Water-based UV (ultraviolet) photocuring polyurethane acrylate coating as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of photocureable coatings, and particularly relates to a water-based UV photocureable polyurethane acrylate coating and a preparation method and application thereof, the water-based UV photocureable polyurethane acrylate coating is suitable for high-end coating occasions needing weather resistance and wear resistance, and particularly, fluorine-containing modified polyether polyol and silicon-containing polyether modified polyether polyol are cooperatively introduced into a polyurethane main chain, so that the water-based UV photocureable polyurethane acrylate coating is obtained. The weather resistance, the pollution resistance and the surface hydrophobicity of a coating film are effectively improved; and meanwhile, a synergistic light stabilization system compounded by an ultraviolet absorbent and a hindered amine light stabilizer is constructed, so that the ultraviolet aging resistance and yellowing resistance of the coating are remarkably enhanced. Furthermore, a high-functionality acrylate diluent is adopted to improve the crosslinking density of the coating, so that the coating film has excellent hardness and wear resistance, and the obtained water-based UV coating emulsion is uniform in particle size distribution, high in transparency and good in storage stability and has good multi-substrate adaptability and construction adaptability.

Description

Technical Field

[0001] The present invention belongs to the technical field of light-curing coatings, and specifically relates to a water-based UV light-curing polyurethane acrylate coating, a preparation method and an application thereof, which is suitable for high-end coating occasions requiring weather resistance and wear resistance. Background Art

[0002] With increasingly stringent environmental regulations and a growing emphasis on sustainable development, traditional solvent-based coatings with high VOC (volatile organic compound) emissions are being gradually restricted or phased out. Water-based and UV-curable coatings are becoming the mainstream choice in the coatings industry due to their environmental friendliness, high efficiency, and excellent performance. Water-based UV-curable polyurethane acrylate (WPUA) coatings, a combination of these two high-performance coating systems, are not only low in VOC, safe, environmentally friendly, and energy-efficient, but also widely used in mid- to high-end coating applications such as wood, plastics, metals, electronic components, and automotive interiors due to their excellent mechanical and film-forming properties.

[0003] However, most water-based UV-curable WPUA coatings currently on the market are susceptible to environmental factors such as ultraviolet radiation, water vapor erosion, and alternating hot and cold temperatures during long-term outdoor use, resulting in performance degradation issues such as yellowing, chalking, gloss loss, and decreased adhesion. These problems seriously affect the appearance and durability of the coatings, limiting the promotion of WPUA coatings in high-end outdoor applications. To improve the weather resistance and wear resistance of WPUA coatings, researchers have tried a variety of methods: First, simply adding a light stabilizer can delay the aging of the coating to a certain extent, but the effect is often limited and it is difficult to meet the needs of long-term outdoor use; second, increasing the content of hard acrylic monomers can increase the hardness of the coating, but it often leads to a decrease in flexibility, poor construction adaptability, and may even affect the adhesion and durability of the coating.

[0004] There are also studies in the prior art aimed at improving the performance of WPUA coatings, such as patent CN118931367A - a UV light-cured modified polyurethane acrylate water-based coating, which effectively solves the oxygen inhibition effect produced by the photopolymerization reaction by introducing thiol compounds and mixing them with two different oxygen-eliminating inhibition systems, glucose oxidase and glucose, thereby improving the polymerization rate and monomer conversion rate of UV light curing. However, this technology mainly focuses on solving the oxygen inhibition problem during UV curing, and has limited effect on improving the weather resistance and wear resistance of the coating; patent CN116970272A - A water-based polyurethane acrylate emulsion, a preparation method thereof, and a water-based UV high-gloss paint, which improve the leveling and fullness of the paint by optimizing the emulsion formula and preparation process, but also do not study the weather resistance and wear resistance of the paint; Patent CN106866912A - A UV-curable water-based polyurethane acrylate and a preparation method thereof, which improves the solid content and hardness of the paint by optimizing the prepolymer synthesis process and chain extension reaction. This technology also does not study and design the weather resistance and wear resistance of the paint, and it is difficult to meet the needs of high-end outdoor applications.

