Synergistic compound light stabilizer for automobile coating and preparation method thereof

Abstract

The invention discloses a synergistic compound light stabilizer for an automobile coating and a preparation method of the synergistic compound light stabilizer, and belongs to the technical field of coating additives. The light stabilizer comprises the following components in percentage by mass: 30-50% of a hindered amine light stabilizer, 20-40% of an ultraviolet light absorber, 5-15% of surface modified nano cerium dioxide, 5-10% of a hyperbranched polyester anti-migration aid and the balance of a solvent, wherein the ultraviolet light absorber is a mixture of benzotriazole and triazine in a mass ratio of (1: 1)-(1: 3); the particle size of the nano cerium dioxide is 10-50nm, and the surface of the nano cerium dioxide is coated with a silane coupling agent; the preparation method comprises the following steps: modifying the surface of nano cerium dioxide, shearing and dispersing multiple components at a high speed, and adjusting and filtering a solvent; the weather resistance of the automobile coating is remarkably improved and the service life of the automobile coating is remarkably prolonged through the synergistic effect of a plurality of light stabilizing components and the combination of the photocatalytic degradation capability of the nano cerium dioxide and the anti-migration characteristic of the hyperbranched polyester.

Description

Technical Field

[0001] The present invention relates to the technical field of coating additives, in particular to a synergistic compounded light stabilizer for automobile coatings and a preparation method thereof. Background Art

[0002] With the rapid development of the automotive industry, automotive coatings, as a crucial component of vehicle exterior protection, are receiving increasing attention for their weather resistance and aging resistance. During long-term outdoor use, automotive coatings are susceptible to environmental factors such as UV radiation, high temperature, and humidity, leading to aging phenomena such as yellowing, fading, cracking, and gloss loss, seriously impacting the vehicle's appearance and service life. To improve the weather resistance of automotive coatings, the use of light stabilizers has become particularly important.

[0003] Currently, commonly used automotive coating light stabilizers on the market primarily include hindered amine light stabilizers (HALS), UV absorbers, antioxidants, and nano-inorganic materials. The mechanism of action of hindered amine light stabilizers (HALS) is not to directly absorb UV light or quench excited states, but rather to inhibit photooxidative degradation by capturing free radicals. After capturing free radicals, HALS forms a stable nitroxide radical, which can further capture more free radicals, forming a chain reaction and effectively terminating the free radical chain reaction, thereby blocking the photooxidative degradation process. UV absorbers absorb harmful UV rays and convert them into harmless heat energy. UV absorbers can absorb UV rays within a specific wavelength range, thereby protecting polymers from UV damage. Nano-inorganic materials such as silica, titanium dioxide, and ceria have excellent UV shielding and scattering capabilities.

[0004] To further enhance the light stabilization effect, composite light stabilizers have gradually become a research hotspot. By combining UV absorbers, light stabilizers, and antioxidants, the components can achieve synergistic effects.

[0005] However, the light stabilizers in the existing technology still have some problems: First, traditional single light stabilizers such as HALS or UV absorbers are prone to failure under long-term exposure conditions, and there are problems such as migration and volatilization, which make it difficult to meet the long-term use requirements of automotive coatings; second, existing compound light stabilizers mostly adopt a simple physical mixing method, and the synergistic effect between the components is insufficient, and the advantages of each component cannot be fully utilized; third, nanomaterials such as cerium dioxide have poor dispersibility and compatibility in coatings, and are prone to agglomeration, affecting the light stabilization effect; finally, the existing technology lacks effective anti-migration technology, which leads to the gradual loss of light stabilizers in the coating during long-term use, making it difficult to maintain a lasting protective effect.

[0006] Therefore, there is an urgent need to develop a composite light stabilizer with efficient synergistic effects, good dispersibility and anti-migration properties to solve the problems of yellowing, fading, cracking, and gloss loss that easily occur in automotive coatings under high temperature, high humidity and strong ultraviolet light environments, and to improve the weather resistance and service life of automotive coatings. Summary of the Invention

[0007] In order to solve the technical problems that traditional light stabilizers are prone to failure under long-term exposure, have migration and volatilization problems, and the synergistic effect of compound light stabilizers is insufficient, and it is impossible to balance long-term stability and environmental protection, especially the problem that automotive coatings are prone to yellowing, fading, cracking, and loss of gloss in high temperature, high humidity, and strong ultraviolet light environments, the present invention provides a synergistic compound light stabilizer for automotive coatings.

