Durable super-hydrophilic and oleophobic flame-retardant cotton fabric and preparation method and application thereof

Abstract

The application discloses a kind of durable super-hydrophilic-oleophobic flame-retardant cotton fabrics and its preparation method and application, comprising the following steps: S1, cotton fabric is alternatively immersed in cationic polymer solution and phosphorus-containing organic acid solution, and phosphorus-nitrogen synergistic flame-retardant coating is constructed on the surface of cotton fabric by layer-by-layer self-assembly, to obtain modified cotton fabric;Hydrophilic nanoparticles, fluorine surfactant and silane coupling agent are dispersed in solvent to obtain functional dispersion liquid;S2, the functional dispersion liquid is applied to the surface of the modified cotton fabric, and the micro-nano composite rough structure is constructed on the surface of flame-retardant coating by drying and curing, to obtain the durable super-hydrophilic-oleophobic flame-retardant cotton fabric.The above preparation method is simple in operation and easy to mass production;The obtained fabric not only has excellent flame-retardant property, but also realizes the dual extreme wettability of super-hydrophilic-oleophobic in air, and the coating durability is good, which can be used in flame-retardant protective clothing, oil-water separation membrane and self-cleaning textiles and other fields.

Description

Technical Field

[0001] This invention relates to the field of functional textile preparation technology, specifically to a durable cotton fabric with superhydrophilic-oleophobic wetting and flame retardant properties, its preparation method, and its applications in flame retardant protection, oil-water separation, and self-cleaning. Background Technology

[0002] Cotton fabrics are widely used in clothing, home textiles, and industrial fabrics due to their excellent moisture absorption, breathability, wearing comfort, and low cost. However, cellulose, the main component of cotton fiber, is highly flammable, with a limiting oxygen index (LOI) of only about 18%. It is extremely flammable upon contact with a source of ignition, and the flame spreads rapidly, easily causing flashover, posing a serious threat to personal safety and property. Therefore, flame-retardant functional treatment of cotton fabrics to reduce their fire safety hazards has become an important research direction in the functional modification of textiles.

[0003] Currently, the preparation of flame-retardant cotton fabrics mainly employs surface modification methods. This involves introducing flame-retardant agents, such as those containing phosphorus or nitrogen, onto the fabric surface to construct a flame-retardant coating, thus imparting flame-retardant properties. However, existing flame-retardant cotton fabrics typically possess both hydrophilic and oleophilic properties. When used in high-risk, flammable, and explosive workplaces such as oil refining, mining, and chemical industries, they are easily wetted and penetrated by oily liquids (such as crude oil and organic solvents). Once oil contamination penetrates the fabric, it not only covers or damages the flame-retardant layer, leading to a significant decrease in flame-retardant performance, but can also act as fuel in the event of a fire, intensifying the combustion process and causing more serious secondary hazards. Furthermore, the existing flame-retardant coatings and cotton fibers primarily rely on physical adsorption or weak interactions. Under frequent washing or mechanical friction, flame-retardant loss easily occurs, resulting in poor flame-retardant durability and a shortened service life.

[0004] To address the issue of flame-retardant fabrics being easily contaminated by oil, researchers have attempted to construct superhydrophobic-oleophobic surfaces. This is achieved by introducing micro- and nano-rough structures and modifying them with low surface energy materials. However, these surfaces exhibit extremely strong hydrophobicity, presenting significant drawbacks in practical applications: First, hydrophobic surfaces easily accumulate static charges, which, in flammable and explosive environments, could become hidden ignition sources, potentially causing fires or explosions and posing a major safety hazard. Second, superhydrophobic surfaces have extremely poor moisture absorption, severely impacting the fabric's moisture wicking and wearing comfort, making it difficult to meet the needs of workers wearing them for extended periods.

[0005] Superhydrophilic-oleophobic surfaces have attracted attention as a novel type of extremely wettable material. These surfaces can simultaneously achieve rapid water spread (superhydrophilicity) and oil repulsion (oleophobicity) in the air, theoretically combining oil-repellent and moisture-wicking / antistatic properties. Furthermore, these materials possess unique self-cleaning and easy-to-remove characteristics: oil stains can be spontaneously removed by soaking or rinsing with water without the need for detergents, effectively reducing flame retardant loss due to frequent washing and extending material lifespan. In the field of oil-water separation, superhydrophilic-oleophobic materials allow water to pass through quickly while trapping oil droplets, simultaneously avoiding membrane fouling caused by oil adsorption, offering advantages such as high-efficiency separation and easy cleaning and reuse. However, since the surface energy of water is much higher than that of oil, according to Young's equation, there is a fundamental contradiction in thermodynamically achieving both superhydrophilicity and oleophobicity. Balancing hydrophilicity and oleophobicity at the molecular design and surface structure level remains a major scientific challenge in this field.

[0006] Currently, research reports on superhydrophilic-oleophobic flame-retardant fabrics are extremely limited. Although a few studies have used layer-by-layer self-assembly or physical coating methods to composite flame-retardant coatings with fluorinated functional layers, these methods generally suffer from the following problems: the functional layer and the substrate mainly rely on electrostatic adsorption, hydrogen bonding, or physical adhesion with adhesives, lacking stable chemical bonding. This leads to the coating easily detaching under external forces such as washing and friction, resulting in poor durability. After a single wash, the oleophobic properties are lost, and the flame-retardant properties decrease significantly.

[0007] To address the aforementioned issues, there is an urgent need to develop a durable flame-retardant cotton fabric that combines excellent oil-repellent properties with moisture-absorbing and antistatic properties, enabling efficient oil-water separation and self-cleaning. This would meet the demands of flammable and explosive environments for multifunctional protective fabrics and the environmental remediation sector for efficient separation materials. Summary of the Invention

[0008] This invention addresses the problems of poor durability in existing superhydrophilic-oleophobic flame-retardant cotton fabrics, such as weak adhesion between the coating and the substrate and poor interfacial compatibility of the functional layers. The invention provides a durable superhydrophilic-oleophobic flame-retardant cotton fabric and its preparation method. A phosphorus-nitrogen synergistic flame-retardant coating is constructed on the surface of cotton fibers using a layer-by-layer self-assembly technique. Then, a functional layer of hydrophilic nanoparticles, fluorinated surfactants, and silane coupling agents is introduced using a spraying technique. The silane coupling agent acts as a "bridge," anchoring the nanoparticles to the flame-retardant coating surface through chemical bonds, constructing a stable micro-nano composite rough structure that integrates both flame retardancy and superwetting. The cotton fabric prepared by this method not only exhibits excellent flame-retardant properties but also demonstrates extreme dual wettability in air, exhibiting superhydrophilic-oleophobic properties, and even superhydrophilic-superoleophobic properties. Furthermore, the coating is robust and durable, showing promising application prospects in flame-retardant protective clothing, oil-water separation membranes, and self-cleaning textiles.

