Fluorine-free environment-friendly anti-fouling and anti-skid sand-textured powder coating and preparation method thereof

Abstract

This invention relates to the field of powder coating technology, specifically to a fluorine-free, environmentally friendly, stain-resistant, anti-slip, and textured powder coating and its preparation method. The powder coating is composed of carboxyl-terminated polyester resin, bisphenol A type epoxy resin, modified nano-zinc oxide, polyethylene microwax powder, and PDMS-coated silica, among other raw materials. During preparation, the terminal carboxyl groups of the carboxyl-terminated polyester resin can undergo a grafting reaction with the active groups on the modified nano-zinc oxide, improving the dispersibility of the nanoparticles. During coating curing, the terminal carboxyl groups can also crosslink with the bisphenol A type epoxy resin, forming a dense three-dimensional network structure. Simultaneously, by introducing polydimethylsiloxane segments into the resin and using modified nano-zinc oxide with surface-grafted indole quaternary ammonium salts, the coating possesses both low surface energy characteristics and spectral antibacterial capabilities. This powder coating integrates fluorine-free environmental protection, stain resistance, anti-slip properties, antibacterial properties, and excellent mechanical properties, solving the technical problem of poor functional synergy in traditional textured coatings.

Description

Technical Field

[0001] This invention relates to the field of powder coating technology, and in particular to a fluorine-free, environmentally friendly, stain-resistant, anti-slip, sand-textured powder coating and its preparation method. Background Technology

[0002] With increasingly stringent environmental regulations and rising consumer demand for diverse coating functions, powder coatings are finding wider application in building decoration, home furnishings, and industrial equipment due to their advantages of zero volatile organic compound (VOC) emissions and high resource utilization. Among these, sand-textured powder coatings, with their unique rough surface texture, excellent anti-slip properties, and ability to conceal minor imperfections, are widely used in applications such as flooring, stair railings, and kitchen and bathroom fixtures—situations requiring a balance between practicality and aesthetics—leading to continued market demand growth.

[0003] However, existing sand-textured powder coatings still have many technical challenges that need to be addressed. In terms of environmental friendliness, traditional sand-textured coatings rely on the addition of fluorinated compounds to achieve excellent hydrophobic and stain-resistant properties. These substances are bioaccumulative and can pose potential harm to the ecological environment and human health, and do not conform to the current development trend of "fluorine-free environmental protection." Some fluorine-free sand-textured coatings, on the other hand, lack highly efficient hydrophobic components, resulting in a significant decrease in stain resistance, making it easy for oil stains, juice stains, and other dirt to adhere and difficult to clean.

[0004] In terms of core functional synergy, existing products struggle to simultaneously achieve anti-slip, stain-resistant, and antibacterial properties. Most textured coatings rely solely on their surface roughness for anti-slip performance, which is susceptible to a sharp drop in friction coefficient due to water film lubrication in humid environments, resulting in poor anti-slip stability. Stain resistance is limited by the compatibility of the resin and fillers, leading to insufficient coating density and easy penetration and residue of liquid stains. Furthermore, for antibacterial requirements in special settings such as hospitals and food processing workshops, existing textured coatings often achieve this by adding additional antibacterial agents. However, the poor compatibility of these agents with the coating system leads to agglomeration and precipitation, resulting in short-lived and uneven antibacterial effects, failing to achieve long-term, stable, broad-spectrum antibacterial properties.

[0005] In terms of structural stability and appearance, existing sand texture coatings rely heavily on single wax powders or fillers for sand texture control, which can easily lead to uneven sand texture and particle agglomeration, affecting the consistency of appearance. The unreasonable cross-linking structure design of the resin system results in poor mechanical properties of the coating, weak impact and bending resistance, and easy cracking and peeling after long-term use. In addition, the poor dispersibility of nanofillers in the coating not only fails to fully exert their functional characteristics, but also further affects the weather resistance of the coating, causing it to lose its gloss and discolor when used outdoors, thus shortening its service life.

[0006] Therefore, developing a fluorine-free, environmentally friendly powder coating that combines high-efficiency anti-slip properties, long-lasting stain resistance, broad-spectrum antibacterial functions, and uniform and delicate sand texture with excellent mechanical properties and weather resistance has become a pressing technical challenge for the industry. This is of great significance for expanding the application scenarios of powder coatings and meeting the demands of the high-end market. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the existing technology and to propose a fluorine-free, environmentally friendly, stain-resistant, anti-slip sand texture powder coating and its preparation method.

[0008] To achieve the above objectives, this invention provides a fluorine-free, environmentally friendly, stain-resistant, anti-slip, sand-textured powder coating and its preparation method, comprising the following raw materials in parts by weight: carboxyl-terminated polyester resin: 30-40 parts, bisphenol A type epoxy resin: 20-30 parts, modified nano zinc oxide: 1.5-2.5 parts, polyethylene micro wax powder: 2-4 parts, leveling agent: 0.8-1.5 parts, PDMS-coated silica: 1-2 parts, light stabilizer: 0.5-0.8 parts, curing accelerator: 0.1-0.3 parts;

[0009] The preparation method of the carboxyl-terminated polyester resin is as follows:

[0010] Adipic acid, neopentyl glycol, polydimethylsiloxane diol, tridecanoic acid, 1,4-cyclohexanediethanol, and trimethylolpropane were added to a reactor equipped with a water separator. Under nitrogen protection, the temperature was raised to 180-200℃, and the stirring speed was 150-200 rpm for 2-3 hours. The temperature was then raised to 220-240℃, and the vacuum was gradually reduced to ≤50 Pa for 2.5-3.5 hours. During this period, the acid value was measured every 30 minutes. The reaction was stopped when the acid value dropped to 20-30 mg KOH / g. After the reaction was completed, the temperature was lowered to 180℃, and nitrogen was introduced into the reactor to break the vacuum. The molten resin was discharged onto a stainless steel tray preheated to 100℃. After naturally cooling to room temperature, the resin was pulverized to a particle size of ≤5 mm to obtain a branched terminal carboxyl polyester containing dimethylsiloxane segments. Trimethylolpropane provided the branched structure.

[0011] The modified nano zinc oxide is prepared as follows:

[0012] (1) 2,3,3-trimethyl-3H-indole-5-carboxylic acid and 1,3-propanesulfonyl lactone were added to anhydrous 1,4-dioxane. The mixture was heated to 80-100℃ under nitrogen protection and stirred for 3-5 h. After the reaction was completed, the mixture was cooled to room temperature and added to diethyl ether. The resulting solid was collected by suction filtration, washed three times with ethyl acetate, and dried to obtain intermediate A. The chemical reaction equation is as follows:

[0013] The product was characterized by ¹H NMR. In this step, in 2,3,3-trimethyl-3H-indole-5-carboxylic acid, the N atom on the indole pyrrole ring is electron-rich and highly nucleophilic, while the cyclic ether structure of 1,3-propane sulfonyl lactone has electron-deficient carbon atoms due to the electronegativity of the oxygen atom, which become electrophilic reaction sites. The lone pair of electrons of the indole N atom attacks the cyclic ether carbon of 1,3-propane sulfonyl lactone, initiating the cyclic ether ring-opening reaction. The indole N atom thus becomes positively charged. The sulfonate ion formed after the ring-opening of sulfonyl lactone serves as the equilibrium anion, ultimately generating intermediate A with a quaternary ammonium salt structure.