[0008] To achieve the above object, the present invention provides the following technical solutions: The present invention provides a synergistic compounded light stabilizer for automotive coatings, which comprises the following components by mass percentage: Hindered amine light stabilizer 30-50%; UV absorber 20-40%; Surface modified nano-cerium dioxide 5-15%; Hyperbranched polyester anti-migration agent 5-10%; The balance is solvent; Furthermore, the surface-modified nano-cerium dioxide is a nano-cerium dioxide surface coated with a silane coupling agent, the particle size of the surface-modified nano-cerium dioxide is 10-50 nm, and the silane coupling agent is one of γ-aminopropyltriethoxysilane coupling agent, methyltrimethoxysilane coupling agent, octadecyltrimethoxysilane coupling agent, 3-glycidyloxypropyltrimethoxysilane coupling agent, and vinyltrimethoxysilane coupling agent.

[0009] Furthermore, the hyperbranched polyester anti-migration agent is one of hydroxyl-terminated hyperbranched polyester, ester-terminated hyperbranched polyester, epoxy-terminated hyperbranched polyester, hydroxyl- and ester-mixed hyperbranched polyester, and amino-terminated hyperbranched polyester.

[0010] Furthermore, the ultraviolet absorber is a mixture of a benzotriazole ultraviolet absorber and a triazine ultraviolet absorber in a mass ratio of 1:1-1:3.

[0011] Furthermore, the triazole ultraviolet absorber is one of 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole, and 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)benzotriazole; the triazine ultraviolet absorber is 2,4,6- One of tris(2,4-dimethylphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-octyloxyphenyl)-1,3,5-triazine, 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-[(hexyl)oxy]-phenol, 2,4-bis(2,4-dimethylphenyl)-6-(2-hydroxy-4-methoxyphenyl)-1,3,5-triazine, and 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-[(octyl)oxy]-phenol.

[0012] Furthermore, the hindered amine light stabilizer is one of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis(2,2,6,6-tetramethyl-4-piperidinyl) succinate, poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidinylethanol) succinate, and 2,2,6,6-tetramethyl-4-piperidinyl stearate. Furthermore, the solvent is an environmentally friendly ester solvent, such as sec-butyl acetate or mixed dibasic acid dimethyl ester.

[0013] Preferably, the solvent is one or a mixture of two of sec-butyl acetate, propylene glycol methyl ether acetate, n-butanol, propylene glycol methyl ether, butyl acetate, xylene, cyclohexanone, propylene glycol methyl ether acetate, ethyl acetate, and acetone.

[0014] The present invention also provides a method for preparing the above-mentioned synergistic composite light stabilizer for automotive coatings, comprising the following steps: Adding the pretreated nano-cerium dioxide to the silane coupling agent, stirring and reacting at 60-80° C. for 4-6 hours to obtain surface-modified nano-cerium dioxide; Add hindered amine light stabilizer, ultraviolet absorber, modified nano-cerium dioxide, and hyperbranched polyester anti-migration agent in sequence, and shear and disperse at high speed (10000-15000rpm) to form a uniform dispersion system; Add solvent to adjust the viscosity, stir evenly and filter through a 3μm filter membrane to obtain a transparent light stabilizer solution with a viscosity of 150-350mPa·s, a density of 1.03-1.12g / cm³ and a pH value of 6.0-8.0.

[0015] Furthermore, the pretreatment of nano-cerium dioxide in step (1) is as follows: dispersing the nano-cerium dioxide in an organic solvent, ultrasonically treating the nano-cerium dioxide for 30 minutes to form a suspension, and obtaining pretreated nano-cerium dioxide, wherein the organic solvent is one of ethanol, isopropanol, and toluene.

