A method for drying cellulose-based aerogel fibers under atmospheric pressure

Abstract

The present invention discloses a method for drying cellulose-based aerogel fibers under atmospheric pressure, which comprises the following steps: dispersing and dissolving the washed and pulverized cellulose raw materials in a cellulose solvent, and then obtaining a cellulose spinning solution after defoaming and filtration, wherein the mass fraction of cellulose in the spinning solution is 4% - 9%; extruding the cellulose spinning solution through a spinneret into a coagulation bath to obtain one-dimensional cellulose wet gel fibers, and the extrusion speed is 6 - 50 ml / min; passing the cellulose wet gel fibers through a displacement tank containing a mixed solution of tert-butanol with paraffin alkane to exchange the moisture inside the wet gel fibers for a mixed solution containing alkane. After modifying the wet gel fibers prepared by continuous wet spinning, the present invention adopts a method of rapid freezing and then atmospheric pressure drying to obtain aerogel fibers. The atmospheric pressure drying has a fast speed and relatively low energy consumption. Compared with the prior art, the present invention can meet the continuous production of the whole process of cellulose fibers, has scalability, and improves the yield of aerogel fibers.

Description

Technical Field

[0001] The present invention relates to the technical field of new material preparation, and particularly to a method for drying cellulose-based aerogel fibers under atmospheric pressure. Background Art

[0002] Aerogel is a unique solid material composed of a three-dimensional solid network connected to each other and a large number of pores filled with air. The development of aerogel in fiber form provides a customizable and multifunctional assembly strategy. Its ductile one-dimensional characteristics can be manufactured into multi-dimensional configurations through textile strategies, which can help avoid the brittleness and flexibility problems of traditional aerogels and broaden the application fields. However, for all future research directions, the large-scale manufacturing of aerogel fibers is a particular concern because in most applications, a large amount of fiber aggregates are highly desired, especially for thermal insulation applications in textiles and high-tech fields. The large-scale implementation is closely related to spinning technology and drying technology, which will affect the production speed of aerogel fibers. Therefore, there is an urgent need to develop new technologies that are scalable, multifunctional, and continuously preparable to produce new aerogel fibers with well-defined microstructures.

[0003] Cellulose is the most abundant natural polymer on earth. It has remarkable properties such as biodegradability, renewability, and hydrophilicity, and combines the excellent properties of aerogels, making it a promising candidate material for preparing various cellulose-based aerogels. Usually, wet spinning methods are used to prepare cellulose wet gel fibers. After gel formation, drying is a necessary step to obtain the final aerogel fibers. However, removing the liquid solvent from the gel while avoiding shrinkage or cracking of the established network structure is a major challenge because the fine nanostructures in the wet gel may not be able to withstand the collapse due to the surface tension at the liquid-gas interface during direct drying and cannot form a uniform and ordered nanopore network.

[0004] The prior art CN201610473161.1 discloses a continuous cellulose aerogel fiber and its preparation method. The cellulose spinning process is dynamically continuous, but the wet fibers after gelation need to be collected and then dried by supercritical drying and freeze-drying methods. These drying processes are not continuous and have a series of disadvantages such as high danger, long drying time, and high energy consumption. Therefore, it is still difficult to achieve large-scale industrial production of biomass-based aerogels to this day.

[0005] The prior art CN202210809209.7 discloses a nanofibrillated cellulose aerogel and its preparation method. The drying process of this aerogel belongs to atmospheric pressure drying, but the raw material selected is nanofibrillated cellulose fiber, and the fiber gelation process is through the static gelation of metal ions, which cannot be used for the continuous spinning of cellulose. Therefore, this process route still cannot be used to prepare cellulose aerogel fibers.

[0006] The prior art CN202310478630.9 discloses a bagasse cellulose aerogel and a preparation method thereof. The gelation process of this cellulose is completed by chemical static cross-linking with glutaraldehyde for 45 to 48 hours, and then atmospheric drying is carried out after gelation to obtain the aerogel. Glutaraldehyde has certain toxicity and great harm to the human body. At the same time, this static cross-linking process is too long and still difficult to meet the actual production needs of aerogel fibers.

