A solvent-free type anti-graffiti coating agent, a preparation method and application thereof

Abstract

This invention relates to the field of coating technology, specifically to a solvent-free anti-graffiti topcoat, its preparation method, and its application. The solvent-free anti-graffiti topcoat is composed of the following raw materials in weight percentages: 80wt%-95wt% solvent-free methylphenyl silicone resin, 1wt%-5wt% curing agent, 3wt%-8wt% adhesion enhancer, 0.5wt%-3wt% anti-graffiti additive, and optionally 0wt%-6wt% matting agent. The core component is that the adhesion enhancer is a reinforced silane coupling agent, prepared by molecular-level chemical bonding of a titanium compound, a silane coupling agent, and a self-made anti-fouling agent. This invention's topcoat has advantages such as high adhesion, excellent stain resistance, and adjustable gloss, making it suitable for substrate protection in various scenarios, including building exterior walls, home ceramic coatings, and artistic coatings.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a solvent-free anti-graffiti topcoat agent, its preparation method, and its application. Background Technology

[0002] As the final protective layer of a coating system, the topcoat directly determines the coating's durability, decorative properties, and anti-graffiti performance. Traditional water-based topcoats have poor abrasion resistance and virtually no anti-graffiti properties; even ordinary pencils and crayons cannot erase them. Solvent-based topcoats, while performing reasonably well, contain large amounts of volatile organic compounds (VOCs), posing a threat to the environment and human health. With increasingly stringent environmental regulations, the development of solvent-free, high-performance topcoats has become an urgent industry need. However, simply removing the solvent leads to increased system viscosity, decreased stability, and poses greater challenges to substrate adhesion and long-term anti-graffiti performance.

[0003] Existing solvent-free topcoats mostly use silicone resin as a matrix, relying on its low surface energy to achieve anti-graffiti function. However, this has inherent limitations: on the one hand, the adhesion between silicone resin and inorganic substrates (such as stone and metal) is generally weak, requiring the use of silane coupling agents to improve it; on the other hand, traditional physically blended silane coupling agents have a single function, only acting as an adhesive bridge and unable to participate in system cross-linking. They also do not inhibit the migration and loss of small-molecule anti-graffiti additives, leading to a rapid decline in anti-graffiti performance. In addition, a single formulation cannot meet the diverse decorative needs such as high gloss and matte finishes.

[0004] While existing research has attempted to improve performance by adding titanate catalysts or composite silanes, these efforts have largely remained at the physical blending stage, lacking molecular-level synergy among the components and prone to phase separation or functional cancellation. How to simultaneously address key issues such as adhesion, durable anti-graffiti properties, and gloss control without introducing solvents remains a critical technological bottleneck that urgently needs to be overcome in this field. Therefore, developing a solvent-free topcoat agent that combines environmental friendliness with comprehensive performance is of great significance for promoting technological upgrades in the industry. Summary of the Invention

[0005] To address the shortcomings of the existing technology, this invention provides a solvent-free anti-graffiti coating agent, its preparation method, and its application.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A solvent-free anti-graffiti topcoat is composed of the following raw materials in weight percentages:

[0008] Solvent-free methylphenyl silicone resin 80wt%-95wt%,

[0009] Hardener 1wt%-5wt%,

[0010] Adhesion enhancer 3wt%-8wt%,

[0011] Anti-graffiti additive 0.5wt%-3wt%,

[0012] And optional matting agent 0wt%-6wt%.

[0013] Preferably, when the topcoat is glossy, it does not contain a matte agent; when the topcoat is matte, it contains 3wt%-6wt% of a matte agent.

[0014] Preferably, the curing agent is selected from one or more of titanate, isocyanate, and amino resin;

[0015] The adhesion enhancer is a reinforced silane coupling agent; the anti-graffiti additive is selected from one or more of hydroxyl silicone oil, amino silicone oil, and hydrogen-containing silicone oil; the matting agent is hydrophobic fumed silica.

