Cellulose-based passive radiation refrigeration fiber as well as preparation method and application thereof

Abstract

The invention discloses a cellulose-based passive radiation refrigeration fiber as well as a preparation method and application thereof. The preparation method comprises the following steps: (1) preparing gel fibers from a cellulose solution through a spinning process; and (2) enabling the gel fiber to sequentially pass through a first functional component coagulating bath and a second functional component coagulating bath, and then carrying out hot drying treatment to prepare the cellulose-based passive radiation refrigeration fiber. The fiber prepared by the method has both refrigeration performance and mechanical property: when the fiber is woven into a fabric, the requirement on the mechanical property of the fiber is extremely high, and the process is used for coating the surface of the gel fiber without damaging the structure of the cellulose fiber, so that the mechanical property can be close to that of the non-coated cellulose fiber; and commercial weaving requirements are met.

Description

Technical Field

[0001] The present invention belongs to the field of natural polymer materials, and specifically, relates to a cellulose-based passive radiative cooling fiber, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid development of the economic society, air-conditioning refrigeration has become an indispensable means for buildings to maintain a comfortable internal temperature. The air-conditioning refrigeration technology represented by air compression not only consumes a large amount of electricity, generates a large amount of greenhouse gases, but also causes an environmental "net" warming effect. In addition, the leakage of the refrigerant of the compressor during use will damage the atmospheric ozone layer and exacerbate other environmental problems. In contrast, the passive daytime radiative cooling (PDRC) technology with net refrigeration capacity has a very high reflectivity to sunlight, and at the same time can dissipate its own heat to outer space through the atmospheric transparent window with a wavelength of 8-13 μm. Therefore, it can achieve spontaneous cooling of the building surface without consuming electrical energy, and is expected to replace the air compression refrigeration system, which has a positive significance for the world energy pattern and mitigating global warming.

[0003] The principle of radiative cooling is to use the net radiative heat transfer formed by the inherent temperature difference in nature (such as between the human body and the surrounding environment, between the earth and outer space) to achieve efficient cooling. If the radiative cooling technology can be integrated into human fabrics, it will inevitably greatly reduce the use of traditional high-energy-consuming refrigeration equipment and contribute to the realization of the "dual carbon" goal.

[0004] However, most of the current human fabrics developed based on passive radiative cooling technology use petroleum-based polymers, such as polyethylene, polyvinylidene fluoride, etc. On the one hand, these materials are non-degradable and cause a serious environmental burden; on the other hand, the comfort for human wearing needs to be improved.

[0005] Cotton fabric, as one of the most popular textile materials, is expected to be used in passive radiative cooling fabrics. Combining the rich thermal radiation functional groups C-O and C-O-C bonds of cellulose, it can conduct radiative heat exchange with the cold outer space, but the overall reflectivity in the sunlight band is only about 60%. Therefore, when using cellulose materials in passive radiative cooling fabrics, the urgent problem to be solved is to improve its reflectivity in the sunlight band. Summary of the Invention

[0006] Based on the deficiencies of the prior art, the present invention provides a cellulose-based passive radiative cooling fiber, a preparation method thereof, and an application thereof. The present invention prepares cellulose fibers by regenerating a cellulose solution, and when the fiber is in a gel state, functional components of a reflective layer and a protective layer are introduced into the pores or on the surface of the gel fiber through diffusion in a coagulation bath.

[0007] The present invention provides the following technical solutions:

[0008] A preparation method of a cellulose-based passive radiative cooling fiber, the preparation method comprising the following steps:

[0009] (1) Preparing gel fibers from a cellulose solution through a spinning process;

[0010] (2) Sequentially passing the gel fibers through a first functional component coagulation bath and a second functional component coagulation bath, and then performing heat drying treatment to prepare the cellulose-based passive radiative cooling fiber.

[0011] According to an embodiment of the present invention, the gel fibers are obtained by extruding and regenerating the cellulose solution through a spinning can nozzle. Preferably, the regeneration refers to regeneration in a first coagulation bath. Preferably, the first coagulation bath is selected from water or an alcohol solution.

[0012] Preferably, the alcohol solution is selected from methanol, ethanol, propanol, n-butanol, glycerol, ethylene glycol, isopropanol, or isobutanol.

[0013] According to an embodiment of the present invention, the cellulose solution comprises a cellulose material and a solvent. Preferably, the cellulose solution is a homogeneous solution.

[0014] According to an embodiment of the present invention, in the cellulose solution, the concentration (solid content) of the cellulose material is 3 wt% - 15 wt%.

[0015] According to an embodiment of the present invention, the cellulose material is selected from one or more of the following substances: microcrystalline cellulose, bacterial cellulose, cotton pulp, wood pulp, bamboo pulp, straw pulp, refined cotton, defatted cotton, cotton linter, and at least one of bagasse, wood, and straw; preferably one or more of microcrystalline cellulose, refined cotton, defatted cotton, and wood pulp.

[0016] According to an embodiment of the present invention, the first functional component coagulation bath comprises a protective component and an aqueous solution of a first component.

[0017] According to an embodiment of the present invention, the protective component is selected from at least one of sodium alginate, silk fibroin, etc.

[0018] According to an embodiment of the present invention, the first component comprises an inorganic acid root ion or a metal ion. Preferably, the inorganic acid root ion is selected from at least one of sulfate ion, carbonate ion, hydroxide ion, etc. Preferably, the metal ion is, for example, selected from calcium ion, barium ion, and magnesium ion.