[0009] Specifically, the following technical solutions are provided: This invention provides a method for preparing a durable superhydrophilic-oleophobic flame-retardant cotton fabric, comprising the following steps: S1. The cotton fabric is alternately immersed in a cationic polymer solution and a phosphorus-containing organic acid solution, and a phosphorus-nitrogen synergistic flame-retardant coating is constructed on the surface of the cotton fabric through layer-by-layer self-assembly to obtain the modified cotton fabric. Hydrophilic nanoparticles, a fluorinated surfactant, and a silane coupling agent are dispersed in a solvent to obtain a functional dispersion; the silane coupling agent contains at least one of the following groups: amino, mercapto, or epoxy; the mass percentage of the silane coupling agent in the functional dispersion is 0.5 wt%-5 wt%. S2. The functional dispersion is applied to the surface of the modified cotton fabric and dried and cured to form a micro-nano composite rough structure on the surface of the phosphorus-nitrogen synergistic flame retardant coating of the modified cotton fabric, thereby obtaining the durable superhydrophilic-oleophobic flame retardant fabric.

[0010] To address the shortcomings of existing superhydrophilic-oleophobic flame-retardant fabric coatings, such as weak adhesion to the fabric, poor interfacial compatibility of functional layers, and poor durability, this invention proposes a preparation method based on a "chemical bridge" anchoring mechanism and a multi-level synergistic construction strategy. A silane coupling agent containing both specific active groups (amino, mercapto, epoxy) and alkoxysilane groups (such as trimethoxysilane and triethoxysilane) is used as the key interfacial linking molecule, successfully preparing a durable superhydrophilic-oleophobic flame-retardant cotton fabric. Details are as follows: In this invention, the specific active functional groups attached to one end of the silane coupling agent can react with organic or inorganic surfaces. For example, amino groups can form ionic or hydrogen bonds with the phosphate groups of phosphorus-containing organic acids in the flame-retardant coating; epoxy groups can undergo ring-opening addition reactions with the amino groups of cationic polymers (such as polyethyleneimine) to form covalent bonds; and thiol groups can also interact with the active groups in the coating. Through these chemical bonding methods, one end of the silane coupling agent is firmly anchored to the surface of the flame-retardant coating. Meanwhile, the alkoxysilane groups attached to the other end of the silane coupling agent hydrolyze to generate silanol groups during the drying and curing process. These silanol groups can, on the one hand, undergo condensation reactions with the hydroxyl groups on the surface of hydrophilic nanoparticles (such as silica) to form Si-O-Si covalent bonds, firmly grafting the nanoparticles onto the surface of the flame-retardant coating; on the other hand, the silanol groups can also condense with each other to form a cross-linked network around the nanoparticles, further enhancing the structural stability of the coating with its micro-nano composite rough structure. Through the above mechanism, the silane coupling agent plays a key "chemical bridge" role between the flame-retardant coating and the superhydrophilic-oleophobic functional layer, achieving the durable anchoring of the functional layer.

[0011] In addition, the silanol groups formed after the hydrolysis of the above-mentioned silane coupling agent can form hydrogen bonds or electrostatic interactions with the hydrophilic head groups (such as sulfonate groups) of fluorinated surfactants. At the same time, there are also van der Waals forces and hydrophobic interactions between the two, which allows the fluorinated surfactants to be uniformly adsorbed and stabilized on the cross-linked network and micro-nano rough structure surface constructed by the silane coupling agent. Thus, while giving cotton fabrics durable oleophobic properties, it does not affect the chemical anchoring effect of the silane coupling agent on nanoparticles and the superhydrophilic properties of cotton fabrics.

[0012] Furthermore, the mass percentage of silane coupling agent in the aforementioned functional dispersion directly affects the hydrophilicity, oleophobicity, and durability of the fabric. If the mass fraction of silane coupling agent in the functional dispersion is too low, for example, less than 0.5 wt%, sufficient chemical anchoring points cannot be formed between the flame-retardant coating and the hydrophilic nanoparticles. The nanoparticles, relying solely on physical adsorption, are easily detached during washing or friction, leading to the destruction of the micro-nano rough structure and rapid loss of oleophobic properties. At the same time, the fluorosurfactant also lacks a stable cross-linking network support, making it difficult to distribute evenly. If the content of silane coupling agent is too high (e.g., the mass fraction of silane coupling agent in the functional dispersion is greater than 5 wt%), the silane coupling agent will form multilayer coatings or even self-aggregates on the surface of the nanoparticles after hydrolysis, excessively shielding the hydrophilic hydroxyl groups on the particle surface, resulting in a decrease in the hydrophilicity of the fabric and an inability to achieve superhydrophilicity (water contact angle ≈ 0°). In addition, excessive silane coupling agent will fill the micro-nano pores formed by the accumulation of nanoparticles, reducing surface roughness and thus affecting oleophobic properties. It will also make the fabric feel stiffer and reduce its breathability. Therefore, the mass percentage of silane coupling agent in the functional dispersion needs to be controlled within the range of 0.5 wt%-5 wt%, such as 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, etc.

[0013] Furthermore, in step S1, the number of cycles of alternating impregnation is preferably 2-20 times, and the time of each impregnation is preferably 5-60 minutes, so as to ensure sufficient adsorption and complete reaction to form a dense flame-retardant coating.

