Method for preparing super hydrophobic flame retardant flexible material using water-dispersible nanocellulose composite

Abstract

The present invention relates to the technical field of hydrophobic flame-retardant materials, and discloses a method for preparing a superhydrophobic flame-retardant flexible material from a water-dispersed nanocellulose composite, comprising the following steps: a nanocellulose suspension; synthesizing silica nanoparticles; preparing a precursor suspension: mixing SiO2 nanoparticles, methyltrimethoxysilane and the nanocellulose suspension in proportion and reacting to obtain a precursor suspension; preparing a polyvinyl alcohol solution; preparing a water-dispersible plant nanocellulose composite mixture and performing a freezing treatment; subjecting the material after the freezing treatment to freeze-drying treatment and heat treatment to obtain a superhydrophobic flame-retardant flexible material. The method for preparing a superhydrophobic flame-retardant flexible material from the water-dispersed nanocellulose composite according to the present invention has a green and pollution-free material preparation process, and the prepared flexible material has characteristics such as high elasticity, high oil absorption, reusability, fire resistance, and degradability, and can be applied to various fields.

Description

Technical Field

[0001] The invention relates to the technical field of hydrophobic flame retardant materials, in particular to a method for preparing a super hydrophobic flame retardant flexible material with a water-dispersed nano cellulose composite. Background Art

[0002] Organic pollutants have the characteristics of high toxicity, low solubility, and high persistence, which cause serious harm to aquatic organisms and human health. With the advancement of global industrialization, a large amount of organic pollutants are discharged into water bodies. Therefore, there is an urgent need to develop materials and methods that can effectively remove organic pollutants from water bodies. However, the preparation of most materials usually involves harmful or expensive precursors, complex processes and equipment, and there is an urgent need to find a green, environmentally friendly and economical way to solve this problem. Cellulose is the most abundant natural polymer material in nature. It has the advantages of being completely biodegradable, non-toxic, pollution-free, easy to modify, and good biocompatibility. However, hundreds of millions of tons of cellulose-rich biomass resources are directly crushed, buried or burned every year, causing serious waste of resources and environmental pollution. Corn stalks produced in agricultural production in my country are abundant, and the cellulose content in corn stalks is as high as 32%. Therefore, how to turn waste into treasure and use corn and other crop straws efficiently and at low cost has become a research and development hotspot in the field of biomass resource utilization in countries around the world.

[0003] Silicon dioxide (SiO 2 ) is an inorganic compound that is ubiquitous in nature and is widely used in industry mainly for its stable physical and chemical properties. In addition, it also has the advantages of high fire resistance, high temperature resistance, insulation, corrosion resistance, piezoelectricity, resonance and optical properties. In the present invention, nano-scale SiO 2 It is synthesized with tetraethyl orthosilicate as silicon source and ammonia water as catalyst. Nanocellulose (CNF) has the advantages of wide source, renewable, rich in hydroxyl, stable structure, biodegradable, and strong biocompatibility. In the present invention, CNF is obtained from agricultural and forestry wastes by hot solvent pretreatment, low eutectic solvent separation, sodium chlorite solution bleaching, and high-intensity ultrasonic treatment. Methyltrimethoxysilane (MTMS) is an organic silicon compound with excellent heat resistance, chemical stability, adhesion, hydrophobicity, and surface activity. In the water-dispersible plant nanocellulose composite of the present invention, a large amount of nano-scale SiO 2 Wrapped on the surface of CNF to form a covering layer, it will become a barrier between the subsequent condensed phase and the flame to isolate oxygen and achieve a flame retardant effect; MTMS can react with CNF and SiO 2The hydroxyl groups on the surface form strong chemical bonds, enhancing their adhesion and completing hydrophobic modification; the addition of polyvinyl alcohol (PVA) will improve the composite and dispersibility of the above materials in water, greatly enhancing the flexibility and mechanical stability of the materials; the three-dimensional ultra-porous structure formed by the super-hydrophobic flame-retardant flexible material prepared by freeze-drying will diffuse the heat, making it impossible to focus, reducing the heat fed back to the material, thereby inhibiting its own thermal cracking and combustion reactions, achieving complete combustion to remove internal pollutants and continuing the purpose of recycling.

[0004] Most hydrophobic materials are organic dispersion systems before molding, or are prepared by further treating hydrophilic materials with hydrophobic modified solutions (generally in organic solvents). The present invention uses water instead of organic solvents as a dispersion medium to obtain a water-dispersible plant nanocellulose composite, and then prepares a super-hydrophobic flame-retardant flexible material with rich pores. The material has the characteristics of high elasticity, high porosity, low density, high oil absorption, high throughput, reusability, fire resistance, and degradability. The preparation process is green and pollution-free, and better avoids safety hazards such as air pollution and fire caused by the volatilization of organic solvents. Compared with organic solvents, water resources are more abundant and easy to obtain, and in the preparation process of super-hydrophobic flame-retardant flexible materials, resources and costs can be greatly saved. Accordingly, the present invention proposes a method for preparing a super-hydrophobic flame-retardant flexible material using a water-dispersible plant nanocellulose composite and its application. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a super-hydrophobic flame-retardant flexible material from a water-dispersible nanocellulose composite. The material preparation process is green and pollution-free, and the prepared flexible material has the characteristics of high elasticity, high oil absorption, reusability, fire resistance, degradability, etc., and can be applied to a variety of fields.

[0006] To achieve the above object, the present invention provides a method for preparing a super-hydrophobic flame-retardant flexible material by using a water-dispersible nanocellulose composite, comprising the following steps:

[0007] Step 1, nanocellulose CNF suspension;

[0008] Step 2: Synthesis of silica nanoparticles SiO 2 NPS;

[0009] Step 3, preparation of precursor suspension CSM: SiO 2 Nanoparticles, methyltrimethoxysilane MTMS and nanocellulose suspension are mixed in proportion and reacted to obtain a precursor suspension CSM;

[0010] Step 4, preparing a polyvinyl alcohol (PVA) solution: adding PVA solid to deionized water, heating and stirring at 85° C. until completely dissolved, to obtain a PVA solution;

[0011] Step 5, preparing a water-dispersible plant nanocellulose composite CSM-PVA mixed solution: blending the materials prepared in step 3 and step 4 to prepare a CSM-PVA mixed solution, and freezing the mixture;

[0012] Step 6, freeze-drying the frozen material, and then placing it in an oven for heat treatment to obtain a super hydrophobic flame retardant flexible material.

[0013] Furthermore, the preparation method of the nanocellulose CNF suspension in step 1 is: the straw raw material is prepared by hot solvent pretreatment, low eutectic solvent separation, sodium chlorite solution bleaching, and high-intensity ultrasonic treatment; the concentration of the nanocellulose CNF suspension is 0.95~1.05 wt%.

