A paint anticorrosive additive, a preparation method thereof and an anticorrosive paint

Abstract

The application belongs to the technical field of paint, and relates to a paint anticorrosive additive as well as a preparation method and application thereof. The preparation method of the paint anticorrosive additive comprises the following steps: S1, performing a dehydration condensation reaction on carbon material and double-end amino polysiloxane in the presence of a solvent, and then performing solid-liquid separation, so that a modified carbon material is obtained; S2, dispersing the modified carbon material obtained in step S1, aniline and 2-acrylamido-2-methylpropanesulfonic acid in water, performing an oxidation polymerization reaction on the obtained dispersion liquid in the presence of an initiator, and then performing solid-liquid separation, so that the paint anticorrosive additive is obtained. The paint anticorrosive additive obtained by the method has good short-term and long-term anticorrosive performance.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, and relates to a coating anti-corrosion additive, its preparation method and application. Background Technology

[0002] With the continuous advancement of global industrialization and infrastructure construction, metal corrosion has become a key factor restricting equipment lifespan and operational safety. Carbon materials possess excellent physical barrier properties, forming an effective isolation layer between the metal surface and corrosive media, thereby extending the penetration path of corrosive media (such as water, salt, and oxygen), demonstrating unique advantages in the field of anti-corrosion coatings. Polyaniline, through its unique electronic structure, can passivate metal surfaces, forming a dense protective film on the metal substrate surface, preventing the intrusion of oxygen, moisture, and other corrosive ions, thus inhibiting the metal corrosion process.

[0003] When carbon materials and polyaniline are combined as additives in anti-corrosion coatings, the carbon materials fill the gaps in the coating and act as a barrier, prolonging the intrusion of corrosive media such as water and oxygen, thereby inhibiting the corrosion process of the metal. Simultaneously, the polyaniline, uniformly dispersed in the coating, exerts a unique anti-corrosion effect. The two work synergistically to enhance the anti-corrosion performance of the coating. However, although carbon material and polyaniline composite anti-corrosion coatings have significant potential in the field of corrosion protection, their short-term anti-corrosion performance (the anti-corrosion performance immediately after the coating is prepared) still needs improvement, while their long-term anti-corrosion performance (the anti-corrosion performance after a period of time after the coating is prepared) is relatively poor. The main reasons for this are twofold: First, both carbon materials and polyaniline possess a certain degree of conductivity, making them prone to forming corrosion galvanes with the metal substrate. This is especially true when the coating develops cracks or scratches, potentially acting as a cathode to form micro-galvanic corrosion with the metal substrate, accelerating localized corrosion and resulting in poor short-term corrosion protection. Second, the rigid structure of polyaniline makes it prone to agglomeration in anti-corrosion coatings. Furthermore, carbon materials such as carbon nanotubes and graphene oxide, due to van der Waals forces and π-π interactions, are also prone to agglomeration. Stable dispersion cannot be achieved using traditional mechanical stirring or ultrasonic dispersion, and after a certain period of settling, the particles easily re-agglomerate, leading to decreased coating density, coating defects, and affecting long-term corrosion protection. Therefore, there is an urgent need to improve the corrosion protection performance of anti-corrosion coatings that possess both excellent short-term and long-term corrosion protection properties. Summary of the Invention

[0004] The primary objective of this invention is to provide a novel method for preparing a coating anti-corrosion additive, which yields an anti-corrosion additive with both good short-term and long-term anti-corrosion properties.

[0005] A second objective of this invention is to provide a coating anti-corrosion additive prepared by the above method.

[0006] A third objective of this invention is to provide an anti-corrosion coating containing epoxy resin and the aforementioned anti-corrosion additives.

[0007] The preparation method of the anti-corrosion additive for coatings provided by the present invention includes the following steps: S1. Carbon material and diamino-terminated polysiloxane undergo a dehydration condensation reaction in the presence of a solvent, followed by solid-liquid separation. The carbon material contains carboxylated carbon nanotubes, and the resulting solid product is a modified carbon material. The chemical formula of the diamino-terminated polysiloxane is R. 1 SiMe2O(SiOMeR 2 ) a (SiOMeR 3 ) b SiMe2R 1 R 1 -(CH2) n NH2,R 2 Selected from C1-C18 alkyl, C6-C20 phenyl and -CH2CH2C m F 2m+1 At least one of them, R 3 -(CH2) p NHR 4 , a=10-200, b=3-20, n=1-6, m=1-12, p=1-6, R 4 It is a C1-C18 alkyl and / or C5-C7 cycloalkyl; S2. The modified carbon material, aniline and 2-acrylamido-2-methylpropanesulfonic acid obtained in step S1 are dispersed in water. The resulting dispersion is subjected to an oxidative polymerization reaction in the presence of an initiator, followed by solid-liquid separation. The resulting solid product is the coating anti-corrosion additive.

