A coating material with hydrophilic self-cleaning ability and its preparation method and application

Abstract

The application discloses a coating with hydrophilic self-cleaning capability and a preparation method and application thereof, and belongs to the technical field of coatings. The coating comprises modified terpene phenolic resin, compounded hydrophilic agent, functional filler, modified garnet powder, naphthenic acid metal salt and the like. The modified terpene phenolic resin is obtained by grafting modification of terpene phenolic resin with polytetrahydrofuran diol, the compounded hydrophilic agent is obtained by compounding C8-C10 alkyl glycoside and sorbitol, the functional filler is obtained by in-situ loading of modified barium metaborate in sepiolite by a silane coupling agent and then preparing a silicon dioxide layer on the surface, the modified garnet powder is obtained by modifying garnet powder with an alkyl silane coupling agent, and the naphthenic acid metal salt is obtained by compounding naphthenic acid zinc and naphthenic acid aluminum. The obtained coating has excellent curing performance, and has the performances of hydrophilic self-cleaning, anti-erosion, anti-microbial erosion and temperature change resistance, and can meet the long-term protection use requirements of high-speed rail power facilities under the subtropical humid climate.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, specifically a coating with hydrophilic self-cleaning ability, its preparation method, and its application. Background Technology

[0002] The Sichuan Basin and surrounding mountainous areas, as well as the eastern Sichuan valley region, are densely covered with high-speed rail lines. Several core trunk lines, including the Chongqing-Kunming High-Speed ​​Railway and the Southern Sichuan Intercity Railway, traverse complex terrain of mountains and valleys. These lines house numerous critical power supply facilities, such as transmission towers, contact network hardware, pole-mounted and suspension insulators, and outdoor distribution boxes, forming a core supporting system for ensuring the safe and stable operation of the region's high-speed rail network. This region has a typical subtropical humid climate with abundant forest vegetation, a very high proportion of bridges and tunnels, and frequent cloud cover and persistently saturated air humidity. Furthermore, the area faces multiple challenges, including wheel-rail dust, fine particles from mountainous soil and rock, and microbial erosion. These environmental factors easily lead to surface contamination, substrate corrosion and aging, and insulation degradation of high-speed rail electrical equipment, increasing the risk of safety hazards. Therefore, hydrophilic self-cleaning coatings with long-lasting protective advantages are a core protective measure for preventing contamination and corrosion and ensuring insulation safety of the high-speed rail electrical facilities in this region.

[0003] Currently, most hydrophilic self-cleaning coatings on the market use nationally standardized formulas, without being optimized for specific operating conditions based on the unique climate, geography, and ecological characteristics of the region. This results in numerous technical shortcomings during field service, as detailed below: Firstly, the fine conductive metal dust generated by the long-term friction between train wheels and rails, under the continuous entrainment of high-speed airflow, will exert a continuous micro-cutting and erosion effect on the surface of the equipment coating. Commercially available hydrophilic coatings mostly use organic hydrophilic modified components, resulting in relatively low overall mechanical hardness. After long-term erosion and wear by metal dust, they are prone to forming localized pit defects, damaging the hydrophilic microstructure of the coating surface, leading to a significant reduction in the coating's self-cleaning function, and in severe cases, localized functional failure. Simultaneously, conductive metal dust adhering to coating defects can contact the equipment substrate in high-humidity environments and form a galvanic cell circuit, inducing electrochemical corrosion of the substrate, gradually weakening the interfacial bonding strength between the coating and the substrate, and continuously deteriorating the overall protective performance of the coating. Furthermore, the fine particles of mountainous soil and rock distributed along the route are mostly hydrophobic, easily embedding into the micropores of the coating surface, blocking hydrophilic channels, hindering the continuous spread of water film on the equipment surface and rainwater runoff, further reducing the coating's self-cleaning ability, causing various types of dirt to remain on the coating surface for longer periods.

[0004] Secondly, the region experiences frequent cloud cover and fog throughout the year, with frequent nighttime rain, resulting in a persistently saturated high-humidity environment. Under such conditions, static condensation forms on equipment surfaces, without continuous rainwater runoff to create a dynamic water film, hindering the effective self-cleaning function of hydrophilic coatings. Furthermore, the warm, humid environment easily fosters the growth of microorganisms such as Aspergillus niger and Penicillium, forming dense biofilms. The organic acids produced by Aspergillus niger's metabolism corrode the coating resin matrix and degrade surface hydrophilic active groups, leading to coating chalking and performance degradation. The sticky biofilm formed by Penicillium locks in moisture on the equipment surface, accelerating water vapor penetration, creating a chain reaction of destructive effects from the combined effects of high humidity and microbial erosion.

[0005] Thirdly, the high-speed rail lines in the region have dense bridge and tunnel connections. When a train exits a tunnel, the temperature difference between the inside and outside can reach 15-25°C. The rapid convergence of warm and cold air causes a large amount of condensation to quickly form on the equipment surface. This, combined with the high-speed gusts of wind that are present at the tunnel entrance year-round, subjects the coating to the triple coupling effect of sudden temperature changes, condensation wetting, and high-speed airflow erosion. The general hydrophilic coating resin system has poor adaptability to cold and heat cycles and thermal expansion matching. Long-term repeated temperature stress easily induces network microcracks inside the coating and at the coating-substrate interface. Condensed water vapor and surface dirt and corrosive media will continue to penetrate along the microcracks, gradually expanding the fine cracks into penetrating cracks, causing the coating to peel, detach, and break over a large area, weakening the protective effect of the overall protective system.