[0014] Furthermore, the specific operation of step 2 is: anhydrous ethanol, deionized water and ammonia water are mixed, and a solution A is prepared after ultrasonic treatment; tetraethyl orthosilicate TEOS and anhydrous ethanol are mixed, and a solution B is prepared after ultrasonic treatment; at 45°C, the solution A is slowly poured into the solution B twice in a ratio of 3 / 4 and 1 / 4, and every 1 hour, after the reaction is completed, centrifuge, rinse with deionized water and ethanol, and dry to obtain SiO 2 Nanoparticles.

[0015] Further, in step 3, the nanocellulose suspension: SiO 2 The mass ratio of nanoparticles: methyltrimethoxysilane is 3.70~3.80 g: 0.025~0.031 g: 0.9~1.1 g.

[0016] Furthermore, the concentration of the PVA solution in step 4 is 9.5-10.5 mg / mL.

[0017] Furthermore, the specific operation of step 5 is: the precursor suspension CSM and the PVA solution are blended in proportion, and mechanically stirred at a speed of 1950-2050 rpm for 4-6 min to obtain a water-dispersible plant nanocellulose composite CSM-PVA mixed solution.

[0018] Furthermore, the dosage ratio of the precursor suspension CSM and the PVA solution is (1-5): (1-5).

[0019] The present invention also provides a super-hydrophobic flame-retardant flexible material prepared by the method.

[0020] The present invention also provides application of the super-hydrophobic flame-retardant flexible material in separation of oily wastewater and emulsion.

[0021] The present invention also provides the use of the super-hydrophobic flame-retardant flexible material in flame retardancy, circulating oil adsorption, and combustion desorption.

[0022] The advantages and positive effects of the method for preparing super-hydrophobic flame-retardant flexible materials using the water-dispersible nanocellulose composite of the present invention are:

[0023] 1. The present invention uses water as a dispersion medium, and the preparation process of the super hydrophobic flame retardant flexible material is non-toxic, environmentally friendly, green and pollution-free, and better avoids the potential safety hazards such as air pollution and fire caused by the volatilization of organic solvents. Compared with organic solvents, water resources are more abundant and easy to obtain, which can greatly save the preparation cost of super hydrophobic flame retardant flexible materials.

[0024] 2. SiO in the present invention 2 After the silanol groups of cellulose are combined with the hydroxyl groups of cellulose, a large amount of nano-sized SiO 2 The superhydrophobic flame-retardant flexible material will form a covering layer on the surface of CNF, which will become a barrier between the subsequent condensed phase and the flame to isolate oxygen and achieve a flame retardant effect. At the same time, the three-dimensional ultra-porous structure of the super-hydrophobic flame-retardant flexible material will diffuse the heat, making it impossible to focus, reducing the heat fed back to the material, thereby inhibiting its own thermal cracking and combustion reactions, achieving complete combustion to remove internal pollutants and continue to recycle.

[0025] 3. MTMS, CNF and SiO in the present invention 2 The hydroxyl groups on the surface form strong chemical bonds, enhancing their adhesion and completing hydrophobic modification. The addition of polyvinyl alcohol (PVA) improves the composite and dispersibility of the above materials in water. Freeze-drying and further heat treatment give the materials excellent superhydrophobicity, flame retardancy, flexibility and mechanical stability.

[0026] 4. The super hydrophobic flame retardant flexible material of the present invention has extremely high specific surface area and porosity, and the adsorption capacity of the super hydrophobic flame retardant flexible material is very considerable. Therefore, the material is very suitable for purification of oil-containing water bodies, and has the advantages of stable structure, low cost, environmental friendliness, and convenient carrying.

[0027] 5. The three-dimensional super-porous structure of the super-hydrophobic flame-retardant flexible material in the present invention is conducive to the rapid diffusion and flow of liquid molecules, and its continuous channels also make its adsorption process more efficient; in the field of oil spill wastewater treatment, it can selectively and quickly absorb, store and transport oil, greatly improving the material's purification ability and separation efficiency for oily wastewater.

[0028] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a flow chart for preparing the CSM-PVA super-hydrophobic flame-retardant flexible material in an embodiment of the present invention;

[0030] Figure 2 CSM-PVA in the embodiment of the present invention6 The proportion of each component in water-dispersible plant nanocellulose composites;

[0031] Figure 3 The contact angle images of the surfaces of 9 CSM-PVA super-hydrophobic flame-retardant flexible materials prepared by the present invention in air, wherein (a) is the water contact angle, and (b) is the oil contact angle;

[0032] Figure 4 A in Figure 3 9 CSM-PVA super-hydrophobic flame-retardant flexible material surface contact angle bar graph, B is CSM-PVA in air 6 Changes in water contact angle of super hydrophobic flame retardant flexible material within 6 minutes;

[0033] Figure 5 CSM-PVA 6 Scanning electron microscope (SEM) images at different magnifications, where (a) is 100 times magnification, (b) is 500 times magnification, (c) is 5000 times magnification, and (d) is 30000 times magnification;

[0034] Figure 6 CSM-PVA 6 The super-hydrophobic flame-retardant flexible material is placed in the oil and water of the mixed liquid, where (a) is in the oil, (b) is in the water, and (c) is an enlarged view of point ① in (b);

[0035] Figure 7 (a) shows the effect of oil droplets and water droplets on the surface of unheat-treated CSM-PVA material, and (b) shows the effect of oil droplets and water droplets on the surface of heat-treated CMS-PVA. 6 The effect of the surface of super hydrophobic flame retardant flexible material, (c) oil droplets and water droplets on CMS-PVA prepared by heat treatment 6 The rendering of the interior of the super-hydrophobic flame-retardant flexible material, with red representing oil droplets and blue representing water droplets;

[0036] Figure 8 CMS-PVA prepared in the embodiment of the present invention 6 Manual compression rebound performance test of super hydrophobic flame retardant flexible material, where (a) is before compression, (b) is during compression, and (c) is after compression;

[0037] Fig. 9 Place the weight on CMS-PVA 6 Compression rebound performance test was carried out on the super hydrophobic flame retardant flexible material, where (a) is before the test and (b) is after the test;

[0038] Fig.10 CMS-PVA prepared in the embodiment of the present invention 6Results of 30 cycles of compression test of super hydrophobic flame retardant flexible material at 80% strain;

[0039] Fig.11 CMS-PVA for universal testing machine 6 Test of super hydrophobic flame retardant flexible material, where (a) is before the test; (b) is after the test;

[0040] Fig.12 Universal testing machine for CMS-PVA in wet state 6 Test of super hydrophobic flame retardant flexible material, where (a) is before the test; (b) is after the test;

[0041] Fig.13 CMS-PVA for oil 6 Photo of water rolling down the surface of a superhydrophobic flame-retardant flexible material;

[0042] Fig.14 CMS-PVA prepared in the embodiment of the present invention 6 Super hydrophobic flame retardant flexible material adsorbs n-hexane and chloroform in water, where (a) is n-hexane, ① is before adsorption, ② is after adsorption; (b) is chloroform, ③ is before adsorption, ④ is after adsorption;

