Method of making an ultraviolet resistant silk screen coating

Abstract

The present application relates to the technical field of coating, especially to a preparation method of anti-ultraviolet silk screen coating, comprising the following steps: adding deionized water, heating and stirring; adding nano titanium dioxide, zinc oxide and dispersing agent, high-speed dispersing to obtain nano particle dispersion liquid; mixing acrylic resin and polyurethane dispersion to obtain resin mixture; dissolving ultraviolet absorber and adding into the resin mixture, stirring; adding hindered amine light stabilizer, stirring; adding the nano particle dispersion liquid into the mixture, stirring and homogenizing; adding leveling agent and defoaming agent, stirring; adjusting solid content, filtering; vacuum degassing; filling and storing. The coating prepared by the method has excellent anti-ultraviolet performance, and various ultraviolet absorbers, light stabilizers and nano oxides are synergistically designed to achieve multiple protection mechanisms.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and in particular to a method for preparing UV-resistant screen printing coatings. Background Technology

[0002] In the modern printing and packaging industry, UV-resistant screen printing coatings play an increasingly important role. With rising demands for product appearance and durability, as well as increasing environmental awareness, the development of high-performance, environmentally friendly UV-resistant screen printing coatings has become an urgent industry need.

[0003] Traditional UV-resistant screen-printed coatings typically use a single type of UV absorber, such as benzotriazole compounds, to absorb and shield UV rays. However, this method often fails to provide full-spectrum UV protection and is prone to performance degradation over long-term use. Some improvements attempt to increase the amount of UV absorber to enhance protection, but this leads to new problems such as decreased coating transparency and increased costs.

[0004] On the other hand, most existing UV-resistant coatings use solvent-based systems. While these offer certain performance advantages, the emission of high volatile organic compounds (VOCs) remains a significant challenge for the industry. Water-based systems, although environmentally friendly, often fail to meet the demanding application requirements in terms of weather resistance, adhesion, and printability.

[0005] Furthermore, existing UV-resistant screen printing coatings also have shortcomings in terms of abrasion resistance, printability, and long-term stability. Especially in outdoor applications, coatings often struggle to simultaneously provide UV resistance and other physical and mechanical properties, leading to shorter product lifespans and failing to meet the growing market demands.

[0006] In view of the above problems, there is an urgent need to develop a new type of UV-resistant screen printing coating that can provide comprehensive UV protection while also possessing excellent abrasion resistance, printability, and long-term stability, and meeting environmental protection requirements. This invention is an innovative solution proposed to address this technical need. Summary of the Invention

[0007] In view of the above problems, there is an urgent need to develop a new type of UV-resistant screen printing coating that can provide comprehensive UV protection while also possessing excellent abrasion resistance, printability, and long-term stability, and meeting environmental protection requirements. This invention is an innovative solution proposed to address this technical need.

[0008] The purpose of this invention is to provide a method for preparing an anti-UV screen printing coating, comprising the following steps: (1) First, add 40-60 parts by weight of deionized water to the reaction vessel, heat to 30-35℃, and set the stirring speed to 300-400 rpm; (2) Next, slowly add 5-15 parts by weight of nano titanium dioxide, 3-10 parts by weight of nano zinc oxide and 1-3 parts by weight of dispersant to the solution obtained in step (1), increase the stirring speed to 800-1000 rpm, raise the temperature to 50-55℃, disperse at high speed for 30-40 minutes to obtain nanoparticle dispersion. (3) Then, mix 40-60 parts by weight of acrylic resin and 10-30 parts by weight of polyurethane dispersion in another reaction vessel, stirring at 300-400 rpm for 10-15 minutes at room temperature to obtain a resin mixture. (4) Next, dissolve 3-8 parts by weight of benzotriazole UV absorber and 2-6 parts by weight of triazine UV absorber in 3-8 parts by weight of ethylene glycol monobutyl ether, stir evenly and slowly add to the resin mixture obtained in step (3), and continue stirring for 15-20 minutes. (5) Further, dissolve 2-5 parts by weight of hindered amine light stabilizer in a small amount of ethylene glycol monobutyl ether, add it to the mixture obtained in step (4), and stir for 10-15 minutes; (6) Subsequently, the nanoparticle dispersion obtained in step (2) is slowly added to the mixture obtained in step (5), the stirring speed is increased to 600-800 rpm, the temperature is maintained at 45-50℃, and the mixture is stirred and homogenized for 30-40 minutes. (7) Next, add 0.5-2 parts by weight of leveling agent and 0.3-1 parts by weight of defoamer in sequence, reduce the stirring speed to 300-400 rpm, and continue stirring for 15-20 minutes; (8) Then, adjust the solid content to 30-35% with deionized water, stir evenly, and filter with a 100-mesh sieve; (9) Subsequently, the filtered coating was degassed under vacuum at -0.08 ~ -0.09 MPa for 15-20 minutes; (10) Finally, fill the defoamed paint into a clean, sealed container and store it at room temperature away from light.

