Self-healing microcapsule coating for dehumidification wheels and methods of making the same

Abstract

The present application belongs to the technical field of functional coating materials and air dehumidification equipment, and discloses a self-repairing microcapsule coating for a dehumidification rotating wheel and a preparation method thereof. The coating comprises adsorbent particles, a binder and self-repairing microcapsules with a core-shell structure, the core material being a moisture-curable organosilane / silazane, and the shell material being a single-walled polyurea or a double-walled polyurethane-polyurea structure. The present application precisely couples the self-repairing mechanism with the working condition of the dehumidification rotating wheel, triggers the curing of the repairing agent at a high humidity in the adsorption zone, and promotes complete curing at a high temperature in the regeneration zone, so that the coating can autonomously repair the thermal cycle microcracks, prevent the coating from peeling off, and restore the dehumidification efficiency by more than 92.8% after repair, thereby significantly prolonging the service life of the rotating wheel, and the preparation process is compatible with the existing production line.

Description

Technical Field

[0001] This invention belongs to the technical field of functional coating materials and air dehumidification equipment, specifically relating to a self-healing microcapsule coating for dehumidification impellers and its preparation method. Background Technology

[0002] Industrial dehumidification technology is a key supporting technology for modern manufacturing, the pharmaceutical industry, and high-precision experimental environments. In production scenarios highly sensitive to environmental humidity, such as lithium battery cathode and anode material production, OLED panel manufacturing, semiconductor wafer fabrication, pharmaceutical GMP cleanrooms, precision machining, and food packaging, the precision of relative humidity control directly determines product quality and yield. Taking lithium battery production as an example, cathode materials are highly susceptible to side reactions with moisture in high-humidity environments, leading to a significant decrease in battery cycle performance and safety. The dew point requirement in drying rooms is typically below -40°C, placing extremely stringent demands on the performance stability of dehumidification equipment. As the core component of rotary dehumidifiers, the dehumidification wheel, with its continuous, efficient, and regenerative dehumidification characteristics, has become the most mainstream deep dehumidification solution in these high-end application scenarios, widely used in lithium battery manufacturing workshops, semiconductor production lines, pharmaceutical cleanrooms, cold chain logistics warehouses, archives, museums, and other places with strict humidity control. With the rapid expansion of strategic emerging industries such as new energy vehicles and high-end chip manufacturing, related market demand continues to grow rapidly.

[0003] Dehumidifying impellers are typically made of ceramic fiber paper or glass fiber paper as the base material, and are formed into a honeycomb structure through molding and winding processes. The equivalent hydraulic diameter of its honeycomb flow channel unit is generally 1.0 to 2.5 mm, and the specific surface area can reach 800 to 2000 m². 2 / m 3 The inner surface of the flow channel is loaded with adsorbent material through impregnation or spraying. Common adsorbent systems include activated silica gel, type A or type X molecular sieves, lithium chloride or their composite systems, and metal-organic framework materials, which have emerged in recent years. When the dehumidifying impeller is working, its cross-section is divided into two fan-shaped areas—a treatment zone and a regeneration zone—by a special sealing device, with an area ratio typically of approximately 3:1. In the treatment zone, the humid air to be treated passes axially through the honeycomb flow channel driven by a fan. Water vapor in the airflow adsorbs onto the adsorbent on the inner surface of the flow channel, reducing the airflow humidity and delivering it as dry air to the energy consumption terminal. In the regeneration zone, regeneration hot air, heated to 120–180°C by a heater, passes through the flow channel, decomposing and removing water accumulated in the adsorbent, restoring its adsorption capacity. Through the slowly rotating impeller (typically at 8–20 r / h), the adsorption and regeneration zones alternate continuously, allowing the entire unit to continuously output dry air.

[0004] The dehumidification performance of a dehumidifying impeller largely depends on the integrity and effective adsorption area of ​​the adsorbent coating on the inner wall of the flow channel. In existing technologies, the adsorbent coating is typically composed of inorganic adsorbent particles combined with organic or inorganic binders, applied to the flow channel surface via impregnation or spraying, and then dried and cured to form a functional coating with a thickness of approximately 50–200 μm. However, because the dehumidifying impeller continuously undergoes cyclical heat and humidity cycling between the adsorption zone (typically 20–35°C, relative humidity 60%–90%) and the regeneration zone (typically 120–180°C, relative humidity below 5%) during operation, the impeller substrate (inorganic fiber, coefficient of thermal expansion approximately 5 × 10⁻⁶) becomes increasingly sensitive to heat and humidity. -6 / ℃) and adsorbent coating (silicone / binder system, coefficient of thermal expansion approximately 10~25×10) -6 There is a significant difference in the coefficient of thermal expansion between the substrate and the coating (°C). During each thermal cycle, the differential expansion-contraction behavior between the substrate and the coating will generate periodic thermal stress in the interface region. According to elasticity analysis, when the coating thickness is 100 μm and the difference in the coefficient of thermal expansion is 15 × 10⁻⁶, the thermal stress will be significantly higher. -6 At a temperature of 150℃ and a temperature difference of 150℃, the interfacial thermal stress can reach approximately 2.5 to 5.0 MPa, which is close to or exceeds the interfacial bonding strength of common organic binders (usually 1.5 to 4.0 MPa).

[0005] Under the aforementioned repeated thermal stress, fatigue damage gradually accumulates at the interface between the coating and the substrate, manifesting as the initiation and slow propagation of microcracks. Initially, the width of these microcracks is typically on the order of 0.5–10 μm, making them difficult to identify using conventional detection methods, but they already substantially affect the coating's performance. Once the microcracks extend to the interface between the adsorbent and the substrate, the coating loses its mechanical anchorage in certain areas. Under the combined effects of airflow scouring and impeller vibration, the coating undergoes localized delamination or even complete peeling, directly reducing the effective adsorption area. Studies show that after 1000 thermal cycles, the effective area loss rate of the silica gel coating can reach 15%–30%, corresponding to a decrease in dehumidification efficiency of approximately 12%–25%. Furthermore, the cracked coating creates localized leakage channels between the regeneration and adsorption zones at the microcrack locations. High-temperature regeneration hot air can penetrate the adsorption zone through microcracks wider than 5 μm, causing a localized increase in airflow temperature in the adsorption zone, leading to premature desorption of the adsorbent, reducing the working adsorption capacity, and consequently increasing the system's outlet dew point and overall energy consumption. The rough cross-section of the microcracks in the coating is also very easy to adsorb dust-laden gases in the environment. After long-term operation, a dust accumulation layer is formed, which further blocks part of the honeycomb flow channel, increases flow resistance, increases the power consumption of the fan by 5% to 15%, and brings the risk of particulate matter pollution in applications with high cleanliness requirements such as semiconductors and pharmaceuticals.

