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

Abstract

The application discloses super-hydrophilic-oil-repellent flame-retardant cotton fabric and a preparation method and application thereof, and comprises the following steps: S1, dispersing hydrophilic nanoparticles, ammonium polyphosphate, a fluorine surfactant and a curing agent in a solvent to obtain a functional treatment liquid; the curing agent is a blocked polyisocyanate; S2, immersing cotton fabric in the functional treatment liquid, stirring until sufficient adsorption, taking out the cotton fabric for drying treatment, releasing isocyanate groups of the curing agent, and crosslinking reaction with hydroxyl groups on the cotton fabric fibers and active groups on the ammonium polyphosphate, to obtain the super-hydrophilic-oil-repellent flame-retardant cotton fabric. The preparation method is simple in operation, can complete the construction of a multifunctional coating with excellent flame-retardant performance and super-hydrophilic-oil-repellent in one step, is suitable for industrialized production, and has a good application prospect in the fields of flame-retardant protective clothing, oil-water separation membranes and self-cleaning textiles, etc.

Description

Technical Field

[0001] This invention relates to the field of functional textile preparation technology, specifically to a multifunctional 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 textiles due to their excellent breathability, comfort, and low cost. However, cotton fibers are flammable and burn rapidly, posing a serious fire hazard. Furthermore, the hydrophilic and oleophilic properties of cotton fabrics make them susceptible to oil contamination. In flammable and explosive workplaces such as oil refineries and chemical plants, oil penetration into the fabric can lead to a loss of flame retardant properties, actually promoting combustion. Frequent washing also causes surface flame retardants to be easily washed away, shortening the material's lifespan.

[0003] Superhydrophilic-oleophobic surfaces are a type of special wetting material proposed in recent years. Their water contact angle is lower than their oil contact angle, thus repelling oil while simultaneously removing it with water. For fabrics, these superhydrophilic-oleophobic properties provide both excellent hygroscopicity and airborne oil repellency. Oil stains can be removed spontaneously by soaking in water without detergent, effectively reducing flame retardant loss. Furthermore, the good hygroscopicity prevents static electricity buildup, eliminating the safety hazard of superhydrophilic materials becoming "hidden ignition sources."

[0004] However, integrating superhydrophilic-oleophobic properties with flame-retardant functionality into a single cotton fabric faces significant challenges. On one hand, according to Young's equation, the surface energy of water is far higher than that of oil, making a theoretically both hydrophilic and oleophobic surface difficult to achieve. On the other hand, the compatibility and synergy of multiple components such as flame retardants, nanoparticles, and fluorinated surfactants within the same system have not yet been effectively resolved. Currently, there are few reports on superhydrophilic-oleophobic flame-retardant fabrics. Existing technologies often employ multi-step methods to construct multi-layer coatings, which are not only complex but also lack effective chemical bonding between the functional layers and the substrate, resulting in poor coating adhesion. For example, methods that construct a flame-retardant layer through layer-by-layer self-assembly followed by impregnation with a fluorinated functional layer rely on electrostatic adsorption or physical adhesion with adhesives, leading to coating detachment after washing or friction and poor durability.

[0005] Therefore, there is an urgent need to develop a simple process for preparing superhydrophilic-oleophobic flame-retardant cotton fabrics suitable for industrial production, and to develop a functional layer that can form a strong chemical bond with cotton fibers, thereby possessing both excellent flame-retardant properties and superhydrophilic-oleophobic characteristics, as well as good durability. Summary of the Invention

[0006] To address the problems of cumbersome preparation processes, weak bonding between the functional layer and the cotton fabric, and poor durability of existing superhydrophilic-oleophobic flame-retardant cotton fabrics, this invention provides a superhydrophilic-oleophobic flame-retardant cotton fabric, its preparation method, and its application. Hydrophilic nanoparticles, ammonium polyphosphate flame retardant, fluorinated surfactants, and end-capped isocyanate curing agents are mixed in the same functional treatment liquid. A one-step impregnation method allows the functional components to be uniformly adsorbed onto the surface of the cotton fabric. High-temperature curing then releases isocyanate groups from the curing agent, which cross-link with the hydroxyl groups on the cotton fibers, the hydroxyl groups on the surface of the hydrophilic nanoparticles, and the active groups on the ammonium polyphosphate. This chemically anchors the functional components firmly to the fabric surface, achieving a one-step synergistic integration of superhydrophilic-oleophobic properties and flame-retardant function. Furthermore, the prepared superhydrophilic-oleophobic flame-retardant cotton fabric exhibits excellent durability.

