A multifunctional coating for boards and its preparation method

Abstract

This invention belongs to the field of coating technology, specifically relating to a multifunctional coating for boards and its preparation method, including the following steps: (1) preparing molybdenum disulfide nanosheets modified with aminosilane coupling agent; (2) reacting 10-20wt% graphene oxide, inorganic nanoparticles, and modified molybdenum disulfide nanosheets for a period of time, then adding the remaining graphene oxide to continue the reaction, obtaining graphene oxide modified molybdenum disulfide nanosheets; (3) stirring and dispersing graphene oxide modified molybdenum disulfide nanosheets and aqueous polyurethane dispersion, then adding additives, and mixing evenly again to obtain a multifunctional coating for boards. This invention uses graphene oxide and inorganic nanoparticles to modify molybdenum disulfide. The modified molybdenum disulfide nanosheets can be uniformly dispersed in the coating, forming a highly cross-linked three-dimensional network structure, which significantly improves the anti-corrosion ability of the aqueous polyurethane coating.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, specifically relating to a multifunctional coating for boards and its preparation method. Background Technology

[0002] Metallic materials are a crucial foundation of modern industry and technology, finding wide application across various fields. However, they are also susceptible to corrosion. This occurs when metallic materials undergo electrochemical reactions with surrounding substances such as oxygen, water, acids, alkalis, and salts, leading to deterioration of the metal's surface properties and even severe damage. Metal corrosion not only reduces the reliability of materials and the safety and lifespan of engineering facilities but also results in resource waste and environmental pollution.

[0003] Metal corrosion is related to many factors, such as the composition, structure, shape, and surface condition of the metal material, as well as environmental conditions, such as the properties of the corrosive substance, temperature, humidity, pH, and redox potential. Furthermore, metal corrosion is a highly complex process; different metals exhibit different corrosion patterns under different environmental conditions. Therefore, to prevent or mitigate metal corrosion, it is essential to first fully understand its principles and mechanisms, and then propose corresponding protective measures and methods for different metal materials under varying environmental conditions.

[0004] Today, with the continuous development of technology and the increasing demands of enterprises, people have researched and invented many methods to prevent metal corrosion. These include: selecting materials with excellent corrosion resistance; applying a protective coating to the metal surface; adding substances that can slow down the corrosion rate; using electrochemical methods to protect the metal substrate; designing new alloy materials and modifying the properties of existing materials; controlling necessary environmental conditions; and monitoring and predicting real-time changes in metal corrosion. It is essential to fully utilize the advantages of each method while mitigating its disadvantages, and to select the appropriate protection scheme based on the specific circumstances.

[0005] Metal protection is crucial for preventing metal corrosion and encompasses a series of measures and methods to slow down, inhibit, or prevent corrosion of metals in specific environments. The goal of metal protection is to ensure that metals can operate stably and reliably for extended periods in various environments, thereby reducing damage caused by corrosion and extending the service life of metallic materials.

[0006] To improve the corrosion resistance of metals, a coating is often applied to their surface. Among these, polyurethane coatings are the most commonly used. The preparation of polyurethane resin coatings typically involves the reaction of isocyanates with polyols. This reaction produces polymer chains, forming a robust polyurethane structure. The coating is applied to the substrate surface, and the polyurethane chains generated by the reaction form a protective film. For example, CN120795774A discloses an easy-to-apply, one-component polyurethane waterproof coating and its preparation method. The raw materials include: polyol, plasticizer, solid filler, isocyanate, catalyst, and solvent; the polyol includes polyether diol and polyether triol; the plasticizer includes tributyl acetylacetate; and the catalyst includes bismuth neodecanoate catalyst and dimorpholine diethyl ether (DMDEE) catalyst. By combining the bismuth neodecanoate catalyst and the dimorpholine diethyl ether (DMDEE) catalyst, the viscosity of the waterproof coating is effectively reduced, facilitating application; at the same time, the drying speed of the waterproof coating is increased. Although the above-mentioned patented technology improves the mechanical properties of the coating, it uses toxic and expensive chemical reagents, resulting in high costs, which does not meet the requirements of green chemistry development. Summary of the Invention

[0007] The purpose of this invention is to address the above-mentioned problems by providing a multifunctional coating for boards and its preparation method. The coating of this invention has excellent mechanical properties, as well as properties such as easy application, weather resistance, high adhesion, and strong salt spray resistance, and has broad application prospects.

[0008] The technical solution of this invention is implemented as follows:

[0009] A method for preparing a multifunctional coating for boards includes the following steps:

[0010] (1) The aminosilane coupling agent and molybdenum disulfide nanosheets were dispersed in a solvent and modified molybdenum disulfide nanosheets were obtained after the reaction.

[0011] (2) Disperse 10-20wt% graphene oxide and catalyst in a solvent, then add inorganic nanoparticles and modified molybdenum disulfide nanosheets, stir evenly, and after reacting for a period of time, add the remaining graphene oxide to continue the reaction to obtain graphene oxide modified molybdenum disulfide nanosheets.

[0012] (3) Graphene oxide modified molybdenum disulfide nanosheets are dispersed in deionized water, water-based polyurethane dispersion is added, and the mixture is stirred and dispersed. Then, anti-settling agent, defoamer and wetting and dispersing agent are added and mixed evenly again to obtain a multifunctional coating for boards.

[0013] Molybdenum disulfide nanosheets exhibit unique sliding properties and excellent corrosion resistance at the microscale, along with good insulation properties, enabling their widespread application in harsh environments. Their layered structure forms an effective barrier, preventing harmful substances and corrosive media from easily eroding the substrate. However, because the nanomaterials have at least one dimension smaller than 100 nm, directly adding them to waterborne polyurethane presents technical challenges such as dispersion difficulties and easy agglomeration.

