A water-based zinc plating sealing agent and a preparation method thereof

Abstract

The application belongs to the technical field of galvanized surface treatment, and specifically provides a water-based galvanizing sealing agent and a preparation method thereof. The water-based galvanizing sealing agent comprises an A agent and a B agent. The A agent comprises modified polyurethane, a composite corrosion inhibitor, a wetting dispersant, a leveling agent, a defoaming agent, a film-forming aid, and deionized water. The B agent is phytic acid or rhein acid. The water-based galvanizing sealing agent prepared by the application has good corrosion resistance, adhesion, and self-repairing performance.

Description

Technical Field

[0001] This application belongs to the field of zinc plating surface treatment technology, and in particular relates to a water-based zinc plating sealant and its preparation method. Background Technology

[0002] Zinc plating, as a typical protective coating, holds an important position in electroplating processes due to its sacrificial anodic protection mechanism and low cost. This plating method is characterized by its simple process, good operability, and excellent economic corrosion resistance, and is widely used in aerospace, automotive, motorcycle, electronics and communications, and computer manufacturing industries. However, in humid environments, galvanized steel sheets are prone to corrosion, resulting in white corrosion products or a dark gray color on the surface, affecting the product's appearance and corrosion resistance, and limiting its further application. Therefore, chromate passivation is commonly used to improve the long-term corrosion resistance of galvanized parts. Chromium in the chromate passivation film mainly exists in the forms of Cr(III) and Cr(VI), forming a dense passivation film with high corrosion resistance. However, hexavalent chromium is highly toxic and carcinogenic, posing a serious drawback. Therefore, chromium-free passivation sealants have gradually become widely used.

[0003] Waterborne polyurethane sealants have become one of the mainstream materials for protecting galvanized layers due to their advantages such as environmental friendliness, good film-forming properties, and strong adhesion. However, traditional waterborne sealants are prone to microcracks or localized damage during long-term use due to mechanical damage, corrosive media penetration, or film aging, leading to a decline in protective performance and a lack of self-repair capabilities, thus affecting the service life of galvanized parts. Currently, to improve the corrosion resistance and functionality of sealants, corrosion inhibitors such as molybdates and silane coupling agents are often introduced, or nanoparticles are added to enhance the film density. For example, application publication number CN 116334610 A discloses an environmentally friendly chromium-free passivating agent with high corrosion resistance and its preparation method. In this application, a silane coupling agent, ammonium molybdate, tannic acid, nano-silicon, and cerium sulfate are used to prepare an environmentally friendly chromium-free passivating agent with high corrosion resistance, resulting in a smooth, uniform, and bright passivation film that effectively improves the corrosion resistance of galvanized sheets, while eliminating surface defects such as galvanized particles, microcracks, and scratches.

[0004] The aforementioned document describes how optimizing the formulations of cerium sulfate, sodium citrate, and cobalt nitrate improves the smoothness of the passivation film, resulting in a uniform and bright chromium-free passivation film. This effectively reduces the surface electron transport efficiency and improves the corrosion resistance of galvanized sheets. However, its protection mainly relies on a complete and dense passivation film. Damage to the film layer may trigger rapid localized corrosion, and the damaged area cannot self-repair. Summary of the Invention

[0005] To address the aforementioned issues and further improve the long-term corrosion resistance of water-based zinc plating sealants, this application provides a water-based zinc plating sealant and its preparation method.

[0006] This application first provides a water-based zinc plating sealant, comprising agent A and agent B;

[0007] The A agent comprises the following components by weight: 50-60 parts modified polyurethane, 5-12 parts composite corrosion inhibitor, 0.5-1.5 parts wetting and dispersing agent, 0.2-0.5 parts leveling agent, 0.1-0.3 parts defoamer, 1-3 parts film-forming aid, and the balance being deionized water;

[0008] Agent B is phytic acid or rhein.

[0009] Furthermore, the preparation method of the modified polyurethane includes the following steps: X1, epoxy resin, 1,4-butanediol, dimethylolpropionic acid, and TDI are reacted stepwise and then capped with methanol to obtain an epoxy resin modified polyurethane polymer; X2, the epoxy resin modified polyurethane polymer is reacted with vinyl phosphoric acid through a ring-opening reaction and then neutralized and emulsified to obtain the modified polyurethane.

[0010] Furthermore, in X2, the mass ratio of vinylphosphonic acid to epoxy resin modified polyurethane polymer is 1:5-8.