[0016] While the direct addition of ordinary silane coupling agents can improve adhesion to some extent, this invention has several inherent drawbacks. First, its function is limited; it acts only as a physical adhesive bridge and cannot actively participate in and optimize the cross-linking network of the system, resulting in a minimal improvement in adhesion. Second, regarding anti-graffiti properties, it does not possess anti-graffiti functionality itself and cannot address the issues of easy migration and precipitation of small-molecule anti-graffiti additives. In fact, compatibility problems may exacerbate additive loss, leading to a rapid decline in anti-graffiti performance.

[0017] Adding enhanced silane coupling agents can effectively overcome the defects of ordinary silane coupling agents. In terms of adhesion, enhanced silane coupling agents couple titanium compounds with silanes through the reaction between the substances. It is not only an adhesive bridge, but also catalyzes the cross-linking reaction between itself and the substrate, and between itself and the resin in situ, forming a robust transition layer with a higher cross-linking density at the interface. This achieves a leap from direct physical coating to chemical fusion, resulting in adhesion strength and durability far exceeding that of ordinary silanes. In terms of anti-graffiti durability, the key lies in the covalent chemical integration of the anti-graffiti components into the molecular chain. The anti-graffiti components are fixed in the network by chemical bonds, avoiding the problem of small molecules in physical blends failing due to rapid migration and precipitation. It can be slowly released with environmental action, continuously replenishing the anti-graffiti layer on the surface. Even if the surface is worn, the internal structure can continue to work, thus achieving long-lasting anti-graffiti capability. In terms of gloss control, its larger molecular structure and excellent compatibility improve the stability of the system. More importantly, its built-in titanium catalyst can promote the formation of a more uniform and stable cross-linking structure in the entire system. This structure can effectively lock the matting agent particles, preventing them from flocculating or settling, ensuring the uniformity and stability of the gloss of matte products, and achieving precise control over the final appearance.

[0018] Preferably, the adhesion enhancer is an enhanced silane coupling agent, which is prepared by a method including the following steps: mixing a titanium compound, a silane coupling agent, an antifouling agent and an organic solvent and reacting them, and then removing the organic solvent after the reaction.

[0019] Preferably, the titanium compound is titanium diammonium tetrachloride; the antifouling agent is prepared by reacting an alkanolamine compound with an acrylate compound in an alcohol solvent.

[0020] Preferably, the silane coupling agent is selected from at least one of silane coupling agents containing amino and carboxyl groups.

[0021] Furthermore, the silane coupling agent is at least one or two of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, N-[β-(N,N-diacetyl)aminoethyl]-γ-(N-acetyl)aminopropyltrimethoxysilane, acrylamidopropyltrimethoxysilane, and allyltriethoxysilane; even further, the silane coupling agent is a compound of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and N-[β-(N,N-diacetyl)aminoethyl]-γ-(N-acetyl)aminopropyltrimethoxysilane in a mass ratio of 1:(1-3).

[0022] The reaction mechanism of enhanced silane coupling agents is as follows: The titanium (IV) center coordinates with the hydroxyl and amide oxygen atoms in the antifouling agent molecule to form a chelate ring. The titanium (IV) center coordinates with the carboxyl group in carboxyl-containing silane coupling agents (such as N-[β-(N,N-diacetyl)aminoethyl]-γ-(N-acetyl)aminopropyltrimethoxysilane) and / or forms ionic bonds. Under certain reaction conditions, a titanium-oxygen bond may also be partially formed. The titanium (IV) center interacts with amino-containing silane coupling agents. The amino group in the coupling agent (such as 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane) undergoes coordination; at the same time, the titanium (IV) center undergoes strong coordination and / or ionic bonding with the carboxyl group on the carboxylated silane coupling agent; if the silane coupling agent used contains electron-donating functional groups such as amino groups, it can also undergo additional coordination with the titanium center, forming a multinuclear hybrid structure centered on titanium, thereby significantly improving the stability and durability of the coating.

[0023] Preferably, the preparation method of the enhanced silane coupling agent is as follows: including the following steps: under an inert atmosphere, 6-12 parts by weight of titanium compound, 12-20 parts by weight of silane coupling agent, 3-8 parts by weight of antifouling agent and 200-400 parts by weight of organic solvent are mixed evenly, and stirred at 60-80°C for 2-6 hours. Then, the organic solvent is removed by vacuum distillation to obtain the enhanced silane coupling agent.