[0043] Fig.15 To drive the CSM-PVA via a peristaltic pump 6 Super hydrophobic flame-retardant flexible materials for oil-water separation, where (a) is n-butane / water, ① is before separation, ② is after separation; (b) is chloroform / water, ③ is before separation, ④ is after separation; (c) is dichloromethane / water, ⑤ is before separation, ⑥ is after separation; (d) is dichloroethane / water, ⑦ is before separation, ⑧ is after separation;

[0044] Fig.16 Gravity-driven filtration device for oil-water separation, where (a) is the oil-water separation device and (b) is the CSM-PVA 6 The separation flux and separation efficiency of super hydrophobic flame retardant flexible materials for n-hexane / water, dichloroethane / water, dichloromethane / water and chloroform / water mixtures. (c) is the oil-water separation model diagram;

[0045] Fig.17 CSM-PVA prepared in the present invention 6 Separation flux and efficiency of super hydrophobic flame retardant flexible material after 12 times of chloroform / water mixture test;

[0046] Fig.18 CSM-PVA prepared in the present invention 5 、CSM-PVA 6 and CSM-PVA 7Adsorption capacity of superhydrophobic flame-retardant flexible materials for various oils (chloroform, ethylene dichloride, dichloromethane, and hexane);

[0047] Fig.19 This is a test effect diagram of a gravity-driven filtering device in an embodiment of the present invention;

[0048] Fig. 20 The effect diagram of the gravity-driven filtration device for oil-in-water emulsion separation in the embodiment of the present invention, wherein (a) is dichloromethane, ① is the effect before separation, ② is the effect after separation; (b) is chloroform, ③ is the effect before separation, ④ is the effect after separation; (c) is dichloroethane, ⑤ is the effect before separation, ⑥ is the effect after separation; (d) is n-hexane, ⑦ is the effect before separation, ⑧ is the effect after separation;

[0049] Fig.21 CSM-PVA prepared in the present invention 6 Separation flux and efficiency of superhydrophobic flame-retardant flexible materials for four oil-in-water emulsions (ethylene dichloride / water, dichloromethane / water, chloroform / water, and hexane / water);

[0050] Fig. 22 CSM-PVA prepared in the present invention 6 Separation flux and efficiency of super hydrophobic flame retardant flexible materials after 10 times of dichloroethane water emulsion test;

[0051] Fig.23 CSM-PVA prepared in the present invention 6 Flame retardant performance test of super hydrophobic flame retardant flexible material in air, (a) before combustion, (b) after 4s combustion, (c) after 6s combustion, (d) after 8s combustion;

[0052] Fig.24 (a) shows the unextruded CSM-PVA under the saturated state of n-hexane adsorption 6 Flame retardant performance test of super hydrophobic flame retardant flexible material in air, ① before combustion, ② after combustion; (b) CSM-PVA after extrusion under hexane adsorption saturation state 6 Flame retardant performance test of super hydrophobic flame retardant flexible material in air, ③ is before combustion, ④ is after combustion;

[0053] Fig.25 CSM-PVA after oil absorption 6 Flame retardant performance test of super hydrophobic flame retardant flexible material in a vial, where (a) is before combustion, (b) is after 60 seconds of combustion, (c) is after 120 seconds of combustion, and (d) is after 160 seconds of combustion;

[0054] Fig.26 CSM-PVA prepared in the present invention 6Adsorption-combustion-desorption cycle performance test of super hydrophobic flame-retardant flexible materials;

[0055] Fig. 27 CSM-PVA prepared in the present invention 6 Comparison of the super-hydrophobic flame-retardant flexible material before and after 10 adsorption-combustion-desorption cycle tests, where (a) is before the test and (b) is after the test;

[0056] Fig.28 CSM-PVA prepared in the present invention 6 Contact angles of superhydrophobic flame-retardant flexible materials to liquids of different pH values. DETAILED DESCRIPTION

[0057] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0058] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0059] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention. The experimental methods without specific conditions in the following examples are usually measured in accordance with national standards. The experimental instruments, equipment and reagents without source indication in the following examples are all commercially available raw materials.

[0060] Unless otherwise defined or described, all professional and scientific terms used in the present invention have the same meanings as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to those described herein can be applied to the method of the present invention. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0061] Example 1

[0062] A method for preparing a nanocellulose suspension comprises the following steps:

[0063] (1) Thermal solvent treatment: 5 g corn straw powder, wheat straw powder, poplar wood powder or pine wood powder was mixed with 30 mL anhydrous ethanol, 15 mL deionized water and 190 μL concentrated sulfuric acid, stirred evenly and placed in a reactor for heat treatment at 185 °C for 90 min. After the reaction was complete, the reactor was taken out and continuously rinsed with a small stream of water until it reached room temperature. After cooling, the reactants in the reactor were taken out and rinsed with 65% ethanol solution until neutral. The reactants were filtered with a funnel, and the ethanol was washed with deionized water. The solid powder of corn straw, wheat straw, poplar wood or pine wood was obtained after drying in an oven at 60 °C for 2 h.

[0064] (2) Preparation of deep eutectic solvent (DES): Choline chloride and oxalic acid were mixed in a mass ratio of 2.1:1.9 and heated at 80 °C for 1 h until a transparent solution was obtained to obtain a deep eutectic solvent (DES).

[0065] (3) High-temperature oil bath treatment: The corn stalk powder treated in step (1) and the low eutectic solvent in step (2) are mixed in a mass ratio of 1:20, stirred evenly, and placed in an oil bath pot. The mixture is reacted at 110 °C for 8 h and then cooled to room temperature. The residual solid is placed in a funnel and filtered, and then rinsed with deionized water and a small amount of anhydrous ethanol until the filtrate is completely transparent and clean.

[0066] (4) Sodium chlorite bleaching treatment: 3 g of the residual solid after treatment in step (3) was mixed with 100 mL of 1.5-2 wt% sodium chlorite solution, and the pH of the solution was adjusted to 3 using glacial acetic acid (300 μL). The solution was placed in a water bath at a constant temperature of 80 °C and magnetically stirred for 1 h. Finally, the residual solid after bleaching was placed in a funnel for suction filtration, and then rinsed with deionized water until the filtrate was completely transparent and clean, thereby obtaining a high-purity cellulose solid powder.

[0067] (5) High-intensity ultrasonic treatment: 1 g of the high-purity cellulose solid powder obtained in step (4) was uniformly dispersed in 99 mL of deionized water, and then subjected to high-intensity ultrasonic treatment in an ultrasonic cell disruptor (900 W) for 30 min to obtain a 1 wt% nanocellulose suspension.

[0068] Example 2

[0069] Another method for preparing a nanocellulose suspension comprises the following steps:

[0070] (1) Sodium chlorite bleaching treatment: Take 5 g corn straw, wheat straw, poplar wood powder or pine wood powder, mix it with 150 mL sodium chlorite solution (1.5 wt%), use glacial acetic acid (300 μL) to adjust the pH of the above solution to 3, and keep stirring for 6 h at a constant temperature of 80 °C in a water bath. During the reaction, add 300 μL glacial acetic acid and 0.2 g sodium chlorite solid to the above mixture every 1 h. Finally, the residual solid after bleaching is placed in a funnel for suction filtration, and then rinsed with deionized water until the filtrate is completely transparent and clean, to obtain bleached corn straw, wheat straw, poplar wood powder or pine wood powder solid powder.

