A method for preparing a green and efficient modified polyaniline anticorrosive coating

Abstract

This invention relates to a method for preparing a green and efficient modified polyaniline anticorrosive coating, wherein the modified polyaniline is prepared by emulsion polymerization. The advantages of this invention are: the products generated by the reaction of ozone with the catalyst precursor Fe(II) in an acidic environment are water and oxygen, both of which are environmentally friendly and do not affect the subsequent product purification process. Fe(III) acts as a catalyst for the oxidative polymerization of aniline, generating fewer byproducts during the reaction, thus achieving efficient product purification and correspondingly reducing waste liquid generation and detergent consumption. Introducing microbubble generation technology into the O3-Fe(III) system optimizes the system and improves the material synthesis efficiency. The entire preparation process is economical, green, and efficient. The prepared modified polyaniline anticorrosive coating exhibits excellent corrosion resistance and stability, the preparation process is environmentally friendly and safe, and the quality is stable.

Description

Technical Field

[0001] This invention belongs to the field of materials technology, specifically relating to a method for preparing a green and efficient modified polyaniline anti-corrosion coating. Background Technology

[0002] Corrosion protection of metallic materials plays a crucial role in solving metal corrosion problems. Organic coatings, acting as a physical barrier between the metal surface and corrosive substances, are widely used in corrosion prevention. Polyaniline, due to its relatively low cost, environmental friendliness, chemical stability, and excellent corrosion resistance, has become one of the most promising polymer materials in corrosion protection, and it is widely used as a functional filler in organic coatings. However, polyaniline also faces problems such as poor dispersibility and poor mechanical properties. Some researchers have observed that polyaniline coatings fail quickly and even accelerate corrosion. Therefore, corresponding optimization measures should be taken when preparing polyaniline coatings to compensate for the shortcomings of polyaniline and obtain better coating performance.

[0003] Modified polyaniline doped with organic protic acids often exhibits superior electrical conductivity, significantly improved solubility and redox reversibility, further enhancing its ability to passivate metals and more effectively preventing the intrusion of corrosive media, thereby improving the barrier properties of the corresponding polyaniline coating. In addition, the organic protic acid doped in polyaniline can react with the metal matrix or the corrosion products of the metal to form a barrier layer, which can delay corrosion (see references: (1) Liu S, Dong Z, Wang XZ, Fu XZ, Luo JL. Different acid doped polyaniline waterborneepoxy coatings: Anticorrosion and passivation performance on 5083 Al alloy. Progress in Organic Coatings. 2022; 173:107182. (2) Ma Y, Fan B, Liu H, Fan G, HaoH, Yang B. Enhanced corrosion inhibition of aniline derivatives electropolymerized coatings on copper: Preparation, characterization and mechanism modeling. Applied Surface Science. 2020; 514: 146086.). Chinese Patent CN 112574645 A discloses a method for preparing polyaniline coatings with good anti-corrosion, conductivity, and stability. Different ferrocene-based polyanilines are prepared by introducing different acid doping during the copolymerization of ferrocene derivatives and aniline, and then used as fillers in epoxy resin / polyamide to prepare novel modified polyaniline anti-corrosion coatings. Chinese Patent CN 103849295 B discloses a phthalocyanine sulfonic acid-doped polyaniline anti-corrosion coating, using an aqueous epoxy resin solution as the film-forming substance and methylated melamine-formaldehyde resin as the curing agent. The prepared anti-corrosion coating effectively overcomes the dedoping phenomenon and is simple to prepare, has good adhesion, and excellent anti-corrosion performance. This invention uses emulsion polymerization to synthesize 2-acrylamido-2-methylpropanesulfonic acid-doped polyaniline, and the preparation process is economical, green, and efficient. Using alicyclic epoxy resin as the film-forming material and neutral polythiol as the curing agent, the prepared modified polyaniline anticorrosive coating can effectively prevent the dedoping of organic protic acids, and the coating has good long-term anticorrosive performance.

[0004] Ammonium persulfate, as a strong oxidant with a high standard electrode potential (1.94V), is a commonly used initiator for aniline monomer polymerization. However, due to its strong oxidizing properties, and the exothermic polymerization of aniline, the process becomes exceptionally vigorous at room temperature or high temperatures, easily leading to product peroxidation and reduced product quality. Furthermore, the redox reaction between ammonium persulfate and aniline generates numerous acidic byproducts containing polluting elements, hindering efficient product purification and resulting in excessive detergent consumption and large amounts of waste liquid during product cleaning. From an environmental and cost-saving perspective, ammonium persulfate is not suitable as an initiator in the chemical polymerization of aniline.

