Wide-spectrum ultraviolet absorbent with sandwich structure as well as preparation method and application of wide-spectrum ultraviolet absorbent

Abstract

The invention belongs to the field of coatings, and discloses a broad-spectrum ultraviolet absorbent with a sandwich structure as well as a preparation method and application of the broad-spectrum ultraviolet absorbent. An ultraviolet absorbent is adsorbed on the upper surface and the lower surface of graphene oxide through the action of a hydrogen bond and a pi-pi bond to form a compact ultraviolet absorbent layer, then the surface of graphene oxide is chemically modified through a diamine compound, amino is grafted, and the wide-spectrum ultraviolet absorbent of a'discrete point / surface / discrete point 'sandwich structure is obtained. The ultraviolet absorbent filler, the cardanol-based reactive diluent and the epoxy resin are compounded, so that the ultraviolet aging resistance, the barrier corrosion resistance and the hydrophobicity of the prepared composite coating are synergistically enhanced and exceed those of an anti-ultraviolet epoxy coating material reported at present.

Description

Technical Field

[0001] This invention belongs to the field of coatings, specifically relating to a sandwich-structured broadband ultraviolet absorber, its preparation method, and its application. Background Technology

[0002] For a long time, corrosion of metallic materials has caused serious safety accidents and economic losses, and is considered a serious global problem. Therefore, research on metal corrosion prevention is urgently needed. Epoxy resin coatings are widely used due to their superior electrical insulation properties, chemical inertness, low cost, and strong adhesion. Although traditional petroleum-based epoxy resins have excellent anti-corrosion properties, their non-degradability and high carbon footprint are inconsistent with the current trend of green and sustainable development. Therefore, the gradual replacement of petroleum-based epoxy resins with bio-based epoxy resins has attracted much attention.

[0003] However, in practical applications, bio-based epoxy resins face significant challenges due to the frequent outdoor exposure of industrial and marine facilities. Bio-based epoxy resins (such as cashew phenol epoxy resin) contain numerous unsaturated bonds and highly reactive groups like hydroxyl groups in their molecular chains. Under ultraviolet (UV) irradiation, these chains are prone to breakage, forming free radicals, leading to yellowing, cracking, and chalking failure of the coating. Currently, a common UV-resistant strategy for polymer materials involves adding UV absorbers such as benzotriazole to the resin to improve the coating's resistance to UV radiation and extend its service life. The UV absorber molecules dispersed in the coating can be considered as multiple scattered points absorbing UV rays. Therefore, to efficiently capture and absorb UV rays and achieve strong UV resistance, a large amount of UV absorber is usually required. However, excessive UV absorber dispersion in the material can disrupt the integrity of the internal structure, thereby reducing the overall performance of the resin coating. In addition, UV absorber molecules are prone to migration and escape, and a single UV absorber can only absorb UV light within a specific wavelength range, failing to provide broad-spectrum UV absorption (broad-spectrum: UV absorbers can effectively absorb UVA wavelengths of 320nm-400nm and UVB wavelengths of 320nm-400nm simultaneously), thus having significant limitations in practical applications.

[0004] To address the above issues, previous studies have proposed three main strategies for the application of UV absorbers: (1) Chemical modification grafting. UV absorbers are grafted onto the molecular chains of polymers through chemical modification. For example, Xu et al. modified nanofiber membranes with 2-hydroxy-4-oxobenzophenone (UV531) to make the membranes exhibit UV resistance (J Colloid Interface Sci. 2017 Dec 15; 508: 508-516.); (2) Inorganic material loading. UV absorbers are loaded onto the surface of inorganic nanoparticles such as TiO2 and ZnO. For example, Guo et al. modified waterborne polyurethane coatings with boric acid / borax and UV absorbers (triazole UV1130, nano titanium dioxide and nano silica) to improve the weather resistance of the coating (doi.org / 10.3390 / coatings13040687); (3) Intercalated hydroxides. UV absorber molecules are loaded into the interlayer space of layered double hydroxides (LDHs). For example, Wang et al. synthesized 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid (UV absorber, BP) layered double hydroxides (LDHs) to enhance the anti-aging properties of styrene-butadiene-styrene block copolymer modified asphalt (doi.org / 10.1016 / j.molliq.2024.125634). However, chemical modification reduces the conformational freedom of UV absorber molecules due to covalent bonding, thus decreasing the UV absorption efficiency. Furthermore, loading UV absorbers onto inorganic nanomaterials faces inherent challenges related to inorganic-organic interface bonding and compatibility. Therefore, designing UV absorbers that simultaneously possess wide-range, high-efficiency UV absorption, high stability, and strong interfacial bonding remains a technical challenge, given the complex application environments and requirements of bio-based epoxy composite coatings. Summary of the Invention

[0005] The first technical problem to be solved by the present invention is to provide a sandwich-structured broadband ultraviolet absorber to overcome the problems of low ultraviolet absorption efficiency and single absorption wavelength range of existing ultraviolet absorbers.