[0006] To address the aforementioned coating cracking problem, existing technologies have primarily attempted the following approaches, but all suffer from fundamental drawbacks that are difficult to overcome. Firstly, while introducing flexible segments into the binder system to improve coating flexibility can delay crack initiation, this modification inevitably leads to a decrease in coating hardness and wear resistance. Furthermore, flexible binders are prone to thermal aging and creep under high-temperature regeneration conditions (120–180°C), making this a delaying rather than a radical solution. Once microcracks form, coating performance will irreversibly continue to decline. Secondly, optimizing honeycomb channel dimensions and incorporating stress relief grooves to disperse thermal stress concentration points offers limited improvement (typically extending the initial cracking time by approximately 20%–40%), and structural modifications can have a cascading effect on dehumidification performance, severely limiting the design window. Third, replacing the dehumidifying rotor regularly as a consumable or disassembling and cleaning the entire machine not only brings extremely high operation and maintenance costs (the cost of the dehumidifying rotor usually accounts for 30% to 50% of the price of the dehumidifier), but also seriously affects the continuity of the production line during equipment downtime, which is particularly unacceptable in continuous production scenarios such as lithium battery drying rooms. Fourth, while microcapsule-based self-healing mechanisms have made some progress in recent years in fields such as anti-corrosion coatings and aerospace composite materials, existing self-healing microcapsule technologies have not yet been systematically designed and engineered for the specific operating conditions of dehumidification rotors. There are three key technical bottlenecks: the curing mechanism of the repair agent is disconnected from the rotor's operating conditions (most repair agents rely on two-component mixing or specific temperature triggering, which is incompatible with the normal temperature and high humidity conditions in the rotor's adsorption zone); the mechanical-thermal compatibility between the microcapsule shell material and the rotor's operating conditions is insufficient (existing single-layer urea-formaldehyde or melamine-formaldehyde shell materials are prone to thermal softening or even thermal decomposition at high temperatures of 120–180℃ in the regeneration zone, leading to premature rupture and loss of control); and the chemical compatibility between the repair agent and the adsorbent matrix has not been systematically studied (if a continuous covering layer forms on the adsorbent surface after the repair agent cures, it will block the adsorbent pores, thus exacerbating the dehumidification performance degradation).

[0007] In summary, existing technologies for addressing microcracks in dehumidifier rotor coatings either remain at a passive, damage-delaying defense level or face core technological obstacles related to mechanism-condition mismatch, failing to achieve active, in-situ, and autonomous repair of coating damage. Given the rapid market trend towards high-end, precision, and long-life dehumidifiers, there is an urgent need to develop a self-healing coating system that can be precisely coupled with the inherent operating conditions of dehumidifier rotors: a system capable of utilizing ambient moisture in the adsorption zone to achieve in-situ curing of the repair agent; microcapsule shells possessing both mechanical triggering sensitivity at room temperature and thermal stability under high-temperature regeneration conditions; the cured repair agent products being chemically compatible with the adsorbent matrix and not blocking effective pores; and the entire system seamlessly integrating with existing rotor manufacturing processes, demonstrating feasibility for large-scale production. Summary of the Invention

[0008] To address the technical problems in the prior art, this application provides a self-healing microcapsule coating for dehumidifying rotors and a method for preparing the same.

[0009] First, this application provides a self-healing microcapsule coating for dehumidifying rotors, employing the following technical solution:

[0010] A self-healing microcapsule coating for a dehumidifying impeller, the coating being applied to the inner wall surface of the honeycomb flow channel of the dehumidifying impeller, comprising adsorbent particles, a binder, and self-healing microcapsules; the self-healing microcapsules have a core-shell structure, the core material being a moisture-curing organosilane or organosilazane repair agent, and the shell material being a single-walled polyurea structure or a double-walled structure consisting of an inner flexible polyurethane layer and an outer brittle polyurea / urea-formaldehyde resin layer; the microcapsule particle size is 5–30 μm, and the core material mass content is ≥70 wt%.

[0011] In one specific feasible implementation, the moisture-curing organosilane repair agent is a mixture of one or more of methyltrimethoxysilane, methyltriethoxysilane, and isocyanate-based triethoxysilane with α,ω-diaminopropyl polydimethylsiloxane; the repair agent, under normal temperature and relative humidity ≥50%, has a hydrolysis gelation time of 15-90 min, a cured product elastic modulus of 0.4-1.5 GPa, and a curing shrinkage rate ≤5%.

[0012] In one specific feasible implementation, when the shell material has a double-wall structure, the inner layer is a flexible polyurethane layer with a thickness of 0.5 to 1.0 μm, formed by interfacial polymerization of toluene diisocyanate and ethylene glycol, which maintains elastic integrity under regeneration conditions at a temperature ≤180℃; the outer layer is a brittle polyurea layer with a thickness of 1.0 to 2.0 μm, formed by interfacial polymerization of diphenylmethane diisocyanate and diethylenetriamine, with a fracture stress of 2.5 to 4.0 MPa.

[0013] In one specific implementation scheme, the self-healing microcapsules are uniformly distributed in a monolayer within the coating, with a microcapsule spacing of 5–20 μm; the mass ratio of adsorbent particles to binder solids is 8:2, and the microcapsules account for 15–18 wt% of the total solids content of the coating; the total coating thickness is 80–120 μm; the adsorbent particles are silica gel powder, molecular sieves, or a composite of both, with an average particle size of 10–30 μm and a BET specific surface area ≥700 m². 2 / g; The binder is an aqueous polyacrylate emulsion with an elongation at break of ≥150% after film formation.

[0014] In one specific implementation, the coating further contains modified nano-silica, with nano-SiO2 particles having a size of 15–30 nm, and the surface modified with silane coupling agent KH-560, accounting for 3–6 wt% of the total solid content of the coating.

[0015] In one specific implementation scheme, when the coating is applied to an enthalpy recovery type or total heat recovery type dehumidifier rotor with a regeneration zone temperature of 40-60°C, the shell material is a single-wall polyurea structure with a shell thickness of 1.2-2.0 μm and a room temperature crack stress of 1.8-2.8 MPa.

[0016] Secondly, this application provides a method for preparing a self-healing microcapsule coating, using the following technical solution:

[0017] The method for preparing the above-mentioned self-healing microcapsule coating is characterized by comprising the following steps:

[0018] Step 1: Preparation of self-healing microcapsules: A moisture-curing repair agent core material is prepared into an O / W emulsion using a high-speed shear emulsification method, controlling the core material droplet D50 to be 8–20 μm. A shell material is grown on the surface of the core material droplets using in-situ polymerization or interfacial polymerization to form a single-walled or double-walled core-shell structure. The reaction temperature is 45–70℃, and the reaction time is 1.5–4 h. After completion, the mixture is filtered, washed three times with deionized water, and vacuum dried at 40℃ to obtain microcapsule powder.

[0019] Step 2, prepare the self-healing coating solution: Mix the adsorbent particles and binder emulsion at a solid content mass ratio of 8:2, add deionized water to adjust the solid content to 30% to 35%, and after full dispersion, stir at low speed and add microcapsule powder. The viscosity of the coating solution is controlled at 200 to 400 mPa·s.

[0020] Step 3, Coating application and curing: After pretreatment of the surface of the rotary honeycomb channel, the coating liquid is applied by dip-coating or air pressure spraying, the dry film thickness is controlled at 80-120μm, and the coating is dried and cured at 60℃ for 2h to obtain a self-healing functional coating.

[0021] In one specific feasible implementation, during the preparation of double-walled shell microcapsules in step one, two steps of interfacial polymerization are performed sequentially:

[0022] The first step involves dissolving toluene diisocyanate in toluene and then adding the repair agent to the core material to emulsify and form a W / O emulsion. An external aqueous phase containing ethylene glycol is then added to carry out the first interfacial polymerization, forming a polyurethane flexible inner layer on the surface of the core material. The reaction temperature is 50°C and the reaction time is 2 hours.

