A coating for aluminum profiles and its preparation method

Abstract

This invention discloses an aluminum profile coating and its preparation method, belonging to the field of coating technology. The invention utilizes the strong chemical bonding of epoxy groups on the aluminum substrate through the compounding of PVDF fluorocarbon resin and epoxy-modified acrylic resin in the primer, significantly improving coating adhesion. Simultaneously, the active groups in the primer form interlayer chemical bonds or cross-linked structures with the topcoat. Furthermore, the PVDF fluorocarbon resin and hydroxyl acrylic resin in the topcoat cross-link to form a dense three-dimensional network, which overlaps with the primer's cross-linked network and effectively fills microscopic voids through interlayer chemical bonding, greatly enhancing the coating's barrier ability against water, oxygen, and corrosive ions, thus endowing the coating with excellent corrosion resistance. In addition, this invention recycles the overspray generated during the spraying process as a recovered paint mist component for reuse in the primer and topcoat, exhibiting excellent compatibility and participating in film-forming cross-linking. This achieves waste utilization while ensuring the overall performance of the coating, combining outstanding environmental benefits with cost advantages.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and more specifically, to an aluminum profile coating and its preparation method. Background Technology

[0002] Fluorocarbon coatings, due to the extremely high bond energy of the CF bonds in fluorocarbon resins (485.6 kJ / mol), far exceeding the energy of ultraviolet light (411 kJ / mol), possess excellent weather resistance, chemical corrosion resistance, and self-cleaning properties. They are widely used for surface protection and decoration of outdoor decorative materials such as aluminum profile building curtain walls, doors, and windows. With the construction industry's increasingly stringent requirements for the quality of aluminum profile decorative surfaces, the adhesion, cross-linking density, corrosion resistance, and weather resistance of fluorocarbon coatings have become key indicators for evaluating their performance.

[0003] Currently, aluminum profile coatings typically employ a primer and topcoat system. The primer enhances adhesion and provides corrosion protection, while the topcoat offers decorative appeal and weather resistance. For example, Chinese patent CN120648302A discloses a modified FEVE fluorocarbon resin coating and its preparation method. This method modifies FEVE fluorocarbon resin with linoleic acid and introduces nanocomposite particles (modified nano-titanium dioxide and graphene oxide) to improve the coating's stain resistance, weather resistance, and corrosion resistance. While this technical solution improves the durability of fluorocarbon resin coatings to some extent, it primarily targets a single-layer coating system and does not address the coordinated design of primer and topcoat. Furthermore, it lacks a systematic consideration of optimizing the interfacial bonding between the primer and topcoat, leaving room for improvement in the overall density of the coating. Another example is Chinese patent CN106905784A, which provides a high-crosslinking-density fluorocarbon resin coating. This coating introduces reactive nanofiller particles as chemical crosslinking points, increasing the crosslinking density and reducing porosity, thus providing better protection against solvent corrosion. However, this technical solution also focuses on improving the crosslinking density of a single coating, without addressing the synergistic design of interlayer chemical crosslinking in the primer and topcoat composite coating system.

[0004] In addition, existing technologies do not address the recycling and reuse of overspray paint mist generated during the fluorocarbon coating process of aluminum profiles. The waste of paint mist during the fluorocarbon coating process restricts the utilization rate of coatings and the control of production costs.

[0005] During the fluorocarbon coating process on aluminum profiles, due to the characteristics of liquid coating, over 40% of the paint forms overspray mist. Water curtain spray booths, as the core environmental protection equipment in the fluorocarbon coating line for aluminum profiles, capture the paint mist in the air through a flowing water curtain. However, the captured paint mist usually becomes hazardous waste in the form of paint sludge or paint residue, causing not only a serious waste of paint resources but also additional environmental treatment costs. Although some literature reports on fluorocarbon paint recycling systems, such as CN115889047A which discloses an online fluorocarbon paint recycling system and method, using a filter assembly to adsorb floating fluorocarbon paint particles and using an immersion assembly to dissolve and recover them; and CN103254702A which discloses a PVDF fluorocarbon paint waste residue recycling process, utilizing the differences in solubility of different solvents to separate PVDF resin, acrylic resin, and pigments. However, existing technologies mainly focus on the recycling process itself, and have not yet provided effective solutions for how to reuse the recycled paint mist components in the formulation design of high-performance fluorocarbon coatings, especially how to use the recycled paint mist components in the primer and topcoat in a targeted manner and ensure that the coating performance is not degraded.

