A water-based phenolic epoxy passivator, its preparation method and application

Abstract

The application provides a water-based phenolic epoxy passivator, a preparation method and application thereof. The passivator is compounded by A component and B component; the A component comprises: 15-50 parts of water-based phenolic epoxy resin, 2-5 parts of coupling agent, 1-6 parts of film forming aid, 0.1-2 parts of molybdenum salt, 0.05-2 parts of titanium salt, 0.05-2 parts of vanadium salt, 0-1 part of functional aid and water; the water-based phenolic epoxy resin is polyether modified phenolic epoxy resin, the epoxy equivalent weight is 340-400, and the polyether content is 10-20%; the B component is mixed by phenolic amine and polyether amine according to solid content 1-2:1, the active hydrogen equivalent weight of the B component is 90-110 g / eq; the A component and the B component are compounded according to the epoxy equivalent weight and the active hydrogen equivalent weight 1.05-1.2:1. The passivation film formed by the passivator is crosslinked and dense, the salt spray resistance is greater than or equal to 240 h, the solvent resistance, the alkali resistance and the high temperature yellowing resistance are all less than or equal to 1.8, the 180° bending has no crack, and the passivator is environment-friendly and chromium-free.

Description

Technical Field

[0001] This invention belongs to the field of metal material surface treatment technology, specifically relating to a water-based phenolic epoxy passivating agent, its preparation method, and its application. Background Technology

[0002] Galvanized steel sheets are widely used in construction, automotive, and home appliance industries due to their excellent corrosion resistance, mechanical strength, and cost advantages. However, a loose oxide layer easily forms on the surface of galvanized steel sheets, making them highly susceptible to corrosion in humid or salt spray environments. This leads to surface failure and shortened service life, necessitating passivation treatment to improve their corrosion resistance. While traditional chromate passivating agents are highly effective, hexavalent chromium is highly toxic and carcinogenic, and its use has been restricted by environmental regulations in many countries. Therefore, developing chromium-free, environmentally friendly, and high-performance passivating agents has become an industry trend.

[0003] Currently, existing chromium-free passivators mainly include zirconium-titanium, molybdate, rare earth, and organic resin systems. While zirconium-titanium passivators are environmentally friendly, the passivation films they form are relatively thin, with limited corrosion resistance and adhesion. Furthermore, some systems contain fluorides, posing certain environmental risks. Molybdate passivators are low in toxicity and have some advantages in replacing chromates, but hexavalent molybdates have weaker oxidizing power than hexavalent chromates, resulting in passivation films with poor corrosion resistance. Rare earth passivators are environmentally friendly, but suffer from slow film formation speed, poor film uniformity, and high cost, making large-scale industrial application difficult. While ordinary organic resin passivators can improve film adhesion, their wide molecular weight distribution and poor film density make them prone to pinholes and cracks, leading to poor corrosion resistance of the passivation film.

[0004] In addition, organic-inorganic composite passivating agents have become a research hotspot in recent years due to their synergistic effect. However, existing technologies still have the following problems: CN104178757A discloses a chromium-free composite passivating agent containing zirconium salt. Although the metal film formed by this passivating agent has good corrosion resistance, its film layer is relatively thin and its solvent resistance and alkali resistance are insufficient. CN105937029A proposes an inorganic-organic composite passivating liquid, which has good environmental protection properties, but the preparation process is relatively complex and the film uniformity is poor. CN117867484A discloses an alkaline chromium-free passivating agent, which can improve the yellowing resistance and alkali resistance of the film layer, but its salt spray resistance and film crosslinking density still need to be improved.

[0005] Therefore, there is an urgent need to develop a chromium-free passivating agent that is environmentally friendly, forms dense films, is resistant to chemical corrosion, and is resistant to solvents. Summary of the Invention

[0006] In view of the insufficient crosslinking density of the film layer in the existing chromium-free passivating agent for galvanized steel sheets, which makes it difficult to achieve the coating's corrosion resistance, solvent resistance, and alkali resistance, the purpose of this invention is to provide a water-based phenolic epoxy passivating agent, its preparation method, and its application. By rationally designing the resin structure and optimizing the ratio of inorganic salts to organic amines, a high crosslinking density and multiple resistances of the passivation film can be achieved.

[0007] To achieve the above technical objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides an aqueous phenolic epoxy passivating agent, wherein the passivating agent is prepared by compounding separately stored component A and component B before use; wherein component A is composed of raw materials in a total weight of 100 parts: 15-50 parts aqueous phenolic epoxy resin, 2-5 parts coupling agent, 1-6 parts film-forming aid, 0.1-2 parts molybdenum salt, 0.05-2 parts titanium salt, 0.05-2 parts vanadium salt, 0-1 parts functional aid, and the balance being water; The waterborne phenolic epoxy resin in component A is a polyether-modified phenolic epoxy resin with an epoxy equivalent of 340-400 g / eq, and the mass content of polyether segments in the waterborne phenolic epoxy resin is 10-20%. Component B is a mixture of phenolic amine and polyether amine in a solid mass ratio of 1 to 2:1. Component B also contains a solvent. The solid content of component B is 60 to 80%. The active hydrogen equivalent of component B is 90 to 110 g / eq. The components A and B are compounded at a ratio of 1.05-1.2:1, based on the epoxy equivalent in component A and the active hydrogen equivalent in component B. Preferably, component A, in 100 parts by weight, comprises: 20-40 parts of waterborne phenolic epoxy resin, 2-4 parts of coupling agent, 2-5 parts of film-forming aid, 0.5-1.5 parts of molybdenum salt, 0.5-1.5 parts of titanium salt, 0.5-1.5 parts of vanadium salt, 0.5-1.0 parts of functional additive, and the balance being water.