[0009] Preferably, the acrylic resin is Joncryl 682 waterborne acrylic emulsion from BASF.

[0010] Preferably, the polyurethane dispersion is Bayhydrol U 2757 waterborne polyurethane dispersion from Bayer.

[0011] Preferably, the benzotriazole UV absorber is Tinuvin 11302 from BASF.

[0012] Preferably, the triazine-based ultraviolet absorber is Ciba's Tinuvin 400.

[0013] Preferably, the hindered amine light stabilizer is Tinuvin 292 from BASF.

[0014] Preferably, the nano-titanium dioxide is DuPont's Ti-Pure R-706.

[0015] Preferably, the nano zinc oxide is BASF's Z-Cote HP1.

[0016] Preferably, the dispersant is BYK's DISPERBYK-190.

[0017] Preferably, the leveling agent is BYK-378 from BYK Corporation, and the defoamer is Silbreak400 from Momentive Corporation.

[0018] The UV-resistant screen printing coating preparation method proposed in this invention ingeniously solves the above-mentioned problems. The innovation of this solution is mainly reflected in the following aspects: This invention, through a deep understanding of molecular structure, elemental properties, and functional group interactions, ingeniously integrates various UV absorbers, light stabilizers, and nano-oxides in a synergistic design to achieve multiple protective mechanisms. For example, benzotriazole and triazine UV absorbers contain conjugated systems in their molecular structures, enabling them to effectively absorb and convert UV energy; hindered amine light stabilizers contain nitric oxide radicals that can capture free radicals generated during photo-oxidation, blocking the photodegradation chain reaction; and nano-titanium dioxide and zinc oxide not only provide physical shielding, but their semiconductor properties may also produce photocatalytic effects, endowing the coating with self-cleaning capabilities.

[0019] From the perspective of molecular orbital theory and atomic theory, the synergistic effect of these components forms a multi-layered protective network: after absorbing photons, the π-electron system of the ultraviolet absorber releases energy in the form of heat through a rapid intramolecular deactivation process; the nitroxide radicals of the light stabilizer can react with highly reactive alkyl radicals to form stable alkoxyamines; and the valence band and conduction band structure of the nano-oxides enable them to absorb light of specific wavelengths and consume light energy through the formation and recombination of electron-hole pairs.

[0020] Furthermore, this invention fully utilizes the complementary properties of acrylic resin and polyurethane dispersion through the compounding of the two resins. Acrylic resin provides excellent weather resistance and hardness, while polyurethane dispersion imparts good flexibility and adhesion to the coating. This compounding is not merely a physical mixing, but rather a process of mutual penetration and entanglement at the molecular level, forming a unique network structure that greatly improves the overall performance of the coating.

[0021] In terms of the preparation process, this invention employs a meticulously designed multi-step process to ensure the full dispersion and uniform mixing of each component. In particular, the pre-dispersion process of the nano-oxides, through high-speed shearing and temperature control, effectively prevents the aggregation of nanoparticles, ensuring the transparency and uniformity of the coating. This process design not only optimizes the coating performance but also improves the repeatability and stability of production.

[0022] An unexpected technical effect of this invention is that it significantly improves the printability of the coating while enhancing its UV resistance. This is likely due to the synergistic effect between functional additives (such as leveling agents and defoamers) and other components, which optimizes the rheological properties and surface tension of the coating, thereby resulting in excellent leveling and pattern accuracy during printing.

[0023] Another notable effect is the coating's self-cleaning ability. This likely stems from the photocatalytic effect of nano-titanium dioxide and zinc oxide under ultraviolet light, which decomposes organic contaminants adsorbed on the surface, keeping the coating clean. This property has significant practical implications for printed materials exposed to outdoor environments for extended periods.

[0024] In summary, this invention successfully addresses multiple technical challenges faced by traditional UV-resistant screen printing coatings through the synergistic design of multiple components and an innovative preparation process. It not only achieves excellent UV resistance, abrasion resistance, and printability but also meets environmental requirements, providing a new technological path for the sustainable development of the industry. This comprehensive performance improvement and environmentally friendly characteristics make this invention significantly innovative and practical in the field of UV-resistant screen printing coatings, and it is expected to drive the entire industry towards higher quality and more environmentally friendly development. Detailed Implementation

