Ageing-resistant water-based protective coating for metal rust prevention and preparation method of aging-resistant water-based protective coating

Abstract

The invention discloses an anti-aging water-based protective coating for metal rust prevention and a preparation method thereof, belongs to the technical field of water-based coating processing, and aims to solve the technical problem that the water resistance, salt mist resistance, impact resistance and aging resistance of a water-based protective coating in the prior art need to be further improved. The anti-rust paint specifically comprises the following components in parts by weight: 40-45 parts of polyurethane emulsion, 8-9 parts of anti-rust filler and 3-4 parts of additive. According to the invention, the polyurethane emulsion is prepared from fluorine-modified silicone oil enhanced polyurethane, and then the polyurethane emulsion is combined with the antirust filler to prepare the anti-aging water-based protective coating for metal rust prevention, so that the salt mist resistance and water resistance of the antirust coating are effectively improved, and the impact resistance and aging resistance of the antirust coating are also effectively improved; and the long-term aging resistance of the protective coating is enhanced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water-based paint processing, in particular to a metal anti-rust water-based protective coating with aging resistance and a preparation method thereof. BACKGROUND

[0002] Metal materials play an indispensable role in many fields such as industrial production, infrastructure construction and daily life due to their excellent mechanical properties, processing properties and wide application adaptability. However, metal is prone to corrosion in natural environment or specific working conditions. Coating anti-rust paint on the surface of metal can effectively slow down or prevent metal corrosion.

[0003] At present, metal protective coatings are mainly solvent-based epoxy resin, alkyd resin or chlorinated rubber systems. Such coatings have good protective performance, but generally have the defects of high emission of volatile organic compounds, strong irritating odor, serious environmental pollution during film formation, etc., which do not meet the current green and low-carbon development needs. With the acceleration of water-based trend in the coating industry, environmentally friendly resins such as water-based polyurethane, water-based epoxy and water-based acrylic have gradually become an important research direction for metal protective coatings.

[0004] However, the hydrophilicity of the water-based resin in the water-based anti-rust coating in the prior art leads to water absorption and swelling of the coating film in a high-humidity or water-immersed environment, thereby reducing the compactness of the coating, and corrosion medium is easily transferred to the metal interface, causing corrosion. The water-based coating film has good flexibility, but the impact resistance is limited, and cracks are easily produced when subjected to external impact or thermal expansion and contraction, which accelerates the spread of corrosion. In addition, the water-based anti-rust coating system is prone to main chain degradation, rupture or powdering under ultraviolet radiation and alternating wet and hot environments, resulting in insufficient aging resistance, and the protective ability of the coating in long-term outdoor environment continuously decreases. Conventional inorganic fillers such as talc powder, heavy calcium carbonate and mica powder mainly play the role of filling and shielding, but it is difficult to meet the comprehensive requirements of barrier property, rust resistance and interface stability at the same time, so the long-term salt spray and water resistance of the coating film still cannot meet the high standard requirements.

[0005] In view of the technical defects in this regard, a solution is proposed. SUMMARY

[0006] The present application relates to the technical field of water-based paint processing, in particular to a metal anti-rust water-based protective coating with aging resistance and a preparation method thereof.

[0007] The purpose of the present application can be achieved by the following technical solution: a metal anti-rust water-based protective coating with aging resistance, comprising the following components by weight: polyurethane emulsion 40-45 parts, anti-rust filler 8-9 parts, and additive 3-4 parts.

[0008] The preparation method of polyurethane emulsion is as follows: Under an inert gas atmosphere, polytetrahydrofuran ether diol, fluorinated silicone oil, catalyst and tetrahydrofuran are mixed, the temperature of the reaction system is raised to 50-60℃, diisocyanate is added to the reaction system, the reaction is kept at the temperature for 40-50 min, an end-capping agent is added to the reaction system, the reaction is kept at the temperature for 50-70 min, an emulsifying dispersion is added to the reaction system, the emulsification and dispersion is carried out for 3-4 h, and the post-treatment is performed to obtain polyurethane emulsion.

[0009] The reactions involved in the synthesis of polyurethane emulsions include:

[0010]

[0011] In the formula:

[0012] ;

[0013] .

[0014] Furthermore, the ratio of polytetrahydrofuran ether diol, fluorinated silicone oil, catalyst, tetrahydrofuran, end-capping agent, and emulsion dispersion is 8-10g:6-7g:0.01g:50mL:3-4g:40mL. The catalyst is dibutyltin dilaurate, the end-capping agent is glycidyl ether, and the emulsion dispersion is composed of sodium dodecyl sulfate, OP-10, potassium persulfate, and deionized water at a ratio of 2-3g:1.6-1.8g:1.5g:100mL. The emulsion dispersion speed is 6000-7000 r / min. The post-treatment includes: after the reaction is complete, the reaction system temperature is lowered to room temperature, and the mixture is passed through a 200-mesh sieve to obtain a polyurethane emulsion.

[0015] Furthermore, the preparation method of fluorine-modified silicone oil is as follows: octamethylcyclotetrasiloxane, trifluoropropylmethylcyclotrisiloxane, diethoxy-5-hexen-1-ylmethylsilane and sulfuric acid are mixed, the reaction system temperature is raised to 90-95℃, and the reaction is maintained at this temperature for 90-120 min. Then, (1,1,3,3-tetramethyl-1,3-disiloxanediyl)diethanol is added to the reaction system, and the reaction is maintained at this temperature for 2-3 h. After post-treatment, fluorine-modified silicone oil is obtained.