[0023] In the second step, the emulsion after the inner layer is formed is redispersed in an aqueous solution containing diethylenetriamine for a second interfacial polymerization to grow a brittle polyurea outer layer on the inner layer surface. The reaction temperature is 50℃ and the reaction time is 1.5h. The resulting double-walled microcapsules have a D50 of 9-12μm and a total shell thickness of 1.5-3.0μm.

[0024] This application includes at least one of the following beneficial technical effects:

[0025] 1. Working condition coupled autonomous repair without external intervention: The high humidity environment of the dehumidification wheel adsorption zone triggers the hydrolysis and cross-linking of the moisture-curing repair agent, and the high temperature in the regeneration zone promotes the complete condensation reaction, realizing active and in-situ repair of coating microcracks without additional energy input or manual operation.

[0026] 2. The double-walled microcapsules are precisely controllable and have excellent thermal stability: the inner flexible polyurethane layer can withstand high-temperature regeneration conditions of 180℃, avoiding premature leakage of the repair agent; the outer brittle polyurea layer only breaks when the stress is concentrated at the crack tip, so that the repair agent can be released on demand, and the shell integrity rate is still ≥96% at 180℃.

[0027] 3. The repair agent and adsorbent are chemically compatible, resulting in a high retention rate of dehumidification performance: After curing, the repair agent forms a Si-O-Si covalent bond with the silicone substrate, which will not block the pores of the adsorbent. After 100 thermal cycles, the dehumidification efficiency recovery rate can reach 97.8%, the service life of the rotor is extended by more than 2 times, and the total life cycle maintenance cost is reduced by more than 40%. Attached Figure Description

[0028] Figure 1 This is a scanning electron microscope image of the inner wall surface of the dehumidifying impeller honeycomb channel without the coating of this application;

[0029] Figure 2 This is a scanning electron microscope image of the coating surface on the inner wall of the honeycomb flow channel of the dehumidifying impeller after the self-healing microcapsule coating of this application has been applied, subjected to thermal cycling accelerated aging test and completed the self-healing process. Detailed Implementation

[0030] This application provides a self-healing microcapsule coating for dehumidifier rotors and its preparation method. The core concept of this coating system lies in the precise functional coupling of microcapsule self-healing technology with the inherent operating conditions of the dehumidifier rotor: a core-shell structure microcapsule is used, with the core material being a moisture-curing repair agent. The shell material employs a double-wall structure consisting of an inner flexible polyurethane layer and an outer brittle polyurea or urea-formaldehyde resin layer. This ensures the integrity of the shell material in the high-temperature regeneration zone while precisely triggering rupture under the stress field at the microcrack tip. The repair agent system uses moisture-curing organosilanes or organosilazanes, which naturally couple with the high-humidity environment of the dehumidifier rotor's adsorption zone. Through a hydrolysis-condensation reaction, an elastic filler chemically bonded to the silica gel substrate is generated, forming a Si-O-Si covalent anchor at the crack, thus sealing the crack without blocking the effective pores of the adsorbent. The entire repair process is automatically completed using the rotor's inherent operating conditions, requiring no external energy input or manual intervention.

[0031] The technical problem to be solved by this application is: the adsorbent coating of the dehumidifying rotor channel develops microcracks due to long-term thermal cycling stress, which leads to coating peeling, continuous decline in dehumidification performance, and high maintenance costs. The application aims to achieve active, in-situ, and autonomous repair of coating damage.

[0032] The achieved technical effects are as follows: microcracks in the dehumidifying rotor flow channel coating can be repaired autonomously, effectively preventing crack propagation and coating peeling; the repair mechanism is naturally coupled with the rotor's operating conditions, requiring no external energy input or manual intervention; the effective service life of the rotor is significantly extended, and the maintenance cost throughout the entire life cycle is greatly reduced; the manufacturing process is compatible with existing rotor manufacturing processes, and the threshold for industrialization is low.

[0033] The technical solution of this application will be described in detail below through five specific embodiments and three comparative examples.

[0034] Example 1: Self-healing microcapsule coating with urea-formaldehyde resin as shell material and MTMS as core material

[0035] 1.1 Microcapsule Preparation

[0036] Raw materials: Methyltrimethoxysilane (MTMS, analytical grade, molecular weight 136.22 g / mol, viscosity ≤1.5 mPa·s@25℃, moderate hydrolysis reaction rate, and elastic modulus of cured product approximately 0.8–1.5 GPa) as core material; melamine (analytical grade) and 37% formaldehyde aqueous solution as shell precursors; sodium dodecylbenzenesulfonate (SDBS, mass fraction 0.5%, prepared with deionized water) as emulsifier; triethanolamine (TEA) and hydrochloric acid as pH adjusters.

[0037] Preparation steps:

[0038] S1. Synthesis of melamine-formaldehyde (MF) prepolymer

[0039] 20g of melamine and 58g of 37% formaldehyde solution were added to a three-necked flask equipped with a reflux condenser. The pH was adjusted to 8.5–9.0 with triethanolamine. The mixture was stirred slowly (200 rpm) in a 70°C water bath for 30 minutes to obtain a clear, transparent MF prepolymer solution. The molar ratio of melamine to formaldehyde in the prepolymer was 1:3, and the solid content of the prepolymer was approximately 45%.

[0040] S2: Preparation of MTMS oil-in-water emulsion

[0041] Add 100 mL of SDBS solution to an emulsification tank. Measure 60 g of MTMS core material (density 0.955 g / mL, volume approximately 63 mL) and slowly add it dropwise to the emulsion. Emulsify for 15 min using a high-speed shear emulsifier (8000 rpm), controlling the oil droplet size (D50) to be 10–20 μm, D90 ≤ 30 μm, and standard deviation ≤ 5 μm. MTMS is immiscible with water (water solubility < 0.5 g / 100 mL @ 25℃), forming a stable O / W emulsion.

[0042] S3: In-situ polymerization coating

[0043] The MF prepolymer solution was slowly added dropwise to the MTMS emulsion (dropping rate approximately 1 mL / min) at a stirring rate of 200 rpm. The pH of the system was then slowly lowered from 8.5 to 4.5–5.0 using hydrochloric acid (adjustment rate approximately 0.5 pH units / 10 min to avoid insufficient shell density due to rapid pH reduction). The system temperature was maintained at 60°C, and the reaction continued for 3 hours. Melamine-formaldehyde resin completed in-situ polymerization on the surface of the MTMS oil droplets, forming a shell.

[0044] S4: Separation and Drying

[0045] After the reaction was completed, the mixture was cooled to room temperature, filtered, washed three times with deionized water (each time using the same volume of water as the product), and dried in a vacuum oven at 40°C for 2 hours to obtain approximately 78g of free-flowing white microcapsule powder.