[0025] Example 1 This embodiment provides a method for preparing an anti-UV screen printing coating, the components and preparation method of which are as follows: Components: 40 parts by weight of acrylic resin (BASF's Joncryl 682 waterborne acrylic emulsion); 10 parts by weight of polyurethane dispersion (Bayhydrol U 2757 waterborne polyurethane dispersion from Bayer). 3 parts by weight of benzotriazole UV absorber (BASF's Tinuvin 1130); 2 parts by weight of triazine UV absorber (Ciba's Tinuvin 400); 2 parts by weight of hindered amine light stabilizer (BASF's Tinuvin 292); 5 parts by weight of nano titanium dioxide (DuPont's Ti-Pure R-706); 3 parts by weight of nano zinc oxide (BASF's Z-Cote HP1); Dispersant (BYK's DISPERBYK-190) 1 part by weight; Leveling agent (BYK-378 from BYK Corporation) 0.5 parts by weight; Defoamer (Silbreak 400 from Momentive) 0.3 parts by weight; 3 parts by weight of ethylene glycol monobutyl ether; 90.2 parts by weight of deionized water; The preparation method includes the following steps: First, in a 5L four-necked flask equipped with a stirrer, thermometer, and reflux condenser, add 40 parts by weight of deionized water, heat to 30°C, and set the stirring speed to 300 rpm. Next, slowly add 5 parts by weight of nano-titanium dioxide and 3 parts by weight of nano-zinc oxide to the above solution, along with 1 part by weight of dispersant. Increase the stirring speed to 800 rpm, raise the temperature to 50°C, and disperse at high speed for 30 minutes.

[0026] Then, in another 2L reactor, 40 parts by weight of acrylic resin and 10 parts by weight of polyurethane dispersion were added and mixed at 300 rpm for 10 minutes at room temperature. Next, 3 parts by weight of benzotriazole UV absorber and 2 parts by weight of triazine UV absorber were dissolved in 3 parts by weight of ethylene glycol monobutyl ether, stirred evenly, and then slowly added to the resin system, and stirring was continued for 15 minutes.

[0027] Further, 2 parts by weight of hindered amine light stabilizer were dissolved in a small amount of ethylene glycol monobutyl ether and added to the above mixture, and stirred for 10 minutes. Subsequently, the nanoparticle dispersion was slowly added to the above mixture, the stirring speed was increased to 600 rpm, the temperature was maintained at 45°C, and the mixture was stirred and homogenized for 30 minutes.

[0028] Next, add 0.5 parts by weight of leveling agent and 0.3 parts by weight of defoamer, reduce the stirring speed to 300 rpm, and continue stirring for 15 minutes. Then, adjust the solid content to 30% with deionized water, stir evenly, and filter through a 100-mesh sieve.

[0029] Finally, the filtered coating is placed in a vacuum degassing device and degassed at -0.08 MPa for 15 minutes. The degassed coating is then filled into clean, sealed containers and stored at room temperature away from light.

[0030] Preferably, in the embodiments of the present invention, the blending of acrylic resin and polyurethane dispersion improves the flexibility and weather resistance of the coating while maintaining good printability. The combination of benzotriazole and triazine UV absorbers provides broad-spectrum UV protection, covering both UVA and UVB bands, while hindered amine light stabilizers extend the coating life by capturing free radicals, forming complementary protection with the UV absorbers. Nano-titanium dioxide and nano-zinc oxide not only provide physical shielding but also catalytically decompose organic pollutants, enhancing the coating's self-cleaning ability.

[0031] Example 2 This embodiment provides another method for preparing an anti-UV screen printing coating, the components and preparation method of which are as follows: Components: Acrylic resin 60 parts by weight; polyurethane dispersion 30 parts by weight; benzotriazole UV absorber 8 parts by weight; triazine UV absorber 6 parts by weight; hindered amine light stabilizer 5 parts by weight; nano titanium dioxide 15 parts by weight; nano zinc oxide 10 parts by weight; dispersant 3 parts by weight; leveling agent 2 parts by weight; defoamer 1 part by weight; ethylene glycol monobutyl ether 8 parts by weight; deionized water balance to 71.5 parts by weight; The preparation method includes the following steps: First, add 60 parts by weight of deionized water to the reaction vessel, heat to 35°C, and set the stirring speed to 400 rpm. Second, slowly add 15 parts by weight of nano-titanium dioxide, 10 parts by weight of nano-zinc oxide, and 3 parts by weight of dispersant to the solution, increase the stirring speed to 1000 rpm, raise the temperature to 55°C, and disperse at high speed for 40 minutes to obtain a nanoparticle dispersion.

[0032] Then, in another reaction vessel, 60 parts by weight of acrylic resin and 30 parts by weight of polyurethane dispersion were mixed at 400 rpm for 15 minutes at room temperature to obtain a resin mixture. Next, 8 parts by weight of benzotriazole UV absorber and 6 parts by weight of triazine UV absorber were dissolved in 8 parts by weight of ethylene glycol monobutyl ether, stirred until homogeneous, and then slowly added to the resin mixture, and stirring was continued for 20 minutes.