[0006] Based on this, we need to develop a special coating that is suitable for the above-mentioned complex working conditions and has comprehensive properties such as long-lasting hydrophilic self-cleaning, high insulation, resistance to cold and heat cracking, resistance to media corrosion, and resistance to biological aging. This coating has good engineering application value and promotion significance. Summary of the Invention

[0007] The purpose of this invention is to provide a coating with hydrophilic self-cleaning ability, its preparation method and application. The coating has good erosion resistance, antimicrobial erosion, temperature change resistance, high insulation and corrosion resistance, and can meet the long-term use needs of power facilities along high-speed railways in subtropical humid climates.

[0008] The objective of this invention is achieved through the following technical solution: A coating with hydrophilic self-cleaning properties comprises the following raw materials in parts by weight: 46-54 parts modified terpene phenolic resin, 7-9 parts compounded hydrophilic agent, 13-16 parts functional filler, 5-7 parts modified garnet powder, 2-4 parts naphthenic acid metal salt, 0.5-1.5 parts cerium-zirconium composite drying agent, and 18-25 parts deionized water; The modified terpene phenolic resin is obtained by grafting terpene phenolic resin with polytetrahydrofuran diol.

[0009] The compound hydrophilic agent is composed of C8~C10 alkyl glycosides and sorbitol; The preparation process of the functional filler is as follows: barium metaborate is modified with a silane coupling agent to obtain modified barium metaborate, and then the modified barium metaborate is loaded in situ onto sepiolite, and then a silica layer is formed on the surface of the loaded product by acidic silica sol, thus obtaining the functional filler; the acidic silica sol is a silica sol acidified with nitric acid to pH=2~3.

[0010] The modified garnet powder is obtained by modifying garnet powder with an alkylsilane coupling agent; The naphthenic acid metal salt is obtained by compounding zinc naphthenate and aluminum naphthenate.

[0011] The coating provided by this invention has the following functions for each component: Modified terpene phenolic resin serves as the primary film-forming material in coatings. The terpene phenolic copolymer framework imparts excellent resistance to temperature changes, substrate adhesion, and hydrolysis resistance to the coating. Chemically bonded flexible polyether segments mitigate the excessive rigidity of pure terpene phenolic resin, buffering residual interfacial stress generated during resin curing and reducing nanoscale micro-debonding within the coating. This modified system inhibits water absorption and deformation of polar segments in high-humidity, foggy environments, enhancing the adhesion stability and wear resistance of the coating under alternating tunnel winds and repeated temperature-dependent load conditions. Furthermore, compared to physical blending systems, grafting modification effectively prevents the migration and precipitation of additives during long-term service. Simultaneously, the flexible segments grafted onto the resin molecules form a protective layer, mitigating the corrosive and damaging effects of fungal metabolites on the resin matrix.

[0012] The compounded hydrophilic agent is composed of C8-C10 alkyl glycosides and sorbitol. The numerous hydroxyl groups in these two components synergistically build a continuous and stable hydrophilic network, enabling the coating to maintain its hydrophilic structure integrity in high-humidity environments and achieving a self-cleaning effect through a uniform surface water film. This hydrophilic system balances the coating's hydrophilic properties with its high-voltage insulation performance, mitigating the problem of decreased surface insulation performance caused by continuous water film adhesion.

[0013] In the functional filler, barium metaborate is first surface-modified using a silane coupling agent. The silanol groups generated from silane hydrolysis form a stable bond structure with the surface-active groups of barium metaborate, passivating some highly active sites and inhibiting the explosive release of borate ions from the source. Simultaneously, sufficient surface-active sites are retained to maintain contact antibacterial ability, achieving initial slow-release of ions and prolonging the antibacterial effect. The silane organic segments improve the surface state of barium metaborate, enhancing its binding ability with the inner wall of sepiolite, laying the foundation for subsequent stable loading. Subsequently, the modified barium metaborate is loaded onto sepiolite, utilizing the porous fibrous structure of sepiolite to adsorb organic matter from the environment, reducing the nutrient source required for mold growth. Finally, silica sol was used to modify the outer surface of sepiolite, regularizing and narrowing the surface pores. On the one hand, the pore-limiting effect, combined with the inner silane layer, creates a synergistic slow-release effect, further slowing down the rate of outward migration and diffusion of boron ions. This effectively avoids the problem of increased surface conductivity and decreased high-voltage insulation performance caused by the free migration of boron ions. On the other hand, the narrowed surface pores can form physical confinement, preventing the load powder from detaching and enhancing the overall load stability. This surface structure can block the spread of hyphae into the depth of the coating. The micropores remaining on the sepiolite surface allow surface microorganisms to contact the barium metaborate on the sepiolite to exert an antibacterial effect, while also ensuring the continuous trace release of ions. Silica sol can also regulate the micro-pore structure of sepiolite, optimize the overall surface polarity of the powder, and improve the compatibility of composite powder with organic coating systems. At the same time, it can improve the compatibility differences between sepiolite and garnet powders: sepiolite has a porous fibrous structure, which differs from garnet powder with high hard edges in terms of mechanical properties and dry and wet deformation performance. Direct compounding can easily lead to micro-stress concentration and uneven pores inside the coating. Under the long-term action of high humidity condensation and alternating loads of tunnel gusts, local water vapor enrichment is likely to occur, affecting the hydrophilic uniformity and local insulation stability of the coating.