[0014] (2) Add intermediate A to anhydrous 1,4-dioxane, stir to dissolve, then add γ-glycidoxypropyltrimethoxysilane, heat to 70-80℃ under nitrogen protection, stir and react for 2-4 hours. After the reaction is completed, remove the solvent by vacuum distillation to obtain intermediate B; the chemical reaction equation is as follows:

[0015] The product was characterized by ¹H NMR. This step was based on a ring-opening addition reaction between a carboxyl group and an epoxy group, using intermediate A and γ-glycidoxypropyltrimethoxysilane (KH560) as reactants and anhydrous 1,4-dioxane as solvent. The carboxyl group in intermediate A is an acidic nucleophile, and its own H... + The oxygen atom of the epoxy group in KH560 can be protonated to enhance the electrophilicity of the epoxy group, thereby promoting the nucleophilic attack of the oxygen atom in the carboxyl group on the carbon atom of the epoxy group, causing the epoxy ring to open. After ring opening, intermediate A and KH560 are covalently linked through the newly formed ester group. At the same time, the trimethoxysilyl group at the end of KH560 does not participate in the reaction and is completely preserved as the active site for subsequent grafting of nano zinc oxide.

[0016] (3) Add nano zinc oxide to ethanol, ultrasonically disperse for 10-20 min, adjust pH to 5-6 with dilute hydrochloric acid, add intermediate B, heat to 70-80℃, stir for 2-3 h, after the reaction is complete, filter to collect the solid precipitate, wash and dry to obtain modified nano zinc oxide; the chemical reaction is shown below:

[0017] In this step, silanol groups undergo a condensation reaction with hydroxyl groups on the surface of nano-zinc oxide, anchoring intermediate B on the surface of nano-zinc oxide. Dilute hydrochloric acid adjusts the pH to a weakly acidic environment of 5-6, catalyzing the hydrolysis of trimethoxysilane in intermediate B to generate highly reactive silanol groups. Hydroxyl groups naturally exist on the surface of nano-zinc oxide. The silanol groups undergo a dehydration condensation reaction with Zn-OH at 70-80℃ to form stable Si-O-Zn covalent bonds, firmly connecting intermediate B containing quaternary ammonium salt structure to the surface of nano-zinc oxide.

[0018] Preferably, the leveling agent refers to one of polyacrylate leveling agents or silicone-acrylate leveling agents.

[0019] More preferably, the leveling agent is selected from MONENG-1153 or TEGO Glide410.

[0020] Preferably, the light stabilizer refers to a mixture of hindered amine light stabilizer and ultraviolet absorber in a weight ratio of 1:1.

[0021] More preferably, the light stabilizer refers to a mixture of light stabilizer 770 and ultraviolet absorber UV-326 in a weight ratio of 1:1.

[0022] Preferably, the curing accelerator refers to 2-methylimidazole.

[0023] Preferably, in the preparation method of the carboxyl-terminated polyester resin, the molar ratio of adipic acid, neopentyl glycol, polydimethylsiloxane diol, tridecanoic acid, 1,4-cyclohexanediethanol and trimethylolpropane is 1-1.2:0.6-0.8:0.2-0.3:0.4-0.6:0.3-0.4:0.1-0.2.

[0024] Preferably, in the method for preparing the carboxyl-terminated polyester resin, the number-average molecular weight of the polydimethylsiloxane diol is 1500.

[0025] Preferably, in (1), the molar ratio of 2,3,3-trimethyl-3H-indole-5-carboxylic acid and 1,3-propanesulfonyl lactone is 1:1-1.2.

[0026] Preferably, in (1), 2,3,3-trimethyl-3H-indole-5-carboxylic acid, anhydrous 1,4-dioxane and diethyl ether are in a weight ratio of 1:8-12:10-20.

[0027] Preferably, in (2), intermediate A and γ-glycidyl etheroxypropyltrimethoxysilane have a molar ratio of 1:1-1.2.

[0028] Preferably, in (2), intermediate A and anhydrous 1,4-dioxane are in a weight ratio of 1:8-12.

[0029] Preferably, in (3), the nano zinc oxide, ethanol and intermediate B are in a weight ratio of 1:8-12:0.12-0.2.

[0030] Preferably, the concentration of dilute hydrochloric acid in (3) is 0.1-0.5 mol / L.

[0031] Furthermore, the present invention also provides a method for preparing a fluorine-free, environmentally friendly, stain-resistant, anti-slip, sand-textured powder coating, comprising the following steps:

[0032] S1. Mix carboxyl-terminated polyester resin, bisphenol A epoxy resin, modified nano zinc oxide, polyethylene micro wax powder, leveling agent, PDMS-coated silica, light stabilizer, and curing accelerator, and stir at high speed of 1000-1500 rpm for 10-20 min to obtain a premixed material.

[0033] S2. Add the premixed material to a twin-screw extruder and melt-extrude to obtain a uniform molten strip;

[0034] S3. Cool the molten strip to room temperature via a cooling conveyor belt, and then feed it into a pulverizer to pulverize it to a particle size of 30-50μm to obtain the pulverized material;

[0035] S4. The crushed material is sieved through a 180-200 mesh stainless steel screen to remove coarse particles, resulting in a fluorine-free, environmentally friendly, stain-resistant, anti-slip sand texture powder coating.

[0036] Preferably, in S2, the temperature of the first zone of the twin-screw extruder is 95-105℃, the temperature of the second zone is 105-115℃, the temperature of the third zone is 115-125℃, the die head temperature is 115-125℃, and the screw speed is 30-50 rpm.

[0037] Preferably, the mechanism of action of the fluorine-free, environmentally friendly, stain-resistant, anti-slip, sand-textured powder coating of the present invention is explained as follows:

[0038] The film-forming core of the coating of this invention relies on the synergistic crosslinking reaction between carboxyl-terminated polyester resin and bisphenol A type epoxy resin. Under the catalysis of the curing accelerator 2-methylimidazole, the carboxyl groups at the end of the polyester resin and the epoxy groups of the epoxy resin undergo a ring-opening addition reaction to form a three-dimensional network crosslinked structure. This structure not only endows the coating with excellent mechanical properties, but also prevents the penetration of small molecules through the tight binding of molecular chains, laying the foundation for stain resistance and weather resistance. At the same time, the coating does not use fluorine-containing compounds throughout the entire process. Instead, it introduces polydimethylsiloxane diol into the polyester resin and uses PDMS to coat silica in the filler. The low surface energy characteristics of PDMS replace traditional fluorides to achieve hydrophobic and antifouling functions. From the selection of raw materials to the reaction process, it meets the requirements of fluorine-free environmental protection and avoids the potential harm of fluorides to the environment.

[0039] To achieve the sand texture effect, on the one hand, the polyethylene microwax powder in the formula is uniformly dispersed in the resin matrix during melt extrusion and baking to form a film. Its low surface energy and low flowability characteristics hinder the leveling process after the resin melts, forming tiny protrusions on the coating surface. On the other hand, the tridecanoic acid and 1,4-cyclohexanediethanol introduced into the carboxyl-terminated polyester resin molecular chain will cause uneven arrangement of the resin molecular chain due to the steric hindrance effect, further enhancing the micro-roughness of the surface. Under the synergistic effect of the two, the coating finally forms a uniform and delicate sand texture structure. Furthermore, the addition of PDMS-coated silica can further fine-tune the sand texture (through particle filling to assist in shaping), avoiding appearance defects caused by sand texture that is too coarse or too fine.

