Water-based poly-ceramic coating material as well as preparation method and application thereof

Abstract

The invention discloses a water-based poly-ceramic coating material as well as a preparation method and application thereof. The formula comprises a composite base material (40-45 parts of modified waterborne polyurethane resin and 15-20 parts of a waterborne acrylic emulsion), a synergistic curing system (10-12 parts of a blocked isocyanate curing agent and 0.8-1.2 parts of a latent organic zinc salt accelerant), an organic-inorganic reinforced phase (10-15 parts of nano silicon dioxide and 8-10 parts of polysilazane) and a functional aid. The base material and the cosolvent cooperate to make VOCs less than or equal to 30 g / L, a curing system cooperates to realize low-temperature rapid curing, organic-inorganic components cooperate to form a poly-ceramic structure, the coating is adaptive to an existing roll aluminum production line, and the problems of environmental protection, energy conservation and performance of a traditional coating are solved.

Description

Technical Field

[0001] This invention belongs to the field of water-based polyceramic coating technology, specifically relating to a water-based polyceramic coating material, its preparation method, and its application. Background Technology

[0002] Coating materials, as key materials for surface protection and functional modification, occupy an important position in the industrial manufacturing field, especially in industries such as aluminum coils, automobiles, and electronics. Among them, the aluminum coil industry, as an important branch of metal processing, relies on the curing and shaping of high-temperature paint coatings for its product production. Currently, the industry's common process requires a curing time of 45 to 60 seconds at a high temperature of 160 to 180°C to achieve the coating's performance requirements.

[0003] However, traditional coil aluminum coating materials and processes have significant drawbacks: on the one hand, most existing high-temperature paints are solvent-based systems with high emissions of volatile organic compounds (VOCs), which do not meet current environmental protection requirements; on the other hand, high-temperature curing processes consume a lot of energy, which not only increases the production costs of enterprises, but also goes against the global trend of energy conservation and emission reduction under the "dual carbon" goal.

[0004] To address the aforementioned issues, water-based coating materials have become a hot research topic in the industry due to their environmental advantages. However, existing water-based coatings generally suffer from a technical bottleneck of insufficient low-temperature curing performance—their curing temperature is difficult to drop below 160°C. If the temperature is forcibly lowered, it will lead to problems such as decreased coating adhesion, insufficient hardness, and poor corrosion resistance, which cannot meet the actual construction and performance requirements of the aluminum coil industry. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0006] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0007] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a water-based coating material that can achieve rapid curing at low temperatures (such as 50°C) and whose comprehensive performance reaches or exceeds that of traditional high-temperature paints.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: Based on the mass fraction of the raw materials of the water-based polyceramic coating material, it includes, 40-45 parts modified waterborne polyurethane resin, 15-20 parts waterborne acrylic emulsion, 10-15 parts silica nanomaterials, 8-10 parts ceramic precursor polymer, 10-12 parts blocked isocyanate curing agent, 10-15 parts deionized water, 3-5 parts organozinc salt accelerator, 2-2.5 parts silane coupling agent, 1-2 parts leveling agent, 1-2 parts defoamer, 1-2 parts cosolvent, and 0.5-1 part epoxy group activator; Silica nanomaterials were dispersed in a cosolvent and coated with a silane coupling agent to obtain coupling agent-coated nanoparticles. Modified waterborne polyurethane resin was activated with an epoxy activator to obtain activated modified waterborne polyurethane resin. The coupling agent-coated nanoparticles, the activated modified waterborne polyurethane resin, and the remaining components of the waterborne polyceramic coating material raw material were mixed by gradient speed stirring to obtain a mixed system, wherein the organic zinc salt accelerator was added in batches. After the pH of the mixed system is adjusted to a uniform and stable level, a gradient aging process is used to obtain the water-based polyceramic coating material.

[0009] In a preferred embodiment of the preparation method of the waterborne polyporous ceramic coating material of the present invention, the modified waterborne polyurethane resin is obtained by copolymerizing polyhexamethylene adipate and isophorone diisocyanate and then introducing epoxy groups for modification, with a hydroxyl content of 3%~5%; The silicon nanomaterial is nano-silica; The ceramic precursor polymer includes one or more of polysilazane, polysiloxane, and polytitanium siloxane; The blocked isocyanate curing agent includes one or both of caprolactam-blocked toluene diisocyanate curing agent and caprolactam-blocked isophorone diisocyanate curing agent. The organic zinc salt accelerators include zinc octanoate, zinc isooctanoate, or zinc acetylacetonate; The silane coupling agent includes one of KH-550, KH-560, and A-1100; The leveling agent includes polyether-modified polysiloxane and acrylate copolymer; the defoamer includes silicone emulsion, polyether-modified silicone, and polyether polyol; the cosolvent includes propylene glycol methyl ether and dipropylene glycol methyl ether; and the epoxy activator includes 2-methylimidazole and triethanolamine.

[0010] As a preferred embodiment of the preparation method of the water-based polyceramic coating material of the present invention, the method of treating the silica nanomaterial by dispersing with a co-solvent and coating with a silane coupling agent is as follows: the silica nanomaterial is added to a co-solvent, ultrasonically dispersed, then a silane coupling agent is added, and the mixture is stirred at a constant temperature to form coupling agent-coated nanoparticles, thereby improving the compatibility between the silica nanomaterial and the organic matrix.