[0019] According to an embodiment of the present invention, the concentration of the protective component is 0.1 wt% - 10 wt%.

[0020] According to an embodiment of the present invention, the concentration ratio of the protective component to the first component is 1 - 5:1 - 10.

[0021] According to an embodiment of the present invention, the coagulation bath of the second functional component is selected from aqueous solutions containing a second component. Preferably, the second component includes inorganic acid root ions or metal ions, and the second component is different from the first component.

[0022] According to an embodiment of the present invention, in the first component and the second component, the molar ratio of metal ions to inorganic acid root ions is 0.1 - 2:0.1 - 2.

[0023] According to an embodiment of the present invention, the temperature of the heat drying treatment is 60°C - 100°C.

[0024] The present invention also provides a cellulose-based passive radiative cooling fiber, which has a skin-core structure and sequentially includes a fiber core layer and a functional layer from the inside to the outside; the functional layer includes a reflective component and a protective component;

[0025] Among them, the reflective component is selected from at least one of barium sulfate, calcium carbonate, barium carbonate, calcium sulfate, etc.; the protective component is selected from at least one of sodium alginate, silk fibroin, etc.

[0026] According to an embodiment of the present invention, the reflective component is obtained by the first component in the first functional coagulation bath diffusing into the surface or the pores on the surface of the fiber core layer, and then in-situ precipitating with the second component in the coagulation bath of the second functional component on the surface or the pores on the surface of the gel core layer.

[0027] According to an embodiment of the present invention, the protective component is coated on the surface of the fiber core layer and adheres to the surface of the fiber core layer after regeneration in the coagulation bath of the second functional component.

[0028] According to an embodiment of the present invention, the fiber core layer is selected from cellulose-based fibers. Preferably, the cellulose-based fiber includes the cellulose material.

[0029] According to an embodiment of the present invention, the size (diameter) range of the cellulose-based passive radiative cooling fiber is 5μm - 500μm.

[0030] According to an embodiment of the present invention, the cellulose-based passive radiative cooling fiber is prepared by the above preparation method.

[0031] The present invention also provides the application of the above cellulose-based passive radiative cooling fiber in the field of radiative cooling.

[0032] Advantages of the present invention:

[0033] The present invention prepares cellulose-based radiative cooling fibers by regenerating a cellulose solution. When the fibers are in the gel state, a reflective component and a protective component are introduced into the pores or on the surface of the gel fibers through diffusion in a coagulation bath to obtain a functional layer, thereby preparing cellulose-based radiative cooling fibers.

[0034] (1) The present invention can realize the continuous preparation of cellulose-based passive radiative cooling fibers: through the continuous spinning process of the cellulose solution, functional components are introduced through diffusion in a coagulation bath during continuous spinning, thereby realizing the continuous production of cellulose-based passive radiative cooling fibers with a core-shell structure.

[0035] (2) The fibers prepared by the present invention take into account both radiative cooling performance and mechanical properties: when the fibers are woven into fabrics, there are extremely high requirements for the mechanical properties of the fibers. In this process, the surface of the gel fibers is coated without damaging the structure of the cellulose fibers themselves. Therefore, the mechanical properties can be close to those of uncoated cellulose fibers, meeting the commercial weaving requirements.

[0036] (3) After being woven, the fibers prepared by the present invention can increase the reflectivity in the sunlight band to 95.16% and the emissivity in the near-infrared band to 98.13%. In actual simulation applications, the temperature is reduced by 12.8 °C compared to the direct action of sunlight on human skin, and the temperature is reduced by 6.9 °C compared to the fabric woven from untreated cellulose fibers.

[0037] (4) The cellulose-based passive radiative cooling fibers prepared by the present invention are biodegradable and will not cause environmental pollution.

[0038] (5) After being woven, the cellulose-based passive radiative cooling fibers prepared by the present invention have good gas permeability and moisture absorption ability, and are relatively comfortable to wear.

[0039] (6) The present invention adopts a continuous coating process for gel fibers. Since the gel fibers have a pore structure in the gel state, ion diffusion is satisfied, and in-situ precipitation coating is thereby realized. Compared with directly using dry fibers, the stability of the functional components is extremely high. Description of the Drawings

[0040] Figure 1 It is a cross-sectional view of the tow fiber of Example 1.

[0041] Figure 2 It is a surface view of the tow fiber of Example 1. Detailed Description of the Invention

[0042] [Preparation Method of Cellulose-Based Passive Radiative Cooling Fibers]

[0043] As described above, the present invention provides a preparation method of cellulose-based passive radiative cooling fibers, and the method includes the following steps:

[0044] (1) Prepare gel fibers from a cellulose solution through a spinning process.

[0045] (2) Pass the gel fibers through a first functional component coagulation bath and a second functional component coagulation bath in sequence, and then perform heat drying treatment to prepare the cellulose-based passive radiative cooling fibers.

[0046] According to an embodiment of the present invention, the spinning process can be selected from the spinning processes known in the art, and the present invention does not make specific limitations. For example, it is extruded through a spinning can nozzle. In the present invention, the size of the pressure of the spinning can nozzle is not particularly limited as long as the cellulose solution can be extruded from the nozzle. Exemplarily, the gel fibers are obtained by extruding and regenerating the cellulose solution through the spinning can nozzle. Preferably, the regeneration refers to regeneration in a first coagulation bath. Preferably, the first coagulation bath is selected from water or an alcohol solution. In the present invention, the size of the pressure is not particularly limited as long as the cellulose solution can be extruded from the nozzle.

