Preparation method of agarose-cellulose-polyurea composite aerogel fiber

Abstract

The invention discloses a method for preparing agarose-cellulose-polyurea composite aerogel fiber, which relates to the field of aerogel materials. The method comprises the following steps: connecting a polyfluoroethylene hose to a syringe needle to enable an agarose-cellulose spinning solution to gel into a fiber shape in a coagulation bath due to its self-gelling property; controlling the gelation rate by adjusting the temperature of the coagulation bath, thereby preparing continuous agarose-cellulose composite fibers; reacting the agarose-cellulose composite fibers with components A and B of a synthetic polyurea to in-situ composite the agarose-cellulose composite fibers with polyurea; and finally drying the fibers with supercritical carbon dioxide to obtain agarose-cellulose-polyurea composite aerogel fibers having hydrophobicity and flexibility.

Description

Technical Field

[0001] The present invention relates to the field of aerogel materials, and in particular to a method for preparing agarose-cellulose-polyurea composite aerogel fiber. Background Art

[0002] Aerogel is an ultra-porous three-dimensional nanomaterial. Its unique microstructure gives it excellent properties such as low density, high porosity, large specific surface area and low thermal conductivity, making it have good application prospects in many fields such as thermal insulation, separation, energy storage, batteries, aerospace, etc. However, traditional inorganic aerogel materials are too brittle to be used in practical applications. At present, aerogel materials mainly exist in one-dimensional and three-dimensional forms, such as particles, powders, felt materials and blocks, and two-dimensional materials are mainly membrane materials. Therefore, in order to improve the mechanical properties of aerogels and enrich the application fields of aerogels, researchers have developed an aerogel fiber material with excellent performance to broaden the practical application scenarios of aerogels.

[0003] Aerogel fibers have a fibrous macromorphology and a high aspect ratio, resulting in excellent flexibility and weavability. They also possess the high porosity, low density, and low thermal conductivity of aerogels, and have enormous application potential. However, the preparation process for aerogel fibers currently under study is relatively complex, and the internal structure of aerogel fibers easily collapses during the spinning process, making continuous spinning difficult.

[0004] Chinese patent publication number CN116288782A discloses a recyclable, high-performance heteroaromatic aerogel fiber and its preparation method. However, the preparation method is complex, requiring the polybenzimidazole polymer and cobalt ion solution to be dissolved in the same solvent before mixing to produce the spinning solution. During wet spinning, the coagulation bath requires a mixture of an organic solvent and water containing an oxidant to achieve gelation, and the preparation conditions are stringent.

[0005] Chinese patent publication number CN114182371B discloses a sheath-core aerogel fiber and its preparation method. The spinning solution A used in this method is a mixed solution, which is expensive and costly. The spinning process requires secondary coagulation, and the spun fibers must be immersed in a coagulation bath for a period of time to remove residual organic solvent. This complex preparation process has limited its practical application to a certain extent.

[0006] Therefore, there is an urgent need for a simple and effective method to prepare aerogel fiber materials with good mechanical properties. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for preparing agarose-cellulose-polyurea composite aerogel fiber, so as to solve the problem that the existing aerogel fiber has poor mechanical properties.

[0008] In order to solve the above problems, the present invention adopts the following technical solutions:

[0009] The present invention provides a method for preparing agarose-cellulose-polyurea composite aerogel fiber, comprising the following steps:

[0010] Step S1: mixing an agarose solution and a cellulose solution to prepare an agarose-cellulose spinning solution.

[0011] In an exemplary embodiment of the present disclosure, the mass concentration of the agarose solution used is 1-3%, and the mass concentration of the cellulose used is 0.2-0.8%. If the spinning solution concentration exceeds this range, the viscosity of the spinning solution may clog the syringe and prevent subsequent processing. If the concentration is below this range, the gel fiber may not form.

[0012] In an exemplary embodiment of the present disclosure, the agarose solution is repeatedly heated in a microwave oven to dissolve the agarose solution. The agarose solution and cellulose are stirred and mixed at a temperature of 60-90° C. using a magnetic stirrer for 0.5-2 h.

[0013] Step S2: contacting the agarose-cellulose spinning solution with a coagulation bath gel to obtain agarose-cellulose composite fibers.

