Method for preparing and using supertough cellulose aerogel fibers

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 applications) This application claims priority to Chinese Patent Application No. 202310753071.8, filed on 25 June 2023, with the title "Supertough Cellulose Aerogel Fibers, Method for Preparation of the Same, and Uses therefor," the entirety of which is incorporated herein by reference.

[0002] (Technical field) The present invention relates to the technology of nanoporous materials and functional fibers, and more specifically to supertough cellulose aerogel fibers, methods for preparing them, and their applications. [Background technology]

[0003] Aerogels are materials with a three-dimensional porous network structure formed using a sol-gel process that creates a disordered and continuous colloidal network in solution. After drying, they form an even more porous material, and their unique pore structure and surface chemical properties make them promising for a wide range of applications in several fields. Compared to other porous materials, aerogels have a more uniform pore size and distribution, a larger surface area and higher porosity, and extremely low density and thermal conductivity. The preparation process for aerogels typically involves methods such as supercritical drying or freeze-drying, which maintain the gel's shape and network structure by converting the liquid in the wet gel into a gas. Currently, aerogels have evolved from conventional inorganic aerogels to organic aerogels, and the constituent units of the skeletal structure have expanded from conventional nanoparticles to one-dimensional nanofibers and two-dimensional nanosheets, greatly broadening their application fields and functions. Aerogels are expected to have a wide range of applications in fields such as environmental protection, energy storage and conversion, and heat insulation. For example, in the field of environmental protection, aerogel materials can be used in water treatment and air purification, cleaning the environment by adsorbing and catalytically decomposing harmful substances. In the energy sector, aerogel materials can be used in the preparation of batteries and supercapacitors to improve energy density and energy storage efficiency. In the fields of construction and aerospace, aerogel materials can be used in the preparation of insulation materials to improve energy utilization efficiency.

[0004] Aerogel materials are attracting increasing attention from researchers due to their unique properties and potential for a wide range of applications, and research is progressing rapidly. Currently, most aerogel research focuses on blocks, films, and microsphere aerogels, with relatively little research on aerogel fibers. Aerogel materials possess unique properties such as low density, thermal conductivity, high porosity, and specific surface area. However, conventional aerogel materials generally have drawbacks such as poor mechanical properties, brittleness, and low toughness, which significantly limit the development of aerogel materials for practical applications. Because aerogels have low skeletal strength and a porous network structure, it is difficult to prepare them as fibers and impart long, slender, and flexible properties to them.

[0005] Currently, 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. Current methods for preparing aerogel fibers mainly involve preparing nanomaterial dispersions of the corresponding material, such as aramid nanofiber dispersions, graphene dispersions, and cellulose nanocrystalline dispersions, using the nanomaterial dispersion as a spinning solution, obtaining gel fibers, and then drying them to obtain aerogel fibers. While this method allows for the preparation of aerogel fibers from different materials, the connections between nanomaterials are usually achieved by hydrogen bonding or simple physical lap joints, resulting in weak connections between nanomaterials within the fiber. Consequently, the resulting aerogel fibers mainly exhibit the properties of rigid materials, making them susceptible to damage and breakage in practical applications, and thus difficult to apply to the textile field. For example, Chinese Patent Application Publication No. 105970325 proposes continuous cellulose aerogel fibers and a method for preparing them. First, cellulose is dispersed in a dispersion medium formed by dissolving NaOH and thiourea in water to form a cellulose nanocrystal spinning stock, which is then spun and dried to obtain aerogel fibers. Another example is Chinese Patent Application Publication Nos. 105970326 and 106012107. Compared to Chinese Patent Application Publication No. 105970325, the former differs in that it transforms solid cellulose aerogel fibers into hollow cellulose aerogel fibers, while the latter differs in that it subjects cellulose aerogel fibers to high-temperature carbonization treatment. Clearly, while cellulose aerogel fibers can be obtained using the prior art techniques, the hydrogen bond strength between cellulose nanocrystals is weak, and the cellulose aerogel fibers cannot obtain high strength and toughness.

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

[0007] Therefore, the development of high-strength, ultra-tough cellulose aerogel fibers and methods for preparing them is extremely necessary. [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] In view of this, the present invention aims to solve the above problems by providing a super-tough cellulose aerogel fiber, a method for preparing the same, and its applications, thereby solving the difficult problems of aerogel fibers prepared by prior art, such as low mechanical properties, poor toughness, difficulty in solvent recovery, and high cost, and further expanding the practical range of aerogel fibers. [Means for solving the problem]

[0009] To achieve the above objectives, the present invention provides a supertough cellulose aerogel fiber, employing wet spinning technology to prepare a cellulose molecular grade solution using a cellulose polymer as a raw material, using the cellulose molecular grade solution as a spinning solution, and in the spinning process causing in-situ self-assembly and hydrogen bond crosslinking reactions in the cellulose polymer to form a multilayer 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 tension progresses, the degree of orientation along the longitudinal direction of the three-dimensional multi-stage pore network structure gradually increases, and the strength of the connection points between nanofibers constitutes the strength of the fiber body, thereby forming the cellulose gel fiber having supertoughness.