[0024] The reaction mechanism of the antifouling agent: The amino group in diethanolamine undergoes a Michael addition reaction with butyl acrylate. The secondary amino group in the diethanolamine molecule acts as a nucleophilic center, launching a nucleophilic attack on the β-carbon atom in the acryloyl group of butyl acrylate, which is activated by the conjugation effect, resulting in a Michael addition reaction and ultimately forming a CN bond. The antifouling agent molecule in this invention also contains polydentate coordinating groups such as hydroxyl and amide groups, which can coordinate or covalently bond with titanium compounds and carboxyl / amino silanes, participating in the crosslinking network of reinforced silane coupling agents and silicone resins. This avoids the easy migration and loss of ordinary small molecule additives, and continuously exerts antifouling effects inside the paint film and at the interface. At the same time, these chemically fixed antifouling groups selectively accumulate on the coating surface during film formation, synergistically reducing surface energy with organosilicon resins and silicone oil-based antigraffiti additives, making it difficult for water and stains to wet and adhere, and easy to clean, thus achieving long-lasting antigraffiti effect.

[0025] Preferably, the antifouling agent is prepared by the following method: 6-10 parts by weight of diethanolamine, 8-16 parts by weight of butyl acrylate and 100-180 parts by weight of anhydrous ethanol are mixed evenly, stirred and reacted at 50-70°C for 1-5 hours, and then the ethanol is removed by vacuum distillation to obtain the antifouling agent.

[0026] The preparation method of the solvent-free anti-graffiti topcoat includes the following steps: mixing the solvent-free methylphenyl silicone resin, curing agent, adhesion enhancer, anti-graffiti additive and optional matting agent in the specified mass percentages, and stirring at high speed until uniform to obtain the topcoat.

[0027] A method for anti-graffiti treatment of a substrate includes the steps of applying the solvent-free anti-graffiti topcoat agent described above to the surface of the substrate and allowing it to cure.

[0028] The roles of each substance in this invention:

[0029] Solvent-free methylphenyl silicone resin: As the matrix resin of the system, it forms the skeleton and continuous phase of the paint film. Its role is to provide excellent weather resistance, low surface energy for anti-graffiti properties, and ensure environmental safety. The organosilicon backbone endows the coating with extremely strong UV resistance, high and low temperature resistance, and is not prone to yellowing or chalking, with a lifespan far exceeding that of ordinary organic resins. Simultaneously, its inherent low surface energy produces excellent hydrophobic effects, making it difficult for water and water-borne contaminants to adhere. Methyl groups provide hydrophobicity and flexibility, while phenyl groups enhance heat resistance, hardness, and compatibility with other components. Furthermore, the solvent-free nature essentially eliminates VOC emissions, meeting environmental protection requirements and ensuring construction safety.

[0030] Hardener: The crosslinking engine of the system, its core role is to chemically react with the active groups of silicone resin, transforming the liquid coating into a robust solid film. This crosslinking process is crucial, significantly improving the final properties of the film, including hardness, abrasion resistance, chemical resistance, and anti-blocking properties. Without a hardener, the coating will not achieve sufficient mechanical strength and service durability.

[0031] Adhesion enhancers: acting as molecular bridges between the coating and the substrate, their core function is to solve the key problem of insufficient adhesion of high-performance silicone coatings on inorganic substrates. Ordinary silane coupling agents achieve this function through their amphiphilic structure: the hydrolyzable group at one end forms a strong Si-O-Si covalent bond with the substrate; the organic functional group at the other end chemically bonds or physically entangles with the resin system.

[0032] Anti-graffiti additives are functional modifiers for the paint film surface. Their core function is to migrate to the coating surface, forming a dynamic, extremely low surface energy protective layer, thereby enhancing and maintaining the anti-graffiti performance of the system. Different types of silicone oils have their own characteristics: hydroxyl silicone oils improve the feel and contribute hydrophobicity; amino silicone oils, due to their polarity, can be oriented, providing more durable hydrophobic and oleophobic properties; hydrogen-containing silicone oils can crosslink under the action of a catalyst, forming a stronger and more durable anti-graffiti layer. Their compatibility with silicone resins, but not complete compatibility, ensures that they can migrate slowly and continuously to the surface. Even if the surface layer fails due to wear or aging, the internal additives can be replenished in time, thus overcoming the defects of small molecule additives being easily lost and having a short anti-graffiti lifespan.