[0014] To address the aforementioned issues, this invention modifies molybdenum disulfide using graphene oxide and inorganic nanoparticles. The macroscopic structure of graphene oxide is similar to that of molybdenum disulfide nanosheets, both exhibiting a two-dimensional sheet structure with a high aspect ratio. Compared to the inert structure of molybdenum disulfide nanosheets, the basal surfaces and edges of graphene oxide sheets are covered with numerous oxygen-containing functional groups such as carboxyl and epoxy groups. These polar groups are hydrophilic, making the originally hydrophobic graphene framework highly hydrophilic. Modifying inert molybdenum disulfide nanosheets with hydrophilic graphene oxide can effectively improve the dispersion performance of molybdenum disulfide nanosheets in waterborne polyurethane coatings.

[0015] First, molybdenum disulfide nanosheets were modified using an aminosilane coupling agent, introducing amino and alkane chains onto their surface. The alkane chains exhibit steric hindrance, which can, to some extent, prevent the molybdenum disulfide nanosheets from stacking themselves. Subsequently, after reacting with the oxygen-containing functional groups on the surface of graphene oxide, graphene oxide is uniformly distributed on the surface of the molybdenum disulfide nanosheets, preventing the re-stacking of the nanosheet layers. One end of the aminosilane coupling agent is bonded to the molybdenum disulfide nanosheets via silicon-oxygen bonds, while the amino group at the other end chemically reacts or strongly interacts with the oxygen-containing functional groups on the graphene oxide. This transforms the molybdenum disulfide nanosheets from a free filler into a strongly chemically bonded component with graphene oxide, significantly improving the dispersibility of molybdenum disulfide. Furthermore, during the grafting reaction between graphene oxide and the modified molybdenum disulfide nanosheets, a small amount of zero-dimensional inorganic nanoparticles were also added. Inorganic nanoparticles, with their spherical structure, exhibit superior fluidity compared to the nanosheet-like structures of graphene oxide and molybdenum disulfide. Adding these nanoparticles to the reaction system of graphene oxide and modified molybdenum disulfide nanosheets prevents the stacking of sheet-like structures during the reaction, promoting dispersion and increasing the efficiency of the grafting reaction. The modified molybdenum disulfide nanosheets can be uniformly dispersed in the coating, forming a highly cross-linked three-dimensional network structure. Corrosive media must bypass these densely packed sheets, extending the diffusion path and significantly enhancing the physical barrier properties of the coating.

[0016] In one embodiment, the specific process steps of step (1) are as follows: the aminosilane coupling agent and molybdenum disulfide nanosheets are dispersed in a solvent, and after the reaction, the modified molybdenum disulfide nanosheets are obtained by filtration, washing and drying.

[0017] In one embodiment, the mass ratio of aminosilane coupling agent to molybdenum disulfide nanosheets is (0.1-0.4):1. Specifically, the mass ratio of aminosilane coupling agent to molybdenum disulfide nanosheets can be 0.1:1, 0.2:1, 0.3:1, or 0.4:1. Particularly, it can be (0.2-0.3):1. Insufficient aminosilane coupling agent will not effectively cover the surface of the molybdenum disulfide sheets, resulting in low grafting density and insufficient steric hindrance effect. Excessive aminosilane coupling agent will not only easily lead to self-condensation but also prevent the uniform dispersion of small amounts of graphene oxide on the surface of the molybdenum disulfide nanosheets, thus reducing the modification effect.

[0018] In one embodiment, the aminosilane coupling agent is one or more of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-diethylenetriaminopropyltrimethoxysilane, 3-diethylenetriaminopropyltriethoxysilane, 3-diethylenetriaminopropylmethyldimethoxysilane, and 3-diethylenetriaminopropylmethyldiethoxysilane. Specifically, 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane with suitable reactivity can be selected.

[0019] In one embodiment, the solvent is a mixed solvent of ethanol and deionized water in a volume ratio of (0.5-5):1. Specifically, the volume ratio of ethanol to deionized water can be 0.5:1, 1:1, 2:1, 3:1, 4:1, or 5:1.

[0020] In one embodiment, the reaction temperature is 55-65°C and the reaction time is 2-3 hours. Specifically, the reaction temperature is 60°C and the reaction time is 2.5 hours.

[0021] In one embodiment, the specific process steps of step (2) are as follows: 10-20wt% of graphene oxide and catalyst are dispersed in a solvent, and then inorganic nanoparticles and modified molybdenum disulfide nanosheets are added. The mixture is stirred evenly and reacted for a period of time. Then the remaining graphene oxide is added to continue the reaction. After filtration, washing and drying, graphene oxide modified molybdenum disulfide nanosheets are obtained.

[0022] The surface of molybdenum disulfide nanosheets modified with aminosilane coupling agents is grafted with a large number of amino groups, while the surface of graphene oxide is rich in functional groups such as carboxyl and epoxy groups. When the modified molybdenum disulfide nanosheets are mixed with graphene oxide, a reaction occurs between the amino groups and the oxygen-containing functional groups. If all the graphene oxide is added at once or too much is added initially, the dispersion of the modified molybdenum disulfide itself is relatively limited. In the early stage of the reaction, the local concentration is too high, and the newly added graphene oxide does not have time to disperse before reacting with the modified molybdenum disulfide nanosheets. Some molybdenum disulfide nanosheets have a high concentration of graphene oxide loaded on them, while others do not have enough time to react with the graphene oxide, resulting in a decrease in the grafting efficiency of the modified molybdenum disulfide. Adding a small amount of graphene oxide first can reduce the grafting rate and allow the modified molybdenum disulfide to be fully and uniformly loaded with graphene oxide. After the reaction has been going on for a period of time, adding the remaining graphene oxide can better promote the reaction between graphene oxide and modified molybdenum disulfide, so that the graphene oxide is evenly dispersed on the surface of each molybdenum disulfide nanosheet and its dispersion performance is improved.

