Coating composition, waterborne polyurethane waterproof and moisture permeable coating and method for preparing the same

Abstract

The application discloses a coating composition, a water-based polyurethane waterproof and moisture-permeable coating and a preparation method thereof. The coating composition comprises, in mass parts, 80-120 parts of a water-based polyurethane emulsion, 5-15 parts of hydrophobic mesoporous silica microspheres and 2-8 parts of hydrophobic tubular cotton fibers. Furthermore, the water-based polyurethane waterproof and moisture-permeable coating is prepared based on the coating composition. The hydrophobic tubular cotton fibers and the hydrophobic mesoporous silica microspheres form an interlaced network structure, so that the formed coating not only has excellent waterproofness, high moisture permeability, but also has good mechanical properties, and can be applied in the fields of outdoor clothes, medical protective fabrics and the like.

Description

Technical Field

[0001] This application belongs to the field of polyurethane coating technology, specifically relating to a coating composition, an aqueous polyurethane waterproof and breathable coating prepared based on the coating composition, and a method for preparing the coating. Background Technology

[0002] In the field of functional textile fabrics, the waterproof and breathable properties of fabrics are core performance indicators for evaluating their technological advancement and application value. Waterborne polyurethane (WPU) coating technology, due to its environmental friendliness, low toxicity, and excellent adhesion to the substrate, has become one of the main technical approaches to achieving waterproof and breathable functions in fabrics.

[0003] To overcome the shortcomings of traditional waterborne polyurethane coatings in terms of insufficient moisture permeability under high humidity and heat environments, existing technologies have disclosed an improved scheme that introduces mesoporous silica microspheres as functional fillers. This aims to utilize the regular, interconnected nanoscale pore structure of mesoporous silica to construct efficient water vapor transport channels within the coating film, thereby significantly improving the coating's moisture permeability. However, mesoporous silica exhibits poor compatibility with the waterborne polyurethane matrix, and its rigid inorganic particle characteristics severely interfere with the continuity of polyurethane polymer chains and stress transmission. This leads to a significant deterioration in the mechanical properties of the composite coating film, particularly tensile strength and tear strength, making it difficult to meet the stringent durability requirements of coated fabrics in high-end applications such as outdoor clothing and medical protective equipment.

[0004] To address the negative impact of mesoporous silica on the mechanical properties of waterborne polyurethane, while adding other reinforcing materials or improving the process can achieve some improvement, the results are not ideal. For example, adding some conventional inorganic reinforcing materials can improve mechanical properties to a certain extent, but it will block the gas-conducting channels of mesoporous silica, leading to a decrease in moisture permeability; while improving the preparation process often involves problems such as complex operation, high cost, and unstable results. Summary of the Invention

[0005] In view of this, the primary objective of this application is to provide a coating composition comprising waterborne polyurethane, hydrophobic mesoporous silica, and hydrophobic tubular cotton fibers, such that the hydrophobic tubular cotton fibers and hydrophobic mesoporous silica microspheres form an interwoven network structure, thereby creating a coating that not only has excellent waterproof and high moisture permeability but also good mechanical properties, enabling its application in fields such as outdoor clothing and medical protective fabrics.

[0006] To achieve the above objectives, this application adopts the following technical solution: One aspect of this application discloses a coating composition comprising, by weight parts: 80-120 parts of waterborne polyurethane emulsion, 5-15 parts of hydrophobic mesoporous silica microspheres, and 2-8 parts of hydrophobic tubular cotton fibers.

[0007] Another aspect of this application discloses a waterborne polyurethane waterproof and breathable coating, formed by coating the coating composition described in this application onto the surface of a base fabric; wherein the coating comprises: The matrix is ​​waterborne polyurethane; The continuous gas-conducting channels distributed within the matrix are composed of directionally arranged hydrophobic mesoporous silica microspheres. And hydrophobic tubular cotton fibers, which interweave with the continuous air-guiding channels to form an interlaced network structure.

[0008] Another aspect of this application discloses a method for preparing the waterborne polyurethane waterproof and breathable coating described in this application, comprising the following steps: Mesoporous silica is provided, and the mesoporous silica is hydrophobically modified with a silane coupling agent to obtain hydrophobic mesoporous silica microspheres. A tubular cotton fiber is provided, and a hydrophobic emulsion or hydrophobic monomer is coated on the surface of the tubular cotton fiber to obtain a hydrophobic tubular cotton fiber. Hydrophobic mesoporous silica microspheres, hydrophobic tubular cotton fibers, and other functional additives are added to the heated aqueous polyurethane emulsion and stirred thoroughly to form a composite slurry. The composite slurry is directionally coated onto the surface of the base fabric and dried to form a water-based polyurethane waterproof and breathable coating.