[0047] Preferably, the alcohol solution is selected from the alcohol solutions known in the art, and the present invention does not make specific limitations. For example, the alcohol solution is selected from methanol, ethanol, propanol, n-butanol, glycerol, ethylene glycol, isopropanol or isobutanol.

[0048] According to an embodiment of the present invention, the cellulose solution includes a cellulose material and a solvent. Preferably, the cellulose solution is a homogeneous solution.

[0049] According to an embodiment of the present invention, in the cellulose solution, the concentration (solid content) of the cellulose material is 3 wt% - 15 wt%; specifically 6 wt% - 9 wt%; Exemplarily, it can be 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt% or 15 wt%.

[0050] According to an embodiment of the present invention, the cellulose material is selected from one or more of the following substances: microcrystalline cellulose, bacterial cellulose, cotton pulp, wood pulp, bamboo pulp, straw pulp, refined cotton, defatted cotton, cotton linter, and at least one of bagasse, wood and straw; preferably one or more of microcrystalline cellulose, refined cotton, defatted cotton, and wood pulp.

[0051] According to an embodiment of the present invention, the first functional component coagulation bath includes a protective component and an aqueous solution of a first component.

[0052] According to an embodiment of the present invention, the protective component is selected from at least one of sodium alginate, silk fibroin, etc.

[0053] According to an embodiment of the present invention, the first component comprises an inorganic acid radical ion or a metal ion. Preferably, the inorganic acid radical ion is selected from at least one of sulfate ion, carbonate ion, hydroxide ion, etc. Preferably, the metal ion is selected from calcium ion, barium ion, magnesium ion, for example.

[0054] According to an embodiment of the present invention, the concentration of the protective component can be 0.1 wt% - 10 wt%, for example, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%.

[0055] According to an embodiment of the present invention, the concentration ratio of the protective component to the first component is 1 - 5:1 - 10, for example, 1:1, 1:5, 1:10, 5:1, 5:5, 5:10.

[0056] According to an embodiment of the present invention, the coagulation bath of the second functional component is selected from an aqueous solution containing a second component. Preferably, the second component comprises an inorganic acid radical ion or a metal ion, and the second component is different from the first component. Exemplarily, when the first component comprises an inorganic acid radical ion, the second component comprises a metal ion; when the second component comprises an inorganic acid radical ion, the first component comprises a metal ion. Further, a white precipitate is obtained by the reaction of the metal ion and the inorganic acid radical ion.

[0057] According to an embodiment of the present invention, in the first component and the second component, the molar ratio of the metal ion to the inorganic acid radical ion is 0.1 - 2:0.1 - 2, for example, 1:1.

[0058] According to an exemplary embodiment of the present invention, the coagulation bath of the first functional component is selected from an aqueous solution containing sodium alginate and sodium sulfate; the coagulation bath of the second functional component is selected from an aqueous solution containing calcium chloride and / or barium chloride.

[0059] According to an exemplary embodiment of the present invention, the coagulation bath of the first functional component is selected from an aqueous solution containing fibroin water and barium chloride; the coagulation bath of the second functional component is selected from an aqueous solution containing ammonium sulfate.

[0060] According to an embodiment of the present invention, the temperature of the heat drying treatment is 60°C - 100°C; preferably 80°C.

[0061] In the present invention, the inventors found that the protective component in the coagulation bath of the first component is adsorbed on the surface of the gel fiber. At the same time, after passing through the second coagulation bath, the metal ion or inorganic acid radical ion forms a reflective component on the surface or in the pores on the surface of the gel fiber. The reflective component and the protective component are mixed on the surface of the gel fiber to form a functional layer, preferably a uniformly mixed functional layer.

[0062] [Cellulose-based passive radiative cooling fiber]

[0063] As described above, the present invention provides a cellulose-based passive radiative cooling fiber. The fiber has a skin-core structure and sequentially includes a fiber core layer and a functional layer from the inside out; the functional layer includes a reflection component and a protection component;

[0064] Among them, the reflection component is selected from at least one of barium sulfate, calcium carbonate, barium carbonate, calcium sulfate, etc.; the protection component is selected from at least one of sodium alginate, silk fibroin, etc.

[0065] According to an embodiment of the present invention, the reflection component is obtained by the first component in the first functional coagulation bath diffusing into the surface or the pores on the surface of the fiber core layer, and then in-situ precipitating with the second component in the second functional component coagulation bath on the surface or the pores on the surface of the gel core layer.

[0066] According to an embodiment of the present invention, the protection component is coated on the surface of the fiber core layer and adheres to the surface of the fiber core layer after regeneration in the second functional component coagulation bath.

[0067] According to an embodiment of the present invention, the shape of the cross-section of the cellulose-based passive radiative cooling fiber is not specifically limited, for example, it is circular.

[0068] According to an embodiment of the present invention, the fiber core layer is selected from cellulose-based fibers. Preferably, the cellulose-based fiber includes a cellulose material, and the cellulose material has the meaning as described above.

[0069] According to an embodiment of the present invention, in the cellulose-based passive radiative cooling fiber, the fiber core layer is used to provide strength and infrared emission performance. Among the functional components, the reflection component is used to reflect sunlight, and the protection component is used to protect the stability of the reflection layer.

