A method for improving the dispersibility of layered bimetallic hydroxides in epoxy coatings

Abstract

This invention provides a method for improving the dispersibility of layered bimetallic hydroxides in epoxy coatings. The method involves modifying layered bimetallic hydroxides with siloxanes of varying fluorine content to obtain modified layered bimetallic hydroxides. These modified layered bimetallic hydroxides are then added to an epoxy coating to obtain a modified epoxy coating. The performance of the modified epoxy coating is characterized to determine the influence of siloxanes of different fluorine contents on the dispersibility of the layered bimetallic hydroxides and the epoxy coating. This method effectively improves the dispersibility of layered bimetallic hydroxides in epoxy coatings, thereby improving coating performance and providing a new method for coating preparation in industrial applications. By modifying layered bimetallic hydroxides with siloxanes of different fluorine contents, their surface properties can be altered, improving their compatibility with epoxy coatings.

Description

Technical Field

[0001] This invention relates to the field of corrosion coating technology, and more specifically, to a method for improving the dispersibility of layered bimetallic hydroxides in epoxy coatings. Background Technology

[0002] Layered bimetallic hydroxides (LDHs) are widely used in coating systems due to their unique layered structure and anion exchange properties. Corrosion inhibitor ions are embedded between the layers of LDHs through ion exchange reactions, acting as containers for the corrosion inhibitor. When chloride ion corrosion occurs, the corrosion inhibitor is gradually released through ion exchange reactions between chloride ions in the environment and the anions in the interlayer, thus inhibiting corrosion (Progress in Organic Coatings 174(2023)107299; Colloids and Surfaces A: Physicochemical and Engineering Aspects 655(2022)130339; Chemical Engineering Journal 446(2022)137078). However, LDH surfaces are rich in hydroxyl (-OH) groups, resulting in high surface energy, which makes their surface structure unstable and prone to aggregation. Furthermore, the presence of hydroxyl groups on the LDH surface facilitates the formation of hydrogen bonds between particles, also leading to the formation of aggregated particles. When added to coatings, LDH aggregation not only affects the coating's barrier properties, but its uneven distribution also impacts its corrosion resistance and self-healing effects. This directly affects its commercial application in coatings. Therefore, improving the dispersibility of LDH in coatings and reducing its aggregation are of significant theoretical and practical importance for enhancing its final corrosion protection capability in coatings.

[0003] Chinese patent CN 113930157 A discloses a water-based coating and its preparation method, mainly utilizing the method of modifying MgAl-LDH with organosiloxane. The resulting coating exhibits high hardness, good air permeability, and good water and alkali resistance. However, this method does not consider the influence of siloxane modification on the dispersion of LDH in the coating. Chinese patent CN 115156010 A discloses a method for constructing a corrosion-inhibiting superhydrophobic self-healing anti-corrosion coating. Polydimethylsiloxane and laurate-intercalated LDH are uniformly dispersed in the coating, and after curing, an anti-corrosion coating is formed on the surface of the substrate. However, this patent does not analyze the effect of surface modification or the influence of siloxane on the dispersion of LDH in the coating. Zhang et al. modified the Mg-Al0LDH coating on the surface of AZ80 magnesium alloy with a low surface energy perfluorooctyltriethoxysilane (Mitigation of Corrosion on Magnesium Alloy by Predesigned Surface Corrosion, Sci. Rep. 5 (2015) 17399.). The superhydrophobic surface provided the magnesium alloy with long-lasting corrosion resistance. However, current research has not considered the influence of the fluorine content of the siloxane on the dispersion of LDH in the coating and the compatibility between LDH and the coating. This is a very critical issue in practical applications and directly restricts the industrialization of LDH in anti-corrosion coatings. Summary of the Invention

[0004] In view of this, the present invention aims to propose a method for improving the dispersibility of layered bimetallic hydroxides in epoxy coatings. This addresses the fact that existing research has not considered the impact of the fluorine content of siloxanes on the dispersibility of LDH in coatings, as well as the influence of the fluorine content of siloxanes on the compatibility of LDH with the coating. These are critical issues in practical applications, directly hindering the industrialization of LDH in anti-corrosion coatings.