[0033] Further, 5 parts by weight of hindered amine light stabilizer were dissolved in a small amount of ethylene glycol monobutyl ether and added to the above mixture, and stirred for 15 minutes. Subsequently, the nanoparticle dispersion was slowly added to the mixture, the stirring speed was increased to 800 rpm, the temperature was maintained at 50°C, and the mixture was stirred and homogenized for 40 minutes.

[0034] Next, add 2 parts by weight of leveling agent and 1 part by weight of defoamer, reduce the stirring speed to 400 rpm, and continue stirring for 20 minutes. Then, adjust the solid content to 35% with deionized water, stir evenly, and filter through a 100-mesh sieve.

[0035] Finally, the filtered coating was degassed under vacuum at -0.09 MPa for 20 minutes, and the degassed coating was then filled into a clean, sealed container and stored at room temperature away from light.

[0036] Preferably, this embodiment increases the amount of acrylic resin and polyurethane dispersion, as well as the content of ultraviolet absorbers and light stabilizers. This formulation design can further improve the weather resistance and UV resistance of the coating. Simultaneously, the increased content of nano-oxides enhances the physical shielding effect of the coating, which is beneficial for improving the long-term stability of the coating.

[0037] Example 3 This embodiment provides a third method for preparing an anti-UV screen printing coating, the components and preparation method of which are as follows: Components: 50 parts by weight of acrylic resin; 20 parts by weight of polyurethane dispersion; 5.5 parts by weight of benzotriazole UV absorber; 4 parts by weight of triazine UV absorber; 3.5 parts by weight of hindered amine light stabilizer; 10 parts by weight of nano titanium dioxide; 6.5 parts by weight of nano zinc oxide; 2 parts by weight of dispersant; 1.25 parts by weight of leveling agent; 0.65 parts by weight of defoamer; 5.5 parts by weight of ethylene glycol monobutyl ether. 81.6 parts by weight of deionized water The preparation method includes the following steps: First, 50 parts by weight of deionized water were added to the reaction vessel, and the temperature was raised to 32.5°C. The stirring speed was set to 350 rpm. Next, 10 parts by weight of nano-titanium dioxide, 6.5 parts by weight of nano-zinc oxide, and 2 parts by weight of dispersant were slowly added to the solution. The stirring speed was increased to 900 rpm, the temperature was raised to 52.5°C, and high-speed dispersion was carried out for 35 minutes to obtain a nanoparticle dispersion.

[0038] Then, in another reaction vessel, 50 parts by weight of acrylic resin and 20 parts by weight of polyurethane dispersion were mixed at 350 rpm for 12.5 minutes at room temperature to obtain a resin mixture. Next, 5.5 parts by weight of benzotriazole UV absorber and 4 parts by weight of triazine UV absorber were dissolved in 5.5 parts by weight of ethylene glycol monobutyl ether, stirred until homogeneous, and then slowly added to the resin mixture, and stirring was continued for 17.5 minutes.

[0039] Further, 3.5 parts by weight of hindered amine light stabilizer were dissolved in a small amount of ethylene glycol monobutyl ether and added to the above mixture, and stirred for 12.5 minutes. Subsequently, the nanoparticle dispersion was slowly added to the mixture, the stirring speed was increased to 700 rpm, the temperature was maintained at 47.5°C, and the mixture was stirred and homogenized for 35 minutes.

[0040] Next, add 1.25 parts by weight of leveling agent and 0.65 parts by weight of defoamer, reduce the stirring speed to 350 rpm, and continue stirring for 17.5 minutes. Then, adjust the solid content to 32.5% with deionized water, stir evenly, and filter through a 100-mesh sieve.

[0041] Finally, the filtered coating was degassed under vacuum at -0.085 MPa for 17.5 minutes, and the degassed coating was filled into a clean, sealed container and stored at room temperature away from light.

[0042] Preferably, this embodiment uses intermediate values ​​for each component to balance the various properties of the coating. This formulation design can ensure the coating's UV resistance while also considering cost and processability. In particular, the coating performance can be optimized by adjusting the proportions of nano-oxides, UV absorbers, and light stabilizers.

[0043] Example 4 This embodiment provides a fourth method for preparing an anti-UV screen printing coating, the components and preparation method of which are as follows: Components: 55 parts by weight of acrylic resin; 25 parts by weight of polyurethane dispersion; 7 parts by weight of benzotriazole ultraviolet absorber; 5 parts by weight of triazine ultraviolet absorber; 4 parts by weight of hindered amine light stabilizer; 12 parts by weight of nano-titanium dioxide; 8 parts by weight of nano zinc oxide; 2.5 parts by weight of dispersant; Leveling agent 1.5 parts by weight; 0.8 parts by weight of defoamer; 6.5 parts by weight of ethylene glycol monobutyl ether; 74.7 parts by weight of deionized water.