[0070] In the present invention, the reflection component is distributed in the pores on the surface of the fiber core layer (i.e., inside the matrix of the gel fiber) and / or on the surface of the fiber core layer, the protection component is distributed on the surface of the fiber core layer, and the reflection material and the protection material are mixed to form the functional layer.

[0071] According to an embodiment of the present invention, the cellulose-based passive radiative cooling fiber can be a tow or a single fiber; specifically, the size (diameter) range of the fiber is 5μm - 500μm, and it can be detected by optical microscopy and cryo-scanning electron microscopy data. Preferably, the size (diameter) is 10μm - 50μm.

[0072] According to an embodiment of the present invention, the cellulose-based passive radiative cooling fiber is prepared by the above preparation method.

[0073] [Application]

[0074] The present invention also provides the application of the above-mentioned cellulose-based passive radiative cooling fiber in the field of radiative cooling (such as human cooling clothes, cooling car clothes, etc.).

[0075] [Cellulose-based Passive Radiative Cooling Fiber Solution and Its Preparation]

[0076] As described above, the fiber core layer of the cellulose-based passive radiative cooling fiber of the present invention is prepared from a cellulose solution. In the process of preparing the cellulose solution, the solvent used is not particularly limited and can be any solvent known in the art that can dissolve (the dissolution includes complete dissolution and partial dissolution) the above-mentioned cellulose materials.

[0077] According to the embodiments of the present invention, the solvent can be selected from one or more of the following solvents: organic solvents, ionic liquids, inorganic salts, organic salts; exemplarily, selected from at least one of choline-based deep eutectic solvent systems, organic solvent / salt systems, amine oxide systems (NMMO), carbamate systems, base / water systems, base / urea systems, base / thiourea systems, liquid ammonia / NH4SCN, organic acids, metal salt aqueous solutions, alcohol solutions of metal hydrates, or water-alcohol mixed solutions of metal hydrates and the like solvent systems.

[0078] Among them, the organic solvent can be selected from one or more of N,N-dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), N-methylimidazole, imidazole, pyridine, ethylenediamine, hexafluoroacetone, hexafluoroisopropanol, glycerol, methyl isobutyl ketone, tetrahydrofuran, dioxane, γ-valerolactone (GVL).

[0079] Among them, the organic solvent / salt system is an organic solvent / metal salt or an organic solvent / organic salt, and can be selected from one or more of N,N-dimethylacetamide / lithium chloride (DMAc / LiCl) system, N,N-dimethyl sulfoxide / tetrabutylammonium fluoride system (DMSO / TBAF).

[0080] Among them, the base / water system can be selected from one or two of NaOH / H2O and KOH / H2O.

[0081] Among them, the base / urea system is NaOH / Urea.

[0082] Among them, the base / thiourea system is NaOH / thio-urea.

[0083] Among them, the organic acid can be selected from one or more of formic acid, acetic acid, propionic acid, butyric acid, succinic acid, lactic acid, glutamic acid, glycine, dichloroacetic acid, trichloroacetic acid, benzenesulfonic acid, phosphoric acid, etc.

[0084] Among them, the aqueous metal salt solution is selected from aqueous solutions of metal salts such as CaCl2, ZnCl2, LiClO4, Ca(SCN)2, LiSCN, Ca(NO)2, etc.

[0085] Among them, the alcoholic solution of the metal salt hydrate can be selected from the methanol solution of CaBr2·H2O or the methanol solution of CaCl2·2H2O.

[0086] Among them, the water-alcohol mixed solution of the metal salt hydrate can be selected from the methanol aqueous solution of CaBr2·H2O or the methanol aqueous solution of CaCl2·2H2O.

[0087] Among them, the amine oxide system can be the NMMO / H2O / DMSO system, the NMMO / H2O / diethyltriamine, or the NMMO / H2O system.

[0088] Among them, the ionic liquid is selected from organic molten salts formed by cations such as imidazole, pyridine, pyrrole, etc. and anions with a melting point below 100°C, preferably an organic molten salt that can dissolve cellulose.

[0089] For example, the cation of the ionic liquid is selected from one or more of imidazole, pyridine, pyrrole, amine, phosphine, choline, diazabicyclo, amino acid-type cations that are unsubstituted or substituted by one, two, or more substituents; for example, the substituent can be C 1-6 alkyl, C 1-6 alkoxy, hydroxyl, -C 1-6 -OH, C 1-6 alkenyl, phenyl, C 1-6 alkoxy-substituted phenyl or C 1-6 alkyl-substituted phenyl; preferably, the substituent is one or more of methyl, ethyl, propyl, butyl, allyl, benzyl, methoxymethyl, methoxyethyl, hydroxyethyl, pentyl, m-methoxybenzyl, m-methylbenzyl;