[0040] The anti-slip performance mainly stems from the synergy between the microstructure design of the coating surface and the functional fillers: Firstly, the textured structure itself constructs a "micro-protrusion array," significantly increasing the actual contact area between the coating surface and the contacting object, thereby increasing the coefficient of friction and directly enhancing friction through physical roughness; Secondly, PDMS-coated silica nanoparticles are evenly distributed on the textured protrusion surface, forming "secondary friction points." These nanoparticles can be embedded in the micro-gaps of the coating, further enhancing friction; In addition, the low surface energy characteristics of the coating can reduce the adhesion of water films on the surface, avoiding slippage caused by water film lubrication in humid environments.

[0041] The stain resistance is achieved through a dual mechanism of "low surface energy anti-adhesion + dense structure anti-penetration": First, the PDMS diol in the carboxyl-terminated polyester resin and the PDMS-coated silica form a siloxane-rich molecular layer on the coating surface. The low surface energy of PDMS is far lower than that of oil, dust, and other contaminants, making it difficult for contaminants to adhere to the coating surface. Even if a small amount adheres, it can be removed by light wiping, avoiding the problem of "contaminants embedded in crevices and difficult to clean" in traditional coatings. Second, the highly dense three-dimensional cross-linked structure formed by the resin and epoxy resin can prevent liquid contaminants from penetrating into the interior of the coating, avoiding the formation of permanent stains. Simultaneously, although the sulfonic acid groups on the modified nano-zinc oxide surface are strong... While it contains hydrophilic groups, it is the core hydrophilic component of anionic surfactants (such as sodium dodecylbenzene sulfonate). In this invention, the sulfonic acid group and the long alkyl chain of the quaternary ammonium salt form a hydrophilic-hydrophobic amphiphilic structure. When hydrophilic stains (such as juice or sauce) come into contact with the coating, the hydrophobic end of this unit adsorbs the organic components in the stain, while the hydrophilic sulfonic acid group combines with water. With the help of the external force of daily wiping, the hydrophilic stain is emulsified and dispersed, avoiding its residue. This amphiphilic structure only acts on the stains that come into contact with it and does not change the overall low surface energy characteristics of the coating. Therefore, it utilizes the auxiliary detergency of the sulfonic acid group without affecting the coating's anti-adhesion properties to hydrophobic stains such as oil stains, further enhancing the ease of cleaning after stain resistance.

[0042] The antibacterial function is achieved by modified nano-zinc oxide: the quaternary ammonium salt structure grafted on its surface can adsorb negatively charged bacterial cell membranes through electrostatic interaction, and the alkyl chains insert into the cell membrane, disrupting its integrity, leading to leakage of bacterial contents and death; at the same time, nano-zinc oxide itself can slowly release Zn 2+ Under light, it generates reactive oxygen species (ROS), which form a synergistic antibacterial effect with quaternary ammonium salts, effectively inhibiting common bacteria such as Escherichia coli and Staphylococcus aureus. Weather resistance depends on light stabilizers: UV absorbers preferentially absorb ultraviolet rays from sunlight, preventing UV rays from directly damaging the resin molecular chains; hindered amine light stabilizers delay the degradation of the resin cross-linking structure by capturing free radicals generated during coating aging. The two work together to ensure that the coating can maintain the stability of its texture, stain resistance and antibacterial properties in outdoor environments, avoiding loss of gloss, discoloration or performance degradation.

[0043] The beneficial effects of this invention are:

[0044] 1. This invention does not use any fluorinated compounds throughout the entire process. By introducing polydimethylsiloxane (PDMS) diol into the carboxyl-terminated polyester resin and coating silica with PDMS in the filler, the low surface energy of PDMS replaces traditional fluorides. This avoids the potential harm of fluorides to the environment and human health, and forms a continuous siloxane molecular layer on the coating surface, effectively preventing the adhesion of hydrophobic stains such as oil. Simultaneously, the coating preparation process has no volatile organic compound (VOC) emissions, has high raw material utilization, conforms to current environmental regulations, and balances environmental friendliness with hydrophobic and anti-fouling practicality.

[0045] 2. This invention constructs a "triple synergistic antibacterial mechanism" by modifying nano-zinc oxide. The indole quaternary ammonium salt grafted on its surface can disrupt the microbial structure through electrostatic adsorption and membrane penetration, in conjunction with the Zn released by the nano-zinc oxide. 2+ Reactive oxygen species (ROS) generated by light can effectively inhibit Gram-positive bacteria, Gram-negative bacteria, and fungi. Furthermore, the modified nano-zinc oxide is anchored by Si-O-Zn covalent bonds, preventing migration and precipitation, thus maintaining its antibacterial activity for a long time. It eliminates the need for additional antibacterial agents that easily aggregate, making it particularly suitable for environments with high hygiene requirements, such as hospitals, food processing workshops, and bathrooms.

[0046] 3. This invention achieves excellent stain resistance while enhancing anti-slip performance through a "dual friction-enhancing structure": polyethylene micro-wax powder and resin steric hindrance form uniform sand-textured protrusions, increasing the contact area; PDMS-coated silica forms "secondary friction points," increasing frictional resistance; the low surface energy of the coating also reduces water film lubrication in humid environments. Furthermore, the sulfonic acid-quaternary ammonium salt amphiphilic structure of modified nano-zinc oxide emulsifies hydrophilic stains, which can be removed with a light wipe, solving the core pain points of traditional sand-textured coatings—poor stain resistance and easy slippage in damp conditions—significantly improving the user experience.

[0047] 4. This invention utilizes the steric hindrance of tridecanoic acid and 1,4-cyclohexanediethanol in the carboxyl-terminated polyester resin, the leveling resistance of polyethylene micro-wax powder, and the particle shaping effect of PDMS-coated silica to achieve uniform texture and prevent coarse particle agglomeration, resulting in a strong consistency in appearance and texture. Simultaneously, the dense three-dimensional cross-linked structure formed by the carboxyl-terminated polyester resin and epoxy resin, combined with the flexible segments of PDMS diol, endows the coating with excellent impact and bending resistance. The synergistic effect of the light stabilizer and PDMS in resisting ultraviolet radiation delays resin degradation, ensuring that the coating does not lose gloss or discolor over long-term use, thus extending the product's service life. Attached Figure Description

[0048] Figure 1 The H NMR spectrum of intermediate A prepared in Example 5 of this invention;

[0049] Figure 2 The H NMR spectrum of intermediate B prepared in Example 5 of this invention. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0051] Preparation Example 1: The specific preparation method of carboxyl-terminated polyester resin includes the following steps:

[0052] 1 kg of adipic acid, 427.60 g of neopentyl glycol, 2.052 kg of polydimethylsiloxane diol, 688.76 g of tridecanoic acid, 296.04 g of 1,4-cyclohexanediethanol, and 91.91 g of trimethylolpropane were added to a reactor equipped with a water separator. Under nitrogen protection, the mixture was heated to 180°C and stirred at 150 rpm for 2 hours. The temperature was then increased to 220°C, and the vacuum was gradually reduced to ≤50 Pa for 2.5 hours. During this period, the acid value was measured every 30 minutes. The reaction was stopped when the acid value dropped to 20-30 mg KOH / g. After the reaction was completed, the temperature was lowered to 180°C, and nitrogen was introduced into the reactor to break the vacuum. The molten resin was discharged onto a stainless steel tray preheated to 100°C. After naturally cooling to room temperature, the resin was pulverized to a particle size of ≤5 mm to obtain carboxyl-terminated polyester resin.