[0006] To address the shortcomings of the existing technologies, this invention provides an aluminum profile coating and its preparation method. Through the synergistic formulation design of primer and topcoat, combined with the rational reuse of recycled paint mist components, the technical effects of excellent adhesion between primer and topcoat, higher density after cross-linking, and significantly improved corrosion resistance and weather resistance are achieved. Summary of the Invention

[0007] In view of this, and in order to solve one of the above-mentioned technical problems in the prior art, the present invention provides an aluminum profile coating and its preparation method, the specific technical solution of which is as follows: An aluminum profile coating, wherein the aluminum profile coating is formed by a primer and a topcoat; wherein, The primer comprises the following raw materials in parts by weight: 30-40 parts PVDF fluorocarbon resin, 15-20 parts epoxy modified acrylic resin, 10-20 parts recycled paint mist component, 7-10 parts rust inhibitor, 9-15 parts modified filler, 0.1-3 parts dispersant, 0.3-2 parts leveling agent, 0.2-1 part defoamer, 3-8 parts curing agent, and 20-30 parts solvent; The topcoat comprises the following raw materials in parts by weight: 40-50 parts PVDF fluorocarbon resin, 10-20 parts hydroxyl acrylic resin, 10-20 parts recycled paint mist component, 10-15 parts titanium dioxide, 5-10 parts modified nano silica, 0.1-3 parts dispersant, 0.3-2 parts leveling agent, 1-5 parts ultraviolet absorber, 1-2 parts hindered amine light stabilizer, 0.1-1 part crosslinking agent, 0.2-1 part defoamer, 5-10 parts curing agent, and 25-40 parts solvent.

[0008] Furthermore, the recovered paint mist component is the overspray paint mist product captured and recovered by the water curtain spray booth during the fluorocarbon coating process of aluminum profiles. The overspray paint mist product includes the following components in weight percentage: 40-55% PVDF fluorocarbon resin, 15-25% acrylic resin, 15-30% filler, and 5-10% additives.

[0009] Furthermore, the rust inhibitor in the primer is at least one of zinc phosphate, aluminum tripolyphosphate, and strontium chromate.

[0010] Furthermore, the modified filler in the primer is a filler surface-modified with a silane coupling agent, and the filler is at least one of talc, barium sulfate, and mica powder.

[0011] Furthermore, the modified nano-silica is nano-silica with a particle size of 10~50nm, which has been surface-modified by a silane coupling agent.

[0012] Furthermore, the curing agent in the primer is at least one of a blocked polyisocyanate and an amino resin.

[0013] Furthermore, the curing agent in the topcoat is at least one of hexamethylene diisocyanate trimer and isophorone diisocyanate trimer.

[0014] Further, the solvent is at least one of xylene, butyl acetate, cyclohexanone, and ethylene glycol ethyl ether acetate.

[0015] Furthermore, the dry film thickness of the primer coating is 15~30μm, and the dry film thickness of the topcoat coating is 20~35μm.

[0016] In addition, the present invention also provides a method for preparing an aluminum profile coating, the method comprising the following steps: S1. Add PVDF fluorocarbon resin, epoxy modified acrylic resin, recycled paint mist components, rust inhibitor, modified filler, dispersant, leveling agent, defoamer and solvent to a dispersion kettle, disperse at high speed for 30~60min, then transfer to a sand mill to grind to fineness ≤30μm, then add curing agent, stir at 100~300r / min for 30~60min, filter and discharge to obtain primer; S2. Add PVDF fluorocarbon resin, hydroxyl acrylic resin, recycled paint mist components, titanium dioxide, modified nano silica, dispersant, leveling agent, ultraviolet absorber, hindered amine light stabilizer, crosslinking agent, defoamer, and solvent to a dispersion vessel and disperse at high speed for 30-90 min. Then transfer to a sand mill and grind to a fineness ≤25μm. Add curing agent and stir at 100-300 r / min for 30-60 min. Filter the material to obtain the topcoat. S3. Perform surface treatment on the aluminum profile substrate, spray the primer, and bake at 80~120℃ for 5~15 minutes after spraying; after the temperature drops to 50~60℃, continue to spray the topcoat, and bake at 150~220℃ for 10~30 minutes after spraying to form an aluminum profile coating.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. In the primer of this invention, PVDF fluorocarbon resin and epoxy-modified acrylic resin are compounded. The epoxy groups contained in the epoxy-modified acrylic resin have excellent chemical bonding effects on the aluminum profile substrate, which can significantly improve the adhesion between the primer and the metal substrate. At the same time, the components in the primer can undergo chemical bonding reactions with the crosslinking agent (aziridine or polycarbodiimide) and polyisocyanate curing agent in the topcoat to form interlayer chemical crosslinks, which significantly improves the adhesion and density of the coating.