[0016] The present invention also provides a use of the synergistic compound light stabilizer in automobile coatings, wherein the amount of the synergistic compound light stabilizer is 0.8-3.5% of the total amount of the automobile coating.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention significantly improves the weather resistance, UV aging resistance, and long-term stability of the coating through the synergistic effect of multiple light-stabilizing ingredients. Specifically, the hindered amine light stabilizer effectively captures free radicals; the UV absorber shields the UV-A / UV-B bands; nano-cerium dioxide scatters UV-C and inhibits photocatalytic reactions; and the hyperbranched polyester locks in the active ingredients through steric hindrance, reducing migration. The recommended addition level of this product in automotive coatings is 0.8-3.5%. In a 3000-hour xenon lamp aging test according to SAE J2527, the color difference ΔE was less than 1.5 (compared to the control group ΔE > 3.0), and the gloss retention rate was ≥90%. This highly effective, synergistic, low-migration, and environmentally friendly light stabilization effect effectively addresses the aging issues of automotive coatings in extreme climates. The composite light stabilizer of this invention has broad applicability and compatibility with a variety of coating systems. Compared with the existing technology, the light stabilizer of the present invention overcomes the shortcomings of traditional single light stabilizers that are easily ineffective under long-term exposure conditions, solves the problem of insufficient synergistic effect between the components of existing compound light stabilizers, improves the dispersibility and compatibility of nanomaterials in coatings, and effectively prevents the loss of light stabilizers in the coating through the hyperbranched polyester anti-migration agent. DETAILED DESCRIPTION

[0018] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention. Example 1

[0019] A synergistic compound light stabilizer for automotive coatings, comprising the following components by weight: 40% hindered amine light stabilizer (HALS); 30% ultraviolet absorber; 10% surface-modified nano-cerium dioxide; 8% hyperbranched polyester anti-migration agent; and 12% solvent.

[0020] Among them, the hindered amine light stabilizer is bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate. This HALS has excellent light stability and weather resistance, can effectively capture free radicals, block the photooxidative degradation chain reaction, and extend the service life of the coating.

[0021] The UV absorber is a mixture of benzotriazoles and triazines in a 1:2 mass ratio. The benzotriazole is 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, and the triazine is 2,4,6-tris(2,4-dimethylphenyl)-1,3,5-triazine. This combination provides broad-spectrum absorption within the 280-400nm wavelength range, effectively preventing UV damage to the coating substrate.

[0022] The surface-modified nano-cerium dioxide has a particle size of 30 nm and is coated with γ-aminopropyltriethoxysilane (silane coupling agent KH-550). Nano-cerium dioxide has excellent UV shielding capabilities and photocatalytic activity. Surface modification can improve its dispersibility and stability in organic systems while reducing the adverse effects of photocatalytic activity on the coating.

[0023] The hyperbranched polyester anti-migration additive uses a hydroxyl-terminated hyperbranched polyester (Boltorn H30) with a molecular weight of 3000-5000 and a hydroxyl value of 100-150 mgKOH / g. This additive can fix the light stabilizer molecules through multi-point hydrogen bonding, reducing their migration and volatilization in the coating and prolonging the durability of the light stabilization effect.

[0024] The solvent selected is propylene glycol methyl ether acetate (PMA), which has good solubility and moderate volatilization rate, and can ensure that each component is fully dissolved and forms a stable solution.

[0025] The preparation method of the light stabilizer comprises the following steps: (1) Surface modification of nano-cerium dioxide: 30 g of nano-cerium dioxide (SS-CE420) was dispersed in 200 g of anhydrous ethanol and ultrasonically treated for 30 minutes to form a uniform suspension; 9 g of γ-aminopropyltriethoxysilane was added and refluxed at 70 °C for 4 hours; the mixture was centrifuged, washed with ethanol three times, and vacuum dried at 60 °C for 12 hours to obtain surface-modified nano-cerium dioxide.

[0026] (2) Multi-component high-speed shear dispersion: Dissolve 40g of hindered amine light stabilizer, 20g of benzotriazole UV absorber and 40g of triazine UV absorber in 80g of propylene glycol methyl ether acetate and stir until completely dissolved; add 10g of surface-modified nano-cerium dioxide and disperse at high speed (speed 10000rpm) for 30 minutes; add 8g of hyperbranched polyester anti-migration aid and continue high-speed shear dispersion for 20 minutes to form a uniform dispersion system.

