Amphoteric polyaniline coated silicon dioxide suspension and preparation method and application thereof

Abstract

The invention belongs to the technical field of water-based coatings, and relates to an amphoteric polyaniline coated silicon dioxide suspension and a preparation method and application thereof.Hydrophobic nano silicon dioxide sol is prepared in the presence of an emulsifier and organic liquid through an improved sol-gel method and an emulsion polymerization technology; carrying out surface grafting by utilizing a silane coupling agent containing an epoxy group to obtain an epoxy functionalized silicon dioxide suspension; then under an acidic low-temperature condition, taking the suspension as a core, enabling aniline, fumaric acid and long-chain hydrophobic silane to be subjected to reactivity reaction under the action of an oxidizing agent, and firmly grafting polyaniline to the surface of silicon dioxide through ring-opening reaction of an epoxy group and an amino group to form an interpenetrating network shell layer with hydrophobic long-chain alkyl and hydrophilic carboxyl. The obtained filler is not additionally added with a surfactant, has good dispersity and hydrophilicity in a water suspension state, and shows super-hydrophobicity and excellent corrosion resistance after being dried into powder, and the filler suspension can be directly added into an anionic water-based coating, so that the physical shielding and electrochemical protection capabilities of the coating are remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of water-based coating technology, and relates to an amphoteric polyaniline-coated silica suspension, its preparation method, and its application. Background Technology

[0002] Polyaniline, due to its excellent electrical conductivity and redox properties, shows promising application prospects in the field of metal corrosion protection. Currently, commercially available polyaniline anti-corrosion coatings exist abroad, such as CORRPASSIV™, ORMECON™, and Versicon™ coatings. Domestically, companies like Fenyangtang (Shanghai) Industrial Co., Ltd. have industrialized products, but their application is not widespread, and the market has not yet truly opened up. This is mainly because polyaniline is a rigid oligomer with poor compatibility with the matrix polymer, is insoluble in water, difficult to melt, and has poor processing performance.

[0003] Improving the dispersibility of polyaniline (PAN) is crucial because it exhibits hydrophilic properties in aqueous dispersions but superhydrophobic properties (amphotropic characteristics) in dried powder forms. This is a key challenge for effectively utilizing PAN's anti-corrosion properties in water-based coatings. Existing technologies for preparing PAN for water-based coatings suffer from at least the following problems: Most existing PAN powders are designed for organic solvent-based coatings, with few reports on their application in water-based coatings; many researchers improve the dispersibility of dried PAN powder by directly polymerizing PAN on the surface of nanoparticles, but the bonding strength between PAN and the powder is weak, resulting in poor hydrophilicity and easy agglomeration in water; some patents report using hydrophilic silicates as a core followed by PAN polymerization to increase PAN's hydrophilicity, but the powder still exhibits hydrophilicity, which is detrimental to the hydrophobic and anti-corrosion properties of water-based coatings. These methods for improving PAN's dispersibility only achieve good dispersion in the powder stage or in aqueous solutions, but the powder still agglomerates after drying, exhibiting hydrophilicity and thus not being practically applicable to water-based superhydrophobic coating formulations. In addition, the multifunctionality of fillers is the current development direction, but most of the polyaniline preparation methods provided by research only have single anti-corrosion properties. Combining other properties such as hydrophobicity, flexibility and water dispersibility with the anti-corrosion properties of polyaniline is an urgent problem that needs to be solved in water-based polyaniline industrial paints. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides an amphoteric polyaniline-coated silica suspension, its preparation method, and its applications. On one hand, the sol-gel method is improved by introducing emulsifiers and organic liquids, utilizing emulsion polymerization, and employing a ring-opening reaction between epoxy groups and amino groups in the oil phase to increase the bonding strength between polyaniline and the core, thereby improving hydrophobicity, particle size uniformity, and dispersibility. On the other hand, through a competitive polymerization reaction of aniline, long-chain silanes, and fumaric acid, an interpenetrating network shell layer is grafted onto the surface of the nano-silica carrier in the oil phase. This shell layer simultaneously contains hydrophobic methyl and methylene groups as well as hydrophilic carboxyl groups, adsorbing onto steel surfaces and exhibiting hydrophobic and anti-corrosion properties. Through these two technical means, a novel polyaniline filler is obtained, exhibiting hydrophilic properties in the suspension state and superhydrophobic and corrosion-resistant, uniformly sized polyaniline filler in the dried powder stage.

[0005] This invention is achieved through the following technical solution: A method for preparing an amphoteric polyaniline-coated silica suspension, comprising: S1. Add a mixed solution of tetraethyl orthosilicate and methyltrimethoxysilane to a mixed solution of anionic emulsifier and organic liquid to obtain a silica pre-emulsion. S2. After adding ammonia and nonionic emulsifier to the silica pre-emulsion, hydrophobic nano silica sol is obtained. S3. Add the silane coupling agent and anionic emulsifier to a mixed solution of organic liquid and deionized water to obtain a modifier pre-emulsion. S4. Add the pre-emulsion of the modifier to the hydrophobic nano silica sol to prepare a water-dispersible nano silica suspension grafted with epoxy groups. S5. Under acidic low temperature conditions, fumaric acid and ammonium persulfate were added to a water-dispersible nano-silica suspension grafted with epoxy groups, followed by the addition of long-chain hydrophobic silane, nonionic emulsifier and aniline, and the reaction was carried out to obtain a polyaniline-coated silica reaction pre-emulsion. S6. Add ammonium persulfate and nonionic emulsifier to the pre-emulsion of polyaniline-coated silica reaction, followed by fumaric acid and long-chain hydrophobic silane. After the reaction, wash the reaction product until neutral, and then adjust the solution with deionized water and ammonia to obtain an amphoteric polyaniline-coated silica suspension.