[0005] Fe(III) is a common catalyst with excellent catalytic stability, low price, and wide availability. Although its redox potential (0.771 V) is low, Fe(III) has the ability to polymerize aniline, and the low potential allows the reaction to proceed slowly at room temperature, resulting in fewer byproducts during polymerization. Ozone, as a strong oxidant, has a considerable redox potential (2.07 V) and can convert Fe(II) to Fe(III). The synthesis process of ozone is also relatively simple, usually using high-voltage discharge to cause an electrochemical reaction of oxygen molecules in an electric field to obtain ozone. Chinese patent CN 1056163 C discloses a novel method for preparing polyaniline, using hydrogen peroxide as an oxidant and transition metals as catalysts, and employing emulsion polymerization to prepare highly soluble, ultra-low molecular weight polyaniline and its derivatives.

[0006] This invention uses ozone as an oxidant and one or more ferrous compounds, including magnetic iron oxide (Fe3O4), as catalyst precursors to prepare polyaniline. The oxidative polymerization reaction mainly consists of two steps: the first step is that at the beginning of polymerization, Fe(II) in the ferrous compound is oxidized to Fe(III) by ozone; the second step is that Fe(III) oxidizes and polymerizes aniline and converts itself back to Fe(II). Throughout the process, as ozone is introduced, Fe(III) continuously participates in the polymerization reaction of aniline until the aniline reaction is complete. As an oxidant, ozone reacts with Fe(II) in an acidic environment to produce water and oxygen as byproducts, which are both environmentally friendly and do not affect the subsequent product purification process. Fe(III) acts as a catalyst initiator, producing fewer byproducts during the oxidative polymerization of aniline. After the reaction, Fe(III) retains its original properties and state or exists in the liquid phase as Fe(II), thus achieving efficient product purification with correspondingly lower wastewater generation and detergent consumption. Furthermore, after the reaction is complete, magnetic iron(III) oxide can be adsorbed and recovered using a magnet. The entire preparation process is green, efficient, and economical.

[0007] Microbubbles are tiny bubbles with diameters of 10 to 100 μm generated during bubble formation. They are formed by large bubbles with diameters of millimeters or more subjected to high-speed and strong shear forces and high-frequency pressures generated at the gas-liquid interface. The generation of microbubbles increases the specific surface area of ​​the gas-liquid contact, improves the solubility of the gas in the liquid phase, and prolongs the residence time. In addition, since the transfer coefficient is positively correlated with the specific surface area, microbubbles have a higher mass transfer rate in fluids (see references: (1) Bae K, Go GS, Noh NS, Lim YI, Bae J, Lee DH. Bubble characteristics in pressurized bubble column associated with micro-bubble dispersion. Chemical Engineering Journal. 2020; 386: 121339. (2) Gao Y, Li M, Sun C, Zhang X. Microbubble-enhanced water activation by cold plasma. Chemical Engineering Journal. 2022; 446: 137318.). The idea of ​​combining the O3-Fe(III) system with microbubble generation technology in this invention opens up a new path for improving the efficiency of gas-liquid phase reactions and provides constructive opinions and ideas for developing new synthesis methods of polyaniline.

[0008] This invention uses ozone as an oxidant and Fe(III) as a catalyst to synthesize 2-acrylamido-2-methylpropanesulfonic acid-doped polyaniline via emulsion polymerization. Ozone, as the oxidant, is introduced into the emulsion in the form of ordinary bubbles (500 μm to 10 mm particle size) and microbubbles (50 to 100 μm particle size). The modified polyaniline is then added as a filler to the resin matrix to form a composite coating, improving the barrier properties, corrosion resistance, and mechanical properties of the original epoxy coating. Summary of the Invention

[0009] The purpose of this invention is to address the shortcomings and deficiencies of existing technologies by using ozone as an oxidant, Fe(III) as a catalyst, and introducing microbubble generation technology to synthesize modified polyaniline via emulsion polymerization. This preparation method is characterized by its economy, high efficiency, and environmental friendliness. Modified polyaniline is then used as a filler for alicyclic epoxy resin / polythiol to prepare novel anti-corrosion coatings. This material exhibits good stability, adhesion, and corrosion resistance, and can be applied to metal corrosion protection.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A method for preparing a green and efficient modified polyaniline anticorrosive coating includes the following steps:

[0012] (1) Dissolve the aniline monomer and the doped acid in an oily solvent and deionized water respectively, and stir magnetically until completely dissolved. Then add the two solutions to the reaction vessel and stir vigorously to obtain an emulsion. Introduce the emulsion into the circulation pipe (5), and then turn on the booster pump (4) to make the emulsion flow in the circulation pipe.

