A highly weather-resistant coating and the color steel plate prepared therefrom

Abstract

The present invention belongs to the technical field of coatings, and particularly relates to a high weather-resistant coating and a color steel plate prepared therefrom. The present invention uses graphene and amino-modified nano-silica as blend fillers to modify waterborne polyurethane. By selecting graphene with a carbon-oxygen ratio of (25-40):1, it not only endows the surface of graphene with certain activity, but also takes into account the mechanical properties of graphene, further improving the dispersion performance of graphene in the coating. The amino-modified nano-silica has good dispersion in waterborne polyurethane, and the presence of active amino groups also easily reacts with oxygen-containing functional groups on the surface of graphene or residual active groups on polyurethane and forms hydrogen bonds, improving its crosslinking ability with graphene with a specific carbon-oxygen ratio and polyurethane, further promoting the formation of a crosslinked dense structure, and improving the anti-corrosion performance of the coating.

Description

Technical Field

[0001] The present invention belongs to the technical field of coatings, and particularly relates to a high weather-resistant coating and a color steel plate prepared therefrom. Background Art

[0002] In recent years, color steel plates have become increasingly popular in the construction industry, with continuous increase in production, and are widely used in building fields such as factory buildings, warehouses, movable houses, and renovation of old houses. However, due to the influence of sunlight exposure, rain, urban or industrial air pollutants, etc., after a period of time, problems such as loss of gloss, fading, chalking, and rusting will occur on the surface coating of the color steel plate for building structures. Therefore, the problem of the aging resistance of color steel plates is one of the most prominent problems. For example, in some projects, the color steel plates used show serious quality problems such as surface loss of gloss, fading, and rusting within 1 - 2 years after being put into use. Once the above situation occurs, it is necessary to promptly maintain or renovate the color steel plates to extend their service life, which provides a huge market for the finishing project of color steel plates. At the same time, it also poses higher requirements for the quality of coating products, and new challenges are put forward on how to provide high-performance, environmentally friendly, simple-to-construct, and energy-saving color steel plate finishing coatings.

[0003] As the finishing layer of color steel plates, coatings integrate multiple functions such as rust prevention, corrosion prevention, and decoration. Currently, most color steel plate coatings are solvent-based, and the commonly used resins are polyester resin, epoxy resin, polyurethane resin, etc. The biggest drawback of this type of coating is the use of a large amount of organic solvents, which not only wastes resources but also pollutes the environment. Therefore, replacing traditional solvent-based coatings with waterborne anticorrosive coatings for the finishing project of color steel plates is the development direction. The biggest feature of waterborne metal anticorrosive coatings is that water is used to replace organic solvents as the solvent or dispersion medium. It not only has a low price, rich resources, convenient access, is non-toxic, odorless, green and environmentally friendly, significantly reduces the use of organic materials, and reduces the pollution to the atmosphere caused by the volatilization of organic solvents in the coatings, but also uses water as the solvent, which has high safety during storage, construction, and transportation, without the danger of combustion, explosion, or poisoning, and fully meets the requirements of environmental protection.

[0004] Polyurethane is an organic compound obtained by the polymerization reaction of polyisocyanate monomers and polyol monomers. Among them, the polyol monomers constitute the soft segments in the main chain structure of the polyurethane molecule, and the polyisocyanate monomers and other small molecule monomers constitute the hard segments in the main chain structure of the polyurethane molecule. This unique molecular structure of hard and soft segments endows polyurethane with excellent properties, including good mechanical properties, wear resistance, flexibility and other material characteristics. At the same time, it has strong adhesion and good light retention, so it has been widely used in many fields such as the textile industry, synthetic leather processing, coatings, adhesives, inks and fibers. In order to meet the usage requirements of different fields, polyurethanes with different material characteristics can be obtained by designing the molecular structure, selecting different polyol monomers and polyisocyanate monomers for polymerization, adjusting the content ratio of hard and soft segments, or performing filler modification and other methods.

[0005] As an environmentally friendly material, waterborne polyurethane has received increasing attention from researchers. Waterborne polyurethane is a polyurethane dispersion system with water as the dispersion medium. Different from traditional solvent-based polyurethanes, there are no organic solvents in the waterborne polyurethane system, which is non-toxic and does not pollute the environment. Therefore, the emission of VOCs is effectively reduced during use, meeting the requirements of green environmental protection. At the same time, in addition to inheriting some excellent mechanical properties of solvent-based polyurethanes, waterborne polyurethane also has the advantages of low price, easy transportation and storage, good film-forming property at low temperature, relatively convenient use, good low-temperature resistance, wear resistance and adhesion. However, in the preparation process of waterborne polyurethane, in order to ensure its good dispersion in water, a large number of hydrophilic groups need to be introduced into the main chain structure of the waterborne polyurethane molecule, thereby increasing the hydrophilicity of the molecular chain, which will lead to a significant decrease in the water resistance and corrosion resistance of the waterborne polyurethane. In addition, waterborne polyurethane also has disadvantages such as poor thermal stability, poor solvent resistance, poor surface gloss and poor film feel, so its application and promotion are restricted to a certain extent. Therefore, in order to further improve the properties of waterborne polyurethane and expand its application range, it is necessary to modify waterborne polyurethane to meet the actual use requirements. Summary of the Invention