[0005] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0006] A method for improving the dispersibility of layered bimetallic hydroxides in epoxy coatings involves modifying layered bimetallic hydroxides with siloxanes of different fluorine contents to obtain modified layered bimetallic hydroxides, adding the modified layered bimetallic hydroxides to an epoxy coating to obtain a modified epoxy coating, and characterizing the performance of the modified epoxy coating to obtain the influence of siloxanes of different fluorine contents on the dispersibility of layered bimetallic hydroxides and epoxy coatings.

[0007] This setup effectively improves the dispersibility of layered bimetallic hydroxides in epoxy coatings, thereby enhancing coating performance and providing a novel method for coating preparation in industrial applications. By modifying layered bimetallic hydroxides with siloxanes of varying fluorine content, their surface properties can be altered, improving their compatibility with epoxy coatings. Simultaneously, this method effectively enhances the dispersibility of layered bimetallic hydroxides in epoxy coatings, thus improving coating performance.

[0008] Furthermore, the specific steps include the following:

[0009] S1. Preparation of nitrate-intercalated layered bimetallic hydroxides by coprecipitation method;

[0010] S2. Prepare a fluorinated siloxane solution of a certain concentration;

[0011] S3. The nitrate-intercalated layered bimetallic hydroxide prepared in S1 is added to a certain volume of fluorinated siloxane solution at a certain mass and stirred magnetically at room temperature for a certain time. After stirring, centrifugation is performed.

[0012] S4. After centrifugation, the sample is placed in an oven for drying. After drying, the modified layered bimetallic hydroxide is obtained.

[0013] S5. The modified layered bimetallic hydroxide is added to the epoxy coating to obtain the modified epoxy coating.

[0014] This method can improve the dispersibility of layered bimetallic hydroxides in epoxy coatings, thereby improving the coating performance. In addition, this method also has the advantages of simple preparation, convenient operation and low cost.

[0015] Furthermore, the layered bimetallic hydroxide is one of MgAl-LDH, CaAl-LDH, and ZnAl-LDH.

[0016] Furthermore, siloxanes with different fluorine contents include tetramethoxysilane, triethoxy-1H,1H,2H,2H-perfluorodecylsilane, and 1H,1H,2H,2H-perfluorooctyltriethoxysilane.

[0017] The different fluorine contents of siloxanes in this setup can adjust the compatibility and dispersibility of layered bimetallic hydroxides with epoxy coatings, and determine the influence of different fluorine contents of siloxanes on the compatibility and dispersibility of layered bimetallic hydroxides with epoxy coatings.

[0018] Further, in step S2, the concentration of the fluorinated siloxane solution is 0.02-0.06 mol / L.

[0019] This configuration allows for better dispersibility and compatibility between layered bimetallic hydroxides and epoxy coatings.

[0020] Further, in step S3, the mass of the nitrate-intercalated layered bimetallic hydroxide is 0.1-4 g, the volume of the fluorinated siloxane solution is 50-400 mL, and the magnetic stirring time at room temperature is 0.1-3 h.

[0021] Furthermore, in step S3, the centrifuge speed is set to 4000-8000 r / min, and the centrifugation time is set to 2-8 min.

[0022] Furthermore, in step S4, the oven temperature is set to 60-120℃, and the drying time is 20-80h.

[0023] Further, in step S5, the modified layered bimetallic hydroxide accounts for 1 to 3 wt.% of the epoxy coating by mass percentage.

[0024] Further, the specific steps of step S1 are as follows: a mixed solution of Ca(NO3)2 and Al(NO3)3 is used as a precursor solution and added dropwise to a mixed solution of NaNO3 and NaOH. The water bath temperature is controlled at 50-70°C. The reactants are placed in a hydrothermal reactor for hydrothermal reaction at 110-130°C for 12-48 hours. After the hydrothermal reaction is completed, the mixture is cooled to room temperature. The reaction product is then removed, centrifuged, and washed. The washed product is then placed in an oven for drying to obtain a nitrate-intercalated layered bimetallic hydroxide.