[0044] The preparation method includes the following steps: First, 55 parts by weight of deionized water were added to the reaction vessel, and the temperature was raised to 33°C. The stirring speed was set to 375 rpm. Next, 12 parts by weight of nano-titanium dioxide, 8 parts by weight of nano-zinc oxide, and 2.5 parts by weight of dispersant were slowly added to the solution. The stirring speed was increased to 950 rpm, the temperature was raised to 53°C, and high-speed dispersion was carried out for 37 minutes to obtain a nanoparticle dispersion.

[0045] Then, in another reaction vessel, 55 parts by weight of acrylic resin and 25 parts by weight of polyurethane dispersion were mixed at 375 rpm for 13 minutes at room temperature to obtain a resin mixture. Next, 7 parts by weight of benzotriazole UV absorber and 5 parts by weight of triazine UV absorber were dissolved in 6.5 parts by weight of ethylene glycol monobutyl ether, stirred until homogeneous, and then slowly added to the resin mixture, and stirring was continued for 18 minutes.

[0046] Further, 4 parts by weight of hindered amine light stabilizer were dissolved in a small amount of ethylene glycol monobutyl ether and added to the above mixture, and stirred for 13 minutes. Subsequently, the nanoparticle dispersion was slowly added to the mixture, the stirring speed was increased to 750 rpm, the temperature was maintained at 48°C, and the mixture was stirred and homogenized for 37 minutes.

[0047] Next, add 1.5 parts by weight of leveling agent and 0.8 parts by weight of defoamer in sequence, reduce the stirring speed to 375 rpm, and continue stirring for 18 minutes. Then, adjust the solid content to 33% with deionized water, stir evenly, and filter through a 100-mesh sieve.

[0048] Finally, the filtered coating was degassed under vacuum at -0.087 MPa for 18 minutes, and the degassed coating was filled into a clean, sealed container and stored at room temperature away from light.

[0049] Preferably, this embodiment uses upper-middle values ​​for each component to further optimize coating performance. This formulation design improves the coating's flexibility and weather resistance by increasing the proportion of acrylic resin and polyurethane dispersion. Simultaneously, appropriately increasing the content of UV absorbers and light stabilizers enhances the coating's UV resistance. Furthermore, adjusting the nano-oxide content helps balance the coating's physical shielding effect and transparency.

[0050] In embodiments of the present invention, the use of a dispersant ensures stable dispersion of nanoparticles in the system, preventing agglomeration and thus guaranteeing the transparency and protective effect of the coating. The addition of leveling agents and defoamers improves the printability and appearance quality of the coating. In particular, by adjusting the amount of these functional additives, the processing performance and final appearance of the coating can be further optimized.

[0051] It is worth noting that this invention employs an aqueous system, effectively reducing VOC emissions and meeting environmental protection requirements. Simultaneously, the addition of ethylene glycol monobutyl ether optimizes the drying characteristics of the coating, contributing to improved film-forming quality and printability. This aqueous system design not only meets environmental requirements but also achieves a comprehensive improvement in coating performance through the careful selection of solvent components.

[0052] Comparative Example 1: Single UV Absorber Formulation This comparative example aims to demonstrate the superiority of the synergistic use of multiple ultraviolet absorbers in this invention. The components and preparation methods are as follows: Components: 50 parts by weight of acrylic resin 20 parts by weight of polyurethane dispersion 9.5 parts by weight of benzotriazole UV absorber 3.5 parts by weight of hindered amine light stabilizer 10 parts by weight of nano titanium dioxide 6.5 parts by weight of nano zinc oxide 2 parts by weight of dispersant Leveling agent 1.25 parts by weight 0.65 parts by weight of defoamer 5.5 parts by weight of ethylene glycol monobutyl ether 91.1 parts by weight of deionized water The preparation method includes the following steps: First, 91.1 parts by weight of deionized water were added to the reaction vessel, and the temperature was raised to 32.5°C. The stirring speed was set to 350 rpm. Next, 10 parts by weight of nano-titanium dioxide, 6.5 parts by weight of nano-zinc oxide, and 2 parts by weight of dispersant were slowly added to the solution. The stirring speed was increased to 900 rpm, the temperature was raised to 52.5°C, and high-speed dispersion was carried out for 35 minutes to obtain a nanoparticle dispersion.

[0053] Then, in another reaction vessel, 50 parts by weight of acrylic resin and 20 parts by weight of polyurethane dispersion were mixed at 350 rpm for 12.5 minutes at room temperature to obtain a resin mixture. Next, 9.5 parts by weight of benzotriazole UV absorber were dissolved in 5.5 parts by weight of ethylene glycol monobutyl ether, stirred until homogeneous, and then slowly added to the resin mixture, with stirring continued for 17.5 minutes.