[0014] In this invention, the number of alternating impregnation cycles affects the thickness of the flame-retardant layer, the breathability and moisture permeability of the fabric, and the stability of the coating. If the number of alternating impregnation cycles is too small (e.g., only 1 time), the resulting flame-retardant layer is too thin, resulting in poor flame-retardant performance and insufficient sites for bonding with the silane coupling agent, thus affecting the adhesion between the superhydrophilic-oleophobic functional layer and the substrate. However, the number of cycles should not be too large either. Excessive assembly (e.g., more than 20 cycles) will cause the coating to accumulate at the fiber junctions, filling the inherent macroporous structure between fibers, significantly reducing the breathability and moisture permeability of the fabric, making it feel stiff, and the excessively thick coating is prone to cohesive fracture from the middle layer of the coating when subjected to friction or bending, leading to coating peeling. Preferably, the number of alternating impregnation cycles is controlled within 2-20 times, more preferably 5-15 times, such as 5 times, 10 times, etc., to ensure flame-retardant performance while providing sufficient anchoring groups to improve the interfacial adhesion between coatings, and at the same time ensuring unobstructed pores between fibers to maintain good breathability and moisture permeability.

[0015] Furthermore, in step S1, the mass percentage of the phosphorus-nitrogen synergistic flame-retardant coating in the dried modified cotton fabric is preferably 5%-40%.

[0016] Further, in step S1, the cationic polymer can be selected from one or more of polyethyleneimine, chitosan, and polyacrylamide, and the phosphorus-containing organic acid can be selected from one or more of phytic acid, aminotrimethylenephosphonic acid, and hydroxyethylidene diphosphonic acid; in some preferred embodiments, the cationic polymer is preferably polyethyleneimine with a molecular weight of 600-70000. If the molecular weight is too low (less than 600), the cross-linking network will not be strong, and if the molecular weight is too high (greater than 70000), the solution viscosity will be too high, making it difficult to penetrate into the fiber interior; the phosphorus-containing organic acid is preferably phytic acid, which is abundant and has a high phosphorus content.

[0017] Further, in step S1, the concentration of the cationic polymer solution is preferably 1-50 mg / mL, such as 1 mg / mL, 5 mg / mL, 10 mg / mL, 15 mg / mL, 20 mg / mL, 25 mg / mL, 30 mg / mL, 35 mg / mL, 40 mg / mL, 45 mg / mL, 50 mg / mL, etc., including but not limited to the concentration values ​​listed above; the concentration of the phosphorus-containing organic acid solution is preferably 1-50 mg / mL, such as 1 mg / mL, 5 mg / mL, 10 mg / mL, 15 mg / mL, 20 mg / mL, 25 mg / mL, 30 mg / mL, 35 mg / mL, 40 mg / mL, 45 mg / mL, 50 mg / mL, etc., including but not limited to the concentration values ​​listed above. Treating cotton fabric with a cationic polymer solution and a phosphorus-containing organic acid solution of suitable concentrations forms a dense and uniform flame-retardant coating on its surface.

[0018] Further, in step S1, the solvent of the cationic polymer solution is water and / or an alcohol solvent, and the solvent of the phosphorus-containing organic acid solution is water and / or an alcohol solvent; the alcohol solvent includes one or more of methanol, ethanol, and isopropanol.

[0019] Furthermore, in step S1, after each immersion, a water washing and drying process is performed to remove excess physically adsorbed components and ensure the uniformity and adhesion of the coating; more preferably, the drying temperature is preferably 100-150 ℃ and the drying time is preferably 5-60 min.

[0020] Further, in step S1, the hydrophilic nanoparticles are selected from one or more of silica nanoparticles, titanium dioxide nanoparticles, and alumina nanoparticles.

[0021] More preferably, in this invention, the hydrophilic nanoparticles comprise silica nanoparticles. Silica nanoparticles not only serve as a key component in constructing a superhydrophilic-oleophobic surface micro / nano-roughened structure, but also as an important component of the flame-retardant system. Together with nitrogen (cationic polymers, such as polyethyleneimine) and phosphorus (phosphorus-containing organic acids, such as phytic acid) in the flame-retardant coating, they construct an NP-Si synergistic flame-retardant system, reducing the heat release rate and inhibiting smoke generation. Simultaneously, they make the char layer more viscous and tough, effectively preventing the formation of molten droplets on cotton fabrics during combustion, thus avoiding secondary combustion or burns caused by molten droplets. Furthermore, since hydrophilic nanoparticles with excessively small particle sizes are prone to agglomeration, while excessively large particle sizes are not conducive to forming a stable micro / nano-roughened structure, in some preferred embodiments, the hydrophilic nanoparticles are silica nanoparticles with a diameter of 20-200 nm.

[0022] Furthermore, in step S1, the fluorosurfactant is selected from one or more of amphoteric fluorocarbon surfactants, anionic fluorocarbon surfactants, and cationic fluorocarbon surfactants, such as amphoteric fluorocarbon surfactant FS-50. This type of fluorosurfactant has low surface energy, good oleophobic effect, and is environmentally friendly.

[0023] Further, in step S1, the silane coupling agent may be selected from one or more of 3-aminopropyltriethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-glycidyl etheroxypropyltrimethoxysilane.

[0024] Further, in step S1, the solvent is water and / or ethanol, more preferably a mixed solvent of ethanol and water, such as a mixed solvent obtained by mixing ethanol and water in a volume ratio of 4:1. The ethanol / water mixed solvent is beneficial for the uniform dispersion of each component and has a moderate evaporation rate, which facilitates the formation of a uniform coating.

[0025] Further, in step S1, the mass percentage of hydrophilic nanoparticles in the functional dispersion is 0.5 wt%-5 wt%, for example, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, etc.; the mass percentage of fluorosurfactant in the functional dispersion is 0.1 wt%-5 wt%, for example, 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, etc.; more preferably, the mass ratio of the hydrophilic nanoparticles to the fluorosurfactant is (1:5)-(4:1), for example, 1:5, 1:1, 2:1, 3:1, 4:1, etc.

[0026] Furthermore, in step S2, the application method includes, but is not limited to, spraying, dipping, brushing, etc., with spraying being more preferred, resulting in a more uniform coating and easier control of coating thickness; in some preferred embodiments, the spraying distance is 10-20 cm, the spraying pressure is 0.1-0.3 MPa, and the fabric weight gain rate after spraying is 2%-15%.

[0027] Furthermore, in step S2, the drying and curing temperature is 100-150 ℃, for example, 110 ℃, 120 ℃, 130 ℃, etc., and the time is 10-60 min. Under these drying and curing conditions, the silane coupling agent can be fully condensed to form a strong chemical bond, while ensuring that the solvent completely evaporates.

