Gradient-like liquid release coating and method of making same

Abstract

The application provides a gradient liquid-like anti-adhesion coating and a preparation method thereof, and belongs to the technical field of surface coating. The gradient liquid-like anti-adhesion coating comprises a bearing bottom layer, a buffer middle layer and a liquid-like molecular brush surface layer arranged in sequence from the surface of a base material outward; the gradient liquid-like anti-adhesion coating comprises silicone resin, inorganic nano-filler, silane coupling agent, metal alkoxide coupling agent and liquid-like molecular chain; the content of the inorganic nano-filler and the content of the metal alkoxide coupling agent decrease in the bearing bottom layer, the buffer middle layer and the liquid-like molecular brush surface layer in sequence, and the content of the liquid-like molecular chain decreases in the liquid-like molecular brush surface layer, the buffer middle layer and the bearing bottom layer in sequence; the silicone resin forms a flexible continuous phase, the inorganic nano-filler forms a heat-resistant support skeleton, and the metal alkoxide coupling agent forms a covalent bridge between the silicone resin, the inorganic nano-filler and the liquid-like molecular chain through a hydrolysis and condensation process.

Description

Technical Field

[0001] This invention relates to the field of surface coating technology, and in particular to a gradient liquid anti-stick coating and its preparation method. Background Technology

[0002] Industrial heating devices, heat exchangers, heating pipes, heat treatment furnaces, molded hot plates, and high-temperature conveying components are typically operated under high temperatures and complex media environments. Material adhesion, oil residue, dust deposition, coking, and carbon buildup can easily occur on metal heating surfaces or the inner walls of flow channels. These deposits not only increase thermal resistance and reduce heat transfer efficiency but can also lead to localized overheating, flow channel blockage, and increased equipment maintenance frequency.

[0003] Therefore, how to inhibit material adhesion, reduce coking and carbon buildup, extend cleaning cycles, and maintain equipment heat transfer efficiency in high-temperature environments are important issues that need to be addressed in the field of surface protection for industrial heating components. Summary of the Invention

[0004] In view of this, in order to at least partially solve the aforementioned technical problems, the present invention provides a gradient liquid anti-stick coating and a method for preparing the same.

[0005] According to one embodiment of the present invention, a gradient liquid-like anti-stick coating is provided, comprising a carrier underlayer, a buffer middle layer, and a liquid-like molecular brush layer disposed sequentially from the surface of a substrate; the gradient liquid-like anti-stick coating comprises an organosilicon resin, an inorganic nanofiller, a silane coupling agent, a metal alkoxide coupling agent, and liquid-like molecular chains; the content of the inorganic nanofiller and the content of the metal alkoxide coupling agent decrease sequentially in the carrier underlayer, the buffer middle layer, and the liquid-like molecular brush layer, and the content of the liquid-like molecular chains decreases sequentially in the liquid-like molecular brush layer, the buffer middle layer, and the carrier underlayer; the organosilicon resin forms a flexible continuous phase, the inorganic nanofiller forms a heat-resistant supporting framework, and the metal alkoxide coupling agent forms a covalent bridge between the organosilicon resin, the inorganic nanofiller, and the liquid-like molecular chains through hydrolysis and condensation processes.

[0006] According to one aspect of the present invention, a method for preparing a gradient liquid anti-stick coating as described above is provided, employing a layered gradient spraying method, comprising: mixing organosilicon resin, inorganic nanofiller, metal alkoxide coupling agent, and silane coupling agent in a solvent, optionally adding liquid-like molecular chains, and stirring to obtain a carrier bottom layer coating liquid with a low content of liquid-like molecular chains; mixing organosilicon resin, inorganic nanofiller, metal alkoxide coupling agent, silane coupling agent, and liquid-like molecular chains in a solvent, adjusting the content of inorganic nanofiller and metal alkoxide coupling agent to be lower than the content of the corresponding raw materials in the carrier bottom layer, and increasing the content of liquid-like molecular chains, and stirring to obtain a buffer middle layer coating liquid; mixing organosilicon resin, liquid-like molecular chains, and optionally inorganic nanofiller in a solvent, adding silane coupling agent and metal alkoxide coupling agent, adjusting the content of inorganic nanofiller and metal alkoxide coupling agent to be lower than the content of the corresponding raw materials in the buffer middle layer coating liquid, so that the liquid-like molecular chains are mixed to form a liquid-like liquid. The content of liquid molecular chains is higher than the corresponding raw material content in the coating liquid of the buffer intermediate layer. A coating liquid for a liquid-like molecular brushing surface layer is obtained by stirring. The coating liquid of the bearing bottom layer is applied to the surface of the substrate, leveled at room temperature, and pre-dried to obtain a substrate with the initial bearing bottom layer on the surface. The coating liquid of the buffer intermediate layer is applied to the surface of the initial bearing bottom layer and subjected to pre-crosslinking treatment to obtain a substrate with the initial buffer intermediate layer on the surface. The coating liquid for the liquid-like molecular brushing surface layer is applied to the surface of the initial buffer intermediate layer and subjected to a first thermosetting treatment to obtain a substrate with the initial liquid-like molecular brushing surface layer on the surface, thereby obtaining a gradient liquid-like anti-stick coating. The solvent includes at least one of ethanol, isopropanol, n-butanol, ethyl acetate, butyl acetate, propylene glycol methyl ether acetate, toluene, xylene, cyclohexane, n-hexane, and tetrahydrofuran. The additives include at least one of dispersants, leveling agents, defoamers, thixotropic agents, adhesion promoters, antioxidants, and abrasion-resistant additives.

[0007] According to another aspect of the present invention, a method for preparing a gradient liquid anti-stick coating is provided, which employs a continuous gradient spraying method, comprising: mixing an organosilicon resin, an inorganic nanofiller, a metal alkoxide coupling agent, a silane coupling agent, and a liquid-like molecular chain in a solvent, optionally adding an additive to obtain a coating system for continuous gradient spraying; continuously spraying the coating system onto the surface of a substrate, gradually reducing the mass content of the inorganic nanofiller and the metal alkoxide coupling agent and gradually increasing the mass content of the liquid-like molecular chain during the spraying process; and performing leveling, pre-drying, pre-crosslinking, and thermosetting treatments sequentially after spraying to obtain the gradient liquid anti-stick coating.

[0008] The gradient liquid anti-stick coating of this invention, through its gradient structure of an outermost anti-stick layer, a middle buffer layer, and a bottom load-bearing layer, utilizes the dynamic flexible chain movement of the liquid-like molecular brush layer to exhibit low adhesion to both polar and non-polar liquids, resulting in superior anti-fouling performance. The organosilicon resin in the components forms a dense, continuous phase, preventing the penetration of molten material or tar generated during high-temperature heating (350~400℃) into the coating. Furthermore, the organosilicon resin itself is chemically stable, possessing excellent high-temperature resistance and anti-fouling properties, reducing coking and thus avoiding frequent rust and scale removal maintenance, extending the continuous operating time and cleaning cycle of the equipment. Based on the decreasing content of inorganic nanofillers and metal alkoxide coupling agents from the inside out, the internal stress generated by the different coefficients of thermal expansion at high temperatures is effectively alleviated, preventing coating cracking or peeling. Metal alkoxide coupling agents form strong covalent bonds between the organic phase (organosilicon resin), inorganic phase (inorganic nanofiller), and liquid-like molecular chains through hydrolysis and condensation, enhancing the coating's cohesion and adhesion to the substrate. This enables the coating to withstand high-temperature thermal shock and material erosion, thereby ensuring the structural integrity of the coating at 350~400℃.

[0009] According to the method for preparing a gradient liquid anti-stick coating according to embodiments of the present invention, the gradient liquid anti-stick coating can be prepared by either layered gradient spraying or continuous gradient spraying. The layered gradient spraying method forms a gradient structure by separately adjusting the component ratios of the underlying substrate, the buffer intermediate layer, and the liquid-like molecular brush layer; the continuous gradient spraying method forms a continuous compositional gradient structure by continuously changing the component ratios of the coating system during spraying. Both methods can achieve a gradient distribution with decreasing inorganic components and increasing liquid-like molecular chains from the substrate side to the outer surface. Attached Figure Description

[0010] The above and other objects, features and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings.