[0016] The synthesis reaction formula for fluorine-modified silicone oil is as follows:

[0017]

[0018] Furthermore, the ratio of octamethylcyclotetrasiloxane, trifluoropropylmethylcyclotrisiloxane, diethoxy-5-hexen-1-ylmethylsilane, sulfuric acid, and (1,1,3,3-tetramethyl-1,3-disiloxanediyl)diethanol is 12-14g:8-9g:3-4g:2mL:4-5g, and the mass fraction of the sulfuric acid is 60-80%. The post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, 1wt% sodium bicarbonate aqueous solution is added to the reaction system to adjust the pH of the system to 9-10, the system is allowed to stand and separated, the upper organic matter is washed with purified water until neutral, and then transferred to a rotary evaporator with a water bath temperature of 90-100℃ to remove low-boiling substances under reduced pressure to obtain fluorinated silicone oil.

[0019] Furthermore, the rust-inhibiting filler is prepared by the following steps:

[0020] A1. Mix and stir the modified montmorillonite and pyrrole solution. Raise the temperature of the reaction system to 50-60℃, add the catalyst to the reaction system, and maintain the temperature for 6-8 hours. After post-treatment, obtain the montmorillonite-based filler.

[0021] A2. Mix montmorillonite-based filler, zinc phosphate, KH-560, and anhydrous methanol, and ultrasonically disperse for 30-50 min. Raise the temperature of the reaction system to 50-60℃, add 5wt% sodium hydroxide solution to the reaction system, and keep the reaction at this temperature for 20-30 min. Add 3,5-di-tert-butyl-4-hydroxybenzyl alcohol to the reaction system, and keep the reaction at this temperature for 50-70 min. After post-treatment, obtain the rust-preventive filler.

[0022] Further, in step A1, the ratio of the modified montmorillonite, pyrrole solution, and catalyst is 5g:50mL:1g. The pyrrole solution is composed of pyrrole, deionized water, and polyethylene glycol 800 in a ratio of 3g:70mL:1g. The catalyst is composed of 30wt% hydrogen peroxide and ferric chloride in a ratio of 5mL:1g. The post-treatment includes: after the reaction is complete, the temperature of the reaction system is lowered to room temperature, filtered, and the filter cake is transferred to a freeze dryer at a temperature of -30℃ and freeze-dried to constant weight to obtain montmorillonite-based filler.

[0023] Further, in step A2, the ratio of the montmorillonite-based packing material, zinc phosphate, KH-560, anhydrous methanol, 5wt% sodium hydroxide solution, and 3,5-di-tert-butyl-4-hydroxybenzyl alcohol is 4g:2g:1.9-2.1g:50mL:5mL:0.6-0.8g. The post-treatment includes: after the reaction is complete, the reaction system temperature is lowered to room temperature, filtered, the filter cake is washed with purified water until neutral, dried, the filter cake is transferred to a drying oven at 60-70℃ and dried to constant weight, pulverized, and passed through a 200-mesh sieve to obtain the rust-preventive packing material.

[0024] Furthermore, the load-modified montmorillonite is obtained by the following steps:

[0025] B1. Mix sodium-based montmorillonite, intercalating agent, and deionized water. Raise the temperature of the reaction system to 70-80℃, stir and disperse for 8-10 hours, and then perform post-treatment to obtain intercalated montmorillonite.

[0026] B2. Mix the intercalated montmorillonite and zinc-based solution, ultrasonically disperse for 40-60 min, add sodium hydroxide solution to the reaction system at room temperature to adjust the pH of the system to 8-9, stir and disperse for 20-30 min, and then wash and calcine to obtain the loaded modified montmorillonite.

[0027] Further, in step B1, the ratio of sodium-based montmorillonite, intercalating agent, and deionized water is 3g:1.2-1.6g:50mL. The intercalating agent is composed of hexadecyltrimethylammonium bromide and 5-carboxy-N,N,N-trimethyl-1-pentanemium bromide in a weight ratio of 3:1. The post-treatment includes: after the reaction is complete, the temperature of the reaction system is lowered to room temperature, filtered, the filter cake is washed three times with purified water and then dried, and the filter cake is transferred to a drying oven at a temperature of 65-75℃ and dried to constant weight to obtain intercalated montmorillonite.

[0028] Further, in step B2, the ratio of the layered montmorillonite to the zinc-based solution is 1g:6-7mL. The zinc-based solution is composed of zinc acetate, glacial acetic acid, and deionized water at a ratio of 2-3g:5g:100mL. The concentration of the sodium hydroxide solution is 2-3mol / L. The washing and calcination process includes: stirring and dispersing followed by filtration; washing the filter cake twice with purified water and then drying it; transferring the filter cake to a drying oven at 80-90℃ and drying it to constant weight; then transferring it to a tube furnace at 560-620℃ and calcining it in an inert gas atmosphere for 3-4 hours; allowing it to cool naturally to room temperature; and finally discharging the material to obtain the loaded modified montmorillonite.

[0029] The present invention also proposes a method for preparing an aging-resistant water-based protective coating for metal rust prevention, wherein polyurethane emulsion, montmorillonite-based activated filler and additives are mixed and homogeneously dispersed for 30-50 minutes, and deionized water is added to the reaction system for dilution to obtain an aging-resistant water-based protective coating for metal rust prevention with a viscosity of 400-600 mPa·s.

[0030] Furthermore, the additives consist of a thickener, a dispersant, a defoamer, a leveling agent, and a flash rust inhibitor in a weight ratio of 5:3:2:2:2. The thickener is a nonionic polyurethane associative thickener, the dispersant is polyethylene glycol 800, the defoamer is an organosilicon defoamer, and the leveling agent is a BASF leveling agent. The homogeneous dispersion speed is 1200-1800 r / min.

[0031] The present invention has the following beneficial effects:

[0032] 1. This invention involves deep modification of the film-forming resin structure, achieving excellent weather resistance, corrosion resistance, and mechanical durability. The introduction of fluorinated silicone oil significantly reduces the surface energy of the coating, forming a stable hydrophobic barrier structure, thereby reducing the penetration of moisture and salt spray. Simultaneously, the compliant siloxane backbone and the soft segment structure of polyurethane work together to enhance the flexibility and impact resistance of the coating film, and mitigate the damage of ultraviolet radiation to the polyurethane backbone, enabling the coating to maintain high impact strength and stable mechanical properties before and after aging. Furthermore, through the participation of alkenyl groups in crosslinking, the structural density of the polyurethane system is enhanced, further improving water erosion resistance and providing a fundamental support for the overall protective performance.