[0007] Specifically, the following technical solutions are provided: This invention provides a method for preparing a superhydrophilic-oleophobic flame-retardant cotton fabric, comprising the following steps: S1. Hydrophilic nanoparticles, ammonium polyphosphate, fluorinated surfactant and curing agent are dispersed in a solvent to obtain a functional treatment solution; The degree of polymerization of the ammonium polyphosphate is less than 50, and the mass percentage of ammonium polyphosphate in the functional treatment liquid is 5 wt%-35 wt% (more preferably 5 wt%-20 wt%, such as 10 wt%, 12 wt%, 15 wt%, etc.); the fluorosurfactant is a fully ionic fluorocarbon surfactant; and the curing agent is a capped polyisocyanate. S2. Immerse the cotton fabric in the functional treatment solution, stir until fully absorbed, remove the cotton fabric and dry it to obtain the superhydrophilic-oleophobic flame-retardant cotton fabric; the drying temperature is not lower than 100 ℃.

[0008] Furthermore, the terminated polyisocyanate molecule contains at least two isocyanate groups, and the isocyanate groups are protected by a blocking agent at room temperature and are deblocked and released under heating conditions of 100-180 °C, and can undergo cross-linking reactions with hydroxyl groups on cotton fabric fibers, active groups on ammonium polyphosphate and hydroxyl groups on the surface of hydrophilic nanoparticles; in some preferred embodiments of the present invention, the curing agent is isocyanate curing agent CR-40S.

[0009] Furthermore, ammonium polyphosphate with a degree of polymerization of less than 50 is used, more preferably ammonium polyphosphate with a degree of polymerization of less than 20. It is easily soluble in water and can be directly used to prepare water-based functional treatment solutions, making it more suitable for impregnation treatment of cotton fabrics. While not affecting the construction of the superwetting functional layer, it can form a stable chemical anchor with the curing agent.

[0010] To address the problems of cumbersome preparation processes, weak bonding between functional layers and cotton fabrics, and poor durability in existing superhydrophilic-oleophobic flame-retardant cotton fabrics, this invention proposes a one-step impregnation method combined with chemical bonding technology to prepare superhydrophilic-oleophobic flame-retardant cotton fabrics. Specifically: all functional components (hydrophilic nanoparticles, ammonium polyphosphate flame retardant, and fluorosurfactant) are mixed with a specific curing agent in the same treatment solution. Utilizing the curing agent's "latent at room temperature - activated at high temperature" characteristic, the components coexist stably and are uniformly adsorbed onto the cotton fabric surface during the impregnation stage. During the thermal curing stage, the curing agent releases active groups and simultaneously undergoes a cross-linking reaction with the hydroxyl groups on the cotton fibers and the active groups on the ammonium polyphosphate, forming a chemical bonding network. This firmly anchors the nanoparticles, flame retardant, and fluorosurfactant to the fabric surface in one step, achieving chemical bonding and fixation of the functional coating (taking curing agent CR-40S as an example, in dry...). During the drying process, CR-40S unblocks and releases isocyanate groups (-NCO), which preferentially react with hydroxyl groups on cotton fibers to form urethane bonds, achieving bottom-layer chemical anchoring. Simultaneously, -NCO reacts with the phosphate groups of the APP end groups to generate urethane phosphate bonds, firmly crosslinking the APP to the vicinity of the fiber surface. It also reacts with hydroxyl groups on the surface of hydrophilic nanoparticles to form urethane bonds, covalently anchoring the nanoparticles to the crosslinked network. Meanwhile, the fluorinated surfactant, due to its extremely low surface energy, spontaneously migrates to the air interface during curing. Through its hydrophilic head groups, it generates hydrogen bonds and electrostatic interactions with the remaining hydroxyl groups on the surface of the hydrophilic nanoparticles, forming a directional monolayer on the surface of the micro-nano rough structure formed by the accumulation of nanoparticles. This ultimately constructs a layered structure with "flame retardant inside and oleophobic outside," achieving a one-step synergistic integration of chemical bonding and anchoring of functional components with superhydrophilic-superoleophobic properties. This method is not only simple to operate, but the modified cotton fabric prepared also exhibits excellent flame retardant properties while achieving dual extreme wettability in air, including superhydrophilicity and oleophobicity, or even superoleophobicity. The specific principle is as follows: Superhydrophilic-oleophobic (superoleophobic) dual extreme wettability: Hydrophilic nanoparticles self-assemble on the fabric surface to form a micro-nano composite rough structure, providing abundant capillary channels and air trapping sites. When the fabric comes into contact with water, the capillary effect allows water to spread and penetrate rapidly, achieving superhydrophilicity. When the fabric comes into contact with oil, the gaps between the nanoparticles trap air, forming a solid-air composite interface. Combined with the low surface energy modification of fluorosurfactants, oil droplets stand upright in a spherical shape, achieving superoleophobicity. The synergistic effect of nanoparticles and fluorosurfactants endows the fabric with dual extreme wettability of superhydrophilic-superoleophobic properties.

[0011] Synergistic enhancement of flame retardant performance: Ammonium polyphosphate, as an intumescent phosphorus-based flame retardant, decomposes upon heating to generate phosphoric acid and polyphosphoric acid, which promotes the dehydration of cellulose into char and forms a dense char layer to insulate against heat and oxygen; hydrophilic nanoparticles not only construct a rough structure, but also act as a physical barrier to enhance the strength of the char layer, forming a synergistic flame retardant effect with ammonium polyphosphate, significantly improving flame retardant performance.