[0014] In an exemplary embodiment of the present disclosure, the coagulation bath is formed by deionized water, and the temperature of the coagulation bath is -6 to -16°C.

[0015] In an exemplary embodiment of the present disclosure, an agarose-cellulose spinning solution is passed through a syringe and brought into contact with a coagulation bath via a tetrafluoroethylene hose to obtain agarose-cellulose composite fibers. The syringe is connected to the tetrafluoroethylene hose in order to gel the agarose-cellulose spinning solution into fibers of a specific thickness. The tetrafluoroethylene hose preferably has a diameter of 0.5 to 1.0 mm and a length of 30 to 50 cm. When the diameter of the tetrafluoroethylene hose is lower than the specified range, the spun fibers are too thin and have poor mechanical properties. When the length of the tetrafluoroethylene hose exceeds the specified range, the agarose-cellulose spinning solution gels in the tetrafluoroethylene hose before contacting the coagulation bath, causing blockage.

[0016] In an exemplary embodiment of the present disclosure, the syringe is fixed on a micro-injection pump, and a box that can support the polyfluoroethylene hose is placed under the polyfluoroethylene hose so that the hose is in a straight state. The polyfluoroethylene hose is fixed vertically above the coagulation bath, and it is in a curved state. The spinning solution contacts the coagulation bath gel through the polyfluoroethylene hose connected to the syringe. The injection rate of the micro-injection pump is preferably 10~80 mL / h. When the injection rate is higher than the limit range, discontinuous fibers will appear; when the injection rate is lower than the limit range, gel will appear in the hose, causing the hose to be blocked. The height of the outlet of the polyfluoroethylene hose from the coagulation bath is 5~15 cm.

[0017] Step S3, fully replacing the agarose-cellulose composite fiber with anhydrous ethanol and acetonitrile solvents in sequence; then reacting the agarose-cellulose composite fiber with a component A solution and a component B solution that can react to form polyurea in sequence to obtain an agarose-cellulose-polyurea composite gel fiber; wherein component A is an isocyanate component and component B is an amino compound.

[0018] Supplementary Note: Directly displacing the agarose-cellulose composite fibers with acetonitrile solvent can lead to incomplete displacement, resulting in residual water reacting violently with components A and B, causing gelation during the reaction. Therefore, in the present invention, the water in the agarose-cellulose composite fibers is first displaced with anhydrous ethanol, followed by the replacement of the anhydrous ethanol with acetonitrile.

[0019] In an exemplary embodiment of the present disclosure, component A is an isocyanate, or diphenylmethane diisocyanate (MDI-50), or a mixture of diphenylmethane diisocyanate (MDI-50) and polypropylene glycol (PPG-3000), or a mixture of diphenylmethane diisocyanate (MDI-50) and polypropylene glycol (PPG-4000), or toluene diisocyanate (TDI), or xylylene diisocyanate (XDI).

[0020] In an exemplary embodiment of the present disclosure, component B in step S3 is amino-terminated polyether (D-2000), or a mixture of amino-terminated polyether (D-2000 and T-2000), or a mixture of amino-terminated polyether (D-2000 and T-2000) and 4,4-bis-sec-butylaminodiphenylmethane (MDBA), or a mixture of amino-terminated polyether (D-2000 and T-2000) / 4,4-bis-sec-butylaminodiphenylmethane (MDBA) / diisobutyltoluenediamine (DETDA-80) mixture, or a mixture of amino-terminated polyether (D-2000) / 4,4-bis-sec-butylaminodiphenylmethane (MDBA) / diisobutyltoluenediamine (DETDA-80).

[0021] Because pure solutions or mixtures of components A and B are both very viscous, in an exemplary embodiment of the present disclosure, components A and B are diluted with a solvent to prepare a diluted component A solution and a diluted component B solution for use in the above method. The solvent used for dilution is any one of acetonitrile, n-hexane, toluene, and acetone.

[0022] In an exemplary embodiment of the present disclosure, a diphenylmethane diisocyanate (MDI-50) solution and acetonitrile are mixed in a volume ratio of 1:1 to 8 to prepare a component A diluent.

[0023] In an exemplary embodiment of the present disclosure, amino-terminated polyether (D-2000), 4,4-bis-sec-butylaminodiphenylmethane (MDBA), and diisobutyltoluenediamine (DETDA-80) are mixed in a molar ratio of 2:1:1, and then mixed with acetonitrile in a volume ratio of 1:1-8 to prepare a diluent of component B.