[0011] Figure 1 A schematic diagram of the structure of a gradient liquid anti-stick coating according to an embodiment of the present invention is shown;

[0012] Figure 2 A schematic diagram illustrating the preparation process mechanism of the gradient liquid anti-stick coating according to an embodiment of the present invention is shown;

[0013] Figure 3 A flowchart illustrating a method for preparing a gradient liquid anti-stick coating according to an embodiment of the present invention is shown;

[0014] Figure 4The thermogravimetric analysis curve of the gradient liquid anti-stick coating of Embodiment 3 of the present invention is shown, which is obtained by heating from 30°C to 800°C at a heating rate of 10°C / min under nitrogen atmosphere.

[0015] Figure 5 The bar chart shows the contact angle changes of the gradient liquid anti-stick coating of Embodiment 3 of the present invention after heating at 350°C for different times;

[0016] Figure 6 The bar chart shows the surface energy change of the gradient liquid anti-stick coating of Embodiment 3 of the present invention after heating at 350°C for different times;

[0017] Figure 7 The images show physical photos of the gradient liquid anti-stick coating of Embodiment 5 of the present invention before heating and after heating at 350°C for 500 hours. In the images, a shows the coating before heating and b shows the coating after heating for 500 hours.

[0018] In the above figures, the reference numerals are as follows:

[0019] 1. Supporting layer; 2. Buffering middle layer; 3. Liquid-like molecular brush surface layer; 4. Base layer. Detailed Implementation

[0020] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0021] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "comprising" as used herein indicates the presence of features, steps, or operations, but does not exclude the presence or addition of one or more other features.

[0022] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0023] Under operating conditions of 350~400℃, the metal heating surfaces or inner walls of flow channels in industrial heating devices, heat exchangers, heating pipes, heat treatment furnaces, molding hot plates, and high-temperature conveying components are prone to material adhesion, oil residue, dust deposition, coking, and carbon buildup. Once these deposits form, they significantly increase thermal resistance, reduce heat transfer efficiency, and lead to increased energy consumption. Simultaneously, carbon deposits and coke can cause localized overheating, flow channel blockage, equipment corrosion, and mechanical wear, thereby shortening equipment lifespan and increasing the frequency of downtime for cleaning.

[0024] To address these issues, related technologies typically modify the substrate surface with anti-stick, anti-fouling, or heat-resistant coatings to reduce material adhesion and deposition on heated surfaces. While existing coatings can provide some anti-sticking protection under medium-low temperature or short-term high-temperature conditions, they are prone to surface performance degradation, interface failure, or structural damage under long-term operation at 350–400°C accompanied by thermal cycling, mechanical friction, and complex media conditions. This makes it difficult to simultaneously achieve comprehensive performance characteristics such as high-temperature resistance, low adhesion, anti-coking, and thermal shock resistance.

[0025] In realizing the concept of this invention, it was discovered that by forming a gradient liquid-like anti-stick coating, using high-temperature resistant organosilicon resin as a flexible continuous phase and inorganic nanofillers as a heat-resistant reinforcing skeleton, a covalent bridging network is constructed between the organosilicon resin, inorganic nanofillers, and liquid-like molecular chains through metal alkoxide coupling agents and silane coupling agents. Through the formed coating structure, the content of metal alkoxide coupling agents and inorganic nanofillers is higher on the side close to the substrate, and the content of liquid-like molecular chains is higher on the side away from the substrate. This results in a coating that simultaneously possesses high adhesion, high temperature resistance, thermal shock resistance, wear resistance, and durable anti-stick properties.

[0026] Specifically, according to one embodiment of the present invention, a gradient-type liquid anti-stick coating is provided. Figure 1 A schematic diagram of the structure of a gradient liquid anti-stick coating according to an embodiment of the present invention is shown; Figure 2 A crosslinking mechanism diagram of a gradient liquid anti-stick coating according to an embodiment of the present invention is shown, wherein metal alkoxide coupling agents participate in the formation of a Si-OM bridging structure, and silane coupling agents participate in the formation of a Si-O-Si connection structure. Figure 1 As shown, the gradient liquid anti-stick coating includes a carrier bottom layer 1, a buffer middle layer 2, and a liquid-like molecular brush layer 3, sequentially disposed from the surface of the substrate 4 outwards; the gradient liquid anti-stick coating comprises silicone resin, inorganic nanofillers, silane coupling agents, metal alkoxide coupling agents, and liquid-like molecular chains; the content of inorganic nanofillers and metal alkoxide coupling agents decreases sequentially in the carrier bottom layer 1, buffer middle layer 2, and liquid-like molecular brush layer 3, and the content of liquid-like molecular chains decreases sequentially in the liquid-like molecular brush layer 3, buffer middle layer 2, and carrier bottom layer 1. Figure 2As shown, the organosilicon resin forms a flexible continuous phase, the inorganic nanofiller forms a heat-resistant supporting framework, and the metal alkoxide coupling agent forms a covalent bridge between the organosilicon resin, the inorganic nanofiller, and the liquid-like molecular chain through hydrolysis and condensation processes.

[0027] According to embodiments of the present invention, a gradient liquid-like anti-stick coating is constructed by synergistically building a gradient liquid-like anti-stick coating with organosilicon resin, inorganic nanofiller, silane coupling agent, metal alkoxide coupling agent, and liquid-like molecular chains. By integrating the above-mentioned different functional materials through covalent bridging and gradient structure, a synergistic improvement in high temperature resistance, anti-sticking properties, improved adhesion to the substrate, and wear resistance is achieved.

[0028] Specifically, unlike existing technologies that use silica sol condensation or inorganic particle physical filling, this invention uses the hydrolysis and condensation reaction of metal alkoxide coupling agents to form a chemical bridge between organosilicon resin, inorganic nanofillers, and liquid-like molecular chains, constructing a Si-OM synergistic dense network. M is the metal central element in the metal alkoxide coupling agent, which improves the thermal stability, structural density, and interfacial bonding strength of the coating.

[0029] By capping the ends of liquid-like molecular chains with polar groups, such as hydroxyl, alkoxy, and silane groups, an interaction is created between the polar groups and the organic-inorganic network, as... Figure 2 The chemical linkage shown here fixes one end of the liquid-like molecular chain to the coating surface in a covalently anchored manner, while the other end has the ability to move segments, forming a stable liquid-like molecular brush interface on the coating surface, thereby maintaining low surface energy and low adhesion performance under high temperature conditions.

[0030] This invention constructs a gradient liquid-like anti-stick coating consisting of a carrier bottom layer with a gradient of inorganic content from high to low, a buffer middle layer, and a liquid-like molecular brush top layer. Unlike the single-layer coating or bottom / top layer dual-layer structure in related technologies, this invention adjusts the inorganic content, crosslinking density, and liquid-like molecular chain content to create a gradient change in mechanical properties, thermal stability, and surface chemical composition from the substrate side to the air side, thereby simultaneously meeting the requirements of substrate adhesion, thermal stress buffering, and surface anti-sticking.

[0031] This invention focuses on the structural design for preventing sticking, coking, and carbon buildup in industrial heating components operating at 350-400℃. Many existing non-stick coatings are primarily used in cookware, for room-temperature stain prevention, self-cleaning, or general friction reduction applications, lacking comprehensive designs specifically addressing high-temperature oil stains, smoke, material residues, and coking precursors. This invention, considering the long-term high-temperature operation and thermal cycling characteristics of industrial heating components, proposes a combined scheme of a high-temperature stable network, a low-adhesion surface layer, and a gradient buffer structure, with a clear engineering application focus.