[0018] 2. The passivation effect of the rust inhibitor in the primer of this invention, the physical barrier of the high-density cross-linked network, and the shielding effect enhanced by the modified filler work synergistically to give the coating not only excellent corrosion resistance, but also excellent aging resistance due to the synergistic effect of the primer and topcoat as the main components, combined with the UV absorber and hindered amine light stabilizer in the topcoat.

[0019] 3. In the topcoat of the present invention, PVDF fluorocarbon resin and hydroxyl acrylic resin are compounded and combined with the topcoat components to form a dense three-dimensional network structure through cross-linking. The primer can also form a dense cross-linked network structure. The superposition of the two cross-linked networks and the interlayer chemical bonding effectively fill the microscopic gaps inside the coating, achieving a synergistic effect. The increased density can effectively block the penetration of water molecules, oxygen molecules and corrosion-resistant ions, providing an excellent protective barrier for aluminum profile substrates.

[0020] 4. The present invention adds recycled paint mist components to both the primer and the topcoat, which has excellent compatibility and film-forming properties, helps to improve the adhesion and density of the coating, and the optimized process parameters can effectively reduce coating defects and further ensure the cross-linking density of the coating.

[0021] 5. In this invention, the overspray paint mist captured in the water curtain spray booth during the fluorocarbon coating application process on aluminum profiles is separated and purified, then recycled as a paint mist component for use in primer and topcoat formulations. After appropriate reinforcement, the components can directly participate in the film-forming and cross-linking reactions of the coating. This not only transforms paint sludge into usable raw materials, significantly reducing the generation of hazardous waste and environmental disposal costs, but also lowers the consumption of expensive raw materials such as PVDF fluorocarbon resin, significantly saving coating production costs. Furthermore, the pigments, fillers, and additives already contained in the recycled paint mist component have good compatibility and synergistic effects with fresh resin, enabling high-value recycling of waste while ensuring that the overall performance of the coating is not reduced. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to its embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of protection of the invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0024] An aluminum profile coating according to one embodiment of the present invention is formed by a primer and a topcoat; wherein, The primer comprises the following raw materials in parts by weight: 30-40 parts PVDF fluorocarbon resin, 15-20 parts epoxy modified acrylic resin, 10-20 parts recycled paint mist component, 7-10 parts rust inhibitor, 9-15 parts modified filler, 0.1-3 parts dispersant, 0.3-2 parts leveling agent, 0.2-1 part defoamer, 3-8 parts curing agent, and 20-30 parts solvent; The topcoat comprises the following raw materials in parts by weight: 40-50 parts PVDF fluorocarbon resin, 10-20 parts hydroxyl acrylic resin, 10-20 parts recycled paint mist component, 10-15 parts titanium dioxide, 5-10 parts modified nano silica, 0.1-3 parts dispersant, 0.3-2 parts leveling agent, 1-5 parts ultraviolet absorber, 1-2 parts hindered amine light stabilizer, 0.1-1 part crosslinking agent, 0.2-1 part defoamer, 5-10 parts curing agent, and 25-40 parts solvent.

[0025] In one embodiment, the recovered paint mist component is an overspray paint mist product captured and recovered by a water curtain spray booth during the fluorocarbon coating process of aluminum profiles. The overspray paint mist product includes the following components by mass percentage: 40-55% PVDF fluorocarbon resin, 15-25% acrylic resin, 15-30% filler, and 5-10% additives.

[0026] In one embodiment, the overspray paint mist product comprises the following components by weight percentage: 52% PVDF fluorocarbon resin, 21% acrylic resin, 18% boron nitride, and 9% perfluorooctyltriethoxysilane.

[0027] In one embodiment, the rust inhibitor in the primer is at least one of zinc phosphate, aluminum tripolyphosphate, and strontium chromate.

[0028] In one embodiment, the modified filler in the primer is a filler surface-modified with a silane coupling agent, and the filler is at least one of talc, barium sulfate, and mica powder.

[0029] In one embodiment, the modified nano-silica is nano-silica with a particle size of 10-50 nm that has been surface-modified with a silane coupling agent.

[0030] In one embodiment, the silane coupling agent is at least one selected from tetraethoxysilane, methyltrimethoxysilane, and 3-glycidoxypropyltrimethoxysilane.

[0031] In one embodiment, the ultraviolet absorber is at least one of UV-12, UV-71, and UV-326.

[0032] In one embodiment, the hindered amine light stabilizer is at least one of light stabilizer 2020 and light stabilizer 944.

[0033] In one embodiment, the crosslinking agent is at least one of aziridine and polycarbodiimide.