[0033] 2. This invention also uses sodium-based montmorillonite as raw material to construct a composite filler system with layered shielding and multiple corrosion inhibition properties, which significantly improves the corrosion resistance of the coating. The loaded modified montmorillonite forms a "maze effect" through organic intercalation, lamellar regularization and uniform anchoring of ZnO nanoparticles, which effectively extends the diffusion path of corrosive media. At the same time, ZnO provides active corrosion inhibition sites, enhancing the buffering and passivation ability of the coating in humid and hot and salt spray environments. The further formed polypyrrole conductive network and zinc phosphate slow-release system enable the coating to have local self-passivation function, which can inhibit corrosion diffusion after the occurrence of local defects such as scratches, and improve the continuous protection ability of the composite corrosion inhibition structure of the coating.

[0034] 3. This invention also achieves uniform and dense overall coating structure and improved interfacial bonding through interface engineering design and film-forming process control. Silane coupling agents form stable covalent bonds between inorganic fillers and organic resins, improving filler dispersibility and interfacial strength, and reducing the generation of interfacial microcracks; hindered phenolic antioxidants form an anti-aging protective layer on the filler surface, effectively weakening the damage of ultraviolet rays and oxidizing media to fillers and resins, and reducing the performance degradation after coating aging; in addition, through the optimized ratio of homogeneous dispersion and leveling, thickening, and defoaming additives, the coating film is more dense and has a lower defect rate, further enhancing water resistance, salt spray resistance, and aging resistance, ensuring that the coating maintains a longer water resistance time and good protective stability after irradiation aging. Detailed Implementation

[0035] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0036] In this application, the flash rust inhibitor is a commercially available product from Shanghai Huiyan New Materials Co., Ltd., model number HY-DA120.

[0037] In this application, the silicone defoamer is a commercially available product of Shandong Yuxing Fine Chemical Co., Ltd., model number LAS;

[0038] In this application, the BASF leveling agent is a commercially available product of Shanghai Zhenlishi Network Technology Co., Ltd., model number EFKA FL 3777 AN;

[0039] In this application, the nonionic polyurethane associative thickener is a commercially available product selected from Shanghai Zhenlishi Network Technology Co., Ltd., model ACRYSOL RM-8W;

[0040] In this application, polytetrahydrofuran ether diol is a commercially available product of Jining Fangyu Chemical Co., Ltd., model number PTMG650;

[0041] In this application, sodium montmorillonite is a commercially available product of Lingshou County Chengnuo Mineral Products Co., Ltd., with a content of 99%, and is white powder with a mesh size of 325.

[0042] In this application, KH-560 is γ-glycidoxypropyltrimethoxysilane, CAS No. 2530-83-8.

[0043] Example 1

[0044] This embodiment provides a method for preparing an aging-resistant water-based protective coating for metal rust prevention, comprising the following steps:

[0045] Step S1: Preparation of fluorine-modified silicone oil

[0046] Weigh out 120g of octamethylcyclotetrasiloxane, 80g of trifluoropropylmethylcyclotrisiloxane, 30g of diethoxy-5-hexen-1-ylmethylsilane, and 20mL of 60wt% sulfuric acid and add them to a reaction flask. Stir the mixture and raise the temperature of the reaction flask to 90℃. Keep the reaction at this temperature for 90min. Add 40g of (1,1,3,3-tetramethyl-1,3-disiloxanediyl)diethanol to the reaction flask and keep the reaction at this temperature for 2h. Lower the temperature of the reaction flask to room temperature and add 1wt% sodium bicarbonate aqueous solution to adjust the pH of the system to 9. Allow the mixture to stand and separate the layers. Wash the upper organic matter with purified water until neutral and transfer it to a rotary evaporator with a water bath temperature of 90℃. Remove low-boiling substances by vacuum evaporation to obtain fluorinated silicone oil.

[0047] In the reaction, under the action of sulfuric acid, octamethylcyclotetrasiloxane, trifluoropropylmethylcyclotrisiloxane, and alkenyl-containing diethoxysilane undergo protonation-induced Si–O bond ring opening, thereby achieving copolymerization of multiple siloxane units through cationic ring-opening polymerization. The fluoroalkyl side chain and alkenyl structure are simultaneously embedded into the polysiloxane backbone. After (1,1,3,3-tetramethyl-1,3-disiloxanediyl)diethanol is added to the system as a capping agent, the silanol produced by its hydrolysis further condenses with the active silicon atoms at the chain end, so that the chain end is capped by the dihydroxysilane structure, controlling the polymer molecular weight and introducing hydroxyl functional groups that can continue to react, resulting in a fluorinated modified silicone oil with a stable structure, fluorinated side chain and unsaturated olefin double bond modification.

[0048] Step S2: Preparation of polyurethane emulsion

[0049] Sodium dodecyl sulfate, OP-10, potassium persulfate and deionized water were mixed evenly at a ratio of 2g:1.6g:1.5g:100mL to obtain an emulsion dispersion.

[0050] Weigh out 80g of polytetrahydrofuran ether glycol, 60g of fluorinated silicone oil, 0.1g of dibutyltin dilaurate catalyst, and 500mL of tetrahydrofuran. Add these to an argon-protected reaction flask and stir. Raise the temperature of the reaction flask to 50℃. Calculate the amount of isophorone diisocyanate to be added based on 0.55 times the molar amount of hydroxyl groups in the mixture of polytetrahydrofuran ether glycol and fluorinated silicone oil. Weigh out the calculated amount and add it to the reaction flask. Keep the reaction temperature constant for 40 min. Add 30g of glycidyl ether to the reaction flask and keep the reaction temperature constant for 50 min. Add 400mL of emulsion dispersion to the reaction flask. Set the stirring speed to 6000r / min and emulsify and disperse for 3 h. Lower the temperature of the reaction flask to room temperature and pass it through a 200-mesh sieve to obtain a polyurethane emulsion.

