Super Tough Cellulose Aerogel Fiber and Its Preparation Method and Use

Abstract

The present invention provides super-tough cellulose aerogel fibers, a preparation method thereof, and uses thereof. The preparation method adopts wet spinning technology, prepares a cellulose molecular-level solution using a cellulose polymer as a raw material, uses the cellulose molecular-level solution as a spinning solution, and causes in-situ self-assembly and hydrogen bond cross-linking reaction of the cellulose polymer in the spinning process to form a multi-layer nanofiber structure, and the nanofiber structure is a continuous three-dimensional multi-stage pore network structure. The cellulose aerogel fibers prepared by adopting the technical solution of the present invention not only have excellent physical properties such as high strength and high toughness, but also have good adsorption and heat preservation performance due to their multi-stage pore structure, and can be applied not only to the technical field of textiles, but also to technical fields such as air purification, heavy metal adsorption, inhalation particulate matter adsorption, indoor harmful gas adsorption, filter materials or heat insulation materials, and can be widely applied.

Description

Technical Field

[0001] (Related Application) This application claims the priority of Chinese Patent Application No. 202310753071.8, filed on June 25, 2023, with the invention title "Super Tough Cellulose Aerogel Fiber and Its Preparation Method and Use", and all the contents of that application are incorporated herein by reference.

[0002] (Technical Field) The present invention relates to the technical field of nanoporous materials and functional fibers, and specifically, to super tough cellulose aerogel fibers and their preparation methods and uses.

Background Art

[0003] An aerogel is a material with a three-dimensional porous network structure using a sol-gel process that forms a disordered and continuous colloidal network in solution. After drying, it is formed as a porous material, and due to its unique pore structure and surface chemical properties, it is expected to have a wide range of applications in several fields. Compared with other porous materials, aerogel materials have a more uniform pore size and distribution, a larger surface area, a higher porosity, and extremely low density and thermal conductivity. In the preparation process of aerogel materials, methods such as supercritical drying and freeze-drying are usually used to convert the liquid in the wet gel into gas to maintain the shape and network structure of the gel. Currently, aerogel materials have developed from conventional inorganic aerogels to organic aerogels, and the structural units of the framework structure have also expanded from conventional nanoparticles to one-dimensional nanofibers, two-dimensional nanosheets, etc., and their application fields and functions have been greatly expanded. Aerogel materials are expected to have a wide range of applications in fields such as environmental protection, energy storage and conversion, heat insulation and heat preservation. For example, in the field of environmental protection, aerogel materials can be used for water treatment and air purification, and purify the environment by adsorbing and catalytically decomposing harmful substances. In the energy field, aerogel materials can be used in the preparation of batteries and supercapacitors to improve the energy density and energy storage efficiency. In the fields of architecture and aviation, using aerogel materials in the preparation of thermal insulation materials can improve the energy utilization efficiency.

[0004] Due to its unique properties and wide application possibilities, aerogel materials are attracting increasing attention from researchers and research is being carried out. Currently, most of the aerogel research focuses on block, film, and microsphere aerogels, and there is relatively little research on aerogel fibers. Aerogel materials have unique properties such as low density, thermal conductivity, high porosity, and specific surface area, but conventional aerogel materials generally have drawbacks such as low mechanical properties, brittleness, and low toughness, which significantly limit the development of aerogel materials for practical applications. Since aerogels have a low skeletal strength and a porous network structure, it is difficult to prepare them as fibers and endow them with elongated and flexible properties.

[0005] At present, the preparation and application of aerogel fibers are being developed through the efforts of researchers. Aerogel fibers based on materials such as cellulose (Chinese Patent Application Publication No. 105970325), aramid (Chinese Patent Application Publication No. 115073803), and graphene (Chinese Patent Application Publication No. 113215828) are being developed one after another. The current methods for preparing aerogel fibers mainly involve preparing nanofluid dispersions of corresponding materials such as aramid nanofiber dispersions, graphene dispersions, and cellulose nanocrystal dispersions, using the nanofluid dispersions as spinning solutions for spinning, and drying the gel fibers to obtain aerogel fibers. Although this method can be used to prepare aerogel fibers of different materials, the connection between nanomaterials is usually achieved by hydrogen bonding or simple physical lap joints, resulting in weak connections between nanomaterials within the fibers. As a result, the obtained aerogel fibers mainly exhibit the properties of rigid materials, are prone to damage and breakage in practical applications, and are difficult to apply in the fiber field. For example, Chinese Patent Application Publication No. 105970325 proposes continuous cellulose aerogel fibers and a method for preparing the same. First, cellulose is dispersed in a dispersion medium formed by dissolving NaOH and thiourea in water to form a cellulose nanocrystal spinning stock solution, which is then spun and dried to obtain aerogel fibers. Another example is Chinese Patent Application Publication No. 105970326 and Chinese Patent Application Publication No. 106012107. Compared with Chinese Patent Application Publication No. 105970325, the former is different in that it changes solid cellulose aerogel fibers to hollow cellulose aerogel fibers, and the latter is different in that it subjects cellulose aerogel fibers to high-temperature carbonization treatment. Obviously, although cellulose aerogel fibers can be obtained by the prior art technology, the hydrogen bond strength between cellulose nanocrystals is weak, and cellulose aerogel fibers cannot obtain strong strength and toughness.

[0006] In summary, although great progress has been made in the preparation of aerogel fibers, cellulose aerogel fibers with high strength and good toughness have not been developed so far, and there are limitations in the practical application of cellulose aerogel fibers.

[0007] Therefore, it is highly necessary to develop high-strength and super-tough cellulose aerogel fibers and their preparation methods.

Summary of the Invention

Problems to be Solved by the Invention

[0008] In view of this, in order to solve the above problems, the present invention solves difficult problems such as low mechanical properties, poor toughness, difficult solvent recovery, and high cost of aerogel fibers prepared by prior art, and aims to further expand the practical range of aerogel fibers, and provides super-tough cellulose aerogel fibers, their preparation methods and uses.

