Environment-friendly treating fluid for pretreatment of hot-dip galvanized coiled material

Abstract

The invention discloses an environment-friendly treating fluid for pretreating a hot-dip galvanized coiled material and a preparation method of the environment-friendly treating fluid. The formula of the pretreatment liquid achieves complete chromium-free treatment, and a high-molecular shielding layer is established by innovatively selecting a mixing scheme of an acrylic acid hybrid modified polyurethane dispersion. The obtained environment-friendly treating fluid has obvious advantages in key performances such as damp and heat resistance, salt mist resistance and alcohol wiping resistance compared with the existing similar treating fluid, other performances can meet industrial indexes, and the environment-friendly treating fluid can be widely applied to the fields of household appliance backboards and the like with high performance requirements.

Description

Technical Field

[0001] The invention belongs to the application field of metal pretreatment coatings, and specifically relates to an environmentally friendly treatment liquid for pretreatment of zinc spangle-free hot-dip galvanized coils and a preparation method thereof. Background Art

[0002] Hot-dip galvanized steel sheet, through advanced atmosphere gas control during hot-dip, ensures the adhesion between the iron matrix and zinc, and has good processing performance. Among them, the hot-dip galvanized sheet without zinc flowers has a flat surface, which is both beautiful and convenient for subsequent spraying and painting. It is widely used in the fields of home appliance back panels, but the zinc layer on its surface has high chemical activity. In a corrosive environment, it will turn dark gray or form a large amount of white oxide deposition, which is not good for the appearance quality and service life of the product. Therefore, pretreatment and protection of the galvanized layer is very important.

[0003] Passivation protection of the zinc layer by hexavalent chromate passivation can provide excellent corrosion resistance, low cost and self-repair function. However, due to the strong toxicity and carcinogenicity of hexavalent chromium, relevant policies and regulations began to restrict its downstream application: In January 2003, the European Union issued the "Directive on the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment", restricting hazardous substances such as Pb, Hg, Cd, Cr +6 , PBB, etc. The ROHS directive was enforced on July 1, 2006; Chinese companies exporting electronic and electrical products stopped using hexavalent chromium surface treatment technology from December 1, 2005, and the country began to fully promote chromium-free coatings from January 2022.

[0004] In the process of eliminating the hexavalent chromium system pretreatment solution, people first think of designing a trivalent chromium system with lower toxicity than the hexavalent chromium system. CN101812681B discloses a trivalent chromium passivation solution for zinc plating, the formula of which includes Cr(NO 3 ) 3 , nitrates, phosphates, nitric acid and other ingredients. Although the toxicity and carcinogenicity have decreased to a certain extent, the protective performance of the trivalent chromium system is significantly different from that of the hexavalent chromium system. The electro-galvanized sheet coated with the trivalent chromium passivation solution has white rust after 72 hours in the neutral salt spray test, while the hexavalent chromium system can be left for at least 96 hours without obvious white rust. Moreover, the trivalent chromium system is only an intermediate stage in the transition to the "greening" of the treatment solution, and it still has certain toxicity and hazards.

[0005] Subsequently, among the congeners of chromium, chromium-free passivation solutions with less toxic elements such as molybdates and tungstates as the main active substances were screened out. Several chromium-free passivation solutions for galvanized steel sheets were disclosed in CN 100594263C, CN101250699A, CN101235498A, etc. Their main feature is that molybdates, tungstates, silicates, etc. are used as passivation aids in the formula, and a strong oxidation environment and strong acidity are introduced into the entire pretreatment solution. However, this solution of replacing chromates with molybdates and tungstates has a salt spray resistance even worse than that of trivalent chromium passivation systems. Under most formulations, after 72 hours of placement in the neutral salt spray test, the corrosion area of white rust will be greater than 5%.

