Zinc-based anticorrosive filler as well as preparation method and application thereof

Abstract

The invention discloses a zinc-based anticorrosive filler as well as a preparation method and application thereof, and belongs to the technical field of metal corrosion and protection. The zinc-based anticorrosive filler comprises a zinc complex crystal material with zero-dimensional structural characteristics, and the molecular formula of the zinc complex crystal material is Zn2 (L1) 4 (L2) 2; wherein Zn is a zinc ion; l1 is a deprotonated organic carboxylic acid ligand 3, 5-bis (trifluoromethyl) benzoic acid; and L2 is 2-methylimidazole. The material has the characteristics of a paddle-wheel-shaped binuclear zinc cluster structure, and can be dissolved in most of common organic solvents. The zinc complex crystal material can be used as an anti-corrosion filler and is uniformly doped in an epoxy resin coating, so that the anti-corrosion performance of the coating is effectively improved.

Description

Technical Field

[0001] The present application relates to a zinc-based anti-corrosion filler, a preparation method thereof and an application thereof, belonging to the technical field of metal corrosion and protection. Background Art

[0002] With the development of modern industry, the application of metal materials is becoming increasingly widespread. At the same time, the effective protection against metal corrosion has become an urgent problem to be solved. Adding an anti-corrosion coating with good anti-permeability performance on the metal surface is one of the effective ways to solve the metal corrosion problem. Epoxy resin is widely used in fields such as construction structure engineering, machining of mechanical parts, and aviation industry manufacturing due to its high adhesiveness, heat resistance, corrosion resistance, and convenient construction. However, when the pure epoxy resin coating is affected by strong ultraviolet radiation, acid-base erosion, thermal cycling, etc., its tight three-dimensional network structure is prone to generate micropores and cracks, resulting in a reduction in the anti-corrosion performance of the coating. The prior art often improves its defects by adding nano-fillers with specific functions. Therefore, the research and development of efficient, economical, and stable nano-functional fillers contribute to the development of more advanced and excellent functional anti-corrosion coatings and solve the metal corrosion problem in engineering and industrial processes. Summary of the Invention

[0003] In order to solve the deficiencies in performance, economy, and stability of the anti-corrosion coating in the prior art of metal anti-corrosion, the present application provides a technical solution of a zinc complex crystal material, which is a zinc complex material formed by mixing and coordinating an imidazole-based organic ligand with a corrosion inhibition effect and a carboxylic acid-based organic ligand with a hydrophobic property. This material has the structural characteristics of a paddle-wheel-shaped binuclear metal cluster, is soluble in most organic solvents, and when used as an additive and doped into the epoxy resin coating, it improves the anti-corrosion performance of the coating.

[0004] The present application adopts the following technical solutions:

[0005] According to the first aspect of the present application, there is provided a zinc-based anti-corrosion filler, and the zinc-based anti-corrosion filler includes a zinc complex crystal material;

[0006] The molecular formula of the zinc complex crystal material is Zn2(L1)4(L2)2;

[0007] Wherein, Zn is a zinc ion;

[0008] L1 is the deprotonated organic carboxylic acid ligand 3,5-bis(trifluoromethyl)benzoic acid;

[0009] L2 is 2-methylimidazole.

[0010] Optionally, the zinc complex crystal material has a paddle-wheel-shaped binuclear zinc cluster structure constructed by the 3,5-bis(trifluoromethyl)benzoic acid, the 2-methylimidazole and the zinc ion through coordination bonds.

[0011] Optionally, the zinc complex crystal material crystallizes in the triclinic system, space group P-1.

[0012] Optionally, the unit cell parameters of the zinc complex crystal material are as follows: α = 90.764(4)°, β = 95.061(4)°, γ = 96.455(4)°.

[0013] Optionally, the asymmetric unit of the zinc complex crystal material contains 1 Zn 2+ ion, 2 deprotonated 3,5-bis(trifluoromethyl)benzoic acid ligands, and 1 2-methylimidazole ligand.

[0014] Optionally, in the asymmetric unit of the zinc complex crystal material, the Zn 2+ ion adopts a pentacoordinate square pyramid mode, with four oxygen atoms from carboxylic acid groups forming the bottom of the square pyramid, and one nitrogen atom from the imidazole group occupying the apex position of the square pyramid.