[0014] Garnet itself possesses high hardness, excellent chemical inertness, and stable insulation properties. When incorporated into the system, it can enhance the surface hardness of the coating, strengthening its resistance to micro-cutting and erosion wear from wheel and rail metal dust. Simultaneously, the powder particles can fill microscopic defects within the coating, reducing contamination accumulation sites, lowering the risk of electrochemical corrosion, and mitigating the self-cleaning performance degradation caused by fine particles from mountainous soil clogging the hydrophilic channels of the coating. Modifying the garnet powder with an alkylsilane coupling agent results in a uniform organic coating layer on the powder surface, improving the interfacial compatibility and bonding strength between the inorganic powder and the organic resin matrix, addressing the problem of insufficient resin coating, and reducing localized insulation fluctuations caused by water vapor penetration along the powder interface under high humidity conditions.

[0015] Naphthenic acid metal salts, composed of zinc naphthenate and aluminum naphthenate, can be used as functional additives to optimize the curing effect of terpene phenolic resins, densify the internal network structure of the coating, reduce internal pore defects, lower the saturated water absorption rate of the coating, and help improve the overall insulation stability of the coating, making it suitable for the complex service environment of high humidity and frequent temperature changes in the mountain valleys of eastern Sichuan.

[0016] This system introduces a cerium-zirconium-based waterborne rare earth composite drier. This component accelerates the crosslinking of modified terpene phenolic resin at room temperature, achieving rapid drying at room temperature, suitable for both on-site field construction and factory pre-coating. Simultaneously, it forms a synergistic curing effect with zinc naphthenate and aluminum naphthenate, allowing the coating to cure uniformly from the surface inwards, further densifying the micropores and reducing water absorption. This invention preferably uses a cerium-zirconium composite system, rather than other single rare earth elements such as lanthanum and neodymium, and also avoids traditional heavy metal driers such as cobalt, manganese, and lead. The cerium component possesses excellent surface curing ability, while the zirconium component enhances the internal crosslinking and pore densification of the coating. The combination of the two achieves simultaneous drying from the surface to the interior, resulting in optimal overall performance. Lanthanum and neodymium rare earth driers suffer from uneven drying speeds and are prone to fogging of the coating, while cobalt, manganese, and lead driers, due to the presence of free heavy metal ions, can increase the coating's conductivity, damage high-voltage insulation performance, and easily cause yellowing of the coating; therefore, they are all unsuitable for this system. This drying agent has mild chemical properties and will hardly damage the flexible grafted chains of polytetrahydrofuran glycol on the resin surface, the multi-level ion-release structure of the functional filler, or the hydrophilic network of the coating. Its addition amount is limited to 0.5–1.5 parts by weight. Dosage below 0.5 parts results in insufficient curing acceleration, slow surface drying of the coating, and easy dust accumulation on-site. Dosage above 1.5 parts will generate excessive free rare earth ions, reducing insulation performance and causing coating defects such as pinholes and microcracks. This dosage range ensures fast drying at room temperature while also taking into account the coating's comprehensive properties such as insulation, hydrophilicity, and weather resistance. In summary, this application, relying on the reasonable compatibility and complementary performance advantages of each component, improves the shortcomings of conventional hydrophilic coatings in terms of erosion resistance, temperature change resistance, and insulation stability. The overall protective performance of the coating can meet the long-term service requirements of the power facilities of the Sichuan East Ridge Valley High-speed Railway.

[0017] As some possible implementations of this application, the mass ratio of the C8~C10 alkyl glycoside to sorbitol is 2.5~3.5:2.

[0018] As some possible embodiments of this application, in the functional filler, the mass ratio of silane coupling agent to barium metaborate is 1:8 to 12.

[0019] As some possible embodiments of this application, the thickness of the silicon dioxide layer in the functional filler is 20-50 nm.

[0020] As some possible embodiments of this application, in the naphthenic acid metal salt, the mass ratio of zinc naphthenate to aluminum naphthenate is 1.5 to 2.5:1.

[0021] As some possible embodiments of this application, the amount of alkylsilane coupling agent added to the modified garnet powder is 2% to 4% of the mass of the garnet powder.

[0022] Furthermore, to achieve the above objectives, the present invention also provides a method for preparing a coating with hydrophilic self-cleaning ability. After uniformly mixing modified terpene phenolic resin, naphthenic acid metal salt, and cerium-zirconium composite drying agent, functional filler and modified garnet powder are added in sequence. After sufficient dispersion, a compounded hydrophilic agent and deionized water are added, mixed evenly, and filtered to obtain the finished coating.

[0023] As one possible implementation method of this application, the filter mesh size is 180 to 250 mesh.

[0024] Furthermore, to achieve the above objectives, this application also provides an application of a coating with hydrophilic self-cleaning capabilities, which is applied to power facilities along high-speed railway lines in subtropical humid climates. It is particularly suitable for the mountainous areas surrounding the Sichuan Basin and the valley regions of eastern Sichuan, including high-speed railway transmission towers, column insulators, outdoor distribution boxes, and contact network hardware that traverse mountains, valleys, and have dense bridges and tunnels, such as the Chongqing-Kunming High-Speed ​​Railway and the Southern Sichuan Intercity Railway.