Means for Solving the Problems

[0009] To achieve the above object, the present invention provides super-tough cellulose aerogel fibers, adopts wet spinning technology, prepares a cellulose molecular-level solution using cellulose polymer as a raw material, uses the cellulose molecular-level solution as a spinning solution, and causes in-situ self-assembly and hydrogen bond cross-linking reaction of cellulose polymer in the spinning process to form a multi-layer nanofiber structure, wherein the nanofiber structure is a continuous three-dimensional multi-stage pore network structure, and when pulled by an external force, the pore structure in the three-dimensional multi-stage pore network structure becomes smaller, and as the pulling progresses, the degree of orientation along the length direction of the three-dimensional multi-stage pore network structure gradually increases, and the connection point strength between nanofibers constitutes the fiber body strength, thereby forming the cellulose gel fiber with super-tough performance.

[0010] Here, the cellulose molecular-level solution is a polymer solution.

[0011] Preferably, the toughness of the cellulose aerogel fiber is 5 MJ / m 3 or more.

[0012] Based on the technical problems existing in the prior art, the cellulose aerogel fiber proposed in the present invention is a technology of high-strength and high-toughness aerogel fiber constructed by the method of in-situ self-assembly hydrogen bond crosslinking integration of cellulose macromolecules with hydrogen bond crosslinking. This technology adopts a cellulose molecular-level solution as the spinning solution, generates in-situ self-assembly and hydrogen bond crosslinking of cellulose macromolecules during the spinning process, forms a continuous three-dimensional network structure, and this three-dimensional network structure is a nanofiber network structure with uniform and multi-layer pores, without obvious network defects. When pulled by an external force, the strength of a large number of connection points between nanofibers constitutes the strength of the fiber body. Therefore, when the entire network deforms to the limit, slip damage occurs, resulting in super-toughness characteristics. Compared with the aerogel fiber obtained by a simple nanostructure, the toughness of the aerogel fiber is improved by orders of magnitude.

Advantages of the Invention

[0013] The present invention has the following beneficial technical effects.

[0014] 1. The technical solution of the present invention is a preparation technology of high-strength and high-toughness aerogel fiber constructed by the method of in-situ self-assembly hydrogen bond crosslinking integration of cellulose macromolecules. The prepared super-tough cellulose aerogel fiber has the characteristics of high strength, ultra-high toughness, low low thermal conductivity, high porosity, continuous spinnability, good flexibility, strong knitting property, and excellent skeleton structure stability.

[0015] 2. The cellulose aerogel fiber prepared by the technical solution of the present invention not only has excellent physical properties, but also has good adsorption and heat insulation properties due to its multi-level pore structure. It can be applied not only in the field of textile technology, but also in the fields of air purification, heavy metal adsorption, inhalation particulate matter adsorption, indoor harmful gas adsorption, filter material or heat insulation material technology, and can be widely applied.

[0016] 3. By adopting the technical solution of the present invention, combining cellulose molecules with wet spinning technology, the raw materials are easily available from a wide range of sources. The raw materials used are not limited to absorbent cotton balls, and super-tough cellulose aerogel fibers can be obtained by directly using cellulose and other materials rich in cellulose. It is low-cost and highly economically efficient. In particular, since the solvent used can be almost 100% recovered, the raw material cost is significantly reduced. Since the process is an existing technology, industrial production can be carried out based on existing processing equipment, without preliminary investment in equipment, and it meets the conditions for industrial production.

[0017] 4. By adopting the technical solution of the present invention, the preparation process of super-tough cellulose aerogel fibers is simple, the reaction conditions are mild, it can be continuously prepared, with low energy consumption, environmentally friendly, and low cost, so it can also be applied to industrial production, mass production, and popularization.

[0018] 5. By adopting the technical solution of the present invention, using ionic liquid as the solvent, it can be almost 100% recovered after production, and there is no need to use organic solvents that cause great damage to the ecological environment and human health throughout the process. Furthermore, since the dissolution process is relatively fast and cellulose is widely available and inexpensive, the preparation cycle is significantly shortened and the production cost is reduced.

Brief Description of the Drawings

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Embodiments for Carrying Out the Invention

[0020] To make the objectives, technical solutions and advantages of the embodiments of this application clearer, the following will clearly and completely explain the technical solutions of the embodiments of this application in conjunction with the accompanying drawings of the embodiments of this application. However, it is obvious that the described embodiments are only some embodiments of this application, not all embodiments.

[0021] The present invention provides super-tough cellulose aerogel fibers. Using a cellulose molecular-level solution as a spinning solution, when it enters the coagulation bath, the ionic liquid diffuses into the coagulation bath, and the free cellulose molecular chains can undergo self-organization in situ. At the same time, since a large number of hydroxyl groups exist on the cellulose molecular chains, a hydrogen bond cross-linking reaction can occur. Under the dual action of in-situ self-organization and hydrogen bond cross-linking reaction, the cellulose polymer forms a nanofiber structure with multi-layer pores.

[0022] The nanofiber structure is a continuous three-dimensional multi-stage pore network structure. When pulled by an external force, the pore structure in the three-dimensional multi-stage pore network structure becomes smaller. As the pulling progresses, the degree of orientation along the length direction of the three-dimensional multi-stage pore network structure gradually increases. The strength of the connection points between nanofibers constitutes the strength of the fiber body, forming cellulose gel fibers with super-tough performance.

[0023] Here, the cellulose molecular-level solution is a cellulose polymer solution.

[0024] In some specific embodiments, the three-dimensional multi-stage pore network structure includes micropores with a pore diameter of 2 nm or less, mesopores with a pore diameter of 2 - 50 nm, and macropores with a pore diameter of 50 nm - 100 nm.

[0025] In some specific embodiments, the toughness of the super-tough cellulose aerogel fiber is 5 MJ / m 3 or more.