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

[0011] Preferably, the toughness of the cellulose aerogel fiber is 5 MJ / m 3 That's all.

[0012] Based on the technical problems present in the prior art, the cellulose aerogel fiber proposed in this invention is a high-strength, high-toughness aerogel fiber technology constructed by an in-situ self-assembly hydrogen-bonded crosslinking integration method of cellulose polymers with hydrogen bond crosslinking. This technology employs a cellulose molecular-grade solution as the spinning solution, and during the spinning process, the cellulose polymer undergoes in-situ self-assembly and hydrogen bond crosslinking, forming a continuous three-dimensional network structure. This three-dimensional network structure is a uniform nanofiber network structure with multilayer pores, and has no obvious network defects. When pulled by an external force, the strength of the numerous connection points between the nanofibers constitutes the strength of the fiber itself. Therefore, when the entire network deforms to its limit, slip damage occurs, resulting in super-toughness. Compared to aerogel fibers obtained by simple nanostructures, the toughness of the aerogel fiber is orders of magnitude improved. [Effects of the Invention]

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

[0014] 1. The technical solution of the present invention is a technique for preparing high-strength, high-toughness aerogel fibers constructed by an in-situ self-assembly hydrogen bond crosslinking integration method of cellulose polymers. The prepared super-toughness cellulose aerogel fibers are characterized by high strength, super-high toughness, low thermal conductivity, high porosity, continuous spinnability, good flexibility, strong knitability, and excellent skeletal structure stability.

[0015] 2. The cellulose aerogel fibers prepared by the technical solution of the present invention not only possess excellent physical properties, but also have good adsorption and heat insulation properties due to their multi-layered porosity structure, and can be applied not only in the field of textile technology, but also in the fields of air purification, heavy metal adsorption, airborne particle adsorption, indoor harmful gas adsorption, filter media, or heat insulation and heat retention material technology, and can be applied in a wide range of applications.

[0016] 3. By adopting the technical solution of the present invention and 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 degreased 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 economical. In particular, since the solvent used can be almost 100% recovered, the raw material cost is significantly reduced. Because the process is an existing technology, industrial production can be carried out based on existing processing equipment without preliminary investment in equipment, meeting 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 no organic solvent that causes great damage to the ecological environment and human health is used throughout the process. Furthermore, the dissolution process is relatively fast, and cellulose is widely available and inexpensive, so the preparation cycle is significantly shortened and the production cost is reduced.

Brief Description of the Drawings

[0019] [Figure 1] It is an optical photograph of the cellulose gel fiber prepared in Example 1 of the present invention. [Figure 2] It is an optical photograph of the cellulose aerogel fiber prepared in Example 1 of the present invention. [Figure 3] It is a scanning electron microscope photograph of the surface of the cellulose aerogel fiber prepared in Example 1 of the present invention. [Figure 4a] They are respectively scanning electron microscope photographs of the cross-section (Figure 4a) and its partial enlargement (Figure 4b) of the cellulose aerogel fiber prepared in Example 1 of the present invention. [Figure 4b]They are respectively the cross-sectional view (Figure 4a) of the cellulose aerogel fiber prepared in Example 1 of the present invention and its partial enlarged view (Figure 4b) scanning electron micrograph. [Figure 5a] They are respectively the surface view (Figure 5a) of the cellulose aerogel fiber after knotting prepared in Example 1 of the present invention and its partial enlarged view (Figure 5b) scanning electron micrograph. [Figure 5b] They are respectively the surface view (Figure 5a) of the cellulose aerogel fiber after knotting prepared in Example 1 of the present invention and its partial enlarged view (Figure 5b) scanning electron micrograph. [Figure 6] It is the nitrogen adsorption-desorption isotherm diagram of the cellulose aerogel fiber prepared in Example 1 of the present invention. [Figure 7] It is the pore size distribution diagram of the cellulose aerogel fiber prepared in Example 1 of the present invention. [Figure 8] It is the tensile stress-strain curve diagram of the cellulose aerogel fiber prepared in Example 1 of the present invention. [Figure 9] They are respectively the cross-sectional scanning electron micrographs of the cellulose aerogel fiber before and after tensile test prepared in Example 1 of the present invention. [Figure 10] It is the infrared curve diagram of the cellulose aerogel fiber before and after tensile test prepared in Example 1 of the present invention. [Figure 11] It is the XRD pattern of the cellulose aerogel fiber and cellulose prepared in Example 1 of the present invention. [Figure 12] It is the TG curve diagram of the cellulose aerogel fiber and cellulose prepared in Example 1 of the present invention. [Figure 13] It is the photograph of the contact angle of the cellulose aerogel fiber before hydrophobization prepared in Example 1 of the present invention. [Figure 14] It is the photograph of the contact angle of the cellulose aerogel fiber at different times after hydrophobization prepared in Example 1 of the present invention. [Figure 15] It is the tensile stress-strain curve diagram of the cellulose aerogel fiber prepared in Example 6 of the present invention. [Figure 16]This is an optical photograph of a cloth woven from cellulose aerogel fibers prepared in Example 1 of the present invention. [Figure 17] This is an optical photograph of a mesh pocket woven from cellulose aerogel fibers prepared in Example 1 of the present invention. [Modes for carrying out the invention]