[0009] Another aspect of this application discloses the application of the coating compositions, coatings, or coatings prepared by the methods described in this application in outdoor clothing fabrics or medical protective fabrics.

[0010] The beneficial effects of this application are: This application incorporates hydrophobic mesoporous silica microspheres and hydrophobic tubular cotton fibers into a waterborne polyurethane-based coating composition. The directional arrangement of the hydrophobic mesoporous silica within the waterborne polyurethane matrix creates continuous moisture-permeable channels, achieving high moisture permeability. Simultaneously, the hydrophobic tubular cotton fibers and hydrophobic mesoporous silica microspheres form an interwoven network, significantly enhancing tensile strength and resolving the conflict between moisture permeability and mechanical properties. Furthermore, both the mesoporous silica and tubular cotton fibers in this application are hydrophobically modified, synergistically forming a hydrophobic surface with the waterborne polyurethane matrix, effectively preventing liquid water intrusion. In addition, the coating composition of this application is entirely water-based, with no volatile organic solvent emissions. The modification and molding processes are mild, enabling continuous industrial production. The resulting coating can be widely used in high-end fabric fields such as outdoor clothing and medical protective equipment. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the overall structure of the coating formed in this application.

[0012] Figure 2 This is an enlarged schematic diagram of the hydrophobic mesoporous silica microspheres in Embodiment 1 of this application.

[0013] Figure 3 This is a schematic diagram of the hydrophobic cotton fiber optical microscope used in Embodiment 1 of this application.

[0014] Figure 4 This is a SEM image of the coating obtained in Example 1 of this application.

[0015] Figure 5 This is a schematic diagram showing the contact angle of WPU blended with different contents of hydrophobic mesoporous silica microspheres and hydrophobic tubular cotton fibers in this application. Detailed Implementation

[0016] The embodiments of this application will be clearly and completely described below. The technical solutions in the embodiments described below are exemplary and only possible technical implementations of this application, not all possible implementations. Those skilled in the art can combine the embodiments of this application to obtain other embodiments without creative effort, and these embodiments are also within the protection scope of this application.

[0017] The first aspect of this application discloses a coating composition comprising, by weight parts: 80-120 parts of waterborne polyurethane emulsion, 5-15 parts of hydrophobic mesoporous silica microspheres, and 2-8 parts of hydrophobic tubular cotton fibers.

[0018] Specifically, the number of parts of the waterborne polyurethane emulsion can be any value from 80 parts, 85 parts, 90 parts, 95 parts, 100 parts, 105 parts, 110 parts, 115 parts, and 120 parts, or any value between the two.

[0019] The hydrophobic mesoporous silica microspheres can be any value or a range between 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, and 15 parts, preferably 7-12 parts.

[0020] The hydrophobic tubular cotton fibers can be any value or a range between 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, and 8 parts, preferably 3-6 parts.

[0021] In this application, the aqueous polyurethane emulsion is a conventional composition in the art and is not particularly limited, and it is used to construct the aqueous polyurethane matrix layer of the coating as the continuous phase matrix of the coating.

[0022] In some specific examples, the structure of the waterborne polyurethane is as follows: ; Where R is Where x represents the number of repeating units in the polyurethane main chain, preferably 10-150, for example, any integer or a range between 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150; R is a polyether or polycarbonate soft segment, the number of internal repeats y of which is preferably 10-80, for example, any integer or a range between 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 65, 70, 75, 80.

[0023] In this application, the hydrophobic mesoporous silica microspheres are silane coupling agent modified mesoporous silica microspheres. The silane coupling agent is a reagent with excellent hydrophobicity, chemical stability, and good interfacial interaction, thereby ensuring optimized mechanical properties while improving the waterproofness of the coating.

[0024] In some specific examples, the silane coupling agent is at least one of hexadecyltriethoxysilane, perfluorooctyltriethoxysilane, or 1,3,3-tetramethyldisilazane.

[0025] Specific hydrophobic modification methods can employ surface treatment techniques well-known in the art, without particular limitation. For example, in some specific examples, the hydrophobic mesoporous silica microspheres are obtained by fully dispersing the mesoporous silica microspheres in a dispersant, followed by adding a silane coupling agent and stirring thoroughly. The dispersant is preferably at least one of n-heptane, tetrahydrofuran, and dichloromethane, and the silane coupling agent has a mass percentage of 5%-20% in the dispersant, for example, any value or range between 5%, 8%, 10%, 12%, 14%, 15%, 16%, 18%, and 20%.