[0011] Furthermore, the preparation method of the composite corrosion inhibitor includes the following steps: Y1, ball milling aluminum particles under nitrogen protection to obtain flake aluminum powder; Y2, immersing the flake aluminum powder in a modified glycyrrhizic acid solution and stirring to react to obtain the composite corrosion inhibitor.

[0012] Furthermore, in Y2, the weight-to-volume ratio of flake aluminum powder to modified glycyrrhizic acid solution is 0.1-0.3 g: 5 mL.

[0013] Furthermore, the preparation method of the modified glycyrrhizic acid includes the following steps: Z1, glycyrrhizic acid reacts with phosphorus oxychloride in pyridine, and after acidification, precipitation, and purification, phosphorylated glycyrrhizic acid is obtained; Z2, polyethylene glycol reacts with TsCl and then undergoes ammonolysis to obtain amino-terminated polyethylene glycol; Z3, phosphorylated glycyrrhizic acid and amino-terminated polyethylene glycol undergo an amidation reaction to obtain modified glycyrrhizic acid.

[0014] Furthermore, in Z3, the molar ratio of terminal amino polyethylene glycol to phosphorylated glycyrrhizic acid is 0.5-0.7:1.

[0015] Furthermore, this application provides a method for preparing an aqueous zinc plating sealant, comprising the following steps: S1, dispersing and mixing a composite corrosion inhibitor, a wetting and dispersing agent, and a portion of deionized water to obtain a composite solution; under stirring, slowly adding modified polyurethane to the composite solution and mixing evenly; then sequentially adding a film-forming aid, a leveling agent, and a defoamer and mixing evenly; finally adding a pH adjuster and the remaining deionized water to obtain agent A; S2, using phytic acid as agent B, which is stored separately from agent A, and when used, agent B is diluted and mixed with agent A.

[0016] Furthermore, in S2, the dilution ratio of agent B is 10-20%.

[0017] Furthermore, this application provides an application of a water-based zinc plating sealant, wherein the water-based zinc plating sealant is coated onto the surface of a zinc-plated substrate and cured at room temperature for 24-48 hours.

[0018] Compared with the prior art, this application has the following beneficial effects:

[0019] In the water-based zinc plating sealant, polyurethane modified with vinyl phosphate allows the phosphate groups to form coordination bonds with zinc ions in the zinc plating layer, greatly enhancing the sealant's adhesion. Simultaneously, it forms a stable passivation layer on the metal surface. The composite corrosion inhibitor is made by coating flake aluminum powder with modified glycyrrhizic acid. The flake aluminum powder alters the path of the corrosive medium from the sealant to the zinc plating layer, effectively extending the penetration time of the corrosive medium. The modified glycyrrhizic acid is modified through phosphorylation-polyethylene glycol grafting. The phosphate groups form stable PO-Al bonds with the alumina layer on the surface of the flake aluminum powder, while the polyethylene glycol segments enhance the water solubility and dispersibility of the modified glycyrrhizic acid. It can also form intermolecular entanglement with polyurethane, enhancing the compatibility between the composite corrosion inhibitor and polyurethane.

[0020] When coating damage leads to localized corrosion, the H in the microenvironment... + and Cl - It can destroy the alumina passivation film on the surface of aluminum powder, activate the internal aluminum powder, and thus act as a sacrificial anode to undergo controlled dissolution, release aluminum ions, and protect the zinc plating layer; at the same time, aluminum ions can cross-link with free phytic acid and modified glycyrrhizic acid residual carboxyl groups in the sealant, forming a gel-like protective layer at the damaged area, repairing the damaged area, blocking the penetration of corrosive media, and enhancing the corrosion resistance of water-based zinc plating sealant. Attached Figure Description

[0021] Figure 1 The equivalent circuit diagrams for the self-healing tests of Examples 1-3 and Comparative Examples 1-2 are shown.

[0022] Figure 2 The sealing layer resistance R before and after repair in self-healing tests of Examples 1-3 and Comparative Examples 1-2 pore Value graph. Detailed Implementation

[0023] To make the inventive objectives, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. Obviously, the described embodiments are only a portion of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0024] 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 application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0025] When using “including,” “having,” and “contains” as described herein, the intention is to cover non-exclusive inclusion, unless an explicit qualifying term such as “only” is used, in which case another component may be added.

[0026] In this application, "at least one" means one or more, such as one, two, or more. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layered" means at least two layers, such as two layers, three layers, etc., unless otherwise explicitly specified. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise explicitly specified.