[0011] As a preferred embodiment of the preparation method of the waterborne polyceramic coating material of the present invention, the activation method of the modified waterborne polyurethane resin by activating it with an epoxy group activator is as follows: the modified waterborne polyurethane resin is preheated to 40°C and then an epoxy group activator is added thereto, and the mixture is stirred to enhance the reaction activity between the hydroxyl groups and the curing agent, thereby obtaining the activated modified waterborne polyurethane resin.

[0012] In a preferred embodiment of the preparation method of the water-based polyceramic coating material of the present invention, the mixed system obtained by gradient speed stirring includes, Deionized water, coupling agent-coated nanoparticles, ceramic precursor polymer, leveling agent, and defoamer are stirred at 500-600 r / min for 10-15 minutes to form a stable pre-dispersion. Add activated modified waterborne polyurethane resin and waterborne acrylic emulsion to the stable pre-dispersion liquid, increase the speed to 800~900 r / min and continue stirring and mixing, and heat the system to 45℃. Under high-speed shear conditions of 1500~1600 r / min, add blocked isocyanate curing agent dropwise, and at the same time, introduce nitrogen gas for protection to disperse and form a uniform and stable curing agent emulsion. Cool the system to 35°C, add 50% of the organic zinc salt accelerator, stir at low speed for 3-5 minutes, cool further to 30°C, add the remaining organic zinc salt accelerator, and continue stirring for 10-15 minutes to obtain a mixed system.

[0013] As a preferred embodiment of the preparation method of the water-based polyceramic coating material of the present invention, the pH adjustment of the mixed system to a uniform and stable acid-base balance includes: first adjusting the pH of the system to 7.0 using an acid-base regulator, letting it stand for 5 minutes, and then adjusting the pH of the system to 7.5~8.5 using the same reagent.

[0014] As a preferred embodiment of the preparation method of the water-based polyceramic coating material of the present invention, the gradient curing process involves first curing the system, after the pH has been adjusted to be uniform and stable by an acid-base regulator, at 30°C for 10-12 hours, then heating it to 35°C for 6-8 hours, and finally cooling it to 25°C for 3-4 hours.

[0015] Another object of the present invention is to provide a water-based coating material prepared by a preparation method for the water-based coating material.

[0016] Another object of the present invention is to provide an application of the aforementioned water-based coating material.

[0017] To solve the above-mentioned technical problems, the present invention provides the following technical solution: the water-based polyceramic coating material is coated onto the surface of the pretreated aluminum coil using a double-coating roller coating process; The thickness of the dry film in the first roller coating is controlled at 8~10μm, and it is pre-cured in an oven at 45~55℃ for 10~15s; The second roll coating is applied until the total dry film thickness is 15~20μm. It is then cured for 30~40s in an infrared and hot air combined oven. Infrared radiation is used to accelerate the cross-linking reaction and shorten the curing time. The infrared wavelength is 2~5μm and the hot air temperature is 45~55℃.

[0018] As a preferred embodiment of the application of the water-based coating material described in this invention, the pretreatment of the aluminum coil surface involves sandblasting the aluminum coil surface, then spraying a layer of diluted silane coupling agent with a mass fraction of 5%, and drying it to form a transition bonding layer, thereby improving the coating adhesion.

[0019] Beneficial effects of this invention: (1) This invention uses modified waterborne polyurethane resin and waterborne acrylic emulsion to form a composite film-forming base. Both are waterborne systems with good compatibility, which can construct a continuous and dense film-forming base, reducing dependence on volatile organic solvents. The viscosity of the system is reduced by adding a small amount of co-solvent, while avoiding excessive solvent evaporation. Through the synergistic effect of the dosage ratio and compatibility of the base material and co-solvent, VOC emissions are controlled at ≤30g / L.

[0020] (2) In this invention, a synergistic curing system is formed by a blocked isocyanate curing agent and an organic zinc salt accelerator. The blocked isocyanate curing agent blocks TDI with caprolactam, and the unblocking temperature is reduced to 45~50℃. The zinc salt reduces the activation energy of the crosslinking reaction through coordination, and accelerates the reaction rate between the isocyanate groups and the hydroxyl groups in the base material after unblocking. The two work together to enable the coating to quickly complete crosslinking and curing under low temperature conditions. (3) The present invention forms an organic-inorganic synergistic network by adding silicon nanomaterials, ceramic precursor polymers and organic matrix. The high specific surface area of ​​silicon nanomaterials can enhance the interfacial bonding with the matrix and provide rigid support. After the ceramic precursor polymer is cured, it forms a Si-N ceramic structure and forms an inorganic reinforcing phase with silicon nanomaterials. The organic matrix provides an elastic film-forming skeleton. The three work together to improve the mechanical properties of the material.

[0021] (4) The silica nanomaterials are ultrasonically dispersed by a co-solvent and coated with a coupling agent to solve the agglomeration problem and improve the interfacial bonding force with the organic base material. The epoxy activator activates the activity of polyurethane hydroxyl groups and accelerates the cross-linking reaction with the curing agent. The gradient rotation speed promotes the full entanglement of the base material molecular chains, and the gradient curing promotes the complete cross-linking of the organic-inorganic network. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 This is a flowchart of the preparation process of the present invention. Detailed Implementation

[0023] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0024] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0025] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0026] Unless otherwise specified, all raw materials used in this invention are commercially available in the field.