[0028] The second aspect of the present invention provides a durable superhydrophilic-oleophobic flame-retardant cotton fabric, which is prepared by the preparation method described in the first aspect. The durable superhydrophilic-oleophobic flame-retardant cotton fabric includes a cotton fabric, a phosphorus-nitrogen synergistic flame-retardant coating disposed on the surface of the cotton fabric, and a micro-nano structure layer disposed on the side of the phosphorus-nitrogen synergistic flame-retardant coating away from the cotton fabric. The micro-nano structure layer is anchored to the surface of the phosphorus-nitrogen synergistic flame-retardant coating by chemical bonds.

[0029] Furthermore, the root mean square roughness (Rq) of the micro / nano structure layer is 50-300 nm; the contact angle of the durable superhydrophilic-oleophobic flame-retardant cotton fabric with water is 0°, and the contact angle with oil is greater than 150°; the limiting oxygen index of the durable superhydrophilic-oleophobic flame-retardant cotton fabric is ≥32%, and the vertical burning char length is ≤8 cm.

[0030] The third aspect of the present invention provides the application of a durable superhydrophilic-oleophobic flame-retardant cotton fabric prepared by the preparation method described in the first aspect in flame-retardant protective clothing, oil-water separation membranes, or self-cleaning textiles.

[0031] The beneficial effects of this invention are: This invention provides a method for preparing a durable, superhydrophilic-oleophobic flame-retardant cotton fabric. A phosphorus-nitrogen synergistic flame-retardant coating is constructed on the surface of the cotton fabric through layer-by-layer self-assembly. This is followed by the creation of a micro-nano composite rough structure using spraying technology, and the two are firmly bonded together by the chemical bonding of a silane coupling agent. This successfully yields a multifunctional cotton fabric with both excellent flame-retardant properties and superhydrophilic-oleophobic (or even dual extreme wettability) properties. The above preparation method employs layer-by-layer self-assembly and spraying techniques, is simple to operate, operates under mild conditions, is easy to industrialize, uses widely available and environmentally friendly raw materials, and meets the requirements of green chemistry.

[0032] The durable superhydrophilic-oleophobic flame-retardant cotton fabric prepared by the above method not only has excellent flame-retardant performance (limiting oxygen index ≥25%, vertical burning char length ≤8 cm, afterflame time 0 s), but also has multi-media adaptability characteristics of being superhydrophilic in air (water contact angle ≈0°) and oleophobic or even superoleophobic (oil contact angle >150°) as well as being superhydrophilic in oil and oleophobic underwater, breaking through the limitation of the single function of existing cotton fabrics.

[0033] In addition, the durable superhydrophilic-oleophobic flame-retardant cotton fabric prepared by the present invention utilizes the chemical anchoring effect of silane coupling agent to form a strong chemical bond between the functional layer and the substrate, exhibiting excellent durability. After 20 standard water washes, the oleophobic and flame-retardant properties remain good, and the service life is significantly better than that of similar products prepared by physical coating method.

[0034] The durable, superhydrophilic, oleophobic, and flame-retardant cotton fabric provided by this invention has a wide range of applications and significant practical value. In the field of flame retardant protection, this product combines flame retardancy and oil resistance, ensuring safe use in fire-hazardous environments while preventing oil adhesion that could reduce its flame-retardant performance. In the field of oil-water separation, this product achieves a separation efficiency of up to 99.5% for oil-water mixtures, its oleophobic properties effectively prevent membrane fouling, and its flame-retardant properties ensure its safety in environments containing flammable solvents. Furthermore, in the field of self-cleaning, surface oil stains can be completely removed with simple water rinsing, making it suitable for hotels, hospitals, and other places with high hygiene requirements. Attached Figure Description

[0035] Figure 1 These are scanning electron microscope (SEM) images of the modified cotton fabric prepared in Example 1 of the present invention, where a is a SEM image under low magnification and b is a SEM image under high magnification. Figure 2 This is an atomic force microscope (AFM) image of the modified cotton fabric prepared in Example 1 of this invention; Figure 3 This refers to the water contact angle of the modified cotton fabric prepared in Example 1 of this invention; Figure 4 It is the contact angle of the modified cotton fabric prepared in Example 1 of this invention with oil (hexadecane); Figure 5 The images show vertical burning tests of the modified cotton fabrics prepared in Example 1 of this invention, where a is a vertical burning test image of the cotton fabric before modification and b is a vertical burning test image of the cotton fabric after modification. Figure 6 These are scanning electron microscope (SEM) images of the modified cotton fabric prepared in Comparative Example 5 of this invention. a is the SEM image under low magnification conditions, and b is the SEM image under high magnification conditions. Figure 7 This is an atomic force microscope (AFM) image of the modified cotton fabric prepared in Comparative Example 5 of this invention; Figure 8 This refers to the water contact angle of the modified cotton fabric prepared in Comparative Example 5 of this invention. Figure 9 It is the contact angle of the modified cotton fabric prepared in Comparative Example 5 of this invention with oil (hexadecane). Detailed Implementation

[0036] 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 invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term “and / or” as used herein includes any and all combinations of one or more of the associated listed items. The terms “comprising” or “including” as used herein may also be replaced with the closed form “is” or “consisting of”.

[0037] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0038] Example 1: This example relates to the preparation of a durable superhydrophilic-superoleophobic flame-retardant cotton fabric, specifically including the following steps: (1) First, immerse the cotton fabric in a polyethyleneimine solution with a molecular weight of 1800 at a concentration of 10 mg / mL for 30 min at room temperature, then take it out and wash it with water; then immerse it in a phytic acid solution with a concentration of 15 mg / mL for 30 min at room temperature, then take it out and wash it with water; the above is one cycle, repeat 5 cycles and then dry it at 80 ℃ to obtain flame-retardant modified cotton fabric.

[0039] Hydrophilic silica nanoparticles with a particle size of 50 nm, fluorosurfactant FS-50, and silane coupling agent 3-aminopropyltriethoxysilane were dispersed in a mixed solvent of ethanol / water at a volume ratio of 4:1 to obtain a functional dispersion with a solid content of 10%. The mass ratio of silica nanoparticles to fluorocarbon surfactant FS-50 was 1:2, and the content of 3-aminopropyltriethoxysilane was 3%.