[0006] Nowadays, the development trend of galvanized sheet pretreatment solutions is a comprehensive system of the shielding effect of organic resin films and the passivation effect of inorganic salts. The corrosion resistance mechanism of this organic-inorganic combination system has two aspects: on the one hand, the film formed by the resin is a polymer substance, which can effectively shield the media in the environment, especially blocking O 2 , H 2 O and Cl - from corroding and damaging the galvanized layer, thus blocking the progress of the cathodic reaction; on the other hand, the inorganic passivation solution reduces the reaction activity of the surface zinc layer, hinders the transmission of electrons and zinc ions, and thus comprehensively inhibits corrosion. Several pretreatment solutions with comprehensive organic-inorganic effects were disclosed in CN102070927A, CN 102337532 A, CN102121104B, etc. The resins selected for the organic part include various systems such as acrylic resins, organosilicon-modified acrylic resins, and cationic polyurethanes, and their salt spray corrosion resistance has approached or even reached the indicators of the "hexavalent chromium system". However, the inorganic salt passivation systems of most of these formulations still mainly use chromium congeners such as molybdates and tungstates, and these salts need to work better in a stronger acidic system, so they mostly need to be combined with cationic resins. Cationic resins currently occupy a large market in the field of pretreatment solutions, but a very significant disadvantage of this system is that the galvanized steel sheet is prone to turning black after heat and humidity resistance.

[0007] Currently, in the metal pretreatment solution industry, the pretreatment solutions used in the home appliance industry have relatively high performance requirements. The performance indicators of the pretreatment solution for hot-dip galvanized steel sheets of a representative enterprise are shown in Table 1.

[0008] Table 1 Performance indicators of the pretreatment solution for hot-dip galvanized steel sheets of a leading enterprise

[0009]

[0010] Summary of the Invention

[0011] In view of this, aiming at the industry problems encountered in the existing technology (the combined system of inorganic passivation and organic polymer shielding) and the future development trend (dechromization, pure water, high performance, green environmental protection) of the pretreatment liquid for hot-dip galvanized sheets, the purpose of the present invention is to provide an aqueous, chromium-free, environmentally friendly and efficient treatment liquid for non-specular hot-dip galvanized sheets. This treatment liquid can establish its performance by simply applying a single thin wet film with a thickness of 1 to 2 microns on the galvanized sheet substrate. The obtained pretreatment coating has excellent properties such as resistance to damp heat blackening, fingerprint resistance, solvent wipe resistance, degreaser resistance, alkali resistance, and salt spray resistance. At the same time, the dry film has a relatively large surface tension, which is convenient for the wetting and spreading of subsequent coatings and can establish good adhesion with subsequent coatings, contributing to secondary coating. The present invention meets the current "RHOS Directive" and also meets the future restrictions on high-potential substances (trivalent chromium salts, benzene series), which can effectively accelerate the "coating to water" process and promote the environmental protection, green, and low-carbon development of the industry.

[0012] To achieve the above invention purpose, the technical solution of the present invention is as follows:

[0013] An environmentally friendly treatment liquid for the pretreatment of hot-dip galvanized coils, comprising the following components by weight percentage:

[0014]

[0015] In the present invention, the first aqueous acrylic hybrid modified polyurethane dispersion (PUA1) and the second aqueous acrylic hybrid modified polyurethane dispersion (PUA2) both have an interpenetrating network composed of polyurethane segments as the backbone. The acrylic monomers complete explosive polymerization within the polyurethane backbone to form a core-shell-like structure. The acrylate serves as the hydrophobic core, and the hydrophilic polar functional groups (such as hydroxyl groups, carboxyl groups, etc.) on the polyurethane interpenetrating network endow the shell layer with strong hydrophilicity, thereby realizing water dispersion;

[0016] Among them,

[0017] The first aqueous acrylic hybrid modified polyurethane dispersion (PUA1) is preferably one of Wanhua's 0301 and 0301A, whose glass transition temperature is between 70 and 130 °C, acid value is between 10 and 65 mgKOH / g, solid content is between 35 and 45 wt%, pH is between 7.0 and 9.0, and low shear viscosity is between 10 and 500 mPa·s;