[0034] In one embodiment, the dispersant is sodium polyacrylate.

[0035] In one embodiment, the leveling agent is at least one of a silicone leveling agent and a polyacrylate leveling agent.

[0036] In one embodiment, the defoamer is a polyether-modified silicone defoamer.

[0037] In one embodiment, the curing agent in the primer is at least one of a blocked polyisocyanate and an amino resin.

[0038] In one embodiment, the curing agent in the topcoat is at least one of hexamethylene diisocyanate trimer and isophorone diisocyanate trimer.

[0039] In one embodiment, the solvent is at least one of xylene, butyl acetate, cyclohexanone, and ethylene glycol ethyl ether acetate.

[0040] In one embodiment, the dry film thickness of the primer coating is 15~30μm, and the dry film thickness of the topcoat coating is 20~35μm.

[0041] In addition, the present invention also provides a method for preparing an aluminum profile coating, the method comprising the following steps: S1. Add PVDF fluorocarbon resin, epoxy modified acrylic resin, recycled paint mist components, rust inhibitor, modified filler, dispersant, leveling agent, defoamer and solvent to a dispersion kettle, disperse at high speed for 30~60min, then transfer to a sand mill to grind to fineness ≤30μm, then add curing agent, stir at 100~300r / min for 30~60min, filter and discharge to obtain primer; S2. Add PVDF fluorocarbon resin, hydroxyl acrylic resin, recycled paint mist components, titanium dioxide, modified nano silica, dispersant, leveling agent, ultraviolet absorber, hindered amine light stabilizer, crosslinking agent, defoamer, and solvent to a dispersion vessel and disperse at high speed for 30-90 min. Then transfer to a sand mill and grind to a fineness ≤25μm. Add curing agent and stir at 100-300 r / min for 30-60 min. Filter the material to obtain the topcoat. S3. Perform surface treatment on the aluminum profile substrate, spray the primer, and bake at 80~120℃ for 5~15 minutes after spraying; after the temperature drops to 50~60℃, continue to spray the topcoat, and bake at 150~220℃ for 10~30 minutes after spraying to form an aluminum profile coating.

[0042] In one embodiment, in step S3, after spraying the primer, the temperature is increased to 80-120°C at a heating rate of 5-10°C / min and baked for 5-15 minutes; after the temperature drops to 50-60°C, the topcoat is sprayed, and after spraying the topcoat, the temperature is increased to 150-220°C at a heating rate of 5-10°C / min and baked for 10-30 minutes to form an aluminum profile coating. In this invention, controlling the baking temperature of 80-120°C during the primer stage allows the blocked polyisocyanate curing agent to fully unblock and crosslink, while avoiding excessive curing of the primer due to excessive temperature, which would affect the interlayer chemical bonding activity. Then, cooling to 50-60°C before spraying the topcoat avoids excessively rapid solvent flash evaporation caused by high-temperature spraying, which could lead to defects such as orange peel and pinholes in the paint film. A slow heating rate of 5-10°C / min facilitates orderly solvent evaporation and a stable crosslinking reaction, preventing stress concentration and microcracks within the coating caused by rapid heating. A baking temperature of 150-220°C ensures a complete crosslinking reaction between the polyisocyanate curing agent and the hydroxyl acrylic resin, while also allowing the residual active groups in the primer to undergo interlayer crosslinking with the topcoat crosslinking agent. This ultimately ensures the crosslinking density of the coating, reduces coating defects, and thus helps improve the coating's corrosion resistance.

[0043] The above-mentioned scheme optimizes the composition of the primer and topcoat, utilizes epoxy-modified acrylic resin and blocked polyisocyanate, hydroxyl acrylic resin and polyisocyanate curing agent to construct a double cross-linking network within and between layers, combined with silane coupling agent-modified filler and nano-silica to synergistically enhance the coating density, and the passivation effect of rust-preventive components, resulting in a composite coating with excellent adhesion, salt spray resistance, and weather resistance. Simultaneously, the overspray paint mist captured in the water curtain spray booth is separated, purified, and recycled as a component for use in the primer and topcoat, achieving high-value resource utilization of paint mist waste and reducing raw material costs. Finally, a step-by-step temperature curing process effectively reduces coating defects and ensures complete cross-linking reaction. Overall, it significantly improves the comprehensive performance of the coating while also providing outstanding environmental and economic benefits, showing promising prospects for industrial application.

[0044] The implementation schemes of the present invention will now be described in detail with reference to specific embodiments.