[0025] Compared with the prior art, the beneficial effects of the present invention are: This invention provides a coating with hydrophilic self-cleaning ability. Through the synergistic effect of the components—modified terpene phenolic resin, compounded hydrophilic agent, multi-level structural functional filler, modified garnet powder, naphthenic acid metal salt, and cerium-zirconium composite drying agent—the overall protective performance of the coating is significantly improved. The specific properties are as follows: The coating of this invention exhibits excellent curing performance, achieving a curing grade of A. Surface drying time is ≤29 min, and complete drying time is ≤1.8 h, enabling rapid and uniform curing. In high-humidity microbial erosion environments, the coating's mass loss rate is ≤0.43%, demonstrating good resistance to biological aging. After being subjected to combined erosion from wheel dust and mountain soil particles, the coating's damage grade is A, effectively resisting media abrasion. The coating surface has a water contact angle ≤22.8°, demonstrating outstanding hydrophilic self-cleaning properties, while its volume resistivity is ≥8.5×10¹³ Ω. The coating exhibits excellent insulation properties. After undergoing alternating hot and cold condensation tests, the coating integrity remained at Grade A, with no defects such as cracking or peeling. The coating adhesion was ≥6.7 MPa, demonstrating strong bonding with the substrate. In the ion deposition resistance insulation test, the immersion solution conductivity was ≤1.8 μS / cm, and the coating breakdown voltage was ≥14.2 kV, demonstrating excellent ion deposition resistance and insulation stability. Under neutral salt spray test conditions, the corrosion grade was Grade A, with no significant corrosion observed in either the coating or the substrate. After conducting multi-factor comprehensive operating condition simulation tests, the coating appearance grade remained Grade A, with a comprehensive test adhesion ≥5.0 MPa and a dirt residue rate ≤3.3%, indicating good resistance to dirt accumulation. This coating is effectively adaptable to the complex service conditions of power facilities along high-speed railways in subtropical humid climates, possessing multiple advantages such as hydrophilic self-cleaning, erosion resistance, resistance to microbial erosion, temperature change resistance, high insulation, and corrosion resistance, making it highly valuable for engineering applications. Detailed Implementation

[0026] Example 1

[0027] 1. Preparation of unconventional components (those without a mentioned preparation method are either simple mixing methods or commercially available): (1) Preparation of modified terpene phenolic resin: terpene phenolic resin and polytetrahydrofuran diol (PTMG-1000) were mixed at a mass ratio of 100:12. Then, 0.3% of the total material mass of p-toluenesulfonic acid catalyst was added. The stirring speed was 160 r / min. The system was evacuated to a vacuum degree ≥0.08 MPa. The temperature was raised to 150℃ and the reaction was kept constant for 4 h while continuously removing water from the system. The dehydration process was considered to end when no obvious liquid water droplets were distilled out of the condenser. After the reaction was completed, the temperature was lowered to room temperature, the material was discharged and pulverized to 120 mesh to obtain modified terpene phenolic resin.

[0028] Terpene phenolic resin can be commercially available or prepared by copolymerizing α-pinene and phenol in a molar ratio of 1.1:1: α-pinene and phenol are added to a reaction vessel, and 3% of the total mass of p-toluenesulfonic acid is added. The mixture is stirred and heated to 120°C, and reacted at a constant temperature for 7 hours. After the reaction is complete, the mixture is neutralized to pH=7 with dilute sodium hydroxide solution, washed twice with water, and the low-boiling substances are removed by atmospheric distillation, followed by vacuum drying. By controlling the reaction temperature and time, terpene phenolic resin with a number average molecular weight of 1800~2500 can be obtained.

[0029] (2) Preparation of functional filler: Weigh silane coupling agent KH-550 and barium metaborate (industrial ultrafine powder, 325 mesh) at a mass ratio of 1:10, put them into a high-speed mixer, and stir at 220 r / min for 25 min at room temperature to obtain modified barium metaborate; mix modified barium metaborate with sepiolite (200 mesh, fiber aspect ratio 15~20:1, purity ≥85%, moisture ≤1.5%) at a mass ratio of 3:7, add 5 times the mass of deionized water to the mixture, stir at 180 r / min at room temperature for 1.5 h, filter, and dry the filter cake in hot air at 60℃ to constant weight; Add 15% by weight of acidic silica sol (solid content 25%, colloidal particle size 8~15 nm) to the dry powder, stir at 170 r / min at room temperature for 30 min, then age at room temperature for 10 min, and then place in an 80℃ oven to cure for 2 h, controlling the thickness of the surface silica layer to be 30~40 nm, and finally pulverize to 180 mesh to obtain the functional filler.

[0030] (3) Preparation of modified garnet powder: Based on the total mass of garnet powder [selected calcium iron garnet (Ca3Fe2(SiO4)3), 300 mesh, Mohs hardness 7.5~8.0], add 3% silane coupling agent KH-560, put the material into a high-speed mixer, mix at room temperature at 200 r / min for 30 min, then dry at low temperature at 65℃ for 1.5 h, and pulverize to 200 mesh to obtain modified garnet powder.

[0031] (4) Preparation of compound hydrophilic agent: C8~C10 alkyl glycoside (APG0810) and food grade sorbitol were selected as raw materials and weighed according to a mass ratio of 3:2. The two raw materials were mixed and placed in a room temperature environment. The mixture was stirred at a low speed of 150 r / min for 15 min. After stirring and mixing evenly, it was allowed to stand for 5 min to obtain the compound hydrophilic agent.