[0046] Microcapsule characterization results:

[0047] Particle size (SEM measurement): D50=13.2μm, D90=24.5μm, uniformly distributed;

[0048] Shell thickness (cross-sectional SEM): approximately 2.0–3.5 μm;

[0049] Core material content (thermogravimetric analysis, TGA, mass loss rate below 200℃): 72.8 wt%;

[0050] Shell integrity rate (optical microscope statistics): ≥97%;

[0051] Nuclear integrity rate after heating at 120℃ for 30 min: ≥92%;

[0052] 1.2 Preparation of self-healing coating

[0053] Raw material: Spherical silica powder, average particle size 25μm, BET specific surface area 750m² 2 / g, pore volume 1.2cm 3 / g, saturated moisture absorption ≥38wt% (25℃, RH=90%) as adsorbent; aqueous polyacrylate emulsion (solid content 50%, Tg=-12℃, tensile strength after film formation 8MPa, elongation at break 180%) as binder; microcapsule powder (prepared as above).

[0054] Specific preparation: Slowly disperse 68g of silica gel powder and 24g of binder emulsion in 50mL of deionized water, and stir thoroughly (600rpm, 20min) to ensure the silica gel is uniformly suspended. Then add 14.1g of capsule powder to the coating and stir at low speed (200rpm, 10min) to ensure uniform dispersion, avoiding high-speed shearing that could damage the microcapsule walls. The final coating viscosity should be controlled between 200 and 400 mPa·s (rotational viscometer, 25℃).

[0055] Coating process: The prepared coating solution was injected into the immersion tank. The pre-treated (purged for dust removal, surface coated with KH-550 silane coupling agent primer) rotor module (size: φ200mm×100mm honeycomb rotor sample module) was immersed in the coating solution for 5 minutes. After immersion, it was slowly lifted out at a speed of 5 cm / min and placed on a drying rack in a 60℃ oven for 2 hours. The resulting coating thickness was approximately 80–100 μm, with microcapsules uniformly distributed in a monolayer on the flow channel surface.

[0056] Example 2: Self-healing microcapsules of a two-component repair agent system using polyurethane / polyurea double-wall structure as shell material and platinum-containing catalyst.

[0057] This embodiment provides a self-healing microcapsule coating with a polyurethane (inner layer) / polyurea (outer layer) double-wall structure as the shell material and a polydimethylsiloxane end-capped with low-viscosity methylhydrodiethoxysilane (MHDES) and alkoxysilane as the co-healing agent system. It is suitable for application scenarios with the highest requirements for repair speed, thermal cycle life and overall dehumidification performance recovery rate.

[0058] 2.1 Microcapsule Preparation

[0059] A composite repair agent core material was prepared by mixing low-viscosity methyltriethoxysilane (MTES, viscosity approximately 0.8 mPa·s) and α,ω-diaminopropylpolydimethylsiloxane (NH2-PDMS, molecular weight approximately 1000 g / mol, viscosity approximately 15 mPa·s) at a mass ratio of 7:3. MTES rapidly hydrolyzes to methyltrisilyl alcohol under the influence of ambient moisture, which then undergoes a co-condensation reaction with the terminal silane groups of NH2-PDMS and the silanol groups on the surface of silica gel, generating a polymethylsiloxane / PDMS interpenetrating network elastomer with flexible chain segments.

[0060] Design and fabrication of double-wall shell structure:

[0061] Inner layer (polyurethane layer) preparation:

[0062] 5.0 g of toluene diisocyanate (TDI, 80:20 isomer mixture) was dissolved in 20 mL of toluene solution containing 0.3 g of Span-80 emulsifier as the oil phase. 30 g of the composite repair agent core material (MTES+NH2-PDMS composite solution) was used as the dispersed phase and emulsified in the above oil phase by high-speed shearing (10000 rpm, 10 min) to form a W / O emulsion (core material droplet D50 = 8–12 μm). 1.8 g of ethylene glycol (EG, as a crosslinking agent) was dissolved in 100 mL of water to prepare the outer aqueous phase. The W / O emulsion was slowly added dropwise to the outer aqueous phase to form an O / W emulsion. The reaction was carried out at 50 °C for 2 h. TDI and EG in the outer aqueous phase underwent interfacial polymerization at the oil-water interface, forming a polyurethane inner shell on the surface of the core material oil droplets. The inner shell thickness was approximately 0.5–1.0 μm, providing elastic protection to the microcapsules at high temperatures (≤180 °C).

[0063] Outer layer (polyurea layer) preparation (interfacial polymerization method):

[0064] The emulsion after forming the inner shell was filtered and washed, then dispersed in an aqueous solution (150 mL, pH=8.5) containing diethylenetriamine (DETA, 3.5 g). The reaction was continued with stirring at 50 °C for 1.5 h. Unreacted free TDI and DETA further reacted on the surface of the inner shell to form a polyurea outer layer. The outer shell is brittle and thin (approximately 1.0–2.0 μm thick), and can easily fracture when stress is concentrated at the crack tip, triggering core material release.

[0065] Post-processing: Filter and wash 3 times, vacuum dry at 40℃ for 3 hours to obtain PU / PUrea double-walled microcapsule powder, which is white powder and free-flowing.

[0066] Characterization results:

[0067] Particle size: D50 = 9.5 μm, D90 = 17.8 μm;

[0068] Total shell thickness (TEM section): approximately 1.5–3.0 μm;

[0069] Core material content (TGA, weight loss below 200℃): 76.3 wt%;

[0070] Thermal stability (shell integrity rate after holding at 180℃ for 30 min): ≥96%;

[0071] Rupture stress (single capsule compression test using a micromanipulator): 2.5–4.0 MPa;

[0072] Core material 24h leakage rate: ≤0.3wt%;

[0073] 2.2 Preparation of self-healing coating

[0074] formula:

[0075] Silica gel powder / molecular sieve composite adsorbent (mass ratio 7:3): 75g;

[0076] Water-based polyacrylate adhesive (50% solids): 30g (15g solids);

[0077] Microcapsule powder: 16.5g (15.5wt% of total solid content = 75 + 15 + 16.5 = 106.5g);

[0078] Wetting agent (BYK-346, nonionic): 0.5g;

[0079] Deionized water was used to adjust the total solids content to 35%.

[0080] Coating process: A co-spraying integrated process is adopted. The coating liquid is uniformly sprayed onto the surface of the pre-primed impeller module flow channel at an air pressure of 0.3MPa through a 0.5mm nozzle spray gun. The wet film thickness of a single spray is controlled at 300-350μm (corresponding to a dry film thickness of approximately 100-120μm), and then dried at 60℃ for 2 hours. Microcapsules are uniformly distributed in a single layer in the dried coating, with a capsule spacing of approximately 5-20μm.

[0081] Example 3: A fast-curing self-healing microcapsule coating with urea-formaldehyde resin as the shell material and ethoxylated isocyanate as the core material.

[0082] This embodiment is designed for high-frequency cycling applications that require rapid repair and crack filling within a single adsorption-regeneration cycle (approximately 30 minutes) (such as heat pump-driven high-speed rotary dehumidifiers with a rotation speed > 50 r / h), employing a core material system with a faster curing rate.

[0083] 3.1 Microcapsule Preparation

[0084] Core material: Isocyanate-based triethoxysilane (ICTES, viscosity approximately 2.0 mPa·s @ 25℃) is selected. This core material has both isocyanate groups (which can react rapidly with water to form urethane / urea bonds) and triethoxysilane groups (hydrolysis and condensation). The dual curing mechanism allows the repair agent to complete the initial cross-linking within 15 minutes after contact with water, and the gel time is significantly shorter than that of the MTMS system in Example 1 (MTMS gel time is approximately 30-45 minutes).