[0045] Example 1: A method for preparing a coating on aluminum profiles, the method comprising the following steps: S1. By weight, 32 parts of PVDF fluorocarbon resin, 18 parts of epoxy modified acrylic resin, 15 parts of recycled paint mist component, 8 parts of zinc phosphate, 10 parts of tetraethoxysilane modified talc, 0.5 parts of sodium polyacrylate, 0.3 parts of silicone leveling agent, 0.3 parts of polyether modified silicone defoamer, and 30 parts of butyl acetate are added to a dispersion kettle and dispersed at high speed for 35 min. Then, the mixture is transferred to a sand mill and ground until the fineness is ≤30 μm. Next, 5 parts of blocked polyisocyanate are added and stirred at 300 r / min for 50 min. The mixture is then filtered to obtain the primer. The recovered paint mist component is the overspray paint mist product captured and recovered by the water curtain spray booth during the fluorocarbon coating process of aluminum profiles. The overspray paint mist product includes the following components by mass percentage: 52% PVDF fluorocarbon resin, 21% acrylic resin, 18% boron nitride, and 9% perfluorooctyltriethoxysilane. S2. By weight, 43 parts of PVDF fluorocarbon resin, 17 parts of hydroxyl acrylic resin, 10 parts of recycled paint mist component, 10 parts of titanium dioxide, 7 parts of modified nano silica, 0.5 parts of sodium polyacrylate, 0.3 parts of organosilicon leveling agent, 1 part of UV-12, 1 part of light stabilizer 2020, 0.6 parts of aziridine, 0.3 parts of polyether modified organosilicon defoamer, and 40 parts of butyl acetate are added to a dispersion vessel and dispersed at high speed for 40 minutes. Then, the mixture is transferred to a sand mill and ground until the fineness is ≤25μm. Next, 8 parts of hexamethylene diisocyanate trimer are added and stirred at 300r / min for 60 minutes. The mixture is then filtered to obtain the topcoat. The modified nano-silica is nano-silica with a particle size of 45 nm, which has been surface-modified with methyltrimethoxysilane. The recovered paint mist component is the overspray paint mist product captured and recovered by the water curtain spray booth during the fluorocarbon coating process of aluminum profiles. The overspray paint mist product includes the following components by mass percentage: 52% PVDF fluorocarbon resin, 21% acrylic resin, 18% boron nitride, and 9% perfluorooctyltriethoxysilane. S3. The aluminum profile substrate is surface treated. After spraying the primer, the temperature is increased to 100°C at a heating rate of 8°C / min and baked for 15 minutes. After the temperature drops to 60°C, the topcoat is sprayed. After spraying the topcoat, the temperature is increased to 200°C at a heating rate of 10°C / min and baked for 25 minutes to form an aluminum profile coating. The dry film thickness of the primer coating is 20 μm, and the dry film thickness of the topcoat coating is 30 μm.

[0046] Example 2: A method for preparing a coating on aluminum profiles, the method comprising the following steps: S1. By weight, 33 parts of PVDF fluorocarbon resin, 17 parts of epoxy modified acrylic resin, 15 parts of recycled paint mist component, 7 parts of zinc phosphate, 12 parts of tetraethoxysilane modified talc, 0.6 parts of sodium polyacrylate, 0.4 parts of silicone leveling agent, 0.4 parts of polyether modified silicone defoamer, and 30 parts of butyl acetate are added to a dispersion kettle and dispersed at high speed for 40 min. Then, the mixture is transferred to a sand mill and ground until the fineness is ≤30 μm. Next, 7 parts of blocked polyisocyanate are added and stirred at 300 r / min for 60 min. The mixture is then filtered to obtain the primer. The recovered paint mist component is the overspray paint mist product captured and recovered by the water curtain spray booth during the fluorocarbon coating process of aluminum profiles. The overspray paint mist product includes the following components by mass percentage: 52% PVDF fluorocarbon resin, 21% acrylic resin, 18% boron nitride, and 9% perfluorooctyltriethoxysilane. S2. By weight, 45 parts of PVDF fluorocarbon resin, 15 parts of hydroxyl acrylic resin, 10 parts of recycled paint mist component, 12 parts of titanium dioxide, 6 parts of modified nano silica, 0.5 parts of sodium polyacrylate, 0.4 parts of organosilicon leveling agent, 1 part of UV-12, 1 part of light stabilizer 2020, 0.5 parts of aziridine, 0.4 parts of polyether modified organosilicon defoamer, and 40 parts of butyl acetate are added to a dispersion vessel and dispersed at high speed for 45 min. Then, the mixture is transferred to a sand mill and ground until the fineness is ≤25 μm. Next, 7 parts of hexamethylene diisocyanate trimer are added and stirred at 300 r / min for 60 min. The mixture is then filtered to obtain the topcoat. The modified nano-silica is nano-silica with a particle size of 45 nm, which has been surface-modified with methyltrimethoxysilane. The recovered paint mist component is the overspray paint mist product captured and recovered by the water curtain spray booth during the fluorocarbon coating process of aluminum profiles. The overspray paint mist product includes the following components by mass percentage: 52% PVDF fluorocarbon resin, 21% acrylic resin, 18% boron nitride, and 9% perfluorooctyltriethoxysilane. S3. The aluminum profile substrate is surface treated. After spraying the primer, the temperature is increased to 120°C at a heating rate of 10°C / min and baked for 12 minutes. After the temperature drops to 60°C, the topcoat is sprayed. After spraying the topcoat, the temperature is increased to 220°C at a heating rate of 10°C / min and baked for 20 minutes to form an aluminum profile coating. The dry film thickness of the primer coating is 20 μm, and the dry film thickness of the topcoat coating is 30 μm.