[0008] The key to this invention lies in using a composite of carbon materials and polyaniline as a coating anti-corrosion additive, and employing bi-terminated amino polysiloxanes and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) for synergistic modification. The resulting coating anti-corrosion additive exhibits both good short-term and long-term anti-corrosion performance. The reason for this is speculated to be: firstly, the introduction of a bi-terminated amino polysiloxane structure into the polyaniline / carbon composite material. The low surface energy of the bi-terminated amino polysiloxane structure facilitates its migration to the material surface, thereby improving the material's hydrophobic properties and slowing the penetration of corrosive substances into the anti-corrosion coating. Simultaneously, the bi-terminated amino polysiloxane possesses excellent flexibility and film-forming properties, which can fill micropores and cracks in the coating, enhancing its density. The introduction of 2-acrylamido-2-methylpropanesulfonic acid further promotes the densification of the coating structure, effectively preventing the penetration of corrosive media and improving the coating's anti-corrosion performance. Secondly, the introduction of 2-acrylamido-2-methylpropanesulfonic acid can adjust the conductivity of the coating, thereby improving its... The sulfonic acid groups and other functional groups in the molecular structure form chemical bonds with the metal substrate, reducing galvanic corrosion. Simultaneously, the flexibility of the double-terminated amino polysiloxane can alleviate stress concentration caused by excessive conductivity in the coating, further improving its stability. Furthermore, the introduction of 2-acrylamido-2-methylpropanesulfonic acid into the polyaniline / carbon composite material allows for the grafting of 2-acrylamido-2-methylpropanesulfonic acid onto the polyaniline molecular chain through chemical polymerization, forming a PANI-AMPS copolymer. This modification not only enhances the interfacial bonding between polyaniline and carbon materials but also improves the adhesion of the composite material to the metal matrix through the introduction of sulfonic acid groups, effectively inhibiting the penetration of corrosive substances. These factors contribute to the excellent short-term anti-corrosion performance of the coating anti-corrosion additive. On the other hand, the sulfonic acid groups in 2-acrylamido-2-methylpropanesulfonic acid, after dissociation, carry a negative charge, which can generate electrostatic repulsion with the negative charge on the surface of carbon materials. This electrostatic repulsion helps to prevent direct contact and aggregation between carbon material sheets and / or particles, thus maintaining their uniform dispersion in the coating. The presence of vinyl groups in 2-acrylamido-2-methylpropanesulfonic acid makes it easy to copolymerize with aniline monomers during the oxidative polymerization of polyaniline, forming a long-chain polymer. This long-chain polymer can wrap around the carbon material sheets and / or particles to form a thin film, increasing the steric hindrance between the carbon material sheets and / or particles. This steric hindrance effect can further prevent the aggregation of carbon materials. These factors contribute to the excellent long-term anti-corrosion performance of coating anti-corrosion additives.

[0009] The anti-corrosion coating provided by the present invention uses epoxy resin as the main body. The double-terminated amino polysiloxane introduced in the anti-corrosion additive of the coating contains primary amino and / or secondary amino groups, which can react with epoxy resin to play a toughening role and improve the toughness of the anti-corrosion coating.

[0010] In a preferred embodiment, the dehydration condensation reaction is carried out in the presence of rare earth metal salts and / or rare earth metal oxides, which imparts superior short-term and long-term anti-corrosion performance to the anti-corrosion coating. This is presumably because rare earth elements have a unique electronic structure; their 4f electron layer can interact with the π electron cloud of carbon materials. This interaction alters the electron distribution on the carbon material surface, reducing the π-π conjugation effect between layers and / or particles. The π-π conjugation effect is one of the main driving forces for carbon material agglomeration; its reduction can significantly inhibit agglomeration. Simultaneously, the use of rare earth elements can form charged groups on the carbon material surface, generating electrostatic repulsion. This repulsion counteracts the van der Waals forces between carbon material layers and / or particles, effectively preventing the layers from approaching and stacking. This allows the carbon material to remain uniformly dispersed in the solvent, avoiding agglomeration and thus effectively maintaining its anti-corrosion performance over a long period. Detailed Implementation

[0011] The preparation method of the anti-corrosion additive for coatings provided by the present invention includes the following steps: S1. Carbon material and diamino-terminated polysiloxane are subjected to a dehydration condensation reaction in the presence of a solvent, followed by solid-liquid separation. The resulting solid product is the modified carbon material. S2. The modified carbon material, aniline and 2-acrylamido-2-methylpropanesulfonic acid obtained in step S1 are dispersed in water. The resulting dispersion is subjected to an oxidative polymerization reaction in the presence of an initiator, followed by solid-liquid separation. The resulting solid product is the coating anti-corrosion additive.

[0012] In this invention, in step S1, the carbon material contains carboxylated carbon nanotubes, and preferably further contains graphene oxide and / or graphene quantum dots. That is, the carbon material can be carboxylated carbon nanotubes or a mixture of carboxylated carbon nanotubes and graphene oxide and / or graphene quantum dots. Utilizing the high reactivity of the carboxyl groups on the surface of the carboxylated carbon nanotubes and the epoxy groups on the surface of the graphene oxide and / or graphene quantum dots with the primary amino groups at both ends of the diamino-terminated polysiloxane, the diamino-terminated polysiloxane is grafted onto the surface of the carbon material.