[0006] The second technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned sandwich-structured broadband ultraviolet absorber.

[0007] The third technical problem to be solved by the present invention is to provide the application of the above-mentioned sandwich structure of a broadband ultraviolet absorber.

[0008] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0009] A sandwich-structured broadband ultraviolet absorber (BZT@N-GO) uses aminated graphene oxide as the face and the ultraviolet absorber as the discrete points. The aminated graphene oxide self-assembles with the ultraviolet absorber through hydrogen bonding and π-π bonding to form a sandwich structure of discrete points / faces / discrete points.

[0010] The ultraviolet absorber includes any one or more of benzotriazole compounds, benzothiazole compounds, and benzophenone compounds; preferably, the benzotriazole compound is 2-(2H-benzotriazole-2-yl)-4,6-di-tert-pentylphenol (BZT).

[0011] The preparation method of the sandwich-structured broadband ultraviolet absorber includes the following steps:

[0012] (1) Graphene oxide (GO) aqueous solution was prepared by Hummer's method. After washing with ethanol by centrifugation, the GO was uniformly dispersed in ethanol to obtain graphene oxide ethanol solution.

[0013] (2) The ultraviolet absorber was added to the graphene oxide ethanol solution, and the mixture was ultrasonicated and stirred to obtain mixture A;

[0014] (3) Mixture A is washed by centrifugation with ethanol and then by centrifugation with water to obtain mixture B;

[0015] (4) Add the aqueous solution of the amine compound to the mixture B and mix well to obtain mixture C;

[0016] (5) The mixture C is heated to react and obtain mixture D;

[0017] (6) The mixture D is centrifuged, washed with water and vacuum dried to obtain the final product.

[0018] In step (1), the Hummer's method for preparing the graphene oxide aqueous solution is described in accordance with the preparation method of "Preparation of fully exfoliated graphite oxide nanoplatelets in organic solvents"; the centrifugation washing is performed at a centrifugation rate of 2000-10000 rpm for 5-20 min, and 1-6 times; and / or, the graphene oxide ethanol solution has a graphene oxide concentration of 1-10 g / L.

[0019] In step (2), the ultraviolet absorber includes any one or more of benzotriazole compounds, benzothiazole compounds, and benzophenone compounds; preferably, the benzotriazole compound is 2-(2H-benzotriazole-2-yl)-4,6-di-tert-pentylphenol (BZT); and / or, the mass ratio of the ultraviolet absorber to the graphene oxide is 0.1:1 to 10:1; and / or, the ultrasonication time is 10 to 60 min; and / or, the stirring time is 30 to 60 min.

[0020] In step (3), the centrifugal washing is performed at a speed of 2000-10000 rpm for 5-20 min; and / or the ethanol centrifugal washing is performed 1-3 times; and / or the water centrifugal washing is performed 1-5 times.

[0021] In step (4), the amine compound includes any one or more of maleic diamine, p-phenylenediamine and trimethylamine; and / or, the mass ratio of the amine compound to the graphene oxide is 1:1 to 10:1; the mixing is performed by ultrasonication for 5 to 60 minutes and magnetic stirring for 10 to 60 minutes.

[0022] In step (5), the heating reaction is carried out at a temperature of 50 to 100°C for 8 to 12 hours.

[0023] In step (6), the centrifugation rate is 2000-10000 rpm and the time is 5-20 min; and / or, the water washing is centrifugal washing, the centrifugation speed is 2000-10000 rpm and the time is 5-20 min, and the number of washing times is 1-5; and / or, the vacuum drying is carried out at a temperature of 40-100℃ for 6-24 h and a pressure of 10 Pa-1000 Pa.

[0024] The sandwich-structured broadband ultraviolet absorber can effectively absorb ultraviolet rays in the UVA and UVB bands.

[0025] The application of the sandwich-structured broadband ultraviolet absorber in the preparation of bio-based epoxy anti-corrosion coatings is also within the scope of protection of this invention.

[0026] The sandwich-structured broad-spectrum ultraviolet absorber is dispersed in anhydrous ethanol, and then cashew phenol-based reactive diluent is added and mixed evenly. After evaporating to remove the anhydrous ethanol, it is mixed with petroleum-based epoxy resin. Finally, cashew phenol-based curing agent, defoamer, leveling agent and anti-settling agent are added and mixed evenly to obtain a bio-based epoxy anti-corrosion coating.