[0053] Preparation Example 2: The specific preparation method of carboxyl-terminated polyester resin includes the following steps:

[0054] 1 kg of adipic acid, 453.52 g of neopentyl glycol, 2.332 kg of polydimethylsiloxane diol, 759.95 g of tridecanoic acid, 313.98 g of 1,4-cyclohexanediethanol, and 125.19 g of trimethylolpropane were added to a reactor equipped with a water separator. Under nitrogen protection, the temperature was raised to 190°C, and the stirring rate was 180 rpm for 2.5 h. The temperature was then raised to 230°C, and the vacuum was gradually reduced to ≤50 Pa for 3 h. During this period, the acid value was measured every 30 min. The reaction was stopped when the acid value dropped to 20-30 mg KOH / g. After the reaction was completed, the temperature was lowered to 180°C, and nitrogen was introduced into the reactor to break the vacuum. The molten resin was discharged onto a stainless steel tray preheated to 100°C. After naturally cooling to room temperature, the resin was pulverized to a particle size of ≤5 mm to obtain carboxyl-terminated polyester resin.

[0055] Preparation Example 3: The specific preparation method of carboxyl-terminated polyester resin includes the following steps:

[0056] 1 kg adipic acid, 475.12 g neopentyl glycol, 2.566 kg polydimethylsiloxane diol, 835.94 g tridecanoic acid, 328.93 g 1,4-cyclohexanediethanol, and 153.02 g trimethylolpropane were added to a reactor equipped with a water separator. Under nitrogen protection, the temperature was raised to 200°C, and the stirring speed was 150-200 rpm for 3 h. The temperature was then raised to 240°C, and the vacuum was gradually reduced to ≤50 Pa for 3.5 h. During this period, the acid value was measured every 30 min. The reaction was stopped when the acid value dropped to 20-30 mg KOH / g. After the reaction was completed, the temperature was lowered to 180°C, and nitrogen was introduced into the reactor to break the vacuum. The molten resin was discharged onto a stainless steel tray preheated to 100°C. After naturally cooling to room temperature, the resin was pulverized to a particle size ≤5 mm to obtain carboxyl-terminated polyester resin.

[0057] Preparation Example 4: The specific preparation method of modified nano zinc oxide includes the following steps:

[0058] (1) 10g of 2,3,3-trimethyl-3H-indole-5-carboxylic acid and 6.01g of 1,3-propanesulfonyl lactone were added to 80g of anhydrous 1,4-dioxane. The mixture was heated to 80℃ under nitrogen protection and stirred for 3h. After the reaction was completed, it was cooled to room temperature and added to 100g of diethyl ether. The resulting solid was collected by suction filtration, washed three times with ethyl acetate, and dried to obtain intermediate A.

[0059] (2) Add 10g of intermediate A to 80g of anhydrous 1,4-dioxane, stir to dissolve, then add 7.26g of γ-glycidyl etheroxypropyltrimethoxysilane, heat to 70℃ under nitrogen protection, stir and react for 2h, and after the reaction is completed, remove the solvent by vacuum distillation to obtain intermediate B.

[0060] (3) Add 50g of nano zinc oxide to 400g of ethanol, sonicate for 10min, adjust the pH to 5-6 with 0.1mol / L dilute hydrochloric acid, add 6g of intermediate B, heat to 70℃, stir for 2h, after the reaction is completed, filter to collect the solid precipitate, wash and dry to obtain modified nano zinc oxide.

[0061] Preparation Example 5: The specific preparation method of modified nano zinc oxide includes the following steps:

[0062] (1) 10g of 2,3,3-trimethyl-3H-indole-5-carboxylic acid and 6.61g of 1,3-propanesulfonyl lactone were added to 100g of anhydrous 1,4-dioxane. The mixture was heated to 90℃ under nitrogen protection and stirred for 4h. After the reaction was completed, it was cooled to room temperature and added to 150g of diethyl ether. The resulting solid was collected by suction filtration, washed three times with ethyl acetate, and dried to obtain intermediate A. The structure of the product was confirmed by H NMR.

[0063] (2) 10g of intermediate A was added to 100g of anhydrous 1,4-dioxane and stirred until dissolved. Then, 7.99g of γ-glycidyl etheroxypropyltrimethoxysilane was added. The mixture was heated to 75°C under nitrogen protection and stirred for 3h. After the reaction was completed, the solvent was removed by vacuum distillation to obtain intermediate B. The structure of the product was confirmed by H NMR.

[0064] (3) Add 50g of nano zinc oxide to 500g of ethanol, sonicate for 15min, adjust the pH to 5-6 with 0.3mol / L dilute hydrochloric acid, add 9g of intermediate B, heat to 75℃, stir for 2.5h, after the reaction is completed, filter to collect the solid precipitate, wash and dry to obtain modified nano zinc oxide.

[0065] Preparation Example 6: The specific preparation method of modified nano zinc oxide includes the following steps:

[0066] (1) 10g of 2,3,3-trimethyl-3H-indole-5-carboxylic acid and 7.21g of 1,3-propanesulfonyl lactone were added to 120g of anhydrous 1,4-dioxane. The mixture was heated to 100℃ under nitrogen protection and stirred for 5h. After the reaction was completed, it was cooled to room temperature and added to diethyl ether. The resulting solid was collected by suction filtration, washed three times with ethyl acetate, and dried to obtain intermediate A.

[0067] (2) Add 10g of intermediate A to 120g of anhydrous 1,4-dioxane, stir to dissolve, then add 8.72g of γ-glycidoxypropyltrimethoxysilane, heat to 80℃ under nitrogen protection, stir and react for 4h, and after the reaction is completed, remove the solvent by vacuum distillation to obtain intermediate B.

[0068] (3) Add 40g of nano zinc oxide to 480g of ethanol, disperse ultrasonically for 20min, adjust the pH to 5-6 with 0.5mol / L dilute hydrochloric acid, add 8g of intermediate B, heat to 80℃, stir for 3h, after the reaction is completed, filter to collect the solid precipitate, wash and dry to obtain modified nano zinc oxide.

[0069] Comparative Preparation Example 1: The difference between Comparative Preparation Example 1 and Preparation Example 2 is that polydimethylsiloxane diol is not added. The specific preparation method is as follows: The specific preparation method of the carboxyl-terminated polyester resin includes the following steps:

[0070] 1 kg of adipic acid, 518.31 g of neopentyl glycol, 759.95 g of tridecanoic acid, 448.54 g of 1,4-cyclohexanediethanol, and 125.19 g of trimethylolpropane were added to a reactor equipped with a water separator. Under nitrogen protection, the temperature was raised to 190°C, and the stirring speed was 180 rpm for 2.5 h. The temperature was then raised to 230°C, and the vacuum was gradually reduced to ≤50 Pa for 3 h. During this period, the acid value was measured every 30 min. The reaction was stopped when the acid value dropped to 20-30 mg KOH / g. After the reaction was completed, the temperature was lowered to 180°C, and nitrogen was introduced into the reactor to break the vacuum. The molten resin was discharged onto a stainless steel tray preheated to 100°C. After naturally cooling to room temperature, the resin was pulverized to a particle size of ≤5 mm to obtain carboxyl-terminated polyester resin.