[0090] Preferably, the cation is selected from one or more of the following cations: 1-ethyl-3-methylimidazolium cation ([EMIM] + )、3-methylimidazolium cation ([MIM] + )、1-propyl-3-methylimidazolium cation ([PMIM] + )、1-allyl-3-methylimidazolium cation ([AMIM] + )、1-butyl-3-methylimidazolium cation ([BMIM]+ ) 1-butyl-2,3-dimethylimidazolium cation ([BMMIM] + ) 1,3-dimethylimidazolium cation ([MMIM] + ) 1-methoxyethyl-3-methylimidazolium cation ([MeOEMIM] + ) 1-methoxymethyl-3-methylimidazolium cation ([MeOMMIM] + ) 1-hydroxy-3-methyl-imidazolium cation ([HMIM] + ) 1-(2-hydroxyethyl)-3-methylimidazolium cation ([HOEMIM] + ) 1-methyl-3-benzylimidazolium cation ([MBzIM] + ) 1-pentyl-3-methylimidazolium cation ([PeMIM] + ) 1-benzyl-3-methylimidazolium cation ([BzMIM] + ) 1-m-methoxybenzyl-3-methylimidazolium cation ([MeOBzMIM] + ) 1-m-methylbenzyl-3-methylimidazolium cation ([MeBzMIM] + ) N-methylpyridinium cation ([MPyr] + ) N-ethylpyridinium cation ([EPyr] + ) N-butylpyridinium cation ([BPyr] + ) N-n-hexylpyridinium cation ([HPyr] + ) 1-butyl-3-methylpyrrolidinium ion ([BMPyrr] + ) tris(2-hydroxyethyl)methylamine ([THEMA] + ) tetrabutylammonium ([TBA] + ) tetrabutylphosphonium ([PBu4] + ) glycine cation ([Gly] + ) choline cation ([Ch] + ) 1,5-diazabicyclo[4.3.0]non-5-ene ([DBNH] + ) one or more of the following cations.

[0091] More preferably, the cation is selected from one or more of the following cations: 1-ethyl-3-methylimidazolium cation ([EMIM] + ) 1-allyl-3-methylimidazolium cation ([AMIM] + ) 1-butyl-3-methylimidazolium cation ([BMIM] + ) choline cation ([Ch] + ) one or more of the following.

[0092] For example, the anion is selected from one or more of halogen anions, organic acid root ions, organic acid ester anions, amino acid type anions, etc.

[0093] Preferably, the anion is selected from one or more of the following anions: chloride ion ([Cl]-), bromide ion ([Br]-), fluoride ion ([F] - ), formate ion ([HCOO]-), acetate ion ([CH3COO]- or [Ac]-), glycolate ion ([HOCH2COO]-), propionate ion ([CH3CH2COO]- or [OPr]-), butyrate ion ([CH3CH2CH2COO]- or [OBu]-), octylate ([Oct]-), benzoate ion ([C6H5COO]- or [PhCOO]-), lactate ion ([CH3CH(OH)COO] - or [Lac] - ), thioglycolate ion ([HSCH2COO] - ), hexafluorophosphate ion ([PF6] - ), trifluoroborate ([BF3] - ), methyl phosphate ion ([(MeO)HPO2] - or [MP] - ), dimethyl phosphate ion ([(MeO)2PO2] - or [DMP] - ), diethyl phosphate ion ([(EtO)2PO2] - or [DEP] - ), methyl sulfonate anion ([MeOSO3] - ), trifluoromethyl sulfonate anion ([CF3SO3] - ), glycine anion ([Gly] - ), lysine anion ([Lys] - ), valine anion ([Val] - ), dicyanamide anion ([N(CN)2] - or [DCA] - ), bis(trifluoromethylsulfonyl)imide ([Tf2N] - ), etc.

[0094] More preferably, the anion is selected from one or more of the following anions: chloride ion ([Cl] - ), formate ion ([HCOO] - ), acetate ion ([Ac] -) Methyl phosphate ion ([(MeO)HPO2] - or [MP] - ) Dimethyl phosphate ion ([(MeO)2PO2] - or [DMP] - ) and dicyanamide anion ([N(CN)2] - or [DCA] - ) or one or more of them.

