Cellulose-based high-thermal-conductivity phase change fiber and preparation method thereof

Abstract

The invention discloses a cellulose-based high-thermal-conductivity phase change fiber and a preparation method thereof. The method comprises the following steps: activating cellulose, and dissolving hydroxylated boron nitride nanosheets and activated cellulose to obtain a shell spinning solution; emulsifying hydroxylated boron nitride nanosheets, nanocellulose and a phase change medium in deionized water to obtain a core layer spinning solution; cellulose, a phase change medium and a high-thermal-conductivity component BNNs-OH are assembled into the phase change fiber material, the phase change fiber material can exert the phase change capacity at the temperature of 20-60 DEG C, the thermal conductivity coefficient is 0.5-10 W / (m.K), and the phase change fiber material has good thermal management performance and excellent thermal conductivity and is used as a thermal management fabric, so that the thermal management fabric has good thermal management performance. The catalyst consists of biomass components, can be prepared by a one-step method, and is mild in condition, high in operability, high in production efficiency and suitable for large-scale production and application.

Description

Technical Field

[0001] The present invention belongs to the field of thermal regulation technology, and specifically relates to a cellulose-based high thermal conductivity phase change fiber and a preparation method thereof. Background Art With the development of science and technology, people have developed various advanced thermal regulation equipment and technologies to provide two-way thermal regulation (i.e. heating and cooling) for the human body to meet the thermal comfort needs under different environmental conditions, thus generating a large amount of carbon dioxide emissions and consuming a lot of energy. In this context, the emergence of smart phase change fibers designed for temperature regulation has attracted great attention.

[0002] Traditional phase change textiles mainly adopt strategies such as surface modification of phase change medium, impregnation of porous materials and microcapsule encapsulation. These materials can effectively control temperature to a certain extent, but they also have some shortcomings. For example, surface modification of phase change materials is easy to leak under high temperature conditions and the performance is unstable; although the impregnation of porous materials has good stability under high temperature environment, its temperature control ability is closely related to the filling amount of internal phase change medium. A large filling amount is likely to cause a decrease in the mechanical properties of the material. Although the above preparation methods have played a great role in the actual field of thermal management, the thermal conductivity of most polymer matrix materials is low, which limits the thermal management ability of phase change fibers. Therefore, it is of great practical significance to find a simple, efficient, highly thermally conductive phase change fiber suitable for thermal management in various environments. In recent years, biomass materials have gradually attracted the attention of scientific researchers due to their wide sources, low cost and environmental friendliness. Among them, cellulose, as one of the main components of plant cells, is an important renewable resource. Cellulose-based materials have great potential in the preparation of phase change fibers, mainly due to their excellent physical and chemical properties and environmental advantages.

[0003] Cellulose-based biomass phase change fibers have the following advantages: Cellulose and its derivatives, including viscose and Lyocell fibers, are used in the textile industry and advanced functional fibers because they have good renewability, sustainability, hygroscopicity and breathability. A Chinese patent with application number 202310878877.X and titled "An elastic phase change fiber and its preparation method" mentioned that the prepared elastic phase change fiber needs to be freeze-dried after solidification and molding. At the same time, during the freeze-drying molding process, a large number of pores appear inside the fiber, which will block the transfer of heat. Therefore, the prepared phase change fiber has poor thermal conductivity, which limits its application. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a cellulose-based high thermal conductivity phase change fiber and a preparation method thereof. The preparation method is simple, and the wet-spun cellulose fibers are further activated, and the cellulose, phase change medium and high thermal conductivity component BNNs-OH are assembled into a phase change fiber material through a one-step coaxial wet spinning method. The phase change fiber material has good thermal management performance and excellent thermal conductivity. As a thermal management fabric, it is composed of biomass components, can be prepared in one step, has mild conditions, strong operability, high production efficiency, and is suitable for large-scale production and application.