[0026] In some more specific embodiments, the toughness of the super-tough cellulose aerogel fiber is 5 - 25 MJ / m 3 is.

[0027] In some specific embodiments, the diameter of the super-tough cellulose aerogel fiber is 0.1 μm to 1 mm, the specific surface area is 290 - 372 m 2 / g, the porosity is 80 - 90%, and the density is 0.18 - 0.25 g / cm 3 is.

[0028] Compared with conventional inorganic, organic, and composite material aerogel fibers, the super-tough cellulose aerogel fibers of the present invention enable the cellulose molecular chains to undergo in-situ self-assembly and hydrogen bond cross-linking, followed by orientation treatment to obtain a multi-layer nanofiber structure. Specifically, its maximum tensile strength is 17 - 30 MPa, and the elongation at break is 82 - 110%.

[0029] On the other hand, the present invention further provides a method for preparing the above-mentioned super-tough cellulose aerogel fiber. The preparation method uses a polymer solution of cellulose as a spinning solution, and performs in-situ self-assembly and hydrogen bond cross-linking reactions by wet spinning technology to obtain cellulose gel fibers, and then cellulose aerogel fibers can be obtained by solvent replacement and drying treatment. In this method, in-situ self-assembly and hydrogen bond cross-linking reactions are carried out.

[0030] In some preferred embodiments, the method for preparing the super-tough cellulose aerogel fiber specifically includes (1) a step of dissolving a cellulose polymer in a solvent to obtain a cellulose molecular solution; (2) a step of generating in-situ self-assembly and hydrogen bond cross-linking reactions of the cellulose molecular solution to the cellulose polymer by wet spinning technology, and obtaining cellulose gel fibers in combination with orientation treatment; (3) performing solvent replacement and drying treatment on the cellulose gel fibers to obtain super-tough cellulose aerogel fibers.

[0031] In some preferred embodiments, the cellulose polymer and its source include any one or a combination of two or more of polymer cellulose, lignin fibers, cellulose ethers, methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, cotton, linen, wood materials, straw, cereal husks, bamboo and other natural plant materials.

[0032] In some preferred embodiments, the solvent includes an ionic liquid, or a mixture of any one or two or more ionic liquids of DMSO, NMP, DMAC or deionized water, but is not limited thereto.

[0033] In some more preferred embodiments, for the ionic liquid, the liquid composed entirely of ions includes, but is not limited to, imidazolium-based ionic liquids, pyridine-based ionic liquids, quaternary ammonium salt-based ionic liquids, etc.

[0034] In some preferred embodiments, when the ionic liquid is used in combination with other reagents, the mass ratio of the ionic liquid to the other reagents is 1:1, and the other reagents include one or a combination of two or more of DMSO, NMP, DMAC or deionized water, but are not limited thereto.

[0035] In some preferred embodiments, the cellulose molecular solution is composed of a cellulose polymer and an ionic liquid, wherein the concentration of the cellulose polymer in the cellulose molecular solution is 0.1 - 20 wt%, preferably 4 - 6 wt%.

[0036] In some preferred embodiments, the degree of polymerization of the cellulose polymer is 6000 - 11000.

[0037] In some preferred embodiments, the dissolution temperature of the cellulose polymer in the solvent is 50 - 100°C, preferably 70 - 80°C.

[0038] In some preferred embodiments, the dissolution time of the cellulose polymer in the solvent is 0.3 - 96 h, preferably 72 h. The dissolution time is set according to the cellulose content in the polymer solution. The lower the cellulose content, the shorter the required dissolution time.

[0039] In some preferred embodiments, the wet spinning technique is realized by a method using a coagulation bath. Specifically, based on water, absolute ethanol, and a mixed solution of any ratio between them, the coagulation rate is adjusted by adding or not adding a good solvent or a poor solvent.

[0040] In some preferred embodiments, the wet spinning technique includes using a cellulose molecular solution with a selected concentration as a spinning solution, using absolute ethanol as a coagulation bath, extruding the spinning solution with an injection pump, flowing it into the coagulation bath, causing in-situ self-assembly and hydrogen bond cross-linking reactions in the cellulose polymer in the cellulose molecular solution, and then performing an orientation treatment to obtain cellulose gel fibers.

[0041] Furthermore, the process conditions used in the wet spinning technique include the following. The concentration of the cellulose molecular solution is 0.1 - 20 wt%, the diameter of the extrusion needle is 0.1 μm - 1 cm, and the range of the extrusion rate is 0.1 - 1000 mL / min.

[0042] In some preferred embodiments, the orientation method used in the wet spinning technique includes any one or a combination of two or more of flow orientation, draw orientation, and directional freezing orientation.

[0043] In some preferred embodiments, the solvent replacement in the preparation method includes first replacing the solvent that is difficult to dry in the cellulose gel fiber with a solvent that is easy to dry, and then performing a drying treatment on the replaced cellulose gel fiber to obtain cellulose aerogel fibers.

[0044] In some preferred embodiments, the solvent that is easy to dry includes any one or a combination of two or more of water, methanol, ethanol, tert-butanol, acetone, cyclohexane, and n-hexane, but is not limited thereto.

[0045] In some preferred embodiments, the drying treatment includes any one or a combination of two or more of a supercritical fluid drying method, a vacuum freeze-drying method, and a reduced-pressure drying method.

[0046] By the above technical solutions, the preparation method proposed in the present invention can have a high degree of orientation through orientation treatment and obtain great mechanical strength and ultra-high toughness. The aerogel fibers have the mesoporous characteristics and the flexible and elongated characteristics of the fibers due to the lightweight of the aerogel, and can have a wider application in the fields of smart fabrics and wearables. Compared with the inorganic, organic, and composite material aerogel fibers reported so far, the preparation method of the ultra-strong and tough cellulose aerogel fibers proposed in the present invention has two distinct advantages. First, in this method, an ionic liquid is used as the solvent, so it can be almost 100% recovered after production, and no organic solvent with high harmfulness to the ecological environment and the human body is used in the whole process. This is because the ionic liquid is almost non-volatile and can be almost 100% recovered only by heating even when mixed with other solvents. Furthermore, since the dissolution process is relatively fast and cellulose is widely available and inexpensive, the preparation cycle is significantly shortened and the manufacturing cost is reduced. Second, the raw materials used in this method are not limited to absorbent cotton balls, and ultra-tough cellulose aerogel fibers can be obtained by directly using cellulose and other materials rich in cellulose.