[0020] To further clarify the purpose, technical solutions, and advantages of the embodiments of this application, the technical solutions of the embodiments of this application will be described clearly and completely below, together with the accompanying drawings of the embodiments of this application. However, it is clear that the embodiments described are only a selection of the embodiments of this application, and not all of them.

[0021] This invention provides supertough cellulose aerogel fibers. When a cellulose molecular-grade solution is used as the spinning solution and placed in a coagulation bath, the ionic liquid diffuses into the coagulation bath, allowing the free cellulose molecular chains to self-assemble in situ. Simultaneously, due to the presence of a large number of hydroxyl groups on the cellulose molecular chains, hydrogen bonding crosslinking reactions can occur. Under the dual action of situ self-assembly and hydrogen bonding crosslinking reactions, the cellulose polymer forms a nanofiber structure with multilayer pores.

[0022] The nanofiber structure is a continuous three-dimensional multi-layered pore network structure. When pulled by an external force, the pore structure within the three-dimensional multi-layered pore network structure becomes smaller. As tension progresses, the degree of orientation along the length of the three-dimensional multi-layered pore network structure gradually increases, and the strength of the connection points between nanofibers constitutes the strength of the fiber itself, forming a cellulose gel fiber with super-toughness.

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

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

[0025] In some specific embodiments, the toughness of the supertough cellulose aerogel fiber is 5 MJ / m 3 That's all.

[0026] In some more specific embodiments, the toughness of the supertough cellulose aerogel fibers is 5-25 MJ / m 3 That is the case.

[0027] In some specific embodiments, the diameter of the supertough cellulose aerogel fibers is 0.1 μm to 1 mm, and the specific surface area is 290 to 372 m². 2 The porosity is 80-90%, and the density is 0.18-0.25 g / cm³. 3 That is the case.

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

[0029] On the other hand, the present invention further provides a method for preparing the above-mentioned supertough cellulose aerogel fibers, the preparation method comprising using a polymer solution of cellulose as a spinning solution, performing in-situ self-assembly and hydrogen bond crosslinking reactions by wet spinning technology to obtain cellulose gel fibers, and then obtaining cellulose aerogel fibers by solvent replacement and drying treatment. In this method, in-situ self-assembly and hydrogen bond crosslinking reactions are performed.

[0030] In some preferred embodiments, the method for preparing the supertough cellulose aerogel fibers is, 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 using a wet spinning technique to induce in-situ self-assembly and hydrogen bond crosslinking reactions in a cellulose molecular solution, in conjunction with an orientation treatment. (3) The step of performing solvent replacement and drying treatment on cellulose gel fibers to obtain supertough cellulose aerogel fibers.

[0031] In some preferred embodiments, the cellulose polymer and its source include one or more combinations of high molecular weight cellulose, lignin fibers, cellulose ethers, methylcellulose, hydroxypropyl methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, cotton, flax, woody materials, straw, grain husks, bamboo, and other natural plant materials.

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

[0033] In some more preferred embodiments, the ionic liquids, which consist entirely of ions, include, but are not limited to, imidazolium-type ionic liquids, pyridine-type ionic liquids, and quaternary ammonium salt-type ionic liquids.

[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, but are not limited to, DMSO, NMP, DMAC, or a combination of two or more deionized water.

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

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

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

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

[0039] In some preferred embodiments, the wet spinning technique is implemented by a coagulation bath method, specifically by adjusting the coagulation rate by adding or omitting a good or bad solvent to a mixed solution of water, anhydrous ethanol, and any proportions thereof.

[0040] In some preferred embodiments, the wet spinning technique includes using a cellulose molecular solution of a selected concentration as the spinning solution, using anhydrous ethanol as the coagulation bath, squeezing the spinning solution with an injection pump and flowing it into the coagulation bath, inducing in-situ self-assembly and hydrogen bonding crosslinking 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 technology include the following: the concentration of the cellulose molecular solution is 0.1 to 20 wt%, the diameter of the extrusion needle is 0.1 μm to 1 cm, and the extrusion speed range is 0.1 to 1000 mL / min.

[0042] In some preferred embodiments, the orientation method used in the wet spinning technique includes one or more combinations of flow orientation, draw orientation, and directional freeze orientation.