[0008] Preferably, the polyether is at least one of polyethylene glycol, polypropylene glycol, ethylene oxide-propylene oxide block polyether, and polytetrahydrofuran ether; more preferably, the molecular weight of the polyether is between 600 and 2000.

[0009] Preferably, the coupling agent is at least one of a silane coupling agent, a titanate coupling agent, and an aluminate coupling agent; wherein the titanate coupling agent is selected from at least one of KR138S and KR238S; the aluminate coupling agent is selected from at least one of ACA-EAA1 / HY-1804; the silane coupling agent is at least one of KH550, KH560, KH540, and Z6121; and / or, the film-forming aid is at least one of trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, alkoxylated glycerol triacrylate, ethylene glycol butyl ether, propylene glycol butyl ether, diethylene glycol butyl ether, dipropylene glycol butyl ether, propylene glycol methyl ether acetate, methyl 3-methoxypropionate, propylene glycol methyl ether, dipropylene glycol methyl ether acetate, tripropylene glycol n-butyl ether, dipropylene glycol n-butyl ether, and alcohol ester twelve.

[0010] More preferably, the coupling agent is a silane coupling agent.

[0011] Preferably, the molybdenum salt is selected from at least one of sodium molybdate, potassium molybdate, ammonium molybdate, and ammonium phosphomolybdate; and / or, the titanium salt is selected from at least one of titanium sulfate, titanium oxysulfate, and ammonium fluorotitanate; and / or, the vanadium salt is selected from at least one of sodium metavanadate, ammonium metavanadate, potassium metavanadate, and vanadium oxysulfate.

[0012] Preferably, the functional additives include at least one of wetting agents, defoamers, colorants, and dispersants.

[0013] The wetting agent can be selected from sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, nonylphenol polyoxyethylene ether, polyether-modified silicone oil (TEGO Twin series, Surfynol series, Silok 8035, Hydropalat® WE). One of 3229 and KLTL4100; the defoamer can be a polyether (AF-337B, AF-343L, AF-2070) or a polyether-modified silicone defoamer (AF-1815C, BD-3037, AF-1816C); the colorant can be a commercially available organic dye; the dispersant can be anionic surfactants (sodium dodecylbenzenesulfonate, α-olefin sulfonate, sodium dodecyl sulfate, sodium fatty alcohol polyoxyethylene ether sulfate, sodium stearate, sodium oleate, alkylphenol polyoxyethylene ether phosphate), nonionic surfactants (lauryl alcohol polyoxyethylene ether, cetearyl alcohol polyether, nonylphenol polyoxyethylene ether, sorbitan ester, polyoxyethylene sorbitan ester, cocoyl diethanolamide), aminotrimethylphosphonic acid (ATMP), hydroxyethylidene diphosphonic acid (HEDP), or polytetrafluoroethylene concentrated dispersion.

[0014] Preferably, the phenolic amine is a mixture of polyether-type phenolic amine and cashew phenolic amine; more preferably, the phenolic amine is a mixture of polyether-type phenolic amine and cashew phenolic amine at a solid content ratio of 1~1.5:1; and / or, the polyether amine is a secondary amino-type polyether amine.

[0015] Optionally, the solvent may be selected from one of the following: ethylene glycol butyl ether, dipropylene glycol butyl ether, propylene glycol methyl ether, propylene glycol butyl ether, dipropylene glycol methyl ether, propylene glycol methyl ether acetate, ethanol, benzyl alcohol, acetone, butanone, ethyl acetate, butyl acetate, propylene glycol methyl ether and water, ethylene glycol butyl ether and water, dipropylene glycol methyl ether and water, ethanol and water, or acetone and water.

[0016] In a second aspect, the present invention provides a method for preparing the passivating agent as described in the first aspect, comprising the following steps: S1. Mix the formulated amount of waterborne phenolic epoxy resin with water to obtain the first mixture; S2. Heat the first mixture to 40~60℃, add the amount of coupling agent specified in the formula, and keep the reaction at this temperature for 1~3 hours to obtain the second mixture. S3. Cool the second mixture to room temperature, and add the film-forming aid, molybdenum salt, titanium salt, vanadium salt and functional aid in sequence to obtain component A; S4. Mix the formulated amount of phenolic amine and polyether amine, add an appropriate amount of solvent, and obtain component B with a solid content of 60-80%. The solvent can be selected from: ethylene glycol butyl ether, dipropylene glycol butyl ether, propylene glycol methyl ether, propylene glycol butyl ether, dipropylene glycol methyl ether, propylene glycol methyl ether acetate, ethanol, benzyl alcohol, acetone, butanone, ethyl acetate, butyl acetate, propylene glycol methyl ether and water, ethylene glycol butyl ether and water, dipropylene glycol methyl ether and water, ethanol and water, or acetone and water.