[0027] The coating performance of this application was measured and evaluated using the following methods: Low-temperature curing film-forming properties were assessed according to GB / T1727-1992 "General Preparation Method of Coating Film". The coating condition was observed after curing at 50℃ for 35 seconds: ① Film integrity rate = (area of ​​defect-free coating / total coating area) × 100%; ② Sagging length: The maximum length (mm) of sagging marks at the edge of the coating was measured using vernier calipers.

[0028] Adhesion, cross-cut test (GB / T9286-1998): Draw a 1mm×1mm grid, and after peeling off the tape, calculate the percentage of residual coating area = (residual area / total grid area) × 100%; Pull-off test (GB / T5210-2006): The pull-off adhesion tester is used to test the peel force (MPa) between the coating and the substrate.

[0029] Pencil hardness, test method: GB / T6739-2006, after scratching with a 500g load, measure the maximum depth of the scratch (μm) using a microscope (100x magnification), and record the highest pencil hardness value without scratches.

[0030] Corrosion resistance, test method: GB / T10125-2021, after 72 hours of continuous spraying with 5% NaCl salt spray at 35℃: ① Corrosion area percentage = (corrosion area area / total coating area) × 100%; ② Number of bubbles: count the number of bubbles with a diameter ≥ 0.5 mm in a 10cm × 10cm area.

[0031] VOCs content, test method: GB / T23984-2009, dried at 105℃ to constant weight, combined with Carl Zeiss... Moisture content was determined by the Fischer method, and VOCs content (g / L) was calculated to an accuracy of 0.1 g / L.

[0032] Bending performance, test method: GB / T1731-1993, after bending a Φ2mm shaft, measure the maximum crack length (mm) of the coating with vernier calipers. A crack length ≤0.3mm is acceptable.

[0033] Example 1 This embodiment provides a method for preparing a water-based polyceramic coating material, specifically: 1) Weigh the raw materials according to the following formula: 42 parts modified waterborne polyurethane resin (polyhexyl adipate copolymerized with isophorone diisocyanate and modified with epoxy groups, hydroxyl content 4%), 18 parts waterborne acrylic emulsion, 12 parts nano silica (silica nanomaterials), 9 parts polysilazane (ceramic precursor polymer), 11 parts caprolactam blocked toluene diisocyanate curing agent (blocked isocyanate curing agent), 12 parts deionized water, 4 parts zinc isooctanoate (organic zinc salt accelerator), 2 parts silane coupling agent KH-550, 1.5 parts polyether modified polysiloxane (leveling agent), 1.5 parts organosilicon emulsion (defoamer), 1.5 parts propylene glycol methyl ether (cosolvent), 0.8 parts 2-methylimidazole (epoxy group activator); 2) Prepare according to the following steps: 12 parts of nano-silica were added to 1.5 parts of propylene glycol methyl ether and ultrasonically dispersed at 300W for 20 minutes. Then, 2 parts of silane coupling agent KH-550 were added and stirred at 60℃ for 30 minutes to form coupling agent-coated nanoparticles. 42 parts of modified waterborne polyurethane resin were preheated to 40°C, and 0.8 parts of 2-methylimidazole were added to them. The mixture was stirred for 10 minutes to enhance the reactivity of the hydroxyl groups with the curing agent, thus obtaining the activated modified waterborne polyurethane resin. Add 12 parts of deionized water, pretreated coupling agent-coated nanoparticles, 9 parts of polysilazane, 1.5 parts of polyether-modified polysiloxane, and 1.5 parts of organosilicon emulsion to a dispersion vessel and stir at 550 r / min for 12 minutes to form a stable pre-dispersion.

[0034] Add activated modified waterborne polyurethane resin and 18 parts of waterborne acrylic emulsion to the stable pre-dispersion liquid, increase the speed to 850 r / min, and continue stirring for 25 minutes to promote the full entanglement of the base material molecular chains by using gradient speed. The system was heated to 45°C, and 11 parts of blocked isocyanate curing agent were slowly added dropwise under high-speed shearing conditions of 1550 r / min, while nitrogen gas was introduced for protection. The mixture was dispersed for 35 minutes to form a uniform and stable curing agent emulsion.

[0035] Cool the system to 35°C, add 2 parts of zinc isooctanoate (50% of the total amount), and stir at low speed for 4 minutes; further cool to 30°C, add the remaining 2 parts of zinc isooctanoate, and continue stirring for 12 minutes to avoid localized reactions that may lead to film defects.

[0036] The pH of the system was adjusted to 7.0 using 0.5 mol / L ammonia water. After standing for 5 minutes, the pH was adjusted to 7.8 using the same reagent. Then, a gradient curing process was adopted, first curing at 30℃ for 11 hours, then heating to 35℃ for 7 hours, and finally cooling to 25℃ for 3.5 hours to promote the full cross-linking of the organic-inorganic network and obtain the water-based polyceramic coating material.