[0024] In an exemplary embodiment of the present disclosure, the reaction temperature of the agarose-cellulose composite fiber and the diluted solution of component A is 70-90° C., and the reaction time is 0.5-4 h.

[0025] In an exemplary embodiment of the present disclosure, the reaction temperature of the agarose-cellulose composite fiber and the diluted solution of component B is 25-50° C., and the reaction time is 0.5-4 h.

[0026] In an exemplary embodiment of the present disclosure, the agarose-cellulose composite fiber is reacted with the component A solution and then washed with acetonitrile to remove the unreacted or residual solution on the fiber surface.

[0027] In an exemplary embodiment of the present disclosure, the agarose-cellulose composite fiber is reacted with the component B solution and then washed with acetonitrile to remove the unreacted or residual solution on the fiber surface.

[0028] Step S4: replacing the agarose-cellulose-polyurea composite gel fiber with anhydrous ethanol solvent, and then drying it with supercritical carbon dioxide to obtain agarose-cellulose-polyurea composite aerogel fiber.

[0029] In an exemplary embodiment of the present disclosure, the drying temperature of supercritical carbon dioxide drying is 40-60° C., and the drying pressure is 11-20 MPa.

[0030] The present invention provides a method for preparing agarose-cellulose-polyurea composite aerogel fibers. The resulting aerogel fibers have a diameter of 0.6-0.7 mm, a contact angle of 124-131°, a tensile strength of 1.3-2.0 MPa, and an elongation at break of 26-40%. These fibers exhibit excellent mechanical properties. The process is relatively simple, and the wet spinning gel formation process is a physical gelation process without chemical reactions.

[0031] In addition, the wet spinning process in the prior art is to gel into fibers in a coagulation bath, in which the spinning solution is ejected through the spinneret and contacts the coagulation bath to gel. The coagulation bath is not a simple deionized water coagulation bath, but a coagulation bath to which other solvents or oxidants are added, which makes it difficult to achieve fiber continuity. To address this problem, the present invention connects a polyfluoro hose to the syringe needle so that the spinning solution can contact the coagulation bath to gel into fibers through its self-gelling properties. By adjusting the temperature of the coagulation bath to control the gelation rate, continuous agarose-cellulose composite fibers can be prepared. The agarose-cellulose composite fibers are then reacted with components A and B of a synthetic polyurea to in-situ composite polyurea on the surface of the agarose-cellulose composite fibers. Finally, supercritical carbon dioxide drying is performed to obtain agarose-cellulose-polyurea composite aerogel fibers with hydrophobicity and flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 IR spectra of agarose-cellulose-polyurea composite aerogel fibers prepared in Examples 1-4 and Comparative Example 1 of the present invention.

[0033] Figure 2 Scanning electron microscope images of agarose-cellulose-polyurea composite aerogel fibers prepared in Examples 1-4 of the present invention and Comparative Example 1.

[0034] Figure 3 Graph showing stress-strain curves of agarose-cellulose-polyurea composite aerogel fibers prepared in Examples 1-4 and Comparative Example 1 of the present invention under tensile testing.

[0035] Figure 4 This is a diagram showing the knotting condition of the agarose-cellulose-polyurea composite aerogel fiber sample prepared in Example 1 of the present invention and the weight it bears.

[0036] Figure 5 Graphs showing contact angles of agarose-cellulose-polyurea composite aerogel fibers prepared in Examples 1-4 and Comparative Example 1 of the present invention.

[0037] Figure 6 Thermogravimetric diagrams of agarose-cellulose-polyurea composite aerogel fibers prepared in Examples 1-4 and Comparative Example 1 of the present invention.

[0038] Figure 7 This is a diagram showing the thermal insulation effect of the agarose-cellulose-polyurea composite aerogel fiber prepared in Examples 1-4 of the present invention and Comparative Example 1.

[0039] Figure 8 This invention Figure 2 Enlarged view of d. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to specific examples. The following description is only used to illustrate the technical solutions of the present invention and is not intended to limit the present invention. The experimental methods used in the examples are conventional methods unless otherwise specified. The materials, reagents, etc. used, unless otherwise specified, can be obtained from commercial channels, such as agarose from Zhongke Ruitai Biotechnology Co., Ltd.