[0006] Preferably, the mixing ratio of tetraethyl orthosilicate and methyltrimethoxysilane in S1 is 4:1; the addition ratio of anionic emulsifier and organic liquid in S1 is 0.15~0.25g:10~15mL; The addition ratio of the organic liquid to the mixed solution of tetraethyl orthosilicate and methyltrimethoxysilane in S1 is 10~15mL: 30~40mL; The amount of ammonia added in S2 is 15~30mL, and the amount of nonionic emulsifier added is 0.1~0.2g; The reaction temperature in S2 is 50~60℃, and the reaction time is 0.5~1h; The addition ratio of silane coupling agent to anionic emulsifier in S3 is 2~3mL:0.1~0.15g, and the addition amount of the mixed solution of organic liquid and deionized water is 10~20mL; the volume ratio of organic liquid to deionized water is 1:4.

[0007] Preferably, in step S4, when the pre-emulsion of the modifier is added dropwise to the hydrophobic nano-silica sol, 5-10 mL of deionized water needs to be added dropwise to the reaction system, and the reaction time is 1-1.5 h.

[0008] Preferably, the acidic low-temperature conditions described in S5 specifically involve adjusting the pH of the water-dispersible nano-silica suspension with grafted epoxy groups to 1-2 using hydrochloric acid solution; and setting the low-temperature temperature to 5-10°C. The amount of fumaric acid added is 0.3~0.6g, and the amount of ammonium persulfate added is 1~1.2g; The addition ratio of the long-chain hydrophobic silane, nonionic emulsifier and aniline is 2~3mL: 0.1~0.15g: 2~3mL.

[0009] Preferably, in S6, the addition ratio of ammonium persulfate, fumaric acid and long-chain hydrophobic silane is 5~7g:0.3~0.5g:1~2mL; the reaction temperature is 60~70℃; and the reaction time is 20~30min.

[0010] Preferably, the anionic emulsifier is at least one selected from sodium dodecylbenzenesulfonate, sodium oleate, sodium dodecyl diphenyl ether disulfonate, sodium dodecyl sulfate, sodium stearate, and sodium laurate. The organic liquid is any one of n-octane, n-heptane, n-dodecane, and n-tetradecane; The nonionic emulsifier is selected from at least one of sorbitan trioleate, diethylene glycol monolaurate, fatty alcohol polyoxyethylene ether, polyethylene glycol 400 dioleate, polyoxyethylene (4) octylphenol ether, polyethylene glycol 600 dioleate and octylphenol polyoxyethylene ether.

[0011] Preferably, the long-chain hydrophobic silane is octadecyltrimethoxysilane or octadecyltriethoxysilane; The silane coupling agent is a silane coupling agent with epoxy groups and methoxy or ethoxy groups at both ends, and its structure is shown below: , R1 is a carbon chain or a carbon chain containing ether bonds.

[0012] Preferably, the absolute value of the Zeta potential of the silica pre-emulsion, the modifier pre-emulsion, and the water-dispersible nano-silica suspension grafted with epoxy groups is controlled by the amount of anionic emulsifier and ammonia added, and is greater than 30mV. The amphoteric polyaniline-coated silica suspension is controlled by adding ammonia to maintain an absolute Zeta potential greater than 15 mV, a pH of 9-10, and a conductivity greater than 10. -3 S·cm -1 .

[0013] An amphoteric polyaniline-coated silica suspension is prepared based on the aforementioned method for preparing an amphoteric polyaniline-coated silica suspension.

[0014] Application of an amphoteric polyaniline-coated silica suspension in water-based coatings An amphoteric polyaniline-coated silica suspension was prepared to a concentration of 60 wt%~70 wt% and then added to a water-based coating. The water-based coating includes one of anionic emulsion coatings, anionic water-dispersible resin coatings, or anionic water-soluble resin coatings.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: This invention provides an amphoteric polyaniline-coated silica suspension, its preparation method, and its applications. On one hand, the sol-gel method is modified by introducing emulsifiers and organic liquids, utilizing emulsion polymerization, and employing ring-opening reactions of epoxy groups and amino groups in the oil phase to increase the bonding strength between polyaniline and the core, thereby improving hydrophobicity, particle size uniformity, and dispersibility. On the other hand, through a competitive polymerization reaction of aniline, long-chain silanes, and fumaric acid, an interpenetrating network shell layer is grafted onto the surface of the nano-silica carrier in the oil phase. This shell layer simultaneously contains hydrophobic methyl and methylene groups as well as hydrophilic carboxyl groups, adsorbing onto steel surfaces and exhibiting hydrophobic and anti-corrosion properties. Through these two technical means, a novel polyaniline filler is obtained, exhibiting hydrophilic properties in the suspension state and superhydrophobic and corrosion-resistant, uniformly sized polyaniline filler in the dried powder stage.

[0016] The amphoteric polyaniline-coated silica prepared by this invention does not require drying, mechanical grinding, or surfactant dispersion; it exhibits good dispersibility. A suspension of amphoteric polyaniline-coated silica can be directly obtained by adding deionized water and ammonia in a certain proportion, making it suitable for use in water-based coatings. The 60-70 wt% suspension has a Zeta potential absolute value greater than 15 mV and a conductivity greater than 102. -3 S·cm -1 It exhibits good suspension dispersion stability and electrical conductivity, is highly practical and easy to operate, and when added to water-based coatings, it can form a hydrophobic, anti-corrosion, and passivation film on the surface of steel.