[0023] In one embodiment, the mass ratio of graphene oxide, inorganic nanoparticles, and modified molybdenum disulfide nanosheets is (0.05-0.2):(0.05-0.2):1. Further, the mass ratio of graphene oxide, inorganic nanoparticles, and modified molybdenum disulfide nanosheets is (0.08-0.18):(0.08-0.18):1; particularly, it can be (0.1-0.15):(0.1-0.15):1. The present invention uses a relatively small amount of graphene oxide and inorganic nanoparticles because although graphene oxide has good dispersibility, its mechanical properties are poor, and pure graphene oxide is a conductor; if it directly contacts the metal substrate, it will act as a cathode, accelerating metal corrosion. A suitable amount of graphene oxide and inorganic nanoparticles can better balance the dispersion of molybdenum disulfide and the strengthening effect of the coating.

[0024] In one embodiment, the inorganic nanoparticles are one or more of nano-silica, nano-titanium dioxide, nano-zinc oxide, nano-calcium carbonate, and nano-wollastonite. The type and particle size of the inorganic nanoparticles are not particularly limited; specifically, nano-silica with a particle size of 20-80 nm can be selected. In particular, this invention selects nano-silica with an average particle size of 50 nm.

[0025] In one embodiment, the solvent is deionized water. The amount of deionized water used is not particularly limited. Specifically, the mass-to-volume ratio of modified molybdenum disulfide nanosheets to deionized water is 8 mg: (0.1-10) mL.

[0026] In one embodiment, the catalyst is a mixture of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). Specifically, the mass ratio of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC), N-hydroxysuccinimide (NHS), and graphene oxide is (1.2-1.6):(0.8-1.1):1; more specifically, it can be (1.3-1.5):(0.9-1.0):1. By adding the catalyst, the reaction potential energy can be reduced, thus better promoting the bonding of graphene oxide with modified molybdenum disulfide.

[0027] In one embodiment, the reaction time is 4-8 hours, and the continued reaction time is 20-30 hours. The reaction temperature is not particularly limited; in particular, it can be carried out at room temperature.

[0028] In one embodiment, the solid content of the aqueous polyurethane dispersion is 50-70%.

[0029] In one embodiment, the mass ratio of graphene oxide-modified molybdenum disulfide nanosheets to the aqueous polyurethane dispersion is (5-10):100. Specifically, it can be 5:100, 6:100, 7:100, 8:100, 9:100, or 10:100. Further, it can be (5.5-8.5):100. An appropriate amount of graphene oxide-modified molybdenum disulfide nanosheets can be better dispersed in the aqueous polyurethane matrix resin, enhancing the coating performance. Generally, as the amount of graphene oxide-modified molybdenum disulfide nanosheets increases, salt spray resistance improves; however, excessive amounts may lead to dispersion difficulties, causing salt spray resistance to plateau or even decrease, while coating adhesion will significantly decrease. Within the above-mentioned ratio range, the mechanical properties and corrosion resistance of the coating can be balanced, preventing excessive filler from affecting coating adhesion.

[0030] In one embodiment, the mass ratio of the anti-settling agent, defoamer, wetting and dispersing agent to the aqueous polyurethane dispersion is (1-2):(1-2):(1-2):100. Specifically, it can be (1.2-1.7):(1.2-1.7):(1.2-1.7):100.

[0031] In one embodiment, the anti-settling agent is one or more of BYK420, BYK425, and BYK430.

[0032] In one embodiment, the defoamer is an organosilicone defoamer or a mineral oil defoamer. Specifically, it can be polydimethylsiloxane.

[0033] In one embodiment, the wetting and dispersing agent is one or more of sodium polyacrylate, ammonium polyacrylate, and polyphosphate. Specifically, it can be sodium polyacrylate.

[0034] On the other hand, the present invention also provides a multifunctional coating for sheet metal prepared by the above method. This coating has excellent mechanical properties, is easy to apply, and has good weather resistance, and has broad application prospects in the coating field, especially in the field of insulating and anti-corrosion coatings for metal sheets.

[0035] Beneficial effects:

[0036] This invention modifies molybdenum disulfide using graphene oxide and inorganic nanoparticles. Compared to the inert structure of molybdenum disulfide nanosheets, graphene oxide sheets have a large number of oxygen-containing functional groups such as carboxyl and epoxy groups distributed on their basal surfaces and edges. These polar groups are hydrophilic. Modifying molybdenum disulfide nanosheets with graphene oxide can effectively improve their dispersion in waterborne polyurethane coatings. Furthermore, a small amount of inorganic nanoparticles are added during the grafting reaction of graphene oxide and modified molybdenum disulfide nanosheets. These inorganic nanoparticles have a spherical structure and better flowability than the nanosheet-like structure of graphene oxide and molybdenum disulfide. Adding inorganic nanoparticles to the reaction system of graphene oxide and modified molybdenum disulfide nanosheets can prevent the stacking of sheet-like structures during the reaction, promote the dispersion of the nanosheet-like structures, and improve the efficiency of the grafting reaction. Moreover, the addition of inorganic nanoparticles further improves the corrosion resistance and mechanical properties of waterborne polyurethane. The modified molybdenum disulfide nanosheets can be uniformly dispersed in the coating, and a highly cross-linked three-dimensional network structure can be formed by adding a small amount of modified molybdenum disulfide nanosheets. Corrosive media must bypass these densely packed sheets, extending the diffusion path and significantly improving the physical barrier properties of the waterborne polyurethane coating. Detailed Implementation

[0037] To better illustrate the purpose, technical solution, and advantages of this application, the following will provide further explanation in conjunction with specific embodiments. In the following embodiments and comparative examples, unless otherwise specified, the experimental methods used are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0038] Performance testing: Parallel experiments were conducted to test the adhesion of the coating film (GB / T 5210-2006) and the salt spray resistance (GB / T 1771-2007) of the boards prepared in the following examples and comparative examples using multifunctional coatings.