[0041] Example 1

[0042] A method for preparing agarose-cellulose-polyurea composite aerogel fiber, the specific steps are as follows:

[0043] (1) Prepare 2% agarose solution and 0.5% cellulose solution, respectively, and mix them at 80°C for 1 h to obtain agarose-cellulose spinning solution, which is then loaded into a 10 ml syringe;

[0044] (2) Fix the syringe on the micro-syringe pump, connect and fix the PTFE hose (Φ0.6 mm, length 35 cm) to the needle of the syringe (20G), with the tail of the PTFE hose bent and perpendicular to the coagulation bath, at a height of 10 cm from the coagulation bath;

[0045] (3) The agarose-cellulose spinning solution was spun through a syringe needle and a PTFE hose, and then contacted with a coagulation bath (temperature of -10°C) to gel into fibers to obtain agarose-cellulose composite fibers. The injection rate of the micro-syringe pump was set to 30 mL / h.

[0046] (4) The agarose-cellulose composite fiber obtained in step (3) was immersed in a diluent of component A (diphenylmethane diisocyanate (MDI-50) and acetonitrile solution in a volume ratio of 1:2) and reacted at 80°C for 2.5 h. The reacted agarose-cellulose composite fiber was then immersed in an acetonitrile solution to remove the unreacted component A solution. The fiber was then immersed in a diluent of component B (the molar ratio of the D-2000 / MDBA / DETDA-80 mixture was 2:1:1, and the volume ratio of the D-2000 / MDBA / DETDA-80 mixture to acetonitrile was 1:2) and reacted at 25°C for 2.5 h. The reacted composite fiber was then immersed in an acetonitrile solution to remove the unreacted component B solution. Finally, the agarose-cellulose-polyurea composite gel fiber was obtained by sufficient solvent replacement with anhydrous ethanol.

[0047] (5) Agarose-cellulose-polyurea composite gel fibers were dried with supercritical carbon dioxide to obtain agarose-cellulose-polyurea composite aerogel fibers (CAFs-2) at a drying temperature of 45 °C and a drying pressure of 11 MPa.

[0048] The diameter of the agarose-cellulose-polyurea composite aerogel fiber (CAFs-2) prepared in this example is about 0.65 mm, the contact angle is about 130.2°, the tensile strength is about 2.0 MPa, and the elongation at break is about 40%. The scanning electron micrograph of the agarose-cellulose-polyurea composite aerogel fiber (CAFs-2) prepared in this example is shown in FIG. Figure 2 As shown in df, Figure 8 yes Figure 2 d is an enlarged view; the tensile test stress-strain curve is as follows Figure 3 As shown, the knotting condition of the sample and the weight of the weight are shown in the figure below. Figure 4 As shown in the contact angle diagram Figure 5 shown.

[0049] Comparative Example 1

[0050] The difference from Example 1 is that the prepared agarose-cellulose composite fiber is immersed in the diluted solution of component A and reacted at 25°C for 2.5 hours, and then immersed in the diluted solution of component B and reacted at 25°C for 2.5 hours.

[0051] That is, compared with Example 1, this example only lowers the reaction temperature of the agarose-cellulose composite fiber immersed in the diluted solution of components A and B.

[0052] The diameter of the agarose-cellulose-polyurea composite aerogel fiber (CAFs-1) prepared in this embodiment is about 0.42 mm, the contact angle is about 80.8°, the tensile strength is about 1.3 MPa, and the elongation at break is about 40%; the scanning electron micrograph of the agarose-cellulose-polyurea composite aerogel fiber (CAFs-1) of this embodiment is shown in FIG. Figure 2 ac, the tensile test stress-strain curve is shown in Figure 3 As shown in the contact angle diagram Figure 5 shown.

[0053] Example 2

[0054] The difference from Example 1 is that:

[0053] the diluent of component A is a mixture of diphenylmethane diisocyanate (MDI-50) and acetonitrile solution in a volume ratio of 1:4; the diluent of component B is a mixture of amino-terminated polyether / 4,4-bis-sec-butylaminodiphenylmethane / diisotoluenediamine (D-2000 / MDBA / DETDA-80) in a molar ratio of 2:1:1, and then diluted with acetonitrile in a volume ratio of 1:4.