[0032] This invention focuses not only on the initial low surface energy of gradient liquid anti-stick coatings, but also on the retention of low surface energy and structural integrity after high-temperature thermal cycling. In existing technologies, some coatings exhibit good water contact angles or low frictional properties in their initial state, but their performance degrades significantly after high-temperature aging, friction and wear, or thermal cycling. This invention inhibits the migration of surface functional components through a dense Si-OM network and covalently anchored liquid molecular chains, and reduces thermal stress concentration through a gradient structure, thereby improving long-term service stability.

[0033] According to embodiments of the present invention, the high-temperature gradient liquid anti-stick coating of the present invention is suitable for the surface of metal, ceramic, glass, alloy or other heat-resistant substrates, especially suitable for the surface of high-temperature components such as industrial heating devices, heat exchangers, heating pipes, inner walls of heat treatment furnaces, molding hot plates, heating rollers and high-temperature conveying components that are prone to coking, carbon deposits, material adhesion or oil residue.

[0034] This invention utilizes a three-phase synergy of an organosilicon resin matrix, an inorganic framework, and a liquid-like molecular brush. High-temperature resistant organosilicon resin serves as a flexible continuous phase, while nano-inorganic oxide nanoparticles act as a heat-resistant reinforcing framework. Covalent bridging networks are constructed between the organosilicon resin matrix, the inorganic nanoframework, and the liquid-like molecular chains using metal alkoxide coupling agents and silane coupling agents, forming a gradient structure that gradually changes from the substrate to the outer surface. This gradient structural design enables the coating to simultaneously possess high adhesion, high-temperature resistance, thermal shock resistance, wear resistance, and durable non-stick properties.

[0035] Specifically, organosilicon resins contain a Si-O-Si backbone structure with high bond energy, resulting in excellent heat resistance, flexibility, and film-forming properties, making them suitable as a continuous phase matrix for gradient liquid anti-stick coatings. Inorganic nanofillers possess high thermal stability and mechanical strength, forming a heat-resistant supporting framework within the coating and contributing to improved hardness, wear resistance, and resistance to thermal deformation. Metal alkoxide coupling agents can form MO-Si bonds during hydrolysis and condensation, where M is a metal element, thereby creating a covalent bridge between the organosilicon resin, inorganic nanofillers, and liquid-like molecular chains.

[0036] In some specific embodiments, the silicone resin includes one or more of methyl silicone resin, phenyl silicone resin, methylphenyl silicone resin, epoxy-modified silicone resin, acrylic-modified silicone resin, hydroxyl silicone resin, and alkoxy silicone resin. Such materials contribute to providing superior heat resistance, flexibility, and film-forming properties.

[0037] Preferably, the silicone resin is a methylphenyl silicone resin or a phenyl silicone resin to further improve the heat resistance and film stability of the coating.

[0038] In some specific embodiments, the inorganic nanofiller includes one or more of nano-SiO2, nano-Al2O3, nano-ZrO2, nano-TiO2, silicates, glass powder, and boron nitride. This helps to provide a heat-resistant supporting framework through the above materials, improving the coating's hardness, wear resistance, and resistance to thermal deformation. The silicate can be, for example, nano-silicate particles, layered silicates (mica sheets), or chain silicates (wollastonite), etc.

[0039] Preferably, the inorganic nanofiller is nano-SiO2, more preferably nano-SiO2 with an average particle size of 10~100nm, and its surface has hydroxyl groups or is nano-SiO2 modified with silane.

[0040] In some specific embodiments, the metal alkoxide coupling agent includes one or more of titanate coupling agents, zirconate coupling agents, and aluminate coupling agents. M-OR represents the metal alkoxy structure in the metal alkoxide coupling agent, and Si-OH represents the hydroxyl groups on the surface of organosilicon resin, silane coupling agent, hydrolyzed silane, or nano-SiO2. Through hydrolysis and condensation reactions, a Si-O-Si and Si-OM synergistic crosslinking network is formed inside the coating, so that the organic and inorganic phases are no longer solely dependent on physical mixing, but are connected by chemical bonds into a continuous and dense hybrid structure.

[0041] Preferably, the metal alkoxide coupling agent is one or more selected from tetrabutyl titanate, isopropyl titanate, titanium acetylacetonate, n-propyl zirconate, zirconium acetylacetonate, or aluminum acetylacetonate. These metal alkoxide coupling agents are more conducive to catalyzing and participating in the sol-gel reaction, forming a Si-OM synergistic dense network.

[0042] In some specific embodiments, the silane coupling agent includes one or more of vinyltrimethoxysilane, vinyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, and tetraethoxysilane. Silane coupling agents are used to improve the interfacial bonding between substrates, inorganic nanofillers, silicone resins, and liquid-like molecular chains.

[0043] In some specific embodiments, the liquid-like molecular chain comprises a siloxane polymer with polar groups as end groups or side chains. These polar groups include at least one of hydroxyl, alkoxy, silane, amino, epoxy, carboxyl, and siloxane groups.

[0044] Preferably, the liquid-like molecular chain can be polydimethylsiloxane (PDMS) with hydroxyl-terminated groups, PDMS with siloxy-terminated groups, PDMS with silyl-terminated groups, PDMS with amino-terminated groups, or PDMS with epoxy-terminated groups. These liquid-like molecular chains have low glass transition temperatures and high segmental flexibility, enabling the formation of a liquid-like molecular brush interface on the coating surface, where one end is chemically anchored (between the organic-inorganic hybrid network) and the other end has a certain degree of segmental mobility. Due to the low surface energy of PDMS segments and the ability of segments to dynamically rearrange, the coating surface exhibits low adhesion, low friction, and easy-to-clean properties.

[0045] In some embodiments, the number average molecular weight of the liquid-like molecular chains is 500-100000 Da, preferably 1000-30000 Da, and more preferably 1000-10000 Da.

[0046] In some specific embodiments, the liquid-like molecular chains are cross-linked with organosilicon resin through polar groups, metal alkoxide coupling agents, and form a synergistic cross-linked network of Si-OM and Si-O-Si, wherein M is titanium, zirconium, or aluminum.

[0047] In some embodiments, the thickness of the gradient liquid anti-stick coating is 11–200 μm. This provides sufficient resistance to thermal shock and material erosion, further ensuring the structural integrity of the coating at 350–400°C.

[0048] In some preferred embodiments, the thickness of the gradient liquid anti-stick coating is 30~80μm, more preferably 30~50μm.

[0049] In some implementations, the thickness of the load-bearing base layer is 5-80 μm, the thickness of the buffer middle layer is 5-80 μm, and the thickness of the liquid-like molecular brush surface layer is 1-40 μm. The thickness of each layer can be adjusted according to the size of the component, the type of substrate, and the requirements of the operating conditions under actual high-temperature conditions.

[0050] According to another aspect of the present invention, a method for preparing a gradient liquid anti-stick coating as described above is provided, wherein the method employs a layered gradient spraying method. Figure 3 A flowchart illustrating a method for preparing a gradient liquid anti-stick coating according to an embodiment of the present invention is shown, as follows: Figure 3 As shown, the preparation method includes operations S301 to S306.

[0051] In operation S301, organosilicon resin, inorganic nanofiller, metal alkoxide coupling agent, silane coupling agent and optional liquid molecular chain are mixed in a solvent, and optional additives are added. Stirring yields a coating liquid that supports the substrate.

[0052] In operation S302, organosilicon resin, inorganic nanofiller, metal alkoxide coupling agent, silane coupling agent, and liquid-like molecular chains are mixed in a solvent. The content of inorganic nanofiller and metal alkoxide coupling agent is adjusted to be lower than the corresponding raw material content in the coating liquid of the underlying substrate, so that the content of liquid-like molecular chains is higher than the corresponding raw material content in the coating liquid of the underlying substrate. The mixture is stirred to obtain the coating liquid of the buffer middle layer.

[0053] In operation S303, silicone resin, liquid-like molecular chains, and optional inorganic nanofillers are mixed in a solvent. Silane coupling agent and metal alkoxide coupling agent are added, and the content of inorganic nanofillers and metal alkoxide coupling agents is adjusted to be lower than the corresponding raw material content in the buffer layer coating liquid, so that the content of liquid-like molecular chains is higher than the corresponding raw material content in the buffer layer coating liquid. The mixture is stirred to obtain the liquid-like molecular brushing coating liquid.