[0026] Furthermore, in some specific examples, the mesoporous silica microspheres can be obtained by methods known in the art or developed in-house, or they can be obtained commercially, without specific requirements, as long as the relevant parameters are met. As a preferred example, the mesoporous silica microspheres are obtained by hydrolysis and polycondensation using hexadecyltrimethylammonium bromide as a template agent and tetraethyl orthosilicate as a silicon source, followed by calcination to remove the template agent. As a preferred example, the hydrolysis and polycondensation process is as follows: ethanol, hexadecyltrimethylammonium bromide, diethanolamine, and water are mixed and stirred at 60-70°C for 30-40 minutes, then tetraethyl orthosilicate is added and stirred for 1.5-2.5 hours, wherein the mass ratio of tetraethyl orthosilicate to hexadecyltrimethylammonium bromide is 1:0.5-2. The calcination conditions are maintained at 400-600°C for 4-8 hours.

[0027] In this application, the hydrophobic mesoporous silica microspheres have a particle size of 50-400 nm, for example, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 220 nm, 240 nm, 260 nm, 280 nm, 300 nm, 320 nm, or 340 nm. The particle size can be any particle size in the range of 360nm, 380nm, 400nm, or any value between two of these ranges; the mesopore size is 2-20nm, for example, it can be any pore size in the range of 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm, 17nm, 18nm, 19nm, 20nm or any value between two of these ranges; the surface water static contact angle is ≥100°.

[0028] In this application, the hydrophobic tubular cotton fiber is obtained by coating tubular cotton fiber with a hydrophobic emulsion or grafting it with a hydrophobic monomer. Specifically, the tubular cotton fiber is subjected to alkali boiling, water washing and drying in sequence, and then modified by hydrophobic emulsion coating or hydrophobic monomer grafting. After curing, the hydrophobic tubular cotton fiber is obtained, which can be achieved by methods known in the art or independently developed.

[0029] In some specific examples, the hydrophobic emulsion is a fluoropolymer emulsion or an organosilicon resin emulsion, which can be of a type known in the art or independently developed, to bring excellent hydrophobic properties to the tubular cotton fibers. Specifically, the coating involves immersing the tubular cotton fibers in the hydrophobic emulsion for 10-20 minutes, then removing them and drying and curing them at 100-120°C for 1-2 hours.

[0030] In other specific examples, the hydrophobic monomer is octadecyl methacrylate or styrene, and the grafting modification process is carried out under the action of an initiator. For example, as a specific example, ammonium persulfate is used as the initiator, the initiation temperature is 70-80℃, and the reaction time is 3-5h.

[0031] In some specific examples, the inner diameter of the hydrophobic tubular cotton fiber is 1-5 μm, for example, it can be any value or a range between 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, and 5 μm; the length is 50-200 μm, for example, it can be any value or a range between 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, and 200 μm; the surface water static contact angle is ≥95°, and the water absorption rate is ≤5%.

[0032] In this coating composition, hydrophobic mesoporous silica microspheres and hydrophobic tubular cotton fibers have significant advantages within the scope defined in this application. They can synergistically construct a stable microscopic multi-scale channel-fiber network, achieving a balance between moisture permeability and mechanical properties. Specifically, if the content of hydrophobic mesoporous silica is too low, the number of channels is insufficient, and the moisture permeability decreases significantly; if it is too high, its rigid aggregates disrupt the continuity of the polyurethane matrix, leading to a decrease in mechanical properties. Conversely, if the content of hydrophobic tubular cotton fibers is too low, the fiber network is difficult to form, resulting in insufficient reinforcement; if it is too high, the fibers become entangled and aggregated, affecting the uniformity of the slurry and blocking some air-conducting channels.

[0033] Furthermore, it is understood that other functional additives can be selectively added to the waterproof coating of this application according to performance requirements. These functional additives can improve the performance of the coating composition slurry, thereby further improving the overall performance of the coating. Specific examples of these functional additives include, but are not limited to, film-forming aids, defoamers, dispersants, pH adjusters, thickeners, anti-settling agents, and crosslinking agents. For example, the film-forming aid can be at least one of dipropylene glycol, triethylene glycol, propylene glycol methyl ether, dipropylene glycol methyl ether, and dipropylene glycol propyl ether; the defoamer can be at least one of polyether-modified silicone oil, silicone defoamer, mineral oil-based defoamer, or polyether defoamer; the pH adjuster can be at least one of TEA, AMP-95, ammonia, and DMAE. In addition, polycarboxylic acid dispersants, HEUR-type rheology modifiers, organobentonite anti-settling agents, or a small amount of isocyanate crosslinking agents can also be added to improve the water resistance and mechanical properties of the coating film.