[0047] Based on the cellulose aerogel fibers provided by the above technical solution, the present invention further provides uses of the super-tough aerogel fibers in the fields such as textile preparation, composite material preparation, air purification, heavy metal adsorption, inhalation particulate matter adsorption, indoor harmful gas adsorption, filter media or heat insulation materials.

[0048] Hereinafter, the technical solution of the present invention will be described in more detail with specific examples.

[0049] (Example 1) This example provides a method for preparing super-tough cellulose aerogel fibers, specifically including the following steps: (1) Preparation of spinning solution: Dissolve cellulose (absorbent cotton) with an ionic liquid (1-allyl-3-methylimidazolium chloride) at 80 °C, heat and stir slowly for 72 h to prepare a cellulose molecular solution with a concentration of 5 wt%, and the degree of polymerization of the cellulose polymer is ~9000. (2) Wet spinning: Obtain cellulose gel fibers from the 5 wt% cellulose molecular solution by wet spinning method through orientation treatment (flow orientation). Specifically, the cellulose molecular solution is extruded at a rate of 300 μL / min through a catheter and a spinning needle (diameter 300 μm), and then put into an anhydrous ethanol coagulation bath to obtain preliminary cellulose gel fibers, and finally cellulose gel fibers are obtained by orientation treatment (flow orientation). (3) Preparation of super-tough cellulose aerogel fibers: After solvent substitution (the easily dried solvent used is anhydrous ethanol) is performed on the cellulose gel fibers in step (2), super-tough cellulose aerogel fibers are obtained by freeze-drying.

[0050] The specific physical properties of the super-tough cellulose aerogel fibers are shown in Table 1.

[0051] Figures 1 and 2 are optical photographs of the cellulose gel fibers and super-tough cellulose aerogel fibers obtained by the above steps of this example, respectively. As can be seen from the figures, the super-tough cellulose aerogel fibers prepared in this example have a uniform and consistent appearance. In other words, the aerogel fibers prepared by the method provided in this embodiment have uniform thickness and fineness and have the possibility of being prepared and manufactured in bulk.

[0052] Figures 3, 4a and 4b are scanning electron microscope photographs of the surface and cross-section of the super-tough cellulose aerogel fibers prepared in this example, respectively. As can be seen from the figures, the surface of the super-tough cellulose aerogel fibers prepared in this example is uniform and crack-free, and the interior of the fibers is a continuous three-dimensional multi-stage pore network structure.

[0053] Figures 5a and 5b are scanning electron microscope photographs of the surface after knotting and its local enlarged view of the super-tough cellulose aerogel fibers prepared in this example, respectively. As can be seen from the figures, the super-tough cellulose aerogel fibers prepared in this example have good flexibility, and the fibers do not break even when knotted, making it possible to be put into practical use in fields such as textiles.

[0054] Figures 6 and 7 are nitrogen adsorption-desorption isotherm curves and pore size distribution diagrams of the super-tough cellulose aerogel fibers prepared in this example, respectively. As can be seen from Figure 6, the curve has an obvious hysteresis loop and is a typical type IV adsorption-desorption isotherm, indicating that the cellulose aerogel fibers have a three-dimensional multi-stage pore network structure composed of a typical mesoporous structure, including micropores with a pore size of less than 2 nm, mesopores with a pore size of 2 - 50 nm, and macropores with a pore size of 50 nm - 100 nm. Due to the multi-stage pore network structure, the cellulose aerogel fibers have excellent adsorption capacity.

[0055] As can be seen from Figure 7, the pore size distribution has a very wide distribution in the mesopore size range of 10 nm or more, mainly concentrated in the range of 15 - 30 nm.

[0056] Figure 8 shows the tensile stress-strain curve of the super-tough cellulose aerogel fibers prepared in this example. As can be seen from the figure, the tensile strength of the super-tough aerogel fibers prepared in this example increases with the increase of tensile strain. Here, its tensile strength reaches 20 MPa, and the fracture tensile strain can reach 84%.

[0057] Figure 9 shows the cross-sectional scanning electron microscope photos of the super-tough cellulose aerogel fibers prepared in this example before and after tension. As can be seen from the figure, during the process of the super-tough aerogel fibers prepared in this example being stretched by an external force and elongated, its macropores gradually become smaller, and the degree of orientation along the fiber length direction gradually increases. Specifically, the pore structure in the three-dimensional multi-stage pore network structure becomes smaller. As the tension progresses, the degree of orientation of the pore fibers along the fiber length direction gradually increases, and the strength of the connection points between nanofibers constitutes the fiber body strength. Based on this, the cellulose aerogel fibers provided by this example have super-tough performance, that is, with the tension of the external force, the change in the degree of orientation of its pore fibers converges to the consistency of the orientation of the connection points of nanofibers, forming the strength of the fiber body, and the orientation direction is indicated by the arrow in the figure.

[0058] Figure 10 shows the infrared curve diagrams of the super-tough cellulose aerogel fibers prepared in this example before and after tension. As can be seen from the figure, after the super-tough aerogel fibers prepared in this example are stretched, the formed hydrogen bonds increase, and the O-H bond undergoes a blue shift phenomenon.