[0027] (3) Solvent adjustment and filtration: Add 40 g of propylene glycol methyl ether acetate to adjust the viscosity and stir evenly; filter through a 5 μm filter membrane to remove possible agglomerates to obtain a clear and transparent light stabilizer solution.

[0028] The prepared light stabilizer is a light yellow, transparent liquid with a viscosity of 200-300 mPa·s (25°C), a density of 1.05-1.10 g / cm³, and a pH of 6.5-7.5. The recommended dosage of this light stabilizer in automotive coatings is 1-3% of the total coating weight; in this example, the addition amount is 2%. The automotive coating is preferably a BASF water-based basecoat, and all the automotive coatings in the following examples are BASF water-based basecoats.

[0029] The light stabilizer has the following advantages: (1) Multiple components work synergistically to form a full-band UV protection barrier; (2) The introduction of surface-modified nano-cerium dioxide enhances the UV shielding effect and improves the thermal stability of the light stabilizer; (3) The hyperbranched polyester anti-migration agent effectively reduces the migration and loss of the light stabilizer in the coating, thereby prolonging the protection effect; (4) The optimized distribution ratio of each component ensures the compatibility and long-term stability of the light stabilizer in the coating. Example 2

[0030] A synergistic compound light stabilizer for automotive coatings, comprising the following components in percentage by weight: 30% hindered amine light stabilizer (HALS); 40% ultraviolet absorber; 15% surface-modified nano-cerium dioxide; 5% hyperbranched polyester anti-migration agent; and 10% solvent.

[0031] Among them, the hindered amine light stabilizer is bis(2,2,6,6-tetramethyl-4-piperidinyl)succinate. This type of HALS has good heat resistance and acid resistance and is suitable for acid-catalyzed curing coating systems.

[0032] The UV absorber is a mixture of benzotriazoles and triazines in a mass ratio of 1:3. The benzotriazole is 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)benzotriazole, and the triazine is 2,4,6-tris(2-hydroxy-4-octyloxyphenyl)-1,3,5-triazine. This combination provides a wider UV absorption range, particularly enhancing absorption of long-wave UV rays.

[0033] Surface-modified nano-cerium dioxide (SS-CE420) has a particle size of 10 nm and is coated with a methyltrimethoxysilane coupling agent. Small-particle nano-cerium dioxide has a larger specific surface area and higher UV shielding efficiency. The hydrophobic coating of methyltrimethoxysilane improves the dispersion stability of the nanoparticles in organic solvents.

[0034] The hyperbranched polyester anti-migration additive utilizes an ester-terminated hyperbranched polyester (BIS-MPA polyester-64-hydroxy) with a molecular weight of 2000-3000 and an acid value of less than 5mgKOH / g. This additive, through its compatibility with the coating resin, secures the position of the light stabilizer molecules within the coating, reducing their migration and volatilization.

[0035] The solvent used is a mixed solvent of n-butanol and propylene glycol methyl ether (mass ratio 1:1). This mixed solvent has good dissolving ability and moderate volatilization rate, and can meet the needs of different coating systems.

[0036] The preparation method of the light stabilizer comprises the following steps: (1) Surface modification of nano-cerium dioxide: 45 g of nano-cerium dioxide was dispersed in 300 g of isopropanol and ultrasonically treated for 45 minutes to form a uniform suspension; 12 g of methyltrimethoxysilane was added and refluxed at 65 °C for 5 hours; the mixture was centrifuged, washed with isopropanol 4 times, and vacuum dried at 50 °C for 15 hours to obtain surface-modified nano-cerium dioxide.

[0037] (2) Multi-component high-speed shear dispersion: Dissolve 30g of hindered amine light stabilizer, 10g of benzotriazole UV absorber and 30g of triazine UV absorber in 60g of mixed solvent and stir until completely dissolved; add 15g of surface-modified nano-cerium dioxide and disperse at high speed (speed 12000rpm) for 40 minutes; add 5g of hyperbranched polyester anti-migration aid and continue high-speed shear dispersion for 25 minutes to form a uniform dispersion system.