[0006] Based on this, the purpose of the present invention is to overcome the above-mentioned deficiencies of the prior art and provide a high-weather-resistant coating and the color steel plate prepared therefrom. The coating has high hardness and good salt spray resistance, and can effectively improve the stability of the color steel plate.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] A high-weather-resistant coating, comprising the following components in parts by weight:

[0009] 120 - 140 parts of aqueous polyurethane dispersion, 7 - 14 parts of graphene, 3 - 6 parts of amino-modified nano-silica, 0.2 - 3 parts of anti-settling agent, 0.2 - 3 parts of defoaming agent, 0.2 - 3 parts of wetting and dispersing agent, 60 - 100 parts of deionized water; the carbon-oxygen ratio of the graphene is (25 - 40):1.

[0010] Although aqueous polyurethane has received extensive attention in the research and application fields of coatings in recent years due to its advantages of being green, environmentally friendly, pollution-free, and having excellent mechanical properties, wear resistance, adhesion, and toughness. However, compared with solvent-based polyurethane, due to the presence of hydrophilic groups in the molecular chain structure of aqueous polyurethane, the aqueous polyurethane materials currently generally have disadvantages such as poor water resistance and poor chemical resistance, which greatly limit the further development of aqueous polyurethane coatings. Therefore, it is necessary to modify aqueous polyurethane to further improve its comprehensive performance, broaden the application scope, and extend the service life.

[0011] The present invention uses graphene and amino-modified nano-silica as blend fillers to modify waterborne polyurethane. The operation process of blend modification is simple and convenient, allowing for free selection and combination, with adjustable ratios and low economic costs. Compared with single waterborne polyurethane, the material properties such as water resistance and mechanical properties of the emulsion of the blend-modified product have been improved to a certain extent. Due to the good hydrophilicity of graphene oxide, the inventor used graphene oxide as a modified filler for waterborne polyurethane in previous work. However, graphene oxide has many defects and poor mechanical properties, requiring the simultaneous addition of a large amount of other inert fillers, resulting in high costs and limited improvement in the performance of polyurethane coatings. Graphene has unique geometric shapes and physical properties: ultra-high specific surface area, excellent mechanical properties, high aspect ratio, excellent barrier properties, and the advantages of easy availability of raw materials. Using graphene as a modified filler can greatly improve the salt spray resistance and hardness of the coating and enhance the stability of the coating. The present invention selects graphene with a carbon-oxygen ratio of (25 - 40):1, which not only imparts certain activity to the graphene surface but also takes into account the mechanical properties of graphene. When the carbon-oxygen ratio is too low, there are too many oxygen-containing functional groups on the graphene surface, increasing the defects and resulting in a decrease in the mechanical properties and barrier properties of graphene. When the carbon-oxygen ratio is too high, the number of oxygen-containing functional groups is too small, reducing the activity and resulting in poor dispersibility in waterborne polyurethane and poor binding performance with the matrix. The oxygen-containing functional groups on the graphene surface are prone to react with groups such as urethane, residual isocyanate, and hydroxyl in waterborne polyurethane or form hydrogen bonds, further improving the dispersibility of graphene in the coating. At the same time, to promote the dispersibility of graphene, a certain amount of amino-modified nano-silica is added in the present invention. The amino-modified nano-silica has good dispersibility in waterborne polyurethane, and the presence of active amino groups also easily reacts with the oxygen-containing functional groups on the graphene surface or the remaining active groups on the polyurethane and forms hydrogen bonds, improving the crosslinking ability of silica with graphene with a specific carbon-oxygen ratio and polyurethane, and further enhancing the denseness of the coating.

[0012] In addition, during the film-forming and curing process of the coating, due to the volatilization of the solvent, some micropores will inevitably be left in the film layer, and the existence of the micropores will affect the corrosion resistance of the film layer. Nano-silica can play a filling role to prevent the intrusion of corrosive substances. Further, in the coating, the amount of graphene is 9 - 12 parts and the amount of amino-modified nano-silica is 3.5 - 5.5 parts; by adjusting the dosage of the modifier, not only the dispersibility is improved, but also the formation of a crosslinked dense structure can be promoted, enhancing the anti-corrosion ability of the coating. When the amount of graphene is small, it is not easy to form a dense crosslinked network and a barrier structure cannot be formed; when the amount of graphene is too large, the problem of difficult dispersibility is faced.