[0059] Figure 11 shows the XRD patterns of the super-tough cellulose aerogel fibers and cellulose prepared in this example. As can be seen from the patterns, significant changes occur in the diffraction peaks of cellulose due to the dissolution in ionic liquid and regeneration in a solvent. The main peaks of cellulose before dissolution are distributed at 15.05°, 16.76°, and 22.76°, corresponding to the (101), (101), and (002) crystal planes of the cellulose I crystal form. Therefore, the cellulose in raw cotton, which is the raw material, mainly exists as cellulose I crystals. The main peak in the regenerated cellulose aerogel fibers is at 20.45°, corresponding to the (200) crystal plane of the cellulose II crystal form, indicating the transition from the virgin cellulose I crystal form to the regenerated cellulose II crystal form.

[0060] Figure 12 shows the TG curve diagrams of the super-tough cellulose aerogel fibers and cellulose prepared in this example. As can be seen from the figure, the decomposition temperature of the cellulose aerogel fibers is slightly lower than that of the raw material before dissolution, and the thermal stability is slightly reduced. However, the residual mass is higher than that of the original fibers. This is because during the preparation process of the cellulose aerogel fibers, cellulose is converted from type I crystals to type II crystals, and the conformation of cellulose type II crystals is more likely to undergo conformational inversion compared to type I, and is more likely to be dehydrated and decarboxylated to form residues. Therefore, it is considered that the amount of residual carbon has increased.

[0061] Figure 13 shows the contact angle photograph of the super-tough cellulose aerogel fibers before hydrophobization prepared in this example. As can be seen from the figure, the super-tough cellulose aerogel fibers have good hydrophilicity, and after water absorption, the three-dimensional network structure is prone to sagging or collapsing.

[0062] Figure 14 is a photograph showing the change in the contact angle of the super-tough cellulose aerogel fibers prepared in this example at different times after hydrophobization. As can be seen from the figure, the cellulose aerogel fibers can have excellent hydrophobic performance after hydrophobization treatment. The hydrophobic modification method is as follows: methyltrimethoxysilane is used as a low-temperature plasma gas source. In the plasma device, the dried cellulose aerogel was placed in a low-temperature plasma chamber and treated under a glow discharge system. The discharge system was activated when the degree of vacuum reached a certain value (set to about 200 Pa ± 50 Pa in the experiment). Finally, hydrophobic cellulose aerogel fibers were obtained at a specific power (150 W in the experiment) and time (3 - 10 minutes in the experiment).

[0063] (Example 2) This example provides a method for preparing super-tough cellulose aerogel fibers, specifically including the following steps: (1) Preparation of the spinning solution: Dissolve cellulose (absorbent cotton) in an ionic liquid (1-allyl-3-methylimidazolium chloride) at 80 °C, heat and stir slowly for 48 h to prepare a cellulose molecular solution with a concentration of 4 wt%. The cellulose molecular solution is a cellulose polymer solution, and the degree of polymerization of the cellulose polymer is ~9500. (2) Wet spinning: Obtain cellulose gel fibers from the 4 wt% cellulose molecular solution by wet spinning method through orientation treatment (flow orientation). Specifically, the cellulose molecular solution is extruded at a rate of 300 μL / min through a catheter and a spinning needle (diameter 300 μm), and then put into an anhydrous ethanol coagulation bath to obtain preliminary cellulose gel fibers, and finally orientation treatment is carried out to obtain cellulose gel fibers. (3) Preparation of super-tough cellulose aerogel fibers: After solvent replacement (the easily dried solvent used is anhydrous ethanol) is performed on the cellulose gel fibers in step (2), super-tough cellulose aerogel fibers are obtained by freeze-drying.

[0064] After going through the above steps, the specific performance of the super-tough cellulose aerogel fibers obtained in this example is shown in Table 1.

[0065] (Example 3) This example provides a method for preparing super-tough cellulose aerogel fibers, specifically including the following steps: (1) Preparation of spinning solution: At 80 °C, cellulose (absorbent cotton) is dissolved in an ionic liquid (1-allyl-3-methylimidazolium chloride), heated and slowly stirred for 96 h to prepare a 6 wt% cellulose molecular solution. The degree of polymerization of the cellulose polymer is ~9000. (2) Wet spinning: The 6 wt% cellulose molecular solution is used to obtain cellulose gel fibers through an orientation treatment (flow orientation) by the wet spinning method. Specifically, the cellulose molecular solution is extruded at a rate of 300 μL / min through a catheter and a spinning needle (diameter 300 μm), and then put into an anhydrous ethanol coagulation bath to obtain preliminary cellulose gel fibers, and finally an orientation treatment is carried out to obtain cellulose gel fibers. (3) Preparation of super-tough cellulose aerogel fibers: After solvent substitution (the easily dried solvent used is anhydrous ethanol) is performed on the cellulose gel fibers in step (2), super-tough cellulose aerogel fibers are obtained by freeze-drying.

[0066] After going through the above steps, the stress-strain curve of the super-tough cellulose aerogel fibers obtained in this example is shown in Figure 15, and the specific performance is shown in Table 1.

[0067] (Example 4) This example provides a method for preparing super-tough cellulose aerogel fibers, specifically including the following steps: (1) Preparation of spinning solution: At 80 °C, cellulose (absorbent cotton) is dissolved in a mixture of an ionic liquid (1-allyl-3-methylimidazolium chloride) and DMSO (mass ratio 1:1), heated and slowly stirred for 72 h to prepare a 5 wt% cellulose molecular solution. The degree of polymerization of the cellulose polymer is ~7000. (2) Wet spinning: A 5 wt% cellulose molecular solution is used to obtain cellulose gel fibers by means of wet spinning through an orientation treatment (flow orientation). Specifically, the cellulose molecular solution is extruded at a rate of 300 μL / min through a catheter and a spinning needle (diameter 300 μm), and then put into an absolute ethanol coagulation bath to obtain preliminary cellulose gel fibers, and finally, through orientation treatment, cellulose gel fibers are obtained. (3) Preparation of super-tough cellulose aerogel fibers: After solvent substitution (the easily dried solvent used is absolute ethanol) is performed on the cellulose gel fibers in step (2), super-tough cellulose aerogel fibers are obtained by freeze-drying.