[0071] (2) Thermal solvent treatment: The bleached corn straw powder, wheat straw powder, poplar wood powder or pine wood powder in step (1) is mixed with 45 mL of anhydrous ethanol, 15 mL of deionized water and 190 μL of concentrated sulfuric acid, stirred evenly and placed in a reactor for thermal treatment at 185°C for 90 min. After the reaction is complete, the reactor is taken out and continuously rinsed with a small stream of water until it reaches room temperature. After cooling, the reactants in the reactor are taken out and rinsed with a 65% ethanol solution until it is neutral. The reactants are filtered with a funnel, and the ethanol is washed off with deionized water. The solid powder of the treated corn straw, wheat straw, poplar wood or pine wood is obtained after drying in an oven at 60°C for 2 h.

[0072] (3) Further bleaching treatment: 10 mL of hydrogen peroxide (H 2 O 2 ) was mixed evenly with 45 mL of NaOH solution (1 wt%), and then the residual solid in step (2) was added, followed by stirring and reacting for 90 min in a water bath at a constant temperature of 50 °C to complete the further removal of lignin and hemicellulose. Then, the residual solid was placed in a funnel for suction filtration, and then rinsed with deionized water until the filtrate was completely transparent and clean, to obtain a high-purity cellulose solid powder.

[0073] (4) High-intensity ultrasonic treatment: 1 g of the high-purity cellulose solid powder in step (4) was uniformly dispersed in 99 mL of deionized water, and then subjected to high-intensity ultrasonic treatment in an ultrasonic cell disruptor (900 W) for 30 min to obtain a 1 wt% nanocellulose suspension.

[0074] Example 3

[0075] A method for preparing a super-hydrophobic flame-retardant flexible material from a water-dispersible plant nanocellulose composite comprises the following steps:

[0076] S1. Prepare a nanocellulose suspension, as in Example 1 and Example 2.

[0077] S2, synthesis of silica nanoparticles (SiO 2 NPS).

[0078] (1) Preparation of Solution A: Mix 4 mL of deionized water, 12 mL of aqueous ammonia, and 150 mL of anhydrous ethanol and treat with an ultrasonic cleaner for 15 min to obtain Solution A.

[0079] (2) Preparation of Solution B: Mix 6 mL of TEOS with 50 mL of anhydrous ethanol and ultrasonically treat the mixture for 25 min to obtain Solution B.

[0080] (3) Preparation of SiO 2NPS: Under the condition of magnetic stirring at a constant temperature of 45 ℃ in a water bath, ¾ of liquid A was slowly poured into liquid B and reacted for 1 h until the solution gradually became turbid. Then, the remaining liquid A was poured into the above solution and continued to react for 1 h. After the reaction was completed, centrifuged (speed 10300 r / min, 15 min), rinsed with deionized water and ethanol, repeated three times and dried (60 ℃, 6 h) to obtain SiO 2 Nanoparticles.

[0081] S3. Prepare precursor suspension CSM.

[0082] (1) Take 45 mL of CNF suspension (1 wt%) and 0.34 g SiO 2 NPS mixed well.

[0083] (2) Add 5 mL of CNF suspension and 6 mL of MTMS to the mixed solution in step (1), and stir continuously for 1 h at a constant temperature of 80 °C in a water bath to obtain a precursor suspension CSM.

[0084] S4. Prepare polyvinyl alcohol (PVA) solution.

[0085] 1 g of PVA solid was added into 99 mL of deionized water and stirred continuously for 1 h in a water bath at a constant temperature of 80 °C to prepare a 1 wt% PVA solution.

[0086] S5. Prepare water-dispersible plant nanocellulose composite (CSM-PVA mixed solution).

[0087] The precursor suspension CSM in step S3 and the PVA solution in step S4 are mixed and homogenized in accordance with the steps to prepare water-dispersible plant nanocellulose composites (CSM-PVA mixed solutions) with different proportions, and then the composites are transferred into a mold for freezing treatment.

[0088] S6. Preparation of superhydrophobic flame-retardant flexible materials using water-dispersible plant nanocellulose composites.

[0089] The composite in step S5 was freeze-dried for 48 h and then placed in an oven at a constant temperature of 100 °C for 3 h to obtain a biomass flame-retardant flexible material CSM-PVA with superhydrophobic and superoleophilic properties. The overall preparation process is shown in the following figure: Figure 1 shown.

[0090] Different biomass flame retardant flexible materials CSM-PVA were prepared by adjusting the ratio of the precursor suspension CSM and the PVA solution. The preparation method was the same as that in Example 3, except for the ratio of the precursor suspension CSM and the PVA solution.

[0091] The prepared biomass flame retardant flexible material CSM-PVA is shown in Table 1.

[0092] Table 1 Biomass flame retardant flexible material CSM-PVA

[0093] ;

[0094] Biomass flame retardant flexible material CSM-PVA 6 The proportions of the components are as follows Figure 2 shown.

[0095] Performance Testing

[0096] 1. Performance test of the prepared super hydrophobic flame retardant flexible material:

[0097] (1) Optimization of special wetting properties and structural stability of super hydrophobic flame retardant flexible material CSM-PVA:

[0098] ① The prepared CSM-PVA super-hydrophobic flame-retardant flexible material was heat-treated, and then the water contact angle and oil contact angle on its surface and inside were measured using a contact angle meter, proving the excellent super-hydrophobicity and super-oleophilicity of the CSM-PVA super-hydrophobic flame-retardant flexible material.

[0099] Figure 2 Super hydrophobic flame retardant flexible material CSM-PVA 6 The proportion of each component is shown in the fan-shaped chart. Among them, CNF suspension accounts for 37.41%; SiO 2 NPS accounts for 0.28%; MTMS accounts for 2.44%; PVA solution accounts for 59.86%. Super hydrophobic flame retardant flexible material CSM-PVA 6 The diameter is 10.24 mm, the height is 14.91 mm, the weight is 0.226 g, and the density is 0.046 g / cm -3 .

[0100] Figure 3 a is the CSM-PVA prepared by mixing the precursor suspension CSM and PVA solution in different proportions 1 、CSM-PVA 2 、CSM-PVA 3 、CSM-PVA 4 、CSM-PVA 5 、CSM-PVA 6 、CSM-PVA 7 、CSM-PVA 8 、CSM-PVA 9 Graph showing the water contact angle effect on the surface of superhydrophobic flame-retardant flexible material in air. Figure 3 b in the figure is CSM-PVA 1、CSM-PVA 2 、CSM-PVA 3 、CSM-PVA 4 、CSM-PVA 5 、CSM-PVA 6 、CSM-PVA 7 、CSM-PVA 8 、CSM-PVA 9 Oil contact angle effect of superhydrophobic flame-retardant flexible material surface in air. Figure 4 A in the middle is a bar graph of the water contact angle in air of superhydrophobic flame-retardant flexible materials made from water-dispersible plant nanocellulose composites in different proportions. Figure 4 B in the figure is CSM-PVA 6 The change of water contact angle of super hydrophobic flame retardant flexible material in air within 6 min shows that CSM-PVA 6 Superhydrophobic flame-retardant flexible materials have excellent superhydrophobic-superoleophilic properties.

