Uvioresistant high gloss acrylic paint and its preparation method

Abstract

The application belongs to the technical field of functional coating, and discloses a kind of UV-aging resistant high-gloss acrylic coating and its preparation method, the coating is two-component system, including main agent and aliphatic isocyanate curing agent;Main agent includes resin pre-coated nano UV shielding slurry, acrylic compatibilized light stabilizing microdispersion, hydroxyl acrylic resin and auxiliary agent.Preparation, first nano UV shielding agent is pre-wetted, dispersed, ground and cured with hydroxyl acrylic resin, to obtain resin pre-coated slurry;Then make compatibilized microdispersion with UV absorber, hindered amine light stabilizer and hydroxyl acrylic resin;Then low-temperature compounding and adjusting paint.The application can reduce the agglomeration of nano UV shielding agent and the migration of light stabilizer, improve the UV-aging resistant performance, gloss retention rate and storage stability of coating film.

Description

Technical Field

[0001] This invention belongs to the field of functional coatings technology, specifically relating to a UV-resistant, high-gloss acrylic coating and its preparation method. Background Technology

[0002] Acrylic coatings are widely used in outdoor metal components, plastic products, architectural decorations, signage, and industrial protection due to their good decorative properties, adhesion, color retention, and ease of application. However, for high-gloss acrylic coatings used outdoors, prolonged exposure to ultraviolet radiation, oxygen, moisture, and temperature variations can cause photo-oxidative degradation of the resin matrix, leading to problems such as yellowing, loss of gloss, chalking, cracking, and decreased adhesion, thus affecting the coating's decorative effect and protective lifespan.

[0003] In existing technologies, the UV resistance of acrylic coatings is typically improved by adding inorganic UV shielding agents such as nano-zinc oxide, rutile nano-titanium dioxide, and nano-cerium oxide, or organic light-stabilizing components such as benzotriazole UV absorbers, hydroxyphenyltriazine UV absorbers, and hindered amine light stabilizers. However, inorganic nano-UV shielding agents have large specific surface areas and high surface energies, making them prone to agglomeration and storage coarsening in acrylic resin systems. This leads to increased micro-roughness of the coating surface, resulting in decreased gloss, increased haze, and appearance defects. Meanwhile, organic UV absorbers and hindered amine light stabilizers, if directly added to systems containing nanoparticles, are easily adsorbed by inorganic particles during high-speed dispersion or grinding, or migrate and precipitate due to uneven distribution, reducing their long-term anti-aging effect. Therefore, UV-resistant acrylic coatings often face the challenge of simultaneously improving weather resistance and maintaining high gloss. Summary of the Invention

[0004] To address the shortcomings mentioned in the background art, the present invention aims to provide a UV-resistant, high-gloss acrylic coating and its preparation method. This involves separately preparing a resin-pre-coated nano-UV-shielding slurry and an acrylic-compatible light-stabilized microdispersion, then combining the two at low temperature with remaining resin and additives to form the main agent. An aliphatic isocyanate curing agent is added before use. This invention improves the dispersion stability of nanoparticles, reduces light stabilizer migration, and enhances the UV aging resistance, gloss retention, and storage stability of the coating film.

[0005] The objective of this invention can be achieved through the following technical solutions: A method for preparing a UV-resistant, high-gloss acrylic coating includes the following steps: The hydroxyl acrylic resin is divided into three parts: Part 1, Part 2, and Part 3. S1. Mix the first part of hydroxy acrylic resin, organic solvent, dispersant and wetting agent to obtain resin pre-wetting liquid. Add nano UV shielding agent to the resin pre-wetting liquid. After wetting, pre-dispersion, shear dispersion and grinding treatment, the mixture is matured to obtain resin pre-coated nano UV shielding slurry. S2. Mix the ultraviolet absorber, hindered amine light stabilizer and compatibility solvent and heat and stir to obtain a light stabilizer mixture. Add the second part of hydroxyl acrylic resin and dispersant to the light stabilizer mixture and stir and mature to obtain acrylic compatibility light stabilized microdispersion. S3. Cool the resin pre-coated nano UV shielding slurry to 25–35°C, mix it with the acrylic acid compatibility light-stabilized micro-dispersion, add the third part of hydroxyl acrylic resin, leveling agent, defoamer and organic solvent, filter and degas to obtain the main agent. S4. Before use, add an aliphatic isocyanate curing agent to the main agent and mix to obtain the UV-resistant high-gloss acrylic coating.