[0017] Thirdly, the present invention provides an application of the passivating agent as described in the first aspect for passivation treatment of galvanized sheet surface.

[0018] Preferably, the passivating agent A and B are mixed evenly at a ratio of epoxy equivalent in component A to active hydrogen equivalent in component B of 1.05-1.2:1. The mixture is then coated onto the surface of the galvanized sheet and baked at 80-100°C for 6-10 seconds to form a passivation film with a thickness of 0.8-1.2 μm.

[0019] Compared with the prior art, the present invention has the following beneficial effects: Firstly, the passivating agent of this invention, through a two-component design and cross-linking with organic amines, can form a dense three-dimensional network structure, significantly improving the density and corrosion resistance of the film. Experiments show that the film formed using this passivating agent has excellent resistance: salt spray resistance ≥240h, solvent and alkali resistance ΔE ≤1.8 or even 0.5, high temperature yellowing resistance ΔE ≤3.0, or even lower than 1.7; strong film-substrate adhesion, the passivated film shows no cracks or peeling after 180° bending test; the film appearance is uniform with no color difference, no yellow edges, and no color variation.

[0020] Secondly, in the passivating agent of the present invention, component A and component B are stored separately and mixed evenly during use, which allows the passivating agent to be stored for a long time (not less than 1 year) under normal conditions (such as room temperature 20-35℃, sealed). Moreover, through the screening of suitable water-based phenolic epoxy and organic amine, the trial period of the mixture of components A and B is about 24 hours, which meets the needs of industrial production.

[0021] Third, the passivating agent of this invention does not contain heavy metals such as hexavalent chromium, lead, mercury, and cadmium. The production process produces no toxic wastewater or exhaust gas, and the waste can be naturally degraded, thus eliminating the risk of environmental pollution from the source and ensuring safety and environmental protection.

[0022] Fourth, the passivating agent preparation process of the present invention is simple, the conditions are mild, no special equipment is required, the production input is low, and large-scale continuous production can be achieved, which has significant economic and social benefits.

[0023] Fifth, the passivating agent of this invention is applicable to various types of galvanized sheets, including hot-dip galvanized sheets, electro-galvanized sheets, alloyed galvanized sheets, etc., and can be widely used in many fields such as automobiles, home appliances, construction, and hardware, with strong practicality and market promotion value.

[0024] Sixth, compared with CN104178757A, this invention achieves a synergistic effect of salt spray resistance ≥240h and solvent resistance ΔE as low as 0.35 by introducing waterborne phenolic epoxy resin with specific phenolic and polyether contents and compounding it with a ternary inorganic system of molybdenum salt, titanium salt and vanadium salt. Detailed Implementation

[0025] The main raw materials used in the embodiments and comparative examples of this invention are as follows, but are not limited thereto. The invention is merely illustrated using these raw materials as examples, and is not intended to be limiting. It should be noted that other optional components of the raw materials in this invention can also yield results largely similar to those disclosed in the embodiments: (1) Waterborne phenolic epoxy resin: synthesized in the laboratory. The specific synthesis process is as follows: Step 1: Grafting reaction of polyether with phenolic epoxy resin F-44 type linear phenolic multifunctional epoxy resin (or F-51 type linear phenolic multifunctional epoxy resin) was added to a reactor, along with an appropriate amount of ethylene glycol butyl ether (or propylene glycol methyl ether as a solvent). The mixture was heated to approximately 100°C and stirred until dissolved. Polyethylene glycol and triphenylphosphine catalyst were added according to the designed ratio (in this example, the final mass content of the polyether segment in the aqueous phenolic epoxy resin was controlled to be 14%). The amount of triphenylphosphine catalyst added was 5% of the mass of the F-44 type linear phenolic multifunctional epoxy resin. The temperature was raised to 120°C and maintained for 2 hours. During the reaction, the hydroxyl groups at the end of the polyether reacted with the epoxy groups of the phenolic epoxy resin in a ring-opening addition reaction, chemically bonding the polyether segment to the side chains of the phenolic epoxy backbone. The reaction progress was monitored by periodically sampling and measuring the epoxy equivalent (epoxy equivalent measurement refers to GB / T 4612-2008) until the epoxy equivalent reached the target range of 340-400.

[0026] In the above process, the polyether is one of polyethylene glycol, polypropylene glycol, ethylene oxide-propylene oxide block polyether, or polytetrahydrofuran ether.

[0027] Step 2: Water-based treatment The modified resin was cooled to approximately 40°C, and an appropriate amount of surfactant NP8836 was added to assist emulsification (other emulsifiers from the NP series can also be used). The amount of NP8836 added was 1.5% of the total mass of the F-44 type linear phenolic polyfunctional epoxy resin and polyether. The system was neutralized to pH 6.5 using triethanolamine as a neutralizing agent. Deionized water was slowly added under high-speed stirring to achieve reverse emulsification, yielding an aqueous phenolic epoxy resin emulsion with a solid content of 40-60%.

[0028] The polyether used in the preparation of the waterborne phenolic epoxy resin can also be polypropylene glycol, ethylene oxide-propylene oxide block polyether, or polytetrahydrofuran ether, with a molecular weight of 600-2000.

[0029] The above describes a laboratory synthesis method for waterborne phenolic epoxy resin. This invention can also use commercially available waterborne phenolic epoxy resin as a raw material.