[0013] Further, the solid content of the aqueous polyurethane dispersion is 50 - 70%. The type of aqueous polyurethane is not particularly limited, and it can be prepared by introducing hydrophilic components during the preparation of polyurethane. For example, after reacting polyether diol and diisocyanate for a certain period of time, a hydrophilic chain extender (such as dimethylolbutyric acid) and an amine compound are added and the reaction is continued to obtain a prepolymer, and then a small molecule diol is added for chain extension reaction to obtain the aqueous polyurethane dispersion.

[0014] Further, the lateral size of the graphene is 0.5 - 10 μm. More preferably, the lateral size of the graphene is 1 - 3 μm.

[0015] Further, the amino-modified nano-silica is nano-silica modified with an amino-silane coupling agent.

[0016] Further, the specific preparation process of the amino-modified nano-silica is as follows: The nano-silica is ultrasonically dispersed in a mixed solution of ethanol and water, then an amino-silane coupling agent is added, and the reaction is carried out by heating; after the reaction is completed, filtration, washing, and drying are carried out to obtain the amino-modified nano-silica.

[0017] Further, the volume average particle size (D50) of the nano-silica is 20 - 100 nm. Specifically, it can be 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, etc. Particularly, the volume average particle size of the nano-silica is 40 - 70 nm. By adjusting the particle size of the nano-silica, its reinforcement and dispersion properties can be balanced. If the particle size is too small, as the particle size of the nanoparticles decreases, the specific surface area of the nanoparticles increases, the number of surface atoms increases, and the number of surface coordination-unsaturated atoms also increases sharply, resulting in a relatively high surface energy of the nanoparticles. This high-energy state makes the nanoparticles very unstable and prone to agglomeration to reach a stable state, and the nano-effect of the nanoparticles cannot be fully exerted. If the particle size is too large, it cannot be combined and dispersed with graphene, and it cannot play the role of plugging micropores.

[0018] Further, the amino-silane coupling agent is one or more of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-β(aminoethyl)–γ-aminopropyltriethoxysilane.

[0019] Further, the temperature of the heating reaction is 50 - 60 °C, and the reaction time is 1 - 2 h. The mass ratio of the amino-silane coupling agent to the nano-silica is (0.3 - 0.6):1.

[0020] Furthermore, there is no particular limitation on the types of anti-settling agents, defoamers, and wetting dispersants, and common types in the art can be used. Specifically, the anti-settling agent is one or a mixture of more than one of BYK420, BYK425, and BYK430; the defoamer is a silicone defoamer or a mineral oil defoamer; the wetting dispersant is one or a mixture of more than one of sodium polyacrylate salts, ammonium polyacrylate salts, and polyphosphates.

[0021] Furthermore, the preparation method of the high weather-resistant coating includes the following steps:

[0022] S1. Weigh each component by weight parts;

[0023] S2. After uniformly mixing graphene, amino-modified nano-silica, and deionized water, add the aqueous polyurethane dispersion, stir and disperse, and then add the anti-settling agent, defoamer, and wetting dispersant, and mix evenly again to obtain a high weather-resistant coating.

[0024] On the other hand, the present invention provides a color steel plate, which is prepared by coating a high weather-resistant coating on the surface of a color steel plate that has been cleaned.

[0025] Beneficial effects: The present invention uses graphene and amino-modified nano-silica as co-blending fillers to modify aqueous polyurethane. By selecting graphene with a carbon-oxygen ratio of (25-40):1, it not only imparts a certain activity to the surface of graphene but also takes into account the mechanical properties of graphene, further improving the dispersion performance of graphene in the coating. The amino-modified nano-silica has good dispersion in aqueous polyurethane, and the presence of active amino groups also easily reacts with oxygen-containing functional groups on the surface of graphene or residual active groups on polyurethane and forms hydrogen bonds, improving its cross-linking ability with graphene and polyurethane with a specific carbon-oxygen ratio, further promoting the formation of a cross-linked dense structure, and improving the anti-corrosion performance of the coating. Specific embodiments

[0026] To better illustrate the purpose, technical solutions, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments. In the embodiments, the experimental methods used are all conventional methods unless otherwise specified, and the materials, reagents, etc. used can be obtained from commercial channels unless otherwise specified.