[0006] More preferably, in step S1, the resin pre-coated nano-UV shielding slurry is prepared from the following raw materials in parts by weight: 10–30 parts of hydroxyl acrylic resin, 3–12 parts of nano-UV shielding agent, 0.5–4 parts of dispersant, 0.1–1.5 parts of wetting agent, 0.1–0.5 parts of defoamer, and 10–35 parts of organic solvent.

[0007] More preferably, in step S1, the fineness of the slurry after grinding is ≤10μm, the aging temperature is 30–45℃, and the aging time is 2–6h.

[0008] More preferably, in step S1, the nano-UV shielding agent is selected from one or more of nano-zinc oxide, rutile nano-titanium dioxide, and nano-cerium oxide, and the average primary particle size of the nano-UV shielding agent is 10–100 nm.

[0009] More preferably, in step S2, the acrylic acid compatibility light-stabilized microdispersion is prepared from the following raw materials in parts by weight: 1-4 parts of ultraviolet absorber, 0.5-3 parts of hindered amine light stabilizer, 5-20 parts of hydroxyl acrylic resin, 5-20 parts of compatibility solvent, and 0.1-1.5 parts of dispersant.

[0010] More preferably, in step S2, the temperature at which the UV absorber, hindered amine light stabilizer, and compatibility solvent are mixed and heated with stirring is 35–45°C for 30–90 min; the temperature at which stirring and ripening is 25–35°C for 1–4 h.

[0011] More preferably, the ultraviolet absorber is one or more of benzotriazole ultraviolet absorbers, hydroxyphenyltriazine ultraviolet absorbers, and benzophenone ultraviolet absorbers; the hindered amine light stabilizer is selected from one or more of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, and triazine-piperidinyl polymeric hindered amine light stabilizers.

[0012] More preferably, the organic solvent and the compatibility solvent are each independently selected from one or more of butyl acetate, propylene glycol methyl ether acetate, methyl isobutyl ketone, and xylene; the dispersant is selected from one or more of polyurethane-type polymeric dispersants, polyester-type polymeric dispersants, and phosphate-modified polymeric dispersants; and the wetting agent is one or two of polyether-modified siloxane wetting agents and organosilicon-modified nonionic wetting agents.

[0013] More preferably, in step S3, the mixing time of the resin pre-coated nano-UV shielding slurry and the acrylic acid compatible light-stabilized micro-dispersion is 30–90 min, and the filtration uses a 5–20 μm filter cartridge; in step S4, the aliphatic isocyanate curing agent is selected from one or more of hexamethylene diisocyanate trimer, isophorone diisocyanate trimer, and hexamethylene diisocyanate biuret; the leveling agent is a polyether-modified siloxane leveling agent or an acrylate leveling agent; and the defoamer is selected from one or more of polyether siloxane defoamer, polysiloxane defoamer, and non-silicone polymer defoamer.

[0014] A UV-resistant, high-gloss acrylic coating, the coating being a two-component coating comprising a main agent and a curing agent, wherein the coating comprises the following components in parts by weight, based on the total amount of each raw material added during the preparation of the main agent and the curing agent: 40–70 parts hydroxyl acrylic resin, 3–12 parts nano UV shielding agent, 1–4 parts UV absorber, 0.5–3 parts hindered amine light stabilizer, 0.5–4 parts dispersant, 0.1–1.5 parts wetting agent, 0.1–1 part leveling agent, 0.1–1 part defoamer, 10–35 parts organic solvent, 5–20 parts compatibility solvent, 0.1–1.5 parts dispersing aid, and 8–25 parts aliphatic isocyanate curing agent; The main agent includes resin pre-coated nano UV shielding slurry, acrylic acid compatible light-stabilized micro-dispersion, hydroxyl acrylic resin, leveling agent, defoamer and organic solvent, and the curing agent includes aliphatic isocyanate curing agent; The resin pre-coated nano-UV shielding slurry is prepared by wetting, pre-dispersing, shearing dispersion, grinding and maturation of hydroxyl acrylic resin, organic solvent, dispersant, wetting agent and nano-UV shielding agent; The acrylic acid compatibility light-stabilized microdispersion is prepared by mixing, heating and stirring, and aging of ultraviolet absorber, hindered amine light stabilizer, compatibility solvent, hydroxy acrylic resin and dispersing agent.