[0071] Comparative Preparation Example 2: The difference between Comparative Preparation Example 2 and Preparation Example 2 is that trimethylolpropane is not added. The specific preparation method is as follows: The specific preparation method of the carboxyl-terminated polyester resin includes the following steps:

[0072] 1 kg of adipic acid, 485.91 g of neopentyl glycol, 2.799 kg of polydimethylsiloxane diol, 759.95 g of tridecanoic acid, and 358.83 g of 1,4-cyclohexanediethanol were added to a reactor equipped with a water separator. Under nitrogen protection, the temperature was raised to 190°C, the stirring speed was 180 rpm, and the reaction was carried out for 2.5 h. The temperature was then raised to 230°C, and the vacuum was gradually evacuated to ≤50 Pa, and the reaction was carried out for 3 h. During this period, the acid value was measured every 30 min. When the acid value dropped to 20-30 mg KOH / g, the reaction was stopped. After the reaction was completed, the temperature was lowered to 180°C, and nitrogen was introduced into the reactor to break the vacuum. The molten resin was discharged into a stainless steel tray preheated to 100°C. After naturally cooling to room temperature, it was pulverized by a pulverizer to a particle size ≤5 mm to obtain carboxyl-terminated polyester resin.

[0073] Comparative Preparation Example 3: The difference between Comparative Preparation Example 3 and Preparation Example 2 is that the molar ratio of adipic acid, neopentyl glycol, polydimethylsiloxane diol, tridecanoic acid, 1,4-cyclohexanediethanol and trimethylolpropane is controlled so that the total molar ratio of the diol is 1.2 times the total molar ratio of the dicarboxylic acid, and hydroxyl-terminated polyester resin is obtained.

[0074] Comparative Preparation Example 4: The difference between Comparative Preparation Example 4 and Preparation Example 5 is that steps (1) and (2) are omitted, and intermediate B is directly replaced with γ-glycidoxypropyltrimethoxysilane in step (3).

[0075] Example 1: A specific preparation method for a fluorine-free, environmentally friendly, stain-resistant, anti-slip, sand-textured powder coating, comprising the following steps:

[0076] S1. Mix 300g of carboxyl-terminated polyester resin prepared according to Preparation Example 1, 200g of bisphenol A type epoxy resin, 15g of modified nano zinc oxide prepared according to Preparation Example 4, 20g of polyethylene micro wax powder, 8g of leveling agent MONENG-1153, 10g of PDMS coated silica, 5g of light stabilizer (a mixture of light stabilizer 770 and ultraviolet absorber UV-326 in a weight ratio of 1:1), and 1g of 2-methylimidazole, and stir at a high speed of 1000 rpm for 10 min to obtain a premixed material;

[0077] S2. Add the premixed material to the twin-screw extruder. The temperature of the first zone of the twin-screw extruder is 95℃, the temperature of the second zone is 105℃, the temperature of the third zone is 115℃, the die head temperature is 115℃, and the screw speed is 30 rpm. Melt extrusion yields a uniform molten strip.

[0078] S3. Cool the molten strip to room temperature via a cooling conveyor belt, and then feed it into a pulverizer to pulverize it to a particle size of 30-50μm to obtain the pulverized material;

[0079] S4. The crushed material is sieved through a 180-mesh stainless steel screen to remove coarse particles, resulting in a fluorine-free, environmentally friendly, stain-resistant, anti-slip sand-textured powder coating.

[0080] Example 2: A specific preparation method for a fluorine-free, environmentally friendly, stain-resistant, anti-slip, sand-textured powder coating, comprising the following steps:

[0081] S1. Mix 350g of carboxyl-terminated polyester resin prepared according to Preparation Example 2, 250g of bisphenol A type epoxy resin, 20g of modified nano zinc oxide prepared according to Preparation Example 5, 30g of polyethylene microwax powder, 12g of leveling agent MONENG-1153, 15g of PDMS-coated silica, 6.5g of light stabilizer (a mixture of light stabilizer 770 and ultraviolet absorber UV-326 in a weight ratio of 1:1), and 2g of 2-methylimidazole, and stir at a high speed of 1200 rpm for 15 min to obtain a premixed material;

[0082] S2. Add the premixed material to the twin-screw extruder. The temperature of the first zone of the twin-screw extruder is 100℃, the temperature of the second zone is 110℃, the temperature of the third zone is 120℃, the die head temperature is 120℃, and the screw speed is 40 rpm. Melt extrusion is performed to obtain a uniform melt strip.

[0083] S3. Cool the molten strip to room temperature via a cooling conveyor belt, and then feed it into a pulverizer to pulverize it to a particle size of 30-50μm to obtain the pulverized material;

[0084] S4. The crushed material is sieved through a 190-mesh stainless steel screen to remove coarse particles, resulting in a fluorine-free, environmentally friendly, stain-resistant, anti-slip sand texture powder coating.

[0085] Example 3: A specific preparation method for a fluorine-free, environmentally friendly, stain-resistant, anti-slip, sand-textured powder coating, comprising the following steps:

[0086] S1. Mix 400g of carboxyl-terminated polyester resin prepared according to Preparation Example 3, 300g of bisphenol A type epoxy resin, 25g of modified nano zinc oxide prepared according to Preparation Example 6, 40g of polyethylene microwax powder, 15g of leveling agent MONENG-1153, 20g of PDMS-coated silica, 8g of light stabilizer (a mixture of light stabilizer 770 and ultraviolet absorber UV-326 in a weight ratio of 1:1), and 3g of 2-methylimidazole, and stir at a high speed of 1500 rpm for 20 min to obtain a premixed material;

[0087] S2. Add the premixed material to the twin-screw extruder. The temperature of the first zone of the twin-screw extruder is 105℃, the temperature of the second zone is 115℃, the temperature of the third zone is 125℃, the die head temperature is 125℃, and the screw speed is 50 rpm. Melt extrusion is performed to obtain a uniform melt strip.

[0088] S3. Cool the molten strip to room temperature via a cooling conveyor belt, and then feed it into a pulverizer to pulverize it to a particle size of 30-50μm to obtain the pulverized material;

[0089] S4. The crushed material is sieved through a 200-mesh stainless steel screen to remove coarse particles, resulting in a fluorine-free, environmentally friendly, stain-resistant, anti-slip sand-textured powder coating.

[0090] Example 4: The difference between Example 4 and Example 2 is that the leveling agent MONENG-1153 is replaced with the leveling agent TEGO Glide410.

[0091] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that the carboxyl-terminated polyester resin prepared according to Preparation Example 2 is replaced with the carboxyl-terminated polyester resin prepared according to Comparative Preparation Example 1.

[0092] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that the carboxyl-terminated polyester resin prepared according to Preparation Example 2 is replaced with the carboxyl-terminated polyester resin prepared according to Comparative Preparation Example 2.

[0093] Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that the carboxyl-terminated polyester resin prepared according to Preparation Example 2 is replaced with the hydroxyl-terminated polyester resin prepared according to Comparative Preparation Example 3.