[0013] In this invention, in step S1, the general chemical formula of the dual-terminated amino polysiloxane is R. 1 SiMe2O(SiOMeR 2 ) a (SiOMeR 3 ) b SiMe2R 1 R 1 -(CH2) n NH2,R 2 Selected from C1-C18 alkyl, C6-C20 phenyl and -CH2CH2C m F2m+1 At least one of them, R 3 -(CH2) p NHR 4 , a=10-200, b=3-20, n=1-6, m=1-12, p=1-6, R 4 It is a C1-C18 alkyl and / or C5-C7 cycloalkyl group. The diamino-terminated polysiloxane can be commercially available or prepared according to various methods disclosed in the art. For example, the diamino-terminated polysiloxane can be prepared using the end-capping agent NH2(CH2). n Me2SiOSiMe2(CH2) n NH2 and its corresponding siloxane cyclic forms (such as octamethylcyclotetrasiloxane, tetramethyltetraphenylcyclotetrasiloxane, tris(trifluoropropyl)trimethylcyclotrisiloxane, etc.) and (OR) 5 )2SiOMeR 3 It is obtained by polymerization under an alkaline catalyst, wherein n and R 3 The meaning is as above, R 5 It can be selected from C1-C5 alkyl groups. Specifically, an example of a polymerization reaction can be listed as follows: Octamethylcyclotetrasiloxane and cyclohexylaminopropylmethyldimethoxysilane are added to a container at a molar ratio of (5-10):1. Then, 1%-10% of the weight of octamethylcyclotetrasiloxane and cyclohexylaminopropylmethyldimethoxysilane and 1%-10% of the end-capping agent NH2(CH2)3Me2SiOSiMe2(CH2)3NH2 are added. Next, 0.5%-2% of the total weight of the reaction raw materials and 1wt%-5wt% of tetramethylammonium hydroxide siloxane alcohol are added. The pressure of the reaction system is controlled at -0.001 MPa to -0.01 MPa. The temperature is raised to 110℃-120℃ and reacted for 1-5 hours. The temperature is then raised to 138℃-140℃ to destroy the catalyst for 0.1-1 hour. The temperature is further raised to 150℃-160℃, and the pressure is adjusted to below -0.099 MPa to remove low-boiling substances, thus obtaining a double-terminated amino polysiloxane.

[0014] In this invention, in step S1, the solvent can be an organic solvent or an acidic aqueous solution with a pH of 0-4. The organic solvent can be selected from at least one of anhydrous ethanol, tetrahydrofuran, ethyl acetate, butyrate, N,N-dimethylformamide (DMF), and N-methylpyrrolidone (NMP). The purpose of the acidic aqueous solution is to protonate the primary and / or secondary amino groups in the diamino-terminated polysiloxane to form cationic groups, thereby improving the water solubility of the diamino-terminated polysiloxane and facilitating its reaction with the carboxyl and epoxy groups on the surface of the carbon material. The acidic aqueous solution can be at least one of hydrochloric acid solution, sulfuric acid solution, phosphoric acid solution, etc. Furthermore, the concentration of the carbon material dispersed in the solvent is not particularly limited, for example, it can be 0.02-1 mg / mL, specifically 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.00 mg / mL, etc.

[0015] In this invention, in step S1, the ratio of the total molar number of carboxyl groups and epoxy groups on the surface of the carbon material to the molar number of diamino-terminated polysiloxane is preferably 1:(0.3-5), specifically 1:0.3, 1:0.5, 1:0.8, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, etc.

[0016] In a preferred embodiment, the ratio of the total molar number of carboxyl groups and epoxy groups on the surface of the carbon material to the molar number of diamino-terminated polysiloxane is 1:(0.3-0.5) (excluding 1:0.5), specifically 1:0.3, 1:0.32, 1:0.35, 1:0.37, 1:0.4, 1:0.43, 1:0.45, 1:0.47, 1:0.49, etc., can be achieved by controlling the ratio of the total molar number of carboxyl groups and epoxy groups on the surface of the carbon material to the molar number of diamino-terminated polysiloxane. When the molar ratio of polysiloxanes is within the above range, the two primary amino groups and the secondary amino groups in the side chain of the diamino-terminated polysiloxane can react with carboxyl groups and / or epoxy groups on the same carbon material sheet and / or particle surface to form a cyclic structure, or react with carboxyl groups and / or epoxy groups on different carbon material sheets and / or particle surfaces to form an interlocked structure. The resulting modified carbon material forms a more complex interaction with polyaniline, which improves the effect of the anti-corrosion additive in the coating.