[0012] Excellent durability: Each functional component is firmly anchored to the fabric surface through chemical bonds, ensuring the long-term durability of the coating.

[0013] Further, in step S1, the hydrophilic nanoparticles are selected from one or more of titanium dioxide nanoparticles, silica nanoparticles, zinc oxide nanoparticles, and alumina nanoparticles. In some preferred embodiments of the present invention, using titanium dioxide nanoparticles as hydrophilic nanoparticles to prepare superhydrophilic-oleophobic flame-retardant cotton fabrics can not only construct a rough structure on the surface of the cotton fabric, but also endow the fabric with photocatalytic degradation function. If silica nanoparticles are used as hydrophilic nanoparticles to prepare superhydrophilic-oleophobic flame-retardant cotton fabrics, it is beneficial to further improve the flame-retardant performance of the cotton fabrics.

[0014] More preferably, in step S1, the hydrophilic nanoparticles have a particle size of 10 nm-200 nm. If the particle size is too small, they are prone to agglomeration, and if the particle size is too large, they are not conducive to forming a stable micro-nano rough structure. Preferably, the hydrophilic nanoparticles have a particle size of 10 nm-200 nm.

[0015] Further, in step S1, the fluorocarbon surfactant is selected from one or more of anionic fluorocarbon surfactants, cationic fluorocarbon surfactants, and amphoteric fluorocarbon surfactants; more preferably, it is fluorocarbon surfactant FS-50, which has low surface energy, good oleophobic effect, and is environmentally friendly.

[0016] Further, in step S1, the solvent is water or a mixture of water and an alcohol solvent (the mass ratio of water to alcohol solvent is 2-9:1, for example 4:1). Preferably, the alcohol solvent is ethanol. Adding an appropriate amount of alcohol solvent helps to achieve uniform dispersion of each component, while water is beneficial for the swelling and adsorption of cotton fabric.

[0017] Further, in step S1, the mass percentage of hydrophilic nanoparticles in the functional treatment liquid is preferably 0.5 wt%-5 wt%, the mass percentage of fluorosurfactant is preferably 0.5 wt%-5 wt%, and the mass percentage of curing agent is preferably 0.5 wt%-5 wt%. More preferably, the mass ratio of the hydrophilic nanoparticles to the fluorosurfactant is (1:5)-(1:1), for example, 1:5, 1:3, 1:1, etc.

[0018] In this invention, the content of each functional component and the curing agent in the functional treatment liquid affects the flame retardancy, hydrophilicity, oleophobicity, and durability of the modified cotton fabric. Hydrophilic nanoparticles and fluorosurfactants, when used in appropriate amounts, can synergistically construct the micro-nano rough structure and low surface energy layer required for superhydrophilic-oleophobic properties, preventing excessive components from clogging fiber pores or damaging wettability. Ammonium polyphosphate at 5 wt% or higher provides basic flame retardant performance, while controlling it below 35 wt% effectively prevents fabric stiffness and strength reduction, while avoiding excessive ammonium polyphosphate from affecting oleophobic properties. The curing agent, at 0.5-5 wt%, achieves a suitable chemical crosslinking density, firmly anchoring the flame retardant, nanoparticles, and fluorosurfactants to the cotton fibers, while avoiding excessive crosslinking that leads to coating embrittlement, deterioration of hand feel, and filling of the functional structure. By controlling the mass proportion of each raw material in the functional treatment liquid within the above range, a multiple balance can be achieved between flame retardant performance, superhydrophilic-oleophobic properties, durability, and fabric comfort.

[0019] Furthermore, in step S1, the dispersion method is ultrasonic dispersion, the ultrasonic dispersion power is 50-600W, and the time is preferably 30-120 min, to ensure that each component is fully dispersed.

[0020] Further, in step S2, the mass ratio of the cotton fabric to the functional treatment liquid is 1:(10-50); the stirring time is preferably 10-90 min; so that the cotton fabric can fully and evenly absorb the components in the functional treatment liquid.

[0021] Furthermore, in step S2, the drying temperature is preferably 100-180 ℃ and the time is preferably 3-60 min. Under this temperature condition, the curing agent can de-encapsulate and release isocyanate groups, and fully react with the hydroxyl groups on the cotton fibers, the phosphate groups of ammonium polyphosphate, and the hydroxyl groups on the surface of hydrophilic nanoparticles to build a stable multifunctional coating on the surface of the cotton fabric. At the same time, it can avoid the mechanical properties of the cotton fibers from being affected by excessively high drying temperatures.

[0022] The second aspect of the present invention provides a superhydrophilic-oleophobic flame-retardant cotton fabric, which is prepared by the preparation method described in the first aspect. The superhydrophilic-oleophobic flame-retardant cotton fabric includes a cotton fabric and a multifunctional coating disposed on the surface of the cotton fabric. The multifunctional coating is anchored to the surface of the cotton fabric by chemical bonds.