[0015] Optionally, in the asymmetric unit of the zinc complex crystal material, the deprotonated 3,5-bis(trifluoromethyl)benzoic acid ligand adopts a μ2-bridging coordination mode, connecting two zinc ions to form a dinuclear zinc cluster unit.

[0016] Optionally, in the asymmetric unit of the zinc complex crystal material, the 2-methylimidazole ligand adopts a μ1 coordination mode, providing one nitrogen atom, which occupies the top of the square pyramid model through a Zn-N coordination bond, preventing the extension of the structure.

[0017] In the present application, the zinc complex crystal material has a paddle-wheel-shaped dinuclear zinc cluster structural feature and is soluble in most common organic solvents.

[0018] In the present application, the zinc complex crystal material is a dinuclear zinc complex crystal material with a zero-dimensional structural feature.

[0019] According to the second aspect of the present application, there is provided a method for preparing the above zinc complex crystal material, including the following steps:

[0020] Heat a mixed solution containing 3,5-bis(trifluoromethyl)benzoic acid, a base, 2-methylimidazole, zinc nitrate, and water, and then cool it to obtain the zinc complex crystal material.

[0021] Optionally, the method for preparing the zinc complex crystal material provided in the present application is a solvothermal method, which has the advantages of simple preparation and mild reaction conditions.

[0022] Optionally, the molar ratio of 3,5-bis(trifluoromethyl)benzoic acid to zinc nitrate is 2:1.

[0023] Optionally, the molar ratio of the 2-methylimidazole to zinc nitrate is 1:1.

[0024] Optionally, the molar ratio of the 3,5-bis(trifluoromethyl)benzoic acid to the base is 1:1.

[0025] In this application, the inventors found that the amounts of the raw materials in the mixed solution need to be strictly in accordance with the ratios defined above. Otherwise, impurities are likely to appear in the products after reaction.

[0026] Optionally, the heating conditions include: the heating temperature is 80°C to 120°C, and the heating time is 24 h to 72 h.

[0027] Optionally, the cooling conditions include: cooling to room temperature at a cooling rate of 2°C / h to 12°C / h.

[0028] Optionally, the specific range of room temperature is not strictly limited, and those skilled in the art can select it according to the implementation requirements, such as 15°C to 25°C.

[0029] Optionally, the preparation process of the mixed solution includes: stirring the aqueous solution containing 3,5-bis(trifluoromethyl)benzoic acid and the base until it becomes colorless, and then sequentially adding the aqueous solution of 2-methylimidazole and the aqueous solution of zinc nitrate.

[0030] Optionally, before heating, adding nitric acid aqueous solution to adjust the pH of the mixed solution is also included;

[0031] The molar ratio of nitric acid in the nitric acid aqueous solution to the 3,5-bis(trifluoromethyl)benzoic acid is 0 to 0.2:1.

[0032] Optionally, the base is selected from sodium bicarbonate or sodium hydroxide.

[0033] According to the third aspect of this application, there is provided an application of the above zinc-based anti-corrosion filler, or a zinc-based anti-corrosion filler containing a zinc complex crystal material prepared by the preparation method according to any one of the above in a modified anti-corrosion coating.

[0034] Optionally, the modified anti-corrosion coating is a modified epoxy resin anti-corrosion coating.

[0035] The zinc complex crystal material is uniformly doped in the epoxy resin coating as an anti-corrosion filler, which can effectively improve the anti-corrosion performance of the coating.

[0036] The beneficial effects of this application include:

[0037] (1) The zinc-based anti-corrosion filler provided by this application belongs to a zinc complex crystal material formed by the mixed coordination of an imidazole-based organic ligand with a corrosion inhibition effect and a carboxylic acid-based organic ligand with hydrophobic properties. It can be used as an additive and doped into an epoxy resin coating, effectively improving the anti-corrosion performance of the coating. This material has the structural characteristics of paddle-wheel-shaped binuclear metal clusters, is soluble in most organic solvents, effectively improves the doping uniformity, and enhances the stability of the anti-corrosion performance of the coating.