[0038] (3) Solvent adjustment and filtration: Add 50 g of mixed solvent to adjust the viscosity and stir evenly; filter through a 3 μm filter membrane to remove possible agglomerates to obtain a clear and transparent light stabilizer solution.

[0039] The prepared light stabilizer is a light yellow, transparent liquid with a viscosity of 150-250 mPa·s (25°C), a density of 1.03-1.08 g / cm³, and a pH of 6.0-7.0. The recommended dosage of this light stabilizer in automotive coatings is 1.5-3.5% of the total coating weight; in this example, the dosage is 3%. Example 3

[0040] A synergistic compound light stabilizer for automotive coatings, comprising the following components in percentage by weight: 50% hindered amine light stabilizer (HALS); 20% ultraviolet absorber; 5% surface-modified nano-cerium dioxide; 10% hyperbranched polyester anti-migration agent; and 15% solvent.

[0041] Among them, the hindered amine light stabilizer is poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidinylethanol) succinate. This type of HALS has excellent light stability and alkali resistance and is suitable for alkaline catalytic curing coating systems.

[0042] The UV absorber is a mixture of benzotriazoles and triazines in a 1:1 mass ratio. The benzotriazole is 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, while the triazine is 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]-phenol. This combination provides balanced absorption in the UV region while exhibiting excellent heat and light resistance.

[0043] Surface-modified nano-cerium dioxide (SS-CE420) has a particle size of 50 nm and is coated with an octadecyltrimethoxysilane coupling agent. Larger nano-cerium dioxide particles exhibit improved optical transparency, while the long-chain alkylsilane coating provides excellent hydrophobicity and organic compatibility.

[0044] Hyperbranched polyester anti-migration additives utilize epoxy-terminated hyperbranched polyester (Hyper 102) with a molecular weight of 4000-6000 and an epoxy value of 0.2-0.4 eq / 100g. This additive chemically reacts with the coating resin through the epoxy groups, firmly anchoring the light stabilizer within the coating network and completely resolving the migration issue.

[0045] The solvent used is a mixed solvent of butyl acetate and xylene (mass ratio 3:2). The mixed solvent has good dissolving ability and moderate volatilization rate and is suitable for various automotive coating systems.

[0046] The preparation method of the light stabilizer comprises the following steps: (1) Surface modification of nano-cerium dioxide: 15 g of nano-cerium dioxide was dispersed in 150 g of toluene and ultrasonically treated for 35 minutes to form a uniform suspension; 6 g of octadecyltrimethoxysilane was added and refluxed at 75 °C for 6 hours; the mixture was centrifuged, washed with toluene three times, and vacuum dried at 70 °C for 10 hours to obtain surface-modified nano-cerium dioxide.

[0047] (2) Multi-component high-speed shear dispersion: Dissolve 50g of hindered amine light stabilizer, 10g of benzotriazole UV absorber and 10g of triazine UV absorber in 90g of mixed solvent and stir until completely dissolved; add 5g of surface-modified nano-cerium dioxide and disperse at high speed (speed 15000rpm) for 25 minutes; add 10g of hyperbranched polyester anti-migration aid and continue high-speed shear dispersion for 15 minutes to form a uniform dispersion system.

[0048] (3) Solvent adjustment and filtration: Add 60 g of mixed solvent to adjust the viscosity and stir evenly; filter through a 2 μm filter membrane to remove possible agglomerates to obtain a clear and transparent light stabilizer solution.

[0049] The prepared light stabilizer is a light yellow, transparent liquid with a viscosity of 250-350 mPa·s (25°C), a density of 1.06-1.12 g / cm³, and a pH of 7.0-8.0. The recommended dosage of this light stabilizer for automotive coatings is 0.8-2.5% of the total coating weight; in this example, the dosage is 1.3%. Example 4

[0050] A synergistic compound light stabilizer for automotive coatings, comprising the following components in percentage by weight: 45% hindered amine light stabilizer (HALS); 25% ultraviolet absorber; 12% surface-modified nano-cerium dioxide; 7% hyperbranched polyester anti-migration agent; and 11% solvent.

[0051] The hindered amine light stabilizer uses a hybrid HALS, comprising bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate and poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidinylethanol) succinate, in a mass ratio of 3:2. This hybrid HALS can adapt to coating systems with different pH values, providing a wider range of applications.