[0039] Example 1

[0040] A method for preparing a multifunctional coating for boards includes the following steps:

[0041] (1) The aminosilane coupling agent 3-aminopropyltriethoxysilane and molybdenum disulfide nanosheets were dispersed in a mixed solvent of ethanol and deionized water in a volume ratio of 3:1. After reacting at 55°C for 3 h, the mixture was filtered, washed and dried to obtain modified molybdenum disulfide nanosheets. The mass ratio of aminosilane coupling agent to molybdenum disulfide nanosheets was 0.1:1.

[0042] (2) 10wt% graphene oxide and catalysts 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) were dispersed in deionized water, and then nano-silica and modified molybdenum disulfide nanosheets were added. The mixture was stirred evenly and reacted for 4 hours. Then, the remaining graphene oxide was added and the reaction was continued for 30 hours. After filtration, washing and drying, graphene oxide modified molybdenum disulfide nanosheets were obtained. The mass ratio of graphene oxide, nano-silica and modified molybdenum disulfide nanosheets was 0.05:0.17:1; the mass-volume ratio of modified molybdenum disulfide nanosheets to deionized water was 8 mg:1 mL; and the mass ratio of EDC, NHS and graphene oxide was 1.4:0.9:1.

[0043] (3) Graphene oxide-modified molybdenum disulfide nanosheets were dispersed in deionized water, and an aqueous polyurethane dispersion (60% solid content) was added. The mixture was stirred and dispersed, and then anti-settling agent BYK420, defoamer polydimethylsiloxane, and wetting and dispersing agent sodium polyacrylate were added. The mixture was then stirred evenly again to obtain a multifunctional coating for boards. The mass ratio of graphene oxide-modified molybdenum disulfide nanosheets, anti-settling agent, defoamer, wetting and dispersing agent, and aqueous polyurethane dispersion was 5:1:1:1:100. The coating film adhesion was tested to be 4.3 MPa, and the salt spray resistance was 630 h.

[0044] Example 2

[0045] A method for preparing a multifunctional coating for boards includes the following steps:

[0046] (1) The aminosilane coupling agent 3-aminopropyltrimethoxysilane and molybdenum disulfide nanosheets were dispersed in a mixed solvent of ethanol and deionized water in a volume ratio of 3:1. After reacting at 65°C for 2 h, the mixture was filtered, washed and dried to obtain modified molybdenum disulfide nanosheets. The mass ratio of aminosilane coupling agent to molybdenum disulfide nanosheets was 0.4:1.

[0047] (2) 20wt% graphene oxide and catalysts 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) were dispersed in deionized water, and then nano-silica and modified molybdenum disulfide nanosheets were added. The mixture was stirred evenly and reacted for 8 hours. Then, the remaining graphene oxide was added and the reaction was continued for 20 hours. After filtration, washing and drying, graphene oxide modified molybdenum disulfide nanosheets were obtained. The mass ratio of graphene oxide, nano-silica and modified molybdenum disulfide nanosheets was 0.18:0.05:1. The mass-volume ratio of modified molybdenum disulfide nanosheets to deionized water was 8 mg:1 mL. The mass ratio of EDC, NHS and graphene oxide was 1.4:0.9:1.

[0048] (3) Graphene oxide-modified molybdenum disulfide nanosheets were dispersed in deionized water, and an aqueous polyurethane dispersion (60% solid content) was added. The mixture was stirred and dispersed, and then anti-settling agent BYK425, defoamer polydimethylsiloxane, and wetting and dispersing agent sodium polyacrylate were added. The mixture was then stirred evenly again to obtain a multifunctional coating for boards. The mass ratio of graphene oxide-modified molybdenum disulfide nanosheets, anti-settling agent, defoamer, wetting and dispersing agent, and aqueous polyurethane dispersion was 9:2:2:2:100. The coating film adhesion was tested to be 4.8 MPa, and the salt spray resistance was 790 h.

[0049] Example 3

[0050] A method for preparing a multifunctional coating for boards includes the following steps:

[0051] (1) The aminosilane coupling agent 3-aminopropyltriethoxysilane and molybdenum disulfide nanosheets were dispersed in a mixed solvent of ethanol and deionized water in a volume ratio of 3:1. After reacting at 60°C for 2.5 h, the mixture was filtered, washed and dried to obtain modified molybdenum disulfide nanosheets. The mass ratio of aminosilane coupling agent to molybdenum disulfide nanosheets was 0.25:1.

[0052] (2) 15wt% graphene oxide and catalysts 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) were dispersed in deionized water, and then nano-silica and modified molybdenum disulfide nanosheets were added. The mixture was stirred evenly and reacted for 6 hours. Then, the remaining graphene oxide was added and the reaction was continued for 25 hours. After filtration, washing and drying, graphene oxide modified molybdenum disulfide nanosheets were obtained. The mass ratio of graphene oxide, nano-silica and modified molybdenum disulfide nanosheets was 0.2:0.1:1; the mass-volume ratio of modified molybdenum disulfide nanosheets to deionized water was 8 mg:1 mL; and the mass ratio of EDC, NHS and graphene oxide was 1.4:0.9:1.

[0053] (3) Graphene oxide-modified molybdenum disulfide nanosheets were dispersed in deionized water, and an aqueous polyurethane dispersion (60% solid content) was added. The mixture was stirred and dispersed, and then anti-settling agent BYK425, defoamer polydimethylsiloxane, and wetting and dispersing agent sodium polyacrylate were added. The mixture was then stirred again until homogeneous to obtain a multifunctional coating for boards. The mass ratio of graphene oxide-modified molybdenum disulfide nanosheets, anti-settling agent, defoamer, wetting and dispersing agent, and aqueous polyurethane dispersion was 8:1.5:1.5:1.5:100. The coating film adhesion was tested to be 4.9 MPa, and the salt spray resistance was 770 h.