[0040] (2) Then, the functional dispersion prepared in step S1 is applied evenly to the surface of the modified cotton fabric prepared in step S1 by spraying (spraying distance 15 cm, pressure 0.2 MPa), dried and cured at 120 ℃ for 10 min, and then placed in deionized water for 10 min to remove the functional layer components that are not firmly attached. After drying, a durable superhydrophilic-oleophobic flame retardant cotton fabric is obtained.

[0041] Figure 1 and Figure 2 Scanning electron microscope (SEM) and atomic force microscope (AFM) images of the durable superhydrophilic-oleophobic flame-retardant cotton fabric (modified cotton fabric) prepared in this embodiment are shown. A uniform and tightly bonded modification layer can be observed on the surface of the cotton fabric, and the surface roughness of the fibers is significantly increased. The contact angles of the modified cotton fabric prepared in this embodiment with water and hexadecane in air were tested, and the results are shown below. Figure 3 As shown in Figure 4, water droplets on the surface of the modified cotton fabric spread completely in just 0.54 s ( Figure 3 ), exhibiting superhydrophilicity; by Figure 4 It can be seen that the modified cotton fabric has a contact angle greater than 150° with oil droplets (hexadecane), exhibiting superoleophobic properties. Therefore, the modified cotton fabric prepared in this embodiment has superhydrophilic-oleophobic properties.

[0042] In addition, the vertical burning performance of the unmodified cotton fabric and the durable superhydrophilic-oleophobic flame-retardant cotton fabric prepared in this embodiment (modified cotton fabric) was tested, and the results are as follows: Figure 5 As shown, the unmodified cotton fabric burns rapidly upon contact with a flame, continues to burn after being removed from the flame, and eventually burns completely without any obvious residue. The modified cotton fabric, however, does not exhibit violent burning upon contact with a flame, does not continue to burn after being removed from the flame, and the damaged length is approximately 70 mm, while the damaged portion retains its original shape. Therefore, the modified cotton fabric prepared in this embodiment exhibits excellent flame retardancy, with a limiting oxygen index of 36%, a non-flammable surface, and superior flame-retardant properties.

[0043] Example 2: This example relates to the preparation of a durable superhydrophilic-superoleophobic flame-retardant cotton fabric. The only difference from Example 1 is that the cationic polymer in step (1) is chitosan (degree of deacetylation ≥90%). All other conditions are the same, and the corresponding durable superhydrophilic-oleophobic flame-retardant cotton fabric is prepared.

[0044] The contact angles of water and oil on the surface of the durable superhydrophilic-oleophobic flame-retardant cotton fabric prepared in this embodiment were tested. The results showed that in hexane, the water spread completely in 0.65 s; the contact angle of hexadecane was greater than 150º, exhibiting superhydrophilic-superoleophobic properties. The limiting oxygen index of the durable superhydrophilic-oleophobic flame-retardant cotton fabric prepared in this embodiment was tested, and the results showed that the limiting oxygen index was 29%.

[0045] Example 3: This example relates to the preparation of a durable superhydrophilic-superoleophobic flame-retardant cotton fabric. The only difference from Example 1 is that the phosphorus-containing organic acid in step (1) is aminotrimethylenephosphonic acid. All other conditions are the same, and the corresponding durable superhydrophilic-superoleophobic flame-retardant cotton fabric is prepared.

[0046] The contact angles of water and oil on the surface of the durable superhydrophilic-superoleophobic flame-retardant cotton fabric prepared in this embodiment were tested. The results showed that in hexane, the water spread completely in 0.7 s; the contact angle of hexadecane was greater than 150º, exhibiting superhydrophilic-superoleophobic properties. The limiting oxygen index of the durable superhydrophilic-superoleophobic flame-retardant cotton fabric prepared in this embodiment was tested, and the results showed that the limiting oxygen index was 31%.

[0047] Example 4: This example relates to the preparation of a durable superhydrophilic-superoleophobic flame-retardant cotton fabric. The only difference from Example 1 is that the hydrophilic nanoparticles with a particle size of 50 nm in step (1) are titanium dioxide nanoparticles. All other conditions are the same, and the corresponding durable superhydrophilic-superoleophobic flame-retardant cotton fabric is prepared.

[0048] The contact angles of water and oil on the surface of the durable superhydrophilic-superoleophobic flame-retardant cotton fabric prepared in this embodiment were tested. The results showed that in hexane, the water spread completely in 0.7 s; the contact angle of hexadecane was greater than 150º, exhibiting superhydrophilic-superoleophobic properties. The limiting oxygen index of the durable superhydrophilic-superoleophobic flame-retardant cotton fabric prepared in this embodiment was tested, and the results showed that the limiting oxygen index was 33%.

[0049] Example 5: This example relates to the preparation of a durable superhydrophilic-oleophobic flame-retardant cotton fabric. The only difference from Example 1 is that in step (1), the mass ratio of silica nanoparticles to fluorocarbon surfactant FS-50 is 4:1, the solid content of the functional dispersion is 10%, and the other conditions are the same, and the corresponding modified cotton fabric is prepared.

[0050] The contact angles of water and oil on the surface of the modified cotton fabric prepared in this embodiment were tested. The results showed that in hexane, the water spread completely in 0.50 s; the contact angle in hexadecane was 109º, exhibiting superhydrophilic-oleophobic properties. The limiting oxygen index of the modified cotton fabric prepared in this embodiment was tested, and the results showed that the limiting oxygen index was 35%.

[0051] Example 6: This example relates to the preparation of a durable superhydrophilic-oleophobic flame-retardant cotton fabric. The only difference from Example 1 is that in step (1), the mass ratio of silica nanoparticles to fluorocarbon surfactant FS-50 is 1:5, the solid content of the functional dispersion is 10%, and the other conditions are the same, and the corresponding modified cotton fabric is prepared.

[0052] The contact angles of water and oil on the surface of the modified cotton fabric prepared in this embodiment were tested. The results showed that the water completely spread in hexane in 0.60 s, and the contact angle in hexadecane was 135º, exhibiting superhydrophilic-oleophobic properties. The limiting oxygen index of the modified cotton fabric prepared in this embodiment was tested, and the results showed that the limiting oxygen index was 33%.

[0053] Example 7: This example relates to the preparation of a durable superhydrophilic-oleophobic flame-retardant cotton fabric. The only difference from Example 1 is that the content of 3-aminopropyltriethoxysilane in step (1) is 5%, the solid content of the functional dispersion is 12%, and the other conditions are the same, and the corresponding modified cotton fabric is prepared.