[0047] Example 3: A method for preparing a coating on aluminum profiles, the method comprising the following steps: S1. By weight, 35 parts of PVDF fluorocarbon resin, 15 parts of epoxy modified acrylic resin, 15 parts of recycled paint mist component, 8 parts of zinc phosphate, 13 parts of tetraethoxysilane modified talc, 0.8 parts of sodium polyacrylate, 0.5 parts of silicone leveling agent, 0.3 parts of polyether modified silicone defoamer, and 30 parts of butyl acetate are added to a dispersion kettle and dispersed at high speed for 40 min. Then, the mixture is transferred to a sand mill and ground until the fineness is ≤30 μm. Next, 8 parts of blocked polyisocyanate are added and stirred at 300 r / min for 60 min. The mixture is then filtered to obtain the primer. The recovered paint mist component is the overspray paint mist product captured and recovered by the water curtain spray booth during the fluorocarbon coating process of aluminum profiles. The overspray paint mist product includes the following components by mass percentage: 52% PVDF fluorocarbon resin, 21% acrylic resin, 18% boron nitride, and 9% perfluorooctyltriethoxysilane. S2. By weight, 48 parts of PVDF fluorocarbon resin, 12 parts of hydroxyl acrylic resin, 10 parts of recycled paint mist component, 13 parts of titanium dioxide, 7 parts of modified nano silica, 0.6 parts of sodium polyacrylate, 0.5 parts of organosilicon leveling agent, 1 part of UV-12, 1 part of light stabilizer 2020, 0.6 parts of aziridine, 0.4 parts of polyether modified organosilicon defoamer, and 40 parts of butyl acetate are added to a dispersion vessel and dispersed at high speed for 45 min. Then, the mixture is transferred to a sand mill and ground until the fineness is ≤25 μm. Next, 8 parts of hexamethylene diisocyanate trimer are added and stirred at 300 r / min for 60 min. The mixture is then filtered to obtain the topcoat. The modified nano-silica is nano-silica with a particle size of 45 nm, which has been surface-modified with methyltrimethoxysilane. The recovered paint mist component is the overspray paint mist product captured and recovered by the water curtain spray booth during the fluorocarbon coating process of aluminum profiles. The overspray paint mist product includes the following components by mass percentage: 52% PVDF fluorocarbon resin, 21% acrylic resin, 18% boron nitride, and 9% perfluorooctyltriethoxysilane. S3. The aluminum profile substrate is surface treated. After spraying the primer, the temperature is increased to 100°C at a heating rate of 8°C / min and baked for 15 minutes. After the temperature drops to 60°C, the topcoat is sprayed. After spraying the topcoat, the temperature is increased to 220°C at a heating rate of 10°C / min and baked for 20 minutes to form an aluminum profile coating. The dry film thickness of the primer coating is 20 μm, and the dry film thickness of the topcoat coating is 30 μm.

[0048] Comparative Example 1: The difference between Comparative Example 1 and Example 3 is that no epoxy-modified acrylic resin was added to the primer of Comparative Example 1, while the rest is the same as Example 3.

[0049] Comparative Example 2: The difference between Comparative Example 2 and Example 3 is that no recycled paint mist component was added to the primer of Comparative Example 2, while the rest is the same as Example 3.

[0050] Comparative Example 3: The difference between Comparative Example 3 and Example 3 is that no hydroxyl acrylic resin was added to the topcoat of Comparative Example 3, but otherwise it is the same as Example 3.

[0051] Comparative Example 4: The difference between Comparative Example 4 and Example 3 is that no recycled paint mist component was added to the topcoat of Comparative Example 4, while the rest is the same as Example 3.

