Chromium-free fingerprint-resistant liquid as well as preparation method and application thereof

Abstract

The invention relates to the technical field of fingerprint-resistant materials, and particularly discloses chromium-free fingerprint-resistant liquid as well as a preparation method and application thereof. The invention discloses a chromium-free fingerprint-resistant liquid. The chromium-free fingerprint-resistant liquid is composed of a component A and a component B, the component A comprises a polyurethane emulsion, a coalescing agent, a defoaming agent, a flatting agent and water; the polyurethane emulsion is prepared from polyol, polymethylene polyphenyl polyisocyanate, a catalyst, a plasticizer and a chain extender; the component B comprises a fluorosilicone emulsion, a modified filler and a coupling agent; the modified filler is prepared from ethyl orthosilicate, an ethanol water solution, ammonia water, perfluorooctyltriethoxysilane, sodium molybdate and zirconium phytate; the coupling agent is formed by mixing a titanate coupling agent, a long-chain alkyl silane coupling agent and a short-chain cross-linking type silane coupling agent. The prepared chromium-free fingerprint-resistant liquid has excellent fingerprint resistance, and the acid and alkali resistance and the salt spray corrosion resistance of the material are excellent.

Description

Technical Field

[0001] This application relates to the technical field of fingerprint-resistant materials, specifically to a chromium-free fingerprint-resistant liquid, its preparation method, and its application. Background Technology

[0002] Fingerprint-resistant steel sheets are high-value-added products made by coating galvanized steel sheets with a conductive film. They possess excellent fingerprint resistance and corrosion resistance and are widely used in the electronics and electrical appliance industries. Traditional fingerprint-resistant solutions form a dense, self-healing passivation film containing Cr(III) and Cr(VI) in a dual-oxide state on the surface of galvanized steel sheets. However, hexavalent chromium compounds are highly toxic and carcinogenic, and have mutagenic effects. With increasingly stringent environmental regulations and growing environmental awareness, developing green and environmentally friendly passivation processes that can replace hexavalent chromium compound passivation systems has become an inevitable trend in the field of metal surface treatment.

[0003] Current chromium-free fingerprint-resistant liquids have the following drawbacks: they are mainly composed of titanium salts in acidic media and mainly composed of titanium and zirconium salts in alkaline media. Under the presence of acidic and alkaline media, the surface of the fingerprint-resistant board is easily corroded by acid and alkali, forming an inorganic passivation film. Its corrosion resistance is not as good as that of resin-type films, and its fingerprint resistance is also far inferior to that of resin-type films. It is easy to leave sweat fingerprints on the fingerprint-resistant board and cause rust.

[0004] Therefore, the market urgently needs to develop high-performance, chromium-free, fingerprint-resistant coating materials. Summary of the Invention

[0005] To address the aforementioned technical problems, this application provides a chromium-free fingerprint-resistant liquid, its preparation method, and its application.

[0006] This application provides a chromium-free fingerprint-resistant liquid, which is composed of component A and component B in a weight ratio of 7-8:2-3; Component A specifically comprises the following components in parts by weight: 40-50 parts polyurethane emulsion, 2-4 parts film-forming aid, 0.1-1.5 parts defoamer, 0.2-2 parts leveling agent, and 20-30 parts water; the polyurethane emulsion is prepared from polyol, polymethylene polyphenyl polyisocyanate, catalyst, plasticizer, and chain extender in a weight ratio of 90-100:80-90:0.1-1.0:2-6:6-12. Component B specifically comprises the following components in parts by weight: 12-18 parts of fluorosilicone emulsion, 6-9 parts of modified filler, and 1-4 parts of coupling agent; the modified filler is prepared from tetraethyl orthosilicate, 60-80 wt% ethanol aqueous solution, ammonia, perfluorooctyltriethoxysilane, sodium molybdate, and zirconium phytate in a weight ratio of 1-5:10-16:0.5-1.5:0.2-0.6:0.1-0.5:0.1-0.5; the coupling agent is composed of a mixture of titanate coupling agent, long-chain alkylsilane coupling agent, and short-chain cross-linked silane coupling agent in a weight ratio of 5-9:3-5:1-3.