[0054] The contact angles of water and oil on the surface of the modified cotton fabric prepared in this embodiment were tested. The results showed that the water completely spread in hexane in 4.7 s, and the contact angle in hexadecane was 116º, exhibiting superhydrophilic-oleophobic properties. The limiting oxygen index of the modified cotton fabric prepared in this embodiment was tested, and the results showed that the limiting oxygen index was 32%.

[0055] Example 8: This example relates to the preparation of a durable superhydrophilic-oleophobic flame-retardant cotton fabric. The only difference from Example 1 is that the content of 3-aminopropyltriethoxysilane in step (1) is 0.5%, the solid content of the functional dispersion is 7.5%, and the other conditions are the same, and the corresponding modified cotton fabric is prepared.

[0056] The contact angles of water and oil on the surface of the modified cotton fabric prepared in this embodiment were tested. The results showed that the water completely spread in hexane in 0.8 s, and the contact angle in hexadecane was 110º, exhibiting superhydrophilic-oleophobic properties. The limiting oxygen index of the modified cotton fabric prepared in this embodiment was tested, and the results showed that the limiting oxygen index was 30%.

[0057] Example 9: This example relates to the preparation of a durable superhydrophilic-superoleophobic flame-retardant cotton fabric. The only difference from Example 1 is that the molecular weight of polyethyleneimine in step (1) is 600. All other conditions are the same, and the corresponding durable superhydrophilic-superoleophobic flame-retardant cotton fabric is prepared.

[0058] The contact angles of water and oil on the surface of the durable superhydrophilic-superoleophobic flame-retardant cotton fabric prepared in this embodiment were tested. The results showed that in hexane, the water spread completely in 0.35 s; the contact angle of hexadecane was greater than 150º, exhibiting superhydrophilic-superoleophobic properties. The limiting oxygen index of the durable superhydrophilic-superoleophobic flame-retardant cotton fabric prepared in this embodiment was tested, and the results showed that the limiting oxygen index was 28%.

[0059] Example 10: This example relates to the preparation of a durable superhydrophilic-superoleophobic flame-retardant cotton fabric. The only difference from Example 1 is that the molecular weight of polyethyleneimine in step (1) is 10,000. All other conditions are the same, and the corresponding durable superhydrophilic-superoleophobic flame-retardant cotton fabric is prepared.

[0060] The contact angles of water and oil on the surface of the durable superhydrophilic-superoleophobic flame-retardant cotton fabric prepared in this embodiment were tested. The results showed that in hexane, the water spread completely in 2.3 s; the contact angle of hexadecane was greater than 150º, exhibiting superhydrophilic-superoleophobic properties. The limiting oxygen index of the durable superhydrophilic-superoleophobic flame-retardant cotton fabric prepared in this embodiment was tested, and the results showed that the limiting oxygen index was 37%, but the fabric had high stiffness and poor softness.

[0061] Example 11: This example relates to the preparation of a durable superhydrophilic-superoleophobic flame-retardant cotton fabric. The only difference from Example 1 is that the number of cycles of impregnation with phytic acid and polyethyleneimine in step (1) is 2, and the other conditions are the same. The corresponding durable superhydrophilic-superoleophobic flame-retardant cotton fabric is prepared.

[0062] The contact angles of water and oil on the surface of the durable superhydrophilic-superoleophobic flame-retardant cotton fabric prepared in this embodiment were tested. The results showed that in hexane, the water spread completely in 0.5 s; the contact angle of hexadecane was greater than 150º, exhibiting superhydrophilic-superoleophobic properties. The limiting oxygen index of the durable superhydrophilic-superoleophobic flame-retardant cotton fabric prepared in this embodiment was tested, and the results showed that the limiting oxygen index was 25%.

[0063] Example 12: This example relates to the preparation of a durable superhydrophilic-superoleophobic flame-retardant cotton fabric. The only difference from Example 1 is that the number of cycles of impregnation with phytic acid and polyethyleneimine in step (1) is 10, and the other conditions are the same, and the corresponding durable superhydrophilic-superoleophobic flame-retardant cotton fabric is prepared.

[0064] The contact angles of water and oil on the surface of the durable superhydrophilic-superoleophobic flame-retardant cotton fabric prepared in this embodiment were tested. The results showed that in hexane, the water spread completely in 4.5 s; the contact angle in hexadecane was greater than 150º, exhibiting superhydrophilic-superoleophobic properties. The limiting oxygen index of the durable superhydrophilic-superoleophobic flame-retardant cotton fabric prepared in this embodiment was tested, and the results showed that the limiting oxygen index was 38%, indicating high fabric stiffness and poor softness.

[0065] Comparative Example 1: This comparative example relates to the preparation of a modified cotton fabric. The only difference from Example 1 is that the content of 3-aminopropyltriethoxysilane in step (1) is 0, the solid content of the functional dispersion is 7%, and the other conditions are the same, and the corresponding modified cotton fabric is prepared.

[0066] The contact angles of water and oil on the surface of the modified cotton fabric prepared in this comparative example were tested. The results showed that the water completely spread in hexane in 1.2 s, and the contact angle in hexadecane was 105º, exhibiting superhydrophilic-oleophobic properties. The limiting oxygen index of the modified cotton fabric prepared in this comparative example was tested, and the results showed that the limiting oxygen index was 28%.

[0067] Comparative Example 2: This comparative example relates to the preparation of a modified cotton fabric. The only difference from Example 1 is that the content of 3-aminopropyltriethoxysilane in step (1) is 10%, the solid content of the functional dispersion is 17%, and the other conditions are the same, and the corresponding modified cotton fabric is prepared.

[0068] The contact angles of water and oil on the surface of the modified cotton fabric prepared in this comparative example were tested. The results showed that water spread completely in hexane in 8 s, while the contact angle in hexadecane was 95º, exhibiting superhydrophilic-oleophobic properties. The limiting oxygen index of the modified cotton fabric prepared in this comparative example was tested, and the results showed that the limiting oxygen index was 35%, indicating high fabric stiffness and poor softness.

[0069] Comparative Example 3: This comparative example relates to the preparation of a modified cotton fabric. The only difference from Example 1 is that in step (1), the phytic acid solution and the polyethyleneimine solution are directly mixed, and the cotton fabric is then soaked in the solution for 30 min, washed, and soaked in the solution 5 times. All other operations are the same, and the corresponding modified cotton fabric is prepared (the phytic acid and polyethyleneimine immediately produce a white flocculent precipitate after mixing, forming a polyelectrolyte complex. This precipitate is difficult to effectively penetrate and adhere to the surface of the cotton fibers).