[0015] The beneficial effects of this invention are: To address the problems of easy agglomeration and storage roughness leading to gloss loss of nano-UV shielding agents in existing UV-resistant acrylic coatings, and the easy adsorption, migration, or precipitation of organic light stabilizers by inorganic powders when directly added, this invention constructs a resin-pre-coated nano-UV shielding slurry and an acrylic-compatible light-stabilized microdispersion. The former involves pre-wetting, dispersing, grinding, and curing the nano-UV shielding agent with hydroxyl acrylic resin, forming a resin adsorption layer compatible with the film-forming resin on the surface of the nanoparticles, thereby improving the dispersion stability of the nanoparticles and reducing surface roughness and gloss loss. The latter involves forming a microdispersion of UV absorbers, hindered amine light stabilizers, and hydroxyl acrylic resin, allowing the light-stabilizing components to be more uniformly distributed in the continuous resin phase, reducing ineffective adsorption and later migration during grinding. After low-temperature compounding, the two intermediates synergistically combine inorganic UV shielding, organic UV absorption, and free radical scavenging effects, improving the UV aging resistance of the coating while maintaining high gloss and good storage stability, thus achieving a balance between weather resistance and decorative properties. Attached Figure Description

[0016] The invention will now be further described with reference to the accompanying drawings.

[0017] Figure 1 The images show the SEM images of the nanoparticle dispersion state in Example 3 and Comparative Example 1 of the present invention. A is a 3000x magnified SEM image of the nanoparticle dispersion state in Example 3, and B is a 3000x magnified SEM image of the nanoparticle dispersion state in Comparative Example 1. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] The hydroxyl acrylic resin used in this invention is a solvent-based hydroxyl acrylic resin with a solid content of 60% and a hydroxyl value of 80 mg KOH / g; the amount of aliphatic isocyanate curing agent added in this invention is determined according to the NCO / OH equivalent ratio of 0.9–1.2; the following amounts of raw materials are based on the mass of commercially available raw materials.

[0020] Example 1: A method for preparing a UV-resistant, high-gloss acrylic coating, comprising the following steps: S1. Weigh 10g of hydroxyl acrylic resin, 6g of butyl acetate, 4g of propylene glycol methyl ether acetate, 0.5g of phosphate-modified polyester polymeric dispersant, 0.1g of polyether-modified siloxane wetting agent, and 0.1g of polyether siloxane defoamer. Add these to a dispersion vessel and stir at 400 rpm for 15 min to obtain a resin pre-wetting solution. Then, slowly add 3g of nano zinc oxide (average primary particle size approximately 30nm, preferably 30–50nm) while stirring. Wet at 500 rpm for 20 min, then increase to 1200 rpm for pre-dispersion for 25 min, followed by shear dispersion at 2800 rpm for 40 min. Transfer the resulting slurry to a sand mill and grind until the scraper fineness is ≤10μm. After grinding, mature the slurry at 40℃ and 300 rpm for 4 h to obtain a resin pre-coated nano UV shielding slurry.

[0021] S2. Weigh 1g of 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol, 0.5g of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, and 5g of compatibility solvent (3g butyl acetate and 2g methyl isobutyl ketone), add them to a reaction vessel, and stir at 35℃ for 30min to obtain a light stabilizer mixture. Then add 5g of hydroxyl acrylic resin and 0.1g of nonionic polymer dispersant, and stir at 25℃ at 500rpm for 1h to obtain an acrylic compatibility light-stabilized microdispersion.

[0022] S3. Cool the resin pre-coated nano UV shielding slurry to 25°C, add the above-mentioned acrylic compatibility light-stabilized micro-dispersion, and stir at 500 rpm for 30 min; then add 25 g hydroxyl acrylic resin, 0.2 g polyether modified siloxane leveling agent, 0.2 g polyether siloxane defoamer, 5 g butyl acetate and 3 g propylene glycol methyl ether acetate, and continue stirring for 30 min. Filter with a 15 μm filter and let stand for 20 min to remove bubbles to obtain the main agent.