[0101] ②CSM-PVA 6 Scanning electron microscope (SEM) images at different magnifications.

[0102] like Figure 5 As shown, CSM-PVA 6 The three-dimensional porous structure of CNF and PVA is interconnected through hydrogen bonding. This structure gives the material the advantages of high separation efficiency, flux and adsorption capacity. Figure 5 Middle (a) and middle (b)), CSM-PVA 6 The large and small pores are interlaced with each other to form a dense pore structure. Under 5000-30000 magnification ( Figure 5 In (c) and (d)), there are more SiO 2 NPs are semi-embedded on the surface of the structure through hydrogen bonding interactions between silanol and a large number of hydroxyl groups, which greatly enhances the interaction between molecules and improves the mechanical properties and structural stability of the flexible material. 2 NPs are wrapped around the surface of the structure to form a covering layer, which becomes a barrier between the subsequent condensed phase and the flame, isolating oxygen to achieve a flame retardant effect.

[0103] ③ Prepare CSM-PVA 6 The super-hydrophobic flame-retardant flexible material was placed in an oil-water mixture and water respectively to observe the necessary conditions for achieving oil-water separation and emulsion separation.

[0104] like Figure 6 As shown, CSM-PVA 6The super hydrophobic flame retardant flexible material is placed in an oil-water mixture (such as Figure 6 in (a)) or water (such as Figure 6 In (b), CSM-PVA 6 The super hydrophobic flame retardant flexible material always floats on the water surface or under the oil surface of the oil layer. 6 The rough surface structure and super-hydrophobicity of the super-hydrophobic flame-retardant flexible material make it appear a hydration layer that is completely isolated from water molecules when immersed in an aqueous solution. This shows that CSM-PVA 6 Superhydrophobic flame-retardant flexible materials have the advantages of ultra-light structure, superhydrophobicity, superoleophilicity, etc., and fully meet the expected necessary conditions for oil-water separation and emulsion separation.

[0105] ④ Comparison of CSM-PVA flexible material without heat treatment and CSM-PVA prepared by heat treatment 6 Surface and internal wettability of superhydrophobic flame-retardant flexible materials.

[0106] like Figure 7 As shown, (a) is the hydrophilic-lipophilic effect diagram of CSM-PVA flexible material without heat treatment, (b) and (c) are the hydrophilic-lipophilic effect diagram of CMS-PVA after heat treatment. 6 The super-hydrophobic and super-oleophilic effects of the surface and interior of the super-hydrophobic flame-retardant flexible material. 2 The CMS-PVA super-hydrophobic flame-retardant flexible material prepared by NPS and freeze-drying method has good rough structure and mechanical properties. Secondly, chemical modification of MTMS can generate silicon-oxygen bonds that are highly repellent to water molecules. That is, when MTMS comes into contact with the surface of a material rich in hydroxyl groups, the methyl and methoxy groups in MTMS will react with the hydroxyl groups on the surface of the material to form a silicon-oxygen bond covering layer, thereby making CMS-PVA 6 The surface and internal structure of the superhydrophobic flame-retardant flexible material produce excellent superhydrophobicity and corrosion resistance.

[0107] ⑤CSM-PVA 6 Compression rebound performance test of superhydrophobic flame retardant flexible materials under different conditions.

[0108] The mechanical properties of flexible materials are also important indicators for achieving oil-water separation. Figure 8 As shown, CMS-PVA 6 Super hydrophobic flame retardant flexible materials can achieve excellent rebound effect after multiple compressions. Fig. 9 As shown, a 200 g weight is placed on the CMS-PVA 6The upper surface of the super-hydrophobic flame-retardant flexible material can still rebound well after being kept for 60 s. In addition, the original height (H), radius (R), volume (V), mass (M), and density (P) of the flexible material are 14.91 mm, 10.24 mm, and 4.912 cm, respectively. 3 , 0.226 g, 0.046 g·cm -3 . For CMS-PVA 6 After the super-hydrophobic flame-retardant flexible material was subjected to a weight static pressure test for 60 s, the height, radius, volume, mass, and density of the flexible material changed very slightly, which were 14.80 mm, 10.26 mm, and 4.895 cm, respectively. 3 , 0.226 g, 0.0462 g·cm -3 It was calculated that the volume of the flexible material after compression for 60 s still remained at 99.65% of its original volume, while its density only increased by 0.43% compared with the original density.

[0109] like Fig.10 As shown, CMS-PVA was evaluated using a universal testing machine. 6 The cyclic stress-strain curve of the super hydrophobic flame retardant flexible material at a strain of 80% for 30 times. The maximum stress of the flexible material under 1, 5, 10, 15, 20, 25, and 30 cyclic compression-rebound tests are 88.8 kPa, 87.5 kPa, 76.5 kPa, 64.5 kPa, 60.9 kPa, 45.3 kPa, and 40 kPa, respectively. Fig.10 It can be seen that after 10 cycles of testing, the compressive strength did not decrease significantly, which means that the changes in the material structure during this stage were minimal. After 30 cycles of testing, its internal structure collapsed to a certain extent, resulting in a decrease in the overall compressive strength of the flexible material, but its appearance and structure remained good, showing good deformation recovery ability, which also provided an important basis for its application in the fields of oil-water separation and flame retardancy.

[0110] Fig.11 To measure CMS-PVA using a universal testing machine 6 The effect diagram of the compression-rebound performance test of super hydrophobic flame retardant flexible material. The material can quickly restore its original structure after compression. Fig.12 As shown, CMS-PVA 6 After being wetted with chloroform, the super-hydrophobic flame-retardant flexible material also has good compression resilience under 80% stress-strain conditions. This also shows that CMS-PVA 6 Super-hydrophobic flame-retardant flexible materials can achieve the circulation and continuous separation of oil-water mixtures through adsorption-extrusion.

[0111] (2) CSM-PVA 6 Tests on the oil-water separation performance of superhydrophobic flame-retardant flexible materials and the adsorption capacity of superhydrophobic flame-retardant flexible materials for various light oils and heavy oils at different ratios.

[0112] ①Observation of CSM-PVA 6 The dynamic contact angle of water under oil of superhydrophobic flame-retardant flexible material determines its excellent superhydrophobicity and anti-pollution properties.

[0113] like Fig.13 As shown, CSM-PVA 6 The superhydrophobic flame-retardant flexible material was placed in n-hexane, and water droplets dyed with methylene blue were continuously squeezed out of the needle. The needle was positioned under the oil and on the upper surface of the flexible material. It was observed that the blue droplets continuously squeezed out from the needle were discharged from the CSM-PVA 6 The surface of the superhydrophobic flame-retardant flexible material slides quickly, indicating that CSM-PVA 6 The surface and interior of the superhydrophobic flame-retardant flexible material are fully covered with hydrophobic long-chain groups.