[0068] Through the above steps, the specific performance of the super-tough cellulose aerogel fibers obtained in this example is shown in Table 1.

[0069] (Example 5) The difference between this example and Example 1 is in step 1. Here, step 1 includes the preparation of the spinning solution: Dissolve cellulose (absorbent cotton) with an ionic liquid (1-allyl-3-methylimidazolium chloride) at 80°C, heat and slowly stir for 20 h to prepare a 5 wt% cellulose molecular solution, and the degree of polymerization of the cellulose polymer is ~9000.

[0070] (Example 6) The difference between this example and Example 1 is in step 1. Here, step 1 includes the preparation of the spinning solution: Dissolve cellulose (absorbent cotton) with an ionic liquid (1-allyl-3-methylimidazolium chloride) at 80°C, heat and slowly stir for 72 h to prepare a 20 wt% cellulose molecular solution, and the degree of polymerization of the cellulose polymer is ~9300.

[0071] (Example 7) The difference between this example and Example 1 is Step 1. Here, Step 1 includes the following: Preparation of the spinning solution: Dissolve cellulose (absorbent cotton) in an ionic liquid (1-allyl-3-methylimidazolium chloride) at 50 °C, heat and slowly stir for 72 h to prepare a cellulose molecular solution with a concentration of 20 wt%, and the degree of polymerization of the cellulose polymer is ~9200.

[0072] (Example 8) The cellulose aerogel fibers prepared in Example 1 were woven into fabrics in the longitudinal and transverse directions, respectively. As shown in Figure 16, it can be applied to high-temperature heat insulation and low-temperature heat preservation.

[0073] (Example 9) The cellulose aerogel fibers prepared in Example 1 were interwoven in the longitudinal and transverse directions to form a mesh pocket. As shown in Figure 17, it can be applied to high-place catching.

[0074] (Comparative Example 1) This comparative example uses urea and thiourea as raw materials and provides cellulose gel fibers prepared by adopting the technical solution of the present invention. The specific preparation steps include the following: (1) Preparation of the spinning solution: Dissolve cellulose in a solution (mass ratio is 16:16:13:155 respectively) composed of NaOH, urea, thiourea and water at 80 °C to dissolve a 5 wt% cellulose spinning dope. (2) Wet spinning: The 5 wt% cellulose spinning dope is subjected to orientation treatment by a wet spinning method to obtain cellulose gel fibers. Specifically, the cellulose molecular solution is extruded at a speed of 300 μL / min, passed through a catheter and a spinning needle (diameter 300 μm), and then put into an absolute ethanol coagulation bath to obtain preliminary cellulose gel fibers, and finally orientation treatment is carried out to obtain cellulose gel fibers. (3) Preparation of cellulose aerogel fibers: After solvent replacement (the easily dried solvent used is absolute ethanol) is performed on the cellulose gel fibers in Step (2), cellulose aerogel fibers are obtained by freeze-drying.

[0075] After going through the above steps and comparing with Example 1, the strength and toughness of the cellulose aerogel fibers obtained in this comparative example are much lower than those of Example 1 of the present invention, and their specific performance is shown in Table 1.

[0076] Refer to Table 1 for the structural and physical performance parameters of the cellulose aerogel fibers obtained in Examples 1-7 and Comparative Example 1 of the present invention.

[0077] (Table 1 Performance parameters of cellulose aerogel fibers obtained in Examples 1-7 and Comparative Example 1)

Table 1

[0078] As can be seen from Table 1, the toughness of Examples 1-7 is all 5 MJ / m 3 or more, reaching a maximum of 22 MJ / m 3 and compared with the prior art, its toughness has been greatly improved.

[0079] Furthermore, compared with Comparative Example 1, Example 1 has significantly improved tensile strength, elongation at break and toughness, that is, the cellulose aerogel fibers constructed by utilizing the in-situ self-assembled hydrogen and cross-linking integration technology of the cellulose molecular solution of the present invention have greatly improved physical performance.

[0080] The cellulose aerogel fibers of Examples 1 to 7 prepared from different cellulose molecular solutions at different coagulation rates can all achieve high-strength and high-toughness cellulose aerogel fibers. In particular, when comparing Example 1 and Example 3, when the concentration of the cellulose molecular solution increased from 5 wt% to 6 wt%, the cellulose dissolution time was extended from 72 h to 96 h, and its physical performance was significantly improved. Furthermore, when comparing Example 1 and Example 4, only the ionic liquid in Step 1 changed. In Example 1, only 1-allyl-3-methylimidazolium chloride was used, while in Example 4, a mixture of 1-allyl-3-methylimidazolium chloride and DMSO was used. Although the performance of both was almost the same, in Example 4, it decreased slightly.

[0081] In summary, with the above technical solution, the present invention provides a method for preparing ultra-strong and tough cellulose aerogel fibers with a simple preparation process, few preparation steps, a relatively short preparation cycle, no need for harmful solvents that are difficult to recycle, low cost, high economic benefits, and conditions suitable for industrial production.

[0082] Furthermore, this method can be continuously prepared, the solvent used can be recycled almost 100%, the raw material source is widely available and inexpensive, so there is a prospect of industrialization. The obtained ultra-strong aerogel fibers have characteristics such as high strength, ultra-high toughness, low thermal conductivity, high porosity, continuous spinnability, good flexibility, strong textile properties, and excellent stability of the skeletal structure. They can be woven and applied even under harsh or special environments, further expanding the application range of these materials.