[0007] Component A (polyurethane matrix) provides flexibility, adhesion, and film-forming properties, forming a continuous phase. Film-forming aids lower the film-forming temperature of the fingerprint-resistant liquid system, promote uniform film formation, and improve the smoothness and density of the coating. Defoamers effectively eliminate bubbles generated during the preparation process, preventing defects such as pitting and pinholes in the coating. Leveling agents improve the leveling properties of the coating, enhancing the smoothness and gloss of the coating surface.

[0008] Component B (fluorosilicone emulsion + modified filler) serves as a functional phase, providing low surface energy, corrosion resistance, and mechanical strength. SD-5681 fluorosilicone emulsion is an anionic emulsion polymerized from acrylate monomers, fluorine monomers, and various functional monomers, endowing the system with properties such as acid and alkali resistance, salt spray resistance, anti-whitening, high weather resistance, hydrophobicity, and oleophobicity. In the modified filler, silica nanoparticles act as rigid fillers, effectively filling micropores and defects in the coating film, improving its hardness and wear resistance. Simultaneously, surface-grafted organic segments improve the compatibility between the filler and organic resin, preventing phase separation and ensuring a uniform and dense coating film. Perfluorooctyl chains possess low surface energy, giving the modified filler surface hydrophobic properties and forming a low surface energy protective layer. Molybdate forms an insoluble molybdate film on the metal surface, inhibiting anodic dissolution. Phytic acid molecules form stable chelates with metal ions, repairing coating defects. Zirconium ions react with silanol groups to enhance interfacial adhesion; all three synergistically improve acid and alkali resistance and salt spray resistance. Coupling agents bridge the gap between the organic and inorganic phases, improve interfacial compatibility, prevent phase separation, and achieve synergistic effects.

[0009] Meanwhile, to improve the corrosion resistance and chemical resistance of the fingerprint-resistant film, this application introduces a coupling agent composed of titanate-based coupling agents, long-chain alkylsilane coupling agents, and short-chain cross-linked silane coupling agents. The titanate-based coupling agent can react rapidly and strongly with hydroxyl groups (-OH) or physically adsorbed water on the surface of the metal substrate to form strong Ti-OM (M is a metal) chemical bonds; it also improves the wet adhesion between the coating and the substrate, blocking water, oxygen, and corrosive ions from contacting the metal substrate, thus enhancing corrosion resistance. The long-chain alkyl alkyl groups of the long-chain alkylsilane coupling agent can be oriented on the film surface to form a low surface energy structure, providing water and oil repellency. The short-chain cross-linked silane can hydrolyze and condense during film formation to form a dense Si-O-Si inorganic network, significantly improving the hardness, wear resistance, and solvent resistance of the film. During the hydrolysis-condensation process, the three coupling agents form an organic-inorganic hybrid interpenetrating network structure through chemical bonds such as Ti-O-Si and Si-O-Si. This structure improves the fingerprint resistance performance through a triple mechanism of enhanced adhesion, increased penetration resistance, and active hydrophobicity.

[0010] Furthermore, after component A and component B are mixed, the polyurethane emulsion and fluorosilicone emulsion can form a continuous and dense coating film that effectively blocks the penetration of corrosive media such as water, oxygen, and chloride ions.

[0011] Preferably, in the method for preparing the polyurethane emulsion, the polyol is selected from any one or more of castor oil polyol, soybean oil polyol, sunflower seed oil polyol, linseed oil polyol, castor oil polyol, and tallow polyol; the catalyst is selected from any one of dibutyltin dilaurate and triethylenediamine; the plasticizer is pentaerythritol; and the chain extender is selected from any one of isobutyl 3,5-diamino-p-chlorobenzoate and diethyltoluenediamine.

[0012] Preferably, the film-forming aid is one or more of propylene glycol methyl ether acetate, ethylene glycol ethyl ether, and dipropylene glycol butyl ether; the defoamer is one or more of silicone defoamers and polyether defoamers; and the leveling agent is one or more of polyacrylate leveling agents and silicone leveling agents.

[0013] Preferably, the modified filler is prepared from tetraethyl orthosilicate, 65-75wt% aqueous ethanol solution, ammonia, perfluorooctyltriethoxysilane, sodium molybdate, and zirconium phytate in a weight ratio of 2-4:12-14:0.8-1.2:0.3-0.5:0.2-0.4:0.2-0.4.

[0014] Experimental analysis shows that the modified filler prepared by this application using the above-mentioned weight ratio of tetraethyl orthosilicate, aqueous ethanol solution, ammonia, perfluorooctyltriethoxysilane, sodium molybdate, and zirconium phytate can significantly improve the fingerprint resistance performance.