[0027] The cashew nut phenol-based reactive diluent is cashew nut phenol-based difunctional glycidyl ether; and / or, the petroleum-based epoxy resin is any one of bisphenol A epoxy resins E-44, E-51, E-54, or E-55 (preferably E-51); and / or, the cashew nut phenol-based curing agent is cashew nut phenolic amine epoxy curing agent; and / or, the defoamer is an organosilicon defoamer (preferably BYK1610); and / or, the leveling agent is BYK333; and / or, the anti-settling agent is fumed silica; and / or, the raw materials are added in the following proportions by weight:

[0028]

[0029] Beneficial effects:

[0030] (1) This invention adsorbs ultraviolet absorbers onto the upper and lower surfaces of graphene oxide (GO) through hydrogen bonding and π-π bonding, constructing a "discrete point / surface / discrete point" sandwich structure. On the one hand, the hydrogen bonds between GO and the ultraviolet absorber significantly enhance its ultraviolet absorption capacity and broaden the absorption wavelength range, achieving broadband ultraviolet absorption. On the other hand, GO can enrich ultraviolet absorber molecules, forming a dense two-dimensional anti-ultraviolet barrier, while effectively blocking oxygen and inhibiting free radical chain reactions initiated by ultraviolet radiation, thereby greatly improving the anti-ultraviolet efficiency. This invention realizes the transformation of the anti-ultraviolet mechanism from "discrete point" to "two-dimensional surface," which has important guiding significance for the application strategy of ultraviolet absorbers in polymer materials.

[0031] (2) The physical adsorption of ultraviolet absorber molecules and modification with diamine compounds proposed in this invention reduce the van der Waals forces between graphene oxide sheets, improve the aggregation of graphene oxide in the matrix, enhance its dispersion stability, and improve the hydrophobic properties of the GO surface. On the other hand, the amino modification of the graphene oxide surface allows the amino groups on the surface to participate in the crosslinking reaction of the epoxy coating, thereby effectively improving the compatibility of graphene oxide in epoxy resin, enhancing the interfacial bonding between graphene oxide and epoxy resin, and further improving the anti-corrosion performance of the composite coating.

[0032] (3) The sandwich-structured UV absorber designed in this invention, as a filler, can achieve synergistic reinforcement of high weather resistance, high barrier properties, and high corrosion resistance in bio-based epoxy coatings. This greatly promotes the application of bio-based epoxy coatings in complex industrial environments and under high demands, and provides an effective strategy for the synergistic reinforcement and multifunctionalization of other organic polymer materials. Attached Figure Description

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0034] Figure 1 A schematic diagram of a broadband ultraviolet absorber with a discrete point / surface / discrete point sandwich structure;

[0035] Figure 2 The infrared spectra of the broadband ultraviolet absorbers BZT@N-GO, GO, and BZT with discrete point / surface / discrete point sandwich structure in Example 1 are shown.

[0036] Figure 3 The EDS elemental energy spectrum of the broadband ultraviolet absorber BZT@N-GO with discrete point / surface / discrete point sandwich structure in Example 1;

[0037] Figure 4 The UV absorption spectra of the broadband UV absorbers BZT@N-GO, GO, and BZT with discrete point / surface / discrete point sandwich structure in Example 1 are shown.

[0038] Figure 5 The water contact angle diagrams for the broadband UV absorbers BZT@N-GO, GO, and BZT in the discrete point / surface / discrete point sandwich structure of Example 1 are shown.

[0039] Figure 6 Optical photographs taken on day 1 of the stability test of BZT@N-GO and GO aqueous solutions in Example 1;

[0040] Figure 7 This is an optical photograph taken on day 30 of the stability test of BZT@N-GO and GO aqueous solutions in Example 1.

[0041] Figure 8 The UV absorption spectra of the broadband UV absorbers BZT@N-GO, GO, and BZT with discrete point / surface / discrete point sandwich structure in Example 3 are shown.

[0042] Figure 9 Electrochemical impedance Bode plots of the composite coatings in Example 1 and Comparative Examples 1, 2, and 4 after immersion in salt water without ultraviolet radiation for 280 days;

[0043] Figure 10 The electrochemical impedance spectroscopy (EIS) Bode plots of the composite coatings in Example 1 and Comparative Examples 1, 2, and 4 after irradiation with ultraviolet light for 200 hours and immersion in salt water for 120 days are shown. Detailed Implementation

[0044] In the embodiments of the present invention, the Hummer's method is used to prepare an aqueous solution of graphene oxide, referring to the prior art: D.Cai, MJJoMCSong, Preparation of fully exfoliated graphite oxide nanoplatelets in organic solvents, 17(2007)3678-3680.

[0045] Example 1

[0046] (1) Graphene oxide (GO) aqueous solution was obtained by high-power continuous ultrasonic exfoliation of graphene oxide using Hummer's method. Then, the graphene oxide was washed 6 times by centrifugation with ethanol at a speed of 8000 rpm for 20 min. The obtained graphene oxide was dispersed in ethanol to finally obtain graphene oxide ethanol solution (concentration of 1 g / L).

[0047] (2) The ultraviolet absorber 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (BZT) was added to the graphene oxide ethanol solution at a mass ratio (BZT:GO=10:1), and the mixture was sonicated for 10 min and magnetically stirred for 30 min to obtain mixture A.