[0017] Furthermore, this invention improves the sol-gel method by introducing anionic emulsifiers, nonionic emulsifiers, and organic liquids, and by changing the amount of ammonia added. This results in a silica pre-emulsion with a high stability and a water-dispersible nano-silica suspension with grafted epoxy groups, characterized by an absolute Zeta potential greater than 30mV. The emulsion polymerization method is used, and a special silane coupling agent is employed in the oil phase to perform a ring-opening reaction between the epoxy groups on the polyaniline and the amino groups on the polyaniline. This increases the bonding strength between the polyaniline and the nano-silica core, thereby improving hydrophobicity, particle size uniformity, and dispersibility.

[0018] Furthermore, this invention controls the competitive polymerization reaction of aniline, long-chain silane, and fumaric acid, and grafts an interpenetrating network shell layer onto the surface of a nano-silica carrier in the oil phase. This shell layer simultaneously contains hydrophobic methyl and methylene groups as well as hydrophilic carboxyl groups. In suspension and under alkaline conditions, the carboxyl-containing chains elongate, exhibiting hydrophilic properties. However, in the drying powder stage, ammonia evaporates, causing the carboxyl chains to contract and the hydrophobic methyl chains to elongate, resulting in superhydrophobicity and corrosion resistance. This improves the thixotropic, hydrophobic, and corrosion-resistant properties of waterborne coatings. The contact angle of the dried amphoteric polyaniline-coated silica powder is greater than 150° as measured by a contact angle meter. After 240 hours of accelerated neutral salt spray testing, no rust was found at the scratches of the waterborne coating containing 2 wt% amphoteric polyaniline-coated silica. The waterborne coating base material is an anionic emulsion, anionic water-dispersible resin, or anionic water-soluble resin. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 Scanning electron microscope image of blank nano-silica; Figure 2 Scanning electron microscope image of water-dispersible silica nanoparticles grafted with epoxy groups; Figure 3 Optical diagram of the contact angle of blank polyaniline-coated silica powder with deionized water; Figure 4 Optical image of a 60 wt% amphoteric polyaniline-coated silica suspension; Figure 5 Scanning electron microscope image of amphoteric polyaniline coated with silica; Figure 6The particle size distribution of blank nano-silica, water-dispersible nano-silica grafted with epoxy groups, and amphoteric polyaniline-coated silica powder; Figure 7 Optical diagram of the contact angle of amphoteric polyaniline-coated silica powder with deionized water; Figure 8 Optical image of a blank water-based coating (commercial anionic water-based paint) after 240 hours of accelerated neutral salt spray testing; Figure 9 Optical image of the sample plate after 240 hours of accelerated neutral salt spray testing on amphoteric polyaniline coated with silica. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0022] A method for preparing an amphoteric polyaniline-coated silica anticorrosive filler and its suspension, specifically comprising: T1: Synthesis of Epoxidized Nano-Silica Suspension a. Add 100-120 mL of deionized water to a four-necked flask, add 0.15-0.25 g of anionic emulsifier, and add 10-15 mL of organic liquid. Stir evenly for 10-15 min. b. Take 30-40 mL of a mixed solution of tetraethyl orthosilicate and methyltrimethoxysilane, wherein the ratio of tetraethyl orthosilicate to methyltrimethoxysilane is 4:1. Slowly add the solution dropwise to the mixed solution in step a while stirring slowly. Then adjust the stirring speed to 400-500 rpm and stir for 10-20 min to obtain a silica pre-emulsion. In this invention, the process of preparing silica nanoparticles via the sol-gel method involves the hydrolysis of tetraethyl orthosilicate to generate silanol, which then condenses to form a Si-O-Si network. The methyl group of methyltrimethoxysilane provides hydrophobicity. c. Heat the water bath to 50-60℃, place the silica pre-emulsion in it, and slowly add 15-30mL of 25% ammonia water dropwise while stirring magnetically at 50-100 rpm. During this process, add 0.1-0.2g of nonionic emulsifier diluted to 10mL. The addition of ammonia water and nonionic emulsifier allows the ammonia water to catalyze the hydrolysis and condensation reaction, promoting the formation and growth of silica nanoparticles, while the nonionic emulsifier helps stabilize the formed nanoparticles. d. After the addition is complete, react for 0.5~1h to obtain a hydrophobic nano silica sol rich in hydroxyl groups and a small amount of methyl groups; e. Dilute 2-3 mL of silane coupling agent and 0.1-0.15 g of anionic emulsifier into a mixed solution of 10-20 mL of organic liquid and deionized water to obtain a pre-emulsion of the modifier, wherein the ratio of organic liquid to deionized water is 1:4; the silane coupling agent containing epoxy groups reacts with the silanol groups on the surface of silica to graft the epoxy groups onto the surface of silica; f. Under magnetic stirring at 50-100 rpm, the pre-emulsion of the modifier is slowly added dropwise to the hydrophobic nano-silica sol, and 5-10 mL of deionized water is added dropwise in a timely and slow manner. The reaction is allowed to proceed for 1-1.5 h, and then cooled to room temperature to obtain a water-dispersible nano-silica suspension grafted with epoxy groups. In this invention, the pre-emulsion of the modifier is added to the silica sol. One end of the silane coupling agent undergoes hydrolytic condensation with the silanol on the silica surface to form Si-O-Si bonds, while the other end provides epoxy groups.