[0025] Compared to existing technologies, the method for improving the dispersibility of layered bimetallic hydroxides in epoxy coatings described in this invention has the following advantages:

[0026] 1. This invention modifies layered bimetallic hydroxides by using siloxanes with different fluorine contents, thereby changing their surface properties and improving their compatibility with epoxy coatings. At the same time, this method can effectively improve the dispersibility of layered bimetallic hydroxides in epoxy coatings, thereby improving the performance of the coating. This method is of great significance for improving the service life of epoxy coatings and substrates, reducing the number of coating repairs, reducing labor costs, and improving facility safety.

[0027] 2. The modified epoxy coating obtained by the method of the present invention is smoother and has fewer defects, better exerts the physical barrier effect of layered bimetallic hydroxide in the coating, gives the coating better barrier performance against water molecules and corrosive ions, and exhibits better corrosion protection performance against the substrate. Attached Figure Description

[0028] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0029] Figure 1 The XRD patterns of CaAl-LDH, CaAl-LDH-TTOS prepared in Example 1 and CaAl-LDH-PFDTMS prepared in Example 2 of this invention at 2θ of 0 to 80°;

[0030] Figure 2 (a1~a3) are scanning electron microscope images of CaAl-LDH prepared in Example 1 of the present invention;

[0031] Figure 2 (b1~b3) are scanning electron microscope images of CaAl-LDH-TTOS prepared in Example 1 of the present invention;

[0032] Figure 2 (c1~c3) are scanning electron microscope images of CaAl-LDH-PFDTMS prepared in Example 2 of the present invention;

[0033] Figure 3 (a) Scanning electron microscope image of an epoxy coating without the addition of layered bimetallic hydroxide;

[0034] Figure 3 (b) is a scanning electron microscope image of an epoxy coating containing 2 wt.% CaAl-LDH;

[0035] Figure 3 (c) is a scanning electron microscope image of the epoxy coating containing 2 Wt.% CaAl-LDH-TTOS in Example 1 of the present invention;

[0036] Figure 3 (d) is a scanning electron microscope image of the epoxy coating containing 2 Wt.% CaAl-LDH-PFDTMS in Example 2 of the present invention. Detailed Implementation

[0037] The present invention will be further described in detail below through specific embodiments, but it should not be construed as limiting the scope of the invention to the following examples. Various substitutions or modifications made based on ordinary technical knowledge and conventional methods in the art without departing from the above-described methodological spirit of the invention should be included within the scope of the invention.

[0038] Example 1

[0039] (1) A mixed solution of 200 mL of 0.5 mol / L Ca(NO3)2 and 0.25 mol / L Al(NO3)3 was selected as the precursor solution and added dropwise to a mixed solution of 100 mL of 2 mol / L NaNO3 and 3 mol / L NaOH. The water bath temperature was controlled at 65℃. The reaction product was placed in a hydrothermal reactor for hydrothermal reaction at 120℃ for 24 h. After the hydrothermal reaction was completed, the product was cooled to room temperature, centrifuged, and washed. The centrifuge speed was set to 8000 r / min and the centrifugation time was set to 5 min. The washed product was dried in an oven at 60℃ for 24 h to obtain calcium-aluminum layered bimetallic hydroxide, abbreviated as CaAl-LDH. The properties of the calcium-aluminum layered bimetallic hydroxide were characterized as follows: Figures 1-3 .

[0040] (2) Surface modification of the CaAl-LDH obtained in step (1): 0.5 g of CaAl-LDH powder was added to a 0.05 mol / L tetramethoxysilane (TTOS) solution, magnetically stirred for 0.5 h, and then placed in an oven for 3 h at a temperature of 50 °C. The reaction product was then removed, centrifuged, and washed. The centrifuge speed was set to 8000 r / min, and the centrifugation time was set to 5 min. The washed product was then placed in an oven for drying at a temperature of 60 °C for 24 h to obtain tetramethoxysilane-modified calcium-aluminum layered bimetallic hydroxide, abbreviated as CaAl-LDH-TTOS. The performance of CaAl-LDH-TTOS was characterized as follows: Figures 1-3 ;

[0041] (3) CaAl-LDH-TTOS was added to the epoxy coating at a mass fraction of 2 wt%. The epoxy coating, by weight, comprised 200 parts of 6101 epoxy resin, 100 parts of n-butanol, and 84 parts of 2519 epoxy curing agent. Scanning electron microscopy (SEM) was performed on the epoxy coating, and the results are as follows: Figure 3 As shown in (c).