[0048] (3) Wash mixture A twice with ethanol by centrifugation at 8000 rpm for 20 min. Then wash it five times with deionized water by centrifugation at 8000 rpm for 20 min to obtain mixture B;

[0049] (4) Slowly add 40 mL of maleic diamine aqueous solution (concentration of 2.5 g / L) to 200 mL of mixture B aqueous solution (0.1 g / L), sonicate for 10 min, and magnetically stir for 10 min to obtain mixture C;

[0050] (5) Place mixture C in a three-necked flask and reflux at 80°C for 8 hours to obtain mixture D.

[0051] (6) Centrifuge mixture D at 6000 rpm for 10 min. Wash with deionized water 5 times by centrifugation at 6000 rpm for 10 min. Dry under vacuum at 40℃ for 12 h (pressure 1000 Pa) to obtain the broadband ultraviolet absorber (BZT@N-GO) with a discrete point / surface / discrete point sandwich structure.

[0052] (7) Add 0.3 parts of the broadband ultraviolet absorber filler (BZT@N-GO) with discrete point / surface / discrete point sandwich structure to anhydrous ethanol, and sonicate and mechanically stir at 600 r / min for 30 min to obtain mixture E;

[0053] (8) Add 40 parts of cashew phenol-based active diluent (PLR602A) to mixture E, sonicate and mechanically stir at 800 r / min for 30 min, and then remove anhydrous ethanol by rotary evaporation to obtain mixture F;

[0054] (9) Add 60 parts of petroleum-based epoxy resin (E-51) to mixture F and mechanically stir at 800 r / min for 30 min to obtain mixture G;

[0055] (10) Add 42 parts of cashew phenol-based curing agent (cashew phenol-based phenolic amine epoxy curing agent), 0.03 parts of defoamer (BYK1610), 0.05 parts of leveling agent (BYK333), and 0.05 parts of anti-settling agent (fumed silica) to mixture G. After mechanically stirring at 800 r / min for 20 min, an epoxy composite coating with a discrete point / surface / discrete point sandwich structure as a broad-spectrum ultraviolet absorber as a filler (BZT@N-GO / cashew phenol-based reactive diluent / epoxy resin composite coating) is obtained.

[0056] Figure 1 This is a schematic diagram of a broad-spectrum UV absorber with a discrete point / surface / discrete point sandwich structure. The UV absorber is adsorbed onto the upper and lower surfaces of graphene oxide through hydrogen bonds and π-π bonds, forming a "discrete point / surface / discrete point" sandwich structure. Furthermore, maleic acid diamine modification grafts amino groups onto the graphene oxide surface. This two-dimensional UV absorption shielding structure not only broadens the UV absorption wavelength range of the UV absorber and enhances its UV absorption capacity through hydrogen bonds formed between the UV absorber and graphene oxide, but also improves the dispersibility and compatibility of graphene oxide in epoxy resin, resolving the interface problem between graphene oxide and epoxy resin, thereby comprehensively improving the UV resistance and corrosion resistance of the epoxy composite coating.

[0057] Figure 2 The images show the infrared spectra of the broadband UV absorbers BZT@N-GO, GO, and BZT with the discrete point / surface / discrete point sandwich structure from Example 1. As can be seen from the images, the -OH group shifts significantly to lower frequencies due to the influence of hydrogen bonding, confirming the formation of hydrogen bonds. The characteristic peak of the benzene ring decreases from 881 cm⁻¹. -1 The shift to lower frequencies demonstrates the π-π bond interaction of the benzene ring, further supporting the realization of the structure.

[0058] Figure 3 This is the EDS elemental spectrum of the broadband UV absorber BZT@N-GO with the discrete point / surface / discrete point sandwich structure in Example 1. As can be seen from the figure, due to the adsorption of BZT and surface amination modification, nitrogen is distributed on the surface of graphene oxide, which further proves the realization of the structure.

[0059] Figure 4 This is the UV absorption spectrum of the broadband UV absorbers BZT@N-GO, GO, and BZT with the discrete point / surface / discrete point sandwich structure in Example 1. As can be seen from the figure, BZT@N-GO exhibits an absorption rate of approximately 99% in the UV wavelength range of 200 nm to 400 nm, achieving ultra-high UV absorption over a wide wavelength range.

[0060] Figure 5 This is a water contact angle diagram of the broadband UV absorber BZT@N-GO, GO, and BZT in Example 1, which features a discrete point / surface / discrete point sandwich structure. The diagram shows that the water contact angle of graphene oxide is 78°. The UV absorber BZT adsorbs onto the graphene oxide surface, increasing the water contact angle to 119°. This demonstrates that the UV absorber with the discrete point / surface / discrete point sandwich structure proposed in this invention can enhance the hydrophobicity of the GO surface.

[0061] Figure 6 This is an optical photograph taken on day 1 of the stability test of BZT@N-GO and GO aqueous solution in Example 1. GO (left) and BZT@N-GO (right) were dispersed in aqueous solution, mixed evenly, and allowed to stand to test the stability of the material dispersion in water.