[0095] According to the present invention, the ionic liquid may be selected from 1-ethyl-3-methylimidazolium chloride ionic liquid ([EMIM][Cl]), 1-ethyl-3-methylimidazolium bromide ionic liquid ([EMIM][Br]), 1-ethyl-3-methylimidazolium formate ionic liquid ([EMIM][HCOO]), 1-ethyl-3-methylimidazolium acetate ionic liquid ([EMIM][Ac]), 1-ethyl-3-methylimidazolium octanoate ionic liquid ([EMIM][Oct]), 1-ethyl-3-methylimidazolium methyl phosphate ionic liquid ([EMIM][MP]), 1-ethyl-3-methylimidazolium dimethyl phosphate ionic liquid ([EMIM][DMP]), 1-ethyl-3-methylimidazolium diethyl phosphate ionic liquid ([EMIM][DEP]), 1-ethyl-3-methylimidazolium propionate ionic liquid ([EMIM][OPr]), 1-ethyl-3-methylimidazolium butyrate ionic liquid ([EMIM][OBu]), 1-ethyl-3-methylimidazolium glycinate ionic liquid ([EMIM][Gly]), 1-ethyl-3-methylimidazolium lysinate ionic liquid ([EMIM][Lys]), 1-allyl-3-methylimidazolium chloride ionic liquid ([AMIM][Cl]), 1-allyl-3-methylimidazolium bromide ionic liquid ([AMIM][Br]), 1-allyl-3-methylimidazolium formate ionic liquid ([AMIM][HCOO]), 1-allyl-3-methylimidazolium acetate ionic liquid ([AMIM][Ac]), 1-butyl-3-methylimidazolium chloride ionic liquid ([BMIM][Cl]), 1-butyl-3-methylimidazolium bromide ionic liquid ([BMIM][Br]), 1-butyl-3-methylimidazolium formate ionic liquid ([BMIM][HCOO]), 1-butyl-3-methylimidazolium acetate ionic liquid ([BMIM][Ac]), 1-butyl-3-methylimidazolium glycolate ionic liquid ([BMIM][HOCH2COO]), 1-butyl-3-methylimidazolium propionate ionic liquid ([BMIM][CH3CH2COO]), 1-butyl-3-methylimidazolium lactate ionic liquid [BMIM][Lac], 1-butyl-3-methylimidazolium butyrate ionic liquid ([BMIM][CH3CH2CH2COO]), 1-butyl-3-methylimidazolium benzoate ionic liquid ([BMIM][C6H5COO]), 1-butyl-3-methylimidazolium glycinate ionic liquid ([BMIM][H2NCH2COO]), 1-butyl-3-methylimidazolium dicyanamide ionic liquid ([BMIM][N(CN)2]), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid ([BMIM][Tf2N]), 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid ([BMIM][PF6]).1-Butyl-3-methylimidazolium tetrafluoroborate ionic liquid ([BMIM][BF4]), 1-butyl-3-methylimidazolium methylsulfonate ionic liquid ([BMIM][MeOSO3]), 1-butyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid ([BMIM][CF3SO3]), 1-butyl-2,3-dimethylimidazolium tetrafluoroborate ionic liquid ([BMMIM][BF4]), 3-methylimidazolium formate ionic liquid ([MIM][HCOO]), 1,3-dimethylimidazolium chloride ionic liquid ([MMIM][Cl]), 1,3-dimethylimidazolium methyl phosphate ionic liquid ([MMIM][MP]), 1,3-dimethylimidazolium dimethyl phosphate ionic liquid ([MMIM][DMP]), 1,3-dimethylimidazolium methylsulfonate ionic liquid ([MMIM][MeOSO3]), 1-hydroxy-3-methyl-imidazolium chloride ionic liquid ([HMIM][Cl]), 1-hydroxy-3-methyl-imidazolium trifluoromethanesulfonate ionic liquid ([HMIM][CF3SO3]), 1-(2-hydroxyethyl)-3-methylimidazolium chloride ionic liquid ([HOEMIM][Cl]), 1-methoxymethyl-3-methylimidazolium bromide ionic liquid ([MeOMMIM][Br]), 1-methoxyethyl-3-methylimidazolium bromide ionic liquid ([MeOEMIM][Br]), N-ethylpyridinium chloride ionic liquid ([EPyr][Cl]), N-ethylpyridinium bromide ionic liquid ([EPyr][Br]), N-methylpyridinium formate ionic liquid ([MPyr][HCOO]), tris(2-hydroxyethyl)methylammonium acetate ionic liquid ([THEMA][Ac]), tris(2-hydroxyethyl)methylammonium methylsulfonate ionic liquid ([THEMA][MeOSO3]), tris(2-hydroxyethyl)methylammonium trifluoromethanesulfonate ionic liquid [THEMA][CF3SO3], tetrabutylphosphonium valinate ionic liquid [PBu4][Val], tetrabutylphosphonium lysinate ionic liquid [PBu4][Lys], tetrabutylphosphonium glycinate ionic liquid [PBu4][Gly], 1-benzyl-3-methylimidazolium chloride ionic liquid ([BzMIM][Cl]), 1-benzyl-3-methylimidazolium dicyanamide ionic liquid ([BzMIM][DCA]), 1-meta-methylbenzyl-3-methylimidazolium chloride ionic liquid ([MeBzMIM][Cl]), 1-meta-methoxybenzyl-3-methylimidazolium chloride ionic liquid ([MeOBzMIM][Cl]), choline chloride ionic liquid ([Ch][Cl]), choline bromide ionic liquid ([Ch][Br]) choline acetate ionic liquid ([Ch][CH3COO]), choline propionate ionic liquid ([Ch][CH3CH2COO])One or more of ionic liquids such as choline butyrate ionic liquid ([Ch][CH3CH2CH2COO]), glycine hydrochloride ionic liquid ([Gly][Cl]), 1,5-diazabicyclo[4.3.0]non-5-ene acetate ionic liquid ([DBNH][Ac]), etc.

[0096] Preferably, the choline-based deep eutectic solvent system is selected from one or more of [Ch][Cl] / urea, [Ch][Br] / urea, [Ch][Cl] / thiourea, [Ch][Cl] / glycerol, [Ch][Cl] / lactic acid.

[0097] Exemplarily, the solvent for dissolving cellulose has the above meaning; more preferably, the solvent for dissolving cellulose is selected from one or more of [AMIM][Cl], [BMIM][Cl], [EMIM][Ac], [BMIM][Ac].

[0098] The technical solutions of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only for illustrative and explanatory purposes of the present invention, and should not be construed as limiting the protection scope of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0099] Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available products, or can be prepared by known methods.

[0100] Example 1

[0101] 6 g of wood pulp with a polymerization degree of 549 after drying was added to a three-necked flask, and 94 g of 1-allyl-3-methylimidazolium chloride ionic liquid ([AMIM][Cl]) was added. After stirring at 80 °C for 2 h, a cellulose solution was formed. After defoaming the cellulose solution, it was poured into a spinning can, and the solution was extruded from the spinning can nozzle under the action of pressure, and then passed through a stretching roller into a water coagulation bath, and then into a first functional component coagulation bath. The coagulation bath contained a 1 wt% sodium alginate solution, and the solution contained 10 wt% sodium sulfate. Subsequently, it was stretched and entered a second functional component coagulation bath. The second functional component coagulation bath contained 5 wt% BaCl2 and 5 wt% CaCl2. In the coagulation bath, sodium alginate was chelated and regenerated by calcium ions, and sulfate ions formed barium sulfate with barium ions. Subsequently, the cellulose-based passive radiative cooling fiber was obtained by hot roller drying treatment, and its size (diameter) was about 15 μm. The reflectance of the fiber in the sunlight band was 95.16% after being woven into a fabric.