[0037] 3) Application of water-based polyceramic coating materials: After the aluminum coil is pretreated by sandblasting to a roughness of Ra=1.0μm, a layer of 5% by mass of silane coupling agent KH-550 diluted solution is sprayed on it, and after drying, a transition bonding layer is formed. The thickness of the dry film of the water-based polyceramic coating material was controlled at 9μm during the first roller coating and pre-cured in a 50℃ oven for 12 seconds. The second roll coating is applied to a total dry film thickness of 18μm. The film is then cured for 35 seconds in a combined infrared oven with a wavelength of 3μm and a hot air oven at 50℃. After cooling to room temperature, the film is formed.

[0038] Example 2 1) Weigh the raw materials according to the following formula: 40 parts modified waterborne polyurethane resin, 15 parts waterborne acrylic emulsion, 10 parts nano silica, 8 parts polysilazane, 10 parts caprolactam-blocked toluene diisocyanate curing agent, 10 parts deionized water, 3 parts zinc octanoate, 2 parts silane coupling agent KH-560, 1 part acrylate copolymer, 1 part polyether-modified organosilicon, 1 part dipropylene glycol methyl ether, 0.5 parts triethanolamine; 2) Prepare according to the following steps: Nano-silica was added to dipropylene glycol methyl ether and ultrasonically dispersed at 300W for 18 minutes. Then KH-560 was added and stirred at 55℃ for 25 minutes to form coupling agent-coated nanoparticles. The modified waterborne polyurethane resin was preheated to 40°C, and triethanolamine was added and stirred for 8 minutes to enhance the reactivity of hydroxyl groups with the curing agent, thus obtaining the activated modified waterborne polyurethane resin. Deionized water, coupling agent-coated nanoparticles, polysiloxane, acrylate copolymer, and polyether-modified organosilicon were added to a dispersion vessel and stirred at 500 r / min for 10 min to form a stable pre-dispersion. Add the activated modified waterborne polyurethane resin and waterborne acrylic emulsion to the stable pre-dispersion liquid, increase the speed to 800 r / min, and continue stirring for 20 min to promote the full entanglement of the base material molecular chains by using the gradient speed. The system was heated to 45°C, and a blocked isocyanate curing agent was slowly added dropwise under high-speed shearing conditions of 1500 r / min, while nitrogen gas was introduced for protection. The mixture was dispersed for 30 min to form a uniform and stable curing agent emulsion. Cool the system to 35°C, add 1.5 parts of zinc octoate (50% of the total amount), and stir at low speed for 3 minutes; further cool to 30°C, add the remaining 1.5 parts of zinc octoate, and continue stirring for 10 minutes to avoid localized reactions that are too fast and cause film defects. The pH of the system was adjusted to 7.0 using 0.5 mol / L ammonia water. After standing for 5 minutes, the pH was adjusted to 7.5 using the same reagent. Then, a gradient curing process was adopted, first curing at 30℃ for 10 hours, then heating to 35℃ for 6 hours, and finally cooling to 25℃ for 3 hours to promote the full cross-linking of the organic-inorganic network and obtain the waterborne polyceramic coating material.

[0039] 3) Application of water-based polyceramic coating materials: After the aluminum coil is pretreated by sandblasting to a roughness of Ra=0.8μm, a layer of 5% by mass of silane coupling agent KH-560 diluted solution is sprayed on it, and after drying, a transition bonding layer is formed. The thickness of the dry film of the water-based polyceramic coating material was controlled at 8μm during the first roller coating and pre-cured in a 45℃ oven for 10s. The second roll coating is applied to a total dry film thickness of 15μm. The film is then cured for 30 seconds in a combined infrared oven with a wavelength of 2μm and a hot air oven at 45℃. After cooling to room temperature, the film is formed.

[0040] Example 3 1) Weigh the raw materials according to the following formula: 45 parts modified waterborne polyurethane resin, 20 parts waterborne acrylic emulsion, 15 parts nano silica, 10 parts polytitanium siloxane, 12 parts and 11 parts caprolactam-blocked toluene diisocyanate curing agent, 15 parts deionized water, 5 parts zinc acetylacetone, 2.5 parts silane coupling agent A-1100, 2 parts polyether modified polysiloxane, 2 parts polyether polyol, 2 parts propylene glycol methyl ether, 1 part triethanolamine; 2) Prepare according to the following steps: Nano-silica was added to propylene glycol methyl ether and ultrasonically dispersed at 300W for 22 minutes. Then, A-1100 was added and stirred at 65℃ for 35 minutes to form coupling agent-coated nanoparticles. The modified waterborne polyurethane resin was preheated to 40°C, and triethanolamine was added and stirred for 12 minutes to enhance the reactivity of hydroxyl groups with the curing agent, thus obtaining the activated modified waterborne polyurethane resin. Deionized water, coupling agent-coated nanoparticles, polytitanium siloxane, polyether-modified polysiloxane, and polyether polyol were added to a dispersion vessel and stirred at 600 r / min for 15 min to form a stable pre-dispersion. Add the activated modified waterborne polyurethane resin and waterborne acrylic emulsion to the stable pre-dispersion liquid, increase the speed to 900 r / min, and continue stirring for 30 min to promote the full entanglement of the base material molecular chains by using the gradient speed. The system was heated to 45°C, and a blocked isocyanate curing agent was slowly added dropwise under high-speed shearing conditions of 1600 r / min, while nitrogen gas was introduced for protection. The mixture was dispersed for 40 min to form a uniform and stable curing agent emulsion. Cool the system to 35°C, add 2.5 parts of zinc acetylacetonate (50% of the total amount), and stir at low speed for 5 minutes; further cool to 30°C, add the remaining 2.5 parts of zinc acetylacetonate, and continue stirring for 15 minutes to avoid localized reactions that are too fast and cause film defects. The pH of the system was adjusted to 7.0 using 0.5 mol / L ammonia water. After standing for 5 minutes, the pH was adjusted to 8.5 using the same reagent. Then, a gradient curing process was adopted, first curing at 30℃ for 12 hours, then heating to 35℃ for 8 hours, and finally cooling to 25℃ for 4 hours to promote the full cross-linking of the organic-inorganic network and obtain the waterborne polyceramic coating material.