[0032] (5) Preparation of cerium-zirconium composite drying agent: waterborne cerium nitrate and waterborne zirconium nitrate were mixed at a mass ratio of cerium to zirconium metal ions of 2:1, and deionized water was added to prepare a rare earth mixed solution with a solid content of 20%; the mixture was stirred at a low speed of 120 r / min for 20 min at room temperature, and then 5% of the total mass of rare earth metal ions of citric acid was slowly added dropwise to adjust the pH of the system to 6.0~6.5. The complexation reaction was continued at a constant temperature for 1 h, and the mixture was allowed to stand for 30 min to mature, thus obtaining the cerium-zirconium composite drying agent.

[0033] 2. Coating Preparation

[0034] Take 50 parts of modified terpene phenolic resin, 3 parts of naphthenic acid metal salt (the naphthenic acid metal salt is composed of zinc naphthenate and aluminum naphthenate in a mass ratio of 2:1), and 1.0 part of cerium-zirconium composite drying agent and put them into a mixing tank. Stir at 25℃ and 160 r / min for 12 min to mix evenly. Then add 14.5 parts of functional filler and disperse at 220 r / min for 20 min. Next, add 6 parts of modified garnet powder and continue to disperse at the same speed for 10 min. Then add 8 parts of compound hydrophilic agent and 21 parts of deionized water, reduce the speed to 140 r / min and stir for 10 min. Finally, filter through a 220 mesh filter to obtain the finished coating.

[0035] Example 2

[0036] Compared to Example 1, only the following parameters were adjusted, while all other adjustments not mentioned remained the same as in Example 1.

[0037] 1. Preparation of non-commercially available components: Modified garnet powder: The amount of silane coupling agent KH-560 added is adjusted to 2% based on the total mass of garnet powder.

[0038] 2. Coating Preparation: 46 parts modified terpene phenolic resin, 7 parts compounded hydrophilic agent (C8~C10 alkyl glycoside to sorbitol mass ratio of 2.5:2), 13 parts functional filler, 5 parts modified garnet powder, 2 parts naphthenic acid metal salt (the naphthenic acid metal salt has a naphthenic acid metal salt with a naphthenic acid zinc to naphthenic acid mass ratio of 1.5:1), 0.5 parts cerium-zirconium composite drying agent, and 18 parts deionized water. The coating is finally filtered using an 180-mesh filter.

[0039] Example 3

[0040] Compared to Example 1, only the following parameters were adjusted, while all other adjustments not mentioned remained the same as in Example 1.

[0041] 1. Preparation of non-commercially available components: (1) Functional filler: The mass ratio of silane coupling agent KH-550 to barium metaborate was adjusted to 1:12, while the other preparation parameters remained unchanged, to obtain the functional filler.

[0042] (2) Modified garnet powder: Based on the total mass of garnet powder, the amount of silane coupling agent KH-560 added was adjusted to 4%, and the other preparation parameters remained unchanged to obtain modified garnet powder.

[0043] 2. Coating preparation: 54 parts modified terpene phenolic resin, 9 parts compound hydrophilic agent (C8~C10 alkyl glycoside to sorbitol mass ratio of 3.5:2), 16 parts functional filler, 7 parts modified garnet powder, 4 parts naphthenic acid metal salt (zinc naphthenate to aluminum naphthenate mass ratio of 2.5:1), 1.5 parts cerium-zirconium composite drying agent, and 25 parts deionized water; the coating is finally filtered using a 250-mesh filter.

[0044] Comparative Example 1

[0045] Compared to Example 1, the ratio of terpene phenolic resin to polytetrahydrofuran diol is retained, the chemical grafting modification process is cancelled and replaced with room temperature physical blending, and the rest of the preparation process, raw material ratio and parameters are consistent with Example 1.

[0046] Comparative Example 2

[0047] Compared to Example 1, the silane coupling agent modification step was omitted when preparing the functional filler. The original barium metaborate and sepiolite were directly used for loading treatment. The preparation process of other unconventional components, the ratio of coating raw materials, the preparation operation and all process parameters were consistent with those in Example 1.

[0048] Comparative Example 3

[0049] Compared to Example 1, when preparing the functional filler, after completing the barium metaborate and sepiolite loading process, the silica sol coating and curing to form a silica layer are no longer performed. The preparation process of the other unconventional components, the ratio of coating raw materials, the preparation operation and all process parameters are consistent with those of Example 1.

[0050] Comparative Example 4

[0051] Compared to Example 1, the original garnet powder without alkylsilane coupling agent treatment was used directly, and the powder modification process was omitted. The preparation process of other unconventional components, the ratio of coating raw materials, the preparation operation and all process parameters were consistent with those in Example 1.

[0052] Comparative Example 5

[0053] Compared to Example 1, the cerium-zirconium composite drying agent component was directly removed from the coating formulation, while the preparation process of the remaining unconventional components, the ratio of coating raw materials, the preparation operation, and all process parameters remained the same as in Example 1.

[0054] Comparative Example 6

[0055] Compared to Example 1, the cerium-zirconium composite drying agent in the coating was replaced with an equal mass of traditional cobalt naphthenate drying agent. The preparation process of the remaining unconventional components, the ratio of coating raw materials, the preparation operation and all process parameters were kept the same as in Example 1.

[0056] Comparative Example 7

[0057] Compared to Example 1, the naphthenic acid metal salt component composed of zinc naphthenate and aluminum naphthenate was removed from the coating formulation. The preparation process of the remaining unconventional components, the ratio of coating raw materials, the preparation operation and all process parameters were kept the same as in Example 1.