[0027] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0028] Unless otherwise specified, all steps in this application may be performed sequentially or randomly. For example, the method comprising steps (a) and (b) indicates that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc. Unless otherwise stated, singular terms may include plural forms and should not be construed as having a quantity of one.

[0029] The present application will be further illustrated by the following examples, but these examples do not limit the scope of the present application.

[0030] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in this application, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. All reagents or instruments whose manufacturers are not specified are conventional products that can be purchased commercially. In addition to the specific methods, equipment, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description in this application, any prior art methods, equipment, and materials similar to or equivalent to those described, used, or made by the methods, equipment, and materials in the embodiments of this application may be used to implement this application.

[0031] Example 1

[0032] In this embodiment, the water-based zinc plating sealant A comprises the following components by weight: 50g modified polyurethane, 5g composite corrosion inhibitor, 0.5g wetting and dispersing agent, 0.2g leveling agent, 0.1g defoamer, 1g film-forming aid, and the balance being deionized water; agent B is phytic acid.

[0033] The modified polyurethane in this embodiment is prepared as follows:

[0034] X1. 1.1 g of pre-dehydrated BDO and 7.44 g of epoxy resin E51 were added to a dry three-necked flask equipped with a reflux condenser and a stirring rod. 70 mL of acetone was added, followed by 2.68 g of dimethylolpropionic acid and 20 mg of dibutyltin dilaurate. The temperature was raised to 60 °C, and 10.92 g of TDI was added dropwise with stirring. After the addition was complete, the temperature was raised to 75 °C to start the prepolymerization reaction. When the amount of residual -NCO in the prepolymer reached the theoretical value, the temperature was lowered to 60 °C and the end-capped with 10 mL of methanol for 3 h to obtain the epoxy resin modified polyurethane polymer.

[0035] X2, add 26.16g of epoxy resin modified polyurethane polymer and 50mL of acetone to a flask, heat to 60℃, add 3.46g of vinyl phosphoric acid, and react for 8h; after the reaction is complete, wash and purify the product, slowly add 4.5g of TEA with a neutralization degree of 100% for 30min, and emulsify and disperse with 150mL of deionized water under high speed stirring to obtain modified polyurethane.

[0036] The preparation method of the composite corrosion inhibitor in this embodiment is as follows:

[0037] Y1, aluminum particles are ground in a ball mill under nitrogen protection to obtain flaky aluminum powder;

[0038] Y2, modified glycyrrhizic acid was dissolved in an ethanol-water mixture and stirred in a warm water bath for 1 hour to obtain a 1 wt% modified glycyrrhizic acid solution. At room temperature, 0.1 g of flake aluminum powder was immersed in 5 mL of the solution and stirred in a round-bottom flask for 2 hours. After filtration, the solution was washed with ethanol and dried to obtain a composite corrosion inhibitor.

[0039] The modified glycyrrhizic acid in this embodiment is prepared as follows:

[0040] Z1. 1 g of glycyrrhizic acid was dispersed in 30 mL of anhydrous pyridine solution. Under ice bath conditions, 220 μL of phosphorus oxychloride was added dropwise. After stirring at room temperature for 8 h, the mixture was poured into ice water and acidified with hydrochloric acid to pH 5. The precipitate was then collected by filtration. The crude product was redissolved in tetrahydrofuran, and the pH was adjusted to 9 with sodium hydroxide. After being poured into ethyl acetate, a precipitate was formed. The precipitate was collected by filtration and dissolved in water. It was then acidified with hydrochloric acid to pH 5. The precipitate was then filtered, washed three times with water, and dried under vacuum to obtain phosphorylated glycyrrhizic acid.

[0041] Z2, 4g of PEG-600 was dissolved in 35mL of CH2Cl2, 1.35g of TsCl and 10mL of pyridine were added, the mixture was stirred and reacted at 25℃ for 24h; the mixture was extracted three times with 3mol / L HCl, the organic layer was collected, excess sodium bicarbonate was added and stirred, filtered, and the filtrate was evaporated to dryness to obtain crude PEG-OTs; the crude product was sonicated and dissolved in THF, then ether was added, the mixture was frozen at 0℃ for 20min, filtered, and vacuum dried at 35℃ overnight to obtain PEG-OTs; 23mL of ammonia and 1mmol of PEG-OTS were added to a 50mL round-bottom flask, the mixture was sonicated and dissolved, the mixture was heated under reflux for 4h and then cooled to room temperature, extracted three times with 15mL of CH2Cl2, the organic phases were combined, 40mL of NaOH solution (1mol / L) was added, the mixture was stirred at 25℃ for 2h, the oily liquid was separated, washed with 40mL of distilled water until neutral, and vacuum dried to obtain amino-terminated polyethylene glycol.