[0094] Comparative Example 4: The difference between Comparative Example 4 and Example 2 is that the modified nano zinc oxide prepared according to Preparation Example 5 is replaced with the modified nano zinc oxide prepared according to Comparative Preparation Example 4.

[0095] Comparative Example 5: The difference between Comparative Example 5 and Example 2 is that the modified nano zinc oxide prepared according to Preparation Example 5 is replaced with nano zinc oxide.

[0096] Comparative Example 6: The difference between Comparative Example 6 and Example 2 is that PDMS-coated silica is not added.

[0097] Performance testing:

[0098] 1. Antibacterial performance test: Referring to GB / T 21510-2008 "Test Method for Antibacterial Performance of Nano-Inorganic Materials", Escherichia coli (ATCC 25922), Staphylococcus aureus (ATCC 6538), Pseudomonas aeruginosa (ATCC 27853), and Candida albicans (ATCC 10231) were selected as test strains, and 1×10⁻⁶ strains were prepared respectively. 6CFU / mL bacterial solution was used to electrostatically spray the coating samples from each example and comparative example onto 50mm×50mm×1mm tinplate test plates (voltage 60-80kV, air pressure 0.3-0.5MPa, spray gun distance 15-20cm), and cured at 120-140℃ for 15-20min to form a coating with a thickness of 60±5μm. The coating was then placed at 23±2℃ and 50%±5% relative humidity for 24h. Each bacterial solution was evenly applied to the surface of each coating, ensuring that the bacterial solutions did not cross-contaminate. The inoculation amount for each test plate was 0.2 mL. After covering with sterile polyethylene film, the plates were placed in a constant temperature and humidity incubator at 37℃ and 90% relative humidity for 24 h. After incubation, the coating surface was rinsed with 5 mL of sterile physiological saline. The rinsing solution was collected and serially diluted. 0.1 mL of the diluted solution was spread on nutrient agar medium and incubated for another 24 h before counting the colonies. At the same time, an uncoated tinplate test plate was set up as a blank control. The antibacterial rate was calculated as (number of colonies in the blank group - number of colonies in the sample group) / number of colonies in the blank group × 100%. The experimental results are shown in Table 1.

[0099] 2. Stain Resistance Test: Two typical stains were selected: hydrophilic stains (freshly squeezed orange juice and soybean paste, solid content 15%) and hydrophobic stains (chili oil). Before the test, all coating samples were electrostatically sprayed onto a 100mm×100mm×1mm cold-rolled steel plate. After curing, the coating thickness was controlled at 60±5μm, and the plates were conditioned for 24 hours under standard conditions (23±2℃, 50%±5% RH). For hydrophilic stains, 0.5mL was evenly dripped onto the coating surface using a pipette to form a stain spot with a diameter of about 10mm. After standing at room temperature for 30 minutes, the stain was wiped with a standard lint-free cloth (80g / m²). 2 Wipe the stain in the same direction with a constant pressure of 5N and record the number of wipings required to completely remove the stain. For hydrophobic stains, repeat the above operation with 0.5mL of chili oil. The experimental results are shown in Table 2.

[0100] 3. Anti-slip performance test: According to the friction coefficient test method in Appendix M of GB / T 4100-2015 "Ceramic Tiles", an MXD-01 friction coefficient meter was used. The sample of the example and the comparative example were sprayed onto a ceramic substrate of 150mm×150mm×5mm, with a coating thickness of 60±5μm. After curing, the sample was placed in a standard environment for 48 hours. The dry environment test was carried out directly in the standard environment. The test rubber block (Shore hardness 70±5°) was in contact with the coating surface, a vertical load of 10N was applied, and the block was moved horizontally at a speed of 50mm / min. The friction coefficients (static friction coefficient μs and dynamic friction coefficient μd) were recorded. For the humid environment test, 0.5mL of deionized water was sprayed evenly on the coating surface, and the above operation was repeated after standing for 5 minutes. The experimental results are shown in Table 3.

[0101] 4. Sand Texture Appearance Test: The powder coatings of each embodiment and comparative example were electrostatically sprayed onto a 100mm×150mm×1mm tinplate substrate. Under natural diffused light, the uniformity and fineness of the sand texture of the coating samples were observed and evaluated according to three levels: "uniform and fine (no obvious difference in coarseness), relatively uniform (slight local unevenness), and uneven (obvious coarse particle agglomeration)". The adhesion performance was also tested simultaneously, referring to GB / T 9286-2021 "Paints and Varnishes Cross-cut Test". A cross-cut interval of 1mm was used, and a special cross-cut knife was used to penetrate the coating to the substrate. Standard pressure-sensitive tape (adhesion 600g / 25mm) was then applied and peeled off at a speed of 10mm / s, and rated from 0 to 5 (0 being the best). The experimental results are shown in Table 4.

[0102] 5. Hydrophobicity Test: The water contact angle was tested using a JC2000D1 contact angle meter. The example and comparative samples were electrostatically sprayed onto a 50mm×50mm×1mm glass substrate, with a coating thickness of 50±5μm. After curing, the coating was placed in a standard environment for 24 hours. 5μL of deionized water was slowly dropped onto the coating surface using a microsyringe. After standing for 10 seconds, the droplet morphology was photographed using a high-speed camera. The contact angle was calculated using the tangent method. The experimental results are shown in Table 5.

[0103] 6. Weathering performance test: Referring to GB / T 1865-2009 "Artificial weathering and artificial radiation exposure of paints and varnishes - Part 1: General rules", a QUV / Spray type xenon lamp aging test chamber was used. The coating test panels (150mm×70mm) of the examples and comparative examples were placed in the test chamber. The xenon lamp power was set to 600W, the black panel temperature to 63±3℃, the relative humidity to 65%±5%, and the rainfall cycle to 18min / 102min (rainfall / drying). The cumulative aging time was 1000h. The gloss of the coating at 60° was tested with a BYK-Gardner4560 gloss meter before and after aging, and the gloss retention rate was calculated as (gloss after aging / gloss before aging × 100%). At the same time, the color difference ΔE of the coating was tested with a CR-400 colorimeter, and the color change was recorded. The experimental results are shown in Table 6.

[0104] 7. Mechanical property testing: Impact resistance was tested according to GB / T 1732-2020 "Determination of Impact Resistance of Coating Films". A QCJ impact tester was used. The coated test plate (100mm×50mm) was fixed on the test table. A 1kg hammer with an 8mm diameter steel ball was used. The hammer height was gradually increased from 20cm, increasing by 5cm each time. The maximum hammer height at which the coating did not crack or peel off was used as the impact strength index. Bending performance was tested according to GB / T 1731-1993 "Determination of Flexibility of Coating Films". A T-type bending tester was used. A 100mm×25mm coated test plate (substrate was 0.3mm thick cold-rolled steel plate) was bent to 120° at 23±2℃. The coating was observed to see if cracks appeared. The experimental results are shown in Table 7.