[0030] In this invention, the waterborne phenolic epoxy resin is used in the form of a laboratory-synthesized emulsion, and the solid content of the emulsion is 40% to 60% (50% in all examples).

[0031] (2) Commercially available ordinary waterborne acrylic resin: average molecular weight 45,000; and commercially available ordinary waterborne polyurethane resin: average molecular weight 25,000. (3) Silane coupling agents: KH550, KH540, KH570, Z6121, KH560; Titanate coupling agents and aluminate coupling agents have the same function as silane coupling agents in the passivating agents of the present invention, and the results are slightly worse, but there is no substantial difference overall. In the examples, only silane coupling agents are used as examples for illustration. (4) Film-forming aids: ethylene glycol butyl ether, propylene glycol methyl ether acetate, and alcohol ester dodecyl; (5) Molybdenum salts: ammonium molybdate, potassium molybdate, ammonium phosphomolybdate; (6) Titanium salts: titanium oxysulfate, titanium sulfate, ammonium fluorotitanate; (7) Vanadium salts: sodium metavanadate, ammonium metavanadate, potassium metavanadate, vanadium oxysulfate; (8) Functional additives: polysiloxane wetting agent (BYK-024), polyether modified silicone defoamer (BYK-348); (9) Polyether-type phenolic amine: purchased from Carderley, model NC-541; cashew phenol-type phenolic amine: purchased from Carderley, model NC-540; polyether amine: purchased from Huntsman, D-400.

[0032] Furthermore, the passivating agent provided in this embodiment of the invention consists of two components, A and B. Before use, components A and B are mixed uniformly in a ratio of epoxy equivalent and active hydrogen equivalent of 1.05-1.2:1. Below this ratio, the crosslinking density is low, the flexibility is slightly better, the rigidity is slightly worse, and the chemical resistance of the coating will also decrease; above this ratio, the crosslinking density is high, the flexibility is slightly worse, the coating is slightly brittle, and the free amine does not participate in crosslinking, which will also lead to a decrease in the chemical resistance of the coating. Among them, according to 100 parts in total, component A consists of 20-40 parts of waterborne phenolic epoxy resin, 2-4 parts of silane coupling agent, 2-5 parts of film-forming aid, 0.5-1.5 parts of molybdenum salt, 0.5-1.5 parts of titanium salt, 0.5-1.5 parts of vanadium salt, 0.5-1.0 parts of functional additive, and the balance water. Component B is an organic composite amine, specifically: phenolic amine and polyether amine are compounded at a solid content ratio of 1~2:1, wherein the phenolic amine is a mixture of polyether-type phenolic amine and cashew phenolic amine at a solid content ratio of 1~1.5:1; the polyether amine is a secondary amino-type polyether amine. Phenolic amine has good chemical resistance but is brittle and has poor flexibility; polyether amine has good flexibility but poor chemical resistance. Within the compounding range of this invention, the advantages of both can be fully utilized to compensate for each other's shortcomings, so that the flexibility of the passivating agent reaches the optimal balance, forming a dense film structure with excellent resistance. In the embodiments of this invention, the preparation method of the passivating agent is as follows: S1. Add the formulated amount of waterborne phenolic epoxy resin and deionized water to the reaction vessel, and stir at a speed of 200~300r / min for 5~10min until completely dispersed to obtain the first mixture. S2. Heat the first mixture to about 50°C, slowly add the formulated amount of silane coupling agent dropwise to the above resin aqueous solution, and then keep it warm for 2 hours to obtain the second mixture. S3. Return the second mixture to room temperature, then add the film-forming aid, molybdenum salt, titanium salt, vanadium salt, and functional aid in sequence according to the formulation amount, and stir for 10-15 min to obtain component A; S4. Phenolic amine and polyether amine are mixed according to the specified ratio, and an appropriate amount of solvent is added to obtain component B with a solid content of 60-80%. In the example, the solvent used is a mixture of propylene glycol methyl ether and water at a volume ratio of 3:1.

[0033] Furthermore, it should be noted that unless specific conditions are specified in the examples, they should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0034] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for illustrative purposes only and not for limiting the scope of protection of the present invention. Furthermore, it should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning understood by those skilled in the art.

[0035] Examples 1-12 Examples 1-12 relate to water-based phenolic epoxy passivating agents and their preparation methods. The components of the passivating agents in each example are as follows: Example 1: Based on a total weight of 100g, component A consists of: 20g of waterborne phenolic epoxy resin (epoxy equivalent of 360 g / eq, polyether content of 14%, polyether being polyethylene glycol 600), 2g of KH560, 2g of dodecyl alcohol ester, 0.5g of ammonium molybdate, 0.5g of titanium oxysulfate, 0.5g of sodium metavanadate, 0.5g of wetting agent BYK-024, 0.5g of defoamer BYK-348, and the balance being deionized water; Component B: Phenolic amine, which is a mixture of polyether-type phenolic amine and cashew phenolic amine at a solid content ratio of 1.5:1; polyether amine, which is a secondary amino-type polyether amine; the phenolic amine and polyether amine are mixed at a solid content ratio of 2:1, and the solid content of component B is adjusted to 70% with propylene glycol methyl ether and water. The active hydrogen equivalent in component B is 100 g / eq.