[0042] Z3. Dissolve 3g of phosphorylated glycyrrhizic acid in 30mL of DMSO. After complete dissolution, add 1.104g of NHS and 1.7994g of DCC at 25℃. Stir the mixture for 20min, add terminal amino polyethylene glycol and stir until homogeneous. React at 45℃ for 6h. After washing and purification, vacuum dry for 48h to obtain modified glycyrrhizic acid. The molar amount of terminal amino polyethylene glycol is 0.5 times the molar amount of phosphorylated glycyrrhizic acid.

[0043] The preparation method of the water-based zinc plating sealant in this embodiment is as follows:

[0044] S1. The composite corrosion inhibitor, wetting and dispersing agent and deionized water are fully dispersed and mixed to obtain a composite solution. Modified polyurethane is slowly added to the composite solution under stirring at 200 rpm and mixed evenly. Then, film-forming aid, leveling agent and defoamer are added slowly in sequence. Each aid needs to be stirred for 10 minutes after being added. Finally, the pH of the system is slowly adjusted to 8.5-9.0 with pH adjuster to obtain agent A.

[0045] S2, using phytic acid as agent B, diluted by 10%, and mixed evenly with agent A to obtain a water-based zinc plating sealant.

[0046] Example 2

[0047] In this embodiment, the water-based zinc plating sealant A comprises the following components by weight: 55g modified polyurethane, 8g composite corrosion inhibitor, 1g wetting and dispersing agent, 0.4g leveling agent, 0.2g defoamer, 2g film-forming aid, and the balance being deionized water; agent B is phytic acid.

[0048] The modified polyurethane in this embodiment is prepared as follows:

[0049] X1. 1.1 g of pre-dehydrated BDO and 7.44 g of epoxy resin E51 were added to a dry three-necked flask equipped with a reflux condenser and a stirring rod. 70 mL of acetone was added, followed by 2.68 g of dimethylolpropionic acid and 20 mg of dibutyltin dilaurate. The temperature was raised to 60 °C, and 10.92 g of TDI was added dropwise with stirring. After the addition was complete, the temperature was raised to 75 °C to start the prepolymerization reaction. When the amount of residual -NCO in the prepolymer reached the theoretical value, the temperature was lowered to 60 °C and the end-capped with 10 mL of methanol for 3 h to obtain the epoxy resin modified polyurethane polymer.

[0050] X2, add 26.16g of epoxy resin modified polyurethane polymer and 50mL of acetone to a flask, heat to 60℃, add 4.32g of vinyl phosphoric acid, and react for 8h; after the reaction is complete, wash and purify the product, slowly add 4.5g of TEA with a neutralization degree of 100% for 30min, and emulsify and disperse with 150mL of deionized water under high speed stirring to obtain modified polyurethane.

[0051] The preparation method of the composite corrosion inhibitor in this embodiment is as follows:

[0052] Y1, aluminum particles are ground in a ball mill under nitrogen protection to obtain flaky aluminum powder;

[0053] Y2, modified glycyrrhizic acid was dissolved in an ethanol-water mixture and stirred in a warm water bath for 1 hour to obtain a 1 wt% modified glycyrrhizic acid solution. At room temperature, 0.2 g of flake aluminum powder was immersed in 5 mL of the solution and stirred in a round-bottom flask for 2 hours. After filtration, the solution was washed with ethanol and dried to obtain a composite corrosion inhibitor.

[0054] The modified glycyrrhizic acid in this embodiment is prepared as follows:

[0055] Z1. 1 g of glycyrrhizic acid was dispersed in 30 mL of anhydrous pyridine solution. Under ice bath conditions, 220 μL of phosphorus oxychloride was added dropwise. After stirring at room temperature for 8 h, the mixture was poured into ice water and acidified with hydrochloric acid to pH 5. The precipitate was then collected by filtration. The crude product was redissolved in tetrahydrofuran, and the pH was adjusted to 9 with sodium hydroxide. After being poured into ethyl acetate, a precipitate was formed. The precipitate was collected by filtration and dissolved in water. It was then acidified with hydrochloric acid to pH 5. The precipitate was then filtered, washed three times with water, and dried under vacuum to obtain phosphorylated glycyrrhizic acid.