[0023] S4. Before use, add 8g of hexamethylene diisocyanate trimer curing agent to the main agent, stir evenly to obtain UV-resistant high-gloss acrylic coating.

[0024] Example 2: A method for preparing a UV-resistant, high-gloss acrylic coating, comprising the following steps: S1. Weigh 30g of hydroxyl acrylic resin, 18g of butyl acetate, 12g of propylene glycol methyl ether acetate, 4g of phosphate-modified polyester polymeric dispersant, 1.5g of polyether-modified siloxane wetting agent, and 0.5g of polyether siloxane defoamer. Add these to a dispersion vessel and stir at 500rpm for 20min to obtain a uniform pre-wetting resin solution. While continuously stirring, slowly add 8g of nano-zinc oxide (average primary particle size approximately 30nm, preferably 30–50nm) and 4g of rutile nano-titanium dioxide. After wetting for 20min, pre-disperse at 1500rpm for 30min, then increase to 3200rpm for shear dispersion for 50min. Subsequently, place the slurry in a sand mill and grind using 0.8–1.0mm zirconia beads until the scraper fineness is ≤10μm. After grinding, the slurry was stirred and matured at 400 rpm at 40°C for 4 hours to obtain a resin-pre-coated nano-UV shielding slurry. S2. Weigh 4g of hydroxyphenyltriazine UV absorber, 3g of triazine-piperidine polymeric hindered amine light stabilizer, and 20g of compatibility solvent (12g of butyl acetate and 8g of methyl isobutyl ketone) and add them to a reaction vessel. Stir at 45℃ for 90min to obtain a light stabilizer mixture. Then add 20g of hydroxyacrylic resin and 1.5g of nonionic polymer dispersant, and stir at 35℃ and 400rpm for 4h to obtain an acrylic compatibility light-stabilized microdispersion.

[0025] S3. Cool the resin-pre-coated nano-UV shielding slurry to 35℃, add the acrylic-compatible light-stabilized micro-dispersion, and stir at low speed for 90 minutes to ensure full dispersion. Then add 15g of hydroxyl acrylic resin, 0.3g of polyether-modified siloxane leveling agent, 0.3g of polyether siloxane defoamer, 7g of butyl acetate, and 5g of propylene glycol methyl ether acetate, and continue stirring for 30 minutes. After mixing, filter using a 10μm filter cartridge and allow to stand for 30 minutes to degas, obtaining the main agent.

[0026] S4. Before use, add 16g of hexamethylene diisocyanate trimer curing agent to the main agent and stir evenly to obtain UV-resistant high-gloss acrylic coating.

[0027] Example 3: A method for preparing a UV-resistant, high-gloss acrylic coating, comprising the following steps: S1. Weigh 20g of hydroxyl acrylic resin, 12g of butyl acetate, 8g of propylene glycol methyl ether acetate, 2g of phosphate-modified polyester polymeric dispersant, 0.5g of polyether-modified siloxane wetting agent, and 0.2g of polyether siloxane defoamer. Add these to a dispersion vessel and stir at 500rpm for 15min to obtain a resin pre-wetting solution. While stirring, slowly add 6g of nano-zinc oxide (average primary particle size approximately 30nm, preferably 30–50nm) and 2g of rutile nano-titanium dioxide. After wetting for 20min, pre-disperse at 1500rpm for 25min, then increase to 3000rpm for shear dispersion for 45min. Place the slurry in a sand mill and grind using 0.8–1.0mm zirconia beads until the scraper fineness is ≤10μm. After grinding, mature the slurry at 40℃ and 400rpm for 4h to obtain a resin pre-coated nano-UV shielding slurry.

[0028] S2. Weigh 2g of benzotriazole UV absorber, 1.5g of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, and 10g of compatibility solvent (6g of butyl acetate and 4g of methyl isobutyl ketone) and add them to a reaction vessel. Stir at 40℃ for 60min to obtain a light stabilizer mixture. Then add 12g of hydroxyl acrylic resin and 0.5g of nonionic polymer dispersant, and stir at 30℃ and 400rpm for 2h to obtain an acrylic compatibility light-stabilized microdispersion.