[0023] T2: Preparation of Multifunctional Amphoteric Polyaniline-Coated Silica Anticorrosive Filler and Suspension a. Cool the water bath and four-necked flask to 5-10°C by adding ice, and control the temperature with a thermometer to prepare for the polyaniline grafting reaction. b. Adjust the pH of the nano-silica suspension grafted with epoxy groups to 1-2 by adding a certain amount of 36% hydrochloric acid solution. Add 0.3-0.6g of fumaric acid to a four-necked flask and stir evenly. Then add 1-1.2g of ammonium persulfate and activate the reaction for 20-30 minutes. Immediately afterward, add 2-3mL of long-chain hydrophobic silane. During this process, add 0.1-0.15g of nonionic emulsifier diluted to 10mL and stir for 10-15 minutes. Then add 2-3mL of aniline and adjust the speed to 60-100 rpm. Stir for 5-10 minutes to form a pre-emulsion for polyaniline-coated silica reaction. Ammonium persulfate oxidizes aniline and initiates the polymerization reaction. The carboxyl groups of fumaric acid can react with the amino groups of aniline or the epoxy groups on the silica surface. The long-chain hydrophobic silane reacts with the surface to increase hydrophobicity. Aniline polymerizes on the silica surface to form a polyaniline shell. c. Next, dissolve 5-7g of ammonium persulfate in 20-30mL of water and add it dropwise at 1-2 drops per second, while adding 0.06-0.1g of nonionic emulsifier during the process. Observe the suspension change from milky white to yellow, and then to dark green. Heat the water bath to 60-70℃, add 0.3-0.5g of fumaric acid and 1-2mL of long-chain hydrophobic silane, and react for 20-30 minutes. The reaction is then complete, and a water-dispersible polyaniline-coated silica suspension with high conductivity is obtained. d. The obtained high-conductivity water-dispersible polyaniline-coated silica suspension is filtered to remove unreacted substances and washed until the filtrate is neutral. In order to further promote the polymerization and grafting reactions and form a more complete coating layer, unreacted substances are washed away. Finally, the pH and zeta potential are adjusted with ammonia to ensure the stability of the suspension. e. Add 25-35 mL of deionized water and 3-5 mL of ammonia to the neutrally wetted polyaniline-coated silica to prepare a 60-70 wt% multifunctional amphoteric polyaniline-coated silica suspension that can be directly added to water-based coatings.

[0024] The anionic emulsifier used in step T1 is sodium dodecylbenzene sulfonate, sodium oleate, sodium dodecyl diphenyl ether disulfonate, sodium dodecyl sulfate, sodium stearate, or sodium laurate. The organic liquid involved in step T1 is any one of n-octane, n-heptane, n-dodecane, and n-tetradecane, which contain hydrophobic groups. Among them, the absolute value of the Zeta potential of the silica pre-emulsion, the modifier pre-emulsion and the water-dispersible nano-silica suspension grafted with epoxy groups in step T1 is controlled by the amount of anionic emulsifier and ammonia added, and is greater than 30mV. In step T1, the silane coupling agent must be a silane coupling agent with epoxy groups and methoxy or ethoxy groups at both ends, as shown below, where R1 is a carbon chain or a carbon chain containing ether bonds:

[0025] Preferably, it is any one of 5,6-epoxyhexyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and 3-glycidoxypropylmethyldimethoxysilane; In particular, the long-chain hydrophobic silane in step T2 must be octadecyltrimethoxysilane or octadecyltriethoxysilane with more than 18 carbon atoms. The nonionic emulsifiers used in steps T1 and T2 are sorbitan trioleate, diethylene glycol monolaurate, fatty alcohol polyoxyethylene ether, polyethylene glycol 400 dioleate, polyoxyethylene (4) octylphenol ether, polyethylene glycol 600 dioleate, or octylphenol polyoxyethylene ether (OP-10). In step T2, the multifunctional amphoteric polyaniline-coated silica suspension is controlled by adding ammonia to maintain an absolute Zeta potential greater than 15 mV, a pH of 9-10, and a conductivity greater than 10. -3 S·cm -1 .

[0026] Among them, the water-based coating systems for which the amphoteric polyaniline-coated silica suspension is applicable are anionic emulsion coatings, anionic water-dispersible resin coatings, or anionic water-soluble resin coatings.

[0027] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1 The reaction and preparation steps are as follows: T1: Synthesis of Epoxidized Nano-Silica Suspension a. Add 120 mL of deionized water to a four-necked flask, add 0.15~0.25 g of sodium lauryl flask, and add 10-15 mL of n-octane. Stir evenly for 15 min. b. Take 40 mL of a mixed solution of tetraethyl orthosilicate and methyltrimethoxysilane, wherein the ratio of tetraethyl orthosilicate to methyltrimethoxysilane is 4:1. Slowly add it dropwise to the mixed solution in step a and stir slowly. Then adjust the speed to 500 rpm and stir for 20 min to obtain a silica pre-emulsion. c. Heat the water bath to 60°C, place the silica pre-emulsion in the bath, and slowly add 15-30 mL of 25% ammonia water dropwise while stirring magnetically at 50 rpm. During this process, add 0.1-0.2 g of sorbitan trioleate diluted to 10 mL. d. After the addition is complete, react for 1 hour to obtain a nano-hydrophobic silica sol rich in hydroxyl groups and a small amount of methyl groups; e. Dilute 3 mL of 5,6-epoxyhexyltriethoxysilane and 0.1~0.15 g of sodium dodecyl diphenyl ether disulfonate into a mixed solution of 10~20 mL of n-octane and deionized water to obtain a pre-emulsion of the modifier, wherein the ratio of n-octane to deionized water is 1:4. f. Under magnetic stirring at 50 rpm, the pre-emulsion of the modifier is slowly added dropwise to the nano-hydrophobic silica sol, and 10 mL of deionized water is added dropwise in a timely manner. The reaction is carried out for 1.5 h, and then cooled to room temperature to obtain a water-dispersible nano-silica suspension grafted with epoxy groups.