[0070] The contact angles of water and oil on the surface of the modified cotton fabric prepared in this comparative example were tested. The results showed that water completely spread in hexane in 0.6 s; the contact angle of hexadecane was less than 90º, exhibiting superhydrophilic-oleophilic properties. The limiting oxygen index of the modified cotton fabric prepared in this comparative example was tested, and the results showed that the limiting oxygen index was 20%.

[0071] Comparative Example 4: This comparative example relates to the preparation of a modified cotton fabric. The only difference from Example 1 is that the drying temperature in step (2) is 80 °C, and the other conditions are the same, and the corresponding modified cotton fabric is prepared.

[0072] The contact angles of water and oil on the surface of the modified cotton fabric prepared in this comparative example were tested. The results showed that in hexane, the water spread completely in 0.7 s; the contact angle of hexadecane was less than 90º, exhibiting superhydrophilic-oleophilic properties. The limiting oxygen index of the modified cotton fabric prepared in this comparative example was tested, and the results showed that the limiting oxygen index was 33%.

[0073] Comparative Example 5: This comparative example relates to the preparation of a modified cotton fabric. The only difference from Example 1 is that the flame-retardant modified cotton fabric obtained in step (1) was not treated in step (2). All other conditions were the same, and the corresponding modified cotton fabric was obtained.

[0074] Figure 6 and Figure 7 The images shown are scanning electron microscope (SEM) and atomic force microscope (AFM) images of the modified cotton fabric prepared in this comparative example. A uniform and tightly bonded modification layer can be observed on the surface of the cotton fabric, and the surface roughness of the fibers is reduced compared to the modified cotton fabric prepared in Example 1. The contact angles of water and oil on the surface of the modified cotton fabric prepared in this comparative example were tested, and the results are as follows: Figure 8 , 9 As shown: In n-hexane, the time for water to spread completely is 2.5 s ( Figure 8 The contact angle of hexadecane is 0º. Figure 9 It exhibits superhydrophilic-superoleophilic properties. The limiting oxygen index of the modified cotton fabric prepared in this comparative example was tested, and the results showed a limiting oxygen index of 33%.

[0075] The contact angle test results of water and oil in air for the modified cotton fabrics prepared in the above embodiments and comparative examples are shown in Table 1 below: Table 1

[0076] As shown in Table 1, compared with the modified cotton fabric obtained by preparing a flame-retardant layer only on the surface of cotton fabric in Comparative Example 5, the modified cotton fabrics obtained by constructing a flame-retardant coating on the surface of cotton fabric through layer-by-layer self-assembly and then constructing a micro-nano composite rough structure by combining spraying technology can have both excellent flame-retardant properties and superhydrophilic-oleophobic or superoleophobic properties. Among them, by controlling the mass ratio of hydrophilic nanoparticles to fluorocarbon surfactants and the content of silane coupling agents within a suitable range, modified cotton fabrics with flame-retardant properties comparable to or even better than those of Comparative Example 5 and with superhydrophilic-superoleophobic properties can be obtained (such as Examples 1 and 4).

[0077] As shown in Example 1 and Comparative Examples 1 and 2, both excessive and insufficient silane coupling agent content in the functional dispersion will affect the hydrophilic-oleophobic properties of the prepared modified cotton fabric, significantly reducing the oil contact angle. Furthermore, the flame retardant properties of the modified cotton fabric prepared without the addition of silane coupling agent (Comparative Example 1) also decreased. Therefore, in this invention, the content of silane coupling agent in the functional dispersion must be controlled within a suitable range to obtain a modified cotton fabric that possesses both excellent flame retardant properties and superhydrophilic-oleophobic properties.

[0078] As shown in Example 1 and Comparative Example 3, if the cationic polymer is first mixed with a phosphorus-containing organic acid, and then the cotton fabric is immersed in the mixture and the modified cotton fabric is prepared by repeated immersion, the flame retardant performance will be significantly reduced, even significantly worse than that of Comparative Example 5. Moreover, the surface of the modified cotton fabric is still oleophilic and cannot effectively prevent oil stains. This is because the silane coupling agent cannot chemically anchor the nanoparticles to the fabric surface, and the fluorinated surfactant cannot effectively bind to the fabric surface by physical adsorption alone. After preparation, the water washing step will remove a large number of nanoparticles and fluorinated surfactants, resulting in the cotton fabric surface still exhibiting oleophilic properties. In addition, the modified cotton fabric prepared by lowering the drying and curing temperature in Comparative Example 4 exhibits oleophilic properties. This is because at excessively low drying and curing temperatures (such as 80 °C), the silane coupling agent does not undergo complete hydrolysis and condensation, and cannot effectively anchor the nanoparticles, leading to the destruction of the micro-nano structure and thus failing to achieve an oleophobic effect.

[0079] Test Example 1: Following the 2A test procedure in AATCC 61-2006 "Colorfastness to Washing: Accelerated Washing", the durable superhydrophilic-superoleophobic flame-retardant cotton fabric prepared in Example 1 and the modified cotton fabric prepared in Comparative Example 1 were subjected to accelerated washing tests. Specific conditions were: washing temperature 49±3 ℃, washing time 45 min, deionized water (200 mL) as the washing solution, and each accelerated washing cycle being equivalent to 5 standard household washes. The test results are shown in Table 2 below. Table 2

[0080] As shown in Table 2, the durable superhydrophilic-superoleophobic flame-retardant cotton fabric prepared in Example 1 of the present invention can still maintain excellent flame-retardant properties and superhydrophilic-superoleophobic properties after 20 washes. However, the modified cotton fabric prepared in Comparative Example 1 without the addition of silane coupling agent, after only 5 washes, the contact angle between the surface of the modified cotton fabric and soybean oil decreased to 0º, which is a superoleophilic property, and it completely lost its oil-repellent effect. Moreover, after 20 washes, the limiting oxygen index of the modified cotton fabric also decreased significantly.