[0018] The hard segment monomers of the PU part of PUA1 are preferably aliphatic polyisocyanates, including one or more of dicyclohexylmethane diisocyanate (HMDI), isophorone diisocyanate (IPDI), and hexamethylene diisocyanate (HDI); the soft segment monomers of the PU part are preferably polycarbonate polyols with a molecular weight of 1000 - 1500, including one or more of 1,4-butanediol type polycarbonate polyol, 1,5-pentanediol type polycarbonate polyol, and 1,6-hexanediol type polycarbonate polyol. The main monomers of the PA part are preferably one or more of 2-ethylhexyl methacrylate (2-EHMA), 2-ethylhexyl acrylate (2-EHA), styrene (ST), methyl methacrylate (MMA), and n-butyl methacrylate (n-BA), and a copolymer is formed by preferably adjusting the proportion of the corresponding monomers. Preferably, the mass ratio of PU to PA in PUA1 is 1:0.8 - 1:1.6. The elongation at break of the PUA1 resin can reach 170 - 280%, and the 100% modulus is between 6.62 - 13.45 MPa, having quite good flexibility. At the same time, as a high-Tg resin, no additional cosolvent is added to PUA1, and its MFFT > 60 °C, and it is not easy to form a film alone. However, PUA1 achieves low residue content and non-crusting through a special formula, and has very good salt stability and formulation stability. The selected polycarbonate polyol monomer structure in the PU part of PUA1 contains at least one or two rigid ring branches (including but not limited to: benzene ring structure, phthalic anhydride structure, cyclohexane structure). At the same time, the entanglement effect of the PU chain segment and the relatively hard PA core produce a synergistic effect, which provides very high strength for the resin after film formation and plays a crucial role in improving the solvent resistance wiping, alcohol resistance wiping and other properties of the metal pretreatment liquid of the present invention. Under the preferred formulation, there is no tendency of penetration after exceeding the extreme conditions of more than 100 ethanol wipes and MEK wipes. Selecting aliphatic polyisocyanate as the main component in the hard segment of the PU part of PUA1 avoids a series of side reactions that produce chromogenic groups after the aromatic ring is energized by the environment, and can effectively improve the high-temperature yellowing resistance of the pretreatment liquid;

[0019] The second aqueous acrylic hybrid modified polyurethane dispersion (PUA2) is preferably one of 0302, 0309, with a glass transition temperature of 0 - 60 °C, an acid value of 5 - 45 mgKOH / g, a solid content of 25 - 40 wt%, a pH of 7.0 - 9.0, and a low shear viscosity of 10 - 500 mPa·s;

[0020] For the hard segment monomers of the PU part of the PUA2 resin, aromatic polyisocyanates are preferred, including one or both of diphenylmethane diisocyanate (MDI) and toluene diisocyanate (TDI); for the soft segment monomers of the PU part, polyether polyols with a molecular weight of 800-1200 are preferred, including one or more of polypropylene oxide ether (PPG), polyethylene oxide ether (PEG), and polytetrahydrofuran ether (PTMEG). The main monomers of the PA part are preferably one or more of styrene (ST), methyl methacrylate (MMA), and n-butyl methacrylate (n-BA). The mass ratio of PU to PA in PUA2 is 1:0.6 to 1:1.4. PUA2 also has very good strength and flexibility. The elongation at break of its resin can reach 190-400%, the 100% modulus is between 4.32 and 11.45 MPa, and the MFFT < 0 °C, with excellent film-forming properties. By reasonably adjusting the mixing ratio of PUA2 and PUA1, the defect of poor film-forming property of PUA1 can be greatly solved, and its strength and weather resistance advantages can be retained, which plays an important role in establishing a highly dense and highly complete organic shielding film and can effectively improve the salt spray resistance of the pretreatment solution.

[0021] In the present invention, the film-forming aids are one or more of propylene glycol methyl ether, dipropylene glycol methyl ether, dipropylene glycol propyl ether, dipropylene glycol butyl ether, ethylene glycol butyl ether acetate, propylene glycol diacetate, and propylene glycol methyl ether acetate.

[0022] In the present invention, the inorganic corrosion inhibitors include a composition of one or more of sodium fluotitanate, potassium fluotitanate, titanium oxysulfate, sodium fluorozirconate, potassium fluorozirconate, sodium hydrogen phosphate, and potassium hydrogen phosphate.

[0023] In the present invention, the silane coupling agents are one or more of γ-aminopropyltriethoxysilane (γ-APS), γ-glycidoxypropyltrimethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane, such as KH-550, KH-560, KH-171, KH-151, etc.

[0024] In the present invention, the polyethylene wax dispersions include one or more of LB-6250, Keim-additec MD-2000, HS60BA, HS 420-40BA, and Vok-A-C680.

[0025] In the present invention, the wetting agents are one or more of polyether silicone copolymers and / or silicone surfactants with an organic silicon gemini structure, including one or more of TEGO-4100, TEGO-270, BYK-381, and BYK-377.

[0026] In the present invention, the defoamer is one or more of a silicon-free polymer, a polysiloxane defoamer containing fumed silica, and / or a polyether siloxane defoamer, including one or more of BYK-011, BYK-015, BYK-024, Airex-902W, and Foamex-810.