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

[0044] In some preferred embodiments, the easily drying solvent includes, but is not limited to, water, methanol, ethanol, tert-butanol, acetone, cyclohexane, and n-hexane in combination with one or more others.

[0045] In some preferred embodiments, the drying process includes one or more combinations of supercritical fluid drying, vacuum freeze-drying, and reduced-pressure drying.

[0046] Through the above technical solutions, the preparation method proposed in this invention can achieve a high degree of orientation through orientation treatment, resulting in high mechanical strength and ultra-high toughness. The aerogel fibers combine the mesoporous properties of aerogel with the flexible and elongated properties of fibers, making them suitable for a wider range of applications in smart fabrics and wearables. Compared to previously reported inorganic, organic, and composite aerogel fibers, the preparation method for ultra-tough cellulose aerogel fibers proposed in this invention has two clear advantages. Firstly, since this method uses an ionic liquid as a solvent, it can be recovered almost 100% after production, and does not use organic solvents that are highly harmful to the ecological environment and human body throughout the entire process. This is because ionic liquids are almost non-volatile and can be recovered almost 100% simply by heating even when mixed with other solvents. Furthermore, the dissolution process is relatively fast, and cellulose is widely available and inexpensive, so the preparation cycle is significantly shortened and production costs are reduced. Secondly, the method is not limited to absorbed cotton balls as raw materials; ultra-tough cellulose aerogel fibers can be obtained by directly using cellulose and other cellulose-rich materials.

[0047] Based on the cellulose aerogel fibers provided by the above technical solutions, the present invention further provides applications for the supertough aerogel fibers in fields such as spinning preparation, composite material preparation, air purification, heavy metal adsorption, airborne particle adsorption, indoor harmful gas adsorption, filter media, or thermal insulation materials.

[0048] The technical solutions of the present invention will be described in more detail below with reference to specific examples.

[0049] (Example 1) This embodiment provides a method for preparing supertough cellulose aerogel fibers, which specifically includes the following steps: (1) Preparation of spinning solution: Dissolve cellulose (absorbent cotton) in ionic liquid (1-allyl-3-methylimidazolium chloride) at 80°C, heat and stir slowly for 72 hours to prepare a 5 wt% cellulose molecular solution, with a degree of polymerization of cellulose polymer of ~9000. (2) Wet spinning: A 5 wt% cellulose molecular solution is used in a wet spinning method to obtain cellulose gel fibers through orientation treatment (flow orientation). Specifically, the cellulose molecular solution is passed through a catheter and a spinning needle (diameter 300 μm) at an extrusion rate of 300 μL / min, then placed in an anhydrous ethanol coagulation bath to obtain preliminary cellulose gel fibers, and finally obtained by orientation treatment (flow orientation). (3) Preparation of supertough cellulose aerogel fibers: After solvent replacement of the cellulose gel fibers from step (2) (anhydrous ethanol is used as the easily drying solvent), supertough cellulose aerogel fibers are obtained by freeze-drying.

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

[0051] Figures 1 and 2 are optical photographs of the cellulose gel fibers and supertough cellulose aerogel fibers obtained by the above steps of this embodiment, respectively. As can be seen from the figures, the supertough cellulose aerogel fibers prepared in this embodiment 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 can be prepared and manufactured in bulk.

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

[0053] Figures 5a and 5b show the surface of the supertough cellulose aerogel fibers prepared in this embodiment after knotting, and magnified scanning electron microscope images of the surface and localized areas thereof, respectively. As can be seen from the figures, the supertough cellulose aerogel fibers prepared in this embodiment have good flexibility and toughness, and the fibers do not crack even after knotting, making them suitable for practical use in fields such as textiles.

[0054] Figures 6 and 7 show the nitrogen adsorption / desorption curve and pore size distribution diagram of the supertough cellulose aerogel fibers prepared in this embodiment, respectively. As can be seen from Figure 6, the curve has a clear 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 consisting of a typical mesopore structure, including micropores with a diameter of 2 nm or less, mesopores with a diameter of 2 to 50 nm, and macropores with a diameter of 50 nm to 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 is very broad in the mesopore size range of 10 nm or more, and is mainly concentrated in the 15-30 nm range.

[0056] Figure 8 shows the tensile stress-strain curve of the supertough cellulose aerogel fiber prepared in this embodiment. As can be seen from the figure, the tensile strength of the supertough aerogel fiber prepared in this embodiment increases with increasing tensile strain. Here, the tensile strength can reach 20 MPa, and the tensile strain at fracture can reach 84%.