[0007] Therefore, it is necessary to provide a method for atmospheric drying of cellulose-based aerogel fibers to solve the above technical problems. Summary of the Invention

[0008] The present invention overcomes the deficiencies of the prior art and provides a method for atmospheric drying of cellulose-based aerogel fibers.

[0009] To achieve the above object, the technical solution adopted by the present invention is: A method for atmospheric drying of cellulose-based aerogel fibers, comprising the following steps:

[0010] S1. Dispersedly dissolve the washed and pulverized cellulose raw material in a cellulose solvent, and then after defoaming and filtering, obtain a cellulose spinning solution, wherein the mass fraction of cellulose in the spinning solution is 4% to 9%;

[0011] S2. Extrude the cellulose spinning solution through a spinneret into a coagulation bath to obtain one-dimensional cellulose wet gel fibers, and the extrusion speed is 6 to 50 ml / min;

[0012] S3. Pass the cellulose wet gel fibers through a displacement tank containing a mixed solution of paraffin alkane and tert-butanol to exchange the water inside the wet gel fibers for a mixed solution containing alkane;

[0013] S4. Pass the cellulose wet gel fibers through a low-temperature freezing zone, and immediately after the fibers are frozen, introduce them into a high-temperature drying zone for solvent removal to obtain cellulose aerogel fibers.

[0014] In a preferred embodiment of the present invention, in the step S1, the cellulose raw material is at least one of bamboo pulp, cotton pulp, bacterial cellulose, or regenerated viscose.

[0015] In a preferred embodiment of the present invention, in the step S1, the cellulose solvent is a solution containing one or more of ionic liquid, N-methylmorpholine-N-oxide (NMMO), sodium hydroxide / urea, and lithium chloride / dimethylacetamide.

[0016] In a preferred embodiment of the present invention, in the step S2, the coagulation bath is an aqueous solution containing 5 to 15 wt% citric acid, 2.5 to 5 wt% trisodium citrate, and 10 to 40 wt% tert-butanol, the temperature of the coagulation bath is 20°C to 25°C, and the length of the coagulation bath tank is 1 to 2 m.

[0017] In a preferred embodiment of the present invention, in the step S2, the size of the spinneret holes is 0.1 - 1.6 mm, and the number of holes is 10 - 30.

[0018] In a preferred embodiment of the present invention, in the step S3, the alkane in the tert-butanol mixed solution containing paraffin alkane is at least one of straight-chain saturated alkanes with 16 - 22 carbon atoms, the volume fraction is 1:10 - 20, the length of the displacement tank is 1.5 - 3 m, and the number of tanks is 1 - 5.

[0019] In a preferred embodiment of the present invention, in the step S4, the temperature of the freezing zone is -10 - -35 °C, the length of the freezing zone is 0.5 - 2 m, and the transmission speed of the cellulose wet gel fiber is 1 m / min.

[0020] In a preferred embodiment of the present invention, in the step S4, the temperature of the high-temperature drying zone is 85 - 150 °C, the length of the drying zone is 0.5 - 2 m, and the transmission speed of the cellulose wet gel fiber is 1 m / min.

[0021] In a preferred embodiment of the present invention, the tert-butanol solution after high-temperature vaporization is collected, condensed, and then introduced into the displacement tank for solvent recycling.

[0022] The cellulose aerogel fiber prepared by the method for preparing cellulose-based aerogel fiber under atmospheric pressure as described above, the cross-sectional diameter of the cellulose aerogel fiber is 100 - 800 um, and the density of the cellulose aerogel fiber is 0.1 - 0.3 g / cm 3 , and the specific surface area is 250 - 350 m 2 / g.