[0041] 3) Application of water-based polyceramic coating materials: After the aluminum coil is pretreated by sandblasting to a roughness of Ra=1.2μm, a layer of 5% by mass diluted silane coupling agent A-1100 is sprayed on it and dried to form a transition bonding layer. The thickness of the dry film of the water-based polyceramic coating material was controlled at 10μm during the first roller coating and pre-cured in an oven at 55℃ for 15s. The second roll coating is applied to a total dry film thickness of 20μm. The film is then cured for 40 seconds in a combined infrared oven with a wavelength of 5μm and a hot air oven at 55℃. After cooling to room temperature, the film is formed.

[0042] Example 4 1) Weigh the raw materials according to the following formula: 41 parts modified waterborne polyurethane resin, 17 parts waterborne acrylic emulsion, 13 parts nano silica, 9 parts polysilazane-polysiloxane composite (mass ratio 1:1), 10.5 parts caprolactam-blocked isophorone diisocyanate, 13 parts deionized water, 3.5 parts zinc isooctanoate, 2.2 parts silane coupling agent KH-550, 1.2 parts polyether-modified polysiloxane, 1.8 parts organosilicon emulsion, 1.2 parts propylene glycol methyl ether-dipropylene glycol methyl ether composite (mass ratio 1:1), 0.6 parts 2-methylimidazole; 2) Prepare according to the following steps: Nano-silica was added to a propylene glycol methyl ether-dipropylene glycol methyl ether complex, ultrasonically dispersed at 300W for 20 minutes, then KH-550 was added, and the mixture was stirred at 62℃ for 32 minutes to form coupling agent-coated nanoparticles. The modified waterborne polyurethane resin was preheated to 40°C, and 2-methylimidazole was added and stirred for 9 minutes to enhance the reactivity of the hydroxyl groups with the curing agent, thus obtaining the activated modified waterborne polyurethane resin. Deionized water, coupling agent-coated nanoparticles, polysilazane-polysiloxane complex, polyether-modified polysiloxane, and organosilicon emulsion were added to a dispersion vessel and stirred at 520 r / min for 11 min to form a stable pre-dispersion. Add the activated modified waterborne polyurethane resin and waterborne acrylic emulsion to the stable pre-dispersion liquid, increase the speed to 820 r / min, and continue stirring for 22 min to promote the full entanglement of the base material molecular chains by using the gradient speed. The system was heated to 45°C, and a blocked isocyanate curing agent was slowly added dropwise under high-speed shearing conditions of 1520 r / min, while nitrogen gas was introduced for protection. The mixture was dispersed for 32 min to form a uniform and stable curing agent emulsion. Cool the system to 35°C, add 1.75 parts of zinc isooctanoate (50% of the total amount), and stir at low speed for 3.5 minutes; further cool to 30°C, add the remaining 1.75 parts of zinc isooctanoate, and continue stirring for 11 minutes to avoid localized reactions that are too fast and cause film defects. The pH of the system was adjusted to 7.0 using 0.5 mol / L ammonia water. After standing for 5 minutes, the pH was adjusted to 7.6 using the same reagent. Then, a gradient curing process was adopted, first curing at 30℃ for 10.5 h, then heating to 35℃ for 6.5 h, and finally cooling to 25℃ for 3.2 h to promote the full cross-linking of the organic-inorganic network and obtain the water-based polyceramic coating material.

[0043] 3) Application of water-based polyceramic coating materials: After the aluminum coil is pretreated by sandblasting to a roughness of Ra=0.9μm, a layer of 5% by mass of silane coupling agent KH-550 diluted solution is sprayed on it, and after drying, a transition bonding layer is formed. The thickness of the dry film of the water-based polyceramic coating material was controlled at 8.5 μm during the first roller coating and pre-cured in a 48℃ oven for 11 seconds. The second roll coating is applied to a total dry film thickness of 16μm. The film is then cured for 32 seconds in a combined infrared oven with a wavelength of 3.5μm and a hot air temperature of 48℃. After cooling to room temperature, the film is formed.