[0013] (2) Disperse the catalyst precursor in deionized water, start the ozone generator (1), and adjust the rotor flow meter (2) to control the ozone flow rate. The ozone gas is introduced into the emulsion in the form of microbubbles through the venturi tube (3), and the catalyst precursor suspension is added to the emulsion dropwise through the peristaltic pump (6) to react.

[0014] (3) After the reaction is complete, the collected precipitate is centrifuged, washed and dried to obtain modified polyaniline.

[0015] (4) The modified polyaniline in step (3) is uniformly dispersed in a small amount of oily solvent, an appropriate amount of film-forming material is added, and the modified polyaniline is fully dispersed in the film-forming material using a high-speed disperser. A very small amount of leveling agent and an appropriate amount of curing agent are added, and the mixture is stirred, dispersed, and centrifuged at low speed to obtain the modified polyaniline anti-corrosion coating.

[0016] In step (1), the aniline monomer is at least one of aniline, acetaniline, o-benzylaniline, 2-ethynylaniline, 3-ethoxyaniline, 2,6-diisopropylaniline, 2,4-dimethoxyaniline, and 2-isopropenylphenylaniline; the oily solvent is at least one of toluene, xylene, ethanol, N-methylpyrrolidone, N,N-dimethylformamide, tetrahydrofuran, trichloroethylene, and carbon disulfide.

[0017] In step (1), the doped acid is at least one of hydrochloric acid, perfluorooctanoic acid, 2-acrylamide-2-methylpropanesulfonic acid, dodecylbenzenesulfonic acid, salicylic acid, p-toluenesulfonic acid, phosphoric acid, and camphorsulfonic acid.

[0018] In step (1), the molar ratio of aniline monomers to doped acid is 5:1 to 15:1, and the emulsion flow rate is 0.5 to 1.5 m / s.

[0019] In step (2), the catalyst precursor is at least one of magnetic iron oxide, ferrous chloride, ferrous fumarate, ferrous ethylenediammonium sulfate, ferrous lactate, ferrous oxalate, ferrous trifluoromethanesulfonate, and ferrous gluconate.

[0020] In step (2), the ozone flow rate is 1~3 L / min and the concentration is 50~200 mg / L; after the catalyst precursor suspension is added, the molar ratio of aniline monomers to catalyst precursors in the emulsion is 1:1~5:1, the concentration of aniline monomers is 0.1~2 mol / L, the concentration of doped acid is 0.01~0.2 mol / L, the concentration of catalyst precursors is 0.05~1 mol / L, and the volume ratio of oily solvent to deionized water is 1:3~1:1; the reaction temperature is 20~60 ℃, the reaction time is 90~180 min, and the dropping rate of the catalyst precursor suspension is 1 drop / 5 s.

[0021] In step (3), the detergent is at least one of deionized water, methanol, ethanol, and acetone; the drying temperature is 40~60℃ and the drying time is 12~24 h.

[0022] In step (4), the oily solvent is at least one of toluene, xylene, ethanol, N-methylpyrrolidone, N,N-dimethylformamide, tetrahydrofuran, trichloroethylene, and carbon disulfide; the film-forming substance is at least one of alicyclic epoxy resin, bisphenol A type epoxy resin, alkyd resin, phenolic resin, acrylic resin, polyurethane resin, and silicone resin; and the curing agent is at least one of polythiol, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydroanhydride, methylhexahydroanhydride, trimellitic anhydride, and pyromellitic anhydride.

[0023] In step (4), the mass ratio of modified polyaniline, film-forming substance and curing agent is 1:50:50~1:20:20, and the mass ratio of modified polyaniline and leveling agent is 5:1~15:1; the speed of the high-speed disperser is 1000~3000 rpm, and the stirring time is 5~10 min.