[0034] As a preferred example, the coating composition comprises: 80-120 parts of waterborne polyurethane emulsion, 5-15 parts of hydrophobic mesoporous silica microspheres, 2-8 parts of hydrophobic tubular cotton fibers, 3-8 parts of film-forming aid, 0.5-2 parts of defoamer, and 1-3 parts of pH adjuster.

[0035] The second aspect of this application discloses a waterborne polyurethane waterproof and breathable coating, which is formed by coating the surface of a base fabric with the coating composition described in this application; wherein the coating comprises: The matrix is ​​waterborne polyurethane; The continuous gas-conducting channels distributed within the matrix are composed of directionally arranged hydrophobic mesoporous silica microspheres. And hydrophobic tubular cotton fibers, which interweave with the continuous air-guiding channels to form an interlaced network structure. For a detailed structural diagram, please refer to [link / reference needed]. Figure 1 .

[0036] The specific coating thickness can be designed according to performance requirements without particular limitation. In some specific examples, the coating thickness is 20-50 μm, for example, it can be any thickness among 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, and 50 μm, or any range between two thicknesses; the static contact angle is ≥99°, and the moisture permeability is ≥950 g / (m²). 2 • 24h), tensile strength ≥ 8MPa.

[0037] A third aspect of this application discloses a method for preparing the waterborne polyurethane waterproof and breathable coating described in this application, comprising the following steps: Mesoporous silica is provided, and the mesoporous silica is hydrophobically modified with a silane coupling agent to obtain hydrophobic mesoporous silica microspheres. A tubular cotton fiber is provided, and a hydrophobic emulsion or hydrophobic monomer is coated on the surface of the tubular cotton fiber to obtain a hydrophobic tubular cotton fiber. Hydrophobic mesoporous silica microspheres, hydrophobic tubular cotton fibers, and other functional additives are added to the heated aqueous polyurethane emulsion and stirred thoroughly to form a composite slurry. The composite slurry is directionally coated onto the surface of the base fabric and dried to form a water-based polyurethane waterproof and breathable coating.

[0038] The hydrophobic mesoporous silica microspheres and hydrophobic tubular cotton fibers can be obtained by referring to the methods described above or by using existing or independently developed technologies, and will not be elaborated on here.

[0039] In some specific examples, the heating temperature of the aqueous polyurethane emulsion is 40-60°C.

[0040] As a preferred example, the preparation method of the composite slurry is as follows: Waterborne polyurethane emulsion is heated to 40-60℃, film-forming aid and defoamer are added sequentially, and the mixture is stirred and dispersed for 10-20 minutes. The pH value is adjusted to 7-9, then hydrophobic mesoporous silica microspheres are added, and the mixture is ultrasonically dispersed for 20-40 minutes. Finally, hydrophobic tubular cotton fibers are added, and the mixture is stirred at high speed for 15-30 minutes to obtain the composite slurry. The high-speed stirring speed is 2000-3000 r / min.

[0041] In some specific examples, the directional coating is achieved by a directional coating device with a coating speed of 0.5-2 m / min.

[0042] In some specific examples, the drying process involves infrared pre-baking or hot air curing, wherein the infrared pre-baking temperature is 80-100℃ and the time is 5-10 minutes. The hot air curing temperature is 120-150℃ and the time is 10-20 minutes.

[0043] The waterborne polyurethane waterproof and breathable coating in this application achieves an optimized balance between waterproofness, breathability, and mechanical properties through a comprehensive design of its microstructure, creating a composite structure with synergistic effects of "multi-scale channels + directional arrangement + fiber reinforcement." The coating consists of a waterborne polyurethane matrix, hydrophobic mesoporous silica microspheres, and hydrophobic tubular cotton fibers. Its structural composition and design principles are as follows: Waterborne polyurethane matrix layer: As the continuous phase matrix of the coating, waterborne polyurethane undertakes the functions of film formation, adhesion, and flexible support. Its soft and hard segment structure can interact with the hydrophobic mesoporous silica microspheres and cotton fibers, thereby forming a stable dispersion environment for each functional filler. Specifically, waterborne polyurethane provides overall adhesion and flexibility to the coating while maintaining the film's density and preventing liquid water penetration; in addition, it serves as a carrier for the arrangement of microspheres and fibers, enabling the composite structure to have a stable three-dimensional network.