[0057] Figure 9 shows cross-sectional scanning electron microscope images of the supertough cellulose aerogel fibers prepared in this embodiment before tension and after fracture. As can be seen from the figure, during the process of the supertough aerogel fibers prepared in this embodiment being stretched by an external force, their macropores gradually become smaller and the degree of orientation along the length of the fibers gradually increases. Specifically, the pore structure in the three-dimensional multi-stage pore network structure becomes smaller, and as tension progresses, the degree of orientation along the length of the pore fibers gradually increases, and the strength of the connection points between nanofibers constitutes the strength of the fiber body. Based on this, the cellulose aerogel fibers provided in this embodiment have supertough properties, that is, with tension from an external force, the change in the degree of orientation of the pore fibers converges the orientation of the connection points of the 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 curves of the supertough cellulose aerogel fibers prepared in this embodiment before and after tension. As can be seen from the figure, after the supertough aerogel fibers prepared in this embodiment are stretched, the number of hydrogen bonds formed increases, and the OH bonds undergo a blue shift phenomenon.

[0059] Figure 11 shows the XRD patterns of the supertough cellulose aerogel fibers and cellulose prepared in this embodiment. As can be seen from the patterns, dissolution in the ionic liquid and regeneration in the solvent cause significant changes in the diffraction peaks of cellulose. 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 cellulose I crystalline type, indicating that the cellulose in the raw material, absorbent cotton, 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 cellulose II crystalline type, which indicates a transition from virgin cellulose I crystalline type to regenerated cellulose II crystalline type.

[0060] Figure 12 shows the TG curve diagrams for the supertough cellulose aerogel fibers and cellulose prepared in this embodiment. As can be seen from the figure, the decomposition temperature of the cellulose aerogel fibers is slightly lower than that of the raw materials before dissolution, and the thermal stability is slightly lower. However, the residual mass is higher than that of the original fibers. This is thought to be because, during the preparation process of cellulose aerogel fibers, cellulose is converted from type I crystals to type II crystals. When comparing the conformation of type II cellulose crystals with that of type I, structural inversion is more likely to occur, and dehydration and decarboxylation are more likely to occur, resulting in a higher residual carbon content.

[0061] Figure 13 is a photograph of the contact angle of the supertough cellulose aerogel fibers prepared in this embodiment before hydrophobicization. As can be seen from the figure, the supertough cellulose aerogel fibers have good hydrophilicity, and after water absorption, the three-dimensional network structure is prone to sagging and collapse.

[0062] Figure 14 shows photographs of the change in contact angle at different times after hydrophobization of the supertough cellulose aerogel fibers prepared in this embodiment. As can be seen from the figure, the cellulose aerogel fibers can have excellent hydrophobic properties after hydrophobization treatment. The hydrophobic modification method is as follows, using methyltrimethoxysilane as a low-temperature plasma gas source. In the plasma apparatus, 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 vacuum level reached a certain value (set to approximately 200 Pa ± 50 Pa in the experiment). Hydrophobic cellulose aerogel fibers were finally obtained with a specific power (150 W in the experiment) and time (3 to 10 minutes in the experiment).

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

[0064] The specific performance of the supertough cellulose aerogel fibers obtained in this embodiment through the above steps is shown in Table 1.

[0065] (Example 3) This embodiment provides a method for preparing supertough cellulose aerogel fibers, which specifically includes the following steps: (1) Preparation of spinning solution: Dissolve cellulose (absorbent cotton) in ionic liquid (1-allyl-3-methylimidazolium chloride) at 80°C, heat and stir slowly for 96 hours to prepare a 6 wt% cellulose molecular solution, the degree of polymerization of the cellulose polymer being ~9000, (2) Wet spinning: A 6 wt% cellulose molecular solution is used in a wet spinning method, and cellulose gel fibers are obtained through orientation treatment (flow orientation). Specifically, the cellulose molecular solution is passed through a catheter and a spinning needle (diameter 300 μm) at an extrusion rate of 300 μL / min, then placed in an anhydrous ethanol coagulation bath to obtain preliminary cellulose gel fibers, and finally subjected to orientation treatment to obtain cellulose gel fibers. (3) Preparation of supertough cellulose aerogel fibers: After solvent replacement of the cellulose gel fibers from step (2) (anhydrous ethanol is used as the easily drying solvent), supertough cellulose aerogel fibers are obtained by freeze-drying.

[0066] Following the steps described above, the stress-strain curve of the supertough cellulose aerogel fiber obtained in this embodiment is shown in Figure 15, and its specific performance is shown in Table 1.