[0024] The method for synthesizing modified polyaniline in this invention is economical, green, and efficient. The method for preparing polyaniline coatings is simple to operate, has mild conditions, readily available materials, and is environmentally friendly. The resulting anti-corrosion coating has excellent barrier properties, anti-corrosion properties, and mechanical properties.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] (1) In this invention, ozone is used as an oxidant and Fe(III) is used as a catalyst to oxidize and polymerize aniline. The preparation process is economical, green and efficient. Furthermore, the ferric oxide precursor can be recycled after the reaction.

[0027] (2) The microbubble generation technology introduced in this invention can prolong the residence time of ozone in the emulsion, increase the contact opportunity between ozone and Fe(II), improve the utilization rate of ozone, generate more Fe(III) in the same time and participate in the oxidative polymerization reaction of aniline, accelerate the oxidative polymerization reaction rate of aniline, and improve the synthesis efficiency of the material.

[0028] (3) The polyaniline anti-corrosion coating obtained by the present invention uses alicyclic epoxy resin as the main film-forming substance, and has good thermal stability, weather resistance, electrical insulation properties and process performance. The polythiol curing agent is a neutral substance. Adding it to the polyaniline coating will not cause the dedoping of organic protic acid in the modified polyaniline. Compared with conventional alkaline curing agents, polythiol can enhance the corrosion resistance of the coating and extend the service life of the coating.

[0029] (4) The polyaniline anticorrosive coating obtained by the present invention has excellent barrier properties, anticorrosive properties and mechanical properties. Compared with pure epoxy resin coatings, it exhibits superior stability and long-term anticorrosive properties.

[0030] (5) The preparation process of the polyaniline anti-corrosion coating of the present invention is environmentally friendly and safe, with stable quality and high industrial application value. Attached Figure Description

[0031] Figure 1 This is a schematic diagram illustrating the microbubble generation principle in Embodiment 2 of the present invention;

[0032] Figure 2 This is a basic structural diagram of the Chinese-style treble tube in Embodiment 2 of the present invention;

[0033] Figure 3 The image shows the FTIR spectrum of the modified polyaniline in Example 2 of this invention.

[0034] Figure 4 The image shows the XRD pattern of the modified polyaniline in Example 2 of this invention.

[0035] Figure 5 This is a SEM image of the modified polyaniline in Example 2 of the present invention;

[0036] Figure 6 The GPC spectrum of the modified polyaniline in Example 1 of this invention is shown below.

[0037] Figure 7 The GPC spectrum of the modified polyaniline in Example 2 of this invention is shown below.

[0038] Figure 8 The yield graphs are for the modified polyaniline in Examples 1 and 2 of this invention.

[0039] Figure 9 This is a Nyquist plot of the epoxy coating in the comparative example of this invention;

[0040] Figure 10 This is a Nyquist plot of the modified polyaniline coating in Example 1 of the present invention;

[0041] Figure 11 This is a Nyquist plot of the modified polyaniline coating in Example 2 of the present invention;

[0042] Figure 12 The graph shows the variation of the low-frequency impedance modulus of the coating in Embodiments 1 and 2 and the comparative example of the present invention;

[0043] Explanation of reference numerals in the attached diagram: 1 Ozone generator, 2 Rotor flow meter, 3 Venturi tube, 4 Booster pump, 5 Circulation pipeline, 6 Peristaltic pump, 7 Inlet section, 8 Contraction section, 9 Inlet, 10 Throat section, 11 Diffusion section, 12 Outlet section. Detailed Implementation

[0044] The embodiments of the present invention will be described in detail below with reference to the examples. Those skilled in the art will understand that the following examples are only preferred embodiments of the present invention in order to better understand the present invention, but the scope of protection of the present invention is not limited to the following examples.

[0045] Example 1

[0046] A method for preparing a green and efficient modified polyaniline anticorrosive coating, comprising the following steps:

[0047] 1) Add 0.78 g of 2-acrylamide-2-methylpropanesulfonic acid and 120 ml of deionized water to a beaker, and stir magnetically for 10 min to fully dissolve the 2-acrylamide-2-methylpropanesulfonic acid. Then pour the solution into a glass reactor. Next, add 3.5 g of aniline and 120 ml of o-xylene to the beaker, and stir magnetically for 5 min to fully dissolve the aniline. Then pour the solution into the glass reactor and stir vigorously for 30 min to fully emulsify the mixture into an emulsion.