[0015] Preferably, the modified filler is prepared by mixing tetraethyl orthosilicate and an aqueous ethanol solution, stirring and adding ammonia, then adding perfluorooctyltriethoxysilane, and reacting in a sealed environment at a temperature of 30-40°C for 5-10 hours to obtain a silica suspension; then adding sodium molybdate and zirconium phytate, and continuing the sealed reaction at a temperature of 30-40°C for 4-8 hours to obtain the modified filler.

[0016] Preferably, the coupling agent is composed of a mixture of titanate coupling agents, long-chain alkyl silane coupling agents, and short-chain cross-linked silane coupling agents in a weight ratio of 6-8:3.5-4.5:1.2-2.5.

[0017] Preferably, in the coupling agent, the titanate coupling agent is one or more of isopropyltris(dioctylpyrophosphoyloxy)titanate, bis(dioctylpyrophosphoyloxy)ethylene titanate, and tetraisopropyldi(dioctyl phosphite)titanate; the long-chain alkylsilane coupling agent is one or more of hexadecyltrimethoxysilane and octadecyltriethoxysilane; and the short-chain crosslinked silane coupling agent is one or more of tetraethoxysilane, methyltrimethoxysilane, and γ-glycidoxypropyltrimethoxysilane.

[0018] Preferably, the coupling agent is composed of isopropyltris(dioctylpyrophosphate)titanate, hexadecyltrimethoxysilane, and γ-glycidoxypropyltrimethoxysilane in a weight ratio of 6-8:3.5-4.5:1.2-2.5.

[0019] In one specific embodiment, the weight ratio of isopropyltris(dioctylpyrophosphoryloxy)titanate, hexadecyltrimethoxysilane, and γ-glycidyl etheroxypropyltrimethoxysilane in the coupling agent can be 5:3:1, 6:3:1, 7:3:1, 8:3:1, 9:3:1, 8:4:1, 9:4:1, 5:5:1, 6:5:1, 7:5:1, 8:5:1, 6:3:2, 7:3:2, 8:3:2, 9:3:2, 5:4:2, 6:4:2, 7:4:2, 8:4:2, 9:4:2, 5:5:2, 5:3:3, 6:3:3, 7:3:3, 8:3:3, 9:3:3, 5:4:3, 6:4:3, 7:4:3, 8:4:3, or 9:5:3.

[0020] Experimental analysis shows that the coupling agent composed of isopropyltris(dioctylpyrophosphate)titanate, hexadecyltrimethoxysilane, and γ-glycidyl etheroxypropyltrimethoxysilane in the above weight ratio can further improve the overall performance of fingerprint resistance.

[0021] This application also provides a method for preparing the chromium-free fingerprint-resistant liquid, comprising the following steps: Preparation of Component A: Under stirring, film-forming aid, defoamer, and leveling agent are added to water in sequence and mixed evenly. Then, they are mixed evenly with polyurethane to obtain Component A. Preparation of component B: Under stirring, the fluorosilicone emulsion, modified filler and coupling agent are mixed evenly and stirred at 30-40℃ for 10-30 min to obtain component B; Main mixing: Under stirring, add component B to component A and mix evenly to obtain the chromium-free fingerprint-resistant liquid.

[0022] This application also provides the application of the chromium-free fingerprint-resistant liquid in the surface treatment of metallic materials.

[0023] In summary, the technical solution of this application has the following effects: This application uses a specific component design and preparation process to prepare component A with polyurethane emulsion, film-forming aid, defoamer, leveling agent and water, and component B with fluorosilicone emulsion, modified filler and coupling agent, so that the resulting coating film has a good water and oil repellency effect, and at the same time has excellent fingerprint resistance, acid and alkali resistance and corrosion resistance. Detailed Implementation

[0024] The present application will be further described in detail below with reference to embodiments, comparative examples and performance test results. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0025] Example

[0026] Example 1

[0027] Example 1 provides a chromium-free fingerprint-resistant liquid and its preparation method.