[0044] The directional arrangement of hydrophobic mesoporous silica microspheres: The hydrophobic mesoporous silica microspheres of this application have a particle size of 50-200 nm and a mesoporous structure of 2-10 nm. After modification with hydrophobic silane, their interfacial energy with the polyurethane matrix is ​​significantly reduced, making it easy to form a locally directional arrangement or channel-like stacking structure during the coating curing process. The directional arrangement of hydrophobic mesoporous silica microspheres not only constructs continuous microscale moisture-permeable channels, significantly shortening the water vapor migration path; but also, the hydrophobic surface reduces the surface energy of the coating, helping to achieve a static contact angle >99°; more importantly, it does not block the overall compactness of the membrane, enabling selective transport of moisture while keeping water impermeable. It should be noted that their directional arrangement structure is the key to achieving high moisture permeability in the coating of this application.

[0045] Three-dimensional reinforcement network of hydrophobic tubular cotton fibers: Hydrophobic tubular cotton fibers have a high aspect ratio and a hollow tubular structure. After hydrophobic regulation, their outer surface can form a stable interface with microspheres and polyurethane matrix. The cotton fibers are randomly interwoven or locally oriented in the coating, forming a mesoscale three-dimensional reinforcement network. Its core functions mainly include: (1) providing mechanical reinforcement: The fiber network can effectively disperse stress and improve the tensile and tear resistance of the coating; (2) constructing auxiliary moisture permeability path: The fiber lumen and the microsphere mesopores are interconnected to form a multi-scale air conduction structure; (3) improving coating toughness: The flexibility of cotton fibers can suppress the membrane embrittlement problem caused by microsphere filling. The "channel-fiber" synergistic structure formed between the fiber network and the microsphere channels is the key feature of the coating that has both high strength and high moisture permeability.

[0046] In summary, this application constructs a continuous and stable multi-scale gas-conducting reinforcement system within a polyurethane matrix by organically coupling the microscale pore structure of microspheres with the mesoscale network structure of cotton fibers. Specifically: To address the issue of mesoporous silica damaging mechanical properties, hydrophobic tubular cotton fibers are introduced into the air-conducting channels of the hydrophobic mesoporous silica. Cotton fibers are natural fibers with a longitudinally twisted, ribbon-like hollow tubular structure and distinct fiber cavities. This hollow structure endows cotton fibers with lightweight, high flexibility, and good stress dispersion capabilities. In this application, the natural tubular structure of cotton fibers serves as a mesoscale auxiliary moisture-permeable channel, synergistically constructing a multi-scale air-conducting network with the microscale channels formed by the mesoporous silica microspheres, thereby significantly improving the moisture permeability of the coating. Simultaneously, the high aspect ratio of cotton fibers allows them to form a reinforcing network within the coating, improving the coating's tensile strength and tear resistance. After hydrophobic treatment, the interfacial compatibility between the outer wall of the cotton fibers and the polyurethane matrix is ​​further enhanced, facilitating their stable distribution in the coating and maintaining the integrity of the channel structure. Furthermore, on the one hand, the cotton fibers and mesoporous silica form an interwoven network structure, which works together to maintain the integrity of the air-conducting channels and ensure that the transmission of water vapor is not affected; on the other hand, there is a strong interfacial interaction between the cotton fibers and the waterborne polyurethane matrix. When the coating is subjected to external forces, it can effectively disperse stress through the stretching and bridging mechanisms of the fibers, making up for the loss of mechanical properties caused by the mesoporous silica, and significantly improving the tensile strength, tear strength and fatigue resistance of the coating.

[0047] The present application will be further illustrated below with reference to specific embodiments. It should be noted that the specific embodiments below are for illustrative purposes only and do not limit the scope of the present application in any way.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.

[0049] In addition, unless otherwise specified, methods without detailed conditions or steps are conventional methods, and the reagents and materials used are commercially available.

[0050] Example 1 This embodiment discloses a coating composition, a method for preparing a coating, and the resulting coating.

[0051] 1.1 Coating Composition By weight, it includes: 100 parts waterborne polyurethane emulsion, 5 parts propylene glycol methyl ether acetate, 1 part silicone defoamer, 8 parts hydrophobic silica, 5 parts hydrophobic tubular cotton fibers, and an appropriate amount of pH adjuster.