[0023] Furthermore, the superhydrophilic-oleophobic flame-retardant cotton fabric has a water contact angle of 0° and a complete spreading time of ≤2.5s, more preferably ≤0.5s; the superhydrophilic-oleophobic flame-retardant cotton fabric has an oil contact angle of greater than 120°, more preferably greater than 150°; and the superhydrophilic-oleophobic flame-retardant cotton fabric has a limiting oxygen index of ≥22%, more preferably ≥32%.

[0024] The third aspect of the present invention provides the application of a 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.

[0025] The beneficial effects of this invention are: This invention is the first to achieve the synergistic integration of flame retardancy and superhydrophilic-oleophobic functions through a one-step impregnation method. Compared with existing multi-step methods for constructing multi-layer coatings to achieve multi-functional integration, the process of this invention is extremely simple, has a short cycle time, is easy to operate, and is suitable for continuous industrial production. It significantly reduces equipment investment and energy consumption costs, and overcomes the technical defects of existing technologies, such as complex processes and low efficiency.

[0026] This invention achieves chemical bonding and anchoring of functional components through a thermally activated crosslinking mechanism of a curing agent. Under heating conditions, a specific curing agent undergoes a covalent crosslinking reaction with the active groups on components such as the hydroxyl groups and ammonium polyphosphate of cotton fibers, firmly anchoring nanoparticles, flame retardants, and fluorosurfactants to the fabric surface. The coating durability is significantly better than that of physical adsorption or adhesive fixation. After multiple washes, the coating retention rate is significantly improved, with flame retardant and wetting properties both maintaining a retention rate of over 90%, solving the common problem of easy peeling off of existing flame-retardant and super-wetting coatings during washing.

[0027] This invention achieves synergistic optimization of superhydrophilicity, superoleophobicity, and flame retardant properties. The cotton fabric prepared by this invention exhibits dual extreme wettability: ultrafast hydrophilic response (≤2.5 s, even ≤0.5 s) and oleophobicity or even superoleophobicity in air (>150°). Simultaneously, the limiting oxygen index is not less than 22%, even ≥32%, and flame retardant properties are excellent. The superhydrophilic properties endow the fabric with good moisture absorption, antistatic properties, and self-cleaning properties, while the superoleophobic properties effectively prevent oil stains from adhering and penetrating, overcoming the inherent defects of superhydrophobic fabrics such as easy static electricity and poor moisture absorption.

[0028] This invention endows the product with a wide range of application advantages and significant practical value. In the field of flame retardant protection, the product combines flame retardant and oil-proof functions, preventing oil stains from causing a decrease in flame retardant performance; in the field of oil-water separation, it has high separation efficiency and prevents membrane fouling; in the field of self-cleaning, surface oil stains can be completely removed by rinsing with water; in the field of photocatalysis, the introduction of functional nanoparticles such as titanium dioxide enables the fabric to have functions such as degrading organic pollutants and antibacterial properties, expanding the product's application prospects.

[0029] In summary, this invention has successfully prepared cotton fabrics with both superhydrophilic and oleophobic properties and excellent flame retardant performance through a one-step impregnation method combined with chemical bonding technology. It has achieved breakthrough progress in terms of process simplicity, coating durability and functional integration, and has significant technological advancements and broad industrialization prospects. Attached Figure Description

[0030] Figure 1This is a scanning electron microscope (SEM) image of the superhydrophilic-superoleophobic flame-retardant cotton fabric prepared in Example 1 of the present invention; Figure 2 This is a test diagram of the contact angle of the superhydrophilic-superoleophobic flame-retardant cotton fabric prepared in Example 1 of the present invention with water; Figure 3 This is a test diagram of the contact angle of the superhydrophilic-superoleophobic flame-retardant cotton fabric prepared in Example 1 of the present invention with soybean oil. Figure 4 This is a vertical combustion test diagram of the superhydrophilic-superoleophobic flame-retardant cotton fabric prepared in Example 1 of the present invention; Figure 5 This is a vertical burning test diagram of the superhydrophilic-superoleophobic cotton fabric prepared in Comparative Example 1 of this invention; Figure 6 This is a SEM image of the superhydrophilic-superoleophobic flame-retardant cotton fabric prepared in Example 1 of this invention after 50 washes; Figure 7 This is a test diagram of the contact angle of the superhydrophilic-superoleophobic flame-retardant cotton fabric prepared in Example 1 of the present invention with water after 50 washes; Figure 8 This is a test diagram of the contact angle of the superhydrophilic-superoleophobic flame-retardant cotton fabric prepared in Example 1 of the present invention with soybean oil after 50 washes. Figure 9 This is a vertical combustion test image of the superhydrophilic-superoleophobic flame-retardant cotton fabric prepared in Example 1 of the present invention after 50 washes. Detailed Implementation

[0031] 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”.