[0054] In operation S304, the coating liquid of the bearing substrate is applied to the surface of the substrate, and after leveling and pre-drying at room temperature, a substrate with the initial bearing substrate is obtained.

[0055] In operation S305, the coating liquid of the buffer intermediate layer is applied to the surface of the initial bearing substrate for pre-crosslinking treatment, resulting in a substrate with the initial buffer intermediate layer on the surface.

[0056] In operation S306, the liquid coating of the liquid-like molecular brush layer is applied to the surface of the initial buffer layer and subjected to a first thermosetting treatment to obtain a substrate with the initial liquid-like molecular brush layer on the surface, thereby obtaining a gradient liquid-like anti-stick coating.

[0057] According to embodiments of the present invention, by forming an initial support underlayer with a high content of inorganic nanofillers and metal alkoxide coupling agents, the adhesion between the underlayer and the substrate is improved. The substrate can be, for example, the aforementioned metal, ceramic, glass, alloy, or other heat-resistant substrate, while also considering heat load-bearing capacity and thermal shock resistance. When forming the initial support underlayer, liquid-like molecular chains can be added or not, depending on actual needs. If added, the amount of liquid-like molecular chains is low, preferably not added. When no liquid-like molecular chains are added to the support underlayer, the inorganic reinforcement effect of the underlayer can be further improved; when a small amount of liquid-like molecular chains are added, the interlayer flexibility and interfacial compatibility can be further improved. When forming the initial buffer intermediate layer composed of organic-inorganic synergy, a transition between the underlayer and the top layer is provided, reducing interlayer stress. When forming the liquid-like molecular brush top layer, a high content of liquid-like molecular chains and a low content of inorganic nanofillers provide low surface energy and anti-stick properties, ensuring that the coating surface has a liquid-like interface with dynamic chain segment movement capability.

[0058] According to embodiments of the present invention, by performing staged curing during the formation of each of the three layers, it is helpful to improve the compatibility between the layers and further ensure its thermal shock resistance and thermal stability.

[0059] According to embodiments of the present invention, the solvent includes at least one selected from ethanol, isopropanol, n-butanol, ethyl acetate, butyl acetate, propylene glycol methyl ether acetate, toluene, xylene, cyclohexane, n-hexane, and tetrahydrofuran. A solvent with low water content is preferred to avoid excessively rapid hydrolysis of the metal alkoxide coupling agent, which could lead to gelation or unstable dispersion.

[0060] It is understood that the gradient liquid anti-stick coating of the present invention may or may not include additives. When additives are included, the additives may be one or more of the following: dispersants, leveling agents, defoamers, thixotropic agents, adhesion promoters, antioxidants, or abrasion-resistant additives.

[0061] In some embodiments, the solid components of the substrate coating liquid, by mass fraction, include: 20-70 parts of silicone resin, 20-70 parts of inorganic nanofiller, 1-20 parts of metal alkoxide coupling agent, 0.5-15 parts of silane coupling agent, 0-10 parts of liquid-like molecular chain, and 0-5 parts of additives. The high inorganic content substrate, containing a higher proportion of nano-inorganic filler and metal alkoxide coupling agent, can form a dense inorganic reinforcing network on the substrate surface, improving the adhesion, hardness, and heat resistance between the coating and the substrate.

[0062] In some specific embodiments, the solid components of the buffer intermediate layer coating liquid, by mass fraction, include: 30-80 parts of silicone resin, 10-50 parts of inorganic nanofiller, 1-15 parts of metal alkoxide coupling agent, 0.5-15 parts of silane coupling agent, 1-20 parts of liquid-like molecular chains, and 0-5 parts of additives. The organic-inorganic synergistic buffer intermediate layer is located between the load-bearing underlayer and the liquid-like molecular brush layer. Its silicone resin content and inorganic nanofiller content are at intermediate levels, which can buffer the modulus difference and thermal expansion difference between the load-bearing underlayer and the liquid-like molecular brush layer, improving the structural integrity of the coating during thermal cycling.

[0063] In some specific embodiments, the solid components of the liquid coating for the liquid-like molecular brush layer, by mass fraction, include: 20-70 parts of silicone resin, 0-30 parts of inorganic nanofiller, 0.5-10 parts of metal alkoxide coupling agent, 0.5-15 parts of silane coupling agent, 5-60 parts of liquid-like molecular chains, and 0-5 parts of additives. This higher concentration of liquid-like molecular chains facilitates covalent anchoring with the organic-inorganic hybrid network through end-group reactions, forming a liquid-like interface on the outer surface of the coating with low surface energy, low adhesion, and dynamic chain segment movement capabilities.

[0064] In some specific embodiments, the leveling conditions are as follows: leveling at 20-40°C for 5-60 minutes to ensure a uniform coating surface and release air bubbles. Pre-drying conditions are as follows: pre-drying at 50-100°C for 10-120 minutes to remove most of the solvent. Pre-crosslinking treatment conditions are as follows: pre-crosslinking at 100-180°C for 10-180 minutes to induce initial condensation of the silicone resin, silane coupling agent, and metal alkoxide coupling agent. The first thermosetting treatment conditions are as follows: thermosetting at 180-350°C for 10-240 minutes to further densify the Si-O-Si and Si-OM networks and covalently anchor the liquid-like molecular chains to the coating surface through end-group reactions or silane condensation reactions.

[0065] It should be noted that the heating rate during the first thermosetting process is preferably 0.5~10℃ / min to avoid pinholes, shrinkage cavities, cracks or blistering caused by rapid solvent evaporation or a sudden increase in thermal stress.

[0066] In some embodiments, the substrate includes at least one of metal, ceramic, glass, and alloy.

[0067] In some embodiments, the preparation method further includes: sequentially washing, sandblasting or grinding, and blowing the surface of the initial substrate to obtain the substrate. The above methods may specifically include sandblasting, grinding, degreasing, acid washing, alkaline washing, plasma treatment, flame treatment, silane priming treatment, or combinations thereof, to increase the surface roughness and reactivity of the substrate, and improve the mechanical interlocking and chemical bonding between the coating and the substrate.

[0068] In some embodiments, the preparation method further includes: heat-treating the gradient liquid anti-stick coating at a temperature of 250–400°C for 5–120 min. This heat treatment can be performed on coatings requiring higher temperature resistance to further improve the density and thermal stability of the inorganic network. The preferred heating rate during heat treatment is 0.5–10°C / min to avoid pinholes, shrinkage cavities, cracking, or blistering caused by rapid solvent evaporation or a sudden increase in thermal stress.

[0069] According to another aspect of the present invention, a method for preparing a gradient liquid anti-stick coating as described above is provided. The method employs a continuous gradient spraying method and includes the following operations A to B.

[0070] In step A, organosilicon resin, inorganic nanofiller, metal alkoxide coupling agent, silane coupling agent and liquid-like molecular chain are mixed in a solvent, and optional additives are added. The mixture is stirred to obtain a liquid-like anti-stick coating liquid.

[0071] In operation B, a liquid-like anti-stick coating is continuously sprayed onto the surface of the substrate. During the spraying process, the mass content of inorganic nanofillers and metal alkoxide coupling agents in the coating is gradually reduced, while the mass content of liquid-like molecular chains is gradually increased. Then, the coating undergoes room temperature leveling, pre-drying, pre-crosslinking treatment, and first thermosetting treatment in sequence to prepare a gradient liquid-like anti-stick coating.

[0072] According to an embodiment of the present invention, by means of continuous gradient spraying, that is, by gradually reducing the content of inorganic nanofillers and metal alkoxide coupling agents and gradually increasing the content of liquid-like molecular chains during the spraying process, the coating forms a continuous gradient distribution from the substrate side to the outer surface, rather than a clear layered structure.