[0052] Preparation of hydrophobic mesoporous silica microspheres: 4.5 g of ethanol, 5.2 g of 25% CTBA aqueous solution, 0.1 g of DEA, and 32 ml of water were mixed, and 3.65 ml of TEOS was added for reaction. The mixture was calcined at 450 °C for 6 h. The calcined product was then added to n-heptane and stirred for 2 h. Subsequently, 5 g of hexadecyltriethoxysilane was added, and stirring was continued for 5 h. The volume ratio of the hydrophobic modifier hexadecyltriethoxysilane to n-heptane was 1:100. Hydrophobic silica microspheres (particle size 100 nm, contact angle 105°) were obtained.

[0053] Preparation of hydrophobic tubular cotton fibers: After alkaline boiling, tubular cotton fibers are coated with 20% silicone resin emulsion and then cured to obtain hydrophobic tubular cotton fibers (inner diameter 3μm, contact angle 98%, water absorption rate 3%).

[0054] Among them, such as Figure 2 The image shown is a transmission electron microscope (TEM) image of hydrophobic mesoporous silica microspheres. Figure 2 As can be seen from (a)-(b), the silica microspheres are approximately spherical in shape, well-dispersed, and their particle size is mainly distributed in the range of 150-300 nm, with an average particle size of approximately 200-250 nm. Figure 2 The high-magnification images (c)-(d) show that the microspheres have a distinct wormhole / sponge-like mesoporous structure, with pore sizes mainly distributed in the range of 5-15 nm, classifying them as typical mesoporous materials. Figure 4 The image shown is an optical microscope image of hydrophobically modified cotton fibers. Figure 3As can be seen in (a) and (b), the cotton fibers have a hollow tubular structure with an outer diameter of about 2-5 μm, indicating that the cotton fibers maintain tubular / hollow characteristics in the coating, which is conducive to the formation of a continuous air-guiding channel structure.

[0055] 1.2 Coating Preparation Prepare the coating composition according to section 1.1. Add 5 parts of propylene glycol methyl ether acetate and 1 part of silicone defoamer to 100 parts of waterborne polyurethane emulsion, adjust the pH to 8, add 8 parts of hydrophobic silica and 5 parts of hydrophobic cotton fiber, prepare the slurry and coat it, and cure at 130°C for 15 min.

[0056] Figure 4 The characterization results of the coating in this application are shown. Figure 4 As shown in the left-middle image, the hydrophobically modified tubular cotton fibers are continuously distributed within the coating, with different fibers interlacing and overlapping to form a three-dimensional interwoven network structure that penetrates the coating matrix. Figure 4 The right-hand image further illustrates the excellent interfacial bonding between the cotton fibers and the waterborne polyurethane matrix. The fiber surface is coated with resin and filler particles, without any obvious debonding or porosity defects. This indicates that the fibers not only act as reinforcement but also participate in constructing the coating's microstructure as continuous structural units. This interwoven network structure facilitates the formation of continuous microscale air-conducting channels within the coating, improving the water vapor transport efficiency without compromising its density and waterproofness, while simultaneously enhancing the overall mechanical stability of the coating.

[0057] Example 2 This embodiment discloses a coating composition, a method for preparing a coating, and the resulting coating.

[0058] 2.1 Coating Composition By weight, it includes: 100 parts waterborne polyurethane emulsion, 4 parts film-forming aid, 7 parts hydrophobic silica, 3 parts hydrophobic tubular cotton fiber, and an appropriate amount of pH adjuster.

[0059] Preparation of hydrophobic mesoporous silica microspheres: 4.5 g of ethanol, 5.2 g of 25% CTBA aqueous solution, 0.1 g of DEA, and 32 ml of water were mixed, and 4 ml of TEOS was added for reaction. The mixture was calcined at 500 °C for 6 h. The calcined product was then added to n-heptane and stirred for 2 h. Subsequently, 3 g of perfluorooctyltriethoxysilane was added, and stirring was continued for 5 h. The volume ratio of the hydrophobic modifier hexadecyltriethoxysilane to n-heptane was 1:100. Hydrophobic silica microspheres (particle size 80 nm, contact angle 110°) were obtained.

[0060] Preparation of hydrophobic tubular cotton fibers: After alkaline boiling, tubular cotton fibers were modified by styrene grafting to obtain hydrophobic tubular cotton fibers (inner diameter 2μm, contact angle 100°, water absorption rate 2.5%).

[0061] 2.2 Coating Preparation Prepare the coating composition according to section 2.1, add 4 parts of film-forming aid to 100 parts of waterborne polyurethane emulsion, adjust the pH to 8, add 7 parts of hydrophobic silica and 3 parts of hydrophobic cotton fiber, prepare the slurry and coat it, and cure at 130°C for 15 min.