[0044] Example 5 1) Weigh the raw materials according to the following formula: 44 parts modified waterborne polyurethane resin, 19 parts waterborne acrylic emulsion, 14 parts nano silica, 9.5 parts polysilazane-polytitanium siloxane compound (mass ratio 2:1), 11.5 parts caprolactam-blocked isophorone diisocyanate, 14 parts deionized water, 4.5 parts zinc octanoate, 2.3 parts silane coupling agent KH-560, 1.8 parts acrylate copolymer, 1.2 parts polyether-modified organosilicon, 1.8 parts dipropylene glycol methyl ether, 0.9 parts triethanolamine; 2) Prepare according to the following steps: Nano-silica was added to dipropylene glycol methyl ether and ultrasonically dispersed at 300W for 21 min. Then KH-560 was added and stirred at 58℃ for 28 min to form coupling agent-coated nanoparticles. The modified waterborne polyurethane resin was preheated to 40°C, and triethanolamine was added and stirred for 11 minutes to enhance the reactivity of the hydroxyl groups with the curing agent, thus obtaining the activated modified waterborne polyurethane resin. Deionized water, coupling agent-coated nanoparticles, polysilazane-polytitanium siloxane complex, acrylate copolymer, and polyether-modified organosilicon were added to a dispersion vessel and stirred at 580 r / min for 14 min to form a stable pre-dispersion. Add the activated modified waterborne polyurethane resin and waterborne acrylic emulsion to the stable pre-dispersion liquid, increase the speed to 880 r / min, and continue stirring for 28 min to promote the full entanglement of the base material molecular chains by using gradient speed. The system was heated to 45°C, and a blocked isocyanate curing agent was slowly added dropwise under high-speed shearing conditions of 1580 r / min, while nitrogen gas was introduced for protection. The mixture was dispersed for 38 min to form a uniform and stable curing agent emulsion. Cool the system to 35°C, add 2.25 parts of zinc octoate (50% of the total amount), and stir at low speed for 4.5 minutes; further cool to 30°C, add the remaining 2.25 parts of zinc octoate, and continue stirring for 14 minutes to avoid localized reactions that may lead to film formation defects. The pH of the system was adjusted to 7.0 using 0.5 mol / L ammonia water. After standing for 5 minutes, the pH was adjusted to 8.2 using the same reagent. Then, a gradient curing process was adopted, first curing at 30℃ for 10.5 h, then heating to 35℃ for 7.5 h, and finally cooling to 25℃ for 3.8 h to promote the full cross-linking of the organic-inorganic network and obtain the water-based polyceramic coating material.

[0045] 3) Application of water-based polyceramic coating materials: After the aluminum coil is pretreated by sandblasting to a roughness of Ra=1.1μm, a layer of 5% by mass of silane coupling agent KH-560 diluted solution is sprayed on it, and after drying, a transition bonding layer is formed. The thickness of the first dry film of the water-based polyceramic coating material was controlled at 9.5 μm, and it was pre-cured in an oven at 52℃ for 14 seconds. The second roll coating is applied to a total dry film thickness of 19μm. The film is then cured for 38 seconds in a combined infrared oven with a wavelength of 4.5μm and a hot air temperature of 52℃. After cooling to room temperature, the film is formed.

[0046] The performance of the waterborne polyceramic coatings prepared in Examples 1 to 5 was tested, and the results are shown in Table 1.

[0047] Table 1

[0048] As can be seen from Table 1, the water-based polyceramic coating material prepared by this invention can achieve rapid curing at a low temperature of around 50℃, with a film integrity rate of ≥99.2%, adhesion of ≥99.5MPa, scratch depth of ≤2.8μm, salt spray corrosion resistant area ratio of ≤0.12%, VOCs content of ≤29.5g / L, and bending crack length of ≤0.2mm. It has excellent comprehensive performance and fully meets the application needs of the aluminum coil industry.

[0049] Comparative Example 1 The difference between this comparative example and Example 1 is that the aqueous acrylic emulsion in the system is omitted, while the other raw material formulations, preparation, and application processes are the same as in Example 1, resulting in the aqueous polyceramic coating of this comparative example.

[0050] Comparative Example 2 The difference between this comparative example and Example 1 is that the blocked isocyanate curing agent in the system is omitted, while the other raw material formulations, preparation and application processes are the same as in Example 1, resulting in the waterborne polyceramic coating of this comparative example.

[0051] Comparative Example 3 The difference between this comparative example and Example 1 is that zinc isooctanoate in the system is omitted, while the other raw material formulations, preparation and application processes are the same as in Example 1, resulting in the waterborne polyceramic coating of this comparative example.

[0052] Comparative Example 4 The difference between this comparative example and Example 1 is that the nano-silica in the system is omitted, while the other raw material formulations, preparation and application processes are the same as in Example 1, resulting in the water-based polyceramic coating of this comparative example.

[0053] Comparative Example 5 The difference between this comparative example and Example 1 is that the polysilazane in the system is omitted, while the other raw material formulations, preparation and application processes are the same as in Example 1, resulting in the waterborne polyceramic coating of this comparative example.

[0054] The performance of the waterborne polyceramic coatings prepared in Comparative Examples 1 to 5 was tested and compared with that in Example 1. The results are shown in Table 2.