[0029] S3. Cool the resin-pre-coated nano-UV shielding slurry to 30℃, add the acrylic-compatible light-stabilized micro-dispersion, and stir at low speed for 60 minutes to ensure full dispersion. Then add the remaining 25g of hydroxyl acrylic resin, 0.2g of polyether-modified siloxane leveling agent, 0.2g of polyether siloxane defoamer, 5g of butyl acetate, and 3g of propylene glycol methyl ether acetate, and continue stirring for 30 minutes. After mixing, filter using a 10μm filter cartridge and allow to stand for 30 minutes to degas, obtaining the main agent.

[0030] S4. Before use, add 8g of hexamethylene diisocyanate trimer curing agent to the main agent and stir evenly to obtain UV-resistant high-gloss acrylic coating.

[0031] Comparative Example 1: Instead of preparing the resin-pre-coated nano-UV shielding slurry and the acrylic-compatible light-stabilized microdispersion separately, all raw materials were mixed at once. S1. Add 40g of hydroxyl acrylic resin, 6g of nano zinc oxide, 2g of rutile nano titanium dioxide, 2g of benzotriazole UV absorber, 1.5g of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, 10g of compatibility solvent (6g of butyl acetate + 4g of methyl isobutyl ketone), 8g of organic solvent (5g of butyl acetate and 3g of propylene glycol methyl ether acetate), 2g of phosphate-modified polyester polymeric dispersant, 0.5g of polyether-modified siloxane wetting agent, 0.2g of polyether-modified siloxane defoamer, 0.2g of polyether-modified siloxane leveling agent, and 0.5g of nonionic polymeric dispersant to the dispersion vessel in one step.

[0032] S2. First, stir at a low speed of 500 rpm for 15 minutes to make the components initially mixed evenly; then increase to a medium speed of 1500 rpm for 25 minutes for pre-dispersion, and then increase to a high speed of 2800 rpm for high-speed shear dispersion for 40 minutes until the slurry is uniform and the scraper fineness is ≤10μm.

[0033] S3. Filter the mixed slurry through a 10μm filter cartridge and let it stand for 30 minutes to remove bubbles, thus obtaining the main agent.

[0034] S4. Before use, add 8g of hexamethylene diisocyanate trimer curing agent to the main agent and stir evenly to obtain the UV-resistant high-gloss acrylic coating of Comparative Example 1.

[0035] Comparative Example 2: Hydroxyl-free acrylic resin pre-coated nano-UV shielding agent S1. Add 6g of nano zinc oxide and 2g of rutile nano titanium dioxide, 2g of phosphate-modified polyester polymeric dispersant, 0.5g of polyether-modified siloxane wetting agent and 0.2g of polyether siloxane defoamer to the dispersion vessel, add 5g of butyl acetate and 3g of propylene glycol methyl ether acetate (organic solvent) and mix evenly. Stir at 500rpm for 15min, then pre-disperse at 1500rpm for 25min, and then shear disperse at 2800rpm for 40min to make the nano powder uniformly dispersed with a scraper fineness ≤10μm.

[0036] S2. Add 40g of hydroxyl acrylic resin, 2g of benzotriazole UV absorber, 1.5g of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, 10g of compatibility solvent (6g of butyl acetate and 4g of methyl isobutyl ketone), 0.5g of nonionic polymer dispersant, 0.2g of polyether-modified siloxane leveling agent, 0.2g of polyether siloxane defoamer, and 8g of organic solvent (5g of butyl acetate and 3g of propylene glycol methyl ether acetate) to the uniformly dispersed nanoparticle slurry. Stir at low speed for 30 minutes to ensure that all components are mixed evenly.

[0037] S3. Filter the mixed main agent through a 10μm filter and let it stand for 30 minutes to degas.

[0038] S4. Before use, add 8g of hexamethylene diisocyanate trimer curing agent, stir evenly, and obtain the coating of Comparative Example 2.