[0052] The UV absorber is a mixture of benzotriazoles and triazines in a mass ratio of 1:1.5. The benzotriazole is 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole, and the triazine is 2,4-bis(2,4-dimethylphenyl)-6-(2-hydroxy-4-methoxyphenyl)-1,3,5-triazine. This combination provides excellent UV absorption and durability.

[0053] The surface-modified nano-cerium dioxide (SS-CE420) has a particle size of 25 nm and is coated with a 3-glycidyloxypropyltrimethoxysilane coupling agent. This coupling agent contains epoxy groups that react with the coating resin, improving the fixation and dispersion stability of the nanoparticles in the coating.

[0054] The hyperbranched polyester anti-migration additive is a mixed hydroxyl and ester-terminated hyperbranched polyester (Boltorn H30 and BIS-MPA polyester-64-hydroxy, in a 1:1 weight ratio). It has a molecular weight of 3500-4500 and a hydroxyl value of 80-120 mgKOH / g. This additive fixes the light stabilizer through multiple mechanisms, including hydrogen bonding, compatibility, and some chemical bonding.

[0055] The solvent used is a mixed solvent of cyclohexanone and propylene glycol methyl ether acetate (mass ratio 2:3). The mixed solvent has good dissolving ability and moderate volatilization rate and is suitable for various automotive coating systems.

[0056] The preparation method of the light stabilizer comprises the following steps: (1) Surface modification of nano-cerium dioxide: 36 g of nano-cerium dioxide was dispersed in 250 g of ethanol and ultrasonically treated for 40 minutes to form a uniform suspension; 10.8 g of 3-glycidyloxypropyltrimethoxysilane was added and refluxed at 68 °C for 5.5 hours; the mixture was centrifuged, washed with ethanol 4 times, and vacuum dried at 65 °C for 14 hours to obtain surface-modified nano-cerium dioxide.

[0057] (2) Multi-component high-speed shear dispersion: Dissolve 27g of tetramethylpiperidinyl quaternary ammonium salt HALS and 18g of N-alkoxypiperidine HALS, 10g of benzotriazole UV absorber and 15g of triazine UV absorber in 70g of mixed solvent and stir until completely dissolved; add 12g of surface-modified nano-cerium dioxide and disperse at high speed (speed 13000rpm) for 35 minutes; add 7g of hyperbranched polyester anti-migration agent and continue high-speed shear dispersion for 22 minutes to form a uniform dispersion system.

[0058] (3) Solvent adjustment and filtration: Add 41 g of mixed solvent to adjust the viscosity and stir evenly; filter through a 4 μm filter membrane to remove possible agglomerates to obtain a clear and transparent light stabilizer solution.

[0059] The prepared light stabilizer is a light yellow, transparent liquid with a viscosity of 220-320 mPa·s (25°C), a density of 1.04-1.09 g / cm³, and a pH of 6.8-7.8. The recommended dosage of this light stabilizer for automotive coatings is 1.2-3.0% of the total coating weight; in this example, the dosage was 2.2%. Example 5

[0060] A synergistic compound light stabilizer for automotive coatings, comprising the following components in percentage by weight: 35% hindered amine light stabilizer (HALS); 35% ultraviolet absorber; 8% surface-modified nano-cerium dioxide; 9% hyperbranched polyester anti-migration agent; and 13% solvent.

[0061] The hindered amine light stabilizer used is 2,2,6,6-tetramethyl-4-piperidinyl stearate, with a molecular weight of 500-1500. This type of HALS has excellent durability and thermal stability and is suitable for high-temperature baking and curing automotive coating systems.

[0062] The UV absorber is a mixture of benzotriazoles and triazines in a mass ratio of 1:2.5. The benzotriazole is 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)benzotriazole, and the triazine is 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[(octyl)oxy]-phenol. This combination provides broad-spectrum UV absorption, particularly enhanced absorption in the UVA region.

[0063] The surface-modified nano-cerium dioxide (SS-CE420) has a particle size of 15 nm and is coated with a vinyltrimethoxysilane coupling agent. The vinyl groups participate in polymerization during the coating curing process, firmly anchoring the nanoparticles within the coating network and enhancing the durability of the photostabilization effect.