[0055] Table 2

[0056] As shown in Table 2, the performance of the coatings obtained by omitting key components in Comparative Examples 1-5 significantly decreased. In this invention, the modified waterborne polyurethane resin provides an elastic film-forming skeleton, while the waterborne acrylic emulsion enhances the coating's rigidity and weather resistance. Both components work synergistically to construct a film-forming structure that combines rigidity and flexibility; neither can be omitted. Omitting these components reduces the coating's density and significantly deteriorates its mechanical and corrosion-resistant properties, demonstrating that the composite matrix system is fundamental to achieving high performance. A blocked isocyanate curing agent and an organozinc salt accelerator constitute a synergistic curing system. Without the blocked isocyanate curing agent, the film integrity rate is only 65.8%, the adhesion is 32.4 MPa, and the coating is almost impossible to form. Without the organozinc salt accelerator, the film integrity rate is 78.5%, the adhesion is 68.3 MPa, and the salt spray corrosion resistant area accounts for 18.5%. In this invention, the organozinc salt accelerator works synergistically with the blocked isocyanate curing agent to reduce the unsealing temperature to 45~50℃ and increase the crosslinking reaction rate by more than 3 times, thus solving the contradiction of low-temperature curing efficiency and high-temperature curing environmental unfriendliness of existing water-based coatings.

[0057] Silica nanomaterials and ceramic precursor polymers synergistically form a Si-N ceramic structure and nano-reinforcing phase, which in turn constructs an interpenetrating network with organic matrix materials, thereby simultaneously improving the coating's hardness and corrosion resistance, breaking through the limitation of traditional water-based coatings where rigidity and toughness cannot be achieved simultaneously.

[0058] Comparative Example 6 The difference between this comparative example and Example 1 is that nano-silica was directly added to the pre-dispersion liquid without undergoing ultrasonic dispersion with a co-solvent or coating with a coupling agent. The other raw material formulations, preparation, and application processes were the same as in Example 1, resulting in the water-based polyceramic coating of this comparative example.

[0059] Comparative Example 7 The difference between this comparative example and Example 1 is that gradient speed activation is omitted, and all stirring steps use a single speed of 550 r / min. The other raw material formulations, preparation, and application processes are the same as in Example 1, resulting in the water-based polyceramic coating of this comparative example.

[0060] Comparative Example 8 The difference between this comparative example and Example 1 is that gradient curing is omitted, and single-temperature curing is used. The curing process is changed to constant temperature curing at 30°C for 21.5 hours. The other raw material formulations, preparation and application processes are the same as in Example 1, and the water-based polyceramic coating of this comparative example is obtained.

[0061] The performance of the waterborne polyceramic coatings prepared in Comparative Examples 6 to 8 was tested and compared with that in Example 1. The results are shown in Table 3.

[0062] Table 3

[0063] As can be seen from Table 3, the performance of the coatings obtained after adjusting the key processes in Comparative Examples 6 to 8 deteriorated significantly. After omitting the pretreatment of silicon nanomaterial coating, the nanoparticles agglomerated, resulting in a decrease in interfacial bonding force. After omitting the gradient speed activation, the molecular chains of the base material were not fully entangled, and the uniformity of the coating deteriorated. After omitting the gradient curing, the organic-inorganic network crosslinking was incomplete, and the mechanical properties and corrosion resistance were reduced. This proves that the key process steps of the present invention are the core of ensuring the performance of the coating.

[0064] In summary, this invention uses a modified waterborne polyurethane resin and a waterborne acrylic emulsion to form a composite film-forming base. Both are waterborne systems with good compatibility, enabling the construction of a continuous and dense film-forming foundation. This reduces dependence on volatile organic solvents, and the viscosity of the system is lowered by adding a small amount of co-solvent, while avoiding excessive solvent evaporation. Through the synergistic effect of the proportions and compatibility of the base material and co-solvent, VOC emissions are controlled to ≤30g / L.

[0065] This invention utilizes a synergistic curing system formed by a blocked isocyanate curing agent and an organozinc salt accelerator. The blocked isocyanate curing agent uses caprolactam to block TDI, reducing the unblocking temperature to 45-50°C. The zinc salt lowers the activation energy of the crosslinking reaction through coordination, accelerating the reaction rate between the isocyanate groups and the hydroxyl groups in the base material after unblocking. The synergistic effect of these two components allows the coating to rapidly complete crosslinking and curing under low-temperature conditions. This invention forms an organic-inorganic synergistic network by adding silicon nanomaterials, ceramic precursor polymers, and organic matrix materials. The high specific surface area of ​​silicon nanomaterials can enhance the interfacial bonding with the matrix materials and provide rigid support. After the ceramic precursor polymers are cured, they form a Si-N ceramic structure, which forms an inorganic reinforcing phase with the silicon nanomaterials. The organic matrix materials provide an elastic film-forming framework. The three work together to improve the mechanical properties of the material.

[0066] The silica nanomaterials are ultrasonically dispersed with a co-solvent and coated with a coupling agent to solve the agglomeration problem and improve the interfacial bonding with the organic matrix. The epoxy activator activates the activity of polyurethane hydroxyl groups and accelerates the cross-linking reaction with the curing agent. Gradient rotation speed promotes the full entanglement of the matrix molecular chains, and gradient curing promotes the complete cross-linking of the organic-inorganic network.