[0017] In a preferred embodiment, the ratio of the total molar number of carboxyl groups and epoxy groups on the surface of the carbon material to the molar number of diamino-terminated polysiloxane is 1:(0.5-1) (excluding 1:1), specifically 1:0.5, 1:0.55, 1:0.6, 1:0.65, 1:0.7, 1:0.75, 1:0.8, 1:0.85, 1:0.9, 1:0.95, 1:0.99, etc., by controlling the carboxyl groups and epoxy groups on the surface of the carbon material. When the ratio of the number of moles of amino groups to the number of moles of diamino-terminated polysiloxane is within the above range, the two primary amino groups in the diamino-terminated polysiloxane mainly react with the carboxyl groups and / or epoxy groups on the surface of carbon material sheets and / or particles. The secondary amino groups (which have much lower reactivity than the primary amino groups) react less with the carboxyl groups and / or epoxy groups on the surface of carbon material sheets and / or particles. The resulting modified carbon material also forms a more complex interaction with polyaniline, which improves the effect of the anti-corrosion additive in the coating.

[0018] In a preferred embodiment, the ratio of the total molar number of carboxyl groups and epoxy groups on the surface of the carbon material to the molar number of diamino-terminated polysiloxane is 1:(1-5), specifically 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, etc. By controlling the ratio of the total molar number of carboxyl groups and epoxy groups on the surface of the carbon material to the molar number of diamino-terminated polysiloxane within the above range, since the diamino-terminated polysiloxane is in excess relative to the carboxyl groups and epoxy groups, basically only one primary amino group participates in the reaction in one diamino-terminated polysiloxane molecule, and the polysiloxane molecule forms a comb-like structure on the surface of the carbon material.

[0019] In a preferred embodiment, in step S1, the values ​​of a and b satisfy: a ≥ 30, b / a ≤ 0.1. By adopting the above preferred technical solution, the secondary amino groups in the diamino-terminated polysiloxane molecule, within the above range, can have a better interaction with polyaniline, which is more conducive to further improving the anti-corrosion performance.

[0020] In this invention, in step S2, the weight ratio of the modified carbon material to the aniline monomer is preferably 1:(0.5-20), more preferably 1:(1-10), and can specifically be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, etc.

[0021] In this invention, in step S2, the molar ratio of 2-acrylamido-2-methylpropanesulfonic acid to aniline is preferably (0.01-0.1):1, specifically it can be 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1, etc.

[0022] In this invention, in step S2, the molar ratio of the aniline monomer to the initiator is preferably 1:(0.5-2), specifically 1:0.5, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2, etc.

[0023] In this invention, in step S2, the initiator may be at least one of ammonium persulfate, sodium persulfate, and potassium persulfate.

[0024] In this invention, in step S2, the amount of water used is preferably such that the concentration of the modified carbon material is 1-20 mg / mL, for example, 1 mg / mL, 5 mg / mL, 8 mg / mL, 10 mg / mL, 12 mg / mL, 13 mg / mL, 14 mg / mL, 15 mg / mL, 16 mg / mL, 17 mg / mL, 18 mg / mL, 19 mg / mL, 20 mg / mL, etc.

[0025] In this invention, the conditions for the dehydration condensation reaction preferably include a temperature of 15℃-60℃, specifically 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, etc.; and a time of 1h-10h, specifically 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, etc.

[0026] In this invention, the preferred conditions for the oxidative polymerization reaction include a temperature of 0℃-40℃, specifically 0℃, 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, etc.; and a reaction time of 5h-24h, specifically 5h, 8h, 10h, 12h, 15h, 18h, 20h, 22h, 24h, etc.

[0027] In a preferred embodiment, the dehydration condensation reaction is carried out in the presence of rare earth metal salts and / or rare earth metal oxides. The mass ratio of the total amount of the rare earth metal salts and rare earth metal oxides to the carbon material is preferably (0.01-0.1):1, such as 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1, etc. The rare earth metal salts are particularly preferably at least one selected from cerium nitrate, cerium ammonium nitrate, etc. The rare earth metal oxides are particularly preferably at least one selected from cerium oxide, lanthanum nitrate, and dysprosium oxide.

[0028] The improved method for preparing the anti-corrosion additive for coatings generally includes steps of cleaning and drying the solid products obtained in steps S1 and S2, which can further improve the anti-corrosion performance of the coating. The solvent used for cleaning can be water or an alcohol compound.

[0029] The present invention also provides a coating anti-corrosion additive prepared by the above method.

[0030] This invention also provides an anti-corrosion coating comprising an epoxy resin and the aforementioned anti-corrosion additives. Preferably, the anti-corrosion additives comprise 1-15 wt% of the weight of the anti-corrosion coating, more preferably 2-10 wt%, specifically 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, 8 wt%, 8.5 wt%, 9 wt%, 9.5 wt%, 10 wt%, etc. Furthermore, the epoxy resin can be unmodified epoxy resin, silicone-modified epoxy resin, etc., without particular limitation. In addition, the anti-corrosion coating generally also contains a curing agent, specifically a polyamine compound, anhydride compound, etc. Examples of polyamine compounds include at least one selected from ethylenediamine, diethylenetriamine, m-phenylenediamine, and m-phenylenediamine. The anhydride compounds may include at least one of the following: maleic anhydride, phthalic anhydride, etc.