[0058] Comparative Example 8

[0059] Compared to Example 1, the stepwise feeding and graded dispersion process of the coating is eliminated. All raw material components are added to the mixing tank at once. The preparation process, raw material ratio, total stirring time, and filtration parameters of the remaining unconventional components are kept the same as in Example 1. Specifically, the modified terpene phenolic resin, naphthenic acid metal salt, cerium-zirconium composite drying agent, functional filler, modified garnet powder, compound hydrophilic agent, and deionized water are all mixed at once. First, the mixture is dispersed at high speed of 220 r / min for 30 min, then stirred at low speed of 140 r / min for 10 min, and finally filtered through a 220 mesh filter to obtain the coating.

[0060] Comparative Example 9

[0061] Compared to Example 1, the compound hydrophilic agent was replaced with an equal mass of a single alkyl glycoside hydrophilic agent, the sorbitol compound system was eliminated, and the preparation process of the remaining unconventional components, the ratio of coating raw materials, the preparation operation and all process parameters were kept the same as in Example 1.

[0062] Comparative Example 10

[0063] Compared to Example 1, the modified garnet powder was replaced by calcium carbonate powder (300 mesh) treated with the same KH-560 modification process. The powder modification process parameters were completely consistent with those of the garnet modification in Example 1. The preparation processes of other unconventional components, the proportion of coating raw materials, the preparation operations and all process parameters were consistent with those of Example 1.

[0064] Comparative Example 11

[0065] Compared to Example 1, the modified terpene phenolic resin was replaced with an equal mass of pure terpene phenolic resin, and polytetrahydrofuran diol was no longer added. The remaining raw material components, preparation process, and parameters were completely consistent with those of Example 1.

[0066] Experimental Example

[0067] The coatings prepared in Examples 1-3 (denoted as S1-S3) and Comparative Examples 1-11 (denoted as D1-D11) were uniformly applied to the surface of a Q235 steel substrate with dimensions of 100mm × 100mm × 3mm. The dry film thickness was uniformly controlled at 500 μm, and the coatings were cured at room temperature for 7 days to obtain standard test samples. Based on the actual working conditions of this coating applied to power facilities along high-speed railway lines in subtropical humid climates, comprehensive performance tests were conducted. The test results are shown in Table 1. The test parameters, complete operation procedures, and testing requirements are as follows: (1) Room temperature curing performance test: The test was conducted at a room temperature of 25 ℃ and a relative humidity of 60%. The surface drying time was determined by the finger touch method according to GB / T 1728-2020. The surface was considered dry when the finger touched the coating surface lightly at intervals and no coating stuck to the finger or any obvious traces were left. The drying time was determined using the cotton ball method. A degreased cotton ball was gently placed on the coating surface and a standard weight was placed on it. After standing for 10 seconds, the weight and cotton ball were removed. The coating was considered dry when there was no cotton lint adhering to it or any indentation.

[0068] After timing, use a utility knife to vertically cut the coating down to the substrate. Then, use a cotton swab soaked in acetone to repeatedly wipe the cut surface of the coating three times. The coating's curing status is divided into three levels: Grade A (completely cured inside and out): uniform surface and internal texture, no dissolving or stickiness when wiped; Grade B (surface cured, internal slightly soft / not completely dry): hard surface, soft and sticky internal; Grade C (uneven curing): uneven overall hardness, locally sticky. Test items: surface drying time, complete drying time, curing grade.

[0069] (2) High-humidity microbial erosion test: After cleaning the surface dust of the cured sample, place it on a sterile operating table and use a sterile sprayer to uniformly spray the coating with a spore concentration of [missing information]. The mixed bacterial solution of Aspergillus niger and Penicillium was sprayed at a rate controlled at the following rate per unit area: To ensure the coating was completely wetted and free of continuous droplet flow, the sample was placed in a constant temperature and humidity incubator and cultured continuously for 60 days at 30 ℃ and 95% relative humidity. After the culture, the sample was removed, and loose mycelia and mold spots on the surface were gently brushed away with a soft brush, without scraping off the coating itself. The sample was then gently rinsed with deionized water and dried in a 40 ℃ oven until constant weight. The total mass of the sample was weighed using an analytical balance before and after the experiment, and the coating mass loss rate was calculated.

[0070] (3) Composite erosion test of wheel-rail metal dust + mountain soil particles: The sample was horizontally fixed on the test platform of the composite dust erosion test device, with the coating surface facing the nozzle. Wheel-rail metal fine dust and mountain soil fine particles with a mass ratio of 1:1 and a particle size range of 0.02~0.3 mm were used as the erosion medium. The impact wind speed was set to 20 m / s and the impact distance to 40 cm. The erosion was carried out continuously for 40 min. After the test, the dust adhering to the coating surface was removed with a dry soft brush according to: Grade A: No obvious damage, minor scratches (no coating peeling); Grade B: Moderate scratches (localized thinning of coating, no peeling); Grade C: Obvious scratches + localized damage (coating peeling area <10%); Grade D: Severe damage (coating peeling area ≥10%). The coating damage level is determined by the above five-level standard. Then, a contact angle meter is used to measure the water contact angle of the coating surface, and a high resistance meter is used to test the volume resistivity of the coating surface.