[0027] Example 1

[0028] A highly weather-resistant coating, comprising the following components in parts by weight: 120 parts of an aqueous polyurethane dispersion, 9 parts of graphene, 3 parts of amino-modified nano-silica, 1 part of an anti-settling agent, 2 parts of an anti-foaming agent, 0.5 part of a wetting and dispersing agent, and 60 parts of deionized water; the carbon-oxygen ratio of the graphene is 25:1; the solid content of the aqueous polyurethane dispersion is 60%; the average lateral size of the graphene is 2 μm; the specific preparation process of the amino-modified nano-silica is as follows: ultrasonically disperse the nano-silica in a mixed solution of ethanol and water, then add an amino-silane coupling agent, and heat for reaction; after the reaction is completed, filter, wash, and dry to obtain the amino-modified nano-silica; the volume-average particle size of the nano-silica is 40 nm; the amino-silane coupling agent is 3-aminopropyltriethoxysilane; the temperature of the heating reaction is 50 °C, and the reaction time is 2 h; the mass ratio of the amino-silane coupling agent to the nano-silica is 0.3:1; the anti-settling agent is BYK430; the anti-foaming agent is polydimethylsiloxane; the wetting and dispersing agent is ammonium polyacrylate salt.

[0029] Example 2

[0030] A highly weather-resistant coating, comprising the following components in parts by weight: 140 parts of an aqueous polyurethane dispersion, 12 parts of graphene, 6 parts of amino-modified nano-silica, 3 parts of an anti-settling agent, 3 parts of an anti-foaming agent, 3 parts of a wetting and dispersing agent, and 90 parts of deionized water; the carbon-oxygen ratio of the graphene is 40:1; the solid content of the aqueous polyurethane dispersion is 60%; the average lateral size of the graphene is 2 μm; the specific preparation process of the amino-modified nano-silica is as follows: ultrasonically disperse the nano-silica in a mixed solution of ethanol and water, then add an amino-silane coupling agent, and heat for reaction; after the reaction is completed, filter, wash, and dry to obtain the amino-modified nano-silica; the volume-average particle size of the nano-silica is 70 nm; the amino-silane coupling agent is 3-aminopropyltrimethoxysilane; the temperature of the heating reaction is 60 °C, and the reaction time is 1 h; the mass ratio of the amino-silane coupling agent to the nano-silica is 0.6:1; the anti-settling agent is BYK425; the anti-foaming agent is polydimethylsiloxane; the wetting and dispersing agent is sodium polyacrylate.

[0031] Example 3

[0032] A highly weather-resistant coating, comprising the following components in parts by weight: 120 parts of an aqueous polyurethane dispersion, 12 parts of graphene, 3 parts of amino-modified nano-silica, 3 parts of an anti-settling agent, 0.8 part of an anti-foaming agent, 2.6 parts of a wetting and dispersing agent, and 85 parts of deionized water; the carbon-oxygen ratio of the graphene is 25:1; the solid content of the aqueous polyurethane dispersion is 60%; the average lateral size of the graphene is 2 μm; the specific preparation process of the amino-modified nano-silica is as follows: ultrasonically disperse the nano-silica in a mixed solution of ethanol and water, then add an amino-silane coupling agent, and heat for reaction; after the reaction is completed, filter, wash, and dry to obtain the amino-modified nano-silica; the volume-average particle size of the nano-silica is 40 nm; the amino-silane coupling agent is 3-aminopropyltriethoxysilane; the temperature of the heating reaction is 55 °C, and the reaction time is 1.3 h; the mass ratio of the amino-silane coupling agent to the nano-silica is 0.3:1; the anti-settling agent is BYK420; the anti-foaming agent is polydimethylsiloxane; the wetting and dispersing agent is sodium polyacrylate salt.

[0033] Example 4

[0034] A highly weather-resistant coating, comprising the following components in parts by weight: 125 parts of an aqueous polyurethane dispersion, 10 parts of graphene, 3.5 parts of amino-modified nano-silica, 1.2 parts of an anti-settling agent, 1.1 parts of an anti-foaming agent, 1.4 parts of a wetting and dispersing agent, and 70 parts of deionized water; the carbon-oxygen ratio of the graphene is 30:1; the solid content of the aqueous polyurethane dispersion is 60%; the average lateral size of the graphene is 2 μm; the specific preparation process of the amino-modified nano-silica is as follows: ultrasonically disperse the nano-silica in a mixed solution of ethanol and water, then add an amino-silane coupling agent, and heat for reaction; after the reaction is completed, filter, wash, and dry to obtain the amino-modified nano-silica; the volume-average particle size of the nano-silica is 50 nm; the amino-silane coupling agent is 3-aminopropyltriethoxysilane; the temperature of the heating reaction is 52 °C, and the reaction time is 1.8 h; the mass ratio of the amino-silane coupling agent to the nano-silica is 0.4:1; the anti-settling agent is BYK430; the anti-foaming agent is polydimethylsiloxane; the wetting and dispersing agent is sodium polyacrylate salt.