[0085] Shell material: urea-formaldehyde resin (UF resin), using in-situ polymerization, with a urea to formaldehyde molar ratio of 1:2, and slow curing at pH adjusted to 3.5-4.0.

[0086] Key preparation parameters:

[0087] Emulsification stage: 8000 rpm, 12 min, ICTES oil droplet D50 = 11 μm;

[0088] In-situ polymerization: 60°C, pH=4.0, 4h (the reaction time was extended compared to Example 1, which improved the shell density).

[0089] Microcapsule particle size: D50 = 12.8 μm, shell thickness: 2.5–4.0 μm;

[0090] Core material content: 70.5wt%;

[0091] The isocyanate groups in ICTES are highly sensitive to moisture. The entire preparation process must be carried out under dry conditions (RH < 20%). Anhydrous organic solvent systems (such as anhydrous n-hexane / ethyl acetate mixed solvent) should be used to replace the aqueous phase in the emulsion. An appropriately adjusted process route should be adopted for emulsification and encapsulation to avoid premature deactivation of the core material during the preparation stage.

[0092] 3.2 Coating Formulation and Preparation

[0093] The formulation is similar to that of Example 1, but the core material is replaced with ICTES capsules, and the proportion of microcapsules is increased to 18 wt% (because the repair agent cannot be reused after a single curing, increasing the capsule density ensures the reserve of multiple repair capabilities). The coating thickness is controlled at 80-90 μm to ensure that the microcapsules can still be arranged in a single layer in a relatively thin coating.

[0094] Example 4: Low-temperature rapid-curing self-healing coating based on polyurea single-shell microcapsules

[0095] This embodiment provides a self-healing microcapsule system that can complete repair within the entire temperature range (20-60°C) for ambient temperature and humidity conversion rotors without regeneration heating processes (such as rotors used for total heat recovery / enthalpy recovery, where the highest temperature in the regeneration zone is only 40-50°C).

[0096] 4.1 Microcapsule Preparation

[0097] Core material: Waterborne silazane oligomer (molecular weight approximately 800–2000 g / mol, viscosity approximately 5–20 mPa·s; hydrolyzes and gels within 2–5 minutes at room temperature upon contact with water; curing temperature can be as low as 20°C). During hydrolysis, silazane generates Si-OH, which subsequently undergoes dehydration condensation to form a Si-O-Si network. The reaction rate is approximately 3–5 times that of equimolar MTMS.

[0098] Shell material: Polyurea, formed by interfacial polymerization of diphenylmethane diisocyanate and diethylenetriamine at the water / toluene interface. The polyurea shell has moderate brittleness and can be controlled to fracture under stress concentration of ≥2.0MPa, making it suitable for stress triggering at room temperature.

[0099] Preparation steps:

[0100] (1) Dissolve 6.0g of MDI in 20mL of toluene to prepare the oil phase, add 40g of silazane core material, emulsify at 10000rpm for 12min, D50=8.5μm;

[0101] (2) The emulsion was slowly added dropwise to 120 mL of deionized water containing 4.0 g of DETA and reacted at 45 °C for 1.5 h.

[0102] (3) Filter, wash, and vacuum dry at 40℃.

[0103] Characterization: D50=9.2μm, shell thickness approximately 1.2~2.0μm, core material content 75.8wt%, room temperature breaking stress 1.8~2.8MPa, shell integrity rate ≥98% after heat preservation at 60℃ for 4h, exhibiting good low temperature thermal stability.

[0104] Example 5: A composite functional coating integrating microcapsule self-healing and nanoparticle reinforcement

[0105] This embodiment, based on the double-walled microcapsule system of Example 2, further introduces nano-silica (nSiO2, particle size 20nm, BET surface area 200m²). 2 / g, with surface modified by KH-560 silane coupling agent) as coating reinforcing particles, to construct a composite coating system with dual functions of self-healing and mechanical reinforcement, further improving the initial cracking resistance of the coating under thermal cycling shock.

[0106] 5.1 Formula Adjustment

[0107] Based on the coating formulation of Example 2, 5g of modified nano-SiO2 was added, and ultrasonic dispersion (400W, 20min) was used to ensure that the nanoparticles were uniformly dispersed in the coating and did not form agglomerates. Nano-SiO2 enhances the coating hardness and elastic modulus after the binder cures through a dual mechanism of physical filling and surface chemical bonding. Simultaneously, the epoxy groups of the surface KH-560 coupling agent react with the hydroxyl groups in the binder, further strengthening the coating's cohesive strength.

[0108] 5.2 Preparation and Coating

[0109] The preparation method is the same as in Example 2. The nano-SiO2 dispersion is premixed with binder and silica powder and stirred thoroughly before being added to the microcapsules. Then, the microcapsules are added at a low speed to avoid damage to the microcapsules due to high-speed shearing. After coating, the microcapsules are dried at 60°C for 2 hours and then cured at 80°C for 1 hour to fully activate the chemical bonding of the KH-560 coupling agent.

[0110] Comparative Example 1: Traditional silicone adsorbent coating without microcapsule self-healing function

[0111] Preparation: The coating formulation was the same as in Example 1, but without the addition of microcapsules. The coating solution was prepared by mixing silica powder and water-based polyacrylate binder (8:2 mass ratio). The rest of the coating process was exactly the same as in Example 1. The coating thickness was about 90-100 μm, which served as a baseline control group.

[0112] Comparative Example 2: Coating of microcapsules (core material is SiO2 / montmorillonite composite powder) with single-walled urea-formaldehyde resin as shell material and inorganic nanoparticle encapsulation.

[0113] Preparation: Vapor-phase nano-SiO2 (20 nm particle size) and montmorillonite (5 μm particle size) were ultrasonically dispersed in ethanol (20% solid content) at a mass ratio of 7:3 to form a core material suspension. Microcapsules were prepared by in-situ polymerization using UF resin as the shell material (process as in Example 1). Due to the high density of solid particles and the poor stability of the emulsion, the resulting microcapsules had a wide particle size distribution (D10=8 μm, D90=65 μm), and the core material powder content was only about 45 wt% (the remainder being solvent and shell material).

[0114] Comparative Example 3: A control experiment showing that the repair failed due to premature shell fracture at high temperatures caused by the absence of a double-walled structure (single-walled polyurea only).

[0115] Preparation of single-walled polyurea microcapsules: A single-layer polyurea shell was formed directly using MDI / DETA interfacial polymerization, with a shell thickness of approximately 2.0–2.5 μm. Characterization: D50 = 10.2 μm, core material content 71.5 wt%, room temperature rupture stress 2.5–4.0 MPa.

[0116] Testing standards and methods

[0117] 1. Thermal cycling accelerated aging test

[0118] Phase A (Adsorption Condition Simulation): Temperature 25±2℃, Relative Humidity 80±3%, Duration 15min;

[0119] Phase B (Regeneration Simulation): Temperature 150±5℃, Relative Humidity 3±1%, Duration 15min;

[0120] Heating rate from A to B: approximately 10℃ / min; Cooling rate from B to A: approximately 8℃ / min;

[0121] Total number of cycles: 100 and 500;

[0122] Testing equipment: Constant temperature and humidity test chamber;

[0123] 2. Observation of surface micromorphology

[0124] Testing points: before thermal cycling (0 times), after thermal cycling (50 times, 100 times, 200 times, 500 times), and each stage after repair;

[0125] Test item: Crack density (cracks / mm) 2 ), maximum crack width (μm), microcapsule rupture rate (%), and repair filler continuity rating (1-5).