[0028] The preparation method of the chromium-free fingerprint-resistant liquid in the above embodiments is as follows: Castor oil polyol, dibutyltin dilaurate catalyst, pentaerythritol plasticizer, and isobutyl 3,5-diamino-p-chlorobenzoate chain extender were mixed together; then, polymethylene polyphenyl polyisocyanate (product brand PM200, Wanhua Chemical Group Co., Ltd.) was added and stirred until homogeneous to obtain a hydrophobic polyurethane material. The weight ratio of polyol, polymethylene polyphenyl polyisocyanate, catalyst, plasticizer, and chain extender was 95:85:0.5:4:9.

[0029] Preparation of modified filler: Tetraethyl orthosilicate and 70wt% aqueous ethanol solution were mixed, stirred, and ammonia was added. Then perfluorooctyltriethoxysilane was added, and the mixture was reacted in a sealed environment at 35℃ for 8 hours to obtain a silica suspension. Sodium molybdate and zirconium phytate were then added, and the mixture was reacted in a sealed environment at 35℃ for another 6 hours to obtain the modified filler. The weight ratio of tetraethyl orthosilicate, 70wt% aqueous ethanol solution, ammonia, perfluorooctyltriethoxysilane, sodium molybdate, and zirconium phytate was 3:13:1:0.4:0.3:0.3.

[0030] Preparation of Component A: Under stirring at 200 rpm, add 3g of film-forming aid, 1g of defoamer, and 1g of leveling agent to 25g of water in sequence, mix evenly, and then mix evenly with 45g of polyurethane to obtain Component A; Preparation of Component B: Under stirring at 200 rpm, 14 g of fluorosilicone emulsion (SD-5681 fluorosilicone emulsion, sourced from Jiangsu Shengda New Material Technology Co., Ltd.), 8 g of modified filler, and 3 g of coupling agent (composed of isopropyltris(dioctylpyrophosphoryloxy)titanate, hexadecyltrimethoxysilane, and γ-glycidyl etheroxypropyltrimethoxysilane in a weight ratio of 7:4:2) were mixed evenly and stirred at 35 °C for 20 min to obtain Component B; Main mixing: Under stirring at 200 rpm, add 25g of component B to 75g of component A (the weight ratio of component A to component B is 7.5:2.5), mix evenly, and the chromium-free fingerprint-resistant liquid is obtained.

[0031] Examples 2-4 Examples 2-4 respectively provide a chromium-free fingerprint-resistant liquid and its preparation method.

[0032] The difference between the above embodiments and Embodiment 1 is that the amount of each raw material in component B is different, as shown below.

[0033] In Example 2: the amount of fluorosilicone emulsion used was 16g, the amount of modified filler used was 7g, and the amount of coupling agent used was 2g.

[0034] In Example 3: the amount of fluorosilicone emulsion used was 12g, the amount of modified filler used was 9g, and the amount of coupling agent used was 4g.

[0035] In Example 4: the amount of fluorosilicone emulsion used was 18g, the amount of modified filler used was 6g, and the amount of coupling agent used was 1g.

[0036] All other process parameters in the above embodiments are the same as those in Embodiment 1.

[0037] Examples 5-8 Examples 5-8 respectively provide a chromium-free fingerprint-resistant liquid and its preparation method.

[0038] The difference between the above embodiments and Embodiment 1 is that the preparation methods of the modified fillers are different, as shown below.

[0039] In Example 5: In the preparation method of the modified filler, the weight ratio of tetraethyl orthosilicate, 70wt% aqueous ethanol solution, ammonia, perfluorooctyltriethoxysilane, sodium molybdate, and zirconium phytate is 2:14:0.8:0.5:0.2:0.4.

[0040] In Example 6: In the preparation method of the modified filler, the weight ratio of tetraethyl orthosilicate, 70wt% aqueous ethanol solution, ammonia, perfluorooctyltriethoxysilane, sodium molybdate, and zirconium phytate is 4:12:1.2:0.3:0.4:0.2.

[0041] In Example 7: In the preparation method of the modified filler, the weight ratio of tetraethyl orthosilicate, 70wt% aqueous ethanol solution, ammonia, perfluorooctyltriethoxysilane, sodium molybdate, and zirconium phytate is 1:16:0.5:0.6:0.1:0.5.

[0042] In Example 8: In the preparation method of the modified filler, the weight ratio of tetraethyl orthosilicate, 70wt% aqueous ethanol solution, ammonia, perfluorooctyltriethoxysilane, sodium molybdate, and zirconium phytate is 5:10:1.5:0.2:0.5:0.1.