[0023] The present invention solves the defects in the background technology, and the present invention has the following beneficial effects:

[0024] (1) The present invention provides a method for preparing cellulose-based aerogel fiber under atmospheric pressure. After modifying the wet gel fiber prepared by continuous wet spinning, the aerogel fiber is obtained by rapid freezing followed by atmospheric pressure drying. The atmospheric pressure drying speed is fast and the energy consumption is relatively low. Compared with the prior art, the present invention can meet the continuous production of the whole process of cellulose fiber, has scalability, improves the output of aerogel fiber, and can meet the needs of commercial large-scale applications.

[0025] (2) After modifying the wet gel fiber prepared by continuous wet spinning and then obtaining the aerogel fiber by atmospheric pressure drying, the density of the cellulose aerogel fiber prepared by the present invention is controlled at 0.1 - 0.3 g / cm 3 , and the specific surface area is 250 - 350 m 2 / g, and similar microtopographies, with excellent heat insulation properties, and have potential application values in the fields of personal thermal management and healthcare management.

[0026] (3) In the present invention, the tert-butanol solution that has undergone high-temperature vaporization is recovered, condensed, and then introduced into the replacement tank, avoiding the direct discharge of tert-butanol gas generated during the drying process into the atmosphere. A tert-butanol recovery and separation device is installed at the top of the high-temperature drying chamber. After the tert-butanol vapor is recovered, it is introduced into the replacement tank to achieve the recycling of the solution, solving the problems of waste of tert-butanol products and potential safety hazards to the environment and health. Brief Description of the Drawings

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings;

[0028] Figure 1 is the flowchart of the method of the preferred embodiment of the present invention;

[0029] Figure 2 is the continuous preparation flowchart of cellulose aerogel fibers of the preferred embodiment of the present invention;

[0030] Figure 3 is the microtopography of the cross-section of cellulose aerogel fibers obtained in Example 1 of the present invention at different magnification levels;

[0031] Figure 4 is the mechanical property analysis diagram of cellulose aerogel fibers obtained in Example 1, Example 2, and Example 3 of the present invention;

[0032] Figure 5 is the nitrogen adsorption curve of cellulose aerogel fibers obtained in Example 1, Example 2, and Example 3 of the present invention.

[0033] Figure 6 is the pore size distribution curve obtained based on the desorption branch of the isotherm of cellulose aerogel fibers obtained in Example 1, Example 2, and Example 3 of the present invention.

[0034] In the figure: 1, spinning solution; 2, spinneret; 3, guide roller; 4, coagulation bath; 5, wet gel fiber; 6, replacement bath; 7, tert-butanol transportation pipeline; 8, low-temperature freezer; 9, tert-butanol recovery device; 10, blast drying chamber; 11, aerogel fiber; 12, collecting roller. Detailed Embodiments

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0036] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention may be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0037] In the description of the present application, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the protection scope of the present application.

[0038] In the description of the present application, it should be noted that, unless otherwise clearly defined and limited, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.

[0039] As Figure 1 shown, the present invention provides a method for drying cellulose-based aerogel fibers under atmospheric pressure, comprising the following steps:

[0040] S1. Dispersedly dissolve the cleaned and pulverized cellulose raw materials in a cellulose solvent, and then obtain a cellulose spinning solution after defoaming and filtering. The mass fraction of cellulose in the spinning solution is 4% to 9%; wherein, the cellulose raw material is at least one of bamboo pulp, cotton pulp, bacterial cellulose or regenerated viscose; and the cellulose solvent is a solution containing one or more of ionic liquid, N-methylmorpholine-N-oxide (NMMO), sodium hydroxide / urea, and lithium chloride / dimethylacetamide.

[0041] S2. Extrude the cellulose spinning solution through a spinneret into a coagulation bath to obtain one-dimensional cellulose wet gel fibers, with an extrusion speed of 6 - 50 ml / min. Among them, the coagulation bath is an aqueous solution containing 5 - 15 wt% citric acid, 2.5 - 5 wt% trisodium citrate, and 10 - 40 wt% tert-butanol. The temperature of the coagulation bath is 20°C - 25°C, the length of the coagulation bath tank is 1 - 2 m; the size of the spinneret holes is 0.1 - 1.6 mm, and the number of holes is 10 - 30.