[0032] 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 are not intended to limit the present invention. In the present invention, unless otherwise specified, all equipment and raw materials are commercially available or commonly used in the industry. Unless otherwise specified, the methods in the following embodiments are conventional methods in the art.

[0033] The materials used in the following embodiments are shown in the table below:

[0034] Example 1: This example relates to the preparation of a superhydrophilic-superoleophobic flame-retardant cotton fabric, specifically including the following steps: (1) Hydrophilic titanium dioxide nanoparticles, ammonium polyphosphate (degree of polymerization <20), fluorosurfactant FS-50, and isocyanate curing agent CR-40S were dispersed in a mixed solvent of water and ethanol at a mass ratio of 4:1, and ultrasonicated for 1 hour to obtain a functionally homogeneous treatment solution. Among them, the mass percentage of titanium dioxide nanoparticles was 1%, the mass percentage of fluorosurfactant FS-50 was 3%, the mass ratio of titanium dioxide nanoparticles to fluorocarbon surfactant FS-50 was 1:3, the mass percentage of ammonium polyphosphate was 12%, and the mass percentage of isocyanate curing agent CR-40S was 3%.

[0035] (2) Soak 5 g of cotton fabric in 100 g of the functional treatment solution prepared in step (1) and stir for 30 min. Take it out and dry it at 150 °C. Then stir it in deionized water for 10 min to remove unreacted components and obtain modified cotton fabric.

[0036] Figure 1 The image shows a scanning electron microscope (SEM) image of the modified cotton fabric prepared in this embodiment. A distinct rough coating can be observed on the surface of the cotton fabric.

[0037] The contact angles of the modified cotton fabric prepared in this embodiment with water and soybean oil in air were tested, and the results are as follows: Figure 2 , Figure 3 As shown, water droplets on the modified cotton fabric surface spread completely in just 0.5 s ( Figure 2 It exhibits superhydrophilicity, with a contact angle greater than 150º for oil droplets (soybean oil). Figure 3 This indicates that the modified cotton fabric prepared in this embodiment exhibits superhydrophilic-superoleophobic properties.

[0038] This embodiment tests the limiting oxygen index of the modified cotton fabric, and the results are as follows: Figure 4 As shown, the limiting oxygen index of the modified cotton fabric is 33%. Therefore, the modified cotton fabric prepared in this embodiment exhibits excellent flame retardancy.

[0039] In addition, the modified cotton fabric prepared in this embodiment was subjected to an accelerated washing test (equivalent to 50 standard household washes) according to AATCC 61-2006 standard. After washing, the fabric surface still maintained a clear coating structure. Figure 6 The water contact angle remains 0°. Figure 7 The contact angle of soybean oil is still greater than 150°. Figure 8 The vertical burning test showed that it was still self-extinguishing and the char length was ≤8 cm. Figure 9 This indicates that the coating has excellent water-wash resistance and durability.

[0040] Example 2: This example relates to the preparation of a superhydrophilic-superoleophobic flame-retardant cotton fabric. The only difference from Example 1 is that the mass ratio of ammonium polyphosphate (degree of polymerization <20) in the functional treatment solution is 5%, and all other conditions are the same, and the corresponding modified cotton fabric is prepared.

[0041] 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 complete spreading time of water was 0.50 s, and the contact angle of soybean oil was greater than 150º, exhibiting superhydrophilic-superoleophobic 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 of the modified cotton fabric was 25%.

[0042] Example 3: This example relates to the preparation of a superhydrophilic-oleophobic flame-retardant cotton fabric. The only difference from Example 1 is that the mass ratio of ammonium polyphosphate (degree of polymerization <20) in the functional treatment solution is 20%, and all other conditions are the same, and the corresponding modified cotton fabric is prepared.

[0043] 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 complete spreading time of water was 1.2 s, and the contact angle of soybean oil was 142º, 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 of the modified cotton fabric was 35%.

[0044] Example 4: This example relates to the preparation of a superhydrophilic-oleophobic flame-retardant cotton fabric. The only difference from Example 1 is that the mass ratio of isocyanate curing agent CR-40S in the functional treatment liquid is 0.5%, and all other conditions are the same, and the corresponding modified cotton fabric is prepared.

[0045] 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 complete spreading time of water was 0.5 s, and the contact angle of soybean oil was 125º, 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 of the modified cotton fabric was 22%.

[0046] Example 5: This example relates to the preparation of a superhydrophilic-oleophobic flame-retardant cotton fabric. The only difference from Example 1 is that the mass ratio of isocyanate curing agent CR-40S in the functional treatment liquid is 5%, and all other conditions are the same, and the corresponding modified cotton fabric is prepared.

[0047] 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 complete spreading time of water was 2.5 s, and the contact angle of soybean oil was 138º, 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 of the modified cotton fabric was 33%.