[0105] Table 1. Antibacterial performance test results

[0106]

[0107] Table 2 Results of stain resistance test

[0108]

[0109] Table 3. Anti-slip performance test results

[0110]

[0111] Table 4. Test results of sand texture appearance

[0112]

[0113] Table 5 Hydrophobicity test results

[0114]

[0115] Table 6 Weather resistance test results

[0116]

[0117] Table 7 Mechanical Performance Test Results

[0118]

[0119] Performance Analysis:

[0120] As can be seen from the experimental data in Tables 1-7, the coatings of the various embodiments of the present invention, relying on the synergistic effect of end-carboxyl polyester resin, modified nano zinc oxide, and PDMS-coated silica, exhibit excellent performance in antibacterial, stain-resistant, anti-slip, hydrophobic, weather-resistant, and mechanical properties; among them, Example 2 has the best overall performance.

[0121] Example 2 demonstrates excellent antibacterial properties, likely due to the "triple synergistic mechanism" of modified nano-zinc oxide: the positively charged indole quaternary ammonium salt adsorbs the negatively charged microbial cell membrane, the rigid indole ring penetrates the membrane phospholipid bilayer; and the Zn released by the nano-zinc oxide... 2+ Interfering with enzyme activity and blocking DNA replication, light-induced reactive oxygen species (ROS) are generated to oxidize the film components; the dense cross-linking of end-carboxyl polyester resin and epoxy resin ensures uniform distribution of antibacterial components, improves contact efficiency with microorganisms, and achieves broad-spectrum inhibition. The antibacterial properties of each comparative example are weaker than those of Example 2: Comparative Example 1 lacks polydimethylsiloxane diol, resulting in reduced coating density and low contact efficiency of antibacterial components; Comparative Example 2 lacks trimethylolpropane, resulting in fewer resin cross-linking points, a loose structure, and uneven distribution of antibacterial components; Comparative Example 3 uses end-hydroxyl resin, which has low cross-linking efficiency and cannot be grafted onto modified nano-zinc oxide, resulting in poor component distribution; Comparative Example 4 uses modified nano-zinc oxide without indole quaternization, lacking "adsorption-penetration" function, making it difficult to inhibit stubborn microorganisms; Comparative Example 5 uses ordinary nano-zinc oxide, relying solely on Zn... 2+ Compared with ROS, it has a narrow antibacterial range; compared with PDMS-coated silica, the surface structure of the control sample is slightly changed, resulting in a slight decrease in antibacterial activity.

[0122] Example 2 demonstrates excellent stain resistance, which may be due to the continuous low surface energy layer formed by PDMS diol and PDMS-coated silica, preventing the adhesion of hydrophobic stains; the dense cross-linked structure prevents the penetration of liquid stains; and the amphiphilic structure of the modified nano zinc oxide sulfonic acid-quaternary ammonium salt can emulsify hydrophilic stains, which can be removed with a light wipe without damaging the hydrophobic properties of the coating. The stain resistance of each comparative example was worse than that of Example 2: Comparative Example 1 lacked PDMS diol, resulting in a discontinuous low surface energy layer and easy adhesion of hydrophobic stains; Comparative Example 2 lacked trimethylolpropane, resulting in loose resin crosslinking and easy penetration of stains; Comparative Example 3 used hydroxyl-terminated resin, resulting in a large number of exposed hydroxyl groups, which both adsorbed hydrophilic stains (forming hydrogen bonds with polar components) and damaged the low surface energy layer, significantly reducing stain resistance; Comparative Example 4, modified nano zinc oxide, lacked indole quaternization and amphiphilic structure, making it unable to emulsify hydrophilic stains; Comparative Example 5 used ordinary nano zinc oxide, which lacked hydrophilic stain removal function and had poor coating density, making stains easy to remain; Comparative Example 6 lacked PDMS-coated silica, resulting in an incomplete low surface energy layer and lack of dispersion of PDMS-coated silica-terminated carboxyl polyester resin, resulting in insufficient dispersion of branched polyester resin chains, easy aggregation of hydrophobic phase, and decreased anti-adhesion of hydrophobic stains.

[0123] Example 2 demonstrates superior anti-slip properties, primarily due to the uniform dispersion of polyethylene microwax powder, which hinders resin leveling and forms microscopic sand-like raised textures. The steric hindrance of the long-chain tridecanedioic acid and the 1,4-cyclohexanediethanol alicyclic ring in the carboxyl-terminated polyester resin enhances surface roughness and increases contact area. PDMS-coated silica forms "secondary friction points," embedding into the gaps between contact objects to produce a "biting effect." The low surface energy of the coating reduces water film lubrication in humid environments, preventing slippage. All comparative examples exhibit weaker anti-slip properties than Example 2: Comparative Example 1 lacks PDMS diol, resulting in reduced resin flexibility, gentler sand-like raised textures, and a smaller friction area; Comparative Example 2 lacks trimethylolpropane, leading to insufficient cross-linking, uneven sand-like textures, and fluctuating frictional contact; Comparative Example 3 uses hydroxyl-terminated resin, resulting in loose cross-linking, reduced sand-like raised texture height and density, and a significantly lower coefficient of friction; Comparative Examples 4 and 5 only show slightly poor coating density, resulting in a minor decrease in anti-slip properties; Comparative Example 6 lacks PDMS-coated silica, has no "secondary friction points," and poor sand-like texture shaping, leading to a significant decrease in the coefficient of friction.

[0124] Example 2 exhibits a fine texture and excellent adhesion due to the synergistic effect of "structural regulation and dense cross-linking": the steric hindrance of the 1,4-cyclohexanediethanol alicyclic ring and the long chain of tridecanedioic acid in the carboxyl-terminated polyester resin lays the foundation for the texture; polyethylene microwax powder hinders leveling and strengthens surface protrusions; PDMS-coated silica particles fill and shape the surface, preventing coarse particle agglomeration; and the efficient cross-linking of the carboxyl-terminated and epoxy groups ensures a strong bond between the coating and the substrate. All comparative examples are inferior to Example 2: Comparative Example 1 lacks PDMS diol, yet the texture remains fine, but the resin flexibility decreases, resulting in a slight decrease in adhesion; Comparative Example 2 lacks trimethylolpropane, leading to loose cross-linking, uneven resin flow during film formation, localized uneven texture, and decreased adhesion; Comparative Example 3 uses hydroxyl-terminated resin, resulting in low cross-linking efficiency, significantly uneven texture, weak bonding between the coating and the substrate, and a substantial decrease in adhesion; Comparative Examples 4 and 5 only show slightly poor coating density and a slight decrease in adhesion; Comparative Example 6 lacks PDMS-coated silica, resulting in a decrease in texture fineness but no significant impact on adhesion.

[0125] Example 2 exhibits excellent hydrophobicity because the PDMS diol and PDMS-coated silica work synergistically to form a continuous siloxane layer (low surface energy) on the coating surface, preventing water molecules from spreading. The dense crosslinking of the carboxyl-terminated polyester resin and epoxy resin ensures the stability of the siloxane layer and prevents component migration. The hydrophobicity of each comparative example is weaker than that of Example 2: Comparative Example 1 lacks PDMS diol, resulting in a discontinuous siloxane layer and easy water molecule spreading; Comparative Example 2 lacks trimethylolpropane, resulting only in slightly poor coating surface smoothness and a slightly lower water contact angle; Comparative Example 3 uses a hydroxyl-terminated resin, making it difficult for PDMS chains to migrate to the surface, and the hydroxyl groups are hydrophilic, resulting in a significantly lower water contact angle; Comparative Examples 4 and 5 only have slightly poor coating density and a slightly reduced hydrophobicity; Comparative Example 6 lacks PDMS-coated silica, resulting in an incomplete siloxane layer and a reduced water contact angle.