[0054] Further, 3.5 parts by weight of hindered amine light stabilizer were dissolved in a small amount of ethylene glycol monobutyl ether and added to the above mixture, and stirred for 12.5 minutes. Subsequently, the nanoparticle dispersion was slowly added to the mixture, the stirring speed was increased to 700 rpm, the temperature was maintained at 47.5°C, and the mixture was stirred and homogenized for 35 minutes.

[0055] Next, add 1.25 parts by weight of leveling agent and 0.65 parts by weight of defoamer, reduce the stirring speed to 350 rpm, and continue stirring for 17.5 minutes. Then, adjust the solid content to 32.5% with deionized water, stir evenly, and filter through a 100-mesh sieve.

[0056] Finally, the filtered coating was degassed under vacuum at -0.085 MPa for 17.5 minutes, and the degassed coating was filled into a clean, sealed container and stored at room temperature away from light.

[0057] Comparative Example 2: Formulation without Nano-Oxides This comparative example aims to demonstrate the importance of nano-oxides in providing physical shielding and self-cleaning capabilities. Its components and preparation method are as follows: Components: 50 parts by weight of acrylic resin 20 parts by weight of polyurethane dispersion 5.5 parts by weight of benzotriazole UV absorber 4 parts by weight of triazine ultraviolet absorber 3.5 parts by weight of hindered amine light stabilizer 2 parts by weight of dispersant Leveling agent 1.25 parts by weight 0.65 parts by weight of defoamer 5.5 parts by weight of ethylene glycol monobutyl ether 107.6 parts by weight of deionized water The preparation method includes the following steps: First, 50 parts by weight of acrylic resin and 20 parts by weight of polyurethane dispersion were mixed in a reaction vessel at a stirring speed of 350 rpm for 12.5 minutes at room temperature to obtain a resin mixture. Next, 5.5 parts by weight of benzotriazole UV absorber and 4 parts by weight of triazine UV absorber were dissolved in 5.5 parts by weight of ethylene glycol monobutyl ether, stirred until homogeneous, and then slowly added to the resin mixture. Stirring was continued for 17.5 minutes.

[0058] Next, dissolve 3.5 parts by weight of the hindered amine light stabilizer in a small amount of ethylene glycol monobutyl ether, add it to the above mixture, and stir for 12.5 minutes. Then, add 2 parts by weight of the dispersant and stir until homogeneous.

[0059] Next, add 1.25 parts by weight of leveling agent and 0.65 parts by weight of defoamer, reduce the stirring speed to 350 rpm, and continue stirring for 17.5 minutes. Then, adjust the solid content to 32.5% with 107.6 parts by weight of deionized water, stir evenly, and filter through a 100-mesh sieve.

[0060] Finally, the filtered coating was degassed under vacuum at -0.085 MPa for 17.5 minutes, and the degassed coating was filled into a clean, sealed container and stored at room temperature away from light.

[0061] Comparative Example 3: Formulation without light stabilizer This comparative example aims to demonstrate the importance of light stabilizers in extending coating life. Its components and preparation method are as follows: Components: 50 parts by weight of acrylic resin 20 parts by weight of polyurethane dispersion 5.5 parts by weight of benzotriazole UV absorber 4 parts by weight of triazine ultraviolet absorber 10 parts by weight of nano titanium dioxide 6.5 parts by weight of nano zinc oxide 2 parts by weight of dispersant Leveling agent 1.25 parts by weight 0.65 parts by weight of defoamer 5.5 parts by weight of ethylene glycol monobutyl ether 94.6 parts by weight of deionized water The preparation method is basically the same as in Example 3, but the step of adding hindered amine light stabilizers is omitted, and the amount of deionized water is adjusted accordingly.

[0062] Comparative Example 4: Single Resin Formulation This comparative example aims to demonstrate the superiority of the combination of acrylic resin and polyurethane dispersion. Its components and preparation method are as follows: Components: 70 parts by weight of acrylic resin 5.5 parts by weight of benzotriazole UV absorber 4 parts by weight of triazine ultraviolet absorber 3.5 parts by weight of hindered amine light stabilizer 10 parts by weight of nano titanium dioxide 6.5 parts by weight of nano zinc oxide 2 parts by weight of dispersant Leveling agent 1.25 parts by weight 0.65 parts by weight of defoamer 5.5 parts by weight of ethylene glycol monobutyl ether 91.1 parts by weight of deionized water The preparation method is basically the same as in Example 3, but the amount of acrylic resin is increased to 70 parts by weight, and the step of adding polyurethane dispersion is omitted.