[0051] In the reaction, the hydroxyl groups in polytetrahydrofuran ether diol and fluorinated silicone oil first undergo a typical step-addition urethane reaction with isophorone diisocyanate under the catalysis of dibutyltin dilaurate to generate a fluorinated-silicon prepolymer. Subsequently, the epoxy groups of glycidyl ether further undergo ring-opening addition with the residual isocyanate groups to introduce a hydrophilic structure, so that the prepolymer forms end-group reactive polyurethane segments with a certain degree of branching. Finally, in the emulsion dispersion system constructed by emulsifier and potassium persulfate, the free radical polymerization of olefin double bonds on the polyurethane segments is achieved by high-speed shearing, forming an aqueous phase dispersion and particle stabilization of polyurethane segments with entanglement and cross-linking, thereby obtaining a polyurethane emulsion with uniformly distributed fluorinated silicone segments.

[0052] Step S3: Preparation of load-modified montmorillonite

[0053] Hexadecyltrimethylammonium bromide and 5-carboxy-N,N,N-trimethyl-1-pentaneammonium bromide were mixed evenly at a weight ratio of 3:1 to obtain an intercalating agent;

[0054] Weigh out 30g of sodium montmorillonite, 12g of intercalating agent, and 500mL of deionized water and add them to the reaction flask. Stir the mixture and raise the temperature of the reaction flask to 70℃. Stir and disperse for 8 hours. Lower the temperature of the reaction flask to room temperature and filter. Wash the filter cake three times with purified water and then dry it. Transfer the filter cake to a drying oven at 65℃ and dry it to constant weight to obtain intercalated montmorillonite.

[0055] Zinc acetate, glacial acetic acid and deionized water were mixed evenly at a ratio of 2g:5g:100mL to obtain a zinc-based solution.

[0056] Weigh out 30g of layered montmorillonite and 180mL of zinc-based solution and add them to a reaction flask. Disperse the mixture ultrasonically for 40min. At room temperature, add 2mol / L sodium hydroxide solution to the reaction flask to adjust the pH of the system to 8. Stir and disperse for 20min. Filter the mixture. Wash the filter cake twice with purified water and dry it. Transfer the filter cake to a drying oven at 80℃ and dry it to constant weight. Then transfer it to a tube furnace at 560℃ and calcine it under an argon atmosphere for 3h. Allow it to cool naturally to room temperature and discharge the material to obtain the loaded modified montmorillonite.

[0057] In the reaction, quaternary ammonium salt intercalators, through cation exchange between sodium-based montmorillonite layers, allow hexadecyltrimethylammonium cations and carboxyl-containing trimethylpentanemonium cations to intercalate by substituting Na⁺ between the montmorillonite layers. This transforms the originally hydrophilic layered structure into an organo-montmorillonite with certain hydrophobicity and compatibility with the organic phase. Subsequently, under the action of a zinc-based solution, zinc ions are adsorbed on the surface and between the intercalated montmorillonite layers through complexation and converted into zinc hydroxide under alkaline conditions, thus forming a uniformly loaded inorganic precursor. After high-temperature calcination, the zinc hydroxide further decomposes to generate nano-sized ZnO, which is firmly anchored to the montmorillonite layers and surface, constructing a loaded modified montmorillonite structure with multiple active sites and excellent interfacial bonding ability.

[0058] Step S4: Prepare rust-preventive filler

[0059] Pyrrole, deionized water, and polyethylene glycol 800 were mixed at a ratio of 3g:70mL:1g, heated to 50℃, and stirred until the system dissolved to obtain a pyrrole solution.

[0060] Weigh out 50g of modified montmorillonite and 500mL of pyrrole solution and add them to the reaction flask. Stir the mixture and raise the temperature of the reaction flask to 50℃. Add 10g of catalyst to the reaction flask and keep it at this temperature for 6 hours. Then lower the temperature of the reaction flask to room temperature and filter the mixture. Transfer the filter cake to a freeze dryer at -30℃ and freeze dry it to constant weight to obtain montmorillonite-based filler. The catalyst is composed of 30wt% hydrogen peroxide and ferric chloride in a ratio of 5mL:1g. The hydrogen peroxide and ferric chloride are added separately in two separate steps.

[0061] Weigh out 60g of montmorillonite-based filler, 30g of zinc phosphate, 28.5g of KH-560, and 750mL of anhydrous methanol. Add these to a reaction flask and ultrasonically disperse for 30min. Fix the reaction flask in a water bath with mechanical stirring. Raise the temperature of the reaction flask to 50℃. Add 75mL of 5wt% sodium hydroxide solution to the reaction flask and keep it at this temperature for 20min. Add 9g of 3,5-di-tert-butyl-4-hydroxybenzyl alcohol to the reaction flask and keep it at this temperature for 50min. Lower the temperature of the reaction flask to room temperature and filter. Wash the filter cake with purified water until neutral and then dry it. Transfer the filter cake to a drying oven at 60℃ and dry it to constant weight. Crush the filter cake and pass it through a 200-mesh sieve to obtain the rust-inhibiting filler.

[0062] In the reaction, pyrrole undergoes oxidative polymerization in the FeCl3 / hydrogen peroxide oxidation system, and polypyrrole chains are directionally deposited on the surface of montmorillonite and between the layers, enabling the inorganic layers to achieve a synergistic effect of conductive corrosion inhibition and shielding. Subsequently, the zinc phosphate and montmorillonite-based complex undergo partial precipitation and complexation under alkaline conditions, so that the zinc salt corrosion inhibitor phase is uniformly fixed in the system. Covalent bonding between the inorganic surface and the organic phase is achieved through the silane hydrolysis condensation of KH-560. 3,5-Di-tert-butyl-4-hydroxybenzyl alcohol, as a hindered phenolic antioxidant, has hydroxyl groups on its molecules that can condense with epoxy groups, further forming an anti-aging protective layer on its surface, thus obtaining a composite rust-preventive filler with multiple functions such as conductive corrosion inhibition, zinc salt slow release, and interface strengthening.