[0005] In summary, the existing water-based UV-curable WPUA coatings have not been studied for their weather resistance and abrasion resistance, making it difficult to meet the needs of long-term high-end outdoor applications. Therefore, a new technical solution is needed to solve the above technical problems. Summary of the Invention

[0006] The purpose of the present invention is to provide a water-based UV light-curing polyurethane acrylate coating and its preparation method and application, so as to solve the problems raised in the above background technology that the current water-based UV light-curing WPUA coating has not been studied for its weather resistance and wear resistance, making it difficult to meet the needs of long-term high-end outdoor applications.

[0007] To achieve the above object, the present invention adopts the following technical solutions: In the first aspect, the present invention provides a water-based UV light-curing polyurethane acrylate coating, comprising the following components in percentage by mass: 15-25% of a modified polyether polyol, 10-18% of an isocyanate component, 2-10% of a hydroxyl functional monomer, 1.5-3% of dimethylol propionic acid, 2-5% of a photoinitiator, 0.5-2% of an ultraviolet absorber, 0.2-1% of a hindered amine light stabilizer, 5-15% of a multifunctional acrylate diluent, and the balance being deionized water, wherein the modified polyether polyol is a mixture of one or more of a fluorine-containing modified polyether polyol and a silicon-containing modified polyether polyol, and the mass ratio of the ultraviolet absorber to the hindered amine light stabilizer is 2:1-4:1.

[0008] Furthermore, the fluorine-modified polyether polyol is a fluorinated polyether, the silicon-modified polyether polyol is a polyether-modified polysiloxane; the isocyanate component is one of isophorone diisocyanate, hexamethylene diisocyanate, and toluene diisocyanate; the hydroxyl functional monomer is one of hydroxyethyl methacrylate and hydroxypropyl methacrylate; the photoinitiator is 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy- The invention relates to a mixture of one or more of 2-methyl-1-propanone; the ultraviolet absorber is one of benzophenone, benzotriazole and triazine compounds; the hindered amine light stabilizer is a mixture of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate and 1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol, or one of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate; the multifunctional acrylate diluent is one or more of trimethylolpropane triacrylate, pentaerythritol triacrylate and bis(trimethylolpropane) tetraacrylate.

[0009] In a second aspect, the present invention provides a method for preparing a waterborne UV light-curing polyurethane acrylate coating, wherein the steps for preparing the waterborne UV light-curing polyurethane acrylate coating according to the above components are as follows: S1. First, a mixture of one or more of a fluorine-modified polyether polyol and a silicon-modified polyether polyol, an isocyanate component, and dimethylol propionic acid are reacted at 70-80° C. for 2-4 hours under the action of a catalyst. After the reaction, a hydroxyl functional monomer is added to introduce an acrylate end, and then the pH value is neutralized to neutral with triethylamine. Then, deionized water is slowly added under high-speed stirring to form a milky white emulsion, thereby obtaining a waterborne polyurethane prepolymer with a solid content of 30-40 wt%; S2. Under stirring, add ultraviolet absorber and hindered amine light stabilizer to the waterborne polyurethane prepolymer obtained in S1, continue stirring for 15 to 25 minutes, then cool to room temperature, add multifunctional acrylate diluent, stir and mix evenly, and then filter to obtain a waterborne polyurethane-acrylate composite coating, that is, a waterborne UV light-curing polyurethane acrylate coating.

[0010] In a third aspect, the present invention provides an application of a water-based UV light-curing polyurethane acrylate coating in ABS or metal sheets, comprising the following specific steps: uniformly applying the water-based UV light-curing polyurethane acrylate coating to the surface of the ABS or metal sheet by spraying, roller coating or flow coating, with a wet film thickness of 25 to 35 μm, and irradiating with a UV light source in the 365 to 405 nm band and an irradiation intensity of 600 to 1000 mW / cm² for 5 to 15 seconds to cure into a film.