[0063] Comparative Example 5: High-content nano-oxide formulation This comparative example aims to demonstrate the importance of an appropriate amount of nano-oxide. Its composition and preparation method are as follows: Components: 50 parts by weight of acrylic resin 20 parts by weight of polyurethane dispersion 5.5 parts by weight of benzotriazole UV absorber 4 parts by weight of triazine ultraviolet absorber 3.5 parts by weight of hindered amine light stabilizer 20 parts by weight of nano titanium dioxide 15 parts by weight of nano zinc oxide 3 parts by weight of dispersant Leveling agent 1.25 parts by weight 0.65 parts by weight of defoamer 5.5 parts by weight of ethylene glycol monobutyl ether 71.6 parts by weight of deionized water The preparation method is basically the same as in Example 3, but the amount of nano titanium dioxide and nano zinc oxide is increased, and the amount of dispersant and deionized water is adjusted accordingly.

[0064] Comparative Example 6: Formulation without functional additives This comparative example aims to demonstrate the importance of functional additives in improving coating performance. Its components and preparation method are as follows: Components: 50 parts by weight of acrylic resin 20 parts by weight of polyurethane dispersion 5.5 parts by weight of benzotriazole UV absorber 4 parts by weight of triazine ultraviolet absorber 3.5 parts by weight of hindered amine light stabilizer 10 parts by weight of nano titanium dioxide 6.5 parts by weight of nano zinc oxide 5.5 parts by weight of ethylene glycol monobutyl ether 95.5 parts by weight of deionized water The preparation method is basically the same as in Example 3, but the steps of adding dispersant, leveling agent and defoamer are omitted, and the amount of deionized water is adjusted accordingly.

[0065] To comprehensively evaluate the effectiveness and superiority of the UV-resistant screen printing coating preparation method of this invention, a series of test experiments were designed. These experiments covered multiple aspects, including the coating's UV resistance, weather resistance, printability, and physical and mechanical properties. The detailed test methods and results analysis are as follows: 1. UV resistance performance test Test Method: The QUV accelerated aging tester from Q-Lab was used, and the test was conducted according to ASTM G154 standard. The coated samples were exposed to a UVA-340 lamp and subjected to 8 hours of UV irradiation (60°C) and 4 hours of condensation (50°C) in cycles. The yellowing index (YI) and gloss retention of the samples were tested every 500 hours.

[0066] Test results: Table 1. Results of UV resistance test

[0067] 2. Abrasion resistance test Test method: The abrasion resistance tester was used, and the test was conducted according to ASTM D4060 standard. A CS-10 grinding wheel was used, and a load of 500g was applied to test the weight loss after 1000 cycles.

[0068] Test results: Table 2. Abrasion resistance test results

[0069] 3. Printability test Test method: An automatic screen printing machine was used with a 300-mesh polyester screen, and the printing speed was set to 30 times / minute. The leveling properties of the coating, screen openness, and pattern accuracy were evaluated.

[0070] Test results: Table 3. Printability Test Results

[0071] 4. Adhesion test Test method: Perform cross-scratch test according to ASTM D3359 standard. Use a blade to scratch a 10x10 grid on the coating surface, apply tape, and then quickly peel it off to observe the peeling.

[0072] Test results: Table 4. Adhesion Test Results

[0073] Based on the above test results, the following conclusions can be drawn: 1. UV Resistance: Examples 1-4 all exhibited excellent UV resistance, with a significantly lower yellowing index after 1500 hours of aging compared to the comparative example, and a gloss retention rate exceeding 90%. This demonstrates that the synergistic effect of various UV absorbers, light stabilizers, and nano-oxides effectively improved the coating's UV resistance.

[0074] 2. Abrasion Resistance: The abrasion resistance of Examples 1-4 is significantly better than most comparative examples, especially Example 4, which performs best. This indicates that the combination of acrylic resin and polyurethane dispersion, as well as the addition of nano-oxide, significantly improves the abrasion resistance of the coating.

[0075] 3. Printability: Examples 1-4 all demonstrated excellent performance in terms of leveling, screen opening, and pattern accuracy, especially Example 4. This demonstrates the importance of functional additives (such as leveling agents and defoamers) and the positive impact of overall formulation optimization on printability.

[0076] 4. Adhesion: Examples 2 and 4 achieved the highest 5B adhesion rating, and other examples also performed well. This indicates that the resin compound and the addition of nano-oxides effectively improved the adhesion between the coating and the substrate.

[0077] Best Example: Considering all performance indicators, Example 4 performs best and can be considered the best example of the present invention. It achieves optimal or near-optimal levels in terms of UV resistance, abrasion resistance, printability, and adhesion.

[0078] This invention exhibits the following unexpected technical effects: 1. Synergistic Effect: The combination of multiple UV absorbers, light stabilizers, and nano-oxides not only provides excellent UV resistance but also significantly improves the abrasion resistance of the coating. This synergistic effect goes beyond the simple additive effect of single components, indicating a complex interaction mechanism between the components.

[0079] 2. Balance between printability and weather resistance: Generally, improving the weather resistance of a coating sacrifices its printability. However, this invention successfully achieves a balance between the two through a carefully designed formulation and preparation process, which is a breakthrough in the field of UV-resistant screen printing coatings.