[0031] The technical solution of the present invention will be further described and illustrated below with reference to various embodiments. Unless otherwise specified, the parts mentioned in the following embodiments, comparative examples, and test examples are parts by weight.

[0032] In the following examples and comparative examples, carboxylated carbon nanotubes were prepared by the following method: Under ice bath and stirring conditions, 25 mL of concentrated nitric acid (68%) was slowly added to 75 mL of concentrated sulfuric acid (98%). Then, 200 mg of single-walled carbon nanotubes (diameter 1 nm ± 0.2 nm, average aspect ratio 30:1) were added to the resulting composite acid solution. The mixture was then magnetically stirred and dispersed for 30 min under ice bath conditions. The resulting reaction system was then placed in an oil bath and stirred at 50 °C for 3 h. After the reaction was completed, the mixture was cooled to room temperature, diluted with 100 mL of deionized water, and filtered through a 0.22 µm filter membrane. The solid product was washed with water until the pH of the filtrate was neutral. Then, the product was dried at 60 °C for 12 h to obtain carboxylated carbon nanotubes.

[0033] Example 1 The chemical formula of the diamino-terminated polysiloxane is R 1 SiMe2O(SiOMe2) a (SiOMeR 3 ) b SiMe2R 1 R 1 For -(CH2)3NH2, R 3 Cyclohexylaminopropyl (-(CH2)3NHC6H)11 (a=70.4, b=6.3). The molar ratio of the diamino-terminated polysiloxane to the molar ratio of carboxyl groups in the carboxylated carbon nanotubes is 0.35:1. The rare earth metal salt is cerium nitrate. The mass ratio of the rare earth metal salt to the carboxylated carbon nanotubes is 0.05:1. The molar ratio of the carboxyl groups in the carboxylated carbon nanotubes to the molar ratios of EDC and NHS is 1:2:2.

[0034] S1. Carboxylated carbon nanotubes were ultrasonically dispersed in N,N-dimethylformamide (DMF) to prepare a dispersion with a concentration of 0.2 mg / mL. The ultrasonic dispersion conditions included a power of 500 W and a time of 2 h. Bisamine-terminated polysiloxane, cerium nitrate, EDC and NHS were added. The mixture was stirred and dispersed at room temperature for 2 h, heated to 55 °C and reacted for 1 h. The mixture was centrifuged at 15000 rpm for 20 min, and the solid was collected. The solid was washed twice with anhydrous ethanol and dried overnight in an oven at 60 °C to obtain the modified carbon material.

[0035] S2. Dissolve 2-acrylamido-2-methylpropanesulfonic acid in water to obtain an acid solution with a concentration of 1 mol / L. Disperse 1 part of the above modified carbon material in the acid solution, add 3 parts of aniline and stir evenly. Control the molar ratio of 2-acrylamido-2-methylpropanesulfonic acid to aniline at 0.1:1. Place the resulting mixture in a 0℃ environment, and add 20wt% ammonium persulfate solution dropwise at an equimolar ratio of ammonium persulfate to aniline. After the addition is complete, stir at a constant temperature for 4 hours, filter, wash the obtained solid product with water and dry it to obtain the coating anti-corrosion additive.

[0036] Example 2 The chemical formula of the diamino-terminated polysiloxane is R 1 SiMe2O(SiOMe2) a (SiOMeR 3 ) b SiMe2R 1 R 1 For -(CH2)3NH2, R 3 Cyclohexylaminopropyl (-(CH2)3NHC6H) 11 (a=70.4, b=6.3). The molar ratio of the diamino-terminated polysiloxane to the molar ratio of carboxyl groups in the carboxylated carbon nanotubes is 0.5:1. The rare earth metal salt is cerium nitrate. The mass ratio of the rare earth metal salt to the carboxylated carbon nanotubes is 0.01:1. The molar ratio of the carboxyl groups in the carboxylated carbon nanotubes to the molar ratios of EDC and NHS is 1:2:2.

[0037] S1. Carboxylated carbon nanotubes were ultrasonically dispersed in N-methylpyrrolidone (NMP) to prepare a dispersion with a concentration of 0.2 mg / mL. The ultrasonic dispersion conditions included a power of 500 W and a time of 2 h. Bisamine-terminated polysiloxane, cerium nitrate, EDC and NHS were added. The mixture was stirred and dispersed at room temperature for 2 h, heated to 55 °C and reacted for 1 h. The mixture was centrifuged at 15000 rpm for 20 min, and the solid was collected. The solid was washed twice with anhydrous ethanol and dried overnight in an oven at 60 °C to obtain the modified carbon material.