[0126] 3. Dehumidification efficiency test

[0127] Test conditions: Inlet air temperature 25℃, relative humidity 80%, airflow velocity 1.5m / s;

[0128] Testing indicators: relative humidity of outlet air (RH_%), dehumidification capacity per unit time (g / h), and dehumidification efficiency recovery rate (%).

[0129] Detection nodes: Initial, after 50 cycles (without repair), after 50 cycles (after 20 working cycles of repair), after 100 cycles (after repair);

[0130] 4. Coating adhesion test

[0131] Testing conditions: 3×3mm grid, blade spacing 1mm, scratch depth to substrate, rating after tape tearing (0~5, 0 is the best).

[0132] 5. Microcapsule thermal stability test

[0133] Methods: Microcapsule powder was placed in ovens at different temperatures (60℃, 100℃, 120℃, 150℃, 180℃) for 30 min, and the shell integrity rate was observed by SEM after removal.

[0134] Evaluation indicators: Shell integrity rate (%) at various temperatures; the highest temperature at which the shell integrity rate is >90% is taken as the upper limit of safe operating temperature;

[0135] 6. Repair rate test

[0136] Methods: Standard cracks (width 15±2μm, depth 50μm) were created by wire cutting on samples containing microcapsule coatings. The samples were then placed in an environment of 25℃ / RH=75% and samples were taken at 5 min, 15 min, 30 min, 60 min and 120 min. The crack filling rate (%) was observed by SEM.

[0137] 7. Adsorbent pore structure influence test

[0138] Test samples: pure silica gel adsorbent, coated control group (without microcapsules), coated with self-healing coating (Examples 1 to 5), coated with self-healing coating and repaired by 100 thermal cycles, and the coating powder was scraped off to detect BET specific surface area and pore volume respectively;

[0139] Objective: To verify that the cured product of the repair agent does not clog the effective pores of the adsorbent.

[0140] Performance test results

[0141] Table 1: Comparison of crack parameters after thermal cycling tests (100 thermal cycles) between each embodiment and the comparative example

[0142] serial number First cracking week <![CDATA[crack density after 100 cycles (cracks / mm 2 )]]> Maximum crack width (μm) after 100 cycles Localized area of ​​coating peeling (%) Example 1 22 8.3 5.2 <0.5 Example 2 28 5.7 3.8 <0.2 Example 3 20 9.1 5.6 <0.8 Example 4 18 11.2 7.1 <1.2 Example 5 42 3.4 2.1 <0.1 Comparative Example 1 15 18.6 14.8 8.5～15 Comparative Example 2 17 14.2 9.8 4.5～7.2 Comparative Example 3 16 15.8 11.5 6.8～12.3

[0143] Note: The first cracking cycle is defined as the minimum number of thermal cycles required for SEM to observe a crack with a width ≥2μm.

[0144] Table 2: Comparison of dehumidification performance recovery rates between each embodiment and the comparative example

[0145] serial number Initial dehumidification efficiency (g / h) Dehumidification efficiency (g / h) not restored after 100 cycles Dehumidification efficiency after repair (g / h) Recovery rate after repair (%) Repair completion time (min) Example 1 102.5 88.3 96.5 94.2 ~90 Example 2 103.2 91.8 100.2 97.1 ~30 Example 3 101.8 87.5 95.3 93.6 ~30 Example 4 98.5 83.6 91.4 92.8 ~60 Example 5 104.1 93.2 101.8 97.8 ~25 Comparative Example 1 101.9 79.0 No repair capability Attenuation of 22.5% — Comparative Example 2 100.5 82.3 79.0 78.6 — Comparative Example 3 102.8 84.7 84.7 82.4 —

[0146] Note: Recovery rate = Dehumidification efficiency after repair / Initial dehumidification efficiency × 100%. Comparative Examples 2 and 3 had significantly lower recovery rates after repair than the examples due to poor repair results.

[0147] Table 3: Comparison of thermal stability of microcapsules in each embodiment and comparative example (shell integrity rate, incubation for 30 min)

[0148] serial number 60℃ 100℃ 120℃ 150℃ 180℃ Safe temperature (°C) Example 1 (MF Single Wall) 100 99.2 97.5 93.8 82.1 ~150 Example 2 (PU / PUrea double wall) 100 100 99.5 98.2 96.1 >180 Example 3 (UF Single Wall) 100 99.5 96.8 91.5 79.3 ~145 Example 4 (PUrea single-walled) 100 100 99.1 93.5 72.4 ~145 <![CDATA[Example 5 (PU / PUrea double wall + nSiO₂)]]> 100 100 99.7 98.5 96.8 >180 Comparative Example 3 (PUrea Single-walled) 100 99.2 96.5 90.8 68.2 ~145

[0149] Note: The safe temperature is defined as the highest temperature at which the shell integrity rate is ≥90%. Examples 2 and 5 show that the double-walled structure is effective throughout the process at ≤180℃ and is adaptable to all types of dehumidifying rotor regeneration conditions.

[0150] Table 4: Comparison of Effective BET Specific Surface Area of ​​Adsorbents

[0151] sample <![CDATA[BET specific surface area (m 2 / g)]]> <![CDATA[Pore volume (cm 3 / g)]]> Relative retention rate (%) Pure silica gel adsorbent (standard) 752.4 1.22 100 Control group coating (after adhesive application) 698.5 1.09 92.8 Example 2: Coating (Before Repair) 685.3 1.06 91.1 Example 2 Coating (after 100 cycles of repair) 671.8 1.03 89.3 Comparative Example 2: Coating (solid particle filling, after 100 cycles) 603.2 0.88 80.2 Comparative Example 3: Coating (single-wall PUrea, after 100 cycles) 624.5 0.91 83.0

[0152] Note: The BET specific surface area retention rate (89.3%) of the coating in Example 2 after 100 cycles of repair was significantly better than that of Comparative Example 2 (80.2%) and Comparative Example 3 (83.0%), confirming that the cured product of the repair agent in this application does not block the main pores of the adsorbent.

[0153] Table 5: Comparison of overall performance scores of each embodiment and comparative example (maximum score 10 points)

[0154] Evaluation Dimensions Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Dehumidification efficiency recovery rate after repair 8.5 9.7 8.4 8.3 9.8 0 3.9 4.1 Thermal stability (applicable temperature range) 7.5 9.5 7.0 7.2 9.6 — 6.5 6.8 First cracking delay effect 7.5 9.0 7.0 6.5 9.8 — 6.5 6.2 Repair completion speed 6.0 8.5 8.5 7.0 8.8 — 3.5 4.0 Effect on adsorbent pores 8.5 9.3 8.0 9.0 9.3 9.0 6.5 7.0 Preparation process maturity 9.5 8.0 8.0 8.5 8.0 10 7.5 8.0 Comprehensive weighted score 7.8 9.1 7.7 7.6 9.4 3.1 5.6 5.9

[0155] Note: The comprehensive weighted score is calculated by weighting the repair efficiency (30%), thermal stability (20%), first cracking delay (20%), repair speed (15%), pore channel influence (10%), and preparation maturity (5%).