[0048] 2) Open the side valve of the glass reactor to allow the emulsion to enter the circulation pipeline, and then start the booster pump to make the emulsion flow slowly in the circulation device at a flow rate of 0.5 m / s.

[0049] 3) Weigh 5.84 g of magnetic iron oxide (Fe3O4) and add 60 ml of deionized water. Disperse the mixture ultrasonically for 10 min. Turn on the oxygen-source ozone generator. Ozone is introduced into the emulsion through a venturi tube in the form of ordinary bubbles (particle size 500 μm ~ 10 mm). Simultaneously, the magnetic iron oxide suspension is added dropwise (1 drop / 5 s) to the emulsion. The ozone flow rate is 2 L / min, the concentration is maintained at 100 mg / L (meaning that for every 1 L of gas produced by the ozone generator, the ozone content is 100 mg), and the introduction time is 120 min, i.e., the reaction time is 120 min. The entire reaction is carried out at 40 ℃ with continuous mechanical stirring.

[0050] 4) After the reaction is complete, pour 150 mL of acetone into the reaction system to demulsify, stir for 10 min, and then let it stand to separate into layers. Take the upper dark green solution, add an appropriate amount of acetone, stir and centrifuge to obtain the product.

[0051] 5) The collected precipitate was repeatedly washed with deionized water and acetone until all impurities were removed. The product was then vacuum dried at 60 °C for 24 h to obtain 2-acrylamido-2-methylpropanesulfonic acid-doped polyaniline.

[0052] 6) Weigh 125 mg of 2-acrylamide-2-methylpropanesulfonic acid-doped polyaniline and disperse it evenly in 4 mL of o-xylene solvent using an ultrasonic cleaner. Add 4 g of alicyclic epoxy resin TDE-85 and disperse the modified polyaniline in the alicyclic epoxy resin using a high-speed disperser at 1800 rpm for 8 min. Then add 10 mg of leveling agent and 4 g of polythiol 405 curing agent, stir and disperse, and centrifuge at low speed to obtain the modified polyaniline anticorrosive coating at 1800 rpm for 5 min. Finally, spray the prepared coating onto the iron sheet.

[0053] Example 2

[0054] A method for preparing a green and efficient modified polyaniline anticorrosive coating, comprising the following steps:

[0055] 1) Add 0.78 g of 2-acrylamide-2-methylpropanesulfonic acid and 120 ml of deionized water to a beaker, and stir magnetically for 10 min to fully dissolve the 2-acrylamide-2-methylpropanesulfonic acid. Then pour the solution into a glass reactor. Next, add 3.5 g of aniline and 120 ml of o-xylene to the beaker, and stir magnetically for 5 min to fully dissolve the aniline. Then pour the solution into the glass reactor and stir vigorously for 30 min to fully emulsify the mixture into an emulsion.

[0056] 2) Open the side valve of the glass reactor to allow the emulsion to enter the circulation pipeline, and then start the booster pump to make the emulsion flow rapidly in the circulation device at a flow rate of 1.5 m / s.

[0057] 3) Weigh 5.84 g of magnetic iron(III) oxide and add 60 ml of deionized water. Disperse the mixture ultrasonically for 10 min. Turn on the oxygen source ozone generator. Ozone is introduced into the emulsion via a venturi tube in the form of microbubbles (50-100 μm in diameter). Simultaneously, the magnetic iron(III) oxide suspension is added dropwise (1 drop / 5 s) to the emulsion. The ozone flow rate is 2 L / min, the concentration is maintained at 100 mg / L, and the introduction time is 120 min, i.e., the reaction time is 120 min. The entire reaction is carried out at 40 ℃ with continuous mechanical stirring.

[0058] 4) After the reaction is complete, pour 150 mL of acetone into the reaction system to demulsify, stir for 10 min, and then let it stand to separate into layers. Take the upper dark green solution, add an appropriate amount of acetone, stir and centrifuge to obtain the product.

[0059] 5) The collected precipitate was repeatedly washed with deionized water and acetone until all impurities were removed. The product was then vacuum dried at 60 °C for 24 h to obtain 2-acrylamido-2-methylpropanesulfonic acid-doped polyaniline.