[0036] Component A and Component B are compounded at a ratio of 1.1:1 (epoxide equivalent in Component A to active hydrogen equivalent in Component B). Component A is used in an amount of 100g, and Component B in an amount of 3.61g. Mix immediately before use. The passivating agent preparation method is described below.

[0037] Example 2: Based on a total weight of 100g, component A consists of: 30g of waterborne phenolic epoxy resin (epoxy equivalent of 360 g / eq, polyether content of 14%, polyether being polypropylene glycol 1000), 2.5g of KH550, 3g of ethylene glycol butyl ether, 0.5g of potassium molybdate, 0.5g of titanium sulfate, 0.5g of ammonium metavanadate, 0.5g of wetting agent BYK-024, 0.5g of defoamer BYK-348, and the balance being deionized water; Component B: Same as in Example 1.

[0038] The proportions and preparation methods for both components are the same as in Example 1. Component A is used in an amount of 100g, and component B is used in an amount of 5.41g.

[0039] Example 3: Based on a total weight of 100g, component A consists of: 30g of waterborne phenolic epoxy resin (with an epoxy equivalent of 360 g / eq, a polyether content of 14%, and the polyether being ethylene oxide-propylene oxide block polyether 1200), 3g of KH570, 4g of propylene glycol methyl ether acetate, 1.5g of ammonium phosphomolybdate, 1.5g of ammonium fluorotitanate, 1.5g of potassium metavanadate, 0.5g of wetting agent BYK-024, 0.5g of defoamer BYK-348, and the remainder being deionized water; Component B: Same as in Example 1.

[0040] The proportions and preparation methods for both components are the same as in Example 1. Component A is used in an amount of 100g, and component B is used in an amount of 5.41g.

[0041] Example 4: Based on a total weight of 100g, component A consists of: 40g of waterborne phenolic epoxy resin (epoxy equivalent of 360 g / eq, polyether content of 14%, polyether being polytetrahydrofuran ether 2000), 4 parts of KH560, 5g of dodecyl alcohol ester, 1.5g of ammonium phosphomolybdate, 1.5g of titanium oxysulfate, 1.5g of vanadium oxysulfate, 0.5g of wetting agent BYK-024, 0.5g of defoamer BYK-348, and the balance of deionized water; Component B: Same as in Example 1.

[0042] The proportions and preparation methods for both components are the same as in Example 1. Component A is used in an amount of 100g, and component B is used in an amount of 7.22g.

[0043] Example 5 The difference from Example 1 is that the polyether in the waterborne phenolic epoxy resin is polypropylene glycol 1000 (with an epoxy equivalent of 380 g / eq), and the rest is the same as in Example 1. The amount of component A is 100 g, and the amount of component B is 3.42 g.

[0044] Example 6 The difference from Example 1 is that the polyether in the waterborne phenolic epoxy resin is ethylene oxide-propylene oxide block polyether 1200 (its epoxy equivalent is 400 g / eq), and the rest is the same as in Example 1. The amount of component A is 100 g, and the amount of component B is 3.25 g.

[0045] Example 7 The difference from Example 1 is that the polyether in the waterborne phenolic epoxy resin is polytetrahydrofuran ether 2000 (with an epoxy equivalent of 390 g / eq), and the rest is the same as in Example 1. The amount of component A is 100 g, and the amount of component B is 3.33 g.

[0046] Example 8 The difference from Example 1 is that the amount of waterborne phenolic epoxy resin used is 50g, and the amount of water is reduced by 30g accordingly; otherwise, it is the same as Example 1. The amount of component A is 100g, and the amount of component B is 9.02g.

[0047] Example 9 The difference from Example 1 is that the amount of waterborne phenolic epoxy resin used is 15g, and the amount of water is increased by 5g accordingly; the rest is the same as in Example 1. The amount of component A is 100g, and the amount of component B is 2.71g.

[0048] Example 10 The difference from Example 1 is that the polyether content in the waterborne phenolic epoxy resin is 10% (its epoxy equivalent is 340 g / eq), and the rest is the same as in Example 1. The amount of component A is 100 g, and the amount of component B is 3.82 g.

[0049] Example 11 The difference from Example 1 is that the polyether content in the waterborne phenolic epoxy resin is 20% (its epoxy equivalent is 400 g / eq), and the rest is the same as in Example 1. The amount of component A is 100 g, and the amount of component B is 3.25 g.

[0050] Example 12 The difference from Example 1 is that in component B, phenolic amine and polyether amine are mixed in a 1:1 solid content ratio, and the active hydrogen equivalent in component B is 90 g / eq. The rest is the same as in Example 1. The amount of component A is 100 g, and the amount of component B is 3.40 g.

[0051] Comparative Example 1: The difference from Example 1 is that the waterborne phenolic epoxy resin is replaced with an equal amount of waterborne acrylic resin with an average molecular weight of 45,000, and the rest is the same as in Example 1.

[0052] Comparative Example 2: The difference from Example 1 is that the waterborne phenolic epoxy resin is replaced with an equal amount of waterborne polyurethane resin with an average molecular weight of 25,000, and the rest is the same as in Example 1.

[0053] Comparative Example 3: The difference from Example 1 is that the amount of waterborne phenolic epoxy resin used is 10g, while the rest is the same as in Example 1. The amount of component A is 100g, and the amount of component B is 1.80g.