[0029] T2: Preparation of Multifunctional Amphoteric Polyaniline-Coated Silica Anticorrosive Filler and Suspension a. Cool the water bath and four-necked flask to 5°C by adding ice, and control the temperature with a thermometer to prepare for the polyaniline grafting reaction. b. Adjust the pH of the nano-silica suspension grafted with epoxy groups to 1 by adding a certain amount of 36% hydrochloric acid solution. Add 0.6g of fumaric acid to a four-necked flask and stir evenly. Then add 1g of ammonium persulfate and activate for 30min. Immediately afterward, add 3mL of octadecyltrimethoxysilane. During this process, add 0.15g of sorbitan trioleate diluted to 10mL and stir for 15min. Then add 3mL of aniline, adjust the speed to 60 rpm, and stir for 10min to form a pre-emulsion of polyaniline-coated silica. c. Next, dissolve 5g of ammonium persulfate in 30mL of water and add it drop by drop using a dropper, while adding 0.1g of diethylene glycol monolaurate during the process. Observe the suspension change from milky white to yellow, and then to dark green. Heat the water bath to 70℃, add 0.3g of fumaric acid and 1mL of octadecyltrimethoxysilane, and react for 30min. The reaction is then complete, and a water-dispersible polyaniline-coated silica suspension with high conductivity is obtained. d. Remove unreacted substances from the obtained polyaniline-coated silica suspension by passing it through a vacuum filter and washing until the filtrate is neutral; e. Add 25 mL of deionized water and 3 mL of ammonia to the neutrally wetted polyaniline-coated silica to prepare a 70 wt% multifunctional amphoteric polyaniline-coated silica suspension that can be directly added to water-based coatings.

[0030] In step T1, the zeta potential was measured using a nanoparticle size and zeta potential analyzer to evaluate the dispersion stability of the obtained silica preemulsion and water-dispersible grafted epoxy group nano-silica suspension. The zeta potentials of the silica preemulsion and water-dispersible grafted epoxy group nano-silica suspension with different reagent contents were studied, as shown in Table 1. With increasing amounts of sodium laurylate anionic emulsifier and n-octane, the absolute value of the zeta potential of the silica preemulsion generally increased. When the amounts of sodium laurylate were 0.15–0.25 g and n-octane were 10–17.5 mL, the absolute value of the zeta potential of the silica preemulsion was above 30 mV (an absolute value above 30 mV indicates excellent dispersion stability of the emulsion), reaching a maximum of 33.2 mV, as shown in Table 1. Following this, based on the silica pre-emulsion, the amounts of 25% ammonia, sorbitan trioleate nonionic emulsifier, sodium dodecyl diphenyl ether disulfonate anionic emulsifier, and n-octane were increased. The absolute value of the Zeta potential of the water-dispersible grafted epoxy group nano silica suspension also generally increased. When 15-30 mL of 25% ammonia, 0.1-0.2 g of sorbitan trioleate, 0.1-0.15 g of sodium dodecyl diphenyl ether disulfonate, and 2-4 mL of n-octane were added, the absolute value of the Zeta potential of the water-dispersible grafted epoxy group nano silica suspension was above 30 mV, and could reach a maximum of 33.4 mV, as shown in Table 1. Considering the stability of the pre-emulsion and the increased cost due to increased reagent usage, the following steps are used: sodium laurate 0.15-0.25g and n-octane 10-15mL in steps a and b; 25% ammonia 15-30mL, sorbitan trioleate 0.1-0.2g, sodium dodecyl diphenyl ether disulfonate 0.1-0.15g and n-octane 2-4mL in steps c, d, e and f.

[0031] Table 1. Zeta potential values ​​of silica preemulsion and water-dispersible nano-silica suspension with grafted epoxy groups at different reagent contents.

[0032] The blank nano-silica exhibits severe agglomeration, such as Figure 1 As shown; Figure 2 As shown, this invention, by improving the sol-gel method and using anionic emulsifiers, nonionic emulsifiers, organic liquids, and ammonia to control the absolute value of the Zeta potential of water-dispersible grafted epoxy group nano-silica above 30mV, can obtain nano-silica suspensions and powders with excellent dispersibility and uniform particle size. (Comparison) Figure 1 and Figure 2 This demonstrates that the solution provided by the present invention can fundamentally solve the agglomeration problem, easily obtain nanoparticles with uniform particle size, and provide active sites for the competitive polymerization reaction of polyaniline, fumaric acid and long-chain hydrophobic silanes.

[0033] Example 2 The preparation was carried out according to the steps of Example 1, but differed from Example 1 in that: T1: Synthesis of Epoxidized Nano-Silica Suspension a. Add 0.15g of anionic emulsifier sodium dodecylbenzenesulfonate and 10mL of n-dodecane, and stir evenly for 10min; c. Add 0.1g of nonionic emulsifier polyethylene glycol 600 dioleate; e. 2 mL of γ-glycidyl oxypropyltrimethoxysilane coupling agent, 0.1 g of sodium stearate, and 2 mL of n-dodecane; f. Magnetic stirring at 60 rpm.