[0042] S3. Pass the cellulose wet gel fibers through a displacement tank containing a mixed solution of tert-butanol with paraffin alkanes to exchange the water inside the wet gel fibers for a mixed solution containing alkanes. The alkane in the mixed solution of tert-butanol with paraffin alkanes is at least one of straight-chain saturated alkanes with 16 - 22 carbon atoms, and the volume fraction is 1:10 - 20. The length of the displacement tank is 1.5 - 3 m, and the number of tanks is 1 - 5.

[0043] S4. Pass the cellulose wet gel fibers through a low-temperature freezing zone. Immediately after the fibers are frozen, introduce them into a high-temperature drying zone for solvent removal to obtain cellulose aerogel fibers. The temperature of the freezing zone is -10°C - -35°C, the length of the freezing zone is 0.5 - 2 m, and the transmission speed of the cellulose wet gel fibers is 1 m / min; the temperature of the high-temperature drying zone is 85°C - 150°C, the length of the drying zone is 0.5 - 2 m, and the transmission speed of the cellulose wet gel fibers is 1 m / min.

[0044] In the present invention, after modifying the wet gel fibers prepared by continuous wet spinning, the aerogel fibers are obtained by first freezing the fibers at low temperature and then drying them under normal pressure. Low-temperature freezing causes the aggregation and entanglement of cellulose molecular chains, strengthens the fiber network, and helps to resist the capillary force that drives the collapse of the structure during the drying process. In contrast, directly drying the aerogel without freezing will result in obvious shrinkage due to structural collapse. Compared with the methods of ultra-low-pressure freeze-drying and supercritical drying, drying under normal pressure is fast and energy-efficient. Compared with the prior art, the present invention can meet the continuous production of the entire process of cellulose fibers, has scalability, increases the yield of aerogel fibers, and can meet the needs of commercial large-scale applications.

[0045] In this embodiment, the tert-butanol solution vaporized at high temperature is collected, condensed, and then introduced into the displacement tank for solvent recycling.

[0046] Recycling the tert-butanol solution vaporized at high temperature, condensing it, and then introducing it into the displacement tank avoids the direct discharge of the tert-butanol gas generated during the drying process into the atmosphere. A tert-butanol recovery and separation device is installed at the top of the high-temperature drying chamber. After recovering the tert-butanol vapor, it is introduced into the displacement tank to realize the recycling of the solution, solving the problems of waste of tert-butanol products and potential safety hazards to the environment and health.

[0047] AsFigure 2 As shown in the figure, the present invention also provides a device for drying cellulose-based aerogel fibers under normal pressure, including: a coagulation bath 4, a number of replacement baths 6, a low-temperature freezer 8, a blast drying chamber 10 arranged in sequence, and a number of guide rollers 3 for transporting fibers during the preparation process; a spinneret 2 is arranged in the coagulation bath 4 for extruding the spinning solution 1 input therein into the coagulation bath.

[0048] A number of guide rollers 3 are respectively arranged inside and outside the coagulation bath 4, the replacement bath 6, and the low-temperature freezer 8. The number of guide rollers 3 arranged inside the coagulation bath 4 and the replacement bath 6 are arranged in a staggered up-and-down manner to extend the transmission path of the fibers in the coagulation bath 4 and the replacement bath 6. The number of guide rollers 3 arranged outside are used to introduce the wet gel fibers 5 from the coagulation bath 4 into the replacement bath 6 and from the replacement bath 6 into the low-temperature freezer 8; a collection roller 12 is arranged at the outlet end of the blast drying chamber 10 for collecting the dried aerogel fibers 11.