[0063] Step S5: Preparation of water-based protective coating

[0064] The nonionic polyurethane associative thickener, polyethylene glycol 800, silicone defoamer, BASF leveling agent and flash rust inhibitor were mixed evenly in a weight ratio of 5:3:2:2:2 to obtain the additives.

[0065] Weigh out 40 parts of polyurethane emulsion, 8 parts of rust-preventive filler, and 3 parts of additives by weight and add them to a homogenizer. Set the homogenization speed to 1200 r / min and homogenize for 30 min. Add deionized water to the reaction flask to dilute and obtain a water-based protective coating for metal rust prevention and aging resistance with a viscosity of 400 mPa·s.

[0066] Example 2

[0067] This embodiment provides a method for preparing an aging-resistant water-based protective coating for metal rust prevention, comprising the following steps:

[0068] Step S1: Preparation of fluorine-modified silicone oil

[0069] Weigh out 130g of octamethylcyclotetrasiloxane, 85g of trifluoropropylmethylcyclotrisiloxane, 35g of diethoxy-5-hexen-1-ylmethylsilane, and 20mL of 70wt% sulfuric acid and add them to a reaction flask. Stir the mixture and raise the temperature of the reaction flask to 93℃. Maintain the temperature for 105min. Add 45g of (1,1,3,3-tetramethyl-1,3-disiloxanediyl)diethanol to the reaction flask and maintain the temperature for 2.5h. Lower the temperature of the reaction flask to room temperature and add 1wt% sodium bicarbonate aqueous solution to adjust the pH of the system to 9.5. Allow the mixture to stand and separate the layers. Wash the upper organic matter with purified water until neutral and transfer it to a rotary evaporator with a water bath temperature of 95℃. Remove low-boiling substances by vacuum evaporation to obtain fluorinated silicone oil.

[0070] Step S2: Preparation of polyurethane emulsion

[0071] Sodium dodecyl sulfate, OP-10, potassium persulfate and deionized water were mixed evenly at a ratio of 2.5g:1.7g:1.5g:100mL to obtain an emulsion dispersion.

[0072] Weigh out 90g of polytetrahydrofuran ether diol, 65g of fluorinated silicone oil, 0.1g of dibutyltin dilaurate catalyst, and 500mL of tetrahydrofuran. Add these to an argon-protected reaction flask and stir. Raise the temperature of the reaction flask to 55℃. Calculate the amount of isophorone diisocyanate to be added based on 0.55 times the molar amount of hydroxyl groups in the mixture of polytetrahydrofuran ether diol and fluorinated silicone oil. Weigh the calculated amount and add it to the reaction flask. Keep the reaction temperature constant for 45 min. Add 35g of glycidyl ether to the reaction flask and keep the reaction temperature constant for 60 min. Add 400mL of emulsion dispersion to the reaction flask. Set the stirring speed to 6500r / min and emulsify and disperse for 3.5 h. Lower the temperature of the reaction flask to room temperature and pass the emulsion through a 200-mesh sieve to obtain a polyurethane emulsion.

[0073] Step S3: Preparation of load-modified montmorillonite

[0074] Hexadecyltrimethylammonium bromide and 5-carboxy-N,N,N-trimethyl-1-pentaneammonium bromide were mixed evenly at a weight ratio of 3:1 to obtain an intercalating agent;

[0075] Weigh out 30g of sodium montmorillonite, 14g of intercalating agent, and 500mL of deionized water and add them to the reaction flask. Stir the mixture and raise the temperature of the reaction flask to 75℃. Stir and disperse for 9 hours. Lower the temperature of the reaction flask to room temperature and filter. Wash the filter cake three times with purified water and then dry it. Transfer the filter cake to a drying oven at 70℃ and dry it to constant weight to obtain intercalated montmorillonite.

[0076] Zinc acetate, glacial acetic acid, and deionized water were mixed evenly at a ratio of 2.5g:5g:100mL to obtain a zinc-based solution.

[0077] Weigh out 30g of layered montmorillonite and 195mL of zinc-based solution and add them to a reaction flask. Disperse the mixture ultrasonically for 50min. At room temperature, add 2.5mol / L sodium hydroxide solution to the reaction flask to adjust the pH of the system to 8.5. Stir and disperse for 25min. Filter the mixture. Wash the filter cake twice with purified water and dry it. Transfer the filter cake to a drying oven at 85℃ and dry it to constant weight. Then transfer it to a tube furnace at 590℃ and calcine it under an argon atmosphere for 3.5h. Allow it to cool naturally to room temperature and discharge the material to obtain the loaded modified montmorillonite.

[0078] Step S4: Prepare rust-preventive filler

[0079] Pyrrole, deionized water, and polyethylene glycol 800 were mixed at a ratio of 3g:70mL:1g, heated to 55℃, and stirred until the system dissolved to obtain a pyrrole solution.

[0080] Weigh out 50g of modified montmorillonite and 500mL of pyrrole solution and add them to the reaction flask. Stir the mixture and raise the temperature of the reaction flask to 55℃. Add 10g of catalyst to the reaction flask and keep it at this temperature for 7h. Then lower the temperature of the reaction flask to room temperature and filter the mixture. Transfer the filter cake to a freeze dryer at -30℃ and freeze dry it to constant weight to obtain montmorillonite-based filler. The catalyst is composed of 30wt% hydrogen peroxide and ferric chloride in a ratio of 5mL:1g. The hydrogen peroxide and ferric chloride are added separately in two separate steps.