[0035] Example 5

[0036] A highly weather-resistant coating, comprising the following components in parts by weight: 130 parts of an aqueous polyurethane dispersion, 11 parts of graphene, 5 parts of amino-modified nano-silica, 2.5 parts of an anti-settling agent, 2.1 parts of an anti-foaming agent, 2 parts of a wetting and dispersing agent, and 85 parts of deionized water; the carbon-oxygen ratio of the graphene is 35:1; the solid content of the aqueous polyurethane dispersion is 60%; the average lateral size of the graphene is 2 μm; the specific preparation process of the amino-modified nano-silica is as follows: ultrasonically disperse the nano-silica in a mixed solution of ethanol and water, then add an amino-silane coupling agent, and heat for reaction; after the reaction is completed, filter, wash, and dry to obtain the amino-modified nano-silica; the volume-average particle size of the nano-silica is 60 nm; the amino-silane coupling agent is 3-aminopropyltrimethoxysilane; the temperature of the heating reaction is 58 °C, and the reaction time is 1.3 h; the mass ratio of the amino-silane coupling agent to the nano-silica is 0.5:1; the anti-settling agent is BYK425; the anti-foaming agent is polydimethylsiloxane; the wetting and dispersing agent is ammonium polyacrylate salt.

[0037] Example 6

[0038] A highly weather-resistant coating, comprising the following components in parts by weight: 130 parts of an aqueous polyurethane dispersion, 7 parts of graphene, 4 parts of amino-modified nano-silica, 1 part of an anti-settling agent, 1.5 parts of an anti-foaming agent, 1.2 parts of a wetting and dispersing agent, and 80 parts of deionized water; the carbon-oxygen ratio of the graphene is 30:1; the solid content of the aqueous polyurethane dispersion is 60%; the average lateral size of the graphene is 2 μm; the specific preparation process of the amino-modified nano-silica is as follows: ultrasonically disperse the nano-silica in a mixed solution of ethanol and water, then add an amino-silane coupling agent, and heat for reaction; after the reaction is completed, filter, wash, and dry to obtain the amino-modified nano-silica; the volume-average particle size of the nano-silica is 50 nm; the amino-silane coupling agent is 3-aminopropyltriethoxysilane; the temperature of the heating reaction is 54 °C, and the reaction time is 1.5 h; the mass ratio of the amino-silane coupling agent to the nano-silica is 0.5:1; the anti-settling agent is BYK420; the anti-foaming agent is polydimethylsiloxane; the wetting and dispersing agent is sodium polyacrylate.

[0039] Example 7

[0040] A highly weather-resistant coating, comprising the following components in parts by weight: 130 parts of aqueous polyurethane dispersion, 14 parts of graphene, 4 parts of amino-modified nano-silica, 1 part of anti-settling agent, 1.5 parts of defoaming agent, 1.2 parts of wetting and dispersing agent, and 80 parts of deionized water; the carbon-oxygen ratio of the graphene is 30:1; the solid content of the aqueous polyurethane dispersion is 60%; the average lateral size of the graphene is 2 μm; the specific preparation process of the amino-modified nano-silica is as follows: ultrasonic-disperse the nano-silica in a mixed solution of ethanol and water, then add an amino-silane coupling agent, and heat for reaction; after the reaction is completed, filter, wash, and dry to obtain the amino-modified nano-silica; the volume-average particle size of the nano-silica is 50 nm; the amino-silane coupling agent is 3-aminopropyltriethoxysilane; the temperature of the heating reaction is 54 °C, and the reaction time is 1.5 h; the mass ratio of the amino-silane coupling agent to the nano-silica is 0.5:1; the anti-settling agent is BYK420; the defoaming agent is polydimethylsiloxane; the wetting and dispersing agent is sodium polyacrylate salt.

[0041] Example 8

[0042] A highly weather-resistant coating, comprising the following components in parts by weight: 130 parts of aqueous polyurethane dispersion, 10 parts of graphene, 4 parts of amino-modified nano-silica, 1 part of anti-settling agent, 1.5 parts of defoaming agent, 1.2 parts of wetting and dispersing agent, and 80 parts of deionized water; the carbon-oxygen ratio of the graphene is 30:1; the solid content of the aqueous polyurethane dispersion is 60%; the average lateral size of the graphene is 2 μm; the specific preparation process of the amino-modified nano-silica is as follows: ultrasonic-disperse the nano-silica in a mixed solution of ethanol and water, then add an amino-silane coupling agent, and heat for reaction; after the reaction is completed, filter, wash, and dry to obtain the amino-modified nano-silica; the volume-average particle size of the nano-silica is 20 nm; the amino-silane coupling agent is 3-aminopropyltriethoxysilane; the temperature of the heating reaction is 54 °C, and the reaction time is 1.5 h; the mass ratio of the amino-silane coupling agent to the nano-silica is 0.5:1; the anti-settling agent is BYK420; the defoaming agent is polydimethylsiloxane; the wetting and dispersing agent is sodium polyacrylate salt.