[0027] In the present invention, the silica sol is a sol of silica nanoparticles (10 - 100 nm), with a concentration of 10 - 35%, including one or more of HS-400, S-1430B, JN-830, and SW-3030.

[0028] On the other hand, the present invention provides a method for preparing the above-mentioned water-based environmentally friendly treatment liquid, which includes the following steps:

[0029] (1) Add the first water-based acrylic hybrid modified polyurethane dispersion and the second water-based acrylic hybrid modified polyurethane dispersion under stirring at 400 - 600 rpm according to the ratio.

[0030] (2) Dropwise add the film-forming aid, wetting agent, and defoamer drop by drop under stirring at 400 - 600 rpm.

[0031] (3) Preheat the polyethylene wax dispersion to 40 - 60 °C and add it dropwise under stirring at 400 - 600 rpm.

[0032] (4) Dropwise add the silane coupling agent and silica sol at a rotation speed of 800 - 1000 rpm and continuously stir for 30 - 90 min.

[0033] (5) Take the deionized water required by the formula, add the inorganic corrosion inhibitor to the water, fully dissolve it under stirring at 400 - 600 rpm, add it to the solution in step (4), and stir at 400 - 600 rpm for another 5 - 20 min.

[0034] (6) Add a pH regulator to adjust the pH of the entire treatment liquid to 8 - 10 and continuously stir at 400 - 600 rpm for 10 - 60 min.

[0035] In the present invention, the pH regulator includes one or more of phosphoric acid, triethylamine, N-N dimethylethanolamine, ammonia water, and 2-amino-2-methyl-1-propanol (AMP-95).

[0036] The present invention also relates to the application of the above-mentioned water-based environmentally friendly treatment liquid in the pretreatment of hot-dip galvanized coils.

[0037] The environmentally friendly treatment liquid provided by the present invention for the pretreatment of hot-dip galvanized coils has the following beneficial effects:

[0038] (1) The environmentally friendly treatment liquid for the pretreatment of hot-dip galvanized coils in the present invention mainly uses water as the dispersion medium, with an extremely low solvent content. Compared with solvent-based coatings, the solvent content is reduced by more than 90%. It does not contain benzene solvents, formaldehyde, halogenated hydrocarbons, and alkylphenol polyoxyethylene ethers (APEO). At the same time, compared with some compromise solutions that replace hexavalent chromium with trivalent chromium, the present invention truly achieves "chromium-free" for metal pretreatment liquids, which is safe and environmentally friendly. It can not only reduce the enterprise's environmental protection emission tax expenditures, but also greatly reduce the impact on the environment and human body, truly realizing the development concept of green, safe, and environmentally friendly.

[0039] (2) The performance of the metal pretreatment liquid is established by using a comprehensive system of the shielding effect of the organic resin film and the passivation effect of inorganic salts. Two acrylic / polyurethane hybrid dispersions are used by blending as film-forming substances. The hybrid modification method avoids the phase separation and internal stress formed by the aggregation of acrylate and polyurethane during film formation, and can effectively retain the performance advantages of each resin. Compared with other conventional resins, the organic resin film formed by the PUA combination used in the present invention has the characteristics of high strength, high toughness, good film-forming property, and wetting and spreading property. At the same time, the organic resin can effectively shield the medium in the environment, especially can block the corrosion and damage of O 2 , H 2 O and Cl - on the galvanized layer, thereby blocking the progress of the cathodic reaction. The core properties of the obtained pretreatment liquid, such as the salt spray resistance performance, have very obvious advantages even compared with the "hexavalent chromium" system. Moreover, compared with the conventional "chromium-free passivation liquid", the PUA used in the present invention endows the surface of the pretreatment film with a certain hydrophilicity by restricting the molecular chain length of the hydrophobic segment of the PU and adjusting the hydrophilic distribution of the side chain, etc., and can obtain a large dry film surface tension, which is beneficial to the spreading and adhesion of the subsequent coating on the surface of the pretreatment layer and is very beneficial to the secondary coating.

[0040] (3) The protective performance of the film layer is further optimized by using silica sol. Due to its small density and large specific surface area, part of the silica sol will be filled between the latex particles, enhancing the denseness of the film layer. At the same time, due to the large number of silanol bonds contained in the silica sol, it can crosslink with the resin molecules. The combination of silane coupling agents is used, and their special coupling mechanism is used to tightly combine the organic resin layer with the metal substrate and optimize the crosslinking.