[0056] Z2, 4g of PEG-600 was dissolved in 35mL of CH2Cl2, 1.35g of TsCl and 10mL of pyridine were added, the mixture was stirred and reacted at 25℃ for 24h; the mixture was extracted three times with 3mol / L HCl, the organic layer was collected, excess sodium bicarbonate was added and stirred, filtered, and the filtrate was evaporated to dryness to obtain crude PEG-OTs; the crude product was sonicated and dissolved in THF, then ether was added, the mixture was frozen at 0℃ for 20min, filtered, and vacuum dried at 35℃ overnight to obtain PEG-OTs; 23mL of ammonia and 1mmol of PEG-OTS were added to a 50mL round-bottom flask, the mixture was sonicated and dissolved, the mixture was heated under reflux for 4h and then cooled to room temperature, extracted three times with 15mL of CH2Cl2, the organic phases were combined, 40mL of NaOH solution (1mol / L) was added, the mixture was stirred at 25℃ for 2h, the oily liquid was separated, washed with 40mL of distilled water until neutral, and vacuum dried to obtain amino-terminated polyethylene glycol.

[0057] Z3. Dissolve 3g of phosphorylated glycyrrhizic acid in 30mL of DMSO. After complete dissolution, add 1.104g of NHS and 1.7994g of DCC at 25℃. Stir the mixture for 20min, then add terminal amino polyethylene glycol and stir until homogeneous. React at 45℃ for 6h. After washing and purification, vacuum dry for 48h to obtain modified glycyrrhizic acid. The molar amount of terminal amino polyethylene glycol is 0.6 times the molar amount of phosphorylated glycyrrhizic acid.

[0058] The preparation method of the water-based zinc plating sealant in this embodiment is as follows:

[0059] S1. The composite corrosion inhibitor, wetting and dispersing agent and deionized water are fully dispersed and mixed to obtain a composite solution. Modified polyurethane is slowly added to the composite solution under stirring at 200 rpm and mixed evenly. Then, film-forming aid, leveling agent and defoamer are added slowly in sequence. Each aid needs to be stirred for 10 minutes after being added. Finally, the pH of the system is slowly adjusted to 8.5-9.0 with pH adjuster to obtain agent A.

[0060] S2, using phytic acid as agent B, diluted by 12% and mixed evenly with agent A to prepare a water-based zinc plating sealant.

[0061] Example 3

[0062] In this embodiment, the water-based zinc plating sealant A comprises the following components by weight: 60g modified polyurethane, 10g composite corrosion inhibitor, 1.5g wetting and dispersing agent, 0.5g leveling agent, 0.3g defoamer, 3g film-forming aid, and the balance being deionized water; and agent B is phytic acid.

[0063] The modified polyurethane in this embodiment is prepared as follows:

[0064] X1. 1.1 g of pre-dehydrated BDO and 7.44 g of epoxy resin E51 were added to a dry three-necked flask equipped with a reflux condenser and a stirring rod. 70 mL of acetone was added, followed by 2.68 g of dimethylolpropionic acid and 20 mg of dibutyltin dilaurate. The temperature was raised to 60 °C, and 10.92 g of TDI was added dropwise with stirring. After the addition was complete, the temperature was raised to 75 °C to start the prepolymerization reaction. When the amount of residual -NCO in the prepolymer reached the theoretical value, the temperature was lowered to 60 °C and the end-capped with 10 mL of methanol for 3 h to obtain the epoxy resin modified polyurethane polymer.

[0065] X2, add 26.16g of epoxy resin modified polyurethane polymer and 50mL of acetone to a flask, heat to 60℃, add 5.19g of vinyl phosphoric acid, and react for 8h; after the reaction is complete, wash and purify the product, slowly add 4.5g of TEA with a neutralization degree of 100% for 30min, and emulsify and disperse with 150mL of deionized water under high speed stirring to obtain modified polyurethane.

[0066] The preparation method of the composite corrosion inhibitor in this embodiment is as follows:

[0067] Y1, aluminum particles are ground in a ball mill under nitrogen protection to obtain flaky aluminum powder;

[0068] Y2, modified glycyrrhizic acid was dissolved in an ethanol-water mixture and stirred in a warm water bath for 1 hour to obtain a 1 wt% modified glycyrrhizic acid solution. At room temperature, 0.3 g of flake aluminum powder was immersed in 5 mL of the solution and stirred in a round-bottom flask for 2 hours. After filtration, the solution was washed with ethanol and dried to obtain a composite corrosion inhibitor.