[0005] The present invention is achieved through the following technical solutions: A method for preparing a cellulose-based high thermal conductivity phase change fiber comprises the following steps: S1, activating cellulose to obtain cellulose with reduced intermolecular hydrogen bond entanglement; S2, dissolving hydroxylated boron nitride nanosheets and the cellulose obtained in S1 in a solvent, wherein the hydroxylated boron nitride nanosheets account for 5% to 50% of the mass of the cellulose, to obtain a shell spinning solution; emulsifying hydroxylated boron nitride nanosheets, nanocellulose and phase change medium in deionized water to obtain a core spinning solution; S3, spinning the shell layer spinning solution and the core layer spinning solution by a coaxial wet spinning one-step method, wherein the stretching ratio is 100%-350%, to obtain a cellulose-based high thermal conductivity phase change fiber.

[0006] Preferably, S1 activates cellulose in an activator at 80-160° C. for 30-120 min at a mass ratio of 1:10, wherein the activator is N,N-dimethylformamide, N,N-dimethylacetamide or a 20% by mass sodium hydroxide solution, and then dries to obtain cellulose with reduced intermolecular hydrogen bond entanglement.

[0007] Preferably, the hydroxylated boron nitride nanosheets in S2 are obtained by the following process: The boron nitride nanosheets are hydrothermally reacted in a sodium hydroxide solution with a concentration of 0.5-1.5 mol / L for 12-36 h, the ratio of boron nitride nanosheets to sodium hydroxide is (6-10) g: (0.05-0.15) mol, and the temperature of the sodium hydroxide solution is 80-120°C. The resulting reaction solution is then centrifuged, washed, and finally dried to obtain hydroxylated boron nitride nanosheets.

[0008] Preferably, the solvent described in S2 is a 78%-84% by mass NMMO aqueous solution, an 8% by mass LiCl N,N-dimethylacetamide solution, or a mixed solution of sodium hydroxide and urea.

[0009] Furthermore, the mass ratio of cellulose obtained by S1 to the solvent was 1:20, and when the solvent was a mixed solution of sodium hydroxide and urea, the hydroxylated boron nitride nanosheets and the cellulose obtained by S1 were stirred in a solvent at 55-65°C for 12-24 h to obtain a shell spinning solution; When the solvent is a 78%-84% by mass NMMO aqueous solution or an 8% by mass LiCl N,N-dimethylacetamide solution, the hydroxylated boron nitride nanosheets and the cellulose obtained by S1 are stirred in the solvent at room temperature for 12-24 h to obtain a shell spinning solution.

[0010] Preferably, in S2, the mass ratio of hydroxylated boron nitride nanosheets, nanocellulose, phase change medium and deionized water is (0.1-1): (0.5-5): (40-80): (10-57).

[0011] Furthermore, the nanocellulose is TEMPO-CNF, and the phase change medium is paraffin or polyethylene glycol with a molecular weight of 1000-20000.

[0012] Preferably, in S3, the volume ratio of the shell layer spinning solution to the core layer spinning solution is 1:1, the flow rate of the core layer spinning solution is 2-20 ml / h, and the flow rate of the shell layer spinning solution is 5-50 ml / h.

[0013] Furthermore, the coagulation bath used in the one-step coaxial wet spinning method is water, ethanol solution or calcium chloride solution.

[0014] A cellulose-based high thermal conductivity phase change fiber obtained by the preparation method of the cellulose-based high thermal conductivity phase change fiber described in any one of the above items can exert phase change ability at 20°C-60°C, and the thermal conductivity is 0.5-10 W / (m·K).