[0054] Example 4

[0055] A method for preparing a multifunctional coating for boards includes the following steps:

[0056] (1) The aminosilane coupling agent 3-aminopropyltrimethoxysilane and molybdenum disulfide nanosheets were dispersed in a mixed solvent of ethanol and deionized water in a volume ratio of 3:1. After reacting at 55°C for 2 h, the mixture was filtered, washed and dried to obtain modified molybdenum disulfide nanosheets. The mass ratio of aminosilane coupling agent to molybdenum disulfide nanosheets was 0.15:1.

[0057] (2) 19wt% graphene oxide and catalysts 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) were dispersed in deionized water, and then nano-silica and modified molybdenum disulfide nanosheets were added. The mixture was stirred evenly and reacted for 4 hours. Then, the remaining graphene oxide was added and the reaction was continued for 20 hours. After filtration, washing and drying, graphene oxide modified molybdenum disulfide nanosheets were obtained. The mass ratio of graphene oxide, nano-silica and modified molybdenum disulfide nanosheets was 0.18:0.17:1; the mass-volume ratio of modified molybdenum disulfide nanosheets to deionized water was 8 mg:1 mL; and the mass ratio of EDC, NHS and graphene oxide was 1.4:0.9:1.

[0058] (3) Graphene oxide-modified molybdenum disulfide nanosheets were dispersed in deionized water, and an aqueous polyurethane dispersion (60% solid content) was added. The mixture was stirred and dispersed, and then anti-settling agent BYK430, defoamer polydimethylsiloxane, and wetting and dispersing agent sodium polyacrylate were added. The mixture was then stirred evenly again to obtain a multifunctional coating for boards. The mass ratio of graphene oxide-modified molybdenum disulfide nanosheets, anti-settling agent, defoamer, wetting and dispersing agent, and aqueous polyurethane dispersion was 5.6:2:1:2:100. The coating film adhesion was tested to be 5.2 MPa, and the salt spray resistance was 670 h.

[0059] Example 5

[0060] A method for preparing a multifunctional coating for boards includes the following steps:

[0061] (1) The aminosilane coupling agent 3-aminopropyltriethoxysilane and molybdenum disulfide nanosheets were dispersed in a mixed solvent of ethanol and deionized water in a volume ratio of 3:1. After reacting at 60°C for 2.5 h, the mixture was filtered, washed and dried to obtain modified molybdenum disulfide nanosheets. The mass ratio of aminosilane coupling agent to molybdenum disulfide nanosheets was 0.25:1.

[0062] (2) 15wt% graphene oxide and catalysts 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) were dispersed in deionized water, and then nano-silica and modified molybdenum disulfide nanosheets were added. The mixture was stirred evenly and reacted for 6 hours. Then, the remaining graphene oxide was added and the reaction was continued for 25 hours. After filtration, washing and drying, graphene oxide modified molybdenum disulfide nanosheets were obtained. The mass ratio of graphene oxide, nano-silica and modified molybdenum disulfide nanosheets was 0.12:0.2:1; the mass-volume ratio of modified molybdenum disulfide nanosheets to deionized water was 8 mg:1 mL; and the mass ratio of EDC, NHS and graphene oxide was 1.4:0.9:1.

[0063] (3) Graphene oxide-modified molybdenum disulfide nanosheets were dispersed in deionized water, and an aqueous polyurethane dispersion (60% solid content) was added. The mixture was stirred and dispersed, and then anti-settling agent BYK425, defoamer polydimethylsiloxane, and wetting and dispersing agent sodium polyacrylate were added. The mixture was then stirred again until homogeneous to obtain a multifunctional coating for boards. The mass ratio of graphene oxide-modified molybdenum disulfide nanosheets, anti-settling agent, defoamer, wetting and dispersing agent, and aqueous polyurethane dispersion was 8:1.5:1.5:1.5:100. The coating film adhesion was tested to be 4.6 MPa, and the salt spray resistance was 780 h.

[0064] Example 6

[0065] A method for preparing a multifunctional coating for boards includes the following steps:

[0066] (1) The aminosilane coupling agent 3-aminopropyltriethoxysilane and molybdenum disulfide nanosheets were dispersed in a mixed solvent of ethanol and deionized water in a volume ratio of 3:1. After reacting at 58°C for 2.8 h, the mixture was filtered, washed and dried to obtain modified molybdenum disulfide nanosheets. The mass ratio of aminosilane coupling agent to molybdenum disulfide nanosheets was 0.2:1.

[0067] (2) 13wt% graphene oxide and catalysts 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) were dispersed in deionized water, and then nano-silica and modified molybdenum disulfide nanosheets were added. The mixture was stirred evenly and reacted for 5 hours. Then, the remaining graphene oxide was added and the reaction was continued for 27 hours. After filtration, washing and drying, graphene oxide modified molybdenum disulfide nanosheets were obtained. The mass ratio of graphene oxide, nano-silica and modified molybdenum disulfide nanosheets was 0.1:0.1:1; the mass-volume ratio of modified molybdenum disulfide nanosheets to deionized water was 8 mg:1 mL; and the mass ratio of EDC, NHS and graphene oxide was 1.4:0.9:1.

[0068] (3) Graphene oxide-modified molybdenum disulfide nanosheets were dispersed in deionized water, and an aqueous polyurethane dispersion (60% solid content) was added. The mixture was stirred and dispersed, and then anti-settling agent BYK420, defoamer polydimethylsiloxane, and wetting and dispersing agent sodium polyacrylate were added. The mixture was then stirred again until homogeneous to obtain a multifunctional coating for boards. The mass ratio of graphene oxide-modified molybdenum disulfide nanosheets, anti-settling agent, defoamer, wetting and dispersing agent, and aqueous polyurethane dispersion was 6:1.2:1.2:1.2:100. The coating film adhesion was tested to be 4.7 MPa, and the salt spray resistance was 650 h.