[0064] Hyperbranched polyester anti-migration additives use amino-terminated hyperbranched polyester (Hyper N10) with a molecular weight of 1500-3500. This additive forms a network structure through a chemical reaction with the coating resin, effectively fixing the light stabilizer molecules and preventing their migration and loss.

[0065] The solvent used is a mixed solvent of ethyl acetate and acetone (mass ratio 4:1). This mixed solvent has good dissolving ability and a fast volatilization rate and is suitable for quick-drying automobile repair coatings.

[0066] The preparation method of the light stabilizer comprises the following steps: (1) Surface modification of nano-cerium dioxide: 24 g of nano-cerium dioxide was dispersed in 180 g of ethanol and ultrasonically treated for 38 minutes to form a uniform suspension; 7.2 g of vinyltrimethoxysilane was added and refluxed at 72 °C for 4.5 hours; the mixture was centrifuged, washed with ethanol three times, and vacuum dried at 55 °C for 13 hours to obtain surface-modified nano-cerium dioxide.

[0067] (2) Multi-component high-speed shear dispersion: Dissolve 35g of hindered amine light stabilizer, 10g of benzotriazole UV absorber and 25g of triazine UV absorber in 75g of mixed solvent and stir until completely dissolved; add 8g of surface-modified nano-cerium dioxide and disperse at high speed (speed 14000rpm) for 32 minutes; add 9g of hyperbranched polyester anti-migration aid and continue high-speed shear dispersion for 18 minutes to form a uniform dispersion system.

[0068] (3) Solvent adjustment and filtration: Add 55 g of mixed solvent to adjust the viscosity and stir evenly; filter through a 3.5 μm filter membrane to remove possible agglomerates to obtain a clear and transparent light stabilizer solution.

[0069] The prepared light stabilizer is a light yellow, transparent liquid with a viscosity of 180-280 mPa·s (25°C), a density of 1.02-1.07 g / cm³, and a pH of 6.5-7.5. The recommended dosage of this light stabilizer for automotive coatings is 1.0-2.8% of the total coating weight; in this example, the dosage was 1.9%. Comparative Example 1

[0070] The rest is the same as Implementation 1. The difference between Comparative Example 1 and Example 1 is that the components by mass percentage are: hindered amine light stabilizer (HALS) 70%; ultraviolet absorber 0; surface modified nano-cerium dioxide 10%; hyperbranched polyester anti-migration agent 8%; and solvent 12%. Comparative Example 2

[0071] The other steps are the same as those in Example 1. The difference between Comparative Example 2 and Example 1 is that the weight percentage components are: hindered amine light stabilizer (HALS) 0; ultraviolet absorber 70%; surface modified nano-cerium dioxide 10%; hyperbranched polyester anti-migration agent 8%; and solvent 12%. Comparative Example 3

[0072] The rest is the same as Implementation 3. The difference between Comparative Example 3 and Example 3 is that the weight percentage components are: hindered amine light stabilizer (HALS) 70%; ultraviolet absorber 0; surface modified nano-cerium dioxide 5%; hyperbranched polyester anti-migration aid 10%; solvent 15%.

[0073] The following are examples and comparative examples performance evaluation methods and results: Preparation of coating: The coatings of the above examples and comparative examples were sprayed on a steel plate already coated with electrophoretic paint, with a total film thickness of 100-120 μm. The outermost layer was a varnish cured layer, and the corresponding coating was obtained after baking.

[0074] Xenon arc aging test was performed according to standard SAE J2527.

[0075] The test results are shown in Table 1 below: Table 1 .

[0076] As shown in Table 1, the automotive coatings prepared in this example exhibit high gloss retention after film curing, with color variation within the standard range. Compared to the single light stabilizer used in the comparative example, the synergistic light stabilizer blended in this example significantly improves the anti-aging properties of the automotive coating, inhibiting pigment oxidation and resin degradation, and maintaining color vividness and surface gloss over the long term.

[0077] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0078] It should be noted that the above content merely illustrates the technical idea of ​​the present invention and cannot be used to limit the scope of protection of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications all fall within the scope of protection of the claims of the present invention.