[0062] Figure 7 These are optical photographs taken on day 30 of the stability test of BZT@N-GO and GO aqueous solutions in Example 1. It can be seen that after 30 days of standing, the GO aqueous solution on the left shows obvious precipitation and stratification, while the BZT@N-GO aqueous solution on the right does not show obvious stratification. This indicates that the adsorption and amination modification of BZT greatly improves the dispersibility and stability of BZT@N-GO.

[0063] Example 2

[0064] (1) Graphene oxide (GO) aqueous solution was obtained by high-power continuous ultrasonic exfoliation of graphene oxide using Hummer's method. Then, the graphene oxide was washed 6 times by centrifugation with ethanol at a speed of 8000 rpm for 20 min. The obtained graphene oxide was dispersed in ethanol to finally obtain graphene oxide ethanol solution (concentration of 1 g / L).

[0065] (2) The ultraviolet absorber 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (BZT) was added to the graphene oxide ethanol solution at a mass ratio (BZT:GO=10:1), and the mixture was sonicated for 10 min and magnetically stirred for 30 min to obtain mixture A.

[0066] (3) Wash mixture A twice with ethanol by centrifugation at 8000 rpm for 20 min. Then wash it five times with deionized water by centrifugation at 8000 rpm for 20 min to obtain mixture B;

[0067] (4) Slowly add 40 mL of maleic diamine aqueous solution (concentration of 2.5 g / L) to 200 mL of mixture B aqueous solution (0.1 g / L), sonicate for 10 min, and magnetically stir for 10 min to obtain mixture C;

[0068] (5) Place mixture C in a three-necked flask and reflux at 80°C for 8 hours to obtain mixture D.

[0069] (6) Centrifuge mixture D at 6000 rpm for 10 min. Wash with deionized water 5 times by centrifugation at 6000 rpm for 10 min. Vacuum dry at 40℃ for 12 h (pressure 1000 Pa) to obtain the broadband ultraviolet absorber filler (BZT@N-GO) with discrete point / surface / discrete point sandwich structure.

[0070] (7) Add 0.4 parts of the broadband ultraviolet absorber filler (BZT@N-GO) with discrete point / surface / discrete point sandwich structure to anhydrous ethanol and sonicate, and then mechanically stir at 600 r / min for 30 min to obtain mixture E;

[0071] (8) Add 40 parts of cashew phenolic active diluent (PLR602A) to mixture E and sonicate, and then combine with mechanical stirring at 800 r / min for 30 min and rotary evaporate to remove anhydrous ethanol to obtain mixture F;

[0072] (9) Add 60 parts of petroleum-based epoxy resin (E-51) to mixture F and mechanically stir at 800 r / min for 30 min to obtain mixture G;

[0073] (10) Add 42 parts of cashew phenol-based curing agent (cashew phenol-based phenolic amine epoxy curing agent), 0.03 parts of defoamer (BYK1610), 0.05 parts of leveling agent (BYK333), and 0.05 parts of anti-settling agent (fumed silica) to mixture G. After mechanical stirring at 800 r / min for 20 min, an epoxy composite coating with a discrete point / surface / discrete point sandwich structure as a filler (BZT@N-GO / cashew phenol-based reactive diluent / epoxy resin composite coating) is obtained.

[0074] Example 3

[0075] (1) Graphene oxide (GO) aqueous solution was obtained by high-power continuous ultrasonic exfoliation of graphene oxide using Hummer's method. Then, the graphene oxide was washed 6 times by centrifugation with ethanol at a speed of 8000 rpm for 20 min. The obtained graphene oxide was dispersed in ethanol to finally obtain graphene oxide ethanol solution (concentration of 1 g / L).

[0076] (2) The ultraviolet absorber 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (BZT) was added to the graphene oxide ethanol solution at a mass ratio (BZT:GO=0.1:1), and the mixture was sonicated for 10 min and magnetically stirred for 30 min to obtain mixture A;

[0077] (3) Wash mixture A twice with ethanol by centrifugation at 8000 rpm for 20 min. Then wash it five times with deionized water by centrifugation at 8000 rpm for 20 min to obtain mixture B;

[0078] (4) Slowly add 40 mL of p-phenylenediamine aqueous solution (concentration of 2.5 g / L) to 200 mL of mixture B aqueous solution (0.1 g / L), sonicate for 10 min, and magnetically stir for 10 min to obtain mixture C;

[0079] (5) Place mixture C in a three-necked flask and reflux at 80°C for 8 hours to obtain mixture D.

[0080] (6) Centrifuge mixture D at 6000 rpm for 10 min. Wash with deionized water 5 times by centrifugation at 6000 rpm for 10 min. Vacuum dry at 40℃ for 12 h (pressure 1000 Pa) to obtain the broadband ultraviolet absorber filler (BZT@N-GO) with discrete point / surface / discrete point sandwich structure.