[0048] Example 6: This example relates to the preparation of a superhydrophilic-superoleophobic flame-retardant cotton fabric. The only difference from Example 1 is that the hydrophilic nanoparticles are silica nanoparticles. All other conditions are the same, and the corresponding modified cotton fabric is prepared.

[0049] 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 complete spreading time of water was 0.5 s, and the contact angle of soybean oil was greater than 150º, exhibiting superhydrophilic-superoleophobic 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 of the modified cotton fabric was 35%.

[0050] Example 7: This example relates to the preparation of a superhydrophilic-oleophobic flame-retardant cotton fabric. The only difference from Example 1 is that the drying temperature in step (2) is 100 ℃, and the other conditions are the same, and the corresponding modified cotton fabric is prepared.

[0051] 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 complete spreading time of water was 0.5 s, and the contact angle of soybean oil was 145º, exhibiting superhydrophilic-superoleophobic 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 of the modified cotton fabric was 29%.

[0052] Example 8: This example relates to the preparation of a superhydrophilic-superoleophobic flame-retardant cotton fabric. The only difference from Example 1 is that the drying temperature in step (2) is 180 ℃, and the other conditions are the same. The corresponding modified cotton fabric is prepared and the fabric surface turns yellow.

[0053] 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 spread completely in 0.5 s, and the contact angle of soybean oil was greater than 150º, exhibiting superhydrophilic-superoleophobic 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 of the modified cotton fabric was 33%.

[0054] Example 9: This example relates to the preparation of a superhydrophilic-oleophobic flame-retardant cotton fabric. The only difference from Example 1 is that the mass ratio of hydrophilic titanium dioxide nanoparticles is 2%, the mass ratio of fluorinated surfactant FS-50 is 2%, and the mass ratio of hydrophilic titanium dioxide nanoparticles to fluorinated surfactant FS-50 is 1:1. All other conditions are the same, and the corresponding modified cotton fabric is prepared.

[0055] 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 complete spreading time of water was 0.6 s, and the contact angle of soybean oil was 123º, 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 of the modified cotton fabric was 34%.

[0056] Example 10: This example relates to the preparation of a superhydrophilic-superoleophobic flame-retardant cotton fabric. The only difference from Example 1 is that the mass ratio of hydrophilic titanium dioxide nanoparticles is 0.67%, the mass ratio of fluorinated surfactant FS-50 is 3.33%, and the mass ratio of hydrophilic titanium dioxide nanoparticles to fluorinated surfactant FS-50 is 1:5. All other conditions are the same, and the corresponding modified cotton fabric is prepared.

[0057] 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 complete spreading time of water was 0.5 s, and the contact angle of soybean oil was greater than 150º, exhibiting superhydrophilic-superoleophobic 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 of the modified cotton fabric was 30%.

[0058] Comparative Example 1: This comparative example relates to the preparation of a superhydrophilic-superoleophobic cotton fabric. The only difference from Example 1 is that ammonium polyphosphate was not added, while all other conditions were the same, and the corresponding modified cotton fabric was prepared.

[0059] 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 complete spreading time of water was 0.1 s, and the contact angle of soybean oil was greater than 150º, exhibiting superhydrophilic-superoleophobic 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 of the modified cotton fabric was 18%.

[0060] Comparative Example 2: This comparative example relates to the preparation of a superhydrophilic-oleophilic flame-retardant cotton fabric. The only difference from Example 1 is that the isocyanate curing agent CR-40S was not added, while all other conditions were the same, and the corresponding modified cotton fabric was prepared.

[0061] 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 time for water to spread completely was 1.0 s, and the contact angle for soybean oil was 0º, 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 of the modified cotton fabric was 20%.

[0062] Comparative Example 3: This comparative example relates to the preparation of a superhydrophilic-oleophobic flame-retardant cotton fabric. The only difference from Example 1 is that hydrophilic titanium dioxide nanoparticles were not added, while all other conditions were the same, and the corresponding modified cotton fabric was prepared.

[0063] 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 complete spreading time of water was 2.7 s, and the contact angle of soybean oil was 138º, 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 of the modified cotton fabric was 30%.

[0064] Comparative Example 4: This comparative example relates to the preparation of a superhydrophilic-oleophobic flame-retardant cotton fabric. The only difference from Example 1 is that the mass ratio of ammonium polyphosphate in the functional treatment solution is 2%, and all other conditions are the same. The corresponding modified cotton fabric was prepared.

[0065] 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 complete spreading time of water was 0.5 s, and the contact angle of soybean oil was 140º, 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 of the modified cotton fabric was 22%.

[0066] Comparative Example 5: This comparative example relates to the preparation of a superhydrophilic-oleophilic flame-retardant cotton fabric. The only difference from Example 1 is that the mass ratio of ammonium polyphosphate in the functional treatment solution is 40%, and all other conditions are the same, and the corresponding modified cotton fabric is prepared.

[0067] 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 complete spreading time of water was 3.5 s, and the contact angle of soybean oil 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 of the modified cotton fabric was 36%.