[0156] Figure 1The image shows a scanning electron microscope (SEM) image of the inner wall surface of the honeycomb channel of the dehumidifying rotor without the coating of this application. The image was taken using a ZEISS field emission scanning electron microscope with an accelerating voltage of 10.00 kV, a magnification of 3000x (3.00 K×), a working distance of 13.5 mm, and the SE1 secondary electron signal imaging mode. The image shows the typical corrugated channel inner wall morphology of the honeycomb fiber paper substrate of the dehumidifying rotor. The regular layered structure of the substrate fibers and the smooth surface can be observed. This surface has not yet been loaded with any adsorbent or functional coating, representing the initial state of the rotor when it leaves the factory.

[0157] Figure 2 This is a scanning electron microscope (SEM) image of the coating surface on the inner wall of the honeycomb flow channel of the dehumidifying impeller after the self-healing microcapsule coating of this application has been applied, subjected to accelerated aging test (100 adsorption-regeneration cycles) and completed the self-healing process. Figure 1 The same imaging parameters (ZEISS SEM, 10.00 kV, 3.00 K×, WD=13.5 mm, SE1 mode) clearly show that the microcracks on the coating surface caused by thermal stress have been effectively filled and healed by the cured product of the repair agent. A continuous and seamless interface bond is formed between the repaired area and the surrounding original coating. Characteristic cured morphologies formed after the release of the repair agent can be seen at some microcapsule rupture sites, which directly verifies the effectiveness of the self-healing mechanism of this application.

[0158] like Figure 1 As shown, the inner wall of the dehumidifying rotor honeycomb channel without the coating of this application exhibits a typical inorganic fiber paper substrate morphology: at a magnification of 3000x, the corrugated pleated structure and the layered arrangement of the fiber skeleton of the honeycomb paper substrate can be clearly distinguished. The surface is smooth and flat overall, with no adsorbent particles or functional coatings visible. The equivalent hydraulic diameter of this substrate is 1.0–2.5 mm, and the specific surface area is 800–2000 m² / m³. Although its exposed fiber surface has a large geometric surface area, it lacks the specific adsorption capacity for water vapor molecules and cannot directly meet the functional requirements of deep dehumidification. It must be loaded with an adsorbent functional coating on its inner wall through impregnation or spraying processes before it can be put into use. Figure 1 The substrate morphology shown also reveals the challenges faced by subsequent coating adhesion: the surface roughness of the fiber paper is limited, and the mechanical anchoring effect between the coating and the substrate mainly depends on the penetration and physical integration of the adhesive. Under long-term thermal cycling conditions, the interfacial bonding area will become the preferred site for fatigue damage.

[0159] like Figure 2As shown, after undergoing 100 simulated thermal cycles (adsorption zone 25℃ / RH80% → regeneration zone 150℃ / RH3%, 30 min per cycle) accelerated aging test on the inner wall surface of the dehumidifier impeller coated with the self-healing microcapsule coating of this application, multiple microcracks with a width of approximately 3–8 μm appeared on the coating surface. However, during the subsequent 20 working cycles (approximately 10 h) of normal operation, all of the above cracks were successfully repaired. This can be clearly observed from the SEM microstructure:

[0160] (1) Repair integrity: The cracked area has been completely covered by a continuous and dense repair filler. There is no obvious boundary or peeling gap between the filler and the original coating matrix, indicating that the cured product of the repair agent has formed a good chemical bond (Si-O-Si covalent bond) with the silicone matrix.

[0161] (2) Interface compatibility: The surface of the repair filler exhibits a microstructure and grayscale characteristics similar to the surrounding coating, indicating that the composition and density of the cured product are highly matched with the original coating, and there are no heterogeneous inclusions or pore defects.

[0162] (3) Triggering mechanism confirmation: residual fragments of microcapsule shell material and fan-shaped diffusion traces formed after the release of repair agent can be identified on some crack paths, confirming the directional fracture and controllable release mechanism of core-shell structure microcapsules triggered by stress concentration at the crack tip.

[0163] (4) Spatial adaptability: The surface smoothness of the repaired coating was significantly restored, and no protrusions or flow marks caused by excessive overflow of repair agent were observed, indicating that the release amount of repair agent and the crack volume achieved good spatial adaptability.

[0164] The above microscopic morphology observation results correspond to the performance test data of this application.

[0165] Figure 2 The SEM images provide a direct, microscopic view of the self-healing microcapsule coating of this application, demonstrating that it can achieve in-situ, autonomous, and efficient repair of thermally cycle-induced microcracks, effectively preventing crack propagation and coating peeling, thereby ensuring the performance stability and operational reliability of the dehumidification rotor throughout its entire life cycle.

[0166] analyze

[0167] Examples 1 and 3 employ single-wall shell materials (MF resin / UF resin) prepared using a mature in-situ polymerization process. This process has a low industrialization threshold and is suitable for cost-sensitive, low-to-mid-range dehumidifier rotor applications with regeneration temperatures ≤150℃. Example 1 uses MTMS core material, whose cured product has strong affinity for silicone, and the process is the most mature, serving as the basic implementation case of this application's technical solution (supporting low-end applications). Example 3, on the other hand, utilizes ICTES core material to provide a faster curing rate, supporting the demands of high-frequency cycling scenarios.

[0168] Example 2 uses a double-walled PU / PUrea shell and an MTES+NH2-PDMS composite core material, achieving optimal comprehensive performance in terms of thermal stability, core material encapsulation amount, repair rate, and dehumidification efficiency recovery rate. It is the core example of this application where all technical parameters are in the optimal combination range (intermediate value), representing the best preferred solution.

[0169] Example 4 addresses the special operating conditions of low-temperature enthalpy recovery rotors by employing a polyurea single-walled core material with silazane fast-curing properties. This achieves efficient self-healing under low-temperature conditions while also catering to ambient temperature rotor applications (supporting the lower limit of the temperature range).

[0170] Example 5 builds upon Example 2 by adding a nano-SiO2 mechanical enhancement strategy, further improving the first cracking delay and overall performance (supporting the upper limit of the optimal range), representing the highest performance level of the technical solution in this application.

[0171] Explanation of the core differences between the comparative examples and the embodiments:

[0172] Key technology differences This application (Examples 1-5) Comparative Example 1 Comparative Example 2 Comparative Example 3 Does it contain self-healing microcapsules? yes no Yes (solid core material) Yes (single-wall shell material) Core material type Liquid moisture-cured organosilicon — Solid nanoparticle suspension Liquid organosilanes Shell structure Single-walled or double-walled (including a flexible polyurethane inner layer) — Single-wall UF Single-walled PUrea (lacking PU inner layer) Shell material stability in high-temperature zones (160℃) Good (≥91.5%) — Average (~88%) Poor (~62%, many premature ruptures) Repair agent chemically bonds with crack wall It contains (Si-O-Si bonds) — None (physical fill) Some Dehumidification recovery rate after 100 cycles 92.8%～97.8% 77.5% (attenuation) 78.6% 82.4%

[0173] Based on all the experimental data from the above embodiments and comparative examples, the inventive core of the technical solution of this application is reflected in three interrelated key technical features, and each feature has been fully experimentally verified through the comparative examples.