[0062] Example 3 This embodiment discloses a coating composition, a method for preparing a coating, and the resulting coating.

[0063] 3.1 Coating Composition By weight, it includes: 100 parts of waterborne polyurethane emulsion, 3 parts of film-forming aid, 12 parts of hydrophobic silica, 6 parts of hydrophobic tubular cotton fiber, and an appropriate amount of pH adjuster.

[0064] Preparation of hydrophobic mesoporous silica microspheres and hydrophobic tubular cotton fibers: Same as in Example 1.

[0065] 3.2 Coating Preparation Prepare the coating composition according to section 3.1, add 3 parts of film-forming aid to 100 parts of waterborne polyurethane emulsion, adjust the pH to 8, add 12 parts of hydrophobic silica and 6 parts of hydrophobic cotton fiber, prepare the slurry and coat it, and cure at 130°C for 15 min.

[0066] Example 4 This embodiment discloses a coating composition, a method for preparing a coating, and the resulting coating.

[0067] 4.1 Coating Composition By weight, it includes: 100 parts waterborne polyurethane emulsion, 3 parts film-forming aid, 5 parts hydrophobic silica, 2 parts hydrophobic tubular cotton fiber, and an appropriate amount of pH adjuster.

[0068] Preparation of hydrophobic mesoporous silica microspheres and hydrophobic tubular cotton fibers: Same as in Example 1.

[0069] 4.2 Coating Preparation Prepare the coating composition according to section 4.1, add 3 parts of film-forming aid to 100 parts of waterborne polyurethane emulsion, adjust the pH to 8, add 5 parts of hydrophobic silica and 2 parts of hydrophobic cotton fiber, prepare the slurry and coat it, and cure at 130°C for 15 min.

[0070] Example 5 This embodiment discloses a coating composition, a method for preparing a coating, and the resulting coating.

[0071] 5.1 Coating Composition By weight, it includes: 100 parts waterborne polyurethane emulsion, 8 parts film-forming aid, 15 parts hydrophobic silica, 8 parts hydrophobic tubular cotton fiber, and an appropriate amount of pH adjuster.

[0072] Preparation of hydrophobic mesoporous silica microspheres and hydrophobic tubular cotton fibers: Same as in Example 1.

[0073] 4.2 Coating Preparation Prepare the coating composition according to section 5.1, add 8 parts of film-forming aid to 100 parts of waterborne polyurethane emulsion, adjust the pH to 8, add 15 parts of hydrophobic silica and 8 parts of hydrophobic cotton fiber, prepare the slurry and coat it, and cure at 130°C for 15 min.

[0074] Comparative Example 1 This comparative example discloses another method for preparing a coating and the resulting coating.

[0075] The composition of the coating composition is the same as that in Example 1, except that hydrophobic tubular cotton fibers were not added in this comparative example.

[0076] Preparation of mesoporous silica dispersion: Same as in Example 1.

[0077] Preparation of the mixture: Same as in Example 1.

[0078] Coating preparation: Same as in Example 1.

[0079] Comparative Example 2 This comparative example discloses another method for preparing a coating and the resulting coating.

[0080] The composition of the coating composition is the same as that in Example 1, except that hydrophobic mesoporous silica microspheres were not added in this comparative example.

[0081] Preparation of cotton fiber suspension: Same as in Example 1.

[0082] Preparation of the mixture: Same as in Example 1.

[0083] Coating preparation: Same as in Example 1.

[0084] Comparative Example 3 This comparative example discloses another method for preparing a coating and the resulting coating.

[0085] The same aqueous polyurethane emulsion as in Example 1 was used; hydrophobic mesoporous silica microspheres (pore size 20 nm, specific surface area 800 m²) were also used. 2 / g), the only difference is that the hydrophobic tubular cotton fibers are replaced with an equal mass of cotton cellulose.

[0086] Preparation of mesoporous silica dispersion and cotton cellulose suspension: same as in Example 1.

[0087] Preparation of the mixture: Same as in Example 1.

[0088] Coating preparation: Same as in Example 1.

[0089] Comparative Example 4 Similar to Example 1, the difference is that the components in the coating are randomly distributed and not arranged in a specific direction, that is, no orientation equipment is used for coating.

[0090] Performance testing Table 1 Performance Test Results

[0091] Table 1 shows the tests conducted according to the following methods or standards: Moisture permeability: Tested according to ASTM E96 standard, unit is g / m²·24h.

[0092] Tensile strength: Tested according to ASTM D5034 standard, unit is MPa.