[0068] Comparative Example 6: This comparative example relates to the preparation of a superhydrophilic-superoleophilic flame-retardant cotton fabric. The only difference from Example 1 is that the drying temperature in step (2) is 60°C, and the other conditions are the same, and the corresponding modified cotton fabric is prepared.

[0069] 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 complete spreading time of water was 0.6 s, and the contact angle of soybean oil was 0º, exhibiting superhydrophilic-superoleophilic 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 of the modified cotton fabric was 20%.

[0070] Comparative Example 7: This comparative example relates to the preparation of a superhydrophilic-superoleophilic flame-retardant cotton fabric. The only difference from Example 1 is that an equal amount of siloxane coupling agent vinylsilane is used to replace the isocyanate curing agent CR-40S. All other conditions are the same, and the corresponding modified cotton fabric is prepared.

[0071] 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 complete spreading time of water was 0.8 s, and the contact angle of soybean oil was 0º, exhibiting superhydrophilic-superoleophilic 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 of the modified cotton fabric was 20%.

[0072] Comparative Example 8: This comparative example relates to the preparation of a superhydrophilic-superoleophilic flame-retardant cotton fabric. The only difference from Example 1 is that an equal amount of melamine polyphosphate is used to replace ammonium polyphosphate, while all other conditions are the same, and the corresponding modified cotton fabric is prepared.

[0073] This comparative example could not prepare a stable functional solution. Melamine polyphosphate was difficult to wet in a water / ethanol mixed solvent and could not be uniformly dispersed in the solvent. After ultrasonic dispersion, it formed flocculent aggregates, which quickly settled after standing and could not uniformly adhere to the cotton fiber surface. The contact angles of water and oil on the modified cotton fabric surface were tested. The results showed that water spread completely in 1.5 s, while the contact angle of soybean oil was 0º, exhibiting superhydrophilic-superoleophilic 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 of the modified cotton fabric was 22%.

[0074] Comparative Example 9: This comparative example relates to the preparation of a superhydrophilic-superoleophilic flame-retardant cotton fabric. The only difference from Example 1 is that an equal amount of ammonium polyphosphate with a degree of polymerization ≥1000 is used instead of ammonium polyphosphate with a degree of polymerization <20. All other conditions are the same, and the corresponding modified cotton fabric is prepared.

[0075] This comparative example could not prepare a stable functional solution. The highly polymerized ammonium polyphosphate was difficult to wet in a water / ethanol mixed solvent and could not be uniformly dispersed. After ultrasonic dispersion and standing, it rapidly settled and could not uniformly adhere to the cotton fiber surface. The contact angles of water and oil on the modified cotton fabric surface were tested. The results showed that water spread completely in 1.6 s, while the contact angle of soybean oil was 0º, exhibiting superhydrophilic-superoleophilic 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 of the modified cotton fabric was 18%.

[0076] The test results of the modified cotton fabrics prepared in the above embodiments and comparative examples regarding the contact angles of water and oil in air and the limiting oxygen index are summarized in the table below. In the table, A:B represents the mass ratio of hydrophilic nanoparticles to fluorinated surfactants.

[0077] As shown in the table above, this invention successfully prepared modified cotton fabrics with both excellent flame retardant properties and superhydrophilic-oleophobic (superoleophobic) properties through a one-step impregnation method. Examples 1-3 and Comparative Examples 1, 4, and 5 show that the amount of ammonium polyphosphate added as a flame retardant affects the flame retardancy of the modified cotton fabric. Too little addition significantly reduces the limiting oxygen index (LOI) of the modified cotton fabric, while too much addition does not significantly improve the LIO and instead affects the hydrophilic and oleophobic properties of the modified cotton fabric. When the addition amount increases to 40%, the prepared modified cotton fabric becomes oleophilic. Therefore, to obtain modified cotton fabrics with both high flame retardancy and superhydrophilic-oleophobic properties, the amount of ammonium polyphosphate added as a flame retardant needs to be controlled within a suitable range, more preferably within the range of 5 wt%-20 wt%.

[0078] As shown in Examples 1, 4, 5 and Comparative Example 2, the amount of curing agent added directly affects the flame retardant, hydrophilic, and oleophobic properties of the prepared modified cotton fabric. Insufficient addition leads to insufficient stability of the functional layer, and some functional components are removed after washing, resulting in a significant decrease in oleophobic properties. The modified cotton fabric prepared without the curing agent (Comparative Example 2) directly transforms into an oleophilic fabric. However, the modified cotton fabric prepared with excessive curing agent (e.g., in Example 5) exhibits a decrease in hydrophilic-oleophobic properties compared to Example 1.

[0079] Furthermore, as shown in Examples 1, 7, 8 and Comparative Example 6, if the drying temperature is too low, the curing agent cannot unblock and release isocyanate groups for crosslinking, resulting in the prepared functional layer failing to bond stably to the surface of the cotton fabric. After washing, the functional layer falls off, and the prepared modified cotton fabric remains oleophilic with a significant decrease in flame retardancy. However, if the drying temperature is too high, it will affect the mechanical properties of the cotton fabric and cause the fabric to yellow.