[0038] S2. Dissolve 2-acrylamido-2-methylpropanesulfonic acid in water to obtain an acid solution with a concentration of 1 mol / L. Disperse 1 part of the above modified carbon material in the acid solution, add 3 parts of aniline and stir evenly. Control the molar ratio of 2-acrylamido-2-methylpropanesulfonic acid to aniline at 0.05:1. Place the resulting mixture at 5°C, and add 20 wt% ammonium persulfate solution dropwise at an equimolar ratio of ammonium persulfate to aniline. After the addition is complete, stir at a constant temperature for 4 hours, filter, wash the resulting solid product with water and dry it to obtain the coating anti-corrosion additive.

[0039] Example 3 The chemical formula of the diamino-terminated polysiloxane is R 1 SiMe2O(SiOMe2) a (SiOMeR 3 ) b SiMe2R 1 R 1 For -(CH2)3NH2, R 3 Cyclohexylaminopropyl (-(CH2)3NHC6H) 11 (a=70.4, b=6.3). The ratio of the molar number of diamino-terminated polysiloxanes to the molar number of carboxyl groups in carboxylated carbon nanotubes is 0.3:1. The rare earth metal salt is cerium nitrate. The mass ratio of the rare earth metal salt to carboxylated carbon nanotubes is 0.1:1, and the ratio of the molar number of carboxyl groups in carboxylated carbon nanotubes to the molar number of EDC and NHS is 1:2:2.

[0040] S1. Carboxylated carbon nanotubes were ultrasonically dispersed in N,N-dimethylformamide (DMF) to prepare a dispersion with a concentration of 0.2 mg / mL. The ultrasonic dispersion conditions included a power of 500 W and a time of 2 h. Bisamine-terminated polysiloxane, cerium nitrate, EDC and NHS were added. The mixture was stirred and dispersed at room temperature for 2 h, heated to 55 °C and reacted for 1 h. The mixture was centrifuged at 15000 rpm for 20 min, and the solid was collected. The solid was washed twice with anhydrous ethanol and dried overnight in an oven at 60 °C to obtain the modified carbon material.

[0041] S2. Dissolve 2-acrylamido-2-methylpropanesulfonic acid in water to obtain an acid solution with a concentration of 1 mol / L. Disperse 1 part of the above modified carbon material in the acid solution, add 3 parts of aniline and stir evenly. Control the molar ratio of 2-acrylamido-2-methylpropanesulfonic acid to aniline at 0.01:1. Place the resulting mixture at 2°C, and add 20 wt% ammonium persulfate solution dropwise at an equimolar ratio of ammonium persulfate to aniline. After the addition is complete, stir at a constant temperature for 4 hours, filter, wash the resulting solid product with water and dry it to obtain the coating anti-corrosion additive.

[0042] Example 4 The coating anti-corrosion additive was prepared according to the method of Example 1, except that cerium nitrate was not added in step S1, and the other conditions were the same as in Example 1, and the coating anti-corrosion additive was obtained.

[0043] Example 5 The chemical formula of the diamino-terminated polysiloxane is R 1 SiMe2O(SiOMe2) a (SiOMeR 3 ) b SiMe2R 1 R 1 For -(CH2)3NH2, R 3 Cyclohexylaminopropyl (-(CH2)3NHC6H) 11 (a=70.4, b=6.3). The molar ratio of diamino-terminated polysiloxane to the molar ratio of carboxyl groups in carboxylated carbon nanotubes is 0.2:1. The molar ratio of diamino-terminated polysiloxane to the molar ratio of epoxy groups in Hummers-processed graphene oxide is 0.15:1. The rare earth metal salt is cerium nitrate. The mass ratio of the rare earth metal salt to the total mass of carboxylated carbon nanotubes and Hummers-processed graphene oxide is 0.05:1. The molar ratio of carboxyl groups in carboxylated carbon nanotubes to the molar ratios of EDC and NHS is 1:2:2.

[0044] S1. Carboxylated carbon nanotubes and Hummers-processed graphene oxide were ultrasonically dispersed in N,N-dimethylformamide (DMF) to prepare a dispersion with a concentration of 0.2 mg / mL. The ultrasonic dispersion conditions included a power of 500 W and a time of 2 h. Bisamine-terminated polysiloxane, cerium nitrate, EDC and NHS were added. The mixture was stirred and dispersed at room temperature for 2 h, heated to 55 °C and reacted for 1 h. The mixture was centrifuged at 15000 rpm for 20 min, and the solid was collected. The solid was washed twice with anhydrous ethanol and dried overnight in an oven at 60 °C to obtain the modified carbon material.

[0045] S2. Dissolve 2-acrylamido-2-methylpropanesulfonic acid in water to obtain an acid solution with a concentration of 1 mol / L. Disperse 1 part of the above modified carbon material in the acid solution, add 3 parts of aniline and stir evenly. Control the molar ratio of 2-acrylamido-2-methylpropanesulfonic acid to aniline at 0.1:1. Place the resulting mixture in a 0℃ environment, and add 20wt% ammonium persulfate solution dropwise at an equimolar ratio of ammonium persulfate to aniline. After the addition is complete, stir at a constant temperature for 4 hours, filter, wash the obtained solid product with water and dry it to obtain the coating anti-corrosion additive.