[0093] Tear strength: Tested according to ASTM D2261 standard, unit is kN / m.

[0094] As can be seen from the test results in Table 1, the waterborne polyurethane waterproof and breathable coating prepared using the coating composition of this application has an excellent static contact angle (≥100°) and excellent transparency. In addition, it also has tensile strength and tear strength, and its comprehensive performance is excellent, indicating that the coating in this application is very suitable for outdoor clothing or medical protective fabrics.

[0095] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A coating composition, characterized in that, The coating composition comprises, by weight parts: 80-120 parts of waterborne polyurethane emulsion, 5-15 parts of hydrophobic mesoporous silica microspheres and 2-8 parts of hydrophobic tubular cotton fibers. Preferably, the coating composition comprises: 100 parts of waterborne polyurethane emulsion, 7-12 parts of hydrophobic mesoporous silica microspheres, and 3-6 parts of hydrophobic tubular cotton fibers.

2. The coating composition according to claim 1, characterized in that, The hydrophobic mesoporous silica microspheres are silane coupling agent modified mesoporous silica microspheres; Preferably, the silane coupling agent is at least one of hexadecyltriethoxysilane, perfluorooctyltriethoxysilane, or 1,3,3-tetramethyldisilazane; Preferably, the hydrophobic mesoporous silica microspheres have a particle size of 50-400 nm, a mesopore size of 2-20 nm, and a surface water static contact angle ≥100°.

3. The coating composition according to claim 1, characterized in that, The hydrophobic tubular cotton fiber is obtained by coating tubular cotton fiber with a hydrophobic emulsion or grafting it with a hydrophobic monomer; Preferably, the hydrophobic emulsion is a fluorinated resin emulsion or an organosilicon resin emulsion; the hydrophobic monomer is octadecyl methacrylate or styrene. Preferably, the hydrophobic tubular cotton fiber has an inner diameter of 1-5 μm, a length of 50-200 μm, a surface water static contact angle ≥95°, and a water absorption rate ≤5%.

4. A water-based polyurethane waterproof and breathable coating, characterized in that, The coating composition according to any one of claims 1-3 is applied to the surface of a base fabric to form a coating; wherein the coating comprises: The matrix is ​​waterborne polyurethane; The continuous gas-conducting channels distributed within the matrix are composed of directionally arranged hydrophobic mesoporous silica microspheres. And hydrophobic tubular cotton fibers, which interweave with the continuous air-guiding channels to form an interlaced network structure.

5. The water-based polyurethane waterproof and breathable coating as described in claim 4, characterized in that, The coating has a thickness of 20-50 μm, a static contact angle ≥99°, and a moisture permeability ≥950 g / (m²). 2 • 24h), tensile strength ≥ 8MPa.

6. A method for preparing the waterborne polyurethane waterproof and breathable coating according to claim 4 or 5, characterized in that, Includes the following steps: Mesoporous silica is provided, and the mesoporous silica is hydrophobically modified with a silane coupling agent to obtain hydrophobic mesoporous silica microspheres. A tubular cotton fiber is provided, and a hydrophobic emulsion or hydrophobic monomer is coated on the surface of the tubular cotton fiber to obtain a hydrophobic tubular cotton fiber. Hydrophobic mesoporous silica microspheres, hydrophobic tubular cotton fibers, and other functional additives are added to the heated aqueous polyurethane emulsion and stirred thoroughly to form a composite slurry. The composite slurry is directionally coated onto the surface of the base fabric and dried to form a water-based polyurethane waterproof and breathable coating.

7. The method as described in claim 6, characterized in that, The hydrophobic modification of the mesoporous silica is achieved by adding mesoporous silica microspheres to a dispersant and dispersing them thoroughly, followed by adding a silane coupling agent and stirring thoroughly. Preferably, the silane coupling agent has a mass percentage content of 5%-20% in the dispersant; and / or, the dispersant is at least one of n-heptane, tetrahydrofuran, and dichloromethane.

8. The method as described in claim 6, characterized in that, The hydrophobic tubular cotton fibers are obtained by immersing the tubular cotton fibers in a hydrophobic emulsion and then drying and curing them; or by immersing the tubular fibers in a solution containing an initiator and a grafting monomer and then grafting them through a polymerization reaction.

9. The method as described in claim 6, characterized in that, The directional coating speed is 0.5-2 m / min.

10. The application of the coating composition according to any one of claims 1-3, or the coating according to any one of claims 4-5, or the coating obtained by the method according to any one of claims 6-9, in outdoor clothing fabrics or medical protective fabrics.

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