[0114] ②CSM-PVA 6 The stability of superhydrophobic flame-retardant flexible materials in oil-water mixtures (n-hexane / water, chloroform / water), and the adsorption efficiency of various oils (Sudan Red III dyeing).

[0115] like Fig.14 (a) and (b) are mixtures of n-hexane / water and chloroform / water, respectively, with 3 mL of n-hexane and chloroform each. 6 The super hydrophobic flame retardant flexible material was placed in two different oil-water mixtures. When it first came into contact with the mixture, CSM-PVA 6 The superhydrophobic flame-retardant flexible material showed excellent adsorption efficiency, that is, it selectively and quickly absorbed the oil in it. In 5 seconds, it was able to achieve complete adsorption of light oil (n-hexane) and heavy oil (chloroform), which was attributed to CSM-PVA. 6 Superhydrophobic flame-retardant flexible materials with rich pore structure and superhydrophobic-superoleophilic properties.

[0116] ③ Drive CSM-PVA through a peristaltic pump 6 The oil-water separation performance of superhydrophobic flame-retardant flexible materials was tested.

[0117] n-Hexane, dichloroethylene, dichloromethane and chloroform were used as oil spill models of light oil and heavy oil respectively and then mixed with water to prepare oil-water mixture. Fig.15 Shown is CSM-PVA 6 The oil-water separation test process of super hydrophobic flame retardant flexible materials for four oil-water mixtures. Connect one end of the hose to CSM-PVA 6The super-hydrophobic flame-retardant flexible material is immersed in an oil-water mixture, and the other end of the hose is placed in a beaker for oil spill repair and collection, so as to achieve continuous recovery of various types of oil products from oily wastewater.

[0118] Since CSM-PVA 6 The super oleophilicity of the super hydrophobic flame retardant flexible material and the pressure difference generated by the peristaltic pump cause the oil in the oily wastewater to be sucked into the hose from the inside of the super hydrophobic flame retardant flexible material. 6 The super-hydrophobic flame-retardant flexible material is placed on the water surface, and the n-hexane floating on the water surface is pumped into the beaker through the hose, leaving only clear water in the beaker that originally contained the oil-water mixture. 6 The super-hydrophobic flame-retardant flexible material was placed under the water surface and brought into contact with the heavy oil at the bottom. The heavy oil at the bottom was also quickly pumped into the filter beaker, and only clear water remained in the beaker that originally contained the oil-water mixture, indicating that CSM-PVA 6 Super hydrophobic flame retardant flexible materials have excellent water repellency and oil-water separation effects. CSM-PVA once again proves 6 Superhydrophobic flame-retardant flexible materials have great potential in oil-water separation applications. They can simultaneously handle the collection of high-throughput oil spills and the continuous separation of oil-water mixtures, and have broad application prospects in large-scale oil spill treatment.

[0119] ④CSM-PVA driven by gravity 6 Performance test of superhydrophobic flame-retardant flexible materials in separating oil-water mixtures.

[0120] Fig.16 The equipment in (a) is divided into three parts. The upper part is the cylinder, and the middle part is the filter layer (where CSM-PVA is placed). 6 Super hydrophobic flame retardant flexible material), the lower part is a collection bottle, that is, a gravity-driven separation device. Hexane, dichloroethylene, dichloromethane and chloroform are used as oil spill models of light oil and heavy oil respectively, and then mixed with water to obtain an oil-water mixture. Fig.16 (c) is CSM-PVA 6 The oil spill treatment process of super hydrophobic flame retardant flexible materials. When the oil-water mixture is poured into the cylinder, the oil (dyed with Sudan III) quickly passes through the CSM-PVA in the filter layer. 6 The super-hydrophobic flame-retardant flexible material is used to absorb the oil and is collected by the collection bottle below, while the water (dyed with methylene blue) is completely blocked at the top by the super-hydrophobic flame-retardant flexible material, realizing gravity-driven recovery of various types of oil in oily wastewater. Fig.16 (b) is CSM-PVA 6The separation flux and efficiency of super hydrophobic flame retardant flexible materials for four oil-water mixtures: n-hexane / water, dichloroethane / water, dichloromethane / water and chloroform / water. The separation flux of chloroform is 18462 L·m -2 ·h -1 The separation efficiency is 99.6%; the separation flux of dichloromethane is 15923 L·m -2 ·h -1 The separation efficiency is 99.3%; the separation flux of n-hexane is 15625 L·m -2 ·h -1 The separation efficiency is 99.2%; the separation flux of ethylene dichloride is 15873 L·m -2 ·h -1 , the separation efficiency is 99.5%.

[0121] ⑤ Gravity-driven CSM-PVA 6 Test of the recycling performance of superhydrophobic flame-retardant flexible materials in separating oil-water mixtures.

[0122] When the chloroform / water mixture (V:V = 1:1) is poured into the filter, the chloroform (Sudan III dye) quickly passes through the CSM-PVA. 6 The super-hydrophobic flame-retardant flexible material is collected by the collection bottle below, while the water (methylene blue dye) is completely trapped by the super-hydrophobic flame-retardant flexible material on its upper part. Fig.17 As shown, CSM-PVA 6 In the first separation test of chloroform / water mixture, the super-hydrophobic flame-retardant flexible material achieved a filtration flux of 18462 L·m -2 ·h -1 , the separation efficiency is as high as 99.6%. In addition, at the end of each cycle, CSM-PVA can be squeezed and washed with ethanol to 6 The super hydrophobic flame retardant flexible material was regenerated and then subjected to the next separation test. After 12 cycles, CSM-PVA 6 The separation flux and efficiency of the superhydrophobic flame-retardant flexible material remained at 76.3% and 98.5% of the initial values, respectively, indicating that the material has good stability and reusability.

[0123] ⑥The influence of the ratio of CSM and PVA on the adsorption capacity of CSM-PVA superhydrophobic flame retardant flexible material for various light oils and heavy oils.

[0124] like Fig.18 As shown, CSM-PVA 5The adsorption capacities of super hydrophobic flame retardant flexible materials for chloroform, ethylene dichloride, dichloromethane and n-hexane are 10.04 g / g, 11.25 g / g, 11.5 g / g and 4.68 g / g, respectively; CSM-PVA 6 The adsorption capacities of superhydrophobic flame-retardant flexible materials for chloroform, ethylene dichloride, dichloromethane and n-hexane are 34.2 g / g, 27.78 g / g, 22.34 g / g and 8.14 g / g, respectively; CSM-PVA 7 The adsorption capacities of the super hydrophobic flame retardant flexible material for chloroform, ethylene dichloride, dichloromethane and n-hexane are 28.48 g / g, 24 g / g, 11.6 g / g and 5.23 g / g, respectively. 6 The superhydrophobic flame-retardant flexible material has the highest adsorption capacity for various oils (chloroform, ethylene dichloride, dichloromethane and n-hexane), indicating that its three-dimensional porous structure and interconnected pores provide sufficient accommodation space for the adsorption of light or heavy oils.