[0011] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention significantly improves the weather resistance of waterborne UV light-curing polyurethane acrylate coatings by introducing the synergistic effect of fluorine-modified polyether polyols and silicon-modified polyether polyols. The fluorine-modified polyether polyols give the coating surface excellent hydrophobicity and low surface energy properties, effectively resisting ultraviolet radiation and water vapor erosion. The silicon-modified polyether polyols enhance the crosslinking density and cohesive strength of the coating, thereby improving the durability of the coating. The synergistic modification of the two enables the coating to maintain stable physical and chemical properties during long-term outdoor use, significantly extending the service life of the coating. On this basis, the addition of a multifunctional acrylate diluent further improves the crosslinking density of the coating. , thereby giving the coating higher hardness and wear resistance, while also effectively improving the coating's flexibility and impact resistance, so that the coating can effectively resist wear and cracking when subjected to mechanical friction or impact, maintaining the integrity and aesthetics of the coating; by carefully designing the mass ratio of UV absorber and hindered amine light stabilizer, a high-efficiency synergistic light stabilization system is constructed, which significantly improves the coating's anti-yellowing performance and durability, allowing the coating to maintain bright color and good gloss during long-term outdoor use. Through the design of the molecular structure, the coating's weather resistance, wear resistance and anti-yellowing performance are comprehensively improved, meeting the high-end coating field's demand for both environmental protection and performance. 2. The present invention adopts a two-step preparation process, namely, first preparing a waterborne polyurethane prepolymer, and then adding an ultraviolet absorber, a hindered amine light stabilizer, and a multifunctional acrylate diluent to this, to ultimately obtain a waterborne UV light-curing polyurethane acrylate coating. This process not only simplifies the preparation process and reduces production costs, but also improves production efficiency, which is conducive to the industrial production and application promotion of coatings. Through the optimized polyurethane prepolymer synthesis process and photoinitiator system ratio, the resulting waterborne UV coating emulsion has a uniform particle size distribution, high transparency, and good storage stability. It can be stored under sealed and light-proof conditions for three months without obvious sedimentation or particle size change, and at the same time has good adaptability to multiple substrates and construction. 3. The present invention uses a specific curing process and formula design to ensure that the resulting coating has excellent weather resistance and wear resistance. Even during long-term outdoor use, the coating can maintain stable physical and chemical properties, significantly extending the service life of the coating. On this basis, the introduction of a synergistic light stabilization system makes the coating less likely to yellow under ultraviolet light irradiation, maintaining the coating's bright color and good gloss. By using a UV light source in the 365-405nm band and an irradiation intensity of 600-1000mW / cm² for 5-15s, the coating can be rapidly cured to form a film. This not only has low energy consumption and high speed, which helps to reduce production costs and energy consumption, but also significantly shortens the production cycle and improves production efficiency. It is very suitable for industrial large-scale production. At the same time, it does not produce volatile organic compounds (VOCs), meets environmental protection requirements, and is beneficial to protecting the environment and human health. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a physical comparison diagram of Example 5 of the present invention and commercially available products A and B. DETAILED DESCRIPTION

[0013] The following examples are used to further illustrate the present invention but do not limit its application. The percentages in the following examples are by mass. Example 1:

[0014] This embodiment provides a water-based UV light-curing polyurethane acrylate coating, which has the following steps: First, 20% fluoropolyether (FPOE), 14% isophorone diisocyanate (IPDI), 3% hydroxypropyl methacrylate (HPMA), and 3% 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO) were selected as the components of a waterborne UV-curable polyurethane acrylate coating. This formulation did not include any silicon-containing modified components or light stabilizers, and its overall performance was primarily based on the improved weather resistance of the fluorine-modified coating. Secondly, 20% fluoropolyether, 14% isophorone diisocyanate, 3% hydroxypropyl methacrylate and catalyst dibutyltin dilaurate (DBTDL) were added to a four-necked flask and heated to 70-80°C. The mixture was reacted for 2-4 hours until the NCO content dropped to the theoretical value (about 4%). After cooling to 40-50°C, 3% hydroxypropyl methacrylate was added to introduce acrylate ends, and the mixture was neutralized with triethylamine to a pH of 7. Deionized water was slowly added under high-speed stirring to form a milky white emulsion, thus obtaining a waterborne polyurethane prepolymer (WPU prepolymer) with a solid content of 30-40wt%. Then, 3% 2,4,6-trimethylbenzoyl-diphenylphosphine oxide was added to the waterborne polyurethane prepolymer under stirring; stirring was continued for 15 to 25 minutes, and then the mixture was cooled to room temperature, and trimethylolpropane triacrylate (TMPTA) was added. After stirring and mixing, the mixture was filtered through a 400-mesh filter to obtain a waterborne polyurethane-acrylate composite coating (waterborne WPUA coating) with stable performance, i.e., a waterborne UV light-cured polyurethane acrylate coating. The obtained emulsion had an average particle size of 80 to 150 nm, and no obvious sedimentation or particle size change was observed after being sealed and stored away from light for 3 months. Finally, the prepared water-based UV light-curing polyurethane acrylate coating is evenly applied to the surface of ABS (acrylonitrile-butadiene-styrene copolymer) or metal plate by spraying, roller coating or flow coating, with a wet film thickness of 25 to 35 μm. It is then irradiated with a UV light source in the 365 to 405 nm band and an irradiation intensity of 600 to 1000 mW / cm² for 5 to 15 seconds to form a cured film. The resulting coating has excellent adhesion, transparency and wear resistance. Example 2:

[0015] This example is based on Example 1, except that 20% of the fluoropolyether is replaced with 20% of a polyether-modified polysiloxane (POE-siloxane) to improve the flexibility, scratch resistance, and self-cleaning properties of the coating. The isocyanate component is adjusted from IPDI to 16% of hexamethylene diisocyanate (HDI) to further improve the hardness and wear resistance of the coating. The hydroxy acrylate monomer uses 4% of hydroxyethyl methacrylate (HEMA), and the trifunctional diluent (trimethylolpropane triacrylate) is upgraded to 8% of tetrafunctional bis(trimethylolpropane) tetraacrylate (DiTMPTA) to enhance the crosslinking density of the coating. The photoinitiator is 3% of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Irgacure 819) to optimize the curing depth. This example does not contain fluorine-containing components or light stabilizers, and focuses on the effect of silicon modification on improving the performance of the coating. Example 3:

[0016] This embodiment is based on Example 2, and 10% fluoropolyether is added to the formula to form a fluorine-containing and silicon-containing synergistic modification system (10% each), which takes into account low surface energy and flexibility, and significantly improves the weather resistance and stability of the coating; the isocyanate content is adjusted to 15% IPDI, the hydroxyl monomer uses 3% HEMA, the diluent is adjusted to 8% trifunctional TMPTA, and the photoinitiator is 3% TPO; this formula has not yet added UV absorbers and hindered amine light stabilizers, and the performance mainly depends on the physical modification effect. Example 4:

[0017] This example, based on Example 3, further introduces 1.2% of a UV absorber benzotriazole (Tinuvin 400) and 0.4% of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (HALS 770) to construct a synergistic light stabilization system. This effectively blocks the energy of UV-B and part of the UV-A band in ultraviolet light, while scavenging free radicals, significantly improving the anti-yellowing and light aging stability of the coating. The photoinitiator is changed to a compound system of 2% TPO and 2% Irgacure 819, taking into account both surface and deep-layer curing effects. The diluent is adjusted to 6% TMPTA to balance hardness and flexibility. Example 5:

[0018] In this embodiment, based on Example 4, the ratio of fluorine-containing and silicon-containing polyether polyols is optimized to 12% and 10%, further improving the density and mechanical properties of the coating film; the ultraviolet absorber Tinuvin 400 and the hindered amine light stabilizer HALS 770 are increased to 1.5% and 0.5%, respectively, and the light stabilizer compounding ratio is 3:1, achieving the best anti-yellowing effect; the diluent is a compound of TMPTA and DiTMPTA, and the total amount is increased to 12%, improving the crosslinking density and scratch resistance; the isocyanate content is increased to 16% IPDI, and the photoinitiator compounding ratio is maintained at 2% TPO and 2% Irgacure 819; the coating composition of this embodiment has the best overall performance and fully meets the application requirements of environmentally friendly, highly weather-resistant coatings for outdoor plastic substrates.

[0019] The following is a comparative table of the formulation compositions of Examples 1-5 (mass percentage %): ; As can be seen from the above table, Example 5 is the best technical solution for the water-based UV light-curing polyurethane acrylate coating of the present invention.