[0039] Comparative Example 3: Nano-UV shielding slurry without resin pre-coating and curing S1. Weigh 20g of hydroxyl acrylic resin, 12g of butyl acetate, 8g of propylene glycol methyl ether acetate, 2g of phosphate-modified polyester polymeric dispersant, 0.5g of polyether-modified siloxane wetting agent, and 0.2g of polyether siloxane defoamer. Add these to a dispersion vessel and stir at 500rpm for 15min to obtain a pre-wetting resin solution. Then, slowly add 6g of nano-zinc oxide and 2g of rutile nano-titanium dioxide while stirring. After wetting for 20min, pre-disperse at 1500rpm for 25min, then increase to 3000rpm for shear dispersion for 45min. Subsequently, perform sand milling (using 0.8–1.0mm zirconia beads) until the scraper fineness is ≤10μm. Do not perform a curing step; directly cool to 30℃ for the next compounding step.

[0040] S2. Weigh 2g of benzotriazole UV absorber, 1.5g of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, and 10g of compatibility solvent (6g of butyl acetate and 4g of methyl isobutyl ketone, mass ratio 3:2) and add them to a reaction vessel. Stir at 40℃ for 60min to obtain a light stabilizer mixture. Then add 12g of hydroxyl acrylic resin and 0.5g of nonionic polymer dispersant, and stir at 30℃ and 400rpm for 2h to obtain an acrylic compatibility light-stabilized microdispersion.

[0041] S3. Cool the uncured resin pre-coated nano-UV shielding slurry to 30℃, add the acrylic-compatible light-stabilized micro-dispersion, and stir at low speed for 60 minutes to ensure thorough mixing. Then add the remaining 25g of hydroxyl acrylic resin, 0.2g of polyether-modified siloxane leveling agent, 0.2g of polyether siloxane defoamer, 5g of butyl acetate, and 3g of propylene glycol methyl ether acetate, and continue stirring for 30 minutes. After mixing, filter using a 10μm filter cartridge and allow to stand for 30 minutes to degas, obtaining the main agent.

[0042] S4. Before use, add 8g of hexamethylene diisocyanate trimer curing agent to the main agent and stir evenly to obtain the UV-resistant high-gloss acrylic coating of Comparative Example 3.

[0043] Comparative Example 4: No acrylic acid-compatible light-stabilized microdispersion was prepared; the light stabilizer was directly added to the main agent. S1. Weigh 20g of hydroxyl acrylic resin, 12g of butyl acetate, 8g of propylene glycol methyl ether acetate, 2g of phosphate-modified polyester polymeric dispersant, 0.5g of polyether-modified siloxane wetting agent, and 0.2g of polyether siloxane defoamer. Add these to a dispersion vessel and stir at 500rpm for 15min to obtain a pre-wetting resin solution. Then, slowly add 6g of nano zinc oxide and 2g of rutile nano titanium dioxide while stirring. After wetting for 20min, pre-disperse at 1500rpm for 25min, then increase to 3000rpm for shear dispersion for 45min. Grind the slurry with 0.8–1.0mm zirconia beads until the scraper fineness is ≤10μm. After grinding, mature the slurry at 40℃ and 400rpm for 4h to obtain a resin pre-coated nano UV shielding slurry.

[0044] S2. Cool the resin-pre-coated nano-UV shielding slurry to 30℃, then add the remaining 25g of hydroxyl acrylic resin, 2g of benzotriazole UV absorber, 1.5g of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, 10g of compatibility solvent (6g of butyl acetate + 4g of methyl isobutyl ketone), 8g of organic solvent (5g of butyl acetate + 3g of propylene glycol methyl ether acetate), 0.5g of nonionic polymer dispersant, 0.2g of polyether-modified siloxane leveling agent, and 0.2g of polyether siloxane defoamer. Stir at a low speed of 400–500 rpm for 60 minutes to ensure uniform dispersion of the light stabilizer.

[0045] S3. After mixing, filter using a 10μm filter cartridge and let stand for 30 minutes to remove bubbles, thus obtaining the main agent.

[0046] S4. Before use, add 8g of hexamethylene diisocyanate trimer curing agent, stir evenly, and obtain the UV-resistant high-gloss acrylic coating of Comparative Example 4.

[0047] Performance testing To verify the performance of the UV-resistant high-gloss acrylic coating prepared by this invention, gloss, UV resistance, and nanoparticle dispersibility tests were conducted.