[0033] Matting agents are optical property modifiers in a system. They reduce surface gloss and achieve a matte or satin finish by creating microscopic roughness in the paint film to scatter light. This formulation uses hydrophobic fumed silica, which, after surface treatment, exhibits good compatibility with solvent-free silicone resin systems and can be uniformly dispersed to form a large number of micron / nanometer-scale scattering points. This not only meets the diverse aesthetic demands of the market but also greatly improves production efficiency and the versatility of the formulation.

[0034] This formulation system achieves its goals through the interaction of its components. The resin and curing agent crosslink to form a robust paint film framework, laying the foundation for weather resistance and mechanical properties. The enhanced silane coupling agent acts as a core bridge, chemically bonding the substrate and resin network at both ends, fundamentally solving adhesion problems. Simultaneously, its built-in anti-fouling and catalytic components work in synergy with the system. Anti-graffiti additives dynamically migrate to the surface, working synergistically with the resin's inherent low surface energy and the coupling agent's anti-fouling function. The matting agent precisely controls gloss without compromising system compatibility. The entire system achieves integrated synergy from interfacial adhesion, overcoming the problems of poor adhesion, short-lasting anti-graffiti performance, and limited functionality inherent in traditional products.

[0035] The beneficial effects of this invention are:

[0036] This invention provides a solvent-free anti-graffiti topcoat, its preparation method, and its application. By employing an enhanced silane coupling agent, a breakthrough improvement in coating performance is successfully achieved. This component chemically bonds titanium compounds, silane coupling agents, and antifouling agents into a single structure. The titanium center provides a powerful catalytic cross-linking function, significantly enhancing interfacial adhesion and forming a dense paint film network. The chemically bonded antifouling agent establishes a durable antifouling mechanism, effectively solving the technical problem of easy migration and loss of traditional physically blended antifouling agents. This molecular-level functional integration enables the product to maintain its solvent-free and environmentally friendly characteristics while achieving beneficial properties such as Grade 0 adhesion, stain resistance, and water resistance.

[0037] 2. The topcoat system of this invention exhibits excellent applicability and stability. By adjusting the amount of matting agent added, a series of products ranging from high gloss to matte can be flexibly prepared on the same technical platform to meet the decorative needs of different application scenarios. The titanium catalyst in the enhanced silane coupling agent effectively stabilizes the matting agent dispersion system, prevents particle flocculation and sedimentation, and ensures the uniformity and stability of the gloss of matte products. This invention successfully overcomes common industry problems such as insufficient adhesion, rapid decay of anti-graffiti performance, and limited functionality of traditional topcoats, providing a comprehensive and environmentally friendly protective solution with excellent performance for building exterior walls, home ceramic coatings, and artistic coatings. Detailed Implementation

[0038] The invention will now be described in further detail with reference to specific embodiments, but it should not be construed as limiting the scope of the invention to the following embodiments.

[0039] The raw materials described in this application are partially described; all other raw materials not described are commercially available.

[0040] The solvent-free methylphenyl silicone resin was purchased from Hubei Longsheng Sihai New Materials Co., Ltd., grade: SH-3047.

[0041] The hydrophobic fumed silica was purchased from Shanghai Zhenlishi Network Technology Co., Ltd., model number: TS620.

[0042] The hydroxyl silicone oil was purchased from Shandong Juneng Chemical Co., Ltd., model: JN-204.

[0043] Example 1

[0044] A solvent-free anti-graffiti topcoat, wherein when the topcoat is glossy, it is composed of the following raw materials in weight percentage: 92wt% solvent-free methylphenyl silicone resin, 2wt% curing agent, 5wt% adhesion enhancer, and 1wt% anti-graffiti additive.