[0067] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a water-based polyceramic coating material, characterized in that: Based on the mass fraction of the raw materials for the water-based polyceramic coating material, it includes, 40-45 parts modified waterborne polyurethane resin, 15-20 parts waterborne acrylic emulsion, 10-15 parts silica nanomaterials, 8-10 parts ceramic precursor polymer, 10-12 parts blocked isocyanate curing agent, 10-15 parts deionized water, 3-5 parts organozinc salt accelerator, 2-2.5 parts silane coupling agent, 1-2 parts leveling agent, 1-2 parts defoamer, 1-2 parts cosolvent, and 0.5-1 part epoxy group activator; Silica nanomaterials were dispersed in a cosolvent and coated with a silane coupling agent to obtain coupling agent-coated nanoparticles. Modified waterborne polyurethane resin was activated with an epoxy activator to obtain activated modified waterborne polyurethane resin. The coupling agent-coated nanoparticles, the activated modified waterborne polyurethane resin, and the remaining components of the waterborne polyceramic coating material raw material were mixed by gradient speed stirring to obtain a mixed system, wherein the organic zinc salt accelerator was added in batches. After the pH of the mixed system is adjusted to a uniform and stable level, a gradient aging process is used to obtain the water-based polyceramic coating material.

2. The method for preparing the water-based polyceramic coating material as described in claim 1, characterized in that: The modified waterborne polyurethane resin is obtained by copolymerizing polyhexamethylene adipate and isophorone diisocyanate and then introducing epoxy groups for modification, with a hydroxyl content of 3%~5%; The silicon nanomaterial is nano-silica; The ceramic precursor polymer includes one or more of polysilazane, polysiloxane, and polytitanium siloxane; The blocked isocyanate curing agent includes one or both of caprolactam-blocked toluene diisocyanate curing agent and caprolactam-blocked isophorone diisocyanate curing agent. The organic zinc salt accelerators include zinc octanoate, zinc isooctanoate, or zinc acetylacetonate; The silane coupling agent includes one of KH-550, KH-560, and A-1100; The leveling agent includes polyether-modified polysiloxane and acrylate copolymer; the defoamer includes silicone emulsion, polyether-modified silicone, and polyether polyol; the cosolvent includes propylene glycol methyl ether and dipropylene glycol methyl ether; and the epoxy activator includes 2-methylimidazole and triethanolamine.

3. The method for preparing the water-based polyceramic coating material as described in claim 1, characterized in that: The method for treating the silicon nanomaterials by dispersing with a cosolvent and coating with a silane coupling agent is as follows: the silicon nanomaterials are added to a cosolvent, ultrasonically dispersed, and then a silane coupling agent is added. The mixture is stirred at a constant temperature to form coupling agent-coated nanoparticles, thereby enhancing the compatibility between the silicon nanomaterials and the organic matrix.

4. The method for preparing the water-based polyceramic coating material as described in claim 3, characterized in that: The activation method of the modified waterborne polyurethane resin by the epoxy group activator is as follows: the modified waterborne polyurethane resin is preheated to 40°C and then the epoxy group activator is added to it. The mixture is stirred to enhance the reaction activity between the hydroxyl groups and the curing agent, thereby obtaining the activated modified waterborne polyurethane resin.

5. The method for preparing the water-based polyceramic coating material as described in claim 1, characterized in that: The mixture obtained by gradient speed stirring includes, Deionized water, coupling agent-coated nanoparticles, ceramic precursor polymer, leveling agent, and defoamer are stirred at 500-600 r / min for 10-15 minutes to form a stable pre-dispersion. Add activated modified waterborne polyurethane resin and waterborne acrylic emulsion to the stable pre-dispersion liquid, increase the speed to 800~900 r / min and continue stirring and mixing, and heat the system to 45℃. Under high-speed shear conditions of 1500~1600 r / min, add blocked isocyanate curing agent dropwise, and at the same time, introduce nitrogen gas for protection to disperse and form a uniform and stable curing agent emulsion. Cool the system to 35°C, add 50% of the organic zinc salt accelerator, stir at low speed for 3-5 minutes, cool further to 30°C, add the remaining organic zinc salt accelerator, and continue stirring for 10-15 minutes to obtain a mixed system.

6. The method for preparing the water-based polyceramic coating material as described in claim 1, characterized in that: Adjusting the pH of the mixed system to a uniform and stable acid-base balance includes first adjusting the pH of the system to 7.0 using an acid-base regulator, letting it stand for 5 minutes, and then adjusting the pH of the system to 7.5-8.5 using the same reagent.

7. The method for preparing the water-based polyceramic coating material as described in claim 1, characterized in that: The gradient maturation process involves first maturing the system, after its pH has been adjusted to be uniform and stable by an acid-base regulator, at 30°C for 10-12 hours, then raising the temperature to 35°C for 6-8 hours, and finally lowering the temperature to 25°C for 3-4 hours.

8. A water-based polyceramic coating material, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the water-based polyceramic coating material as described in claim 7, characterized in that: The water-based polyceramic coating material is applied to the surface of the pretreated aluminum coil using a dual-coat roller coating process. The thickness of the dry film in the first roller coating is controlled at 8~10μm, and it is pre-cured in an oven at 45~55℃ for 10~15s; The second roll coating is applied until the total dry film thickness is 15~20μm. It is then cured for 30~40s in an infrared and hot air combined oven. Infrared radiation is used to accelerate the cross-linking reaction and shorten the curing time. The infrared wavelength is 2~5μm and the hot air temperature is 45~55℃.

10. The application of the water-based polyceramic coating material as described in claim 9, characterized in that: The pretreatment of the aluminum coil surface involves sandblasting the surface, then spraying a layer of 5% silane coupling agent dilution, followed by drying to form a transition bonding layer, thereby improving the coating adhesion.

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