[0081] (7) Add 0.3 parts of the broadband ultraviolet absorber filler (BZT@N-GO) with discrete point / surface / discrete point sandwich structure to anhydrous ethanol and sonicate, and then mechanically stir at 600 r / min for 30 min to obtain mixture E;

[0082] (8) Add 40 parts of cashew phenolic active diluent (PLR602A) to mixture E and sonicate, and then combine with mechanical stirring at 800 r / min for 30 min and rotary evaporate to remove anhydrous ethanol to obtain mixture F;

[0083] (9) Add 60 parts of petroleum-based epoxy resin (E-51) to mixture F and mechanically stir at 800 r / min for 30 min to obtain mixture G;

[0084] (10) Add 42 parts of cashew phenol-based curing agent (cashew phenol-based phenolic amine epoxy curing agent), 0.03 parts of defoamer (BYK1610), 0.05 parts of leveling agent (BYK333), and 0.05 parts of anti-settling agent (fumed silica) to mixture G. After mechanical stirring at 800 r / min for 20 min, an epoxy composite coating with a discrete point / surface / discrete point sandwich structure as a filler (BZT@N-GO / cashew phenol-based reactive diluent / epoxy resin composite coating) is obtained.

[0085] Figure 8 This is the UV absorption spectrum of the broadband UV absorbers BZT@N-GO, GO, and BZT with discrete point / surface / discrete point sandwich structure in Example 3. As can be seen from the figure, the novel UV absorber BZT@N-GO proposed in this invention, compared to UV absorber BZT, increases the UV absorbance from 5.5% to 35%, achieving an improvement of nearly 536%, significantly enhancing the UV absorption capacity of the UV absorber.

[0086] Comparative Example 1

[0087] (1) Add 60 parts of petroleum-based epoxy resin (E-51) to 40 parts of cashew phenolic reactive diluent (PLR602A) and mechanically stir at 800 r / min for 30 min to obtain mixture A;

[0088] (2) Add 42 parts of cashew nut phenol-based curing agent (cashew nut phenolic amine epoxy curing agent), 0.03 parts of defoamer (BYK1610), 0.05 parts of leveling agent (BYK333), and 0.05 parts of anti-settling agent (fumed silica) to mixture A, and mechanically stir at 800 r / min for 20 min to obtain epoxy resin composite coating (cashew nut phenol-based reactive diluent / epoxy resin composite coating).

[0089] Comparative Example 2

[0090] (1) Graphene oxide aqueous solution was obtained by high-power continuous ultrasonic exfoliation of graphene oxide using Hummer's method.

[0091] (2) Slowly add 40 ml of maleic diamine aqueous solution (concentration of 2.5 g / L) to 200 mL of graphene oxide aqueous solution (0.1 g / L), sonicate for 10 min, and magnetically stir for 10 min to obtain mixture A;

[0092] (3) Place mixture A in a three-necked flask and reflux at 80°C for 8 hours to obtain mixture B.

[0093] (4) Centrifuge mixture B at 6000 rpm for 10 min. Wash it five times with deionized water at 6000 rpm for 10 min. Dry it under vacuum at 40℃ for 12 h (pressure 1000 Pa) to obtain chemically modified graphene oxide filler (N-GO).

[0094] (5) Add 0.3 parts of chemically modified graphene oxide filler (N-GO) filler to anhydrous ethanol, sonicate and mechanically stir at 600 r / min for 30 min to obtain mixture E;

[0095] (6) Add 40 parts of cashew phenolic active diluent (PLR602A) to mixture E, sonicate and mechanically stir at 800 r / min for 30 min, and then remove anhydrous ethanol by rotary evaporation to obtain mixture F;

[0096] (7) Add 60 parts of petroleum-based epoxy resin (E-51) to mixture F and mechanically stir at 800 r / min for 30 min to obtain mixture G;

[0097] (8) Add 42 parts of cashew phenol-based curing agent (cashew phenol-based phenolic amine epoxy curing agent), 0.03 parts of defoamer (BYK1610), 0.05 parts of leveling agent (BYK333), and 0.05 parts of anti-settling agent (fumed silica) to mixture G and mechanically stir at 800 r / min for 20 min to obtain a chemically modified graphene oxide epoxy composite coating (N-GO / cashew phenol-based reactive diluent / epoxy resin composite coating).

[0098] Comparative Example 3

[0099] (1) Graphene oxide aqueous solution was obtained by high-power continuous ultrasonic exfoliation of graphene oxide using Hummer's method.

[0100] (2) Slowly add 40 ml of maleic diamine aqueous solution (concentration of 2.5 g / L) to 200 mL of graphene oxide aqueous solution (0.1 g / L), sonicate for 10 min, and magnetically stir for 10 min to obtain mixture A;

[0101] (3) Place mixture A in a three-necked flask and reflux at 80°C for 8 hours to obtain mixture B.

[0102] (4) Centrifuge mixture B at 6000 rpm for 10 min. Wash it five times with deionized water at 6000 rpm for 10 min. Dry it under vacuum at 40℃ for 12 h (pressure 1000 Pa) to obtain chemically modified graphene oxide filler (N-GO).