[0046] Example 6 The coating anti-corrosion additive was prepared according to the method of Example 4, except that the ratio of the molar number of diamino-terminated polysiloxane to the molar number of carboxyl groups in the carboxylated carbon nanotubes was controlled at 5:1, and the other conditions were the same as in Example 4, thus obtaining the coating anti-corrosion additive.

[0047] Comparative Example 1 One part of carboxylated carbon nanotubes was dispersed in 99 parts of 1 mol / L hydrochloric acid, and three parts of aniline were added. The mixture was placed at 0°C, and a 20 wt% ammonium persulfate solution was added dropwise at an equimolar ratio of ammonium persulfate to aniline. After the addition was complete, the mixture was stirred at a constant temperature for 4 hours, filtered, washed with water, and dried to obtain the reference coating anticorrosive additive.

[0048] Comparative Example 2 The anti-corrosion additive for coatings was prepared according to the method of Example 4, except that in step S1, no double-terminated amino polysiloxane was added. The other conditions were the same as in Example 4. The specific steps are as follows: S1. Carboxylated carbon nanotubes were ultrasonically dispersed in N,N-dimethylformamide (DMF) to prepare a dispersion with a concentration of 0.2 mg / mL. The ultrasonic dispersion conditions included a power of 500 W and a time of 2 h. After that, the dispersion was stirred at room temperature for 2 h, heated to 55 °C and reacted for 1 h. The mixture was centrifuged at 15000 rpm for 20 min, and the solid was collected. The solid was washed twice with anhydrous ethanol and dried overnight in an oven at 60 °C to obtain the modified carbon material.

[0049] S2. Dissolve 2-acrylamido-2-methylpropanesulfonic acid in water to obtain an acid solution with a concentration of 1 mol / L. Disperse 1 part of the above modified carbon material in the acid solution, add 3 parts of aniline and stir evenly. Control the molar ratio of 2-acrylamido-2-methylpropanesulfonic acid to aniline at 0.1:1. Place the resulting mixture in a 0°C environment, and add 20 wt% ammonium persulfate solution dropwise at an equimolar ratio of ammonium persulfate to aniline. After the addition is complete, stir at a constant temperature for 4 hours, filter, wash the resulting solid product with water and dry it to obtain the reference coating anti-corrosion additive.

[0050] Comparative Example 3 The coating anti-corrosion additive was prepared according to the method of Example 4, except that in step S2, 2-acrylamido-2-methylpropanesulfonic acid was replaced with the same molar amount of sulfuric acid, and the other conditions were the same as in Example 4. The specific steps are as follows: S1. Carboxylated carbon nanotubes were ultrasonically dispersed in N,N-dimethylformamide (DMF) to prepare a dispersion with a concentration of 0.2 mg / mL. The ultrasonic dispersion conditions included a power of 500 W and a time of 2 h. Bisamine-terminated polysiloxane, EDC and NHS were added. The mixture was stirred and dispersed at room temperature for 2 h, heated to 55 °C and reacted for 1 h. The mixture was centrifuged at 15000 rpm for 20 min, and the solid was collected. The solid was washed twice with anhydrous ethanol and dried overnight in an oven at 60 °C to obtain the modified carbon material.

[0051] S2. Disperse 1 part of the above modified carbon material in a 1 mol / L sulfuric acid aqueous solution, add 3 parts of aniline and stir evenly. The molar ratio of sulfuric acid to aniline is controlled at 0.1:1. Place the resulting mixture in a 0℃ environment, and add 20 wt% ammonium persulfate solution dropwise according to the equimolar ratio of ammonium persulfate and aniline. After the addition is complete, stir at a constant temperature for 4 hours, filter, wash the obtained solid product with water and dry it to obtain the reference coating anti-corrosion additive.

[0052] Test case Four parts of the anti-corrosion additive for coatings obtained according to the above examples and the reference anti-corrosion additive for coatings obtained according to the comparative example were added to 48 parts of curing agent polyamide 650, stirred and dispersed evenly, and then 48 parts of epoxy resin E44 were added and stirred evenly to obtain an anti-corrosion coating. The anti-corrosion coating was applied to a clean tinplate surface with a coating thickness of about 30 μm, and a short-term sample was obtained after curing.

[0053] Four parts of the anti-corrosion additive for coatings obtained according to the above examples and the reference anti-corrosion additive for coatings obtained in the comparative example were added to 48 parts of curing agent polyamide 650, stirred and dispersed evenly, and then 48 parts of epoxy resin E44 were added and stirred evenly to obtain an anti-corrosion coating. The anti-corrosion coating was left to stand at room temperature for six months, and then applied to a clean tinplate surface with a coating thickness of about 30 μm. After curing, a long-term sample was obtained.