[0052] Comparative Example 5: The difference between Comparative Example 5 and Example 3 is that no aziridine (crosslinking agent) was added to the topcoat of Comparative Example 5; otherwise, they are the same as Example 3.

[0053] Comparative Example 6: The difference between Comparative Example 6 and Example 3 is that the coating in Comparative Example 6 only has a primer (i.e. no topcoat is applied), while the rest is the same as in Example 3.

[0054] Comparative Example 7: The difference between Comparative Example 7 and Example 3 is that step S3 in Comparative Example 7 is different, while the rest is the same as in Example 3. The process of step S3 in Comparative Example 7 is as follows: the aluminum profile substrate is surface treated, a primer is sprayed, and then the temperature is raised to 100°C at a heating rate of 15°C / min and baked for 15 minutes; the topcoat is sprayed, and after the topcoat is sprayed, the temperature is raised to 220°C at a heating rate of 15°C / min and baked for 20 minutes to form an aluminum profile coating.

[0055] The aluminum profile coatings prepared in Examples 1-3 and Comparative Examples 1-7 were subjected to performance tests. Adhesion testing was performed according to GB / T 9286-2021, using the cross-cut test, 1mm spacing, and 3M 610 tape peel test, with a rating of 0-5. Impact strength testing was performed according to GB / T 1732-2020. Weather resistance (xenon lamp aging) testing was performed according to GB / T 1865-2009, "Artificial Climate Aging and Artificial Radiation Exposure to Filtered Xenon Arc Radiation for Paints and Varnishes", with a blackboard temperature of 65±3℃, relative humidity of 60±5%, and irradiance of 0.51W / (m²). 2 Weather resistance was assessed by gloss retention rate (·nm), over a period of 4000 hours. The results are shown in Table 1.

[0056] Salt spray resistance test was performed according to GB / T 10125-2012, "Artificial Atmosphere Corrosion Test - Salt Spray Test", using 5% NaCl solution, 35℃, continuous spraying, and observing bubbling and corrosion. The results are shown in Table 2.

[0057] Table 1: Performance Test Results

[0058] Table 2: Salt spray resistance test results

[0059] Analysis of the data in Tables 1 and 2 shows that the present invention, through the synergistic formulation design of the primer and topcoat and the step-by-step curing process, can achieve a comprehensive improvement in coating adhesion, density, corrosion resistance, and weather resistance, exhibiting excellent overall performance. Compared with Example 3, the primer in Comparative Example 1 did not contain epoxy-modified acrylic resin. Since the epoxy groups contained in the epoxy-modified acrylic resin have excellent chemical bonding with the aluminum profile substrate, and its active groups can also participate in interlayer chemical crosslinking reactions, the lack of epoxy-modified acrylic resin weakens the chemical bonding between the primer and the aluminum substrate, and significantly reduces the interlayer crosslinking density between the primer and the topcoat, resulting in performance inferior to Example 3. Comparative Example 2's primer did not contain recycled paint mist components. Since the recycled paint mist components contain PVDF fluorocarbon resin, acrylic resin, and fillers that are highly compatible with the primer system, the lack of these components weakens the continuity of the resin matrix and the filler gradation effect in the primer, increases the microscopic voids within the coating, and reduces its density. This indicates that the recycled paint mist components are not simply inert fillers, but functional components that can effectively participate in film formation, improve coating density and adhesion. Their addition achieves resource recycling while ensuring no performance degradation. Comparative Example 3's topcoat did not contain hydroxyl acrylic resin. Since hydroxyl acrylic resin is the main film-forming substance in the topcoat that undergoes a cross-linking reaction with the polyisocyanate curing agent, its absence prevents the topcoat from forming a dense three-dimensional cross-linked network. This results in severely insufficient density and mechanical properties of the topcoat layer, leading to performance inferior to Example 3. Comparative Example 4's topcoat did not contain recycled paint mist components. Since recycled paint mist components also play a role in improving resin compatibility, optimizing filler packing density, and reducing microscopic defects in the coating, the absence of this component resulted in decreased coating density and increased penetration pathways for corrosive media, leading to overall performance inferior to Example 3. Comparative Example 5's topcoat did not contain aziridine crosslinking agent. Aziridine crosslinking agent helps promote crosslinking between the primer and topcoat, forming interlayer chemical bonds, and can also participate in the crosslinking reaction within the topcoat. Without the crosslinking agent, the interlayer bonding force between the primer and topcoat was significantly weakened, resulting in overall performance inferior to Example 3. Comparative Example 6's coating consisted only of primer without topcoat. Since a single primer coating cannot form a sufficient physical barrier layer, its density and thickness are insufficient to resist long-term corrosion from salt spray environments, resulting in overall performance inferior to Example 3. In the curing process of Comparative Example 7, the heating rate was too fast, which made the coating prone to stress concentration and microcrack defects. At the same time, the excessively fast heating was not conducive to the full progress of the interlayer chemical cross-linking reaction, resulting in performance that was not as good as that of Example 3.