[0126] Example 2 exhibits excellent weather resistance, likely due to the preferential absorption of UV-326 by the UV absorber, the capture of aging free radicals by the hindered amine light stabilizer 770, the UV-resistant siloxane chains of PDMS diol forming a "protective layer," and the dense cross-linked structure blocking UV and oxygen penetration, thus delaying resin degradation. After xenon lamp aging, it maintains high gloss and exhibits minimal color difference. All comparative examples show inferior weather resistance compared to Example 2: Comparative Example 1 lacks PDMS diol and has no siloxane layer protection, making the resin easily degraded by UV radiation; Comparative Example 2 lacks trimethylolpropane, resulting in loose cross-linking and easy penetration of UV and oxygen; Comparative Example 3 uses hydroxyl-terminated resin, leading to poor cross-linking and easy oxidation of hydroxyl groups (generating aldehydes and ketones), resulting in rapid resin chain breakage, reduced gloss retention, and significant color difference; Comparative Examples 4 and 5 only show slightly poor coating density, resulting in a minor decrease in weather resistance; Comparative Example 6 lacks PDMS-coated silica, resulting in weak PDMS synergistic anti-aging and insufficient resin protection.

[0127] Example 2 exhibits excellent mechanical properties, likely due to the efficient cross-linking of terminal carboxyl groups and epoxy groups under 2-methylimidazole catalysis, forming a three-dimensional dense structure that imparts high impact resistance and adhesion. The flexible segments of PDMS diol absorb impact energy, enhancing flexibility. Trimethylolpropane increases the cross-linking point density, strengthening structural stability and resulting in strong impact and bending resistance. All comparative examples exhibit weaker mechanical properties than Example 2: Comparative Example 1 lacks PDMS diol and flexible segments, leading to reduced impact resistance and flexibility; Comparative Example 2 lacks trimethylolpropane, resulting in fewer cross-linking points, a looser structure, poor impact resistance and flexibility, and easy cracking upon bending; Comparative Example 3 uses terminal hydroxyl resin, resulting in low cross-linking efficiency and low structural density, significantly reducing impact resistance, with cracking appearing at creases and crease edges; Comparative Examples 4 and 5 only show slightly poor coating density, resulting in a slight decrease in mechanical properties; Comparative Example 6 lacks PDMS-coated silica, resulting in only slightly poor coating filling properties and a slight decrease in impact resistance.

[0128] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A non-fluorine, environmentally friendly, stain-resistant, slip-resistant, sand-textured powder coating, characterized by, The raw materials include the following parts by weight: carboxyl-terminated polyester resin: 30-40 parts, bisphenol A type epoxy resin: 20-30 parts, modified nano zinc oxide: 1.5-2.5 parts, polyethylene micro wax powder: 2-4 parts, leveling agent: 0.8-1.5 parts, PDMS coated silica: 1-2 parts, light stabilizer: 0.5-0.8 parts, curing accelerator: 0.1-0.3 parts; The end-carboxyl polyester resin is a branched end-carboxyl polyester containing dimethylsiloxane segments. The modified nano-zinc oxide is a nano-zinc oxide containing indole quaternary ammonium salt and hydrophilic sulfonic acid groups grafted via Si-O-Zn covalent bonds; its preparation method is as follows: (1) 2,3,3-trimethyl-3H-indole-5-carboxylic acid and 1,3-propanesulfonyl lactone were added to anhydrous 1,4-dioxane, heated to 80-100℃ under nitrogen protection, and stirred for 3-5 h. After the reaction was completed, the mixture was cooled to room temperature and added to diethyl ether. The resulting solid was collected by suction filtration, washed three times with ethyl acetate, and dried to obtain intermediate A. (2) Add intermediate A to anhydrous 1,4-dioxane, stir to dissolve, add γ-glycidoxypropyltrimethoxysilane, heat to 70-80℃ under nitrogen protection, stir to react for 2-4 hours, and after the reaction is completed, remove the solvent by vacuum distillation to obtain intermediate B. (3) Add nano zinc oxide to ethanol, ultrasonically disperse for 10-20 min, adjust pH to 5-6 with dilute hydrochloric acid, add intermediate B, heat to 70-80℃, stir for 2-3 h, after the reaction is completed, filter to collect solid precipitate, wash and dry to obtain modified nano zinc oxide.

2. The fluorine-free, environmentally friendly, stain-resistant, anti-slip, sand-textured powder coating according to claim 1, characterized in that, The leveling agent refers to one of polyacrylate leveling agents or silicone-acrylate leveling agents; the light stabilizer refers to a mixture of hindered amine light stabilizer and ultraviolet absorber in a weight ratio of 1:1; the curing accelerator refers to 2-methylimidazole.

3. The fluorine-free, environmentally friendly, stain-resistant, anti-slip, sand-textured powder coating according to claim 1, characterized in that, In (1), the molar ratio of 2,3,3-trimethyl-3H-indole-5-carboxylic acid and 1,3-propanesulfonyl lactone is 1:1-1.2; the weight ratio of 2,3,3-trimethyl-3H-indole-5-carboxylic acid, anhydrous 1,4-dioxane and diethyl ether is 1:8-12:10-20.

4. The fluorine-free, environmentally friendly, stain-resistant, anti-slip, sand-textured powder coating according to claim 1, characterized in that, In (2), intermediate A and γ-glycidyl etheroxypropyltrimethoxysilane are in a molar ratio of 1:1-1.2; intermediate A and anhydrous 1,4-dioxane are in a weight ratio of 1:8-12.

5. The fluorine-free, environmentally friendly, stain-resistant, anti-slip, sand-textured powder coating according to claim 1, characterized in that, In (3), the nano zinc oxide, ethanol and intermediate B are in a weight ratio of 1:8-12:0.12-0.2; the concentration of dilute hydrochloric acid is 0.1-0.5 mol / L.

6. The fluorine-free, environmentally friendly, stain-resistant, anti-slip, sand-textured powder coating according to claim 1, characterized in that, The preparation method of the carboxyl-terminated polyester resin is as follows: Adipic acid, neopentyl glycol, polydimethylsiloxane diol, tridecanoic acid, 1,4-cyclohexanediethanol, and trimethylolpropane were added to a reactor equipped with a water separator. Under nitrogen protection, the temperature was raised to 180-200℃ and stirred for 2-3 hours. The temperature was then raised to 220-240℃, and the vacuum was gradually reduced to ≤50Pa. The reaction was continued for 2.5-3.5 hours. After the reaction was completed, the temperature was lowered to 180℃, and nitrogen was introduced into the reactor to break the vacuum. The molten resin was discharged and allowed to cool naturally to room temperature. It was then pulverized to a particle size of ≤5mm to obtain carboxyl-terminated polyester resin.

7. The fluorine-free, environmentally friendly, stain-resistant, anti-slip, sand-textured powder coating according to claim 6, characterized in that, In the preparation method of the carboxyl-terminated polyester resin, the molar ratio of adipic acid, neopentyl glycol, polydimethylsiloxane diol, tridecanoic acid, 1,4-cyclohexanediethanol and trimethylolpropane is 1-1.2:0.6-0.8:0.2-0.3:0.4-0.6:0.3-0.4:0.1-0.2; the number average molecular weight of polydimethylsiloxane diol is 1500.

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