[0081] Weigh out 60g of montmorillonite-based filler, 30g of zinc phosphate, 30g of KH-560, and 750mL of anhydrous methanol. Add these to a reaction flask and ultrasonically disperse for 40min. Fix the reaction flask in a water bath with mechanical stirring. Raise the temperature of the reaction flask to 55℃. Add 75mL of 5wt% sodium hydroxide solution to the reaction flask and keep it at this temperature for 25min. Add 10.5g of 3,5-di-tert-butyl-4-hydroxybenzyl alcohol to the reaction flask and keep it at this temperature for 60min. Lower the temperature of the reaction flask to room temperature, filter, wash the filter cake with purified water until neutral, and then dry it. Transfer the filter cake to a drying oven at 65℃ and dry it to constant weight. Crush the filter cake and pass it through a 200-mesh sieve to obtain the rust-inhibiting filler.

[0082] Step S5: Preparation of water-based protective coating

[0083] The nonionic polyurethane associative thickener, polyethylene glycol 800, silicone defoamer, BASF leveling agent and flash rust inhibitor were mixed evenly in a weight ratio of 5:3:2:2:2 to obtain the additives.

[0084] Weigh out the following components by weight: 43 parts of polyurethane emulsion, 8.5 parts of rust-inhibiting filler, and 3.5 parts of additives. Add them to a homogenizer and disperse them at a speed of 1500 r / min for 40 min. Dilute with deionized water in a reaction flask to obtain a water-based protective coating for metal rust prevention and aging resistance with a viscosity of 500 mPa·s.

[0085] Example 3

[0086] This embodiment provides a method for preparing an aging-resistant water-based protective coating for metal rust prevention, comprising the following steps:

[0087] Step S1: Preparation of fluorine-modified silicone oil

[0088] Weigh out 140g of octamethylcyclotetrasiloxane, 90g of trifluoropropylmethylcyclotrisiloxane, 40g of diethoxy-5-hexen-1-ylmethylsilane, and 20mL of 80wt% sulfuric acid and add them to a reaction flask. Stir the mixture and raise the temperature of the reaction flask to 95℃. Keep the reaction at this temperature for 120min. Add 50g of (1,1,3,3-tetramethyl-1,3-disiloxanediyl)diethanol to the reaction flask and keep the reaction at this temperature for 3h. Lower the temperature of the reaction flask to room temperature and add 1wt% sodium bicarbonate aqueous solution to adjust the pH of the system to 10. Allow the mixture to stand and separate the layers. Wash the upper organic matter with purified water until neutral and then transfer it to a rotary evaporator with a water bath temperature of 100℃. Remove low-boiling substances by vacuum evaporation to obtain fluorinated modified silicone oil.

[0089] Step S2: Preparation of polyurethane emulsion

[0090] Sodium dodecyl sulfate, OP-10, potassium persulfate and deionized water were mixed evenly at a ratio of 3g:1.8g:1.5g:100mL to obtain an emulsion dispersion.

[0091] Weigh out 100g of polytetrahydrofuran ether glycol, 70g of fluorinated silicone oil, 0.1g of dibutyltin dilaurate catalyst, and 500mL of tetrahydrofuran. Add these to an argon-protected reaction flask and stir. Raise the temperature of the reaction flask to 60℃. Calculate the amount of isophorone diisocyanate to be added based on 0.55 times the molar amount of hydroxyl groups in the mixture of polytetrahydrofuran ether glycol and fluorinated silicone oil. Weigh the calculated amount and add it to the reaction flask. Keep the reaction temperature constant for 50 min. Add 40g of glycidyl ether to the reaction flask and keep the reaction temperature constant for 70 min. Add 400mL of emulsion dispersion to the reaction flask. Set the stirring speed to 7000r / min and emulsify and disperse for 4 h. Lower the temperature of the reaction flask to room temperature and pass the emulsion through a 200-mesh sieve to obtain a polyurethane emulsion.

[0092] Step S3: Preparation of load-modified montmorillonite

[0093] Hexadecyltrimethylammonium bromide and 5-carboxy-N,N,N-trimethyl-1-pentaneammonium bromide were mixed evenly at a weight ratio of 3:1 to obtain an intercalating agent;

[0094] Weigh out 30g of sodium montmorillonite, 16g of intercalating agent, and 500mL of deionized water and add them to the reaction flask. Stir the mixture and raise the temperature of the reaction flask to 80℃. Stir and disperse for 10h. Lower the temperature of the reaction flask to room temperature and filter. Wash the filter cake three times with purified water and then dry it. Transfer the filter cake to a drying oven at 75℃ and dry it to constant weight to obtain intercalated montmorillonite.

[0095] Zinc acetate, glacial acetic acid and deionized water were mixed evenly at a ratio of 3g:5g:100mL to obtain a zinc-based solution.

[0096] Weigh out 30g of layered montmorillonite and 210mL of zinc-based solution and add them to a reaction flask. Disperse the mixture ultrasonically for 60min. At room temperature, add 3mol / L sodium hydroxide solution to the reaction flask to adjust the pH of the system to 9. Stir and disperse for 30min. Filter the mixture. Wash the filter cake twice with purified water and dry it. Transfer the filter cake to a drying oven at 90℃ and dry it to constant weight. Then transfer it to a tube furnace at 620℃ and calcine it under an argon atmosphere for 4h. Allow it to cool naturally to room temperature and discharge the material to obtain the loaded modified montmorillonite.

[0097] Step S4: Prepare rust-preventive filler

[0098] Pyrrole, deionized water, and polyethylene glycol 800 were mixed at a ratio of 3g:70mL:1g, heated to 60℃, and stirred until the system dissolved to obtain a pyrrole solution.