[0020] The following is a comparison table of performance tests of Examples 1-5: ; The test methods in the above table are as follows: (1) Coating thickness Coating thickness was measured non-destructively using a dry film thickness gauge (BYK 4563) in accordance with GB / T13452.2-2008. Dry film thickness was measured at five randomly selected locations on each sample, and the average value was calculated. Test results are reported in microns (μm). Coating thickness was maintained within a range of (40 ± 5) μm to ensure accuracy and consistency in comparison data. (2) Yellowing resistance (Δb value) Accelerated aging tests were conducted using an artificial climate accelerated aging chamber (Q-Lab QUV / se) in accordance with GB / T 1865-2009, using UV-A340 lamps. The temperature was set at 60°C and the humidity was controlled at 50% RH for 500 hours. The b value of the coating was measured before and after aging using a spectrophotometer (Konica Minolta CM-700d), and the color change, Δb, was calculated. A smaller value indicates better yellowing resistance. (3) Glossiness change rate Measurements were performed using a gloss meter (BYK Gardner Micro-TRI-Gloss) at a 60° angle, in compliance with GB / T 9754-2007. The gloss values ​​of the coating were measured before and after aging, and the relative gloss retention was calculated. The smaller the gloss change, the greater the material's resistance to environmental factors and the better the decorative retention. (4) Pencil hardness In accordance with GB / T 6739-2006, an Elcometer 501 pencil hardness tester is used. The pencil is held at a 45° angle to the sample surface and uniform pressure is applied. The test is performed step by step from 6B to 9H, and the highest grade that does not leave a scratch on the film surface is recorded to indicate the scratch resistance of the coating. (5) Number of times the rubber is rubbed Using a Taber Abraser Model 5135 abrasion tester with a CS-10 wheel and a 1000g load, the test was performed in accordance with ASTM D4060-14. The number of cycles required for visible damage to the coating was recorded. A high number of abrasion cycles indicates excellent mechanical durability. (6) Adhesion The test was conducted using the cross-hatch method, according to GB / T 9286-1998. An Elcometer 107 cross-hatch cutter was used to create 100 cuts with a 1mm spacing. 3M tape was then applied and peeled off at a 90° angle. The peeled area was observed and the adhesion rating was assessed on a scale of 0 to 5, with higher ratings indicating better adhesion. (7) Flexibility Flexibility is measured using a TQC Sheen bend tester in accordance with GB / T 1732-1993. Wrap the dry coating sample around a cylinder and bend it 180°. Record the minimum bend radius without cracking or falling off (in mm). The better the flexibility, the smaller the minimum bend radius. (8) Water resistance According to GB / T 1733-2021, immersion tests were conducted on samples in a constant temperature and humidity chamber (model: SH-241). The samples were immersed in deionized water at a temperature of (23±2)°C for 168 hours. After immersion, the samples were dried and allowed to stand for 1 hour. Inspect for abnormalities such as bubbling, shedding, gloss loss, and discoloration. The extent of any changes was recorded and the water resistance rating was evaluated. Therefore, it can be seen from the above table that Examples 1-5 show a trend of gradually progressive performance improvement. Example 1, as a basic formula, has certain yellowing resistance and basic mechanical properties, but the overall performance is general; after Example 2 introduces silicon-containing polyether polyol, the hardness and friction resistance are improved; Example 3 realizes fluorosilicone synergistic modification, significantly reduces the Δb value and improves flexibility; Example 4 introduces ultraviolet absorbers and light stabilizers on the basis of synergistic modification, and the gloss retention and weather resistance are significantly improved; Example 5 is the optimal formula, taking into account appearance stability, durability and mechanical properties, and has the best comprehensive performance. The Δb value is controlled at 1.8, which is far better than other examples.

[0021] The following is a performance comparison table of the optimal solution of the present invention and commercially available products A and B: ; As can be seen from the table above, the preferred embodiment 5 of the present invention is superior to the two commercially available brand products A and B (such as Figure 1 As shown in the figure, it performs particularly well in terms of UV stability and mechanical properties, with adhesion reaching level 0, which greatly demonstrates the system's strong interface bonding and adaptability.