[0073] In some preferred embodiments, the room temperature leveling conditions are leveling at 20~40℃ for 5~60 min, the pre-drying conditions are pre-drying at 50~100℃ for 10~120 min, the pre-crosslinking treatment conditions are pre-crosslinking at 100~180℃ for 10~180 min, and the first thermosetting treatment conditions are thermosetting at 180~350℃ for 10~240 min. These parameters are basically the same as the aforementioned layered gradient spraying method, and will not be repeated here.

[0074] According to embodiments of the present invention, a layered spraying or continuous gradient spraying method suitable for preparing coatings on the surface of engineering components is provided. This method allows for adjustment of the formulations of the base layer, intermediate layer, and top layer according to different component shapes and operating conditions, and achieves solvent release, pre-crosslinking, network densification, and molecular brush anchoring through staged curing. Compared with traditional single-coating and one-time curing methods, this method is more advantageous for obtaining high-temperature resistant, non-stick coatings with uniform film thickness, stable adhesion, fewer defects, and scalable production.

[0075] The present invention will be further illustrated below through embodiments and related test experiments and results. In the following detailed description, numerous specific details are set forth for ease of explanation to provide a comprehensive understanding of the embodiments of the present invention. However, it will be apparent that one or more embodiments may be practiced without these specific details. Moreover, the details in the following embodiments can be arbitrarily combined to form other feasible embodiments without conflict.

[0076] It should be noted that the specific embodiments described below are merely illustrative examples, and the scope of protection of this invention is not limited thereto. The chemicals and raw materials used in the following embodiments are all commercially available or prepared using recognized processing methods.

[0077] In the embodiments and comparative examples of this invention, unless otherwise stated, the substrate is made of 304 stainless steel plate with dimensions of 50mm × 50mm × 2mm. The substrate is ultrasonically cleaned sequentially with acetone and ethanol, dried, and then sandblasted to control the surface roughness Ra to 2.0μm.

[0078] The coating was prepared by spraying, and after curing, its film thickness, surface energy, water contact angle, adhesion, thermal cycling stability, high-temperature friction coefficient, and anti-stick residue were tested.

[0079] Example 1:

[0080] (1) By weight, the coating liquid supporting the substrate comprises the following components according to a fixed composition:

[0081] The composition includes 50 parts of methylphenyl silicone resin, 40 parts of nano-SiO2 with an average particle size of 30 nm, 8 parts of tetrabutyl titanate, and 5 parts of γ-glycidyl etheroxypropyltrimethoxysilane, without the addition of liquid-like molecular chains; and 2 parts of additives, including 1 part of leveling agent, 0.5 parts of defoamer, and 0.5 parts of dispersant.

[0082] Methylphenyl silicone resin was dissolved in xylene to obtain a resin solution. Nano-SiO2 was added to the resin solution, mechanically stirred, and then ultrasonically dispersed to ensure uniform dispersion of the nano-SiO2. Tetrabutyl titanate and γ-glycidoxypropyltrimethoxysilane were then added, and stirring was continued to allow them to undergo pre-hydrolysis and pre-condensation reactions with the hydroxyl or alkoxy groups on the surface of the methylphenyl silicone resin and nano-SiO2. Finally, leveling agent, defoamer, and dispersant were added, and the mixture was filtered to obtain a coating liquid with a high inorganic content as the carrier substrate.

[0083] The substrate surface after the aforementioned sandblasting treatment is coated with a substrate-bearing underlayer coating liquid. The coating is first leveled at 25°C for 30 minutes to make the coating surface uniform and release air bubbles. Then, it is pre-dried at 80°C for 30 minutes to remove most of the solvent, resulting in a substrate with an initial substrate-bearing underlayer.

[0084] (2) By mass, the coating liquid of the buffer intermediate layer comprises the following components according to the fixed composition:

[0085] The composition includes 55 parts of methylphenyl silicone resin, 25 parts of nano-SiO2 with an average particle size of 30 nm, 5 parts of tetrabutyl titanate, 5 parts of γ-glycidyl etheroxypropyltrimethoxysilane, and 10 parts of polydimethylsiloxane with hydroxyl groups at both ends of the molecular chain (number average molecular weight of 2000 Da); and 2 parts of additives, including 1 part of leveling agent, 0.5 parts of defoamer, and 0.5 parts of dispersant.

[0086] Methylphenyl silicone resin, nano-SiO2, tetrabutyl titanate, γ-glycidyl etheroxypropyltrimethoxysilane and polydimethylsiloxane with hydroxyl groups at both ends of the molecular chain are added to xylene. The mixture is first mechanically stirred, then ultrasonically dispersed, and after being mixed evenly, filtered to obtain a buffer intermediate layer coating liquid.

[0087] The buffer intermediate layer coating liquid is applied to the initial bearing substrate and pre-crosslinked at 150°C for 60 min to allow the methylphenyl silicone resin, silane coupling agent and tetrabutyl titanate to undergo preliminary condensation, resulting in a substrate with the initial buffer intermediate layer on the surface.

[0088] (3) The coating liquid for the surface layer of the liquid molecular brush includes the following components according to the fixed composition:

[0089] The composition includes 45 parts of methylphenyl silicone resin, 10 parts of nano-SiO2 with an average particle size of 30 nm, 3 parts of tetrabutyl titanate, 5 parts of γ-glycidyl etheroxypropyltrimethoxysilane, and 30 parts of polydimethylsiloxane with hydroxyl groups at both ends of the molecular chain (number average molecular weight of 2000 Da); and 2 parts of additives, including 1 part of leveling agent, 0.5 parts of defoamer, and 0.5 parts of dispersant.

[0090] Methylphenyl silicone resin and polydimethylsiloxane with hydroxyl groups at both ends of the molecular chain were added to xylene and stirred. Then, nano-SiO2, γ-glycidoxypropyltrimethoxysilane and tetrabutyl titanate were added and stirred to disperse. Polydimethylsiloxane with hydroxyl groups at both ends of the molecular chain can chemically graft or covalently anchor with the organic-inorganic network during the subsequent curing process. After degassing and filtration, a liquid-like molecular brush coating liquid was obtained.

[0091] The liquid-like molecular brush coating is applied to the initial buffer layer and then heat-cured at 280℃ for 60 minutes to further densify the Si-O-Si and Si-O-Ti networks. The liquid-like molecular chains are covalently anchored to the surface of the gradient liquid-like anti-stick coating through terminal hydroxyl reactions, further enhancing the effect of inhibiting material adhesion.

[0092] The thickness of the aforementioned underlying layer is 20 μm, the thickness of the buffer middle layer is 15 μm, and the thickness of the liquid-like molecular brush surface layer is 10 μm, with a total thickness of 45 μm.

[0093] Example 2:

[0094] The mass fractions and preparation process of each layer in Example 2 are the same as in Example 1, except that the silicone resin, inorganic nanofiller, metal alkoxide coupling agent, liquid-like molecular chain, and curing conditions are replaced as shown in Table 1. The resulting load-bearing bottom layer has a thickness of 22 μm, the buffer middle layer has a thickness of 17 μm, and the liquid-like molecular brush top layer has a thickness of 11 μm, for a total thickness of 50 μm.

[0095] Example 3:

[0096] The mass fractions and preparation process of each layer in Example 3 are the same as in Example 1, except that the liquid-like molecular chains used and the curing conditions are replaced as shown in Table 1. The thickness of the resulting load-bearing bottom layer is 18 μm, the thickness of the buffer middle layer is 14 μm, and the thickness of the liquid-like molecular brush surface layer is 10 μm, with a total thickness of 42 μm.

[0097] Example 4:

[0098] In Example 4, the mass proportions and preparation process of each layer are the same as in Example 1. The difference lies in that methyl silicone resin and phenyl silicone resin are compounded in a 1:1 mass ratio, nano-SiO2 and nano-ZrO2 are compounded in a 3:1 mass ratio, n-propyl zirconate is used as the metal alkoxide coupling agent, and other materials and curing conditions are replaced as shown in Table 1. The resulting load-bearing underlayer has a thickness of 21 μm, the buffer middle layer has a thickness of 16 μm, and the liquid-like molecular brush surface layer has a thickness of 11 μm, for a total thickness of 48 μm.