[0060] 6) Weigh 125 mg of 2-acrylamide-2-methylpropanesulfonic acid-doped polyaniline and disperse it evenly in 4 mL of o-xylene solvent using an ultrasonic cleaner. Add 4 g of alicyclic epoxy resin TDE-85 and disperse the modified polyaniline in the alicyclic epoxy resin using a high-speed disperser at 1800 rpm for 8 min. Then add 10 mg of leveling agent and 4 g of polythiol 405 curing agent, stir and disperse, and centrifuge at low speed to obtain the modified polyaniline anticorrosive coating at 1800 rpm for 5 min. Finally, spray the prepared coating onto the iron sheet.

[0061] Comparative Example 1

[0062] To investigate the effect of modified polyaniline as a filler in epoxy coatings on their anti-corrosion performance, this comparative example used the same coating preparation process as Example 1. 4 mL of o-xylene solvent was measured and 4 g of alicyclic epoxy resin TDE-85 was added. The xylene and alicyclic epoxy resin were thoroughly mixed using a high-speed disperser at 1800 rpm for 8 min. Then, 10 mg of leveling agent and 4 g of polythiol 405 curing agent were added, and the mixture was stirred to obtain the epoxy coating at 1800 rpm for 5 min. Finally, the prepared coating was sprayed onto an iron sheet.

[0063] Figure 1This is a schematic diagram of the basic process for preparing modified polyaniline in Example 2 of the present invention. Figure 2 The diagram shows the basic structure of the Venturi tube in Embodiment 2 of this invention. Based on fluid dynamics calculations, the local pressure at the throat of the Venturi tube is lower than the ambient pressure. The fluid entering the generator rotates at high speed under pressure, forming a negative pressure shaft in the middle of the generator, thus drawing the gas into the generator. When the gas comes into contact with the rapidly flowing emulsion, high-speed and strong shearing and high-frequency pressure changes occur at the gas-liquid interface, generating a large number of micron and nano-sized bubbles.

[0064] Figure 3 This is the FTIR spectrum of the modified polyaniline in Example 2 of this invention. 1565 cm⁻¹ -1 and 1483 cm -1 The characteristic absorption peaks at 1296 cm⁻¹ are attributed to stretching vibrations of the quinone structure and the benzene structure, respectively; -1 The characteristic absorption peak at 1126 cm⁻¹ is caused by the CN stretching of the aromatic amine; -1 and 793 cm -1 The characteristic absorption peaks are attributed to the in-plane and out-of-plane bending vibrations of the aromatic CH groups on the 1,4-disubstituted aromatic ring, respectively; at 3443 cm⁻¹ -1 The broadband observed at 2892 cm⁻¹ is related to the stretching and contraction of HNH, indicating that the polyaniline structure has been formed. Meanwhile, at 2892 cm⁻¹... -1 A more characteristic peak appeared nearby, which may be related to the CH stretching of the methyl group in the 2-acrylamido-2-methylpropanesulfonic acid molecule, indicating that 2-acrylamido-2-methylpropanesulfonic acid has been successfully doped into the polyaniline molecular chain.

[0065] Figure 4The image shows the XRD pattern of the modified polyaniline in Example 2 of this invention. It can be seen from the image that there are obvious characteristic peaks at 2θ = 21.2° and 2θ = 25.3°. The peak at 2θ = 21.2° represents the periodic arrangement of the polyaniline molecular chains in the parallel direction, corresponding to the (020) crystal plane diffraction peak of polyaniline. This is attributed to the amorphous nature of polyaniline, where amorphous scattering mainly occurs around 2θ = 21.2°. The characteristic diffraction peak related to the interplanar spacing between anilines is located at 2θ = 25.3°, representing the periodic arrangement of the polyaniline molecular chains in the perpendicular direction, corresponding to the (200) crystal plane diffraction peak of polyaniline, indicating that the crystallinity of polyaniline has been improved. This is because the incorporation of organic acids into polyaniline induces a protonation effect in the polymer chains, while also increasing the spacing between the polyaniline molecular chains. 2-Acrylamido-2-methylpropanesulfonic acid, being a macromolecular dopant, can improve the crystallinity of polyaniline. The polymer chains are arranged in a periodic, ordered parallel state, enhancing the stability and regularity of the polyaniline structure. Therefore, as an anti-corrosion filler, polyaniline exhibits a lower percolation threshold and better electrical conductivity. This improved conductivity further enhances polyaniline's ability to passivate metals, more effectively preventing the intrusion of corrosive media, thereby improving the anti-corrosion performance of the corresponding polyaniline coating.