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention discloses a method for preparing cellulose-based high thermal conductivity phase change fiber. After cellulose is activated, the degree of hydrogen bond entanglement between its molecules is reduced, which can further improve the solubility of cellulose in solvents. Then, it can be combined with hydroxylated boron nitride nanosheets (BNNs-OH) to prepare shell spinning solution. When the amount of BNNs-OH added as a high thermal conductivity filler is less than 5%, the effect of significantly improving the thermal conductivity coefficient cannot be achieved. When the amount exceeds 50%, a large amount of thermal conductive filler will cause the viscosity of the spinning solution to increase, the thermal conductive filler will aggregate, and it cannot be completely dispersed, resulting in a decrease in the thermal conductivity coefficient. The molecular structure of nanocellulose contains A large number of hydroxyl groups and other active groups can induce the orientation of the thermal conductive filler by forming hydrogen bonds with the high thermal conductive filler. The core layer spinning solution is prepared by deionized water, which can reduce the viscosity of the core layer spinning solution. The shell layer spinning solution and the core layer spinning solution adopt a coaxial wet spinning one-step method to prepare a cellulose-based high thermal conductive phase change fiber. The fiber diameter is different under different stretching ratios. As the tensile force increases, the fiber diameter becomes thinner, and the fiber is subjected to axial tensile force inside. Under the action of hydrogen bonds, the BNNS-OH in the shell layer and the core layer lamellae state moves with the cellulose and CNF chain segments and is arranged horizontally along the axial direction. The larger the stretching ratio, the more regular the arrangement, but when the stretching ratio exceeds 300%, a certain degree of defects will appear on the fiber surface. If it continues to increase to 350%, it will cause the phase change medium to leak. The raw material source biomass raw material cellulose of the present invention is easy to obtain, abundant and cheap, and the degradation products of cellulose-based phase change fibers in the environment are harmless to the environment, which conforms to the concept of environmental protection. High thermal conductive phase change fibers can be industrialized and have significant benefits.

[0016] When the phase change fiber of the present invention is made into a fabric and covered on the arm in an environment of 40°C, since the phase change medium can be converted from solid to liquid and absorb heat, the skin temperature can be reduced by more than 4 degrees Celsius within 60 seconds. At the same time, in an environment below 20°C, the phase change medium can be converted from liquid to solid again, releasing heat, ensuring that the skin temperature can be maintained at around 37°C for more than 10 minutes. It has good high-temperature thermal conductivity and excellent thermal management performance, and can be used stably in various environments (such as the temperature range of minus 10°C-80°C). As a fiber material, it has a high proportion of biomass components, is easy to degrade, and is easy to operate, providing a more sustainable choice for the field of temperature protection and thermal management. The cellulose-based high thermal conductivity phase change fiber of the present invention can withstand a temperature range of 20°C-80°C and remain stable, can exert phase change ability at 20°C-60°C, and has a thermal conductivity of 0.5-10 W / (m·K). It is an environmentally friendly, efficient and reliable alternative, and will play an important role in the field of phase change fibers. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a sample photo of the cellulose-based high thermal conductivity phase change fiber prepared in Example 1 of the present invention.

[0018] Figure 2 This is a scanning electron microscope image of the cellulose-based high thermal conductivity phase change fiber prepared in Example 4 of the present invention.

[0019] Figure 3 This is an infrared imaging photograph of the cellulose-based high thermal conductivity phase change fiber fabric prepared in Example 5 of the present invention during the thermal management process. DETAILED DESCRIPTION

[0020] The technical solution of the present invention will be clearly and completely described below in conjunction with specific drawings, process steps, implementation conditions and materials. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] The present invention provides a method for preparing a cellulose-based high thermal conductivity phase change fiber, comprising the following steps: 1) The cellulose is activated through an activation process (activated in an activator and then dried, with the mass ratio of the activator to cellulose being 10:1) to reduce the degree of hydrogen bond entanglement between cellulose molecules and further improve the solubility of cellulose in solvents.

[0022] The activating agent of the activation process is one of N, N dimethylformamide (DMF), N, N dimethylacetamide (DMAc), and 20% by mass sodium hydroxide solution. The activation temperature is 80-160° C., and the activation time is 30-120 min.

[0023] 2) The high thermal conductivity material boron nitride nanosheets (BNNs) were prepared by hydrothermal reaction to hydroxylated boron nitride nanosheets (BNNs-OH).

[0024] The solvent used for the hydrothermal reaction is sodium hydroxide aqueous solution with a concentration of 0.5-1.5 mol / L, the ratio of BNNs to sodium hydroxide aqueous solution is 6-10 g:100 ml, the reaction temperature is 80-120°C, the time is 12-36 h, and the resulting reaction solution is then centrifuged, washed, and finally dried to obtain BNNs-OH.

[0025] 3) Dissolve BNNs-OH and activated cellulose in 20 g of solvent (corresponding to 1 g of activated cellulose) to prepare a shell spinning solution.

[0026] The solvent is a mixed solution of 78%-84% by mass of NMMO (N-methylmorpholine-N-oxide) aqueous solution, 8% by mass of LiCl in N,N-dimethylacetamide (DMAc) solution, sodium hydroxide and urea, and the stirring time is 12-24 h.