[0067] (Example 4) This embodiment provides a method for preparing supertough cellulose aerogel fibers, which specifically includes the following steps: (1) Preparation of spinning solution: Dissolve cellulose (absorbent cotton) in a mixture of ionic liquid (1-allyl-3-methylimidazolium chloride) and DMSO (mass ratio 1:1) at 80°C, heat and stir slowly for 72 hours to prepare a 5 wt% cellulose molecular solution, the degree of polymerization of the cellulose polymer being ~7000, (2) Wet spinning: A 5 wt% cellulose molecular solution is used in a wet spinning method, and cellulose gel fibers are obtained through orientation treatment (flow orientation). Specifically, the cellulose molecular solution is passed through a catheter and a spinning needle (diameter 300 μm) at an extrusion rate of 300 μL / min, then placed in an anhydrous ethanol coagulation bath to obtain preliminary cellulose gel fibers, and finally subjected to orientation treatment to obtain cellulose gel fibers. (3) Preparation of supertough cellulose aerogel fibers: After solvent replacement of the cellulose gel fibers from step (2) (anhydrous ethanol is used as the easily drying solvent), supertough cellulose aerogel fibers are obtained by freeze-drying.

[0068] Following the steps described above, the specific performance of the supertough cellulose aerogel fibers obtained in this embodiment is shown in Table 1.

[0069] (Example 5) The difference between this example and Example 1 lies in step 1, where step 1 includes the 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 20 hours to prepare a 5 wt% cellulose molecular solution with a degree of polymerization of ~9000.

[0070] (Example 6) The difference between this example and Example 1 lies in step 1, where step 1 includes the preparation of the spinning solution: dissolving cellulose (absorbent cotton) in an ionic liquid (1-allyl-3-methylimidazolium chloride) at 80°C, heating and stirring slowly for 72 hours to prepare a 20 wt% cellulose molecular solution with a degree of polymerization of approximately 9300.

[0071] (Example 7) The difference between this example and Example 1 lies in Step 1, where 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 stir slowly for 72 hours to prepare a 20 wt% cellulose molecular solution with a degree of polymerization of approximately 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 insulation and low-temperature heat retention.

[0073] (Example 9) The cellulose aerogel fibers prepared in Example 1 were woven together in the longitudinal and transverse directions to form mesh pockets. As shown in Figure 17, this can be applied to high-altitude catches.

[0074] (Comparative Example 1) This comparative example provides cellulose gel fibers prepared using urea and thiourea as raw materials and employing the technical solution of the present invention, and the specific preparation steps include the following: (1) Preparation of spinning solution: Dissolve cellulose in a solution consisting of NaOH, urea, thiourea, and water at 80°C (mass ratio of 16:16:13:155, respectively), and dissolve a 5 wt% cellulose spinning stock solution in it. (2) Wet spinning: A 5wt% cellulose spinning stock solution is orientation-treated by a wet spinning method to obtain cellulose gel fibers. Specifically, the cellulose molecular solution is passed through a catheter and a spinning needle (diameter 300 μm) at an extrusion rate of 300 μL / min, then placed in an anhydrous ethanol coagulation bath to obtain preliminary cellulose gel fibers, and finally orientation-treated to obtain cellulose gel fibers. (3) Preparation of cellulose aerogel fibers: After solvent replacement of the cellulose gel fibers from step (2) (anhydrous ethanol is used as the easily drying solvent), cellulose aerogel fibers are obtained by freeze-drying.

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

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

[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 to 7 is 5 MJ / m² in all cases. 3 The above is the maximum 22 MJ / m 3 This represents a significant improvement in toughness compared to prior art.

[0079] Furthermore, compared to Comparative Example 1, Example 1 showed significantly improved tensile strength, elongation at break, and toughness. In other words, the cellulose aerogel fibers constructed using the in-situ self-assembling hydrogen and crosslinking integration technology of the cellulose molecular-grade solution of the present invention exhibited greatly improved physical properties.

[0080] The cellulose aerogel fibers of Examples 1 to 7, prepared with different cellulose molecular solutions and different solidification rates, all demonstrated high strength and toughness. In particular, comparing Example 1 and Example 3, when the concentration of the cellulose molecular solution was 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, comparing Example 1 and Example 4, only the ionic liquid in Step 1 was 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. The performance of both was almost the same, but in Example 4, it was slightly lower.

[0081] In summary, the above technical solutions provide a method for preparing ultra-tough cellulose aerogel fibers that is simple, requires few preparation steps, has a relatively short preparation cycle, does not require hazardous solvents that are difficult to recycle, is low-cost, offers high economic benefits, and is suitable for industrial production.

[0082] Furthermore, this method allows for continuous preparation, the solvents used are almost 100% recyclable, and the raw materials are widely available and inexpensive, thus having potential for industrialization. The resulting ultra-tough aerogel fibers possess characteristics such as high strength, ultra-high toughness, low thermal conductivity, high porosity, continuous spinnability, good flexibility, strong weaving properties, and excellent stability of the skeletal structure. They can be woven and applied even in harsh or special environments, further expanding the range of applications for these materials.