[0048] Gloss test: The coating was brushed onto a standard metal substrate with a wet film thickness of 50 μm. After drying at room temperature for 24 hours, the gloss values ​​were measured at 5 random points on the coating surface using a 60° gloss meter (ASTM D523) and the average value was taken.

[0049] UV aging resistance test: The coating was placed in a QUV accelerated aging chamber with a UV-A lamp, a light intensity of 0.89 W / m², a temperature of 60℃, and a humidity of 50%. The cycle consisted of 8 hours of light exposure followed by 4 hours of water mist exposure, for a total of 200 hours. The ΔE value and 60° gloss were measured every 50 hours, and the retention rate of the ΔE value and 60° gloss was recorded after 200 cycles.

[0050] Nanoparticle dispersion: The distribution of the nano-shielding agent in the coating cross-section was observed using transmission electron microscopy (TEM). Coating slices with a thickness of approximately 70–100 nm were prepared. The particle size distribution of nanoparticles in the slurry and coating was statistically analyzed, and D10 / D50 / D90 were recorded separately.

[0051] The results are shown in Table 1 below.

[0052] Table 1. Overall Performance Analysis of Examples and Comparative Examples

[0053] As shown in the table, the coatings of Examples 1–3 exhibited a high gloss of 83–88 GU in the 60° gloss test, significantly higher than the 72–76 GU of the comparative sample. This indicates that the low-temperature stepwise composite process of resin pre-coating nano-UV shielding agent and acrylic compatible light-stabilized microdispersion can significantly improve the surface smoothness and reflectivity of the coating. In the UV aging resistance test, the ΔE value of the examples was only 1.0–1.3, with a gloss retention rate of 90–94%, while the ΔE value of the comparative sample was 2.5–3.0, with a gloss retention rate of 82–84%. This shows that the coatings of the examples showed significantly less yellowing and gloss reduction under 200 hours of UV-A accelerated aging, indicating that the synergistic effect of the nano-shielding agent and the light stabilizer in this invention effectively improved the light aging resistance of the coating. TEM observation and particle size analysis showed that the nanoparticles in the examples all had a D90 of less than 2.6 μm and were uniformly distributed, resulting in good coating uniformity. In contrast, the comparative samples had a D90 of 3.8–4.5 μm, exhibiting significant agglomeration, with some coatings showing particle accumulation. These results indicate that the pre-coating and low-temperature stepwise composite process not only stabilized the nanoparticle dispersion but also improved coating uniformity and reduced the generation of micro-defects.

[0054] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0055] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for preparing a UV-resistant, high-gloss acrylic coating, characterized in that, Includes the following steps: The hydroxyl acrylic resin is divided into three parts: Part 1, Part 2, and Part 3. S1. Mix the first part of hydroxy acrylic resin, organic solvent, dispersant and wetting agent to obtain resin pre-wetting liquid. Add nano UV shielding agent to the resin pre-wetting liquid. After wetting, pre-dispersion, shear dispersion and grinding treatment, the mixture is matured to obtain resin pre-coated nano UV shielding slurry. S2. Mix the ultraviolet absorber, hindered amine light stabilizer and compatibility solvent and heat and stir to obtain a light stabilizer mixture. Add the second part of hydroxyl acrylic resin and dispersant to the light stabilizer mixture and stir and mature to obtain acrylic compatibility light stabilized microdispersion. S3. Cool the resin pre-coated nano UV shielding slurry to 25–35°C, mix it with the acrylic acid compatibility light-stabilized micro-dispersion, add the third part of hydroxyl acrylic resin, leveling agent, defoamer and organic solvent, filter and degas to obtain the main agent. S4. Before use, add an aliphatic isocyanate curing agent to the main agent and mix to obtain the UV-resistant high-gloss acrylic coating.

2. The preparation method according to claim 1, characterized in that, In step S1, the resin pre-coated nano-UV shielding slurry is prepared from the following raw materials in parts by weight: 10-30 parts of hydroxyl acrylic resin, 3-12 parts of nano-UV shielding agent, 0.5-4 parts of dispersant, 0.1-1.5 parts of wetting agent, 0.1-0.5 parts of defoamer, and 10-35 parts of organic solvent.