[0027] The preferred solution is LiCl in DMAc. Although the NNMO aqueous solution is environmentally friendly and controllable, it requires strict process control to prevent explosion. The mixed solution of sodium hydroxide and urea has some obstacles to the dispersibility of high thermal conductive fillers and needs to be stirred at 55-65°C, so the operation is relatively troublesome (other solvents are at room temperature). According to the thermal conductivity requirement, the amount of BNNs-OH added is 5-50% of the cellulose mass. As the amount of BNNs-OH added reaches 50%, the thermal conductivity of the fiber rises to the maximum value. If the amount of BNNs-OH added is further increased, the thermal conductivity of the fiber decreases. This is mainly because a large amount of thermally conductive fillers will increase the viscosity of the spinning solution, and the thermally conductive fillers will aggregate and cannot be completely dispersed, resulting in a decrease in thermal conductivity.

[0028] 4) According to the mass ratio of (0.1-1): (0.5-5): (40-80): (10-57), BNNs-OH and nanocellulose (CNF) as well as phase change medium and deionized water were mixed and emulsified (stirred at 90°C for 30 min and cooled to room temperature) to prepare the core spinning solution. Under the action of CNF, paraffin and CNF chain segments were wrapped to form phase change microspheres, and the hydroxyl groups on the outer CNF were combined with the hydroxyl groups of BNNS-OH through hydrogen bonds. If the phase change medium is replaced by PEG, all three contain hydroxyl groups, which are randomly combined through hydrogen bonds. Dispersing and emulsifying in water mainly reduces the viscosity of the core spinning solution.

[0029] CNF is TEMPO-CNF, the phase change medium is paraffin with different phase change temperatures, and finally the particles are dispersed in water, or PEG (polyethylene glycol) of various molecular weights (1000-20000). The corresponding phase change material is selected according to different needs. The amount of BNNs-OH is determined according to different heat transfer rate requirements. The greater the heat transfer rate, the closer the amount of BNNs-OH required is to 70% of the maximum value.

[0030] 5) High thermal conductivity phase change fibers were prepared by a one-step coaxial wet spinning process using a shell spinning solution and a core spinning solution with a volume ratio of 1:1.

[0031] The spinning process parameters are: the flow rate of the core layer spinning solution is 2-20ml / h, and the flow rate of the shell layer spinning solution is 5-50ml / h. The stretching ratio of the spinning process is 100-350%, preferably 300%. The spinning coagulation bath is one of water, an aqueous solution of ethanol and an aqueous solution of calcium chloride. The fiber diameter is different under different stretching ratios. As the stretching force increases, the fiber diameter becomes thinner, and the fiber is subjected to axial stretching force. Under the action of hydrogen bonds, the BNNS-OH in the lamellar state of the shell and core layers moves with the cellulose and CNF chain segments and is arranged horizontally along the axial direction. The larger the stretching ratio, the more regular the arrangement, but if the stretching ratio exceeds 300%, a certain degree of defects will appear on the fiber surface. If it continues to increase to 350%, it will cause leakage of the phase change medium.

[0032] Example 1 Take 100g of DMF, add 10g of cellulose into it, set the temperature to 80℃, activate for 1h, and dry to obtain activated fibers.

[0033] 10 g of BNNs were added into 100 ml of 1 mol / L sodium hydroxide solution and reacted at 100 °C for 20 h. The resulting reaction solution was then centrifuged, washed, and finally dried to obtain BNNs-OH.

[0034] Then, 1 g of activated cellulose and 0.5 g of BNNs-OH were added to a 20 g LiCl DMAc solution (the amount of LiCl was 1.6 g), and stirred at room temperature for 12 h to obtain a shell spinning solution.

[0035] Take 0.1g BNNs-OH, 0.2g TEMPO-CNF, 6g paraffin with a phase transition temperature of 37°C and 3.7g water, stir at 90°C for 30 min, and cool to room temperature to obtain the core layer spinning solution.