[0099] It should be noted that Examples 1 to 4 employ a layered spraying method, achieving a gradient structure of the coating along the thickness direction by separately adjusting the composition of the underlying layer, the buffer middle layer, and the liquid-like molecular brush layer.

[0100] In addition to the layered spraying method described above, the present invention can also employ a continuous gradient spraying method. By continuously adjusting the supply ratio of different compositional coating liquids during the spraying process, the content of inorganic components and the content of liquid-like molecular chains continuously change along the coating thickness direction, thereby forming a continuous compositional gradient structure. Both methods belong to the preparation methods of the gradient liquid-like anti-stick coating of the present invention.

[0101] Example 5:

[0102] Preparation of non-layered gradient liquid anti-stick coatings using continuous gradient spraying:

[0103] Continuous gradient spraying uses an online mixing and feeding system for starting coating liquid A and ending coating liquid B. Both coating liquids use xylene as a solvent, γ-glycidyl etheroxypropyltrimethoxysilane as the silane coupling agent, and each contains 2 parts of additives, including 1 part leveling agent, 0.5 parts defoamer, and 0.5 parts dispersant.

[0104] The starting coating solution A consists of 50 parts of methylphenyl silicone resin, 40 parts of nano-SiO2 with an average particle size of 30 nm, 8 parts of tetrabutyl titanate, and 5 parts of γ-glycidyl etheroxypropyltrimethoxysilane, without the addition of liquid-like molecular chains; the terminating coating solution B consists of 45 parts of methylphenyl silicone resin, 10 parts of nano-SiO2 with an average particle size of 30 nm, 3 parts of tetrabutyl titanate, 5 parts of γ-glycidyl etheroxypropyltrimethoxysilane, and 30 parts of polydimethylsiloxane (number average molecular weight of 5000) with silyl groups at both ends of the molecular chain.

[0105] Starting coating solution A and ending coating solution B were prepared separately: Organosilicon resin was dissolved in xylene, and a corresponding amount of nano-SiO2 was added. The mixture was first mechanically stirred, and then ultrasonically dispersed. Subsequently, corresponding amounts of tetrabutyl titanate and γ-glycidoxypropyltrimethoxysilane were added. The ending coating solution B was further supplemented with polydimethylsiloxane with silyl groups at both ends of the molecular chain. Finally, leveling agent, defoamer and dispersant were added, stirred evenly and filtered to obtain starting coating solution A and ending coating solution B, respectively.

[0106] A dual-channel metering pump is used to continuously spray the starting coating solution A and the ending coating solution B onto the substrate surface after online mixing, while maintaining a constant total spray flow rate. Throughout the spraying process, the supply ratio of the starting coating solution A is gradually reduced from 100% to 0%, while the supply ratio of the ending coating solution B is gradually increased from 0% to 100%. This results in a gradual decrease in the content of nano-SiO2 and tetrabutyl titanate from the substrate side to the outer surface, while the content of liquid-like molecular chains gradually increases, forming a continuous gradient distribution. This continuous change is achieved by adjusting the online ratio of the two coating solutions with different compositions, rather than by changing the components in a single coating solution through immediate reaction.

[0107] The coated layer was cured in stages: first, it was leveled at 25°C for 30 min, then pre-dried at 80°C for 30 min; then, it was pre-crosslinked at 150°C for 60 min, allowing the methylphenyl silicone resin, silane coupling agent, and tetrabutyl titanate to undergo initial condensation; finally, it was thermally cured at 300°C for 60 min, further densifying the Si-O-Si and Si-O-Ti networks and covalently anchoring the liquid-like molecular chains to the coating surface through silane condensation reaction. The total thickness of the coating was 46 μm.

[0108] Comparative Example 1:

[0109] Comparative Example 1 uses commercially available polytetrafluoroethylene (PTFE) anti-stick coating. The coating was uniformly sprayed onto the surface of a stainless steel substrate that had undergone the same pretreatment, pre-dried at 120°C for 20 min, then heated to 380°C for sintering for 20 min, and after cooling, a PTFE anti-stick coating with a thickness of 40 μm was obtained.

[0110] Comparative Example 2:

[0111] Comparative Example 2 is a ceramic-type anti-stick coating. Silica sol and silane were mixed at a mass ratio of 4:1 to form a base liquid. Then, nano-SiO2, the same as in Example 1, was added and dispersed evenly to obtain a spraying liquid. The spraying liquid was applied to the surface of a stainless steel substrate that had undergone the same pretreatment, and sintered at 150°C for 60 min. Then, the temperature was raised to 300°C and sintered for another 60 min to form a ceramic-type anti-stick coating with a thickness of 45 μm.

[0112] Comparative Example 3:

[0113] Comparative Example 3 is a non-gradient homogeneous composite coating. By mass parts, the non-gradient homogeneous composite spray coating liquid comprises the following components according to a fixed composition:

[0114] The composition includes 50 parts of methylphenyl silicone resin, 25 parts of nano-SiO2 with an average particle size of 30 nm, 5 parts of tetrabutyl titanate, 5 parts of γ-glycidyl etheroxypropyltrimethoxysilane, and 10 parts of polydimethylsiloxane with hydroxyl groups at both ends of the molecular chain (number average molecular weight of 2000); and 2 parts of additives, including 1 part of leveling agent, 0.5 parts of defoamer, and 0.5 parts of dispersant.

[0115] Methylphenyl silicone resin was dissolved in xylene, and nano-SiO2 was added. The mixture was first mechanically stirred and then ultrasonically dispersed. Tetrabutyl titanate, γ-glycidoxypropyltrimethoxysilane and polydimethylsiloxane with hydroxyl groups at both ends of the molecular chain were then added and stirred and mixed. Finally, leveling agent, defoamer and dispersant were added, and the mixture was filtered to obtain a non-gradient homogeneous composite spray coating liquid.

[0116] Non-gradient homogeneous composite spray coating liquid is sprayed onto the substrate surface, and the coated single layer is cured in stages: first, leveling at 25℃ for 30 min, then pre-drying at 80℃ for 30 min, then pre-crosslinking at 150℃ for 60 min, and finally heat curing at 280℃ for 60 min. The total thickness of the coating is 45 μm.

[0117] Comparative Example 4:

[0118] The main process of Comparative Example 4 is similar to that of Comparative Example 3, with the differences shown in Table 1 below. No metal alkoxide coupling agent was added and the curing conditions were slightly adjusted, resulting in a total coating thickness of 43 μm.

[0119] Table 1

[0120]

[0121] The coatings prepared in Examples 1-5 and Comparative Examples 1-4 were tested under the same conditions. Thermogravimetric analysis was performed using the gradient liquid anti-stick coating sample from Example 3, heated from 30°C to 800°C at a rate of 10°C / min under a nitrogen atmosphere. High-temperature thermal cycling was performed under the following conditions: heating from room temperature to 350°C, holding for 10 min, and then cooling to room temperature, constituting one cycle, for a total of 1000 cycles. Short-term thermal shock was performed at 400°C for 10 min. High-temperature friction was performed using an Al2O3 ball, a load of 5 N, a rotation speed of 200 rpm, and a temperature of 350°C. For the anti-stick residue test, oil / dust was used to simulate mixed contaminants. After coating the sample surface, it was treated at 350°C for 30 min, cooled, and then purged with airflow and lightly wiped. The residue per unit area was measured and compared with that of an uncoated stainless steel substrate. The results are shown in Table 2 below.

[0122] Table 2

[0123]

[0124] Figure 4 The thermogravimetric analysis curves of the gradient liquid anti-stick coating of Example 3 are shown, obtained by heating from 30°C to 800°C at a heating rate of 10°C / min under nitrogen atmosphere. Figure 5 The contact angle changes of the gradient liquid anti-stick coating of Example 3 after heating at 350°C for different times are shown. Figure 6 The surface energy changes of the gradient liquid anti-stick coating of Example 3 after heating at 350°C for different times are shown. Figures 4-6 As shown in Tables 1 and 2, compared with the comparative examples, the high-temperature gradient liquid anti-stick coatings prepared in Examples 1-5 all exhibited lower surface energy, higher water contact angle, better adhesion, lower high-temperature friction coefficient, and lower contaminant residue rate.