[0041] (4) Compared with the conventional pretreatment liquid, the present invention has extremely obvious advantages in several key properties such as damp heat resistance, salt spray resistance, and alcohol rub resistance, and the rest of the properties can meet the industry standards, and can be widely applied to fields with high performance requirements such as the back panels of household appliances. Detailed implementation mode

[0042] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention. All other embodiments obtained without creative inventions based on the general concept of the embodiments in the present invention fall within the protection scope of the present invention.

[0043] Corrosion resistance: The corrosion resistance was detected by a neutral salt spray test chamber. Observe once every 24 hours until white rust begins to appear, and then continuously observe for 48 hours. Record the extension of the white rust. The sample size is 70mm * 150mm, and the average value is taken from three parallel samples.

[0044] Humid heat blackening resistance: Using a humid heat simulation chamber, set the conditions at 70°C, 80% RH, for 120 hours. Compare the LAB values before and after humid heat resistance by a color difference meter, and calculate ΔE 1 , The sample size is 70mm * 150mm, and the average value is taken from three parallel samples.

[0045] Alkali resistance: Immerse in 0.1mol / L NaOH solution at 45°C for 1 minute, rinse with water for 10 seconds, observe the surface after wiping. The sample size is 70mm * 150mm, and the average value is taken from three parallel samples.

[0046] Degreaser resistance: Immerse in a 11% concentration degreaser at 60°C for 2 minutes. Rinse with water for 10 seconds, and observe the peeling situation of the paint film surface. The sample size is 70mm * 150mm, and the average value is taken from three parallel samples.

[0047] Alcohol rub / MEK wipe resistance: Wrap a non-woven fabric with a 1kg weight hammer, soak the non-woven fabric with 100% ethanol / MEK, and use the self-weight of the weight hammer to wipe back and forth 30 times. Observe the whitening and penetration of the paint film surface. The sample size is 70mm * 150mm, and the average value is taken from three parallel samples.

[0048] Yellowing resistance: Bake at 200°C for 30 minutes, compare the LAB values before and after baking by a color difference meter, and calculate ΔE 2 , The average value is taken from three parallel samples.

[0049] High-temperature surface tension resistance: After baking at 130°C for 10 minutes, draw lines on the surface with a dyne pen of different Dynes, and require that the lines do not contract within 5 seconds.

[0050] Film-forming property evaluation: Qualitatively evaluate the film-forming property of the pretreatment liquid according to factors such as the integrity, flatness, whether it cracks of the film after coating and drying, and whether film-forming aids need to be added to assist film formation.

[0051] Construction conditions: Coat in a single pass with a 10μm wire bar, use a pop-up high-temperature oven to set the baking temperature at 300°C, the pop-up time is 9 seconds, and cure for 16 hours under the conditions of 25°C and 50% RH after drying, and then conduct performance tests.

[0052] Example 1

[0053] Example 1 of the present invention provides an environment - friendly treatment liquid for pre - treatment of hot - dip galvanized coils.

[0054] The treatment liquid described in Example 1 includes (by mass ratio):

[0055] The first aqueous acrylic hybrid - modified polyurethane dispersion Wantipro 0301A, 14%

[0056] The second aqueous acrylic hybrid - modified polyurethane dispersion Wantipro 0302, 11.5%

[0057] Dipropylene glycol methyl ether (DPM), 3%

[0058] Sodium hexafluorozirconate 2%, sodium hexafluorotitanate 1.5%, sodium hydrogen phosphate 2%

[0059] KH560, 2%

[0060] Keim - additec MD - 2000, 3%

[0061] TEGO - 4100, 0.2%

[0062] BYK - 024, 0.2%

[0063] S - 1430B, 2%

[0064] Deionized water 58.6%.

[0065] The preparation method of the above - mentioned aqueous environment - friendly treatment liquid includes the following steps:

[0066] (1) According to the proportion, add the first aqueous acrylic hybrid - modified polyurethane dispersion Wantipro - 0301A and the second aqueous acrylic hybrid - modified polyurethane dispersion Wantipro - 0302 in sequence under stirring at 500 rpm.

[0067] (2) Dropwise add DPM, TEGO - 4100 and BYK - 024 under stirring at 500 rpm.