[0080] 3. Self-cleaning effect: Although not specifically tested, the synergistic effect of nano-titanium dioxide and nano-zinc oxide may endow the coating with a certain photocatalytic self-cleaning ability, which is of great significance for printed materials that are exposed to the outdoor environment for a long time.

[0081] 4. Environmental friendliness: As a water-based system, this invention not only reduces VOC emissions, but also surpasses traditional solvent-based coatings in various performance indicators, which is of great significance for promoting the industry towards green and environmentally friendly development.

[0082] 5. Broad-spectrum protection: By rationally combining different types of ultraviolet absorbers and light stabilizers, this invention achieves comprehensive protection against UVA and UVB. At the same time, the addition of light stabilizers can effectively capture free radicals, protecting the coating and substrate from multiple levels.

[0083] These unexpected technical effects stem from the unique formulation design and preparation process of this invention, reflecting in-depth mechanistic research and innovative thinking. Through the synergistic effect of multiple components, this invention not only solves the performance-processability contradiction faced by traditional UV-resistant coatings, but also achieves a qualitative leap in overall performance, opening up a new direction for the development of UV-resistant screen printing coatings.

[0084] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A method for preparing an anti-UV screen printing coating, characterized in that, Includes the following steps: (1) First, add 40-60 parts by weight of deionized water to the reaction vessel, heat to 30-35℃, and set the stirring speed to 300-400 rpm; (2) Next, slowly add 5-15 parts by weight of nano titanium dioxide, 3-10 parts by weight of nano zinc oxide and 1-3 parts by weight of dispersant to the solution obtained in step (1), increase the stirring speed to 800-1000 rpm, raise the temperature to 50-55℃, disperse at high speed for 30-40 minutes to obtain nanoparticle dispersion. (3) Then, mix 40-60 parts by weight of acrylic resin and 10-30 parts by weight of polyurethane dispersion in another reaction vessel, stirring at 300-400 rpm for 10-15 minutes at room temperature to obtain a resin mixture. (4) Next, dissolve 3-8 parts by weight of benzotriazole UV absorber and 2-6 parts by weight of triazine UV absorber in 3-8 parts by weight of ethylene glycol monobutyl ether, stir evenly and slowly add to the resin mixture obtained in step (3), and continue stirring for 15-20 minutes. (5) Further, dissolve 2-5 parts by weight of hindered amine light stabilizer in a small amount of ethylene glycol monobutyl ether, add it to the mixture obtained in step (4), and stir for 10-15 minutes; (6) Subsequently, the nanoparticle dispersion obtained in step (2) is slowly added to the mixture obtained in step (5), the stirring speed is increased to 600-800 rpm, the temperature is maintained at 45-50℃, and the mixture is stirred and homogenized for 30-40 minutes. (7) Next, add 0.5-2 parts by weight of leveling agent and 0.3-1 parts by weight of defoamer in sequence, reduce the stirring speed to 300-400 rpm, and continue stirring for 15-20 minutes; (8) Then, adjust the solid content to 30-35% with deionized water, stir evenly, and filter with a 100-mesh sieve; (9) Subsequently, the filtered coating was degassed under vacuum at -0.08 ~ -0.09 MPa for 15-20 minutes; (10) Finally, fill the defoamed paint into a clean, sealed container and store it at room temperature away from light.

2. The method for preparing an anti-UV screen printing coating according to claim 1, characterized in that, The acrylic resin is Joncryl 682 waterborne acrylic emulsion from BASF.

3. The method for preparing an anti-UV screen printing coating according to claim 1, characterized in that, The polyurethane dispersion is Bayhydrol U 2757 waterborne polyurethane dispersion from Bayer.

4. The method for preparing an anti-UV screen printing coating according to claim 1, characterized in that, The benzotriazole UV absorber is Tinuvin 11302 from BASF.

5. The method for preparing an anti-UV screen printing coating according to claim 1, characterized in that, The triazine-based ultraviolet absorber is Ciba's Tinuvin 400.

6. The method for preparing an anti-UV screen printing coating according to claim 1, characterized in that, The hindered amine light stabilizer is Tinuvin 292 from BASF.

7. The method for preparing an anti-UV screen printing coating according to claim 1, characterized in that, The nano-titanium dioxide is DuPont's Ti-Pure R-706.

8. The method for preparing an anti-UV screen printing coating according to claim 1, characterized in that, The nano zinc oxide is BASF's Z-Cote HP1.

9. The method for preparing an anti-UV screen printing coating according to claim 1, characterized in that, The dispersant is BYK's DISPERBYK-190.

10. The method for preparing an anti-UV screen printing coating according to claim 1, characterized in that, The leveling agent is BYK-378 from BYK Corporation, and the defoamer is Silbreak 400 from Momentive Corporation.

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