[0054] Comparative Example 4: The difference from Example 1 is that the amount of waterborne phenolic epoxy resin used is 55g, while the rest is the same as in Example 1. The amount of component A is 100g, and the amount of component B is 9.92g.

[0055] Comparative Example 5: The difference from Example 1 is that the polyether content in the waterborne phenolic epoxy resin is 8% (its epoxy equivalent is 310 g / eq), and the rest is the same as in Example 1. The amount of component A is 100g, and the amount of component B is 4.19g.

[0056] Comparative Example 6: The difference from Example 1 is that the polyether content in the waterborne phenolic epoxy resin is 22% (its epoxy equivalent is 420 g / eq), and the rest is the same as in Example 1. The amount of component A is 100 g, and the amount of component B is 3.09 g.

[0057] Comparative Example 7: The difference from Example 1 is that component A does not contain ammonium molybdate, and the amount of water is increased accordingly; otherwise, it is the same as Example 1.

[0058] Comparative Example 8: The difference from Example 1 is that component A does not contain titanium oxysulfate, and the amount of water is increased accordingly; otherwise, it is the same as Example 1.

[0059] Comparative Example 9: The difference from Example 1 is that component A does not contain sodium metavanadate, and the amount of water is increased accordingly; otherwise, it is the same as Example 1.

[0060] The passivating agents in Examples 1-12 are prepared as follows: S1. Add the formulated amount of waterborne phenolic epoxy resin and deionized water to the reaction vessel, and stir at 300 r / min for 5 min until completely dispersed to obtain the first mixture. S2. Heat the first mixture to about 50°C, and slowly add the formulated amount of silane coupling agent dropwise to the above resin aqueous solution. Keep warm for 2 hours to obtain the second mixture. S3. Return the second mixture to room temperature, then add the film-forming aid, molybdenum salt, titanium salt, vanadium salt, and other functional aids in sequence, and stir for 15 minutes to obtain component A; S4. Mix phenolic amine and polyether amine according to the specified ratio, add an appropriate amount of solvent, and obtain component B with a solid content of 70%.

[0061] Component A and Component B shall be mixed evenly according to the equivalent ratio before use.

[0062] The passivating agents of Comparative Examples 1 to 9 were prepared by referring to the preparation method of the passivating agents in the Examples.

[0063] Application Example 1: The passivating agents of Examples 1-12 and Comparative Examples 1-9 were applied to galvanized steel sheets (model: DC51D+Z, thickness 1mm) produced by Wuhan Iron and Steel Group, and their relevant properties were tested, as follows: I. Passivation treatment of galvanized sheet (1) Pretreatment: The hot-dip galvanized sheet is degreased in sequence (using alkaline degreaser BONDERITE 1022, produced by Henkel, 50℃, 10min), washed with water (room temperature, 2min), pickled (5% dilute hydrochloric acid, room temperature, 1min), washed with water (room temperature, 2min), and dried (80℃, 5min).

[0064] (2) Passivation: The pretreated galvanized sheet was coated with the passivating agents of Examples 1-12 and Comparative Examples 1-9 by a wire rod, and baked in an oven at 100°C for 10 seconds to form 21 passivation films with a thickness of about 1 μm (samples to be tested).

[0065] II. Performance Testing and Evaluation The galvanized sheets of the above embodiments and comparative examples were subjected to the following performance tests, and the results are shown in Tables 1 and 2.

[0066] (1) Solvent resistance test: Each passivated electro-galvanized steel sheet sample was wiped back and forth 10 times with acetone and ethanol respectively, and the color difference value ΔE was measured with a colorimeter. The requirement was that there should be no significant change on the surface of each electro-galvanized steel sheet sample before and after wiping, and the color difference ΔE ≤ 3. (2) Alkali resistance test: Each electro-galvanized steel sheet sample was sprayed with an alkaline NaOH solution (pH=12) at 40℃ for 2 minutes, and the color difference ΔE was measured using a colorimeter. The requirement was that there should be no significant change in the color of each electro-galvanized steel sheet sample, and the color difference ΔE ≤ 3. (3) High-temperature yellowing resistance test: After treatment, each electro-galvanized steel sheet was placed in a 300℃ oven for 30 minutes. The color difference ΔE before and after the oven was measured using a colorimeter. The surface film condition was observed, and the color difference ΔE of each electro-galvanized steel sheet was required to be ≤3. (4) Salt spray resistance test: Neutral Salt Spray (NSS) Test: In accordance with ASTM B117-2016, the sealed test specimen was placed in a salt spray chamber for a 240-hour spray test. (5) 180° passivation film bending test: According to GB / T 13448-2019 standard, the test sample is bent 180° and the passivation film is observed to see if there are visible cracks. After being peeled off with 3M tape, there is no peeling or falling off.

[0067] The test results are shown in Tables 1 and 2.