[0055] The diameter of the agarose-cellulose-polyurea composite aerogel fiber (CAFs-3) prepared in this embodiment is about 0.64 mm, the contact angle is about 128.3°, the tensile strength is about 1.7 MPa, and the elongation at break is about 35%; the scanning electron micrograph of the agarose-cellulose-polyurea composite aerogel fiber (CAFs-3) prepared in this embodiment is as follows: Figure 2 As shown in gi, the tensile test stress-strain curve is as follows Figure 3 As shown in the contact angle diagram Figure 5 shown.

[0056] Example 3

[0057] The difference from Example 1 is that the diluent of Component A is a mixture of diphenylmethane diisocyanate (MDI-50) and acetonitrile solution in a volume ratio of 1:6. The diluent of Component B is a mixture of amino-terminated polyether / 4,4-bis-sec-butylaminodiphenylmethane / diisotoluenediamine (D-2000 / MDBA / DETDA-80) in a molar ratio of 2:1:1, which is then diluted with acetonitrile in a volume ratio of 1:6.

[0058] The diameter of the agarose-cellulose-polyurea composite aerogel fiber (CAFs-4) prepared in this embodiment is about 0.63 mm, the contact angle is about 126.7°, the tensile strength is about 1.4 MPa, and the elongation at break is about 30%; the scanning electron micrograph of the agarose-cellulose-polyurea composite aerogel fiber (CAFs-4) prepared in this embodiment is as follows: Figure 2 As shown in jl, the tensile test stress-strain curve is as follows Figure 3 As shown in the contact angle diagram Figure 5 shown.

[0059] Example 4

[0060] The difference from Example 1 is that the diluent of Component A is a mixture of diphenylmethane diisocyanate (MDI-50) and acetonitrile solution in a volume ratio of 1:8. The diluent of Component B is a mixture of amino-terminated polyether / 4,4-bis-sec-butylaminodiphenylmethane / diisotoluenediamine (D-2000 / MDBA / DETDA-80) in a molar ratio of 2:1:1, which is then diluted with acetonitrile in a volume ratio of 1:8.

[0061] The diameter of the agarose-cellulose-polyurea composite aerogel fiber (CAFs-5) prepared in this embodiment is about 0.63 mm, the contact angle is about 124.6°, the tensile strength is about 1.3 MPa, and the elongation at break is about 26%. The scanning electron micrograph of the agarose-cellulose-polyurea composite aerogel fiber (CAFs-5) in this embodiment is shown in FIG. Figure 2 As shown in mo, the tensile test stress-strain curve is as follows Figure 3 As shown in the contact angle diagram Figure 5 shown.

[0062] 1. Infrared spectrum test:

[0063] like Figure 1 As shown in the figure, the infrared spectra of CAFs-1 prepared in Comparative Example 1 are basically consistent with those of CAFs-2 to CAFs-5 prepared in the other examples. -1 The asymmetric stretching vibration peak attributed to COC appeared at 2970 cm -1 and 2900 cm -1 The stretching vibration peaks attributed to CH appeared at 2865 cm -1 The peak at 1305 cm-1, which is attributed to the stretching vibration of NH, preliminarily proves the existence of polyurea. -1 The stretching vibration peak of tertiary amine group appeared at 1228 cm -1 The stretching vibration peak of CN appears at 1540 cm -1 The bending vibration of NH on the urea group appeared at 1720 cm -1 The stretching vibration peaks of C=O appeared, which are characteristic peaks of polyurea. From the peak intensity in the figure, it can be seen that the polyurea content of CAFs-1 in Comparative Example 1 is relatively the lowest.