[0038] (2) The preparation method of the zinc-based anti-corrosion filler provided by this application uses solvothermal method, which has the advantages of simple preparation and mild reaction conditions. Description of the Drawings

[0039] Figure 1 It is a schematic structural diagram of the zinc complex crystal material.

[0040] Figure 2 It is the X-ray powder diffraction pattern of the zinc complex crystal material.

[0041] Figure 3 It is the hydrogen spectrum of the zinc complex crystal material.

[0042] Figure 4 It is the electrochemical impedance spectroscopy diagram of the epoxy resin coating doped with 0.2 wt% of the zinc complex crystal material immersed in 3.5 wt% NaCl for different times.

[0043] Figure 5 It is the electrochemical impedance spectroscopy diagram of the epoxy resin coating doped with 2.0 wt% of the zinc complex crystal material immersed in 3.5 wt% NaCl for different times. Detailed Embodiments

[0044] The following describes this application in detail with reference to the embodiments, but this application is not limited to these embodiments.

[0045] Unless otherwise specified, the raw materials in the embodiments of this application are all purchased through commercial channels.

[0046] Unless otherwise specified, the test methods are all conventional methods, and the instrument settings are all the settings recommended by the manufacturer.

[0047] The analysis methods in the embodiments of this application are as follows:

[0048] Single crystal X-ray diffraction analysis is carried out using an Agilent SuperNova single crystal diffractometer.

[0049] Powder X-ray diffraction analysis is carried out using a Rigaku Miniflex600 desktop powder diffractometer.

[0050] Hydrogen spectrum analysis is carried out using a Bruker Avance III 400 MHz nuclear magnetic resonance spectrometer.

[0051] Elemental analysis was carried out using an Elementar Vario ELIII elemental analyzer.

[0052] Impedance analysis was carried out using an Autolab PGSTAT 302N electrochemical workstation.

[0053] Example 1 Preparation of Zinc Complex Crystal Material

[0054] In a 20 mL glass bottle, 0.258 g of 3,5-bis(trifluoromethyl)benzoic acid, 0.084 g of NaHCO3, and 5 mL of distilled water were stirred until completely dissolved to obtain a colorless solution. Then, 1.0 mL of 2-methylimidazole aqueous solution (0.5 M) and 1.0 mL of Zn(NO)3 aqueous solution (0.5 M) were added in sequence. Subsequently, the pH of the reaction mixture was adjusted with 50 μL of nitric acid aqueous solution (2.0 M). After the mixture was stirred evenly, it was heated at a constant temperature of 100 °C for 1 day, and then cooled to room temperature at a rate of 6 °C / h. The colorless crystal product, namely the zinc complex crystal material, was collected by filtration, and the yield was 63%. Elemental analysis results (experimental value / calculated value): C: 40.33 / 39.93%, N: 4.21 / 4.23%, H: 1.73 / 1.82%. 1H NMR analysis results (400 MHz, deuterated methanol): 8.54 (s, 4H), 8.05 (s, 2H), 7.16 (d, J = 3.1 Hz, 2H), 2.53 (s, 3H).

[0055] Examples 2 - 6

[0056] In Examples 2 - 5, the zinc complex crystal material was prepared using the same preparation process as in Example 1, except that the amounts of nitric acid aqueous solution (2.0 M) in Examples 2 - 5 were 0 μL, 25 μL, 75 μL, 100 μL, 125 μL, and 150 μL, respectively. It was found that when the amount of nitric acid aqueous solution (2.0 M) was less than 100 μL, the prepared zinc complex crystals were exactly the same as the crystal product of Example 1, while when the amount of nitric acid aqueous solution (2.0 M) was greater than 100 μL, impurities began to appear in the prepared zinc complex crystals.

[0057] During the preparation process of the examples in this application, the inventors found that when the dosage ratio between the raw materials used changed, impurities were likely to appear in the crystal product after the reaction.