[0054] (1) Neutral salt spray resistance: The obtained short-term and long-term samples were placed in a salt spray test chamber. The salt spray solution was a 50 g / L sodium chloride solution with a pH of 7 ± 0.2. The test temperature was maintained at (35 ± 2) ℃. The salt spray solution was sprayed evenly onto the surface of the sample coating through a nozzle. Every 12 hours, the samples were taken out to observe whether cracking, bubbling, or peeling occurred on the surface of the paint film. The test was terminated when at least one of the following phenomena occurred: cracking, bubbling, or peeling. The obtained duration was recorded as the short-term / long-term neutral salt spray resistance performance. The results are shown in Table 1 below.

[0055] (2) Acid salt spray resistance: The obtained short-term and long-term samples were placed in a salt spray test chamber. The salt spray solution was a 50 g / L sodium chloride solution, and the pH value was adjusted to 3 ± 0.2 with acetic acid. The test temperature was maintained at (35 ± 2) ℃. The salt spray solution was sprayed evenly onto the surface of the sample coating through the nozzle. Every 12 hours, the samples were taken out to observe whether cracking, bubbling, or peeling occurred on the surface of the paint film. The test was terminated when at least one of the following phenomena occurred: cracking, bubbling, or peeling. The obtained duration was recorded as the short-term / long-term acid salt spray resistance performance. The results are shown in Table 1 below.

[0056] Table 1

[0057] A comparison of Examples 1-6 with Comparative Examples 1-3 shows that the anti-corrosion additive for coatings provided by the present invention has good short-term and long-term anti-corrosion performance. A comparison of Examples 1 and 4 shows that the dehydration condensation reaction is carried out in the presence of rare earth metal salts and / or rare earth metal oxides, which imparts superior short-term and long-term anti-corrosion performance to the anti-corrosion coating. A comparison of Examples 1 and 6 shows that when the ratio of the total molar number of carboxyl groups and epoxy groups on the surface of the carbon material to the molar number of diamino-terminated polysiloxanes is controlled within a preferred range, it is more beneficial to improve the short-term and long-term anti-corrosion performance of the anti-corrosion additive for coatings.

[0058] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method for preparing a coating anti-corrosion additive, characterized in that, The method includes the following steps: S1. Carbon material and diamino-terminated polysiloxane undergo a dehydration condensation reaction in the presence of a solvent, followed by solid-liquid separation. The carbon material is carboxylated carbon nanotubes, and the resulting solid product is a modified carbon material. The chemical formula of the diamino-terminated polysiloxane is R. 1 SiMe2O(SiOMeR 2 ) a (SiOMeR 3 ) b SiMe2R 1 R 1 -(CH2) n NH2,R 2 Selected from C1-C18 alkyl, C6-C20 phenyl and -CH2CH2C m F 2m+1 At least one of them, R 3 -(CH2) p NHR 4 , a=10-200, b=3-20, n=1-6, m=1-12, p=1-6, R 4 It is C1-C18 alkyl and / or C5-C7 cycloalkyl; the values ​​of a and b satisfy: a≥30, b / a≤0.1; the ratio of the molar number of carboxyl groups to the molar number of diamino-terminated polysiloxanes on the surface of the carbon material is 1:(0.3-5); S2. The modified carbon material, aniline and 2-acrylamido-2-methylpropanesulfonic acid obtained in step S1 are dispersed in water. The resulting dispersion is subjected to an oxidative polymerization reaction in the presence of an initiator, followed by solid-liquid separation. The resulting solid product is the coating anti-corrosion additive.

2. The method for preparing the anti-corrosion additive for coatings according to claim 1, characterized in that, In step S1, the solvent is an organic solvent.

3. The method for preparing the anti-corrosion additive for coatings according to claim 1, characterized in that, In step S2, the weight ratio of the modified carbon material to aniline is 1:(0.5-20).

4. The method for preparing the anti-corrosion additive for coatings according to claim 1, characterized in that, In step S2, the molar ratio of 2-acrylamido-2-methylpropanesulfonic acid to aniline is (0.01-0.1):

1.

5. The method for preparing the anti-corrosion additive for coatings according to claim 1, characterized in that, The conditions for the dehydration condensation reaction include a temperature of 15℃-60℃ and a time of 1h-10h; the conditions for the oxidative polymerization reaction include a temperature of 0℃-40℃ and a time of 5h-24h.

6. The method for preparing the anti-corrosion additive for coatings according to claim 1, characterized in that, The dehydration condensation reaction is carried out in the presence of rare earth metal salts and / or rare earth metal oxides.

7. The method for preparing the anti-corrosion additive for coatings according to claim 6, characterized in that, The total amount of rare earth metal salts and rare earth metal oxides used is in a mass ratio of (0.01-0.1):1 with the carbon material.

8. A coating anti-corrosion additive prepared by the method according to any one of claims 1-7.

9. An anti-corrosion coating, characterized in that, The anti-corrosion coating contains epoxy resin and the anti-corrosion additives described in claim 8.

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