[0036] Take 10 ml of core layer spinning solution and shell layer spinning solution respectively, add them into a 10 ml syringe, and prepare high thermal conductivity phase change fiber by coaxial wet spinning. The core liquid flow rate is 6 ml / h, the shell layer flow rate is 10 ml / h, the coagulation bath is water, and the stretching ratio is 300%. Cellulose-based high thermal conductivity phase change fiber can be obtained.

[0037] Example 2 Take 100g of 20% by mass sodium hydroxide, add 10g of cellulose, set the temperature to 80°C, activate for 90min, and dry to obtain activated fibers.

[0038] 10 g of BNNs were added into 100 ml of 0.5 mol / L sodium hydroxide solution and reacted at 120 °C for 36 h. The resulting reaction solution was then centrifuged, washed, and finally dried to obtain BNNs-OH.

[0039] Then, 1 g of activated cellulose and 0.5 g of BNNs-OH were added to a mixed solution of 20 g of urea and sodium hydroxide (the mass ratio of NaOH, urea, and water was 7:12:81), and stirred at 60°C for 12 h to obtain a shell spinning solution.

[0040] Take 0.1g BNNs-OH, 0.2g TEMPO-CNF, 4g PEG with a molecular weight of 12000 and 5.7g water, stir at 90℃ for 30 min, and cool to room temperature to obtain the core spinning solution.

[0041] Take 10 ml of core layer spinning liquid and shell layer spinning liquid respectively, add them into a 10 ml syringe, and prepare high thermal conductivity phase change fiber by coaxial wet spinning. The core liquid flow rate is 16 ml / h, the shell layer flow rate is 30 ml / h, the coagulation bath is 75% by mass ethanol aqueous solution, and the stretching ratio is 150%. Cellulose-based high thermal conductivity phase change fiber can be obtained.

[0042] Example 3 Take 100g of DMAc, add 10g of cellulose into it, set the temperature to 120℃, activate for 30min, and dry to obtain activated fibers.

[0043] 10 g of BNNs were added into 100 ml of 0.5 mol / L sodium hydroxide solution and reacted at 80 °C for 15 h. The resulting reaction solution was then centrifuged, washed, and finally dried to obtain BNNs-OH.

[0044] Then, 1 g of activated cellulose and 0.3 g of BNNs-OH were added to a 20 g LiCl DMAc solution (the amount of LiCl was 1.6 g), and stirred at room temperature for 12 h to obtain a shell spinning solution.

[0045] Take 0.1g BNNs-OH, 0.2g TEMPO-CNF, 5g PEG with a molecular weight of 8000 and 4.7g water, stir at 90℃ for 30 min, and cool to room temperature to obtain the core spinning solution.

[0046] Take 10 ml of core layer spinning liquid and shell layer spinning liquid respectively, add them into a 10 ml syringe, and prepare high thermal conductivity phase change fiber by coaxial wet spinning. The core liquid flow rate is 8 ml / h, the shell layer flow rate is 10 ml / h, the coagulation bath is 70% by mass ethanol aqueous solution, and the stretching ratio is 200%. Cellulose-based high thermal conductivity phase change fiber can be obtained.

[0047] Example 4 Take 100g of DMAc, add 10g of cellulose into it, set the temperature to 120℃, activate for 30min, and dry to obtain activated fibers.

[0048] 8 g of BNNs were added into 100 ml of 0.5 mol / L sodium hydroxide solution and reacted at 80° C. for 15 h. The resulting reaction solution was then centrifuged, washed, and finally dried to obtain BNNs-OH.

[0049] Then, 1 g of activated cellulose and 0.3 g of BNNs-OH were added to a 20 g LiCl DMAc solution (the amount of LiCl was 1.6 g), and stirred at room temperature for 12 h to obtain a shell spinning solution.

[0050] Take 0.1g BNNs-OH, 0.2g TEMPO-CNF, 5g paraffin with a phase transition temperature of 45℃ and 4.7g water, stir at 90℃ for 30 min, and cool to room temperature to obtain the core layer spinning solution.

[0051] Take 10 ml of core layer spinning liquid and shell layer spinning liquid respectively, add them into a 10 ml syringe, and prepare high thermal conductivity phase change fiber by coaxial wet spinning. The core liquid flow rate is 8 ml / h, the shell layer flow rate is 10 ml / h, the coagulation bath is 50% by mass ethanol aqueous solution, and the stretching ratio is 200%. Cellulose-based high thermal conductivity phase change fiber can be obtained.