[0064] 2. Composite aerogel fiber micromorphology test:

[0065] like Figure 2 As shown, compared with CAFs-2 to CAFs-5 prepared in the other examples, the CAFs-1 agarose-cellulose composite fiber prepared in Comparative Example 1 reacted at 25°C during the composite process with polyurea, causing the composite fiber to shrink as a whole. However, the fiber cross-section of the composite polyurea under heating conditions did not shrink and was relatively smooth. This is mainly because when reacting with the A and B components of the polyurea under heating conditions, a large amount of isocyanate reacted with the hydroxyl groups on the agarose and cellulose, further generating active sites that can react with the B component. After being soaked in the B component, the small molecules in the B component can enter the interior of the agarose-cellulose composite fiber to react to form polyurea, which can further increase the strength of the skeleton and prevent the skeleton from collapsing in the subsequent reaction. On the surface of the composite fiber, the B component not only reacts with the free A component to form attached polyurea, but also reacts with the active sites at the other end of the diisocyanate that reacts with the agarose and cellulose, thereby constructing a more stable three-dimensional network structure of polyurea. Therefore, the composite aerogel fiber does not shrink during the subsequent reaction and drying process.

[0066] 3. Mechanical properties test

[0067] like Figure 3 As shown, the composite aerogel fibers CAFs-2 to CAFs-5 prepared in Examples 1 to 5 have different composite polyurea contents from CAFs-1 in Comparative Example 1, resulting in different mechanical properties. As the polyurea content gradually increases, the tensile strength is significantly enhanced, and the elongation at break gradually increases. The tensile strength of the prepared composite aerogel fibers can reach up to 2.0 MPa. Figure 4 As shown, the composite aerogel fiber CAFs-2 prepared in Example 1 can be bent and knotted, and can bear the weight of a 50 g weight, indicating that it has excellent flexibility and mechanical strength, which is extremely important for the application in the field of thermal insulation of textiles.

[0068] 4. Wettability test:

[0069] like Figure 5 As shown, the contact angle of the composite aerogel fiber CAFs-1 prepared in Comparative Example 1 after the reaction with isocyanate without heating was small, and the fiber gradually absorbed some water droplets over time. This is because when reacting at room temperature, isocyanate has difficulty reacting with agarose and cellulose. Therefore, the small amount of polyurea produced mainly adheres to the fiber, and the hydrophilic groups on the CAFs skeleton are not covered, resulting in very weak hydrophobicity. In particular, after soaking in component A at room temperature and then washing with acetonitrile, a large amount of isocyanate groups are lost, resulting in a small amount of polyurea produced, showing hydrophilicity. After the composite aerogel fibers CAFs-2 to CAFs-5 in the examples are heated to react with isocyanate groups, a large number of hydrophilic groups (-OH and -COOH) on the fibers are covered with polyurea. Due to the widespread presence of hydrophobic groups such as methyl and benzene rings in the polyurea, the CAFs exhibit good hydrophobic properties.

[0070] 5. Thermal stability test:

[0071] like Figure 6As shown, in the 40-120°C stage, the composite aerogel fibers CAFs-2 to CAFs-5 in the examples experienced a slight mass loss, which was due to the small amount of moisture contained in the fibers. The CAFs-1 prepared in Comparative Example 1 experienced a greater mass loss than the other samples during this stage, as its poor hydrophobicity caused it to absorb more moisture from the air, consistent with the contact angle test results. Between 250 and 600°C, the composite aerogel fibers CAFs-2 to CAFs-5 prepared in the examples exhibited continuous, staged weight loss. At 600°C, the mass stabilized, and the remaining mass indicated that some substances that were difficult to pyrolyze remained. It is noteworthy that the CAFs-1 prepared in Comparative Example 1 stabilized at approximately 550°C, 50°C lower than the other samples, due to the lower content of attached polyurea. The comparative gel fibers reacted with component A at room temperature and under heating conditions, and it was found that the thermal weight loss under heating conditions was less, proving that the heating reaction provided more polyurea, resulting in an increase in its residual mass. In addition, as the dilution ratio of components A and B increases, the mass loss also gradually increases. Therefore, increasing the polyurea content can effectively increase the thermal stability of the composite aerogel fiber.

[0072] 6. Thermal insulation performance test:

[0073] like Figure 7 As shown, by arranging the composite aerogel fibers into a mesh and then placing them on heating platforms at different temperatures, the temperature of the surface of the composite aerogel fibers and the bottom heating platform are monitored by an infrared thermal imager. It is shown that the composite aerogel fibers CAFs-2 to CAFs-5 prepared in the embodiment have better thermal insulation properties than CAFs-1 in comparative example 1.

[0074] The above embodiments are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments. For those skilled in the art, other variations in different forms can be made based on the above description. Obvious variations derived therefrom fall within the scope of protection of the present invention. Finally, it should be noted that the terms "comprise," "include," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article, or device.