[0043] Example 9

[0044] A highly weather-resistant coating, comprising the following components in parts by weight: 130 parts of an aqueous polyurethane dispersion, 10 parts of graphene, 4 parts of amino-modified nano-silica, 1 part of an anti-settling agent, 1.5 parts of an anti-foaming agent, 1.2 parts of a wetting and dispersing agent, and 80 parts of deionized water; the carbon-oxygen ratio of the graphene is 30:1; the solid content of the aqueous polyurethane dispersion is 60%; the average lateral size of the graphene is 2 μm; the specific preparation process of the amino-modified nano-silica is as follows: ultrasonically disperse the nano-silica in a mixed solution of ethanol and water, then add an amino-silane coupling agent and heat for reaction; after the reaction is completed, filter, wash, and dry to obtain the amino-modified nano-silica; the volume average particle size of the nano-silica is 100 nm; the amino-silane coupling agent is 3-aminopropyltriethoxysilane; the temperature of the heating reaction is 54 °C, and the reaction time is 1.5 h; the mass ratio of the amino-silane coupling agent to the nano-silica is 0.5:1; the anti-settling agent is BYK420; the anti-foaming agent is polydimethylsiloxane; the wetting and dispersing agent is sodium polyacrylate salt.

[0045] Example 10

[0046] A highly weather-resistant coating, comprising the following components in parts by weight: 130 parts of an aqueous polyurethane dispersion, 10 parts of graphene, 4 parts of amino-modified nano-silica, 1 part of an anti-settling agent, 1.5 parts of an anti-foaming agent, 1.2 parts of a wetting and dispersing agent, and 80 parts of deionized water; the carbon-oxygen ratio of the graphene is 30:1; the solid content of the aqueous polyurethane dispersion is 60%; the average lateral size of the graphene is 2 μm; the specific preparation process of the amino-modified nano-silica is as follows: ultrasonically disperse the nano-silica in a mixed solution of ethanol and water, then add an amino-silane coupling agent and heat for reaction; after the reaction is completed, filter, wash, and dry to obtain the amino-modified nano-silica; the volume average particle size of the nano-silica is 50 nm; the amino-silane coupling agent is 3-aminopropyltriethoxysilane; the temperature of the heating reaction is 54 °C, and the reaction time is 1.5 h; the mass ratio of the amino-silane coupling agent to the nano-silica is 0.5:1; the anti-settling agent is BYK420; the anti-foaming agent is polydimethylsiloxane; the wetting and dispersing agent is sodium polyacrylate salt.

[0047] Comparative Example 1

[0048] A highly weather-resistant coating, comprising the following components in parts by weight: 130 parts of aqueous polyurethane dispersion, 0 part of graphene, 14 parts of amino-modified nano-silica, 1 part of anti-settling agent, 1.5 parts of defoaming agent, 1.2 parts of wetting and dispersing agent, and 80 parts of deionized water; the solid content of the aqueous polyurethane dispersion is 60%; the specific preparation process of the amino-modified nano-silica is as follows: ultrasonic disperse the nano-silica in a mixed solution of ethanol and water, then add an amino-silane coupling agent, and heat for reaction; after the reaction is completed, filter, wash, and dry to obtain the amino-modified nano-silica; the volume average particle size of the nano-silica is 50 nm; the amino-silane coupling agent is 3-aminopropyltriethoxysilane; the temperature of the heating reaction is 54 °C, and the reaction time is 1.5 h; the mass ratio of the amino-silane coupling agent to the nano-silica is 0.5:1; the anti-settling agent is BYK420; the defoaming agent is polydimethylsiloxane; the wetting and dispersing agent is sodium polyacrylate salt.

[0049] Comparative Example 2

[0050] A highly weather-resistant coating, comprising the following components in parts by weight: 130 parts of aqueous polyurethane dispersion, 14 parts of graphene, 0 part of amino-modified nano-silica, 1 part of anti-settling agent, 1.5 parts of defoaming agent, 1.2 parts of wetting and dispersing agent, and 80 parts of deionized water; the carbon-oxygen ratio of the graphene is 30:1; the solid content of the aqueous polyurethane dispersion is 60%; the lateral average size of the graphene is 2 μm; the anti-settling agent is BYK420; the defoaming agent is polydimethylsiloxane; the wetting and dispersing agent is sodium polyacrylate salt.