[0066] Figure 5 This is a SEM image of the modified polyaniline in Example 2 of the present invention. The polyaniline surface in the image is relatively rough, generally exhibiting a granular structure, with some areas showing a certain degree of agglomeration. The spherical particles on the material surface are closely arranged and interwoven, exhibiting good uniformity and density.

[0067] Figure 6 and Figure 7 The GPC spectra of the modified polyaniline in Examples 1 and 2 of this invention are shown below. Figure 8 The figures show the yields of modified polyaniline in Examples 1 and 2 of this invention. When ozone was introduced into the emulsion in the form of ordinary bubbles, the yield of modified polyaniline after the reaction was 49.2%, and the weight-average molecular weight was 3604. As can be seen from the yield and weight-average molecular weight of Example 2, the yield and weight-average molecular weight of modified polyaniline under the same reaction conditions were improved after introducing microbubble generation technology. This is because microbubbles have a higher mass transfer rate and energy in the fluid. Their formation increases the specific surface area of ​​gas-liquid contact, enhances the solubility of gas in the fluid, and prolongs the residence time of ozone in the emulsion. Therefore, it increases the contact opportunities between ozone and Fe(II), improves the utilization rate of ozone, and generates more Fe(III) in the same time period, participating in the oxidative polymerization reaction of aniline, thus improving the reaction efficiency of the entire polymerization process.

[0068] Figure 9This is a Nyquist plot of the epoxy coating in the comparative example of this invention. Figure 12 The graphs show the changes in the low-frequency impedance modulus of the coatings in Examples 1 and 2 of this invention, as well as the comparative example. From the Nyquist plot of the epoxy coating, it can be seen that the radius of the capacitive arc decreases sharply with the increase of immersion days, indicating that the anti-corrosion performance of the coating gradually declines. Furthermore, we can observe that when the immersion time continues to the 5th day, the shape of the Nyquist curve changes compared to before; the curve changes from a single capacitive arc to two capacitive arcs of different radii. This indicates that the corrosive medium has penetrated into the coating and caused a corrosive reaction on the metal surface. The coating gradually loses its original protective effect during immersion and no longer provides long-term corrosion resistance to the metal. Combined with… Figure 12 After 7 days of immersion, the low-frequency impedance modulus value of the coating (|Z|) 0.01 Hz The value is 1.4 × 10 7 Ω·cm 2 . Figure 10 The image shows the Nyquist plot of the modified polyaniline coating in Example 1 of this invention. The plot shows that the radius of the capacitive arc first decreases, then increases, and then decreases again, indicating that the coating has a certain corrosion inhibition effect. Combined with... Figure 12 The coating's |Z| 0.01 Hz The value ranges from 4.67 × 10 9 Ω·cm 2 (1h) decreased to 1.01×10 9 Ω·cm 2 (1d), then rose to 2.62×10 9 Ω·cm 2 (2d), then the |Z| of the coating 0.01 Hz The value increased from 2.62 × 10 on the second day. 9 Ω·cm 2 It continued to decline to 5.97 × 10 on the 7th day. 7 Ω·cm 2 Compared with the EIS results of the epoxy coating in the comparative example, the modified polyaniline coating in Example 1 exhibited superior corrosion resistance and barrier properties. Figure 11 The image shows the Nyquist plot of the modified polyaniline coating in Example 2 of this invention. The trend of the change in the capacitive arc radius is similar to that of the modified polyaniline coating in Example 1. Combined with... Figure 12 , its |Z| 0.01 Hz The value is from 8.89 × 10 9 Ω·cm 2 (1h) decreased to 1.03×10 8 Ω·cm 2 (4 days), gradually increasing to 2.63 × 10 8 Ω·cm 2(6 days), then decreased to 7.71 × 10 7 Ω·cm 2 Compared to the modified polyaniline coating in Example 1, the modified polyaniline coating in Example 2 exhibits higher |Z| during immersion. 0.01 Hz It has a high value and also exhibits better long-term anti-corrosion effect.