[0080] As can be seen from Example 1 and Comparative Examples 7-9, the type of flame retardant, degree of polymerization, and type of crosslinking agent directly affect whether the formed functional coating has high flame retardancy and oleophobic properties. When melamine polyphosphate or high-polymerization-degree ammonium polyphosphate is used to replace low-polymerization-degree ammonium polyphosphate to prepare functional coatings, the resulting modified cotton fabric has poor flame retardancy and is still oleophilic. The modified cotton fabric (Comparative Example 7) prepared by using the silane coupling agent vinylsilane to replace the isocyanate curing agent CR-40S has similar problems. It is speculated that this is because vinylsilane does not contain active groups that react with the system and cannot play a crosslinking anchoring role.

[0081] 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 equivalent to 5 standard household washes. The test results are shown in the table below:

[0082] As shown in the table above, the 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 by Comparative Example 2 without adding curing agent and Comparative Example 9 using high-polymerization degree ammonium polyphosphate, after only 5 washes, the limiting oxygen index of the modified cotton fabric is consistent with that of the cotton fabric without flame retardant modification (Comparative Example 1).

[0083] 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 superhydrophilic-oleophobic flame-retardant cotton fabric, characterized in that, Includes the following steps: S1. Hydrophilic nanoparticles, ammonium polyphosphate, fluorinated surfactant and curing agent are dispersed in a solvent to obtain a functional treatment solution; The degree of polymerization of the ammonium polyphosphate is less than 50, and the mass percentage of ammonium polyphosphate in the functional treatment liquid is 5 wt%-35 wt%; the fluorosurfactant is a fully ionic fluorocarbon surfactant; and the curing agent is a capped polyisocyanate. In the functional treatment liquid, the mass percentage of hydrophilic nanoparticles is 0.5 wt%-5 wt%, the mass percentage of fluorosurfactant is 0.5 wt%-5 wt%, the mass percentage of curing agent is 0.5 wt%-5 wt%, and the mass ratio of the hydrophilic nanoparticles to the fluorosurfactant is (1:5)-(1:1). S2. Immerse the cotton fabric in the functional treatment solution, stir until fully absorbed, remove the cotton fabric and dry it to obtain the superhydrophilic-oleophobic flame-retardant cotton fabric; the drying temperature is not lower than 100 ℃.

2. The preparation method according to claim 1, characterized in that, In step S1, the hydrophilic nanoparticles are selected from one or more of titanium dioxide nanoparticles, silicon dioxide nanoparticles, zinc oxide nanoparticles, and aluminum oxide nanoparticles. And / or, the fluorocarbon surfactant is selected from one or more of anionic fluorocarbon surfactants, cationic fluorocarbon surfactants, and amphoteric fluorocarbon surfactants; And / or, the solvent is water or a mixture of water and an alcohol solvent.

3. The preparation method according to claim 2, characterized in that, In step S1, the hydrophilic nanoparticles have a particle size of 10 nm-200 nm; And / or, the degree of polymerization of the ammonium polyphosphate is less than 20; And / or, the fluorocarbon surfactant is fluorocarbon surfactant FS-50; And / or, the curing agent is an isocyanate curing agent CR-40S; And / or, the alcohol solvent is ethanol.

4. The preparation method according to claim 1, characterized in that, In step S1, the dispersion method is ultrasonic dispersion, and the ultrasonic dispersion power is 50-600 W, and the time is 30-120 min.

5. The preparation method according to claim 1, characterized in that, In step S2, the mass ratio of the cotton fabric to the functional treatment liquid is 1:(10-50). And / or, the stirring time is 10-90 min.

6. The preparation method according to claim 1, characterized in that, In step S2, the drying process is carried out at a temperature of 100-180 ℃ for 3-60 min.

7. A superhydrophilic-oleophobic flame-retardant cotton fabric, characterized in that, The superhydrophilic-oleophobic flame-retardant cotton fabric, prepared by any one of claims 1-6, comprises a cotton fabric and a multifunctional coating disposed on the surface of the cotton fabric, wherein the multifunctional coating is anchored to the surface of the cotton fabric by chemical bonds.

8. The superhydrophilic-oleophobic flame-retardant cotton fabric according to claim 7, characterized in that, The superhydrophilic-oleophobic flame-retardant cotton fabric has a water contact angle of 0° and a complete spreading time of ≤2.5 s; And / or, the superhydrophilic-oleophobic flame-retardant cotton fabric has a contact angle with oil greater than 120°; And / or, the limiting oxygen index of the superhydrophilic-oleophobic flame-retardant cotton fabric is ≥22%.

9. The application of a superhydrophilic-oleophobic flame-retardant cotton fabric prepared by any one of claims 1-6 in flame-retardant protective clothing, oil-water separation membranes, or self-cleaning textiles.

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