[0174] Firstly, the moisture-curing liquid organosilane repair agent system—using Comparative Example 1 as a reference—establishes the fundamental superiority of liquid repair agent + chemical bonding curing over traditional coatings without repair capabilities; using Comparative Example 2 as a reference, it further reveals the comprehensive advantages of liquid repair agent over solid particle-filled repair agent in terms of crack penetration depth, interfacial chemical bonding strength, and repair continuity; the repair agent forms Si-O-Si covalent bonds on the crack wall through hydrolysis-condensation, making the repair filler a chemical extension of the coating structure rather than a heterogeneous inclusion, thus ensuring the durability of the repair and resistance to re-cracking from a mechanistic perspective.

[0175] Secondly, the dual-walled core-shell microcapsule structure (flexible polyurethane inner layer + brittle polyurea outer layer) – using Comparative Example 3 as a reference, rigorously verified the irreplaceable role of the PU inner layer in preventing high-temperature runaway cracking; the dual-walled structure achieves precise control of the repair timing through a mechanical cascade triggering mechanism (crack stress concentration → precise cracking of the brittle outer layer → directional cracking of the elastic inner layer → directional release of the repair agent), transforming the self-repair behavior from passive, disordered, and prematurely exhausted to active, on-demand, and continuously effective; after being kept at 180℃ for 30 min, the shell integrity rate of this dual-walled structure is ≥96%, which is the highest thermal stability level among microcapsules in the currently reported dehumidification application field, and is the structural invention point that distinguishes this application from all existing single-walled self-healing coating technologies.

[0176] Third, the functional coupling design of the repair mechanism and the working conditions of the rotor—this application creatively integrates two originally independent rotor operation elements, namely, the high humidity (RH≥60%) in the adsorption zone providing the repair agent to solidify the moisture and the high temperature (120~180℃) in the regeneration zone promoting condensation and solidification, into the built-in driving force of the repair process. This allows the entire self-repairing closed loop to be completed automatically during the normal operation of the rotor, without any external energy input, sensor triggering, or manual intervention. This forms a positive cycle mechanism that becomes more self-repairing the more it runs. This design concept is unprecedented in the published patent literature related to dehumidification equipment and is the overall inventiveness of this application at the system level.

[0177] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A self-healing microcapsule coating for a dehumidifying impeller, characterized in that, The coating is applied to the inner wall surface of the dehumidifying impeller honeycomb channel and includes adsorbent particles, binder, and self-healing microcapsules. The self-healing microcapsules have a core-shell structure, with the core material being a moisture-curing organosilane or organosilazane repair agent, and the shell material being a single-walled polyurea structure or a double-walled structure consisting of an inner flexible polyurethane layer and an outer brittle polyurea / urea-formaldehyde resin layer. The microcapsule particle size is 5–30 μm, and the core material mass content is ≥70 wt%.

2. The self-healing microcapsule coating according to claim 1, characterized in that, The moisture-curing organosilane repair agent is a mixture of one or more of methyltrimethoxysilane, methyltriethoxysilane, and isocyanate-based triethoxysilane with α,ω-diaminopropyl polydimethylsiloxane; the repair agent has a hydrolysis gelation time of 15-90 min at room temperature and relative humidity ≥50%, the elastic modulus of the cured product is 0.4-1.5 GPa, and the curing shrinkage rate is ≤5%.

3. The self-healing microcapsule coating according to claim 1, characterized in that, When the shell material has a double-wall structure, the inner layer is a flexible polyurethane layer with a thickness of 0.5 to 1.0 μm, formed by interfacial polymerization of toluene diisocyanate and ethylene glycol, which maintains elastic integrity under regeneration conditions at a temperature ≤180℃; the outer layer is a brittle polyurea layer with a thickness of 1.0 to 2.0 μm, formed by interfacial polymerization of diphenylmethane diisocyanate and diethylenetriamine, with a fracture stress of 2.5 to 4.0 MPa.

4. The self-healing microcapsule coating according to claim 1, characterized in that, The self-healing microcapsules are uniformly distributed in a single layer within the coating, with a microcapsule spacing of 5–20 μm; the mass ratio of adsorbent particles to binder solids is 8:2, and the microcapsules account for 15–18 wt% of the total solids in the coating; the total coating thickness is 80–120 μm; the adsorbent particles are silica gel powder, molecular sieves, or a composite of both, with an average particle size of 10–30 μm and a BET specific surface area ≥700 m². 2 / g; The binder is an aqueous polyacrylate emulsion with an elongation at break of ≥150% after film formation.

5. The self-healing microcapsule coating according to claim 1, characterized in that, The coating also contains modified nano-silica, with nano-SiO2 particles having a size of 15-30 nm, and the surface is modified with silane coupling agent KH-560, accounting for 3-6 wt% of the total solid content of the coating.

6. The self-healing microcapsule coating according to claim 1, characterized in that, When the coating is applied to an enthalpy recovery type or total heat recovery type dehumidifier rotor with a regeneration zone temperature of 40-60℃, the shell material is a single-wall polyurea structure with a shell thickness of 1.2-2.0μm and a room temperature crack stress of 1.8-2.8MPa.

7. A method for preparing the self-healing microcapsule coating according to any one of claims 1 to 6, characterized in that, Includes the following steps: Step 1: Preparation of self-healing microcapsules: A moisture-curing repair agent core material is prepared into an O / W emulsion using a high-speed shear emulsification method, controlling the core material droplet D50 to be 8–20 μm. A shell material is grown on the surface of the core material droplets using in-situ polymerization or interfacial polymerization to form a single-walled or double-walled core-shell structure. The reaction temperature is 45–70℃, and the reaction time is 1.5–4 h. After completion, the mixture is filtered, washed three times with deionized water, and vacuum dried at 40℃ to obtain microcapsule powder. Step 2, prepare the self-healing coating solution: Mix the adsorbent particles and binder emulsion at a solid content mass ratio of 8:2, add deionized water to adjust the solid content to 30% to 35%, and after full dispersion, stir at low speed and add microcapsule powder. The viscosity of the coating solution is controlled at 200 to 400 mPa·s. Step 3, Coating application and curing: After pretreatment of the surface of the rotary honeycomb channel, the coating liquid is applied by dip-coating or air pressure spraying, the dry film thickness is controlled at 80-120μm, and the coating is dried and cured at 60℃ for 2h to obtain a self-healing functional coating.

8. The preparation method according to claim 7, characterized in that, In step one, during the preparation of the double-walled shell microcapsules, two steps of interfacial polymerization are performed sequentially: The first step involves dissolving toluene diisocyanate in toluene and then adding the repair agent to the core material to emulsify and form a W / O emulsion. An external aqueous phase containing ethylene glycol is then added to carry out the first interfacial polymerization, forming a polyurethane flexible inner layer on the surface of the core material. The reaction temperature is 50°C and the reaction time is 2 hours. In the second step, the emulsion after the inner layer is formed is redispersed in an aqueous solution containing diethylenetriamine for a second interfacial polymerization to grow a brittle polyurea outer layer on the inner layer surface. The reaction temperature is 50℃ and the reaction time is 1.5h. The resulting double-walled microcapsules have a D50 of 9-12μm and a total shell thickness of 1.5-3.0μm.

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