[0058] Test Example 1

[0059] The colorless crystal product prepared in Example 1 was subjected to X-ray single crystal diffraction analysis, and the chemical formula of the compound was found to be Zn2(L1)4(L2)2 (L1 = deprotonated 3,5-bis(trifluoromethyl)benzoic acid, L2 = 2-methylimidazole). The specific structure of the colorless crystal product of this application is as shown in Figure 1 shown. The Zn 2+ ion adopts a square pyramidal coordination mode. Four oxygen atoms from the carboxylic acid groups form the bottom of the square pyramid, and one nitrogen atom from the imidazole group occupies the apex position of the square pyramid. The deprotonated 3,5-bis(trifluoromethyl)benzoic acid ligand adopts a μ2-bridging coordination mode, connecting two zinc ions to form a centrosymmetric binuclear zinc cluster unit. The 2-methylimidazole ligand adopts a μ1 coordination mode and occupies the top of the square pyramid model through the Zn-N coordination bond, preventing the extension of the structure, thus obtaining an isolated cluster structure. As shown in Figures 2 - 3 shown, the colorless crystal product prepared in Example 1 was characterized by X-ray powder diffraction, hydrogen spectrum analysis, and elemental analysis, indicating that the product has no impurities.

[0060] Preparation of a composite epoxy resin coating doped with 0.2 wt% zinc complex in Example 7

[0061] 7.3 mg of the zinc complex crystal material powder prepared in Example 1 was mixed with 0.65 mL of a mixed solution of n-butanol and xylene (volume ratio 7:3) and sonicated for 5 minutes to obtain a clear solution. Subsequently, 3.50 g of epoxy resin was added and mechanically stirred for 60 minutes, then 1.75 g of polyamide curing agent was added and mechanically stirred for 15 minutes. The mixture was degassed by vacuum to obtain a mixture. The mixture was coated on a smooth and clean steel sheet using a four-sided film applicator, cured at room temperature for 2 days, and then transferred to an 80 °C oven and dried for 4 h. A composite epoxy resin coating doped with 0.2 wt% zinc complex (based on the mass of epoxy resin) was obtained.

[0062] Preparation of a composite epoxy resin coating doped with 2.0 wt% zinc complex in Example 8

[0063] 70.1 mg of the zinc complex crystal material powder prepared in Example 1 was mixed with 0.65 mL of a mixed solution of n-butanol and xylene (volume ratio 7:3) and sonicated for 5 minutes to obtain a clear solution. Subsequently, 3.55 g of epoxy resin was added and mechanically stirred for 60 minutes, then 1.76 g of polyamide curing agent was added and mechanically stirred for 15 minutes. The mixture was degassed by vacuum to obtain a mixture. The mixture was coated on a smooth and clean steel sheet using a four-sided film applicator, cured at room temperature for 2 days, and then transferred to an 80 °C oven and dried for 4 h. A composite epoxy resin coating doped with 2.0 wt% zinc complex (based on the mass of epoxy resin) was obtained.

[0064] Test Example 2

[0065] The corrosion resistance of the composite epoxy resin coatings doped with zinc complexes prepared in Example 7 and Example 8 was tested: The steel sheets covered with the composite epoxy resin coatings doped with zinc complexes and the steel sheets with pure epoxy resin coatings prepared in Example 7 and Example 8 were used as electrodes and immersed in 3.5 wt% NaCl solution respectively, and their corrosion resistance was evaluated by an electrochemical workstation. The results are as Figure 4 , Figure 5 shown (in the figure, D represents the number of days). After being immersed in the salt solution for two months, the surfaces of the composite epoxy resin coatings with different doping amounts of zinc complexes still remained smooth and transparent, and the impedance modulus value remained at 10 10 Ω·cm 2 order of magnitude at 0.01 Hz. For the steel sheet electrode with pure epoxy resin coating, after being immersed in 3.5 wt% NaCl solution for 44 days, the impedance modulus value had dropped to 10 8 Ω·cm 2 order of magnitude (refer to Patent 202410433203.3). The experimental results show that the zinc complex can be used as an effective additive, doped into the epoxy resin coating, acting as a zinc-based anti-corrosion filler, and improving the anti-corrosion performance of the coating.

[0066] The above are only several embodiments of the present application, and do not impose any form of limitation on the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any person skilled in the art, without departing from the scope of the technical solution of the present application, makes some changes or modifications using the technical content disclosed above, which are equivalent to equivalent implementation cases and all fall within the scope of the technical solution.