[0083] (Note) (Note 1) The method involves employing wet spinning technology to prepare a cellulose molecular grade solution using cellulose polymer as a raw material; using the cellulose molecular grade solution as a spinning solution; in the spinning process, in-situ self-assembly and hydrogen bond crosslinking reactions are induced in the cellulose polymer to form a multilayer 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 tension progresses, the degree of orientation along the longitudinal 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, and the cellulose gel fiber having super-toughness is formed. Here, the cellulose molecular grade solution is a cellulose polymer solution, The toughness of the cellulose aerogel fiber is 5 MJ / m 3 The above-mentioned supertough cellulose aerogel fiber.

[0084] (Note 2) The source of the cellulose polymer includes one or more combinations of polymer cellulose, lignin fibers, cellulose ethers, methylcellulose, hydroxypropyl methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, or natural plant materials. and / or, the natural plant material includes one or more combinations of cotton, flax, woody material, straw, grain husk, and bamboo. The supertough cellulose aerogel fiber according to Appendix 1, characterized in that and / or the degree of polymerization of the cellulose polymer is 6000 to 11000.

[0085] (Note 3) The cellulose polymer is dissolved in a solvent to obtain a cellulose molecular-grade solution. and / or, the solvent comprises an ionic liquid, or a mixture of an ionic liquid with one or more of DMSO, NMP, DMAC, or deionized water. And / or, the liquid consisting entirely of ions for the ionic liquid includes imidazolium-based ionic liquids, pyridine-based ionic liquids, and quaternary ammonium salt-based ionic liquids. And / or, the ionic liquid is recyclable, and the super-tough cellulose aerogel fiber according to appended claim 2 is characterized in that.

[0086] (Appended claim 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 - 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 The super-tough cellulose aerogel fiber according to any one of appended claims 1 - 3 is characterized in that.

[0087] (Appended claim 5) The maximum tensile strength of the cellulose aerogel fiber is 17 - 30 MPa, the elongation at break is 82 - 110%, and the toughness of the cellulose aerogel fiber is 5 - 25 MJ / m 3 The super-tough cellulose aerogel fiber according to any one of appended claims 1 - 3 is characterized in that.

[0088] (Appended claim 6) A method for preparing the super-tough cellulose aerogel fiber according to any one of appended claims 1 - 5, specifically, (1) Dissolving a cellulose polymer in a solvent to obtain a cellulose molecular solution; (2) Subjecting the cellulose molecular solution to in-situ self-assembly and hydrogen bond cross-linking reactions of the cellulose polymer by wet spinning technology, and obtaining cellulose gel fibers in combination with orientation treatment; (3) Performing solvent substitution and drying treatment on the cellulose gel fibers to obtain super-tough cellulose aerogel fibers, and the preparation method is characterized in that it includes the above steps.

[0089] (Note 7) The wet spinning technique is characterized by comprising preparing a cellulose molecular solution of a selective concentration as a spinning solution, using anhydrous ethanol as a coagulation bath, squeezing the spinning solution with an injection pump and flowing it into the coagulation bath, inducing in-situ self-assembly and hydrogen bond crosslinking reactions in the cellulose polymer in the cellulose molecular solution, and then performing an orientation treatment to obtain cellulose gel fibers, as described in Appendix 6.

[0090] (Note 8) The method for preparing supertough cellulose aerogel fibers according to Appendix 7, characterized in that the concentration of cellulose polymer in the cellulose molecular solution is 0.1 to 20 wt%, preferably 4 to 6 wt%.

[0091] (Note 9) A method for preparing supertough cellulose aerogel fibers as described in Appendix 7, characterized in that the dissolution temperature of the cellulose polymer in the solvent is 50 to 100°C, the dissolution time is 0.3 to 96 hours, and preferably 72 to 96 hours.

[0092] (Note 10) The method for preparing supertough cellulose aerogel fibers as described in Appendix 7, characterized in that the wet spinning technique employs process conditions in which 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.

[0093] (Note 11) The method for preparing supertough cellulose aerogel fibers according to Appendix 7, characterized in that the orientation treatment method includes one or more combinations of flow orientation, draw orientation, and directional freeze orientation.

[0094] (Note 12) A method for preparing supertough cellulose aerogel fibers according to any one of appendices 6 to 11, characterized in that the solvent substitution includes first replacing the solvent in the cellulose gel fibers that is difficult to dry 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.

[0095] (Note 13) The method for preparing supertough cellulose aerogel fibers according to Appendix 12, characterized in that the readily drying solvent includes one or more combinations of water, methanol, ethanol, tert-butanol, acetone, cyclohexane, and n-hexane.

[0096] (Note 14) The method for preparing supertough cellulose aerogel fibers according to Appendix 12, characterized in that the drying process includes one or more combinations of supercritical fluid drying, vacuum freeze-drying, and reduced-pressure drying.

[0097] (Note 15) Applications of the supertough cellulose aerogel fibers described in Appendix 1 to 5 in the fields of spinning product preparation, composite material preparation, air purification, heavy metal adsorption, airborne particle adsorption, indoor harmful gas adsorption, filter media, or thermal insulation materials.