[0125] (3) CSM-PVA 6 Optimization of water-in-oil emulsion separation performance of superhydrophobic flame-retardant flexible materials.

[0126] ①CSM-PVA 6 The separation performance of superhydrophobic flame-retardant flexible materials on various emulsions prepared with Span-80 emulsifier was tested.

[0127] In addition to the immiscible oil-water mixture, oily wastewater also contains small droplet emulsions with stable surface activity, and the use of high-throughput separation technology to treat emulsions and emulsions faces major challenges. Four different types of emulsions (dichloromethane / water, chloroform / water, dichloroethane / water, and hexane / water) treated with Span-80 emulsifier have excellent stability. Fig.19 The equipment is divided into three parts, the upper part is the cylinder, the middle part is the filter layer (where CSM-PVA is placed 6 Super hydrophobic flame retardant flexible material), the lower part is a collecting bottle, which is a gravity-driven separation device. Fig. 20 The following is a comparison of the effects of four different types of emulsions before and after separation. Fig.21 As shown in Figure 2, the separation flux of dichloromethane / water emulsion is 5000 L·m -2 ·h -1 The separation efficiency is 99.6%; the separation flux of chloroform / water emulsion is 10000 L·m -2 ·h -1 The separation efficiency is 99.5%; the separation flux of dichloroethane / water emulsion is 13333 L·m -2 ·h -1The separation efficiency is 99.4%; the separation flux of n-hexane / water emulsion is 10526 L·m -2 ·h -1 The separation efficiency is 99.1%. The test results show that the separated solution is clear and transparent, indicating that CSM-PVA 6 Superhydrophobic flame-retardant flexible materials have remarkable separation properties for oil-water emulsions.

[0128] ②CSM-PVA 6 Cyclic separation performance test of superhydrophobic flame-retardant flexible materials on various emulsions.

[0129] like Fig. 22 As shown, taking dichloroethane / water emulsion as an example, the CSM-PVA 6 The superhydrophobic flame-retardant flexible material was tested for 10 oil-water separation cycles. In the first cycle test, the separation flux of ethylene dichloride / water emulsion reached 13333 L·m -2 ·h -1 The separation efficiency was as high as 99.4%, which confirmed the high separation effect of the super hydrophobic flame retardant flexible material on oil-water mixture. In addition, after each test, the CSM-PVA can be squeezed and washed with ethanol to 6 The super hydrophobic flame retardant flexible material was regenerated and then subjected to the next separation test. After 10 cycles, CSM-PVA 6 The separation flux and efficiency of the superhydrophobic flame-retardant flexible material remained at 80.2% and 98.8% of the initial values, respectively, indicating that the material has good stability and reusability.

[0130] (2) CSM-PVA 6 Flame retardant properties and adsorption-combustion-desorption cycle performance test of superhydrophobic flame retardant flexible materials.

[0131] ①CSM-PVA 6 Flame retardant performance test of super hydrophobic flame retardant flexible material in air.

[0132] like Fig.23 As shown, CSM-PVA completely exposed to air 6 The super hydrophobic flame retardant flexible material lasted for 6 seconds in the combustion test and extinguished itself within 2 seconds, showing excellent flame retardancy and fire resistance. This is due to the CSM-PVA 6 SiO loaded inside super hydrophobic flame retardant flexible material 2 NPS and its hierarchical porous structure significantly enhance its flame retardancy, making it a promising ultra-light fire-resistant material.

[0133] ②CSM-PVA after oil absorption 6Flame retardant performance test of super hydrophobic flame retardant flexible material in air.

[0134] Fig.24 (a) shows CSM-PVA under saturated state of n-hexane adsorption 6 Comparison of super hydrophobic flame retardant flexible materials before and after burning. Because a large amount of flammable n-hexane is adsorbed inside the structure and it is completely exposed to the air, CSM-PVA 6 After burning, the super hydrophobic flame retardant flexible material has a slight collapse in its axial structure and a more serious carbonization phenomenon. 6 The super hydrophobic flame retardant flexible material is extruded to remove most of the flammable n-hexane in its internal structure. The comparison effect before and after combustion is shown in the figure below. Fig.24 As shown in (b). 6 The super hydrophobic flame retardant flexible material is extruded so that its internal structure contains only a small amount of residual flammable oil. Therefore, although it is fully exposed to the air, at the end of the combustion, CSM-PVA 6 The overall structure of the superhydrophobic flame-retardant flexible material hardly collapsed, and only carbonization occurred on its surface.

[0135] ③CSM-PVA after oil absorption 6 Testing of the flame retardant properties of superhydrophobic flame retardant flexible materials when isolated from most of the air.

[0136] like Fig.25 As shown, CSM-PVA 6 The super-hydrophobic flame-retardant flexible material was placed in a small glass bottle and fixed upside down with an iron stand to make a simple combustion test device that isolates most of the air. 6 Most of the oil in the superhydrophobic flame-retardant flexible material structure has been burned away. 6 The oil in the internal structure of the superhydrophobic flame-retardant flexible material was further removed by combustion. 6 The residual oil inside the super hydrophobic flame retardant flexible material was completely removed by combustion. 6 The overall structure and morphology of the superhydrophobic flame-retardant flexible material hardly changed, indicating its excellent cyclic adsorption-combustion-desorption performance and flame-retardant properties.

[0137] ④CSM-PVA 6 Research on the high adsorption performance, adsorption-desorption combustion cycle performance and rapid combustion regeneration process of superhydrophobic flame-retardant flexible materials.

[0138] Fig.26 CSM-PVA 6The super hydrophobic flame retardant flexible material was subjected to 10 cycles of adsorption-combustion desorption of n-hexane. CSM-PVA can be completely removed by combustion without destroying its overall structure. 6 Hexane adsorbed inside super hydrophobic flame retardant flexible material. CSM-PVA 6 The first adsorption capacity and mass of n-hexane by the superhydrophobic flame-retardant flexible material are 8.69 g / g and 0.055 g / cm -3 Even after 10 consecutive adsorption-combustion-desorption cycles, CSM-PVA 6 The oil absorption of the superhydrophobic flame-retardant flexible material remains at 90.5% of the original oil absorption, and its own weight remains at 94.1% of the original mass.

[0139] Fig. 27 CSM-PVA 6 Photos of the super-hydrophobic flame-retardant flexible material before and after 10 cycles of adsorption-combustion-desorption testing. Although its surface morphology and radial microstructure have slightly blackened and shrunk, after multiple cycles of adsorption-combustion-desorption testing, it still retains its original structural stability and oil absorption capacity, demonstrating the CSM-PVA 6 Super hydrophobic flame retardant flexible material has excellent recyclability. With its superior oil absorption capacity and recycling stability, CSM-PVA 6 Superhydrophobic flame-retardant flexible materials have become an ideal choice for oil removal in practical applications, especially in the field of offshore oil spills.

[0140] (3) CSM-PVA 6 Test on the strong acid, alkali and salt resistance of super hydrophobic flame retardant flexible materials.