Claims

1. A synergistic compounded light stabilizer for automotive coatings, characterized in that: Calculated by mass percentage, it includes the following components: Low molecular weight hindered amine light stabilizer 30-50%; UV absorber 20-40%; Surface modified nano-cerium dioxide 5-15%; Hyperbranched polyester anti-migration agent 5-10%; The balance is solvent.

2. The synergistic compounded light stabilizer for automotive coatings according to claim 1, characterized in that: The surface-modified nano-cerium dioxide is nano-cerium dioxide with a surface-coated silane coupling agent. The particle size of the surface-modified nano-cerium dioxide is 10-50 nm. The silane coupling agent is one of γ-aminopropyltriethoxysilane coupling agent, methyltrimethoxysilane coupling agent, octadecyltrimethoxysilane coupling agent, 3-glycidyloxypropyltrimethoxysilane coupling agent, and vinyltrimethoxysilane coupling agent.

3. The synergistic compounded light stabilizer for automotive coatings according to claim 1, characterized in that: The hyperbranched polyester anti-migration agent is one of hydroxyl-terminated hyperbranched polyester, ester-terminated hyperbranched polyester, epoxy-terminated hyperbranched polyester, hydroxyl- and ester-mixed hyperbranched polyester, and amino-terminated hyperbranched polyester.

4. The synergistic compounded light stabilizer for automotive coatings according to claim 1, characterized in that: The ultraviolet absorber is a mixture of a benzotriazole ultraviolet absorber and a triazine ultraviolet absorber in a mass ratio of 1:1 to 1:

3.

5. The synergistic compounded light stabilizer for automotive coatings according to claim 1, characterized in that: The triazole ultraviolet absorber is one of 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole, and 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)benzotriazole; the triazine ultraviolet absorber is 2,4,6-tris(2 ,4-dimethylphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-octyloxyphenyl)-1,3,5-triazine, 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-[(hexyl)oxy]-phenol, 2,4-bis(2,4-dimethylphenyl)-6-(2-hydroxy-4-methoxyphenyl)-1,3,5-triazine, 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-[(octyl)oxy]-phenol.

6. The synergistic compounded light stabilizer for automotive coatings according to claim 1, characterized in that: The hindered amine light stabilizer is one of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis(2,2,6,6-tetramethyl-4-piperidinyl) succinate, poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidinethanol) succinate, and 2,2,6,6-tetramethyl-4-piperidinyl stearate.

7. The synergistic compounded light stabilizer for automotive coatings according to claim 1, characterized in that: The solvent is one or a mixture of two of sec-butyl acetate, propylene glycol methyl ether acetate, n-butanol, propylene glycol methyl ether, butyl acetate, xylene, cyclohexanone, propylene glycol methyl ether acetate, ethyl acetate and acetone.

8. A method for preparing the synergistic compounded light stabilizer for automotive coatings according to any one of claims 1 to 7, characterized in that: The following steps are involved: Adding the pretreated nano-cerium dioxide to the silane coupling agent, stirring and reacting at 60-80° C. for 4-6 hours to obtain surface-modified nano-cerium dioxide; Add hindered amine light stabilizer, ultraviolet absorber, modified nano-cerium dioxide, and hyperbranched polyester anti-migration agent in sequence, and disperse by high-speed shearing to form a uniform dispersion system; Add solvent to adjust the viscosity, stir evenly and filter through a 3μm filter membrane to obtain a transparent light stabilizer solution with a viscosity of 150-350mPa·s, a density of 1.03-1.12g / cm³ and a pH value of 6.0-8.

0.

9. The method for preparing a synergistic compounded light stabilizer for automotive coatings according to claim 8, characterized in that: The pretreatment of nano-cerium dioxide in step (1) is as follows: dispersing the nano-cerium dioxide in an organic solvent, ultrasonically treating the organic solvent for 30 minutes to form a suspension, and obtaining pretreated nano-cerium dioxide. The organic solvent is one of ethanol, isopropanol, and toluene.

10. Use of the synergistic compounded light stabilizer according to any one of claims 1 to 7 in automotive coatings, characterized in that: The dosage of the synergistic compounded light stabilizer is 0.8-3.5% of the total amount of the automotive coating.