[0042] Example 2

[0043] (1) A mixed solution of 200 mL of 0.5 mol / L Ca(NO3)2 and 0.25 mol / L Al(NO3)3 was selected as the precursor solution and added dropwise to a mixed solution of 100 mL of 2 mol / L NaNO3 and 3 mol / L NaOH. The water bath temperature was controlled at 65℃. The reaction product was placed in a hydrothermal reactor for hydrothermal reaction at 120℃ for 24 h. After the hydrothermal reaction was completed, the product was cooled to room temperature, centrifuged, and washed. The centrifuge speed was set to 8000 r / min and the centrifugation time was set to 5 min. The washed product was placed in an oven for drying at 60℃ for 24 h to obtain calcium-aluminum layered bimetallic hydroxide, abbreviated as CaAl-LDH. The properties of the calcium-aluminum layered bimetallic hydroxide were characterized as follows: Figures 1-3 .

[0044] (2) Surface modification of the CaAl-LDH obtained in step (1): 0.5 g of CaAl-LDH powder was added to a 0.05 mol / L solution of 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTMS), and the mixture was magnetically stirred for 0.5 h, then placed in an oven for 3 h at a temperature of 50 °C. The reaction product was then removed, centrifuged, and washed. The centrifuge speed was set to 8000 r / min, and the centrifugation time was set to 5 min. The washed product was then placed in an oven for drying at a temperature of 60 °C for 24 h, yielding a 1H,1H,2H,2H-perfluorodecyltriethoxysilane-modified calcium-aluminum layered bimetallic hydroxide, abbreviated as CaAl-LDH-PFDTMS. The performance of CaAl-LDH-PFDTMS was characterized as follows: Figures 1-3 ;

[0045] (3) CaAl-LDH-PFDTMS was added to the epoxy coating at a mass fraction of 2 wt.% to obtain a modified epoxy coating. By weight, the epoxy coating comprised 200 parts of 6101 epoxy resin, 100 parts of n-butanol, and 84 parts of 2519 epoxy curing agent. The modified epoxy coating was subjected to scanning electron microscopy (SEM) testing, and the results are as follows: Figure 3 As shown in (d).

[0046] Comparative Example 1

[0047] The epoxy coating does not contain calcium-aluminum layered bimetallic hydroxide. The epoxy coating formulation includes 200 parts of 6101 epoxy resin, 100 parts of n-butanol, and 84 parts of 2519 epoxy curing agent. Scanning electron microscopy (SEM) analysis of the epoxy coating yielded the following results: Figure 3 As shown in (a).

[0048] Comparative Example 2

[0049] The difference from Comparative Example 1 is that a calcium-aluminum layered bimetallic hydroxide was added to the epoxy coating. This calcium-aluminum layered bimetallic hydroxide was prepared in Example 1, and the amount added was calculated as a mass percentage, with the calcium-aluminum layered bimetallic hydroxide accounting for 2 wt.% of the epoxy coating. Scanning electron microscopy was performed on the epoxy coating after adding the calcium-aluminum layered bimetallic hydroxide, and the results are as follows: Figure 3 As shown in (b).

[0050] Performance test analysis

[0051] Figure 1 XRD patterns of layered bimetallic hydroxides before and after modification with siloxanes of different fluorine contents are shown. The three samples are unmodified CaAl-LDH, CaAl-LDH-TTOS modified with tetramethoxysilane (TTOS), and CaAl-LDH-PFDTMS modified with 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTMS). Figure 1 It can be seen that the XRD patterns of the three samples are very similar, with characteristic peaks of the (003) and (006) crystal planes appearing at 10° and 20°. These characteristic peaks correspond to the nitrate ions embedded in the interlayer. This result also shows that the modification of TTOS and PFDTMS did not damage the layered structure of LDH and did not enter its interlayer, but only modified the surface.