[0069] The modified glycyrrhizic acid in this embodiment is prepared as follows:

[0070] Z1. 1 g of glycyrrhizic acid was dispersed in 30 mL of anhydrous pyridine solution. Under ice bath conditions, 220 μL of phosphorus oxychloride was added dropwise. After stirring at room temperature for 8 h, the mixture was poured into ice water and acidified with hydrochloric acid to pH 5. The precipitate was then collected by filtration. The crude product was redissolved in tetrahydrofuran, and the pH was adjusted to 9 with sodium hydroxide. After being poured into ethyl acetate, a precipitate was formed. The precipitate was collected by filtration and dissolved in water. It was then acidified with hydrochloric acid to pH 5. The precipitate was then filtered, washed three times with water, and dried under vacuum to obtain phosphorylated glycyrrhizic acid.

[0071] Z2, 4g of PEG-600 was dissolved in 35mL of CH2Cl2, 1.35g of TsCl and 10mL of pyridine were added, the mixture was stirred and reacted at 25℃ for 24h; the mixture was extracted three times with 3mol / L HCl, the organic layer was collected, excess sodium bicarbonate was added and stirred, filtered, and the filtrate was evaporated to dryness to obtain crude PEG-OTs; the crude product was sonicated and dissolved in THF, then ether was added, the mixture was frozen at 0℃ for 20min, filtered, and vacuum dried at 35℃ overnight to obtain PEG-OTs; 23mL of ammonia and 1mmol of PEG-OTS were added to a 50mL round-bottom flask, the mixture was sonicated and dissolved, the mixture was heated under reflux for 4h and then cooled to room temperature, extracted three times with 15mL of CH2Cl2, the organic phases were combined, 40mL of NaOH solution (1mol / L) was added, the mixture was stirred at 25℃ for 2h, the oily liquid was separated, washed with 40mL of distilled water until neutral, and vacuum dried to obtain amino-terminated polyethylene glycol.

[0072] Z3. Dissolve 3g of phosphorylated glycyrrhizic acid in 30mL of DMSO. After complete dissolution, add 1.104g of NHS and 1.7994g of DCC at 25℃. Stir the mixture for 20min, then add terminal amino polyethylene glycol and stir until homogeneous. React at 45℃ for 6h. After washing and purification, vacuum dry for 48h to obtain modified glycyrrhizic acid. The molar amount of terminal amino polyethylene glycol is 0.7 times the molar amount of phosphorylated glycyrrhizic acid.

[0073] The preparation method of the water-based zinc plating sealant in this embodiment is as follows:

[0074] S1. The composite corrosion inhibitor, wetting and dispersing agent and deionized water are fully dispersed and mixed to obtain a composite solution. Modified polyurethane is slowly added to the composite solution under stirring at 200 rpm and mixed evenly. Then, film-forming aid, leveling agent and defoamer are added slowly in sequence. Each aid needs to be stirred for 10 minutes after being added. Finally, the pH of the system is slowly adjusted to 8.5-9.0 with pH adjuster to obtain agent A.

[0075] S2, using rhein as agent B, diluted by 15% and mixed evenly with agent A to prepare a water-based zinc plating sealant.

[0076] Comparative Example 1

[0077] In this comparative example, the water-based zinc plating sealant A consists of the following components by weight: 55g modified polyurethane, 1g wetting and dispersing agent, 0.4g leveling agent, 0.2g defoamer, 2g film-forming aid, and the balance being deionized water; agent B is phytic acid.

[0078] The preparation method of the water-based zinc plating sealant in this comparative example is as follows:

[0079] S1. Fully disperse and mix flake aluminum powder, wetting and dispersing agent and deionized water to obtain a composite solution; under stirring at 200 rpm, slowly add modified polyurethane to the composite solution and mix evenly. Then slowly add film-forming aid, leveling agent and defoamer in sequence. Stir for 10 minutes after each aid is added. Finally, use pH adjuster to slowly adjust the pH of the system to 8.5-9.0 to obtain agent A.

[0080] S2, using phytic acid as agent B, diluted by 12% and mixed evenly with agent A to prepare a water-based zinc plating sealant.