[0081] Test Example 2: The durable superhydrophilic-superoleophobic flame-retardant cotton fabric prepared in Example 1 and the modified cotton fabric prepared in Comparative Example 5 were named Modified Cotton Fabric 1 and 2, respectively. Modified Cotton Fabric 1 and 2 were used to test the separation efficiency, separation flux, and durability of oil-water mixtures. The test process is as follows: Preparation of oil-water mixture: 50 g of water and 50 g of hexadecane are mixed to prepare an oil-water mixture; Test method for oil-water mixture separation efficiency: Weigh the separated oil using a balance, and then calculate the efficiency according to the formula. Calculate the separation efficiency of the oil-water mixture, where E is the separation efficiency of the oil-water mixture, C1 is the mass of the oil after separation, and C0 is the mass of the oil before separation.

[0082] Separation flux testing method: The volume of permeate passing through a unit membrane area per unit time, calculated according to the formula... Calculate the separation flux J, where V is the permeate volume in L; A is the effective membrane area in m². 2 t represents the running time, in hours (h).

[0083] Durability test method: Repeat the above separation operation on the oil-water mixture 50 times, and calculate the corresponding separation efficiency after 50 cycles.

[0084] The test results are shown in Table 3 below: Table 3

[0085] As shown in Table 3, the modified cotton fabric 1 prepared in Example 1 achieved an initial separation efficiency of up to 99.5% for the oil-water mixture. However, due to the superhydrophilic-superoleophilic wetting properties of the surface of the modified cotton fabric 2, when the mixture of hexadecane and water was poured into the separation device, the less dense hexadecane would first contact the fabric and permeate through it. Some of the fabric that had not been permeated with hexadecane would allow water to pass through when it subsequently came into contact with water, thus resulting in the inability to effectively separate the water and oil mixture. In addition, the modified cotton fabric 1 has excellent fastness, and the separation efficiency remains at 98.3% after 50 cycles of separation, demonstrating excellent durability.

[0086] The embodiments described above are merely preferred examples to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A method for preparing a durable superhydrophilic-oleophobic flame-retardant cotton fabric, characterized in that, Includes the following steps: S1. The cotton fabric is alternately immersed in a cationic polymer solution and a phosphorus-containing organic acid solution, and a phosphorus-nitrogen synergistic flame-retardant coating is constructed on the surface of the cotton fabric through layer-by-layer self-assembly to obtain the modified cotton fabric. Hydrophilic nanoparticles, a fluorinated surfactant, and a silane coupling agent are dispersed in a solvent to obtain a functional dispersion; the silane coupling agent contains at least one of the following groups: amino, mercapto, or epoxy; the mass percentage of the silane coupling agent in the functional dispersion is 0.5 wt%-5 wt%. S2. The functional dispersion is applied to the surface of the modified cotton fabric and dried and cured to form a micro-nano composite rough structure on the surface of the phosphorus-nitrogen synergistic flame retardant coating of the modified cotton fabric, thereby obtaining the durable superhydrophilic-oleophobic flame retardant fabric.

2. The preparation method according to claim 1, characterized in that, Step S1 includes at least one of the following features: (1) The number of cycles of alternating immersion is 2-20 times, and the time of each immersion is 5-60 min; (2) The cationic polymer is selected from one or more of polyethyleneimine, chitosan, and polyacrylamide; (3) The phosphorus-containing organic acid is selected from one or more of phytic acid, aminotrimethylene phosphonic acid, and hydroxyethylidene diphosphonic acid; (4) The concentration of the cationic polymer solution is 1-50 mg / mL; (5) The concentration of the phosphorus-containing organic acid solution is 1-50 mg / mL.

3. The preparation method according to claim 2, characterized in that, The cationic polymer is polyethyleneimine with a molecular weight of 600-70000, and the phosphorus-containing organic acid is phytic acid; And / or, after each immersion, the sample is washed and dried.

4. The preparation method according to claim 1, characterized in that, In step S1, the hydrophilic nanoparticles are selected from one or more of silica nanoparticles, titanium dioxide nanoparticles, and alumina nanoparticles. And / or, the fluorosurfactant is selected from one or more of amphoteric fluorocarbon surfactants, anionic fluorocarbon surfactants, and cationic fluorocarbon surfactants; And / or, the solvent is water and / or ethanol.

5. The preparation method according to claim 4, characterized in that, The hydrophilic nanoparticles are silica nanoparticles with a particle size of 20-200 nm. And / or, the fluorosurfactant is an amphoteric fluorocarbon surfactant FS-50; And / or, the silane coupling agent is selected from one or more of 3-aminopropyltriethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-glycidyl etheroxypropyltrimethoxysilane.

6. The preparation method according to claim 1, characterized in that, In step S1, the mass percentage of hydrophilic nanoparticles in the functional dispersion is 0.5 wt%-5 wt%. And / or, the fluorosurfactant in the functional dispersion accounts for 0.1 wt%-5 wt% by mass; And / or, the mass ratio of the hydrophilic nanoparticles to the fluorosurfactant is (1:5) to (4:1).

7. The preparation method according to claim 1, characterized in that, In step S2, the application method is spraying; And / or, the drying and curing temperature is 100-150 ℃ and the time is 10-60 min.

8. A durable, superhydrophilic-oleophobic, flame-retardant cotton fabric, characterized in that, The durable superhydrophilic-oleophobic flame-retardant cotton fabric, prepared by any one of claims 1-7, comprises a cotton fabric, a phosphorus-nitrogen synergistic flame-retardant coating disposed on the surface of the cotton fabric, and a micro-nano structure layer disposed on the side of the phosphorus-nitrogen synergistic flame-retardant coating away from the cotton fabric, wherein the micro-nano structure layer is anchored to the surface of the phosphorus-nitrogen synergistic flame-retardant coating by chemical bonds.

9. A durable superhydrophilic-oleophobic flame-retardant cotton fabric according to claim 8, characterized in that, The root mean square roughness Rq of the micro / nano structure layer is 50-300 nm. And / or, the durable superhydrophilic-oleophobic flame-retardant cotton fabric has a water contact angle of 0° and an oil contact angle of greater than 150°; And / or, the limiting oxygen index of the durable superhydrophilic-oleophobic flame-retardant cotton fabric is ≥32%, and the vertical burning char length is ≤8cm.

10. The application of a durable superhydrophilic-oleophobic flame-retardant cotton fabric prepared by the preparation method according to any one of claims 1-7 in flame-retardant protective clothing, oil-water separation membranes, or self-cleaning textiles.

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