[0069] Example 7

[0070] A method for preparing a multifunctional coating for boards includes the following steps:

[0071] (1) The aminosilane coupling agent 3-aminopropyltriethoxysilane and molybdenum disulfide nanosheets were dispersed in a mixed solvent of ethanol and deionized water in a volume ratio of 3:1. After reacting at 60°C for 2.5 h, the mixture was filtered, washed and dried to obtain modified molybdenum disulfide nanosheets. The mass ratio of aminosilane coupling agent to molybdenum disulfide nanosheets was 0.25:1.

[0072] (2) 15wt% graphene oxide and catalysts 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) were dispersed in deionized water, and then nano-silica and modified molybdenum disulfide nanosheets were added. The mixture was stirred evenly and reacted for 6 hours. Then, the remaining graphene oxide was added and the reaction was continued for 25 hours. After filtration, washing and drying, graphene oxide modified molybdenum disulfide nanosheets were obtained. The mass ratio of graphene oxide, nano-silica and modified molybdenum disulfide nanosheets was 0.12:0.1:1; the mass-volume ratio of modified molybdenum disulfide nanosheets to deionized water was 8 mg:1 mL; and the mass ratio of EDC, NHS and graphene oxide was 1.4:0.9:1.

[0073] (3) Graphene oxide-modified molybdenum disulfide nanosheets were dispersed in deionized water, and an aqueous polyurethane dispersion (60% solid content) was added. The mixture was stirred and dispersed, and then anti-settling agent BYK425, defoamer polydimethylsiloxane, and wetting and dispersing agent sodium polyacrylate were added. The mixture was then stirred again until homogeneous to obtain a multifunctional coating for boards. The mass ratio of graphene oxide-modified molybdenum disulfide nanosheets, anti-settling agent, defoamer, wetting and dispersing agent, and aqueous polyurethane dispersion was 10:1.5:1.5:1.5:100. The coating film adhesion was tested to be 4.5 MPa, and the salt spray resistance was 800 h.

[0074] Example 8

[0075] A method for preparing a multifunctional coating for boards includes the following steps:

[0076] (1) The aminosilane coupling agent 3-aminopropyltrimethoxysilane and molybdenum disulfide nanosheets were dispersed in a mixed solvent of ethanol and deionized water in a volume ratio of 3:1. After reacting at 62℃ for 2.3h, the mixture was filtered, washed and dried to obtain modified molybdenum disulfide nanosheets; the mass ratio of aminosilane coupling agent to molybdenum disulfide nanosheets was 0.3:1.

[0077] (2) 17wt% graphene oxide and catalysts 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) were dispersed in deionized water, and then nano-silica and modified molybdenum disulfide nanosheets were added. The mixture was stirred evenly and reacted for 7 hours. Then, the remaining graphene oxide was added and the reaction was continued for 23 hours. After filtration, washing and drying, graphene oxide modified molybdenum disulfide nanosheets were obtained. The mass ratio of graphene oxide, nano-silica and modified molybdenum disulfide nanosheets was 0.16:0.15:1; the mass-volume ratio of modified molybdenum disulfide nanosheets to deionized water was 8 mg:1 mL; and the mass ratio of EDC, NHS and graphene oxide was 1.4:0.9:1.

[0078] (3) Graphene oxide-modified molybdenum disulfide nanosheets were dispersed in deionized water, and an aqueous polyurethane dispersion (60% solid content) was added. The mixture was stirred and dispersed, and then anti-settling agent BYK430, defoamer polydimethylsiloxane, and wetting and dispersing agent sodium polyacrylate were added. The mixture was then stirred again until homogeneous to obtain a multifunctional coating for boards. The mass ratio of graphene oxide-modified molybdenum disulfide nanosheets, anti-settling agent, defoamer, wetting and dispersing agent, and aqueous polyurethane dispersion was 7:1.8:1.8:1.8:100. The coating film adhesion was tested to be 4.4 MPa, and the salt spray resistance was 720 h.

[0079] Example 9

[0080] A method for preparing a multifunctional coating for boards includes the following steps:

[0081] (1) The aminosilane coupling agent 3-aminopropyltriethoxysilane and molybdenum disulfide nanosheets were dispersed in a mixed solvent of ethanol and deionized water in a volume ratio of 3:1. After reacting at 57°C for 2.6 h, the mixture was filtered, washed and dried to obtain modified molybdenum disulfide nanosheets. The mass ratio of aminosilane coupling agent to molybdenum disulfide nanosheets was 0.26:1.

[0082] (2) 14wt% graphene oxide and catalysts 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) were dispersed in deionized water, and then nano-silica and modified molybdenum disulfide nanosheets were added. The mixture was stirred evenly and reacted for 5.5 h. Then the remaining graphene oxide was added and the reaction was continued for 26 h. After filtration, washing and drying, graphene oxide modified molybdenum disulfide nanosheets were obtained. The mass ratio of graphene oxide, nano-silica and modified molybdenum disulfide nanosheets was 0.13:0.09:1. The mass-volume ratio of modified molybdenum disulfide nanosheets to deionized water was 8 mg:1 mL. The mass ratio of EDC, NHS and graphene oxide was 1.4:0.9:1.

[0083] (3) Graphene oxide-modified molybdenum disulfide nanosheets were dispersed in deionized water, and an aqueous polyurethane dispersion (60% solid content) was added. The mixture was stirred and dispersed, and then anti-settling agent BYK420, defoamer polydimethylsiloxane, and wetting and dispersing agent sodium polyacrylate were added. The mixture was then stirred again until homogeneous to obtain a multifunctional coating for boards. The mass ratio of graphene oxide-modified molybdenum disulfide nanosheets, anti-settling agent, defoamer, wetting and dispersing agent, and aqueous polyurethane dispersion was 6.5:1.4:1.6:1.1:100. The coating film adhesion was tested to be 5.0 MPa, and the salt spray resistance was 750 h.