[0045] The curing agent is tetrabutyl titanate.

[0046] The adhesion enhancer is a reinforced silane coupling agent.

[0047] The anti-graffiti additive is hydroxy silicone oil.

[0048] The adhesion enhancer is a reinforced silane coupling agent, and the preparation method of the reinforced silane coupling agent is as follows:

[0049] Under nitrogen atmosphere, 9 parts by weight of diammonium tetrachloride, 15 parts by weight of silane coupling agent, 6 parts by weight of antifouling agent and 300 parts by weight of DMF are mixed evenly and added to a sealed stirred reactor. The mixture is stirred at 70°C and 400 rpm for 5 hours. DMF is removed by vacuum distillation to obtain the enhanced silane coupling agent.

[0050] The antifouling agent is prepared by the following method: 8 parts by weight of diethanolamine, 12 parts by weight of butyl acrylate and 120 parts by weight of anhydrous ethanol are mixed evenly and stirred at 60°C and 200 rpm for 2.5 h. The ethanol is removed by vacuum distillation to obtain the antifouling agent.

[0051] The silane coupling agent is a mixture of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and N-[β-(N,N-diacetyl)aminoethyl]-γ-(N-acetyl)aminopropyltrimethoxysilane in a mass ratio of 1:2.

[0052] The preparation method of the solvent-free anti-graffiti topcoat is as follows: Mix solvent-free methylphenyl silicone resin, curing agent, adhesion enhancer and anti-graffiti additive, and stir at 800 rpm for 30 min to obtain the solvent-free anti-graffiti topcoat.

[0053] Example 2

[0054] The method is basically the same as Example 1, except that the silane coupling agent used in the preparation method of the enhanced silane coupling agent is 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane.

[0055] Example 3

[0056] The method is basically the same as Example 1, except that the silane coupling agent in the preparation method of the enhanced silane coupling agent is N-[β-(N,N-diacetyl)aminoethyl]-γ-(N-acetyl)aminopropyltrimethoxysilane.

[0057] Example 4

[0058] The process is basically the same as in Example 1, except that when the topcoat is matte, a matting agent is added to the raw materials of the solvent-free anti-graffiti topcoat, which consists of the following raw materials by mass percentage: 88wt% solvent-free methylphenyl silicone resin, 2wt% curing agent, 5wt% adhesion enhancer, 1wt% anti-graffiti additive, and 4wt% matting agent.

[0059] The curing agent is the same as that used in Example 1.

[0060] The anti-graffiti additive is the same as in Example 1.

[0061] The matting agent is hydrophobic fumed silica.

[0062] The adhesion enhancer is the same as in Example 1.

[0063] Comparative Example 1

[0064] A solvent-free anti-graffiti topcoat, wherein when the topcoat is glossy, it is composed of the following raw materials in weight percentage: 92wt% solvent-free methylphenyl silicone resin, 2wt% curing agent, 5wt% adhesion enhancer, and 1wt% anti-graffiti additive.

[0065] The curing agent is tetrabutyl titanate.

[0066] The adhesion enhancer is a reinforced silane coupling agent.

[0067] The anti-graffiti additive is hydroxy silicone oil.

[0068] The adhesion enhancer is a reinforced silane coupling agent, and the preparation method of the reinforced silane coupling agent is as follows:

[0069] Under nitrogen atmosphere, 9 parts by weight of diammonium tetrachloride, 15 parts by weight of silane coupling agent, 6 parts by weight of antifouling agent and 300 parts by weight of DMF are mixed evenly and added to a sealed stirred reactor. The mixture is stirred at 70°C and 400 rpm for 5 hours. DMF is removed by vacuum distillation to obtain the enhanced silane coupling agent.

[0070] The antifouling agent is prepared by the following method: 8 parts by weight of diethanolamine, 12 parts by weight of butyl acrylate and 120 parts by weight of anhydrous ethanol are mixed evenly and stirred at 60°C and 200 rpm for 2.5 h. The ethanol is removed by vacuum distillation to obtain the antifouling agent.