[0043] All other process parameters in the above embodiments are the same as those in Embodiment 1.

[0044] Examples 9-12 Examples 9-12 respectively provide a chromium-free fingerprint-resistant liquid and its preparation method.

[0045] The specific differences between the above embodiments and Embodiment 1 are as follows:

[0046] In Example 9: The coupling agent is composed of a mixture of bis(dioctylpyrophosphoryloxy)ethylene titanate, octadecyltriethoxysilane and methyltrimethoxysilane in a weight ratio of 7:4:2.

[0047] In Example 10: the coupling agent is composed of a mixture of tetraisopropyl di(dioctyl phosphite) titanate, hexadecyltrimethoxysilane and tetraethoxysilane in a weight ratio of 7:4:2.

[0048] In Example 11: The coupling agent is composed of isopropyltris(dioctylpyrophosphate)titanate, hexadecyltrimethoxysilane, and γ-glycidoxypropyltrimethoxysilane in a weight ratio of 5:5:1.

[0049] In Example 12: The coupling agent is composed of isopropyltris(dioctylpyrophosphate)titanate, hexadecyltrimethoxysilane, and γ-glycidoxypropyltrimethoxysilane in a weight ratio of 9:3:3.

[0050] All other process parameters in the above embodiments are the same as those in Embodiment 1.

[0051] Comparative Example Comparative Examples 1-6 Comparative Examples 1-6 each provide a chromium-free fingerprint-resistant liquid and its preparation method.

[0052] The difference between the above comparative examples and Example 1 is as shown in Table 1.

[0053] In Comparative Example 1, an equal amount of fluoroacrylic emulsion (SD-568 fluorosilicone emulsion, sourced from Jiangsu Shengda New Material Technology Co., Ltd.) was used to replace SD-5681 fluorosilicone emulsion.

[0054] In Comparative Example 2: the amount of fluorosilicone emulsion used was 10g, the amount of modified filler used was 14.5g, and the amount of coupling agent used was 0.5g.

[0055] In Comparative Example 3: In the preparation method of the modified filler, the weight ratio of tetraethyl orthosilicate, 70wt% aqueous ethanol solution, ammonia, perfluorooctyltriethoxysilane, sodium molybdate, and zirconium phytate is 6:16:0.5:0.6:0.6:0.05.

[0056] In Comparative Example 4, the coupling agent was composed of a mixture of bis(dioctylpyrophosphoryloxy) ethylene titanate and octadecyltriethoxysilane γ-glycidyl etheroxypropyltrimethoxysilane in a weight ratio of 7:6.

[0057] In Comparative Example 5, the coupling agent was composed of isopropyltris(dioctylpyrophosphoryloxy)titanate, hexadecyltrimethoxysilane, and γ-glycidoxypropyltrimethoxysilane in a weight ratio of 4:2:7.

[0058] In Comparative Example 6: The preparation method of chromium-free fingerprint-resistant liquid is as follows: under the stirring state of 200 rpm, 3g of film-forming aid, 1g of defoamer and 1g of leveling agent are added to 25g of water in sequence, mixed evenly, and then mixed evenly with 14g of fluorosilicone emulsion to obtain component A; Preparation of Component B: Under stirring at 200 rpm, 45 g of polyurethane, 8 g of modified filler, and 3 g of coupling agent (composed of isopropyltris(dioctylpyrophosphoryloxy)titanate, hexadecyltrimethoxysilane, and γ-glycidyl etheroxypropyltrimethoxysilane in a weight ratio of 7:4:2) were mixed evenly and stirred at 35 °C for 20 min to obtain Component B. Main mixing: Under stirring at 200 rpm, add component B to component A and mix evenly to obtain the chromium-free fingerprint-resistant liquid.

[0059] All other process parameters in the above comparative examples are the same as those in Example 1.

[0060] Performance testing The chromium-free fingerprint-resistant liquids prepared in the examples and comparative examples were coated on galvanized steel plates, and after curing and drying, performance tests were conducted.

[0061] (1) Fingerprint resistance: The color difference value △E of the test sample before and after applying Vaseline.

[0062] (2) Acid and alkali resistance: Under the condition of room temperature of 25 degrees, the test sample was immersed in 1% HCl solution and 1% NaOH solution for 1 hour respectively. After taking it out, washing it with water and drying it, the surface color difference value △E was tested.