[0034] T2: Preparation of Multifunctional Amphoteric Polyaniline-Coated Silica Anticorrosive Filler and Suspension a. Cool the water bath and four-necked flask to 10°C by adding ice. b. Adjust the pH of the nano-silica suspension grafted with epoxy groups to 2 by adding a certain amount of 36% hydrochloric acid solution. Add 0.3g of fumaric acid to a four-necked flask and stir evenly. Then add 1.2g of ammonium persulfate and activate for 20min. Immediately afterward, add 0.7mL of octadecyltriethoxysilane. During this process, add 0.1g of polyethylene glycol 600 dioleate diluted to 10mL and stir for 15min. Then add 2mL of aniline, adjust the speed to 100 rpm, and stir for 5min to form a pre-emulsion of polyaniline-coated silica. c. Next, dissolve 7g of ammonium persulfate in 20mL of water and add it drop by drop using a dropper, while adding 0.1g of fatty alcohol polyoxyethylene ether and 2mL of octadecyltriethoxysilane during the process. e. Wash the polyaniline-coated silica to neutral wetness, add deionized water and a certain amount of ammonia water to prepare a 60-70 wt% multifunctional amphoteric polyaniline-coated silica suspension that can be directly added to water-based coatings.

[0035] Table 2 shows the Zeta potential and conductivity of amphoteric polyaniline-coated silica suspensions with different percentage contents and pH values. In step S2, deionized water and a certain amount of ammonia were added to the neutrally wetted polyaniline-coated silica, controlling the pH to 9-10. No surfactant was used. By measuring the Zeta potential and conductivity of the amphoteric polyaniline-coated silica suspension, it was shown that the 60wt% multifunctional amphoteric polyaniline-coated silica suspension had better stability (Zeta potential absolute value of 5-30mV indicates good dispersion stability of the emulsion) and 5.7×10⁻⁶. -3 S·cm -1High electrical conductivity. Considering the stability and corrosion resistance of the amphoteric polyaniline-coated silica suspension, and the fact that the pH value of water-based coatings is generally 9-10, the pH of the amphoteric polyaniline-coated silica suspension is controlled at 9-10, the content at 60-70 wt%, and the electrical conductivity at 10. -3 S·cm -1 above.

[0036] Table 2. Zeta potential and conductivity of amphoteric polyaniline-coated silica suspensions at different percentage contents and pH values.

[0037] The powder wettability test method involves spreading the powder evenly on the surface of a glass slide, and then placing it on the sample stage of a contact angle measuring instrument to measure the contact angle.

[0038] like Figure 3 As shown, the blank polyaniline-coated silica powder, which is produced by polymerizing only polyaniline on the silica surface, exhibits hydrophilicity with a contact angle of approximately 10°. A 60 wt% amphoteric polyaniline-coated silica suspension with pH=9 was obtained, exhibiting good dispersibility and hydrophilic properties, such as... Figure 4 As shown; Figure 5 As shown in the scanning electron microscope image of amphoteric polyaniline coated with silica, it is evident that the improved method of this invention facilitates a competitive polymerization reaction on the particle surface, further enhancing powder dispersibility; Figure 6 As shown, this further demonstrates that the amphoteric polyaniline-coated silica obtained by the method of this invention has a narrow and uniform particle size distribution and improved powder dispersibility. When the amphoteric polyaniline-coated silica is dried into powder, its contact angle with deionized water is greater than 150°, exhibiting superhydrophobic properties, such as... Figure 7 As shown, the method of this invention yields a polyaniline filler with hydrophilic properties and good dispersion stability in the suspension state, and superhydrophobic and corrosion-resistant properties in the dried powder stage, exhibiting uniform particle size.

[0039] Example 3 The preparation was carried out according to the steps of Example 1, but differed from Example 1 in that: T1: Synthesis of Epoxidized Nano-Silica Suspension a. Add 0.2g of anionic emulsifier sodium dodecyl sulfate and 12.5mL of n-heptane, and stir evenly for 12min; b. Take 35 mL of a mixed solution of tetraethyl orthosilicate and methyltrimethoxysilane, adjust the speed to 450 rpm, and stir for 15 min. c. Heat the water bath to 55℃, and under magnetic stirring at 70 rpm, slowly add 25 mL of 25% ammonia water and 0.15 g of nonionic emulsifier polyethylene glycol 400 dioleate. e. 2.5 mL of 3-glycidyl etheroxypropyl methyl dimethoxysilane coupling agent, 0.12 g of sodium oleate, and 3 mL of n-heptane; f. Stir magnetically at 100 rpm, add 5 mL of deionized water, and react for 1 hour.

[0040] T2: Preparation of Multifunctional Amphoteric Polyaniline-Coated Silica Anticorrosive Filler and Suspension a. Cool the water bath and four-necked flask to 7°C by adding ice. b. Adjust the pH of the nano-silica suspension grafted with epoxy groups to 2 by adding a certain amount of 36% hydrochloric acid solution. Add 0.4g of fumaric acid to a four-necked flask and stir evenly. Then add 1.1g of ammonium persulfate and activate for 25min. Immediately afterward, add 2mL of octadecyltriethoxysilane. During this process, add 0.12g of polyethylene glycol 600 dioleate diluted to 10mL and stir for 10min. Then add 2.5mL of aniline, adjust the speed to 75 rpm, and stir for 6min to form a pre-emulsion of polyaniline-coated silica. c. Next, dissolve 6g of ammonium persulfate in 25mL of water and add it dropwise at 2 drops per second, while adding 0.06g of octylphenol polyoxyethylene ether (OP-10) during the process. Heat the water bath to 60℃, add 0.4g of fumaric acid and 2mL of octadecyltriethoxysilane, and react for 20min; e. Add 25 mL of deionized water and 3 mL of ammonia to the neutrally wetted polyaniline-coated silica to prepare a 70 wt% multifunctional amphoteric polyaniline-coated silica suspension that can be directly added to water-based coatings.