[0069] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for preparing a green and efficient modified polyaniline anticorrosive coating, characterized in that, Includes the following steps: (1) Dissolve the aniline monomer and the doped acid in an oily solvent and deionized water respectively, stir magnetically until completely dissolved, and then pour them into a glass reactor and stir thoroughly to obtain an emulsion; (2) Introduce the emulsion into the circulation pipe (5), and then turn on the booster pump (4) to make the emulsion flow in the circulation pipe; (3) Disperse the catalyst precursor in deionized water; start the ozone generator (1), and at the same time adjust the rotor flow meter (2) to control the flow rate of ozone. The ozone gas is introduced into the emulsion in the form of microbubbles through the venturi tube (3). At the same time, the catalyst precursor suspension is added to the emulsion dropwise through the peristaltic pump (6) for reaction. (4) After the reaction is complete, the collected precipitate is centrifuged, washed and dried to obtain modified polyaniline; (5) The modified polyaniline in step (4) is uniformly dispersed in an oily solvent, a film-forming substance is added, and the modified polyaniline is fully dispersed in the film-forming substance using a high-speed disperser. Then, a leveling agent and a curing agent are added, and the mixture is stirred, dispersed, and centrifuged at low speed to obtain the modified polyaniline anti-corrosion coating. In step (3), the ozone flow rate is 1~3 L / min and the concentration is 100 mg / L; the microbubble particle size is 50~100 μm; After the catalyst precursor suspension is added dropwise, the molar ratio of aniline monomers to catalyst precursors in the emulsion is 1~5:1, the concentration of aniline monomers is 0.1~2 mol / L, the concentration of doped acid is 0.01~0.2 mol / L, the concentration of catalyst precursors is 0.05~1 mol / L, and the volume ratio of oily solvent to deionized water is 1:1~3; the reaction temperature is 20~60 ℃, the reaction time is 90~180 min, and the dropping rate of the catalyst precursor suspension is 1 drop / 5 s; In step (5), the oily solvent is at least one of toluene, xylene, ethanol, N-methylpyrrolidone, N,N-dimethylformamide, tetrahydrofuran, trichloroethylene, and carbon disulfide; the film-forming substance is an alicyclic epoxy resin; and the curing agent is polythiol. In step (5), the mass ratio of modified polyaniline, film-forming substance and curing agent is 1:20~50:20~50; the mass ratio of modified polyaniline and leveling agent is 5~15:1; the speed of high-speed disperser is 1000~3000 rpm, and the stirring time is 5~10 min.

2. The preparation method of the green and efficient modified polyaniline anticorrosive coating according to claim 1, characterized in that: In step (1), the aniline monomer is at least one of aniline, acetaniline, o-benzylaniline, 2-ethynylaniline, 3-ethoxyaniline, 2,6-diisopropylaniline, 2,4-dimethoxyaniline, and 2-isopropenylphenylaniline; the oily solvent is at least one of toluene, xylene, ethanol, N-methylpyrrolidone, N,N-dimethylformamide, tetrahydrofuran, trichloroethylene, and carbon disulfide.

3. The preparation method of the green and efficient modified polyaniline anticorrosive coating according to claim 1, characterized in that: In step (1), the doped acid is at least one of hydrochloric acid, perfluorooctanoic acid, 2-acrylamide-2-methylpropanesulfonic acid, dodecylbenzenesulfonic acid, salicylic acid, p-toluenesulfonic acid, phosphoric acid, and camphorsulfonic acid.

4. The preparation method of the green and efficient modified polyaniline anticorrosive coating according to claim 1, characterized in that: In step (1), the molar ratio of aniline monomers to doped acid is 5~15:

1.

5. The preparation method of the green and efficient modified polyaniline anticorrosive coating according to claim 1, characterized in that: In step (2), the emulsion flow rate is 0.5~1.5 m / s.

6. The method for preparing the green and efficient modified polyaniline anticorrosive coating according to claim 1, characterized in that: In step (3), the catalyst precursor is at least one of magnetic iron oxide, ferrous chloride, ferrous fumarate, ferrous ethylenediammonium sulfate, ferrous lactate, ferrous oxalate, ferrous trifluoromethanesulfonate, and ferrous gluconate.

7. The preparation method of the green and efficient modified polyaniline anticorrosive coating according to claim 1, characterized in that: In step (4), the detergent is at least one of deionized water, methanol, ethanol, and acetone; the drying temperature is 40~60 ℃ and the drying time is 12~24 h.

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