[0071] (4) Alternating hot and cold condensation test: The sample was placed in a high and low temperature alternating test chamber, and a single cycle was set to -20℃ for 3 h. Then the temperature was rapidly increased to 45℃ and water vapor was introduced at a rate of 100 mL / min. The relative humidity in the chamber was increased to more than 95% within 10 min to form uniform saturated condensation. The sample was kept at a constant temperature for 3 h. The duration of each cycle was 6 h, and a total of 60 cycles were completed. After the cycle, the sample was removed and allowed to air dry at room temperature. The integrity of the coating was divided into two grades: Grade A (intact coating): no cracks, peeling, or flaking defects; Grade B (damaged coating): defects such as microcracks, cracks, peeling, and flaking exist. Finally, the adhesion between the coating and the substrate was tested using a pull-off tester.

[0072] (5) Ionization resistance insulation test: The sample is completely immersed in a sealed glass container containing sufficient deionized water and soaked at room temperature for 15 days. After the soaking period, the sample is taken out, rinsed with deionized water and dried. The conductivity of the soaking solution is detected by a conductivity meter, and the breakdown voltage of the coating is determined by a withstand voltage tester.

[0073] (6) Neutral salt spray corrosion resistance test: Prepare a sodium chloride aqueous solution with a mass fraction of 5% and a pH value adjusted to 6.5~7.2. Place the sample at an angle in the salt spray test chamber with the coated surface facing upwards. Set the spray temperature to 35 ℃ and the salt spray deposition rate to 1.5 mL / (80 cm²). Spray continuously for 1000 h. After the test, take out the sample and let it air dry at room temperature. The corrosion status of the coating and the substrate is divided into two levels: Level A (no corrosion): no blistering, cracking, or peeling of the coating, and no rust spots on the substrate; Level B (corrosion present): blistering, cracking, or peeling of the coating, and rust spots and corrosion on the substrate.

[0074] (7) Multi-factor actual working condition comprehensive simulation test: The sample was placed in the comprehensive environmental test chamber, and a single basic cycle was divided into two stages of alternating operation. First stage: The temperature inside the chamber was 30 ℃, and salt spraying was carried out continuously. The salt spray deposition was controlled at 1.5 mL / (80 cm²). In the first stage, a condensation environment forms inside the chamber, creating a high-humidity environment conducive to mold growth, lasting 12 hours. In the second stage, the chamber is cooled to a constant temperature of -20°C, and a mixture of wheel-rail metal dust and fine mountain soil particles is continuously introduced for erosion, lasting 6 hours. The completion of these two stages constitutes one basic cycle, with a total cycle time of 18 hours. Samples are removed after every 5 basic cycles. Rinse continuously with clean water for 15 minutes. After rinsing, put the sample back into the chamber and continue the test.

[0075] The entire test consisted of 90 basic cycles, including 18 water rinsings. After the test, the samples were dried in a 35°C oven to constant weight. After cooling to room temperature, the coating appearance grade was assessed, and the mass m1 of the sample with residual dirt was weighed. Then, all dirt on the coating surface was thoroughly removed with water and a soft sponge. The samples were dried again to constant weight, and the mass m2 of the clean sample was weighed. The dirt residue rate was calculated using the formula: dirt residue rate (%) = (m1-m2) / m0 × 100%. Finally, the coating adhesion was determined using the pull-off method on the clean and dry sample surface.

[0076] Where m0 is the mass of the sample after drying to constant weight following the curing process before the test.

[0077] The coating appearance is divided into two grades: Grade A (perfect appearance): no defects such as cracking, peeling, flaking, chalking, or dirt accumulation; Grade B (defects in appearance): defects such as cracking, peeling, flaking, chalking, dirt accumulation, and structural failure exist.

[0078] Table 1: Performance test results of each sample

[0079]

[0080] It is worth noting that: " / " in the table indicates that no test was conducted. The reason why the comprehensive experiment was not conducted is that the individual performance tests of each sample have exposed performance defects, and there is no need to continue to conduct multi-factor comprehensive working condition tests. The reason why the contact angle test was not conducted is that, except for Comparative Example 9, the other comparative examples did not significantly change the hydrophilic components, so no test was required.

[0081] Table 1 shows that the coatings prepared in Examples 1-3 exhibited relatively excellent performance in all aspects. The coating curing grade was Grade A for all examples; the surface drying time was ≤29 min, and the actual drying time was ≤1.8 h. After exposure to high humidity and microbial erosion, the mass loss rate was ≤0.43%. After being subjected to combined dust particle erosion, the damage grade was Grade A for all examples. The water contact angle on the coating surface was ≤22.8°, indicating good hydrophilicity, and the volume resistivity was ≥8.5×10¹³ Ω. The coating exhibits ideal insulation performance. After undergoing alternating hot and cold condensation tests, the coating integrity level was consistently Grade A, with an adhesion strength ≥6.7 MPa. After immersion, the conductivity of the soaking solution was ≤1.8 μS / cm, and the coating breakdown voltage was ≥14.2 kV, demonstrating good resistance to ion deposition and insulation stability. Under neutral salt spray testing, the corrosion level was consistently Grade A, with no significant corrosion issues observed. In multi-factor comprehensive operating condition simulation tests, the coating appearance level was consistently Grade A, with a comprehensive adhesion strength ≥5.0 MPa and a dirt residue rate ≤3.3%, demonstrating overall suitability for the complex service environment of high-speed railway power facilities in subtropical humid climates.

[0082] Comparative Example 1 uses unmodified terpene phenolic resin and physical blending. The stress buffering capacity of the resin system is weakened, the coating curing effect is worse, and the overall performance declines significantly after being subjected to microbial erosion, media erosion and temperature change. The insulation, corrosion protection and other related capabilities are also affected to varying degrees.