[0081] The preparation method of the modified polyurethane in this comparative example is the same as that in Example 2.

[0082] Comparative Example 2

[0083] In this comparative example, the water-based zinc plating sealant comprises the following components by weight: 55g polyurethane, 8g composite corrosion inhibitor, 1g wetting and dispersing agent, 0.4g leveling agent, 0.2g defoamer, 2g film-forming aid, and the balance being deionized water.

[0084] The preparation method of the composite corrosion inhibitor in this comparative example is as follows:

[0085] Y1, aluminum particles are ground in a ball mill under nitrogen protection to obtain flaky aluminum powder;

[0086] Y2, glycyrrhizic acid was dissolved in an ethanol-water mixture and stirred in a warm water bath for 1 hour to obtain a 1 wt% glycyrrhizic acid solution. At room temperature, 0.2 g of flake aluminum powder was immersed in 5 mL of this solution and stirred in a round-bottom flask for 2 hours. After filtration, the solution was washed with ethanol and dried to obtain a composite corrosion inhibitor.

[0087] The preparation method of the water-based zinc plating sealant in this comparative example is as follows:

[0088] S1. The composite corrosion inhibitor, wetting and dispersing agent and deionized water are fully dispersed and mixed to obtain a composite solution. Under stirring at 200 rpm, polyurethane is slowly added to the composite solution and mixed evenly. Then, film-forming aid, leveling agent and defoamer are added slowly in sequence. Each aid needs to be stirred for 10 minutes after addition. Finally, the pH of the system is slowly adjusted to 8.5-9.0 with a pH adjuster to obtain a water-based zinc plating sealant.

[0089] Performance testing

[0090] Water-based galvanized sealing layer adhesion test: Adhesion of the sealing layer was tested using an adhesion cross-cut test according to GB / T 9286-2021 standard. Eleven intersecting scratches with a 1mm spacing were made on the paint film surface, forming 100 squares. Transparent tape was then adhered to the scratched surface and quickly peeled off at a 45°-60° angle. The extent of paint film peeling off the squares was observed. According to the standard, the best result is grade 0, with completely smooth cut edges and no paint peeling off the squares. The worst result is grade 5, with paint peeling exceeding 65%.

[0091] Corrosion resistance test: Following GB / T 40299-2021 "Corrosion Testing of Metals and Alloys - Applicable Conventions for Electrochemical Measurement Methods", a three-electrode system was used. A self-prepared water-based zinc-plated sealing layer was used as the working electrode, a 1cm diameter Pt electrode as the counter electrode, and a saturated calomel electrode as the reference electrode. The auxiliary platinum electrode was aligned parallel to the working electrode to ensure a uniform current distribution around the electrode. The reference electrode was always immersed in the bulk solution to reduce voltage. The corrosion current and corrosion voltage were then measured.

[0092] Impact resistance test: The impact resistance of the coating is tested using a paint film impact tester according to GB / T 1732-1993 standard. The coating is placed face up on a base, and the impact hammer is raised to a certain height and dropped freely. The coating surface is observed for any damage or other defects. For reverse impact, the coating is placed face down, and the remaining steps are the same as for forward impact. Multiple tests are performed, and the average value is taken. It is required that the impact point not fall within 10cm of the coating edge, and the distance between each impact point should not be less than 10cm to prevent experimental errors.

[0093] Self-healing test: A scratch was made on the sealing layer with a sharp knife, and then the sample was placed in a salt spray chamber. The sealing layer was divided into three groups: the original sample, the sample marked with the surface scratch (damaged sample), and the sample marked after self-healing (repaired sample). Electrochemical impedance spectroscopy was performed using an electrochemical workstation to analyze the self-healing performance. A three-electrode system was used: a tinplate plate coated with the sealing layer as the working electrode, a saturated calomel electrode as the reference electrode, and a graphite rod as the counter electrode. The electrolyte solution was a solution containing 3.5% NaCl. The frequency range of the test was 10 Hz. -2 Hz-10 5 Hz.

[0094] Table 1. Performance test results of the water-based zinc plating sealant in Examples 1-3 and Comparative Examples 1-2

[0095]

[0096] Analyze Examples 1-3 and Comparative Examples 1-2, in conjunction with Table 1, Figures 1-2It can be seen that by modifying polyurethane with phosphoric acid and incorporating glycyrrhizic acid grafted with phosphorylated polyethylene glycol to coat the flake aluminum powder, the water-based zinc plating sealant has good adhesion, corrosion resistance, impact resistance and self-healing properties.