3. The preparation method according to claim 1, characterized in that, In step S1, the fineness of the slurry after grinding is ≤10μm, the aging temperature is 30–45℃, and the aging time is 2–6h.

4. The preparation method according to claim 1, characterized in that, In step S1, the nano-UV shielding agent is selected from one or more of nano-zinc oxide, rutile nano-titanium dioxide, and nano-cerium oxide, and the average primary particle size of the nano-UV shielding agent is 10–100 nm.

5. The preparation method according to claim 1, characterized in that, In step S2, the acrylic acid compatibility light-stabilized microdispersion is prepared from the following raw materials in parts by weight: 1-4 parts of ultraviolet absorber, 0.5-3 parts of hindered amine light stabilizer, 5-20 parts of hydroxyl acrylic resin, 5-20 parts of compatibility solvent, and 0.1-1.5 parts of dispersant.

6. The preparation method according to claim 1, characterized in that, In step S2, the ultraviolet absorber, hindered amine light stabilizer and compatibility solvent are mixed and heated and stirred at a temperature of 35–45°C for 30–90 min; the stirring and aging temperature is 25–35°C for 1–4 h.

7. The preparation method according to claim 1, characterized in that, The ultraviolet absorber is one or more of benzotriazole ultraviolet absorbers, hydroxyphenyltriazine ultraviolet absorbers, and benzophenone ultraviolet absorbers; the hindered amine light stabilizer is one or more of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, and triazine-piperidinyl polymeric hindered amine light stabilizers.

8. The preparation method according to claim 1, characterized in that, The organic solvent and the compatibility solvent are each independently selected from one or more of butyl acetate, propylene glycol methyl ether acetate, methyl isobutyl ketone, and xylene; the dispersant is selected from one or more of polyurethane-type polymeric dispersants, polyester-type polymeric dispersants, and phosphate-modified polymeric dispersants; the wetting agent is one or two of polyether-modified siloxane wetting agents and organosilicon-modified nonionic wetting agents.

9. The preparation method according to claim 1, characterized in that, In step S3, the mixing time of the resin pre-coated nano-UV shielding slurry and the acrylic compatible light-stabilized micro-dispersion is 30–90 min, and the filtration uses a 5–20 μm filter cartridge; in step S4, the aliphatic isocyanate curing agent is selected from one or more of hexamethylene diisocyanate trimer, isophorone diisocyanate trimer, and hexamethylene diisocyanate biuret; the leveling agent is a polyether-modified siloxane leveling agent or an acrylate leveling agent; the defoamer is selected from one or more of polyether siloxane defoamer, polysiloxane defoamer, and non-silicone polymer defoamer.

10. A UV-resistant, high-gloss acrylic coating, characterized in that, The coating is a two-component coating, comprising a main agent and a curing agent. Based on the total amount of each raw material added when preparing the main agent and the curing agent, the coating comprises the following components in parts by weight: 40–70 parts of hydroxyl acrylic resin, 3–12 parts of nano UV shielding agent, 1–4 parts of UV absorber, 0.5–3 parts of hindered amine light stabilizer, 0.5–4 parts of dispersant, 0.1–1.5 parts of wetting agent, 0.1–1 part of leveling agent, 0.1–1 part of defoamer, 10–35 parts of organic solvent, 5–20 parts of compatibility solvent, 0.1–1.5 parts of dispersing aid, and 8–25 parts of aliphatic isocyanate curing agent; The main agent includes resin pre-coated nano UV shielding slurry, acrylic acid compatible light-stabilized micro-dispersion, hydroxyl acrylic resin, leveling agent, defoamer and organic solvent, and the curing agent includes aliphatic isocyanate curing agent; The resin pre-coated nano-UV shielding slurry is prepared by wetting, pre-dispersing, shearing dispersion, grinding and maturation of hydroxyl acrylic resin, organic solvent, dispersant, wetting agent and nano-UV shielding agent; The acrylic acid compatibility light-stabilized microdispersion is prepared by mixing, heating and stirring, and aging of ultraviolet absorber, hindered amine light stabilizer, compatibility solvent, hydroxy acrylic resin and dispersing agent.

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