[0125] As shown in Tables 1 and 2, especially after 1000 thermal cycles at 350°C and short-term thermal shock at 400°C, the coatings of the embodiments did not show obvious cracking, blistering or peeling, indicating that the present invention can significantly improve the stability of the coating under high-temperature anti-sticking conditions through the synergistic effect of gradient structure, Si-OM synergistic network and liquid-like molecular brush surface layer.

[0126] Although Comparative Example 1 had a low initial surface energy, it exhibited yellowing, blistering, and increased mass loss after high-temperature thermal cycling, indicating that traditional fluorinated anti-stick coatings are insufficient for long-term high-temperature applications. Comparative Example 2 showed good heat resistance and adhesion, but its high surface energy resulted in a significantly increased contaminant residue rate, suggesting that a single ceramic or silicon-oxygen network is insufficient to achieve durable low-adhesion performance. Although Comparative Example 3 contained organosilicon resin, inorganic nanofillers, and PDMS molecular chains, its non-gradient homogeneous structure made it prone to stress concentration and localized peeling during thermal cycling. Comparative Example 4 lacked a metal alkoxide coupling agent and a Si-OM covalent bridging network, leading to the migration or failure of low surface energy components after high temperatures, resulting in increased surface energy and decreased anti-stick performance.

[0127] In further engineering adaptation tests, the coating prepared in Example 5 was sprayed onto the inner wall of a simulated heating pipe, and an A / B comparison test was conducted with an uncoated stainless steel pipe section. The test conditions were 350°C hot air circulation, continuous introduction of mixed oil mist and dust contaminants, and a cumulative operation time of 500 hours. The results showed that the residual contaminants on the inner wall of the pipe section coated with the coating of this invention were reduced by 91.7% compared to the uncoated section, the cleaning cycle was extended by approximately 3.2 times, and the heat transfer efficiency decreased by less than 5% after stable operation. Figure 7 The diagram shows physical images of the gradient liquid anti-stick coating of Embodiment 5 of the present invention before heating and after heating at 350°C for 500 hours. Image a shows the coating before heating; image b shows the coating after heating for 500 hours. Figure 7 As shown, the coating showed virtually no surface change after heating at 350°C for 500 hours. These results demonstrate that the coating of this invention not only possesses high-temperature resistance and non-stick properties at the laboratory scale, but also has engineering adaptability potential for application in industrial heating components.

[0128] Compared with the prior art, the present invention has at least the following beneficial effects:

[0129] First, this invention addresses the problems of insufficient high-temperature resistance and limited high-temperature safety of existing fluoropolymer anti-stick coatings. While traditional fluoropolymer anti-stick coatings such as PTFE, FEP, and PFA have low surface energy, they are prone to thermal aging, yellowing, blistering, performance degradation, and even decomposition during long-term use above 350°C. This invention utilizes organosilicon resin, inorganic nanoparticles, metal alkoxide coupling agents, and liquid-like molecular chains to construct a fluorine-free anti-stick coating. This achieves low surface energy and low adhesion without relying on fluoropolymer resins, thus improving high-temperature safety and environmental adaptability.

[0130] Secondly, this invention addresses the problem of insufficient anti-sticking performance of existing ceramic coatings. While ordinary ceramic coatings possess high heat resistance and wear resistance, their high surface energy makes them prone to adsorbing oil, dust, and coking precursors, leading to severe pollutant residue. This invention, based on an inorganic framework providing heat resistance, covalently anchors PDMS liquid-like molecular brushes to a liquid-like molecular brush surface layer. This creates a liquid-like interface on the coating surface with low surface energy, low adhesion, and dynamic chain segment movement capabilities, thereby significantly reducing the adhesion of materials, oil, dust, and carbon deposit precursors to high-temperature surfaces.

[0131] Third, this invention addresses the problems of insufficient interfacial bonding and easy migration of low surface energy components in existing organic-inorganic composite coatings. Many existing composite coatings rely mainly on the physical filling of inorganic particles or the simple mixing of low surface energy components, which are prone to phase separation, migration, volatilization, or surface performance degradation during high temperatures and thermal cycling. This invention constructs Si-OM and Si-O-Si synergistic covalent networks using metal alkoxide coupling agents and silane coupling agents, forming chemical bridges between the organosilicon resin, inorganic nanofillers, and liquid-like molecular chains. This improves the internal structural density and interfacial stability of the coating, and inhibits the migration or loss of low surface energy components at high temperatures.

[0132] Fourth, this invention solves the problems of cracking, blistering, and peeling that occur with existing homogeneous coatings or simple double-layer coatings during thermal cycling. Traditional coating structures often exhibit abrupt changes in modulus, coefficient of thermal expansion, and component distribution, which easily lead to thermal stress concentration during high-temperature thermal cycling. This invention employs a gradient structure design from the substrate to the outer surface, forming a high-inorganic-content adhesion bearing layer in the bearing bottom layer, an organic-inorganic synergistic buffer in the buffer middle layer, and a low-surface-energy surface layer in the liquid-like molecular brush layer. This structure can buffer thermal expansion mismatch and interlayer stress while ensuring substrate adhesion and heat resistance, thereby improving the structural integrity of the coating under conditions of 350-400℃.

[0133] Fifth, this invention achieves synergistic optimization of high temperature resistance, low surface energy, high adhesion, low friction, and high-temperature anti-sticking properties simultaneously. Example results show that the surface energy of the coating of this invention can be as low as approximately 20-22 mN / m, the water contact angle can reach over 115°, the pull-out adhesion can reach over 5 MPa, and it maintains low mass loss and good appearance integrity after 1000 thermal cycles at 350℃. These results demonstrate that this invention does not simply improve a single performance characteristic, but rather achieves a balanced improvement in multiple properties through the combined effects of material composition, interfacial chemistry, and gradient structure.

[0134] Sixth, this invention has good engineering adaptability. The coating of this invention can be prepared by spraying, scraping, dipping, roller coating, or continuous gradient spraying, and is suitable for the surfaces of flat plates, pipes, inner walls, rollers, hot press molds, and complex geometric components. Through staged curing and online film thickness control, the risks of pinholes, shrinkage cavities, sagging, and cracking can be reduced, which is beneficial for the large-scale preparation and subsequent maintenance of industrial heating component surfaces.

[0135] Seventh, this invention can reduce the deposition of contaminants on the surface of industrial heating components and the frequency of cleaning and maintenance. Due to the low adhesion and liquid-like dynamic lubrication characteristics of the coating surface, oil, dust, molten materials and coking precursors are not easy to adhere firmly to the surface, which can reduce the degree of carbon deposits and coking, reduce the frequency of downtime cleaning, extend the equipment maintenance cycle, and reduce the decrease in heat transfer efficiency and increase in energy consumption caused by the deposit layer.

[0136] In summary, this invention addresses the shortcomings of existing technologies, such as insufficient high-temperature resistance of fluorinated anti-stick coatings, insufficient anti-stick properties of ceramic coatings, easy migration of low surface energy components in organic-inorganic composite coatings, insufficient high-temperature stability of ordinary liquid coatings, and easy failure of homogeneous coatings during thermal cycling. It proposes a high-temperature resistant gradient liquid anti-stick coating and its preparation method. This technology achieves a comprehensive effect of high-temperature anti-sticking, thermal shock resistance, low friction, high adhesion, and fluorine-free environmental friendliness through the synergistic effect of Si-OM synergistic network, gradient structure, and covalently anchored liquid molecular brushes.