[0049] A tert-butanol recovery device 9 is arranged on the upper part of the blast drying chamber 10. A tert-butanol transportation pipeline 7 is arranged on one side of the tert-butanol recovery device 9, and the other end of the tert-butanol transportation pipeline 7 is inserted into the inside of the replacement bath 6; the tert-butanol recovery device 9 is used to recover the tert-butanol solution vaporized at high temperature and has a condensation function to re-liquefy the vaporized tert-butanol solution, and then pass the recovered tert-butanol solution into the replacement bath 6 through the tert-butanol transportation pipeline 7.

[0050] The cellulose aerogel fibers prepared by the method for drying cellulose-based aerogel fibers under normal pressure as described above, the cross-sectional diameter of the cellulose aerogel fibers is 100 - 800 um, and the density of the cellulose aerogel fibers is 0.1 - 0.3 g / cm 3 , and the specific surface area is 250 - 350 m 2 / g.

[0051] After modifying the wet gel fibers prepared by continuous wet spinning and then using the method of rapid freezing followed by drying under normal pressure to obtain aerogel fibers, the density of the cellulose aerogel fibers prepared by the present invention is controlled at 0.1 - 0.3 g / cm 3 , and the specific surface area is 250 - 350 m 2 / g, and has a similar microscopic morphology, with excellent heat insulation properties and potential application value in the fields of personal thermal management and healthcare management.

[0052] Example 1

[0053] Use the above method for drying cellulose-based aerogel fibers under normal pressure to prepare a cellulose aerogel fiber sample. The specific steps are as follows:

[0054] (1) Pulverize bamboo pulp and disperse it in a cellulose solvent. After defoaming and filtration, a cellulose spinning solution is obtained. The cellulose solvent is a mixed solution of urea and a 40 wt% tetrabutylammonium hydroxide solution, where the proportion of urea is 28 wt%, and the cellulose content in the spinning solution is 6 wt%.

[0055] (2) Extrude the obtained cellulose spinning solution through a spinneret into a coagulation bath to obtain one-dimensional cellulose wet gel fibers. In the coagulation bath, citric acid / sodium citrate / tert-butanol / water = 15 / 5 / 36 / 40 wt%, the extrusion speed is 15 ml / min, and the spinneret hole size is 0.8 mm.

[0056] (3) Pass the cellulose wet gel fibers through a displacement tank containing a mixed solution of n-octadecane and tert-butanol to exchange the water inside the wet gel fibers for a tert-butanol solution containing alkane, where n-octadecane accounts for 10 wt% of the mixed solution.

[0057] (4) Pass the displaced cellulose wet gel fibers through a low-temperature freezer at -20 °C. Immediately after the fibers are frozen, introduce them into a high-temperature drying zone at 100 °C to remove the solvent, and finally obtain cellulose aerogel fibers.

[0058] Example Two

[0059] Use the above method for drying cellulose-based aerogel fibers under normal pressure to prepare cellulose aerogel fiber samples. The specific steps are as follows:

[0060] (1) Cool the sodium hydroxide / urea / water solution to -10 to -12 °C, then add a certain amount of bacteriocellulose dried to absolute dryness, stir and maintain the temperature of the solution until the cellulose is completely dissolved, and then slowly raise the temperature to 0 to 5 °C to obtain a transparent cellulose solution. The cellulose solution becomes a spinning solution after filtration and degassing. The cellulose fibers are obtained by wet spinning the spinning solution in a coagulation bath containing sulfuric acid and sodium sulfate. Among them, in the dissolution system, sodium hydroxide / urea / water = 7:12:81 (wt%), and the dissolved cellulose content is 5 wt%.

[0061] (2) Extrude the obtained cellulose spinning solution through a spinneret into a coagulation bath to obtain one-dimensional cellulose wet gel fibers. In the coagulation bath, sodium sulfate / sulfuric acid / water = 6 / 5 / 39 wt%, the extrusion speed is 10 ml / min, and the spinneret hole size is 1.2 mm.