[0071] The silane coupling agent is a mixture of octyltriethoxysilane and N-[β-(N,N-diacetyl)aminoethyl]-γ-(N-acetyl)aminopropyltrimethoxysilane in a mass ratio of 1:2.

[0072] The preparation method of the solvent-free anti-graffiti coating agent is the same as that in Example 1.

[0073] Comparative Example 2

[0074] The process is basically the same as in Example 1, except that the solvent-free anti-graffiti topcoat is composed of the following raw materials in glossy form: 92 wt% solvent-free methylphenyl silicone resin, 2 wt% curing agent, 5 wt% adhesion enhancer, and 1 wt% anti-graffiti additive.

[0075] The adhesion enhancer is not a chemically bonded reinforcing silane coupling agent, but rather a physical mixture of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and N-[β-(N,N-diacetyl)aminoethyl]-γ-(N-acetyl)aminopropyltrimethoxysilane in a mass ratio of 1:2, which is then used directly as an adhesion enhancer.

[0076] The curing agent is the same as that used in Example 1.

[0077] The anti-graffiti additive is the same as in Example 1.

[0078] The preparation method of the solvent-free anti-graffiti coating agent is the same as that in Example 1.

[0079] Comparative Example 3

[0080] The method is basically the same as in Example 1, except that the titanium compound diammonium tetrachloride in the preparation method of the enhanced silane coupling agent is replaced with titanium dichlorodicenocene.

[0081] Comparative Example 4

[0082] It is basically the same as Example 1, except that the adhesion enhancer is a reinforced silane coupling agent.

[0083] The preparation method of the enhanced silane coupling agent is as follows:

[0084] Under nitrogen atmosphere, 9 parts by weight of diammonium tetrachloride, 15 parts by weight of silane coupling agent and 300 parts by weight of DMF were mixed evenly and added to a sealed stirred reactor. The mixture was stirred and reacted at 70°C and 400 rpm for 5 hours. DMF was removed by vacuum distillation to obtain the enhanced silane coupling agent.

[0085] The silane coupling agent is a mixture of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and N-[β-(N,N-diacetyl)aminoethyl]-γ-(N-acetyl)aminopropyltrimethoxysilane in a mass ratio of 1:2.

[0086] Comparative Example 5

[0087] The process is basically the same as in Example 1, except that the antifouling agent is prepared by the following method: 8 parts by weight of 2-amino-2-methyl-1-propanol, 12 parts by weight of butyl acrylate and 120 parts by weight of anhydrous ethanol are mixed evenly and stirred at 60°C and 200 rpm for 2.5 h. The ethanol is removed by vacuum distillation to obtain the antifouling agent.

[0088] Test Example 1

[0089] Performance index determination: Referring to the industry standard HG / T 5065-2016 "Topcoat Varnish for Architectural Coatings", the solvent-free anti-graffiti topcoat prepared in the above examples and comparative examples were tested. The stain resistance was tested using black marker, colored pen and cement paste as the staining medium to evaluate the residual rate after cleaning. Each set of data can be tested 4 times and the average value is taken. The results are shown in Table 1.

[0090] Table 1 Performance Index Measurement Results

[0091]