[0099] Weigh out 50g of modified montmorillonite and 500mL of pyrrole solution and add them to the reaction flask. Stir the mixture and raise the temperature of the reaction flask to 60℃. Add 10g of catalyst to the reaction flask and keep it at this temperature for 8 hours. Then lower the temperature of the reaction flask to room temperature and filter the mixture. Transfer the filter cake to a freeze dryer at -30℃ and freeze dry it to constant weight to obtain montmorillonite-based filler. The catalyst is composed of 30wt% hydrogen peroxide and ferric chloride in a ratio of 5mL:1g. The hydrogen peroxide and ferric chloride are added separately in two separate steps.

[0100] Weigh out 60g of montmorillonite-based filler, 30g of zinc phosphate, 31.5g of KH-560, and 750mL of anhydrous methanol. Add these to a reaction flask and ultrasonically disperse for 50min. Fix the reaction flask in a water bath with a mechanical stirrer. Raise the temperature of the reaction flask to 60℃. Add 75mL of 5wt% sodium hydroxide solution to the reaction flask and keep it at this temperature for 30min. Add 12g of 3,5-di-tert-butyl-4-hydroxybenzyl alcohol to the reaction flask and keep it at this temperature for 70min. Lower the temperature of the reaction flask to room temperature, filter, wash the filter cake with purified water until neutral, and then dry it. Transfer the filter cake to a drying oven at 70℃ and dry it to constant weight. Crush the filter cake and pass it through a 200-mesh sieve to obtain the rust-inhibiting filler.

[0101] Step S5: Preparation of water-based protective coating

[0102] The nonionic polyurethane associative thickener, polyethylene glycol 800, silicone defoamer, BASF leveling agent and flash rust inhibitor were mixed evenly in a weight ratio of 5:3:2:2:2 to obtain the additives.

[0103] Weigh out 45 parts of polyurethane emulsion, 9 parts of rust-inhibiting filler, and 4 parts of additives by weight and add them to a homogenizer. Set the homogenization speed to 1800 r / min and homogenize for 50 min. Add deionized water to the reaction flask to dilute and obtain a water-based protective coating for metal rust prevention and aging resistance with a viscosity of 600 mPa·s.

[0104] Comparative Example 1

[0105] The difference between this comparative example and Example 3 is that trifluoropropylmethylcyclotrisiloxane was not added in step S1.

[0106] Comparative Example 2

[0107] The difference between this comparative example and Example 3 is that potassium persulfate was not added to the emulsion dispersion in step S2.

[0108] Comparative Example 3

[0109] The difference between this comparative example and Example 3 is that, in step S3, 5-carboxy-N,N,N-trimethyl-1-pentanemonium bromide was not added to the intercalating agent.

[0110] Comparative Example 4

[0111] The difference between this comparative example and Example 3 is that, in step S4, load-modified montmorillonite is used instead of montmorillonite-based filler in the preparation of rust-preventive filler.

[0112] Performance testing:

[0113] Referring to the standard GB / T 1727-2021 "General Preparation Method of Coating Film", the water-based protective coatings for metal rust prevention and aging resistance prepared in Examples 1-3 and Comparative Examples 1-4 were brushed onto tinplate using the brushing method, forming a protective coating with a thickness of 90±5μm on the tinplate, and the test sample was obtained.

[0114] According to method B in standard GB / T 23987-2009 "Artificial weathering exposure of paint and varnish coatings to fluorescent ultraviolet light and water", cyclic irradiation exposure was carried out for 100 hours.

[0115] The impact resistance of the test sample before and after irradiation aging was determined in accordance with the standard GB / T 1732-2020 "Test Method for Impact Resistance of Coating Film".

[0116] Refer to Method A in GB / T 1733-1993 "Determination of Water Resistance of Paint Films" to determine the water resistance of the test sample before and after irradiation aging. When phenomena such as loss of gloss, discoloration, blistering, wrinkling, peeling, and rust are observed, record the water resistance time of the test sample before and after irradiation aging.

[0117] Referring to the standard GB / T 1771-2007 "Determination of resistance to neutral salt spray of paints and varnishes", before the test, a line was drawn on the central axis of the coating with a utility knife, parallel to the long side, to break the coating. A salt spray environment was formed by spraying a 50 g / L sodium chloride solution onto the sample surface. The salt spray test was carried out in a salt spray test chamber, and the results were observed every 12 hours. When the unidirectional erosion at the scratch of the paint film exceeded 1.5 mm, the salt spray resistance time of the test sample before and after irradiation aging was recorded. The specific test data are shown in Table 1 below.

[0118] Table 1 - Performance Test Data of Samples

[0119]

[0120] Data Analysis:

[0121] Comparative analysis of the data in Table 1 shows that the water-based protective coating for metal rust prevention prepared by this invention exhibits the following performance characteristics before irradiation aging: impact strength of 65 kg / cm, salt spray resistance of 610 h, and water resistance of 238 h. After irradiation aging, the impact strength reaches 58 kg / cm, salt spray resistance of 520 h, and water resistance of 180 h. All performance test data are superior to the comparative example. This indicates that the present invention, by preparing a polyurethane emulsion using fluorine-modified silicone oil to reinforce polyurethane, and then combining it with rust-preventive fillers, prepares a water-based protective coating for metal rust prevention that effectively improves not only the salt spray and water resistance of the rust-preventive coating, but also its impact and aging resistance, enhancing the long-term aging resistance of the protective coating.

[0122] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A water-based protective coating for rust prevention and aging resistance in metals, characterized in that, It includes the following components by weight: 40-45 parts polyurethane emulsion, 8-9 parts rust-inhibiting filler, and 3-4 parts additives; The preparation method of polyurethane emulsion is as follows: Under an inert gas atmosphere, polytetrahydrofuran ether diol, fluorinated silicone oil, catalyst and tetrahydrofuran are mixed, the temperature of the reaction system is raised to 50-60℃, diisocyanate is added to the reaction system, the reaction is kept at the temperature for 40-50 min, an end-capping agent is added to the reaction system, the reaction is kept at the temperature for 50-70 min, an emulsifying dispersion is added to the reaction system, the emulsification and dispersion is carried out for 3-4 h, and the post-treatment is performed to obtain polyurethane emulsion.