[0103] (5) Add 0.4 parts of chemically modified graphene oxide filler (N-GO) filler to anhydrous ethanol, sonicate and combine with mechanical stirring at 600 r / min for 30 min to obtain mixture E;

[0104] (6) Add 40 parts of cashew phenolic active diluent (PLR602A) to mixture E, sonicate and mechanically stir at 800 r / min for 30 min, and then remove anhydrous ethanol by rotary evaporation to obtain mixture F;

[0105] (7) Add 60 parts of petroleum-based epoxy resin (E-51) to mixture F and mechanically stir at 800 r / min for 30 min to obtain mixture G;

[0106] (8) Add 42 parts of cashew phenol-based curing agent (cashew phenol-based phenolic amine epoxy curing agent), 0.03 parts of defoamer (BYK1610), 0.05 parts of leveling agent (BYK333), and 0.05 parts of anti-settling agent (fumed silica) to mixture G and mechanically stir at 800 r / min for 20 min to obtain a chemically modified graphene oxide epoxy composite coating (N-GO / cashew phenol-based reactive diluent / epoxy resin composite coating).

[0107] Comparative Example 4

[0108] (1) Add 3 parts of the ultraviolet absorber 2-(2H-benzotriazol-2-yl)-4,6-ditert-pentylphenol (BZT) to anhydrous ethanol, sonicate and combine with mechanical stirring at 600 r / min for 30 min to obtain mixture A;

[0109] (2) Add 40 parts of cashew phenolic active diluent (PLR602A) to mixture A, sonicate and mechanically stir at 800 r / min for 30 min, and then remove anhydrous ethanol by rotary evaporation to obtain mixture B;

[0110] (3) Add 60 parts of petroleum-based epoxy resin (E-51) to mixture B and mechanically stir at 800 r / min for 30 min to obtain mixture C;

[0111] (4) Add 42 parts of cashew phenol-based curing agent (cashew phenol-based phenolic amine epoxy curing agent), 0.03 parts of defoamer (BYK1610), 0.05 parts of leveling agent (BYK333), and 0.05 parts of anti-settling agent (fumed silica) to mixture C. After mechanically stirring at 800 r / min for 20 min, a UV absorber BZT epoxy composite coating (BZT / cashew phenol-based reactive diluent / epoxy resin composite coating) is obtained.

[0112] Example 4: Determination of the Corrosion Resistance of Composite Coatings

[0113] The different composite coating samples prepared in Example 1 and Comparative Examples 1, 2 and 4 were uniformly coated on the surface of Q235 carbon steel. After curing at room temperature for 12 hours, they were cured in an oven at 60°C for 12 hours to obtain the composite coating sample to be tested. The sample thickness was 100±5μm.

[0114] The corrosion resistance of the composite coating was tested using electrochemical impedance spectroscopy. A traditional three-electrode system was used, with a silver / silver chloride electrode as the reference electrode, a platinum sheet electrode as the counter electrode, and the composite coating sample as the working electrode. The electrolyte was a 3.5 wt% NaCl aqueous solution. After the open-circuit potential of the coating stabilized, the test frequency range was set to 10 Hz. -2 ~10 5 Hz, AC voltage amplitude is 20mV, experimental results are as follows Figures 9-10 As shown.

[0115] Figure 9 These are the electrochemical impedance Bode plots of the composite coatings from Examples 1 and Comparative Examples 1, 2, and 4 after 280 days of immersion in salt water without UV irradiation. The impedances of the BZT composite coating and the pure epoxy coating have significantly decreased, to 10⁻⁶ respectively. 6.8 and 10 5.5 The phase angle diagram indicates that the salt water has penetrated the coating, causing it to be broken through by the corrosive medium and lose its protective ability. In contrast, the BZT@N-GO composite coating maintained a stable resistivity of 10 ohms after immersion in 3.5 wt% salt water for 280 days. 10 The resistance values ​​are around 10, indicating that the BZT@N-GO coating still exhibit excellent corrosion resistance. After immersion in 3.5 wt% salt water for 280 days, the N-GO composite coating's resistance remained stable at 10. 9.8 The corrosion resistance is around 100%, slightly lower than that of BZT@N-GO coatings, but it still provides good corrosion protection. This is due to the self-barrier effect of graphene oxide and the interfacial reinforcement effect of amino groups participating in cross-linking.