[0097] Figure 1 In the equivalent circuit diagram, R s It is the solution resistance, R pore It is the resistance of the sealing layer, R ct It is charge transfer resistance, Q c It is a polarization element, Q dl It is a constant phase element, where Q c Q dl These represent closed-layer capacitors and double-layer capacitors, respectively.

[0098] analyze Figures 1-2 As shown in Table 1, the water-based zinc plating sealant prepared in Comparative Example 1, compared to Examples 1-3, did not contain flake aluminum powder or modified glycyrrhizic acid, but it underwent phosphorylation modification of polyurethane. This resulted in better adhesion for the water-based zinc plating sealant in Comparative Example 1, but its corrosion current density increased significantly while its corrosion potential decreased significantly. The water-based zinc plating sealant prepared in Comparative Example 2, compared to Examples 1-3, did not modify the polyurethane, nor did it modify glycyrrhizic acid or add phytic acid. This made it difficult to form a good cross-linking network, resulting in a significant decrease in the adhesion of the water-based zinc plating sealant in Comparative Example 2 and a decrease in the sealing layer resistance R. pore There was no significant recovery after the injury.

[0099] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A water-based zinc plating sealant, characterized in that, Includes Agent A and Agent B; The A agent comprises the following components by weight: 50-60 parts modified polyurethane, 5-12 parts composite corrosion inhibitor, 0.5-1.5 parts wetting and dispersing agent, 0.2-0.5 parts leveling agent, 0.1-0.3 parts defoamer, 1-3 parts film-forming aid, and the balance being deionized water; Agent B is phytic acid or rhein; The preparation method of the modified polyurethane includes the following steps: X1, epoxy resin, 1,4-butanediol, dimethylolpropionic acid, and TDI are reacted stepwise and then capped with methanol to obtain epoxy resin modified polyurethane polymer; X2, the epoxy resin modified polyurethane polymer is reacted with vinyl phosphate through a ring-opening reaction and then neutralized and emulsified to obtain modified polyurethane. The preparation method of the composite corrosion inhibitor includes the following steps: Y1, ball milling aluminum particles under nitrogen protection to obtain flake aluminum powder; Y2, immersing the flake aluminum powder in a modified glycyrrhizic acid solution and stirring to react to obtain the composite corrosion inhibitor; The preparation method of the modified glycyrrhizic acid includes the following steps: Z1, glycyrrhizic acid reacts with phosphorus oxychloride in pyridine, and after acidification, precipitation and purification, phosphorylated glycyrrhizic acid is obtained; Z2, polyethylene glycol reacts with TsCl and then undergoes ammonolysis to obtain amino-terminated polyethylene glycol; Z3, phosphorylated glycyrrhizic acid and amino-terminated polyethylene glycol undergo an amidation reaction to obtain modified glycyrrhizic acid.

2. The water-based zinc plating sealant according to claim 1, characterized in that, In X2, the mass ratio of vinylphosphonic acid to epoxy resin modified polyurethane polymer is 1:5-8.

3. The water-based zinc plating sealant according to claim 1, characterized in that, In Y2, the weight-to-volume ratio of flake aluminum powder to modified glycyrrhizic acid solution is 0.1-0.3 g: 5 mL.

4. The water-based zinc plating sealant according to claim 1, characterized in that, In Z3, the molar ratio of amino-terminated polyethylene glycol to phosphorylated glycyrrhizic acid is 0.5-0.7:

1.

5. A method for preparing a water-based zinc plating sealant as described in any one of claims 1-4, characterized in that, The process includes the following steps: S1, dispersing and mixing the composite corrosion inhibitor, wetting and dispersing agent with a portion of deionized water to obtain a composite solution; slowly adding the modified polyurethane to the composite solution under stirring, and mixing evenly; then adding the film-forming aid, leveling agent, and defoamer in sequence, and mixing evenly; finally adding the pH adjuster and the remaining deionized water to obtain agent A; S2, using phytic acid as agent B, storing it separately from agent A, and diluting agent B before use and mixing it with agent A.

6. The method for preparing a water-based zinc plating sealant according to claim 5, characterized in that, In S2, the dilution ratio of agent B is 10-20%.

7. The application of a water-based zinc plating sealant as described in any one of claims 1-4, characterized in that, Apply water-based zinc plating sealant to the surface of the zinc-plated substrate and cure at room temperature for 24-48 hours.

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