Claims

1. A method for preparing agarose-cellulose-polyurea composite aerogel fiber, characterized by comprising: Step S1, mixing an agarose solution and a cellulose solution to prepare an agarose-cellulose spinning solution; Step S2, contacting the agarose-cellulose spinning solution with a coagulation bath gel to obtain agarose-cellulose composite fibers; Step S3, fully replacing the agarose-cellulose composite fiber with anhydrous ethanol and acetonitrile solvents in sequence; then reacting the agarose-cellulose composite fiber with a component A solution and a component B solution capable of reacting to form polyurea in sequence to obtain an agarose-cellulose-polyurea composite gel fiber; wherein component A is an isocyanate component and component B is an amino compound; Step S4, replacing the agarose-cellulose-polyurea composite gel fiber with anhydrous ethanol solvent, and then drying it with supercritical carbon dioxide to obtain agarose-cellulose-polyurea composite aerogel fiber; In step S2, the coagulation bath is formed by deionized water, and the temperature of the coagulation bath is -6 to -16°C; In step S2, the agarose-cellulose spinning solution is passed through a syringe and a polyfluoroethylene hose to contact the coagulation bath gel to obtain agarose-cellulose composite fibers; the polyfluoroethylene hose has a diameter of 0.5-1.0 mm and a length of 30-50 cm; the syringe is fixed on a micro-injection pump, and the height of the outlet of the polyfluoroethylene hose from the coagulation bath is 5-15 cm; the injection rate of the micro-injection pump is 10-80 mL / h.

2. The method for preparing agarose-cellulose-polyurea composite aerogel fiber according to claim 1, wherein: The mass concentration of the agarose solution used in step S1 is 1-3%, and the mass concentration of the cellulose used is 0.2-0.8%.

3. The method for preparing agarose-cellulose-polyurea composite aerogel fiber according to claim 1, wherein: In step S1, the agarose solution and cellulose are stirred and mixed at a temperature of 60-90° C. using a magnetic stirrer for 0.5-2 h.

4. The method for preparing agarose-cellulose-polyurea composite aerogel fiber according to claim 1, wherein: The component A used in step S3 is an isocyanate, or diphenylmethane diisocyanate MDI-50, or a mixture of diphenylmethane diisocyanate MDI-50 and polypropylene glycol PPG-3000, or a mixture of diphenylmethane diisocyanate MDI-50 and polypropylene glycol PPG-4000, or toluene diisocyanate TDI, or xylylene diisocyanate XDI.

5. The method for preparing agarose-cellulose-polyurea composite aerogel fiber according to claim 1, wherein: In step S3, component B is amino-terminated polyether D-2000, or a mixture of amino-terminated polyether D-2000 and T-2000, or a mixture of amino-terminated polyether D-2000, T-2000 and 4,4-bis-sec-butylaminodiphenylmethane MDBA, or a mixture of amino-terminated polyether D-2000 and T-2000 / 4,4-bis-sec-butylaminodiphenylmethane MDBA / diisotoluenediamine DETDA-80, or a mixture of amino-terminated polyether D-2000 / 4,4-bis-sec-butylaminodiphenylmethane MDBA / diisotoluenediamine DETDA-80.

6. The method for preparing agarose-cellulose-polyurea composite aerogel fiber according to claim 1, wherein: In step S3, component A and component B are diluted with a solvent to prepare a component A dilution solution and a component B dilution solution; the solvent used for dilution is any one of acetonitrile, n-hexane, toluene, and acetone.

7. The method for preparing agarose-cellulose-polyurea composite aerogel fiber according to claim 6, wherein: Mix component A and acetonitrile in a volume ratio of 1:1-8 to prepare component A dilution solution; mix component B and acetonitrile in a volume ratio of 1:1-8 to prepare component B dilution solution.

8. The method for preparing agarose-cellulose-polyurea composite aerogel fiber according to claim 1, wherein: The reaction temperature of agarose-cellulose composite fiber and component A dilution was 70-90℃, and the reaction time was 0.5-4 h; the reaction temperature of agarose-cellulose composite fiber and component B dilution was 25-50℃, and the reaction time was 0.5-4 h.

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