[0041] The obtained silica pre-emulsion and water-dispersible nano-silica suspension with grafted epoxy groups had Zeta potentials of -31.4 mV and -32.1 mV, respectively; the Zeta potential of the 70 wt% amphoteric polyaniline-coated silica suspension was -15.7 mV, pH=9, and conductivity was 3.9 × 10⁻⁶. -3 S·cm -1 Furthermore, the water contact angle of the dried amphoteric polyaniline-coated silica is 150.9 ± 0.7°.

[0042] Example 4 The preparation was carried out according to the steps of Example 1, but differed from Example 1 in that: T1: Synthesis of Epoxidized Nano-Silica Suspension a. Add 0.25g of anionic emulsifier sodium dodecylbenzenesulfonate and 15mL of n-tetradecane to 100mL of deionized water, and stir evenly for 11min. b. Take 30 mL of a mixed solution of tetraethyl orthosilicate and methyltrimethoxysilane, adjust the speed to 400 rpm, and stir for 10 min; c. Heat the water bath to 50℃, and under magnetic stirring at 100 rpm, slowly add 15 mL of 25% ammonia water and 0.2 g of polyethylene glycol 600 dioleate. d. The reaction continues for 0.6 hours after the addition is complete; e. 3 mL of γ-glycidyl oxypropyltrimethoxysilane coupling agent, 0.15 g of sodium dodecyl sulfate, and 4 mL of n-heptane; f. Stir magnetically at 70 rpm, add 10 mL of deionized water dropwise, and react for 1.2 h.

[0043] T2: Preparation of Multifunctional Amphoteric Polyaniline-Coated Silica Anticorrosive Filler and Suspension a. Cool the water bath and four-necked flask to 6°C by adding ice. b. Adjust the pH of the nano-silica suspension grafted with epoxy groups to 1 by adding a certain amount of 36% hydrochloric acid solution. Add 0.5g of fumaric acid to a four-necked flask and stir evenly. Then add 1.2g of ammonium persulfate and activate for 25min. Immediately afterward, add 2mL of octadecyltriethoxysilane. During this process, add 0.15g of polyoxyethylene (4) octylphenol ether diluted to 10mL and stir for 13min. Then add 2.5mL of aniline, adjust the speed to 80 rpm, and stir for 7min to form a pre-emulsion of polyaniline-coated silica. c. Next, dissolve 6.5g of ammonium persulfate in 24mL of water and add it drop by drop, 1 drop per second, while adding 0.09g of dehydrated sorbitan trioleate during the process. Heat the water bath to 65℃, add 0.5g of fumaric acid and 1mL of octadecyltriethoxysilane, and react for 25min; e. Add 35 mL of deionized water and 5 mL of ammonia to the neutrally wetted polyaniline-coated silica to prepare a 60 wt% multifunctional amphoteric polyaniline-coated silica suspension that can be directly added to water-based coatings.

[0044] The obtained silica pre-emulsion and water-dispersible nano-silica suspension with grafted epoxy groups had Zeta potentials of -32.6 mV and -31.9 mV, respectively; the zeta potential of the 60 wt% amphoteric polyaniline-coated silica suspension was measured to be -15.3 mV, pH=10, and conductivity was 4.5 × 10⁻⁶. -3 S·cm -1 Furthermore, the water contact angle of the dried amphoteric polyaniline-coated silica is 152.3 ± 0.5°.

[0045] Application Example 1 Corrosion resistance verification of amphoteric polyaniline-coated silica suspension in aqueous coatings: Blank water-based coating, commercial anionic water-based coating with a pH of 9-10.

[0046] A 2wt% amphoteric polyaniline-coated silica coating was prepared by adding a 60wt% amphoteric polyaniline-coated silica suspension to a commercial anionic waterborne coating.

[0047] Blank water-based coating and amphoteric polyaniline-coated silica coating were applied to the surface of test-grade tinplate by brushing. The coatings were dried at 25°C to form a film, and then subjected to a neutral salt spray accelerated test at 50°C by spraying with a 5wt% sodium chloride solution. Figure 7 and 8 As shown, after 240 hours of testing, the blank water-based coating showed many corrosion products at the scratches, while the amphoteric polyaniline-coated silica coating showed no corrosion marks after 240 hours of testing. The results indicate that the amphoteric polyaniline-coated silica suspension can be well dispersed in water-based coatings without the addition of surfactants and form a dense passivation film on the surface of the metal substrate, which can further improve the anti-corrosion performance of water-based coatings.

[0048] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0049] Unless otherwise specified, all the technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0050] In this invention, unless otherwise specified, percentage (%) or parts refer to weight percentage or parts relative to the composition.

[0051] Unless otherwise specified, the components or preferred components involved in this invention can be combined with each other to form new technical solutions.

[0052] In this invention, unless otherwise specified, the numerical range "a~b" represents an abbreviation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "6~22" means that all real numbers between "6~22" have been listed in this document, and "6~22" is simply an abbreviation of these numerical combinations.

[0053] The "scope" disclosed in this invention can be in the form of a lower limit and an upper limit, and can be one or more lower limits and one or more upper limits, respectively.

[0054] In this invention, the term "and / or" as used herein refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes such combinations.

[0055] In this invention, unless otherwise stated, the various reactions or operation steps may be performed sequentially or in a particular order. Preferably, the reaction methods described herein are performed sequentially.

[0056] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be used in this invention.