[0063] (3) Salt spray resistance: According to GB / T 10125-2021, the test sample was placed in a salt spray chamber at a temperature of 36℃ and subjected to a 5wt% sodium chloride salt solution with a pH of 7.0 at a spray rate of 1.0 kgf / cm³ at a pressure chamber temperature of 45℃. 2 Spraying was performed using air pressure; after spraying the sample for 120h, 180h, and 240h, the sample was washed with water and dried, and the surface was observed for any rust, cracking, or other adverse corrosion phenomena; the corrosion results were evaluated according to GB12335-90 (expressed as a percentage of the total area of ​​corrosion). A smaller corrosion area is better.

[0064] Test results are shown in Table 1.

[0065] Table 1. Performance test results of chromium-free fingerprint-resistant liquid in the examples and comparative examples.

[0066] As can be seen from the test results in Table 1 above, the chromium-free fingerprint-resistant liquid prepared using the technical solution provided in this application has excellent fingerprint resistance, and the material has excellent acid and alkali resistance and salt spray corrosion resistance.

[0067] Comparing the test results of Examples 1-4 and Comparative Examples 1-2, it can be seen that in Comparative Example 1, using an equal amount of SD-568 fluoroacrylic emulsion instead of SD-5681 fluorosilicone emulsion, and in Comparative Example 2, using 10g of fluorosilicone emulsion, 14.5g of modified filler, and 0.5g of coupling agent, the chromium-free fingerprint-resistant liquid material prepared had poor performance. In contrast, the present application, using 12-18 parts of fluorosilicone emulsion, 6-9 parts of modified filler, and 1-4 parts of coupling agent as component B in the preparation of the fingerprint-resistant liquid, produces a chromium-free fingerprint-resistant liquid material with excellent performance.

[0068] By comparing the test results of Examples 1, 4-8, and Comparative Example 3, it can be seen that the chromium-free fingerprint-resistant material prepared in Comparative Example 3 with a weight ratio of tetraethyl orthosilicate, 70wt% ethanol aqueous solution, ammonia, perfluorooctyltriethoxysilane, sodium molybdate, and zirconium phytate of 6:16:0.5:0.6:0.6:0.05 has poor performance. In contrast, the modified filler prepared in this application with a weight ratio of tetraethyl orthosilicate, 60-80wt% ethanol aqueous solution, ammonia, perfluorooctyltriethoxysilane, sodium molybdate, and zirconium phytate of 1-5:10-16:0.5-1.5:0.2-0.6:0.1-0.5:0.1-0.5 has excellent performance.

[0069] By comparing the test results of Examples 1, 9-12 and Comparative Examples 4-5, it can be seen that the coupling agent composed of a mixture of titanate coupling agent, long-chain alkylsilane coupling agent and short-chain cross-linked silane coupling agent in a weight ratio of 5-9:3-5:1-3 can significantly improve the overall performance of fingerprint resistance liquid.

[0070] By comparing the test results of Example 1 and Comparative Example 6, it can be seen that the chromium-free fingerprint-resistant liquid material prepared in Comparative Example 6, which uses fluorosilicone emulsion, film-forming aid, defoamer, leveling agent, and water to prepare component A, and fluorosilicone emulsion, modified filler, and coupling agent to prepare component B, has poor performance. In contrast, the chromium-free fingerprint-resistant liquid material prepared in this application, which uses fluorosilicone emulsion, film-forming aid, defoamer, leveling agent, and water to prepare component A, and fluorosilicone emulsion, modified filler, and coupling agent to prepare component B, exhibits excellent performance.

[0071] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A chromium-free fingerprint-resistant liquid, characterized in that, It consists of component A and component B in a weight ratio of 7-8:2-3; Component A specifically comprises the following components in parts by weight: 40-50 parts polyurethane emulsion, 2-4 parts film-forming aid, 0.1-1.5 parts defoamer, 0.2-2 parts leveling agent, and 20-30 parts water; the polyurethane emulsion is prepared from polyol, polymethylene polyphenyl polyisocyanate, catalyst, plasticizer, and chain extender in a weight ratio of 90-100:80-90:0.1-1.0:2-6:6-12. Component B specifically comprises the following components in parts by weight: 12-18 parts of fluorosilicone emulsion, 6-9 parts of modified filler, and 1-4 parts of coupling agent; the modified filler is prepared from tetraethyl orthosilicate, 60-80 wt% ethanol aqueous solution, ammonia, perfluorooctyltriethoxysilane, sodium molybdate, and zirconium phytate in a weight ratio of 1-5:10-16:0.5-1.5:0.2-0.6:0.1-0.5:0.1-0.5; the coupling agent is composed of a mixture of titanate coupling agent, long-chain alkylsilane coupling agent, and short-chain cross-linked silane coupling agent in a weight ratio of 5-9:3-5:1-3.