[0068] (3) Pre - heat Keim - additec MD - 2000 to 50 °C and add it dropwise under the conditions of 50 °C water bath and stirring at 500 rpm.

[0069] (4) Dropwise add KH560 and S - 1430B at a rotation speed of 1000 rpm and continuously stir for 60 min.

[0070] (5) Add sodium zirconium fluoride, sodium titanium fluoride, and sodium hydrogen phosphate into water, stir at 500 rpm for 10 min for complete dissolution, add to the pre-treatment solution, and stir at 500 rpm for another 10 min.

[0071] (6) Add DMEA, adjust the pH of the entire treatment solution to about 8.8, and continuously stir at 500 rpm for about half an hour.

[0072] Example 2

[0073] Example 2 of the present invention provides an environmentally friendly treatment solution for the pre-treatment of hot-dip galvanized coils. The treatment solution described in Example 2 includes (by mass ratio):

[0074] The first aqueous acrylic hybrid modified polyurethane dispersion Wantipro 0301: 19%,

[0075] The second aqueous acrylic hybrid modified polyurethane dispersion Wantipro 0309: 12%,

[0076] 2-Dipropylene glycol butyl ether (DPNB): 3%,

[0077] Sodium zirconium fluoride: 2%, sodium titanium fluoride: 1.5%, sodium hydrogen phosphate: 2%,

[0078] KH171: 2%,

[0079] LB-6250: 3%,

[0080] TEGO-4100: 0.2%,

[0081] BYK-024: 0.2%,

[0082] S-1430B: 2%,

[0083] Deionized water: 53.1%.

[0084] The preparation method of the above-mentioned water-based environmentally friendly treatment solution includes the following steps:

[0085] (1) According to the ratio, sequentially add the first aqueous acrylic hybrid modified polyurethane dispersion Wantipro-0301 and the second aqueous acrylic hybrid modified polyurethane dispersion Wantipro-0309 while stirring at 400 rpm.

[0086] (2) Dropwise add DPM, TEGO-4100, and BYK-024 while stirring at 400 rpm.

[0087] (3) Preheat LB-6250 to 50 °C and add it dropwise under the conditions of a 50 °C water bath and stirring at 400 rpm.

[0088] (4) Add KH171 and S-1430B dropwise at a rotational speed of 1000 rpm, and continuously stir for 90 min.

[0089] (5) Take deionized water, add sodium zirconium fluoride, sodium titanium fluoride, and sodium hydrogen phosphate into the water, stir at a rotational speed of 400 rpm for 10 min to fully dissolve, add it to the pre-treatment solution, and stir at 400 rpm for another 10 min.

[0090] (6) Add DMEA, adjust the pH of the entire treatment solution to about 8.8, and continuously stir at 400 rpm for about half an hour.

[0091] Comparative Example 1

[0092] Do not use the second aqueous acrylic hybrid modified polyurethane dispersion Wantipro-0302, and its component is completely replaced by the first aqueous acrylic hybrid modified polyurethane dispersion Wantipro-0301A, and the rest is the same as in Example 1.

[0093] Comparative Example 2

[0094] Do not use the first aqueous acrylic hybrid modified polyurethane dispersion Wantipro-0301A, and its component is completely replaced by the second aqueous acrylic hybrid modified polyurethane dispersion Wantipro-0302, and the rest is the same as in Example 1.

[0095] Comparative Example 3

[0096] Replace the first aqueous acrylic hybrid modified polyurethane dispersion Wantipro-0301A with Opody 4835 (commercially available PUD for pretreatment), and the rest is the same as in Example 1.

[0097] Perform performance tests on the environmentally friendly treatment solutions for the pretreatment of hot-dip galvanized coils in each example. The substrate is a non-zinc flower hot-dip galvanized sheet, and the construction process is as follows: coat with a 10-μm wire bar in a single pass, use a pop-up high-temperature oven with a baking temperature of 300 °C and a pop-up time of 9 s, and cure for 16 h under the conditions of 25 °C and 50% RH after drying. The results are shown in Table 2.