[0057] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0059] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Those skilled in the art can readily implement the present invention based on the accompanying drawings and the above description. However, any modifications, alterations, or variations made by those skilled in the art without departing from the scope of the present invention, utilizing the disclosed technical content, are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, or variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing an amphoteric polyaniline-coated silica suspension, characterized in that, include: S1. Add a mixed solution of tetraethyl orthosilicate and methyltrimethoxysilane to a mixed solution of anionic emulsifier and organic liquid to obtain a silica pre-emulsion. S2. After adding ammonia and nonionic emulsifier to the silica pre-emulsion, hydrophobic nano silica sol is obtained. S3. Add the silane coupling agent and anionic emulsifier to a mixed solution of organic liquid and deionized water to obtain a modifier pre-emulsion. S4. Add the pre-emulsion of the modifier to the hydrophobic nano silica sol to prepare a water-dispersible nano silica suspension grafted with epoxy groups. S5. Under acidic low temperature conditions, fumaric acid and ammonium persulfate were added to a water-dispersible nano-silica suspension grafted with epoxy groups, followed by the addition of long-chain hydrophobic silane, nonionic emulsifier and aniline, and the reaction was carried out to obtain a polyaniline-coated silica reaction pre-emulsion. S6. Add ammonium persulfate and nonionic emulsifier to the pre-emulsion of polyaniline-coated silica reaction, followed by fumaric acid and long-chain hydrophobic silane. After the reaction, wash the reaction product until neutral, and then adjust the solution with deionized water and ammonia to obtain an amphoteric polyaniline-coated silica suspension.

2. The method for preparing an amphoteric polyaniline-coated silica suspension according to claim 1, characterized in that, The mixing ratio of tetraethyl orthosilicate and methyltrimethoxysilane in S1 is 4:1; the addition ratio of anionic emulsifier and organic liquid in S1 is 0.15~0.25g:10~15mL; The addition ratio of the organic liquid to the mixed solution of tetraethyl orthosilicate and methyltrimethoxysilane in S1 is 10~15mL: 30~40mL; The amount of ammonia added in S2 is 15~30mL, and the amount of nonionic emulsifier added is 0.1~0.2g; The reaction temperature in S2 is 50~60℃, and the reaction time is 0.5~1h; The addition ratio of silane coupling agent to anionic emulsifier in S3 is 2~3mL:0.1~0.15g, and the addition amount of the mixed solution of organic liquid and deionized water is 10~20mL; the volume ratio of organic liquid to deionized water is 1:

4.

3. The method for preparing an amphoteric polyaniline-coated silica suspension according to claim 1, characterized in that, In S4, when the pre-emulsion of the modifier is added dropwise to the hydrophobic nano silica sol, 5-10 mL of deionized water needs to be added dropwise to the reaction system, and the reaction time is 1-1.5 h.

4. The method for preparing an amphoteric polyaniline-coated silica suspension according to claim 1, characterized in that, The acidic low-temperature conditions described in S5 are as follows: the pH value of the water-dispersible nano-silica suspension grafted with epoxy groups is adjusted to 1~2 by hydrochloric acid solution; the low-temperature temperature is 5~10℃. The amount of fumaric acid added is 0.3~0.6g, and the amount of ammonium persulfate added is 1~1.2g; The addition ratio of the long-chain hydrophobic silane, nonionic emulsifier and aniline is 2~3mL: 0.1~0.15g: 2~3mL.

5. The method for preparing an amphoteric polyaniline-coated silica suspension according to claim 1, characterized in that, In S6, the addition ratio of ammonium persulfate, fumaric acid and long-chain hydrophobic silane is 5~7g:0.3~0.5g:1~2mL; the reaction temperature is 60~70℃; and the reaction time is 20~30min.

6. The method for preparing an amphoteric polyaniline-coated silica suspension according to claim 1, characterized in that, The anionic emulsifier is at least one of sodium dodecylbenzenesulfonate, sodium oleate, sodium dodecyl diphenyl ether disulfonate, sodium dodecyl sulfate, sodium stearate, and sodium laurate. The organic liquid is any one of n-octane, n-heptane, n-dodecane, and n-tetradecane; The nonionic emulsifier is selected from at least one of sorbitan trioleate, diethylene glycol monolaurate, fatty alcohol polyoxyethylene ether, polyethylene glycol 400 dioleate, polyoxyethylene (4) octylphenol ether, polyethylene glycol 600 dioleate and octylphenol polyoxyethylene ether.

7. The method for preparing an amphoteric polyaniline-coated silica suspension according to claim 1, characterized in that, The long-chain hydrophobic silane is octadecyltrimethoxysilane or octadecyltriethoxysilane; The silane coupling agent is a silane coupling agent with epoxy groups and methoxy or ethoxy groups at both ends, and its structure is shown below: ， R1 is a carbon chain or a carbon chain containing ether bonds.

8. The method for preparing an amphoteric polyaniline-coated silica suspension according to claim 1, characterized in that, The absolute value of the Zeta potential of the silica pre-emulsion, the modifier pre-emulsion, and the water-dispersible nano-silica suspension grafted with epoxy groups is controlled by the amount of anionic emulsifier and ammonia added, and is greater than 30mV. The amphoteric polyaniline-coated silica suspension is controlled by adding ammonia to maintain an absolute Zeta potential greater than 15 mV, a pH of 9-10, and a conductivity greater than 10. -3 S·cm -1 .

9. An amphoteric polyaniline-coated silica suspension, prepared according to the preparation method of an amphoteric polyaniline-coated silica suspension according to any one of claims 1-8.

10. The application of the amphoteric polyaniline-coated silica suspension according to claim 9 in water-based coatings, characterized in that, include: An amphoteric polyaniline-coated silica suspension was prepared to a concentration of 60wt%~70wt% and then added to water-based coatings. The water-based coating includes one of anionic emulsion coatings, anionic water-dispersible resin coatings, or anionic water-soluble resin coatings.

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