[0102] The cross-sectional view of the cellulose-based passive radiative cooling fiber prepared in this example is as Figure 1 shown. FromFigure 1 and Figure 2 As can be seen from Figure 1 and Figure 2 , the surface of the cellulose-based passive radiative cooling fiber in Example 1 has a functional layer (i.e., the functional layer formed by mixing barium sulfate and sodium alginate), and the middle part of each single-filament fiber is a fiber core layer. The functional layer adheres to the surface of the fiber core layer, that is, the cellulose-based passive radiative cooling fiber prepared in this example has a skin-core structure.

[0103] Example 2

[0104] 6 g of dried wood pulp with a degree of polymerization of 549 was added to a three-necked flask, and 94 g of 1-allyl-3-methylimidazolium chloride ionic liquid ([AMIM][Cl]) was added. After stirring at 80 °C for 2 h, a cellulose solution was formed. After degassing the cellulose solution, it was poured into a spinning can, and the solution was extruded from the spinning can nozzle under the action of pressure. Subsequently, it passed through a drafting roller and entered a water coagulation bath, and then entered a first functional component coagulation bath. The coagulation bath contained a 1 wt% sodium alginate solution, and the solution contained 5 wt% sodium sulfate. Subsequently, it was drawn and entered a second functional component coagulation bath. The second functional component coagulation bath contained 5 wt% BaCl2 and 5 wt% CaCl2. In the coagulation bath, sodium alginate was chelated and regenerated by calcium ions, and sulfate ions formed barium sulfate with barium ions. Subsequently, the cellulose-based passive radiative cooling fiber was obtained by hot roller drying treatment, and its size (diameter) was 15 μm. After the fiber was woven into a fabric, the reflectance in the sunlight band was measured to be 89.16%.

[0105] Example 3

[0106] 6 g of dried wood pulp with a degree of polymerization of 549 was added to a three-necked flask, and 94 g of 1-allyl-3-methylimidazolium chloride ionic liquid ([AMIM][Cl]) was added. After stirring at 80 °C for 2 h, a cellulose solution was formed. After degassing the cellulose solution, it was poured into a spinning can, and the solution was extruded from the spinning can nozzle under the action of pressure. Subsequently, it passed through a drafting roller and entered a water coagulation bath, and then entered a first functional component coagulation bath. The coagulation bath contained a 1 wt% sodium alginate solution, and the solution contained 1 wt% sodium sulfate. Subsequently, it was drawn and entered a second functional component coagulation bath. The second functional component coagulation bath contained 5 wt% BaCl2 and 5 wt% CaCl2. In the coagulation bath, sodium alginate was chelated and regenerated by calcium ions, and sulfate ions formed barium sulfate with barium ions. Subsequently, the cellulose-based passive radiative cooling fiber was obtained by hot roller drying treatment, and its size (diameter) was 15 μm. After the fiber was woven into a fabric, the reflectance in the sunlight band was measured to be 80.16%.

[0107] As can be seen from Examples 1-3, adjusting the concentration of the coagulation bath can control the reflectance of the cellulose-based passive radiative cooling fiber.

[0108] Example 4

[0109] 6 g of dried wood pulp with a degree of polymerization of 549 was added to a three-necked flask, and 94 g of 1-allyl-3-methylimidazolium chloride ionic liquid ([AMIM][Cl]) was added. After stirring at 80 °C for 2 h, a cellulose solution was formed. After degassing the cellulose solution, it was poured into a spinning can. The solution was extruded from the spinning can nozzle under the action of pressure, then passed through a stretching roller into a water coagulation bath, and then into a first functional component coagulation bath. The coagulation bath contained a 5 wt% aqueous solution of silk fibroin, and the solution contained 10 wt% barium chloride. Subsequently, it was stretched and entered a second functional component coagulation bath. The second functional component coagulation bath contained 5 wt% ammonium sulfate. In the coagulation bath, silk fibroin was regenerated by ammonium sulfate, and sulfate ions formed barium sulfate with barium ions. Subsequently, the cellulose-based passive radiative cooling fiber was obtained by hot roller drying treatment, and its size (diameter) was 15 μm. After the fiber was woven into a fabric, the reflectance in the sunlight band was measured to be 94.26%.

[0110] Example 5

[0111] 6 g of dried wood pulp with a degree of polymerization of 549 was added to a three-necked flask, and 94 g of 1-allyl-3-methylimidazolium chloride ionic liquid ([AMIM][Cl]) was added. After stirring at 80 °C for 2 h, a cellulose solution was formed. After degassing the cellulose solution, it was poured into a spinning can. The solution was extruded from the spinning can nozzle under the action of pressure, then passed through a stretching roller into a water coagulation bath, and then into a first functional component coagulation bath. The coagulation bath contained a 5 wt% aqueous solution of silk fibroin, and the solution contained 5 wt% barium chloride. Subsequently, it was stretched and entered a second functional component coagulation bath. The second functional component coagulation bath contained 5 wt% ammonium sulfate. In the coagulation bath, silk fibroin was regenerated by ammonium sulfate, and sulfate ions formed barium sulfate with barium ions. Subsequently, the cellulose-based passive radiative cooling fiber was obtained by hot roller drying treatment, and its size (diameter) was 15 μm. After the fiber was woven into a fabric, the reflectance in the sunlight band was measured to be 90.25%.