[0116] Figure 10 The images show the Bode plots of the electrochemical impedance spectroscopy (EIS) of the composite coatings in Example 1 and Comparative Examples 1, 2, and 4 after 200 hours of UV irradiation and 120 days of brine immersion. It can be observed that after UV irradiation, the EIS of the pure epoxy coating and the N-GO / BZT composite coating decreased significantly after 120 days of brine immersion, while the resistance of the BZT@N-GO composite coating remained stable at 10 Ω·cm. 10.2The presence of a sandwich-structured UV absorber with excellent corrosion resistance indicates that the epoxy coating exhibits very strong UV resistance, even surpassing the UV resistance of epoxy composite coatings with the same mass fraction of BZT as the UV absorber itself. This demonstrates the significant advantage of the two-dimensional "surface" UV resistance concept compared to the "scattered" approach, representing a major breakthrough and providing guidance for the application strategy of UV absorbers in polymer materials. Furthermore, the interaction between the UV absorber BZT and graphene oxide to generate numerous hydrogen bonds further enhances UV absorption, increasing the UV absorption capacity of the absorber. More importantly, this also proves that the sandwich-structured UV absorber designed in this invention, as a filler, can achieve synergistic reinforcement of high weather resistance, high barrier properties, and high corrosion resistance in bio-based epoxy coatings. This greatly promotes the application of bio-based epoxy coatings in complex industrial environments and under high demands, providing an effective strategy for the synergistic reinforcement and multifunctionalization of other organic polymer materials.

[0117] This invention provides a sandwich-structured broad-spectrum ultraviolet absorber, its preparation method, and its application. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A sandwich-structured broadband ultraviolet absorber, characterized in that, Using aminated graphene oxide as the surface and ultraviolet absorbers as discrete points, the aminated graphene oxide self-assembles with the ultraviolet absorbers through hydrogen bonding and π-π bonding to form a sandwich structure of discrete points / surfaces / discrete points.

2. The sandwich-structured broadband ultraviolet absorber according to claim 1, characterized in that, The ultraviolet absorber includes any one or more of benzotriazole compounds, benzothiazole compounds, and benzophenone compounds; preferably, the benzotriazole compound is 2-(2H-benzotriazole-2-yl)-4,6-di-tert-pentylphenol.

3. The method for preparing the sandwich-structured broad-spectrum ultraviolet absorber according to claim 1, characterized in that, Includes the following steps: (1) Graphene oxide aqueous solution was prepared by Hummer's method. After washing with ethanol by centrifugation, the graphene oxide was uniformly dispersed in ethanol to obtain graphene oxide ethanol solution. (2) The ultraviolet absorber was added to the graphene oxide ethanol solution, and the mixture was ultrasonicated and stirred to obtain mixture A; (3) Mixture A is washed by centrifugation with ethanol and then by centrifugation with water to obtain mixture B; (4) Add the aqueous solution of the amine compound to the mixture B and mix well to obtain mixture C; (5) The mixture C is heated to react and obtain mixture D; (6) The mixture D is centrifuged, washed with water and vacuum dried to obtain the final product.

4. The preparation method according to claim 3, characterized in that, In step (1), the graphene oxide ethanol solution has a graphene oxide concentration of 1-10 g / L.

5. The preparation method according to claim 3, characterized in that, In step (2), the ultraviolet absorber includes any one or more of benzotriazole compounds, benzothiazole compounds, and benzophenone compounds; preferably, the benzotriazole compound is 2-(2H-benzotriazole-2-yl)-4,6-di-tert-pentylphenol; and / or, the mass ratio of the ultraviolet absorber to the graphene oxide is 0.1:1 to 10:1; and / or, the ultrasonication time is 10 to 60 min; and / or, the stirring time is 30 to 60 min.

6. The preparation method according to claim 3, characterized in that, In step (4), the amine compound includes any one or more of maleic diamine, p-phenylenediamine and trimethylamine; and / or, the mass ratio of the amine compound to the graphene oxide is 1:1 to 10:1; the mixing is performed by ultrasonication for 5 to 60 minutes and magnetic stirring for 10 to 60 minutes.

7. The preparation method according to claim 3, characterized in that, In step (5), the heating reaction is carried out at a temperature of 50-100°C for 8-12 hours; in step (6), the vacuum drying is carried out at a temperature of 40-100°C for 6-24 hours and a pressure of 10Pa-1000Pa.

8. The application of the sandwich-structured broadband ultraviolet absorber of claim 1 in the preparation of bio-based epoxy anti-corrosion coatings.

9. The application according to claim 8, characterized in that, The sandwich-structured broad-spectrum ultraviolet absorber is dispersed in anhydrous ethanol, and then cashew phenol-based reactive diluent is added and mixed evenly. After evaporating to remove the anhydrous ethanol, it is mixed with petroleum-based epoxy resin. Finally, cashew phenol-based curing agent, defoamer, leveling agent and anti-settling agent are added and mixed evenly to obtain a bio-based epoxy anti-corrosion coating.

10. The application according to claim 9, characterized in that, The cashew nut phenol-based reactive diluent is cashew nut phenol-based difunctional glycidyl ether; and / or, the petroleum-based epoxy resin is any one of bisphenol A epoxy resin E-44, E-51, E-54, or E-55; and / or, the cashew nut phenol-based curing agent is cashew nut phenolic amine epoxy curing agent; and / or, the defoamer is an organosilicon defoamer; and / or, the leveling agent is BYK333. And / or, the anti-settling agent is fumed silica; and / or, the raw materials are added in the following proportions by mass:

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