[0051] Comparative Example 3

[0052] A highly weather-resistant coating, comprising the following components in parts by weight: 130 parts of aqueous polyurethane dispersion, 10 parts of graphene, 4 parts of amino-modified nano-silica, 1 part of anti-settling agent, 1.5 parts of defoaming agent, 1.2 parts of wetting and dispersing agent, and 80 parts of deionized water; the carbon-oxygen ratio of the graphene is 15:1; the solid content of the aqueous polyurethane dispersion is 60%; the lateral average size of the graphene is 2 μm; the specific preparation process of the amino-modified nano-silica is as follows: ultrasonic disperse the nano-silica in a mixed solution of ethanol and water, then add an amino-silane coupling agent, and heat for reaction; after the reaction is completed, filter, wash, and dry to obtain the amino-modified nano-silica; the volume average particle size of the nano-silica is 50 nm; the amino-silane coupling agent is 3-aminopropyltriethoxysilane; the temperature of the heating reaction is 54 °C, and the reaction time is 1.5 h; the mass ratio of the amino-silane coupling agent to the nano-silica is 0.5:1; the anti-settling agent is BYK420; the defoaming agent is polydimethylsiloxane; the wetting and dispersing agent is sodium polyacrylate salt.

[0053] Comparative Example 4

[0054] A highly weather-resistant coating, comprising the following components in parts by weight: 130 parts of aqueous polyurethane dispersion, 10 parts of graphene, 4 parts of amino-modified nano-silica, 1 part of anti-settling agent, 1.5 parts of defoaming agent, 1.2 parts of wetting and dispersing agent, 80 parts of deionized water; the carbon-oxygen ratio of the graphene is 50:1; the solid content of the aqueous polyurethane dispersion is 60%; the average lateral size of the graphene is 2 μm; the specific preparation process of the amino-modified nano-silica is: ultrasonically disperse the nano-silica in a mixed solution of ethanol and water, then add an amino-silane coupling agent, and heat for reaction; after the reaction is completed, filter, wash, and dry to obtain the amino-modified nano-silica; the volume average particle size of the nano-silica is 50 nm; the amino-silane coupling agent is 3-aminopropyltriethoxysilane; the temperature of the heating reaction is 54 °C, and the reaction time is 1.5 h; the mass ratio of the amino-silane coupling agent to the nano-silica is 0.5:1; the anti-settling agent is BYK420; the defoaming agent is polydimethylsiloxane; the wetting and dispersing agent is sodium polyacrylate salt.

[0055] Comparative Example 5

[0056] A highly weather-resistant coating, comprising the following components in parts by weight: 130 parts of aqueous polyurethane dispersion, 10 parts of graphene, 9 parts of amino-modified nano-silica, 1 part of anti-settling agent, 1.5 parts of defoaming agent, 1.2 parts of wetting and dispersing agent, 80 parts of deionized water; the carbon-oxygen ratio of the graphene is 30:1; the solid content of the aqueous polyurethane dispersion is 60%; the average lateral size of the graphene is 2 μm; the specific preparation process of the amino-modified nano-silica is: ultrasonically disperse the nano-silica in a mixed solution of ethanol and water, then add an amino-silane coupling agent, and heat for reaction; after the reaction is completed, filter, wash, and dry to obtain the amino-modified nano-silica; the volume average particle size of the nano-silica is 50 nm; the amino-silane coupling agent is 3-aminopropyltriethoxysilane; the temperature of the heating reaction is 54 °C, and the reaction time is 1.5 h; the mass ratio of the amino-silane coupling agent to the nano-silica is 0.5:1; the anti-settling agent is BYK420; the defoaming agent is polydimethylsiloxane; the wetting and dispersing agent is sodium polyacrylate salt.

[0057] The specific preparation processes of the highly weather-resistant coatings in the above examples and comparative examples include the following steps:

[0058] S1. Weigh each component according to the parts by weight;

[0059] S2. After uniformly mixing graphene, amino-modified nano-silica, and deionized water, add an aqueous polyurethane dispersion, stir and disperse, then add an anti-settling agent, a defoaming agent, and a wetting and dispersing agent, and mix evenly again to obtain a highly weather-resistant coating.

[0060] Performance test: Perform hardness test (GB / T6739 - 2006), film adhesion test (GB / T 5210 - 2006), and salt spray resistance test (GB / T 1771 - 2007) on the highly weather-resistant coatings prepared in Examples 1 - 10 and Comparative Examples 1 - 5; the results are shown in Table 1.