[0092] The results above show that the solvent-free anti-graffiti topcoat prepared by this invention has good gloss, stain resistance, water resistance, and adhesion. Specifically, as shown in Examples 1-3, Example 1 uses a combination of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and N-[β-(N,N-diacetyl)aminoethyl]-γ-(N-acetyl)aminopropyltrimethoxysilane as a coupling agent. The technical effect is significantly better than that of Examples 2 and 3 using any one of these coupling agents. This is because the bisaminosilane, through coordination bonds, and the carboxylic acid silane, through covalent / ionic bonds, firmly fix the silane molecules around the titanium center through two different chemical forces, forming an exceptionally stable structure. Therefore, the adhesion, water resistance, and durability are all superior to those using a single silane. Furthermore, as can be seen from Examples 1 and 1 Comparative Example, Example 1 uses a highly active amino / carboxylsilane, which can form strong coordination and covalent bonds with the titanium center to create a more stable hybrid interface layer. In contrast, Comparative Example 1 uses an inert octylsilane, whose alkyl chains cannot chemically interact with the titanium center, resulting in the failure of the interface bridging function. This not only causes a sharp drop in adhesion but also damages the overall cross-linking network, leading to a decline in stain resistance / graffiti resistance and water resistance. When Comparative Example 2 uses a physically mixed silane, the components are independent of each other and cannot construct a stable hybrid structure centered on titanium. It lacks both interfacial catalytic cross-linking function and, due to the easy loss of anti-graffiti additives, cannot achieve a durable stain resistance / graffiti effect, resulting in a comprehensive decline in overall performance. Comparative Example 3 uses titanium dichlorodicyclopentadiene, whose stable cyclopentadiene structure and chloride ions make it difficult to react with the silane in this system as expected, failing to form an effective molecular bridging structure, resulting in the failure of the interface strengthening function and a significant decrease in performance. In particular, Comparative Example 4, lacking a chemically bonded antifouling agent and relying solely on physically blended additives, experiences rapid migration and loss, leading to a sharp decline in stain resistance / graffiti resistance. Comparative Example 5 uses 2-amino-2-methyl-1-propanol, which has high steric hindrance and few coordination sites, resulting in poor chelation stability with titanium, leading to a decrease in the slow-release efficiency of the antifouling agent and a significant reduction in stain resistance. Furthermore, a comparison between Examples 1 and 4 shows that adhesion and stain resistance are reduced, while water resistance remains excellent. By introducing 4 wt% of a hydrophobic fumed silica matting agent, the 60° gloss level can be significantly reduced, achieving an adjustable appearance from high gloss to matte. However, the comparative examples did not simultaneously achieve both the above-mentioned performance and gloss control.

Claims

1. A solvent-free type anti-graffiti overcoat characterized by comprising: consists of the following raw materials in percentage by mass: a solvent-free methyl phenyl silicone resin 80wt%-95wt%, a curing agent 1wt%-5wt%, an adhesion enhancer 3wt%-8wt%, an anti-graffiti aid 0.5wt%-3wt%, and optionally a matting agent 0wt%-6wt%; the adhesion enhancer is an enhanced silane coupling agent, which is prepared by mixing 6-12 parts by weight of a titanium compound, 12-20 parts by weight of a silane coupling agent, 3-8 parts by weight of an anti-fouling agent and 200-400 parts by weight of an organic solvent uniformly under an inert atmosphere, stirring and reacting at 60-80℃ for 2-6h, and then removing the organic solvent by distillation under reduced pressure; the titanium compound is titanium diammine tetrachloride; the silane coupling agent is at least one or two of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, N-[β-(N,N-diethylcarboxyl)aminoethyl]-γ-(N-ethoxyl)aminopropyl trimethoxysilane, and acrylamidopropyl trimethoxysilane; the anti-fouling agent is prepared by mixing 6-10 parts by weight of diethanolamine, 8-16 parts by weight of butyl acrylate and 100-180 parts by weight of anhydrous ethanol uniformly, stirring and reacting at 50-70℃ for 1-5h, and then removing ethanol by distillation under reduced pressure; the anti-graffiti aid is selected from one or more of hydroxyl silicone oil, amino silicone oil, and hydrogen-containing silicone oil.

2. The solvent-free anti-graffiti overcoat of claim 1, wherein, When the finish is of the glossy type, it does not contain a matting agent; when the finish is of the matte type, it contains 3wt%-6wt% of a matting agent.

3. The solvent-free anti-graffiti overcoat of claim 1, wherein, the curing agent is selected from one or more of titanate, isocyanate, and amino resin; and the matting agent is hydrophobic fumed silica.

4. The process for the preparation of a solvent-free anti-graffiti overcoat according to any one of claims 1 to 3, characterized in that, comprising the step of mixing the solvent-free methyl phenyl silicone resin, the curing agent, the adhesion enhancer, the anti-graffiti aid, and the optional matting agent, and stirring at high speed until uniform, to obtain the finish.

5. A method for anti-graffiti treatment of a substrate, characterized in that comprising the step of applying the solvent-free anti-graffiti finish of any one of claims 1-3 to the surface of a substrate, and allowing it to cure.

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