2. The water-based protective coating for rust prevention and aging resistance of metals according to claim 1, characterized in that, The ratio of polytetrahydrofuran ether diol, fluorinated silicone oil, catalyst, tetrahydrofuran, end-capping agent, and emulsion dispersion is 8-10g:6-7g:0.01g:50mL:3-4g:40mL. The catalyst is dibutyltin dilaurate, the end-capping agent is glycidyl ether, and the emulsion dispersion is composed of sodium dodecyl sulfate, OP-10, potassium persulfate, and deionized water at a ratio of 2-3g: The composition is 1.6-1.8g:1.5g:100mL, and the emulsification and dispersion speed is 6000-7000r / min.

3. The water-based protective coating for rust prevention and aging resistance of metals according to claim 1, characterized in that, The preparation method of fluorine-modified silicone oil is as follows: octamethylcyclotetrasiloxane, trifluoropropylmethylcyclotrisiloxane, diethoxy-5-hexen-1-ylmethylsilane and sulfuric acid are mixed, the reaction system temperature is raised to 90-95℃, and the reaction is maintained at this temperature for 90-120 min. Then (1,1,3,3-tetramethyl-1,3-disiloxanediyl)diethanol is added to the reaction system, and the reaction is maintained at this temperature for 2-3 h. After post-treatment, fluorine-modified silicone oil is obtained.

4. The water-based protective coating for rust prevention and aging resistance of metals according to claim 3, characterized in that, The ratio of octamethylcyclotetrasiloxane, trifluoropropylmethylcyclotrisiloxane, diethoxy-5-hexen-1-ylmethylsilane, sulfuric acid, and (1,1,3,3-tetramethyl-1,3-disiloxanediyl)diethanol is 12-14g:8-9g:3-4g:2mL:4-5g, and the mass fraction of the sulfuric acid is 60-80%.

5. The water-based protective coating for rust prevention and aging resistance of metals according to claim 1, characterized in that, The rust-inhibiting filler is prepared by the following steps: A1. Mix and stir the modified montmorillonite and pyrrole solution. Raise the temperature of the reaction system to 50-60℃, add the catalyst to the reaction system, and maintain the temperature for 6-8 hours. After post-treatment, obtain the montmorillonite-based filler. A2. Mix montmorillonite-based filler, zinc phosphate, KH-560, and anhydrous methanol, and ultrasonically disperse for 30-50 min. Raise the temperature of the reaction system to 50-60℃, add 5wt% sodium hydroxide solution to the reaction system, and keep the reaction at this temperature for 20-30 min. Add 3,5-di-tert-butyl-4-hydroxybenzyl alcohol to the reaction system, and keep the reaction at this temperature for 50-70 min. After post-treatment, obtain the rust-preventive filler.

6. The water-based protective coating for rust prevention and aging resistance of metals according to claim 5, characterized in that, In step A1, the ratio of the modified montmorillonite, pyrrole solution, and catalyst is 5g:50mL:1g. The pyrrole solution is composed of pyrrole, deionized water, and polyethylene glycol 800 in a ratio of 3g:70mL:1g. The catalyst is composed of 30wt% hydrogen peroxide and ferric chloride in a ratio of 5mL:1g. In step A2, the ratio of the montmorillonite-based filler, zinc phosphate, KH-560, anhydrous methanol, 5wt% sodium hydroxide solution, and 3,5-di-tert-butyl-4-hydroxybenzyl alcohol is 4g:2g:1.9-2.1g:50mL:5mL:0.6-0.8g.

7. The water-based protective coating for rust prevention and aging resistance of metals according to claim 5, characterized in that, Load-modified montmorillonite is obtained by the following steps: B1. Mix sodium-based montmorillonite, intercalating agent, and deionized water. Raise the temperature of the reaction system to 70-80℃, stir and disperse for 8-10 hours, and then perform post-treatment to obtain intercalated montmorillonite. B2. Mix the intercalated montmorillonite and zinc-based solution, ultrasonically disperse for 40-60 min, add sodium hydroxide solution to the reaction system at room temperature to adjust the pH of the system to 8-9, stir and disperse for 20-30 min, and then wash and calcine to obtain the loaded modified montmorillonite.

8. The water-based protective coating for rust prevention and aging resistance of metals according to claim 7, characterized in that, In step B1, the ratio of sodium-based montmorillonite, intercalating agent, and deionized water is 3g:1.2-1.6g:50mL. The intercalating agent is composed of hexadecyltrimethylammonium bromide and 5-carboxy-N,N,N-trimethyl-1-pentanemium bromide in a weight ratio of 3:

1. In step B2, the ratio of intercalated montmorillonite and zinc-based solution is 1g:6-7mL. The zinc-based solution is composed of zinc acetate, glacial acetic acid, and deionized water in a ratio of 2-3g:5g:100mL. The concentration of the sodium hydroxide solution is 2-3mol / L.

9. A method for preparing an aging-resistant water-based protective coating for metal rust prevention according to any one of claims 1-8, characterized in that, Polyurethane emulsion, montmorillonite-based activated filler, and additives are mixed and homogeneously dispersed for 30-50 minutes. Deionized water is added to the reaction system for dilution to obtain a water-based protective coating for metal rust prevention and aging resistance with a viscosity of 400-600 mPa·s.

10. The method for preparing an aging-resistant water-based protective coating for metal rust prevention according to claim 9, characterized in that, The additives consist of a thickener, a dispersant, a defoamer, a leveling agent, and a flash rust inhibitor in a weight ratio of 5:3:2:2:

2. The thickener is a nonionic polyurethane associative thickener, the dispersant is polyethylene glycol 800, the defoamer is an organosilicon defoamer, and the leveling agent is a BASF leveling agent. The homogeneous dispersion speed is 1200-1800 r / min.

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