[0061] Table 1 Properties of the highly weather-resistant coatings prepared in Examples 1 - 10 and Comparative Examples 1 - 5

[0062]

[0063] Continued Table 1

[0064]

[0065] As can be seen from Table 1, the present invention uses graphene and amino-modified nano-silica as blend fillers to modify aqueous polyurethane. Compared with single aqueous polyurethane, the material properties such as corrosion resistance and adhesion of the blend-modified product have been improved to a certain extent. From Examples 10 and Comparative Examples 1 - 2, it can be seen that the present invention selects graphene with a carbon-oxygen ratio of (25 - 40):1, which not only endows the surface of graphene with certain activity but also takes into account the mechanical properties of graphene. The amino-modified nano-silica has good dispersibility in aqueous polyurethane, and the presence of active amino groups also easily reacts with oxygen-containing functional groups on the surface of graphene or residual active groups on polyurethane and forms hydrogen bonds, improving its cross-linking ability with graphene and polyurethane with a specific carbon-oxygen ratio, further improving the compactness of the coating to improve its salt spray resistance. Among them, the lamellar graphene can form a connection structure with amino-modified nano-silica due to the presence of certain oxygen-containing active groups; during the blend stirring process, the lamellar graphene with a specific carbon-oxygen ratio and the granular nano-silica modified with amino groups assist each other to promote their dispersion; while simply adding graphene will cause the graphene to merge and stack in the solvent, unable to fully play its blocking role; pure silica is also prone to agglomeration due to the lack of the barrier of the lamellar structure. Comparative Examples 1 - 2 show that there are technical problems of uneven dispersion in single lamellar graphene or granular silica, resulting in a decline in coating performance.

[0066] Comparative Examples 3-4 show that when the carbon-oxygen ratio is too low, there are too many oxygen-containing functional groups on the surface of graphene, and the defects increase, resulting in a decrease in the mechanical properties and barrier properties of graphene. Moreover, it may undergo excessive crosslinking with polyurethane and amino-modified nano-silica, making it difficult to disperse evenly. When the carbon-oxygen ratio is too high, the number of oxygen-containing functional groups is too small, the activity decreases, and the dispersibility in waterborne polyurethane is poor, and it cannot form a crosslinked structure with amino-modified nano-silica. Comparative Example 5 shows that the amino-modified nano-silica has good dispersibility in waterborne polyurethane. Moreover, the presence of active amino groups also easily reacts with the oxygen-containing functional groups on the surface of graphene or the remaining active groups on polyurethane and forms hydrogen bonds, improving its crosslinking ability with graphene and polyurethane with a specific carbon-oxygen ratio, and further improving the denseness of the coating. However, when its dosage is too much, it not only cannot promote the dispersion of graphene, but also faces the problem of difficult dispersion itself.

[0067] Obviously, the above-mentioned embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limiting the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all implementation manners here. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A highly weather-resistant coating, characterized in that, It consists of the following components in parts by weight: 120 - 140 parts of aqueous polyurethane dispersion, 9 - 12 parts of graphene, 3.5 - 5.5 parts of amino-modified nano-silica, 0.2 - 3 parts of anti-settling agent, 0.2 - 3 parts of defoaming agent, 0.2 - 3 parts of wetting and dispersing agent, 60 - 100 parts of deionized water; the carbon-oxygen ratio of the graphene is (25 - 40):1; the solid content of the aqueous polyurethane dispersion is 50 - 70%; the amino-modified nano-silica is nano-silica modified with an amino-silane coupling agent; the volume average particle size of the nano-silica is 40 - 70 nm.

2. The high weather-resistant coating according to claim 1, wherein The lateral size of the graphene is 0.5 - 10 μm.

3. A highly weather-resistant coating according to claim 1, characterized in that, The specific preparation process of the amino-modified nano-silica is as follows: ultrasonically disperse the nano-silica in a mixed solution of ethanol and water, then add the amino-silane coupling agent, and heat for reaction; after the reaction is completed, filter, wash, and dry to obtain the amino-modified nano-silica.

4. The high weather-resistant coating according to claim 3, wherein The amino-silane coupling agent is one or more of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β(aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-β(aminoethyl)–γ-aminopropyltriethoxysilane.

5. The high weather-resistant coating according to claim 3, characterized in that, The temperature of the heating reaction is 50 - 60 °C, and the reaction time is 1 - 2 h; the mass ratio of the amino-silane coupling agent to the nano-silica is (0.3 - 0.6):

1.

6. The high weather-resistant coating according to claim 1, characterized in that, The preparation method of the high weather resistance coating includes the following steps: S1. Weigh each component according to the parts by weight. S2. After uniformly mixing graphene, amino-modified nano-silica, and deionized water, add the aqueous polyurethane dispersion, stir and disperse, then add the anti-settling agent, defoaming agent, and wetting and dispersing agent, and mix uniformly again to obtain a high weather resistance coating.

7. A color steel plate, characterized in that, It is obtained by coating the surface of a cleaned color steel plate with the high weather resistance coating according to any one of claims 1 - 6.

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