[0060] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0061] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A coating for aluminum profiles, characterized in that, The aluminum profile coating is formed by a primer and a topcoat; wherein... The primer comprises the following raw materials in parts by weight: 30-40 parts PVDF fluorocarbon resin, 15-20 parts epoxy modified acrylic resin, 10-20 parts recycled paint mist component, 7-10 parts rust inhibitor, 9-15 parts modified filler, 0.1-3 parts dispersant, 0.3-2 parts leveling agent, 0.2-1 part defoamer, 3-8 parts curing agent, and 20-30 parts solvent; The topcoat comprises the following raw materials in parts by weight: 40-50 parts PVDF fluorocarbon resin, 10-20 parts hydroxyl acrylic resin, 10-20 parts recycled paint mist component, 10-15 parts titanium dioxide, 5-10 parts modified nano silica, 0.1-3 parts dispersant, 0.3-2 parts leveling agent, 1-5 parts ultraviolet absorber, 1-2 parts hindered amine light stabilizer, 0.1-1 part crosslinking agent, 0.2-1 part defoamer, 5-10 parts curing agent, and 25-40 parts solvent.

2. The aluminum profile coating according to claim 1, characterized in that, The recovered paint mist component is the overspray paint mist product captured and recovered by the water curtain spray booth during the fluorocarbon coating process of aluminum profiles. The overspray paint mist product includes the following components by mass percentage: 40-55% PVDF fluorocarbon resin, 15-25% acrylic resin, 15-30% filler, and 5-10% additives.

3. The aluminum profile coating according to claim 1, characterized in that, The rust inhibitor in the primer is at least one of zinc phosphate, aluminum tripolyphosphate, and strontium chromate.

4. The aluminum profile coating according to claim 1, characterized in that, The modified filler in the primer is a filler that has been surface-modified with a silane coupling agent, and the filler is at least one of talc, barium sulfate, and mica powder.

5. The aluminum profile coating according to claim 1, characterized in that, The modified nano-silica is nano-silica with a particle size of 10~50nm, which has been surface modified with a silane coupling agent.

6. The aluminum profile coating according to claim 1, characterized in that, The curing agent in the primer is at least one of a blocked polyisocyanate and an amino resin.

7. The aluminum profile coating according to claim 1, characterized in that, The curing agent in the topcoat is at least one of hexamethylene diisocyanate trimer and isophorone diisocyanate trimer.

8. The aluminum profile coating according to claim 1, characterized in that, The solvent is at least one of xylene, butyl acetate, cyclohexanone, and ethylene glycol ethyl ether acetate.

9. The aluminum profile coating according to claim 1, characterized in that, The dry film thickness of the primer coating is 15~30μm, and the dry film thickness of the topcoat coating is 20~35μm.

10. A method for preparing a coating on an aluminum profile, characterized in that, The preparation method is used to prepare the aluminum profile coating as described in any one of claims 1 to 9, and the preparation method includes the following steps: S1. Add PVDF fluorocarbon resin, epoxy modified acrylic resin, recycled paint mist components, rust inhibitor, modified filler, dispersant, leveling agent, defoamer and solvent to a dispersion kettle, disperse at high speed for 30~60min, then transfer to a sand mill to grind to fineness ≤30μm, then add curing agent, stir at 100~300r / min for 30~60min, filter and discharge to obtain primer; S2. Add PVDF fluorocarbon resin, hydroxyl acrylic resin, recycled paint mist components, titanium dioxide, modified nano silica, dispersant, leveling agent, ultraviolet absorber, hindered amine light stabilizer, crosslinking agent, defoamer, and solvent to a dispersion vessel and disperse at high speed for 30-90 min. Then transfer to a sand mill and grind to a fineness ≤25μm. Add curing agent and stir at 100-300 r / min for 30-60 min. Filter the material to obtain the topcoat. S3. Perform surface treatment on the aluminum profile substrate, spray the primer, and bake at 80~120℃ for 5~15 minutes after spraying; after the temperature drops to 50~60℃, continue to spray the topcoat, and bake at 150~220℃ for 10~30 minutes after spraying to form an aluminum profile coating.

Images