[0052] Example 5 Take 100g of DMAc, add 10g of cellulose into it, set the temperature to 120℃, activate for 30min, and dry to obtain activated fibers.

[0053] 6 g of BNNs were added into 100 ml of 0.5 mol / L sodium hydroxide solution and reacted at 100° C. for 15 h. The resulting reaction solution was then centrifuged, washed, and finally dried to obtain BNNs-OH.

[0054] Then, 1 g of activated cellulose and 0.3 g of BNNs-OH were added to a 20 g LiCl DMAc solution (the amount of LiCl was 1.6 g), and stirred at room temperature for 12 h to obtain a shell spinning solution.

[0055] Take 0.2g BNNs-OH, 0.2g TEMPO-CNF, 5g paraffin with a phase transition temperature of 60℃ and 4.6g water, stir at 90℃ for 30 min, and cool to room temperature to obtain the core layer spinning solution.

[0056] Take 15 ml of core layer spinning liquid and shell layer spinning liquid respectively, add them into a 20 ml syringe, and prepare high thermal conductivity phase change fiber by coaxial wet spinning. The core liquid flow rate is 10 ml / h, the shell layer flow rate is 18 ml / h, the coagulation bath is 45% by mass ethanol aqueous solution, and the stretching ratio is 300%. Cellulose-based high thermal conductivity phase change fiber can be obtained.

[0057] Example 6 Take 100g of DMF, add 10g of cellulose into it, set the temperature to 120℃, activate for 120min, and dry to obtain activated fibers.

[0058] 9 g of BNNs were added into 100 ml of 1 mol / L sodium hydroxide solution and reacted at 100° C. for 20 h. The resulting reaction solution was then centrifuged, washed, and dried to obtain BNNs-OH.

[0059] Then, 1 g of activated cellulose and 0.3 g of BNNs-OH were added to a 20 g LiCl DMAc solution (the amount of LiCl was 1.6 g), and stirred at room temperature for 12 h to obtain a shell spinning solution.

[0060] Take 0.2g BNNs-OH, 0.2g TEMPO-CNF, 5g paraffin with a phase transition temperature of 25℃ and 4.6g water, stir at 90℃ for 30 min, and cool to room temperature to obtain the core layer spinning solution.

[0061] Take 15 ml of core layer spinning liquid and shell layer spinning liquid respectively, add them into a 20 ml syringe, and prepare high thermal conductivity phase change fiber by coaxial wet spinning. The core liquid flow rate is 9 ml / h, the shell layer flow rate is 20 ml / h, the coagulation bath is ethanol / water solution, and the stretching ratio is 300%. Cellulose-based high thermal conductivity phase change fiber can be obtained.

[0062] like Figure 1 As shown, the prepared core-shell phase change fibers are wound on a collecting roller, and the prepared fibers have uniform diameters and a certain degree of glossiness on the surface.

[0063] like Figure 2 The cross-sectional SEM image of the prepared phase change fiber shows that the fiber has a two-layer structure, with the core layer being the phase change medium paraffin and CNF (the wrinkles inside are caused by CNF aggregation). The outer surface of the fiber is somewhat rough. The thickness of the fiber shell is about 50μm.

[0064] The fibers of Example 5 were woven into fabrics. First, they were placed on a 60°C hot plate and the temperature changes were recorded using an infrared imager. The yellow background in the first column indicates that the temperature of the hot plate is constant at 60°C. The surface temperature of the fabric was recorded at different times. The second example is the fabric cooling process. After the fabric is heated up, it is placed on a 20°C stainless steel plate and the cooling process is recorded according to time. Figure 3 As shown in the infrared imaging diagram, we can see that when the temperature rises, 5s is 30.9℃, 10s is 32.1℃, 30s is 34.3℃, 60s is 42.3℃, 300s is 50.0℃, 600s is 55.6℃, and 900s is 55.9℃; when the temperature drops, 5s is 53.1℃, 10s is 52.0℃, 15s is 50.8℃, 30s is 49.1℃, 60s is 46.0℃, 120s is 32.8℃, and 300s is 26.5℃. Therefore, it has certain temperature buffering and thermal management capabilities in both hot and cold environments.