[0068] Table 1. Performance test results of passivation films formed by passivating agents in Examples 1-12 Table 2. Performance test results of passivation films formed by passivating agents in Comparative Examples 1-9 Results analysis: As shown in Table 1, the passivation films formed using the technical solution of this invention in Examples 1-12 all exhibited excellent results in various performance tests. Specifically, in the salt spray resistance test: all examples passed the 240-hour neutral salt spray test without any white rust or blistering, indicating that the passivation film has excellent long-term corrosion resistance. In the solvent resistance test: the ΔE range for ethanol wiping was 0.08~0.89, and the ΔE range for acetone wiping was 0.32~1.79, both far exceeding the target requirement (ΔE≤3). Example 4 showed the best performance (ethanol ΔE=0.08, acetone ΔE=0.32), indicating that the film layer is densely cross-linked and has strong resistance to organic solvent erosion. In the alkali resistance test: the ΔE range was 0.09~1.56, all exceeding the target requirement (ΔE≤3), with Example 4 showing the best performance (ΔE=0.09), indicating that the passivation film has good stability in alkaline environments. In the high-temperature yellowing resistance test, the ΔE ranged from 0.96 to 2.53, all exceeding the target (ΔE≤3), with Example 4 showing the best result (ΔE=0.96), indicating that the film layer exhibits excellent anti-yellowing performance under high-temperature conditions. Furthermore, all examples showed no cracks or peeling after 180° bending tests, demonstrating that the passivation film possesses both good flexibility and adhesion. These results fully demonstrate that the present invention, through polyether modification of waterborne phenolic epoxy resin, rational compounding of component B (organic amine), and synergistic curing of components A / B, successfully constructed a three-dimensional network structure with high cross-linking density, achieving a good balance between the passivation film's corrosion resistance, chemical resistance, and flexibility.

[0069] Of all the embodiments, Example 4 exhibited the best overall performance (resistance to solvents ethanol ΔE=0.08, acetone ΔE=0.32, alkali resistance ΔE=0.09, and high-temperature yellowing resistance ΔE=0.96), indicating that when the amount of waterborne phenolic epoxy resin was 40 parts and the polyether was polytetrahydrofuran ether 2000, the rigid crosslinking density provided by the phenolic skeleton and the flexibility provided by the polyether segments achieved the best synergistic balance, forming the densest film structure. Examples 2 and 7 also performed excellently and are both preferred embodiments.

[0070] Furthermore, the data in Table 2 show that when the waterborne phenolic epoxy resin of the present invention was replaced with ordinary waterborne acrylic resin (Comparative Example 1) and waterborne polyurethane resin (Comparative Example 2) in Comparative Examples 1 and 2, respectively, all properties deteriorated significantly. This indicates that the polyether-modified phenolic epoxy resin used in the present invention, due to its unique synergistic structure of rigid phenolic skeleton and flexible polyether segments, is key to forming a highly dense cross-linked network, which cannot be replaced by ordinary waterborne resin. Comparative Example 3 (resin dosage 10g, lower than the lower limit of the present invention by 15 parts): Although the bending test was passed, corrosion occurred after only 120h of salt spray resistance, and the solvent resistance and alkali resistance also decreased significantly, indicating that insufficient resin dosage cannot form a sufficiently thick dense film layer. Comparative Example 4 (resin content 55g, exceeding the upper limit of 50 parts in this invention): Although all resistance indicators were still acceptable (no white rust after 240h salt spray resistance), the excessively high resin content increased costs, and the viscosity of its component A increased significantly. In tests simulating industrial roller coating processes, significant poor leveling and uneven coating were observed. Furthermore, its high-temperature yellowing resistance (ΔE=2.89) was inferior to most examples. Comparative Example 5 (polyether content 8%, below the lower limit of 10% in this invention): Although it passed 240h salt spray resistance, the coating cracked during the 180° bending test, indicating that when the polyether content is too low, the flexibility provided by the polyether segments is insufficient, increasing the film's brittleness and failing to meet flexibility requirements. Comparative Example 6 (polyether content 22%, exceeding the upper limit of 20% in this invention): All resistance indicators (solvent resistance, alkali resistance, high-temperature yellowing resistance) were inferior to the corresponding Example 11 (polyether content 20%), indicating that excessively high polyether content would overly dilute the rigid crosslinking density of the phenolic resin, leading to a decrease in film density. The passivation films in Comparative Examples 7-9 showed extensive corrosion within 120 hours, failing to meet basic corrosion resistance requirements. This result indicates that molybdenum salt, titanium salt, and vanadium salt are all indispensable; the absence of any one component leads to a sharp drop in salt spray resistance from 240 hours to 120 hours. This demonstrates a significant synergistic effect among the three inorganic salts during film formation: molybdenum salt provides corrosion inhibition and passivation, titanium salt promotes the formation of the inorganic conversion film and cross-links with organic resins, and vanadium salt enhances the film's self-healing ability and corrosion resistance. Only through the combined action of all three can a complete multi-layered composite protective system be constructed. Based on the above data, the superior performance of the passivating agent of this invention stems from the following multi-layered synergistic mechanism: 1) Inorganic conversion film layer: The molybdenum / titanium / vanadium ternary inorganic salt reacts with zinc on the surface of the galvanized sheet to form a dense chemical conversion film, which acts as the first physical barrier to block the penetration of corrosive media; 2) Silane bridging layer: Silane coupling agent achieves strong chemical bond connection between inorganic and organic layers through its bifunctional structure (bonded to the inorganic layer at one end and to the organic resin at the other end), thereby improving the film-substrate adhesion. 3) Organic cross-linking network: The epoxy groups of the polyether-modified phenolic epoxy resin in component A undergo a cross-linking and curing reaction with the active hydrogen of the phenolic amine / polyether amine in component B, forming a high-density three-dimensional network structure, which endows the film with excellent compactness and resistance to media permeation. 4) Rigid-flexible balanced structure: The phenolic skeleton provides rigid cross-linking points to ensure the film's density and chemical resistance, while the polyether segments provide flexible intervals to ensure the film's toughness and crack resistance. The two achieve the best balance at a specific ratio (polyether content 10%~20%).