[0137] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A gradient liquid-like anti-stick coating, comprising a carrier underlayer, a buffer middle layer, and a liquid-like molecular brush layer disposed sequentially from the surface of a substrate outwards; in, The gradient liquid anti-stick coating comprises organosilicon resin, inorganic nanofiller, silane coupling agent, metal alkoxide coupling agent, and liquid-like molecular chain; The content of the inorganic nanofiller and the content of the metal alkoxide coupling agent decrease sequentially in the supporting bottom layer, the buffer middle layer and the liquid-like molecular brush layer, and the content of the liquid-like molecular chain decreases sequentially in the liquid-like molecular brush layer, the buffer middle layer and the supporting bottom layer. The organosilicon resin forms a flexible continuous phase, the inorganic nanofiller forms a heat-resistant supporting framework, and the metal alkoxide coupling agent forms a covalent bridge between the organosilicon resin, the inorganic nanofiller, and the liquid-like molecular chains through hydrolysis and condensation processes.

2. The gradient liquid anti-stick coating according to claim 1, wherein, The thickness of the gradient liquid anti-stick coating is 11~200μm, preferably 30~80μm.

3. The gradient liquid anti-stick coating according to claim 2, wherein, The thickness of the underlying support layer is 5~80μm, the thickness of the buffer middle layer is 5~80μm, and the thickness of the liquid-like molecular brush surface layer is 1~40μm.

4. The gradient liquid anti-stick coating according to any one of claims 1 to 3, wherein, The organosilicon resin includes one or more of methyl organosilicon resin, phenyl organosilicon resin, methylphenyl organosilicon resin, epoxy-modified organosilicon resin, acrylic-modified organosilicon resin, hydroxyl silicone resin, and alkoxy silicone resin; The inorganic nanofiller includes one or more of nano-SiO2, nano-Al2O3, nano-ZrO2, nano-TiO2, silicates, glass powder, and boron nitride; The metal alkoxide coupling agent includes one or more of titanate coupling agents, zirconate coupling agents, and aluminate coupling agents; The silane coupling agent includes one or more of vinyltrimethoxysilane, vinyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, and tetraethoxysilane. The liquid-like molecular chain comprises a siloxane polymer with polar groups as end groups or side chains. The polar groups include at least one of hydroxyl, alkoxy, silane, amino, epoxy, carboxyl, and siloxane groups. The number average molecular weight of the liquid-like molecular chain is 500 to 100,000 Da.

5. The gradient liquid anti-stick coating according to claim 4, wherein, The liquid-like molecular chains are cross-linked with organosilicon resin through the polar groups, metal alkoxide coupling agents, and form a synergistic cross-linked network of Si-OM and Si-O-Si, wherein M is titanium, zirconium, or aluminum.

6. A method for preparing a gradient liquid anti-stick coating as described in any one of claims 1 to 5, wherein the preparation method employs a layered gradient spraying method, comprising: Organosilicon resin, inorganic nanofiller, metal alkoxide coupling agent, silane coupling agent and optional liquid molecular chain are mixed in a solvent, and optional additives are added. Stirring yields a coating liquid that supports the bottom layer. Organosilicon resin, inorganic nanofiller, metal alkoxide coupling agent, silane coupling agent, and liquid-like molecular chain are mixed in a solvent. The content of inorganic nanofiller and metal alkoxide coupling agent is adjusted to be lower than the content of the corresponding raw materials in the coating liquid of the supporting bottom layer, so that the content of the liquid-like molecular chain is higher than the content of the corresponding raw materials in the coating liquid of the supporting bottom layer. The mixture is stirred to obtain the coating liquid of the buffer middle layer. Organosilicon resin, liquid-like molecular chains, and optional inorganic nanofillers are mixed in a solvent. Silane coupling agents and metal alkoxide coupling agents are added. The content of inorganic nanofillers and metal alkoxide coupling agents is adjusted to be lower than the content of the corresponding raw materials in the coating liquid of the buffer middle layer, so that the content of liquid-like molecular chains is higher than the content of the corresponding raw materials in the coating liquid of the buffer middle layer. The mixture is stirred to obtain a coating liquid for the liquid-like molecular brush surface layer. The coating liquid of the bearing underlayer is applied to the surface of the substrate, and after leveling and pre-drying at room temperature, a substrate with the initial bearing underlayer is obtained. The coating liquid of the buffer intermediate layer is applied to the surface of the initial bearing substrate and pre-crosslinked to obtain a substrate with the initial buffer intermediate layer on the surface. The coating liquid of the liquid-like molecular brush surface layer is applied to the surface of the initial buffer intermediate layer and subjected to a first thermosetting treatment to obtain a substrate with the initial liquid-like molecular brush surface layer on the surface, thereby obtaining the gradient liquid-like anti-stick coating. The solvent includes at least one of ethanol, isopropanol, n-butanol, ethyl acetate, butyl acetate, propylene glycol methyl ether acetate, toluene, xylene, cyclohexane, n-hexane, and tetrahydrofuran; the additives include at least one of dispersants, leveling agents, defoamers, thixotropic agents, adhesion promoters, antioxidants, and abrasion resistant agents.

7. The preparation method according to claim 6, wherein, The solid components of the coating liquid supporting the substrate, by mass fraction, include: 20-70 parts of organosilicon resin, 20-70 parts of inorganic nanofiller, 1-20 parts of metal alkoxide coupling agent, 0.5-15 parts of silane coupling agent, 0-10 parts of liquid-like molecular chain, and 0-5 parts of additives; The solid components of the coating liquid in the buffer intermediate layer, by mass fraction, include: The ingredients include 30-80 parts of organosilicon resin, 10-50 parts of inorganic nanofiller, 1-15 parts of metal alkoxide coupling agent, 0.5-15 parts of silane coupling agent, 1-20 parts of liquid-like molecular chain, and 0-5 parts of additives. The solid components of the liquid coating liquid used for brushing the surface layer, by mass fraction, include: The ingredients include 20-70 parts of organosilicon resin, 0-30 parts of inorganic nanofiller, 0.5-10 parts of metal alkoxide coupling agent, 0.5-15 parts of silane coupling agent, 5-60 parts of liquid-like molecular chain, and 0-5 parts of additives.

8. The preparation method according to claim 6 or 7, wherein, The conditions for leveling at room temperature are 5-60 min at 20-40℃, the conditions for pre-drying are 10-120 min at 50-100℃, the conditions for pre-crosslinking treatment are 10-180 min at 100-180℃, and the conditions for the first thermosetting treatment are 10-240 min at 180-350℃.

9. The preparation method according to any one of claims 6 to 8, wherein, The substrate includes at least one of metal, ceramic, glass, and alloy; The preparation method further includes: The initial substrate surface is sequentially subjected to washing, sandblasting or grinding, and blowing to obtain the substrate.

10. The preparation method according to any one of claims 6 to 9, wherein, The preparation method further includes: The gradient liquid anti-stick coating is subjected to heat treatment at a temperature of 250~400℃ for 5~120 min.

11. The method for preparing a gradient liquid anti-stick coating according to claim 1 or 2, characterized in that, The preparation method employs a continuous gradient spraying technique, including: Organosilicon resin, inorganic nanofiller, metal alkoxide coupling agent, silane coupling agent and liquid-like molecular chain are mixed in a solvent, and optional additives are added. The mixture is stirred to obtain a liquid-like anti-stick coating liquid. The coating liquid of the liquid-like anti-stick coating is continuously sprayed onto the surface of the substrate. During the spraying process, the mass content of inorganic nanofillers and metal alkoxide coupling agents in the coating liquid is gradually reduced, while the mass content of the liquid-like molecular chains is gradually increased. Then, the coating liquid is sequentially subjected to room temperature leveling, pre-drying, pre-crosslinking treatment and first thermosetting treatment to prepare the gradient liquid-like anti-stick coating. Preferably, the room temperature leveling conditions are leveling at 20~40℃ for 5~60 min, the pre-drying conditions are pre-drying at 50~100℃ for 10~120 min, the pre-crosslinking treatment conditions are pre-crosslinking at 100~180℃ for 10~180 min, and the first thermosetting treatment conditions are thermosetting at 180~350℃ for 10~240 min.

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