[0084] Example 10

[0085] A method for preparing a multifunctional coating for boards includes the following steps:

[0086] (1) The aminosilane coupling agent 3-aminopropyltriethoxysilane and molybdenum disulfide nanosheets were dispersed in a mixed solvent of ethanol and deionized water in a volume ratio of 3:1. After reacting at 60°C for 2.5 h, the mixture was filtered, washed and dried to obtain modified molybdenum disulfide nanosheets. The mass ratio of aminosilane coupling agent to molybdenum disulfide nanosheets was 0.25:1.

[0087] (2) 15wt% graphene oxide and catalysts 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) were dispersed in deionized water, and then nano-silica and modified molybdenum disulfide nanosheets were added. The mixture was stirred evenly and reacted for 6 hours. Then, the remaining graphene oxide was added and the reaction was continued for 25 hours. After filtration, washing and drying, graphene oxide modified molybdenum disulfide nanosheets were obtained. The mass ratio of graphene oxide, nano-silica and modified molybdenum disulfide nanosheets was 0.12:0.1:1; the mass-volume ratio of modified molybdenum disulfide nanosheets to deionized water was 8 mg:1 mL; and the mass ratio of EDC, NHS and graphene oxide was 1.4:0.9:1.

[0088] (3) Graphene oxide-modified molybdenum disulfide nanosheets were dispersed in deionized water, and an aqueous polyurethane dispersion (60% solid content) was added. The mixture was stirred and dispersed, and then anti-settling agent BYK425, defoamer polydimethylsiloxane, and wetting and dispersing agent sodium polyacrylate were added. The mixture was then stirred again until homogeneous to obtain a multifunctional coating for boards. The mass ratio of graphene oxide-modified molybdenum disulfide nanosheets, anti-settling agent, defoamer, wetting and dispersing agent, and aqueous polyurethane dispersion was 8:1.5:1.5:1.5:100. The coating film adhesion was tested to be 5.1 MPa, and the salt spray resistance was 790 h.

[0089] Comparative Example 1

[0090] A method for preparing a multifunctional coating for boards includes the following steps:

[0091] (1) The aminosilane coupling agent 3-aminopropyltriethoxysilane and molybdenum disulfide nanosheets were dispersed in a mixed solvent of ethanol and deionized water in a volume ratio of 3:1. After reacting at 60°C for 2.5 h, the mixture was filtered, washed and dried to obtain modified molybdenum disulfide nanosheets. The mass ratio of aminosilane coupling agent to molybdenum disulfide nanosheets was 0.25:1.

[0092] (2) 85wt% graphene oxide and catalysts 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) were dispersed in deionized water, and then nano-silica and modified molybdenum disulfide nanosheets were added. The mixture was stirred evenly and reacted for 6 hours. Then, the remaining graphene oxide was added and the reaction was continued for 25 hours. After filtration, washing and drying, graphene oxide modified molybdenum disulfide nanosheets were obtained. The mass ratio of graphene oxide, nano-silica and modified molybdenum disulfide nanosheets was 0.12:0.1:1; the mass-volume ratio of modified molybdenum disulfide nanosheets to deionized water was 8 mg:1 mL; and the mass ratio of EDC, NHS and graphene oxide was 1.4:0.9:1.

[0093] (3) Graphene oxide-modified molybdenum disulfide nanosheets were dispersed in deionized water, and an aqueous polyurethane dispersion (60% solid content) was added. The mixture was stirred and dispersed, and then anti-settling agent BYK425, defoamer polydimethylsiloxane, and wetting and dispersing agent sodium polyacrylate were added. The mixture was then stirred again until homogeneous to obtain a multifunctional coating for boards. The mass ratio of graphene oxide-modified molybdenum disulfide nanosheets, anti-settling agent, defoamer, wetting and dispersing agent, and aqueous polyurethane dispersion was 8:1.5:1.5:1.5:100. The coating film adhesion was tested to be 3.5 MPa, and the salt spray resistance was 510 h.

[0094] Comparative Example 2

[0095] A method for preparing a multifunctional coating for boards includes the following steps:

[0096] (1) The aminosilane coupling agent 3-aminopropyltriethoxysilane and molybdenum disulfide nanosheets were dispersed in a mixed solvent of ethanol and deionized water in a volume ratio of 3:1. After reacting at 60°C for 2.5 h, the mixture was filtered, washed and dried to obtain modified molybdenum disulfide nanosheets. The mass ratio of aminosilane coupling agent to molybdenum disulfide nanosheets was 0.25:1.

[0097] (2) 15wt% graphene oxide and catalysts 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) were dispersed in deionized water, and then modified molybdenum disulfide nanosheets were added. The mixture was stirred evenly and reacted for 6 hours. Then, the remaining graphene oxide was added and the reaction was continued for 25 hours. After filtration, washing and drying, graphene oxide modified molybdenum disulfide nanosheets were obtained. The mass ratio of graphene oxide to modified molybdenum disulfide nanosheets was 0.12:1; the mass-volume ratio of modified molybdenum disulfide nanosheets to deionized water was 8 mg:1 mL; and the mass ratio of EDC, NHS and graphene oxide was 1.4:0.9:1.

[0098] (3) Graphene oxide-modified molybdenum disulfide nanosheets and nano-silica were dispersed in deionized water, and an aqueous polyurethane dispersion (60% solid content) was added. The mixture was stirred and dispersed, and then anti-settling agent BYK425, defoamer polydimethylsiloxane, and wetting and dispersing agent sodium polyacrylate were added. The mixture was then stirred again until homogeneous, thus obtaining a multifunctional coating for boards. The mass ratio of nano-silica to modified molybdenum disulfide nanosheets was 0.1:1; the mass ratio of graphene oxide-modified molybdenum disulfide nanosheets to nano-silica, and the mass ratio of anti-settling agent, defoamer, wetting and dispersing agent to aqueous polyurethane dispersion was 8:1.5:1.5:1.5:100. The coating film adhesion was tested to be 3.8 MPa, and the salt spray resistance was 580 h.