[0112] Example 6

[0113] 6 g of wood pulp with a polymerization degree of 549 after drying was added to a three-necked flask, and 94 g of 1-allyl-3-methylimidazolium chloride ionic liquid ([AMIM][Cl]) was added. After stirring at 80 °C for 2 h, a cellulose solution was formed. After degassing the cellulose solution, it was poured into a spinning can, and the solution was extruded from the spinning can nozzle under the action of pressure, then passed through a stretching roller into a water coagulation bath, and then into a first functional component coagulation bath. The coagulation bath contained a 5 wt% aqueous solution of silk fibroin, and the solution contained 1 wt% barium chloride. Subsequently, it was stretched and entered a second functional component coagulation bath. The second functional component coagulation bath contained 5 wt% ammonium sulfate. In the coagulation bath, silk fibroin was regenerated by ammonium sulfate, and sulfate ions formed barium sulfate with barium ions. Subsequently, the cellulose-based passive radiative cooling fiber was obtained by hot roller drying treatment, and its size (diameter) was 15 μm. After the fiber was woven into a fabric, the reflectance in the solar light band was measured to be 86.36%.

[0114] It can be seen from Examples 4-6 that when using coagulation baths with different protective layers, the reflectance of the cellulose-based passive radiative cooling fiber is higher than 86%, still meeting the requirements of the present invention.

[0115] The above describes the exemplary embodiments of the present invention. However, the protection scope of this application is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made by those skilled in the art within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a cellulose-based passive radiative cooling fiber, characterized in that, The preparation method includes the following steps: (1) Preparing gel fibers from a cellulose solution through a spinning process; (2) Sequentially passing the gel fibers through a first functional component coagulation bath and a second functional component coagulation bath, and then performing heat drying treatment to prepare the cellulose-based passive radiative cooling fibers.

2. The preparation method according to claim 1, characterized in that, The gel fibers are obtained by extruding and regenerating the cellulose solution through a spinning can nozzle. Preferably, the regeneration refers to regeneration in a first coagulation bath. Preferably, the first coagulation bath is selected from water or an alcohol solution. Preferably, the alcohol solution is selected from methanol, ethanol, propanol, n-butanol, glycerol, ethylene glycol, isopropanol or isobutanol.

3. The preparation method according to claim 1 or 2, characterized in that, The cellulose solution includes a cellulose material and a solvent. Preferably, in the cellulose solution, the concentration of the cellulose material is 3 wt% - 15 wt%. Preferably, the cellulose material is selected from one or more of the following substances: microcrystalline cellulose, bacterial cellulose, cotton pulp, wood pulp, bamboo pulp, straw pulp, refined cotton, degreased cotton, cotton linter, and at least one of bagasse, wood and straw.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The first functional component coagulation bath includes a protective component and an aqueous solution of a first component. Preferably, the protective component is selected from at least one of sodium alginate and silk fibroin.

5. The preparation method according to any one of claims 1-4, characterized in that, The first component includes an inorganic acid root ion or a metal ion. Preferably, the inorganic acid root ion is selected from at least one of sulfate ion, carbonate ion and hydroxide ion. Preferably, the metal ion is selected from calcium ion, barium ion and magnesium ion. Preferably, the concentration of the protective component is 0.1 wt% - 10 wt%. Preferably, the concentration ratio of the protective component to the first component is 1 - 5:1 - 10.

6. The preparation method according to any one of claims 1-5, characterized in that, The second functional component coagulation bath is selected from an aqueous solution containing a second component. Preferably, the second component includes an inorganic acid root ion or a metal ion, and the second component is different from the first component. Preferably, in the first component and the second component, the molar ratio of the metal ion to the inorganic acid root ion is 0.1 - 2:0.1 - 2. Preferably, the temperature of the heat drying treatment is 60°C - 100°C.

7. A cellulose-based passive radiative cooling fiber, characterized in that, The fiber has a skin-core structure and sequentially includes a fiber core layer and a functional layer from the inside out; the functional layer includes a reflective component and a protective component; Among them, the reflective component is selected from at least one of barium sulfate, calcium carbonate, barium carbonate and calcium sulfate; the protective component is selected from at least one of sodium alginate and silk fibroin.

8. The cellulose-based passive radiative cooling fiber according to claim 7, wherein, The reflective component is obtained by the first component in the first functional coagulation bath diffusing into the surface or the pores on the surface of the fiber core layer, and then in-situ precipitating with the second component in the second functional component coagulation bath on the surface or the pores on the surface of the gel core layer. Preferably, the protective component is coated on the surface of the fiber core layer and adheres to the surface of the fiber core layer after regenerating in the second functional component coagulation bath. Preferably, the fiber core layer is selected from cellulose-based fibers.

9. The cellulose-based passive radiative cooling fiber according to claim 7 or 8, wherein, The size of the cellulose-based passive radiative cooling fiber is 5 μm - 500 μm. Preferably, the cellulose-based passive radiative cooling fiber is prepared by the preparation method described in any one of claims 1 - 6.

10. Use of the cellulose-based passive radiative cooling fiber according to any one of claims 7-9 in the field of radiative cooling.

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