[0071] In summary, the passivating agent of this invention has a multi-layer composite protection mechanism that combines an inorganic conversion film as the base layer with a silane coupling agent for bridging and an organic amine for cross-linking. The components work synergistically to form a highly dense and durable passivating film, solving the problems of insufficient cross-linking density and poor durability of existing chromium-free passivating agent films.

[0072] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A water-based phenolic epoxy passivating agent, characterized in that, The passivating agent is prepared by compounding separately stored components A and B before use; wherein, component A is composed of raw materials in a total of 100 parts by weight: 15-50 parts of waterborne phenolic epoxy resin, 2-5 parts of coupling agent, 1-6 parts of film-forming aid, 0.1-2 parts of molybdenum salt, 0.05-2 parts of titanium salt, 0.05-2 parts of vanadium salt, 0-1 parts of functional aid, and the balance being water; The waterborne phenolic epoxy resin in component A is a polyether-modified phenolic epoxy resin with an epoxy equivalent of 340-400 g / eq, and the mass content of polyether segments in the waterborne phenolic epoxy resin is 10-20%. Component B is a mixture of phenolic amine and polyether amine in a solid mass ratio of 1 to 2:

1. Component B also contains a solvent. The solid content of component B is 60 to 80%. The active hydrogen equivalent of component B is 90 to 110 g / eq. The components A and B are compounded at a ratio of 1.05-1.2:1, based on the epoxy equivalent in component A and the active hydrogen equivalent in component B.

2. The passivating agent according to claim 1, characterized in that, The composition of component A, in a total of 100 parts by weight, is as follows: 20-40 parts of waterborne phenolic epoxy resin, 2-4 parts of coupling agent, 2-5 parts of film-forming aid, 0.5-1.5 parts of molybdenum salt, 0.5-1.5 parts of titanium salt, 0.5-1.5 parts of vanadium salt, 0.5-1.0 parts of functional additive, and water as the balance.

3. The passivating agent according to claim 1 or 2, characterized in that, The polyether is at least one of polyethylene glycol, polypropylene glycol, ethylene oxide-propylene oxide block polyether, and polytetrahydrofuran ether; preferably, the molecular weight of the polyether is 600-2000.

4. The passivating agent according to claim 1 or 2, characterized in that, The coupling agent is at least one of silane coupling agents, titanate coupling agents, and aluminate coupling agents; and / or, the film-forming aid is at least one of trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, alkoxylated glycerol triacrylate, ethylene glycol butyl ether, propylene glycol butyl ether, diethylene glycol butyl ether, dipropylene glycol butyl ether, propylene glycol methyl ether acetate, methyl 3-methoxypropionate, propylene glycol methyl ether, dipropylene glycol methyl ether acetate, tripropylene glycol n-butyl ether, dipropylene glycol n-butyl ether, and alcohol ester twelve.

5. The passivating agent according to claim 1 or 2, characterized in that, The molybdenum salt is selected from at least one of sodium molybdate, potassium molybdate, ammonium molybdate, and ammonium phosphomolybdate; and / or, the titanium salt is selected from at least one of titanium sulfate, titanium oxysulfate, and ammonium fluorotitanate; and / or, the vanadium salt is selected from at least one of sodium metavanadate, ammonium metavanadate, potassium metavanadate, and vanadium oxysulfate.

6. The passivating agent according to claim 1 or 2, characterized in that, The functional additives include at least one of wetting agents, defoamers, colorants, and dispersants.

7. The passivating agent according to claim 1, characterized in that, The phenolic amine is a mixture of polyether-type phenolic amine and cashew phenolic amine; preferably, the phenolic amine is a mixture of polyether-type phenolic amine and cashew phenolic amine at a solid content ratio of 1~1.5:1; and / or, the polyether amine is a secondary amino-type polyether amine.

8. A method for preparing the passivating agent according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Mix the formulated amount of waterborne phenolic epoxy resin with water to obtain the first mixture; S2. Heat the first mixture to 40~60℃, add the amount of coupling agent specified in the formula, and keep the reaction at this temperature for 1~3 hours to obtain the second mixture. S3. Cool the second mixture to room temperature, and add the film-forming aid, molybdenum salt, titanium salt, vanadium salt and functional aid in sequence to obtain component A; S4. Mix the phenolic amine and polyether amine according to the formula, add an appropriate amount of solvent, and obtain component B with a solid content of 60~80%.

9. An application of the passivating agent as described in any one of claims 1 to 7, characterized in that, Used for passivation treatment of galvanized sheet surfaces.

10. The application according to claim 9, characterized in that, Mix components A and B of the passivating agent evenly at a ratio of epoxy equivalent in component A to active hydrogen equivalent in component B of 1.05-1.2:

1. Then coat the mixture onto the surface of the galvanized sheet and bake at 80-100℃ for 6-10s to form a passivation film with a thickness of 0.8-1.2μm.

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