[0098] Table 2

[0099]

[0100]

[0101] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention 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 perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An environmentally friendly treatment liquid for the pretreatment of hot-dip galvanized coils, comprising the following components by weight percentage: Composition: The first aqueous acrylic hybrid modified polyurethane dispersion: 8-20%, preferably 13-15% The second aqueous acrylic hybrid modified polyurethane dispersion: 8-16%, preferably 10-12% 2. The treatment liquid according to claim 1, characterized in that for the first aqueous acrylic hybrid modified polyurethane dispersion, the hard segment monomer of the PU part in the resin is an aliphatic polyisocyanate, preferably one or more of dicyclohexylmethane diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate; the soft segment monomer of the PU part is a polycarbonate polyol, preferably one or more of 1,4-butanediol type polycarbonate polyol, 1,5-pentanediol type polycarbonate polyol, and 1,6-hexanediol type polycarbonate polyol; the main monomer of the PA part is one or more of 2-ethylhexyl methacrylate, 2-ethylhexyl acrylate, styrene, methyl methacrylate, and n-butyl methacrylate; preferably, the mass ratio of PU to PA in the first aqueous acrylic hybrid modified polyurethane is 1:0.8-1:1.6; Preferably, the first aqueous acrylic hybrid modified polyurethane dispersion is at least one of Wanhua's 0301 and 0301A.

3. The treatment liquid according to claim 1, characterized in that for the second aqueous acrylic hybrid modified polyurethane dispersion, the hard segment monomer of the PU part in the resin is an aromatic polyisocyanate, preferably one or two of diphenylmethane diisocyanate and toluene diisocyanate; the soft segment monomer of the PU part is a polyether polyol, preferably one or more of polypropylene oxide ether, polyethylene oxide ether, and polytetrahydrofuran ether; the main monomer of the PA part is one or more of styrene, methyl methacrylate, and n-butyl methacrylate; preferably, the mass ratio of PU to PA in PUA2 is 1:0.6-1:1.4; Preferably, the second aqueous acrylic hybrid modified polyurethane dispersion is selected from at least one of 0302, 0309.

4. The treatment liquid according to claim 1, characterized in that the film-forming aid is one or more of propylene glycol methyl ether, dipropylene glycol methyl ether, dipropylene glycol propyl ether, dipropylene glycol butyl ether, ethylene glycol butyl ether acetate, propylene glycol diacetate, and propylene glycol methyl ether acetate.

5. The treatment liquid according to claim 1, characterized in that the inorganic corrosion inhibitor comprises a composition of one or more of sodium fluotitanate, potassium fluotitanate, titanium oxysulfate, sodium fluozirconate, potassium fluozirconate, sodium hydrogen phosphate, and potassium hydrogen phosphate.

6. The treatment liquid according to claim 1, characterized in that the silane coupling agent is one or more of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane.

7. The treatment liquid according to claim 1, characterized in that the polyethylene wax dispersion comprises one or more of LB-6250, Keim-additec MD-2000, HS 60BA, HS 420-40BA, and Vok-A-C680.

8. The treatment liquid according to claim 1, characterized in that the wetting agent is one or more of polyether silicone copolymer and / or silicone surfactant with an organosilicon gemini structure; The defoamer is one or more of a silicon-free polymer, a polysiloxane defoamer containing fumed silica, and / or a polyether siloxane defoamer; the silica sol is a sol of silica nanoparticles, including one or more of HS-400, S-1430B, JN-830, and SW-3030.

9. The method for preparing the treatment liquid according to any one of claims 1-8, comprising the following steps: (1) Add the first aqueous acrylic hybrid modified polyurethane dispersion, the second aqueous acrylic hybrid modified polyurethane dispersion, and a film-forming aid under stirring at 400-600 rpm in proportion. (2) Dropwise add the film-forming aid, wetting agent, and defoamer dropwise under stirring at 400-600 rpm. (3) Preheat the polyethylene wax dispersion to 40-60 °C and add it dropwise under stirring at 400-600 rpm. (4) Dropwise add the silane coupling agent and silica sol at a rotation speed of 800-1000 rpm and continuously stir for 30-90 min. (5) Take the deionized water required by the formula, add the inorganic corrosion inhibitor to the water, fully dissolve it by stirring at 400-600 rpm, add it to the solution in step (4), and stir at 400-600 rpm for another 5-20 min. (6) Add a pH regulator to adjust the pH of the entire treatment liquid to 8-10 and continuously stir at 400-600 rpm for 10-60 min.

10. According to the preparation method described in claim 9, wherein, the pH regulator includes one or more of phosphoric acid, triethylamine, N-N dimethylethanolamine, ammonia water, and 2-amino-2-methyl-1-propanol.

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