step (1), continue stirring, and react with free radical polymerization at 60-65° C. for 40-48 hours. After natural cooling, filter to obtain a black precipitate, wash the black precipitate with hydrochloric acid, ethanol and deionized water in sequence, and then freeze-dry to obtain a modified graphene material; (3) Take an appropriate amount of phosphotungstic acid H3PW 12 O 40 . nH2O and the modified graphene material prepared in step (2) are ultrasonically dispersed in deionized hydrochloric acid water with a pH value of 4.8-5.2 at a temperature of 30-35°C for a dispersion time of 1-2h, and filtered, washed and dried to obtain a heteropolyacid-modified graphene filler.

3. A self-repairing modified graphene water-based coating composition as claimed in claim 2, characterized in that In step (1), the amount of graphene used is 150-200 mg, the amount of potassium persulfate used is 15-20 mg, the amount of 4-phenylpyridine used is 2-2.5 mg, and the amount of deionized water used is 50-60 mL.

4. A self-repairing modified graphene water-based coating composition as claimed in claim 2, characterized in that In step (3), the amount of phosphotungstic heteropoly acid used is 100-150 mg, the amount of modified graphene material used is 150-200 mg, and the amount of deionized water used is 40-50 mL.

5. A self-repairing modified graphene water-based coating composition as claimed in claim 1, characterized in that The film-forming aid is selected from diethylene glycol methyl ether or dipropylene glycol methyl ether; the dispersant is selected from EFKA-5065 or EFKA-4540 dispersant.

6. A self-repairing modified graphene water-based coating composition as claimed in claim 1, characterized in that The defoaming agent is selected from BYK BKY052 or BYK BKY054 defoaming agent; the wetting agent is selected from SN-WET990 or SN-WET996 wetting agent.

7. A self-repairing modified graphene water-based coating composition as claimed in claim 1, characterized in that The thickener is selected from SN-612 or SN-636 thickener; the leveling agent is selected from Rohm and Haas RM-2020; and the pH adjuster is selected from ammonia water or triethylamine.

8. The use of the self-repairing modified graphene water-based coating composition according to any one of claims 1 to 7, characterized in that Used in architectural coatings, interior decoration coatings, metal protection or electronic terminal outer coatings.

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