[0052] Figure 2 Figures show the SEM images of layered bimetallic hydroxides at different magnifications. The results indicate that all three exhibit a similar hexagonal morphology. Figure (a) shows the microstructure of CaAl-LDH; the comparison reveals that the CaAl-LDH particles are relatively small, and particle aggregation is severe. Figures (b) and (c) show the layered bimetallic hydroxides modified with TTOS and PFDTMS, respectively. The results show that the modified layered bimetallic hydroxides still possess a hexagonal structure and maintain their layered structure intact, with significantly reduced particle aggregation. The aggregation degree of PFDTMS-modified CaAl-LDH is much less than that of TTOS-modified CaAl-LDH.

[0053] Figure 3 (a) shows the microstructure of the epoxy coating without the addition of LDH powder. Figure 3Figures (b)-(d) show the microstructure of samples with LDH powder as a filler in epoxy coatings. As can be seen from the figures, the coating is smoother and the porosity and defects are reduced after adding CaAl-LDH. The defects are further reduced after adding CaAl-LDH-TTOS and CaAl-LDH-PFDTMS, and no LDH flake aggregation was observed, demonstrating the good compatibility between the TTOS- and PFDTMS-modified LDH and the coating. The coating with CaAl-LDH-PFDTMS is smoother and has fewer defects than the coating with CaAl-LDH-TTOS.

[0054] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method of improving the dispersibility of layered double hydroxides in an epoxy coating, characterized in that, The fluorine-containing siloxane is used for modifying the layered double hydroxide to obtain the modified layered double hydroxide, and the modified layered double hydroxide is added into an epoxy coating to obtain a modified epoxy coating. S1, nitrate intercalated layered double hydroxide is prepared by coprecipitation method; S2, a fluorine-containing siloxane solution with a certain concentration is prepared; S3, the nitrate intercalated layered double hydroxide prepared in S1 is added into a certain volume of the fluorine-containing siloxane solution with a certain mass, and is magnetically stirred at room temperature for a certain time, and then is centrifuged; S4, the sample after centrifugation is dried in an oven to obtain the modified layered double hydroxide; S5, the modified layered double hydroxide is added into the epoxy coating to obtain the modified epoxy coating. The layered double hydroxide is one of MgAl-LDH, CaAl-LDH and ZnAl-LDH. The fluorine-containing siloxane includes one or more of triethoxy-1H, 1H, 2H, 2H-perfluorodecylsilane and 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane.

2. The method of improving dispersibility of layered double hydroxide in an epoxy coating according to claim 1, characterized in that, In step S2, the concentration of the fluorine-containing siloxane solution is 0.02-0.06 mol / L.

3. The method of improving dispersibility of layered double hydroxide in an epoxy coating according to claim 1, characterized in that, In step S3, the mass of the nitrate intercalated layered double hydroxide is 0.1-4 g, the volume of the fluorine-containing siloxane solution is 50-400 mL, and the magnetic stirring time at room temperature is 0.1-3 h.

4. The method of improving dispersibility of layered double hydroxide in an epoxy coating of claim 1, wherein, In step S3, the centrifuge speed is set to 4000-8000 r / min, and the centrifugation time is set to 2-8 min.

5. The method of improving dispersibility of layered double hydroxide in an epoxy coating of claim 1, wherein, In step S4, the oven temperature is set to 60-120℃, and the drying time is 20-80 h.

6. The method of improving dispersibility of layered double hydroxide in an epoxy coating of claim 1, wherein, In step S5, the weight of the modified layered double hydroxide accounts for 1-3 Wt.% of the epoxy coating.

7. The method of improving dispersibility of layered double hydroxide in an epoxy coating of claim 2, wherein, The specific steps of step S1 are as follows: a mixed solution of Ca(NO3)2 and Al(NO3)3 is used as a precursor solution, and is added dropwise into a mixed solution of NaNO3 and NaOH, and the water bath temperature is controlled, wherein the water bath temperature is 50-70℃, the reaction is carried out in a hydrothermal kettle, wherein the hydrothermal reaction temperature is 110-130℃, the hydrothermal reaction time is 12-48 h, after the hydrothermal reaction, the reaction product is cooled to room temperature, and then is centrifuged, washed and dried in an oven to obtain the nitrate intercalated layered double hydroxide.

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