[0062] (3) Pass the cellulose wet gel fibers through 3 displacement tanks containing a mixed solution of n-eicosane and tert-butanol to exchange the water inside the wet gel fibers for a tert-butanol solution containing alkane, where n-eicosane accounts for 10 wt% of the mixed solution.

[0063] (4) Pass the replaced cellulose wet gel fibers through a -20°C low-temperature freezer. Immediately after the fibers are frozen, introduce them into a 120°C high-temperature drying zone to remove the solvent, and finally obtain cellulose aerogel fibers.

[0064] Example 3

[0065] Use the above method for preparing cellulose-based aerogel fibers by atmospheric pressure drying to prepare a cellulose aerogel fiber sample. The specific steps are as follows:

[0066] (1) Activate waste viscose fibers with a 10 wt% ethylenediamine solution at 40°C for 90 min. Wash with a large amount of distilled water and methanol and then vacuum dry at 80°C. Then use lithium chloride (LiCl) / dimethylacetamide (DMAc) solvent to dissolve the activated viscose fibers. Heat to 100°C and stir at 300 r / min for 3 h, then let it stand at room temperature for 12 h. The cellulose is completely dissolved. After defoaming and filtration, a cellulose spinning solution is obtained. The LiCl concentration in the cellulose dissolution system is 8 wt%, and the cellulose content in the spinning solution is 3 wt%.

[0067] (2) Pass the obtained cellulose spinning solution through a spinneret into a water coagulation bath to obtain one-dimensional cellulose wet gel fibers. The extrusion speed is 20 ml / min, and the spinneret hole size is 1 mm.

[0068] (3) Pass the cellulose wet gel fibers through two replacement tanks containing a mixed solution of n-hexadecane and tert-butanol to exchange the water inside the wet gel fibers for a tert-butanol solution containing alkanes, where n-hexadecane accounts for 10 wt% of the mixed solution.

[0069] (4) Pass the replaced cellulose wet gel fibers through a -20°C low-temperature freezer. Immediately after the fibers are frozen, introduce them into an 85°C high-temperature drying zone to remove the solvent, and finally obtain cellulose aerogel fibers.

[0070] As Figure 3 shown, for the cross-section of the cellulose aerogel fibers prepared in Example 1 at different magnifications (a. magnified 300 times; b. magnified 5000 times; c. magnified 40000 times), it can be seen that the cross-section of the cellulose aerogel fibers prepared by the present invention is approximately circular, with an average diameter of 604 um. There are wrinkles on the outer layer of the fibers, and an interconnected open-cell 3D network structure is presented after internal magnification.

[0071] As Figure 4As shown in the figure, the mechanical properties of the cellulose aerogel fibers prepared in the examples were tested. Tensile tests were carried out along the longitudinal direction of the fibers. The elongation at break of the aerogel fibers obtained in Example 1 was 16.7%, and the tensile strength reached 29.8 Mpa. The elongation at break of the aerogel fibers obtained in Example 2 was 16.7%, and the tensile strength reached 29.8 Mpa. The elongation at break of the aerogel fibers obtained in Example 3 was 16.7%, and the tensile strength reached 29.8 Mpa.

[0072] As Figure 5 and Figure 6 shown, the nitrogen adsorption curve of the cellulose aerogel fibers prepared in the examples is presented (the inserted figure is the corresponding pore size distribution). The nitrogen adsorption-desorption isotherm of the aerogel fibers conforms to the Type-IV isotherm and has an obvious hysteresis loop, indicating that the prepared aerogel fibers have a mesoporous structure. The specific surface area of the aerogel fibers obtained in Example 1 was 251 m 2 / g, and the most probable pore size was 30.1 nm; the specific surface area of the aerogel fibers obtained in Example 2 was 285 m 2 / g, and the most probable pore size was 35.4 nm; the specific surface area of the aerogel fibers obtained in Example 3 was 332 m 2 / g, and the most probable pore size was 73.1 nm.