[0022] In summary, Examples 1-5 of the present invention effectively improve the comprehensive performance of water-based coatings by gradually optimizing the modification system (fluorine, silicon, synergy, and additive combination). They are suitable for industrial, architectural, and decorative applications that require high appearance durability, and have significant promotion value.

Claims

1. A water-based UV light-curing polyurethane acrylate coating, characterized in that: The invention comprises the following components in percentage by mass: 15-25% of modified polyether polyol, 10-18% of isocyanate component, 2-10% of hydroxyl functional monomer, 1.5-3% of dimethylol propionic acid, 2-5% of photoinitiator, 0.5-2% of ultraviolet absorber, 0.2-1% of hindered amine light stabilizer, 5-15% of multifunctional acrylate diluent, and the balance is deionized water, wherein the modified polyether polyol is a mixture of one or more of fluorine-containing modified polyether polyol and silicon-containing modified polyether polyol, and the mass ratio of ultraviolet absorber to hindered amine light stabilizer is 2:1-4:

1.

2. A water-based UV light-curing polyurethane acrylate coating according to claim 1, characterized in that: The fluorine-containing modified polyether polyol is a fluorinated polyether, and the silicon-containing modified polyether polyol is a polyether-modified polysiloxane.

3. The water-based UV light-curing polyurethane acrylate coating according to claim 1, characterized in that: The isocyanate component is one of isophorone diisocyanate, hexamethylene diisocyanate and toluene diisocyanate.

4. The water-based UV light-curing polyurethane acrylate coating according to claim 1, characterized in that: The hydroxyl functional monomer is one of hydroxyethyl methacrylate and hydroxypropyl methacrylate.

5. The water-based UV light-curing polyurethane acrylate coating according to claim 1, characterized in that: The photoinitiator is one of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propanone, or a mixture of several thereof.

6. The water-based UV light-curing polyurethane acrylate coating according to claim 1, characterized in that: The ultraviolet absorber is one of benzophenone, benzotriazole and triazine compounds.

7. The water-based UV light-curing polyurethane acrylate coating according to claim 1, characterized in that: The hindered amine light stabilizer is a mixture of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate and 1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol, or bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate.

8. The water-based UV light-curing polyurethane acrylate coating according to claim 1, characterized in that: The multifunctional acrylate diluent is one or a mixture of trimethylolpropane triacrylate, pentaerythritol triacrylate, and di(trimethylolpropane) tetraacrylate.

9. The method for preparing a water-based UV light-curing polyurethane acrylate coating according to any one of claims 1 to 8, characterized in that: The specific steps are as follows: S1. First, a mixture of one or more of a fluorine-modified polyether polyol and a silicon-modified polyether polyol, an isocyanate component, and dimethylol propionic acid are reacted at 70-80° C. for 2-4 hours under the action of a catalyst. After the reaction, a hydroxyl functional monomer is added to introduce an acrylate end, and then the pH value is neutralized to neutral with triethylamine. Then, deionized water is slowly added under high-speed stirring to form a milky white emulsion, thereby obtaining a waterborne polyurethane prepolymer with a solid content of 30-40 wt%; S2. Under stirring, add ultraviolet absorber and hindered amine light stabilizer to the waterborne polyurethane prepolymer obtained in S1, continue stirring for 15 to 25 minutes, then cool to room temperature, add multifunctional acrylate diluent, stir and mix evenly, and then filter to obtain a waterborne polyurethane-acrylate composite coating, that is, a waterborne UV light-curing polyurethane acrylate coating.

10. The use of the waterborne UV light-curing polyurethane acrylate coating according to any one of claims 1 to 8 on ABS or metal sheets, comprising the following specific steps: uniformly applying the waterborne UV light-curing polyurethane acrylate coating to the surface of the ABS or metal sheet by spraying, roller coating, or curtain coating, with a wet film thickness of 25 to 35 μm, and irradiating the surface with a UV light source having a wavelength of 365 to 405 nm and an irradiation intensity of 600 to 1000 mW / cm² for 5 to 15 seconds to cure the surface.

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