[0141] In order to adapt to complex environments, chemical durability is the evaluation of CSM-PVA 6 An important indicator of the universality of super-hydrophobic flame-retardant flexible materials. Various extreme environments from strong alkali to strong acid are simulated by sodium hydroxide and concentrated sulfuric acid solutions. Fig.28 As shown, CSM-PVA 6 When the superhydrophobic flame-retardant flexible material is placed in a strong acid environment with a pH value ranging from 1 to 7, its surface water contact angle is always stable above 150°; 6 When the super-hydrophobic flame-retardant flexible material is placed in a strong alkaline environment with a pH value of 8 to 12, its surface water contact angle is always stable at 150°. Since the Si-OC group is more easily hydrolyzed in a strong base than in a strong acid, CSM-PVA 6 The acid resistance of super hydrophobic flame retardant flexible materials is better than their alkali resistance. In addition, we also use CMS-PVA 6The super-hydrophobic flame-retardant flexible material was cut into pieces to study the structural stability and tolerance of its surface and internal structure under extreme environments of strong acid, strong alkali and salt. 6 After being immersed in a strong acid solution of pH=1, a strong base solution of pH=14, and a 5 wt% salt solution for 168 h, the superhydrophobic flame-retardant flexible material still maintained excellent structural stability, demonstrating its tolerance to strong acid, strong base, and high-concentration salt solutions. 6 Super hydrophobic flame-retardant flexible materials can achieve good oil / organic solvent adsorption under various harsh conditions, and good reusability and chemical stability make CSM-PVA 6 Superhydrophobic flame-retardant flexible materials have broad application prospects in marine oil spill incidents.

[0142] The present invention sequentially forms silicon dioxide nanoparticles (SiO 2 After the reaction of NPS, methyltrimethoxysilane (MTMS) and nanocellulose (CNF) suspension was completed, it was mixed with low concentration polyvinyl alcohol (PVA) solution to obtain a water-dispersible plant nanocellulose composite, which was further freeze-dried to prepare a super-hydrophobic flame-retardant flexible material with a three-dimensional super-porous structure. 2 NPS is attached to the surface of nanocellulose, simulating a large number of nano-rod structures attached to the raised structures on the surface of lotus leaves, changing the rough structure of the material surface while enhancing its structural stability and giving it flame retardant properties; the surface and interior of the material are modified by silane long-chain grafting through MTMS to achieve a low surface energy hydrophobic effect similar to that of a lotus leaf; the introduction of PVA solution blending can give the material better flexibility.

[0143] The present invention uses water to replace organic solvent as a water dispersion system of the dispersion medium to realize the preparation of a porous super-hydrophobic flame-retardant flexible material from a water-dispersible plant nanocellulose composite. The material preparation process is green and pollution-free, and the safety hazards such as air pollution and fire caused by the volatilization of organic solvents are better avoided, and the material has the characteristics of high elasticity, high oil absorption, reusability, fire resistance, and degradability. The present invention can effectively reduce the production cost of the material and good flame retardancy. Not only has it broadened the application field of the material, but it has also improved its safety, cycle stability and reusability in oil-water separation applications. The flexible material prepared by the present invention can not only achieve its rapid and highly selective separation by various methods such as adsorption, filtration, and suction filtration when separating oil-water mixed liquids, emulsions, etc., but also can be used as a recyclable organic liquid fuel carrier, and the internal oil pollution of the material after burning is completely removed, and it still has excellent super-hydrophobicity, high oil absorption, flame retardancy and flexibility, showing excellent reusability.

[0144] Therefore, the present invention adopts the method for preparing super-hydrophobic flame-retardant flexible materials using the above-mentioned water-dispersible nanocellulose composites. The material preparation process is green and pollution-free, and the prepared flexible material has the characteristics of high elasticity, high oil absorption, reusability, fire resistance, degradability, etc., and can be applied to various fields.

[0145] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for preparing a super-hydrophobic flame-retardant flexible material by using a water-dispersible nanocellulose composite, characterized in that: The following steps are involved: Step 1, nanocellulose CNF suspension; Step 2, synthesizing silicon dioxide nanoparticles SiO2 NPS; Step 3, preparing a precursor suspension CSM: mixing SiO2 nanoparticles, methyltrimethoxysilane MTMS and nanocellulose suspension in proportion, reacting to obtain a precursor suspension CSM; Among them, the mass ratio of nanocellulose suspension: SiO2 nanoparticles: methyltrimethoxysilane is 3.70~3.80 g: 0.025~0.031 g: 0.9~1.1 g; Step 4, preparing a polyvinyl alcohol (PVA) solution: adding PVA solid to deionized water, heating and stirring at 85° C. until completely dissolved, to obtain a PVA solution; Step 5, preparing a water-dispersible plant nanocellulose composite CSM-PVA mixed solution: blending the materials prepared in step 3 and step 4 to prepare a CSM-PVA mixed solution, and freezing the mixture; The specific operation is as follows: the precursor suspension CSM and the PVA solution are mixed and reacted in proportion, and mechanically stirred at a speed of 1950-2050 rpm for 4-6 min to obtain a water-dispersible plant nanocellulose composite CSM-PVA mixed solution; wherein the amount ratio of the precursor suspension CSM and the PVA solution is (1-5): (1-5); Step 6, freeze-drying the frozen material, and then placing it in an oven for heat treatment to obtain a super hydrophobic flame retardant flexible material.

2. The method for preparing a super-hydrophobic flame-retardant flexible material from a water-dispersible nanocellulose composite according to claim 1, characterized in that: The preparation method of the nanocellulose CNF suspension in step 1 is: the straw raw material is prepared by hot solvent pretreatment, low eutectic solvent separation, sodium chlorite solution bleaching, and high-intensity ultrasonic treatment; the concentration of the nanocellulose CNF suspension is 0.95~1.05 wt%.

3. The method for preparing a super-hydrophobic flame-retardant flexible material from a water-dispersible nanocellulose composite according to claim 1, characterized in that: The specific operation of step 2 is: mixing anhydrous ethanol, deionized water and ammonia water, and preparing liquid A after ultrasonic treatment; mixing tetraethyl orthosilicate TEOS and anhydrous ethanol, and preparing liquid B after ultrasonic treatment; at 45°C, slowly pouring liquid A into liquid B twice in a ratio of 3 / 4 and 1 / 4, every 1 hour, after the reaction is completed, centrifuging in a centrifuge, rinsing with deionized water and ethanol, and drying to obtain SiO2 nanoparticles.

4. The method for preparing a super-hydrophobic flame-retardant flexible material from a water-dispersible nanocellulose composite according to claim 1, characterized in that: The concentration of the PVA solution in step 4 is 9.5-10.5 mg / mL.

5. The super hydrophobic flame retardant flexible material prepared by the method according to any one of claims 1 to 4.

6. Use of the super hydrophobic flame retardant flexible material as claimed in claim 5 in separation of oily wastewater and emulsion separation.

7. Use of the super hydrophobic flame retardant flexible material as claimed in claim 5 in flame retardancy, circulating oil adsorption and combustion desorption.

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