[0073] Based on the ideal embodiments of the present invention as inspiration, through the above description, relevant personnel can make various changes and modifications completely within the scope without departing from the technical idea of the present invention. The technical scope of the present invention is not limited to the content in the specification, and the technical scope must be determined according to the scope of the claims.

Claims

1. A method for drying cellulose-based aerogel fibers at atmospheric pressure, characterized in that, It includes the following steps: S1. Dispersedly dissolve the cleaned and pulverized cellulose raw material in a cellulose solvent, and then obtain a cellulose spinning solution after defoaming and filtration. The mass fraction of cellulose in the spinning solution is 4% - 9%; S2. Extrude the cellulose spinning solution into a coagulation bath through a spinneret to obtain one-dimensional cellulose wet gel fibers, and the extrusion speed is 6 - 50 ml / min; S3. Pass the cellulose wet gel fibers through a displacement tank containing a mixed solution of tert-butanol and paraffin alkane to exchange the water inside the wet gel fibers for a mixed solution containing alkane. Among them, the alkane in the mixed solution of tert-butanol and paraffin alkane is at least one of straight-chain saturated alkanes with 16 - 22 carbon atoms, and the volume fraction is 1:10 - 20; S4. Pass the cellulose wet gel fibers through a low-temperature freezing zone, and immediately after the fibers are frozen, introduce them into a high-temperature drying zone to remove the solvent to obtain cellulose aerogel fibers; Among them, the temperature of the freezing zone is -10 - -35 °C, and the length of the freezing zone is 0.5 - 2 m; the temperature of the high-temperature drying zone is 85 - 150 °C, and the length of the drying zone is 0.5 - 2 m.

2. The method for drying cellulose-based aerogel fibers at atmospheric pressure according to claim 1, characterized in that, In the above S1, the cellulose raw material is at least one of bamboo pulp, cotton pulp, bacterial cellulose or regenerated viscose.

3. A method for drying cellulose-based aerogel fibers at atmospheric pressure according to claim 1, characterized in that, In the above S1, the cellulose solvent is a solution containing one or more of ionic liquid, N-methylmorpholine-N-oxide (NMMO), sodium hydroxide / urea, lithium chloride / dimethylacetamide.

4. A method for drying cellulose-based aerogel fibers at atmospheric pressure according to claim 1, characterized in that, In the above S2, the coagulation bath is an aqueous solution containing 5 - 15 wt% citric acid, 2.5 - 5 wt% trisodium citrate, and 10 - 40 wt% tert-butanol. The temperature of the coagulation bath is 20 °C - 25 °C, and the length of the coagulation bath tank is 1 - 2 m.

5. A method for drying cellulose-based aerogel fibers at atmospheric pressure according to claim 1, characterized in that, In the above S2, the size of the spinneret holes is 0.1 - 1.6 mm, and the number of holes is 10 - 30.

6. A method for drying cellulose-based aerogel fibers under atmospheric pressure according to claim 1, characterized in that, In the above S3, the length of the displacement tank is 1.5 - 3 m, and the number of tanks is 1 - 5.

7. A method for drying cellulose-based aerogel fibers at atmospheric pressure according to claim 1, characterized in that, In the above S4, the transmission speed of the cellulose wet gel fibers is 1 m / min.

8. A method for drying cellulose-based aerogel fibers under normal pressure according to claim 1, characterized in that, Collect the tert-butanol solution after high-temperature vaporization, condense it, and then introduce it into the displacement tank for solvent recycling.

9. A cellulose aerogel fiber prepared by the method of any one of claims 1-8 for drying a cellulose-based aerogel fiber at atmospheric pressure, characterized in that, The cross-sectional diameter of the cellulose aerogel fiber is 100 to 800 μm, and the density of the cellulose aerogel fiber is 0.1 to 0.3 g / cm 3 , and the specific surface area is 250 to 350 m 2 / g.

Images