Claims

1. A method for preparing a cellulose-based high thermal conductivity phase change fiber, It is characterized in that The following steps are involved: S1, activating cellulose to obtain cellulose with reduced intermolecular hydrogen bond entanglement; S2, dissolving hydroxylated boron nitride nanosheets and the cellulose obtained in S1 in a solvent, wherein the hydroxylated boron nitride nanosheets account for 5% to 50% of the mass of the cellulose, to obtain a shell spinning solution; emulsifying hydroxylated boron nitride nanosheets, nanocellulose and phase change medium in deionized water to obtain a core spinning solution; S3, spinning the shell layer spinning solution and the core layer spinning solution by a coaxial wet spinning one-step method, wherein the stretching ratio is 100%-350%, to obtain a cellulose-based high thermal conductivity phase change fiber.

2. The method for preparing the cellulose-based high thermal conductivity phase change fiber according to claim 1, It is characterized in that S1 activates cellulose in an activator at 80-160° C. for 30-120 min at a mass ratio of 1:10, wherein the activator is N,N-dimethylformamide, N,N-dimethylacetamide or a 20% by mass sodium hydroxide solution, and then dries to obtain cellulose with a reduced degree of intermolecular hydrogen bond entanglement.

3. The method for preparing the cellulose-based high thermal conductivity phase change fiber according to claim 1, It is characterized in that The hydroxylated boron nitride nanosheets described in S2 are obtained by the following process: The boron nitride nanosheets are hydrothermally reacted in a sodium hydroxide solution with a concentration of 0.5-1.5 mol / L for 12-36 h, the ratio of boron nitride nanosheets to sodium hydroxide is (6-10) g: (0.05-0.15) mol, and the temperature of the sodium hydroxide solution is 80-120°C. The resulting reaction solution is then centrifuged, washed, and finally dried to obtain hydroxylated boron nitride nanosheets.

4. The method for preparing the cellulose-based high thermal conductivity phase change fiber according to claim 1, It is characterized in that The solvent described in S2 is a 78%-84% by mass NMMO aqueous solution, an 8% by mass LiCl N,N-dimethylacetamide solution, or a mixed solution of sodium hydroxide and urea.

5. The method for preparing the cellulose-based high thermal conductivity phase change fiber according to claim 4, It is characterized in that The mass ratio of cellulose obtained by S1 to the solvent was 1:

20. When the solvent was a mixed solution of sodium hydroxide and urea, the hydroxylated boron nitride nanosheets and the cellulose obtained by S1 were stirred in a solvent at 55-65°C for 12-24 h to obtain a shell spinning solution. When the solvent is a 78%-84% by mass NMMO aqueous solution or an 8% by mass LiCl N,N-dimethylacetamide solution, the hydroxylated boron nitride nanosheets and the cellulose obtained by S1 are stirred in the solvent at room temperature for 12-24 h to obtain a shell spinning solution.

6. The method for preparing the cellulose-based high thermal conductivity phase change fiber according to claim 1, It is characterized in that In S2, the mass ratios of hydroxylated boron nitride nanosheets, nanocellulose, phase change medium and deionized water are (0.1-1):(0.5-5):(40-80):(10-57).

7. The method for preparing the cellulose-based high thermal conductivity phase change fiber according to claim 6, It is characterized in that The nanocellulose is TEMPO-CNF, and the phase change medium is paraffin or polyethylene glycol with a molecular weight of 1000-20000.

8. The method for preparing the cellulose-based high thermal conductivity phase change fiber according to claim 1, It is characterized in that In S3, the volume ratio of the shell layer spinning solution to the core layer spinning solution is 1:1, the flow rate of the core layer spinning solution is 2-20 ml / h, and the flow rate of the shell layer spinning solution is 5-50 ml / h.

9. The method for preparing the cellulose-based high thermal conductivity phase change fiber according to claim 8, It is characterized in that The coagulation bath used in the one-step coaxial wet spinning method is water, ethanol solution or calcium chloride solution.

10. A cellulose-based high thermal conductivity phase change fiber obtained by the preparation method of the cellulose-based high thermal conductivity phase change fiber according to any one of claims 1 to 9.

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