[0099] As can be seen from the above examples and comparative examples, this invention uses graphene oxide and inorganic nanoparticles to modify molybdenum disulfide. Compared to the inert structure of molybdenum disulfide nanosheets, the basal surface and edges of graphene oxide sheets have a large number of oxygen-containing functional groups such as carboxyl groups and epoxy groups. These polar groups are hydrophilic. Modifying molybdenum disulfide nanosheets with graphene oxide can effectively improve the dispersion of molybdenum disulfide nanosheets in waterborne polyurethane coatings. Furthermore, during the grafting reaction between graphene oxide and modified molybdenum disulfide nanosheets, this invention also adds a small amount of inorganic nanoparticles. Inorganic nanoparticles have a spherical structure, and their flowability is superior to that of graphene oxide and molybdenum disulfide, which have a nanosheet structure. Adding inorganic nanoparticles to the reaction system of graphene oxide and modified molybdenum disulfide nanosheets can prevent the stacking of sheet structures during the reaction, promote the dispersion of nanosheet structures, and improve the efficiency of the grafting reaction. Moreover, the addition of inorganic nanoparticles further improves the corrosion resistance and mechanical properties of waterborne polyurethane. The modified molybdenum disulfide nanosheets can be uniformly dispersed in the coating, forming a highly cross-linked three-dimensional network structure.

[0100] Specifically, in Example 10, 15 wt% graphene oxide was added initially, and the remaining 85 wt% graphene oxide was added after a period of reaction. In contrast, in Comparative Example 1, too much graphene oxide was added initially, resulting in limited dispersion of the modified molybdenum disulfide. The local concentration was too high in the early stages of the reaction, and the newly added graphene oxide reacted with the modified molybdenum disulfide nanosheets before it could disperse. Some molybdenum disulfide nanosheets had excessively high graphene oxide concentrations, while others did not react with the graphene oxide, leading to a decrease in the grafting efficiency of the modified molybdenum disulfide. This indicates that adding a small amount of graphene oxide initially can reduce the grafting rate, allowing the modified molybdenum disulfide to be fully and uniformly loaded with graphene oxide. Adding the remaining graphene oxide after a period of reaction can better promote the reaction between graphene oxide and modified molybdenum disulfide, ensuring that the graphene oxide is uniformly dispersed on the surface of each molybdenum disulfide nanosheet and improving its dispersion performance.

[0101] Compared to Example 10, Comparative Example 2 did not add inorganic nanoparticles during the reaction of graphene oxide and modified molybdenum disulfide nanosheets. Instead, it added an equal amount of inorganic nanoparticles during the final blending process. This failed to prevent the stacking of the sheet-like structures, resulting in reduced filler dispersibility. The above examples and comparative examples demonstrate that adjusting the feeding method of graphene oxide and inorganic nanoparticles can better modify molybdenum disulfide nanosheets, improve their dispersion performance in waterborne polyurethane, and enable them to better construct a reinforcing and barrier network, thereby improving the corrosion resistance and adhesion of the coating.

[0102] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a multifunctional coating for boards, characterized in that, Includes the following steps: (1) The aminosilane coupling agent and molybdenum disulfide nanosheets were dispersed in a solvent and modified molybdenum disulfide nanosheets were obtained after the reaction. (2) Disperse 10-20wt% graphene oxide and catalyst in a solvent, then add inorganic nanoparticles and modified molybdenum disulfide nanosheets, stir evenly, and after reacting for a period of time, add the remaining graphene oxide to continue the reaction to obtain graphene oxide modified molybdenum disulfide nanosheets; the mass ratio of graphene oxide, inorganic nanoparticles and modified molybdenum disulfide nanosheets is (0.05-0.2):(0.05-0.2):1; (3) Graphene oxide modified molybdenum disulfide nanosheets are dispersed in deionized water, and aqueous polyurethane dispersion is added. The mixture is stirred and dispersed, and then anti-settling agent, defoamer and wetting and dispersing agent are added. The mixture is mixed evenly again to obtain a multifunctional coating for boards. The mass ratio of graphene oxide modified molybdenum disulfide nanosheets to aqueous polyurethane dispersion is (5-10):

100.

2. The method for preparing a multifunctional coating for boards as described in claim 1, characterized in that, In step (1), the mass ratio of aminosilane coupling agent to molybdenum disulfide nanosheets is (0.1-0.4):

1.

3. The method for preparing a multifunctional coating for boards as described in claim 1, characterized in that, In step (1), the solvent is a mixture of ethanol and deionized water in a volume ratio of (0.5-5):

1.

4. The method for preparing a multifunctional coating for boards as described in claim 1, characterized in that, In step (2), the inorganic nanoparticles are one or more of nano-silica, nano-titanium dioxide, nano-zinc oxide, nano-calcium carbonate, and nano-wollastonite.

5. The method for preparing a multifunctional coating for boards as described in claim 1, characterized in that, In step (3), the mass ratio of anti-settling agent, defoamer, wetting and dispersing agent to aqueous polyurethane dispersion is (1-2):(1-2):(1-2):

100.

6. The method for preparing a multifunctional coating for boards as described in claim 1, characterized in that, The anti-settling agent in step (3) is one or more of BYK420, BYK425, and BYK430.

7. The method for preparing a multifunctional coating for boards as described in claim 1, characterized in that, The defoamer in step (3) is an organosilicon defoamer or a mineral oil defoamer.

8. The method for preparing a multifunctional coating for boards as described in claim 1, characterized in that, In step (3), the wetting and dispersing agent is one or more of sodium polyacrylate, ammonium polyacrylate, and polyphosphate.

9. A multifunctional coating for boards, characterized in that, The coating is prepared by any one of the following methods for a multifunctional coating for sheet materials according to claims 1-8.