[0083] (Appendix) (Appendix 1) Adopt wet spinning technology, prepare a cellulose molecular solution using cellulose polymer as raw material, use the cellulose molecular solution as a spinning solution, cause in-situ self-assembly and hydrogen bond cross-linking reaction of cellulose polymer in the spinning process to form a multi-layer nanofiber structure, the nanofiber structure is a continuous three-dimensional multi-stage pore network structure, when pulled by an external force, the pore structure in the three-dimensional multi-stage pore network structure becomes smaller, and as the pulling progresses, the degree of orientation along the length direction of the three-dimensional multi-stage pore network structure gradually increases, the connection point strength between nanofibers constitutes the fiber body strength, and form the cellulose gel fiber with super toughness performance, including Here, the cellulose molecular solution is a cellulose polymer solution, The toughness of the cellulose aerogel fiber is 5 MJ / m 3 or more, which is characterized by the super tough cellulose aerogel fiber.

[0084] (Appendix 2) The source of the cellulose polymer includes any one or a combination of two or more of polymer cellulose, lignin fiber, cellulose ether, methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose or natural plant materials, and / or, the natural plant materials include any one or a combination of two or more of cotton, linen, wood materials, straw, cereal husks, bamboo, and / or, the degree of polymerization of the cellulose polymer is 6000 - 11000, which is characterized by the super tough cellulose aerogel fiber described in Appendix 1.

[0085] (Appendix 3) Dissolve the cellulose polymer in a solvent to obtain a cellulose molecular solution, and / or, the solvent includes ionic liquid, or a mixture of any one or two or more of DMSO, NMP, DMAC, deionized water and ionic liquid, And / or, the liquid consisting entirely of ions for the ionic liquid includes imidazolium-type ionic liquids, pyridine-type ionic liquids, and quaternary ammonium salt-type ionic liquids. And / or, the ionic liquid is recyclable. The super-tough cellulose aerogel fiber according to Supplementary Note 2 is characterized by this.

[0086] (Supplementary Note 4) The three-dimensional multi-stage pore network structure includes micropores with a pore diameter of 2 nm or less, mesopores with a pore diameter of 2 to 50 nm, and macropores with a pore diameter of 50 nm to 100 nm. And / or, the toughness of the cellulose aerogel fiber is 5 MJ / m 3 or more, the diameter is 0.1 μm to 1 mm, the specific surface area is 290 to 372 m 2 / g, the porosity is 80 to 90%, and the density is 0.18 to 0.25 g / cm 3 The super-tough cellulose aerogel fiber according to any one of Supplementary Notes 1 to 3 is characterized by this.

[0087] (Supplementary Note 5) The maximum tensile strength of the cellulose aerogel fiber is 17 to 30 MPa, the elongation at break is 82 to 110%, and the toughness of the cellulose aerogel fiber is 5 to 25 MJ / m 3 The super-tough cellulose aerogel fiber according to any one of Supplementary Notes 1 to 3 is characterized by this.

[0088] (Supplementary Note 6) A method for preparing the super-tough cellulose aerogel fiber according to any one of Supplementary Notes 1 to 5. Specifically, (1) A step of dissolving a cellulose polymer in a solvent to obtain a cellulose molecular solution. (2) A step of causing in-situ self-assembly and hydrogen bond cross-linking reaction of the cellulose polymer in the cellulose molecular solution by wet spinning technology, and obtaining cellulose gel fibers in combination with orientation treatment. (3) A step of performing solvent substitution and drying treatment on the cellulose gel fiber to obtain a super-tough cellulose aerogel fiber. The preparation method is characterized by including this.

[0089] (Appendix 7) The wet spinning technology is characterized in that a cellulose molecular solution with a selected concentration is prepared as a spinning solution, absolute ethanol is used as a coagulation bath, the spinning solution is extruded by an injection pump, flows into the coagulation bath, and in-situ self-assembly and hydrogen bond cross-linking reaction occur in the cellulose polymer in the cellulose molecular solution, and then an orientation treatment is carried out to obtain cellulose gel fibers, which is the method for preparing super-tough cellulose aerogel fibers described in Appendix 6.

[0090] (Appendix 8) The concentration of the cellulose polymer in the cellulose molecular solution is 0.1-20 wt%, preferably 4-6 wt%, which is the method for preparing super-tough cellulose aerogel fibers described in Appendix 7.

[0091] (Appendix 9) The dissolution temperature of the cellulose polymer in the solvent is 50-100 °C, the dissolution time is 0.3-96 h, preferably 72-96 h, which is the method for preparing super-tough cellulose aerogel fibers described in Appendix 7.

[0092] (Appendix 10) The wet spinning technology adopts the process conditions that the diameter of the extrusion needle of the injection pump is 0.1 μm-1 cm and the extrusion speed is 0.1-1000 mL / min, which is the method for preparing super-tough cellulose aerogel fibers described in Appendix 7.

[0093] (Appendix 11) The orientation treatment method includes any one or a combination of two or more of flow orientation, draw orientation and directional freezing orientation, which is the method for preparing super-tough cellulose aerogel fibers described in Appendix 7.

[0094] (Appendix 12) The solvent replacement includes first replacing the solvent that is difficult to dry in the cellulose gel fiber with a solvent that is easy to dry, and then performing a drying treatment on the replaced cellulose gel fiber to obtain cellulose aerogel fiber, and is characterized by being the method for preparing the super-tough cellulose aerogel fiber according to any one of Appendices 6 to 11.

[0095] (Appendix 13) The solvent that is easy to dry includes any one or a combination of two or more of water, methanol, ethanol, tert-butanol, acetone, cyclohexane, and n-hexane, and is characterized by being the method for preparing the super-tough cellulose aerogel fiber according to Appendix 12.

[0096] (Appendix 14) The drying treatment includes any one or a combination of two or more of the supercritical fluid drying method, the vacuum freeze-drying method, and the vacuum drying method, and is characterized by being the method for preparing the super-tough cellulose aerogel fiber according to Appendix 12.

[0097] (Appendix 15) Use of the super-tough cellulose aerogel fiber according to Appendices 1 to 5 in the fields of textile preparation, composite material preparation, air purification, heavy metal adsorption, inhalation particulate matter adsorption, indoor harmful gas adsorption, filter material, or heat insulation material.