Claims

1. A zinc-based anti-corrosion filler, characterized in that, The zinc-based anticorrosive filler includes a zinc complex crystal material; The molecular formula of the zinc complex crystal material is Zn2(L1)4(L2)2; wherein, Zn is a zinc ion; L1 is the deprotonated organic carboxylic acid ligand 3,5-bis(trifluoromethyl)benzoic acid; L2 is 2-methylimidazole.

2. The zinc-based anti-corrosion filler according to claim 1, wherein The zinc complex crystal material has a paddle-wheel-shaped binuclear zinc cluster structure constructed by the 3,5-bis(trifluoromethyl)benzoic acid, the 2-methylimidazole and the zinc ion through coordination bonds.

3. The zinc-based anti-corrosion filler according to claim 1, wherein The zinc complex crystal material crystallizes in the triclinic system, space group P-1; Preferably, the unit cell parameters of the zinc complex crystal material are as follows: α = 90.764(4)°, β = 95.061(4)°, γ = 96.455(4)°.

4. The zinc-based anti-corrosion filler according to claim 3, characterized in that, The asymmetric unit of the zinc complex crystal material contains one Zn 2+ ion, two deprotonated 3,5-bis(trifluoromethyl)benzoic acid ligands, and one 2-methylimidazole ligand; Preferably, in the asymmetric unit of the zinc complex crystal material, Zn 2+ ions adopt a five-coordinate square pyramid mode, with four oxygen atoms from carboxylic acid groups forming the bottom of the square pyramid, and one nitrogen atom from the imidazole group occupying the apex position of the square pyramid; Preferably, in the asymmetric unit of the zinc complex crystal material, the deprotonated 3,5-bis(trifluoromethyl)benzoic acid ligand adopts a μ2-bridging coordination mode to connect two zinc ions to form a binuclear zinc cluster unit; Preferably, in the asymmetric unit of the zinc complex crystal material, the 2-methylimidazole ligand adopts a μ1 coordination mode to provide a nitrogen atom, which occupies the top of the square pyramid model through a Zn-N coordination bond, preventing the extension of the structure.

5. The preparation method of the zinc complex crystal material according to any one of claims 1 to 4, characterized in that, It includes the following steps: Heating a mixed solution containing 3,5-bis(trifluoromethyl)benzoic acid, a base, 2-methylimidazole, zinc nitrate, and water, and then cooling to obtain the zinc complex crystal material.

6. The preparation method according to claim 5, characterized in that, The molar ratio of the 3,5-bis(trifluoromethyl)benzoic acid to the zinc nitrate is 2:1; Preferably, the molar ratio of the 2-methylimidazole to the zinc nitrate is 1:1; Preferably, the molar ratio of the 3,5-bis(trifluoromethyl)benzoic acid to the base is 1:

1.

7. The preparation method according to claim 5, characterized in that, The conditions for the heating include: the heating temperature is 80°C to 120°C, and the heating time is 24 h to 72 h; Preferably, the conditions for the cooling include: cooling to room temperature at a cooling rate of 2°C / h to 12°C / h.

8. The preparation method according to claim 5, characterized in that, The preparation process of the mixed solution includes: stirring an aqueous solution containing 3,5-bis(trifluoromethyl)benzoic acid and a base until it is colorless, and then successively adding an aqueous solution of 2-methylimidazole and an aqueous solution of zinc nitrate.

9. The preparation method according to claim 5, characterized in that, Before the heating, it also includes adding a nitric acid aqueous solution to adjust the pH of the mixed solution; The molar ratio of the nitric acid in the nitric acid aqueous solution to the 3,5-bis(trifluoromethyl)benzoic acid is 0 to 0.2:1; Preferably, the base is selected from sodium bicarbonate or sodium hydroxide.

10. The application of the zinc-based anticorrosive filler according to any one of claims 1 to 5, or the zinc-based anticorrosive filler containing the zinc complex crystal material prepared by the preparation method according to any one of claims 6 to 9 in a modified anticorrosive coating; Preferably, the modified anticorrosive coating is a modified epoxy resin anticorrosive coating.

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