2. The chromium-free fingerprint-resistant liquid according to claim 1, characterized in that, In the preparation method of the polyurethane emulsion, the polyol is selected from any one or more of castor oil polyol, soybean oil polyol, sunflower seed oil polyol, flaxseed oil polyol, castor oil polyol, and tallow polyol; the catalyst is selected from any one of dibutyltin dilaurate and triethylenediamine; the plasticizer is pentaerythritol; and the chain extender is selected from any one of isobutyl 3,5-diamino-p-chlorobenzoate and diethyltoluenediamine.

3. The chromium-free fingerprint-resistant liquid according to claim 1, characterized in that, The film-forming aid is one or more of propylene glycol methyl ether acetate, ethylene glycol ethyl ether, and dipropylene glycol butyl ether; the defoamer is one or more of silicone defoamers and polyether defoamers; and the leveling agent is one or more of polyacrylate leveling agents and silicone leveling agents.

4. The chromium-free fingerprint-resistant liquid according to claim 1, characterized in that, The modified filler was prepared from tetraethyl orthosilicate, 65-75wt% aqueous ethanol solution, ammonia, perfluorooctyltriethoxysilane, sodium molybdate, and zirconium phytate in a weight ratio of 2-4:12-14:0.8-1.2:0.3-0.5:0.2-0.4:0.2-0.

4.

5. The chromium-free fingerprint-resistant liquid according to claim 1, characterized in that, The modified filler is prepared by mixing tetraethyl orthosilicate and an aqueous ethanol solution, stirring and adding ammonia, then adding perfluorooctyltriethoxysilane, and reacting in a sealed environment at 30-40℃ for 5-10 hours to obtain a silica suspension; then adding sodium molybdate and zirconium phytate, and continuing the sealed reaction at 30-40℃ for 4-8 hours to obtain the modified filler.

6. The chromium-free fingerprint-resistant liquid according to claim 1, characterized in that, The coupling agent is prepared in a weight ratio of 6-8: 3.5-4.5: A mixture of titanate coupling agents, long-chain alkyl silane coupling agents, and short-chain cross-linked silane coupling agents with a strength of 1.2-2.

5.

7. The chromium-free fingerprint-resistant liquid according to claim 1, characterized in that, In the coupling agent, the titanate coupling agent is one or more of isopropyltris(dioctylpyrophosphoyloxy)titanate, bis(dioctylpyrophosphoyloxy)ethylene titanate, and tetraisopropyldi(dioctyl phosphite)titanate; the long-chain alkylsilane coupling agent is one or more of hexadecyltrimethoxysilane and octadecyltriethoxysilane; and the short-chain crosslinked silane coupling agent is one or more of tetraethoxysilane, methyltrimethoxysilane, and γ-glycidoxypropyltrimethoxysilane.

8. The chromium-free fingerprint-resistant liquid according to claim 1, characterized in that, The coupling agent is prepared in a weight ratio of 6-8: 3.5-4.5: Composed of 1.2-2.5% isopropyltris(dioctylpyrophosphoryloxy)titanate, hexadecyltrimethoxysilane, and γ-glycidyloxypropyltrimethoxysilane.

9. A method for preparing a chromium-free fingerprint-resistant liquid as described in any one of claims 1-8, characterized in that, Includes the following steps: Preparation of Component A: Under stirring, film-forming aid, defoamer, and leveling agent are added to water in sequence and mixed evenly. Then, they are mixed evenly with polyurethane to obtain Component A. Preparation of component B: Under stirring, the fluorosilicone emulsion, modified filler and coupling agent are mixed evenly and stirred at 30-40℃ for 10-30 min to obtain component B; Main mixing: Under stirring, add component B to component A and mix evenly to obtain the chromium-free fingerprint-resistant liquid.

10. The application of the chromium-free fingerprint-resistant liquid as described in any one of claims 1-8 in the surface treatment of metallic materials.

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