Claims

1. A method for preparing supertough cellulose aerogel fibers, The method involves employing wet spinning technology to prepare a cellulose molecular grade solution using cellulose polymer as a raw material; using the cellulose molecular grade solution as a spinning solution; in the spinning process, in-situ self-assembly and hydrogen bond crosslinking reactions are induced in the cellulose polymer to form a multilayer 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; as tension progresses, the degree of orientation along the longitudinal 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, and thus forming a cellulose aerogel fiber having super-toughness. The toughness of the cellulose aerogel fiber is 5 MJ / m³ or more. The cellulose molecular grade solution is a cellulose polymer solution, (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 using a wet spinning technique to induce in-situ self-assembly and hydrogen bond crosslinking reactions in a cellulose molecular solution, in conjunction with an orientation treatment. (3) The step of performing solvent replacement and drying treatment on cellulose gel fibers to obtain supertough cellulose aerogel fibers, The solvent includes an ionic liquid, The wet spinning technique includes preparing a cellulose molecular solution of a selective concentration as a spinning solution, using anhydrous ethanol as a coagulation bath, squeezing the spinning solution with an injection pump and flowing it into the coagulation bath, inducing in-situ self-assembly and hydrogen bonding crosslinking reactions in the cellulose polymer in the cellulose molecular solution, and then performing the orientation treatment to obtain the cellulose gel fibers. A method for preparing supertough cellulose aerogel fibers, characterized in that the orientation treatment method includes spinning by one or more combinations of flow orientation, draw orientation, and directional freeze orientation.

2. The source of the cellulose polymer includes one or more combinations of polymer cellulose, cellulose ether, methylcellulose, hydroxypropyl methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, or natural plant materials. and / or, the natural plant material includes one or more of the following: cotton, flax, woody material, straw, grain husk, and bamboo. The method for preparing supertough cellulose aerogel fibers according to claim 1, characterized in that and / or the degree of polymerization of the cellulose polymer is 6,000 to 11,000.

3. The cellulose polymer is dissolved in a solvent to obtain a cellulose molecular-grade solution. and / or, the solvent comprises an ionic liquid, or a mixture of an ionic liquid with one or more of DMSO, NMP, DMAC, or deionized water. and / or, the ionic liquid includes an imidazolium-type ionic liquid, a pyridine-type ionic liquid, and a quaternary ammonium salt-type ionic liquid. The method for preparing supertough cellulose aerogel fibers according to claim 2, characterized in that the ionic liquid is recyclable.

4. The three-dimensional multi-stage pore network structure includes micropores with a diameter of 2 nm or less, mesopores with a diameter of 2 to 50 nm, and macropores with a diameter of 50 nm to 100 nm. and / or, the cellulose aerogel fibers have a diameter of 0.1 μm to 1 mm and a specific surface area of ​​290 to 372 m². ２ It has a density of 0.18–0.25 g / cm³, a porosity of 80–90%, and a density of 0.18–0.25 g / cm³. ３ A method for preparing supertough cellulose aerogel fibers according to any one of claims 1 to 3, characterized in that...

5. A method for preparing supertough cellulose aerogel fibers according to any one of claims 1 to 3, characterized in that the cellulose aerogel fibers have a maximum tensile strength of 17 to 30 MPa and an elongation at break of 82 to 110%.

6. The method for preparing supertough cellulose aerogel fibers according to claim 1, characterized in that the concentration of cellulose polymer in the cellulose molecular solution is 0.1 to 20 wt%.

7. The method for preparing supertough cellulose aerogel fibers according to claim 1, characterized in that the dissolution temperature of the cellulose polymer in the solvent is 50 to 100°C and the dissolution time is 0.3 to 96 hours.

8. The method for preparing supertough cellulose aerogel fibers according to claim 1, characterized in that the wet spinning technique employs process conditions in which 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.

9. The method for preparing supertough cellulose aerogel fibers according to claim 1, characterized in that the solvent substitution includes first substituting a first solvent in the cellulose gel fibers with a second solvent that dries more easily than the first solvent, and then performing a drying treatment on the substituted cellulose gel fibers to obtain cellulose aerogel fibers.

10. The method for preparing supertough cellulose aerogel fibers according to claim 9, characterized in that the second solvent comprises one or more combinations of water, methanol, ethanol, tert-ptanol, acetone, cyclohexane, and n-hexane.

11. The method for preparing supertough cellulose aerogel fibers according to claim 9, characterized in that the drying process includes one or more combinations of supercritical fluid drying, vacuum freeze-drying, and reduced-pressure drying.

12. Use of supertough cellulose aerogel fibers prepared by the method for preparing supertough cellulose aerogel fibers described in any one of claims 1 to 3 in the fields of spinning product preparation, composite material preparation, air purification, heavy metal adsorption, airborne particle adsorption, indoor harmful gas adsorption, filter media, or heat insulating materials.

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