[0083] In Comparative Example 2, the silane coupling agent modification process was omitted during the preparation of the functional filler, resulting in decreased barium metaborate loading stability, interference with antibacterial and ion slow-release effects, and a reduction in the coating's resistance to microbial erosion, insulation, and corrosion resistance.

[0084] The functional filler in Comparative Example 3 lacked a silica protective layer, resulting in poorer control over boron ion release and easier propagation of mycelium into the coating, leading to varying degrees of reduction in the coating's protective properties.

[0085] Comparative Example 4 uses unmodified garnet powder, which results in poor interfacial bonding between the inorganic filler and the resin matrix, thus affecting the coating's erosion resistance, insulation stability, and corrosion resistance.

[0086] Comparative Example 5: After removing the cerium-zirconium composite drier, the curing rate of the coating slowed down, the internal density of the coating was insufficient, and the number of pore defects increased, which in turn led to a reduction in the overall protective performance such as corrosion resistance, insulation and anti-corrosion.

[0087] In Comparative Example 6, when the traditional cobalt naphthenate drier was replaced, the free heavy metal ions negatively affected the coating's insulation performance. At the same time, the coating's curing uniformity deteriorated, making it prone to defects, and various protective indicators declined.

[0088] Comparative Example 7: Removing the naphthenic acid metal salt component reduced the density of the internal network structure of the coating, resulting in weakened insulation stability and overall protection capability under high humidity and temperature change conditions.

[0089] Comparative Example 8: The preparation process of stepwise feeding and graded dispersion was changed. The uniformity of raw material mixing was insufficient, and micro-defects and stress concentration were easily formed inside the coating, resulting in a decrease in erosion resistance, temperature change resistance and corrosion resistance.

[0090] Comparative Example 9 used a single alkyl glycoside as a hydrophilic agent, lacking the synergistic effect of sorbitol. This resulted in a decrease in the stability of the hydrophilic network of the coating, a significant impact on self-cleaning properties, and slight fluctuations in other basic protective indicators.

[0091] Comparative Example 10: Modified calcium carbonate was used to replace modified garnet powder. The hardness and structural characteristics of the filler changed, and the coating’s resistance to dust erosion decreased. The effects of this formulation change on coating curing, resistance to microbial attack, insulation and corrosion resistance were relatively limited.

[0092] Comparative Example 11 directly used terpene phenolic resin without any modification treatment and without introducing polytetrahydrofuran diol component. The resin system was too rigid and the internal stress was difficult to release. The overall performance of the coating was greatly reduced. The curing effect, resistance to microbial attack, erosion resistance, insulation performance, temperature change resistance and corrosion resistance were all significantly reduced.

Claims

1. A coating with hydrophilic self-cleaning ability, characterized in that, The ingredients include the following parts by weight: 46-54 parts modified terpene phenolic resin, 7-9 parts compounded hydrophilic agent, 13-16 parts functional filler, 5-7 parts modified garnet powder, 2-4 parts naphthenic acid metal salt, 0.5-1.5 parts cerium-zirconium composite drying agent, and 18-25 parts deionized water; The modified terpene phenolic resin is obtained by grafting polytetrahydrofuran diol onto terpene phenolic resin. The compound hydrophilic agent is composed of C8~C10 alkyl glycosides and sorbitol; The preparation process of the functional filler is as follows: barium metaborate is modified with a silane coupling agent to obtain modified barium metaborate, and then the modified barium metaborate is loaded in situ onto sepiolite, and then a silica layer is prepared on the surface of the loaded product to obtain the functional filler. The modified garnet powder is obtained by modifying garnet powder with an alkylsilane coupling agent; The naphthenic acid metal salt is obtained by compounding zinc naphthenate and aluminum naphthenate.

2. The coating with hydrophilic self-cleaning ability according to claim 1, characterized in that, The mass ratio of the C8~C10 alkyl glycoside to sorbitol is 2.5~3.5:

2.

3. The coating with hydrophilic self-cleaning ability according to claim 1, characterized in that, In the functional filler, the mass ratio of silane coupling agent to barium metaborate is 1:8 to 12.

4. The coating with hydrophilic self-cleaning ability according to claim 1, characterized in that, In the functional filler, the thickness of the silicon dioxide layer is 20–50 nm.

5. The coating with hydrophilic self-cleaning ability according to claim 1, characterized in that, In the naphthenic acid metal salt, the mass ratio of zinc naphthenate to aluminum naphthenate is 1.5 to 2.5:

1.

6. The coating with hydrophilic self-cleaning ability according to claim 1, characterized in that, In the modified garnet powder, the amount of alkylsilane coupling agent added is 2% to 4% of the mass of the garnet powder.

7. A method for preparing a coating with hydrophilic self-cleaning ability as described in any one of claims 1 to 6, characterized in that, After the modified terpene phenolic resin, naphthenic acid metal salt, and cerium-zirconium composite drying agent are mixed evenly, functional filler and modified garnet powder are added in sequence. After being fully dispersed, compound hydrophilic agent and deionized water are added, mixed evenly, and filtered to obtain the finished coating.

8. The method for preparing the coating with hydrophilic self-cleaning ability according to claim 7, characterized in that, The filter mesh size is 180-250 mesh.

9. The application of a coating with hydrophilic self-cleaning ability as described in any one of claims 1 to 6, characterized in that, The coating is applied to power facilities along high-speed railway lines in subtropical humid climates.

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