Claims

1. Adopting wet spinning technology, preparing a cellulose molecular-level solution using a cellulose polymer as a raw material, using the cellulose molecular-level solution as a spinning solution, generating in-situ self-assembly and hydrogen bond cross-linking reactions in the cellulose polymer during the spinning process to form a multi-layer nanofiber structure, the nanofiber structure being a continuous three-dimensional multi-stage pore network structure, when pulled by an external force, the pore structure in the three-dimensional multi-stage pore network structure becomes smaller, and as the pulling progresses, the degree of orientation along the length direction of the three-dimensional multi-stage pore network structure gradually increases, the connection point strength between nanofibers constitutes the fiber body strength, and forming the cellulose gel fiber with super-tough performance, including, wherein the cellulose molecular-level solution is a cellulose polymer solution, The toughness of the cellulose aerogel fiber is 5 MJ / m ３ or more, and the super-tough cellulose aerogel fiber is characterized by this.

2. The source of the cellulose polymer includes any one or a combination of two or more of polymer cellulose, lignin fiber, cellulose ether, methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose or natural plant materials, and / or, the natural plant materials include any one or a combination of two or more of cotton, linen, wood materials, straw, cereal husks, bamboo, and / or, the degree of polymerization of the cellulose polymer is 6000 - 11000, The super-tough cellulose aerogel fiber according to Claim 1, characterized in that.

3. Dissolving the cellulose polymer in a solvent to obtain a cellulose molecular-level solution, and / or, the solvent includes an ionic liquid, or a mixture of any one or two or more of DMSO, NMP, DMAC, deionized water and an ionic liquid, and / or, the liquid consisting entirely of ions for the ionic liquid includes imidazolium-type ionic liquid, pyridine-type ionic liquid, quaternary ammonium salt-type ionic liquid, and / or, the ionic liquid is recyclable, The super-tough cellulose aerogel fiber according to Claim 2, characterized in that.

4. The three-dimensional multi-stage pore network structure includes micropores with a pore diameter of 2 nm or less, mesopores with a pore diameter of 2 - 50 nm, and macropores with a pore diameter of 50 nm - 100 nm, And / or, the toughness of the cellulose aerogel fiber is 5 MJ / m ３ or more, the diameter is 0.1 μm to 1 mm, and the specific surface area is 290 to 372 m ２ / g, the porosity is 80 to 90%, and the density is 0.18 to 0.25 g / cm ３ The super-tough cellulose aerogel fiber according to any one of claims 1 to 3, characterized in that it is so.

5. The maximum tensile strength of the cellulose aerogel fiber is 17 to 30 MPa, the elongation at break is 82 to 110%, and the toughness of the cellulose aerogel fiber is 5 to 25 MJ / m ３ The super-tough cellulose aerogel fiber according to any one of claims 1 to 3, characterized in that it is as described above.

6. A method for preparing the super-tough cellulose aerogel fiber according to any one of Claims 1 - 5, specifically, (1) a step of dissolving a cellulose polymer in a solvent to obtain a cellulose molecular solution, (2) A step of obtaining cellulose gel fibers by subjecting a cellulose molecular solution to in-situ self-assembly and hydrogen bond cross-linking reaction of cellulose polymers by wet spinning technology, and performing orientation treatment in combination therewith; (3) A step of performing solvent substitution and drying treatment on the cellulose gel fibers to obtain super-tough cellulose aerogel fibers, characterized in that the preparation method includes these steps.

7. The wet spinning technology is characterized in that a cellulose molecular solution with a selected concentration is prepared as a spinning solution, absolute ethanol is used as a coagulation bath, the spinning solution is extruded by an injection pump, flowed into the coagulation bath, and in-situ self-assembly and hydrogen bond cross-linking reaction of cellulose polymers in the cellulose molecular solution are generated, and then orientation treatment is performed to obtain cellulose gel fibers. The method for preparing super-tough cellulose aerogel fibers according to claim 6 is characterized by including these steps.

8. The concentration of cellulose polymers in the cellulose molecular solution is 0.1 to 20 wt%, preferably 4 to 6 wt%. The method for preparing super-tough cellulose aerogel fibers according to claim 7 is characterized by this.

9. The dissolution temperature of cellulose polymers in the solvent is 50 to 100 °C, the dissolution time is 0.3 to 96 h, preferably 72 to 96 h. The method for preparing super-tough cellulose aerogel fibers according to claim 7 is characterized by this.

10. The wet spinning technology adopts process conditions that the diameter of the extrusion needle of the injection pump is 0.1 μm to 1 cm and the extrusion speed is 0.1 to 1000 mL / min. The method for preparing super-tough cellulose aerogel fibers according to claim 7 is characterized by this.

11. The orientation treatment method includes any one or a combination of two or more of flow orientation, draw orientation, and directional freezing orientation. The method for preparing super-tough cellulose aerogel fibers according to claim 7 is characterized by this.

12. Solvent substitution includes first substituting the solvent that is difficult to dry in the cellulose gel fibers with a solvent that is easy to dry, and then performing a drying treatment on the substituted cellulose gel fibers to obtain cellulose aerogel fibers. The method for preparing super-tough cellulose aerogel fibers according to any one of claims 6 to 11 is characterized by including these steps.

13. The solvent that is easy to dry includes any one or a combination of two or more of water, methanol, ethanol, tert-butanol, acetone, cyclohexane, and n-hexane. The method for preparing the super-tough cellulose aerogel fiber according to claim 12 is characterized by this.

14. The drying treatment includes any one or a combination of two or more of a supercritical fluid drying method, a vacuum freeze-drying method, and a reduced-pressure drying method. The method for preparing the super-tough cellulose aerogel fiber according to claim 12 is characterized by this.

15. Use of the super-tough cellulose aerogel fiber according to claims 1 to 5 in the fields of textile preparation, composite material preparation, air purification, heavy metal adsorption, inhalation particulate matter adsorption, indoor harmful gas adsorption, filter material, or heat insulation material.

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